High efficiency multilayer blazed gratings for EUV and soft X-rays: Recent developments (open access)

High efficiency multilayer blazed gratings for EUV and soft X-rays: Recent developments

Multilayer coated blazed gratings with high groove density are the best candidates for use in high resolution EUV and soft x-ray spectroscopy. Theoretical analysis shows that such a grating can be potentially optimized for high dispersion and spectral resolution in a desired high diffraction order without significant loss of diffraction efficiency. In order to realize this potential, the grating fabrication process should provide a perfect triangular groove profile and an extremely smooth surface of the blazed facets. Here we report on recent progress achieved at the Advanced Light Source (ALS) in fabrication of high quality multilayer coated blazed gratings. The blazed gratings were fabricated using scanning beam interference lithography followed by wet anisotropic etching of silicon. A 200 nm period grating coated with a Mo/Si multilayer composed with 30 bi-layers demonstrated an absolute efficiency of 37.6percent in the 3rd diffraction order at 13.6 nm wavelength. The groove profile of the grating was thoroughly characterized with atomic force microscopy before and after the multilayer deposition. The obtained metrology data were used for simulation of the grating efficiency with the vector electromagnetic PCGrate-6.1 code. The simulations showed that smoothing of the grating profile during the multilayer deposition is the main reason for …
Date: July 26, 2011
Creator: Voronov, Dmitriy; Ahn, Minseung; Anderson, Erik; Cambie, Rossana; Chang, Chih-Hao; Goray, Leonid et al.
Object Type: Article
System: The UNT Digital Library
A model for improving microbial biofuel production using a synthetic feedback loop (open access)

A model for improving microbial biofuel production using a synthetic feedback loop

Cells use feedback to implement a diverse range of regulatory functions. Building synthetic feedback control systems may yield insight into the roles that feedback can play in regulation since it can be introduced independently of native regulation, and alternative control architectures can be compared. We propose a model for microbial biofuel production where a synthetic control system is used to increase cell viability and biofuel yields. Although microbes can be engineered to produce biofuels, the fuels are often toxic to cell growth, creating a negative feedback loop that limits biofuel production. These toxic effects may be mitigated by expressing efflux pumps that export biofuel from the cell. We developed a model for cell growth and biofuel production and used it to compare several genetic control strategies for their ability to improve biofuel yields. We show that controlling efflux pump expression directly with a biofuel-responsive promoter is a straight forward way of improving biofuel production. In addition, a feed forward loop controller is shown to be versatile at dealing with uncertainty in biofuel production rates.
Date: July 14, 2011
Creator: Dunlop, Mary; Keasling, Jay & Mukhopadhyay, Aindrila
Object Type: Article
System: The UNT Digital Library
Definitive Alkene Identification Needed for In-Vitro Studies with Ole (Olefin Synthesis) Proteins (open access)

Definitive Alkene Identification Needed for In-Vitro Studies with Ole (Olefin Synthesis) Proteins

None
Date: July 11, 2011
Creator: Beller, Harry; Goh, Ee-Been & Keasling, Jay
Object Type: Article
System: The UNT Digital Library
Direct probe of Mott-Hubbard to charge-transfer insulator transition and electronic structure evolution in transition-metal systems (open access)

Direct probe of Mott-Hubbard to charge-transfer insulator transition and electronic structure evolution in transition-metal systems

We report the most direct experimental verification of Mott-Hubbard and charge-transfer insulators through x-ray emission spectroscopy in transition-metal (TM) fluorides. The p-d hybridization features in the spectra allow a straightforward energy alignment of the anion-2p and metal-3d valence states, which visually shows the difference between the two types of insulators. Furthermore, in parallel with the theoretical Zaanen-Sawatzky-Allen diagram, a complete experimental systematics of the 3d Coulomb interaction and the 2p-3d charge-transfer energy is reported and could serve as a universal experimental trend for other TM systems including oxides.
Date: July 11, 2011
Creator: Olalde-Velasco, P.; Jimenez-Mier, J.; Denlinger, J. D.; Hussain, Z. & Yang, W. L.
Object Type: Article
System: The UNT Digital Library
Automated Demand Response Technology Demonstration Project for Small and Medium Commercial Buildings (open access)

Automated Demand Response Technology Demonstration Project for Small and Medium Commercial Buildings

Small and medium commercial customers in California make up about 20-25% of electric peak load in California. With the roll out of smart meters to this customer group, which enable granular measurement of electricity consumption, the investor-owned utilities will offer dynamic prices as default tariffs by the end of 2011. Pacific Gas and Electric Company, which successfully deployed Automated Demand Response (AutoDR) Programs to its large commercial and industrial customers, started investigating the same infrastructures application to the small and medium commercial customers. This project aims to identify available technologies suitable for automating demand response for small-medium commercial buildings; to validate the extent to which that technology does what it claims to be able to do; and determine the extent to which customers find the technology useful for DR purpose. Ten sites, enabled by eight vendors, participated in at least four test AutoDR events per site in the summer of 2010. The results showed that while existing technology can reliably receive OpenADR signals and translate them into pre-programmed response strategies, it is likely that better levels of load sheds could be obtained than what is reported here if better understanding of the building systems were developed and the DR response …
Date: July 1, 2011
Creator: Page, Janie; Kiliccote, Sila; Dudley, Junqiao Han; Piette, Mary Ann; Chiu, Albert K.; Kellow, Bashar et al.
Object Type: Report
System: The UNT Digital Library
Qualification of the Second Batch Production 9-Cell Cavities Manufactured by AES and Validation of the First US Industrial Cavity Vendor for ILC (open access)

Qualification of the Second Batch Production 9-Cell Cavities Manufactured by AES and Validation of the First US Industrial Cavity Vendor for ILC

One of the major goals of ILC SRF cavity R&D is to develop industrial capabilities of cavity manufacture and processing in all three regions. In the past several years, Jefferson Lab, in collaboration with Fermi National Accelerator Laboratory, has processed and tested all the 9-cell cavities of the first batch (4 cavities) and second batch (6 cavities) production cavities manufactured by Advanced Energy Systems Inc. (AES). Over the course, close information feedback was maintained, resulting in changes in fabrication and processing procedures. A light buffered chemical polishing was introduced, removing the weld splatters that could not be effectively removed by heavy EP alone. An 800 Celsius 2 hour vacuum furnace heat treatment procedure replaced the original 600 Celsius 10 hour procedure. Four out of the six 9-cell cavities of the second production bath achieved a gradient of 36-41 MV/m at a Q0 of more than 8E9 at 35 MV/m. This result validated AES as the first ''ILC certified'' industrial vendor in the US for ILC cavity manufacture.
Date: July 1, 2011
Creator: Geng, R. L.; Golden, B. A.; Kushnick, P.; Overton, R. B.; Calderaro, M.; Peterson, E. et al.
Object Type: Article
System: The UNT Digital Library
Soft ionization of thermally evaporated hypergolic ionic liquid aerosols (open access)

Soft ionization of thermally evaporated hypergolic ionic liquid aerosols

Isolated ion pairs of a conventional ionic liquid, 1-Ethyl-3-Methyl-Imidazolium Bis(trifluoromethylsulfonyl)imide ([Emim+][Tf2N?]), and a reactive hypergolic ionic liquid, 1-Butyl-3-Methyl-Imidazolium Dicyanamide ([Bmim+][Dca?]), are generated by vaporizing ionic liquid submicron aerosol particles for the first time; the vaporized species are investigated by dissociative ionization with tunable vacuum ultraviolet (VUV) light, exhibiting clear intact cations, Emim+ and Bmim+, presumably originating from intact ion pairs. Mass spectra of ion pair vapor from an effusive source of the hypergolic ionic liquid show substantial reactive decomposition due to the internal energy of the molecules emanating from the source. Photoionization efficiency curves in the near threshold ionization region of isolated ion pairs of [Emim+][Tf2N?]ionic liquid vapor are compared for an aerosol source and an effusive source, revealing changes in the appearance energy due to the amount of internal energy in the ion pairs. The aerosol source has a shift to higher threshold energy (~;;0.3 eV), attributed to reduced internal energy of the isolated ion pairs. The method of ionic liquid submicron aerosol particle vaporization, for reactive ionic liquids such as hypergolic species, is a convenient, thermally ?cooler? source of isolated intact ion pairs in the gas phase compared to effusive sources.
Date: July 19, 2011
Creator: Koh, Christine J.; Liu, Chen-Lin; Harmon, Christopher W.; Strasser, Daniel; Golan, Amir; Kostko, Oleg et al.
Object Type: Article
System: The UNT Digital Library
Preparation and Testing of the SRF Cavities for the CEBAF 12 GeV Upgrade (open access)

Preparation and Testing of the SRF Cavities for the CEBAF 12 GeV Upgrade

Eighty new 7-cell, low-loss cell-shaped cavities are required for the CEBAF 12 GeV Upgrade project. In addition to ten pre-production units fabricated at JLab, the full set of commercially-produced cavities have been delivered. An efficient processing routine, which includes a controlled 30 micron electropolish, has been established to transform these cavities into qualified 8-cavity strings. This work began in 2010 and will run through the end of 2011. The realized cavity performance consistently exceeds project requirements and also the maximum useful gradient in CEBAF: 25 MV/m. We will describe the cavity processing and preparation protocols and summarize test results obtained to date.
Date: July 1, 2011
Creator: Reilly, A. V.; Bass, T.; Burrill, A.; Davis, G. K.; Marhauser, F.; Reece, C. E. et al.
Object Type: Article
System: The UNT Digital Library
Ideal MHD Stability of ITER Steady State Scenarios with ITBs (open access)

Ideal MHD Stability of ITER Steady State Scenarios with ITBs

One of ITER goals is to demonstrate feasibility of continuous operations using non-inductive current drive. Two main candidates have been identified for advanced operations: the long duration, high neutron fluency hybrid scenario and the steady state scenario, both operating at a plasma current lower than the reference ELMy scenario [1][2] to minimize the required current drive. The steady state scenario targets plasmas with current 7-10 MA in the flat-top, 50% of which will be provided by the self-generated, pressure-driven bootstrap current. It has been estimated that, in order to obtain a fusion gain Q > 5 at a current of 9 MA, it should be ΒN > 2.5 and H > 1.5 [3]. This implies the presence of an Internal Transport Barrier (ITB). This work discusses how the stability of steady state scenarios with ITBs is affected by the external heating sources and by perturbations of the equilibrium profiles.
Date: July 27, 2011
Creator: Poli, F. M.; Kessel, C. E.; Jardin, S.; Manickam, J.; Chance, M. & Chen, J.
Object Type: Article
System: The UNT Digital Library
Hydrogen Fuel Cell Development in Columbia (SC) (open access)

Hydrogen Fuel Cell Development in Columbia (SC)

This is an update to the final report filed after the extension of this program to May of 2011. The activities of the present program contributed to the goals and objectives of the Fuel Cell element of the Hydrogen, Fuel Cells and Infrastructure Technologies Program of the Department of Energy through five sub-projects. Three of these projects have focused on PEM cells, addressing the creation of carbon-based metal-free catalysts, the development of durable seals, and an effort to understand contaminant adsorption/reaction/transport/performance relationships at low contaminant levels in PEM cells. Two programs addressed barriers in SOFCs; an effort to create a new symmetrical and direct hydrocarbon fuel SOFC designs with greatly increased durability, efficiency, and ease of manufacturing, and an effort to create a multiphysics engineering durability model based on electrochemical impedance spectroscopy interpretations that associate the micro-details of how a fuel cell is made and their history of (individual) use with specific prognosis for long term performance, resulting in attendant reductions in design, manufacturing, and maintenance costs and increases in reliability and durability.
Date: July 31, 2011
Creator: Reifsnider, Kenneth
Object Type: Report
System: The UNT Digital Library
MicrobesOnline: an integrated portal for comparative and functional genomics (open access)

MicrobesOnline: an integrated portal for comparative and functional genomics

Since 2003, MicrobesOnline (http://www.microbesonline.org) has been providing a community resource for comparative and functional genome analysis. The portal includes over 1000 complete genomes of bacteria, archaea and fungi and thousands of expression microarrays from diverse organisms ranging from model organisms such as Escherichia coli and Saccharomyces cerevisiae to environmental microbes such as Desulfovibrio vulgaris and Shewanella oneidensis. To assist in annotating genes and in reconstructing their evolutionary history, MicrobesOnline includes a comparative genome browser based on phylogenetic trees for every gene family as well as a species tree. To identify co-regulated genes, MicrobesOnline can search for genes based on their expression profile, and provides tools for identifying regulatory motifs and seeing if they are conserved. MicrobesOnline also includes fast phylogenetic profile searches, comparative views of metabolic pathways, operon predictions, a workbench for sequence analysis and integration with RegTransBase and other microbial genome resources. The next update of MicrobesOnline will contain significant new functionality, including comparative analysis of metagenomic sequence data. Programmatic access to the database, along with source code and documentation, is available at http://microbesonline.org/programmers.html.
Date: July 14, 2011
Creator: Dehal, Paramvir; Joachimiak, Marcin; Price, Morgan; Bates, John; Baumohl, Jason; Chivian, Dylan et al.
Object Type: Article
System: The UNT Digital Library
Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control (open access)

Colliding Laser Pulses for Laser-Plasma Accelerator Injection Control

Decoupling injection from acceleration is a key challenge to achieve compact, reliable, tunable laser-plasma accelerators (LPA). In colliding pulse injection the beat between multiple laser pulses can be used to control energy, energy spread, and emittance of the electron beam by injecting electrons in momentum and phase into the accelerating phase of the wake trailing the driver laser pulse. At LBNL, using automated control of spatiotemporal overlap of laser pulses, two-pulse experiments showed stable operation and reproducibility over hours of operation. Arrival time of the colliding beam was scanned, and the measured timing window and density of optimal operation agree with simulations. The accelerator length was mapped by scanning the collision point.
Date: July 19, 2011
Creator: Plateau, Guillaume; Geddes, Cameron; Matlis, Nicholas; Cormier-Michel, Estelle; Mittelberger, Daniel; Nakamura, Kei et al.
Object Type: Article
System: The UNT Digital Library
Integrated Genome-Based Studies of Shewanella Ecophysiology (open access)

Integrated Genome-Based Studies of Shewanella Ecophysiology

We have constructed in-frame deletions of 7 of the 10 PAS-GGDEF-EAL proteins in Shewanella oneidensis MR-1. We are currently in the process of characterizing the deletion mutants under a wide range of growth conditions. In addition to characterizing growth, we will also examine the biofilm formation of the deletion mutants. In addition to the genetic analyses of the mutants, we are also interested in comparing the activities of the various PAS-GGDEF-EAL proteins. Proteins containing PAS, GGDEF and EAL amino acid sequence motifs may play an important role in regulating c-di-GMP signaling in response to environmental conditions. A genetic and biochemical analysis into the roles of these proteins is underway. PDE activity was observed for several PAS-GGDEF-EAL proteins. One of these proteins, SO0427, also demonstrates possible DGC activity in vitro. Currently, we are studying the growth, motility and biofilm formation characteristics of deletion mutants, as well as the activity of the purified proteins.
Date: July 12, 2011
Creator: Spormann, Alfred
Object Type: Report
System: The UNT Digital Library
Radionuclide Concentrations in Terrestrial Vegetation and Soil Samples On and Around the Hanford Site, 1971 Through 2008 (open access)

Radionuclide Concentrations in Terrestrial Vegetation and Soil Samples On and Around the Hanford Site, 1971 Through 2008

Environmental monitoring is conducted on the U.S. Department of Energy (DOE) Hanford Site to comply with DOE Orders and federal and state regulations. Major objectives of the monitoring are to characterize contaminant levels in the environment and to determine site contributions to the contaminant inventory. This report focuses on surface soil and perennial vegetation samples collected between 1971 and 2008 as part of the Pacific Northwest National Laboratory Surface Environmental Surveillance Project performed under contract to DOE. Areas sampled under this program are located on the Hanford Site but outside facility boundaries and on public lands surrounding the Hanford Site. Additional samples were collected during the past 8 years under DOE projects that evaluated parcels of land for radiological release. These data were included because the same sampling methodology and analytical laboratory were used for the projects. The spatial and temporal trends of six radionuclides collected over a 38-year period were evaluated. The radionuclides----cobalt-60, cesium-137, strontium-90, plutonium-238, plutonium-239/240, and uranium (reported either as uranium-238 or total uranium)----were selected because they persist in the environment and are still being monitored routinely and reported in Hanford Site environmental reports. All these radionuclides were associated with plutonium production and waste management of activities …
Date: July 29, 2011
Creator: Simmons, Mary Ann; Poston, Ted M.; Fritz, Brad G. & Bisping, Lynn E.
Object Type: Report
System: The UNT Digital Library
Gradient Improvement by Removal of Identified Local Defects (open access)

Gradient Improvement by Removal of Identified Local Defects

Recent experience of ILC cavity processing and testing at Jefferson Lab has shown that some 9-cell cavities are quench limited at a gradient in the range of 15-25 MV/m. Further studies reveal that these quench limits are often correlated with sub-mm sized and highly localized geometrical defects at or near the equator weld. There are increasing evidence to show that these genetic defects have their origin in the material or in the electron beam welding process (for example due to weld irregularities or splatters on the RF surface and welding porosity underneath the surface). A local defect removal method has been proposed at Jefferson Lab by locally re-melting the niobium material. Several 1-cell cavities with known local defects have been treated by using the JLab local e-beam re-melting method, resulting in gradient and Q0 improvement. We also sent 9-cell cavities with known gradient limiting local defects to KEK for local grinding and to FNAL for global mechanical polishing. We report on the results of gradient improvements by removal of local defects in these cavities.
Date: July 2011
Creator: Geng, R. L.; Clemens, W. A.; Cooper, C. A.; Hayano, H. & Watanabe, K.
Object Type: Article
System: The UNT Digital Library
Mechanical Study of Superconducting Parallel-Bar Deflecting/Crabbing Cavities (open access)

Mechanical Study of Superconducting Parallel-Bar Deflecting/Crabbing Cavities

The superconducting parallel-bar deflecting/crabbing cavities have improved properties compared to conventional cavity structures. It is currently being considered for number of applications. The mechanical design analysis is performed on two designs of the 499 MHz parallel-bar deflecting cavity for the Jefferson Lab 12 GeV upgrade. The main purpose of the mechanical study is to examine the structural stability of the cavities under the operating conditions in the accelerators. The study results will suggest the need for additional structural strengthening. Also the study results will help to develop a concept of the tuning method. If the cavity is to be installed in the accelerator it should satisfy a certain design parameters due to the safety requirements (for example, pressure system requirements) which are much severe condition than the actual operating condition.
Date: July 1, 2011
Creator: H. Park, J.R. Delayen, S.U. De Silva
Object Type: Article
System: The UNT Digital Library
Time Lens Based Single-Shot Ultrafast Waveform Recording: From High Repetition Rate to High Dynamic Range (open access)

Time Lens Based Single-Shot Ultrafast Waveform Recording: From High Repetition Rate to High Dynamic Range

None
Date: July 22, 2011
Creator: Bennett, C. V.; Hernandez, V. J.; Moran, B. D.; Lowry, M. E.; Vernon, S. P.; Steele, P. T. et al.
Object Type: Article
System: The UNT Digital Library
Retrograde Melting and Internal Liquid Gettering in Silicon (open access)

Retrograde Melting and Internal Liquid Gettering in Silicon

Retrograde melting (melting upon cooling) is observed in silicon doped with 3d transition metals, via synchrotron-based temperature-dependent X-ray microprobe measurements. Liquid metal-silicon droplets formed via retrograde melting act as efficient sinks for metal impurities dissolved within the silicon matrix. Cooling results in decomposition of the homogeneous liquid phase into solid multiple-metal alloy precipitates. These phenomena represent a novel pathway for engineering impurities in semiconductor-based systems.
Date: July 1, 2011
Creator: Hudelson, Steve; Newman, Bonna K.; Bernardis, Sarah; Fenning, David P.; Bertoni, Mariana I.; Marcus, Matthew A. et al.
Object Type: Article
System: The UNT Digital Library
Superconducting DC and RF Properties of Ingot Niobium (open access)

Superconducting DC and RF Properties of Ingot Niobium

The thermal conductivity, DC magnetization and penetration depth of large-grain niobium hollow cylindrical rods fabricated from ingots, manufactured by CBMM subjected to chemical and heat treatment were measured. The results confirm the influence of chemical and heat-treatment processes on the superconducting properties, with no significant dependence on the impurity concentrations in the original ingots. Furthermore, RF properties, such as the surface resistance and quench field of the niobium rods were measured using a TE{sub 011} cavity. The hollow niobium rod is the center conductor of this cavity, converting it to a coaxial cavity. The quench field is limited by the critical heat flux through the rods' cooling channel.
Date: July 1, 2011
Creator: Pashupati Dhakal, Gianluigi Ciovati, Peter Kneisel, Ganapati Rao Myneni
Object Type: Article
System: The UNT Digital Library
Final Report: Imaging of Buried Nanoscale Optically Active Materials (open access)

Final Report: Imaging of Buried Nanoscale Optically Active Materials

This is a final report covering work done at University of Maryland to develop a Ballistic Electron Emission Luminescence (BEEL) microscope. This technique was intended to examine the carrier transport and photon emission in deeply buried optically-active layers and thereby provide a means for materials science to unmask the detailed consequences of experimentally controllable growth parameters, such as quantum dot size, statistics and orientation, and defect density and charge recombination pathways.
Date: July 5, 2011
Creator: Appelbaum, Ian
Object Type: Report
System: The UNT Digital Library
EFFECT OF COMPRESSION ON CONDUCTIVITY AND MORPHOLOGY OF PFSA MEMBRANES (open access)

EFFECT OF COMPRESSION ON CONDUCTIVITY AND MORPHOLOGY OF PFSA MEMBRANES

Polymer-Electrolyte-Fuel-Cells (PEFCs) are promising candidates for powering vehicles and portable devices using renewable-energy sources. The core of a PEFC is the solid electrolyte membrane that conducts protons from anode to cathode, where water is generated. The conductivity of the membrane, however, depends on the water content of the membrane, which is strongly related to the cell operating conditions. The membrane and other cell components are typically compressed to minimize various contact resistances. Moreover, the swelling of a somewhat constrained membrane in the cell due to the humidity changes generates additional compressive stresses in the membrane. These external stresses are balanced by the internal swelling pressure of the membrane and change the swelling equilibrium. It was shown using a fuel-cell setup that compression could reduce the water content of the membrane or alter the cell resistance. Nevertheless, the effect of compression on the membrane’s transport properties is yet to be understood, as well as its implications in the structure-functions relationships of the membrane. We previously studied, both experimentally and theoretically, how compression affects the water content of the membrane.6 However, more information is required the gain a fundamental understanding of the compression effects. In this talk, we present the results of …
Date: July 20, 2011
Creator: Kusoglu, Ahmet; Weber, Adam; Jiang, Ruichin & Gittleman, Craig
Object Type: Article
System: The UNT Digital Library
FeMn/Fe/Co/Cu(1,1,10) films studied using the magneto-optic Kerr effect and photoemission electron microscopy (open access)

FeMn/Fe/Co/Cu(1,1,10) films studied using the magneto-optic Kerr effect and photoemission electron microscopy

FeMn/Fe/Co/Cu(1,1,10) films were grown epitaxially and investigated using the magneto-optic Kerr effect and photoemission electron microscopy. We found that FeMn/Fe/Co/Cu(1,1,10) exhibits the same properties as FeMn/Co/Cu(1,1,10) for the ferromagnetic phase of the face centered cubic (fcc) Fe film but a different property for the non-ferromagnetic phase of the fcc Fe film. This result indicates that the characteristic property reported in the literature for FeMn/Co/Cu(001) comes from the FeMn spin structure and is independent of the ferromagnetic layer.
Date: July 31, 2011
Creator: Meng, Y.; Li, J.; Tan, A.; Park, J.; Jin, E.; Son, H. et al.
Object Type: Article
System: The UNT Digital Library
Water Uptake in PEMFC Catalyst Layers (open access)

Water Uptake in PEMFC Catalyst Layers

Water uptake profiles of proton-exchange-membrane fuel-cell catalyst layers are characterized in the form of capillary-pressure saturation (Pc-S) curves. The curves indicate that the catalyst layers tested are highly hydrophilic and require capillary pressures as low as -80 kPa to eject imbibed water. Comparison of materials made with and without Pt indicates a difference in water ejection and uptake phenomena due to the presence of Pt. The addition of Pt increases the tendency of the catalyst layer to retain water. Dynamic vapor sorption (DVS) is used to characterize the water-vapor sorption onto Nafion, Pt/C, and C surfaces. The DVS results align with the trends found from the Pc-S curves and show an increased propensity for water uptake in the presence of Pt. The effect of the ion in Nafion, sodium or protonated form, is also compared and demonstrates that although the protonation of the Nafion in the catalyst layer also increases hydrophilicity, the effect is not as great as that caused by Pt.
Date: July 1, 2011
Creator: Gunterman, Haluna P.; Kwong, Anthony H.; Gostick, Jeffrey T.; Kusoglu, Ahmet & Weber, Adam Z.
Object Type: Article
System: The UNT Digital Library
American Recovery & Reinvestment Act: Fuel Cell Hybrid Power Packs and Hydrogen Refueling for Lift Trucks (open access)

American Recovery & Reinvestment Act: Fuel Cell Hybrid Power Packs and Hydrogen Refueling for Lift Trucks

HEB Grocery Company, Inc. (H-E-B) is a privately-held supermarket chain with 310 stores throughout Texas and northern Mexico. H-E-B converted 14 of its lift reach trucks to fuel cell power using Nuvera Fuel Cells’ PowerEdge™ units to verify the value proposition and environmental benefits associated with the technology. Issues associated with the increasing power requirements of the distribution center operation, along with high ambient temperature in the summer and other operating conditions (such as air quality and floor surface condition), surfaced opportunities for improving Nuvera’s PowerEdge fuel cell system design in high-throughput forklift environments. The project included on-site generation of hydrogen from a steam methane reformer, called PowerTap™ manufactured by Nuvera. The hydrogen was generated, compressed and stored in equipment located outside H-E-B’s facility, and provided to the forklifts by hydrogen dispensers located in high forklift traffic areas. The PowerEdge fuel cell units logged over 25,300 operating hours over the course of the two-year project period. The PowerTap hydrogen generator produced more than 11,100 kg of hydrogen over the same period. Hydrogen availability at the pump was 99.9%. H-E-B management has determined that fuel cell forklifts help alleviate several issues in its distribution centers, including truck operator downtime associated with …
Date: July 31, 2011
Creator: Block, Gus
Object Type: Report
System: The UNT Digital Library