The goal of this work is to develop tools and test procedures for identifying ferrites suitable for use in shock line applications. Electromagnetic shocklines have been used to provide fast rising voltage pulses for many applications. In these applications a slow rising pulse is injected into the line where currents drive the ferrites into saturation leading to a fast rising output pulse. A shockline’s unique capabilities could be applied to new detonator configurations. A properly conditioned voltage pulse is critical for fire set applications. A carefully designed shockline could provide a passive solution to generating a fast rising voltage pulse for the fire set. Traditional circuits use ferrites operating in a linear regime. Shock lines push the ferrites well into the nonlinear regime where very few tools and data currently exist. Ferrite material is key to the operation of these shock lines, and tools for identifying suitable ferrites are critical. This report describes an experimental setup to that allows testing of ferrite samples and comparison to models with the goal of identifying optimal ferrites for shockline use.
Life Extension Program (LEP) is a program to repair/replace components of nuclear weapons to ensure the ability to meet military requirements. The W78/88-1 LEP encompasses the modernization of two major nuclear weapon reentry systems into an interoperable warhead. Several design concepts exist to provide different options for robust safety and security themes, maximum non-nuclear commonality, and cost. Simulation is one capability used to evaluate the mechanical performance of the designs in various operational environments, plan for system and component qualification efforts, and provide insight into the survivability of the warhead in environments that are not currently testable. The simulation efforts use several Sandia-developed tools through the Advanced Simulation and Computing program, including Cubit for mesh generation, the DART Model Manager, SIERRA codes running on the HPC TLCC2 platforms, DAKOTA, and ParaView. Several programmatic objectives were met using the simulation capability including: (1) providing early environmental specification estimates that may be used by component designers to understand the severity of the loads their components will need to survive, (2) providing guidance for load levels and configurations for subassembly tests intended to represent operational environments, and (3) recommending design options including modified geometry and material properties. These objectives were accomplished through regular interactions with component, system, and test engineers while using the laboratory's computational infrastructure to effectively perform ensembles of simulations. Because NNSA has decided to defer the LEP program, simulation results are being documented and models are being archived for future reference. However, some advanced and exploratory efforts will continue to mature key technologies, using the results from these and ongoing simulations for design insights, test planning, and model validation.
This project aims at the development of advanced low-threshold Ge detection technology and proof of its applicability to reactor monitoring via the as-yet undetected coherent neutrino nucleus scattering (CNNS) process.
A spallation based multiplicity detector has been constructed and deployed to the Kimballton Underground Research Facility to measure the cosmogenic fast neutron flux anti-coincident from the initiating muon. Two of the three planned measurements have been completed (~380 and ~600 m.w.e) with sufficient statistics. The third measurement at level 14 (~4450 m.w.e.) is currently being performed. Current results at ~600 m.w.e. compare favourably to the one previous measurement at 550 m.w.e. For neutron energies between 100 and 200 MeV measurements at ~380 m.w.e. produce fluxes between 1e-8 and 7e-9 n/cm2/s/MeV and at ~600 m.w.e. measurements produce fluxes between 7e-9 and 1e-11 n/cm2/s/MeV.
Brubaker, E.; Hilton, Nathan R.; Johnson, William; Marleau, Peter; Kupinski, Matthew; Macgahan, Christopher J.
Future arms control treaty verification regimes may use radiation imaging measurements to confirm and track nuclear warheads or other treaty accountable items (TAIs). This project leverages advanced inference methods developed for medical and adaptive imaging to improve task performance in arms control applications. Additionally, we seek a method to acquire and analyze imaging data of declared TAIs without creating an image of those objects or otherwise storing or revealing any classified information. Such a method would avoid the use of classified-information barriers (IB).
We find for infrared wavelengths there are broad ranges of particle sizes and refractive indices that represent fog and rain where the use of circular polarization can persist to longer ranges than linear polarization. Using polarization tracking Monte Carlo simulations for varying particle size, wavelength, and refractive index systematically, we show that for specific scene parameters circular polarization outperforms linear polarization in maintaining the intended polarization state for large optical depths. This enhancement in circular polarization can be exploited to improve range and target detection in obscurant environments that are important in many critical sensing applications. Specifically, circular polarization persists better than linear for radiation fog in the short-wave infrared, for advection fog in the short-wave infrared and the long-wave infrared, and large particle sizes of Sahara dust around the 4 micron wavelength.
Lignin is a potentially plentiful source of renewable organics, with %7E50Mtons/yr produced by the pulp/paper industry and 200-300 Mtons/yr projected production by a US biofuels industry. This industry must process approximately 1 billion tons of biomass to meet the US Renewable Fuel goals. However, there are currently no efficient processes for converting lignin to value-added chemicals and drop-in fuels. Lignin is therefore an opportunity for production of valuable renewable chemicals, but presents staggering technical and economic challenges due to the quantities of material involved and the strong chemical bonds comprising this polymer. Aggressive chemistries and high temperatures are required to degrade lignin without catalysts. Moreover, chemical non-uniformity among lignins leads to complex product mixtures that tend to repolymerize. Conventional petrochemical approaches (pyrolysis, catalytic cracking, gasification) are energy intensive (400-800 degC), require complicated separations, and remove valuable chemical functionality. Low-temperature (25-200 degC) alternatives are clearly desirable, but enzymes are thermally fragile and incompatible with liquid organic compounds, making them impractical for large-scale biorefining. Alternatively, homogeneous catalysts, such as recently developed vanadium complexes, must be separated from product mixtures, while many heterogenous catalysts involve costly noble metals. The objective of this project is to demonstrate proof of concept that an entirely new class of biomimetic, efficient, and industrially robust synthetic catalysts based on nanoporous Metal- Organic Frameworks (MOFs) can be developed. Although catalytic MOFs are known, catalysis of bond cleavage reactions needed for lignin degradation is completely unexplored. Thus, fundamental research is required that industry and most sponsoring agencies are currently unwilling to undertake. We introduce MOFs infiltrated with titanium and nickel species as catalysts for the C-O bond hydrogenolysis in model compounds, which mimic the b-O-4, a-O-4, and 4-O-5 linkages of natural lignin. The versatile IRMOF-74(n) series is proposed as a platform for creating efficient hydrogenolysis catalysts as it not only displays tunable pore sizes, but also has the required thermal and chemical stability. The catalytic C-O bond cleavage occurs at 10 bar hydrogen pressure and temperatures as low as 120 degC. The conversion efficiency of the aromatic ether substrates into the corresponding hydrocarbons and phenols varies as PhCH 2 CH 2 OPh > PhCH 2 OPh > PhOPh (Ph = phenyl), while the catalytic activity generally follows the following trend Ni@IRMOF-74>Ti@IRMOF-74>IRMOF-74. Conversions as high as 80%, coupled with good selectivity for hydrogenolysis vs. hydrogenation, highlight the potential of MOF-based catalysts for the selective cleavage of recalcitrant aryl-ether bonds found in lignin and other biopolymers. This project supports the DOE Integrated Biorefinery Program goals, the objective of which is to convert biomass to fuels and high-value chemicals, by addressing an important technology gap: the lack of low-temperature catalysts suitable for industrial lignin degradation. Biomass, which is %7E30 wt% lignin, constitutes a potentially major source of platform chemicals that could improve overall profitability and productivity of all energy-related products, thereby benefiting consumers and reducing national dependence on imported oil. Additionally, DoD has a strong interest in low-cost drop-in fuels (Navy Biofuel Initiative) and has signed a Memorandum of Understanding with DOE and USDA to develop a sustainable biofuels industry.
Electro-optical organic materials hold great promise for the development of high-efficiency devices based on exciton formation and dissociation, such as organic photovoltaics (OPV) and organic light-emitting devices (OLEDs). However, the external quantum efficiency (EQE) of both OPV and OLEDs must be improved to make these technologies economical. Efficiency rolloff in OLEDs and inability to control morphology at key OPV interfaces both reduce EQE. Only by creating materials that allow manipulation and control of the intimate assembly and communication between various nanoscale excitonic components can we hope to first understand and then engineer the system to allow these materials to reach their potential. The aims of this proposal are to: 1) develop a paradigm-changing platform for probing excitonic processes composed of Crystalline Nanoporous Frameworks (CNFs) infiltrated with secondary materials (such as a complimentary semiconductor); 2) use them to probe fundamental aspects of excitonic processes; and 3) create prototype OPVs and OLEDs using infiltrated CNF as active device components. These functional platforms will allow detailed control of key interactions at the nanoscale, overcoming the disorder and limited synthetic control inherent in conventional organic materials. CNFs are revolutionary inorganic-organic hybrid materials boasting unmatched synthetic flexibility that allow tuning of chemical, geometric, electrical, and light absorption/generation properties. For example, bandgap engineering is feasible and polyaromatic linkers provide tunable photon antennae; rigid 1-5 nm pores provide an oriented, intimate host for triplet emitters (to improve light emission in OLEDs) or secondary semiconducting polymers (creating a charge-separation interface in OPV). These atomically engineered, ordered structures will enable critical fundamental questions to be answered concerning charge transport, nanoscale interfaces, and exciton behavior that are inaccessible in disordered systems. Implementing this concept also creates entirely new dimensions for device fabrication that could both improve performance, increase durability, and reduce costs with unprecedented control of over properties. This report summarizes the key results of this project and is divided into sections based on publications that resulted from the work. We begin in Section 2 with an investigation of light harvesting and energy transfer in a MOF infiltrated with donor and acceptor molecules of the type typically used in OPV devices (thiophenes and fullerenes, respectively). The results show that MOFs can provide multiple functions: as a light harvester, as a stabilizer and organizer or the infiltrated molecules, and as a facilitator of energy transfer. Section 3 describes computational design of MOF linker groups to accomplish light harvesting in the visible and facilitate charge separation and transport. The predictions were validated by UV-visible absorption spectroscopy, demonstrating that rational design of MOFs for light-harvesting purposes is feasible. Section 4 extends the infiltration concept discussed in Section to, which we now designate as "Molecule@MOF" to create an electrically conducting framework. The tailorability and high conductivity of this material are unprecedented, meriting publication in the journal Science and spawning several Technical Advances. Section 5 discusses processes we developed for depositing MOFs as thin films on substrates, a critical enabling technology for fabricating MOF-based electronic devices. Finally, in Section 6 we summarize results showing that a MOF thin film can be used as a sensitizer in a DSSC, demonstrating that MOFs can serve as active layers in excitonic devices. Overall, this project provides several crucial proofs-of- concept that the potential of MOFs for use in optoelectronic devices that we predicted several years ago [ 3 ] can be realized in practice.
With over 5 billion cellphones in a world of 7 billion inhabitants, mobile phones are the most quickly adopted consumer technology in the history of the world. Miniaturized, power-efficient sensors, especially video-capable cameras, are becoming extremely widespread, especially when one factors in wearable technology like Apples Pebble, GoPro video systems, Google Glass, and lifeloggers. Tablet computers are becoming more common, lighter weight, and power-efficient. In this report the authors explore recent developments in mobile computing and their potential application to on-site inspection for arms control verification and treaty compliance determination. We examine how such technology can effectively be applied to current and potential future inspection regimes. Use cases are given for both host-escort and inspection teams. The results of field trials and their implications for on-site inspections are discussed.
We have theoretically and experimentally investigated the possibility of single atom deposition using laser cooled sources. In our theoretical work, we investigated an atom source composed of out-coupling from a Bose-Einstein condensate in a trap. A model was developed for Bose-Einstein-condensate-based devices. To illustrate its application, a 2-well system is studied. The results show interesting and possibly useful differences between operation with coherent (phased-locked) and incoherent (unlocked) population transfer between levels in the two wells. The two modes of operation are governed by an interplay among scattering, energy renormalizations and coupling between wells. In parallel, we have experimentally investigated the possibility of controlled deposition of single cesium atoms onto surfaces using optical tweezers. We have measured the rate limit for translation of single atoms in optical tweezers to be 45 mm/s for stepped translation, and have constructed an apparatus for deposition of single atoms on a sapphire substrate for future work.
Wind turbines have grown in size and capacity with today's average turbine having a power capacity of around 1.9 MW, reaching to heights of over 495 feet from ground to blade tip, and operating with speeds at the tip of the blade up to 200 knots. When these machines are installed within the line-of-sight of a radar system, they can cause significant clutter and interference, detrimentally impacting the primary surveillance radar (PSR) performance. The Massachusetts Institute of Technology's Lincoln Laboratory (MIT LL) and Sandia National Laboratories (SNL) were co-funded to conduct field tests and evaluations over two years in order to: I. Characterize the impact of wind turbines on existing Program-of-Record (POR) air surveillance radars; II. Assess near-term technologies proposed by industry that have the potential to mitigate the interference from wind turbines on radar systems; and III. Collect data and increase technical understanding of interference issues to advance development of long-term mitigation strategies. MIT LL and SNL managed the tests and evaluated resulting data from three flight campaigns to test eight mitigation technologies on terminal (short) and long-range (60 nmi and 250 nmi) radar systems. Combined across the three flight campaigns, more than 460 of hours of flight time were logged. This paper summarizes the Interagency Field Test & Evaluation (IFT&E) program and publicly- available results from the tests. It will also discuss the current wind turbine-radar interference evaluation process within the government and a proposed process to deploy mitigation technologies.
This report summarizes our development of spectroscopic chemical analysis techniques and spectral modeling for trace-gas measurements of highly-regulated low-concentration species present in flue gas emissions from utility coal boilers such as HCl under conditions of high humidity. Detailed spectral modeling of the spectroscopy of HCl and other important combustion and atmospheric species such as H 2 O, CO 2 , N 2 O, NO 2 , SO 2 , and CH 4 demonstrates that IR-laser spectroscopy is a sensitive multi-component analysis strategy. Experimental measurements from techniques based on IR laser spectroscopy are presented that demonstrate sub-ppm sensitivity levels to these species. Photoacoustic infrared spectroscopy is used to detect and quantify HCl at ppm levels with extremely high signal-to-noise even under conditions of high relative humidity. Additionally, cavity ring-down IR spectroscopy is used to achieve an extremely high sensitivity to combustion trace gases in this spectral region; ppm level CH 4 is one demonstrated example. The importance of spectral resolution in the sensitivity of a trace-gas measurement is examined by spectral modeling in the mid- and near-IR, and efforts to improve measurement resolution through novel instrument development are described. While previous project reports focused on benefits and complexities of the dual-etalon cavity ring-down infrared spectrometer, here details on steps taken to implement this unique and potentially revolutionary instrument are described. This report also illustrates and critiques the general strategy of IR- laser photodetection of trace gases leading to the conclusion that mid-IR laser spectroscopy techniques provide a promising basis for further instrument development and implementation that will enable cost-effective sensitive detection of multiple key contaminant species simultaneously.
Jove-Colon, Carlos F.; Weck, Philippe F.; Sassani, David H.; Zheng, Liange; Rutqvist, Jonny; Steefel, Carl I.; Kim, Kunhwi; Nakagawa, Seiji; Houseworth, James; Birkholzer, Jens; Caporuscio, Florie A.; Cheshire, Michael; Rearick, Michael S.; Mccarney, Mary K.; Zavarin, Mavrik; Benedicto, Ana; Kersting, Annie B.; Sutton, Mark; Jerden, James; Frey, Kurt E.; Copple, Jacqueline M.; Ebert, William
Radioactive waste disposal in shale/argillite rock formations has been widely considered given its desirable isolation properties (low permeability), geochemically reduced conditions, anomalous groundwater pressures, and widespread geologic occurrence. Clay/shale rock formations are characterized by their high content of clay minerals such as smectites and illites where diffusive transport and chemisorption phenomena predominate. These, in addition to low permeability, are key attributes of shale to impede radionuclide mobility. Shale host-media has been comprehensively studied in international nuclear waste repository programs as part of underground research laboratories (URLs) programs in Switzerland, France, Belgium, and Japan. These investigations, in some cases a decade or more long, have produced a large but fundamental body of information spanning from site characterization data (geological, hydrogeological, geochemical, geomechanical) to controlled experiments on the engineered barrier system (EBS) (barrier clay and seals materials). Evaluation of nuclear waste disposal in shale formations in the USA was conducted in the late 70’s and mid 80’s. Most of these studies evaluated the potential for shale to host a nuclear waste repository but not at the programmatic level of URLs in international repository programs.
This report describes a test of an instrumented surrogate PWR fuel assembly on a truck trailer conducted to simulate normal conditions of truck transport. The purpose of the test was to measure strains and accelerations on a Zircaloy-4 fuel rod during the transport of the assembly on the truck. This test complements tests conducted in FY13 in which the same assembly was placed on a shaker and subjected to vertical vibrations and shocks simulating truck transport. The results of those tests are in the report “FUEL ASSEMBLY SHAKER TEST for Determining Loads on a PWR Assembly under Surrogate Normal Conditions of Transport” McConnell, et al., SAND2013-5210P, Rev. 0.1, FCRD-UFD-2013-000190, June 30, 2013 (revised December 1, 2013). This report constitutes the Milestone M2FT-14SN0813041 for the DOE/NE Fuel Cycle Research and Development Used Fuel Disposition Campaign ST Transportation Work Package FT-14SN081304 (Rev. 1). The strains measured on the instrumented Zircaloy-4 rod over a 40.2 mile route in the Albuquerque area over a variety of road conditions – rough dirt to Interstate highway (Figure S.1) – never exceeded 150 µin./in. – a very low level of strain well below the elastic limit/yield strength of Zircaloy-4, Figure S.1. The strains measured in the truck test were slightly lower than those measured in the shaker tests.
The accompanying raw data is composslection. Each file is 3 columns and tab-delimited with the first column being the data address, the second column being the first byte of the data, and the third column being the second byte of the data.
Recent studies have assessed closed-loop supercritical carbon dioxide (s-CO2) Brayton cycles to be a higher energy-density system in comparison to equivalent superheated steam Rankine systems. At turbine inlet conditions of 700°C and 20 MPa, a cycle thermal efficiency of ~50% can be achieved. Achieving these high efficiencies will help concentrating solar power (CSP) technologies to become a competitive alternative to current power generation methods. To incorporate an s-CO2 Brayton power cycle in a solar power tower system, the development of a solar receiver capable of providing an outlet temperature of 700°C (at 20 MPa) is necessary. To satisfy the temperature requirements of an s-CO2 Brayton cycle with recuperation and recompression, the s-CO2 must undergo a temperature rise of ~200°C as it flows through the solar receiver. The main objective is to develop an optical-thermal-fluid and structural model to validate a tubular receiver that will receive a heat input ~0.33 MWth from the heliostat field at the National Solar Thermal Test Facility (NSTTF), Albuquerque, NM, USA. We also commenced the development of computational models and testing of air receivers being developed by the Indian Institute of Science (IISc) and the Indian Institute of Technology in Bombay (IIT-B). The helical tubular receiver is expected to counteract the effect of thermal expansion while using a cavity to reduce the radiative and convective losses. Initially, this receiver will be tested for a temperature range of 100-300°C under 1 MPa of pressurized air. The helical air receiver will be exposed to 10kWth to achieve a temperature rise of ~200°C. Preliminary tests to validate the modeling will be performed before the design and construction of a larger scale receiver. Lastly, I focused on the development of a new computational tool that would allow us to perform a nodal creep-fatigue analysis on the receivers and heat exchangers being developed. This tool was developed using MATLAB and is capable of processing the results obtained from ANSYS Fluent and Structural combined, which was limited when using commercial software. The main advantage of this code is that it can be modified to run in parallel making it more affordable and faster compared to commercial codes available. The code is in the process of validation and is currently being compared to nCode Design Life.
In this study, we introduce a simplification to the previously demonstrated hybrid Potts–phase field (hPPF), which relates interfacial energies to microstructural sharp interfaces. The model defines interfacial energy by a Potts-like discrete interface approach of counting unlike neighbors, which we use to compute local curvature. The model is compared to the hPPF by studying interfacial characteristics and grain growth behavior. The models give virtually identical results, while the new model allows the simulator more direct control of interfacial energy.
Iridium alloys are known to have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-strain -rate performance are needed for understanding high-speed impacts in severe environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain -rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. In this study, we analyzed the difficulties encountered in high-temperature Kolsky bar testing of thin iridium alloy specimens in compression. Appropriate modifications were then made to the current high-temperature Kolsky bar technique to obtain reliable compressive stress–strain response of an iridium alloy at high-strain rates (300–10 000 s-1) and temperatures (750 and 1030 °C). Finally, the compressive stress–strain response of the iridium alloy showed significant sensitivity to both strain rate and temperature.
A pair of redox flow batteries containing polyoxometalates was tested as part of an ongoing program in stationary energy storage. The iron-containing dimer, (SiFe3W9(OH)3O34) 2(OH)311-, cycled between (SiFe 3W9(OH)3O34)2(OH) 311-/(SiFe3W9(OH)3O 34)2(OH)314-and (SiFe 3W9(OH)3O34)2(OH) 317-/(SiFe3W9(OH)3O 34)2(OH)314- for the positive and negative electrode, respectively. This compound demonstrated a coulombic efficiency of 83% after 20 cycles with an electrochemical yield (measured discharge capacity as a percentage of theoretical capacity) of 55%. Cyclic voltammetry on the Lindqvist ion, cis-V2W4O 194-, showed quasi-reversible vanadium electrochemistry, but tungsten reduction was mostly irreversible. In a flow cell configuration, cis-V2W4O194-had a coulombic efficiency of 45% (for a two-electron process) and an electrochemical yield of 16% after 20 cycles. The poor performance of cis-V2W 4O194-was attributed primarily to its higher charge density. Collectively, the results showed that both polyoxometalate size and charge density are both important parameters to consider in battery material performance.
We assess the measurement of hyperspectral reflectance for the outdoor monitoring of green algae and cyanobacteria cultures with a multi-channel, fiber-coupled spectroradiometer. Reflectance data acquired over a four-week period are interpreted via numerical inversion of a reflectance model, in which the above-water reflectance is expressed as a quadratic function of the single backscattering albedo, dependent on the absorption and backscatter coefficients. The absorption coefficient is treated as the sum of component spectra consisting of the cultured species (green algae or cyanobacteria), dissolved organic matter, and water (including the temperature dependence of the water absorption spectrum). The backscatter coefficient is approximated as the scaled Hilbert transform of the culture absorption spectrum with a wavelength-independent vertical offset. Additional terms in the reflectance model account for the pigment fluorescence features and the water surface reflection of sunlight and skylight. For both the green algae and cyanobacteria, the wavelength-independent vertical offset of the backscatter coefficient is found to scale linearly with daily dry weight measurements, providing the capability for a non-sampling measurement of biomass in outdoor ponds. Other fitting parameters in the reflectance model are compared to auxiliary measurements and physics-based calculations. The magnitudes of the sunlight and skylight water-surface contributions derived from the reflectance model compare favorably with Fresnel reflectance calculations, while the reflectance-derived quantum efficiency of Chl-a fluorescence is found to be in agreement with literature values. To conlclude, the water temperature derived from the reflectance model exhibits excellent agreement with thermocouple measurements during the morning hours and highlights significantly elevated temperatures in the afternoon hours.
Flow cytometry in combination with fluorescent in situ hybridization (flow-FISH) is a powerful technique that can be utilized to rapidly detect nucleic acids at single-cell resolution without the need for homogenization or nucleic acid extraction. Here, we describe a microfluidic-based method which enables the detection of microRNAs or miRNAs in single intact cells by flow-FISH using locked nucleic acid (LNA)-containing probes. Our method can be applied to all RNA species including mRNA and small noncoding RNA and is suitable for multiplexing with protein immunostaining in the same cell. For demonstration of our method, this chapter details the detection of miR155 and CD69 protein in PMA and ionomycin-stimulated Jurkat cells. Here, we also include instructions on how to set up a microfluidic chip sample preparation station to prepare cells for imaging and analysis on a commercial flow cytometer or a custom-built micro-flow cytometer.
This work demonstrates the use of FIB implanted Ga as a lithographic mask for plasma etching of Nb films. Using a highly collimated Ga beam of a FIB, Nb is implanted 12 nm deep with a 14 nm thick Ga layer providing etch selectivity better than 15:1 with fluorine based etch chemistry. Implanted square test patterns, both 10 um by and 10 um and 100 um by 100 um, demonstrate that doses above than 7.5 x 1015 cm-2 at 30 kV provide adequate mask protection for a 205 nm thick, sputtered Nb film. The resolution of this dry lithographic technique is demonstrated by fabrication of nanowires 75 nm wide by 10 um long connected to 50 um wide contact pads. The residual resistance ratio of patterned Nb films was 3. The superconducting transition temperature, Tc =7.7 K, was measured using MPMS. This nanoscale, dry lithographic technique was extended to sputtered TiN and Ta here and could be used on other fluorine etched superconductors such as NbN, NbSi, and NbTi.
Genes for the RNA tmRNA and protein SmpB, partners in the trans-translation process that rescues stalled ribosomes, have previously been found in all bacteria and some organelles. We validate recent identification of tmRNA homologs in oomycete mitochondria by finding partner genes from oomycete nuclei that target SmpB to the mitochondrion. Exhaustive search now identifies a small number of complete, often highly derived, bacterial genomes that appear to lack a functional copy of one or the other partner gene (but not both). Three groups with reduced genomes have lost the central loop of SmpB, which is thought to improve alanylation and EF-Tu activation: Carsonella, Hodgkinia and the hemplasmas (hemotropic Mycoplasma). Carsonella has also lost the SmpB C-terminal tail, thought to stimulate the decoding center of the ribosome. Carsonella moreover exhibits gene overlap such that tmRNA maturation should produce a non-stop smpB mRNA, and one isolate exhibits complete degradation of the tmRNA gene yet its smpB shows no evidence for relaxed selective constraint. After loss of the SmpB central loop in the hemoplasmas, a subclade apparently lost tmRNA. At least some of the tmRNA/SmpB-deficient strains appear to further lack the ArfA and ArfB backup systems for ribosome rescue. The most frequent neighbors of smpB are the tmRNA gene, a ratA/rnfH unit, and the gene for RNaseR, a known physical and functional partner of tmRNA-SmpB. The tmRNA Website has moved and been updated, adding an SmpB sequence database (http://bioinformatics.sandia.gov/tmrna).
In this paper, we study the Bloch oscillations of a two-dimensional electron gas with a strong periodic potential-modulation and miniband transport along the field at low temperatures, assuming a free motion in the transverse direction. The dependence of the current on the field, the electron density, and the temperature is investigated by using a relaxation-time approximation for inelastic scattering. Moreover, for a fixed total scattering rate, the field dependence of the current is sensitive to the ratio of the elastic and inelastic scattering rates in contrast with the recent result of a multiband but otherwise similar model with a weak potential modulation.
Classical density functional theory (DFT) is used to calculate the structure of the electrical double layer and the differential capacitance of model molten salts. The DFT is shown to give good qualitative agreement with Monte Carlo simulations in the molten salt regime. The DFT is then applied to three common molten salts, KCl, LiCl, and LiKCl, modeled as charged hard spheres near a planar charged surface. The DFT predicts strong layering of the ions near the surface, with the oscillatory density profiles extending to larger distances for larger electrostatic interactions resulting from either lower temperature or lower dielectric constant. In conclusion, overall the differential capacitance is found to be bell-shaped, in agreement with recent theories and simulations for ionic liquids and molten salts, but contrary to the results of the classical Gouy-Chapman theory.
Proceedings of the National Academy of Sciences of the United States of America
Foulk, James W.; Wu, X.; Ward, D.R.; Prance, J.R.; Kim, Dohun; Mohr, R.T.; Shi, Zhan; Lagally, M.G.; Friesen, Mark; Coppersmith, S.N.; Eriksson, M.A.
The qubit is the fundamental building block of a quantum computer. We fabricate a qubit in a silicon double-quantum dot with an integrated micromagnet in which the qubit basis states are the singlet state and the spin-zero triplet state of two electrons. Because of the micromagnet, the magnetic field difference ΔB between the two sides of the double dot is large enough to enable the achievement of coherent rotation of the qubit’s Bloch vector around two different axes of the Bloch sphere. By measuring the decay of the quantum oscillations, the inhomogeneous spin coherence time T*2 is determined. Lastly, by measuring T*2 at many different values of the exchange coupling J and at two different values of ΔB, we provide evidence that the micromagnet does not limit decoherence, with the dominant limits on T*2 arising from charge noise and from coupling to nuclear spins.
This report and set of appendices are a collection of memoranda originally drafted circa 2007-2009 for the purpose of describing and detailing a models-based systems engineering approach for satisfying enterprise and system-of-systems life cycle process requirements. At the time there was interest and support to move from Capability Maturity Model Integration (CMMI) Level One (ad hoc processes) to Level Three. The main thrust of the material presents a rational exposâe of a structured enterprise development life cycle that uses the scientific method as a framework, with further rigor added from adapting relevant portions of standard systems engineering processes. While the approach described invokes application of the Department of Defense Architectural Framework (DoDAF), it is suitable for use with other architectural description frameworks.
The objective of this work was to characterize the neutron irradiation system consisting of americium-241 beryllium (241AmBe) neutron sources placed in a polyethylene shielding for use at Sandia National Laboratories (SNL) Low Dose Rate Irradiation Facility (LDRIF). With a total activity of 0.3 TBq (9 Ci), the source consisted of three recycled 241AmBe sources of different activities that had been combined into a single source. The source in its polyethylene shielding will be used in neutron irradiation testing of components. The characterization of the source-shielding system was necessary to evaluate the radiation environment for future experiments. Characterization of the source was also necessary because the documentation for the three component sources and their relative alignment within the Special Form Capsule (SFC) was inadequate. The system consisting of the source and shielding was modeled using Monte Carlo N-Particle transport code (MCNP). The model was validated by benchmarking it against measurements using multiple techniques. To characterize the radiation fields over the full spatial geometry of the irradiation system, it was necessary to use a number of instruments of varying sensitivities. First, the computed photon radiography assisted in determining orientation of the component sources. With the capsule properly oriented inside the shielding, the neutron spectra were measured using a variety of techniques. A N-probe Microspec and a neutron Bubble Dosimeter Spectrometer (BDS) set were used to characterize the neutron spectra/field in several locations. In the third technique, neutron foil activation was used to ascertain the neutron spectra. A high purity germanium (HPGe) detector was used to characterize the photon spectrum. The experimentally measured spectra and the MCNP results compared well. Once the MCNP model was validated to an adequate level of confidence, parametric analyses was performed on the model to optimize for potential experimental configurations and neutron spectra for component irradiation. The final product of this work is a MCNP model validated by measurements, an overall understanding of neutron irradiation system including photon/neutron transport and effective dose rates throughout the system, and possible experimental configurations for future irradiation of components.
Tonopah Test Range (TTR) in Nevada and Kauai Test Facility (KTF) in Hawaii are government-owned, contractor-operated facilities managed and operated by Sandia Corporation (Sandia), a wholly owned subsidiary of Lockheed Martin Corporation. The U.S. Department of Energy (DOE), National Nuclear Security Administration (NNSA), through the Sandia Field Office (SFO), in Albuquerque, New Mexico, administers the contract and oversees contractor operations at TTR and KTF. Sandia manages and conducts operations at TTR in support of the DOE/NNSA’s Weapons Ordnance Program and has operated the site since 1957. Navarro Research and Engineering subcontracts to Sandia in administering most of the environmental programs at TTR. Sandia operates KTF as a rocket preparation launching and tracking facility. This Annual Site Environmental Report summarizes data and the compliance status of the sustainability, environmental protection, and monitoring program at TTR and KTF through Calendar Year 2013. The compliance status of environmental regulations applicable at these sites include state and federal regulations governing air emissions, wastewater effluent, waste management, terrestrial surveillance, Environmental Restoration (ER) cleanup activities, and the National Environmental Policy Act. Sandia is responsible only for those environmental program activities related to its operations. The DOE/NNSA/Nevada Field Office retains responsibility for the cleanup and management of TTR ER sites. Environmental monitoring and surveillance programs are required by DOE Order 231.1B, Environment, Safety, and Health Reporting (DOE 2012).
Carbon-manganese steels are candidates for the structural materials in hydrogen gas pipelines; however, it is well known that these steels are susceptible to hydrogen embrittlement. Decades of research and industrial experience have established that hydrogen embrittlement compromises the structural integrity of steel components. This experience has also helped identify the failure modes that can operate in hydrogen containment structures. As a result, there are tangible ideas for managing hydrogen embrittlement in steels and quantifying safety margins for steel hydrogen containment structures. For example, fatigue crack growth aided by hydrogen embrittlement is a well-established failure mode for steel hydrogen containment structures subjected to pressure cycling. This pressure cycling represents one of the key differences in operating conditions between current hydrogen pipelines and those anticipated in a hydrogen delivery infrastructure. Applying structural integrity models in design codes coupled with measurement of relevant material properties allows quantification of the reliability/integrity of steel hydrogen pipelines subjected to pressure cycling. Furthermore, application of these structural integrity models is aided by the development of physics-based predictive models, which provide important insights such as the effects of microstructure on hydrogen-assisted fatigue crack growth. Successful implementation of these structural integrity and physics-based models enhances confidence in the design codes and enables decisions about materials selection and operating conditions for reliable and efficient steel hydrogen pipelines.
A principal challenge to the widespread adoption of hydrogen infrastructure is the lack of quantifiable data on its safety envelope and concerns about additional risk from hydrogen. To convince regulatory officials, local fire marshals, fuel suppliers, and the public at large that hydrogen refueling is safe for consumer use, the risk to personnel and bystanders must be quantified and minimized to an acceptable level. Such a task requires strong confidence in the safety performance of high pressure hydrogen systems. Developing meaningful materials characterization and qualification methodologies in addition to enhancing understanding of performance of materials is critical to eliminating barriers to the development of safe, low-cost, high-performance high-pressure hydrogen systems for the consumer environment.
Through the SNL New Mexico Small Business Assistance (NMSBA) program, several Sandia engineers worked with the Environmental Restoration Group (ERG) Inc. to verify and validate a novel algorithm used to determine the scanning Critical Level (L c ) and Minimum Detectable Concentration (MDC) (or Minimum Detectable Areal Activity) for the 102F scanning system. Through the use of Monte Carlo statistical simulations the algorithm mathematically demonstrates accuracy in determining the L c and MDC when a nearest-neighbor averaging (NNA) technique was used. To empirically validate this approach, SNL prepared several spiked sources and ran a test with the ERG 102F instrument on a bare concrete floor known to have no radiological contamination other than background naturally occurring radioactive material (NORM). The tests conclude that the NNA technique increases the sensitivity (decreases the L c and MDC) for high-density data maps that are obtained by scanning radiological survey instruments.
Electric field-induced reversal of spontaneous polarization is the defining characteristic of a ferroelectric material, but the process(es) and mechanism(s) associated with the initial nucleation of reverse-polarity domains are poorly understood. This report describes studies carried out using phase field modeling of LiTaO3, a relatively simple prototype ferroelectric material, in order to explore the effects of either mechanical deformation or optically-induced free charges on nucleation and resulting domain configuration during field-induced polarization reversal. Conditions were selected to approximate as closely as feasible those of accompanying experimental work in order to provide not only support for the experimental work but also ensure that additional experimental validation of the simulations could be carried out in the future. Phase field simulations strongly support surface mechanical damage/deformation as effective for dramatically reducing the overall coercive field (Ec) via local field enhancements. Further, optically-nucleated polarization reversal appears to occur via stabilization of latent nuclei via the charge screening effects of free charges.
The Reference Model Project (RMP), sponsored by the U.S. Department of Energy’s (DOE) Wind and Water Power Technologies Program within the Office of Energy Efficiency & Renewable Energy (EERE), aims at expediting industry growth and efficiency by providing non-proprietary Reference Models (RM) of MHK technology designs as study objects for open-source research and development (Neary et al. 2014a,b). As part of this program, MHK turbine models were tested in a large open channel facility at the University of Minnesota’s St. Anthony Falls Laboratory (UMN - SAFL) . Reference Model 2 (RM2) is a 1:15 geometric scale dual - rotor cross flow vertical axis device with counter - rotating rotors, each with a rotor diameter dT = 0.43m and rotor height, hT = 0.323 m. RM2 is a river turbine designed for a site modeled after a reach in the lower Mississippi River near Baton Rouge, Louisiana (Barone et al. 2014) . Precise blade angular position and torque measurements were synchronized with three acoustic Doppler velocimeters (ADV) aligned with each rotor and the midpoint for RM2 . Flow conditions for each case were controlled such that depth, h = 1m, and volumetric flow rate, Qw = 2. 35m3s-1 , resulting in a hub height velocity of approximately Uhub = 1. 2 ms-1 and blade chord length Reynolds numbers of Rec = 6 .1x104. Vertical velocity profiles collected in the wake of each device from 1 to 10 rotor diameters are used to estimate the velocity recovery and turbulent characteristics in the wake, as well as the interaction of the counter-rotating rotor wakes. The development of this high resolution laboratory investigation provides a robust dataset that enables assessing computational fluid dynamics (CFD) models and their ability to accurately simulate turbulent inflow environments, device performance metrics, and to reproduce wake velocity deficit, recovery and higher order turbulent statistics.
Current techniques for building detection in Synthetic Aperture Radar (SAR) imagery can be computationally expensive and/or enforce stringent requirements for data acquisition. The desire is to present a technique that is effective and efficient at determining an approximate building location. This approximate location can be used to extract a portion of the SAR image to then perform a more robust detection. The proposed technique assumes that for the desired image, bright lines and shadows, SAR artifact effects, are approximately labeled. These labels are enhanced and utilized to locate buildings, only if the related bright lines and shadows can be grouped. In order to find which of the bright lines and shadows are related, all of the bright lines are connected to all of the shadows. This allows the problem to be solved from a connected graph viewpoint. Where the nodes are the bright lines and shadows and the arcs are the connections between bright lines and shadows. Constraints based on angle of depression and the relationship between connected bright lines and shadows are applied to remove unrelated arcs. Once the related bright lines and shadows are grouped, their locations are combined to provide an approximate building location. Experimental results are provided showing the outcome of the technique.
The purpose of this report is to document a basic installation of the Anasazi eigensolver package and provide a brief discussion on the numerical solution of some graph eigenvalue problems.
In modern multi-sensor multi-mode Intelligence, Surveillance, and Reconnaissance (ISR) platforms, the plethora of options available to a sensor/payload operator are quite large, leading to an over-worked operator often down-selecting to favorite sensors and modes. For example, Full Motion Video (FMV) is justifiably a favorite sensor at the expense of radar modes, even if radar modes can offer unique and advantageous information. The challenge is then to increase the utilization of the radar modes in a manner attractive to the sensor/payload operator. We propose that this is best accomplished by combining sensor modes and displays into ‘super-modes’.
We have been using RedSky to investigate the physics of donor atoms in silicon for use as qubits for quantum computing. Quantum computing promises to dramatically change the performance of certain algorithms; this work is part of a quantum computing project led by Malcolm Carroll. We have investigated the magnitude of energy barriers for transferring electrons between donor centers and to elecrostaticallydefined quantum dots at the silicon oxide interface. Understanding these barriers helps us design structures that we think will be robust to noise and decoherence effects, and will help us understand experimental results as we build preliminary structures. There are only a few other research groups in the world conducting research along these lines. The work has been an important element of understanding the design principles that constrain computing devices at low temperature. We will continue this work in the future, in particular to analyze experimental results we anticipate coming from CINT collaborators.
This report consolidates technical information on several materials and material classes for a fire assessment. The materials include three polymeric materials, wood, and hydraulic oil. The polymers are polystyrene, polyurethane, and melamine- formaldehyde foams. Samples of two of the specific materials were tested for their behavior in a fire - like environment. Test data and the methods used to test the materials are presented. Much of the remaining data are taken from a literature survey. This report serves as a reference source of properties necessary to predict the behavior of these materials in a fire.
The Unstructured Time - Domain ElectroMagnetics (UTDEM) portion of the EMPHASIS suite solves Maxwell's equations using finite - element techniques on unstructured meshes. This document provides user - specific information to facilitate the use of the code for ap plications of interest. Acknowledgement The authors would like to thank all of those individuals who have helped to bring EMPHASIS/Nevada to the point it is today, including Bill Bohnhoff, Rich Drake, and all of the NEVADA code team.