14 CFR 93.125 - Arrival or departure reservation.

Code of Federal Regulations, 2012 CFR

2012-01-01

... (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports... may operate an aircraft to or from an airport designated as a high density traffic airport unless he...

14 CFR 93.125 - Arrival or departure reservation.

Code of Federal Regulations, 2013 CFR

2013-01-01

... (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports... may operate an aircraft to or from an airport designated as a high density traffic airport unless he...

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

DOE PAGES

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Yong; ...

2016-02-11

Here we demonstrate for the first time that planar Na-NiCl 2 batteries can be operated at an intermediate temperature of 190°C with ultra-high energy density. A specific energy density of 350 Wh/kg, which is 3 times higher than that of conventional tubular Na-NiCl 2 batteries operated at 280°C, was obtained for planar Na-NiCl 2 batteries operated at 190°C over a long-term cell test (1000 cycles). The high energy density and superior cycle stability are attributed to the slower particle growth of the cathode materials (NaCl and Ni) at 190°C. The results reported in this work demonstrate that planar Na-NiCl 2more » batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.« less

14 CFR 93.213 - Definitions and general provisions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Carrier IFR Operations at High Density Traffic Airports § 93.213 Definitions and general provisions. (a... operation each day during a specific hour or 30 minute period at one of the High Density Traffic Airports...

14 CFR 93.219 - Allocation of slots for essential air service operations and applicable limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... SPECIAL AIR TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic... or from a High Density Traffic Airport under the Department of Transportation's Essential Air Service...

14 CFR 93.217 - Allocation of slots for international operations and applicable limitations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic Airports § 93... available, additional slots during the high density hours shall be allocated at Kennedy Airport for new...

75 FR 9017 - Orders Limiting Scheduled Operations at John F. Kennedy International Airport, LaGuardia Airport...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-26

...; High Density Rule at Reagan National Airport AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... by February 16. Under the FAA's High Density Rule and orders limiting scheduled operations at the...

14 CFR 93.217 - Allocation of slots for international operations and applicable limitations.

Code of Federal Regulations, 2011 CFR

2011-01-01

... TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic Airports § 93... available, additional slots during the high density hours shall be allocated at Kennedy Airport for new...

14 CFR 93.217 - Allocation of slots for international operations and applicable limitations.

Code of Federal Regulations, 2014 CFR

2014-01-01

... TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic Airports § 93... available, additional slots during the high density hours shall be allocated at Kennedy Airport for new...

14 CFR 93.217 - Allocation of slots for international operations and applicable limitations.

Code of Federal Regulations, 2013 CFR

2013-01-01

... TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic Airports § 93... available, additional slots during the high density hours shall be allocated at Kennedy Airport for new...

14 CFR 93.219 - Allocation of slots for essential air service operations and applicable limitations.

Code of Federal Regulations, 2013 CFR

2013-01-01

... SPECIAL AIR TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic... or from a High Density Traffic Airport under the Department of Transportation's Essential Air Service...

14 CFR 93.217 - Allocation of slots for international operations and applicable limitations.

Code of Federal Regulations, 2012 CFR

2012-01-01

... TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic Airports § 93... available, additional slots during the high density hours shall be allocated at Kennedy Airport for new...

14 CFR 93.219 - Allocation of slots for essential air service operations and applicable limitations.

Code of Federal Regulations, 2014 CFR

2014-01-01

... SPECIAL AIR TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic... or from a High Density Traffic Airport under the Department of Transportation's Essential Air Service...

14 CFR 93.219 - Allocation of slots for essential air service operations and applicable limitations.

Code of Federal Regulations, 2011 CFR

2011-01-01

... SPECIAL AIR TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic... or from a High Density Traffic Airport under the Department of Transportation's Essential Air Service...

14 CFR 93.219 - Allocation of slots for essential air service operations and applicable limitations.

Code of Federal Regulations, 2012 CFR

2012-01-01

... SPECIAL AIR TRAFFIC RULES Allocation of Commuter and Air Carrier IFR Operations at High Density Traffic... or from a High Density Traffic Airport under the Department of Transportation's Essential Air Service...

The quiescent H-mode regime for high performance edge localized mode-stable operation in future burning plasmas [The quiescent H-mode regime for high performance ELM-stable operation in future burning plasmas

DOE PAGES

Garofalo, Andrea M.; Burrell, Keith H.; Eldon, David; ...

2015-05-26

For the first time, DIII-D experiments have achieved stationary quiescent H-mode (QH-mode) operation for many energy confinement times at simultaneous ITER-relevant values of beta, confinement, and safety factor, in an ITER similar shape. QH-mode provides excellent energy confinement, even at very low plasma rotation, while operating without edge localized modes (ELMs) and with strong impurity transport via the benign edge harmonic oscillation (EHO). By tailoring the plasma shape to improve the edge stability, the QH-mode operating space has also been extended to densities exceeding 80% of the Greenwald limit, overcoming the long-standing low-density limit of QH-mode operation. In the theory,more » the density range over which the plasma encounters the kink-peeling boundary widens as the plasma cross-section shaping is increased, thus increasing the QH-mode density threshold. Here, the DIII-D results are in excellent agreement with these predictions, and nonlinear MHD analysis of reconstructed QH-mode equilibria shows unstable low n kink-peeling modes growing to a saturated level, consistent with the theoretical picture of the EHO. Furthermore, high density operation in the QH-mode regime has opened a path to a new, previously predicted region of parameter space, named “Super H-mode” because it is characterized by very high pedestals that can be more than a factor of two above the peeling-ballooning stability limit for similar ELMing H-mode discharges at the same density.« less

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density.

PubMed

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y; Meinhardt, Kerry D; Chang, Hee Jung; Canfield, Nathan L; Sprenkle, Vincent L

2016-02-11

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg(-1), higher than that of conventional tubular sodium-nickel chloride batteries (280 °C), is obtained for planar sodium-nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

NASA Astrophysics Data System (ADS)

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y.; Meinhardt, Kerry D.; Chang, Hee Jung; Canfield, Nathan L.; Sprenkle, Vincent L.

2016-02-01

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg-1, higher than that of conventional tubular sodium-nickel chloride batteries (280 °C), is obtained for planar sodium-nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.

Library Off-Site Shelving: Guide for High-Density Facilities.

ERIC Educational Resources Information Center

Nitecki, Danuta A., Ed.; Kendrick, Curtis L., Ed.

This collection of essays addresses the planning, construction, and operating issues relating to high-density library shelving facilities. The volume covers essential topics that address issues relating to the building, its operations, and serving the collections. It begins with an introduction by the volume's editors, "The Paradox and…

Raising the Bar: Increased Hydraulic Pressure Allows Unprecedented High Power Densities in Pressure-Retarded Osmosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Straub, AP; Yip, NY; Elimelech, M

2014-01-01

Pressure-retarded osmosis (PRO) has the potential to generate sustainable energy from salinity gradients. PRO is typically considered for operation with river water and seawater, but a far greater energy of mixing can be harnessed from hypersaline solutions. This study investigates the power density that can be obtained in PRO from such concentrated solutions. Thin-film composite membranes with an embedded woven mesh were supported by tricot fabric feed spacers in a specially designed crossflow cell to maximize the operating pressure of the system, reaching a stable applied hydraulic pressure of 48 bar (700 psi) for more than 10 h. Operation atmore » this increased hydraulic pressure allowed unprecedented power densities, up to 60 W/m(2) with a 3 M (180 g/L) NaCl draw solution. Experimental power densities demonstrate reasonable agreement with power densities modeled using measured membrane properties, indicating high-pressure operation does not drastically alter membrane performance. Our findings exhibit the promise of the generation of power from high-pressure PRO with concentrated solutions.« less

Advanced intermediate temperature sodium–nickel chloride batteries with ultra-high energy density

PubMed Central

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y.; Meinhardt, Kerry D.; Chang, Hee Jung; Canfield, Nathan L.; Sprenkle, Vincent L.

2016-01-01

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium–nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg−1, higher than that of conventional tubular sodium–nickel chloride batteries (280 °C), is obtained for planar sodium–nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium–nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs. PMID:26864635

75 FR 72858 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-26

... Activities: Requests for Comments; Clearance of Renewed Approval of Information Collection: High Density... records of slot transfers at High Density Traffic Airports. The information is provided by air carriers and commuter operators, or other persons holding a slot at High Density Airports. DATES: Written...

75 FR 52802 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-27

... Activities: Requests for Comments; Clearance of Renewed Approval of Information Collection: High Density... maintain accurate records of slot transfers at High Density Traffic Airports. The information is provided by air carriers and commuter operators, or other persons holding a slot at High Density Airports...

The major results from W7-AS stellarator

NASA Astrophysics Data System (ADS)

Wagner, Friedrich

2002-11-01

W7-AS has terminated operation this summer. In the last phase, W7-AS was equipped with an island divertor using the natural edge islands of the low-shear, n=5 design. NBI heating has been done with co-injection (3 MW), ECRH was successfully extended to high density with the OXB scheme, and ICRH was applied in all standard modes but also in beach wave heating. The island divertor allowed high β and provided excellent exhaust conditions thanks to the accessibility to high densities (ne <= 4 × 10^20 m-3). 3D edge modelling with the EMC3-EIRENE code predicted and explained the absence of the high-recycling regime and the low-density high-temperature momentum losses associated with the prominent role of the cross-field transport. The confinement of W7-AS is determined by two concept dependent features low shear and 3D geometry: τE depends strongly on low-order rationals; in the plasma core the neo-classical bifurcation between ion and electron roots is observed. A distinct difference to tokamaks is the lack of Te - profile resilience. The H-mode operational range is governed by poloidal flow damping. At high density, a further bifurcation appears into a regime characterised by good energy and low impurity confinement (HDH). Because of its appealing features, this regime will be described in detail. The most visible MHD are beam driven global Alfven modes and ELMs. The operational limits are set by NBI power: The balance of heating and edge radiation determines the density limit; the maximal β is limited to 3.1%. The operation at high densities and high β is quiescent and quasi-steady state. The intrinsic stellarator features - steady state and no disruptions - remain close to operational limits. The results of W7-AS confirm the design criteria of W7-X and contribute to establish the stellarator line as independent route to a reactor.

High density operation for reactor-relevant power exhaust

NASA Astrophysics Data System (ADS)

Wischmeier, M.; ASDEX Upgrade Team; Jet Efda Contributors

2015-08-01

With increasing size of a tokamak device and associated fusion power gain an increasing power flux density towards the divertor needs to be handled. A solution for handling this power flux is crucial for a safe and economic operation. Using purely geometric arguments in an ITER-like divertor this power flux can be reduced by approximately a factor 100. Based on a conservative extrapolation of current technology for an integrated engineering approach to remove power deposited on plasma facing components a further reduction of the power flux density via volumetric processes in the plasma by up to a factor of 50 is required. Our current ability to interpret existing power exhaust scenarios using numerical transport codes is analyzed and an operational scenario as a potential solution for ITER like divertors under high density and highly radiating reactor-relevant conditions is presented. Alternative concepts for risk mitigation as well as strategies for moving forward are outlined.

14 CFR 93.121 - Applicability.

Code of Federal Regulations, 2010 CFR

2010-01-01

... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.121 Applicability. This subpart designates high density traffic airports and prescribes air traffic rules for...

14 CFR 93.121 - Applicability.

Code of Federal Regulations, 2012 CFR

2012-01-01

... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.121 Applicability. This subpart designates high density traffic airports and prescribes air traffic rules for...

14 CFR 93.121 - Applicability.

Code of Federal Regulations, 2014 CFR

2014-01-01

... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.121 Applicability. This subpart designates high density traffic airports and prescribes air traffic rules for...

14 CFR 93.121 - Applicability.

Code of Federal Regulations, 2011 CFR

2011-01-01

... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.121 Applicability. This subpart designates high density traffic airports and prescribes air traffic rules for...

14 CFR 93.121 - Applicability.

Code of Federal Regulations, 2013 CFR

2013-01-01

... AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.121 Applicability. This subpart designates high density traffic airports and prescribes air traffic rules for...

Operation of the ORNL High Particle Flux Helicon Plasma Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goulding, R. H.; Biewer, T. M.; Caughman, J. B. O.

2011-12-23

A high power, high particle flux rf-based helicon plasma source has been constructed at ORNL and operated at power levels up to 30 kW. High-density hydrogen and helium plasmas have been produced. The source has been designed as the basis for a linear plasma materials interaction (PMI) test facility that will generate particle fluxes {Gamma}{sub p}10{sup 23} m{sup -3} s{sup -1}, and utilize additional ion and electron cyclotron heating to produce high parallel (to the magnetic field) heat fluxes of {approx}10 MW/m{sup 2}. An rf-based source for PMI research is of interest because high plasma densities are generated with nomore » internal electrodes, allowing true steady state operation with minimal impurity generation. The ORNL helicon source has a diameter of 15 cm and to-date has operated at a frequency f = 13.56 MHz, with magnetic field strength |B| in the antenna region up to {approx}0.15 T. Maximum densities of 3x10{sup 19} m{sup -3} in He and 2.5x10{sup 19} m{sup -3} in H have been achieved. Radial density profiles have been seen to be dependent on the axial |B| profile.« less

Operation of the ORNL High Particle Flux Helicon Plasma Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goulding, Richard Howell; Biewer, Theodore M; Caughman, John B

2011-01-01

A high power, high particle flux rf-based helicon plasma source has been constructed at ORNL and operated at power levels up to 30 kW. High-density hydrogen and helium plasmas have been produced. The source has been designed as the basis for a linear plasma materials interaction (PMI) test facility that will generate particle fluxes Gamma(p) > 10(23) M-3 s(-1), and utilize additional ion and electron cyclotron heating to produce high parallel (to the magnetic field) heat fluxes of similar to 10 MW/m(2). An rf-based source for PMI research is of interest because high plasma densities are generated with no internalmore » electrodes, allowing true steady state operation with minimal impurity generation. The ORNL helicon source has a diameter of 15 cm and to-date has operated at a frequency f = 13.56 MHz, with magnetic field strength vertical bar B vertical bar in the antenna region up to similar to 0.15 T. Maximum densities of 3 x 10(19) M-3 in He and 2.5 x 10(19) m(-3) in H have been achieved. Radial density profiles have been seen to be dependent on the axial vertical bar B vertical bar profile.« less

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions.

PubMed

Martins, Vitor L; Rennie, Anthony J R; Sanchez-Ramirez, Nedher; Torresi, Roberto M; Hall, Peter J

2018-02-01

Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN) 4 ] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm -1 ). Herein, we report the use of ILs containing the [B(CN) 4 ] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two-electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g -1 @ 15 A g -1 ). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs.

The low density type III ELMy H-mode regime on JET-ILW: a low density H-mode compatible with a tungsten divertor?

NASA Astrophysics Data System (ADS)

Delabie, E.; Hillesheim, J. C.; Mailloux, J.; Maggi, C. F.; Rimini, F.; Solano, E. R.; JET contributors Team

2016-10-01

The threshold power to access H-mode on JET-ILW has a minimum as function of density. Power ramps in the low and high density branch show qualitatively very different behavior above threshold. In the high density branch, edge density and temperature abruptly increase after the L-H transition, and the plasma evolves into a type I ELMy H-mode. Transitions in the low density branch are gradual and lead to the formation of a temperature pedestal, without increase in edge density. These characteristics are reminiscent of the I-mode regime, but with high frequency ELM activity. The small ELMs allow stable H-mode operation with tolerable tungsten contamination, as long as both density and power stay below the type I ELM boundary. The density range in which the low density branch can be accessed scales favourably with toroidal field but unfavourably with isotope mass. At BT=3.4T, a stable H-mode has been obtained at = 2.9 1019 m-3 with up to 15 MW of heating power at H98y 0.9. Better knowledge of the operational boundaries of this high frequency ELM regime could provide insight in how to sustain it at higher heating power for high temperature scenarios. Work supported, in part, by the US DOE under Contract No. DE-AC05-00OR22725.

14 CFR 93.221 - Transfer of slots.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Operations at High Density Traffic Airports § 93.221 Transfer of slots. (a) Except as otherwise provided in... high density traffic airport. Transfers, including leases, shall comply with the following conditions...

14 CFR 93.221 - Transfer of slots.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Operations at High Density Traffic Airports § 93.221 Transfer of slots. (a) Except as otherwise provided in... high density traffic airport. Transfers, including leases, shall comply with the following conditions...

14 CFR 93.221 - Transfer of slots.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Operations at High Density Traffic Airports § 93.221 Transfer of slots. (a) Except as otherwise provided in... high density traffic airport. Transfers, including leases, shall comply with the following conditions...

14 CFR 93.221 - Transfer of slots.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Operations at High Density Traffic Airports § 93.221 Transfer of slots. (a) Except as otherwise provided in... high density traffic airport. Transfers, including leases, shall comply with the following conditions...

14 CFR 93.221 - Transfer of slots.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Operations at High Density Traffic Airports § 93.221 Transfer of slots. (a) Except as otherwise provided in... high density traffic airport. Transfers, including leases, shall comply with the following conditions...

Titanium Disulfide Coated Carbon Nanotube Hybrid Electrodes Enable High Energy Density Symmetric Pseudocapacitors.

PubMed

Zang, Xining; Shen, Caiwei; Kao, Emmeline; Warren, Roseanne; Zhang, Ruopeng; Teh, Kwok Siong; Zhong, Junwen; Wei, Minsong; Li, Buxuan; Chu, Yao; Sanghadasa, Mohan; Schwartzberg, Adam; Lin, Liwei

2018-02-01

While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS 2 ) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g -1 in an Li-rich electrolyte. A symmetric cell demonstrates an energy density of 60.9 Wh kg -1 -the highest among symmetric pseudocapacitors using metal oxides, conducting polymers, 2D transition metal carbides (MXene), and other transition metal dichalcogenides. Nanostructures prepared by an atomic layer deposition/sulfurization process facilitate ion transportation and surface reactions to result in a high power density of 1250 W kg -1 with stable operation over 10 000 cycles. A flexible solid-state supercapacitor prepared by transferring the TiS 2 -VACNT composite film onto Kapton tape is demonstrated to power a 2.2 V light emitting diode (LED) for 1 min. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garofalo, Andrea M.; Burrell, Keith H.; Eldon, David

For the first time, DIII-D experiments have achieved stationary quiescent H-mode (QH-mode) operation for many energy confinement times at simultaneous ITER-relevant values of beta, confinement, and safety factor, in an ITER similar shape. QH-mode provides excellent energy confinement, even at very low plasma rotation, while operating without edge localized modes (ELMs) and with strong impurity transport via the benign edge harmonic oscillation (EHO). By tailoring the plasma shape to improve the edge stability, the QH-mode operating space has also been extended to densities exceeding 80% of the Greenwald limit, overcoming the long-standing low-density limit of QH-mode operation. In the theory,more » the density range over which the plasma encounters the kink-peeling boundary widens as the plasma cross-section shaping is increased, thus increasing the QH-mode density threshold. Here, the DIII-D results are in excellent agreement with these predictions, and nonlinear MHD analysis of reconstructed QH-mode equilibria shows unstable low n kink-peeling modes growing to a saturated level, consistent with the theoretical picture of the EHO. Furthermore, high density operation in the QH-mode regime has opened a path to a new, previously predicted region of parameter space, named “Super H-mode” because it is characterized by very high pedestals that can be more than a factor of two above the peeling-ballooning stability limit for similar ELMing H-mode discharges at the same density.« less

Investigation of physical processes limiting plasma density in H-mode on DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maingi, R.; Mahdavi, M.A.; Jernigan, T.C.

1996-12-01

A series of experiments was conducted on the DIII-D tokamak to investigate the physical processes which limit density in high confinement mode (H-mode) discharges. The typical H-mode to low confinement mode (L-mode) transition limit at high density near the empirical Greenwald density limit was avoided by divertor pumping, which reduced divertor neutral pressure and prevented formation of a high density, intense radiation zone (MARFE) near the X-point. It was determined that the density decay time after pellet injection was independent of density relative to the Greenwald limit and increased non-linearly with the plasma current. Magnetohydrodynamic (MHD) activity in pellet-fueled plasmasmore » was observed at all power levels, and often caused unacceptable confinement degradation, except when the neutral beam injected (NBI) power was {le} 3 MW. Formation of MARFEs on closed field lines was avoided with low safety factor (q) operation but was observed at high q, qualitatively consistent with theory. By using pellet fueling and optimizing discharge parameters to avoid each of these limits, an operational space was accessed in which density {approximately} 1.5 {times} Greenwald limit was achieved for 600 ms, and good H-mode confinement was maintained for 300 ms of the density flattop. More significantly, the density was successfully increased to the limit where a central radiative collapse was observed, the most fundamental density limit in tokamaks.« less

Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator.

PubMed

Zhu, Yun Guang; Du, Yonghua; Jia, Chuankun; Zhou, Mingyue; Fan, Li; Wang, Xingzhu; Wang, Qing

2017-05-10

Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO 4 with a bifunctional redox mediator, 2,3,5,6-tetramethyl-p-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm 2 , and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO 4 , which provides insightful information on the redox targeting process, critical to the device operation and optimization.

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions

PubMed Central

Martins, Vitor L.; Rennie, Anthony J. R.; Sanchez‐Ramirez, Nedher; Torresi, Roberto M.; Hall, Peter J.

2018-01-01

Abstract Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN)4] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm−1). Herein, we report the use of ILs containing the [B(CN)4] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two‐electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g−1 @ 15 A g−1). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs. PMID:29577008

Large-Area Permanent-Magnet ECR Plasma Source

NASA Technical Reports Server (NTRS)

Foster, John E.

2007-01-01

A 40-cm-diameter plasma device has been developed as a source of ions for material-processing and ion-thruster applications. Like the device described in the immediately preceding article, this device utilizes electron cyclotron resonance (ECR) excited by microwave power in a magnetic field to generate a plasma in an electrodeless (noncontact) manner and without need for an electrically insulating, microwave-transmissive window at the source. Hence, this device offers the same advantages of electrodeless, windowless design - low contamination and long operational life. The device generates a uniform, high-density plasma capable of sustaining uniform ion-current densities at its exit plane while operating at low pressure [<10(exp -4) torr (less than about 1.3 10(exp -2) Pa)] and input power <200 W at a frequency of 2.45 GHz. Though the prototype model operates at 2.45 GHz, operation at higher frequencies can be achieved by straightforward modification to the input microwave waveguide. Higher frequency operation may be desirable in those applications that require even higher background plasma densities. In the design of this ECR plasma source, there are no cumbersome, power-hungry electromagnets. The magnetic field in this device is generated by a permanent-magnet circuit that is optimized to generate resonance surfaces. The microwave power is injected on the centerline of the device. The resulting discharge plasma jumps into a "high mode" when the input power rises above 150 W. This mode is associated with elevated plasma density and high uniformity. The large area and uniformity of the plasma and the low operating pressure are well suited for such material-processing applications as etching and deposition on large silicon wafers. The high exit-plane ion-current density makes it possible to attain a high rate of etching or deposition. The plasma potential is <3 V low enough that there is little likelihood of sputtering, which, in plasma processing, is undesired because it is associated with erosion and contamination. The electron temperature is low and does not vary appreciably with power.

Cascaded lattice Boltzmann method with improved forcing scheme for large-density-ratio multiphase flow at high Reynolds and Weber numbers.

PubMed

Lycett-Brown, Daniel; Luo, Kai H

2016-11-01

A recently developed forcing scheme has allowed the pseudopotential multiphase lattice Boltzmann method to correctly reproduce coexistence curves, while expanding its range to lower surface tensions and arbitrarily high density ratios [Lycett-Brown and Luo, Phys. Rev. E 91, 023305 (2015)PLEEE81539-375510.1103/PhysRevE.91.023305]. Here, a third-order Chapman-Enskog analysis is used to extend this result from the single-relaxation-time collision operator, to a multiple-relaxation-time cascaded collision operator, whose additional relaxation rates allow a significant increase in stability. Numerical results confirm that the proposed scheme enables almost independent control of density ratio, surface tension, interface width, viscosity, and the additional relaxation rates of the cascaded collision operator. This allows simulation of large density ratio flows at simultaneously high Reynolds and Weber numbers, which is demonstrated through binary collisions of water droplets in air (with density ratio up to 1000, Reynolds number 6200 and Weber number 440). This model represents a significant improvement in multiphase flow simulation by the pseudopotential lattice Boltzmann method in which real-world parameters are finally achievable.

[Nutritional status, body composition and bone mineral density in gastric bypass females: impact of socioeconomic level].

PubMed

de la Maza, María Pía; Leiva, Laura; Barrera, Gladys; Boggiano, Carolina; Herrera, Tomás; Pérez, Yanet; Gattás, Vivien; Bunout, Daniel; Hirsch, Sandra

2008-11-01

Roux-en-Y gastric bypass (RYGBP) has had a posilive impact on co-mobidities associated with obesity. However, in the long-term it can induce micronutrient deficiencies. To petform a complete nutritional assessment in a group of women previously operated of RYGBP from different socioeconomic levels (SEL). Thirtyy three women (19 high SEL and 14 low SEL), were assessed by dietary recalls, anthropometric measurements, muscle strength, bone mineral density, routine clinical laboratory, semm leeds of vitamin B12, 25OH-vitamin D, folate, calcium, ferritine ceruloplasmin and indicators of bone tutnoter (paratbohormone, osteocalcin and urinary pyridinolines). Their values were compared to those of 30 control women (18 high SEL and 12 low SEL). Low SEL operated women consumed fewer vitamin and mineral supplements compared with their high SEL pairs. No cases of vitamin B12, folic acid or copper deficiencies were detected. Frequency of iron deficiency was similar in patients and controls. Vitamin D insufficiency was higher among patients than in controls (p = 0.047), regardless SEL. Patients had also a higher frequency of high senum P771 and osteocakin and urinary pyridinoline levels. However, no differences in bone mineral density were obseived between operated women and controls. Vitamin and mineral deficiencies were lower than expected among operated women. However problems associated with vitamin D deficiency were highly prevalent among patients operated of RYGBP, irrespective SEL. These alterations were only detectable through specific markers at this stage, because they did not translate into lower bone mineral density (BMD) of sutgical patients, probably due to the higher pre-operative BMD of these moibid obese patients

76 FR 19517 - Orders Limiting Scheduled Operations at John F. Kennedy International Airport, LaGuardia Airport...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-07

... Liberty International Airport; High Density Rule at Reagan National Airport AGENCY: Federal Aviation... support for the ATA request for waiver. FAA Analysis Under the FAA's High Density Rule and Orders limiting...

High-Density Free Fluid on Computed Tomography: a Predictor of Surgical Intervention in Patients with Adhesive Small Bowel Obstruction.

PubMed

Matsushima, Kazuhide; Inaba, Kenji; Dollbaum, Ryan; Cheng, Vincent; Khan, Moazzam; Herr, Keith; Strumwasser, Aaron; Asturias, Sabrina; Dilektasli, Evren; Demetriades, Demetrios

2016-11-01

Patients with adhesive small bowel obstruction (ASBO) often develop intraabdominal free fluid (IFF). While IFF is a finding on abdominopelvic computed tomography (CT) associated with the need for surgical intervention, many patients with IFF can be still managed non-operatively. A previous study suggested that a higher red blood cell count of IFF is highly predictive of strangulated ASBO. We hypothesized that radiodensity in IFF (Hounsfield unit (HU)) on CT would predict the need for surgical intervention. Patients with clinicoradiological evidence of ASBO between January 2009 and December 2013 were identified. In patients with IFF > 3 cm 2 identified on CT, the HU was measured in the largest pocket of IFF. A sensitivity analysis was performed to determine a high-density HU threshold. The HU of patients who underwent therapeutic laparotomy was compared with those successfully discharged with non-operative management. A total of 318 patients with ASBO (median age 52 years, 56.0 % male) were identified. Of 111 patients who had IFF on CT, 55.9 % underwent therapeutic laparotomy and 15.3 % required bowel resection. Radiodensity of IFF in the operative group was significantly higher than that in the non-operative group (18.2 vs. 7.0 HU, p < 0.01). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of high-density IFF (>10 HU) to predict the need for surgical intervention were 83.9, 65.3, 75.4, 76.2, and 75.6 %, respectively. High-density IFF on CT was significantly associated with the need for surgical intervention in patients with ASBO. Prospective study to validate the predictive value of high-density IFF on CT will be warranted.

Highly-Ordered 3D Vertical Resistive Switching Memory Arrays with Ultralow Power Consumption and Ultrahigh Density.

PubMed

Al-Haddad, Ahmed; Wang, Chengliang; Qi, Haoyuan; Grote, Fabian; Wen, Liaoyong; Bernhard, Jörg; Vellacheri, Ranjith; Tarish, Samar; Nabi, Ghulam; Kaiser, Ute; Lei, Yong

2016-09-07

Resistive switching random access memories (RRAM) have attracted great scientific and industrial attention for next generation data storage because of their advantages of nonvolatile properties, high density, low power consumption, fast writing/erasing speed, good endurance, and simple and small operation system. Here, by using a template-assisted technique, we demonstrate a three-dimensional highly ordered vertical RRAM device array with density as high as that of the nanopores of the template (10(8)-10(9) cm(-2)), which can also be fabricated in large area. The high crystallinity of the materials, the large contact area and the intimate semiconductor/electrode interface (3 nm interfacial layer) make the ultralow voltage operation (millivolt magnitude) and ultralow power consumption (picowatt) possible. Our procedure for fabrication of the nanodevice arrays in large area can be used for producing many other different materials and such three-dimensional electronic device arrays with the capability to adjust the device densities can be extended to other applications of the next generation nanodevice technology.

High-density magnetoresistive random access memory operating at ultralow voltage at room temperature.

PubMed

Hu, Jia-Mian; Li, Zheng; Chen, Long-Qing; Nan, Ce-Wen

2011-11-22

The main bottlenecks limiting the practical applications of current magnetoresistive random access memory (MRAM) technology are its low storage density and high writing energy consumption. Although a number of proposals have been reported for voltage-controlled memory device in recent years, none of them simultaneously satisfy the important device attributes: high storage capacity, low power consumption and room temperature operation. Here we present, using phase-field simulations, a simple and new pathway towards high-performance MRAMs that display significant improvements over existing MRAM technologies or proposed concepts. The proposed nanoscale MRAM device simultaneously exhibits ultrahigh storage capacity of up to 88 Gb inch(-2), ultralow power dissipation as low as 0.16 fJ per bit and room temperature high-speed operation below 10 ns.

High-density magnetoresistive random access memory operating at ultralow voltage at room temperature

PubMed Central

Hu, Jia-Mian; Li, Zheng; Chen, Long-Qing; Nan, Ce-Wen

2011-01-01

The main bottlenecks limiting the practical applications of current magnetoresistive random access memory (MRAM) technology are its low storage density and high writing energy consumption. Although a number of proposals have been reported for voltage-controlled memory device in recent years, none of them simultaneously satisfy the important device attributes: high storage capacity, low power consumption and room temperature operation. Here we present, using phase-field simulations, a simple and new pathway towards high-performance MRAMs that display significant improvements over existing MRAM technologies or proposed concepts. The proposed nanoscale MRAM device simultaneously exhibits ultrahigh storage capacity of up to 88 Gb inch−2, ultralow power dissipation as low as 0.16 fJ per bit and room temperature high-speed operation below 10 ns. PMID:22109527

Selective magnetic resonance imaging (MRI) in invasive lobular breast cancer based on mammographic density: does it lead to an appropriate change in surgical treatment?

PubMed

Bansal, Gaurav J; Santosh, Divya; Davies, Eleri L

2016-01-01

The purpose of this study was to evaluate whether high mammographic density can be used as one of the selection criteria for MRI in invasive lobular breast cancer (ILC). In our institute, high breast density has been used as one of the indications for performing MRI scan in patients with ILC. We divided the patients in two groups, one with MRI performed pre-operatively and other without MRI. We compared their surgical procedures and analyzed whether surgical plan was altered after MRI. In case of alteration of plan, we analyzed whether the change was adequate by comparing post-operative histological findings. Between 2011 and 2015, there were a total of 1601 breast cancers with 97 lobular cancers, out of which 36 had pre-operative MRI and 61 had no MRI scan. 12 (33.3%) had mastectomy following MRI, out of which 9 (25%) had change in surgical plan from conservation to mastectomy following MRI. There were no unnecessary mastectomies in the MRI group. However, utilization of MRI in this cohort of patients did not reduce reoperation rate (19.3%). Lobular carcinoma in situ (LCIS) was identified in 60% of reoperations on post-surgical histology. Patients in the "No MRI" group had higher mastectomy rate 26 (42.6%), which was again appropriate. High mammographic density is a useful risk stratification criterion for selective MRI in ILC within a multidisciplinary team meeting setting. Provided additional lesions identified on MRI are confirmed with biopsy, pre-operative MRI does not cause unnecessary mastectomies. Used in this selective manner, reoperation rates were not eliminated, albeit reduced when compared to literature. High mammographic breast density can be used as one of the selection criteria for pre-operative MRI in ILC without an increase in inappropriate mastectomies with potential time and cost savings. In this cohort, re-excisions were not reduced markedly with pre-operative MRI.

Operation Everest II. Plasma Lipid and Hormonal Responses

DTIC Science & Technology

1988-01-01

cholesterol [TC] and high density lipoprotein cholesterol [ HDL -C] concentrations are shown in Fig 2. Pre-ascent...of altitude on fasting total cholesterol and high density lipoprotein ( HDL ) cholesterol concentrations. ** = p<O.Ol from 760 Torr Figure 3: The effect...157.7*9.7 mg/dl, decreased by 25% to .6 118.3*13.5 mg/dl following the 40-day exposure (p<O.Ol). High density lipoprotein [ HDL -C] levels

Advanced Electrical Materials and Components Being Developed

NASA Technical Reports Server (NTRS)

Schwarze, Gene E.

2004-01-01

All aerospace systems require power management and distribution (PMAD) between the energy and power source and the loads. The PMAD subsystem can be broadly described as the conditioning and control of unregulated power from the energy source and its transmission to a power bus for distribution to the intended loads. All power and control circuits for PMAD require electrical components for switching, energy storage, voltage-to-current transformation, filtering, regulation, protection, and isolation. Advanced electrical materials and component development technology is a key technology to increasing the power density, efficiency, reliability, and operating temperature of the PMAD. The primary means to develop advanced electrical components is to develop new and/or significantly improved electronic materials for capacitors, magnetic components, and semiconductor switches and diodes. The next important step is to develop the processing techniques to fabricate electrical and electronic components that exceed the specifications of presently available state-of-the-art components. The NASA Glenn Research Center's advanced electrical materials and component development technology task is focused on the following three areas: 1) New and/or improved dielectric materials for the development of power capacitors with increased capacitance volumetric efficiency, energy density, and operating temperature; 2) New and/or improved high-frequency, high-temperature soft magnetic materials for the development of transformers and inductors with increased power density, energy density, electrical efficiency, and operating temperature; 3) Packaged high-temperature, high-power density, high-voltage, and low-loss SiC diodes and switches.

Determining Usability Versus Cost and Yields of a Regional Transport

NASA Technical Reports Server (NTRS)

Gvozdenovic, Slobodan

1999-01-01

Regional transports are designed to operate on air networks having the basic characteristics of short trip distances and low density passengers/cargo, i.e. small numbers of passengers per flight. Regional transports passenger capacity is from 10 to 100 seats and operate on routes from 350 to 1000 nautical miles (nm). An air network operated by regional transports has the following characteristics: (1) connecting regional centers; (2) operating on low density passengers/cargo flow services with minimum two frequencies per day; (3) operating on high density passengers/cargo flow with more than two frequencies per day; and (4) operating supplemental services whenever market demands in order to help bigger capacity aircraft already operating the same routes. In order to meet passenger requirements providing low fares and high or required number of frequencies, airlines must constantly monitor operational costs and keep them low. It is obvious that costs of operating aircraft must be lower than yield obtained by transporting passengers and cargo. The requirement to achieve favorable yield/cost ratio must provide the answer to the question of which aircraft will best meet a specific air network. An air network is defined by the number of services, the trip distance of each service, and the number of flights (frequencies) per day and week.

High Energy Density Li-ion Cells for EV’s Based on Novel, High Voltage Cathode Material Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kepler, Keith D.; Slater, Michael

This Li-ion cell technology development project had three objectives: to develop advanced electrode materials and cell components to enable stable high-voltage operation; to design and demonstrate a Li-ion cell using these materials that meets the PHEV40 performance targets; and to design and demonstrate a Li-ion cell using these materials that meets the EV performance targets. The major challenge to creating stable high energy cells with long cycle life is system integration. Although materials that can give high energy cells are known, stabilizing them towards long-term cycling in the presence of other novel cell components is a major challenge. The majormore » technical barriers addressed by this work include low cathode specific energy, poor electrolyte stability during high voltage operation, and insufficient capacity retention during deep discharge for Si-containing anodes. Through the course of this project, Farasis was able to improve capacity retention of NCM materials for 4.4+ V operation, through both surface treatment and bulk-doping approaches. Other material advances include increased rate capability and of HE-NCM materials through novel synthesis approach, doubling the relative capacity at 1C over materials synthesized using standard methods. Silicon active materials proved challenging throughout the project and ultimately were the limiting factor in the energy density vs. cycle life trade off. By avoiding silicon anodes for the lower energy PHEV design, we manufactured cells with intermediate energy density and long cycle life under high voltage operation for PHEV applications. Cells with high energy density for EV applications were manufactured targeting a 300 Wh/kg design and were able to achieve > 200 cycles.« less

Small City Transit : East Chicago, Indiana : Free-Fare Transit in a High Density, Industrialized Area

DOT National Transportation Integrated Search

1976-03-01

East Chicago, Indiana, is an illustration of a free-fare transit service operating in a high density area. The transit service was devised with a minimum of help from professional consultants, and without sophisticated routing, scheduling, or marketi...

Plasma density behavior with new graphite limiters in the Hefei Tokamak-7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asif, M.; Gao, X.; Li, J.

A new set of actively cooled toroidal double-ring graphite limiters has been developed in the Hefei Tokamak-7 (HT-7) [X. Gao et al., Phys. Plasmas 7, 2933 (2000)] for long pulse operation. The extension of operational region and density behavior with graphite (C) limiters have been studied in this paper. Extended high-density region at the high plasma current low-q{sub a} was obtained. The density profile with the C limiter was studied to compare with the previous molybdenum (Mo) limiter. The critical density of multifaceted asymmetric radiation from the edge (MARFE) onset is observed in the region of Z{sub eff}{sup 1/2}f{sub GW}=0.9{approx}1.2,more » where f{sub GW}=n{sub e}/n{sub GW}. (Here n{sub e} is the maximum line average electron density and n{sub GW} is the Greenwald density.) Under the same injected power, the critical density of MARFE onset with the new C limiter is much higher than the previous Mo limiter.« less

High-power AlGaInN lasers for Blu-ray disc system

NASA Astrophysics Data System (ADS)

Takeya, Motonubu; Ikeda, Shinroh; Sasaki, Tomomi; Fujimoto, Tsuyoshi; Ohfuji, Yoshio; Mizuno, Takashi; Oikawa, Kenji; Yabuki, Yoshifumi; Uchida, Shiro; Ikeda, Masao

2003-07-01

This paper describes an improved laser structure for AlGaInN based blue-violet lasers (BV-LDs). The design realizes a small beam divergence angle perpendicular to the junction plane and high characteristic temperature wihtout significant increase in threshold current density (Jth) by optimizing the position of the Mg-doped layer and introducing an undoped AlGaN layer between the active layer and the Mg-doped electron-blocking layer. The mean time to failure (MTTF) of devices based on this design was found to be closely related to the dislocation density of ELO-GaN basal layer. Under 50 mW CW operation at 70°C, a MTTF of over 5000 h was realized whenthe dark spot density (indicative of dislocation density) is less than ~5×106 cm-2. Power consumption under 50mW CW operation at 70°C was approximately 0.33 W, independent of the dislocation density.

Numerical analyses of baseline JT-60SA design concepts with the COREDIV code

NASA Astrophysics Data System (ADS)

Zagórski, R.; Gałązka, K.; Ivanova-Stanik, I.; Stępniewski, W.; Garzotti, L.; Giruzzi, G.; Neu, R.; Romanelli, M.

2017-06-01

JT-60SA reference design scenarios at high (#3) and low (#2) density have been analyzed with the help of the self-consistent COREDIV code. Simulations results for a standard C wall and full W wall have been compared in terms of the influence of impurities, both intrinsic (C, W) and seeded (N, Ar, Ne, Kr), on the radiation losses and plasma parameters. For scenario #3 in a C environment, the regime of detachment on divertor plates can be achieved with N or Ne seeding, whereas for the low density and high power scenario (#2), the C and seeding impurity radiation does not effectively reduce power to the targets. In this case, only an increase of either average density or edge density together with Kr seeding might help to develop conditions with strong radiation losses and semi-detached conditions in the divertor. The calculations show that, in the case of a W divertor, the power load to the plate is mitigated by seeding and the central plasma dilution is smaller compared to the C divertor. For the high density case (#3) with Ne seeding, operation in full detachment mode is predicted. Ar seems to be an optimal choice for the low-density high-power scenario #2, showing a wide operating window, whereas Ne leads to high plasma dilution at high seeding levels albeit not achieving semi-detached conditions in the divertor.

Advanced Power Electronics Components

NASA Technical Reports Server (NTRS)

Schwarze, Gene E.

2004-01-01

This paper will give a description and status of the Advanced Power Electronics Materials and Components Technology program being conducted by the NASA Glenn Research Center for future aerospace power applications. The focus of this research program is on the following: 1) New and/or significantly improved dielectric materials for the development of power capacitors with increased volumetric efficiency, energy density, and operating temperature. Materials being investigated include nanocrystalline and composite ceramic dielectrics and diamond-like carbon films; 2) New and/or significantly improved high frequency, high temperature, low loss soft magnetic materials for the development of transformers/inductors with increased power/energy density, electrical efficiency, and operating temperature. Materials being investigated include nanocrystalline and nanocomposite soft magnetic materials; 3) Packaged high temperature, high power density, high voltage, and low loss SiC diodes and switches. Development of high quality 4H- and 6H- SiC atomically smooth substrates to significantly improve device performance is a major emphasis of the SiC materials program; 4) Demonstration of high temperature (> 200 C) circuits using the components developed above.

Investigating the origin of efficiency droop by profiling the temperature across the multi-quantum well of an operating light-emitting diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jung, Euihan; Hwang, Gwangseok; Chung, Jaehun

2015-01-26

Performance degradation resulting from efficiency droop during high-power operation is a critical problem in the development of high-efficiency light-emitting diodes (LEDs). In order to resolve the efficiency droop and increase the external quantum efficiency of LEDs, the droop's origin should be identified first. To experimentally investigate the cause of efficiency droop, we used null-point scanning thermal microscopy to quantitatively profile the temperature distribution on the cross section of the epi-layers of an operating GaN-based vertical LED with nanoscale spatial resolution at four different current densities. The movement of temperature peak towards the p-GaN side as the current density increases suggestsmore » that more heat is generated by leakage current than by Auger recombination. We therefore suspect that at higher current densities, current leakage becomes the dominant cause of the droop problem.« less

High density electronic circuit and process for making

DOEpatents

Morgan, William P.

1999-01-01

High density circuits with posts that protrude beyond one surface of a substrate to provide easy mounting of devices such as integrated circuits. The posts also provide stress relief to accommodate differential thermal expansion. The process allows high interconnect density with fewer alignment restrictions and less wasted circuit area than previous processes. The resulting substrates can be test platforms for die testing and for multi-chip module substrate testing. The test platform can contain active components and emulate realistic operational conditions, replacing shorts/opens net testing.

High accuracy satellite drag model (HASDM)

NASA Astrophysics Data System (ADS)

Storz, M.; Bowman, B.; Branson, J.

The dominant error source in the force models used to predict low perigee satellite trajectories is atmospheric drag. Errors in operational thermospheric density models cause significant errors in predicted satellite positions, since these models do not account for dynamic changes in atmospheric drag for orbit predictions. The Air Force Space Battlelab's High Accuracy Satellite Drag Model (HASDM) estimates and predicts (out three days) a dynamically varying high-resolution density field. HASDM includes the Dynamic Calibration Atmosphere (DCA) algorithm that solves for the phases and amplitudes of the diurnal, semidiurnal and terdiurnal variations of thermospheric density near real-time from the observed drag effects on a set of Low Earth Orbit (LEO) calibration satellites. The density correction is expressed as a function of latitude, local solar time and altitude. In HASDM, a time series prediction filter relates the extreme ultraviolet (EUV) energy index E10.7 and the geomagnetic storm index a p to the DCA density correction parameters. The E10.7 index is generated by the SOLAR2000 model, the first full spectrum model of solar irradiance. The estimated and predicted density fields will be used operationally to significantly improve the accuracy of predicted trajectories for all low perigee satellites.

Ion extraction capabilities of closely spaced grids

NASA Technical Reports Server (NTRS)

Rovang, D. C.; Wilbur, P. J.

1982-01-01

The ion extraction capabilities of accelerator systems with small screen hole diameters (less than 2.0 mm) are investigated at net-accelerating voltages of 100, 300, and 500 V. Results show that the impingement-limited perveance is not dramatically affected by reductions in screen hole diameter to 1.0 mm, but impingement-limited performance was found to be dependent on the grid separation distance, the discharge-to-total accelerating voltage ratio, and the net-to-total accelerating voltage ratio. Results obtained using small hole diameters and closely spaced grids indicate a new mode of grid operation where high current density operation can be achieved with a specified net acceleration voltage by operating the grids at a high rather than low net-to-total acceleration voltage. Beam current densities as high as 25 mA/sq cm were obtained using grids with 1.0 mm diameter holes operating at a net accelerating voltage of 500 V.

Feedforward, high density, programmable read only neural network based memory system

NASA Technical Reports Server (NTRS)

Daud, Taher; Moopenn, Alex; Lamb, James; Thakoor, Anil; Khanna, Satish

1988-01-01

Neural network-inspired, nonvolatile, programmable associative memory using thin-film technology is demonstrated. The details of the architecture, which uses programmable resistive connection matrices in synaptic arrays and current summing and thresholding amplifiers as neurons, are described. Several synapse configurations for a high-density array of a binary connection matrix are also described. Test circuits are evaluated for operational feasibility and to demonstrate the speed of the read operation. The results are discussed to highlight the potential for a read data rate exceeding 10 megabits/sec.

Complete reduction of high-density UO2 to metallic U in molten Li2O-LiCl

NASA Astrophysics Data System (ADS)

Choi, Eun-Young; Lee, Jeong

2017-10-01

The large size and high density of spent fuel pellets make it difficult to use the pellets directly in electrolytic reduction (also called as oxide reduction, OR) for pyroprocessing owing to the slow diffusion of molten Li2O-LiCl salt electrolyte into the pellets. In this study, we investigated complete OR of high-density UO2 to metallic U without any remaining UO2. Only partial reductions near the surface of high-density UO2 pellets were observed under operation conditions employing fast electrolysis rate that allowed previously complete reduction of low-density UO2 pellets. Complete reduction of high-density UO2 pellets was observed at fast electrolysis rate when the pellet size was reduced. The complete reduction of high-density UO2 pellets without size reduction was achieved at slow electrolysis rate, which allowed sufficient chemical reduction of UO2 with the lithium metal generated by the cathode reaction.

14 CFR 93.123 - High density traffic airports.

Code of Federal Regulations, 2014 CFR

2014-01-01

... operations conducted by air carriers with turboprop and reciprocating engine aircraft having a certificated... of operations conducted by air carriers with turboprop and reciprocating engine aircraft having a...

14 CFR 93.123 - High density traffic airports.

Code of Federal Regulations, 2013 CFR

2013-01-01

... operations conducted by air carriers with turboprop and reciprocating engine aircraft having a certificated... of operations conducted by air carriers with turboprop and reciprocating engine aircraft having a...

14 CFR 93.123 - High density traffic airports.

Code of Federal Regulations, 2012 CFR

2012-01-01

... operations conducted by air carriers with turboprop and reciprocating engine aircraft having a certificated... of operations conducted by air carriers with turboprop and reciprocating engine aircraft having a...

W7-AS: One step of the Wendelstein stellarator linea)

NASA Astrophysics Data System (ADS)

Wagner, F.; Bäumel, S.; Baldzuhn, J.; Basse, N.; Brakel, R.; Burhenn, R.; Dinklage, A.; Dorst, D.; Ehmler, H.; Endler, M.; Erckmann, V.; Feng, Y.; Gadelmeier, F.; Geiger, J.; Giannone, L.; Grigull, P.; Hartfuss, H.-J.; Hartmann, D.; Hildebrandt, D.; Hirsch, M.; Holzhauer, E.; Igitkhanov, Y.; Jänicke, R.; Kick, M.; Kislyakov, A.; Kisslinger, J.; Klinger, T.; Klose, S.; Knauer, J. P.; König, R.; Kühner, G.; Laqua, H. P.; Maassberg, H.; McCormick, K.; Niedermeyer, H.; Nührenberg, C.; Pasch, E.; Ramasubramanian, N.; Ruhs, N.; Rust, N.; Sallander, E.; Sardei, F.; Schubert, M.; Speth, E.; Thomsen, H.; Volpe, F.; Weller, A.; Werner, A.; Wobig, H.; Würsching, E.; Zarnstorff, M.; Zoletnik, S.

2005-07-01

This paper is a summary of some of the major results from the Wendelstein 7-AS stellarator (W7-AS). W7-AS [G. Grieger et al., Phys. Fluids B 4, 2081 (1992)] has demonstrated the feasibility of modular coils and has pioneered the island divertor and the modeling of its three-dimensional characteristics with the EMC3/EIRENE code [Y. Feng, F. Sardei et al., Plasma Phys. Controlled Fusion 44, 611 (2002)]. It has extended the operational range to high density (4×1020m-3 at 2.5T) and high ⟨β⟩ (3.4% at 0.9T); it has demonstrated successfully the application of electron cyclotron resonance heating (ECRH) beyond cutoff via electron Bernstein wave heating, and it has utilized the toroidal variation of the magnetic field strength for ion cyclotron resonance frequency beach-wave heating. In preparation of W7-X [J. Nührenberg et al., Trans. Fusion Technol. 27, 71 (1995)], aspects of the optimization concept of the magnetic design have been successfully tested. W7-AS has accessed the H-mode, the first time in a "non-tokamak" and has extended H-mode operation toward high density by the discovery of the high-density H-mode (HDH), characterized by H-mode energy and L-mode-level impurity confinement. In the HDH-mode quasisteady state operation is possible close to operational limits without noticeable degradation in the plasma properties. High-β phases up to tpulse/τE=65 have been achieved, which can already be taken as an indication of the intrinsic stellarator capability of steady-state operation. Confinement issues will be discussed with emphasis on the similarities to tokamak confinement (general transport properties, H-mode transition physics) but also with respect to distinct differences (no confinement degradation toward operational boundaries, positive density scaling, lack of profile resilience, no distinct isotope effect, H-mode operational window). W7-AS turned out to be an important step in the development of the Wendelstein stellarator line towards an independent fusion power plant concept.

RF Plasma Source for Heavy Ion Beam Charge Neutralization

NASA Astrophysics Data System (ADS)

Efthimion, P. C.; Gilson, E.; Grisham, L.; Davidson, R. C.

2003-10-01

Highly ionized plasmas are being employed as a medium for charge neutralizing heavy ion beams in order to focus to a small spot size. Calculations suggest that plasma at a density of 1 - 100 times the ion beam density and at a length 0.1-0.5 m would be suitable for achieving a high level of charge neutralization. An ECR source has been built at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 0-10 gauss. The goal is to operate the source at pressures 10-5 Torr at full ionization. The initial operation of the source has been at pressures of 10-4 - 10-1 Torr. Electron densities in the range of 10^8 - 10^11 cm-3 have been achieved. Recently, pulsed operation of the source has enabled operation at pressures in the 10-6 Torr range with densities of 10^11 cm-3. Near 100% ionization has been achieved. The source has been integrated with NTX and is being used in the experiments. The plasma is approximately 10 cm in length in the direction of the beam propagation. Modifications to the source will be presented that increase its length in the direction of beam propagation.

High Temperature Silicon Carbide (SiC) Traction Motor Drive

DTIC Science & Technology

2011-08-09

UNCLASSIFIED Distribution Statement A. Approved for public release; distribution is unlimited. UNCLASSIFIED HIGH TEMPERATURE SILICON CARBIDE...be modular and conveniently distributed. Small component size and operation with high - temperature liquid coolant are essential factors in the...these densities, power modules capable of high - temperature operation were developed using SiC normally-off JFETs. This paper will discuss the unique

Plasma characteristics of argon glow discharge produced by AC power supply operating at low frequencies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kongpiboolkid, Watcharapon; Mongkolnavin, Rattachat; Plasma Technology and Nuclear Fusion Research Unit, Chulalongkorn University, Bangkok

2015-04-24

Non-thermal properties of Argon glow discharge operating with various operating pressures were measured and presented in this work. The Argon plasma is produced by a parallel conducting electrodes coupling with a high voltage AC power supply. The power supply can generate high AC voltage at various frequencies. The frequencies for the operation are in the range of a few kHz. The system is capable of generating electric field between the two metal electrodes discharge system. The characteristics of plasma produced were measured by optical emission spectroscopy (OES) technique where electron temperature (T{sub e}) and electron number density (n{sub e}) canmore » be determined by line intensity ratio method. The value of electron number density was then determined from the Saha-Eggert equation. Our results show that the electron number density of the discharge obtained is of the order of 10{sup −17} − 10{sup −18} m{sup −3} where the electron temperature is between 1.00−2.00 eV for various operating frequencies used which are in good agreement with similar results published earlier.« less

Effects of mental workload on physiological and subjective responses during traffic density monitoring: A field study.

PubMed

Fallahi, Majid; Motamedzade, Majid; Heidarimoghadam, Rashid; Soltanian, Ali Reza; Miyake, Shinji

2016-01-01

This study evaluated operators' mental workload while monitoring traffic density in a city traffic control center. To determine the mental workload, physiological signals (ECG, EMG) were recorded and the NASA-Task Load Index (TLX) was administered for 16 operators. The results showed that the operators experienced a larger mental workload during high traffic density than during low traffic density. The traffic control center stressors caused changes in heart rate variability features and EMG amplitude, although the average workload score was significantly higher in HTD conditions than in LTD conditions. The findings indicated that increasing traffic congestion had a significant effect on HR, RMSSD, SDNN, LF/HF ratio, and EMG amplitude. The results suggested that when operators' workload increases, their mental fatigue and stress level increase and their mental health deteriorate. Therefore, it maybe necessary to implement an ergonomic program to manage mental health. Furthermore, by evaluating mental workload, the traffic control center director can organize the center's traffic congestion operators to sustain the appropriate mental workload and improve traffic control management. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

An analytic model for limiting high density LH transition by the onset of the tertiary instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Raghvendra, E-mail: rsingh129@gmail.com; Jhang, Hogun; Kaang, Helen H.

2016-07-15

We perform an analytic study of the tertiary instability driven by a strong excitation of zonal flows during high density low to high (LH) mode transition. The drift resistive ballooning mode is assumed to be a dominant edge turbulence driver. The analysis reproduces main qualitative features of early computational results [Rogers and Drake, Phys. Rev. Lett. 81, 4396 (1998); Guzdar et al., Phys. Plasmas 14, 020701 (2007)], as well as new characteristics of the maximum edge density due to the onset of the tertiary instability. An analytical scaling indicates that the density scaling of LH transition power may be determinedmore » by the onset condition of the tertiary instability when the operating density approaches to the Greenwald density.« less

High density electronic circuit and process for making

DOEpatents

Morgan, W.P.

1999-06-29

High density circuits with posts that protrude beyond one surface of a substrate to provide easy mounting of devices such as integrated circuits are disclosed. The posts also provide stress relief to accommodate differential thermal expansion. The process allows high interconnect density with fewer alignment restrictions and less wasted circuit area than previous processes. The resulting substrates can be test platforms for die testing and for multi-chip module substrate testing. The test platform can contain active components and emulate realistic operational conditions, replacing shorts/opens net testing. 8 figs.

Extension of electron cyclotron heating at ASDEX Upgrade with respect to high density operation

NASA Astrophysics Data System (ADS)

Schubert, Martin; Stober, Jörg; Herrmann, Albrecht; Kasparek, Walter; Leuterer, Fritz; Monaco, Francesco; Petzold, Bernhard; Plaum, Burkhard; Vorbrugg, Stefan; Wagner, Dietmar; Zohm, Hartmut

2017-10-01

The ASDEX Upgrade electron cyclotron resonance heating operates at 105 GHz and 140 GHz with flexible launching geometry and polarization. In 2016 four Gyrotrons with 10 sec pulse length and output power close to 1 MW per unit were available. The system is presently being extended to eight similar units in total. High heating power and high plasma density operation will be a part of the future ASDEX Upgrade experiment program. For the electron cyclotron resonance heating, an O-2 mode scheme is proposed, which is compatible with the expected high plasma densities. It may, however, suffer from incomplete single-pass absorption. The situation can be improved significantly by installing holographic mirrors on the inner column, which allow for a second pass of the unabsorbed fraction of the millimetre wave beam. Since the beam path in the plasma is subject to refraction, the beam position on the holographic mirror has to be controlled. Thermocouples built into the mirror surface are used for this purpose. As a protective measure, the tiles of the heat shield on the inner column were modified in order to increase the shielding against unabsorbed millimetre wave power.

Neutral-depletion-induced axially asymmetric density in a helicon source and imparted thrust

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Takao, Yoshinori; Ando, Akira

2016-02-01

The high plasma density downstream of the source is observed to be sustained only for a few hundreds of microsecond at the initial phase of the discharge, when pulsing the radiofrequency power of a helicon plasma thruster. Measured relative density of argon neutrals inside the source implies that the neutrals are significantly depleted there. A position giving a maximum plasma density temporally moves to the upstream side of the source due to the neutral depletion and then the exhausted plasma density significantly decreases. The direct thrust measurement demonstrates that the higher thrust-to-power ratio is obtained by using only the initial phase of the high density plasma, compared with the steady-state operation.

High density fuel qualification for a gas turbine engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macleod, J.D.; Orbanski, B.; Hastings, P.R.

1992-01-01

A program for the evaluation of gas turbine engine performance, carried out in the Engine Laboratory of the National Research Council of Canada, is described. Problems under consideration include performance alteration between JP-4 fuel and a high energy density fuel, called strategic military fuel (SMF); performance deterioration during the accelerated endurance test; and emission analysis. The T56 fuel control system is found to be capable of operation on the higher energy density fuel with no detrimental effects regarding control of the engine's normal operating regime. The deterioration of the engine performance during 150-hour endurance tests on SMF was very high,more » which was caused by an increase in turbine nozzle effective flow area and turbine blade untwist. The most significant performance losses during the endurance tests were on corrected output power, fuel flow, specific fuel consumption and compressor and turbine presure ratio. 9 refs.« less

High power density dc-to-dc converters for aerospace applications

NASA Technical Reports Server (NTRS)

Divan, Deepakraj M.

1990-01-01

Three dc-to-dc converter topologies aimed at high-power high-frequency applications are introduced. Major system parasitics, namely, the leakage inductance of the transformer and the device output capacitance are efficiently utilized. Of the three circuits, the single-phase and three-phase versions of the dual active bridge topology demonstrate minimal stresses, better utilization of the transformer, bidirectional, and buck-boost modes of operation. All circuits operate at a constant switching frequency, thus simplifying design of the reactive elements. The power transfer characteristics and soft-switching regions on the Vout-Iout plane are identified. Two coaxial transformers with different cross-sections were built for a rating of 50 kVA. Based on the single-phase dual active bridge topology, a 50 kW, 50 kHz converter operating at an input voltage of 200 Vdc and an output voltage of 1600 Vdc was fabricated. Characteristics of current-fed output make the dual active bridge topologies amenable to paralleling and hence extension to megawatt power levels. Projections to a 1 MW system operating from a 500 Vdc input, at an output voltage of 10 kVdc and a switching frequency of 50 kHz, using MOS-controlled thyristors, coaxially wound transformers operating at three times the present current density with cooling, and multilayer ceramic capacitors, suggests an overall power density of 0.075 to 0.08 kg/kW and an overall efficiency of 96 percent.

High speed FPGA-based Phasemeter for the far-infrared laser interferometers on EAST

NASA Astrophysics Data System (ADS)

Yao, Y.; Liu, H.; Zou, Z.; Li, W.; Lian, H.; Jie, Y.

2017-12-01

The far-infrared laser-based HCN interferometer and POlarimeter/INTerferometer\\break (POINT) system are important diagnostics for plasma density measurement on EAST tokamak. Both HCN and POINT provide high spatial and temporal resolution of electron density measurement and used for plasma density feedback control. The density is calculated by measuring the real-time phase difference between the reference beams and the probe beams. For long-pulse operations on EAST, the calculation of density has to meet the requirements of Real-Time and high precision. In this paper, a Phasemeter for far-infrared laser-based interferometers will be introduced. The FPGA-based Phasemeter leverages fast ADCs to obtain the three-frequency signals from VDI planar-diode Mixers, and realizes digital filters and an FFT algorithm in FPGA to provide real-time, high precision electron density output. Implementation of the Phasemeter will be helpful for the future plasma real-time feedback control in long-pulse discharge.

A High-Density, High-Efficiency, Isolated On-Board Vehicle Battery Charger Utilizing Silicon Carbide Power Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitaker, B; Barkley, A; Cole, Z

2014-05-01

This paper presents an isolated on-board vehicular battery charger that utilizes silicon carbide (SiC) power devices to achieve high density and high efficiency for application in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs). The proposed level 2 charger has a two-stage architecture where the first stage is a bridgeless boost ac-dc converter and the second stage is a phase-shifted full-bridge isolated dc-dc converter. The operation of both topologies is presented and the specific advantages gained through the use of SiC power devices are discussed. The design of power stage components, the packaging of the multichip power module, and themore » system-level packaging is presented with a primary focus on system density and a secondary focus on system efficiency. In this work, a hardware prototype is developed and a peak system efficiency of 95% is measured while operating both power stages with a switching frequency of 200 kHz. A maximum output power of 6.1 kW results in a volumetric power density of 5.0 kW/L and a gravimetric power density of 3.8 kW/kg when considering the volume and mass of the system including a case.« less

Simulation Of Wave Function And Probability Density Of Modified Poschl Teller Potential Derived Using Supersymmetric Quantum Mechanics

NASA Astrophysics Data System (ADS)

Angraini, Lily Maysari; Suparmi, Variani, Viska Inda

2010-12-01

SUSY quantum mechanics can be applied to solve Schrodinger equation for high dimensional system that can be reduced into one dimensional system and represented in lowering and raising operators. Lowering and raising operators can be obtained using relationship between original Hamiltonian equation and the (super) potential equation. In this paper SUSY quantum mechanics is used as a method to obtain the wave function and the energy level of the Modified Poschl Teller potential. The graph of wave function equation and probability density is simulated by using Delphi 7.0 programming language. Finally, the expectation value of quantum mechanics operator could be calculated analytically using integral form or probability density graph resulted by the programming.

Steady state and transient simulation of anion exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Dekel, Dario R.; Rasin, Igal G.; Page, Miles; Brandon, Simon

2018-01-01

We present a new model for anion exchange membrane fuel cells. Validation against experimental polarization curve data is obtained for current densities ranging from zero to above 2 A cm-2. Experimental transient data is also successfully reproduced. The model is very flexible and can be used to explore the system's sensitivity to a wide range of material properties, cell design specifications, and operating parameters. We demonstrate the impact of gas inlet relative humidity (RH), operating current density, ionomer loading and ionomer ion exchange capacity (IEC) values on cell performance. In agreement with the literature, high air RH levels are shown to improve cell performance. At high current densities (>1 A cm-2) this effect is observed to be especially significant. Simulated hydration number distributions across the cell reveal the related critical dependence of cathode hydration on air RH and current density values. When exploring catalyst layer design, optimal intermediate ionomer loading values are demonstrated. The benefits of asymmetric (cathode versus anode) electrode design are revealed, showing enhanced performance using higher cathode IEC levels. Finally, electrochemical reaction profiles across the electrodes uncover inhomogeneous catalyst utilization. Specifically, at high current densities the cathodic reaction is confined to a narrow region near the membrane.

Acoustic emission analysis for the detection of appropriate cutting operations in honing processes

NASA Astrophysics Data System (ADS)

Buj-Corral, Irene; Álvarez-Flórez, Jesús; Domínguez-Fernández, Alejandro

2018-01-01

In the present paper, acoustic emission was studied in honing experiments obtained with different abrasive densities, 15, 30, 45 and 60. In addition, 2D and 3D roughness, material removal rate and tool wear were determined. In order to treat the sound signal emitted during the machining process, two methods of analysis were compared: Fast Fourier Transform (FFT) and Hilbert Huang Transform (HHT). When density 15 is used, the number of cutting grains is insufficient to provide correct cutting, while clogging appears with densities 45 and 60. The results were confirmed by means of treatment of the sound signal. In addition, a new parameter S was defined as the relationship between energy in low and high frequencies contained within the emitted sound. The selected density of 30 corresponds to S values between 0.1 and 1. Correct cutting operations in honing processes are dependent on the density of the abrasive employed. The density value to be used can be selected by means of measurement and analysis of acoustic emissions during the honing operation. Thus, honing processes can be monitored without needing to stop the process.

Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage

NASA Astrophysics Data System (ADS)

Tao, Jiayou; Liu, Nishuang; Rao, Jiangyu; Ding, Longwei; Al Bahrani, Majid Raissan; Li, Luying; Su, Jun; Gao, Yihua

2014-11-01

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage.Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04819a

High-Potential Metalless Nanocarbon Foam Supercapacitors Operating in Aqueous Electrolyte.

PubMed

Liu, Chueh; Li, Changling; Ahmed, Kazi; Mutlu, Zafer; Lee, Ilkeun; Zaera, Francisco; Ozkan, Cengiz S; Ozkan, Mihrimah

2018-04-01

Light-weight graphite foam decorated with carbon nanotubes (dia. 20-50 nm) is utilized as an effective electrode without binders, conductive additives, or metallic current collectors for supercapacitors in aqueous electrolyte. Facile nitric acid treatment renders wide operating potentials, high specific capacitances and energy densities, and long lifespan over 10 000 cycles manifested as 164.5 and 111.8 F g -1 , 22.85 and 12.58 Wh kg -1 , 74.6% and 95.6% capacitance retention for 2 and 1.8 V, respectively. Overcharge protection is demonstrated by repetitive cycling between 2 and 2.5 V for 2000 cycles without catastrophic structural demolition or severe capacity fading. Graphite foam without metallic strut possessing low density (≈0.4-0.45 g cm -3 ) further reduces the total weight of the electrode. The thorough investigation of the specific capacitances and coulombic efficiencies versus potential windows and current densities provides insights into the selection of operation conditions for future practical devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Quasi-Solid-State Sodium-Ion Capacitor with High Energy Density.

PubMed

Wang, Faxing; Wang, Xiaowei; Chang, Zheng; Wu, Xiongwei; Liu, Xiang; Fu, Lijun; Zhu, Yusong; Wu, Yuping; Huang, Wei

2015-11-18

A quasi-solid-state sodium-ion capacitor is demonstrated with nanoporous disordered carbon and macroporous graphene as the negative and positive electrodes, respectively, using a sodium-ion-conducting gel polymer electrolyte. It can operate at a cell voltage as high as 4.2 V with an energy density of record high 168 W h kg(-1). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Miniature Internal Combustion Engine-Generator for High Energy Density Portable Power

DTIC Science & Technology

2008-12-01

Operation on JP-8 from cold startup to steady operation has been demonstrated at the 300 W scale. Miniature engine/generators can be acoustically silenced...design that uses a spring for energy storage . MICE is a high Q system, operating at the resonant frequency of the spring-mass system with very low...development • Demonstrated 94% efficiency of 300 W linear alternator • Demonstrated full operation of MICE generator from cold startup to net power output

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, Alan F.; Modine, Normand A.

We show scaling results for materials of interest in Sandia Radiation-Effects and High-Energy-Density-Physics Mission Areas. Each timing is from a self-consistent calculation for bulk material. Two timings are given: (1) walltime for the construction of the CR exchange operator (Exchange-Operator) and (2) walltime for everything else (non-Exchange-Operator).

Barium-Dispenser Thermionic Cathode

NASA Technical Reports Server (NTRS)

Wintucky, Edwin G.; Green, M.; Feinleib, M.

1989-01-01

Improved reservoir cathode serves as intense source of electrons required for high-frequency and often high-output-power, linear-beam tubes, for which long operating lifetime important consideration. High emission-current densities obtained through use of emitting surface of relatively-low effective work function and narrow work-function distribution, consisting of coat of W/Os deposited by sputtering. Lower operating temperatures and enhanced electron emission consequently possible.

Using NVMe Gen3 PCIe SSD Cards in High-density Servers for High-performance Big Data Transfer Over Multiple Network Channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Chin

This Technical Note describes how the Zettar team came up with a data transfer cluster design that convincingly proved the feasibility of using high-density servers for high-performance Big Data transfers. It then outlines the tests, operations, and observations that address a potential over-heating concern regarding the use of Non-Volatile Memory Host Controller Interface Specification (NVMHCI aka NVM Express or NVMe) Gen 3 PCIe SSD cards in high-density servers. Finally, it points out the possibility of developing a new generation of high-performance Science DMZ data transfer system for the data-intensive research community and commercial enterprises.

Plasma Properties of Microwave Produced Plasma in a Toroidal Device

NASA Astrophysics Data System (ADS)

Singh, Ajay; Edwards, W. F.; Held, Eric

2011-10-01

We have modified a small tokamak, STOR-1M, on loan from University of Saskatchewan, to operate as a low-temperature (~5 eV) toroidal plasma machine with externally induced toroidal magnetic fields ranging from zero to ~50 G. The plasma is produced using microwave discharges at relatively high pressures. Microwaves are produced by a kitchen microwave-oven magnetron operating at 2.45 GHz in continuous operating mode, resulting in pulses ~0.5 s in duration. Initial measurements of plasma formation in this device with and without applied magnetic fields are presented. Plasma density and temperature profiles have been measured using Langmuir probes and the magnetic field profile inside the plasma has been obtained using Hall probes. When the discharge is created with no applied toroidal magnetic field, the plasma does not fill the entire torus due to high background pressure. However, when a toroidal magnetic field is applied, the plasma flows along the applied field, filling the torus. Increasing the applied magnetic field seems to aid plasma formation - the peak density increases and the density gradient becomes steeper. Above a threshold magnetic field, the plasma develops low-frequency density oscillations due to probable excitation of flute modes in the plasma.

Overview of ASDEX Upgrade results

DOE PAGES

Aguiam, D.

2017-06-28

Here, the ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of 3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF operation. As predicted, a factor two reduction on the ICRF-induced W plasma content could be achieved by the reduction of the sheath voltage at the antenna limiters via the compensation of the image currents of the central and side straps in the antenna frame. There are two main operational scenario lines in AUG. Experiments with low collisionality, which comprise current drive, ELM mitigation/suppression and fast ion physics, are mainly done with freshly boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full ELM suppression and non-inductive operation up to a plasma current ofmore » $${{I}_{\\text{p}}}=0.8$$ MA could be obtained at low plasma density. Plasma exhaust is studied under conditions of high neutral divertor pressure and separatrix electron density, where a fresh boronization is not required. Substantial progress could be achieved for the understanding of the confinement degradation by strong D puffing and the improvement with nitrogen or carbon seeding. Inward/outward shifts of the electron density profile relative to the temperature profile effect the edge stability via the pressure profile changes and lead to improved/decreased pedestal performance. Seeding and D gas puffing are found to effect the core fueling via changes in a region of high density on the high field side (HFSHD).« less

Modeling and experimental performance of an intermediate temperature reversible solid oxide cell for high-efficiency, distributed-scale electrical energy storage

NASA Astrophysics Data System (ADS)

Wendel, Christopher H.; Gao, Zhan; Barnett, Scott A.; Braun, Robert J.

2015-06-01

Electrical energy storage is expected to be a critical component of the future world energy system, performing load-leveling operations to enable increased penetration of renewable and distributed generation. Reversible solid oxide cells, operating sequentially between power-producing fuel cell mode and fuel-producing electrolysis mode, have the capability to provide highly efficient, scalable electricity storage. However, challenges ranging from cell performance and durability to system integration must be addressed before widespread adoption. One central challenge of the system design is establishing effective thermal management in the two distinct operating modes. This work leverages an operating strategy to use carbonaceous reactant species and operate at intermediate stack temperature (650 °C) to promote exothermic fuel-synthesis reactions that thermally self-sustain the electrolysis process. We present performance of a doped lanthanum-gallate (LSGM) electrolyte solid oxide cell that shows high efficiency in both operating modes at 650 °C. A physically based electrochemical model is calibrated to represent the cell performance and used to simulate roundtrip operation for conditions unique to these reversible systems. Design decisions related to system operation are evaluated using the cell model including current density, fuel and oxidant reactant compositions, and flow configuration. The analysis reveals tradeoffs between electrical efficiency, thermal management, energy density, and durability.

High performance asymmetric supercapacitor based on polypyrrole/graphene composite and its derived nitrogen-doped carbon nano-sheets

NASA Astrophysics Data System (ADS)

Zhu, Jianbo; Feng, Tianyu; Du, Xianfeng; Wang, Jingping; Hu, Jun; Wei, LiPing

2017-04-01

Neutral aqueous medium is a promising electrolyte for supercapacitors because it is low-cost, environmental-friendly and can achieve rapid charging/discharging with high power density. However, the energy density of such supercapacitor is significantly limited by its narrow operational voltage window. Herein, we demonstrated an effective approach to broaden the operational voltage window by fabricating an asymmetric supercapacitor (ASC) with polypyrrole/reduced graphene oxide (PPy/rGO) composite and its derived Nitrogen-doped carbon nano-sheets (NCs) as positive and negative electrode material, respectively. The homogeneous nano-sheet and mesoporous structure of PPy/rGO and NCs can facilitate rapid charge/ion migration and provide more active sites for ions adsorption/exchange to improve their electrochemical performance. Benefiting from high capacitance and good rate performance of PPy/rGO and NCs electrodes, the as-fabricated ASCs devices in a polyvinyl alcohol/LiCl gel electrolyte can realize a wide operational voltage of 1.6 V and deliver high energy density of 15.8 wh kg-1 (1.01 mWh cm-3) at 0.14 kW kg-1 (19.3 mW cm-3), which still remains 9.5 wh kg-1as power density increases to 6.56 kW kg-1, as well as excellent long-term cycling stability with about 88.7% capacitance retention after 10000 cycles. The remarkable performances suggest that the ASCs devices are promising for future energy storage applications.

High accuracy satellite drag model (HASDM)

NASA Astrophysics Data System (ADS)

Storz, Mark F.; Bowman, Bruce R.; Branson, Major James I.; Casali, Stephen J.; Tobiska, W. Kent

The dominant error source in force models used to predict low-perigee satellite trajectories is atmospheric drag. Errors in operational thermospheric density models cause significant errors in predicted satellite positions, since these models do not account for dynamic changes in atmospheric drag for orbit predictions. The Air Force Space Battlelab's High Accuracy Satellite Drag Model (HASDM) estimates and predicts (out three days) a dynamically varying global density field. HASDM includes the Dynamic Calibration Atmosphere (DCA) algorithm that solves for the phases and amplitudes of the diurnal and semidiurnal variations of thermospheric density near real-time from the observed drag effects on a set of Low Earth Orbit (LEO) calibration satellites. The density correction is expressed as a function of latitude, local solar time and altitude. In HASDM, a time series prediction filter relates the extreme ultraviolet (EUV) energy index E10.7 and the geomagnetic storm index ap, to the DCA density correction parameters. The E10.7 index is generated by the SOLAR2000 model, the first full spectrum model of solar irradiance. The estimated and predicted density fields will be used operationally to significantly improve the accuracy of predicted trajectories for all low-perigee satellites.

The impact of hybrid energy storage on power quality, when high power pulsed DC loads are operated on a microgrid testbed

NASA Astrophysics Data System (ADS)

Kelley, Jay Paul

As the Navy's demands for high power transient loads evolves, so too does the need for alternative energy sources to back-up the more traditional power generation. Such applications in need of support include electrical grid backup and directed energy weapon systems such as electromagnetic launchers, laser systems, and high power microwave generators, among others. Among the alternative generation sources receiving considerable attention are energy storage devices such as rechargeable electrochemical batteries and capacitors. In such applications as those mentioned above, these energy storage devices offer the ability to serve a dual role as both a power source to the various loads as well high power loads themselves to the continual generation when the high power transient loads are in periods of downtime. With the recent developments in electrochemical energy storage, lithium-ion batteries (LIBs) seem like the obvious choice, but previous research has shown that the elevated rates of charging can be detrimental to both the cycle life and the operational life span of the device. In order to preserve the batteries, their charge rate must be limited. One proposed method to accomplish the dual role task mentioned above, while preserving the life of the batteries, is by combining high energy density LIBs with high power density electric double layer capacitors (EDLCs) or lithium-ion capacitors (LICs) using controllable power electronics to adjust the flow of power to and from each device. Such a configuration is typically referred to as hybrid energy storage module (HESM). While shipboard generators start up, the combined high energy density and high power density of the HESM provides the capability to source critical loads for an extended period of time at the high rates they demand. Once the generator is operationally efficient, the HESM can act as a high energy reservoir to harvest the energy from the generator while the loads are in short periods of inactivity. This enables the generator to maintain its operation at levels of high efficiency thereby increasing the power quality of the AC bus. The work discussed here is aimed at evaluating how the use of energy storage impacts the power quality on MicroGrid's AC bus when high rate DC and AC loads are sourced simultaneously. Also HESM has been developed and evaluated as a mean to optimizing both the power and energy density of the energy storage installed.

Three-Dimensional Expanded Graphene-Metal Oxide Film via Solid-State Microwave Irradiation for Aqueous Asymmetric Supercapacitors.

PubMed

Yang, MinHo; Lee, Kyoung G; Lee, Seok Jae; Lee, Sang Bok; Han, Young-Kyu; Choi, Bong Gill

2015-10-14

Carbon-based electrochemical double-layer capacitors and pseudocapacitors, consisting of a symmetric configuration of electrodes, can deliver much higher power densities than batteries, but they suffer from low energy densities. Herein, we report the development of high energy and power density supercapacitors using an asymmetric configuration of Fe2O3 and MnO2 nanoparticles incorporated into 3D macroporous graphene film electrodes that can be operated in a safe and low-cost aqueous electrolyte. The gap in working potential windows of Fe2O3 and MnO2 enables the stable expansion of the cell voltage up to 1.8 V, which is responsible for the high energy density (41.7 Wh kg(-1)). We employ a household microwave oven to simultaneously create conductivity, porosity, and the deposition of metal oxides on graphene films toward 3D hybrid architectures, which lead to a high power density (13.5 kW kg(-1)). Such high energy and power densities are maintained for over 5000 cycles, even during cycling at a high current density of 16.9 A g(-1).

Rapid Assemblers for Voxel-Based VLSI Robotics

DTIC Science & Technology

2014-02-12

relied on coin- cell batteries with high energy density, but low power density. Each of the actuators presented requires relatively high power...The device consists of a low power DC- DC low to high voltage converter operated by 4A cell batteries and an assembler, which is a grid of electrodes...design, simulate and fabricate complex 3D machines, as well as to repair, adapt and recycle existing machines, and to perform rigorous design

A magnesium–sodium hybrid battery with high operating voltage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Hui; Li, Yifei; Liang, Yanliang

2016-06-10

We report a high performance magnesium-sodium hybrid battery utilizing a magnesium-sodium dual-salt electrolyte, a magnesium anode, and a Berlin green cathode. The cell delivers an average discharge voltage of 2.2 V and a reversible capacity of 143 mAh g -1. We also demonstrate the cell with an energy density of 135 Wh kg -1 and a high power density of up to 1.67 kW kg -1.

Effect with high density nano dot type storage layer structure on 20 nm planar NAND flash memory characteristics

NASA Astrophysics Data System (ADS)

Sasaki, Takeshi; Muraguchi, Masakazu; Seo, Moon-Sik; Park, Sung-kye; Endoh, Tetsuo

2014-01-01

The merits, concerns and design principle for the future nano dot (ND) type NAND flash memory cell are clarified, by considering the effect of storage layer structure on NAND flash memory characteristics. The characteristics of the ND cell for a NAND flash memory in comparison with the floating gate type (FG) is comprehensively studied through the read, erase, program operation, and the cell to cell interference with device simulation. Although the degradation of the read throughput (0.7% reduction of the cell current) and slower program time (26% smaller programmed threshold voltage shift) with high density (10 × 1012 cm-2) ND NAND are still concerned, the suppress of the cell to cell interference with high density (10 × 1012 cm-2) plays the most important part for scaling and multi-level cell (MLC) operation in comparison with the FG NAND. From these results, the design knowledge is shown to require the control of the number of nano dots rather than the higher nano dot density, from the viewpoint of increasing its memory capacity by MLC operation and suppressing threshold voltage variability caused by the number of dots in the storage layer. Moreover, in order to increase its memory capacity, it is shown the tunnel oxide thickness with ND should be designed thicker (>3 nm) than conventional designed ND cell for programming/erasing with direct tunneling mechanism.

Dual-lasing channel quantum cascade laser based on scattering-assisted injection design.

PubMed

Wen, Boyu; Xu, Chao; Wang, Siyi; Wang, Kaixi; Tam, Man Chun; Wasilewski, Zbig; Ban, Dayan

2018-04-02

A dual lasing channel Terahertz Quantum Cascade laser (THz QCL) based on GaAs/Al 0.17 Ga 0.83 As material system is demonstrated. The device shows the lowest reported threshold current density (550A/cm 2 at 50K) of GaAs/Al x Ga 1-x As material system based scattering-assisted (SA) structures and operates up to a maximum lasing temperature of 144K. Dual lasing channel operation is investigated theoretically and experimentally. The combination of low frequency emission, dual lasing channel operation, low lasing threshold current density and high temperature performance make such devices ideal candidates for low frequency applications, and initiates the design strategy for achieving high-temperature performance terahertz quantum cascade laser with wide frequency coverage at low frequency.

Space nuclear power applied to electric propulsion

NASA Technical Reports Server (NTRS)

Vicente, F. A.; Karras, T.; Darooka, D.; Isenberg, L.

1989-01-01

Space reactor power systems with characteristics ideal for advanced spacecraft systems applications are discussed. These characteristics are: high power-to-weight ratio (15 to 33 W/kg); high volume density (high ballistic coefficient); no preferential orientation in orbit; long operational life; high reliability; and total launch and operational safety. These characteristics allow the use of electric propulsion to raise spacecraft from low earth parking orbits to operational orbits, greatly increasing the useful orbit payload for a given launch vehicle by eliminating the need for a separation injection stage. A proposed demonstration mission is described.

Microstructural analysis of mass transport phenomena in gas diffusion media for high current density operation in PEM fuel cells

NASA Astrophysics Data System (ADS)

Kotaka, Toshikazu; Tabuchi, Yuichiro; Mukherjee, Partha P.

2015-04-01

Cost reduction is a key issue for commercialization of fuel cell electric vehicles (FCEV). High current density operation is a solution pathway. In order to realize high current density operation, it is necessary to reduce mass transport resistance in the gas diffusion media commonly consisted of gas diffusion layer (GDL) and micro porous layer (MPL). However, fundamental understanding of the underlying mass transport phenomena in the porous components is not only critical but also not fully understood yet due to the inherent microstructural complexity. In this study, a comprehensive analysis of electron and oxygen transport in the GDL and MPL is conducted experimentally and numerically with three-dimensional (3D) microstructural data to reveal the structure-transport relationship. The results reveal that the mass transport in the GDL is strongly dependent on the local microstructural variations, such as local pore/solid volume fractions and connectivity. However, especially in the case of the electrical conductivity of MPL, the contact resistance between carbon particles is the dominant factor. This suggests that reducing the contact resistance between carbon particles and/or the number of contact points along the transport pathway can improve the electrical conductivity of MPL.

Polyethylene Ear Reconstruction: A State-of-the-Art Surgical Journey.

PubMed

Reinisch, John; Tahiri, Youssef

2018-02-01

The use of a porous high-density polyethylene implant for ear reconstruction is gradually gaining acceptance because it allows for a pleasing ear reconstruction in young children before they enter school. In response to this growing interest, the authors decided to write an article clarifying in detail all the steps of this challenging procedure. In this article, the authors also answer all the common questions that surgeons have when they come to observe the operation, or when they go back to their respective practices and start performing this procedure. The authors describe in detail the operative steps that allow for a successful ear reconstruction using porous high-density polyethylene. The key parts of this operation are to meticulously harvest a well-vascularized superficial temporoparietal fascia flap and to use appropriate color-matched skin grafts. This method allows for a pleasing ear reconstruction with excellent definition, projection, symmetry, and long-term viability. The use of porous high-density polyethylene with a thin superficial temporoparietal fascia flap coverage is the authors' preferred method of ear reconstruction because it can be performed at an earlier age, in a single stage, as an outpatient procedure, and with minimal discomfort and psychological trauma for the patients and parents.

Super H-mode: theoretical prediction and initial observations of a new high performance regime for tokamak operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Snyder, Philip B.; Solomon, Wayne M.; Burrell, Keith H.

2015-07-21

A new “Super H-mode” regime is predicted, which enables pedestal height and predicted fusion performance substantially higher than for H-mode operation. This new regime is predicted to exist by the EPED pedestal model, which calculates criticality constraints for peeling-ballooning and kinetic ballooning modes, and combines them to predict the pedestal height and width. EPED usually predicts a single (“H-mode”) pedestal solution for each set of input parameters, however, in strongly shaped plasmas above a critical density, multiple pedestal solutions are found, including the standard “Hmode” solution, and a “Super H-Mode” solution at substantially larger pedestal height and width. The Supermore » H-mode regime is predicted to be accessible by controlling the trajectory of the density, and to increase fusion performance for ITER, as well as for DEMO designs with strong shaping. A set of experiments on DIII-D has identified the predicted Super H-mode regime, and finds pedestal height and width, and their variation with density, in good agreement with theoretical predictions from the EPED model. Finally, the very high pedestal enables operation at high global beta and high confinement, including the highest normalized beta achieved on DIII-D with a quiescent edge.« less

2.097μ Cth:YAG flashlamp pumped high energy high efficiency laser operation (patent pending)

NASA Astrophysics Data System (ADS)

Bar-Joseph, Dan

2018-02-01

Flashlamp pumped Cth:YAG lasers are mainly used in medical applications (urology). The main laser transition is at 2.13μ and is called a quasi-three level having an emission cross-section of 7x10-21 cm2 and a ground state absorption of approximately 5%/cm. Because of the relatively low absorption, combined with a modest emission cross-section, the laser requires high reflectivity output coupling, and therefore high intra-cavity energy density which limits the output to approximately 4J/pulse for reliable operation. This paper will describe a method of efficiently generating high output energy at low intra-cavity energy density by using an alternative 2.097μ transition having an emission cross-section of 5x10-21 cm2 and a ground level absorption of approximately 14%/cm.

High/variable mixture ratio O2/H2 engine

NASA Technical Reports Server (NTRS)

Adams, A.; Parsley, R. C.

1988-01-01

Vehicle/engine analysis studies have identified the High/Dual Mixture Ratio O2/H2 Engine cycle as a leading candidate for an advanced Single Stage to Orbit (SSTO) propulsion system. This cycle is designed to allow operation at a higher than normal O/F ratio of 12 during liftoff and then transition to a more optimum O/F ratio of 6 at altitude. While operation at high mixture ratios lowers specific impulse, the resultant high propellant bulk density and high power density combine to minimize the influence of atmospheric drag and low altitude gravitational forces. Transition to a lower mixture ratio at altitude then provides improved specific impulse relative to a single mixture ratio engine that must select a mixture ratio that is balanced for both low and high altitude operation. This combination of increased altitude specific impulse and high propellant bulk density more than offsets the compromised low altitude performance and results in an overall mission benefit. Two areas of technical concern relative to the execution of this dual mixture ratio cycle concept are addressed. First, actions required to transition from high to low mixture ratio are examined, including an assessment of the main chamber environment as the main chamber mixture ratio passes through stoichiometric. Secondly, two approaches to meet a requirement for high turbine power at high mixture ratio condition are examined. One approach uses high turbine temperature to produce the power and requires cooled turbines. The other approach incorporates an oxidizer-rich preburner to increase turbine work capability via increased turbine mass flow.

A selective electrocatalyst–based direct methanol fuel cell operated at high concentrations of methanol

PubMed Central

Feng, Yan; Liu, Hui; Yang, Jun

2017-01-01

Owing to the serious crossover of methanol from the anode to the cathode through the polymer electrolyte membrane, direct methanol fuel cells (DMFCs) usually use dilute methanol solutions as fuel. However, the use of high-concentration methanol is highly demanded to improve the energy density of a DMFC system. Instead of the conventional strategies (for example, improving the fuel-feed system, membrane development, modification of electrode, and water management), we demonstrate the use of selective electrocatalysts to run a DMFC at high concentrations of methanol. In particular, at an operating temperature of 80°C, the as-fabricated DMFC with core-shell-shell Au@Ag2S@Pt nanocomposites at the anode and core-shell Au@Pd nanoparticles at the cathode produces a maximum power density of 89.7 mW cm−2 at a methanol feed concentration of 10 M and maintains good performance at a methanol concentration of up to 15 M. The high selectivity of the electrocatalysts achieved through structural construction accounts for the successful operation of the DMFC at high concentrations of methanol. PMID:28695199

A selective electrocatalyst-based direct methanol fuel cell operated at high concentrations of methanol.

PubMed

Feng, Yan; Liu, Hui; Yang, Jun

2017-06-01

Owing to the serious crossover of methanol from the anode to the cathode through the polymer electrolyte membrane, direct methanol fuel cells (DMFCs) usually use dilute methanol solutions as fuel. However, the use of high-concentration methanol is highly demanded to improve the energy density of a DMFC system. Instead of the conventional strategies (for example, improving the fuel-feed system, membrane development, modification of electrode, and water management), we demonstrate the use of selective electrocatalysts to run a DMFC at high concentrations of methanol. In particular, at an operating temperature of 80°C, the as-fabricated DMFC with core-shell-shell Au@Ag 2 S@Pt nanocomposites at the anode and core-shell Au@Pd nanoparticles at the cathode produces a maximum power density of 89.7 mW cm -2 at a methanol feed concentration of 10 M and maintains good performance at a methanol concentration of up to 15 M. The high selectivity of the electrocatalysts achieved through structural construction accounts for the successful operation of the DMFC at high concentrations of methanol.

Hybrid neural network for density limit disruption prediction and avoidance on J-TEXT tokamak

NASA Astrophysics Data System (ADS)

Zheng, W.; Hu, F. R.; Zhang, M.; Chen, Z. Y.; Zhao, X. Q.; Wang, X. L.; Shi, P.; Zhang, X. L.; Zhang, X. Q.; Zhou, Y. N.; Wei, Y. N.; Pan, Y.; J-TEXT team

2018-05-01

Increasing the plasma density is one of the key methods in achieving an efficient fusion reaction. High-density operation is one of the hot topics in tokamak plasmas. Density limit disruptions remain an important issue for safe operation. An effective density limit disruption prediction and avoidance system is the key to avoid density limit disruptions for long pulse steady state operations. An artificial neural network has been developed for the prediction of density limit disruptions on the J-TEXT tokamak. The neural network has been improved from a simple multi-layer design to a hybrid two-stage structure. The first stage is a custom network which uses time series diagnostics as inputs to predict plasma density, and the second stage is a three-layer feedforward neural network to predict the probability of density limit disruptions. It is found that hybrid neural network structure, combined with radiation profile information as an input can significantly improve the prediction performance, especially the average warning time ({{T}warn} ). In particular, the {{T}warn} is eight times better than that in previous work (Wang et al 2016 Plasma Phys. Control. Fusion 58 055014) (from 5 ms to 40 ms). The success rate for density limit disruptive shots is above 90%, while, the false alarm rate for other shots is below 10%. Based on the density limit disruption prediction system and the real-time density feedback control system, the on-line density limit disruption avoidance system has been implemented on the J-TEXT tokamak.

Transport studies in polymer electrolyte fuel cell with porous metallic flow field at ultra high current density

NASA Astrophysics Data System (ADS)

Srouji, Abdul-Kader

Achieving cost reduction for polymer electrolyte fuel cells (PEFC) requires a simultaneous effort in increasing power density while reducing precious metal loading. In PEFCs, the cathode performance is often limiting due to both the slow oxygen reduction reaction (ORR), and mass transport limitation caused by limited oxygen diffusion and liquid water flooding at high current density. This study is motivated by the achievement of ultra-high current density through the elimination of the channel/land (C/L) paradigm in PEFC flow field design. An open metallic element (OME) flow field capable of operating at unprecedented ultra-high current density (3 A/cm2) introduces new advantages and limitations for PEFC operation. The first part of this study compares the OME with a conventional C/L flow field, through performance and electrochemical diagnostic tools such as electrochemical impedance spectroscopy (EIS). The results indicate the uniqueness of the OME's mass transport improvement. No sign of operation limitation due to flooding is noted. The second part specifically examines water management at high current density using the OME flow field. A unique experimental setup is developed to measure steady-state and transient net water drag across the membrane, in order to characterize the fundamental aspects of water transport at high current density with the OME. Instead of flooding, the new limitation is identified to be anode side dry-out of the membrane, caused by electroosmotic drag. The OME improves water removal from the cathode, which immediately improves oxygen transport and performance. However, the low water content in the cathode reduces back diffusion of water to the membrane, and electroosmotic drag dominates at high current density, leading to dry-out. The third part employs the OME flow field as a tool that avoids C/L effects endemic to a typical flow field, in order to study oxygen transport resistance at the catalyst layer of a PEFC. In open literature, a resistance of unknown origin, was shown to directly or indirectly scale with Pt loading. A lack of understanding of the mechanism responsible for such resistance is noted, and several possible theories have been proposed. This lack of fundamental understanding of the origins of this resistance adds complexity to computational models which are designed to capture performance behavior with ultra-low loading electrodes. By employing the OME flow field as a tool to study this phenomena, the origins of the transport resistance appearing at ultra-low Platinum (Pt) loading is proposed to be an increase in oxygen dilution resistance through water film.

Understanding the structure and structural degradation mechanisms in high-voltage lithium-ion battery cathode oxides. A review of materials diagnostics

DOE PAGES

Mohanty, Debasish; Li, Jianlin; Nagpure, Shrikant C; ...

2015-12-21

Materials diagnostic techniques are the principal tools used in the development of low-cost, high-performance electrodes for next-generation lithium-based energy storage technologies. Also, this review highlights the importance of materials diagnostic techniques in unraveling the structure and the structural degradation mechanisms in high-voltage, high-capacity oxides that have the potential to be implemented in high-energy-density lithium-ion batteries for transportation that can use renewable energy and is less-polluting than today. The rise in CO 2 concentration in the earth’s atmosphere due to the use of petroleum products in vehicles and the dramatic increase in the cost of gasoline demand the replacement of currentmore » internal combustion engines in our vehicles with environmentally friendly, carbon free systems. Therefore, vehicles powered fully/partially by electricity are being introduced into today’s transportation fleet. As power requirements in all-electric vehicles become more demanding, lithium-ion battery (LiB) technology is now the potential candidate to provide higher energy density. Moreover, discovery of layered high-voltage lithium-manganese–rich (HV-LMR) oxides has provided a new direction toward developing high-energy-density LiBs because of their ability to deliver high capacity (~250 mA h/g) and to be operated at high operating voltage (~4.7 V). Unfortunately, practical use of HV-LMR electrodes is not viable because of structural changes in the host oxide during operation that can lead to fundamental and practical issues. This article provides the current understanding on the structure and structural degradation pathways in HV-LMR oxides, and manifests the importance of different materials diagnostic tools to unraveling the key mechanism(s). Furthermore, the fundamental insights reported, might become the tools to manipulate the chemical and/or structural aspects of HV-LMR oxides for low cost, high-energy-density LiB applications.« less

Polymeric and Molecular Materials for Advanced Organic Electronics

DTIC Science & Technology

2011-07-25

printable variants. All have excellent dielectric and insulating properties, a remarkable ability to minimize trapped charge between thin film transistor... trapped charge density, and hence the corresponding OTFT device performance. Under this program we first discovered that OTFT performance is...deep, high- density charge traps must be overcome for efficient FET operation, it has been postulated that in most OFETs, shallow lower-density (~10

Durability of Polymer Electrolyte Membrane Fuel Cells Operated at Subfreezing Temperatures

DOE PAGES

Macauley, Natalia; Lujan, Roger W.; Spernjak, Dusan; ...

2016-09-15

The structure, composition, and interfaces of membrane electrode assemblies (MEA) and gas-diffusion layers (GDLs) have a significant effect on the performance of single-proton-exchange-membrane (PEM) fuel cells operated isothermally at subfreezing temperatures. During isothermal constant-current operation at subfreezing temperatures, water forming at the cathode initially hydrates the membrane, then forms ice in the catalyst layer and/or GDL. This ice formation results in a gradual decay in voltage. High-frequency resistance initially decreases due to an increase in membrane water content and then increases over time as the contact resistance increases. The water/ice holding capacity of a fuel cell decreases with decreasing subfreezingmore » temperature (-10°C vs. -20°C vs. -30°C) and increasing current density (0.02 A cm -2 vs. 0.04 A cm -2). Ice formation monitored using in-situ high-resolution neutron radiography indicated that the ice was concentrated near the cathode catalyst layer at low operating temperatures (≈-20°C) and high current densities (0.04 A cm -2). Significant ice formation was also observed in the GDLs at higher subfreezing temperatures (≈-10°C) and lower current densities (0.02 A cm -2). These results are in good agreement with the long-term durability observations that show more severe degradation at lower temperatures (-20°C and -30°C).« less

Characterization of wastewater treatment by two microbial fuel cells in continuous flow operation.

PubMed

Kubota, Keiichi; Watanabe, Tomohide; Yamaguchi, Takashi; Syutsubo, Kazuaki

2016-01-01

A two serially connected single-chamber microbial fuel cell (MFC) was applied to the treatment of diluted molasses wastewater in a continuous operation mode. In addition, the effect of series and parallel connection between the anodes and the cathode on power generation was investigated experimentally. The two serially connected MFC process achieved 79.8% of chemical oxygen demand removal and 11.6% of Coulombic efficiency when the hydraulic retention time of the whole process was 26 h. The power densities were 0.54, 0.34 and 0.40 W m(-3) when electrodes were in individual connection, serial connection and parallel connection modes, respectively. A high open circuit voltage was obtained in the serial connection. Power density decreased at low organic loading rates (OLR) due to the shortage of organic matter. Power generation efficiency tended to decrease as a result of enhancement of methane fermentation at high OLRs. Therefore, high power density and efficiency can be achieved by using a suitable OLR range.

Growth characteristics of aquatic macrophytes cultured in nutrient-enriched water. I. Water hyacinth, water lettuce, and pennywort

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, K.R.; DeBusk, W.F.

Seasonal growth characteristics and biomass yield potential of 3 floating aquatic macrophytes cultured in nutrient nonlimiting conditions were evaluated in central Florida's climatic conditions. Growth cycle (growth curve) of the plants was found to be complete when maximum plant density was reached and no additional increase in growth was recorded. Biomass yield per unit area and time was found to be maximum in the linear phase of the growth curve; plant density in this phase was defined as ''operational plant density,'' a density range in which a biomass production system is operated to obtain the highest possible yields. Biomass yieldsmore » were found to be 106, 72, and 41 t(dry wt) ha/sup -1/yr/sup -1/, respectively, for water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), and pennywort (Hydrocotyle umbellata). Operational plant density was found to be in the range of 500-2000 g dry wt m/sup -2/ for water hyacinth, 200-700 g dry wt m/sup -2/ for water lettuce, and 250-650 g dry wt/sup -2/ for pennywort. Seasonality was observed in growth rates but not in operational plant density. Specific growth rate (% increase per day) was found to maximum at low plant densities and decreased as the plant density increased. Results show that water hyacinth and water lettuce can be successfully grown for a period of about 10 mo, while pennywort, a cool season plant, can be integrated into water hyacinth/water lettuce biomass production system to obtain high yields in the winter.« less

Growth characteristics of aquatic macrophytes cultured in nutrient-enriched water. I. Water hyacinth, water lettuce, and pennywort

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, K.R.; DeBusk, W.F.

Seasonal growth characteristics and biomass yield potential of 3 floating aquatic macrophytes cultured in nutrient nonlimiting conditions were evaluated in central Florida's climatic conditions. Growth cycle (growth curve) of the plants was found to be complete when maximum plant density was reached and no additional increase in growth was recorded. Biomass yield per unit area and time was found to be maximum in the linear phase of the growth curve; plant density in this phase was defined as operational plant density, a density range in which a biomass production system is operated to obtain the highest possible yields. Biomass yieldsmore » were found to be 106, 72, and 41 t (dry wt) ha/sup -1/ yr/sup -1/, respectively, for water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), and pennywort (Hydrocotyle umbellata). Operational plant density was found to be in the range of 500-2,000 g dry wt m/sup -2/ for water hyacinth, 200-700 g dry wt m/sup -2/ for water lettuce, and 250-650 g dry wt m/sup -2/ for pennywort. Seasonality was observed in growth rates but not in operational plant density. Specific growth rate (% increase per day) was found to maximum at low plant densities and decreased as the plant density increased. Results show that water hyacinth and water lettuce can be successfully grown for a period of about 10 mo, while pennywort, a cool season plant, can be integrated into water hyacinth/water lettuce biomass production system to obtain high yields in the winter.« less

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array.

PubMed

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao; Luo, Hang

2018-02-01

Polymer-based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400-600 kV mm -1 , which may bring more challenges relating to the failure probability. Here, a simple two-step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm -3 is achieved at low electric fields, i.e., 143 kV mm -1 , which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm -2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis.

In-plane structuring of proton exchange membrane fuel cell cathodes: Effect of ionomer equivalent weight structuring on performance and current density distribution

NASA Astrophysics Data System (ADS)

Herden, Susanne; Riewald, Felix; Hirschfeld, Julian A.; Perchthaler, Markus

2017-07-01

Within the active area of a fuel cell inhomogeneous operating conditions occur, however, state of the art electrodes are homogenous over the complete active area. This study uses current density distribution measurements to analyze which ionomer equivalent weight (EW) shows locally the highest current densities. With this information a segmented cathode electrode is manufactured by decal transfer. The segmented electrode shows better performance especially at high current densities compared to homogenous electrodes. Furthermore this segmented catalyst coated membrane (CCM) performs optimal in wet as well as dry conditions, both operating conditions arise in automotive fuel cell applications. Thus, cathode electrodes with an optimized ionomer EW distribution might have a significant impact on future automotive fuel cell development.

Impact of stone density on outcomes in percutaneous nephrolithotomy (PCNL): an analysis of the clinical research office of the endourological society (CROES) pcnl global study database.

PubMed

Anastasiadis, Anastasios; Onal, Bulent; Modi, Pranjal; Turna, Burak; Duvdevani, Mordechai; Timoney, Anthony; Wolf, J Stuart; De La Rosette, Jean

2013-12-01

This study aimed to explore the relationship between stone density and outcomes of percutaneous nephrolithotomy (PCNL) using the Clinical Research Office of the Endourological Society (CROES) PCNL Global Study database. Patients undergoing PCNL treatment were assigned to a low stone density [LSD, ≤ 1000 Hounsfield units (HU)] or high stone density (HSD, > 1000 HU) group based on the radiological density of the primary renal stone. Preoperative characteristics and outcomes were compared in the two groups. Retreatment for residual stones was more frequent in the LSD group. The overall stone-free rate achieved was higher in the HSD group (79.3% vs 74.8%, p = 0.113). By univariate regression analysis, the probability of achieving a stone-free outcome peaked at approximately 1250 HU. Below or above this density resulted in lower treatment success, particularly at very low HU values. With increasing radiological stone density, operating time decreased to a minimum at approximately 1000 HU, then increased with further increase in stone density. Multivariate non-linear regression analysis showed a similar relationship between the probability of a stone-free outcome and stone density. Higher treatment success rates were found with low stone burden, pelvic stone location and use of pneumatic lithotripsy. Very low and high stone densities are associated with lower rates of treatment success and longer operating time in PCNL. Preoperative assessment of stone density may help in the selection of treatment modality for patients with renal stones.

Fabrication of Solid-State Multilayer Glass Capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilke, Rudeger H. T.; Brown-Shaklee, Harlan James; Casias, Adrian L.

Alkali-free glasses show immense promise for the development of high-energy density capacitors. The high breakdown strengths on single-layer sheets of glass suggest the potential for improved energy densities over existing state-of-the art polymer capacitors. In this paper, we demonstrate the ability to package thin glass to make solid-state capacitors. Individual layers are bonded using epoxy, leading to capacitors that exhibit stable operation over the temperature range -55 °C to +65 °C. Here, this fabrication approach is scalable and allows for proof testing individual layers prior to incorporation of the stack, providing a blueprint for the fabrication of high-energy density capacitors.

Fabrication of Solid-State Multilayer Glass Capacitors

DOE PAGES

Wilke, Rudeger H. T.; Brown-Shaklee, Harlan James; Casias, Adrian L.; ...

2017-07-31

Alkali-free glasses show immense promise for the development of high-energy density capacitors. The high breakdown strengths on single-layer sheets of glass suggest the potential for improved energy densities over existing state-of-the art polymer capacitors. In this paper, we demonstrate the ability to package thin glass to make solid-state capacitors. Individual layers are bonded using epoxy, leading to capacitors that exhibit stable operation over the temperature range -55 °C to +65 °C. Here, this fabrication approach is scalable and allows for proof testing individual layers prior to incorporation of the stack, providing a blueprint for the fabrication of high-energy density capacitors.

Relativistic density functional theory with picture-change corrected electron density based on infinite-order Douglas-Kroll-Hess method

NASA Astrophysics Data System (ADS)

Oyama, Takuro; Ikabata, Yasuhiro; Seino, Junji; Nakai, Hiromi

2017-07-01

This Letter proposes a density functional treatment based on the two-component relativistic scheme at the infinite-order Douglas-Kroll-Hess (IODKH) level. The exchange-correlation energy and potential are calculated using the electron density based on the picture-change corrected density operator transformed by the IODKH method. Numerical assessments indicated that the picture-change uncorrected density functional terms generate significant errors, on the order of hartree for heavy atoms. The present scheme was found to reproduce the energetics in the four-component treatment with high accuracy.

Effect of high density on the short term Calomys musculinus spacing behaviour: A fencing experiment

NASA Astrophysics Data System (ADS)

Sommaro, Lucía V.; Steinmann, Andrea R.; Chiappero, Marina B.; Priotto, José W.

2010-05-01

We studied the short term spacing behavioural responses of corn mice ( Calomys musculinus) with regard to population density in four 0.25 ha enclosures (two control and two experimental) in the 2007 breeding season. The goal of this research was to test the hypothesis that spacing behaviour only operates among C. musculinus adult females. We estimated 207 home ranges to study: 1) the home range size and the overlap degree of adult males and females in relation to population density; 2) the settlement distances of juveniles to the centre of activity of their mothers and the home range overlap proportion between them and their mothers in relation to population density. We found that home range size and overlap degree in C. musculinus adults were determined by sex and density. At high population density males had significant smaller and more exclusive home ranges, and this might reflect induced territoriality derived from social restrictions. Female home range sizes remained similar irrespective of population density, and they kept exclusive home ranges in both control and experimental enclosures. Thus, females maintained their territories independent of the population density values. The settlement distances of juveniles from their mothers and the overlap proportion between them and their mothers were independent of population density. We conclude that spacing behaviour only operates among C. musculinus adult females and it could have a role in regulating population abundances limiting the number of females that acquire breeding spaces.

Design, construction and long life endurance testing of cathode assemblies for use in microwave high-power transmitting tubes

NASA Technical Reports Server (NTRS)

Gorshe, R.

1982-01-01

The ability of state of the art cathode types to produce current densities of 2A/sq cm, respectively, over a minimum designed life of 30,000 hours of continuous operation without failures was demonstrated. The performance of the state of the art cathode types was evaluated by endurance testing while operating under identical electrical geometrical, and vacuum conditions that realistically duplicate the operating conditions present in a transmitter tube. Although there has been considerable life testing done on high current density types of cathodes, these have beem primarily limited to diodes. A diode and high power microwave tube are grossly different devices. A comparison of these two devices is provided. A diode and high power microwave tube are quite different; one could therefore assume different internal environments, especially in the cathode region. Therefore, in order to establish life capabilities of the cathodes just mentioned, they should be tested in a vehicle which has an internal environment similar to that of a high power microwave tube.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes.

PubMed

Kumar, Niraj; Pal, Dharmendra Kumar; Jadon, Arvind Singh; Pal, Udit Narayan; Rahaman, Hasibur; Prakash, Ram

2016-03-01

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electron beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.

A multiple gap plasma cathode electron gun and its electron beam analysis in self and trigger breakdown modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Niraj; Pal, Udit Narayan; Prakash, Ram

In the present paper, a pseudospark discharge based multiple gap plasma cathode electron gun is reported which has been operated separately in self and trigger breakdown modes using two different gases, namely, argon and hydrogen. The beam current and beam energy have been analyzed using a concentric ring diagnostic arrangement. Two distinct electron beams are clearly seen with hollow cathode and conductive phases. The hollow cathode phase has been observed for ∼50 ns where the obtained electron beam is having low beam current density and high energy. While in conductive phase it is high current density and low energy electronmore » beam. It is inferred that in the hollow cathode phase the beam energy is more for the self breakdown case whereas the current density is more for the trigger breakdown case. The tailor made operation of the hollow cathode phase electron beam can play an important role in microwave generation. Up to 30% variation in the electron beam energy has been achieved keeping the same gas and by varying the breakdown mode operations. Also, up to 32% variation in the beam current density has been achieved for the trigger breakdown mode at optimized trigger position by varying the gas type.« less

Feedback controlled, reactor relevant, high-density, high-confinement scenarios at ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Lang, P. T.; Blanken, T. C.; Dunne, M.; McDermott, R. M.; Wolfrum, E.; Bobkov, V.; Felici, F.; Fischer, R.; Janky, F.; Kallenbach, A.; Kardaun, O.; Kudlacek, O.; Mertens, V.; Mlynek, A.; Ploeckl, B.; Stober, J. K.; Treutterer, W.; Zohm, H.; ASDEX Upgrade Team

2018-03-01

One main programme topic at the ASDEX Upgrade all-metal-wall tokamak is development of a high-density regime with central densities at reactor grade level while retaining high-confinement properties. This required development of appropriate control techniques capable of coping with the pellet tool, a powerful means of fuelling but one which presented challenges to the control system for handling of related perturbations. Real-time density profile control was demonstrated, raising the core density well above the Greenwald density while retaining the edge density in order to avoid confinement losses. Recently, a new model-based approach was implemented that allows direct control of the central density. Investigations focussed first on the N-seeding scenario owing to its proven potential to yield confinement enhancements. Combining pellets and N seeding was found to improve the divertor buffering further and enhance the operational range accessible. For core densities up to about the Greenwald density, a clear improvement with respect to the non-seeding reference was achieved; however, at higher densities this benefit is reduced. This behaviour is attributed to recurrence of an outward shift of the edge density profile, resulting in a reduced peeling-ballooning stability. This is similar to the shift seen during strong gas puffing, which is required to prevent impurity influx in ASDEX Upgrade. First tests indicate that highly-shaped plasma configurations like the ITER base-line scenario, respond very well to pellet injection, showing efficient fuelling with no measurable impact on the edge density profile.

Development program on a cold cathode electron gun

NASA Technical Reports Server (NTRS)

Spindt, C. A.; Holland, C. E.

1985-01-01

During this phase of the cathode development program, SRI improved the multiple electron beam exposure system used to print hole patterns for the cathode arrays, studied anisotropic etch processes, conducted cathode investigations using an emission microscope, reviewed possible alternate materials for cathode fabrication, studied cathode storage techniques, conducted high power operation experiments, and demonstrated high-current-density operation with small arrays of tips.

Electrical Impact of SiC Structural Crystal Defects on High Electric Field Devices

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.

1999-01-01

Commercial epilayers are known to contain a variety of crystallographic imperfections. including micropipes, closed core screw dislocations. low-angle boundaries, basal plane dislocations, heteropolytypic inclusions, and non-ideal surface features like step bunching and pits. This paper reviews the limited present understanding of the operational impact of various crystal defects on SiC electrical devices. Aside from micropipes and triangular inclusions whose densities have been shrinking towards manageably small values in recent years, many of these defects appear to have little adverse operational and/or yield impact on SiC-based sensors, high-frequency RF, and signal conditioning electronics. However high-power switching devices used in power management and distribution circuits have historically (in silicon experience) demanded the highest material quality for prolonged safe operation, and are thus more susceptible to operational reliability problems that arise from electrical property nonuniformities likely to occur at extended crystal defects. A particular emphasis is placed on the impact of closed-core screw dislocations on high-power switching devices, because these difficult to observe defects are present in densities of thousands per cm,in commercial SiC epilayers. and their reduction to acceptable levels seems the most problematic at the present time.

A Cryogenic High-Power-Density Bearingless Motor for Future Electric Propulsion

NASA Technical Reports Server (NTRS)

Choi, Benjamin; Siebert, Mark

2008-01-01

The NASA Glenn Research Center (GRC) is developing a high-power-density switched-reluctance cryogenic motor for all-electric and pollution-free flight. However, cryogenic operation at higher rotational speeds markedly shortens the life of mechanical rolling element bearings. Thus, to demonstrate the practical feasibility of using this motor for future flights, a non-contact rotor-bearing system is a crucial technology to circumvent poor bearing life that ordinarily accompanies cryogenic operation. In this paper, a bearingless motor control technology for a 12-8 (12 poles in the stator and 8 poles in the rotor) switched-reluctance motor operating in liquid nitrogen (boiling point, 77 K (-196 C or -321 F)) was presented. We pushed previous disciplinary limits of electromagnetic controller technique by extending the state-of-the-art bearingless motor operating at liquid nitrogen for high-specific-power applications. The motor was levitated even in its nonlinear region of magnetic saturation, which is believed to be a world first for the motor type. Also we used only motoring coils to generate motoring torque and levitation force, which is an important feature for developing a high specific power motor.

Long-term biological legacies of herbivore density in a landscape-scale experiment: forest understories reflect past deer density treatments for at least 20 years

Treesearch

Tim Nuttle; Todd E. Ristau; Alejandro A. Royo

2014-01-01

Ungulate browsers, when at high densities, are major drivers of vegetation change in forests world-wide. Their effects operate via a variety of generalizable mechanisms related to plant palatability and relative growth rate with respect to browsing pressure. Though such impacts are obviously long-lasting when they determine composition of tree regeneration, we document...

A magnesium–sodium hybrid battery with high operating voltage

DOE PAGES

Dong, Hui; Li, Yifei; Liang, Yanliang; ...

2016-06-10

Here, we report a high performance magnesium-sodium hybrid battery utilizing a magnesium-sodium dual-salt electrolyte, a magnesium anode, and a Berlin green cathode. The cell delivers an average discharge voltage of 2.2 V and a reversible capacity of 143 mA h g –1. We also demonstrate the cell with an energy density of 135 W h kg –1 and a high power density of up to 1.67 kW kg –1.

All-graphene-battery: bridging the gap between supercapacitors and lithium ion batteries

NASA Astrophysics Data System (ADS)

Kim, Haegyeom; Park, Kyu-Young; Hong, Jihyun; Kang, Kisuk

2014-06-01

Herein, we propose an advanced energy-storage system: all-graphene-battery. It operates based on fast surface-reactions in both electrodes, thus delivering a remarkably high power density of 6,450 W kg-1total electrode while also retaining a high energy density of 225 Wh kg-1total electrode, which is comparable to that of conventional lithium ion battery. The performance and operating mechanism of all-graphene-battery resemble those of both supercapacitors and batteries, thereby blurring the conventional distinction between supercapacitors and batteries. This work demonstrates that the energy storage system made with carbonaceous materials in both the anode and cathode are promising alternative energy-storage devices.

All-graphene-battery: bridging the gap between supercapacitors and lithium ion batteries.

PubMed

Kim, Haegyeom; Park, Kyu-Young; Hong, Jihyun; Kang, Kisuk

2014-06-13

Herein, we propose an advanced energy-storage system: all-graphene-battery. It operates based on fast surface-reactions in both electrodes, thus delivering a remarkably high power density of 6,450 W kg(-1)(total electrode) while also retaining a high energy density of 225 Wh kg(-1)(total electrode), which is comparable to that of conventional lithium ion battery. The performance and operating mechanism of all-graphene-battery resemble those of both supercapacitors and batteries, thereby blurring the conventional distinction between supercapacitors and batteries. This work demonstrates that the energy storage system made with carbonaceous materials in both the anode and cathode are promising alternative energy-storage devices.

High data volume and transfer rate techniques used at NASA's image processing facility

NASA Technical Reports Server (NTRS)

Heffner, P.; Connell, E.; Mccaleb, F.

1978-01-01

Data storage and transfer operations at a new image processing facility are described. The equipment includes high density digital magnetic tape drives and specially designed controllers to provide an interface between the tape drives and computerized image processing systems. The controller performs the functions necessary to convert the continuous serial data stream from the tape drive to a word-parallel blocked data stream which then goes to the computer-based system. With regard to the tape packing density, 1.8 times 10 to the tenth data bits are stored on a reel of one-inch tape. System components and their operation are surveyed, and studies on advanced storage techniques are summarized.

Low Temperature Performance of High Power Density DC/DC Converter Modules

NASA Technical Reports Server (NTRS)

Elbuluk, Malik E.; Hammond, Ahmad; Gerber, Scott; Patterson, Richard L.; Overton, Eric

2001-01-01

In this paper, two second-generation high power density DC/DC converter modules have been evaluated at low operating temperatures. The power rating of one converter (Module 1) was specified at 150 W with an input voltage range of 36 to 75 V and output voltage of 12 V. The other converter (Module 2) was specified at 100 W with the same input voltage range and an output voltage of 3.3 V. The converter modules were evaluated in terms of their performance as a function of operating temperature in the range of 25 to -140 C. The experimental procedures along with the experimental data obtained are presented and discussed in this paper.

All-graphene-battery: bridging the gap between supercapacitors and lithium ion batteries

PubMed Central

Kim, Haegyeom; Park, Kyu-Young; Hong, Jihyun; Kang, Kisuk

2014-01-01

Herein, we propose an advanced energy-storage system: all-graphene-battery. It operates based on fast surface-reactions in both electrodes, thus delivering a remarkably high power density of 6,450 W kg−1total electrode while also retaining a high energy density of 225 Wh kg−1total electrode, which is comparable to that of conventional lithium ion battery. The performance and operating mechanism of all-graphene-battery resemble those of both supercapacitors and batteries, thereby blurring the conventional distinction between supercapacitors and batteries. This work demonstrates that the energy storage system made with carbonaceous materials in both the anode and cathode are promising alternative energy-storage devices. PMID:24923290

Polymer electrolyte membrane water electrolysis: Restraining degradation in the presence of fluctuating power

NASA Astrophysics Data System (ADS)

Rakousky, Christoph; Reimer, Uwe; Wippermann, Klaus; Kuhri, Susanne; Carmo, Marcelo; Lueke, Wiebke; Stolten, Detlef

2017-02-01

Polymer electrolyte membrane (PEM) water electrolysis generates 'green' hydrogen when conducted with electricity from renewable - but fluctuating - sources like wind or solar photovoltaic. Unfortunately, the long-term stability of the electrolyzer performance is still not fully understood under these input power profiles. In this study, we contrast the degradation behavior of our PEM water electrolysis single cells that occurs under operation with constant and intermittent power and derive preferable operating states. For this purpose, five different current density profiles are used, of which two were constant and three dynamic. Cells operated at 1 A cm-2 show no degradation. However, degradation was observed for the remaining four profiles, all of which underwent periods of high current density (2 A cm-2). Hereby, constant operation at 2 A cm-2 led to the highest degradation rate (194 μV h-1). Degradation can be greatly reduced when the cells are operated with an intermittent profile. Current density switching has a positive effect on durability, as it causes reversible parts of degradation to recover and results in a substantially reduced degradation per mole of hydrogen produced. Two general degradation phenomena were identified, a decreased anode exchange current density and an increased contact resistance at the titanium porous transport layer (Ti-PTL).

The NOL ballistic piston compressor 2: Operation up to 5,000 ATM

NASA Technical Reports Server (NTRS)

Hammond, G. L.; Lalos, G. T.

1971-01-01

Experiments are described which demonstrated the feasibility of rapidly compressing inert gases in a ballistic piston compressor to simultaneously high temperatures and densities previously unobtainable in the laboratory. With argon, temperatures of the order of 6000 K and accompanying densities of the order of 100 Amagats have been obtained; and with nitrogen, temperatures and densities of 3000 K and 400 Amagats have been approached. Details of the design, assembly, instrumentation, and operating procedures are presented, and the results of mechanical and thermal performance tests up to 5000 atmospheres pressure are described. Emphasis is placed on experiments which demonstrated the usefulness of this apparatus for spectral line broadening studies.

ECR Plasma Source for Heavy Ion Beam Charge Neutralization

NASA Astrophysics Data System (ADS)

Efthimion, P. C.; Gilson, E.; Grishman, L.; Kolchin, P.; Davidson, R. C.

2002-01-01

Highly ionized plasmas are being considered as a medium for charge neutralizing heavy ion beams in order to focus beyond the space-charge limit. Calculations suggest that plasma at a density of 1 - 100 times the ion beam density and at a length of approximately 0.1-2 m would be suitable for achieving a high level of charge neutralization. An ECR source has been built at the Princeton Plasma Physics Laboratory (PPPL) to support a joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 1-10 gauss. The goal is to operate the source at pressures of approximately 10-6 torr at full ionization. The initial operation of the source has been at pressures of 10-4 - 10-1. Electron densities in the range of 108 - 1011 per cubic centimeter have been achieved. Low-pressure operation is important to reduce ion beam ionization. A cusp magnetic field has been installed to improve radial confinement and reduce the field strength on the beam axis. In addition, axial confinement is believed to be important to achieve lower-pressure operation. To further improve breakdown at low pressure, a weak electron source will be placed near the end of the ECR source.

Overview of ASDEX Upgrade results

NASA Astrophysics Data System (ADS)

Zohm, H.; Adamek, J.; Angioni, C.; Antar, G.; Atanasiu, C. V.; Balden, M.; Becker, W.; Behler, K.; Behringer, K.; Bergmann, A.; Bertoncelli, T.; Bilato, R.; Bobkov, V.; Boom, J.; Bottino, A.; Brambilla, M.; Braun, F.; Brüdgam, M.; Buhler, A.; Chankin, A.; Classen, I.; Conway, G. D.; Coster, D. P.; de Marné, P.; D'Inca, R.; Drube, R.; Dux, R.; Eich, T.; Engelhardt, K.; Esposito, B.; Fahrbach, H.-U.; Fattorini, L.; Fink, J.; Fischer, R.; Flaws, A.; Foley, M.; Forest, C.; Fuchs, J. C.; Gál, K.; García Muñoz, M.; Gemisic Adamov, M.; Giannone, L.; Görler, T.; Gori, S.; da Graça, S.; Granucci, G.; Greuner, H.; Gruber, O.; Gude, A.; Günter, S.; Haas, G.; Hahn, D.; Harhausen, J.; Hauff, T.; Heinemann, B.; Herrmann, A.; Hicks, N.; Hobirk, J.; Hölzl, M.; Holtum, D.; Hopf, C.; Horton, L.; Huart, M.; Igochine, V.; Janzer, M.; Jenko, F.; Kallenbach, A.; Kálvin, S.; Kardaun, O.; Kaufmann, M.; Kick, M.; Kirk, A.; Klingshirn, H.-J.; Koscis, G.; Kollotzek, H.; Konz, C.; Krieger, K.; Kurki-Suonio, T.; Kurzan, B.; Lackner, K.; Lang, P. T.; Langer, B.; Lauber, P.; Laux, M.; Leuterer, F.; Likonen, J.; Liu, L.; Lohs, A.; Lunt, T.; Lyssoivan, A.; Maggi, C. F.; Manini, A.; Mank, K.; Manso, M.-E.; Mantsinen, M.; Maraschek, M.; Martin, P.; Mayer, M.; McCarthy, P.; McCormick, K.; Meister, H.; Meo, F.; Merkel, P.; Merkel, R.; Mertens, V.; Merz, F.; Meyer, H.; Mlynek, A.; Monaco, F.; Müller, H.-W.; Münich, M.; Murmann, H.; Neu, G.; Neu, R.; Neuhauser, J.; Nold, B.; Noterdaeme, J.-M.; Pautasso, G.; Pereverzev, G.; Poli, E.; Potzel, S.; Püschel, M.; Pütterich, T.; Pugno, R.; Raupp, G.; Reich, M.; Reiter, B.; Ribeiro, T.; Riedl, R.; Rohde, V.; Roth, J.; Rott, M.; Ryter, F.; Sandmann, W.; Santos, J.; Sassenberg, K.; Sauter, P.; Scarabosio, A.; Schall, G.; Schilling, H.-B.; Schirmer, J.; Schmid, A.; Schmid, K.; Schneider, W.; Schramm, G.; Schrittwieser, R.; Schustereder, W.; Schweinzer, J.; Schweizer, S.; Scott, B.; Seidel, U.; Sempf, M.; Serra, F.; Sertoli, M.; Siccinio, M.; Sigalov, A.; Silva, A.; Sips, A. C. C.; Speth, E.; Stäbler, A.; Stadler, R.; Steuer, K.-H.; Stober, J.; Streibl, B.; Strumberger, E.; Suttrop, W.; Tardini, G.; Tichmann, C.; Treutterer, W.; Tröster, C.; Urso, L.; Vainonen-Ahlgren, E.; Varela, P.; Vermare, L.; Volpe, F.; Wagner, D.; Wigger, C.; Wischmeier, M.; Wolfrum, E.; Würsching, E.; Yadikin, D.; Yu, Q.; Zasche, D.; Zehetbauer, T.; Zilker, M.

2009-10-01

ASDEX Upgrade was operated with a fully W-covered wall in 2007 and 2008. Stationary H-modes at the ITER target values and improved H-modes with H up to 1.2 were run without any boronization. The boundary conditions set by the full W wall (high enough ELM frequency, high enough central heating and low enough power density arriving at the target plates) require significant scenario development, but will apply to ITER as well. D retention has been reduced and stationary operation with saturated wall conditions has been found. Concerning confinement, impurity ion transport across the pedestal is neoclassical, explaining the strong inward pinch of high-Z impurities in between ELMs. In improved H-mode, the width of the temperature pedestal increases with heating power, consistent with a \\beta_{pol,ped}^{1/2} scaling. In the area of MHD instabilities, disruption mitigation experiments using massive Ne injection reach volume averaged values of the total electron density close to those required for runaway suppression in ITER. ECRH at the q = 2 surface was successfully applied to delay density limit disruptions. The characterization of fast particle losses due to MHD has shown the importance of different loss mechanisms for NTMs, TAEs and also beta-induced Alfven eigenmodes (BAEs). Specific studies addressing the first ITER operational phase show that O1 ECRH at the HFS assists reliable low-voltage breakdown. During ramp-up, additional heating can be used to vary li to fit within the ITER range. Confinement and power threshold in He are more favourable than in H, suggesting that He operation could allow us to assess H-mode operation in the non-nuclear phase of ITER operation.

Advanced electron cyclotron heating and current drive experiments on the stellarator Wendelstein 7-X

NASA Astrophysics Data System (ADS)

Stange, Torsten; Laqua, Heinrich Peter; Beurskens, Marc; Bosch, Hans-Stephan; Bozhenkov, Sergey; Brakel, Rudolf; Braune, Harald; Brunner, Kai Jakob; Cappa, Alvaro; Dinklage, Andreas; Erckmann, Volker; Fuchert, Golo; Gantenbein, Gerd; Gellert, Florian; Grulke, Olaf; Hartmann, Dirk; Hirsch, Matthias; Höfel, Udo; Kasparek, Walter; Knauer, Jens; Langenberg, Andreas; Marsen, Stefan; Marushchenko, Nikolai; Moseev, Dmitry; Pablant, Novomir; Pasch, Ekkehard; Rahbarnia, Kian; Mora, Humberto Trimino; Tsujimura, Toru; Turkin, Yuriy; Wauters, Tom; Wolf, Robert

2017-10-01

During the first operational phase (OP 1.1) of Wendelstein 7-X (W7-X) electron cyclotron resonance heating (ECRH) was the exclusive heating method and provided plasma start-up, wall conditioning, heating and current drive. Six gyrotrons were commissioned for OP1.1 and used in parallel for plasma operation with a power of up to 4.3 MW. During standard X2-heating the spatially localized power deposition with high power density allowed controlling the radial profiles of the electron temperature and the rotational transform. Even though W7-X was not fully equipped with first wall tiles and operated with a graphite limiter instead of a divertor, electron densities of n e > 3·1019 m-3 could be achieved at electron temperatures of several keV and ion temperatures above 2 keV. These plasma parameters allowed the first demonstration of a multipath O2-heating scenario, which is envisaged for safe operation near the X-cutoff-density of 1.2·1020 m-3 after full commissioning of the ECRH system in the next operation phase OP1.2.

On the density limit in the helicon plasma sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotelnikov, Igor A., E-mail: I.A.Kotelnikov@inp.nsk.su

2014-12-15

Existence of the density limit in the helicon plasma sources is revisited. The low- and high-frequency regimes of a helicon plasma source operation are distinguished. In the low-frequency regime with ω<√(ω{sub ci}ω{sub ce}), the density limit is deduced from the Golant-Stix criterion of the accessibility of the lower hybrid resonance. In the high-frequency case, ω>√(ω{sub ci}ω{sub ce}), an appropriate limit is given by the Shamrai-Taranov criterion. Both these criteria are closely related to the phenomenon of the coalescence of the helicon wave with the Trivelpiece-Gould mode. We draw a conclusion that the derived density limits are not currently achieved inmore » existing devices, perhaps, because of high energy cost of gas ionization.« less

Ultra-High Intensity Magnetic Field Generation in Dense Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisch, Nathaniel J.

2014-01-08

The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereas the efficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new formsmore » of current drive in regimes appropriate for new fusion concepts.« less

ECR Plasma Source for Heavy Ion Beam Charge Neutralization

NASA Astrophysics Data System (ADS)

Efthimion, P. C.; Gilson, E.; Grisham, L.; Davidson, R. C.; Yu, S.; Logan, B. G.

2002-11-01

Highly ionized plasmas are being considered as a medium for charge neutralizing heavy ion beams in order to focus beyond the space-charge limit. Calculations suggest that plasma at a density of 1 - 100 times the ion beam density and at a length ˜ 0.1-0.5 m would be suitable for achieving a high level of charge neutralization. An ECR source has been built at the Princeton Plasma Physics Laboratory (PPPL) to support a joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 1-10 gauss. The goal is to operate the source at pressures ˜ 10-5 Torr at full ionization. The initial operation of the source has been at pressures of 10-4 - 10-1 Torr. Electron densities in the range of 10^8 - 10^11 cm-3 have been achieved. Low-pressure operation is important to reduce ion beam ionization. A cusp magnetic field has been installed to improve radial confinement and reduce the field strength on the beam axis. In addition, axial confinement is believed to be important to achieve lower-pressure operation. At moderate pressures (> 1 mTorr) the wave damping is collisional, and at low pressures (< 1 mTorr) there is a distinct electron cyclotron resonance. The source has recently been configured to operate with 2.45 GHz microwaves with similar results. At the present operating range the source can simulate the plasma produced by photo-ionization in the target chamber.

A solar-pumped Nd:YAG laser in the high collection efficiency regime

NASA Astrophysics Data System (ADS)

Lando, Mordechai; Kagan, Jacob; Linyekin, Boris; Dobrusin, Vadim

2003-07-01

Solar-pumped lasers can be used for space and terrestrial applications. We report on solar side-pumped Nd:YAG laser experiments, which included comprehensive beam quality measurements and demonstrated record collection efficiency and day long operation. A 6.75 m 2 segmented primary mirror was mounted on a commercial two-axis positioner and focused the solar radiation towards a stationary non-imaging-optics secondary concentrator, which illuminated a Nd:YAG laser rod. Solar side-pumped laser experiments were conducted in both the low and the high pumping density regimes. The low density system was composed of a 89 × 98-mm 2 aperture two-dimensional compound parabolic concentrator (CPC) and a 10-mm diameter 130-mm long Nd:YAG laser rod. The laser emitted up to 46 W and operated continuously for 5 h. The high density system was composed of a three-dimensional CPC with 98 mm entrance diameter and 24 mm exit diameter, followed by a two-dimensional CPC with a rectangular 24 × 33 mm 2 aperture. It pumped a 6-mm diameter 72 mm long Nd:YAG laser rod, which emitted up to 45 W. The results constitute a record collection efficiency of 6.7 W/m 2 of primary mirror. We compare the current results to previous solar side-pumped laser experiments, including experiments at higher pumping density but with low collection efficiency. Finally, we present a scaled up design for a 400 W laser pumped by a solar collection area of 60 m 2, incorporating simultaneously high collection efficiency and high pumping density.

High energy density propulsion systems and small engine dynamometer

NASA Astrophysics Data System (ADS)

Hays, Thomas

2009-07-01

Scope and Method of Study. This study investigates all possible methods of powering small unmanned vehicles, provides reasoning for the propulsion system down select, and covers in detail the design and production of a dynamometer to confirm theoretical energy density calculations for small engines. Initial energy density calculations are based upon manufacturer data, pressure vessel theory, and ideal thermodynamic cycle efficiencies. Engine tests are conducted with a braking type dynamometer for constant load energy density tests, and show true energy densities in excess of 1400 WH/lb of fuel. Findings and Conclusions. Theory predicts lithium polymer, the present unmanned system energy storage device of choice, to have much lower energy densities than other conversion energy sources. Small engines designed for efficiency, instead of maximum power, would provide the most advantageous method for powering small unmanned vehicles because these engines have widely variable power output, loss of mass during flight, and generate rotational power directly. Theoretical predictions for the energy density of small engines has been verified through testing. Tested values up to 1400 WH/lb can be seen under proper operating conditions. The implementation of such a high energy density system will require a significant amount of follow-on design work to enable the engines to tolerate the higher temperatures of lean operation. Suggestions are proposed to enable a reliable, small-engine propulsion system in future work. Performance calculations show that a mature system is capable of month long flight times, and unrefueled circumnavigation of the globe.

Improvement of the environmental and operational characteristics of vehicles through decreasing the motor fuel density.

PubMed

Magaril, Elena

2016-04-01

The environmental and operational characteristics of motor transport, one of the main consumers of motor fuel and source of toxic emissions, soot, and greenhouse gases, are determined to a large extent by the fuel quality which is characterized by many parameters. Fuel density is one of these parameters and it can serve as an indicator of fuel quality. It has been theoretically substantiated that an increased density of motor fuel has a negative impact both on the environmental and operational characteristics of motor transport. The use of fuels with a high density leads to an increase in carbonization within the engine, adversely affecting the vehicle performance and increasing environmental pollution. A program of technological measures targeted at reducing the density of the fuel used was offered. It includes a solution to the problem posed by changes in the refining capacities ratio and the temperature range of gasoline and diesel fuel boiling, by introducing fuel additives and adding butanes to the gasoline. An environmental tax has been developed which allows oil refineries to have a direct impact on the production of fuels with improved environmental performance, taking into account the need to minimize the density of the fuel within a given category of quality.

Overview of ASDEX Upgrade results

NASA Astrophysics Data System (ADS)

A. Kallenbachthe ASDEX Upgrade Team; the EUROfusion MST1 Team

2017-10-01

The ASDEX Upgrade (AUG) programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of 3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF operation. As predicted, a factor two reduction on the ICRF-induced W plasma content could be achieved by the reduction of the sheath voltage at the antenna limiters via the compensation of the image currents of the central and side straps in the antenna frame. There are two main operational scenario lines in AUG. Experiments with low collisionality, which comprise current drive, ELM mitigation/suppression and fast ion physics, are mainly done with freshly boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full ELM suppression and non-inductive operation up to a plasma current of {{I}\\text{p}}=0.8 MA could be obtained at low plasma density. Plasma exhaust is studied under conditions of high neutral divertor pressure and separatrix electron density, where a fresh boronization is not required. Substantial progress could be achieved for the understanding of the confinement degradation by strong D puffing and the improvement with nitrogen or carbon seeding. Inward/outward shifts of the electron density profile relative to the temperature profile effect the edge stability via the pressure profile changes and lead to improved/decreased pedestal performance. Seeding and D gas puffing are found to effect the core fueling via changes in a region of high density on the high field side (HFSHD). The integration of all above mentioned operational scenarios will be feasible and naturally obtained in a large device where the edge is more opaque for neutrals and higher plasma temperatures provide a lower collisionality. The combination of exhaust control with pellet fueling has been successfully demonstrated. High divertor enrichment values of nitrogen {{E}\\text{N}}≥slant 10 have been obtained during pellet injection, which is a prerequisite for the simultaneous achievement of good core plasma purity and high divertor radiation levels. Impurity accumulation observed in the all-metal AUG device caused by the strong neoclassical inward transport of tungsten in the pedestal is expected to be relieved by the higher neoclassical temperature screening in larger devices.

Automated Air Traffic Control Operations with Weather and Time-Constraints: A First Look at (Simulated) Far-Term Control Room Operations

NASA Technical Reports Server (NTRS)

Prevot, Thomas; Homola, Jeffrey R.; Martin, Lynne H.; Mercer, Joey S.; Cabrall, Christopher C.

2011-01-01

In this paper we discuss results from a recent high fidelity simulation of air traffic control operations with automated separation assurance in the presence of weather and time-constraints. We report findings from a human-in-the-loop study conducted in the Airspace Operations Laboratory (AOL) at the NASA Ames Research Center. During four afternoons in early 2010, fifteen active and recently retired air traffic controllers and supervisors controlled high levels of traffic in a highly automated environment during three-hour long scenarios, For each scenario, twelve air traffic controllers operated eight sector positions in two air traffic control areas and were supervised by three front line managers, Controllers worked one-hour shifts, were relieved by other controllers, took a 3D-minute break, and worked another one-hour shift. On average, twice today's traffic density was simulated with more than 2200 aircraft per traffic scenario. The scenarios were designed to create peaks and valleys in traffic density, growing and decaying convective weather areas, and expose controllers to heavy and light metering conditions. This design enabled an initial look at a broad spectrum of workload, challenge, boredom, and fatigue in an otherwise uncharted territory of future operations. In this paper we report human/system integration aspects, safety and efficiency results as well as airspace throughput, workload, and operational acceptability. We conclude that, with further refinements. air traffic control operations with ground-based automated separation assurance can be an effective and acceptable means to routinely provide very high traffic throughput in the en route airspace.

Flute type micropores activated carbon from cotton stalk for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Tian, Xun; Ma, Hongru; Li, Zhe; Yan, Shaocun; Ma, Lei; Yu, Feng; Wang, Gang; Guo, Xuhong; Ma, Yanqing; Wong, Chingping

2017-08-01

Flute type micropores activated carbon (FTMAC) has been successfully obtained from cotton stalk via KOH-chemical activation method. The synthesized carbon material exhibits an ordered pore structure with high specific surface area of 1964.46 m2 g-1 and pore volume of 1.03 m3 g-1. The assembled FTMAC-based electrode delivers a high specific capacitance of 254 F g-1 at a current density of 0.2 A g-1 in 1 M H2SO4 aqueous electrolyte. It still can maintain 221 F g-1at a current density of 10 A g-1, demonstrating a good rate capacity (87% retention), as well as long cyclic stability of 96% capacitance retention after 10000 charging and discharging cycles at current density of 1 A g-1. Moreover, the symmetric supercapacitor can deliver a high energy density of 18.14 W h kg-1 and a power density of 450.37 W kg-1 which is operated in the voltage range of 0-1.8 V.

Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage.

PubMed

Tao, Jiayou; Liu, Nishuang; Rao, Jiangyu; Ding, Longwei; Al Bahrani, Majid Raissan; Li, Luying; Su, Jun; Gao, Yihua

2014-12-21

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO(2) nanowire/carbon nanotube (CNT) composites and MoO(3) nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm(-3) at a scan rate of 2 mV s(-1) and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm(-3) at a power density of 261.4 mW cm(-3), and exhibits excellent cycling performance of 99.6% capacitance retention over 10,000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage.

High power density yeast catalyzed microbial fuel cells

NASA Astrophysics Data System (ADS)

Ganguli, Rahul

Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density increase was shown to quickly saturate with cell mass attached on the electrode. Based on recent modelling data that suggested that the electrode currents might be limited by the poor electrical conductivity of the anode, the power density versus electrical conductivity of a yeast-immobilized anode was investigated. Introduction of high aspect ratio carbon fiber filaments to the immobilization matrix increased the electrical conductivity of the anode. Although a higher electrical conductivity clearly led to an increase in power densities, it was shown that the principal limitation to power density increase was coming from proton transfer limitations in the immobilized anode. Partial overcoming of the gradients lead a power density of ca. 250 microW cm-2, which is the highest reported for yeast powered MFCs. A yeast-catalyzed microbial fuel cell was investigated as a power source for low power sensors using raw tree sap. It was shown that yeast can efficiently utilize the sucrose present in the raw tree sap to produce electricity when excess salt is added to the medium. Therefore the salinity of a potential energy source is an important consideration when MFCs are being considered for energy harvesting from natural sources.

Grade Crossing Protection in High-Speed, High-Density, Passenger-Service Rail Corridors

DOT National Transportation Integrated Search

1973-01-01

The report is a preliminary examination of special aspects of grade crossing protection for operation of high-speed passenger trains in rail corridors for which complete grade separation is not possible. Overall system needs and constraints are indic...

Enabling Airspace Integration for High-Density On-Demand Mobility Operations

NASA Technical Reports Server (NTRS)

Mueller, Eric; Kopardekar, Parimal; Goodrich, Kenneth H.

2017-01-01

Aviation technologies and concepts have reached a level of maturity that may soon enable an era of on-demand mobility (ODM) fueled by quiet, efficient, and largely automated air taxis. However, successfully bringing such a system to fruition will require introducing orders of magnitude more aircraft to a given airspace volume than can be accommodated by the traditional air traffic control system, among other important technical challenges. The airspace integration problem is further compounded by requirements to set aside appropriate ground infrastructure for take-off and landing areas and ensuring these new aircraft types and their operations do not burden traditional airspace users and air traffic control. This airspace integration challenge may be significantly reduced by extending the concepts and technologies developed to manage small unmanned aircraft systems (UAS) at low altitudethe UAS traffic management (UTM) systemto higher altitudes and new aircraft types, or by equipping ODM aircraft with advanced sensors, algorithms, and interfaces. The precedent of operational freedom inherent in visual flight rules and the technologies developed for large UAS and commercial aircraft automation will contribute to the evolution of an ODM system enabled by UTM. This paper describes the set of air traffic services, normally provided by the traditional air traffic system, that an ODM system would implement to achieve the high densities needed for ODMs economic viability. Finally, the paper proposes a framework for integrating, evaluating, and deploying low-, medium-, and high-density ODM concepts that build on each other to ensure operational and economic feasibility at every step.

Active Control of Charge Density Waves at Degenerate Semiconductor Interfaces

NASA Astrophysics Data System (ADS)

Vinnakota, Raj; Genov, Dentcho

We present numerical modeling of an active electronically controlled highly confined charge-density waves, i.e. surface plasmon polaritons (SPPs) at the metallurgic interfaces of degenerate semiconductor materials. An electro-optic switching element for fully-functional plasmonic circuits based on p-n junction semiconductor Surface Plasmon Polariton (SPP) waveguide is shown. Two figures of merits are introduced and parametric study has been performed identifying the device optimal operation range. The Indium Gallium Arsenide (In0.53Ga0.47As) is identified as the best semiconductor material for the device providing high optical confinement, reduced system size and fast operation. The electro-optic SPP switching element is shown to operate at signal modulation up to -24dB and switching rates surpassing 100GHz, thus potentially providing a new pathway toward bridging the gap between electronic and photonic devices. The current work is funded by the NSF EPSCoR CIMM project under award #OIA-1541079.

An Introduction to System-Level, Steady-State and Transient Modeling and Optimization of High-Power-Density Thermoelectric Generator Devices Made of Segmented Thermoelectric Elements

NASA Astrophysics Data System (ADS)

Crane, D. T.

2011-05-01

High-power-density, segmented, thermoelectric (TE) elements have been intimately integrated into heat exchangers, eliminating many of the loss mechanisms of conventional TE assemblies, including the ceramic electrical isolation layer. Numerical models comprising simultaneously solved, nonlinear, energy balance equations have been created to simulate these novel architectures. Both steady-state and transient models have been created in a MATLAB/Simulink environment. The models predict data from experiments in various configurations and applications over a broad range of temperature, flow, and current conditions for power produced, efficiency, and a variety of other important outputs. Using the validated models, devices and systems are optimized using advanced multiparameter optimization techniques. Devices optimized for particular steady-state operating conditions can then be dynamically simulated in a transient operating model. The transient model can simulate a variety of operating conditions including automotive and truck drive cycles.

Technical challenges and future direction for high-efficiency metal hydride thermal energy storage systems

NASA Astrophysics Data System (ADS)

Ward, Patrick A.; Corgnale, Claudio; Teprovich, Joseph A.; Motyka, Theodore; Hardy, Bruce; Sheppard, Drew; Buckley, Craig; Zidan, Ragaiy

2016-04-01

Recently, there has been increasing interest in thermal energy storage (TES) systems for concentrated solar power (CSP) plants, which allow for continuous operation when sunlight is unavailable. Thermochemical energy storage materials have the advantage of much higher energy densities than latent or sensible heat materials. Furthermore, thermochemical energy storage systems based on metal hydrides have been gaining great interest for having the advantage of higher energy densities, better reversibility, and high enthalpies. However, in order to achieve higher efficiencies desired of a thermal storage system by the US Department of Energy, the system is required to operate at temperatures >600 °C. Operation at temperatures >600 °C presents challenges including material selection, hydrogen embrittlement and permeation of containment vessels, appropriate selection of heat transfer fluids, and cost. Herein, the technical difficulties and proposed solutions associated with the use of metal hydrides as TES materials in CSP applications are discussed and evaluated.

Gridded precipitation fields at high temporal and spatial resolution for operational flood forecasting in the Rhine basin

NASA Astrophysics Data System (ADS)

van Osnabrugge, Bart; Weerts, Albrecht; Uijlenhoet, Remko

2017-04-01

Gridded areal precipitation, as one of the most important hydrometeorological input variables for initial state estimation in operational hydrological forecasting, is available in the form of raster data sets (e.g. HYRAS and EOBS) for the River Rhine basin. These datasets are compiled off-line on a daily time step using station data with the highest possible spatial density. However, such a product is not available operationally and at an hourly discretisation. Therefore, we constructed an hourly gridded precipitation dataset at 1.44 km2 resolution for the Rhine basin for the period from 1998 to present using a REGNIE-like interpolation procedure (Weerts et al., 2008) using a low and a high density rain gauge network. The datasets were validated against daily HYRAS (Rauthe, 2013) and EOBS (Haylock, 2008) data. The main goal of the operational procedure is to emulate the HYRAS dataset as good as possible, as the daily HYRAS dataset is used in the off-line calibration of the hydrological model. Our main findings are that even with low station density, the spatial patterns found in the HYRAS data set are well reproduced. With low station density (years 1999-2006) our dataset underestimates precipitation compared to HYRAS and EOBS, notably during the winter. However, interpolation based on the same set of stations overestimates precipitation compared to EOBS for the years 2006-2014. This discrepancy disappears when switching to the high station density. We also analyze the robustness of the hourly precipitation fields by comparing with stations not used during interpolation. Specific issues regarding the data when creating the gridded precipitation fields will be highlighted. Finally, the datasets are used to drive an hourly and daily gridded WFLOW_HBV model of the Rhine at the same spatial resolution. Haylock, M.R., N. Hofstra, A.M.G. Klein Tank, E.J. Klok, P.D. Jones and M. New. 2008: A European daily high-resolution gridded dataset of surface temperature and precipitation. J. Geophys. Res (Atmospheres), 113, D20119, doi:10.1029/2008JD10201 Rauthe, M., Steiner, H., Riediger, U., Mazurkiewicz, A., Gratzki, A. 2013: A Central European precipitation climatology - Part 1: Generation and validation of a high-resolution gridded daily data set (HYRAS). Meteorologische Zeitschrift, 22(3), 235 256 Weerts, A.H., D. Meißner, and S. Rademacher, 2008. Input data rainfall-runoff model operational system FEWS-NL & FEWS-DE. Technical report, Deltares.

Supercapacitors based on self-assembled graphene organogel.

PubMed

Sun, Yiqing; Wu, Qiong; Shi, Gaoquan

2011-10-14

Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability.

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array

PubMed Central

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao

2017-01-01

Abstract Polymer‐based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400–600 kV mm−1, which may bring more challenges relating to the failure probability. Here, a simple two‐step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm−3 is achieved at low electric fields, i.e., 143 kV mm−1, which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm−2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis. PMID:29610724

Lithium thionyl chloride high rate discharge

NASA Technical Reports Server (NTRS)

Klinedinst, K. A.

1980-01-01

Improvements in high rate lithium thionyl chloride power technology achieved by varying the electrolyte composition, operating temperature, cathode design, and cathode composition are discussed. Discharge capacities are plotted as a function of current density, cell voltage, and temperature.

Power-Efficient, High-Current-Density, Long-Life Thermionic Cathode Developed for Microwave Amplifier Applications

NASA Technical Reports Server (NTRS)

Wintucky, Edwin G.

2002-01-01

A power-efficient, miniature, easily manufactured, reservoir-type barium-dispenser thermionic cathode has been developed that offers the significant advantages of simultaneous high electron-emission current density (>2 A/sq cm) and very long life (>100,000 hr of continuous operation) when compared with the commonly used impregnated-type barium-dispenser cathodes. Important applications of this cathode are a wide variety of microwave and millimeter-wave vacuum electronic devices, where high output power and reliability (long life) are essential. We also expect it to enable the practical development of higher purveyance electron guns for lower voltage and more reliable device operation. The low cathode heater power and reduced size and mass are expected to be particularly beneficial in traveling-wave-tube amplifiers (TWTA's) for space communications, where future NASA mission requirements include smaller onboard spacecraft systems, higher data transmission rates (high frequency and output power) and greater electrical efficiency.

Gain and energy storage in holmium YLF

NASA Technical Reports Server (NTRS)

Storm, Mark E.; Deyst, John P.

1991-01-01

It is demonstrated that Q-switched holmium lasers are capable of high-gain and high-energy operation at 300 K. Small-signal gain coefficients of 0.50 and 0.12/cm have been measured in YLF and YAG, respectively. Small-signal gains of 0.50/cm are comparable to those achievable in Nd:YAG and are not typical of low-gain materials. This large gain in the Ho:YLF material is made possible by operating the amplifier in the ground state depletion mode. The amplifier performance data and associated analysis presented demonstrate that efficient energy storage is possible with very high excited state ion densities of the Ho 5I7 upper laser level. This is an important result since upconversion can limit the 5I7 population. Although upconversion was still present in this experiment, it was possible to achieve efficient energy storage, demonstrating that the problem is manageable even at high excitation densities in YLF.

Diagnostic Validity of High-Density Barium Sulfate in Gastric Cancer Screening: Follow-up of Screenees by Record Linkage with the Osaka Cancer Registry

PubMed Central

Yamamoto, Kenyu; Yamazaki, Hideo; Kuroda, Chikazumi; Kubo, Tsugio; Oshima, Akira; Katsuda, Toshizo; Kuwano, Tadao; Takeda, Yoshihiro

2010-01-01

Background The use of high-density barium sulfate was recommended by the Japan Society of Gastroenterological Cancer Screening (JSGCS) in 2004. We evaluated the diagnostic validity of gastric cancer screening that used high-density barium sulfate. Methods The study subjects were 171 833 residents of Osaka, Japan who underwent gastric cancer screening tests at the Osaka Cancer Prevention and Detection Center during the period from 1 January 2000 through 31 December 2001. Screening was conducted using either high-density barium sulfate (n = 48 336) or moderate-density barium sulfate (n = 123 497). The subjects were followed up and their medical records were linked to those of the Osaka Cancer Registry through 31 December 2002. The results of follow-up during 1 year were defined as the gold standard, and test performance values were calculated. Results The sensitivity and specificity of the screening test using moderate-density barium sulfate were 92.3% and 91.0%, respectively, while the sensitivity and specificity of the high-density barium test were 91.8% and 91.4%, respectively. The results of area under receiver-operating-characteristic (ROC) curve analysis revealed no significant difference between the 2 screening tests. Conclusions Screening tests using high- and moderate-density barium sulfate had similar validity, as determined by sensitivity, specificity, and ROC curve analysis. PMID:20551581

Comparison of low density and high density pedicle screw instrumentation in Lenke 1 adolescent idiopathic scoliosis.

PubMed

Shen, Mingkui; Jiang, Honghui; Luo, Ming; Wang, Wengang; Li, Ning; Wang, Lulu; Xia, Lei

2017-08-02

The correlation between implant density and deformity correction has not yet led to a precise conclusion in adolescent idiopathic scoliosis (AIS). The aim of this study was to evaluate the effects of low density (LD) and high density (HD) pedicle screw instrumentation in terms of the clinical, radiological and Scoliosis Research Society (SRS)-22 outcomes in Lenke 1 AIS. We retrospectively reviewed 62 consecutive Lenke 1 AIS patients who underwent posterior spinal arthrodesis using all-pedicle screw instrumentation with a minimum follow-up of 24 months. The implant density was defined as the number of screws per spinal level fused. Patients were then divided into two groups according to the average implant density for the entire study. The LD group (n = 28) had fewer than 1.61 screws per level, while the HD group (n = 34) had more than 1.61 screws per level. The radiographs were analysed preoperatively, postoperatively and at final follow-up. The perioperative and SRS-22 outcomes were also assessed. Independent sample t tests were used between the two groups. Comparisons between the two groups showed no significant differences in the correction of the main thoracic curve and thoracic kyphosis, blood transfusion, hospital stay, and SRS-22 scores. Compared with the HD group, there was a decreased operating time (278.4 vs. 331.0 min, p = 0.004) and decreased blood loss (823.6 vs. 1010.9 ml, p = 0.048), pedicle screws needed (15.1 vs. 19.6, p < 0.001), and implant costs ($10,191.0 vs. $13,577.3, p = 0.003) in the LD group. Both low density and high density pedicle screw instrumentation achieved satisfactory deformity correction in Lenke 1 AIS patients. However, the operating time and blood loss were reduced, and the implant costs were decreased with the use of low screw density constructs.

Studies in High Current Density Ion Sources for Heavy Ion Fusion Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chacon-Golcher, Edwin

This dissertation develops diverse research on small (diameter ~ few mm), high current density (J ~ several tens of mA/cm 2) heavy ion sources. The research has been developed in the context of a programmatic interest within the Heavy Ion Fusion (HIF) Program to explore alternative architectures in the beam injection systems that use the merging of small, bright beams. An ion gun was designed and built for these experiments. Results of average current density yield () at different operating conditions are presented for K + and Cs + contact ionization sources and potassium aluminum silicate sources. Maximum valuesmore » for a K + beam of ~90 mA/cm 2 were observed in 2.3 μs pulses. Measurements of beam intensity profiles and emittances are included. Measurements of neutral particle desorption are presented at different operating conditions which lead to a better understanding of the underlying atomic diffusion processes that determine the lifetime of the emitter. Estimates of diffusion times consistent with measurements are presented, as well as estimates of maximum repetition rates achievable. Diverse studies performed on the composition and preparation of alkali aluminosilicate ion sources are also presented. In addition, this work includes preliminary work carried out exploring the viability of an argon plasma ion source and a bismuth metal vapor vacuum arc (MEVVA) ion source. For the former ion source, fast rise-times (~ 1 μs), high current densities (~ 100 mA/cm +) and low operating pressures (< 2 mtorr) were verified. For the latter, high but acceptable levels of beam emittance were measured (ε n ≤ 0.006 π· mm · mrad) although measured currents differed from the desired ones (I ~ 5mA) by about a factor of 10.« less

The world`s first 27 T and 30 T resistive magnets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bird, M.D.; Bole, S.; Eyssa, Y.M.

1996-07-01

The authors describe in detail a 30 Tesla, 32mm warm bore,m 15 MW resistive magnet which was put into operation at the National High Magnetic Field Laboratory in Tallahassee, FL in March 1995. The magnet consists of three concentric axially-cooled Bitter stacks connected electrically in series. This magnet employs a substantial new development in Bitter magnet technology which allows high current densities without the usually accompanying high stresses. Details of magnet optimization, design, construction, testing and operation are presented. The authors also report on operating experience with the 27 T magnets.

High performance electrodes in vanadium redox flow batteries through oxygen-enriched thermal activation

NASA Astrophysics Data System (ADS)

Pezeshki, Alan M.; Clement, Jason T.; Veith, Gabriel M.; Zawodzinski, Thomas A.; Mench, Matthew M.

2015-10-01

The roundtrip electrochemical energy efficiency is improved from 63% to 76% at a current density of 200 mA cm-2 in an all-vanadium redox flow battery (VRFB) by utilizing modified carbon paper electrodes in the high-performance no-gap design. Heat treatment of the carbon paper electrodes in a 42% oxygen/58% nitrogen atmosphere increases the electrochemically wetted surface area from 0.24 to 51.22 m2 g-1, resulting in a 100-140 mV decrease in activation overpotential at operationally relevant current densities. An enriched oxygen environment decreases the amount of treatment time required to achieve high surface area. The increased efficiency and greater depth of discharge doubles the total usable energy stored in a fixed amount of electrolyte during operation at 200 mA cm-2.

Daikin Advanced Lithium Ion Battery Technology – High Voltage Electrolyte - REVISED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sunstrom, Joseph; Hendershot, Ron E.

An evaluation of high voltage electrolytes which contain fluorochemicals as solvents/additive has been completed with the objective of formulating a safe, stable electrolyte capable of operation to 4.6 V. Stable cycle performance has been demonstrated in LiNi1/3Mn1/3Co1/3O2 (NMC111)/graphite cells to 4.5 V. The ability to operate at high voltage results in significant energy density gain (>30%) which would manifest as longer battery life resulting in higher range for electric vehicles. Alternatively, a higher energy density battery can be made smaller without sacrificing existing energy. In addition, the fluorinated electrolytes examined showed better safety performance when tested in abuse conditions. Themore » results are promising for future advanced battery development for vehicles as well as other applications.« less

High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric

PubMed Central

Fujii, Mami N.; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

2015-01-01

The use of indium–gallium–zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic–inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic–inorganic hybrid devices. PMID:26677773

High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric.

PubMed

Fujii, Mami N; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

2015-12-18

The use of indium-gallium-zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic-inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic-inorganic hybrid devices.

CO2 concentration and occupancy density in the critical zones served by the VAV system

NASA Astrophysics Data System (ADS)

Etoua Evina, Ghislaine; Kajl, Stanislaw; Lamarche, Louis; Beltran-Galindo, Javier

2017-11-01

This article presents the results obtained from monitoring a VAV system with highly diversified zone occupancy density are presented in the article. The investigated VAV system meets the load for 72 zones (68 perimeters and 4 interiors) consisting of classrooms, offices, conference rooms, etc. with highly diversified occupancy densities from 1.875 to 2.5 m2/person for the classrooms and from 10 to 15 m2/person for the offices. The monitoring shows that the CO2 concentration can exceed the set point in the critical rooms. Simulation results are also presented in the article to show that it is often impossible to adjust the operation of such VAV systems because the adjusted System Outdoor Air Fractions, % OA, can reach 100% even where the zone CO2 concentration is not respected. The presented monitoring and simulation results were obtained in the winter, with the VAV system operating at partial load and with the minimum outdoor air flowrate required by the economizer system. As shown in the article, to respect the zone set point CO2 concentration in such period, the VAV system must operate mostly at a %OA equal to 100% instead of its minimum value. To circumvent this, the supply zone air flow rate may have to be designed taking into account the CO2 concentration resulting from the critical zones occupancy density.

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for High Energy Density plasmas at energies below 10 keV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdivia, M. P.; Stutman, D.; Finkenthal, M.

2014-07-15

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities.more » We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.« less

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for high energy density plasmas at energies below 10 keV.

PubMed

Valdivia, M P; Stutman, D; Finkenthal, M

2014-07-01

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael, Stephan; Chow, Weng; Schneider, Hans

In the framework of a microscopic model for intersubband gain from electrically pumped quantum-dot structures we investigate electrically pumped quantum-dots as active material for a mid-infrared quantum cascade laser. Our previous calculations have indicated that these structures could operate with reduced threshold current densities while also achieving a modal gain comparable to that of quantum well active materials. We study the influence of two important quantum-dot material parameters, here, namely inhomogeneous broadening and quantum-dot sheet density, on the performance of a proposed quantum cascade laser design. In terms of achieving a positive modal net gain, a high quantum-dot density canmore » compensate for moderately high inhomogeneous broadening, but at a cost of increased threshold current density. By minimizing quantum-dot density with presently achievable inhomogeneous broadening and total losses, significantly lower threshold densities than those reported in quantum-well quantum-cascade lasers are predicted by our theory.« less

Wearable Solid-State Supercapacitors Operating at High Working Voltage with a Flexible Nanocomposite Electrode.

PubMed

Li, Xiaoyan; Wang, Jun; Zhao, Yaping; Ge, Fengyan; Komarneni, Sridhar; Cai, Zaisheng

2016-10-05

The proposed approach for fabricating ultralight self-sustained electrodes facilitates the structural integration of highly flexible carbon nanofibers, amino-modified multiwalled carbon nanotubes (AM-MWNT), and MnO 2 nanoflakes for potential use in wearable supercapacitors. Because of the higher orientation of AM-MWNT and the sublimation of terephthalic acid (PTA) in the carbonization process, freestanding electrodes could be realized with high porosity and flexibility and could possess remarkable electrochemical properties without using polymer substrates. Wearable symmetric solid-state supercapacitors were further assembled using a LiCl/PVA gel electrolyte, which exhibit a maximum energy density of 44.57 Wh/kg (at a power density of 337.1 W/kg) and a power density of 13330 W/kg (at an energy density of 19.64 Wh/kg) with a working voltage as high as 1.8 V. Due to the combination of several favorable traits such as flexibility, high energy density, and excellent electrochemical cyclability, the presently developed wearable supercapacitors with wide potential windows are expected to be useful for new kinds of portable electric devices.

Fluorinated Carbon Composite Cathode for a High Energy Lithium Battery (Briefing Charts)

DTIC Science & Technology

2011-02-16

REPORT DOCUMENTATION PAGE Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 Form Approved OMB No. 0704-0188 The public reporting burden...monofluoride (Li/ CFx ) primary batteries have double energy density over state-of-the-art Li/MnO2 and Li/SO2 primary batteries (theoretically 2203 Wh/kg...temperature operating conditions. This invention relates to a high energy density Li/ CFx primary battery technology with substantial reduction in

Production of high transient heat and particle fluxes in a linear plasma device

NASA Astrophysics Data System (ADS)

De Temmerman, G.; Zielinski, J. J.; van der Meiden, H.; Melissen, W.; Rapp, J.

2010-08-01

We report on the generation of high transient heat and particle fluxes in a linear plasma device by pulsed operation of the plasma source. A capacitor bank is discharged into the source to transiently increase the discharge current up to 1.7 kA, allowing peak densities and temperature of 70×1020 m-3 and 6 eV corresponding to a surface power density of about 400 MW m-2.

Online mass storage system detailed requirements document

NASA Technical Reports Server (NTRS)

1976-01-01

The requirements for an online high density magnetic tape data storage system that can be implemented in a multipurpose, multihost environment is set forth. The objective of the mass storage system is to provide a facility for the compact storage of large quantities of data and to make this data accessible to computer systems with minimum operator handling. The results of a market survey and analysis of candidate vendor who presently market high density tape data storage systems are included.

Multilayer core-shell structured composite paper electrode consisting of copper, cuprous oxide and graphite assembled on cellulose fibers for asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wan, Caichao; Jiao, Yue; Li, Jian

2017-09-01

An easily-operated and inexpensive strategy (pencil-drawing-electrodeposition-electro-oxidation) is proposed to synthesize a novel class of multilayer core-shell structured composite paper electrode, which consists of copper, cuprous oxide and graphite assembled on cellulose fibers. This interesting electrode structure plays a pivotal role in providing more active sites for electrochemical reactions, facilitating ion and electron transport and shorting their diffusion pathways. This electrode demonstrates excellent electrochemical properties with a high specific capacitance of 601 F g-1 at 2 A g-1 and retains 83% of this capacitance when operated at an ultrahigh current density of 100 A g-1. In addition, a high energy density of 13.4 W h kg-1 at the power density of 0.40 kW kg-1 and a favorable cycling stability (95.3%, 8000 cycles) were achieved for this electrode. When this electrode was assembled into an asymmetric supercapacitor with carbon paper as negative electrode, the device displays remarkable electrochemical performances with a large areal capacitances (122 mF cm-2 at 1 mA cm-2), high areal energy density (10.8 μW h cm-2 at 402.5 μW cm-2) and outstanding cycling stability (91.5%, 5000 cycles). These results unveil the potential of this composite electrode as a high-performance electrode material for supercapacitors.

Threshold-voltage modulated phase change heterojunction for application of high density memory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Baihan; Tong, Hao, E-mail: tonghao@hust.edu.cn; Qian, Hang

2015-09-28

Phase change random access memory is one of the most important candidates for the next generation non-volatile memory technology. However, the ability to reduce its memory size is compromised by the fundamental limitations inherent in the CMOS technology. While 0T1R configuration without any additional access transistor shows great advantages in improving the storage density, the leakage current and small operation window limit its application in large-scale arrays. In this work, phase change heterojunction based on GeTe and n-Si is fabricated to address those problems. The relationship between threshold voltage and doping concentration is investigated, and energy band diagrams and X-raymore » photoelectron spectroscopy measurements are provided to explain the results. The threshold voltage is modulated to provide a large operational window based on this relationship. The switching performance of the heterojunction is also tested, showing a good reverse characteristic, which could effectively decrease the leakage current. Furthermore, a reliable read-write-erase function is achieved during the tests. Phase change heterojunction is proposed for high-density memory, showing some notable advantages, such as modulated threshold voltage, large operational window, and low leakage current.« less

Frequency-tuning radiofrequency plasma source operated in inductively-coupled mode under a low magnetic field

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Nakano, Yudai; Ando, Akira

2017-07-01

A radiofrequency (rf) inductively-coupled plasma source is operated with a frequency-tuning impedance matching system, where the rf frequency is variable in the range of 20-50 MHz and the maximum power is 100 W. The source consists of a 45 mm-diameter pyrex glass tube wound by an rf antenna and a solenoid providing a magnetic field strength in the range of 0-200 Gauss. A reflected rf power for no plasma case is minimized at the frequency of ˜25 MHz, whereas the frequency giving the minimum reflection with the high density plasma is about 28 MHz, where the density jump is observed when minimizing the reflection. A high density argon plasma above 1× {{10}12} cm-3 is successfully obtained in the source for the rf power of 50-100 W, where it is observed that an external magnetic field of a few tens of Gauss yields the highest plasma density in the present configuration. The frequency-tuning plasma source is applied to a compact and high-speed silicon etcher in an Ar-SF6 plasma; then the etching rate of 8~μ m min-1 is obtained for no bias voltage to the silicon wafer, i.e. for the case that a physical ion etching process is eliminated.

Hydrodynamic and material properties experiments using pulsed power techniques

NASA Astrophysics Data System (ADS)

Reinovsky, R. E.; Trainor, R. J.

2000-04-01

Within the last five years, a new approach to the exploration of dynamic material properties and advanced hydrodynamics at extreme conditions has joined the traditional techniques of high velocity guns and explosives. This new application uses electromagnetic energy to accelerate solid density material to produce shocks in a cylindrical target. The principal tool for producing high energy density environments is the high precision, magnetically imploded, near-solid density cylindrical liner. The most attractive pulsed power system for driving such experiments is an ultrahigh current, low impedance, microsecond time scale source that is economical both to build and to operate. Two families of pulsed power systems can be applied to drive such experiments. The 25-MJ Atlas capacitor bank system currently under construction at Los Alamos is the first system of its scale specifically designed to drive high precision solid liners. Delivering 30 MA, Atlas will provide liner velocities 12-15 km/sec and kinetic energies of 1-2 MJ/cm with extensive diagnostics and excellent reproducibility. Explosive flux compressor technology provides access to currents exceeding 100 MA producing liner velocities above 25 km/sec and kinetic energies of 5-20 MJ/cm in single shot operations

High-power operation of highly reliable narrow stripe pseudomorphic single quantum well lasers emitting at 980 nm

NASA Technical Reports Server (NTRS)

Larsson, A.; Forouhar, S.; Cody, J.; Lang, R. J.

1990-01-01

Ridge waveguide pseudomorphic InGaAs/GaAs/AlGaAs single-quantum-well lasers exhibiting record high quantum efficiencies and high output power densities (105 mW per facet from a 6 micron wide stripe) at a lasing wavelength of 980 nm are discussed that were fabricated from a graded index separate confinement heterostructure grown by molecular beam epitaxy. Life testing at an output power of 30 mW per uncoated facet reveals a slow gradual degradation during the initial 500 h of operation after which the operating characteristics of the lasers become stable. The emission wavelength, the high output power, and the fundamental lateral mode operation render these lasers suitable for pumping Er3+-doped fiber amplifiers.

Excited argon 1s5 production in micro-hollow cathode discharges for use as potential rare gas laser sources

NASA Astrophysics Data System (ADS)

Peterson, Richard D.; Eshel, Ben; Rice, Christopher A.; Perram, Glen P.

2018-02-01

The diode-pumped rare gas laser (DPRGL) has been suggested as a potential high-gain, high-energy laser which requires densities on the order of 1013 cm-3 at pressures around 1 atmosphere for efficient operation. Argon 1s5 number densities have been measured in micro-hollow cathode discharges with electrode gaps of 127 and 254 μm and hole diameters from 100-400 μm. The dependency of the metastable argon (1s5) density on total gas pressure, electrode gap distance and hole diameter were explored. The measured densities were all in the range of 0.5 - 2 × 1013 cm-3 with the 400 μm hole diameters being the lowest.

Test bed ion engine development

NASA Technical Reports Server (NTRS)

Aston, G.; Deininger, W. D.

1984-01-01

A test bed ion (TBI) engine was developed to serve as a tool in exploring the limits of electrostatic ion thruster performance. A description of three key ion engine components, the decoupled extraction and amplified current (DE-AC) accelerator system, field enhanced refractory metal (FERM) hollow cathode and divergent line cusp (DLC) discharge chamber, whose designs and operating philosophies differ markedly from conventional thruster technology is given. Significant program achievements were: (1) high current density DE-AC accelerator system operation at low electric field stress with indicated feasibility of a 60 mA/sq cm argon ion beam; (2) reliable FERM cathode start up times of 1 to 2 secs. and demonstrated 35 ampere emission levels; (3) DLC discharge chamber plasma potentials negative of anode potential; and (4) identification of an efficient high plasma density engine operating mode. Using the performance projections of this program and reasonable estimates of other parameter values, a 1.0 Newton thrust ion engine is identified as a realizable technology goal. Calculations show that such an engine, comparable in beam area to a J series 30 cm thruster, could, operating on Xe or Hg, have thruster efficiencies as high as 0.76 and 0.78 respectively, with a 100 eV/ion discharge loss.

Reliable enumeration of malaria parasites in thick blood films using digital image analysis.

PubMed

Frean, John A

2009-09-23

Quantitation of malaria parasite density is an important component of laboratory diagnosis of malaria. Microscopy of Giemsa-stained thick blood films is the conventional method for parasite enumeration. Accurate and reproducible parasite counts are difficult to achieve, because of inherent technical limitations and human inconsistency. Inaccurate parasite density estimation may have adverse clinical and therapeutic implications for patients, and for endpoints of clinical trials of anti-malarial vaccines or drugs. Digital image analysis provides an opportunity to improve performance of parasite density quantitation. Accurate manual parasite counts were done on 497 images of a range of thick blood films with varying densities of malaria parasites, to establish a uniformly reliable standard against which to assess the digital technique. By utilizing descriptive statistical parameters of parasite size frequency distributions, particle counting algorithms of the digital image analysis programme were semi-automatically adapted to variations in parasite size, shape and staining characteristics, to produce optimum signal/noise ratios. A reliable counting process was developed that requires no operator decisions that might bias the outcome. Digital counts were highly correlated with manual counts for medium to high parasite densities, and slightly less well correlated with conventional counts. At low densities (fewer than 6 parasites per analysed image) signal/noise ratios were compromised and correlation between digital and manual counts was poor. Conventional counts were consistently lower than both digital and manual counts. Using open-access software and avoiding custom programming or any special operator intervention, accurate digital counts were obtained, particularly at high parasite densities that are difficult to count conventionally. The technique is potentially useful for laboratories that routinely perform malaria parasite enumeration. The requirements of a digital microscope camera, personal computer and good quality staining of slides are potentially reasonably easy to meet.

Improved Density Control in the Pegasus Toroidal Experiment using Internal Fueling

NASA Astrophysics Data System (ADS)

Thome, K. E.; Bongard, M. W.; Cole, J. A.; Fonck, R. J.; Redd, A. J.; Winz, G. R.

2012-10-01

Routine density control up to and exceeding the Greenwald limit is critical to key Pegasus operational scenarios, including non-solenoidal startup plasmas created using single-point helicity injection and high β Ohmic plasmas. Confinement scalings suggest it is possible to achieve very high β plasmas in Pegasus by lowering the toroidal field and increasing ne/ng. In the past, Pegasus achieved β ˜ 20% in high recycling Ohmic plasmas without running into any operational boundaries.footnotetext Garstka, G.D. et al., Phys. Plasmas 10, 1705 (2003) However, recent Ohmic experiments have demonstrated that Pegasus currently operates in an extremely low-recycling regime with R < 0.8 and Zeff ˜ 1 using improved vacuum conditioning techniques, such as Ti gettering and cryogenic pumping. Hence, it is difficult to achieve ne/ng> 0.3 with these improved wall conditions. Presently, gas is injected using low-field side (LFS) modified PV-10 valves. To attain high ne/ng operation and coincidentally separate core plasma and local current source fueling two new gas fueling capabilities are under development. A centerstack capillary injection system has been commissioned and is undergoing initial tests. A LFS movable midplane needle gas injection system is currently under design and will reach r/a ˜ 0.25. Initial results from both systems will be presented.

Measurement of Radioactive Contamination on Work Clothing of Workers Engaged in Decontamination Operations

NASA Astrophysics Data System (ADS)

Tsujimura, Norio; Yoshida, Tadayoshi; Hoshi, Katsuya

To rationally judge the necessity of the contamination screening measurements required in the decontamination work regulations, a field study of the surface contamination density on the clothing of the workers engaged in decontamination operations was performed. The clothing and footwear of 20 workers was analyzed by high-purity germanium (HPGe) gamma-ray spectroscopy. The maximum radiocesium activities (134Cs + 137Cs) observed were 3600, 1300, and 2100 Bq for the work clothing, gloves, and boots, respectively, and the derived surface contamination densities were below the regulatory limit of 40 Bq/cm2. The results of this field study suggest that the upper bounds of the surface contamination density on the work clothing, gloves, and boots are predictable from the maximum soil loading density on the surface of clothing and footwear and the radioactivity concentration in soil at the site.

Implementation and Initial Validation of a 100-Kilowatt Class Nested-Channel Hall Thruster

NASA Technical Reports Server (NTRS)

Hall, Scott J.; Florenz, Roland E.; Gallimore, Alec D.; Kamhawi, Hani; Brown, Daniel L.; Polk, James E.; Goebel, Dan; Hofer, Richard R.

2014-01-01

The X3 is a 100-kilowatt class nested-channel Hall thruster developed by the Plasmadynamics and Electric Propulsion Laboratory at the University of Michigan in collaboration with the Air Force Research Laboratory and NASA. The cathode, magnetic circuit, boron nitride channel rings, and anodes all required specific design considerations during thruster development, and thermal modeling was used to properly account for thermal growth in material selection and component design. A number of facility upgrades were required at the University of Michigan to facilitate operation of the X3. These upgrades included a re-worked propellant feed system, a completely redesigned power and telemetry break-out box, and numerous updates to thruster handling equipment. The X3 was tested on xenon propellant at two current densities, 37% and 73% of the nominal design value. It was operated to a maximum steady-state discharge power of 60.8 kilowatts. The tests presented here served as an initial validation of thruster operation. Thruster behavior was monitored with telemetry, photography and high-speed current probes. The photography showed a uniform plume throughout testing. At constant current density, reductions in mass flow rate of 18% and 26% were observed in the three-channel operating configuration as compared to the superposition of each channel running individually. The high-speed current probes showed that the thruster was stable at all operating points and that the channels influence each other when more than one is operating simultaneously. Additionally, the ratio of peak-to-peak AC-coupled discharge current oscillations to mean discharge current did not exceed 51% for any operating points reported here, and did not exceed 17% at the higher current density.

Twenty Years of Research on the Alcator C-Mod Tokamak

NASA Astrophysics Data System (ADS)

Greenwald, Martin

2013-10-01

Alcator C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since its start in 1993, contributing data that extended tests of critical physical models into new parameter ranges and into new regimes. Using only RF for heating and current drive with innovative launching structures, C-Mod operates routinely at very high power densities. Research highlights include direct experimental observation of ICRF mode-conversion, ICRF flow drive, demonstration of Lower-Hybrid current drive at ITER-like densities and fields and, using a set of powerful new diagnostics, extensive validation of advanced RF codes. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing components--an approach adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and EDA H-mode regimes which have high performance without large ELMs and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and found that self-generated flow shear can be strong enough to significantly modify transport. C-Mod made the first quantitative link between pedestal temperature and H-mode performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. Work supported by U.S. DoE

Millimeter-wave irradiation heating for operation of doped CeO2 electrolyte-supported single solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Che Abdullah, Salmie Suhana Binti; Teranishi, Takashi; Hayashi, Hidetaka; Kishimoto, Akira

2018-01-01

High operation temperature of solid oxide fuel cell (SOFC) results in high cell and operation cost, time consuming and fast cell degradation. Developing high performance SOFC that operates at lower temperature is required. Here we demonstrate 24 GHz microwave as a rapid heating source to replace conventional heating method for SOFC operation using 20 mol% Sm doped CeO2 electrolyte-supported single cell. The tested cell shows improvement of 62% in maximum power density at 630 °C under microwave heating. This improvement governs by bulk conductivity of the electrolyte. Investigation of ionic transference number reveals that the value is unchanged under microwave irradiation, confirming the charge carrier is dominated by oxygen ion species. This work shows a potential new concept of high performance as well as cost and energy effective SOFC.

Electrodeposited Nanolaminated CoNiFe Cores for Ultracompact DC-DC Power Conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J; Kim, M; Herrault, F

2015-09-01

Laminated metallic alloy cores (i.e., alternating layers of thin film metallic alloy and insulating material) of appropriate lamination thickness enable suppression of eddy current losses at high frequencies. Magnetic cores comprised of many such laminations yield substantial overall magnetic volume, thereby enabling high-power operation. Previously, we reported nanolaminated permalloy (Ni-80 Fe-20) cores based on a sequential electrodeposition technique, demonstrating negligible eddy current losses at peak flux densities up to 0.5 T and operating at megahertz frequencies. This paper demonstrates improved performance of nanolaminated cores comprising tens to hundreds of layers of 300-500-nm-thick CoNiFe films that exhibit superior magnetic properties (e.g.,more » higher saturation flux density and lower coercivity) than permalloy. Nanolaminated CoNiFe cores can be operated up to a peak flux density of 0.9 T, demonstrating improved power handling capacity and exhibiting 30% reduced volumetric core loss, attributed to lowered hysteresis losses compared to the nanolaminated permalloy core of the same geometry. Operating these cores in a buck dc-dc power converter at a switching frequency of 1 MHz, the nanolaminated CoNiFe cores achieved a conversion efficiency exceeding 90% at output power levels up to 7 W, compared to an achieved permalloy core conversion efficiency below 86% at 6 W.« less

Ultra-High Density Holographic Memory Module with Solid-State Architecture

NASA Technical Reports Server (NTRS)

Markov, Vladimir B.

2000-01-01

NASA's terrestrial. space, and deep-space missions require technology that allows storing. retrieving, and processing a large volume of information. Holographic memory offers high-density data storage with parallel access and high throughput. Several methods exist for data multiplexing based on the fundamental principles of volume hologram selectivity. We recently demonstrated that a spatial (amplitude-phase) encoding of the reference wave (SERW) looks promising as a way to increase the storage density. The SERW hologram offers a method other than traditional methods of selectivity, such as spatial de-correlation between recorded and reconstruction fields, In this report we present the experimental results of the SERW-hologram memory module with solid-state architecture, which is of particular interest for space operations.

Reversible chemical delithiation/lithiation of LiFePO4: towards a redox flow lithium-ion battery.

PubMed

Huang, Qizhao; Li, Hong; Grätzel, Michael; Wang, Qing

2013-02-14

Reversible chemical delithiation/lithiation of LiFePO(4) was successfully demonstrated using ferrocene derivatives, based on which a novel energy storage system--the redox flow lithium-ion battery (RFLB), was devised by integrating the operation flexibility of a redox flow battery and high energy density of a lithium-ion battery. Distinct from the recent semi-solid lithium rechargeable flow battery, the energy storage materials of RFLB stored in separate energy tanks remain stationary upon operation, giving us a fresh perspective on building large-scale energy storage systems with higher energy density and improved safety.

Bird migration flight altitudes studied by a network of operational weather radars.

PubMed

Dokter, Adriaan M; Liechti, Felix; Stark, Herbert; Delobbe, Laurent; Tabary, Pierre; Holleman, Iwan

2011-01-06

A fully automated method for the detection and quantification of bird migration was developed for operational C-band weather radar, measuring bird density, speed and direction as a function of altitude. These weather radar bird observations have been validated with data from a high-accuracy dedicated bird radar, which was stationed in the measurement volume of weather radar sites in The Netherlands, Belgium and France for a full migration season during autumn 2007 and spring 2008. We show that weather radar can extract near real-time bird density altitude profiles that closely correspond to the density profiles measured by dedicated bird radar. Doppler weather radar can thus be used as a reliable sensor for quantifying bird densities aloft in an operational setting, which--when extended to multiple radars--enables the mapping and continuous monitoring of bird migration flyways. By applying the automated method to a network of weather radars, we observed how mesoscale variability in weather conditions structured the timing and altitude profile of bird migration within single nights. Bird density altitude profiles were observed that consisted of multiple layers, which could be explained from the distinct wind conditions at different take-off sites. Consistently lower bird densities are recorded in The Netherlands compared with sites in France and eastern Belgium, which reveals some of the spatial extent of the dominant Scandinavian flyway over continental Europe.

Bird migration flight altitudes studied by a network of operational weather radars

PubMed Central

Dokter, Adriaan M.; Liechti, Felix; Stark, Herbert; Delobbe, Laurent; Tabary, Pierre; Holleman, Iwan

2011-01-01

A fully automated method for the detection and quantification of bird migration was developed for operational C-band weather radar, measuring bird density, speed and direction as a function of altitude. These weather radar bird observations have been validated with data from a high-accuracy dedicated bird radar, which was stationed in the measurement volume of weather radar sites in The Netherlands, Belgium and France for a full migration season during autumn 2007 and spring 2008. We show that weather radar can extract near real-time bird density altitude profiles that closely correspond to the density profiles measured by dedicated bird radar. Doppler weather radar can thus be used as a reliable sensor for quantifying bird densities aloft in an operational setting, which—when extended to multiple radars—enables the mapping and continuous monitoring of bird migration flyways. By applying the automated method to a network of weather radars, we observed how mesoscale variability in weather conditions structured the timing and altitude profile of bird migration within single nights. Bird density altitude profiles were observed that consisted of multiple layers, which could be explained from the distinct wind conditions at different take-off sites. Consistently lower bird densities are recorded in The Netherlands compared with sites in France and eastern Belgium, which reveals some of the spatial extent of the dominant Scandinavian flyway over continental Europe. PMID:20519212

Deriving Sea Surface Salinity and Density Variations from Satellite and Aircraft Microwave Radiometer Measurements: Application to Coastal Plumes Using STARRS

DTIC Science & Technology

2007-11-01

again, with of the prevailing T, S, and, hence, D gradients through the the advent of high-performance spaceborne altimeters (e.g., high- aspect - ratio ... rectangular domains with linear dimensions largely , if not completely, eliminated by the differencing oper- of about 60 km in a 4-h flight. (See...strongest A simple four- quadrant arctangent of the terms in the density in the 00 and 1800 directions, whereas compensation is most ratio would serve our

Effect of Discontinuities and Penetrations on the Shielding Efficacy of High Temperature Superconducting Magnetic Shields

NASA Astrophysics Data System (ADS)

Hatwar, R.; Kvitkovic, J.; Herman, C.; Pamidi, S.

2015-12-01

High Temperature Superconducting (HTS) materials have been demonstrated to be suitable for applications in shielding of both DC and AC magnetic fields. Magnetic shielding is required for protecting sensitive instrumentation from external magnetic fields and for preventing the stray magnetic fields produced by high power density equipment from affecting neighbouring devices. HTS shields have high current densities at relatively high operating temperatures (40-77 K) and can be easily fabricated using commercial HTS conductor. High current densities in HTS materials allow design and fabrication of magnetic shields that are lighter and can be incorporated into the body and skin of high power density devices. HTS shields are particularly attractive for HTS devices because a single cryogenic system can be used for cooling the device and the associated shield. Typical power devices need penetrations for power and signal cabling and the penetrations create discontinuities in HTS shields. Hence it is important to assess the effect of the necessary discontinuities on the efficacy of the shields and the design modifications necessary to accommodate the penetrations.

Energy storage options for space power

NASA Astrophysics Data System (ADS)

Hoffman, H. W.; Martin, J. F.; Olszewski, M.

Including energy storage in a space power supply enhances the feasibility of using thermal power cycles (Rankine or Brayton) and providing high-power pulses. Superconducting magnets, capacitors, electrochemical batteries, thermal phase-change materials (PCM), and flywheels are assessed; the results obtained suggest that flywheels and phase-change devices hold the most promise. Latent heat storage using inorganic salts and metallic eutectics offers thermal energy storage densities of 1500 kJ/kg to 2000 kJ/kg at temperatures to 1675 K. Innovative techniques allow these media to operate in direct contact with the heat engine working fluid. Enhancing thermal conductivity and/or modifying PCM crystallization habit provide other options. Flywheels of low-strain graphite and Kevlar fibers have achieved mechanical energy storage densities of 300 kJ/kg. With high-strain graphite fibers, storage densities appropriate to space power needs (about 500 kJ/kg) seem feasible. Coupling advanced flywheels with emerging high power density homopolar generators and compulsators could result in electric pulse-power storage modules of significantly higher energy density.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wierer, Jonathan J.; Tsao, Jeffrey Y.; Sizov, Dmitry S.

Solid-state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light-emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission,more » can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state-of-the-art input-power-density-dependent power-conversion efficiencies; potential improvements both in their peak power-conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL.« less

Enabling Airspace Integration for High-Density On-Demand Mobility Operations

NASA Technical Reports Server (NTRS)

Mueller, Eric; Kopardekar, Parimal; Goodrich, Kenneth H.

2017-01-01

Aviation technologies and concepts have reached a level of maturity that may soon enable an era of on-demand mobility (ODM) fueled by quiet, efficient, and largely automated air taxis. However, successfully bringing such a system to fruition will require introducing orders of magnitude more aircraft to a given airspace volume than can be accommodated by the traditional air traffic control system, among other important technical challenges. The airspace integration problem is further compounded by requirements to set aside appropriate ground infrastructure for take-off and landing areas and ensuring these new aircraft types and their operations do not burden traditional airspace users and air traffic control. This airspace integration challenge may be significantly reduced by extending the concepts and technologies developed to manage small unmanned aircraft systems (UAS) at low altitude - the UAS traffic management (UTM) system - to higher altitudes and new aircraft types, or by equipping ODM aircraft with advanced sensors, algorithms, and interfaces. The precedent of operational freedom inherent in visual flight rules and the technologies developed for large UAS and commercial aircraft automation will contribute to the evolution of an ODM system enabled by UTM. This paper describes the set of air traffic services, normally provided by the traditional air traffic system, that an ODM system would implement to achieve the high densities needed for ODM's economic viability. Finally, the paper proposes a framework for integrating, evaluating, and deploying low-, medium-, and high-density ODM concepts that build on each other to ensure operational and economic feasibility at every step.

77 FR 13387 - Pipeline Safety: Notice to Operators of Driscopipe® 8000 High Density Polyethylene Pipe of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-06

[email protected] . Pipeline operators with potentially affected pipe or anyone with questions specific to... affected pipe. Chemical contamination was considered a potential source for degradation, but after... investigation of this incident included checking for the possibility of nylon contamination in the pipe material...

Transport dynamics of a high-power-density matrix-type hydrogen-oxygen fuel cell

NASA Technical Reports Server (NTRS)

Prokopius, P. R.; Hagedorn, N. H.

1974-01-01

Experimental transport dynamics tests were made on a space power fuel cell of current design. Various operating transients were introduced and transport-related response data were recorded with fluidic humidity sensing instruments. Also, sampled data techniques were developed for measuring the cathode-side electrolyte concentration during transient operation.

Development of Long-Pulse Heating and Current Drive Actuators and Operational Techniques Compatible with a High-Z Divertor and First Wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Guiding

Accurate measurement of the edge electron density profile is essential to optimizing antenna coupling and assessment of impurity contamination in studying long-pulse plasma heating and current drive in fusion devices. Measurement of the edge density profile has been demonstrated on the US fusion devices such as C-Mod, DIII-D, and TFTR amongst many devices, and has been used for RF loading and impurity modeling calculations for many years. University of Science and Technology of China (USTC) has recently installed a density profile reflectometer system on the EAST fusion device at the Institute of Plasma Physics, Chinese Academy of Sciences in Chinamore » based on the University of California Los Angeles (UCLA)-designed reflectometer system on the DIII-D fusion device at General Atomics Company in San Diego, California. UCLA has been working with USTC to optimize the existing microwave antenna, waveguide system, microwave electronics, and data analysis to produce reliable edge density profiles. During the past budget year, progress has been made in all three major areas: effort to achieve reliable system operations under various EAST operational conditions, effort to optimize system performance, and effort to provide quality density profiles into EAST’s database routinely.« less

Overview of HIT-SI Results and Plans

NASA Astrophysics Data System (ADS)

Ennis, D. A.; Akcay, C.; Hansen, C. J.; Hicks, N. K.; Hossack, A. C.; Jarboe, T. R.; Marklin, G. J.; Nelson, B. A.; Victor, B. S.

2011-10-01

Experiments in the Helicity Injected Torus-Steady Inductive (HIT-SI) device have achieved record spheromak current amplification during operations in deuterium plasmas. HIT-SI investigates steady inductive helicity injection with the aim of forming and sustaining a high-beta equilibrium in a spheromak geometry using two semi-toroidal injectors. Recent operations in deuterium plasmas have produced toroidal plasma currents greater than 50 kA, with current amplifications (Itor / Iinj) > 3 , and poloidal flux amplifications (ψpol /ψinj) > 10 . High performance deuterium discharges are achieved by initially conditioning the plasma-facing alumina surface of the HIT-SI confinement volume with helium plasmas. During subsequent deuterium operation the alumina surface strongly pumps deuterium, thereby limiting the density in the confinement volume. Additional measurements during high current deuterium discharges demonstrate reduced current and electron density fluctuations, impurity O III ion temperatures up to 50 eV and a toroidal current persistence for 0.6 ms after the injectors are shut off. Progress and plans for the HIT-SI3 configuration, with three injectors mounted on the same side of the confinement volume, will also be presented. Work supported by USDoE and ARRA.

The conceptual design of high temporal resolution HCN interferometry for atmospheric pressure air plasmas

NASA Astrophysics Data System (ADS)

Zhang, J. B.; Liu, H. Q.; Jie, Y. X.; Wei, X. C.; Hu, L. Q.

2018-01-01

A heterodyne interferometer operating at the frequency f = 890 GHz has been designed for measuring the electron density of atmospheric pressure air plasmas, it's density range is from 1015 to 3×1019 m-3 and the pressure range is from 1 Pa to 20 kPa. The system is configured as a Mach\

METHOD AND APPARATUS FOR EARTH PENETRATION

DOEpatents

Adams, W.M.

1963-12-24

A nuclear reactor apparatus for penetrating into the earth's crust is described. The apparatus comprises a cylindrical nuclear core operating at a temperature that is higher than the melting temperature of rock. A high-density ballast member is coupled to the nuclear core such that the overall density of the core-ballast assembly is greater than the density of molten rock. The nuclear core is thermally insulated so that its heat output is constrained to flow axially, with radial heat flow being minimized. In operation, the apparatus is placed in contact with the earth's crust at the point desired to be penetrated. The heat output of the reactor melts the underlying rock, and the apparatus sinks through the resulting magma. The fuel loading of the reactor core determines the ultimate depth of crust penetration. (AEC)

Advances on Sensitive Electron-injection based Cameras for Low-Flux, Short-Wave-Infrared Applications

NASA Astrophysics Data System (ADS)

Fathipour, Vala; Bonakdar, Alireza; Mohseni, Hooman

2016-08-01

Short-wave infrared (SWIR) photon detection has become an essential technology in the modern world. Sensitive SWIR detector arrays with high pixel density, low noise levels and high signal-to-noise-ratios are highly desirable for a variety of applications including biophotonics, light detection and ranging, optical tomography, and astronomical imaging. As such many efforts in infrared detector research are directed towards improving the performance of the photon detectors operating in this wavelength range. We review the history, principle of operation, present status and possible future developments of a sensitive SWIR detector technology, which has demonstrated to be one of the most promising paths to high pixel density focal plane arrays for low flux applications. The so-called electron-injection (EI) detector was demonstrated for the first time (in 2007). It offers an overall system-level sensitivity enhancement compared to the p-i-n diode due to a stable internal avalanche-free gain. The amplification method is inherently low noise, and devices exhibit an excess noise of unity. The detector operates in linear-mode and requires only bias voltage of a few volts. The stable detector characteristics, makes formation of high yield large-format, and high pixel density focal plane arrays less challenging compared to other detector technologies such as avalanche photodetectors. Detector is based on the mature InP material system (InP/InAlAs/GaAsSb/InGaAs), and has a cutoff wavelength of 1700 nm. It takes advantage of a unique three-dimensional geometry and combines the efficiency of a large absorbing volume with the sensitivity of a low-dimensional switch (injector) to sense and amplify signals. Current devices provide high-speed response ~ 5 ns rise time, and low jitter ~ 12 ps at room temperature. The internal dark current density is ~ 1 μA/cm2 at room temperature decreasing to 0.1 nA/cm2 at 160 K. EI detectors have been designed, fabricated, and tested during two generations of development and optimization cycles. We review our imager results using the first-generation detectors. In the second-generation devices, the dark current is reduced by two orders of magnitude, and bandwidth is improved by 4 orders of magnitude. The dark current density of the EI detector is shown to outperform the state-of-the-art technology, the

NUMERICAL SIMULATION OF THREE-DIMENSIONAL TUFT CORONA AND ELECTROHYDRODYNAMICS

EPA Science Inventory

The numerical simulation of three-dimensional tuft corona and electrohydrodynamics (EHD) is discussed. The importance of high-voltage and low-current operation in the wire-duct precipitator has focused attention on collecting high-resistivity dust. The local current density of in...

Free Flight Simulation: An Initial Examination of Air-Ground Integration Issues

NASA Technical Reports Server (NTRS)

Lozito, Sandra; McGann, Alison; Cashion, Patricia; Dunbar, Melisa; Mackintosh, Margaret; Dulchinos, Victoria; Jordan, Kevin; Remington, Roger (Technical Monitor)

2000-01-01

The concept of "free flight" is intended to emphasize more flexibility for operators in the National Airspace System (RTCA, 1995). This may include the potential for aircraft self-separation. The purpose of this simulation was to begin examining some of the communication and procedural issues associated with self-separation in an integrated air-ground environment. Participants were 10 commercial U.S. flight crews who flew the B747-400 simulator and 10 Denver ARTCC controllers who monitored traffic in an ATC simulation. A prototypic airborne alerting logic and flight deck display features were designed to allow for increased traffic and maneuvering information. Eight different scenarios representing different conflict types were developed. The effects of traffic density (high and low) and different traffic convergence angles (obtuse, acute, and right) were assessed. Conflict detection times were found to be lower for the flight crews in low density compared to high density scenarios. For the controllers, an interaction between density and convergence angle was revealed. Analyses on the controller detection times found longer detection times in the obtuse high density compared to obtuse low density, as well as the shortest detection times in the high density acute angle condition. Maneuvering and communication events are summarized, and a discussion of future research issues is provided.

LANL OPERATING EXPERIENCE WITH THE WAND AND HERCULES PROTOTYPE SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

K. M. GRUETZMACHER; C. L. FOXX; S. C. MYERS

2000-09-01

The Waste Assay for Nonradioactive Disposal (WAND) and the High Efficiency Radiation Counters for Ultimate Low Emission Sensitivity (HERCULES) prototype systems have been operating at Los Alamos National Laboratory's (LANL's) Solid Waste Operation's (SWO'S) non-destructive assay (NDA) building since 1997 and 1998, respectively. These systems are the cornerstone of the verification program for low-density Green is Clean (GIC) waste at the Laboratory. GIC waste includes all non-regulated waste generated in radiological controlled areas (RCAS) that has been actively segregated as clean (i.e., nonradioactive) through the use of waste generator acceptable knowledge (AK). The use of this methodology alters LANL's pastmore » practice of disposing of all room trash generated in nuclear facilities in radioactive waste landfills. Waste that is verified clean can be disposed of at the Los Alamos County Landfill. It is estimated that 50-90% of the low-density room trash from radioactive material handling areas at Los Alamos might be free of contamination. This approach avoids the high cost of disposal of clean waste at a radioactive waste landfill. It also reduces consumption of precious space in the radioactive waste landfill where disposal of this waste provides no benefit to the public or the environment. Preserving low level waste (LLW) disposal capacity for truly radioactive waste is critical in this era when expanding existing radioactive waste landfills or permitting new ones is resisted by regulators and stakeholders. This paper describes the operating experience with the WAND and HERCULES since they began operation at SWO. Waste for verification by the WAND system has been limited so far to waste from the Plutonium Facility and the Solid Waste Operations Facility. A total of461 ft3 (13.1 m3) of low-density shredded waste and paper have been verified clean by the WAND system. The HERCULES system has been used to verify waste from four Laboratory facilities. These are the Solid Waste Operations Facility, the TA-48 Chemistry Facility, the Shops Facility, and the Environmental Facility. A total of 3150 ft3 (89.3 m3) of low-density waste has been verified clean by the HERCULES system.« less

Compensatory mortality in mule deer populations: Final technical report, January 1, 1985--December 31, 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, G.C.

1989-03-01

The hypothesis of compensatory mortality is critical to understanding population dynamics of wildlife species. This knowledge is vital regardless of whether populations are managed for recreational hunting or habitats are altered via energy development projects. This research tested for compensatory mortality in the juvenile (fawn) portion of a mule deer population. Two experimental manipulations were used employing radio-collared deer. In this study, /approximately/20% of the population was moved from a treatment area and fawn survival rates compared to those on the control area. In the pasture study, deer were stocked in pastures at 3 densities of 44, 89, and 139more » deer/km/sup 2/. Lowering of density in the field portion of the study did not appear to affect fawn survival. This is attributed to not removing enough animals for existing range conditions that have been imparted by high deer densities during the last 3 decades. Also, the effect of removal was tempered by an increase in yearling males brought about by antler-point restrictions during the harvest. Deer removed from the treatment area were used to stock 3 large pastures at low, medium, and high densities of 44, 89, and 139 deer/km/sup 2/, respectively. Fawn survival was significantly different between densities (P < 0.001), with the low density pasture showing the highest survival and the high density pasture showing the lowest survival. The main cause of death was starvation suggesting that food supplies were limiting. A strong compensatory mortality process is operating in this mule deer population as evidenced by the pasture data. We did not detect this process in the field portion of the study because the removal of /approximately/20% of the population was insufficient to allow an immediate improvement in fawn nutrition. The density-dependent survival response in the controlled pasture study demonstrated that compensatory mortality is operating in this population. 57 refs., 7 figs., 6 tabs.« less

Electrochemical treatment of cetrimonium chloride with boron-doped diamond anodes. A technical and economical approach.

PubMed

de Araújo, Brenda R S; Linares León, José J

2018-05-15

This study presents the results of the electrochemical degradation of the emulsifier cetrimonium chloride (CTAC) on a boron-doped diamond (BDD) anode under different current densities and flow rates. Higher values of these parameters result in a more rapid removal. Nevertheless, operation at low current reduces the required applied charge and increases the chemical oxygen demand (COD) removal efficiency, as there is less development of ineffective parasitic reactions. On the other hand, high flow rates reduce the required volumetric applied charge and increase the COD removal current efficiency. In order to assist and enrich the study, an economic analysis has been performed. For short expected plant lifespans, operation at low current is advantageous due to the lower investment required, whereas for longer expected lifespans, the operational costs make the lower current densities less costly. High flow rates are always advantageous from a financial point of view. Copyright © 2018 Elsevier Ltd. All rights reserved.

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes

NASA Astrophysics Data System (ADS)

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-01

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ˜75 F g-1, ˜987 kW kg-1 and ˜27 W h kg-1, respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (˜158 F g-1) and energy density (˜53 W h kg-1). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices.

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes.

PubMed

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-20

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ~75 F g(-1), ~987 kW kg(-1) and ~27 W h kg(-1), respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (~158 F g(-1)) and energy density (~53 W h kg(-1)). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices. © 2012 IOP Publishing Ltd

Study, selection, and preparation of solid cationic conductors. [characteristics of solid electrolytes for rechargeable high energy and high power density batteries

NASA Technical Reports Server (NTRS)

Roth, W. L.; Muller, O.

1974-01-01

Crystal chemical principles and transport theory have been used to predict structures and specific compounds which might find application as solid electrolytes in rechargeable high energy and high power density batteries operating at temperatures less than 200 C. Structures with 1-, 2-, and 3-dimensional channels were synthesized and screened by nuclear magnetic resonance, dielectric loss, and conductivity. There is significant conductivity at room temperature in some of the materials but none attain a level that is comparable to beta-alumina. Microwave and fast pulse methods were developed to measure conductivity in powders and in small crystals.

ECR plasma source for heavy ion beam charge neutralization

NASA Astrophysics Data System (ADS)

Efthimion, Philip C.; Gilson, Erik; Grisham, Larry; Kolchin, Pavel; Davidson, Ronald C.; Yu, Simon; Logan, B. Grant

2003-01-01

Highly ionized plasmas are being considered as a medium for charge neutralizing heavy ion beams in order to focus beyond the space-charge limit. Calculations suggest that plasma at a density of 1 100 times the ion beam density and at a length [similar]0.1 2 m would be suitable for achieving a high level of charge neutralization. An Electron Cyclotron Resonance (ECR) source has been built at the Princeton Plasma Physics Laboratory (PPPL) to support a joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 1 10 gauss. The goal is to operate the source at pressures [similar]10[minus sign]6 Torr at full ionization. The initial operation of the source has been at pressures of 10[minus sign]4 10[minus sign]1 Torr. Electron densities in the range of 108 to 1011 cm[minus sign]3 have been achieved. Low-pressure operation is important to reduce ion beam ionization. A cusp magnetic field has been installed to improve radial confinement and reduce the field strength on the beam axis. In addition, axial confinement is believed to be important to achieve lower-pressure operation. To further improve breakdown at low pressure, a weak electron source will be placed near the end of the ECR source. This article also describes the wave damping mechanisms. At moderate pressures (> 1 mTorr), the wave damping is collisional, and at low pressures (< 1 mTorr) there is a distinct electron cyclotron resonance.

Elevated elephant density does not improve ecotourism opportunities: convergence in social and ecological objectives.

PubMed

Maciejewski, Kristine; Kerley, Graham I H

2014-07-01

In order to sustainably conserve biodiversity, many protected areas, particularly private protected areas, must find means of self-financing. Ecotourism is increasingly seen as a mechanism to achieve such financial sustainability. However, there is concern that ecotourism operations are driven to achieve successful game-viewing, influencing the management of charismatic species. An abundance of such species, including the African elephant (Loxodonta africana), has been stocked in protected areas under the assumption that they will increase ecotourism value. At moderate to high densities, the impact of elephants is costly; numerous studies have documented severe changes in biodiversity through the impacts of elephants. Protected areas that focus on maintaining high numbers of elephants may therefore face a conflict between socioeconomic demands and the capacity of ecological systems. We address this conflict by analyzing tourist elephant-sighting records from six private and one statutory protected area, the Addo Elephant National Park (AENP), in the Eastern Cape Province of South Africa, in relation to elephant numbers. We found no relationship between elephant density and elephant-viewing success. Even though elephant density in the AENP increased over time, a hierarchical partitioning analysis indicated that elephant density was not a driver of tourist numbers. In contrast, annual tourist numbers for the AENP were positively correlated with general tourist numbers recorded for South Africa. Our results indicate that the socioeconomic and ecological requirements of protected areas in terms of tourism and elephants, respectively, converge. Thus, high elephant densities and their associated ecological costs are not required to support ecotourism operations for financial sustainability. Understanding the social and ecological feedbacks that dominate the dynamics of protected areas, particularly within private protected areas, can help to elucidate the management challenges of minimizing ecological trade-offs while meeting ecotourist demands and achieving sustainability.

Investigation of low temperature solid oxide fuel cells for air-independent UUV applications

NASA Astrophysics Data System (ADS)

Moton, Jennie Mariko

Unmanned underwater vehicles (UUVs) will benefit greatly from high energy density (> 500 Wh/L) power systems utilizing high-energy-density fuels and air-independent oxidizers. Current battery-based systems have limited energy densities (< 400 Wh/L), which motivate development of alternative power systems such as solid oxide fuel cells (SOFCs). SOFC-based power systems have the potential to achieve the required UUV energy densities, and the current study explores how SOFCs based on gadolinia-doped ceria (GDC) electrolytes with operating temperatures of 650°C and lower may operate in the unique environments of a promising UUV power plant. The plant would contain a H 2O2 decomposition reactor to supply humidified O2 to the SOFC cathode and exothermic aluminum/H2O combustor to provide heated humidified H2 fuel to the anode. To characterize low-temperature SOFC performance with these unique O2 and H2 source, SOFC button cells based on nickel/GDC (Gd0.1Ce0.9O 1.95) anodes, GDC electrolytes, and lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ or LSCF)/GDC cathodes were fabricated and tested for performance and stability with humidity on both the anode and the cathode. Cells were also tested with various reactant concentrations of H2 and O2 to simulate gas depletion down the channel of an SOFC stack. Results showed that anode performance depended primarily on fuel concentration and less on the concentration of the associated increase in product H2O. O 2 depletion with humidified cathode flows also caused significant loss in cell current density at a given voltage. With the humidified flows in either the anode or cathode, stability tests of the button cells at 650 °C showed stable voltage is maintained at low operating current (0.17 A/cm2) at up to 50 % by mole H2O, but at higher current densities (0.34 A/cm2), irreversible voltage degradation occurred at rates of 0.8-3.7 mV/hour depending on exposure time. From these button cell results, estimated average current densities over the length of a low-temperature SOFC stack were estimated and used to size a UUV power system based on Al/H 2O oxidation for fuel and H2O2 decomposition for O2. The resulting system design suggested that energy densities above 300 Wh/L may be achieved at neutral buoyancy with seawater if the cell is operated at high reactant utilizations in the SOFC stack for missions longer than 20 hours.

Injection of auxiliary electrons for increasing the plasma density in highly charged and high intensity ion sources.

PubMed

Odorici, F; Malferrari, L; Montanari, A; Rizzoli, R; Mascali, D; Castro, G; Celona, L; Gammino, S; Neri, L

2016-02-01

Different electron guns based on cold- or hot-cathode technologies have been developed since 2009 at INFN for operating within ECR plasma chambers as sources of auxiliary electrons, with the aim of boosting the source performances by means of a higher plasma lifetime and density. Their application to microwave discharge ion sources, where plasma is not confined, has required an improvement of the gun design, in order to "screen" the cathode from the plasma particles. Experimental tests carried out on a plasma reactor show a boost of the plasma density, ranging from 10% to 90% when the electron guns are used, as explained by plasma diffusion models.

Double-cavity radiometer for high-flux density solar radiation measurements.

PubMed

Parretta, A; Antonini, A; Armani, M; Nenna, G; Flaminio, G; Pellegrino, M

2007-04-20

A radiometric method has been developed, suitable for both total power and flux density profile measurement of concentrated solar radiation. The high-flux density radiation is collected by a first optical cavity, integrated, and driven to a second optical cavity, where, attenuated, it is measured by a conventional radiometer operating under a stationary irradiation regime. The attenuation factor is regulated by properly selecting the aperture areas in the two cavities. The radiometer has been calibrated by a pulsed solar simulator at concentration levels of hundreds of suns. An optical model and a ray-tracing study have also been developed and validated, by which the potentialities of the radiometer have been largely explored.

A high-rate long-life Li4Ti5O12/Li[Ni0.45Co0.1Mn1.45]O4 lithium-ion battery.

PubMed

Jung, Hun-Gi; Jang, Min Woo; Hassoun, Jusef; Sun, Yang-Kook; Scrosati, Bruno

2011-11-01

Lithium batteries are receiving considerable attention as storage devices in the renewable energy and sustainable road transport fields. However, low-cost, long-life lithium batteries with higher energy densities are required to facilitate practical application. Here we report a lithium-ion battery that can be cycled at rates as high as 10 C has a life exceeding 500 cycles and an operating temperature range extending from -20 to 55 °C. The estimated energy density is 260 W h kg(-1), which is considerably higher than densities delivered by the presently available Li-ion batteries.

High-temperature passive direct methanol fuel cells operating with concentrated fuels

NASA Astrophysics Data System (ADS)

Zhao, Xuxin; Yuan, Wenxiang; Wu, Qixing; Sun, Hongyuan; Luo, Zhongkuan; Fu, Huide

2015-01-01

Conventionally, passive direct methanol fuel cells (DMFC) are fed with diluted methanol solutions and can hardly be operated at elevated temperatures (>120 °C) because the ionic conductivity of Nafion-type proton exchange membranes depends strongly on water content. Such a system design would limit its energy density and power density in mobile applications. In this communication, a passive vapor feed DMFC capable of operating with concentrated fuels at high temperatures is reported. The passive DMFC proposed in this work consists of a fuel reservoir, a perforated silicone sheet, a vapor chamber, two current collectors and a membrane electrode assembly (MEA) based on a phosphoric acid doped polybenzimidazole (PBI) membrane. The experimental results reveal that the methanol crossover through a PBI membrane is substantially low when compared with the Nafion membranes and the PBI-based passive DMFC can yield a peak power density of 37.2 mW cm-2 and 22.1 mW cm-2 at 180 °C when 16 M methanol solutions and neat methanol are used respectively. In addition, the 132 h discharge test indicates that the performance of this new DMFC is quite stable and no obvious performance degradation is observed after activation, showing its promising applications in portable power sources.

Modeling the hydrodynamic and electrochemical efficiency of semi-solid flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunini, VE; Chiang, YM; Carter, WC

2012-05-01

A mathematical model of flow cell operation incorporating hydrodynamic and electrochemical effects in three dimensions is developed. The model and resulting simulations apply to recently demonstrated high energy-density semi-solid flow cells. In particular, state of charge gradients that develop during low flow rate operation and their effects on the spatial non-uniformity of current density within flow cells are quantified. A one-dimensional scaling model is also developed and compared to the full three-dimensional simulation. The models are used to demonstrate the impact of the choice of electrochemical couple on flow cell performance. For semi-solid flow electrodes, which can use solid activemore » materials with a wide variety of voltage-capacity responses, we find that cell efficiency is maximized for electrochemical couples that have a relatively flat voltage vs. capacity curve, operated under slow flow conditions. For example, in flow electrodes limited by macroscopic charge transport, an LiFePO4-based system requires one-third the polarization to reach the same cycling rate as an LiCoO2-based system, all else being equal. Our conclusions are generally applicable to high energy density flow battery systems, in which flow rates can be comparatively low for a given required power. (C) 2012 Elsevier Ltd. All rights reserved.« less

Achieving high power factor and output power density in p-type half-Heuslers Nb1-xTixFeSb.

PubMed

He, Ran; Kraemer, Daniel; Mao, Jun; Zeng, Lingping; Jie, Qing; Lan, Yucheng; Li, Chunhua; Shuai, Jing; Kim, Hee Seok; Liu, Yuan; Broido, David; Chu, Ching-Wu; Chen, Gang; Ren, Zhifeng

2016-11-29

Improvements in thermoelectric material performance over the past two decades have largely been based on decreasing the phonon thermal conductivity. Enhancing the power factor has been less successful in comparison. In this work, a peak power factor of ∼106 μW⋅cm -1 ⋅K -2 is achieved by increasing the hot pressing temperature up to 1,373 K in the p-type half-Heusler Nb 0.95 Ti 0.05 FeSb. The high power factor subsequently yields a record output power density of ∼22 W⋅cm -2 based on a single-leg device operating at between 293 K and 868 K. Such a high-output power density can be beneficial for large-scale power generation applications.

Achieving high power factor and output power density in p-type half-Heuslers Nb1-xTixFeSb

PubMed Central

He, Ran; Kraemer, Daniel; Mao, Jun; Zeng, Lingping; Jie, Qing; Lan, Yucheng; Li, Chunhua; Shuai, Jing; Kim, Hee Seok; Liu, Yuan; Broido, David; Chu, Ching-Wu; Chen, Gang; Ren, Zhifeng

2016-01-01

Improvements in thermoelectric material performance over the past two decades have largely been based on decreasing the phonon thermal conductivity. Enhancing the power factor has been less successful in comparison. In this work, a peak power factor of ∼106 μW⋅cm−1⋅K−2 is achieved by increasing the hot pressing temperature up to 1,373 K in the p-type half-Heusler Nb0.95Ti0.05FeSb. The high power factor subsequently yields a record output power density of ∼22 W⋅cm−2 based on a single-leg device operating at between 293 K and 868 K. Such a high-output power density can be beneficial for large-scale power generation applications. PMID:27856743

Polymer/metal oxide hybrid dielectrics for low voltage field-effect transistors with solution-processed, high-mobility semiconductors

NASA Astrophysics Data System (ADS)

Held, Martin; Schießl, Stefan P.; Miehler, Dominik; Gannott, Florentina; Zaumseil, Jana

2015-08-01

Transistors for future flexible organic light-emitting diode (OLED) display backplanes should operate at low voltages and be able to sustain high currents over long times without degradation. Hence, high capacitance dielectrics with low surface trap densities are required that are compatible with solution-processable high-mobility semiconductors. Here, we combine poly(methyl methacrylate) (PMMA) and atomic layer deposition hafnium oxide (HfOx) into a bilayer hybrid dielectric for field-effect transistors with a donor-acceptor polymer (DPPT-TT) or single-walled carbon nanotubes (SWNTs) as the semiconductor and demonstrate substantially improved device performances for both. The ultra-thin PMMA layer ensures a low density of trap states at the semiconductor-dielectric interface while the metal oxide layer provides high capacitance, low gate leakage and superior barrier properties. Transistors with these thin (≤70 nm), high capacitance (100-300 nF/cm2) hybrid dielectrics enable low operating voltages (<5 V), balanced charge carrier mobilities and low threshold voltages. Moreover, the hybrid layers substantially improve the bias stress stability of the transistors compared to those with pure PMMA and HfOx dielectrics.

Mid-Infrared Quantum-Dot Quantum Cascade Laser: A Theoretical Feasibility Study

DOE PAGES

Michael, Stephan; Chow, Weng; Schneider, Hans

2016-05-01

In the framework of a microscopic model for intersubband gain from electrically pumped quantum-dot structures we investigate electrically pumped quantum-dots as active material for a mid-infrared quantum cascade laser. Our previous calculations have indicated that these structures could operate with reduced threshold current densities while also achieving a modal gain comparable to that of quantum well active materials. We study the influence of two important quantum-dot material parameters, here, namely inhomogeneous broadening and quantum-dot sheet density, on the performance of a proposed quantum cascade laser design. In terms of achieving a positive modal net gain, a high quantum-dot density canmore » compensate for moderately high inhomogeneous broadening, but at a cost of increased threshold current density. By minimizing quantum-dot density with presently achievable inhomogeneous broadening and total losses, significantly lower threshold densities than those reported in quantum-well quantum-cascade lasers are predicted by our theory.« less

Advanced intermediate temperature sodium copper chloride battery

NASA Astrophysics Data System (ADS)

Yang, Li-Ping; Liu, Xiao-Min; Zhang, Yi-Wei; Yang, Hui; Shen, Xiao-Dong

2014-12-01

Sodium metal chloride batteries, also called as ZEBRA batteries, possess many merits such as low cost, high energy density and high safety, but their high operation temperature (270-350 °C) may cause several issues and limit their applications. Therefore, decreasing the operation temperature is of great importance in order to broaden their usage. Using a room temperature ionic liquid (RTIL) catholyte composed of sodium chloride buffered 1-ethyl-3-methylimidazolium chloride-aluminum chloride and a dense β″-aluminates solid electrolyte film with 500 micron thickness, we report an intermediate temperature sodium copper chloride battery which can be operated at only 150 °C, therefore alleviating the corrosion issues, improving the material compatibilities and reducing the operating complexities associated with the conventional ZEBRA batteries. The RTIL presents a high ionic conductivity (0.247 S cm-1) at 150 °C and a wide electrochemical window (-2.6 to 2.18 vs. Al3+/Al). With the discharge plateau at 2.64 V toward sodium and the specific capacity of 285 mAh g-1, this intermediate temperature battery exhibits an energy density (750 mWh g-1) comparable to the conventional ZEBRA batteries (728-785 mWh g-1) and superior to commercialized Li-ion batteries (550-680 mWh g-1), making it very attractive for renewable energy integration and other grid related applications.

Performance of ceramic superconductors in magnetic bearings

NASA Technical Reports Server (NTRS)

Kirtley, James L., Jr.; Downer, James R.

1993-01-01

Magnetic bearings are large-scale applications of magnet technology, quite similar in certain ways to synchronous machinery. They require substantial flux density over relatively large volumes of space. Large flux density is required to have satisfactory force density. Satisfactory dynamic response requires that magnetic circuit permeances not be too large, implying large air gaps. Superconductors, which offer large magnetomotive forces and high flux density in low permeance circuits, appear to be desirable in these situations. Flux densities substantially in excess of those possible with iron can be produced, and no ferromagnetic material is required. Thus the inductance of active coils can be made low, indicating good dynamic response of the bearing system. The principal difficulty in using superconductors is, of course, the deep cryogenic temperatures at which they must operate. Because of the difficulties in working with liquid helium, the possibility of superconductors which can be operated in liquid nitrogen is thought to extend the number and range of applications of superconductivity. Critical temperatures of about 98 degrees Kelvin were demonstrated in a class of materials which are, in fact, ceramics. Quite a bit of public attention was attracted to these new materials. There is a difficulty with the ceramic superconducting materials which were developed to date. Current densities sufficient for use in large-scale applications have not been demonstrated. In order to be useful, superconductors must be capable of carrying substantial currents in the presence of large magnetic fields. The possible use of ceramic superconductors in magnetic bearings is investigated and discussed and requirements that must be achieved by superconductors operating at liquid nitrogen temperatures to make their use comparable with niobium-titanium superconductors operating at liquid helium temperatures are identified.

77 FR 68196 - Orders Limiting Operations at John F. Kennedy International Airport, LaGuardia Airport, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-15

... to an extratropical storm that caused widespread power outages, severe flooding, and severe... storm. FAA Analysis Under the FAA's High Density Rule at DCA and Orders limiting operations at LGA, JFK... area or northeastern U.S. affected by the storm. These circumstances may have created a unique hardship...

Effect of soil properties on Hydraulic characteristics under subsurface drip irrigation

NASA Astrophysics Data System (ADS)

Fan, Wangtao; Li, Gang

2018-02-01

Subsurface drip irrigation (SDI) is a technique that has a high potential in application because of its high efficiency in water-saving. The hydraulic characteristics of SDI sub-unit pipe network can be affected by soil physical properties as the emitters are buried in soils. The related research, however, is not fully explored. The laboratory tests were carried out in the present study to determine the effects of hydraulic factors including operating pressure, initial soil water content, and bulk density on flow rate and its sensitivity to each hydraulic factor for two types of SDI emitters (PLASSIM emitter and Heping emitter). For this purpose, three soils with contrasting textures (i.e., light sand, silt loam, and light clay) were repacked with two soil bulk density (1.25 and1.40 g cm-3) with two initial soil water content (12% and 18%) in plexiglass columns with 40 cm in diameter and 40 cm in height. Drip emitters were buried at depth of 20 cm to measure the flow rates under seven operating pressures (60, 100, 150, 200, 250, 300, and 370 kPa). We found that the operating pressure was the dominating factor of flow rate of the SDI emitter, and flow rate increased with the increase of operating pressure. The initial soil water content and bulk density also affected the flow rate, and their effects were the most notable in the light sand soil. The sensitivity of flow rate to each hydraulic factor was dependent on soil texture, and followed a descending order of light sand>silt loam>light clay for both types of emitters. Further, the sensitivity of flow rate to each hydraulic factor decreased with the increase of operating pressure, initial soil water content, and bulk density. This study may be used to guide the soil specific-design of SDI emitters for optimal water use and management.

The enhanced ASDEX Upgrade pellet centrifuge launcher

NASA Astrophysics Data System (ADS)

Plöckl, B.; Lang, P. T.

2013-10-01

Pellets played an important role in the program of ASDEX Upgrade serving both for investigations on efficient particle fuelling and high density scenarios but also for pioneering work on Edge Localised Mode (ELM) pacing and mitigation. Initially designed for launching fuelling pellets from the magnetic low field side, the system was converted already some time ago to inject pellets from the magnetic high field side as much higher fuelling efficiency was found using this configuration. In operation for more than 20 years, the pellet launching system had to undergo a major revision and upgrading, in particular of its control system. Furthermore, the control system installed adjacent to the launcher had to be transferred to a more distant location enforcing a complete galvanic separation from torus potential and a fully remote control solution. Changing from a hybrid system consisting of PLC S5/S7 and some hard wired relay control to a state of the art PLC system allowed the introduction of several new operational options enabling more flexibility in the pellet experiments. This article describes the new system architecture of control hardware and software, the operating procedure, and the extended operational window. First successful applications for ELM pacing and triggering studies are presented as well as utilization for the development of high density scenarios.

Results from an Interval Management (IM) Flight Test and Its Potential Benefit to Air Traffic Management Operations

NASA Technical Reports Server (NTRS)

Baxley, Brian; Swieringa, Kurt; Berckefeldt, Rick; Boyle, Dan

2017-01-01

NASA's first Air Traffic Management Technology Demonstration (ATD-1) subproject successfully completed a 19-day flight test of an Interval Management (IM) avionics prototype. The prototype was built based on IM standards, integrated into two test aircraft, and then flown in real-world conditions to determine if the goals of improving aircraft efficiency and airport throughput during high-density arrival operations could be met. The ATD-1 concept of operation integrates advanced arrival scheduling, controller decision support tools, and the IM avionics to enable multiple time-based arrival streams into a high-density terminal airspace. IM contributes by calculating airspeeds that enable an aircraft to achieve a spacing interval behind the preceding aircraft. The IM avionics uses its data (route of flight, position, etc.) and Automatic Dependent Surveillance-Broadcast (ADS-B) state data from the Target aircraft to calculate this airspeed. The flight test demonstrated that the IM avionics prototype met the spacing accuracy design goal for three of the four IM operation types tested. The primary issue requiring attention for future IM work is the high rate of IM speed commands and speed reversals. In total, during this flight test, the IM avionics prototype showed significant promise in contributing to the goals of improving aircraft efficiency and airport throughput.

The enhanced ASDEX Upgrade pellet centrifuge launcher.

PubMed

Plöckl, B; Lang, P T

2013-10-01

Pellets played an important role in the program of ASDEX Upgrade serving both for investigations on efficient particle fuelling and high density scenarios but also for pioneering work on Edge Localised Mode (ELM) pacing and mitigation. Initially designed for launching fuelling pellets from the magnetic low field side, the system was converted already some time ago to inject pellets from the magnetic high field side as much higher fuelling efficiency was found using this configuration. In operation for more than 20 years, the pellet launching system had to undergo a major revision and upgrading, in particular of its control system. Furthermore, the control system installed adjacent to the launcher had to be transferred to a more distant location enforcing a complete galvanic separation from torus potential and a fully remote control solution. Changing from a hybrid system consisting of PLC S5/S7 and some hard wired relay control to a state of the art PLC system allowed the introduction of several new operational options enabling more flexibility in the pellet experiments. This article describes the new system architecture of control hardware and software, the operating procedure, and the extended operational window. First successful applications for ELM pacing and triggering studies are presented as well as utilization for the development of high density scenarios.

The enhanced ASDEX Upgrade pellet centrifuge launcher

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plöckl, B.; Lang, P. T.

2013-10-15

Pellets played an important role in the program of ASDEX Upgrade serving both for investigations on efficient particle fuelling and high density scenarios but also for pioneering work on Edge Localised Mode (ELM) pacing and mitigation. Initially designed for launching fuelling pellets from the magnetic low field side, the system was converted already some time ago to inject pellets from the magnetic high field side as much higher fuelling efficiency was found using this configuration. In operation for more than 20 years, the pellet launching system had to undergo a major revision and upgrading, in particular of its control system.more » Furthermore, the control system installed adjacent to the launcher had to be transferred to a more distant location enforcing a complete galvanic separation from torus potential and a fully remote control solution. Changing from a hybrid system consisting of PLC S5/S7 and some hard wired relay control to a state of the art PLC system allowed the introduction of several new operational options enabling more flexibility in the pellet experiments. This article describes the new system architecture of control hardware and software, the operating procedure, and the extended operational window. First successful applications for ELM pacing and triggering studies are presented as well as utilization for the development of high density scenarios.« less

Flexible and Self-Healing Aqueous Supercapacitors for Low Temperature Applications: Polyampholyte Gel Electrolytes with Biochar Electrodes.

PubMed

Li, Xinda; Liu, Li; Wang, Xianzong; Ok, Yong Sik; Elliott, Janet A W; Chang, Scott X; Chung, Hyun-Joong

2017-05-10

A flexible and self-healing supercapacitor with high energy density in low temperature operation was fabricated using a combination of biochar-based composite electrodes and a polyampholyte hydrogel electrolyte. Polyampholytes, a novel class of tough hydrogel, provide self-healing ability and mechanical flexibility, as well as low temperature operation for the aqueous electrolyte. Biochar is a carbon material produced from the low-temperature pyrolysis of biological wastes; the incorporation of reduced graphene oxide conferred mechanical integrity and electrical conductivity and hence the electrodes are called biochar-reduced-graphene-oxide (BC-RGO) electrodes. The fabricated supercapacitor showed high energy density of 30 Wh/kg with ~90% capacitance retention after 5000 charge-discharge cycles at room temperature at a power density of 50 W/kg. At -30 °C, the supercapacitor exhibited an energy density of 10.5 Wh/kg at a power density of 500 W/kg. The mechanism of the low-temperature performance excellence is likely to be associated with the concept of non-freezable water near the hydrophilic polymer chains, which can motivate future researches on the phase behaviour of water near polyampholyte chains. We conclude that the combination of the BC-RGO electrode and the polyampholyte hydrogel electrolyte is promising for supercapacitors for flexible electronics and for low temperature environments.

The 77 K operation of a multi-resonant power converter

NASA Technical Reports Server (NTRS)

Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

1995-01-01

The liquid-nitrogen temperature (77 K) operation of a 55 W, 200 kHz, 48/28 V zero-voltage switching multi-resonant dc/dc converter designed with commercially available components is reported. Upon dipping the complete converter (power and control circuits) into liquid-nitrogen, the converter performance improved as compared to the room-temperature operation. The switching frequency, resonant frequency, and the characteristic impedance did not change significantly. Accordingly, the zero-voltage switching was maintained from no-load to full-load for the specified line variations. Cryoelectronics can provide high density power converters, especially for high power applications.

A spin transfer torque magnetoresistance random access memory-based high-density and ultralow-power associative memory for fully data-adaptive nearest neighbor search with current-mode similarity evaluation and time-domain minimum searching

NASA Astrophysics Data System (ADS)

Ma, Yitao; Miura, Sadahiko; Honjo, Hiroaki; Ikeda, Shoji; Hanyu, Takahiro; Ohno, Hideo; Endoh, Tetsuo

2017-04-01

A high-density nonvolatile associative memory (NV-AM) based on spin transfer torque magnetoresistive random access memory (STT-MRAM), which achieves highly concurrent and ultralow-power nearest neighbor search with full adaptivity of the template data format, has been proposed and fabricated using the 90 nm CMOS/70 nm perpendicular-magnetic-tunnel-junction hybrid process. A truly compact current-mode circuitry is developed to realize flexibly controllable and high-parallel similarity evaluation, which makes the NV-AM adaptable to any dimensionality and component-bit of template data. A compact dual-stage time-domain minimum searching circuit is also developed, which can freely extend the system for more template data by connecting multiple NM-AM cores without additional circuits for integrated processing. Both the embedded STT-MRAM module and the computing circuit modules in this NV-AM chip are synchronously power-gated to completely eliminate standby power and maximally reduce operation power by only activating the currently accessed circuit blocks. The operations of a prototype chip at 40 MHz are demonstrated by measurement. The average operation power is only 130 µW, and the circuit density is less than 11 µm2/bit. Compared with the latest conventional works in both volatile and nonvolatile approaches, more than 31.3% circuit area reductions and 99.2% power improvements are achieved, respectively. Further power performance analyses are discussed, which verify the special superiority of the proposed NV-AM in low-power and large-memory-based VLSIs.

Prospects for steady-state scenarios on JET

NASA Astrophysics Data System (ADS)

Litaudon, X.; Bizarro, J. P. S.; Challis, C. D.; Crisanti, F.; DeVries, P. C.; Lomas, P.; Rimini, F. G.; Tala, T. J. J.; Akers, R.; Andrew, Y.; Arnoux, G.; Artaud, J. F.; Baranov, Yu F.; Beurskens, M.; Brix, M.; Cesario, R.; DeLa Luna, E.; Fundamenski, W.; Giroud, C.; Hawkes, N. C.; Huber, A.; Joffrin, E.; Pitts, R. A.; Rachlew, E.; Reyes-Cortes, S. D. A.; Sharapov, S. E.; Zastrow, K. D.; Zimmermann, O.; JET EFDA contributors, the

2007-09-01

In the 2006 experimental campaign, progress has been made on JET to operate non-inductive scenarios at higher applied powers (31 MW) and density (nl ~ 4 × 1019 m-3), with ITER-relevant safety factor (q95 ~ 5) and plasma shaping, taking advantage of the new divertor capabilities. The extrapolation of the performance using transport modelling benchmarked on the experimental database indicates that the foreseen power upgrade (~45 MW) will allow the development of non-inductive scenarios where the bootstrap current is maximized together with the fusion yield and not, as in present-day experiments, at its expense. The tools for the long-term JET programme are the new ITER-like ICRH antenna (~15 MW), an upgrade of the NB power (35 MW/20 s or 17.5 MW/40 s), a new ITER-like first wall, a new pellet injector for edge localized mode control together with improved diagnostic and control capability. Operation with the new wall will set new constraints on non-inductive scenarios that are already addressed experimentally and in the modelling. The fusion performance and driven current that could be reached at high density and power have been estimated using either 0D or 1-1/2D validated transport models. In the high power case (45 MW), the calculations indicate the potential for the operational space of the non-inductive regime to be extended in terms of current (~2.5 MA) and density (nl > 5 × 1019 m-3), with high βN (βN > 3.0) and a fraction of the bootstrap current within 60-70% at high toroidal field (~3.5 T).

Observation of the ballooning mode that limits the operation space of the high-density super-dense-core plasma in the LHD

NASA Astrophysics Data System (ADS)

Ohdachi, S.; Watanabe, K. Y.; Tanaka, K.; Suzuki, Y.; Takemura, Y.; Sakakibara, S.; Du, X. D.; Bando, T.; Narushima, Y.; Sakamoto, R.; Miyazawa, J.; Motojima, G.; Morisaki, T.; LHD Experiment Group

2017-06-01

The central beta of the super-dense-core (SDC) plasma in the large helical device (LHD) is limited by a large scale MHD event called ‘core density collapse’ (CDC). The detailed measurement reveals that a new type of ballooning mode, quite localized in space and destabilized from the 3D nature of Heliotron devices, is the cause of the CDC. It is the first observation of an unstable mode in a region with global negative magnetic shear. Avoidance of the excitation of this mode is a key to expand the operational limit of the LHD.

High energy density battery based on complex hydrides

DOEpatents

Zidan, Ragaiy

2016-04-26

A battery and process of operating a battery system is provided using high hydrogen capacity complex hydrides in an organic non-aqueous solvent that allows the transport of hydride ions such as AlH.sub.4.sup.- and metal ions during respective discharging and charging steps.

High temperature, high intensity solar array. [for Venus Radar Mapper mission

NASA Technical Reports Server (NTRS)

Smith, B. S.; Brooks, G. R.; Pinkerton, R.

1985-01-01

The solar array for the Venus Radar Mapper mission will operate in the high temperature, high intensity conditions of a low Venus orbit environment. To fulfill the performance requirements in this environment at minimum cost and mass while maximizing power density and packing factor on the panel surface, several features were introduced into the design. These features included the use of optical surface reflectors (OSR's) to reduce the operating temperature; new adhesives for conductive bonding of OSR's to avoid electrostatic discharges; custom-designed large area cells and novel shunt diode circuit and panel power harness configurations.

Low-temperature operation of a Buck DC/DC converter

NASA Technical Reports Server (NTRS)

Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

1995-01-01

Low-temperature (77 K) operation of a 42/28 V, 175 W, 50 kHz PWM Buck DC/DC converter designed with commercially available components is reported. Overall, the converter losses decreased at 77 K compared to room temperature operation. A full-load efficiency of 97 percent was recorded at liquid-nitrogen temperature, compared to 95.8 percent at room temperature. Power MOSFET operation improved significantly where as the output rectifier operation deteriorated at low-temperature. The performance of the output filter inductor and capacitor did not change significantly at 77 K compared to room temperature performance. It is possible to achieve high-density and high efficiency power conversion at low-temperatures due to improved electronic, electrical and thermal properties of materials.

Ti-Doped GaOx Resistive Switching Memory with Self-Rectifying Behavior by Using NbOx/Pt Bilayers.

PubMed

Park, Ju Hyun; Jeon, Dong Su; Kim, Tae Geun

2017-12-13

Crossbar arrays (CBAs) with resistive random access memory (ReRAM) constitute an established architecture for high-density memory. However, sneak paths via unselected cells increase the total power consumption of these devices and limit the array size. To eliminate such sneak-path problems, we propose a Ti/GaO x /NbO x /Pt structure with a self-rectifying resistive-switching (RS) behavior. In this structure, to reduce the operating voltage, we used a Ti/GaO x stack to increase the number of trap sites in the RS GaO x layer through interfacial reactions between the Ti and GaO x layers. This increase enables easier carrier transport with reduced electric fields. We then adopted a NbO x /Pt stack to add rectifying behavior to the RS GaO x layer. This behavior is a result of the large Schottky barrier height between the NbO x and Pt layers. Finally, both the Ti/GaO x and NbO x /Pt stacks were combined to realize a self-rectifying ReRAM device, which exhibited excellent performance. Characteristics of the device include a low operating voltage range (-2.8 to 2.5 V), high on/off ratios (∼20), high selectivity (∼10 4 ), high operating speeds (200-500 ns), a very low forming voltage (∼3 V), stable operation, and excellent uniformity for high-density CBA-based ReRAM applications.

Helicon normal modes in Proto-MPEX

NASA Astrophysics Data System (ADS)

Piotrowicz, P. A.; Caneses, J. F.; Green, D. L.; Goulding, R. H.; Lau, C.; Caughman, J. B. O.; Rapp, J.; Ruzic, D. N.

2018-05-01

The Proto-MPEX helicon source has been operating in a high electron density ‘helicon-mode’. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the ‘helicon-mode’. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besides directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region. ).

Helicon normal modes in Proto-MPEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piotrowicz, Pawel A.; Caneses, Juan F.; Green, David L.

Here, the Proto-MPEX helicon source has been operating in a high electron density 'helicon-mode'. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the 'helicon-mode'. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besidesmore » directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region.« less

Using the MCNP Taylor series perturbation feature (efficiently) for shielding problems

NASA Astrophysics Data System (ADS)

Favorite, Jeffrey

2017-09-01

The Taylor series or differential operator perturbation method, implemented in MCNP and invoked using the PERT card, can be used for efficient parameter studies in shielding problems. This paper shows how only two PERT cards are needed to generate an entire parameter study, including statistical uncertainty estimates (an additional three PERT cards can be used to give exact statistical uncertainties). One realistic example problem involves a detailed helium-3 neutron detector model and its efficiency as a function of the density of its high-density polyethylene moderator. The MCNP differential operator perturbation capability is extremely accurate for this problem. A second problem involves the density of the polyethylene reflector of the BeRP ball and is an example of first-order sensitivity analysis using the PERT capability. A third problem is an analytic verification of the PERT capability.

Ultra-wide-range measurements of thin-film filter optical density over the visible and near-infrared spectrum.

PubMed

Lequime, Michel; Liukaityte, Simona; Zerrad, Myriam; Amra, Claude

2015-10-05

We present the improved structure and operating principle of a spectrophotometric mean that allows us for the recording of the transmittance of a thin-film filter over an ultra-wide range of optical densities (from 0 to 11) between 400 and 1000 nm. The operation of this apparatus is based on the combined use of a high power supercontinuum laser source, a tunable volume hologram filter, a standard monochromator and a scientific grade CCD camera. The experimentally recorded noise floor is in good accordance with the optical density values given by the theoretical approach. A demonstration of the sensitivity gain provided by this new set-up with respect to standard spectrophotometric means is performed via the characterization of various types of filters (band-pass, long-pass, short-pass, and notch).

Helicon normal modes in Proto-MPEX

DOE PAGES

Piotrowicz, Pawel A.; Caneses, Juan F.; Green, David L.; ...

2018-05-22

Here, the Proto-MPEX helicon source has been operating in a high electron density 'helicon-mode'. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the 'helicon-mode'. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besidesmore » directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region.« less

Fission-gas release from uranium nitride at high fission rate density

NASA Technical Reports Server (NTRS)

Weinstein, M. B.; Kirchgessner, T. A.; Tambling, T. N.

1973-01-01

A sweep gas facility has been used to measure the release rates of radioactive fission gases from small UN specimens irradiated to 8-percent burnup at high fission-rate densities. The measured release rates have been correlated with an equation whose terms correspond to direct recoil release, fission-enhanced diffusion, and atomic diffusion (a function of temperature). Release rates were found to increase linearly with burnups between 1.5 and 8 percent. Pore migration was observed after operation at 1550 K to over 6 percent burnup.

Bipolar and Monopolar Lithium-Ion Battery Technology at Yardney

NASA Technical Reports Server (NTRS)

Russell, P.; Flynn, J.; Reddy, T.

1996-01-01

Lithium-ion battery systems offer several advantages: intrinsically safe; long cycle life; environmentally friendly; high energy density; wide operating temperature range; good discharge rate capability; low self-discharge; and no memory effect.

Study of short haul high-density V/STOL transportation systems, volume 1

NASA Technical Reports Server (NTRS)

Solomon, H. L.

1972-01-01

The relative advantages of STOL aircraft concepts were examined by simulating the operations of a short haul high-density intercity STOL system set in two arenas, the California corridor and the Chicago-Detroit-Cleveland triangle, during the 1980 time period. The study was constrained to the use of three aircraft concepts designated as the deflected slipstream turboprop, externally blown flap, and augmentor wing turbofan configurations. The projected demographic, economic, travel demand, and travel characteristics of the representative arenas were identified. The STOL airline operating scenarios were then formulated and through the use of the aerospace modal split simulation program, the traveler modal choices involving alternative STOL concepts were estimated in the context of the total transportation environment for 1980. System combinations that presented the best potential for economic return and traveler acceptance were then identified for each STOL concept.

Regenerative fuel cell study for satellites in GEO orbit

NASA Technical Reports Server (NTRS)

Levy, Alexander; Vandine, Leslie L.; Stedman, James K.

1987-01-01

Summarized are the results of a 12-month study to identify high performance regenerative hydrogen-oxygen fuel cell concepts for geosynchronous satellite application. Emphasis was placed on concepts with the potential for high energy density (W-hr/lb) and passive means for water and heat management to maximize system reliability. Both polymer membrane and alkaline electrolyte fuel cells were considered, with emphasis on the alkaline cell because of its high performance, advanced state of development, and proven ability to operate in a launch and space environment. Three alkaline system concepts were studied. The first, the integrated design, utilized a configuration in which the fuel cell and electrolysis cells are alternately stacked inside a pressure vessel. Product water is transferred by diffusion during electrolysis and waste heat is conducted through the pressure wall, thus using completely passive means for transfer and control. The second alkaline system, the dedicated design, uses a separate fuel cell and electrolysis stack so that each unit can be optimized in size and weight based on its orbital operating period. The third design was a dual function stack configuration, in which each cell can operate in both fuel cell and electrolysis mode, thus eliminating the need for two separate stacks and associated equipment. Results indicate that using near term technology energy densities between 46 and 52 W-hr/lb can be achieved at efficiencies of 55 percent. System densities of 115 W-hr/lb are contemplated.

A real-space stochastic density matrix approach for density functional electronic structure.

PubMed

Beck, Thomas L

2015-12-21

The recent development of real-space grid methods has led to more efficient, accurate, and adaptable approaches for large-scale electrostatics and density functional electronic structure modeling. With the incorporation of multiscale techniques, linear-scaling real-space solvers are possible for density functional problems if localized orbitals are used to represent the Kohn-Sham energy functional. These methods still suffer from high computational and storage overheads, however, due to extensive matrix operations related to the underlying wave function grid representation. In this paper, an alternative stochastic method is outlined that aims to solve directly for the one-electron density matrix in real space. In order to illustrate aspects of the method, model calculations are performed for simple one-dimensional problems that display some features of the more general problem, such as spatial nodes in the density matrix. This orbital-free approach may prove helpful considering a future involving increasingly parallel computing architectures. Its primary advantage is the near-locality of the random walks, allowing for simultaneous updates of the density matrix in different regions of space partitioned across the processors. In addition, it allows for testing and enforcement of the particle number and idempotency constraints through stabilization of a Feynman-Kac functional integral as opposed to the extensive matrix operations in traditional approaches.

Overview on the high power excimer laser technology

NASA Astrophysics Data System (ADS)

Liu, Jingru

2013-05-01

High power excimer laser has essential applications in the fields of high energy density physics, inertial fusion energy and industry owing to its advantages such as short wavelength, high gain, wide bandwidth, energy scalable and repetition operating ability. This overview is aimed at an introduction and evaluation of enormous endeavor of the international high power excimer laser community in the last 30 years. The main technologies of high power excimer laser are reviewed, which include the pumping source technology, angular multiplexing and pulse compressing, beam-smoothing and homogenous irradiation, high efficiency and repetitive operation et al. A high power XeCl laser system developed in NINT of China is described in detail.

Measurements of beam halo diffusion and population density in the Tevatron and in the Large Hadron Collider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stancari, Giulio

2015-03-01

Halo dynamics influences global accelerator performance: beam lifetimes, emittance growth, dynamic aperture, and collimation efficiency. Halo monitoring and control are also critical for the operation of high-power machines. For instance, in the high-luminosity upgrade of the LHC, the energy stored in the beam tails may reach several megajoules. Fast losses can result in superconducting magnet quenches, magnet damage, or even collimator deformation. The need arises to measure the beam halo and to remove it at controllable rates. In the Tevatron and in the LHC, halo population densities and diffusivities were measured with collimator scans by observing the time evolution ofmore » losses following small inward or outward collimator steps, under different experimental conditions: with single beams and in collision, and, in the case of the Tevatron, with a hollow electron lens acting on a subset of bunches. After the LHC resumes operations, it is planned to compare measured diffusivities with the known strength of transverse damper excitations. New proposals for nondestructive halo population density measurements are also briefly discussed.« less

Design and experimental validation for direct-drive fault-tolerant permanent-magnet vernier machines.

PubMed

Liu, Guohai; Yang, Junqin; Chen, Ming; Chen, Qian

2014-01-01

A fault-tolerant permanent-magnet vernier (FT-PMV) machine is designed for direct-drive applications, incorporating the merits of high torque density and high reliability. Based on the so-called magnetic gearing effect, PMV machines have the ability of high torque density by introducing the flux-modulation poles (FMPs). This paper investigates the fault-tolerant characteristic of PMV machines and provides a design method, which is able to not only meet the fault-tolerant requirements but also keep the ability of high torque density. The operation principle of the proposed machine has been analyzed. The design process and optimization are presented specifically, such as the combination of slots and poles, the winding distribution, and the dimensions of PMs and teeth. By using the time-stepping finite element method (TS-FEM), the machine performances are evaluated. Finally, the FT-PMV machine is manufactured, and the experimental results are presented to validate the theoretical analysis.

Designing Carbon Based Supercapacitors with High Energy Density: A Summary of Recent Progress.

PubMed

Han, Yi; Lai, Zhengzhe; Wang, Zifan; Yu, Minghao; Tong, Yexiang; Lu, Xihong

2018-05-23

Carbon based supercapacitors (CSCs), with high output power and long lifespan, are considered as promising power sources for modern electronic devices. The rush to find new approaches for optimizing their electrochemical behaviors is still vibrant, and particularly, widespread enthusiasm was focused on improving the energy density of CSCs through improving the specific capacitance and expanding the operating voltage. In this regard, this article provides a brief review about recent progress and new understanding about the assembly of CSCs with high energy density. Novel applied strategies were highlighted and discussed from the aspects of electrolyte, electrodes, and device modulation. Dynamic and mechanism factors associated with the energy storage process of CSCs are particularly emphasized. Finally, the opportunities and challenges are elaborated in the hope of guiding the promising direction for the design of high-energy CSCs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory.

PubMed

Schwarz, S; Baumann, T M; Kittimanapun, K; Lapierre, A; Snyder, A

2014-02-01

The Electron Beam Ion Trap (EBIT) in NSCL's reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT's superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assess the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm(2) has been reached when the EBIT magnet was operated at 4 T.

A high-current electron gun for the electron beam ion trap at the National Superconducting Cyclotron Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwarz, S., E-mail: schwarz@nscl.msu.edu; Baumann, T. M.; Kittimanapun, K.

The Electron Beam Ion Trap (EBIT) in NSCL’s reaccelerator ReA uses continuous ion injection and accumulation. In order to maximize capture efficiency and minimize breeding time into high charge states, the EBIT requires a high-current/high current-density electron beam. A new electron gun insert based on a concave Ba-dispenser cathode has been designed and built to increase the current transmitted through the EBIT’s superconducting magnet. With the new insert, stable EBIT operating conditions with 0.8 A of electron beam have been established. The design of the electron gun is presented together with calculated and measured perveance data. In order to assessmore » the experimental compression of the electron beam, a pinhole CCD camera has been set up to measure the electron beam radius. The camera observes X-rays emitted from highly charged ions, excited by the electron beam. Initial tests with this camera setup will be presented. They indicate that a current density of 640 A/cm{sup 2} has been reached when the EBIT magnet was operated at 4 T.« less

PASOTRON high-energy microwave source

NASA Astrophysics Data System (ADS)

Goebel, Dan M.; Schumacher, Robert W.; Butler, Jennifer M.; Hyman, Jay, Jr.; Santoru, Joseph; Watkins, Ron M.; Harvey, Robin J.; Dolezal, Franklin A.; Eisenhart, Robert L.; Schneider, Authur J.

1992-04-01

A unique, high-energy microwave source, called PASOTRON (Plasma-Assisted Slow-wave Oscillator), has been developed. The PASOTRON utilizes a long-pulse E-gun and plasma- filled slow-wave structure (SWS) to produce high-energy pulses from a simple, lightweight device that utilizes no externally produced magnetic fields. Long pulses are obtained from a novel E-gun that employs a low-pressure glow discharge to provide a stable, high current- density electron source. The electron accelerator consists of a high-perveance, multi-aperture array. The E-beam is operated in the ion-focused regime where the plasma filling the SWS space-charge neutralizes the beam, and the self-pinch force compresses the beamlets and increases the beam current density. A scale-model PASOTRON, operating as a backward- wave oscillator in C-band with a 100-kV E-beam, has produced output powers in the 3 to 5 MW range and pulse lengths of over 100 microsecond(s) ec, corresponding to an integrated energy per pulse of up to 500 J. The E-beam to microwave-radiation power conversion efficiency is about 20%.

A High Performance H2-Cl2 Fuel Cell for Space Power Applications

NASA Technical Reports Server (NTRS)

Anderson, Everett B.; Taylor, E. Jennings; Wilemski, Gerald; Gelb, Alan

1993-01-01

NASA has numerous airborne/spaceborne applications for which high power and energy density power sources are needed. The proton exchange membrane fuel cell (PEMFC) is an attractive candidate for such a power source. PEMFC's offer many advantages for airborne/spaceborne applications. They have high power and energy densities, convert fuel to electrical power with high efficiency at both part and full load, and can rapidly startup and shutdown. In addition, PEMFC's are lightweight and operate silently. A significant impediment to the attainment of very high power and energy densities by PEMFC's is their current exclusive reliance on oxygen as the oxidant. Conventional PEMFC's oxidize hydrogen at the anode and reduce oxygen at the cathode. The electrode kinetics of oxygen reduction are known to be highly irreversible, incurring large overpotential losses. In addition, the modest open circuit potential of 1.2V for the H2-O2 fuel cell is unattainable due to mixed potential effects at the oxygen electrode. Because of the high overpotential losses, cells using H2 and O2 are capable of achieving high current densities only at very low cell voltages, greatly curtailing their power output. Based on experimental work on chlorine reduction in a gas diffusion electrode, we believe significant increases in both the energy and power densities of PEMFC systems can be achieved by employing chlorine as an alternative oxidant.

The high voltage homopolar generator

NASA Astrophysics Data System (ADS)

Price, J. H.; Gully, J. H.; Driga, M. D.

1986-11-01

System and component design features of proposed high voltage homopolar generator (HVHPG) are described. The system is to have an open circuit voltage of 500 V, a peak output current of 500 kA, 3.25 MJ of stored inertial energy and possess an average magnetic-flux density of 5 T. Stator assembly components are discussed, including the stator, mount structure, hydrostatic bearings, main and motoring brushgears and rotor. Planned operational procedures such as monitoring the rotor to full speed and operation with a superconducting field coil are delineated.

Progress in the planar CPn SOFC system design verification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elangovan, S.; Hartvigsen, J.; Khandkar, A.

1996-04-01

SOFCo is developing a high efficiency, modular and scaleable planar SOFC module termed the CPn design. This design has been verified in a 1.4 kW module test operated directly on pipeline natural gas. The design features multistage oxidation of fuel wherein the fuel is consumed incrementally over several stages. High efficiency is achieved by uniform current density distribution per stage, which lowers the stack resistance. Additional benefits include thermal regulation and compactness. Test results from stack modules operating in pipeline natural gas are presented.

Design of an Airlift Bioreactor

DOE Data Explorer

Jiao, Yongqin; Park, Dan; Ho, Lewis

2017-03-13

An important consideration for the process design is cell immobilization-enabled flow-through operation. Large-scale biosorption relies on cells that are immobilized on a supporting substrate and used to 'attract' metal ions. Cell immobilization allows easy separation of the feed solution and REEs that are attached to the cell surface. It also allows continuous operation without the need of energy-intensive centrifugation or filtration. Lightweight, high surface area, low cost (~$200/m3) high-density polyethylene (HDPE) plastic disks are used as cell carriers for biofilm formation.

High Packing Density Unidirectional Arrays of Vertically Aligned Graphene with Enhanced Areal Capacitance for High-Power Micro-Supercapacitors.

PubMed

Zheng, Shuanghao; Li, Zhilin; Wu, Zhong-Shuai; Dong, Yanfeng; Zhou, Feng; Wang, Sen; Fu, Qiang; Sun, Chenglin; Guo, Liwei; Bao, Xinhe

2017-04-25

Interfacial integration of a shape-engineered electrode with a strongly bonded current collector is the key for minimizing both ionic and electronic resistance and then developing high-power supercapacitors. Herein, we demonstrated the construction of high-power micro-supercapacitors (VG-MSCs) based on high-density unidirectional arrays of vertically aligned graphene (VG) nanosheets, derived from a thermally decomposed SiC substrate. The as-grown VG arrays showed a standing basal plane orientation grown on a (0001̅) SiC substrate, tailored thickness (3.5-28 μm), high-density structurally ordering alignment of graphene consisting of 1-5 layers, vertically oriented edges, open intersheet channels, high electrical conductivity (192 S cm -1 ), and strong bonding of the VG edges to the SiC substrate. As a result, the demonstrated VG-MSCs displayed a high areal capacitance of ∼7.3 mF cm -2 and a fast frequency response with a short time constant of 9 ms. Furthermore, VG-MSCs in both an aqueous polymer gel electrolyte and nonaqueous ionic liquid of 1-ethyl-3-methylimidazolium tetrafluoroborate operated well at high scan rates of up to 200 V s -1 . More importantly, VG-MSCs offered a high power density of ∼15 W cm -3 in gel electrolyte and ∼61 W cm -3 in ionic liquid. Therefore, this strategy of producing high-density unidirectional VG nanosheets directly bonded on a SiC current collector demonstrated the feasibility of manufacturing high-power compact supercapacitors.

Review of GaN-based devices for terahertz operation

NASA Astrophysics Data System (ADS)

Ahi, Kiarash

2017-09-01

GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ˜90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaN-based devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.

Scoping study for compact high-field superconducting net energy tokamaks

NASA Astrophysics Data System (ADS)

Mumgaard, R. T.; Greenwald, M.; Freidberg, J. P.; Wolfe, S. M.; Hartwig, Z. S.; Brunner, D.; Sorbom, B. N.; Whyte, D. G.

2016-10-01

The continued development and commercialization of high temperature superconductors (HTS) may enable the construction of compact, net-energy tokamaks. HTS, in contrast to present generation low temperature superconductors, offers improved performance in high magnetic fields, higher current density, stronger materials, higher temperature operation, and simplified assembly. Using HTS along with community-consensus confinement physics (H98 =1) may make it possible to achieve net-energy (Q>1) or burning plasma conditions (Q>5) in DIII-D or ASDEX-U sized, conventional aspect ratio tokamaks. It is shown that, by operating at high plasma current and density enabled by the high magnetic field (B>10T), the required triple products may be achieved at plasma volumes under 20m3, major radii under 2m, with external heating powers under 40MW. This is at the scale of existing devices operated by laboratories, universities and companies. The trade-offs in the core heating, divertor heat exhaust, sustainment, stability, and proximity to known plasma physics limits are discussed in the context of the present tokamak experience base and the requirements for future devices. The resulting HTS-based design space is compared and contrasted to previous studies on high-field copper experiments with similar missions. The physics exploration conducted with such HTS devices could decrease the real and perceived risks of ITER exploitation, and aid in quickly developing commercially-applicable tokamak pilot plants and reactors.

Performance characterization of Lithium-ion cells possessing carbon-carbon composite-based anodes capable of operating over a wide temperature range

NASA Technical Reports Server (NTRS)

Smart, M. C.; Hossain, S.; Ratnakumar, B. V.; Loutfy, R.; Whitcanack, L. D.; Chin, K. B.; Davies, E. D.; Surampudi, S.; Narayanan, S. R.

2004-01-01

NASA has interest in secondary energy storage batteries that display high specific energy, high energy density, long life characteristics, and perform well over a wide range of temperatures, in order to enable a number of future applications.

DMS cyclone separation processes for optimization of plastic wastes recycling and their implications.

PubMed

Gent, Malcolm Richard; Menendez, Mario; Toraño, Javier; Torno, Susana

2011-06-01

It is demonstrated that substantial reductions in plastics presently disposed of in landfills can be achieved by cyclone density media separation (DMS). In comparison with the size fraction of plastics presently processed by industrial density separations (generally 6.4 to 9.5 mm), cyclone DMS methods are demonstrated to effectively process a substantially greater range of particle sizes (from 0.5 up to 120 mm). The purities of plastic products and recoveries obtained with a single stage separation using a cylindrical cyclone are shown to attain virtually 100% purity and recoveries >99% for high-density fractions and >98% purity and recoveries were obtained for low-density products. Four alternative schemas of multi-stage separations are presented and analyzed as proposed methods to obtain total low- and high-density plastics fraction recoveries while maintaining near 100% purities. The results of preliminary tests of two of these show that the potential for processing product purities and recoveries >99.98% of both density fractions are indicated. A preliminary economic comparison of capital costs of DMS systems suggests cyclone DMS methods to be comparable with other DMS processes even if the high volume capacity for recycling operations of these is not optimized.

Close-Spaced High Temperature Knudsen Flow.

DTIC Science & Technology

1986-07-15

work~was a study of discharge processes in Knudsen mode (collisionless), thermionic energy converters. Areas of research involve’mechanisms for reducing ...power densities. The mechanisms/we have chosen to study are: reduction of space-charge through a very close interelectrode gap (less than 10 microns...In order to operate at practical current densities, the effect of electron space charge must be reduced . This can be done through very close

Advanced chemical hydride-based hydrogen generation/storage system for fuel cell vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breault, R.W.; Rolfe, J.

1998-08-01

Because of the inherent advantages of high efficiency, environmental acceptability, and high modularity, fuel cells are potentially attractive power supplies. Worldwide concerns over clean environments have revitalized research efforts on developing fuel cell vehicles (FCV). As a result of intensive research efforts, most of the subsystem technology for FCV`s are currently well established. These include: high power density PEM fuel cells, control systems, thermal management technology, and secondary power sources for hybrid operation. For mobile applications, however, supply of hydrogen or fuel for fuel cell operation poses a significant logistic problem. To supply high purity hydrogen for FCV operation, Thermomore » Power`s Advanced Technology Group is developing an advanced hydrogen storage technology. In this approach, a metal hydride/organic slurry is used as the hydrogen carrier and storage media. At the point of use, high purity hydrogen will be produced by reacting the metal hydride/organic slurry with water. In addition, Thermo Power has conceived the paths for recovery and regeneration of the spent hydride (practically metal hydroxide). The fluid-like nature of the spent hydride/organic slurry will provide a unique opportunity for pumping, transporting, and storing these materials. The final product of the program will be a user-friendly and relatively high energy storage density hydrogen supply system for fuel cell operation. In addition, the spent hydride can relatively easily be collected at the pumping station and regenerated utilizing renewable sources, such as biomass, natural, or coal, at the central processing plants. Therefore, the entire process will be economically favorable and environmentally friendly.« less

The Grid Density Dependence of the Unsteady Pressures of the J-2X Turbines

NASA Technical Reports Server (NTRS)

Schmauch, Preston B.

2011-01-01

The J-2X engine was originally designed for the upper stage of the cancelled Crew Launch Vehicle. Although the Crew Launch Vehicle was cancelled the J-2X engine, which is currently undergoing hot-fire testing, may be used on future programs. The J-2X engine is a direct descendent of the J-2 engine which powered the upper stage during the Apollo program. Many changes including a thrust increase from 230K to 294K lbf have been implemented in this engine. As part of the design requirements, the turbine blades must meet minimum high cycle fatigue factors of safety for various vibrational modes that have resonant frequencies in the engine's operating range. The unsteady blade loading is calculated directly from CFD simulations. A grid density study was performed to understand the sensitivity of the spatial loading and the magnitude of the on blade loading due to changes in grid density. Given that the unsteady blade loading has a first order effect on the high cycle fatigue factors of safety, it is important to understand the level of convergence when applying the unsteady loads. The convergence of the unsteady pressures of several grid densities will be presented for various frequencies in the engine's operating range.

A pulser-sustainer carbon monoxide electric-discharge supersonic laser

NASA Technical Reports Server (NTRS)

Monson, D. J.; Srinivasan, G.

1977-01-01

Operation of a CW CO electric-discharge supersonic laser with a pulser-sustainer discharge is described. High-power operation as well as independent control over electron energy and density are demonstrated. Maximum input power achieved to date is 100 kW. The maximum output power is 6 kW or 10% of the sustainer positive-column power. Much improved performance appears possible.

Alkaline anion exchange membrane water electrolysis: Effects of electrolyte feed method and electrode binder content

NASA Astrophysics Data System (ADS)

Cho, Min Kyung; Park, Hee-Young; Lee, Hye Jin; Kim, Hyoung-Juhn; Lim, Ahyoun; Henkensmeier, Dirk; Yoo, Sung Jong; Kim, Jin Young; Lee, So Young; Park, Hyun S.; Jang, Jong Hyun

2018-04-01

Herein, we investigate the effects of catholyte feed method and anode binder content on the characteristics of anion exchange membrane water electrolysis (AEMWE) to construct a high-performance electrolyzer, revealing that the initial AEMWE performance is significantly improved by pre-feeding 0.5 M aqueous KOH to the cathode. The highest long-term activity during repeated voltage cycling is observed for AEMWE operation in the dry cathode mode, for which the best long-term performance among membrane electrode assemblies (MEAs) featuring polytetrafluoroethylene (PTFE) binder-impregnated (5-20 wt%) anodes is detected for a PTFE content of 20 wt%. MEAs with low PTFE content (5 and 9 wt%) demonstrate high initial performance, rapid performance decay, and significant catalyst loss from the electrode during long-term operation, whereas the MEA with 20 wt% PTFE allows stable water electrolysis for over 1600 voltage cycles. Optimization of cell operating conditions (i.e., operation in dry cathode mode at an optimum anode binder content following an initial solution feed) achieves an enhanced water splitting current density (1.07 A cm-2 at 1.8 V) and stable long-term AEMWE performance (0.01% current density reduction per voltage cycle).

Local Fitting of the Kohn-Sham Density in a Gaussian and Plane Waves Scheme for Large-Scale Density Functional Theory Simulations.

PubMed

Golze, Dorothea; Iannuzzi, Marcella; Hutter, Jürg

2017-05-09

A local resolution-of-the-identity (LRI) approach is introduced in combination with the Gaussian and plane waves (GPW) scheme to enable large-scale Kohn-Sham density functional theory calculations. In GPW, the computational bottleneck is typically the description of the total charge density on real-space grids. Introducing the LRI approximation, the linear scaling of the GPW approach with respect to system size is retained, while the prefactor for the grid operations is reduced. The density fitting is an O(N) scaling process implemented by approximating the atomic pair densities by an expansion in one-center fit functions. The computational cost for the grid-based operations becomes negligible in LRIGPW. The self-consistent field iteration is up to 30 times faster for periodic systems dependent on the symmetry of the simulation cell and on the density of grid points. However, due to the overhead introduced by the local density fitting, single point calculations and complete molecular dynamics steps, including the calculation of the forces, are effectively accelerated by up to a factor of ∼10. The accuracy of LRIGPW is assessed for different systems and properties, showing that total energies, reaction energies, intramolecular and intermolecular structure parameters are well reproduced. LRIGPW yields also high quality results for extended condensed phase systems such as liquid water, ice XV, and molecular crystals.

Integrated anode structure for passive direct methanol fuel cells with neat methanol operation

NASA Astrophysics Data System (ADS)

Wu, Huijuan; Zhang, Haifeng; Chen, Peng; Guo, Jing; Yuan, Ting; Zheng, Junwei; Yang, Hui

2014-02-01

A microporous titanium plate based integrated anode structure (Ti-IAS) suitable for passive direct methanol fuel cells (DMFCs) fueled with neat methanol is reported. This anode structure incorporates a porous titanium plate as a methanol mass transfer barrier and current collector, pervaporation film for passively vaporizing methanol, vaporous methanol cavity for evenly distributing fuel, and channels for carbon dioxide venting. With the effective control of methanol delivery rate, the Ti-IAS based DMFC allows the direct use of neat methanol as the fuel source. In the meantime, the required water for methanol-oxidation reaction at the anode can also be fully recovered from the cathode with the help of the highly hydrophobic microporous layer in the cathode. DMFCs incorporating this new anode structure exhibit a power density as high as 40 mW cm-2 and a high volumetric energy density of 489 Wh L-1 operating with neat methanol and at 25 °C. Importantly, no obvious performance degradation of the passive DMFC system is observed after more than 90 h of continuous operation. The experimental results reveal that the compact DMFC based on the Ti-IAS exhibits a substantial potential as power sources for portable applications.

Power Electronic Transformer based Three-Phase PWM AC Drives

NASA Astrophysics Data System (ADS)

Basu, Kaushik

A Transformer is used to provide galvanic isolation and to connect systems at different voltage levels. It is one of the largest and most expensive component in most of the high voltage and high power systems. Its size is inversely proportional to the operating frequency. The central idea behind a power electronic transformer (PET) also known as solid state transformer is to reduce the size of the transformer by increasing the frequency. Power electronic converters are used to change the frequency of operation. Steady reduction in the cost of the semiconductor switches and the advent of advanced magnetic materials with very low loss density and high saturation flux density implies economic viability and feasibility of a design with high power density. Application of PET is in generation of power from renewable energy sources, especially wind and solar. Other important application include grid tied inverters, UPS e.t.c. In this thesis non-resonant, single stage, bi-directional PET is considered. The main objective of this converter is to generate adjustable speed and magnitude pulse width modulated (PWM) ac waveforms from an ac or dc grid with a high frequency ac link. The windings of a high frequency transformer contains leakage inductance. Any switching transition of the power electronic converter connecting the inductive load and the transformer requires commutation of leakage energy. Commutation by passive means results in power loss, decrease in the frequency of operation, distortion in the output voltage waveform, reduction in reliability and power density. In this work a source based partially loss-less commutation of leakage energy has been proposed. This technique also results in partial soft-switching. A series of converters with novel PWM strategies have been proposed to minimize the frequency of leakage inductance commutation. These PETs achieve most of the important features of modern PWM ac drives including 1) Input power factor correction, 2) Common-mode voltage suppression at the load end, 3) High quality output voltage waveform (comparable to conventional space vector PWM modulated two level inverter) and 4) Minimization of output voltage loss, common-mode voltage switching and distortion of the load current waveform due to leakage inductance commutation. All of the proposed topologies along with the proposed control schemes have been analyzed and simulated in MATLABSimulink. A hardware prototype has been fabricated and tested. The simulation and experimental results verify the operation and advantages of the proposed topologies and their control.

High frequency pressure oscillator for microcryocoolers.

PubMed

Vanapalli, S; ter Brake, H J M; Jansen, H V; Zhao, Y; Holland, H J; Burger, J F; Elwenspoek, M C

2008-04-01

Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80 K, delivering a cooling power of 10 mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5 MPa and compression volume of about 22.6 mm(3) when operating the actuator with a peak-to-peak sinusoidal voltage of 100 V at a frequency of 1 kHz. The electrical power input was 2.73 W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

High frequency pressure oscillator for microcryocoolers

NASA Astrophysics Data System (ADS)

Vanapalli, S.; ter Brake, H. J. M.; Jansen, H. V.; Zhao, Y.; Holland, H. J.; Burger, J. F.; Elwenspoek, M. C.

2008-04-01

Microminiature pulse tube cryocoolers should operate at a frequency of an order higher than the conventional macro ones because the pulse tube cryocooler operating frequency scales inversely with the square of the pulse tube diameter. In this paper, the design and experiments of a high frequency pressure oscillator is presented with the aim to power a micropulse tube cryocooler operating between 300 and 80K, delivering a cooling power of 10mW. Piezoelectric actuators operate efficiently at high frequencies and have high power density making them good candidates as drivers for high frequency pressure oscillator. The pressure oscillator described in this work consists of a membrane driven by a piezoelectric actuator. A pressure ratio of about 1.11 was achieved with a filling pressure of 2.5MPa and compression volume of about 22.6mm3 when operating the actuator with a peak-to-peak sinusoidal voltage of 100V at a frequency of 1kHz. The electrical power input was 2.73W. The high pressure ratio and low electrical input power at high frequencies would herald development of microminiature cryocoolers.

Counter-facing plasma guns for efficient extreme ultra-violet plasma light source

NASA Astrophysics Data System (ADS)

Kuroda, Yusuke; Yamamoto, Akiko; Kuwabara, Hajime; Nakajima, Mitsuo; Kawamura, Tohru; Horioka, Kazuhiko

2013-11-01

A plasma focus system composed of a pair of counter-facing coaxial guns was proposed as a long-pulse and/or repetitive high energy density plasma source. We applied Li as the source of plasma for improvement of the conversion efficiency, the spectral purity, and the repetition capability. For operation of the system with ideal counter-facing plasma focus mode, we changed the system from simple coaxial geometry to a multi-channel configuration. We applied a laser trigger to make synchronous multi-channel discharges with low jitter. The results indicated that the configuration is promising to make a high energy density plasma with high spectral efficiency.

High voltage and high current density vertical GaN power diodes

DOE PAGES

Fischer, A. J.; Dickerson, J. R.; Armstrong, A. M.; ...

2016-01-01

We report on the realization of a GaN high voltage vertical p-n diode operating at > 3.9 kV breakdown with a specific on-resistance < 0.9 mΩ.cm 2. Diodes achieved a forward current of 1 A for on-wafer, DC measurements, corresponding to a current density > 1.4 kA/cm 2. An effective critical electric field of 3.9 MV/cm was estimated for the devices from analysis of the forward and reverse current-voltage characteristics. Furthermore this suggests that the fundamental limit to the GaN critical electric field is significantly greater than previously believed.

High power densities from high-temperature material interactions. [in thermionic energy conversion and metallic fluid heat pipes

NASA Technical Reports Server (NTRS)

Morris, J. F.

1981-01-01

Thermionic energy conversion (TEC) and metallic-fluid heat pipes (MFHPs), offering unique advantages in terrestrial and space energy processing by virtue of operating on working-fluid vaporization/condensation cycles that accept great thermal power densities at high temperatures, share complex materials problems. Simplified equations are presented that verify and solve such problems, suggesting the possibility of cost-effective applications in the near term for TEC and MFHP devices. Among the problems discussed are: the limitation of alkali-metal corrosion, protection against hot external gases, external and internal vaporization, interfacial reactions and diffusion, expansion coefficient matching, and creep deformation.

Modeling of laser cladding with application to fuel cell manufacturing.

DOT National Transportation Integrated Search

2010-01-01

Polymer electrolyte membrane (PEM) fuel cells have many advantages such as compactness, : lightweight, high power density, low temperature operation and near zero emissions. Although : many research organizations have intensified their efforts toward...

Potential impacts of advanced technologies on the ATC capacity of high-density terminal areas

NASA Technical Reports Server (NTRS)

Simpson, R. W.; Odoni, A. R.; Salas-Roche, F.

1986-01-01

Advanced technologies for airborne systems (automatic flight control, flight displays, navigation) and for ground ATC systems (digital communications, improved surveillance and tracking, automated decision-making) create the possibility of advanced ATC operations and procedures which can bring increased capacity for runway systems. A systematic analysis is carried out to identify certain such advanced ATC operations, and then to evaluate the potential benefits occurring over time at typical US high-density airports (Denver and Boston). The study is divided into three parts: (1) A Critical Examination of Factors Which Determine Operational Capacity of Runway Systems at Major Airports, is an intensive review of current US separation criteria and terminal area ATC operations. It identifies 11 new methods to increase the capacity of landings and takeoffs for runway systems; (2) Development of Risk Based Separation Criteria is the development of a rational structure for establishing reduced ATC separation criteria which meet a consistent Target Level of Safety using advanced technology and operational procedures; and (3) Estimation of Capacity Benefits from Advanced Terminal Area Operations - Denver and Boston, provides an estimate of the overall annual improvement in runway capacity which might be expected at Denver and Boston from using some of the advanced ATC procedures developed in Part 1. Whereas Boston achieved a substantial 37% increase, Denver only achieved a 4.7% increase in its overall annual capacity.

High performance, flexible, poly(3,4-ethylenedioxythiophene) supercapacitors achieved by doping redox mediators in organogel electrolytes

NASA Astrophysics Data System (ADS)

Zhang, Huanhuan; Li, Jinyu; Gu, Cheng; Yao, Mingming; Yang, Bing; Lu, Ping; Ma, Yuguang

2016-11-01

The relatively low energy density is now a central issue hindering the development of supercapacitors as energy storage devices. Various approaches are thus developed to enhance the energy density, mainly centering on the fabrication of electrode materials or optimization of cell configurations. Compared with these approaches, modifications in electrolytes are much simple and versatile. Herein, we integrate the wide voltages endowed by organic electrolytes and the additional capacitances brought by redox mediators, to fabricate high energy density supercapacitors. On the basis of this idea, supercapacitors with poly(3,4-ethylenedioxythiophene) (PEDOT) as electrode material exhibit extended operating voltage of 1.5 V, extraordinary capacitance of 363 F g-1 and high energy density of 27.4 Wh kg-1. The redox mediators reported here, ferrocene and 4-oxo-2,2,6,6-tetramethylpiperidinooxy, are the first time being applied in supercapacitors, especially in the gel state. While providing additional faradaic capacitances, they also exhibit synergistic interaction with PEDOT and improve the cycling stability of supercapacitors.

Novel Superdielectric Materials: Aqueous Salt Solution Saturated Fabric

PubMed Central

Phillips, Jonathan

2016-01-01

The dielectric constants of nylon fabrics saturated with aqueous NaCl solutions, Fabric-Superdielectric Materials (F-SDM), were measured to be >105 even at the shortest discharge times (>0.001 s) for which reliable data could be obtained using the constant current method, thus demonstrating the existence of a third class of SDM. Hence, the present results support the general theoretical SDM hypothesis, which is also supported by earlier experimental work with powder and anodized foil matrices: Any material composed of liquid containing dissolved, mobile ions, confined in an electrically insulating matrix, will have a very high dielectric constant. Five capacitors, each composed of a different number of layers of salt solution saturated nylon fabric, were studied, using a galvanostat operated in constant current mode. Capacitance, dielectric constant, energy density and power density as a function of discharge time, for discharge times from ~100 s to nearly 0.001 s were recorded. The roll-off rate of the first three parameters was found to be nearly identical for all five capacitors tested. The power density increased in all cases with decreasing discharge time, but again the observed frequency response was nearly identical for all five capacitors. Operational limitations found for F-SDM are the same as those for other aqueous solution SDM, particularly a low maximum operating voltage (~2.3 V), and dielectric “constants” that are a function of voltage, decreasing for voltages higher than ~0.8 V. Extrapolations of the present data set suggest F-SDM could be the key to inexpensive, high energy density (>75 J/cm3) capacitors. PMID:28774037

Frequency Rectification Applied to Piezoelectric Energy Harvesting and Improving Available Power of Piezoelectric Motors

NASA Astrophysics Data System (ADS)

Kuroda, Kazuaki; LCGT Collaboration

Piezoelectric materials are just now, within the last decade, coming into their own as a commercial material. Capable of converting energy from the mechanical domain to the electrical domain; piezos are ideal sensors, vibration dampers, energy harvesters, and actuators. Frequency rectification, or the conversion of small, high frequency piezoelectric vibrations into useful low frequency actuation, is required to obtain widespread industrial use of piezoelectric devices. This work examines three manifestations of piezoelectric frequency rectification: energy harvesting, a hydraulic motor, and friction based commercial-off-the-shelf motors. An energy harvesting device is developed, manufactured, and tested in this work, resulting in the development of a high Energy Density (J/m 3), high Power Density (W/m3) energy harvester. The device is shown to have an Energy Density nearly twice that of a similar conventional energy harvesting device. The result of this work is the development of an energy harvesting system that generates more energy in a given volume of piezoelectric material, opening the possibility of miniaturization of energy harvesting devices. Also presented is an effort to integrate a high frequency, high flow rate micromachined valve array into a PiezoHydraulic Pump (PHP), enabling resonant operation of the PHP. Currently, the device is limited by the resonant frequency of the proprietary passive check valves. The PHP is fully characterized, and the microvalve array is tested to determine its resonant frequency in a fluid medium. The valve testing resulted in a resonant frequency of 6.9 kHz, slightly lower than the target operating frequency of 10 kHz. Finally, the results of an examination of frequency rectification as applied to COTS piezoelectric motors are presented. Currently, motors are almost universally characterized based upon their available mechanical power. A better comparison is one based upon the actual Energy Density of the piezoelectric material utilized in the motor compared to the theoretical maximum Energy Density under the motor operating conditions (i.e., frequency, applied electric field). The result of this work is a more descriptive metric to evaluate piezoelectric motors that provides information on the effectiveness of the motor drive train; that is, how effectively the motion of the piezoelectric is transferred to the outside world.

Injection of auxiliary electrons for increasing the plasma density in highly charged and high intensity ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Odorici, F., E-mail: fabrizio.odorici@bo.infn.it; Malferrari, L.; Montanari, A.

Different electron guns based on cold- or hot-cathode technologies have been developed since 2009 at INFN for operating within ECR plasma chambers as sources of auxiliary electrons, with the aim of boosting the source performances by means of a higher plasma lifetime and density. Their application to microwave discharge ion sources, where plasma is not confined, has required an improvement of the gun design, in order to “screen” the cathode from the plasma particles. Experimental tests carried out on a plasma reactor show a boost of the plasma density, ranging from 10% to 90% when the electron guns are used,more » as explained by plasma diffusion models.« less

Hydrological impact of high-density small dams in a humid catchment, Southeast China

NASA Astrophysics Data System (ADS)

Lu, W.; Lei, H.; Yang, D.

2017-12-01

The Jiulong River basin is a humid catchment with a drainage area of 14,741 km2; however, it has over 1000 hydropower stations within it. Such catchment with high-density small dams is scarce in China. Yet few is known about the impact of high-density small dams on streamflow changes. To what extent the large number of dams alters the hydrologic patterns is a fundamental scientific issue for water resources management, flood control, and aquatic ecological environment protection. Firstly, trend and change point analyses are applied to determine the characteristics of inter-annual streamflow. Based on the detected change point, the study period is divided into two study periods, the ``natural'' and ``disturbed'' periods. Then, a geomorphology-based hydrological model (GBHM) and the fixing-changing method are adopted to evaluate the relative contributions of climate variations and damming to the changes in streamflow at each temporal scale (i.e., from daily, monthly to annual). Based on the simulated natural streamflow, the impact of dam construction on hydrologic alteration and aquatic ecological environment will be evaluated. The hydrologic signatures that will be investigated include flood peak, seasonality of streamflow, and the inter-annual variability of streamflow. In particular, the impacts of damming on aquatic ecological environment will be investigated using eco-flow metrics and indicators of hydrologic alteration (IHA) which contains 33 individual streamflow statistics that are closely related to aquatic ecosystem. The results of this study expect to provide a reference for reservoir operation considering both ecological and economic benefits of such operations in the catchment with high-density dams.

An empirical/theoretical model with dimensionless numbers to predict the performance of electrodialysis systems on the basis of operating conditions.

PubMed

Karimi, Leila; Ghassemi, Abbas

2016-07-01

Among the different technologies developed for desalination, the electrodialysis/electrodialysis reversal (ED/EDR) process is one of the most promising for treating brackish water with low salinity when there is high risk of scaling. Multiple researchers have investigated ED/EDR to optimize the process, determine the effects of operating parameters, and develop theoretical/empirical models. Previously published empirical/theoretical models have evaluated the effect of the hydraulic conditions of the ED/EDR on the limiting current density using dimensionless numbers. The reason for previous studies' emphasis on limiting current density is twofold: 1) to maximize ion removal, most ED/EDR systems are operated close to limiting current conditions if there is not a scaling potential in the concentrate chamber due to a high concentration of less-soluble salts; and 2) for modeling the ED/EDR system with dimensionless numbers, it is more accurate and convenient to use limiting current density, where the boundary layer's characteristics are known at constant electrical conditions. To improve knowledge of ED/EDR systems, ED/EDR models should be also developed for the Ohmic region, where operation reduces energy consumption, facilitates targeted ion removal, and prolongs membrane life compared to limiting current conditions. In this paper, theoretical/empirical models were developed for ED/EDR performance in a wide range of operating conditions. The presented ion removal and selectivity models were developed for the removal of monovalent ions and divalent ions utilizing the dominant dimensionless numbers obtained from laboratory scale electrodialysis experiments. At any system scale, these models can predict ED/EDR performance in terms of monovalent and divalent ion removal. Copyright © 2016 Elsevier Ltd. All rights reserved.

NASA TLA workload analysis support. Volume 1: Detailed task scenarios for general aviation and metering and spacing studies

NASA Technical Reports Server (NTRS)

Sundstrom, J. L.

1980-01-01

The techniques required to produce and validate six detailed task timeline scenarios for crew workload studies are described. Specific emphasis is given to: general aviation single pilot instrument flight rules operations in a high density traffic area; fixed path metering and spacing operations; and comparative workload operation between the forward and aft-flight decks of the NASA terminal control vehicle. The validation efforts also provide a cursory examination of the resultant demand workload based on the operating procedures depicted in the detailed task scenarios.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Simulation of SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling

NASA Astrophysics Data System (ADS)

Gong, Yue-Feng; Song, Zhi-Tang; Ling, Yun; Liu, Yan; Feng, Song-Lin

2009-11-01

A three-dimensional finite element model for phase change random access memory (PCRAM) is established for comprehensive electrical and thermal analysis during SET operation. The SET behaviours of the heater addition structure (HS) and the ring-type contact in bottom electrode (RIB) structure are compared with each other. There are two ways to reduce the RESET current, applying a high resistivity interfacial layer and building a new device structure. The simulation results indicate that the variation of SET current with different power reduction ways is little. This study takes the RESET and SET operation current into consideration, showing that the RIB structure PCRAM cell is suitable for future devices with high heat efficiency and high-density, due to its high heat efficiency in RESET operation.

Development of a current collection loss management system for SDI homopolar power supplies

NASA Astrophysics Data System (ADS)

Brown, D. W.

1991-04-01

High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operate continuously at 2 kA/sq cm, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To date, no system has achieved these conditions simultaneously. This is the final report covering the three year period of performance on DOE contract AC03-86SF-16518. Major areas covered include design, construction and operation of a cryogenically cooled brush test rig, design and construction of a high speed brush test rig, optimization study for homopolar machines, loss analysis of the current collection system, and an application study which defines the air-core homopolar construction necessary to achieve the goal of 80 kW/kg generator power density.

Thermo-Electron Ballistic Coolers or Heaters

NASA Technical Reports Server (NTRS)

Choi, Sang H.

2003-01-01

Electronic heat-transfer devices of a proposed type would exploit some of the quantum-wire-like, pseudo-superconducting properties of single-wall carbon nanotubes or, optionally, room-temperature-superconducting polymers (RTSPs). The devices are denoted thermo-electron ballistic (TEB) coolers or heaters because one of the properties that they exploit is the totally or nearly ballistic (dissipation or scattering free) transport of electrons. This property is observed in RTSPs and carbon nanotubes that are free of material and geometric defects, except under conditions in which oscillatory electron motions become coupled with vibrations of the nanotubes. Another relevant property is the high number density of electrons passing through carbon nanotubes -- sufficient to sustain electron current densities as large as 100 MA/square cm. The combination of ballistic motion and large current density should make it possible for TEB devices to operate at low applied potentials while pumping heat at rates several orders of magnitude greater than those of thermoelectric devices. It may also enable them to operate with efficiency close to the Carnot limit. In addition, the proposed TEB devices are expected to operate over a wider temperature range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esswein, AJ; Surendranath, Y; Reece, SY

A high surface area electrode is functionalized with cobalt-based oxygen evolving catalysts (Co-OEC = electrodeposited from pH 7 phosphate, Pi, pH 8.5 methylphosphonate, MePi, and pH 9.2 borate electrolyte, Bi). Co-OEC prepared from MePi and operated in Pi and Bi achieves a current density of 100 mA cm(-2) for water oxidation at 442 and 363 mV overpotential, respectively. The catalyst retains activity in near-neutral pH buffered electrolyte in natural waters such as those from the Charles River (Cambridge, MA) and seawater (Woods Hole, MA). The efficacy and ease of operation of anodes functionalized with Co-OEC at appreciable current density togethermore » with its ability to operate in near neutral pH buffered natural water sources bodes well for the translation of this catalyst to a viable renewable energy storage technology.« less

Analysis of operational requirements for medium density air transportation. Volume 1: Summary

NASA Technical Reports Server (NTRS)

1975-01-01

The medium density air travel market was studied to determine the aircraft design and operational requirements. The impact of operational characteristics on the air travel system and the economic viability of the study aircraft were also evaluated. Medium density is defined in terms of numbers of people transported (20 to 500 passengers per day on round trip routes), and frequency of service ( a minumium of two and maximum of eight round trips per day) for 10 regional carriers. The operational characteristics of aircraft best suited to serve the medium density air transportation market are determined and a basepoint aircraft is designed from which tradeoff studies and parametric variations could be conducted. The impact of selected aircraft on the medium density market, economics, and operations is ascertained. Research and technology objectives for future programs in medium density air transportation are identified and ranked.

Edge-enriched, porous carbon-based, high energy density supercapacitors for hybrid electric vehicles.

PubMed

Kim, Yong Jung; Yang, Cheol-Min; Park, Ki Chul; Kaneko, Katsumi; Kim, Yoong Ahm; Noguchi, Minoru; Fujino, Takeshi; Oyama, Shigeki; Endo, Morinobu

2012-03-12

Supercapacitors can store and deliver energy by a simple charge separation, and thus they could be an attractive option to meet transient high energy density in operating fuel cells and in electric and hybrid electric vehicles. To achieve such requirements, intensive studies have been carried out to improve the volumetric capacitance in supercapacitors using various types and forms of carbons including carbon nanotubes and graphenes. However, conventional porous carbons are not suitable for use as electrode material in supercapacitors for such high energy density applications. Here, we show that edge-enriched porous carbons are the best electrode material for high energy density supercapacitors to be used in vehicles as an auxiliary powertrain. Molten potassium hydroxide penetrates well-aligned graphene layers vertically and consequently generates both suitable pores that are easily accessible to the electrolyte and a large fraction of electrochemically active edge sites. We expect that our findings will motivate further research related to energy storage devices and also environmentally friendly electric vehicles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of Physical Processes Limiting Plasma Density in DIII--D

NASA Astrophysics Data System (ADS)

Maingi, R.

1996-11-01

Understanding the physical processes which limit operating density is crucial in achieving peak performance in confined plasmas. Studies from many of the world's tokamaks have indicated the existence(M. Greenwald, et al., Nucl. Fusion 28) (1988) 2199 of an operational density limit (Greenwald limit, n^GW_max) which is proportional to the plasma current and independent of heating power. Several theories have reproduced the current dependence, but the lack of a heating power dependence in the data has presented an enigma. This limit impacts the International Thermonuclear Experimental Reactor (ITER) because the nominal operating density for ITER is 1.5 × n^GW_max. In DIII-D, experiments are being conducted to understand the physical processes which limit operating density in H-mode discharges; these processes include X-point MARFE formation, high core recycling and neutral pressure, resistive MHD stability, and core radiative collapse. These processes affect plasma properties, i.e. edge/scrape-off layer conduction and radiation, edge pressure gradient and plasma current density profile, and core radiation, which in turn restrict the accessible density regime. With divertor pumping and D2 pellet fueling, core neutral pressure is reduced and X-point MARFE formation is effectively eliminated. Injection of the largest-sized pellets does cause transient formation of divertor MARFEs which occasionally migrate to the X-point, but these are rapidly extinguished in pumped discharges in the time between pellets. In contrast to Greenwald et al., it is found that the density relaxation time after pellets is largely independent of the density relative to the Greenwald limit. Fourier analysis of Mirnov oscillations indicates the de-stabilization and growth of rotating, tearing-type modes (m/n= 2/1) when the injected pellets cause large density perturbations, and these modes often reduce energy confinement back to L-mode levels. We are examining the mechanisms for de-stabilization of the mode, the primary ones being neo-classical pressure gradient drivers. Discharges with a gradual density increase are often free of large amplitude tearing modes, allowing access to the highest density regimes in which off-axis beam deposition can lead to core radiative collapse, i.e. a central power balance limit. The highest achieved barne was 1.5 × n^GW_max with τ_E/τ_E^JET-DIII-D >= 0.9. The highest density obtained in L-mode discharges was 3 × n^GW_max. Implications of these results for ITER will be discussed.

The density-matrix renormalization group: a short introduction.

PubMed

Schollwöck, Ulrich

2011-07-13

The density-matrix renormalization group (DMRG) method has established itself over the last decade as the leading method for the simulation of the statics and dynamics of one-dimensional strongly correlated quantum lattice systems. The DMRG is a method that shares features of a renormalization group procedure (which here generates a flow in the space of reduced density operators) and of a variational method that operates on a highly interesting class of quantum states, so-called matrix product states (MPSs). The DMRG method is presented here entirely in the MPS language. While the DMRG generally fails in larger two-dimensional systems, the MPS picture suggests a straightforward generalization to higher dimensions in the framework of tensor network states. The resulting algorithms, however, suffer from difficulties absent in one dimension, apart from a much more unfavourable efficiency, such that their ultimate success remains far from clear at the moment.

Magnetostrictive direct drive motors

NASA Technical Reports Server (NTRS)

Naik, Dipak; Dehoff, P. H.

1992-01-01

A new rare earth alloy, Terfenol-D, combines low frequency operation and extremely high energy density with high magnetostriction. Its material properties make it suitable as a drive element for actuators requiring high output torque. The high strains, the high forces and the high controllability of Terfenol alloys provide a powerful and challenging basis for new ways to generate motion in actuators. Two prototypes of motors using Terfenol-D rods were developed at NASA Goddard. The basic principles of operation are provided of the motor along with other relevant details. A conceptual design of a torque limiting safety clutch/brake under development is illustrated. Also, preliminary design drawings of a linear actuator using Terfenol-D is shown.

A simple microfluidic Coriolis effect flowmeter for operation at high pressure and high temperature.

PubMed

Harrison, Christopher; Jundt, Jacques

2016-08-01

We describe a microfluidic Coriolis effect flowmeter that is simple to assemble, operates at elevated temperature and pressure, and can be operated with a lock-in amplifier. The sensor has a flow rate sensitivity greater than 2° of phase shift per 1 g/min of mass flow and is benchmarked with flow rates ranging from 0.05 to 2.0 g/min. The internal volume is 15 μl and uses off-the-shelf optical components to measure the tube motion. We demonstrate that fluid density can be calculated from the frequency of the resonating element with proper calibration.

Development of an engineering model traveling wave tube amplifier for space communication systems

NASA Technical Reports Server (NTRS)

Eallonardo, C. M.; Songli, J.; Basiulis, A.

1972-01-01

A design has been made of a 100 watt traveling-wave tube amplifier for use in space communication applications. The features of very high overall efficiency and heat rejection of waste heat at low thermal densities were predominant in the design concept. The design concept was proven by building a series of tubes, operating at efficiencies up to 50%. These tubes utilized heat pipe cooling and heat distribution such that 150 watts of waste heat was rejected at a density of less than 1.5 watts per square inch. A power supply to convert a 28 volt primary line of the needs of the TWT was built and operated at 85% efficiency.

High-Energy-Density Electrolytic Capacitors

NASA Technical Reports Server (NTRS)

Yen, Shiao-Ping S.; Lewis, Carol R.

1993-01-01

Reductions in weight and volume make new application possible. Supercapacitors and improved ultracapacitors advanced electrolytic capacitors developed for use as electric-load-leveling devices in such applications as electric vehicle propulsion systems, portable power tools, and low-voltage pulsed power supplies. One primary advantage: offer power densities much higher than storage batteries. Capacitors used in pulse mode, with short charge and discharge times. Derived from commercially available ultracapacitors. Made of lightweight materials; incorporate electrode/electrolyte material systems capable of operation at voltages higher than previous electrode/electrolyte systems. By use of innovative designs and manufacturing processes, made in wide range of rated capacitances and in rated operating potentials ranging from few to several hundred volts.

New electrocatalysts for hydrogen-oxygen fuel cells

NASA Technical Reports Server (NTRS)

Cattabriga, R. A.; Giner, J.; Parry, J.; Swette, L. L.

1970-01-01

Platinum-silver, palladium-gold, and platinum-gold alloys serve as oxygen reduction catalysts in high-current-density cells. Catalysts were tested on polytetrafluoroethylene-bonded cathodes and a hydrogen anode at an operating cell temperature of 80 degrees C.

14 CFR 93.123 - High density traffic airports.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Airport Class of user LaGuardia 4, 5 Newark O'Hare 2, 3, 5 Ronald Reagan National 1 Air carriers 48 40 120... aircraft operations at Ronald Reagan Washington National Airport, the term “commuters” means aircraft...

14 CFR 93.123 - High density traffic airports.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Airport Class of user LaGuardia 4, 5 Newark O'Hare 2, 3, 5 Ronald Reagan National 1 Air carriers 48 40 120... aircraft operations at Ronald Reagan Washington National Airport, the term “commuters” means aircraft...

Solid Polymer Electrolyte (SPE) fuel cell technology program

NASA Technical Reports Server (NTRS)

1978-01-01

Many previously demonstrated improved fuel cell features were consolidated to (1) obtain a better understanding of the observed characteristics of the operating laboratory-sized cells; (2) evaluate appropriate improved fuel cell features in 0.7 sq ft cell hardware; and (3) study the resultant fuel cell capability and determine its impact on various potential fuel cell space missions. The observed performance characteristics of the fuel cell at high temperatures and high current densities were matched with a theoretical model based on the change in Gibbs free energy voltage with respect to temperature and internal resistance change with current density. Excellent agreement between the observed and model performance was obtained. The observed performance decay with operational time on cells with very low noble metal loadings (0.05 mg/sq cm) were shown to be related to loss in surface area. Cells with the baseline amount of noble catalyst electrode loading demonstrated over 40,000 hours of stable performance.

Ablative material testing for low-pressure, low-cost rocket engines

NASA Technical Reports Server (NTRS)

Richter, G. Paul; Smith, Timothy D.

1995-01-01

The results of an experimental evaluation of ablative materials suitable for the production of light weight, low cost rocket engine combustion chambers and nozzles are presented. Ten individual specimens of four different compositions of silica cloth-reinforced phenolic resin materials were evaluated for comparative erosion in a subscale rocket engine combustion chamber. Gaseous hydrogen and gaseous oxygen were used as propellants, operating at a nominal chamber pressure of 1138 kPa (165 psi) and a nominal mixture ratio (O/F) of 3.3. These conditions were used to thermally simulate operation with RP-1 and liquid oxygen, and achieved a specimen throat gas temperature of approximately 2456 K (4420 R). Two high-density composition materials exhibited high erosion resistance, while two low-density compositions exhibited approximately 6-75 times lower average erosion resistance. The results compare favorably with previous testing by NASA and provide adequate data for selection of ablatives for low pressure, low cost rocket engines.

High-temperature superconducting undulator magnets

DOE PAGES

Kesgin, Ibrahim; Kasa, Matthew; Ivanyushenkov, Yury; ...

2017-02-13

Here, this paper presents test results on a prototype superconducting undulator magnet fabricated using 15% Zr-doped rare-earth barium copper oxide high temperature superconducting (HTS) tapes. On an 11-pole magnet we demonstrate an engineering current density, J e, of more than 2.1 kA mm -2 at 4.2 K, a value that is 40% higher than reached in comparable devices wound with NbTi-wire, which is used in all currently operating superconducting undulators. A novel winding scheme enabling the continuous winding of tape-shaped conductors into the intricate undulator magnets as well as a partial interlayer insulation procedure were essential in reaching this advancemore » in performance. Currently, there are rapid advances in the performance of HTS; therefore, achieving even higher current densities in an undulator structure or/and operating it at temperatures higher than 4.2 K will be possible, which would substantially simplify the cryogenic design and reduce overall costs.« less

New developments in the field of high voltage and extra-high voltage cables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jocteur, R.

1990-04-01

In this paper, the author presents the developments in progress at the present time in France concerning the high voltage (HV) and extra-high voltage (EHV) cables with synthetic insulation and their accessories up to the 500 kV range. The authors have adopted a maximum operating field strength approaching 16 kV/mm (405 V/mil) for low density polyethylene (LDPE) insulated cables. The on-going studies should allow to bring the maximum operating field strength for crosslinked polyethylene (XLPE) insulation from 7 to 10 kV/mm (180 to 255 V/mil) and cables could be manufactured more economically with this material.

New types of high field pinning centers and pinning centers for the peak effect

NASA Astrophysics Data System (ADS)

Gajda, Daniel; Zaleski, Andrzej; Morawski, Andrzej; Hossain, Md Shahriar A.

2017-08-01

In this article, we report the results of a study that shows the existence of pinning centers inside grains and between grains in NbTi wires. We accurately show the ranges of magnetic fields in which the individual pinning centers operate. The pinning centers inside grains are activated in high magnetic fields above 6 T. We show the range of magnetic fields in which individual defects, dislocations, precipitates inside grains and substitutions in the crystal lattice can operate. We show the existence of a new kind of high field pinning center, which operates in high magnetic fields from 8 to ˜9.5 T. We indicate that dislocations create pinning centers in the range of magnetic fields from 6 to 8 T. In addition, our measurements suggest that the peak effect (increased critical current density (J c) near the upper critical field (B c2)) could be attributed to martensitic (needle-shaped) α‧-Ti inclusions inside grains. These centers are very important because they work very effectively in magnetic fields above 9.5-10 T. We also show that the α-Ti precipitates (between grains) with a thickness similar to the coherence length create pinning centers which work very effectively in magnetic fields from 3 to 6 T. In magnetic fields below 3 T, they act very efficiently in grain boundaries. The measurements indicate that the pinning centers created by dislocations only can be tested by transport measurements. This indicates that dislocations do not increase the magnetic critical current density (J cm). Cold drawing improves pinning centers at grain boundaries and increases the dislocation density, and cold-drawing pinning centers are responsible for the peak effect.

Extremely fine structured cathode for solid oxide fuel cells using Sr-doped LaMnO3 and Y2O3-stabilized ZrO2 nano-composite powder synthesized by spray pyrolysis

NASA Astrophysics Data System (ADS)

Shimada, Hiroyuki; Yamaguchi, Toshiaki; Sumi, Hirofumi; Nomura, Katsuhiro; Yamaguchi, Yuki; Fujishiro, Yoshinobu

2017-02-01

A solid oxide fuel cell (SOFC) for high power density operation was developed with a microstructure-controlled cathode using a nano-composite powder of Sr-doped LaMnO3 (LSM) and Y2O3-stabilized ZrO2 (YSZ) synthesized by spray pyrolysis. The individual LSM-YSZ nano-composite particles, formed by crystalline and amorphous nano-size LSM and YSZ particles, showed spherical morphology with uniform particle size. The use of this powder for cathode material led to an extremely fine microstructure, in which all the LSM and YSZ grains (approximately 100-200 nm) were highly dispersed and formed their own network structures. This microstructure was due to the two phase electrode structure control using the powder, namely, nano-order level in each particle and micro-order level between particles. An anode-supported SOFC with the LSM-YSZ cathode using humidified H2 as fuel and ambient air as oxidant exhibited high power densities, such as 1.29 W cm-2 under a voltage of 0.75 V and a maximum power density of 2.65 W cm-2 at 800 °C. Also, the SOFC could be stably operated for 250 h with no degradation, even at a high temperature of 800 °C.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chauhan, Aditya; Patel, Satyanarayan; Vaish, Rahul, E-mail: rahul@iitmandi.ac.in

With the advent of modern power electronics, embedded circuits and non-conventional energy harvesting, the need for high performance capacitors is bound to become indispensible. The current state-of-art employs ferroelectric ceramics and linear dielectrics for solid state capacitance. However, lead-free ferroelectric ceramics propose to offer significant improvement in the field of electrical energy storage owing to their high discharge efficiency and energy storage density. In this regards, the authors have investigated the effects of compressive stress as a means of improving the energy storage density of lead-free ferroelectric ceramics. The energy storage density of 0.91(Bi{sub 0.5}Na{sub 0.5})TiO{sub 3}-0.07BaTiO{sub 3}-0.02(K{sub 0.5}Na{sub 0.5})NbO{submore » 3} ferroelectric bulk ceramic was analyzed as a function of varying levels of compressive stress and operational temperature .It was observed that a peak energy density of 387 mJ.cm{sup -3} was obtained at 100 MPa applied stress (25{sup o}C). While a maximum energy density of 568 mJ.cm{sup -3} was obtained for the same stress at 80{sup o}C. These values are indicative of a significant, 25% and 84%, improvement in the value of stored energy compared to an unloaded material. Additionally, material's discharge efficiency has also been discussed as a function of operational parameters. The observed phenomenon has been explained on the basis of field induced structural transition and competitive domain switching theory.« less

Ion thruster performance model

NASA Technical Reports Server (NTRS)

Brophy, J. R.

1984-01-01

A model of ion thruster performance is developed for high flux density, cusped magnetic field thruster designs. This model is formulated in terms of the average energy required to produce an ion in the discharge chamber plasma and the fraction of these ions that are extracted to form the beam. The direct loss of high energy (primary) electrons from the plasma to the anode is shown to have a major effect on thruster performance. The model provides simple algebraic equations enabling one to calculate the beam ion energy cost, the average discharge chamber plasma ion energy cost, the primary electron density, the primary-to-Maxwellian electron density ratio and the Maxwellian electron temperature. Experiments indicate that the model correctly predicts the variation in plasma ion energy cost for changes in propellant gas (Ar, Kr and Xe), grid transparency to neutral atoms, beam extraction area, discharge voltage, and discharge chamber wall temperature. The model and experiments indicate that thruster performance may be described in terms of only four thruster configuration dependent parameters and two operating parameters. The model also suggests that improved performance should be exhibited by thruster designs which extract a large fraction of the ions produced in the discharge chamber, which have good primary electron and neutral atom containment and which operate at high propellant flow rates.

High Specific Power Motors in LN2 and LH2

NASA Technical Reports Server (NTRS)

Brown, Gerald V.; Jansen, Ralph H.; Trudell, Jeffrey J.

2007-01-01

A switched reluctance motor has been operated in liquid nitrogen (LN2) with a power density as high as that reported for any motor or generator. The high performance stems from the low resistivity of Cu at LN2 temperature and from the geometry of the windings, the combination of which permits steady-state rms current density up to 7000 A/cm2, about 10 times that possible in coils cooled by natural convection at room temperature. The Joule heating in the coils is conducted to the end turns for rejection to the LN2 bath. Minimal heat rejection occurs in the motor slots, preserving that region for conductor. In the end turns, the conductor layers are spaced to form a heat-exchanger-like structure that permits nucleate boiling over a large surface area. Although tests were performed in LN2 for convenience, this motor was designed as a prototype for use with liquid hydrogen (LH2) as the coolant. End-cooled coils would perform even better in LH2 because of further increases in copper electrical and thermal conductivities. Thermal analyses comparing LN2 and LH2 cooling are presented verifying that end-cooled coils in LH2 could be either much longer or could operate at higher current density without thermal runaway than in LN2.

High Specific Power Motors in LN2 and LH2

NASA Technical Reports Server (NTRS)

Brown, Gerald V.; Jansen, Ralph H.; Trudell, Jeffrey J.

2007-01-01

A switched reluctance motor has been operated in liquid nitrogen (LN2) with a power density as high as that reported for any motor or generator. The high performance stems from the low resistivity of Cu at LN2 temperature and from the geometry of the windings, the combination of which permits steady-state rms current density up to 7000 A/sq cm, about 10 times that possible in coils cooled by natural convection at room temperature. The Joule heating in the coils is conducted to the end turns for rejection to the LN2 bath. Minimal heat rejection occurs in the motor slots, preserving that region for conductor. In the end turns, the conductor layers are spaced to form a heat-exchanger-like structure that permits nucleate boiling over a large surface area. Although tests were performed in LN2 for convenience, this motor was designed as a prototype for use with liquid hydrogen (LH2) as the coolant. End-cooled coils would perform even better in LH2 because of further increases in copper electrical and thermal conductivities. Thermal analyses comparing LN2 and LH2 cooling are presented verifying that end-cooled coils in LH2 could be either much longer or could operate at higher current density without thermal runaway than in LN2.

Modeling two-phase flow in three-dimensional complex flow-fields of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Kim, Jinyong; Luo, Gang; Wang, Chao-Yang

2017-10-01

3D fine-mesh flow-fields recently developed by Toyota Mirai improved water management and mass transport in proton exchange membrane (PEM) fuel cell stacks, suggesting their potential value for robust and high-power PEM fuel cell stack performance. In such complex flow-fields, Forchheimer's inertial effect is dominant at high current density. In this work, a two-phase flow model of 3D complex flow-fields of PEMFCs is developed by accounting for Forchheimer's inertial effect, for the first time, to elucidate the underlying mechanism of liquid water behavior and mass transport inside 3D complex flow-fields and their adjacent gas diffusion layers (GDL). It is found that Forchheimer's inertial effect enhances liquid water removal from flow-fields and adds additional flow resistance around baffles, which improves interfacial liquid water and mass transport. As a result, substantial improvements in high current density cell performance and operational stability are expected in PEMFCs with 3D complex flow-fields, compared to PEMFCs with conventional flow-fields. Higher current density operation required to further reduce PEMFC stack cost per kW in the future will necessitate optimizing complex flow-field designs using the present model, in order to efficiently remove a large amount of product water and hence minimize the mass transport voltage loss.

Mode conversion and heating in a UCLA-high schools collaborative experiment

NASA Astrophysics Data System (ADS)

Smith, Miana; Buckley-Bonnano, Samuel; Pribyl, Patrick; Gekelman, Walter; Wise, Joe; Baker, Bob; Marmie, Ken

2016-10-01

A small plasma device is in operation for use by undergraduates and high school students at UCLA. Magnetic field up to 100 G, with density 108 <=ne <=1011cm-3 and temperature Te < 3eV are available in a 50 cm diameter plasma 2 meters long. The plasma is generated by an ICP source at one end operating at about 500 kHz. For this experiment, a small plate located near the edge of the plasma column is used as an electrostatic launcher. High frequency waves ωce < ω < 3ωce are launched radially from the plate in the low-density region, with electric field perpendicular to B and to the density gradient. A Langmuir probe located some distance away axially measures plasma heating along a field line that passes several cm in front of the launcher, localized in radius with δr 1cm Absorption and strong electron heating are observed at the plasma resonant layer. We explore the ``double resonance condition at which ωpe = 2ωce . Here strong interaction with electron Bernstein waves is expected. The Bernstein waves are also launched at low power and their dispersion relation verified. Work done at the BaPSF at UCLA which is supported by the DOE/NSF.

High-rate nano-crystalline Li 4Ti 5O 12 attached on carbon nano-fibers for hybrid supercapacitors

NASA Astrophysics Data System (ADS)

Naoi, Katsuhiko; Ishimoto, Shuichi; Isobe, Yusaku; Aoyagi, Shintaro

A lithium titanate (Li 4Ti 5O 12)-based electrode which can operate at unusually high current density (300 C) was developed as negative electrode for hybrid capacitors. The high-rate Li 4Ti 5O 12 electrode has a unique nano-structure consisting of unusually small nano-crystalline Li 4Ti 5O 12 (ca. 5-20 nm) grafted onto carbon nano-fiber anchors (nc-Li 4Ti 5O 12/CNF). This nano-structured nc-Li 4Ti 5O 12/CNF composite are prepared by simple sol-gel method under ultra-centrifugal force (65,000 N) followed by instantaneous annealing at 900 °C for 3 min. A model hybrid capacitor cell consisting of a negative nc-Li 4Ti 5O 12/CNF composite electrode and a positive activated carbon electrode showed high energy density of 40 Wh L -1 and high power density of 7.5 kW L -1 comparable to conventional EDLCs.

Ab initio Computations of the Electronic, Mechanical, and Thermal Properties of Ultra High Temperature Ceramics (UHTC) ZrB2 and HfB2

NASA Technical Reports Server (NTRS)

Lawson, John W.; Bauschlicher, Charles W.; Daw, Murray

2011-01-01

Refractory materials such as metallic borides, often considered as ultra high temperature ceramics (UHTC), are characterized by high melting point, high hardness, and good chemical inertness. These materials have many applications which require high temperature materials that can operate with no or limited oxidation. Ab initio, first principles methods are the most accurate modeling approaches available and represent a parameter free description of the material based on the quantum mechanical equations. Using these methods, many of the intrinsic properties of these material can be obtained. We performed ab initio calculations based on density functional theory for the UHTC materials ZrB2 and HfB2. Computational results are presented for structural information (lattice constants, bond lengths, etc), electronic structure (bonding motifs, densities of states, band structure, etc), thermal quantities (phonon spectra, phonon densities of states, specific heat), as well as information about point defects such as vacancy and antisite formation energies.

Impact of Te and ne on edge current density profiles in ELM mitigated regimes on ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Dunne, M. G.; Rathgeber, S.; Burckhart, A.; Fischer, R.; Giannone, L.; McCarthy, P. J.; Schneider, P. A.; Wolfrum, E.; the ASDEX Upgrade Team

2015-01-01

ELM resolved edge current density profiles are reconstructed using the CLISTE equilibrium code. As input, highly spatially and temporally resolved edge electron temperature and density profiles are used in addition to data from the extensive set of external poloidal field measurements available at ASDEX Upgrade, flux loop difference measurements, and current measurements in the scrape-off layer. Both the local and flux surface averaged current density profiles are analysed for several ELM mitigation regimes. The focus throughout is on the impact of altered temperature and density profiles on the current density. In particular, many ELM mitigation regimes rely on operation at high density. Two reference plasmas with type-I ELMs are analysed, one with a deuterium gas puff and one without, in order to provide a reference for the behaviour in type-II ELMy regimes and high density ELM mitigation with external magnetic perturbations at ASDEX Upgrade. For type-II ELMs it is found that while a similar pedestal top pressure is sustained at the higher density, the temperature gradient decreases in the pedestal. This results in lower local and flux surface averaged current densities in these phases, which reduces the drive for the peeling mode. No significant differences between the current density measured in the type-I phase and ELM mitigated phase is seen when external perturbations are applied, though the pedestal top density was increased. Finally, ELMs during the nitrogen seeded phase of a high performance discharge are analysed and compared to ELMs in the reference phase. An increased pedestal pressure gradient, which is the source of confinement improvement in impurity seeded discharges, causes a local current density increase. However, the increased Zeff in the pedestal acts to reduce the flux surface averaged current density. This dichotomy, which is not observed in other mitigation regimes, could act to stabilize both the ballooning mode and the peeling mode at the same time.

75 FR 29357 - Notice of Availability of the Draft Programmatic Environmental Assessment for the Deployment and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-25

... technology that is used to aid in inspecting high-density cargo containers for contraband such as illicit... DEPARTMENT OF HOMELAND SECURITY U.S. Customs and Border Protection Notice of Availability of the Draft Programmatic Environmental Assessment for the Deployment and Operation of High Energy X-Ray...

Ammonia excretion and oxygen consumption rates of juvenile pompano on six experimental poultry by-product diets

USDA-ARS?s Scientific Manuscript database

Florida pompano is a high market value marine finfish and recirculating aquaculture systems provide a sustainable culture method for growing these fish at high production densities in inland where agricultural land is more affordable. To reduce the feed load burden on the operating costs of the RAS ...

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

PubMed Central

2017-01-01

We report on high-power terahertz quantum cascade lasers based on low effective electron mass InGaAs/InAlAs semiconductor heterostructures with excellent reproducibility. Growth-related asymmetries in the form of interface roughness and dopant migration play a crucial role in this material system. These bias polarity dependent phenomena are studied using a nominally symmetric active region resulting in a preferential electron transport in the growth direction. A structure based on a three-well optical phonon depletion scheme was optimized for this bias direction. Depending on the sheet doping density, the performance of this structure shows a trade-off between high maximum operating temperature and high output power. While the highest operating temperature of 155 K is observed for a moderate sheet doping density of 2 × 1010 cm–2, the highest peak output power of 151 mW is found for 7.3 × 1010 cm–2. Furthermore, by abutting a hyperhemispherical GaAs lens to a device with the highest doping level a record output power of 587 mW is achieved for double-metal waveguide structures. PMID:28470028

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers.

PubMed

Deutsch, Christoph; Kainz, Martin Alexander; Krall, Michael; Brandstetter, Martin; Bachmann, Dominic; Schönhuber, Sebastian; Detz, Hermann; Zederbauer, Tobias; MacFarland, Donald; Andrews, Aaron Maxwell; Schrenk, Werner; Beck, Mattias; Ohtani, Keita; Faist, Jérôme; Strasser, Gottfried; Unterrainer, Karl

2017-04-19

We report on high-power terahertz quantum cascade lasers based on low effective electron mass InGaAs/InAlAs semiconductor heterostructures with excellent reproducibility. Growth-related asymmetries in the form of interface roughness and dopant migration play a crucial role in this material system. These bias polarity dependent phenomena are studied using a nominally symmetric active region resulting in a preferential electron transport in the growth direction. A structure based on a three-well optical phonon depletion scheme was optimized for this bias direction. Depending on the sheet doping density, the performance of this structure shows a trade-off between high maximum operating temperature and high output power. While the highest operating temperature of 155 K is observed for a moderate sheet doping density of 2 × 10 10 cm -2 , the highest peak output power of 151 mW is found for 7.3 × 10 10 cm -2 . Furthermore, by abutting a hyperhemispherical GaAs lens to a device with the highest doping level a record output power of 587 mW is achieved for double-metal waveguide structures.

Polymer/metal oxide hybrid dielectrics for low voltage field-effect transistors with solution-processed, high-mobility semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Held, Martin; Schießl, Stefan P.; Gannott, Florentina

Transistors for future flexible organic light-emitting diode (OLED) display backplanes should operate at low voltages and be able to sustain high currents over long times without degradation. Hence, high capacitance dielectrics with low surface trap densities are required that are compatible with solution-processable high-mobility semiconductors. Here, we combine poly(methyl methacrylate) (PMMA) and atomic layer deposition hafnium oxide (HfO{sub x}) into a bilayer hybrid dielectric for field-effect transistors with a donor-acceptor polymer (DPPT-TT) or single-walled carbon nanotubes (SWNTs) as the semiconductor and demonstrate substantially improved device performances for both. The ultra-thin PMMA layer ensures a low density of trap states atmore » the semiconductor-dielectric interface while the metal oxide layer provides high capacitance, low gate leakage and superior barrier properties. Transistors with these thin (≤70 nm), high capacitance (100–300 nF/cm{sup 2}) hybrid dielectrics enable low operating voltages (<5 V), balanced charge carrier mobilities and low threshold voltages. Moreover, the hybrid layers substantially improve the bias stress stability of the transistors compared to those with pure PMMA and HfO{sub x} dielectrics.« less

Penetration of Liquid Jets into a High-velocity Air Stream

NASA Technical Reports Server (NTRS)

Chelko, Louis J

1950-01-01

Data are presented showing the penetration characteristics of liquid jets directed approximately perpendicular to a high-velocity air stream for jet-nozzle-throat diameters from 0.0135 to 0.0625 inch, air stream densities from 0.0805 to 0.1365 pound per cubic foot, liquid jet velocities from 168.1 to 229.0 feet per second and a liquid jet density of approximately 62 pounds per cubic foot. The data were analyzed and a correlation was developed that permitted the determination of the penetration length of the liquid jet for any operation condition within the range of variables investigated.

Investigation Into Radiation-Induced Compaction of Zerodur (trademark)

NASA Technical Reports Server (NTRS)

Edwards, D. L.; Herren, K.; Hayden, M.; McDonald, K.; Sims, J. A.; Semmel, C. L.

1996-01-01

Zerodur is a low coefficient of thermal expansion glass-ceramic material. This property makes Zerodur an excellent material for high precision optical substrates. Functioning as a high precision optical substrate, a material must be dimensionally stable in the system operating environment. Published data indicate that Zerodur is dimensionally unstable when exposed to large doses of ionizing radiation. The dimensional instability is discussed as an increase in Zerodur density. This increase in density is described as a compaction. Experimental data showing proton-induced compaction of Zerodur is presented. The dependence of compaction on proton dose was determined to be a power law relationship.

Investigation Into Radiation-Induced Compaction of Zerodur (trademark)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edwards, D.L.; Herren, K.; Hayden, M.

1996-03-01

Zerodur is a low coefficient of thermal expansion glass-ceramic material. This property makes Zerodur an excellent material for high precision optical substrates. Functioning as a high precision optical substrate, a material must be dimensionally stable in the system operating environment. Published data indicate that Zerodur is dimensionally unstable when exposed to large doses of ionizing radiation. The dimensional instability is discussed as an increase in Zerodur density. This increase in density is described as a compaction. Experimental data showing proton-induced compaction of Zerodur is presented. The dependence of compaction on proton dose was determined to be a power law relationship.

Neural network evaluation of reflectometry density profiles for control purposes

NASA Astrophysics Data System (ADS)

Santos, J.; Nunes, F.; Manso, M.; Nunes, I.

1999-01-01

Broadband reflectometry is a diagnostic that is able to measure the density profile with high spatial and temporal resolutions, therefore it can be used to improve the performance of advanced tokamak operation modes and to supplement or correct the magnetics for plasma position control. To perform these tasks real-time processing is needed. Here we present a method that uses a neural network to make a fast evaluation of radial positions for selected density layers. Typical ASDEX Upgrade density profiles were used to generate the simulated network training and test sets. It is shown that the method has the potential to meet the tight timing requirements of control applications with the required accuracy. The network is also able to provide an accurate estimation of the position of density layers below the first density layer which is probed by an O-mode reflectometer, provided that it is trained with a realistic density profile model.

High cell density fed-batch fermentations for lipase production: feeding strategies and oxygen transfer.

PubMed

Salehmin, M N I; Annuar, M S M; Chisti, Y

2013-11-01

This review is focused on the production of microbial lipases by high cell density fermentation. Lipases are among the most widely used of the enzyme catalysts. Although lipases are produced by animals and plants, industrial lipases are sourced almost exclusively from microorganisms. Many of the commercial lipases are produced using recombinant species. Microbial lipases are mostly produced by batch and fed-batch fermentation. Lipases are generally secreted by the cell into the extracellular environment. Thus, a crude preparation of lipases can be obtained by removing the microbial cells from the fermentation broth. This crude cell-free broth may be further concentrated and used as is, or lipases may be purified from it to various levels. For many large volume applications, lipases must be produced at extremely low cost. High cell density fermentation is a promising method for low-cost production: it allows a high concentration of the biomass and the enzyme to be attained rapidly and this eases the downstream recovery of the enzyme. High density fermentation enhances enzyme productivity compared with the traditional submerged culture batch fermentation. In production of enzymes, a high cell density is generally achieved through fed-batch operation, not through perfusion culture which is cumbersome. The feeding strategies used in fed-batch fermentations for producing lipases and the implications of these strategies are discussed. Most lipase-producing microbial fermentations require oxygen. Oxygen transfer in such fermentations is discussed.

Enabling Airspace Integration for High Density Urban Air Mobility

NASA Technical Reports Server (NTRS)

Mueller, Eric Richard

2017-01-01

Aviation technologies and concepts have reached a level of maturity that may soon enable an era of on-demand mobility (ODM) fueled by quiet, efficient, and largely automated air taxis. However, successfully bringing such a system to fruition will require introducing orders of magnitude more aircraft to a given airspace volume than can be accommodated by the traditional air traffic control system, among other important technical challenges. The airspace integration problem is further compounded by requirements to set aside appropriate ground infrastructure for take-off and landing areas and ensuring these new aircraft types and their operations do not burden traditional airspace users and air traffic control. These challenge for ODM may be significantly reduced by extending the concepts and technologies developed to manage small unmanned aircraft systems (UAS) at low altitude the UAS traffic management (UTM) system to higher altitudes and aircraft with humans onboard in controlled airspace, or by equipping ODM aircraft with advanced sensors, algorithms, and interfaces. The precedent of operational freedom inherent in visual flight rules and the technologies developed for large UAS and commercial aircraft automation will contribute to the evolution of an ODM system enabled by UTM. This paper describes the set of air traffic services, normally provided by the traditional air traffic system, that an ODM system would implement to achieve the high densities needed for ODMs economic viability. Finally, the paper proposes a framework for integrating, evaluating, and deploying low-, medium-, and high-density ODM concepts that build on each other to ensure operational and economic feasibility at every step.

An ultra-compact processor module based on the R3000

NASA Astrophysics Data System (ADS)

Mullenhoff, D. J.; Kaschmitter, J. L.; Lyke, J. C.; Forman, G. A.

1992-08-01

Viable high density packaging is of critical importance for future military systems, particularly space borne systems which require minimum weight and size and high mechanical integrity. A leading, emerging technology for high density packaging is multi-chip modules (MCM). During the 1980's, a number of different MCM technologies have emerged. In support of Strategic Defense Initiative Organization (SDIO) programs, Lawrence Livermore National Laboratory (LLNL) has developed, utilized, and evaluated several different MCM technologies. Prior LLNL efforts include modules developed in 1986, using hybrid wafer scale packaging, which are still operational in an Air Force satellite mission. More recent efforts have included very high density cache memory modules, developed using laser pantography. As part of the demonstration effort, LLNL and Phillips Laboratory began collaborating in 1990 in the Phase 3 Multi-Chip Module (MCM) technology demonstration project. The goal of this program was to demonstrate the feasibility of General Electric's (GE) High Density Interconnect (HDI) MCM technology. The design chosen for this demonstration was the processor core for a MIPS R3000 based reduced instruction set computer (RISC), which has been described previously. It consists of the R3000 microprocessor, R3010 floating point coprocessor and 128 Kbytes of cache memory.

Effect of culture density on biomass production and light utilization efficiency of Synechocystis sp. PCC 6803.

PubMed

Straka, Levi; Rittmann, Bruce E

2018-02-01

The viability of large-scale microalgae cultivation depends on providing optimal growth conditions, for which a key operational parameter is culture density. Using Synechocystis sp. PCC 6803, we conducted a series of fixed-density, steady-state experiments and one batch-growth experiment to investigate the role of culture density on biomass production and light utilization efficiency. In all cases, the fixed-density, steady-state experiments and batch-growth experiment showed good agreement. The highest biomass production rates (260 mg L -1  d -1 ) and efficiency for converting light energy to biomass (0.80 μg (μmol photons) -1 ) occurred together at a culture density near 760 mg L -1 , which approximately corresponded to the lowest culture density where almost all incident light was absorbed. The ratio of OD 680 /OD 735 increased with culture density up to the point of maximum productivity, where it plateaued (at a value of 2.4) for higher culture densities. This change in OD 680 /OD 735 indicates a photoacclimation effect that depended on culture density. Very high culture densities led to a sharp decline in efficiency of biomass production per photons absorbed, likely due to a combination of increased decay relative to growth, metabolic changes due to cell-cell interactions, and photodamage due to mixing between regions with high light intensity and zero light intensity. © 2017 Wiley Periodicals, Inc.

Cryogenic properties of dispersion strengthened copper for high magnetic fields

NASA Astrophysics Data System (ADS)

Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

2014-01-01

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

Classified one-step high-radix signed-digit arithmetic units

NASA Astrophysics Data System (ADS)

Cherri, Abdallah K.

1998-08-01

High-radix number systems enable higher information storage density, less complexity, fewer system components, and fewer cascaded gates and operations. A simple one-step fully parallel high-radix signed-digit arithmetic is proposed for parallel optical computing based on new joint spatial encodings. This reduces hardware requirements and improves throughput by reducing the space-bandwidth produce needed. The high-radix signed-digit arithmetic operations are based on classifying the neighboring input digit pairs into various groups to reduce the computation rules. A new joint spatial encoding technique is developed to present both the operands and the computation rules. This technique increases the spatial bandwidth product of the spatial light modulators of the system. An optical implementation of the proposed high-radix signed-digit arithmetic operations is also presented. It is shown that our one-step trinary signed-digit and quaternary signed-digit arithmetic units are much simpler and better than all previously reported high-radix signed-digit techniques.

Low-Temperature Supercapacitors

NASA Technical Reports Server (NTRS)

Brandon, Erik J.; West, William C.; Smart, Marshall C.

2008-01-01

An effort to extend the low-temperature operational limit of supercapacitors is currently underway. At present, commercially available non-aqueous supercapacitors are rated for a minimum operating temperature of -40 C. A capability to operate at lower temperatures would be desirable for delivering power to systems that must operate in outer space or in the Polar Regions on Earth. Supercapacitors (also known as double-layer or electrochemical capacitors) offer a high power density (>1,000 W/kg) and moderate energy density (about 5 to 10 Wh/kg) technology for storing energy and delivering power. This combination of properties enables delivery of large currents for pulsed applications, or alternatively, smaller currents for low duty cycle applications. The mechanism of storage of electric charge in a supercapacitor -- at the electrical double-layer formed at a solid-electrode/liquid-electrolyte interface -- differs from that of a primary or secondary electrochemical cell (i.e., a battery) in such a manner as to impart a long cycle life (typically >10(exp 6) charge/discharge cycles).

Electrochemical Supercapacitor Electrodes from Sponge-like Graphene Nanoarchitectures with Ultrahigh Power Density.

PubMed

Xu, Zhanwei; Li, Zhi; Holt, Chris M B; Tan, Xuehai; Wang, Huanlei; Amirkhiz, Babak Shalchi; Stephenson, Tyler; Mitlin, David

2012-10-18

We employed a microwave synthesis process of cobalt phthalocyanine molecules templated by acid-functionalized multiwalled carbon nanotubes to create three-dimensional sponge-like graphene nanoarchitectures suited for ionic liquid-based electrochemical capacitor electrodes that operate at very high scan rates. The sequential "bottom-up" molecular synthesis and subsequent carbonization process took less than 20 min to complete. The 3D nanoarchitectures are able to deliver an energy density of 7.1 W·h kg(-1) even at an extra high power density of 48 000 W kg(-1). In addition, the ionic liquid supercapacitor based on this material works very well at room temperature due to its fully opened structures, which is ideal for the high-power energy application requiring more tolerance to temperature variation. Moreover, the structures are stable in both ionic liquids and 1 M H2SO4, retaining 90 and 98% capacitance after 10 000 cycles, respectively.

Regenerative fuel cell study for satellites in GEO orbit

NASA Technical Reports Server (NTRS)

Vandine, Leslie; Gonzalez-Sanabria, Olga; Levy, Alexander

1987-01-01

The results of a 12 month study to identify high performance regenerative hydrogen-oxygen fuel cell concepts for geosynchronous satellite application are summarized. Emphasis was placed on concepts with the potential for high energy density and passive means for water and heat management to maximize system reliability. Both polymer membrane and alkaline electrolyte fuel cells were considered, with emphasis on the alkaline cell because of its high performance, advanced state of development, and proven ability to operate in a launch and space environment. Three alkaline system concepts were studied. Results indicate that using near term technology energy densities between 46 and 52 watt-hour/lb can be achieved at efficiencies of 55 percent. Using advanced light weight cell construction which was achieved in experimental cells, composite tankage material for the reactant gases and the reversible stack concept, system energy densities of 115 watt-hours/lb can be projected.

Long-range corrected density functional theory with accelerated Hartree-Fock exchange integration using a two-Gaussian operator [LC-ωPBE(2Gau)].

PubMed

Song, Jong-Won; Hirao, Kimihiko

2015-10-14

Since the advent of hybrid functional in 1993, it has become a main quantum chemical tool for the calculation of energies and properties of molecular systems. Following the introduction of long-range corrected hybrid scheme for density functional theory a decade later, the applicability of the hybrid functional has been further amplified due to the resulting increased performance on orbital energy, excitation energy, non-linear optical property, barrier height, and so on. Nevertheless, the high cost associated with the evaluation of Hartree-Fock (HF) exchange integrals remains a bottleneck for the broader and more active applications of hybrid functionals to large molecular and periodic systems. Here, we propose a very simple yet efficient method for the computation of long-range corrected hybrid scheme. It uses a modified two-Gaussian attenuating operator instead of the error function for the long-range HF exchange integral. As a result, the two-Gaussian HF operator, which mimics the shape of the error function operator, reduces computational time dramatically (e.g., about 14 times acceleration in C diamond calculation using periodic boundary condition) and enables lower scaling with system size, while maintaining the improved features of the long-range corrected density functional theory.

OPERATING THE WAND AND HERCULES PROTOTYPE SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

K. GRUETZMACHER; ET AL

2001-01-01

Two prototype systems for low-density Green is Clean (GIC) waste at Los Alamos National Laboratory (LANL) have been in operation for three years at the Solid Waste Operation's (SWOs) non-destructive assay (NDA) building. The Waste Assay for Nonradioactive Disposal (WAND) and the High Efficiency Radiation Counters for Ultimate Low Emission Sensitivity (HERCULES) are used to verify the waste generator's acceptable knowledge (AK) that low-density waste is nonradioactive. GIC waste includes all non-regulated waste generated in radiological controlled areas (RCAs) that has been actively segregated as ''clean'' (i.e., nonradioactive) through the use of waste generator AK. GIC waste that is verifiedmore » clean can be disposed of at the Los Alamos County Landfill. It is estimated that 50-90% of the low-density room trash from RCAs at LANL might be free of contamination. To date, with pilot programs at five facilities at LANL, 3000 cubic feet of GIC waste has been verified clean by these two prototype systems. Both the WAND and HERCULES systems are highly sensitive measurement systems optimized to detect very small quantities of common LANL radionuclides. Both of the systems use a set of phoswich scintillation detectors in close proximity to the waste, which have the capability of detecting plutonium-239 concentrations below 3 pCi per gram of low density waste. Both systems detect low-energy x-rays and a broad range of gamma rays (10-2000 keV), while the WAND system also detects high energy beta particles (>100 keV). The WAND system consists of a bank of six shielded detectors which screen low density shredded waste or stacked sheets of paper moving under the detectors in a twelve inch swath on a conveyor belt. The WAND system was developed and tested at the Los Alamos Plutonium Facility in conjunction with instrument system designers from the Los Alamos Safeguards Science and Technology group. The HERCULES system consists of a bank of three shielded detectors which screen low-density waste in two cubic foot cardboard boxes or in bags sitting on a turntable. Waste that does not pass the verification process can be examined within the facility to determine the type and quantity of the contamination and its origin within a waste container. The paper discusses lessons learned that have helped generators improve their AK segregation.« less

Efficient evaluation of nonlocal operators in density functional theory

NASA Astrophysics Data System (ADS)

Chen, Ying-Chih; Chen, Jing-Zhe; Michaud-Rioux, Vincent; Shi, Qing; Guo, Hong

2018-02-01

We present a method which combines plane waves (PW) and numerical atomic orbitals (NAO) to efficiently evaluate nonlocal operators in density functional theory with periodic boundary conditions. Nonlocal operators are first expanded using PW and then transformed to NAO so that the problem of distance-truncation is avoided. The general formalism is implemented using the hybrid functional HSE06 where the nonlocal operator is the exact exchange. Comparison of electronic structures of a wide range of semiconductors to a pure PW scheme validates the accuracy of our method. Due to the locality of NAO, thus sparsity of matrix representations of the operators, the computational complexity of the method is asymptotically quadratic in the number of electrons. Finally, we apply the technique to investigate the electronic structure of the interface between a single-layer black phosphorous and the high-κ dielectric material c -HfO2 . We predict that the band offset between the two materials is 1.29 eV and 2.18 eV for valence and conduction band edges, respectively, and such offsets are suitable for 2D field-effect transistor applications.

Burn Control in Fusion Reactors via Isotopic Fuel Tailoring

NASA Astrophysics Data System (ADS)

Boyer, Mark D.; Schuster, Eugenio

2011-10-01

The control of plasma density and temperature are among the most fundamental problems in fusion reactors and will be critical to the success of burning plasma experiments like ITER. Economic and technological constraints may require future commercial reactors to operate with low temperature, high-density plasma, for which the burn condition may be unstable. An active control system will be essential for stabilizing such operating points. In this work, a volume-averaged transport model for the energy and the densities of deuterium and tritium fuel ions, as well as the alpha particles, is used to synthesize a nonlinear feedback controller for stabilizing the burn condition. The controller makes use of ITER's planned isotopic fueling capability and controls the densities of these ions separately. The ability to modulate the DT fuel mix is exploited in order to reduce the fusion power during thermal excursions without the need for impurity injection. By moving the isotopic mix in the plasma away from the optimal 50:50 mix, the reaction rate is slowed and the alpha-particle heating is reduced to desired levels. Supported by the NSF CAREER award program (ECCS-0645086).

Highly-reliable operation of 638-nm broad stripe laser diode with high wall-plug efficiency for display applications

NASA Astrophysics Data System (ADS)

Yagi, Tetsuya; Shimada, Naoyuki; Nishida, Takehiro; Mitsuyama, Hiroshi; Miyashita, Motoharu

2013-03-01

Laser based displays, as pico to cinema laser projectors have gathered much attention because of wide gamut, low power consumption, and so on. Laser light sources for the displays are operated mainly in CW, and heat management is one of the big issues. Therefore, highly efficient operation is necessitated. Also the light sources for the displays are requested to be highly reliable. 638 nm broad stripe laser diode (LD) was newly developed for high efficiency and highly reliable operation. An AlGaInP/GaAs red LD suffers from low wall plug efficiency (WPE) due to electron overflow from an active layer to a p-cladding layer. Large optical confinement factor (Γ) design with AlInP cladding layers is adopted to improve the WPE. The design has a disadvantage for reliable operation because the large Γ causes high optical density and brings a catastrophic optical degradation (COD) at a front facet. To overcome the disadvantage, a window-mirror structure is also adopted in the LD. The LD shows WPE of 35% at 25°C, highest record in the world, and highly stable operation at 35°C, 550 mW up to 8,000 hours without any catastrophic optical degradation.

Investigation of Tokamak Solid Divertor Target Options.

DTIC Science & Technology

1981-05-26

but materials are not known which could operate at the high resulting wall temperatures . Mist- steam flows would also demand a relatively high ...flux P = coolant density = bulk coolant viscosity w = coolant viscosity at average wall temperature = units conversion At high heat loads and moderate...therefore, the inner wall temperature will be over 300 OF, posing a high temp- erature materials challenge. E. Swirl and Mixed Flow Schemes Extensive work

To Demonstrate an Integrated Solution for Plasma-Material Interfaces Compatible with an Optimized Core Plasma

NASA Astrophysics Data System (ADS)

Goldston, Robert; Brooks, Jeffrey; Hubbard, Amanda; Leonard, Anthony; Lipschultz, Bruce; Maingi, Rajesh; Ulrickson, Michael; Whyte, Dennis

2009-11-01

The plasma facing components in a Demo reactor will face much more extreme boundary plasma conditions and operating requirements than any present or planned experiment. These include 1) Power density a factor of four or more greater than in ITER, 2) Continuous operation resulting in annual energy and particle throughput 100-200 times larger than ITER, 3) Elevated surface operating temperature for efficient electricity production, 4) Tritium fuel cycle control for safety and breeding requirements, and 5) Steady state plasma confinement and control. Consistent with ReNeW Thrust 12, design options are being explored for a new moderate-scale facility to assess core-edge interaction issues and solutions. Key desired features include high power density, sufficient pulse length and duty cycle, elevated wall temperature, steady-state control of an optimized core plasma, and flexibility in changing boundary components as well as access for comprehensive measurements.

Hierarchical Pore-Patterned Carbon Electrodes for High-Volumetric Energy Density Micro-Supercapacitors.

PubMed

Kim, Cheolho; Moon, Jun Hyuk

2018-06-13

Micro-supercapacitors (MSCs) are attractive for applications in next-generation mobile and wearable devices and have the potential to complement or even replace lithium batteries. However, many previous MSCs have often exhibited a low volumetric energy density with high-loading electrodes because of the nonuniform pore structure of the electrodes. To address this issue, we introduced a uniform-pore carbon electrode fabricated by 3D interference lithography. Furthermore, a hierarchical pore-patterned carbon (hPC) electrode was formed by introducing a micropore by chemical etching into the macropore carbon skeleton. The hPC electrodes were applied to solid-state MSCs. We achieved a constant volumetric capacitance and a corresponding volumetric energy density for electrodes of various thicknesses. The hPC MSC reached a volumetric energy density of approximately 1.43 mW h/cm 3 . The power density of the hPC MSC was 1.69 W/cm 3 . We could control the capacitance and voltage additionally by connecting the unit MSC cells in series or parallel, and we confirmed the operation of a light-emitting diode. We believe that our pore-patterned electrodes will provide a new platform for compact but high-performance energy storage devices.

Fuel Cells for Space Science Applications

NASA Technical Reports Server (NTRS)

Burke, Kenneth A.

2003-01-01

Fuel cell technology has been receiving more attention recently as a possible alternative to the internal combustion engine for our automobile. Improvements in fuel cell designs as well as improvements in lightweight high-pressure gas storage tank technology make fuel cell technology worth a look to see if fuel cells can play a more expanded role in space missions. This study looks at the specific weight density and specific volume density of potential fuel cell systems as an alternative to primary and secondary batteries that have traditionally been used for space missions. This preliminary study indicates that fuel cell systems have the potential for energy densities of greater than 500 W-hr/kg, greater than 500W/kg and greater than 400 W-hr/liter, greater than 200 W/liter. This level of performance makes fuel cells attractive as high-power density, high-energy density sources for space science probes, planetary rovers and other payloads. The power requirements for these space missions are, in general, much lower than the power levels where fuel cells have been used in the past. Adaptation of fuel cells for space science missions will require down-sizing the fuel cell stack and making the fuel cell operate without significant amounts of ancillary equipment.

Sulfur poisoning of Ni/Gadolinium-doped ceria anodes: A long-term study outlining stable solid oxide fuel cell operation

NASA Astrophysics Data System (ADS)

Riegraf, Matthias; Zekri, Atef; Knipper, Martin; Costa, Rémi; Schiller, Günter; Friedrich, K. Andreas

2018-03-01

This work presents an analysis of the long-term behavior of nickel/gadolinium-doped ceria (CGO) anode-based solid oxide fuel cells (SOFC) under sulfur poisoning conditions. A parameter study of sulfur-induced irreversible long-term degradation of commercial, high-performance single cells was carried out at 900 °C for different H2/N2/H2S fuel gas atmospheres, current densities and Ni/CGO anodes. The poisoning periods of the cells varied from 200 to 1500 h. The possibility of stable long-term Ni/CGO anode operation under sulfur exposure is established and the critical operating regime is outlined. Depending on the operating conditions, two degradation phenomena can be observed. Small degradation of the ohmic resistance was witnessed for sulfur exposure times of approximately 1000 h. Moreover, degradation of the anode charge transfer resistance was observed to be triggered by the combination of a small anodic potential step and high sulfur coverage on Ni. The microstructural evolution of altered Ni/CGO anodes was examined post-mortem by means of SEM and FIB/SEM, and is correlated to the anode performance degradation under critical operating conditions, establishing Ni depletion, porosity increase and a tripe phase boundary density decrease in the anode functional layer. It is shown that short-term sulfur poisoning behavior can be used to assess long-term stability.

A torque-measuring micromotor provides operator independent measurements marking four different density areas in maxillae.

PubMed

Di Stefano, Danilo Alessio; Arosio, Paolo; Piattelli, Adriano; Perrotti, Vittoria; Iezzi, Giovanna

2015-02-01

Bone density at implant placement site is a key factor to obtain the primary stability of the fixture, which, in turn, is a prognostic factor for osseointegration and long-term success of an implant supported rehabilitation. Recently, an implant motor with a bone density measurement probe has been introduced. The aim of the present study was to test the objectiveness of the bone densities registered by the implant motor regardless of the operator performing them. A total of 3704 bone density measurements, performed by means of the implant motor, were registered by 39 operators at different implant sites during routine activity. Bone density measurements were grouped according to their distribution across the jaws. Specifically, four different areas were distinguished: a pre-antral (between teeth from first right maxillary premolar to first left maxillary premolar) and a sub-antral (more distally) zone in the maxilla, and an interforaminal (between and including teeth from first left mandibular premolar to first right mandibular premolar) and a retroforaminal (more distally) zone in the lower one. A statistical comparison was performed to check the inter-operators variability of the collected data. The device produced consistent and operator-independent bone density values at each tooth position, showing a reliable bone-density measurement. The implant motor demonstrated to be a helpful tool to properly plan implant placement and loading irrespective of the operator using it.

Microcombustor-thermoelectric power generator for 10-50 watt applications

NASA Astrophysics Data System (ADS)

Marshall, Daniel S.; Cho, Steve T.

2010-04-01

Fuel-based portable power systems, including combustion and fuel cell systems, take advantage of the 80x higher energy density of fuel over lithium battery technologies and offer the potential for much higher energy density power sources - especially for long-duration applications, such as unattended sensors. Miniaturization of fuel-based systems poses significant challenges, including processing of fuel in small channels, catalyst poisoning, and coke and soot formation. Recent advances in micro-miniature combustors in the 200Watt thermal range have enabled the development of small power sources that use the chemical energy of heavy fuel to drive thermal-to-electric converters for portable applications. CUBE Technology has developed compact Micro-Furnace combustors that efficiently deliver high-quality heat to optimized thermal-to-electric power converters, such as advanced thermoelectric power modules and Stirling motors, for portable power generation at the 10-50Watt scale. Key innovations include a compact gas-gas recuperator, innovative heavy fuel processing, coke- & soot-free operation, and combustor optimization for low balance-of-plant power use while operating at full throttle. This combustor enables the development of robust, high energy density, miniature power sources for portable applications.

Ultrahigh-current-density metal-ion implantation and diamondlike-hydrocarbon films for tribological applications

NASA Astrophysics Data System (ADS)

Wilbur, P. J.

1993-09-01

The metal-ion-implantation system used to implant metals into substrates are described. The metal vapor required for operation is supplied by drawing sufficient electron current from the plasma discharge to an anode-potential crucible so a solid, pure metal placed in the crucible will be heated to the point of vaporization. The ion-producing, plasma discharge is initiated within a graphite-ion-source body, which operates at high temperature, by using an argon flow that is turned off once the metal vapor is present. Extraction of ion beams several cm in diameter at current densities ranging to several hundred micro-A/sq cm on a target 50 cm downstream of the ion source were demonstrated using Mg, Ag, Cr, Cu, Si, Ti, V, B, and Zr. These metals were implanted into over 100 substrates (discs, pins, flats, wires). A model describing thermal stresses induced in materials (e.g. ceramic plates) during high-current-density implantation is presented. Tribological and microstructural characteristics of iron and 304-stainless-steel samples implanted with Ti or B are examined. Diamondlike-hydrocarbon coatings were applied to steel surfaces and found to exhibit good tribological performance.

All-solid-state asymmetric supercapacitors based on Fe-doped mesoporous Co3O4 and three-dimensional reduced graphene oxide electrodes with high energy and power densities.

PubMed

Zhang, Cheng; Wei, Jun; Chen, Leiyi; Tang, Shaolong; Deng, Mingsen; Du, Youwei

2017-10-19

An asymmetric supercapacitor offers opportunities to effectively utilize the full potential of the different potential windows of the two electrodes for a higher operating voltage, resulting in an enhanced specific capacitance and significantly improved energy without sacrificing the power delivery and cycle life. To achieve high energy and power densities, we have synthesized an all-solid-state asymmetric supercapacitor with a wider voltage range using Fe-doped Co 3 O 4 and three-dimensional reduced graphene oxide (3DrGO) as the positive and negative electrodes, respectively. In contrast to undoped Co 3 O 4 , the increased density of states and modified charge spatial separation endow the Fe-doped Co 3 O 4 electrode with greatly improved electrochemical capacitive performance, including high specific capacitance (1997 F g -1 and 1757 F g -1 at current densities of 1 and 20 A g -1 , respectively), excellent rate capability, and superior cycling stability. Remarkably, the optimized all-solid-state asymmetric supercapacitor can be cycled reversibly in a wide range of 0-1.8 V, thus delivering a high energy density (270.3 W h kg -1 ), high power density (9.0 kW kg -1 at 224.2 W h kg -1 ), and excellent cycling stability (91.8% capacitance retention after 10 000 charge-discharge cycles at a constant current density of 10 A g -1 ). The superior capacitive performance suggests that such an all-solid-state asymmetric supercapacitor shows great potential for developing energy storage systems with high levels of energy and power delivery.

Fission Systems for Mars Exploration

NASA Technical Reports Server (NTRS)

Houts, Michael G.; Kim, T.; Dorney, D. J.; Swint, Marion Shayne

2012-01-01

Fission systems are used extensively on earth, and 34 such systems have flown in space. The energy density of fission is over 10 million times that of chemical reactions, giving fission the potential to eliminate energy density constraints for many space missions. Potential safety and operational concerns with fission systems are well understood, and strategies exist for affordably developing such systems. By enabling a power-rich environment and highly efficient propulsion, fission systems could enable affordable, sustainable exploration of Mars.

Investigation of a Light Gas Helicon Plasma Source for the VASIMR Space Propulsion System

NASA Technical Reports Server (NTRS)

Squire, J. P.; Chang-Diaz, F. R.; Jacobson, V. T.; Glover, T. W.; Baity, F. W.; Carter, M. D.; Goulding, R. H.; Bengtson, R. D.; Bering, E. A., III

2003-01-01

An efficient plasma source producing a high-density (approx.10(exp 19/cu m) light gas (e.g. H, D, or He) flowing plasma with a high degree of ionization is a critical component of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept. We are developing an antenna to apply ICRF power near the fundamental ion cyclotron resonance to further accelerate the plasma ions to velocities appropriate for space propulsion applications. The high degree of ionization and a low vacuum background pressure are important to eliminate the problem of radial losses due to charge exchange. We have performed parametric (e.g. gas flow, power (0.5 - 3 kW), magnetic field , frequency (25 and 50 MHz)) studies of a helicon operating with gas (H2 D2, He, N2 and Ar) injected at one end with a high magnetic mirror downstream of the antenna. We have explored operation with a cusp and a mirror field upstream. Plasma flows into a low background vacuum (<10(exp -4) torr) at velocities higher than the ion sound speed. High densities (approx. 10(exp 19/cu m) have been achieved at the location where ICRF will be applied, just downstream of the magnetic mirror.

A fast algorithm for identifying friends-of-friends halos

NASA Astrophysics Data System (ADS)

Feng, Y.; Modi, C.

2017-07-01

We describe a simple and fast algorithm for identifying friends-of-friends features and prove its correctness. The algorithm avoids unnecessary expensive neighbor queries, uses minimal memory overhead, and rejects slowdown in high over-density regions. We define our algorithm formally based on pair enumeration, a problem that has been heavily studied in fast 2-point correlation codes and our reference implementation employs a dual KD-tree correlation function code. We construct features in a hierarchical tree structure, and use a splay operation to reduce the average cost of identifying the root of a feature from O [ log L ] to O [ 1 ] (L is the size of a feature) without additional memory costs. This reduces the overall time complexity of merging trees from O [ L log L ] to O [ L ] , reducing the number of operations per splay by orders of magnitude. We next introduce a pruning operation that skips merge operations between two fully self-connected KD-tree nodes. This improves the robustness of the algorithm, reducing the number of merge operations in high density peaks from O [δ2 ] to O [ δ ] . We show that for cosmological data set the algorithm eliminates more than half of merge operations for typically used linking lengths b ∼ 0 . 2 (relative to mean separation). Furthermore, our algorithm is extremely simple and easy to implement on top of an existing pair enumeration code, reusing the optimization effort that has been invested in fast correlation function codes.

Density Dependence and Growth Rate: Evolutionary Effects on Resistance Development to Bt (Bacillus thuringiensis).

PubMed

Martinez, Jeannette C; Caprio, Michael A; Friedenberg, Nicholas A

2018-02-09

It has long been recognized that pest population dynamics can affect the durability of a pesticide, but dose remains the primary component of insect resistance management (IRM). For transgenic pesticidal traits such as Bt (Bacillus thuringiensis Berliner (Bacillales: Bacillaceae)), dose (measured as the mortality of susceptibles caused by a toxin) is a relatively fixed characteristic and often falls below the standard definition of high dose. Hence, it is important to understand how pest population dynamics modify durability and what targets they present for IRM. We used a deterministic model of a generic arthropod pest to examine how timing and strength of density dependence interacted with population growth rate and Bt mortality to affect time to resistance. As in previous studies, durability typically reached a minimum at intermediate doses. However, high population growth rates could eliminate benefits of high dose. The timing of density dependence had a more subtle effect. If density dependence operated simultaneously with Bt mortality, durability was insensitive to its strengths. However, if density dependence was driven by postselection densities, decreasing its strength could increase durability. The strength of density dependence could affect durability of both single traits and pyramids, but its influence depended on the timing of density dependence and size of the refuge. Our findings suggest the utility of a broader definition of high dose, one that incorporates population-dynamic context. That maximum growth rates and timing and strength of interactions causing density dependent mortality can all affect durability, also highlights the need for ecologically integrated approaches to IRM research. © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Effects of watershed densities of animal feeding operations on nutrient concentrations and estrogenic activity in agricultural streams

USGS Publications Warehouse

Ciparis, S.; Iwanowicz, L.R.; Voshell, J.R.

2012-01-01

Application of manures from animal feeding operations (AFOs) as fertilizer on agricultural land can introduce nutrients and hormones (e.g. estrogens) to streams. A landscape-scale study was conducted in the Shenandoah River watershed (Virginia, USA) in order to assess the relationship between densities of AFOs in watersheds of agricultural streams and in-stream nutrient concentrations and estrogenic activity. The effect of wastewater treatment plants (WWTPs) on nutrients and estrogenic activity was also evaluated. During periods of high and low flow, dissolved inorganic nitrogen (DIN) and orthophosphate (PO 4-P) concentrations were analyzed and estrogens/estrogenic compounds were extracted and quantified as17??-estradiol equivalents (E2Eq) using a bioluminescent yeast estrogen screen. Estrogenic activity was measurable in the majority of collected samples, and 20% had E2Eq concentrations >1ng/L. Relatively high concentrations of DIN (>1000??g/L) were also frequently detected. During all sampling periods, there were strong relationships between watershed densities of AFOs and in-stream concentrations of DIN (R 2=0.56-0.81) and E2Eq (R 2=0.39-0.75). Relationships between watershed densities of AFOs and PO 4-P were weaker, but were also significant (R 2=0.27-0.57). When combined with the effect of watershed AFO density, streams receiving WWTP effluent had higher concentrations of PO 4-P than streams without WWTP discharges, and PO 4-P was the only analyte with a consistent relationship to WWTPs. The results of this study suggest that as the watershed density of AFOs increases, there is a proportional increase in the potential for nonpoint source pollution of agricultural streams and their receiving waters by nutrients, particularly DIN, and compounds that can cause endocrine disruption in aquatic organisms. ?? 2011 Elsevier B.V.

Effects of watershed densities of animal feeding operations on nutrient concentrations and estrogenic activity in agricultural streams

USGS Publications Warehouse

Ciparis, Serena; Iwanowicz, Luke R.; Voshell, J. Reese

2012-01-01

Application of manures from animal feeding operations (AFOs) as fertilizer on agricultural land can introduce nutrients and hormones (e.g. estrogens) to streams. A landscape-scale study was conducted in the Shenandoah River watershed (Virginia, USA) in order to assess the relationship between densities of AFOs in watersheds of agricultural streams and in-stream nutrient concentrations and estrogenic activity. The effect of wastewater treatment plants (WWTPs) on nutrients and estrogenic activity was also evaluated. During periods of high and low flow, dissolved inorganic nitrogen (DIN) and orthophosphate (PO4-P) concentrations were analyzed and estrogens/estrogenic compounds were extracted and quantified as17β-estradiol equivalents (E2Eq) using a bioluminescent yeast estrogen screen. Estrogenic activity was measurable in the majority of collected samples, and 20% had E2Eq concentrations > 1 ng/L. Relatively high concentrations of DIN (> 1000 μg/L) were also frequently detected. During all sampling periods, there were strong relationships between watershed densities of AFOs and in-stream concentrations of DIN (R2 = 0.56–0.81) and E2Eq (R2 = 0.39–0.75). Relationships between watershed densities of AFOs and PO4-P were weaker, but were also significant (R2 = 0.27–0.57). When combined with the effect of watershed AFO density, streams receiving WWTP effluent had higher concentrations of PO4-P than streams without WWTP discharges, and PO4-P was the only analyte with a consistent relationship to WWTPs. The results of this study suggest that as the watershed density of AFOs increases, there is a proportional increase in the potential for nonpoint source pollution of agricultural streams and their receiving waters by nutrients, particularly DIN, and compounds that can cause endocrine disruption in aquatic organisms.

Design and Experimental Validation for Direct-Drive Fault-Tolerant Permanent-Magnet Vernier Machines

PubMed Central

Liu, Guohai; Yang, Junqin; Chen, Ming; Chen, Qian

2014-01-01

A fault-tolerant permanent-magnet vernier (FT-PMV) machine is designed for direct-drive applications, incorporating the merits of high torque density and high reliability. Based on the so-called magnetic gearing effect, PMV machines have the ability of high torque density by introducing the flux-modulation poles (FMPs). This paper investigates the fault-tolerant characteristic of PMV machines and provides a design method, which is able to not only meet the fault-tolerant requirements but also keep the ability of high torque density. The operation principle of the proposed machine has been analyzed. The design process and optimization are presented specifically, such as the combination of slots and poles, the winding distribution, and the dimensions of PMs and teeth. By using the time-stepping finite element method (TS-FEM), the machine performances are evaluated. Finally, the FT-PMV machine is manufactured, and the experimental results are presented to validate the theoretical analysis. PMID:25045729

Dynamic behaviour of interphases and its implication on high-energy-density cathode materials in lithium-ion batteries

PubMed Central

Li, Wangda; Dolocan, Andrei; Oh, Pilgun; Celio, Hugo; Park, Suhyeon; Cho, Jaephil; Manthiram, Arumugam

2017-01-01

Undesired electrode–electrolyte interactions prevent the use of many high-energy-density cathode materials in practical lithium-ion batteries. Efforts to address their limited service life have predominantly focused on the active electrode materials and electrolytes. Here an advanced three-dimensional chemical and imaging analysis on a model material, the nickel-rich layered lithium transition-metal oxide, reveals the dynamic behaviour of cathode interphases driven by conductive carbon additives (carbon black) in a common nonaqueous electrolyte. Region-of-interest sensitive secondary-ion mass spectrometry shows that a cathode-electrolyte interphase, initially formed on carbon black with no electrochemical bias applied, readily passivates the cathode particles through mutual exchange of surface species. By tuning the interphase thickness, we demonstrate its robustness in suppressing the deterioration of the electrode/electrolyte interface during high-voltage cell operation. Our results provide insights on the formation and evolution of cathode interphases, facilitating development of in situ surface protection on high-energy-density cathode materials in lithium-based batteries. PMID:28443608

Doping and controllable pore size enhanced electrochemical performance of free-standing 3D graphene films

NASA Astrophysics Data System (ADS)

Wang, Liping; Qin, Kaiqiang; Li, Jiajun; Zhao, Naiqin; Shi, Chunsheng; Ma, Liying; He, Chunnian; He, Fang; Liu, Enzuo

2018-01-01

High quality free-standing 3D nanoporous graphene (3DNG) films were fabricated using nanoporous nickel as template and catalyst. The effect of heteroatom doping and pore size on the electrochemical performance of the 3D graphene films as supercapacitor electrodes are systematically studied. Compared with macroporous graphene films, nanoporous graphene films exhibit an extraordinarily large operational window in neutral, acidic and alkaline aqueous electrolytes, as well as high packing density. Nitrogen and oxygen doping play different roles in different aqueous electrolytes on the electrical conductivity and pseudocapacitance of 3DNG. The realization of both high packing density, 3.65 mg/cm2, and the maximum working window, as well as the synergistic effect between N and O doping, gives rise to a high areal capacitance of 435 mF/cm2 in neutral electrolyte and excellent cycle stability up to 5000 cycles. The results provide a potential strategy to further increase the volumetric or areal energy density of carbon-based aqueous supercapacitor.

Graphene Carbon Nanotube Carpets Grown Using Binary Catalysts for High-Performance Lithium-Ion Capacitors.

PubMed

Salvatierra, Rodrigo Villegas; Zakhidov, Dante; Sha, Junwei; Kim, Nam Dong; Lee, Seoung-Ki; Raji, Abdul-Rahman O; Zhao, Naiqin; Tour, James M

2017-03-28

Here we show that a versatile binary catalyst solution of Fe 3 O 4 /AlO x nanoparticles enables homogeneous growth of single to few-walled carbon nanotube (CNT) carpets from three-dimensional carbon-based substrates, moving past existing two-dimensional limited growth methods. The binary catalyst is composed of amorphous AlO x nanoclusters over Fe 3 O 4 crystalline nanoparticles, facilitating the creation of seamless junctions between the CNTs and the underlying carbon platform. The resulting graphene-CNT (GCNT) structure is a high-density CNT carpet ohmically connected to the carbon substrate, an important feature for advanced carbon electronics. As a demonstration of the utility of this approach, we use GCNTs as anodes and cathodes in binder-free lithium-ion capacitors, producing stable devices with high-energy densities (∼120 Wh kg -1 ), high-power density capabilities (∼20,500 W kg -1 at 29 Wh kg -1 ), and a large operating voltage window (4.3 to 0.01 V).

High-definition and low-noise muography of the Sakurajima volcano with gaseous tracking detectors.

PubMed

Oláh, László; Tanaka, Hiroyuki K M; Ohminato, Takao; Varga, Dezső

2018-02-16

Muography is a novel method to highly resolve the internal structure of active volcanoes by taking advantage of the cosmic muon's strong penetration power. In this paper, we present the first high-definition image in the vicinity of craters of an erupting volcano called Sakurajima, Kyushu, Japan. The muography observation system based on the technique of multi-wire proportional chamber (mMOS) has been operated reliably during the data taking period of 157 days. The mMOS measured precisely the flux of muons up to the thickness of 5,000 meter-water-equivalent. It was shown that high-definition density maps around the Craters A, B and Showa could be determined with a precision of less than 7.5 × 7.5 m 2 which earlier had not yet been achieved. The observed density distribution suggests that the fall back deposits filled the magma pathway and increased their density underneath Craters A and B.

Dynamic behaviour of interphases and its implication on high-energy-density cathode materials in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Li, Wangda; Dolocan, Andrei; Oh, Pilgun; Celio, Hugo; Park, Suhyeon; Cho, Jaephil; Manthiram, Arumugam

2017-04-01

Undesired electrode-electrolyte interactions prevent the use of many high-energy-density cathode materials in practical lithium-ion batteries. Efforts to address their limited service life have predominantly focused on the active electrode materials and electrolytes. Here an advanced three-dimensional chemical and imaging analysis on a model material, the nickel-rich layered lithium transition-metal oxide, reveals the dynamic behaviour of cathode interphases driven by conductive carbon additives (carbon black) in a common nonaqueous electrolyte. Region-of-interest sensitive secondary-ion mass spectrometry shows that a cathode-electrolyte interphase, initially formed on carbon black with no electrochemical bias applied, readily passivates the cathode particles through mutual exchange of surface species. By tuning the interphase thickness, we demonstrate its robustness in suppressing the deterioration of the electrode/electrolyte interface during high-voltage cell operation. Our results provide insights on the formation and evolution of cathode interphases, facilitating development of in situ surface protection on high-energy-density cathode materials in lithium-based batteries.

MICROBIAL SOURCE TRACKING GUIDE DOCUMENT

EPA Science Inventory

Approximately 13% of surface waters in the United States do not meet designated use criteria as determined by high densities of fecal indicator bacteria. Although some of the contamination is attributed to point sources such as confined animal feeding operation (CAFO) and wastew...

Surface modification of lignocellulosic fibers using high-frequency ultrasound

Treesearch

Jayant B. Gadhe; Ram B. Gupta; Thomas Elder

2005-01-01

Enzymatic and chemical oxidation of fiber surfaces has been reported in the literature as a method for producing medium density fiberboards without using synthetic adhesives. This work focuses on modifying the surface properties of wood fibers by the generation of free radicals using high-frequency ultrasound. A sonochemical reactor operating at 610 kHz is used to...

High performance Si nanowire field-effect-transistors based on a CMOS inverter with tunable threshold voltage.

PubMed

Van, Ngoc Huynh; Lee, Jae-Hyun; Sohn, Jung Inn; Cha, Seung Nam; Whang, Dongmok; Kim, Jong Min; Kang, Dae Joon

2014-05-21

We successfully fabricated nanowire-based complementary metal-oxide semiconductor (NWCMOS) inverter devices by utilizing n- and p-type Si nanowire field-effect-transistors (NWFETs) via a low-temperature fabrication processing technique. We demonstrate that NWCMOS inverter devices can be operated at less than 1 V, a significantly lower voltage than that of typical thin-film based complementary metal-oxide semiconductor (CMOS) inverter devices. This low-voltage operation was accomplished by controlling the threshold voltage of the n-type Si NWFETs through effective management of the nanowire (NW) doping concentration, while realizing high voltage gain (>10) and ultra-low static power dissipation (≤3 pW) for high-performance digital inverter devices. This result offers a viable means of fabricating high-performance, low-operation voltage, and high-density digital logic circuits using a low-temperature fabrication processing technique suitable for next-generation flexible electronics.

Ionomer-Liquid Electrolyte Hybrid Ionic Conductor for High Cycling Stability of Lithium Metal Electrodes

PubMed Central

Song, Jongchan; Lee, Hongkyung; Choo, Min-Ju; Park, Jung-Ki; Kim, Hee-Tak

2015-01-01

The inhomogeneous Li electrodeposition of lithium metal electrode has been a major impediment to the realization of rechargeable lithium metal batteries. Although single ion conducting ionomers can induce more homogeneous Li electrodeposition by preventing Li+ depletion at Li surface, currently available materials do not allow room-temperature operation due to their low room temperature conductivities. In the paper, we report that a highly conductive ionomer/liquid electrolyte hybrid layer tightly laminated on Li metal electrode can realize stable Li electrodeposition at high current densities up to 10 mA cm−2 and permit room-temperature operation of corresponding Li metal batteries with low polarizations. The hybrid layer is fabricated by laminating few micron-thick Nafion layer on Li metal electrode followed by soaking 1 M LiPF6 EC/DEC (1/1) electrolyte. The Li/Li symmetric cell with the hybrid layer stably operates at a high current density of 10 mA cm−2 for more than 2000 h, which corresponds to more than five-fold enhancement compared with bare Li metal electrode. Also, the prototype Li/LiCoO2 battery with the hybrid layer offers cycling stability more than 350 cycles. These results demonstrate that the hybrid strategy successfully combines the advantages of bi-ionic liquid electrolyte (fast Li+ transport) and single ionic ionomer (prevention of Li+ depletion). PMID:26411701

Ionomer-Liquid Electrolyte Hybrid Ionic Conductor for High Cycling Stability of Lithium Metal Electrodes

NASA Astrophysics Data System (ADS)

Song, Jongchan; Lee, Hongkyung; Choo, Min-Ju; Park, Jung-Ki; Kim, Hee-Tak

2015-09-01

The inhomogeneous Li electrodeposition of lithium metal electrode has been a major impediment to the realization of rechargeable lithium metal batteries. Although single ion conducting ionomers can induce more homogeneous Li electrodeposition by preventing Li+ depletion at Li surface, currently available materials do not allow room-temperature operation due to their low room temperature conductivities. In the paper, we report that a highly conductive ionomer/liquid electrolyte hybrid layer tightly laminated on Li metal electrode can realize stable Li electrodeposition at high current densities up to 10 mA cm-2 and permit room-temperature operation of corresponding Li metal batteries with low polarizations. The hybrid layer is fabricated by laminating few micron-thick Nafion layer on Li metal electrode followed by soaking 1 M LiPF6 EC/DEC (1/1) electrolyte. The Li/Li symmetric cell with the hybrid layer stably operates at a high current density of 10 mA cm-2 for more than 2000 h, which corresponds to more than five-fold enhancement compared with bare Li metal electrode. Also, the prototype Li/LiCoO2 battery with the hybrid layer offers cycling stability more than 350 cycles. These results demonstrate that the hybrid strategy successfully combines the advantages of bi-ionic liquid electrolyte (fast Li+ transport) and single ionic ionomer (prevention of Li+ depletion).

A nickel metal hydride battery for electric vehicles

NASA Astrophysics Data System (ADS)

Ovshinsky, S. R.; Fetcenko, M. A.; Ross, J.

1993-04-01

An efficient battery is the key technological element to the development of practical electric vehicles. The science and technology of a nickel metal hydride battery, which stores hydrogen in the solid hydride phase and has high energy density, high power, long life, tolerance to abuse, a wide range of operating temperature, quick-charge capability, and totally sealed maintenance-free operation, is described. A broad range of multi-element metal hydride materials that use structural and compositional disorder on several scales of length has been engineered for use as the negative electrode in this battery. The battery operates at ambient temperature, is made of nontoxic materials, and is recyclable. Demonstration of the manufacturing technology has been achieved.

Spectroscopic results in helium from the NASA Lewis Bumpy Torus plasma. [ion heating by Penning discharge in confinement geometry

NASA Technical Reports Server (NTRS)

Richardson, R. W.

1974-01-01

Spectroscopic measurements were carried out on the NASA Lewis Bumpy Torus experiment in which a steady state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. Electron temperatures in pure helium are measured from the ratio of spectral line intensities. Measured electron temperatures range from 10 to 100 eV. Relative electron densities are also measured over the range of operating conditions. Radial profiles of temperature and relative density are measured in the two basic modes of operation of the device called the low and high pressure modes. The electron temperatures are used to estimate particle confinement times based on a steady state particle balance.

Correlation Decay in Fermionic Lattice Systems with Power-Law Interactions at Nonzero Temperature

NASA Astrophysics Data System (ADS)

Hernández-Santana, Senaida; Gogolin, Christian; Cirac, J. Ignacio; Acín, Antonio

2017-09-01

We study correlations in fermionic lattice systems with long-range interactions in thermal equilibrium. We prove a bound on the correlation decay between anticommuting operators and generalize a long-range Lieb-Robinson-type bound. Our results show that in these systems of spatial dimension D with, not necessarily translation invariant, two-site interactions decaying algebraically with the distance with an exponent α ≥2 D , correlations between such operators decay at least algebraically to 0 with an exponent arbitrarily close to α at any nonzero temperature. Our bound is asymptotically tight, which we demonstrate by a high temperature expansion and by numerically analyzing density-density correlations in the one-dimensional quadratic (free, exactly solvable) Kitaev chain with long-range pairing.

Hierarchical equations of motion method applied to nonequilibrium heat transport in model molecular junctions: Transient heat current and high-order moments of the current operator

NASA Astrophysics Data System (ADS)

Song, Linze; Shi, Qiang

2017-02-01

We present a theoretical approach to study nonequilibrium quantum heat transport in molecular junctions described by a spin-boson type model. Based on the Feynman-Vernon path integral influence functional formalism, expressions for the average value and high-order moments of the heat current operators are derived, which are further obtained directly from the auxiliary density operators (ADOs) in the hierarchical equations of motion (HEOM) method. Distribution of the heat current is then derived from the high-order moments. As the HEOM method is nonperturbative and capable of treating non-Markovian system-environment interactions, the method can be applied to various problems of nonequilibrium quantum heat transport beyond the weak coupling regime.

High Temperature Polymers for use in Fuel Cells

NASA Technical Reports Server (NTRS)

Peplowski, Katherine M.

2004-01-01

NASA Glenn Research Center (GRC) is currently working on polymers for fuel cell and lithium battery applications. The desire for more efficient, higher power density, and a lower environmental impact power sources has led to interest in proton exchanges membrane fuels cells (PEMFC) and lithium batteries. A PEMFC has many advantages as a power source. The fuel cell uses oxygen and hydrogen as reactants. The resulting products are electricity, heat, and water. The PEMFC consists of electrodes with a catalyst, and an electrolyte. The electrolyte is an ion-conducting polymer that transports protons from the anode to the cathode. Typically, a PEMFC is operated at a temperature of about 80 C. There is intense interest in developing a fuel cell membrane that can operate at higher temperatures in the range of 80 C- 120 C. Operating the he1 cell at higher temperatures increases the kinetics of the fuel cell reaction as well as decreasing the susceptibility of the catalyst to be poisoned by impurities. Currently, Nafion made by Dupont is the most widely used polymer membrane in PEMFC. Nafion does not function well above 80 C due to a significant decrease in the conductivity of the membrane from a loss of hydration. In addition to the loss of conductivity at high temperatures, the long term stability and relatively high cost of Nafion have stimulated many researches to find a substitute for Nafion. Lithium ion batteries are popular for use in portable electronic devices, such as laptop computers and mobile phones. The high power density of lithium batteries makes them ideal for the high power demand of today s advanced electronics. NASA is developing a solid polymer electrolyte that can be used for lithium batteries. Solid polymer electrolytes have many advantages over the current gel or liquid based systems that are used currently. Among these advantages are the potential for increased power density and design flexibility. Automobiles, computers, and cell phones require highly efficient power density for lowering emissions and meeting increasing consumer demands. Many of the solutions can be provided by proton exchange membrane fuel cells and lithium batteries. NASA Glenn Research Center has recognized this need, and is presently engaged in a solution. The goals for the summer include mastering synthesis techniques, understanding the reactions occurring during the synthesis, and characterizing the resulting polymer membranes using NMR, DSC, and TGA for the PEMFC and lithium batteries.

Levitation or suspension: Which one is better for the heavy-load HTS maglev transportation

NASA Astrophysics Data System (ADS)

Liu, Wei; Kang, Dong; Yang, X. F.; Wang, Fei; Peng, G. H.; Zheng, Jun; Ma, G. T.; Wang, J. S.

2015-09-01

Because of the limitation of permanent magnet (PM), the efficient of bulk high-Tc superconductor (HTSC) in a high-Tc superconducting (HTS) maglev system is not very high. It is better to magnetize the bulk HTSC with a high trapped field to increase the force density. The different application type of magnetized bulk HTSC in a maglev system, namely, levitation or suspension type, will bring quite different operation performance. This paper discusses the influence of application type on operation performance of magnetized bulk HTSC by experiments and simulations. From the discussion, it can be found which application type is better for the heavy-load HTS maglev system.

A user-friendly, low-cost turbidostat with versatile growth rate estimation based on an extended Kalman filter.

PubMed

Hoffmann, Stefan A; Wohltat, Christian; Müller, Kristian M; Arndt, Katja M

2017-01-01

For various experimental applications, microbial cultures at defined, constant densities are highly advantageous over simple batch cultures. Due to high costs, however, devices for continuous culture at freely defined densities still experience limited use. We have developed a small-scale turbidostat for research purposes, which is manufactured from inexpensive components and 3D printed parts. A high degree of spatial system integration and a graphical user interface provide user-friendly operability. The used optical density feedback control allows for constant continuous culture at a wide range of densities and offers to vary culture volume and dilution rates without additional parametrization. Further, a recursive algorithm for on-line growth rate estimation has been implemented. The employed Kalman filtering approach based on a very general state model retains the flexibility of the used control type and can be easily adapted to other bioreactor designs. Within several minutes it can converge to robust, accurate growth rate estimates. This is particularly useful for directed evolution experiments or studies on metabolic challenges, as it allows direct monitoring of the population fitness.

Advanced rechargeable sodium batteries with novel cathodes

NASA Technical Reports Server (NTRS)

Distefano, S.; Ratnakumar, B. V.; Bankston, C. P.

1989-01-01

Various high energy density rechargeable batteries are being considered for future space applications. Of these, the sodium-sulfur battery is one of the leading candidates. The primary advantage is the high energy density (760 Wh/kg theoretical). Energy densities in excess of 180 Wh/kg were realized in practical batteries. Other technological advantages include its chemical simplicity, absence of self-discharge, and long cycle life possibility. More recently, other high temperature sodium batteries have come into the spotlight. These systems can be described as follow: Na/Beta Double Prime-Al2O3/NaAlCl4/Metal Dichloride Sodium/metal dichloride systems are colloquially known as the zebra system and are currently being developed for traction and load leveling applications. The sodium-metal dichloride systems appear to offer many of the same advantages of the Na/S system, especially in terms of energy density and chemical simplicity. The metal dichloride systems offer increased safety and good resistance to overcharge and operate over a wide range of temperatures from 150 to 400 C with less corrosion problems.

High-frequency Total Focusing Method (TFM) imaging in strongly attenuating materials with the decomposition of the time reversal operator associated with orthogonal coded excitations

NASA Astrophysics Data System (ADS)

Villaverde, Eduardo Lopez; Robert, Sébastien; Prada, Claire

2017-02-01

In the present work, the Total Focusing Method (TFM) is used to image defects in a High Density Polyethylene (HDPE) pipe. The viscoelastic attenuation of this material corrupts the images with a high electronic noise. In order to improve the image quality, the Decomposition of the Time Reversal Operator (DORT) filtering is combined with spatial Walsh-Hadamard coded transmissions before calculating the images. Experiments on a complex HDPE joint demonstrate that this method improves the signal-to-noise ratio by more than 40 dB in comparison with the conventional TFM.

Lithium-antimony-lead liquid metal battery for grid-level energy storage

NASA Astrophysics Data System (ADS)

Wang, Kangli; Jiang, Kai; Chung, Brice; Ouchi, Takanari; Burke, Paul J.; Boysen, Dane A.; Bradwell, David J.; Kim, Hojong; Muecke, Ulrich; Sadoway, Donald R.

2014-10-01

The ability to store energy on the electric grid would greatly improve its efficiency and reliability while enabling the integration of intermittent renewable energy technologies (such as wind and solar) into baseload supply. Batteries have long been considered strong candidate solutions owing to their small spatial footprint, mechanical simplicity and flexibility in siting. However, the barrier to widespread adoption of batteries is their high cost. Here we describe a lithium-antimony-lead liquid metal battery that potentially meets the performance specifications for stationary energy storage applications. This Li||Sb-Pb battery comprises a liquid lithium negative electrode, a molten salt electrolyte, and a liquid antimony-lead alloy positive electrode, which self-segregate by density into three distinct layers owing to the immiscibility of the contiguous salt and metal phases. The all-liquid construction confers the advantages of higher current density, longer cycle life and simpler manufacturing of large-scale storage systems (because no membranes or separators are involved) relative to those of conventional batteries. At charge-discharge current densities of 275 milliamperes per square centimetre, the cells cycled at 450 degrees Celsius with 98 per cent Coulombic efficiency and 73 per cent round-trip energy efficiency. To provide evidence of their high power capability, the cells were discharged and charged at current densities as high as 1,000 milliamperes per square centimetre. Measured capacity loss after operation for 1,800 hours (more than 450 charge-discharge cycles at 100 per cent depth of discharge) projects retention of over 85 per cent of initial capacity after ten years of daily cycling. Our results demonstrate that alloying a high-melting-point, high-voltage metal (antimony) with a low-melting-point, low-cost metal (lead) advantageously decreases the operating temperature while maintaining a high cell voltage. Apart from the fact that this finding puts us on a desirable cost trajectory, this approach may well be more broadly applicable to other battery chemistries.

Lithium-antimony-lead liquid metal battery for grid-level energy storage.

PubMed

Wang, Kangli; Jiang, Kai; Chung, Brice; Ouchi, Takanari; Burke, Paul J; Boysen, Dane A; Bradwell, David J; Kim, Hojong; Muecke, Ulrich; Sadoway, Donald R

2014-10-16

The ability to store energy on the electric grid would greatly improve its efficiency and reliability while enabling the integration of intermittent renewable energy technologies (such as wind and solar) into baseload supply. Batteries have long been considered strong candidate solutions owing to their small spatial footprint, mechanical simplicity and flexibility in siting. However, the barrier to widespread adoption of batteries is their high cost. Here we describe a lithium-antimony-lead liquid metal battery that potentially meets the performance specifications for stationary energy storage applications. This Li||Sb-Pb battery comprises a liquid lithium negative electrode, a molten salt electrolyte, and a liquid antimony-lead alloy positive electrode, which self-segregate by density into three distinct layers owing to the immiscibility of the contiguous salt and metal phases. The all-liquid construction confers the advantages of higher current density, longer cycle life and simpler manufacturing of large-scale storage systems (because no membranes or separators are involved) relative to those of conventional batteries. At charge-discharge current densities of 275 milliamperes per square centimetre, the cells cycled at 450 degrees Celsius with 98 per cent Coulombic efficiency and 73 per cent round-trip energy efficiency. To provide evidence of their high power capability, the cells were discharged and charged at current densities as high as 1,000 milliamperes per square centimetre. Measured capacity loss after operation for 1,800 hours (more than 450 charge-discharge cycles at 100 per cent depth of discharge) projects retention of over 85 per cent of initial capacity after ten years of daily cycling. Our results demonstrate that alloying a high-melting-point, high-voltage metal (antimony) with a low-melting-point, low-cost metal (lead) advantageously decreases the operating temperature while maintaining a high cell voltage. Apart from the fact that this finding puts us on a desirable cost trajectory, this approach may well be more broadly applicable to other battery chemistries.

High power broadband millimeter wave TWTs

NASA Astrophysics Data System (ADS)

James, Bill G.

1999-05-01

In the early 1980's the requirement for high power broadband millimeter wave sources encouraged the development of microwave vacuum device amplifiers for radar and communication systems. Many government funded programs were implemented for the development of high power broadband millimeter wave amplifiers that would meet the needs of the high power community. The tube design capable of meeting these goals was the slow wave coupled cavity traveling wave device, which had a proven technology base at the lower frequencies (X Band). However scaling this technology to the millimeter frequencies had severe shortcomings in both thermal and manufacturing design. These shortcomings were overcome with the development of the Ladder Circuit technology. In conjunction with the circuit development high power electron beam systems had to be developed for the generation of high rf powers. These beam systems had to be capable of many megawatts of beam power density and high current densities. The cathode technology required to be capable of operating at current densities of 10 amperes per square centimeter at long pulse lengths and high duty cycle. Since the introduction of the Ladder Circuit technology a number of high power broadband millimeter wave amplifiers have been developed using this technology, and have been deployed in operating radar and communication systems. Broadband millimeter wave sources have been manufactured in the frequency range from 27 GHz to 100 GHz with power levels ranging from 100 watts to 50 kilowatts. Today the power levels achieved by these devices are nearing the limits of this technology; therefore to gain a significant increase in power at the millimeter wave frequencies other technologies will have to be considered particularly fast wave devices. This paper will briefly review the ladder circuit technology and present the designs of a number of broadband high power devices developed at Ka and W band. The discussion will include the beam systems employed in these devices which are the highest power density linear beams generated to date. In conclusion the limits of the power generating capability of this technology will be presented.

High Power Broadband Millimeter Wave TWTs

NASA Astrophysics Data System (ADS)

James, Bill G.

1998-04-01

In the early 1980's the requirement for high power broadband millimeter wave sources encouraged the development of microwave vacuum device amplifiers for radar and communication systems. Many government funded programs were implemented for the development of high power broadband millimeter wave amplifiers that would meet the needs of the high power community. The tube design capable of meeting these goals was the slow wave coupled cavity traveling wave device, which had a proven technology base at the lower frequencies (X Band). However scaling this technology to the millimeter frequencies had severe shortcomings in both thermal and manufacturing design. These shortcomings were overcome with the development of the Ladder Circuit technology. In conjunction with the circuit development high power electron beam systems had to be developed for the generation of high rf powers. These beam systems had to be capable of many megawatts of beam power density and high current densities. The cathode technology required to be capable of operating at current densities of 10 amperes per square centimeter at long pulse lengths and high duty cycle. Since the introduction of the Ladder Circuit technology a number of high power broadband millimeter wave amplifiers have been developed and deployed in operating radar and communication systems. Broadband millimeter wave sources have been manufactured in the frequency range from 27 GHz to 100 GHz with power levels ranging from 100 watts CW to 10 kilowatts Peak at W band over a 2 GHz bandwidth. Also a 50 kW peak power and 10 kW average power device at Ka band with 2 GHz bandwidth has been developed. Today the power levels achieved by these devices are nearing the limits of this technology; therefore to gain a significant increase in power at the millimeter wave frequencies, other technologies will have to be considered, particularly fast wave devices. This paper will briefly review the ladder circuit technology and present the designs of a number of broadband high power devices developed at Ka and W band. The discussion will include the beam systems employed in these devices which are the highest power density linear beams generated to date. In conclusion the limits of the power generating capability of this technology will be presented.

Staging and laser acceleration of ions in underdense plasma

NASA Astrophysics Data System (ADS)

Ting, Antonio; Hafizi, Bahman; Helle, Michael; Chen, Yu-Hsin; Gordon, Daniel; Kaganovich, Dmitri; Polyanskiy, Mikhail; Pogorelsky, Igor; Babzien, Markus; Miao, Chenlong; Dover, Nicholas; Najmudin, Zulfikar; Ettlinger, Oliver

2017-03-01

Accelerating ions from rest in a plasma requires extra considerations because of their heavy mass. Low phase velocity fields or quasi-electrostatic fields are often necessary, either by operating above or near the critical density or by applying other slow wave generating mechanisms. Solid targets have been a favorite and have generated many good results. High density gas targets have also been reported to produce energetic ions. It is interesting to consider acceleration of ions in laser-driven plasma configurations that will potentially allow continuous acceleration in multiple consecutive stages. The plasma will be derived from gaseous targets, producing plasma densities slightly below the critical plasma density (underdense) for the driving laser. Such a plasma is experimentally robust, being repeatable and relatively transparent to externally injected ions from a previous stage. When optimized, multiple stages of this underdense laser plasma acceleration mechanism can progressively accelerate the ions to a high final energy. For a light mass ion such as the proton, relativistic velocities could be reached, making it suitable for further acceleration by high phase velocity plasma accelerators to energies appropriate for High Energy Physics applications. Negatively charged ions such as antiprotons could be similarly accelerated in this multi-staged ion acceleration scheme.

Hydrate-melt electrolytes for high-energy-density aqueous batteries

NASA Astrophysics Data System (ADS)

Yamada, Yuki; Usui, Kenji; Sodeyama, Keitaro; Ko, Seongjae; Tateyama, Yoshitaka; Yamada, Atsuo

2016-10-01

Aqueous Li-ion batteries are attracting increasing attention because they are potentially low in cost, safe and environmentally friendly. However, their low energy density (<100 Wh kg-1 based on total electrode weight), which results from the narrow operating potential window of water and the limited selection of suitable negative electrodes, is problematic for their future widespread application. Here, we explore optimized eutectic systems of several organic Li salts and show that a room-temperature hydrate melt of Li salts can be used as a stable aqueous electrolyte in which all water molecules participate in Li+ hydration shells while retaining fluidity. This hydrate-melt electrolyte enables a reversible reaction at a commercial Li4Ti5O12 negative electrode with a low reaction potential (1.55 V versus Li+/Li) and a high capacity (175 mAh g-1). The resultant aqueous Li-ion batteries with high energy density (>130 Wh kg-1) and high voltage (˜2.3-3.1 V) represent significant progress towards performance comparable to that of commercial non-aqueous batteries (with energy densities of ˜150-400 Wh kg-1 and voltages of ˜2.4-3.8 V).

Compact Holographic Data Storage

NASA Technical Reports Server (NTRS)

Chao, T. H.; Reyes, G. F.; Zhou, H.

2001-01-01

NASA's future missions would require massive high-speed onboard data storage capability to Space Science missions. For Space Science, such as the Europa Lander mission, the onboard data storage requirements would be focused on maximizing the spacecraft's ability to survive fault conditions (i.e., no loss in stored science data when spacecraft enters the 'safe mode') and autonomously recover from them during NASA's long-life and deep space missions. This would require the development of non-volatile memory. In order to survive in the stringent environment during space exploration missions, onboard memory requirements would also include: (1) survive a high radiation environment (1 Mrad), (2) operate effectively and efficiently for a very long time (10 years), and (3) sustain at least a billion write cycles. Therefore, memory technologies requirements of NASA's Earth Science and Space Science missions are large capacity, non-volatility, high-transfer rate, high radiation resistance, high storage density, and high power efficiency. JPL, under current sponsorship from NASA Space Science and Earth Science Programs, is developing a high-density, nonvolatile and rad-hard Compact Holographic Data Storage (CHDS) system to enable large-capacity, high-speed, low power consumption, and read/write of data in a space environment. The entire read/write operation will be controlled with electrooptic mechanism without any moving parts. This CHDS will consist of laser diodes, photorefractive crystal, spatial light modulator, photodetector array, and I/O electronic interface. In operation, pages of information would be recorded and retrieved with random access and high-speed. The nonvolatile, rad-hard characteristics of the holographic memory will provide a revolutionary memory technology meeting the high radiation challenge facing the Europa Lander mission. Additional information is contained in the original extended abstract.

Use of adsorption using granular activated carbon (GAC) for the enhancement of removal of chromium from synthetic wastewater by electrocoagulation.

PubMed

Vivek Narayanan, N; Ganesan, Mahesh

2009-01-15

The present work deals with removal of hexavalent chromium from synthetic effluents in a batch stirred electrocoagulation cell with iron-aluminium electrode pair coupled with adsorption using granular activated carbon (GAC). Several working parameters such as pH, current density, adsorbent concentration and operating time were studied in an attempt to achieve higher removal capacity. Results obtained with synthetic wastewater revealed that most effective removal capacities of chromium (VI) could be achieved when the initial pH was near 8. The removal of chromium (VI) during electrocoagulation, is due to the combined effect of chemical precipitation, coprecipitation, sweep coagulation and adsorption. In addition, increasing current density in a range of 6.7-26.7mA/cm2 and operating time from 20 to 100min enhanced the treatment rate to reduce metal ion concentration below admissible legal levels. The addition of GAC as adsorbent resulted in remarkable increase in the removal rate of chromium at lower current densities and operating time, than the conventional electrocoagulation process. The method was found to be highly efficient and relatively fast compared to existing conventional techniques.

Platinum- and membrane-free swiss-roll mixed-reactant alkaline fuel cell.

PubMed

Aziznia, Amin; Oloman, Colin W; Gyenge, Előd L

2013-05-01

Eliminating the expensive and failure-prone proton exchange membrane (PEM) together with the platinum-based anode and cathode catalysts would significantly reduce the high capital and operating costs of low-temperature (<373 K) fuel cells. We recently introduced the Swiss-roll mixed-reactant fuel cell (SR-MRFC) concept for borohydride-oxygen alkaline fuel cells. We now present advances in anode electrocatalysis for borohydride electrooxidation through the development of osmium nanoparticulate catalysts supported on porous monolithic carbon fiber materials (referred to as an osmium 3D anode). The borohydride-oxygen SR-MRFC operates at 323 K and near atmospheric pressure, generating a peak power density of 1880 W m(-2) in a single-cell configuration by using an osmium-based anode (with an osmium loading of 0.32 mg cm(-2)) and a manganese dioxide gas-diffusion cathode. To the best of our knowledge, 1880 W m(-2) is the highest power density ever reported for a mixed-reactant fuel cell operating under similar conditions. Furthermore, the performance matches the highest reported power densities for conventional dual chamber PEM direct borohydride fuel cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Compatibility of separatrix density scaling for divertor detachment with H-mode pedestal operation in DIII-D

NASA Astrophysics Data System (ADS)

Leonard, A. W.; McLean, A. G.; Makowski, M. A.; Stangeby, P. C.

2017-08-01

The midplane separatrix density is characterized in response to variations in upstream parallel heat flux density and central density through deuterium gas injection. The midplane density is determined from a high spatial resolution Thomson scattering diagnostic at the midplane with power balance analysis to determine the separatrix location. The heat flux density is varied by scans of three parameters, auxiliary heating, toroidal field with fixed plasma current, and plasma current with fixed safety factor, q 95. The separatrix density just before divertor detachment onset is found to scale consistent with the two-point model when radiative dissipation is taken into account. The ratio of separatrix to pedestal density, n e,sep/n e,ped varies from  ⩽30% to  ⩾60% over the dataset, helping to resolve the conflicting scaling of core plasma density limit and divertor detachment onset. The scaling of the separatrix density at detachment onset is combined with H-mode power threshold scaling to obtain a scaling ratio of minimum n e,sep/n e,ped expected in future devices.

Development of miniature, high frequency pulse tube cryocoolers

NASA Astrophysics Data System (ADS)

Radebaugh, Ray; Garaway, Isaac; Veprik, Alexander M.

2010-04-01

Because acoustic power density is proportional to frequency, the size of pulse tube cryocoolers for a given refrigeration power can be reduced by operating them at higher frequencies. A frequency of about 60 Hz had been considered the maximum frequency that could be used while maintaining high efficiency. Recently, we have shown through modeling that by decreasing the volume and hydraulic diameter of the regenerator and increasing the average pressure, it is possible to maintain high efficiency even for frequencies of several hundred hertz. Subsequent experimental results have demonstrated high efficiencies for frequencies of 100 to 140 Hz. The very high power density achieved at higher pressures and higher frequencies leads to very short cooldown times and very compact devices. The use of even higher frequencies requires the development of special compressors designed for such conditions and the development of regenerator matrices with hydraulic diameters less than about 30 Μm. To demonstrate the advantages of higher frequency operation, we discuss here the development of a miniature pulse tube cryocooler designed to operate at 80 K with a frequency of 150 Hz and an average pressure of 5.0 MPa. The regenerator diameter and length are 4.4 mm and 27 mm, respectively. The lowest temperature achieved to date has been 97 K, but a net refrigeration power of 530 mW was achieved at 120 K. Acoustic mismatches with existing compressors significantly limit the efficiency, but necessary modifications to improve the acoustic impedance match between the compressor and the cold head are discussed briefly.

High-Density Digital Data Storage System

NASA Technical Reports Server (NTRS)

Wright, Kenneth D.; Gray, David L.

1995-01-01

High-density digital data storage system designed for cost-effective storage of large amounts of information acquired during experiments. System accepts up to 20 channels of 16-bit digital data with overall transfer rates of 500 kilobytes per second. Data recorded on 8-millimeter magnetic tape in cartridges, each capable of holding up to five gigabytes of data. Each cartridge mounted on one of two tape drives. Operator chooses to use either or both of drives. One drive used for primary storage of data while other can be used to make a duplicate record of data. Alternatively, other drive serves as backup data-storage drive when primary one fails.

A case study of dissolved air flotation for seasonal high turbidity water in Korea.

PubMed

Kwon, S B; Ahn, H W; Ahn, C J; Wang, C K

2004-01-01

A DAF (Dissolved-Air-Flotation) process has been designed considering raw water quality characteristics in Korea. Although direct filtration is usually operated, DAF is operated when freshwater algae blooms occur or raw water turbidity becomes high. Pre-sedimentation is operated in case when the raw water turbidity is very high due to rainstorms. A main feature of this plant is that the operation mode can be changed (controlled) based on the characteristics of the raw water to optimize the effluent quality and the operation costs. Treatment capacity (surface loading rate) and efficiency of DAF was found to be better than the conventional sedimentation process. Moreover, low-density particles (algae and alum flocs) are easily separated while the removal of them by sedimentation is more difficult. One of the main concerns for DAF operation is a high raw water turbidity. DAF is not adequate for raw water, which is more turbid than 100 NTU. In order to avoid this problem, pre-sedimentation basins are installed in the DAF plant to decrease the turbidity of the DAF inflow. For simulation of the actual operation, bench and full-scale tests were performed for highly turbid water conditions. Consequently, it is suggested that pre-sedimentation with optimum coagulation prior to DAF is the appropriate treatment scheme.

High Current Density Cathodes for Future Vacuum Electronics Applications

DTIC Science & Technology

2008-05-30

Tube - device for generating high levels of RF power DARPA Defense Advanced Research Agency PBG Photonic band gap W- Band 75-111 GHz dB Decibels GHz...Extended interaction klystron 1. Introduction All RF vacuum electron sources require a high quality electron beam for efficient operation. Research on...with long life. Pres- ently, only thermionic dispenser cathodes are practical for high power RF sources. Typical thermi- onic cathodes consists of a

A High-Performing Direct Carbon Fuel Cell with a 3D Architectured Anode Operated Below 600 °C.

PubMed

Wu, Wei; Zhang, Yunya; Ding, Dong; He, Ting

2018-01-01

Direct carbon fuel cells (DCFCs) are highly efficient power generators fueled by abundant and cheap solid carbons. However, the limited triple-phase boundaries (TPBs) in the fuel electrode, due to the lack of direct contact among carbon, electrode, and electrolyte, inhibit the performance and result in poor fuel utilization. To address the challenges of low carbon oxidation activity and low carbon utilization, a highly efficient, 3D solid-state architected anode is developed to enhance the performance of DCFCs below 600 °C. The cell with the 3D textile anode framework, Gd:CeO 2 -Li/Na 2 CO 3 composite electrolyte, and Sm 0.5 Sr 0.5 CoO 3 cathode demonstrates excellent performance with maximum power densities of 143, 196, and 325 mW cm -2 at 500, 550, and 600 °C, respectively. At 500 °C, the cells can be operated steadily with a rated power density of ≈0.13 W cm -2 at a constant current density of 0.15 A cm -2 with a carbon utilization over 85.5%. These results, for the first time, demonstrate the feasibility of directly electrochemical oxidation of solid carbon at 500-600 °C, representing a promising strategy in developing high-performing fuel cells and other electrochemical systems via the integration of 3D architected electrodes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assessment of quasi-linear effect of RF power spectrum for enabling lower hybrid current drive in reactor plasmas

NASA Astrophysics Data System (ADS)

Cesario, Roberto; Cardinali, Alessandro; Castaldo, Carmine; Amicucci, Luca; Ceccuzzi, Silvio; Galli, Alessandro; Napoli, Francesco; Panaccione, Luigi; Santini, Franco; Schettini, Giuseppe; Tuccillo, Angelo Antonio

2017-10-01

The main research on the energy from thermonuclear fusion uses deuterium plasmas magnetically trapped in toroidal devices. To suppress the turbulent eddies that impair thermal insulation and pressure tight of the plasma, current drive (CD) is necessary, but tools envisaged so far are unable accomplishing this task while efficiently and flexibly matching the natural current profiles self-generated at large radii of the plasma column [1-5]. The lower hybrid current drive (LHCD) [6] can satisfy this important need of a reactor [1], but the LHCD system has been unexpectedly mothballed on JET. The problematic extrapolation of the LHCD tool at reactor graded high values of, respectively, density and temperatures of plasma has been now solved. The high density problem is solved by the FTU (Frascati Tokamak Upgrade) method [7], and solution of the high temperature one is presented here. Model results based on quasi-linear (QL) theory evidence the capability, w.r.t linear theory, of suitable operating parameters of reducing the wave damping in hot reactor plasmas. Namely, using higher RF power densities [8], or a narrower antenna power spectrum in refractive index [9,10], the obstacle for LHCD represented by too high temperature of reactor plasmas should be overcome. The former method cannot be used for routinely, safe antenna operations, Thus, only the latter key is really exploitable in a reactor. The proposed solutions are ultimately necessary for viability of an economic reactor.

A three-dimensional reticulate CNT-aerogel for a high mechanical flexibility fiber supercapacitor.

PubMed

Li, Yong; Kang, Zhuo; Yan, Xiaoqin; Cao, Shiyao; Li, Minghua; Guo, Yan; Huan, Yahuan; Wen, Xiaosong; Zhang, Yue

2018-05-17

In recent years, the rapid development of portable and wearable electronic products has promoted the prosperity of fiber supercapacitors (FSCs), which serve as flexible and lightweight energy supply devices. However, research on FSCs is still in its infancy and the energy density of FSCs is far below the level of lithium-ion batteries. Here, we report a facile method to prepare a novel fibrous CNT-aerogel by electrochemical activation and freeze-drying. The fibrous CNT-aerogel electrode possesses a large specific surface area, high mechanical strength, excellent electrical conductivity, as well as a high specific capacitance of 160.8 F g-1 at 0.5 mA and long cycling stability. Then we assembled a non-faradaic FSC based on a fibrous CNT-aerogel as the electrode and a P(VDF-HFP)/EMIMBF4 ionogel as the electrolyte. The introduction of the ionogel electrolyte increases the operating voltage of the FSC to 3 V, and makes the device combine the intrinsic high power density (27.3 kW kg-1) of non-faradaic SCs with an ultrahigh energy density of 29.6 W h kg-1. More importantly, the assembled FSCs show excellent flexibility and bending-stability, and can still operate normally within a wide working temperature window (0-80 °C). The outstanding electrochemical performance and the mechanical/thermal stability indicate that the assembled FSC device is a promising power source for flexible electronics.

14 CFR 93.133 - Exceptions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Exceptions. 93.133 Section 93.133 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.133...

14 CFR 93.133 - Exceptions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 2 2013-01-01 2013-01-01 false Exceptions. 93.133 Section 93.133 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.133...

14 CFR 93.133 - Exceptions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 2 2012-01-01 2012-01-01 false Exceptions. 93.133 Section 93.133 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.133...

14 CFR 93.133 - Exceptions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Exceptions. 93.133 Section 93.133 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.133...

14 CFR 93.133 - Exceptions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 2 2014-01-01 2014-01-01 false Exceptions. 93.133 Section 93.133 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93.133...

Opportunities and limitations in low earth subsonic testing for qualification of extraterrestrial supersonic parachute designs

NASA Technical Reports Server (NTRS)

Steltzner, A.; Cruz, J.; Bruno, R.; Mitcheltree, R.

2003-01-01

Parachutes for Mars and other planetary missions often need to operate at supersonic speeds in very low density atmospheres. Flight testing of such parachutes at appropriate conditions in the Earth's atmosphere is possible at high altitudes.

Investigating the role of capacitive coupling between the operating table and the return electrode of an electrosurgery unit in the modification of the current density distribution within the patients' body.

PubMed

Bifulco, Paolo; Massa, Rita; Cesarelli, Mario; Romano, Maria; Fratini, Antonio; Gargiulo, Gaetano D; McEwan, Alistair L

2013-08-12

Electrosurgery units are widely employed in modern surgery. Advances in technology have enhanced the safety of these devices, nevertheless, accidental burns are still regularly reported. This study focuses on possible causes of sacral burns as complication of the use of electrosurgery. Burns are caused by local densifications of the current, but the actual pathway of current within patient's body is unknown. Numerical electromagnetic analysis can help in understanding the issue. To this aim, an accurate heterogeneous model of human body (including seventy-seven different tissues), electrosurgery electrodes, operating table and mattress was build to resemble a typical surgery condition. The patient lays supine on the mattress with the active electrode placed onto the thorax and the return electrode on his back. Common operating frequencies of electrosurgery units were considered. Finite Difference Time Domain electromagnetic analysis was carried out to compute the spatial distribution of current density within the patient's body. A differential analysis by changing the electrical properties of the operating table from a conductor to an insulator was also performed. Results revealed that distributed capacitive coupling between patient body and the conductive operating table offers an alternative path to the electrosurgery current. The patient's anatomy, the positioning and the different electromagnetic properties of tissues promote a densification of the current at the head and sacral region. In particular, high values of current density were located behind the sacral bone and beneath the skin. This did not occur in the case of non-conductive operating table. Results of the simulation highlight the role played from capacitive couplings between the return electrode and the conductive operating table. The concentration of current density may result in an undesired rise in temperature, originating burns in body region far from the electrodes. This outcome is concordant with the type of surgery-related sacral burns reported in literature. Such burns cannot be immediately detected after surgery, but appear later and can be confused with bedsores. In addition, the dosimetric analysis suggests that reducing the capacity coupling between the return electrode and the operating table can decrease or avoid this problem.

High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode

NASA Astrophysics Data System (ADS)

Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

2013-08-01

Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm-2 (specific capacitance of 50 F g-1) at a charge/discharge current density of 1 mA cm-2 and a maximum energy density of 39.9 W h kg-1 (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm-2, with a capacitance retention of 95% after 3000 cycles.

High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode.

PubMed

Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

2013-09-07

Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm(-2) (specific capacitance of 50 F g(-1)) at a charge/discharge current density of 1 mA cm(-2) and a maximum energy density of 39.9 W h kg(-1) (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm(-2), with a capacitance retention of 95% after 3000 cycles.

A High Temperature Silicon Carbide mosfet Power Module With Integrated Silicon-On-Insulator-Based Gate Drive

DOE PAGES

Wang, Zhiqiang; Shi, Xiaojie; Tolbert, Leon M.; ...

2014-04-30

Here we present a board-level integrated silicon carbide (SiC) MOSFET power module for high temperature and high power density application. Specifically, a silicon-on-insulator (SOI)-based gate driver capable of operating at 200°C ambient temperature is designed and fabricated. The sourcing and sinking current capability of the gate driver are tested under various ambient temperatures. Also, a 1200 V/100 A SiC MOSFET phase-leg power module is developed utilizing high temperature packaging technologies. The static characteristics, switching performance, and short-circuit behavior of the fabricated power module are fully evaluated at different temperatures. Moreover, a buck converter prototype composed of the SOI gate drivermore » and SiC power module is built for high temperature continuous operation. The converter is operated at different switching frequencies up to 100 kHz, with its junction temperature monitored by a thermosensitive electrical parameter and compared with thermal simulation results. The experimental results from the continuous operation demonstrate the high temperature capability of the power module at a junction temperature greater than 225°C.« less

The Support of Air Operations Under Extreme Hot and Cold Weather Conditions (Les Operatons Aeriennes en Environnement Extreme Chaud/Froid)

DTIC Science & Technology

1993-10-01

particular subject’s water turnover data could be considered triglyceride , high density lipoprotein ( HDL ), low density an outlier (20). Ali results are... Cholesterol and triglycerides values tended to decrease pre- retrospectively distinguish the bars enough to accurately rate to post-study. Further...there was an increase in the HDL them individually. However, the field data show that even fraction and a decrease in the LDL fraction of cholesterol

Magnetically operated beam dump for dumping high power beams in a neutral beamline

DOEpatents

Dagenhart, W.K.

1984-01-27

It is an object of this invention to provide a beam dump system for a neutral beam generator which lowers the time-averaged power density of the beam dump impingement surface. Another object of this invention is to provide a beam dump system for a neutral particle beam based on reionization and subsequent magnetic beam position modulation of the beam onto a beam dump surface to lower the time-averaged power density of the beam dump ion impingement surface.

Development of a current collection loss management system for SDI homopolar power supplies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, D.W.

1989-01-01

High speed, high power density current collection systems have been identified as an enabling technology required to construct homopolar power supplies to meet SDI missions. This work is part of a three-year effort directed towards the analysis, experimental verification, and prototype construction of a current collection system designed to operate continuously at 2 kA/cm{sup 2}, at a rubbing speed of 200 m/s, and with acceptable losses in a space environment. To data, no system has achieved these conditions simultaneously. This is the annual report covering the second year period of performance on DOE contract DE-AC03-86SF16518. Major areas covered include design,more » construction and operation of a cryogenically cooled brush test rig, design and construction of a high speed brush test rig, optimization study for homopolar machines, loss analysis of the current collection system, and an application study which defines the air-core homopolar construction necessary to achieve the goal of 80--90 kW/kg generator power density. 17 figs., 2 tabs.« less

High energy density capacitors for vacuum operation with a pulsed plasma load

NASA Technical Reports Server (NTRS)

Guman, W. J.

1976-01-01

Results of the effort of designing, fabricating, and testing of a 40 joules/lb (88.2 joules/Kg) high voltage energy storage capacitor suitable for operating a pulsed plasma thruster in a vacuum environment for millions of pulses are presented. Using vacuum brazing and heli-arc welding techniques followed by vacuum and high pressure helium leak tests it was possible to produce a hermetically sealed relatively light weight enclosure for the dielectric system. An energy density of 40 joules/lb was realized with a KF-polyvinylidene fluoride dielectric system. One capacitor was D.C. life tested at 4 KV (107.8 joules/lb) for 2,000 hours before it failed. Another exceeded 2,670 hours without failure at 38.3 joules/lb. Pulse life testing in a vacuum exceeded 300,000 discharges with testing still in progress. The D.C. life test data shows a small decrease in capacitance and an increase in dissipation factor with time. Heat transfer from the load to the capacitor must also be considered besides the self-heat generated by the capacitor.

Discharge runaway in high power impulse magnetron sputtering of carbon: the effect of gas pressure, composition and target peak voltage

NASA Astrophysics Data System (ADS)

Vitelaru, Catalin; Aijaz, Asim; Constantina Parau, Anca; Kiss, Adrian Emil; Sobetkii, Arcadie; Kubart, Tomas

2018-04-01

Pressure and target voltage driven discharge runaway from low to high discharge current density regimes in high power impulse magnetron sputtering of carbon is investigated. The main purpose is to provide a meaningful insight of the discharge dynamics, with the ultimate goal to establish a correlation between discharge properties and process parameters to control the film growth. This is achieved by examining a wide range of pressures (2–20 mTorr) and target voltages (700–850 V) and measuring ion saturation current density at the substrate position. We show that the minimum plasma impedance is an important parameter identifying the discharge transition as well as establishing a stable operating condition. Using the formalism of generalized recycling model, we introduce a new parameter, ‘recycling ratio’, to quantify the process gas recycling for specific process conditions. The model takes into account the ion flux to the target, the amount of gas available, and the amount of gas required for sustaining the discharge. We show that this parameter describes the relation between the gas recycling and the discharge current density. As a test case, we discuss the pressure and voltage driven transitions by changing the gas composition when adding Ne into the discharge. We propose that standard Ar HiPIMS discharges operated with significant gas recycling do not require Ne to increase the carbon ionization.

High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target

DOE PAGES

Gauthier, M.; Kim, J. B.; Curry, C. B.; ...

2016-08-24

Here, we report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams. With its high purity, limited size, near-critical density, and high-repetitionmore » rate capability, this target is promising for future applications.« less

High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gauthier, M., E-mail: maxence.gauthier@stanford.edu; Kim, J. B.; Curry, C. B.

2016-11-15

We report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams. With its high purity, limited size, near-critical density, and high-repetition ratemore » capability, this target is promising for future applications.« less

Discharge Characterization of 40 cm-Microwave ECR Ion Source and Neutralizer

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.; Britton, Melissa

2003-01-01

Discharge characteristics of a 40 cm, 2.45 GHz Electron Cyclotron Resonance (ECR) ion thruster discharge chamber and neutralizer were acquired. Thruster bulk discharge plasma characteristics were assessed using a single Langmuir probe. Total extractable ion current was measured as a function of input microwave power and flow rate. Additionally, radial ion current density profiles at the thruster.s exit plane were characterized using five equally spaced Faraday probes. Distinct low and high density operating modes were observed as discharge input power was varied from 0 to 200 W. In the high mode, extractable ion currents as high as 0.82 A were measured. Neutralizer emission current was characterized as a function of flow rate and microwave power. Neutralizer extraction currents as high as 0.6 A were measured.

Safely Enabling UAS Operations in Low-Altitude Airspace

NASA Technical Reports Server (NTRS)

Kopardekar, Parimal H.

2016-01-01

Flexibility where possible, and structure where necessary. Consider the needs of national security, safe airspace operations, economic opportunities, and emerging technologies. Risk-based approach based on population density, assets on the ground, density of operations, etc. Digital, virtual, dynamic, and as needed UTM services to manage operations.

Phase contrast in high resolution electron microscopy

DOEpatents

Rose, H.H.

1975-09-23

This patent relates to a device for developing a phase contrast signal for a scanning transmission electron microscope. The lens system of the microscope is operated in a condition of defocus so that predictable alternate concentric regions of high and low electron density exist in the cone of illumination. Two phase detectors are placed beneath the object inside the cone of illumination, with the first detector having the form of a zone plate, each of its rings covering alternate regions of either higher or lower electron density. The second detector is so configured that it covers the regions of electron density not covered by the first detector. Each detector measures the number of electrons incident thereon and the signal developed by the first detector is subtracted from the signal developed by the record detector to provide a phase contrast signal. (auth)

High field superconductors for superconducting machines

NASA Astrophysics Data System (ADS)

Rupp, G.; Wilhelm, M.; Wohlleben, K.; Ziegler, G.; Springer, E.

1980-11-01

High current capacity Nb3Sn multifilament conductors were fabricated. A solid state diffusion process was used. The number of conductor filaments approaches 70,000 with filament diameters being approximately 1.5 microns. Effective current densities reach 86,000 A/sq cm at a magnetic flux density of 10 T and operating temperature of 4.2 K. Calibrated flattened cables of twisted strands were fabricated for higher currents (up to 1000 A at 10 T). Generally, quantitative relations can be given for the rise in the critical current of Nb3Sn multifilament conductors, observed under the influence of mechanical stresses. Long lengths (km) of these conductors were used to manufacture superconducting solenoids two different ways. These rise to the short sample current, usually without conditioning, and deliver magnetic flux densities up to 14 T with an 8.5 T NbTi background field.

Numerical analysis of direct-current microdischarge for space propulsion applications using the particle-in-cell/Monte Carlo collision (PIC/MCC) method

NASA Astrophysics Data System (ADS)

Kong, Linghan; Wang, Weizong; Murphy, Anthony B.; Xia, Guangqing

2017-04-01

Microdischarges are an important type of plasma discharge that possess several unique characteristics, such as the presence of a stable glow discharge, high plasma density and intense excimer radiation, leading to several potential applications. The intense and controllable gas heating within the extremely small dimensions of microdischarges has been exploited in micro-thruster technologies by incorporating a micro-nozzle to generate the thrust. This kind of micro-thruster has a significantly improved specific impulse performance compared to conventional cold gas thrusters, and can meet the requirements arising from the emerging development and application of micro-spacecraft. In this paper, we performed a self-consistent 2D particle-in-cell simulation, with a Monte Carlo collision model, of a microdischarge operating in a prototype micro-plasma thruster with a hollow cylinder geometry and a divergent micro-nozzle. The model takes into account the thermionic electron emission including the Schottky effect, the secondary electron emission due to cathode bombardment by the plasma ions, several different collision processes, and a non-uniform argon background gas density in the cathode-anode gap. Results in the high-pressure (several hundreds of Torr), high-current (mA) operating regime showing the behavior of the plasma density, potential distribution, and energy flux towards the hollow cathode and anode are presented and discussed. In addition, the results of simulations showing the effect of different argon gas pressures, cathode material work function and discharge voltage on the operation of the microdischarge thruster are presented. Our calculated properties are compared with experimental data under similar conditions and qualitative and quantitative agreements are reached.

Remotely operable compact instruments for measuring atmospheric CO2 and CH4 column densities at surface monitoring sites

NASA Astrophysics Data System (ADS)

Kobayashi, N.; Inoue, G.; Kawasaki, M.; Yoshioka, H.; Minomura, M.; Murata, I.; Nagahama, T.; Matsumi, Y.; Tanaka, T.; Morino, I.; Ibuki, T.

2010-08-01

Remotely operable compact instruments for measuring atmospheric CO2 and CH4 column densities were developed in two independent systems: one utilizing a grating-based desktop optical spectrum analyzer (OSA) with a resolution enough to resolve rotational lines of CO2 and CH4 in the regions of 1565-1585 and 1674-1682 nm, respectively; the other is an application of an optical fiber Fabry-Perot interferometer (FFPI) to obtain the CO2 column density. Direct sunlight was collimated via a small telescope installed on a portable sun tracker and then transmitted through an optical fiber into the OSA or the FFPI for optical analysis. The near infrared spectra of the OSA were retrieved by a least squares spectral fitting algorithm. The CO2 and CH4 column densities deduced were in excellent agreement with those measured by a Fourier transform spectrometer with high resolution. The rovibronic lines in the wavelength region of 1570-1575 nm were analyzed by the FFPI. The I0 and I values in the Beer-Lambert law equation to obtain CO2 column density were deduced by modulating temperature of the FFPI, which offered column CO2 with the statistical error less than 0.2% for six hours measurement.

UF6 Density and Mass Flow Measurements for Enrichment Plants using Acoustic Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Good, Morris S.; Smith, Leon E.; Warren, Glen A.

A key enabling capability for enrichment plant safeguards being considered by the International Atomic Energy Agency (IAEA) is high-accuracy, noninvasive, unattended measurement of UF6 gas density and mass flow rate. Acoustic techniques are currently used to noninvasively monitor gas flow in industrial applications; however, the operating pressures at gaseous centrifuge enrichment plants (GCEPs) are roughly two orders magnitude below the capabilities of commercial instrumentation. Pacific Northwest National Laboratory is refining acoustic techniques for estimating density and mass flow rate of UF6 gas in scenarios typical of GCEPs, with the goal of achieving 1% measurement accuracy. Proof-of-concept laboratory measurements using amore » surrogate gas for UF6 have demonstrated signatures sensitive to gas density at low operating pressures such as 10–50 Torr, which were observed over the background acoustic interference. Current efforts involve developing a test bed for conducting acoustic measurements on flowing SF6 gas at representative flow rates and pressures to ascertain the viability of conducting gas flow measurements under these conditions. Density and flow measurements will be conducted to support the evaluation. If successful, the approach could enable an unattended, noninvasive approach to measure mass flow in unit header pipes of GCEPs.« less

Wargaming the Enemy Unmanned Aircraft System (UAS) Threat

DTIC Science & Technology

2013-01-01

and various current and future short range air defense systems. In addition, the EWF experiments had Army high altitude airship (HAA) with a...component during these experiments dealt with controlling high speed fighters operating at low altitude over the ground commander’s AO. The...JAGIC).18 “”During experimentation with JAGIC, the ACA delegated a volume of airspace, either below a coordinating altitude or within a high density

Effects of ICRF power on SOL density profiles and LH coupling during simultaneous LH and ICRF operation on Alcator C-Mod

NASA Astrophysics Data System (ADS)

Lau, C.; Lin, Y.; Wallace, G.; Wukitch, S. J.; Hanson, G. R.; Labombard, B.; Ochoukov, R.; Shiraiwa, S.; Terry, J.

2013-09-01

A dedicated experiment during simultaneous lower hybrid (LH) and ion cyclotron range-of-frequencies (ICRF) operations is carried out to evaluate and understand the effects of ICRF power on the scrape-off-layer (SOL) density profiles and on the resultant LH coupling for a wide range of plasma parameters on Alcator C-Mod. Operation of the LH launcher with the adjacent ICRF antenna significantly degrades LH coupling while operation with the ICRF antenna that is not magnetically connected to the LH launcher minimally affects LH coupling. An X-mode reflectometer system at three poloidal locations adjacent to the LH launcher and a visible video camera imaging the LH launcher are used to measure local SOL density profile and emissivity modifications with the application of LH and LH + ICRF power. These measurements confirm that the density in front of the LH launcher depends strongly on the magnetic field line mapping of the active ICRF antenna. Reflectometer measurements also observe both ICRF-driven and LH-driven poloidal density profile asymmetries, especially a strong density depletion at certain poloidal locations in front of the LH launcher during operation with a magnetically connected ICRF antenna. The results indicate that understanding both LH-driven flows and ICRF sheath driven flows may be necessary to understand the observed density profile modifications and LH coupling results during simultaneous LH + ICRF operation.

Propellant Technologies: A Persuasive Wave of Future Propulsion Benefits

NASA Technical Reports Server (NTRS)

Palaszewski, Bryan; Ianovski, Leonid S.; Carrick, Patrick

1997-01-01

Rocket propellant and propulsion technology improvements can be used to reduce the development time and operational costs of new space vehicle programs. Advanced propellant technologies can make the space vehicles safer, more operable, and higher performing. Five technology areas are described: Monopropellants, Alternative Hydrocarbons, Gelled Hydrogen, Metallized Gelled Propellants, and High Energy Density Materials. These propellants' benefits for future vehicles are outlined using mission study results and the technologies are briefly discussed.

Plasma Source Development

NASA Astrophysics Data System (ADS)

Walker, Jonathan; Heinrich, Jonathon; Font, Gabriel; Ebersohn, Frans; Garrett, Michael

2017-10-01

A 100 kW class lanthanum-hexaboride plasma source is under continuing development for the Lockheed Martin Compact Fusion Reactor program. The current experiment, T4B, has become a test bed for plasma source operation with the goal of creating a high density plasma target for neutral beam heating. We present operation and performance of different plasma source geometries, results of plasma source coupling, and future plasma source development plans. ©2017 Lockheed Martin Corporation. All Rights Reserved.

Mapping low- and high-density clouds in astrophysical nebulae by imaging forbidden line emission

NASA Astrophysics Data System (ADS)

Steiner, J. E.; Menezes, R. B.; Ricci, T. V.; Oliveira, A. S.

2009-06-01

Emission line ratios have been essential for determining physical parameters such as gas temperature and density in astrophysical gaseous nebulae. With the advent of panoramic spectroscopic devices, images of regions with emission lines related to these physical parameters can, in principle, also be produced. We show that, with observations from modern instruments, it is possible to transform images taken from density-sensitive forbidden lines into images of emission from high- and low-density clouds by applying a transformation matrix. In order to achieve this, images of the pairs of density-sensitive lines as well as the adjacent continuum have to be observed and combined. We have computed the critical densities for a series of pairs of lines in the infrared, optical, ultraviolet and X-rays bands, and calculated the pair line intensity ratios in the high- and low-density limit using a four- and five-level atom approximation. In order to illustrate the method, we applied it to Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (GMOS-IFU) data of two galactic nuclei. We conclude that this method provides new information of astrophysical interest, especially for mapping low- and high-density clouds; for this reason, we call it `the ld/hd imaging method'. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the National Science Foundation on behalf of the Gemini partnership: the National Science Foundation (United States); the Science and Technology Facilities Council (United Kingdom); the National Research Council (Canada), CONICYT (Chile); the Australian Research Council (Australia); Ministério da Ciência e Tecnologia (Brazil) and Secretaria de Ciencia y Tecnologia (Argentina). E-mail: steiner@astro.iag.usp.br

Experimental investigation of a throttlable 15 cm hollow cathode ion thruster

NASA Technical Reports Server (NTRS)

Wilbur, P. J.

1972-01-01

The use of dished high perveance grids on a 15 cm modified SERT 2 thruster is shown to facilitate throttled operation over a beam current range from 60 to 600 mA. Effects of increasing the radial component of the magnetic field in the main discharge chamber and decreasing the dimensions of the cathode discharge region are examined and found to degrade performance to the extent that primary electrons are forced in toward the center-line of the thruster. Studies of the baffle aperture region of two thrusters indicate that the electric potential gradient vector is perpendicular to the local magnetic field lines when the thruster is operating properly. The correlation between the shape of the ion beam current density and that of the ion density at the screen grid within the thruster is shown to be 94%. Additional experimental studies on maximum propellant utilization, plasma ion production cost, neutral density in the cathode discharge region, double ion production in hollow cathode thrusters and thermal flow meter performance are discussed.

A low cost, high energy density and long cycle life potassium-sulfur battery for grid-scale energy storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xiaochuan; Bowden, Mark E.; Sprenkle, Vincent L.

2015-08-15

Alkali metal-sulfur batteries are attractive for energy storage applications because of their high energy density. Among the batteries, lithium-sulfur batteries typically use liquid in the battery electrolyte, which causes problems in both performance and safety. Sodium-sulfur batteries can use a solid electrolyte such as beta alumina but this requires a high operating temperature. Here we report a novel potassium-sulfur battery with K+-conducting beta-alumina as the electrolyte. Our studies indicate that liquid potassium exhibits much better wettability on the surface of beta-alumina compared to liquid sodium at lower temperatures. Based on this observation, we develop a potassium-sulfur battery that can operatemore » at as low as 150°C with excellent performance. In particular, the battery shows excellent cycle life with negligible capacity fade in 1000 cycles because of the dense ceramic membrane. This study demonstrates a new battery with a high energy density, long cycle life, low cost and high safety, which is ideal for grid-scale energy storage.« less

Nanoscale cross-point diode array accessing embedded high density PCM

NASA Astrophysics Data System (ADS)

Wang, Heng; Liu, Yan; Liu, Bo; Gao, Dan; Xu, Zhen; Zhan, Yipeng; Song, Zhitang; Feng, Songlin

2017-08-01

The main bottlenecks in the development of current embedded phase change memory (PCM) technology are the current density and data storage density. In this paper, we present a PCM with 4F2 cross-point diode selector and blade-type bottom electrode contact (BEC). A blade TiN BEC with a cross-sectional area of 630 nm2 (10 nm × 63 nm) reduces the reset current down to about 750 μA. The optimized diode array could supply this 750 μA reset current at about 1.7 V and low off-current 1 × 10-4 μA at about -5.05 V. The on-off ratio of this device is 7.5 × 106. The proposed nanoscale PCM device simultaneously exhibits an operation voltage as low as 3 V and a high density drive current with an ultra small cell size of 4F2 (108 nm × 108 nm). Over 106 cycling endurance properties guarantee that it can work effectively on the embedded memory.

High-temperature, high-power-density thermionic energy conversion for space

NASA Technical Reports Server (NTRS)

Morris, J. F.

1977-01-01

Theoretic converter outputs and efficiencies indicate the need to consider thermionic energy conversion (TEC) with greater power densities and higher temperatures within reasonable limits for space missions. Converter-output power density, voltage, and efficiency as functions of current density were determined for 1400-to-2000 K emitters with 725-to-1000 K collectors. The results encourage utilization of TEC with hotter-than-1650 K emitters and greater-than-6W sq cm outputs to attain better efficiencies, greater voltages, and higher waste-heat-rejection temperatures for multihundred-kilowatt space-power applications. For example, 1800 K, 30 A sq cm TEC operation for NEP compared with the 1650 K, 5 A/sq cm case should allow much lower radiation weights, substantially fewer and/or smaller emitter heat pipes, significantly reduced reactor and shield-related weights, many fewer converters and associated current-collecting bus bars, less power conditioning, and lower transmission losses. Integration of these effects should yield considerably reduced NEP specific weights.

Monolithic microchannel heatsink

DOEpatents

Benett, W.J.; Beach, R.J.; Ciarlo, D.R.

1996-08-20

A silicon wafer has slots sawn in it that allow diode laser bars to be mounted in contact with the silicon. Microchannels are etched into the back of the wafer to provide cooling of the diode bars. To facilitate getting the channels close to the diode bars, the channels are rotated from an angle perpendicular to the diode bars which allows increased penetration between the mounted diode bars. This invention enables the fabrication of monolithic silicon microchannel heatsinks for laser diodes. The heatsinks have low thermal resistance because of the close proximity of the microchannels to the laser diode being cooled. This allows high average power operation of two-dimensional laser diode arrays that have a high density of laser diode bars and therefore high optical power density. 9 figs.

Monolithic microchannel heatsink

DOEpatents

Benett, William J.; Beach, Raymond J.; Ciarlo, Dino R.

1996-01-01

A silicon wafer has slots sawn in it that allow diode laser bars to be mounted in contact with the silicon. Microchannels are etched into the back of the wafer to provide cooling of the diode bars. To facilitate getting the channels close to the diode bars, the channels are rotated from an angle perpendicular to the diode bars which allows increased penetration between the mounted diode bars. This invention enables the fabrication of monolithic silicon microchannel heatsinks for laser diodes. The heatsinks have low thermal resistance because of the close proximity of the microchannels to the laser diode being cooled. This allows high average power operation of two-dimensional laser diode arrays that have a high density of laser diode bars and therefore high optical power density.

Molecular Electronic Angular Motion Transducer Broad Band Self-Noise.

PubMed

Zaitsev, Dmitry; Agafonov, Vadim; Egorov, Egor; Antonov, Alexander; Shabalina, Anna

2015-11-20

Modern molecular electronic transfer (MET) angular motion sensors combine high technical characteristics with low cost. Self-noise is one of the key characteristics which determine applications for MET sensors. However, until the present there has not been a model describing the sensor noise in the complete operating frequency range. The present work reports the results of an experimental study of the self-noise level of such sensors in the frequency range of 0.01-200 Hz. Based on the experimental data, a theoretical model is developed. According to the model, self-noise is conditioned by thermal hydrodynamic fluctuations of the operating fluid flow in the frequency range of 0.01-2 Hz. At the frequency range of 2-100 Hz, the noise power spectral density has a specific inversely proportional dependence of the power spectral density on the frequency that could be attributed to convective processes. In the high frequency range of 100-200 Hz, the noise is conditioned by the voltage noise of the electronics module input stage operational amplifiers and is heavily reliant to the sensor electrical impedance. The presented results allow a deeper understanding of the molecular electronic sensor noise nature to suggest the ways to reduce it.

Giant magnetoresistive sensor

DOEpatents

Stearns, Daniel G.; Vernon, Stephen P.; Ceglio, Natale M.; Hawryluk, Andrew M.

1999-01-01

A magnetoresistive sensor element with a three-dimensional micro-architecture is capable of significantly improved sensitivity and highly localized measurement of magnetic fields. The sensor is formed of a multilayer film of alternately magnetic and nonmagnetic materials. The sensor is optimally operated in a current perpendicular to plane mode. The sensor is useful in magnetic read/write heads, for high density magnetic information storage and retrieval.

75 FR 61770 - Notice of Availability of the Final Programmatic Environmental Assessment and Finding of No...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-06

... inspection technology that is used to scan high-density cargo containers for contraband such as illicit drugs... DEPARTMENT OF HOMELAND SECURITY U.S. Customs and Border Protection Notice of Availability of the... Operation of High Energy X-Ray Inspection Systems at Sea and Land Ports of Entry AGENCY: U.S. Customs and...

High-rate composting-vermicomposting of water hyacinth (Eichhornia crassipes, Mart. Solms).

PubMed

Gajalakshmi, S; Ramasamy, E V; Abbasi, S A

2002-07-01

In an attempt to develop a system with which the aquatic weed water hyacinth (Eichhornia crassipes, Mart. Solms) can be economically processed to generate vermicompost in large quantities, the weed was first composted by a 'high-rate' method and then subjected to vermicomposting in reactors operating at much larger densities of earthworm than recommended hitherto: 50, 62.5, 75, 87.5, 100, 112.5, 125, 137.5, and 150 adults of Eudrilus eugeniae Kinberg per litre of digester volume. The composting step was accomplished in 20 days and the composted weed was found to be vermicomposted three times as rapidly as uncomposted water hyacinth [Bioresource Technology 76 (2001) 177]. The studies substantiated the feasibility of high-rate composting-vermicomposting systems, as all reactors yielded consistent vermicast output during seven months of operation. There was no earthworm mortality during the first four months in spite of the high animal densities in the reactors. In the subsequent three months a total of 79 worms died out of 1650, representing less than 1.6% mortality per month. The results also indicated that an increase in the surface-to-volume ratio of the reactors might further improve their efficiency.

U2 8 + -intensity record applying a H2 -gas stripper cell

NASA Astrophysics Data System (ADS)

Barth, Winfried; Adonin, Aleksey; Düllmann, Christoph E.; Heilmann, Manuel; Hollinger, Ralph; Jäger, Egon; Khuyagbaatar, Jadambaa; Krier, Joerg; Scharrer, Paul; Vormann, Hartmut; Yakushev, Alexander

2015-04-01

To meet the Facility for Antiproton and Ion Research science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. For this an advanced upgrade program for the UNILAC is ongoing. Stripping is a key technology for all heavy ion accelerators. For this an extensive research and development program was carried out to optimize for high brilliance heavy ion operation. After upgrade of the supersonic N2 -gas jet (2007), implementation of high current foil stripping (2011) and preliminary investigation of H2 -gas jet operation (2012), recently (2014) a new H2 -gas cell using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An obviously enhanced stripper gas density as well as a simultaneously reduced gas load for the pumping system result in an increased stripping efficiency, while the beam emittance remains the same. A new record intensity (7.8 emA) for 238U2 8 + beams at 1.4 MeV /u has been achieved applying the pulsed high density H2 stripper target to a high intensity 238U4 + beam from the VARIS ion source with a newly developed extraction system. The experimental results are presented in detail.

PFISR GPS tracking mode for researching high-latitude ionospheric electron density gradients associated with GPS scintillation

NASA Astrophysics Data System (ADS)

Loucks, D. C.; Palo, S. E.; Pilinski, M.; Crowley, G.; Azeem, S. I.; Hampton, D. L.

2016-12-01

Ionospheric behavior in the high-latitudes can significantly impact Ultra High Frequency (UHF) signals in the 300 MHz to 3 GHz band, resulting in degradation of Global Positioning System (GPS) position solutions and satellite communications interruptions. To address these operational concerns, a need arises to identify and understand the ionospheric structure that leads to disturbed conditions in the Arctic. Structures in the high-latitude ionosphere are known to change on the order of seconds or less, can be decameters to kilometers in scale, and elongate across magnetic field lines at auroral latitudes. Nominal operations at Poker Flat Incoherent Scatter Radar (PFISR) give temporal resolution on the order of minutes, and range resolution on the order of tens of kilometers, while specialized GPS receivers available for ionospheric sensing have a 100Hz observation sampling rate. One of these, ASTRA's Connected Autonomous Space Environment Sensor (CASES) is used for this study. We have developed a new GPS scintillation tracking mode for PFISR to address open scientific questions regarding temporal and spatial electron density gradients. The mode will be described, a number of experimental campaigns will be analyzed, and results and lessons learned will be presented.

14 CFR 93.130 - Suspension of allocations.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Suspension of allocations. 93.130 Section 93.130 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93...

14 CFR 93.130 - Suspension of allocations.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 2 2012-01-01 2012-01-01 false Suspension of allocations. 93.130 Section 93.130 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93...

14 CFR 93.130 - Suspension of allocations.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Suspension of allocations. 93.130 Section 93.130 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93...

14 CFR 93.130 - Suspension of allocations.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 2 2014-01-01 2014-01-01 false Suspension of allocations. 93.130 Section 93.130 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93...

14 CFR 93.130 - Suspension of allocations.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 14 Aeronautics and Space 2 2013-01-01 2013-01-01 false Suspension of allocations. 93.130 Section 93.130 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIR TRAFFIC AND GENERAL OPERATING RULES SPECIAL AIR TRAFFIC RULES High Density Traffic Airports § 93...

Ultracompliant Heterogeneous Copper-Tin Nanowire Arrays Making a Supersolder.

PubMed

Gong, Wei; Li, Pengfei; Zhang, Yunheng; Feng, Xuhui; Major, Joshua; DeVoto, Douglas; Paret, Paul; King, Charles; Narumanchi, Sreekant; Shen, Sheng

2018-06-13

Due to the substantial increase in power density, thermal interface resistance that can constitute more than 50% of the total thermal resistance has generally become a bottleneck for thermal management in electronics. However, conventional thermal interface materials (TIMs) such as solder, epoxy, gel, and grease cannot fulfill the requirements of electronics for high-power and long-term operation. Here, we demonstrate a high-performance TIM consisting of a heterogeneous copper-tin nanowire array, which we term "supersolder" to emulate the role of conventional solders in bonding various surfaces. The supersolder is ultracompliant with a shear modulus 2-3 orders of magnitude lower than traditional solders and can reduce the thermal resistance by two times as compared with the state-of-the-art TIMs. This supersolder also exhibits excellent long-term reliability with >1200 thermal cycles over a wide temperature range. By resolving this critical thermal bottleneck, the supersolder enables electronic systems, ranging from microelectronics and portable electronics to massive data centers, to operate at lower temperatures with higher power density and reliability.

Very high-current-density Nb/AlN/Nb tunnel junctions for low-noise submillimeter mixers

NASA Astrophysics Data System (ADS)

Kawamura, Jonathan; Miller, David; Chen, Jian; Zmuidzinas, Jonas; Bumble, Bruce; LeDuc, Henry G.; Stern, Jeff A.

2000-04-01

We have fabricated and tested submillimeter-wave superconductor-insulator-superconductor (SIS) mixers using very high-current-density Nb/AlN/Nb tunnel junctions (Jc≈30 kA cm-2). The junctions have low-resistance-area products (RNA≈5.6 Ω μm2), good subgap-to-normal resistance ratios Rsg/RN≈10, and good run-to-run reproducibility. From Fourier transform spectrometer measurements, we infer that ωRNC=1 at 270 GHz. This is a factor of 2.5 improvement over what is generally available with Nb/AlOx/Nb junctions suitable for low-noise mixers. The AlN-barrier junctions are indeed capable of low-noise operation: we measure an uncorrected double-sideband receiver noise temperature of TRX=110 K at 533 GHz for an unoptimized device. In addition to providing wider bandwidth operation at lower frequencies, the AlN-barrier junctions will considerably improve the performance of THz SIS mixers by reducing rf loss in the tuning circuits.

Coordinated Control of Cross-Flow Turbines

NASA Astrophysics Data System (ADS)

Strom, Benjamin; Brunton, Steven; Polagye, Brian

2016-11-01

Cross-flow turbines, also known as vertical-axis turbines, have several advantages over axial-flow turbines for a number of applications including urban wind power, high-density arrays, and marine or fluvial currents. By controlling the angular velocity applied to the turbine as a function of angular blade position, we have demonstrated a 79 percent increase in cross-flow turbine efficiency over constant-velocity control. This strategy uses the downhill simplex method to optimize control parameter profiles during operation of a model turbine in a recirculating water flume. This optimization method is extended to a set of two turbines, where the blade motions and position of the downstream turbine are optimized to beneficially interact with the coherent structures in the wake of the upstream turbine. This control scheme has the potential to enable high-density arrays of cross-flow turbines to operate at cost-effective efficiency. Turbine wake and force measurements are analyzed for insight into the effect of a coordinated control strategy.

Measurements of crossed-field demagnetisation rate of trapped field magnets at high frequencies and below 77 K

NASA Astrophysics Data System (ADS)

Baskys, A.; Patel, A.; Glowacki, B. A.

2018-06-01

Design requirements of the next generation of electric aircraft place stringent requirements on the power density required from electric motors. A future prototype planned in the scope of the European project ‘Advanced Superconducting Motor Experimental Demonstrator’ (ASuMED) considers a permanent magnet synchronous motor, where the conventional ferromagnets are replaced with superconducting trapped field magnets, which promise higher flux densities and thus higher output power without adding weight. Previous work has indicated that stacks of tape show lower cross-field demagnetisation rates to bulk (RE)BCO whilst retaining similar performance for their size, however the crossed-field demagnetisation rate has not been studied in the temperature, the magnetic field and frequency range that are relevant for the operational prototype motor. This work investigates crossed-field demagnetisation in 2G high temperature superconducting stacks at temperatures below 77 K and a frequency range above 10 Hz. This information is crucial in developing designs and determining operational time before re-magnetisation could be required.

A Concept for Robust, High Density Terminal Air Traffic Operations

NASA Technical Reports Server (NTRS)

Isaacson, Douglas R.; Robinson, John E.; Swenson, Harry N.; Denery, Dallas G.

2010-01-01

This paper describes a concept for future high-density, terminal air traffic operations that has been developed by interpreting the Joint Planning and Development Office s vision for the Next Generation (NextGen) Air Transportation System and coupling it with emergent NASA and other technologies and procedures during the NextGen timeframe. The concept described in this paper includes five core capabilities: 1) Extended Terminal Area Routing, 2) Precision Scheduling Along Routes, 3) Merging and Spacing, 4) Tactical Separation, and 5) Off-Nominal Recovery. Gradual changes are introduced to the National Airspace System (NAS) by phased enhancements to the core capabilities in the form of increased levels of automation and decision support as well as targeted task delegation. NASA will be evaluating these conceptual technological enhancements in a series of human-in-the-loop simulations and will accelerate development of the most promising capabilities in cooperation with the FAA through the Efficient Flows Into Congested Airspace Research Transition Team.

Multiple-relaxation-time color-gradient lattice Boltzmann model for simulating two-phase flows with high density ratio

NASA Astrophysics Data System (ADS)

Ba, Yan; Liu, Haihu; Li, Qing; Kang, Qinjun; Sun, Jinju

2016-08-01

In this paper we propose a color-gradient lattice Boltzmann (LB) model for simulating two-phase flows with high density ratio and high Reynolds number. The model applies a multirelaxation-time (MRT) collision operator to enhance the stability of the simulation. A source term, which is derived by the Chapman-Enskog analysis, is added into the MRT LB equation so that the Navier-Stokes equations can be exactly recovered. Also, a form of the equilibrium density distribution function is used to simplify the source term. To validate the proposed model, steady flows of a static droplet and the layered channel flow are first simulated with density ratios up to 1000. Small values of spurious velocities and interfacial tension errors are found in the static droplet test, and improved profiles of velocity are obtained by the present model in simulating channel flows. Then, two cases of unsteady flows, Rayleigh-Taylor instability and droplet splashing on a thin film, are simulated. In the former case, the density ratio of 3 and Reynolds numbers of 256 and 2048 are considered. The interface shapes and spike and bubble positions are in good agreement with the results of previous studies. In the latter case, the droplet spreading radius is found to obey the power law proposed in previous studies for the density ratio of 100 and Reynolds number up to 500.

20 years of research on the Alcator C-Mod tokamaka)

NASA Astrophysics Data System (ADS)

Greenwald, M.; Bader, A.; Baek, S.; Bakhtiari, M.; Barnard, H.; Beck, W.; Bergerson, W.; Bespamyatnov, I.; Bonoli, P.; Brower, D.; Brunner, D.; Burke, W.; Candy, J.; Churchill, M.; Cziegler, I.; Diallo, A.; Dominguez, A.; Duval, B.; Edlund, E.; Ennever, P.; Ernst, D.; Faust, I.; Fiore, C.; Fredian, T.; Garcia, O.; Gao, C.; Goetz, J.; Golfinopoulos, T.; Granetz, R.; Grulke, O.; Hartwig, Z.; Horne, S.; Howard, N.; Hubbard, A.; Hughes, J.; Hutchinson, I.; Irby, J.; Izzo, V.; Kessel, C.; LaBombard, B.; Lau, C.; Li, C.; Lin, Y.; Lipschultz, B.; Loarte, A.; Marmar, E.; Mazurenko, A.; McCracken, G.; McDermott, R.; Meneghini, O.; Mikkelsen, D.; Mossessian, D.; Mumgaard, R.; Myra, J.; Nelson-Melby, E.; Ochoukov, R.; Olynyk, G.; Parker, R.; Pitcher, S.; Podpaly, Y.; Porkolab, M.; Reinke, M.; Rice, J.; Rowan, W.; Schmidt, A.; Scott, S.; Shiraiwa, S.; Sierchio, J.; Smick, N.; Snipes, J. A.; Snyder, P.; Sorbom, B.; Stillerman, J.; Sung, C.; Takase, Y.; Tang, V.; Terry, J.; Terry, D.; Theiler, C.; Tronchin-James, A.; Tsujii, N.; Vieira, R.; Walk, J.; Wallace, G.; White, A.; Whyte, D.; Wilson, J.; Wolfe, S.; Wright, G.; Wright, J.; Wukitch, S.; Zweben, S.

2014-11-01

The object of this review is to summarize the achievements of research on the Alcator C-Mod tokamak [Hutchinson et al., Phys. Plasmas 1, 1511 (1994) and Marmar, Fusion Sci. Technol. 51, 261 (2007)] and to place that research in the context of the quest for practical fusion energy. C-Mod is a compact, high-field tokamak, whose unique design and operating parameters have produced a wealth of new and important results since it began operation in 1993, contributing data that extends tests of critical physical models into new parameter ranges and into new regimes. Using only high-power radio frequency (RF) waves for heating and current drive with innovative launching structures, C-Mod operates routinely at reactor level power densities and achieves plasma pressures higher than any other toroidal confinement device. C-Mod spearheaded the development of the vertical-target divertor and has always operated with high-Z metal plasma facing components—approaches subsequently adopted for ITER. C-Mod has made ground-breaking discoveries in divertor physics and plasma-material interactions at reactor-like power and particle fluxes and elucidated the critical role of cross-field transport in divertor operation, edge flows and the tokamak density limit. C-Mod developed the I-mode and the Enhanced Dα H-mode regimes, which have high performance without large edge localized modes and with pedestal transport self-regulated by short-wavelength electromagnetic waves. C-Mod has carried out pioneering studies of intrinsic rotation and demonstrated that self-generated flow shear can be strong enough in some cases to significantly modify transport. C-Mod made the first quantitative link between the pedestal temperature and the H-mode's performance, showing that the observed self-similar temperature profiles were consistent with critical-gradient-length theories and followed up with quantitative tests of nonlinear gyrokinetic models. RF research highlights include direct experimental observation of ion cyclotron range of frequency (ICRF) mode-conversion, ICRF flow drive, demonstration of lower-hybrid current drive at ITER-like densities and fields and, using a set of novel diagnostics, extensive validation of advanced RF codes. Disruption studies on C-Mod provided the first observation of non-axisymmetric halo currents and non-axisymmetric radiation in mitigated disruptions. A summary of important achievements and discoveries are included.

Cell size, genome size and the dominance of Angiosperms

NASA Astrophysics Data System (ADS)

Simonin, K. A.; Roddy, A. B.

2016-12-01

Angiosperms are capable of maintaining the highest rates of photosynthetic gas exchange of all land plants. High rates of photosynthesis depends mechanistically both on efficiently transporting water to the sites of evaporation in the leaf and on regulating the loss of that water to the atmosphere as CO2 diffuses into the leaf. Angiosperm leaves are unique in their ability to sustain high fluxes of liquid and vapor phase water transport due to high vein densities and numerous, small stomata. Despite the ubiquity of studies characterizing the anatomical and physiological adaptations that enable angiosperms to maintain high rates of photosynthesis, the underlying mechanism explaining why they have been able to develop such high leaf vein densities, and such small and abundant stomata, is still incomplete. Here we ask whether the scaling of genome size and cell size places a fundamental constraint on the photosynthetic metabolism of land plants, and whether genome downsizing among the angiosperms directly contributed to their greater potential and realized primary productivity relative to the other major groups of terrestrial plants. Using previously published data we show that a single relationship can predict guard cell size from genome size across the major groups of terrestrial land plants (e.g. angiosperms, conifers, cycads and ferns). Similarly, a strong positive correlation exists between genome size and both stomatal density and vein density that together ultimately constrains maximum potential (gs, max) and operational stomatal conductance (gs, op). Further the difference in the slopes describing the covariation between genome size and both gs, max and gs, op suggests that genome downsizing brings gs, op closer to gs, max. Taken together the data presented here suggests that the smaller genomes of angiosperms allow their final cell sizes to vary more widely and respond more directly to environmental conditions and in doing so bring operational photosynthetic metabolism closer to maximum potential photosynthesis.EndFragment

Two-step hydrothermal synthesis of NiCo2S4/Co9S8 nanorods on nickel foam for high energy density asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Xu, Rui; Lin, Jianming; Wu, Jihuai; Huang, Miaoliang; Fan, Leqing; Chen, Hongwei; He, Xin; Wang, Yiting; Xu, Zedong

2018-03-01

It is still a huge challenge to obtain a high-energy-density asymmetric supercapacitors and develop an active electrode material with excellent electrochemical characteristics. Although NiCo2S4 has been considered as one of the promising positive electrode materials for asymmetric supercapacitors, the electrochemical performance of the NiCo2S4-based positive electrodes is still relatively low and cannot meet the demand in the devices. Herein, NiCo2S4/Co9S8 nanorods with a large capacitance are synthesized via a simple two-step hydrothermal treatment. A high-performance asymmetric supercapacitor operating at 1.6 V is successfully assembled using the NiCo2S4/Co9S8 nanorods as positive electrode and activated carbon as negative electrode in 3 M KOH aqueous electrolyte, which demonstrates a fairly high energy density of 49.6 Wh kg-1 at a power density of 123 W kg-1, an excellent capacitance of 0.91 F cm-2 (139.42 F g-1) at current density of 1 mA cm-2 as well as a remarkable cycling stability due to the high physical strength, the large specific surface area, and the good conductivity for NiCo2S4/Co9S8 nanorods and the brilliant synergistic effect for NiCo2S4 and Co9S8 electrode materials. The as-prepared NiCo2S4/Co9S8 nanorods open up a new platform as positive electrode material for high-energy-density asymmetric supercapacitors in energy-storage.

Summary and Evaluation of the Strategic Defense Initiative Space Power Architecture Study

DTIC Science & Technology

1989-03-01

coolant as fuel) and operates at high efficiency . It was also lower in vibration and dynamic effects than the combustion turbine. The fuel cell ...achievable with development. The main question with fuel cells is — can both high power density and high efficiency be achieved simultaneously? In...energy in a flywheel, fuel cell (power an electrolyzer) or battery. High power for weapon burst is obtained by discharging the storage device over a

A Nuclear Cryogenic Propulsion Stage for Near-Term Space Missions

NASA Technical Reports Server (NTRS)

Houts, Michael G.; Kim, Tony; Emrich, William J.; Hickman, Robert R.; Broadway, Jeramie W.; Gerrish, Harold P.; Doughty, Glen E.; Adams, Robert B.; Bechtel, Ryan D.; Borowski, Stanley K.;

Energy Navigation: Simulation Evaluation and Benefit Analysis

NASA Technical Reports Server (NTRS)

Williams, David H.; Oseguera-Lohr, Rosa M.; Lewis, Elliot T.

2011-01-01

This paper presents results from two simulation studies investigating the use of advanced flight-deck-based energy navigation (ENAV) and conventional transport-category vertical navigation (VNAV) for conducting a descent through a busy terminal area, using Continuous Descent Arrival (CDA) procedures. This research was part of the Low Noise Flight Procedures (LNFP) element within the Quiet Aircraft Technology (QAT) Project, and the subsequent Airspace Super Density Operations (ASDO) research focus area of the Airspace Project. A piloted simulation study addressed development of flight guidance, and supporting pilot and Air Traffic Control (ATC) procedures for high density terminal operations. The procedures and charts were designed to be easy to understand, and to make it easy for the crew to make changes via the Flight Management Computer Control-Display Unit (FMC-CDU) to accommodate changes from ATC.

Twenty barrel in situ pipe gun type solid hydrogen pellet injector for the Large Helical Device.

PubMed

Sakamoto, Ryuichi; Motojima, Gen; Hayashi, Hiromi; Inoue, Tomoyuki; Ito, Yasuhiko; Ogawa, Hideki; Takami, Shigeyuki; Yokota, Mitsuhiro; Yamada, Hiroshi

2013-08-01

A 20 barrel solid hydrogen pellet injector, which is able to inject 20 cylindrical pellets with a diameter and length of between 3.0 and 3.8 mm at the velocity of 1200 m/s, has been developed for the purpose of direct core fueling in LHD (Large Helical Device). The in situ pipe gun concept with the use of compact cryo-coolers enables stable operation as a fundamental facility in plasma experiments. The combination of the two types of pellet injection timing control modes, i.e., pre-programing mode and real-time control mode, allows the build-up and sustainment of high density plasma around the density limit. The pellet injector has demonstrated stable operation characteristics during the past three years of LHD experiments.

Operator pencil passing through a given operator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biggs, A., E-mail: khudian@manchester.ac.uk, E-mail: adam.biggs@student.manchester.ac.uk; Khudaverdian, H. M., E-mail: khudian@manchester.ac.uk, E-mail: adam.biggs@student.manchester.ac.uk

Let Δ be a linear differential operator acting on the space of densities of a given weight λ{sub 0} on a manifold M. One can consider a pencil of operators Π-circumflex(Δ)=(Δ{sub λ}) passing through the operator Δ such that any Δ{sub λ} is a linear differential operator acting on densities of weight λ. This pencil can be identified with a linear differential operator Δ-circumflex acting on the algebra of densities of all weights. The existence of an invariant scalar product in the algebra of densities implies a natural decomposition of operators, i.e., pencils of self-adjoint and anti-self-adjoint operators. We studymore » lifting maps that are on one hand equivariant with respect to divergenceless vector fields, and, on the other hand, with values in self-adjoint or anti-self-adjoint operators. In particular, we analyze the relation between these two concepts, and apply it to the study of diff (M)-equivariant liftings. Finally, we briefly consider the case of liftings equivariant with respect to the algebra of projective transformations and describe all regular self-adjoint and anti-self-adjoint liftings. Our constructions can be considered as a generalisation of equivariant quantisation.« less

Density Functional Methods for Shock Physics and High Energy Density Science

NASA Astrophysics Data System (ADS)

Desjarlais, Michael

2017-06-01

Molecular dynamics with density functional theory has emerged over the last two decades as a powerful and accurate framework for calculating thermodynamic and transport properties with broad application to dynamic compression, high energy density science, and warm dense matter. These calculations have been extensively validated against shock and ramp wave experiments, are a principal component of high-fidelity equation of state generation, and are having wide-ranging impacts on inertial confinement fusion, planetary science, and shock physics research. In addition to thermodynamic properties, phase boundaries, and the equation of state, one also has access to electrical conductivity, thermal conductivity, and lower energy optical properties. Importantly, all these properties are obtained within the same theoretical framework and are manifestly consistent. In this talk I will give a brief history and overview of molecular dynamics with density functional theory and its use in calculating a wide variety of thermodynamic and transport properties for materials ranging from ambient to extreme conditions and with comparisons to experimental data. I will also discuss some of the limitations and difficulties, as well as active research areas. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Preventing Raman Lasing in High-Q WGM Resonators

NASA Technical Reports Server (NTRS)

Savchenkov, Anatoliy; Matsko, Andrey; Strekalov, Dmitry; Maleki, Lute

2007-01-01

A generic design has been conceived to suppress the Raman effect in whispering- gallery-mode (WGM) optical resonators that have high values of the resonance quality factor (Q). Although it is possible to exploit the Raman effect (even striving to maximize the Raman gain to obtain Raman lasing), the present innovation is intended to satisfy a need that arises in applications in which the Raman effect inhibits the realization of the full potential of WGM resonators as frequency-selection components. Heretofore, in such applications, it has been necessary to operate high-Q WGM resonators at unattractively low power levels to prevent Raman lasing. (The Raman-lasing thresholds of WGM optical resonators are very low and are approximately proportional to Q(sup -2)). Heretofore, two ways of preventing Raman lasting at high power levels have been known, but both entail significant disadvantages: A resonator can be designed so that the optical field is spread over a relatively large mode volume to bring the power density below the threshold. For any given combination of Q and power level, there is certain mode volume wherein Raman lasing does not start. Unfortunately, a resonator that has a large mode volume also has a high spectral density, which is undesirable in a typical photonic application. A resonator can be cooled to the temperature of liquid helium, where the Raman spectrum is narrower and, therefore, the Raman gain is lower. However, liquid-helium cooling is inconvenient. The present design overcomes these disadvantages, making it possible to operate a low-spectral-density (even a single-mode) WGM resonator at a relatively high power level at room temperature, without risk of Raman lasing.

Phage-Bacterial Dynamics with Spatial Structure: Self Organization around Phage Sinks Can Promote Increased Cell Densities

PubMed Central

Bull, James J.; Christensen, Kelly A.; Scott, Carly; Crandall, Cameron J.; Krone, Stephen M.

2018-01-01

Bacteria growing on surfaces appear to be profoundly more resistant to control by lytic bacteriophages than do the same cells grown in liquid. Here, we use simulation models to investigate whether spatial structure per se can account for this increased cell density in the presence of phages. A measure is derived for comparing cell densities between growth in spatially structured environments versus well mixed environments (known as mass action). Maintenance of sensitive cells requires some form of phage death; we invoke death mechanisms that are spatially fixed, as if produced by cells. Spatially structured phage death provides cells with a means of protection that can boost cell densities an order of magnitude above that attained under mass action, although the effect is sometimes in the opposite direction. Phage and bacteria self organize into separate refuges, and spatial structure operates so that the phage progeny from a single burst do not have independent fates (as they do with mass action). Phage incur a high loss when invading protected areas that have high cell densities, resulting in greater protection for the cells. By the same metric, mass action dynamics either show no sustained bacterial elevation or oscillate between states of low and high cell densities and an elevated average. The elevated cell densities observed in models with spatial structure do not approach the empirically observed increased density of cells in structured environments with phages (which can be many orders of magnitude), so the empirical phenomenon likely requires additional mechanisms than those analyzed here. PMID:29382134

Multibit Polycristalline Silicon-Oxide-Silicon Nitride-Oxide-Silicon Memory Cells with High Density Designed Utilizing a Separated Control Gate

NASA Astrophysics Data System (ADS)

Rok Kim, Kyeong; You, Joo Hyung; Dal Kwack, Kae; Kim, Tae Whan

2010-10-01

Unique multibit NAND polycrystalline silicon-oxide-silicon nitride-oxide-silicon (SONOS) memory cells utilizing a separated control gate (SCG) were designed to increase memory density. The proposed NAND SONOS memory device based on a SCG structure was operated as two bits, resulting in an increase in the storage density of the NVM devices in comparison with conventional single-bit memories. The electrical properties of the SONOS memory cells with a SCG were investigated to clarify the charging effects in the SONOS memory cells. When the program voltage was supplied to each gate of the NAND SONOS flash memory cells, the electrons were trapped in the nitride region of the oxide-nitride-oxide layer under the gate to supply the program voltage. The electrons were accumulated without affecting the other gate during the programming operation, indicating the absence of cross-talk between two trap charge regions. It is expected that the inference effect will be suppressed by the lower program voltage than the program voltage of the conventional NAND flash memory. The simulation results indicate that the proposed unique NAND SONOS memory cells with a SCG can be used to increase memory density.

Plasma characteristics of direct current enhanced cylindrical inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Yue, HUA; Jian, SONG; Zeyu, HAO; Chunsheng, REN

2018-06-01

Experimental results of a direct current enhanced inductively coupled plasma (DCE-ICP) source which consists of a typical cylindrical ICP source and a plate-to-grid DC electrode are reported. With the use of this new source, the plasma characteristic parameters, namely, electron density, electron temperature and plasma uniformity, are measured by Langmuir floating double probe. It is found that DC discharge enhances the electron density and decreases the electron temperature, dramatically. Moreover, the plasma uniformity is obviously improved with the operation of DC and radio frequency (RF) hybrid discharge. Furthermore, the nonlinear enhancement effect of electron density with DC + RF hybrid discharge is confirmed. The presented observation indicates that the DCE-ICP source provides an effective method to obtain high-density uniform plasma, which is desirable for practical industrial applications.

Unmanned Aerial Systems Traffic Management (UTM): Safely Enabling UAS Operations in Low-Altitude Airspace

NASA Technical Reports Server (NTRS)

Jung, Jaewoo; Kopardekar, Parimal H.

2016-01-01

Flexibility where possible, and structure where necessary. Consider the needs of national security, safe airspace operations, economic opportunities, and emerging technologies. Risk-based approach based on population density, assets on the ground, density of operations, etc. Digital, virtual, dynamic, and as needed UTM services to manage operations.

Unmanned Aerial Systems Traffic Management (UTM): Safely Enabling UAS Operations in Low-Altitude Airspace

NASA Technical Reports Server (NTRS)

Kopardekar, Parimal H.; Cavolowsky, John

2015-01-01

Flexibility where possible, and structure where necessary. Consider the needs of national security, safe airspace operations, economic opportunities, and emerging technologies. Risk-based approach based on population density, assets on the ground, density of operations, etc. Digital, virtual, dynamic, and as needed UTM services to manage operations.

Dissipation of ‘dark energy’ by cortex in knowledge retrieval

NASA Astrophysics Data System (ADS)

Capolupo, Antonio; Freeman, Walter J.; Vitiello, Giuseppe

2013-03-01

We have devised a thermodynamic model of cortical neurodynamics expressed at the classical level by neural networks and at the quantum level by dissipative quantum field theory. Our model is based on features in the spatial images of cortical activity newly revealed by high-density electrode arrays. We have incorporated the mechanism and necessity for so-called dark energy in knowledge retrieval. We have extended the model first using the Carnot cycle to define our measures for energy, entropy and temperature, and then using the Rankine cycle to incorporate criticality and phase transitions. We describe the dynamics of two interactive fields of neural activity that express knowledge, one at high and the other at low energy density, and the two operators that create and annihilate the fields. We postulate that the extremely high density of energy sequestered briefly in cortical activity patterns can account for the vividness, richness of associations, and emotional intensity of memories recalled by stimuli.

Dissipation of 'dark energy' by cortex in knowledge retrieval.

PubMed

Capolupo, Antonio; Freeman, Walter J; Vitiello, Giuseppe

2013-03-01

We have devised a thermodynamic model of cortical neurodynamics expressed at the classical level by neural networks and at the quantum level by dissipative quantum field theory. Our model is based on features in the spatial images of cortical activity newly revealed by high-density electrode arrays. We have incorporated the mechanism and necessity for so-called dark energy in knowledge retrieval. We have extended the model first using the Carnot cycle to define our measures for energy, entropy and temperature, and then using the Rankine cycle to incorporate criticality and phase transitions. We describe the dynamics of two interactive fields of neural activity that express knowledge, one at high and the other at low energy density, and the two operators that create and annihilate the fields. We postulate that the extremely high density of energy sequestered briefly in cortical activity patterns can account for the vividness, richness of associations, and emotional intensity of memories recalled by stimuli. Copyright © 2013 Elsevier B.V. All rights reserved.

High energy density aluminum-oxygen cell

NASA Technical Reports Server (NTRS)

Rudd, E. J.; Gibbons, D. W.

1993-01-01

An alternative to a secondary battery as the power source for vehicle propulsion is a fuel cell. An example of this is the metal-air fuel cell using metals such as aluminum, zinc, or iron. Aluminum is a particularly attractive candidate, having high energy and power densities, being environmentally acceptable, and having a large, established industrial base for production and distribution. An aluminum-oxygen system is currently under development for a UUV test vehicle, and recent work has focussed upon low corrosion aluminum alloys and an electrolyte management system for processing the by-products of the energy-producing reactions. This paper summarizes the progress made in both areas. Anode materials capable of providing high utilization factors over current densities ranging from S to 150 mA/sq cm have been identified. These materials are essential to realizing an acceptable mission life for the UUV. With respect to the electrolyte management system, a filter/precipitator unit has been successfully operated for over 250 hours in a large scale, half-cell system.

A modified thermal conductivity for low density plasma magnetic flux tubes

NASA Technical Reports Server (NTRS)

Comfort, R. H.; Craven, P. D.; Richards, P. G.

1995-01-01

In response to inconsistencies which have arisen in results from a hydrodynamic model in simulation of high ion temperature (1-2 eV) observed in low density, outer plasmasphere flux tubes, we postulate a reduced thermal conductivity coefficient in which only particles in the loss cone of the quasi-collisionless plasma contribute to the thermal conduction. Other particles are assumed to magnetically mirror before they reach the topside ionosphere and therefore not to remove thermal energy from the plasmasphere. This concept is used to formulate a mathematically simple, but physically limiting model for a modified thermal conductivity coefficient. When this modified coefficient is employed in the hydrodynamic model in a case study, the inconsistencies between simulation results and observations are largely resolved. The high simulated ion temperatures are achieved with significantly lower ion temperatures in the topside ionosphere. We suggest that this mechanism may be operative under the limited low density, refilling conditions in which high ion temperatures are observed.

Impact of membrane characteristics on the performance and cycling of the Br₂–H₂ redox flow cell

DOE PAGES

Tucker, Michael C.; Cho, Kyu Taek; Spingler, Franz B.; ...

2015-03-04

The Br₂/H₂ redox flow cell shows promise as a high-power, low-cost energy storage device. In this paper, the effect of various aspects of material selection and processing of proton exchange membranes on the operation of the Br₂/H₂ redox flow cell is determined. Membrane properties have a significant impact on the performance and efficiency of the system. In particular, there is a tradeoff between conductivity and crossover, where conductivity limits system efficiency at high current density and crossover limits efficiency at low current density. The impact of thickness, pretreatment procedure, swelling state during cell assembly, equivalent weight, membrane reinforcement, and additionmore » of a microporous separator layer on this tradeoff is assessed. NR212 (50 μm) pretreated by soaking in 70 °C water is found to be optimal for the studied operating conditions. For this case, an energy efficiency of greater than 75% is achieved for current density up to 400 mA cm⁻², with a maximum obtainable energy efficiency of 88%. A cell with this membrane was cycled continuously for 3164 h. Membrane transport properties, including conductivity and bromine and water crossover, were found to decrease moderately upon cycling but remained higher than those for the as-received membrane.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saperstein, E. E., E-mail: saper@mbslab.kiae.ru; Tolokonnikov, S. V.

Recent results obtained on the basis of the self-consistent theory of finite Fermi systems by employing the energy density functional proposed by Fayans and his coauthors are surveyed. These results are compared with the predictions of Skyrme–Hartree–Fock theory involving several popular versions of the Skyrme energy density functional. Spherical nuclei are predominantly considered. The charge radii of even and odd nuclei and features of low-lying 2{sup +} excitations in semimagic nuclei are discussed briefly. The single-particle energies ofmagic nuclei are examined inmore detail with allowance for corrections to mean-field theory that are induced by particle coupling to low-lying collective surfacemore » excitations (phonons). The importance of taking into account, in this problem, nonpole (tadpole) diagrams, which are usually disregarded, is emphasized. The spectroscopic factors of magic and semimagic nuclei are also considered. In this problem, only the surface term stemming from the energy dependence induced in the mass operator by the exchange of surface phonons is usually taken into account. The volume contribution associated with the energy dependence initially present in the mass operator within the self-consistent theory of finite Fermi systems because of the exchange of high-lying particle–hole excitations is also included in the spectroscopic factor. The results of the first studies that employed the Fayans energy density functional for deformed nuclei are also presented.« less

Design of Iron(II) Phthalocyanine-Derived Oxygen Reduction Electrocatalysts for High-Power-Density Microbial Fuel Cells.

PubMed

Santoro, Carlo; Gokhale, Rohan; Mecheri, Barbara; D'Epifanio, Alessandra; Licoccia, Silvia; Serov, Alexey; Artyushkova, Kateryna; Atanassov, Plamen

2017-08-24

Iron(II) phthalocyanine (FePc) deposited onto two different carbonaceous supports was synthesized through an unconventional pyrolysis-free method. The obtained materials were studied in the oxygen reduction reaction (ORR) in neutral media through incorporation in an air-breathing cathode structure and tested in an operating microbial fuel cell (MFC) configuration. Rotating ring disk electrode (RRDE) analysis revealed high performances of the Fe-based catalysts compared with that of activated carbon (AC). The FePc supported on Black-Pearl carbon black [Fe-BP(N)] exhibits the highest performance in terms of its more positive onset potential, positive shift of the half-wave potential, and higher limiting current as well as the highest power density in the operating MFC of (243±7) μW cm -2 , which was 33 % higher than that of FePc supported on nitrogen-doped carbon nanotubes (Fe-CNT(N); 182±5 μW cm -2 ). The power density generated by Fe-BP(N) was 92 % higher than that of the MFC utilizing AC; therefore, the utilization of platinum group metal-free catalysts can boost the performances of MFCs significantly. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of membrane electrode assembly for high temperature proton exchange membrane fuel cell by catalyst coating membrane method

NASA Astrophysics Data System (ADS)

Liang, Huagen; Su, Huaneng; Pollet, Bruno G.; Pasupathi, Sivakumar

2015-08-01

Membrane electrode assembly (MEA), which contains cathode and anode catalytic layer, gas diffusion layers (GDL) and electrolyte membrane, is the key unit of a PEMFC. An attempt to develop MEA for ABPBI membrane based high temperature (HT) PEMFC is conducted in this work by catalyst coating membrane (CCM) method. The structure and performance of the MEA are examined by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and I-V curve. Effects of the CCM preparation method, Pt loading and binder type are investigated for the optimization of the single cell performance. Under 160 °C and atmospheric pressure, the peak power density of the MEA, with Pt loading of 0.5 mg cm-2 and 0.3 mg cm-2 for the cathode and the anode, can reach 277 mW cm-2, while a current density of 620 A cm-2 is delivered at the working voltage of 0.4 V. The MEA prepared by CCM method shows good stability operating in a short term durability test: the cell voltage maintained at ∼0.45 V without obvious drop when operated at a constant current density of 300 mA cm-2 and 160 °C under ambient pressure for 140 h.