WorldWideScience

Sample records for carrier field emission

  1. Distinction between the Poole-Frenkel and tunneling models of electric field-stimulated carrier emission from deep levels in semiconductors

    OpenAIRE

    Ganichev, Sergey; Ziemann, E.; Yassievich, Irina; Prettl, Wilhelm; Istratov, A.; Weber, E.

    2000-01-01

    The enhancement of the emission rate of charge carriers from deep-level defects in electric field is routinely used to determine the charge state of the defects. However, only a limited number of defects can be satisfactorily described by the Poole-Frenkel theory. An electric field dependence different from that expected from the Poole-Frenkel theory has been repeatedly reported in the literature, and no unambiguous identification of the charge state of the defect could be made. In this artic...

  2. Efficient Carrier-to-Exciton Conversion in Field Emission Tunnel Diodes Based on MIS-Type van der Waals Heterostack.

    Science.gov (United States)

    Wang, Shunfeng; Wang, Junyong; Zhao, Weijie; Giustiniano, Francesco; Chu, Leiqiang; Verzhbitskiy, Ivan; Zhou Yong, Justin; Eda, Goki

    2017-08-09

    We report on efficient carrier-to-exciton conversion and planar electroluminescence from tunnel diodes based on a metal-insulator-semiconductor (MIS) van der Waals heterostack consisting of few-layer graphene (FLG), hexagonal boron nitride (hBN), and monolayer tungsten disulfide (WS 2 ). These devices exhibit excitonic electroluminescence with extremely low threshold current density of a few pA·μm -2 , which is several orders of magnitude lower compared to the previously reported values for the best planar EL devices. Using a reference dye, we estimate the EL quantum efficiency to be ∼1% at low current density limit, which is of the same order of magnitude as photoluminescence quantum yield at the equivalent excitation rate. Our observations reveal that the efficiency of our devices is not limited by carrier-to-exciton conversion efficiency but by the inherent exciton-to-photon yield of the material. The device characteristics indicate that the light emission is triggered by injection of hot minority carriers (holes) to n-doped WS 2 by Fowler-Nordheim tunneling and that hBN serves as an efficient hole-transport and electron-blocking layer. Our findings offer insight into the intelligent design of van der Waals heterostructures and avenues for realizing efficient excitonic devices.

  3. Structural investigations on nanoemulsions, solid lipid nanoparticles and nanostructured lipid carriers by cryo-field emission scanning electron microscopy and Raman spectroscopy.

    Science.gov (United States)

    Saupe, Anne; Gordon, Keith C; Rades, Thomas

    2006-05-11

    Recently, colloidal dispersions based on solid lipids (solid lipid nanoparticles, SLN) and mixtures of solid and liquid lipids (nanostructured lipid carriers, NLC) were described as innovative carrier systems. A spherical particle shape is the basis of features such as a high loading capacity and controlled drug release characteristics due to smaller lipid-water interfaces and longer diffusion pathways when compared to thin platelets. The structures of SLN and the influence of oil load (NLC) on particle properties were investigated by photon correlation spectroscopy (PCS), laser diffractometry (LD), cryo-field emission scanning electron microscopy (cryo-FESEM), Raman spectroscopy and infrared spectroscopy (IR), and compared to a conventional nanoemulsion. PCS and LD data show similar size and size distribution for SLN and NLC (approximately 210 nm, polydispersity index approximately 0.15) and suggested a long term physical stability for the dispersions which had been stored for up to 12 months at different temperatures. Using cryo-FESEM droplets (for the nanoemulsion) and almost spherical particles for SLN and NLC were observed. Raman spectroscopy resulted in spectra for NLC that are weighted to the SLN spectra, suggesting an undisturbed crystal structure. Infrared spectra of the NLC are predominantly SLN in nature. Importantly the SLN bands are unshifted in the NLC spectrum indicating that the crystalline structure is unaffected by the presence of the oil.

  4. Field emission electronics

    CERN Document Server

    Egorov, Nikolay

    2017-01-01

    This book is dedicated to field emission electronics, a promising field at the interface between “classic” vacuum electronics and nanotechnology. In addition to theoretical models, it includes detailed descriptions of experimental and research techniques and production technologies for different types of field emitters based on various construction principles. It particularly focuses on research into and production of field cathodes and electron guns using recently developed nanomaterials and carbon nanotubes. Further, it discusses the applications of field emission cathodes in new technologies such as light sources, flat screens, microwave and X-ray devices.

  5. Heat to electricity conversion by cold carrier emissive energy harvesters

    Energy Technology Data Exchange (ETDEWEB)

    Strandberg, Rune [Department of Engineering Sciences, University of Agder, Jon Lilletuns vei 9, 4879 Grimstad (Norway)

    2015-12-07

    This paper suggests a method to convert heat to electricity by the use of devices called cold carrier emissive energy harvesters (cold carrier EEHs). The working principle of such converters is explained and theoretical power densities and efficiencies are calculated for ideal devices. Cold carrier EEHs are based on the same device structure as hot carrier solar cells, but works in an opposite way. Whereas a hot carrier solar cell receives net radiation from the sun and converts some of this radiative heat flow into electricity, a cold carrier EEH sustains a net outflux of radiation to the surroundings while converting some of the energy supplied to it into electricity. It is shown that the most basic type of cold carrier EEHs have the same theoretical efficiency as the ideal emissive energy harvesters described earlier by Byrnes et al. In the present work, it is also shown that if the emission from the cold carrier EEH originates from electron transitions across an energy gap where a difference in the chemical potential of the electrons above and below the energy gap is sustained, power densities slightly higher than those given by Byrnes et al. can be achieved.

  6. Field Emission in Vacuum Microelectronics

    CERN Document Server

    Fursey, George; Schwoebel, Paul

    2005-01-01

    Field emission is a phenomenon described by quantum mechanics. Its emission capability is millions times higher than that of any other known types of electron emission. Nowadays this phenomenon is experiencing a new life due to wonderful applications in the atomic resolution microscopy, in electronic holography, and in the vacuum micro- and nanoelectronics in general. The main field emission properties, and some most remarkable experimental facts and applications, are described in this book.

  7. Ultrafast carrier dynamics in graphene under a high electric field.

    Science.gov (United States)

    Tani, Shuntaro; Blanchard, François; Tanaka, Koichiro

    2012-10-19

    We investigated ultrafast carrier dynamics in graphene with near-infrared transient absorption measurement after intense half-cycle terahertz pulse excitation. The terahertz electric field efficiently drives the carriers, inducing large transparency in the near-infrared region. Theoretical calculations using the Boltzmann transport equation quantitatively reproduce the experimental findings. This good agreement suggests that the intense terahertz field should promote a remarkable impact ionization process and increase the carrier density.

  8. Field emission from crystalline niobium

    Directory of Open Access Journals (Sweden)

    Arti Dangwal Pandey

    2009-02-01

    Full Text Available Appreciable suppression of field emission (FE from metallic surfaces has been achieved by the use of improved surface cleaning techniques. In order to understand the effects of surface preparation on field emission, systematic measurements were performed on five single crystal and three large grain samples of high purity (RRR>300 niobium by means of atomic force microscope, x-ray diffraction, scanning electron microscope (SEM, and dc field emission scanning microscope. The samples were treated with buffered chemical polishing (BCP, half of those for 30  μm and others for 100  μm removal of surface layer, followed by a final high pressure water rinsing. These samples provided the emission at minimum surface fields of 150  MV/m and those with longer BCP treatment showed the onset of field emission at slightly higher fields. A low temperature (∼150°C heat treatment in a high vacuum (10^{-6}  mbar chamber for 14 hours, on a selected large grain Nb sample, gives the evidence for the grain boundary assisted FE at very high fields of 250 and 300  MV/m. Intrinsic field emission measurements on the present Nb surfaces revealed anisotropic values of work function for different orientations. Finally, an interesting correlation between sizes of all investigated emitters derived from SEM images with respect to their respective onset fields has been found, which might facilitate the quality control of superconducting radio-frequency cavities for linear accelerators.

  9. Diffusion of minority carriers against electric field (high injection level)

    Science.gov (United States)

    Gert, A. V.; Dmitriev, A. P.; Levinshtein, M. E.; Yuferev, V. S.; Palmour, J. W.

    2017-11-01

    A one-dimensional analytic model describing the motion of minority carriers against the electric field direction under the conditions of high injection level is developed. The results of the model can also be used to estimate the motion of carriers against the field in the case of an arbitrary injection level. The model makes it possible to describe, in good agreement with the results of computer simulation, the modulation of the collector layer resistance in a high voltage SiC bipolar transistor.

  10. Field emission behavior of boron nitride nanotubes

    Science.gov (United States)

    Yun, Ki Nam; Lee, Sang Heon; Han, Jun Soo; Song, Yoon-Ho; Lee, Cheol Jin

    2018-02-01

    The field emission properties of boron nitride nanotube (BNNT) field emitters according to vacuum pressure were demonstrated. During the short-term emission operation, the field emission behaviors were almost similar, regardless of the vacuum pressure, even though the turn-on electric field of the BNNT field emitter was slightly increased as the vacuum pressure increased. On the other hand, during the long-term emission operation, both the degradation and fluctuations of the emission current of the BNNT field emitters were dramatically increased as the vacuum pressure increased. The degradation of field emission properties of the BNNT emitters according to vacuum pressure is mainly attributed to the ion bombardment effect, rather than the oxidation effect. The field emission behavior under Ar ambient also strongly demonstrates that the degradation and the fluctuation of the emission current are largely dependent on the ion bombardment effect.

  11. Influence of Carrier Cooling on the Emission Dynamics of Semiconductor Microcavity Lasers

    Science.gov (United States)

    Hilpert, M.; Hofmann, M.; Ellmers, C.; Oestreich, M.; Schneider, H. C.; Jahnke, F.; Koch, S. W.; Rühle, W. W.; Wolf, H. D.; Bernklau, D.; Riechert, H.

    1997-11-01

    We investigate the influence of carrier relaxation on the emission dynamics of a semiconductor microcavity laser. The structure is optically excited with energies of 1.477 down to 1.346 eV (resonant excitation). The stimulated emission dynamics clearly becomes faster for decreasing excitation energy and the influence of the light hole on the emission dynamics is demonstrated. Theoretical calculations reproduce the results only if the nonequilibrium carrier dynamics is treated on the basis of a microscopic model.

  12. Recent advances in the field of nanometric drug carriers.

    Science.gov (United States)

    Ogier, Julien; Arnauld, Thomas; Doris, Eric

    2009-07-01

    Over the past few years, health and medicine have been domains where nanotechnologies have shown great promise, in particular in the area of drug carriers and drug targeting. Many active substances suffer from poor solubility, instability in biological medium and low bioavailability. Inaccurate distribution and accumulation of the drug in the body could lead to some side effects possibly detrimental to drug development. With the advent of nanosciences applied to medicine, new tools are becoming available, giving rise to a whole range of drug carriers with different properties and functionalities. Nanocarriers should play a crucial role in the controlled and sustained delivery of drugs. Various types of functional nanosystems are currently being explored and the aim of this review is to give an overview of the most recent advances in the field of nanometric drug carriers, including future strategies and perspectives.

  13. Carriers

    Science.gov (United States)

    ... addition, a small percentage of carriers have a mutation that cannot be identified through current testing. In this case, it will appear as though the disease has been caused by a single carrier. Carrier Testing A DNA test is the only way to detect carrier ...

  14. Hot Carrier-Based Near-Field Thermophotovoltaic Energy Conversion.

    Science.gov (United States)

    St-Gelais, Raphael; Bhatt, Gaurang Ravindra; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

    2017-03-28

    Near-field thermophotovoltaics (NFTPV) is a promising approach for direct conversion of heat to electrical power. This technology relies on the drastic enhancement of radiative heat transfer (compared to conventional blackbody radiation) that occurs when objects at different temperatures are brought to deep subwavelength distances (typically conversion of heat to electricity with a greater efficiency than using current solid-state technologies (e.g., thermoelectric generators). One of the main challenges in the development of this technology, however, is its incompatibility with conventional silicon PV cells. Thermal radiation is weak at frequencies larger than the ∼1.1 eV bandgap of silicon, such that PV cells with lower excitation energies (typically 0.4-0.6 eV) are required for NFTPV. Using low bandgap III-V semiconductors to circumvent this limitation, as proposed in most theoretical works, is challenging and therefore has never been achieved experimentally. In this work, we show that hot carrier PV cells based on Schottky junctions between silicon and metallic films could provide an attractive solution for achieving high efficiency NFTPV electricity generation. Hot carrier science is currently an important field of research and several approaches are investigated for increasing the quantum efficiency (QE) of hot carrier generation beyond conventional Fowler model predictions. If the Fowler limit can indeed be overcome, we show that hot carrier-based NFTPV systems-after optimization of their thermal radiation spectrum-could allow electricity generation with up to 10-30% conversion efficiencies and 10-500 W/cm 2 generated power densities (at 900-1500 K temperatures). We also discuss how the unique properties of thermal radiation in the extreme near-field are especially well suited for investigating recently proposed approaches for high QE hot carrier junctions. We therefore expect our work to be of interest for the field of hot carrier science and-by relying

  15. Field Emission from Nanostructure Carbon Films

    Science.gov (United States)

    Lim, Sung Hoon; Kim, Hong Sik; Jang, Jin; Lee, Choong Hun

    We studied the field emission properties of carbon nanostructure, which comprised of high density carbon nanotips on Si. These carbon nanotips are grown on metal coated Si by a high density plasma chemical vapor deposition (HDPCVD) using an inductively coupled plasma. The emission current increases with increasing the growth temperature. They exhibited an emission current density of 1 mA/cm2 at a field of 1.95 V/μm when the growth temperature was 700°C. We developed high brightness field emission lamps using the carbon nanotips.

  16. Accurate calculation of field and carrier distributions in doped semiconductors

    Directory of Open Access Journals (Sweden)

    Wenji Yang

    2012-06-01

    Full Text Available We use the numerical squeezing algorithm(NSA combined with the shooting method to accurately calculate the built-in fields and carrier distributions in doped silicon films (SFs in the micron and sub-micron thickness range and results are presented in graphical form for variety of doping profiles under different boundary conditions. As a complementary approach, we also present the methods and the results of the inverse problem (IVP - finding out the doping profile in the SFs for given field distribution. The solution of the IVP provides us the approach to arbitrarily design field distribution in SFs - which is very important for low dimensional (LD systems and device designing. Further more, the solution of the IVP is both direct and much easy for all the one-, two-, and three-dimensional semiconductor systems. With current efforts focused on the LD physics, knowing of the field and carrier distribution details in the LD systems will facilitate further researches on other aspects and hence the current work provides a platform for those researches.

  17. Field Emission Measurements from Niobium Electrodes

    Energy Technology Data Exchange (ETDEWEB)

    M. BastaniNejad, P.A. Adderley, J. Clark, S. Covert, J. Hansknecht, C. Hernandez-Garcia, R. Mammei, M. Poelker

    2011-03-01

    Increasing the operating voltage of a DC high voltage photogun serves to minimize space charge induced emittance growth and thereby preserve electron beam brightness, however, field emission from the photogun cathode electrode can pose significant problems: constant low level field emission degrades vacuum via electron stimulated desorption which in turn reduces photocathode yield through chemical poisoning and/or ion bombardment and high levels of field emission can damage the ceramic insulator. Niobium electrodes (single crystal, large grain and fine grain) were characterized using a DC high voltage field emission test stand at maximum voltage -225kV and electric field gradient > 10MV/m. Niobium electrodes appear to be superior to diamond-paste polished stainless steel electrodes.

  18. Pulsar Emission Geometry and Accelerating Field Strength

    Science.gov (United States)

    DeCesar, Megan E.; Harding, Alice K.; Miller, M. Coleman; Kalapotharakos, Constantinos; Parent, Damien

    2012-01-01

    The high-quality Fermi LAT observations of gamma-ray pulsars have opened a new window to understanding the generation mechanisms of high-energy emission from these systems, The high statistics allow for careful modeling of the light curve features as well as for phase resolved spectral modeling. We modeled the LAT light curves of the Vela and CTA I pulsars with simulated high-energy light curves generated from geometrical representations of the outer gap and slot gap emission models. within the vacuum retarded dipole and force-free fields. A Markov Chain Monte Carlo maximum likelihood method was used to explore the phase space of the magnetic inclination angle, viewing angle. maximum emission radius, and gap width. We also used the measured spectral cutoff energies to estimate the accelerating parallel electric field dependence on radius. under the assumptions that the high-energy emission is dominated by curvature radiation and the geometry (radius of emission and minimum radius of curvature of the magnetic field lines) is determined by the best fitting light curves for each model. We find that light curves from the vacuum field more closely match the observed light curves and multiwavelength constraints, and that the calculated parallel electric field can place additional constraints on the emission geometry

  19. THE DIFFUSE INTERSTELLAR BANDS AND ANOMALOUS MICROWAVE EMISSION MAY ORIGINATE FROM THE SAME CARRIERS

    Energy Technology Data Exchange (ETDEWEB)

    Bernstein, L. S.; Cline, J. A. [Spectral Sciences, Inc., 4 Fourth Avenue, Burlington, MA 01803 (United States); Clark, F. O. [Wopeco Research 125 South Great Road, Lincoln, MA 01773 (United States); Lynch, D. K., E-mail: larry@spectral.com, E-mail: jcline@spectral.com, E-mail: frank.clark@gmail.com, E-mail: dave@thulescientific.com [Thule Scientific, P.O. Box 953, Topanga, CA 90290 (United States)

    2015-11-10

    We argue that the observed spectroscopic and statistical properties of the diffuse interstellar band (DIB) carriers are those that are needed to produce the anomalous microwave emission (AME). We explore this idea using a carrier-impartial model for AME based on the observed DIB statistical properties. We show that an observed distribution of profile widths for narrow DIBs can be mapped into an AME spectrum. The mapping model is applied to width distributions observed for HD 204827 and HD 183143, selected because their spectroscopic and statistical properties bracket those for most other sight lines. The predicted AME spectra for these sight lines agree well with the range of spectral shapes, and peak frequencies, ∼23–31 GHz, typically observed for AME. We use the AME spectral profiles to derive a strong constraint between the average carrier size and its rotational temperature. The constraint is applied to a variety of postulated molecular carrier classes, including polycyclic aromatic hydrocarbons, fulleranes, hydrocarbon chains, and amorphous hydrocarbon clusters. The constraint favors small, cold carriers with average sizes of ∼8–15 carbon atoms, and average rotational temperatures of ∼3–10 K, depending on carrier type. We suggest new observations, analyses, and modeling efforts to help resolve the ambiguities with regard to carrier size and class, and to further clarify the DIB–AME relationship.

  20. A Model for Prediction of Propulsion Power and Emissions – Tankers and Bulk Carriers

    DEFF Research Database (Denmark)

    Lützen, Marie; Kristensen, Hans Otto Holmegaard

    design standards. The IHS Fairplay World Fleet Statistics for vessels built in the period 1990 – 2010 is used as a basis for the modeling of the main dimensions. The model can be used to calculate exhaust gas emissions, including emissions of carbon dioxide (CO2), from bulk carriers and tankers......To get an idea of the reduction in propulsion power and associated emissions by varying the speed and other ship design main parameters, a generic model for parameter studies of tankers and bulk carriers has been developed. With only a few input parameters of which the maximum deadweight capacity...... it is possible to estimate the influence of the different parameters on the power demand. The model is based on previously well-established power prediction methods which have been updated and verified by model test results and full-scale data, meaning that the predictions are up to date according to modern ship...

  1. Stable field emission from nanoporous silicon carbide

    Science.gov (United States)

    Kang, Myung-Gyu; Lezec, Henri J.; Sharifi, Fred

    2013-02-01

    We report on a new type of stable field emitter capable of electron emission at levels comparable to thermal sources. Such an emitter potentially enables significant advances in several important technologies which currently use thermal electron sources. These include communications through microwave electronics, and more notably imaging for medicine and security where new modalities of detection may arise due to variable-geometry x-ray sources. Stable emission of 6 A cm-2 is demonstrated in a macroscopic array, and lifetime measurements indicate these new emitters are sufficiently robust to be considered for realistic implementation. The emitter is a monolithic structure, and is made in a room-temperature process. It is fabricated from a silicon carbide wafer, which is formed into a highly porous structure resembling an aerogel, and further patterned into an array. The emission properties may be tuned both through control of the nanoscale morphology and the macroscopic shape of the emitter array.

  2. Integrated field emission array for ion desorption

    Science.gov (United States)

    Resnick, Paul J; Hertz, Kristin L; Holland, Christopher; Chichester, David; Schwoebel, Paul

    2013-09-17

    An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

  3. Integrated field emission array for ion desorption

    Energy Technology Data Exchange (ETDEWEB)

    Resnick, Paul J; Hertz, Kristin L.; Holland, Christopher; Chichester, David

    2016-08-23

    An integrated field emission array for ion desorption includes an electrically conductive substrate; a dielectric layer lying over the electrically conductive substrate comprising a plurality of laterally separated cavities extending through the dielectric layer; a like plurality of conically-shaped emitter tips on posts, each emitter tip/post disposed concentrically within a laterally separated cavity and electrically contacting the substrate; and a gate electrode structure lying over the dielectric layer, including a like plurality of circular gate apertures, each gate aperture disposed concentrically above an emitter tip/post to provide a like plurality of annular gate electrodes and wherein the lower edge of each annular gate electrode proximate the like emitter tip/post is rounded. Also disclosed herein are methods for fabricating an integrated field emission array.

  4. Field efficacy of inorganic carrier based formulations of Serratia ...

    African Journals Online (AJOL)

    In the present study, an attempt was taken to reduce the use of chemical pesticide and fertilizer by using two inorganic carriers (talcum powder and vermiculite) based formulation of S. entomophila in sesame. From the experimental results it was evident that the vermiculite based formulation of S. entomophila AB2 proved a ...

  5. Ultrafast electron field emission from gold resonant antennas studied by two terahertz pulse experiments

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew C.

    2015-01-01

    Summary form only given. Ultrafast electron field emission from gold resonant antennas induced by strong terahertz (THz) transient is investigated using two THz pulse experiments. It is shown that UV emission from nitrogen plasma generated by liberated electrons is a good indication of the local...... electric field at the antenna tip. Using this method resonant properties of antennas fabricated on high resistivity silicon are investigated in the strong field regime. Decrease of antenna Q-factor due to ultrafast carrier multiplication in the substrate is observed....

  6. Processing of materials for uniform field emission

    Science.gov (United States)

    Pam, L.S.; Felter, T.E.; Talin, A.; Ohlberg, D.; Fox, C.; Han, S.

    1999-01-12

    This method produces a field emitter material having a uniform electron emitting surface and a low turn-on voltage. Field emitter materials having uniform electron emitting surfaces as large as 1 square meter and turn-on voltages as low as 16V/{micro}m can be produced from films of electron emitting materials such as polycrystalline diamond, diamond-like carbon, graphite and amorphous carbon by the method of the present invention. The process involves conditioning the surface of a field emitter material by applying an electric field to the surface, preferably by scanning the surface of the field emitter material with an electrode maintained at a fixed distance of at least 3 {micro}m above the surface of the field emitter material and at a voltage of at least 500V. In order to enhance the uniformity of electron emission the step of conditioning can be preceded by ion implanting carbon, nitrogen, argon, oxygen or hydrogen into the surface layers of the field emitter material. 2 figs.

  7. Spectroscopy of Charge Carriers and Traps in Field-Doped Single Crystal Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang [Columbia Univ., New York, NY (United States); Frisbie, Daniel [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-03-31

    The proposed research aims to achieve quantitative, molecular level understanding of charge carriers and traps in field-doped crystalline organic semiconductors via in situ linear and nonlinear optical spectroscopy, in conjunction with transport measurements and molecular/crystal engineering.

  8. Influence of carrier relaxation on the dynamics of stimulated emission in microcavity lasers

    Science.gov (United States)

    Hilpert, M.; Klann, H.; Hofmann, M.; Ellmers, C.; Oestreich, M.; Schneider, H. C.; Jahnke, F.; Koch, S. W.; Rühle, W. W.; Wolf, H. D.; Bernklau, D.; Riechert, H.

    1997-12-01

    The influence of carrier relaxation on the emission dynamics of a semiconductor microcavity laser is investigated using femtosecond optical excitation. For moderate excitation intensities, the dynamics of the output laser pulse becomes significantly slower when the photon energy of the pump laser is tuned from the quantum well band-gap energy towards higher energies. Theoretical calculations reproduce this trend only if the interaction-induced dephasing of the polarization driven by the pump pulse, the formation, and relaxation of the nonequilibrium carrier distribution as well as the chirp of the excitation pulse are taken into account. Additionally, band-structure effects such as excitation of light holes influence the thermalization dynamics and lead to discontinuities in the general trend.

  9. Intraband carrier kinetics and picosecond pulse shaping in field-enhanced bulk semiconductor absorbers.

    Science.gov (United States)

    Uskov, A V; McInerney, J; Karin, J R; Bowers, J E

    1998-03-01

    Picosecond pulse propagation through a field-enhanced waveguide bulk semiconductor saturable absorber is studied numerically. Fast switching from unsaturated absorption to delayed strong saturation and gain, as well as the predicted dependence of saturation energy on electric field, is based on intraband carrier kinetics and electric-field dynamics in the absorber and can lead to improved, controllable pulse shaping.

  10. Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices

    Science.gov (United States)

    Chen, Yonghua; Xia, Yingdong; Smith, Gregory M.; Gu, Yu; Yang, Chuluo; Carroll, David L.

    2013-01-01

    In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

  11. Nitrogen plasma formation through terahertz-induced ultrafast electron field emission

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew

    2015-01-01

    . Terahertz (THz) radiation, commonly understood to be nonionizing due to its low photon energy, is here shown to produce electron field emission. We demonstrate that a carrier-envelope phase-stable single-cycle optical field at THz frequencies interacting with a metallic microantenna can generate...... and accelerate ultrashort and ultrabright electron bunches into free space, and we use these electrons to excite and ionize ambient nitrogen molecules near the antenna. The associated UV emission from the gas forms a novel THz wave detector, which, in contrast with conventional photon-counting or heat...

  12. A novel field emission microscopy method to study field emission characteristics of freestanding carbon nanotube arrays

    Science.gov (United States)

    Li, Yunhan; Sun, Yonghai; Jaffray, David A.; Yeow, John T. W.

    2017-04-01

    Field emission (FE) uniformity and the mechanism of emitter failure of freestanding carbon nanotube (CNT) arrays have not been well studied due to the difficulty of observing and quantifying FE performance of each emitter in CNT arrays. Herein a field emission microscopy (FEM) method based on poly(methyl methacrylate) (PMMA) thin film is proposed to study the FE uniformity and CNT emitter failure of freestanding CNT arrays. FE uniformity of freestanding CNT arrays and different levels of FE current contributions from each emitter in the arrays are recorded and visualized. FEM patterns on the PMMA thin film contain the details of the CNT emitter tip shape and whether multiple CNT emitters occur at an emission site. Observation of real-time FE performance and the CNT emitter failure process in freestanding CNT arrays are successfully achieved using a microscopic camera. High emission currents through CNT emitters causes Joule heating and light emission followed by an explosion of the CNTs. The proposed approach is capable of resolving the major challenge of building the relationship between FE performance and CNT morphologies, which can significantly facilitate the study of FE non-uniformity, the emitter failure mechanism and the development of stable and reliable FE devices in practical applications.

  13. Geothermal emissions data base, Wairakei geothermal field

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, S.R. (comp.)

    1978-04-01

    A database subset on the gaseous emissions from the Wairakei geothermal field is presented. Properties and states of the reservoir fluid such as flow rates, wellhead pressure, and enthalpy are included in the file along with the well name and constituent measurement. This subset is the result of an initial screening of the data covering 1965 to 1971, and new additions will be appended periodically to the file. The data is accessed by a database management system as are all other subsets in the file. Thereby, one may search the database for specific data requirements and print selective output. For example, one may wish to locate reservoir conditions for cases only when the level of the constituent exceeded a designated value. Data output is available in the form of numerical compilations such as the attached, or graphical displays disposed to paper, film or magnetic tape.

  14. Scanning Anode Field Emission Characterisation of Carbon Nanotube emitter arrays

    NARCIS (Netherlands)

    Berhanu, S.; Gröning, O.; Chen, Z.; Merikhi, J.; Bachmann, P.K.

    2011-01-01

    Scanning anode field emission microscopy (SAFEM) was used to characterise carbon nanotube (CNT) emitter arrays produced within Philips CediX-Technotubes' activities. Four different samples were investigated and compared. The field enhancement distributions were determined and the local field

  15. Current enhancement due to field-induced dark carrier multiplication in graphene

    Science.gov (United States)

    Jago, Roland; Wendler, Florian; Malic, Ermin

    2017-06-01

    We present a microscopic study on current generation in graphene in response to an electric field. While scattering is generally considered to reduce the current, we reveal that in graphene Auger processes give rise to a current enhancement via a phenomenon we denote dark carrier multiplication. Based on a microscopic approach, we show that, if other scattering channels are absent, this prevents the carrier distribution to reach a stationary value. Taking into account scattering with phonons a finite current is restored, however its value exceeds the stationary current without scattering.

  16. An atom in a multi-frequency laser emission field

    Energy Technology Data Exchange (ETDEWEB)

    Delone, N.B.; Kovarskii, V.A.; Masalov, A.V.; Perelman, N.F.

    1980-01-01

    An analysis of the features of the interaction between a nonmonochromatic multi-frequency laser emission field and an isolated atom is given. The multi-photon excitation and non-linear ionization of the atom during the excitation of the atomic levels by the laser emission field are examined. Specific cases of the interaction between the atom and the field are examined in detail: the case of a broad laser emission laser spectrum (rapid field fluctuations) and the case of a narrow spectrum (slow fluctuation). The available experimental data relating to these problems are analyzed.

  17. Two-Dimensional Transition Metal Dichalcogenides and Their Charge Carrier Mobilities in Field-Effect Transistors

    Science.gov (United States)

    Ahmed, Sohail; Yi, Jiabao

    2017-10-01

    Two-dimensional (2D) materials have attracted extensive interest due to their excellent electrical, thermal, mechanical, and optical properties. Graphene has been one of the most explored 2D materials. However, its zero band gap has limited its applications in electronic devices. Transition metal dichalcogenide (TMDC), another kind of 2D material, has a nonzero direct band gap (same charge carrier momentum in valence and conduction band) at monolayer state, promising for the efficient switching devices (e.g., field-effect transistors). This review mainly focuses on the recent advances in charge carrier mobility and the challenges to achieve high mobility in the electronic devices based on 2D-TMDC materials and also includes an introduction of 2D materials along with the synthesis techniques. Finally, this review describes the possible methodology and future prospective to enhance the charge carrier mobility for electronic devices.

  18. Scanning probe microscopy and field emission schemes for studying electron emission from polycrystalline diamond

    OpenAIRE

    Chubenko, Oksana; Baturin, Stanislav S.; Baryshev, Sergey V.

    2016-01-01

    The letter introduces a diagram that rationalizes tunneling atomic force microscopy (TUNA) observations of electron emission from polycrystalline diamonds as described in recent publications. The direct observations of electron emission from grain boundary sites by TUNA could indeed be evidence of electrons originating from grain boundaries under external electric fields. At the same time, from the diagram it follows that TUNA and field emission schemes are complimentary rather than equivalen...

  19. Probing and modeling of carrier motion in organic devices by electric-field-induced optical second-harmonic generation

    Science.gov (United States)

    Iwamoto, Mitsumasa; Manaka, Takaaki; Taguchi, Dai

    2014-10-01

    By probing dielectric polarization originating from dipoles and electrons in materials, we can study dynamical carrier behaviors in materials and also in devices. Maxwell displacement current (MDC) measurement allows us to directly probe orientational dipolar motion in monolayers, while electric-field-induced optical second-harmonic generation (EFISHG) measurement allows dynamical electron and hole transport in solids to be probed directly. By probing nonlinear polarization induced in solids by coupling with incident electromagnetic waves of laser beam and dc electric field that originate from moving carriers, long-range carrier motion is visualized. Experiments using a time-resolved EFISHG technique reveal carrier transfer in organic devices such as organic field-effect transistors, organic light-emitting diodes, organic memory devices, and organic solar cells, and thus enable us to model the carrier transport mechanism. We anticipate that this novel technique using EFISHG can be a powerful tool for studying carrier behaviors in organic devices as well as in organic materials.

  20. Spacecraft mass spectrometer ion source employing field emission cathodes

    Science.gov (United States)

    Curtis, C. C.; Hsieh, K. C.

    1986-01-01

    An ion source that utilizes a pair of thin-film field emission cathodes to provide current for electric impact ionization is studied. The field emission cathodes are composed of microscopically small needle tips and an extraction electrode; the cathodes generate a 200-eV, 0.1-mA electron beam. The multistep process for the manufacturing of the field emission cathodes is examined. The operation of the ion source, which ionizes atoms and molecules that enter the mass spectrometer with a ram velocity of about 80 km/sec, is described.

  1. Recent progress in nanostructured next-generation field emission devices

    Science.gov (United States)

    Mittal, Gaurav; Lahiri, Indranil

    2014-08-01

    Field emission has been known to mankind for more than a century, and extensive research in this field for the last 40-50 years has led to development of exciting applications such as electron sources, miniature x-ray devices, display materials, etc. In the last decade, large-area field emitters were projected as an important material to revolutionize healthcare and medical devices, and space research. With the advent of nanotechnology and advancements related to carbon nanotubes, field emitters are demonstrating highly enhanced performance and novel applications. Next-generation emitters need ultra-high emission current density, high brightness, excellent stability and reproducible performance. Novel design considerations and application of new materials can lead to achievement of these capabilities. This article presents an overview of recent developments in this field and their effects on improved performance of field emitters. These advancements are demonstrated to hold great potential for application in next-generation field emission devices.

  2. Field emission properties of single crystal chromium disilicide nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Valentin, L. A.; Carpena-Nunez, J.; Yang, D.; Fonseca, L. F. [Department of Physics, University of Puerto Rico, Rio Piedras Campus, P.O. Box 70377, San Juan, 00931 (Puerto Rico)

    2013-01-07

    The composition, crystal structure, and field emission properties of high-crystallinity chromium disilicide (CrSi{sub 2}) nanowires synthesized by a vapor deposition method have been studied. High resolution transmission electron microscopy, energy dispersive spectroscopy, and selected area electron diffraction studies confirm the single-crystalline structure and composition of the CrSi{sub 2} nanowires. Field emission measurements show that an emission current density of 0.1 {mu}A/cm{sup 2} was obtained at a turn-on electric field intensity of 2.80 V/{mu}m. The maximum emission current measured was 1.86 mA/cm{sup 2} at 3.6 V/{mu}m. The relation between the emission current density and the electric field obtained follows the Fowler-Nordheim equation, with an enhancement coefficient of 1140. The electrical conductivity of single nanowires was measured by using four-point-probe specialized microdevices at different temperatures, and the calculated values are close to those reported in previous studies for highly conductive single crystal bulk CrSi{sub 2}. The thermal tolerance of the nanowires was studied up to a temperature of 1100 Degree-Sign C. The stability of the field emission current, the I-E values, their thermal tolerance, and high electrical conductivity make CrSi{sub 2} nanowires a promising material for field emission applications.

  3. Field emission properties of single crystal chromium disilicide nanowires

    Science.gov (United States)

    Valentín, L. A.; Carpena-Nuñez, J.; Yang, D.; Fonseca, L. F.

    2013-01-01

    The composition, crystal structure, and field emission properties of high-crystallinity chromium disilicide (CrSi2) nanowires synthesized by a vapor deposition method have been studied. High resolution transmission electron microscopy, energy dispersive spectroscopy, and selected area electron diffraction studies confirm the single-crystalline structure and composition of the CrSi2 nanowires. Field emission measurements show that an emission current density of 0.1 μA/cm2 was obtained at a turn-on electric field intensity of 2.80 V/μm. The maximum emission current measured was 1.86 mA/cm2 at 3.6 V/μm. The relation between the emission current density and the electric field obtained follows the Fowler-Nordheim equation, with an enhancement coefficient of 1140. The electrical conductivity of single nanowires was measured by using four-point-probe specialized microdevices at different temperatures, and the calculated values are close to those reported in previous studies for highly conductive single crystal bulk CrSi2. The thermal tolerance of the nanowires was studied up to a temperature of 1100 °C. The stability of the field emission current, the I-E values, their thermal tolerance, and high electrical conductivity make CrSi2 nanowires a promising material for field emission applications.

  4. Rf Gun with High-Current Density Field Emission Cathode

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield

    2005-12-19

    High current-density field emission from an array of carbon nanotubes, with field-emission-transistor control, and with secondary electron channel multiplication in a ceramic facing structure, have been combined in a cold cathode for rf guns and diode guns. Electrodynamic and space-charge flow simulations were conducted to specify the cathode configuration and range of emission current density from the field emission cold cathode. Design of this cathode has been made for installation and testing in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 0.1-1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes

  5. Photogeneration of charge carrier correlated with amplified spontaneous emission in single crystals of a thiophene/phenylene co-oligomer.

    Science.gov (United States)

    Saeki, Akinori; Seki, Shu; Shimizu, Yasuhiro; Yamao, Takeshi; Hotta, Shu

    2010-04-07

    Thiophene/phenylene co-oligomers have substantial promise for the use of not only organic electronics but also organic optical devices. However, considerably less is known about the correlation between their optical and optoelectronic properties. We have investigated the charge carrier generation in 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5) single crystals by flash-photolysis time-resolved microwave conductivity (TRMC) and transient absorption spectroscopy (TAS). It was found that the dependence of photocarrier generation efficiency on excitation photon density differed from that of emission efficiency once amplified spontaneous emission (ASE) and resultant spectrally narrowed emission occur upon exposure to 355 nm. In contrast, the dependences of emission and photocarrier generation efficiencies were identical when ASE was not involved at a different excitation wavelength (193 nm). An approximated analytical solution of rate equation considering ASE or singlet-singlet annihilation was applied to the experiments, exhibiting good agreement. On the basis of TRMC, TAS, and extinction coefficient of radical cation assessed by pulse radiolysis, the minimum charge carrier mobility was estimated, without electrodes, to be 0.12 cm(2) V(-1) s(-1). The dynamics of charge carrier and triplet excited state is discussed, accompanying with examination by time-dependent density functional theory. The present work would open the way to a deeper understanding of the fate of excited state in optically robust organic semiconducting crystals.

  6. Can dust emission mechanisms be determined from field measurements?

    Science.gov (United States)

    Field observations are needed to develop and test theories on dust emission for use in dust modeling systems. The dust emission mechanism (aerodynamic entrainment, saltation bombardment, aggregate disintegration) as well as the amount and particle-size distribution of emitted dust may vary under sed...

  7. Laser terahertz emission microscopy with near-field probes

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Mittleman, Daniel M.

    2016-01-01

    Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm....

  8. Cold cathode rf guns based study on field emission

    Directory of Open Access Journals (Sweden)

    Xiangkun Li

    2013-12-01

    Full Text Available Recently cold cathodes based on field emission have drawn attention and been considered to drive accelerators and free electron lasers, due to the progress in field emitter arrays and planar emitters like diamond films. In this paper, we reviewed the characteristics of field emission in rf fields. Simulations of S-band rf guns consisting of a cathode cell and a full cell were done. We showed that a shorter cathode cell with a length of 0.25–0.3 of λ/2 is in favor of obtaining both low emittance and low energy spread bunches when the amplitude of electric field on the cathode surface ranges from 60 to 80  MV/m. A single cell test cavity has been installed to study field emission of diamond films and the measured beam current showed a good agreement with theoretical calculations.

  9. Can dust emission mechanisms be determined from field measurements?

    Science.gov (United States)

    Klose, Martina; Webb, Nicholas; Gill, Thomas E.; Van Pelt, Scott; Okin, Gregory

    2017-04-01

    Field observations are needed to develop and test theories on dust emission for use in dust modeling systems. The dust emission mechanism (aerodynamic entrainment, saltation bombardment, aggregate disintegration) as well as the amount and particle-size distribution of emitted dust may vary under sediment supply- and transport-limited conditions. This variability, which is caused by heterogeneity of the surface and the atmosphere, cannot be fully captured in either field measurements or models. However, uncertainty in dust emission modeling can be reduced through more detailed observational data on the dust emission mechanism itself. To date, most measurements do not provide enough information to allow for a determination of the mechanisms leading to dust emission and often focus on a small variety of soil and atmospheric settings. Additionally, data sets are often not directly comparable due to different measurement setups. As a consequence, the calibration of dust emission schemes has so far relied on a selective set of observations, which leads to an idealization of the emission process in models and thus affects dust budget estimates. Here, we will present results of a study which aims to decipher the dust emission mechanism from field measurements as an input for future model development. Detailed field measurements are conducted, which allow for a comparison of dust emission for different surface and atmospheric conditions. Measurements include monitoring of the surface, loose erodible material, transported sediment, and meteorological data, and are conducted in different environmental settings in the southwestern United States. Based on the field measurements, a method is developed to differentiate between the different dust emission mechanisms.

  10. Mapping Free-Carriers in Multijunction Silicon Nanowires Using Infrared Near-Field Optical Microscopy.

    Science.gov (United States)

    Ritchie, Earl T; Hill, David J; Mastin, Tucker M; Deguzman, Panfilo C; Cahoon, James F; Atkin, Joanna M

    2017-11-08

    We report the use of infrared (IR) scattering-type scanning near-field optical microscopy (s-SNOM) as a nondestructive method to map free-carriers in axially modulation-doped silicon nanowires (SiNWs) with nanoscale spatial resolution. Using this technique, we can detect local changes in the electrically active doping concentration based on the infrared free-carrier response in SiNWs grown using the vapor-liquid-solid (VLS) method. We demonstrate that IR s-SNOM is sensitive to both p-type and n-type free-carriers for carrier densities above ∼1 × 1019 cm-3. We also resolve subtle changes in local conductivity properties, which can be correlated with growth conditions and surface effects. The use of s-SNOM is especially valuable in low mobility materials such as boron-doped p-type SiNWs, where optimization of growth has been difficult to achieve due to the lack of information on dopant distribution and junction properties. s-SNOM can be widely employed for the nondestructive characterization of nanostructured material synthesis and local electronic properties without the need for contacts or inert atmosphere.

  11. Current fluctuation of electron and hole carriers in multilayer WSe{sub 2} field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Seung-Pil; Shin, Jong Mok; Jang, Ho-Kyun; Jin, Jun Eon; Kim, Gyu-Tae, E-mail: gtkim@korea.ac.kr [School of Electrical Engineering, Korea University, Seoul 02481 (Korea, Republic of); Kim, Yong Jin; Kim, Young Keun [Department of Materials Science and Engineering, Korea University, Seoul 02481 (Korea, Republic of); Shin, Minju [School of Electrical Engineering, Korea University, Seoul 02481 (Korea, Republic of); IMEP-LAHC, Grenoble INP-MINATEC, 3 Parvis Louis Neel, 38016 Grenoble (France)

    2015-12-14

    Two-dimensional materials have outstanding scalability due to their structural and electrical properties for the logic devices. Here, we report the current fluctuation in multilayer WSe{sub 2} field effect transistors (FETs). In order to demonstrate the impact on carrier types, n-type and p-type WSe{sub 2} FETs are fabricated with different work function metals. Each device has similar electrical characteristics except for the threshold voltage. In the low frequency noise analysis, drain current power spectral density (S{sub I}) is inversely proportional to frequency, indicating typical 1/f noise behaviors. The curves of the normalized drain current power spectral density (NS{sub I}) as a function of drain current at the 10 Hz of frequency indicate that our devices follow the carrier number fluctuation with correlated mobility fluctuation model. This means that current fluctuation depends on the trapping-detrapping motion of the charge carriers near the channel interface. No significant difference is observed in the current fluctuation according to the charge carrier type, electrons and holes that occurred in the junction and channel region.

  12. Field electron emission from a carbon-covered iridium tip

    Science.gov (United States)

    Bernatskii, D. P.; Pavlov, V. G.

    2017-11-01

    The formation of a carbon coating on an iridium field-emission electron emitter by benzene vapor pyrolysis has been studied. Processes on an emitting tip differ from those studied earlier on flat metal surfaces. The resulting coating either represents a monoatomic graphene film on the flat faces of the emitter or consists of graphene clusters. The field electron emission is localized on the edges and in the corners of a faceted graphite outgrowth. After alkali metals are adsorbed on the carbon coating, emissions from the flat faces anomalously grows and localizes on graphene-coated faces with alkali atoms present on the surface and under the graphene film.

  13. Field emission properties of the graphenated carbon nanotube electrode

    Energy Technology Data Exchange (ETDEWEB)

    Zanin, H., E-mail: hudson.zanin@bristol.ac.uk [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Faculdade de Engenharia Elétrica e Computação, Departamento de Semicondutores, Instrumentos e Fotônica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N. 400, CEP 13 083-852 Campinas, São Paulo (Brazil); Ceragioli, H.J.; Peterlevitz, A.C.; Baranauskas, Vitor [Faculdade de Engenharia Elétrica e Computação, Departamento de Semicondutores, Instrumentos e Fotônica, Universidade Estadual de Campinas, UNICAMP, Av. Albert Einstein N. 400, CEP 13 083-852 Campinas, São Paulo (Brazil); Marciano, F.R.; Lobo, A.O. [Laboratory of Biomedical Nanotechnology/Institute of Research and Development at UNIVAP, Av. Shishima Hifumi, 2911, CEP 12244-000 Sao Jose dos Campos, SP (Brazil)

    2015-01-01

    Graphical abstract: - Highlights: • Facile method to prepare graphenated carbon nanotubes (g-CNTs). • The electric field emission behaviour of g-CNTs was studied. • g-CNTs show better emission current stability than non-graphenated CNTs. - Abstract: Reduced graphene oxide-coated carbon nanotubes (RGO-CNT) electrodes have been prepared by hot filament chemical vapour deposition system in one-step growth process. We studied RGO-CNT electrodes behaviour as cold cathode in field emission test. Our results show that RGO-CNT retain the low threshold voltage typical of CNTs, but with greatly improved emission current stability. The field emission enhancement value is significantly higher than that expected being caused by geometric effect (height divided by the radius of nanotube). This suggested that the field emission of this hybrid structure is not only from a single tip, but eventually it is from several tips with contribution of graphene nanosheets at CNT's walls. This phenomenon explains why the graphenated carbon nanotubes do not burn out as quickly as CNT does until emission ceases completely. These preliminaries results make nanocarbon materials good candidates for applications as electron sources for several devices.

  14. Carbon-11-Pittsburgh compound B positron emission tomography imaging of amyloid deposition in presenilin 1 mutation carriers.

    Science.gov (United States)

    Knight, William D; Okello, Aren A; Ryan, Natalie S; Turkheimer, Federico E; Rodríguez Martinez de Llano, Sofia; Edison, Paul; Douglas, Jane; Fox, Nick C; Brooks, David J; Rossor, Martin N

    2011-01-01

    (11)Carbon-Pittsburgh compound B positron emission tomography studies have suggested early and prominent amyloid deposition in the striatum in presenilin 1 mutation carriers. This cross-sectional study examines the (11)Carbon-Pittsburgh compound B positron emission tomography imaging profiles of presymptomatic and mildly affected (mini-mental state examination ≥ 20) carriers of seven presenilin 1 mutations, comparing them with groups of controls and symptomatic sporadic Alzheimer's disease cases. Parametric ratio images representing (11)Carbon-Pittsburgh compound B retention from 60 to 90 min were created using the pons as a reference region and nine regions of interest were studied. We confirmed that increased amyloid load may be detected in presymptomatic presenilin 1 mutation carriers with (11)Carbon-Pittsburgh compound B positron emission tomography and that the pattern of retention is heterogeneous. Comparison of presenilin 1 and sporadic Alzheimer's disease groups revealed significantly greater thalamic retention in the presenilin 1 group and significantly greater frontotemporal retention in the sporadic Alzheimer's disease group. A few individuals with presenilin 1 mutations showed increased cerebellar (11)Carbon-Pittsburgh compound B retention suggesting that this region may not be as suitable a reference region in familial Alzheimer's disease.

  15. Locally Resolved Electron Emission Area and Unified View of Field Emission from Ultrananocrystalline Diamond Films

    Energy Technology Data Exchange (ETDEWEB)

    Chubenko, Oksana [Department of Physics, The George Washington University, 725 21st Street NW, Washington, D.C. 20052, United States; Euclid TechLabs, 365 Remington Boulevard, Bolingbrook, Illinois 60440, United States; Baturin, Stanislav S. [PSD Enrico; Kovi, Kiran K. [Euclid TechLabs, 365 Remington Boulevard, Bolingbrook, Illinois 60440, United States; Sumant, Anirudha V. [Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, Illinois 60439, United States; Baryshev, Sergey V. [Euclid TechLabs, 365 Remington Boulevard, Bolingbrook, Illinois 60440, United States

    2017-09-13

    One of the common problems in case of field emission from polycrystalline diamond films, which typically have uniform surface morphology, is uncertainty in determining exact location of electron emission sites across the surface. Although several studies have suggested that grain boundaries are the main electron emission source, it is not particularly clear what makes some sites emit more than the others. It is also practically unclear how one could quantify the actual electron emission area and therefore field emission current per unit area. In this paper we study the effect of actual, locally resolved, field emission (FE) area on electron emission characteristics of uniform planar highly conductive nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) field emitters. It was routinely found that field emission from as-grown planar (N)UNCD films is always confined to a counted number of discrete emitting centers across the surface which varied in size and electron emissivity. It was established that the actual FE area critically depends on the applied electric field, as well as that the actual FE area and the overall electron emissivity improve with sp2 fraction present in the film irrespectively of the original substrate roughness and morphology. To quantify the actual FE area and its dependence on the applied electric field, imaging experiments were carried out in a vacuum system in a parallel-plate configuration with a specialty anode phosphor screen. Electron emission micrographs were taken concurrently with I-V characteristics measurements. In addition, a novel automated image processing algorithm was developed to process extensive imaging datasets and calculate emission area per image. By doing so, it was determined that the emitting area was always significantly smaller than the FE cathode surface area. Namely, the actual FE area would change from 5×10-3 % to 1.5 % of the total cathode area with the applied electric field increased. Finally and most

  16. Methane emission from wetland rice fields

    NARCIS (Netherlands)

    Denier van der Gon, H.A.C.

    1996-01-01


    Methane (CH 4 ) is an important greenhouse gas and plays a key role in tropospheric and stratospheric chemistry. Wetland rice fields are an important source of methane, accounting for approximately 20% of the global anthropogenic

  17. Field Emission of ITO-Coated Vertically Aligned Nanowire Array.

    KAUST Repository

    Lee, Changhwa

    2010-04-29

    An indium tin oxide (ITO)-coated vertically aligned nanowire array is fabricated, and the field emission characteristics of the nanowire array are investigated. An array of vertically aligned nanowires is considered an ideal structure for a field emitter because of its parallel orientation to the applied electric field. In this letter, a vertically aligned nanowire array is fabricated by modified conventional UV lithography and coated with 0.1-μm-thick ITO. The turn-on electric field intensity is about 2.0 V/μm, and the field enhancement factor, β, is approximately 3,078 when the gap for field emission is 0.6 μm, as measured with a nanomanipulator in a scanning electron microscope.

  18. Superior field emission properties of layered WS2-RGO nanocomposites.

    Science.gov (United States)

    Rout, Chandra Sekhar; Joshi, Padmashree D; Kashid, Ranjit V; Joag, Dilip S; More, Mahendra A; Simbeck, Adam J; Washington, Morris; Nayak, Saroj K; Late, Dattatray J

    2013-11-21

    We report here the field emission studies of a layered WS2-RGO composite at the base pressure of ~1 × 10(-8) mbar. The turn on field required to draw a field emission current density of 1 μA/cm(2) is found to be 3.5, 2.3 and 2 V/μm for WS2, RGO and the WS2-RGO composite respectively. The enhanced field emission behavior observed for the WS2-RGO nanocomposite is attributed to a high field enhancement factor of 2978, which is associated with the surface protrusions of the single-to-few layer thick sheets of the nanocomposite. The highest current density of ~800 μA/cm(2) is drawn at an applied field of 4.1 V/μm from a few layers of the WS2-RGO nanocomposite. Furthermore, first-principles density functional calculations suggest that the enhanced field emission may also be due to an overalp of the electronic structures of WS2 and RGO, where graphene-like states are dumped in the region of the WS2 fundamental gap.

  19. Re-grown aligned carbon nanotubes with improved field emission.

    Science.gov (United States)

    Lim, Xiaodai; Zhu, Yanwu; Varghese, Binni; Gao, Xingyu; Wee, Andrew Thye Shen; Sow, Chorng-Haur

    2012-01-01

    In this work, a simple technique to improve the field emission property of multi-walled carbon nanotubes is presented. Re-grown multi-walled carbon nanotubes are grown on the same substrates after the as-grown multi-walled carbon nanotubes are transferred to other substrates using polydimethylsiloxane as intermediation. For the duration of the synthesis of the re-grown multi-walled carbon nanotubes, similar synthesis parameters used in growing the as-grown multi-walled carbon nanotubes are utilized. As a form of possible application, field emission studies show -2.6 times improvement in field enhancement factor and more uniform emission for the re-grown multi-walled carbon nanotubes. In addition, the turn-on field is reduced from 2.85 V/microm to 1.40 V/microm. Such significant improvements are attributed to new emission sites comprising of sharp carbonaceous impurities encompassing both tip and upper portion of the multi-walled carbon nanotubes. As such, this technique presents a viable route for the production of multi-walled carbon nanotubes with better field emission quality.

  20. Carbon adsorption on tungsten and electronic field emission

    Science.gov (United States)

    Márquez-Mijares, Maykel; Lepetit, Bruno; Lemoine, Didier

    2016-03-01

    Electronic emission taking place at the electrodes of high voltage systems and responsible for detrimental breakdown processes is known to be strongly dependent on the cathode surface state and in particular on the presence of carbon contamination. To understand better the effect of carbon adsorption on cathode electronic emission, density functional theory calculations are reported for bulk bcc tungsten as well as for clean and carbon-covered W(100) surfaces for several coverages up to 2 ML. Adsorption geometries and energies, work functions and electronic densities of states are analyzed to assess the effect of the presence of adlayers on surface electronic field emission properties. It is shown that flat carbon adlayer deposition on clean W(100) surfaces induces an increase of the surface work function and a decrease of electronic density near the Fermi level. Both factors contribute to reducing electronic field emission levels.

  1. High carrier mobility in single ultrathin colloidal lead selenide nanowire field effect transistors.

    Science.gov (United States)

    Graham, Rion; Yu, Dong

    2012-08-08

    Ultrathin colloidal lead selenide (PbSe) nanowires with continuous charge transport channels and tunable bandgap provide potential building blocks for solar cells and photodetectors. Here, we demonstrate a room-temperature hole mobility as high as 490 cm(2)/(V s) in field effect transistors incorporating single colloidal PbSe nanowires with diameters of 6-15 nm, coated with ammonium thiocyanate and a thin SiO(2) layer. A long carrier diffusion length of 4.5 μm is obtained from scanning photocurrent microscopy (SPCM). The mobility is increased further at lower temperature, reaching 740 cm(2)/(V s) at 139 K.

  2. Field emission study of MWCNT/conducting polymer nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Alvi, M.A., E-mail: maalvee@yahoo.co.in [Department of Physics, King Abdulaziz University, Jeddah-21589 (Saudi Arabia); Al-Ghamdi, A.A. [Department of Physics, King Abdulaziz University, Jeddah-21589 (Saudi Arabia); Husain, M. [Department of Physics, Jamia Millia Islamia, New Delhi-110025 (India)

    2014-12-01

    MWCNTs/Polypyrrole nanocomposites were synthesized by solution mixing method. These synthesized nanocomposites were studied carefully by Raman Spectroscopy and Scanning Electron Microscopy measurements. The field emission study of MWCNTs/Polypyrrole nanocomposites were performed in diode arrangement under vacuum of the order of 10{sup −5} Torr. The emission current under exploration depends on applied voltage. The prepared nanocomposites depict low turn-on field at 1.4 V/μm that reaches to a maximum emission current density 0.020 mA/cm{sup 2} at 2.4 V/µm, which is calculated from the graph of current density (J) against the applied electric field (E) and from Fowler–Nordheim (F–N) plot.

  3. Field emission characteristics of regular arrays of carbon nanotubes.

    Science.gov (United States)

    Al-Ghamdi, A A; Al-Heniti, S; Al-Hazmi, F S; Faidah, Adel S; Shalaan, E; Husain, M

    2014-06-01

    The developments of electronic devices based on micron-sized vacuum electron sources during the last decades have triggered intense research on highly efficient carbon based thin film electron emitters. The synthesis of massive arrays of carbon nanotubes that are oriented on patterned Fe catalyst deposited on quartz substrates is reported. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotubes devices integrated into future technology. The emission from carbon nanotubes array is explained by Fowler-Nordheim tunneling of electrons from tip-like structures in the nanometer range, which locally amplify the applied field by the field enhancement factor beta. We found that the low pressure chemical vapour deposition (LPCVD) system can produce nanotubes capable of excellent emission currents at lower voltages. The carbon nanotubes array shows good field emission with turn on field E(alpha) = 1.30 V/microm at the current density of 3.50 mA/cm2 with enhancement factor beta = 1.22 x 10(2).

  4. Optimization of electric field distribution by free carrier injection in silicon detectors operated at low temperatures

    CERN Document Server

    Eremin, V V; Verbitskaya, E

    2002-01-01

    This study presents the results on the modeling of the electric field distribution, which is controlled by injection and trapping of non- equilibrium carriers, in Si detectors irradiated by high neutron fluences. Analytical calculation of the electric field distribution in detectors irradiated by neutron fluences of H-10**1**4 to 5-10**1**5 cm**-**2 has been performed, which shows possibility of full depletion voltage reduction at low operational temperatures with hole injection. All calculations are focused on the improvement of charge collection efficiency and prediction for detector behavior in LHC experiments. Comparison of the results of calculations to the experimental data published earlier shows a good qualitative agreement. 10 Refs.

  5. Spectroscopy of Charge Carriers and Traps in Field-Doped Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiaoyang; Frisbie, C Daniel

    2012-08-13

    This research project aims to achieve quantitative and molecular level understanding of charge carriers and traps in field-doped organic semiconductors via in situ optical absorption spectroscopy, in conjunction with time-resolved electrical measurements. During the funding period, we have made major progress in three general areas: (1) probed charge injection at the interface between a polymeric semiconductor and a polymer electrolyte dielectric and developed a thermodynamic model to quantitatively describe the transition from electrostatic to electrochemical doping; (2) developed vibrational Stark effect to probe electric field at buried organic semiconductor interfaces; (3) used displacement current measurement (DCM) to study charge transport at organic/dielectric interfaces and charge injection at metal/organic interfaces.

  6. Field electron emission from dense array of microneedles of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Okuyama, F.; Aoyagi, M.; Kitai, T.; Ishikawa, K.

    1978-01-01

    Characteristics of field electron emission from the dense array of microneedles of tungsten prepared on a 10-..mu..m tungsten filament were measured at an environmental pressure of approx.1 x 10/sup -8/ Torr (1.33 x 10/sup -6/ Pa). Electron emission was not uniform over the filament surface, but the variation of emission current with applied voltage explicitly obeyed the Fowler-Nordheim relationship. At an emission current of approx.10/sup -4/ A, a vacuum arc was induced that led to a permanent change in current-voltage characteristic. Current fluctuation was dependent on emitter temperature and applied voltage, and the lowest fluctuation of about 4% was routinely obtained at approx.550 K and at applied voltages several percent lower than the arc-inducing voltage. Macroscopic current density amounted to approx.20-80 mA/cm/sup 2/ at the best stability.

  7. Influence of local field on spontaneous light emission by nanoparticles

    DEFF Research Database (Denmark)

    Keller, Ole; Lozovski, V.; Iezhokin, I.

    2009-01-01

    A self-consistent approach based on the local-field concept has been proposed to calculate the direction patterns of light emission by nanoparticles with various shapes. The main idea of the method consists in constructing self-consistent equations for the electromagnetic field at any point...... demonstrated to interact as almost point dipoles at distances that exceed their linear dimensions. This fact can be used to substantiate applications of the dipole approximation to studying the optical properties of submonolayer molecular coatings....

  8. Development of Field-Emission Electron Gun from Carbon Nanotubes

    CERN Document Server

    Hozumi, Y

    2004-01-01

    Aiming to use a narrow energy-spread electron beam easily and low costly on injector electron guns, we have been tested field emission cathodes of carbon nanotubes (CNTs). Experiments for these three years brought us important suggestions and a few rules of thumb. Now at last, anode current of 3.0 [A/cm2

  9. Electron field emission from sp 2-induced insulating to metallic ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 33; Issue 3. Electron field emission from 2-induced insulating to metallic behaviour of amorphous carbon (-C) films. Pitamber Mahanandia P N Viswakarma Prasad Vishnu Bhotla S V Subramanyam Karuna Kar Nanda. Thin Films and Nanomatter Volume 33 Issue 3 ...

  10. Assessment of environmental influence of bentonite and lustrous carbon carrier - in an aspect of gases emission

    Directory of Open Access Journals (Sweden)

    A. Bobrowski

    2009-01-01

    Full Text Available The emission results of the selected gases from a bentonite-carbon mixture and from dusts originated from dry de-dusting of thegreen sand processing plant (at high temperatures are presented in the paper. In order to check and compare samples of dusts andbentonite-carbon mixtures in respect of emission of gases the Evolved Gas Analysis (EGA was performed by means of the massspectrometry method. This method allows to determine emission conditions of the selected chemical compounds.

  11. 75 FR 57191 - Compliance With Interstate Motor Carrier Noise Emission Standards: Exhaust Systems

    Science.gov (United States)

    2010-09-20

    ... may allow vehicle operators to remove mufflers and still meet the Federal inspection requirements if... are operated by interstate motor carriers to be ``* * * equipped with a muffler or other noise... ``* * * equipped with either a muffler or other noise dissipative device, such as a turbocharger (supercharger...

  12. Quiver-quenched optical-field-emission from carbon nanotubes

    Science.gov (United States)

    Li, Chi; Zhou, Xu; Zhai, Feng; Li, Zhenjun; Yao, Fengrui; Qiao, Ruixi; Chen, Ke; Yu, Dapeng; Sun, Zhipei; Liu, Kaihui; Dai, Qing

    2017-09-01

    Carbon nanotubes (CNTs) enable large electric field enhancement for an extremely broad bandwidth spanning from the optical domain down to static fields. This is due to their high aspect ratio, small tip radius, and high structural stability. CNTs therefore represent an ideal model-system for the investigation of nonlinear and strong-field phenomena. In this paper, we extend the range of optical-field-emission materials from metal nanostructures to CNTs. Quiver-quenched optical-field-emission (i.e., the transition to a sub-cycle regime) is observed for CNTs tips in a short-wavelength laser field of 820 nm that requires a mid-infrared excitation field of conventional metal tips emitters. This special property relies on the ultrasmall tips radius (˜1 nm) and the high optical-field enhancement (˜21.6) properties of CNTs. This study suggests that CNTs are excellent candidates for optically driven ultrafast electron sources with both high spatial and high temporal coherence. They also provide more freedom for the manipulation and control of electron dynamics at the attosecond timescale, which extends the bandwidth of light-wave electronic devices.

  13. Carrier relaxation in (In,Ga)As quantum dots with magnetic field-induced anharmonic level structure

    Energy Technology Data Exchange (ETDEWEB)

    Kurtze, H.; Bayer, M. [Experimentelle Physik 2, TU Dortmund, D-44221 Dortmund (Germany)

    2016-07-04

    Sophisticated models have been worked out to explain the fast relaxation of carriers into quantum dot ground states after non-resonant excitation, overcoming the originally proposed phonon bottleneck. We apply a magnetic field along the quantum dot heterostructure growth direction to transform the confined level structure, which can be approximated by a Fock–Darwin spectrum, from a nearly equidistant level spacing at zero field to strong anharmonicity in finite fields. This changeover leaves the ground state carrier population rise time unchanged suggesting that fast relaxation is maintained upon considerable changes of the level spacing. This corroborates recent models explaining the relaxation by polaron formation in combination with quantum kinetic effects.

  14. Heterogeneous nucleation promotes carrier transport in solution-processed organic field-effect transistors

    KAUST Repository

    Li, Ruipeng

    2012-09-04

    A new way to investigate and control the growth of solution-cast thin films is presented. The combination of in situ quartz crystal microbalance measurements with dissipation capabilities (QCM-D) and in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) in an environmental chamber provides unique quantitative insights into the time-evolution of the concentration of the solution, the onset of nucleation, and the mode of growth of the organic semiconductor under varied drying conditions. It is demonstrated that careful control over the kinetics of solution drying enhances carrier transport significantly by promoting phase transformation predominantly via heterogeneous nucleation and sustained surface growth of a highly lamellar structure at the solid-liquid interface at the expense of homogeneous nucleation. A new way to investigate and control the growth of drop-cast thin films is presented. The solution-processing of small-molecule thin films of TIPS-pentacene is investigated using time-resolved techniques to reveal the mechanisms of nucleation and growth leading to solid film formation. By tuning the drying speed of the solution, the balance between surface and bulk growth modes is altered, thereby controlling the lamellar formation and tuning the carrier mobility in organic field-effect transistors Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Enhancement of field emission characteristics of carbon nanotubes on oxidation.

    Science.gov (United States)

    Mathur, Ashish; Roy, Susanta Sinha; Ray, Sekhar Chandra; Hazra, Kiran Shankar; Hamilton, Jeremy; Dickinson, Calum; McLaughlin, James; Misra, Devi Shankar

    2011-08-01

    Vertically aligned multi-walled carbon nanotubes (CNTs) were grown on p-type silicon wafer using thermal chemical vapor deposition process and subsequently treated with oxygen plasma for oxidation. It was observed that the electron field emission (EFE) characteristics are enhanced. It showed that the turn-on electric field (E(TOE)) of CNTs decreased from 0.67 (untreated) to 0.26 V/microm (oxygen treated). Raman spectra showed that the numbers of defects are increased, which are generated by oxygen-treatment, and absorbed molecules on the CNTs are responsible for the enhancement of EFE. Scanning electron microscopy and Transmission electron microscopy images were used to identify the quality and physical changes of the nanotube morphology and surfaces; revealing the evidence of enhancement in the field emission properties after oxygen-plasma treatment.

  16. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

    Science.gov (United States)

    Chaffin, deceased, Roger J.; Dawson, Ralph; Fritz, Ian J.; Osbourn, Gordon C.; Zipperian, Thomas E.

    1989-01-01

    A field effect transistor comprises a semiconductor having a source, a drain, a channel and a gate in operational relationship. The semiconductor is a strained layer superlattice comprising alternating quantum well and barrier layers, the quantum well layers and barrier layers being selected from the group of layer pairs consisting of InGaAs/AlGaAs, InAs/InAlGaAs, and InAs/InAlAsP. The layer thicknesses of the quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice which has a superlattice conduction band energy level structure in k-vector space which includes a lowest energy .GAMMA.-valley and a next lowest energy L-valley, each k-vector corresponding to one of the orthogonal directions defined by the planes of said layers and the directions perpendicular thereto. The layer thicknesses of the quantum well layers are selected to provide a superlattice L.sub.2D -valley which has a shape which is substantially more two-dimensional than that of said bulk L-valley.

  17. The use of total simulator training in transitioning air-carrier pilots: A field evaluation

    Science.gov (United States)

    Randle, R. J., Jr.; Tanner, T. A.; Hamerman, J. A.; Showalter, T. H.

    1981-01-01

    A field study was conducted in which the performance of air carrier transitioning pilots who had landing training in a landing maneuver approved simulator was compared with the performance of pilots who had landing training in the aircraft. Forty-eight trainees transitioning to the B-727 aircraft and eighty-seven trainees transitioning to the DC-10 were included in the study. The study results in terms of both objectively measured performance indicants and observer and check-pilot ratings did not demonstrate a clear distinction between the two training groups. The results suggest that, for these highly skilled transitioning pilots, a separate training module in the aircraft may be of dubious value.

  18. Enhanced field emission from reduced graphene oxide polymer composites.

    Science.gov (United States)

    Viskadouros, Georgios M; Stylianakis, Minas M; Kymakis, Emmanuel; Stratakis, Emmanuel

    2014-01-08

    Results on electron field emission (FE) from reduced graphene oxide (rGO):poly(3-hexylthiophene) (P3HT) composite layers are presented. Three different FE cathodes were tested and compared: rGO layers on (a) n(+)-Si, (b) composite films with different rGO:P3HT ratios, (c) rGO layers on composite films with different rGO:P3HT ratios. Experiments show that there is a critical rGO:P3HT ratio in which the field-emission performance is remarkably improved. Notably, such performance is always superior to that of the optimum rGO/n(+)-Si cathode. On the contrary, it is inferior to that attained upon deposition of a second rGO layer on top of the rGO:P3HT composite showed the best FE performance that showed turn-on field of as low as ~0.9 V/μm and field enhancement factor of ~1900. The contributions of the composite film morphology as well as the role of rGO sheet-substrate interaction on the emission performance are evaluated and discussed.

  19. Discrete space charge affected field emission: Flat and hemisphere emitters

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Kevin L., E-mail: kevin.jensen@nrl.navy.mil [Code 6854, Naval Research Laboratory, Washington, DC 20375 (United States); Shiffler, Donald A.; Tang, Wilkin [Air Force Research Laboratory, Kirtland AFB, New Mexico 87117 (United States); Rittersdorf, Ian M. [Code 6770, Naval Research Laboratory, Washington, DC 20375 (United States); Lebowitz, Joel L. [Department of Mathematics and Department of Physics, Rutgers University, Piscataway, New Jersey 08854-8019 (United States); Harris, John R. [U.S. Navy Reserve, New Orleans, Louisiana 70143 (United States); Lau, Y. Y. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109 (United States); Petillo, John J. [Leidos, Billerica, Massachusetts 01821 (United States); Luginsland, John W. [Physics and Electronics Directorate, AFOSR, Arlington, Virginia 22203 (United States)

    2015-05-21

    Models of space-charge affected thermal-field emission from protrusions, able to incorporate the effects of both surface roughness and elongated field emitter structures in beam optics codes, are desirable but difficult. The models proposed here treat the meso-scale diode region separate from the micro-scale regions characteristic of the emission sites. The consequences of discrete emission events are given for both one-dimensional (sheets of charge) and three dimensional (rings of charge) models: in the former, results converge to steady state conditions found by theory (e.g., Rokhlenko et al. [J. Appl. Phys. 107, 014904 (2010)]) but show oscillatory structure as they do. Surface roughness or geometric features are handled using a ring of charge model, from which the image charges are found and used to modify the apex field and emitted current. The roughness model is shown to have additional constraints related to the discrete nature of electron charge. The ability of a unit cell model to treat field emitter structures and incorporate surface roughness effects inside a beam optics code is assessed.

  20. Stabilization of enhanced field emission of the film DLC structure in conditions of field localization

    Science.gov (United States)

    Aban'shin, Nikolay P.; Akchurin, Garif G.; Avetisyan, Yuri A.; Loginov, Alexander P.; Mosiyash, Denis S.; Yakunin, Alexander N.

    2017-04-01

    Multiple factors and their impact on the stability of DLC field emission structures are discussed in the present work. Planar multi-electrode structures, in which the formation of zones of localization the electrostatic field of a certain topology performed, are examined. Estimates carried out demonstrated the existence of an effective solution for creating reliable and durable vacuum devices for electronics and photonics. Conclusions are confirmed by the results of experimental studies. Samples of devices showed an average current density of field emission 0.30-0.35 A/cm2.

  1. Research on Field Emission and Dark Current in ILC Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Kexin; Li, Yongming; Palczewski, Ari; Geng, Rongli

    2013-09-01

    Field emission and dark current are issues of concern for SRF cavity performance and SRF linac operation. Complete understanding and reliable control of the issue are still needed, especially in full-scale multi-cell cavities. Our work aims at developing a generic procedure for finding an active field emitter in a multi-cell cavity and benchmarking the procedure through cavity vertical test. Our ultimate goal is to provide feedback to cavity preparation and cavity string assembly in order to reduce or eliminate filed emission in SRF cavities. Systematic analysis of behaviors of field emitted electrons is obtained by ACE3P developed by SLAC. Experimental benchmark of the procedure was carried out in a 9-cell cavity vertical test at JLab. The energy spectrum of Bremsstrahlung X-rays is measured using a NaI(Tl) detector. The end-point energy in the X-ray energy spectrum is taken as the highest kinetic electron energy to predict longitudinal position of the active field emitter. Angular location of the field emitter is determined by an array of silicon diodes around irises of the cavity. High-resolution optical inspection was conducted at the predicted field emitter location.

  2. Continuous measurements of N2O emissions from arable fields

    Science.gov (United States)

    Wallman, Magdalena; Lammirato, Carlo; Rütting, Tobias; Delin, Sofia; Weslien, Per; Klemedtsson, Leif

    2017-04-01

    Agriculture represents 59 % of the anthropogenic nitrous oxide (N2O) emissions, according to the IPCC (Ciais et al. 2013). N2O emissions are typically irregular and vary widely in time and space, which makes it difficult to get a good representation of the emissions (Henault et al. 2012), particularly if measurements have low frequency and/or cover only a short time period. Manual measurements are, for practical reasons, often short-term and low-frequent, or restricted to periods where emissions are expected to be high, e.g. after fertilizing. However, the nature of N2O emissions, being largely unpredictable, calls for continuous or near-continuous measurements over long time periods. So far, rather few long-term, high resolution measurements of N2O emissions from arable fields are reported; among them are Flessa et al. (2002) and Senapati et al. (2016). In this study, we have a two-year data set (2015-2017) with hourly measurements from ten automatic chambers, covering unfertilized controls as well as different nitrogen fertilizer treatments. Grain was produced on the field, and effects of tillage, harvest and other cropping measures were covered. What we can see from the experiment is that (a) the unfertilized control plots seem to follow the same emission pattern as the fertilized plots, at a level similar to the standard mineral fertilized plots (120 kg N ha-1 yr-1) and (b) freeze/thaw emissions are comparable in size to emissions after fertilizing. These two findings imply that the importance of fertilizing to the overall N2O emissions from arable soils may be smaller than previously expected. References: Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell et al. 2013: Carbon and Other Biogeochemical Cycles. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung et

  3. BVOC emission pattern from Quercus robur under field conditions

    Science.gov (United States)

    Pokorska, O.; Dewulf, J.; Joó; Šimpraga, M.; Steppe, K.; Amelynck, C.; Schoon, N.; Muller, J. J.; van Langenhove, H.

    2010-12-01

    Over the past decades biogenic volatile organic compounds (BVOC) have been widely studied not only for better understanding their functions, biosynthesis and regulation, but also because they have great impact on regional and global air quality [1]. Since all BVOCs react with hydroxyl radicals (OH●) and may also react with nitrate radicals (NO3●) and ozone (O3), they contribute to the formation of ozone and secondary organic aerosols. In this study we focus on Quercus robur which is a widely spread tree species in Europe and known as a strong isoprene emitter. We aimed to investigate seasonal patterns of BVOC emissions from Quercus robur under field conditions and to explore the intra-species variations within Quercus robur trees as both are of great importance for accurate modeling and regional inventories. Measurements were performed during a period from May till October 2009 at the campus of Ghent University (Belgium) using a dynamic branch enclosure system. Experiments were conducted on four potted Quercus robur trees with a varying 1-1.5 m height. Samples were collected on Tenax TA-Carbotrap adsorbent tubes and analyzed by TD-GC-MS. Isoprene was the predominant compound released by Quercus robur (QR1) with a pronounced seasonal emission. The normalized emission rates for isoprene calculated according to Guenther’s algorithm (standard conditions of temperature 30°C and PAR 1000 µmol m-2 s-1) varied from 29.89 µg h-1 g(DW)-1 in Spring (May) to 28.62 µg h-1 g(DW)-1 in Fall (October) reaching peak of 105.51 µg h-1 g(DW)-1 in August. Apart from isoprene, through the whole measurement period trans-β-ocimene and β-caryophyllene were the only BVOC emitted in detectable range (sum of the emissions varied between 0.15 µg h-1 g(DW)-1 in July and 0.24 µg h-1 g(DW)-1 in October). No clear seasonal pattern was observed for those compounds. In May when acorns where developing on enclosed branch, emissions of limonene and β-farnesene were also observed. The

  4. New vacuum packaging method of field emission display

    Science.gov (United States)

    Ju, Byeong-Kwon; Choi, Woo-Beom; Jeong, S. J.; Lee, Nam Young; Han, Jeong-In; Cho, K. I.; Oh, Myung-Hwan

    1997-11-01

    Two ITO-coated glass wafers are successfully bonded by the typical Si-Pyrex electrostatic bonding mechanism. Both Si- 7740 and Ti-(Li-doped SiO$02)) interlayer systems can be employed for the electrostatic bonding of 7059-7059 and 0080-0080 glass wafer pairs. This glass-to-glass electrostatic bonding process can be applied to the clean and tubeless packaging of field emission display panels.

  5. Semi-shunt field emission in electronic devices

    Energy Technology Data Exchange (ETDEWEB)

    Karpov, V. G., E-mail: victor.karpov@utoledo.edu [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Shvydka, Diana, E-mail: diana.shvydka@utoledo.edu [Department of Radiation Oncology, University of Toledo, Toledo, Ohio 43606 (United States)

    2014-08-04

    We introduce a concept of semi-shunts representing needle shaped metallic protrusions shorter than the distance between a device electrodes. Due to the lightening rod type of field enhancement, they induce strong electron emission. We consider the corresponding signature effects in photovoltaic applications; they are: low open circuit voltages and exponentially strong random device leakiness. Comparing the proposed theory with our data for CdTe based solar cells, we conclude that stress can stimulate semi-shunts' growth making them shunting failure precursors. In the meantime, controllable semi-shunts can play a positive role mitigating the back field effects in photovoltaics.

  6. Application of the empirical force field to macrocyclic ion carriers, siderophores, and biomimetic analogs.

    Science.gov (United States)

    Felder, Clifford E; Shanzer, Abraham

    2003-03-01

    The empirical force field (EFF), developed by Prof. Lifson, was applied to the study of macrocyclic alkali ion carriers and to di- and tripodal and open chain siderophores and synthetic biomimetic molecules binding transition metals. The highly symmetric nature of these structures facilitated a favorable coordination geometry of the ligating groups about the metal, which helped organize the entire molecule into a fairly rigid structure. In our combined experimental-theoretical approach, EFF calculations were used to help predict likely candidates to synthesize, and provided a wealth of structural data to complement what we learned from the spectroscopic measurements, while feedback from these measurements allowed us to continue improving the EFF itself. The simple, highly modular design of the biomimetic analogs allowed rapid synthesis and systematic examination of a large number of related structures, as well as facilitating an efficient, piecewise conformational scanning for the theoretical calculations. In the early years, we focused on macrocyclic polylactones and lactams binding monovalent alkali ions, particularly the natural products enniatin and valinomycin, including inside a crystal lattice. Later we switched to bi- and tridentate siderophores, natural microbial iron carriers, and synthetic biomimetic analogs-in particular, of enterobactin, ferrichrome, and ferrioxamine B. Over the years a large number of biomimetic siderophores have been prepared, some active in a broad range of microorganisms while others are highly species specific. The results of this work have broad applications in many areas, including the design of novel drugs and antimicrobial agents, helical polymeric structures, and polynuclear metal complexes. Copyright 2003 Wiley Periodicals, Inc. Biopolymers: 407-421, 2003

  7. SOI detector with drift field due to majority carrier flow - an alternative to biasing in depletion

    Energy Technology Data Exchange (ETDEWEB)

    Trimpl, M.; Deptuch, G.; Yarema, R.; /Fermilab

    2010-11-01

    This paper reports on a SOI detector with drift field induced by the flow of majority carriers. It is proposed as an alternative method of detector biasing compared to standard depletion. N-drift rings in n-substrate are used at the front side of the detector to provide charge collecting field in depth as well as to improve the lateral charge collection. The concept was verified on a 2.5 x 2.5 mm{sup 2} large detector array with 20 {micro}m and 40 {micro}m pixel pitch fabricated in August 2009 using the OKI semiconductor process. First results, obtained with a radioactive source to demonstrate spatial resolution and spectroscopic performance of the detector for the two different pixel sizes will be shown and compared to results obtained with a standard depletion scheme. Two different diode designs, one using a standard p-implantation and one surrounded by an additional BPW implant will be compared as well.

  8. Field emission properties of a graphene/polymer composite.

    Science.gov (United States)

    Patole, Shashikant P; Lee, Jong Hak; Park, Jae Hong; Yu, Seong Man; Makotchenko, V G; Nazarov, A S; Fedorov, V E; Shin, Dong Wook; Alegaonkar, Prashant S; More, Mahendra A; Yoo, Ji-Beom

    2013-11-01

    Thin graphene/polymer sheet composites were fabricated using easily soluble expanded graphite (ESEG), and their field emission (FE) parameters were examined. Due to the high dispersability of ESEG, a stable graphene suspension was prepared by ultrasonication in toluene without the need for a surfactant. The suspension consisted of exfoliated graphene sheets with a thickness of 1 - 2 nm. Using a calendering process, the solution was further shear mixed with ethyl cellulose to obtain a well-dispersed graphene/polymer composite. The composite was screen printed onto a conducing substrate to fabricate the FE cathode layers. The FE measurements were taken in a diode configuration at an applied electrostatic field and inter-electrode distance of 1.7 to 6 V/microm and approximately 200 microm, respectively. The threshold turn-on-field was approximately 3.5 V/microm at a current density of approximately 10 microA/cm2 with a corresponding mean field enhancement factor of 1350 +/- 50. Emission occurred mainly from the edges and bends of the graphene layers. The luminescence uniformity of the composite cathode layers was examined using a phosphor-coated anode.

  9. Dynamics of charge carrier trapping in NO2 sensors based on ZnO field-effect transistors

    NARCIS (Netherlands)

    Andringa, Anne-Marije; Vlietstra, Nynke; Smits, Edsger C. P.; Spijkman, Mark-Jan; Gomes, Henrique L.; Klootwijk, Johan H.; Blom, Paul W. M.; de Leeuw, Dago M.

    2012-01-01

    Nitrogen dioxide (NO2) detection with ZnO field-effect transistors is based on charge carrier trapping. Here we investigate the dynamics of charge trapping and recovery as a function of temperature by monitoring the threshold voltage shift. The threshold voltage shifts follow a stretched-exponential

  10. Electronic field emission models beyond the Fowler-Nordheim one

    Science.gov (United States)

    Lepetit, Bruno

    2017-12-01

    We propose several quantum mechanical models to describe electronic field emission from first principles. These models allow us to correlate quantitatively the electronic emission current with the electrode surface details at the atomic scale. They all rely on electronic potential energy surfaces obtained from three dimensional density functional theory calculations. They differ by the various quantum mechanical methods (exact or perturbative, time dependent or time independent), which are used to describe tunneling through the electronic potential energy barrier. Comparison of these models between them and with the standard Fowler-Nordheim one in the context of one dimensional tunneling allows us to assess the impact on the accuracy of the computed current of the approximations made in each model. Among these methods, the time dependent perturbative one provides a well-balanced trade-off between accuracy and computational cost.

  11. Carrier thermalization under stimulated emission in In{sub 0.17}Ga{sub 0.83}N epilayer at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Shang, Z. J.; Yang, C.; Chen, Y., E-mail: xinhezheng@ustb.edu.cn, E-mail: ychen@ee.ecnu.edu.cn; Li, B.; Sun, L.; Tang, Z. [Key Laboratory of Polar Materials and Devices, East China Normal University, Shanghai 200241 (China); Zheng, X. H., E-mail: xinhezheng@ustb.edu.cn, E-mail: ychen@ee.ecnu.edu.cn [Department of Physics, Beijing University of Science and Technology, Beijing 100083, People' s Republic of China and Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Science, Suzhou 215123 (China); Zhao, D. G. [Institute of Semiconductors, Chinese Academy of Science, Beijing 100083 (China)

    2014-12-08

    We elucidate a strong room temperature stimulated emission (SE) of In{sub 0.17}Ga{sub 0.83}N epilayer grown by molecular beam epitaxy under the subpicosecond pulse excitation. The SE peak at 428 nm emerges on the higher energy side of the spontaneous emission in photoluminescence spectra when the excitation density exceeds the threshold of ∼3.68 mJ/cm{sup 2}. Nondegenerate transient differential reflectivity measurements show that a multi-stage carrier thermalization from excited states to localized edge states and stimulated emission dominate the decay processes of photogenerated carriers under various excitation densities. Our results indicate that the existence of phonon bottleneck effect could result in a slow thermalization process in the InGaN material even under the condition of stimulated emission.

  12. Carrier polarity engineering in carbon nanotube field-effect transistors by induced charges in polymer insulator

    Science.gov (United States)

    Aikawa, Shinya; Kim, Sungjin; Thurakitseree, Theerapol; Einarsson, Erik; Inoue, Taiki; Chiashi, Shohei; Tsukagoshi, Kazuhito; Maruyama, Shigeo

    2018-01-01

    We present that the electrical conduction type in carbon nanotube field-effect transistors (CNT-FETs) can be converted by induced charges in a polyvinyl alcohol (PVA) insulator. When the CNT channels are covered with pure PVA, the FET characteristics clearly change from unipolar p-type to ambipolar. The addition of ammonium ions (NH4+) in the PVA leads to further conversion to unipolar n-type conduction. The capacitance - voltage characteristics indicate that a high density of positive charges is induced at the PVA/SiO2 interface and within the bulk PVA. Electrons are electrostatically accumulated in the CNT channels due to the presence of the positive charges, and thus, stable n-type conduction of PVA-coated CNT-FETs is observed, even under ambient conditions. The mechanism for conversion of the conduction type is considered to be electrostatic doping due to the large amount of positive charges in the PVA. A blue-shift of the Raman G-band peak was observed for CNTs coated with NH4+-doped PVA, which corresponds to unipolar n-type CNT-FET behavior. These results confirm that carrier polarity engineering in CNT-FETs can be achieved with a charged PVA passivation layer.

  13. Field-emission cathode gating for rf electron guns

    OpenAIRE

    Lewellen, J. W.; J. Noonan

    2005-01-01

    We present a novel method of combining the most desirable characteristics of thermionic-cathode and photocathode rf guns, using a field-emission cathode and multiple rf frequencies. Simulations indicate that extremely low-emittance beams (on the order of 2 nm normalized emittance) at moderate beam currents (1 mA) and beam energies of ∼2  MeV can be obtained using this technique. The resulting gun design promises to be useful as a driver source for a number of applications, including high-volt...

  14. Thermionic field emission of electrons from the paraboloidal metal micropoint

    Science.gov (United States)

    Petrin, A. B.

    2017-06-01

    The problem of determining the emission current as a function of voltage, radius of the micropoint curvature, and the distance between the micropoint and a conducting plane is considered on the basis of the theoretical method developed for determining the electric field in the vicinity of a paraboloidal micropoint near a plane metal surface. The universal current-voltage characteristics for a copper micropoint, which are considered for various distances between the micropoint and the plane, can be used for obtaining quantitative estimates of currents in various physics problems.

  15. Emission of Methyl halides from Japanese rice paddy fields.

    Science.gov (United States)

    Komori, D.; Sudo, S.; Akiyama, H.; Nishimura, S.; Yagi, K.; Hayashi, K.; Tanaka, Y.; Yamada, K.; Toyoda, S.; Koba, K.; Yoshida, N.

    2005-12-01

    Rice paddy field is one of emission source of methyl halide (MeX: X = Cl, Br, I) which are concerned about stratospheric ozone depletion and enhanced aerosol formation. Although significant amounts of MeX which are estimated to be emitted from rice paddies affect to regional and global atmospheric environment, understandings and recent estimations of production and consumption mechanisms of MeX have large uncertainty with depending on environmental conditions. In this study, new flux data sets of MeX emissions from Japanese rice paddy fields were reported. The fluxes of MeX were compared with environmental data sets which included meteorological parameters (ambient air temperature, ambient MeX concentrations, humidity, solar irradiance), soil parameters (soil temperature, pH, redox potential, soil water contents) to understand the emission mechanisms of MeX. Gas fluxes of C2H4 were also measured, which indicate rice plants growth and ageing. Observations of MeX flux were conducted with using automated closed chamber sampling system in Tsukuba, Japan, during a cultivation season of rice from May 2005 to September 2005. Rice plants were cultivated under intermittent irrigation. Soil gases were collected manually by using evacuated 1L stainless canisters once a week and every 4 hours in certain day during this period. Other environmental parameters were automatically obtained every 10 minutes. Seasonal variation of gas emissions of C2H4 were observed in maximum tillering phase and heading phase. In addition, clearly diurnal flux trends of C2H4 depending on solar irradiance were observed. These results suggested rice plant was remarkably growing in these phase. Similarly, large amounts of gas emissions of MeBr and MeI were observed in the same phase. Diurnal flux trends of MeBr and MeI were associated with solar irradiance. Results were generally consistent with previous reports (Redeker et al., 2000). On the other hand, MeCl flux was increased in later periods than

  16. Graphene enhanced field emission from InP nanocrystals

    Science.gov (United States)

    Iemmo, L.; Di Bartolomeo, A.; Giubileo, F.; Luongo, G.; Passacantando, M.; Niu, G.; Hatami, F.; Skibitzki, O.; Schroeder, T.

    2017-12-01

    We report the observation of field emission (FE) from InP nanocrystals (NCs) epitaxially grown on an array of p-Si nanotips. We prove that FE can be enhanced by covering the InP NCs with graphene. The measurements are performed inside a scanning electron microscope chamber with a nano-controlled W-thread used as an anode. We analyze the FE by Fowler–Nordheim theory and find that the field enhancement factor increases monotonically with the spacing between the anode and the cathode. We also show that InP/p-Si junction has a rectifying behavior, while graphene on InP creates an ohmic contact. Understanding the fundamentals of such nanojunctions is key for applications in nanoelectronics.

  17. Graphene enhanced field emission from InP nanocrystals.

    Science.gov (United States)

    Iemmo, L; Di Bartolomeo, A; Giubileo, F; Luongo, G; Passacantando, M; Niu, G; Hatami, F; Skibitzki, O; Schroeder, T

    2017-12-08

    We report the observation of field emission (FE) from InP nanocrystals (NCs) epitaxially grown on an array of p-Si nanotips. We prove that FE can be enhanced by covering the InP NCs with graphene. The measurements are performed inside a scanning electron microscope chamber with a nano-controlled W-thread used as an anode. We analyze the FE by Fowler-Nordheim theory and find that the field enhancement factor increases monotonically with the spacing between the anode and the cathode. We also show that InP/p-Si junction has a rectifying behavior, while graphene on InP creates an ohmic contact. Understanding the fundamentals of such nanojunctions is key for applications in nanoelectronics.

  18. N{sub 2}O Emission from energy crop fields

    Energy Technology Data Exchange (ETDEWEB)

    Joergensen, B.J. [The Royal Veterinary and Agricultural Univ., Dept. of Agricultural Sciences, Section of Soil, Water and Plant Nutrition (Denmark); Nyholm Joergensen, R. [Research Centre Foulum, The Danish Inst. of Plant and Soil Science, Dept. of Soil Science (Denmark)

    1996-03-01

    The interest in N{sub 2}O emissions from soils with energy crops is a results of its properties as a greenhouse gas, since the global warming potential of N{sub 2}O per unit mass is about 320 times greater than CO{sub 2}. The contribution of N{sub 2}O from the soil to the atmosphere may increase due to agricultural management. Consequently, large N{sub 2}O emissions can lower the reduction of the greenhouse effect achieved by the substitution of fossil fuels by energy crops. For this reason it is crucial to find the crops for combustion with the lowest potential for emission of N{sub 2}O from the soil per produced energy unit. The aims of this study were to assess the annual N{sub 2}O flux from a Miscanthus `Giganteus` (M. `Giganteus`) and winter rye (Secale cereale) field, and to investigate the factors affecting the N{sub 2}O emission. To obtain these aims a method was developed for measurements in tall crops. The thesis contains a literature review on the N{sub 2}O emission from the soils, a section with development of the technique for N{sub 2}O flux measurements, and an experimental section. Finally, the thesis contains a section where the results are discussed in relation to the use of energy crops. In all the filed studies, the N{sub 2}O emission was measured by using a new developed closed-chamber technique. The main advantages of the chamber method were the ability to contain growing plants up to a height of 3 m, and the relatively large area (2X2m) covered by each other. Soils with annual and perennial crops can be expected to emit less then 3 kg N{sub 2}O ha{sup -1} yr{sup -1}. This amount corresponds to 960 kg CO{sub 2} ha{sup -1} yr{sup -1} compared to a total CO{sub 2} reduction of 10 to 19 tons CO{sub 2} ha{sup -1} yr{sup -1} using the energy crops as substituion for fossil fuels. An efficient way to reduce the N{sub 2}O emission is to exclude use of fertiliser but this also reduces the dry matter yield and consequently also the CO{sub 2} reduction

  19. High carrier mobility of CoPc wires based field-effect transistors using bi-layer gate dielectric

    Directory of Open Access Journals (Sweden)

    Murali Gedda

    2013-11-01

    Full Text Available Polyvinyl alcohol (PVA and anodized Al2O3 layers were used as bi-layer gate for the fabrication of cobalt phthalocyanine (CoPc wire base field-effect transistors (OFETs. CoPc wires were grown on SiO2 surfaces by organic vapor phase deposition method. These devices exhibit a field-effect carrier mobility (μEF value of 1.11 cm2/Vs. The high carrier mobility for CoPc molecules is attributed to the better capacitive coupling between the channel of CoPc wires and the gate through organic-inorganic dielectric layer. Our measurements also demonstrated the way to determine the thicknesses of the dielectric layers for a better process condition of OFETs.

  20. Continuous field investigation assessing nitrogen and phosphorus emission from irrigated paddy field

    Science.gov (United States)

    Kogure, Kanami; Aichi, Masaatsu; Zessner, Matthias

    2016-04-01

    In order to maintain good river environment, it is very important to understand and to control nutrient behavior such as Nitrogen and Phosphorus. Other than urban and industrial waste water, nutrient emission from agricultural activity is dominant pollution source into the river system. Rice is one of the staple products of Asia and paddy field occupies large areas in Asian countries. Rice is also widely cultivated in Japan. Paddy field occupies large areas in Japanese river basin areas. While paddy field can deteriorate river water quality by discharging fertilizer, it is also suggested that paddy field has water purification function. Regarding to nutrient emission from paddy field, existing monitored data are insufficient so as to discuss quantitatively seasonal change of material behavior including flooding season and dry season and to evaluate year round comprehensive impact from paddy field to the river system. These are not sufficient data for discussion of material flow and emission impact quantitatively as well as qualitatively. We have carried out field investigation in paddy fields in middle reach of the Tone River Basin. The aim of the survey is understanding of water and nutrient balance in paddy field. In order to understand emission impact from paddy field to river system, all input and output flow are measured to calculate nutrient balance in paddy field. Therefore we observed quantity of water flow into/from paddy field, water quality change of inflow and outflow during flooding season. We set focus on a monitoring paddy field IM, and monitored continuously water and nutrient behavior. By measuring water quality and flow rate of inflow, outflow, infiltrating water, ground water and depth of flooding water, we tried to quantitatively understand N and P cycle around paddy field including seasonal tendency, change accompanying with rainy events and occurred according to agricultural events like fertilization. At the beginning of flooding season, we

  1. The influence of magnetic fields on absorption and emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Heshou; Yan, Huirong [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Potsdam Univ. (Germany). Inst. fuer Physik und Astronomie; Richter, Philipp [Potsdam Univ. (Germany). Inst. fuer Physik und Astronomie; Leibniz-Institut fuer Astrophysik Potsdam (AIP) (Germany)

    2016-10-15

    Spectroscopic observations play essential roles in astrophysics. They are crucial for determining important physical parameters, providing information about the composition of various objects in the universe, as well as depicting motions in the universe. However, spectroscopic studies often do not consider the influence of magnetic fields. In this paper, we explore the influence of magnetic fields on the spectroscopic observations arising from Ground State Alignment (GSA). Synthetic spectra are generated to show the measurable changes of the spectra due to GSA. The influences of atomic alignment on absorption from DLAs, emission from H II Regions, submillimeter fine-structure lines from star forming regions are presented as examples to illustrate the effect in diffuse gas. Furthermore, we demonstrate the influence of atomic alignment on physical parameters derived from spectral line ratios, such as the alpha-to-iron ratio([X/Fe]), interstellar temperature, and ionization rate. Results in our paper show that due to GSA, magnetic fields will affect the spectra of diffuse gas with high signal-to-noise(S/N) ratio under the condition that photon-excitation is much more efficient than thermal collision.

  2. Fowler-Nordheim field emission effects in semiconductor nanostructures

    CERN Document Server

    Bhattacharya, Sitangshu

    2012-01-01

    This monograph solely presents the Fowler-Nordheim field emission (FNFE) from semiconductors and their nanostructures. The materials considered are quantum confined non-linear optical, III-V, II-VI, Ge, Te, carbon nanotubes, PtSb2, stressed materials, Bismuth, GaP, Gallium Antimonide, II-V, Bi2Te3, III-V, II-VI, IV-VI and HgTe/CdTe superlattices with graded interfaces and effective mass superlattices under magnetic quantization and quantum wires of the aforementioned superlattices. The FNFE in opto-electronic materials and their quantum confined counterparts is studied in the presence of light waves and intense electric fields on the basis of newly formulated electron dispersion laws that control the studies of such quantum effect devices. The importance of band gap measurements in opto-electronic materials in the presence of external fields is discussed from this perspective. This monograph contains 200 open research problems which form the very core and are useful for Ph. D students and researchers. The boo...

  3. Field-emission cathode gating for rf electron guns

    Directory of Open Access Journals (Sweden)

    J. W. Lewellen

    2005-03-01

    Full Text Available We present a novel method of combining the most desirable characteristics of thermionic-cathode and photocathode rf guns, using a field-emission cathode and multiple rf frequencies. Simulations indicate that extremely low-emittance beams (on the order of 2 nm normalized emittance at moderate beam currents (1 mA and beam energies of ∼2  MeV can be obtained using this technique. The resulting gun design promises to be useful as a driver source for a number of applications, including high-voltage electron microscopy, precision electron-beam welding, and long-wavelength (THz radiation generation; we include performance calculations for the electron microscopy and precision welding applications.

  4. Field-emission cathode gating for rf electron guns

    Science.gov (United States)

    Lewellen, J. W.; Noonan, J.

    2005-03-01

    We present a novel method of combining the most desirable characteristics of thermionic-cathode and photocathode rf guns, using a field-emission cathode and multiple rf frequencies. Simulations indicate that extremely low-emittance beams (on the order of 2 nm normalized emittance) at moderate beam currents (1 mA) and beam energies of ˜2 MeV can be obtained using this technique. The resulting gun design promises to be useful as a driver source for a number of applications, including high-voltage electron microscopy, precision electron-beam welding, and long-wavelength (THz) radiation generation; we include performance calculations for the electron microscopy and precision welding applications.

  5. Geothermal emissions data base: Cerro Prieto geothermal field

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, S.R. (comp.)

    1978-04-01

    A new database subset on the gaseous emissions from the Cerro Prieto geothermal field is presented. Properties and states of the reservoir fluid such as flow rates, wellhead pressure, and enthalpy are included in the file along with the well name and constituent measurement. This subset is the result of an initial screening of the data covering 1967 to 1969, and new additions will be appended periodically to the file. The data are accessed by a database management system as are all other subsets in the file. Thereby, one may search the database for specific data requirements and print selective output. For example, one may wish to locate reservoir conditions for cases only when the level of the constituent exceeded a designated value. Data output is available in the form of numerical compilations such as the attached, or graphical displays disposed to paper, film, or magnetic tape.

  6. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tong [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

    2002-09-18

    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To

  7. Stable field emission from arrays of vertically aligned free-standing metallic nanowires

    DEFF Research Database (Denmark)

    Xavier, S.; Mátéfi-Tempfli, Stefan; Ferain, E.

    2008-01-01

    the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is ∼1 m...... fabrication and large surfaces. This technique offers an excellent control of the orientation, shape and nanowires density. It is applied to fabricate field emission arrays with a good control of the emission site density. We have prepared Co, Ni, Cu and Rh nanowires with a height of 3 μm, a diameter of 80 nm...... and a density of ∼10 cm. The electron field emission measurements and total energy distributions show that the as-grown nanowires exhibit a complex behaviour, first with emission activation under high field, followed by unstable emission. A model taking into account the effect of an oxide layer covering...

  8. Emission Laws and Influence Factors of Greenhouse Gases in Saline-Alkali Paddy Fields

    National Research Council Canada - National Science Library

    Jie Tang; Shuang Liang; Zhaoyang Li; Hao Zhang; Sining Wang; Nan Zhang

    2016-01-01

    ...) emission laws and influence factors in saline-alkali paddy fields. Overall, GHG emissions of paddy soil during the growing season increased, then decreased, and then increased again and peaked at booting stage...

  9. Application of Near-Field Emission Processing for Microwave Circuits under Ultra-Short Duration Perturbations

    Directory of Open Access Journals (Sweden)

    Y. Liu

    2012-10-01

    Full Text Available This paper is dealing with a time-frequency modeling method of electromagnetic (EM near-field (NF radiated by electronic devices excited by transient pulse signals. The model developed enables to calculate the EM NF maps at different distances from the given device and also the synthesis of radiation sources enabling to reproduce the field maps. The method proposed is based on the ultra wide band (UWB frequency model of EM NF maps. The number of EM NF maps can be reduced by considering an innovative algorithm in order to establish simply the dipole model. Then, the transient model can be realized by considering the convolution between the transient excitation signals and the dipole-array model. The method proposed was validated by a standard 3D EM tool with a planar microstrip device excited by microwave signal modulating 1.25-GHz-carrier with 0.5-GHz-bandwidth. As expected, good correlation is found between results from simulation and the investigated modelling method.  The method introduced in this paper is particularly useful for the investigation of time-domain emissions for EMC applications by considering transient EM interferences (EMIs.

  10. Field investigation to assess nutrient emission from paddy field to surface water in river catchment

    Science.gov (United States)

    Kogure, Kanami; Aichi, Masaatsu; Zessner, Matthias

    2015-04-01

    In order to maintain good river environment, it is remarkably important to understand and to control nutrient behavior such as Nitrogen and Phosphorus. Our former research dealing with nutrient emission analysis in the Tone River basin area in Japan, in addition to urban and industrial waste water, nutrient emission from agricultural activity is dominant pollution source into the river system. Japanese style agriculture produces large amount of rice and paddy field occupies large areas in Japanese river basin areas. While paddy field can deteriorate river water quality by outflow of fertilizer, it is also suggested that paddy field has water purification function. As we carried out investigation in the Tone River Basin area, data were obtained which dissolved nitrogen concentration is lower in discharging water from paddy field than inflowing water into the field. Regarding to nutrient emission impact from paddy field, sufficient data are required to discuss quantitatively seasonal change of material behavior including flooding season and dry season, difference of climate condition, soil type, and rice species, to evaluate year round comprehensive impact from paddy field to the river system. In this research, field survey in paddy field and data collection relating rice production were carried out as a preliminary investigation to assess how Japanese style paddy field contributes year round on surface water quality. Study sites are three paddy fields located in upper reach of the Tone River basin area. The fields are flooded from June to September. In 2014, field investigations were carried out three times in flooding period and twice in dry period. To understand characteristics of each paddy field and seasonal tendency accompanying weather of agricultural event, short term investigations were conducted and we prepare for further long term investigation. Each study site has irrigation water inflow and outflow. Two sites have tile drainage system under the field and

  11. Analytical model for the quantum-confined Stark effect including electric field screening by non-equilibrium carriers

    Energy Technology Data Exchange (ETDEWEB)

    Bulashevich, K.A. [Ioffe Physico-Technical Institute, RAS, 26 Polytekhnicheskaya, St. Petersburg 194021 (Russian Federation); Soft-Impact Ltd., P.O. Box 83, 27 Engels av., St. Petersburg 194156 (Russian Federation); Karpov, S.Yu. [Soft-Impact Ltd., P.O. Box 83, 27 Engels av., St. Petersburg 194156 (Russian Federation); Suris, R.A. [Ioffe Physico-Technical Institute, RAS, 26 Polytekhnicheskaya, St. Petersburg 194021 (Russian Federation)

    2006-06-15

    We have derived an analytical approximation for the energy levels in a symmetric quantum well applicable in a wide range of the electric field variation. Suppression of the quantum-confined Stark effect due to the electric field screening by non-equilibrium carriers is considered self-consistently within the perturbation theory. Theoretical predictions are compared with available observations. Specific features of the quantum-confined Stark effect in light-emitting diode heterostructures are discussed. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Study of thermal-field emission properties and investigation of temperature dependent noise in the field emission current from vertical carbon nanotube emitters

    Science.gov (United States)

    Kolekar, Sadhu; Patole, S. P.; Patil, Sumati; Yoo, J. B.; Dharmadhikari, C. V.

    2017-10-01

    We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well-defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD) in order to understand the effect of temperature on distribution of electron emission spots and ring like structures in Field Emission Microscope (FEM) image. The FEM images could be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 from FEM image is typically, 4.5 × 107 and the actual number emitters per cm2 present as per Atomic Force Microscopy (AFM) data is 1.2 × 1012. The measured Current-Voltage (I-V) characteristics exhibit non linear Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current were recorded at different temperatures and Fast Fourier transformed into temperature dependent power spectral density. The latter was found to obey power law relation S(f) = A(Iδ/fξ), where δ and ξ are temperature dependent current and frequency exponents respectively.

  13. Device Physics of Contact Issues for the Overestimation and Underestimation of Carrier Mobility in Field-Effect Transistors

    Science.gov (United States)

    Liu, Chuan; Li, Gongtan; Di Pietro, Riccardo; Huang, Jie; Noh, Yong-Young; Liu, Xuying; Minari, Takeo

    2017-09-01

    Very high values of carrier mobility have been recently reported in newly developed materials for field-effect transistors (FETs) or thin-film transistors (TFTs). However, there is an increasing concern of whether the values are overestimated. In this paper, we investigate how much contact resistance a FET or TFT can tolerate to allow the conventional current-voltage equations, which is derived for no contact resistance. We contend that mobility in transistors with resistive contact can be underestimated with the presence of the injection barrier, whereas mobility in transistors with gated Schottky contact can be overestimated by more than 10 times. The latter phenomenon occurs even in long-channel devices, and it becomes more severe when using low-k dielectrics. This is because the band bending and injection barrier experience a complicated evolution on account of electrostatic doping in the semiconducting layer; thus, they do not follow a capacitance approximation. When the band bending is weak, the accumulation is as weak as that in the subthreshold regime. Accordingly, the carrier concentration nonlinearly increases with the gate field. This mechanism can occur with or without exhibiting the "kink" feature in the transfer curves, which has been suggested as the signature of overestimation. For precision, carrier mobility should be presented against gate voltage and should be examined by other recommended extraction methods.

  14. Tuning THz emission properties of Bi2Sr2CaCu2O8+δ intrinsic Josephson junction stacks by charge carrier injection

    Science.gov (United States)

    Kizilaslan, O.; Rudau, F.; Wieland, R.; Hampp, J. S.; Zhou, X. J.; Ji, M.; Kiselev, O.; Kinev, N.; Huang, Y.; Hao, L. Y.; Ishii, A.; Aksan, M. A.; Hatano, T.; Koshelets, V. P.; Wu, P. H.; Wang, H. B.; Koelle, D.; Kleiner, R.

    2017-03-01

    We report on doping and undoping experiments of terahertz (THz) emitting intrinsic Josephson junction stacks, where the change in charge carrier concentration is achieved by heavy current injection. The experiments were performed on stand-alone structures fabricated from a Bi2Sr2CaCu2O{}8+δ single crystal near optimal doping. The stacks contained about 930 intrinsic Josephson junctions. On purpose, the doping and undoping experiments were performed over only a modest range of charge carrier concentrations, changing the critical temperature of the stack by less than 1 K. We show that both undoping and doping is feasible also for the large intrinsic Josephson junction stacks used for THz generation. Even moderate changes in doping introduce large changes in the THz emission properties of the stacks. The highest emission power was achieved after doping a pristine sample.

  15. Experimental Development of Low-emittance Field-emission Electron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Lueangaranwong, A. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Buzzard, C. [Northern Illinois Univ., DeKalb, IL (United States); Divan, R. [Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials; Korampally, V. [Northern Illinois Univ., DeKalb, IL (United States); Piot, P. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2016-10-10

    Field emission electron sources are capable of extreme brightness when excited by static or time-dependent electro- magnetic fields. We are currently developing a cathode test stand operating in DC mode with possibility to trigger the emission using ultra-short (~ 100-fs) laser pulses. This contribution describes the status of an experiment to investigate field-emission using cathodes under development at NIU in collaboration with the Argonne’s Center for Nanoscale Materials.

  16. Improved Visualization of Vertebrate Nuclear Pore Complexes by Field Emission Scanning Electron Microscopy

    National Research Council Canada - National Science Library

    Shaulov, Lihi; Harel, Amnon

    2012-01-01

    Field emission scanning electron microscopy (FESEM) can provide high-resolution three-dimensional surface imaging of many biological structures, including nuclear envelopes and nuclear pore complexes (NPCs...

  17. Plasma-induced field emission study of carbon nanotube cathode

    Directory of Open Access Journals (Sweden)

    Yi Shen

    2011-10-01

    Full Text Available An investigation on the plasma-induced field emission (PFE properties of a large area carbon nanotube (CNT cathode on a 2 MeV linear induction accelerator injector is presented. Experimental results show that the cathode is able to emit intense electron beams. Intense electron beams of 14.9–127.8  A/cm^{2} are obtained from the cathode. The CNT cathode desorbs gases from the CNTs during the PFE process. The fast cathode plasma expansion affects the diode perveance. The amount of outgassing is estimated to be 0.06–0.49  Pa·L, and the ratio of outgassing and electron are roughly calculated to be within the range of 170–350 atoms per electron. The effect of the outgassing is analyzed, and the outgassing mass spectrum of the CNT cathode has been studied during the PFE. There is a significant desorption of CO_{2}, N_{2}(CO, and H_{2} gases, which plays an important role during the PFE process. All the experiments demonstrate that the outgassing plays an important role in the formation of the cathode plasma. Moreover, the characteristic turn-on time of the CNT cathode was measured to be 39 ns.

  18. The ALFAM2 database on ammonia emission from field-applied manure

    DEFF Research Database (Denmark)

    Hafner, Sasha D; Pacholski, Andreas; Bittman, Shabtai

    2017-01-01

    Abstract Ammonia (NH3) emission from animal manure contributes to air pollution and ecosystem degradation, and the loss of reactive nitrogen (N) from agricultural systems. Estimates of NH3 emission are necessary for national inventories and nutrient management, and NH3 emission from field...

  19. Tuning vertical alignment and field emission properties of multi-walled carbon nanotube bundles

    Science.gov (United States)

    Sreekanth, M.; Ghosh, S.; Srivastava, P.

    2018-01-01

    We report the growth of vertically aligned carbon nanotube bundles on Si substrate by thermal chemical vapor deposition technique. Vertical alignment was achieved without any carrier gas or lithography-assisted deposition. Growth has been carried out at 850 °C for different quantities of solution of xylene and ferrocene ranging from 2.25 to 3.00 ml in steps of 0.25 ml at a fixed concentration of 0.02 gm (ferrocene) per ml. To understand the growth mechanism, deposition was carried out for different concentrations of the solution by changing only the ferrocene quantity, ranging from 0.01 to 0.03 gm/ml. A tunable vertical alignment of multi-walled carbon nanotubes (CNTs) has been achieved by this process and examined by scanning and transmission electron microscopic techniques. Micro-crystalline structural analysis has been done using Raman spectroscopy. A systematic variation in field emission (FE) current density has been observed. The highest FE current density is seen for the film grown with 0.02 gm/ml concentration, which is attributed to the better alignment of CNTs, less structural disorder and less entanglement of CNTs on the surface. The alignment of CNTs has been qualitatively understood on the basis of self-assembled catalytic particles.

  20. Field Measurements of PCB emissions from Building Surfaces Using a New Portable Emission Test Cell

    DEFF Research Database (Denmark)

    Lyng, Nadja; Haven, Rune; Gunnarsen, Lars Bo

    2016-01-01

    Danish elementary school. The emission test cell was capable of measuring widely varying specific emission rates of PCBtotal (8-3357 ng/(m2·h)). Remediated measures were found to reduce the emission rates by more than 96% compared with similar untreated surfaces. Emission rates may be affected......The purpose of the study was to measure PCB-emission rates from indoor surfaces on-site in contaminated buildings using a newly developed portable emission test cell. Emission rates were measured from six different surfaces; three untreated surfaces and three remediated surfaces in a contaminated...... by the conditions in the test cell (such as clean air and increased air velocity) and thereby potentially be different without the test cell attached to the surface. Still the measured emission rates obtained by using the test cell are valuable for determination of mitigation strategies. Additionally the test cell...

  1. Enhanced performance of photodetector and photovoltaic based on carrier reflector and back surface field generated by doped graphene

    Science.gov (United States)

    Chang, Che-Wei; Wang, Di-Yan; Tan, Wei-Chun; Huang, I.-Sheng; Wang, I.-Sheng; Chen, Chia-Chun; Yang, Ying-Jay; Chen, Yang-Fang

    2012-08-01

    We report the influence of carrier reflector and back surface field generated by doped graphene on n-ZnO nanoridges/p-silicon photodetectors and silicon solar cells. It is found that the p-type graphene not only acts as an electron blocking layer, but also helps the collection of photogenerated holes. Quite surprisingly, the on/off ratio of the photodetector with the insertion of doped graphene can be increased by up to 40 times. Moreover, we demonstrate that typical silicon solar cells with the doped graphene, the cell efficiency can be enhanced by about 20%. Our approach would expand numerous applications for graphene-based optoelectronic devices.

  2. New perspectives in vacuum high voltage insulation. I. The transition to field emission

    CERN Document Server

    Diamond, W T

    1998-01-01

    Vacuum high-voltage insulation has been investigated for many years. Typically, electrical breakdown occurs between two broad-area electrodes at electric fields 100-1000 times lower than the breakdown field (about 5000 MV/m) between a well-prepared point cathode and a broad-area anode. Explanations of the large differences remain unsatisfactory, usually evoking field emission from small projections on the cathode that are subject to higher peak fields. The field emission then produces secondary effects that lead to breakdown. This article provides a significant resolution to this long standing problem. Field emission is not present at all fields, but typically starts after some process occurs at the cathode surface. Three effects have been identified that produce the transition to field emission: work function changes; mechanical changes produced by the strong electrical forces on the electrode surfaces; and gas desorption from the anode with sufficient density to support an avalanche discharge. Material adso...

  3. Carrier-envelope phase dependence of the directional fragmentation and hydrogen migration in toluene in few-cycle laser fields

    Directory of Open Access Journals (Sweden)

    Hui Li

    2016-07-01

    Full Text Available The dissociative ionization of toluene initiated by a few-cycle laser pulse as a function of the carrier envelope phase (CEP is investigated using single-shot velocity map imaging. Several ionic fragments, CH3+, H2+, and H3+, originating from multiply charged toluene ions present a CEP-dependent directional emission. The formation of H2+ and H3+ involves breaking C-H bonds and forming new bonds between the hydrogen atoms within the transient structure of the multiply charged precursor. We observe appreciable intensity-dependent CEP-offsets. The experimental data are interpreted with a mechanism that involves laser-induced coupling of vibrational states, which has been found to play a role in the CEP-control of molecular processes in hydrocarbon molecules, and appears to be of general importance for such complex molecules.

  4. Band-gap dependence of field emission from one-dimensional nanostructures grown on n-type and p-type silicon substrates

    Science.gov (United States)

    Chang, C. S.; Chattopadhyay, S.; Chen, L. C.; Chen, K. H.; Chen, C. W.; Chen, Y. F.; Collazo, R.; Sitar, Z.

    2003-09-01

    Field emission of electrons from narrow-band-gap and wide-band-gap one-dimensional nanostructures were studied. N-type silicon substrates enhanced the emission from the low-band-gap silicon nanowires and carbon nanotubes, whereas p-type substrates were a better choice for field emission from wide-band-gap silicon carbon nitride nanocrystalline thin films and nanorods. The role of the substrate-nanostructure interface was modeled based on different junction mechanisms to explain, qualitatively, the fundamentally different emission behavior of these nanostructures when n- and p-type silicon substrates were used. The results could be explained on the basis of simple carrier transport across the silicon-silicon nanowire interface and subsequent tunneling of electrons for the silicon nanowires. Schottky barrier theory can explain the better field emission of electrons from the n-type silicon supported carbon nanotubes. The decreased barrier height at the interface of the silicon-silicon carbon nitride heterojunction, when p-type silicon substrate was used, could explain the superior field emission in comparison to when n-type silicon substrates were used.

  5. Field Measurements of PCB emissions from Building Surfaces Using a New Portable Emission Test Cell

    DEFF Research Database (Denmark)

    Lyng, Nadja; Haven, Rune; Gunnarsen, Lars Bo

    2016-01-01

    The purpose of the study was to measure PCB-emission rates from indoor surfaces on-site in contaminated buildings using a newly developed portable emission test cell. Emission rates were measured from six different surfaces; three untreated surfaces and three remediated surfaces in a contaminated...

  6. Symmetry-controlled time structure of high-harmonic carrier fields from a solid.

    Science.gov (United States)

    Langer, F; Hohenleutner, M; Huttner, U; Koch, S W; Kira, M; Huber, R

    2017-04-01

    High-harmonic (HH) generation in crystalline solids1-6 marks an exciting development, with potential applications in high-efficiency attosecond sources7, all-optical bandstructure reconstruction8,9, and quasiparticle collisions10,11. Although the spectral1-4 and temporal shape5 of the HH intensity has been described microscopically1-6,12, the properties of the underlying HH carrier wave have remained elusive. Here we analyse the train of HH waveforms generated in a crystalline solid by consecutive half cycles of the same driving pulse. Extending the concept of frequency combs13-15 to optical clock rates, we show how the polarization and carrier-envelope phase (CEP) of HH pulses can be controlled by crystal symmetry. For some crystal directions, we can separate two orthogonally polarized HH combs mutually offset by the driving frequency to form a comb of even and odd harmonic orders. The corresponding CEP of successive pulses is constant or offset by π, depending on the polarization. In the context of a quantum description of solids, we identify novel capabilities for polarization- and phase-shaping of HH waveforms that cannot be accessed with gaseous sources.

  7. Space-Time mapping of terahertz-induced electron field emission

    DEFF Research Database (Denmark)

    Lange, Simon Lehnskov; Kristensen, Thea M. B.; Iwaszczuk, Krzysztof

    2017-01-01

    We present simulations and experiments showing how THz induced electron field emission from gold antennas can be mapped indirectly in space and time. Our simulations predict the spatiotemporal electron distribution after single-cycle THz-induced field emission. Two different experiments validate...... this through a time-accumulated, spatial electron mapping due to both short- and long-time irradiation with THz transients....

  8. In-FEEP ion beam neutralization with thermionic and field emission cathodes

    Science.gov (United States)

    Marrese, C.; Polk, J.; Mueller, J.; Owens, A.; Tajmar, M.; Fink, R.; Spindt, C.

    2002-01-01

    Charge neutralization of an In-FEEP thruster was demonstrated with three different electron sources by zeroing the floating potential of the thruster and neutralizer system. The three cathodes used in the investigation include a mixed metal thermionic cathode, a carbon nanotube field emission cathode, and a Spindt-type Mo field emission array cathode.

  9. Large-area field emission diode for semiconductor annealing

    Science.gov (United States)

    Luches, A.; Nassisi, V.; Perrone, A.; Perrone, M. R.

    1981-03-01

    We report the characteristics of a low energy electron beam generator used for annealing of materials of interest as electron devices and photovoltaic cells. The high voltage pulser is a two-stage Marx circuit which supplies 10-50 kV pulses. A Blumlein line gives the pulses an almost square shape and a length of 50 ns. This short pulse is applied to a field emission diode. Various kinds of cathodes are used. They deliver electron pulses of up to 20 kA. Tungsten needles are used for small-area beams and blade arrays or graphite cathodes for large-area beams. Consequently, the beam diameter can vary from 2 to 120 mm with a good beam homogeneity. The anode is movable to vary the vacuum diode impedance and consequently the current-voltage characteristic of the electron beam. Energy densities varying from 0.1 to 100 J/cm 2 are obtained on the anode. The anode can be formed by a semiconductor monocrystalline wafer. We used crystalline silicon wafers covered by a thin (≈100 nm) layer of vacuum deposited near-noble and refractory metals. Under electron beam bombardment with discharge energy densities ranging from 0.4 to 10 J/cm 2, silicide formation is evident over all the annealed anodes. Metastable compounds are formed because of the fast heating and cooling rates. Silicon monocrystalline wafers, doped with 10 14-10 15 ions/cm 2 of B or P ions exhibit a complete recovery of their crystalline structure after a single discharge.

  10. Analysis of a copper sample for the CLIC ACS study in a field emission scanning microscope

    CERN Document Server

    Muranaka, Tomoko; Leifer, Klaus; Ziemann, Volker; Navitski, Aliaksandr; Müller, Günter

    2011-01-01

    We report measurements on a diamond turned Copper sample of material intended for the CLIC accelerating structures. The first part of the measurements was performed at Bergische Universität Wuppertal using a field emission scanning microscope to localize and characterize strong emission sites. In a second part the sample was investigated in an optical microscope, a white-light profilometer and scanning electron microscope in the microstructure laboratory in Uppsala to attempt to identify the features responsible for the field emission.

  11. Analysis of the Extremely Low Frequency Magnetic Field Emission from Laptop Computers

    Directory of Open Access Journals (Sweden)

    Brodić Darko

    2016-03-01

    Full Text Available This study addresses the problem of magnetic field emission produced by the laptop computers. Although, the magnetic field is spread over the entire frequency spectrum, the most dangerous part of it to the laptop users is the frequency range from 50 to 500 Hz, commonly called the extremely low frequency magnetic field. In this frequency region the magnetic field is characterized by high peak values. To examine the influence of laptop’s magnetic field emission in the office, a specific experiment is proposed. It includes the measurement of the magnetic field at six laptop’s positions, which are in close contact to its user. The results obtained from ten different laptop computers show the extremely high emission at some positions, which are dependent on the power dissipation or bad ergonomics. Eventually, the experiment extracts these dangerous positions of magnetic field emission and suggests possible solutions.

  12. The field emission properties from the pristine/B-doped graphene–C{sub 70} composite

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiaoju; Wang, Yan; Yang, Ping, E-mail: yangpingdm@ujs.edu.cn

    2017-06-28

    The aim of this paper is to implement a theoretical prediction and evaluation on the quality of graphene–C{sub 70} composite as cathode material. The pristine graphene–C{sub 70} composite and the B-doped graphene–C{sub 70} composites were constructed to investigate their field emission properties. The results suggest that the work function (WF) and ionization potential (IP) of the composites decrease with the increasing electric field. It implies that the electron emission becomes more and more easy. Under the field, the molecular orbital energy levels close to the vacuum level and their energy gap also has a declining trend. It means a good trend for improving the field emission properties of the composites. The above mentioned results show that the composites have the advanced capacity for electron emission and the potential for cathode material. It makes us believe that the composites will be the good field emission electron sources in the electronic device fabrication and the investigation can give a theoretical guidance for the corresponding experiments and may develop the application of fullerene for field emission. - Highlights: • We implement a theoretical prediction on graphene–C{sub 70} composite as cathode materials. • We detect the work function of the composite decrease with increasing electric field. • The ionization potential of the composites decrease with increasing electric field. • We find the molecular orbital energy level close to the vacuum level under the field. • The composites have the advanced capacity for electron emission as cathode material.

  13. Far-Field Testing Method of Spurious Emission Produced by HF RFID

    Directory of Open Access Journals (Sweden)

    Nikola Gvozdenovic

    2016-01-01

    Full Text Available We present measurements of spurious emission produced by high-frequency radio frequency identification (HF RFID using carrier frequency of 13.56 MHz. HF RFID tags produce unwanted emission due to rectification and more generally due to nonlinearity of analog front end. Depending on the conducting material of an HF RFID coil and surrounding dielectric material, the coil behaves as more or less good antenna on some harmonic frequencies. Exact characterization and analysis of unwanted emission is important from the security perspective as well as from the perspective of interference with other systems. Consequently we measured the harmonics produced in the integrated circuitry and characterized radiation properties of the antenna. Finally we present the measurements of the spurious emission performed in a Gigahertz Transverse Electromagnetic (GTEM cell.

  14. Fabrication of graphene and ZnO nanocones hybrid structure for transparent field emission device

    Energy Technology Data Exchange (ETDEWEB)

    Zulkifli, Zurita [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan); Faculty of Electrical Engineering, Universiti Teknologi Mara (Malaysia); Shinde, Sachin M.; Suguira, Takatoshi [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan); Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Tanemura, Masaki [Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology (Japan)

    2015-11-30

    Graphical abstract: Fabrication of a transparent field emission device with chemical vapor deposited graphene and zinc oxide nanocones showing low turn-on field due to locally enhance electric field. - Highlights: • Demonstrated transparent field emission device with CVD graphene and ZnO nanocones. • Graphene film was coated on carbon doped ZnO nanocone prepared by ion irradiation. • Low turn-on field for the graphene/C:ZnO nanocones hybrid structure is achieved. • Graphene/C:ZnO heterostructure is promising for transparent field emission devices. - Abstract: Fabrication of a transparent and high performance electron emission device is the key challenge for suitable display applications. Here, we demonstrate fabrication of a transparent and efficient field emission device integrating large-area chemical vapor deposited graphene and carbon doped zinc oxide (C:ZnO) nanocones. The ZnO nanocones were obtained with ion irradiation process at room temperature, over which the graphene film was transferred without destroying nanocone tips. Significant enhancement in field emission properties were observed with the transferred graphene film on C:ZnO nanocones. The threshold field for hybrid and pristine C:ZnO nanocones film at current density of 1 μA/cm{sup 2} was obtained as 4.3 V/μm and 6.5 V/μm, respectively. The enhanced field emission properties with low turn-on field for the graphene/C:ZnO nanocones can be attributed to locally enhance electric field. Our finding shows that a graphene/C:ZnO hybridized structure is very promising to fabricate field emission devices without compromising with high transparency.

  15. Field emission stability of anodic aluminum oxide carbon nanotube field emitter in the triode structure.

    Science.gov (United States)

    Li, Yiming; Cheng, Hui-Wen

    2009-05-01

    In this work, fabricated field emission (FE) triode arrays with the anodic aluminum oxide (AAO) template carbon nanotube (CNTs) as the field emitters are numerically analyzed. To obtain physically sound self-consistent solution, a set of Maxwell's equations coupling with Lorentz equation are solved simultaneously using a finite difference time domain particle-in-cell method. The FE current is then computed with the Fowler-Nordheim equation. To validate the simulation model, we firstly calibrate the collected electron current density between the measured AAO-CNTs and calculated result. The FE current is dominated by, such as density, height, diameter, and tilt angle of CNTs, and applied bias, respectively. A high density of CNTs will result in strong screening effect among adjacent CNTs and reduce the magnitude of electric field. Consequently, it significantly affects the emitted and collected electron current densities. However, the structure with much higher density of CNTs obviously emits more stable current than that of a low density of CNTs. There is an optimal setting on the height and diameter of the CNTs within the explored structure which exhibits the highest current density. When we vary the density of CNTs, the structure with high density (say the number of CNTs is greater than 30) shows the most stable and smallest fluctuation on the current density against the randomly generated samples of the height and tilt angle of CNTs.

  16. Field emission properties of the caterpillar-like structural carbon film grown by magnetic and electric fields coupling HFCVD

    Science.gov (United States)

    Wang, Yijia; Wei, Qiuping; Yu, Zhiming; Long, Hangyu; Deng, Zejun; Xie, Youneng; Li, Jiaxin; Lin, Cheng-Te; Ma, Li; Zhou, Kechao

    2017-11-01

    Caterpillar-like structural carbon film was directly fabricated by the method of magnetic and electric fields coupling hot filament chemical vapor deposition (HFCVD). The caterpillar-like structural carbon film showed a graphitic feature with numerous carbon nanosheets (CNSs). We supposed that the appearance of CNSs should be ascribed to the role of electric field. Raman and field emission transmission electron microscopy (TEM) results demonstrated that CNSs were composed of multiple graphene layers. Field emission results indicated that the micro caterpillar-like structural carbon film exhibited a low turn-on field of 3.66 V/μm and good performance in emission stability with less than 8% of fluctuation in current density.

  17. Greenhouse gas emissions from Indian rice fields: calibration and upscaling using the DNDC model

    Directory of Open Access Journals (Sweden)

    H. Pathak

    2005-01-01

    Full Text Available The Denitrification and Decomposition (DNDC model was evaluated for its ability to simulate methane (CH4, nitrous oxide (N2O and carbon dioxide (CO2 emissions from Indian rice fields with various management practices. The model was calibrated and validated for field experiments in New Delhi, India. The observed yield, N uptake and greenhouse gas (GHG emissions were in good agreement with the values predicted by the model. The model was then applied for estimation of GHG emissions from rice fields in India using a newly compiled soil/climate/land use database. Continuous flooding of rice fields (42.25 million ha resulted in annual net emissions of 1.07-1.10, 0.04-0.05 and 21.16-60.96 Tg of CH4-C, N2O-N and CO2-C, respectively, with a cumulated global warming potential (GWP of 130.93-272.83 Tg CO2 equivalent. Intermittent flooding of rice fields reduced annual net emissions to 0.12-0.13 Tg CH4-C and 16.66-48.80 Tg CO2-C while N2O emission increased to 0.05-0.06 Tg N2O-N. The GWP, however, reduced to 91.73-211.80 Tg CO2 equivalent. The study suggested that the model could be applied for estimating the GHG emissions and the influences of agronomic management, soil and climatic parameters on the GHG emissions from rice fields in India.

  18. Carrier redistribution between different potential sites in semipolar (202¯1) InGaN quantum wells studied by near-field photoluminescence

    KAUST Repository

    Marcinkevičius, S.

    2014-09-15

    © 2014 AIP Publishing LLC. Scanning near-field photoluminescence (PL) spectroscopy at different excitation powers was applied to study nanoscale properties of carrier localization and recombination in semipolar (202¯1) InGaN quantum wells (QWs) emitting in violet, blue, and green-yellow spectral regions. With increased excitation power, an untypical PL peak energy shift to lower energies was observed. The shift was attributed to carrier density dependent carrier redistribution between nm-scale sites of different potentials. Near-field PL scans showed that in (202¯1) QWs the in-plane carrier diffusion is modest, and the recombination properties are uniform, which is advantageous for photonic applications.

  19. Method of synthesizing small-diameter carbon nanotubes with electron field emission properties

    Science.gov (United States)

    Liu, Jie (Inventor); Du, Chunsheng (Inventor); Qian, Cheng (Inventor); Gao, Bo (Inventor); Qiu, Qi (Inventor); Zhou, Otto Z. (Inventor)

    2009-01-01

    Carbon nanotube material having an outer diameter less than 10 nm and a number of walls less than ten are disclosed. Also disclosed are an electron field emission device including a substrate, an optionally layer of adhesion-promoting layer, and a layer of electron field emission material. The electron field emission material includes a carbon nanotube having a number of concentric graphene shells per tube of from two to ten, an outer diameter from 2 to 8 nm, and a nanotube length greater than 0.1 microns. One method to fabricate carbon nanotubes includes the steps of (a) producing a catalyst containing Fe and Mo supported on MgO powder, (b) using a mixture of hydrogen and carbon containing gas as precursors, and (c) heating the catalyst to a temperature above 950.degree. C. to produce a carbon nanotube. Another method of fabricating an electron field emission cathode includes the steps of (a) synthesizing electron field emission materials containing carbon nanotubes with a number of concentric graphene shells per tube from two to ten, an outer diameter of from 2 to 8 nm, and a length greater than 0.1 microns, (b) dispersing the electron field emission material in a suitable solvent, (c) depositing the electron field emission materials onto a substrate, and (d) annealing the substrate.

  20. Field Emission from Self-Assembled Arrays of Lanthanum Monosulfide Nanoprotrusions

    Directory of Open Access Journals (Sweden)

    V. Semet

    2008-01-01

    Full Text Available The field emission properties of LaS nanoprotrusions called nanodomes, formed by pulsed laser deposition on porous anodic alumina films, have been analyzed with scanning anode field emission microscopy. The voltage necessary to produce a given field emission current is ∼3.5 times less for nanodomes than for thin films. Assuming the same work function for LaS thin films and nanoprotrusions, that is, ∼1 eV, a field enhancement factor of ∼5.8 is extracted for the nanodome emitters from Fowler-Nordheim plots of the field emission data. This correlates well with the aspect ratio of the tallest nanodomes observed in atomic force micrograph measurements.

  1. Leakage and field emission in side-gate graphene field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Di Bartolomeo, A., E-mail: dibant@sa.infn.it; Iemmo, L.; Romeo, F.; Cucolo, A. M. [Physics Department “E.R. Caianiello,” University of Salerno, via G. Paolo II, 84084 Fisciano (Italy); CNR-SPIN Salerno, via G. Paolo II, 84084 Fisciano (Italy); Giubileo, F. [CNR-SPIN Salerno, via G. Paolo II, 84084 Fisciano (Italy); Russo, S.; Unal, S. [Physics Department, University of Exeter, Stocker Road 6, Exeter, Devon EX4 4QL (United Kingdom); Passacantando, M.; Grossi, V. [Department of Physical and Chemical Sciences, University of L' Aquila, Via Vetoio, 67100 Coppito, L' Aquila (Italy)

    2016-07-11

    We fabricate planar graphene field-effect transistors with self-aligned side-gate at 100 nm from the 500 nm wide graphene conductive channel, using a single lithographic step. We demonstrate side-gating below 1 V with conductance modulation of 35% and transconductance up to 0.5 mS/mm at 10 mV drain bias. We measure the planar leakage along the SiO{sub 2}/vacuum gate dielectric over a wide voltage range, reporting rapidly growing current above 15 V. We unveil the microscopic mechanisms driving the leakage, as Frenkel-Poole transport through SiO{sub 2} up to the activation of Fowler-Nordheim tunneling in vacuum, which becomes dominant at higher voltages. We report a field-emission current density as high as 1 μA/μm between graphene flakes. These findings are important for the miniaturization of atomically thin devices.

  2. Testing the near field/far field model performance for prediction of particulate matter emissions in a paint factory

    DEFF Research Database (Denmark)

    Koivisto, A.J.; Jensen, A.C.Ø.; Levin, Marcus

    2015-01-01

    A Near Field/Far Field (NF/FF) model is a well-accepted tool for precautionary exposure assessment but its capability to estimate particulate matter (PM) concentrations is not well studied. The main concern is related to emission source characterization which is not as well defined for PM emitters...

  3. Room temperature Coulomb blockade mediated field emission via self-assembled gold nanoparticles

    Science.gov (United States)

    Wang, Fei; Fang, Jingyue; Chang, Shengli; Qin, Shiqiao; Zhang, Xueao; Xu, Hui

    2017-02-01

    Coulomb blockade mediated field-emission current was observed in single-electron tunneling devices based on self-assembled gold nanoparticles at 300 K. According to Raichev's theoretical model, by fixing a proper geometric distribution of source, island and drain, the transfer characteristics can be well explained through a combination of Coulomb blockade and field emission. Coulomb blockade and field emission alternately happen in our self-assembled devices. The Coulomb island size derived from the experimental data is in good agreement with the average size of the gold nanoparticles used in the device. The integrated tunneling can be adjusted via a gate electrode.

  4. Study into mechanisms of the enhancement of multibubble sonoluminescence emission in interacting fields of different frequencies.

    Science.gov (United States)

    Ciuti, P; Dezhkunov, N V; Francescutto, A; Calligaris, F; Sturman, F

    2003-10-01

    The main factor of the enhancement of sonoluminescence (SL) emission by the interaction of two fields of highly different frequencies is the generation of new cavitation nuclei upon collapse of bubbles driven by the low-frequency (LF) field. The factors connected with the direct interaction of the two fields play a significant role in the enhancement of SL emission only in the case when intensities of the fields are less or not much higher than the corresponding thresholds of SL emission. The phenomena of afteraction of the LF field on cavitation generated by the high-frequency field is explained also by the generation of new nuclei upon collapse of bubbles driven by the LF fields.

  5. Polaron effects and electric field dependence of the charge carrier mobility in conjugated polymers.

    Science.gov (United States)

    Jakobsson, Mattias; Stafström, Sven

    2011-10-07

    Charge transport in conjugated polymers has been investigated using Monte Carlo simulations implemented on top of the Marcus theory for donor-acceptor transition rates. In particular, polaron effects and the dependency of the mobility on the temperature and the applied electric field have been studied. The conclusions are that while the qualitative temperature dependence is similar to that predicted by Miller-Abrahams theory in the Gaussian disorder model (GDM), the electric field dependence is characterized by a crossover into the Marcus inverted region, not present in the GDM. Furthermore, available analytical approximations to describe the electric field dependence of the mobility in Marcus theory fail to fit the simulation data and hence cannot be used to directly draw conclusions about the importance of polaron effects for charge transport in conjugated polymers. © 2011 American Institute of Physics

  6. Effects of ZnO Quantum Dots Decoration on the Field Emission Behavior of Graphene.

    Science.gov (United States)

    Sun, Lei; Zhou, Xiongtu; Lin, Zhixian; Guo, Tailiang; Zhang, Yongai; Zeng, Yongzhi

    2016-11-23

    ZnO quantum dots (QDs) have been decorated on graphene deposited on patterned Ag electrodes as a field emission cathode by a solution process. Effects of ZnO QDs on the field emission behavior of graphene are studied by experiment and first-principles calculations. The results indicate that the attachment of ZnO QDs with a C atom leads to the enhancement of electron emission from graphene, which is mainly attributed to the reduction of the work function and ionization potential, and the increase of the Fermi level of graphene after the decoration. A change in the local density distribution and the density of states near the Fermi level may also account for this behavior. Our study may help to develop new field emission composites and expand ZnO QDs in applications for electron emission devices as well.

  7. Effect of Biochar on Greenhouse Gas Emissions and Nitrogen Cycling in Laboratory and Field Experiments

    Science.gov (United States)

    Hagemann, Nikolas; Harter, Johannes; Kaldamukova, Radina; Ruser, Reiner; Graeff-Hönninger, Simone; Kappler, Andreas; Behrens, Sebastian

    2014-05-01

    The extensive use of nitrogen (N) fertilizers in agriculture is a major source of anthropogenic N2O emissions contributing 8% to global greenhouse gas emissions. Soil biochar amendment has been suggested as a means to reduce both CO2 and non-CO2 greenhouse gas emissions. The reduction of N2O emissions by biochar has been demonstrated repeatedly in field and laboratory experiments. However, the mechanisms of the reduction remain unclear. Further it is not known how biochar field-weathering affects GHG emissions and how agro-chemicals, such as the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), that is often simultaneously applied together with commercial N-fertilizers, impact nitrogen transformation and N2O emissions from biochar amended soils. In order investigate the duration of the biochar effect on soil N2O emissions and its susceptibility to DMPP application we performed a microcosm and field study with a high-temperature (400 ° C) beech wood derived biochar (60 t ha-1 and 5 % (w/w) biochar in the field and microcosms, respectively). While the field site contained the biochar already for three years, soil and biochar were freshly mixed for the laboratory microcosm experiments. In both studies we quantified GHG emissions and soil nitrogen speciation (nitrate, nitrite, ammonium). While the field study was carried out over the whole vegetation period of the sunflower Helianthus annuus L., soil microcosm experiments were performed for up to 9 days at 28° C. In both experiments a N-fertilizer containing DMPP was applied either before planting of the sunflowers or at the beginning of soil microcosms incubation. Laboratory microcosm experiments were performed at 60% water filled pore space reflecting average field conditions. Our results show that biochar effectively reduced soil N2O emissions by up to 60 % in the field and in the soil microcosm experiments. No significant differences in N2O emission mitigation potential between field-aged and fresh

  8. Multi-field electron emission pattern of 2D emitter: Illustrated with graphene

    Science.gov (United States)

    Luo, Ma; Li, Zhibing

    2016-11-01

    The mechanism of laser-assisted multi-field electron emission of two-dimensional emitters is investigated theoretically. The process is basically a cold field electron emission but having more controllable components: a uniform electric field controls the emission potential barrier, a magnetic field controls the quantum states of the emitter, while an optical field controls electron populations of specified quantum states. It provides a highly orientational vacuum electron line source whose divergence angle over the beam plane is inversely proportional to square root of the emitter height. Calculations are carried out for graphene with the armchair emission edge, as a concrete example. The rate equation incorporating the optical excitation, phonon scattering, and thermal relaxation is solved in the quasi-equilibrium approximation for electron population in the bands. The far-field emission patterns, that inherit the features of the Landau bands, are obtained. It is found that the optical field generates a characteristic structure at one wing of the emission pattern.

  9. Emissions from prescribed burning of agricultural fields in the Pacific Northwest

    Science.gov (United States)

    A. L. Holder; B. K. Gullett; S. P. Urbanski; R. Elleman; S. O' Neill; D. Tabor; W. Mitchell; K. R. Baker

    2017-01-01

    Prescribed burns of winter wheat stubble and Kentucky bluegrass fields in northern Idaho and eastern Washington states (U.S.A.) were sampled using ground-, aerostat-, airplane-, and laboratory-based measurement platforms to determine emission factors, compare methods, and provide a current and comprehensive set of emissions data for air quality models, climate models,...

  10. Enhanced performance of thermal-assisted electron field emission based on barium oxide nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Yunkang [Department of Mathematics and Physics, Nanjing Institute of technology, Nanjing, 211167 (China); Chen, Jing, E-mail: chenjingmoon@gmail.com [School of Electronic Science & Engineering, Southeast University, Nanjing, 210096 (China); Zhang, Yuning; Zhang, Xiaobing; Lei, Wei; Di, Yunsong [School of Electronic Science & Engineering, Southeast University, Nanjing, 210096 (China); Zhang, Zichen, E-mail: zz241@ime.ac.cn [Integrated system for Laser applications Group, Institute of Microelectronics of Chinese Academy of Sciences, 100029, Beijing (China)

    2017-02-28

    Highlights: • A possible mechanism for thermal-assisted electric field was demonstrated. • A new path for the architecture of the novel nanomaterial and methodology for its potential application in the field emission device area was provided. • The turn-on field, the threshold field and the field emission current density were largely related to the temperature of the cathode. • The relationship between the work function of emitter material and the temperature of emitter was found. - Abstract: In this paper, thermal-assisted field emission properties of barium oxide (BaO) nanowire synthesized by a chemical bath deposition method were investigated. The morphology and composition of BaO nanowire were characterized by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SED), X-ray diffraction (XRD), and energy dispersive X-ray spectrometer (EDX) respectively. The turn-on field, threshold field and the emission current density could be affected relatively due to the thermal-assisted effect when the electric field was applied, in the meanwhile, the turn-on field for BaO nanowire was measured to be decreased from 1.12 V/μm to 0.66 V/μm when the temperature was raised from 293 K to 593 K, whereas for the threshold field was found to decrease from 3.64 V/μm to 2.12 V/μm. The improved performance was demonstrated due to the reduced work function of the BaO nanowire as the agitation temperature increasing, leading to the higher probability of electrons tunneling through the energy barrier and enhancement of the field emission properties of BaO emitters.

  11. Sensitivity of detection of fugitive methane emissions from coal seam gas fields

    Science.gov (United States)

    Feitz, A. J.; Berko, H.; Wilson, P.; Jenkins, C.; Loh, Z. M.; Etheridge, D.

    2013-12-01

    There is increasing recognition that minimising methane emissions from the oil and gas sector is a key step in reducing global greenhouse gas emissions in the near term. Atmospheric monitoring techniques are likely to play an important future role in measuring the extent of existing emissions and verifying emission reductions. They can be very suitable for monitoring gas fields as they are continuous and integrate emissions from a number of potential point and diffuse sources that may vary in time. Geoscience Australia and CSIRO Marine & Atmospheric Research have collected three years of continuous methane and carbon dioxide measurements at their atmospheric composition monitoring station ('Arcturus') in the Bowen Basin, Australia. Methane signals in the Bowen Basin are likely to be influenced by cattle production, landfill, coal production, and conventional and coal seam gas (CSG) production. Australian CSG is typically 'dry' and is characterised by a mixed thermogenic-biogenic methane source with an absence of C3-C6+ alkanes. The range of δ13C isotopic signatures of the CSG is similar to methane from landfill gas and cattle emissions. The absence of standard in-situ tracers for CSG fugitive emissions suggests that having a comprehensive baseline will be critical for successful measurement of fugitive emissions using atmospheric techniques. In this paper we report on the sensitivity of atmospheric techniques for the detection of fugitive emissions from a simulated new CSG field against a three year baseline signal. Simulation of emissions was performed for a 1-year period using the coupled prognostic meteorological and air pollution model TAPM at different fugitive emission rates (i.e. estimates of <1% to up to 10% of production lost) and distances (i.e. 10 - 50 km) from the station. Emissions from the simulated CSG field are based on well density, production volumes, and field size typical of CSG fields in Australia. The distributions of the perturbed and

  12. Contribution of Metal Layer Thickness for Quantitative Backscattered Electron Imaging of Field Emission Scanning Electron Microscopy

    National Research Council Canada - National Science Library

    Kim, Hyonchol; Takei, Hiroyuki; Negishi, Tsutomu; Kudo, Masato; Terazono, Hideyuki; Yasuda, Kenji

    2012-01-01

    ...) imaging in field emission scanning electron microscopy (FE-SEM) were studied to evaluate the potential of using these particles as simultaneously distinguishable labels of target molecules in FE-SEM studies...

  13. Intelligent transportation systems field operational test cross-cutting study : emissions management using ITS technology

    Science.gov (United States)

    1998-09-01

    Emissions Management Using ITS Technology report summarizes and interprets the results of three Intelligent Transportation Systems (ITS) Field Operational Tests (FOTs) that evaluated the use of emerging technologies to help authorities measure emissi...

  14. Thermal carrier emission and nonradiative recombinations in nonpolar (Al,Ga)N/GaN quantum wells grown on bulk GaN

    Energy Technology Data Exchange (ETDEWEB)

    Corfdir, P.; Dussaigne, A.; Giraud, E.; Ganiere, J.-D.; Grandjean, N.; Deveaud-Pledran, B. [Institute of Condensed Matter Physics, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Teisseyre, H. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Institute of High Pressure Physics, Polish Academy of Sciences, 01-142 Warsaw (Poland); Suski, T.; Grzegory, I. [Institute of High Pressure Physics, Polish Academy of Sciences, 01-142 Warsaw (Poland); Lefebvre, P. [Laboratoire Charles Coulomb - UMR5221 - CNRS - Universite Montpellier 2, 34095 Montpellier (France)

    2012-02-01

    We investigate, via time-resolved photoluminescence, the temperature-dependence of charge carrier recombination mechanisms in nonpolar (Al,Ga)N/GaN single quantum wells (QWs) grown via molecular beam epitaxy on the a-facet of bulk GaN crystals. We study the influence of both QW width and barrier Al content on the dynamics of excitons in the 10-320 K range. We first show that the effective lifetime of QW excitons {tau} increases with temperature, which is evidence that nonradiative mechanisms do not play any significant role in the low-temperature range. The temperature range for increasing {tau} depends on the QW width and Al content in the (Al,Ga)N barriers. For higher temperatures, we observe a reduction in the QW emission lifetime combined with an increase in the decay time for excitons in the barriers, until both exciton populations get fully thermalized. Based on analysis of the ratio between barrier and QW emission intensities, we demonstrate that the main mechanism limiting the radiative efficiency in our set of samples is related to nonradiative recombination in the (Al,Ga)N barriers of charge carriers that have been thermally emitted from the QWs.

  15. A Platform to Optimize the Field Emission Properties of Carbon Nanotube Based Fibers (Postprint)

    Science.gov (United States)

    2016-08-25

    AFRL-RX-WP-JA-2017-0351 A PLATFORM TO OPTIMIZE THE FIELD EMISSION PROPERTIES OF CARBON - NANOTUBE -BASED FIBERS (POSTPRINT) Steven B...28 April 2017 Interim 6 May 2010 – 20 August 2016 4. TITLE AND SUBTITLE A PLATFORM TO OPTIMIZE THE FIELD EMISSION PROPERTIES OF CARBON - NANOTUBE ...ieeexplore.ieee.org DOI: 10.1109/IVNC.2016.7551456 14. ABSTRACT (Maximum 200 words) Building on recent efforts [1-4] to characterize carbon nanotube

  16. Review on peculiar issues of field emission in vacuum nanoelectronic devices

    Science.gov (United States)

    Filip, Valeriu; Filip, Lucian Dragoş; Wong, Hei

    2017-12-01

    Some of the modern aspects of field emission based electron sources have been collated in a short and comprehensive review. The usually overlooked peculiar aspects in this research field have been particularly emphasized in order to increase the interest in further fundamental studies and technological applications. The vast material was roughly split in two main branches which occasionally overlap: the electron emission devices based on chemically homogeneous nanostructured surfaces and the more complex nanocomposite emitting surfaces.

  17. Enhanced field emission of graphene–ZnO quantum dots hybrid structure

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Lei [Zhicheng College, Fuzhou University, Fuzhou 350002 (China); National & Local United Engineer Laboratory of Flat Panel Display Technology, Fuzhou University, Fuzhou 350002 (China); Zhou, Xiongtu [National & Local United Engineer Laboratory of Flat Panel Display Technology, Fuzhou University, Fuzhou 350002 (China); Zhang, Yongai, E-mail: yongaizhang@fzu.edu.cn [National & Local United Engineer Laboratory of Flat Panel Display Technology, Fuzhou University, Fuzhou 350002 (China); Guo, Tailiang, E-mail: gtl_fzu@hotmail.com [National & Local United Engineer Laboratory of Flat Panel Display Technology, Fuzhou University, Fuzhou 350002 (China)

    2015-05-25

    Highlights: • ZnO quantum dots decorated graphene by solution process. • The hybrid emitters exhibited efficient field emission properties. • The enhancement is attributed to ZnO quantum dots. - Abstract: The cathode of graphene was prepared by the electrophoretic deposition (EPD) and ZnO quantum dots (QDs) were grown on the surface of graphene sheets by solution method to improve the field emission (FE) properties. The graphene/ZnO QDs hybrid emitters exhibited efficient field emission with lower turn-on field of 0.9 V/μm, lower threshold field of 2.6 V/μm, higher field enhancement factor of 3923 and more stable emission current stability than pristine graphene. The improved field emission performance was attributed to ZnO QDs, which introduce more defects, increase the number of emitting sites and decrease the work function. This investigation proposed that graphene/ZnO QDs composites are promising field cathodes in FE applications.

  18. Room temperature Coulomb blockade mediated field emission via self-assembled gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fei [College of Physics and Electronics, Central South University, Changsha, Hunan 410073 (China); College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China); Fang, Jingyue, E-mail: fjynudt@aliyun.com [College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China); Chang, Shengli; Qin, Shiqiao; Zhang, Xueao [College of Science, National University of Defense Technology, Changsha, Hunan 410073 (China); Xu, Hui, E-mail: cmpxhg@csu.edu.cn [College of Physics and Electronics, Central South University, Changsha, Hunan 410073 (China)

    2017-02-05

    Coulomb blockade mediated field-emission current was observed in single-electron tunneling devices based on self-assembled gold nanoparticles at 300 K. According to Raichev's theoretical model, by fixing a proper geometric distribution of source, island and drain, the transfer characteristics can be well explained through a combination of Coulomb blockade and field emission. Coulomb blockade and field emission alternately happen in our self-assembled devices. The Coulomb island size derived from the experimental data is in good agreement with the average size of the gold nanoparticles used in the device. The integrated tunneling can be adjusted via a gate electrode. - Highlights: • The phenomenon of single-electron field emission in a transistor setting using self-assembled gold nanoparticles was investigated. • The transfer characteristics can be well explained by the model that is a combination of Coulomb blockage and field emission. • This transport mechanism is novel and may be used in many applications in field emission devices.

  19. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Science.gov (United States)

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal

    2014-03-01

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  20. Preparation and characterization of monoatomic C-chains: unraveling and field emission

    Energy Technology Data Exchange (ETDEWEB)

    Mikhailovskij, I M [National Scientific Center, Kharkov Institute of Physics and Technology, Academicheskaja, 1, 61108 Kharkov (Ukraine); Wanderka, N [Hahn-Meitner-Institute Berlin, Glinikerstrasse 100, D-14109 Berlin (Germany); Ksenofontov, V A [National Scientific Center, Kharkov Institute of Physics and Technology, Academicheskaja, 1, 61108 Kharkov (Ukraine); Mazilova, T I [National Scientific Center, Kharkov Institute of Physics and Technology, Academicheskaja, 1, 61108 Kharkov (Ukraine); Sadanov, E V [National Scientific Center, Kharkov Institute of Physics and Technology, Academicheskaja, 1, 61108 Kharkov (Ukraine); Velicodnaja, O A [National Scientific Center, Kharkov Institute of Physics and Technology, Academicheskaja, 1, 61108 Kharkov (Ukraine)

    2007-11-28

    Combined field ion and electron microscopy and mass-spectrometry have revealed the presence of linear carbon chains at the surface of sharpened carbon fibers treated by electric fields of the order of 10{sup 11} V m{sup -1}. Linear chains attached to carbon tips consisting of more than ten atoms can be produced in situ in a field emission microscope using low-temperature pulsed-voltage field evaporation. The process of field evaporation is sporadic with an anomalously large instant rate of evaporation. Current versus voltage field electron characteristics of monoatomic carbon wires were investigated. By employing molecular dynamics simulation it was shown that atomic C-chains can be produced during the high-field unraveling of nanofibers. These chains are perfectly resolved both in electron and ion modes of the field emission microscope.

  1. Enhancing carrier injection in the active region of a 280nm emission wavelength LED using graded hole and electron blocking layers

    KAUST Repository

    Janjua, Bilal

    2014-02-27

    A theoretical investigation of AlGaN UV-LED with band engineering of hole and electron blocking layers (HBL and EBL, respectively) was conducted with an aim to improve injection efficiency and reduce efficiency droop in the UV LEDs. The analysis is based on energy band diagrams, carrier distribution and recombination rates (Shockley-Reed-Hall, Auger, and radiative recombination rates) in the quantum well, under equilibrium and forward bias conditions. Electron blocking layer is based on AlaGa1-aN / Al b → cGa1-b → 1-cN / AldGa 1-dN, where a < d < b < c. A graded layer sandwiched between large bandgap AlGaN materials was found to be effective in simultaneously blocking electrons and providing polarization field enhanced carrier injection. The graded interlayer reduces polarization induced band bending and mitigates the related drawback of impediment of holes injection. Similarly on the n-side, the Alx → yGa1-x → 1-yN / AlzGa 1-zN (x < z < y) barrier acts as a hole blocking layer. The reduced carrier leakage and enhanced carrier density in the active region results in significant improvement in radiative recombination rate compared to a structure with the conventional rectangular EBL layers. The improvement in device performance comes from meticulously designing the hole and electron blocking layers to increase carrier injection efficiency. The quantum well based UV-LED was designed to emit at 280nm, which is an effective wavelength for water disinfection application.

  2. Evaluation of field emission properties from multiple-stacked Si quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Takeuchi, Daichi, E-mail: d_takeut@nuee.nagoya-u.ac.jp [Graduate School of Engineering, Nagoya University, Nagoya (Japan); Makihara, Katsunori [Graduate School of Engineering, Nagoya University, Nagoya (Japan); Ohta, Akio [Venture Business Laboratory, Nagoya University, Nagoya (Japan); Ikeda, Mitsuhisa [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima (Japan); Miyazaki, Seiichi [Graduate School of Engineering, Nagoya University, Nagoya (Japan)

    2016-03-01

    Multiple-stacked Si quantum dots (QDs) with ultrathin SiO{sub 2} interlayers were formed on ultrathin SiO{sub 2} layers by repeating a process sequence consisting of the formation of Si-QDs by low pressure chemical vapor deposition using a SiH{sub 4} gas and the surface oxidation and subsequent surface modification by remote hydrogen and oxygen plasmas, respectively. To clarify the electron emission mechanism from multiple-stacked Si-QDs covered with an ultrathin Au top electrode, the energy distribution of the emitted electrons and its electric field dependence was measured using a hemispherical electron energy analyzer in an X-ray photoelectron spectroscopy system under DC bias application to the multiple-stacked Si-QD structure. At − 6 V and over, the energy distributions reached a peak at ~ 2.5 eV with a tail toward the higher energy side. While the electron emission intensity was increased exponentially with an increase in the applied DC bias, there was no significant increase in the emission peak energy. The observed emission characteristics can be interpreted in terms of field emissions from the second and/or third topmost Si-QDs resulting from the electric concentration there. - Highlights: • Electron field emission from 6-fold stack of Si-QDs has been evaluated. • AFM measurements show the local electron emission from individual Si-QDs. • Impact of applied bias on the electron emission energy distribution was investigated.

  3. Emission Laws and Influence Factors of Greenhouse Gases in Saline-Alkali Paddy Fields

    Directory of Open Access Journals (Sweden)

    Jie Tang

    2016-02-01

    Full Text Available The study of greenhouse gas emissions has become a global focus, but few studies have considered saline-alkali paddy fields. Gas samples and saline-alkali soil samples were collected during the green, tillering, booting, heading and grain filling stages. The emission fluxes of CO2, CH4, and N2O as well as the pH, soil soluble salt, available nitrogen, and soil organic carbon contents were detected to reveal the greenhouse gas (GHG emission laws and influence factors in saline-alkali paddy fields. Overall, GHG emissions of paddy soil during the growing season increased, then decreased, and then increased again and peaked at booting stage. The emission fluxes of CO2 and CH4 were observed as having two peaks and a single peak, respectively. Both the total amount of GHG emission and its different components of CO2, CH4, and N2O increased with the increasing reclamation period of paddy fields. A positive correlation was found between the respective emission fluxes of CO2, CH4, and N2O and the available nitrogen and SOC, whereas a negative correlation was revealed between the fluxes of CO2, CH4, and N2O and soil pH and soil conductivity. The study is beneficial to assessing the impact of paddy reclamation on regional greenhouse gas emissions and is relevant to illustrating the mechanisms concerning the carbon cycle in paddy soils.

  4. Interstellar Magnetic Fields and Polarimetry of Dust Emission

    Science.gov (United States)

    Dowell, Darren

    2010-01-01

    Magnetic fields are an important ingredient in the stormy cosmos. Magnetic fields: (1) are intimately involved with winds from Active Galactic Nuclei (AGN) and stars (2) create at least some of the structures observed in the ISM (3) modulate the formation of clouds, cores, and stars within a turbulent medium (4) may be dynamically important in protostellar accretion disks (5) smooth weak shocks (C-shocks).

  5. Net summertime emission of ammonia from corn and triticale fields

    Science.gov (United States)

    Richter, Undine; Smith, Jeremy; Brümmer, Christian

    2016-04-01

    Recent advancements in laser spectrometry offer new opportunities to investigate ecosystem-atmosphere exchange of environmentally relevant trace gases. In this study, we used a quantum cascade laser (QCL) absorption spectrometer to continuously measure high-frequency concentrations of ammonia and the net exchange between an agricultural site and the atmosphere based on the eddy-covariance approach. The footprint was split into two main sectors, one planted with corn (Zea mays) and the other one with triticale. Ammonia concentrations were highly variable between 2 and almost 100 ppb with an average value of 8.1 ppb during the observation period from April to September 2015. While both deposition and emission of ammonia was observed, the total campaign exchange resulted in a loss of 3.3 kg NH3-N ha-1. Highest average emission fluxes of 65 ng N m-2 s-1 were recorded after fertilization at the beginning of the campaign in April and May. Afterwards the exchange of ammonia with the atmosphere decreased considerably, but the site remained on average a consistent source with sporadic lower peaks and an average flux of 13 ng N m-2 s-1. While management in the form of fertilization was the main driver for ammonia concentration and exchange at the site, biophysical controls from temperature, wind regime, and surface wetness are also presented.

  6. [Hourly measurement on aerosol NH3 and gas NO(x) emission in the rice field].

    Science.gov (United States)

    Gong, Wei-Wei; Luan, Sheng-Ji

    2012-11-01

    Aerosol NH3 and gas NO(x) are the major components in atmospheric particles and precipitation, which are key precursors to form aerosols. The intensive N fertilization in arable land is an important source of aerosol NH3 and gas NO(x), which have not been well characterized yet. During May to October in 2010, the characteristics of aerosol NH3 and gas NO(x) emission from rice field after urea application were investigated. The time resolutions of measurements were set to be one hour. The aerosol NH3 emission and metrological factors within 20 d of continuous sampling after fertilization in four experiments were monitored. The experiment on gas NO(x) emission and metrological factors influencing the emission were carried out from the beginning of the forth test, which lasted for 47 days. Results indicated that the aerosol NH3 emission factors of four tests were 2.6%, 5.5%, 4.0% and 1.6%, respectively. The corresponding aerosol NH3 emission flux of four tests were 3.97, 2.08, 1.52 and 1.22 kg x hm(-2), respectively. Temperature (air temperature and soil temperature) was found to be the main factor influencing aerosol NH3 emission in rice fields after fertilization, while the impacts of air humidity and soil moisture were not clear. After analyzing the monitoring data, it can be concluded that the ratio of the emission amount of NO2 -N and NO-N in rice fields after fertilization was 9/4; the emission factor and the emission flux of gas NO(x) were 0.14% and 0.30 kg x hm(-2), respectively. The relationship between metrological factors and gas NO(x) emission flux was also examined.

  7. Effect of Electric Field in the Stabilized Premixed Flame on Combustion Process Emissions

    Science.gov (United States)

    Otto, Krickis

    2017-10-01

    The effect of the AC and DC electrical field on combustion processes has been investigated by various researchers. The results of these experiments do not always correlate, due to different experiment conditions and experiment equipment variations. The observed effects of the electrical field impact on the combustion process depends on the applied voltage polarity, flame speed and combustion physics. During the experiment was defined that starting from 1000 V the ionic wind takes the effect on emissions in flue gases, flame shape and combustion instabilities. Simulation combustion process in hermetically sealed chamber with excess oxygen amount 3 % in flue gases showed that the positive effect of electrical field on emissions lies in region from 30 to 400 V. In aforementioned voltage range carbon monoxide emissions were reduced by 6 % and at the same time the nitrogen oxide emissions were increased by 3.5 %.

  8. Enhancement of field emission and photoluminescence properties of graphene-SnO2 composite nanostructures.

    Science.gov (United States)

    Ding, Jijun; Yan, Xingbin; Li, Jun; Shen, Baoshou; Yang, Juan; Chen, Jiangtao; Xue, Qunji

    2011-11-01

    In this study, the SnO(2) nanostructures and graphene-SnO(2) (G-SnO(2)) composite nanostructures were prepared on n-Si (100) substrates by electrophoretic deposition and magnetron sputtering techniques. The field emission of SnO(2) nanostructures is improved largely by depositing graphene buffer layer, and the field emission of G-SnO(2) composite nanostructures can also further be improved by decreasing sputtering time of Sn nanoparticles to 5 min. The photoluminescence (PL) spectra of the SnO(2) nanostructures revealed multipeaks, which are consistent with previous reports except for a new peak at 422 nm. Intensity of six emission peaks increased after depositing graphene buffer layer. Our results indicated that graphene can also be used as buffer layer acting as interface modification to simultaneity improve the field emission and PL properties of SnO(2) nanostructures effectively.

  9. Greenhouse Gas Emissions from Peat Soils Cultivated to Rice Field, Oil Palm and Vegetable

    Directory of Open Access Journals (Sweden)

    Rosenani Abu Bakar

    2012-05-01

    Full Text Available Presently, about 20% of oil palm (Elaeis guineensis Jacq fields in Indonesia are on peat soil, in addition to that otherarea of peat soil has been conventionally used for rice field and vegetables. To elucidate the global warmingpotentials of peat soils cultivated to oil palm, vegetable or rice field, field experiment has been carried out in SouthKalimantan. Air samples were taken from rice field, oil palm and vegetable fields in weekly basis for six month periodand analyzed for concentrations of N2O, CH4 and CO2. The global warming potentials (GWP of the three gases werecalculated by multiplying the emission of each gas with their respective mole warming potential. This step wasfollowed by the addition of the three gases’ GWP to have the total GWP. The results showed that the emissions ofgreenhouse gases from peat soils changed seasonally and varied with the crops cultivated. Oil palm has resultedthe highest GWP, mostly contributed by N2O. There was no statistical different in total GWP of paddy andvegetable fields. The annual N2O emission from oil palm field was 4,582 g N ha-1 yr-1. Water, nutrients and organicmatter managements are among the potential techniques to minimize gas emissions from oil palm field which needfield trials.

  10. Effect of synthesis parameters on morphology of polyaniline (PANI) and field emission investigation of PANI nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Bankar, Prashant K.; More, Mahendra A., E-mail: mam@physics.unipune.ac.in [Center for Advanced Studies in Materials Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune-411007 (India); Patil, Sandip S. [Department of Physics, Modern College of Arts, Science and Commerce, Shivajinagar, Pune-411005. India (India)

    2015-06-24

    Polyaniline (PANI) nanostructures have been synthesized by simple chemical oxidation route at different monomer concentration along with variation in synthesis temperature. The effect of variation of synthesis parameters has been revealed using different characterization techniques. The structural and morphological characterization of the synthesized PANI nanostructures was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), whereas Fourier Transform Infrared spectroscopy (FTIR) has been used to reveal the chemical properties. With the variation in the synthesis temperature and monomer concentration, various morphologies characterized by formation of PANI nanoparticles, nanofibres, nanotubes and nanospheres, are revealed from the SEM analysis. The FTIR analysis reveals the formation of conducting state of PANI under prevailing experimental conditions. The field emission investigation of the conducting PANI nanotubes was performed in all metal UHV system at base pressure of 1x10{sup −8} mbar. The turn on field required to draw emission of 1 nA current was observed to be ∼ 2.2 V/μm and threshold field (corresponding to emission current density of 1 µA/cm2) was found to be 3.2 V/μm. The emission current was observed to be stable for more than three hours at a preset value 1 µA. The simple synthesis route and good field emission characteristics indicate potential of PANI nanofibres as a promising emitter for field emission based micro/nano devices.

  11. Effect of synthesis parameters on morphology of polyaniline (PANI) and field emission investigation of PANI nanotubes

    Science.gov (United States)

    Bankar, Prashant K.; Patil, Sandip S.; More, Mahendra A.

    2015-06-01

    Polyaniline (PANI) nanostructures have been synthesized by simple chemical oxidation route at different monomer concentration along with variation in synthesis temperature. The effect of variation of synthesis parameters has been revealed using different characterization techniques. The structural and morphological characterization of the synthesized PANI nanostructures was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), whereas Fourier Transform Infrared spectroscopy (FTIR) has been used to reveal the chemical properties. With the variation in the synthesis temperature and monomer concentration, various morphologies characterized by formation of PANI nanoparticles, nanofibres, nanotubes and nanospheres, are revealed from the SEM analysis. The FTIR analysis reveals the formation of conducting state of PANI under prevailing experimental conditions. The field emission investigation of the conducting PANI nanotubes was performed in all metal UHV system at base pressure of 1x10-8 mbar. The turn on field required to draw emission of 1 nA current was observed to be ˜ 2.2 V/μm and threshold field (corresponding to emission current density of 1 µA/cm2) was found to be 3.2 V/μm. The emission current was observed to be stable for more than three hours at a preset value 1 µA. The simple synthesis route and good field emission characteristics indicate potential of PANI nanofibres as a promising emitter for field emission based micro/nano devices.

  12. Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study.

    Science.gov (United States)

    Baken, Stijn; Regelink, Inge C; Comans, Rob N J; Smolders, Erik; Koopmans, Gerwin F

    2016-08-01

    Colloidal phosphorus (P) may represent an important fraction of the P in natural waters, but these colloids remain poorly characterized. In this work, we demonstrate the applicability of asymmetric flow field-flow fractionation (AF4) coupled to high resolution ICP-MS for the characterization of low concentrations of P-bearing colloids. Colloids from five streams draining catchments with contrasting properties were characterized by AF4-ICP-MS and by membrane filtration. All streams contain free humic substances (2-3 nm) and Fe-bearing colloids (3-1200 nm). Two soft water streams contain primary Fe oxyhydroxide-humic nanoparticles (3-6 nm) and aggregates thereof (up to 150 nm). In contrast, three harder water streams contain larger aggregates (40-1200 nm) which consist of diverse associations between Fe oxyhydroxides, humic substances, clay minerals, and possibly ferric phosphate minerals. Despite the diversity of colloids encountered in these contrasting streams, P is in most of the samples predominantly associated with Fe-bearing colloids (mostly Fe oxyhydroxides) at molar P:Fe ratios between 0.02 and 1.5. The molar P:Fe ratio of the waters explains the partitioning of P between colloids and truly dissolved species. Waters with a high P:Fe ratio predominantly contain truly dissolved species because the Fe-rich colloids are saturated with P, whereas waters with a low P:Fe ratio mostly contain colloidal P species. Overall, AF4-ICP-MS is a suitable technique to characterize the diverse P-binding colloids in natural waters. Such colloids may increase the mobility or decrease the bioavailability of P, and they therefore need to be considered when addressing the transport and environmental effects of P in catchments. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Electric field distribution and current emission in a miniaturized geometrical diode

    Science.gov (United States)

    Lin, Jinpu; Wong, Patrick Y.; Yang, Penglu; Lau, Y. Y.; Tang, W.; Zhang, Peng

    2017-06-01

    We study the electric field distribution and current emission in a miniaturized geometrical diode. Using Schwarz-Christoffel transformation, we calculate exactly the electric field inside a finite vacuum cathode-anode (A-K) gap with a single trapezoid protrusion on one of the electrode surfaces. It is found that there is a strong field enhancement on both electrodes near the protrusion, when the ratio of the A-K gap distance to the protrusion height d /h COMSOL simulations. We calculate the effective field enhancement factor for the field emission current, by integrating the local Fowler-Nordheim current density along the electrode surfaces. We systematically examine the electric field enhancement and the current rectification of the miniaturized geometrical diode for various geometric dimensions and applied electric fields.

  14. Emissions from prescribed burning of agricultural fields in the Pacific Northwest

    Science.gov (United States)

    Holder, A. L.; Gullett, B. K.; Urbanski, S. P.; Elleman, R.; O'Neill, S.; Tabor, D.; Mitchell, W.; Baker, K. R.

    2017-10-01

    Prescribed burns of winter wheat stubble and Kentucky bluegrass fields in northern Idaho and eastern Washington states (U.S.A.) were sampled using ground-, aerostat-, airplane-, and laboratory-based measurement platforms to determine emission factors, compare methods, and provide a current and comprehensive set of emissions data for air quality models, climate models, and emission inventories. Batch measurements of PM2.5, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated dibenzodioxins/dibenzofurans (PCDDs/PCDFs), and continuous measurements of black carbon (BC), particle mass by size, CO, CO2, CH4, and aerosol characteristics were taken at ground level, on an aerostat-lofted instrument package, and from an airplane. Biomass samples gathered from the field were burned in a laboratory combustion facility for comparison with these ground and aerial field measurements. Emission factors for PM2.5, organic carbon (OC), CH4, and CO measured in the field study platforms were typically higher than those measured in the laboratory combustion facility. Field data for Kentucky bluegrass suggest that biomass residue loading is directly proportional to the PM2.5 emission factor; no such relationship was found with the limited wheat data. CO2 and BC emissions were higher in laboratory burn tests than in the field, reflecting greater carbon oxidation and flaming combustion conditions. These distinctions between field and laboratory results can be explained by measurements of the modified combustion efficiency (MCE). Higher MCEs were recorded in the laboratory burns than from the airplane platform. These MCE/emission factor trends are supported by 1-2 min grab samples from the ground and aerostat platforms. Emission factors measured here are similar to other studies measuring comparable fuels, pollutants, and combustion conditions. The size distribution of refractory BC (rBC) was single modal with a log-normal shape, which was

  15. Improved field emission from indium decorated multi-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Sreekanth, M.; Ghosh, S., E-mail: santanu1@physics.iitd.ernet.in; Biswas, P.; Kumar, S.; Srivastava, P.

    2016-10-15

    Graphical abstract: Improved field emission properties have been achieved for Indium (In) decorated MWCNTs and are shown using the schematic of field emission set up with In/CNT cathode, and a plot of J-E characteristics for pristine and In decorated CNTs. - Highlights: • Field emission (FE) properties have been studied for the first time from Indium (In) decorated MWCNT films. • Observed increased density of states near the Fermi level for In decorated films. • Superior field emission properties have been achieved for In decorated CNT films. - Abstract: Multi-walled carbon nanotube (MWCNT) films were grown using thermal chemical vapor deposition (T-CVD) process and were decorated with indium metal particles by thermal evaporation technique. The In metal particles are found to get oxidized. The In decorated films show 250% enhancement in the FE current density, lower turn-on and threshold fields, and better temporal stability as compared to their undecorated counterpart. This improvement in field emission properties is primarily attributed to increased density of states near the Fermi level. The presence of O 2p states along with a small contribution from In 5s states results in the enhancement of density of states in the vicinity of the Fermi level.

  16. High performance field emission and Nottingham effect observed from carbon nanotube yarn

    Science.gov (United States)

    Choi, Young Chul; Kang, Jun-Tae; Park, Sora; Go, Eunsol; Jeon, Hyojin; Kim, Jae-Woo; Jeong, Jin-Woo; Park, Kyung-Ho; Song, Yoon-Ho

    2017-02-01

    Vertically aligned CNTs were synthesized on a four inch wafer, followed by the preparation of a CNT yarn. The yarn emitter was found to have an extremely high field enhancement factor, which was confirmed to have originated from multi-stage effect. In addition to superb field emission characteristics, the energy exchange during field emission, called Nottingham effect, was observed from the CNT yarn emitter. A CNT yarn was attached to the thermistor whose resistance depends on temperature. Then, the change of resistance was monitored during the field emission, which enabled us to calculate the energy exchange. It was found that the observed heating originated from both Nottingham and Joule heating. Nottingham heating was dominant at low current region while Joule heating became larger contribution at high current region. Very large Nottingham region of up to 33.35 mA was obtained, which is due presumably to the high performance field emission characteristics of a CNT yarn. This is believed to be an important observation for developing reliable field emission devices with suppressed Joule heating effect.

  17. Enhanced electron field emission from carbon nanotubes irradiated by energetic C ions.

    Science.gov (United States)

    Sun, Peng-Cheng; Deng, Jian-Hua; Cheng, Guo-An; Zheng, Rui-Ting; Ping, Zhao-Xia

    2012-08-01

    The field emission performance and structure of the vertically aligned multi-walled carbon nanotube arrays irradiated by energetic C ion with average energy of 40 keV have been investigated. During energetic C ion irradiation, the curves of emission current density versus the applied field of samples shift firstly to low applied fields when the irradiation doses are less than 9.6 x 10(16) cm(-2), and further increase of dose makes the curves reversing to a high applied field, which shows that high dose irradiation in carbon nanotube arrays makes their field emission performance worse. After energetic ion irradiation with a dose of 9.6 x 1016 cm(-2), the turn-on electric field and the threshold electric field of samples decreased from 0.80 and 1.13 V/microm to 0.67 and 0.98 V/microm respectively. Structural analysis of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy indicates that the amorphous carbon nanowire/carbon nanotube hetero nano-structures have been fabricated in the C ion irradiated carbon nanotubes. The enhancement of electron field emission is due to the formation of amorphous carbon nanowires at the tip of carbon nanotube arrays, which is an electron emitting material with low work function.

  18. Field emission from individual multiwalled carbon nanotubes prepared in an electron microscope

    NARCIS (Netherlands)

    de Jonge, N.; van Druten, N.J.

    2003-01-01

    Individual multiwalled carbon nanotube field emitters were prepared in a scanning electron microscope. The angular current density, energy spectra, and the emission stability of the field-emitted electrons were measured. An estimate of the electron source brightness was extracted from the

  19. Field-induced electron emission from nanoporous carbon of various types

    Directory of Open Access Journals (Sweden)

    Alexander V. Arkhipov

    2015-03-01

    Full Text Available The influence of fabrication technology on field electron emission properties of nanoporous carbon (NPC has been investigated. Samples of NPC derived from different carbides via chlorination at different temperatures demonstrated similar low-field emission ability with the threshold electric field strength of 2–3 V/μm. This property correlated with the presence of nanopores with the characteristic size of 0.5–1.2 nm determining high values of specific surface area (more than 800 m2/g of the material. In most cases, voltage–current characteristics of emission were approximately linear in Fowler–Nordheim (FN coordinates (excluding the low-current part near the emission threshold, but the plot slope angles were in notable disagreement with the known material morphology and electronic properties, and this could not be explained within the frames of FN emission theory. We suggest that the actual emission mechanism for NPC involves hot electrons generated at internal boundaries, and that emission centers may be associated with relatively large (20–100 nm onion-like particles observed in many microscopy images.

  20. [Effects of controlled release fertilizers on N2O emission from paddy field].

    Science.gov (United States)

    Li, Fangmin; Fan, Xiaolin; Liu, Fang; Wang, Qiang

    2004-11-01

    With close chamber method, this paper studied the effects of controlled release fertilizer (CRF), non-coated compound fertilizer (Com) and conventional urea (CK) on N2O emission from paddy field. The results showed that within 10 days after transplanting, the ammonium and nitrate concentrations in the surface water of the plot treated with CRF were significantly different from those treated with Com. The partial coefficient between N2O emission rates and corresponding nitrate concentrations in the water was significantly high (r = 0.6834). Compared with Com, CRF was able to reduce N2O emission from the paddy field. Within 100 days after basal application, the N2O emission rate of treatment CRF was only 13.45%-21.26% of Corn and 71.17%-112.47% of CK. The N2O emission of Com was mainly concentrated in 1-25 d after basal fertilization and mid-aeration period, but that of CRF was remarkably lower during same period, while the peak of N2O emission of CK was postponed and reduced. It was concluded that both one-time fertilization of CRF and several-time fertilizations of conventional urea were able to reduce N2O emission from the paddy field.

  1. Study of Thermal-Field Emission Properties and Investigation of Temperature dependent Noise in the Emission Current form vertical Carbon nanotube emitters

    KAUST Repository

    Kolekar, Sadhu

    2017-05-05

    We have investigated temperature dependent field electron emission characteristics of vertical carbon nanotubes (CNTs). The generalized expression for electron emission from well defined cathode surface is given by Millikan and Lauritsen [1] for the combination of temperature and electric field effect. The same expression has been used to explain the electron emission characteristics from vertical CNT emitters. Furthermore, this has been applied to explain the electron emission for different temperatures ranging from room temperature to 1500 K. The real-time field electron emission images at room temperature and 1500 K are recorded by using Charge Coupled Device (CCD), in order to understand the effect of temperature on electron emission spots in image morphology (as indicated by ring like structures) and electron emission spot intensity of the emitters. Moreover, the field electron emission images can be used to calculate the total number of emitters per cm2 for electron emission. The calculated number of emitters per cm2 is 4.5x107 and, the actual number emitters per cm2 present for electron emission calculated from Atomic Force Microscopy (AFM) data is 1.2x1012. The measured Current-Voltage (I-V) characteristics obey the Folwer-Nordheim (F-N) type behavior. The fluctuations in the emission current are recorded at different temperatures and, temperature dependence of power spectral density obeys power law relation s(f)=I2/f2 with that of emission current and frequency.

  2. Field electron emission from hydrogen plasma treated nano-ZnO thin films.

    Science.gov (United States)

    Wang, Xiao-Ping; Liu, Xin-Xin; Wang, Li-Jun; Li, Huai-Hui; Mei, Cui-Yu; Liu, Xiao-Fei; Can, Yang

    2012-08-01

    A nano-Zno films are deposited on the Mo film/ceramic substrates by using the electron beam vapor deposition technique. Then a hydrogen plasma treated method is used to improve the characteristics of ZnO thin films by microwave plasma chemical vapor deposition system. Effects of process parameters on morphologies and structures of the ZnO thin films are detected and analysed by field emission scanning electron microscopy, X-ray diffraction spectrum and energy dispersive spectrum. The experimental result indicates that the hydrogen plasma treated techniques can essentially reduce the surface resistance and improve the field emission current density of the nano-ZnO thin films. For the hydrogen plasma treated sample, its field emission current density can increased more than three times at 2.2 V/microm electric field condition.

  3. [Effects of winter cover crop on methane and nitrous oxide emission from paddy field].

    Science.gov (United States)

    Tang, Hai-ming; Tang, Wen-guang; Shuai, Xi-qiang; Yang, Guang-li; Tang, Hai-tao; Xiao, Xiao-Ping

    2010-12-01

    Static chamber-GC technique was employed to study the effects of different treatment winter cover crops, including no-tillage and directly sowing ryegrass (T1), no-tillage and directly sowing Chinese milk vetch (T2), tillage and transplanting rape (T3), no-tillage and directly sowing rape (T4), and fallowing (CK), on the CH4 and N2O emission from double cropping rice paddy field. During the growth period of test winter cover crops, the CH4 and N2O emission in treatments T1-T4 was significantly higher than that in CK (P cover crops returned to field, the CH4 emission from early and late rice fields in treatments T1, T2, T3, and T4 was larger than that in CK. In early rice field, treatments T1 and T2 had the largest CH4 emission (21.70 and 20.75 g x m(-2)); while in late rice field, treatments T3 and T4 had the largest one (58.90 and 54.51 g x m(-2) respectively). Treatments T1-T4 also had larger N2O emission from early and late rice fields than the CK did. The N2O emission from early rice field in treatments T1, T2, T3, and T4 was increased by 53.7%, 12.2%, 46.3%, and 29.3%, and that from late rice field in corresponding treatments was increased by 28.6%, 3.8%, 34.3%, and 27.6%, respectively, compared with CK.

  4. Light Emission from Carbon Nanotube Field Effect Transistors

    Science.gov (United States)

    Misewich, James

    2004-03-01

    Since their discovery in 1991, research in carbon nanotubes has grown rapidly. Part of this interest is driven by the remarkable electrical and mechanical properties demonstrated by carbon nanotubes which could have significant technological impact (1,2). Recent progress has included demonstrations of interesting opto-electronic properties of carbon nanotubes. In one experiment we have shown that single carbon nanotubes can be a source of infrared optical emission (3). We have also shown how a single carbon nanotube can be used as a photoconductive detector (4). In this talk, we will examine the opto-electronic properties of individual single wall carbon nanotubes. (1) M.S. Dresselhaus, G. Dresselhaus, and Ph. Avouris (eds.), "Carbon Nanotubes", Topics Appl. Phys. 80, (2001). (2) Ph. Avouris, Acct. Chem. Res. 35, 1026 (2002). (3) J.A. Misewich, R. Martel, Ph. Avouris, J. Tsang, S. Heinze, and J. Tersoff, Science 300, 783 (2003). (4) M. Freitag, Y. Martin, J.A. Misewich, R. Martel, and Ph. Avouris, Nanoletters 3, 1067 (2003).

  5. Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?

    Directory of Open Access Journals (Sweden)

    J. Sintermann

    2012-05-01

    Full Text Available The EMEP/EEA guidebook 2009 for agricultural emission inventories reports an average ammonia (NH3 emission factor (EF by volatilisation of 55% of the applied total ammoniacal nitrogen (TAN content for cattle slurry, and 35% losses for pig slurry, irrespective of the type of surface or slurry characteristics such as dry matter content and pH. In this review article, we compiled over 350 measurements of EFs published between 1991 and 2011. The standard slurry application technique during the early years of this period, when a large number of measurements were made, was spreading by splash plate, and as a result reference EFs given in many European inventories are predominantly based on this technique. However, slurry application practices have evolved since then, while there has also been a shift in measurement techniques and investigated plot sizes. We therefore classified the available measurements according to the flux measurement technique or measurement plot size and year of measurement. Medium size plots (usually circles between 20 to 50 m radius generally yielded the highest EFs. The most commonly used measurement setups at this scale were based on the Integrated Horizontal Flux method (IHF or the ZINST method (a simplified IHF method. Several empirical models were published in the years 1993 to 2003 predicting NH3 EFs as a function of meteorology and slurry characteristics (Menzi et al., 1998; Søgaard et al., 2002. More recent measurements show substantially lower EFs which calls for new measurement series in order to validate the various measurement approaches against each other and to derive revised inputs for inclusion into emission inventories.

  6. Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

    Directory of Open Access Journals (Sweden)

    Meng Song

    2015-09-01

    Full Text Available Integrating carbon nanotubes (CNTs and graphene into hybrid structures provides a novel approach to three dimensional (3D materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm2, and field enhancement factor of ∼1.3 × 104. The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport.

  7. Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

    Science.gov (United States)

    Song, Meng; Xu, Peng; Song, Yenan; Wang, Xu; Li, Zhenhua; Shang, Xuefu; Wu, Huizhen; Zhao, Pei; Wang, Miao

    2015-09-01

    Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm2, and field enhancement factor of ˜1.3 × 104. The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport.

  8. Influence of ZnO nanowire array morphology on field emission characteristics.

    Science.gov (United States)

    Garry, S; McCarthy, É; Mosnier, J-P; McGlynn, E

    2014-04-04

    In this work the growth and field emission properties of vertically aligned and spatially ordered and unordered ZnO nanowires are studied. Spatially ordered nanowire arrays of controlled array density are synthesized by both chemical bath deposition and vapour phase transport using an inverse nanosphere lithography technique, while spatially unordered arrays are synthesized by vapour phase transport without lithography. The field emission characteristics of arrays with 0.5, 1.0, and 1.5 μm inter-wire distances, as well as unordered arrays, are examined, revealing that, within the range of values examined, field emission properties are mainly determined by variations in nanowire height, and show no correlation with nanowire array density. Related to this, we find that a significant variation in nanowire height in an array also leads to a reduction in catastrophic damage observed on samples during field emission because arrays with highly uniform heights are found to suffer significant arcing damage. We discuss these results in light of recent computational studies of comparable nanostructure arrays and find strong qualitative agreement between our results and the computational predictions. Hence the results presented in this work should be useful in informing the design of ZnO nanowire arrays in order to optimize their field emission characteristics generally.

  9. GHG emissions from slurry and digestates during storage and after field application

    DEFF Research Database (Denmark)

    Baral, Khagendra Raj; Nguyen, Quan Van; Petersen, Søren O.

    , but environmental impacts, such as greenhouse gas (GHG) emissions, during storage and after field application should take into account. Mainly, methane (CH4) is produced during storage and nitrous oxide (N2O) after field application. Currently, direct (CH4, N2O) and indirect (NH3) GHG emissions during storage...... are determined in a pilot-scale study with digested materials from Maabjerg Bioenergy and Fredericia Wastewater Treatment Facility, using untreated cattle and pig slurry as reference. These and other results will be used to model the effect of temperature and pre-treatment on CH4 emissions. The composition...... of volatile solids (VS) is critical for predicting GHG emissions and the effect of biogas treatment. Volatile solids may be considered to have an easily degradable VS (VSd) and a slowly degradable VS (VSnd) fraction. A new approach to estimate VSd was investigated using the short-term evolution of CO2-C from...

  10. Vacuum Ultraviolet Field Emission Lamp Consisting of Neodymium Ion Doped Lutetium Fluoride Thin Film as Phosphor

    Directory of Open Access Journals (Sweden)

    Masahiro Yanagihara

    2014-01-01

    Full Text Available A vacuum ultraviolet (VUV field emission lamp was developed by using a neodymium ion doped lutetium fluoride (Nd3+ : LuF3 thin film as solid-state phosphor and carbon nanofiber field electron emitters. The thin film was synthesized by pulsed laser deposition and incorporated into the lamp. The cathodoluminescence spectra of the lamp showed multiple emission peaks at 180, 225, and 255 nm. These emission spectra were in good agreement with the spectra reported for the Nd3+ : LuF3 crystal. Moreover, application of an acceleration voltage effectively increased the emission intensity. These results contribute to the performance enhancement of the lamp operating in the VUV region.

  11. Low Emittance Gun Project based on Field Emission

    CERN Document Server

    Ganter, Romain; Dehler, M; Gobrecht, Jens; Gough, Chris; Ingold, Gerhard; Leemann, Simon C; Shing-Bruce-Li, Kevin; Paraliev, Martin; Pedrozzi, Marco; Raguin, Jean Yves; Rivkin, Leonid; Schlott, Volker; Sehr, Harald; Streun, Andreas; Wrulich, Albin F; Zelenika, Sasa

    2004-01-01

    The design of an electron gun capable of producing beam emittance one order of magnitude lower than current technology would reduce considerably the cost and size of a free electron laser emitting at 0.1nm. Field emitter arrays (FEAs) including a gate and a focusing layer are an attractive technology for such high brightness sources. Electrons are extracted from micrometric tips thanks to voltage pulses between gate and tips. The focusing layer should then reduce the initial divergence of each emitted beamlets. This FEA will be inserted in a high gradient diode configuration coupled with a radiofrequency structure. In the diode part very high electric field pulses (several hundreds of MV/m) will limit the degradation of emittance due to space charge effect. This first acceleration will be obtained with high voltage pulses (typically a megavolt in a few hundred of nanoseconds) synchronized with the low voltage pulses applied to the FEA (typically one hundred of volts in one nanosecond at frequency below kilohe...

  12. Nanometer-scale discernment of field emission from tungsten surface with single carbon monoxide molecule

    Science.gov (United States)

    Matsunaga, Soichiro; Suwa, Yuji; Katagiri, Souichi

    2017-12-01

    Unusual quantized beam fluctuations were found in the emission current from a cold-field emitter (CFE) operating in an extremely high vacuum of 10-10 Pa. To clarify the microscopic mechanism behind these fluctuations, we developed a new calculation method to evaluate the field emission from a heterogeneous surface under a strong electric field of 4 × 109 V/m by using the local potential distribution obtained by a first-principles calculation, instead of by using the work function. As a result of the first-principles calculations of a single molecule adsorbed on a tungsten surface, we found that dissociative adsorption of a carbon monoxide (CO) molecule enhances the emission current by changing the potential barrier in the area surrounding the C and O adatoms when these two atoms are placed at their most stable positions. It is also found that the migration of the O atom from the most stable position reduces the emission current. These types of enhancement and reduction of the emission current quantitatively explain the observed quantized fluctuations of the CFE emission current.

  13. Characteristics of Greenhouse Gas Emissions from the Wheat Fields with Different Returning Methods of Maize Straws

    Directory of Open Access Journals (Sweden)

    LI Xin-hua

    2016-03-01

    Full Text Available In order to investigate the effect of different returning methods of maize straw on the greenhouse gas emissions from the wheat fields, we explored the greenhouse gas CO2, N2O and CH4 emissions from the wheat fields using static chamber-gas chromatograph technique from December 2013 to May 2014. The experiments set four treatments including no maize straw returning(CK, direct maize straw returning directly(CS, maize straw-rumen-cattle dung returning(CGS and maize straw-mushroom residue returning(CMS, and the four treatments were investigated under the same watering and fertilizing conditions. The results showed that the greenhouse gas emissions from the wheat fields all had distinct seasonal variations and the cumulative emissions of greenhouse gas emissions were different. During the maize growing season, the cumulative emissions of both CO2 and N2O were emitted and in the order of CK >CGS >CS >CMS while the cumulative absorptions of CH4 were in the order of CS >CGS >CK >CMS with the significant difference between different treatments(PCGS >CK >CMS under the different returning methods of maize straw, which indicated that direct straw returning could significantly increase the global warming potential of greenhouse gases from the wheat field, followed by CGS while the straw-mushroom residue returning(CMS could decrease the global warming potential of greenhouse gases from the wheat field. The method of straw-mushroom residue returning should be recommended from the viewpoint of reducing GWP of the greenhouse gas. In all, our study could provide the scientific foundation for the efficiency straw recycle and reducing greenhouse gas emission.

  14. STATISTICS OF OCCURRENCE OF PRE-SEISMIC ANOMALIES IN GEOACOUSTIC EMISSION AND IN ATMOSPHERIC FIELD

    Directory of Open Access Journals (Sweden)

    M. A. Mishchenko

    2016-11-01

    Full Text Available Statistics of occurrence of anomalous disturbances in high-frequency geoacoutic emis-sion of the near surface sedimentary rocks and in atmospheric electric field by the ground surface before earthquakes is presented. Long-term continuous series of measure-ments of geoacoustic emission for the period of 2003-2012 at «Mikizha» site and the data of measurements of atmospheric electric field obtained for the summer-autumn periods of 2006-2008 at «Mikizha» site and for 2009-2012 at «Karymshina» site were used in the analysis. Anomalous disturbances of the emission and of the field were compared with the earthquake catalogue of Kamchatka Branch of Geophysical Service RAS.

  15. Nanocrystalline silicon as the light emitting material of a field emission display device.

    Science.gov (United States)

    Biaggi-Labiosa, A; Solá, F; Resto, O; Fonseca, L F; González-Berríos, A; De Jesús, J; Morell, G

    2008-06-04

    A nanocrystalline Si-based paste was successfully tested as the light emitting material in a field emission display test device that employed a film of carbon nanofibers as the electron source. Stable emission in the 550-850 nm range was obtained at 16 V µm(-1). This relatively low field required for intense cathodoluminescence (CL) from the PSi paste may lead to longer term reliability of both the electron emitting and the light emitting materials, and to lower power consumption. Here we describe the synthesis, characterization, and analyses of the light emitting nanostructured Si paste and the electron emitting C nanofibers used for building the device, including x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The corresponding spectra and field emission curves are also shown and discussed.

  16. Structural origination of charge transfer complex nanostructures: Excellent candidate for field emission

    Energy Technology Data Exchange (ETDEWEB)

    Pal, Shreyasi; Chattopadhyay, Kalyan Kumar [Thin Films and Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700032 (India)

    2016-05-23

    Worldwide strategies for amalgamating rationally controlled one-dimensional organic nanowires are of fundamental importance for their applications in flexible, cheaper and lighter electronics. In this work we have fabricated large-area, ordered CuTCNQ (copper-7,7,8,8-tetracyanoquinodimethane) nano architecture arrays over flexible conducting substrate and discussed the rational growth and integration of nanostructures. Here we adopted the organic solid phase reaction (VLS) technique for the growth of organic hierarchies and investigated how field emission properties changes by tuning the nanostructures morphology i.e., by varying length, diameter, alignment and orientation over flexible substrate. The CuTCNQ nanowires with optimized geometry exhibit excellent high field emission performance with low turn-on and threshold field values. The result strongly indicate that CuTCNQ nanowires on flexible carbon cloth substrate are promising candidates for constructing cold cathode based emission display devices, vacuum nanoelectronics, and etc.

  17. Ammonia emissions from a grazed field estimated by miniDOAS measurements and inverse dispersion modelling

    Science.gov (United States)

    Bell, Michael; Flechard, Chris; Fauvel, Yannick; Häni, Christoph; Sintermann, Jörg; Jocher, Markus; Menzi, Harald; Hensen, Arjan; Neftel, Albrecht

    2017-05-01

    Ammonia (NH3) fluxes were estimated from a field being grazed by dairy cattle during spring by applying a backward Lagrangian stochastic model (bLS) model combined with horizontal concentration gradients measured across the field. Continuous concentration measurements at field boundaries were made by open-path miniDOAS (differential optical absorption spectroscopy) instruments while the cattle were present and for 6 subsequent days. The deposition of emitted NH3 to clean patches on the field was also simulated, allowing both net and gross emission estimates, where the dry deposition velocity (vd) was predicted by a canopy resistance (Rc) model developed from local NH3 flux and meteorological measurements. Estimated emissions peaked during grazing and decreased after the cattle had left the field, while control on emissions was observed from covariance with temperature, wind speed and humidity and wetness measurements made on the field, revealing a diurnal emission profile. Large concentration differences were observed between downwind receptors, due to spatially heterogeneous emission patterns. This was likely caused by uneven cattle distribution and a low grazing density, where hotspots of emissions would arise as the cattle grouped in certain areas, such as around the water trough. The spatial complexity was accounted for by separating the model source area into sub-sections and optimising individual source area coefficients to measured concentrations. The background concentration was the greatest source of uncertainty, and based on a sensitivity/uncertainty analysis the overall uncertainty associated with derived emission factors from this study is at least 30-40 %.Emission factors can be expressed as 6 ± 2 g NH3 cow-1 day-1, or 9 ± 3 % of excreted urine-N emitted as NH3, when deposition is not simulated and 7 ± 2 g NH3 cow-1 day-1, or 10 ± 3 % of excreted urine-N emitted as NH3, when deposition is included in the gross emission model. The results suggest

  18. Field emission studies of CNTs/ZnO nanostructured thin films for display devices

    Science.gov (United States)

    Alvi, M. A.; Al-Ghamdi, A. A.; Husain, M.

    2017-09-01

    Zinc oxide (ZnO) nanoparticles were coated on the surface of multi walled carbon nanotubes (MWCNTs) to improve the field emission characteristic of MWCNTs. The synthesis of MWCNTs was made by chemical vapor deposition (CVD). RF sputtering was used to prepare MWCNTs/ZnO nanocomposite. The as-prepared nanocomposites were identified by electron microscopes (transmission and scanning), Raman spectroscopy and X-Ray diffractometer (HRXRD) to establish the linking of ZnO nanoparticles on MWCNTs. The field emission studies of MWCNTs/ZnO nanocomposites show that the current density is increased remarkably. After attachment of ZnO nanoparticles, it is observed that the turn-on field of MWCNTs decreases. These results have been shown in terms of enhanced current density and field enhancement factor after surface modification of MWCNTs field emitters.

  19. Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes

    Science.gov (United States)

    Li, Xin; Zhou, Wei-Man; Liu, Wei-Hua; Wang, Xiao-Li

    2015-05-01

    Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the Penn-Plummer method. The ZnO NPs reconstruct the ZnO-CNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. Project supported by the National Natural Science Foundation of China (Grant Nos. 91123018, 61172040, and 61172041) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7277).

  20. Enhancement in field emission characteristics of multifunctional ZnO/C hybrid nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, Subhranshu [Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711 103 (India); Basu Mallick, A., E-mail: abasumallick@metal.becs.ac.in [Department of Metallurgy and Materials Engineering, Bengal Engineering and Science University, Shibpur, Howrah 711 103 (India)

    2012-08-15

    Multifunctional hybrid nanostructures have recently drawn immense attention due to their interesting physical and chemical properties and also due to their potential for applications in novel electronic devices. Herein, we report the luminescence and enhancement of field emission (FE) properties of multifunctional ZnO/C hybrid nanostructures prepared by the decomposition of zinc acetate and dextrose inside the nanopores of anodic aluminium oxide templates, which are fabricated by controlled electrochemical anodization of pure aluminium. Microscopic investigations show that the average pore diameter of the as prepared templates is {approx}50 nm and ZnO/C hybrid nanostructures are formed around the inner pore walls. The template, containing the ZnO/C hybrids, exhibits visible light emission in blue wavelength region along with luminescence in the ultra-violet region. Investigations on the field emission property of the hybrid ZnO/C nanostructures reveals, that they are better and more efficient field emission material compared to one dimensional ZnO nanostructures. -- Highlights: Black-Right-Pointing-Pointer Nanoporous alumina templates are prepared by two stage electrochemical anodization. Black-Right-Pointing-Pointer ZnO/C hybrids are synthesized inside the nanopores of the alumina template. Black-Right-Pointing-Pointer ZnO/C hybrid nanostructures show enhanced luminescent and field emission property.

  1. Circularly polarized vacuum field in three-dimensional chiral photonic crystals probed by quantum dot emission

    Science.gov (United States)

    Takahashi, S.; Ota, Y.; Tajiri, T.; Tatebayashi, J.; Iwamoto, S.; Arakawa, Y.

    2017-11-01

    The modification of a circularly polarized vacuum field in three-dimensional chiral photonic crystals was measured by spontaneous emission from quantum dots in the structures. Due to the circularly polarized eigenmodes along the helical axis in the GaAs-based mirror-asymmetric structures we studied, we observed highly circularly polarized emission from the quantum dots. Both spectroscopic and time-resolved measurements confirmed that the obtained circularly polarized light was influenced by a large difference in the photonic density of states between the orthogonal components of the circular polarization in the vacuum field.

  2. Forced vibration of a carbon nanotube with emission currents in an electromagnetic field

    Science.gov (United States)

    Bulyarskiy, S. V.; Dudin, A. A.; Orlov, A. P.; Pavlov, A. A.; Leont'ev, V. L.

    2017-11-01

    The occurrence of vibrations in a single carbon nanotubes placed in an electromagnetic field through which constant field-emission current passes has been analyzed. It has been shown experimentally that the emission current, along with the constant component, has a variable one that resonates at a certain frequency. Calculations show a relationship between the resonance frequency and the parameters of the whole system and nanotube itself. The conditions under which resonance may occur in the terahertz range of vibration frequencies have been analyzed.

  3. Synthesis and Field Emission Properties of Hierarchical ZnO Nanostructures

    Directory of Open Access Journals (Sweden)

    Deyan Peng

    2010-01-01

    Full Text Available Three novel kinds of hierarchical ZnO nanostructures: nanocombs nanoscrewdrivers and nanonails, have been synthesized in large quantities via a simple thermal evaporation process in the same run of growth in different regions of the quartz tube. The morphologies could be well controlled by adjusting the distances between the source materials and the substrates. These ZnO products were investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The field emission properties of the ZnO nanostructures were investigated. These hierarchical ZnO nanostructures may be attractive building blocks for field emission microelectronic devices and other devices.

  4. A carbon nanotube field emission cathode with high current density and long-term stability

    Energy Technology Data Exchange (ETDEWEB)

    Calderon-Colon, Xiomara; Zhou, Otto [Curriculum in Applied Science and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Geng Huaizhi; Gao Bo [Xintek, Incorporated, 7020 Kit Creek Road, Research Triangle Park, NC (United States); An Lei; Cao Guohua [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States)

    2009-08-12

    Carbon nanotube (CNT) field emitters are now being evaluated for a wide range of vacuum electronic applications. However, problems including short lifetime at high current density, instability under high voltage, poor emission uniformity, and pixel-to-pixel inconsistency are still major obstacles for device applications. We developed an electrophoretic process to fabricate composite CNT films with controlled nanotube orientation and surface density, and enhanced adhesion. The cathodes have significantly enhanced macroscopic field emission current density and long-term stability under high operating voltages. The application of this CNT electron source for high-resolution x-ray imaging is demonstrated.

  5. Estimation of methane and nitrous oxide emissions from rice field with rice straw management in Cambodia.

    Science.gov (United States)

    Vibol, S; Towprayoon, S

    2010-02-01

    To estimate the greenhouse gas emissions from paddy fields of Cambodia, the methodology of the Intergovernmental Panel on Climate Change (IPCC) guidelines, IPCC coefficients, and emission factors from the experiment in Thailand and another country were used. Total area under rice cultivation during the years 2005-2006 was 2,048,360 ha in the first crop season and 298,529 ha in the second crop season. The emission of methane from stubble incorporation with manure plus fertilizer application areas in the first crop season was estimated to be 192,783.74 ton higher than stubble with manure, stubble with fertilizer, and stubble without fertilizer areas. The fields with stubble burning emitted the highest emission of methane (75,771.29 ton) followed by stubble burning with manure (22,251.08 ton), stubble burning with fertilizer (13,213.27 ton), and stubble burning with fertilizer application areas (3,222.22 ton). The total emission of methane from rice field in Cambodia for the years 2005-2006 was approximately 342,649.26 ton (342.65 Gg) in the first crop season and 36,838.88 ton (36.84 Gg) in the second crop season. During the first crop season in the years 2005-2006, Battambang province emitted the highest amount of CH(4) (38,764.48 ton) and, in the second crop season during the years 2005-2006, the highest emission (8,262.34 ton) was found in Takeo province (8,262.34 ton). Nitrous oxide emission was between 2.70 and 1,047.92 ton in the first crop season and it ranged from 0 to 244.90 ton in the second crop season. Total nitrous oxide emission from paddy rice field was estimated to be 9,026.28 ton in the first crop season and 1,091.93 ton in the second crop season. Larger area under cultivation is responsible for higher emission of methane and nitrous oxide. Total emission of nitrous oxide by using IPCC default emission coefficient was approximately 2,328.85 ton. The total global warming potential of Cambodian paddy rice soil is 11,723,217.03 ton (11,723 Gg

  6. Effect of inorganic fertilizers (N, P, K) on methane emission from tropical rice field of India

    Science.gov (United States)

    Datta, A.; Santra, S. C.; Adhya, T. K.

    2013-02-01

    In the tropical experimental rice field of Central Rice Research Institute, Odisha, India, an experiment was conducted during the dry season (January-April) and wet season (July-November) of rice cultivation to study the effect of nitrogen (N), phosphorus (P) and potassium (K) fertilizer application on grain yield and methane (CH4) emission. The experiment was carried out with five treatments (No fertilizer (control), N-fertilizer, P-fertilizer, K-fertilizer and N + P + K fertilizer) with three replicates of each under a completely randomized block design. Significantly higher CH4 emission was recorded from all plots during wet season. Among fertilizer applied plots, significantly higher CH4 emission was recorded from N-fertilizer applied plots (dry season: 80.27 kg ha-1; wet season: 451.27 kg ha-1), while significantly lower CH4 emission was recorded from N + P + K applied plots (dry season: 34.60 kg ha-1; wet season: 233.66 kg ha-1). Low cumulative CH4 emission to grain yield ratio was recorded from N + P + K applied plots during both seasons (83.57 kg Mg-1 grain yield during dry season and 77.14 kg Mg-1 grain yield during wet season). CH4 emission from different treatment was positively correlated with microbial biomass carbon (r = 0.516), readily mineralizable carbon (r = 0.621) and sugar (r = 0.340) content of the soil. Negative CH4 emission was recorded during the fallow period which may be attributed to higher methanotrophic bacterial population. Study suggests that the effects of P and K-fertilizer on CH4 emission from rice field along with the CH4 emission during the fallow period need to be considered to reduce the uncertainty in upscaling process.

  7. A model to relate wind tunnel measurements to open field odorant emissions from liquid area sources

    Science.gov (United States)

    Lucernoni, F.; Capelli, L.; Busini, V.; Sironi, S.

    2017-05-01

    Waste Water Treatment Plants are known to have significant emissions of several pollutants and odorants causing nuisance to the near-living population. One of the purposes of the present work is to study a suitable model to evaluate odour emissions from liquid passive area sources. First, the models describing volatilization under a forced convection regime inside a wind tunnel device, which is the sampling device that typically used for sampling on liquid area sources, were investigated. In order to relate the fluid dynamic conditions inside the hood to the open field and inside the hood a thorough study of the models capable of describing the volatilization phenomena of the odorous compounds from liquid pools was performed and several different models were evaluated for the open field emission. By means of experimental tests involving pure liquid acetone and pure liquid butanone, it was verified that the model more suitable to describe precisely the volatilization inside the sampling hood is the model for the emission from a single flat plate in forced convection and laminar regime, with a fluid dynamic boundary layer fully developed and a mass transfer boundary layer not fully developed. The proportionality coefficient for the model was re-evaluated in order to account for the specific characteristics of the adopted wind tunnel device, and then the model was related with the selected model for the open field thereby computing the wind speed at 10 m that would cause the same emission that is estimated from the wind tunnel measurement furthermore, the field of application of the proposed model was clearly defined for the considered models during the project, discussing the two different kinds of compounds commonly found in emissive liquid pools or liquid spills, i.e. gas phase controlled and liquid phase controlled compounds. Lastly, a discussion is presented comparing the presented approach for emission rates recalculation in the field, with other approaches

  8. The improvement of the field emission properties from graphene films: Ti transition layer and annealing process

    Directory of Open Access Journals (Sweden)

    Jun Li

    2012-06-01

    Full Text Available Chemical-reduced graphene oxide (rGO films were deposited on titanium (Ti-coated silicon substrates by a simple electrophoretic deposition. The rGO films were annealed under argon atmosphere at different temperatures. The morphology and microstructure of the rGO films before and after annealing were characterized using scanning electron microscope, X-ray diffraction and Raman spectroscope. The field emission behaviors from these rGO films were investigated. The results show that, Ti-based transition layer can improve the stability of field emission from the rGO film, and the annealing at appropriate temperature is in favor of the field emission. Particularly, the rGO film displays an unexpected vacuum breakdown phenomenon at a relatively high current density. In addition, it is found that the field emission property of the rGO film is dependent on anode-sample distance and the film exhibits lower turn on field at larger anode-sample distance.

  9. Mitigating nitrous oxide emissions from tea field soil using bioaugmentation with a Trichoderma viride biofertilizer.

    Science.gov (United States)

    Xu, Shengjun; Fu, Xiaoqing; Ma, Shuanglong; Bai, Zhihui; Xiao, Runlin; Li, Yong; Zhuang, Guoqiang

    2014-01-01

    Land-use conversion from woodlands to tea fields in subtropical areas of central China leads to increased nitrous oxide (N2O) emissions, partly due to increased nitrogen fertilizer use. A field investigation of N2O using a static closed chamber-gas chromatography revealed that the average N2O fluxes in tea fields with 225 kg N ha(-1) yr(-1) fertilizer application were 9.4 ± 6.2 times higher than those of woodlands. Accordingly, it is urgent to develop practices for mitigating N2O emissions from tea fields. By liquid-state fermentation of sweet potato starch wastewater and solid-state fermentation of paddy straw with application of Trichoderma viride, we provided the tea plantation with biofertilizer containing 2.4 t C ha(-1) and 58.7 kg N ha(-1). Compared to use of synthetic N fertilizer, use of biofertilizer at 225 kg N ha(-1) yr(-1) significantly reduced N2O emissions by 33.3%-71.8% and increased the tea yield by 16.2%-62.2%. Therefore, the process of bioconversion/bioaugmentation tested in this study was found to be a cost-effective and feasible approach to reducing N2O emissions and can be considered the best management practice for tea fields.

  10. Mitigating Nitrous Oxide Emissions from Tea Field Soil Using Bioaugmentation with a Trichoderma viride Biofertilizer

    Directory of Open Access Journals (Sweden)

    Shengjun Xu

    2014-01-01

    Full Text Available Land-use conversion from woodlands to tea fields in subtropical areas of central China leads to increased nitrous oxide (N2O emissions, partly due to increased nitrogen fertilizer use. A field investigation of N2O using a static closed chamber-gas chromatography revealed that the average N2O fluxes in tea fields with 225 kg N ha−1 yr−1 fertilizer application were 9.4 ± 6.2 times higher than those of woodlands. Accordingly, it is urgent to develop practices for mitigating N2O emissions from tea fields. By liquid-state fermentation of sweet potato starch wastewater and solid-state fermentation of paddy straw with application of Trichoderma viride, we provided the tea plantation with biofertilizer containing 2.4 t C ha−1 and 58.7 kg N ha−1. Compared to use of synthetic N fertilizer, use of biofertilizer at 225 kg N ha−1 yr−1 significantly reduced N2O emissions by 33.3%–71.8% and increased the tea yield by 16.2%–62.2%. Therefore, the process of bioconversion/bioaugmentation tested in this study was found to be a cost-effective and feasible approach to reducing N2O emissions and can be considered the best management practice for tea fields.

  11. Effects of organic matter application on methane emission from paddy fields adopting organic farming system

    Directory of Open Access Journals (Sweden)

    P Nungkat

    2015-01-01

    Full Text Available A study that was aimed to determine the effect of the use of organic manure and azolla on methane emission on paddy field of organic systems was conducted on paddy fields in the Gempol Village, Sambirejo District of Sragen Regency, Indonesia. The experimental design performed for this study was a completely randomized block design consisting of three factors; the factor I was rice cultivars (Mira-1; Mentik Wangi; Merah Putih; factor II was dose of organic manure (0 t/ha and 10 t/ha and factor III was Azolla inoculums dose (0 t/ha and 2 t/ha. Gas sampling was conducted 3 times in one growing season when the rice plants reached ages of 38, 66 and 90 days after planting. The results showed that there was no correlation between the uses of organic fertilizers for rice production on methane emission. The increase of methane emission was very much influenced by the redox potential. Methane emission from Mira-1 field was higher than that from Mentik Wangi and Merah Putih fields. Emission of methane gas from Mira-1 field ranged from -509.82 to 791.34 kg CH4/ha; that from Wangi ranged from -756.77 to d 547.50 kg CH4/ha and that from Merah Putih ranged from -399.63 to 459.94 kg CH4/ha. Application of 10 t organic manure /ha and 2 t azolla/ha in Mentik Wangi reduced methane emissions with a high rice production compared to Merah Putih and Mira-1.

  12. Synthesis, characterization and field emission properties of rare-earth hexaboride nanowires

    Science.gov (United States)

    Zhang, Han

    Rare-earth hexaborides are a family of compounds which have low work function, high melting point, and high mechanical strength. These properties are highly suitable for electron field emission applications. To explore this possibility, we developed a chemical vapor deposition method and produced three different types of 1D nano-structures, which include single crystalline nanowires of LaB6, CeB6, and GdB6; polycrystalline nanowires of YB12, LaB12, MgO, and Mg3N 2; core-shell nanocables of MgB2-in-MgO and LaB6-in-CNT. TEM, SEM, EELS and EDX techniques were applied to characterize structural and chemical information about the synthesized nano-structures. Vapor-solid growth, catalyst-assisted vapor-liquid-solid growth and CNT-assisted template growth are proposed to be accounted for the formation mechanisms of these 1D nano-structures and the theoretical predictions match the experimental observations quantitatively. To fabricate a single nanowire field emitter, direct contact, electron beam lithography and focused ion beam welding techniques were used to attach a single LaB6 nanowire to the tip of a tungsten wire. Cold field emission properties were measured from such made single nanowire emitters. Work function values of 2.6 eV and 1.5 eV were obtained from a LaB 6 nanowire emitter and GdB6 nanowire emitter respectively. An Emission Current density as high as 5x105 A/cm 2 was obtained from a single LaB6 nanowire emitter, under an extraction voltage of 800 V. Emission current stability was also studied for the nanowire emitter and the results indicate surface-contamination induced emission current fluctuations. A home-designed TEM in-situ field emission measurement holder was fabricated for a JEOL 2010F HRTEM. Field electron emission was performed on a single LaB6 nanowire field electron emitter simultaneously with high resolution TEM imaging. Image contrast changes were observed at under-focus imaging conditions when a series of negative biases were applied to the

  13. High-performance field emission of carbon nanotube paste emitters fabricated using graphite nanopowder filler

    Science.gov (United States)

    Sun, Yuning; Yun, Ki Nam; Leti, Guillaume; Lee, Sang Heon; Song, Yoon-Ho; Lee, Cheol Jin

    2017-02-01

    Carbon nanotube (CNT) paste emitters were fabricated using graphite nanopowder filler. The CNT paste emitters consist of CNTs as the emitting material, graphite nanopowder as the filler and a graphite rod as the cathode. Rather than metal or inorganic materials, graphite nanopowder was adapted as a filler material to make the CNT paste emitters. After fabricating the emitters, sandpaper treatment was applied to increase the density of emission sites. The CNT paste emitters showed a high field emission performance, for example a high emission current of 8.5 mA from a cylindrical emitter with a diameter of 0.7 mm (corresponding to a current density of 2.2 A cm-2) and an extremely stable emission current at 1 mA (260 mA cm-2 for 20 h). Interestingly, after a number of electrical arcing events, the emitters still showed a high emission current of 5-8 mA (higher than 1 A cm-2). In addition to the sound electrical and thermal properties of the graphite filler, effective mechanical adhesion of the CNTs onto the graphite cathode induced by the use of the graphite nanopowder filler contributed the excellent field emission properties of the CNT paste emitters.

  14. Field emission response from multi-walled carbon nanotubes grown on electrochemically engineered copper foil

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, Amit Kumar; Jain, Vaibhav [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Saini, Krishna [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Centre of Excellence: Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Lahiri, Indranil, E-mail: indrafmt@iitr.ac.in [Nanomaterials and Applications Lab., Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India); Centre of Excellence: Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand (India)

    2017-02-01

    Exciting properties of carbon nanotube has proven it to be a promising candidate for field emission applications, if its processing cost can be reduced effectively. In this research, a new electrochemical technique is proposed for growing carbon nanotubes in selective areas by thermal chemical vapour deposition. In this process, electrochemical processing is used to create localized pits and deposition of catalysts, which act as roots to support growth and alignment of the CNTs on copper substrate. CNTs grown thus were characterized and studied using scanning electron microscope, transmission electron microscope and Raman spectroscopy, elucidating presence of multiwall carbon nanotubes (MWCNT). These CNT emitters have comparatively lower turn-on field and higher field enhancement factor. - Highlights: • Electrochemical pitting for localized carbon nanotube growth is proposed. • Electrochemical pitting method shows patterning effect on the substrate. • Size and density of pits depend on voltage, pH and temperature. • CNTs thus grown shows good field emission response.

  15. Combined effect of nitrogen doping and nanosteps on microcrystalline diamond films for improvement of field emission

    Energy Technology Data Exchange (ETDEWEB)

    Mengui, U.A., E-mail: ursulamengui@gmail.com [INPE – Instituto Nacional de Pesquisas Espaciais Laboratório Associado de Sensores e Materiais – LAS, Av. dos Astronautas 1758, CP 515, CEP 12.245-970, São José dos Campos, SP (Brazil); Campos, R.A.; Alves, K.A.; Antunes, E.F. [INPE – Instituto Nacional de Pesquisas Espaciais Laboratório Associado de Sensores e Materiais – LAS, Av. dos Astronautas 1758, CP 515, CEP 12.245-970, São José dos Campos, SP (Brazil); Hamanaka, M.H.M.O. [Centro de Tecnologia da Informação Renato Archer, Divisão de Superfícies de Interação e Displays, Rodovia D. Pedro I (SP 65) km 143.6, CP 6162, CEP 13089-500, Campinas, SP (Brazil); Corat, E.J.; Baldan, M.R. [INPE – Instituto Nacional de Pesquisas Espaciais Laboratório Associado de Sensores e Materiais – LAS, Av. dos Astronautas 1758, CP 515, CEP 12.245-970, São José dos Campos, SP (Brazil)

    2015-04-15

    Highlights: • Hot filament chemical vapor deposition using methane, hydrogen and a solution of urea in methanol produced nitrogen-doped diamond films. • Diamonds had the grain morphology changed for long growth time (28 h), and the nitrogen doping were evaluated by Raman spectroscopy. • Field emission characterization shows a decrease up to 70% in threshold field, related to reference diamond layer. - Abstract: Nitrogen-doped microcrystalline diamond (N-MCD) films were grown on Si substrates using a hot filament reactor with methanol solution of urea as N source. Electrostatic self-assembly seeding of nanocrystalline diamond were used to obtain continuous and uniform films. Simultaneous changes in grains morphology and work function of diamond by nitrogen doping decreased the threshold field and the angular coefficient of Fowler–Nordhein plots. The field emission properties of our N-MCD films are comparable to carbon nanotube films.

  16. SURFACE FILMS TO SUPPRESS FIELD EMISSION IN HIGH-POWER MICROWAVE COMPONENTS

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay l

    2014-02-07

    Results are reported on attempts to reduce the RF breakdown probability on copper accelerator structures by applying thin surface films that could suppress field emission of electrons. Techniques for application and testing of copper samples with films of metals with work functions higher than copper are described, principally for application of platinum films, since platinum has the second highest work function of any metal. Techniques for application of insulating films are also described, since these can suppress field emission and damage on account of dielectric shielding of fields at the copper surface, and on account of the greater hardness of insulating films, as compared with copper. In particular, application of zirconium oxide films on high-field portions of a 11.424 GHz SLAC cavity structure for breakdown tests are described.

  17. Enhanced field emission of ZnO nanoneedle arrays via solution etching at room temperature

    DEFF Research Database (Denmark)

    Ma, Huanming; Qin, Zhiwei; Wang, Zaide

    2017-01-01

    ZnO nanoneedle arrays (ZnO nns) were synthesized by a facile two-step solution-phase method based on the etching of pre-synthesized ZnO nanowire arrays (ZnO nws) with flat ends at room temperature. Field emission measurement results showed that the turn-on electronic fields of ZnO nns and nws wer...... 2.7 and 5.3 V μm−1 at a current density of 10 μA cm−2, and the field enhancement factors were 4939.3 for ZnO nns and 1423.6 for ZnO nws. The enhanced field emission properties in ZnO nns were ascribed to the sharp tip geometry....

  18. Enhanced field emission from nanosecond laser based surface micro-structured stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Singh, A.K., E-mail: anilks@barc.gov.in [Laser & Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400085< p/ostalC> (India); Shinde, Deodatta; More, Mahendra A. [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Sinha, Sucharita [Laser & Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400085< p/ostalC> (India)

    2015-12-01

    Highlights: • Stainless steel (SS) sheets have been surface treated using a frequency doubled nanosecond pulsed Nd:YAG laser at laser fluence level ∼0.7 J/cm{sup 2} resulting in formation of micro protrusions. • In regions near periphery of the laser treated spot showed formation of micro-protrusions with density as high as ∼4.5 × 10{sup 7} cones/cm{sup 2}. • Energy dispersive X-ray spectroscopy (EDS) analysis of untreated and laser treated samples reveals trend in change of elemental composition of the sample on laser treatment. • Grazing incidence X-ray diffraction analysis of untreated and laser treated samples shows formation of oxides and nitrides of iron upon laser treatment. • Field emission study on the laser micro-structured (SS) sample has shown low turn on field in comparison to untreated stainless steel. • Parameters characterizing large area field emitters such as turn ON field, macroscopic field enhancement factor and pre exponential factor corresponding to the laser micro-structured steel surface have been estimated. • Field emission current has shown good stability when tested over a period of 140 min at a preset level of 4 μA. - Abstract: This paper presents results of field emission study of laser based surface micro-structured stainless steel (SS). Surface micro-structuring of SS samples has been performed by direct irradiation of sample surface with a frequency doubled Nd:YAG nanosecond (ns) laser in atmospheric ambience. Laser treated samples have been characterized in terms of their surface morphology, elemental composition and field emission properties. Our results reveal formation of micro-protrusions of varying height and tip diameter depending on incident laser fluence. Within the laser irradiated spot, regions near periphery showed formation of micro-protrusions with number density as high as 4.5 × 10{sup 7} protrusions/cm{sup 2}. Such laser micro-structured samples have shown much lower turn on electric field (7.5 V

  19. Wide-field microscopic FRET imaging using simultaneous spectral unmixing of excitation and emission spectra.

    Science.gov (United States)

    Du, Mengyan; Zhang, Lili; Xie, Shusen; Chen, Tongsheng

    2016-07-11

    Simultaneous spectral unmixing of excitation and emission spectra (ExEm unmixing) has the inherent ability to resolve donor emission, fluorescence resonance energy transfer (FRET)-sensitized acceptor emission and directly excited acceptor emission. We here develop an ExEm unmixing-based quantitative FRET measurement method (EES-FRET) independent of excitation intensity and detector parameter setting. The ratio factor (rK), predetermined using a donor-acceptor tandem construct, of total acceptor absorption to total donor absorption in excitation wavelengths used is introduced for determining the concentration ratio of acceptor to donor. We implemented EES-FRET method on a wide-field microscope to image living cells expressing tandem FRET constructs with different donor-acceptor stoichiometry.

  20. Development of self-aligned gated porous silicon microtip field emission arrays for vacuum microelectronic applications

    Science.gov (United States)

    Jessing, Jeffrey Richard

    Solid state microelectronics is the dominate technology in the present day electronics industry. However, as the physical dimensions decrease, it is becoming apparent that solid state devices have inherent performance limitations, such as finite saturation drift velocity, high temperature degradation, and failure in extreme radiation environments. To address these problems a relatively new technology, called vacuum microelectronics, has emerged. Vacuum microelectronics encompasses the fabrication, characterization, and application of various devices whose operation is based on vacuum ballistic transport of field emitted electrons from microminiature electrodes. The field of vacuum microelectronics has advanced at a rapid rate over the past decade; however, there remain key issues to be addressed prior to any widespread commercialization of this technology. Field emission arrays (FEAs) must operate at low voltages and generate high current densities with uniform, long-lifetime operation. The use of porous silicon cathodes in vacuum microelectronic applications is a promising alternative to existing silicon and metal field emitters. Surface modification of bulk crystalline silicon by electrochemical anodization in a concentrated hydrofluoric acid (HF) solution has been shown to produce large submicroscopic field enhancement and large emission area. The primary focus of this research was the development of novel gated FEAs based on porous silicon microtip cathodes. Device design consisted of both experimental and theoretical efforts. Employing semiconductor process technology, the successful fabrication of an operational self-aligned gated porous silicon microtip FEA was demonstrated. Small arrays exhibited Fowler-Nordheim characteristics over several decades of anode current. A peak stable current of approximately 60 to 70 nA per tip was obtained at less than 125 V. A correlation of anodization conditions with emission properties has been found, and a simple emission

  1. Study of direct-current, pulsed, and temperature--field emission from LaB/sub 6//tungsten field emitter

    Energy Technology Data Exchange (ETDEWEB)

    Khairnar, R. S.; Dharmadhikari, C. V.; Joag, D. S.; Kanitkar, P. L.; Nigavekar, A. S.

    1989-07-01

    This paper reports dc, temperature--field (/ital T/--/ital F/), and pulsed emission from a lanthanum hexaboride (LaB/sub 6/)--tungsten (W) field emitter. Various parameters are drived from the Fowler--Nordheim plots for the three configurations of the emitter, viz., clean tungsten, LaB/sub 6/ overgrowth on W(111) plane (''two spot''), and LaB/sub 6/ equilibrated W surface (''well spread''). The current stability is observed at 300, 730, and 850 K, (and 1065 K for well spread) under /ital T/--/ital F/ operation. A comparison is made with various types of field emitting cathodes and the results are discussed from the point of view of LaB/sub 6//W field emitting cathodes.

  2. Enhanced field electron emission of graphene sheets by CsI coating after electrophoretic deposition.

    Science.gov (United States)

    Liu, Jianlong; Zeng, Baoqing; Wu, Zhe; Sun, Hao

    2012-03-01

    Because of the large quantities of edges, graphene can serve as an efficient edge emitter for field emission (FE). Cesium iodide (CsI) coating was promising to enhance the electron emission and utilized in FE applications. In this work, FE of graphene sheets after electrophoretic deposition (ED) was studied. Electron emission property of GS was obviously improved by coating with CsI. The turn-on field of GS decreased from 4.4 to 2.5 V/ μm; and threshold field decreased from 9 to 5.8 V/μm, respectively. This FE improvement must due to a higher effective density of emission site generated around the GS surface after coating. Scanning electron microscopy (SEM) and computation were taken to reveal the influence after coating. Investigations of CsI coated MWCNTs were also compared in order to better understand the origin of the low turn-on electric field obtained by GS. © 2012 American Chemical Society

  3. Field Emission Vacuum (FEV) Electronic Devices for Operation Above 500 Degrees Celsius

    Science.gov (United States)

    Peltz, L.; Jones, W. M.; Frampton, R. V.; Keith, A. R.; Scherer, A.

    2017-11-01

    Boeing is teamed with Caltech to develop FEV (Field-Emission Vacuum) electronics. Our Boeing-Caltech team has recently begun work, under NASA ROSES C.24 HOTTech program, to demonstrate robust FEV operating at 500C, towards Venus surface missions.

  4. Optimizing grain yields reduces CH4 emissions from rice paddy fields

    NARCIS (Netherlands)

    Denier van der Gon, H.A.C.; Kropff, M.J.; Breemen, van N.; Wassmann, R.; Lantin, R.S.; Aduna, E.; Corton, T.M.; Laar, van H.H.

    2002-01-01

    Microbial production in anoxic wetland rice soils is a major source of atmospheric CH4, the most important non-CO2 greenhouse gas. Much higher CH4 emissions from well managed irrigated rice fields in the wet than in the dry season could not be explained by seasonal differences in temperature. We

  5. Estimating GHG Emissions from the Manufacturing of Field-Applied Biochar Pellets

    Science.gov (United States)

    Richard D. Bergman; Hanwen Zhang; Karl Englund; Keith Windell; Hongmei Gu

    2016-01-01

    Biochar application to forest soils can provide direct and indirect benefits, including carbon sequestration. Biochar, the result of thermochemical conversion of biomass, can have positive environmental climate benefits and can be more stable when field-applied to forest soils than wood itself. Categorizing greenhouse gas (GHG) emissions and carbon sequestration...

  6. Field emission scanning electron microscopy (FE-SEM) as an approach for nanoparticle detection inside cells

    Czech Academy of Sciences Publication Activity Database

    Havrdová, M.; Poláková, K.; Skopalík, J.; Vůjtek, M.; Mokdad, A.; Homolková, M.; Tuček, J.; Nebesářová, Jana; Zbořil, R.

    2014-01-01

    Roč. 67, DEC 2014 (2014), s. 149-154 ISSN 0968-4328 Institutional support: RVO:60077344 Keywords : Field emission scanning electronmicroscopy (FE-SEM) * Stem cells * Iron oxide nanoparticles * Cellular morphology * Endosomes * Cell uptake Subject RIV: FD - Oncology ; Hematology Impact factor: 1.988, year: 2014

  7. Manipulating carbon nanotubes Towards the application as novel field emission sources

    NARCIS (Netherlands)

    Heeres, Erwin Cornelis

    2014-01-01

    This thesis is about the research performed on novel field emission sources. Having a better electron source can reduce the time needed to obtain an electron microscope image and enable studying processes at a higher resolution. We chose to fabricate electron sources by means of mounting

  8. Field Emission Properties of the Dendritic Carbon Nanotubes Film Embedded with ZnO Quantum Dots

    Directory of Open Access Journals (Sweden)

    Shu Zuo

    2011-01-01

    Full Text Available Response on the effects of individual differences of common carbon nanotubes on the field emission current stability and the luminescence uniformity of cathode film, a new type of cathode film made of dendritic carbon nanotubes embedded with Zinc oxide quantum dots is proposed. The film of dendritic carbon nanotubes was synthesized through high-temperature pyrolysis of iron phthalocyanine on a silicon substrate coated with zinc oxide nanoparticles. The dendritic structure looks like many small branches protrude from the main branches in SEM and TEM images, and both the branch and the trunk are embedded with Zinc oxide quantum dots. The turn-on field of the dendritic structure film is ∼1.3 V/μm at a current of 2 μA, which is much lower than that of the common carbon nanotube film, and the emission current and the luminescence uniformity are better than that of the common one. The whole film emission uniformity has been improved because the multi-emission sites out from the dendritic structure carbon nanotubes cover up the failure and defects of the single emission site.

  9. Cold field emission gun-scanning electron microscopy: a new tool for morphological and ultrastructural analysis of liposomes.

    Science.gov (United States)

    De Rosa, G; De Stefano, M; Ungaro, F; La Rotonda, M I

    2008-10-01

    Liposomes are lipid vesicles largely investigated in the past 30 years as pharmaceutical carriers. In the development of new liposome-based formulations, the study of liposome surface properties remains a crucial step. For this purpose, microscopy techniques can provide useful information, although each such technique suffers from some limitations. Here, we have used cold field emission gun-scanning electron microscopy (cFEG-SEM) to acquire detailed images of liposome surface. In particular, we observed PEGylated and non-PEGylated liposomes in different size ranges. In the case of nanosized liposomes (mean diameter about 200 nm), a morphological evaluation of the whole preparation was obtained. On the other hand, in the case of giant liposomes (mean diameter about 2 microm), it was possible to observe the different surface ultrastructures of the two formulations. In particular, a regular and only slightly wrinkled surface was observed in the case of non-PEGylated liposomes, while a very irregular surface ultrastructure was visible in the case of PEGylated liposomes. This study shows, for the first time, the potential of cFEG-SEM as a new and powerful tool to obtain information on liposome morphology and, at least in the case of giant liposomes, on ultrastructure of the liposome surface.

  10. Signatures and mechanisms of plasmon-enhanced electron emission from clusters in few-cycle laser fields

    Science.gov (United States)

    Seiffert, Lennart; Köhn, Jörg; Peltz, Christian; Kling, Matthias F.; Fennel, Thomas

    2017-11-01

    Intense laser pulses with well-defined waveforms enable unprecedented control over electronic strong-field processes in atoms, molecules and nanostructures. In particular, carrier-envelope phase (CEP) controlled few-cycle pulses allow the modification of various features in high-harmonic or photoelectron spectra. Vice versa, such signatures open up the opportunity to identify the underlying physical processes. Here, we utilize this approach to investigate plasmon-enhanced electron emission from simple metal clusters under resonant few-cycle laser pulses. Photoelectron energy spectra extracted from our semiclassical trajectory simulations reveal a set of pronounced but strongly intertwined CEP-dependent signatures. We find, that electron trajectories associated with these signatures can be categorized by two characteristic timestamps, i.e. the escape from the cluster and the last transit through its central plane. A correlation analysis of these times enables us to disentangle the intertwined features and to associate them with different acceleration mechanisms. We expect that our results will support the interpretation of specific patterns in the photoelectron spectra of future CEP-resolved cluster experiments.

  11. Low temperature synthesis and field emission characteristics of single to few layered graphene grown using PECVD

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Avshish; Khan, Sunny; Zulfequar, M.; Harsh; Husain, Mushahid, E-mail: mush_reslab@rediffmail.com

    2017-04-30

    Highlights: • Graphene was synthesized by PECVD system at a low temperature of 600 °C. • From different characterization techniques, the presence of single and few layered graphene was confirmed. • X-ray diffraction pattern of the graphene showed single crystalline nature of the film. • The as-grown graphene films were observed extremely good field emitters with long term emission current stability. - Abstract: In this work, high-quality graphene has successfully been synthesized on copper (Cu) coated Silicon (Si) substrate at very large-area by plasma enhanced chemical vapor deposition system. This method is low cost and highly effective for synthesizing graphene relatively at low temperature of 600 °C. Electron microscopy images have shown that surface morphology of the grown samples is quite uniform consisting of single layered graphene (SLG) to few layered graphene (FLG). Raman spectra reveal that graphene has been grown with high-quality having negligible defects and the observation of G and G' peaks is also an indicative of stokes phonon energy shift caused due to laser excitation. Scanning probe microscopy image also depicts the synthesis of single to few layered graphene. The field emission characteristics of as-grown graphene samples were studied in a planar diode configuration at room temperature. The graphene samples were observed to be a good field emitter having low turn-on field, higher field amplification factor and long term emission current stability.

  12. Sedimentation field-flow fractionation for characterization of citric acid-modified Hβ zeolite particles: Effect of particle dispersion and carrier composition.

    Science.gov (United States)

    Dou, Haiyang; Bai, Guoyi; Ding, Liang; Li, Yueqiu; Lee, Seungho

    2015-11-27

    In this study, sedimentation field-flow fractionation (SdFFF) was, for the first time, applied for determination of size distribution of Hβ zeolite particles modified by citric acid (CA-Hβ). Effects of the particle dispersion and the carrier liquid composition (type of dispersing reagent (surfactant) and salt added in the carrier liquid, ionic strength, and pH) on SdFFF elution behavior of CA-Hβ zeolite particles were systematically investigated. Also the SdFFF separation efficiency of the particles was discussed in terms of the forces such as van der Waals, hydrophobic, and induced-dipole interactions. Results reveal that the type of salt and pH of the carrier liquid significantly affect the SdFFF separation efficiency of the zeolite particles. It was found that addition of a salt (NaN3) into the carrier liquid affects the characteristic of the SdFFF channel surface. It was found that the use of an acidic medium (pH 3.2) leads to a particle-channel interaction, while the use of a basic medium (pH 10.6) promotes an inter-particle hydrophobic interaction. Result from SdFFF was compared with those from scanning electron microscopy (SEM) and dynamic light scattering (DLS). It seems that, once the experimental conditions are optimized, SdFFF becomes a valuable tool for size characterization of the zeolite particles. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Injection-modulated polarity conversion by charge carrier density control via a self-assembled monolayer for all-solution-processed organic field-effect transistors.

    Science.gov (United States)

    Roh, Jeongkyun; Lee, Taesoo; Kang, Chan-Mo; Kwak, Jeonghun; Lang, Philippe; Horowitz, Gilles; Kim, Hyeok; Lee, Changhee

    2017-04-12

    We demonstrated modulation of charge carrier densities in all-solution-processed organic field-effect transistors (OFETs) by modifying the injection properties with self-assembled monolayers (SAMs). The all-solution-processed OFETs based on an n-type polymer with inkjet-printed Ag electrodes were fabricated as a test platform, and the injection properties were modified by the SAMs. Two types of SAMs with different dipole direction, thiophenol (TP) and pentafluorobenzene thiol (PFBT) were employed, modifying the work function of the inkjet-printed Ag (4.9 eV) to 4.66 eV and 5.24 eV with TP and PFBT treatments, respectively. The charge carrier densities were controlled by the SAM treatment in both dominant and non-dominant carrier-channel regimes. This work demonstrates that control of the charge carrier densities can be efficiently achieved by modifying the injection property with SAM treatment; thus, this approach can achieve polarity conversion of the OFETs.

  14. Electron beam confinement and image contrast enhancement in near field emission scanning electron microscopy.

    Science.gov (United States)

    Kirk, T L; De Pietro, L G; Pescia, D; Ramsperger, U

    2009-04-01

    In conventional scanning electron microscopy (SEM), the lateral resolution is limited by the electron beam diameter impinging on the specimen surface. Near field emission scanning electron microscopy (NFESEM) provides a simple means of overcoming this limit; however, the most suitable field emitter remains to be determined. NFESEM has been used in this work to investigate the W (110) surface with single-crystal tungsten tips of (310), (111), and (100)-orientations. The topographic images generated from both the electron intensity variations and the field emission current indicate higher resolution capabilities with decreasing tip work function than with polycrystalline tungsten tips. The confinement of the electron beam transcends the resolution limitations of the geometrical models, which are determined by the minimum beam width.

  15. Synthesis of octahedral ZnGa2O4 particles and their field-emission properties

    Science.gov (United States)

    Zhang, Xitian; Rao, Yangyan; Liang, Yao; Deng, Rui; Liu, Zhuang; Hark, Suikong; Yuen, Yingkit; Wong, Saipeng

    2008-05-01

    ZnGa2O4 particles that are regular octahedra in shape and uniform in size were synthesized on Si substrates via catalyst-free chemical vapour deposition. The surfaces of the octahedra are bounded by {1 1 1} facets. A model based on surface energy dependent growth rate is proposed for interpreting the appearance of the octahedra. The field-emission (FE) properties of the octahedral particles were measured. The turn-on field required for producing an emission current density of 0.1 µA cm-2 is 11 V µm-1, and the field enhancement factor (β) is about 1256, which is high enough for various FE applications.

  16. Effect of water management on methane emission from a Japanese rice paddy field: Automated methane monitoring

    Science.gov (United States)

    Yagi, Kazuyuki; Tsuruta, Haruo; Kanda, Ken-Ichi; Minami, Katsuyuki

    1996-06-01

    The effect of differing water management schemes on the emission of methane (CH4) from rice paddies to the atmosphere was studied in a Japanese paddy field. Using an automated sampling and analyzing system, the test site was divided into two plots: a continuously flooded plot which was maintained flooded by constant irrigation from May to August, and an intermittently drained plot in which short-term draining practices were performed several times during the flooding period . The draining practice had a strong effect on CH4 emission. A large flush of CH4 emission was observed in the intermittently drained plot immediately after each drainage. It was followed by a rapid decrease in CH4 flux in most of the cases. A large flush of CH4 was observed after the final drainage at the end of August in the continuously flooded plot, accounting for about 7% of the total CH4 emitted in the plot. Total emission rates of CH4 during the cultivation period were 14.8 and 8.63 g m-2 for 1991 and 9.49 and 5.18 g m-2 for 1993 in the continuously flooded and intermittently drained plots, respectively. Companion N2O flux measurements showed that almost no N2O was emitted from either plot until the final drainage. These results indicate that short-term draining practices strongly reduce CH4 emission from rice paddy fields, and that improvement in water management can be one of the most important mitigation strategies for CH4 emission from rice paddy fields.

  17. Simulation of radio emission from air showers in atmospheric electric fields

    OpenAIRE

    Buitink, S.

    2010-01-01

    We study the effect of atmospheric electric fields on the radio pulse emitted by cos- mic ray air showers. Under fair weather conditions the dominant part of the radio emission is driven by the geomagnetic field. When the shower charges are acceler- ated and deflected in an electric field additional radiation is emitted. We simulate this effect with the Monte Carlo code REAS2, using CORSIKA-simulated showers as input. In both codes a routine has been implemented that treats the effect of the ...

  18. Template free synthesis of mesoporous CuO nano architects for field emission applications.

    Science.gov (United States)

    Das, Swati; Maiti, Soumen; Saha, Subhajit; Das, Nirmalya Sankar; Chattopadhyay, Kalyan Kumar

    2013-04-01

    Cupric oxide mesospheres composed of its nanoparticles have been synthesized by a simple template free chemical route at different temperatures. Thermal aging followed by higher temperature (350 degrees C, 6 hours) annealing on these architects transformed them into hollow mesospheres consisting of sharp needle like structures with high aspect ratio (- 10(3)). A detailed analysis of field emission scanning electron microscopy confirmed a uniform registry of the prepared nanostructures. High resolution transmission electron microscopy showed that the as-grown mesospheres have hollow inner cavity with a thin outer shell. X-ray photoelectron spectroscopic analysis showed no obvious changes in the chemical composition of the nanostructures after annealing, confirming that the elements in the final products were in the proper oxidation states. Electron emission under electric field was investigated from these interesting structures. It was found that both of these nanostructures showed electron emission, but emission performance of the hollow mesospheres consisting of nanoneedles exhibited excellent performance with turn-on field as low as 2.8 V/microm and high enhancement factor (beta) - 5537.

  19. Stochastic fields method for sub-grid scale emission heterogeneity in mesoscale atmospheric dispersion models

    Directory of Open Access Journals (Sweden)

    M. Cassiani

    2010-01-01

    Full Text Available The stochastic fields method for turbulent reacting flows has been applied to the issue of sub-grid scale emission heterogeneity in a mesoscale model. This method is a solution technique for the probability density function (PDF transport equation and can be seen as a straightforward extension of currently used mesoscale dispersion models. It has been implemented in an existing mesoscale model and the results are compared with Large-Eddy Simulation (LES data devised to test specifically the effect of sub-grid scale emission heterogeneity on boundary layer concentration fluctuations. The sub-grid scale emission variability is assimilated in the model as a PDF of the emissions. The stochastic fields method shows excellent agreement with the LES data without adjustment of the constants used in the mesoscale model. The stochastic fields method is a stochastic solution of the transport equations for the concentration PDF of dispersing scalars, therefore it possesses the ability to handle chemistry of any complexity without the need to introduce additional closures for the high order statistics of chemical species. This study shows for the first time the feasibility of applying this method to mesoscale chemical transport models.

  20. Chemical ionization mass spectrometry using carbon nanotube field emission electron sources.

    Science.gov (United States)

    Radauscher, Erich J; Keil, Adam D; Wells, Mitch; Amsden, Jason J; Piascik, Jeffrey R; Parker, Charles B; Stoner, Brian R; Glass, Jeffrey T

    2015-11-01

    A novel chemical ionization (CI) source has been developed based on a carbon nanotube (CNT) field emission electron source. The CNT-based electron source was evaluated and compared with a standard filament thermionic electron source in a commercial explosives trace detection desktop mass spectrometer. This work demonstrates the first reported use of a CNT-based ion source capable of collecting CI mass spectra. Both positive and negative modes were investigated. Spectra were collected for a standard mass spectrometer calibration compound, perfluorotributylamine (PFTBA), as well as trace explosives including trinitrotoluene (TNT), Research Department explosive (RDX), and pentaerythritol tetranitrate (PETN). The electrical characteristics, lifetime at operating pressure, and power requirements of the CNT-based electron source are reported. The CNT field emission electron sources demonstrated an average lifetime of 320 h when operated in constant emission mode under elevated CI pressures. The ability of the CNT field emission source to cycle on and off can provide enhanced lifetime and reduced power consumption without sacrificing performance and detection capabilities. Graphical Abstract ᅟ.

  1. Field emission device driven by self-powered contact-electrification: Simulation and experimental analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiangyu, E-mail: chenxiangyu@binn.cas.cn, E-mail: ouyangwei@phy.ecnu.edu.cn; Jiang, Tao [Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083 (China); Sun, Zhuo; Ou-Yang, Wei, E-mail: chenxiangyu@binn.cas.cn, E-mail: ouyangwei@phy.ecnu.edu.cn [Engineering Research Center for Nanophotonics and Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, 3663 North Zhongshan Road, Shanghai 200062 (China)

    2015-09-14

    A self-powered field emission device (FED) driven by a single-electrode tribo-electric nanogenerator (TENG) is demonstrated. The mechanical motion works as both a power supply to drive the FED and a control unit to regulate the amount of emitted electrons. By using the Fowler-Nordheim equation and Kirchhoff laws, a theoretical model of this self-powered FED is proposed, and accordingly the real-time output characteristics of the device are systematically investigated. It is found that the motion distance of the TENG controls switch-on of the FED and determines the charge amount for emission, while the motion velocity regulates the amplitude of emission current. The minimum contact area for the TENG to generate field emission is about 9 cm{sup 2}, which can be improved by optimizing FED structure and the tribo-materials of TENG. The demonstrated concept of this self-powered FED as well as the proposed physical analysis can serve as guidance for further applications of FED in such fields of self-powered electronics and soft electronics.

  2. Oil palm and the emission of greenhouse gasses- from field measurements in Indonesia

    Science.gov (United States)

    Rahman, Niharika; Bruun, Thilde Bech; Giller, Ken E.; Magid, Jakob; van de Ven, Gerrie; de Neergaard, Andreas

    2017-04-01

    Palm oil from the oil palm (Elaeis guianensis) has in recent years become the world's most important vegetable oil. The increasing demand for palm oil has led to expansion of oil palm plantations, which has caused environmental controversies associated with carbon losses and the use of large amounts of mineral fertilizers. Efforts to increase sustainability of oil palm cultivation, include recycling of oil-mill residues and pruning's, but with this comes increased potential for methane emission from the plantations. Until now no field-based data on greenhouse gas emissions from oil palm plantations have been reported. Here for the first time we present data from a long term (360 days) field trial in Bah Lias Research Station, North Sumatra, Indonesia on greenhouse gas emissions from an oil palm plantation with various treatments of recycled oil palm waste products, fertilizers and simulated rainfall. The first experiment was conducted over a full year (dry + wet season) with mineral fertilizer treatments including urea and ammonium sulphate, and organic fertilizer treatments constituting: empty fruit bunches (EFB), enriched mulch (EFB + palm oil mill effluent (POME) ) and pruned oil palm fronds (OPF). Treatment doses represent the current management in Indonesian plantations and the higher doses that are expected in the imminent future. For the organic treatments several methods of application (applied in inter-rows, piles, patches or bands) were evaluated. The second experiment investigated effects of soil water saturation on GHG emissions through adding 25 mm simulated rainfall per day for 21 days. Each palm tree received 1 kg of N fertilizer as urea or ammonium sulphate and enriched mulch. The gas fluxes in the fields was measured by a large static-chamber (1.8 m x 1.2 m) method and CH4 and N2O concentrations were determined using gas chromatographs. We found that emissions were significantly affected by the type and dose of mineral fertilizers. Application of

  3. Intelligent Heat System - High-Energy Efficient Wood Stoves with Low Emissions. Field Tests

    DEFF Research Database (Denmark)

    Illerup, Jytte Boll; Nickelsen, Joachim; Hansen, Brian Brun

    2014-01-01

    Wood stoves have the potential of providing CO2-neutral energy without transmission loss—but with the significant drawbacks of high emissions of pollutants and particulate matter at low altitude close to private homes, and with an uneven heat release profile which produces non-optimal heating com...... in 2012. The automatic control system developed for wood stoves in this project ensures optimal combustion conditions, thereby minimizing the emissions throughout a complete wood log combustion cycle. This improved performance has been verified by field tests in private homes....

  4. Long term continuous field survey to assess nutrient emission impact from irrigated paddy field into river catchment

    Science.gov (United States)

    Kogure, Kanami; Aichi, Masaatsu; Zessner, Matthias

    2017-04-01

    In order to achieve good river environment, it is very important to understand and to control nutrient behavior such as Nitrogen and Phosphorus. As we could reduce impact from urban and industrial activities by wastewater treatment, pollution from point sources are likely to be controlled. Besides them, nutrient emission from agricultural activity is dominant pollution source into the river system. In many countries in Asia and Africa, rice is widely cultivated and paddy field covers large areas. In Japan 54% of its arable land is occupied with irrigated paddy field. While paddy field can deteriorate river water quality due to fertilization, it is also suggested that paddy field can purify water. We carried out field survey in middle reach of the Tone River Basin with focus on a paddy field IM. The objectives of the research are 1) understanding of water and nutrient balance in paddy field, 2) data collection for assessing nutrient emission. Field survey was conducted from June 2015 to October 2016 covering two flooding seasons in summer. In our measurement, all input and output were measured regarding water, N and P to quantify water and nutrient balance in the paddy field. By measuring water quality and flow rate of inflow, outflow, infiltrating water, ground water and flooding water, we tried to quantitatively understand water, N and P cycle in a paddy field including seasonal trends, and changes accompanied with rainy events and agricultural activities like fertilization. Concerning water balance, infiltration rate was estimated by following equation. Infiltration=Irrigation water + Precipitation - Evapotranspiration -Outflow We estimated mean daily water balance during flooding season. Infiltration is 11.9mm/day in our estimation for summer in 2015. Daily water reduction depth (WRD) is sum of Evapotranspiration and Infiltration. WRD is 21.5mm/day in IM and agrees with average value in previous research. Regarding nutrient balance, we estimated an annual N and

  5. METHANE EMISSION FROM PADDY FIELDS AS INFLUENCED BY DIFFERENT WATER REGIMES IN CENTRAL JAVA

    Directory of Open Access Journals (Sweden)

    Prihasto Setyanto

    2013-07-01

    Full Text Available The concentration of methane (CH4 in the atmosphere is increasing at 1% per annum and rice fields are one of the sources that contribute to about 10-15% of the atmospheric CH4. One of the options to reduce greenhouse gas emission from rice fields is probably through water management. A field study was conducted to investigate the effects of water management practices on CH4 emission from rice field plots on a silty sand Aeric Tropaquept soil at Research Station for Agricultural Environment Preservation, Jakenan, Central Java, Indonesia, during the dry season of March to June 2002. Four water regimes tested were: (1 5 cm continuous flooding (CF, (2 0-1 cm continuous flooding (ST, (3 intermittent irrigation (IR where plots received continuously 5 cm of flooding with two times of draining at 15-20 and 25-30 days after transplanting (DAT, and (4 pulse irrigation (PI where plots were watered until 5 cm level and left to dry by itself until the water table reached 30 cm beneath soil surface then watered again. The total CH4 emissions of the four water treatments were 254, 185, 136 and 96 kg CH4 ha-1 for CF, ST, IR and PI, respectively. Methane emission increased during the early growing season, which coincided with the low redox potential of -100 to -150 mV in all treatments. Dry matter weight of straw and filled grain among the water treatments did not show significant differences. Likewise, total grain yield at 14% moisture content was not significantly different among treatments. However, this result should be carefully interpreted because the rice plants in all water treatments were infested by stem borer, which reduced the total grain yield of IR64 between 11% and 16%. This study suggests that intermittent and pulse irrigation practices will be important not only for water use efficiency, but also for CH4 emission reduction.

  6. Analysis and Simulation of Generating Terahertz Surface Waves in Laser-Assisted Field Emission

    Science.gov (United States)

    Hagmann, Mark; Kumar, Gagan; Pandey, Shashank; Nahata, Ajay

    2011-03-01

    When the radiation from two lasers is focused on a field emission diode the electric field from the radiation is superimposed on the applied DC field, and the nonlinear dependence of the emitted current on the electric field causes the current to oscillate at the difference frequency for the two lasers. Finite Difference-Time Domain simulations and analytical solutions for a paraboloidal model of the field emission tip show that the current oscillations create a transverse-magnetic (TM) surface wave on the tip. The analytical solution for the TM fields in paraboloidal coordinates consists of products of regular and irregular Coulomb wave functions. The width of the tip is much smaller than the skin depth so interior and exterior solutions are required and a summation of the products is required to satisfy the boundary conditions at the surface of the tip. The simulations are consistent with the analytical solution and show that there is a quasi-stationary region near the apex, a transition region where the surface waves are formed, and the far-field where the waves propagate outward on the tip.

  7. Transport in organic semiconductors in large electric fields: From thermal activation to field emission

    Science.gov (United States)

    Worne, J. H.; Anthony, J. E.; Natelson, D.

    2010-02-01

    Understanding charge transport in organic semiconductors in large electric fields is relevant to many applications. We present transport measurements in organic field-effect transistors based on poly(3-hexylthiophene) and 6,13-bis(triisopropyl-silylethynyl) (TIPS) pentacene with short channels, from room temperature down to 4.2 K. Near 300 K transport in both systems is well described by thermally assisted hopping with Poole-Frenkel-type enhancement of the mobility. At low temperatures and large gate voltages, transport in both materials becomes nearly temperature independent, crossing over into field-driven tunneling. These data, particularly in TIPS-pentacene, show that great caution must be exercised when considering more exotic (e.g., Tomonaga-Luttinger liquid) interpretations of transport.

  8. Highly enhanced and temporally stable field emission from MWCNTs grown on aluminum coated silicon substrate

    Directory of Open Access Journals (Sweden)

    M. Sreekanth

    2015-06-01

    Full Text Available In this work, a detailed field emission study of multi-walled carbon nanotubes (MWCNTs grown on Si and Al coated Si substrates is reported. Morphological and microstructural studies of the films show higher entanglement of CNTs in the case of CNT/Si film as compared to CNT/Al/Si film. Raman studies show that the defect mediated peak (D is substantially suppressed as compared to graphitic peak (G resulting in significant reduction in ID/IG value in CNT/Al/Si film. Field emission (FE current density of CNT/Al/Si film (∼25 mA/cm2 is significantly higher as compared to that of CNT/Si film (∼1.6 mA/cm2. A substantial improvement in temporal stability is also observed in CNT/Al/Si film. This enhancement in field emission current is attributed to strong adhesion between substrate and CNTs, low work function, high local field enhancement factor at the CNT tips and less entanglement of CNTs grown on Al/Si. The temporally stable CNT/Al/Si cold cathode can be a potential candidate to replace conventional electron sources in prototype devices.

  9. Field emission properties of gold nanoparticle-decorated ZnO nanopillars.

    Science.gov (United States)

    Chang, Yuan-Ming; Lin, Man-Ling; Lai, Tung-Yen; Lee, Hsin-Yi; Lin, Chih-Ming; Wu, Yew-Chung Sermon; Juang, Jenh-Yih

    2012-12-01

    The structural and optoelectronic properties of ZnO nanopillars (ZnO-NPs) grown on Si substrates by the vapor transport deposition method were investigated. In particular, by varying the deposition duration and hence the morphology of the vertically aligned ZnO-NPs, the resultant field emission characteristics were systematically compared. In addition to identifying the advantageous field emission properties exhibited in the pencil-like ZnO-NPs, we observed that by adhering Au nanoparticles on the surface of the ZnO-NPs the turn-on field and the maximum current density can be drastically improved from 3.15 V/μm and 0.44 mA/cm(2) at 5 V/μm for the best ZnO-NPs to 2.65 V/μm and 2.11 mA/cm(2) at 5 V/μm for Au/ZnO-NPs, respectively. The enhancement of field emission characteristics that resulted from Au-nanoparticle decoration is discussed on the basis of charge-transfer-induced band structure modifications.

  10. Enhanced Field Emission Performance of Hierarchical ZnO/Si Nanotrees with Spatially Branched Heteroassemblies.

    Science.gov (United States)

    Lv, Shasha; Li, Zhengcao; Chen, Chienhua; Liao, Jiecui; Wang, Guojing; Li, Mingyang; Miao, Wei

    2015-06-24

    Silicon nanorods (SiNRs) with a large interspace and regularly aligned structure were fabricated by combining silver-catalyzed etching with a polysterene (PS) sphere template, then a hydrothermal reaction was utilized to synthesize large-scale ZnO nanowires (NWs) on Si nanorods. Compared with the as-prepared SiNRs and ZnO NWs, the high-density ZnO NWs on SiNRs have exhibited predominant field emission (FE) characteristics with a low turn-on field of 2.18 V/μm and a high field enhancement factor of ∼8100. The FE enhancement was attributed to highly crystallized ZnO NWs densely distributed on the surface of SiNRs, which can effectively increase emission site density, diminish screening effect, favor electron transfer due to band bending, and quickly transmit heat from the nanotrees to substrate. Our results indicate that ZnO/Si hierarchical structures might be an effective candidate for field emission cathode.

  11. Emission-Line Galaxies from the HST PEARS Grism Survey Southern Fields

    Science.gov (United States)

    Straughn, Amber; Pirzkal, N.; Meurer, G.; Cohen, S.; Windhorst, R.; Malhotra, S.; Gardner, J.; Rhoads, J.; Hathi, N.; Xu, C.

    2009-01-01

    We have detected a sample of emission-line galaxies (ELGs) from the PEARS (Probing Evolution And Reionization Spectroscopically) HST/ACS grism survey Southern Fields. The PEARS Southern Fields consist of five ACS pointings (including the Hubble Ultra Deep Field) with the G800L grism for a total of 120 orbits, revealing thousands of faint object spectra in the GOODS-South region of the sky. Using a 2-dimensional detection and extraction procedure, we find 320 emission lines orginating from 230 galaxy ``knots'' within 203 individual galaxies. Line identification results in 118 new grism-spectroscopic redshifts for galaxies in the GOODS-South Field. Our detection method has allowed us to observe emission lines from distinct giant star-forming regions across individual galaxies at redshifts z 0.5. We find that the radial distances of these HII regions generally reside near the galaxies' optical continuum half-light radii, similar to those of giant HII regions in local galaxies.

  12. Perovskites beyond photovoltaics: field emission from morphology-tailored nanostructured methylammonium lead triiodide.

    Science.gov (United States)

    Besra, Nripen; Pal, Shreyasi; Das, Bikram Kumar; Chattopadhyay, Kalyan Kumar

    2017-10-11

    Herein, methylammonium lead triiodide (CH3NH3PbI3) nanorods and nanocrystals were prepared by a facile room-temperature wet chemical method via simple variation of the synthesis parameters. Proper phase formation was confirmed by X-ray diffraction studies, whereas the morphological features were investigated using field emission scanning electron microscopy and transmission electron microscopy. The bonding information and the presence of organic functional groups within the synthesized nanostructures were confirmed using Fourier transform infrared spectroscopy. The work function of the material was calculated using first principles studies. In an attempt to explore the potential of the perovskites beyond photovoltaic applications, the field emission performance of the nanostructured CH3NH3PbI3 was investigated. The turn-on field (electric field corresponding to a 10 μA cm-2 current density) was obtained as 4.2 V μm-1 with the current density reaching up to 96 μA cm-2 for an inter-electrode spacing of 200 μm for the nanorod samples. The emission current stability was tested to be good enough for as long as 2 hours. Finally, finite element-based simulations were performed using ANSYS to obtain a theoretical perception of our experimental findings.

  13. Modulation of field emission properties of znO nanorods during arc discharge.

    Science.gov (United States)

    Fang, F; Kennedy, J; Carder, D A; Futter, J; Murmu, P; Markwitz, A

    2010-12-01

    Zinc oxide (ZnO) nanorods have been synthesized via the arc discharge method. Different oxygen partial pressures were applied in the arc discharge chamber to modulate the field emission properties of the as-synthesized ZnO nanorods. Scanning electron microscopy (SEM) was carried out to analyze the morphology of the ZnO nanorods. The ion beam analysis technique of proton induced X-ray emission (PIXE) was performed to probe the impurities in ZnO nanorods. SEM images clearly revealed the formation of randomly oriented ZnO nanorods with diameters between 10-50 nm. It was found that the morphology and the electrical properties of the ZnO nanorods were dependent on the oxygen partial pressure during arc discharge. In addition enhanced UV-sensitive photoconductivity was found for ZnO nanorods synthesized at high oxygen partial pressure during arc discharge. The field emission properties of the nanorods were studied. The turn-on field, which is defined at a current density of 10 microA cm(-2), was about 3 V microm(-1) for ZnO nanorods synthesized at 99% oxygen partial pressure during arc discharge. The turn-on field for ZnO nanorods increased with the decrease of oxygen partial pressure during arc discharge. The simplicity of the synthesis route coupled with the modulation of field emission properties due to the arc discharge method make the ZnO nanorods a promising candidate for a low cost and compact cold cathode material.

  14. SLAC T-510: Radio emission from particle cascades in the presence of a magnetic field

    Science.gov (United States)

    Mulrey, Katharine

    2017-03-01

    Cosmic ray induced particle cascades radiate in radio frequencies in the Earth's atmosphere. Geomagnetic and Askaryan emission provide an effective way to detect ultra-high energy cosmic rays. The SLAC T-510 experiment was the first to measure magnetically induced radiation from particle cascades in a controlled laboratory setting. An electron beam incident upon a dense dielectric target produced a particle cascade in the presence of a variable magnetic field. Antennas covering a band of 30-3000 MHz sampled RF emission in vertical and horizontal polarizations. Results from T-510 are compared to particle-level RF-emission simulations which are critical for reconstructing the energy and composition of detected ultra-high energy cosmic ray air showers. We discuss the experimental set up, the data processing, the systematic errors and the main results of the experiment, which we found in a good agreement with the simulations.

  15. Field Emission Characteristics of the Structure of Vertically Aligned Carbon Nanotube Bundles.

    Science.gov (United States)

    Lin, Pao-Hung; Sie, Cong-Lin; Chen, Ching-An; Chang, Hsuan-Chen; Shih, Yi-Ting; Chang, Hsin-Yueh; Su, Wei-Jhih; Lee, Kuei-Yi

    2015-12-01

    In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height (R) of field emitters. The hexagon arrangement with R = 2 had the lowest turn-on electric field (E to) and highest enhancement factor, whereas the square arrangement with R = 3 had the most stable field emission (FE) characteristic. The number density can reveal the correlation to the lowest E to and highest enhancement factor more effectively than can the R or L. The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents. The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

  16. HIGH-CURRENT COLD CATHODE FIELD EMISSION ARRAY FOR ELECTRON LENS APPLICATION

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L

    2012-12-28

    During Phase I, the following goals were achieved: (1) design and fabrication of a novel, nano-dimensional CNT field emitter assembly for high current density application, with high durability; (2) fabrication of a ceramic based micro channel plate (MCP) and characterization of its secondary electron emission; and (3) characterizing the CNT/MCP cathode for high field emission and durability. As a result of these achievements, a relatively high current density of ~ 1.2 A/cm2 from a CNT cathode and single channel MCP were measured. The emission current was also extremely stable with a peak-to-peak variation of only 1.8%. The emission current could be further enhanced to meet requirements for electron lens applications by increasing the number of MCP channels. A calculation for maximum possible current density with a 1200 channel/cm2 MCP, placed over a cathode with 1200 uniformly functioning CNTs, would be ~1.46 kA/cm2, neglecting space charge limitations. Clearly this level of emission is far greater than what is needed for the electron lens application, but it does offer a highly comforting margin to account for sub-standard emitters and/or to allow the lesser challenge of building a cathode with fewer channels/cm2. A satisfactory goal for the electron lens application would be a controllable emission of 2-4 mA per channel in an ensemble of 800-1200 uniformly-functioning channels/cm2, and a cathode with overall area of about 1 cm2.

  17. Direct probing of charge carrier behavior in multilayered organic light-emitting diode devices by time-resolved electric-field-induced sum-frequency generation spectroscopy

    Science.gov (United States)

    Miyamae, Takayuki; Takada, Noriyuki; Ohata, Hiroshi; Tsutsui, Tetsuo

    2017-10-01

    Time-resolved electric-field-induced sum-frequency generation (EFI-SFG) spectroscopy was employed to study the charge behavior of multilayer organic light-emitting diodes (OLEDs). Through application of the square wave pulse bias to the OLEDs, compensation for the polarization charges in the electron transport layer and the generation of 4,4‧-bis[N-(1-naphthyl-N-phenylamino)-biphenyl] (α-NPD) cations were observed. When the pulse voltage was turned off, the α-NPD cations immediately disappeared, confirming that charge recombination occurs at the interfaces. We therefore concluded that time-resolved EFI-SFG is useful for directly probing the carrier behavior in OLEDs in addition to identifying the origin of the charge carriers present in OLEDs.

  18. Incorporating denitrification-decomposition method to estimate field emissions for Life Cycle Assessment.

    Science.gov (United States)

    Deng, Yelin; Paraskevas, Dimos; Cao, Shi-Jie

    2017-09-01

    This study focuses on a detailed Life Cycle Assessment (LCA) for flax cultivation in Northern France. Nitrogen related field emissions are derived both from a process-oriented DeNitrification-DeComposition (DNDC) method and the generic Intergovernmental Panel on Climate Change (IPCC) method. Since the IPCC method is synthesised from field measurements at sites with various soil types, climate conditions, and crops, it contains significant uncertainties. In contrast, the outputs from the DNDC method are considered as more site specific as it is built according to complex models of soil science. As it is demonstrated in this paper the emission factors from the DNDC method and the recommended values from the IPCC method exhibit significant variations for the case of flax cultivation. The DNDC based emission factor for direct N2O emission, which is a strong greenhouse gas, is 0.25-0.5%, significantly lower than the recommend 1% level derived from the IPCC method. The DNDC method leads to a reduction of 17% in the impact category of climate change per kg retted flax straw production from the level obtained from the IPCC method. Much higher reductions are recorded for particulate matter formation, terrestrial acidification, and marine eutrophication impact categories. Meanwhile, based on the DNDC and IPCC methods, a comparative LCA per kg flax straw is presented. For both methods sensitivity analysis as well as comparison of uncertainties parameterisation of the N2O estimates via Monte-Carlo analysis are performed. The DNDC method incorporates more relevant field emissions from the agricultural life cycle phase, which can also improve the quality of the Life Cycle Inventory as well as allow more precise uncertainty calibration in the LCA inventory. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Field test of available methods to measure remotely SOx and NOx emissions from ships

    Science.gov (United States)

    Balzani Lööv, J. M.; Alfoldy, B.; Gast, L. F. L.; Hjorth, J.; Lagler, F.; Mellqvist, J.; Beecken, J.; Berg, N.; Duyzer, J.; Westrate, H.; Swart, D. P. J.; Berkhout, A. J. C.; Jalkanen, J.-P.; Prata, A. J.; van der Hoff, G. R.; Borowiak, A.

    2014-08-01

    Methods for the determination of ship fuel sulphur content and NOx emission factors based on remote measurements have been compared in the harbour of Rotterdam and compared to direct stack emission measurements on the ferry Stena Hollandica. The methods were selected based on a review of the available literature on ship emission measurements. They were either optical (LIDAR, Differential Optical Absorption Spectroscopy (DOAS), UV camera), combined with model-based estimates of fuel consumption, or based on the so called "sniffer" principle, where SO2 or NOx emission factors are determined from simultaneous measurement of the increase of CO2 and SO2 or NOx concentrations in the plume of the ship compared to the background. The measurements were performed from stations at land, from a boat and from a helicopter. Mobile measurement platforms were found to have important advantages compared to the land-based ones because they allow optimizing the sampling conditions and sampling from ships on the open sea. Although optical methods can provide reliable results it was found that at the state of the art level, the "sniffer" approach is the most convenient technique for determining both SO2 and NOx emission factors remotely. The average random error on the determination of SO2 emission factors comparing two identical instrumental set-ups was 6%. However, it was found that apparently minor differences in the instrumental characteristics, such as response time, could cause significant differences between the emission factors determined. Direct stack measurements showed that about 14% of the fuel sulphur content was not emitted as SO2. This was supported by the remote measurements and is in agreement with the results of other field studies.

  20. Solar wind charge exchange emission in the Chandra deep field north

    Energy Technology Data Exchange (ETDEWEB)

    Slavin, Jonathan D.; Wargelin, Bradford J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Koutroumpa, Dimitra [LATMOS/IPSL, CNRS, Université Versailles Saint Quentin, 11 Boulevard d' Alembert, F-78280, Guyancourt (France)

    2013-12-10

    The diffuse soft X-ray background comes from distant galaxies, from hot Galactic gas, and from within the solar system. The latter emission arises from charge exchange between highly charged solar wind ions and neutral gas. This so-called solar wind charge exchange (SWCX) emission is spatially and temporally variable and interferes with our measurements of more distant cosmic emission while also providing important information on the nature of the solar wind-interstellar medium interaction. We present the results of our analysis of eight Chandra observations of the Chandra Deep Field North (CDFN) with the goal of measuring the cosmic and SWCX contributions to the X-ray background. Our modeling of both geocoronal and heliospheric SWCX emission is the most detailed for any observation to date. After allowing for ∼30% uncertainty in the SWCX emission and subtracting it from the observational data, we estimate that the flux of cosmic background for the CDFN in the O VII Kα, Kβ, and O VIII Lyα lines totals 5.8 ± 1.1 photons s{sup –1} cm{sup –2} sr{sup –1} (or LU). Heliospheric SWCX emission varied for each observation due to differences in solar wind conditions and the line of sight through the solar system, but was typically about half as strong as the cosmic background (i.e., one-third of the total) in those lines. The modeled geocoronal emission was 0.82 LU in one observation but averaged only 0.15 LU in the others. Our measurement of the cosmic background is lower than but marginally consistent with previous estimates based on XMM-Newton data.

  1. Non-dipolar magnetic field models and patterns of radio emission: Uranus and Neptune compared

    Science.gov (United States)

    Evans, D. R.

    1994-01-01

    The magnetic field geometries of Uranus and Neptune are superficially similar, and are similarly unlike those of other planets: the field strengths are similar, and they contain extraordinarily large non-dipolar components. As a corollary, the best dipolar field models of each of the two planets comprises a dipole that is considerably offset from the planetary center and tilted away from the rotational axis. However, in other respects the best field models of the two planets are quite different. Uranus has a quadrupole model in which all the terms are well determined and in which none of the higher order terms is determined. To represent the magnetometer data acquired during Voyager's Neptune encounter requires a model of order 8 (instead of Uranus' order 2), yet many of the coefficients are poorly determined. A second model, an octupole model comprising the terms up to order three of the order 8 model, has been suggested by the magnetometer team as being useful; its use, however, is limited only to the region outside of about 2R(exp N), whereas planetary radio emissions have their sources well inside this surface. Computer code has been written that permits an analysis of the detailed motion of low energy charged particles moving in general planetary magnetic fields. At Uranus, this code reveals the existence of an isolated region of the inner magnetosphere above the day side in which particles may be trapped, separate from the more general magnetospheric trapping. An examination of the so-call ordinary mode uranian radio emissions leads us to believe that these emissions are in fact extraordinary mode emissions coming from particles trapped in this isolated region. A similar attempt to discover trapping regions at Neptune has proved, unfortunately, to be impossible. This arises from three factors: (1) the computation needed to track particles in an eighth order field is more than an order of magnitude greater than that needed to perform a similar calculation in a

  2. Emission Characteristics of Amorphous Silicon Field Emitter Arrays Sealed in a Vacuum Package

    Science.gov (United States)

    Gamo, Hidenori; Kai, Teruhiko; Kanemaru, Seigo; Itoh, Junji

    1999-12-01

    Emission characteristics of amorphous silicon field emitter arrays (a-Si FEAs) in a vacuum package sealed with TO-5 have been measured and evaluated. The TO-5 header mounted with a FEA, was inserted through a hole in a glass plate and was hermetically sealed to the glass plate using epoxy resin as a sealant. In the same a-Si FEA device, lower emission currents have been observed in the vacuum package, as compared with those measured in an ultra-high vacuum (UHV) chamber. On the other hand, an a-Si FEA monolithically integrated with a thin-film transistor (TFT) has exhibited almost the same emission characteristics both in the vacuum package and in the UHV chamber at the region of saturated emission currents due to the TFT function. A highly stable emission current of approximately 0.1 µA and with fluctuations of less than 2% has been achieved in the vacuum package at the TFT gate and the extraction voltages of 14 V and 150 V, respectively.

  3. Fabrication, characterization, cathodoluminescence, and field-emission properties of silica (SiO{sub 2}) nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Xu, J.Q. [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, 305-0044 Ibaraki (Japan); Department of Physics Electronic Engineering, Xinyang Normal University, Xinyang 464000 (China); Onodera, H.; Sekiguchi, T. [Advanced Electronic Materials Center, National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, 305-0044 Ibaraki (Japan); Golberg, D.; Bando, Y. [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, 305-0044 Ibaraki (Japan); Mori, T., E-mail: MORI.Takao@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, 305-0044 Ibaraki (Japan)

    2012-11-15

    High-quality one dimensional amorphous SiO{sub 2} nanostructures with different morphologies (nanowires and starfish-like nanostructures) are synthesized through a simple catalysis-free approach and effective thermal evaporation process. The morphologies, microstructures, and compositions of the products are investigated by X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A promising optical property (cathodoluminescence (CL) in a strong ultraviolet (UV) emission and a weak blue emission at room temperature) was detected in the as-synthesized nanostructures. Field-emission measurements show that the SiO{sub 2} nanostructures may also be a promising FE emitter candidate if we can improve the conductivity and decrease the density of the nanostructures. - Highlights: Black-Right-Pointing-Pointer A simple catalysis-free approach and effective thermal evaporation process Black-Right-Pointing-Pointer High-quality one dimensional amorphous SiO{sub 2} nanostructures Black-Right-Pointing-Pointer A strong ultraviolet (UV) emission and a weak blue emission at room temperature Black-Right-Pointing-Pointer A promising FE emitter's candidate.

  4. Black carbon cookstove emissions: A field assessment of 19 stove/fuel combinations

    Science.gov (United States)

    Garland, Charity; Delapena, Samantha; Prasad, Rajendra; L'Orange, Christian; Alexander, Donee; Johnson, Michael

    2017-11-01

    Black carbon (BC) emissions from household cookstoves consuming solid fuel produce approximately 25 percent of total anthropogenic BC emissions. The short atmospheric lifetime of BC means that reducing BC emissions would result in a faster climate response than mitigating CO2 and other long-lived greenhouse gases. This study presents the results of optical BC measurements of two new cookstove emissions field assessments and 17 archived cookstove datasets. BC was determined from attenuation of 880 nm light, which is strongly absorbed by BC, and linearly related between 1 and 125 attenuation units. A relationship was experimentally determined correlating BC mass deposition on quartz filters determined via thermal optical analysis (TOA) and on PTFE and quartz filters using transmissometry, yielding an attenuation cross-section (σATN) for both filter media types. σATN relates TOA measurements to optical measurements on PTFE and quartz (σATN(PTFE) = 13.7 cm-2 μg, R2 = 0.87, σATN(Quartz) = 15.6 cm-2 μg, R2 = 0.87). These filter-specific σATN, optical measurements of archived filters were used to determine BC emission factors and the fraction of particulate matter (PM) in the form of black carbon (BC/PM). The 19 stoves measured fell into five stove classes; simple wood, rocket, advanced biomass, simple charcoal, and advanced charcoal. Advanced biomass stoves include forced- and natural-draft gasifiers which use wood or biomass pellets as fuel. Of these classes, the simple wood and rocket stoves demonstrated the highest median BC emission factors, ranging from 0.051 to 0.14 g MJ-1. The lowest BC emission factors were seen in charcoal stoves, which corresponds to the generally low PM emission factors observed during charcoal combustion, ranging from 0.0084 to 0.014 g MJ-1. The advanced biomass stoves generally showed an improvement in BC emissions factors compared to simple wood and rocket stoves, ranging from 0.0031 to 0.071 g MJ-1. BC/PM ratios were highest for the

  5. Development of a Cryogenic Radiation Detector for Mapping Radio Frequency Superconducting Cavity Field Emissions

    CERN Document Server

    Dotson, Danny W

    2005-01-01

    There is a relationship between field emissions in a Super Conducting RF cavity and the production of radiation (mostly X-rays). External (room temperature) detectors are shielded from the onset of low energy X-rays by the vacuum and cryogenic stainless steel module walls. An internal measuring system for mapping field emissions would assist scientists and engineers in perfecting surface deposition and acid washing module surfaces. Two measurement systems are undergoing cryogenic testing at JLab. One is an active CsI photodiode array and the second is an X-ray film camera. The CsI array has operated sucessfully in a cavity in liquid Helium but saturated at higher power due to scattering in the cavity. A shield with an aperature similar to the X-ray film detector is being designed for the next series of tests which will be completed before PAC-05.

  6. Field emission from entangled carbon nanotubes coated on/in a hollow metallic tube

    CERN Document Server

    Tokura, Y; Ohigashi, N; Akita, S; Nakayama, Y; Imasaki, K; Mima, K; Nakai, S

    2001-01-01

    Field emission properties of entangled carbon nanotubes were studied for an electron beam source of Cherenkov or Smith-Purcell free electron laser. The cathode was made of carbon nanotubes which were mixed with a very small amount of resin and coated on/in a hollow metallic tube with outer diameter of 0.5 mm. The emission current was as high as 2.2 mA with a fluctuation of <4%. It seems that some entangled nanotubes were frayed under the high electric field and then electrons were emitted mainly from their tips. Reduction of the work function of the carbon nanotubes was observed with the degradation of vacuum pressure in the experimental apparatus.

  7. Effect of aircraft exhaust sulfur emissions on near field plume aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Brown, R.C.; Miake-Lye, R.C.; Anderson, M.R.; Kolb, C.E. [Aerodyne Research, Inc., Billerica, MA (United States). Center for Chemical and Environmental Physics

    1997-12-31

    Based on estimated exit plane sulfur speciation, a two dimensional, axisymmetric flow field model with coupled gas phase oxidation kinetics and aerosol nucleation and growth dynamics is used to evaluate the effect of fuel sulfur oxidation in the engine on the formation and growth of volatile H{sub 2}SO{sub 4}/H{sub 2}O aerosols in the near field plume. The conversion of fuel sulfur to sulfur trioxide and sulfuric acid in the engine is predicted to significantly increase the number density and surface area density of volatile H{sub 2}SO{sub 4}/H{sub 2}O aerosols and the chemical activation of exhaust soot particulates. This analysis indicates the need for experimental measurements of exhaust SO{sub x} emissions to fully assess the atmospheric impact of aircraft emissions. (author) 18 refs.; Submitted to Geophysical Research Letters

  8. Modified NEGF method for atomistic modeling of field emission from carbon nanotube

    Science.gov (United States)

    Monshipouri, Mahta; Behrooz, Milad; Abdi, Yaser

    2017-09-01

    A model to simulate the atomistic properties of the field emission (FE) from a zigzag-single walled carbon nanotube (Z-SWCNT) is presented. By a modification of the self-energy in non-equilibrium Green's function (NEGF) method, we simulated the field emission current, considering the quantum transport of electrons within the CNT. The paper involves investigation on the effect of the n index of the (n , 0) Z-SWCNT and the number of carbon dimers in the length direction as well as the anode-cathode separation on the FE current. Effect of additional gate voltage and substitutional impurities on the FE current is also studied. A comparison between the experimental data and simulation results are also included in the paper. The model can be used to consider different quantum effects of the atomistic emitter structure on the FE current.

  9. Fluxon induced surface resistance and field emission in niobium films at 1.5 GHz

    CERN Document Server

    Benvenuti, Cristoforo; Darriulat, Pierre; Peck, M A; Valente, A M; Van't Hof, C A

    2001-01-01

    The surface resistance of superconducting niobium films induced by the presence of trapped magnetic flux, presumably in the form of a pinned fluxon lattice, is shown to be modified by the presence of a field emitting impurity or defect. The modification takes the form of an additional surface resistance proportional to the density of the fluxon lattice and increasing linearly with the amplitude of the microwave above a threshold significantly lower than the field emission threshold. Such an effect, a precursor of electron emission, is observed for the first time in a study using radiofrequency cavities operating at their fundamental 1.5 GHz frequency. The measured properties of the additional surface resistance severely constrain possible explanations of the observed effect. (23 refs).

  10. Uncertainty budget and interlaboratory field tests in SO2 and NOx emission measurements

    OpenAIRE

    Poulleau, Jean; Raventos, Cécile; Blank, Frans; Emmenegger, Lukas; Gould, Richard; Kassman, Hakan; Pilage, Emile; Reynaud, Serge; Rokkjaer, Joern; Waeber, Michael

    2004-01-01

    International audience; This paper compares two techniques to assess uncertainty on emission measurements. The first one, described in ISO 14956, gives an appropriate procedure to establish uncertainty budgets from systematic assessment of factors influencing the result. The second approach consists in the quantification of the fidelity of the method during inter and intra-laboratory field experiments set out according to ISO 5725-2. The comparison has been carried out for two reference metho...

  11. Electron emission from conductors subjected to intense, short-pulse electric fields

    Science.gov (United States)

    Scarpetti, R. D.; Goerz, D. A.; Bowen, P. R.; Hodgin, R. L.; Wong, K. C.; Champney, P. D'a.

    1987-06-01

    We studied electron emission from metal electrodes subjected to electric fields ranging from 0.5 to 2.5 MV/cm for pulse durations of 3 to 10 ns. We used two high-voltage pulsers for these tests; a 500 to 700 kV, 72 ohm pulser that generated a 3 ns Gaussian pulse; and a 2 MV, 60 ohm pulser that generated a 10 ns flat-top pulse with a 1-ns risetime. The high voltage levels allowed emission studies using electrode spacings of several millimeters to several centimeters. Our studies emphasized bare and anodized aluminum surface shaving surface finishes that ranged from rolled stock to machined finishes of 2 to 400 micron-in roughness. We also investigated polished stainless steel and brass. Emphasis was on first-shot performance with subsequent pulses applied to check for possible conditioning. The background pressure was typically .00005 Torr. Our studies showed that for 10 ns pulse lengths, anodized aluminum surfaces could hold off more than twice the electric field strength of bare aluminum surfaces without appreciable electron emission. Anodized surfaces performed well at 1.0 to 1.5 MV/cm, while bare surfaces emitted at 0.5 to 0.7 MV/cm. For the shorter, 3 ns pulse lengths, anodizing was less effective at improving suppression of electron emission, while surface finish became the important factor. Electrodes with surface finishes of 40 micro-in or better roughness performed well at field strengths of up to 2.4 MV/cm. The behavior of velvet cloth as an emitter was also investigated using the 3 ns pulser. We found that velvet would emit within 3 ns at field strengths approaching 100 kV/cm.

  12. Stochastic fields method for sub-grid scale emission heterogeneity in mesoscale atmospheric dispersion models

    OpenAIRE

    M. Cassiani; Vinuesa, J.F.; Galmarini, S.; Denby, B

    2010-01-01

    The stochastic fields method for turbulent reacting flows has been applied to the issue of sub-grid scale emission heterogeneity in a mesoscale model. This method is a solution technique for the probability density function (PDF) transport equation and can be seen as a straightforward extension of currently used mesoscale dispersion models. It has been implemented in an existing mesoscale model and the results are compared with Large-Eddy Simulation (LES) data devised to test specifically the...

  13. The improvement of the field emission properties from graphene films: Ti transition layer and annealing process

    OpenAIRE

    Jun Li; Jiangtao Chen; Baomin Luo; Xingbin Yan; Qunji Xue

    2012-01-01

    Chemical-reduced graphene oxide (rGO) films were deposited on titanium (Ti)-coated silicon substrates by a simple electrophoretic deposition. The rGO films were annealed under argon atmosphere at different temperatures. The morphology and microstructure of the rGO films before and after annealing were characterized using scanning electron microscope, X-ray diffraction and Raman spectroscope. The field emission behaviors from these rGO films were investigated. The results show that, Ti-based t...

  14. Statistical simulation of the energy spectra of field-emission electrons

    Science.gov (United States)

    Egorov, N. V.; Antonov, A. Yu.; Demchenko, N. S.

    2017-02-01

    Random energies of electrons that escape from the source in the course of field emission are simulated using energy spectra. A relationship of the random values of total energy and the energy related to the normal (with respect to surface) component of momentum is established. A family of quadrature formulas needed for the integration of the distribution density of particles is analyzed. A hypothesis on the compliance of selected random energies with desired distribution laws is statistically tested.

  15. Curvature aided efficient axial field emission from carbon nanofiber–reduced graphene oxide superstructures on tungsten wire substrate

    Energy Technology Data Exchange (ETDEWEB)

    Jha, Arunava [School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700032 (India); Roy, Rajarshi; Sen, Dipayan [Thin Film and Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700032 (India); Chattopadhyay, Kalyan K., E-mail: kalyan_chattopadhyay@yahoo.com [School of Materials Science and Nanotechnology, Jadavpur University, Kolkata 700032 (India); Thin Film and Nanoscience Laboratory, Department of Physics, Jadavpur University, Kolkata 700032 (India)

    2016-03-15

    Graphical abstract: - Highlights: • Efficient axial field emitter was fabricated through deposition of thin RGO layer by Langmuir–Blodgett method. • Tungsten wire substrate was used. • The CNF–RGO superstructure produced better field emission characteristics compared to bare CNF. - Abstract: Field emission characteristics found in reduced graphene oxide (RGO) and RGO based composite systems have always been an area of research interest mainly due to presence of prolific quasi aligned edges working as emitter sites. However, the specific role and extent of edge curvature geometry in RGO systems in regards to the enhancement of field emission has not discussed thoroughly prior to this work. In this work we demonstrate enhanced axial field emission due to top assembly of thin RGO layer over a quasi-vertically aligned carbon nanofiber thin film supported on a tungsten wire substrate. Furthermore, simulation analysis for our RGO based hybrid system using finite element modeling showed that two-stage local field amplification in RGO is responsible for the overall improvement of field emission characteristics. In support of our findings, a tentative explanation has been proposed based on the additional emission from RGO edges in between the CNF network resulting to the enhancement of axial field emission in the nanocomposite superstructure.

  16. Active vacuum brazing of CNT films to metal substrates for superior electron field emission performance.

    Science.gov (United States)

    Longtin, Rémi; Ramon Sanchez-Valencia, Juan; Shorubalko, Ivan; Furrer, Roman; Hack, Erwin; Elsener, Hansrudolf; Gröning, Oliver; Greenwood, Paul; Rupesinghe, Nalin; Teo, Kenneth; Leinenbach, Christian; Gröning, Pierangelo

    2015-02-01

    The joining of macroscopic films of vertically aligned multiwalled carbon nanotubes (CNTs) to titanium substrates is demonstrated by active vacuum brazing at 820 °C with a Ag-Cu-Ti alloy and at 880 °C with a Cu-Sn-Ti-Zr alloy. The brazing methodology was elaborated in order to enable the production of highly electrically and thermally conductive CNT/metal substrate contacts. The interfacial electrical resistances of the joints were measured to be as low as 0.35 Ω. The improved interfacial transport properties in the brazed films lead to superior electron field-emission properties when compared to the as-grown films. An emission current of 150 μA was drawn from the brazed nanotubes at an applied electric field of 0.6 V μm-1. The improvement in electron field-emission is mainly attributed to the reduction of the contact resistance between the nanotubes and the substrate. The joints have high re-melting temperatures up to the solidus temperatures of the alloys; far greater than what is achievable with standard solders, thus expanding the application potential of CNT films to high-current and high-power applications where substantial frictional or resistive heating is expected.

  17. Electron field emission from freestanding Diamond nanomembranes and Application to time-of-flight mass spectrometry

    Science.gov (United States)

    Kim, Hyunseok; Park, Jonghoo; Shin, Hyuncheol; Blick, Robert H.

    2013-03-01

    We introduce a prototype of a freestanding diamond nanomembrane for large protein detection in time-of-flight mass spectrometry. Doped diamond as a material for mass spectroscopy is extremely interesting due to its mechanical and electrical properties. The freestanding diamond nanomembranes we are able to fabricate have lateral extensions of 400 μm × 400 μm with a thickness of 100nm. We employ optical lithography and a Buffered Oxide Etch (BOE) of SiO2 followed by anisotropic etching of the substrate silicon using TMAH solution and finally removing SiO2. The electron field emission from the surface of the membrane is traced in the IV characteristics at room temperature. The membrane is then applied for detection of the large ionized proteins using time-of-flight mass spectrometry. Ion detection is demonstrated in our nanomembrane MALDI-TOF analysis of Insulin (5,735 Da). That is when the ions with a large kinetic energy bombard the nanomembrane, their energy is thermalized upon impact into phonons. The phonons give a thermal energy to the electrons with the membrane, which are then excited to higher energetic states. Given an extraction voltage this leads to electron field emission from the membrane which we labeled phonon-assisted field emission (PAFE). In other words, the MALDI mass spectra are obtained by exploiting ballistic phonon propagation and quasi-diffusive phonon propagation.

  18. Enhancement of Field Emission Properties of Carbon Nanotubes by ECR-Plasma Treatment

    Directory of Open Access Journals (Sweden)

    Javid Ali

    2014-01-01

    Full Text Available We report a significant improvement in electron field emission property of carbon nanotubes film by using an electron cyclotron resonance plasma treatment. Our research results reveal that plasma treatment can modify the surface morphology and enhance the field emission characteristics of carbon nanotubes. Raman spectra indicate that plasma treated CNTs sample has lesser defects. Before plasma treatment, low current density of 6.5 mA/cm2 at 3.0 V/μm and at a high turn-on field Eto of 2.4 V/μm was observed. ECR plasma treated CNTs showed a high current density of 20.0 mA/cm2 at 3.0 V/μm and at a low Eto of 1.6 V/μm. The calculated enhancement factors are 694 and 8721 for ECR-plasma untreated and treated carbon nanotubes, respectively. We found an increase in the enhancement factor and emission current after the ECR-plasma treatment. This may be attributed to creation of geometrical features through the removal of amorphous carbon and catalyst particles.

  19. Fabrication and temperature-dependent field-emission properties of bundlelike VO2 nanostructures.

    Science.gov (United States)

    Yin, Haihong; Luo, Min; Yu, Ke; Gao, Yanfeng; Huang, Rong; Zhang, Zhengli; Zeng, Min; Cao, Chuanxiang; Zhu, Ziqiang

    2011-06-01

    Bundlelike VO(2)(B) nanostructures were synthesized via a hydrothermal method, and VO(2)(M(1)/R) nanobundles were obtained after a heat-treatment process. Structural characterization shows that these nanobundles are self-assembled by VO(2) nanowires, and VO(2)(M(1)/R) nanobundles have better crystallinity. Temperature-dependent field-emission (FE) measurement indicates that FE properties of these two phases of nanobundles can both be improved by increasing the ambient temperature. Moreover, for the VO(2)(M(1)/R) nanobundles, their FE properties are also strongly dependent on the temperature-induced metal-insulator transitions process. Compared with poor FE properties found in the insulating phase, FE properties were significantly improved by increasing the temperature, and about a three-orders-of-magnitude increasing of the emission current density has been observed at a fixed field of 6 V/μm. Work function measurement and density-functional theory calculations indicated that the decrease of work function with temperature is the main reason that caused the improvement of FE properties. These characteristics make VO(2)(M(1)/R) a candidate material for application of new type of temperature-controlled field emitters, whose emission density can be adjusted by ambient temperature. © 2011 American Chemical Society

  20. Aqueous Phase Synthesis and Enhanced Field Emission Properties of ZnO-Sulfide Heterojunction Nanowires

    OpenAIRE

    Guojing Wang; Zhengcao Li; Mingyang Li; Chienhua Chen; Shasha Lv; Jiecui Liao

    2016-01-01

    ZnO-CdS, ZnO-ZnS, and ZnO-Ag2S core-shell heterojunction structures were fabricated using low-temperature, facile and simple aqueous solution approaches. The polycrystalline sulfide shells effectively enhance the field emission (FE) properties of ZnO nanowires arrays (NWAs). This results from the formation of the staggered gap heterointerface (ZnO-sulfide) which could lead to an energy well at the interfaces. Hence, electrons can be collected when an electric field is applied. It is observed ...

  1. Imaging the atomic orbitals of carbon atomic chains with field-emission electron microscopy

    Science.gov (United States)

    Mikhailovskij, I. M.; Sadanov, E. V.; Mazilova, T. I.; Ksenofontov, V. A.; Velicodnaja, O. A.

    2009-10-01

    A recently developed high-field technique of atomic chains preparation has made it possible to attain the ultrahigh resolution of field-emission electron microscopy (FEEM), which can be used to direct imaging the intra-atomic electronic structure. By applying cryogenic FEEM, we are able to resolve the spatial configuration of atomic orbitals, which correspond to quantized states of the end atom in free-standing carbon atomic chains. Knowledge of the intra-atomic structure will make it possible to visualize generic aspects of quantum mechanics and also lead to approaches for a wide range of nanotechnological applications.

  2. Chirped Auger electron emission due to field-assisted post-collision interaction

    Directory of Open Access Journals (Sweden)

    Bonitz M.

    2013-03-01

    Full Text Available We have investigated the Auger decay in the temporal domain by applying a terahertz streaking light field. Xenon and krypton atoms were studied by implementing the free-electron laser in Hamburg (FLASH as well as a source of high-order harmonic radiation combined with terahertz pulses from an optical rectification source. The observed linewidth asymmetries in the streaked spectra suggest a chirped Auger electron emission which is understood in terms of field-assisted post-collision interaction. The experimentally obtained results agree well with model calculations.

  3. Aeolian dust emissions in Southern Africa: field measurements of dynamics and drivers

    Science.gov (United States)

    Wiggs, Giles; Thomas, David; Washington, Richard; King, James; Eckardt, Frank; Bryant, Robert; Nield, Joanna; Dansie, Andrew; Baddock, Matthew; Haustein, Karsten; Engelstaedter, Sebastian; von Holdt, Johannah; Hipondoka, Martin; Seely, Mary

    2016-04-01

    Airborne dust derived from the world's deserts is a critical component of Earth System behaviour, affecting atmospheric, oceanic, biological, and terrestrial processes as well as human health and activities. However, very few data have been collected on the factors that control dust emission from major source areas, or on the characteristics of the dust that is emitted. Such a paucity of data limits the ability of climate models to properly account for the radiative and dynamical impacts triggered by atmospheric dust. This paper presents field data from the DO4 Models (Dust Observations for Models) project that aims to understand the drivers of variability in dust emission processes from major source areas in southern Africa. Data are presented from three field campaigns undertaken between 2011 and 2015. We analysed remote sensing data to identify the key geomorphological units in southern Africa which are responsible for emission of atmospheric dust. These are the Makgadikgadi pans complex in northern Botswana, the ephemeral river valleys of western Namibia, and Etosha Pan in northern Namibia. Etosha Pan is widely recognised as perhaps the most significant source of atmospheric dust in the southern hemisphere. We deployed an array of field equipment within each source region to measure the variability in and dynamics of aeolian erosivity, as well as dust concentration and flux characteristics. This equipment included up to 11 meteorological stations measuring wind shear stress and other standard climatic parameters, Cimel sun photometers, a LiDAR, sediment transport detectors, high-frequency dust concentration monitors, and dust flux samplers. Further data were gathered at each site on the dynamics of surface characteristics and erodibility parameters that impact upon erosion thresholds. These data were augmented by use of a Pi-Swerl portable wind tunnel. Our data represent the first collected at source for these key dust emission areas and highlight the

  4. A fast draw. Analysis of a level playing field for a high-speed line and low cost carriers; Snel naar gelijk spel. Aanzet tot analyse van een gelijk speelveld voor hoge snelheidslijn en low cost carriers

    Energy Technology Data Exchange (ETDEWEB)

    Van Essen, H.P.; Warringa, G.E.A.; Boon, B.H.

    2004-11-01

    For several lines in Europe Low Cost Carriers (LCCs) are considered as competitive means of transportation for high-speed lines (HSL in Dutch). A desk study has been carried out to gain insight in marginal external costs and levies of LCCs and HSLs in the Netherlands. The results can contribute to the discussion on a level playing field in this sector. Also an overview is given of other costs and levies. [Dutch] Low Cost Carriers (LCC's) worden op verschillende trajecten in Europa nogal eens beschouwd als concurrenten van de hoge snelheidslijnen (HSL). Om inzicht te verkrijgen in de externe kosten van LCC's en HSL en daarmee een bijdrage te leveren aan de discussie over een gelijk speelveld ('level playing field') heeft CE in opdracht van het Ministerie van Verkeer en Waterstaat DG Luchtvaart een deskstudie uitgevoerd naar de marginale externe kosten en heffingen van LCC's en HSL in Nederland. Daarnaast is een globale inventarisatie gemaakt van de overige kosten en heffingen. Tegenover de meeste externe kostenposten staat geen noemenswaardige heffing om de kosten te internaliseren,met als enige uitzondering geluidsoverlast door het vliegtuig. Dit betekent dat in het algemeen er te weinig rekening wordt gehouden met de externe effecten die zowel de HSL als het vliegtuig veroorzaken. Deze studie vormt een eerste aanzet tot een antwoord op de vraag naar een gelijk speelveld en rechtvaardigt geen definitief oordeel. Voor een eerlijke vergelijking tussen HSL en LCC dienen naast de externe kosten, in het bijzonder de kosten, afschrijvingen en overdrachten van bestaande luchtvaart- en HSL-infrastructuur en verschillende vormen van directe en indirecte overheidssteun nader te worden onderzocht.

  5. Tip-morphology-dependent field emission from ZnO nanorod arrays

    Energy Technology Data Exchange (ETDEWEB)

    Pan Nan; Xue Haizhou; Yu Minghui; Cui Xuefeng; Wang Xiaoping; Hou, J G [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Huang Jianxing; Deng, S Z, E-mail: xpwang@ustc.edu.cn [Guangdong Provincial Key Laboratory of Display Materials and Technology, Sun Yat-Sen University, Guangzhou, Guangdong 510275 (China)

    2010-06-04

    Vertically well-aligned ZnO nanorod arrays with three kinds of tip morphology-abruptly sharpened, tapered and plane-have been controllably fabricated with wafer size uniformity by vapor phase transport and condensation. Except that the tip morphology is distinctly different, all of these nanorods are single crystalline, growing along their wurtzite (0001) axis, with similar diameters, lengths and densities. The field emission properties of these nanorod arrays are comparatively investigated and are found to be strongly affected by the tip morphology. A nanorod with the abruptly sharpened tip possesses the lowest turn-on and threshold electric fields as well as the highest field enhancement factor. Further analysis reveals that the abruptly sharpened tip morphology can reduce the screening effect more efficiently than the others. These results are very helpful for the design, fabrication and optimization of integrated field emitters using 1D nanostructures as the cathode material.

  6. Controlling quantum-dot light absorption and emission by a surface-plasmon field.

    Science.gov (United States)

    Huang, Danhong; Easter, Michelle; Gumbs, Godfrey; Maradudin, A A; Lin, Shawn-Yu; Cardimona, D A; Zhang, Xiang

    2014-11-03

    The possibility for controlling both the probe-field optical gain and absorption, as well as photon conversion by a surface-plasmon-polariton near field is explored for a quantum dot located above a metal surface. In contrast to the linear response in the weak-coupling regime, the calculated spectra show an induced optical gain and a triply-split spontaneous emission peak resulting from the interference between the surface-plasmon field and the probe or self-emitted light field in such a strongly-coupled nonlinear system. Our result on the control of the mediated photon-photon interaction, very similar to the 'gate' control in an optical transistor, may be experimentally observable and applied to ultra-fast intrachip/interchip optical interconnects, improvement in the performance of fiber-optic communication networks, and developments of optical digital computers and quantum communications.

  7. Electronic structure and field emission properties of nitrogen doped graphene nano-flakes (GNFs:N) and carbon nanotubes (CNTs:N)

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Sekhar C., E-mail: Raysc@unisa.ac.za [Department of Physics, College of Science, Engineering and Technology, University of South Africa, Private Bag X6, Florida, 1710, Science Campus, Christiaan de Wet and Pioneer Avenue, Florida Park, Johannesburg (South Africa); Pong, W.F. [Department of Physics, Tamkang University, Tamsui 251, New Taipei City, Taiwan (China); Papakonstantinou, P. [Nanotechnology and Integrated Bio-Engineering Centre, University of Ulster, Shore Road, Newtownabbey BT37 0QB (United Kingdom)

    2016-09-01

    Highlights: • Nitrogen doped graphene nano-flakes (GNFs:N) and carbon nano-tubes (CNTs:N) are used to study the electronic/bonding structure along with their defects state. • The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy used for the study of the defects states of CNTs:N than GNFs:N. • The electron field emission result shows that the turn on electric field is lower in case of CNTs:N than GNFs:N. • All results are good agreement with XANES and the results obtained from Raman spectra. - Abstract: Substitution of hetero-atom doping is a promising route to modulate the outstanding material properties of carbon nanotubes and graphene for customized applications. Nitrogen-doping has been introduced to ensure tunable work-function, enhanced n-type carrier concentration, diminished surface energy, and manageable polarization. Along with the promising assessment of N-doping effects, research on the N-doped carbon based composite structures is emerging for the synergistic integration with various functional materials. Nitrogen undoped/doped graphene nano-flakes (GNFs/GNFs:N) and multiwall carbon nano-tubes (MWCNTs/MWCNTs:N) are used for comparative study of their electronic/bonding structure along with their defects state. X-ray absorption near edge structure (XANES) spectroscopy shows that the GNFs:N produce mainly pyridine like structure; whereas MWCNTs:N shows graphitic nitrogen atoms are attached with the carbon lattice. The I{sub D}/I{sub G} ratio obtained from Raman spectroscopy shows that the defects is higher in MWCNTs:N than GNFs:N. The electron field emission result shows that the turn on electric field is lower (higher electron emission current) in case of MWCNTs:N than GNFs:N and are good agreement with XANES and the results obtained from Raman spectra.

  8. Ammonia and greenhouse gas emissions from a subtropical wheat field under different nitrogen fertilization strategies.

    Science.gov (United States)

    Liu, Shuai; Wang, Jim J; Tian, Zhou; Wang, Xudong; Harrison, Stephen

    2017-07-01

    Minimizing soil ammonia (NH 3 ) and nitrous oxide (N 2 O) emission factors (EFs) has significant implications in regional air quality and greenhouse gas (GHG) emissions besides nitrogen (N) nutrient loss. The aim of this study was to investigate the impacts of different N fertilizer treatments of conventional urea, polymer-coated urea, ammonia sulfate, urease inhibitor (NBPT, N-(n-butyl) thiophosphoric triamide)-treated urea, and nitrification inhibitor (DCD, dicyandiamide)-treated urea on emissions of NH 3 and GHGs from subtropical wheat cultivation. A field study was established in a Cancienne silt loam soil. During growth season, NH 3 emission following N fertilization was characterized using active chamber method whereas GHG emissions of N 2 O, carbon dioxide (CO 2 ), and methane (CH 4 ) were by passive chamber method. The results showed that coated urea exhibited the largest reduction (49%) in the EF of NH 3 -N followed by NBPT-treated urea (39%) and DCD-treated urea (24%) over conventional urea, whereas DCD-treated urea had the greatest suppression on N 2 O-N (87%) followed by coated urea (76%) and NBPT-treated urea (69%). Split fertilization of ammonium sulfate-urea significantly lowered both NH 3 -N and N 2 O-N EF values but split urea treatment had no impact over one-time application of urea. Both NBPT and DCD-treated urea treatments lowered CO 2 -C flux but had no effect on CH 4 -C flux. Overall, application of coated urea or urea with NPBT or DCD could be used as a mitigation strategy for reducing NH 3 and N 2 O emissions in subtropical wheat production in Southern USA. Copyright © 2017. Published by Elsevier B.V.

  9. Transformation of ZnO nanorods into nanotubes and their field emission studies

    Science.gov (United States)

    Khare, Ruchita; More, Mahendra A.; Chakravarty, Disha

    2015-03-01

    Synthesis of vertically well-aligned ZnO nanorods on Au coated silicon substrate by a facile electrochemical route has been carried out. The transformation of as-deposited ZnO nanorods into nanotubes was achieved via simple, single step, chemical etching process using KOH as etchant. The influence of various parameters of the etching, such as concentration of the etchant, bath temperature and duration on morphological features of the ZnO nanotubes has been investigated. It is observed that formation of ZnO nanotubes with smooth inner and outer surfaces is achieved when the etching was performed at 65°C for 1 h duration, and at higher bath temperatures and longer durations, over etching of nanorods takes place. Field emission investigations of the ZnO nanorods and nanotubes were carried out at base pressure of 1 × 10-8 mbar. The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 7.2 V/μm and 8.4 V/μm, corresponding to ZnO nanorods and nanotubes emitter respectively, and emission current density of 352.5 μA/cm2 has been drawn from the ZnO nanotubes emitter at an applied field of 13.77 V/μm. The ZnO nanotubes emitter exhibits excellent emission current stability at the preset value of 1 μA over duration of 3 h, indicating its potential as electron source for practical applications.

  10. Laboratory and field measurements of enantiomeric monoterpene emissions as a function of chemotype, light and temperature

    Science.gov (United States)

    Song, W.; Staudt, M.; Bourgeois, I.; Williams, J.

    2014-03-01

    Plants emit significant amounts of monoterpenes into the earth's atmosphere, where they react rapidly to form a multitude of gas phase species and particles. Many monoterpenes exist in mirror-image forms or enantiomers. In this study the enantiomeric monoterpene profile for several representative plants (Quercus ilex L., Rosmarinus officinalis L., and Pinus halepensis Mill.) was investigated as a function of chemotype, light and temperature both in the laboratory and in the field. Analysis of enantiomeric monoterpenes from 19 Quercus ilex individuals from Southern France and Spain revealed four regiospecific chemotypes (genetically fixed emission patterns). In agreement with previous work, only Quercus ilex emissions increased strongly with light. However, for all three plant species no consistent enantiomeric variation was observed as a function of light, and the enantiomeric ratio of α-pinene was found to vary by less than 20% from 100 and 1000 μmol m-2 s-1 PAR (photosynthetically active radiation). The rate of monoterpene emission increased with temperature from all three plant species, but little variation in the enantiomeric distribution of α-pinene was observed with temperature. There was more enantiomeric variability between individuals of the same species than could be induced by either light or temperature. Field measurements of α-pinene enantiomer mixing ratios in the air, taken at a Quercus ilex forest in Southern France, and several other previously reported field enantiomeric ratio diel cycle profiles are compared. All show smoothly varying diel cycles (some positive and some negative) even over changing wind directions. This is surprising in comparison with variations of enantiomeric emission patterns shown by individuals of the same species.

  11. Nitrous oxide emission from an agricultural field fertilized with liquid lagoonal swine effluent

    Science.gov (United States)

    Whalen, S. C.; Phillips, R. L.; Fischer, E. N.

    2000-06-01

    Contemporary agriculture is characterized by the intensive production of livestock in confined facilities and land application of stored waste as an organic fertilizer. Emission of nitrous oxide (N2O) from receiving soils is an important but poorly constrained term in the atmospheric N2O budget. In particular, there are few data for N2O emissions from spray fields associated with industrial scale swine production facilities that have rapidly expanded in the southeastern United States. In an intensive, 24-day investigation over three spray cycles, we followed the time course for changes in N2O emission and soil physicochemical variables in an agricultural field irrigated with liquid lagoonal swine effluent. The total N (535 mg L-1) of the liquid waste was almost entirely NH4+-N (>90%) and thus had a low mineralization potential. Soil profiles for nitrification and denitrification indicated that >90% of potential activity was localized in the surface 20 cm. Application of this liquid fertilizer to warm (19° to 28°C) soils in a form that is both readily volatilized and immediately utilizable by the endogenous N-cycling microbial community resulted in a sharp decline in soil NH4+-N and supported a rapid but short-lived (i.e., days) burst of nitrification, denitrification, and N2O emission. Nitrous oxide fluxes as high as 9200 μg N2O-N m-2 h-1 were observed shortly after fertilization, but emissions decreased to prefertilization levels within a few days. Poor correlations between N2O efflux and soil physicochemical variables (temperature, moisture, NO3--N, NH4+-N) and fertilizer loading rate point to the complexity of interacting factors affecting N2O production and emission. Total fertilizer N applied and N2O-N emitted were 29.7 g m-2 (297 kg N ha-1) and 395 mg m-2, respectively. The fractional loss of applied N to N2O (corrected for background emission) was 1.4%, in agreement with the mean of 1.25% reported for mineral fertilizers. The direct effects of fertilizer

  12. Study of carrier blocking property of poly-linalyl acetate thin layer by electric-field-induced optical second-harmonic generation measurement

    Science.gov (United States)

    Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa; Anderson, Liam J.; Jacob, Mohan V.

    2014-02-01

    By using electric-field-induced optical second-harmonic generation (EFISHG) measurement, we studied the carrier-blocking property of poly-linalyl acetate (PLA) thin layers sandwiched in indium-zinc-oxide (IZO)/PLA/C60/Al double-layer diodes. Results showed that the PLA layer totally blocks electrons crossing the C60 layer, and also blocks holes entering from the IZO layer. The EFISHG measurement effectively substantiates the hole-blocking electron-blocking property of the PLA layer sandwiched in double layer diodes.

  13. Effectively Improved Field Emission Properties of Multiwalled Carbon Nanotubes/Graphenes Composite Field Emitter by Covering on the Si Pyramidal Structure

    DEFF Research Database (Denmark)

    Chen, Leifeng; Yu, Hua; Zhong, Jiasong

    2015-01-01

    The composite nanostructure emitter of multiwalled carbon nanotubes and graphenes was deposited on pyramidal silicon substrate by the simple larger scale electrophoretic deposition process. The field emission (FE) properties of the composite/pyramidal Si device were greatly improved compared...

  14. Synthesis and photoluminescence, field emission properties of stalactite-like ZnS-ZnO composite nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Li, J.; Fang, G.J. [Wuhan University, Key Laboratory of Acoustic and Photonic Materials and Devices of Ministry of Education, and Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan (China); Chinese Academy of Sciences, State Key Laboratory of Transducer Technology, Shanghai (China); Li, C.; Yuan, L.Y.; Ai, L.; Liu, N.S.; Zhao, D.S.; Zhao, X.Z. [Wuhan University, Key Laboratory of Acoustic and Photonic Materials and Devices of Ministry of Education, and Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan (China); Ding, K.; Li, G.H. [Chinese Academy of Sciences, National Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Beijing (China)

    2008-03-15

    Wurtzite stalactite-like quasi-one-dimensional ZnS nanoarrays with ZnO protuberances were synthesized through a thermal evaporation route. The structure and morphology of the samples are studied and the growth mechanism is discussed. X-ray diffraction (XRD) results show both the ZnS stem and the ZnO protuberances have wurtzite structure and show preferred [001] oriented growth. The photoluminescence and field emission properties have also been investigated. Room temperature photoluminescence result shows it has a strong green light emission, which has potential application for green light emitter. Experimental results also show that the stalactite arrays have a good field emission property, with turn-on field of 11.4 V/{mu}m, and threshold field of 16 V/{mu}m. The ZnO protuberances on the ZnS stem might enhance the field emission notably. (orig.)

  15. The effect of surface treatments on the field emission characteristics of patterned carbon nanotubes on KOVAR substrate

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Keunsoo; Lee, Yang Doo; Kang, Byung Hyun; Dong, Ki-Young; Baek, Jinho; Fai, Vincent Lau Chun [Korea University, Display and Nanosystem Laboratory, College of Engineering (Korea, Republic of); Kim, Won-Seok [Electronic Materials Research Group, Hyosung Corporation, R and D Business Laboratory (Korea, Republic of); Yang, Cheol-Min [Korea Institute of Science and Technology, Institute of Advanced Composite Materials (Korea, Republic of); Ju, Byeong-Kwon, E-mail: bkju@korea.ac.kr [Korea University, Display and Nanosystem Laboratory, College of Engineering (Korea, Republic of)

    2012-07-15

    The field emission characteristics of patterned carbon nanotubes (CNTs) the average diameter of which is 16 nm cathodes on substrates with different surface treatments were investigated. The surface treatments of the substrate were performed by nickel electroless plating and palladium coating, which is an activation procedure of electroless plating. CNTs were patterned on the surface-treated substrate with radius of 200 {mu}m through conventional photolithography process. Two deposition methods, electrophoresis deposition and spray deposition, were used to investigate the effects of deposition methods on field emission characteristics of the cathodes. It was revealed that the two deposition methods showed similar turn-on field trends, which means that the different surface morphologies of the substrates have more influence on the field emission characteristics than the different deposition methods performed in this study. Through the surface treatments, the roughness of the surface increased and cathodes with a high roughness factor showed better field emission characteristics compared to non-treated ones.

  16. Aqueous Phase Synthesis and Enhanced Field Emission Properties of ZnO-Sulfide Heterojunction Nanowires

    Science.gov (United States)

    Wang, Guojing; Li, Zhengcao; Li, Mingyang; Chen, Chienhua; Lv, Shasha; Liao, Jiecui

    2016-01-01

    ZnO-CdS, ZnO-ZnS, and ZnO-Ag2S core-shell heterojunction structures were fabricated using low-temperature, facile and simple aqueous solution approaches. The polycrystalline sulfide shells effectively enhance the field emission (FE) properties of ZnO nanowires arrays (NWAs). This results from the formation of the staggered gap heterointerface (ZnO-sulfide) which could lead to an energy well at the interfaces. Hence, electrons can be collected when an electric field is applied. It is observed that ZnO-ZnS NWAs have the lowest turn-on field (3.0 Vμm−1), compared with ZnO-CdS NWAs (6.3 Vμm−1) and ZnO-Ag2S NWAs (5.0 Vμm−1). This may be associated with the pyramid-like ZnS shell which increases the number of emission nanotips. Moreover, the Fowler-Nordheim (F-N) plot displays a nonlinear relationship in the low and high electric field regions caused by the double well potential effect of the heterojunction structures. PMID:27387653

  17. Optical emission of graphene and electron-hole pair production induced by a strong terahertz field

    Science.gov (United States)

    Oladyshkin, I. V.; Bodrov, S. B.; Sergeev, Yu. A.; Korytin, A. I.; Tokman, M. D.; Stepanov, A. N.

    2017-10-01

    We report on experimental observation of optical emission of graphene induced by an intense terahertz (THz) pulse. P-doped chemical-vapor-deposition graphene with an initial Fermi energy of about 200 meV was used; optical photons were detected in the 2.0-3.5 eV range. Emission started when the THz field amplitude exceeded 100 kV/cm. For the THz fields from 200 to 300 kV/cm, the temperature of optical radiation was constant, while the number of emitted photons increased by several dozen times. This fact clearly indicates multiplication of electron-hole pairs induced by an external field and not electron heating. The experimental data are in good agreement with the theory of Landau-Zener interband transitions. It is shown theoretically that Landau-Zener transitions are possible even in the case of heavily doped graphene because the strong THz field removes quasiparticles from the region of interband transitions for several femtoseconds, which cancels the Pauli blocking effect.

  18. Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

    Energy Technology Data Exchange (ETDEWEB)

    Suriani, A.B., E-mail: absuriani@yahoo.com [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Dalila, A.R. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Mohamed, A.; Isa, I.M.; Kamari, A.; Hashim, N. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Department of Chemistry, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, Tanjung Malim, Perak 35900 (Malaysia); Soga, T.; Tanemura, M. [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2015-10-15

    Highlights: • Waste chicken fat is used as a starting material to produce CNFs via TCVD method. • High heating rate applied resulted in aggregation of catalyst particles. • Aggregated catalyst produced sea urchin-like CNFs with amorphous nature. • The as-grown CNFs presented a potential for field electron emission applications. - Abstract: Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750 °C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the core of the sea urchin-like CNFs was composed of Fe{sub 3}C formed within the first 20 min of synthesis time. The growth of amorphous CNFs from agglomerated Fe{sub 3}C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6 V μm{sup −1} at current density of 1 and 10 μA cm{sup −2}, respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters.

  19. Morphology dependent field emission of acid-spun carbon nanotube fibers

    Science.gov (United States)

    Fairchild, S. B.; Boeckl, J.; Back, T. C.; Ferguson, J. B.; Koerner, H.; Murray, P. T.; Maruyama, B.; Lange, M. A.; Cahay, M. M.; Behabtu, N.; Young, C. C.; Pasquali, M.; Lockwood, N. P.; Averett, K. L.; Gruen, G.; Tsentalovich, D. E.

    2015-03-01

    Acid spun carbon nanotube (CNT) fibers were investigated for their field emission properties and performance was determined to be dependent on fiber morphology. The fibers were fabricated by wet-spinning of pre-made CNTs. Fiber morphology was controlled by a fabrication method and processing conditions, as well as purity, size, and type of the CNT starting material. The internal fiber structure consisted of CNT fibrils held together by van der Waals forces. Alignment and packing density of the CNTs affects the fiber’s electrical and thermal conductivity. Fibers with similar diameters and differing morphology were compared, and those composed of the most densely packed and well aligned CNTs were the best field emitters as exhibited by a lower turn-on voltage and a larger field enhancement factor. Fibers with higher electrical and thermal conductivity demonstrated higher maximum current before failure and longer lifetimes. A stable emission current at 3 mA was obtained for 10 h at a field strength of fibers excellent candidates for use as low voltage electron sources for vacuum electronic devices.

  20. Effect of Secondary Electron Emission on Electron Cross-Field Current in E×B Discharges

    Energy Technology Data Exchange (ETDEWEB)

    Yevgeny Raitses, Igor D. Kaganovich, Alexander Khrabrov, Dmytro Sydorenko, Nathaniel J. Fisch and Andrei Smolyakov

    2011-02-10

    This paper reviews and discusses recent experimental, theoretical, and numerical studies of plasma-wall interaction in a weakly collisional magnetized plasma bounded with channel walls made from different materials. A lowpressure ExB plasma discharge of the Hall thruster was used to characterize the electron current across the magnetic field and its dependence on the applied voltage and electron-induced secondary electron emission (SEE) from the channel wall. The presence of a depleted, anisotropic electron energy distribution function with beams of secondary electrons was predicted to explain the enhancement of the electron cross-field current observed in experiments. Without the SEE, the electron crossfield transport can be reduced from anomalously high to nearly classical collisional level. The suppression of SEE was achieved using an engineered carbon velvet material for the channel walls. Both theoretically and experimentally, it is shown that the electron emission from the walls can limit the maximum achievable electric field in the magnetized plasma. With nonemitting walls, the maximum electric field in the thruster can approach a fundamental limit for a quasineutral plasma.

  1. Effect of Substrate Morphology on Growth and Field Emission Properties of Carbon Nanotube Films

    Directory of Open Access Journals (Sweden)

    Kumar Vikram

    2008-01-01

    Full Text Available AbstractCarbon nanotube (CNT films were grown by microwave plasma-enhanced chemical vapor deposition process on four types of Si substrates: (i mirror polished, (ii catalyst patterned, (iii mechanically polished having pits of varying size and shape, and (iv electrochemically etched. Iron thin film was used as catalytic material and acetylene and ammonia as the precursors. Morphological and structural characteristics of the films were investigated by scanning and transmission electron microscopes, respectively. CNT films of different morphology such as vertically aligned, randomly oriented flowers, or honey-comb like, depending on the morphology of the Si substrates, were obtained. CNTs had sharp tip and bamboo-like internal structure irrespective of growth morphology of the films. Comparative field emission measurements showed that patterned CNT films and that with randomly oriented morphology had superior emission characteristics with threshold field as low as ~2.0 V/μm. The defective (bamboo-structure structures of CNTs have been suggested for the enhanced emission performance of randomly oriented nanotube samples.

  2. Excellent Field Emission Properties of Short Conical Carbon Nanotubes Prepared by Microwave Plasma Enhanced CVD Process

    Directory of Open Access Journals (Sweden)

    Vankar Vasant

    2007-01-01

    Full Text Available AbstractRandomly oriented short and low density conical carbon nanotubes (CNTs were prepared on Si substrates by tubular microwave plasma enhanced chemical vapor deposition process at relatively low temperature (350–550 °C by judiciously controlling the microwave power and growth time in C2H2 + NH3gas composition and Fe catalyst. Both length as well as density of the CNTs increased with increasing microwave power. CNTs consisted of regular conical compartments stacked in such a way that their outer diameter remained constant. Majority of the nanotubes had a sharp conical tip (5–20 nm while its other side was either open or had a cone/pear-shaped catalyst particle. The CNTs were highly crystalline and had many open edges on the outer surface, particularly near the joints of the two compartments. These films showed excellent field emission characteristics. The best emission was observed for a medium density film with the lowest turn-on and threshold fields of 1.0 and 2.10 V/μm, respectively. It is suggested that not only CNT tip but open edges on the body also act as active emission sites in the randomly oriented geometry of such periodic structures.

  3. Electron field emission characteristics of different surface morphologies of ZnO nanostructures coated on carbon nanotubes.

    Science.gov (United States)

    Li, Kuan-Wei; Lian, Huan-Bin; Cai, Jhen-Hong; Wang, Yao-Te; Lee, Kuei-Yi

    2011-12-01

    The optimal carbon nanotube (CNT) bundles with a hexagonal arrangement were synthesized using thermal chemical vapor deposition (TCVD). To enhance the electron field emission characteristics of the pristine CNTs, the zinc oxide (ZnO) nanostructures coated on CNT bundles using another TCVD technique. Transmission electron microscopy (TEM) images showed that the ZnO nanostructures were grown onto the CNT surface uniformly, and the surface morphology of ZnO nanostructures varied with the distance between the CNT bundle and the zinc acetate. The results of field emissions showed that the ZnO nanostructures grown onto the CNTs could improve the electron field emission characteristics. The enhancement of field emission characteristics was attributed to the increase of emission sites formed by the nanostructures of ZnO grown onto the CNT surface, and each ZnO nanostructure could be regarded as an individual field emission site. In addition, ZnO-coated CNT bundles exhibited a good emission uniformity and stable current density. These results demonstrated that ZnO-coated CNTs is a promising field emitter material.

  4. Morphology-dependent field emission properties and wetting behavior of ZnO nanowire arrays

    Directory of Open Access Journals (Sweden)

    Ma Li

    2011-01-01

    Full Text Available Abstract The fabrication of three kinds of ZnO nanowire arrays with different structural parameters over Au-coated silicon (100 by facile thermal evaporation of ZnS precursor is reported, and the growth mechanism are proposed based on structural analysis. Field emission (FE properties and wetting behavior were revealed to be strongly morphology dependent. The nanowire arrays in small diameter and high aspect ratio exhibited the best FE performance showing a low turn-on field (4.1 V/μm and a high field-enhancement factor (1745.8. The result also confirmed that keeping large air within the films was an effective way to obtain super water-repellent properties. This study indicates that the preparation of ZnO nanowire arrays in an optimum structural model is crucial to FE efficiency and wetting behavior.

  5. Thermally enhanced field emission from a laser-illuminated tungsten tip: temperature rise of tip

    Energy Technology Data Exchange (ETDEWEB)

    Lee, M.J.G.; Reifenberger, R.; Robins, E.S.; Lindenmayr, H.G.

    1980-09-01

    Thermal field emission of electrons has been investigated from a tungsten field emitter illuminated by the focused beam of a laser operating at a range of wavelengths in the visible region of the spectrum. The temperature rise of the tip is determined as a function of the displacement of the focused spot of light along the shank, and of its polarization. The experimental data are compared with the results of a first-principle calculation of the temperature rise, based on an experimental investigation of the intensity distribution within the focused spot of light and of the geometry of the field emitter. The comparison shows that when the laser beam is focused close to the tip the temperature rise is anomalously large; evidence is presented which suggests that the temperature rise of the tip is substantially enhanced by diffraction effects.

  6. Effect of aircraft exhaust sulfur emissions on near field plume aerosols

    Science.gov (United States)

    Brown, R. C.; Miake-Lye, R. C.; Anderson, M. R.; Kolb, C. E.

    A two dimensional, axisymmetric flowfield model with coupled gas phase oxidation kinetics and aerosol nucleation and growth dynamics is used to evaluate the effect of fuel sulfur oxidation in the Concorde engine on the formation and growth of volatile H2SO4/H2O aerosols in the near field plume. Rased on estimated exit plane sulfur speciation, results are shown for between 2% and 20% conversion of the fuel sulfur to S(VI) (SO3 and H2SO4) in engine. The primary motivation is to provide estimates for the changes in the number density and surface area density of sulfuric acid aerosols due to sulfur oxidation in the engine. This analysis indicates the need for experimental measurements of sulfur emissions at the exhaust exit, in addition to soot properties, to fully assess the atmospheric impact of aircraft emissions.

  7. Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field

    Energy Technology Data Exchange (ETDEWEB)

    Valette-Silver, J.N.; Esquer P., I.; Elders, W.A.; Collier, P.C.; Hoagland, J.R.

    1981-01-01

    A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samples from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180 C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristic products of the discharge from high intensity geothermal fields.

  8. Effects of Magnetic Field Geometry on the Broadband Emission of Blazars

    Science.gov (United States)

    Joshi, Manasvita; Marscher, Alan; Boettcher, Markus

    2018-01-01

    The knowledge of the structure of the magnetic field inside a blazar jet, as deduced from polarization observations at radio to opticalwavelengths, is closely related to the formation and propagation of relativistic jets that result from accretion onto supermassive blackholes. However, a largely unexplored aspect of the theoretical understanding of radiation transfer physics in blazar jets has beenthe magnetic field geometry as revealed by the polarized emission and the connection between the variability in polarization and flux acrossthe spectrum.Here, we explore the effects of various magnetic geometries that can exist inside a blazar jet: parallel, transverse, oblique, toroidal,helical, and tangled. We investigate the effects of changing the orientation of the magnetic field, according to the above-mentionedgeometries, on the resulting high-energy spectral energy distributions (SEDs) and spectral variability patterns (SVPs) of a typicalblazar. We use the MUlti-ZOne Radiation Feedback (MUZORF) model to carry out this study and to relate the geometry of the field to the observed SEDs. One of the goals of the study is to address the issue of the reason for the appearance of some of the gamma-ray "orphan flares" observed in a few blazars. This can be associated with the directionality of the magnetic field, which creates a difference in the radiation field as seen by an observer versus that seen by the electrons in the emission region.This research was supported in part by NASA through Fermi grants NNX10AO59G, NNX08AV65G, and NNX08AV61G, NASA through Swift grants NNX09AR11G, NNX10AL13G, and NNX10AF88G, and by NSF grant AST-0907893.

  9. Nitrous oxide emission from highland winter wheat field after long-term fertilization

    Science.gov (United States)

    Wei, X. R.; Hao, M. D.; Xue, X. H.; Shi, P.; Horton, R.; Wang, A.; Zang, Y. F.

    2010-10-01

    Nitrous oxide (N2O) is an important greenhouse gas. N2O emissions from soils vary with fertilization and cropping practices. The response of N2O emission to fertilization of agricultural soils plays an important role in global N2O emission. The objective of this study was to assess the seasonal pattern of N2O fluxes and the annual N2O emissions from a rain-fed winter wheat (Triticum aestivum L.) field in the Loess Plateau of China. A static flux chamber method was used to measure soil N2O fluxes from 2006 to 2008. The study included 5 treatments with 3 replications in a randomized complete block design. Prior to initiating N2O measurements the treatments had received the same fertilization for 22 years. The fertilizer treatments were unfertilized control (CK), manure (M), nitrogen (N), nitrogen + phosphorus (NP), and nitrogen + phosphorus + manure (NPM). Soil N2O fluxes in the highland winter wheat field were highly variable temporally and thus were fertilization dependent. The highest fluxes occurred in the warmer and wetter seasons. Relative to CK, m slightly increased N2O flux while N, NP and NPM treatments significantly increased N2O fluxes. The fertilizer induced increase in N2O flux occurred mainly in the first 30 days after fertilization. The increases were smaller in the relatively warm and dry year than in the cold and wet year. Combining phosphorous and/or manure with mineral N fertilizer partly offset the nitrogen fertilizer induced increase in N2O flux. N2O fluxes at the seedling stage were mainly controlled by nitrogen fertilization, while fluxes at other plant growth stages were influenced by plant and environmental conditions. The cumulative N2O emissions were always higher in the fertilized treatments than in the non-fertilized treatment (CK). Mineral and manure nitrogen fertilizer enhanced N2O emissions in wetter years compared to dryer years. Phosphorous fertilizer offset 0.50 and 1.26 kg N2O-N ha-1 increases, while manure + phosphorous offset 0

  10. Quantifying fire-wide carbon emissions in interior Alaska using field measurements and Landsat imagery

    Science.gov (United States)

    Rogers, B. M.; Veraverbeke, S.; Azzari, G.; Czimczik, C. I.; Holden, S. R.; Mouteva, G. O.; Sedano, F.; Treseder, K. K.; Randerson, J. T.

    2014-08-01

    Carbon emissions from boreal forest fires are projected to increase with continued warming and constitute a potentially significant positive feedback to climate change. The highest consistent combustion levels are reported in interior Alaska and can be highly variable depending on the consumption of soil organic matter. Here we present an approach for quantifying emissions within a fire perimeter using remote sensing of fire severity. Combustion from belowground and aboveground pools was quantified at 22 sites (17 black spruce and five white spruce-aspen) within the 2010 Gilles Creek burn in interior Alaska, constrained by data from eight unburned sites. We applied allometric equations and estimates of consumption to calculate carbon losses from aboveground vegetation. The position of adventitious spruce roots within the soil column, together with estimated prefire bulk density and carbon concentrations, was used to quantify belowground combustion. The differenced Normalized Burn Ratio (dNBR) exhibited a clear but nonlinear relationship with combustion that differed by forest type. We used a multiple regression model based on transformed dNBR and deciduous fraction to scale carbon emissions to the fire perimeter, and a Monte Carlo framework to assess uncertainty. Because of low-severity and unburned patches, mean combustion across the fire perimeter (1.98 ± 0.34 kg C m-2) was considerably less than within a defined core burn area (2.67 ± 0.40 kg C m-2) and the mean at field sites (2.88 ± 0.23 kg C m-2). These areas constitute a significant fraction of burn perimeters in Alaska but are generally not accounted for in regional-scale estimates. Although total combustion in black spruce was slightly lower than in white spruce-aspen forests, black spruce covered most of the fire perimeter (62%) and contributed the majority (67 ± 16%) of total emissions. Increases in spring albedo were found to be a viable alternative to dNBR for modeling emissions.

  11. THE EFFECT OF RICE CULTIVARS ON METHANE EMISSION FROM IRRIGATED RICE FIELD

    Directory of Open Access Journals (Sweden)

    P. Setyanto

    2016-10-01

    Full Text Available Rice plants have been reported to affect methane (CH4 emission from rice fields. The objectives of this study were to determine the effect of rice cultivars on CH4 emission from flooded rice and to develop crop management strategies with low emitting rice cultivars while sustaining high yield. The four rice cultivars studied were Memberamo, Cisadane, IR64, and Way Apoburu. The CH4 emissions were determined in the wet season of 2001/2002 (November-February using an automated closed chamber technique in an irrigated field condition. Farmyard manure at the rate of 5 t ha-1 was given to the plots to ensure carbon was not limited. Root weight, root length, biomass, and number of tillers were determined at 17, 36, and 57 days after transplanting (DAT. The results showed that the mean CH4 emission was highest in the plot planted with Cisadane (94.8 kg CH4 ha-1, and the lowest with IR64 (37.7 kg CH4 ha-1. The plots treated with emberamo and Way Apoburu resulted an intermediate CH4 emission at the average of 61.1 and 58.9 kg CH4 ha-1, respectively. There was no significant difference in yield between the cultivars tested. The yield of Memberamo, Cisadane, IR64, and Way Apoburu were 5.882, 5.764, 5.873 and 6.065 t ha-1, respectively. Statistical analysis showed that there were no significant differences in the root weight and root length among cultivars. However, Cisadane gave the highest dry matter weight (222 g hill-1 at 57 DAT compared to the other cultivars (175-190 g hill-1. Plant tillers did not show significant differences between the cultivars. Regression analysis showed that CH4 flux was significantly related with root weight, root length, aboveground biomass, and number of plant tillers. This finding shows that the use of selected cultivars, such as IR64, can potentially lower CH4 emission without scarifying yield.

  12. Magnetic Field Emission Comparison at Different Quality Factors with Series-Parallel Compensation Network for Wireless Power Transfer to Vehicles

    DEFF Research Database (Denmark)

    Batra, Tushar; Schaltz, Erik

    2014-01-01

    to the surroundings also increase with increase in the quality factor. In this paper, first analytical expressions are developed for comparing magnetic emissions at different quality factors. Theoretical and simulation (Comsol) results show comparatively lower increase for the magnetic field emissions to the linear...

  13. DIRECT OBSERVATION OF SOLAR CORONAL MAGNETIC FIELDS BY VECTOR TOMOGRAPHY OF THE CORONAL EMISSION LINE POLARIZATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kramar, M. [Physics Department, The Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064 (United States); Lin, H. [Institute for Astronomy, University of Hawaii at Manoa, 34 Ohia Ku Street, Pukalani, Maui, HI 96768 (United States); Tomczyk, S., E-mail: kramar@cua.edu, E-mail: lin@ifa.hawaii.edu, E-mail: tomczyk@ucar.edu [High Altitude Observatory, 3080 Center Green Drive, Boulder, CO 80301 (United States)

    2016-03-10

    We present the first direct “observation” of the global-scale, 3D coronal magnetic fields of Carrington Rotation (CR) Cycle 2112 using vector tomographic inversion techniques. The vector tomographic inversion uses measurements of the Fe xiii 10747 Å Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and 3D coronal density and temperature derived from scalar tomographic inversion of Solar Terrestrial Relations Observatory (STEREO)/Extreme Ultraviolet Imager (EUVI) coronal emission lines (CELs) intensity images as inputs to derive a coronal magnetic field model that best reproduces the observed polarization signals. While independent verifications of the vector tomography results cannot be performed, we compared the tomography inverted coronal magnetic fields with those constructed by magnetohydrodynamic (MHD) simulations based on observed photospheric magnetic fields of CR 2112 and 2113. We found that the MHD model for CR 2112 is qualitatively consistent with the tomography inverted result for most of the reconstruction domain except for several regions. Particularly, for one of the most noticeable regions, we found that the MHD simulation for CR 2113 predicted a model that more closely resembles the vector tomography inverted magnetic fields. In another case, our tomographic reconstruction predicted an open magnetic field at a region where a coronal hole can be seen directly from a STEREO-B/EUVI image. We discuss the utilities and limitations of the tomographic inversion technique, and present ideas for future developments.

  14. Substituting EMC emission measurement by field and cable scan method using measured transfer function

    Science.gov (United States)

    Rinas, D.; Jia, J.; Zeichner, A.; Frei, S.

    2013-07-01

    Today EMC emissions of automotive components are often measured in anechoic chambers by an antenna at fixed position according to CISPR 25 (ALSE-method). The antenna voltage often cannot sufficiently describe the behaviour of the measured electronic components and systems. Furthermore space requirements and costs are very high for the ALSE-method. Field- and cable-scan methods combined with near-field to far-field transformation techniques might be a good alternative. Residual reflections from the walls, the metallic floor, the measuring table, interaction of the antenna with the environment, and other factors affect the measurements. Thus, models which only regard the current distribution for near- and far field calculation cannot produce results equal to a chamber measurement. In this paper methods for computing transfer functions for the substitution of EMC antenna measurements with field- and cable scans in a specified calibration area are introduced. To consider influences of the environment, the environment is characterized in a first step and included with transfer functions in the calculation process for the equivalent ALSE-field.

  15. Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Amitava, E-mail: roy@fzu.cz, E-mail: aroy@barc.gov.in [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic); Murtaza Hassan, Syed; Harilal, Sivanandan S.; Hassanein, Ahmed [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); Endo, Akira; Mocek, Tomas [HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic)

    2014-05-15

    We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasma show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.

  16. Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

    Science.gov (United States)

    Roy, Amitava; Murtaza Hassan, Syed; Harilal, Sivanandan S.; Endo, Akira; Mocek, Tomas; Hassanein, Ahmed

    2014-05-01

    We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5-15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ˜0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasma show that the ion flux reduces by a factor of ˜5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ˜1.2 cm/μs and reduced to ˜0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.

  17. Potencial de emissão de metano em lavouras de arroz irrigado Methane emission potential in flooded rice fields

    Directory of Open Access Journals (Sweden)

    Dirceu Agostinetto

    2002-12-01

    responsible for such phenomenon. The main gases that cause the greenhouse effect are carbon dioxide (CO2, methane (CH4, nitrous oxide (N2O, and chlorofluorocarbons (CFCs. Methane stands out amongst them by the amount produced and by its activity in the absorbing atmospheric heat. The main methane producing sources are soils naturally flooded or cultivated under flooding conditions, which represent approximately 40% of the total methane emitted; from this amount, 37% is emitted by rice cultivated under flooding conditions. In this context, the present review has as main purposes to describe processes responsible for methane production and emission, as well as to discuss management practices and rice plant characteristics which affect emission of this gas. From the total methane originated in rice fields during its growth cycle, between 60 to 90% comes from rice plants. Although methane is not the main gas responsible for the greenhouse effect and rice crop does not represent the main methane source, the reduction in the emission could be accomplished through changes in rice cultural practices. Amongst alternatives that can be worked out are management of irrigation water and fertilizer applied, and cropping of rice cultivars that present lower number of aerenchyma and lower biomass production, whereas maintaining rice grain yields potential.

  18. Sub-microanalysis of solid samples with near-field enhanced atomic emission spectroscopy

    Science.gov (United States)

    Wang, Xiaohua; Liang, Zhisen; Meng, Yifan; Wang, Tongtong; Hang, Wei; Huang, Benli

    2018-03-01

    A novel approach, which we have chosen to name it as near-field enhanced atomic emission spectroscopy (NFE-AES), was proposed by introducing a scanning tunnelling microscope (STM) system into a laser-induced breakdown spectrometry (LIBS). The near-field enhancement of a laser-illuminated tip was utilized to improve the lateral resolution tremendously. Using the hybrid arrangement, pure metal tablets were analyzed to verify the performance of NFE-AES both in atmosphere and in vacuum. Due to localized surface plasmon resonance (LSPR), the incident electromagnetic field is enhanced and confined at the apex of tip, resulting in sub-micron scale ablation and elemental emission signal. We discovered that the signal-to-noise ratio (SNR) and the spectral resolution obtained in vacuum condition are better than those acquired in atmospheric condition. The quantitative capability of NFE-AES was demonstrated by analyzing Al and Pb in Cu matrix, respectively. Submicron-sized ablation craters were achieved by performing NFE-AES on a Si wafer with an Al film, and the spectroscopic information from a crater of 650 nm diameter was successfully obtained. Due to its advantage of high lateral resolution, NFE-AES imaging of micro-patterned Al lines on an integrated circuit of a SIM card was demonstrated with a sub-micron lateral resolution. These results reveal the potential of the NFE-AES technique in sub-microanalysis of solids, opening an opportunity to map chemical composition at sub-micron scale.

  19. Electrochemical Charging of Carbon Nanotubes for Tunable Electron Field Emission Cathodes

    Science.gov (United States)

    Kuznetsov, Alexander; Barisci, Norman; Zakhidov, Anvar; Zakhidov, Alexander

    2009-03-01

    Carbon nanotubes (CNTs) have very promising applications as electron field emitters. Work function of CNTs greatly affects the performance of such cold electron emitters. It is possible to change emission currents by several orders of magnitude by electrochemical charging. Electrochemical charging changes work function of CNTs by creating so called double layer. It was recently demonstrated that double layer structure remains for several hours after removing the CNTs from an electrolyte [1]. The extensive study of charging single wall carbon nanotube (SWNT) paper in different electrolytes has been performed at different charging potentials Vch. Field emission currents and threshold fields dependence on the charging potential and polarity is studied for various ions, with different valency and size: Na, Mg, Cs. Clear dependence of work function on Vch is demonstrated. AFM micro-imaging with a Kelvin probe allowed to study the micropatterns of work function modulation. Also dissipation of positive charge in air was investigated and its stability was significantly increased. 1. Suh Dong-Seok, Baughman Ray, Zakhidov Anvar, US Patent 20070170071 (2007)

  20. Experimental study of the reduction of field emission by gas injection in vacuum for accelerator applications

    Directory of Open Access Journals (Sweden)

    K. Almaksour

    2014-10-01

    Full Text Available Field emission current from surfaces under vacuum and at high field strengths can be reduced by the injection of gas into the evacuated volume. In this paper, the effects of H_{2}, He, N_{2}, and Ar on this “dark” current emitted from a tungsten carbide point cathode for 2 cm gap distance is studied. Exposure to any of these gases at pressures on the order of 10^{−3}–10^{−2}  Pa was found to reduce the emission current by up to 90% with a time constant on the order of ∼1  minute as compared to the current at 10^{−6}  Pa. The effect was strongly dependent on the gas nature, with Ar and N_{2} having larger effects at lower pressures than He and H_{2}. The reduction was reversible, with the current increasing to near its original value with a time constant on the order of ∼1–10  minutes after pumping down. The effect of the gas remained in the absence of electric field, whatever the gas pressure. Mechanisms for these and related phenomena are discussed.

  1. Experimental study of the reduction of field emission by gas injection in vacuum for accelerator applications

    Science.gov (United States)

    Almaksour, K.; Kirkpatrick, M. J.; Dessante, Ph.; Odic, E.; Simonin, A.; de Esch, H. P. L.; Lepetit, B.; Alamarguy, D.; Bayle, F.; Teste, Ph.

    2014-10-01

    Field emission current from surfaces under vacuum and at high field strengths can be reduced by the injection of gas into the evacuated volume. In this paper, the effects of H2, He, N2, and Ar on this "dark" current emitted from a tungsten carbide point cathode for 2 cm gap distance is studied. Exposure to any of these gases at pressures on the order of 10-3-10-2 Pa was found to reduce the emission current by up to 90% with a time constant on the order of ˜1 minute as compared to the current at 10-6 Pa. The effect was strongly dependent on the gas nature, with Ar and N2 having larger effects at lower pressures than He and H2. The reduction was reversible, with the current increasing to near its original value with a time constant on the order of ˜1-10 minutes after pumping down. The effect of the gas remained in the absence of electric field, whatever the gas pressure. Mechanisms for these and related phenomena are discussed.

  2. Developing field emission electron sources based on ultrananocrystalline diamond for accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Baryshev, Sergey V.; Jing, Chunguang; Qiu, Jiaqi; Antipov, Sergey; Jabotinski, Vadim; Shao, Jiahang; Gai, Wei; Sumant, Anirudha V.

    2016-08-25

    Radiofrequency (RF) electron guns work by establishing an RF electromagnetic field inside a cavity having conducting walls. Electrons from a cathode are generated in the injector and immediately become accelerated by the RF electric field, and exit the gun as a series of electron bunches. Finding simple solutions for electron injection is a long standing problem. While energies of 30-50 MeV are achievable in linear accelerators (linacs), finding an electron source able to survive under MW electric loads and provide an average current of 1-10 mA is important. Meeting these requirements would open various linac applications for industry. The natural way to simplify and integrate RF injector architectures with the electron source would be to place the source directly into the RF cavity with no need for additional heaters/lasers. Euclid TechLabs in collaboration with Argonne National Lab are prototyping a family of highly effective field emission electron sources based on a nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) platform. Determined metrics suggest that our emitters are emissive enough to meet requirements for magnetized cooling at electron-ion colliders, linac-based radioisotope production and X-ray sterilization, and others.

  3. In-field greenhouse gas emissions from cookstoves in rural Mexican households

    Science.gov (United States)

    Johnson, Michael; Edwards, Rufus; Alatorre Frenk, Claudio; Masera, Omar

    The majority of estimates of the greenhouse gas emissions associated with changes from traditional to improved cookstoves in developing countries come from water-boiling tests (WBTs) conducted in simulated kitchens. Little is known about the bias in these estimates relative to typical stove use by residents in rural communities. To assess this bias, the reductions in emissions as a result of installation of an improved wood-burning "Patsari" stove were quantified in both simulated kitchens and field conditions in eight homes with open fire stoves and 13 homes with Patsari stoves in Purépecha communities of Michoacán, Mexico. The results demonstrate that nominal combustion efficiencies (NCEs) of open fire cookstoves were significantly lower ( pproducts on incomplete combustion (PICs) emitted. Since emissions from the rural residential sector are important in the modeling of atmospheric trace greenhouse gas concentrations in areas that rely on solid fuel use for primary energy provision, if these open fires reflect conditions in other areas of the world, substantial underestimation of emissions from open fires may be present in current emission databases. Conversely, NCEs for the improved Patsari stoves were significantly higher ( p<0.01) in rural homes during daily cooking activities (92.3±1.3%) compared to during WBTs in simulated kitchens (87.2±4.3%), as WBTs do not reflect cooking activities in rural homes. Thus the Patsari emits 25% less PICs per kg fuelwood used than the open fire, and carbon emission reductions of Patsari and similar improved stoves are also likely underestimated. Finally, in addition to a reduction in overall particulate emissions for rural homes during daily activities, the ratio of organic carbon (OC) to elemental carbon (EC) within the aerosol fraction decreased between the open fire and improved Patsari stoves. While the overall EC contribution for the brick Patsari was reduced, the fraction of EC increased relative to OC, which makes

  4. Simple Monte Carlo model with generalized carrier-trajectory tracking equations for prediction of avalanche multiplication statistics in avalanche photodiodes with arbitrary electric field gradient

    Science.gov (United States)

    Ong, J. S. L.; Charin, C.; Leong, J. H.

    2017-09-01

    A set of highly generalized electron-trajectory tracking equations are derived based on the fundamental of high field carrier transport and are employed in a Simple Monte Carlo model for gain and avalanche multiplication noise prediction in APDs with arbitrary electric field gradients. Using the model and assuming electron-only ionization, simulations are carried out on two one-sided abrupt np+ and n+p junctions with doping concentrations in the n and p regions set to 1.0×1018 cm-3 and the p+ and n+ regions set to infinity. Preliminary simulation results of gain, avalanche multiplication noise, and positions of electron ionizations obtained from the Simple Monte Carlo model employing the electron-trajectory tracking equations show excellent agreement with those obtained from the conventional Simple Monte Carlo model even though the one-sided abrupt np+ and n+p junctions are subjected to steep electric field gradient across the avalanche multiplication regions. These simulation results, and the positions of electron ionizations in particular, strongly imply that the electron-trajectory tracking equations employed in the Simple Monte Carlo model for avalanche photodiodes are able to track the trajectory of the electrons and valid, and the equations are highly generalized for APDs with arbitrary electric field gradients, ranging from uniform electric fields to steep electric field gradients.

  5. Mechanical Modulation of Phonon-Assisted Field Emission in a Silicon Nanomembrane Detector for Time-of-Flight Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Jonghoo Park

    2016-02-01

    Full Text Available We demonstrate mechanical modulation of phonon-assisted field emission in a free-standing silicon nanomembrane detector for time-of-flight mass spectrometry of proteins. The impacts of ion bombardment on the silicon nanomembrane have been explored in both mechanical and electrical points of view. Locally elevated lattice temperature in the silicon nanomembrane, resulting from the transduction of ion kinetic energy into thermal energy through the ion bombardment, induces not only phonon-assisted field emission but also a mechanical vibration in the silicon nanomembrane. The coupling of these mechanical and electrical phenomenon leads to mechanical modulation of phonon-assisted field emission. The thermal energy relaxation through mechanical vibration in addition to the lateral heat conduction and field emission in the silicon nanomembrane offers effective cooling of the nanomembrane, thereby allowing high resolution mass analysis.

  6. Imaging metazoan nuclear pore complexes by field emission scanning electron microscopy.

    Science.gov (United States)

    Fichtman, Boris; Shaulov, Lihi; Harel, Amnon

    2014-01-01

    High resolution three-dimensional surface images of nuclear pore complexes (NPCs) can be obtained by field emission scanning electron microscopy. We present a short retrospective view starting from the early roots of microscopy, through the discovery of the cell nucleus and the development of some modern techniques for sample preparation and imaging. Detailed protocols are presented for assembling anchored nuclei in a Xenopus cell-free reconstitution system and for the exposure of the nuclear surface in mammalian cell nuclei. Immunogold labeling of metazoan NPCs and a promising new technique for delicate coating with iridium are also discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Seasonal trends and environmental controls of methane emissions in a rice paddy field in Northern Italy

    Directory of Open Access Journals (Sweden)

    A. Meijide

    2011-12-01

    Full Text Available Rice paddy fields are one of the greatest anthropogenic sources of methane (CH4, the third most important greenhouse gas after water vapour and carbon dioxide. In agricultural fields, CH4 is usually measured with the closed chamber technique, resulting in discontinuous series of measurements performed over a limited area, that generally do not provide sufficient information on the short-term variation of the fluxes. On the contrary, aerodynamic techniques have been rarely applied for the measurement of CH4 fluxes in rice paddy fields. The eddy covariance (EC technique provides integrated continuous measurements over a large area and may increase our understanding of the underlying processes and diurnal and seasonal pattern of CH4 emissions in this ecosystem.

    For this purpose a Fast Methane Analyzer (Los Gatos Research Ltd. was installed in a rice paddy field in the Po Valley (Northern Italy. Methane fluxes were measured during the rice growing season with both EC and manually operated closed chambers. Methane fluxes were strongly influenced by the height of the water table, with emissions peaking when it was above 10–12 cm. Soil temperature and the developmental stage of rice plants were also responsible of the seasonal variation on the fluxes. The measured EC fluxes showed a diurnal cycle in the emissions, which was more relevant during the vegetative period, and with CH4 emissions being higher in the late evening, possibly associated with higher water temperature. The comparison between the two measurement techniques shows that greater fluxes are measured with the chambers, especially when higher fluxes are being produced, resulting in 30 % higher seasonal estimations with the chambers than with the EC (41.1 and 31.7 g CH4 m−2 measured with chambers and EC respectively and even greater differences are found if shorter periods with high chamber sampling

  8. Relativistic quantum dynamics in strong fields: Photon emission from heavy, few-electron ions

    Energy Technology Data Exchange (ETDEWEB)

    Fritzsche, S. [Kassel Univ. (Germany). Inst. fuer Physik; Indelicato, P. [Lab. Kastler Brossel, Ecole Normale Superieure et Universite Pierre et Marie Curie, Paris (France); Stoehlker, T. [Frankfurt Univ. (Germany). Inst. fuer Kernphysik

    2005-03-01

    Recent progress in the study of the photon emission from highly-charged heavy ions is reviewed. These investigations show that high-Z ions provide a unique tool for improving the understanding of the electron-electron and electron-photon interaction in the presence of strong fields. Apart from the bound-state transitions, which are accurately described in the framework of quantum electrodynamics, much information has been obtained also from the radiative capture of (quasi-) free electrons by high-Z ions. Many features in the observed spectra hereby confirm the inherently relativistic behavior of even the simplest compound quantum systems in nature. (orig.)

  9. Effects of nitrogen application rate, nitrogen synergist and biochar on nitrous oxide emissions from vegetable field in south China.

    Directory of Open Access Journals (Sweden)

    Qiong Yi

    Full Text Available Globally, vegetable fields are the primary source of greenhouse gas emissions. A closed-chamber method together with gas chromatography was used to measure the fluxes of nitrous oxide (N2O emissions in typical vegetable fields planted with four vegetables sequentially over time in the same field: endive, lettuce, cabbage and sweet corn. Results showed that N2O fluxes occurred in pulses with the N2O emission peak varying greatly among the crops. In addition, N2O emissions were linearly associated with the nitrogen (N application rate (r = 0.8878, n = 16. Excessive fertilizer N application resulted in N loss through nitrous oxide gas emitted from the vegetable fields. Compared with a conventional fertilization (N2 treatment, the cumulative N2O emissions decreased significantly in the growing seasons of four plant species from an nitrogen synergist (a nitrification inhibitor, dicyandiamide and biochar treatments by 34.6% and 40.8%, respectively. However, the effects of biochar on reducing N2O emissions became more obvious than that of dicyandiamide over time. The yield-scaled N2O emissions in consecutive growing seasons for four species increased with an increase in the N fertilizer application rate, and with continuous application of N fertilizer. This was especially true for the high N fertilizer treatment that resulted in a risk of yield-scaled N2O emissions. Generally, the additions of dicyandiamide and biochar significantly decreased yield-scaled N2O-N emissions by an average of 45.9% and 45.7%, respectively, compared with N2 treatment from the consecutive four vegetable seasons. The results demonstrated that the addition of dicyandiamide or biochar in combination with application of a rational amount of N could provide the best strategy for the reduction of greenhouse gas emissions in vegetable field in south China.

  10. Effects of nitrogen application rate, nitrogen synergist and biochar on nitrous oxide emissions from vegetable field in south China

    Science.gov (United States)

    Zhang, Mu; Pang, Yuwan; Huang, Xu; Huang, Qiaoyi

    2017-01-01

    Globally, vegetable fields are the primary source of greenhouse gas emissions. A closed-chamber method together with gas chromatography was used to measure the fluxes of nitrous oxide (N2O) emissions in typical vegetable fields planted with four vegetables sequentially over time in the same field: endive, lettuce, cabbage and sweet corn. Results showed that N2O fluxes occurred in pulses with the N2O emission peak varying greatly among the crops. In addition, N2O emissions were linearly associated with the nitrogen (N) application rate (r = 0.8878, n = 16). Excessive fertilizer N application resulted in N loss through nitrous oxide gas emitted from the vegetable fields. Compared with a conventional fertilization (N2) treatment, the cumulative N2O emissions decreased significantly in the growing seasons of four plant species from an nitrogen synergist (a nitrification inhibitor, dicyandiamide and biochar treatments by 34.6% and 40.8%, respectively. However, the effects of biochar on reducing N2O emissions became more obvious than that of dicyandiamide over time. The yield-scaled N2O emissions in consecutive growing seasons for four species increased with an increase in the N fertilizer application rate, and with continuous application of N fertilizer. This was especially true for the high N fertilizer treatment that resulted in a risk of yield-scaled N2O emissions. Generally, the additions of dicyandiamide and biochar significantly decreased yield-scaled N2O-N emissions by an average of 45.9% and 45.7%, respectively, compared with N2 treatment from the consecutive four vegetable seasons. The results demonstrated that the addition of dicyandiamide or biochar in combination with application of a rational amount of N could provide the best strategy for the reduction of greenhouse gas emissions in vegetable field in south China. PMID:28419127

  11. Improved field emission properties of α-Fe2O3 nanoflakes with current aging treatment and morphology optimization

    Science.gov (United States)

    Wu, Junqing; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

    2018-02-01

    α-Fe2O3 nanomaterials were synthesized by thermal oxidation of pure iron foil and the effects of current aging treatment and morphology on their field emission properties were systematically investigated. The current aging treatment was found to be an efficient method to improve the field emission properties of α-Fe2O3 nanoflakes. The emission current density was largely enhanced from 0.05–5.70 mA cm‑2 under an applied electrical field of 7.8 MV m‑1, and their threshold field decreased from than 11.0–6.6 MV m‑1 after the current aging treatment. The mechanism of the improvement in the field emission performance of α-Fe2O3 nanoflakes induced by the current aging treatment is discussed. α-Fe2O3 nanostructures with various morphologies were synthesized by adjusting the growth temperatures between 300 °C–450 °C to optimize their morphologies. α-Fe2O3 nanoflakes synthesized at 350 °C were superior field emitters with a low threshold field of 5.1 MV m‑1, high current density of 63.4 mA cm‑2, and stable emission, which demonstrated that α-Fe2O3 nanoflakes could be a promising material for application as field emitters.

  12. Field emission study from an array of hierarchical micro protrusions on stainless steel surface generated by femtosecond pulsed laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Singh, A.K., E-mail: anilks@barc.gov.in [Laser & Plasma Technology Division, BARC, Mumbai, 400085 (India); Suryawanshi, Sachin R.; More, M.A. [Department of Physics, Savitribai Phule Pune University, Pune, 411007 (India); Basu, S. [Solid State Physics Division, BARC, Mumbai, 40085 (India); Sinha, Sucharita [Laser & Plasma Technology Division, BARC, Mumbai, 400085 (India)

    2017-02-28

    Highlights: • Array of self assembled micro-protrusions have been generated on stainless steel surfaces by femtosecond pulsed laser irradiation. • Density of the formed micro-protrusions is ∼5.6 × 105 protrusions/cm{sup 2}. • Laser treated surface is mainly composed of iron oxide and cementite phases. • Micro-structured sample has shown good field emission properties – low turn on field, high field enhancement factor and stable emission current. - Abstract: This paper reports our results on femtosecond (fs) pulsed laser induced surface micro/nano structuring of stainless steel 304 (SS 304) samples and their characterization in terms of surface morphology, formed material phases on laser irradiation and field emission studies. Our investigations reveal that nearly uniform and dense array of hierarchical micro-protrusions (density: ∼5.6 × 10{sup 5} protrusions/cm{sup 2}) is formed upon laser treatment. Typical tip diameters of the generated protrusions are in the range of 2–5 μm and these protrusions are covered with submicron sized features. Grazing incidence X-ray diffraction (GIXRD) analysis of the laser irradiated sample surface has shown formation mainly of iron oxides and cementite (Fe{sub 3}C) phases in the treated region. These laser micro-structured samples have shown good field emission properties such as low turn on field (∼4.1 V/μm), high macroscopic field enhancement factor (1830) and stable field emission current under ultra high vacuum conditions.

  13. Nitrous oxide emissions from European agriculture - an analysis of variability and drivers of emissions from field experiments

    DEFF Research Database (Denmark)

    Rees, R M; Agustin, J; Alberti, G

    2013-01-01

    Nitrous oxide emissions from a network of agricultural experiments in Europe were used to explore the relative importance of site and management controls of emissions. At each site, a selection of management interventions were compared within replicated experimental designs in plot-based experime...

  14. Influence of heterojunction interface on exciplex emission from organic light-emitting diodes under electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shengyi; Zhang, Xiulong; Lou, Zhidong; Hou, Yanbing [Beijing Jiaotong University, Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing (China)

    2008-03-15

    In this paper, electroluminescence from organic light-emitting diodes based on 2-(4'-biphenyl)-5-(4{sup ''}-tert-butylphenyl)-1,3,4-oxadiazole (PBD) and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD) is reported. Based on the exciplex emission from the TPD/PBD interface under high electric fields, the influence of the TPD/PBD interface on exciplex emission was investigated by increasing the number of TPD/PBD interfaces while keeping both the total thickness of the TPD layer and the PBD layer constant in the multiple quantum-wells (MQW) device ITO/TPD/[PBD/TPD]{sub n}/PBD/Al (n is the well number that was varied from 0 to 3). Our experimental data shows that exciplex emission can be enhanced by suitably increasing the well number of this kind of MQW-like device. (orig.)

  15. Tunneling-assisted transport of carriers through heterojunctions.

    Energy Technology Data Exchange (ETDEWEB)

    Wampler, William R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Myers, Samuel M. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Modine, Normand A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-10-01

    The formulation of carrier transport through heterojunctions by tunneling and thermionic emission is derived from first principles. The treatment of tunneling is discussed at three levels of approximation: numerical solution of the one-band envelope equation for an arbitrarily specified potential profile; the WKB approximation for an arbitrary potential; and, an analytic formulation assuming constant internal field. The effects of spatially varying carrier chemical potentials over tunneling distances are included. Illustrative computational results are presented. The described approach is used in exploratory physics models of irradiated heterojunction bipolar transistors within Sandia's QASPR program.

  16. Carrier Screening

    Science.gov (United States)

    ... pregnant are offered carrier screening for cystic fibrosis, hemoglobinopathies , and spinal muscular atrophy . You can have screening ... caused by a change in genes or chromosomes. Hemoglobinopathies: Any inherited disorder caused by changes in the ...

  17. Aircraft Carriers

    DEFF Research Database (Denmark)

    Nødskov, Kim; Kværnø, Ole

    in Asia and will balance the carrier acquisitions of the United States, the United Kingdom, Russia and India. China’s current military strategy is predominantly defensive, its offensive elements being mainly focused on Taiwan. If China decides to acquire a large carrier with offensive capabilities......, then the country will also acquire the capability to project military power into the region beyond Taiwan, which it does not possess today. In this way, China will have the military capability to permit a change of strategy from the mainly defensive, mainland, Taiwan-based strategy to a more assertive strategy......, with potentially far-reaching consequences for the countries of the region. The Chinese have bought several retired carriers, which they have studied in great detail. The largest is the Russian-built carrier Varyag of the Kuznetsov class, which today is anchored in the Chinese Naval Base at Dalian. If they decide...

  18. The influence of organophilic clay on field electron emission uniformity and lifetime of screen printed carbon nanotube film

    Energy Technology Data Exchange (ETDEWEB)

    Lisunova, Milana O., E-mail: milana.lisunova@samsung.co [Corporate R and D Center, Samsung SDI 428-5, Gongse-dong, Giheung-gu, Yongin-si, Gyeonggi-do, 446-577 (Korea, Republic of); Lisunova, Yuliya O.; Lee, Sora; Kim, Jaemyung; Joo, Kyunam; Zang, Dongsik [Corporate R and D Center, Samsung SDI 428-5, Gongse-dong, Giheung-gu, Yongin-si, Gyeonggi-do, 446-577 (Korea, Republic of)

    2009-11-02

    The effect of adding clay, modified by a silane coupling agent, into the carbon nanotube (CNT) paste on the field electron emission and a lifetime of screen printed CNT film was studied. The composition of organophilic clay and CNTs was characterized by a combination of X-ray diffraction, and scanning electron microscopy. The incorporation of clay improved the dispersivity, adhesiveness, and conductive networking of paste, therewith enhancing the field emission's uniformity and stability. The improvement of this gas barrier on the CNT film by clay loading prevents emission degradation.

  19. Bright and durable field emission source derived from refractory taylor cones

    Science.gov (United States)

    Hirsch, Gregory

    2016-12-20

    A method of producing field emitters having improved brightness and durability relying on the creation of a liquid Taylor cone from electrically conductive materials having high melting points. The method calls for melting the end of a wire substrate with a focused laser beam, while imposing a high positive potential on the material. The resulting molten Taylor cone is subsequently rapidly quenched by cessation of the laser power. Rapid quenching is facilitated in large part by radiative cooling, resulting in structures having characteristics closely matching that of the original liquid Taylor cone. Frozen Taylor cones thus obtained yield desirable tip end forms for field emission sources in electron beam applications. Regeneration of the frozen Taylor cones in-situ is readily accomplished by repeating the initial formation procedures. The high temperature liquid Taylor cones can also be employed as bright ion sources with chemical elements previously considered impractical to implement.

  20. Effects of Phonon Coupling and Free Carriers on Band-Edge Emission at Room Temperature in n-type ZnO Crystals

    National Research Council Canada - National Science Library

    Giles, N. C; Xu, Chunchuan; Callahan, M. J; Wang, Buguo; Neal, J. S; Boatner, L. A

    2008-01-01

    Room-temperature photoluminescence has been studied in II-type bulk ZnO crystals representing three different growth methods and having free-carrier concentrations (n) ranging from 10(exp 13) to 10(exp 18) /cu cm...

  1. Synthesis, structural, and field electron emission properties of quasi-aligned carbon nanotubes from gutter oil

    Energy Technology Data Exchange (ETDEWEB)

    Suriani, A.B., E-mail: absuriani@yahoo.com [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjung Malim, Perak (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjung Malim, Perak (Malaysia); Dalila, A.R. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjung Malim, Perak (Malaysia); Department of Physics, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjung Malim, Perak (Malaysia); Mohamed, A. [Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjung Malim, Perak (Malaysia); Department of Chemistry, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjung Malim, Perak (Malaysia); Soga, T.; Tanemura, M. [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555 (Japan)

    2015-09-01

    Quasi-aligned carbon nanotubes (CNTs) have been successfully synthesised from the simple pyrolysis of gutter oil as starting material and ferrocene as a catalyst. The synthesis process was performed at synthesis and vaporisation temperatures of 800 and 250 °C, respectively, in a thermal chemical vapour deposition furnace. The CNTs synthesised using gutter oil have an overall diameter of about 30–50 nm, length of 30 μm, I{sub D}/I{sub G} ratio of 0.66, and purity of 81%, comparable to those obtained using conventional carbon sources. A field electron emission study of the CNTs exhibited a low turn-on and threshold field of 1.94 and 2.94 V μm{sup −1}, which corresponded to current densities of 100 μA cm{sup −2} and 1.0 mA cm{sup −2}, respectively which indicate that the CNTs synthesised are suitable candidates for use as field electron emitters. The synthesised CNTs from gutter oil also open up potential mass production applications in energy storage devices. This study demonstrates that gutter oil, a low-cost and readily available resource, can be used as an inexpensive carbon source for the mass production of CNTs. - Highlights: • Gutter oil was used as starting material to synthesise CNTs by TCVD method. • CNTs of good quality (I{sub D}/I{sub G} ∼ 0.66 and purity ∼ 81%) were successfully produced. • The synthesised CNTs show a potential for field electron emission application.

  2. Structure and field emission of graphene layers on top of silicon nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Bohr-Ran; Chan, Hui-Wen [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Jou, Shyankay, E-mail: sjou@mail.ntust.edu.tw [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Chen, Guan-Yu [Graduate Institute of Electro-Optical Engineering and Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Kuo, Hsiu-An; Song, Wan-Jhen [Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China)

    2016-01-30

    Graphical abstract: - Highlights: • We prepared graphene on top of silicon nanowires by transfer-print technique. • Graphene changed from discrete flakes to a continuous by repeated transfer-print. • The triple-layer graphene had high electron field emission due to large edge ratio. - Abstract: Monolayer graphene was grown on copper foils and then transferred on planar silicon substrates and on top of silicon nanowire (SiNW) arrays to form single- to quadruple-layer graphene films. The morphology, structure, and electron field emission (FE) of these graphene films were investigated. The graphene films on the planar silicon substrates were continuous. The single- to triple-layer graphene films on the SiNW arrays were discontinuous and while the quadruple-layer graphene film featured a mostly continuous area. The Raman spectra of the graphene films on the SiNW arrays showed G and G′ bands with a singular-Lorentzian shape together with a weak D band. The D band intensity decreased as the number of graphene layers increased. The FE efficiency of the graphene films on the planar silicon substrates and the SiNW arrays varied with the number of graphene layers. The turn-on field for the single- to quadruple-layer graphene films on planar silicon substrates were 4.3, 3.7, 3.5 and 3.4 V/μm, respectively. The turn-on field for the single- to quadruple-layer graphene films on SiNW arrays decreased to 3.9, 3.3, 3.0 and 3.3 V/μm, respectively. Correlation of the FE with structure and morphology of the graphene films is discussed.

  3. Field determination of multipollutant, open area combustion source emission factors with a hexacopter unmanned aerial vehicle

    Science.gov (United States)

    Aurell, J.; Mitchell, W.; Chirayath, V.; Jonsson, J.; Tabor, D.; Gullett, B.

    2017-10-01

    An emission sensor/sampler system was coupled to a National Aeronautics and Space Administration (NASA) hexacopter unmanned aerial vehicle (UAV) to characterize gases and particles in the plumes emitted from open burning of military ordnance. The UAV/sampler was tested at two field sites with test and sampling flights spanning over 16 h of flight time. The battery-operated UAV was remotely maneuvered into the plumes at distances from the pilot of over 600 m and at altitudes of up to 122 m above ground level. While the flight duration could be affected by sampler payload (3.2-4.6 kg) and meteorological conditions, the 57 sampling flights, ranging from 4 to 12 min, were typically terminated when the plume concentrations of CO2 were diluted to near ambient levels. Two sensor/sampler systems, termed ;Kolibri,; were variously configured to measure particulate matter, metals, chloride, perchlorate, volatile organic compounds, chlorinated dioxins/furans, and nitrogen-based organics for determination of emission factors. Gas sensors were selected based on their applicable concentration range, light weight, freedom from interferents, and response/recovery times. Samplers were designed, constructed, and operated based on U.S. Environmental Protection Agency (EPA) methods and quality control criteria. Results show agreement with published emission factors and good reproducibility (e.g., 26% relative standard deviation for PM2.5). The UAV/Kolibri represents a significant advance in multipollutant emission characterization capabilities for open area sources, safely and effectively making measurements heretofore deemed too hazardous for personnel or beyond the reach of land-based samplers.

  4. Emission and distribution of phosphine in paddy fields and its relationship with greenhouse gases.

    Science.gov (United States)

    Chen, Weiyi; Niu, Xiaojun; An, Shaorong; Sheng, Hong; Tang, Zhenghua; Yang, Zhiquan; Gu, Xiaohong

    2017-12-01

    Phosphine (PH 3 ), as a gaseous phosphide, plays an important role in the phosphorus cycle in ecosystems. In this study, the emission and distribution of phosphine, carbon dioxide (CO 2 ) and methane (CH 4 ) in paddy fields were investigated to speculate the future potential impacts of enhanced greenhouse effect on phosphorus cycle involved in phosphine by the method of Pearson correlation analysis and multiple linear regression analysis. During the whole period of rice growth, there was a significant positive correlation between CO 2 emission flux and PH 3 emission flux (r=0.592, p=0.026, n=14). Similarly, a significant positive correlation of emission flux was also observed between CH 4 and PH 3 (r=0.563, p=0.036, n=14). The linear regression relationship was determined as [PH 3 ] flux =0.007[CO 2 ] flux +0.063[CH 4 ] flux -4.638. No significant differences were observed for all values of matrix-bound phosphine (MBP), soil carbon dioxide (SCO 2 ), and soil methane (SCH 4 ) in paddy soils. However, there was a significant positive correlation between MBP and SCO 2 at heading, flowering and ripening stage. The correlation coefficients were 0.909, 0.890 and 0.827, respectively. In vertical distribution, MBP had the analogical variation trend with SCO 2 and SCH 4 . Through Pearson correlation analysis and multiple stepwise linear regression analysis, pH, redox potential (Eh), total phosphorus (TP) and acid phosphatase (ACP) were identified as the principal factors affecting MBP levels, with correlative rankings of Eh>pH>TP>ACP. The multiple stepwise regression model ([MBP]=0.456∗[ACP]+0.235∗[TP]-1.458∗[Eh]-36.547∗[pH]+352.298) was obtained. The findings in this study hold great reference values to the global biogeochemical cycling of phosphorus in the future. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Staircase and saw-tooth field emission steps from nanopatterned n-type GaSb surfaces

    CERN Document Server

    Kildemo, M.; Le Roy, S.; Søndergård, E.

    2009-01-01

    High resolution field emission experiments from nanopatterned GaSb surfaces consisting of densely packed nanocones prepared by low ion-beam-energy sputtering are presented. Both uncovered and metal-covered nanopatterned surfaces were studied. Surprisingly, the field emission takes place by regular steps in the field emitted current. Depending on the field, the steps are either regular, flat, plateaus, or saw-tooth shaped. To the author’s knowledge, this is the first time that such results have been reported. Each discrete jump in the field emission may be understood in terms of resonant tunneling through an extended surface space charge region in an n-type, high aspect ratio, single GaSb nanocone. The staircase shape may be understood from the spatial distribution of the aspect ratio of the cones.

  6. CO2 emission and global warming potential (GWP of energy consumption in paddy field production systems

    Directory of Open Access Journals (Sweden)

    Salman Dastan

    2016-05-01

    Full Text Available The objectives of this study was to estimation of greenhouse gases (GHG emissions and global warming in rice production and identify measures to reducing fossil energy use and greenhouse gases emissions. Three rice production systems included SRI, improved and conventional were studied. All activities, field operation and data in production methods and differents inputs rates were monitored and recorded in 2011e2012. Results showed that averages of total energy input in production systems was 22793.02 MJ ha-1 that the least energy input equal 16102.98 MJ ha-1 was observed in SRI. Electricity had the most contribution of energy input in production systems that the greatest global warming and GHGs accounted. Nitrogen fertilizer and fuel were ranked in second and third in GHGs. Average across rice production, GWP were estimated equal to 2307.33 kg CO2-eq ha-1. The maximum and minimum GWP equal to 1640 and 2554 kg CO2-eq ha-1 equivalent to 255.8 and 479.3 kg eq-CO2 GJ-1 were obtained in SRI and conventional systems, respectively. The minimum and maximum GWP per unit energy input was the minimum were in SRI and was the maximum in conventional system. SRI had the least GWP per unit energy output and improved system was ranked in seconed. Therefore, it was concluded that GWP had the positive correlation with field management methods and inputs use.

  7. Field emission analysis of band bending in donor/acceptor heterojunction

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Yingjie, E-mail: xingyj@pku.edu.cn; Li, Shuai; Wang, Guiwei; Zhao, Tianjiao; Zhang, Gengmin [Laboratory for the Physics and Chemistry of Nanodevices and Department of Electronics, Peking University, Beijing 100871 (China)

    2016-06-28

    The donor/acceptor heterojunction plays an important role in organic solar cells. An investigation of band bending in the donor/acceptor heterojunction is helpful in analysis of the charge transport behavior and for the improvement of the device performance. In this work, we report an approach for detection of band bending in a donor/acceptor heterojunction that has been prepared on a small and sharp tungsten tip. In situ field emission measurements are performed after the deposition process, and a linear Fowler-Nordheim plot is obtained from the fresh organic film surface. The thickness-dependent work function is then measured in the layer-by-layer deposited heterojunction. Several different types of heterojunction (zinc phthalocyanine (ZnPc)/C60, copper phthalocyanine (CuPc)/3,4,9,10-perylenetetracarboxylic bisbenzimidazole, and CuPc/C60) are fabricated and analyzed. The different charge transfer directions in the heterojunctions are distinguished by field emission measurements. The calculation method used to determine the band bending is then discussed in detail. A triple layer heterojunction (C60/ZnPc/CuPc) is also analyzed using this method. A small amount of band bending is measured in the outer CuPc layer. This method provides an independent reference method for determination of the band bending in an organic heterojunction that will complement photoemission spectroscopy and current-voltage measurement methods.

  8. Physical understanding of different drain-induced-barrier-lowering variations in high-k/metal gate n-channel metal-oxide-semiconductor-field-effect-transistors induced by charge trapping under normal and reverse channel hot carrier stresses

    Science.gov (United States)

    Luo, Weichun; Yang, Hong; Wang, Wenwu; Zhao, Lichuan; Xu, Hao; Ren, Shangqing; Tang, Bo; Tang, Zhaoyun; Xu, Yefeng; Xu, Jing; Yan, Jiang; Zhao, Chao; Chen, Dapeng; Ye, Tianchun

    2013-10-01

    In this paper, the drain induced barrier lowering (DIBL) variations in High-k/Metal gate n-channel metal-oxide-semiconductor field effect transistor under the normal and reverse channel hot carrier (CHC) stress are studied. It is found that DIBL decreases under normal CHC stress mode while increases under reverse CHC mode. The different DIBL variation under normal and reverse CHC stresses is proposed to be attributed to stress-induced charge trapping by cold carriers from the channel rather than hot carriers from the pinch off region, which can be explained by energy band bending theory.

  9. Characterization of Rape Field Microwave Emission and Implications to Surface Soil Moisture Retrievals

    Directory of Open Access Journals (Sweden)

    Alexander Loew

    2012-01-01

    Full Text Available In the course of Soil Moisture and Ocean Salinity (SMOS mission calibration and validation activities, a ground based L-band radiometer ELBARA II was situated at the test site Puch in Southern Germany in the Upper Danube Catchment. The experiment is described and the different data sets acquired are presented. The L-band microwave emission of the biosphere (L-MEB model that is also used in the SMOS L2 soil moisture algorithm is used to simulate the microwave emission of a winter oilseed rape field in Puch that was also observed by the radiometer. As there is a lack of a rape parameterization for L-MEB the SMOS default parameters for crops are used in a first step which does not lead to satisfying modeling results. Therefore, a new parameterization for L-MEB is developed that allows us to model the microwave emission of a winter oilseed rape field at the test site with better results. The soil moisture retrieval performance of the new parameterization is assessed in different retrieval configurations and the results are discussed. To allow satisfying results, the periods before and after winter have to be modeled with different parameter sets as the vegetation behavior is very different during these two development stages. With the new parameterization it is possible to retrieve soil moisture from multiangular brightness temperature data with a root mean squared error around 0.045–0.051 m³/m³ in a two parameter retrieval with soil moisture and roughness parameter Hr as free parameters.

  10. Magnetic field control of hysteretic switching in Co/Al2O3 multilayers by carrier injection

    Directory of Open Access Journals (Sweden)

    Alan Kalitsov

    2011-12-01

    Full Text Available We propose a theoretical model of magnetic field dependence of hysteretic switching in magnetic granular system. The model is based on the self-trapped electrons mechanism. Our calculations show that the switching voltage may be significantly decreased with increasing the magnetic field. The underlying mechanism is the influence of the magnetic field on electron occupation of the conduction band, which depends on the materials used in magnetic granular system, concentration of magnetic granules in the insulating matrix, applied voltage, and the charge accumulation on the granules. We support our theoretical calculations by measuring the magnetic field dependence of resistive switching behaviour in Co/Al2O3 granular multilayers. Our experimental results are in qualitative agreement with the proposed theory.

  11. [Rules and impact factors of greenhouse gases emission in the saline-alkali paddy fields in different years].

    Science.gov (United States)

    Tang, Jie; Fang, Tian-Ru; Hou, Ke-Yi; Zhao, Ren-Zhu; Liang, Shuang

    2014-12-01

    With the method of combining field sampling and plot test, we took saline-alkali paddy field of Qianguo county, Jilin province as an investigation object. According to the nature of soil in the area, we monitored CH4 and N2O which released from soil during rice growth period and tested the soil pH and soil organic carbon to analyze the law and reasons of greenhouse gas emission in the paddy fields. The results showed that N2O emission from paddy fields presented three peaks with distinct seasonal patterns. Application of fertilizer provided additional reactive substrate, which affected N2O emission significantly. Under flooding conditions, the main source of N2O is a denitrification process, while after drainage, nitrification was the predominance. CH4 emission showed a single peak at rice tillering stage when rice grew vigorously. That deoxidation condition dominated in the deep water layer in the paddy fields provided suitable conditions for CH4 producing microorganisms, which result in the emergence of CH4 emission peak. The pH doesn't have an obvious influence on CH4 and N2O, while SOC content in soil and pattern of CH4 emission showed a significantly positive correlation.

  12. Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111

    Directory of Open Access Journals (Sweden)

    J. Hennig

    2015-07-01

    Full Text Available We report on GaN based field-effect transistor (FET structures exhibiting sheet carrier densities of n = 2.9 1013 cm−2 for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally xIn = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the InxGa1−xN/GaN/AlN/Al0.87In0.13N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of ISD = 1300 mA/mm (560 mA/mm. In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents.

  13. Investigations of Flare Gas Emissions in Taq Taq Oil Field on the Surrounding Land

    Directory of Open Access Journals (Sweden)

    Jafar A. Ali

    2014-11-01

    Full Text Available Environmental pollution caused by oil takes many different forms; one of the most damaging sources is simply the combustion of oil products, such as a well flare burn-off. This paper presents the results of a survey of the agriculture lands around the Taq Taq Oil Production Company. The aim of the survey was to determine the potential contamination caused by the gas emissions from the well flares. Taq Taq field is located in the Kurdistan Region of Iraq, 60 km north of the giant Kirkuk oil field, 85 km south-east of Erbil and 120 km north-west of Suleimani. Samples of soil were collected from several locations around the site and analyzed to determine the content of Polycyclic Aromatic Hydrocarbons PAH present. A gas chromatography linked to a mass spectrometry (GCMS machine was used for these measurements. The PAH contamination at each location of soil was determined and the 16-PAHs, as listed in the US Environmental Protection Agency (EPA documentation were investigated. The average content of total PAH in all samples of the agricultural soil was 0.654 mg·kg-1 with the concentrations ranging from 0.310 to 0.869 mg·kg-1. It was found that the PAH concentrations decreased with increasing distance from the TTOPCO oil field, indicating that pollution was evident, the area close to the field being more affected by the gas pollution.

  14. Direct Measurements of Terahertz Meta-atoms with Near-Field Emission of Terahertz Waves

    Science.gov (United States)

    Serita, Kazunori; Darmo, Juraj; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi

    2017-09-01

    We present the direct measurements of terahertz meta-atoms, an elementary unit of metamaterials, by using locally generated terahertz waves in the near-field region. In contrast to a conventional far-field terahertz spectroscopy or imaging, our technique features the localized emission of coherent terahertz pulses on a sub-wavelength scale, which has a potential for visualizing details of dynamics of each meta-atom. The obtained data show the near-field coupling among the meta-atoms and the impact of the electric field distribution from the excited meta-atom to neighbor meta-atoms. The observable LC resonance response is enhanced with an increase of numbers of meta-atoms. Furthermore, our approach also has a potential for visualizing the individual mode of meta-atom at different terahertz irradiation spots. These data can help us to understand the important role of the meta-atom in metamaterials and develop the novel terahertz components and devices such as active terahertz metamaterial and compact, high-sensitive bio-sensor devices.

  15. Optimizing the e-beam profile of a single carbon nanotube field emission device for electric propulsion systems

    Directory of Open Access Journals (Sweden)

    Juliano Fujioka Mologni

    2010-04-01

    Full Text Available Preliminary studies on field emission (FE arrays comprised of carbon nanotubes (CNT as an electron source for electric propulsion system show remarkably promising results. Design parameters for a carbon nanotube (CNT field-emission device operating on triode configuration were numerically simulated and optimized in order to enhance the e-beam focusing quality. An additional focus gate (FG was integrated to the device to control the profile of the emitted e-beam. An axisymmetric finite element model was developed to calculate the electric field distribution on the vacuum region and a modified Fowler-Nordheim (FN equation was used to evaluate the current density emission and the effective emitter area. Afterward, a FE simulation was employed in order to calculate the trajectory of the emitted electrons and define the electron-optical properties of the e-beam. The integration of the FG was fully investigated via computational intelligence techniques. The best performance device according to our simulations presents a collimated e-beam profile that suits well for field emission displays, magnetic field detection and electron microscopy. The automated computational design tool presented in this study strongly benefits the robust design of integrated electron-optical systems for vacuum field emission applications, including electrodynamic tethering and electric propulsion systems.

  16. Effect of catalyst thickness and plasma pretreatment on the growth of carbon nanotubes and their field emission properties.

    Science.gov (United States)

    Uh, Hyung Soo; Park, Sang Sik; Kim, Byung Whan

    2007-11-01

    We demonstrated that the diameter and the density of carbon nanotubes (CNTs) which had a close relation to electric-field-screening effect could be easily changed by the control of catalytic Ni thickness combined with NH3 plasma pretreatment. Since the diameter and the density of CNTs had a tremendous impact on the field-emission characteristics, optimized thickness of catalyst and application of plasma pretreatment greatly improved the emission efficiency of CNTs. In the field emission test using diode-type configuration, well-dispersed thinner CNTs exhibited lower turn-on voltage and higher field enhancement factor than the densely-packed CNTs. A CNT film grown using a plasma-pretreated 25 angstroms-thick Ni catalyst showed excellent field emission characteristics with a very low turn-on field of 1.1 V/microm @ 10 microA/cm2 and a high emission current density of 1.9 mA/cm2 @ 4.0 V/microm, respectively.

  17. A comparative analysis of well-to-wheel primary energy demand and greenhouse gas emissions for the operation of alternative and conventional vehicles in Switzerland, considering various energy carrier production pathways

    Science.gov (United States)

    Yazdanie, Mashael; Noembrini, Fabrizio; Dossetto, Lionel; Boulouchos, Konstantinos

    2014-03-01

    This study provides a comprehensive analysis of well-to-wheel (WTW) primary energy demand and greenhouse gas (GHG) emissions for the operation of conventional and alternative passenger vehicle drivetrains. Results are determined based on a reference vehicle, drivetrain/production process efficiencies, and lifecycle inventory data specific to Switzerland. WTW performance is compared to a gasoline internal combustion engine vehicle (ICEV). Both industrialized and novel hydrogen and electricity production pathways are evaluated. A strong case is presented for pluggable electric vehicles (PEVs) due to their high drivetrain efficiency. However, WTW performance strongly depends on the electricity source. A critical electricity mix can be identified which divides optimal drivetrain performance between the EV, ICEV, and plug-in hybrid vehicle. Alternative drivetrain and energy carrier production pathways are also compared by natural resource. Fuel cell vehicle (FCV) performance proves to be on par with PEVs for energy carrier (EC) production via biomass and natural gas resources. However, PEVs outperform FCVs via solar energy EC production pathways. ICE drivetrains using alternative fuels, particularly biogas and CNG, yield remarkable WTW energy and emission reductions as well, indicating that alternative fuels, and not only alternative drivetrains, play an important role in the transition towards low-emission vehicles in Switzerland.

  18. Investigation of intermittent enhancement of ion emission from a tungsten surface using the field-ion microscope.

    Science.gov (United States)

    Weizer, V. G.

    1971-01-01

    The blinking effect, or the intermittent enhancement of ion emission, which is observed when a few parts per million neon are added to the imaging gas in a helium-tungsten field-ion microscope, has been investigated. Measurements of the characteristic quantities involved - i.e., blinking rate, voltage limits, etc. - and their variation with temperature, field, and gas pressure, are described.

  19. A field-based comparison of ammonia emissions from six Irish soil types following urea fertiliser application

    Directory of Open Access Journals (Sweden)

    Burchill W.

    2016-12-01

    Full Text Available Ammonia (NH3 emissions from a range of soil types have been found to differ under laboratory conditions. However, there is lack of studies comparing NH3 emissions from different soil types under field conditions. The objective was to compare NH3 emissions from six different soil types under similar environmental conditions in the field following urea fertiliser application. The study was conducted on a lysimeter unit and NH3 emissions were measured, using wind tunnels, from six different soil types with varying soil characteristics following urea fertiliser application (80 kg N/ha. On average, 17.6% (% total N applied was volatilised, and there was no significant difference in NH3 emissions across all soil types. Soil variables, including pH, cation exchange capacity and volumetric moisture, were not able to account for the variation in emissions. Further field studies are required to improve the urea-NH3 emission factor used for Ireland’s NH3 inventory.

  20. Cost-Effective Reciprocating Engine Emissions Control and Monitoring for E&P Field and Gathering Engines

    Energy Technology Data Exchange (ETDEWEB)

    Kirby S. Chapman; Sarah R. Nuss-Warren

    2007-02-01

    The objective of this project is to identify, develop, test, and commercialize emissions control and monitoring technologies that can be implemented by exploration and production (E&P) operators to significantly lower the cost of environmental compliance and expedite project permitting. The project team takes considerable advantage of the emissions control research and development efforts and practices that have been underway in the gas pipeline industry for the last 12 years. These efforts and practices are expected to closely interface with the E&P industry to develop cost-effective options that apply to widely-used field and gathering engines, and which can be readily commercialized. The project is separated into two phases. Phase 1 work establishes an E&P industry liaison group, develops a frequency distribution of installed E&P field engines, and identifies and assesses commercially available and emerging engine emissions control and monitoring technologies. Current and expected E&P engine emissions and monitoring requirements are reviewed, and priority technologies are identified for further development. The identified promising technologies are tested on a laboratory engine to confirm their generic viability. In addition, a full-scale field test of prototype emissions controls will be conducted on at least ten representative field engine models with challenging emissions profiles. Emissions monitoring systems that are integrated with existing controls packages will be developed. Technology transfer/commercialization is expected to be implemented through compressor fleet leasing operators, engine component suppliers, the industry liaison group, and the Petroleum Technology Transfer Council. This topical report discusses work completed during Phase 1 of the project Cost Effective Reciprocating Engine Emissions Control and Monitoring for E&P Field and Gathering Engines. In this report information, data, and results are compiled and summarized from quarterly

  1. Effect of graphene-oxide on the microstructure and charge carrier transport of polyaniline nanocomposites under low applied electric fields

    Science.gov (United States)

    Mombrú, Dominique; Romero, Mariano; Faccio, Ricardo; Mombrú, Álvaro W.

    2017-01-01

    We report a study on the preparation and characterization of polyaniline-graphene oxide (PANI-GO-X) nanocomposites focusing in the study of its structure, microstructure, and correlations with electrical transport properties under low applied electric fields. X-ray diffraction analysis showed evidence of graphene oxide (GO) blending between polyaniline fibers, and according to small angle X-ray scattering, the fractal dimensionality was quasi-one dimensional for all nanocomposites. Confocal Raman spectroscopy revealed that the addition of GO leads to a notorious decrease of the polaron population of polyaniline. A significant increase in resistivity was observed for PANI-GO-X nanocomposites with respect to pure polyaniline, in agreement with the decrease in the polaron population. The electrical transport mechanism could be explained by an Arrhenius behavior at high temperatures (T > 255 K) and a broad transition with a logarithmic dependence of the activation energy with temperature for the low temperature regime (T Poole-Frenkel type dependence in the presence of low applied electric fields. At low temperatures, X = 7% GO nanocomposites showed a notorious increase in the Poole-Frenkel slope at low applied electric fields with respect to pure polyaniline. The enhancement on the electric response using low applied electric fields (E ˜ 2 V/cm) could be of great interest for the development of new organic electronic devices.

  2. Water management reduces greenhouse gas emissions in a Mediterranean rice paddy field

    Science.gov (United States)

    Gruening, Carsten; Meijide, Ana; Manca, Giovanni; Goded, Ignacio; Seufert, Guenther; Cescatti, Alessandro

    2016-04-01

    Rice paddy fields are one of the biggest anthropogenic sources of methane (CH4), the second most important greenhouse gas (GHG) after carbon dioxide (CO2). Therefore most studies on greenhouse gases (GHG) in these agricultural systems focus on the evaluation of CH4 production. However, there are other GHGs such as CO2 and nitrous oxide (N2O) also exchanged within the atmosphere. Since each of the GHGs has its own radiative forcing effect, the total GHG budget of rice cultivation and its global warming potential (GWP) must be assessed. For this purpose a field experiment was carried out in a Mediterranean rice paddy field in the Po Valley (Italy), the largest rice producing region in Europe. Ecosystem CO2 and CH4 fluxes were assessed using the eddy covariance technique, while soil respiration and soil CH4 and N2O fluxes were measured with closed chambers for two complete years. Combining all GHGs measured, the rice paddy field acted as a sink of -368 and -828 g CO2 eq m-2 year-1 in the first and second years respectively. Both years, it was a CO2 sink and a CH4 source, while the N2O contribution to the GWP was relatively small. Differences in the GHG budget between the two years of measurements were mainly caused by the greater CH4 emissions in the first year (37.4 g CH4 m-2 compared to 21.03 g CH4 m-2 in the second year), probably as a consequence of the drainage of the water table in the middle of the growing season during the second year, which resulted in lower CH4 emissions without significant increases of N2O and CO2 fluxes. However, midseason drainage also resulted in small decreases of yield, indicating that GHG budget studies from agricultural systems should consider carbon exports through the harvest. The balance between net GWP and carbon yield indicated a loss of carbon equivalents from the system, which was more than 30-fold higher in the first year. Our results therefore suggest that an adequate management of the water table has the potential to be an

  3. Cost-Effective Reciprocating Engine Emissions Control and Monitoring for E & P Field and Gathering Engines

    Energy Technology Data Exchange (ETDEWEB)

    Kirby S. Chapman; Sarah R. Nuss-Warren

    2006-09-30

    Continuing work in controlled testing uses a one cylinder Ajax DP-115 (a 13.25 in bore x 16 in stroke, 360 rpm engine) to assess a sequential analysis and evaluation of a series of engine upgrades. As with most of the engines used in the natural gas industry, the Ajax engine is a mature engine with widespread usage throughout the gas gathering industry. The end point is an assessment of these technologies that assigns a cost per unit reduction in NO{sub X} emissions. Technologies including one pre-combustion chamber, in-cylinder sensors, the means to adjust the air-to-fuel ratio, and modification of the air filter housing have been evaluated in previous reports. Current work tests non-production, prototype, mid-pressure fuel valves and begins analysis of these tests. This analysis reveals questions which must be answered before coming to any firm conclusions about the use of the180 psig fuel valve. The research team plans to continue with the remaining pre-combustion chamber tests in the coming quarter. By using the Ajax DP-115 these tests are completed in a low-cost and efficient manner. The various technologies can be quickly exchanged with different hardware, and it is inexpensive to run the engine. Progress in moving toward field testing is discussed, and a change in strategy is suggested. Although field engines are available to test, it is suggested that the final field testing be put on hold due to information from outside publications during this last quarter. Instead, KSU would focus on related field-testing and characterization in an outside project that will close an apparent technology gap. The results of this characterization will give a more solid footing to the field testing that will complete this project.

  4. Temperature dependent field emission performances of carbon nanotube arrays: Speculation on oxygen desorption and defect annealing

    Energy Technology Data Exchange (ETDEWEB)

    Deng Jianhua; Yang Yumei; Zheng Ruiting [Key Laboratory of Beam Technology and Material Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Cheng Guoan, E-mail: gacheng@bnu.edu.cn [Key Laboratory of Beam Technology and Material Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China)

    2012-07-01

    We report here a systematic study of the field emission (FE) properties of highly ordered carbon nanotube (CNT) arrays at different temperatures. The FE characteristics of the CNT arrays are significantly improved with temperature increasing from 298 K to 473 K, as evidenced by the decreases of turn-on electric field at 10 {mu}A/cm{sup 2} from 1.064 to 0.774 V/{mu}m and threshold field at 10 mA/cm{sup 2} from 1.628 to 1.418 V/{mu}m, respectively. Moreover, the stability behavior of the CNT arrays is ameliorated at or after suffering to temperatures. Raman, EDS, XPS, and photoelectron spectrometer were employed to characterize the CNT arrays before and after the FE-Temperature measurements for comparison. Our results demonstrate that the oxygen desorption induced work function decrease (from 4.89 to 4.68 eV) of the CNT arrays after longtime exposure to temperature is responsible for the improved FE behavior, while the annealing of defects on CNTs is the main reason for the improved FE stability, which provides an effective approach to stabilizing emitters by temperature processing.

  5. Synthesis, Electrical Measurement, and Field Emission Properties of α-Fe2O3Nanowires

    Directory of Open Access Journals (Sweden)

    Hsiao Chun-Yen

    2008-01-01

    Full Text Available Abstractα-Fe2O3nanowires (NWs were formed by the thermal oxidation of an iron film in air at 350 °C for 10 h. The rhombohedral structure of the α-Fe2O3NWs was grown vertically on the substrate with diameters of 8–25 nm and lengths of several hundred nm. It was found that the population density of the NWs per unit area (DNWs can be varied by the film thickness. The thicker the iron film, the more NWs were grown. The growth mechanism of the NWs is suggested to be a combination effect of the thermal oxidation rate, defects on the film, and selective directional growth. The electrical resistivity of a single NW with a length of 800 nm and a diameter of 15 nm was measured to be 4.42 × 103 Ωcm using conductive atomic force microscopy. The field emission characteristics of the NWs were studied using a two-parallel-plate system. A low turn–on field of 3.3 V/μm and a large current density of 10−3 A/cm2(under an applied field of about 7 V/μm can be obtained using optimal factors ofDNWsin the cathode.

  6. Process-based modelling of ammonia emission over a urine patch - Towards developing a field scale emission model for regional use

    Science.gov (United States)

    Moring, Andrea; Vieno, Massimo; Doherty, Ruth; Sutton, Mark A.

    2014-05-01

    This work investigates the influence of meteorological factors on ammonia related atmospheric processes, with a special focus on emission from grazing. For this purpose we are developing a process-based model (GAG: Generation of Ammonia from Grazing) driven by meteorology that can simulate the ammonia emission from a field covered by urine patches. The aim of this work is to implement the GAG model into the EMEP atmospheric chemical transport model (ACTM), and examine the changes of surface ammonia concentrations under future climate scenarios. The research is carried out within the framework of the ECLAIRE project (Effects of Climate Change on Air Pollution and Response Strategies for European Ecosystems). To estimate the sensitivity of surface concentrations of ammonia to a temperature dependent emission approach, we applied a temperature function in the EMEP model for the agricultural ammonia emissions from the UK. With the original emissions the resulting surface ammonia concentration has a bimodal seasonal tendency, with a peak in the beginning of the spring when agricultural management starts and with a second maximum during the autumn when fertilizer is typically spread. With our new temperature dependent approach the seasonal cycle became unimodal with a peak in June. This significant difference supports the need for a dynamic emission approach in ACTMs. The GAG model currently works for a single urine patch. Before it calculates the ammonia emission flux over the urine patch the model simulates the ammoniacal nitrogen budget and the water budget under the patch. The preliminary results for emission fluxes are in good agreement with the measurements. However, the differences highlight that further improvements are necessary.

  7. Emission characteristics of PBDEs during flame-retardant plastics extruding process: field investigation and laboratorial simulation.

    Science.gov (United States)

    Deng, Chao; Li, Ying; Li, Jinhui; Chen, Yuan; Li, Huafen

    2017-10-01

    Though mechanical recycling of WEEE plastics is supposed to be a promising method, PBDEs release and the resulting contamination during its processing remain unclear yet. The distribution of PBDEs pollution in production lines was investigated from two flame-retardant plastic modification plants in Southern China. This was followed by laboratory simulation experiments to characterize the emission processes. PBDEs concentrations ranged from 37 to 31,305 ng/L in cooling water and from 40,043 to 216,653 ng/g dry wt in solid samples taken during the field investigation. In the laboratory simulation, concentrations ranged from 146 to 433 ng/L in cooling water and from 411,436 to 747,516 ng/Nm3 in flue gas. All samples were dominated by BDE-209 among the congeners. Temperatures and impurities in plastic substrate can significantly affect PBDEs release. Special attention should be paid to the risks of water directly discharge from the cooling system, especially for the biological sludge and sediments, as well as flue gas emissions to the environment.

  8. High-contrast en bloc staining of neuronal tissue for field emission scanning electron microscopy.

    Science.gov (United States)

    Tapia, Juan Carlos; Kasthuri, Narayanan; Hayworth, Kenneth J; Schalek, Richard; Lichtman, Jeff W; Smith, Stephen J; Buchanan, JoAnn

    2012-01-12

    Conventional heavy metal poststaining methods on thin sections lend contrast but often cause contamination. To avoid this problem, we tested several en bloc staining techniques to contrast tissue in serial sections mounted on solid substrates for examination by field emission scanning electron microscopy (FESEM). Because FESEM section imaging requires that specimens have higher contrast and greater electrical conductivity than transmission electron microscopy (TEM) samples, our technique uses osmium impregnation (OTO) to make the samples conductive while heavily staining membranes for segmentation studies. Combining this step with other classic heavy metal en bloc stains, including uranyl acetate (UA), lead aspartate, copper sulfate and lead citrate, produced clean, highly contrasted TEM and scanning electron microscopy (SEM) samples of insect, fish and mammalian nervous systems. This protocol takes 7-15 d to prepare resin-embedded tissue, cut sections and produce serial section images.

  9. Imaging plant nuclei and membrane-associated cytoskeleton by field emission scanning electron microscopy.

    Science.gov (United States)

    Fišerová, Jindřiška; Goldberg, Martin W

    2014-01-01

    Scanning electron microscopy (SEM) is a powerful technique that can image exposed surfaces in 3D. Modern scanning electron microscopes, with field emission electron sources and in-lens specimen chambers, achieve resolutions of better than 0.5 nm and thus offer views of ultrastructural details of subcellular structures or even macromolecular complexes. Obtaining a reliable image is, however, dependent on sample preparation methods that robustly but accurately preserve biological structures. In plants, exposing the object of interest may be difficult due to the existence of a cell wall. This protocol shows how to isolate plant nuclei for SEM imaging of the nuclear envelope and associated structures from both sides of the nuclear envelope in cultured cells as well as in leaf or root cells. Further, it provides a method for uncovering membrane-associated cytoskeletal structures.

  10. Field emission scanning electron microscopy of biofilm-growing bacteria involved in nosocomial infections.

    Science.gov (United States)

    Vuotto, Claudia; Donelli, Gianfranco

    2014-01-01

    Scanning electron microscopy (SEM) provides useful information on the shape, size, and localization within the biofilm of single bacteria as well as on the steps of biofilm formation process, on bacterial interactions, and on production of extracellular polymeric substances.When biofilms are constituted by microbial species involved in health care-associated infections, information provided by SEM can be fruitfully used not only for basic researches but also for diagnostic purposes.The protocols currently used in our laboratory for biofilm investigation by SEM are reported here. Particularly, the procedures to fix, dehydrate, and metalize in vitro-developed biofilms or ex vivo clinical specimens colonized by biofilm-growing microorganisms are described as well as the advantages of the observation of these samples by field emission scanning electron microscopy.

  11. Improved visualization of vertebrate nuclear pore complexes by field emission scanning electron microscopy.

    Science.gov (United States)

    Shaulov, Lihi; Harel, Amnon

    2012-03-07

    Field emission scanning electron microscopy (FESEM) can provide high-resolution three-dimensional surface imaging of many biological structures, including nuclear envelopes and nuclear pore complexes (NPCs). For this purpose, it is important to preserve NPCs as close as possible to their native morphology, embedded in undamaged nuclear membranes. We present optimized methodologies for FESEM imaging in a cell-free reconstitution system and for the direct visualization of mammalian cell nuclei. The use of anchored chromatin templates in the cell-free system is particularly advantageous for imaging fragile intermediates inhibited at early stages of assembly. Our new method for exposing the surface of mammalian nuclei results in an unprecedented quality of NPC images, avoiding detergent-induced and physical damage. These new methodologies pave the way for the combined use of FESEM imaging with biochemical and genetic manipulation, in cell-free systems and in mammalian cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Optical theorem for electromagnetic field scattering by dielectric structures and energy emission from the evanescent wave.

    Science.gov (United States)

    Gulyaev, Yu V; Barabanenkov, Yu N; Barabanenkov, M Yu; Nikitov, S A

    2005-08-01

    We present an optical theorem for evanescent (near field) electromagnetic wave scattering by a dielectric structure. The derivation is based on the formalism of angular spectrum wave amplitudes and block scattering matrix. The optical theorem shows that an energy flux is emitted in the direction of the evanescent wave decay upon scattering. The energy emission effect from an evanescent wave is illustrated in two examples of evanescent wave scattering, first, by the electrical dipole and, second, one-dimensional grating with line-like rulings. Within the latter example, we show that an emitted energy flux upon evanescent wave scattering can travel through a dielectric structure even if the structure has a forbidden gap in the transmission spectrum of incident propagating waves.

  13. Nano-Filament Field Emission Cathode Development Final Report CRADA No. TSB-0731-93

    Energy Technology Data Exchange (ETDEWEB)

    Bernhardt, Tony [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Fahlen, Ted [Candescent Technologies Corporation, San Jose, CA (United States)

    2018-01-17

    At the time the CRADA was established, Silicon Video Corporation, of Cupertino, CA was a one-year-old rapidly growing start-up company. SVC was developing flat panel displays (FPDs) to replace Cathode Ray Terminals (CRTs) for personal computers, work stations and televisions. They planned to base their products on low cost and energy efficient field emission technology. It was universally recognized that the display was both the dominant cost item and differentiating feature of many products such as laptop computers and hand-held electronics and that control of the display technology through U.S. sources was essential to success in these markets. The purpose of this CRADA project was to determine if electrochemical planarization would be a viable, inexpensive alternative to current optical polishing techniques for planarizing the surface of a ceramic backplate of a thin film display.

  14. High field terahertz emission from relativistic laser-driven plasma wakefields

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zi-Yu, E-mail: Ziyu.Chen@uni-duesseldorf.de [Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40225 (Germany); LSD, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621999 (China); Pukhov, Alexander [Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40225 (Germany)

    2015-10-15

    We propose a method to generate high field terahertz (THz) radiation with peak strength of GV/cm level in the THz frequency gap range of 1–10 THz using a relativistic laser interaction with a gaseous plasma target. Due to the effect of local pump depletion, an initially Gaussian laser pulse undergoes leading edge erosion and eventually evolves to a state with leading edge being step function. Interacting with such a pulse, electrons gain transverse residual momentum and excite net transverse currents modulated by the relativistic plasma frequency. These currents give rise to the low frequency THz emission. We demonstrate this process with one and two dimensional particle-in-cell simulations.

  15. CdZnTe detectors for small field of view positron emission tomographic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Drezet, Arnaud [CEA, LETI, MINATEC, Grenoble, F-38054 (France); Monnet, Olivier [CEA, LETI, MINATEC, Grenoble, F-38054 (France); Mathy, Francoise [CEA, LETI, MINATEC, Grenoble, F-38054 (France); Montemont, Guillaume [CEA, LETI, MINATEC, Grenoble, F-38054 (France); Verger, Loick [CEA, LETI, MINATEC, Grenoble, F-38054 (France)]. E-mail: loick.verger@cea.fr

    2007-02-01

    We report the timing performance between two 16x20x0.9 mm{sup 3} cadmium zinc telluride (CZT) detectors equipped with a specific orthogonal electrode geometry (16 anodes and 5 cathodes with 1 and 4 mm pitch, respectively) and a dedicated electronic setup for Positron Emission Tomography (PET) application. The measured coincidence times reach 2.6 ns full-width at half-maximum (FWHM) for a 500 V bias voltage and 300 keV energy threshold. Subsequently, a simulation study was carried out to assess the spatial and efficiency performances of these detectors, which allow the depth of interaction (DOI) measurement and so limit the parallax error. Preliminary results show that the proposed design could reach a better homogeneity of the spatial resolution across the field of view than what is achieved with the standard PET scintillation.

  16. Electromagnetic Emissions During Rock-fracturing Experiments Inside Magnetic Field Free Space

    Science.gov (United States)

    Wang, H.; Zhou, J.; Zhu, T.; Jin, H.

    2012-12-01

    Abnormal electromagnetic emission (EME) signal is one type of the most important precursors before earthquake, which has been widely observed and recorded before large earthquake, but the physical mechanism underlying the phenomenon is unclear and under controversy. Monitoring the EME signals during rock-fracturing experiments in laboratory is an effective way to study the phenomena and their underlying mechanism. Electromagnetic noise is everywhere because industrial and civilian electrical equipments have been widely used, which make difficulties to the in-lab experiments and field monitoring. To avoid the interference from electromagnetic noise, electromagnetic experiments must be carried out inside shielded space. Magnetic Field Free Space (MFFS) was constructed by Institute of Geophysics, China Earthquake Administration in 1980s. MFFS is a near-spherical polyhedron 'space' with 26 faces and inside diameter about 2.3 m. It is enclosed by 8-layer permalloy 1J85 for shielding magnetic field and 2-layer purified aluminium for shielding electric field. MFFS mainly shields static magnetic field by a factor of 160-4000 for the magnetic signals with the frequencies ranging from 0.01 Hz to 10 Hz. The intensity of magnetic field inside the space is less than 20 nT and its fluctuation is less than 0.3 nT in 90 hours. MFFS can dramatically shield EME signals in the frequency range of EME antennas utilized in our experiments, (several to ~320) kHz, by at least 90%, based on observation. Rock specimens (granite, marble) were fractured by two ways inside MFFS. 1) Cuboid bulk specimens were drilled, filled with static cracking agent, and then dilated from inside until fracture. 2) Cylindrical rock specimens were stressed until fracture by using a non-magnetic rock testing machine with the maximum testing force 300kN. EME, acoustic emission (AE) and strain signals were collected synchronously by the same data acquisitor, Acoustic Emission Workstation made by Physical Acoustics

  17. Role of work function in field emission enhancement of Au island decorated vertically aligned ZnO nanotapers

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Avanendra [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Senapati, Kartik, E-mail: kartik@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Kumar, Mohit; Som, Tapobrata [SUNAG Laboratory, Institute of Physics, Bhubaneswar 751005, Odisha (India); Sinha, Anil K. [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Sahoo, Pratap K., E-mail: pratap.sahoo@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India)

    2017-07-31

    Highlights: • Hydrothermally synthesized nanotapers were decorated by gold corrugation using simple evaporation techniques for large area applications. • A significantly enhanced field emission properties of nanotapers were achieved. • The metal induced midgap states formed at the ZnO-Au interface and the reduced effective work function are responsible for low turn-on field. • TUNA measurements revealed a very uniform spatial emission profile in the Au decorated nanotapers. - Abstract: In this report, we demonstrate significantly enhanced field emission properties of ZnO nanotapers achieved via a corrugated decoration of Au. Field emission experiments on these Au-decorated ZnO nanotapers showed emission current densities comparable to the best results in the literature. Au decoration of 5 nm also reduced the effective turn-on field to ∼0.54 V/μm, compared to the as grown ZnO nanotapers, which showed a turn-on field of ∼1.1 V/μm. Tunneling atomic force microscopy measurements revealed a very uniform spatial emission profile in the 5 nm Au decorated nanotapers, which is a basic requirement for any large scale application. We believe that metal induced mid-gap states formed at the ZnO–Au interface are responsible for the observed low turn-on field because such interface states are known to reduce the effective work function. A direct measurement of effective work function using Kelvin probe force microscopy indeed showed more than 1.1 eV drop in the case of 5 nm Au decorated ZnO nanotapers compared to the pristine nanotapers, supporting the above argument.

  18. Thermal-field emission flicker (1/f) noise and diffusive equilibrium density fluctuations

    Science.gov (United States)

    Gesley, Mark; Swanson, Lyn

    1988-06-01

    comparable W(h k l) planes are consistent with field-ion microscopy measurements. The defect vacancy activation energy is estimated from the temperature dependence of the adatom creation rate and is similar to that obtained from emitter surface-tension measurements. For the projection optics of field emission systems spatial resolution is mapped to the Gaussian source diameter dg. Using this new measurement method dg~=20 Å is obtained for 1000 K thermal-field emission from tungsten.

  19. Organic particulate emissions from field burning of garden and agriculture residues

    Science.gov (United States)

    Gonçalves, Cátia; Evtyugina, Margarita; Alves, Célia; Monteiro, Cristina; Pio, Casimiro; Tomé, Mário

    2011-08-01

    To assess the particulate matter (PM) composition, the smoke from three different agriculture and garden residues, commonly subjected to open field burning in Northern Portugal (potato haulm (A), arable weed vegetation (B) and collard greens stalks/pruned green leafy-twigs (C)) have been sampled into 3 different size fractions (PM 2.5, PM 2.5-10 and PM > 10 ). To replicate another frequent practise of reducing or dispose agriculture/garden debris, residue C was complementarily burned in a metal container with addition of used lubricant oil. The size-segregated aerosol samples were analysed for elemental (EC) and organic (OC) carbon by a thermal-optical transmission technique. The organosoluble OC was fractionated by vacuum flash chromatography and analysed by gas chromatography-mass spectrometry (GC-MS). Burning of residue C produced the highest PM emissions. OC was the dominant carbonaceous component in all aerosol samples, contributing to about 98% of total carbon (TC). The detailed chemical profiles of particulate emissions, including organic tracer compounds, have been assessed. The contribution of phenolics (0.2-39% OC, w/w) and organic acids (1.5-13% OC, w/w) to OC was always predominant over other organic compounds, whose distribution patterns were found to vary from one residue to another. The polyphenols, as the guaiacyl derivatives, were particularly abundant in PM from the residue C burning, but anthropogenic constituents completely superimposed the emission profiles after addition of used lubricant oil. It was shown that the prevailing ambient conditions (such as high humidity) likely contributed to atmospheric processes (e.g. coagulation and hygroscopic growth), which influenced the particle size characteristics of the smoke tracers, shifting their distribution to larger diameters. Since it was shown that the relative contribution of different carbon forms and organic compounds may strongly depend on the size of the particulate matter, the barely

  20. Multiple-year nitrous oxide emissions from a greenhouse vegetable field in China: Effects of nitrogen management.

    Science.gov (United States)

    Zhang, Jing; Li, Hu; Wang, Yingchun; Deng, Jia; Wang, Ligang

    2017-11-02

    The greenhouse vegetable (GV) field is an important agricultural system in China. It may also be a hot spot of nitrous oxide (N2O) emissions. However, knowledge on N2O emission from GV fields and its mitigation are limited due to considerable variations of N2O emissions. In this study, we performed a multi-year experiment at a GV field in Beijing, China, using the static opaque chamber method, to quantify N2O emissions from GV fields and evaluated N2O mitigation efficiency of alternative nitrogen (N) managements. The experiment period spanned three rotation periods and included seven vegetable growing seasons. We measured N2O emissions under four treatments, including no N fertilizer use (CK), farmers' conventional fertilizer application (FP), reduced N fertilizer rate (R), and R combined with the nitrification inhibitor "dicyandiamide (DCD)" (R+DCD). The seasonal cumulative N2O emissions ranged between 2.09 and 19.66, 1.13 and 11.33, 0.94 and 9.46, and 0.15 and 3.27kgNha(-1) for FP, R, R+DCD, and CK, respectively. The cumulative N2O emissions of three rotational periods varied from 18.71 to 26.58 (FP), 9.58 to 15.96 (R), 7.11 to 13.42 (R+DCD), and 1.66 to 3.73kgNha(-1) (CK). The R and R+DCD treatments significantly (P<0.05) reduced the N2O emissions under FP by 38.1% to 48.8% and 49.5% to 62.0%, across the three rotational periods, although their mitigation efficiencies were highly variable among different vegetable seasons. This study suggests that GV fields associated with intensive N application and frequent flooding irrigation may substantially contribute to the N2O emissions and great N2O mitigations can be achieved through reasonably reducing the N-fertilizer rate and/or applying a nitrification inhibitor. The large variations in the N2O emission and mitigation across different vegetable growing seasons and rotational periods stress the necessity of multi-year observations for reliably quantifying and mitigating N2O emissions for GV systems. Copyright

  1. [18F]Fluoro-2-deoxy-D-glucose positron emission tomography detects gastric carcinoma in an early stage in an asymptomatic E-cadherin mutation carrier.

    NARCIS (Netherlands)

    Kouwen, M.C.A. van; Drenth, J.P.H.; Oyen, W.J.G.; Bruin, J.H.F.M. de; Ligtenberg, M.J.L.; Bonenkamp, J.J.; Krieken, J.H.J.M. van; Nagengast, F.M.

    2004-01-01

    PURPOSE: Autosomal dominant hereditary diffuse gastric cancer (HDGC) is caused by germ-line E-cadherin (CDH1) gene mutations. Early detection of cancer in carriers is difficult because HDGC escapes endoscopic detection. We hypothesized that the glucose metabolism is enhanced in HDGC and that this

  2. Exploration of ‘hot-spots’ of methane and nitrous oxide emission from the agriculture fields of Assam, India

    Directory of Open Access Journals (Sweden)

    Mishra Satyendra

    2012-10-01

    Full Text Available Abstract Background Agricultural soils contribute towards the emission of CH4 (mainly from paddy fields and N2O (from N-fertilizer application, the two important greenhouse gases causing global warming. Most studies had developed the inventories of CH4 and N2O emission at the country level (larger scale for India, but not many studies are available at the local scale (e.g. district level on these greenhouse gases (GHGs. Assam is an important state in the North Eastern region of India. In addition to being the regional economic hub for the entire region, agriculture is the major contributor to the state’s gross domestic product. In Assam about three-fourths of the area is under paddy cultivation and rice is the staple food. With this background, a district wise inventory of CH4 and N2O emission in the North Eastern state of Assam, India was carried out using different emission factors, viz., IPCC, Indian factors and others, to highlight the discrepancies that arose in the emission estimation of these important GHGs while used at the smaller scale i.e. district level. This study emphasizes the need for better methodologies at the local level for GHGs inventories. This study also reiterates the fact that no emission factor is universally applicable across all regions. The GHGs like CH4 and N2O are highly site and crop specific and the factors required for their inventory are driven by cultural practices, agronomic management, soil resources and socio-economic drivers. Material and methods In this study, Intergovernmental Panel on Climate Change (IPCC methodology was used for the estimation of CH4 and N2O emission. In case of N2O emission, both direct and indirect emission from agricultural soil was estimated for the various districts of Assam. Results The CH4 (base year 2000–2001 and N2O (base year 2001–2002 emission was estimated to be 121 Gg and 1.36 Gg from rice paddy and agricultural fields of Assam state respectively. Conclusions This

  3. Field emission of comb-like chromium disilicide nanowires prepared by an in situ chloride-generated route

    Science.gov (United States)

    Hu, Yemin; Hu, Zheng; Yu, Leshu; Li, Ying; Zhu, Mingyuan; Bai, Qin

    2011-04-01

    Large-area comb-like chromium disilicide (CrSi2) nanowire film has been successfully synthesized on silicon wafer through an in situ chloride-generated route. The sample possesses branch-like nanowires grown out perpendicularly and evenly from both sides of a stem-like microrod, forming 2-fold comb-like hierarchical nanoarchitectures. The formation mechanism of the sample could be understood by a secondary nucleation process occurring on the surface of the firstly formed CrSi2 microrod, followed by epitaxial growth of branch-like nanowires under conditions of proper temperature and sufficient vapor supply in the reaction system. The field-emission behavior of the sample shows a low turn-on field of 5.3-6.5 V/μm at anode-sample distances of 200-400 μm, and agrees well with the conventional Fowler-Nordheim theory. No obvious degradation was observed in a life stability experiment period for over 100 min. The relationship between the field enhancement factor and anode-sample distance follows a universal equation, developed within a two-region field-emission model. The convenient and low-cost preparation of the comb-like CrSi2 nanowires and their remarkable field-emission performance suggest that they can serve as good candidates for field-emission applications.

  4. The angular power spectrum measurement of the Galactic synchrotron emission in two fields of the TGSS survey

    Science.gov (United States)

    Choudhuri, Samir; Bharadwaj, Somnath; Ali, Sk. Saiyad; Roy, Nirupam; Intema, Huib. T.; Ghosh, Abhik

    2017-09-01

    Characterizing the diffuse Galactic synchrotron emission at arcminute angular scales is needed to reliably remove foregrounds in cosmological 21-cm measurements. The study of this emission is also interesting in its own right. Here, we quantify the fluctuations of the diffuse Galactic synchrotron emission using visibility data for two of the fields observed by the TIFR GMRT Sky Survey. We have used the 2D Tapered Gridded Estimator to estimate the angular power spectrum (Cℓ) from the visibilities. We find that the sky signal, after subtracting the point sources, is likely dominated by the diffuse Galactic synchrotron radiation across the angular multipole range 240 ≤ ℓ ≲ 500. We present a power-law fit, C_{ℓ}=A× \\big (1000/l\\big )^{β }, to the measured Cℓ over this ℓ range. We find that (A, β) have values (356 ± 109 mK2, 2.8 ± 0.3) and (54 ± 26 mK2, 2.2 ± 0.4) in the two fields. For the second field, however, there is indication of a significant residual point source contribution and for this field we interpret the measured Cℓ as an upper limit for the diffuse Galactic synchrotron emission. While in both fields the slopes are consistent with earlier measurements, the second field appears to have an amplitude that is considerably smaller compared to similar measurements in other parts of the sky.

  5. Initial Analysis of VOCs Speciation in CREATE Emissions Inventory using the MAPS-Seoul Aircraft Field Campaign

    Science.gov (United States)

    Bu, C.; Woo, J. H.; Lee, Y.; Kim, J.; Choi, K. C.; Kim, Y.; Kim, J.; Jang, Y. K.; Kim, S.

    2016-12-01

    As the first international cooperative air quality field study, the MAPS-Seoul (Megacity Air Pollution Studies-Seoul) aircraft mission was conducted in May - June 2016 over the South Korea, to understand of climate and atmospheric environment. The aircraft carried observation instruments for measurements of GHGs, ozone and its precursors, aerosols, and chemical tracers. The CREATE (Comprehensive Regional Emissions inventory for Atmospheric Environment) emissions inventory and SMOKE-Asia emission processing system were used to support chemical forecasting and to serve as a priori for evaluation. Initial results of comparison studies show large discrepancies in VOC species over the South Korea - especially over urban regions. Several VOC species observed high near megacities and petro-chemical plants but under-predicted by chemical transport models (CTMs) - possibly due to relatively low emissions. The chemical speciation profiles and emissions inventory for each emission sources, therefore, have to be re-visited to improve emissions information. In this study, we have; 1) re-examined our emissions inventory and emission speciation processes, 2) and tried to find possible missing sources and alternative chemical speciation profiles, to improve our modelling emissions inventory. Initial review of the mapping and classification profiles, the original US chemical speciation profiles were found to be low in partitioning painting and surface coating sources, although they are the very significant contributors. Unlike other major national cities in China, Shanghai's VOC emissions fraction seems very similar to that of Seoul. Continuous analysis of major urban and industrial areas of the country will be presented at site.Acknowledgements : This subject is supported by Korea Ministry of Environment as "Climate Change Correspondence Program". This work was supported by a grant from the National Institute of Environment Research (NIER), funded by the Ministry of Environment

  6. Influence of high-energy electron irradiation on field emission properties of multi-walled carbon nanotubes (MWCNTs) films

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Sandip S. [Center for Advanced Studies in Material Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); Koinkar, Pankaj M. [Center for International Cooperation in Engineering Education (CICEE), University of Tokushima, 2-1 Minami-Josanjima-Cho, Tokushima 770-8506 (Japan); Dhole, Sanjay D. [Center for Advanced Studies in Material Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); More, Mahendra A., E-mail: mam@physics.unipune.ac.i [Center for Advanced Studies in Material Science and Condensed Matter Physics, Department of Physics, University of Pune, Pune 411007 (India); Murakami, Ri-ichi, E-mail: murakami@me.tokushima-u.ac.j [Department of Mechanical Engineering, University of Tokushima, 2-1 Minami-Josanjima-Cho, Tokushima 770-8506 (Japan)

    2011-04-15

    The effect of very high energy electron beam irradiation on the field emission characteristics of multi-walled carbon nanotubes (MWCNTs) has been investigated. The MWCNTs films deposited on silicon (Si) substrates were irradiated with 6 MeV electron beam at different fluence of 1x10{sup 15}, 2x10{sup 15} and 3x10{sup 15} electrons/cm{sup 2}. The irradiated films were characterized using scanning electron microscope (SEM) and micro-Raman spectrometer. The SEM analysis clearly revealed a change in surface morphology of the films upon irradiation. The Raman spectra of the irradiated films show structural damage caused by the interaction of high-energy electrons. The field emission studies were carried out in a planar diode configuration at the base pressure of {approx}1x10{sup -8} mbar. The values of the threshold field, required to draw an emission current density of {approx}1 {mu}A/cm{sup 2}, are found to be {approx}0.52, 1.9, 1.3 and 0.8 V/{mu}m for untreated, irradiated with fluence of 1x10{sup 15}, 2x10{sup 15} and 3x10{sup 15} electrons/cm{sup 2}. The irradiated films exhibit better emission current stability as compared to the untreated film. The improved field emission properties of the irradiated films have been attributed to the structural damage as revealed from the Raman studies.

  7. Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

    Energy Technology Data Exchange (ETDEWEB)

    Li, Detian; Cheng, Yongjun [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Wang, Yongjun, E-mail: wyjlxlz@163.com [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Zhang, Huzhong [Science and Technology on Vacuum Technology and Physics Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Dong, Changkun [Institute of Micro-Nano Structures and Optoelectronics, Wenzhou University, Wenzhou 325035 (China); Li, Da [Division of Advanced Nanomaterials, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215125 (China)

    2016-03-01

    Graphical abstract: - Highlights: • The high quality CNT arrays were successfully grown on conductive stainless steel substrates. • The CNT array grown on stainless steel substrate exhibited superior field emission properties. • A high vacuum level about 10–8 Pa was measured by resultant CNT-based ionization gauge. • The ionization gauge with CNT cathode demonstrated a high stability. - Abstract: Vertically aligned carbon nanotube (CNT) arrays were fabricated by chemical vapor deposition (CVD) technique on different substrates. Microstructures and field emission characteristics of the as-grown CNT arrays were investigated systematically, and its application in ionization gauge was also evaluated preliminarily. The results indicate that the as-grown CNT arrays are vertically well-aligned relating to the substrate surfaces, but the CNTs grown on stainless steel substrate are longer and more crystalline than the ones grown on silicon wafer substrate. The field emission behaviors of the as-grown CNT arrays are strongly dependent upon substrate properties. Namely, the CNT array grown on stainless steel substrate has better field emission properties, including lower turn on and threshold fields, better emission stability and repeatability, compared with the one grown on silicon wafer substrate. The superior field emission properties of the CNT array grown on stainless steel substrate are mainly attributed to low contact resistance, high thermal conductivity, good adhesion strength, etc. In addition, the metrological behaviors of ionization gauge with the CNT array grown on stainless steel substrate as an electron source were investigated, and this novel cathode ionization gauge extends the lower limit of linear pressure measurement to 10{sup −8} Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

  8. Electroluminescence of superatom-like Ge-core/Si-shell quantum dots by alternate field-effect-induced carrier injection

    Science.gov (United States)

    Makihara, Katsunori; Ikeda, Mitsuhisa; Fujimura, Nobuyuki; Yamada, Kentaro; Ohta, Akio; Miyazaki, Seiichi

    2018-01-01

    We have fabricated high-density superatom-like Si–Ge-based quantum dots (Si-QDs with Ge core) and studied their luminescence properties. Electroluminescence was observed from the Si-QDs with Ge core at room temperature in the near-infrared region by the application of square-wave pulsed bias of ±1 V at 500 kHz, which was attributed to radiative recombination between quantized states in the Ge core with deep potential well for holes caused by field-effect-induced alternate electron/hole injection from the substrate. The results lead to the development of Si-based light-emitting devices that are highly compatible with ultra-large-scale integration processing, which was found difficult to realize in silicon photonics.

  9. Thirty per cent contrast in secondary-electron imaging by scanning field-emission microscopy.

    Science.gov (United States)

    Zanin, D A; De Pietro, L G; Peter, Q; Kostanyan, A; Cabrera, H; Vindigni, A; Bähler, Th; Pescia, D; Ramsperger, U

    2016-11-01

    We perform scanning tunnelling microscopy (STM) in a regime where primary electrons are field-emitted from the tip and excite secondary electrons out of the target-the scanning field-emission microscopy regime (SFM). In the SFM mode, a secondary-electron contrast as high as 30% is observed when imaging a monoatomic step between a clean W(110)- and an Fe-covered W(110)-terrace. This is a figure of contrast comparable to STM. The apparent width of the monoatomic step attains the 1 nm mark, i.e. it is only marginally worse than the corresponding width observed in STM. The origin of the unexpected strong contrast in SFM is the material dependence of the secondary-electron yield and not the dependence of the transported current on the tip-target distance, typical of STM: accordingly, we expect that a technology combining STM and SFM will highlight complementary aspects of a surface while simultaneously making electrons, selected with nanometre spatial precision, available to a macroscopic environment for further processing.

  10. The use of field emission scanning electron microscopy to assess recombinant adenovirus stability.

    Science.gov (United States)

    Obenauer-Kutner, Linda J; Ihnat, Peter M; Yang, Tong-Yuan; Dovey-Hartman, Barbara J; Balu, Arthi; Cullen, Constance; Bordens, Ronald W; Grace, Michael J

    2002-09-20

    A field emission scanning electron microscopy (FESEM) method was developed to assess the stability of a recombinant adenovirus (rAd). This method was designed to simultaneously sort, count, and size the total number of rAd viral species observed within an image field. To test the method, a preparation of p53 transgene-expressing recombinant adenovirus (rAd/p53) was incubated at 37 degrees C and the viral particles were evaluated by number, structure, and degree of aggregation as a function of time. Transmission electron microscopy (TEM) was also used to obtain ultrastructural detail. In addition, the infectious activity of the incubated rAd/p53 samples was determined using flow cytometry. FESEM image-analysis revealed that incubation at 37 degrees C resulted in a time-dependent decrease in the total number of detectable single rAd/p53 virus particles and an increase in apparent aggregates composed of more than three adenovirus particles. There was also an observed decrease in both the diameter and perimeter of the single rAd/p53 viral particles. TEM further revealed the accumulation of damaged single particles with time at 37 degrees C. The results of this study demonstrate that FESEM, coupled with sophisticated image analysis, may be an important tool in quantifying the distribution of aggregated species and assessing the overall stability of rAd samples.

  11. Cryo-field emission scanning electron microscopy imaging of a rigid surfactant mesophase.

    Science.gov (United States)

    Tan, Grace; Xu, Peng; John, Vijay T; He, Jibao; McPherson, Gary L; Agarwal, Vivek; Bose, Arijit

    2008-10-07

    The aerosol OT/ L-alpha-phosphatidylcholine/isooctane/water system forms a rigid mesophase that transitions from reverse hexagonal to multilamellar in structure at specific water contents. This study shows that characteristics of ordered liquid-crystalline mesophases can be distinguished and imaged in high clarity using cryo-field emission scanning electron microscopy (cryo-FESEM). The reverse hexagonal phase consists of bundles of long cylinders, some with length scales of over 2 microm, that are randomly oriented as part of a larger domain. Cryo-imaging allows the visualization of the intercylinder spacings and the details of transitions from one domain to another. The multilamellar structured mesophase consists of spherical vesicles of 100 nm to 10 microm in diameter, with intervening noncrystalline isotropic regions. Coexistence regions containing both the reverse hexagonal and lamellar structures are also observed in the transition from the reverse hexagonal to the lamellar phase. These results complement and qualitatively verify our earlier studies with small-angle neutron scattering, high-field nuclear magnetic resonance spectroscopy, and freeze-fracture direct imaging transmission electron microscopy. The information is useful in understanding materials templating in these rigid systems.

  12. Field evaluation of Fourier transform infrared continuous emissions monitoring (FTIR CEM) systems

    Science.gov (United States)

    Dunder, Thomas A.; Geyer, Thomas J.; Kinner, Laura L.; Plummer, Grant M.

    1995-02-01

    Recent environmental regulations, including the Clean Air Act and the Enhanced Monitoring Regulations, may require continuous emissions monitoring (CEM) of hazardous air pollutants (HAPs). A promising technique for this application is Fourier transform infrared spectroscopy (FTIR). FTIR spectroscopy can, in principle, be used to monitor virtually any gas phase species. Two evaluations of FTIR CEM systems are discussed. The first study, performed in 1993 - 94, compared two FTIR CEM systems on a side-by-side basis in an extended field test at two coal-fired electric power plants. The FTIR CEM systems monitored the legally mandated criteria pollutants and diluents (CO, CO2, NO, NO2, and SO2) as well as H2O. In addition, one system monitored two HAPs (HCl and HF) and NH3. The FTIR CEM measurements were compared with those from the compliance CEM systems at the facilities. Several relative accuracy test audits were also performed to verify the FTIR CEM accuracy. The second evaluation was recently commenced on behalf of the Environmental Protection Agency. In this study, FTIR CEM systems are evaluated specifically for the monitoring of HAP species by conducting laboratory and field tests. The evaluation culminates in the development of proposed performance specifications and protocols for FTIR CEM systems.

  13. Carbon and nitrogen emissions from stored manure and cropped fields in irrigated mountain oases of Oman

    Directory of Open Access Journals (Sweden)

    Jens Gebauer

    2010-04-01

    Full Text Available Little is known about gaseous carbon (C and nitrogen (N emissions from traditional terrace agriculture in irrigated high mountain agroecosystems of the subtropics. In an effort towards filling this knowledge gap measurements of carbon dioxide (CO_2, methane (CH_4, ammonia (NH_3 and dinitrous oxide (N_2O were taken with a mobile photoacoustic infrared multi-gas monitor on manure-filled PE-fibre storage bags and on flood-irrigated untilled and tilled fields in three mountain oases of the northen Omani Al Jabal al Akhdar mountains. During typical 9-11 day irrigation cycles of March, August and September 2006 soil volumetric moisture contents of fields dominated by fodder wheat, barley, oats and pomegranate ranged from 46-23%. While manure incorporation after application effectively reduced gaseous N losses, prolonged storage of manure in heaps or in PE-fibre bags caused large losses of C and N. Given the large irrigation-related turnover of organic C, sustainable agricultural productivity of oasis agriculture in Oman seems to require the integration of livestock which allows for several applications of manure per year at individual rates of 20 t dry matter ha^−1.

  14. Raman spectroscopy and field emission characterization of delafossite CuFeO2

    Science.gov (United States)

    Pavunny, Shojan P.; Kumar, Ashok; Katiyar, R. S.

    2010-01-01

    Delafossite p-type CuFeO2 (CFO) semiconductors were synthesized by a modified solid state reaction technique and investigated by x-ray diffraction, x-ray photoemission spectroscopy (XPS), energy dispersive x-ray spectroscopy, and scanning electron microscopy, revealing the single-phase nature of CFO with 1:1 Cu/Fe atomic ratio. The valance states of CFO were examined by XPS and suggest Cu and Fe ions are in +1 and +3 valance states with high spin S=5/2. The "turn-on field" which is the macroscopic field needed to get an emission current of 9 nA, was calculated as 5.72 V/μm. Room temperature Raman spectra of CFO displayed two main Raman active modes at Eg˜351 cm-1 and Ag˜692 cm-1 in accord with other delafossite structures. Temperature dependent Raman spectra showed that both the modes shifted to lower frequency with significant decrease in intensity with increase in temperature. Frequency shift and linewidth of both phonon lines matched well with the theoretical damped harmonic oscillator model based on thermal expansion of the lattice and their anharmonicity coupling with other phonons.

  15. Focus Ion Beam Fabrication of Individual Carbon Nanotube Field Emission Tips

    Science.gov (United States)

    Chai, Guangyu; Byahut, Sitaram; Chow, Lee

    2003-11-01

    Individual CNTs are excellent candidates as electron sources for electron microscopes. Comparing to conventional electron sources, CNTs have the following advantages: (1) unique geometry, (2) highly coherent electron beams, and (3) stability. In our laboratory, carbon fibers with a nanotube core have been synthesized with a conventional chemical vapor deposition method. The whole assembly of nanotube/fiber is similar to a coaxial cable with CNT sticking out from one end of the carbon fiber. In order to pick up individual CNT field emitters, focus ion beam (FIB) technique is applied for cutting and adhering the samples. The carbon fiber with nanotube tip was first welded onto a micro-manipulator. Afterwards, by applying the FIB milling function, the fiber was cut from the base. This enables us to handle the individual CNT tips conveniently. By the same method, we can attach the nanotube tip on a sharpened clean tungsten wire for field emission experiment. FIB is proven to be appropriate and powerful for the nano-fabrication.

  16. The Adaptation Law for emissions trading. Part 2. A level playing field for emissions trading?; De Aanpassingswet handel in emissierechten. Deel 2. Een level playing field voor emissiehandel?

    Energy Technology Data Exchange (ETDEWEB)

    Simonetti, S. [Praktijkgroep Energy and Carbon, De Brauw Blackstone Westbroek, Amsterdam (Netherlands)

    2010-05-15

    To supplement, clarify and simplify the regulations for emission trading, the Amendment Act emission trading II was submitted to the Dutch Lower Chamber end of 2009. This article discusses the pending bill and comments on a number of remarkable stipulations that may be important to the market parties. First a brief overview is provided of the basic principles of emission trading and the players in the CO2 market. [Dutch] Ter 'aanvulling, verduidelijking en vereenvoudiging' van de regelgeving m.b.t. emissiehandel werd eind 2009 bij de Tweede Kamer de Aanpassingswet handel in emissierechten II ingediend. Dit artikel bespreekt het hangende wetsvoorstel en plaatst kanttekeningen bij een aantal opmerkelijke bepalingen die voor marktpartijen van belang kunnen zijn. Eerst wordt een kort overzicht gegeven van de basisprincipes van emissiehandel en de spelers op de CO2-markt.

  17. Characteristic Features of Stone-Wales Defects in Single-Walled Carbon Nanotube; Adsorption, Dispersion, and Field Emission

    Directory of Open Access Journals (Sweden)

    Seungkwang Roh

    2010-01-01

    Full Text Available Adsorption behaviors of dodecanethiol (C12H25SH molecules are investigated on the surface of single-walled carbon nanotubes (SWCNTs with vibrational and X-ray photoelectron spectrometers. The active adsorption sites are proved as Stone-Wales (SW defects (5–7 ring defects. The SW defect-removed SWCNTs formed by reacting nanotubes with allyl acrylate molecules are compared with pristine SWCNTs in dispersion and field emission. The former shows higher dispersion and field emission than the latter.

  18. A Study on Field Emission Characteristics of Planar Graphene Layers Obtained from a Highly Oriented Pyrolyzed Graphite Block.

    KAUST Repository

    Lee, Seok Woo

    2009-07-12

    This paper describes an experimental study on field emission characteristics of individual graphene layers for vacuum nanoelectronics. Graphene layers were prepared by mechanical exfoliation from a highly oriented pyrolyzed graphite block and placed on an insulating substrate, with the resulting field emission behavior investigated using a nanomanipulator operating inside a scanning electron microscope. A pair of tungsten tips controlled by the nanomanipulator enabled electric connection with the graphene layers without postfabrication. The maximum emitted current from the graphene layers was 170 nA and the turn-on voltage was 12.1 V.

  19. Biochar's effect on soil nitrous oxide emissions from a maize field with lime adjusted pH treatment

    Science.gov (United States)

    Hüppi, Roman; Leifeld, Jens; Felber, Raphael; Neftel, Albrecht; Six, Johan

    2015-04-01

    Biochar is a carbon-rich, porous product from pyrolysis of organic residues. Especially tropical soils have shown positive response in yield to biochar addition. Its high stability in soil makes biochar a potent carbon sequestration option at the same time. A number of laboratory incubations have shown significantly reduced nitrous oxide (N2O) emissions from soil when mixed with biochar. Emission measurements from the field show the same trend but are much more scarce. One of the hypothesized mechanisms for reduced N2O emissions from soil is owing to the increase in soil pH from the application of alkaline biochar. To test the effect of biochar on N2O emissions from a temperate maize system, we set up a field trial with a 20 t/ha biochar treatment, a limestone treatment adjusted to the same pH as with biochar and a control without addition. An automated static chamber greenhouse gas measurement system measured N2O emissions for each replicated (n=3) every 3.6 hours. The field was conventionally fertilised at a rate of 160 kg-N/ha in 3 doses of 40, 80 and 40 kg-N/ha. Cumulative emissions show a significant reduction for N2O in the biochar treatment by about 55 % relative to the control. The limed treatment shows similar emissions than control but with higher variability. This suggests that the N2O reduction effect of biochar is not mainly due to its liming effect. In conclusion, we confirm that biochar is a promising material to reduce N2O emissions from intensively managed agricultural soils.

  20. Sealing rice field boundaries in Bangladesh: a pilot study demonstrating reductions in water use, arsenic loading to field soils, and methane emissions from irrigation water.

    Science.gov (United States)

    Neumann, Rebecca B; Pracht, Lara E; Polizzotto, Matthew L; Badruzzaman, A Borhan M; Ali, M Ashraf

    2014-08-19

    Irrigation of rice fields in Bangladesh with arsenic-contaminated and methane-rich groundwater loads arsenic into field soils and releases methane into the atmosphere. We tested the water-savings potential of sealing field bunds (raised boundaries around field edges) as a way to mitigate these negative outcomes. We found that, on average, bund sealing reduced seasonal water use by 52 ± 17% and decreased arsenic loading to field soils by 15 ± 4%; greater savings in both water use and arsenic loading were achieved in fields with larger perimeter-to-area ratios (i.e., smaller fields). Our study is the first to quantify emission of methane from irrigation water in Bangladesh, a currently unaccounted-for methane source. Irrigation water applied to unsealed fields at our site emits 18 to 31 g of methane per square-meter of field area per season, potentially doubling the atmospheric input of methane from rice cultivation. Bund sealing reduced the emission of methane from irrigation water by 4 to 19 g/m(2). While the studied outcomes of bund sealing are positive and compelling, widespread implementation of the technique should consider other factors, such as effect on yields, financial costs, and impact on the hydrologic system. We provide an initial and preliminary assessment of these implementation factors.

  1. Near-Field Imaging of Free Carriers in ZnO Nanowires with a Scanning Probe Tip Made of Heavily Doped Germanium

    Science.gov (United States)

    Sakat, Emilie; Giliberti, Valeria; Bollani, Monica; Notargiacomo, Andrea; Pea, Marialilia; Finazzi, Marco; Pellegrini, Giovanni; Hugonin, Jean-Paul; Weber-Bargioni, Alexander; Melli, Mauro; Sassolini, Simone; Cabrini, Stefano; Biagioni, Paolo; Ortolani, Michele; Baldassarre, Leonetta

    2017-11-01

    A novel scanning probe tip made of heavily doped semiconductor is fabricated and used instead of standard gold-coated tips in infrared scattering-type near-field microscopy. Midinfrared near-field microscopy experiments are conducted on ZnO nanowires with a lateral resolution better than 100 nm, using tips made of heavily electron-doped germanium with a plasma frequency in the midinfrared (plasma wavelength of 9.5 μ m ). Nanowires embedded in a dielectric matrix are imaged at two wavelengths, 11.3 and 8.0 μ m , above and below the plasma wavelength of the tips. An opposite sign of the imaging contrasts between the nanowire and the dielectric matrix is observed at the two infrared wavelengths, indicating a clear role of the free-electron plasma in the heavily doped germanium tip in building the imaging contrast. Electromagnetic simulations with a multispherical dipole model accounting for the finite size of the tip are well consistent with the experiments. By comparison of the simulated and measured imaging contrasts, an estimate for the local free-carrier density in the investigated ZnO nanowires in the low 1019 cm-3 range is retrieved. The results are benchmarked against the scattering intensity and phase maps obtained on the same sample with a gold-coated probe tip in pseudoheterodyne detection mode.

  2. Estimate on the uncertainty of predicting radiated emission from near-field scan caused by insufficient or inaccurate near-field data

    DEFF Research Database (Denmark)

    Sørensen, Morten; Radchenko, Andriy; Kam, Keong

    2012-01-01

    Near-field scan on a Huygens’ box can be used in order to predict the maximal radiated emission from a Printed Circuit Board. The significance of step size and phase accuracy, and the importance of a full Huygens’ box are investigated by simulation of two different models with two different numer...

  3. Role of work function in field emission enhancement of Au island decorated vertically aligned ZnO nanotapers

    Science.gov (United States)

    Singh, Avanendra; Senapati, Kartik; Kumar, Mohit; Som, Tapobrata; Sinha, Anil K.; Sahoo, Pratap K.

    2017-07-01

    In this report, we demonstrate significantly enhanced field emission properties of ZnO nanotapers achieved via a corrugated decoration of Au. Field emission experiments on these Au-decorated ZnO nanotapers showed emission current densities comparable to the best results in the literature. Au decoration of 5 nm also reduced the effective turn-on field to ∼0.54 V/μm, compared to the as grown ZnO nanotapers, which showed a turn-on field of ∼1.1 V/μm. Tunneling atomic force microscopy measurements revealed a very uniform spatial emission profile in the 5 nm Au decorated nanotapers, which is a basic requirement for any large scale application. We believe that metal induced mid-gap states formed at the ZnO-Au interface are responsible for the observed low turn-on field because such interface states are known to reduce the effective work function. A direct measurement of effective work function using Kelvin probe force microscopy indeed showed more than 1.1 eV drop in the case of 5 nm Au decorated ZnO nanotapers compared to the pristine nanotapers, supporting the above argument.

  4. Emission Line Astronomy - Coronagraphic Tunable Narrow Band Imaging and Integral Field Spectroscopy. Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to continue our program of emission line astronomy featuring three areas of emphasis: 1) The distribution and nature of high redshift emission line...

  5. Pulsed-laser-deposited amorphous diamond and related materials: synthesis, characterization, and field emission properties

    Science.gov (United States)

    Merkulov, Vladimir I.; Lowndes, Douglas H.; Baylor, Larry R.; Jellison, Gerald E., Jr.; Puretzky, Alexander A.; Geohegan, David B.

    1999-07-01

    Amorphous carbon films with variable sp3 content were produced by ArF pulsed laser deposition. An in-situ ion probe was used to measure kinetic energy of C+ ions. In contrast to measurements made as a function of laser fluence, ion probe measurements of kinetic energy are a convenient as well as more accurate and fundamental method for monitoring deposition conditions, with the advantage of being readily transferable for inter-laboratory comparisons. Electron energy loss spectroscopy and spectroscopic ellipsometry measurement reveal that tetrahedral amorphous carbon films with the most diamond-like properties are obtained at the C ion kinetic energy of approximately 90 eV. Film properties are uniform within a 12-15 degrees angle from the plume centerline. Tapping-mode atomic force microscope measurements show that films deposited at near- optimum kinetic energy are extremely smooth, with rms roughness of only approximately 1 angstrom over distances of several hundred nm. Field emission (FE) measurements show that ta-C does not appear to be a good electron emitter. After conditioning of ta-C films deposited on n-type Si a rather high turn-on voltage of approximately 50 V/micrometers was required to draw current of approximately 1 nA to the probe. The emission was unstable and typically ceased after a few minutes of operation. The FE tests of ta-C and other materials strongly suggest that surface morphology plays a dominant role in the FE process, in agreement with conventional Fowler-Nordheim theory.

  6. Carbon dioxide emission in relation with irrigation and organic amendments from a sweet corn field.

    Science.gov (United States)

    Fares, Ali; Bensley, Adam; Bayabil, Haimanote; Awal, Ripendra; Fares, Samira; Valenzuela, Hector; Abbas, Farhat

    2017-06-03

    minimize soil CO2 emissions, BM soil amendments could be a potential option to reduce soil CO2 fluxes from agricultural fields similar to the one used in this study.

  7. Effect of surface application of ammonium thiosulfate on field-scale emissions of 1,3-dichloropropene.

    Science.gov (United States)

    Yates, S R; Ashworth, D J; Zhang, Q

    2017-02-15

    Soil fumigation is important for food production but has the potential to discharge toxic chemicals into the environment, which may adversely affect human and ecosystem health. A field experiment was conducted to evaluate the effect of applying ammonium thiosulfate fertilizer to the soil surface prior to fumigating with 1,3-dichloropropene (1,3-D). The ammonium thiosulfate solution was applied as a spray with minimal water to minimize the effect on emissions from saturating (e.g. sealing) the soil pores with water. Two independent data sets were collected for determining the emission rate. One data set was used with three micrometeorological approaches: aerodynamic, integrated horizontal flux and theoretical profile shape; the other dataset with two indirect, back calculation methods that used the CALPUFF and ISCST3 dispersion models. Using the five methodologies, the 1,3-D emission rate was obtained for 16days. The maximum emission rates ranged from 7 to 20μgm-2s-1, the maximum 24-hour averaged emission rates ranged from 5 to 13μgm-2s-1, and the total 1,3-D emissions ranged from 12 to 26%. Comparing to fumigation without ammonium thiosulfate spray revealed that emissions were reduced from 3% (CALPUFF) to 29% (ADM). Using a simulation model, ammonium thiosulfate spray would be expected to reduce emissions by almost 21%. These data provide evidence that emissions of 1,3-D can be reduced by spraying ammonium thiosulfate fertilizer on the soil surface prior to soil fumigation, and provides another emission-reduction strategy to those recently reported (e.g., deep injection, water seals and organic amendments). Published by Elsevier B.V.

  8. Physiologically gated microbeam radiation using a field emission x-ray source array

    Energy Technology Data Exchange (ETDEWEB)

    Chtcheprov, Pavel, E-mail: PavelC@unc.edu, E-mail: zhou@email.unc.edu [Department of Biomedical Engineering, University of North Carolina, 152 MacNider Hall, Campus Box 7575, Chapel Hill, North Carolina 27599 (United States); Burk, Laurel; Inscoe, Christina; Ger, Rachel; Hadsell, Michael; Lu, Jianping [Department of Physics and Astronomy, University of North Carolina, Phillips Hall, CB #3255, 120 East Cameron Avenue, Chapel Hill, North Carolina 27599 (United States); Yuan, Hong [Department of Radiology, University of North Carolina, 2006 Old Clinic, CB #7510, Chapel Hill, North Carolina 27599 (United States); Zhang, Lei [Department of Applied Physical Sciences, University of North Carolina, Chapman Hall, CB#3216, Chapel Hill, North Carolina 27599 (United States); Chang, Sha [Department of Radiation Oncology, University of North Carolina, 101 Manning Drive, Chapel Hill, North Carolina 27514 and UNC Lineberger Comprehensive Cancer Center, University of North Carolina, 101 Manning Drive, Chapel Hill, North Carolina 27514 (United States); Zhou, Otto, E-mail: PavelC@unc.edu, E-mail: zhou@email.unc.edu [Department of Physics and Astronomy, University of North Carolina, Phillips Hall, CB #3255, 120 East Cameron Avenue, Chapel Hill, North Carolina 27599 and UNC Lineberger Comprehensive Cancer Center, University of North Carolina, 101 Manning Drive, Chapel Hill, North Carolina 27514 (United States)

    2014-08-15

    Purpose: Microbeam radiation therapy (MRT) uses narrow planes of high dose radiation beams to treat cancerous tumors. This experimental therapy method based on synchrotron radiation has been shown to spare normal tissue at up to 1000 Gy of peak entrance dose while still being effective in tumor eradication and extending the lifetime of tumor-bearing small animal models. Motion during treatment can lead to significant movement of microbeam positions resulting in broader beam width and lower peak to valley dose ratio (PVDR), which reduces the effectiveness of MRT. Recently, the authors have demonstrated the feasibility of generating microbeam radiation for small animal treatment using a carbon nanotube (CNT) x-ray source array. The purpose of this study is to incorporate physiological gating to the CNT microbeam irradiator to minimize motion-induced microbeam blurring. Methods: The CNT field emission x-ray source array with a narrow line focal track was operated at 160 kVp. The x-ray radiation was collimated to a single 280 μm wide microbeam at entrance. The microbeam beam pattern was recorded using EBT2 Gafchromic{sup ©} films. For the feasibility study, a strip of EBT2 film was attached to an oscillating mechanical phantom mimicking mouse chest respiratory motion. The servo arm was put against a pressure sensor to monitor the motion. The film was irradiated with three microbeams under gated and nongated conditions and the full width at half maximums and PVDRs were compared. An in vivo study was also performed with adult male athymic mice. The liver was chosen as the target organ for proof of concept due to its large motion during respiration compared to other organs. The mouse was immobilized in a specialized mouse bed and anesthetized using isoflurane. A pressure sensor was attached to a mouse's chest to monitor its respiration. The output signal triggered the electron extraction voltage of the field emission source such that x-ray was generated only

  9. Design, Fabrication, and Characterization of Carbon Nanotube Field Emission Devices for Advanced Applications

    Science.gov (United States)

    Radauscher, Erich Justin

    Carbon nanotubes (CNTs) have recently emerged as promising candidates for electron field emission (FE) cathodes in integrated FE devices. These nanostructured carbon materials possess exceptional properties and their synthesis can be thoroughly controlled. Their integration into advanced electronic devices, including not only FE cathodes, but sensors, energy storage devices, and circuit components, has seen rapid growth in recent years. The results of the studies presented here demonstrate that the CNT field emitter is an excellent candidate for next generation vacuum microelectronics and related electron emission devices in several advanced applications. The work presented in this study addresses determining factors that currently confine the performance and application of CNT-FE devices. Characterization studies and improvements to the FE properties of CNTs, along with Micro-Electro-Mechanical Systems (MEMS) design and fabrication, were utilized in achieving these goals. Important performance limiting parameters, including emitter lifetime and failure from poor substrate adhesion, are examined. The compatibility and integration of CNT emitters with the governing MEMS substrate (i.e., polycrystalline silicon), and its impact on these performance limiting parameters, are reported. CNT growth mechanisms and kinetics were investigated and compared to silicon (100) to improve the design of CNT emitter integrated MEMS based electronic devices, specifically in vacuum microelectronic device (VMD) applications. Improved growth allowed for design and development of novel cold-cathode FE devices utilizing CNT field emitters. A chemical ionization (CI) source based on a CNT-FE electron source was developed and evaluated in a commercial desktop mass spectrometer for explosives trace detection. This work demonstrated the first reported use of a CNT-based ion source capable of collecting CI mass spectra. The CNT-FE source demonstrated low power requirements, pulsing

  10. Electrostatically focused addressable field emission array chips (AFEA's) for high-speed massively parallel maskless digital E-beam direct write lithography and scanning electron microscopy

    Science.gov (United States)

    Thomas, Clarence E.; Baylor, Larry R.; Voelkl, Edgar; Simpson, Michael L.; Paulus, Michael J.; Lowndes, Douglas H.; Whealton, John H.; Whitson, John C.; Wilgen, John B.

    2002-12-24

    Systems and methods are described for addressable field emission array (AFEA) chips. A method of operating an addressable field-emission array, includes: generating a plurality of electron beams from a pluralitly of emitters that compose the addressable field-emission array; and focusing at least one of the plurality of electron beams with an on-chip electrostatic focusing stack. The systems and methods provide advantages including the avoidance of space-charge blow-up.

  11. Effect of substrate material on the growth and field emission characteristics of large-area carbon nanotube forests

    Science.gov (United States)

    Ummethala, Raghunandan; Wenger, Daniela; Tedde, Sandro F.; Täschner, Christine; Leonhardt, Albrecht; Büchner, Bernd; Eckert, Jürgen

    2016-01-01

    Carbon nanotubes (CNTs) are a promising replacement for tungsten filaments as electron emitters in conventional x-ray sources, owing to their higher aspect ratio, superior mechanical stability, chemical inertness, and high electrical and thermal conductivities. Conditions for realizing the best emission behavior from CNTs have been formulated over the last few years. In this paper, we report the relatively less-investigated factor, namely, the influence of the nature of substrate material on the growth as well as field emission characteristics of large-area multiwalled CNTs for their practical application in medical x-ray sources. We compare the morphology of CNTs on a variety of substrates such as stainless steel, copper, molybdenum, graphite, few-layer graphene, and carbon nanowalls grown by thermal chemical vapor deposition following a simple drop-coating of catalyst. We find that CNTs grown on stainless steel and graphite show the best combination of emission characteristics under pulsed operation mode. These studies are helpful in selecting the optimum substrate material for field emission applications. Ex situ studies on field emission degradation of CNTs are presented towards the end.

  12. Effect of substrate material on the growth and field emission characteristics of large-area carbon nanotube forests

    Energy Technology Data Exchange (ETDEWEB)

    Ummethala, Raghunandan; Täschner, Christine; Leonhardt, Albrecht; Büchner, Bernd [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Wenger, Daniela; Tedde, Sandro F. [Siemens Healthcare GmbH, Technology Centre, Guenther-Scharowsky-Strasse 1, 91058 Erlangen (Germany); Eckert, Jürgen [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstrasse 12, A-8700 Leoben (Austria); Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben (Austria)

    2016-01-28

    Carbon nanotubes (CNTs) are a promising replacement for tungsten filaments as electron emitters in conventional x-ray sources, owing to their higher aspect ratio, superior mechanical stability, chemical inertness, and high electrical and thermal conductivities. Conditions for realizing the best emission behavior from CNTs have been formulated over the last few years. In this paper, we report the relatively less-investigated factor, namely, the influence of the nature of substrate material on the growth as well as field emission characteristics of large-area multiwalled CNTs for their practical application in medical x-ray sources. We compare the morphology of CNTs on a variety of substrates such as stainless steel, copper, molybdenum, graphite, few-layer graphene, and carbon nanowalls grown by thermal chemical vapor deposition following a simple drop-coating of catalyst. We find that CNTs grown on stainless steel and graphite show the best combination of emission characteristics under pulsed operation mode. These studies are helpful in selecting the optimum substrate material for field emission applications. Ex situ studies on field emission degradation of CNTs are presented towards the end.

  13. Exploring a suitable nitrogen fertilizer rate to reduce greenhouse gas emissions and ensure rice yields in paddy fields

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Yiming; Wang, Xiaopeng; Yang, Jingping, E-mail: jpyang@zju.edu.cn; Zhao, Xing; Ye, Xinyi

    2016-09-15

    The application rate of nitrogen fertilizer was believed to dramatically influence greenhouse gas (GHG) emissions from paddy fields. Thus, providing a suitable nitrogen fertilization rate to ensure rice yields, reducing GHG emissions and exploring emission behavior are important issues for field management. In this paper, a two year experiment with six rates (0, 75, 150, 225, 300, 375 kg N/ha) of nitrogen fertilizer application was designed to examine GHG emissions by measuring carbon dioxide (CO{sub 2}), methane (CH{sub 4}), nitrous oxide (N{sub 2}O) flux and their cumulative global warming potential (GWP) from paddy fields in Hangzhou, Zhejiang in 2013 and 2014. The results indicated that the GWP and rice yields increased with an increasing application rate of nitrogen fertilizer. Emission peaks of CH{sub 4} mainly appeared at the vegetative phase, and emission peaks of CO{sub 2}, and N{sub 2}O mainly appeared at reproductive phase of rice growth. The CO{sub 2} flux was significantly correlated with soil temperature, while the CH{sub 4} flux was influenced by logging water remaining period and N{sub 2}O flux was significantly associated with nitrogen application rates. This study showed that 225 kg N/ha was a suitable nitrogen fertilizer rate to minimize GHG emissions with low yield-scaled emissions of 3.69 (in 2013) and 2.23 (in 2014) kg CO{sub 2}-eq/kg rice yield as well as to ensure rice yields remained at a relatively high level of 8.89 t/ha in paddy fields. - Highlights: • Exploiting co-benefits of rice yield and reduction of greenhouse gas emission. • Global warming potential and rice yield increased with nitrogen fertilizer rate up. • Emission peaks of CH{sub 4,} CO{sub 2} and N{sub 2}O appeared at vegetative and reproductive phase. • 225 kg N/ha rate benefits both rice yields and GWP reduction.

  14. Contributions of transported Prudhoe Bay oil field emissions to the aerosol population in Utqiagvik, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Gunsch, Matthew J.; Kirpes, Rachel M.; Kolesar, Katheryn R.; Barrett, Tate E.; China, Swarup; Sheesley, Rebecca J.; Laskin, Alexander; Wiedensohler, Alfred; Tuch, Thomas; Pratt, Kerri A.

    2017-01-01

    Loss of sea ice is opening the Arctic to increasing development involving oil and gas extraction and shipping. Given the significant impacts of absorbing aerosol and secondary aerosol precursors emitted within the rapidly warming Arctic region, it is necessary to characterize local anthropogenic aerosol sources and compare to natural conditions. From August to September 2015 in Utqiagvik (Barrow), AK, the chemical composition of individual atmospheric particles was measured by computer-controlled scanning electron microscopy with energy-dispersive X-ray spectroscopy (0.13–4 µm projected area diameter) and real-time single-particle mass spectrometry (0.2–1.5 µm vacuum aerodynamic diameter). During periods influenced by the Arctic Ocean (70 % of the study), our results show that fresh sea spray aerosol contributed ~20 %, by number, of particles between 0.13 and 0.4 µm, 40–70 % between 0.4 and 1 µm, and 80–100 % between 1 and 4 µm particles. In contrast, for periods influenced by emissions from Prudhoe Bay (10 % of the study), the third largest oil field in North America, there was a strong influence from submicron (0.13–1 µm) combustion-derived particles (20–50 % organic carbon, by number; 5–10% soot by number). While sea spray aerosol still comprised a large fraction of particles (90 % by number from 1 to 4 µm) detected under Prudhoe Bay influence, these particles were internally mixed with sulfate and nitrate indicative of aging processes during transport. In addition, the overall mode of the particle size number distribution shifted from 76 nm during Arctic Ocean influence to 27 nm during Prudhoe Bay influence, with particle concentrations increasing from 130 to 920 cm-3 due to transported particle emissions from the oil fields. The increased contributions of carbonaceous combustion products and partially aged sea spray aerosol should be considered in future Arctic atmospheric composition and climate simulations.

  15. Effects of straw incorporation along with microbial inoculant on methane and nitrous oxide emissions from rice fields

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Gang; Yu, Haiyang [State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, No. 71 East Beijing Road, Nanjing 210008 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Ma, Jing [State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, No. 71 East Beijing Road, Nanjing 210008 (China); Xu, Hua, E-mail: hxu@issas.ac.cn [State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, No. 71 East Beijing Road, Nanjing 210008 (China); Wu, Qinyan; Yang, Jinghui; Zhuang, Yiqing [Zhenjiang Institute of Agricultural Science of Hilly Regions in Jiangsu, Jurong 212400 (China)

    2015-06-15

    Incorporation of straw together with microbial inoculant (a microorganism agent, accelerating straw decomposition) is being increasingly adopted in rice cultivation, thus its effect on greenhouse gas (GHG) emissions merits serious attention. A 3-year field experiment was conducted from 2010 to 2012 to investigate combined effect of straw and microbial inoculant on methane (CH{sub 4}) and nitrous oxide (N{sub 2}O) emissions, global warming potential (GWP) and greenhouse gas intensity (GHGI) in a rice field in Jurong, Jiangsu Province, China. The experiment was designed to have treatment NPK (N, P and K fertilizers only), treatment NPKS (NPK plus wheat straw), treatment NPKSR (NPKS plus Ruilaite microbial inoculant) and treatment NPKSJ (NPKS plus Jinkuizi microbial inoculant). Results show that compared to NPK, NPKS increased seasonal CH{sub 4} emission by 280–1370%, while decreasing N{sub 2}O emission by 7–13%. When compared with NPKS, NPKSR and NPKSJ increased seasonal CH{sub 4} emission by 7–13% and 6–12%, respectively, whereas reduced N{sub 2}O emission by 10–27% and 9–24%, respectively. The higher CH{sub 4} emission could be attributed to the higher soil CH{sub 4} production potential triggered by the combined application of straw and microbial inoculant, and the lower N{sub 2}O emission to the decreased inorganic N content. As a whole, the benefit of lower N{sub 2}O emission was completely offset by increased CH{sub 4} emission, resulting in a higher GWP for NPKSR (5–12%) and NPKSJ (5–11%) relative to NPKS. Due to NPKSR and NPKSJ increased rice grain yield by 3–6% and 2–4% compared to NPKS, the GHGI values for NPKS, NPKSR and NPKSJ were comparable. These findings suggest that incorporating straw together with microbial inoculant would not influence the radiative forcing of rice production in the terms of per unit of rice grain yield relative to the incorporation of straw alone. - Highlights: • This paper presents 3-year measurements of CH

  16. Shallow tillage generates higher N2O emissions: results of continuous chamber-based measurement in a winter wheat field.

    Science.gov (United States)

    Broux, François; Lognoul, Margaux; Theodorakopoulos, Nicolas; Hiel, Marie-Pierre; Bodson, Bernard; Heinesch, Bernard; Aubinet, Marc

    2017-04-01

    Agriculture is one of the most important contributors to GHG emission, notably through fertilized croplands. Though, few publications have studied simultaneously and through continuous measurement the N2O and CO2 emissions in cultivated lands. We conducted this study to assess the effect of farming practices and climate on both N2O and CO2 emissions from a winter wheat crop. The experiment was held in an experimental field in the loamy region in Belgium from March 2016 till crop harvest in August 2016. The fluxes were measured on two nearby parcels in a winter wheat field with restitution of the residues from previous crop. For the past 8 years, one parcel was subjected to a shallow tillage (ST, 10 cm depth) and the other one to a conventional tillage (CT, 25 cm depth). On each parcel, the emissions are assessed with homemade automated closed chambers. Measurement continuity and good temporal resolution (one mean flux every 4 hours) of the system allowed a fine detection and quantification of the emission peaks which usually represent the major part of N2O fluxes. In addition to gas fluxes, soil water content and temperature were measured continuously. Soil samples were taken regularly to determine soil pH, soil organic carbon and nitrogen pools (total, NO3- and NH4+) and study microbial diversity and nitrification/denitrification gene expression. Unexpectedly, results showed N2O emissions twice as large in the ST parcel as in the CT parcel. On the contrary, less important CO2 emissions were observed under ST. Several emission peaks of N2O were observed during the measurement period. The peaks occurred after fertilization events and seemed to be triggered by an elevation of soil water content. Interesting links could be made between soil NH4-N and NO3-N pools and N2O emissions. Nitrification being the main process originating the fluxes was suggested on the one hand by the temporal evolution of nitrogen pools and N2O emissions and on the other hand by the relation

  17. Theoretical Study Of The Effects Of Magnetic Field Geometry On The High-Energy Emission Of Blazars

    OpenAIRE

    Manasvita Joshi; Alan Marscher; Markus Böttcher

    2016-01-01

    The knowledge of the structure of the magnetic field inside a blazar jet, as deduced from polarization observations at radio to optical wavelengths, is closely related to the formation and propagation of relativistic jets that result from accretion onto supermassive black holes. However, a largely unexplored aspect of the theoretical understanding of radiation transfer physics in blazar jets has been the magnetic field geometry as revealed by the polarized emission and the connection between ...

  18. Mitigation options for methane emissions from rice fields in the Philippines

    Energy Technology Data Exchange (ETDEWEB)

    Lantin, R.S.; Buendia, L.V.; Wassmann, R. [International Rice Research Institute, Laguna (Philippines)] [and others

    1996-12-31

    The contribution of Philippine rice production to global methane emission and breakthroughs in methane emission studies conducted in the country are presented in this paper. A significant impact in the reduction of GHG emissions from agriculture can be achieved if methane emissions from ricefields can be abated. This study presents the contribution of Philippine rice cultivation to global methane emission and breakthroughs in methane emission studies in the country which address the issue of mitigation. Using the derived emission factors from local measurements, rice cultivation contributes 566.6 Gg of methane emission in the Philippines. This value is 62% of the total methane emitted from the agriculture sector. The emission factors employed which are 78% of the IPCC value for irrigated rice and 95% for rainfed rice were derived from measurements with an automatic system taken during the growth duration in the respective ecosystems. Plots drained for 2 weeks at midtillering and before harvest gave a significant reduction in methane emission as opposed to continuously flooded plots and plots drained before harvest. The cultivar Magat reduced methane emission by 50% as compared to the check variety IR72. The application of ammonium sulfate instead of urea reduced methane emission by 10% to 34%. Addition of 6 t ha{sup {minus}1} phosphogypsum in combination with urea reduced emission by 74% as opposed to plots applied with urea alone. It is also from the results of such measurements that abatement strategies are based as regards to modifying treatments such as water management, fertilization, and choice of rice variety. It is not easy to identify and recommend mitigation strategies that will fit a particular cropping system. However, the identified mitigation options provide focus for the abatement of methane emission from ricefields.

  19. LOW-VOLTAGE FIELD-EMISSION SCANNING ELECTRON-MICROSCOPY OF NON-COATED GUINEA-PIG HAIR CELL STEREOCILIA

    NARCIS (Netherlands)

    DUNNEBIER, EA; SEGENHOUT, JM; KALICHARAN, D; JONGEBLOED, WL; WIT, HP; ALBERS, FWJ

    1995-01-01

    The stereociliar structures of the guinea-pig cochlear organ of Corti were studied at low-voltage (1-5 kV) with field-emission scanning electron microscope (SEM) using various pre- and post-fixation methods, such as OTOTO (OsO4/thiocarbohydrazide/OsO4/thiocarbohydrazide/OsO4) and TAO (tannic

  20. Field-emission scanning electron microscopy analysis of morphology and enzyme distribution within an industrial biocatalytic particle

    NARCIS (Netherlands)

    Roon, van J.L.; Aelst, van A.C.; Schroën, C.G.P.H.; Tramper, J.; Beeftink, H.H.

    2005-01-01

    Field-emission scanning electron microscopy (FESEM) was used in a technical feasibility study to obtain insight into the internal morphology and the intraparticle enzyme distribution of Assemblase®, an industrial biocatalytic particle containing immobilized penicillin-G acylase. The results were

  1. Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field

    NARCIS (Netherlands)

    Jelic, V.; de Bruyn, A. G.; Mevius, M.; Abdalla, F. B.; Asad, K. M. B.; Bernardi, G.; Brentjens, M. A.; Bus, S.; Chapman, E.; Ciardi, B.; Daiboo, S.; Fernandez, E. R.; Ghosh, A.; Harker, G.; Jensen, H.; Kazemi, S.; Koopmans, L. V. E.; Labropoulos, P.; Martinez-Rubi, O.; Mellema, G.; Offringa, A. R.; Pandey, V. N.; Patil, A. H.; Thomas, R. M.; Vedantham, H. K.; Veligatla, V.; Yatawatta, S.; Zaroubi, S.; Alexov, A.; Anderson, J.; Avruch, I. M.; Beck, R.; Bell, M. E.; Bentum, M. J.; Best, P.; Bonafede, A.; Bregman, J.; Breitling, F.; Broderick, J.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Conway, J. E.; de Gasperin, F.; de Geus, E.; Deller, A.; Dettmar, R.-J.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fallows, R. A.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hamaker, J. P.; Hassall, T. E.; Haverkorn, M.; Heald, G.; Hessels, J. W. T.; Hoeft, M.; Hörandel, J.; Horneffer, A.; van der Horst, A.; Iacobelli, M.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; van Leeuwen, J.; Maat, P.; Mann, G.; McKay-Bukowski, D.; McKean, J. P.; Munk, H.; Nelles, A.; Norden, M. J.; Paas, H.; Pandey-Pommier, M.; Pietka, G.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H.; Rowlinson, A.; Scaife, A. M. M.; Schwarz, D.; Serylak, M.; Smirnov, O.; Steinmetz, M.; Stewart, A.; Tagger, M.; Tang, Y.; Tasse, C.; ter Veen, S.; Thoudam, S.; Toribio, C.; Vermeulen, R.; Vocks, C.; van Weeren, R. J.; Wijers, R. A. M. J.; Wijnholds, S. J.; Wucknitz, O.; Zarka, P.

    2014-01-01

    Aims: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for extracting of the cosmological 21 cm signal from the LOw-Frequency ARray - Epoch of Reionization (LOFAR-EoR) data. Methods: We used the high band antennas of

  2. A DGTD Scheme for Modeling the Radiated Emission From DUTs in Shielding Enclosures Using Near Electric Field Only

    KAUST Repository

    Li, Ping

    2016-01-13

    To meet the electromagnetic interference regulation, the radiated emission from device under test such as electronic devices must be carefully manipulated and accurately characterized. Instead of resorting to the direct far-field measurement, in this paper, a novel approach is proposed to model the radiated emission from electronic devices placed in shielding enclosures by using the near electric field only. Based on the Schelkkunoff’s equivalence principle and Raleigh–Carson reciprocity theorem, only the tangential components of the electric field over the ventilation slots and apertures of the shielding enclosure are sufficient to obtain the radiated emissions outside the shielding box if the inside of the shielding enclosure was filled with perfectly electric conductor (PEC). In order to efficiently model wideband emission, the time-domain sampling scheme is employed. Due to the lack of analytical Green’s function for arbitrary PEC boxes, the radiated emission must be obtained via the full-wave numerical methods by considering the total radiated emission as the superposition between the direct radiation from the equivalent magnetic currents in free space and the scattered field generated by the PEC shielding box. In this study, the state-of-the-art discontinuous Galerkin time-domain (DGTD) method is utilized, which has the flexibility to model irregular geometries, keep high-order accuracy, and more importantly involves only local operations. For open-region problems, a hybridized DGTD and time-domain boundary integration method applied to rigorously truncate the computational domain. To validate the proposed approach, several representative examples are presented and compared with both analytical and numerical results.

  3. Carrier-phonon interaction in semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Seebeck, Jan

    2009-03-10

    In recent years semiconductor quantum dots have been studied extensively due to their wide range of possible applications, predominantly for light sources. For successful applications, efficient carrier scattering processes as well as a detailed understanding of the optical properties are of central importance. The aims of this thesis are theoretical investigations of carrier scattering processes in InGaAs/GaAs quantum dots on a quantum-kinetic basis. A consistent treatment of quasi-particle renormalizations and carrier kinetics for non-equilibrium conditions is presented, using the framework of non-equilibrium Green's functions. The focus of our investigations is the interaction of carriers with LO phonons. Important for the understanding of the scattering mechanism are the corresponding quasi-particle properties. Starting from a detailed study of quantum-dot polarons, scattering and dephasing processes are discussed for different temperature regimes. The inclusion of polaron and memory effects turns out to be essential for the description of the carrier kinetics in quantum-dot systems. They give rise to efficient scattering channels and the obtained results are in agreement with recent experiments. Furthermore, a consistent treatment of the carrier-LO-phonon and the carrier-carrier interaction is presented for the optical response of semiconductor quantum dots, both giving rise to equally important contributions to the dephasing. Beside the conventional GaAs material system, currently GaN based light sources are of high topical interest due to their wide range of possible emission frequencies. In this material additionally intrinsic properties like piezoelectric fields and strong band-mixing effects have to be considered. For the description of the optical properties of InN/GaN quantum dots a procedure is presented, where the material properties obtained from an atomistic tight-binding approach are combined with a many-body theory for non

  4. Deriving chlorophyll fluorescence emissions of vegetation canopies from high resolution field reflectance spectra

    Science.gov (United States)

    Middleton, Elizabeth M.; Corp, Lawrence A.; Daughtry, Craig S.; Entcheva Campbell, Petya K.; Butcher, L. Maryn

    2005-11-01

    Fluorescence of foliage in the laboratory has proven more rigorous than reflectance for correlation to plant physiology. Especially useful are emissions produced from two stable red and far-red chlorophyll fluorescence (ChlF) peaks centered at 685 nm and 735 nm. Methods have been developed elsewhere to extract steady state solar induced fluorescence (SIF) from apparent reflectance of vegetation canopies/landscapes using the Fraunhofer Line Depth (FLD) principal. Our study utilized these methods in conjunction with field-acquired high spectral resolution canopy reflectance spectra obtained in 2004 and 2005 over corn crops and small tree plots of three deciduous species (red maple, tulip poplar, sweet gum). Leaf level measurements were also made of foliage which included ChlF, photosynthesis, and leaf constituents (photosynthetic pigment, carbon (C), and nitrogen (N) contents). As part of ongoing experiments, measurements were made on N application plots within corn (280, 140, 70, and 0 kg N/ha) and tree (0, 37.5, 75, 112.5, 150 kg N /ha) sites at the USDA/Agriculture Research Service in Beltsville, MD. SIF intensities for ChlF were derived directly from canopy reflectance spectra in specific narrow- band regions associated with atmospheric oxygen absorption features centered at 688 and 760 nm. The red/far-red SIF ratio (SIFratio) derived from these field reflectance spectra successfully discriminated foliar pigment ratios altered by N application rates in both corn crops. This ratio was also positively correlated to the C/N ratio at leaf and canopy levels, for the available corn data (e.g., 2004). No consistent N treatment or species differences in SIF were detected in the tree foliage, but additional 2005 data are forthcoming. This study has relevance to future passive satellite remote sensing approaches to monitoring C dynamics from space.

  5. The Relation Between Magnetic Fields and X-ray Emission for Solar Microflares and Active Regions

    Science.gov (United States)

    Kirichenko, A. S.; Bogachev, S. A.

    2017-09-01

    We present the result of a comparison between magnetic field parameters and the intensity of X-ray emission for solar microflares with Geosynchronous Operational Environmental Satellites (GOES) classes from A0.02 to B5.1. For our study, we used the monochromatic MgXII Imaging Spectroheliometer (MISH), the Full-disk EUV Telescope (FET), and the Solar PHotometer in X-rays (SphinX) instruments onboard the Complex Orbital Observations Near-Earth of Activity of the Sun-Photon CORONAS- Photon spacecraft because of their high sensitivity in soft X-rays. The peak flare flux (PFF) for solar microflares was found to depend on the strength of the magnetic field and on the total unsigned magnetic flux as a power-law function. In the spectral range 2.8 - 36.6 Å, which shows very little increase related to microflares, the power-law index of the relation between the X-ray flux and magnetic flux for active regions is 1.48 ±0.86, which is close to the value obtained previously by Pevtsov et al. ( Astrophys. J. 598, 1387, 2003) for different types of solar and stellar objects. In the spectral range 1 - 8 Å, the power-law indices for PFF(B) and PFF(Φ) for microflares are 3.87 ±2.16 and 3 ±1.6, respectively. We also make suggestions on the heating mechanisms in active regions and microflares under the assumption of loops with constant pressure and heating using the Rosner-Tucker-Vaiana scaling laws.

  6. Profile and Morphology of Fungal Aerosols Characterized by Field Emission Scanning Electron Microscopy (FESEM).

    Science.gov (United States)

    Afanou, Komlavi Anani; Straumfors, Anne; Skogstad, Asbjørn; Skaar, Ida; Hjeljord, Linda; Skare, Øivind; Green, Brett James; Tronsmo, Arne; Eduard, Wijnand

    Fungal aerosols consist of spores and fragments with diverse array of morphologies; however, the size, shape, and origin of the constituents require further characterization. In this study, we characterize the profile of aerosols generated from Aspergillus fumigatus, A. versicolor, and Penicillium chrysogenum grown for 8 weeks on gypsum boards. Fungal particles were aerosolized at 12 and 20 L min-1 using the Fungal Spore Source Strength Tester (FSSST) and the Stami particle generator (SPG). Collected particles were analyzed with field emission scanning electron microscopy (FESEM). We observed spore particle fraction consisting of single spores and spore aggregates in four size categories, and a fragment fraction that contained submicronic fragments and three size categories of larger fragments. Single spores dominated the aerosols from A. fumigatus (median: 53%), while the submicronic fragment fraction was the highest in the aerosols collected from A. versicolor (median: 34%) and P. chrysogenum (median: 31%). Morphological characteristics showed near spherical particles that were only single spores, oblong particles that comprise some spore aggregates and fragments (3.5 μm). Further, the near spherical particles dominated the aerosols from A. fumigatus (median: 53%), while oblong particles were dominant in the aerosols from A. versicolor (68%) and P. chrysogenum (55%). Fiber-like particles represented 21% and 24% of the aerosols from A. versicolor and P. chrysogenum, respectively. This study shows that fungal particles of various size, shape, and origin are aerosolized, and supports the need to include a broader range of particle types in fungal exposure assessment.

  7. Ion milling coupled field emission scanning electron microscopy reveals current misunderstanding of morphology of polymeric nanoparticles.

    Science.gov (United States)

    Francis, Donny; Mouftah, Samiha; Steffen, Robert; Beduneau, Arnaud; Pellequer, Yann; Lamprecht, Alf

    2015-01-01

    Nanoparticles (NPs) are currently used as drug delivery systems for numerous therapeutic macromolecules, e.g. proteins or DNA. Based on the preparation by double emulsion solvent evaporation a sponge-like structure was postulated entrapping hydrophilic drugs inside an internal aqueous phase. However, a direct proof of this hypothesized structure is still missing today. NPs were prepared from different polymers using a double-emulsion method and characterized for their physicochemical properties. Combining ion milling with field emission scanning electron microscopy allowed to cross section single NP and to visualize their internal morphology. The imaging procedure permitted cross-sectioning of NPs and visualization of the internal structure as well as localizing drugs associated with NPs. It was observed that none of the model actives was encapsulated inside the polymeric matrix when particle diameters were below around 470 nm but predominantly adsorbed to the particle surface. Even at larger diameters only a minority of particles of a diameter below 1 μm contained an internal phase. The properties of such drug loaded NPs, i.e. drug release or the observations in cellular uptake or even drug targeting needs to be interpreted carefully since in most cases NP surface properties are potentially dominated by the 'encapsulated' drug characteristics. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Microbe repelling coated stainless steel analysed by field emission scanning electron microscopy and physicochemical methods.

    Science.gov (United States)

    Raulio, Mari; Järn, Mikael; Ahola, Juhana; Peltonen, Jouko; Rosenholm, Jarl B; Tervakangas, Sanna; Kolehmainen, Jukka; Ruokolainen, Timo; Narko, Pekka; Salkinoja-Salonen, Mirja

    2008-07-01

    Coating of stainless steel with diamond-like carbon or certain fluoropolymers reduced or almost eliminated adhesion and biofilm growth of Staphylococcus epidermidis, Deinococcus geothermalis, Meiothermus silvanus and Pseudoxanthomonas taiwanensis. These species are known to be pertinent biofilm formers on medical implants or in the wet-end of paper machines. Field emission scanning electron microscopic analysis showed that Staph. epidermidis, D. geothermalis and M. silvanus grew on stainless steel using thread-like organelles for adhesion and biofilm formation. The adhesion threads were fewer in number on fluoropolymer-coated steel than on plain steel and absent when the same strains were grown in liquid culture. Psx. taiwanensis adhered to the same surfaces by a mechanism involving cell ghosts on which the biofilm of live cells grew. Hydrophilic (diamond-like carbon) or hydrophobic (fluoropolymer) coatings reduced the adherence of the four test bacteria on different steels. Selected topographic parameters, including root-mean-square roughness (S (q)), skewness (S (sk)) and surface kurtosis (S (ku)), were analysed by atomic force microscopy. The surfaces that best repelled microbial adhesion of the tested bacteria had higher skewness values than those only slightly repelling. Water contact angle, measured (theta (m)) or roughness corrected (theta (y)), affected the tendency for biofilm growth in a different manner for the four test bacteria.

  9. Immunogold labeling of amelogenin in developing porcine enamel revealed by field emission scanning electron microscopy.

    Science.gov (United States)

    Du, Chang; Fan, Daming; Sun, Zhi; Fan, Yuwei; Lakshminarayanan, Rajamani; Moradian-Oldak, Janet

    2009-01-01

    The present study describes a method using immunohistochemical labeling in combination with high-resolution imaging (field emission scanning electron microscopy) to investigate the spatial localization of amelogenins on apatite crystallites in developing porcine enamel. Cross-sections of developing enamel tissue from freeze-fractured pig third molar were treated with antiserum against recombinant mouse amelogenin and immunoreactivity confirmed by Western blot analysis. The samples were then treated with the goat anti-rabbit IgG conjugated with 10-nm gold particles. The control samples were treated with the secondary antibody only. The in-lens secondary electrons detector and quadrant back-scattering detector were employed to reveal the high-resolution morphology of enamel structures and gold particle distribution. The immunolabeling showed a preference of the gold particle localization along the side faces of the ribbon-like apatite crystals. The preferential localization of amelogenin in vivo on enamel crystals strongly supports its direct function in controlling crystal morphology. Copyright 2008 S. Karger AG, Basel.

  10. Correlative microscopy of Purkinje dendritic spines: a field emission scanning and transmission electron microscopic study.

    Science.gov (United States)

    Castejón, O J; Castellano, A; Arismendi, G; Apkarian, R

    2004-01-01

    Purkinje dendritic spines (Pds) of mouse cerebellar cortex were examined by field emission scanning electron microscopy (FESEM) and by transmission electron microscopy (TEM) using ultrathin sections and freeze-etching replicas, to study their three-dimensional features and intramembrane morphology. FESEM showed unattached mushroom-type, elongated and lanceolate Pds separated by 100-500 nm on the dendritic shaft surface. High resolution FESEM showed 25-50 nm globular subunits at the spine postsynaptic density corresponding to the localization of postsynaptic proteins and/or postsynaptic receptors. TEM images of ultrathin sections showed gem-like, mushroom-shaped, lanceolate and neckless or stubby spines. Freeze etching replicas exposed postsynaptic intramembrane particles that can be correlated with the globular subunits observed at high resolution FESEM. Parallel and climbing fiber endings were observed making asymmetric synaptic contacts with the Pds heads. Simultaneous contacts with the necks and heads were also found. The variety of Pds shapes were interpreted as spine conformational changes related with spine dynamic, and spine plasticity.

  11. Indirect Immunodetection of Fungal Fragments by Field Emission Scanning Electron Microscopy.

    Science.gov (United States)

    Afanou, Komlavi Anani; Straumfors, Anne; Skogstad, Asbjørn; Nayak, Ajay P; Skaar, Ida; Hjeljord, Linda; Tronsmo, Arne; Eduard, Wijnand; Green, Brett James

    2015-09-01

    Submicronic fungal fragments have been observed in in vitro aerosolization experiments. The occurrence of these particles has therefore been suggested to contribute to respiratory health problems observed in mold-contaminated indoor environments. However, the role of submicronic fragments in exacerbating adverse health effects has remained unclear due to limitations associated with detection methods. In the present study, we report the development of an indirect immunodetection assay that utilizes chicken polyclonal antibodies developed against spores from Aspergillus versicolor and high-resolution field emission scanning electron microscopy (FESEM). Immunolabeling was performed with A. versicolor fragments immobilized and fixed onto poly-l-lysine-coated polycarbonate filters. Ninety percent of submicronic fragments and 1- to 2-μm fragments, compared to 100% of >2-μm fragments generated from pure freeze-dried mycelial fragments of A. versicolor, were positively labeled. In proof-of-concept experiments, air samples collected from moldy indoor environments were evaluated using the immunolabeling technique. Our results indicated that 13% of the total collected particles were derived from fungi. This fraction comprises 79% of the fragments that were detected by immunolabeling and 21% of the spore particles that were morphologically identified. The methods reported in this study enable the enumeration of fungal particles, including submicronic fragments, in a complex heterogeneous environmental sample. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  12. Characterization of novel powder and thin film RGB phosphors for field emissions display application

    Energy Technology Data Exchange (ETDEWEB)

    Chakhovskoi, A.G.; Hunt, C.E. [Univ. of California, Davis, CA (United States). Electrical and Computer Engineering Dept.; Malinowski, M.E.; Felter, T.E.; Talin, A.A. [Sandia National Labs., Livermore, CA (United States)

    1996-12-31

    The spectral response, brightness and outgassing characteristics of new, low-voltage phosphors for application in field-emission flat-panel displays, are presented. The tested phosphor materials include combustion synthesized powders and thin films prepared by RF-diode or magnetron sputtering, laser ablation and molecular beam epitaxy. These cathodoluminescent materials are tested with e-beam excitation at currents up to 50 {mu}A within the 200-2000V (e.g. {open_quotes}low-voltage{close_quotes}) and 3-8 kV (e.g. {open_quotes}medium voltage{close_quotes}) ranges. The spectral coordinates are compared to commercial low-voltage P22 phosphors. Phosphor outgassing, as a function of time is measured with a residual gas analyzer at fixed 50 {mu}A beam current in the low-voltage range. We find that levels of outgassing stabilize to low values after the first few hours of excitation. The desorption rates measured for powder phosphor layers with different thickness are compared to desorption from thin films.

  13. Sensing Properties of a Novel Temperature Sensor Based on Field Assisted Thermal Emission.

    Science.gov (United States)

    Pan, Zhigang; Zhang, Yong; Cheng, Zhenzhen; Tong, Jiaming; Chen, Qiyu; Zhang, Jianpeng; Zhang, Jiaxiang; Li, Xin; Li, Yunjia

    2017-02-27

    The existing temperature sensors using carbon nanotubes (CNTs) are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K-1 was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.

  14. Sensing Properties of a Novel Temperature Sensor Based on Field Assisted Thermal Emission

    Directory of Open Access Journals (Sweden)

    Zhigang Pan

    2017-02-01

    Full Text Available The existing temperature sensors using carbon nanotubes (CNTs are limited by low sensitivity, complicated processes, or dependence on microscopy to observe the experimental results. Here we report the fabrication and successful testing of an ionization temperature sensor featuring non-self-sustaining discharge. The sharp tips of nanotubes generate high electric fields at relatively low voltages, lowering the work function of electrons emitted by CNTs, and thereby enabling the safe operation of such sensors. Due to the temperature effect on the electron emission of CNTs, the collecting current exhibited an exponential increase with temperature rising from 20 °C to 100 °C. Additionally, a higher temperature coefficient of 0.04 K−1 was obtained at 24 V voltage applied on the extracting electrode, higher than the values of other reported CNT-based temperature sensors. The triple-electrode ionization temperature sensor is easy to fabricate and converts the temperature change directly into an electrical signal. It shows a high temperature coefficient and good application potential.

  15. Focussed ion beam thin sample microanalysis using a field emission gun electron probe microanalyser

    Science.gov (United States)

    Kubo, Y.

    2018-01-01

    Field emission gun electron probe microanalysis (FEG-EPMA) in conjunction with wavelength-dispersive X-ray spectrometry using a low acceleration voltage (V acc) allows elemental analysis with sub-micrometre lateral spatial resolution (SR). However, this degree of SR does not necessarily meet the requirements associated with increasingly miniaturised devices. Another challenge related to performing FEG-EPMA with a low V acc is that the accuracy of quantitative analyses is adversely affected, primarily because low energy X-ray lines such as the L- and M-lines must be employed and due to the potential of line interference. One promising means of obtaining high SR with FEG-EPMA is to use thin samples together with high V acc values. This mini-review covers the basic principles of thin-sample FEG-EPMA and describes an application of this technique to the analysis of optical fibres. Outstanding issues related to this technique that must be addressed are also discussed, which include the potential for electron beam damage during analysis of insulating materials and the development of methods to use thin samples for quantitative analysis.

  16. LSDCat: Detection and cataloguing of emission-line sources in integral-field spectroscopy datacubes

    Science.gov (United States)

    Herenz, Edmund Christian; Wisotzki, Lutz

    2017-06-01

    We present a robust, efficient, and user-friendly algorithm for detecting faint emission-line sources in large integral-field spectroscopic datacubes together with the public release of the software package Line Source Detection and Cataloguing (LSDCat). LSDCat uses a three-dimensional matched filter approach, combined with thresholding in signal-to-noise, to build a catalogue of individual line detections. In a second pass, the detected lines are grouped into distinct objects, and positions, spatial extents, and fluxes of the detected lines are determined. LSDCat requires only a small number of input parameters, and we provide guidelines for choosing appropriate values. The software is coded in Python and capable of processing very large datacubes in a short time. We verify the implementation with a source insertion and recovery experiment utilising a real datacube taken with the MUSE instrument at the ESO Very Large Telescope. The LSDCat software is available for download at http://muse-vlt.eu/science/tools and via the Astrophysics Source Code Library at http://ascl.net/1612.002

  17. Investigation of electromigration induced by field emission current flowing through Au nanogaps in ambient air

    Science.gov (United States)

    Inoue, Kazuki; Yagi, Mamiko; Ito, Mitsuki; Ito, Tomoyuki; Shirakashi, Jun-ichi

    2017-08-01

    We developed a simple and controllable nanogap fabrication method called "activation." In the activation technique, electromigration is induced by a field emission current passing through the nanogaps. Activation enables the electrical properties of Ni nanogaps in a vacuum to be controlled and is expected to be applicable to Au nanogaps even in ambient air. In this study, we investigated the activation properties of Au nanogaps in ambient air from a practical point of view. When activation was performed in ambient air, the tunnel resistance of the Au nanogaps decreased from over 100 TΩ to 3.7 MΩ as the preset current increased from 1 nA to 1.5 μA. Moreover, after activation in ambient air with a preset current of 500 nA, the barrier widths and heights of the Au nanogaps were estimated using the Simmons model to be approximately 0.5 nm and 3.3 eV, respectively. The extracted barrier height is smaller than that of 4.6 eV resulting from activation in a vacuum and much lower than the work function of bulk Au. This difference implies the presence of atmospherically derived moisture or contamination adsorbed on the nanogaps. These results suggest that activation can be utilized for Au nanogap fabrication even in ambient air.

  18. Statistical analysis of nitrous oxide emission factors from pastoral agriculture field trials conducted in New Zealand.

    Science.gov (United States)

    Kelliher, F M; Cox, N; van der Weerden, T J; de Klein, C A M; Luo, J; Cameron, K C; Di, H J; Giltrap, D; Rys, G

    2014-03-01

    Between 11 May 2000 and 31 January 2013, 185 field trials were conducted across New Zealand to measure the direct nitrous oxide (N2O) emission factors (EF) from nitrogen (N) sources applied to pastoral soils. The log(EF) data were analysed statistically using a restricted maximum likelihood (REML) method. To estimate mean EF values for each N source, best linear unbiased predictors (BLUPs) were calculated. For lowland soils, mean EFs for dairy cattle urine and dung, sheep urine and dung and urea fertiliser were 1.16 ± 0.19% and 0.23 ± 0.05%, 0.55 ± 0.19% and 0.08 ± 0.02% and 0.48 ± 0.13%, respectively, each significantly different from one another (p 12°, mean EFs were significantly lower. Thus, urine and dung EFs should be disaggregated for sheep and cattle as well as accounting for terrain. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  19. Microstructure and field emission characteristics of ZnO nanoneedles grown by physical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    George, A.; Kumari, P.; Soin, N. [Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), University of Ulster at Jordanstown, Shore Road, Northern Ireland, BT37 0QB (United Kingdom); Roy, S.S., E-mail: s.sinha-roy@ulster.ac.uk [Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), University of Ulster at Jordanstown, Shore Road, Northern Ireland, BT37 0QB (United Kingdom); McLaughlin, J.A., E-mail: jad.mclaughlin@ulster.ac.uk [Nanotechnology and Integrated Bio-Engineering Centre (NIBEC), University of Ulster at Jordanstown, Shore Road, Northern Ireland, BT37 0QB (United Kingdom)

    2010-10-01

    Single crystalline zinc oxide (ZnO) nanoneedles have been grown on Au coated Si (1 0 0) substrates in an inert gas atmosphere by physical vapor deposition (PVD) process. A mixture of ZnO and graphite powder was used as precursor for the production of nanoneedles. Their structure has been assessed by a range of techniques including scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The synthesized ZnO nanoneedles have tip diameter around 30 nm and average length of {approx}5 {mu}m. The XRD patterns and HRTEM measurements revealed the highly crystalline phase of wurtzite single crystalline structure, with a preferred <0 0 0 1> growth direction. Field emission from these nanoneedles was investigated and a low turn on voltage of 5.07 V {mu}m{sup -1} at a current density of 10 {mu}A cm{sup -2} was observed.

  20. Enhancement of carrier mobility in MoS{sub 2} field effect transistors by a SiO{sub 2} protective layer

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Peng-Zhi; Zhao, Hai-Ming; Cao, Hui-Wen; Wang, Xue-Feng; Pang, Yu; Li, Yu-Xing; Deng, Ning-Qin; Yang, Yi; Ren, Tian-Ling, E-mail: RenTL@tsinghua.edu.cn, E-mail: zhangsh@sz.tsinghua.edu.cn [Institute of Microelectronics and Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China); Zhang, Jing [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhang, Guang-Yu [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); CollaborativeInnovation Center of Quantum Matter, Beijing 100190 (China); Zhang, Sheng, E-mail: RenTL@tsinghua.edu.cn, E-mail: zhangsh@sz.tsinghua.edu.cn [Institute of Microelectronics and Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China); The State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Shanghai 200050 (China); Advanced Sensor and Integrated System Lab, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China)

    2016-05-16

    Molybdenum disulfide is a promising channel material for field effect transistors (FETs). In this paper, monolayer MoS{sub 2} grown by chemical vapor deposition (CVD) was used to fabricate top-gate FETs through standard optical lithography. During the fabrication process, charged impurities and interface states are introduced, and the photoresist is not removed cleanly, which both limit the carrier mobility and the source-drain current. We apply a SiO{sub 2} protective layer, which is deposited on the surface of MoS{sub 2}, in order to avoid the MoS{sub 2} directly contacting with the photoresist and the ambient environment. Therefore, the contact property between the MoS{sub 2} and the electrodes is improved, and the Coulomb scattering caused by the charged impurities and the interface states is reduced. Comparing MoS{sub 2} FETs with and without a SiO{sub 2} protective layer, the SiO{sub 2} protective layer is found to enhance the characteristics of the MoS{sub 2} FETs, including transfer and output characteristics. A high mobility of ∼42.3 cm{sup 2}/V s is achieved, which is very large among the top-gate CVD-grown monolayer MoS{sub 2} FETs.

  1. Investigating carrier localization and transfer in InGaN/GaN quantum wells with V-pits using near-field scanning optical microscopy and correlation analysis

    Science.gov (United States)

    Kim, Minkwan; Choi, Sunghan; Lee, Joo-Hyung; Park, Chunghyun; Chung, Tae-Hoon; Baek, Jong Hyeob; Cho, Yong-Hoon

    2017-02-01

    The V-pits and potential fluctuations in InGaN/GaN multiple quantum wells (MQWs) are key factors for understanding the performance of InGaN/GaN-based light-emitting diodes (LEDs). However, photoluminescence (PL) measurements using conventional optical microscopy only provide ensemble information due to the spatial resolution limit, known as the diffraction barrier, which hinders the analysis of dislocations and potential fluctuations. Here, in order to investigate the influence of the V-pits and potential fluctuations on local optical properties, we performed nanoscopic luminescence mapping for standard and V-pit InGaN/GaN MQWs samples with different sized V-pits using near-field scanning optical microscopy (NSOM) with illumination mode (I-mode) at various laser excitation powers. From the nanoscopic PL mapping data, we could clearly observe luminescence features associated with dislocations and potential fluctuations in the InGaN/GaN MQWs. We also employed correlation analysis to quantitatively analyze the nanoscopic PL mapping data for the different MQWs samples. Based on the results of NSOM PL with I-mode and correlation analysis, we could demonstrate that carrier transfer in the MQWs sample with large sized V-pits is suppressed by deeper potential fluctuations and higher energy barriers compared to the standard sample.

  2. Normal Spectral Emissivity Measurement of Molten Cu-Co Alloy Using an Electromagnetic Levitator Superimposed with a Static Magnetic Field

    Science.gov (United States)

    Ueno, Shoya; Nakamura, Yuki; Sugioka, Ken-Ichi; Kubo, Masaki; Tsukada, Takao; Uchikoshi, Masahito; Fukuyama, Hiroyuki

    2017-02-01

    The normal spectral emissivity of molten Cu-Co alloy with different compositions was measured in the wavelength range of 780 nm to 920 nm and in the temperature range of 1430 K to 1770 K including the undercooled condition by an electromagnetic levitator superimposed with a static magnetic field. The emissivity was determined as the ratio of the radiance from a levitated molten Cu-Co droplet measured by a spectrometer to the radiance from a blackbody calculated by Planck's law at a given temperature, where a static magnetic field of 2.5 T to 4.5 T was applied to the levitated droplet to suppress the surface oscillation and translational motion of the sample. We found little temperature dependence of the normal spectral emissivity of molten Cu-Co alloy. Concerning the composition dependence, the emissivity decreased markedly above 80 at%Cu and reached that of pure Cu, although its dependence was low between 20 at%Cu and 80 at%Cu. In addition, this composition dependence of the emissivity of molten Cu-Co alloy can be explained well by the Drude free-electron model.

  3. [Effect of controlled release fertilizer on nitrous oxide emission from paddy field under plastic film mulching cultivation].

    Science.gov (United States)

    Zhang, Yi; Lü, Shi-Hua; Ma, Jing; Xu, Hua; Yuan, Jiang; Dong, Yu-Jiao

    2014-03-01

    A field experiment was conducted to assess the effect of controlled release fertilizer on N2O emission in paddy field under plastic film mulching cultivation (PM) with water-saving irrigation. Results showed that in the rice growing season, cumulative N2O emissions from the plots applied with urea (PM+U) and with controlled release fertilizer (PM+CRF) were (38.2 +/- 4.4) and (21.5 +/- 5.2) mg N x m(-2), respectively. The N2O emission factors were 0.25% and 0.14% in the treatments PM+U and PM+CRF, respectively. The controlled release fertilizer decreased the total N2O emission by 43.6% compared with urea, of which 49.6% was reduced before the drying period. It also reduced the peak of N2O emission by 52.6%. However, it did not affect soil microbial biomass N and soil NH(4+)-N content at any rice growing stage, and grain yield either. No significant correlation was observed between N2O flux and soil Eh or soil temperature at the depth of 5 cm.

  4. Study of the Photospheric Magnetic Field and Coronal Emission from Solar Active Regions

    Science.gov (United States)

    Aguilera, Jordan Armando Guerra

    2016-01-01

    Solar explosive phenomena (flares and Coronal Mass Ejections, CMEs) are examples of how the most dynamical processes within the heliosphere are interconnected and powered by the Sun. Solar flares originate in active regions (AR) -- areas of strong magnetic field on the solar surface. The electromagnetic (EM) energy released during flares, along with the often-seen CMEs, propagate through the heliosphere. In the Earth's vicinity, EM radiation and charged particles have the potential to produce unfavorable conditions for humans and technology in space. From many points of view (scientific, operational, economical) it is thus important to understand and try to predict when solar flares and associated eruptive phenomena will occur. This dissertation explores how to best leverage the available observational data to provide predictive information about the future flaring activity. This dissertation consists of two main components: 1) investigation of the photosphere-corona coupling by analyzing photospheric magnetic field and coronal data in search for signals or behaviors that precede eruptions; and 2) the combination of existing flare prediction methods in order to develop a novel ensemble prediction. For the first part, the data employed correspond to line-of-sight (LOS) magnetograms from the Helioseismic and Magnetic Imager (HMI) and EUV intensity maps from the Atmospheric Imaging Assembly (AIA), both instruments onboard NASA's Solar Dynamics Observatory (SDO) satellite. Photospheric magnetic field and coronal EUV emissions were characterized by measuring the power-law decay of their spatio-temporal spectra and the data statistical associations (auto- and cross-correlations). These measures, calculated with high spatio-temporal resolution, appeared to characterize the AR evolution, provide information about the state of the photospheric plasma, reveal insights into the photospheric conditions for flares, and expose the potential of combining coronal and photospheric

  5. Coherent multiphoton photoelectron emission from single au nanorods: the critical role of plasmonic electric near-field enhancement.

    Science.gov (United States)

    Grubisic, Andrej; Schweikhard, Volker; Baker, Thomas A; Nesbitt, David J

    2013-01-22

    Electron emission from individual Au nanorods deposited on indium-tin-oxide (ITO) following excitation with femtosecond laser pulses near the rod longitudinal plasmon resonance is studied via scanning photoionization microscopy. The measured electron signal is observed to strongly depend on the excitation laser polarization and wavelength. Correlated secondary electron microscopy (SEM) and dark-field microscopy (DFM) studies of the same nanorods unambiguously confirm that maximum electron emission results from (i) laser polarization aligned with the rod long axis and (ii) laser wavelength resonant with the localized surface plasmon resonance. The experimental results are in good agreement with quantitative predictions for a coherent multiphoton photoelectric effect, which is identified as the predominant electron emission mechanism for metal nanoparticles under employed excitation conditions. According to this mechanism, the multiphoton photoemission rate is increased by over 10 orders of magnitude in the vicinity of a localized surface plasmon resonance, due to enhancement of the incident electromagnetic field in the particle near-field. These findings identify multiphoton photoemission as an extremely sensitive metric of local electric fields (i.e., "hot spots") in plasmonic nanoparticles/structures that can potentially be exploited for direct quantitation of local electric field enhancement factors.

  6. The growth of Sea-urchin-like AlN nanostructures by modified CVD and their Field Emission properties

    Science.gov (United States)

    Guo, Lu`an; Chen, Guangde; Zhu, Youzhang; Duan, Xiangyang; Ye, Honggang

    2015-09-01

    AlN complex nanostructures were fabricated by using chemical vapor deposition (CVD) method which was carried out at a low moderate temperature ( 750 °C) and without any catalyst. Field emission scanning electron microscopy (FESEM), X-Ray diffraction, transmission electron microscopy (TEM), and Raman scattering spectrum were used to characterize the microstructures and morphologies of the products. The FESEM results of samples exhibit unordered nanoneedle lawn-like interspersed by the Sea-urchin-like morphology, in which many needle-like nanostructures with the length of 500 nm grow radially from a central nucleus. The results of the X-ray, TEM and Raman scattering spectrum indicate that the samples have a preferential growth along the [0001] direction good quality AlN nanostructure. The field emission device testing shows that the Sea-urchin-like nanostructure has a very low turn-on electric field of 3.6 V/μm (0.01 mA/cm2) and a very high field enhancement factor β (2.1×103) at room temperature. It suggests that it can be used for field emission displays and vacuum microelectronic devices.

  7. Impact of implementing the Meyer-Neldel behavior of carrier emission pre-factors in solar cell and optical detector modeling

    OpenAIRE

    Rubinelli, Francisco Alberto; Ramirez Jimenez, Helena

    2016-01-01

    The Meyer-Neldel behavior reported for the emission probabilities of electrons and holes was included in our code, replacing the gap state capture cross sections of the Shockley-Read-Hall formalisms with capture cross sections containing an exponential function of the trap energy depth. The Meyer-Neldel energies for electrons and holes are the slopes of these exponentials. Our results indicate that emission probabilities of neutral states no deeper than approximately 0.45 eV and 0.37 eV from...

  8. The field emission properties of high aspect ratio diamond nanocone arrays fabricated by focused ion beam milling

    Directory of Open Access Journals (Sweden)

    Z.L. Wang, Q. Wang, H.J. Li, J.J. Li, P. Xu, Q. Luo, A.Z. Jin, H.F. Yang and C.Z. Gu

    2005-01-01

    Full Text Available High aspect ratio diamond nanocone arrays are formed on freestanding diamond film by means of focused ion beam (FIB milling technology and hot-filament chemical vapor deposition (HFCVD method. The structure and phase purity of an individual diamond nanocone are characterized by scanning electron microscopy (SEM and micro-Raman spectroscopy. The result indicates that the diamond cones with high aspect ratio and small tip apex radius can be obtained by optimizing the parameters of FIB milling and diamond growth. The diamond nanocone arrays were also used to study the electron field emission properties and electric field shielding effect, finding high emission current density, low threshold and weak shielding effect, all attributable to the high field enhancement factor and suitable cone density of the diamond nanocone emitter

  9. Impact of dicyandiamide on emissions of nitrous oxide, nitric oxide and ammonia from agricultural field in the North China Plain.

    Science.gov (United States)

    Zhou, Yizhen; Zhang, Yuanyuan; Tian, Di; Mu, Yujing

    2016-02-01

    Nitrous oxide (N2O), nitric oxide (NO) and ammonia (NH3) emissions from an agricultural field in the North China Plain were compared for three treatments during a whole maize growing period from 26 June to 11 October, 2012. Compared with the control treatment (without fertilization, designated as CK), remarkable pulse emissions of N2O, NO and NH3 were observed from the normal fertilization treatment (designated as NP) just after fertilization, whereas only N2O and NH3 pulse emissions were evident from the nitrification inhibitor treatment (designated as ND). The reduction proportions of N2O and NO emissions from the ND treatment compared to those from the NP treatment during the whole maize growing period were 31% and 100%, respectively. A measurable increase of NH3 emission from the ND treatment was found with a cumulative NH3 emission of 3.8 ± 1.2 kg N/ha, which was 1.4 times greater than that from the NP treatment (2.7 ± 0.7 kg N/ha). Copyright © 2015. Published by Elsevier B.V.

  10. An Analysis of Field-Aged Diesel Particulate Filter Performance: Particle Emissions Before, During and After Regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Barone, Teresa L [ORNL; Storey, John Morse [ORNL; Domingo, Norberto [ORNL

    2010-01-01

    A field-aged, passive diesel particulate filter (DPF) employed in a school bus retrofit program was evaluated for emissions of particle mass and number concentration before, during and after regeneration. For the particle mass measurements, filter samples were collected for gravimetric analysis with a partial flow sampling system, which sampled proportionally to the exhaust flow. Total number concentration and number-size distributions were measured by a condensation particle counter and scanning mobility particle sizer, respectively. The results of the evaluation show that the number concentration emissions decreased as the DPF became loaded with soot. However after soot removal by regeneration, the number concentration emissions were approximately 20 times greater, which suggests the importance of the soot layer in helping to trap particles. Contrary to the number concentration results, particle mass emissions decreased from 6 1 mg/hp-hr before regeneration to 3 2 mg/hp-hr after regeneration. This indicates that nanoparticles with diameter less than 50 nm may have been emitted after regeneration since these particles contribute little to the total mass. Overall, average particle emission reductions of 95% by mass and 10,000-fold by number concentration after four years of use provided evidence of the durability of a field-aged DPF. In contrast to previous reports for new DPFs in which elevated number concentrations occurred during the first 200 seconds of a transient cycle, the number concentration emissions were elevated during the second half of the heavy-duty federal test procedure when high speed was sustained. This information is relevant for the analysis of mechanisms by which particles are emitted from field-aged DPFs.

  11. A new beam emission polarimetry diagnostic for measuring the magnetic field line angle at the plasma edge of ASDEX Upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Viezzer, E., E-mail: eleonora.viezzer@ipp.mpg.de, E-mail: eviezzer@us.es [Max-Planck-Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany); Department of Atomic, Molecular, and Nuclear Physics, University of Seville, Avda. Reina Mercedes, 41012 Seville (Spain); Dux, R.; Dunne, M. G. [Max-Planck-Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)

    2016-11-15

    A new edge beam emission polarimetry diagnostic dedicated to the measurement of the magnetic field line angle has been installed on the ASDEX Upgrade tokamak. The new diagnostic relies on the motional Stark effect and is based on the simultaneous measurement of the polarization direction of the linearly polarized π (parallel to the electric field) and σ (perpendicular to the electric field) lines of the Balmer line D{sub α}. The technical properties of the system are described. The calibration procedures are discussed and first measurements are presented.

  12. A new beam emission polarimetry diagnostic for measuring the magnetic field line angle at the plasma edge of ASDEX Upgrade.

    Science.gov (United States)

    Viezzer, E; Dux, R; Dunne, M G

    2016-11-01

    A new edge beam emission polarimetry diagnostic dedicated to the measurement of the magnetic field line angle has been installed on the ASDEX Upgrade tokamak. The new diagnostic relies on the motional Stark effect and is based on the simultaneous measurement of the polarization direction of the linearly polarized π (parallel to the electric field) and σ (perpendicular to the electric field) lines of the Balmer line Dα. The technical properties of the system are described. The calibration procedures are discussed and first measurements are presented.

  13. Enhanced field emission properties of tilted graphene nanoribbons on aggregated TiO{sub 2} nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Hung, Shang-Chao, E-mail: schung99@gmail.com [Department of Information Technology & Communication, Shih Chien University Kaohsiung Campus, Neimen, Kaohsiung 845, Taiwan (China); Chen, Yu-Jyun [Graduate Institute of Electro-Optical Engineering & Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China)

    2016-07-15

    Highlights: • Graphene nanoribbons (GNBs) slanted on aggregate TiO{sub 2} nanotube (A-TNTs) as field-emitters. • Turn-on electric field and field enhancement factor β are dependent on the substrate morphology. • Various quantities of GNRs are deposited on top of A-TNTs (GNRs/A-TNTs) with different morphologies. • With an increase of GNBs compositions, the specimens' turn-on electric field is reduced to 2.8 V/μm. • The field enhancement factor increased rapidly to about 1964 with the addition of GNRs. - Abstract: Graphene nanoribbons (GNRs) slanted on aggregate TiO{sub 2} nanotube arrays (A-TNTs) with various compositions as field-emitters are reported. The morphology, crystalline structure, and composition of the as-obtained specimens were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Raman spectrometry. The dependence of the turn-on electric field and the field enhancement factor β on substrate morphology was studied. An increase of GNRs reduces the specimens’ turn-on electric field to 2.8 V/μm and the field enhancement factor increased rapidly to about 1964 with the addition of GNRs. Results show a strong dependence of the field emission on GNR composition aligned with the gradient on the top of the A-TNT substrate. Enhanced FE properties of the modified TNTs can be mainly attributed to their improved electrical properties and rougher surface morphology.

  14. Nanoscale investigation of enhanced electron field emission for silver ion implanted/post-annealed ultrananocrystalline diamond films.

    Science.gov (United States)

    Panda, Kalpataru; Hyeok, Jeong Jin; Park, Jeong Young; Sankaran, Kamatchi Jothiramalingam; Balakrishnan, Sundaravel; Lin, I-Nan

    2017-11-24

    Silver (Ag) ions are implanted in ultrananocrystalline diamond (UNCD) films to enhance the electron field emission (EFE) properties, resulting in low turn-on field of 8.5 V/μm with high EFE current density of 6.2 mA/cm 2 (at an applied field of 20.5 V/μm). Detailed nanoscale investigation by atomic force microscopy based peak force-controlled tunneling atomic force microscopy (PF-TUNA) and ultra-high vacuum scanning tunneling microscopy (STM) based current imaging tunneling spectroscopy (CITS) reveal that the UNCD grain boundaries are the preferred electron emission sites. The two scanning probe microscopic results supplement each other well. However, the PF-TUNA measurement is found to be better for explaining the local electron emission behavior than the STM-based CITS technique. The formation of Ag nanoparticles induced abundant sp 2 nanographitic phases along the grain boundaries facilitate the easy transport of electrons and is believed to be a prime factor in enhancing the conductivity/EFE properties of UNCD films. The nanoscale understanding on the origin of electron emission sites in Ag-ion implanted/annealed UNCD films using the scanning probe microscopic techniques will certainly help in developing high-brightness electron sources for flat-panel displays applications.

  15. Development of an ultrafast electron source based on a cold-field emission gun for ultrafast coherent TEM

    Science.gov (United States)

    Caruso, Giuseppe Mario; Houdellier, Florent; Abeilhou, Pierre; Arbouet, Arnaud

    2017-07-01

    We report on the design of a femtosecond laser-driven electron source for ultrafast coherent transmission electron microscopy. The proposed architecture allows introducing an ultrafast laser beam inside the cold field emission source of a commercial TEM, aligning and focusing the laser spot on the apex of the nanoemitter. The modifications of the gun assembly do not deteriorate the performances of the electron source in conventional DC mode and allow easy switching between the conventional and ultrafast laser-driven emission modes. We describe here this ultrafast electron source and discuss its properties.

  16. Cost-Effective Reciprocating Engine Emissions Control and Monitoring for E&P Field and Gathering Engines

    Energy Technology Data Exchange (ETDEWEB)

    Keith Hohn; Sarah R. Nuss-Warren

    2011-08-31

    This final report describes a project intended to identify, develop, test, and commercialize emissions control and monitoring technologies that can be implemented by E&P operators to significantly lower their cost of environmental compliance and expedite project permitting. Technologies were installed and tested in controlled laboratory situations and then installed and tested on field engines based on the recommendations of an industry-based steering committee, analysis of installed horsepower, analysis of available emissions control and monitoring technologies, and review of technology and market gaps. The industry-recognized solution for lean-burn engines, a low-emissions-retrofit including increased airflow and pre-combustion chambers, was found to successfully control engine emissions of oxides of nitrogen (NO{sub X}) and carbon monoxide (CO). However, the standard non-selective catalytic reduction (NSCR) system recognized by the industry was found to be unable to consistently control both NO{sub X} and CO emissions. The standard NSCR system was observed to produce emissions levels that changed dramatically on a day-to-day or even hour-to-hour basis. Because difficulties with this system seemed to be the result of exhaust gas oxygen (EGO) sensors that produced identical output for very different exhaust gas conditions, models were developed to describe the behavior of the EGO sensor and an alternative, the universal exhaust gas oxygen (UEGO) sensor. Meanwhile, an integrated NSCR system using an advanced, signal-conditioned UEGO sensor was tested and found to control both NO{sub X} and CO emissions. In conjunction with this project, advanced monitoring technologies, such as Ion Sense, and improved sensors for emissions control, such as the AFM1000+ have been developed and commercialized.

  17. Evidence for Adsorbate-Enhanced Field Emission from Carbon Nanotube Fibers (Postprint)

    Science.gov (United States)

    2013-07-31

    Laboratory, Directed Energy Directorate, Kirtland AFB, New Mexico 87117, USA ’Department of Chemical and Biomolecular Engineering and Department of...and emission from a s ingle X-H dipole dominates the emis- sion process. Below Ec. the effective emiss ion area is much larger that the fiber cross

  18. Field emission scanning electron microscopy (FE-SEM) as an approach for nanoparticle detection inside cells.

    Science.gov (United States)

    Havrdova, M; Polakova, K; Skopalik, J; Vujtek, M; Mokdad, A; Homolkova, M; Tucek, J; Nebesarova, J; Zboril, R

    2014-12-01

    When developing new nanoparticles for bio-applications, it is important to fully characterize the nanoparticle's behavior in biological systems. The most common techniques employed for mapping nanoparticles inside cells include transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). These techniques entail passing an electron beam through a thin specimen. STEM or TEM imaging is often used for the detection of nanoparticles inside cellular organelles. However, lengthy sample preparation is required (i.e., fixation, dehydration, drying, resin embedding, and cutting). In the present work, a new matrix (FTO glass) for biological samples was used and characterized by field emission scanning electron microscopy (FE-SEM) to generate images comparable to those obtained by TEM. Using FE-SEM, nanoparticle images were acquired inside endo/lysosomes without disruption of the cellular shape. Furthermore, the initial steps of nanoparticle incorporation into the cells were captured. In addition, the conductive FTO glass endowed the sample with high stability under the required accelerating voltage. Owing to these features of the sample, further analyses could be performed (material contrast and energy-dispersive X-ray spectroscopy (EDS)), which confirmed the presence of nanoparticles inside the cells. The results showed that FE-SEM can enable detailed characterization of nanoparticles in endosomes without the need for contrast staining or metal coating of the sample. Images showing the intracellular distribution of nanoparticles together with cellular morphology can give important information on the biocompatibility and demonstrate the potential of nanoparticle utilization in medicine. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Optimized performances of tetrapod-like ZnO nanostructures for a triode structure field emission planar light source.

    Science.gov (United States)

    Chen, Yiren; Hu, Liqin; Song, Hang; Jiang, Hong; Li, Dabing; Miao, Guoqing; Li, Zhiming; Sun, Xiaojuan; Zhang, Zhiwei; Guo, Tailiang

    2014-11-21

    Tetrapod-like ZnO (T-ZnO) nanostructures were synthesized by a simple vapor phase oxidation method without any catalysts or additives. We optimized the performances of T-ZnO nanostructures by adjusting the partial pressure of Zn vapour in the total pressure of the quartz chamber and obtained T-ZnO nanostructure materials of high purity, uniform morphology and size and high aspect ratio with a low turn-on electric field of 2.75 V μm(-1), a large field enhancement factor of 3410 and good field emission stability for more than 70 hour continuous emission. Besides, based on the optimized T-ZnO, we developed metal grid mask-assisted water-based electrostatic spraying technology, and fabricated a large-scale, pollution-free, hole-shaped array T-ZnO nanostructure cathode used in a triode structure field emission planar light source. The controllable performances of the triode device were intensively investigated and the results showed that the triode device uniformly illuminated with a luminous intensity as high as 8000 cd m(-2) under the conditions of 200 V grid voltage and 3300 V anode voltage. The research in this paper will benefit the development of a high performance planar light source based on T-ZnO nanostructures.

  20. Easy synthesis of porous carbon mesospheres and its functionalization with titania nanoparticles for enhanced field emission and photocatalytic activity

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Dheeraj [Thin Film and NanoScience Laboratory, Department of Physics, Jadavpur University, Kolkata 700032 (India); Banerjee, Diptonil [School of Material Science and Nanotechnology, Jadavpur University, Kolkata 700032 (India); Sarkar, Sourav [Thin Film and NanoScience Laboratory, Department of Physics, Jadavpur University, Kolkata 700032 (India); Das, Nirmalya S. [School of Material Science and Nanotechnology, Jadavpur University, Kolkata 700032 (India); Chattopadhyay, Kalyan K., E-mail: kalyan_chattopadhyay@yahoo.com [Thin Film and NanoScience Laboratory, Department of Physics, Jadavpur University, Kolkata 700032 (India); School of Material Science and Nanotechnology, Jadavpur University, Kolkata 700032 (India)

    2016-06-01

    A simple low temperature chemical approach for synthesizing porous carbon microspheres and its hybrid structure with titanium dioxide (TiO{sub 2}) nanoparticle is reported. The carbon spheres and related hybrid structures were characterized by X-ray diffraction, scanning and transmission electron microscopy, Raman and UV–Vis–NIR spectroscopy. The microscopic studies confirm the successful synthesis of hybrid structure of carbon spheres with TiO{sub 2} nanoparticles. Also it reveals that the porous carbon spheres were actually composed of few layers thick carbon flakes. The performance of these as-synthesized pure and hybrid materials on removal of poisonous dyes from water under photon irradiation was studied. It is found that the hybrid sample shows better photocatalytic activity. It is also shown that TiO{sub 2} nanoparticle functionalization enhances the electron field emission properties of carbon sample with reduction of turn-on field from 5.1 to 3.4 V/μm. The enhancement in the photocatalytic activity is due to the combined effect of higher surface area and the injection of electrons from carbon to TiO{sub 2} nanoparticles whereas in case of field emission TiO{sub 2} particles act as additional sites with lower work function and increase the roughness helping enhancement of field strength giving enhanced emission. - Highlights: • Carbon microspheres made of carbon sheet were synthesized by chemical route. • The as synthesized carbon structure has been functionalized with TiO{sub 2} particles. • Hybrid samples show enhanced photocatalytic activity compared to pure sample. • Hybrid sample shows better field emission for an optimized amount of TiO{sub 2} particle.

  1. Environmental assessment of nutrient recycling from biological pig slurry treatment--impact of fertilizer substitution and field emissions.

    Science.gov (United States)

    Brockmann, Doris; Hanhoun, Mary; Négri, Ophélie; Hélias, Arnaud

    2014-07-01

    Pig slurry treatment is an important means in reducing nitrogen loads applied to farmland. Solid phase separation prior to biological treatment further allows for recovering phosphorus with the solid phase. The organic residues from the pig slurry treatment can be applied as organic fertilizers to farmland replacing mineral fertilizers. The environmental impacts of nutrient recycling from aerobic, biological pig slurry treatment were evaluated applying the life cycle assessment (LCA) methodology. LCA results revealed that direct field emissions from organic fertilizer application and the amount of avoided mineral fertilizers dominated the environmental impacts. A modified plant available nitrogen calculation (PAN) was introduced taking into account calculated nitrogen emissions from organic fertilizer application. Additionally, an equation for calculating the quantity of avoided mineral fertilizers based on the modified PAN calculation was proposed, which accounted for nitrogen emissions from mineral fertilizer application. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Field emissions of N2O during biomass production may affect the sustainability of agro-biofuels

    DEFF Research Database (Denmark)

    Carter, Mette Sustmann; Hauggaard-Nielsen, Henrik; Heiske, Stefan

    One way of reducing the emissions of fossil fuel‐derived CO2 is to replace fossil fuels with biofuels produced from agricultural biomasses or residuals. However, cultivation of soils results in emission of other greenhouse gasses, especially nitrous oxide (N2O). Previous studies have shown...... relate measured field emissions of N2O to the reduction in fossil fuel‐derived CO2, which is obtained when agricultural biomasses are used for biofuel production. The analysis includes five organically managed crops (viz. maize, rye, rye‐vetch, vetch and grass‐clover) and three scenarios for conversion...... and biogas or by biogas alone produced from either fresh grass‐clover or whole crop maize. Here the net reduction corresponded to about 8 tons CO2 ha‐1 yr‐1....

  3. High-aspect-ratio HfC nanobelts accompanied by HfC nanowires: Synthesis, characterization and field emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Song, E-mail: tiansong22@126.com [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); School of Materials Science and Engineering, Chongqing Jiaotong University, Chongqing 400074 (China); Zhang, Yulei; Ren, Jincui; Qiang, Xinfa; Zhang, Shouyang [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Hejun, E-mail: lihejun@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072 (China)

    2017-04-30

    Highlights: • HfC naobelts accompanied by HfC nanowires were synthesized by a catalytic CVD method. • HfC nanobelts as a novel structure of HfC ceramic are reported for the first time. • HfC nanobelts have 100–200 μm in lengths and reach up to 10 μm in widths. • The synthesized product is promising field nanoemitters. - Abstract: As a key refractory carbide, hafnium carbide (HfC) is commonly used as structural materials while the field emission (FE) application of HfC in the field of vacuum microelectronics is almost the only one for functional material purposes. Based on its outstanding physical and chemical characteristics, HfC is identified as a potential candidate with satisfactory mechanical properties and long-term and/or high-temperature FE stability for future applications in high-performance field emitters. However, the development of HfC in various FE applications is hindered because it is not facile to fabricate large-scale low-dimensional HfC field nanoemitters. Herein, High-aspect-ratio HfC nanobelts accompanied by HfC nanowires were synthesized on a large scale by a traditional and simple catalytic chemical vapor deposition (CVD) method. Classical vapor–liquid–solid (VLS) theory was employed to explain the growth of the HfC nanowires and nanobelts along axial direction. The thin HfO{sub 2} shell and thin C layer surrounding the nanostructures might give rise to the diameter fluctuation of HfC nanowires and the width increase of HfC nanobelts in lateral direction. Field emission results show that the high-aspect-ratio HfC nanobelts accompanied by the nanowires are promising field nanoemitters, which exhibit excellent field emission properties with a fairly low turn-on field of ∼1.5 V μm{sup −1} and a low current fluctuation less than ∼10%. This suggests that HfC ceramics with high-aspect-ratio nanostructures are ideal cathode material for various field emission applications.

  4. Simulation of nitrous oxide emissions at field scale using the SPACSYS model

    Science.gov (United States)

    Wu, L.; Rees, R.M.; Tarsitano, D.; Zhang, Xubo; Jones, S.K.; Whitmore, A.P.

    2015-01-01

    Nitrous oxide emitted to the atmosphere via the soil processes of nitrification and denitrification plays an important role in the greenhouse gas balance of the atmosphere and is involved in the destruction of stratospheric ozone. These processes are controlled by biological, physical and chemical factors such as growth and activity of microbes, nitrogen availability, soil temperature and water availability. A comprehensive understanding of these processes embodied in an appropriate model can help develop agricultural mitigation strategies to reduce greenhouse gas emissions, and help with estimating emissions at landscape and regional scales. A detailed module to describe the denitrification and nitrification processes and nitrogenous gas emissions was incorporated into the SPACSYS model to replace an earlier module that used a simplified first-order equation to estimate denitrification and was unable to distinguish the emissions of individual nitrogenous gases. A dataset derived from a Scottish grassland experiment in silage production was used to validate soil moisture in the top 10 cm soil, cut biomass, nitrogen offtake and N2O emissions. The comparison between the simulated and observed data suggested that the new module can provide a good representation of these processes and improve prediction of N2O emissions. The model provides an opportunity to estimate gaseous N emissions under a wide range of management scenarios in agriculture, and synthesises our understanding of the interaction and regulation of the processes. PMID:26026411

  5. What can we learn from field experiments about the development of SOC and GHG emissions under different management practices?

    Science.gov (United States)

    Spiegel, Heide; Lehtinen, Taru; Schlatter, Norman; Haslmayr, Hans-Peter; Baumgarten, Andreas; ten Berge, Hein

    2015-04-01

    Successful agricultural management practices are required to maintain or enhance soil quality; at the same time climate change mitigation is becoming increasingly important. Within the EU project CATCH-C we analysed the effects of different agricultural practices not only on crop productivity, but also on soil quality indicators (e.g. soil organic carbon (SOC)) and climate change (CC) mitigation indicators (e.g. CO2, CH4, N2O emissions). European data sets and associated literature, mainly from long-term experiments were evaluated. This evaluation of agricultural management practices was carried out comparing a set of improved ("best") and often applied ("current") management practices. Positive and negative effects occurred when best management practices are adopted. As expected, none of the investigated practices could comply with all objectives simultaneously, i.e. maintaining high yields, mitigating climate change and improving chemical, physical and biological soil quality. The studied soil management practices "non-inversion tillage", "organic fertilisation" (application of farm yard manure, slurry, compost) and "incorporation of crop residues" represent important management practices for farmers to increase SOC, thus improving soil quality. However, CO2 and, especially, N2O emissions may rise as well. The evaluation of CC mitigation is often limited by the lack of data from - preferably - continuous GHG emission measurements. Thus, more long-term field studies are needed to better assess the CO2, CH4 and, especially, N2O emissions following the above mentioned favorably rated MPs. Only if SOC and GHG emissions are measured in the same field experiments, it will be possible to compute overall balances of necessary CO2-C equivalent emissions. CATCH-C is funded within the 7th Framework Programme for Research, Technological Development and Demonstration, Theme 2 - Biotechnologies, Agriculture & Food. (Grant Agreement N° 289782).

  6. Simulation of nitrous oxide emissions at field scale using the SPACSYS model

    Energy Technology Data Exchange (ETDEWEB)

    Wu, L., E-mail: Lianhai.Wu@rothamsted.ac.uk [Sustainable Soils and Grassland Systems Department, Rothamsted Research, North Wyke, Okehampton EX20 2SB (United Kingdom); Rees, R.M.; Tarsitano, D. [Scotland' s Rural College (SRUC), West Mains Road, Edinburgh EH9 3JG (United Kingdom); Zhang, Xubo [Sustainable Soils and Grassland Systems Department, Rothamsted Research, North Wyke, Okehampton EX20 2SB (United Kingdom); Ministry of Agriculture Key Laboratory of Crop Nutrition and Fertilization, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081 (China); Jones, S.K. [Scotland' s Rural College (SRUC), West Mains Road, Edinburgh EH9 3JG (United Kingdom); Whitmore, A.P. [Sustainable Soils Grassland Systems Department, Rothamsted Research, Harpenden AL5 2JQ (United Kingdom)

    2015-10-15

    Nitrous oxide emitted to the atmosphere via the soil processes of nitrification and denitrification plays an important role in the greenhouse gas balance of the atmosphere and is involved in the destruction of stratospheric ozone. These processes are controlled by biological, physical and chemical factors such as growth and activity of microbes, nitrogen availability, soil temperature and water availability. A comprehensive understanding of these processes embodied in an appropriate model can help develop agricultural mitigation strategies to reduce greenhouse gas emissions, and help with estimating emissions at landscape and regional scales. A detailed module to describe the denitrification and nitrification processes and nitrogenous gas emissions was incorporated into the SPACSYS model to replace an earlier module that used a simplified first-order equation to estimate denitrification and was unable to distinguish the emissions of individual nitrogenous gases. A dataset derived from a Scottish grassland experiment in silage production was used to validate soil moisture in the top 10 cm soil, cut biomass, nitrogen offtake and N{sub 2}O emissions. The comparison between the simulated and observed data suggested that the new module can provide a good representation of these processes and improve prediction of N{sub 2}O emissions. The model provides an opportunity to estimate gaseous N emissions under a wide range of management scenarios in agriculture, and synthesises our understanding of the interaction and regulation of the processes. - Highlights: • Microbe-controlled denitrification and N{sub 2}O emissions were built in SPACSYS. • Simulated outputs agreed well with a Scottish grassland dataset. • The simulated emission factors vary with climate, management and forms of applied N. • SPACSYS is capable of simulating the components in C and N cycling in grassland.

  7. Thermo-enhanced field emission from ZnO nanowires: Role of defects and application in a diode flat panel X-ray source

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhipeng; Chen, Daokun; Chen, Wenqing; Chen, Yicong; Song, Xiaomeng; Zhan, Runze; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun, E-mail: stscjun@mail.sysu.edu.cn

    2017-03-31

    Highlights: • A thermo-enhanced field emission phenomenon was observed from dendritic ZnO nanowires under the temperature of 323–723 K. • Defect-assisted field emission mechanism was proposed and quantitative calculation fits well with the experiment results. • The mechanism was verified by the field emission from ZnO nanowires with different defect concentrations. • A diode X-ray source making use of thermo-enhanced field emission phenomenon was proposed for separate tuning of dose and energy. - Abstract: A thermo-enhanced field emission phenomenon was observed from ZnO nanowires. The field emission current increased by almost two orders of magnitude under a constant applied electric field, and the turn-on field decreased from 6.04 MV/m to 5.0 MV/m when the temperature increased from 323 to 723 K. The Poole–Frenkel electron excitation from the defect-induced trapping centers to the conduction band under high electric fields is believed to be the primary cause of the observed phenomenon. The experimental results fit well with the proposed physical model. The field emission from ZnO nanowires with different defect concentrations further confirmed the role of defects. Using the thermo-enhanced field emission phenomenon, a diode flat panel X-ray source was demonstrated, for which the energy and dose can be separately tuned. The thermo-enhanced field emission phenomenon observed from ZnO nanowires could be an effective way to realize a large area flat panel multi-energy X-ray source.

  8. Methane and nitrous oxide emissions from a paddy field with Japanese conventional water management and fertilizer application

    Science.gov (United States)

    Nishimura, Seiichi; Sawamoto, Takuji; Akiyama, Hiroko; Sudo, Shigeto; Yagi, Kazuyuki

    2004-06-01

    The seasonal courses of methane (CH4) and nitrous oxide (N2O) fluxes were simultaneously monitored in a paddy field using a closed chamber system with automated gas sampling and analyzing equipment. Water management and fertilizer application practices followed Japanese conventional ones. CH4 flux gradually increased after the first flood irrigation of the field and reached ˜150 mg CH4 m-2 d-1 at the beginning of July. After the first summer drainage, however, CH4 flux dropped rapidly to almost zero within a few days. CH4 flux then gradually increased again according to intermittent flood irrigations, but was much less than that before the first drainage. Immediately after the first flood irrigation, N2O flux rapidly increased, although its temporal peak lasted only within a few days. During the subsequent continuously and intermittently flooded periods, N2O flux remained at almost zero until the final drainage, except for slight and temporal peaks just after the top-dress application of supplemental fertilizer. About 1 week after the final drainage in autumn, N2O flux gradually increased, and the most significant high peak of N2O flux was observed after the harvest of rice plants, which lasted for about 2 weeks. The amounts of cumulative CH4 and N2O emissions throughout the whole year of 2002 were 3128 mg CH4 m-2 and 60.2 mg N m-2, respectively. Both the amounts of cumulative CH4 and N2O emissions during the rice cultivation period were low compared with those reported in previous studies. These results suggest the advantage of Japanese conventional water management and fertilizer application for reducing the combined effect for global warming by CH4 and N2O emissions from paddy fields, since the practices of drainage and intermittent flood irrigation in summer markedly lessen CH4 emission in the latter half of the rice cultivation period with little enhancement of N2O emission.

  9. PestLCI - a model for estimating field emissions of pesticides in agricultural LCA

    DEFF Research Database (Denmark)

    Birkved, Morten; Hauschild, Michael Zwicky

    2006-01-01

    of a product or service is a specific element of LCA termed life cycle inventory (LCI). Estimation of chemical emissions in agricultural LCA is typically based on standard emission factors which at best are determined by a few physical-chemical substance properties and the use scenario of the chemical compound....... Dynamic and realistic models capable of predicting compartment specific mode of entry fractions for various chemicals and uses under specific temporal and use circumstances are scarce. This lack of appropriate models to estimate emission fractions results in a lower accuracy when accounting for one...

  10. Controlling Quantum-dot Light Absorption and Emission by a Surface-plasmon Field

    Science.gov (United States)

    2014-11-03

    optical carrier cooling in intrinsic semiconductors at low lattice temperatures,” Phys. Rev. B 78, 035206 (2008). 21. H. M. Gibbs, G. Khitrova, and S...Khitrova, H. M. Gibbs, G. Rupper, C. Ell, O. B. Shchekin, and D. G. Deppe, “Vacuum Rabi splitting with a single quantum dot in a photonic crystal...in the photon-dressed electronic states with a Rabi gap and in the feedback from the induced optical polarization of dressed electrons to the incident

  11. Acoustic emission and magnification of atomic lines resolution for laser breakdown of salt water in ultrasound field

    Energy Technology Data Exchange (ETDEWEB)

    Bulanov, Alexey V., E-mail: a-bulanov@me.com [Far Eastern Federal University, Vladivostok, Russia 690950 (Russian Federation); V.I. Il’ichev Pacific Oceanological Institute, Vladivostok, Russia 690041 (Russian Federation); Nagorny, Ivan G., E-mail: ngrn@mail.ru [Far Eastern Federal University, Vladivostok, Russia 690950 (Russian Federation); Institute for automation and control processes, Vladivostok, Russia 690041 (Russian Federation)

    2015-10-28

    Researches of the acoustic effects accompanying optical breakdown in a water, generated by the focused laser radiation with power ultrasound have been carried out. Experiments were performed by using 532 nm pulses from Brilliant B Nd:YAG laser. Acoustic radiation was produced by acoustic focusing systems in the form hemisphere and ring by various resonance frequencies of 10.7 kHz and 60 kHz. The experimental results are obtained, that show the sharply strengthens effects of acoustic emission from a breakdown zone by the joint influence of a laser and ultrasonic irradiation. Essentially various thresholds of breakdown and character of acoustic emission in fresh and sea water are found out. The experimental result is established, testifying that acoustic emission of optical breakdown of sea water at presence and at absence of ultrasound essentially exceeds acoustic emission in fresh water. Atomic lines of some chemical elements like a Sodium, Magnesium and so on were investigated for laser breakdown of water with ultrasound field. The effect of magnification of this lines resolution for salt water in ultrasound field was obtained.

  12. Estimation of Emissions from Sugarcane Field Burning in Thailand Using Bottom-Up Country-Specific Activity Data

    Directory of Open Access Journals (Sweden)

    Wilaiwan Sornpoon

    2014-09-01

    Full Text Available Open burning in sugarcane fields is recognized as a major source of air pollution. However, the assessment of its emission intensity in many regions of the world still lacks information, especially regarding country-specific activity data including biomass fuel load and combustion factor. A site survey was conducted covering 13 sugarcane plantations subject to different farm management practices and climatic conditions. The results showed that pre-harvest and post-harvest burnings are the two main practices followed in Thailand. In 2012, the total production of sugarcane biomass fuel, i.e., dead, dry and fresh leaves, amounted to 10.15 million tonnes, which is equivalent to a fuel density of 0.79 kg∙m−2. The average combustion factor for the pre-harvest and post-harvest burning systems was determined to be 0.64 and 0.83, respectively. Emissions from sugarcane field burning were estimated using the bottom-up country-specific values from the site survey of this study and the results compared with those obtained using default values from the 2006 IPCC Guidelines. The comparison showed that the use of default values lead to underestimating the overall emissions by up to 30% as emissions from post-harvest burning are not accounted for, but it is the second most common practice followed in Thailand.

  13. Aberration corrected 1.2-MV cold field-emission transmission electron microscope with a sub-50-pm resolution

    Energy Technology Data Exchange (ETDEWEB)

    Akashi, Tetsuya; Takahashi, Yoshio; Tanigaki, Toshiaki, E-mail: toshiaki.tanigaki.mv@hitachi.com; Shimakura, Tomokazu; Kawasaki, Takeshi; Furutsu, Tadao; Shinada, Hiroyuki; Osakabe, Nobuyuki [Central Research Laboratory, Hitachi, Ltd., Hatoyama 350-0395 (Japan); Müller, Heiko; Haider, Maximilian [Corrected Electron Optical Systems GmbH, Englerstr. 28, D-69126 Heidelberg (Germany); Tonomura, Akira [Central Research Laboratory, Hitachi, Ltd., Hatoyama 350-0395 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)

    2015-02-16

    Atomic-resolution electromagnetic field observation is critical to the development of advanced materials and to the unveiling of their fundamental physics. For this purpose, a spherical-aberration corrected 1.2-MV cold field-emission transmission electron microscope has been developed. The microscope has the following superior properties: stabilized accelerating voltage, minimized electrical and mechanical fluctuation, and coherent electron emission. These properties have enabled to obtain 43-pm information transfer. On the bases of these performances, a 43-pm resolution has been obtained by correcting lens aberrations up to the third order. Observations of GaN [411] thin crystal showed a projected atomic locations with a separation of 44 pm.

  14. 200 keV cold field emission source using carbon cone nanotip: Application to scanning transmission electron microscopy.

    Science.gov (United States)

    Mamishin, Shuichi; Kubo, Yudai; Cours, Robin; Monthioux, Marc; Houdellier, Florent

    2017-11-01

    We report the use of a pyrolytic carbon cone nanotip as field emission cathode inside a modern 200 kV dedicated scanning transmission electron microscope. We show an unprecedented improvement in the probe current stability while maintaining all the fundamental properties of a cold field emission source such as a small angular current density together with a high brightness. We have also studied the influence of the low extraction voltage, as enabled by the nanosized apex of the cones, on the electron optics properties of the source that prevent the formation of a virtual beam cross-over of the gun. We have addressed this resolution-limiting issue by coming up with a new electron optical source design. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Studies of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS) Field Campaign Report

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Flynn, C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-01

    Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS), a National Aeronautics and Space Administration (NASA) field campaign, was based out of Ellington Field in Houston, Texas, during August and September 2013. The study focused on pollution emissions and the evolution of gases and aerosols in deep convective outflow, and the influences and feedbacks of aerosol particles from anthropogenic pollution and biomass burning on meteorology, clouds, and climate. The project required three aircraft to accomplish these goals. The NASA DC-8 provided observations from near the surface to 12 km, while the NASA ER-2 provided high-altitude observations reaching into the lower stratosphere as well as important remote-sensing observations connecting satellites with observations from lower-flying aircraft and surface sites. The SPEC, Inc. Learjet obtained aerosol and cloud microphysical measurement in convective clouds and convective outflow.

  16. Reply to ``Comment on `Imaging the atomic orbitals of carbon atomic chains with field-emission electron microscopy' ''

    Science.gov (United States)

    Mikhailovskij, I. M.; Sadanov, E. V.; Mazilova, T. I.; Ksenofontov, V. A.; Velicodnaja, O. A.

    2010-03-01

    In our recent paper [I. M. Mikhailovskij, E. V. Sadanov, T. I. Mazilova, V. A. Ksenofontov, and O. A. Velicodnaja, Phys. Rev. B 80, 165404 (2009)], we have presented evidence for field emission from individual orbitals of self-standing carbon chains, which can be used for real-space imaging of the end-atom orbitals with a field-emission electron microscope (FEEM). In this reply to the preceding Comment, we refer to the issues brought up there, which concern the viewpoint that the observed spontaneous mutual transformations of FEEM patterns have been attributed to the ligand-induced symmetry breaking by calling attention to the role of hydrogen atoms unavoidable in most nanostructured carbon materials.

  17. Space-charge-controlled field emission model of current conduction through Al2O3 films

    Science.gov (United States)

    Hiraiwa, Atsushi; Matsumura, Daisuke; Kawarada, Hiroshi

    2016-02-01

    This study proposes a model for current conduction in metal-insulator-semiconductor (MIS) capacitors, assuming the presence of two sheets of charge in the insulator, and derives analytical formulae of field emission (FE) currents under both negative and positive bias. Since it is affected by the space charge in the insulator, this particular FE differs from the conventional FE and is accordingly named the space-charge-controlled (SCC) FE. The gate insulator of this study was a stack of atomic-layer-deposition Al2O3 and underlying chemical SiO2 formed on Si substrates. The current-voltage (I-V) characteristics simulated using the SCC-FE formulae quantitatively reproduced the experimental results obtained by measuring Au- and Al-gated Al2O3/SiO2 MIS capacitors under both biases. The two sheets of charge in the Al2O3 films were estimated to be positive and located at a depth of greater than 4 nm from the Al2O3/SiO2 interface and less than 2 nm from the gate. The density of the former is approximately 1 × 1013 cm-2 in units of electronic charge, regardless of the type of capacitor. The latter forms a sheet of dipoles together with image charges in the gate and hence causes potential jumps of 0.4 V and 1.1 V in the Au- and Al-gated capacitors, respectively. Within a margin of error, this sheet of dipoles is ideally located at the gate/Al2O3 interface and effectively reduces the work function of the gate by the magnitude of the potential jumps mentioned above. These facts indicate that the currents in the Al2O3/SiO2 MIS capacitors are enhanced as compared to those in ideal capacitors and that the currents in the Al-gated capacitors under negative bias (electron emission from the gate) are more markedly enhanced than those in the Au-gated capacitors. The larger number of gate-side dipoles in the Al-gated capacitors is possibly caused by the reaction between the Al and Al2O3, and therefore gate materials that do not react with underlying gate insulators should be chosen

  18. Thermal properties of sand from Thermal Emission Spectrometer (TES) and Thermal Emission Imaging System (THEMIS): Spatial variations within the Proctor Crater dune field on Mars

    Science.gov (United States)

    Fenton, Lori K.; Mellon, Michael T.

    2006-06-01

    Thermal inertia, a parameter calculated from surface temperatures obtained from spacecraft, has long been used to quantify the amount of loose, fine-grained material on the Martian surface. With little ``ground truth'' available, studies often refer to Martian dune fields to calibrate thermal inertias. The well-understood physical properties of dune sand make it an ideal basis for comparison to more complex surfaces. However, higher-resolution data sets available from the TES (Thermal Emission Spectrometer onboard Mars Global Surveyor) and THEMIS (Thermal Emission Imaging System onboard Mars Odyssey) show spatial variations in the thermal properties within dune fields, calling into question their effectiveness as controls for thermal inertia studies. In order to explain these variations, we apply a thermal model developed for TES data to a commonly investigated dune field in Noachis Terra, that on the floor of Proctor Crater. We show that in this dune field, the thermal variations on the scale of 30 J m-2 s-0.5 K-1 are present and correlate spatially with aeolian features in the dune field. These variations correspond to three types of surfaces observed in the Mars Orbital Camera Narrow Angle (MOC NA) images: (1) dune sand, (2) interdunes exposing the surface underlying the dune field, and (3) sand-covered interdunes, or dune troughs. Both the interdunes and the dune troughs have cooler nighttime temperatures than the dune sand, corresponding to lower thermal inertia values. The dune troughs may be sand-covered areas with either minor amounts of dust accumulation or a mean sand grain size lower than that of dune sand. Because fine sand grains tend to preferentially accumulate on dune crests rather than in dune troughs, the second hypothesis is considered less likely than the first. This has implications for the recent sedimentary history of the dune field: Dust accumulation in dune troughs may imply that sand saltation is not prevalent enough to scour away all of

  19. PREP-CHEM-SRC – 1.0: a preprocessor of trace gas and aerosol emission fields for regional and global atmospheric chemistry models

    Directory of Open Access Journals (Sweden)

    S. R. Freitas

    2011-05-01

    Full Text Available The preprocessor PREP-CHEM-SRC presented in the paper is a comprehensive tool aiming at preparing emission fields of trace gases and aerosols for use in atmospheric-chemistry transport models. The considered emissions are from the most recent databases of urban/industrial, biogenic, biomass burning, volcanic, biofuel use and burning from agricultural waste sources. For biomass burning, emissions can be also estimated directly from satellite fire detections using a fire emission model included in the tool. The preprocessor provides emission fields interpolated onto the transport model grid. Several map projections can be chosen. The inclusion of these emissions in transport models is also presented. The preprocessor is coded using Fortran90 and C and is driven by a namelist allowing the user to choose the type of emissions and the databases.

  20. Light emission from thermally generated electron-hole plasma in a field-effect soi-transistor

    CERN Document Server

    Dobrovol's'kij, V M; Nyinyidze, G K; Pavlyuk, S P

    2002-01-01

    Field-effect silicon-on-insulator (SOI) transistors are investigated at extremely high drain currents.These currents heat the silicon film of a transistor and cause the generation of thermal electron-hole plasma there.We discovered the red light emission from such a plasma.Plasma stratification and formation of lighting spots are explained by the occurrence of thermodiffusion auto solitons.

  1. Near-Field Characterization of Methane Emission Variability from a Compressor Station Using a Model Aircraft.

    Science.gov (United States)

    Nathan, Brian J; Golston, Levi M; O'Brien, Anthony S; Ross, Kevin; Harrison, William A; Tao, Lei; Lary, David J; Johnson, Derek R; Covington, April N; Clark, Nigel N; Zondlo, Mark A

    2015-07-07

    A model aircraft equipped with a custom laser-based, open-path methane sensor was deployed around a natural gas compressor station to quantify the methane leak rate and its variability at a compressor station in the Barnett Shale. The open-path, laser-based sensor provides fast (10 Hz) and precise (0.1 ppmv) measurements of methane in a compact package while the remote control aircraft provides nimble and safe operation around a local source. Emission rates were measured from 22 flights over a one-week period. Mean emission rates of 14 ± 8 g CH4 s(-1) (7.4 ± 4.2 g CH4 s(-1) median) from the station were observed or approximately 0.02% of the station throughput. Significant variability in emission rates (0.3-73 g CH4 s(-1) range) was observed on time scales of hours to days, and plumes showed high spatial variability in the horizontal and vertical dimensions. Given the high spatiotemporal variability of emissions, individual measurements taken over short durations and from ground-based platforms should be used with caution when examining compressor station emissions. More generally, our results demonstrate the unique advantages and challenges of platforms like small unmanned aerial vehicles for quantifying local emission sources to the atmosphere.

  2. The Emissions of Carbon Dioxide, Methane, and Nitrous Oxide during Winter without Cultivation in Local Saline-Alkali Rice and Maize Fields in Northeast China

    Directory of Open Access Journals (Sweden)

    Hao Zhang

    2017-10-01

    Full Text Available Agricultural ecosystems are important contributors to atmospheric greenhouse gasses (GHGs; however, in situ winter emission data in saline-alkali fields are scarce. Gas samples were collected during different periods, from three rice (R1–R3 and three maize (M1–M3 fields with different soil pH levels and salinity conditions. Carbon dioxide (CO2 emissions in the rice and maize fields decreased with decreasing temperature during the freezing period and increased with the rising temperature during the thawing period, with the majority of winter CO2 emissions occurring during these two periods. Peaks in methane (CH4 emissions were observed during the freezing period in the rice fields and during the snow-melting period in the rice and maize fields. CH4 emissions in the rice fields and CH4 uptake rates in the maize fields were significantly (P < 0.05 related to surface soil temperature. Nitrous oxide (N2O emissions remained relatively low, except for during the peaks observed during the snow-melting period in both the rice and maize fields, leading to the high GHG contribution of the snow-melting period throughout the winter. Higher pH and salinity conditions consistently resulted in lower CO2, CH4, and N2O emissions, CH4 uptake, and lower global warming potential (GWP. These results can contribute to the assessment of the GWP during winter in saline-alkali regions.

  3. First attempt of at-cavity cryogenic X-ray detection in a CEBAF cryomodule for field emission monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Geng, Rongli [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Daly, Edward [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Drury, Michael [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Palczewski, Ari [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

    2015-09-01

    We report on the first result of at-cavity X-ray detection in a CEBAF cryomodule for field emission monitoring. In the 8-cavity cryomodule F100, two silicon diodes were installed near the end flange of each cavity. Each cavity was individually tested during the cryomodule test in JLab’s cryomodule test facility. The behaviors of these at-cavity cryogenic X-ray detectors were compared with those of the standard ‘in air’ Geiger-Muller (G-M) tubes. Our initial experiments establish correlation between X-ray response of near diodes and the field emission source cavity in the 8-cavity string. For two out of these eight cavities, we also carried out at-cavity X-ray detection experiment during their vertical testing. The aim is to track field emission behavior uniquely from vertical cavity testing to horizontal cavity testing in the cryomodule. These preliminary results confirmed our expectation and warrant further effort toward the establishment of permanent at-cavity cryogenic X-ray detection for SRF development and operation.

  4. Synthesis of bismuth tungstate (Bi{sub 2}WO{sub 6}) nanoflakes and their field emission investigation

    Energy Technology Data Exchange (ETDEWEB)

    Kolhe, P. S.; Sonawane, K. M. [Department of Physics, Fergusson College, Pune 411 004 (India); Bankar, P. K.; Gavhane, D. S.; More, M. A., E-mail: mam@physics.unipune.ac.in [Center for Advanced Studies in materials Science and Condensed Matter Physics, Department of Physics, Savitribai Phule Pune University, Pune-411 00.7 (India); Maiti, N. [Laser & Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India)

    2016-05-23

    The nanoflakes of Bismuth Tungstate (Bi{sub 2}WO{sub 6}) were successfully synthesized by a one-step facile hydrothermal route without using any templates or surfactants and field emission investigations of the Bi{sub 2}WO{sub 6} nanoflakes emitter are reported. Structural and morphological analysis of as-synthesized Bi{sub 2}WO{sub 6} nanoflakes has been carried out using X-ray diffraction (XRD) and scanning electron microscope (SEM). Moreover, the field emission characteristics of the Bi{sub 2}WO{sub 6} nanoflakes are found to be superior to the other semiconductor emitters. The synthesized Bi{sub 2}WO{sub 6} nanoflakes emitter delivers current density of ~222.35 μA/cm{sup 2} at an applied electric field of ~7.2 V/μm. The emission current stability investigated at pre-set value of ~2 μA is observed to be fairly good. These observed results demonstrate potential candidate of the Bi{sub 2}WO{sub 6} cathode as an electron source for practical applications in vacuum microelectronic device.

  5. Carrier delocalization in InAs/InGaAlAs/InP quantum-dash-based tunnel injection system for 1.55 µm emission

    Science.gov (United States)

    Rudno-Rudziński, W.; Syperek, M.; Andrzejewski, J.; Maryński, A.; Misiewicz, J.; Somers, A.; Höfling, S.; Reithmaier, J. P.; Sek, G.

    2017-01-01

    We have investigated optical properties of hybrid two-dimensional-zero-dimensional (2D-0D) tunnel structures containing strongly elongated InAs/InP(001) quantum dots (called quantum dashes), emitting at 1.55 μ m . These quantum dashes (QDashes) are separated by a 2.3 nm-width barrier from an InGaAs quantum well (QW), lattice matched to InP. We have tailored quantum-mechanical coupling between the states confined in QDashes and a QW by changing the QW thickness. By combining modulation spectroscopy and photoluminescence excitation, we have determined the energies of all relevant optical transitions in the system and proven the carrier transfer from the QW to the QDashes, which is the fundamental requirement for the tunnel injection scheme. A transformation between 0D and mixed-type 2D-0D character of an electron and a hole confinement in the ground state of the hybrid system have been probed by time-resolved photoluminescence that revealed considerable changes in PL decay time with the QW width changes. The experimental discoveries have been explained by band structure calculations in the framework of the eight-band kṡp model showing that they are driven by delocalization of the lowest energy hole state. The hole delocalization process from the 0D QDash confinement is unfavorable for optical devices based on such tunnel injection structures.

  6. Carrier delocalization in InAs/InGaAlAs/InP quantum-dash-based tunnel injection system for 1.55 µm emission

    Directory of Open Access Journals (Sweden)

    W. Rudno-Rudziński

    2017-01-01

    Full Text Available We have investigated optical properties of hybrid two-dimensional-zero-dimensional (2D-0D tunnel structures containing strongly elongated InAs/InP(001 quantum dots (called quantum dashes, emitting at 1.55 μm. These quantum dashes (QDashes are separated by a 2.3 nm-width barrier from an InGaAs quantum well (QW, lattice matched to InP. We have tailored quantum-mechanical coupling between the states confined in QDashes and a QW by changing the QW thickness. By combining modulation spectroscopy and photoluminescence excitation, we have determined the energies of all relevant optical transitions in the system and proven the carrier transfer from the QW to the QDashes, which is the fundamental requirement for the tunnel injection scheme. A transformation between 0D and mixed-type 2D-0D character of an electron and a hole confinement in the ground state of the hybrid system have been probed by time-resolved photoluminescence that revealed considerable changes in PL decay time with the QW width changes. The experimental discoveries have been explained by band structure calculations in the framework of the eight-band k⋅p model showing that they are driven by delocalization of the lowest energy hole state. The hole delocalization process from the 0D QDash confinement is unfavorable for optical devices based on such tunnel injection structures.

  7. Aged particles derived from emissions of coal-fired power plants: The TERESA field results

    Science.gov (United States)

    Kang, Choong-Min; Gupta, Tarun; Ruiz, Pablo A.; Wolfson, Jack M.; Ferguson, Stephen T.; Lawrence, Joy E.; Rohr, Annette C.; Godleski, John; Koutrakis, Petros

    2013-01-01

    The Toxicological Evaluation of Realistic Emissions Source Aerosols (TERESA) study was carried out at three US coal-fired power plants to investigate the potential toxicological effects of primary and photochemically aged (secondary) particles using in situ stack emissions. The exposure system designed successfully simulated chemical reactions that power plant emissions undergo in a plume during transport from the stack to receptor areas (e.g., urban areas). Test atmospheres developed for toxicological experiments included scenarios to simulate a sequence of atmospheric reactions that can occur in a plume: (1) primary emissions only; (2) H2SO4 aerosol from oxidation of SO2; (3) H2SO4 aerosol neutralized by gas-phase NH3; (4) neutralized H2SO4 with secondary organic aerosol (SOA) formed by the reaction of α-pinene with O3; and (5) three control scenarios excluding primary particles. The aged particle mass concentrations varied significantly from 43.8 to 257.1 μg/m3 with respect to scenario and power plant. The highest was found when oxidized aerosols were neutralized by gas-phase NH3 with added SOA. The mass concentration depended primarily on the ratio of SO2 to NOx (particularly NO) emissions, which was determined mainly by coal composition and emissions controls. Particulate sulfate (H2SO4 + neutralized sulfate) and organic carbon (OC) were major components of the aged particles with added SOA, whereas trace elements were present at very low concentrations. Physical and chemical properties of aged particles appear to be influenced by coal type,