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695 Matching Results
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Active control for turbulent premixed flame simulations
Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.
Date:
March 26, 2004
Creator:
Bell, John B.; Day, Marcus S.; Grcar, Joseph F. & Lijewski, Michael J.
Object Type:
Article
System:
The UNT Digital Library
Adaptive Sampling for Noisy Problems
The usual approach to deal with noise present in many real-world optimization problems is to take an arbitrary number of samples of the objective function and use the sample average as an estimate of the true objective value. The number of samples is typically chosen arbitrarily and remains constant for the entire optimization process. This paper studies an adaptive sampling technique that varies the number of samples based on the uncertainty of deciding between two individuals. Experiments demonstrate the effect of adaptive sampling on the final solution quality reached by a genetic algorithm and the computational cost required to find the solution. The results suggest that the adaptive technique can effectively eliminate the need to set the sample size a priori, but in many cases it requires high computational costs.
Date:
March 26, 2004
Creator:
Cantu-Paz, E
Object Type:
Article
System:
The UNT Digital Library
Altus Times (Altus, Okla.), Vol. 105, No. 321, Ed. 1 Friday, March 26, 2004
Daily newspaper from Altus, Oklahoma that includes local, state, and national news along with advertising.
Date:
March 26, 2004
Creator:
Andrews, Mike
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
[Andrea and Tracy at MC Awards]
A picture of Andrea Robledo and Tracy sitting at the entrance table for the 2004 Multicultural Center Awards ceremony. Andrea has a binder that she is writing in and Tracy has a color-coded chart in front of her. There are also rows of nametags on the table for attendees.
Date:
March 26, 2004
Creator:
University of North Texas. Multicultural Center.
Object Type:
Photograph
System:
The UNT Digital Library
LOS ANGELES DEPARTMENT OF WATER AND POWER FUEL CELL DEMONSTRATION PROJECT
The Los Angeles Department of Water and Power (LADWP) is currently one of the most active electric utility companies in deploying fuel cell technology. Fuel cells offer many benefits and are now used as an alternative to traditional internal combustion engines in power generation. In continuing it's role as the leader in fuel cell deploying, LADWP installed a Phosphoric Acid Fuel Cell (PAFC) in February 2002 at its Main Street service center. The goal of this project is to evaluate the PAFC's performance and cost benefits. This will provide LADWP an insight for future deployment of fuel cell technology. The fuel cell ran smoothly through the first year of operation with very high efficiency and availability, and only with some minor setbacks. The Main street fuel cell project is funded by LADWP with partial grant funding from the Department of Defense's Climate Change Fuel Cell Buydown Program. The technical evaluation and the benefit-cost evaluation of the Main Street fuel cell are both examined in this report.
Date:
March 26, 2004
Creator:
Glauz, William W.
Object Type:
Report
System:
The UNT Digital Library
Automatic Blocking Of QR and LU Factorizations for Locality
QR and LU factorizations for dense matrices are important linear algebra computations that are widely used in scientific applications. To efficiently perform these computations on modern computers, the factorization algorithms need to be blocked when operating on large matrices to effectively exploit the deep cache hierarchy prevalent in today's computer memory systems. Because both QR (based on Householder transformations) and LU factorization algorithms contain complex loop structures, few compilers can fully automate the blocking of these algorithms. Though linear algebra libraries such as LAPACK provides manually blocked implementations of these algorithms, by automatically generating blocked versions of the computations, more benefit can be gained such as automatic adaptation of different blocking strategies. This paper demonstrates how to apply an aggressive loop transformation technique, dependence hoisting, to produce efficient blockings for both QR and LU with partial pivoting. We present different blocking strategies that can be generated by our optimizer and compare the performance of auto-blocked versions with manually tuned versions in LAPACK, both using reference BLAS, ATLAS BLAS and native BLAS specially tuned for the underlying machine architectures.
Date:
March 26, 2004
Creator:
Yi, Q; Kennedy, K; You, H; Seymour, K & Dongarra, J
Object Type:
Article
System:
The UNT Digital Library
The Baytown Sun (Baytown, Tex.), Vol. 82, No. 115, Ed. 1 Friday, March 26, 2004
Daily newspaper from Baytown, Texas that includes local, state, and national news along with advertising.
Date:
March 26, 2004
Creator:
Cash, Wanda Garner
Object Type:
Newspaper
System:
The Portal to Texas History
The Boerne Star (Boerne, Tex.), Vol. 98, No. 25, Ed. 1 Friday, March 26, 2004
Semiweekly newspaper from Boerne, Texas that includes local, state, and national news along with advertising.
Date:
March 26, 2004
Creator:
Cartwright, Brian & Morgan, Clay
Object Type:
Newspaper
System:
The Portal to Texas History
Brady Standard-Herald and Heart O' Texas News (Brady, Tex.), Ed. 1 Friday, March 26, 2004
Semiweekly newspaper from Brady, Texas that includes local, state, and national news along with advertising.
Date:
March 26, 2004
Creator:
Stewart, James E.
Object Type:
Newspaper
System:
The Portal to Texas History
The Clifton Record (Clifton, Tex.), Vol. 109, No. 22, Ed. 1 Friday, March 26, 2004
Weekly newspaper from Clifton, Texas that includes local, state, and national news along with advertising.
Date:
March 26, 2004
Creator:
Smith, W. Leon
Object Type:
Newspaper
System:
The Portal to Texas History
Colorado Emergency Management and Homeland Security Statutory Authorities Summarized
This report is one of a series that profiles the emergency management and homeland security statutory authorities of the 50 states, the District of Columbia, the Commonwealth of the Northern Mariana Islands, the Commonwealth of Puerto Rico, and three territories (American Samoa, Guam, and the U.S. Virgin Islands). Each profile identifies the more significant elements of state statutes, generally as codified. This report focuses on the state of Colorado.
Date:
March 26, 2004
Creator:
Bea, Keith; Runyon, L. Cheryl & Warnock, Kae M.
Object Type:
Report
System:
The UNT Digital Library
Dallas Voice (Dallas, Tex.), Vol. 20, No. 47, Ed. 1 Friday, March 26, 2004
Weekly newspaper from Dallas, Texas that includes local, state, and national news and advertising of interest to the Lesbian, Gay, Bisexual, and Transgender (LGBT) community.
Date:
March 26, 2004
Creator:
Vercher, Dennis
Object Type:
Newspaper
System:
The UNT Digital Library
Development of Design Criteria for Fluid Induced Structural Vibration in Steam Generators and Heat Exchangers
OAK-B135 Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers. In the nuclear industry, steam generators are often affected by this problem. However, flow-induced vibration is not limited to nuclear power plants, but to any type of heat exchanger used in many industrial applications such as chemical processing, refrigeration and air conditioning. Specifically, shell and tube type heat exchangers experience flow-induced vibration due to the high velocity flow over the tube banks. Flow-induced vibration in these heat exchangers leads to equipment breakdown and hence expensive repair and process shutdown. The goal of this research is to provide accurate measurements that can help modelers to validate their models using the measured experimental parameters and thereby develop better design criteria for avoiding fluid-elastic instability in heat exchangers. The …
Date:
March 26, 2004
Creator:
Catton, Ivan; Dhir, Vijay K.; Alquaddoomi, O.S.; Mitra, Deepanjan & Adinolfi, Pierangelo
Object Type:
Report
System:
The UNT Digital Library
Effect of Initial Conditions on 2D Rayleigh-Taylor Instability and Transition to Turbulence in Planar Blast-wave-driven Systems
Perturbations on an interface driven by a strong blast wave grow in time due to a combination of Rayleigh-Taylor, Richtmyer-Meshkov, and decompression effects. In this paper, we present the first results from a computational study of such a system under drive conditions to be attainable on the National Ignition Facility. Using the multiphysics, AMR, higher order Godunov Eulerian hydrocode, Raptor, we consider the late nonlinear instability evolution for multiple amplitude and phase realizations of a variety of multimode spectral types. We show that compressibility effects preclude the emergence of a regime of self-similar instability growth independent of the initial conditions by allowing for memory of the initial conditions to be retained in the mix width at all times. The loss of transverse spectral information is demonstrated, however, along with the existence of a quasi-self-similar regime over short time intervals. Certain aspects of the initial conditions, including the rms amplitude, are shown to have a strong effect on the time to transition to the quasi-self-similar regime.
Date:
March 26, 2004
Creator:
Miles, A R; Edwards, M J & Greenough, J A
Object Type:
Article
System:
The UNT Digital Library
Electronic Disability Claims Processing: SSA Needs to Address Risks Associated with Its Accelerated Systems Development Strategy
A letter report issued by the General Accounting Office with an abstract that begins "The Social Security Administration's (SSA) AeDib initiative is designed to provide SSA with a more efficient, paperless system that will enable its disability components to electronically view and share claims data and process claims electronically. Yet previous GAO reviews found that SSA's accelerated strategy to develop AeDib involved risks that could threaten a complete and successful transition to this capability. At the Subcommittee's request, GAO reviewed AeDib to assess (1) SSA's progress and strategy, (2) the adequacy of measures taken to avoid software development problems similar to those encountered in SSA's previous efforts, (3) the adequacy of cost/benefit analyses, and (4) SSA's consultation with stakeholders."
Date:
March 26, 2004
Creator:
United States. General Accounting Office.
Object Type:
Report
System:
The UNT Digital Library
The Express-Star (Chickasha, Okla.), Ed. 1 Friday, March 26, 2004
Daily newspaper from Chickasha, Oklahoma that includes local, state, and national news along with advertising.
Date:
March 26, 2004
Creator:
Bush, Kent
Object Type:
Newspaper
System:
The Gateway to Oklahoma History
Failure Forewarning in NPP Equipment NERI2000-109 Final Project Report
The objective of this project is forewarning of machine failures in critical equipment at next-generation nuclear power plants (NPP). Test data were provided by two collaborating institutions: Duke Engineering and Services (first project year), and the Pennsylvania State University (Applied Research Laboratory) during the second and third project years. New nonlinear methods were developed and applied successfully to extract forewarning trends from process-indicative, time-serial data for timely, condition-based maintenance. Anticipation of failures in critical equipment at next-generation NPP will improve the scheduling of maintenance activities to minimize safety concerns, unscheduled non-productive downtime, and collateral damage due to unexpected failures. This approach provides significant economic benefit, and is expected to improve public acceptance of nuclear power. The approach is a multi-tiered, model-independent, and data-driven analysis that uses ORNL's novel nonlinear method to extract forewarning of machine failures from appropriate data. The first tier of the analysis provides a robust choice for the process-indicative data. The second tier rejects data of inadequate quality. The third tier removes signal artifacts that would otherwise confound the analysis, while retaining the relevant nonlinear dynamics. The fourth tier converts the artifact-filtered time-serial data into a geometric representation, that is then transformed to a discrete distribution function …
Date:
March 26, 2004
Creator:
Hively, LM
Object Type:
Report
System:
The UNT Digital Library
Flash X-Ray Injector Study
The study described in this report1 models the FXR injector from the cathode to the exit of the injector. The calculations are compared to actual experimental measurements, table 1. In these measurements the anode voltage was varied by changing the Marks-Bank charging voltage. The anode-cathode spacing was varied by adjusting the location of the cathode in hopes of finding an island of minimum emittance (none found). The bucking coil current was set for zero field on the cathode. In these measurements, a pepper-pot mask was inserted into FXR at beam bug 135 and viewed downstream via a wiggle probe diagnostic at cell gap J21, figure 1. The observed expansion of the beamlets passing through the mask of known geometric layout and hole size allow a calculation of the phase space beam properties.
Date:
March 26, 2004
Creator:
Paul, A C
Object Type:
Report
System:
The UNT Digital Library
Florida Emergency Management and Homeland Security Statutory Authorities Summarized
This report is one of a series that profiles the emergency management and homeland security statutory authorities of the 50 states, the District of Columbia, the Commonwealth of the Northern Mariana Islands, the Commonwealth of Puerto Rico, and three territories (American Samoa, Guam, and the U.S. Virgin Islands). Each profile identifies the more significant elements of state statutes, generally as codified. This report focuses on the state of Florida.
Date:
March 26, 2004
Creator:
Bea, Keith; Runyon, L. Cheryl & Warnock, Kae M.
Object Type:
Report
System:
The UNT Digital Library
[Flyer for Women of Color Conference "Empowered Women"]
A flyer for Women of Color Conference, "Empowered Women: Mentoring Others to Take our Place" that was sponsored by University of North Texas' Multicultural Center. The conference was held on Friday, March 26, 2004 from 8:00 am - 5:00 pm in the University's Union, Silver Eagle Suite.
Date:
March 26, 2004
Creator:
University of North Texas. Multicultural Center.
Object Type:
Pamphlet
System:
The UNT Digital Library
[Funeral Program for Albert Phillips, March 26, 2004]
Funeral program for Mr. Albert "Scratch" Phillips, born September 25, 1918. The funeral was held Friday, March 26, 2004 at F. E. Lewis Memorial Chapel, officiated by Howard Mims. Funeral arrangements were made through Lewis Funeral Home and he was buried in Meadowlawn Memorial Park in San Antonio, Texas.
Date:
March 26, 2004
Creator:
unknown
Object Type:
Pamphlet
System:
The Portal to Texas History
The Harper News (Harper, Tex.), Vol. 1, No. 11, Ed. 1 Friday, March 26, 2004
Biweekly newspaper from Harper, Texas that includes community news along with advertising.
Date:
March 26, 2004
Creator:
Stevens, Martha
Object Type:
Newspaper
System:
The Portal to Texas History
Hudspeth County Herald and Dell Valley Review (Dell City, Tex.), Vol. 48, No. 30, Ed. 1 Friday, March 26, 2004
Weekly newspaper from Dell City, Texas that includes local, state, and national news along with advertising.
Date:
March 26, 2004
Creator:
Lynch, Mary Louise
Object Type:
Newspaper
System:
The Portal to Texas History
Hydrogen Sensor Based on Yttria-Stabilized Zirconia Electrolyte and Tin-Doped Indium Oxide Sensing Electrode
A solid state electrochemical sensor has been developed for hydrogen leak detection in ambient air. The sensor uses an yttria-stabilized electrolyte with a tin-doped indium oxide sensing electrode and a Pt reference electrode. Excellent sensitivity, and response time of one second or less, are reported for hydrogen gas over the concentration range of 0.03 to 5.5% in air. Cross-sensitivity to relative humidity and to CO{sub 2} are shown to be low. The response to methane, a potentially significant source of interference for such a sensor, is significantly less than that for hydrogen. The sensor shows good reproducibility and was unaffected by thermal cycling over the course of this investigation. The effects of sensing electrode thickness and thermal aging are also reported, and the sensing mechanism is discussed. The sensor is intended for use in vehicles powered by hydrogen fuel cells and hydrogen internal combustion engines. Those vehicles will use and/or store significant quantities of hydrogen, and will require safety sensor for monitoring potential hydrogen leakage in order to ensure passenger safety.
Date:
March 26, 2004
Creator:
Martin, L P & Glass, R S
Object Type:
Article
System:
The UNT Digital Library