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Modeling and Simulation of Long-Term Performance of Near-Surface Barriers (open access)

Modeling and Simulation of Long-Term Performance of Near-Surface Barriers

Society has and will continue to generate hazardous wastes whose risks must be managed. For exceptionally toxic, long-lived, and feared waste, the solution is deep burial, e.g., deep geological disposal at Yucca Mtn. For some waste, recycle or destruction/treatment is possible. The alternative for other wastes is storage at or near the ground level (in someone’s back yard); most of these storage sites include a surface barrier (cap) to prevent migration of the waste due to infiltration of surface water. The design lifespan for such barriers ranges from 30 to 1000 years, depending on hazard and regulations. In light of historical performance, society needs a better basis for predicting barrier performance over long time periods and tools for optimizing maintenance of barriers while in service. We believe that, as in other industries, better understanding of the dynamics of barrier system degradation will enable improved barriers (cheaper, longer-lived, simpler, easier to maintain) and improved maintenance. We are focusing our research on earthen caps, especially those with evapo-transpiration and capillary breaks. Typical cap assessments treat the barrier’s structure as static prior to some defined lifetime. Environmental boundary conditions such as precipitation and temperature are treated as time dependent. However, other key elements …
Date: February 1, 2003
Creator: Piet, Steven James; Jacobson, Jacob Jordan; Soto, Rafael; Martian, Pete & Martineau, Richard Charles
System: The UNT Digital Library
Making Sustainable Decisions Using the KONVERGENCE Framework (open access)

Making Sustainable Decisions Using the KONVERGENCE Framework

Hundreds of contaminated facilities and sites must be cleaned up. “Cleanup” includes decommissioning, environmental restoration, and waste management. Cleanup can be complex, expensive, risky, and time-consuming. Decisions are often controversial, can stall or be blocked, and are sometimes re-done - some before implementation, some decades later. Making and keeping decisions with long time horizons involves special difficulties and requires new approaches, including: • New ways (mental model) to analyze and visualize the problem, • Awareness of the option to shift strategy or reframe from a single decision to an adaptable network of decisions, and • Improved tactical processes that account for several challenges. These include the following: • Stakeholder values are a more fundamental basis for decision making and keeping than “meeting regulations.” • Late-entry players and future generations will question decisions. • People may resist making “irreversible” decisions. • People need “compelling reasons” to take action in the face of uncertainties. Our project goal is to make cleanup decisions easier to make, implement, keep, and sustain. By sustainability, we mean decisions that work better over the entire time-period—from when a decision is made, through implementation, to its end point. That is, alternatives that can be kept “as is” or …
Date: February 1, 2003
Creator: Piet, Steven James; Gibson, Patrick Lavern; Joe, Jeffrey Clark; Kerr, Thomas A; Nitschke, Robert Leon & Dakins, Maxine Ellen
System: The UNT Digital Library
Equilibrium in heavy ion collisions (open access)

Equilibrium in heavy ion collisions

We discuss the question of equilibration in heavy ion collisions and how it can be addressed in experiment.
Date: February 1, 2003
Creator: Koch, Volker & Majumder, Abhijit
System: The UNT Digital Library
Testing, Modeling, and Monitoring to Enable Simpler, Cheaper, Longer-Lived Surface Caps (open access)

Testing, Modeling, and Monitoring to Enable Simpler, Cheaper, Longer-Lived Surface Caps

Society has and will continue to generate hazardous wastes whose risks must be managed. For exceptionally toxic, long-lived, and feared waste, the solution is deep burial, e.g., deep geological disposal at Yucca Mtn. For some waste, recycle or destruction/treatment is possible. The alternative for other wastes is storage at or near the ground level (in someone’s back yard); most of these storage sites include a surface barrier (cap) to prevent downward water migration. Some of the hazards will persist indefinitely. As society and regulators have demanded additional proof that caps are robust against more threats and for longer time periods, the caps have become increasingly complex and expensive. As in other industries, increased complexity will eventually increase the difficulty in estimating performance, in monitoring system/component performance, and in repairing or upgrading barriers as risks are managed. An approach leading to simpler, less expensive, longer-lived, more manageable caps is needed. Our project, which started in April 2002, aims to catalyze a Barrier Improvement Cycle (iterative learning and application) and thus enable Remediation System Performance Management (doing the right maintenance neither too early nor too late). The knowledge gained and the capabilities built will help verify the adequacy of past remedial decisions, …
Date: February 1, 2003
Creator: Piet, Steven James; Breckenridge, Robert Paul & Burns, Douglas Edward
System: The UNT Digital Library
Dynamics of the flame flowfields in a low-swirl burner (open access)

Dynamics of the flame flowfields in a low-swirl burner

The concept of using low swirl to stabilize lean premixed turbulent flame was introduced in 1992. Since then, the low-swirl burner (LSB) has become a useful laboratory tool for the study of detailed flame structures as well as turbulent burning speeds. Its main attribute is that the flame is freely propagating and is locally normal to the turbulent approach flow (Figure 1). Therefore, the turbulent flame brush is not influence by physical boundaries. The capability of LSB to support very lean flames and very turbulent flames [1, 2] was further exploited in recent studies to test the validity of the flame regime concept. Using 2D imaging diagnostics (e.g. planar laser induced fluorescence, PLIF, and planar laser induced Rayleigh scattering) our analysis showed that the wrinkled flame regime to be valid at a turbulence intensity level much higher than previously thought [3-5]. This provided experimental verification of a new 'thin reaction zone' regime for the Kalovitz number range of 1 < Ka < 10 (Ka = (u{prime}/s{sub L}){sup 3/2} (l{sub x}/d{sub L}){sup 1/2}) proposed by Peters. Due to its freely propagating nature, modeling and simulations of LSB flames are non-trivial. The flame position cannot be specified a priori because it is …
Date: July 1, 2003
Creator: Cheng, Robert; Johnson, Matthew R. & Cheng, Robert K.
System: The UNT Digital Library
Buildup of electron cloud with different bunch pattern in thepresence of solenoid field (open access)

Buildup of electron cloud with different bunch pattern in thepresence of solenoid field

We have augmented the code POSINST to include solenoidfields, and used it to simulate the build up of electron cloud due toelectron multipacting in the PEP-II positron ring. We find that thedistribution of electrons is strongly affected by the resonancesassociated with the cyclotron period and bunch spacing. In addition, wediscover a threshold beyond which the electron density growsexponentially until it reaches the space charge limit. The threshold doesnot depend on the bunch spacing but does depend on the positron bunchpopulation.
Date: May 1, 2003
Creator: Cai, Yunhai; Pivi, Mauro & Furman, Miguel
System: The UNT Digital Library
Biomonitoring with Wireless Communications (open access)

Biomonitoring with Wireless Communications

This review is divided into three sections: technologies for monitoring physiological parameters; biosensors for chemical assays and wireless communications technologies including image transmissions. Applications range from monitoring high risk patients for heart, respiratory activity and falls to sensing levels of physical activity in military, rescue, and sports personnel. The range of measurements include, heart rate, pulse wave form, respiratory rate, blood oxygen, tissue pCO2, exhaled carbon dioxide and physical activity. Other feasible measurements will employ miniature chemical laboratories on silicon or plastic chips. The measurements can be extended to clinical chemical assays ranging from common blood assays to protein or specialized protein measurements (e.g., troponin, creatine, and cytokines such as TNF and IL6). Though the feasibility of using wireless technology to communicate vital signs has been demonstrated 32 years ago (1) it has been only recently that practical and portable devices and communications net works have become generally available for inexpensive deployment of comfortable and affordable devices and systems.
Date: March 1, 2003
Creator: Budinger, Thomas F.
System: The UNT Digital Library
'Mini'-Roadmapping - Ensuring Timely Sites' Cleanup / Closure by Resolving Science and Technology Issues (open access)

'Mini'-Roadmapping - Ensuring Timely Sites' Cleanup / Closure by Resolving Science and Technology Issues

Roadmapping is a powerful tool to manage technical risks and opportunities associated with complex problems. Roadmapping identifies technical capabilities required for both project- and program-level efforts and provides the basis for plans that ensure the necessary enabling activities will be done when needed. Roadmapping reveals where to focus further development of the path forward by evaluating uncertainties for levels of complexity, impacts, and/or the potential for large payback. Roadmaps can be customized to the application, a “graded approach” if you will. Some roadmaps are less detailed. We have called these less detailed, top-level roadmaps “mini-roadmaps”. These miniroadmaps are created to tie the needed enablers (e.g., technologies, decisions, etc.) to the functions. If it is found during the mini-roadmapping that areas of significant risk exist, then those can be roadmapped further to a lower level of detail. Otherwise, the mini-roadmap may be sufficient to manage the project / program risk. Applying a graded approach to the roadmapping can help keep the costs down. Experience has indicated that it is best to do mini-roadmapping first and then evaluate the risky areas to determine whether to further evaluate those areas. Roadmapping can be especially useful for programs / projects that have participants from …
Date: February 1, 2003
Creator: Luke, Dale & Murphy, James
System: The UNT Digital Library
Agent 2003 Conference on Challenges in Social Simulation (open access)

Agent 2003 Conference on Challenges in Social Simulation

Welcome to the Proceedings of the fourth in a series of agent simulation conferences cosponsored by Argonne National Laboratory and The University of Chicago. Agent 2003 is the second conference in which three Special Interest Groups from the North American Association for Computational Social and Organizational Science (NAACSOS) have been involved in planning the program--Computational Social Theory; Simulation Applications; and Methods, Toolkits and Techniques. The theme of Agent 2003, Challenges in Social Simulation, is especially relevant, as there seems to be no shortage of such challenges. Agent simulation has been applied with increasing frequency to social domains for several decades, and its promise is clear and increasingly visible. Like any nascent scientific methodology, however, it faces a number of problems or issues that must be addressed in order to progress. These challenges include: (1) Validating models relative to the social settings they are designed to represent; (2) Developing agents and interactions simple enough to understand but sufficiently complex to do justice to the social processes of interest; (3) Bridging the gap between empirically spare artificial societies and naturally occurring social phenomena; (4) Building multi-level models that span processes across domains; (5) Promoting a dialog among theoretical, qualitative, and empirical social …
Date: January 1, 2003
Creator: Clemmons, Margaret
System: The UNT Digital Library
Microwave Ion source for low charge state Ion production (open access)

Microwave Ion source for low charge state Ion production

None
Date: April 1, 2003
Creator: Reijonen, Jani; Eardley, Matthew; Gough, Richard; Leung, Ka-Ngo & Thomae, Rainer
System: The UNT Digital Library
Intermediates and the folding of proteins L and G (open access)

Intermediates and the folding of proteins L and G

We use a minimalist protein model, in combination with a sequence design strategy, to determine differences in primary structure for proteins L and G that are responsible for the two proteins folding through distinctly different folding mechanisms. We find that the folding of proteins L and G are consistent with a nucleation-condensation mechanism, each of which is described as helix-assisted {beta}-1 and {beta}-2 hairpin formation, respectively. We determine that the model for protein G exhibits an early intermediate that precedes the rate-limiting barrier of folding and which draws together misaligned secondary structure elements that are stabilized by hydrophobic core contacts involving the third {beta}-strand, and presages the later transition state in which the correct strand alignment of these same secondary structure elements is restored. Finally the validity of the targeted intermediate ensemble for protein G was analyzed by fitting the kinetic data to a two-step first order reversible reaction, proving that protein G folding involves an on-pathway early intermediate, and should be populated and therefore observable by experiment.
Date: July 1, 2003
Creator: Brown, Scott & Head-Gordon, Teresa
System: The UNT Digital Library
Semileptonic Decays and Sides of the Unitarity Triangle (open access)

Semileptonic Decays and Sides of the Unitarity Triangle

The elements of the CKM matrix enter the expressions for the decay rates and mixing amplitudes of hadrons. In some cases, the theoretical expressions are free of strong interaction effects, for example the CP asymmetry in B {yields} J/{psi} K{sub S}{sup 0}, so that measuring the CP asymmetry directly gives the value of sin 2{beta}, with the error in the result given by the experimental error in the measurement. In most cases, however, the experimentally measured quantities depend on strong interactions physics, and it is absolutely essential to have accurate model-free theoretical calculations to compare with experiment. A number of theoretical tools have been developed over the years which now allow us to compute B decays with great accuracy, sometimes at the level of a few percent or better. These calculations are done using effective theory methods applied to QCD, and do not rely on model assumptions. Inclusive decays can be treated using the operator product expansion (OPE). The total decay rate is given by twice the imaginary part of the forward scattering amplitude, using the optical theorem. In heavy hadron decays, the intermediate states in the forward scattering amplitude can be integrated out, so that the decay rate can …
Date: May 1, 2003
Creator: Ligeti, Zoltan; Bauer, C.; Bernard, C.; Bigi, I.; Datta, M.; del Re, D. et al.
System: The UNT Digital Library
A second beam-diagnostic beamline for the advanced lightsource (open access)

A second beam-diagnostic beamline for the advanced lightsource

A second beamline, BL 7.2, completely dedicated to beam diagnostics is being installed at the Advanced Light Source (ALS). The design has been optimized for the measurement of the momentum spread and emittance of the stored beam in combination with the existing diagnostic beamline, BL 3.1. A detailed analysis of the experimental error has allowed the definition of the system parameters. The obtained requirements found a good matching with a simple and reliable system based on the detection of X-ray synchrotron radiation (SR) through a pinhole system. The actual beamline, which also includes a port for visible and infrared SR as well as an X-ray beam position monitor (BPM), is mainly based on the design of two similar diagnostic beamlines at BESSY II. This approach allowed a significant saving in time, cost and engineering effort. The design criteria, including a summary of the experimental error analysis, as well as a brief description of the beamline are presented.
Date: May 1, 2003
Creator: Sannibale, Fernando; Baum, Dennis; Kelez, Nicholas; Scarvie, Tom & Holldack, Karsten
System: The UNT Digital Library
Dynamics of the flame flowfields in a low-swirl burner (open access)

Dynamics of the flame flowfields in a low-swirl burner

None
Date: July 1, 2003
Creator: Cheng, Robert; Johnson, Matthew R. & Cheng, Robert K.
System: The UNT Digital Library
Advanced Interactive Facades - Critical Elements for Future GreenBuildings? (open access)

Advanced Interactive Facades - Critical Elements for Future GreenBuildings?

Building designers and owners have always been fascinated with the extensive use of glass in building envelopes. Today the highly glazed facade has almost become an iconic element for a 'green building' that provides daylighting and a visual connection with the natural environment. Even before the current interest in green buildings there was no shortage of highly glazed building designs. But many of these buildings either rejected sunlight, and some associated daylight and view with highly reflective glazings or used highly transmissive glass and encountered serious internal comfort problems that could only be overcome with large HVAC systems, resulting in significant energy, cost and environmental penalties. From the 1960's to the 1990's innovation in glazing made heat absorbing glass, reflective glass and double glazing commonplace, with an associated set of aesthetic features. In the last decade there has been a subtle shift from trying to optimize an ideal, static design solution using these glazings to making the facade responsive, interactive and even intelligent. More sophisticated design approaches and technologies have emerged using new high-performance glazing, improved shading and solar control systems, greater use of automated controls, and integration with other building systems. One relatively new architectural development is the double …
Date: November 1, 2003
Creator: Selkowitz, Stephen; Aschehoug, Oyvind & Lee, Eleanor S.
System: The UNT Digital Library
Design and Performance of the Van Geet Off-Grid Home: Preprint (open access)

Design and Performance of the Van Geet Off-Grid Home: Preprint

The Van Geet home near Denver, Colorado, demonstrates the successful integration of energy conservation measures and renewable energy supply in a beautiful, comfortable, energy-efficient, 295-m2 (3,176-ft2) off-grid home in a cold, sunny climate. Features include a tight envelope, energy-efficient appliances, passive solar heating (direct gain and Trombe wall), natural cooling, solar hot water, and photovoltaics. In addition to describing this house and its performance, this paper describes the recommended design process of (1) setting a goal for energy efficiency at the outset, (2) applying rules of thumb, and (3) using computer simulation to fine-tune the design. Performance monitoring and computer simulation are combined for the best possible analysis of energy performance. In this case, energy savings are estimated as 89% heating and cooling, 83% electrical, and nearly 100% domestic water heating. The heating and cooling energy use is 8.96 kJ/Cdaym2 (0.44 Btu/Fdayft2).
Date: January 1, 2003
Creator: Barley, C. D.; Torcellini, P. & Van Geet, O.
System: The UNT Digital Library
Physical evidence for dark energy (open access)

Physical evidence for dark energy

The authors present measurements of the angular cross-correlation between luminous red galaxies from the Sloan Digital Sky Survey and the cosmic microwave background temperature maps from the Wilkinson Microwave Anisotropy Probe. They find a statistically significant achromatic positive correlation between these two data sets, which is consistent with the expected signal from the late Integrated Sachs-Wolfe (ISW) effect. they do not detect any anti-correlation on small angular scales as would be produced from a large Sunyaev-Zel'dovich (SZ) effect, although they do see evidence for some SZ effect for their highest redshift samples. Assuming a flat universe, their preliminary detection of the ISW effect provides independent physical evidence for the existence of dark energy.
Date: July 1, 2003
Creator: Scranton, Ryan; Connolly, Andrew J.; Nichol, Robert C.; Stebbins, Albert; Szapudi, Istvan; Eisenstein, Daniel J. et al.
System: The UNT Digital Library
Microstructure of Surface Layers in Cu(In,Ga)Se2 Thin Films (open access)

Microstructure of Surface Layers in Cu(In,Ga)Se2 Thin Films

In most Cu(In,Ga)Se2 thin films used for solar cells, there usually exist interfaces lying about 0.1 to 0.2 m below the surfaces. We report on a convergent-beam electron diffraction and energy-dispersive X-ray spectroscopy study of the microstructure and chemical composition of the surface region in Cu(In,Ga)Se2 thin films. We find that the surface region and the bulk are structurally similar, with no ordered defect chalcopyrite structure observed. However, their composition is slightly different, indicating that they can have different point-defect physics. Our results suggest that the subinterfaces and the bulk absorber may form homojunctions.
Date: May 1, 2003
Creator: Yan, Y.; Jones, K. M.; AbuShama, J.; Young, M.; Asher, S.; Al-Jassim, M. M. et al.
System: The UNT Digital Library
12th Workshop on Crystalline Silicon Solar Cell Materials and Processes: Summary Discussion Sessions (open access)

12th Workshop on Crystalline Silicon Solar Cell Materials and Processes: Summary Discussion Sessions

This report is a summary of the discussion sessions of the 12th Workshop on Crystalline Silicon Solar Cells and Processes. The theme of the workshop was"Fundamental R&D in c-Si: Enabling Progress in Solar-Electric Technology." This theme was chosen to reflect a concern that the current expansion in the PV energy production may redirect basic research efforts to production-oriented issues. The PV industry is installing added production capacity and new production lines that include the latest technologies. Once the technologies are selected, it is difficult to make changes. Consequently, a large expansion can stagnate the technologies and diminish interest in fundamental research. To prevent the fundamental R&D program from being overwhelmed by the desire to address immediate engineering issues, there is a need to establish topics of fundamental nature that can be pursued by the universities and the research institutions. Hence, one of the objectives of the workshop was to identify such areas for fundamental research.
Date: February 1, 2003
Creator: Sopori, B.; Swanson, D.; Sinton, R. & Tan, T.
System: The UNT Digital Library
Positronium in Solids: Computer Simulation of Pick-Off and Self-Annihilation (open access)

Positronium in Solids: Computer Simulation of Pick-Off and Self-Annihilation

Positronium (Ps) is simulated using Path Integral Monte Carlo (PIMC). This method can reproduce the results of previous simple theories in which a single quantum particle is used to represent Ps within an idealized pore. In addition, the calculations treat the e{sup -} and e{sup +} of Ps exactly and realistically model interactions with solid atoms, thereby correcting and extending the simpler theory. They study the pick-off lifetime of o-Ps and the internal contact density, {kappa}, which controls the self-annihilation behavior, for Ps in model voids (spherical pores), defects in a solid (argon), and microporous solids (zeolites).
Date: August 1, 2003
Creator: Bug, A.; Muluneh, M.; Waldman, J. & Sterne, P.
System: The UNT Digital Library
Technologies for Fissile Material Detection and Prevention of Fissile Material Introduction into International Shipping (open access)

Technologies for Fissile Material Detection and Prevention of Fissile Material Introduction into International Shipping

Prevention of the introduction of fissile materials into international shipping, and hence into a given country, is a complex problem. Some pieces of the solution to the puzzle are conceptually well defined, but lack definition of a technical pathway and/or operational implementation. Other elements are a little more fuzzy, and some elements are probably undefined at this point in time. This paper reviews the status of the more well-defined elements, and suggests needed additional measures to enhance the probability that fissile materials are not illicitly introduced into distant countries. International commerce proceeds through a number of steps from point of origin to final destination. Each step offers the possibility of a well-defined choke point to monitor and interdict the illicit shipment of fissile materials. However, because there are so many potential points and venues of entry into a large country such as the United States (e.g., air cargo, shipping containers, truck and rail transport, private vehicles, boats and planes, commercial passenger travel), it behooves the world to ensure that fissile material does not illicitly leave its point of origin.
Date: July 1, 2003
Creator: Richardson, J
System: The UNT Digital Library
RadSensor: Xray Detection by Direct Modulation of an Optical Probe Beam (open access)

RadSensor: Xray Detection by Direct Modulation of an Optical Probe Beam

We present a new x-ray detection technique based on optical measurement of the effects of x-ray absorption and electron hole pair creation in a direct band-gap semiconductor. The electron-hole pairs create a frequency dependent shift in optical refractive index and absorption. This is sensed by simultaneously directing an optical carrier beam through the same volume of semiconducting medium that has experienced an xray induced modulation in the electron-hole population. If the operating wavelength of the optical carrier beam is chosen to be close to the semiconductor band-edge, the optical carrier will be modulated significantly in phase and amplitude. This approach should be simultaneously capable of very high sensitivity and excellent temporal response, even in the difficult high-energy xray regime. At xray photon energies near 10 keV and higher, we believe that sub-picosecond temporal responses are possible with near single xray photon sensitivity. The approach also allows for the convenient and EMI robust transport of high-bandwidth information via fiber optics. Furthermore, the technology can be scaled to imaging applications. The basic physics of the detector, implementation considerations, and preliminary experimental data are presented and discussed.
Date: August 1, 2003
Creator: Lowry, M. E.; Bennett, C. V.; Vernon, S. P.; Bond, T.; Welty, R.; Behymer, E. et al.
System: The UNT Digital Library
Photovoltaic Module Thermal/Wind Performance: Long-Term Monitoring and Model Development for Energy Rating (open access)

Photovoltaic Module Thermal/Wind Performance: Long-Term Monitoring and Model Development for Energy Rating

In order to predict the energy production of photovoltaic (PV) modules, it is necessary to predict the module temperature as a function of ambient temperature, wind speed, wind direction, total irradiance, and relative humidity. This paper presents a mathematical model to predict the module temperature based on the field monitored real data of module temperature, ambient temperature, wind speed, wind direction and relative humidity.
Date: June 1, 2003
Creator: TamizhMani, G.; Ji, L.; Tang, Y.; Petacci, L. & Osterwald, C.
System: The UNT Digital Library
Characterizing Shrapnel and Debris Produced in High Power Laser Experiments (open access)

Characterizing Shrapnel and Debris Produced in High Power Laser Experiments

As large laser facilities increase in beam energy and target size, the propensity to produce shrapnel and debris that may impact target-facing optics lifetimes also increases. We present techniques and results using silica aerogel and thin glass plates to characterize the number, velocity, size, and spatial distribution of shrapnel and mass distribution of debris. We have conducted experiments on the HELEN laser to develop these techniques and provide data to support computer modeling of shrapnel and debris generation. We have begun to measure shrapnel and debris generation on Omega and are evolving plans to make similar measurements on NIF. These techniques appear viable for measuring shrapnel and debris with sufficient resolution to quantify their asymmetric deposition within the target chamber. These passive measurements can confirm improved target designs that reduce target shrapnel and debris effects and therefore aid in extending optics lifetime. Ultimately, these data support the most efficient use of optics in executing experimental campaigns on large laser facilities.
Date: September 1, 2003
Creator: Tobin, Mike; Andrew, Jim; Eder, David; Haupt, David; Johannes, Andrew & Brown, Bill
System: The UNT Digital Library