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Abstract: Air, Thermal and Water Management for PEM Fuel Cell Systems (open access)

Abstract: Air, Thermal and Water Management for PEM Fuel Cell Systems

PEM fuel cells are excellent candidates for transportation applications due to their high efficiencies. PEM fuel cell Balance of Plant (BOP) components, such as air, thermal, and water management sub-systems, can have a significant effect on the overall system performance, but have traditionally not been addressed in research and development efforts. Recognizing this, the U.S. Department of Energy and Honeywell International Inc. are funding an effort that emphasizes the integration and optimization of air, thermal and water management sub-systems. This effort is one of the major elements to assist the fuel cell system developers and original equipment manufacturers to achieve the goal of an affordable and efficient power system for transportation applications. Past work consisted of: (1) Analysis, design, and fabrication of a motor driven turbocompressor. (2) A systematic trade study to select the most promising water and thermal management systems from five different concepts (absorbent wheel humidifier, gas to gas membrane humidifier, porous metal foam humidifier, cathode recycle compressor, and water injection pump.) This presentation will discuss progress made in the research and development of air, water and thermal management sub-systems for PEM fuel cell systems in transportation applications. More specifically, the presentation will discuss: (1) Progress of the …
Date: October 1, 2008
Creator: Mirza, Mark K. Gee Zia
System: The UNT Digital Library
Top Quark Physics (open access)

Top Quark Physics

We review the prospects for studies of the top quark at the LHC.
Date: October 1, 2008
Creator: Varnes, Erich W.
System: The UNT Digital Library
Very Large System Dynamics Models - Lessons Learned (open access)

Very Large System Dynamics Models - Lessons Learned

This paper provides lessons learned from developing several large system dynamics (SD) models. System dynamics modeling practice emphasize the need to keep models small so that they are manageable and understandable. This practice is generally reasonable and prudent; however, there are times that large SD models are necessary. This paper outlines two large SD projects that were done at two Department of Energy National Laboratories, the Idaho National Laboratory and Sandia National Laboratories. This paper summarizes the models and then discusses some of the valuable lessons learned during these two modeling efforts.
Date: October 1, 2008
Creator: Jacobson, Jacob J. & Malczynski, Leonard
System: The UNT Digital Library
ACCURACY OF CO2 SENSORS (open access)

ACCURACY OF CO2 SENSORS

Are the carbon dioxide (CO2) sensors in your demand controlled ventilation systems sufficiently accurate? The data from these sensors are used to automatically modulate minimum rates of outdoor air ventilation. The goal is to keep ventilation rates at or above design requirements while adjusting the ventilation rate with changes in occupancy in order to save energy. Studies of energy savings from demand controlled ventilation and of the relationship of indoor CO2 concentrations with health and work performance provide a strong rationale for use of indoor CO2 data to control minimum ventilation rates1-7. However, this strategy will only be effective if, in practice, the CO2 sensors have a reasonable accuracy. The objective of this study was; therefore, to determine if CO2 sensor performance, in practice, is generally acceptable or problematic. This article provides a summary of study methods and findings ? additional details are available in a paper in the proceedings of the ASHRAE IAQ?2007 Conference8.
Date: October 1, 2008
Creator: Fisk, William J.; Faulkner, David & Sullivan, Douglas P.
System: The UNT Digital Library
Air, Thermal and Water Management for PEM Fuel Cell Systems (open access)

Air, Thermal and Water Management for PEM Fuel Cell Systems

This report has a detailed study of the fuel cells.
Date: October 1, 2008
Creator: Mirza, Mark K. Gee Zia
System: The UNT Digital Library
Potential of Photovoltaics: Preprint (open access)

Potential of Photovoltaics: Preprint

This paper discusses PV in the world energy portfolio, PV basics, PV technologies, and vacuum web-coating applications in PV.
Date: October 1, 2008
Creator: Nelson, B. P.
System: The UNT Digital Library
Small-Scale Readout Systems Prototype for the STAR PIXEL Detector (open access)

Small-Scale Readout Systems Prototype for the STAR PIXEL Detector

A prototype readout system for the STAR PIXEL detector in the Heavy Flavor Tracker (HFT) vertex detector upgrade is presented. The PIXEL detector is a Monolithic Active Pixel Sensor (MAPS) based silicon pixel vertex detector fabricated in a commercial CMOS process that integrates the detector and front-end electronics layers in one silicon die. Two generations ofMAPS prototypes designed specifically for the PIXEL are discussed. We have constructed a prototype telescope system consisting of three small MAPS sensors arranged in three parallel and coaxial planes with a readout system based on the readout architecture for PIXEL. This proposed readout architecture is simple and scales to the size required to readout the final detector. The real-time hit finding algorithm necessary for data rate reduction in the 400 million pixel detector is described, and aspects of the PIXEL system integration into the existing STAR framework are addressed. The complete system has been recently tested and shown to be fully functional.
Date: October 1, 2008
Creator: Szelezniak, Michal A.; Besson, Auguste; Colledani, Claude; Dorokhov, Andrei; Dulinski, Wojciech; Greiner, Leo C. et al.
System: The UNT Digital Library
Charmless b-hadrons decays at CDF (open access)

Charmless b-hadrons decays at CDF

We present CDF results on the branching fractions and time-integrated direct CP asymmetries for Bd, Bs and Lb decay modes into pairs of charmless charged hadrons (pions, kaons and protons). The data-set for these measurements amounts to 1fb{sup -1} of p{bar p} collisions at a center of mass energy 1.96TeV. We report on the first observation of the Bs->Kpi, Lb-ppi and Lb->pK decay modes and on the measurement of their branching fractions and direct CP asymmetries.
Date: October 1, 2008
Creator: Morello, Michael Joseph
System: The UNT Digital Library
Diffractive and Exclusive Production at the Tevatron (open access)

Diffractive and Exclusive Production at the Tevatron

Exclusive Higgs production, in which the event consists of nothing but the leading protons and a Higgs boson, has been proposed as a channel in which to study the properties of the Higgs boson at the Large Hadron Collider (LHC). Although we do not expect to observe exclusive Higgs-boson production at the Tevatron, we can observe similar processes which provide a calibration for theoretical predictions of exclusive Higgs production at the LHC. The CDF measurements of exclusive dijet and diphoton production, examples of such processes, are presented in Sec. 2. Single diffraction has been studied extensively at the Tevatron in Run I, including diffractive dijet and W/Z-boson production. New results with extended kinematical reach allowed by the larger Run II dataset are presented in Sec. 3. CDF II includes forward detectors designed for studying diffractive physics. The MiniPlug calorimeters cover the pseudorapidity region 3.5<|{eta}|<5.1. Beam Shower Counters (BSC) surrounding the beampipe in several locations detect particles in the forward region 5.4<|{eta}|<7.4. A spectrometer consisting of three Roman-pot detectors preceded by Tevatron dipoles is used to track diffractive antiprotons which have lost a fraction 0.03<{zeta}<0.10 of the beam momentum.
Date: October 1, 2008
Creator: Convery, M.E. & Collaboration, for the CDF
System: The UNT Digital Library
GammeV: A gamma to milli-eV particle search at Fermilab (open access)

GammeV: A gamma to milli-eV particle search at Fermilab

GammeV is an experiment conducted at Fermilab that employs the light shining through a wall technique to search for axion-like particles and employs a particle in a jar technique to search for dilaton-like chameleon particles. We obtain limits on the coupling of photons to an axion-like particle that extend previous limits for both scalars and pseudoscalars in the milli-eV mass range. We are able to exclude the axion-like particle interpretation of the anomalous PVLAS 2006 result by more than 5 standard deviations. We also present results on a search for chameleons and set limits on their possible coupling to photons.
Date: October 1, 2008
Creator: Wester, William Carl, III
System: The UNT Digital Library
Real Time RF Simulator (RTS) and control (open access)

Real Time RF Simulator (RTS) and control

The multi-cavity RTS allows LLRF algorithm development and lab testing prior to commissioning with real cavities and cryomodules. The RTS is a valuable tool since it models the functions, errors and disturbances of real RF systems. The advantage of a RTS over an off-line simulator is that it can be implemented on the actual LLRF hardware, on the same FPGA and processor, and run at the same speed of the LLRF control loop. Additionally the RTS can be shared by collaborators who do not have access to RF systems or when the systems are not available to LLRF engineers. The RTS simulator incorporates hardware, firmware and software errors and limitations of a real implementation, which would be hard to identify and time consuming to model in off-line simulations.
Date: October 1, 2008
Creator: Cancelo, G.; Armiento, C.; Treptow, K.; Vignoni, A. & Zmuda, T.
System: The UNT Digital Library
Fresh Fuel Characterization of U-Mo Alloys (open access)

Fresh Fuel Characterization of U-Mo Alloys

The need to provide more accurate property information on U-Mo fuel alloys to reactor operators, modelers, researchers, fabricators, and regulators increases as success of the RERTR program continues. This presentation will provide an overview of fresh fuel U-Mo characterization activities on monolithic fuel occurring at the Idaho National Laboratory. The overview will particularly be focused on properties available through current and previous research, and also on the type of information still needed. The presentation will deal with mechanical, physical, and microstructural properties in terms of both integrated and separate effects. Appropriate discussion in terms of fabrication characteristics, impurities, thermodynamic response, and the effects on the topic areas will be provided, along with a brief background on the characterization techniques being used or being developed to obtain the information. Furthermore, efforts to measure similar characteristics as a function of irradiation conditions and determine end-of-life observations with beginning-of-life behavior will be discussed.
Date: October 1, 2008
Creator: Burkes, D. E.; Wachs, D. M.; Keiser, D. D.; Gan, J.; Rice, F. J.; Prabhakaran, R. et al.
System: The UNT Digital Library
Materials and Component Development for Advanced Turbine Systems (open access)

Materials and Component Development for Advanced Turbine Systems

In order to meet the 2010-2020 DOE Fossil Energy goals for Advanced Power Systems, future oxy-fuel and hydrogen-fired turbines will need to be operated at higher temperatures for extended periods of time, in environments that contain substantially higher moisture concentrations in comparison to current commercial natural gas-fired turbines. Development of modified or advanced material systems, combined with aerothermal concepts are currently being addressed in order to achieve successful operation of these land-based engines. To support the advanced turbine technology development, the National Energy Technology Laboratory (NETL) has initiated a research program effort in collaboration with the University of Pittsburgh (UPitt), and West Virginia University (WVU), working in conjunction with commercial material and coating suppliers as Howmet International and Coatings for Industry (CFI), and test facilities as Westinghouse Plasma Corporation (WPC) and Praxair, to develop advanced material and aerothermal technologies for use in future oxy-fuel and hydrogen-fired turbine applications. Our program efforts and recent results are presented.
Date: October 1, 2008
Creator: Alvin, M. A.; Pettit, F.; Meier, G.; Yanar, N.; Chyu, M.; Mazzotta, D. et al.
System: The UNT Digital Library
Small-Scale Specimen Testing of Monolithic U-Mo Fuel Foils (open access)

Small-Scale Specimen Testing of Monolithic U-Mo Fuel Foils

The objective of this investigation is to develop a shear punch testing (SPT) procedure and standardize it to evaluate the mechanical properties of irradiated fuels in a hot-cell so that the tensile behavior can be predicted using small volumes of material and at greatly reduced irradiation costs. This is highly important in the development of low-enriched uranium fuels for nuclear research and test reactors. The load-displacement data obtained using SPT can be interpreted in terms of and correlated with uniaxial mechanical properties. In order to establish a correlation between SPT and tensile data, sub-size tensile and microhardness testing were performed on U-Mo alloys. In addition, efforts are ongoing to understand the effect of test parameters (such as specimen thickness, surface finish, punch-die clearance, crosshead velocity and carbon content) on the measured mechanical properties, in order to rationalize the technique, prior to employing it on a material of unknown strength.
Date: October 1, 2008
Creator: Prabhakaran, Ramprashad; Burkes, Douglas E.; Cole, James I.; Charit, Indrajit & Wachs, Daniel M.
System: The UNT Digital Library
High power 325 MHz vector modulators for the Fermilab High Intensity Neutrino Source (HINS) (open access)

High power 325 MHz vector modulators for the Fermilab High Intensity Neutrino Source (HINS)

One of the goals of the low energy 60 MeV section of the HINS H{sup -} linac [1] is to demonstrate that a total of {approx}40 RF cavities can be powered by a single 2.5 MW, 325 MHz klystron. This requires individual vector modulators at the input of each RF cavity to independently adjust the amplitude and phase of the RF input signal during the 3.5 ms RF pulse. Two versions of vector modulators have been developed; a 500 kW device for the radiofrequency quadrupole (RFQ) and a 75 kW modulator for the RF cavities. High power tests showing the vector modulator phase and amplitude responses will be presented.
Date: October 1, 2008
Creator: Madrak, Robyn Leigh & Wildman, David
System: The UNT Digital Library
An alkaline spring system within the Del Puerto ophiolite (California USA): A Mars analog site (open access)

An alkaline spring system within the Del Puerto ophiolite (California USA): A Mars analog site

Mars appears to have experienced little compositional differentiation of primitive lithosphere, and thus much of the surface of Mars is covered by mafic lavas. On Earth, mafic and ultramafic rocks present in ophiolites, oceanic crust and upper mantle that have been obducted onto land, are therefore good analogs for Mars. The characteristic mineralogy, aqueous geochemistry, and microbial communities of cold-water alkaline springs associated with these mafic and ultramafic rocks represent a particularly compelling analog for potential life-bearing systems. Serpentinization, the reaction of water with mafic minerals such as olivine and pyroxene, yields fluids with unusual chemistry (Mg-OH and Ca-OH waters with pH values up to {approx}12), as well as heat and hydrogen gas that can sustain subsurface, chemosynthetic ecosystems. The recent observation of seeps from pole-facing crater and canyon walls in the higher Martian latitudes supports the hypothesis that even present conditions might allow for a rockhosted chemosynthetic biosphere in near-surface regions of the Martian crust. The generation of methane within a zone of active serpentinization, through either abiogenic or biogenic processes, could account for the presence of methane detected in the Martian atmosphere. For all of these reasons, studies of terrestrial alkaline springs associated with mafic and ultramafic rocks …
Date: October 1, 2008
Creator: Blank, J. G.; Green, S.; Blake, D.; Valley, J.; Kita, N.; Treiman, A. et al.
System: The UNT Digital Library
Search for Heavy Top-like Quarks t-rime ---> Wq Using Lepton Plus Jets Events in 1.96-TeV p anti-p Collisions (open access)

Search for Heavy Top-like Quarks t-rime ---> Wq Using Lepton Plus Jets Events in 1.96-TeV p anti-p Collisions

We present the results of a search for a new heavy top-like quark, tprime, decaying to a W boson and another quark using the CDF II Detector in Run II of the Tevatron ppbar collider. New top-like quarks are predicted in a number of models of new physics. Using a data sample corresponding to 2.8 fb-1 of integrated luminosity we fit the observed spectrum of total transverse energy and reconstructed quark mass to a combination of background plus signal. We see no evidence for tprime production, so use this result to set limits on the tprime tprimebar production cross section times the branching ratio of tprime to Wq and infer a lower limit of 311 GeV/c2 on the mass of the tprime at 95% CL.
Date: October 1, 2008
Creator: Lister, Alison
System: The UNT Digital Library
Adaptive Projection Subspace Dimension for the Thick-Restart Lanczos Method (open access)

Adaptive Projection Subspace Dimension for the Thick-Restart Lanczos Method

The Thick-Restart Lanczos (TRLan) method is an effective method for solving large-scale Hermitian eigenvalue problems. However, its performance strongly depends on the dimension of the projection subspace. In this paper, we propose an objective function to quantify the effectiveness of a chosen subspace dimension, and then introduce an adaptive scheme to dynamically adjust the dimension at each restart. An open-source software package, nu-TRLan, which implements the TRLan method with this adaptive projection subspace dimension is available in the public domain. The numerical results of synthetic eigenvalue problems are presented to demonstrate that nu-TRLan achieves speedups of between 0.9 and 5.1 over the static method using a default subspace dimension. To demonstrate the effectiveness of nu-TRLan in a real application, we apply it to the electronic structure calculations of quantum dots. We show that nu-TRLan can achieve speedups of greater than 1.69 over the state-of-the-art eigensolver for this application, which is based on the Conjugate Gradient method with a powerful preconditioner.
Date: October 1, 2008
Creator: Yamazaki, Ichitaro; Bai, Zhaojun; Simon, Horst; Wang, Lin-Wang & Wu, K.
System: The UNT Digital Library
Testing and Acceptance of Fuel Plates for RERTR Fuel Development Experiments (open access)

Testing and Acceptance of Fuel Plates for RERTR Fuel Development Experiments

This paper discusses how candidate fuel plates for RERTR Fuel Development experiments are examined and tested for acceptance prior to reactor insertion. These tests include destructive and nondestructive examinations (DE and NDE). The DE includes blister annealing for dispersion fuel plates, bend testing of adjacent cladding, and microscopic examination of archive fuel plates. The NDE includes Ultrasonic (UT) scanning and radiography. UT tests include an ultrasonic scan for areas of “debonds” and a high frequency ultrasonic scan to determine the "minimum cladding" over the fuel. Radiography inspections include identifying fuel outside of the maximum fuel zone and measurements and calculations for fuel density. Details of each test are provided and acceptance criteria are defined. These tests help to provide a high level of confidence the fuel plate will perform in the reactor without a breach in the cladding.
Date: October 1, 2008
Creator: Wight, J.M.; Moore, G.A. & Taylor, S.C.
System: The UNT Digital Library
Project X and its connection to neutrino physics (open access)

Project X and its connection to neutrino physics

Project X is a new high intensity proton source that is being planned at Fermilab to usher in a new era of high intensity physics. The high intensity frontier can provide a wealth of new measurements--the most voracious consumer of protons is the long baseline neutrino program, but with the proton source upgrades being planned there are even more protons available than current neutrino targets can withstand. Those protons can provide a rich program on their own of muon physics and neutrino scattering physics that is complimentary to the long baseline program. In this article we discuss the physics motivation for Project X that comes from these short baseline experiments, and also the status of the design of this new source and what it will take to move forward on that design.
Date: October 1, 2008
Creator: Harris, Deborah & Jansson, Andreas
System: The UNT Digital Library
Evidence of WW+WZ production with lepton + jets final states in p anti-p collisions at s**(1/2) = 1.96-TeV (open access)

Evidence of WW+WZ production with lepton + jets final states in p anti-p collisions at s**(1/2) = 1.96-TeV

We present the first evidence of WW+WZ production with lepton+jets final states at a hadron collider. The data correspond to 1.07 inverse femtobarns of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider in proton-antiproton collisions at sqrt(s)=1.96 TeV. The observed cross section for WW+WZ production is 20.2 +/- 4.5 pb, consistent with the SM prediction of 16.1 +/- 0.9 pb. The probability for background fluctuations to produce an excess equal to or larger than that observed is estimated to be 5.4e-6, corresponding to a significance of 4.4 standard deviations.
Date: October 1, 2008
Creator: Abazov, V. M.; Abbott, B.; Abolins, M.; Acharya, B. S.; Adams, M.; Adams, T. et al.
System: The UNT Digital Library
Infiltration in ASHRAE's Residential Ventilation Standards (open access)

Infiltration in ASHRAE's Residential Ventilation Standards

The purpose of ventilation is to dilute or remove indoor contaminants that an occupant could be exposed to. It can be provided by mechanical or natural means. ASHRAE Standards including standards 62, 119, and 136 have all considered the contribution of infiltration in various ways, using methods and data from 20 years ago. The vast majority of homes in the United States and indeed the world are ventilated through natural means such as infiltration caused by air leakage. Newer homes in the western world are tight and require mechanical ventilation. As we seek to provide acceptable indoor air quality at minimum energy cost, it is important to neither over-ventilate norunder-ventilate. Thus, it becomes critically important to correctly evaluate the contribution infiltration makes to both energy consumption and equivalent ventilation. ASHRAE Standard 62.2 specifies how much mechanical ventilation is considered necessary to provide acceptable indoor air quality, but that standard is weak on how infiltration can contribute towards meeting the total requirement. In the past ASHRAE Standard 136 was used to do this, but new theoretical approaches and expanded weather data have made that standard out of date. This article will describe how to properly treat infiltration as an equivalent ventilation …
Date: October 1, 2008
Creator: Sherman, Max
System: The UNT Digital Library
3D CFD Electrochemical and Heat Transfer Model of an Integrated-Planar Solid Oxide Electrolysis Cells (open access)

3D CFD Electrochemical and Heat Transfer Model of an Integrated-Planar Solid Oxide Electrolysis Cells

A three-dimensional computational fluid dynamics (CFD) electrochemical model has been created to model high-temperature electrolysis cell performance and steam electrolysis in a new novel integrated planar porous-tube supported solid oxide electrolysis cell (SOEC). The model is of several integrated planar cells attached to a ceramic support tube. This design is being evaluated with modeling at the Idaho National Laboratory. Mass, momentum, energy, and species conservation and transport are provided via the core features of the commercial CFD code FLUENT. A solid-oxide fuel cell (SOFC) model adds the electrochemical reactions and loss mechanisms and computation of the electric field throughout the cell. The FLUENT SOFC user-defined subroutine was modified for this work to allow for operation in the SOEC mode. Model results provide detailed profiles of temperature, Nernst potential, operating potential, activation over-potential, anode-side gas composition, cathode-side gas composition, current density and hydrogen production over a range of stack operating conditions. Mean per-cell area-specific-resistance (ASR) values decrease with increasing current density. Predicted mean outlet hydrogen and steam concentrations vary linearly with current density, as expected. Effects of variations in operating temperature, gas flow rate, cathode and anode exchange current density, and contact resistance from the base case are presented. Contour plots …
Date: October 1, 2008
Creator: Hawkes, Grant & O'Brien, James E.
System: The UNT Digital Library
The universal criterion for switching a magnetic vortex core in soft magnetic nanodots (open access)

The universal criterion for switching a magnetic vortex core in soft magnetic nanodots

The universal criterion for ultrafast vortex core switching between core-up and -down vortex bi-states in soft magnetic nanodots was empirically investigated by micromagnetic simulations and combined with an analytical approach. Vortex-core switching occurs whenever the velocity of vortex core motion reaches a critical value, which is {nu}{sub c} = 330 {+-} 37 m/s for Permalloy, as estimated from numerical simulations. This critical velocity was found to be {nu}{sub c} = {eta}{sub c}{gamma} {radical}A{sub ex} with A{sub ex} the exchange stiffness, {gamma} the gyromagnetic ratio, and an estimated proportional constant {eta}{sub c} = 1.66 {+-} 0.18. This criterion does neither depend on driving force parameters nor on the dimension or geometry of the magnetic specimen. The phase diagrams for the vortex core switching criterion and its switching time with respect to both the strength and angular frequency of circular rotating magnetic fields were derived, which offer practical guidance for implementing vortex core switching into future solid state information storage devices.
Date: October 1, 2008
Creator: Lee, K. S.; Kim, S. K.; Yu, Y. S.; Choi, Y. S.; Guslienko, K. Y.; Jung, H. et al.
System: The UNT Digital Library