Operando Positron Annihilation Gamma Spectrometer (OPAGS)

NASA Astrophysics Data System (ADS)

Satyal, S.; Shastry, K.; Mukherjee, S.; Weiss, A. H.

2009-03-01

Surface properties measured under UHV conditions cannot be extended to surfaces interacting with gases under realistic pressures due to surface reconstruction and other strong perturbations of the surface. Surface probing techniques require UHV conditions to perform efficiently and avoid data loss due to scattering of outgoing particles. This poster describes the design of an Operando Positron Annihilation Gamma Spectrometer (OPAGS) currently under construction at the University of Texas at Arlington. The new system will be capable of obtaining surface and defect specific chemical and charge state information from surfaces under realistic pressures. Differential pumping will be used to maintain the sample in a gas environment while the rest of the beam is under UHV. Elemental content of the surface interacting with the gas environment will be determined from the Doppler broadened gamma spectra. This system will also include a time of flight (TOF) Auger spectrometer which correlates with the results of the Doppler measurements at lower pressures. By employing the unique capabilities of OPAGS together with those of the TOF PAES spectroscopy the charge transfer mechanisms at the surface in catalytic systems can be understood.

Design of an Operando Positron Annihilation Gamma Spectrometer (OPAGS)

NASA Astrophysics Data System (ADS)

Satyal, Suman; Shastry, Kartik; Kalaskar, Sushant; Lim, Larry; Joglekar, Vibek; Weiss, Alexander

2009-10-01

Surface properties measured under UHV conditions cannot be extended to surfaces interacting with gases under realistic pressures due to surface reconstruction and other strong perturbations of the surface. Many surface probing techniques used till now have required UHV conditions to avoid data loss due to scattering of outgoing particles. Here we describe the design of an Operando Positron Annihilation Gamma Spectrometer (OPAGS) currently under construction at the University of Texas at Arlington. The new system will be capable of obtaining surface and defect specific chemical and charge state information from surfaces under realistic pressures. Differential pumping will be used to maintain the sample in a gas environment while the rest of the beam is under UHV. The Elemental content of the surface interacting with the gas environment will be determined from the Doppler broadened gamma spectra. This system will also include a time of flight (TOF) positron annihilation induced Auger spectrometer (TOF-PAES) for use in combined annihilation induced Auger and annihilation gamma measurements made under low pressure conditions.

Method for producing an atomic oxygen beam

NASA Technical Reports Server (NTRS)

Outlaw, Ronald A. (Inventor)

1989-01-01

A method for producing an atomic oxygen beam is provided by the present invention. First, a material 10' is provided which dissociates molecular oxygen and dissolves atomic oxygen into its bulk. Next, molecular oxygen is exposed to entrance surface 11' of material 10'. Next, material 10' is heated by heater 17' to facilitate the permeation of atomic oxygen through material 10' to the UHV side 12'. UHV side 12' is interfaced with an ultra-high vacuum (UHV) environment provided by UHV pump 15'. The atomic oxygen on the UHV side 12' is excited to a non-binding state by exciter 14' thus producing the release of atomic oxygen to form an atomic oxygen beam 35'.

Full membrane spanning self-assembled monolayers as model systems for UHV-based studies of cell-penetrating peptides

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

Franz, Johannes; Graham, Daniel J.; Schmüser, Lars

2015-03-01

Biophysical studies of the interaction of peptides with model membranes provide a simple yet effective approach to understand the transport of peptides and peptide based drug carriers across the cell membrane. Therein, the authors discuss the use of self-assembled monolayers fabricated from the full membrane-spanning thiol (FMST) 3-((14-((4'-((5-methyl-1-phenyl-35-(phytanyl)oxy-6,9,12,15,18,21,24,27,30,33,37-undecaoxa-2,3-dithiahenpentacontan-51-yl)oxy)-[1,1'-biphenyl]-4-yl)oxy)tetradecyl)oxy)-2-(phytanyl)oxy glycerol for ultrahigh vacuum (UHV) based experiments. UHV-based methods such as electron spectroscopy and mass spectrometry can provide important information about how peptides bind and interact with membranes, especially with the hydrophobic core of a lipid bilayer. Moreover, near-edge x-ray absorption fine structure spectra and x-ray photoelectron spectroscopy (XPS) data showed thatmore » FMST forms UHV-stable and ordered films on gold. XPS and time of flight secondary ion mass spectrometry depth profiles indicated that a proline-rich amphipathic cell-penetrating peptide, known as sweet arrow peptide is located at the outer perimeter of the model membrane.« less

The research of full automatic oil filtering control technology of high voltage insulating oil

NASA Astrophysics Data System (ADS)

Gong, Gangjun; Zhang, Tong; Yan, Guozeng; Zhang, Han; Chen, Zhimin; Su, Chang

2017-09-01

In this paper, the design scheme of automatic oil filter control system for transformer oil in UHV substation is summarized. The scheme specifically includes the typical double tank filter connection control method of the transformer oil of the UHV substation, which distinguishes the single port and the double port connection structure of the oil tank. Finally, the design scheme of the temperature sensor and respirator is given in detail, and the detailed evaluation and application scenarios are given for reference.

An advanced molecule-surface scattering instrument for study of vibrational energy transfer in gas-solid collisions.

PubMed

Ran, Qin; Matsiev, Daniel; Wodtke, Alec M; Auerbach, Daniel J

2007-10-01

We describe an advanced and highly sensitive instrument for quantum state-resolved molecule-surface energy transfer studies under ultrahigh vacuum (UHV) conditions. The apparatus includes a beam source chamber, two differential pumping chambers, and a UHV chamber for surface preparation, surface characterization, and molecular beam scattering. Pulsed and collimated supersonic molecular beams are generated by expanding target molecule mixtures through a home-built pulsed nozzle, and excited quantum state-selected molecules were prepared via tunable, narrow-band laser overtone pumping. Detection systems have been designed to measure specific vibrational-rotational state, time-of-flight, angular and velocity distributions of molecular beams coming to and scattered off the surface. Facilities are provided to clean and characterize the surface under UHV conditions. Initial experiments on the scattering of HCl(v = 0) from Au(111) show many advantages of this new instrument for fundamental studies of the energy transfer at the gas-surface interface.

Alumina-supported sub-nanometer Pt 10 clusters: Amorphization and role of the support material in a highly active CO oxidation catalyst

DOE PAGES

Yin, Chunrong; Negreiros, Fabio R.; Barcaro, Giovanni; ...

2017-02-03

Catalytic CO oxidation is unveiled on size-selected Pt 10 clusters deposited on two very different ultrathin (≈0.5–0.7 nm thick) alumina films: (i) a highly ordered alumina obtained under ultra-high vacuum (UHV) by oxidation of the NiAl(110) surface and (ii) amorphous alumina obtained by atomic layer deposition (ALD) on a silicon chip that is a close model of real-world supports. Notably, when exposed to realistic reaction conditions, the Pt 10/UHV-alumina system undergoes a morphological transition in both the clusters and the substrate, and becomes closely akin to Pt 10/ALD-alumina, thus reconciling UHV-type surface-science and real-world experiments. The Pt 10 clusters, thoroughlymore » characterized via combined experimental techniques and theoretical analysis, exhibit among the highest CO oxidation activity per Pt atom reported for CO oxidation catalysts, due to the interplay of ultra-small size and support effects. Lastly, a coherent interdisciplinary picture then emerges for this catalytic system.« less

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions

NASA Astrophysics Data System (ADS)

Syed Mohd, A.; Pütter, S.; Mattauch, S.; Koutsioubas, A.; Schneider, H.; Weber, A.; Brückel, T.

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å-1. The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions.

PubMed

Syed Mohd, A; Pütter, S; Mattauch, S; Koutsioubas, A; Schneider, H; Weber, A; Brückel, T

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å -1 . The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

Combined UHV/high-pressure catalysis setup for depth-resolved near-surface spectroscopic characterization and catalytic testing of model catalysts

NASA Astrophysics Data System (ADS)

Mayr, Lukas; Rameshan, Raffael; Klötzer, Bernhard; Penner, Simon; Rameshan, Christoph

2014-05-01

An ultra-high vacuum (UHV) setup for "real" and "inverse" model catalyst preparation, depth-resolved near-surface spectroscopic characterization, and quantification of catalytic activity and selectivity under technologically relevant conditions is described. Due to the all-quartz reactor attached directly to the UHV-chamber, transfer of the catalyst for in situ testing without intermediate contact to the ambient is possible. The design of the UHV-compatible re-circulating batch reactor setup allows the study of reaction kinetics under close to technically relevant catalytic conditions up to 1273 K without contact to metallic surfaces except those of the catalyst itself. With the attached differentially pumped exchangeable evaporators and the quartz-microbalance thickness monitoring equipment, a reproducible, versatile, and standardised sample preparation is possible. For three-dimensional near-surface sample characterization, the system is equipped with a hemispherical analyser for X-ray photoelectron spectroscopy (XPS), electron-beam or X-ray-excited Auger-electron spectroscopy, and low-energy ion scattering measurements. Due the dedicated geometry of the X-ray gun (54.7°, "magic angle") and the rotatable sample holder, depth analysis by angle-resolved XPS measurements can be performed. Thus, by the combination of characterisation methods with different information depths, a detailed three-dimensional picture of the electronic and geometric structure of the model catalyst can be obtained. To demonstrate the capability of the described system, comparative results for depth-resolved sample characterization and catalytic testing in methanol steam reforming on PdGa and PdZn near-surface intermetallic phases are shown.

Portable ultrahigh-vacuum sample storage system for polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy

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

Watanabe, Yoshihide, E-mail: e0827@mosk.tytlabs.co.jp; Nishimura, Yusaku F.; Suzuki, Ryo

A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was demonstratedmore » by a successful PTRF-XAFS study of Pt{sub 4} clusters deposited on a TiO{sub 2}(110) surface.« less

Highly hydrogen-sensitive thermal desorption spectroscopy system for quantitative analysis of low hydrogen concentration (˜1 × 1016 atoms/cm3) in thin-film samples

NASA Astrophysics Data System (ADS)

Hanna, Taku; Hiramatsu, Hidenori; Sakaguchi, Isao; Hosono, Hideo

2017-05-01

We developed a highly hydrogen-sensitive thermal desorption spectroscopy (HHS-TDS) system to detect and quantitatively analyze low hydrogen concentrations in thin films. The system was connected to an in situ sample-transfer chamber system, manipulators, and an rf magnetron sputtering thin-film deposition chamber under an ultra-high-vacuum (UHV) atmosphere of ˜10-8 Pa. The following key requirements were proposed in developing the HHS-TDS: (i) a low hydrogen residual partial pressure, (ii) a low hydrogen exhaust velocity, and (iii) minimization of hydrogen thermal desorption except from the bulk region of the thin films. To satisfy these requirements, appropriate materials and components were selected, and the system was constructed to extract the maximum performance from each component. Consequently, ˜2000 times higher sensitivity to hydrogen than that of a commercially available UHV-TDS system was achieved using H+-implanted Si samples. Quantitative analysis of an amorphous oxide semiconductor InGaZnO4 thin film (1 cm × 1 cm × 1 μm thickness, hydrogen concentration of 4.5 × 1017 atoms/cm3) was demonstrated using the HHS-TDS system. This concentration level cannot be detected using UHV-TDS or secondary ion mass spectroscopy (SIMS) systems. The hydrogen detection limit of the HHS-TDS system was estimated to be ˜1 × 1016 atoms/cm3, which implies ˜2 orders of magnitude higher sensitivity than that of SIMS and resonance nuclear reaction systems (˜1018 atoms/cm3).

Study of Residual Gas Analyser (RGA) Response towards Known Leaks

NASA Astrophysics Data System (ADS)

Pathan, Firozkhan S.; Khan, Ziauddin; Semwal, Pratibha; George, Siju; Raval, Dilip C.; Thankey, Prashant L.; Manthena, Himabindu; Yuvakiran, Paravastu; Dhanani, Kalpesh R.

2012-11-01

Helium leak testing is the most versatile form of weld qualification test for any vacuum application. Almost every ultra-high vacuum (UHV) system utilizes this technique for insuring leak tightness for the weld joints as well as demountable joints. During UHV system under operational condition with many other integrated components, in-situ developed leaks identification becomes one of the prime aspect for maintaining the health of such system and for continuing the experiments onwards. Since online utilization of leak detector (LD) has many practical limitations, residual gas analyser (RGA) can be used as a potential instrument for online leak detection. For this purpose, a co-relation for a given leak rate between Leak Detector and RGA is experimentally established. This paper describes the experimental aspect and the relationship between leak detector and RGA.

Surface science approach to Pt/carbon model catalysts: XPS, STM and microreactor studies

NASA Astrophysics Data System (ADS)

Motin, Abdul Md.; Haunold, Thomas; Bukhtiyarov, Andrey V.; Bera, Abhijit; Rameshan, Christoph; Rupprechter, Günther

2018-05-01

Pt nanoparticles supported on carbon are an important technological catalyst. A corresponding model catalyst was prepared by physical vapor deposition (PVD) of Pt on sputtered HOPG (highly oriented pyrolytic graphite). The carbon substrate before and after sputtering as well as the Pt/HOPG system before and after Pt deposition and annealing were examined by XPS and STM. This yielded information on the surface density of defects, which serve as nucleation centres for Pt, and on the size distribution (mean size/height) of the Pt nanoparticles. Two different model catalysts were prepared with mean sizes of 2.0 and 3.6 nm, both turned out to be stable upon UHV-annealing to 300 °C. After transfer into a UHV-compatible flow microreactor and subsequent cleaning in UHV and under mbar pressure, the catalytic activity of the Pt/HOPG model system for ethylene hydrogenation was examined under atmospheric pressure flow conditions. This enabled to determine temperature-dependent conversion rates, turnover frequencies (TOFs) and activation energies. The catalytic results obtained are in line with the characteristics of technological Pt/C, demonstrating the validity of the current surface science based model catalyst approach.

An ultra-high vacuum scanning tunneling microscope operating at sub-Kelvin temperatures and high magnetic fields for spin-resolved measurements

NASA Astrophysics Data System (ADS)

Salazar, C.; Baumann, D.; Hänke, T.; Scheffler, M.; Kühne, T.; Kaiser, M.; Voigtländer, R.; Lindackers, D.; Büchner, B.; Hess, C.

2018-06-01

We present the construction and performance of an ultra-low-temperature scanning tunneling microscope (STM), working in ultra-high vacuum (UHV) conditions and in high magnetic fields up to 9 T. The cryogenic environment of the STM is generated by a single-shot 3He magnet cryostat in combination with a 4He dewar system. At a base temperature (300 mK), the cryostat has an operation time of approximately 80 h. The special design of the microscope allows the transfer of the STM head from the cryostat to a UHV chamber system, where samples and STM tips can be easily exchanged. The UHV chambers are equipped with specific surface science treatment tools for the functionalization of samples and tips, including high-temperature treatments and thin film deposition. This, in particular, enables spin-resolved tunneling measurements. We present test measurements using well-known samples and tips based on superconductors and metallic materials such as LiFeAs, Nb, Fe, and W. The measurements demonstrate the outstanding performance of the STM with high spatial and energy resolution as well as the spin-resolved capability.

A diamond-based scanning probe spin sensor operating at low temperature in ultra-high vacuum

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

Schaefer-Nolte, E.; Wrachtrup, J.; 3rd Institute of Physics and Research Center SCoPE, University Stuttgart, 70569 Stuttgart

2014-01-15

We present the design and performance of an ultra-high vacuum (UHV) low temperature scanning probe microscope employing the nitrogen-vacancy color center in diamond as an ultrasensitive magnetic field sensor. Using this center as an atomic-size scanning probe has enabled imaging of nanoscale magnetic fields and single spins under ambient conditions. In this article we describe an experimental setup to operate this sensor in a cryogenic UHV environment. This will extend the applicability to a variety of molecular systems due to the enhanced target spin lifetimes at low temperature and the controlled sample preparation under UHV conditions. The instrument combines amore » tuning-fork based atomic force microscope (AFM) with a high numeric aperture confocal microscope and the facilities for application of radio-frequency (RF) fields for spin manipulation. We verify a sample temperature of <50 K even for strong laser and RF excitation and demonstrate magnetic resonance imaging with a magnetic AFM tip.« less

Uhv compatible chopper system

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

Voss, D.E.; Cohen, S.A.

1979-11-01

A time-of-flight system utilizing a novel mechanical chopper has been developed to measure the energy spectrum of neutral deuterium atoms emitted from a tokamak plasma. The chopper system consists of a motor, a magnetically levitated shaft, and a chopper disc. The 20 g disc is rigidly attached to a 159 g shaft assembly and the set is supported against gravity in vacuum by permanent magnets and a stabilizing servo system. All components are uhv compatible to avoid contamination to the tokamak and to the detector. The 25.4 cm OD, .005 cm thick, 301 stainless steel chopper disc has 24 .025more » cm wide slots photoetched at an 11.4 cm radius. An effective aperture time of .55 ..mu..s is achieved during typical steady state operation at 22,500 rpm with a vacuum pressure of 2 x 10/sup -8/ torr.« less

A cryogen-free low temperature scanning tunneling microscope capable of inelastic electron tunneling spectroscopy.

PubMed

Zhang, Shuai; Huang, Di; Wu, Shiwei

2016-06-01

The design and performance of a cryogen-free low temperature scanning tunneling microscope (STM) housed in ultrahigh vacuum (UHV) are reported. The cryogen-free design was done by directly integrating a Gifford-McMahon cycle cryocooler to a Besocke-type STM, and the vibration isolation was achieved by using a two-stage rubber bellow between the cryocooler and a UHV-STM interface with helium exchange gas cooling. A base temperature of 15 K at the STM was achieved, with a possibility to further decrease by using a cryocooler with higher cooling power and adding additional low temperature stage under the exchange gas interface. Atomically sharp STM images and high resolution dI/dV spectra on various samples were demonstrated. Furthermore, we reported the inelastic tunneling spectroscopy on a single carbon monoxide molecule adsorbed on Ag(110) surface with a cryogen-free STM for the first time. Being totally cryogen-free, the system not only saves the running cost significantly but also enables uninterrupted data acquisitions and variable temperature measurements with much ease. In addition, the system is capable of coupling light to the STM junction by a pair of lens inside the UHV chamber. We expect that these enhanced capabilities could further broaden our views to the atomic-scale world.

A cryogen-free low temperature scanning tunneling microscope capable of inelastic electron tunneling spectroscopy

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

Zhang, Shuai; Huang, Di; Wu, Shiwei, E-mail: swwu@fudan.edu.cn

The design and performance of a cryogen-free low temperature scanning tunneling microscope (STM) housed in ultrahigh vacuum (UHV) are reported. The cryogen-free design was done by directly integrating a Gifford-McMahon cycle cryocooler to a Besocke-type STM, and the vibration isolation was achieved by using a two-stage rubber bellow between the cryocooler and a UHV-STM interface with helium exchange gas cooling. A base temperature of 15 K at the STM was achieved, with a possibility to further decrease by using a cryocooler with higher cooling power and adding additional low temperature stage under the exchange gas interface. Atomically sharp STM imagesmore » and high resolution dI/dV spectra on various samples were demonstrated. Furthermore, we reported the inelastic tunneling spectroscopy on a single carbon monoxide molecule adsorbed on Ag(110) surface with a cryogen-free STM for the first time. Being totally cryogen-free, the system not only saves the running cost significantly but also enables uninterrupted data acquisitions and variable temperature measurements with much ease. In addition, the system is capable of coupling light to the STM junction by a pair of lens inside the UHV chamber. We expect that these enhanced capabilities could further broaden our views to the atomic-scale world.« less

An ultrahigh vacuum multipurpose specimen chamber with sample introduction system for in situ transmission electron microscopy investigations

NASA Technical Reports Server (NTRS)

Heinemann, K.; Poppa, H.

1986-01-01

A commercial transmission electron microscope (TEM), with flat-plate upper pole piece configuration of the objective lens, and top-entry specimen introduction was modified by introducing an ultrahigh vacuum (UHV) specimen chamber for in situ TEM experimentation. The pumping and design principles and special features of this UHV chamber, which makes it possible to obtain 5 x 10 to the -10th mbar pressure at the site of the specimen, while maintaining the airlock system that allows operation in the 10 to the -10th mbar range within 15 min after specimen change, are described. Design operating pressures and image quality (resolution of metal particles smaller than 1 nm in size) were achieved. Schematic drawings and design dimensions are included.

Ultrahigh Vacuum Scanning Tunneling Microscopy and Spectroscopy of Single-Walled Carbon Nanotubes Interfaced with Silicon Surfaces

NASA Astrophysics Data System (ADS)

Albrecht, Peter; Lyding, Joseph

2008-03-01

The UHV-STM was used to examine SWNTs directly interfaced with hydrogen-passivated Si(100). Dry contact transfer (DCT) [1] enabled the UHV deposition of SWNTs with minimal disruption of the atomically flat Si(100)-2x1:H surface. Isolated, rather than bundled, SWNTs could be routinely located for atomically resolved imaging, tunneling I-V spectroscopy [2], lateral manipulation [3], and proximal substrate modification. Weakly adsorbed SWNTs initially unstable in the presence of the rastered STM tip could be stabilized by depassivating the underlying H-Si(100) surface via UHV-STM electron-stimulated H desorption [4], which in the case of one chiral semiconducting SWNT also promoted the local alignment of the zigzag symmetry direction on the underside of the tube with the clean Si dimer rows [5]. The growing body of first-principles simulations of the SWNT/Si(100) system [6] was drawn upon in our interpretation of such local perturbations. [1] APL 83, 5029 (2003). [2] Nanotechnology 18, 095204 (2007). [3] Small 3, 146 (2007). [4] Nanotechnology 18, 125302 (2007). [5] Small 3, 1402 (2007). [6] JAP 100, 124304 (2006).

Ultrahigh-viscosity hydroxypropylmethylcellulose blunts postprandial glucose after a breakfast meal in women.

PubMed

Dow, Shireen; Pritchett, Kelly L; Hawk, Susan; Herrington, Stefanie J; Gee, David L

2012-04-01

To determine the effects of two water-soluble dietary fibers, ultrahigh-viscosity hydroxypropylmethylcellulose (UHV-HPMC, nonfermentable) and psyllium fiber (fermentable), on postprandial glucose and second meal effects. In a single-blind crossover design, 12 healthy adult subjects were given standardized, premeasured breakfast and lunch meals with either 4 g of the fiber supplements or a placebo. Blood glucose was measured with a continuous blood glucose monitoring system (DexCom Seven Plus, San Diego, CA). Subjects consuming UHV-HPMC had significantly (p < 0.05) lower blood glucose area under the curve (AUC) 2 hours after breakfast than those receiving a placebo. Subjects consuming psyllium also tended to have lower glucose levels than the placebo group. Peak glucose concentration following breakfast was significantly (p < 0.01) less with UHV-HPMC when compared with the placebo. No significant differences in AUC or peak glucose concentration between treatments following the second meal (lunch) were detected, suggesting no residual effect from the fiber supplements. Supplementation with viscous water-soluble fibers may be an effective means of reducing the glycemic response of a meal in healthy adults.

The Nickel(111)/Alkaline Electrolyte Interface

NASA Technical Reports Server (NTRS)

Wang, Kuilong; Chottiner, G. S.; Scherson, D. A.; Reid, Margaret A.

1991-01-01

The electrochemical properties of Ni (111) prepared and characterized in ultra high vacuum, UHV, by surface analytical techniques have been examined in alkaline media by cyclic voltammetry using an UHV-electrochemical cell transfer system designed and built in this laboratory. Prior to the transfer, the Ni(111) surfaces were exposed to saturation coverages of CO in UHV in an attempt to protect the surface from possible contamination with other gases during the transfer. Temperature Programmed Desorption, TPD, of CO-dosed Ni (111) surfaces displaying sharp c(4x2), LEED patterns, subsequently exposed to water-saturated Ar at atmospheric pressure in an auxiliary UHV compatible chamber and finally transferred back to the main UHV chamber, yielded CO2 and water as the only detectable products. This indicates that the CO-dosed surfaces react with water and/or bicarbonate and hydroxide as the most likely products. Based on the integration of the TPD peaks, the combined amounts of H2O and CO2 were found to be on the order of a single monolayer. The reacted c(4x2)CO/Ni(111) layer seems to protect the surface from undergoing spontaneous oxidation in strongly alkaline solutions. This was evidenced by the fact that the open circuit potential observed immediately after contact with deaerated 0.1 M KOH was about 0.38 V vs. DHE, drifting slightly towards more negative values prior to initiating the voltametric scans. The average ratio of the integrated charge obtained in the first positive linear scan in the range of 0.35 to 1.5 V vs. DHE (initiated at the open circuit potential) and the first (and subsequent) linear negative scans in the same solution yielded for various independent runs a value of 3.5 +/- 0.3. Coulometric analysis of the cyclic voltammetry curves indicate that the electrochemically formed oxyhydroxide layer involves a charge equivalent to 3.2 +/- 0.4 layers of Ni metal.

Development of New Low Temperature Systems at Janis Research

NASA Astrophysics Data System (ADS)

Shvarts, V.; Jirmanus, M. N.; Zhao, Z.

2006-09-01

A new line of ultra low loss He-3 and He-4 superconducting magnet systems and UHV compatible He-3 systems for scanning tunneling microscopy studies have been developed during the past year. This paper discusses the details of the design and performance for the various systems.

System to measure accurate temperature dependence of electric conductivity down to 20 K in ultrahigh vacuum.

PubMed

Sakai, C; Takeda, S N; Daimon, H

2013-07-01

We have developed the new in situ electrical-conductivity measurement system which can be operated in ultrahigh vacuum (UHV) with accurate temperature measurement down to 20 K. This system is mainly composed of a new sample-holder fixing mechanism, a new movable conductivity-measurement mechanism, a cryostat, and two receptors for sample- and four-probe holders. Sample-holder is pushed strongly against the receptor, which is connected to a cryostat, by using this new sample-holder fixing mechanism to obtain high thermal conductivity. Test pieces on the sample-holders have been cooled down to about 20 K using this fixing mechanism, although they were cooled down to only about 60 K without this mechanism. Four probes are able to be touched to a sample surface using this new movable conductivity-measurement mechanism for measuring electrical conductivity after making film on substrates or obtaining clean surfaces by cleavage, flashing, and so on. Accurate temperature measurement is possible since the sample can be transferred with a thermocouple and∕or diode being attached directly to the sample. A single crystal of Bi-based copper oxide high-Tc superconductor (HTSC) was cleaved in UHV to obtain clean surface, and its superconducting critical temperature has been successfully measured in situ. The importance of in situ measurement of resistance in UHV was demonstrated for this HTSC before and after cesium (Cs) adsorption on its surface. The Tc onset increase and the Tc offset decrease by Cs adsorption were observed.

A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum

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

Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.

2016-04-26

A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond timescale in ultrahigh vacuum (UHV). Details of the design, implementation and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ~1010 K/s for temperature increases of ~100 – 200 K are obtained. Subsequent rapid cooling (~5 × 109more » K/s) quenches the film, permitting in-situ, post-mortem analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ~ ± 3% leading to a temperature uncertainty of ~ ± 5 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.« less

A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum.

PubMed

Xu, Yuntao; Dibble, Collin J; Petrik, Nikolay G; Smith, R Scott; Joly, Alan G; Tonkyn, Russell G; Kay, Bruce D; Kimmel, Greg A

2016-04-28

A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ∼10(10) K/s for temperature increases of ∼100-200 K are obtained. Subsequent rapid cooling (∼5 × 10(9) K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ∼±2.7% leading to a temperature uncertainty of ∼±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.

Surface Structure of TiO2 Rutile (011) Exposed to Liquid Water

PubMed Central

2017-01-01

The rutile TiO2(011) surface exhibits a (2 × 1) reconstruction when prepared by standard techniques in ultrahigh vacuum (UHV). Here we report that a restructuring occurs upon exposing the surface to liquid water at room temperature. The experiment was performed in a dedicated UHV system, equipped for direct and clean transfer of samples between UHV and liquid environment. After exposure to liquid water, an overlayer with a (2 × 1) symmetry was observed containing two dissociated water molecules per unit cell. The two OH groups yield an apparent “c(2 × 1)” symmetry in scanning tunneling microscopy (STM) images. On the basis of STM analysis and density functional theory (DFT) calculations, this overlayer is attributed to dissociated water on top of the unreconstructed (1 × 1) surface. Investigation of possible adsorption structures and analysis of the domain boundaries in this structure provide strong evidence that the original (2 × 1) reconstruction is lifted. Unlike the (2 × 1) reconstruction, the (1 × 1) surface has an appropriate density and symmetry of adsorption sites. The possibility of contaminant-induced restructuring was excluded based on X-ray photoelectron spectroscopy (XPS) and low-energy He+ ion scattering (LEIS) measurements. PMID:29285204

Performance analysis of microcomputer based differential protection of UHV lines under selective phase switching

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

Bhatti, A.A.

1990-04-01

This paper examines the effects of primary and secondary fault quantities as well s of mutual couplings of neighboring circuits on the sensitivity of operation and threshold settings of a microcomputer based differential protection of UHV lines under selective phase switching. Microcomputer based selective phase switching allows the disconnection of minimum number of phases involved in a fault and requires the autoreclosing of these phases immediately after the extinction of secondary arc. During a primary fault a heavy current contribution to the healthy phases tends to cause an unwanted tripping. Faulty phases physically disconnected constitute an isolated fault which beingmore » coupled to the system affects the current and voltage levels of the healthy phases still retained in the system and may cause an unwanted tripping. The microcomputer based differential protection, appears to have poor performance when applied to uncompensated lines employing selective pole switching.« less

High pressure reaction cell and transfer mechanism for ultrahigh vacuum spectroscopic chambers

NASA Astrophysics Data System (ADS)

Nelson, A. E.; Schulz, K. H.

2000-06-01

A novel high pressure reaction cell and sample transfer mechanism for ultrahigh vacuum (UHV) spectroscopic chambers is described. The design employs a unique modification of a commercial load-lock transfer system to emulate a tractable microreactor. The reaction cell has an operating pressure range of <1×10-4 to 1000 Torr and can be evacuated to UHV conditions to enable sample transfer into the spectroscopic chamber. Additionally, a newly designed sample holder equipped with electrical and thermocouple contacts is described. The sample holder is capable of resistive specimen heating to 400 and 800 °C with current requirements of 14 A (2 V) and 25 A (3.5 V), respectively. The design enables thorough material science characterization of catalytic reactions and the surface chemistry of catalytic materials without exposing the specimen to atmospheric contaminants. The system is constructed primarily from readily available commercial equipment allowing its rapid implementation into existing laboratories.

Design of an Operando Positron Annihilation Gamma Spectrometer (OPAGS)

NASA Astrophysics Data System (ADS)

Satyal, S.; Joglekar, P.; Kalaskar, S.; Shastry, K.; Weiss, A. H.

2010-03-01

Surface properties measured under UHV conditions cannot be extended to surfaces interacting with gases under realistic pressures due to surface reconstruction and other strong perturbations of the surface. We present the design of an Operando Positron Annihilation Gamma Spectrometer (OPAGS) currently under construction at the University of Texas at Arlington. This new system will enable us to probe the surface and gather defect specific chemical and charge state information from surfaces under realistic pressures. Differential pumping will be used to maintain the sample in a gas environment while the rest of the beam is maintained under UHV. The Elemental content of the surface interacting with the gas environment will be determined from the Doppler broadened gamma spectra. This system will include a time of flight (TOF) positron annihilation induced Auger spectrometer (TOF-PAES) which correlates with the Doppler measurements at lower pressures. These new technique help to understand the charge transfer mechanisms at the surface.

Note: Mechanical in situ exfoliation of van der Waals materials

NASA Astrophysics Data System (ADS)

Pásztor, Á.; Scarfato, A.; Renner, Ch.

2017-07-01

Exfoliation, namely, the peeling of layered materials down to a single unit-cell thin foil, opens promising avenues to fabricate novel electronic materials. New properties and original functionalities emerge in the single and few layer configurations of a number of layered compounds, in particular in transition metal dichalcogenides. However, many of these thin exfoliated materials are very sensitive to ambient conditions impeding the exploration of this new and fascinating parameter space. Here we describe a method of mechanical exfoliation in ultra-high vacuum (UHV). This technique is easily adaptable to any UHV system and allows preparing and studying air sensitive nanoflakes in situ. We present the basic design and proof-of-concept scanning tunneling microscopy imaging of VSe2 nanoflakes.

Ricor's Nanostar water vapor compact cryopump: applications and model overview

NASA Astrophysics Data System (ADS)

Harris, Rodney S.; Nachman, Ilan; Tauber, Tomer; Kootzenko, Michael; Barak, Boris; Aminov, Eli; Gover, Dan

2017-05-01

Ricor Systems has developed a compact, single stage cryopump that fills the gap where GM and other type cryopumps can't fit in. Stirling cycle technology is highly efficient and is the primary cryogenic technology for use in IR, SWIR, HOT FPA, and other IR detector technology in military, security, and aerospace applications. Current GM based dual stage cryopumps have been the legacy type water vapor pumping system for more than 50 years. However, the typically large cryopanel head, compressor footprint, and power requirements make them not cost and use effective for small, tabletop evaporation / sputtering systems, portable analysis systems, and other systems requiring small volume vacuum creation from medium, high, and UHV levels. This single stage cryopump works well in-line with diffusion and molecular turbopumps. Studies have shown effective cooperation with non-evaporable getter technology as well for UHV levels. Further testing in this area are ongoing. Temperatures created by Stirling cycle cryogenic coolers develop a useful temperature range of 40 to 150K. Temperatures of approximately 100 K are sufficient to condense water and all hydrocarbons oil vapors.

Note: Hollow cathode lamp with integral, high optical efficiency isolation valve: a modular vacuum ultraviolet source.

PubMed

Roberts, F Sloan; Anderson, Scott L

2013-12-01

The design and operating conditions of a hollow cathode discharge lamp for the generation of vacuum ultraviolet radiation, suitable for ultrahigh vacuum (UHV) application, are described in detail. The design is easily constructed, and modular, allowing it to be adapted to different experimental requirements. A thin isolation valve is built into one of the differential pumping stages, isolating the discharge section from the UHV section, both for vacuum safety and to allow lamp maintenance without venting the UHV chamber. The lamp has been used both for ultraviolet photoelectron spectroscopy of surfaces and as a "soft" photoionization source for gas-phase mass spectrometry.

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

Baker, A. A.; Hesjedal, T.; Diamond Light Source, Didcot OX11 0DE

We present a miniaturized molecular beam epitaxy (miniMBE) system with an outer diameter of 206 mm, optimized for flexible and high-throughput operation. The three-chamber system, used here for oxide growth, consists of a sample loading chamber, a storage chamber, and a growth chamber. The growth chamber is equipped with eight identical effusion cell ports with linear shutters, one larger port for either a multi-pocket electron beam evaporator or an oxygen plasma source, an integrated cryoshroud, retractable beam-flux monitor or quartz-crystal microbalance, reflection high energy electron diffraction, substrate manipulator, main shutter, and quadrupole mass spectrometer. The system can be combined withmore » ultrahigh vacuum (UHV) end stations on synchrotron and neutron beamlines, or equivalently with other complex surface analysis systems, including low-temperature scanning probe microscopy systems. Substrate handling is compatible with most UHV surface characterization systems, as the miniMBE can accommodate standard surface science sample holders. We introduce the design of the system, and its specific capabilities and operational parameters, and we demonstrate the epitaxial thin film growth of magnetoelectric Cr{sub 2}O{sub 3} on c-plane sapphire and ferrimagnetic Fe{sub 3}O{sub 4} on MgO (001)« less

Surface development of a brazing alloy during heat treatment-a comparison between UHV and APXPS

NASA Astrophysics Data System (ADS)

Rullik, L.; Johansson, N.; Bertram, F.; Evertsson, J.; Stenqvist, T.; Lundgren, E.

2018-01-01

In an attempt to bridge the pressure gap, APXPS was used to follow the surface development of an aluminum brazing sheet during heating in an ambient oxygen-pressure mimicking the environment of an industrial brazing furnace. The studied aluminum alloy brazing sheet is a composite material consisting of two aluminum alloy standards whose surface is covered with a native aluminum oxide film. To emphasize the necessity of studies of this system in ambient sample environments it is compared to measurements in UHV. Changes in thickness and composition of the surface oxide were followed after heating to 300 °C, 400 °C, and 500 °C. The two sets presented in this paper show that the surface development strongly depends on the environment the sample is heated in.

Influence of the surface chemistry on TiO2 - TiO2 nanocontact forces as measured by an UHV-AFM

NASA Astrophysics Data System (ADS)

Kunze, Christian; Giner, Ignacio; Torun, Boray; Grundmeier, Guido

2014-03-01

Particle-wall contact forces between a TiO2 film coated AFM tip and TiO2(1 1 0) single crystal surfaces were analyzed by means of UHV-AFM. As a reference system an octadecylphosphonic acid monolayer covered TiO2(1 1 0) surface was studied. The defect chemistry of the TiO2 substrate was modified by Ar ion bombardment, water dosing at 3 × 10-6 Pa and an annealing step at 473 K which resulted in a varying density of Ti(III) states. The observed contact forces are correlated to the surface defect density and are discussed in terms of the change in the electronic structure and its influence on the Hamaker constant.

Sample mounting and transfer for coupling an ultrahigh vacuum variable temperature beetle scanning tunneling microscope with conventional surface probes

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

Nafisi, Kourosh; Ranau, Werner; Hemminger, John C.

2001-01-01

We present a new ultrahigh vacuum (UHV) chamber for surface analysis and microscopy at controlled, variable temperatures. The new instrument allows surface analysis with Auger electron spectroscopy, low energy electron diffraction, quadrupole mass spectrometer, argon ion sputtering gun, and a variable temperature scanning tunneling microscope (VT-STM). In this system, we introduce a novel procedure for transferring a sample off a conventional UHV manipulator and onto a scanning tunneling microscope in the conventional ''beetle'' geometry, without disconnecting the heating or thermocouple wires. The microscope, a modified version of the Besocke beetle microscope, is mounted on a 2.75 in. outer diameter UHVmore » flange and is directly attached to the base of the chamber. The sample is attached to a tripod sample holder that is held by the main manipulator. Under UHV conditions the tripod sample holder can be removed from the main manipulator and placed onto the STM. The VT-STM has the capability of acquiring images between the temperature range of 180--500 K. The performance of the chamber is demonstrated here by producing an ordered array of island vacancy defects on a Pt(111) surface and obtaining STM images of these defects.« less

Note: Hollow cathode lamp with integral, high optical efficiency isolation valve: A modular vacuum ultraviolet source

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

Sloan Roberts, F.; Anderson, Scott L.

2013-12-15

The design and operating conditions of a hollow cathode discharge lamp for the generation of vacuum ultraviolet radiation, suitable for ultrahigh vacuum (UHV) application, are described in detail. The design is easily constructed, and modular, allowing it to be adapted to different experimental requirements. A thin isolation valve is built into one of the differential pumping stages, isolating the discharge section from the UHV section, both for vacuum safety and to allow lamp maintenance without venting the UHV chamber. The lamp has been used both for ultraviolet photoelectron spectroscopy of surfaces and as a “soft” photoionization source for gas-phase massmore » spectrometry.« less

Surface science and model catalysis with ionic liquid-modified materials.

PubMed

Steinrück, H-P; Libuda, J; Wasserscheid, P; Cremer, T; Kolbeck, C; Laurin, M; Maier, F; Sobota, M; Schulz, P S; Stark, M

2011-06-17

Materials making use of thin ionic liquid (IL) films as support-modifying functional layer open up a variety of new possibilities in heterogeneous catalysis, which range from the tailoring of gas-surface interactions to the immobilization of molecularly defined reactive sites. The present report reviews recent progress towards an understanding of "supported ionic liquid phase (SILP)" and "solid catalysts with ionic liquid layer (SCILL)" materials at the microscopic level, using a surface science and model catalysis type of approach. Thin film IL systems can be prepared not only ex-situ, but also in-situ under ultrahigh vacuum (UHV) conditions using atomically well-defined surfaces as substrates, for example by physical vapor deposition (PVD). Due to their low vapor pressure, these systems can be studied in UHV using the full spectrum of surface science techniques. We discuss general strategies and considerations of this approach and exemplify the information available from complementary methods, specifically photoelectron spectroscopy and surface vibrational spectroscopy. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Industry-relevant magnetron sputtering and cathodic arc ultra-high vacuum deposition system for in situ x-ray diffraction studies of thin film growth using high energy synchrotron radiation.

PubMed

Schroeder, J L; Thomson, W; Howard, B; Schell, N; Näslund, L-Å; Rogström, L; Johansson-Jõesaar, M P; Ghafoor, N; Odén, M; Nothnagel, E; Shepard, A; Greer, J; Birch, J

2015-09-01

We present an industry-relevant, large-scale, ultra-high vacuum (UHV) magnetron sputtering and cathodic arc deposition system purposefully designed for time-resolved in situ thin film deposition/annealing studies using high-energy (>50 keV), high photon flux (>10(12) ph/s) synchrotron radiation. The high photon flux, combined with a fast-acquisition-time (<1 s) two-dimensional (2D) detector, permits time-resolved in situ structural analysis of thin film formation processes. The high-energy synchrotron-radiation based x-rays result in small scattering angles (<11°), allowing large areas of reciprocal space to be imaged with a 2D detector. The system has been designed for use on the 1-tonne, ultra-high load, high-resolution hexapod at the P07 High Energy Materials Science beamline at PETRA III at the Deutsches Elektronen-Synchrotron in Hamburg, Germany. The deposition system includes standard features of a typical UHV deposition system plus a range of special features suited for synchrotron radiation studies and industry-relevant processes. We openly encourage the materials research community to contact us for collaborative opportunities using this unique and versatile scientific instrument.

A UHV compatible source for a highly polarized thermal atomic beam of radioactive 8Li

NASA Astrophysics Data System (ADS)

Jänsch, H. J.; Kirchner, G.; Kühlert, O.; Lisowski, M.; Paggel, J. J.; Platzer, R.; Schillinger, R.; Tilsner, H.; Weindel, C.; Winnefeld, H.; Fick, D.

2000-12-01

A beam of the radioactive isotope 8Li is prepared at thermal velocities. The nuclei are highly spin polarized by transverse optical pumping of the thermal beam. The installation is ultra-high vacuum (UHV) compatible in a non-UHV accelerator environment. Since the atomic beam is used in a surface science experiment, where contamination must be avoided, special emphasis is given to the vacuum coupling of the accelerator/ 8Li production/surface experimental areas. The atomic beam is produced by stopping the nuclear reaction products and evaporating them again from high-temperature graphite. To enhance the atomic beam, a novel tubular thermalizer is applied. The thermal polarized atomic beam intensity is approximately 5×10 8 atoms/s sr.

Isolation, identification, and characterization of novel arenaviruses, the etiological agents of boid inclusion body disease.

PubMed

Hetzel, Udo; Sironen, Tarja; Laurinmäki, Pasi; Liljeroos, Lassi; Patjas, Aino; Henttonen, Heikki; Vaheri, Antti; Artelt, Annette; Kipar, Anja; Butcher, Sarah J; Vapalahti, Olli; Hepojoki, Jussi

2013-10-01

Boid inclusion body disease (BIBD) is a progressive, usually fatal disease of constrictor snakes, characterized by cytoplasmic inclusion bodies (IB) in a wide range of cell types. To identify the causative agent of the disease, we established cell cultures from BIBD-positive and -negative boa constrictors. The IB phenotype was maintained in cultured cells of affected animals, and supernatants from these cultures caused the phenotype in cultures originating from BIBD-negative snakes. Viruses were purified from the supernatants by ultracentrifugation and subsequently identified as arenaviruses. Purified virus also induced the IB phenotype in naive cells, which fulfilled Koch's postulates in vitro. One isolate, tentatively designated University of Helsinki virus (UHV), was studied in depth. Sequencing confirmed that UHV is a novel arenavirus species that is distinct from other known arenaviruses including those recently identified in snakes with BIBD. The morphology of UHV was established by cryoelectron tomography and subtomographic averaging, revealing the trimeric arenavirus spike structure at 3.2-nm resolution. Immunofluorescence, immunohistochemistry, and immunoblotting with a polyclonal rabbit antiserum against UHV and reverse transcription-PCR (RT-PCR) revealed the presence of genetically diverse arenaviruses in a large cohort of snakes with BIBD, confirming the causative role of arenaviruses. Some snakes were also found to carry arenavirus antibodies. Furthermore, mammalian cells (Vero E6) were productively infected with UHV, demonstrating the potential of arenaviruses to cross species barriers. In conclusion, we propose the newly identified lineage of arenaviruses associated with BIBD as a novel taxonomic entity, boid inclusion body disease-associated arenaviruses (BIBDAV), in the family Arenaviridae.

Isolation, Identification, and Characterization of Novel Arenaviruses, the Etiological Agents of Boid Inclusion Body Disease

PubMed Central

Hetzel, Udo; Sironen, Tarja; Laurinmäki, Pasi; Liljeroos, Lassi; Patjas, Aino; Henttonen, Heikki; Vaheri, Antti; Artelt, Annette; Kipar, Anja; Butcher, Sarah J.; Vapalahti, Olli

2013-01-01

Boid inclusion body disease (BIBD) is a progressive, usually fatal disease of constrictor snakes, characterized by cytoplasmic inclusion bodies (IB) in a wide range of cell types. To identify the causative agent of the disease, we established cell cultures from BIBD-positive and -negative boa constrictors. The IB phenotype was maintained in cultured cells of affected animals, and supernatants from these cultures caused the phenotype in cultures originating from BIBD-negative snakes. Viruses were purified from the supernatants by ultracentrifugation and subsequently identified as arenaviruses. Purified virus also induced the IB phenotype in naive cells, which fulfilled Koch's postulates in vitro. One isolate, tentatively designated University of Helsinki virus (UHV), was studied in depth. Sequencing confirmed that UHV is a novel arenavirus species that is distinct from other known arenaviruses including those recently identified in snakes with BIBD. The morphology of UHV was established by cryoelectron tomography and subtomographic averaging, revealing the trimeric arenavirus spike structure at 3.2-nm resolution. Immunofluorescence, immunohistochemistry, and immunoblotting with a polyclonal rabbit antiserum against UHV and reverse transcription-PCR (RT-PCR) revealed the presence of genetically diverse arenaviruses in a large cohort of snakes with BIBD, confirming the causative role of arenaviruses. Some snakes were also found to carry arenavirus antibodies. Furthermore, mammalian cells (Vero E6) were productively infected with UHV, demonstrating the potential of arenaviruses to cross species barriers. In conclusion, we propose the newly identified lineage of arenaviruses associated with BIBD as a novel taxonomic entity, boid inclusion body disease-associated arenaviruses (BIBDAV), in the family Arenaviridae. PMID:23926354

Oxygen accumulation on metal surfaces investigated by XPS, AES and LEIS, an issue for sputter depth profiling under UHV conditions

NASA Astrophysics Data System (ADS)

Steinberger, R.; Celedón, C. E.; Bruckner, B.; Roth, D.; Duchoslav, J.; Arndt, M.; Kürnsteiner, P.; Steck, T.; Faderl, J.; Riener, C. K.; Angeli, G.; Bauer, P.; Stifter, D.

2017-07-01

Depth profiling using surface sensitive analysis methods in combination with sputter ion etching is a common procedure for thorough material investigations, where clean surfaces free of any contamination are essential. Hence, surface analytic studies are mostly performed under ultra-high vacuum (UHV) conditions, but the cleanness of such UHV environments is usually overrated. Consequently, the current study highlights the in principle known impact of the residual gas on metal surfaces (Fe, Mg, Al, Cr and Zn) for various surface analytics methods, like X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and low-energy ion scattering (LEIS). The investigations with modern, state-of-the-art equipment showed different behaviors for the metal surfaces in UHV during acquisition: (i) no impact for Zn, even after long time, (ii) solely adsorption of oxygen for Fe, slight and slow changes for Cr and (iii) adsorption accompanied by oxide formation for Al and Mg. The efficiency of different counter measures was tested and the acquired knowledge was finally used for ZnMgAl coated steel to obtain accurate depth profiles, which exhibited before serious artifacts when data acquisition was performed in an inconsiderate way.

Characterization of a Compact Cryogenic Package Approach to Ion Trap Quantum Comuting

NASA Astrophysics Data System (ADS)

Spivey, Robert; Vrijsen, Geert; Ahn, Byeong-Hyeon; Hudek, Kai; Crain, Stephen; van Rynbach, Andre; Rachel, Noek; Kim, Jungsang

One challenge for the expansion of trapped ion systems to a large scale is the lack of repeatable integration technology to realize compact and stable operating environment. In this work, we present a novel ion trapping environment where conventional ultra-high vacuum (UHV) chambers are replaced with a sealed ceramic package operating in a cryogenic environment. A microfabricated surface ion trap mounted on a 100-pin ceramic pin grid array (CPGA) package is placed in a UHV environment. A titanium lid with windows for optical access is then attached to the CPGA via an indium seal which maintains the UHV conditions for the ion trap. The trap package assembly is operated at cryogenic temperatures (5K) in order to freeze out most of the residual background gas. Activated charcoal is used to pump remaining helium and hydrogen molecules. Metallic Yb ablated using a Q-switched Nd:YAG laser at 1,064 nm is used as the atomic source. A compact radio frequency resonant circuit is used to create the RF potential for trapping. A low output impedance amplifier drives a superconducting inductor of value 2 uH in series with the trap capacitance in order to produce 200V at 26 MHz with low heating at 5K. We present the experimental progress towards trapping ions in this compact cryogenic setup.

Constitutional Dynamics of Metal-Organic Motifs on a Au(111) Surface.

PubMed

Kong, Huihui; Zhang, Chi; Xie, Lei; Wang, Likun; Xu, Wei

2016-06-13

Constitutional dynamic chemistry (CDC), including both dynamic covalent chemistry and dynamic noncovalent chemistry, relies on reversible formation and breakage of bonds to achieve continuous changes in constitution by reorganization of components. In this regard, CDC is considered to be an efficient and appealing strategy for selective fabrication of surface nanostructures by virtue of dynamic diversity. Although constitutional dynamics of monolayered structures has been recently demonstrated at liquid/solid interfaces, most of molecular reorganization/reaction processes were thought to be irreversible under ultrahigh vacuum (UHV) conditions where CDC is therefore a challenge to be achieved. Here, we have successfully constructed a system that presents constitutional dynamics on a solid surface based on dynamic coordination chemistry, in which selective formation of metal-organic motifs is achieved under UHV conditions. The key to making this reversible switching successful is the molecule-substrate interaction as revealed by DFT calculations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spontaneous desorption and phase transitions of self-assembled alkanethiol and alicyclic thiol monolayers chemisorbed on Au(111) in ultrahigh vacuum at room temperature.

PubMed

Ito, Eisuke; Kang, Hungu; Lee, Dongjin; Park, Joon B; Hara, Masahiko; Noh, Jaegeun

2013-03-15

Scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) were used to examine the surface structure and adsorption conditions of hexanethiol (HT) and cyclohexanethiol (CHT) self-assembled monolayers (SAMs) on Au(111) as a function of storage period in ultrahigh vacuum (UHV) conditions of 3×10(-7) Pa at room temperature (RT). STM imaging revealed that after storage for 7 days, HT SAMs underwent phase transitions from c(4×2) phase to low coverage 4×√3 phase. This transition is due to a structural rearrangement of hexanethiolates that results from the spontaneous desorption of chemisorbed HT molecules on Au(111) surface. XPS measurements showed approximately 28% reduction in sulfur coverage, which indicates desorption of hexanethiolates from the surfaces. Contrary to HT SAMs, the structural order of CHT SAMs with (5×2√3)R35° phase completely disappeared after storage for 3 or 7 days. XPS results show desorption of more than 80% of the cyclohexanethiolates, even after storage for 3 days. We found that spontaneous desorption of CHT molecules on Au(111) in UHV at RT occurred quickly, whereas spontaneous desorption of HT molecules was much slower. Thermal desorption spectroscopy (TDS) results suggest CHT SAMs in UHV at RT can desorb more efficiently than HT SAMs due to formation of thiol desorption fragments that result from chemical reactions between surface hydrogen atoms and thiolates on Au(111) surfaces. This study clearly demonstrated that organic thiols chemisorbed on gold surfaces are desorbed spontaneously in UHV at RT and van der Waals interactions play an important role in determining the structural stability of thiolate SAMs in UHV. Copyright © 2012 Elsevier Inc. All rights reserved.

Design and qualification of an UHV system for operation on sounding rockets

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

Grosse, Jens, E-mail: jens.grosse@dlr.de; Braxmaier, Claus; Seidel, Stephan Tobias

The sounding rocket mission MAIUS-1 has the objective to create the first Bose–Einstein condensate in space; therefore, its scientific payload is a complete cold atom experiment built to be launched on a VSB-30 sounding rocket. An essential part of the setup is an ultrahigh vacuum system needed in order to sufficiently suppress interactions of the cooled atoms with the residual background gas. Contrary to vacuum systems on missions aboard satellites or the international space station, the required vacuum environment has to be reached within 47 s after motor burn-out. This paper contains a detailed description of the MAIUS-1 vacuum system, asmore » well as a description of its qualification process for the operation under vibrational loads of up to 8.1 g{sub RMS} (where RMS is root mean square). Even though a pressure rise dependent on the level of vibration was observed, the design presented herein is capable of regaining a pressure of below 5 × 10{sup −10} mbar in less than 40 s when tested at 5.4 g{sub RMS}. To the authors' best knowledge, it is the first UHV system qualified for operation on a sounding rocket.« less

Characterization of the CEBAF 100 kV DC GaAs Photoelectron Gun Vacuum System

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

Stutzman, M L; Adderley, P; Brittian, J

A vacuum system with pressure in the low ultra-high vacuum (UHV) range is essential for long photocathode lifetimes in DC high voltage GaAs photoguns. A discrepancy between predicted and measured base pressure in the CEBAF photoguns motivated this study of outgassing rates of three 304 stainless steel chambers with different pretreatments and pump speed measurements of non-evaporable getter (NEG) pumps. Outgassing rates were measured using two independent techniques. Lower outgassing rates were achieved by electropolishing and vacuum firing the chamber. The second part of the paper describes NEG pump speed measurements as a function of pressure through the lower partmore » of the UHV range. Measured NEG pump speed is high at pressures above 5×10 -11 Torr, but may decrease at lower pressures depending on the interpretation of the data. The final section investigates the pump speed of a locally produced NEG coating applied to the vacuum chamber walls. These studies represent the first detailed vacuum measurements of CEBAF photogun vacuum chambers.« less

In situ sputter cleaning of thin film metal substrates for UHV-TEM corrosion studies.

NASA Technical Reports Server (NTRS)

Heinemann, K.; Poppa, H.

1973-01-01

A prerequisite for conducting valid corrosion experiments by in situ electron microscopy techniques is not only the achievement of UHV background pressure conditions at the site of the specimen but also the ability to clean the surface of the thin metal substrate specimen before initiation of the corrosive interaction. A miniaturized simple ion gun has been constructed for this purpose. The gun is small enough to be incorporated into an UHV electron microscope specimen chamber with hot stage in such a way as to permit bombardment of the substrate specimen while observing it by transmission electron microscopy TEM. It is shown that the ion beam generated is confined well enough to cause a sputtering removal of substrate material at a rate of approximately 5-10 A/min and to prevent the sputter deposition of contaminating material from the specimen holder.

Advanced Photonic Sensors Enabled by Semiconductor Bonding

DTIC Science & Technology

2010-05-31

a dry scroll backing pump to maintain the high differential pressure between the UV gun and the sample/analysis chamber. We also replaced the...semiconductor materials in an ultra-high vacuum (UHV) environment where the properties of the interface can be controlled with atomic-level precision. Such...year research program, we designed and constructed a unique system capable of fusion bonding two wafers in an ultra-high vacuum environment. This system

Experimental approaches to well controlled studies of thin-film nucleation and growth.

NASA Technical Reports Server (NTRS)

Poppa, H.; Moorhead, R. D.; Heinemann, K.

1972-01-01

Particular features and the performance of two experimental systems are described for quantitative studies of thin-film nucleation and growth processes including epitaxial depositions. System I consists of a modified LEED-Auger instrument combined with high-resolution electron microscopy. System II is a UHV electron microscope adapted for in-situ deposition studies. The two systems complement each other ideally, and the combined use of both can result in a comprehensive investigation of vapor deposition processes not obtainable with any other known method.

Ultra high vacuum test setup for electron gun

NASA Astrophysics Data System (ADS)

Pandiyar, M. L.; Prasad, M.; Jain, S. K.; Kumar, R.; Hannurkar, P. R.

2008-05-01

Ultra High Vacuum (UHV) test setup for electron gun testing has been developed. The development of next generation light sources and accelerators require development of klystron as a radio frequency power source, and in turn electron gun. This UHV electron gun test setup can be used to test the electron guns ranging from high average current, quasi-continuous wave to high peak current, single pulse etc. An electron gun has been designed, fabricated, assembled and tested for insulation up to 80 kV under the programme to develop high power klystron for future accelerators. Further testing includes the electron emission parameters characterization of the cathode, as it determines the development of a reliable and efficient electron gun with high electron emission current and high life time as well. This needs a clean ultra high vacuum to study these parameters particularly at high emission current. The cathode emission current, work function and vapour pressure of cathode surface material at high temperature studies will further help in design and development of high power electron gun The UHV electron gun test setup consists of Turbo Molecular Pump (TMP), Sputter Ion Pump (SIP), pressure gauge, high voltage and cathode power supplies, current measurement device, solenoid magnet and its power supply, residual gas analyser etc. The ultimate vacuum less than 2×10-9 mbar was achieved. This paper describes the UHV test setup for electron gun testing.

Characterization and Evaluation of Ti-Zr-V Non-evaporable Getter Films Used in Vacuum Systems

NASA Astrophysics Data System (ADS)

Ferreira, M. J.; Seraphim, R. M.; Ramirez, A. J.; Tabacniks, M. H.; Nascente, P. A. P.

Among several methods used to obtain ultra-high vacuum (UHV) for particles accelerators chambers, it stands out the internal coating with metallic films capable of absorbing gases, called NEG (non-evaporable getter). Usually these materials are constituted by elements of great chemical reactivity and solubility (such as Ti, Zr, and V), at room temperature for oxygen and other gases typically found in UHV, such as H2, CO, and CO2. Gold and ternary Ti-Zr-V films were produced by magnetron sputtering, and their composition, structure, morphology, and aging characteristics were characterized by energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission gun sc anning electronmicroscopy (FEG-SEM), atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM). The comparison between the produced films and commercial samples indicated that the desirable characteristics depend on the nanometric structure of the films and that this structure is sensitive to the heat treatments.

An ultrahigh vacuum fast-scanning and variable temperature scanning tunneling microscope for large scale imaging.

PubMed

Diaconescu, Bogdan; Nenchev, Georgi; de la Figuera, Juan; Pohl, Karsten

2007-10-01

We describe the design and performance of a fast-scanning, variable temperature scanning tunneling microscope (STM) operating from 80 to 700 K in ultrahigh vacuum (UHV), which routinely achieves large scale atomically resolved imaging of compact metallic surfaces. An efficient in-vacuum vibration isolation and cryogenic system allows for no external vibration isolation of the UHV chamber. The design of the sample holder and STM head permits imaging of the same nanometer-size area of the sample before and after sample preparation outside the STM base. Refractory metal samples are frequently annealed up to 2000 K and their cooldown time from room temperature to 80 K is 15 min. The vertical resolution of the instrument was found to be about 2 pm at room temperature. The coarse motor design allows both translation and rotation of the scanner tube. The total scanning area is about 8 x 8 microm(2). The sample temperature can be adjusted by a few tens of degrees while scanning over the same sample area.

Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field

NASA Astrophysics Data System (ADS)

von Allwörden, Henning; Eich, Andreas; Knol, Elze J.; Hermenau, Jan; Sonntag, Andreas; Gerritsen, Jan W.; Wegner, Daniel; Khajetoorians, Alexander A.

2018-03-01

We describe the design and performance of a scanning tunneling microscope (STM) that operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).

Design and performance of an ultra-high vacuum spin-polarized scanning tunneling microscope operating at 30 mK and in a vector magnetic field.

PubMed

von Allwörden, Henning; Eich, Andreas; Knol, Elze J; Hermenau, Jan; Sonntag, Andreas; Gerritsen, Jan W; Wegner, Daniel; Khajetoorians, Alexander A

2018-03-01

We describe the design and performance of a scanning tunneling microscope (STM) that operates at a base temperature of 30 mK in a vector magnetic field. The cryogenics is based on an ultra-high vacuum (UHV) top-loading wet dilution refrigerator that contains a vector magnet allowing for fields up to 9 T perpendicular and 4 T parallel to the sample. The STM is placed in a multi-chamber UHV system, which allows in situ preparation and exchange of samples and tips. The entire system rests on a 150-ton concrete block suspended by pneumatic isolators, which is housed in an acoustically isolated and electromagnetically shielded laboratory optimized for extremely low noise scanning probe measurements. We demonstrate the overall performance by illustrating atomic resolution and quasiparticle interference imaging and detail the vibrational noise of both the laboratory and microscope. We also determine the electron temperature via measurement of the superconducting gap of Re(0001) and illustrate magnetic field-dependent measurements of the spin excitations of individual Fe atoms on Pt(111). Finally, we demonstrate spin resolution by imaging the magnetic structure of the Fe double layer on W(110).

Development of High Quantum Efficiency UV/Blue Photocathode Epitaxial Semiconductor Heterostructures for Scintillation and Cherenkov Radiation Detection

NASA Technical Reports Server (NTRS)

Leopold, Daniel J.

2002-01-01

The primary goal of this research project was to further extend the use of advanced heteroepitaxial-semiconductor crystal growth techniques such as molecular beam epitaxy (MBE) and to demonstrate significant gains in UV/blue photonic detection by designing and fabricating atomically-tailored heteroepitaxial GaAlN/GaInN photocathode device structures. This NASA Explorer technology research program has focused on the development of photocathodes for Cherenkov and scintillation radiation detection. Support from the program allowed us to enhance our MBE system to include a nitrogen plasma source and a magnetic bearing turbomolecular pump for delivery and removal of high purity atomic nitrogen during GaAlN/GaInN film growth. Under this program we have also designed, built and incorporated a cesium activation stage. In addition, a connected UHV chamber with photocathode transfer/positioner components as well as a hybrid phototube stage was designed and built to make in-situ quantum efficiency measurements without ever having to remove the photocathodes from UHV conditions. Thus we have constructed a system with the capability to couple atomically-tailored MBE-grown photocathode heterostructures with real high gain readout devices for single photon detection evaluation.

The EMIL project at BESSY II: Beamline design and performance

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

Hendel, Stefan, E-mail: stefan.hendel@helmholtz-berlin.de; Schäfers, Franz; Reichardt, Gerd

2016-07-27

The Energy Materials In-Situ Laboratory Berlin (EMIL) at BESSY-II is currently under construction. Two canted undulators for soft- and hard X-rays will be installed into the BESSY II storage ring in one straight section, complex beamlines with more than twenty optical elements will be set up and a new laboratory building attached to BESSY II will host three endstations and a large UHV-transfer system connecting various HV- and UHV-deposition systems. The undulators, UE48 and U17, provide a broad energy spectrum of 80 - 10000 eV, of which the harder radiation (>700 eV) is provided by a cryogenic in-vacuum device. Threemore » monochromators (two plane grating monochromators (PGM) and one LN{sub 2}-cooled double crystal monochromator (DCM)) disperse the radiation into separate pathways of 65 m length, while downstream of the monochromators split-mirror chambers distribute the photon beam to one (or simultaneously to two) of five upcoming endstations. Three of these endstations are designed for the full energy range with spatial overlap of the soft and hard foci, whereas one endstation (PEEM) uses only the soft and another one (PINK) only the hard branch, respectively.« less

A fibre-coupled UHV-compatible variable angle reflection-absorption UV/visible spectrometer

NASA Astrophysics Data System (ADS)

Stubbing, J. W.; Salter, T. L.; Brown, W. A.; Taj, S.; McCoustra, M. R. S.

2018-05-01

We present a novel UV/visible reflection-absorption spectrometer for determining the refractive index, n, and thicknesses, d, of ice films. Knowledge of the refractive index of these films is of particular relevance to the astrochemical community, where they can be used to model radiative transfer and spectra of various regions of space. In order to make these models more accurate, values of n need to be recorded under astronomically relevant conditions, that is, under ultra-high vacuum (UHV) and cryogenic cooling. Several design considerations were taken into account to allow UHV compatibility combined with ease of use. The key design feature is a stainless steel rhombus coupled to an external linear drive (z-shift) allowing a variable reflection geometry to be achieved, which is necessary for our analysis. Test data for amorphous benzene ice are presented as a proof of concept, the film thickness, d, was found to vary linearly with surface exposure, and a value for n of 1.43 ± 0.07 was determined.

Versatile, low-cost, computer-controlled, sample positioning system for vacuum applications

NASA Technical Reports Server (NTRS)

Vargas-Aburto, Carlos; Liff, Dale R.

1991-01-01

A versatile, low-cost, easy to implement, microprocessor-based motorized positioning system (MPS) suitable for accurate sample manipulation in a Second Ion Mass Spectrometry (SIMS) system, and for other ultra-high vacuum (UHV) applications was designed and built at NASA LeRC. The system can be operated manually or under computer control. In the latter case, local, as well as remote operation is possible via the IEEE-488 bus. The position of the sample can be controlled in three linear orthogonal and one angular coordinates.

Optimization and testing of solid thin film lubrication deposition processes

NASA Astrophysics Data System (ADS)

Danyluk, Michael J.

A novel method for testing solid thin films in rolling contact fatigue (RCF) under ultra-high vacuum (UHV) and high rotational speeds (130 Hz) is presented in this thesis. The UHV-RCF platform is used to quantify the adhesion and lubrication aspects of two thin film coatings deposited on ball-bearings using a physical vapor deposition ion plating process. Plasma properties during ion plating were measured using a Langmuir probe and there is a connection between ion flux, film stress, film adhesion, process voltage, pressure, and RCF life. The UHV-RCF platform and vacuum chamber were constructed using off-the-shelf components and 88 RCF tests in high vacuum have been completed. Maximum RCF life was achieved by maintaining an ion flux between 10 13 to 1015 (cm-2 s-1) with a process voltage and pressure near 1.5 kV and 15 mTorr. Two controller schemes were investigated to maintain optimal plasma conditions for maximum RCF life: PID and LQR. Pressure disturbances to the plasma have a detrimental effect on RCF life. Control algorithms that mitigate pressure and voltage disturbances already exist. However, feedback from the plasma to detect disturbances has not been explored related to deposition processes in the thin-film science literature. Manometer based pressure monitoring systems have a 1 to 2 second delay time and are too slow to detect common pressure bursts during the deposition process. Plasma diagnostic feedback is much faster, of the order of 0.1 second. Plasma total-current feedback was used successfully to detect a typical pressure disturbance associated with the ion plating process. Plasma current is related to ion density and process pressure. A real-time control application was used to detect the pressure disturbance by monitoring plasma-total current and converting it to feedback-input to a pressure control system. Pressure overshoot was eliminated using a nominal PID controller with feedback from a plasma-current diagnostic measurement tool.

Reactions of NO2 with BaO/Pt(111) Model Catalysts: The Effects of BaO Film Thickness and NO2 Pressure on the Formation of Ba(NOx)2 Species

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

Mudiyanselage, Kumudu; Yi, Cheol-Woo; Szanyi, Janos

2011-05-31

The adsorption and reaction of NO2 on BaO (<1, ~3, and >20 monolayer equivalent (MLE))/Pt(111) model systems were studied with temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRAS) under ultra-high vacuum (UHV) as well as elevated pressure conditions. NO2 reacts with sub-monolayer BaO (<1 MLE) to form nitrites only, whereas the reaction of NO2 with BaO (~3 MLE)/Pt(111) produces mainly nitrites and a small amount of nitrates under UHV conditions (PNO2 ~ 1.0 × 10-9 Torr) at 300 K. In contrast, a thick BaO(>20 MLE) layer on Pt(111) reacts with NO2 to form nitrite-nitratemore » ion pairs under the same conditions. At elevated NO2 pressures (≥ 1.0 × 10-5 Torr), however, BaO layers at all these three coverages convert to amorphous barium nitrates at 300 K. Upon annealing to 500 K, these amorphous barium nitrate layers transform into crystalline phases. The thermal decomposition of the thus-formed Ba(NOx)2 species is also influenced by the coverage of BaO on the Pt(111) substrate: at low BaO coverages, these species decompose at significantly lower temperatures in comparison with those formed on thick BaO films due to the presence of Ba(NOx)2/Pt interface where the decomposition can proceed at lower temperatures. However, the thermal decomposition of the thick Ba(NO3)2 films follows that of bulk nitrates. Results obtained from these BaO/Pt(111) model systems under UHV and elevated pressure conditions clearly demonstrate that both the BaO film thickness and the applied NO2 pressure are critical in the Ba(NOx)2 formation and subsequent thermal decomposition processes.« less

Dual analyzer system for surface analysis dedicated for angle-resolved photoelectron spectroscopy at liquid surfaces and interfaces

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

Niedermaier, Inga; Kolbeck, Claudia; Steinrück, Hans-Peter

The investigation of liquid surfaces and interfaces with the powerful toolbox of ultra-high vacuum (UHV)-based surface science techniques generally has to overcome the issue of liquid evaporation within the vacuum system. In the last decade, however, new classes of liquids with negligible vapor pressure at room temperature—in particular, ionic liquids (ILs)—have emerged for surface science studies. It has been demonstrated that particularly angle-resolved X-ray Photoelectron Spectroscopy (ARXPS) allows for investigating phenomena that occur at gas-liquid and liquid-solid interfaces on the molecular level. The results are not only relevant for IL systems but also for liquids in general. In all ofmore » these previous ARXPS studies, the sample holder had to be tilted in order to change the polar detection angle of emitted photoelectrons, which restricted the liquid systems to very thin viscous IL films coating a flat solid support. We now report on the concept and realization of a new and unique laboratory “Dual Analyzer System for Surface Analysis (DASSA)” which enables fast ARXPS, UV photoelectron spectroscopy, imaging XPS, and low-energy ion scattering at the horizontal surface plane of macroscopically thick non-volatile liquid samples. It comprises a UHV chamber equipped with two electron analyzers mounted for simultaneous measurements in 0° and 80° emission relative to the surface normal. The performance of DASSA on a first macroscopic liquid system will be demonstrated.« less

Mesocorticolimbic Connectivity and Volumetric Alterations in DCC Mutation Carriers.

PubMed

Vosberg, Daniel E; Zhang, Yu; Menegaux, Aurore; Chalupa, Amanda; Manitt, Colleen; Zehntner, Simone; Eng, Conrad; DeDuck, Kristina; Allard, Dominique; Durand, France; Dagher, Alain; Benkelfat, Chawki; Srour, Myriam; Joober, Ridha; Lepore, Franco; Rouleau, Guy; Théoret, Hugo; Bedell, Barry J; Flores, Cecilia; Leyton, Marco

2018-05-16

The axon guidance cue receptor DCC (deleted in colorectal cancer) plays a critical role in the organization of mesocorticolimbic pathways in rodents. To investigate whether this occurs in humans, we measured (1) anatomical connectivity between the substantia nigra/ventral tegmental area (SN/VTA) and forebrain targets, (2) striatal and cortical volumes, and (3) putatively associated traits and behaviors. To assess translatability, morphometric data were also collected in Dcc -haploinsufficient mice. The human volunteers were 20 DCC +/- mutation carriers, 16 DCC +/+ relatives, and 20 DCC +/+ unrelated healthy volunteers (UHVs; 28 females). The mice were 11 Dcc +/- and 16 wild-type C57BL/6J animals assessed during adolescence and adulthood. Compared with both control groups, the human DCC +/- carriers exhibited the following: (1) reduced anatomical connectivity from the SN/VTA to the ventral striatum [ DCC +/+ : p = 0.0005, r ( effect size ) = 0.60; UHV: p = 0.0029, r = 0.48] and ventral medial prefrontal cortex ( DCC +/+ : p = 0.0031, r = 0.53; UHV: p = 0.034, r = 0.35); (2) lower novelty-seeking scores ( DCC +/+ : p = 0.034, d = 0.82; UHV: p = 0.019, d = 0.84); and (3) reduced striatal volume ( DCC +/+ : p = 0.0009, d = 1.37; UHV: p = 0.0054, d = 0.93). Striatal volumetric reductions were also present in Dcc +/- mice, and these were seen during adolescence ( p = 0.0058, d = 1.09) and adulthood ( p = 0.003, d = 1.26). Together these findings provide the first evidence in humans that an axon guidance gene is involved in the formation of mesocorticolimbic circuitry and related behavioral traits, providing mechanisms through which DCC mutations might affect susceptibility to diverse neuropsychiatric disorders. SIGNIFICANCE STATEMENT Opportunities to study the effects of axon guidance molecules on human brain development have been rare. Here, the identification of a large four-generational family that carries a mutation to the axon guidance molecule receptor gene, DCC , enabled us to demonstrate effects on mesocorticolimbic anatomical connectivity, striatal volumes, and personality traits. Reductions in striatal volumes were replicated in DCC -haploinsufficient mice. Together, these processes might influence mesocorticolimbic function and susceptibility to diverse neuropsychiatric disorders. Copyright © 2018 the authors 0270-6474/18/384655-11$15.00/0.

Large area scanning probe microscope in ultra-high vacuum demonstrated for electrostatic force measurements on high-voltage devices.

PubMed

Gysin, Urs; Glatzel, Thilo; Schmölzer, Thomas; Schöner, Adolf; Reshanov, Sergey; Bartolf, Holger; Meyer, Ernst

2015-01-01

The resolution in electrostatic force microscopy (EFM), a descendant of atomic force microscopy (AFM), has reached nanometre dimensions, necessary to investigate integrated circuits in modern electronic devices. However, the characterization of conducting or semiconducting power devices with EFM methods requires an accurate and reliable technique from the nanometre up to the micrometre scale. For high force sensitivity it is indispensable to operate the microscope under high to ultra-high vacuum (UHV) conditions to suppress viscous damping of the sensor. Furthermore, UHV environment allows for the analysis of clean surfaces under controlled environmental conditions. Because of these requirements we built a large area scanning probe microscope operating under UHV conditions at room temperature allowing to perform various electrical measurements, such as Kelvin probe force microscopy, scanning capacitance force microscopy, scanning spreading resistance microscopy, and also electrostatic force microscopy at higher harmonics. The instrument incorporates beside a standard beam deflection detection system a closed loop scanner with a scan range of 100 μm in lateral and 25 μm in vertical direction as well as an additional fibre optics. This enables the illumination of the tip-sample interface for optically excited measurements such as local surface photo voltage detection. We present Kelvin probe force microscopy (KPFM) measurements before and after sputtering of a copper alloy with chromium grains used as electrical contact surface in ultra-high power switches. In addition, we discuss KPFM measurements on cross sections of cleaved silicon carbide structures: a calibration layer sample and a power rectifier. To demonstrate the benefit of surface photo voltage measurements, we analysed the contact potential difference of a silicon carbide p/n-junction under illumination.

In-situ ellipsometric studies of optical and surface properties of GaAs(100) at elevated temperatures

NASA Technical Reports Server (NTRS)

Yao, Huade; Snyder, Paul G.

1991-01-01

A rotating-polarizer ellipsometer was attached to an ultrahigh vacuum (UHV) chamber. A GaAs(100) sample was introduced into the UHV chamber and heated at anumber of fixed elevated temperatures, without arsenic overpressure. In-situ spectroscopic ellipsometric (SE) measurements were taken, through a pair of low-strain quartz windows, to monitor the surface changes and measure the pseudodielectric functions at elevated temperatures. Real-time data from GaAs surface covered with native oxide showed clearly the evolution of oxide desorption at approximately 580 C. In addition, surface degradation was found before and after the oxide desorption. An oxide free and smooth GaAs surface was obtained by depositing an arsenic protective coating onto a molecular beam epitaxy grown GaAs surface. The arsenic coating was evaporated immediately prior to SE measurements. A comparison showed that our room temperature data from this GaAs surface, measured in the UHV, are in good agreement with those in the literature obtained by wet-chemical etching. The surface also remained clean and smooth at higher temperatures, so that reliable temperature-dependent dielectric functions were obtained.

Electrospray deposition of organic molecules on bulk insulator surfaces.

PubMed

Hinaut, Antoine; Pawlak, Rémy; Meyer, Ernst; Glatzel, Thilo

2015-01-01

Large organic molecules are of important interest for organic-based devices such as hybrid photovoltaics or molecular electronics. Knowing their adsorption geometries and electronic structures allows to design and predict macroscopic device properties. Fundamental investigations in ultra-high vacuum (UHV) are thus mandatory to analyze and engineer processes in this prospects. With increasing size, complexity or chemical reactivity, depositing molecules by thermal evaporation becomes challenging. A recent way to deposit molecules in clean conditions is Electrospray Ionization (ESI). ESI keeps the possibility to work with large molecules, to introduce them in vacuum, and to deposit them on a large variety of surfaces. Here, ESI has been successfully applied to deposit triply fused porphyrin molecules on an insulating KBr(001) surface in UHV environment. Different deposition coverages have been obtained and characterization of the surface by in-situ atomic force microscopy working in the non-contact mode shows details of the molecular structures adsorbed on the surface. We show that UHV-ESI, can be performed on insulating surfaces in the sub-monolayer regime and to single molecules which opens the possibility to study a variety of complex molecules.

Surface friction of rock in terrestrial and simulated lunar environments

NASA Technical Reports Server (NTRS)

Roepke, W. W.; Peng, S. S.

1975-01-01

The conventional probe-on-the rotating-disk concept was used to determine the surface friction in mineral probe/specimen interfaces. Nine rocks or minerals and two stainless steels were tested in both new (NT) and same track (ST) tests under three different pressure environments-atmospheric, UHV, and dry nitrogen. Each environment was further subdivided into two testing conditions, that is, ambient and elevated (135 C) temperatures. In NT tests, friction was the lowest in an atmospheric pressure condition for all rock types and increased to the largest in UHV ambient condition except for pyroxene and stainless steel. Friction values measured in dry nitrogen ambient condition lie between the two extremes. Heating tends to increase friction in atmospheric and dry nitrogen environment but decreases in UHV environment with the exception of stainless steel, basalt, and pyroxene. In ST tests, friction was the lowest in the first run and increased in subsequent runs except for stainless steel where the reverse was true. The increases leveled off after a few runs ranging from the second to the seventh depending on rock types.

Application of the double paddle oscillator for quantifying environmental, surface mass variation

NASA Astrophysics Data System (ADS)

Wei, Haoyan; Pomeroy, Joshua

2016-04-01

Sub-monolayer sensitivity to controlled gas adsorption and desorption is demonstrated using a double paddle oscillator (DPO) installed within an ultra-high vacuum (UHV) environmental chamber equipped with in situ film deposition, (multi)gas admission and temperature control. This effort is intended to establish a robust framework for quantitatively comparing mass changes due to gas loading and unloading on different materials systems selected or considered for use as mass artefacts. Our apparatus is composed of a UHV chamber with gas introduction and temperature control and in situ materials deposition for future materials testing enabling in situ preparation of virgin surfaces that can be monitored during initial exposure to gasses of interest. These tools are designed to allow us to comparatively evaluate how different materials gain or lose mass due to precisely controlled environmental excursions, with a long term goal of measuring changes in absolute mass. Herein, we provide a detailed experimental description of the apparatus, an evaluation of the initial performance, and demonstration measurements using nitrogen adsorption and desorption directly on the DPO.

Application of the double paddle oscillator for quantifying environmental, surface mass variation

PubMed Central

Wei, Haoyan; Pomeroy, Joshua

2016-01-01

Sub-monolayer sensitivity to controlled gas adsorption and desorption is demonstrated using a double paddle oscillator (DPO) installed within an UHV (ultra-high vacuum) environmental chamber equipped with in situ film deposition, (multi)gas admission and temperature control. This effort is intended to establish a robust framework for quantitatively comparing mass changes due to gas loading and unloading on different materials systems selected or considered for use as mass artifacts. Our apparatus is composed of a UHV chamber with gas introduction and temperature control and in-situ materials deposition for future materials testing enabling in situ preparation of virgin surfaces that can be monitored during initial exposure to gasses of interest. These tools are designed to allow us to comparatively evaluate how different materials gain or lose mass due to precisely controlled environmental excursions, with a long term goal of measuring changes in absolute mass. Herein, we provide a detailed experimental description of the apparatus, an evaluation of the initial performance, and demonstration measurements using nitrogen adsorption and desorption directly on the DPO. PMID:27212736

The fabrication of a double-layer atom chip with through silicon vias for an ultra-high-vacuum cell

NASA Astrophysics Data System (ADS)

Chuang, Ho-Chiao; Lin, Yun-Siang; Lin, Yu-Hsin; Huang, Chi-Sheng

2014-04-01

This study presents a double-layer atom chip that provides users with increased diversity in the design of the wire patterns and flexibility in the design of the magnetic field. It is more convenient for use in atomic physics experiments. A negative photoresist, SU-8, was used as the insulating layer between the upper and bottom copper wires. The electrical measurement results show that the upper and bottom wires with a width of 100 µm can sustain a 6 A current without burnout. Another focus of this study is the double-layer atom chips integrated with the through silicon via (TSV) technique, and anodically bonded to a Pyrex glass cell, which makes it a desired vacuum chamber for atomic physics experiments. Thus, the bonded glass cell not only significantly reduces the overall size of the ultra-high-vacuum (UHV) chamber but also conducts the high current from the backside to the front side of the atom chip via the TSV under UHV (9.5 × 10-10 Torr). The TSVs with a diameter of 70 µm were etched through by the inductively coupled plasma ion etching and filled by the bottom-up copper electroplating method. During the anodic bonding process, the electroplated copper wires and TSVs on atom chips also need to pass the examination of the required bonding temperature of 250 °C, under an applied voltage of 1000 V. Finally, the UHV test of the double-layer atom chips with TSVs at room temperature can be reached at 9.5 × 10-10 Torr, thus satisfying the requirements of atomic physics experiments under an UHV environment.

The Effects of the Reverse Current Caused by the Series Compensation on the Current Differential Protection

PubMed Central

Tang, Cui; Yin, Xianggen; Qi, Xuanwei; Zhang, Zhe

2014-01-01

The series capacitor compensation is one of the key technologies in the EHV and UHV long distance power transmission lines. This paper analyzes the operation characteristics of the main protection combined with the engineering practice when the transmission line overcompensation due to the series compensation system is modified and analyzes the influence of the transition resistance and the system operation mode on the current differential protection. According to the simulation results, it presents countermeasure on improving the sensitivity of differential current protection. PMID:25247206

The development of a portable ultrahigh vacuum chamber via silicon block.

PubMed

Chuang, Ho-Chiao; Huang, Chia-Shiuan

2014-05-01

This paper describes a nonmetallic, light weight portable chamber for ultra-high vacuum (UHV) applications. The chamber consists of a processed silicon block anodically bonding five polished Pyrex glass windows and a Pyrex glass adapter, without using any screws, bolts or vacuum adhesives. The design features provide an alternative chamber for UHV applications which require nonmetallic components. We have cyclically baked the chamber up to 180 °C for 160 h and have achieved an ultimate pressure of 1.4 × 10(-9) Torr (limited by our pumping station), with no leak detected. Both Pyrex glass windows and Pyrex glass adapter have been used successfully.

UHV-TEM/TED observation of Ag islands grown on Si( 1 1 1 ) 3× 3-Ag surface

NASA Astrophysics Data System (ADS)

Oshima, Yoshifumi; Nakade, Hiroyuki; Shigeki, Sinya; Hirayama, Hiroyuki; Takayanagi, Kunio

2001-11-01

Growths of Ag islands on Si(1 1 1)3×3-Ag surface at room temperature were observed by UHV transmission electron microscopy and diffraction. The Ag islands grown after six monolayer deposition had neither (1 0 0) nor (1 1 0) orientation, but had two complex epitaxial orientations dominantly. One was striped islands which gave rise to a diffraction pattern commensurate with the 3×3 lattice of the Si(1 1 1) surface. The other was the coagulated islands whose diffraction pattern indicated the Ag(1 -3 4) sheet grown parallel to the Si(1 1 1) surface.

NC-AFM observation of atomic scale structure of rutile-type TiO2(110) surface prepared by wet chemical process.

PubMed

Namai, Yoshimichi; Matsuoka, Osamu

2006-04-06

We succeeded in observing the atomic scale structure of a rutile-type TiO2(110) single-crystal surface prepared by the wet chemical method of chemical etching in an acid solution and surface annealing in air. Ultrahigh vacuum noncontact atomic force microscopy (UHV-NC-AFM) was used for observing the atomic scale structures of the surface. The UHV-NC-AFM measurements at 450 K, which is above a desorption temperature of molecularly adsorbed water on the TiO2(110) surface, enabled us to observe the atomic scale structure of the TiO2(110) surface prepared by the wet chemical method. In the UHV-NC-AFM measurements at room temperature (RT), however, the atomic scale structure of the TiO2(110) surface was not observed. The TiO2(110) surface may be covered with molecularly adsorbed water after the surface was prepared by the wet chemical method. The structure of the TiO2(110) surface that was prepared by the wet chemical method was consistent with the (1 x 1) bulk-terminated model of the TiO2(110) surface.

Statistical characteristics of transient enclosure voltage in ultra-high-voltage gas-insulated switchgear

NASA Astrophysics Data System (ADS)

Cai, Yuanji; Guan, Yonggang; Liu, Weidong

2017-06-01

Transient enclosure voltage (TEV), which is a phenomenon induced by the inner dielectric breakdown of SF6 during disconnector operations in a gas-insulated switchgear (GIS), may cause issues relating to shock hazard and electromagnetic interference to secondary equipment. This is a critical factor regarding the electromagnetic compatibility of ultra-high-voltage (UHV) substations. In this paper, the statistical characteristics of TEV at UHV level are collected from field experiments, and are analyzed and compared to those from a repeated strike process. The TEV waveforms during disconnector operations are recorded by a self-developed measurement system first. Then, statistical characteristics, such as the pulse number, duration of pulses, frequency components, magnitude and single pulse duration, are extracted. The transmission line theory is introduced to analyze the TEV and is validated by the experimental results. Finally, the relationship between the TEV and the repeated strike process is analyzed. This proves that the pulse voltage of the TEV is proportional to the corresponding breakdown voltage. The results contribute to the definition of the standard testing waveform of the TEV, and can aid the protection of electronic devices in substations by minimizing the threat of this phenomenon.

Study on Remote Monitoring System of Crossing and Spanning Tangent Tower

NASA Astrophysics Data System (ADS)

Chen, Da-bing; Zhang, Nai-long; Zhang, Meng-ge; Wang, Ze-hua; Zhang, Yan

2017-05-01

In order to grasp the vibration state of overhead transmission line and ensure the operational security of transmission line, the remote monitoring system of crossing and spanning tangent tower was studied. By use of this system, the displacement, velocity and acceleration of the tower, and the local weather data are collected automatically, displayed on computer of remote monitoring centre through wireless network, real-time collection and transmission of vibration signals are realized. The applying results show that the system is excellent in reliability and accuracy and so on. The system can be used to remote monitoring of transmission tower of UHV power transmission lines and in large spanning areas.

Auger electron spectroscopy at high spatial resolution and nA primary beam currents

NASA Technical Reports Server (NTRS)

Todd, G.; Poppa, H.; Moorhead, D.; Bales, M.

1975-01-01

An experimental Auger microprobe system is described which incorporates a field-emission electron gun and total beam currents in the nanoampere range. The distinguishing characteristics of this system include a large multistation UHV specimen chamber, pulse counting and fully digital Auger signal-processing techniques, and digital referencing methods to eliminate the effects of beam instabilities. Some preliminary results obtained with this system are described, and it is concluded that field-emission electron sources can be used for high-resolution Auger electron spectroscopy with primary-beam spots of less than 100 nm and beam currents of the order of 1 nA.

Construction and evaluation of an ultrahigh-vacuum-compatible sputter deposition source

NASA Astrophysics Data System (ADS)

Lackner, Peter; Choi, Joong Il Jake; Diebold, Ulrike; Schmid, Michael

2017-10-01

A sputter deposition source for the use in ultrahigh vacuum (UHV) is described, and some properties of the source are analyzed. The operating principle is based on the design developed by Mayr et al. [Rev. Sci. Instrum. 84, 094103 (2013)], where electrons emitted from a filament ionize argon gas and the Ar+ ions are accelerated to the target. In contrast to the original design, two grids are used to direct a large fraction of the Ar+ ions to the target, and the source has a housing cooled by liquid nitrogen to reduce contaminations. The source has been used for the deposition of zirconium, a material that is difficult to evaporate in standard UHV evaporators. At an Ar pressure of 9 ×1 0-6 mbar in the UHV chamber and moderate emission current, a highly reproducible deposition rate of ≈1 ML in 250 s was achieved at the substrate (at a distance of ≈50 mm from the target). Higher deposition rates are easily possible. X-ray photoelectron spectroscopy shows a high purity of the deposited films. Depending on the grid voltages, the substrate gets mildly sputtered by Ar+ ions; in addition, the substrate is also reached by electrons from the negatively biased sputter target.

Discovery and Utilization of Nanoscale and Mesoscale Enabling Materials and Processes for Optoelectronics and Electronic Interconnects

DTIC Science & Technology

2003-12-01

Heating and Cooling Device 42 5.2.3 Multiple Tip STM ~ 43 5.2.3.1 Novel Nanomanipulator MM3 43 5.2.3.2 Four Tip STM Assembly 44 5.2.3.3 Vibration ...Analysis of Eddy Current Damping System of Multiple TIP STM " 44 5.2.3.4 Active Vibration Damping System 46 5.3 First Results 47 5.3.1 UHV-SEM...side: Actual device side and top view. 44 46. Setup for the vibration analysis experiment. 45 47. Relaxation of the STM unit, (a) without the eddy

A low-energy metal-ion source for primary ion deposition and accelerated ion doping during molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Hasan, M.-A.; Knall, J.; Barnett, S. A.; Rockett, A.; Sundgren, J.-E.

1987-10-01

A single-grid electron-impact ultrahigh vacuum (UHV) compatible low-energy ion gun capable of operating with a low vapor pressure solid source material such as In is presented. The gun consists of a single chamber which integrates the functions of an effusion cell, a vapor transport tube, and a glow discharge ionizer. The initial results of experiments designed to study the role of ion/surface interactions during nucleation and the early stages of crystal growth in UHV revealed that, for deposition on amorphous substrates, the use of a partially ionized In(+) beam resulted in a progressive shift towards larger island sizes, a decreased rate of secondary nucleation, and a more uniform island size distribution.

Ultra high voltage MOS controlled 4H-SiC power switching devices

NASA Astrophysics Data System (ADS)

Ryu, S.; Capell, C.; Van Brunt, E.; Jonas, C.; O'Loughlin, M.; Clayton, J.; Lam, K.; Pala, V.; Hull, B.; Lemma, Y.; Lichtenwalner, D.; Zhang, Q. J.; Richmond, J.; Butler, P.; Grider, D.; Casady, J.; Allen, S.; Palmour, J.; Hinojosa, M.; Tipton, C. W.; Scozzie, C.

2015-08-01

Ultra high voltage (UHV, >15 kV) 4H-silicon carbide (SiC) power devices have the potential to significantly improve the system performance, reliability, and cost of energy conversion systems by providing reduced part count, simplified circuit topology, and reduced switching losses. In this paper, we compare the two MOS based UHV 4H-SiC power switching devices; 15 kV 4H-SiC MOSFETs and 15 kV 4H-SiC n-IGBTs. The 15 kV 4H-SiC MOSFET shows a specific on-resistance of 204 mΩ cm2 at 25 °C, which increased to 570 mΩ cm2 at 150 °C. The 15 kV 4H-SiC MOSFET provides low, temperature-independent, switching losses which makes the device more attractive for applications that require higher switching frequencies. The 15 kV 4H-SiC n-IGBT shows a significantly lower forward voltage drop (VF), along with reasonable switching performance, which make it a very attractive device for high voltage applications with lower switching frequency requirements. An electrothermal analysis showed that the 15 kV 4H-SiC n-IGBT outperforms the 15 kV 4H-SiC MOSFET for applications with switching frequencies of less than 5 kHz. It was also shown that the use of a carrier storage layer (CSL) can significantly improve the conduction performance of the 15 kV 4H-SiC n-IGBTs.

AC Initiation System.

DTIC Science & Technology

An ac initiation system is described which uses three ac transmission signals interlocked for safety by frequency, phase, and power discrimination...The ac initiation system is pre-armed by the application of two ac signals have the proper phases, and activates a load when an ac power signal of the proper frequency and power level is applied. (Author)

High field electron paramagnetic resonance spectroscopy under ultrahigh vacuum conditions—A multipurpose machine to study paramagnetic species on well defined single crystal surfaces

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

Rocker, J.; Cornu, D.; Kieseritzky, E.

2014-08-01

A new ultrahigh vacuum (UHV) electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz to investigate paramagnetic centers on single crystal surfaces is described. It is particularly designed to study paramagnetic centers on well-defined model catalysts using epitaxial thin oxide films grown on metal single crystals. The EPR setup is based on a commercial Bruker E600 spectrometer, which is adapted to ultrahigh vacuum conditions using a home made Fabry Perot resonator. The key idea of the resonator is to use the planar metal single crystal required to grow the single crystalline oxide films as one of the mirrors of themore » resonator. EPR spectroscopy is solely sensitive to paramagnetic species, which are typically minority species in such a system. Hence, additional experimental characterization tools are required to allow for a comprehensive investigation of the surface. The apparatus includes a preparation chamber hosting equipment, which is required to prepare supported model catalysts. In addition, surface characterization tools such as low energy electron diffraction (LEED)/Auger spectroscopy, temperature programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS) are available to characterize the surfaces. A second chamber used to perform EPR spectroscopy at 94 GHz has a room temperature scanning tunneling microscope attached to it, which allows for real space structural characterization. The heart of the UHV adaptation of the EPR experiment is the sealing of the Fabry-Perot resonator against atmosphere. To this end it is possible to use a thin sapphire window glued to the backside of the coupling orifice of the Fabry Perot resonator. With the help of a variety of stabilization measures reducing vibrations as well as thermal drift it is possible to accumulate data for a time span, which is for low temperature measurements only limited by the amount of liquid helium. Test measurements show that the system can detect paramagnetic species with a density of approximately 5 × 10{sup 11} spins/cm{sup 2}, which is comparable to the limit obtained for the presently available UHV-EPR spectrometer operating at 10 GHz (X-band). Investigation of electron trapped centers in MgO(001) films shows that the increased resolution offered by the experiments at W-band allows to identify new paramagnetic species, that cannot be differentiated with the currently available methodology.« less

Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources.

PubMed

Pincelli, T; Petrov, V N; Brajnik, G; Ciprian, R; Lollobrigida, V; Torelli, P; Krizmancic, D; Salvador, F; De Luisa, A; Sergo, R; Gubertini, A; Cautero, G; Carrato, S; Rossi, G; Panaccione, G

2016-03-01

ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

NASA Astrophysics Data System (ADS)

Pincelli, T.; Petrov, V. N.; Brajnik, G.; Ciprian, R.; Lollobrigida, V.; Torelli, P.; Krizmancic, D.; Salvador, F.; De Luisa, A.; Sergo, R.; Gubertini, A.; Cautero, G.; Carrato, S.; Rossi, G.; Panaccione, G.

2016-03-01

ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).

Dispensing of very low volumes of ultra high viscosity alginate gels: a new tool for encapsulation of adherent cells and rapid prototyping of scaffolds and implants.

PubMed

Gepp, Michael M; Ehrhart, Friederike; Shirley, Stephen G; Howitz, Steffen; Zimmermann, Heiko

2009-01-01

We present a tool for dispensing very low volumes (20 nL or more) of ultra high viscosity (UHV) medical-grade alginate hydrogels. It uses a modified piezo-driven micrometering valve, integrated into a versatile system that allows fast prototyping of encapsulation procedures and scaffold production. Valves show excellent dispensing properties for UHV alginate in concentrations of 0.4% and 0.7% and also for aqueous liquids. An optimized process flow provides excellent handling of biological samples under sterile conditions. This technique allows the encapsulation of adherent cells and structuring of substrates for biotechnology and regenerative medicine. A variety of cell lines showed at least 70% viability after encapsulation (including cell lines that are relevant in regenerative medicine like Hep G2), and time-lapse analysis revealed cells proliferating and showing limited motility under alginate spots. Cells show metabolic activity, gene product expression, and physiological function. Encapsulated cells have contact with the substrate and can exchange metabolites while being isolated from macromolecules in the environment. Contactless dispensing allows structuring of substrates with alginate, isolation and transfer of cell-alginate complexes, and the dispensing of biological active hydrogels like extracellular matrix-derived gels.

Design and optimization of a modular setup for measurements of three-dimensional spin polarization with ultrafast pulsed sources

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

Pincelli, T., E-mail: pincelli@iom.cnr.it; Rossi, G.; Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, 34149 Trieste

2016-03-15

ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric andmore » magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).« less

Sonogashira cross-coupling over Au(1 1 1): from UHV to ambient pressure

NASA Astrophysics Data System (ADS)

Johansson, N.; Sisodiya, S.; Shayesteh, P.; Chaudhary, S.; Andersen, J. N.; Knudsen, J.; Wendt, O. F.; Schnadt, J.

2017-11-01

We have studied the reaction of phenylacetylene (PA) with chloro-, bromo-, and iodobenzene on the Au(1 1 1) surface as a model system for the gold-catalysed Sonogashira cross-coupling. Both ultrahigh vacuum-based and ambient pressure x-ray photoelectron spectroscopy show that iodo- and chlorobenzene (IB and CB) undergo the cross-coupling reaction towards diphenylacetylene. Bromobenzene (BB), in contrast, does not react in the UHV experiments. Further, at ambient pressure signs are found for poisoning of the Au(1 1 1) surface by a carbon species formed in the reaction. The understanding obtained in the reaction experiments are based on a thorough investigation of the adsorption of PA, IB, CB, and BB on the Au(1 1 1) surface by soft x-ray absorption spectroscopy and temperature-dependent x-ray photoelectron spectroscopy. In particular, the experiments provide the orientation of the intact adsorbates with respect to the surfaces at liquid nitrogen temperature. Dissociation in the temperature regime between  -80 and  -15 °C is observed for iodo- and chlorobenzene, but not for BB, in agreement with that only IB and CB, but not BB, react with PA to form diphenylacetylene. The difference is tentatively attributed to a difference in surface orientation of the different halobenzenes.

Structural and chemical characterization of terbia thin films grown on hexagonally close packed metal substrates

NASA Astrophysics Data System (ADS)

Cartas, William

Rare earth oxides (REOs) exhibit favorable catalytic performance for a diverse set of chemical transformations, including both partial and complete oxidation reactions. I will discuss our efforts to develop thin film systems of terbia for model surface science investigations of a REO that is effectively reducible, and which is thus expected to promote complete oxidation chemistry of adsorbed species. The growth of terbia on Cu(111) is shown to produce a complex surface that exhibits multiple phases of the oxide as well as exposed substrate. Growing the film on Pt(111) results in more uniform, single phase, and closed film. We used low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) to characterize the structural properties of terbia thin films grown on Pt(111) in ultrahigh vacuum (UHV) using physical vapor deposition. We find that the REO grows as a high quality Tb2O 3(111) film, and adopts oxygen-deficient fluorite structures wherein the metal cations form a hexagonal lattice in registry with the Pt(111) substrate, while oxygen vacancies are randomly distributed within the film. The Tb 2O3(111) films are thermally stable when heated to 1000 K in UHV. LEED and STM show that a fraction of the Tb2O3 forms hexagonal islands when first deposited, and further depositions typically result in three dimensional growth of the film. The Tb2O3 (111) / Pt(111) system produces a coincidence structure, seen very clearly in LEED images. We have also found that Tb2O3(111) films can be oxidized in UHV by exposure to plasma-generated atomic oxygen beams. The oxidized films have an estimated TbO2 stoichiometry and decompose to Tb2O3 during heating, with O2 desorption starting at about 500 K. Terbia films oxidized at 90 K show a weakly bound state of oxygen that is likely chemisorbed. Temperature programmed reaction spectroscopy (TPRS) studies using methanol show that increased oxygen in the film does not modify the chemical selectivity of the film; however, the increased oxygen content does increase the activity of the film toward methanol dehydrogenation. We have found that when methanol is adsorbed onto the terbia-Pt(111) system, it reacts to form formaldehyde and water and reduces the surface. The development of high-quality terbia thin films on Pt(111) provides new opportunities to investigate oxidation chemistry on an REO that has distinct reduction and oxidation properties.

An MBE growth facility for real-time in situ synchrotron x-ray topography studies of strained-layer III-V epitaxial materials

NASA Astrophysics Data System (ADS)

Whitehouse, C. R.; Barnett, S. J.; Soley, D. E. J.; Quarrell, J.; Aldridge, S. J.; Cullis, A. G.; Emeny, M. T.; Johnson, A. D.; Clarke, G. F.; Lamb, W.; Tanner, B. K.; Cottrell, S.; Lunn, B.; Hogg, C.; Hagston, W.

1992-01-01

This paper describes a unique combined UHV MBE growth x-ray topography facility designed to allow the first real-time synchrotron radiation x-ray topography study of strained-layer III-V growth processes. This system will enable unambiguous determination of dislocation nucleation and multiplication processes as a function of controlled variations in growth conditions, and also during post-growth thermal processing. The planned experiments have placed very stringent demands upon the engineering design of the system, and design details regarding the growth chamber; sample manipulator, x-ray optics, and real-time imaging systems are described. Results obtained during a feasibility study are also presented.

An MBE growth facility for real-time in situ synchrotron x-ray topography studies of strained-layer III--V epitaxial materials

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

Whitehouse, C.R.; Barnett, S.J.; Soley, D.E.J.

1992-01-01

This paper describes a unique combined UHV MBE growth x-ray topography facility designed to allow the first real-time synchrotron radiation x-ray topography study of strained-layer III--V growth processes. This system will enable unambiguous determination of dislocation nucleation and multiplication processes as a function of controlled variations in growth conditions, and also during post-growth thermal processing. The planned experiments have placed very stringent demands upon the engineering design of the system, and design details regarding the growth chamber; sample manipulator, x-ray optics, and real-time imaging systems are described. Results obtained during a feasibility study are also presented.

Photoelectron emission yield experiments on evolution of sub-gap states in amorphous In-Ga-Zn-O thin films with post deposition hydrogen treatment

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

Hayashi, Kazushi, E-mail: hayashi.kazushi@kobelco.com; Hino, Aya; Tao, Hiroaki

Total photoyield emission spectroscopy (TPYS) was applied to study the evolution of sub-gap states in hydrogen-treated amorphous In-Ga-Zn-O (a-IGZO) thin films. The a-IGZO thin films were subjected to hydrogen radicals and subsequently annealed in ultra-high vacuum (UHV) conditions. A clear onset of the electron emission was observed at around 4.3 eV from the hydrogen-treated a-IGZO thin films. After successive UHV annealing at 300 °C, the onset in the TPYS spectra was shifted to 4.15 eV, and the photoelectron emission from the sub-gap states was decreased as the annealing temperature was increased. In conjunction with the results of thermal desorption spectrometer, it was deducedmore » that the hydrogen atoms incorporated in the a-IGZO thin films induced metastable sub-gap states at around 4.3 eV from vacuum level just after the hydrogenation. It was also suggested that the defect configuration was changed due to the higher temperature UHV annealing, and that the hydrogen atoms desorbed with the involvement of Zn atoms. These experiments produced direct evidence to show the formation of sub-gap states as a result of hydrogen incorporation into the a-IGZO thin films.« less

System and method for determining stator winding resistance in an AC motor using motor drives

DOEpatents

Lu, Bin; Habetler, Thomas G; Zhang, Pinjia

2013-02-26

A system and method for determining the stator winding resistance of AC motors is provided. The system includes an AC motor drive having an input connectable to an AC source and an output connectable to an input terminal of an AC motor, a pulse width modulation (PWM) converter having switches therein to control current flow and terminal voltages in the AC motor, and a control system connected to the PWM converter. The control system generates a command signal to cause the PWM converter to control an output of the AC motor drive corresponding to an input to the AC motor, selectively generates a modified command signal to cause the PWM converter to inject a DC signal into the output of the AC motor drive, and determines a stator winding resistance of the AC motor based on the DC signal of at least one of the voltage and current.

Rapid prototyping of versatile atom chips for atom interferometry applications.

NASA Astrophysics Data System (ADS)

Kasch, Brian; Squires, Matthew; Olson, Spencer; Kroese, Bethany; Imhof, Eric; Kohn, Rudolph; Stuhl, Benjamin; Schramm, Stacy; Stickney, James

2016-05-01

We present recent advances in the manipulation of ultracold atoms with ex-vacuo atom chips (i.e. atom chips that are not inside to the UHV chamber). Details will be presented of an experimental system that allows direct bonded copper (DBC) atom chips to be removed and replaced in minutes, requiring minimal re-optimization of parameters. This system has been used to create Bose-Einstein condensates, as well as magnetic waveguides with precisely tunable axial parameters, allowing double wells, pure harmonic confinement, and modified harmonic traps. We investigate the effects of higher order magnetic field contributions to the waveguide, and the implications for confined atom interferometry.

Plasma diagnostic development and UHV testing for the ALPHA collaboration at Marquette University

NASA Astrophysics Data System (ADS)

Tharp, T. D.; Alpha Collaboration

2017-10-01

At Marquette, we are developing the next generation of nonneutral plasma diagnostics for the ALPHA experiment at CERN. ALPHA is building a new vertical experiment to test the gravitational interaction of antihydrogen with Earth. This expansion requires significant changes to the design of our plasma diagnostic suites: the next generation of tools must be able to measure plasmas from two directions, and must be capable of operating in a horizontal position. The diagnostic suite includes measurements of plasma density, shape, and temperature. The hardware used includes a MicroChannel Plate (MCP), a Faraday Cup, and an electron gun. In addition, we are building a vacuum chamber to test the viability of 3-d printed components for UHV compatibility, with target pressures of 10-10 mbar.

Surface spectroscopy studies of the oxidation behavior of uranium

NASA Astrophysics Data System (ADS)

Bloch, J.; Atzmony, U.; Dariel, M. P.; Mintz, M. H.; Shamir, N.

1982-02-01

Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) techniques were utilized to study the oxidation behavior of clean uranium surfaces, at very low pressures of various atmospheres (UHV, H 2, O 2, and CO 2), at room temperature. Both for O 2 and CO 2, a precursor chemisorbed oxygen species has been identified at the very initial stage of the oxidation reaction. This chemisorbed oxygen transforms to the oxide form at a rate which depends on the pressure of the oxidizing atmosphere. Residual gaseous carbon compounds which are present even under UHV conditions result in the simultaneous formation of surface carbide which accompanies the initial stage of oxidation. This carbide however decomposes later as oxidation proceeds. Adventitious hydrocarbon adsorption occurs on the formed oxide layer.

A Systematic Multi-Time Scale Solution for Regional Power Grid Operation

NASA Astrophysics Data System (ADS)

Zhu, W. J.; Liu, Z. G.; Cheng, T.; Hu, B. Q.; Liu, X. Z.; Zhou, Y. F.

2017-10-01

Many aspects need to be taken into consideration in a regional grid while making schedule plans. In this paper, a systematic multi-time scale solution for regional power grid operation considering large scale renewable energy integration and Ultra High Voltage (UHV) power transmission is proposed. In the time scale aspect, we discuss the problem from month, week, day-ahead, within-day to day-behind, and the system also contains multiple generator types including thermal units, hydro-plants, wind turbines and pumped storage stations. The 9 subsystems of the scheduling system are described, and their functions and relationships are elaborated. The proposed system has been constructed in a provincial power grid in Central China, and the operation results further verified the effectiveness of the system.

Thrust distribution for attitude control in a variable thrust propulsion system with four ACS nozzles

NASA Astrophysics Data System (ADS)

Lim, Yeerang; Lee, Wonsuk; Bang, Hyochoong; Lee, Hosung

2017-04-01

A thrust distribution approach is proposed in this paper for a variable thrust solid propulsion system with an attitude control system (ACS) that uses a reduced number of nozzles for a three-axis attitude maneuver. Although a conventional variable thrust solid propulsion system needs six ACS nozzles, this paper proposes a thrust system with four ACS nozzles to reduce the complexity and mass of the system. The performance of the new system was analyzed with numerical simulations, and the results show that the performance of the system with four ACS nozzles was similar to the original system while the mass of the whole system was simultaneously reduced. Moreover, a feasibility analysis was performed to determine whether a thrust system with three ACS nozzles is possible.

University of Maryland MRSEC - Facilities: VTSTM

Science.gov Websites

MRSEC Templates Opportunities Search Home » Facilities » UHV-VT-STM Shared Experimental Facilities redistribute the contents without alteration is granted to educational institutions for non-profit

Novel recirculating loop reactor for studies on model catalysts: CO oxidation on Pt/TiO2(110)

NASA Astrophysics Data System (ADS)

Tenney, Samuel A.; Xie, Kangmin; Monnier, John R.; Rodriguez, Abraham; Galhenage, Randima P.; Duke, Audrey S.; Chen, Donna A.

2013-10-01

A novel recirculating loop microreactor coupled to an ultrahigh vacuum (UHV) chamber has been constructed for the kinetic evaluation of model catalysts, which can be fully characterized by UHV surface science techniques. The challenge for this reactor design is to attain sufficient sensitivity to detect reactions on model single-crystal surfaces, which have a low number of active sites compared to conventional catalysts of equivalent mass. To this end, the total dead volume of the reactor system is minimized (32 cm3), and the system is operated in recirculation mode so that product concentrations build up to detectable levels over time. The injection of gas samples into the gas chromatography column and the refilling of the recirculation loop with fresh feed gas are achieved with computer-controlled, automated switching valves. In this manner, product concentrations can be followed over short time intervals (15 min) for extended periods of time (24 h). A proof of principle study in this reactor for CO oxidation at 145-165 °C on Pt clusters supported on a rutile TiO2(110) single crystal yields kinetic parameters that are comparable to those reported in the literature for CO oxidation on Pt clusters on powdered oxide supports, as well as on Pt(100). The calculated activation energy is 16.4 ± 0.7 kcal/mol, the turnover frequency is 0.03-0.06 molecules/(site.s) over the entire temperature range, and the reaction orders in O2 and CO at 160 °C are 0.9 ± 0.2 and -0.82 ± 0.03, respectively.

Study of the Decomposition and Phase Transition of Uranium Nitride under UHV Conditions via TDS, XRD, SEM, and XPS.

PubMed

Wang, Xiaofang; Long, Zhong; Bin, Ren; Yang, Ruilong; Pan, Qifa; Li, Fangfang; Luo, Lizhu; Hu, Yin; Liu, Kezhao

2016-11-07

Uranium nitrides are among the most promising fuels for Generation IV nuclear reactors, but until now, very little has been known about their thermal stability properties under nonequilibrium conditions. In this work, thermal decomposition of nitrogen-rich uranium nitride (denoted as UN 2-x ) under ultrahigh-vacuum (UHV) conditions was investigated by thermal desorption spectroscopy (TDS). It has been shown that the nitrogen TDS spectrum consists of two peaks at about 723 and 1038 K. The X-ray diffraction, scanning electron microscopy, and X-ray photoelectron microscopy results indicate that UN 2-x (UN 2 phase) decomposed into the α-U 2 N 3 phase in the first step and the α-U 2 N 3 phase decomposed into the UN phase in the second step.

Four-probe measurements with a three-probe scanning tunneling microscope.

PubMed

Salomons, Mark; Martins, Bruno V C; Zikovsky, Janik; Wolkow, Robert A

2014-04-01

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position by imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.

Versatile, high-sensitivity faraday cup array for ion implanters

DOEpatents

Musket, Ronald G.; Patterson, Robert G.

2003-01-01

An improved Faraday cup array for determining the dose of ions delivered to a substrate during ion implantation and for monitoring the uniformity of the dose delivered to the substrate. The improved Faraday cup array incorporates a variable size ion beam aperture by changing only an insertable plate that defines the aperture without changing the position of the Faraday cups which are positioned for the operation of the largest ion beam aperture. The design enables the dose sensitivity range, typically 10.sup.11 -10.sup.18 ions/cm.sup.2 to be extended to below 10.sup.6 ions/cm.sup.2. The insertable plate/aperture arrangement is structurally simple and enables scaling to aperture areas between <1 cm.sup.2 and >750 cm.sup.2, and enables ultra-high vacuum (UHV) applications by incorporation of UHV-compatible materials.

The preparation of pure niobium for neutron dosimetry purposes

NASA Astrophysics Data System (ADS)

Schulze, Klaus; Krehl, Michael

1985-06-01

A technique is described for the preparation of high purity niobium for use in fast neutron dosimetry. Based on results of known purification processes for niobium, an optimized method has been developed, consisting of: (1) a double electrolytic refining in an eutectic lithium-, sodium-, potassium-fluoride melt, containing fluoro-potassium niobate (K 2NbF 7), (2) electron beam float zone melting (EBFZM) in ultra high vacuum (UHV) and (3) UHV treatments. Starting with EBFZM of niobium of commercial quality (140 μg/g Ta, 35 μg/g W) the tantalum and tungsten contents were reduced by a first electrolysis to approximately 4 and 4 × 10 -2 μg/g, respectively. For a second electrolytic refining using a salt bath with extremely low tantalum and tungsten contents, this material was subjected to an additional EBFZM process. The niobium metal produced by this step was three times zone melted to reduce those elements (e.g. Fe, Co, Ni, O, N) which increased during the electrolyses. Material produced by this technique has impurity concentrations below 0.4 μg/g of tantalum and 10 -2 μg/g of tungsten. The concentration of the interstitials (C, O, N except H) is below the detection limit of classical analytical methods. A further reduction of the interstitials by annealing treatments in UHV of this material resulted in an electrical residual resistivity ratio (RRR) ρ(295 K)/ ρ(4.2 K) = 24 500 indicating an impurity concentration far below 1 μg/g.

System and method for determining stator winding resistance in an AC motor

DOEpatents

Lu, Bin [Kenosha, WI; Habetler, Thomas G [Snellville, GA; Zhang, Pinjia [Atlanta, GA; Theisen, Peter J [West Bend, WI

2011-05-31

A system and method for determining stator winding resistance in an AC motor is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of an AC motor. The circuit includes at least one contactor and at least one switch to control current flow and terminal voltages in the AC motor. The system also includes a controller connected to the circuit and configured to modify a switching time of the at least one switch to create a DC component in an output of the system corresponding to an input to the AC motor and determine a stator winding resistance of the AC motor based on the injected DC component of the voltage and current.

Study on the marine ejector refrigeration-rotary desiccant air-conditioning system

NASA Astrophysics Data System (ADS)

Zheng, C. Y.; Zheng, G. J.; Yu, W. S.; Chen, W.

2017-08-01

A newly developed ejector refrigeration-rotary desiccant air-conditioning (ERRD A/C) system is proposed to recover ship waste heat as far as possible. Its configuration is built firstly, then its advantages are analyzed, after that, with the help of psychrometric chart, some important parameters such as power consumption, steam consumption and COP of ERRD A/C system are calculated theoretically under design conditions of a real marine A/C, and comparative analysis with conventional A/C is deployed. The results show that the power consumption of ERRD A/C system is only 32.87% of conventional A/C, which meant that ERRD A/C system has potential to make full use of ship waste heat to realize energy saving and environmental protection when using green refrigerant such as water.

Development of a quadrupole-based Secondary-Ion Mass Spectrometry (SIMS) system at Lewis Research Center

NASA Technical Reports Server (NTRS)

Vargas-Aburto, Carlos; Aron, Paul R.; Liff, Dale R.

1990-01-01

The design, construction, and initial use of an ion microprobe to carry out secondary ion mass spectrometry (SIMS) of solid samples is reported. The system is composed of a differentially pumped custom-made UHV (Ultra High Vacuum) chamber, a quadrupole mass spectrometer and a telefocus A-DIDA ion gun with the capability of producing beams of Cesium, as well as inert and reactive gases. The computer control and acquisition of the data were designed and implemented using a personal computer with plug-in boards, and external circuitry built as required to suit the system needs. The software is being developed by using a FORTH-like language. Initial tests aimed at characterizing the system, as well as preliminary surface and depth-profiling studies are presently underway.

At-wavelength metrology facility for soft X-ray reflection optics

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

Sokolov, A., E-mail: andrey.sokolov@helmholtz-berlin.de; Bischoff, P.; Eggenstein, F.

2016-05-15

A new Optics Beamline coupled to a versatile UHV reflectometer is successfully operating at BESSY-II. It is used to carry out at-wavelength characterization and calibration of in-house produced gratings and novel nano-optical devices as well as mirrors and multilayer systems in the UV and XUV spectral region. This paper presents most recent commissioning data of the beamline and shows their correlation with initial beamline design calculations. Special attention is paid to beamline key parameters which determine the quality of the measurements such as high-order suppression and stray light behavior. The facility is open to user operation.

All-aluminum-alloy UHV chamber for molecular beam epitaxy, 1

NASA Astrophysics Data System (ADS)

Suemitsu, M.; Miyamoto, N.

1984-03-01

The first all aluminum alloy (ex. JIS.6263-t6,2219-t87 etc) MBE chamber is constructed and described. After exposure to atmosphere, the chamber is drown to 10(-9) torr in 24 hours, and reaches an ultrahigh vacuum of 1.6x10(-10) torr by a 115 C, 24 bakeout process. The light weight and low cost as well as the short pump-down time and the law outgassing rate of the all aluminum alloy vacuum system seems to have a considerable applicative potentiality for equipment used in semiconductor ultrahigh vacuum processes.

Design and development of high efficiency 140W space TWT with graphite collector

NASA Astrophysics Data System (ADS)

Srivastava, V.; Purohit, G.; Sharma, R. K.; Sharma, S. M.; Bera, A.; Bhaskar, P. V.; Singh, R. R.; Prasad, K.; Kiran, V.

2008-05-01

4-stage graphite collector assembly has been designed and developed for a 140W Ku-band space TWT to achieve the collector efficiency more than 80%. The UHV compatible, high density, copper impregnated POCO graphite (DFP-1C) was used to fabricate the four collector electrodes of the 4-stage depressed collector. Copper impregnated graphite material is used for the collector electrodes because of its low secondary electron emission coefficient, high thermal and electrical conductivities, easy machining and brazing, low thermal expansion coefficient and low weight. The graphite material was characterized for the UHV compatibility. The collector electrodes were precisely fabricated by careful machining, and technology was developed for brazing of graphite electrodes with high voltage alumina insulators. Complete TWT with four-stage graphite collector was developed and 140W output power at gain more than 55 dB was achieved. The TWT was pumped from both the gun and the collector ends.

Four-probe measurements with a three-probe scanning tunneling microscope

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

Salomons, Mark; Martins, Bruno V. C.; Zikovsky, Janik

2014-04-15

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position bymore » imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.« less

Role of thermal processes in dewetting of epitaxial Ag(111) film on Si(111)

DOE PAGES

Sanders, Charlotte E.; Zhang, Chendong D.; Kellogg, Gary L.; ...

2014-08-01

Epitaxially grown silver (Ag) film on silicon (Si) is an optimal plasmonic device platform, but its technological utility has been limited by its tendency to dewet rapidly under ambient conditions (standard temperature and pressure). The mechanisms driving this dewetting have not heretofore been determined. In our study, scanning probe microscopy and low-energy electron microscopy are used to compare the morphological evolution of epitaxial Ag(111)/Si(111) under ambient conditions with that of similarly prepared films heated under ultra-high vacuum (UHV) conditions. Furthermore, dewetting is seen to be initiated with the formation of pinholes, which might function to relieve strain in the film.more » We find that in the UHV environment, dewetting is determined by thermal processes, and while under ambient conditions, thermal processes are not required. Finally, we conclude that dewetting in ambient conditions is triggered by some chemical process, most likely oxidation.« less

Optimal Power Scheduling for a Medium Voltage AC/DC Hybrid Distribution Network

DOE PAGES

Zhu, Zhenshan; Liu, Dichen; Liao, Qingfen; ...

2018-01-26

With the great increase of renewable generation as well as the DC loads in the distribution network; DC distribution technology is receiving more attention; since the DC distribution network can improve operating efficiency and power quality by reducing the energy conversion stages. This paper presents a new architecture for the medium voltage AC/DC hybrid distribution network; where the AC and DC subgrids are looped by normally closed AC soft open point (ACSOP) and DC soft open point (DCSOP); respectively. The proposed AC/DC hybrid distribution systems contain renewable generation (i.e., wind power and photovoltaic (PV) generation); energy storage systems (ESSs); softmore » open points (SOPs); and both AC and DC flexible demands. An energy management strategy for the hybrid system is presented based on the dynamic optimal power flow (DOPF) method. The main objective of the proposed power scheduling strategy is to minimize the operating cost and reduce the curtailment of renewable generation while meeting operational and technical constraints. The proposed approach is verified in five scenarios. The five scenarios are classified as pure AC system; hybrid AC/DC system; hybrid system with interlinking converter; hybrid system with DC flexible demand; and hybrid system with SOPs. Results show that the proposed scheduling method can successfully dispatch the controllable elements; and that the presented architecture for the AC/DC hybrid distribution system is beneficial for reducing operating cost and renewable generation curtailment.« less

Optimal Power Scheduling for a Medium Voltage AC/DC Hybrid Distribution Network

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

Zhu, Zhenshan; Liu, Dichen; Liao, Qingfen

With the great increase of renewable generation as well as the DC loads in the distribution network; DC distribution technology is receiving more attention; since the DC distribution network can improve operating efficiency and power quality by reducing the energy conversion stages. This paper presents a new architecture for the medium voltage AC/DC hybrid distribution network; where the AC and DC subgrids are looped by normally closed AC soft open point (ACSOP) and DC soft open point (DCSOP); respectively. The proposed AC/DC hybrid distribution systems contain renewable generation (i.e., wind power and photovoltaic (PV) generation); energy storage systems (ESSs); softmore » open points (SOPs); and both AC and DC flexible demands. An energy management strategy for the hybrid system is presented based on the dynamic optimal power flow (DOPF) method. The main objective of the proposed power scheduling strategy is to minimize the operating cost and reduce the curtailment of renewable generation while meeting operational and technical constraints. The proposed approach is verified in five scenarios. The five scenarios are classified as pure AC system; hybrid AC/DC system; hybrid system with interlinking converter; hybrid system with DC flexible demand; and hybrid system with SOPs. Results show that the proposed scheduling method can successfully dispatch the controllable elements; and that the presented architecture for the AC/DC hybrid distribution system is beneficial for reducing operating cost and renewable generation curtailment.« less

Description of a dust particle detection system and measurements of particulate contamination from shock, gate valve, and ion pump under ultrahigh vacuum conditions

NASA Astrophysics Data System (ADS)

Dorier, J.-L.; Hilleret, N.

1998-11-01

Dust particle contamination is known to be responsible for reduced quality and yield in microelectronic processing. However it may also limit the operation of particle accelerators as a result of beam lifetime reduction or enhanced field emission in radio-frequency accelerating cavities. Intrinsic dust contamination from sources such as valves or ion pumps has not yet been studied due to the inability of commercial particle counters to be able to detect across large cross sections under ultrahigh vacuum (UHV) conditions. This motivated the development of the dust particle detector described here which is able to quantify, in situ, the level of contamination on a representative part of a vacuum vessel. This system operates under UHV conditions and measures flashes of scattered light from free falling dust particles as they cross a thin laser light sheet across a 100 mm diam vacuum vessel. A calibration using microspheres of known diameter has allowed estimation of the particle size from the scattered signal amplitude. Measurements of particulate contamination generated by shocks onto the vessel walls are presented and determination of the height of origin of dust particles from their transit time across the irradiation sheet is discussed. Measurements of dust particle release right to operation of an all-metal gate valve are also presented in the form of time resolved measurements of dust occurrence during the open/close cycles of the valve, as well as histograms of the particle size distribution. A partial self-cleaning effect is witnessed during the first 10 operation cycles following valve installation. The operation of an ion pump has also been investigated and revealed that, in our conditions, particles were released only at pump startup.

Electrodeless Plasma Source: Phase II Update

NASA Astrophysics Data System (ADS)

Prager, James; Ziemba, Timothy; Miller, Kenneth

2012-10-01

Eagle Harbor Technologies, in collaboration with the University of Washington, has developed a low-impurity, electrode-less plasma source (EPS) for start-up and source plasma injection for fusion science applications. In order to not interfere with the experiment, a pre-ionizer/plasma source must meet a few critical criteria including low impurity production, low electromagnetic interference (EMI), and minimal disruption to the magnetic geometry of the experiment. This system was designed to be UHV compatible and bakable. Here we present the results of the EPS Phase II upgrade. The output plasma density was increased by two orders of magnitude to >10^17 m-3 in hydrogen with no magnetic field injected. EPS system integration with the HIT-SI experiment has begun.

Integrated Inverter And Battery Charger

NASA Technical Reports Server (NTRS)

Rippel, Wally E.

1988-01-01

Circuit combines functions of dc-to-ac inversion (for driving ac motor in battery-powered vehicle) and ac-to-dc conversion (for charging battery from ac line when vehicle not in use). Automatically adapts to either mode. Design of integrated inverter/charger eliminates need for duplicate components, saves space, reduces weight and cost of vehicle. Advantages in other applications : load-leveling systems, standby ac power systems, and uninterruptible power supplies.

Effects of residual hydrogen in sputtering atmosphere on structures and properties of amorphous In-Ga-Zn-O thin films

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

Tang, Haochun; Ishikawa, Kyohei; Ide, Keisuke

2015-11-28

We investigated the effects of residual hydrogen in sputtering atmosphere on subgap states and carrier transport in amorphous In-Ga-Zn-O (a-IGZO) using two sputtering systems with different base pressures of ∼10{sup −4} and 10{sup −7 }Pa (standard (STD) and ultrahigh vacuum (UHV) sputtering, respectively), which produce a-IGZO films with impurity hydrogen contents at the orders of 10{sup 20} and 10{sup 19 }cm{sup −3}, respectively. Several subgap states were observed by hard X-ray photoemission spectroscopy, i.e., peak-shape near-valence band maximum (near-VBM) states, shoulder-shape near-VBM states, peak-shape near-conduction band minimum (near-CBM) states, and step-wise near-CBM states. It was confirmed that the formation of these subgapmore » states were affected strongly by the residual hydrogen (possibly H{sub 2}O). The step-wise near-CBM states were observed only in the STD films deposited without O{sub 2} gas flow and attributed to metallic In. Such step-wise near-CBM state was not detected in the other films including the UHV films even deposited without O{sub 2} flow, substantiating that the metallic In is segregated by the strong reduction effect of the hydrogen/H{sub 2}O. Similarly, the density of the near-VBM states was very high for the STD films deposited without O{sub 2}. These films had low film density and are consistent with a model that voids in the amorphous structure form a part of the near-VBM states. On the other hand, the UHV films had high film densities and much less near-VBM states, keeping the possibility that some of the near-VBM states, in particular, of the peak-shape ones, originate from –OH and weakly bonded oxygen. These results indicate that 2% of excess O{sub 2} flow is required for the STD sputtering to compensate the effects of the residual hydrogen/H{sub 2}O. The high-density near-VBM states and the metallic In segregation deteriorated the electron mobility to 0.4 cm{sup 2}/(V s)« less

Variable Temperature Scanning Tunneling Microscopy

DTIC Science & Technology

1991-07-01

Tomazin, both Electrical Engineering. Build a digital integrator for the STM feedback loop: Kyle Drewry, Electrical Engineering. Write an AutoLisp ...program to automate the AutoCad design of UHV-STM chambers: Alfred Pierce (minority), Mechanical Engineering. Design a 32-bit interface board for the EISA

Custom sample environments at the ALBA XPEEM.

PubMed

Foerster, Michael; Prat, Jordi; Massana, Valenti; Gonzalez, Nahikari; Fontsere, Abel; Molas, Bernat; Matilla, Oscar; Pellegrin, Eric; Aballe, Lucia

2016-12-01

A variety of custom-built sample holders offer users a wide range of non-standard measurements at the ALBA synchrotron PhotoEmission Electron Microscope (PEEM) experimental station. Some of the salient features are: an ultrahigh vacuum (UHV) suitcase compatible with many offline deposition and characterization systems, built-in electromagnets for uni- or biaxial in-plane (IP) and out-of-plane (OOP) fields, as well as the combination of magnetic fields with electric fields or current injection. Electronics providing a synchronized sinusoidal signal for sample excitation enable time-resolved measurements at the 500MHz storage ring RF frequency. Copyright © 2016 Elsevier B.V. All rights reserved.

Power processing and control requirements of dispersed solar thermal electric generation systems

NASA Technical Reports Server (NTRS)

Das, R. L.

1980-01-01

Power Processing and Control requirements of Dispersed Receiver Solar Thermal Electric Generation Systems are presented. Kinematic Stirling Engines, Brayton Engines and Rankine Engines are considered as prime movers. Various types of generators are considered for ac and dc link generations. It is found that ac-ac Power Conversion is not suitable for implementation at this time. It is also found that ac-dc-ac Power Conversion with a large central inverter is more efficient than ac-dc-ac Power Conversion using small dispersed inverters. Ac-link solar thermal electric plants face potential stability and synchronization problems. Research and development efforts are needed in improving component performance characteristics and generation efficiency to make Solar Thermal Electric Generation economically attractive.

A Case Study of Wind-PV-Thermal-Bundled AC/DC Power Transmission from a Weak AC Network

NASA Astrophysics Data System (ADS)

Xiao, H. W.; Du, W. J.; Wang, H. F.; Song, Y. T.; Wang, Q.; Ding, J.; Chen, D. Z.; Wei, W.

2017-05-01

Wind power generation and photovoltaic (PV) power generation bundled with the support by conventional thermal generation enables the generation controllable and more suitable for being sent over to remote load centre which are beneficial for the stability of weak sending end systems. Meanwhile, HVDC for long-distance power transmission is of many significant technique advantages. Hence the effects of wind-PV-thermal-bundled power transmission by AC/DC on power system have become an actively pursued research subject recently. Firstly, this paper introduces the technical merits and difficulties of wind-photovoltaic-thermal bundled power transmission by AC/DC systems in terms of meeting the requirement of large-scale renewable power transmission. Secondly, a system model which contains a weak wind-PV-thermal-bundled sending end system and a receiving end system in together with a parallel AC/DC interconnection transmission system is established. Finally, the significant impacts of several factors which includes the power transmission ratio between the DC and AC line, the distance between the sending end system and receiving end system, the penetration rate of wind power and the sending end system structure on system stability are studied.

Transient AC voltage related phenomena for HVDC schemes connected to weak AC systems

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

Pilotto, L.A.S.; Szechtman, M.; Hammad, A.E.

1992-07-01

In this paper a didactic explanation of voltage stability associated phenomena at HVDC terminals is presented. Conditions leading to ac voltage collapse problems are identified. A mechanism that excites control-induced voltage oscillations is shown. The voltage stability factor is used for obtaining the maximum power limits of ac/dc systems operating with different control strategies. Correlation to Pd {times} Id curves is given. Solutions for eliminating the risks of voltage collapse and for avoiding control-induced oscillations are discussed. The results are supported by detailed digital simulations of a weak ac/dc system using EMTP.

Transdifferentiation of mouse adipose-derived stromal cells into acinar cells of the submandibular gland using a co-culture system

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

Lee, Jingu; Park, Sangkyu; Roh, Sangho, E-mail: sangho@snu.ac.kr

A loss of salivary gland function often occurs after radiation therapy in head and neck tumors, though secretion of saliva by the salivary glands is essential for the health and maintenance of the oral environment. Transplantation of salivary acinar cells (ACs), in part, may overcome the side effects of therapy. Here we directly differentiated mouse adipose-derived stromal cells (ADSCs) into ACs using a co-culture system. Multipotent ADSCs can be easily collected from stromal vascular fractions of adipose tissues. The isolated ADSCs showed positive expression of markers such as integrin beta-1 (CD29), cell surface glycoprotein (CD44), endoglin (CD105), and Nanog. Themore » cells were able to differentiate into adipocytes, osteoblasts, and neural-like cells after 14 days in culture. ADSCs at passage 2 were co-cultured with mouse ACs in AC culture medium using the double-chamber (co-culture system) to avoid mixing the cell types. The ADSCs in this co-culture system expressed markers of ACs, such as α-amylases and aquaporin5, in both mRNA and protein. ADSCs cultured in AC-conditioned medium also expressed AC markers. Cellular proliferation and senescence analyses demonstrated that cells in the co-culture group showed lower senescence and a higher proliferation rate than the AC-conditioned medium group at Days 14 and 21. The results above imply direct conversion of ADSCs into ACs under the co-culture system; therefore, ADSCs may be a stem cell source for the therapy for salivary gland damage. - Highlights: • ADSCs could transdifferentiate into acinar cells (ACs) using ACs co-culture (CCA). • Transdifferentiated ADSCs expressed ACs markers such as α-amylase and aquaporin5. • High proliferation and low senescence were presented in CCA at Day 14. • Transdifferentiation of ADSCs into ACs using CCA may be an appropriate method for cell-based therapy.« less

Life Cycle of Midlatitude Deep Convective Systems in a Lagrangian Framework

NASA Technical Reports Server (NTRS)

Feng, Zhe; Dong, Xiquan; Xie, Baike; McFarlane, Sally A.; Kennedy, Aaron; Lin, Bing; Minnis, Patrick

2012-01-01

Deep Convective Systems (DCSs) consist of intense convective cores (CC), large stratiform rain (SR) regions, and extensive non-precipitating anvil clouds (AC). This study focuses on the evolution of these three components and the factors that affect convective AC production. An automated satellite tracking method is used in conjunction with a recently developed multi-sensor hybrid classification to analyze the evolution of DCS structure in a Lagrangian framework over the central United States. Composite analysis from 4221 tracked DCSs during two warm seasons (May-August, 2010-2011) shows that maximum system size correlates with lifetime, and longer-lived DCSs have more extensive SR and AC. Maximum SR and AC area lag behind peak convective intensity and the lag increases linearly from approximately 1-hour for short-lived systems to more than 3-hours for long-lived ones. The increased lag, which depends on the convective environment, suggests that changes in the overall diabatic heating structure associated with the transition from CC to SR and AC could prolong the system lifetime by sustaining stratiform cloud development. Longer-lasting systems are associated with up to 60% higher mid-tropospheric relative humidity and up to 40% stronger middle to upper tropospheric wind shear. Regression analysis shows that the areal coverage of thick AC is strongly correlated with the size of CC, updraft strength, and SR area. Ambient upper tropospheric wind speed and wind shear also play an important role for convective AC production where for systems with large AC (radius greater than 120-km) they are 24% and 20% higher, respectively, than those with small AC (radius=20 km).

High-Frequency ac Power-Distribution System

NASA Technical Reports Server (NTRS)

Hansen, Irving G.; Mildice, James

1987-01-01

Loads managed automatically under cycle-by-cycle control. 440-V rms, 20-kHz ac power system developed. System flexible, versatile, and "transparent" to user equipment, while maintaining high efficiency and low weight. Electrical source, from dc to 2,200-Hz ac converted to 440-V rms, 20-kHz, single-phase ac. Power distributed through low-inductance cables. Output power either dc or variable ac. Energy transferred per cycle reduced by factor of 50. Number of parts reduced by factor of about 5 and power loss reduced by two-thirds. Factors result in increased reliability and reduced costs. Used in any power-distribution system requiring high efficiency, high reliability, low weight, and flexibility to handle variety of sources and loads.

Activation and evaluation of GaN photocathodes

NASA Astrophysics Data System (ADS)

Qian, Yunsheng; Chang, Benkang; Qiao, Jiangliang; Zhang, Yijun; Fu, Rongguo; Qiu, Yafeng

2009-09-01

Gallium Nitride (GaN) photocathodes are potentially attractive as UV detective materials and electron sources. Based on the activation and evaluation system for GaAs photocathode, which consists of ultra-high vacuum (UHV) activation chamber, multi-information measurement system, X-ray photoelectron spectroscopy (XPS), and ultraviolet ray photoelectron spectroscopy (UPS), the control and measurement system for the activation of UV photocathodes was developed. The developed system, which consists of Xenon lamp, monochromator with scanner, signal-processing module, power control unit of Cs and O source, A/D adapter, digital I/O card, computer and software, can control the activation of GaN photocathodes and measure on-line the spectral response curves of GaN photocathodes. GaN materials on sapphire substrate were grown by Metal-Organic Chemical Vapor Deposition (MOCVD) with p-type Mg doping. The GaN materials were activated by Cs-O. The spectral response and quantum efficiency (QE) were measured and calculated. The experiment results are discussed.

Preparation of clean surfaces and Se vacancy formation in Bi2Se3 by ion bombardment and annealing

NASA Astrophysics Data System (ADS)

Zhou, Weimin; Zhu, Haoshan; Valles, Connie M.; Yarmoff, Jory A.

2017-08-01

Bismuth Selenide (Bi2Se3) is a topological insulator (TI) with a structure consisting of stacked quintuple layers. Single crystal surfaces are commonly prepared by mechanical cleaving. This work explores the use of low energy Ar+ ion bombardment and annealing (IBA) as an alternative method to produce reproducible and stable Bi2Se3 surfaces under ultra-high vacuum (UHV). It is found that a clean and well-ordered surface can be prepared by a single cycle of 1 keV Ar+ ion bombardment and 30 min of annealing. Low energy electron diffraction (LEED) and detailed low energy ion scattering (LEIS) measurements show no differences between IBA-prepared surfaces and those prepared by in situ cleaving in UHV. Analysis of the LEED patterns shows that the optimal annealing temperature is 450 °C. Angular LEIS scans reveal the formation of surface Se vacancies when the annealing temperature exceeds 520 °C.

Stoichiometric and Oxygen-Deficient VO2 as Versatile Hole Injection Electrode for Organic Semiconductors.

PubMed

Fu, Keke; Wang, Rongbin; Katase, Takayoshi; Ohta, Hiromichi; Koch, Norbert; Duhm, Steffen

2018-03-28

Using photoemission spectroscopy, we show that the surface electronic structure of VO 2 is determined by the temperature-dependent metal-insulator phase transition and the density of oxygen vacancies, which depends on the temperature and ultrahigh vacuum (UHV) conditions. The atomically clean and stoichiometric VO 2 surface is insulating at room temperature and features an ultrahigh work function of up to 6.7 eV. Heating in UHV just above the phase transition temperature induces the expected metallic phase, which goes in hand with the formation of oxygen defects (up to 6% in this study), but a high work function >6 eV is maintained. To demonstrate the suitability of VO 2 as hole injection contact for organic semiconductors, we investigated the energy-level alignment with the prototypical organic hole transport material N, N'-di(1-naphthyl)- N, N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB). Evidence for strong Fermi-level pinning and the associated energy-level bending in NPB is found, rendering an Ohmic contact for holes.

Simultaneous distribution of AC and DC power

DOEpatents

Polese, Luigi Gentile

2015-09-15

A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

78 FR 39345 - ACS Wireless, Inc.; Notice of Application

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-01

... on July 31, 1995 under the name MACTEL INC. Alaska Communications Systems Group, Inc. (``ACS Group...-owned subsidiary of ACS Group, held through ACS Group's wholly-owned subsidiary Alaska Communications... presently an investment company as defined in section 3(a) of the Act. 2. On June 4, 2012, ACS Group, ACS...

A new infusion pathway intactness monitoring system.

PubMed

Ogawa, Hidekuni; Yonezawa, Yoshiharu; Maki, Hiromichi; Ninomiya, Ishio; Sata, Koji; Hamada, Shingo; Caldwell, W Morton

2006-01-01

A new infusion pathway monitoring system has been developed for hospital and home use. The system consists of linear integrated circuits and a low-power 8-bit single chip microcomputer which constantly monitors the infusion pathway intactness. An AC (alternating current) voltage is induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. The induced AC voltage can be recorded by a main electrode wrapped around the infusion polyvinyl chloride tube. A reference electrode is wrapped on the electrode to monitor the AC voltage around the main electrode. If the injection needle or infusion tube becomes detached, then the system detects changes in the induced AC voltages and alerts the nursing station, via the nurse call system or PHS (personal handy phone system).

System and method for monitoring and controlling stator winding temperature in a de-energized AC motor

DOEpatents

Lu, Bin [Kenosha, WI; Luebke, Charles John [Sussex, WI; Habetler, Thomas G [Snellville, GA; Zhang, Pinjia [Atlanta, GA; Becker, Scott K [Oak Creek, WI

2011-12-27

A system and method for measuring and controlling stator winding temperature in an AC motor while idling is disclosed. The system includes a circuit having an input connectable to an AC source and an output connectable to an input terminal of a multi-phase AC motor. The circuit further includes a plurality of switching devices to control current flow and terminal voltages in the multi-phase AC motor and a controller connected to the circuit. The controller is configured to activate the plurality of switching devices to create a DC signal in an output of the motor control device corresponding to an input to the multi-phase AC motor, determine or estimate a stator winding resistance of the multi-phase AC motor based on the DC signal, and estimate a stator temperature from the stator winding resistance. Temperature can then be controlled and regulated by DC injection into the stator windings.

High-frequency ac power distribution in Space Station

NASA Technical Reports Server (NTRS)

Tsai, Fu-Sheng; Lee, Fred C. Y.

1990-01-01

A utility-type 20-kHz ac power distribution system for the Space Station, employing resonant power-conversion techniques, is presented. The system converts raw dc voltage from photovoltaic cells or three-phase LF ac voltage from a solar dynamic generator into a regulated 20-kHz ac voltage for distribution among various loads. The results of EASY5 computer simulations of the local and global performance show that the system has fast response and good transient behavior. The ac bus voltage is effectively regulated using the phase-control scheme, which is demonstrated with both line and load variations. The feasibility of paralleling the driver-module outputs is illustrated with the driver modules synchronized and sharing a common feedback loop. An HF sinusoidal ac voltage is generated in the three-phase ac input case, when the driver modules are phased 120 deg away from one another and their outputs are connected in series.

Function analysis of Ac-PCNA and Sf-PCNA during the Autographa californica multiple nucleopolyhedrovirus infection process.

PubMed

Fu, Yuejun; Wang, Ruisheng; Liang, Aihua

2018-06-01

The baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) possesses a gene, ac-pcna or ac49, which encodes a protein with similarity to proliferating cell nuclear antigen (PCNA). Homologs of this gene code for DNA polymerase processivity factors and are essential in the DNA replication systems. But the function of ac-pcna still remains unclear. To define the function of Ac-pcna in AcMNPV and Sf-pcna in host Sf9 cells, Bac-to-Bac baculovirus expression system was used to generate two recombinant baculoviruses: AcMNPV-Ac-pcna-EGFP and AcMNPV-Sf-pcna-EGFP. Results indicated that AcMNPV-mediated overexpression of Ac-PCNA and Sf-PCNA could stimulate replication of AcMNPV genome in the host Sf9 cells. Meanwhile, either AcMNPV-Ac-pcna-EGFP or AcMNPV-Sf-pcna-EGFP had a significant stimulating effect on Sf9 genome replication during infection. We also found that Ac-PCNA and Sf-PCNA could promote the production of budded virus. Ac-PCNA could improve the transcription level of ie2 gene dramatically and further improved the transcription of late gene, for example 38 K and vp39, at 12 h p.i.. Moreover, insecticidal potency test showed that the larvae of Beet armyworm in the AcMNPV-Ac-pcna-EGFP and AcMNPV-Sf-pcna-EGFP groups had a higher mortality rate (83.33 and 91.67%), a lower pupation rate (16.67 and 8.33%), and a lower emergence rate (6.67 and 3.33%), compared with those in AcMNPV-EGFP group. The function of Ac-PCNA and Sf-PCNA was confirmed in this study, which provided the theoretical foundation for using and modifying AcMNPV.

Superconducting magnetic energy storage for asynchronous electrical systems

DOEpatents

Boenig, Heinrich J.

1986-01-01

A superconducting magnetic energy storage coil connected in parallel between converters of two or more ac power systems provides load leveling and stability improvement to any or all of the ac systems. Control is provided to direct the charging and independently the discharging of the superconducting coil to at least a selected one of the ac power systems.

Adenylyl cyclases in the digestive system.

PubMed

Sabbatini, Maria Eugenia; Gorelick, Fred; Glaser, Shannon

2014-06-01

Adenylyl cyclases (ACs) are a group of widely distributed enzymes whose functions are very diverse. There are nine known transmembrane AC isoforms activated by Gαs. Each has its own pattern of expression in the digestive system and differential regulation of function by Ca(2+) and other intracellular signals. In addition to the transmembrane isoforms, one AC is soluble and exhibits distinct regulation. In this review, the basic structure, regulation and physiological roles of ACs in the digestive system are discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

Adenylyl cyclases in the digestive system

PubMed Central

Sabbatini, Maria Eugenia; Gorelick, Fred; Glaser, Shannon

2015-01-01

Adenylyl cyclases (ACs) are a group of widely distributed enzymes whose functions are very diverse. There are nine known transmembrane AC isoforms activated by Gαs. Each has its own pattern of expression in the digestive system and differential regulation of function by Ca2+ and other intracellular signals. In addition to the transmembrane isoforms, one AC is soluble and exhibits distinct regulation. In this review, the basic structure, regulation and physiological roles of ACs in the digestive system are discussed. PMID:24521753

AC propulsion system for an electric vehicle, phase 2

NASA Astrophysics Data System (ADS)

Slicker, J. M.

1983-06-01

A second-generation prototype ac propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the Contractor's site. The system consisted of a Phase 2, 18.7 kw rated ac induction traction motor, a 192-volt, battery powered, pulse-width-modulated, transistorized inverter packaged for under rear seat installation, a 2-axis, 2-speed, automatically-shifted mechanical transaxle and a microprocessor-based powertrain/vehicle controller. A diagnostics computer to assist tuning and fault finding was fabricated. Dc-to-mechanical-system efficiency varied from 78% to 82% as axle speed/torque ranged from 159 rpm/788 nm to 65 rpm/328 nm. Track test efficiency results suggest that the ac system will be equal or superior to dc systems when driving urban cycles. Additional short-term work is being performed under a third contract phase (AC-3) to raise transaxle efficiency to predicted levels, and to improve starting and shifting characteristics. However, the long-term challenge to the system's viability remains inverter cost. A final report on the Phase 2 system, describing Phase 3 modifications, will be issued at the conclusion of AC-3.

AC propulsion system for an electric vehicle, phase 2

NASA Technical Reports Server (NTRS)

Slicker, J. M.

1983-01-01

A second-generation prototype ac propulsion system for a passenger electric vehicle was designed, fabricated, tested, installed in a modified Mercury Lynx vehicle and track tested at the Contractor's site. The system consisted of a Phase 2, 18.7 kw rated ac induction traction motor, a 192-volt, battery powered, pulse-width-modulated, transistorized inverter packaged for under rear seat installation, a 2-axis, 2-speed, automatically-shifted mechanical transaxle and a microprocessor-based powertrain/vehicle controller. A diagnostics computer to assist tuning and fault finding was fabricated. Dc-to-mechanical-system efficiency varied from 78% to 82% as axle speed/torque ranged from 159 rpm/788 nm to 65 rpm/328 nm. Track test efficiency results suggest that the ac system will be equal or superior to dc systems when driving urban cycles. Additional short-term work is being performed under a third contract phase (AC-3) to raise transaxle efficiency to predicted levels, and to improve starting and shifting characteristics. However, the long-term challenge to the system's viability remains inverter cost. A final report on the Phase 2 system, describing Phase 3 modifications, will be issued at the conclusion of AC-3.

Improved transistorized AC motor controller for battery powered urban electric passenger vehicles

NASA Technical Reports Server (NTRS)

Peak, S. C.

1982-01-01

An ac motor controller for an induction motor electric vehicle drive system was designed, fabricated, tested, evaluated, and cost analyzed. A vehicle performance analysis was done to establish the vehicle tractive effort-speed requirements. These requirements were then converted into a set of ac motor and ac controller requirements. The power inverter is a three-phase bridge using power Darlington transistors. The induction motor was optimized for use with an inverter power source. The drive system has a constant torque output to base motor speed and a constant horsepower output to maximum speed. A gear shifting transmission is not required. The ac controller was scaled from the base 20 hp (41 hp peak) at 108 volts dec to an expanded horsepower and battery voltage range. Motor reversal was accomplished by electronic reversal of the inverter phase sequence. The ac controller can also be used as a boost chopper battery charger. The drive system was tested on a dynamometer and results are presented. The current-controlled pulse width modulation control scheme yielded improved motor current waveforms. The ac controller favors a higher system voltage.

Development of a hardware-based AC microgrid for AC stability assessment

NASA Astrophysics Data System (ADS)

Swanson, Robert R.

As more power electronic-based devices enable the development of high-bandwidth AC microgrids, the topic of microgrid power distribution stability has become of increased interest. Recently, researchers have proposed a relatively straightforward method to assess the stability of AC systems based upon the time-constants of sources, the net bus capacitance, and the rate limits of sources. In this research, a focus has been to develop a hardware test system to evaluate AC system stability. As a first step, a time domain model of a two converter microgrid was established in which a three phase inverter acts as a power source and an active rectifier serves as an adjustable constant power AC load. The constant power load can be utilized to create rapid power flow transients to the generating system. As a second step, the inverter and active rectifier were designed using a Smart Power Module IGBT for switching and an embedded microcontroller as a processor for algorithm implementation. The inverter and active rectifier were designed to operate simultaneously using a synchronization signal to ensure each respective local controller operates in a common reference frame. Finally, the physical system was created and initial testing performed to validate the hardware functionality as a variable amplitude and variable frequency AC system.

Reactive and recoverable sorbents for halogenated organic compound remediation in sediments

NASA Astrophysics Data System (ADS)

Werner, David; Taggalou, Villy; Kordulis, Christos; Dolfing, Jan; Karapanagioti, Hrissi K.

2013-04-01

Activated carbon (AC) has been proposed as a sediment amendment for aquatic systems polluted with hydrophobic organic compounds. AC acts as a strong binding agent that lowers the pollutant concentration and thus, its toxicity. A draw back of this in-situ remediation method is that although the pollutant will remain non-bioavailable for many years being sorbed into AC, it actually stays in the system. A reactive sorbent, a sorbent that would, at the same time, facilitate the degradation of the pollutant, would be better accepted by the public or the regulators than AC amendment. So far, catalysts supported on AC with zero valent iron and a reactive metal have been proposed for the dechlorination of chlorinated organic compounds. These reactive metals are usually expensive or toxic and thus, their addition to the environment is not desirable. In the present study, activated carbon modified with reduced iron(AC/Fe) is tested in batch systems in the presence of sediment and DDT sorbed on polyethylene sheets. The batch systems are equilibrated for different contact times. Then, the DDT remaining in the polyethylene sheets is quantified along with DDD produced due to the dechlorination of DDT. A small percentage of DDT is degraded to DDD in the systems containing the AC/Fe material. No degradation of DDT is observed in the control systems containing the pollutant and the sediment or the pollutant, the sediment and AC. Thus, the addition of AC/Fe to the sediment with the DDT is enough to cause the dechlorination of DDT. At the end of the experiments, a magnet rod is used to recover the AC/Fe material from the batches with the sediment. An average recovery of 83% is achieved. This is a high percentage suggesting that the material can be easily recovered. Some drawbacks of the material preparation method are identified after the composite material characterization. For example, the AC/Fe surface area is decreased with the material preparation compared to the initial surface area of the AC. This fact results in decrease of the sorption ability of the AC/Fe material compared to that of the AC. At the same time, more DDT degradation might be achievable by increasing the AC/Fe dosage from the 1% weight used in this study that is lower than commonly used for sediment amendments. More research is necessary to optimize the material preparation and properties.

Method and system for a gas tube-based current source high voltage direct current transmission system

DOEpatents

She, Xu; Chokhawala, Rahul Shantilal; Bray, James William; Sommerer, Timothy John; Zhou, Rui; Zhang, Di

2017-08-29

A high-voltage direct-current (HVDC) transmission system includes an alternating current (AC) electrical source and a power converter channel that includes an AC-DC converter electrically coupled to the electrical source and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and the DC-AC inverter each include a plurality of legs that includes at least one switching device. The power converter channel further includes a commutating circuit communicatively coupled to one or more switching devices. The commutating circuit is configured to "switch on" one of the switching devices during a first portion of a cycle of the H-bridge switching circuits and "switch off" the switching device during a second portion of the cycle of the first and second H-bridge switching circuits.

Mathematical model for the dc-ac inverter for the Space Shuttle

NASA Technical Reports Server (NTRS)

Berry, Frederick C.

1987-01-01

The reader is informed of what was done for the mathematical modeling of the dc-ac inverter for the Space Shuttle. The mathematical modeling of the dc-ac inverter is an essential element in the modeling of the electrical power distribution system of the Space Shuttle. The electrical power distribution system which is present on the Space Shuttle is made up to 3 strings each having a fuel cell which provides dc to those systems which require dc, and the inverters which convert the dc to ac for those elements which require ac. The inverters are units which are 2 wire structures for the main dc inputs and 2 wire structures for the ac output. When 3 are connected together a 4 wire wye connection results on the ac side. The method of modeling is performed by using a Least Squares curve fitting method. A computer program is presented for implementation of the model along with graphs and tables to demonstrate the accuracy of the model.

The AC photovoltaic module is here!

NASA Astrophysics Data System (ADS)

Strong, Steven J.; Wohlgemuth, John H.; Wills, Robert H.

1997-02-01

This paper describes the design, development, and performance results of a large-area photovoltaic module whose electrical output is ac power suitable for direct connection to the utility grid. The large-area ac PV module features a dedicated, integrally mounted, high-efficiency dc-to-ac power inverter with a nominal output of 250 watts (STC) at 120 Vac, 60 H, that is fully compatible with utility power. The module's output is connected directly to the building's conventional ac distribution system without need for any dc wiring, string combiners, dc ground-fault protection or additional power-conditioning equipment. With its advantages, the ac photovoltaic module promises to become a universal building block for use in all utility-interactive PV systems. This paper discusses AC Module design aspects and utility interface issues (including islanding).

Electrostatic coalescence system with independent AC and DC hydrophilic electrodes

DOEpatents

Hovarongkura, A. David; Henry, Jr., Joseph D.

1981-01-01

An improved electrostatic coalescence system is provided in which independent AC and DC hydrophilic electrodes are employed to provide more complete dehydration of an oil emulsion. The AC field is produced between an AC electrode array and the water-oil interface wherein the AC electrode array is positioned parallel to the interface which acts as a grounded electrode. The emulsion is introduced into the AC field in an evenly distributed manner at the interface. The AC field promotes drop-drop and drop-interface coalescence of the water phase in the entering emulsion. The continuous oil phase passes upward through the perforated AC electrode array and enters a strong DC field produced between closely spaced DC electrodes in which small dispersed droplets of water entrained in the continuous phase are removed primarily by collection at hydrophilic DC electrodes. Large droplets of water collected by the electrodes migrate downward through the AC electrode array to the interface. All phase separation mechanisms are utilized to accomplish more complete phase separation.

Ultra high vacuum heating and rotating specimen stage

DOEpatents

Coombs, III, Arthur W.

1995-01-01

A heating and rotating specimen stage provides for simultaneous specimen heating and rotating. The stage is ideally suited for operation in ultrahigh vacuum (1.times.10.sup.-9 torr or less), but is useful at atmosphere and in pressurized systems as well. A specimen is placed on a specimen holder that is attached to a heater that, in turn, is attached to a top housing. The top housing is rotated relative to a bottom housing and electrically connected thereto by electrically conductive brushes. This stage is made of materials that are compatible with UHV, able to withstand high temperatures, possess low outgassing rates, are gall and seize resistant, and are able to carry substantial electrical loading without overheating.

Experimental system for drilling simulated lunar rock in ultrahigh vacuum

NASA Technical Reports Server (NTRS)

Roepke, W. W.

1975-01-01

An experimental apparatus designed for studying drillability of hard volcanic rock in a simulated lunar vacuum of 5 x 10 to the minus 10th power torr is described. The engineering techniques used to provide suitable drilling torque inside the ultrahigh vacuum chamber while excluding all hydrocarbon are detailed. Totally unlubricated bearings and gears were used to better approximate the true lunar surface conditions within the ultrahigh vacuum system. The drilling system has a starting torque of 30 in-lb with an unloaded running torque of 4 in-lb. Nominal torque increase during drilling is 4.5 in-lb or a total drilling torque of 8.5 in-lb with a 100-lb load on the drill bit at 210 rpm. The research shows conclusively that it is possible to design operational equipment for moderate loads operating under UHV conditions without the use of sealed bearings or any need of lubricants whatsoever.

dc Arc Fault Effect on Hybrid ac/dc Microgrid

NASA Astrophysics Data System (ADS)

Fatima, Zahra

The advent of distributed energy resources (DER) and reliability and stability problems of the conventional grid system has given rise to the wide spread deployment of microgrids. Microgrids provide many advantages by incorporating renewable energy sources and increasing the reliability of the grid by isolating from the main grid in case of an outage. AC microgrids have been installed all over the world, but dc microgrids have been gaining interest due to the advantages they provide over ac microgrids. However the entire power network backbone is still ac and dc microgrids require expensive converters to connect to the ac power network. As a result hybrid ac/dc microgrids are gaining more attention as it combines the advantages of both ac and dc microgrids such as direct integration of ac and dc systems with minimum number of conversions which increases the efficiency by reducing energy losses. Although dc electric systems offer many advantages such as no synchronization and no reactive power, successful implementation of dc systems requires appropriate protection strategies. One unique protection challenge brought by the dc systems is dc arc faults. A dc arc fault is generated when there is a gap in the conductor due to insulation degradation and current is used to bridge the gap, resulting in an arc with very high temperature. Such a fault if it goes undetected and is not extinguished can cause damage to the entire system and cause fires. The purpose of the research is to study the effect of the dc arc fault at different locations in the hybrid ac/dc microgrid and provide insight on the reliability of the grid components when it is impacted by arc faults at various locations in the grid. The impact of dc arc fault at different locations on the performance of the PV array, wind generation, and constant power loads (CPL) interfaced with dc/dc converters is studied. MATLAB/Simulink is used to model the hybrid ac/dc microgrid and arc fault.

Controlling hydrogenation activity and selectivity of bimetallic surfaces and catalysts

NASA Astrophysics Data System (ADS)

Murillo, Luis E.

Studies of bimetallic systems are of great interest in catalysis due to the novel properties that they often show in comparison with the parent metals. The goals of this dissertation are: (1) to expand the studies of self-hydrogenation and hydrogenation reactions on bimetallic surfaces under ultra high vacuum conditions (UHV) using different hydrocarbon as probe molecules; (2) to attempt to correlate the surface science findings with supported catalyst studies under more realistic conditions; and (3) to investigate the competitive hydrogenation of C=C versus C=O bonds on Pt(111) modified by different 3d transition metals. Hydrogenation studies using temperature programmed desorption (TPD) on Ni/Pt(111) bimetallic surfaces have demonstrated an enhancement in the low temperature hydrogenation activity relative to that of clean Pt(111). This novel hydrogenation pathway can be achieved under UHV conditions by controlling the structures of the bimetallic surfaces. A low temperature hydrogenation activity of 1-hexene and 1-butene has been observed on a Pt-Ni-Pt(111) subsurface structure, where Ni atoms are mainly present on the second layer of the Pt(111) single crystal. These results are in agreement with previous studies of self-hydrogenation and hydrogenation of cyclohexene. However, a much higher dehydrogenation activity is observed in the reaction of cyclohexene to produce benzene, demonstrating that the hydrocarbon structure has an effect on the reaction pathways. On the other hand, self-hydrogenation of 1-butene is not observed on the Pt-Ni-Pt(111) surface, indicating that the chain length (or molecular weight) has a significant effect on the selfhydrogenation activity. The gas phase reaction of cyclohexene on Ni/Pt supported on alumina catalysts has also shown a higher self-hydrogenation activity in comparison with the same reaction performed on supported monometallic catalysts. The effects of metal loading and impregnation sequence of the metal precursors are also discussed. Chemisorption, TPD, FTIR using a batch reactor for the self-hydrogenation of cyclohexene and CO adsorbed on the bimetallic surfaces were carried out to correlate surface science findings with experiments on supported bimetallic catalysts. To expand the studies on the effect of bimetallic structures on hydrogenation reactions, molecules with multiple functional groups such as alpha,beta-unsaturated aldehydes were also investigated. Studies of selective hydrogenation of a,ss-unsaturated aldehydes toward the desired unsaturated alcohols are of interest for the production of fine chemicals and pharmaceuticals. In these compounds, competitive hydrogenation of the C=C and C=O bonds occurs. TPD and HREELS experiments of acrolein (CH2=CH-CH=O) on Pt-based bimetallic surfaces are performed to investigate their effects on the hydrogenation activity of the C-O bond. The production of the desired unsaturated alcohol, allyl alcohol, has been observed for the first time on Pt-Ni-Pt(111) under UHV conditions. However, the propionaldehyde yield is five times higher than the allyl alcohol yield. Thus, a preferential isomerization reaction of allyl alcohol to propionaldehyde is very likely to occur on the Pt-Ni-Pt(111) surface as observed on the desorption studies of allyl alcohol on this surface. The hydrogenation of acrolein is also carried out under UHV conditions on other 3d-transition metal/Pt(111) surfaces such as Co/Pt(111), Fe/Pt(111), and Cu/Pt(111). So far, the highest activity and allyl alcohol yield are found on the Pt-Ni-Pt(111) surface with pre-adsorbed hydrogen.

Removal of sulfa drugs by sewage treatment in aqueous solution systems: activated carbon treatment and ozone oxidation.

PubMed

Ogata, Fumihiko; Tominaga, Hisato; Kangawa, Moe; Inoue, Kenji; Kawasaki, Naohito

2012-01-01

This study investigates the activated carbon (AC) treatment and ozone oxidation of the sulfa drugs--sulfamethoxazole (SMX), sulfamonomethoxine (SMM), sulfadimidine (SDD), and sulfadimethoxine (SDM)--in aqueous solution systems. Three AC samples were prepared from Shirasagi (AC1 and AC2) and coal (AC3), and the surface functional groups, solution pH, specific surface areas, pore volumes, and morphologies of the three samples were evaluated. The specific surface areas were in the following order: AC1 (1391 m²/g) > AC2 (1053 m²/g) > AC3 (807 m²/g). The pore volume and mean pore diameter of AC3 were greater than those of AC1 and AC2. The concentration of sulfa drugs adsorbed onto the AC samples reached equilibrium within 150 h. Experimental data of the adsorption rate were fitted to a pseudo-second-order model. The amount of sulfa drugs adsorbed onto the AC samples was in the order of SDM < SMM < SDD < SMX; the mechanism of adsorption of the sulfa drugs onto the AC samples depended on the hydrophobicity of the AC surface. The adsorption isotherm data were fitted to Freundlich and Langmuir models. Ozone was generated from oxygen gas using an A-27 ozone generator, and the complete degradation of the sulfa drugs by ozone treatment at 60 mL/min was achieved within 50 min. Ozone treatment caused the structure of the sulfa drugs to decompose via ozone oxidation.

Usefulness of tissue autofluorescence imaging in actinic cheilitis diagnosis.

PubMed

Takahama Junior, Ademar; Kurachi, Cristina; Cosci, Alessandro; Pereira Faustino, Isabel Schausltz; Camisasca, Danielle Resende; da Costa Fontes, Karla Bianca Fernandes; Pires, Fábio Ramôa; Azevedo, Rebeca Souza

2013-07-01

Actinic cheilitis (AC) is a potentially malignant disorder of the lips. Because of its heterogeneous clinical aspect, it is difficult to indicate representative biopsy area. The purpose of this study was to evaluate the usefulness of tissue autofluorescence in AC diagnosis. The system was composed of a 405-nm light-emitting diode, sent to the sample by a dichroic, that allows the fluorescence signal to reach a camera directly plugged in the system. Fifty-seven patients with clinical diagnosis of AC and 45 normal volunteers were selected. According to clinical and fluorescence features, one or more areas were selected for biopsies in the AC group and epithelial dysplasia (ED) grades were established. The autofluorescence images were processed by a clustering algorithm for AC automated diagnosis. The tissue autofluorescence image revealed a heterogeneous pattern of loss and increase of fluorescence in patients with AC. ED was found in 93% of the cases, and most of the areas graded as moderate or severe ED were chosen with the aid of autofluorescence. The processed autofluorescence images from AC patients showed a higher number of spots in an irregular pattern. Tissue autofluorescence image system is a useful technique in association with clinical examination for AC diagnosis.

Small Business Specialists

DTIC Science & Technology

1993-01-01

AF) Ms. Nicole A. Dillon Williams AFB AC 602/988-6618 85224-5004 Fort Huachuca HQ U.S. Army Information Systems Command (A) Mr. Michael P. Dean* ATTN...Army Medical Center (A) Maj Paul G. Michaels ATTN: HSAA-L Mr. William Brundage Presidio of San Francisco AC 415/561-5473/6289 94124-6700 SUPSHIP...Systems Division AC 408/224-7748 P. 0. Box 49028 95161-9028 San Luis Obispo National Guard (A)(AF) Col William T. Mongold USPFO for California AC 805

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

Chang, Hao, E-mail: hc000211@ohio.edu; Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701; Cummings, Marvin

High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beammore » attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.« less

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

Chang, Hao; Cummings, Marvin L.; Shirato, Nozomi

High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the requiredmore » beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.« less

State-dependent effects of transcranial oscillatory currents on the motor system: what you think matters.

PubMed

Feurra, Matteo; Pasqualetti, Patrizio; Bianco, Giovanni; Santarnecchi, Emiliano; Rossi, Alessandro; Rossi, Simone

2013-10-30

Imperceptible transcranial alternating current stimulation (tACS) changes the endogenous cortical oscillatory activity in a frequency-specific manner. In the human motor system, tACS coincident with the idling beta rhythm of the quiescent motor cortex increased the corticospinal output. We reasoned that changing the initial state of the brain (i.e., from quiescence to a motor imagery task that desynchronizes the local beta rhythm) might also change the susceptibility of the corticospinal system to resonance effects induced by beta-tACS. We tested this hypothesis by delivering tACS at different frequencies (theta, alpha, beta, and gamma) on the primary motor cortex at rest and during motor imagery. Motor-evoked potentials (MEPs) were obtained by transcranial magnetic stimulation (TMS) on the primary motor cortex with an online-navigated TMS-tACS setting. During motor imagery, the increase of corticospinal excitability was maximal with theta-tACS, likely reflecting a reinforcement of working memory processes required to mentally process and "execute" the cognitive task. As expected, the maximal MEPs increase with subjects at rest was instead obtained with beta-tACS, substantiating previous evidence. This dissociation provides new evidence of state and frequency dependency of tACS effects on the motor system and helps discern the functional role of different oscillatory frequencies of this brain region. These findings may be relevant for rehabilitative neuromodulatory interventions.

A Novel Multilevel DC - AC Converter from Green Energy Power Generators Using Step-Square Waving and PWM Technique

NASA Astrophysics Data System (ADS)

Fajingbesi, F. E.; Midi, N. S.; Khan, S.

2017-06-01

Green energy sources or renewable energy system generally utilize modular approach in their design. This sort of power sources are generally in DC form or in single cases AC. Due to high fluctuation in the natural origin of this energy (wind & solar) source they are stored as DC. DC power however are difficult to transfer over long distances hence DC to AC converters and storage system are very important in green energy system design. In this work we have designed a novel multilevel DC to AC converter that takes into account the modular design of green energy systems. A power conversion efficiency of 99% with reduced total harmonic distortion (THD) was recorded from our simulated system design.

Augmentation Award for Surface Science Research Training.

DTIC Science & Technology

1996-11-01

atomic force microscopy facility. In particular, he designed an anechoic chamber for minimizing acoustical noise in our air and electrochemistry imaging...well as our new air/electochemical STM/AFM. In addition to the UHV-STM, the 11/20/96 10:43 e773 702 5863 J.F.I. I•On7 new air- levitated vactium rhnrher

High-quality EuO thin films the easy way via topotactic transformation

DOE PAGES

Mairoser, Thomas; Mundy, Julia A.; Melville, Alexander; ...

2015-07-16

Epitaxy is widely employed to create highly oriented crystalline films. A less appreciated, but nonetheless powerful means of creating such films is via topotactic transformation, in which a chemical reaction transforms a single crystal of one phase into a single crystal of a different phase, which inherits its orientation from the original crystal. Topotactic reactions may be applied to epitactic films to substitute, add or remove ions to yield epitactic films of different phases. Here we exploit a topotactic reduction reaction to provide a non-ultra-high vacuum (UHV) means of growing highly oriented single crystalline thin films of the easily over-oxidizedmore » half-metallic semiconductor europium monoxide (EuO) with a perfection rivalling that of the best films of the same material grown by molecular-beam epitaxy or UHV pulsed-laser deposition. Lastly, as the technique only requires high-vacuum deposition equipment, it has the potential to drastically improve the accessibility of high-quality single crystalline films of EuO as well as other difficult-to-synthesize compounds.« less

Scanning probe microscopy induced surface modifications of the topological insulator Bi2Te3 in different environments

NASA Astrophysics Data System (ADS)

Netsou, Asteriona-Maria; Thupakula, Umamahesh; Debehets, Jolien; Chen, Taishi; Hirsch, Brandon; Volodin, Alexander; Li, Zhe; Song, Fengqi; Seo, Jin Won; De Feyter, Steven; Schouteden, Koen; Van Haesendonck, Chris

2017-08-01

We investigated the topological insulator (TI) Bi2Te3 in four different environments (ambient, ultra-high vacuum (UHV), nitrogen gas and organic solvent environment) using scanning probe microscopy (SPM) techniques. Upon prolonged exposure to ambient conditions and organic solvent environments the cleaved surface of the pristine Bi2Te3 is observed to be strongly modified during SPM measurements, while imaging of freshly cleaved Bi2Te3 in UHV and nitrogen gas shows considerably less changes of the Bi2Te3 surface. We conclude that the reduced surface stability upon exposure to ambient conditions is triggered by adsorption of molecular species from ambient, including H2O, CO2, etc which is verified by Auger electron spectroscopy. Our findings of the drastic impact of exposure to ambient on the Bi2Te3 surface are crucial for further in-depth studies of the intrinsic properties of the TI Bi2Te3 and for potential applications that include room temperature TI based devices operated under ambient conditions.

Compact low temperature scanning tunneling microscope with in-situ sample preparation capability

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

Kim, Jungdae; Department of Physics and EHSRC, University of Ulsan, Ulsan 680-749; Nam, Hyoungdo

2015-09-15

We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper andmore » stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.« less

Compact low temperature scanning tunneling microscope with in-situ sample preparation capability.

PubMed

Kim, Jungdae; Nam, Hyoungdo; Qin, Shengyong; Kim, Sang-ui; Schroeder, Allan; Eom, Daejin; Shih, Chih-Kang

2015-09-01

We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper and stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.

Perspective: Chemical reactions in ionic liquids monitored through the gas (vacuum)/liquid interface.

PubMed

Maier, F; Niedermaier, I; Steinrück, H-P

2017-05-07

This perspective analyzes the potential of X-ray photoelectron spectroscopy under ultrahigh vacuum (UHV) conditions to follow chemical reactions in ionic liquids in situ. Traditionally, only reactions occurring on solid surfaces were investigated by X-ray photoelectron spectroscopy (XPS) in situ. This was due to the high vapor pressures of common liquids or solvents, which are not compatible with the required UHV conditions. It was only recently realized that the situation is very different when studying reactions in Ionic Liquids (ILs), which have an inherently low vapor pressure, and first studies have been performed within the last years. Compared to classical spectroscopy techniques used to monitor chemical reactions, the advantage of XPS is that through the analysis of their core levels all relevant elements can be quantified and their chemical state can be analyzed under well-defined (ultraclean) conditions. In this perspective, we cover six very different reactions which occur in the IL, with the IL, or at an IL/support interface, demonstrating the outstanding potential of in situ XPS to gain insights into liquid phase reactions in the near-surface region.

De Novo Design and Experimental Characterization of Ultrashort Self-Associating Peptides

PubMed Central

Xue, Bo; Robinson, Robert C.; Hauser, Charlotte A. E.; Floudas, Christodoulos A.

2014-01-01

Self-association is a common phenomenon in biology and one that can have positive and negative impacts, from the construction of the architectural cytoskeleton of cells to the formation of fibrils in amyloid diseases. Understanding the nature and mechanisms of self-association is important for modulating these systems and in creating biologically-inspired materials. Here, we present a two-stage de novo peptide design framework that can generate novel self-associating peptide systems. The first stage uses a simulated multimeric template structure as input into the optimization-based Sequence Selection to generate low potential energy sequences. The second stage is a computational validation procedure that calculates Fold Specificity and/or Approximate Association Affinity (K*association) based on metrics that we have devised for multimeric systems. This framework was applied to the design of self-associating tripeptides using the known self-associating tripeptide, Ac-IVD, as a structural template. Six computationally predicted tripeptides (Ac-LVE, Ac-YYD, Ac-LLE, Ac-YLD, Ac-MYD, Ac-VIE) were chosen for experimental validation in order to illustrate the self-association outcomes predicted by the three metrics. Self-association and electron microscopy studies revealed that Ac-LLE formed bead-like microstructures, Ac-LVE and Ac-YYD formed fibrillar aggregates, Ac-VIE and Ac-MYD formed hydrogels, and Ac-YLD crystallized under ambient conditions. An X-ray crystallographic study was carried out on a single crystal of Ac-YLD, which revealed that each molecule adopts a β-strand conformation that stack together to form parallel β-sheets. As an additional validation of the approach, the hydrogel-forming sequences of Ac-MYD and Ac-VIE were shuffled. The shuffled sequences were computationally predicted to have lower K*association values and were experimentally verified to not form hydrogels. This illustrates the robustness of the framework in predicting self-associating tripeptides. We expect that this enhanced multimeric de novo peptide design framework will find future application in creating novel self-associating peptides based on unnatural amino acids, and inhibitor peptides of detrimental self-aggregating biological proteins. PMID:25010703

Photovoltaic system with improved AC connections and method of making same

DOEpatents

Cioffi, Philip Michael; Todorovic, Maja Harfman; Herzog, Michael Scott; Korman, Charles Steven; Doherty, Donald M.; Johnson, Neil Anthony

2018-02-13

An alternating current (AC) harness for a photovoltaic (PV) system includes a wire assembly having a first end and a second end, the wire assembly having a plurality of lead wires, and at least one AC connection module positioned at a location along a length of the wire assembly between the first end and the second end. Further, the at least one AC connection module includes a first connection terminal electrically coupled to the plurality of lead wires of the wire assembly and constructed to electrically couple the wire assembly with an output of a first PV module of the PV system. The at least one AC connection module also includes a second connection terminal electrically coupled to the plurality of lead wires of the wire assembly and constructed to electrically couple the wire assembly with an output of a second PV module of the PV system.

AC magnetic field measurement using a small flip coil system for rapid cycling AC magnets at the China Spallation Neutron Source (CSNS)

NASA Astrophysics Data System (ADS)

Zhou, Jianxin; Kang, Wen; Li, Shuai; Liu, Yudong; Liu, Yiqin; Xu, Shouyan; Guo, Xiaoling; Wu, Xi; Deng, Changdong; Li, Li; Wu, Yuwen; Wang, Sheng

2018-02-01

The China Spallation Neutron Source (CSNS) has two major accelerator systems, a linear accelerator and a rapid cycling synchrotron (RCS). The RCS accelerator is used to accumulate and accelerate protons from the energy of 80 MeV to the design energy of 1.6 GeV at the repetition rate of 25 Hz, and extract the high energy beam to the target. The main magnets of the RCS accelerator are excited by AC current with DC bias. The magnetic field quality is very important for the RCS accelerator operation, since it should guarantee and focus a circulating beam. In order to characterize the AC magnets, a small flip coil measurement system has been developed and one of each type of AC magnets has been studied. The measurement system and selected measurement results are presented in this paper.

Chance-Constrained AC Optimal Power Flow for Distribution Systems With Renewables

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

DallAnese, Emiliano; Baker, Kyri; Summers, Tyler

This paper focuses on distribution systems featuring renewable energy sources (RESs) and energy storage systems, and presents an AC optimal power flow (OPF) approach to optimize system-level performance objectives while coping with uncertainty in both RES generation and loads. The proposed method hinges on a chance-constrained AC OPF formulation where probabilistic constraints are utilized to enforce voltage regulation with prescribed probability. A computationally more affordable convex reformulation is developed by resorting to suitable linear approximations of the AC power-flow equations as well as convex approximations of the chance constraints. The approximate chance constraints provide conservative bounds that hold for arbitrarymore » distributions of the forecasting errors. An adaptive strategy is then obtained by embedding the proposed AC OPF task into a model predictive control framework. Finally, a distributed solver is developed to strategically distribute the solution of the optimization problems across utility and customers.« less

Mechanism of enhanced nitrate reduction via micro-electrolysis at the powdered zero-valent iron/activated carbon interface.

PubMed

Luo, Jinghuan; Song, Guangyu; Liu, Jianyong; Qian, Guangren; Xu, Zhi Ping

2014-12-01

Nitrate reduction by zero-valent iron (Fe(0)) powder always works well only at controlled pH lower than 4 due to the formation of iron (hydr)oxides on its surface. Fe(0) powder combined with activated carbon (AC), i.e., Fe(0)/AC micro-electrolysis system, was first introduced to enhance nitrate reduction in aqueous solution. Comparative study was carried out to investigate nitrate reduction by Fe(0)/AC system and Fe(0) under near-neutral conditions, showing that the Fe(0)/AC system successfully reduced nitrate even at initial pH 6 with the reduction efficiency of up to 73%, whereas for Fe(0) only ∼10%. The effect of Fe(0) to AC mass ratio on nitrate reduction efficiency was examined. Easier nitrate reduction was achieved with more contact between Fe(0) and AC as the result of decreasing Fe(0) to AC mass ratio. Ferrous ion and oxidation-reduction potential were measured to understand the mechanism of enhanced nitrate reduction by Fe(0)/AC micro-electrolysis. The results suggest that a relative potential difference drives much more electrons from Fe(0) to AC, thus generating adsorbed atomic hydrogen which makes it possible for nitrate to be reduced at near-neural pH. Fe(0)/AC micro-electrolysis thus presents a great potential for practical application in nitrate wastewater treatment without excessive pH adjustment. Copyright © 2014 Elsevier Inc. All rights reserved.

AC conductivity and Dielectric Study of Chalcogenide Glasses of Se-Te-Ge System

NASA Astrophysics Data System (ADS)

Salman, Fathy

2004-01-01

The ac conductivity and dielectric properties of glassy system SexTe79 - xGe21, with x = 11, 14, 17 at.%, has been studied at temperatures 300 to 450 K and over a wide range of frequencies (50 Hz to 500 kHz). Experimental results indicate that the ac conductivity and the dielectric constants depend on temperature, frequency and Se content. The conductivity as a function of frequency exhibited two components: dc conductivity s dc, and ac conductivity s ac, where s ac ˜ w s. The mechanism of ac conductivity can be reasonably interpreted in terms of the correlated barrier hopping model (CBH). The activation energies are estimated and discussed. The dependence of ac conductivity and dielectric constants on the Se content x can be interpreted as the effect of Se fraction on the positional disorder. The impedance plot at each temperature appeared as a semicircle passes through the origin. Each semicircle is represented by an equivalent circuit of parallel resistance Rb and capacitance Cb.

Pulsed Plasma Thrusters for Small Spacecraft Attitude Control

NASA Technical Reports Server (NTRS)

McGuire, Melissa L.; Myers, Roger M.

1996-01-01

Pulsed plasma thrusters (PPT's) are a new option for attitude control of a small spacecraft and may result in reduced attitude control system (ACS) mass and cost. The primary purpose of an ACS is to orient the spacecraft configuration to the desired accuracy in inertial space. The ACS functions for which the PPT system will be analyzed include disturbance torque compensation and slewing maneuvers such as sun acquisition for which the small impulse bit and high specific impulse of the PPT offers unique advantages. The NASA Lewis Reserach Center (LeRC) currently has a contracted flight PPT system development program in place with Olin Aerospace and a delivery date of October 1997. The PPT system in this study are based upon the work being done under the NASA LeRC program. Analysis of the use of PPT's for ACS showed that the replacement of the standard momentum wheels and torque rods systems with a PTT system to perform the altitude control maneuvers on a small low Earth orbiting spacecraft reduced the ACS mass by 50 to 75 percent with no increase in required power level over comparable wheel-based systems.

Comparative Study of DC and AC Microgrids in Commercial Buildings Across Different Climates and Operating Profiles: Preprint

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

Fregosi, D.; Ravula, S.; Brhlik, D.

2015-04-22

Bosch has developed and demonstrated a novel DC microgrid system designed to maximize utilization efficiency for locally generated photovoltaic energy while offering high reliability, safety, redundancy, and reduced cost compared to equivalent AC systems. Several demonstration projects validating the system feasibility and expected efficiency gains have been completed and additional ones are in progress. This work gives an overview of the Bosch DC microgrid system and presents key results from a large simulation study done to estimate the energy savings of the Bosch DC microgrid over conventional AC systems. The study examined the system performance in locations across the Unitedmore » States for several commercial building types and operating profiles and found that the Bosch DC microgrid uses generated PV energy 6%–8% more efficiently than traditional AC systems.« less

Hybrid AC-High Voltage DC Grid Stability and Controls

NASA Astrophysics Data System (ADS)

Yu, Jicheng

The growth of energy demands in recent years has been increasing faster than the expansion of transmission facility construction. This tendency cooperating with the continuous investing on the renewable energy resources drives the research, development, and construction of HVDC projects to create a more reliable, affordable, and environmentally friendly power grid. Constructing the hybrid AC-HVDC grid is a significant move in the development of the HVDC techniques; the form of dc system is evolving from the point-to-point stand-alone dc links to the embedded HVDC system and the multi-terminal HVDC (MTDC) system. The MTDC is a solution for the renewable energy interconnections, and the MTDC grids can improve the power system reliability, flexibility in economic dispatches, and converter/cable utilizing efficiencies. The dissertation reviews the HVDC technologies, discusses the stability issues regarding the ac and HVDC connections, proposes a novel power oscillation control strategy to improve system stability, and develops a nonlinear voltage droop control strategy for the MTDC grid. To verify the effectiveness the proposed power oscillation control strategy, a long distance paralleled AC-HVDC transmission test system is employed. Based on the PSCAD/EMTDC platform simulation results, the proposed power oscillation control strategy can improve the system dynamic performance and attenuate the power oscillations effectively. To validate the nonlinear voltage droop control strategy, three droop controls schemes are designed according to the proposed nonlinear voltage droop control design procedures. These control schemes are tested in a hybrid AC-MTDC system. The hybrid AC-MTDC system, which is first proposed in this dissertation, consists of two ac grids, two wind farms and a five-terminal HVDC grid connecting them. Simulation studies are performed in the PSCAD/EMTDC platform. According to the simulation results, all the three design schemes have their unique salient features.

Diagnostics of the Fermilab Tevatron using an AC dipole

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

Miyamoto, Ryoichi

2008-08-01

The Fermilab Tevatron is currently the world's highest energy colliding beam facility. Its counter-rotating proton and antiproton beams collide at 2 TeV center-of-mass. Delivery of such intense beam fluxes to experiments has required improved knowledge of the Tevatron's beam optical lattice. An oscillating dipole magnet, referred to as an AC dipole, is one of such a tool to non-destructively assess the optical properties of the synchrotron. We discusses development of an AC dipole system for the Tevatron, a fast-oscillating (f ~ 20 kHz) dipole magnet which can be adiabatically turned on and off to establish sustained coherent oscillations of themore » beam particles without affecting the transverse emittance. By utilizing an existing magnet and a higher power audio amplifier, the cost of the Tevatron AC dipole system became relatively inexpensive. We discuss corrections which must be applied to the driven oscillation measurements to obtain the proper interpretation of beam optical parameters from AC dipole studies. After successful operations of the Tevatron AC dipole system, AC dipole systems, similar to that in the Tevatron, will be build for the CERN LHC. We present several measurements of linear optical parameters (beta function and phase advance) for the Tevatron, as well as studies of non-linear perturbations from sextupole and octupole elements.« less

NEMA image quality phantom measurements and attenuation correction in integrated PET/MR hybrid imaging.

PubMed

Ziegler, Susanne; Jakoby, Bjoern W; Braun, Harald; Paulus, Daniel H; Quick, Harald H

2015-12-01

In integrated PET/MR hybrid imaging the evaluation of PET performance characteristics according to the NEMA standard NU 2-2007 is challenging because of incomplete MR-based attenuation correction (AC) for phantom imaging. In this study, a strategy for CT-based AC of the NEMA image quality (IQ) phantom is assessed. The method is systematically evaluated in NEMA IQ phantom measurements on an integrated PET/MR system. NEMA IQ measurements were performed on the integrated 3.0 Tesla PET/MR hybrid system (Biograph mMR, Siemens Healthcare). AC of the NEMA IQ phantom was realized by an MR-based and by a CT-based method. The suggested CT-based AC uses a template μ-map of the NEMA IQ phantom and a phantom holder for exact repositioning of the phantom on the systems patient table. The PET image quality parameters contrast recovery, background variability, and signal-to-noise ratio (SNR) were determined and compared for both phantom AC methods. Reconstruction parameters of an iterative 3D OP-OSEM reconstruction were optimized for highest lesion SNR in NEMA IQ phantom imaging. Using a CT-based NEMA IQ phantom μ-map on the PET/MR system is straightforward and allowed performing accurate NEMA IQ measurements on the hybrid system. MR-based AC was determined to be insufficient for PET quantification in the tested NEMA IQ phantom because only photon attenuation caused by the MR-visible phantom filling but not the phantom housing is considered. Using the suggested CT-based AC, the highest SNR in this phantom experiment for small lesions (<= 13 mm) was obtained with 3 iterations, 21 subsets and 4 mm Gaussian filtering. This study suggests CT-based AC for the NEMA IQ phantom when performing PET NEMA IQ measurements on an integrated PET/MR hybrid system. The superiority of CT-based AC for this phantom is demonstrated by comparison to measurements using MR-based AC. Furthermore, optimized PET image reconstruction parameters are provided for the highest lesion SNR in NEMA IQ phantom measurements.

Diode-rectified multiphase AC arc for the improvement of electrode erosion characteristics

NASA Astrophysics Data System (ADS)

Tanaka, Manabu; Hashizume, Taro; Saga, Koki; Matsuura, Tsugio; Watanabe, Takayuki

2017-11-01

An innovative multiphase AC arc (MPA) system was developed on the basis of a diode-rectification technique to improve electrode erosion characteristics. Conventionally, electrode erosion in AC arc is severer than that in DC arc. This originated from the fact that the required properties for the cathode and anode are different, although an AC electrode works as the cathode and the anode periodically. To solve this problem, a separation of AC electrodes into pairs of thoriated tungsten cathode and copper anode by diode-rectification was attempted. A diode-rectified multiphase AC arc (DRMPA) system was then successfully established, resulting in a drastic improvement of the erosion characteristics. The electrode erosion rate in the DRMPA was less than one-third of that in the conventional MPA without the diode rectification. In order to clarify its erosion mechanism, electrode phenomena during discharge were visualized by a high-speed camera system with appropriate band-pass filters. Fluctuation characteristics of the electrode temperature in the DRMPA were revealed.

Use of an AC/DC/AC Electrochemical Technique to Assess the Durability of Protection Systems for Magnesium Alloys

NASA Astrophysics Data System (ADS)

Song, Sen; McCune, Robert C.; Shen, Weidian; Wang, Yar-Ming

One task under the U.S. Automotive Materials Partnership (USAMP) "Magnesium Front End Research and Development" (MFERD) Project has been the evaluation of methodologies for the assessment of protective capability for a variety of proposed protection schemes for this hypothesized multi-material, articulated structure. Techniques which consider the entire protection system, including both pretreatments and topcoats are of interest. In recent years, an adaptation of the classical electrochemical impedance spectroscopy (EIS) approach using an intermediate cathodic DC polarization step (viz. AC/DC/AC) has been employed to accelerate breakdown of coating protection, specifically at the polymer-pretreatment interface. This work reports outcomes of studies to employ the AC/DC/AC approach for comparison of protective coatings to various magnesium alloys considered for front end structures. In at least one instance, the protective coating system breakdown could be attributed to the poorer intrinsic corrosion resistance of the sheet material (AZ31) relative to die-cast AM60B.

GABAergic Neural Activity Involved in Salicylate-Induced Auditory Cortex Gain Enhancement

PubMed Central

Lu, Jianzhong; Lobarinas, Edward; Deng, Anchun; Goodey, Ronald; Stolzberg, Daniel; Salvi, Richard J.; Sun, Wei

2011-01-01

Although high doses of sodium salicylate impair cochlear function, it paradoxically enhances sound-evoked activity in the auditory cortex (AC) and augments acoustic startle reflex responses, neural and behavioral metrics associated with hyperexcitability and hyperacusis. To explore the neural mechanisms underlying salicylate-induced hyperexcitability and “increased central gain”, we examined the effects of γ-aminobutyric acid (GABA) receptor agonists and antagonists on salicylate-induced hyperexcitability in the AC and startle reflex responses. Consistent with our previous findings, local or systemic application of salicylate significantly increased the amplitude of sound-evoked AC neural activity, but generally reduced spontaneous activity in the AC. Systemic injection of salicylate also significantly increased the acoustic startle reflex. S-baclofen or R-baclofen, GABA-B agonists, which suppressed sound-evoked AC neural firing rate and local field potentials, also suppressed the salicylate-induced enhancement of the AC field potential and the acoustic startle reflex. Local application of vigabatrin, which enhances GABA concentration in the brain, suppressed the salicylate-induced enhancement of AC firing rate. Systemic injection of vigabatrin also reduced the salicylate-induced enhancement of acoustic startle reflex. Collectively, these results suggest that the sound-evoked behavioral and neural hyperactivity induced by salicylate may arise from a salicylate-induced suppression GABAergic inhibition in the AC. PMID:21664433

Research on Three-phase Four-wire Inverter

NASA Astrophysics Data System (ADS)

Xin, W. D.; Li, X. K.; Huang, G. Z.; Fan, X. C.; Gong, X. J.; Sun, L.; Wang, J.; Zhu, D. W.

2017-05-01

The concept of Voltage Source Converter (VSC) based hybrid AC and DC distribution system architecture is proposed, which can solve the traditional AC distribution power quality problems and respond to the request of DC distribution development. At first, a novel VSC system structure combining the four-leg based three-phase four-wire with LC filter is adopted, using the overall coordination control scheme of the AC current tracking compensation based grid-interfaced VSC. In the end, the 75 kW simulation experimental system is designed and tested to verify the performance of the proposed VSC under DC distribution, distributed DC sources conditions, as well as power quality management of AC distribution.

Low-temperature, ultrahigh-vacuum tip-enhanced Raman spectroscopy combined with molecular beam epitaxy for in situ two-dimensional materials' studies

NASA Astrophysics Data System (ADS)

Sheng, Shaoxiang; Li, Wenbin; Gou, Jian; Cheng, Peng; Chen, Lan; Wu, Kehui

2018-05-01

Tip-enhanced Raman spectroscopy (TERS), which combines scanning probe microscopy with the Raman spectroscopy, is capable to access the local structure and chemical information simultaneously. However, the application of ambient TERS is limited by the unstable and poorly controllable experimental conditions. Here, we designed a high performance TERS system based on a low-temperature ultrahigh-vacuum scanning tunneling microscope (LT-UHV-STM) and combined with a molecular beam epitaxy (MBE) system. It can be used for growing two-dimensional (2D) materials and for in situ STM and TERS characterization. Using a 2D silicene sheet on the Ag(111) surface as a model system, we achieved an unprecedented 109 Raman single enhancement factor in combination with a TERS spatial resolution down to 0.5 nm. The results show that TERS combined with a MBE system can be a powerful tool to study low dimensional materials and surface science.

Comparative Study of DC and AC Microgrids in Commercial Buildings Across Different Climates and Operating Profiles

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

Fregosi, Daniel; Ravula, Sharmila; Brhlik, Dusan

2015-06-07

Bosch has developed and demonstrated a novel direct current (DC) microgrid system that maximizes the efficiency of locally generated photovoltaic energy while offering high reliability, safety, redundancy, and reduced cost compared to equivalent alternating current (AC) systems. Several demonstration projects validating the system feasibility and expected efficiency gains have been completed and additional ones are in progress. This paper gives an overview of the Bosch DC microgrid system and presents key results from a large simulation study done to estimate the energy savings of the Bosch DC microgrid over conventional AC systems. The study examined the system performance in locationsmore » across the United States for several commercial building types and operating profiles. It found that the Bosch DC microgrid uses generated PV energy 6%-8% more efficiently than traditional AC systems.« less

A comparative study of electric power distribution systems for spacecraft

NASA Technical Reports Server (NTRS)

Stuart, Thomas A.; King, Roger J.

1990-01-01

The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems.

Regeneration of LOHC dehydrogenation catalysts: In-situ IR spectroscopy on single crystals, model catalysts, and real catalysts from UHV to near ambient pressure

NASA Astrophysics Data System (ADS)

Amende, Max; Kaftan, Andre; Bachmann, Philipp; Brehmer, Richard; Preuster, Patrick; Koch, Marcus; Wasserscheid, Peter; Libuda, Jörg

2016-01-01

The Liquid Organic Hydrogen Carrier (LOHC) concept offers an efficient route to store hydrogen using organic compounds that are reversibly hydrogenated and dehydrogenated. One important challenge towards application of the LOHC technology at a larger scale is to minimize degradation of Pt-based dehydrogenation catalysts during long-term operation. Herein, we investigate the regeneration of Pt/alumina catalysts poisoned by LOHC degradation. We combine ultrahigh vacuum (UHV) studies on Pt(111), investigations on well-defined Pt/Al2O3 model catalysts, and near-ambient pressure (NAP) measurements on real core⿿shell Pt/Al2O3 catalyst pellets. The catalysts were purposely poisoned by reaction with the LOHC perhydro-dibenzyltoluene (H18-MSH) and with dicyclohexylmethane (DCHM) as a simpler model compound. We focus on oxidative regeneration under conditions that may be applied in real dehydrogenation reactors. The degree of poisoning and regeneration under oxidative reaction conditions was quantified using CO as a probe molecule and measured by infrared reflection-absorption spectroscopy (IRAS) and diffuse reflectance Fourier transform IR spectroscopy (DRIFTS) for planar model systems and real catalysts, respectively. We find that regeneration strongly depends on the composition of the catalyst surface. While the clean surface of a poisoned Pt(111) single crystal is fully restored upon thermal treatment in oxygen up to 700 K, contaminated Pt/Al2O3 model catalyst and core⿿shell pellet were only partially restored under the applied reaction conditions. Whereas partial regeneration on facet-like sites on supported catalysts is more facile than on Pt(111), carbonaceous deposits adsorbed at low-coordinated defect sites impede full regeneration of the Pt/Al2O3 catalysts.

Growth of Graphene by Catalytic Dissociation of Ethylene on CuNi(111)

NASA Astrophysics Data System (ADS)

Ventrice, Carl A., Jr.; Tyagi, Parul; Golden, Max; Mowll, Tyler

2015-03-01

The growth of graphene by the catalytic decomposition of ethylene on a 90:10 CuNi(111) substrate was performed. The growths were done in a UHV system by either heating the substrate to the growth temperature followed by introducing the ethylene precursor or by introducing the ethylene precursor and subsequently heating it to the growth temperature. The growth using the former method results in a two-domain epitaxial graphene overlayer at temperatues as low as 550 °C. However, introducing the ethylene before heating the substrate resulted in considerable rotational disorder within the graphene film. This has been attributed to the formation of a carbide phase below 550 °C. This research was supported by the NSF (DMR-1006411).

Progress of nanopositioning stages development for hard x-ray nanofocusing and coherence preservation optics at the APS

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

Shu, Deming

2015-07-01

Customized flexure mechanisms and precision thermal expansion compensation are needed for the development of nanopositioning stages for hard x-ray nanofocusing and coherence preservation optics at the APS. Recent progress of such stage development is summarized in this paper, which includes: stages designed for alignment apparatus for K-B mirrors with 20 - 50 nm focal spot; alignment apparatus for six Fresnel zone plates stacking with 20 nm focal spot; stages for switchable multiple nanofocusing system; UHV hard x-ray monochromators for coherence related applications; and four-crystal hard x-ray split-and-delay line with coherence preservation. Preliminary test results for mechanical performance of these nanopositioningmore » stages are also discussed in this paper.« less

Electron Lens Construction for the Integrable Optics Test Accelerator at Fermilab

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

McGee, Mike; Carlson, Kermit; Nobrega, Lucy

The Integrable Optics Test Accelerator (IOTA) is proposed for operation at Fermilab. The goal of IOTA is to create practical nonlinear accelerator focusing systems with a large frequency spread and stable particle motion. The IOTA is a 40 m circumference, 150 MeV (e-), 2.5 MeV (p⁺) diagnostic test ring. Construction of an electron lens for IOTA is necessary for both electron and proton operation. Components required for the Electron Lens design include; a 0.8 T conventional water-cooled main solenoid, and magnetic bending and focusing elements. The foundation of the design relies on repurposing the Fermilab Tevatron Electron Lens II (TELII)more » gun and collector under ultra-high vacuum (UHV) conditions.« less

Ultra high vacuum heating and rotating specimen stage

DOEpatents

Coombs, A.W. III

1995-05-02

A heating and rotating specimen stage provides for simultaneous specimen heating and rotating. The stage is ideally suited for operation in ultrahigh vacuum (1{times}10{sup {minus}9} torr or less), but is useful at atmosphere and in pressurized systems as well. A specimen is placed on a specimen holder that is attached to a heater that, in turn, is attached to a top housing. The top housing is rotated relative to a bottom housing and electrically connected thereto by electrically conductive brushes. This stage is made of materials that are compatible with UHV, able to withstand high temperatures, possess low outgassing rates, are gall and seize resistant, and are able to carry substantial electrical loading without overheating. 5 figs.

Quality control for quantitative multicenter whole-body PET/MR studies: A NEMA image quality phantom study with three current PET/MR systems

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

Boellaard, Ronald, E-mail: r.boellaard@vumc.nl; European Association of Nuclear Medicine Research Ltd., Vienna 1060; European Association of Nuclear Medicine Physics Committee, Vienna 1060

2015-10-15

Purpose: Integrated positron emission tomography/magnetic resonance (PET/MR) systems derive the PET attenuation correction (AC) from dedicated MR sequences. While MR-AC performs reasonably well in clinical patient imaging, it may fail for phantom-based quality control (QC). The authors assess the applicability of different protocols for PET QC in multicenter PET/MR imaging. Methods: The National Electrical Manufacturers Association NU 2 2007 image quality phantom was imaged on three combined PET/MR systems: a Philips Ingenuity TF PET/MR, a Siemens Biograph mMR, and a GE SIGNA PET/MR (prototype) system. The phantom was filled according to the EANM FDG-PET/CT guideline 1.0 and scanned for 5more » min over 1 bed. Two MR-AC imaging protocols were tested: standard clinical procedures and a dedicated protocol for phantom tests. Depending on the system, the dedicated phantom protocol employs a two-class (water and air) segmentation of the MR data or a CT-based template. Differences in attenuation- and SUV recovery coefficients (RC) are reported. PET/CT-based simulations were performed to simulate the various artifacts seen in the AC maps (μ-map) and their impact on the accuracy of phantom-based QC. Results: Clinical MR-AC protocols caused substantial errors and artifacts in the AC maps, resulting in underestimations of the reconstructed PET activity of up to 27%, depending on the PET/MR system. Using dedicated phantom MR-AC protocols, PET bias was reduced to −8%. Mean and max SUV RC met EARL multicenter PET performance specifications for most contrast objects, but only when using the dedicated phantom protocol. Simulations confirmed the bias in experimental data to be caused by incorrect AC maps resulting from the use of clinical MR-AC protocols. Conclusions: Phantom-based quality control of PET/MR systems in a multicenter, multivendor setting may be performed with sufficient accuracy, but only when dedicated phantom acquisition and processing protocols are used for attenuation correction.« less

Challenges and solutions in medically managed ACS in the Asia-Pacific region: expert recommendations from the Asia-Pacific ACS Medical Management Working Group.

PubMed

Huo, Yong; Thompson, Peter; Buddhari, Wacin; Ge, Junbo; Harding, Scott; Ramanathan, Letchuman; Reyes, Eugenio; Santoso, Anwar; Tam, Li-Wah; Vijayaraghavan, Govindan; Yeh, Hung-I

2015-03-15

Acute coronary syndromes (ACS) remain a leading cause of mortality and morbidity in the Asia-Pacific (APAC) region. International guidelines advocate invasive procedures in all but low-risk ACS patients; however, a high proportion of ACS patients in the APAC region receive solely medical management due to a combination of unique geographical, socioeconomic, and population-specific barriers. The APAC ACS Medical Management Working Group recently convened to discuss the ACS medical management landscape in the APAC region. Local and international ACS guidelines and the global and APAC clinical evidence-base for medical management of ACS were reviewed. Challenges in the provision of optimal care for these patients were identified and broadly categorized into issues related to (1) accessibility/systems of care, (2) risk stratification, (3) education, (4) optimization of pharmacotherapy, and (5) cost/affordability. While ACS guidelines clearly represent a valuable standard of care, the group concluded that these challenges can be best met by establishing cardiac networks and individual hospital models/clinical pathways taking into account local risk factors (including socioeconomic status), affordability and availability of pharmacotherapies/invasive facilities, and the nature of local healthcare systems. Potential solutions central to the optimization of ACS medical management in the APAC region are outlined with specific recommendations. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Bridging the Gap: From Model Surfaces to Nanoparticle Analogs for Selective Oxidation and Steam Reforming of Methanol and Selective Hydrogenation Catalysis

NASA Astrophysics Data System (ADS)

Boucher, Matthew B.

Most industrial catalysts are very complex, comprising of non-uniform materials with varying structures, impurities, and interaction between the active metal and supporting substrate. A large portion of the ongoing research in heterogeneous catalysis focuses on understanding structure-function relationships in catalytic materials. In parallel, there is a large area of surface science research focused on studying model catalytic systems for which structural parameters can be tuned and measured with high precision. It is commonly argued, however, that these systems are oversimplified, and that observations made in model systems do not translate to robust catalysts operating in practical environments; this discontinuity is often referred to as a "gap." The focus of this thesis is to explore the mutual benefits of surface science and catalysis, or "bridge the gap," by studying two catalytic systems in both ultra-high vacuum (UHV) and near ambient-environments. The first reaction is the catalytic steam reforming of methanol (SRM) to hydrogen and carbon dioxide. The SRM reaction is a promising route for on-demand hydrogen production. For this catalytic system, the central hypothesis in this thesis is that a balance between redox capability and weak binding of reaction intermediates is necessary for high SRM activity and selectivity to carbon dioxide. As such, a new catalyst for the SRM reaction is developed which incorporates very small amounts of gold (<1 atomic %) supported on zinc oxide nanoparticles with controlled crystal structures. The performance of these catalysts was studied in a fixed-bed micro-reactor system at ambient pressures, and their structure was characterized by high-resolution microscopic and spectroscopic techniques. Pre-existing oxygen defects in zinc oxide {0001} surfaces, and those created by a perturbation of the defect equilibrium by addition of gold, provide an anchoring site for highly dispersed gold species. By utilizing shape control of zinc oxide supports, it is found that highly dispersed gold, capable of low-temperature redox behavior is most prominent on zinc oxide {0001} surfaces and leads to high SRM activity and selectivity to carbon dioxide. Like other Group IB metal catalysts the SRM over gold-zinc oxide proceeds through the formation and weak binding of formaldehyde, and subsequent coupling with methoxy to produce methyl formate. Mechanistic clarification of this point was achieved by studying the interaction methanol-water mixtures with model catalyst surfaces. Model catalysts were studied in a UHV chamber where the base pressure was maintained at 10-10 mbar. High resolutions surface science techniques show that hydrogen-bonded networks of water are capable of deprotonating methanol to methoxy on low index surfaces in the absence of atomic oxygen. These UHV studies show that adsorbates, other than oxygen, are capable of activating methanol on Group IB metal surfaces. The second reaction involves the selective hydrogenation of alkynes to alkenes. Selective hydrogenations of carbon-carbon multiple bonds are important for a wide range of industrial processes. The governing hypothesis for this reaction system is that cooperation between a minority metal with a low barrier for hydrogen dissociation, and a less-reactive host metal capable of hydrogen uptake via spillover will lead to high alkene selectivity. A strategy for the preparation of such a catalyst is developed using model catalyst studied in a UHV chamber. The model catalyst features isolated palladium atoms in a copper(111) surface, termed single atom alloy (SAA). Individual, isolated palladium atoms act as sites for hydrogen uptake, dissociation, and spillover onto an otherwise inert copper(111) host. Weak binding offered by copper provides a surface where selective hydrogenation reactions can take place. Palladium-copper SAA model catalysts are highly selective to the partial hydrogenation of acetylene, whereas surfaces containing larger palladium ensembles facilitate complete hydrogenation and decomposition. Nanoparticle analogs of palladium-copper SAAs were prepared to investigate the feasibility of this strategy for practical application. Very small amounts of palladium (<0.2 atomic %) on the surface of copper nanoparticles are highly active and selective catalysts for the partial hydrogenation of phenylacetylene to styrene. The performance of these catalysts was studied in a liquid-phase, stirred-tank batch reactor under a hydrogen head pressure of approximately 7 bar. Palladium alloyed into the surface of otherwise inactive copper nanoparticles shows a marked improvement in selectivity when compared to monometallic palladium catalysts with the same metal loading. This effect is attributed hydrogen spillover onto the copper surface. In summary, the development of new, highly active and selective catalysts for the methanol steam reforming reaction and for the partial hydrogenation of alkynes to alkenes was accomplished by the use of state-of-the-art techniques in both surface science and heterogeneous catalysis. The implications of this work can be extended to a wide variety of catalytic systems.

High voltage AC/AC electrochemical capacitor operating at low temperature in salt aqueous electrolyte

NASA Astrophysics Data System (ADS)

Abbas, Qamar; Béguin, François

2016-06-01

We demonstrate that an activated carbon (AC)-based electrochemical capacitor implementing aqueous lithium sulfate electrolyte in 7:3 vol:vol water/methanol mixture can operate down to -40 °C with good electrochemical performance. Three-electrode cell investigations show that the faradaic contributions related with hydrogen chemisorption in the negative AC electrode are thermodynamically unfavored at -40 °C, enabling the system to work as a typical electrical double-layer (EDL) capacitor. After prolonged floating of the AC/AC capacitor at 1.6 V and -40°C, the capacitance, equivalent series resistance and efficiency remain constant, demonstrating the absence of ageing related with side redox reactions at this temperature. Interestingly, when temperature is increased back to 24 °C, the redox behavior due to hydrogen storage reappears and the system behaves as a freshly prepared one.

Assessing the allelotypic effect of two aminocyclopropane carboxylic acid synthase-encoding genes MdACS1 and MdACS3a on fruit ethylene production and softening in Malus

PubMed Central

Dougherty, Laura; Zhu, Yuandi; Xu, Kenong

2016-01-01

Phytohormone ethylene largely determines apple fruit shelf life and storability. Previous studies demonstrated that MdACS1 and MdACS3a, which encode 1-aminocyclopropane-1-carboxylic acid synthases (ACS), are crucial in apple fruit ethylene production. MdACS1 is well-known to be intimately involved in the climacteric ethylene burst in fruit ripening, while MdACS3a has been regarded a main regulator for ethylene production transition from system 1 (during fruit development) to system 2 (during fruit ripening). However, MdACS3a was also shown to have limited roles in initiating the ripening process lately. To better assess their roles, fruit ethylene production and softening were evaluated at five time points during a 20-day post-harvest period in 97 Malus accessions and in 34 progeny from 2 controlled crosses. Allelotyping was accomplished using an existing marker (ACS1) for MdACS1 and two markers (CAPS866 and CAPS870) developed here to specifically detect the two null alleles (ACS3a-G289V and Mdacs3a) of MdACS3a. In total, 952 Malus accessions were allelotyped with the three markers. The major findings included: The effect of MdACS1 was significant on fruit ethylene production and softening while that of MdACS3a was less detectable; allele MdACS1–2 was significantly associated with low ethylene and slow softening; under the same background of the MdACS1 allelotypes, null allele Mdacs3a (not ACS3a-G289V) could confer a significant delay of ethylene peak; alleles MdACS1–2 and Mdacs3a (excluding ACS3a-G289V) were highly enriched in M. domestica and M. hybrid when compared with those in M. sieversii. These findings are of practical implications in developing apples of low and delayed ethylene profiles by utilizing the beneficial alleles MdACS1-2 and Mdacs3a. PMID:27231553

Lynn Westdal | NREL

Science.gov Websites

Process-relevant Biomass-derived Pentoses in a Biphasic Reaction System," ACS Sustainable Chem. Eng Biomass-derived Pentoses in a Biphasic Reaction System." ACS Sustainable Chem. Eng. (2017)

New Automotive Air Conditioning System Simulation Tool Developed in MATLAB/Simulink

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

Kiss, T.; Chaney, L.; Meyer, J.

Further improvements in vehicle fuel efficiency require accurate evaluation of the vehicle's transient total power requirement. When operated, the air conditioning (A/C) system is the largest auxiliary load on a vehicle; therefore, accurate evaluation of the load it places on the vehicle's engine and/or energy storage system is especially important. Vehicle simulation software, such as 'Autonomie,' has been used by OEMs to evaluate vehicles' energy performance. A transient A/C simulation tool incorporated into vehicle simulation models would also provide a tool for developing more efficient A/C systems through a thorough consideration of the transient A/C system performance. The dynamic systemmore » simulation software Matlab/Simulink was used to develop new and more efficient vehicle energy system controls. The various modeling methods used for the new simulation tool are described in detail. Comparison with measured data is provided to demonstrate the validity of the model.« less

Study of switching transients in high frequency converters

NASA Technical Reports Server (NTRS)

Zinger, Donald S.; Elbuluk, Malik E.; Lee, Tony

1993-01-01

As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented. A current regulated ac/ac PDM converter built using MCT's and IGBT's is evaluated.

Reduced Toxicity Fuel Satellite Propulsion System

NASA Technical Reports Server (NTRS)

Schneider, Steven J. (Inventor)

2001-01-01

A reduced toxicity fuel satellite propulsion system including a reduced toxicity propellant supply for consumption in an axial class thruster and an ACS class thruster. The system includes suitable valves and conduits for supplying the reduced toxicity propellant to the ACS decomposing element of an ACS thruster. The ACS decomposing element is operative to decompose the reduced toxicity propellant into hot propulsive gases. In addition the system includes suitable valves and conduits for supplying the reduced toxicity propellant to an axial decomposing element of the axial thruster. The axial decomposing element is operative to decompose the reduced toxicity propellant into hot gases. The system further includes suitable valves and conduits for supplying a second propellant to a combustion chamber of the axial thruster, whereby the hot gases and the second propellant auto-ignite and begin the combustion process for producing thrust.

Reduced Toxicity Fuel Satellite Propulsion System Including Plasmatron

NASA Technical Reports Server (NTRS)

Schneider, Steven J. (Inventor)

2003-01-01

A reduced toxicity fuel satellite propulsion system including a reduced toxicity propellant supply for consumption in an axial class thruster and an ACS class thruster. The system includes suitable valves and conduits for supplying the reduced toxicity propellant to the ACS decomposing element of an ACS thruster. The ACS decomposing element is operative to decompose the reduced toxicity propellant into hot propulsive gases. In addition the system includes suitable valves and conduits for supplying the reduced toxicity propellant to an axial decomposing element of the axial thruster. The axial decomposing element is operative to decompose the reduced toxicity propellant into hot gases. The system further includes suitable valves and conduits for supplying a second propellant to a combustion chamber of the axial thruster. whereby the hot gases and the second propellant auto-ignite and begin the combustion process for producing thrust.

Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

DOEpatents

Gallegos-Lopez, Gabriel [Torrance, CA; Nagashima, James M [Cerritos, CA; Perisic, Milun [Torrance, CA; Hiti, Silva [Redondo Beach, CA

2012-06-05

A system is provided for controlling two alternating current (AC) machines via a five-phase PWM inverter module. The system comprises a first control loop, a second control loop, and a current command adjustment module. The current command adjustment module operates in conjunction with the first control loop and the second control loop to continuously adjust current command signals that control the first AC machine and the second AC machine such that they share the input voltage available to them without compromising the target mechanical output power of either machine. This way, even when the phase voltage available to either one of the machines decreases, that machine outputs its target mechanical output power.

A compact ultra-clean system for deploying radioactive sources inside the KamLAND detector

NASA Astrophysics Data System (ADS)

Banks, T. I.; Freedman, S. J.; Wallig, J.; Ybarrolaza, N.; Gando, A.; Gando, Y.; Ikeda, H.; Inoue, K.; Kishimoto, Y.; Koga, M.; Mitsui, T.; Nakamura, K.; Shimizu, I.; Shirai, J.; Suzuki, A.; Takemoto, Y.; Tamae, K.; Ueshima, K.; Watanabe, H.; Xu, B. D.; Yoshida, H.; Yoshida, S.; Kozlov, A.; Grant, C.; Keefer, G.; Piepke, A.; Bloxham, T.; Fujikawa, B. K.; Han, K.; Ichimura, K.; Murayama, H.; O`Donnell, T.; Steiner, H. M.; Winslow, L. A.; Dwyer, D. A.; McKeown, R. D.; Zhang, C.; Berger, B. E.; Lane, C. E.; Maricic, J.; Miletic, T.; Batygov, M.; Learned, J. G.; Matsuno, S.; Sakai, M.; Horton-Smith, G. A.; Downum, K. E.; Gratta, G.; Efremenko, Y.; Perevozchikov, O.; Karwowski, H. J.; Markoff, D. M.; Tornow, W.; Heeger, K. M.; Detwiler, J. A.; Enomoto, S.; Decowski, M. P.

2015-01-01

We describe a compact, ultra-clean device used to deploy radioactive sources along the vertical axis of the KamLAND liquid-scintillator neutrino detector for purposes of calibration. The device worked by paying out and reeling in precise lengths of a hanging, small-gauge wire rope (cable); an assortment of interchangeable radioactive sources could be attached to a weight at the end of the cable. All components exposed to the radiopure liquid scintillator were made of chemically compatible UHV-cleaned materials, primarily stainless steel, in order to avoid contaminating or degrading the scintillator. To prevent radon intrusion, the apparatus was enclosed in a hermetically sealed housing inside a glove box, and both volumes were regularly flushed with purified nitrogen gas. An infrared camera attached to the side of the housing permitted real-time visual monitoring of the cable's motion, and the system was controlled via a graphical user interface.

Low conductive support for thermal insulation of a sample holder of a variable temperature scanning tunneling microscope

NASA Astrophysics Data System (ADS)

Hanzelka, Pavel; Vonka, Jakub; Musilova, Vera

2013-08-01

We have designed a supporting system to fix a sample holder of a scanning tunneling microscope in an UHV chamber at room temperature. The microscope will operate down to a temperature of 20 K. Low thermal conductance, high mechanical stiffness, and small dimensions are the main features of the supporting system. Three sets of four glass balls placed in vertices of a tetrahedron are used for thermal insulation based on small contact areas between the glass balls. We have analyzed the thermal conductivity of the contacts between the balls mutually and between a ball and a metallic plate while the results have been applied to the entire support. The calculation based on a simple model of the setup has been verified with some experimental measurements. In comparison with other feasible supporting structures, the designed support has the lowest thermal conductance.

Low conductive support for thermal insulation of a sample holder of a variable temperature scanning tunneling microscope.

PubMed

Hanzelka, Pavel; Vonka, Jakub; Musilova, Vera

2013-08-01

We have designed a supporting system to fix a sample holder of a scanning tunneling microscope in an UHV chamber at room temperature. The microscope will operate down to a temperature of 20 K. Low thermal conductance, high mechanical stiffness, and small dimensions are the main features of the supporting system. Three sets of four glass balls placed in vertices of a tetrahedron are used for thermal insulation based on small contact areas between the glass balls. We have analyzed the thermal conductivity of the contacts between the balls mutually and between a ball and a metallic plate while the results have been applied to the entire support. The calculation based on a simple model of the setup has been verified with some experimental measurements. In comparison with other feasible supporting structures, the designed support has the lowest thermal conductance.

Alkali layered compounds interfaces for energy conversion and energy storage

NASA Technical Reports Server (NTRS)

Papageorgopoulos, Chris A.

1996-01-01

During year one a new ultra-high vacuum, an Ar(+) ion sputterer, a low energy electron diffraction (LEED) system, an Auger electron spectrometer (AES), a work function measurement device with a Kelvin probe, and related accessories were used. The study found a focus in the adsorption of chalcogenides on Si and III-V compound semiconductors. In the second year, a scanning tunneling microscope was obtained along with a quadrapole mass spectrometer, power supplies, a computer, a chart recorder, etc. We started the systematic study on the adsorption of chalcogenides on the compound semiconductor surfaces. The third year saw the mounting of the scanning tunneling microscope (STM) on the existing UHV system. The investigation continued with the adsorption of Cs (alkali) on S-covered Si(100)2x1 surfaces. Then the adsorption of S on Cs-covered Si(100) surfaces was studied.

High performance a-Si solar cells and new fabrication methods for a-Si solar cells

NASA Astrophysics Data System (ADS)

Nakano, S.; Kuwano, Y.; Ohnishi, M.

1986-12-01

The super chamber, a separated UHV reaction-chamber system has been developed. A conversion efficiency of 11.7% was obtained for an a-Si solar cell using a high-quality i-layer deposited by the super chamber, and a p-layer fabricated by a photo-CVD method. As a new material, amorphous superlattice-structure films were fabricated by the photo-CVD method for the first time. Superlattice structure p-layer a-Si solar cells were fabricated, and a conversion efficiency of 10.5% was obtained. For the fabrication of integrated type a-Si solar cell modules, a laser pattering method was investigated. A thermal analysis of the multilayer structure was done. It was confirmed that selective scribing for a-Si, TCO and metal film is possible by controlling the laser power density. Recently developed a-Si solar power generation systems and a-Si solar cell roofing tiles are also described.

Analysis and Assessment of Operation Risk for Hybrid AC/DC Power System based on the Monte Carlo Method

NASA Astrophysics Data System (ADS)

Hu, Xiaojing; Li, Qiang; Zhang, Hao; Guo, Ziming; Zhao, Kun; Li, Xinpeng

2018-06-01

Based on the Monte Carlo method, an improved risk assessment method for hybrid AC/DC power system with VSC station considering the operation status of generators, converter stations, AC lines and DC lines is proposed. According to the sequential AC/DC power flow algorithm, node voltage and line active power are solved, and then the operation risk indices of node voltage over-limit and line active power over-limit are calculated. Finally, an improved two-area IEEE RTS-96 system is taken as a case to analyze and assessment its operation risk. The results show that the proposed model and method can intuitively and directly reflect the weak nodes and weak lines of the system, which can provide some reference for the dispatching department.

Life Cycle Impact Assessment of a Rainwater Harvesting System Compared with an A/C Condensate System

EPA Science Inventory

This study reviewed U.S. commercial buildings to design a decentralized rooftop rainwater harvesting (RWH) system and air-conditioning (AC) condensate harvesting (ACH) system for non-potable use. RWH systems were designed for one-to multi-story buildings selected from each of th...

Laboratory and Field Testing of NYCTA Power Frequency Track Circuits

DOT National Transportation Integrated Search

1986-02-01

This report addresses the possible electromagnetic interference between the electronic AC propulsion control systems and the signaling and train control systems. The potential exists for AC-drive propulsion systems to cause EMI that can adversely aff...

AC/DC Power Systems with Applications for future Lunar/Mars base and Crew Exploration Vehicle

NASA Technical Reports Server (NTRS)

Chowdhury, Badrul H.

2005-01-01

ABSTRACT The Power Systems branch at JSC faces a number of complex issues as it readies itself for the President's initiative on future space exploration beyond low earth orbit. Some of these preliminary issues - those dealing with electric power generation and distribution on board Mars-bound vehicle and that on Lunar and Martian surface may be summarized as follows: Type of prime mover - Because solar power may not be readily available on parts of the Lunar/Mars surface and also during the long duration flight to Mars, the primary source of power will most likely be nuclear power (Uranium fuel rods) with a secondary source of fuel cell (Hydrogen supply). The electric power generation source - With nuclear power being the main prime mover, the electric power generation source will most likely be an ac generator at a yet to be determined frequency. Thus, a critical issue is whether the generator should generate at constant or variable frequency. This will decide what type of generator to use - whether it is a synchronous machine, an asynchronous induction machine or a switched reluctance machine. The type of power distribution system - the distribution frequency, number of wires (3- wire, 4-wire or higher), and ac/dc hybridization. Building redundancy and fault tolerance in the generation and distribution sub-systems so that the system is safe; provides 100% availability to critical loads; continues to operate even with faulted sub-systems; and requires minimal maintenance. This report descril_es results of a summer faculty fellowship spent in the Power Systems Branch with the specific aim of investigating some of the lessons learned in electric power generation and usage from the terrestrial power systems industry, the aerospace industry as well as NASA's on-going missions so as to recommend novel surface and vehicle-based power systems architectures in support of future space exploration initiatives. A hybrid ac/dc architecture with source side and load side redundancies and including emergency generators on both ac and dc sides is proposed. The generation frequency is 400 Hz mostly because of the technology maturity at this frequency in the aerospace industry. Power will be distributed to several ac load distribution buses through solid state variable speed, constant frequency converters on the ac side. A segmented dc ring bus supplied from ac/dc converters and with the capability of connecting/disconnecting the segments will supply power to multiple de load distribution buses. The system will have the capability of reverse flow from dc to ac side in the case of an extreme emergency on the main ac generation side.

Methods, systems and apparatus for controlling operation of two alternating current (AC) machines

DOEpatents

Gallegos-Lopez, Gabriel [Torrance, CA; Nagashima, James M [Cerritos, CA; Perisic, Milun [Torrance, CA; Hiti, Silva [Redondo Beach, CA

2012-02-14

A system is provided for controlling two AC machines. The system comprises a DC input voltage source that provides a DC input voltage, a voltage boost command control module (VBCCM), a five-phase PWM inverter module coupled to the two AC machines, and a boost converter coupled to the inverter module and the DC input voltage source. The boost converter is designed to supply a new DC input voltage to the inverter module having a value that is greater than or equal to a value of the DC input voltage. The VBCCM generates a boost command signal (BCS) based on modulation indexes from the two AC machines. The BCS controls the boost converter such that the boost converter generates the new DC input voltage in response to the BCS. When the two AC machines require additional voltage that exceeds the DC input voltage required to meet a combined target mechanical power required by the two AC machines, the BCS controls the boost converter to drive the new DC input voltage generated by the boost converter to a value greater than the DC input voltage.

Pulsed plasma thrusters for small spacecraft attitude control

NASA Technical Reports Server (NTRS)

McGuire, Melissa L.; Myers, Roger M.

1996-01-01

Pulsed Plasma Thrusters (PPTS) are a new option for attitude control of a small spacecraft and may result in reduced attitude control system (ACS) mass and cost. The primary purpose of an ACS is to orient the spacecraft to the desired accuracy in inertial space. The ACS functions for which the PPT system will be analyzed include disturbance torque compensation, and slewing maneuvers such as sun acquisition for which the small impulse bit and high specific impulse of the PPT offers unique advantages. The NASA Lewis Research Center (LERC) currently has a contracted flight PPT system development program in place with Olin Aerospace with a delivery date of October 1997. The PPT systems in this study are based upon the work being done under the NASA LERC program. Analysis of the use of PPTs for ACS showed that the replacement of the standard momentum wheels and torque rods with a PPT system to perform the attitude control maneuvers on a small low Earth orbiting spacecraft reduced the ACS mass by 50 to 75% with no increase in required power level over comparable wheel-based systems, though rapid slewing power requirements may present an issue.

Transposition of the maize transposable element Ac in barley (Hordeum vulgare L.).

PubMed

Scholz, S; Lörz, H; Lütticke, S

2001-01-01

Transposition of the maize autonomous element Ac (Activator) was investigated in barley (Hordeum vulgare L.) with the aim of developing a transposon tagging system for the latter. The Ac element was introduced into meristematic tissue of barley by microprojectile bombardment. Transposon activity was then examined in the resulting transgenic plants. Multiple excision events were detected in leaf tissue of all plant lines. The mobile elements generated empty donor sites with small DNA sequence alterations, similar to those found in maize. Reintegration of Ac at independent genomic loci in somatic tissue was demonstrated by isolation of new element-flanking regions by AIMS-PCR (amplification of insertion-mutagenized sites). In addition, transmission of transposed Ac elements to progeny plants was confirmed. The results indicate that the introduced Ac element is able to transpose in barley. This is a first step towards the establishment of a transposon tagging system in this economically important crop.

The ac propulsion system for an electric vehicle, phase 1

NASA Astrophysics Data System (ADS)

Geppert, S.

1981-08-01

A functional prototype of an electric vehicle ac propulsion system was built consisting of a 18.65 kW rated ac induction traction motor, pulse width modulated (PWM) transistorized inverter, two speed mechanically shifted automatic transmission, and an overall drive/vehicle controller. Design developmental steps, and test results of individual components and the complex system on an instrumented test frame are described. Computer models were developed for the inverter, motor and a representative vehicle. A preliminary reliability model and failure modes effects analysis are given.

The ac propulsion system for an electric vehicle, phase 1

NASA Technical Reports Server (NTRS)

Geppert, S.

1981-01-01

A functional prototype of an electric vehicle ac propulsion system was built consisting of a 18.65 kW rated ac induction traction motor, pulse width modulated (PWM) transistorized inverter, two speed mechanically shifted automatic transmission, and an overall drive/vehicle controller. Design developmental steps, and test results of individual components and the complex system on an instrumented test frame are described. Computer models were developed for the inverter, motor and a representative vehicle. A preliminary reliability model and failure modes effects analysis are given.

An Annotated Bibliography of High-Voltage Direct-Current Transmission and Flexible AC Transmission (FACTS) Devices, 1991-1993.

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

Litzenberger, Wayne; Lava, Val

1994-08-01

References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS).

19 CFR 128.23 - Entry requirements.

Code of Federal Regulations, 2010 CFR

2010-04-01

... utilizing the procedures in this part shall comply with the requirements of the Customs Automated Commercial System (ACS). These requirements include those under the Automated Manifest System (AMS), Cargo Selectivity, Statement Processing, the Automated Broker Interface System (ABI), and enhancements of ACS. (2...

N-Acetyl-Seryl-Aspartyl-Lysyl-Proline: mechanisms of renal protection in mouse model of systemic lupus erythematosus

PubMed Central

Liao, Tang-Dong; Nakagawa, Pablo; Janic, Branislava; D'Ambrosio, Martin; Worou, Morel E.; Peterson, Edward L.; Rhaleb, Nour-Eddine; Yang, Xiao-Ping

2015-01-01

Systemic lupus erythematosus is an autoimmune disease characterized by the development of auto antibodies against a variety of self-antigens and deposition of immune complexes that lead to inflammation, fibrosis, and end-organ damage. Up to 60% of lupus patients develop nephritis and renal dysfunction leading to kidney failure. N-acetyl-seryl-aspartyl-lysyl-proline, i.e., Ac-SDKP, is a natural tetrapeptide that in hypertension prevents inflammation and fibrosis in heart, kidney, and vasculature. In experimental autoimmune myocarditis, Ac-SDKP prevents cardiac dysfunction by decreasing innate and adaptive immunity. It has also been reported that Ac-SDKP ameliorates lupus nephritis in mice. We hypothesize that Ac-SDKP prevents lupus nephritis in mice by decreasing complement C5-9, proinflammatory cytokines, and immune cell infiltration. Lupus mice treated with Ac-SDKP for 20 wk had significantly lower renal levels of macrophage and T cell infiltration and proinflammatory chemokine/cytokines. In addition, our data demonstrate for the first time that in lupus mouse Ac-SDKP prevented the increase in complement C5-9, RANTES, MCP-5, and ICAM-1 kidney expression and it prevented the decline of glomerular filtration rate. Ac-SDKP-treated lupus mice had a significant improvement in renal function and lower levels of glomerular damage. Ac-SDKP had no effect on the production of autoantibodies. The protective Ac-SDKP effect is most likely achieved by targeting the expression of proinflammatory chemokines/cytokines, ICAM-1, and immune cell infiltration in the kidney, either directly or via C5-9 proinflammatory arm of complement system. PMID:25740596

Reduced Toxicity Fuel Satellite Propulsion System Including Fuel Cell Reformer with Alcohols Such as Methanol

NASA Technical Reports Server (NTRS)

Schneider, Steven J. (Inventor)

2001-01-01

A reduced toxicity fuel satellite propulsion system including a reduced toxicity propellant supply for consumption in an axial class thruster and an ACS class thruster. The system includes suitable valves and conduits for supplying the reduced toxicity propellant to the ACS decomposing element of an ACS thruster. The ACS decomposing element is operative to decompose the reduced toxicity propellant into hot propulsive gases. In addition the system includes suitable valves and conduits for supplying the reduced toxicity propellant to an axial decomposing element of the axial thruster. The axial decomposing element is operative to decompose the reduced toxicity propellant into hot gases. The system further includes suitable valves and conduits for supplying a second propellant to a combustion chamber of the axial thruster, whereby the hot gases and the second propellant auto-ignite and begin the combustion process for producing thrust.

The Implementation of Satellite Attitude Control System Software Using Object Oriented Design

NASA Technical Reports Server (NTRS)

Reid, W. Mark; Hansell, William; Phillips, Tom; Anderson, Mark O.; Drury, Derek

1998-01-01

NASA established the Small Explorer (SNMX) program in 1988 to provide frequent opportunities for highly focused and relatively inexpensive space science missions. The SMEX program has produced five satellites, three of which have been successfully launched. The remaining two spacecraft are scheduled for launch within the coming year. NASA has recently developed a prototype for the next generation Small Explorer spacecraft (SMEX-Lite). This paper describes the object-oriented design (OOD) of the SMEX-Lite Attitude Control System (ACS) software. The SMEX-Lite ACS is three-axis controlled and is capable of performing sub-arc-minute pointing. This paper first describes high level requirements governing the SMEX-Lite ACS software architecture. Next, the context in which the software resides is explained. The paper describes the principles of encapsulation, inheritance, and polymorphism with respect to the implementation of an ACS software system. This paper will also discuss the design of several ACS software components. Specifically, object-oriented designs are presented for sensor data processing, attitude determination, attitude control, and failure detection. Finally, this paper will address the establishment of the ACS Foundation Class (AFC) Library. The AFC is a large software repository, requiring a minimal amount of code modifications to produce ACS software for future projects.

Onboard power line conditioning system for an electric or hybrid vehicle

DOEpatents

Kajouke, Lateef A.; Perisic, Milun

2016-06-14

A power line quality conditioning system for a vehicle includes an onboard rechargeable direct current (DC) energy storage system and an onboard electrical system coupled to the energy storage system. The energy storage system provides DC energy to drive an electric traction motor of the vehicle. The electrical system operates in a charging mode such that alternating current (AC) energy from a power grid external to the vehicle is converted to DC energy to charge the DC energy storage system. The electrical system also operates in a vehicle-to-grid power conditioning mode such that DC energy from the DC energy storage system is converted to AC energy to condition an AC voltage of the power grid.

Versatile variable temperature and magnetic field scanning probe microscope for advanced material research

NASA Astrophysics Data System (ADS)

Jung, Jin-Oh; Choi, Seokhwan; Lee, Yeonghoon; Kim, Jinwoo; Son, Donghyeon; Lee, Jhinhwan

2017-10-01

We have built a variable temperature scanning probe microscope (SPM) that covers 4.6 K-180 K and up to 7 T whose SPM head fits in a 52 mm bore magnet. It features a temperature-controlled sample stage thermally well isolated from the SPM body in good thermal contact with the liquid helium bath. It has a 7-sample-holder storage carousel at liquid helium temperature for systematic studies using multiple samples and field emission targets intended for spin-polarized spectroscopic-imaging scanning tunneling microscopy (STM) study on samples with various compositions and doping conditions. The system is equipped with a UHV sample preparation chamber and mounted on a two-stage vibration isolation system made of a heavy concrete block and a granite table on pneumatic vibration isolators. A quartz resonator (qPlus)-based non-contact atomic force microscope (AFM) sensor is used for simultaneous STM/AFM operation for research on samples with highly insulating properties such as strongly underdoped cuprates and strongly correlated electron systems.

A Consideration of Stable Operating Power Limits of HVDC System Composed of Voltage Source Converters

NASA Astrophysics Data System (ADS)

Konishi, Hiroo; Takahashi, Choei; Kishibe, Hideto; Sato, Hiromichi

The stable operating power limits of a small scale HVDC system composed of voltage source converters (VSC-HVDC system) are analyzed with a simple model. The VSC-HVDC system could operate where the AC system must be somewhat larger in capacity than the VSC-HVDC system capacity. The stable operating power limits were between one and two times the SCR (short circuit ratio). When the inverter of the VSC-HVDC system was operated with lead reactive (capacitive) power control conditions, the stable operating limits were increased through AC voltage stabilization. When the inverter was a STATCOM operation, it could operate regardless of the SCR but regions within allowable AC voltage variations.

Direct current power delivery system and method

DOEpatents

Zhang, Di; Garces, Luis Jose; Dai, Jian; Lai, Rixin

2016-09-06

A power transmission system includes a first unit for carrying out the steps of receiving high voltage direct current (HVDC) power from an HVDC power line, generating an alternating current (AC) component indicative of a status of the first unit, and adding the AC component to the HVDC power line. Further, the power transmission system includes a second unit for carrying out the steps of generating a direct current (DC) voltage to transfer the HVDC power on the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit, detecting a presence or an absence of the added AC component in the HVDC power line, and determining the status of the first unit based on the added AC component.

UHV AFM based colloidal probe studies of adhesive properties of VAlN hard coatings

NASA Astrophysics Data System (ADS)

Wiesing, M.; de los Arcos, T.; Grundmeier, G.

2018-01-01

The adhesion of polystyrene (PS) on V0.27Al0.29N0.44 and the related influence of the oxidation states of both surfaces was investigated using X-Ray Photoelectron Spectroscopy (XPS) and Colloidal Force Spectroscopy (CFS) in Ultra-High Vacuum (UHV). Complementary, the intimate relation between the adhesion force, the chemical structure and surface polarizability was investigated by XPS valence band spectroscopy and the calculation of non-retarded Hamaker coefficients using Lifshitz theory based on optical data as derived from Reflection Electron Energy Loss Spectroscopy (REELS) spectra. The combined electron and force spectroscopic analysis of the interaction forces disclosed quantitatively the separation of the adhesion force in van der Waals and Lewis acid-base contributions. Further, the surface polarizability of VAlN was shown to be unaffected by oxygen incorporation due to the formation of an only gradually oxidized surface comprising a range of vanadium oxidation states. In contrast, the adhesion force analysis revealed additional Lewis acid-base interactions between the oxidized and non-oxidized VAlN surfaces and carboxyl groups present in the surface of PS after an oxidative oxygen beam treatment.

Hybrid inverter for HVDC/weak AC system interconnection

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

Tam, K.S.

1985-01-01

The concept of the hybrid converter is introduced. By independently controlling a naturally commutated converter (NCC) and an artificially commutated converter (ACC), real power and reactive power can be controlled independently. Alternatively, the ac bus voltage can be regulated without affecting the real power transfer. Independent control is feasible only within certain operating boundaries. Twelve pulse operation, sequential control, and complementary circuits may be viewed as variations of the hybrid converter. The concept of the hybrid converter is demonstrated by digital simulation. At the current state of technology, the NCC is best implemented by a 6-pulse bridge using thyristors asmore » the switching elements. A survey of power electronics applicable to HVDC applications reveals that the capacitively commutated current-sourced converters are either technically or economically better than the other alternatives for the implementation of the ACC. The digital simulation results show that the problems of operating an HVDC system into a weak ac system can be solved by using a hybrid inverter. A new control scheme, the zero Q control, is developed. With no reactive power interaction between the dc system and the ac system, the stability of the HVDC/weak ac system operation is significantly improved. System start-up and fault recovery is fast and stable.« less

ac propulsion system for an electric vehicle

NASA Technical Reports Server (NTRS)

Geppert, S.

1980-01-01

It is pointed out that dc drives will be the logical choice for current production electric vehicles (EV). However, by the mid-80's, there is a good chance that the price and reliability of suitable high-power semiconductors will allow for a competitive ac system. The driving force behind the ac approach is the induction motor, which has specific advantages relative to a dc shunt or series traction motor. These advantages would be an important factor in the case of a vehicle for which low maintenance characteristics are of primary importance. A description of an EV ac propulsion system is provided, taking into account the logic controller, the inverter, the motor, and a two-speed transmission-differential-axle assembly. The main barrier to the employment of the considered propulsion system in EV is not any technical problem, but inverter transistor cost.

Systems and methods for initializing a charging system

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

Perisic, Milun; Ransonm, Ray M.; Kojouke, Lateef A.

2017-09-26

Systems and methods are provided for charging a battery. The system, for example, includes, but is not limited to a first interface configured to receive a voltage from an AC voltage source, a matrix conversion module comprising a plurality of switches electrically connected to the first interface and configured to provide a charging voltage to the battery, and a controller communicatively connected to the matrix conversion module, wherein the controller is configured to: determine a voltage of the battery, determine an angle of the AC voltage source to initiate charging of the battery based upon the voltage of the battery,more » and control the plurality of switches to provide the charging voltage to the battery between the determined angle of the AC voltage source and a subsequent zero-crossing of the AC voltage source.« less

Comparison of Solid State Inverters for AC Induction Motor Traction Propulsion Systems

DOT National Transportation Integrated Search

1980-12-01

This report is one of a series concerned with the application of ac machines as traction motors for railroad motive power. It presents results of a laboratory evaluation and computer analysis of different inverter systems. Three inverter systems, sin...

An Efficient, Scalable and Robust P2P Overlay for Autonomic Communication

NASA Astrophysics Data System (ADS)

Li, Deng; Liu, Hui; Vasilakos, Athanasios

The term Autonomic Communication (AC) refers to self-managing systems which are capable of supporting self-configuration, self-healing and self-optimization. However, information reflection and collection, lack of centralized control, non-cooperation and so on are just some of the challenges within AC systems. Since many self-* properties (e.g. selfconfiguration, self-optimization, self-healing, and self-protecting) are achieved by a group of autonomous entities that coordinate in a peer-to-peer (P2P) fashion, it has opened the door to migrating research techniques from P2P systems. P2P's meaning can be better understood with a set of key characteristics similar to AC: Decentralized organization, Self-organizing nature (i.e. adaptability), Resource sharing and aggregation, and Fault-tolerance. However, not all P2P systems are compatible with AC. Unstructured systems are designed more specifically than structured systems for the heterogeneous Internet environment, where the nodes' persistence and availability are not guaranteed. Motivated by the challenges in AC and based on comprehensive analysis of popular P2P applications, three correlative standards for evaluating the compatibility of a P2P system with AC are presented in this chapter. According to these standards, a novel Efficient, Scalable and Robust (ESR) P2P overlay is proposed. Differing from current structured and unstructured, or meshed and tree-like P2P overlay, the ESR is a whole new three dimensional structure to improve the efficiency of routing, while information exchanges take in immediate neighbors with local information to make the system scalable and fault-tolerant. Furthermore, rather than a complex game theory or incentive mechanism, asimple but effective punish mechanism has been presented based on a new ID structure which can guarantee the continuity of each node's record in order to discourage negative behavior on an autonomous environment as AC.

FLUIDIC AC AMPLIFIERS.

DTIC Science & Technology

Several fluidic tuned AC Amplifiers were designed and tested. Interstage tuning and feedback designs are considered. Good results were obtained...corresponding Q’s as high as 12. Element designs and test results of one, two, and three stage amplifiers are presented. AC Modulated Carrier Systems

Evolutionarily Conserved nodE, nodO, T1SS, and Hydrogenase System in Rhizobia of Astragalus membranaceus and Caragana intermedia.

PubMed

Yan, Hui; Xie, Jian Bo; Ji, Zhao Jun; Yuan, Na; Tian, Chang Fu; Ji, Shou Kun; Wu, Zhong Yu; Zhong, Liang; Chen, Wen Xin; Du, Zheng Lin; Wang, En Tao; Chen, Wen Feng

2017-01-01

Mesorhizobium species are the main microsymbionts associated with the medicinal or sand-fixation plants Astragalus membranaceus and Caragana intermedia (AC) in temperate regions of China, while all the Mesorhizobium strains isolated from each of these plants could nodulate both of them. However, Rhizobium yanglingense strain CCBAU01603 could nodulate AC plants and it's a high efficiency symbiotic and competitive strain with Caragana . Therefore, the common features shared by these symbiotic rhizobia in genera of Mesorhizobium and Rhizobium still remained undiscovered. In order to study the genomic background influencing the host preference of these AC symbiotic strains, the whole genomes of two ( M. silamurunense CCBAU01550, M. silamurunense CCBAU45272) and five representative strains ( M. septentrionale CCBAU01583, M. amorphae CCBAU01570, M. caraganae CCBAU01502, M. temperatum CCBAU01399, and R. yanglingense CCBAU01603) originally isolated from AC plants were sequenced, respectively. As results, type III secretion systems (T3SS) of AC rhizobia evolved in an irregular pattern, while an evolutionarily specific region including nodE, nodO , T1SS, and a hydrogenase system was detected to be conserved in all these AC rhizobia. Moreover, nodO was verified to be prevalently distributed in other AC rhizobia and was presumed as a factor affecting the nodule formation process. In conclusion, this research interpreted the multifactorial features of the AC rhizobia that may be associated with their host specificity at cross-nodulation group, including nodE, nodZ , T1SS as the possible main determinants; and nodO , hydrogenase system, and T3SS as factors regulating the bacteroid formation or nitrogen fixation efficiency.

Systemic immunological tolerance to ocular antigens is mediated by TRAIL-expressing CD8+ T cells.

PubMed

Griffith, Thomas S; Brincks, Erik L; Gurung, Prajwal; Kucaba, Tamara A; Ferguson, Thomas A

2011-01-15

Systemic immunological tolerance to Ag encountered in the eye restricts the formation of potentially damaging immune responses that would otherwise be initiated at other anatomical locations. We previously demonstrated that tolerance to Ag administered via the anterior chamber (AC) of the eye required Fas ligand-mediated apoptotic death of inflammatory cells that enter the eye in response to the antigenic challenge. Moreover, the systemic tolerance induced after AC injection of Ag was mediated by CD8(+) regulatory T cells. This study examined the mechanism by which these CD8(+) regulatory T cells mediate tolerance after AC injection of Ag. AC injection of Ag did not prime CD4(+) T cells and led to increased TRAIL expression by splenic CD8(+) T cells. Unlike wild-type mice, Trail(-/-) or Dr5(-/-) mice did not develop tolerance to Ag injected into the eye, even though responding lymphocytes underwent apoptosis in the AC of the eyes of these mice. CD8(+) T cells from Trail(-/-) mice that were first injected via the AC with Ag were unable to transfer tolerance to naive recipient wild-type mice, but CD8(+) T cells from AC-injected wild-type or Dr5(-/-) mice could transfer tolerance. Importantly, the transferred wild-type (Trail(+/+)) CD8(+) T cells were also able to decrease the number of infiltrating inflammatory cells into the eye; however, Trail(-/-) CD8(+) T cells were unable to limit the inflammatory cell ingress. Together, our data suggest that "helpless" CD8(+) regulatory T cells generated after AC injection of Ag enforce systemic tolerance in a TRAIL-dependent manner to inhibit inflammation in the eye.

Systemic immunological tolerance to ocular antigens is mediated by TNF-related apoptosis-inducing ligand (TRAIL)-expressing CD8+ T cells*

PubMed Central

Griffith, Thomas S.; Brincks, Erik L.; Gurung, Prajwal; Kucaba, Tamara A.; Ferguson, Thomas A.

2010-01-01

Systemic immunological tolerance to Ag encountered in the eye restricts the formation of potentially damaging immune responses that would otherwise be initiated at other anatomical locations. We previously demonstrated that tolerance to Ag administered via the anterior chamber (AC) of the eye required FasL-mediated apoptotic death of inflammatory cells that enter the eye in response to the antigenic challenge. Moreover, the systemic tolerance induced after AC injection of Ag was mediated by CD8+ regulatory T cells. The present study examined the mechanism by which these CD8+ regulatory T cells mediate tolerance after AC injection of Ag. AC injection of Ag did not prime CD4+ T cells, and led to increased TRAIL expression by splenic CD8+ T cells. Unlike wildtype mice, Trail−/− or Dr5−/− mice did not develop tolerance to Ag injected into the eye, even though responding lymphocytes underwent apoptosis in the AC of the eyes of these mice. CD8+ T cells from Trail−/− mice that were first injected AC with Ag were unable to transfer tolerance to naïve recipient wildtype mice, but CD8+ T cells from AC-injected wildtype or Dr5−/− mice could transfer tolerance. Importantly, the transferred wildtype (Trail+/+) CD8+ T cells were also able to decrease the number of infiltrating inflammatory cells into the eye; however, Trail−/− CD8+ T cells were unable to limit the inflammatory cell ingress. Together, our data suggest that “helpless” CD8+ regulatory T cells generated after AC injection of Ag enforce systemic tolerance in a TRAIL-dependent manner to inhibit inflammation in the eye. PMID:21169546

Using WRF-Urban to Assess Summertime Air Conditioning Electric Loads and Their Impacts on Urban Weather in Beijing

NASA Astrophysics Data System (ADS)

Xu, Xiaoyu; Chen, Fei; Shen, Shuanghe; Miao, Shiguang; Barlage, Michael; Guo, Wenli; Mahalov, Alex

2018-03-01

The air conditioning (AC) electric loads and their impacts on local weather over Beijing during a 5 day heat wave event in 2010 are investigated by using the Weather Research and Forecasting (WRF) model, in which the Noah land surface model with multiparameterization options (Noah-MP) is coupled to the multilayer Building Effect Parameterization and Building Energy Model (BEP+BEM). Compared to the legacy Noah scheme coupled to BEP+BEM, this modeling system shows a better performance, decreasing the root-mean-square error of 2 m air temperature to 1.9°C for urban stations. The simulated AC electric loads in suburban and rural districts are significantly improved by introducing the urban class-dependent building cooled fraction. Analysis reveals that the observed AC electric loads in each district are characterized by a common double peak at 3 p.m. and at 9 p.m. local standard time, and the incorporation of more realistic AC working schedules helps reproduce the evening peak. Waste heat from AC systems has a smaller effect ( 1°C) on the afternoon 2 m air temperature than the evening one (1.5 2.4°C) if AC systems work for 24 h and vent sensible waste heat into air. Influences of AC systems can only reach up to 400 m above the ground for the evening air temperature and humidity due to a shallower urban boundary layer than daytime. Spatially varying maps of AC working schedules and the ratio of sensible to latent waste heat release are critical for correctly simulating the cooling electric loads and capturing the thermal stratification of urban boundary layer.

Remote Supervision and Control of Air Conditioning Systems in Different Modes

NASA Astrophysics Data System (ADS)

Rafeeq, Mohammed; Afzal, Asif; Rajendra, Sree

2018-01-01

In the era of automation, most of the application of engineering and science are interrelated with system for optimal operation. To get the efficient result of an operation and desired response, interconnected systems should be controlled by directing, regulating and commanding. Here, air conditioning (AC) system is considered for experimentation, to supervise and control its functioning in both, automated and manual mode. This paper reports the work intended to design and develop an automated and manual AC system working in remote and local mode, to increase the level of comfort, easy operation, reducing human intervention and faults occurring in the system. The Programmable Logical Controller (PLC) and Supervisory Control and Data Acquisition (SCADA) system were used for remote supervision and monitoring of AC systems using series ninety protocol and remote terminal unit modbus protocol as communication module to operate in remote mode. PLC was used as remote terminal for continuous supervision and control of AC system. SCADA software was used as a tool for designing user friendly graphical user interface. The proposed SCADA AC system successfully monitors and controls in accordance within the parameter limits like temperature, pressure, humidity and voltage. With all the features, this designed system is capable of efficient handling of the resources like the compressor, humidifier etc., with all the levels of safety and durability. This system also maintains the temperature and controls the humidity of the remote location and also looks after the health of the compressor.

Assessment on the influence of resistive superconducting fault current limiter in VSC-HVDC system

NASA Astrophysics Data System (ADS)

Lee, Jong-Geon; Khan, Umer Amir; Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Park, Byung-Bae; Lee, Bang-Wook

2014-09-01

Due to fewer risk of commutation failures, harmonic occurrences and reactive power consumptions, Voltage Source Converter (VSC) based HVDC system is known as the optimum solution of HVDC power system for the future power grid. However, the absence of suitable fault protection devices for HVDC system hinders the efficient VSC-HVDC power grid design. In order to enhance the reliability of the VSC-HVDC power grid against the fault current problems, the application of resistive Superconducting Fault Current Limiters (SFCLs) could be considered. Also, SFCLs could be applied to the VSC-HVDC system with integrated AC Power Systems in order to enhance the transient response and the robustness of the system. In this paper, in order to evaluate the role of SFCLs in VSC-HVDC systems and to determine the suitable position of SFCLs in VSC-HVDC power systems integrated with AC power System, a simulation model based on Korea Jeju-Haenam HVDC power system was designed in Matlab Simulink/SimPowerSystems. This designed model was composed of VSC-HVDC system connected with an AC microgrid. Utilizing the designed VSC-HVDC systems, the feasible locations of resistive SFCLs were evaluated when DC line-to-line, DC line-to-ground and three phase AC faults were occurred. Consequently, it was found that the simulation model was effective to evaluate the positive effects of resistive SFCLs for the effective suppression of fault currents in VSC-HVDC systems as well as in integrated AC Systems. Finally, the optimum locations of SFCLs in VSC-HVDC transmission systems were suggested based on the simulation results.

Adsorption of lignocelluloses of model pre-hydrolysis liquor on activated carbon.

PubMed

Fatehi, Pedram; Ryan, Jennifer; Ni, Yonghao

2013-03-01

The main objective of this work was to study the adsorption behavior of various components dissolved in the pre-hydrolysis of kraft process on activated carbon. In this work, model prehydrolysis liquor (PHL) solutions (MPHL)s were prepared via mixing various commercially available monosugars, xylan, lignin and furfural; and their adsorption performance on activated carbon (AC) was investigated. In singular (one component) MPHL/AC systems, furfural had the maximum and xylose had the minimum adsorption, and the adsorption of monosugars was basically similar on AC. Also, polydiallyldimethylammonium chloride (PDADMAC) was added (0.5 g/l) to singular xylan or lignin MPHL/AC system, which increased the lignin and xylan adsorptions to 350 and 190 mg/g on AC, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

Dielectric Breakdown Characteristics of Oil-pressboard Insulation System against AC/DC Superposed Voltage

NASA Astrophysics Data System (ADS)

Ebisawa, Yoshihito; Yamada, Shin; Mori, Shigekazu; Ikeda, Masami

This paper describes breakdown characteristics of an oil-pressboard insulation system to a superposition voltage of AC and DC voltages. Although AC electric field is decided by the ratio of the relative permittivity of a pressboard and insulating oil, DC electric field is decided by ratio α of volume resistivities. From the measurement in this study, 13—78 and 1.8—5.7 are obtained as the volume resistivity ratios α at temperature of 30°C and 80°C, respectively. The breakdown voltages against AC, DC, and those superposition voltages are surveyed to insulation models. In normal temperature, the breakdown voltage to the superposition voltage of AC and DC is determined by AC electric field applied to the oil duct. Since the α becomes as low as 2-3 at temperature of 80°C, AC and DC voltages almost equally contribute to the electric field of the oil duct as a result. That is, it became clear that superposed DC voltage boosts the electric field across oil ducts at operating high temperature.

Overexpression of the Type 1 Adenylyl Cyclase in the Forebrain Leads to Deficits of Behavioral Inhibition

PubMed Central

Cao, Hong; Saraf, Amit; Zweifel, Larry S.

2015-01-01

The type 1 adenylyl cyclase (AC1) is an activity-dependent, calcium-stimulated adenylyl cyclase expressed in the nervous system that is implicated in memory formation. We examined the locomotor activity, and impulsive and social behaviors of AC1+ mice, a transgenic mouse strain overexpressing AC1 in the forebrain. Here we report that AC1+ mice exhibit hyperactive behaviors and demonstrate increased impulsivity and reduced sociability. In contrast, AC1 and AC8 double knock-out mice are hypoactive, and exhibit increased sociability and reduced impulsivity. Interestingly, the hyperactivity of AC1+ mice can be corrected by valproate, a mood-stabilizing drug. These data indicate that increased expression of AC1 in the forebrain leads to deficits in behavioral inhibition. PMID:25568126

Development and Test of an Eddy-Current Clutch-Propulsion System

DOT National Transportation Integrated Search

1973-10-01

This report covers the Phase 1 effort which is to develop and to test an/AC-propulsion system for personal rapid- transit vehicles. This propulsion system incorporates an AC-induction motor in conjunction with an eddy-current clutch and brake. Also i...

Phantom evaluation of a cardiac SPECT/VCT system that uses a common set of solid-state detectors for both emission and transmission scans.

PubMed

Bai, Chuanyong; Conwell, Richard; Kindem, Joel; Babla, Hetal; Gurley, Mike; De Los Santos, Romer; Old, Rex; Weatherhead, Randy; Arram, Samia; Maddahi, Jamshid

2010-06-01

We developed a cardiac SPECT system (X-ACT) with low dose volume CT transmission-based attenuation correction (AC). Three solid-state detectors are configured to form a triple-head system for emission scans and reconfigured to form a 69-cm field-of-view detector arc for transmission scans. A near mono-energetic transmission line source is produced from the collimated fluorescence x-ray emitted from a lead target when the target is illuminated by a narrow polychromatic x-ray beam from an x-ray tube. Transmission scans can be completed in 1 min with insignificant patient dose (deep dose equivalent <5 muSv). We used phantom studies to evaluate (1) the accuracy of the reconstructed attenuation maps, (2) the effect of AC on image uniformity, and (3) the effect of AC on defect contrast (DC). The phantoms we used included an ACR phantom, an anthropomorphic phantom with a uniform cardiac insert, and an anthropomorphic phantom with two defects in the cardiac insert. The reconstructed attenuation coefficient of water at 140 keV was .150 +/- .003/cm in the uniform region of the ACR phantom, .151 +/- .003/cm and .151 +/- .002/cm in the liver and cardiac regions of the anthropomorphic phantom. The ACR phantom images with AC showed correction of the bowing effect due to attenuation in the images without AC (NC). The 17-segment scores of the images of the uniform cardiac insert were 78.3 +/- 6.5 before and 87.9 +/- 3.3 after AC (average +/- standard deviation). The inferior-to-anterior wall ratio and the septal-to-lateral wall ratio were .99 and 1.16 before and 1.02 and 1.00 after AC. The DC of the two defects was .528 and .156 before and .628 and .173 after AC. The X-ACT system generated accurate attenuation maps with 1-minute transmission scans. AC improved image quality and uniformity over NC.

Marketing information system online design for craftsmen small medium enterprises (case study: craftsmen ac)

NASA Astrophysics Data System (ADS)

Fitriana, Rina; Kurniawan, Wawan; Barlianto, Anung; Adriansyah Putra, Rizki

2016-02-01

AC is small and medium enterprises which is engaged in the field of crafts. This SME (Small Medium Enterprise) didn't have an integrated information system for managing sales. This research aims to design a marketing Information system online as applications that built as web base. The integrated system is made to manage sales and expand its market share. This study uses a structured analysis and design in its approach to build systems and also implemented a marketing framework of STP (Segmentation, Targeting, Positioning) and 4P (Price, Product, Place, Promotion) to obtain market analysis. The main market target customer craftsmen AC is women aged 13 years to 35 years. The products produced by AC are shoes, brooch, that are typical of the archipelago. The prices is range from Rp. 2000 until Rp. 400.000. Marketing information system online can be used as a sales transaction document, promoting the goods, and for customer booking products.

Hybrid power system intelligent operation and protection involving distributed architectures and pulsed loads

NASA Astrophysics Data System (ADS)

Mohamed, Ahmed

Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system's dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.

Residential Proximity to Major Roadways Is Associated With Increased Levels of AC133+ Circulating Angiogenic Cells.

PubMed

DeJarnett, Natasha; Yeager, Ray; Conklin, Daniel J; Lee, Jongmin; O'Toole, Timothy E; McCracken, James; Abplanalp, Wes; Srivastava, Sanjay; Riggs, Daniel W; Hamzeh, Ihab; Wagner, Stephen; Chugh, Atul; DeFilippis, Andrew; Ciszewski, Tiffany; Wyatt, Brad; Becher, Carrie; Higdon, Deirdre; Ramos, Kenneth S; Tollerud, David J; Myers, John A; Rai, Shesh N; Shah, Jasmit; Zafar, Nagma; Krishnasamy, Sathya S; Prabhu, Sumanth D; Bhatnagar, Aruni

2015-11-01

Previous studies have shown that residential proximity to a roadway is associated with increased cardiovascular disease risk. Yet, the nature of this association remains unclear, and its effect on individual cardiovascular disease risk factors has not been assessed. The objective of this study was to determine whether residential proximity to roadways influences systemic inflammation and the levels of circulating angiogenic cells. In a cross-sectional study, cardiovascular disease risk factors, blood levels of C-reactive protein, and 15 antigenically defined circulating angiogenic cell populations were measured in participants (n=316) with moderate-to-high cardiovascular disease risk. Attributes of roadways surrounding residential locations were assessed using geographic information systems. Associations between road proximity and cardiovascular indices were analyzed using generalized linear models. Close proximity (<50 m) to a major roadway was associated with lower income and higher rates of smoking but not C-reactive protein levels. After adjustment for potential confounders, the levels of circulating angiogenic cells in peripheral blood were significantly elevated in people living in close proximity to a major roadway (CD31(+)/AC133(+), AC133(+), CD34(+)/AC133(+), and CD34(+)/45(dim)/AC133(+) cells) and positively associated with road segment distance (CD31(+)/AC133(+), AC133(+), and CD34(+)/AC133(+) cells), traffic intensity (CD31(+)/AC133(+) and AC133(+) cells), and distance-weighted traffic intensity (CD31(+)/34(+)/45(+)/AC133(+) cells). Living close to a major roadway is associated with elevated levels of circulating cells positive for the early stem marker AC133(+). This may reflect an increased need for vascular repair. Levels of these cells in peripheral blood may be a sensitive index of cardiovascular injury because of residential proximity to roadways. © 2015 American Heart Association, Inc.

MicroPPT-Based Secondary/Backup ACS for a 160-m, 450-kg Solar Sail Spacecraft

NASA Technical Reports Server (NTRS)

Wie, Bong; Murphy, David

2005-01-01

Solar sail tip-mounted, lightweight pulsed plasma thrusters (PPTs) are proposed for a secondary (or backup) attitude control system (ACS) of a 160-m, 450-kg solar sail spacecraft of the Solar Polar Imager (SPI) mission. A propellantless primary ACS of the SPI sailcraft employs trim control masses running along mast lanyards for pitch/yaw control together with roll stabilizer bars at the mast tips for quadrant tilt (roll) control. The robustness of such a propellantless primary ACS would be further enhanced by a secondary ACS utilizing tip-mounted, lightweight PPTs. The microPPT-based ACS is intended mainly for attitude recovery maneuvers from various off-nominal conditions that cannot be reliably handled by the propellantless primary ACS. However, it can also be employed for: i) the checkout or standby mode prior to and during sail deployment, ii) the post-deployment transition mode (prior to the propellantless primary ACS mode operation), iii) the solar sailing cruise mode of a trimmed sailcraft, and iv) the spin-stabilized, sun-pointing, safe mode. Although a conventional bus ACS is required for the SPI mission as the sail is jettisoned at the start of its science mission phase, the microPPT-based ACS option promises greater redundancy and robustness for the SPI mission. For other sailing missions, where the sail is never jettisoned, this secondary ACS provides a lower-cost, lower-mass propulsion for deployment control and greater redundancy than any traditional reaction-jet control system. This paper presents an overview nf the state--of-the--art microPPT technology, the design requirements of microPPTs for solar sail attitude control, and the preliminary ACS design and simulation results.

Artemisia capillaris inhibits atopic dermatitis-like skin lesions in Dermatophagoides farinae-sensitized Nc/Nga mice

PubMed Central

2014-01-01

Background Artemisia capillaries Thunb. (AC) has been used to treat inflammatory and hepatic disorders such as hepatic injury, hepatic fibrosis and hepatitis. However, the efficacy of AC against atopic dermatitis (AD), an inflammatory disease, has not been examined. In the present study, AC was evaluated for anti-inflammatory and anti-AD effects using both in vitro and in vivo systems. Methods The contents of six compounds (chlorogenic acid, caffeic acid, isochlorogenic acid A, hyperoside, isoquercitrin and scoparone) in AC were simultaneously assayed using HPLC system. To evaluate the anti-inflammatory effect of AC, NO production was measured in RAW264.7 cell stimulated with 1 μg/mL LPS. Histamine levels were assayed in MC/9 cells stimulated with 50 nM PMA and 1 μM A23187. To examine the role of AC in vivo, AC (10 mg/mouse/day) was topically applied for four weeks the back and ears of Dermatophagoides farinae-sensitized Nc/Nga mice. Protopic ointment (0.1% tacrolimus) was used as a positive control. Results The contents of the six components in AC range from 0.44 to 43.14 mg/g. Chlorogenic acid (21.06 ± 0.08 mg/g) and isochlorogenic acid A (43.14 ± 0.12 mg/g) were major components in AC. AC inhibited NO and histamine production in cells respectively. In D. farinae-sensitized Nc/Nga mice, the topical application of AC reduced dermatitis scores, hemorrhage, hypertrophy and hyperkeratosis of the epidermis in the dorsal skin and ear. The treatment of AC also reduced the plasma levels of histamine (1.5 fold) and IgE (1.4 fold). Conclusions Our results suggest that AC should be explored as a potential therapeutic agent to treat atopic dermatitis and analysis by HPLC will help to improve the quality of AC. PMID:24624888

Electromechanical systems with transient high power response operating from a resonant AC link

NASA Technical Reports Server (NTRS)

Burrows, Linda M.; Hansen, Irving G.

1992-01-01

The combination of an inherently robust asynchronous (induction) electrical machine with the rapid control of energy provided by a high frequency resonant AC link enables the efficient management of higher power levels with greater versatility. This could have a variety of applications from launch vehicles to all-electric automobiles. These types of systems utilize a machine which is operated by independent control of both the voltage and frequency. This is made possible by using an indirect field-oriented control method which allows instantaneous torque control in all four operating quadrants. Incorporating the AC link allows the converter in these systems to switch at the zero crossing of every half cycle of the AC waveform. This zero loss switching of the link allows rapid energy variations to be achieved without the usual frequency proportional switching loss. Several field-oriented control systems were developed by LeRC and General Dynamics Space Systems Division under contract to NASA. A description of a single motor, electromechanical actuation system is presented. Then, focus is on a conceptual design for an AC electric vehicle. This design incorporates an induction motor/generator together with a flywheel for peak energy storage. System operation and implications along with the associated circuitry are addressed. Such a system would greatly improve all-electric vehicle ranges over the Federal Urban Driving Cycle (FUD).

Method and system for a gas tube switch-based voltage source high voltage direct current transmission system

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

She, Xu; Chokhawala, Rahul Shantilal; Zhou, Rui

A voltage source converter based high-voltage direct-current (HVDC) transmission system includes a voltage source converter (VSC)-based power converter channel. The VSC-based power converter channel includes an AC-DC converter and a DC-AC inverter electrically coupled to the AC-DC converter. The AC-DC converter and a DC-AC inverter include at least one gas tube switching device coupled in electrical anti-parallel with a respective gas tube diode. The VSC-based power converter channel includes a commutating circuit communicatively coupled to one or more of the at least one gas tube switching devices. The commutating circuit is configured to "switch on" a respective one of themore » one or more gas tube switching devices during a first portion of an operational cycle and "switch off" the respective one of the one or more gas tube switching devices during a second portion of the operational cycle.« less

Impact of anti-charge sharing on the zero-frequency detective quantum efficiency of CdTe-based photon counting detector system: cascaded systems analysis and experimental validation

NASA Astrophysics Data System (ADS)

Ji, Xu; Zhang, Ran; Chen, Guang-Hong; Li, Ke

2018-05-01

Inter-pixel communication and anti-charge sharing (ACS) technologies have been introduced to photon counting detector (PCD) systems to address the undesirable charge sharing problem. In addition to improving the energy resolution of PCD, ACS may also influence other aspects of PCD performance such as detector multiplicity (i.e. the number of pixels triggered by each interacted photon) and detective quantum efficiency (DQE). In this work, a theoretical model was developed to address how ACS impacts the multiplicity and zero-frequency DQE [DQE(0)] of PCD systems. The work focused on cadmium telluride (CdTe)-based PCD that often involves the generation and transport of K-fluorescence photons. Under the parallel cascaded systems analysis framework, the theory takes both photoelectric and scattering effects into account, and it also considers both the reabsorption and escape of photons. In a new theoretical treatment of ACS, it was considered as a modified version of the conventional single pixel (i.e. non-ACS) mode, but with reduced charge spreading distance and K-fluorescence travel distance. The proposed theoretical model does not require prior knowledge of the detailed ACS implementation method for each specific PCD, and its parameters can be experimentally determined using a radioisotope without invoking any Monte-Carlo simulation. After determining the model parameters, independent validation experiments were performed using a diagnostic x-ray tube and four different polychromatic beams (from 50 to 120 kVp). Both the theoretical and experimental results demonstrate that ACS increased the first and second moments of multiplicity for a majority of the x-ray energy and threshold levels tested, except when the threshold level was much lower than the x-ray energy level. However, ACS always improved DQE(0) at all energy and threshold levels tested.

Electric Drive Study. Volume 1

DTIC Science & Technology

1987-12-21

CONDITIONER HIGH VOLTAGE DC ICONDITIONER 3 ,300-50 VOLT5), dCONTROL! Figure 5-4. Typical AC Drive System 20 system usable with an induction motor. The...controlling component in an AC drive is the motor power conditioner . This component changes the high voltage DC power to controlled AC power of...selected voltage and frequency which is applied to the drive motors. Since the vehicle gains stored energy as it is accelerated, the motor power conditioner

Protective and control relays as coal-mine power-supply ACS subsystem

NASA Astrophysics Data System (ADS)

Kostin, V. N.; Minakova, T. E.

2017-10-01

The paper presents instantaneous selective short-circuit protection for the cabling of the underground part of a coal mine and central control algorithms as a Coal-Mine Power-Supply ACS Subsystem. In order to improve the reliability of electricity supply and reduce the mining equipment down-time, a dual channel relay protection and central control system is proposed as a subsystem of the coal-mine power-supply automated control system (PS ACS).

Interwell coupling effect in Si/SiGe quantum wells grown by ultra high vacuum chemical vapor deposition

PubMed Central

Wang, Rui; Lu, Fen; Fan, Wei Jun; Liu, Chong Yang; Loh, Ter-Hoe; Nguyen, Hoai Son; Narayanan, Balasubramanian

2007-01-01

Si/Si0.66Ge0.34coupled quantum well (CQW) structures with different barrier thickness of 40, 4 and 2 nm were grown on Si substrates using an ultra high vacuum chemical vapor deposition (UHV-CVD) system. The samples were characterized using high resolution x-ray diffraction (HRXRD), cross-sectional transmission electron microscopy (XTEM) and photoluminescence (PL) spectroscopy. Blue shift in PL peak energy due to interwell coupling was observed in the CQWs following increase in the Si barrier thickness. The Si/SiGe heterostructure growth process and theoretical band structure model was validated by comparing the energy of the no-phonon peak calculated by the 6 + 2-bandk·pmethod with experimental PL data. Close agreement between theoretical calculations and experimental data was obtained.

Physical properties and antibacterial activity of chitosan/acemannan mixed systems.

PubMed

Escobedo-Lozano, Amada Yerén; Domard, Alain; Velázquez, Carlos A; Goycoolea, Francisco M; Argüelles-Monal, Waldo M

2015-01-22

The aim of the present study was to investigate the mechanical and thermal properties of mixed chitosan-acemannan (CS-AC) mixed gels and the antibacterial activity of dilute mixed solutions of both polysaccharides. Physical hydrogels of chitosan comprising varying amounts of non-gelling acemannan were prepared by controlled neutralization of chitosan using ammonia. As the overall acemannan concentration in the mixed hydrogel increased while fixing that of CS, the mechanical strength decreased. These results indicate that AC perturbs the formation of elastic junctions and overall connectivity as it occurs in the isolated CS network. Heterotypic associations between CS and AC leading to the formation of more compact microdomains may be at play in reducing the density of the gel network consolidated by CS, possibly due to shorter gel junctions. Micro-DSC studies at pH 12.0 seem consistent with the suggestion that molecular heterotypic associations between CS and AC may be at play in determining the overall physical properties of the mixed gel systems. In dilute solution, CS showed antimicrobial activity against Staphylococcus aureus but not against Escherichia coli; AC did not exert antimicrobial activity against any of the two bacterial species. In blended solutions of both polysaccharides, as the amount of AC increased, the antimicrobial activity of the system against S. aureus ceased. In conclusion, this study demonstrates that it is feasible to incorporate acemannan in chitosan-acemannan gels and that although the mechanical strength decreases due to the presence of AC, the gel network persists even at high amount of AC. This study anticipates that the CS-AC mixed gels may offer promise for the future development of biomaterials such as scaffolds to be used in wound therapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

Atmospheric Composition Data and Information Services Center (ACDISC)

NASA Technical Reports Server (NTRS)

Kempler, S.

2005-01-01

NASA's GSFC Earth Sciences (GES) Data and Information and Data Services Center (DISC) manages the archive, distribution and data access for atmospheric composition data from AURA'S OMI, MLS, and hopefully one day, HIRDLS instruments, as well as heritage datasets from TOMS, UARS, MODIS, and AIRS. This data is currently archived in the GES Distributed Active Archive Center (DAAC). The GES DISC has begun the development of a community driven data management system that's sole purpose is to manage and provide value added services to NASA's Atmospheric Composition (AC) Data. This system, called the Atmospheric Composition Data and Information Services Center (ACDISC) will provide access all AC datasets from the above mentioned instruments, as well as AC datasets residing at remote archive sites (e.g, LaRC DAAC) The goals of the ACDISC are to: 1) Provide a data center for Atmospheric Scientists, guided by Atmospheric Scientists; 2) Be absolutely responsive to the data and data service needs of the Atmospheric Composition (AC) community; 3) Provide services (i.e., expertise) that will facilitate the effortless access to and usage of AC data; 4) Collaborate with AC scientists to facilitate the use of data from multiple sensors for long term atmospheric research. The ACDISC is an AC specific, user driven, multi-sensor, on-line, easy access archive and distribution system employing data analysis and visualization, data mining, and other user requested techniques that facilitate science data usage. The purpose of this presentation is to provide the evolution path that the GES DISC in order to better serve AC data, and also to receive continued community feedback and further foster collaboration with AC data users and providers.

Evaluation of the antithrombotic abilities of non-vitamin K antagonist oral anticoagulants using the Total Thrombus-formation Analysis System®.

PubMed

Idemoto, Yoshiaki; Miura, Shin-Ichiro; Norimatsu, Kenji; Suematsu, Yasunori; Hitaka, Yuka; Shiga, Yuhei; Morii, Joji; Imaizumi, Satoshi; Kuwano, Takashi; Iwata, Atsushi; Zhang, Bo; Ogawa, Masahiro; Saku, Keijiro

2017-03-01

The Total Thrombus-formation Analysis System (T-TAS ® ) is a novel automated microchip flow-chamber system for the quantitative evaluation of thrombus formation under blood flow conditions. T-TAS ® uses two types of microchip to evaluate thrombus formation: the AR-chip quantifies white thrombus formation and the PL-chip quantifies platelet thrombus formation. We assessed the antithrombotic abilities of various non-vitamin K antagonist oral anticoagulants (NOACs) using T-TAS ® . One hundred and three consecutive patients who were hospitalized with cardiovascular diseases were enrolled. We divided the patients into 2 groups; a control group that did not receive an anticoagulant (non-AC group) and an anticoagulant group (AC group). The AC group was further divided into warfarin, dabigatran, rivaroxaban and apixaban groups. We performed common coagulation tests and evaluated the area under the flow pressure curve (AR-AUC and PL-AUC) to quantify antithrombotic ability using T-TAS ® at the trough. There were no significant differences in patient characteristics between the non-AC and AC groups. Only 55.1 % of patients in the AC group achieved the target blood pressure (BP) of less than 130/80 mmHg. Compared with the non-AC group, AR-AUC was significantly decreased in the AC, warfarin, dabigatran and apixaban groups. Only the rivaroxaban group did not show a significant decrease in AR-AUC. NOACs showed a significant decrease in PL-AUC compared with the non-AC group. In conclusion, T-TAS ® was a useful tool for evaluating anticoagulation activity. NOACs was significantly effective as an antiplatelet agent. BP control should be a higher priority than the selection of an anticoagulant drug, especially NOACs.

Study on emergency power control strategy for AC/DC hybrid power system containing VSC-HVDC

NASA Astrophysics Data System (ADS)

Liu, Lin; Hu, Zhenda; Ye, Rong; Lin, Zhangsui; Yang, Xiaodong; Yi, Yang

2018-04-01

This paper presents a comprehensive emergency power control strategy for AC/DC hybrid power systems containing VSC-HVDC. Firstly, the paper analyzes the power support of the VSC-HVDC to the AC lines using the Power Transferring Relativity Factor (PTRF). Then the power adjustment of the VSC-HVDC in several different circumstances are calculated. Finally, the online power control strategies of VSC-HVDC are designed, which could rapidly control the power of the VSC-HVDC, keeping the power flow of AC lines below the upper limit. Furthermore, the strategy is proven to be effective by the simulations with EMTDC/PSCAD.

System for automatically switching transformer coupled lines

NASA Technical Reports Server (NTRS)

Dwinell, W. S. (Inventor)

1979-01-01

A system is presented for automatically controlling transformer coupled alternating current electric lines. The secondary winding of each transformer is provided with a center tap. A switching circuit is connected to the center taps of a pair of secondary windings and includes a switch controller. An impedance is connected between the center taps of the opposite pair of secondary windings. The switching circuit has continuity when the AC lines are continuous and discontinuity with any disconnect of the AC lines. Normally open switching means are provided in at least one AC line. The switch controller automatically opens the switching means when the AC lines become separated.

Comparative performance evaluation of advanced AC and DC EV propulsion systems

NASA Astrophysics Data System (ADS)

MacDowall, R. D.; Crumley, R. L.

Idaho National Engineering Laboratory (INEL) evaluates EV propulsion systems and components for the U.S. Department of Energy (DOE) Electric and Hybrid Vehicle (EHV) Program. In this study, experimental data were used to evaluate the relative performances of the benchmark Chrysler/GE ETV-1 DC and the Ford/GE First Generation Single-Shaft AC (ETX-I) propulsion systems. Tests were conducted on the INEL's chassis dynamometer using identical aerodynamic and rolling resistance road-load coefficients and vehicle test weights. The results allowed a direct comparison of selected efficiency and performance characteristics for the two propulsion system technologies. The ETX-I AC system exhibited slightly lower system efficiency during constant speed testing than the ETV-1 DC propulsion system.

Electromechanical systems with transient high power response operating from a resonant ac link

NASA Technical Reports Server (NTRS)

Burrows, Linda M.; Hansen, Irving G.

1992-01-01

The combination of an inherently robust asynchronous (induction) electrical machine with the rapid control of energy provided by a high frequency resonant ac link enables the efficient management of higher power levels with greater versatility. This could have a variety of applications from launch vehicles to all-electric automobiles. These types of systems utilize a machine which is operated by independent control of both the voltage and frequency. This is made possible by using an indirect field-oriented control method which allows instantaneous torque control all four operating quadrants. Incorporating the ac link allows the converter in these systems to switch at the zero crossing of every half cycle of the ac waveform. This zero loss switching of the link allows rapid energy variations to be achieved without the usual frequency proportional switching loss. Several field-oriented control systems were developed under contract to NASA.

A new venous infusion pathway monitoring system.

PubMed

Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sata, Koji; Hamada, Shingo; Caldwell, W Morton

2007-01-01

A new infusion catheter pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer has been developed for hospital and home use. The sensor consists of coaxial three-layer conductive tapes wrapped around the polyvinyl chloride infusion tube. The inner tape is the main electrode, which records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. The outside tape layer is a reference electrode to monitor the AC voltage around the main electrode. The center tape layer is connected to system ground and functions as a shield. The microcomputer calculates the ratio of the induced AC voltages recorded by the main and reference electrodes and if the ratio indicates a detached infusion, alerts the nursing station, via the nurse call system or low transmitting power mobile phone.

Solar Dynamic Power System Stability Analysis and Control

NASA Technical Reports Server (NTRS)

Momoh, James A.; Wang, Yanchun

1996-01-01

The objective of this research is to conduct dynamic analysis, control design, and control performance test of solar power system. Solar power system consists of generation system and distribution network system. A bench mark system is used in this research, which includes a generator with excitation system and governor, an ac/dc converter, six DDCU's and forty-eight loads. A detailed model is used for modeling generator. Excitation system is represented by a third order model. DDCU is represented by a seventh order system. The load is modeled by the combination of constant power and constant impedance. Eigen-analysis and eigen-sensitivity analysis are used for system dynamic analysis. The effects of excitation system, governor, ac/dc converter control, and the type of load on system stability are discussed. In order to improve system transient stability, nonlinear ac/dc converter control is introduced. The direct linearization method is used for control design. The dynamic analysis results show that these controls affect system stability in different ways. The parameter coordination of controllers are recommended based on the dynamic analysis. It is concluded from the present studies that system stability is improved by the coordination of control parameters and the nonlinear ac/dc converter control stabilize system oscillation caused by the load change and system fault efficiently.

Power Quality Control and Design of Power Converter for Variable-Speed Wind Energy Conversion System with Permanent-Magnet Synchronous Generator

PubMed Central

Oğuz, Yüksel; Güney, İrfan; Çalık, Hüseyin

2013-01-01

The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS) operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%. PMID:24453905

Power quality control and design of power converter for variable-speed wind energy conversion system with permanent-magnet synchronous generator.

PubMed

Oğuz, Yüksel; Güney, İrfan; Çalık, Hüseyin

2013-01-01

The control strategy and design of an AC/DC/AC IGBT-PMW power converter for PMSG-based variable-speed wind energy conversion systems (VSWECS) operation in grid/load-connected mode are presented. VSWECS consists of a PMSG connected to a AC-DC IGBT-based PWM rectifier and a DC/AC IGBT-based PWM inverter with LCL filter. In VSWECS, AC/DC/AC power converter is employed to convert the variable frequency variable speed generator output to the fixed frequency fixed voltage grid. The DC/AC power conversion has been managed out using adaptive neurofuzzy controlled inverter located at the output of controlled AC/DC IGBT-based PWM rectifier. In this study, the dynamic performance and power quality of the proposed power converter connected to the grid/load by output LCL filter is focused on. Dynamic modeling and control of the VSWECS with the proposed power converter is performed by using MATLAB/Simulink. Simulation results show that the output voltage, power, and frequency of VSWECS reach to desirable operation values in a very short time. In addition, when PMSG based VSWECS works continuously with the 4.5 kHz switching frequency, the THD rate of voltage in the load terminal is 0.00672%.

Baselines and null hypotheses for climate change: Phytoplankton biomass structure in the California Current

NASA Astrophysics Data System (ADS)

Landry, M. R.; Taylor, A. G.

2016-02-01

Phytoplankton community structure is shaped both by the bottom-up influences of the physical-chemical environment and by the top-down impacts of food webs. Emergent patterns in the contemporary ocean can thus be "null hypotheses" of future changes assuming that the underlying structuring relationships remain intact but only shift spatially. To provide such a context for the California Current Ecosystem (CCE) and adjacent open-ocean ecosystems, we used a combination of digital epifluorescence microscopy and flow cytometry to investigate variability of phytoplankton biomass, composition and size structure across gradients of ecosystem richness, as represented by total autotrophic carbon (AC). Biomass of large micro-sized (>20 µm) phytoplankton increases as a power function with system richness. Nano-sized cells (2-20 µm) increase at a lower rate at low AC, and level off at high AC. Pico-sized cells (<2-µm) do not clearly dominate at low AC and decline significantly at high AC, neither predicted by competition theory. This study provides several new insights into structural relationships and mechanisms in the CCE: 1) diatoms and dinoflagellates co-dominate the micro-phytoplankton size class throughout the range of system richness; 2) nano-phytoplankton co-dominate biomass in oligotrophic (low AC) waters, suggesting widespread mixotrophy rather than direct competition with pico-phytoplankton for nutrients; and 3) the pico-phytoplankton decline at high AC impacts small eukaryotes as well as photosynthetic bacteria, consistent with a broad stimulation of grazing pressure on all bacterial-sized cells in richer systems. Observed variability in heterotrophic bacteria and nano-flagellate grazers with system richness is consistent with this mechanism.

Introducing high performance distributed logging service for ACS

NASA Astrophysics Data System (ADS)

Avarias, Jorge A.; López, Joao S.; Maureira, Cristián; Sommer, Heiko; Chiozzi, Gianluca

2010-07-01

The ALMA Common Software (ACS) is a software framework that provides the infrastructure for the Atacama Large Millimeter Array and other projects. ACS, based on CORBA, offers basic services and common design patterns for distributed software. Every properly built system needs to be able to log status and error information. Logging in a single computer scenario can be as easy as using fprintf statements. However, in a distributed system, it must provide a way to centralize all logging data in a single place without overloading the network nor complicating the applications. ACS provides a complete logging service infrastructure in which every log has an associated priority and timestamp, allowing filtering at different levels of the system (application, service and clients). Currently the ACS logging service uses an implementation of the CORBA Telecom Log Service in a customized way, using only a minimal subset of the features provided by the standard. The most relevant feature used by ACS is the ability to treat the logs as event data that gets distributed over the network in a publisher-subscriber paradigm. For this purpose the CORBA Notification Service, which is resource intensive, is used. On the other hand, the Data Distribution Service (DDS) provides an alternative standard for publisher-subscriber communication for real-time systems, offering better performance and featuring decentralized message processing. The current document describes how the new high performance logging service of ACS has been modeled and developed using DDS, replacing the Telecom Log Service. Benefits and drawbacks are analyzed. A benchmark is presented comparing the differences between the implementations.

Design study for LANDSAT D attitude control system

NASA Technical Reports Server (NTRS)

Iwens, R. P.; Bernier, G. E.; Hofstadter, R. F.

1976-01-01

A design and performance evaluation is presented for the LANDSAT D attitude control system (ACS). Control and configuration of the gimballed Ku-band antenna system for communication with the tracking and data relay satellite (TDRS). Control of the solar array drive considered part of the ACS is also addressed.

75 FR 60493 - Advisory Circular 120-79A, Developing and Implementing an Air Carrier Continuing Analysis and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-30

... and Implementing an Air Carrier Continuing Analysis and Surveillance System AGENCY: Federal Aviation... Analysis and Surveillance System''. This new advisory circular (AC) updates AC 120-79 originally issued on... Analysis and Surveillance System (CASS) required for commercial operators and air carriers certificated...

Surface Science at the Solid Liquid Interface

DTIC Science & Technology

1993-10-06

prominent experimental avenue, developed originally by Hubbard et al,_ involves emersing monocrystalline elec- As for metal surfaces in ultrahigh vacuum...reliable means of both preparing and dosateizn ordered monocrystalline metal surfaces in UHV has led to ing appropriate molecular components of...surface atoms in place of bottom panel of Fig. 2, equal intensity contours are shown 23 underlying surface atoms, the compression is 24/23 - I in the

Surface Chemistry of CWAs for Decon Enabling Sciences

DTIC Science & Technology

2014-11-04

representing the formation of a hydrogen-bonded mode. Characteristic modes of the sarin molecule itself are also observed. These experimental results show...Triangle Park, NC 27709-2211 surface science, CWA, uptake, decomposition, decontamination, filtration , XPS, FTIR, TPD, MS, UHV REPORT DOCUMENTATION PAGE 11...Karwacki, Team Leader CBR Filtration Research and Technology Directorate at ECBC. Through this collaboration, we have established a facility for the study

The structure of [MnIII6 CrIII]3+ single-molecule magnets deposited in submono-layers and monolayers on surfaces studied by means of molecular resolved atomic force microscopy (AFM) and Kelvin Probe Force Microscopy in UHV

NASA Astrophysics Data System (ADS)

Heinzmann, U.; Gryzia, A.; Volkmann, T.; Brechling, A.; Hoeke, V.; Glaser, T.

2014-04-01

Single molecule magnets (SMM) deposited in submonolayers and monolayers have been analyzed with respect to their structures by means of non-contact AFM (topographic as well as damping mode) and Kelvin Probe Force Microscopy with molecular resolution.

Removal of trichloroethylene by zerovalent iron/activated carbon derived from agricultural wastes.

PubMed

Su, Yuh-fan; Cheng, Yu-ling; Shih, Yang-hsin

2013-11-15

Activated carbon (AC) and zerovalent iron (ZVI) have been widely used in the adsorption and dehalogenation process, respectively, for the removal of organic compounds in environmental treatments. This study aims to prepare ZVI/AC derived from an agricultural waste, coir pith, through simple one-step pyrolysis. The effect of activation temperature and time on the surface area, iron content, and zerovalent iron ratio of ZVI/AC was systemically investigated. The results indicated that the activation of AC by FeSO4 significantly increased surface area of AC and distributed elemental iron over the AC. The X-ray diffraction (XRD), electron spectroscopy for chemical analysis (ESCA), and X-ray absorption near edge structure (XANES) spectra of ZVI/AC revealed that zerovalent iron was present. As compared to AC without FeSO4 activation, ZVI/AC increased the trichloroethylene removal rate constant by 7 times. The dechlorination ability of ZVI/AC was dominated by the zerovalent iron content. We have shown that lab-made ZVI/AC from coir pith can effectively adsorb and dehalogenate the chlorinated compounds in water. Copyright © 2013 Elsevier Ltd. All rights reserved.

Simulation of Trolleybus Traction Induction Drive With Supercapacitor Energy Storage System

NASA Astrophysics Data System (ADS)

Brazis, V.; Latkovskis, L.; Grigans, L.

2010-01-01

The article considers the possibilities of saving the regenerative braking energy in Škoda 24Tr type trolleybuses by installing the onboard supercapacitor energy storage system (ESS) and improving its performance with automated switching to the autonomous traction mode. Proposed is an ESS control system with constant DC bus voltage in the supercapacitor charging mode and supercapacitor current proportional to the AC drive current in the discharging mode. The authors investigate stability of the trolleybus ESS control system operating together with AC traction drive in various overhead voltage failure modes. The co-simulation of ESS operation was done by Matlab/Simulink AC drive and PSIM ESS continuous models.

Adaptive traffic signal control system (ACS-Lite) for Wolf Road, Albany, New York.

DOT National Transportation Integrated Search

2014-10-01

Adaptive Control Software Lite (ACS : - : Lite) is a : traffic : signal timing optimization system that : dynamically adjusts : traffic : signal timing : s : to meet current traffic demands. : The purpose of this : research project : was : to : deplo...

Construction and evaluation of photovoltaic power generation and power storage system using SiC field-effect transistor inverter

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

Oku, Takeo, E-mail: oku@mat.usp.ac.jp; Matsumoto, Taisuke; Ohishi, Yuya

A power storage system using spherical silicon (Si) solar cells, maximum power point tracking charge controller, lithium-ion battery and a direct current-alternating current (DC-AC) inverter was constructed. Performance evaluation of the DC-AC inverter was carried out, and the DC-AC conversion efficiencies of the SiC field-effect transistor (FET) inverter was improved compared with those of the ordinary Si-FET based inverter.

SALICYLATE INCREASES THE GAIN OF THE CENTRAL AUDITORY SYSTEM

PubMed Central

Sun, W.; Lu, J.; Stolzberg, D.; Gray, L.; Deng, A.; Lobarinas, E.; Salvi, R. J.

2009-01-01

High doses of salicylate, the anti-inflammatory component of aspirin, induce transient tinnitus and hearing loss. Systemic injection of 250 mg/kg of salicylate, a dose that reliably induces tinnitus in rats, significantly reduced the sound evoked output of the rat cochlea. Paradoxically, salicylate significantly increased the amplitude of the sound-evoked field potential from the auditory cortex (AC) of conscious rats, but not the inferior colliculus (IC). When rats were anesthetized with isoflurane, which increases GABA-mediated inhibition, the salicylate-induced AC amplitude enhancement was abolished, whereas ketamine, which blocks N-methyl-d-aspartate receptors, further increased the salicylate-induced AC amplitude enhancement. Direct application of salicylate to the cochlea, however, reduced the response amplitude of the cochlea, IC and AC, suggesting the AC amplitude enhancement induced by systemic injection of salicylate does not originate from the cochlea. To identify a behavioral correlate of the salicylate-induced AC enhancement, the acoustic startle response was measured before and after salicylate treatment. Salicylate significantly increased the amplitude of the startle response. Collectively, these results suggest that high doses of salicylate increase the gain of the central auditory system, presumably by down-regulating GABA-mediated inhibition, leading to an exaggerated acoustic startle response. The enhanced startle response may be the behavioral correlate of hyperacusis that often accompanies tinnitus and hearing loss. Published by Elsevier Ltd on behalf of IBRO. PMID:19154777

Attitude Control Working Group report

NASA Technical Reports Server (NTRS)

Reid, Daniel F.; Studer, Phillip A.

1986-01-01

The goals were to establish the Attitude Control System (ACS) requirements, constraints, technology assessment, technology shortfalls, expected in the year 2000. These were based upon all missions, military and civil, for LEO and GEO. The critical ACS technology issues were identified and ACS programs developed to address these critical issues.

Power conditioning system for energy sources

DOEpatents

Mazumder, Sudip K [Chicago, IL; Burra, Rajni K [Chicago, IL; Acharya, Kaustuva [Chicago, IL

2008-05-13

Apparatus for conditioning power generated by an energy source includes an inverter for converting a DC input voltage from the energy source to a square wave AC output voltage, and a converter for converting the AC output voltage from the inverter to a sine wave AC output voltage.

A new infusion pathway monitoring system utilizing electrostatic induced potential.

PubMed

Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sada, Kouji; Hamada, Shingo; Hahn, Alien W; Caldwell, W Morton

2006-01-01

We have developed a new infusion pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer. The system is available for hospital and home use and it constantly monitors the intactness of the pathway. The sensor is an electro-conductive polymer electrode wrapped around the infusion polyvinyl chloride infusion tube. This records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. If the injection needle or infusion tube becomes detached, then the system detects changes in the induced AC voltage and alerts the nursing station, via the nurse call system or PHS (personal handy phone System).

An improved adaptive weighting function method for State Estimation in Power Systems with VSC-MTDC

NASA Astrophysics Data System (ADS)

Zhao, Kun; Yang, Xiaonan; Lang, Yansheng; Song, Xuri; Wang, Minkun; Luo, Yadi; Wu, Lingyun; Liu, Peng

2017-04-01

This paper presents an effective approach for state estimation in power systems that include multi-terminal voltage source converter based high voltage direct current (VSC-MTDC), called improved adaptive weighting function method. The proposed approach is simplified in which the VSC-MTDC system is solved followed by the AC system. Because the new state estimation method only changes the weight and keeps the matrix dimension unchanged. Accurate and fast convergence of AC/DC system can be realized by adaptive weight function method. This method also provides the technical support for the simulation analysis and accurate regulation of AC/DC system. Both the oretical analysis and numerical tests verify practicability, validity and convergence of new method.

Iron Impregnated Activated Carbon as an Efficient Adsorbent for the Removal of Methylene Blue: Regeneration and Kinetics Studies

PubMed Central

Shah, Irfan; Adnan, Rohana; Wan Ngah, Wan Saime; Mohamed, Norita

2015-01-01

In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation and iron impregnation of activated carbon (AC). Both the AC and FeAC were characterized by pHZPC and FTIR spectroscopy. The removal of Methylene Blue (MB) by AC and FeAC was examined under various experimental conditions. The FeAC showed up to 95% (higher than AC) MB removal in the pH range of 7–10. Although the reaction kinetics was pseudo–second order, the overall rate was controlled by a number of processes such as film diffusion, pore diffusion and intraparticle diffusion. The activation energy values for the MB uptake by AC and FeAC (21.79 and 14.82 kJ/mol, respectively) revealed a physisorption process. In the regeneration study, FeAC has shown consistently ≥ 90% MB removal even up to 10 repeated cycles. The reusable characteristic of the spent FeAC improved the practical use of activated carbon and can be a breakthrough for continuous flow system applications where it can work effectively without any significant reduction in its performance. PMID:25849291

A new approach for AC loss reduction in HTS transformer using auxiliary windings, case study: 25 kA HTS current injection transformer

NASA Astrophysics Data System (ADS)

Heydari, Hossein; Faghihi, Faramarz; Aligholizadeh, Reza

2008-01-01

AC loss is one of the important parameters in HTS (high temperature superconducting) AC devices. Among the HTS AC power devices, the transformer is an essential part in the electrical power system. The AC losses in an HTS tape depend on the magnetic field. One of the techniques usually adopted to mitigate the unwanted magnetic field is using a system of coils that produce a magnetic field opposite to the incident one, reducing the total magnetic field. In this paper adding two auxiliary windings to the HTS transformer to produce this opposite magnetic field is proposed. The proper use of these auxiliary windings could reduce the leakage flux and, therefore, the AC loss. A mathematical model is used to describe the behaviour of a transformer operating with auxiliary windings, based on the theory of electromagnetic coupled circuits. The influence of the auxiliary windings on the leakage field is studied by the finite element method (FEM) and the AC loss of an HTS transformer was calculated. Also, the simulation results show that employing auxiliary windings will improve the HTS transformer efficiency.

Systems and methods for deactivating a matrix converter

DOEpatents

Ransom, Ray M.

2013-04-02

Systems and methods are provided for deactivating a matrix conversion module. An electrical system comprises an alternating current (AC) interface, a matrix conversion module coupled to the AC interface, an inductive element coupled between the AC interface and the matrix conversion module, and a control module. The control module is coupled to the matrix conversion module, and in response to a shutdown condition, the control module is configured to operate the matrix conversion module to deactivate the first conversion module when a magnitude of a current through the inductive element is less than a threshold value.

System and method for motor speed estimation of an electric motor

DOEpatents

Lu, Bin [Kenosha, WI; Yan, Ting [Brookfield, WI; Luebke, Charles John [Sussex, WI; Sharma, Santosh Kumar [Viman Nagar, IN

2012-06-19

A system and method for a motor management system includes a computer readable storage medium and a processing unit. The processing unit configured to determine a voltage value of a voltage input to an alternating current (AC) motor, determine a frequency value of at least one of a voltage input and a current input to the AC motor, determine a load value from the AC motor, and access a set of motor nameplate data, where the set of motor nameplate data includes a rated power, a rated speed, a rated frequency, and a rated voltage of the AC motor. The processing unit is also configured to estimate a motor speed based on the voltage value, the frequency value, the load value, and the set of nameplate data and also store the motor speed on the computer readable storage medium.

Adhesion Between Volcanic Glass and Spacecraft Materials in an Airless Body Environment

NASA Technical Reports Server (NTRS)

Berkebile, Stephen; Street, Kenneth W., Jr.; Gaier, James R.

2012-01-01

The successful exploration of airless bodies, such as the Earth s moon, many smaller moons of the outer planets (including those of Mars) and asteroids, will depend on the development and implementation of effective dust mitigation strategies. The ultrahigh vacuum environment (UHV) on the surfaces of these bodies, coupled with constant ion and photon bombardment from the Sun and micrometeorite impacts (space weathering), makes dust adhesion to critical spacecraft systems a severe problem. As a result, the performance of thermal control surfaces, photovoltaics and mechanical systems can be seriously degraded even to the point of failure. The severe dust adhesion experienced in these environments is thought to be primarily due to two physical mechanisms, electrostatic attraction and high surface energies, but the dominant of these has yet to be determined. The experiments presented here aim to address which of these two mechanisms is dominant by quantifying the adhesion between common spacecraft materials (polycarbonate, FEP and PTFE Teflon, (DuPont) Ti-6-4) and a synthetic noritic volcanic glass, as a function of surface cleanliness and triboelectric charge transfer in a UHV environment. Adhesion force has been measured between pins of spacecraft materials and a plate of synthetic volcanic glass by determining the pull-off force with a torsion balance. Although no significant adhesion is observed directly as a result of high surface energies, the adhesion due to induced electrostatic charge is observed to increase with spacecraft material cleanliness, in some cases by over a factor of 10, although the increase is dependent on the particular material pair. The knowledge gained by these studies is envisioned to aid the development of new dust mitigation strategies and improve existing strategies by helping to identify and characterize mechanisms of glass to spacecraft adhesion for norite volcanic glass particles. Furthermore, the experience of the Apollo missions revealed that dust mitigation strategies must be subjected to high fidelity tests. To facilitate the effectiveness of ground-based testing of mitigation strategies, the issue of a pressure limit for high fidelity tests will be addressed.

X-Ray Scattering Studies of the Liquid-Vapor Interface of Gallium.

NASA Astrophysics Data System (ADS)

Kawamoto, Eric Hitoshi

A UHV system was developed for performing X-ray scattering studies and in situ analyses of liquid metal surfaces. A nearly ideal choice for this study, gallium has a melting point just above room temperature; is amenable to handling in both air and vacuum; its surface oxides can be removed while its cleanliness is maintained and monitored. Using argon glow-discharge sputtering techniques to remove intervening surface oxides, thin wetting layers of gallium were prepared atop nonreactive substrates, to be used as samples suited for liquid surface scattering experiments. Preliminary measurements of X-ray reflectivity from the liquid-vapor interface of gallium were performed with the X-ray UHV chamber configured for use in conjunction with liquid surface spectrometers at two synchrotron beamlines. A novel technique for carrying out and interpreting scattering measurements from curved liquid surfaces was demonstrated. The energy tunability and intense focused white beam flux from a wiggler source was shown to place within reach the large values of wavevector transfer at which specular reflectivity data yield small length scale information about surface structure. Various theoretical treatments and simulations predict quasi-lamellar ordering of atoms near the free surface of metallic liquids due to energetics particular to metals (electron delocalization, the dependence of system energy on ion and electron densities, surface tension and electrostatic energy). However, the experimental data reported to date is insufficient to distinguish between a monotonic, sigmoidal electron density profile found at the free surfaces of dielectric liquids, and the damped oscillatory layer-like profiles anticipated for metallic liquids. Out to a wavevector transfer of Q = 0.55 A ^{-1}, the reflectivity data measured from a curved Ga surface is not inconsistent with what is expected for a liquid-vapor electron density profile of Gaussian width sigma = 1.3 +/- 0.2 A. Subsequent measurements roughly tripled the range of Q, but an oxidized surface led to poor data and hindered interpretation. The analysis presented is speculative at best, but within the context of the thermally excited capillary wave model of simple liquid surfaces, there seems to be no serious deviation from the simple Gaussian interfacial profile with the aforementioned roughness.

Thermal modification of activated carbon surface chemistry improves its capacity as redox mediator for azo dye reduction.

PubMed

Pereira, L; Pereira, R; Pereira, M F R; van der Zee, F P; Cervantes, F J; Alves, M M

2010-11-15

The surface chemistry of a commercial AC (AC(0)) was selectively modified, without changing significantly its textural properties, by chemical oxidation with HNO(3) (AC(HNO3)) and O(2) (AC(O2)), and thermal treatments under H(2) (AC(H2)) or N(2) (AC(N2)) flow. The effect of modified AC on anaerobic chemical dye reduction was assayed with sulphide at different pH values 5, 7 and 9. Four dyes were tested: Acid Orange 7, Reactive Red 2, Mordant Yellow 10 and Direct Blue 71. Batch experiments with low amounts of AC (0.1 g L(-1)) demonstrated an increase of the first-order reduction rate constants, up to 9-fold, as compared with assays without AC. Optimum rates were obtained at pH 5 except for MY10, higher at pH 7. In general, rates increased with increasing the pH of point zero charge (pH(pzc)), following the trend AC(HNO3) < AC(O2) < AC(0) < AC(N2) < AC(H2). The highest reduction rate was obtained for MY10 with AC(H2) at pH 7, which corresponded to the double, as compared with non-modified AC. In a biological system using granular biomass, AC(H2) also duplicated and increase 4.5-fold the decolourisation rates of MY10 and RR2, respectively. In this last experiment, reaction rate was independent of AC concentration in the tested range 0.1-0.6 g L(-1). Copyright © 2010 Elsevier B.V. All rights reserved.

Optimal management of batteries in electric systems

DOEpatents

Atcitty, Stanley; Butler, Paul C.; Corey, Garth P.; Symons, Philip C.

2002-01-01

An electric system including at least a pair of battery strings and an AC source minimizes the use and maximizes the efficiency of the AC source by using the AC source only to charge all battery strings at the same time. Then one or more battery strings is used to power the load while management, such as application of a finish charge, is provided to one battery string. After another charge cycle, the roles of the battery strings are reversed so that each battery string receives regular management.

Power factor control system for AC induction motors

NASA Technical Reports Server (NTRS)

Nola, F. J. (Inventor)

1977-01-01

A power factor control system for use with ac induction motors was designed which samples lines voltage and current through the motor and decreases power input to the motor proportional to the detected phase displacement between current and voltage. This system provides, less power to the motor, as it is less loaded.

Development of software to improve AC power quality on large spacecraft

NASA Technical Reports Server (NTRS)

Kraft, L. Alan

1991-01-01

To insure the reliability of a 20 kHz, AC power system on spacecraft, it is essential to analyze its behavior under many adverse operating conditions. Some of these conditions include overloads, short circuits, switching surges, and harmonic distortions. Harmonic distortions can cause malfunctions in equipment that the power system is supplying, and during extreme distortions such as voltage resonance, it can cause equipment and insulation failures due to the extreme peak voltages. HARMFLO, a power flow computer program, which was capable of analyzing harmonic conditions on three phase, balanced, 60 Hz, AC power systems, was modified to analyze single phase, 20 kHz, AC power systems. Since almost all of the equipment used on spacecraft power systems is electrically different from equipment used on terrestrial power systems, it was also necessary to develop mathematical models for the equipment to be used on the spacecraft. The results are that (1) the harmonic power now has a model of a single phase, voltage controlled, full wave rectifier; and (2) HARMFLO was ported to the SUN workstation platform.

A Review of Microgrid Architectures and Control Strategy

NASA Astrophysics Data System (ADS)

Jadav, Krishnarajsinh A.; Karkar, Hitesh M.; Trivedi, I. N.

2017-12-01

In this paper microgrid architecture and various converters control strategies are reviewed. Microgrid is defined as interconnected network of distributed energy resources, loads and energy storage systems. This emerging concept realizes the potential of distributed generators. AC microgrid interconnects various AC distributed generators like wind turbine and DC distributed generators like PV, fuel cell using inverter. While in DC microgrid output of an AC distributed generator must be converted to DC using rectifiers and DC distributed generator can be directly interconnected. Hybrid microgrid is the solution to avoid this multiple reverse conversions AC-DC-AC and DC-AC-DC that occur in the individual AC-DC microgrid. In hybrid microgrid all AC distributed generators will be connected in AC microgrid and DC distributed generators will be connected in DC microgrid. Interlinking converter is used for power balance in both microgrids, which transfer power from one microgrid to other if any microgrid is overloaded. At the end, review of interlinking converter control strategies is presented.

Imitative modeling automatic system Control of steam pressure in the main steam collector with the influence on the main Servomotor steam turbine

NASA Astrophysics Data System (ADS)

Andriushin, A. V.; Zverkov, V. P.; Kuzishchin, V. F.; Ryzhkov, O. S.; Sabanin, V. R.

2017-11-01

The research and setting results of steam pressure in the main steam collector “Do itself” automatic control system (ACS) with high-speed feedback on steam pressure in the turbine regulating stage are presented. The ACS setup is performed on the simulation model of the controlled object developed for this purpose with load-dependent static and dynamic characteristics and a non-linear control algorithm with pulse control of the turbine main servomotor. A method for tuning nonlinear ACS with a numerical algorithm for multiparametric optimization and a procedure for separate dynamic adjustment of control devices in a two-loop ACS are proposed and implemented. It is shown that the nonlinear ACS adjusted with the proposed method with the regulators constant parameters ensures reliable and high-quality operation without the occurrence of oscillations in the transient processes the operating range of the turbine loads.

Modular inverter system

DOEpatents

Ma, Mingyao; Hu, Haibing; Kutkut, Nasser; Batarseh, Issa; Shen, John; , Bkayrat, Raed

2017-08-01

A system connected to an AC power grid having an AC phase signal includes an inverter module including a first inverter coupled to a DC voltage, actuated based on the AC phase signal. The first inverter provides a first voltage signal having predetermined harmonic components. A second inverter includes second switch elements coupled to the DC voltage and actuated by a second set of control signals phase delayed with respect to the first control signals. A transformer module has first and second primary windings coupled to the first and second inverters. The transformer module further includes a secondary winding coupled to first primary winding, the second primary winding, and the AC power grid. The secondary winding is configured to provide a secondary output voltage to the AC power grid by combining the first voltage signal and the second voltage signal such that the predetermined harmonic components are substantially cancelled.

Characterization and Fabrication of High k dielectric-High Mobility Channel Transistors

NASA Astrophysics Data System (ADS)

Sun, Xiao

As the conventional scaling of Si-based MOSFETs would bring negligible or even negative merits for IC's beyond the 7-nm CMOS technology node, many perceive the use of high-mobility channels to be one of the most likely principle changes, in order to achieve higher performance and lower power. However, interface and oxide traps have become a major obstacle for high-mobility semiconductors (such as Ge, InGaAs, GaSb, GaN...) to replace Si CMOS technology. In this thesis, the distinct properties of the traps in the high-k dielectric/high-mobility substrate system is discussed, as well as the challenges to characterize and passivate them. By modifying certain conventional gate admittance methods, both the fast and slow traps in Ge MOS gate stacks is investigated. In addition, a novel ac-transconductance method originated at Yale is introduced and demonstrated with several advanced transistors provided by collaborating groups, such as ultra-thin-body & box SO1 MOSFETs (CEA-LETI), InGaAs MOSFETs (IMEC, UT Austin, Purdue), and GaN MOS-HEMT (MIT). By use of the aforementioned characterization techniques, several effective passivation techniques on high mobility substrates (Ge, InGaAs, GaSb, GeSn, etc.) are evaluated, including a novel Ba sub-monolayer passivation of Ge surface. The key factors that need to be considered in passivating high mobility substrates are revealed. The techniques that we have established for characterizing traps in advanced field-effect transistors, as well as the knowledge gained about these traps by the use of these techniques, have been applied to the study of ionizing radiation effects in high-mobility-channel transistors, because it is very important to understand such effects as these devices are likely to be exposed to radiation-harsh environments, such as in outer space, nuclear plants, and during X-ray or UHV lithography. In this thesis, the total ionizing dose (TD) radiation effects of InGaAs-based MOSFETs and GaN-based MOS-HEMT are studied, and the results help to reveal the underlying mechanisms and inspire ideas for minimizing the TID radiation effects.

Apple MdACS6 Regulates Ethylene Biosynthesis During Fruit Development Involving Ethylene-Responsive Factor.

PubMed

Li, Tong; Tan, Dongmei; Liu, Zhi; Jiang, Zhongyu; Wei, Yun; Zhang, Lichao; Li, Xinyue; Yuan, Hui; Wang, Aide

2015-10-01

Ethylene biosynthesis in plants involves different 1-aminocyclopropane-1-carboxylic acid synthase (ACS) genes. The regulation of each ACS gene during fruit development is unclear. Here, we characterized another apple (Malus×domestica) ACS gene, MdACS6. The transcript of MdACS6 was observed not only in fruits but also in other tissues. During fruit development, MdACS6 was initiated at a much earlier stage, whereas MdACS3a and MdACS1 began to be expressed at 35 d before harvest and immediateley after harvest, respectively. Moreover, the enzyme activity of MdACS6 was significantly lower than that of MdACS3a and MdACS1, accounting for the low ethylene biosynthesis in young fruits. Overexpression of MdACS6 (MdACS6-OE) by transient assay in apple showed enhanced ethylene production, and MdACS3a was induced in MdACS6-OE fruits but not in control fruits. In MdACS6 apple fruits silenced by the virus-induced gene silencing (VIGS) system (MdACS6-AN), neither ethylene production nor MdACS3a transcript was detectable. In order to explore the mechanism through which MdACS3a was induced in MdACS6-OE fruits, we investigated the expression of apple ethylene-responsive factor (ERF) genes. The results showed that the expression of MdERF2 was induced in MdACS6-OE fruits and inhibited in MdACS6-AN fruits. Yeast one-hybrid assay showed that MdERF2 protein could bind to the promoter of MdACS3a. Moreover, down-regulation of MdERF2 in apple flesh callus led to a decrease of MdACS3a expression, demonstrating the regulation of MdERF2 on MdACS3a. The mechanism through which MdACS6 regulates the action of MdACS3a was discussed. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Probable Mechanisms of Needling Therapies for Myofascial Pain Control

PubMed Central

Chou, Li-Wei; Kao, Mu-Jung; Lin, Jaung-Geng

2012-01-01

Myofascial pain syndrome (MPS) has been defined as a regional pain syndrome characterized by muscle pain caused by myofascial trigger points (MTrPs) clinically. MTrP is defined as the hyperirritable spot in a palpable taut band of skeletal muscle fibers. Appropriate treatment to MTrPs can effectively relieve the clinical pain of MPS. Needling therapies, such as MTrP injection, dry needling, or acupuncture (AcP) can effectively eliminate pain immediately. AcP is probably the first reported technique in treating MPS patients with dry needling based on the Traditional Chinese Medicine (TCM) theory. The possible mechanism of AcP analgesia were studied and published in recent decades. The analgesic effect of AcP is hypothesized to be related to immune, hormonal, and nervous systems. Compared to slow-acting hormonal system, nervous system acts in a faster manner. Given these complexities, AcP analgesia cannot be explained by any single mechanism. There are several principles for selection of acupoints based on the TCM principles: “Ah-Shi” point, proximal or remote acupoints on the meridian, and extra-meridian acupoints. Correlations between acupoints and MTrPs are discussed. Some clinical and animal studies of remote AcP for MTrPs and the possible mechanisms of remote effectiveness are reviewed and discussed. PMID:23346211

Angular cheilitis, part 2: nutritional, systemic, and drug-related causes and treatment.

PubMed

Park, Kelly K; Brodell, Robert T; Helms, Stephen E

2011-07-01

Angular cheilitis (AC) is associated with a variety of nutritional, systemic, and drug-related factors that may act exclusively or in combination with local factors. Establishing the underlying etiology of AC is required to appropriately focus treatment efforts.

AC conductivity of a quantum Hall line junction

NASA Astrophysics Data System (ADS)

Agarwal, Amit; Sen, Diptiman

2009-09-01

We present a microscopic model for calculating the AC conductivity of a finite length line junction made up of two counter- or co-propagating single mode quantum Hall edges with possibly different filling fractions. The effect of density-density interactions and a local tunneling conductance (σ) between the two edges is considered. Assuming that σ is independent of the frequency ω, we derive expressions for the AC conductivity as a function of ω, the length of the line junction and other parameters of the system. We reproduce the results of Sen and Agarwal (2008 Phys. Rev. B 78 085430) in the DC limit (\\omega \\to 0 ), and generalize those results for an interacting system. As a function of ω, the AC conductivity shows significant oscillations if σ is small; the oscillations become less prominent as σ increases. A renormalization group analysis shows that the system may be in a metallic or an insulating phase depending on the strength of the interactions. We discuss the experimental implications of this for the behavior of the AC conductivity at low temperatures.

Synthesis, characterization and catalytic activity of nanosized Ni complexed aminoclay

NASA Astrophysics Data System (ADS)

Ranchani, A. Amala Jeya; Parthasarathy, V.; Devi, A. Anitha; Meenarathi, B.; Anbarasan, R.

2017-11-01

A novel Ni complexed aminoclay (AC) catalyst was prepared by complexation method followed by reduction reaction. Various analytical techniques such as FTIR spectroscopy, UV-visible spectroscopy, DSC, TGA, SEM, HRTEM, EDX, XPS and WCA measurement are used to characterize the synthesized material. The AC-Ni catalyst system exhibited improved thermal stability and fiber-like morphology. The XPS results declared the formation of Ni nanoparticles. Thus, synthesized catalyst was tested towards the Schiff base formation reaction between various bio-medical polymers and aniline under air atmosphere at 85 °C for 24 h. The catalytic activity of the catalyst was studied by varying the % weight loading of the AC-Ni system towards the Schiff base formation. The Schiff base formation was quantitatively calculated by the 1H-NMR spectroscopy. While increasing the % weight loading of the AC-Ni catalyst, the % yield of Schiff base was also increased. The k app and Ti values were determined for the reduction of indole and α-terpineol in the presence of AC-Ni catalyst system. The experimental results were compared with the literature report.

Characterization of un-plasticized and propylene carbonate plasticized carboxymethyl cellulose doped ammonium chloride solid biopolymer electrolytes.

PubMed

Ahmad, N H; Isa, M I N

2016-02-10

Two solid biopolymer electrolytes (SBEs) systems of carboxymethyl cellulose doped ammonium chloride (CMC-AC) and propylene carbonate plasticized (CMC-AC-PC) were prepared via solution casting technique. The ionic conductivity of SBEs were analyzed using electrical impedance spectroscopy (EIS) in the frequency range of 50 Hz-1 MHz at ambient temperature (303K). The highest ionic conductivity of CMC-AC SBE is 1.43 × 10(-3)S/cm for 16 wt.% of AC while the highest conductivity of plasticized SBE system is 1.01 × 10(-2)S/cm when added with 8 wt.% of PC. TGA/DSC showed that the addition of PC had increased the decomposition temperature compared of CMC-AC SBE. Fourier transform infrared (FTIR) spectra showed the occurrence of complexation between the SBE components and it is proved successfully executed by Gaussian software. X-ray diffraction (XRD) indicated that amorphous nature of SBEs. It is believed that the PC is one of the most promising plasticizer to enhance the ionic conductivity and performance for SBE system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cascaded Quadruple Active Bridge Structures for Multilevel DC to Three-Phase AC Conversion

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

Johnson, Brian B; Achanta, Prasanta K; Maksimovic, Dragan

This paper introduces a multilevel architecture comprised of interconnected dc to three-phase ac converter units. To enable series connected operation, each converter unit contains a quadruple active bridge (QAB) converter that provides isolation between the dc side and each of the three ac sides. Since each converter unit transfers dc-side power as constant balanced three-phase power on the ac side, this implies instantaneous input-output power balance and allows elimination of bulk capacitive energy storage. In addition to minimizing required capacitance, the proposed approach simultaneously enables simplified dc-link controllers amenable to decentralized implementation, supports bidirectional power transfer, and exhibits a modularmore » structure to enhance scalability. Isolation provided by the QAB allows a wide range of electrical configurations among multiple units in various dc-ac, ac-dc or ac-ac applications. In this paper, the focus is on series connections on the ac side to emphasize multilevel operation, and the approach is experimentally validated in a dc-ac system containing two cascaded converter units.« less

Phantom evaluation of a cardiac SPECT/VCT system that uses a common set of solid-state detectors for both emission and transmission scans

PubMed Central

Conwell, Richard; Kindem, Joel; Babla, Hetal; Gurley, Mike; De Los Santos, Romer; Old, Rex; Weatherhead, Randy; Arram, Samia; Maddahi, Jamshid

2010-01-01

Background We developed a cardiac SPECT system (X-ACT) with low dose volume CT transmission-based attenuation correction (AC). Three solid-state detectors are configured to form a triple-head system for emission scans and reconfigured to form a 69-cm field-of-view detector arc for transmission scans. A near mono-energetic transmission line source is produced from the collimated fluorescence x-ray emitted from a lead target when the target is illuminated by a narrow polychromatic x-ray beam from an x-ray tube. Transmission scans can be completed in 1 min with insignificant patient dose (deep dose equivalent <5 μSv). Methods We used phantom studies to evaluate (1) the accuracy of the reconstructed attenuation maps, (2) the effect of AC on image uniformity, and (3) the effect of AC on defect contrast (DC). The phantoms we used included an ACR phantom, an anthropomorphic phantom with a uniform cardiac insert, and an anthropomorphic phantom with two defects in the cardiac insert. Results The reconstructed attenuation coefficient of water at 140 keV was .150 ± .003/cm in the uniform region of the ACR phantom, .151 ± .003/cm and .151 ± .002/cm in the liver and cardiac regions of the anthropomorphic phantom. The ACR phantom images with AC showed correction of the bowing effect due to attenuation in the images without AC (NC). The 17-segment scores of the images of the uniform cardiac insert were 78.3 ± 6.5 before and 87.9 ± 3.3 after AC (average ± standard deviation). The inferior-to-anterior wall ratio and the septal-to-lateral wall ratio were .99 and 1.16 before and 1.02 and 1.00 after AC. The DC of the two defects was .528 and .156 before and .628 and .173 after AC. Conclusion The X-ACT system generated accurate attenuation maps with 1-minute transmission scans. AC improved image quality and uniformity over NC. PMID:20169476

Clock Controller For Ac Self-Timing Analysis Of Logic System

DOEpatents

Lo, Tinchee; Flanagan, John D.

2004-05-18

A clock controller and clock generating method are provided for AC self-test timing analysis of a logic system. The controller includes latch circuitry which receives a DC input signal at a data input, and a pair of continuous out-of-phase clock signals at capture and launch clock inputs thereof. The latch circuitry outputs two overlapping pulses responsive to the DC input signal going high. The two overlapping pulses are provided to waveform shaper circuitry which produces therefrom two non-overlapping pulses at clock speed of the logic system to be tested. The two non-overlapping pulses are a single pair of clock pulses which facilitate AC self-test timing analysis of the logic system.

Shapiro steps for skyrmion motion on a washboard potential with longitudinal and transverse ac drives

DOE PAGES

Reichhardt, Charles; Reichhardt, Cynthia Jane

2015-12-28

In this work, we numerically study the behavior of two-dimensional skyrmions in the presence of a quasi-one-dimensional sinusoidal substrate under the influence of externally applied dc and ac drives. In the overdamped limit, when both dc and ac drives are aligned in the longitudinal direction parallel to the direction of the substrate modulation, the velocity-force curves exhibit classic Shapiro step features when the frequency of the ac drive matches the washboard frequency that is dynamically generated by the motion of the skyrmions over the substrate, similar to previous observations in superconducting vortex systems. In the case of skyrmions, the additionalmore » contribution to the skyrmion motion from a nondissipative Magnus force shifts the location of the locking steps to higher dc drives, and we find that the skyrmions move at an angle with respect to the direction of the dc drive. For a longitudinal dc drive and a perpendicular or transverse ac drive, the overdamped system exhibits no Shapiro steps; however, when a finite Magnus force is present, we find pronounced transverse Shapiro steps along with complex two-dimensional periodic orbits of the skyrmions in the phase-locked regimes. Both the longitudinal and transverse ac drives produce locking steps whose widths oscillate with increasing ac drive amplitude. We examine the role of collective skyrmion interactions and find that additional fractional locking steps occur for both longitudinal and transverse ac drives. Finally, at higher skyrmion densities, the system undergoes a series of dynamical order-disorder transitions, with the skyrmions forming a moving solid on the phase locking steps and a fluctuating dynamical liquid in regimes between the steps.« less

The effectiveness of stationary automobiles as shelters in accidental releases of toxic materials

NASA Astrophysics Data System (ADS)

Engelmann, Rudolf J.; Pendergrass, William R.; White, J. Randy; Hall, Mark E.

The protection offered occupants of stationary automobiles against airborne gases and respirable particles, such as might result from an accidental release, was measured and found to be substantial. For the four autos tested with the air conditioning (AC) system on and in recirculate position, the equilibrium ratios of inside/outside concentrations ( I/ O) for 2-μm diameter particles were less than 0.2, and some ratios were as small as 0.014. With both the AC compressor and the system fan off, the I/ O for five autos ranged from 0.04 to 0.18. These low ratios are primarily a result of deposition within the autos. However, three of the five autos had substantially higher I/ O ratios when the AC fan was on than when off, indicating that for some autos the AC caused significant added intake of outside air. Air exchange rates for the five stationary autos were on the order of 0.5h -1 with AC off, and 2.5 h -1 with AC on.

Development of software to improve AC power quality on large spacecraft

NASA Technical Reports Server (NTRS)

Kraft, L. Alan

1991-01-01

To insure the reliability of a 20 kHz, alternating current (AC) power system on spacecraft, it is essential to analyze its behavior under many adverse operating conditions. Some of these conditions include overloads, short circuits, switching surges, and harmonic distortions. Harmonic distortions can become a serious problem. It can cause malfunctions in equipment that the power system is supplying, and, during distortions such as voltage resonance, it can cause equipment and insulation failures due to the extreme peak voltages. To address the harmonic distortion issue, work was begun under the 1990 NASA-ASEE Summer Faculty Fellowship Program. Software, originally developed by EPRI, called HARMFLO, a power flow program capable of analyzing harmonic conditions on three phase, balanced, 60 Hz AC power systems, was modified to analyze single phase, 20 kHz, AC power systems. Since almost all of the equipment used on spacecraft power systems is electrically different from equipment used on terrestrial power systems, it was also necessary to develop mathematical models for the equipment to be used on the spacecraft. The modelling was also started under the same fellowship work period. Details of the modifications and models completed during the 1990 NASA-ASEE Summer Faculty Fellowship Program can be found in a project report. As a continuation of the work to develop a complete package necessary for the full analysis of spacecraft AC power system behavior, deployment work has continued through NASA Grant NAG3-1254. This report details the work covered by the above mentioned grant.

The use of real-time, hardware-in-the-loop simulation in the design and development of the new Hughes HS601 spacecraft attitude control system

NASA Technical Reports Server (NTRS)

Slafer, Loren I.

1989-01-01

Realtime simulation and hardware-in-the-loop testing is being used extensively in all phases of the design, development, and testing of the attitude control system (ACS) for the new Hughes HS601 satellite bus. Realtime, hardware-in-the-loop simulation, integrated with traditional analysis and pure simulation activities is shown to provide a highly efficient and productive overall development program. Implementation of high fidelity simulations of the satellite dynamics and control system algorithms, capable of real-time execution (using applied Dynamics International's System 100), provides a tool which is capable of being integrated with the critical flight microprocessor to create a mixed simulation test (MST). The MST creates a highly accurate, detailed simulated on-orbit test environment, capable of open and closed loop ACS testing, in which the ACS design can be validated. The MST is shown to provide a valuable extension of traditional test methods. A description of the MST configuration is presented, including the spacecraft dynamics simulation model, sensor and actuator emulators, and the test support system. Overall system performance parameters are presented. MST applications are discussed; supporting ACS design, developing on-orbit system performance predictions, flight software development and qualification testing (augmenting the traditional software-based testing), mission planning, and a cost-effective subsystem-level acceptance test. The MST is shown to provide an ideal tool in which the ACS designer can fly the spacecraft on the ground.

Advanced Photon Source accelerator ultrahigh vacuum guide

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

Liu, C.; Noonan, J.

1994-03-01

In this document the authors summarize the following: (1) an overview of basic concepts of ultrahigh vacuum needed for the APS project, (2) a description of vacuum design and calculations for major parts of APS, including linac, linac waveguide, low energy undulator test line, positron accumulator ring (PAR), booster synchrotron ring, storage ring, and insertion devices, and (3) cleaning procedures of ultrahigh vacuum (UHV) components presently used at APS.

A Systematic Cathode Study-Activation of a Thermionic Cathode, and Measuring Cesium Evaporation from a Dispenser Photocathode

DTIC Science & Technology

2010-06-01

QCM Quartz Crystal Deposition Monitor SEM Scanning Electron Microscope SRF Superconducting Radio Frequency T Torr Ti Titanium UHV Ultra...High Vacuum ( ᝺-7 Torr) UM University of Maryland QCM Quartz Crystal Deposition Monitor V Volt VAC Voltage-Alternating Current xvii...event. The two originally had problems with their tungsten filaments crystallizing and breaking. Being experimentalists, they added thorium in an

Stimulated Electron Desorption Studies from Microwave Vacuum Electronics / High Power Microwave Materials

DTIC Science & Technology

2010-02-11

purchase a new gun. Mr. Mike Ackeret ( Transfer Engineering Inc.) Transfer Engineering’s expertise in specialty UHV work and machining propelled...modifications they helped design for the test stand. With UNLV guidance, Transfer Engineering designed and built the original UNLV SEE Test Stand...Staib electron gun, an isolated beam drift tube, a hexanode delay line with a chevron microchannel plate (MCP) stack, an isolated grid, an isolated

Estimation of interaction energy and contact stiffness in atomic-scale sliding on a model sodium chloride surface in ethanol.

PubMed

Agmon, Liron; Shahar, Itai; Yosufov, Danny; Pimentel, Carlos; Pina, Carlos M; Gnecco, Enrico; Berkovich, Ronen

2018-03-16

Friction force microscopy (FFM) in aqueous environments has recently proven to be a very effective method for lattice-resolution imaging of crystal surfaces. Here we demonstrate the use of ethanol for similar measurements on water-soluble materials. Lattice resolved frictional stick-slip traces of a cleaved NaCl(100) surface submerged in ethanol are compared with previous obtained FFM results in ultrahigh vacuum (UHV). We use the Prandtl-Tomlinson framework to estimate the amplitude of the corrugation potential and the contact stiffness. The surface potential amplitude scales with the applied normal loads are in good agreement with data obtained for NaCl measured under UHV conditions, but demonstrates deviations from the ideal periodic potential given by the Prandtl-Tomlinson model. An additional finding is that the use of ethanol allows us to explore higher load ranges without detectable evidence of surface wear. The contact stiffness does not vary significantly with the normal load up to 38 nN, while above it a sudden increase by almost one order of magnitude was observed. Comparing this to previous results suggests that considerable atom rearrangements may occur in the contact region, although the (100) surface structure is preserved by ethanol-assisted diffusion of Na and Cl ions.

Electron-spectroscopy and -diffraction study of the conductivity of CVD diamond ( 0 0 1 )2×1 surface

NASA Astrophysics Data System (ADS)

Kono, S.; Takano, T.; Shimomura, M.; Goto, T.; Sato, K.; Abukawa, T.; Tachiki, M.; Kawarada, H.

2003-04-01

A chemical vapor deposition as-grown diamond (0 0 1) single-domain 2 × 1 surface was studied by electron-spectroscopy and electron-diffraction in ultrahigh vacuum (UHV). In order to change the surface conductivity (SC) of the diamond in UHV, three annealing stages were used; without annealing, annealing at 300 °C and annealing at 550 °C. From low energy electron diffraction and X-ray photoelectron spectroscopic (XPS) studies, an existence of SC was suggested for the first two stages of annealing and an absence of SC was suggested for the last stage of annealing. Changes in C KVV Auger electron spectroscopic spectra, C KVV Auger electron diffraction (AED) patterns and C 1s XPS peak positions were noticed between the annealing stages at 300 and 550 °C. These changes are interpreted as such that the state of hydrogen involvement in a subsurface of diamond (0 0 1)2 × 1 changes as SC changes. In particular, the presence of local disorder in diamond configuration in SC subsurface is pointed out from C KVV AED. From C 1s XPS peak shifts, a lower bound for the Fermi-level for SC layers from the valence band top is presented to be ˜0.5 eV.

Oxidation of palladium on Au(111) and ZnO(0001) supports

DOE PAGES

Lallo, J.; Tenney, S. A.; Kramer, A.; ...

2014-10-21

The oxidation of supported Pd-deposits on Au(111) and ZnO(0001) single crystals has been studied by x- ray photoemission spectroscopy (XPS). Oxidation has been carried out ex-situ in a high-pressure cell with subsequent vacuum-transfer and characterization by XPS in ultrahigh vacuum (UHV), as well as using in-situ characterization by synchrotron based near-ambient pressure XPS. On Au(111) alloying of Pd with the substrate competes with oxidation and only sufficiently thick Pd films have been found to oxidize. For Pd on ZnO the oxidation conditions depend on the amount of deposited Pd. Thicker Pd deposits behave similar to bulk Pd, while thinner filmsmore » oxidize already at lower temperatures. Interestingly, for very small amounts of Pd, in-situ XPS shows full oxidation at room temperature and at less than 0.6 mbar O₂ pressure. This indicates a lowering of the kinetic barriers for oxidation of very small supported Pd-clusters. The formed oxide is, however, not stable in UHV and a slow reduction is observed. The instability of this oxide indicates that the Pd-oxide formed at the interface to ZnO may have different chemical properties compared to bulk PdO or surface oxides on Pd.« less

Electron stimulated desorption of atomic oxygen from silver

NASA Technical Reports Server (NTRS)

Outlaw, R. A.; Peregoy, W. K.; Hoflund, Gar B.; Corallo, Gregory R.

1987-01-01

The electron stimulated desorption (ESD) of neutral oxygen atoms from polycrystalline silver and of oxygen ions from Ag(110) has been studied. Polycrystalline Ag charged with (16)O2 and (18)O2 and bombarded by low-energy electrons (approx 100 eV) under ultrahigh vacuum (UHV) conditions emitted O atom flux levels of 1 x 10 to the 12th power/sq cm/s at a Ag temperature of 300 C. The flux was detected with a quadrupole mass spectrometer operating in the appearance potential mode. The neutral cross section at about 100 C was determined to be 7 x 10 to the -19 sq cm. Ancillary experiments conducted in a UHV chamber equipped with a cylindrical mirror analyzer and rigged for ion energy distribution and ion angular distribution were used to study O ions desorbed from Ag(110). Two primary O(+) energies of 2.4 and 5.4 eV were detected from the Ag(110) after having been dosed with 2500 L of (16)O2. It also appears that in both experiments there was strong evidence for directionality of the emitted flux. The results of this study serve as a proof of concept for the development of a laboratory atomic oxygen beam generator that simulates the gas flux environment experienced by orbiting vehicles.

Interactions of gaseous molecules with X-ray photons and photoelectrons in AP-XPS study of solid surface in gas phase.

PubMed

Tao, Franklin Feng; Nguyen, Luan

2018-04-18

Studies of the surface of a catalyst in the gas phase via photoelectron spectroscopy is an important approach to establish a correlation between the surface of a catalyst under reaction conditions or during catalysis and its corresponding catalytic performance. Unlike the well understood interactions between photoelectrons and the atomic layers of a surface in ultrahigh vacuum (UHV) and the well-developed method of quantitative analysis of a solid surface in UHV, a fundamental understanding of the interactions between X-ray photons and gaseous molecules and between photoelectrons and molecules of the gas phase in ambient pressure X-ray photoelectron spectroscopy (AP-XPS) is lacking. Through well designed experiments, here the impact of the interactions between photoelectrons and gaseous molecules and interactions between X-ray photons and gaseous molecules on the intensity of the collected photoelectrons have been explored. How the changes in photoelectron intensity resulting from these interactions influence measurement of the authentic atomic ratio of element M to A of a solid surface has been discussed herein, and methods to correct the measured nominal atomic ratio of two elements of a solid surface upon travelling through a gas phase to its authentic atomic ratio have been developed.

Multilayer Thin Film Polarizer Design for Far Ultraviolet using Induced Transmission and Absorption Technique

NASA Technical Reports Server (NTRS)

Kim, Jongmin; Zukic, Muamer; Wilson, Michele M.; Park, Jung Ho; Torr, Douglas G.

1994-01-01

Good theoretical designs of far ultraviolet polarizers have been reported using a MgF2/Al/MgF2 three layer structure on a thick Al layer as a substrate. The thicknesses were determined to induce transmission and absorption of p-polarized light. In these designs Al optical constants were used from films produced in ultrahigh vacuum (UHV: 10(exp -10) torr). Reflectance values for polarizers fabricated in a conventional high vacuum (p approx. 10(exp -6 torr)) using the UHV design parameters differed dramatically from the design predictions. Al is a highly reactive material and is oxidized even in a high vacuum chamber. In order to solve the problem other metals have been studied. It is found that a larger reflectance difference is closely related to higher amplitude and larger phase difference of Fresnel reflection coefficients between two polarizations at the boundary of MgF2/metal. It is also found that for one material a larger angle of incidence from the surface normal brings larger amplitude and phase difference. Be and Mo are found good materials to replace Al. Polarizers designed for 121.6 nm with Be at 60 deg and with Mo at 70 deg are shown as examples.

Inverter Output Filter Effect on PWM Motor Drives of a Flywheel Energy Storage System

NASA Technical Reports Server (NTRS)

Santiago, Walter

2004-01-01

NASA Glenn Research Center (GRC) has been involved in the research and development of high speed flywheel systems for small satellite energy storage and attitude control applications. One research and development area has been the minimization of the switching noise produced by the pulsed width modulated (PWM) inverter that drives the flywheel permanent magnet motor/generator (PM M/G). This noise can interfere with the flywheel M/G hardware and the system avionics hampering the full speed performance of the flywheel system. One way to attenuate the inverter switching noise is by placing an AC filter at the three phase output terminals of the inverter with the filter neutral point connected to the DC link (DC bus) midpoint capacitors. The main benefit of using an AC filter in this fashion is the significant reduction of the inverter s high dv/dt switching and its harmonics components. Additionally, common mode (CM) and differential mode (DM) voltages caused by the inverter s high dv/dt switching are also reduced. Several topologies of AC filters have been implemented and compared. One AC filter topology consists of a two-stage R-L-C low pass filter. The other topology consists of the same two-stage R-L-C low pass filter with a series connected trap filter (an inductor and capacitor connected in parallel). This paper presents the analysis, design and experimental results of these AC filter topologies and the comparison between the no filter case and conventional AC filter.

System cost/performance analysis (study 2.3). Volume 1: Executive summary

NASA Technical Reports Server (NTRS)

Kazangey, T.

1973-01-01

The relationships between performance, safety, cost, and schedule parameters were identified and quantified in support of an overall effort to generate program models and methodology that provide insight into a total space vehicle program. A specific space vehicle system, the attitude control system (ACS), was used, and a modeling methodology was selected that develops a consistent set of quantitative relationships among performance, safety, cost, and schedule, based on the characteristics of the components utilized in candidate mechanisms. These descriptive equations were developed for a three-axis, earth-pointing, mass expulsion ACS. A data base describing typical candidate ACS components was implemented, along with a computer program to perform sample calculations. This approach, implemented on a computer, is capable of determining the effect of a change in functional requirements to the ACS mechanization and the resulting cost and schedule. By a simple extension of this modeling methodology to the other systems in a space vehicle, a complete space vehicle model can be developed. Study results and recommendations are presented.

One-power IC with MPPT design

NASA Astrophysics Data System (ADS)

Xu, Shengzhi; Chu, Ian; Zhao, Gengshen; Wang, Qingzhang

2008-03-01

When proceed photovoltaic power system design, engineer needs prepared model of PV cells to evaluate system response, capability performance, and stability, the DC model is not enough, but an accuracy AC model plays a big role. This paper talks first about the AC model of PV cells, and DC model is also introduced in simple. There is a PV controller example explaining the steps to do system simulation in this paper. Two equivalent circuit models are implemented with mixed-signal language verilog-a, one hardware language easy to use and having good speed and high accuracy. Both of two models include solar cell arrays, one buck switched mode DC-DC converter, and the maximum power point tracking algorithm. The difference between them is that Solar cell in one of two models is with ac small signal parameter, another is without. The simulation result is given in comparison. This paper's work shows that ac parameter plays large role in switch-mode PV power system, especially when the switch frequency is higher than 100kHz.

A study of some features of ac and dc electric power systems for a space station

NASA Technical Reports Server (NTRS)

Hanania, J. I.

1983-01-01

This study analyzes certain selected topics in rival dc and high frequency ac electric power systems for a Space Station. The interaction between the Space Station and the plasma environment is analyzed, leading to a limit on the voltage for the solar array and a potential problem with resonance coupling at high frequencies. Certain problems are pointed out in the concept of a rotary transformer, and further development work is indicated in connection with dc circuit switching, special design of a transmission conductor for the ac system, and electric motors. The question of electric shock hazards, particularly at high frequency, is also explored. and a problem with reduced skin resistance and therefore increased hazard with high frequency ac is pointed out. The study concludes with a comparison of the main advantages and disadvantages of the two rival systems, and it is suggested that the choice between the two should be made after further studies and development work are completed.

Approches pour la reduction de l'impact de defaut dans le transport d'energie du parc eolien offshore via VSC-HVDC =

NASA Astrophysics Data System (ADS)

Benadja, Mounir

Dans ce travail est presente un systeme de generation d'energie d'un parc eolien offshore et un systeme de transport utilisant les stations VSC-HVDC connectees au reseau principal AC onshore. Trois configurations ont ete etudiees, modelisees et validees par simulation. Dans chacune des configurations, des contributions ameliorant les cotes techniques et economiques sont decrites ci-dessous : La premiere contribution concerne un nouvel algorithme MPPT (Maximum Power Point Tracking) utilise pour l'extraction de la puissance maximale disponible dans les eoliennes des parcs offshores. Cette technique d'extraction du MPPT ameliore le rendement energetique de la chaine de conversion des energies renouvelables notamment l'energie eolienne a petite et a grande echelles (parc eolien offshore) qui constitue un probleme pour les constructeurs qui se trouvent confrontes a developper des dispositifs MPPT simples, moins couteux, robustes, fiables et capable d'obtenir un rendement energetique maximal. La deuxieme contribution concerne la reduction de la taille, du cout et de l'impact des defauts electriques (AC et DC) dans le systeme construit pour transporter l'energie d'un parc eolien offshore (OWF) vers le reseau principal AC onshore via deux stations 3L-NPC VSCHVDC. La solution developpee utilise des observateurs non-lineaires bases sur le filtre de Kalman etendu (EKF). Ce filtre permet d'estimer la vitesse de rotation et la position du rotor de chacune des generatrices du parc eolien offshore et de la tension du bus DC de l'onduleur DC-AC offshore et des deux stations 3L-NPC-VSC-HVDC (offshore et onshore). De plus, ce developpement du filtre de Kalman etendu a permis de reduire l'impact des defauts AC et DC. Deux commandes ont ete utilisees, l'une (commande indirect dans le plan abc) avec EKF integre destinee pour controler le convertisseur DC-AC offshore et l'autre (commande d-q) avec EKF integre pour controler les convertisseurs des deux stations AC-DC et DC-AC tout en tenant compte des entrees de chacune des stations. L'integration des observateurs non-lineaires (EKF) dans le controle des convertisseurs permet de resoudre le probleme des incertitudes de mesure, des incertitudes dans la modelisation, en cas du dysfonctionnement ou de panne des capteurs de mesure ainsi que le probleme de l'impact des defauts (AC et DC) sur la qualite d'energie dans les systemes de transmission. Ces estimations contribuent a rendre le cout global du systeme moins cher et sa taille moins encombrante ainsi que la reduction de l'impact des defauts (AC et DC) sur le systeme. La troisieme contribution concerne la reduction de la taille, du cout et de l'impact des defauts electriques (AC et DC) dans le systeme construit pour transporter l'energie d'un parc eolien offshore (OWF) vers le reseau principal AC onshore via deux stations VSC-HVDC. La solution developpee utilise des observateurs non-lineaires bases sur le filtre de Kalman etendu (EKF). Ce filtre permet d'estimer la vitesse de rotation et la position du rotor de chacune des generatrices du parc eolien et de la tension du bus DC de l'onduleur DC-AC offshore. La contribution porte surtout sur le developpement des deux commandes des deux stations. La premiere, la commande non-lineaire modifiee pour controler le premier convertisseur de la station VSC-HVDC offshore assurant le transfert de la puissance generee par le parc eolien vers la station VSC-HVDC onshore. La deuxieme commande non-lineaire modifiee avec integration de la regulation de la tension du bus DC et de la commande a modele de reference adaptative (MRAC) pour la compensation des surintensites et surtensions durant les defauts AC et DC. On peut constater que lors d'un defaut AC au PCC (Point of Common Coupling) du cote reseau onshore, la profondeur de l'impact du defaut AC sur l'amplitude des courants du reseau principal AC onshore qui etait reduit a 60% par les travaux de recherche (Erlich, Feltes et Shewarega, 2014), comparativement a la nouvelle commande proposee MRAC qui reduit la profondeur de l'impact a 35%. Lors de l'apparition des defauts AC et DC, une reduction de l'impact des defauts sur l'amplitude des courants de reseau AC terrestre et du temps de reponse a ete observee et la stabilite du systeme a ete renforcee par l'utilisation de la commande adaptative basee sur le modele de reference MRAC. La quatrieme contribution concerne une nouvelle commande basee sur le mode de glissement (SM) appliquee pour la station VSC-HVDC qui relie le parc eolien offshore (OWF) au reseau principal AC. Ce parc est compose de dix eoliennes basees sur des generatrices synchrones a aimant permanent (VSWT/PMSGs) connectees en parallele et chacune est controlee par son propre convertisseur DC-DC. Une comparaison des performances entre la commande SM et de la commande non-lineaire avec des controleurs PI pour les deux conditions (presence et absence de defaut DC) a ete analysee et montre la superiorite de la commande par SM. Un prototype du systeme etudie a echelle reduite a ete realise et teste au laboratoire GREPCI en utilisant la carte dSPACE-DS1104 pour la validation experimentale. L'analyse et la simulation des systemes etudies sont developpees sous l'environnement Matlab/Simulink/Simpowersystem. Les resultats obtenus a partir des configurations developpees sont valides par simulation et par experimentation. Les performances sont tres satisfaisantes du point de vue reponse dynamique, reponse en regime permanent, stabilite du systeme et qualite de l'energie.

Power dissipation in HTS coated conductor coils under the simultaneous action of AC and DC currents and fields

NASA Astrophysics Data System (ADS)

Shen, Boyang; Li, Chao; Geng, Jianzhao; Zhang, Xiuchang; Gawith, James; Ma, Jun; Liu, Yingzhen; Grilli, Francesco; Coombs, T. A.

2018-07-01

This paper presents a comprehensive alternating current (AC) loss study of a circular high temperature superconductor (HTS) coated conductor coil. The AC losses from a circular double pancake coil were measured using the electrical method. A 2D axisymmetric H -formulation model using the FEM package in COMSOL Multiphysics has been established to match the circular geometry of the coil used in the experiment. Three scenarios have been analysed: Scenario 1 with AC transport current and DC magnetic field (experiment and simulation); Scenario 2 with DC transport current and AC magnetic field (simulation); and Scenario 3 with AC transport current and AC magnetic field (simulation and experimental data support). The angular dependence analysis on the coil under a magnetic field with different orientation angle θ has been carried out for all three scenarios. For Scenario 3, the effect of the relative phase difference Δφ between the AC current and the AC field on the total AC loss of the coil has been investigated. In summary, a current/field/angle/phase dependent AC loss ( I , B , θ, Δφ) study of a circular HTS coil has been carried out. The obtained results provide useful indications for the future design and research of HTS AC systems.

Energy dissipation of composite multifilamentary superconductors for high-current ramp-field magnet applications

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

Gung, C.Y.

1993-01-01

Energy dissipation, which is also called AC loss, of a composite multifilamentary superconducting wire is one of the most fundamental concerns in building a stable superconducting magnet. Characterization and reduction of AC losses are especially important in designing a superconducting magnet for generating transient magnetic fields. The goal of this thesis is to improve the understanding of AC-loss properties of superconducting wires developed for high-current ramp-field magnet applications. The major tasks include: (1) building an advanced AC-loss measurement system, (2) measuring AC losses of superconducting wires under simulated pulse magnet operations, (3) developing an analytical model for explaining the newmore » AC-loss properties found in the experiment, and (4) developing a computational methodology for comparing AC losses of a superconducting wire with those of a cable for a superconducting pulse magnet. A new experimental system using an isothermal calorimetric method was designed and constructed to measure the absolute AC losses in a composite superconductor. This unique experimental setup is capable of measuring AC losses of a brittle Nb{sub 3}Sn wire carrying high AC current in-phase with a large-amplitude pulse magnetic field. Improvements of the accuracy and the efficiency of this method are discussed. Three different types of composite wire have been measured: a Nb{sub 3}Sn modified jelly-roll (MJR) internal-tin wire used in a prototype ohmic heating coil, a Nb{sub 3}Sn internal-tin wire developed for a fusion reactor ohmic heating coil, and a NbTi wire developed for the magnets in a particle accelerator. The cross sectional constructions of these wires represent typical commercial wires manufactured for pulse magnet applications.« less

The Use of AC-DC-AC Methods in Assessing Corrosion Resistance Performance of Coating Systems for Magnesium Alloys

NASA Astrophysics Data System (ADS)

McCune, Robert C.; Upadhyay, Vinod; Wang, Yar-Ming; Battocchi, Dante

The potential utility of AC-DC-AC electrochemical methods in comparative measures of corrosion-resisting coating system performance for magnesium alloys under consideration for the USAMP "Magnesium Front End Research and Development" project was previously shown in this forum [1]. Additional studies of this approach using statistically-designed experiments have been conducted with focus on alloy types, pretreatment, topcoat material and topcoat thickness as the variables. Additionally, sample coupons made for these designed experiments were also subjected to a typical automotive cyclic corrosion test cycle (SAE J2334) as well as ASTM B117 for comparison of relative performance. Results of these studies are presented along with advantages and limitations of the proposed methodology.

Forward and reverse control system for induction motors

DOEpatents

Wright, J.T.

1987-09-15

A control system for controlling the direction of rotation of a rotor of an induction motor includes an array of five triacs with one of the triacs applying a current of fixed phase to the windings of the rotor and four of the triacs being switchable to apply either hot ac current or return ac current to the stator windings so as to reverse the phase of current in the stator relative to that of the rotor and thereby reverse the direction of rotation of the rotor. Switching current phase in the stator is accomplished by operating the gates of pairs of the triacs so as to connect either hot ac current or return ac current to the input winding of the stator. 1 fig.

A Shaftless Magnetically Levitated Multifunctional Spacecraft Flywheel Storage System

NASA Technical Reports Server (NTRS)

Stevens, Ken; Thornton, Richard; Clark, Tracy; Beaman, Bob G.; Dennehy, Neil; Day, John H. (Technical Monitor)

2002-01-01

Presently many types of spacecraft use a Spacecraft Attitude Control System (ACS) with momentum wheels for steering and electrochemical batteries to provide electrical power for the eclipse period of the spacecraft orbit. Future spacecraft will use Flywheels for combined use in ACS and Energy Storage. This can be done by using multiple wheels and varying the differential speed for ACS and varying the average speed for energy storage and recovery. Technology in these areas has improved since the 1990s so it is now feasible for flywheel systems to emerge from the laboratory for spacecraft use. This paper describes a new flywheel system that can be used for both ACS and energy storage. Some of the possible advantages of a flywheel system are: lower total mass and volume, higher efficiency, less thermal impact, improved satellite integration schedule and complexity, simplified satellite orbital operations, longer life with lower risk, less pointing jitter, and greater capability for high-rate slews. In short, they have the potential to enable new types of missions and provide lower cost. Two basic types of flywheel configurations are the Flywheel Energy Storage System (FESS) and the Integrated Power and Attitude Control System (IPACS).

Risk-Significant Adverse Condition Awareness Strengthens Assurance of Fault Management Systems

NASA Technical Reports Server (NTRS)

Fitz, Rhonda

2017-01-01

As spaceflight systems increase in complexity, Fault Management (FM) systems are ranked high in risk-based assessment of software criticality, emphasizing the importance of establishing highly competent domain expertise to provide assurance. Adverse conditions (ACs) and specific vulnerabilities encountered by safety- and mission-critical software systems have been identified through efforts to reduce the risk posture of software-intensive NASA missions. Acknowledgement of potential off-nominal conditions and analysis to determine software system resiliency are important aspects of hazard analysis and FM. A key component of assuring FM is an assessment of how well software addresses susceptibility to failure through consideration of ACs. Focus on significant risk predicted through experienced analysis conducted at the NASA Independent Verification & Validation (IV&V) Program enables the scoping of effective assurance strategies with regard to overall asset protection of complex spaceflight as well as ground systems. Research efforts sponsored by NASAs Office of Safety and Mission Assurance (OSMA) defined terminology, categorized data fields, and designed a baseline repository that centralizes and compiles a comprehensive listing of ACs and correlated data relevant across many NASA missions. This prototype tool helps projects improve analysis by tracking ACs and allowing queries based on project, mission type, domain/component, causal fault, and other key characteristics. Vulnerability in off-nominal situations, architectural design weaknesses, and unexpected or undesirable system behaviors in reaction to faults are curtailed with the awareness of ACs and risk-significant scenarios modeled for analysts through this database. Integration within the Enterprise Architecture at NASA IV&V enables interfacing with other tools and datasets, technical support, and accessibility across the Agency. This paper discusses the development of an improved workflow process utilizing this database for adaptive, risk-informed FM assurance that critical software systems will safely and securely protect against faults and respond to ACs in order to achieve successful missions.

Risk-Significant Adverse Condition Awareness Strengthens Assurance of Fault Management Systems

NASA Technical Reports Server (NTRS)

Fitz, Rhonda

2017-01-01

As spaceflight systems increase in complexity, Fault Management (FM) systems are ranked high in risk-based assessment of software criticality, emphasizing the importance of establishing highly competent domain expertise to provide assurance. Adverse conditions (ACs) and specific vulnerabilities encountered by safety- and mission-critical software systems have been identified through efforts to reduce the risk posture of software-intensive NASA missions. Acknowledgement of potential off-nominal conditions and analysis to determine software system resiliency are important aspects of hazard analysis and FM. A key component of assuring FM is an assessment of how well software addresses susceptibility to failure through consideration of ACs. Focus on significant risk predicted through experienced analysis conducted at the NASA Independent Verification Validation (IVV) Program enables the scoping of effective assurance strategies with regard to overall asset protection of complex spaceflight as well as ground systems. Research efforts sponsored by NASA's Office of Safety and Mission Assurance defined terminology, categorized data fields, and designed a baseline repository that centralizes and compiles a comprehensive listing of ACs and correlated data relevant across many NASA missions. This prototype tool helps projects improve analysis by tracking ACs and allowing queries based on project, mission type, domaincomponent, causal fault, and other key characteristics. Vulnerability in off-nominal situations, architectural design weaknesses, and unexpected or undesirable system behaviors in reaction to faults are curtailed with the awareness of ACs and risk-significant scenarios modeled for analysts through this database. Integration within the Enterprise Architecture at NASA IVV enables interfacing with other tools and datasets, technical support, and accessibility across the Agency. This paper discusses the development of an improved workflow process utilizing this database for adaptive, risk-informed FM assurance that critical software systems will safely and securely protect against faults and respond to ACs in order to achieve successful missions.

Systems and methods for commutating inductor current using a matrix converter

DOEpatents

Ransom, Ray M; Kajouke, Lateef A; Perisic, Milun

2012-10-16

Systems and methods are provided for delivering current using a matrix converter in a vehicle. An electrical system comprises an AC interface, a first conversion module coupled to the AC interface, an inductive element coupled between the AC interface and the first conversion module, and a control module coupled to the first conversion module. The control module is configured to operate the first conversion module in a bidirectional operating mode to commutate current bidirectionally. When a magnitude of the current through the inductive element is greater than a first threshold value, the control module operates the conversion module in a unidirectional operating mode, wherein current is commutated unidirectionally.

Pushing the Limits of Cubesat Attitude Control: A Ground Demonstration

NASA Technical Reports Server (NTRS)

Sanders, Devon S.; Heater, Daniel L.; Peeples, Steven R.; Sules. James K.; Huang, Po-Hao Adam

2013-01-01

A cubesat attitude control system (ACS) was designed at the NASA Marshall Space Flight Center (MSFC) to provide sub-degree pointing capabilities using low cost, COTS attitude sensors, COTS miniature reaction wheels, and a developmental micro-propulsion system. The ACS sensors and actuators were integrated onto a 3D-printed plastic 3U cubesat breadboard (10 cm x 10 cm x 30 cm) with a custom designed instrument board and typical cubesat COTS hardware for the electrical, power, and data handling and processing systems. In addition to the cubesat development, a low-cost air bearing was designed and 3D printed in order to float the cubesat in the test environment. Systems integration and verification were performed at the MSFC Small Projects Rapid Integration & Test Environment laboratory. Using a combination of both the miniature reaction wheels and the micro-propulsion system, the open and closed loop control capabilities of the ACS were tested in the Flight Robotics Laboratory. The testing demonstrated the desired sub-degree pointing capability of the ACS and also revealed the challenges of creating a relevant environment for development testin

A compact ultra-clean system for deploying radioactive sources inside the KamLAND detector

DOE PAGES

Banks, T. I.; Freedman, S. J.; Wallig, J.; ...

2014-10-14

We describe a compact, ultra-clean device used to deploy radioactive sources along the vertical axis of the KamLAND liquid-scintillator neutrino detector for purposes of calibration. The device worked by paying out and reeling in precise lengths of a hanging, small-gauge wire rope (cable); an assortment of interchangeable radioactive sources could be attached to a weight at the end of the cable. All components exposed to the radiopure liquid scintillator were made of chemically compatible UHV-cleaned materials, primarily stainless steel, in order to avoid contaminating or degrading the scintillator. To prevent radon intrusion, the apparatus was enclosed in a hermetically sealedmore » housing inside a glove box, and both volumes were regularly flushed with purified nitrogen gas. Finally, an infrared camera attached to the side of the housing permitted real-time visual monitoring of the cable’s motion, and the system was controlled via a graphical user interface.« less

Addressing surface-induced loss and decoherence in superconducting quantum circuits

NASA Astrophysics Data System (ADS)

Fuhrer, Andreas; Mueller, Peter; Kuhlmann, Andreas; Filipp, Stefan; Deshpande, Veeresh; Drechsler, Ute

Many of the advances in coherence and fidelity of superconducting qubits have been made possible by clever engineering of the coupling to the environment and operation at noise-insensitive sweet spots. However, this leads to a compromise in experimental flexibility and device tunability, which can become inhibitive as the system size is scaled up. Material and interface related degrees of freedoms are harder to mitigate and are expected to become increasingly important in more complex systems. They impose limits both on coherence (flux-noise) and lifetimes (surface loss) of superconducting qubits. To study and eliminate these effects we have constructed a reusable UHV-compatible sample enclosure that enables us to perform various surface passivation steps before cooling superconducting devices to cryogenic temperatures. The enclosure can accommodate large chips with up to 18 microwave ports and can be vacuum sealed at pressures below 8e-10 mbar. We discuss its operation principle and present first measurement results of superconducting CPW resonators and qubit devices with and without prior surface treatments.

A Vision of China-Arab Interconnection Transmission Network Planning with UHVDC Technology

NASA Astrophysics Data System (ADS)

Wu, Dan; Liu, Yujun; Yin, Hongyuan; Xu, Qingshan; Xu, Xiaohui; Ding, Maosheng

2017-05-01

Developments in ultra-high-voltage (UHV) power systems and clean energy technologies are paving the way towards unprecedented energy market globalization. In accordance with the international community’s enthusiasm for building up the Global Energy Internet, this paper focuses on the feasibility of transmitting large-size electricity from northwest China to Arab world through a long-distance transnational power interconnection. The complete investigations on the grids of both the sending-end and receiving-end is firstly presented. Then system configuration of the transmission scheme and corridor route planning is proposed with UHVDC technology. Based on transmission costs’ investigation about similar transmission projects worldwide, the costs of the proposed transmission scheme are estimated through adjustment factors which represent differences in latitude, topography and economy. The proposed China-Arab transmission line sheds light on the prospects of power cooperation and resource sharing between China and Arab states, and appeals for more emphasis on green energy concentrated power interconnections from a global perspective.

PHASE I PILOT AIR CONVEYANCE SYSTEM DESIGN, CLEANING, AND CHARACTERIZATION

EPA Science Inventory

The report gives results of a project to develop and refine surface and airborne contamination
measurement techniques that can be used to evaluate air conveyance system (ACS) cleaning.
(NOTE: ACS cleaning is advertized to homeowners as a service having a number of benefits...

Development of magneto-rheologial fluid (MRF) based clutch for output torque control of AC motors

NASA Astrophysics Data System (ADS)

Nguyen, Q. Hung; Do, H. M. Hieu; Nguyen, V. Quoc; Nguyen, N. Diep; Le, D. Thang

2018-03-01

In industry, the AC motor is widely used because of low price, power availability, low cost maintenance. The main disadvantages of AC motors compared to DC motors are difficulty in speed and torque control, requiring expensive controllers with complex control algorithms. This is the basic limitations in the widespread adoption of AC motor systems for industrial automation. One feasible solution for AC motor control is using MRF (magneto-rheological fluid) based clutches (shortly called MR clutches) Although there have been many studies on MR clutches, most of these clutches used traditional configuration with coils wound on the middle cylindrical part and a compotator is used to supply power to the coils. Therefore, this type of MR clutches possesses many disadvantages such as high friction and unstable applied current due to commutator, complex structure which causes difficulty in manufacture, assembly, and maintenance. In addition, the bottleneck problem of magnetic field is also a challenging issue. In this research, we will develop a new type of MR clutches that overcomes the abovementioned disadvantages of traditional MR clutches and more suitable for application in controlling of AC motor. Besides, in this study, speed and torque control system for AC motors using developed MR clutches is designed and experimental validated.

A hybrid air conditioner driven by a hybrid solar collector

NASA Astrophysics Data System (ADS)

Al-Alili, Ali

The objective of this thesis is to search for an efficient way of utilizing solar energy in air conditioning applications. The current solar Air Conditioners (A/C)s suffer from low Coefficient of Performance (COP) and performance degradation in hot and humid climates. By investigating the possible ways of utilizing solar energy in air conditioning applications, the bottlenecks in these approaches were identified. That resulted in proposing a novel system whose subsystem synergy led to a COP higher than unity. The proposed system was found to maintain indoor comfort at a higher COP compared to the most common solar A/Cs, especially under very hot and humid climate conditions. The novelty of the proposed A/C is to use a concentrating photovoltaic/thermal collector, which outputs thermal and electrical energy simultaneously, to drive a hybrid A/C. The performance of the hybrid A/C, which consists of a desiccant wheel, an enthalpy wheel, and a vapor compression cycle (VCC), was investigated experimentally. This work also explored the use of a new type of desiccant material, which can be regenerated with a low temperature heat source. The experimental results showed that the hybrid A/C is more effective than the standalone VCC in maintaining the indoor conditions within the comfort zone. Using the experimental data, the COP of the hybrid A/C driven by a hybrid solar collector was found to be at least double that of the current solar A/Cs. The innovative integration of its subsystems allows each subsystem to do what it can do best. That leads to lower energy consumption which helps reduce the peak electrical loads on electric utilities and reduces the consumer operating cost since less energy is purchased during the on peak periods and less solar collector area is needed. In order for the proposed A/C to become a real alternative to conventional systems, its performance and total cost were optimized using the experimentally validated model. The results showed that for an electricity price of 0.12 $/kW-hr, the hybrid solar A/C's cumulative total cost will be less than that of a standard VCC after 17.5 years of operation.

Steady-state and dynamic characteristics of a 20-kHz spacecraft power system - Control of harmonic resonance

NASA Technical Reports Server (NTRS)

Wasynczuk, O.; Krause, P. C.; Biess, J. J.; Kapustka, R.

1990-01-01

A detailed computer simulation was used to illustrate the steady-state and dynamic operating characteristics of a 20-kHz resonant spacecraft power system. The simulated system consists of a parallel-connected set of DC-inductor resonant inverters (drivers), a 440-V cable, a node transformer, a 220-V cable, and a transformer-rectifier-filter (TRF) AC-to-DC receiver load. Also included in the system are a 1-kW 0.8-pf RL load and a double-LC filter connected at the receiving end of the 20-kHz AC system. The detailed computer simulation was used to illustrate the normal steady-state operating characteristics and the dynamic system performance following, for example, TRF startup. It is shown that without any filtering the given system exhibits harmonic resonances due to an interaction between the switching of the source and/or load converters and the AC system. However, the double-LC filter at the receiving-end of the AC system and harmonic traps connected in series with each of the drivers significantly reduce the harmonic distortion of the 20-kHz bus voltage. Significant additional improvement in the waveform quality can be achieved by including a double-LC filter with each driver.

Modification split type air conditioning unit by installing internal heat exchanger and condenser precooling

NASA Astrophysics Data System (ADS)

Ambarita, H.

2018-03-01

In this paper, a modified of air conditioning (AC) system is proposed. In the modified system, an internal heat exchanger and condenser precooling unit are installed. The objective is to explore the effect of the additional equipment to the performance of the system. An AC with compressor power of 1 PK is modified and compared with the original one. The results show that ER of the modified system is higher than the original one in order of 3.6%. The work of the compressor of the modified system is 12.5% lower than work of the compressor without modification. Finally, the COP of the modified system is 11.71% higher than the original one. These facts reveal that the combination of IHX and condenser precooling shows positive impact on the performance of the AC. It is recommended to use the modified system to improve the energy efficiency of the Air Conditioning system.

On-Chip AC self-test controller

DOEpatents

Flanagan, John D [Rhinebeck, NY; Herring, Jay R [Poughkeepsie, NY; Lo, Tin-Chee [Fishkill, NY

2009-09-29

A system for performing AC self-test on an integrated circuit that includes a system clock for normal operation is provided. The system includes the system clock, self-test circuitry, a first and second test register to capture and launch test data in response to a sequence of data pulses, and a logic circuit to be tested. The self-test circuitry includes an AC self-test controller and a clock splitter. The clock splitter generates the sequence of data pulses including a long data capture pulse followed by an at speed data launch pulse and an at speed data capture pulse followed by a long data launch pulse. The at speed data launch pulse and the at speed data capture pulse are generated for a common cycle of the system clock.

Adhesion in a Vacuum Environment and its Implications for Dust Mitigation Techniques on Airless Bodies

NASA Technical Reports Server (NTRS)

Berkebile, Stephen; Gaier, James R.

2012-01-01

During the Apollo missions, the adhesion of dust to critical spacecraft systems was a greater problem than anticipated and resulted in functional degradation of thermal control surfaces, spacesuit seals, and other spacecraft components. Notably, Earth-based simulation efforts did not predict the magnitude and effects of dust adhesion in the lunar environment. Forty years later, we understand that the ultrahigh vacuum (UHV) environment, coupled with micrometeorite impacts and constant ion and photon bombardment from the sun result in atomically clean and high surface energy dust particles and spacecraft surfaces. However, both the dominant mechanism of adhesion in airless environments and the conditions for high fidelity simulation tests have still to be determined. The experiments presented in here aim to aid in the development of dust mitigation techniques for airless bodies (e.g., lunar surface, asteroids, moons of outer planets). The approach taken consists of (a) quantifying the adhesion between common polymer and metallic spacecraft materials and a synthetic noritic volcanic glass, as a function of surface cleanliness and of triboelectric charge transfer in a UHV environment, and (b) determining parameters for high fidelity tests through investigation of adhesion dependence on vacuum environment and sample treatment. Adhesion force has been measured between pins of spacecraft materials and a plate of synthetic volcanic glass by determining the pull-off force with a torsion balance. Although no significant adhesion is generally observed directly as a result of high surface energies, the adhesion due to induced electrostatic charge is observed to increase with spacecraft material cleanliness, in some cases by over a factor of 10. Furthermore, electrostatically-induced adhesion is found to decrease rapidly above pressures of 10-6 torr. It is concluded that high-fidelity tests should be conducted in high to ultrahigh vacuum and include an ionized surface cleaning process.

Medium-Range Forecast Skill for Extraordinary Arctic Cyclones in Summer of 2008-2016

NASA Astrophysics Data System (ADS)

Yamagami, Akio; Matsueda, Mio; Tanaka, Hiroshi L.

2018-05-01

Arctic cyclones (ACs) are a severe atmospheric phenomenon that affects the Arctic environment. This study assesses the forecast skill of five leading operational medium-range ensemble forecasts for 10 extraordinary ACs that occurred in summer during 2008-2016. Average existence probability of the predicted ACs was >0.9 at lead times of ≤3.5 days. Average central position error of the predicted ACs was less than half of the mean radius of the 10 ACs (469.1 km) at lead times of 2.5-4.5 days. Average central pressure error of the predicted ACs was 5.5-10.7 hPa at such lead times. Therefore, the operational ensemble prediction systems generally predict the position of ACs within 469.1 km 2.5-4.5 days before they mature. The forecast skill for the extraordinary ACs is lower than that for midlatitude cyclones in the Northern Hemisphere but similar to that in the Southern Hemisphere.

Development and characterisation of polymeric microparticle of poly(d,l-lactic acid) loaded with holmium acetylacetonate.

PubMed

de Azevedo, Mariangela de Burgos M; de Melo, Vitor H S; Soares, Carlos Roberto J; Miyamoto, Douglas M; Katayama, Ricardo A; Squair, Peterson L; Barros, Caio H N; Tasic, Ljubica

2018-06-14

Biodegradable polymers containing radioactive isotopes such as Holmium 166 ( 166 Ho) have potential applications as beta particle emitters in tumour tissues. It is also a gamma ray emitter, allowing nuclear imaging of any tissue to be acquired. It is frequently used in the form of complexes such as holmium acetylacetonate (HoAcAc), which may cause damages in tissues next to the targets cancer cells, as it is difficult to control its linkage or healthy tissues radiotherapy effects. Poly(d,l-lactic acid), PDLLA, was used to encapsulate holmium acetylacetonate (HoAcAc) using an emulsion solvent extraction/evaporation technique. Microspheres with sizes between 20-53 µm were extensively characterised. HoAcAc release from the microspheres was assessed through studies using Inductively Coupled Plasma - Optical Emission Spectroscopy, and the microspheres showed no holmium leakage after a period of 10 half-lives and following gamma irradiation. Thus, HoAcAc loaded microspheres are here presented as a potential system for brachytherapy and imaging purposes.

Development of an in-line filter to prevent intrusion of NO2 toxic vapors into A/C systems

NASA Technical Reports Server (NTRS)

Meneghelli, Barry; Mcnulty, R. J.; Springer, Mike; Lueck, Dale E.

1995-01-01

The hypergolic propellant nitrogen tetroxide (N2O4 or NTO) is routinely used in spacecraft launched at Kennedy Space Center (KSC) and Cape Canaveral Air Station (CCAS). In the case of a catastrophic failure of the spacecraft, there would be a release of the unspent propellant in the form of a toxic cloud. Inhalation of this material at downwind concentrations which may be as high as 20 parts per million (ppm) for 30 minutes in duration, may produce irritation to the eyes, nose and respiratory tract. Studies at both KSC and CCAS have shown that the indoor concentrations of N2O4 during a toxic release may range from 1 to 15 ppm and depend on the air change rate (ACR) for a particular building and whether or not the air conditioning (A/C) system has been shut down or left in an operating mode. This project was initiated in order to assess how current A/C systems could be easily modified to prevent personnel from being exposed to toxic vapors. A sample system has been constructed to test the ability of several types of filter material to capture the N2O4 vapors prior to their infiltration into the A/C system. Test results will be presented which compare the efficiencies of standard A/C filters, water wash systems, and chemically impregnated filter material in taking toxic vapors out of the incoming air stream.

Determination of properties of PVE lubricants with HFC refrigerants[PolyVinylEther

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

Kaneko, Masato; Sakanoue, Shuichi; Tazaki, Toshihiro

1999-07-01

Polyalkyleneglycol (PAG) and polyol ester (POE) have been developed as refrigeration lubricants, used with HFC134a. PAG is used for automotive air conditioning systems and POE is used for domestic reciprocating refrigerators and for A/C systems. Although PAG exhibits good lubricity performance, it is difficult to use for domestic reciprocating refrigerators due to its low dielectric property. POE is difficult to use for automotive A/C systems, due to hydrolysis and poor lubricity performance. Polyvinylether (PVE) can be used in place of PAG and POE with HFC refrigerants. PVE is used for A/C systems as well as refrigerator and freezer applications. PVEmore » is an ideal lubricant for use with HFCs.« less

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

Aeloiza, Eddy C.; Burgos, Rolando P.

A step-down AC/AC converter for use in an electric distribution system includes at least one chopper circuit for each one of a plurality of phases of the AC power, each chopper circuit including a four-quadrant switch coupled in series between primary and secondary sides of the chopper circuit and a current-bidirectional two-quadrant switch coupled between the secondary side of the chopper circuit and a common node. Each current-bidirectional two-quadrant switch is oriented in the same direction, with respect to the secondary side of the corresponding chopper circuit and the common node. The converter further includes a control circuit configured tomore » pulse-width-modulate control inputs of the switches, to convert a first multiphase AC voltage at the primary sides of the chopper circuits to a second multiphase AC voltage at the secondary sides of the chopper circuits, the second multiphase AC voltage being lower in voltage than the first multiphase AC voltage.« less

Enabling the Distributed Generation Market of High Temperature Fuel Cell and Absorption Chiller Systems to Support Critical and Commercial Loads

NASA Astrophysics Data System (ADS)

DiMola, Ashley M.

Buildings account for over 18% of the world's anthropogenic Greenhouse Gas (GHG) emissions. As a result, a technology that can offset GHG emissions associated with buildings has the potential to save over 9 Giga-tons of GHG emissions per year. High temperature fuel cell and absorption chiller (HTFC/AC) technology offers a relatively low-carbon option for meeting cooling and electric loads for buildings while producing almost no criteria pollutants. GHG emissions in the state of California would decrease by 7.48 million metric tons per year if every commercial building in the State used HTFC/AC technology to meet its power and cooling requirements. In order to realize the benefits of HTFC/AC technology on a wide scale, the distributed generation market needs to be exposed to the technology and informed of its economic viability and real-world potential. This work characterizes the economics associated with HTFC/AC technology using select scenarios that are representative of realistic applications. The financial impacts of various input factors are evaluated and the HTFC/AC simulations are compared to the economics of traditional building utilities. It is shown that, in addition to the emissions reductions derived from the systems, HTFC/AC technology is financially preferable in all of the scenarios evaluated. This work also presents the design of a showcase environment, centered on a beta-test application, that presents (1) system operating data gathered using a custom data acquisition module, and (2) HTFC/AC technology in a clear and approachable manner in order to serve the target audience of market stakeholders.

Urea adsorption by activated carbon prepared from palm kernel shell

NASA Astrophysics Data System (ADS)

Ooi, Chee-Heong; Sim, Yoke-Leng; Yeoh, Fei-Yee

2017-07-01

Dialysis treatment is crucial for patients suffer from renal failure. The dialysis system removes the uremic toxin to a safe level in a patient's body. One of the major limitations of the current hemodialysis system is the capability to efficiently remove uremic toxins from patient's body. Nanoporous materials can be applied to improve the treatment. Palm kernel shell (PKS) biomass generated from palm oil mills can be utilized to prepare high quality nanoporous activated carbon (AC) and applied for urea adsorption in the dialysis system. In this study, AC was prepared from PKS via different carbonization temperatures and followed by carbon dioxide gas activation processes. The physical and chemical properties of the samples were studied. The results show that the porous AC with BET surface areas ranging from 541 to 622 m2g-1 and with total pore volumes varying from 0.254 to 0.297 cm3g-1, are formed with different carbonization temperatures. The equilibrium constant for urea adsorption by AC samples carbonized at 400, 500 and 600 °C are 0.091, 0.287 and 0.334, respectively. The increase of carbonization temperatures from 400 to 600 °C resulted in the increase in urea adsorption by AC predominantly due to increase in surface area. The present study reveals the feasibility of preparing AC with good porosity from PKS and potentially applied in urea adsorption application.

Building a world-wide open source community around a software framework: progress, dos, and don'ts

NASA Astrophysics Data System (ADS)

Ibsen, Jorge; Antognini, Jonathan; Avarias, Jorge; Caproni, Alessandro; Fuessling, Matthias; Gimenez, Guillermo; Verma, Khushbu; Mora, Matias; Schwarz, Joseph; Staig, Tomás.

2016-08-01

As we all know too well, building up a collaborative community around a software infrastructure is not easy. Besides recruiting enthusiasts to work as part of it, mostly for free, to succeed you also need to overcome a number of technical, sociological, and, to our surprise, some political hurdles. The ALMA Common Software (ACS) was developed at ESO and partner institutions over the course of more than 10 years. While it was mainly intended for the ALMA Observatory, it was early on thought as a generic distributed control framework. ACS has been periodically released to the public through an LGPL license, which encouraged around a dozen non-ALMA institutions to make use of ACS for both industrial and educational applications. In recent years, the Cherenkov Telescope Array and the LLAMA Observatory have also decided to adopt the framework for their own control systems. The aim of the "ACS Community" is to support independent initiatives in making use of the ACS framework and to further contribute to its development. The Community provides access to a growing network of volunteers eager to develop ACS in areas that are not necessarily in ALMA's interests, and/or were not within the original system scope. Current examples are: support for additional OS platforms, extension of supported hardware interfaces, a public code repository and a build farm. The ACS Community makes use of existing collaborations with Chilean and Brazilian universities, reaching out to promising engineers in the making. At the same time, projects actively using ACS have committed valuable resources to assist the Community's work. Well established training programs like the ACS Workshops are also being continued through the Community's work. This paper aims to give a detailed account of the ongoing (second) journey towards establishing a world-wide open source collaboration around ACS. The ACS Community is growing into a horizontal partnership across a decentralized and diversified group of actors, and we are excited about its technical and human potential.

Redox processes at a nanostructured interface under strong electric fields.

PubMed

Steurer, Wolfram; Surnev, Svetlozar; Netzer, Falko P; Sementa, Luca; Negreiros, Fabio R; Barcaro, Giovanni; Durante, Nicola; Fortunelli, Alessandro

2014-09-21

Manipulation of chemistry and film growth via external electric fields is a longstanding goal in surface science. Numerous systems have been predicted to show such effects but experimental evidence is sparse. Here we demonstrate in a custom-designed UHV apparatus that the application of spatially extended, homogeneous, very high (>1 V nm(-1)) DC-fields not only changes the system energetics but triggers dynamic processes which become important much before static contributions appreciably modify the potential energy landscape. We take a well characterized ultrathin NiO film on a Ag(100) support as a proof-of-principle test case, and show how it gets reduced to supported Ni clusters under fields exceeding the threshold of +0.9 V nm(-1). Using an effective model, we trace the observed interfacial redox process down to a dissociative electron attachment resonant mechanism. The proposed approach can be easily implemented and generally applied to a wide range of interfacial systems, thus opening new opportunities for the manipulation of film growth and reaction processes at solid surfaces under strong external fields.

75 FR 27966 - Airworthiness Directives; The Boeing Company Model 747-400 and 747-400D Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-19

... operator experienced a multi-power system loss in-flight of 1, 2, and 3 alternating current (AC) electrical... an operator experienced a multi-power system loss in-flight of 1, 2, and 3 AC electrical power... alternating current electrical power systems located in the main equipment center (MEC). The Federal Aviation...

Magnetic Nanoparticle Thermometer: An Investigation of Minimum Error Transmission Path and AC Bias Error

PubMed Central

Du, Zhongzhou; Su, Rijian; Liu, Wenzhong; Huang, Zhixing

2015-01-01

The signal transmission module of a magnetic nanoparticle thermometer (MNPT) was established in this study to analyze the error sources introduced during the signal flow in the hardware system. The underlying error sources that significantly affected the precision of the MNPT were determined through mathematical modeling and simulation. A transfer module path with the minimum error in the hardware system was then proposed through the analysis of the variations of the system error caused by the significant error sources when the signal flew through the signal transmission module. In addition, a system parameter, named the signal-to-AC bias ratio (i.e., the ratio between the signal and AC bias), was identified as a direct determinant of the precision of the measured temperature. The temperature error was below 0.1 K when the signal-to-AC bias ratio was higher than 80 dB, and other system errors were not considered. The temperature error was below 0.1 K in the experiments with a commercial magnetic fluid (Sample SOR-10, Ocean Nanotechnology, Springdale, AR, USA) when the hardware system of the MNPT was designed with the aforementioned method. PMID:25875188

Ion-exchange equilibrium of N-acetyl-D-neuraminic acid on a strong anionic exchanger.

PubMed

Wu, Jinglan; Ke, Xu; Zhang, Xudong; Zhuang, Wei; Zhou, Jingwei; Ying, Hanjie

2015-09-15

N-acetyl-D-neuraminic acid (Neu5Ac) is a high value-added product widely applied in the food industry. A suitable equilibrium model is required for purification of Neu5Ac based on ion-exchange chromatography. Hence, the equilibrium uptake of Neu5Ac on a strong anion exchanger, AD-1 was investigated experimentally and theoretically. The uptake of Neu5Ac by the hydroxyl form of the resin occurred primarily by a stoichiometric exchange of Neu5Ac(-) and OH(-). The experimental data showed that the selectivity coefficient for the exchange of Neu5Ac(-) with OH(-) was a non-constant quantity. Subsequently, the Saunders' model, which took into account the dissociation reactions of Neu5Ac and the condition of electroneutrality, was used to correlate the Neu5Ac sorption isotherms at various solution pHs and Neu5Ac concentrations. The model provided an excellent fit to the binary exchange data for Cl(-)/OH(-) and Neu5Ac(-)/OH(-), and an approximate prediction of equilibrium in the ternary system Cl(-)/Neu5Ac(-)/OH(-). This basic information combined with the general mass transfer model could lay the foundation for the prediction of dynamic behavior of fixed bed separation process afterwards. Copyright © 2015 Elsevier Ltd. All rights reserved.

Phosphorylation of 1-Aminocyclopropane-1-Carboxylic Acid Synthase by MPK6, a Stress-Responsive Mitogen-Activated Protein Kinase, Induces Ethylene Biosynthesis in ArabidopsisW⃞

PubMed Central

Liu, Yidong; Zhang, Shuqun

2004-01-01

Mitogen-activated protein kinases (MAPKs) are implicated in regulating plant growth, development, and response to the environment. However, the underlying mechanisms are unknown because of the lack of information about their substrates. Using a conditional gain-of-function transgenic system, we demonstrated that the activation of SIPK, a tobacco (Nicotiana tabacum) stress-responsive MAPK, induces the biosynthesis of ethylene. Here, we report that MPK6, the Arabidopsis thaliana ortholog of tobacco SIPK, is required for ethylene induction in this transgenic system. Furthermore, we found that selected isoforms of 1-aminocyclopropane-1-carboxylic acid synthase (ACS), the rate-limiting enzyme of ethylene biosynthesis, are substrates of MPK6. Phosphorylation of ACS2 and ACS6 by MPK6 leads to the accumulation of ACS protein and, thus, elevated levels of cellular ACS activity and ethylene production. Expression of ACS6DDD, a gain-of-function ACS6 mutant that mimics the phosphorylated form of ACS6, confers constitutive ethylene production and ethylene-induced phenotypes. Increasing numbers of stress stimuli have been shown to activate Arabidopsis MPK6 or its orthologs in other plant species. The identification of the first plant MAPK substrate in this report reveals one mechanism by which MPK6/SIPK regulates plant stress responses. Equally important, this study uncovers a signaling pathway that modulates the biosynthesis of ethylene, an important plant hormone, in plants under stress. PMID:15539472

Photovoltaic Power System and Power Distribution Demonstration for the Desert RATS Program

NASA Technical Reports Server (NTRS)

Colozza, Anthony; Jakupca, Ian; Mintz, Toby; Herlacher, Mike; Hussey, Sam

2012-01-01

A stand alone, mobile photovoltaic power system along with a cable deployment system was designed and constructed to take part in the Desert Research And Technology Studies (RATS) lunar surface human interaction evaluation program at Cinder Lake, Arizona. The power system consisted of a photovoltaic array/battery system. It is capable of providing 1 kW of electrical power. The system outputs were 48 V DC, 110 V AC, and 220 V AC. A cable reel with 200 m of power cable was used to provide power from the trailer to a remote location. The cable reel was installed on a small trailer. The reel was powered to provide low to no tension deployment of the cable. The cable was connected to the 220 V AC output of the power system trailer. The power was then converted back to 110 V AC on the cable deployment trailer for use at the remote site. The Scout lunar rover demonstration vehicle was used to tow the cable trailer and deploy the power cable. This deployment was performed under a number of operational scenarios, manned operation, remote operation and tele-robotically. Once deployed, the cable was used to provide power, from the power system trailer, to run various operational tasks at the remote location.

Obtaining continuous BrAC/BAC estimates in the field: A hybrid system integrating transdermal alcohol biosensor, Intellidrink smartphone app, and BrAC Estimator software tools.

PubMed

Luczak, Susan E; Hawkins, Ashley L; Dai, Zheng; Wichmann, Raphael; Wang, Chunming; Rosen, I Gary

2018-08-01

Biosensors have been developed to measure transdermal alcohol concentration (TAC), but converting TAC into interpretable indices of blood/breath alcohol concentration (BAC/BrAC) is difficult because of variations that occur in TAC across individuals, drinking episodes, and devices. We have developed mathematical models and the BrAC Estimator software for calibrating and inverting TAC into quantifiable BrAC estimates (eBrAC). The calibration protocol to determine the individualized parameters for a specific individual wearing a specific device requires a drinking session in which BrAC and TAC measurements are obtained simultaneously. This calibration protocol was originally conducted in the laboratory with breath analyzers used to produce the BrAC data. Here we develop and test an alternative calibration protocol using drinking diary data collected in the field with the smartphone app Intellidrink to produce the BrAC calibration data. We compared BrAC Estimator software results for 11 drinking episodes collected by an expert user when using Intellidrink versus breath analyzer measurements as BrAC calibration data. Inversion phase results indicated the Intellidrink calibration protocol produced similar eBrAC curves and captured peak eBrAC to within 0.0003%, time of peak eBrAC to within 18min, and area under the eBrAC curve to within 0.025% alcohol-hours as the breath analyzer calibration protocol. This study provides evidence that drinking diary data can be used in place of breath analyzer data in the BrAC Estimator software calibration procedure, which can reduce participant and researcher burden and expand the potential software user pool beyond researchers studying participants who can drink in the laboratory. Copyright © 2017. Published by Elsevier Ltd.

Progress on advanced dc and ac induction drives for electric vehicles

NASA Technical Reports Server (NTRS)

Schwartz, H. J.

1982-01-01

Progress is reported in the development of complete electric vehicle propulsion systems, and the results of tests on the Road Load Simulator of two such systems representative of advanced dc and ac drive technology are presented. One is the system used in the DOE's ETV-1 integrated test vehicle which consists of a shunt wound dc traction motor under microprocessor control using a transistorized controller. The motor drives the vehicle through a fixed ratio transmission. The second system uses an ac induction motor controlled by transistorized pulse width modulated inverter which drives through a two speed automatically shifted transmission. The inverter and transmission both operate under the control of a microprocessor. The characteristics of these systems are also compared with the propulsion system technology available in vehicles being manufactured at the inception of the DOE program and with an advanced, highly integrated propulsion system upon which technology development was recently initiated.

A fast and remote magnetonanothermometry for a liquid environment

NASA Astrophysics Data System (ADS)

He, Le; Liu, Wenzhong; Xie, Qingguo; Pi, Shiqiang; Morais, P. C.

2016-02-01

This study reports on a new approach for remote nanothermometry with short response time (milliseconds) aiming to operate in liquid media using AC susceptibility components of a suspended magnetic nanoparticle subjected to the Brownian relaxation mechanism. A simple, low cost, and accurate system was designed to measure AC susceptibility using an AC magnetic field at small amplitude (6 Oe) and frequency range (5 kHz) superimposed on a weak DC magnetic field (up to 30 Oe). A model based on the AC susceptibility of magnetic nanoparticles (30 nm average diameter) was constructed to describe the temperature measurement sensitivity of the dominated Brownian relaxation time. A new approach for remote nanothermometry was achieved with measured AC susceptibility by the designed system and the proposed model. Our experimental results show that our magnetonanothermometer allows temperature errors lower than 0.3 K with standard deviations lower than 0.1 K in the temperature range from 310 to 320 K.

AC power generation from microbial fuel cells

NASA Astrophysics Data System (ADS)

Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

2015-11-01

Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

Histopathologic features in actinic cheilitis by the comparison of grading dysplasia systems.

PubMed

Pilati, Sfm; Bianco, B C; Vieira, Dsc; Modolo, F

2017-03-01

This study aimed to determine the histopathologic findings in actinic cheilitis (AC) and lip squamous cell carcinomas (LSCC) diagnosed at Federal University of Santa Catarina in order to attempt to predict the evolution from AC to LSCC based on the comparison of two dysplasia classification systems. Histopathologic features were evaluated according to the World Health Organization classification of dysplasia and binary system of classification. Also, in LSCC, pattern, stage of invasion, and degree of keratinization were evaluated. A total of 58 cases of AC and 70 cases of LSCC were studied, and data correlation was performed using statistical analysis. The presence of dyskeratosis and keratin pearls was found to be strongly associated with severe dysplasia and could represent higher proximity between the severe dysplasia in AC and LSCC. Also, changes related to the nuclei, such as hyperchromasia, nuclear pleomorphism, anisonucleosis, increase in the number and size of nucleoli, increased number of mitoses, and atypical mitoses, indicate progression in dysplasia spectrum. Knowledge of clinical and histological features of AC and LSCC leads to better understanding of factors possibly associated with malignant transformation of epithelial dysplasia. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

System for transmitting low frequency analog signals over AC power lines

DOEpatents

Baker, Steven P.; Durall, Robert L.; Haynes, Howard D.

1989-01-01

A system for transmitting low frequency analog signals over AC power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an AC power line. The modulation signal frequency range in selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the AC power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal.

System for transmitting low frequency analog signals over AC power lines

DOEpatents

Baker, Steven P.; Durall, Robert L.; Haynes, Howard D.

1989-09-05

A system for transmitting low frequency analog signals over AC power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an AC power line. The modulation signal frequency range in selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the AC power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal.

A system for tranmitting low frequency analog signals over ac power lines

DOEpatents

Baker, S.P.; Durall, R.L.; Haynes, H.D.

1987-07-30

A system for transmitting low frequency analog signals over ac power lines using FM modulation. A low frequency analog signal to be transmitted is first applied to a voltage-to-frequency converter where it is converted to a signal whose frequency varies in proportion to the analog signal amplitude. This signal is then used to modulate the carrier frequency of an FM transmitter coupled to an ac power line. The modulation signal frequency range is selected to be within the response band of the FM transmitter. The FM modulated carrier signal is received by an FM receiver coupled to the ac power line, demodulated and the demodulated signal frequency is converted by a frequency-to-voltage converter back to the form of the original low frequency analog input signal. 4 figs.

Accurate calculation and modeling of the adiabatic connection in density functional theory

NASA Astrophysics Data System (ADS)

Teale, A. M.; Coriani, S.; Helgaker, T.

2010-04-01

Using a recently implemented technique for the calculation of the adiabatic connection (AC) of density functional theory (DFT) based on Lieb maximization with respect to the external potential, the AC is studied for atoms and molecules containing up to ten electrons: the helium isoelectronic series, the hydrogen molecule, the beryllium isoelectronic series, the neon atom, and the water molecule. The calculation of AC curves by Lieb maximization at various levels of electronic-structure theory is discussed. For each system, the AC curve is calculated using Hartree-Fock (HF) theory, second-order Møller-Plesset (MP2) theory, coupled-cluster singles-and-doubles (CCSD) theory, and coupled-cluster singles-doubles-perturbative-triples [CCSD(T)] theory, expanding the molecular orbitals and the effective external potential in large Gaussian basis sets. The HF AC curve includes a small correlation-energy contribution in the context of DFT, arising from orbital relaxation as the electron-electron interaction is switched on under the constraint that the wave function is always a single determinant. The MP2 and CCSD AC curves recover the bulk of the dynamical correlation energy and their shapes can be understood in terms of a simple energy model constructed from a consideration of the doubles-energy expression at different interaction strengths. Differentiation of this energy expression with respect to the interaction strength leads to a simple two-parameter doubles model (AC-D) for the AC integrand (and hence the correlation energy of DFT) as a function of the interaction strength. The structure of the triples-energy contribution is considered in a similar fashion, leading to a quadratic model for the triples correction to the AC curve (AC-T). From a consideration of the structure of a two-level configuration-interaction (CI) energy expression of the hydrogen molecule, a simple two-parameter CI model (AC-CI) is proposed to account for the effects of static correlation on the AC. When parametrized in terms of the same input data, the AC-CI model offers improved performance over the corresponding AC-D model, which is shown to be the lowest-order contribution to the AC-CI model. The utility of the accurately calculated AC curves for the analysis of standard density functionals is demonstrated for the BLYP exchange-correlation functional and the interaction-strength-interpolation (ISI) model AC integrand. From the results of this analysis, we investigate the performance of our proposed two-parameter AC-D and AC-CI models when a simple density functional for the AC at infinite interaction strength is employed in place of information at the fully interacting point. The resulting two-parameter correlation functionals offer a qualitatively correct behavior of the AC integrand with much improved accuracy over previous attempts. The AC integrands in the present work are recommended as a basis for further work, generating functionals that avoid spurious error cancellations between exchange and correlation energies and give good accuracy for the range of densities and types of correlation contained in the systems studied here.

Multifunctional Ultra-high Vacuum Apparatus for Studies of the Interactions of Chemical Warfare Agents on Complex Surfaces

DTIC Science & Technology

2014-01-02

of the formation of a hydrogen-bonded hydroxyl. Characteristic modes of the sarin molecule itself are also ob- served. These experimental results show...chemical warfare agent, surface science, uptake, decontamination, filtration , UHV, XPS, FTIR, TPD REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S...challenges that accompany the research of these toxic, often very low vapor pressure, compounds. While results of vacuum-based surface science

CO oxidation studies over supported noble metal catalysts and single crystals: A review

NASA Technical Reports Server (NTRS)

Boecker, Dirk; Gonzalez, Richard D.

1987-01-01

The catalytic oxidation of CO over noble metal catalysts is reviewed. Results obtained on supported noble metal catalysts and single crystals both at high pressures and under UHV conditions are compared. The underlying causes which result in surface instabilities and multiple steady-state oscillations are considered, in particular, the occurrence of hot spots. CO islands of reactivity, surface oxide formation and phase transformations under oscillatory conditions are discussed.

Comparative single-cell genomics reveals potential ecological niches for the freshwater acI Actinobacteria lineage.

PubMed

Ghylin, Trevor W; Garcia, Sarahi L; Moya, Francisco; Oyserman, Ben O; Schwientek, Patrick; Forest, Katrina T; Mutschler, James; Dwulit-Smith, Jeffrey; Chan, Leong-Keat; Martinez-Garcia, Manuel; Sczyrba, Alexander; Stepanauskas, Ramunas; Grossart, Hans-Peter; Woyke, Tanja; Warnecke, Falk; Malmstrom, Rex; Bertilsson, Stefan; McMahon, Katherine D

2014-12-01

Members of the acI lineage of Actinobacteria are the most abundant microorganisms in most freshwater lakes; however, our understanding of the keys to their success and their role in carbon and nutrient cycling in freshwater systems has been hampered by the lack of pure cultures and genomes. We obtained draft genome assemblies from 11 single cells representing three acI tribes (acI-A1, acI-A7, acI-B1) from four temperate lakes in the United States and Europe. Comparative analysis of acI SAGs and other available freshwater bacterial genomes showed that acI has more gene content directed toward carbohydrate acquisition as compared to Polynucleobacter and LD12 Alphaproteobacteria, which seem to specialize more on carboxylic acids. The acI genomes contain actinorhodopsin as well as some genes involved in anaplerotic carbon fixation indicating the capacity to supplement their known heterotrophic lifestyle. Genome-level differences between the acI-A and acI-B clades suggest specialization at the clade level for carbon substrate acquisition. Overall, the acI genomes appear to be highly streamlined versions of Actinobacteria that include some genes allowing it to take advantage of sunlight and N-rich organic compounds such as polyamines, di- and oligopeptides, branched-chain amino acids and cyanophycin. This work significantly expands the known metabolic potential of the cosmopolitan freshwater acI lineage and its ecological and genetic traits.

75 FR 27414 - Airworthiness Directives; Airbus A318, A319, A320, A321 Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-17

... occurrences of loss of the AC [alternating current] BUS 1 have been reported which led in some instances to the loss of the AC ESS [essential] BUS and DC [direct current] ESS BUS and connected systems. The... condition for the specified products. The MCAI states: Several occurrences of loss of the AC [alternating...

Electroporation of cells using EM induction of ac fields by a magnetic stimulator

NASA Astrophysics Data System (ADS)

Chen, C.; Evans, J. A.; Robinson, M. P.; Smye, S. W.; O'Toole, P.

2010-02-01

This paper describes a method of effectively electroporating mammalian cell membranes with pulsed alternating-current (ac) electric fields at field strengths of 30-160 kV m-1. Although many in vivo electroporation protocols entail applying square wave or monotonically decreasing pulses via needles or electrode plates, relatively few have explored the use of pulsed ac fields. Following our previous study, which established the effectiveness of ac fields for electroporating cell membranes, a primary/secondary coil system was constructed to produce sufficiently strong electric fields by electromagnetic induction. The primary coil was formed from the applicator of an established transcranial magnetic stimulation (TMS) system, while the secondary coil was a purpose-built device of a design which could eventually be implanted into tissue. The effects of field strength, pulse interval and cumulative exposure time were investigated using microscopy and flow cytometry. Results from experiments on concentrated cell suspensions showed an optimized electroporation efficiency of around 50%, demonstrating that electroporation can be practicably achieved by inducing such pulsed ac fields. This finding confirms the possibility of a wide range of in vivo applications based on magnetically coupled ac electroporation.

Automatic generation of the index of productive syntax for child language transcripts.

PubMed

Hassanali, Khairun-nisa; Liu, Yang; Iglesias, Aquiles; Solorio, Thamar; Dollaghan, Christine

2014-03-01

The index of productive syntax (IPSyn; Scarborough (Applied Psycholinguistics 11:1-22, 1990) is a measure of syntactic development in child language that has been used in research and clinical settings to investigate the grammatical development of various groups of children. However, IPSyn is mostly calculated manually, which is an extremely laborious process. In this article, we describe the AC-IPSyn system, which automatically calculates the IPSyn score for child language transcripts using natural language processing techniques. Our results show that the AC-IPSyn system performs at levels comparable to scores computed manually. The AC-IPSyn system can be downloaded from www.hlt.utdallas.edu/~nisa/ipsyn.html .

Comparative study of superconducting fault current limiter both for LCC-HVDC and VSC-HVDC systems

NASA Astrophysics Data System (ADS)

Lee, Jong-Geon; Khan, Umer Amir; Lim, Sung-Woo; Shin, Woo-ju; Seo, In-Jin; Lee, Bang-Wook

2015-11-01

High Voltage Direct Current (HVDC) system has been evaluated as the optimum solution for the renewable energy transmission and long-distance power grid connections. In spite of the various advantages of HVDC system, it still has been regarded as an unreliable system compared to AC system due to its vulnerable characteristics on the power system fault. Furthermore, unlike AC system, optimum protection and switching device has not been fully developed yet. Therefore, in order to enhance the reliability of the HVDC systems mitigation of power system fault and reliable fault current limiting and switching devices should be developed. In this paper, in order to mitigate HVDC fault, both for Line Commutated Converter HVDC (LCC-HVDC) and Voltage Source Converter HVDC (VSC-HVDC) system, an application of resistive superconducting fault current limiter which has been known as optimum solution to cope with the power system fault was considered. Firstly, simulation models for two types of LCC-HVDC and VSC-HVDC system which has point to point connection model were developed. From the designed model, fault current characteristics of faulty condition were analyzed. Second, application of SFCL on each types of HVDC system and comparative study of modified fault current characteristics were analyzed. Consequently, it was deduced that an application of AC-SFCL on LCC-HVDC system with point to point connection was desirable solution to mitigate the fault current stresses and to prevent commutation failure in HVDC electric power system interconnected with AC grid.

Live imaging of H3K9 acetylation in plant cells

PubMed Central

Kurita, Kazuki; Sakamoto, Takuya; Yagi, Noriyoshi; Sakamoto, Yuki; Ito, Akihiro; Nishino, Norikazu; Sako, Kaori; Yoshida, Minoru; Kimura, Hiroshi; Seki, Motoaki; Matsunaga, Sachihiro

2017-01-01

Proper regulation of histone acetylation is important in development and cellular responses to environmental stimuli. However, the dynamics of histone acetylation at the single-cell level remains poorly understood. Here we established a transgenic plant cell line to track histone H3 lysine 9 acetylation (H3K9ac) with a modification-specific intracellular antibody (mintbody). The H3K9ac-specific mintbody fused to the enhanced green fluorescent protein (H3K9ac-mintbody-GFP) was introduced into tobacco BY-2 cells. We successfully demonstrated that H3K9ac-mintbody-GFP interacted with H3K9ac in vivo. The ratio of nuclear/cytoplasmic H3K9ac-mintbody-GFP detected in quantitative analysis reflected the endogenous H3K9ac levels. Under chemically induced hyperacetylation conditions with histone deacetylase inhibitors including trichostatin A, Ky-2 and Ky-14, significant enhancement of H3K9ac was detected by H3K9ac-mintbody-GFP dependent on the strength of inhibitors. Conversely, treatment with a histone acetyltransferase inhibitor, C646 caused a reduction in the nuclear to cytoplasmic ratio of H3K9ac-mintbody-GFP. Using this system, we assessed the environmental responses of H3K9ac and found that cold and salt stresses enhanced H3K9ac in tobacco BY-2 cells. In addition, a combination of H3K9ac-mintbody-GFP with 5-ethynyl-2′-deoxyuridine labelling confirmed that H3K9ac level is constant during interphase. PMID:28418019

Equivalent circuit modeling of a piezo-patch energy harvester on a thin plate with AC-DC conversion

NASA Astrophysics Data System (ADS)

Bayik, B.; Aghakhani, A.; Basdogan, I.; Erturk, A.

2016-05-01

As an alternative to beam-like structures, piezoelectric patch-based energy harvesters attached to thin plates can be readily integrated to plate-like structures in automotive, marine, and aerospace applications, in order to directly exploit structural vibration modes of the host system without mass loading and volumetric occupancy of cantilever attachments. In this paper, a multi-mode equivalent circuit model of a piezo-patch energy harvester integrated to a thin plate is developed and coupled with a standard AC-DC conversion circuit. Equivalent circuit parameters are obtained in two different ways: (1) from the modal analysis solution of a distributed-parameter analytical model and (2) from the finite-element numerical model of the harvester by accounting for two-way coupling. After the analytical modeling effort, multi-mode equivalent circuit representation of the harvester is obtained via electronic circuit simulation software SPICE. Using the SPICE software, electromechanical response of the piezoelectric energy harvester connected to linear and nonlinear circuit elements are computed. Simulation results are validated for the standard AC-AC and AC-DC configurations. For the AC input-AC output problem, voltage frequency response functions are calculated for various resistive loads, and they show excellent agreement with modal analysis-based analytical closed-form solution and with the finite-element model. For the standard ideal AC input-DC output case, a full-wave rectifier and a smoothing capacitor are added to the harvester circuit for conversion of the AC voltage to a stable DC voltage, which is also validated against an existing solution by treating the single-mode plate dynamics as a single-degree-of-freedom system.

Small-Signal Dynamic Analysis of LCC-HVDC with STATCOM at the Inverter Busbar

NASA Astrophysics Data System (ADS)

Liu, Dong; Jiang, Wen; Guo, Chunyi; Rehman, Atiq Ur; Zhao, Chengyong

2018-01-01

This paper develops a linearized small-signal dynamic model of a Line-Commutated-Converter based HVDC (LCC-HVDC) system with STATCOM at the inverter busbar, and validates its accuracy by comparing time-domain responses from small-signal model and PSCAD-based simulation results. Considering the potential impact of Phase-Locked-Loop (PLL) parameters on the study system and the close connection of STATCOM and LCC inverter station at AC busbar, this paper investigates the impact of PLL gains and AC voltage control parameters of STATCOM on the system small-signal stability. The studies show that (i) the PLL gain has highly impact on the study system and smaller PLL gains are preferable; (ii) larger values of both the proportional gain and the integral gain of AC voltage controller of STATCOM could result in oscillation/instability of the system.

Influence of AC system design on the realisation of tractive efforts by high adhesion locomotives

NASA Astrophysics Data System (ADS)

Spiryagin, Maksym; Wolfs, Peter; Cole, Colin; Stichel, Sebastian; Berg, Mats; Manfred, Plöchl

2017-08-01

The main task for heavy haul railway operators is to reduce the cost of exported minerals and enhance the long-term viability of rail transport operations through increasing productivity by running longer and heavier trains. The common opinion is that this is achievable by means of implementation of high adhesion locomotives with advanced AC traction technologies. Modern AC high adhesion locomotives are very complex mechatronic systems and can be designed with two alternative traction topologies of either bogie or individual axle controls. This paper describes a modelling approach for these two types of AC traction systems with the application of an advanced co-simulation methodology, where an electrical system and a traction algorithm are modelled in Matlab/Simulink, and a mechanical system is modelled in a multibody software package. Although the paper concentrates on the analysis of the functioning for these two types of traction control systems, the choice of reference slip values also has an influence on the performance of both systems. All these design variations and issues have been simulated for various adhesion conditions at the wheel-rail interface and their influence on the high traction performance of a locomotive equipped with two three-axle bogies has been discussed.

Grid-connected wind and photovoltaic system

NASA Astrophysics Data System (ADS)

Devabakthuni, Sindhuja

The objective of this thesis is to design a grid connected wind and photovoltaic system. A new model of converter control was designed which maintains the voltage of the bus to grid as constant when combined system of solar and wind is connected to AC bus. The model is designed to track maximum power at each point irrespective of changes in irradiance, temperature and wind speed which affects the power supplied to grid. Solar power from the sun is not constant as it is affected by changes in irradiances and temperature. Even the wind power is affected by wind speed. A MPPT controller was designed for both systems. A boost converter is designed which uses the pulses from MPPT controller to boost the output. Wind system consists of wind turbine block from the MATLAB with a pitch angle controller to maintain optimum pitch angle. The output from wind turbine is connected to a permanent magnet synchronous generator. The unregulated DC output from the photovoltaic system is directly given to boost converter. The AC output from the wind system is given to an uncontrolled rectifier to get a unregulated DC output. The unregulated DC output goes to the boost converter. A voltage source inverter was designed which converts the rectified DC output from the boost converter to AC power. The inverter is designed to maintain constant AC bus voltage irrespective of the disturbances in the power supply. Photovoltaic and wind systems are individually designed for 5KW each in MATLAB-Simulink environment. In this thesis, the models were subjected to changes in irradiance, temperature and wind speed and the results were interpreted. The model was successful in tracking maximum at every instant and the AC bus voltage was maintained constant throughout the simulation.

Free piston variable-stroke linear-alternator generator

DOEpatents

Haaland, Carsten M.

1998-01-01

A free-piston variable stroke linear-alternator AC power generator for a combustion engine. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod.

Reproducibility of Quantitative Brain Imaging Using a PET-Only and a Combined PET/MR System

PubMed Central

Lassen, Martin L.; Muzik, Otto; Beyer, Thomas; Hacker, Marcus; Ladefoged, Claes Nøhr; Cal-González, Jacobo; Wadsak, Wolfgang; Rausch, Ivo; Langer, Oliver; Bauer, Martin

2017-01-01

The purpose of this study was to test the feasibility of migrating a quantitative brain imaging protocol from a positron emission tomography (PET)-only system to an integrated PET/MR system. Potential differences in both absolute radiotracer concentration as well as in the derived kinetic parameters as a function of PET system choice have been investigated. Five healthy volunteers underwent dynamic (R)-[11C]verapamil imaging on the same day using a GE-Advance (PET-only) and a Siemens Biograph mMR system (PET/MR). PET-emission data were reconstructed using a transmission-based attenuation correction (AC) map (PET-only), whereas a standard MR-DIXON as well as a low-dose CT AC map was applied to PET/MR emission data. Kinetic modeling based on arterial blood sampling was performed using a 1-tissue-2-rate constant compartment model, yielding kinetic parameters (K1 and k2) and distribution volume (VT). Differences for parametric values obtained in the PET-only and the PET/MR systems were analyzed using a 2-way Analysis of Variance (ANOVA). Comparison of DIXON-based AC (PET/MR) with emission data derived from the PET-only system revealed average inter-system differences of −33 ± 14% (p < 0.05) for the K1 parameter and −19 ± 9% (p < 0.05) for k2. Using a CT-based AC for PET/MR resulted in slightly lower systematic differences of −16 ± 18% for K1 and −9 ± 10% for k2. The average differences in VT were −18 ± 10% (p < 0.05) for DIXON- and −8 ± 13% for CT-based AC. Significant systematic differences were observed for kinetic parameters derived from emission data obtained from PET/MR and PET-only imaging due to different standard AC methods employed. Therefore, a transfer of imaging protocols from PET-only to PET/MR systems is not straightforward without application of proper correction methods. Clinical Trial Registration: www.clinicaltrialsregister.eu, identifier 2013-001724-19 PMID:28769742

Control Structures for VSC-based FACTS Devices under Normal and Faulted AC-systems

NASA Astrophysics Data System (ADS)

Babaei, Saman

This thesis is concerned with improving the Flexible AC Transmission Systems (FACTS) devices performance under the normal and fault AC-system conditions by proposing new control structures and also converter topologies. The combination of the increasing electricity demand and restrictions in expanding the power system infrastructures has urged the utility owners to deploy the utility-scaled power electronics in the power system. Basically, FACTS is referred to the application of the power electronics in the power systems. Voltage Source Converter (VSC) is the preferred building block of the FACTS devices and many other utility-scale power electronics applications. Despite of advances in the semiconductor technology and ultra-fast microprocessor based controllers, there are still many issues to address and room to improve[25]. An attempt is made in this thesis to address these important issues of the VSC-based FACTS devices and provide solutions to improve them.

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

Colldelram, Carles, E-mail: ccolldelram@cells.es; Nicolas, Josep, E-mail: jnicolas@cells.es; Nikitina, Liudmila, E-mail: lnikitina@cells.es

In this work we report the design and performance of a novel compact in-vacuum actuator, designed to be compatible with all the motions required for the scissor-type ESRF mirror bender. These mirror benders include several linear actuators, which drive the mirror bending torques, as well as the main alignment motions such as pitch and translation along the normal to the mirror surface. The motions are provided by compact linear actuators, which consist of motor, reduction, spindle and nut, encapsulated on a closed air volume to provide vacuum compatibility. The actuator includes a hydroformed bellows to transmit the force to themore » actuator tip, and an electrical feedthrough for the motor cables. The design boundaries for these actuators are quite tight, as they must be integrated in a narrow volume, must be UHV compatible and must provide high resolution, for a relatively high load. As a result, they have limited mechanical performance, and in some cases poor reliability. To overcome these problems, we designed and implemented a different concept. In the proposed concept, the motor rotation is converted onto a linear motion by means of a cam instead of a spindle and a nut. This allows for much shorter and stiffer transmission system, with similar dimensions. The vacuum compatibility is intrinsic for this solution, since the whole mechanism of the actuator is UHV compatible. All motions are preloaded and guided by vacuum compatible (hybrid metal-ceramics) ball bearings. This allows the system reaching a repeatability and backlash well within the micron. The absence of friction allows for a high reliability and releases the maintenance needs of the system. The transmission is intrinsically irreversible, and the system can hold a load of 250 N within a few nanometers without any holding current on the motors. This allows the system to move reliably also in micro-stepping mode, providing a resolution well below the half-step nominal resolution of 100 nm. Performances have been tested on a prototype. We report the results of the tests obtained in air and in vacuum after bake-out. Two units of the new actuator have been installed at the photoemission beamline of ALBA (CIRCE) and are routinely used to align the 3 µm spot on the field of view of the Photoemission Electron Microscope. The absence of any noticeable backlash, or any friction effect and the reliability of the micro-stepping motion has simplified very much the alignment of the photon beam, reducing the alignment process to few minutes. The excellent performances and relatively high load capacity of this new compact actuator make of it a versatile element to be integrated in other systems requiring reliable in-vacuum positioning.« less

A joint swarm intelligence algorithm for multi-user detection in MIMO-OFDM system

NASA Astrophysics Data System (ADS)

Hu, Fengye; Du, Dakun; Zhang, Peng; Wang, Zhijun

2014-11-01

In the multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system, traditional multi-user detection (MUD) algorithms that usually used to suppress multiple access interference are difficult to balance system detection performance and the complexity of the algorithm. To solve this problem, this paper proposes a joint swarm intelligence algorithm called Ant Colony and Particle Swarm Optimisation (AC-PSO) by integrating particle swarm optimisation (PSO) and ant colony optimisation (ACO) algorithms. According to simulation results, it has been shown that, with low computational complexity, the MUD for the MIMO-OFDM system based on AC-PSO algorithm gains comparable MUD performance with maximum likelihood algorithm. Thus, the proposed AC-PSO algorithm provides a satisfactory trade-off between computational complexity and detection performance.

Category (CAT) IIIb Level 1 Test Plan for Global Positioning System (GPS)

DTIC Science & Technology

1993-09-01

applications. CAT 11Tb is defined in Advisory Circular ( AC ) 120-28C [1] as "a precision instrument approach and landing with no decision height (DH), or...2) FAA AC 20-57A (Automatic Landing Systems) [31, AC 120-28C (Criteria for Approval of CAT III Landing Weather Minima) [I] and the FAA tunnel-in...AD-A274 098I I~II l~iiUIRII 11111ilIII2 DOT/FAA/RD-93/21 Category ( CAT ) IIb Level 1 MTR 93W0000102 Research and Test Plan for Global Development

Astrometric Measurements of Triple Star System 15379+3006 STF 1963AB, STF 1963AC

NASA Astrophysics Data System (ADS)

Russell, Harker; Miller, Lindsey; Beltzer-Sweeney, Alexander; Shilts, Trey; Stojimirovic, Irena

2018-04-01

Research team PRSM reports astrometric measurements of the double star system WDS 15379+3006 (STF 1963AB, STF 1963AC) obtained using the iTelescope Network. By performing CCD astrometry, the team determined a position angle of 298.4° ± 0.1° with an angular separation of 05. 28" ± 0.1" for STF 1963AB, and a position angle of 116.1° ± 0.1° with an angular separation of 32.35" ± 0.1" for STF 1963AC. The angular separation and position angle have changed from previous measurements.

Hamiltonian methods of modeling and control of AC microgrids with spinning machines and inverters

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

Matthews, Ronald C.; Weaver, Wayne W.; Robinett, Rush D.

This study presents a novel approach to the modeling and control of AC microgrids that contain spinning machines, power electronic inverters and energy storage devices. The inverters in the system can adjust their frequencies and power angles very quickly, so the modeling focuses on establishing a common reference frequency and angle in the microgrid based on the spinning machines. From this dynamic model, nonlinear Hamiltonian surface shaping and power flow control method is applied and shown to stabilize. From this approach the energy flow in the system is used to show the energy storage device requirements and limitations for themore » system. This paper first describes the model for a single bus AC microgrid with a Hamiltonian control, then extends this model and control to a more general class of multiple bus AC microgrids. Finally, simulation results demonstrate the efficacy of the approach in stabilizing and optimization of the microgrid.« less

Hamiltonian methods of modeling and control of AC microgrids with spinning machines and inverters

DOE PAGES

Matthews, Ronald C.; Weaver, Wayne W.; Robinett, Rush D.; ...

2017-12-22

This study presents a novel approach to the modeling and control of AC microgrids that contain spinning machines, power electronic inverters and energy storage devices. The inverters in the system can adjust their frequencies and power angles very quickly, so the modeling focuses on establishing a common reference frequency and angle in the microgrid based on the spinning machines. From this dynamic model, nonlinear Hamiltonian surface shaping and power flow control method is applied and shown to stabilize. From this approach the energy flow in the system is used to show the energy storage device requirements and limitations for themore » system. This paper first describes the model for a single bus AC microgrid with a Hamiltonian control, then extends this model and control to a more general class of multiple bus AC microgrids. Finally, simulation results demonstrate the efficacy of the approach in stabilizing and optimization of the microgrid.« less

Mitigation of commutation failures in LCC-HVDC systems based on superconducting fault current limiters

NASA Astrophysics Data System (ADS)

Lee, Jong-Geon; Khan, Umer Amir; Lee, Ho-Yun; Lim, Sung-Woo; Lee, Bang-Wook

2016-11-01

Commutation failure in line commutated converter based HVDC systems cause severe damages on the entire power grid system. For LCC-HVDC, thyristor valves are turned on by a firing signal but turn off control is governed by the external applied AC voltage from surrounding network. When the fault occurs in AC system, turn-off control of thyristor valves is unavailable due to the voltage collapse of point of common coupling (PCC), which causes the commutation failure in LCC-HVDC link. Due to the commutation failure, the power transfer interruption, dc voltage drop and severe voltage fluctuation in the AC system could be occurred. In a severe situation, it might cause the protection system to block the valves. In this paper, as a solution to prevent the voltage collapse on PCC and to limit the fault current, the application study of resistive superconducting fault current limiter (SFCL) on LCC-HVDC grid system was performed with mathematical and simulation analyses. The simulation model was designed by Matlab/Simulink considering Haenam-Jeju HVDC power grid in Korea which includes conventional AC system and onshore wind farm and resistive SFCL model. From the result, it was observed that the application of SFCL on LCC-HVDC system is an effective solution to mitigate the commutation failure. And then the process to determine optimum quench resistance of SFCL which enables the recovery of commutation failure was deeply investigated.

AC losses in horizontally parallel HTS tapes for possible wireless power transfer applications

NASA Astrophysics Data System (ADS)

Shen, Boyang; Geng, Jianzhao; Zhang, Xiuchang; Fu, Lin; Li, Chao; Zhang, Heng; Dong, Qihuan; Ma, Jun; Gawith, James; Coombs, T. A.

2017-12-01

This paper presents the concept of using horizontally parallel HTS tapes with AC loss study, and the investigation on possible wireless power transfer (WPT) applications. An example of three parallel HTS tapes was proposed, whose AC loss study was carried out both from experiment using electrical method; and simulation using 2D H-formulation on the FEM platform of COMSOL Multiphysics. The electromagnetic induction around the three parallel tapes was monitored using COMSOL simulation. The electromagnetic induction and AC losses generated by a conventional three turn coil was simulated as well, and then compared to the case of three parallel tapes with the same AC transport current. The analysis demonstrates that HTS parallel tapes could be potentially used into wireless power transfer systems, which could have lower total AC losses than conventional HTS coils.

Increased levels of IAA are required for system 2 ethylene synthesis causing fruit softening in peach (Prunus persica L. Batsch)

PubMed Central

Tatsuki, Miho

2013-01-01

The fruit of melting-flesh peach (Prunus persica L. Batsch) cultivars produce high levels of ethylene caused by high expression of PpACS1 (an isogene of 1-aminocyclopropane-1-carboxylic acid synthase), resulting in rapid fruit softening at the late-ripening stage. In contrast, the fruit of stony hard peach cultivars do not soften and produce little ethylene due to low expression of PpACS1. To elucidate the mechanism for suppressing PpACS1 expression in stony hard peaches, a microarray analysis was performed. Several genes that displayed similar expression patterns as PpACS1 were identified and shown to be indole-3-acetic acid (IAA)-inducible genes (Aux/IAA, SAUR). That is, expression of IAA-inducible genes increased at the late-ripening stage in melting flesh peaches; however, these transcripts were low in mature fruit of stony hard peaches. The IAA concentration increased suddenly just before harvest time in melting flesh peaches exactly coinciding with system 2 ethylene production. In contrast, the IAA concentration did not increase in stony hard peaches. Application of 1-naphthalene acetic acid, a synthetic auxin, to stony hard peaches induced a high level of PpACS1 expression, a large amount of ethylene production and softening. Application of an anti-auxin, α-(phenylethyl-2-one)-IAA, to melting flesh peaches reduced levels of PpACS1 expression and ethylene production. These observations indicate that suppression of PpACS1 expression at the late-ripening stage of stony hard peach may result from a low level of IAA and that a high concentration of IAA is required to generate a large amount of system 2 ethylene in peaches. PMID:23364941

Applying spatio-temporal models to assess variations across health care areas and regions: Lessons from the decentralized Spanish National Health System.

PubMed

Librero, Julián; Ibañez, Berta; Martínez-Lizaga, Natalia; Peiró, Salvador; Bernal-Delgado, Enrique

2017-01-01

To illustrate the ability of hierarchical Bayesian spatio-temporal models in capturing different geo-temporal structures in order to explain hospital risk variations using three different conditions: Percutaneous Coronary Intervention (PCI), Colectomy in Colorectal Cancer (CCC) and Chronic Obstructive Pulmonary Disease (COPD). This is an observational population-based spatio-temporal study, from 2002 to 2013, with a two-level geographical structure, Autonomous Communities (AC) and Health Care Areas (HA). The Spanish National Health System, a quasi-federal structure with 17 regional governments (AC) with full responsibility in planning and financing, and 203 HA providing hospital and primary care to a defined population. A poisson-log normal mixed model in the Bayesian framework was fitted using the INLA efficient estimation procedure. The spatio-temporal hospitalization relative risks, the evolution of their variation, and the relative contribution (fraction of variation) of each of the model components (AC, HA, year and interaction AC-year). Following PCI-CCC-CODP order, the three conditions show differences in the initial hospitalization rates (from 4 to 21 per 10,000 person-years) and in their trends (upward, inverted V shape, downward). Most of the risk variation is captured by phenomena occurring at the HA level (fraction variance: 51.6, 54.7 and 56.9%). At AC level, the risk of PCI hospitalization follow a heterogeneous ascending dynamic (interaction AC-year: 17.7%), whereas in COPD the AC role is more homogenous and important (37%). In a system where the decisions loci are differentiated, the spatio-temporal modeling allows to assess the dynamic relative role of different levels of decision and their influence on health outcomes.

AC loss in YBCO coated conductors at high dB/dt measured using a spinning magnet calorimeter (stator testbed environment)

NASA Astrophysics Data System (ADS)

Murphy, J. P.; Gheorghiu, N. N.; Bullard, T.; Haugan, T.; Sumption, M. D.; Majoros, M.; Collings, E. W.

2017-09-01

A new facility for the measurement of AC loss in superconductors at high dB/dt has been developed. The test device has a spinning rotor consisting of permanent magnets arranged in a Halbach array; the sample, positioned outside of this, is exposed to a time varying AC field with a peak radial field of 0.566 T. At a rotor speed of 3600 RPM the frequency of the AC field is 240 Hz, the radial dB/dt is 543 T/s and the tangential dB/dt is 249 T/s. Loss is measured using nitrogen boiloff from a double wall calorimeter feeding a gas flow meter. The system is calibrated using power from a known resistor. YBCO tape losses were measured in the new device and compared to the results from a solenoidal magnet AC loss system measurement of the same samples (in this latter case measurements were limited to a field of amplitude 0.1 T and a dB/dt of 100 T/s). Solenoidal magnet system AC loss measurements taken on a YBCO sample agreed with the Brandt loss expression associated with a 0-0.1 T Ic of 128 A. Subsequently, losses for two more YBCO tapes nominally identical to the first were individually measured in this spinning magnet calorimeter (SMC) machine with a Bmax of 0.566 T and dB/dt of up to 272 T/s. The losses, compared to a simplified version of the Brandt expression, were consistent with the average Ic expected for the tape in the 0-0.5 T range at 77 K. The eddy current contribution was consistent with a 77 K residual resistance ratio, RR, of 4.0. The SMC results for these samples agreed to within 5%. Good agreement was also obtained between the results of the SMC AC loss measurement and the solenoidal magnet AC loss measurement on the same samples.

Neutrophil elastase increases MUC5AC mRNA and protein expression in respiratory epithelial cells.

PubMed

Voynow, J A; Young, L R; Wang, Y; Horger, T; Rose, M C; Fischer, B M

1999-05-01

Chronic neutrophil-predominant inflammation and hypersecretion of mucus are common pathophysiological features of cystic fibrosis, chronic bronchitis, and viral- or pollution-triggered asthma. Neutrophils release elastase, a serine protease, that causes increased mucin production and secretion. The molecular mechanisms of elastase-induced mucin production are unknown. We hypothesized that as part of this mechanism, elastase upregulates expression of a major respiratory mucin gene, MUC5AC. A549, a human lung carcinoma cell line that expresses MUC5AC mRNA and protein, and normal human bronchial epithelial cells in an air-liquid interface culture were stimulated with neutrophil elastase. Neutrophil elastase increased MUC5AC mRNA levels in a time-dependent manner in both cell culture systems. Neutrophil elastase treatment also increased MUC5AC protein levels in A549 cells. The mechanism of MUC5AC gene regulation by elastase was determined in A549 cells. The induction of MUC5AC gene expression required serine protease activity; other classes of proteases had no effect on MUC5AC gene expression. Neutrophil elastase increased MUC5AC mRNA levels by enhancing mRNA stability. This is the first report of mucin gene regulation by this mechanism.

Analytical Chemistry in Russia.

PubMed

Zolotov, Yuri

2016-09-06

Research in Russian analytical chemistry (AC) is carried out on a significant scale, and the analytical service solves practical tasks of geological survey, environmental protection, medicine, industry, agriculture, etc. The education system trains highly skilled professionals in AC. The development and especially manufacturing of analytical instruments should be improved; in spite of this, there are several good domestic instruments and other satisfy some requirements. Russian AC has rather good historical roots.

An AC modulated near infrared gain calibration system for a "Violin-Mode" transimpedance amplifier, intended for advanced LIGO suspensions.

PubMed

Lockerbie, N A; Tokmakov, K V

2016-07-01

The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a "tall-thin" rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse "Violin-Mode" vibrations of such a fibre, via the oscillatory movement of the shadow cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor's DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor's more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz-300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m(-1) was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio of 922.5 for this sensor, at 500 Hz, translated into a maximum Violin-Mode (AC) responsivity of (1.16 ± 0.05) MV m(-1), at that frequency.

Antitumor efficacy and tolerability of systemically administered gallium acetylacetonate-loaded gelucire-stabilized nanoparticles.

PubMed

Wehrung, Daniel; Bi, Lipeng; Geldenhuys, Werner J; Oyewumi, Moses O

2013-06-01

The widespread clinical success with most gallium compounds in cancer therapy is markedly hampered by lack of tumor specific accumulation, poor tumor permeability and undesirable toxicity to healthy tissues. The aim of this work was to investigate for the first time antitumor mechanism of a new gallium compound (gallium acetylacetonate; GaAcAc) while assessing effectiveness of gelucire-stabilized nanoparticles (NPs) for potential application in gallium-based lung cancer therapy. NPs loaded with GaAcAc (Ga-NPs) were prepared using mixtures of cetyl alcohol with Gelucire 44/14 (Ga-NP-1) or Gelucire 53/13 (Ga-NP-2) as matrix materials. Of special note from this work is the direct evidence of involvement of microtubule disruption in antitumor effects of GaAcAc on human lung adenocarcinoma (A549). In-vivo tolerability studies were based on plasma ALT, creatinine levels and histopathological examination of tissues. The superior in-vivo antitumor efficacy of Ga-NPs over GaAcAc was depicted in marked reduction of tumor weight and tumor volume as well as histological assessment of excised tumors. Compared to free GaAcAc, Ga-NPs showed a 3-fold increase in tumor-to-blood gallium concentrations with minimized overall exposure to healthy tissues. Overall, enhancement of antitumor effects of GaAcAc by gelucire-stabilized NPs coupled with reduced exposure of healthy tissues to gallium would likely ensure desired therapeutic outcomes and safety of gallium-based cancer treatment.

Metabolism of 6-nitrochrysene by intestinal microflora

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

Manning, B.W.; Campbell, W.L.; Franklin, W.

1988-01-01

Since bacterial nitroreduction may play a critical role in the activation of nitropolycyclic aromatic hydrocarbons, we have used batch and semicontinuous culture systems to determine the ability of intestinal microflora to metabolize the carcinogen 6-nitrochrysene (6-NC). 6-NC was metabolized by the intestinal microflora present in the semicontinuous culture system to 6-aminochrysene (6-AC), N-formyl-6-aminochrysene (6-FAC), and 6-nitrosochrysene (6-NOC). These metabolites were isolated and identified by high-performance liquid chromatography, mass spectrometry, and UV-visible spectrophotometry and compared with authentic compounds. Almost all of the 6-NC was metabolized after 10 days. Nitroreduction of 6-NC to 6-AC was rapid; the 6-AC concentration reached a maximummore » at 48 h. The ratio of the formation of 6-AC to 6-FAC to 6-NOC at 48 h was 93.4:6.3:0.3. Interestingly, compared with results in the semicontinuous culture system, the only metabolite detected in the batch studies was 6-AC. The rate of nitroreduction differed among human, rat, and mouse intestinal microflora, with human intestinal microflora metabolizing 6-NC to the greatest extent. Since 6-AC has been shown to be carcinogenic in mice and since nitroso derivatives of other nitropolycyclic aromatic hydrocarbons are biologically active, our results suggest that the intestinal microflora has the enzymatic capacity to generate genotoxic compounds and may play an important role in the carcinogenicity of 6-NC.« less

Remediation of organochlorine pesticides contaminated lake sediment using activated carbon and carbon nanotubes.

PubMed

Hua, Shan; Gong, Ji-Lai; Zeng, Guang-Ming; Yao, Fu-Bing; Guo, Min; Ou, Xiao-Ming

2017-06-01

Organochlorine pesticides (OCPs) in sediment were a potential damage for humans and ecosystems. The aim of this work was to determine the effectiveness of carbon materials remedy hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethanes (DDTs) in sediment. Two different carbon materials including activated carbon (AC) and multi-walled carbon nanotubes (MWCNTs) were used in the present research. Sediment treated with 2 wt% AC and MWCNTs after 150 d contact showed 97%, and 75% reduction for HCH, and 93% and 59% decrease for DDTs in aqueous equilibrium concentration, respectively. Similarly, the reduction efficiencies of DDT and HCH uptake by semipermeable membrane devices (SPMDs) treated with AC (MWCNTs) were 97% (75%) and 92% (63%), respectively under the identical conditions. Furthermore, for 2 wt% AC (MWCNTs) system, a reduction of XAD beads uptake up to 87% (52%) and 73% (67%) was obtained in HCH and DDT flux to overlying water in quiescent system. Adding MWCNTs to contaminated sediment did not significantly decrease aqueous equilibrium concentration and DDTs and HCH availability in SPMDs compared to AC treatment. A series of results indicated that AC had significantly higher remediation efficiency towards HCH and DDTs in sediment than MWCNTs. Additionally, the removal efficiencies of two organic pollutants improved with increasing material doses and contact times. The greater effectiveness of AC was attributed to its greater specific surface area, which was favorable for binding contaminants. These results highlighted the potential for using AC as in-situ sorbent amendments for sediment remediation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solar Sail Attitude Control System for the NASA Near Earth Asteroid Scout Mission

NASA Technical Reports Server (NTRS)

Orphee, Juan; Diedrich, Ben; Stiltner, Brandon; Becker, Chris; Heaton, Andrew

2017-01-01

An Attitude Control System (ACS) has been developed for the NASA Near Earth Asteroid (NEA) Scout mission. The NEA Scout spacecraft is a 6U cubesat with an eighty-six square meter solar sail for primary propulsion that will launch as a secondary payload on the Space Launch System (SLS) Exploration Mission 1 (EM-1) and rendezvous with a target asteroid after a two year journey, and will conduct science imagery. The spacecraft ACS consists of three major actuating subsystems: a Reaction Wheel (RW) control system, a Reaction Control System (RCS), and an Active Mass Translator (AMT) system. The reaction wheels allow fine pointing and higher rates with low mass actuators to meet the science, communication, and trajectory guidance requirements. The Momentum Management System (MMS) keeps the speed of the wheels within their operating margins using a combination of solar torque and the RCS. The AMT is used to adjust the sign and magnitude of the solar torque to manage pitch and yaw momentum. The RCS is used for initial de-tumble, performing a Trajectory Correction Maneuver (TCM), and performing momentum management about the roll axis. The NEA Scout ACS is able to meet all mission requirements including attitude hold, slews, pointing for optical navigation and pointing for science with margin and including flexible body effects. Here we discuss the challenges and solutions of meeting NEA Scout mission requirements for the ACS design, and present a novel implementation of managing the spacecraft Center of Mass (CM) to trim the solar sail disturbance torque. The ACS we have developed has an applicability to a range of potential missions and does so in a much smaller volume than is traditional for deep space missions beyond Earth.

Free piston variable-stroke linear-alternator generator

DOEpatents

Haaland, C.M.

1998-12-15

A free-piston variable stroke linear-alternator AC power generator for a combustion engine is described. An alternator mechanism and oscillator system generates AC current. The oscillation system includes two oscillation devices each having a combustion cylinder and a flying turnbuckle. The flying turnbuckle moves in accordance with the oscillation device. The alternator system is a linear alternator coupled between the two oscillation devices by a slotted connecting rod. 8 figs.

Kinetics of gas phase formic acid decomposition on platinum single crystal and polycrystalline surfaces

NASA Astrophysics Data System (ADS)

Detwiler, Michael D.; Milligan, Cory A.; Zemlyanov, Dmitry Y.; Delgass, W. Nicholas; Ribeiro, Fabio H.

2016-06-01

Formic acid dehydrogenation turnover rates (TORs) were measured on Pt(111), Pt(100), and polycrystalline Pt foil surfaces at a total pressure of 800 Torr between 413 and 513 K in a batch reactor connected to an ultra-high vacuum (UHV) system. The TORs, apparent activation energies, and reaction orders are not sensitive to the structure of the Pt surface, within the precision of the measurements. CO introduced into the batch reactor depressed the formic acid dehydrogenation TOR and increased the reaction's apparent activation energies on Pt(111) and Pt(100), consistent with behavior predicted by the Temkin equation. Two reaction mechanisms were explored which explain the formic acid decomposition mechanism on Pt, both of which include dissociative adsorption of formic acid, rate limiting formate decomposition, and quasi-equilibrated hydrogen recombination and CO adsorption. No evidence was found that catalytic supports used in previous studies altered the reaction kinetics or mechanism.

Structural and magnetic properties of self-assembled cobalt on porous silicon; experimental and micromagnetic investigations

NASA Astrophysics Data System (ADS)

Saidani, M.; Belkacem, W.; Bessais, L.; Mliki, N.

2017-08-01

In this paper, we report on self-assembled Co nanoparticles deposited in and on porous silicon (PS) matrix by using UHV evaporation. Four samples were prepared by varying the Co deposited thickness (t = 3, 5, 7 and 10 nm). All samples have been investigated by means of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Physical Properties Measurement System (PPMS). The increase of t has induced an increase of the nanoparticle diameter from 3 nm to about 150 nm. Referring to the magnetic characterizations, this increase has been followed by a single to multi-domain transition. Therefore, this has been evidenced by a switching from superparamagnetism to purely ferromagnetism accompanied by a change in the magnetic reversal dynamics. Thus, by performing micromagnetic calculation, we have shown that a transition from the uniform rotation to vortex state occurs at a critical diameter of about 55 nm.

Mechanism of growth of the Ge wetting layer upon exposure of Si(100)-2 x 1 to GeH4.

PubMed

Liu, Chie-Sheng; Chou, Li-Wei; Hong, Lu-Sheng; Jiang, Jyh-Chiang

2008-04-23

This paper describes the initial reaction kinetics of Ge deposition after exposure of Si(100)-2 x 1 to GeH4 in a UHV-CVD system. The rate of Ge growth, especially at the wetting layer stage, was investigated using in situ X-ray photoelectron spectroscopy to measure the Ge signal at the onset of deposition. A kinetic analysis of the initial growth of the Ge wetting layer at temperatures ranging from 698 to 823 K revealed an activation energy of 30.7 kcal/mol. Density functional theory calculations suggested that opening of the Si dimer--with a closely matching energy barrier of 29.7 kcal/mol, following hydrogen atom migration--was the rate controlling step for the incorporation of a GeH2 unit into the lattice to complete the growth of the Ge wetting layer after dissociative adsorption of GeH4.

Quantifying interactions between accommodation and vergence in a binocularly normal population.

PubMed

Sweeney, Laura E; Seidel, Dirk; Day, Mhairi; Gray, Lyle S

2014-12-01

Stimulation of the accommodation system results in a response in the vergence system via accommodative vergence cross-link interactions, and stimulation of the vergence system results in an accommodation response via vergence accommodation cross-link interactions. Cross-link interactions are necessary in order to ensure simultaneous responses in the accommodation and vergence systems. The crosslink interactions are represented most comprehensively by the response AC/A (accommodative vergence) and CA/C (vergence accommodation) ratios, although the stimulus AC/A ratio is measured clinically, and the stimulus CA/C ratio is seldom measured in clinical practice. The present study aims to quantify both stimulus and response AC/A and CA/C ratios in a binocularly normal population, and determine the relationship between them. 25 Subjects (mean ± SD age 21.0 ± 1.9 years) were recruited from the university population. A significant linear relationship was found between the stimulus and response ratios, for both AC/A (r² = 0.96, p < 0.001) and CA/C ratios (r² = 0.40, p < 0.05). Good agreement was found between the stimulus and response AC/A ratios (95% CI -0.06 to 0.24 MA/D). Stimulus and response CA/C ratios are linearly related. Stimulus CA/C ratios were higher than response ratios at low values, and lower than response ratios at high values (95% CI -0.46 to 0.42 D/MA). Agreement between stimulus and response CA/C ratios is poorer than that found for AC/A ratios due to increased variability in vergence responses when viewing the Gaussian blurred target. This study has shown that more work is needed to refine the methodology of CA/C ratio measurement.

The stretching of Hercules

NASA Astrophysics Data System (ADS)

Deason, A. J.; Belokurov, V.; Evans, N. W.; Watkins, L. L.; Fellhauer, M.

2012-09-01

We present VLT/FORS2 spectroscopy of candidate blue horizontal branch (BHB) stars in the vicinity of the Hercules ultrafaint dwarf galaxy. We identify eight convincing Hercules BHB members, and a further five stars with similar systemic velocities to that of Hercules, but ˜0.5 kpc from the centre of the galaxy along its major axis. It is likely that these stars once belonged to Hercules, but have been tidally stripped and are now unbound. We emphasize the usefulness of looking for any gradient in the systemic velocity of this stretched system, which would further support our interpretation of the origin of its elongated and distended morphology. E-mail: ajd75@ast.cam.ac.uk (AJD); vasily@ast.cam.ac.uk (VB); nwe@ast.cam.ac.uk (NWE)

Note: Fabrication and characterization of molybdenum tips for scanning tunneling microscopy and spectroscopy

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

Carrozzo, P.; Tumino, F.; Facibeni, A.

We present a method for the preparation of bulk molybdenum tips for Scanning Tunneling Microscopy and Spectroscopy and we assess their potential in performing high resolution imaging and local spectroscopy by measurements on different single crystal surfaces in UHV, namely, Au(111), Si(111)-7 × 7, and titanium oxide 2D ordered nanostructures supported on Au(111). The fabrication method is versatile and can be extended to other metals, e.g., cobalt.

A versatile substrate design for LEED and AES studies in uhv.

NASA Technical Reports Server (NTRS)

Holloway, P. H.; Hudson, J. B.

1972-01-01

A substrate design is described that incorporates a single crystal disk into an electrically isolated, electron bombardment heated mount. Electron and photon leakage from the bombarding filament are prevented, and LEED and AES may be used at elevated temperatures. A cold finger, thermally coupled to the mount, decreases the time lost between cleaning the crystal and cooling it to the desired observation temperature. The cold finger also allows observation at temperatures below ambient.

Ambient atomic resolution atomic force microscopy with qPlus sensors: Part 1.

PubMed

Wastl, Daniel S

2017-01-01

Atomic force microscopy (AFM) is an enormous tool to observe nature in highest resolution and understand fundamental processes like friction and tribology on the nanoscale. Atomic resolution in highest quality was possible only in well-controlled environments like ultrahigh vacuum (UHV) or controlled buffer environments (liquid conditions) and more specified for long-term high-resolution analysis at low temperatures (∼4 K) in UHV where drift is nearly completely absent. Atomic resolution in these environments is possible and is widely used. However, in uncontrolled environments like air, with all its pollutants and aerosols, unspecified thin liquid films as thin as a single molecular water-layer of 200 pm or thicker condensation films with thicknesses up to hundred nanometer, have been a problem for highest resolution since the invention of the AFM. The goal of true atomic resolution on hydrophilic as well as hydrophobic samples was reached recently. In this manuscript we want to review the concept of ambient AFM with atomic resolution. The reader will be introduced to the phenomenology in ambient conditions and the problems will be explained and analyzed while a method for scan parameter optimization will be explained. Recently developed concepts and techniques how to reach atomic resolution in air and ultra-thin liquid films will be shown and explained in detail, using several examples. Microsc. Res. Tech. 80:50-65, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Exploiting basic principles to control the selectivity of the vapor phase catalytic oxidative cross-coupling of primary alcohols over nanoporous gold catalysts

DOE PAGES

Wang, Lu-Cun; Stowers, Kara J.; Zugic, Branko; ...

2015-05-20

It is important to achieve high selectivity for high volume chemical synthesis in order to lower energy consumption through reduction in waste. Here, we report the selective synthesis of methyl esters—methyl acetate and methyl butyrate—through catalytic O 2-assisted cross-coupling of methanol with ethanol or 1-butanol using activated, support-free nanoporous gold (npAu). Both well-controlled studies on ingots in UHV and experiments under ambient pressure catalytic conditions on both ingots and microspherical hollow shell catalysts reveal guiding principles for controlling selectivity. Under UHV conditions, the ester products of the cross-coupling of methanol with both ethanol and 1-butanol evolve near room temperature inmore » temperature-programmed reaction studies, indicating that the reactions occur facilely. Furthermore, under steady-state catalytic operation, high stable activity was observed for cross-coupling in flowing gaseous reactant mixtures at atmospheric pressure and 423 K with negligible combustion. Optimum selectivity for cross-coupling is obtained in methanol-rich mixtures due to a combination of two factors: (1) the relative coverage of the respective alkoxys and (2) the relative facility of their β-H elimination. The relative coverage of the alkoxys is governed by van der Waal’s interactions between the alkyl groups and the surface; here, we demonstrate the importance of these weak interactions in a steady-state catalytic process.« less

NOVEL CHAMBER DESIGN FOR AN IN-VACUUM CRYO-COOLED MINI-GAP UNDULATOR.

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

HU, J.-P.; FOERSTER, C.L.; SKARITKA, J.R.

2006-05-24

A stainless steel, Ultra-High Vacuum (UHV) chamber, featuring a large vertical rectangular port (53''W by 16''H), has been fabricated to house the one-meter magnet assembly of a newly installed undulator insertion device for beamline X-25 at the National Synchrotron Light Source. To achieve UHV, the new chamber is equipped with a differential ion pump, NEG pump, nude ion gauge, residual gas analyzer, and an all metal roughing valve. Temperature of the magnet assembly is maintained below 90 C during vacuum bake. The large rectangular port cover is sealed to the main flange of the chamber using a one-piece flat aluminummore » gasket and special sealing surfaces developed exclusively by Nor-Cal Products, Inc. The large flange provides easy access to the gap of the installed magnet girders for in situ magnetic measurements and shimming. Special window ports were designed into the cover and chamber for manipulation of optical micrometers external to the chamber to provide precise measurements of the in-vacuum magnet gap. The vacuum chamber assembly features independently vacuum-isolated feedthroughs that can be used for either water-or-cryogenic refrigeration-cooling of the monolithic magnet girders. This would allow for cryogenic-cooled permanent magnet operation and has been successfully tested within temperature range of +100 C to -150 C. Details of the undulator assembly for beamline X-25 is described in the paper.« less

Successful Cleaning and Study of Contamination of Si(001) in Ultrahigh Vacuum

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

Gheorghe, N. G.; Lungu, G. A.; Husanu, M. A.

2011-10-03

This paper presents the very first surface physics experiment performed in ultrahigh vacuum (UHV) in Romania, using a new molecular beam epitaxy (MBE) installation. Cleaning of a Si(001) wafer was achieved by using a very simple technique: sequences of annealing at 900-1000 deg. C in ultrahigh vacuum: low 10{sup -8} mbar, with a base pressure of 1.5x10{sup -10} mbar. The preparation procedure is quite reproducible and allows repeated cleaning of the Si(001) after contamination in ultrahigh vacuum. The Si(001) single crystal surface is characterized by low energy electron diffraction (LEED), reflection high energy electron diffraction (RHEED), and Auger electron spectroscopymore » (AES). The latter technique is utilized in order to investigate the sample contamination by the residual gas in the UHV chamber, as determined by a residual gas analyzer (RGA). Unambiguous assignment of oxidized and unoxidized silicon is provided; also, an important feature is that the LVV Auger peak at 90-92 eV cannot be solely attributed to clean Si (i.e. Si surrounded only by Si), but also to silicon atoms bounded with carbon. Even with a sum of partial pressures of oxygen and carbon containing molecules in the range of 5x10{sup -10} mbar, the sample is contaminated very quickly, having a (1/e) lifetime of about 76 minutes.« less

"Un-annealed and Annealed Pd Ultra-Thin Film on SiC Characterized by Scanning Probe Microscopy and X-ray Photoelectron Spectroscopy"

NASA Technical Reports Server (NTRS)

Lu, W. J.; Shi, D. T.; Elshot, K.; Bryant, E.; Lafate, K.; Chen, H.; Burger, A.; Collins, W. E.

1998-01-01

Pd/SiC has been used as a hydrogen and a hydrocarbon gas sensor operated at high temperature. UHV (Ultra High Vacuum)-Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) techniques were applied to study the relationship between the morphology and chemical compositions for Pd ultra-thin films on SiC (less than 30 angstroms) at different annealing temperatures. Pd ultra-thin film on 6H-SiC was prepared by the RF sputtering method. The morphology from UHV-STM and AFM shows that the Pd thin film was well deposited on SiC substrate, and the Pd was partially aggregated to round shaped participates at an annealing temperature of 300 C. At 400 C, the amount of surface participates decreases, and some strap shape participates appear. From XPS, Pd2Si was formed on the surface after annealing at 300 C, and all Pd reacted with SiC to form Pd2Si after annealing at 400 C. The intensity of the XPS Pd peak decreases enormously at 400 C. The Pd film diffused into SiC, and the Schottky barrier height has almost no changes. The work shows the Pd sicilides/SiC have the same electronic properties with Pd/SiC, and explains why the Pd/SiC sensor still responds to hydrogen at high operating temperatures.

X-Ray Photoelectron Spectroscopy and Ultrahigh Vacuum Contactless Capacitance-Voltage Characterization of Novel Oxide-Free InP Passivation Process Using a Silicon Surface Quantum Well

NASA Astrophysics Data System (ADS)

Takahashi, Hiroshi; Hashizume, Tamotsu; Hasegawa, Hideki

1999-02-01

In order to understand and optimize a novel oxide-free InP passivation process using a silicon surface quantum well, a detailed in situ X-ray photoelectron spectroscopy (XPS) and ultrahigh vacuum (UHV) contactless capacitance-voltage (C-V) study of the interface was carried out. Calculation of quantum levels in the silicon quantum well was performed on the basis of the band lineup of the strained Si3N4/Si/InP interface and the result indicated that the interface should become free of gap states when the silicon layer thickness is below 5 Å. Experimentally, such a delicate Si3N4/Si/InP structure was realized by partial nitridation of a molecular beam epitaxially (MBE) grown pseudomorphic silicon layer using an electron cyclotron resonance (ECR) N2 plasma. The progress of nitridation was investigated in detail by angle-resolved XPS. A newly developed UHV contactless C-V method realized in situ characterization of surface electronic properties of InP at each processing step for passivation. It was found that the interface state density decreased substantially into the 1010 cm-2 eV-1 range by optimizing the nitridation process of the silicon layer. It was concluded that both the surface bond termination and state removal by quantum confinement are responsible for the NSS reduction.

Low-Pressure Long-Term Xenon Storage for Electric Propulsion

NASA Technical Reports Server (NTRS)

Back, Dwight D.; Ramos, Charlie; Meyer, John A.

2001-01-01

This Phase 2 effort demonstrated an alternative Xe storage and regulation system using activated carbon (AC) as a secondary storage media (ACSFR). This regulator system is nonmechanical, simple, inexpensive, and lighter. The ACSFR system isolates the thruster from the compressed gas tank, and allows independent multiple setpoint thruster operation. The flow using an ACSFR can also be throttled by applying increments in electrical power. Primary storage of Xe by AC is not superior to compressed gas storage with regard to weight, but AC storage can provide volume reduction, lower pressures in space, and potentially in situ Xe purification. With partial fill designs, a primary AC storage vessel for Xe could also eliminate problems with two-phase storage and regulate pressure. AC could also be utilized in long-term large quantity storage of Xe serving as a compact capture site for boil-off. Several Xe delivery ACSFR protocols between 2 and 45 sccm, and 15 min to 7 hr, were tested with an average flow variance of 1.2 percent, average power requirements of 5 W, and repeatability s of about 0.4 percent. Power requirements are affected by ACSFR bed sizing and flow rate/ duration design points, and these flow variances can be reduced by optimizing PID controller parameters.

Test plan for performance testing of the Eaton AC-3 electric vehicle

NASA Astrophysics Data System (ADS)

Crumley, R.; Heiselmann, H. W.

1985-04-01

An alternating current (ac) propulsion system for an electric vehicle was developed and tested. The test bed vehicle is a modified 1981 Mercury Lynx. The test plan was prepared specifically for the third modification to this test bed and identified as the Eaton AC-3. The scope of the testing done on the Eaton AC-3 includes coastdown and dynamometer tests but does not include environmental, on-road, or track testing. Coastdown testing is performed in accordance with SAE J-1263 (SAE Recommended Practice for Road Load Measurement and Dynamometer Simulation Using Coastdown Techniques).

Numerical simulation of the dielectrophoretic concentration of DNA particles and the effect of AC electroosmosis

NASA Astrophysics Data System (ADS)

Loucaides, N. G.; Georghiou, G. E.; Charalambous, C. D.

2007-04-01

The dielectrophoretic concentration of DNA particles suspended in a solution is investigated in a system of parallel electrodes, where the particles are attracted to the edges of the electrodes by positive dielectrophoresis. The AC electroosmotic motion of the fluid is also considered, as well as the diffusion of the particles, using the solution of the Smoluchowski equation. The results examine the effect of AC electroosmosis in steady state dielectrophoretic concentration of particles, by demonstrating that AC electroosmosis significantly reduces the dielectrophoretic concentration at the edges and moves the particles towards the electrode centres.

A dry-cooled AC quantum voltmeter

NASA Astrophysics Data System (ADS)

Schubert, M.; Starkloff, M.; Peiselt, K.; Anders, S.; Knipper, R.; Lee, J.; Behr, R.; Palafox, L.; Böck, A. C.; Schaidhammer, L.; Fleischmann, P. M.; Meyer, H.-G.

2016-10-01

The paper describes a dry-cooled AC quantum voltmeter system operated up to kilohertz frequencies and 7 V rms. A 10 V programmable Josephson voltage standard (PJVS) array was installed on a pulse tube cooler (PTC) driven with a 4 kW air-cooled compressor. The operating margins at 70 GHz frequencies were investigated in detail and found to exceed 1 mA Shapiro step width. A key factor for the successful chip operation was the low on-chip power consumption of 65 mW in total. A thermal interface between PJVS chip and PTC cold stage was used to avoid a significant chip overheating. By installing the cryocooled PJVS array into an AC quantum voltmeter setup, several calibration measurements of dc standards and calibrator ac voltages up to 2 kHz frequencies were carried out to demonstrate the full functionality. The results are discussed and compared to systems with standard liquid helium cooling. For dc voltages, a direct comparison measurement between the dry-cooled AC quantum voltmeter and a liquid-helium based 10 V PJVS shows an agreement better than 1 part in 1010.

Combining a Toggle Switch and a Repressilator within the AC-DC Circuit Generates Distinct Dynamical Behaviors.

PubMed

Perez-Carrasco, Ruben; Barnes, Chris P; Schaerli, Yolanda; Isalan, Mark; Briscoe, James; Page, Karen M

2018-04-25

Although the structure of a genetically encoded regulatory circuit is an important determinant of its function, the relationship between circuit topology and the dynamical behaviors it can exhibit is not well understood. Here, we explore the range of behaviors available to the AC-DC circuit. This circuit consists of three genes connected as a combination of a toggle switch and a repressilator. Using dynamical systems theory, we show that the AC-DC circuit exhibits both oscillations and bistability within the same region of parameter space; this generates emergent behaviors not available to either the toggle switch or the repressilator alone. The AC-DC circuit can switch on oscillations via two distinct mechanisms, one of which induces coherence into ensembles of oscillators. In addition, we show that in the presence of noise, the AC-DC circuit can behave as an excitable system capable of spatial signal propagation or coherence resonance. Together, these results demonstrate how combinations of simple motifs can exhibit multiple complex behaviors. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Selective Memory to Apoptotic Cell-Derived Self-Antigens with Implications for Systemic Lupus Erythematosus Development.

PubMed

Duhlin, Amanda; Chen, Yunying; Wermeling, Fredrik; Sedimbi, Saikiran K; Lindh, Emma; Shinde, Rahul; Halaby, Marie Jo; Kaiser, Ylva; Winqvist, Ola; McGaha, Tracy L; Karlsson, Mikael C I

2016-10-01

Autoimmune diseases are characterized by pathogenic immune responses to self-antigens. In systemic lupus erythematosus (SLE), many self-antigens are found in apoptotic cells (ACs), and defects in removal of ACs from the body are linked to a risk for developing SLE. This includes pathological memory that gives rise to disease flares. In this study, we investigated how memory to AC-derived self-antigens develops and the contribution of self-memory to the development of lupus-related pathology. Multiple injections of ACs without adjuvant into wild-type mice induce a transient primary autoimmune response without apparent anti-nuclear Ab reactivity or kidney pathology. Interestingly, as the transient Ab response reached baseline, a single boost injection fully recalled the immune response to ACs, and this memory response was furthermore transferable into naive mice. Additionally, the memory response contains elements of pathogenicity, accompanied by selective memory to selective Ags. Thus, we provide evidence for a selective self-memory that underlies progression of the response to self-antigens with implications for SLE development therapy. Copyright © 2016 by The American Association of Immunologists, Inc.

Historical perspective and contemporary management of acute coronary syndromes: from MONA to THROMBINS2.

PubMed

Kline, Kristopher P; Conti, C Richard; Winchester, David E

2015-01-01

Acute coronary syndrome (ACS) remains a major burden on morbidity and mortality in the United States. Medical professionals and students often use the mnemonic 'MONA' (morphine, oxygen, nitroglycerin and aspirin) to recall treatments for ACS; however, this list of therapies is outdated. We provide a historical perspective on 'MONA,' attempt to uncover its origin in the medical literature, and demonstrate the myriad changes that have occurred over the last 50 years of ACS management. We have developed a novel mnemonic, 'THROMBINS2' (thienopyridines, heparin/enoxaparin, renin-angiotensin system blockers, oxygen, morphine, beta blocker, intervention, nitroglycerin, statin/salicylate) to help bedside clinicians recall all the elements of contemporary ACS management. We demonstrate the mortality benefit for each component of contemporary ACS management, correlating the continued improvement with historical data on mortality after myocardial infarction. We encourage providers to utilize this mnemonic to explore options and guide treatments in ACS patients.

Characterization of biological aerosol exposure risks from automobile air conditioning system.

PubMed

Li, Jing; Li, Mingzhen; Shen, Fangxia; Zou, Zhuanglei; Yao, Maosheng; Wu, Chang-yu

2013-09-17

Although use of automobile air conditioning (AC) was shown to reduce in-vehicle particle levels, the characterization of its microbial aerosol exposure risks is lacking. Here, both AC and engine filter dust samples were collected from 30 automobiles in four different geographical locations in China. Biological contents (bacteria, fungi, and endotoxin) were studied using culturing, high-throughput gene sequence, and Limulus amebocyte lysate (LAL) methods. In-vehicle viable bioaerosol concentrations were directly monitored using an ultraviolet aerodynamic particle sizer (UVAPS) before and after use of AC for 5, 10, and 15 min. Regardless of locations, the vehicle AC filter dusts were found to be laden with high levels of bacteria (up to 26,150 CFU/mg), fungi (up to 1287 CFU/mg), and endotoxin (up to 5527 EU/mg). More than 400 unique bacterial species, including human opportunistic pathogens, were detected in the filter dusts. In addition, allergenic fungal species were also found abundant. Surprisingly, unexpected fluorescent peaks around 2.5 μm were observed during the first 5 min use of AC, which was attributed to the reaerosolization of those filter-borne microbial agents. The information obtained here can assist in minimizing or preventing the respiratory allergy or infection risk from the use of automobile AC system.

The Feasibility of Applying AC Driven Low-Temperature Plasma for Multi-Cycle Detonation Initiation

NASA Astrophysics Data System (ADS)

Zheng, Dianfeng

2016-11-01

Ignition is a key system in pulse detonation engines (PDE). As advanced ignition methods, nanosecond pulse discharge low-temperature plasma ignition is used in some combustion systems, and continuous alternating current (AC) driven low-temperature plasma using dielectric barrier discharge (DBD) is used for the combustion assistant. However, continuous AC driven plasmas cannot be used for ignition in pulse detonation engines. In this paper, experimental and numerical studies of pneumatic valve PDE using an AC driven low-temperature plasma igniter were described. The pneumatic valve was jointly designed with the low-temperature plasma igniter, and the numerical simulation of the cold-state flow field in the pneumatic valve showed that a complex flow in the discharge area, along with low speed, was beneficial for successful ignition. In the experiments ethylene was used as the fuel and air as oxidizing agent, ignition by an AC driven low-temperature plasma achieved multi-cycle intermittent detonation combustion on a PDE, the working frequency of the PDE reached 15 Hz and the peak pressure of the detonation wave was approximately 2.0 MPa. The experimental verifications of the feasibility in PDE ignition expanded the application field of AC driven low-temperature plasma. supported by National Natural Science Foundation of China (No. 51176001)

Design and Integration of an All-Magnetic Attitude Control System for FASTSAT-HSV01's Multiple Pointing Objectives

NASA Technical Reports Server (NTRS)

DeKock, Brandon; Sanders, Devon; Vanzwieten, Tannen; Capo-Lugo, Pedro

2011-01-01

The FASTSAT-HSV01 spacecraft is a microsatellite with magnetic torque rods as it sole attitude control actuator. FASTSAT s multiple payloads and mission functions require the Attitude Control System (ACS) to maintain Local Vertical Local Horizontal (LVLH)-referenced attitudes without spin-stabilization, while the pointing errors for some attitudes be significantly smaller than the previous best-demonstrated for this type of control system. The mission requires the ACS to hold multiple stable, unstable, and non-equilibrium attitudes, as well as eject a 3U CubeSat from an onboard P-POD and recover from the ensuing tumble. This paper describes the Attitude Control System, the reasons for design choices, how the ACS integrates with the rest of the spacecraft, and gives recommendations for potential future applications of the work.

Histomorphology and innate immunity during the progression of osteoarthritis: Does synovitis affect cartilage degradation?

PubMed

Wang, Huan; Wang, Qingguo; Yang, Meijuan; Yang, Lili; Wang, Weili; Ding, Haobin; Zhang, Dong; Xu, Jing; Tang, Xuezhang; Ding, Haitao; Wang, Qingfu

2018-02-01

Osteoarthritis (OA) is a common chronic degenerative disease that affects all joints. At present, the pathological processes and mechanisms of OA are still unclear. Innate immunity, a key player in damage to the structure of the joint and the mechanism by which the host attempts to repair OA, affects all pathological stages of the disease. In the present study, our aim was to assess changes in innate immunity during the pathological processes of OA in articular cartilage (AC) and the synovial membrane (SM), which are the major structures in joints, and to systematically examine the histological changes in AC and SM in mild, moderate and severe cases of OA, in order to further speculate about the manner in which the interactions of AC and SM are facilitated by innate immunity. Histological methods (including HE and Safranin O-fast green staining), immunofluorescent double staining, TUNEL stain, and Western blots were used to assess the morphological changes within AC and SM tissues in healthy and mild, moderate, or severe OA rats. Our results showed that the damage to AC and SM within the joints progressively worsened in different degrees during the course of the disease, and that the innate immune system was closely involved in the AC and SM during each stage of OA. These findings also confirmed that SM may affect the pathological changes in AC through the innate immune system, and therefore affect the progress of OA. © 2017 Wiley Periodicals, Inc.

Co-digestion of concentrated black water and kitchen refuse in an accumulation system within the DESAR (decentralized sanitation and reuse) concept.

PubMed

Kujawa-Roeleveld, K; Elmitwalli, T; Gaillard, A; van Leeuwen, M; Zeeman, G

2003-01-01

Co-digestion of concentrated black water and kitchen refuse within the DESAR concept was the objective of this pilot research. The digestion took place in two, non-mixed accumulation reactors (AC1 and AC2) inoculated with digested primary sludge from a WWTP at a temperature of 20 degrees C for a period of around 150 days. Reactor AC1 was fed with a mixture of faeces, urine and kitchen refuse in the equivalent amount that one individual generates per day. The AC2 was fed with a mixture of faeces and kitchen refuse in the equivalent amount that two individuals produce per day. Some contribution of urine to AC2 was not to be avoided. Detailed characterisation of waste(water) was performed. The performance of the stratified reactor was followed by monitoring the reactor content for several reactors' heights as well as being based on the biogas production. In general the system exposed good process stability. The methanisation of 34 and 61% was obtained for AC1 and AC2 respectively. The biogas yield was 26.5 and 50.8 L/p/d for the respective reactors. Proper choice of inoculum as well as good buffering capacity did not lead to accumulation of VFA and an inhibitive effect due to relatively high ammonium concentration. The chosen process is a promising technology showing good process stability especially for high strength influent.

Apoptosis and Self-Destruct: A Contribution to Autonomic Agents?

NASA Technical Reports Server (NTRS)

Sterritt, Roy; Hinchey, Mike

2004-01-01

Autonomic Computing (AC), a self-managing systems initiative based on the biological metaphor of the autonomic nervous system, is increasingly gaining momentum as the way forward in designing reliable systems. Agent technologies have been identified as a key enabler for engineering autonomicity in systems, both in terms of retrofitting autonomicity into legacy systems and designing new systems. The AC initiative provides an opportunity to consider other biological systems and principles in seeking new design strategies. This paper reports on one such investigation; utilizing the apoptosis metaphor of biological systems to provide a dynamic health indicator signal between autonomic agents.

Research notes : pay adjustment system for AC pavements.

DOT National Transportation Integrated Search

1991-10-01

Oregon's use of statistical pay adjustments (contractor incentives) in AC pavements began in 1985 as part of a nationwide trend toward End Result Specifications (ERS's). Oregon State Highway Division (OSHD) management became concerned that the State ...

High-Performance AC Power Source by Applying Robust Stability Control Technology for Precision Material Machining

NASA Astrophysics Data System (ADS)

Chang, En-Chih

2018-02-01

This paper presents a high-performance AC power source by applying robust stability control technology for precision material machining (PMM). The proposed technology associates the benefits of finite-time convergent sliding function (FTCSF) and firefly optimization algorithm (FOA). The FTCSF maintains the robustness of conventional sliding mode, and simultaneously speeds up the convergence speed of the system state. Unfortunately, when a highly nonlinear loading is applied, the chatter will occur. The chatter results in high total harmonic distortion (THD) output voltage of AC power source, and even deteriorates the stability of PMM. The FOA is therefore used to remove the chatter, and the FTCSF still preserves finite system-state convergence time. By combining FTCSF with FOA, the AC power source of PMM can yield good steady-state and transient performance. Experimental results are performed in support of the proposed technology.

DC coupled Doppler radar physiological monitor.

PubMed

Zhao, Xi; Song, Chenyan; Lubecke, Victor; Boric-Lubecke, Olga

2011-01-01

One of the challenges in Doppler radar systems for physiological monitoring is a large DC offset in baseband outputs. Typically, AC coupling is used to eliminate this DC offset. Since the physiological signals of interest include frequency content near DC, it is not desirable to simply use AC coupling on the radar outputs. While AC coupling effectively removes DC offset, it also introduces a large time delay and distortion. This paper presents the first DC coupled IQ demodulator printed circuit board (PCB) design and measurements. The DC coupling is achieved by using a mixer with high LO to RF port isolation, resulting in a very low radar DC offset on the order of mV. The DC coupled signals from the PCB radar system were successfully detected with significant LNA gain without saturation. Compared to the AC coupled results, the DC coupled results show great advantages of less signal distortion and more accurate rate estimation.

Arthroscopic fixation of acute acromioclavicular joint disruption with TightRope™: Outcome and complications after minimum 2 (2-5) years follow-up.

PubMed

Zhang, Li-Feng; Yin, Bo; Hou, Su; Han, Bing; Huang, De-Fa

2017-01-01

To evaluate the midterm results of arthroscopic reconstruction of acute acromioclavicular (AC) joint disruption using TightRope™ system. We retrospectively assess the results of 24 patients of acute AC joint dislocation who were operated using TightRope system. Constant and University of California, Los Angeles (UCLA) scores and coracoclavicular distance were calculated pre- and postoperatively. Data was entered into MS excel and analyzed using the SPSS version 17. The mean follow-up was 39.45 months. Constant and UCLA scores were significantly increased postoperatively. Six patients had partial loss of reduction within 3-6 months and two patients had a failure of construct. Constant score was significantly lower in these patients. TightRope reconstruction of the AC joint is a reproducible and safe alternative to many other techniques of AC joint reconstruction. Early subluxation remains a concern and may reflect the need for technique modification.

Amorphous carbon for photovoltaics

NASA Astrophysics Data System (ADS)

Risplendi, Francesca; Grossman, Jeffrey C.

2015-03-01

All-carbon solar cells have attracted attention as candidates for innovative photovoltaic devices. Carbon-based materials such as graphene, carbon nanotubes (CNT) and amorphous carbon (aC) have the potential to present physical properties comparable to those of silicon-based materials with advantages such as low cost and higher thermal stability.In particular a-C structures are promising systems in which both sp2 and sp3 hybridization coordination are present in different proportions depending on the specific density, providing the possibility of tuning their optoelectronic properties and achieving comparable sunlight absorption to aSi. In this work we employ density functional theory to design suitable device architectures, such as bulk heterojunctions (BHJ) or pn junctions, consisting of a-C as the active layer material.Regarding BHJ, we study interfaces between aC and C nanostructures (such as CNT and fullerene) to relate their optoelectronic properties to the stoichiometry of aC. We demonstrate that the energy alignment between the a-C mobility edges and the occupied and unoccupied states of the CNT or C60 can be widely tuned by varying the aC density to obtain a type II interface.To employ aC in pn junctions we analyze the p- and n-type doping of a-C focusingon an evaluation of the Fermi level and work function dependence on doping.Our results highlight promising features of aC as the active layer material of thin-film solar cells.

Helio-geomagnetic influence in cardiological cases

NASA Astrophysics Data System (ADS)

Katsavrias, Ch.; Preka-Papadema, P.; Moussas, X.; Apostolou, Th.; Theodoropoulou, A.; Papadima, Th.

2013-01-01

The effects of the energetic phenomena of the Sun, flares and coronal mass ejections (CMEs) on the Earth's ionosphere-magnetosphere, through the solar wind, are the sources of the geomagnetic disturbances and storms collectively known as Space Weather. The research on the influence of Space Weather on biological and physiological systems is open. In this work we study the Space Weather impact on Acute Coronary Syndromes (ACS) distinguishing between ST-segment elevation acute coronary syndromes (STE-ACS) and non-ST-segment elevation acute coronary syndromes (NSTE-ACS) cases. We compare detailed patient records from the 2nd Cardiologic Department of the General Hospital of Nicaea (Piraeus, Greece) with characteristics of geomagnetic storms (DST), solar wind speed and statistics of flares and CMEs which cover the entire solar cycle 23 (1997-2007). Our results indicate a relationship of ACS to helio-geomagnetic activity as the maximum of the ACS cases follows closely the maximum of the solar cycle. Furthermore, within very active periods, the ratio NSTE-ACS to STE-ACS, which is almost constant during periods of low to medium activity, changes favouring the NSTE-ACS. Most of the ACS cases exhibit a high degree of association with the recovery phase of the geomagnetic storms; a smaller, yet significant, part was found associated with periods of fast solar wind without a storm.

The in vitro antibiotic release from anti-washout apatite cement using chitosan.

PubMed

Takechi, Masaaki; Miyamoto, Youji; Momota, Yukihiro; Yuasa, Tetsuya; Tatehara, Seikou; Nagayama, Masaru; Ishikawa, Kunio; Suzuki, Kazuomi

2002-10-01

The in vitro antibiotic release from anti-washout apatite cement using chitosan (aw-AC(chi)) was investigated in a preliminary evaluation. Flomoxef sodium was employed as the antibiotic and was incorporated into the powder phase aw-AC(chi) at up to 10%. The setting times were measured for aw-AC(chi) containing various amounts of flomoxef sodium. X-ray diffraction (XRD) analysis was also conducted for the identification of products. To evaluate the drug release profile, set aw-AC was immersed in saline and the released flomoxef sodium was determined at regular intervals. The setting time was prolonged slightly with the addition of flomoxef sodium. The difference at 10% flomoxef sodium (0% vs. 10%) was not significant (p>0.05), and can be negligible in clinic. The XRD analysis revealed that formation of hydroxyapatite (HAP) from aw-AC(chi) was reduced, even after 24 h, when the aw-AC(chi) contained flomoxef sodium at 8% or more. The flomoxef sodium release from aw-AC(chi) showed the typical profile observed in skeleton type drug delivery system (DDS). Changing the concentration of chitosan can control the rate of drug release from aw-AC. Therefore, we conclude that aw-AC(chi) is a good candidate for potential use as a DDS carrier that may be useful in surgical operations.

Comparative transcriptome analysis reveals distinct ethylene-independent regulation of ripening in response to low temperature in kiwifruit.

PubMed

Asiche, William O; Mitalo, Oscar W; Kasahara, Yuka; Tosa, Yasuaki; Mworia, Eric G; Owino, Willis O; Ushijima, Koichiro; Nakano, Ryohei; Yano, Kentaro; Kubo, Yasutaka

2018-03-21

Kiwifruit are classified as climacteric since exogenous ethylene (or its analogue propylene) induces rapid ripening accompanied by ethylene production under positive feedback regulation. However, most of the ripening-associated changes (Phase 1 ripening) in kiwifruit during storage and on-vine occur largely in the absence of any detectable ethylene. This ripening behavior is often attributed to basal levels of system I ethylene, although it is suggested to be modulated by low temperature. To elucidate the mechanisms regulating Phase 1 ripening in kiwifruit, a comparative transcriptome analysis using fruit continuously exposed to propylene (at 20 °C), and during storage at 5 °C and 20 °C was conducted. Propylene exposure induced kiwifruit softening, reduction of titratable acidity (TA), increase in soluble solids content (SSC) and ethylene production within 5 days. During storage, softening and reduction of TA occurred faster in fruit at 5 °C compared to 20 °C although no endogenous ethylene production was detected. Transcriptome analysis revealed 3761 ripening-related differentially expressed genes (DEGs), of which 2742 were up-regulated by propylene while 1058 were up-regulated by low temperature. Propylene exclusively up-regulated 2112 DEGs including those associated with ethylene biosynthesis and ripening such as AcACS1, AcACO2, AcPL1, AcXET1, Acβ-GAL, AcAAT, AcERF6 and AcNAC7. Similarly, low temperature exclusively up-regulated 467 DEGS including AcACO3, AcPL2, AcPMEi, AcADH, Acβ-AMY2, AcGA2ox2, AcNAC5 and AcbZIP2 among others. A considerable number of DEGs such as AcPG, AcEXP1, AcXET2, Acβ-AMY1, AcGA2ox1, AcNAC6, AcMADS1 and AcbZIP1 were up-regulated by either propylene or low temperature. Frequent 1-MCP treatments failed to inhibit the accelerated ripening and up-regulation of associated DEGs by low temperature indicating that the changes were independent of ethylene. On-vine kiwifruit ripening proceeded in the absence of any detectable endogenous ethylene production, and coincided with increased expression of low temperature-responsive DEGs as well as the decrease in environmental temperature. These results indicate that kiwifruit possess both ethylene-dependent and low temperature-modulated ripening mechanisms that are distinct and independent of each other. The current work provides a foundation for elaborating the control of these two ripening mechanisms in kiwifruit.

The release of dissolved actinium to the ocean: A global comparison of different end-members

USGS Publications Warehouse

Geibert, W.; Charette, M.; Kim, G.; Moore, W.S.; Street, J.; Young, M.; Paytan, A.

2008-01-01

The measurement of short-lived 223Ra often involves a second measurement for supported activities, which represents 227Ac in the sample. Here we exploit this fact, presenting a set of 284 values on the oceanic distribution of 227Ac, which was collected when analyzing water samples for short-lived radium isotopes by the radium delayed coincidence counting system. The present work compiles 227Ac data from coastal regions all over the northern hemisphere, including values from ground water, from estuaries and lagoons, and from marine end-members. Deep-sea samples from a continental slope off Puerto Rico and from an active vent site near Hawaii complete the overview of 227Ac near its potential sources. The average 227Ac activities of nearshore marine end-members range from 0.4??dpm m- 3 at the Gulf of Mexico to 3.0??dpm m- 3 in the coastal waters of the Korean Strait. In analogy to 228Ra, we find the extension of adjacent shelf regions to play a substantial role for 227Ac activities, although less pronounced than for radium, due to its weaker shelf source. Based on previously published values, we calculate an open ocean 227Ac inventory of 1.35 * 1018??dpm 227Acex in the ocean, which corresponds to 37??moles, or 8.4??kg. This implies a flux of 127??dpm m-2 y- 1 from the deep-sea floor. For the shelf regions, we obtain a global inventory of 227Ac of 4.5 * 1015??dpm, which cannot be converted directly into a flux value, as the regional loss term of 227Ac to the open ocean would have to be included. Ac has so far been considered to behave similarly to Ra in the marine environment, with the exception of a strong Ac source in the deep-sea due to 231Paex. Here, we present evidence of geochemical differences between Ac, which is retained in a warm vent system, and Ra, which is readily released [Moore, W.S., Ussler, W. and Paull, C.K., 2008-this issue. Short-lived radium isotopes in the Hawaiian margin: Evidence for large fluid fluxes through the Puna Ridge. Marine Chemistry]. Another potential mechanism of producing deviations in 227Ac/228Ra and daughter isotope ratios from the expected production value of lithogenic material is observed at reducing environments, where enrichment in uranium may occur. The presented data here may serve as a reference for including 227Ac in circulation models, and the overview provides values for some end-members that contribute to the global Ac distribution. ?? 2007 Elsevier B.V. All rights reserved.

Novel dielectric reduces corona breakdown in ac capacitors

NASA Technical Reports Server (NTRS)

Loehner, J. L.

1972-01-01

Dielectric system was developed which consists of two layers of 25-gage paper separated by one layer of 50-gage polypropylene to reduce corona breakdown in ac capacitors. System can be used in any alternating current application where constant voltage does not exceed 400 V rms. With a little research it could probably be increased to 700 to 800 V rms.

Scalable Heuristics for Planning, Placement and Sizing of Flexible AC Transmission System Devices

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

Frolov, Vladmir; Backhaus, Scott N.; Chertkov, Michael

Aiming to relieve transmission grid congestion and improve or extend feasibility domain of the operations, we build optimization heuristics, generalizing standard AC Optimal Power Flow (OPF), for placement and sizing of Flexible Alternating Current Transmission System (FACTS) devices of the Series Compensation (SC) and Static VAR Compensation (SVC) type. One use of these devices is in resolving the case when the AC OPF solution does not exist because of congestion. Another application is developing a long-term investment strategy for placement and sizing of the SC and SVC devices to reduce operational cost and improve power system operation. SC and SVCmore » devices are represented by modification of the transmission line inductances and reactive power nodal corrections respectively. We find one placement and sizing of FACTs devices for multiple scenarios and optimal settings for each scenario simultaneously. Our solution of the nonlinear and nonconvex generalized AC-OPF consists of building a convergent sequence of convex optimizations containing only linear constraints and shows good computational scaling to larger systems. The approach is illustrated on single- and multi-scenario examples of the Matpower case-30 model.« less

Three-Phase AC Optimal Power Flow Based Distribution Locational Marginal Price: Preprint

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

Yang, Rui; Zhang, Yingchen

2017-05-17

Designing market mechanisms for electricity distribution systems has been a hot topic due to the increased presence of smart loads and distributed energy resources (DERs) in distribution systems. The distribution locational marginal pricing (DLMP) methodology is one of the real-time pricing methods to enable such market mechanisms and provide economic incentives to active market participants. Determining the DLMP is challenging due to high power losses, the voltage volatility, and the phase imbalance in distribution systems. Existing DC Optimal Power Flow (OPF) approaches are unable to model power losses and the reactive power, while single-phase AC OPF methods cannot capture themore » phase imbalance. To address these challenges, in this paper, a three-phase AC OPF based approach is developed to define and calculate DLMP accurately. The DLMP is modeled as the marginal cost to serve an incremental unit of demand at a specific phase at a certain bus, and is calculated using the Lagrange multipliers in the three-phase AC OPF formulation. Extensive case studies have been conducted to understand the impact of system losses and the phase imbalance on DLMPs as well as the potential benefits of flexible resources.« less

Very low noise AC/DC power supply systems for large detector arrays.

PubMed

Arnaboldi, C; Baù, A; Carniti, P; Cassina, L; Giachero, A; Gotti, C; Maino, M; Passerini, A; Pessina, G

2015-12-01

In this work, we present the first part of the power supply system for the CUORE and LUCIFER arrays of bolometric detectors. For CUORE, it consists of AC/DC commercial power supplies (0-60 V output) followed by custom DC/DC modules (48 V input, ±5 V to ±13.5 V outputs). Each module has 3 floating and independently configurable output voltages. In LUCIFER, the AC/DC + DC/DC stages are combined into a commercial medium-power AC/DC source. At the outputs of both setups, we introduced filters with the aim of lowering the noise and to protect the following stages from high voltage spikes that can be generated by the energy stored in the cables after the release of accidental short circuits. Output noise is very low, as required: in the 100 MHz bandwidth the RMS level is about 37 μV(RMS) (CUORE setup) and 90 μV(RMS) (LUCIFER setup) at a load of 7 A, with a negligible dependence on the load current. Even more importantly, high frequency switching disturbances are almost completely suppressed. The efficiency of both systems is above 85%. Both systems are completely programmable and monitored via CAN bus (optically coupled).

Compensation for Harmonic Currents and Reactive Power in Wind Power Generation System using PWM Inverter

NASA Astrophysics Data System (ADS)

Shinohara, Katsuji; Shinhatsubo, Kurato; Iimori, Kenichi; Yamamoto, Kichiro; Saruban, Takamichi; Yamaemori, Takahiro

In recent year, consciousness of environmental problems is enhancing, and the price of the electric power purchased by an electric power company is established expensive for the power plant utilizing the natural energy. So, the introduction of the wind power generation is promoted in Japan. Generally, squirrel-cage induction machines are widely used as a generator in wind power generation system because of its small size, lightweight and low-cost. However, the induction machines do not have a source of excitation. Thus, it causes the inrush currents and the instantaneous voltage drop when the generator is directly connected to a power grid. To reduce the inrush currents, an AC power regulator is used. Wind power generations are frequently connected to and disconnected from the power grid. However, when the inrush currents are reduced, harmonic currents are caused by phase control of the AC power regulator. And the phase control of AC power regulator cannot control the power factor. Therefore, we propose the use of the AC power regulator to compensate for the harmonic currents and reactive power in the wind power generation system, and demonstrate the validity of its system by simulated and experimental results.

Stress-related phenomena and detoxification mechanisms induced by common pharmaceuticals in alfalfa (Medicago sativa L.) plants.

PubMed

Christou, Anastasis; Antoniou, Chrystalla; Christodoulou, Charalampia; Hapeshi, Evroula; Stavrou, Ioannis; Michael, Costas; Fatta-Kassinos, Despo; Fotopoulos, Vasileios

2016-07-01

Pharmaceutically active compounds (PhACs) have been recently shown to exert phytotoxic effects. The present study explores the uptake, systemic translocation, and abiotic stress responses and detoxification mechanisms induced by the exposure of alfalfa plants grown in sand under greenhouse conditions to four common, individually applied PhACs (10μgL(-1)) (diclofenac, sulfamethoxazole, trimethoprim, 17a-ethinylestradiol) and their mixture. Stress physiology markers (lipid peroxidation, proline, H2O2 and NO content, antioxidant activity assays) and gene expression levels of key plant detoxification components (including glutathione S-transferases, GST7, GST17; superoxide dismutases, CuZnSOD, FeSOD; proton pump, H(+)-ATP, and cytochrome c oxidase, CytcOx), were evaluated. PhACs were detected in significantly higher concentrations in roots compared with leaves. Stress related effects, manifested via membrane lipid peroxidation and oxidative burst, were local (roots) rather than systemic (leaves), and exacerbated when the tested PhACs were applied in mixture. Systemic accumulation of H2O2 in leaves suggests its involvement in signal transduction and detoxification responses. Increased antioxidant enzymatic activities, as well as upregulated transcript levels of GST7, GST17, H(+)-ATPase and CytcOx, propose their role in the detoxification of the selected PhACs in plants. The current findings provide novel biochemical and molecular evidence highlighting the studied PhACs as an emerging abiotic stress factor, and point the need for further research on wastewater flows under natural agricultural environments. Copyright © 2016 Elsevier B.V. All rights reserved.

One-Pot Enzymatic Production of Lignin-Composites.

PubMed

Ion, Sabina; Opris, Cristina; Cojocaru, Bogdan; Tudorache, Madalina; Zgura, Irina; Galca, Aurelian C; Bodescu, Adina M; Enache, Madalin; Maria, Gabriel-Mihai; Parvulescu, Vasile I

2018-01-01

A novel and efficient one-pot system for green production of artificial lignin bio-composites has been developed. Monolignols such as sinapyl (SA) and coniferyl (CA) alcohols were linked together with caffeic acid (CafAc) affording a polymeric network similar with natural lignin. The interaction of the dissolved SA/CA with CafAc already bound on a solid support (S C2 /S C6 -CafAc) allowed the attachment of the polymeric product direct on the support surface (S C2 /S C6 -CafAc-L 1 and S C2 /S C6 -CafAc-L 2 , from CA and SA, respectively). Accordingly, this procedure offers the advantage of a simultaneous polymer production and deposition. Chemically, oxi-copolymerization of phenolic derivatives (SA/CA and CAfAc) was performed with H 2 O 2 as oxidation reagent using peroxidase enzyme (2-1B mutant of versatile peroxidase from Pleurotus eryngii ) as catalyst. The system performance reached a maximum of conversion for SA and CA of 71.1 and 49.8%, respectively. The conversion is affected by the system polarity as resulted from the addition of a co-solvent (e.g., MeOH, EtOH, or THF). The chemical structure, morphology, and properties of the bio-composites surface were investigated using different techniques, e.g., FTIR, TPD-NH 3 , TGA, contact angle, and SEM. Thus, it was demonstrated that the SA monolignol favored bio-composites with a dense polymeric surface, high acidity, and low hydrophobicity, while CA allowed the production of thinner polymeric layers with high hydrophobicity.

Reconstitutional Mutagenesis of the Maize P Gene by Short-Range Ac Transpositions

PubMed Central

Moreno, M. A.; Chen, J.; Greenblatt, I.; Dellaporta, S. L.

1992-01-01

The tendency for Ac to transpose over short intervals has been utilized to develop insertional mutagenesis and fine structure genetic mapping strategies in maize. We recovered excisions of Ac from the P gene and insertions into nearby chromosomal sites. These closely linked Ac elements reinserted into the P gene, reconstituting over 250 unstable variegated alleles. Reconstituted alleles condition a variety of variegation patterns that reflect the position and orientation of Ac within the P gene. Molecular mapping and DNA sequence analyses have shown that reinsertion sites are dispersed throughout a 12.3-kb chromosomal region in the promoter, exons and introns of the P gene, but in some regions insertions sites were clustered in a nonrandom fashion. Transposition profiles and target site sequence data obtained from these studies have revealed several features of Ac transposition including its preference for certain target sites. These results clearly demonstrate the tendency of Ac to transpose to nearby sites in both proximal and distal directions from the donor site. With minor modifications, reconstitutional mutagenesis should be applicable to many Ac-induced mutations in maize and in other plant species and can possibly be extended to other eukaryotic transposon systems as well. PMID:1325389

The influence of utility-interactive PV system characteristics to ac power networks

NASA Astrophysics Data System (ADS)

Takeda, Y.; Takigawa, K.; Kaminosono, H.

Two basic experimental photovoltaic (PV) systems have been built for the study of variation of power quality, aspects of safety, and technical problems. One system uses a line-commutated inverter, while the other system uses a self-commutated inverter. A description is presented of the operating and generating characteristics of the two systems. The systems were connected to an ac simulated network which simulates an actual power distribution system. Attention is given to power generation characteristics, the control characteristics, the harmonics characteristics, aspects of coordination with the power network, and questions regarding the reliability of photovoltaic modules.

Alternating current loss characteristics in (bismuth,lead)SCCO and yttrium barium copper oxide superconducting tapes

NASA Astrophysics Data System (ADS)

Nguyen, Doan Ngoc

Alternating current (AC) loss and current carrying capacity are two of the most crucial considerations in large-scale power applications of high temperature superconducting (HTS) conductors. AC losses result in an increased thermal load for cooling machines, and thus increased operating costs. Furthermore, AC losses can stimulate quenching phenomena or at least decrease the stability margin for superconducting devices. Thus, understanding AC losses is essential for the development of HTS AC applications. The main focus of this dissertation is to make reliable total AC loss measurements and interpret the experimental results in a theoretical framework. With a specially designed magnet, advanced total AC loss measurement system in liquid nitrogen (77 K) has been successfully built. Both calorimetric and electromagnetic methods were employed to confirm the validity of the measured results and to have a more thorough understanding of AC loss in HTS conductors. The measurement is capable of measuring total AC loss in HTS tapes over a wide range of frequency and amplitude of transport current and magnetic field. An accurate phase control technique allows measurement of total AC loss with any phase difference between the transport current and magnetic field by calorimetric method. In addition, a novel total AC loss measurement system with variable temperatures from 30 K to 100 K was successfully built and tested. Understanding the dependence of AC losses on temperature will enable optimization of the operating temperature and design of HTS devices. As a part of the dissertation, numerical calculations using Brandt's model were developed to study electrodynamics and total AC loss in HTS conductors. In the calculations, the superconducting electrical behavior is assumed to follow a power-law model. In general, the practical properties of conductors, including field-dependence of critical current density Jc, n-value and non-uniform distribution of Jc, can be accounted for in the numerical calculations. The numerical calculations are also capable of investigating eddy current loss in the stabilizer and ferromagnetic loss in the substrate of YBa2Cu3O 7-delta (YBCO) coated conductor. AC loss characteristics and electrodynamics in several (Bi,Pb)2 Sr2Ca2Cu3Ox (Bi-2223) and YBCO tapes were studied experimentally and numerically. It was found that AC loss behavior Ax in HTS tapes is strongly affected by the sample parameters such as cross-section, structure, dimensions, critical current distribution as well as by operation parameters including temperature, frequency, the phase difference between transport current and magnetic field, the orientation of magnetic field. The Ni-5%W substrate in YBCO conductors generates some ferromagnetic loss but this loss component is significantly reduced by a small parallel DC magnetic field. At a given AC magnetic field B0, there is a temperature Tmax at which the magnetization loss is maximum. The design of HTS devices needs to be optimized to avoid operating at that temperature. In general, the total AC loss in HTS tapes is still high for many power device applications, especially for those that present a rather high AC applied magnetic field. The development of low loss conductors is therefore crucial for HTS large-scale applications.

Spacecraft attitude control for a solar electric geosynchronous transfer mission

NASA Technical Reports Server (NTRS)

Leroy, B. E.; Regetz, J. D., Jr.

1975-01-01

A study of the Attitude Control System (ACS) is made for a solar electric propulsion geosynchronous transfer mission. The basic mission considered is spacecraft injection into a low altitude, inclined orbit followed by low thrust orbit changing to achieve geosynchronous orbit. Because of the extended thrusting time, the mission performance is a strong function of the attitude control system. Two attitude control system design options for an example mission evolve from consideration of the spacecraft configuration, the environmental disturbances, and the probable ACS modes of operation. The impact of these design options on other spacecraft subsystems is discussed. The factors which must be considered in determining the ACS actuation and sensing subsystems are discussed. The effects of the actuation and sensing subsystems on the mission performance are also considered.

OGLE-IV Transient Search report 31 December 2016, part 1

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Hamanowicz, A.; Kostrzewa-Rutkowska, Z.; Klencki, J.; Sitek, M.; Udalski, A.; Kozlowski, S.; Ulaczyk, K.; Soszynski, I.; Mroz, P.; Szymanski, M. K.; Poleski, R.; Pietrukowicz, P.; Pawlak, M.; Skowron, J.

2016-12-01

The OGLE-IV Transient Detection System (Wyrzykowski et al. 2014, AcA,64,197; Kozlowski et al. 2013; Klencki et al. 2016, AcA, 66,15) announces discovery of 52 transients discovered in last three months.

OGLE-IV Transient Search report 31 December 2016, part 2

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Hamanowicz, A.; Kostrzewa-Rutkowska, Z.; Klencki, J.; Sitek, M.; Udalski, A.; Kozlowski, S.; Ulaczyk, K.; Soszynski, I.; Mroz, P.; Szymanski, M. K.; Poleski, R.; Pietrukowicz, P.; Pawlak, M.; Skowron, J.

2016-12-01

The OGLE-IV Transient Detection System (Wyrzykowski et al. 2014, AcA,64,197; Kozlowski et al. 2013; Klencki et al. 2016, AcA, 66,15) announces discovery of 46 transients discovered in last three months.

ACS sampling system: design, implementation, and performance evaluation

NASA Astrophysics Data System (ADS)

Di Marcantonio, Paolo; Cirami, Roberto; Chiozzi, Gianluca

2004-09-01

By means of ACS (ALMA Common Software) framework we designed and implemented a sampling system which allows sampling of every Characteristic Component Property with a specific, user-defined, sustained frequency limited only by the hardware. Collected data are sent to various clients (one or more Java plotting widgets, a dedicated GUI or a COTS application) using the ACS/CORBA Notification Channel. The data transport is optimized: samples are cached locally and sent in packets with a lower and user-defined frequency to keep network load under control. Simultaneous sampling of the Properties of different Components is also possible. Together with the design and implementation issues we present the performance of the sampling system evaluated on two different platforms: on a VME based system using VxWorks RTOS (currently adopted by ALMA) and on a PC/104+ embedded platform using Red Hat 9 Linux operating system. The PC/104+ solution offers, as an alternative, a low cost PC compatible hardware environment with free and open operating system.

A Survey of Techniques for Approximate Computing

DOE PAGES

Mittal, Sparsh

2016-03-18

Approximate computing trades off computation quality with the effort expended and as rising performance demands confront with plateauing resource budgets, approximate computing has become, not merely attractive, but even imperative. Here, we present a survey of techniques for approximate computing (AC). We discuss strategies for finding approximable program portions and monitoring output quality, techniques for using AC in different processing units (e.g., CPU, GPU and FPGA), processor components, memory technologies etc., and programming frameworks for AC. Moreover, we classify these techniques based on several key characteristics to emphasize their similarities and differences. Finally, the aim of this paper is tomore » provide insights to researchers into working of AC techniques and inspire more efforts in this area to make AC the mainstream computing approach in future systems.« less

Advances in the use of trapping systems for Rhynchophorus ferrugineus (Coleoptera: Curculionidae): traps and attractants.

PubMed

Vacas, S; Primo, J; Navarro-Llopis, V

2013-08-01

Given the social importance related to the red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae), efforts are being made to develop new control methods, such as the deployment of trapping systems. In this work, the efficacy of a new black pyramidal trap design (Picusan) has been verified in comparison with white and black buckets. In addition, the attractant and synergistic effect of ethyl acetate (EtAc) at different release levels has been evaluated under field conditions. The results show that Picusan traps captured 45% more weevils than bucket-type traps, offering significantly better trapping efficacy. The addition of water to traps baited with palm tissues was found to be essential, with catches increasing more than threefold compared with dry traps. EtAc alone does not offer attractant power under field conditions, and the release levels from 57 mg/d to 1 g/d have no synergistic effect with ferrugineol. Furthermore, significantly fewer females were captured when EtAc was released at 2 g/d. The implications of using EtAc dispensers in trapping systems are discussed.

A Line Impedance Conditioner for Saturation Mitigation of Zigzag Transformer in Hybrid AC/DC Transmission System Considering Line Unbalances

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

Liu, Bo; Shi, Xiaojie M.; Li, Yalong

Hybrid ac/dc transmission extends the power transfer capacity of existing long ac lines closer to their thermal limit, by superposing the dc current onto three-phase ac lines through a zigzag transformer. However, this transformer could suffer saturation under unbalanced line impedance conditions. This paper introduces the concept of hybrid line impedance conditioner (HLIC) as a cost-effective approach to compensate for the line unbalance and therefore avoid saturation. The topology and operation principle are presented. The two-level control strategy is described, which enables autonomous adaptive regulation without the need of system-level control. Design and implementation are also analyzed, including dc-link capacitancemore » as one of the key line conditioner components, HLIC installation, and protection under fault conditions. The cost study on this HLIC-based hybrid system is also performed to reveal the benefits of the solution. In conclusion, simulation results and experimental results based on a down-scaled prototype are provided to verify the feasibility of the proposed approach.« less

A Line Impedance Conditioner for Saturation Mitigation of Zigzag Transformer in Hybrid AC/DC Transmission System Considering Line Unbalances

DOE PAGES

Liu, Bo; Shi, Xiaojie M.; Li, Yalong; ...

2016-09-13

Hybrid ac/dc transmission extends the power transfer capacity of existing long ac lines closer to their thermal limit, by superposing the dc current onto three-phase ac lines through a zigzag transformer. However, this transformer could suffer saturation under unbalanced line impedance conditions. This paper introduces the concept of hybrid line impedance conditioner (HLIC) as a cost-effective approach to compensate for the line unbalance and therefore avoid saturation. The topology and operation principle are presented. The two-level control strategy is described, which enables autonomous adaptive regulation without the need of system-level control. Design and implementation are also analyzed, including dc-link capacitancemore » as one of the key line conditioner components, HLIC installation, and protection under fault conditions. The cost study on this HLIC-based hybrid system is also performed to reveal the benefits of the solution. In conclusion, simulation results and experimental results based on a down-scaled prototype are provided to verify the feasibility of the proposed approach.« less

Cadmium-induced ethylene production and responses in Arabidopsis thaliana rely on ACS2 and ACS6 gene expression

PubMed Central

2014-01-01

Background Anthropogenic activities cause metal pollution worldwide. Plants can absorb and accumulate these metals through their root system, inducing stress as a result of excess metal concentrations inside the plant. Ethylene is a regulator of multiple plant processes, and is affected by many biotic and abiotic stresses. Increased ethylene levels have been observed after exposure to excess metals but it remains unclear how the increased ethylene levels are achieved at the molecular level. In this study, the effects of cadmium (Cd) exposure on the production of ethylene and its precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and on the expression of the ACC Synthase (ACS) and ACC Oxidase (ACO) multigene families were investigated in Arabidopsis thaliana. Results Increased ethylene release after Cd exposure was directly measurable in a system using rockwool-cultivated plants; enhanced levels of the ethylene precursor ACC together with higher mRNA levels of ethylene responsive genes: ACO2, ETR2 and ERF1 also indicated increased ethylene production in hydroponic culture. Regarding underlying mechanisms, it was found that the transcript levels of ACO2 and ACO4, the most abundantly expressed members of the ACO multigene family, were increased upon Cd exposure. ACC synthesis is the rate-limiting step in ethylene biosynthesis, and transcript levels of both ACS2 and ACS6 showed the highest increase and became the most abundant isoforms after Cd exposure, suggesting their importance in the Cd-induced increase of ethylene production. Conclusions Cadmium induced the biosynthesis of ACC and ethylene in Arabidopsis thaliana plants mainly via the increased expression of ACS2 and ACS6. This was confirmed in the acs2-1acs6-1 double knockout mutants, which showed a decreased ethylene production, positively affecting leaf biomass and resulting in a delayed induction of ethylene responsive gene expressions without significant differences in Cd contents between wild-type and mutant plants. PMID:25082369

Modulation and control of matrix converter for aerospace application

NASA Astrophysics Data System (ADS)

Kobravi, Keyhan

In the context of modern aircraft systems, a major challenge is power conversion to supply the aircraft's electrical instruments. These instruments are energized through a fixed-frequency internal power grid. In an aircraft, the available sources of energy are a set of variable-speed generators which provide variable-frequency ac voltages. Therefore, to energize the internal power grid of an aircraft, the variable-frequency ac voltages should be converted to a fixed-frequency ac voltage. As a result, an ac to ac power conversion is required within an aircraft's power system. This thesis develops a Matrix Converter to energize the aircraft's internal power grid. The Matrix Converter provides a direct ac to ac power conversion. A major challenge of designing Matrix Converters for aerospace applications is to minimize the volume and weight of the converter. These parameters are minimized by increasing the switching frequency of the converter. To design a Matrix Converter operating at a high switching frequency, this thesis (i) develops a scheme to integrate fast semiconductor switches within the current available Matrix Converter topologies, i.e., MOSFET-based Matrix Converter, and (ii) develops a new modulation strategy for the Matrix Converter. This Matrix Converter and the new modulation strategy enables the operation of the converter at a switching-frequency of 40kHz. To provide a reliable source of energy, this thesis also develops a new methodology for robust control of Matrix Converter. To verify the performance of the proposed MOSFET-based Matrix Converter, modulation strategy, and control design methodology, various simulation and experimental results are presented. The experimental results are obtained under operating condition present in an aircraft. The experimental results verify the proposed Matrix Converter provides a reliable power conversion in an aircraft under extreme operating conditions. The results prove the superiority of the proposed Matrix Converter technology for ac to ac power conversion regarding the existing technologies of Matrix Converters.

Chemical Warfare Agent Surface Adsorption: Hydrogen Bonding of Sarin and Soman to Amorphous Silica

DTIC Science & Technology

2014-03-17

Prior to experiments, the gas manifold and dosing lines were heated, under vacuum, to 100 °C to minimize water contamination. A stainless steel ...23 L UHV chamber constructed out of 316L stainless steel with all ports equipped with con-flat flanges (Kurt J. Lesker Company). The chamber is...dosed as a neat vapor using a multivalved stainless steel high-vacuum manifold. The entire path of the manifold was evacuated and heated to 100 °C

Joint services electronics program

NASA Astrophysics Data System (ADS)

Flynn, George W.; Osgood, Richard M., Jr.

1988-05-01

Several milestones have been reached in GaAs research. The first active GaAs device, a 1 micrometer channel width MESFET, has been made at Columbia. This device is a basic building block in the GaAs CCD program. GaAs surface studies have also born fruit. UV light has been found to oxidize rapidly the surface of GaAs in an UHV environment containing traces of water vapor and O2. The mechanism appears to be related to the generation of hot photocarriers.

Effect of Water Vapor Pressure on Fatigue Crack Growth in Al-Zn-Cu-Mg Alloy Over Wide-Range Stress Intensity Factor Loading

DTIC Science & Technology

2014-05-07

impacts: (a) crack closure, (b) transport of water vapor molecules within the fatigue crack (47], and (c) tensile stress-plastic strain range...sealed stainless steel UHV chamber. Pure water vapor was introduced from a sealed glass flask containing triply distilled water, via a precision leak...lamellar for H1 flow in a fatigue crack in steel ; specifically, flow is dominated by the low dynamic viscosity of a gas (particularly at low pressures) and

NanoBench: An Individually Addressable Nanotube Array

DTIC Science & Technology

2006-03-25

17 (1999). 5 Cai, L., H. Tabata and T. Kawai, "Probing electrical properties of oriented DNA by conducting atomic force microscopy", Nanotechnology 12...the e-beam hits the other side of the NanoBench. This allows the cells to be kept alive in a biological medium while they are being tested. The key...advantage of the NanoBench is that the e-beam never hits the sample. UHV Technologies Inc. 7 NanoBench: An Individually Addressable Nanotube Array Final

Clinicopathological profile and management of 161 cases of actinic cheilitis.

PubMed

Lopes, Maria Luiza Diniz de Sousa; Silva Júnior, Francisco Leonardo da; Lima, Kenio Costa; Oliveira, Patrícia Teixeira de; Silveira, Éricka Janine Dantas da

2015-01-01

Actinic cheilitis (AC) is a potentially malignant disorder of the lip caused by chronic exposure to ultraviolet radiation from the sun. To evaluate the clinical, demographic, morphological and therapeutic management in AC cases data associating to the histopathological grading. Demographic, clinical and management data of 161 patients with AC were analyzed. In biopsied cases, two calibrated examiners performed histopathological grading by binary system. There was a prevalence of males (79.5%), aged 40 years or older (77.5%), light-skinned (85.7%), experiencing occupational exposure to sunlight (80.3%), with AC presenting clinically as white lesions (33.6%). Conservative treatment was adopted in 78 cases and biopsy in 83 cases (60.2% graded as low-risk AC). There were no significant associations between histopathological grading and gender (p= 0.509), age (p=0.416), ethnicity (p=0.388), occupational exposure to sunlight (p=1.000) or clinical presentation (p=0.803). This study reinforces the hypothesis that demographic and clinical characteristics of AC are not related to histopathological grading. Advice on protection from sun exposure should be encouraged to avoid progression of AC and invasive therapies.

Microbial Contamination of Ice Machines Is Mediated by Activated Charcoal Filtration Systems in a City Hospital.

PubMed

Yorioka, Katsuhiro; Oie, Shigeharu; Hayashi, Koji; Kimoto, Hiroo; Furukawa, Hiroyuki

2016-06-01

Although microbial contamination of ice machines has been reported, no previous study has addressed microbial contamination of ice produced by machines equipped with activated charcoal (AC) filters in hospitals. The aim of this study was to provide clinical data for evaluating AC filters to prevent microbial contamination of ice. We compared microbial contamination in ice samples produced by machines with (n = 20) and without an AC filter (n = 40) in Shunan City Shinnanyo Municipal Hospital. All samples from the ice machine equipped with an AC filter contained 10-116 CFUs/g of glucose nonfermenting gram-negative bacteria such as Pseudomonas aeruginosa and Chryseobacterium meningosepticum. No microorganisms were detected in samples from ice machines without AC filters. After the AC filter was removed from the ice machine that tested positive for Gram-negative bacteria, the ice was resampled (n = 20). Analysis found no contaminants. Ice machines equipped with AC filters pose a serious risk factor for ice contamination. New filter-use guidelines and regulations on bacterial detection limits to prevent contamination of ice in healthcare facilities are necessary.

A new bed-exiting alarm system for welfare facility residents.

PubMed

Ogawa, Hidekuni; Yonezawa, Yoshiharu; Maki, Hiromichi; Caldwell, W

2009-01-01

A newly developed alarm system detects welfare facility residents leaving their beds, and does not respond to the care staff, who wear shoes or slippers. It employs a stainless steel tape electrode, several linear integrated circuits and a low-power 8-bit single chip microcomputer. The electrode, which is used as a bed-exiting detection sensor, is attached to the floor mat to record changes in the always-present AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the standard 100 volt, 60 Hz AC utility power wiring in the room walls and ceiling. The resident's body movements, before trying to get out of bed and after leaving the bed, are detected by the microcomputer from changes in the induced AC voltage. The microcomputer alerts the care staff station, via a power line communication system or PHS (personal handy phone System).

Broadband Laser Ranging for Position Measurements in Shock Physics Experiments

NASA Astrophysics Data System (ADS)

Rhodes, Michelle; Bennett, Corey; Daykin, Edward; Younk, Patrick; Lalone, Brandon; Kostinski, Natalie

2017-06-01

Broadband laser ranging (BLR) is a recently developed measurement system that provides an attractive option for determining the position of shock-driven surfaces. This system uses broadband, picosecond (or femtosecond) laser pulses and a fiber interferometer to measure relative travel time to a target and to a reference mirror. The difference in travel time produces a delay difference between pulse replicas that creates a spectral beat frequency. The spectral beating is recorded in real time using a dispersive Fourier transform and an oscilloscope. BLR systems have been designed that measure position at 12.5-40 MHz with better than 100 micron accuracy over ranges greater than 10 cm. We will give an overview of the basic operating principles of these systems. Prepared by LLNL under Contract DE-AC52-07NA27344, by LANL under Contract DE-AC52-06NA25396, and by NSTec Contract DE-AC52-06NA25946.

Study of power management technology for orbital multi-100KWe applications. Volume 3: Requirements

NASA Technical Reports Server (NTRS)

Mildice, J. W.

1980-01-01

Mid to late 1980's power management technology needs to support development of a general purpose space platform, capable of suplying 100 to 250 KWe to a variety of users in low Earth orbit are examined. A typical, shuttle assembled and supplied space platform is illustred, along with a group of payloads which might reasonably be expected to use such a facility. Examination of platform and user power needs yields a set of power requirements used to evaluate power management options for life cycle cost effectivness. The most cost effective ac/dc and dc systems are evaluated, specifically to develop system details which lead to technology goals, including: array and transmission voltages, best frequency for ac power transmission, and advantages and disadvantages of ac and dc systems for this application. System and component requirements are compared with the state-of-the-art to identify areas where technological development is required.

Human Systems Integration: Unmanned Aircraft Control Station Certification Plan Guidance

NASA Technical Reports Server (NTRS)

2005-01-01

This document provides guidance to the FAA on important human factors considerations that can be used to support the certification of a UAS Aircraft Control Station (ACS). This document provides a synopsis of the human factors analysis, design and test activities to be performed to provide a basis for FAA certification. The data from these analyses, design activities, and tests, along with data from certification/qualification tests of other key components should be used to establish the ACS certification basis. It is expected that this information will be useful to manufacturers in developing the ACS Certification Plan,, and in supporting the design of their ACS.

Contract Oversight for Redistribution Property Assistance Team Operations in Afghanistan Needs Improvement

DTIC Science & Technology

2015-05-18

Aircraft Systems ( SUAS ) Project Office, located in Huntsville, AL, for reset. For return to the SUAS Project Office, 401st AFSB officials stated, the...representatives from SUAS Project Office contacted the 401st AFSB COR at BAF to state that the systems arrived in Huntsville, AL. However, prior to SUAS ...circumstances behind the loss. AC First’s research identified that AC First shipped the systems to SUAS officials at BAF instead of the BAF RPAT

FINAL REPORT REGULATORY OFF GAS EMISSIONS TESTING ON THE DM1200 MELTER SYSTEM USING HLW AND LAW SIMULANTS VSL-05R5830-1 REV 0 10/31/05

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

KRUGER AA; MATLACK KS; GONG W

2011-12-29

The operational requirements for the River Protection Project - Waste Treatment Plant (RPP-WTP) Low Activity Waste (LAW) and High Level Waste (HLW) melter systems, together with the feed constituents, impose a number of challenges to the off-gas treatment system. The system must be robust from the standpoints of operational reliability and minimization of maintenance. The system must effectively control and remove a wide range of solid particulate matter, acid mists and gases, and organic constituents (including those arising from products of incomplete combustion of sugar and organics in the feed) to concentration levels below those imposed by regulatory requirements. Themore » baseline design for the RPP-WTP LAW primary off-gas system includes a submerged bed scrubber (SBS), a wet electrostatic precipitator (WESP), and a high efficiency particulate air (HEPA) filter. The secondary off-gas system includes a sulfur-impregnated activated carbon bed (AC-S), a thermal catalytic oxidizer (TCO), a single-stage selective catalytic reduction NOx treatment system (SCR), and a packed-bed caustic scrubber (PBS). The baseline design for the RPP-WTP HLW primary off-gas system includes an SBS, a WESP, a high efficiency mist eliminator (HEME), and a HEPA filter. The HLW secondary off-gas system includes a sulfur-impregnated activated carbon bed, a silver mordenite bed, a TCO, and a single-stage SCR. The one-third scale HLW DM1200 Pilot Melter installed at the Vitreous State Laboratory (VSL) was equipped with a prototypical off-gas train to meet the needs for testing and confirmation of the performance of the baseline off-gas system design. Various modifications have been made to the DM1200 system as the details of the WTP design have evolved, including the installation of a silver mordenite column and an AC-S column for testing on a slipstream of the off-gas flow; the installation of a full-flow AC-S bed for the present tests was completed prior to initiation of testing. The DM1200 system was reconfigured to enable testing of the baseline HLW or LAW off-gas trains to perform off-gas emissions testing with both LAW and HLW simulants in the present work. During 2002 and 2003, many of these off-gas components were tested individually and in an integrated manner with the DM1200 Pilot Melter. Data from these tests are being used to support engineering design confirmation and to provide data to support air permitting activities. In fiscal year 2004, the WTP Project was directed by the Office of River Protection (ORP) to comply with Environmental Protection Agency (EPA) Maximum Achievable Control Technology (MACT) requirements for organics. This requires that the combined melter and off-gas system have destruction and removal efficiency (DRE) of >99.99% for principal organic dangerous constituents (PODCs). In order to provide confidence that the melter and off-gas system are able to achieve the required DRE, testing has been directed with both LAW and HLW feeds. The tests included both 'normal' and 'challenge' WTP melter conditions in order to obtain data for the potential range of operating conditions for the WTP melters and off-gas components. The WTP Project, Washington State Department of Ecology, and ORP have agreed that naphthalene will be used for testing to represent semi-volatile organics and allyl alcohol will be used to represent volatile organics. Testing was also performed to determine emissions of halides, metals, products of incomplete combustion (PICs), dioxins, furans, coplanar PCBs, total hydrocarbons, and COX and NOX, as well as the particle size distribution (PSD) of particulate matter discharged at the end of the off-gas train. A description of the melter test requirements and analytical methods used is provided in the Test Plan for this work. Test Exceptions were subsequently issued which changed the TCO catalyst, added total organic emissions (TOE) to exhaust sampling schedule, and allowing modification of the test conditions in response to attainable plenum temperatures as well as temperature increases in the sulfur impregnated activated carbon (AC-S) column. Data are provided in this final report for all the required emission samples as well as melter and off-gas conditions during all the sampling periods. Appended to this report are previously issued VSL Letter Reports on method development for monitoring allyl alcohol in melter exhaust streams, on the results of characterization of the selected AC-S carbon media (Donnau BAT37), and on DM1200 off-line tests on the AC-S bed; also appended are reports from Air Tech on emissions sampling, and reports from Keika Ventures on validation of analytical data provided by Severn Trent Laboratories of Knoxville, Tennessee.« less

Green Propellant Test Capabilities of the Altitude Combustion Stand at the NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Kubiak, Jonathan M.; Arnett, Lori A.

2016-01-01

The NASA Glenn Research Center (GRC) is committed to providing simulated altitude rocket test capabilities to NASA programs, other government agencies, private industry partners, and academic partners. A primary facility to support those needs is the Altitude Combustion Stand (ACS). ACS provides the capability to test combustion components at a simulated altitude up to 100,000 ft. (approx.0.2 psia/10 Torr) through a nitrogen-driven ejector system. The facility is equipped with an axial thrust stand, gaseous and cryogenic liquid propellant feed systems, data acquisition system with up to 1000 Hz recording, and automated facility control system. Propellant capabilities include gaseous and liquid hydrogen, gaseous and liquid oxygen, and liquid methane. A water-cooled diffuser, exhaust spray cooling chamber, and multi-stage ejector systems can enable run times up to 180 seconds to 16 minutes. The system can accommodate engines up to 2000-lbf thrust, liquid propellant supply pressures up to 1800 psia, and test at the component level. Engines can also be fired at sea level if needed. The NASA GRC is in the process of modifying ACS capabilities to enable the testing of green propellant (GP) thrusters and components. Green propellants are actively being explored throughout government and industry as a non-toxic replacement to hydrazine monopropellants for applications such as reaction control systems or small spacecraft main propulsion systems. These propellants offer increased performance and cost savings over hydrazine. The modification of ACS is intended to enable testing of a wide range of green propellant engines for research and qualification-like testing applications. Once complete, ACS will have the capability to test green propellant engines up to 880 N in thrust, thermally condition the green propellants, provide test durations up to 60 minutes depending on thrust class, provide high speed control and data acquisition, as well as provide advanced imaging and diagnostics such as infrared (IR) imaging.

An AC modulated near infrared gain calibration system for a “Violin-Mode” transimpedance amplifier, intended for advanced LIGO suspensions

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

Lockerbie, N. A.; Tokmakov, K. V.

The background to this work was a prototype shadow sensor, which was designed for retro-fitting to an advanced LIGO (Laser Interferometer Gravitational wave Observatory) test-mass/mirror suspension, in which a 40 kg test-mass/mirror is suspended by four approximately 600 mm long by 0.4 mm diameter fused-silica suspension fibres. The shadow sensor comprised a LED source of Near InfraRed (NIR) radiation, and a “tall-thin” rectangular silicon photodiode detector, which together were to bracket the fibre under test. The photodiode was positioned so as to be sensitive (primarily) to transverse “Violin-Mode” vibrations of such a fibre, via the oscillatory movement of the shadowmore » cast by the fibre, as this moved across the face of the detector. In this prototype shadow sensing system the photodiode was interfaced to a purpose-built transimpedance amplifier, this having both AC and DC outputs. A quasi-static calibration was made of the sensor’s DC responsivity, i.e., incremental rate of change of output voltage versus fibre position, by slowly scanning a fused-silica fibre sample transversely through the illuminating beam. The work reported here concerns the determination of the sensor’s more important AC (Violin-Mode) responsivity. Recognition of the correspondence between direct AC modulation of the source, and actual Violin-Mode signals, and of the transformative role of the AC/DC gain ratio for the amplifier, at any modulation frequency, f, resulted in the construction of the AC/DC calibration source described here. A method for determining in practice the transimpedance AC/DC gain ratio of the photodiode and amplifier, using this source, is illustrated by a specific numerical example, and the gain ratio for the prototype sensing system is reported over the frequency range 1 Hz–300 kHz. In fact, a maximum DC responsivity of 1.26 kV.m{sup −1} was measured using the prototype photodiode sensor and amplifier discussed here. Therefore, the measured AC/DC transimpedance gain ratio of 922.5 for this sensor, at 500 Hz, translated into a maximum Violin-Mode (AC) responsivity of (1.16 ± 0.05) MV m{sup −1}, at that frequency.« less

The Implementation of Satellite Control System Software Using Object Oriented Design

NASA Technical Reports Server (NTRS)

Anderson, Mark O.; Reid, Mark; Drury, Derek; Hansell, William; Phillips, Tom

1998-01-01

NASA established the Small Explorer (SMEX) program in 1988 to provide frequent opportunities for highly focused and relatively inexpensive space science missions that can be launched into low earth orbit by small expendable vehicles. The development schedule for each SMEX spacecraft was three years from start to launch. The SMEX program has produced five satellites; Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX), Fast Auroral Snapshot Explorer (FAST), Submillimeter Wave Astronomy Satellite (SWAS), Transition Region and Coronal Explorer (TRACE) and Wide-Field Infrared Explorer (WIRE). SAMPEX and FAST are on-orbit, TRACE is scheduled to be launched in April of 1998, WIRE is scheduled to be launched in September of 1998, and SWAS is scheduled to be launched in January of 1999. In each of these missions, the Attitude Control System (ACS) software was written using a modular procedural design. Current program goals require complete spacecraft development within 18 months. This requirement has increased pressure to write reusable flight software. Object-Oriented Design (OOD) offers the constructs for developing an application that only needs modification for mission unique requirements. This paper describes the OOD that was used to develop the SMEX-Lite ACS software. The SMEX-Lite ACS is three-axis controlled, momentum stabilized, and is capable of performing sub-arc-minute pointing. The paper first describes the high level requirements which governed the architecture of the SMEX-Lite ACS software. Next, the context in which the software resides is explained. The paper describes the benefits of encapsulation, inheritance and polymorphism with respect to the implementation of an ACS software system. This paper will discuss the design of several software components that comprise the ACS software. Specifically, Object-Oriented designs are presented for sensor data processing, attitude control, attitude determination and failure detection. The paper addresses the benefits of the OOD versus a conventional procedural design. The final discussion in this paper will address the establishment of the ACS Foundation Class (AFC) Library. The AFC is a large software repository, requiring a minimal amount of code modifications to produce ACS software for future projects, saving production time and costs.

The anticoincidence system of the PAMELA satellite experiment: Design of the data acquisition system and performance studies

NASA Astrophysics Data System (ADS)

Lunquist, Johan

PAMELA is a satellite-borne cosmic ray experiment. Its primary scientific objective is to study the antiproton and positron components of the cosmic radiation. This will be done with unprecedented statistics over a wide energy range (~10MeV to ~100GeV). The PAMELA experiment consists of a permanent magnetic spectrometer, an electromagnetic calorimeter, a Time-of-Fight system, a neutron detector and a shower tail catcher. An anticoincidence (AC) system surrounds the spectrometer to detect particles which do not pass cleanly through the acceptance of the spectrometer. PAMELA will be mounted on a Russian Earth-observation satellite, and the launch is scheduled for 2006. The anticoincidence system for PAMELA has been developed by KTH, and consists of plastic scintillator detectors with photomultiplier tube read-out. Extensive testing has been performed during the development phase. Results are presented for environmental tests, tests with cosmic-rays and particle beams. The design of the digital part of the AC electronics has been realised on an FPGA (Field Programmable Gate Array) and a DSP (Digital Signal Processor). It records signals from the 16 AC photomultipliers and from various sensors for over-current and temperature. It also provides functionality for setting the photomultiplier discrimination thresholds, system testing, issuing alarms and communication with the PAMELA main data acquisition system. The design philosophy and functionality needs to be reliable and suitable for use in a space environment. To evaluate the performance of the AC detectors, a test utilizing cosmic-rays has been performed. The primary aim of the test was to calibrate the individual channels to gain knowledge of suitable discriminator levels for flight. A secondary aim was to estimate the AC detector efficiency. A lower limit of (99.89±0.04)% was obtained. An in-orbit simulation study was performed using protons to estimate trigger rates and investigate the AC system performance in a second level trigger. The average orbital trigger rate was estimated to be (8.4±0.6)Hz, consisting of (2.0±0.2)Hz good triggers and (6.4±0.5)Hz background. Inclusion of the AC system in the trigger condition to reduce background (for the purpose of data handling capacity) leads to losses of good triggers due to backscattering from the calorimeter (90% loss for 300GeV electrons and 25% for 100GeV protons). A method, using the calorimeter, for identifying backscattering events was investigated and found to reduce the loss of good events to below 1% (300GeV electrons) and 5% (100GeV protons), while maintaining a background reduction of 70%.

Heading toward Gliese 445

NASA Image and Video Library

2013-09-12

The image taken by the Oschin Schmidt Telescope, shows the star AC +79 3888, also known as Gliese 445. NASA Voyager 1 spacecraft, which is on a trajectory out of our solar system, is headed toward an encounter with AC +79 3888 circled in red.

Expansion of the Adherence Club model for stable antiretroviral therapy patients in the Cape Metro, South Africa 2011-2015.

PubMed

Wilkinson, Lynne; Harley, Beth; Sharp, Joseph; Solomon, Suhair; Jacobs, Shahieda; Cragg, Carol; Kriel, Ebrahim; Peton, Neshaan; Jennings, Karen; Grimsrud, Anna

2016-06-01

The ambitious '90-90-90' treatment targets require innovative models of care to support quality antiretroviral therapy (ART) delivery. While evidence for differentiated models of ART delivery is growing, there are few data on the feasibility of scale-up. We describe the implementation of the Adherence Club (AC) model across the Cape Metro health district in Cape Town, South Africa, between January 2011 and March 2015. Using data from monthly aggregate AC monitoring reports and electronic monitoring systems for the district cohort, we report on the number of facilities offering ACs and the number of patients receiving ART care in the AC model. Between January 2011 and March 2015, the AC programme expanded to reach 32 425 patients in 1308 ACs at 55 facilities. The proportion of the total ART cohort retained in an AC increased from 7.3% at the end of 2011 to 25.2% by March 2015. The number of facilities offering ACs also increased and by the end of the study period, 92.3% of patients were receiving ART at a facility that offered ACs. During this time, the overall ART cohort doubled from 66 616 to 128 697 patients. The implementation of the AC programme offset this increase by 51%. ACs now provide ART care to more than 30 000 patients. Further expansion of the model will require additional resources and support. More research is necessary to determine the outcomes and quality of care provided in ACs and other differentiated models of ART delivery, especially when implemented at scale. © 2016 John Wiley & Sons Ltd.

Novel therapeutic mechanisms determine the effectiveness of lipid-core nanocapsules on melanoma models

PubMed Central

Drewes, Carine C; Fiel, Luana A; Bexiga, Celina G; Asbahr, Ana Carolina C; Uchiyama, Mayara K; Cogliati, Bruno; Araki, Koiti; Guterres, Sílvia S; Pohlmann, Adriana R; Farsky, Sandra P

2016-01-01

Melanoma is a severe metastatic skin cancer with poor prognosis and no effective treatment. Therefore, novel therapeutic approaches using nanotechnology have been proposed to improve therapeutic effectiveness. Lipid-core nanocapsules (LNCs), prepared with poly(ε-caprolactone), capric/caprylic triglyceride, and sorbitan monostearate and stabilized by polysorbate 80, are efficient as drug delivery systems. Here, we investigated the effects of acetyleugenol-loaded LNC (AcE-LNC) on human SK-Mel-28 melanoma cells and its therapeutic efficacies on melanoma induced by B16F10 in C57B6 mice. LNC and AcE-LNC had z-average diameters and zeta potential close to 210 nm and -10.0 mV, respectively. CytoViva® microscopy images showed that LNC and AcE-LNC penetrated into SK-Mel-28 cells, and remained in the cytoplasm. AcE-LNC in vitro treatment (18–90×109 particles/mL; 1 hour) induced late apoptosis and necrosis; LNC and AcE-LNC (3–18×109 particles/mL; 48 hours) treatments reduced cell proliferation and delayed the cell cycle. Elevated levels of nitric oxide were found in supernatant of LNC and AcE-LNC, which were not dependent on nitric oxide synthase expressions. Daily intraperitoneal or oral treatment (days 3–10 after tumor injection) with LNC or AcE-LNC (1×1012 particles/day), but not with AcE (50 mg/kg/day, same dose as AcE-LNC), reduced the volume of the tumor; nevertheless, intraperitoneal treatment caused toxicity. Oral LNC treatment was more efficient than AcE-LNC treatment. Moreover, oral treatment with nonencapsulated capric/caprylic triglyceride did not inhibit tumor development, implying that nanocapsule supramolecular structure is important to the therapeutic effects. Together, data herein presented highlight the relevance of the supramolecular structure of LNCs to toxicity on SK-Mel-28 cells and to the therapeutic efficacy on melanoma development in mice, conferring novel therapeutic mechanisms to LNC further than a drug delivery system. PMID:27099491

40 CFR 86.162-00 - Approval of alternative air conditioning test simulations and descriptions of AC1 and AC2.

Code of Federal Regulations, 2011 CFR

2011-07-01

... conditioning system compressor, converted to an equivalent roadload component, to the normal dynamometer... driving the SC03 cycle with the air conditioning system operating. (1) Engine revolutions/minute (ERPMt...)(i) (A) and (B) are replaced with 76 °F and 50 grains of water/pound of dry air and the solar heat...

Magnetic Properties of nickel hydroxides layers 30A apart obtained by intercalation with dodecyl sulfate ion

NASA Astrophysics Data System (ADS)

Shmavonyan, Gagik; Zadoyan, Ovsanna

2013-03-01

Magnetic systems with reduced dimensionality make good test beds for checks on theoretical models. Here, changes in the nature of magnetic ordering in quasi-2d system of layered Ni hydroxides (LH-Ni-) with variations in the interlayer spacing c are investigated. Magnetic properties of LH-Ni-DS with c ~ 30 A° synthesized by intercalating dodecyl sulfate ion, (C12H25OSO3)- between the layers are compared with those of LH-Ni-Ac (c ~ 8.5 A°) containing the acetate (Ac) ligand. Measurements included those of magnetization M vs. T and H, ac susceptibilities (f = 0.1 Hz - 1000 Hz) and EMR (Electron Magnetic Resonance) spectra at 9.28 GHz. Results show that just like LH-Ni-Ac, LH-Ni-DS also orders ferromagnetically but with Tc ~ 23 Kabout 45 % largerthanT c 16 Kreportedfor LH-Ni-Ac.. In EMR studies, linewidth is strongly temperature-dependent, decreasing with decreasing T from 300 K, reaching a minimum near 45 K and then increasing sharply for T < 45 K, the latter due to short range magnetic ordering. These results differ with the model of Drillon et al in which interlayer dipolar interaction between clusters of correlated spins in the layers yields TC nearly independent of c. Roles of magnetic anisotropy and exchange constants in determining TC in the LH-Ni systems is discussed.

The expression and function of the achaete-scute genes in Tribolium castaneum reveals conservation and variation in neural pattern formation and cell fate specification

NASA Technical Reports Server (NTRS)

Wheeler, Scott R.; Carrico, Michelle L.; Wilson, Beth A.; Brown, Susan J.; Skeath, James B.

2003-01-01

The study of achaete-scute (ac/sc) genes has recently become a paradigm to understand the evolution and development of the arthropod nervous system. We describe the identification and characterization of the ac/sc genes in the coleopteran insect species Tribolium castaneum. We have identified two Tribolium ac/sc genes - achaete-scute homolog (Tc-ASH) a proneural gene and asense (Tc-ase) a neural precursor gene that reside in a gene complex. Focusing on the embryonic central nervous system we find that Tc-ASH is expressed in all neural precursors and the proneural clusters from which they segregate. Through RNAi and misexpression studies we show that Tc-ASH is necessary for neural precursor formation in Tribolium and sufficient for neural precursor formation in Drosophila. Comparison of the function of the Drosophila and Tribolium proneural ac/sc genes suggests that in the Drosophila lineage these genes have maintained their ancestral function in neural precursor formation and have acquired a new role in the fate specification of individual neural precursors. Furthermore, we find that Tc-ase is expressed in all neural precursors suggesting an important and conserved role for asense genes in insect nervous system development. Our analysis of the Tribolium ac/sc genes indicates significant plasticity in gene number, expression and function, and implicates these modifications in the evolution of arthropod neural development.

Failure detection and recovery in the assembly/contingency subsystem

NASA Technical Reports Server (NTRS)

Gantenbein, Rex E.

1993-01-01

The Assembly/Contingency Subsystem (ACS) is the primary communications link on board the Space Station. Any failure in a component of this system or in the external devices through which it communicates with ground-based systems will isolate the Station. The ACS software design includes a failure management capability (ACFM) that provides protocols for failure detection, isolation, and recovery (FDIR). The the ACFM design requirements as outlined in the current ACS software requirements specification document are reviewed. The activities carried out in this review include: (1) an informal, but thorough, end-to-end failure mode and effects analysis of the proposed software architecture for the ACFM; and (2) a prototype of the ACFM software, implemented as a C program under the UNIX operating system. The purpose of this review is to evaluate the FDIR protocols specified in the ACS design and the specifications themselves in light of their use in implementing the ACFM. The basis of failure detection in the ACFM is the loss of signal between the ground and the Station, which (under the appropriate circumstances) will initiate recovery to restore communications. This recovery involves the reconfiguration of the ACS to either a backup set of components or to a degraded communications mode. The initiation of recovery depends largely on the criticality of the failure mode, which is defined by tables in the ACFM and can be modified to provide a measure of flexibility in recovery procedures.

An Overview of Power Electronics Applications in Fuel Cell Systems: DC and AC Converters

PubMed Central

Ali, M. S.; Kamarudin, S. K.; Masdar, M. S.; Mohamed, A.

2014-01-01

Power electronics and fuel cell technologies play an important role in the field of renewable energy. The demand for fuel cells will increase as fuel cells become the main power source for portable applications. In this application, a high-efficiency converter is an essential requirement and a key parameter of the overall system. This is because the size, cost, efficiency, and reliability of the overall system for portable applications primarily depend on the converter. Therefore, the selection of an appropriate converter topology is an important and fundamental aspect of designing a fuel cell system for portable applications as the converter alone plays a major role in determining the overall performance of the system. This paper presents a review of power electronics applications in fuel cell systems, which include various topology combinations of DC converters and AC inverters and which are primarily used in fuel cell systems for portable or stand-alone applications. This paper also reviews the switching techniques used in power conditioning for fuel cell systems. Finally, this paper addresses the current problem encountered with DC converters and AC inverter. PMID:25478581

An overview of power electronics applications in fuel cell systems: DC and AC converters.

PubMed

Ali, M S; Kamarudin, S K; Masdar, M S; Mohamed, A

2014-01-01

Power electronics and fuel cell technologies play an important role in the field of renewable energy. The demand for fuel cells will increase as fuel cells become the main power source for portable applications. In this application, a high-efficiency converter is an essential requirement and a key parameter of the overall system. This is because the size, cost, efficiency, and reliability of the overall system for portable applications primarily depend on the converter. Therefore, the selection of an appropriate converter topology is an important and fundamental aspect of designing a fuel cell system for portable applications as the converter alone plays a major role in determining the overall performance of the system. This paper presents a review of power electronics applications in fuel cell systems, which include various topology combinations of DC converters and AC inverters and which are primarily used in fuel cell systems for portable or stand-alone applications. This paper also reviews the switching techniques used in power conditioning for fuel cell systems. Finally, this paper addresses the current problem encountered with DC converters and AC inverter.

Permian arc evolution associated with Panthalassa subduction along the eastern margin of the South China block, based on sandstone provenance and U-Pb detrital zircon ages of the Kurosegawa belt, Southwest Japan

NASA Astrophysics Data System (ADS)

Hara, Hidetoshi; Hirano, Miho; Kurihara, Toshiyuki; Takahashi, Toshiro; Ueda, Hayato

2018-01-01

We have studied the petrography, geochemistry, and detrital zircon U-Pb ages of sandstones from shallow-marine forearc sediments, accretionary complexes (ACs), and metamorphosed accretionary complexes (Meta-ACs) within the Kurosegawa belt of Southwest Japan. Those rocks formed in a forearc region of a Permian island arc associated with subduction of the Panthalassa oceanic crust along the eastern margin of the South China block (Yangtze block). The provenance of the shallow-marine sediments was dominated by basaltic to andesitic volcanic rocks and minor granitic rocks during the late Middle to Late Permian. The ACs were derived from felsic to andesitic volcanic rocks during the Late Permian. The provenance of Meta-ACs was dominated by andesitic volcanic rocks in the Middle Permian. The provenance, source rock compositions, and zircon age distribution for the forearc sediments, ACs and Meta-ACs have allowed us to reconstruct the geological history of the Permian arc system of the Kurosegawa belt. During the Middle Permian, the ACs were accreted along the eastern margin of the South China block. The Middle Permian arc was an immature oceanic island arc consisting of andesitic volcanic rocks. During the Late Permian, the ACs formed in a mature arc, producing voluminous felsic to andesitic volcanic rocks. A forearc basin developed during the late Middle to Late Permian. Subsequently, the Middle Permian ACs and part of the Late Permian AC underwent low-grade metamorphism in the Late to Early Jurassic, presenting the Meta-ACs.

AC-electric field dependent electroformation of giant lipid vesicles.

PubMed

Politano, Timothy J; Froude, Victoria E; Jing, Benxin; Zhu, Yingxi

2010-08-01

Giant vesicles of larger than 5 microm, which have been of intense interest for their potential as drug delivery vehicles and as a model system for cell membranes, can be rapidly formed from a spin-coated lipid thin film under an electric field. In this work, we explore the AC-field dependent electroformation of giant lipid vesicles in aqueous media over a wide range of AC-frequency from 1 Hz to 1 MHz and peak-to-peak field strength from 0.212 V/mm to 40 V/mm between two parallel conducting electrode surfaces. By using fluorescence microscopy, we perform in-situ microscopic observations of the structural evolution of giant vesicles formed from spin-coated lipid films under varied uniform AC-electric fields. The real-time observation of bilayer bulging from the lipid film, vesicle growth and fusing further examine the critical role of AC-induced electroosmotic flow of surrounding fluids for giant vesicle formation. A rich AC-frequency and field strength phase diagram is obtained experimentally to predict the AC-electroformation of giant unilamellar vesicles (GUVs) of l-alpha-phosphatidylcholine, where a weak dependence of vesicle size on AC-frequency is observed at low AC-field voltages, showing decreased vesicle size with a narrowed size distribution with increased AC-frequency. Formation of vesicles was shown to be constrained by an upper field strength of 10 V/mm and an upper AC-frequency of 10 kHz. Within these parameters, giant lipid vesicles were formed predominantly unilamellar and prevalent across the entire electrode surfaces. Copyright 2010 Elsevier B.V. All rights reserved.

Construction and characterisation of near-isogenic Plutella xylostella (Lepidoptera: Plutellidae) strains resistant to Cry1Ac toxin.

PubMed

Zhu, Xun; Lei, Yanyuan; Yang, Yanjv; Baxter, Simon W; Li, Jianhong; Wu, Qingjun; Wang, Shaoli; Xie, Wen; Guo, Zhaojiang; Fu, Wei; Zhang, Youjun

2015-02-01

Resistance to insecticidal Bacillus thuringiensis (Bt) toxins has arisen in multiple populations of the worldwide Brassica pest Plutella xylostella (L.). To help elucidate the mechanism of resistance to Bt Cry1Ac toxin in a population from Florida, two pairs of near-isogenic lines (NILs) were developed. NILs were generated using either backcross or recombinant inbred line methodologies and evaluated for near-isogenicity with inter-simple-sequence-repeat (ISSR) markers. Backcross line BC6F4 maintained a similar level of Cry1Ac resistance to parental strain DBM1Ac-R (>5000-fold) yet showed 98.24% genetic similarity to the susceptible parental strain DBM1Ac-S. Single-pair backcrosses between DBM1Ac-S and BC6F4 revealed that Cry1Ac resistance was controlled by one recessive autosomal locus. BC6F4 exhibited high levels of cross-resistance to Cry1Ab and Cry1Ah but not to Cry1Ca or Cry1Ie. Near-isogenic strains were constructed to provide a reliable biological system to investigate the mechanism of Cry1Ac resistance in P. xylostella. These data suggest that resistance to Cry1Ac, Cry1Ab and Cry1Ah is probably caused by the alteration of a common receptor not recognised by Cry1Ca or Cry1Ie. Understanding Bt toxin cross-resistance provides valuable information to consider when developing pest control strategies to delay resistance evolution. © 2014 Society of Chemical Industry. © 2014 Society of Chemical Industry.