Stackable middleware services for advanced multimedia applications. Final report for period July 14, 1999 - July 14, 2001 (open access)

Stackable middleware services for advanced multimedia applications. Final report for period July 14, 1999 - July 14, 2001

In this project, the authors propose the research, development, and distribution of a stackable component-based multimedia streaming protocol middleware service. The goals of this stackable middleware interface include: (1) The middleware service will provide application writers and scientists easy to use interfaces that support their visualization needs. (2) The middleware service will support a variety of image compression modes. Currently, many of the network adaptation protocols for video have been developed with DCT-based compression algorithms like H.261, MPEG-1, or MPEG-2 in mind. It is expected that with advanced scientific computing applications that the lossy compression of the image data will be unacceptable in certain instances. The middleware service will support several in-line lossless compression modes for error-sensitive scientific visualization data. (3) The middleware service will support two different types of streaming video modes: one for interactive collaboration of scientists and a stored video streaming mode for viewing prerecorded animations. The use of two different streaming types will allow the quality of the video delivered to the user to be maximized. Most importantly, this service will happen transparently to the user (with some basic controls exported to the user for domain specific tweaking). In the spirit of layered network protocols (like …
Date: February 1, 2002
Creator: Feng, Wu-chi & Crawfis, Roger, Weide, Bruce
Object Type: Report
System: The UNT Digital Library
USDOE Top-of-Rail Lubricant Project (open access)

USDOE Top-of-Rail Lubricant Project

Lubrication of wheel/rail systems has been recognized for the last two decades as a very important issue for railroads. Energy savings and less friction and wear can be realized if a lubricant can be used at the wheel/rail interface. On the other hand, adverse influences are seen in operating and wear conditions if improper or excessive lubrication is used. Also, inefficiencies in lubrication need to be avoided for economic and environmental reasons. The top-of-rail (TOR) lubricant concept was developed by Texaco Corporation to lubricate wheels and rails effectively and efficiently. Tranergy Corporation has been developing its SENTRAEN 2000{trademark} lubrication system for the last ten years, and this revolutionary new high-tech on-board rail lubrication system promises to dramatically improve the energy efficiency, performance, safety, and track environment of railroads. The system is fully computer-controlled and ensures that all of the lubricant is consumed as the end of the train passes. Lubricant quantity dispensed is a function of grade, speed, curve, and axle load. Tranergy also has its LA4000{trademark} wheel and rail simulator, a lubrication and traction testing apparatus. The primary task of this project was collecting and analyzing the volatile and semivolatile compounds produced as the lubricant was used. The volatile …
Date: February 1, 2002
Creator: Alzoubi, Mohumad F.; Fenske, George R.; Erck, Robert A. & Boparai, Amrit S.
Object Type: Report
System: The UNT Digital Library
Forest succession at elevated CO2 (open access)

Forest succession at elevated CO2

We tested hypotheses concerning the response of forest succession to elevated CO2 in the FACTS-1 site at the Duke Forest. We quantified growth and survival of naturally recruited seedlings, tree saplings, vines, and shrubs under ambient and elevated CO2. We planted seeds and seedlings to augment sample sites. We augmented CO2 treatments with estimates of shade tolerance and nutrient limitation while controlling for soil and light effects to place CO2 treatments within the context of natural variability at the site. Results are now being analyzed and used to parameterize forest models of CO2 response.
Date: February 1, 2002
Creator: Clark, James S. & Schlesinger, William H.
Object Type: Report
System: The UNT Digital Library
Modeling decade to century scale variability in the atmosphere/ocean [Final report] (open access)

Modeling decade to century scale variability in the atmosphere/ocean [Final report]

Study of the intrinsic variability of a coupled atmosphere/ocean model called The Fast Ocean/Atmosphere Model (FOAM).
Date: February 4, 2002
Creator: Kutzbach, John E.
Object Type: Report
System: The UNT Digital Library
FISCAL YEAR 2001 ANNUAL REPORT ON THE UNIVERSITY PROGRAMS OF THE ADVANCED ACCELERATOR APPLICATIONS PROGRAM. (open access)

FISCAL YEAR 2001 ANNUAL REPORT ON THE UNIVERSITY PROGRAMS OF THE ADVANCED ACCELERATOR APPLICATIONS PROGRAM.

The Advanced Accelerator Applications (AAA) Program was initiated in fiscal year 2001 (FY-01) by the U.S. Congress, the U.S. Department of Energy (DOE), and the Los Alamos National Laboratory (LANL) in partnership with other national laboratories. The AAA Project and the R&D for its underlying science and technology will require a large cadre of educated scientists and trained technicians in the future. In addition, other applications of nuclear science and engineering (e.g., proliferation monitoring and defense, nuclear medicine, safety regulation, industrial processes, and many others) require increased academic and national infrastructure and student populations. Thus, the DOE AAA Program Office has begun a multi-year program to involve university faculty and students in various phases of the Project to support the infrastructure requirements of nuclear energy, science and technology fields as well as the special needs of the DOE transmutation program. Herein I summarize the goals and accomplishments of the university programs that have supported the AAA Project during FY-01, including the involvement of more than eighty students.
Date: February 16, 2002
Creator: BELLER, DENIS E
Object Type: Report
System: The UNT Digital Library
Atmospheric Dispersion Modeling for Radiological Accident Analyses at LANL Nuclear Facilities. (open access)

Atmospheric Dispersion Modeling for Radiological Accident Analyses at LANL Nuclear Facilities.

None
Date: February 16, 2002
Creator: Heindel, George D.
Object Type: Report
System: The UNT Digital Library
FASEB Summer Research Conference. Genetic Recombination and Chromosome Rearrangements (open access)

FASEB Summer Research Conference. Genetic Recombination and Chromosome Rearrangements

The 2001 meeting entitled ''Genetic Recombination and Genome Rearrangements'' was held July 21-26 in Snowmass, Colorado. The goal of the meeting was to bring together scientists using diverse approaches to study all aspects of genetic recombination. This goal was achieved by integrating talks covering the genetics, biochemistry and structural biology of homologous recombination, site-specific recombination, and nonhomologous recombination. The format of the meeting consisted of a keynote address on the opening evening, two formal plenary sessions on each of the four full meeting days, a single afternoon workshop consisting of short talks chosen from among submitted abstracts, and afternoon poster sessions on each of the four full meeting days. The eight plenary session were entitled: (1) Recombination Mechanisms, (2) Prokaryotic Recombination, (3) Repair and Recombination, (4) Site-specific Recombination and Transposition, (5) Eukaryotic Recombination I, (6) Genome Rearrangements, (7) Meiosis, and (8) Eukaryotic Recombination II. Each session included a mix of genetic, biochemical and structural talks; talks were limited to 20 minutes, followed by 10 minutes of very lively, general discussion. Much of the data presented in the plenary sessions was unpublished, thus providing attendees with the most up-to-date knowledge of this rapidly-moving field.
Date: February 1, 2002
Creator: Jinks-Robertson, Sue
Object Type: Report
System: The UNT Digital Library
Worldwide Historical Estimates of Leaf Area Index, 1932-2000 (open access)

Worldwide Historical Estimates of Leaf Area Index, 1932-2000

Approximately 1000 published estimates of leaf area index (LAI) from nearly 400 unique field sites, covering the period 1932-2000, have been compiled into a single data set. LA1 is a key parameter for global and regional models of biosphere/atmosphere exchange of carbon dioxide, water vapor, and other materials. It also plays an integral role in determining the energy balance of the land surface. This data set provides a benchmark of typical values and ranges of LA1 for a variety of biomes and land cover types, in support of model development and validation of satellite-derived remote sensing estimates of LA1 and other vegetation parameters. The LA1 data are linked to a bibliography of over 300 original source references. These historic LA1 data are mostly from natural and seminatural (managed) ecosystems, although some agricultural estimates are also included. Although methodologies for determining LA1 have changed over the decades, it is useful to represent the inconsistencies (e.g., in maximum value reported for a particular biome) that are actually found in the scientific literature. Needleleaf (coniferous) forests are by far the most commonly measured biome/land cover types in this compilation, with 22% of the measurements from temperate evergreen needleleaf forests, and boreal evergreen needleleaf …
Date: February 6, 2002
Creator: Scurlock, J. M. O; Asner, G. P. & Gower, S. T.
Object Type: Report
System: The UNT Digital Library
Environmental Evaluation of New Generation Vehicles and Vehicle Components (open access)

Environmental Evaluation of New Generation Vehicles and Vehicle Components

This report documents assessments that address waste issues and life cycle impacts associated with the vehicle materials and vehicle technologies being developed under the Partnership for a New Generation of Vehicles (PNGV) program. We refer to these vehicles as 3XVs, referring to the PNGV goal that their fuel mileage be three times better than the baseline vehicle. To meet the program's fuel consumption goals, these vehicles substitute lightweight materials for heavier materials such as steel and iron that currently dominate the composition of vehicles, and use engineering and power system changes. Alternative power systems being developed through the PNGV program include batteries for hybrid electric vehicles and fuel cells. With respect to all these developments, it is imperative to learn what effects they will have on the environment before adopting these designs and technologies on a large-scale basis.
Date: February 6, 2002
Creator: Schexnayder, S.M.
Object Type: Report
System: The UNT Digital Library
Demonstration of New Technologies Required for the Treatment of Mixed Waste Contaminated with {ge}260 ppm Mercury (open access)

Demonstration of New Technologies Required for the Treatment of Mixed Waste Contaminated with {ge}260 ppm Mercury

The Resource Conservation and Recovery Act (RCRA) defines several categories of mercury wastes, each of which has a defined technology or concentration-based treatment standard, or universal treatment standard (UTS). RCRA defines mercury hazardous wastes as any waste that has a TCLP value for mercury of 0.2 mg/L or greater. Three of these categories, all nonwastewaters, fall within the scope of this report on new technologies to treat mercury-contaminated wastes: wastes as elemental mercury; hazardous wastes with less than 260 mg/kg [parts per million (ppm)] mercury; and hazardous wastes with 260 ppm or more of mercury. While this report deals specifically with the last category--hazardous wastes with 260 ppm or more of mercury--the other two categories will be discussed briefly so that the full range of mercury treatment challenges can be understood. The treatment methods for these three categories are as follows: Waste as elemental mercury--RCRA identifies amalgamation (AMLGM) as the treatment standard for radioactive elemental mercury. However, radioactive mercury condensates from retorting (RMERC) processes also require amalgamation. In addition, incineration (IMERC) and RMERC processes that produce residues with >260 ppm of radioactive mercury contamination and that fail the RCRA toxicity characteristic leaching procedure (TCLP) limit for mercury (0.20 mg/L) require …
Date: February 6, 2002
Creator: Morris, M. I.
Object Type: Report
System: The UNT Digital Library
RADIATION LITMUS PAPER (open access)

RADIATION LITMUS PAPER

None
Date: February 16, 2002
Creator: WARNER, BENJAMIN P; JOHNS, DEIDRE M; D'ALESSIO, JOSEPH A & SHEAFE, KIMBERLY S
Object Type: Article
System: The UNT Digital Library
MOLTEN CARBONATE FUEL CELL PRODUCT DESIGN IMPROVEMENT (open access)

MOLTEN CARBONATE FUEL CELL PRODUCT DESIGN IMPROVEMENT

The carbonate fuel cell promises highly efficient, cost-effective and environmentally superior power generation from pipeline natural gas, coal gas, biogas, and other gaseous and liquid fuels. FuelCell Energy, Inc. has been engaged in the development of this unique technology, focusing on the development of the Direct Fuel Cell (DFC{reg_sign}). The DFC{reg_sign} design incorporates the unique internal reforming feature which allows utilization of a hydrocarbon fuel directly in the fuel cell without requiring any external reforming reactor and associated heat exchange equipment. This approach upgrades waste heat to chemical energy and thereby contributes to a higher overall conversion efficiency of fuel energy to electricity with low levels of environmental emissions. Among the internal reforming options, FuelCell Energy has selected the Indirect Internal Reforming (IIR)--Direct Internal Reforming (DIR) combination as its baseline design. The IIR-DIR combination allows reforming control (and thus cooling) over the entire cell area. This results in uniform cell temperature. In the IIR-DIR stack, a reforming unit (RU) is placed in between a group of fuel cells. The hydrocarbon fuel is first fed into the RU where it is reformed partially to hydrogen and carbon monoxide fuel using heat produced by the fuel cell electrochemical reactions. The reformed gases …
Date: February 1, 2002
Creator: Maru, H.C. & Farooque, M.
Object Type: Report
System: The UNT Digital Library
NOVEL COMPOSITE MEMBRANES AND PROCESS FOR NATURAL GAS UPGRADING (open access)

NOVEL COMPOSITE MEMBRANES AND PROCESS FOR NATURAL GAS UPGRADING

The first phase of this project involved the development of a high performance composite membranes for the treatment of natural gas. The objective of the second phase is to demonstrate the commercial potential of a full-size membrane module in a pilot scale field test. This phase is undertaken jointly with our commercial partner, UOP LLC. At the conclusion of Phase I, two composite membrane products had been developed for the enrichment (sweetening) of natural gas. The one was a low pressure membrane with a high CO{sub 2}/CH{sub 4} separation factor that falls within the target range of 25-30 (at 50 C) set for the program. This is a significant improvement over current commercial membranes that have separation factors of around 18-19. The second membrane had excellent high pressure capability and good contamination resistance, with a separation factor of 20-22. Based on the performance and the economic evaluation of the newly developed membranes, and with the input of UOP and DOE, it was decided to devote the demonstration phase of the program to the field testing and commercial evaluation of natural gas dehydration membranes. Due to the events of September 11, the program was also extended by 6 months until June …
Date: February 1, 2002
Creator: LeRoux, Johann
Object Type: Report
System: The UNT Digital Library
NEXT GENERATION TURBINE SYSTEM STUDY (open access)

NEXT GENERATION TURBINE SYSTEM STUDY

Rolls-Royce has completed a preliminary design and marketing study under a Department of Energy (DOE) cost shared contract (DE-AC26-00NT40852) to analyze the feasibility of developing a clean, high efficiency, and flexible Next Generation Turbine (NGT) system to meet the power generation market needs of the year 2007 and beyond. Rolls-Royce evaluated the full range of its most advanced commercial aerospace and aeroderivative engines alongside the special technologies necessary to achieve the aggressive efficiency, performance, emissions, economic, and flexibility targets desired by the DOE. Heavy emphasis was placed on evaluating the technical risks and the economic viability of various concept and technology options available. This was necessary to ensure the resulting advanced NGT system would provide extensive public benefits and significant customer benefits without introducing unacceptable levels of technical and operational risk that would impair the market acceptance of the resulting product. Two advanced cycle configurations were identified as offering significant advantages over current combined cycle products available in the market. In addition, balance of plant (BOP) technologies, as well as capabilities to improve the reliability, availability, and maintainability (RAM) of industrial gas turbine engines, have been identified. A customer focused survey and economic analysis of a proposed Rolls-Royce NGT product …
Date: February 28, 2002
Creator: Macri, Frank
Object Type: Report
System: The UNT Digital Library
Evaluation of Mass Transfer Performance for Caustic-Side Solvent Extraction of Cesium in a Conventional 5-cm Centrifugal Contactor (open access)

Evaluation of Mass Transfer Performance for Caustic-Side Solvent Extraction of Cesium in a Conventional 5-cm Centrifugal Contactor

Tests have been conducted to determine if satisfactory mass transfer performance is achieved using a fully pumping 5-cm centrifugal contactor under conditions present in the Caustic-Side Solvent Extraction (CSSX) process. Tests utilized a commercially available contactor that had been modified by installation of a rotor housing bottom that had straight radial vanes on the process side. As received from the vendor, the housing bottom was equipped with curved (impeller-type) vanes that were intended to promote phase separation by minimizing mixing of influent solutions. Stage efficiencies exceeding 85% were obtained under conditions, present in the extraction section of the CSSX flowsheet. Under CSSX stripping conditions the stage efficiency exceeded 90%. In both cases, the efficiencies obtained exceed the minimum requirement for acceptable transfer of cesium in the CSSX process.
Date: February 19, 2002
Creator: Birdwell, Jr. J.F.
Object Type: Report
System: The UNT Digital Library
Screening of CHP Potential at Federal Sites in Select Regions of the U.S. (open access)

Screening of CHP Potential at Federal Sites in Select Regions of the U.S.

Combined Cooling Heat and Power (CHP) is a master term for onsite power generation technologies that sequentially produce electrical or mechanical energy and useful thermal energy. Some form of CHP has existed for more than 100 years and it is now achieving a greater level of acceptance due to an increasing need for reliable power service and energy cost management. Capturing and using the heat produced as a byproduct of generating electricity from fuel sources increases the usable energy that can be obtained from the original fuel source. CHP technologies have the potential to reduce energy consumption through increased efficiency--decreasing energy bills as well as pollution. The EPA recognizes CHP as a potent climate change mitigation measure. The U.S. Department of Energy (D.O.E.) Federal Energy Management Program (FEMP) is assisting Federal agencies to realize their energy efficiency goals. CHP is an efficiency measure that is receiving growing attention because of its sizable potential to provide efficiency, environmental, and reliability benefits. CHP therefore benefits the host facility, the electric infrastructure, and the U.S. society as a whole. This report and study seeks to make a preliminary inquiry into near term CHP opportunities for federal facilities in selected U.S. regions. It offers …
Date: February 25, 2002
Creator: Energy Nexus Group, . .
Object Type: Report
System: The UNT Digital Library
Indoor carbon dioxide concentrations and sick building syndrome symptoms in the BASE study revisited: Analyses of the 100 building dataset (open access)

Indoor carbon dioxide concentrations and sick building syndrome symptoms in the BASE study revisited: Analyses of the 100 building dataset

In previously published analyses of the 41-building 1994-1996 USEPA Building Assessment Survey and Evaluation (BASE) dataset, higher workday time-averaged indoor minus outdoor CO{sub 2} concentrations (dCO{sub 2}) were associated with increased prevalence of certain mucous membrane and lower respiratory sick building syndrome (SBS) symptoms, even at peak dCO{sub 2} concentrations below 1,000 ppm. For this paper, similar analyses were performed using the larger 100-building 1994-1998 BASE dataset. Multivariate logistic regression analyses quantified the associations between dCO{sub 2} and the SBS symptoms, adjusting for age, sex, smoking status, presence of carpet in workspace, thermal exposure, relative humidity, and a marker for entrained automobile exhaust. Adjusted dCO{sub 2} prevalence odds ratios for sore throat and wheeze were 1.17 and 1.20 per 100-ppm increase in dCO{sub 2} (p <0.05), respectively. These new analyses generally support our prior findings. Regional differences in climate, building design, and operation may account for some of the differences observed in analyses of the two datasets.
Date: February 1, 2002
Creator: Erdmann, Christine A.; Steiner, Kate C. & Apte, Michael G.
Object Type: Article
System: The UNT Digital Library
Screw dislocations in GaN (open access)

Screw dislocations in GaN

GaN has received much attention over the past few years because of several new applications, including light emitting diodes, blue laser diodes and high-power microwave transistors. One of the biggest problems is a high density of structural defects, mostly dislocations, due to a lack of a suitable lattice-matched substrate since bulk GaN is difficult to grow in large sizes. Transmission Electron Microscopy (TEM) has been applied to study defects in plan-view and cross-sections on samples prepared by conventional techniques such as mechanical thinning and precision ion milling. The density of dislocations close to the sample surface of a 1 mm-thick HVPE sample was in the range of 3x109 cm-2. All three types of dislocations were present in these samples, and almost 50 percent were screw dislocations. Our studies suggest that the core structure of screw dislocations in the same material might differ when the material is grown by different methods.
Date: February 15, 2002
Creator: Liliental-Weber, Zuzanna; Jasinski, Jacek B.; Washburn, Jack & O'Keefe, Michael A.
Object Type: Article
System: The UNT Digital Library
Graphite Sublimation Tests for the Muon Collider/Neutrino Factory Target Development Program (open access)

Graphite Sublimation Tests for the Muon Collider/Neutrino Factory Target Development Program

A passively cooled graphite target was proposed for a 1.5 MW neutrino production research facility because of its simplicity and favorable performance as a target material for neutrino production (Ref. 1). The conceptual design for the target in the Reference 1 study was a graphite rod 15 mm in diameter by 800 mm long. Figure 1 shows the graphite target rod supported by graphite spokes, which are mounted to a water-cooled stainless steel support tube. The target is radiatively cooled to the water-cooled surface of the support tube. Based on nuclear analysis results (Ref. 2), the time-averaged power deposition in the target is 35 kW. If this power is deposited uniformly along the axial length of the target, the volumetric power deposition in the target is about 250 MW/m{sup 3}. The target surface temperature required to radiate the deposited power to a water-cooled tube is estimated to be about 1850 C, and the temperature at the center of the target is about 75 C hotter. The sublimation erosion rate (e), estimated assuming that the graphite is submersed in a perfect vacuum environment, can be derived from kinetic theory and is given by: e = p{sub sat} (m/2{pi} kT){sup 1/2} where …
Date: February 7, 2002
Creator: Haines, JR
Object Type: Report
System: The UNT Digital Library
CERAMIC MEMBRANE ENABLING TECHNOLOGY FOR IMPROVED IGCC EFFICIENCY (open access)

CERAMIC MEMBRANE ENABLING TECHNOLOGY FOR IMPROVED IGCC EFFICIENCY

This quarterly technical progress report will summarize work accomplished for Phase 1 Program during the quarter October to December 2001. In task 1 optimization of the substrate material has yielded substantial improvements to membrane life. In task 2, composite development has enabled 50% of the target flux under Type 1B process conditions. In task 3, manufacturing development has demonstrated that 36 inch long tubes can be produced. The work in task 4 has demonstrated that composite OTM elements can produce oxygen at greater than 95% purity for more than 500 hours of the target flux. In task 5 construction of the multi-tube OTM reactor is completed and initial startup testing was carried out.
Date: February 1, 2002
Creator: Prasad, Ravi
Object Type: Report
System: The UNT Digital Library
Restoring Sustainable Forests on Appalachian Mined Lands for Wood Products, Renewable Energy, Carbon Sequestration, and Other Ecosystems Services Quarterly Report (open access)

Restoring Sustainable Forests on Appalachian Mined Lands for Wood Products, Renewable Energy, Carbon Sequestration, and Other Ecosystems Services Quarterly Report

This is the first quarterly Technical Report for the period October-December, 2003. A kick-off meeting was held with NETL administrators and scientists at Morgantown, WV, on December 2, 2002. The purpose of this project is to evaluate the biological and economic feasibility of restoring high-quality forests on mined land, and to measure carbon sequestration and wood production benefits that would be achieved from forest restoration procedures. During this first quarterly reporting period, five Graduate Research Assistants were recruited, an MOA was drafted between Virginia Tech and three industry cooperators, preliminary field locations for controlled studies were located, and a preliminary analysis of a carbon inventory of forest sites on mined land was made.
Date: February 4, 2002
Creator: Burger, James A. (info: Dr.)
Object Type: Report
System: The UNT Digital Library
Measurement of Gas and Liquid Velocities in an Air-Water Two-Phase Flow using Cross-Correlation of Signals from a Double Senor Hot-Film Probe (open access)

Measurement of Gas and Liquid Velocities in an Air-Water Two-Phase Flow using Cross-Correlation of Signals from a Double Senor Hot-Film Probe

Local gas and liquid velocities are measured by cross-correlating signals from a double sensor hot-film anemometer probe in pure water flow and air water two-phase flow. The gas phase velocity measured in two-phase flow agrees with velocity data obtained using high-speed video to within +/-5%. A turbulent structure, present in the liquid phase, allows a correlation to be taken, which is consistent with the expected velocity profiles in pure liquid flow. This turbulent structure is also present in the liquid phase of a two-phase flow system. Therefore, a similar technique can be applied to measure the local liquid velocity in a two-phase system, when conditions permit.
Date: February 19, 2002
Creator: Gurau, B.; Vassalo, P. & Keller, K.
Object Type: Report
System: The UNT Digital Library
Evaluation of the Intrinsic and Extrinsic Fracture Behavior of Iron Aluminides (open access)

Evaluation of the Intrinsic and Extrinsic Fracture Behavior of Iron Aluminides

Comparative finite element modeling simulations of initial intergranular fracture of two iron aluminides (FA186 and FA189) were carried out to study the intrinsic and extrinsic fracture behavior of the alloys as related to hydrogen embrittlement. The computational simulations involved sequentially-coupled stress and mass-diffusion analyses to determine the stress/strain distribution and the extent of hydrogen concentration at the crack tip region. Simulations of initial intergranular fracture of the two alloys under either air or vacuum conditions were conducted. With judicious selection of grain boundary failure strains for each alloy and assumed material degradation at hydrogen diffusion zone, the numerical results agree well with previous experimental test results. We have considered the various methods by which the thermal expansion of Fe{sub 3}Al can be modeled. As a matter of practicality, we have started with a conceptually simple continuum medium modeling, which we have used in initial calculations reported here, despite its limitations in neglecting the effects of optical phonons. This makes the results increasingly suspect for temperatures above the Debye temperature. However, the results we obtain are surprisingly good considering this important limitation. Nevertheless, we regard these results as being suspect. Therefore, in addition, we discuss a wholly new ab-initio-based method which …
Date: February 8, 2002
Creator: Cooper, B. R.
Object Type: Report
System: The UNT Digital Library
STATISTICAL DAMAGE CLASSIFICATION USING SEQUENTIAL PROBABILITY RATIO TESTS. (open access)

STATISTICAL DAMAGE CLASSIFICATION USING SEQUENTIAL PROBABILITY RATIO TESTS.

The primary objective of damage detection is to ascertain with confidence if damage is present or not within a structure of interest. In this study, a damage classification problem is cast in the context of the statistical pattern recognition paradigm. First, a time prediction model, called an autoregressive and autoregressive with exogenous inputs (AR-ARX) model, is fit to a vibration signal measured during a normal operating condition of the structure. When a new time signal is recorded from an unknown state of the system, the prediction errors are computed for the new data set using the time prediction model. When the structure undergoes structural degradation, it is expected that the prediction errors will increase for the damage case. Based on this premise, a damage classifier is constructed using a sequential hypothesis testing technique called the sequential probability ratio test (SPRT). The SPRT is one form of parametric statistical inference tests, and the adoption of the SPRT to damage detection problems can improve the early identification of conditions that could lead to performance degradation and safety concerns. The sequential test assumes a probability distribution of the sample data sets, and a Gaussian distribution of the sample data sets is often used. …
Date: February 16, 2002
Creator: SOHN, HOON; ALLEN, DAVID W; WORDEN, KEITH & FARRAR, CHARLES R
Object Type: Report
System: The UNT Digital Library