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Sample records for improved field emission

  1. Method of improving field emission characteristics of diamond thin films

    DOEpatents

    Krauss, Alan R.; Gruen, Dieter M.

    1999-01-01

    A method of preparing diamond thin films with improved field emission properties. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display.

  2. Method of improving field emission characteristics of diamond thin films

    DOEpatents

    Krauss, A.R.; Gruen, D.M.

    1999-05-11

    A method of preparing diamond thin films with improved field emission properties is disclosed. The method includes preparing a diamond thin film on a substrate, such as Mo, W, Si and Ni. An atmosphere of hydrogen (molecular or atomic) can be provided above the already deposited film to form absorbed hydrogen to reduce the work function and enhance field emission properties of the diamond film. In addition, hydrogen can be absorbed on intergranular surfaces to enhance electrical conductivity of the diamond film. The treated diamond film can be part of a microtip array in a flat panel display. 3 figs.

  3. Improved field emission property of graphene paper by plasma treatment

    SciTech Connect

    Liu Jianlong; Zeng Baoqing; Wu Zhe; Zhu Jinfeng; Liu Xingchong

    2010-07-19

    Lateral orientation and aggregation of the graphene sheets limited field enhancement of graphene paper (GP). To improve the field enhancement of GP, argon plasma treatment was induced to destroy the aggregation and cause formation of surface protrusions. After Ar plasma treatment, turn-on field and threshold field of GP were reduced from 2.3 V/mum to 1.6 V/mum and 4.4 V/mum to 3.0 V/mum, respectively. The enhancement was attributed to the protrusions. Scanning electron microscopy and hydrophobicity had been used to prove the morphology change after plasma treatment.

  4. Laboratory and field investigations of particulate and carbon monoxide emissions from traditional and improved cookstoves

    NASA Astrophysics Data System (ADS)

    Roden, Christoph A.; Bond, Tami C.; Conway, Stuart; Osorto Pinel, Anibal Benjamin; MacCarty, Nordica; Still, Dean

    We implemented a program in which emission characterization is enabled through collaborations between academic, US and international non-governmental entities that focus on evaluation, dissemination, and in-use testing, of improved cookstoves. This effort resulted in a study of field and laboratory emissions from traditional and improved biofuel cookstoves. We found that field measured particulate emissions of actual cooking average three times those measured during simulated cooking in the laboratory. Emission factors are highly dependent on the care and skill of the operator and the resulting combustion; these do not appear to be accurately reproduced in laboratory settings. The single scattering albedo (SSA) of the emissions was very low in both lab and field measurements, averaging about 0.3 for lab tests and around 0.5 for field tests, indicating that the primary particles are climate warming. Over the course of three summers in Honduras, we measured field emissions from traditional cookstoves, relatively new improved cookstoves, and "broken-in" improved cookstoves. We found that well-designed improved cookstoves can significantly reduce PM and CO emission factors below traditional cookstoves. For improved stoves, the presence of a chimney generally resulted in lower emission factors but left the SSA unaffected. Traditional cookstoves had an average PM emission factor of 8.2 g kg -1 - significantly larger than previous studies. Particulate emission factors for improved cookstoves without and with chimneys averaged about 6.6 g kg -1 and 4.5 g kg -1, respectively. The elemental carbon (EC) fraction of PM varied significantly between individual tests, but averaged about 25% for each of the categories.

  5. Improved Field Emission Algorithms for Modeling Field Emission Devices Using a Conformal Finite-Difference Time-Domain Particle-in-Cell Method

    NASA Astrophysics Data System (ADS)

    Lin, M. C.; Loverich, J.; Stoltz, P. H.; Nieter, C.

    2013-10-01

    This work introduces a conformal finite difference time domain (CFDTD) particle-in-cell (PIC) method with an improved field emission algorithm to accurately and efficiently study field emission devices. The CFDTD method is based on the Dey-Mittra algorithm or cut-cell algorithm, as implemented in the Vorpal code. For the field emission algorithm, we employ the elliptic function v(y) found by Forbes and a new fitting function t(y)2 for the Fowler-Nordheim (FN) equation. With these improved correction factors, field emission of electrons from a cathode surface is much closer to the prediction of the exact FN formula derived by Murphy and Good. This work was supported in part by both the U.S. Department of Defense under Grant No. FA9451-07-C-0025 and the U.S. Department of Energy under Grant No. DE-SC0004436.

  6. High Resolution CNT-FED and Improvement in Field-Emission Characteristics

    NASA Astrophysics Data System (ADS)

    Kurachi, Hiroyuki; Uemura, Sashiro; Yotani, Junko; Nagasako, Takeshi; Yamada, Hiromu; Ezaki, Tomotaka; Maesoba, Tsuyoshi; Nakao, Takehiro; Ito, Masaaki; Sakurai, Akira; Shimoda, Hideo; Saito, Yahachi; Shinohara, Hisanori

    A recent study of carbon nanotube (CNT)-field emission display (FED) was described, and luminance uniformity of the experimental panel and the results of the life test of the CNT emitters were revealed. Furthermore, a high-resolution CNT-FED was investigated for graphic-displays. The sub-pixel size was 0.2 mm × 0.6 mm. The configuration of the display was a metal-backed color-phosphor screen, tall-spacer of 0.5-1.0 mm height for individual phosphor line, a metal gate-substrate with tall spacer and chemical vapor deposition (CVD)-grown-CNT on a metal-electrode. In order to improve field-emission characteristics of the CNT cathode, we developed two kinds of new CNT emitters by thermal-CVD. One is an emitter with thin CNTs which were grown on an alumina layer. The emission was extremely increased at lower voltage, compared to our conventional CNT emitter. Another is an emitter with secondary thin CNTs grown on thick CNTs. The emission showed an improvement in emission distribution uniformity.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    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.

  8. Remarkably improved field emission of TiO{sub 2} nanotube arrays by annealing atmosphere engineering

    SciTech Connect

    Liao, Ai-Zhen; Wang, Cheng-Wei Chen, Jian-Biao; Zhang, Xu-Qiang; Li, Yan; Wang, Jian

    2015-10-15

    Highlights: • TNAs were prepared by anodization and annealed in different atmospheres. • The crystal structure and electronic properties of the prepared TNAs were investigated. • The field emission of TNAs was highly dependent on annealing atmosphere. • A low turn-on of 2.44 V/μm was obtained for TNAs annealed in H{sub 2} atmosphere. - Abstract: Highly ordered TiO{sub 2} nanotube arrays (TNAs) were prepared by anodization, and followed by annealing in the atmospheres of Air, Vacuum, Ar, and H{sub 2}. The effect of annealing atmosphere on the crystal structure, composition, and electronic properties of TNAs were systematically investigated. Raman and EDS results indicated that the TNAs annealed in anaerobic atmospheres contained more oxygen vacancies, which result in the substantially improved electron transport properties and reduced work function. Moreover, it was found that the FE properties of TNAs were highly dependent on the annealing atmosphere. By engineering the annealing atmosphere, the turn-on field as low as 2.44 V/μm can be obtained from TNAs annealed in H{sub 2}, which was much lower than the value of 18.23 V/μm from the TNAs annealed in the commonly used atmosphere of Air. Our work suggests an instructive and attractive way to fabricate high performance TNAs field emitters.

  9. Improving the quantification at high spatial resolution using a field emission electron microprobe

    NASA Astrophysics Data System (ADS)

    Pinard, P. T.; Richter, S.

    2014-03-01

    The capabilities of field emitter electron microprobes to perform quantitative measurements at high spatial resolution are discussed. Using Fe-Cr-C particles in a bearing steel (SAE 52100) as example, a generic procedure was established to find the optimal analytical conditions (beam energy, beam current and acquisition time). The influence of these parameters on the accuracy, precision and spatial resolution was evaluated using experimental measurements and Monte Carlo simulations. A quantification procedure was developed for soft X-ray lines, taking into account the overlap of high order X-ray lines and background anomalies. The accuracy of Ka- and La-lines was verified using reference materials. A relationship between experimental and simulated X-ray intensities was determined to evaluate the measurement precision. The spatial resolution of each X-ray line was calculated from the simulated lateral and depth X-ray intensity distribution using simulations integrating experimentally measured beam diameters. The optimal analytical conditions for the studied sample were found to be 5 keV, 10 nA and 10 s acquisition time. Further specialized techniques to improve the spatial resolution are presented: focused ion beam preparation of thin lamella and wedge, and Monte Carlo based reconstruction. The feasibility of the latter to quantify features smaller than the X-ray emission volume was demonstrated.

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

    NASA Astrophysics Data System (ADS)

    Mengui, U. A.; Campos, R. A.; Alves, K. A.; Antunes, E. F.; Hamanaka, M. H. M. O.; Corat, E. J.; Baldan, M. R.

    2015-04-01

    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.

  11. Field emission chemical sensor

    DOEpatents

    Panitz, J.A.

    1983-11-22

    A field emission chemical sensor for specific detection of a chemical entity in a sample includes a closed chamber enclosing two field emission electrode sets, each field emission electrode set comprising (a) an electron emitter electrode from which field emission electrons can be emitted when an effective voltage is connected to the electrode set; and (b) a collector electrode which will capture said electrons emitted from said emitter electrode. One of the electrode sets is passive to the chemical entity and the other is active thereto and has an active emitter electrode which will bind the chemical entity when contacted therewith.

  12. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Improvement of Field Emission Characteristics of Copper Nitride Films with Increasing Copper Content

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Li, Rui-Shan; Pan, Xiao-Jun; Zhang, Pei-Zeng; Zhou, Ming; Song, Xi; Xie, Er-Qing

    2009-06-01

    A copper nitride (Cu3N) thin film is deposited on a Si substrate by the reactive magnetron sputtering method. The XPS measurements of the composite film indicate that the Cu content in the film is increased to 80.82 at. % and the value of the Cu/N ratio to 4.2:1 by introducing 4% H2 into the reactive gas. X-ray diffraction measurements show that the film is composed of Cu3N crystallites with an anti-ReO3 structure. The effects of the increase of copper content on the field emission characteristics of the Cu3N thin film are investigated. Significant improvement in emission current density and emission repeatability could be attributed to the geometric field enhancement, caused by numerous surface nanotips, and the decrease of resistivity of the film.

  13. Improvement of Electrostatic Discharge Protection by Introducing a Spindt-Type Silicon Field Emission Device

    NASA Astrophysics Data System (ADS)

    Chang, Liann-Be; Ferng, Yi-Cherng; Liao, Jhong-Wei; Lin, Ching-Chi

    2012-04-01

    In this paper, an original Spindt-type silicon field emission device (FED) with electrostatic discharge (ESD) regulation capability is proposed. The fabricated FED characteristics, including process parameters, capacitance-voltage (C-V), current-voltage (I-V), and frequency response, are investigated. To verify its capability of ESD protection, we replace the metal oxide varistor (MOV) in a state-of-the-art protection configuration with the fabricated FED under the application conditions of system-level ESD tests. The measured results show that the proposed ESD protection circuit composed of a prestage gas arrestor, an intermediate resistor, and an introduced FED can suppress an injected ESD pulse voltage of 6000 to 3193 V, a reduction of 46.8%, whereas suppression is to 5606 V, a reduction of 6.57%, when using only a gas arrestor.

  14. Field emission electron source

    DOEpatents

    Zettl, Alexander Karlwalter; Cohen, Marvin Lou

    2000-01-01

    A novel field emitter material, field emission electron source, and commercially feasible fabrication method is described. The inventive field emission electron source produces reliable electron currents of up to 400 mA/cm.sup.2 at 200 volts. The emitter is robust and the current it produces is not sensitive to variability of vacuum or the distance between the emitter tip and the cathode. The novel emitter has a sharp turn-on near 100 volts.

  15. Graphene field emission devices

    SciTech Connect

    Kumar, S. Raghavan, S.; Duesberg, G. S.; Pratap, R.

    2014-09-08

    Graphene field emission devices are fabricated using a scalable process. The field enhancement factors, determined from the Fowler-Nordheim plots, are within few hundreds and match the theoretical predictions. The devices show high emission current density of ∼10 nA μm{sup −1} at modest voltages of tens of volts. The emission is stable with time and repeatable over long term, whereas the noise in the emission current is comparable to that from individual carbon nanotubes emitting under similar conditions. We demonstrate a power law dependence of emission current on pressure which can be utilized for sensing. The excellent characteristics and relative ease of making the devices promise their great potential for sensing and electronic applications.

  16. Field evaluation of a new plastic film (vapor safe) to reduce fumigant emissions and improve distribution in soil.

    PubMed

    Qin, Ruijun; Gao, Suduan; Ajwa, Husein; Sullivan, David; Wang, Dong; Hanson, Bradley D

    2011-01-01

    Preplant soil fumigation is an important pest management practice in coastal California strawberry production regions. Potential atmospheric emissions of fumigants from field treatment, however, have drawn intensive environmental and human health concerns; increasingly stringent regulations on fumigant use have spurred research on low-emission application techniques. The objectives of this research were to determine the effects of a new low-permeability film, commonly known as totally impermeable film (TIF), on fumigant emissions and on fumigant distribution in soil. A 50/50 mixture of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) was shank-applied at 314 kg ha in two location-separate field plots (0.4 ha each) in Ventura County, California, in fall 2009. One plot was surface-covered with standard polyethylene (PE) film, and the other was covered with TIF immediately after fumigant application. Data collection included emissions, soil-gas phase concentration profile, air concentration under the film, and soil residuals of the applied fumigants. Peak emission flux of 1,3-D and CP from the TIF field was substantially lower than from the PE field. Total through-film emission loss was 2% for 1,3-D and <1% for CP from the TIF field during a 6-d film covering period, compared with 43% for 1,3-D and 12% for CP from the PE field. However, on film-cutting, greater retention of 1,3-D in the TIF field resulted in a much higher emission surge compared with the PE field, while CP emissions were fairly low in both fields. Higher concentrations and a more uniform distribution in the soil profile for 1,3-D and CP were observed under the TIF compared with the PE film, suggesting that the TIF may allow growers to achieve satisfactory pest control with lower fumigant rates. The surging 1,3-D emissions after film-cutting could result in high exposure risks to workers and bystanders and must be addressed with additional mitigation measures.

  17. Improved field emission properties of carbon nanotubes grown on stainless steel substrate and its application in ionization gauge

    NASA Astrophysics Data System (ADS)

    Li, Detian; Cheng, Yongjun; Wang, Yongjun; Zhang, Huzhong; Dong, Changkun; Li, Da

    2016-03-01

    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 10-8 Pa, which is one order of magnitude lower than the result reported for the same of gauge with CNT cathode.

  18. Field emission property improvement of ZnO nanowires coated with amorphous carbon and carbon nitride films

    NASA Astrophysics Data System (ADS)

    Liao, L.; Li, J. C.; Wang, D. F.; Liu, C.; Liu, C. S.; Fu, Q.; Fan, L. X.

    2005-06-01

    In this paper, we report an approach to prepare a new type of field emitter made up of ZnO nanowires coated with an amorphous carbon (a-C) or carbon nitride film (a-CNx). The coated ZnO nanowires form coaxial nanocables. The best field emission properties, which showed a very low turn-on electric field of 1.5 V µm-1 and an emission current density of 1 mA cm-2 (enough to produce a luminance of 300 cd m-2 from a VGA FED with a typical high-voltage phosphor screen efficacy of 9 lm W-1) under the field of only 2.5 V µm-1, have been obtained from the a-CNx coated ZnO nanowire field emitter among three kinds of emitters: a-C coated ZnO nanowires, a-CNx coated ZnO nanowires and uncoated ZnO nanowires. Microstructures and crystal configuration were investigated by scanning electron microscopy, x-ray diffraction and transmission electron microscopy. Band edge transition without any significant photoluminescence peak relating to intrinsic defects has been observed by photoluminescence measurement. The superior properties of the field emission are attributed to the low work function of the coated carbon nitride film and good electron transport property of the ZnO nanowires with an extremely sharp tip.

  19. Emission Characteristics of Graphite Nanofiber Field Emitter for Field Emission Display

    NASA Astrophysics Data System (ADS)

    Ushirozawa, Mizumoto; Hagiwara, Kei; Yamamoto, Toshihiro; Yokoo, Kuniyoshi

    Graphite nanofiber (GNF) is a field emission material consisting of intricately tangled nano-sized carbon fibers and has similar field emission characteristics to CNT. An important issue in achieving practical use of FED (field emission display) using carbon nano-materials is how to attain emission uniformity. With the objective of uniformity, field emission characteristics of GNF emitter were examined using a scanning Faraday cup emission profiler. The current density of emitted electrons changed considerably over the emitting area at a low field, as high as two orders in intensity in a measuring emitter area of 1 mm2. However, uniformity was significantly improved due to current saturation at a high field. This paper discusses the current saturation in field emission of GNF from the space-charge effect of emitted electrons.

  20. Field-scale simulation of methane emissions from coastal wetlands in China using an improved version of CH4MODwetland.

    PubMed

    Li, Tingting; Xie, Baohua; Wang, Guocheng; Zhang, Wen; Zhang, Qing; Vesala, Timo; Raivonen, Maarit

    2016-07-15

    Coastal wetlands are important CH4 sources to the atmosphere. Coastal wetlands account for ~10% of the total area of natural wetlands in China, but the size of this potential CH4 source remains highly uncertain. We introduced the influence of salinity on CH4 production and CH4 diffusion into a biogeophysical model named CH4MODwetland so that it can be used in coastal wetlands. The improved model can generally simulate seasonal CH4 variations from tidal marshes dominated by Phragmites and Scirpus. However, the model underestimated winter CH4 fluxes from tidal marshes in the Yellow River Delta and YanCheng Estuary. It also failed to capture the accurate timing of the CH4 peaks in YanCheng Estuary and ChongMing Island in 2012. The improved model could generally simulate the difference between the annual mean CH4 fluxes from mangrove sites in GuangZhou and HaiKou city under different salinity and water table depth conditions, although fluxes were systematically underestimated in the mangrove site of HaiKou city. Using the improved model, the seasonal CH4 emissions simulated across all of the coastal wetlands ranged from 0.1 to 44.90gm(-2), with an average value of 7.89gm(-2), which is in good agreement with the observed values. The improved model significantly decreased the RMSE and RMD from 424% to 14% and 314% to -2%, respectively, and improved the EF from -18.30 to 0.99. Model sensitivity analysis showed that CH4 emissions were most sensitive to Pox in the tidal marshes and salinity in the mangroves. The results show that previous studies may have overestimated CH4 emissions on a regional or global scale by neglecting the influence of salinity. In general, the CH4MODwetland model can simulate seasonal CH4 emissions from different types of coastal wetlands under various conditions. Further improvements of CH4MODwetland should include the specific characteristics of CH4 processes in mangroves to decrease the uncertainty in estimating regional or global CH4 emissions

  1. Emission properties of explosive field emission cathodes

    SciTech Connect

    Roy, Amitava; Patel, Ankur; Menon, Rakhee; Sharma, Archana; Chakravarthy, D. P.; Patil, D. S.

    2011-10-15

    The research results of the explosive field emission cathode plasma expansion velocity and the initial emission area in the planar diode configuration with cathodes made of graphite, stainless steel, polymer velvet, carbon coated, and carbon fiber (needle type) cathodes are presented. The experiments have been performed at the electron accelerator LIA-200 (200 kV, 100 ns, and 4 kA). The diode voltage has been varied from 28-225 kV, whereas the current density has been varied from 86-928 A/cm{sup 2} with 100 ns pulse duration. The experimentally obtained electron beam diode perveance has been compared with the 1 dimensional Child-Langmuir- law. It was found that initially only a part of the cathode take part in the emission process. The plasma expands at 1.7-5.2 cm/{mu}s for 4 mm anode-cathode gap for various cathode materials. It was found that the plasma expansion velocity increases with the decrease in the cathode diameter. At the beginning of the accelerating pulse, the entire cathode area participates in the electron emission process only for the multiple needle type carbon fiber cathode.

  2. Junction-based field emission structure for field emission display

    DOEpatents

    Dinh, Long N.; Balooch, Mehdi; McLean, II, William; Schildbach, Marcus A.

    2002-01-01

    A junction-based field emission display, wherein the junctions are formed by depositing a semiconducting or dielectric, low work function, negative electron affinity (NEA) silicon-based compound film (SBCF) onto a metal or n-type semiconductor substrate. The SBCF can be doped to become a p-type semiconductor. A small forward bias voltage is applied across the junction so that electron transport is from the substrate into the SBCF region. Upon entering into this NEA region, many electrons are released into the vacuum level above the SBCF surface and accelerated toward a positively biased phosphor screen anode, hence lighting up the phosphor screen for display. To turn off, simply switch off the applied potential across the SBCF/substrate. May be used for field emission flat panel displays.

  3. Improvement on electrical conductivity and electron field emission properties of Au-ion implanted ultrananocrystalline diamond films by using Au-Si eutectic substrates

    SciTech Connect

    Sankaran, K. J.; Sundaravel, B.; Tai, N. H. E-mail: inanlin@mail.tku.edu.tw; Lin, I. N. E-mail: inanlin@mail.tku.edu.tw

    2015-08-28

    In the present work, Au-Si eutectic layer was used to enhance the electrical conductivity/electron field emission (EFE) properties of Au-ion implanted ultrananocrystalline diamond (Au-UNCD) films grown on Si substrates. The electrical conductivity was improved to a value of 230 (Ω cm){sup −1}, and the EFE properties was enhanced reporting a low turn-on field of 2.1 V/μm with high EFE current density of 5.3 mA/cm{sup 2} (at an applied field of 4.9 V/μm) for the Au-UNCD films. The formation of SiC phase circumvents the formation of amorphous carbon prior to the nucleation of diamond on Si substrates. Consequently, the electron transport efficiency of the UNCD-to-Si interface increases, thereby improving the conductivity as well as the EFE properties. Moreover, the salient feature of these processes is that the sputtering deposition of Au-coating for preparing the Au-Si interlayer, the microwave plasma enhanced chemical vapor deposition process for growing the UNCD films, and the Au-ion implantation process for inducing the nanographitic phases are standard thin film preparation techniques, which are simple, robust, and easily scalable. The availability of these highly conducting UNCD films with superior EFE characteristics may open up a pathway for the development of high-definition flat panel displays and plasma devices.

  4. The induction of a graphite-like phase on diamond films by a Fe-coating/post-annealing process to improve their electron field emission properties

    SciTech Connect

    Huang, Pin-Chang; Shih, Wen-Ching; Chen, Huang-Chin; Lin, I-Nan

    2011-04-15

    The electron field emission (EFE) process for diamond films was tremendously enhanced by Fe-coating and post-annealing processes. Microstructural analysis indicates that the mechanism for the improvement in the EFE process is the formation of nanographites with good crystallinity that surround the Fe (or Fe{sub 3}C) nanoclusters. Presumably the nanographites were formed via the reaction of Fe clusters with diamond films, viz. by the dissolution of carbons into Fe (or Fe{sub 3}C) clusters and the reprecipitation of carbon species to the surface of the clusters, a process similar to the growth of carbon nanotubes via Fe clusters as catalyst. Not only is a sufficiently high post-annealing temperature (900 deg. C) required but also a highly active reducing atmosphere (NH{sub 3}) is needed to give a proper microstructure for enhancing the EFE process. The best EFE properties are obtained by post-annealing the Fe-coated diamond films at 900 deg. C in an NH{sub 3} environment for 5 min. The EFE behavior of the films can be turned on at E{sub 0} = 1.9 V/{mu}m, attaining a large EFE current density of 315 {mu}A/cm{sup 2} at an applied field of 8.8 V/{mu}m (extrapolation using the Fowler-Nordheim model leads to J{sub e} = 40.7 mA/cm{sup 2} at a 20 V/{mu}m applied field).

  5. Improved Biomass Cooking Stoves and Improved Stove Emission Equipment

    SciTech Connect

    HATFIELD, MICHAEL; Still, Dean

    2013-04-15

    In developing countries, there is an urgent need for access to safe, efficient, and more affordable cooking technologies. Nearly 2.5 billion people currently use an open fire or traditional cookstove to prepare their meals, and recent models predict that use of biomass for cooking will continue to be the dominant energy use in rural, resource-poor households through 2030. For these families, cooking poses serious risks to health, safety, and income. An alarming 4 million people, primarily women and children, die prematurely each year from indoor and outdoor exposure to the harmful emissions released by solid fuel combustion. Use of traditional stoves can also have a significant impact on deforestation and climate change. This dire situation creates a critical need for cookstoves that significantly and verifiably reduce fuel use and emissions in order to reach protective levels for human health and the environment. Additionally, advances in the scientific equipment needed to measure and monitor stove fuel use and emissions have not kept pace with the significant need within the industry. While several testing centers in the developed world may have hundred thousand-dollar emissions testing systems, organizations in the field have had little more than a thermometer, a scale, and subjective observations to quantify the performance of stove designs. There is an urgent need for easy-to-use, inexpensive, accurate, and robust stove testing equipment for use by laboratory and field researchers around the world. ASAT and their research partner, Aprovecho Research Center (ARC), have over thirty years of experience addressing these two needs, improved cookstoves and emissions monitoring equipment, with expertise spanning the full spectrum of development from conceptual design to product manufacturing and dissemination. This includes: 1) research, design, and verification of clean biomass cookstove technology and emissions monitoring equipment; 2) mass production of quality

  6. Field scale measurements of NH3 emissions

    NASA Astrophysics Data System (ADS)

    Neftel, Albrecht; Ammann, Christof; Kuhn, Uwe; Sintermann, Jörg; Lehuger, Simon; Gärtner, Andrea; Hirschberger, Rainer

    2010-05-01

    The uncertainty in the ammonia emissions after application of organic manure contributes to a large extent to the overall uncertainties of the nitrogen budget of managed grassland systems (Ammann et al., 2009). Due to the sticky nature of the ammonia molecule and the variability of the emission fluxes the experimental determination is still a major challenge and a wide spread range of emission factors can be found in the literature. We report on two field experiments performed in August 2009 at the NitroEurope site in Oensingen, Switzerland. The ammonia emission flux after liquid manure application was investigated simultaneously by various micrometeorological methods: (1) a mass balance approach measuring the horizontal advection flux with open-path FTIR sensors (Gärtner et al., 2008), (2) aerodynamic gradient methods, and (3) eddy covariance measurements based on a novel fast ammonia analyser. Due to the sequential application of the manure and the fast decrease of the ammonia volatilisation, detailed footprint calculations (Neftel et al., 2008) and corrections with a high temporal resolution were crucial for obtaining representative emission fluxes. The plausibility of flux measurements has been evaluated with back trajectories simulations (WindTrax, Flesch et al., 2009). The results of all applied flux measurement methods confirmed the low emission levels found earlier by Spirig et al. (2009). A comparison of the field observations with results of process oriented models showed considerable differences in the temporal course of the ammonia emission indicating the need for improvements of the models. References: Ammann, C., Spirig, C., Leifeld, J. and Neftel, A.: Assessment of the nitrogen and carbon budget of two managed temperate grassland fields, Agric. Ecosyst. Environ., 133, 150-162, 2009. Flesch, T.K., Harper, L.A., Desjardins, R.L., Gao, Z., and Crenna, B.: Multi-Source Emission Determination Using an Inverse-Dispersion Technique. Boundary-Layer Meteorol

  7. The JPL Field Emission Spectrometer

    NASA Technical Reports Server (NTRS)

    Hook, Simon J.; Kahle, Anne B.

    1995-01-01

    The Jet Propulsion Laboratory (JPL) Field Emission Spectrometer (FES) was built by Designs and Prototypes based on a set of functional requirements supplied by JPL. The instrument has a spectral resolution of 6 wavenumbers (wn) and can acquire spectra from either the Mid Infrared (3-5 mu m) or the Thermal Infrared (8-12 pm) depending on whether the InSb or HgCdTe detector is installed respectively. The instrument consists of an optical head system unit and battery. The optical head which is tripod mounted includes the interferometer and detector dewar assembly. Wavelength calibration of the interferometer is achieved using a Helium-Neon laser diode. The dewar needs replenishing with liquid Nitrogen approximately every four hours. The system unit includes the controls for operation and the computer used for acquiring viewing and processing spectra. Radiometric calibration is achieved with an external temperature-controlled blackbody that mounts on the fore-optics of the instrument. The blackbody can be set at 5 C increments between 10 and 55 C. The instrument is compact and weighs about 33 kg. Both the wavelength calibration and radiometric calibration of the instrument have been evaluated. The wavelength calibration was checked by comparison of the position of water features in a spectrum of the sky with their position in the output from a high resolution atmospheric model. The results indicatethat the features in the sky spectrum are within 6-8 wn of their position ill the model spectrum. The radiometric calibration was checked by first calibrating the instrument using the external blackbody supplied with the instrument and then measuring the radiance from another external blackbody at a series of temperatures. The temperatures of these radiance spectra were then recovered by inventing Planck's law and the recovered temperatures compared lo the measured blackbody temperature. These results indicate that radiometric calibration is good to 0.5 C over the range of

  8. IMPROVING BIOGENIC EMISSION ESTIMATES WITH SATELLITE IMAGERY

    EPA Science Inventory

    This presentation will review how existing and future applications of satellite imagery can improve the accuracy of biogenic emission estimates. Existing applications of satellite imagery to biogenic emission estimates have focused on characterizing land cover. Vegetation dat...

  9. Field Emission and Nanostructure of Carbon Films

    SciTech Connect

    Merkulov, V.I.; Lowndes, D.H.; Baylor, L.R.

    1999-11-29

    The results of field emission measurements of various forms of carbon films are reported. It is shown that the films nanostructure is a crucial factor determining the field emission properties. In particular, smooth, pulsed-laser deposited amorphous carbon films with both high and low sp3 contents are poor field emitters. This is similar to the results obtained for smooth nanocrystalline, sp2-bonded carbon films. In contrast, carbon films prepared by hot-filament chemical vapor deposition (HE-CVD) exhibit very good field emission properties, including low emission turn-on fields, high emission site density, and excellent durability. HF-CVD carbon films were found to be predominantly sp2-bonded. However, surface morphology studies show that these films are thoroughly nanostructured, which is believed to be responsible for their promising field emission properties.

  10. Carbon nanotube emitters and field emission triode

    NASA Astrophysics Data System (ADS)

    Fan, Zhiqin; Zhang, Binglin; Yao, Ning; Zhang, Lan; Ma, Huizhong; Deng, Jicai

    2006-05-01

    Based on our study on field emission from multi-walled carbon nanotubes (MWNTs), we experimentally manufactured field emission display (FED) triode with a MWNTs cold cathode, and demonstrated an excellent performance of MWNTs as field emitters. The measured luminance of the phosphor screens was 1.8*10^(3) cd/m2 for green light. The emission is stable with a fluctuation of only 1.5% at an average current of 260 'mu'A.

  11. Silicon oxynitride: A field emission suppression coating

    NASA Astrophysics Data System (ADS)

    Theodore, Nimel D.

    We have studied coatings deposited using our inductively-coupled RF plasma ion implantation and desposition system to suppress field emission from large, 3-D electrode structures used in high voltage applications, like those used by Thomas Jefferson National Accelerator Facility in their DC-field photoelectron gun. Currently time and labor-intensive hand-polishing procedures are used to minimize field emission from these structures. Previous work had shown that the field emission from polished stainless steel (27 muA of field-emitted current at 15 MV/m) could be drastically reduced with simultaneous deposition of sputtered silicon dioxide during nitrogen implantation (167 pA of field-emitted current at 30 MV/m). We have determined that this unique implantation and deposition procedure produces high-purity silicon oxynitride films that can suppress field emission from stainless steel regardless of their initial surface polish. However, when this implantation procedure was applied to large, 3-D substrates, arcs occurred, damaging the coating and causing unreliable and unrepeatable field emission suppression. We have developed a novel reactive sputtering procedure to deposit high-purity silicon oxynitride coatings without nitrogen ion implantation. We can control the stoichometry and deposition rate of these coatings by adjusting the nitrogen pressure and incident RF-power. Using profilometry, Auger electron spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Rutherford backscattering spectrometry, elastic recoil detection analysis, and current-voltage measurements, we have determined that the elemental composition, chemical bonding, density, and electrical properties of the reactively-sputtered silicon oxynitride coatings are similar to those produced by nitrogen implantation during silicon dioxide deposition. Furthermore, high voltage tests determined that both coatings similarly suppress field emission from 6" diameter, polished

  12. Field Emission from Zinc Oxide Nanobelts.

    PubMed

    Asthanal, A; Yap, Y K; Shahbazian-Yassar, R

    2015-03-01

    We report here, the in-situ field emission (FE) property measurement on the individual ZnO nanobelts inside a high resolution transmission electron microscope (TEM) using a special scanning tunneling microscopy (STM)-TEM system. The field emission properties were found to be size scale dependent. It was found that the threshold voltage decreases and the field enhancement factor increases with the decrease in the diameter of the tip of the nanobelt and increase in the sharpness of the tip. The field emission parameter was estimated following the Fowler-Nordheim (F-N) theory. The ZnO nanobelt with the sharp agave like tip structure (d = 10 nm) showed the highest value of the field enhancement factor, β ≈ 4562, and a high field emission current of ~ 502 µA. PMID:26413652

  13. Field Emission Measurements from Niobium Electrodes

    SciTech Connect

    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.

  14. Field emission from Dirac and Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Mao, Ling-Feng; Li, X.; Ning, H.; Hu, Changjun; Wang, Gaofeng

    2016-09-01

    Based on theoretical investigation on characteristics of the field emission current of Dirac/Weyl semimetals, the dependence of the field emission current on the applied bias is deduced and studied. This theoretical study demonstrates that the field emission current of a Dirac semimetal is much smaller than that of a conventional material when they have similar carrier parameters. This makes Dirac semimetal a better candidate for gate/base electrode material than gold and other conventional metals for an ultra-thin gate oxide metal-oxide-semiconductor field effect transistor. The field emission current of a Dirac semimetal decreases with the effective electron mass, while it increases for a conventional material. This implies that such an effective mass dependence can be used as a simple criterion to probe a Dirac semimetal in practice.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Deducing dust emission mechanisms from field measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  17. OIL AND GAS FIELD EMISSIONS SURVEY

    EPA Science Inventory

    The report gives results of an oil and gas field emissions survey. The production segment of the oil and gas industry has been identified as a source category that requires the development of more reliable emissions inventory methodologies. The overall purpose of the project was ...

  18. Field emission from hydrogen titanate nanotubes

    NASA Astrophysics Data System (ADS)

    Chakraborty, Indrani; Chatterjee, Sriparna; Ayyub, Pushan

    2011-10-01

    Hydrothermally synthesized hydrogen titanate (H2Ti3O7) nanotube meshes and arrays exhibit excellent field emission characteristics. The turn-on field is as low as 1.4 V μm-1 for the mesh and 2.6 V μm-1 for the array, while the electric field corresponding to an emission current density of 10 μA cm-2 is 2 V μm-1 (mesh) and 3.8 V μm-1 (array). The H2Ti3O7 nanotube mesh has one of the lowest reported turn-on voltages and highest enhancement factors. The emission current also shows good long term stability. We attribute the efficient field emission to the presence of mid-gap states arising from the negative surface charge on the H2Ti3O7 nanotubes.

  19. Improvement of field emission properties of α-Fe{sub 2}O{sub 3} nanoflakes due to the lowered back contact barrier after high energy X-ray irradiation

    SciTech Connect

    Wu, J. Q.; Deng, S. Z.; Xu, N. S.; Chen, Jun; Wang, B.; Yi, F. T.

    2013-11-14

    Improvement in the field emission properties of α-Fe{sub 2}O{sub 3} nanoflakes is observed after high energy X-ray irradiation from synchrotron radiation. Field emission threshold field of α-Fe{sub 2}O{sub 3} nanoflakes is found to decrease from 10.1 to 7.8 MV/m after X-ray irradiation with the dose of 9.0 × 10{sup 14} phs/cm{sup 2}. Electrical measurement reveals that the potential barrier at the back contact between the α-Fe{sub 2}O{sub 3} layer and the iron substrate changes after X-ray irradiation. The observed threshold field decrease is well explained by the changes in potential barrier at the back contact of α-Fe{sub 2}O{sub 3} nanoflakes, which indicates the back contact plays an important role in controlling the field emission properties of α-Fe{sub 2}O{sub 3} nanoflakes. Our study shows that the α-Fe{sub 2}O{sub 3} nanoflakes are a promising material for the application as field emitter under X-ray environment.

  20. Structural modification of nanocrystalline diamond films via positive/negative bias enhanced nucleation and growth processes for improving their electron field emission properties

    SciTech Connect

    Saravanan, A.; Huang, B. R.; Sankaran, K. J.; Tai, N. H.; Keiser, G.; Kurian, J.; Lin, I. N.

    2015-06-07

    Electron field emission (EFE) properties of nanocrystalline diamond (NCD) films synthesized by the bias-enhanced growth (beg) process under different bias voltages were investigated. The induction of the nanographitic phases is presumed to be the prime factor in enhancing the EFE properties of negative biased NCD films. Transmission electron microscopic investigations reveal that a negative bias voltage of −300 V increases the rate of growth for NCD films with the size of the grains changing from nano to ultranano size. This effect also is accompanied by the induction of nanographitic filaments in the grain boundaries of the films. The turn-on field (E{sub 0}) for the EFE process then effectively gets reduced. The EFE process of the beg-NCD{sub −300V} films can be turned on at E{sub 0} = 3.86 V/μm, and the EFE current density achieved is 1.49 mA/cm{sup 2} at an applied field of 7.85 V/μm. On the other hand, though a positive-bias beg process (+200 V) results in the reduction of grain size, it does not induce sufficient nanographitic phases to lower the E{sub 0} value of the EFE process. Moreover, the optical emission spectroscopic investigation indicates that one of the primary causes that changes the granular structure of the NCD films is the increase in the proportion of C{sub 2} and CH species induced in the growing plasma. The polarity of the bias voltage is of less importance in the microstructural evolution of the films.

  1. Pulsar Emission Geometry and Accelerating Field Strength

    NASA Technical Reports Server (NTRS)

    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

  2. Polypyrrole nanostructures and their field emission investigations

    NASA Astrophysics Data System (ADS)

    Harpale, Kashmira; More, Mahendra A.; Koinkar, Pankaj M.; Patil, Sandip S.; Sonawane, Kishor M.

    2015-03-01

    Polypyrrole (PPy) nanostructures have been synthesized on indium doped tin oxide (ITO) substrates by a facile electrochemical route employing cyclic voltammetry (CV) mode. The morphology of the PPy thin films was observed to be influenced by the monomer concentration. Furthermore, FTIR revealed formation of electrically conducting state of PPy. Field emission investigations of the PPy nanostructures were carried out at base pressure of 1×10-8mbar. The values of turn-on field, corresponding to emission current density of 1 μA/cm2 were observed to be 0.6, 1.0 and 1.2 V/μm for the PPy films characterized with rod-like, cauliflower and granular morphology, respectively. In case of PPy nanorods maximum current density of 1.2 mA/cm2 has been drawn at electric field of 1 V/μm. The low turn on field, extraction of very high emission current density at relatively lower applied field and good emission stability propose the PPy nanorods as a promising material for field emission based devices.

  3. Electron Field Emission Characteristics of Planar Field Emission Array with Diamondlike Carbon Electron Emitters

    NASA Astrophysics Data System (ADS)

    Lin, Chin-Maw; Chang, Shoou-Jinn; Yokoyama, Meiso; Chuang, Feng-Yu; Tsai, Chun-Hui; Wang, Wen-Chun; Lin, I-Nan

    1999-02-01

    The electron emission characteristics of planar field emission arrays (FEAs), containing undoped and boron-doped diamondlike carbon (DLC) films as emitters, were investigated. The planar DLC FEAs require only 13.3 V/µm to turn on the electron field emission, whereas the boron-doped planar DLC FEAs requires an even lower electric field (9.8 V/µm) to trigger the electron emission. The boron-doped DLC films also possess an electron emission property highly superior to that of the undoped DLC films and exhibit a stable electron emission current of 938 µA under a 20 V/µm bias voltage, which corresponds to a high emission current density of (Je)B-DLC=128 mA/cm2. These superior properties suggest that the boron-doped DLC FEAs are potentially useful as electron emitters in flat panel displays.

  4. Origin of graphitic filaments on improving the electron field emission properties of negative bias-enhanced grown ultrananocrystalline diamond films in CH{sub 4}/Ar plasma

    SciTech Connect

    Sankaran, K. J.; Tai, N. H. E-mail: nhtai@mse.nthu.edu.tw; Huang, B. R.; Saravanan, A.; Lin, I. N. E-mail: nhtai@mse.nthu.edu.tw

    2014-10-28

    Microstructural evolution of bias-enhanced grown (BEG) ultrananocrystalline diamond (UNCD) films has been investigated using microwave plasma enhanced chemical vapor deposition in gas mixtures of CH{sub 4} and Ar under different negative bias voltages ranging from −50 to −200 V. Scanning electron microscopy and Raman spectroscopy were used to characterize the morphology, growth rate, and chemical bonding of the synthesized films. Transmission electron microscopic investigation reveals that the application of bias voltage induced the formation of the nanographitic filaments in the grain boundaries of the films, in addition to the reduction of the size of diamond grains to ultra-nanosized granular structured grains. For BEG-UNCD films under −200 V, the electron field emission (EFE) process can be turned on at a field as small as 4.08 V/μm, attaining a EFE current density as large as 3.19 mA/cm{sup 2} at an applied field of 8.64 V/μm. But the films grown without bias (0 V) have mostly amorphous carbon phases in the grain boundaries, possessing poorer EFE than those of the films grown using bias. Consequently, the induction of nanographitic filaments in grain boundaries of UNCD films grown in CH{sub 4}/Ar plasma due to large applied bias voltage of −200 V is the prime factor, which possibly forms interconnected paths for facilitating the transport of electrons that markedly enhance the EFE properties.

  5. Improved Underwater Excitation-Emission Matrix Fluorometer

    NASA Technical Reports Server (NTRS)

    Moore, Casey; daCunha, John; Rhoades, Bruce; Twardowski, Michael

    2007-01-01

    A compact, high-resolution, two-dimensional excitation-emission matrix fluorometer (EEMF) has been designed and built specifically for use in identifying and measuring the concentrations of organic compounds, including polluting hydrocarbons, in natural underwater settings. Heretofore, most EEMFs have been designed and built for installation in laboratories, where they are used to analyze the contents of samples collected in the field and brought to the laboratories. Because the present EEMF can be operated in the field, it is better suited to measurement of spatially and temporally varying concentrations of substances of interest. In excitation-emission matrix (EEM) fluorometry, fluorescence is excited by irradiating a sample at one or more wavelengths, and the fluorescent emission from the sample is measured at multiple wavelengths. When excitation is provided at only one wavelength, the technique is termed one-dimensional (1D) EEM fluorometry because the resulting matrix of fluorescence emission data (the EEM) contains only one row or column. When excitation is provided at multiple wavelengths, the technique is termed two-dimensional (2D) EEM fluorometry because the resulting EEM contains multiple rows and columns. EEM fluorometry - especially the 2D variety - is well established as a means of simultaneously detecting numerous dissolved and particulate compounds in water. Each compound or pool of compounds has a unique spectral fluorescence signature, and each EEM is rich in information content, in that it can contain multiple fluorescence signatures. By use of deconvolution and/or other mixture-analyses techniques, it is often possible to isolate the spectral signature of compounds of interest, even when their fluorescence spectra overlap. What distinguishes the present 2D EEMF over prior laboratory-type 2D EEMFs are several improvements in packaging (including a sealed housing) and other aspects of design that render it suitable for use in natural underwater

  6. GEIA's Vision for Improved Emissions Information

    NASA Astrophysics Data System (ADS)

    Frost, G. J.; Granier, C.; Middleton, P.; Tarrason, L.

    2013-12-01

    Accurate, timely, and accessible emissions information is critical for understanding and making predictions about the atmosphere. We present recent progress of the Global Emissions InitiAtive (GEIA, http://www.geiacenter.org/), a community-driven joint activity of IGAC/iLEAPS/AIMES within the International Geosphere-Biosphere Programme. Since 1990, GEIA has served as a forum for the exchange of expertise and information on anthropogenic and natural emissions of trace gases and aerosols. GEIA supports a worldwide network of emissions data developers and users, providing a solid scientific foundation for atmospheric chemistry research. By the year 2020, GEIA envisions being a bridge between the environmental science, regulatory, assessment, policy, and operational communities. GEIA's core activities include 1) facilitating analysis that improves the scientific basis for emissions data, 2) enhancing access to emissions information, and 3) strengthening linkages within the international emissions community. GEIA pursues these activities in collaboration with the ECCAD project (http://pole-ether.fr/eccad) and as a member of the GEO Air Quality Community of Practice (http://wiki.esipfed.org/index.php/GEO_AQ_CoP). GEIA welcomes new partnerships that advance emissions knowledge for the future.

  7. Field emission and growth of fullerene nanotubes

    SciTech Connect

    Rinzler, A.G.; Hafner, J.H.; Nilolaev, P.; Colbert, D.T.; Smalley, R.E.

    1994-11-01

    Efforts to control the growth of individual carbon nanotubes from nanotube seed crystals have led to a characterization of their field-induced electron emission behavior. The application of a bias voltage in the growth apparatus was motivated by the prolific formation of nanotubes in the carbon are growth method, in which the electric field appears to play a central role. The authors report here the ability to achieve various tube tip configurations by the controlled application of voltage, heat and chemicals to an individual nanotube, and that these states are well characterized by the emission currents they induce.

  8. Outstanding field emission properties of wet-processed titanium dioxide coated carbon nanotube based field emission devices

    SciTech Connect

    Xu, Jinzhuo; Ou-Yang, Wei Chen, Xiaohong; Guo, Pingsheng; Piao, Xianqing; Sun, Zhuo; Xu, Peng; Wang, Miao; Li, Jun

    2015-02-16

    Field emission devices using a wet-processed composite cathode of carbon nanotube films coated with titanium dioxide exhibit outstanding field emission characteristics, including ultralow turn on field of 0.383 V μm{sup −1} and threshold field of 0.657 V μm{sup −1} corresponding with a very high field enhancement factor of 20 000, exceptional current stability, and excellent emission uniformity. The improved field emission properties are attributed to the enhanced edge effect simultaneously with the reduced screening effect, and the lowered work function of the composite cathode. In addition, the highly stable electron emission is found due to the presence of titanium dioxide nanoparticles on the carbon nanotubes, which prohibits the cathode from the influence of ions and free radical created in the emission process as well as residual oxygen gas in the device. The high-performance solution-processed composite cathode demonstrates great potential application in vacuum electronic devices.

  9. Field emission behavior of carbon nanotube field emitters after high temperature thermal annealing

    SciTech Connect

    Sun, Yuning; Shin, Dong Hoon; Yun, Ki Nam; Leti, Guillaume; Hwang, Yeon Mo; Song, Yenan; Saito, Yahachi; Lee, Cheol Jin

    2014-07-15

    The carbon nanotube (CNT) field emitters have been fabricated by attaching a CNT film on a graphite rod using graphite adhesive material. The CNT field emitters showed much improved field emission properties due to increasing crystallinity and decreasing defects in CNTs after the high temperature thermal annealing at 900 °C in vacuum ambient. The CNT field emitters showed the low turn-on electric field of 1.15 V/μm, the low threshold electric field of 1.62 V/μm, and the high emission current of 5.9 mA which corresponds to a current density of 8.5 A/cm{sup 2}. In addition, the CNT field emitters indicated the enhanced field emission properties due to the multi-stage effect when the length of the graphite rod increases. The CNT field emitter showed good field emission stability after the high temperature thermal annealing. The CNT field emitter revealed a focused electron beam spot without any focusing electrodes and also showed good field emission repeatability.

  10. Influence of field evaporation treatment on the field emission properties of carbon nanotubes array

    NASA Astrophysics Data System (ADS)

    Bai, Xin; Zhang, Wen-Jing; Zhang, Gengmin

    2010-04-01

    Field evaporation was used in the post-fabrication treatment of a carbon nanotubes (CNTs) array and effectively modified the CNTs morphology in favor of the field emission under a moderate field. After the field evaporation treatment, the uniformity of the emission site distribution improved but the onset voltage rose. Using the Fowler-Nordheim theory, the actual onset field and the evaporation field around the CNT were calculated to be -4.6-5 and 9-12 V/nm, respectively. These values are close to those obtained from the individual CNT samples. The above results have provided an alternative to modify the configuration of an array sample and demonstrated the feasibility of tackling the problem of the disparity in the field emission capability of different CNTs in an array.

  11. Status review of field emission displays

    NASA Astrophysics Data System (ADS)

    Ghrayeb, Joseph; Daniels, Reginald

    2001-09-01

    Cathode ray tube (CRT) technology dominates the direct view display market. Mature CRT technology for many designs is still the preferred choice. CRT manufacturers have greatly improved the size and weight of the CRT displays. High performance CRTs continue to be in great demand, however, supply have to contend with the vanishing CRT vendor syndrome. Therefore, the vanishing CRT vendor syndrome fuels the search for an alternate display technology source. Within the past 10 years, field emission display (FED) technology had gained momentum and, at one time, was considered the most viable electronic display technology candidate [to replace the CRT]. The FED community had advocated and promised many advantages over active matrix liquid crystal displays (AMLCD), electro luminescent (EL) or Plasma displays. Some observers, including potential FED manufacturers and the Department of Defense, (especially the Defense Advanced Research Project Agency (DARPA)), consider the FED entry as having leapfrog potential. Despite major investments by US manufacturers as well as Asian manufacturers, reliability and manufacturing difficulties greatly slowed down the advancement of the technology. The FED manufacturing difficulties have caused many would-be FED manufacturing participants to abandon FED research. This paper will examine the trends, which are leading this nascent technology to its downfall. FED technology was once considered to have the potential to leapfrog over AMLCD's dominance in the display industry. At present the FED has suffered severe setbacks and there are very few [FED] manufacturers still pursuing research in the area. These companies have yet to deliver a display beyond the prototype stage.

  12. Improvements In Optically Stimulated Electron Emission

    NASA Technical Reports Server (NTRS)

    Yost, William T.; Welch, Christopher S.; Joe, Edmond J.; Hefner, Bill B., Jr.

    1994-01-01

    Optically stimulated electron emission (OSEE) used in inspection for contamination of critical bonding surfaces in solid rocket motors of Space Shuttle prior to formation of adhesive bonds on surfaces during manufacture and refurbishment. Fundamental OSEE inspection technique described in "Surface-Contamination Inspection Tool for Field Use" (MFS-25581) and "Detecting Contamination With Photoelectron Emission" (MFS-25619). OSEE measurement head easily portable, and measurement operation convenient and rapid, making it useful inspection technique in industrial environment. Reveals contamination in many situations in which other techniques do not work.

  13. Factors affecting methane emission from rice fields

    NASA Astrophysics Data System (ADS)

    Neue, H. U.; Wassmann, R.; Lantin, R. S.; Alberto, Ma C. R.; Aduna, J. B.; Javellana, A. M.

    Emission of CH 4 from ricefields is the result of anoxic bacterial methane production. Global estimates of annual CH 4 emission from ricefields is 100 Tg. CH 4 emission data from limited sites are tentative. It is essential that uncertainty in individual sources is reduced in order to develop feasible and effective mitigation options which do not negate gains in rice production and productivity. Field studies at the International Rice Research Institute show that soil and added organic matter are the sources for initial methane production. Addition of rice straw enhances methane production. Roots and root exudates of wetland rice plants appear to be the major carbon sources at ripening stage. The production and transport of CH 4 to the atmosphere depend on properties of the rice plant. Under the same spacing and fertilization, the traditional variety Dular emitted more CH 4 per day than did the new plant type IR65597. Upon flooding for land preparation anaerobic conditions result in significant amount of methane being formed. Drying the field at midtillering significantly reduced total CH 4 emissions. Large amounts of entrapped CH 4 escape to the atmosphere when floodwater recedes upon drying at harvest. Cultural practices may account for 20% of the overall seasonal CH 4 emissions.

  14. Preliminary Results of Field Emission Cathode Tests

    NASA Technical Reports Server (NTRS)

    Sovey, James S.; Kovaleski, Scott D.

    2001-01-01

    Preliminary screening tests of field emission cathodes such as chemical vapor deposited (CVD) diamond, textured pyrolytic graphite, and textured copper were conducted at background pressures typical of electric thruster test facilities to assess cathode performance and stability. Very low power electric thrusters which provide tens to hundreds micronewtons of thrust may need field emission neutralizers that have a capability of tens to hundreds of microamperes. From current voltage characteristics, it was found that the CVD diamond and textured metals cathodes clearly satisfied the Fowler-Nordheim emission relation. The CVD diamond and a textured copper cathode had average current densities of 270 and 380 mA/sq cm, respectively, at the beginning-of-life. After a few hours of operation the cathode emission currents degraded by 40 to 75% at background pressures in the 10(exp -5) Pa to 10(exp -4) Pa range. The textured pyrolytic graphite had a modest current density at beginning-of-life of 84 mA/sq cm, but this cathode was the most stable of all. Extended testing of the most promising cathodes is warranted to determine if current degradation is a burn-in effect or whether it is a long-term degradation process. Preliminary experiments with ferroelectric emission cathodes, which are ceramics with spontaneous electric polarization, were conducted. Peak current densities of 30 to 120 mA/sq cm were obtained for pulse durations of about 500 ns in the 10(exp -4) Pa pressure range.

  15. On field emission from a semiconducting substrate

    NASA Astrophysics Data System (ADS)

    Waters, Richard; Van Zeghbroeck, Bart

    1999-10-01

    A theoretical examination of field emission from the conduction band of a semiconducting substrate is reported. The analysis includes a comparison with Fowler-Nordheim theory, and it is concluded that the formalism of the Fowler-Nordheim theory is incorrect when applied to carriers originating from a semiconducting substrate. The use of a Fowler-Nordheim analysis results in an error in the extraction of the barrier height that is dependent upon the applied electric field across the oxide, conduction band offset, and temperature. A lower limit of the error was calculated to be between 5% and 15%. An analytical expression is developed to describe the field emission of electrons from the conduction band of a semiconductor.

  16. Luminescent solar concentrator improvement by stimulated emission

    NASA Astrophysics Data System (ADS)

    Kaysir, Md Rejvi; Fleming, Simon; MacQueen, Rowan W.; Schmidt, Timothy W.; Argyros, Alexander

    2015-12-01

    Luminescent solar concentrators (LSCs) offer the prospect of reducing the cost of solar energy, and are a promising candidate for building integrated photovoltaic (PV) structures. However, the realization of commercially viable efficiency of LSCs is currently hindered by reabsorption losses. In this work, a method is introduced for reducing reabsorption as well as improving directional emission in LSCs by using stimulated emission. Light from a seed laser (potentially an inexpensive laser diode) passes through the entire length of the LSC panel, modifying the emission spectrum of excited dye molecules such that it is spectrally narrower, at wavelengths that minimize reabsorption, and directed by the seed laser towards a small target PV cell. A mathematical model of such a system is presented which identifies different physical parameters responsible for the power conversion efficiency and gives the net effective output power.

  17. Diamond-Coated Carbon Nanotubes for Efficient Field Emission

    NASA Technical Reports Server (NTRS)

    Dimitrijevic, Stevan; Withers, James C.

    2005-01-01

    Field-emission cathodes containing arrays of carbon nanotubes coated with diamond or diamondlike carbon (DLC) are undergoing development. Multiwalled carbon nanotubes have been shown to perform well as electron field emitters. The idea underlying the present development is that by coating carbon nanotubes with wideband- gap materials like diamond or DLC, one could reduce effective work functions, thereby reducing threshold electric-field levels for field emission of electrons and, hence, improving cathode performance. To demonstrate feasibility, experimental cathodes were fabricated by (1) covering metal bases with carbon nanotubes bound to the bases by an electrically conductive binder and (2) coating the nanotubes, variously, with diamond or DLC by plasma-assisted chemical vapor deposition. In tests, the threshold electric-field levels for emission of electrons were reduced by as much as 40 percent, relative to those of uncoated- nanotube cathodes. Coating with diamond or DLC could also make field emission-cathodes operate more stably by helping to prevent evaporation of carbon from nanotubes in the event of overheating of the cathodes. Cathodes of this type are expected to be useful principally as electron sources for cathode-ray tubes and flat-panel displays.

  18. Electrochemical sharpening of field emission tips

    DOEpatents

    Bernhardt, Anthony F.

    1999-01-01

    A method for sharpening field emitter tips by electroetching/polishing. In gated field emitters, it is very important to initiate electron emission at the lowest possible voltage and thus the composition of the emitter and the gate, as well as the emitter-gate structure, are important factors. This method of sharpening the emitter tips uses the grid as a counter electrode in electroetching of the emitters, which can produce extremely sharp emitter tips as well as remove asperities and other imperfections in the emitters, each in relation to the specific grid hole in which it resides. This has the effect of making emission more uniform among the emitters as well as lowering the turn-on voltage.

  19. Formation of nanofilament field emission devices

    DOEpatents

    Morse, Jeffrey D.; Contolini, Robert J.; Musket, Ronald G.; Bernhardt, Anthony F.

    2000-01-01

    A process for fabricating a nanofilament field emission device. The process enables the formation of high aspect ratio, electroplated nanofilament structure devices for field emission displays wherein a via is formed in a dielectric layer and is self-aligned to a via in the gate metal structure on top of the dielectric layer. The desired diameter of the via in the dielectric layer is on the order of 50-200 nm, with an aspect ratio of 5-10. In one embodiment, after forming the via in the dielectric layer, the gate metal is passivated, after which a plating enhancement layer is deposited in the bottom of the via, where necessary. The nanofilament is then electroplated in the via, followed by removal of the gate passification layer, etch back of the dielectric, and sharpening of the nanofilament. A hard mask layer may be deposited on top of the gate metal and removed following electroplating of the nanofilament.

  20. Integrated field emission array for ion desorption

    DOEpatents

    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.

  1. Integrated field emission array for ion desorption

    DOEpatents

    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.

  2. Ultrafast thermionic emission from metal irradiated using a femtosecond laser and an electric field in combination

    SciTech Connect

    Wang, Tingfeng; Guo, Jin; Shao, Junfeng; Wang, Dinan; Chen, Anmin E-mail: mxjin@jlu.edu.cn; Jin, Mingxing E-mail: mxjin@jlu.edu.cn

    2015-03-15

    Ultrafast thermionic emission from gold film irradiated with a femtosecond laser pulse in the presence of an additional electric field is analyzed using a two-temperature equation combined with a modified Richardson equation. The calculated results show that the duration of the emission is below 1 ps. Supplying an additional electric field is found to change the emission from the metal surface. Given the same laser fluence, this additional field reduces the work function of the metal, and thus improves the efficiency of thermionic emission. These results help to understand the mechanism and suggest ways to improve emissions in the context of ultrafast thermalized electron systems.

  3. Quasistationary field of thermal emission and near-field radiometry.

    PubMed

    Reznik, A N; Vaks, V L; Yurasova, N V

    2004-11-01

    We provide a theory of radiometry measurements of the quasistationary (near) field of thermal emission from a heated conducting medium. It explains why the Rytov effect, which essentially is a drastic growth of the thermal field energy near the medium surface, cannot be detected experimentally. However, we discovered a measurable near-field effect: the effective depth of formation of the received emission proves to be less than the skin-layer depth, depending on the size of the receiving antenna and its height above the surface. For such measurements highly effective antennas of a small aperture size are necessary. We developed and investigated a variety of microwave antennas whose parameters were fairly suitable for near-field radiometry. The measurements conducted with these antennas yielded experimental evidence of the fact that the quasistationary thermal field really exists. Near-field radiometry opens further opportunities for investigating media. In particular, we demonstrate here a technique for retrieval of the subsurface temperature profile in water with the help of near-field measurements.

  4. Processing of materials for uniform field emission

    DOEpatents

    Pam, Lawrence S.; Felter, Thomas E.; Talin, Alec; Ohlberg, Douglas; Fox, Ciaran; Han, Sung

    1999-01-01

    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/.mu.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 .mu.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 preceeded by ion implanting carbon, nitrogen, argon, oxygen or hydrogen into the surface layers of the field emitter material.

  5. Processing of materials for uniform field emission

    DOEpatents

    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.

  6. Electron Field Emission from Nanostructured Carbon Materials

    NASA Astrophysics Data System (ADS)

    Gupta, Sanju

    2005-03-01

    Fabricating small structures has almost become fashionable and the rationale is that reducing one or more dimensions below some critical length changes the systems' physical properties drastically, where nanocrystalline diamond (n-D) and carbon nanotubes (CNTs) in the class of advanced carbon materials serve model examples. Emission of electrons at room temperature - cold electron emitters - are of vital importance for a variety of vacuum microelectronic devices - electron microscopes, photo multipliers, X-ray generators, lamps, and flat panel displays and microwave cathodes. Electron emitters may lead to otherwise difficult to obtain advantages in performance and/or design. This is the driving force to investigate the carbon-related materials as cold cathodes. In this talk, the performance of various forms of carbon in thin film form including diamond, n-D, and vertically aligned CNTs as cold cathodes for their potential use in field emission displays (FEDs) in terms of I-V characteristics and corresponding spatial imaging will be presented. Physics based models such as, NEA, surface modification, geometric enhancement, and microstructure alteration due to particle bombardment, and doping, will be described to support the experimental observations of electron field enhancement (low turn-on voltage, high current and emission site density) and its reliability from the abovementioned carbon-related materials. Other vacuum device applications such as thermionic power generators will be mentioned briefly.

  7. Measuring methyl bromide emissions from fields

    SciTech Connect

    Yates, S.R.; Gan, J.; Ernst, F.F.; Yates, M.V.

    1995-12-31

    Methyl bromide is used extensively for pest control. Recent evidence suggests that methyl bromide may react with stratospheric ozone and, due to the Clean Air Act, is scheduled for phase-out within the next 5 to 10 years. As indicated in a recent report from The National Agricultural Pesticide Impact Assessment Program, there will be substantial economic impact on the agricultural community if the use of methyl bromide is restricted. There are several areas of uncertainty concerning the agricultural use of methyl bromide. Foremost is the quantification of mass emitted to the atmosphere from agricultural fields. To address this, two field experiments were conducted to directly measure methyl bromide emissions. In the first experiment, methyl bromide was injected at approximately 25 cm depth and the soil was covered with 1 mil high-density polyethylene plastic. The second experiment was similar except that methyl bromide was injected at approximately 68 cm depth and the soil was not covered. From these experiments, the emission rate into the atmosphere and the subsurface transport of methyl bromide was determined. Both experiments include a field-scale mass balance to verify the accuracy of the flux-measurement methods as well as to check data consistency. The volatilization rate and mass lost was determined from estimates of the degradation and from several atmospheric and chamber flux methods.

  8. Apply the fundamentals to improve emissions performance

    SciTech Connect

    Storm, S.K.; Storm, D.S.; McClellan, A.C.; Storm, R.F.; Mulligan, J.

    2006-10-15

    The O & M staff of AES Westover Station in Johnson City, New York wisely took a holistic approach to optimizing combustion within Unit 8's boiler in order to reduce its NOx emissions while maintaining acceptable levels of carbon-in-ash content. The results of major modifications, centered on the addition of a fan boosted overfire air system, were a 60% reduction in NOx levels, improved unit reliability, and a project payback period measured in months rather than years. As this project proved, the whole is more than the sum of its parts. 7 figs., 2 tabs.

  9. Improved Photon-Emission-Microscope System

    NASA Technical Reports Server (NTRS)

    Vu, Duc

    2006-01-01

    An improved photon-emission-microscope (PEM) instrumentation system has been developed for use in diagnosing failure conditions in semiconductor devices, including complex integrated circuits. This system is designed primarily to image areas that emit photons, at wavelengths from 400 to 1,100 nm, associated with device failures caused by leakage of electric current through SiO2 and other dielectric materials used in multilayer semiconductor structures. In addition, the system is sensitive enough to image areas that emit photons during normal operation.

  10. Methyl bromide emissions from tarped fields

    SciTech Connect

    Cicerone, R.J.; Williams, J.; Wang, N.Y.

    1995-12-31

    Once in the stratosphere, bromine atoms can destroy ozone effectively. Because of this potential effect, certain organobromine compounds including methyl bromide (MeBr) are being controlled or eliminated by national and international regulations. It would be valuable to determine the fraction of MeBr used in soil fumigations that subsequently enters the atmosphere to better assess the need for, and value of, strong regulations. We have designed and conducted several experiments accompanying field fumigations with MeBr/chloropicrin mixtures. In each of three field-fumigation experiments new Irvine, CA in which the fumigated field was covered immediately with plastic tarping, we have deployed static flux chambers on top of the tarping and measured escape fluxes of MeBr. After tarp removal, the same chambers were replaced on the bare soil to continue the measurements. We have also measured soil bromide contents before and after the fumigation. One experiment yielded an escape fraction of 80 to 87% (with 19% remaining as bromide) while the other two experiments yielded escape fractions of 30 to 35% (with about 70% remaining as bromide). This paper will summarize stratospheric bromine chemistry, describe the field experiments and discuss factors that influence emissions, including soil pH, moisture and organic content and injection technique. We acknowledge TriCal, Inc. for many helpful discussions and for professional field applications of MeBr.

  11. Field measurement of diesel particulate matter emissions.

    PubMed

    Volkwein, Jon C; Mischler, Steven E; Davies, Brian; Ellis, Clive

    2008-03-01

    A primary means to reduce environmental levels of diesel particulate matter (DPM) exposure to miners is to reduce the amount of DPM emission from the engine. A quick and economic method to estimate engine particulate emission levels has been developed. The method relies on the measurement of pressure increase across a filter element that is briefly used to collect a DPM sample directly from the engine exhaust. The method has been refined with the inclusion of an annular aqueous denuder to the tube which permits dry filter samples to be obtained without addition of dilution air. Tailpipe filter samples may then be directly collected in hot and water-supersaturated exhaust gas flows from water bath-cooled coal mine engines without the need for dilution air. Measurement of a differential pressure (DP) increase with time has been related to the mass of elemental carbon (EC) on the filter. Results for laboratory and field measurements of the method showed agreement between DP increase and EC collected on the filter with R(2) values >0.86. The relative standard deviation from replicate samples of DP and EC was 0.16 and 0.11, respectively. The method may also have applications beyond mining, where qualitative evaluation of engine emissions is desirable to determine if engine or control technology maintenance may be required.

  12. Positron Emission Tomography with improved spatial resolution

    SciTech Connect

    Drukier, A.K.

    1990-04-01

    Applied Research Corporation (ARC) proposed the development of a new class of solid state detectors called Superconducting Granular Detectors (SGD). These new detectors permit considerable improvements in medical imaging, e.g. Positron Emission Tomography (PET). The biggest impact of this technique will be in imaging of the brain. It should permit better clinical diagnosis of such important diseases as Altzheimer's or schizophrenia. More specifically, we will develop an improved PET-imager; a spatial resolution 2 mm may be achievable with SGD. A time-of-flight capability(t {approx} 100 psec) will permit better contrast and facilitate 3D imaging. In the following, we describe the results of the first 9 months of the development.

  13. Magnetic field emission gun with zirconiated emitter.

    PubMed

    Troyon, M

    1989-03-01

    A magnetic-field-superimposed field emission gun with low aberrations and equipped with a zirconiated tungsten emitter has been developed for applications where very stable high probe currents are required. It has been tested on a conventional electron microscope at 10 kV and on an electron beam testing system at 1 kV. Probe current i = 250 nA in a probe size d = 0.4 micron is obtained at 10 kV; at 1 kV the resolution is 0.1 micron with i = 5 nA, and 0.4 micron with i = 30 nA. For these probe currents, the spatial broadening effect due to electron-electron interactions in the beam is the preponderant factor limiting the probe size.

  14. Field Emission Microplasma Actuated Microchannel Flow

    NASA Astrophysics Data System (ADS)

    Tholeti, Siva Sashank; Shivkumar, Gayathri; Alexeenko, Alina

    2015-11-01

    Flow actuation by dielectric barrier discharges (DBD) involve no moving parts and provide high power density for flow enhancement, heating and mixing applications in microthrusters, micropumps and microcombustors. Conventional micro-DBDs require voltages ~ kV for flow enhancement of a few m/s for 500 μm high channel. However for gaps <10 microns, field emission lowers the breakdown voltage following modified Paschen curve. We consider a micropump concept that takes advantage of the field emission from a micro-DBD with dielectric thickness of 3 μm and a peak voltage of -325 V at 10 MHz. At 760 Torr, for electrode thickness of 1 μm, Knudsen number with respect to the e-nitrogen collisions is 0.1. So, kinetic approach of particle-in-cell method with Monte Carlo collisions is applied in nitrogen at 300 K to resolve electron (ne) and ion (ni) number densities. Body force, fb = eE(ni-ne) , where, e is electron charge and E is electric field. The major source of heating from plasma is Joule heating, J.E, where J is current density. At 760 Torr, for fb,avg = 1 mN/cubic mm and J.E = 8 W/cubic mm, micro-DBD induced a flow with a velocity of 4.1 m/s for a 64 mW/m power input for a channel height of 500 μm. The PIC/MCC plasma simulations are coupled to a CFD solver for analysis of the resulting flow actuation in microchannels at various Reynolds numbers. This work was supported by NSF ECCS Grant No. 1202095.

  15. Improved photomultiplier tube for positron emission tomography.

    PubMed

    Woldeselassie, T

    1989-05-01

    The paper describes an investigation in which it is shown that small positive voltage pulses applied to an external conductor placed against the photocathode of a photomultiplier tube can be used to switch the photocathode completely off for the duration of the pulses. This suggests that a photomultiplier tube with a multisegment photocathode can be constructed, the individual cathode segments of which can be switched off independently by means of such pulses. A theoretical explanation for the effect is provided with the aid of a simple circuit model for the photocathode. Analysis of the model also shows that it is possible to identify the particular cathode segment in which a photon is detected when a pulse is recorded at the phototube's anode. A phototube with these characteristics can have important implications for positron emission tomography, as it can provide improved spatial resolution, simultaneous multislice capability and the ability to eliminate distortion due to dead-time effects at high count rates.

  16. Field emission microplasma actuation for microchannel flows

    NASA Astrophysics Data System (ADS)

    Sashank Tholeti, Siva; Shivkumar, Gayathri; Alexeenko, Alina A.

    2016-06-01

    Microplasmas offer attractive flow control methodology for gas transport in microsystems where large viscous losses make conventional pumping methods highly inefficient. We study microscale flow actuation by dielectric-barrier discharge (DBD) with field emission (FE) of electrons, which allows lowering the operational voltage from kV to a few hundred volts and below. A feasibility study of FE-DBD for flow actuation is performed using 2D particle-in-cell method with Monte Carlo collisions (PIC/MCC) at 10 MHz in nitrogen at atmospheric pressure. The free diffusion dominated, high velocity field emission electrons create a large positive space charge and a body force on the order of 106 N m-3. The body force and Joule heat decrease with increase in dielectric thickness and electrode thickness. The body force also decreases at lower pressures. The plasma body force distribution along with the Joule heating is then used in the Navier-Stokes simulations to quantify the flow actuation in a microchannel. Theoretical analysis and simulations for plasma actuated planar Poiseuille flow show that the gain in flow rate is inversely proportional to Reynolds number. This theoretical analysis is in good agreement with the simulations for a microchannel with closely placed actuators under incompressible conditions. Flow rate of FE-DBD driven 2D microchannel is around 100 ml min-1 mm-1 for an input power of 64 μW mm-1. The gas temperature rises by 1500 K due to the Joule heating, indicating FE-DBD’s potential for microcombustion, micropropulsion and chemical sensing in addition to microscale pumping and mixing applications.

  17. Fabrication of carbon nanotube emitters on the graphite rod and their high field emission performance

    SciTech Connect

    Sun, Yuning; Hoon Shin, Dong; Nam Yun, Ki; Song, Yenan; Saito, Yahachi; Jin Lee, Cheol

    2014-01-27

    Carbon nanotube (CNT) emitters with small emission area were fabricated on graphite rods using CNT films. By introducing the edge polishing process, the field emission performance of the CNT emitter was much improved, which showed a very high emission current of 6.34 mA (1.6 A/cm{sup 2}) under an applied electric field of 5.3 V/μm. It also indicates good long-term emission stability, which reveals no degradation in the emission current for 20 h. The emission patterns demonstrate uniform and well-focused electron beam spots. The enhanced field emission performance is mainly attributed to the suppressed edge emission after the edge polishing process.

  18. Field thermal infrared emissivity dependence on soil moisture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Emissivity dependence on soil water content has been already reported and modeled under controlled conditions at the laboratory. This study completes and extends that previous work by providing emissivity measurements under field conditions without elimination of impurities, local heterogeneities or...

  19. Improved attribution of climate forcing to emissions.

    PubMed

    Shindell, Drew T; Faluvegi, Greg; Koch, Dorothy M; Schmidt, Gavin A; Unger, Nadine; Bauer, Susanne E

    2009-10-30

    Evaluating multicomponent climate change mitigation strategies requires knowledge of the diverse direct and indirect effects of emissions. Methane, ozone, and aerosols are linked through atmospheric chemistry so that emissions of a single pollutant can affect several species. We calculated atmospheric composition changes, historical radiative forcing, and forcing per unit of emission due to aerosol and tropospheric ozone precursor emissions in a coupled composition-climate model. We found that gas-aerosol interactions substantially alter the relative importance of the various emissions. In particular, methane emissions have a larger impact than that used in current carbon-trading schemes or in the Kyoto Protocol. Thus, assessments of multigas mitigation policies, as well as any separate efforts to mitigate warming from short-lived pollutants, should include gas-aerosol interactions.

  20. Work function measurements using a field emission retarding potential technique.

    PubMed

    Hamanaka, M H M O; Dall'Agnol, F F; Pimentel, V L; Mammana, V P; Tatsch, P J; den Engelsen, D

    2016-03-01

    Herein we describe the measurement of the work function of a metal with advanced equipment based on the field emission retarding potential (FERP) method using a carbon nanotube (CNT) as cathode. The accuracy of the FERP method using a CNT emitter is described and a comparison between measurements of the work functions of aluminum, barium, calcium, gold, and platinum with published data will be presented. Our FERP equipment could be optimized with the aid of particle tracing simulations. These simulations led us to insert a magnetic collimator to improve the collection efficiency at the anode. PMID:27036828

  1. Stable electron field emission from carbon nanotubes emitter transferred on graphene films

    NASA Astrophysics Data System (ADS)

    Zhao, Ning; Chen, Jing; Qu, Ke; Khan, Qasim; Lei, Wei; Zhang, Xiaobing

    2015-08-01

    Carbon nanotubes (CNTs) arrays grown by microwave plasma enhanced chemical vapor deposition (MPCVD) method was transferred onto the substrate covered with graphene layer obtained by thermal chemical vapor deposition (CVD) technology. The graphene buffer layer provides good electrical and thermal contact to the CNTs. The field emission characteristics of this hybrid structure were investigated in this study. Compared with the CNTs arrays directly grown on the silicon substrate, the hybrid emitter shows better field emission performance, such as high emission current and long-term emission stability. The presence of this graphene layer was shown to improve the field emission behavior of CNTs. This work provides an effective way to realize stable field emission from CNTs emitter and similar hybrid structures.

  2. Emissions of Nonmethane Organic Compounds at an Illinois (USA) Landfill: Preliminary Field Measurements

    SciTech Connect

    Bogner, J.; Spokas, K.; Niemann, M.; Niemann, L.; Baker, J.

    1997-08-01

    Current US regulatory models for estimating emissions of nonmethane organic compounds (NMOCs) from municipal solid waste (MSW) landfills require field validation to determine if the models are realistic. A project was initiated to begin to develop a field method for direct measurement of landfill NMOC emissions and, concurrently, develop improved sampling and analysis methods for individual NMOCs in landfill gas matrices. Two contrasting field sites at the Greene Valley Landfill, DuPage County, Illinois, USA, were established.

  3. Field emission characteristics from graphene on hexagonal boron nitride

    SciTech Connect

    Yamada, Takatoshi; Masuzawa, Tomoaki; Ebisudani, Taishi; Okano, Ken; Taniguchi, Takashi

    2014-06-02

    An attempt has been made to utilize uniquely high electron mobility of graphene on hexagonal boron nitride (h-BN) to electron emitter. The field emission property of graphene/h-BN/Si structure has shown enhanced threshold voltage and emission current, both of which are key to develop novel vacuum nanoelectronics devices. The field emission property was discussed along with the electronic structure of graphene investigated by Fowler-Nordheim plot and ultraviolet photoelectron spectroscopy. The result suggested that transferring graphene on h-BN modified its work function, which changed field emission mechanism. Our report opens up a possibility of graphene-based vacuum nanoelectronics devices with tuned work function.

  4. Improved Radio Emissivities for Satellites of Saturn

    NASA Astrophysics Data System (ADS)

    Ries, Paul

    2010-10-01

    The size distribution of TNOs is one of the most important constraints on the history of the early solar system. However, while TNOs are most detectable in the visible and near-IR wavelengths, their albedos vary substantially, thus creating uncertainty in their sizes when determined from reflected light alone. One way of determining the size distribution for a large number of TNOs is to measure their thermal emission, such as has been done with Spitzer and Herschel. However, in just a few year's time, ALMA will be coming online, and will be able to detect thermal emission from even more TNOs. However, thermal emission from Solar System bodies in the millimeter and submillimeter, such as that which ALMA will detect, is not that of a pure blackbody. Pluto, the Gallillean satellites, and Vesta have all shown deviations from unity emissivity. However, the cause of this variation is not well understood. Here we re-analayze data from the Cassini RADAR instrument at 2.5 cm. Cassini RADAR measured the brightness temperature and emissivity of several of Saturn's icy satellites, at least one of which, Phoebe, is thought to be a captured TNO. Previous emissivity determinations relied on relatively simple thermal models. We recalculate emissivities using thermal models based on recent data obtained with the CIRS (infrared) instrument on Cassini which account for, among other things, diurnal effects and the rotation during the RADAR observations. For one important result, we demonstrate that deviation from unity emissivity on Iapetus is due solely to surface depth effects at long wavelengths when RADAR data at 2.5 cm is combined with data obtained at 3.3 mm on the Green Bank Telescope (GBT). This research is supported by a grant under the NRAO Student Observing Support program.

  5. Systematic Field Study of NO(x) Emission Control Methods for Utility Boilers.

    ERIC Educational Resources Information Center

    Bartok, William; And Others

    A utility boiler field test program was conducted. The objectives were to determine new or improved NO (x) emission factors by fossil fuel type and boiler design, and to assess the scope of applicability of combustion modification techniques for controlling NO (x) emissions from such installations. A statistically designed test program was…

  6. U.S. EPA'S FIELD TEST PROGRAMS TO UPDATE DATA ON LANDFILL GAS EMISSIONS

    EPA Science Inventory

    The paper discusses a field test program in which the EPA is currently engaged to improve data on landfill gas (LFG) emissions. LFG emissions data in use at this time are based on determinations made in the late 1980s and early 1990s; changes in landfill operations, such as using...

  7. Field emission from crystalline copper sulphide nanowire arrays

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Deng, S. Z.; Xu, N. S.; Wang, Suhua; Wen, Xiaogang; Yang, Shihe; Yang, Chunlei; Wang, Jiannong; Ge, Weikun

    2002-05-01

    Straight crystalline copper sulphide (Cu2S) nanowire arrays have been grown by using a simple gas-solid reaction at room temperature. These were demonstrated to exhibit semiconductor properties. Field emission was observed at a field of ˜6 MV/m, and its current-field characteristics deviate from Fowler-Nordheim theory, i.e., showing a nonlinear Fowler-Nordheim plot. The uniform emission from the whole arrays was observed using transparent anode technique, and their variation with applied field was recorded. The emission from individual nanowires was also studied using a field emission microscope, and was found to consist of a number of spatially resolved diffuse spots. Finally, stable emission current at different levels and over time was recorded. These findings indicate that semiconductor nanowires as cold cathode have a potential future, worthy of further comprehensive investigation. The technical importance of using semiconductor nanowires as cold cathode emitter is given.

  8. Nanodiamonds for field emission: state of the art.

    PubMed

    Terranova, Maria Letizia; Orlanducci, Silvia; Rossi, Marco; Tamburri, Emanuela

    2015-03-12

    The aim of this review is to highlight the recent advances and the main remaining challenges related to the issue of electron field emission (FE) from nanodiamonds. The roadmap for FE vacuum microelectronic devices envisages that nanodiamonds could become very important in a short time. The intrinsic properties of the nanodiamond materials indeed meet many of the requirements of cutting-edge technologies and further benefits can be obtained by tailored improvements of processing methodologies. The current strategies used to modulate the morphological and structural features of diamond to produce highly performing emitting systems are reported and discussed. The focus is on the current understanding of the FE process from nanodiamond-based materials and on the major concepts used to improve their performance. A short survey of non-conventional microsized cold cathodes based on nanodiamonds is also reported.

  9. Emission reduction by multipurpose buffer strips on arable fields.

    PubMed

    Sloots, K; van der Vlies, A W

    2007-01-01

    In the area managed by Hollandse Delta, agriculture is under great pressure and the social awareness of the agricultural sector is increasing steadily. In recent years, a stand-still has been observed in water quality, in terms of agrochemicals, and concentrations even exceed the standard. To improve the waterquality a multi-purpose Field Margin Regulation was drafted for the Hoeksche Waard island in 2005. The regulation prescribes a crop-free strip, 3.5 m wide, alongside wet drainage ditches. The strip must be sown with mixtures of grasses, flowers or herbs. No crop protection chemicals or fertilizer may be used on the strips. A total length of approximately 200 km of buffer strip has now been laid. Besides reducing emissions, the buffer strips also stimulate natural pest control methods and encourage local tourism. Finally, the strips should lead to an improvement in the farmers' image. The regulation has proved to be successful. The buffer strips boosted both local tourism and the image of the agricultural sector. Above all, the strips provided a natural shield for emission to surface water, which will lead to an improvement of the water quality and raise the farmers' awareness of water quality and the environment.

  10. Field emission spectroscopy of SiC

    NASA Astrophysics Data System (ADS)

    Nikiforov, K. A.; Trofimov, V. V.; Egorov, N. V.

    2016-08-01

    Experimental set up for the natural experiment and measurement model are presented to obtain the feld emission energy distribution spectrum out of silicon carbide in case of the macro-sample having a macroscopic shape of a tip. The prototype of feld emission 6H - SiC monolithic cathode is proposed for spectroscopy measurements, and characterised by current-voltage dependence at macroscale interelectrode distance.

  11. Experiments with Low Voltage Field Emission EPMA

    NASA Astrophysics Data System (ADS)

    Fournelle, J.; Cathey, H. E.

    2014-12-01

    We report results from 5-7 keV Field Emission EPMA experiments on selected natural minerals and synthetic materials to illustrate some strengths -- and pitfalls --of low keV FE-EPMA. In a silicate mineral in pseudotachylite from South Mountain, AZ (Goodwin, 1999), the spatial resolution (equation of Merlet & Llovet, 2012, with an 80 nm diameter beam) at 7 keV for Si Ka is calculated to be 588 nm, 391 nm for Ca Ka and 641 nm for Fe La. This pseudotachylite contains abundant 5-10 um sieve-textured crystals full of inclusions with low BSE intensity. Previous 15 keV work suggested the sieve phase was amphibole. At 7 keV, it is possible to identify the compositions of the submicron inclusions as SiO2 and a K-rich alumino-silicate phase; the host composition is epidote. The enhanced resolution of FE-EPMA reveals problems with some microanalytical standards. Vicenzi and Rose (2008) showed submicron inclusions in the Smithsonian Kakanui hornblende standard. Our 7 keV experiments show the ~400 nm inclusions consist of a silicate phase (glass?), Fe-Ti oxide and possibly a gas bubble, concentrated along planes or grain boundaries. SEM imaging of an inclusion analyzed with a focused FE beam shows radiating trails of debris on the hornblende host, consistent with residue from a popped vapor bubble in the inclusion. How should FE-EPMA handle standards that may have inclusions? Use a focused beam avoiding inclusions? Sometimes, perhaps. However, we used a defocused beam to "average" the phases. The results show little or no deviation from the published wet chemical analysis. Operation at reduced keV may require use of non-traditional X-ray lines (e.g. Gopon et al, 2013 for Fe Ll vs Fe La). Experiments at 5 keV were also performed upon a synthetic material enriched in Nd (Nd-Mg-Zn). Fischer & Baun (1967) demonstrated problems with the Ma/Mb lines of REE; we find that use of the Nd Mz line is necessary in order to achieve reasonable results in this material (98 wt% total, Nd 36 wt

  12. Enhanced field emission of plasma treated multilayer graphene

    SciTech Connect

    Khare, Ruchita T.; More, Mahendra A.; Gelamo, Rogerio V.; Late, Dattatray J. E-mail: csrout@iitbbs.ac.in; Rout, Chandra Sekhar E-mail: csrout@iitbbs.ac.in

    2015-09-21

    Electron emission properties of multilayer graphene (MLG) prepared by a facile exfoliation technique have been studied. Effect of CO{sub 2} Ar, N{sub 2}, plasma treatment was studied using Raman spectroscopy and investigated for field emission based application. The CO{sub 2} plasma treated multilayer graphene shows an enhanced field emission behavior with a low turn on field of 0.18 V/μm and high emission current density of 1.89 mA/cm{sup 2} at an applied field of 0.35 V/μm. Further the plasma treated MLG exhibits excellent current stability at a lower and higher emission current value.

  13. Beam extraction experiment with field-emission arrays

    SciTech Connect

    Ishizuka, H.; Watanabe, A.; Shiho, M.

    1995-12-31

    An experimental project aimed to develop FEL drivers using a field-emission array is under way. The subject covers design and fabrication of novel micro-emitters, operation of FEAs, beam formation and emittance diagnostics. So far the generation of a focused beam has been demonstrated with an array of double-gated microemitters. Active control of FEAs has greatly improved the stability of the emission current. Large FEAs with an emitting area of up to 2 x 2 cm{sup 2} have been fabricated for the production of high-current beams. DC beams (1 - 5 keV < 100 {mu}A) extracted from Spindt cathodes were propagated over 1 m and projected on a fluorescent screen. Separate images of FEA tips were observed and emittance measurement has been carried out. The cathode is going to be replaced by a double-gated FEA to improve the beam quality. Pulsed extraction of high currents will also be tested, employing a non-gated FEA as the cathode of a 1 MV induction linac. Results of these experiments will be presented and perspectives concerning the FEA gun will be discussed.

  14. Field dependent emission rates in radiation damaged GaAs

    SciTech Connect

    Fleming, R. M.; Myers, S. M.; Wampler, W. R.; Lang, D. V.; Seager, C. H.; Campbell, J. M.

    2014-07-07

    We have measured the temperature and field dependence of emission rates from five traps in electron damaged GaAs. Four of the traps have previously been identified as radiation defects. One of the traps, seen in higher doped diodes, has not been previously identified. We have fit the data to a multiphonon emission theory that allows recombination in GaAs to be characterized over a broad range of temperature and electric field. These results demonstrate an efficient method to calculate field-dependent emission rates in GaAs.

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

    SciTech Connect

    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

  16. A field emission microscope in an advanced students' laboratory

    NASA Astrophysics Data System (ADS)

    Greczylo, Tomasz; Mazur, Piotr; Debowska, Ewa

    2006-03-01

    This paper describes a university level experiment during which students can observe the surface structure and determine the work function of a clean single tungsten crystal and a crystal covered with barium. The authors used a commercial field emission microscope offered by Leybold Didactic and designed an experiment which can be easily reproduced and performed in a students' laboratory. The use of a digital camera and computer allowed simultaneous observation and imaging of the surface of the body-centred cubic structure of the single tungsten crystal. Some interesting results about the changes in tungsten work function with time and with barium coverage are presented and discussed. The data help to improve knowledge and skills in the calculation of measurement uncertainty.

  17. Thermionic field emission transport in carbon nanotube transistors.

    PubMed

    Perello, David J; Lim, Seong Chu; Chae, Seung Jin; Lee, Innam; Kim, Moon J; Lee, Young Hee; Yun, Minhee

    2011-03-22

    With experimental and analytical analysis, we demonstrate a relationship between the metal contact work function and the electrical transport properties saturation current (Isat) and differential conductance (σsd=∂Isd/∂Vsd) in ambient exposed carbon nanotubes (CNT). A single chemical vapor deposition (CVD) grown 6 mm long semiconducting single-walled CNT is electrically contacted with a statistically significant number of Hf, Cr, Ti, Pd, and Au electrodes, respectively. The observed exponentially increasing relationship of Isat and σsd with metal contact work function is explained by a theoretical model derived from thermionic field emission. Statistical analysis and spread of the data suggest that the conduction variability in same CNT devices results from differences in local surface potential of the metal contact. Based on the theoretical model and methodology, an improved CNT-based gas sensing device layout is suggested. A method to experimentally determine gas-induced work function changes in metals is also examined.

  18. PCDD AND PCDF EMISSIONS FROM SIMULATED SUGARCANE FIELD BURNING

    EPA Science Inventory

    The emissions from simulated sugarcane field burns were sampled and analyzed for polychlorinated dibenzodioxins and dibenzofurans (PCDDs and PCDFs). Sugarcane leaves from Hawaii and Florida were burned in a manner simulating the natural physical dimensions and biomass density fou...

  19. Very Stable Electron Field Emission From Strontium Titanate Coated Carbon Nanotube Matrices With Low Emission Thresholds

    SciTech Connect

    Pandey, Archana; Prasad, Abhishek; Moscatello, Jason; Engelhard, Mark H.; Wang, Chong M.; Yap, Yoke K.

    2013-01-22

    PMMA-STO-CNT matrices were created by opened-tip vertically-aligned multiwalled carbon nanotubes (VA-MWCNTs) with conformal coating of strontium titanate and Poly(methyl methacrylate). Emission threshold of 0.8 V/μm was demonstrated, about five-fold lower than that of the as-grown VAMWCNTs. Theoretical simulation and modeling suggest that PMMA-STO-CNT matrices have suppressed screening effects and Coulombs’ repulsion forces between electrons in adjacent CNTs, leading to low emission threshold, high emission density, and prolong emission stability. These findings are important for practical application of VA-MWCNTs in field emission devices.

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

    SciTech Connect

    Tong Wang

    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

  1. Speed Profiles for Improvement of Maritime Emission Estimation

    PubMed Central

    Yau, Pui Shan; Lee, Shun-Cheng; Ho, Kin Fai

    2012-01-01

    Abstract Maritime emissions play an important role in anthropogenic emissions, particularly for cities with busy ports such as Hong Kong. Ship emissions are strongly dependent on vessel speed, and thus accurate vessel speed is essential for maritime emission studies. In this study, we determined minute-by-minute high-resolution speed profiles of container ships on four major routes in Hong Kong waters using Automatic Identification System (AIS). The activity-based ship emissions of NOx, CO, HC, CO2, SO2, and PM10 were estimated using derived vessel speed profiles, and results were compared with those using the speed limits of control zones. Estimation using speed limits resulted in up to twofold overestimation of ship emissions. Compared with emissions estimated using the speed limits of control zones, emissions estimated using vessel speed profiles could provide results with up to 88% higher accuracy. Uncertainty analysis and sensitivity analysis of the model demonstrated the significance of improvement of vessel speed resolution. From spatial analysis, it is revealed that SO2 and PM10 emissions during maneuvering within 1 nautical mile from port were the highest. They contributed 7%–22% of SO2 emissions and 8%–17% of PM10 emissions of the entire voyage in Hong Kong. PMID:23236250

  2. Positional control of plasmonic fields and electron emission

    SciTech Connect

    Word, R. C.; Fitzgerald, J. P. S.; Könenkamp, R.

    2014-09-15

    We report the positional control of plasmonic fields and electron emission in a continuous gap antenna structure of sub-micron size. We show experimentally that a nanoscale area of plasmon-enhanced electron emission can be motioned by changing the polarization of an exciting optical beam of 800 nm wavelength. Finite-difference calculations are presented to support the experiments and to show that the plasmon-enhanced electric field distribution of the antenna can be motioned precisely and predictively.

  3. Fundamental properties of field emission-driven direct current microdischarges

    NASA Astrophysics Data System (ADS)

    Rumbach, Paul; Go, David B.

    2012-11-01

    For half a century, it has been known that the onset of field emission in direct current microdischarges with gap sizes less than 10 μm can lead to breakdown at applied voltages far less than predicted by Paschen's law. It is still unclear how field emission affects other fundamental plasma properties at this scale. In this work, a one-dimensional fluid model is used to predict basic scaling laws for fundamental properties including ion density, electric field due to space charge, and current-voltage relations in the pre-breakdown regime. Computational results are compared with approximate analytic solutions. It is shown that field emission provides an abundance of cathode electrons, which in turn create large ion concentrations through ionizing collisions well before Paschen's criterion for breakdown is met. Breakdown due to ion-enhanced field emission occurs when the electric field due to space charge becomes comparable to the applied electric field. Simple scaling analysis of the 1D Poisson equation demonstrates that an ion density of n+ ≈ 0.1VAɛ0/qd2 is necessary to significantly distort the electric field. Defining breakdown in terms of this critical ion density leads analytically to a simple, effective secondary emission coefficient γ' of the same mathematical form initially suggested by Boyle and Kisliuk [Phys. Rev. 97, 255 (1955)].

  4. Field electron emission from pencil-drawn cold cathodes

    NASA Astrophysics Data System (ADS)

    Chen, Jiangtao; Yang, Bingjun; Liu, Xiahui; Yang, Juan; Yan, Xingbin

    2016-05-01

    Field electron emitters with flat, curved, and linear profiles are fabricated on flexible copy papers by direct pencil-drawing method. This one-step method is free of many restricted conditions such as high-temperature, high vacuum, organic solvents, and multistep. The cold cathodes display good field emission performance and achieve high emission current density of 78 mA/cm2 at an electric field of 3.73 V/μm. The approach proposed here would bring a rapid, low-cost, and eco-friendly route to fabricate but not limited to flexible field emitter devices.

  5. Connecting Photospheric Magnetic Fields and Transition Temperature Plasma Emission

    NASA Astrophysics Data System (ADS)

    Schmit, Donald

    2016-05-01

    The connectivity of quiet sun magnetic fields is not well understood. One observational obstacle to probe this question has been the sparse spectral observations spanning the transition temperatures (3×104 K< T < 1×105K) between the chromosphere and corona. The Si IV lines observed by IRIS provide a rich dataset to address the structure of the cool quiet sun. We use over 900 deep exposures from IRIS to map the correlation between transition-temperature emission structures and magnetic field concentrations. Ultimately, our aim is to discern the topology and energetic equilibrium of the magnetic structures that span the quiet sun. We use both a potential field model and a snapshot of the Bifrost 3D MHD simulation to interpret our emission data. In a broad sense, we find there is a clear correlation between magnetic fields and strong Si IV emission. However, more pointed statistics suggest that the relationship is quite complex. We do not find evidence for cool loops longer than 3 Mm in length, but we see ubiquitous, smooth emission nearly everywhere in the quiet sun. Emission voids on scales larger than 8 Mm cannot be well explained by their proximity to magnetic fields. This evidence suggests that weak-field transition-temperature loops contribute significantly to quiet sun transition-temperature emission measure, and evolutionary effects likely play a role in structuring the magnetic atmosphere.

  6. Nanodiamond vacuum field emission device with gate modulated triode characteristics

    NASA Astrophysics Data System (ADS)

    Hsu, S. H.; Kang, W. P.; Raina, S.; Huang, J. H.

    2013-05-01

    A three-electrode nanodiamond vacuum field emission (VFE) device with gate modulated triode characteristics is developed by integrating nanodiamond emitter with self-aligned silicon gate and anode, employing a mold transfer technique in conjunction with chemical vapor deposition of nanodiamond. Triode behavior showing emission current modulation with high current density at low operating voltages is achieved. A systematic analysis based on modified Fowler-Nordheim theory is used to analyze gate modulated VFE characteristics, confirming the triode field emission mechanism and operating principle. The realization of an efficient VFE microtriode has achieved the fundamental step for further development of vacuum integrated microelectronics.

  7. Field emission from CNT films deposited on porous Si

    NASA Astrophysics Data System (ADS)

    Stepińska, Izabela; Wronka, Halina; Waszuk, Stanisław; Radomska, Joanna; Kozłowski, Mirosław; Czerwosz, ElŻbieta; Craciunoiu, Florea

    2015-09-01

    The carbon nanotubes films on various type of porous Si substrate were prepared. Three methods of porous Si preparation electrolysis, wet etching with silver nitrate and with potassium hydroxide were used. CNTs films were obtained by two step method containing PVD and CVD process. These yield of field emission depended on the type of film. I-U characteristics and F-N plots are discussed for these films. The short-term stability of emission measurements results are also presented. Depending on technological parameters of Si etching the topography of samples is different and it affects on the emission currents intensity and the electric threshold field.

  8. Field emission characteristics of nano-diamond cathode surface by graphitization pretreatment

    NASA Astrophysics Data System (ADS)

    Shi, Yan-mei; Yang, Yan-ning; Liu, Qiao-ping; Li, Wei-xia

    2016-03-01

    Cathode samples of nano-diamond by graphitization pretreatment with different temperatures were fabricated by electrophoresis, then the structures and morphologies of the cathode samples were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), and the field emission tests were conducted. The effects of graphitization pretreatment on the field emission characteristics of nano-diamond cathode surface on titanium substrate are studied. The results indicate that the surface morphologies of nano-diamond cathode samples after graphitization pretreatment change a lot, and the field emission characteristics in low-voltage area are improved obviously. However, in high-voltage area, the curve distortion happens, and it doesn't conform the mechanism of field emission characteristics.

  9. Microbial mechanisms to reduce the uncertainties in the CH4 emissions from global rice fields

    NASA Astrophysics Data System (ADS)

    Kamaljit, K.; Tian, H.; Ren, W.; Yang, J.

    2013-12-01

    In terrestrial ecosystems, methane (CH4) uptake or emission represents the net balance between activities of different microbial organisms including anaerobic Methanogens that produce CH4 and Methanotrophs which oxidize CH4 in the aerobic environments. In this way, anaerobic soil environments such as rice fields are major source of terrestrial CH4 emissions. However, large uncertainties in the CH4 emission estimates have been reported from rice fields. The bottom-up and top-down methods showed a wide range of CH4 emissions estimations ranging from 25 to 300 Tg yr-1 from rice fields. The major reason for uncertainties in the CH4 emissions includes the water management that alters the balance of Methanogens and Methanotrophs in the rice fields. Two kinds of water management practices are followed including continuous flooding (CF) which refers to the continuous submergence as well as alternate wetting and drying (AWD) in which the rice fields are drained for several days during the growing season. The AWD provides aeration stress on Methanogens resulting in lower CH4 emissions than CF water management followed in the rice fields. A single aeration during growing season may significantly reduce the CH4 emission from the rice fields. Currently, most of the models structures assume that Methanogens become active once the soil moisture content is raised to saturation. However, several laboratory scale studies have indicated that following aeration the Methanogens don't become fully functional immediately even if the soil moisture content is raised to saturation. In this study, we integrated the aeration stress mechanisms on the Methanogens in the Dynamic Land Ecosystem Model (DLEM). The improved version of DLEM was used to conduct uncertainty analysis on global CH4 emission estimation following CF and AWD water management in the rice fields. Results of this study have shown that inclusion of the aeration stress mechanism on Methanogens in the modeling framework has

  10. Enhanced Field-Emission Performance from Carbon Nanotube Emitters on Nickel Foam Cathodes

    NASA Astrophysics Data System (ADS)

    Song, Meng; Xu, Peng; Han, Lijing; Yi, Lan; Wang, Xu; Li, Zhenhua; Shang, Xuefu; Wang, Xiumin; Wu, Huizhen; Zhao, Pei; Song, Yenan; Wang, Miao

    2016-04-01

    We present a three-dimensionally configured cathode with enhanced field-emission performance formed by combining carbon nanotube (CNT) emitters with a nickel foam (NiF) substrate via a conventional screen-printing technique. The CNT/NiF cathode has low turn-on electric field of 0.53 V μm-1 (with current density of 10 μA cm-2) and threshold electric field of 0.87 V μm-1 (with current density of 0.1 mA cm-2), and a very high field enhancement factor of 1.4 × 104. The porous structure of the NiF substrate can greatly improve the field-emission properties due to its large specific surface area that can accommodate more CNTs and increase the emitter density, as well as its high electrical and thermal conductivities that facilitate current transition and heat dissipation in the cathode. Most importantly, the local electric field was also enhanced by the multistage effect resulting from the rough metal surface, which furthermore leads to a high field enhancement factor. We believe that this improved field-emission performance makes such cathodes promising candidates for use in various field-emission applications.

  11. Synthesis, characterization and field emission properties of nanotubes and nanowires

    NASA Astrophysics Data System (ADS)

    Dong, Lifeng

    2005-11-01

    In this study, we investigated several novel methods to synthesize carbon nanotubes and nanowires of various compositions with controlled properties, utilized electron microscopy and microanalysis techniques to study their growth mechanisms and effects of growth parameters on their internal structures and morphologies, and set up a field emission microscope and a field emission probe system to study field emission properties of single nanotube/nanowires and thin films of nanostructures. The introduction of H2 during catalyst activation and nanotube growth periods thermodynamically and kinetically facilitates the formation of high quality nanotubes. With the inclusion of H2, the nanotube diameter decreased from 300 nm to 15 nm and growth rate increased from 78 nm/s to 145 nm/s. The growth location and orientation of carbon nanotubes to substrates can be controlled by the position and density of catalysts, respectively. Focused Ion Beam (FIB) techniques were utilized to confine catalyst locations and to directly deposit patterned catalyst precursors. Nanotube internal structures including graphitization and number of graphite layers can be tailored using different hydrocarbon gases (CH4 or C2H2) as carbon sources or by varying catalyst elements (Fe, Ni, or Co). Besides effects of nanoscale radius and high aspect ratio, the internal structures of carbon nanotubes greatly affects their field mission properties including turn-on field, threshold field and enhancement factor. Carbon nanotubes from Fe or Co demonstrate better field emission properties than those from Ni. At high electric fields, nanotube emission deviates from the Fowler-Nordheim (F-N) theory due to space charge and field emission-induced temperature effects. Also, an abnormal noise power spectral density (PSD) peak was observed at the space charge regime and PSD decreases with the increase of emission current due to Joule self-heating. In order to investigate field emission properties of nanostructures

  12. A knife-edge array field emission cathode

    SciTech Connect

    Lee, B.

    1994-08-01

    many cathode applications require a new type of cathode that is able to produce short pulsed electron beams at high emission current. Gated field emitter arrays of micrometer size are recognized as candidates to meet this need and have become the research focus of vacuum microelectronics. Existing fabrication methods produce emitters that are limited either in frequency response or in current emission. One reason is that the structure of these emitters are not sufficiently optimized. In this study, the author investigated the factors that affect the performance of field emitters. An optimum emitter structure, the knife-edge field emitter array, was developed from the analysis. Large field enhancement factor, large effective emission area, and small emitter capacitance are the advantages of the structure. The author next explored various options of fabricating the knife-edge emitter structure. He proposed a unique thin film process procedure and developed the fabrication techniques to build the emitters on (110) silicon wafers. Data from the initial cathode tests showed very low onset voltages and Fowler-Nordheim type emission. Emission simulation based on the fabricated emitter structure indicated that the knife-edge emitter arrays have the potential to produce high performance in modulation frequency and current emission. Several fabrication issues that await further development are discussed and possible solutions are suggested.

  13. Beam Dynamics Simulations of Optically-Enhanced Field Emission from Structured Cathodes

    SciTech Connect

    Seymour, A.; Grote, D.; Mihalcea, D.; Piot, P.; Vay, J.-L.

    2014-01-01

    Structured cathodes - cathodes with a segmented emission surface - are finding an increasing number of applications and can be combined with a variety of emission mechanisms, including photoemission and field emission. These cathodes have been used to enhance the quantum efficiency of metallic cathodes when operated as plasmonic cathodes, have produced high-current electron bunches though field emission from multiple tips, and can be used to form beams with transverse segmentations necessary for improving the performance of accelerator-based light sources. In this report we present recent progress towards the development of finite-difference time-domain particle-in-cell simulations using the emission process in structured cathodes based on the WARP framework. The simulations give further insight on the localized source of the emitted electrons which could be used for additional high-fidelity start-to-end simulations of electron accelerators that employ this type of electron source.

  14. Spontaneous Radiation Emission from Short, High Field Strength Insertion Devices

    SciTech Connect

    Geoffrey Krafft

    2005-09-15

    Since the earliest papers on undulaters were published, it has been known how to calculate the spontaneous emission spectrum from ''short'' undulaters when the magnetic field strength parameter is small compared to unity, or in ''single'' frequency sinusoidal undulaters where the magnetic field strength parameter is comparable to or larger than unity, but where the magnetic field amplitude is constant throughout the undulater. Fewer general results have been obtained in the case where the insertion device is both short, i.e., the magnetic field strength parameter changes appreciably throughout the insertion device, and the magnetic field strength is high enough that ponderomotive effects, radiation retardation, and harmonic generation are important physical phenomena. In this paper a general method is presented for calculating the radiation spectrum for short, high-field insertion devices. It is used to calculate the emission from some insertion device designs of recent interest.

  15. Superior Field Emission Properties of Layered WS2-RGO Nanocomposites

    PubMed Central

    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.

    2013-01-01

    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/cm2 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/cm2 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. PMID:24257504

  16. Secondary nanotube growth on aligned carbon nanofibre arrays for superior field emission.

    PubMed

    Watts, Paul C P; Lyth, Stephen M; Henley, Simon J; Silva, S Ravi P

    2008-04-01

    We report substantial improvement of the field emission properties from aligned carbon nanotubes grown on aligned carbon nanofibres by a two-stage plasma enhanced chemical vapour deposition (PECVD) process. The threshold field decreased from 15.0 to 3.6 V/microm after the secondary growth. The field enhancement factor increased from 240 to 1480. This technique allows for superior emission of electrons for carbon nanotube/nanofibre arrays grown directly on highly doped silicon for direct integration in large area displays. PMID:18572626

  17. Carbon nanotube based field emission X-ray sources

    NASA Astrophysics Data System (ADS)

    Cheng, Yuan

    This dissertation describes the development of field emission (FE) x-ray sources with a carbon-nanotube (CNT) cathode. Field emission x-rays have advantages over conventional x-rays by replacing the thermionic cathode with a cold cathode so that electrons are emitted at room temperature and emission is voltage controllable. CNTs are found to be excellent electron emitters with low threshold fields and high current density which makes them ideal for generate field emission x-rays. Macroscopic CNT cold cathodes are prepared and the parameters to tune their field emission properties are studied: structure and morphology of CNT cathodes, temperature as well as electronic work function of CNT. Macroscopic CNT cathodes with optimized performance are chosen to build a high-resolution x-ray imaging system. The system can readily generate x-ray radiation with continuous variation of temporal resolution up to nanoseconds and spatial resolution down to 10 micron. Its potential applications for dynamic x-ray imaging and micro-computed tomography are also demonstrated. The performance characteristics of this compact and versatile system are promising for non-destructive testing and for non-invasive small-animal imaging for biomedical research.

  18. Edge field emission of large-area single layer graphene

    NASA Astrophysics Data System (ADS)

    Kleshch, Victor I.; Bandurin, Denis A.; Orekhov, Anton S.; Purcell, Stephen T.; Obraztsov, Alexander N.

    2015-12-01

    Field electron emission from the edges of large-area (∼1 cm × 1 cm) graphene films deposited onto quartz wafers was studied. The graphene was previously grown by chemical vapour deposition on copper. An extreme enhancement of electrostatic field at the edge of the films with macroscopically large lateral dimensions and with single atom thickness was achieved. This resulted in the creation of a blade type electron emitter, providing stable field emission at low-voltage with linear current density up to 0.5 mA/cm. A strong hysteresis in current-voltage characteristics and a step-like increase of the emission current during voltage ramp up were observed. These effects were explained by the local mechanical peeling of the graphene edge from the quartz substrate by the ponderomotive force during the field emission process. Specific field emission phenomena exhibited in the experimental study are explained by a unique combination of structural, electronic and mechanical properties of graphene. Various potential applications ranging from linear electron beam sources to microelectromechanical systems are discussed.

  19. High-current-density field emission display fabricated from single-walled carbon nanotube electron sources

    NASA Astrophysics Data System (ADS)

    Zhao, P.; Shang, X. F.; Ma, Y. P.; Zhou, J. J.; Gu, Z. Q.; Li, Z. H.; Xu, Y. B.; Wang, M.

    2008-06-01

    Single-walled carbon nanotubes can be used as electron sources in the process of field emission, and have great potential for practical application of the field emission display (FED) panels with large screen size. We fabricated a FED using the single-walled carbon nanotubes (SWNTs) as the cathode by the screen-printing process. Test showed that the SWNTs emitters exhibit excellent macroscopic emission properties. It has low turn-on voltage (2.7 V/μ m) and high brightness, with a high current density of good uniformity and stability. It was observed that the field emission qualitatively follows the conventional Fowler Nordheim (F N) theory, and aging treatment played an important role in improving the image uniformity and stability. Compared to other complicated processes, the simple fabrication using screen-printing process seems to be advantageous for practical application.

  20. Improving ammonia emissions in air quality modelling for France

    NASA Astrophysics Data System (ADS)

    Hamaoui-Laguel, Lynda; Meleux, Frédérik; Beekmann, Matthias; Bessagnet, Bertrand; Génermont, Sophie; Cellier, Pierre; Létinois, Laurent

    2014-08-01

    We have implemented a new module to improve the representation of ammonia emissions from agricultural activities in France with the objective to evaluate the impact of such emissions on the formation of particulate matter modelled with the air quality model CHIMERE. A novel method has been set up for the part of ammonia emissions originating from mineral fertilizer spreading. They are calculated using the one dimensional 1D mechanistic model “VOLT'AIR” which has been coupled with data on agricultural practices, meteorology and soil properties obtained at high spatial resolution (cantonal level). These emissions display high spatiotemporal variations depending on soil pH, rates and dates of fertilization and meteorological variables, especially soil temperature. The emissions from other agricultural sources (animal housing, manure storage and organic manure spreading) are calculated using the national spatialised inventory (INS) recently developed in France. The comparison of the total ammonia emissions estimated with the new approach VOLT'AIR_INS with the standard emissions provided by EMEP (European Monitoring and Evaluation Programme) used currently in the CHIMERE model shows significant differences in the spatiotemporal distributions. The implementation of new ammonia emissions in the CHIMERE model has a limited impact on ammonium nitrate aerosol concentrations which only increase at most by 10% on the average for the considered spring period but this impact can be more significant for specific pollution episodes. The comparison of modelled PM10 (particulate matter with aerodynamic diameter smaller than 10 μm) and ammonium nitrate aerosol with observations shows that the use of the new ammonia emission method slightly improves the spatiotemporal correlation in certain regions and reduces the negative bias on average by 1 μg m-3. The formation of ammonium nitrate aerosol depends not only on ammonia concentrations but also on nitric acid availability, which

  1. Emissions reductions as a result of automobile improvement.

    PubMed

    Pokharel, Sajal S; Bishop, Gary A; Stedman, Donald H; Slott, Robert

    2003-11-15

    Remote sensing of light duty vehicle on-road tailpipe exhaust has been used to measure on-road mass emissions of automobile fleets in Denver for 13 years and in two other U.S. cities for 5 years. Analysis of these fleets shows that newer automobiles, during a period of fairly constant new car standards, have become continually less polluting independent of measurement location. Improving emissions control technology spurred by federal regulations is thought to have brought about these trends.

  2. Neptune radio emission in dipole and multipole magnetic fields

    NASA Technical Reports Server (NTRS)

    Sawyer, C. B.; King, N. V.; Romig, J. H.; Warwick, J. W.

    1995-01-01

    We study Neptune's smooth radio emission in two ways: we simulate the observations and we then consider the radio effects of Neptune's magnetic multipoles. A procedure to deduce the characteristics of radio sources observed by the Planetary Radio Astronomy experiment minimizes limiting assumptions and maximizes use of the data, including quantitative measurement of circular polarization. Study of specific sources simulates time variation of intensity and apparent polarization of their integrated emission over an extended time period. The method is applied to Neptune smooth recurrent emission (SRE). Time series are modeled with both broad and beamed emission patterns, and at two frequencies which exhibit different time variation of polarization. These dipole-based results are overturned by consideration of more complex models of Neptune's magnetic field. Any smooth emission from the anticipated auroral radio source is weak and briefly observed. Dominant SRE originates complex fields at midlatitude. Possible SRE source locations overlap that of 'high-latitude' emission (HLE) between +(out) and -(in) quadrupoles. This is the first identification of multipolar magnetic structure with a major source of planetary radio emission.

  3. Observation of Field-Emission Dependence on Stored Energy

    NASA Astrophysics Data System (ADS)

    Shao, Jiahang; Antipov, Sergey P.; Baryshev, Sergey V.; Chen, Huaibi; Conde, Manoel; Doran, Darrell S.; Gai, Wei; Jing, Chunguang; Liu, Wanming; Power, John; Qiu, Jiaqi; Shi, Jiaru; Wang, Dan; Wang, Faya; Whiteford, Charles E.; Wisniewski, Eric; Xiao, Liling

    2015-12-01

    Field emission from a solid metal surface has been continuously studied for a century over macroscopic to atomic scales. It is general knowledge that, other than the surface properties, the emitted current is governed solely by the applied electric field. A pin cathode has been used to study the dependence of field emission on stored energy in an L -band rf gun. The stored energy was changed by adjusting the axial position (distance between the cathode base and the gun back surface) of the cathode while the applied electric field on the cathode tip is kept constant. A very strong correlation of the field-emission current with the stored energy has been observed. While eliminating all possible interfering sources, an enhancement of the current by a factor of 5 was obtained as the stored energy was increased by a factor of 3. It implies that under certain circumstances a localized field emission may be significantly altered by the global parameters in a system.

  4. Observation of Field-Emission Dependence on Stored Energy.

    PubMed

    Shao, Jiahang; Antipov, Sergey P; Baryshev, Sergey V; Chen, Huaibi; Conde, Manoel; Doran, Darrell S; Gai, Wei; Jing, Chunguang; Liu, Wanming; Power, John; Qiu, Jiaqi; Shi, Jiaru; Wang, Dan; Wang, Faya; Whiteford, Charles E; Wisniewski, Eric; Xiao, Liling

    2015-12-31

    Field emission from a solid metal surface has been continuously studied for a century over macroscopic to atomic scales. It is general knowledge that, other than the surface properties, the emitted current is governed solely by the applied electric field. A pin cathode has been used to study the dependence of field emission on stored energy in an L-band rf gun. The stored energy was changed by adjusting the axial position (distance between the cathode base and the gun back surface) of the cathode while the applied electric field on the cathode tip is kept constant. A very strong correlation of the field-emission current with the stored energy has been observed. While eliminating all possible interfering sources, an enhancement of the current by a factor of 5 was obtained as the stored energy was increased by a factor of 3. It implies that under certain circumstances a localized field emission may be significantly altered by the global parameters in a system. PMID:26764996

  5. Process system and method for fabricating submicron field emission cathodes

    DOEpatents

    Jankowski, Alan F.; Hayes, Jeffrey P.

    1998-01-01

    A process method and system for making field emission cathodes exists. The deposition source divergence is controlled to produce field emission cathodes with height-to-base aspect ratios that are uniform over large substrate surface areas while using very short source-to-substrate distances. The rate of hole closure is controlled from the cone source. The substrate surface is coated in well defined increments. The deposition source is apertured to coat pixel areas on the substrate. The entire substrate is coated using a manipulator to incrementally move the whole substrate surface past the deposition source. Either collimated sputtering or evaporative deposition sources can be used. The position of the aperture and its size and shape are used to control the field emission cathode size and shape.

  6. Electron Field Emission Properties of Textured Platinum Surfaces

    NASA Technical Reports Server (NTRS)

    Sovey, James S.

    2002-01-01

    During ground tests of electric microthrusters and space tests of electrodynamic tethers the electron emitters must successfully operate at environmental pressures possibly as high as 1x10(exp -4) Pa. High partial pressures of oxygen, nitrogen, and water vapor are expected in such environments. A textured platinum surface was used in this work for field emission cathode assessments because platinum does not form oxide films at low temperatures. Although a reproducible cathode conditioning process did not evolve from this work, some short term tests for periods of 1 to 4 hours showed no degradation of emission current at an electric field of 8 V/mm and background pressures of about 1x10(exp -6) Pa. Increases of background pressure by air flow to about 3x10(exp -4) Pa yield a hostile environment for the textured platinum field emission cathode.

  7. Improving the City-scale Emission Inventory of Anthropogenic Air Pollutants: A Case Study of Nanjing

    NASA Astrophysics Data System (ADS)

    Qiu, L.; Zhao, Y.; Xu, R.; Xie, F.; Wang, H.; Qin, H.; Wu, X.; Zhang, J.

    2014-12-01

    To evaluate the improvement of city-scale emission inventory, a high-resolution emission inventory of air pollutants for Nanjing is first developed combining detailed source information, and then justified through quantitative analysis with observations. The best available domestic emission factors and unit-/facility-based activity level data were compiled based on a thorough field survey on major emission sources. Totally 1089 individual emission sources were identified as point sources and all the emission-related parameters including burner type, combustion technology, fuel quality, and removal efficiency of pollution control devices, are carefully investigated and analyzed. Some new data such as detailed information of city fueling-gas stations, construction sites, monthly activity level, data from continuous emission monitoring systems and traffic flow information were combined to improve spatiotemporal distribution of this inventory. For SO2, NOX and CO, good spatial correlations were found between ground observation (9 state controlling air sampling sites in Nanjing) and city-scale emission inventory (R2=0.34, 0.38 and 0.74, respectively). For TSP, PM10 and PM2.5, however, poorer correlation was found due to relatively weaker accuracy in emission estimation and spatial distribution of road dust. The mixing ratios between specific pollutants including OC/EC, BC/CO and CO2/CO, are well correlated between those from ground observation and emission. Compared to MEIC (Multi-resolution Emission Inventory for China), there is a better spatial consistence between this city-scale emission inventory and NO2 measured by OMI (Ozone Monitoring Instrument). In particular, the city-scale emission inventory still correlated well with satellite observations (R2=0.28) while the regional emission inventory showed little correlation with satellite observations (R2=0.09) when grids containing power plants are excluded. It thus confirms the improvement of city-scale emission

  8. Electron field emission from boron nitride thin films

    NASA Astrophysics Data System (ADS)

    Encarnacion, Pedro Aron

    A systematic study of electron field emission from boron nitride thin films is presented, establishing nanostructured thin film cubic boron nitride (cBN) as a robust and chemically inert material with a low effective workfunction, able to sustain electron emission in a space plasma environment. RHEED data shows the films as polycrystalline, composed of partially oriented crystallites of cBN with predominantly (001) crystallographic texture relative to the Si substrate. FTIR data showed our films to be overwhelmingly cBN, with a volume fraction greater than 75%. AFM images show nanostructures relevant to field enhancement, with a mean feature height of 79 nm, mean RMS roughness of 19 nm, average grain size of 155 nm2 +/- 84 nm2, and a mean feature radius of ˜7 nm. The results are discussed in the light of current theoretical models for electron field emission, including particulars relevant to semiconductors and nanostructured surfaces. Electron emission thresholds were measured from under 1V/mum up to just under 20V/mum in vacuum. Voltage sweep measurements were made both in vacuo and in various gas environments relevant to space applications. Repeatability of emission results was demonstrated, albeit with indications of threshold shifts, possibly due to desorption of adsorbate impurities. Time dependence measurements at constant extraction field show stable field emission over periods of extended operation. An effective barrier height ow of approximately 9.3 meV for the as-grown cBN thin films is measured, based on the application of the generalised Fowler-Nordheim theory to the electron field emission measurements, and employing a model of the film surface as an ensemble of self-assembled protruberances in the shape of prolate half ellipsoids of revolution on a flat surface. To our knowledge, this is the first experimental determination of this important parameter for cBN films. It appears that the low value of o w measured for cBN is a direct consequence of the

  9. Method of depositing multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, J.P.; Friedmann, T.A.

    1999-08-10

    A novel field emitter device is disclosed for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials. 8 figs.

  10. Method of depositing multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, John P.; Friedmann, Thomas A.

    1999-01-01

    A novel field emitter device for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials.

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

    PubMed

    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).

  12. Properties of a field emission-driven Townsend discharge

    NASA Astrophysics Data System (ADS)

    Rumbach, Paul; Go, David

    2012-10-01

    For half a century, it has been known that the onset of field emission in direct current (DC) microplasmas with gap sizes less than 10 μm can lead to breakdown at applied voltages far less than predicted by Paschen's law. It is still unclear how field emission affects other fundamental plasma properties at this scale. In this work, a one-dimensional fluid model is used to predict basic scaling laws for fundamental properties such as ion density, electric field due to space charge, and current voltage relations in the pre-breakdown regime. Computational results are compared with approximate analytic solutions. It is shown that ionizing collisions by field-emitted electrons produce significant ion densities well before Paschen's criteria for breakdown is met. When positive space charge densities become sufficiently large, the effect of ion-enhanced field emission leads to breakdown. Defining breakdown mathematically using a solvability condition leads to a full modified Paschen's curve, while defining it physically in terms of a critical ion density leads analytically to an effective secondary emission coefficient, γ', of the form initially suggested by Boyle and Kisliuk.footnotetextBoyle, W.S. and Kisliuk, P., Phys. Rev. 97, 255 (1955).

  13. A field laboratory for improved oil recovery

    SciTech Connect

    Hildebrandt, A.F.; McDonald, J.; Claridge, E.; Killough, J.

    1992-09-01

    The purpose of Annex III of the Memorandum of Understanding, undertaken by the Houston Petroleum Research Center at the University of Houston, was to develop a field laboratory for research in improved oil recovery using a Gulf Coast reservoir in Texas. The participants: (1) make a field site selection and conducted a high resolution seismic survey in the demonstration field, (2) obtained characteristics of the reservoir (3) developed an evaluation of local flood efficiency in different parts of the demonstration reservoir, (4) used diverse methodology to evaluate the potential recovery of the remaining oil in the test reservoir, (5) developed cross-well seismic tomography, and (6) will transfer the learned technologies to oil operators through publication and workshops. This abstract is an overview of these tasks.

  14. Improved modeling techniques for turbomachinery flow fields

    SciTech Connect

    Lakshminarayana, B.; Fagan, J.R. Jr.

    1995-12-31

    This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbomachinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. This will be accomplished in a cooperative program by Penn State University and the Allison Engine Company. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tenor.

  15. Pollutant emissions from improved coal- and wood-fuelled cookstoves in rural households.

    PubMed

    Shen, Guofeng; Chen, Yuanchen; Xue, Chunyu; Lin, Nan; Huang, Ye; Shen, Huizhong; Wang, Yilong; Li, Tongchao; Zhang, Yanyan; Su, Shu; Huangfu, Yibo; Zhang, Weihao; Chen, Xiaofu; Liu, Guangqing; Liu, Wenxin; Wang, Xilong; Wong, Ming-Hung; Tao, Shu

    2015-06-01

    Residential solid fuel combustion is a major source of many pollutants, resulting in significant impacts on air quality and human health. Improved stoves, especially some modern gasifier biomass models, are being deployed to alleviate household and ambient air pollution. Pollutant emissions from coal burning in improved metal stoves (n = 11) and wood combustion in modern gasifier stoves (n = 8) were measured in field in Hubei, China. The emissions of CO, TSP, OC, EC, and PAHs from coal burning in the improved iron stoves were generally lower than previously reported results for coal in traditional stoves. For pollutants from wood combustion in the gasifier stoves, the emissions were less than literature-reported values for wood burned in traditional stoves, comparable to those in improved stoves, but appeared to be higher than those for pellets in gasifier stoves in laboratory tests. The limitations of scarce data and large variances result in statistical insignificance. Daily emissions of targeted pollutants per household were found to be higher for wood burners, compared with households relying on coal. The gasifier stove had relatively high thermal efficiencies, but emissions of most air pollutants per delivered energy were not significantly different from those from the coal burning in improved iron stoves. Moreover, higher emissions of OC, EC, and PAHs were observed, indicating that caution and additional testing will be needed while designing future clean cookstove intervention programs.

  16. Anomalous high-frequency oscillations in a field emission tube and their significance in pulsed field emission.

    PubMed

    Hagmann, M J; Christensen, D A; Mousa, M S; Baturin, A; Sheshin, E P

    2007-09-01

    Relaxation oscillations occur when a capacitor is inserted in series with a field emission tube, a DC high-voltage power supply, and a ballast resistor. The waveform of these oscillations is highly reproducible with a dominant frequency of 200 MHz and a decay time of 20 ns. The peak current as high as 320 mA has been observed although the tungsten emitter is only rated for 10 microA. We have shown that these oscillations are due to a displacement current, charging of the anode-tip capacitance, and are not of a field emission origin. We conclude that the effects of displacement current should be considered in measurements of field emission with microsecond pulses, where high-current densities can be observed. PMID:17485175

  17. Field Emission Characteristics Depending on Emitter Patterns of A Screen-Printed Carbon Nanotube Field Emission Array

    NASA Astrophysics Data System (ADS)

    Kwon, Sang Jik; Lee, Sang Heon

    2006-01-01

    We have fabricated carbon nanotube field-emission displays (CNT-FEDs) panel with a 2 in. diagonal size using a screen printing method and in-situ vacuum sealing technology. The field emission properties of the CNT-FED panel with square-type CNT emitters were characterized and compared with those of the panel with line-type CNT emitters. As results, the square-type CNT emitters showed a much larger emission current and more stable current-voltage (I-V) characteristics. Light emission started to occur at an electric field of 3.5 V/μm, for a corresponding to an anode-cathode voltage of 700 V. The vacuum level inside of the in-situ vacuum-sealed panel was 1.4× 10-5 Torr. The sealed panel showed similar I-V characteristics with the unsealed one and uniform light emission with very high brightness at a current density of 243 μA/cm2 obtained at an electric field of 10 V/μm.

  18. Optical and field emission properties of Zinc Oxide nanostructures.

    PubMed

    Pan, Hui; Zhu, Yanwu; Ni, Zhenhua; Sun, Han; Poh, Cheekok; Lim, Sanhua; Sow, Chornghaur; Shen, Zexiang; Feng, Yuanping; Lin, Jianyi

    2005-10-01

    Zinc Oxide (ZnO) nano-pikes were produced by oxidative evaporation and condensation of Zn powders. The crystalline structure and optical properties of the ZnO nanostructures (ZnONs) greatly depend on the deposition position of the ZnONs. TEM and XRD indicated that the ZnONs close to the reactor center, ZnON-A, has better crystalline structure than the ZnONs away from the center, ZnON-B. ZnON-A showed the PL and Raman spectra characteristic of perfect ZnO crystals, whereas ZnON-B produced very strong green emission band at 500 nm in the photoluminescence (PL) spectrum and very strong Raman scattering peak at 560 cm(-1), both related to the oxygen deficiency due to insufficient oxidation of zinc vapor. ZnON-B exhibited better field emission properties with higher emission current density and lower turn-on field than ZnON-A.

  19. Electromagnetic plasma wave emissions from the auroral field lines

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1977-01-01

    The most important types of auroral radio emissions are reviewed, both from a historical perspective as well as considering the latest results. Particular emphasis is placed on four types of electromagnetic emissions which are directly associated with the plasma on the auroral field lines. These emissions are (1) auroral hiss, (2) saucers, (3) ELF noise bands, and (4) auroral kilometric radiation. Ray tracing and radio direction finding measurements indicate that both the auroral hiss and auroral kilometric radiation are generated along the auroral field lines relatively close to the earth, at radial distances from about 2.5 to 5 R sub e. For the auroral hiss the favored mechanism appears to be amplified Cerenkov radiation. For the auroral kilometric radiation several mechanisms have been proposed, usually involving the intermediate generation of electrostatic waves by the precipitating electrons.

  20. Field emission and photoluminescence of ZnO nanocombs

    NASA Astrophysics Data System (ADS)

    Wang, B.; Wu, H. Y.; Zheng, Z. Q.; Yang, Y. H.

    2013-11-01

    Three kinds of new comb-shape nanostructures of ZnO have been grown on single silicon substrates without catalyst-assisted thermal evaporation of Zn and active carbon powders. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The growth mechanism of the ZnO nanocombs can be explained on the basis of the vapor-solid (VS) processes. In nanocombs 1 and nanocombs 2, the comb teeth grow along [0001] and the comb stem grows along [], while in nanocombs 3, nanoteeth grow along [] and stem grows along [0001]. The photoluminescence and field-emission properties of ZnO nanocombs 1-3 have been investigated. The turn-on electric field of ZnO nanocombs 1-3, which is defined as the field required to producing a current density of 10 μA/cm2, is 9, 7.7 and 7.1 V/μm, respectively. The field-emission performance relies not only on the tip’s radius of curvature and field enhancement factor, but also on the factor evaluating the degree of the screening effect.

  1. Work function measurements by the field emission retarding potential method

    NASA Technical Reports Server (NTRS)

    Swanson, L. W.; Strayer, R. W.; Mackie, W. A.

    1971-01-01

    Using the field emission retarding potential method true work functions have been measured for the following monocrystalline substrates: W(110), W(111), W(100), Nb(100), Ni(100), Cu(100), Ir(110) and Ir(111). The electron elastic and inelastic reflection coefficients from several of these surfaces have also been examined near zero primary beam energy.

  2. Sub-micronewton thrust measurements of indium field emission thrusters

    NASA Technical Reports Server (NTRS)

    Ziemer, J. K.

    2003-01-01

    The performance of three indium field emission thrusters (In-FETs) developed by the Austrian Research Center Seibersdorf (ARCS) have been measured up to 200 muN, 2 mA, and 20 W using a submicronewton resolution thrust stand.

  3. Field-emission cathodes of glass-insulated microwire

    SciTech Connect

    Donika, F.G.; Miglei, D.F.; Smyslov, V.V.

    1987-08-01

    A method is described for fabricating field-emission cathodes in glass insulation. Cathodes with nickel and germanium emitters have packing densities of 10/sup 2/-10/sup 4/ pieces/mm/sup 2/ and point radii of curvature of 0.1-1 ..mu..m.

  4. Improved modeling techniques for turbomachinery flow fields

    SciTech Connect

    Lakshminarayana, B.; Fagan, J.R. Jr.

    1995-10-01

    This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbo-machinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tensor. Penn State will lead the effort to make direct measurements of the momentum and thermal mixing stress tensors in high-speed multistage compressor flow field in the turbomachinery laboratory at Penn State. They will also process the data by both conventional and conditional spectrum analysis to derive momentum and thermal mixing stress tensors due to blade-to-blade periodic and aperiodic components, revolution periodic and aperiodic components arising from various blade rows and non-deterministic (which includes random components) correlations. The modeling results from this program will be publicly available and generally applicable to steady-state Navier-Stokes solvers used for turbomachinery component (compressor or turbine) flow field predictions. These models will lead to improved methodology, including loss and efficiency prediction, for the design of high-efficiency turbomachinery and drastically reduce the time required for the design and development cycle of turbomachinery.

  5. Aproaches for mitigation of greenhouse gas emission from agricultural fields

    NASA Astrophysics Data System (ADS)

    Sudo, S.; Itoh, M.

    2009-12-01

    Percentage of atmospheric methane emitted form rice paddy is estimated at 60Tg/yr (20 - 100Tg/yr) which is near 10% of total global methane emission of 535Tg/yr (410 - 660Tg) (IPCC(1995), and which is near 30% of anthropogenic CH4 emission. Thus, mitigation of CH4 emission is required to be speed up. CH4 in paddy soil is emanated by the activities of anaerobic bacteria which is called methane producer through reduction of CO2 or decomposition of acetic acid, and it is transported to atmosphere through soil or paddy water surface. It is effective to control methane emission from rice paddy that period is prolonged on intermittent irrigation drainage, composted rice straw is incorporated as fertilizer instead of flesh one, or other. However, empirical approach of these kinds of experiments had not been sufficient because such a kind of experiment required significant times and efforts. In this study, we conducted demonstrative experiments to verify the effects of water management method differences in order to reduce CH4 emission from rice paddy at 9 experimental sites in 8 prefectures. In this, we used new gas analyzer which can measure CH4, CO2 and N2O at once developed by National Institute for Agro-Environmental Sciences (NIAES), Japan. In this report, we show the preliminary results in first year of this study. Nakaboshi (mid-season-drainage) is one of cultivation methods in rice paddy that surface water in paddy field is once drained for about 10 days and the field is maintained like upland field to give adequate stress to rice plant for better harvest qualities and yields. Our targeted evaluation was dependencies of Nakaboshi periods lengths and Nakaboshi periods to CH4 emission reduction amounts for total cultivation periods within harvest yield maintained. The longer length of Nakaboshi period was prolonged, the lesser emission amounts of CH4 decreased even after when Nakaboshi period lasted, as a whole. In some soil types, for example in Kagoshima

  6. Cathodoluminescence studies of nanocrystalline silicon films for field emission displays

    NASA Astrophysics Data System (ADS)

    Biaggi Labiosa, Azlin M.

    The cathodoluminescence (CL) emission from p-type porous silicon (PSi) films excited with low energy electron beams compatible with field emission display (FED) technologies was investigated. First, a study was carried out to find the optimal PSi configuration that would yield the strongest CL emission. It was found that the highest, stable CL intensities were obtained from samples prepared from p-type wafers with resistivity between 1-2 Ocm. Afterwards, the effects on the morphological details and the chemical composition due to the electron irradiation of the PSi films were studied. During a continuous irradiation of 10 hours the CL intensity of the films reduced in less than 10%. In situ SIMS analyses before and after prolonged e-beam excitation showed minor compositional changes of the film and reduced sputtering of the silicon nanoparticles due to the electron irradiation. It was also found that the electron bombardment causes microscale morphological modifications of the films, but the nanoscale features appear to be unchanged. The structural changes are manifested by the increase in the density of the nanoparticles which explains the significant enhancement of the photoluminescence (PL) that follows the electron irradiation. Second, after a thorough characterization of the PSi films under electron irradiation, tuning of the CL emission of PSi films was investigated. The PSi films used for this experiment were non-oxidized films unlike the ones used for the CL characterization that were oxidized films. The tuning was achieved by controlling the average size of the nanostructure thus showing that the origin of this CL emission is associated with the quantum confinement and the surface chemistry effects that are known to exist in the porous silicon system. However, the CL emission obtained from these samples was unstable which is attributed to the breaking of Si--H bonds due to the electron irradiation. Dangling bonds are then formed on the surface and this in

  7. Electron field emission in nanostructures: A first-principles study

    NASA Astrophysics Data System (ADS)

    Driscoll, Joseph Andrew

    The objective of this work was to study electron field emission from several nanostructures using a first-principles framework. The systems studied were carbon nanowires, graphene nanoribbons, and nanotubes of varying composition. These particular structures were chosen because they have recently been identified as showing novel physical phenomena, as well as having tremendous industrial applications. We examined the field emission under a variety of conditions, including laser illumination and the presence of adsorbates. The goal was to explore how these conditions affect the field emission performance. In addition to the calculations, this dissertation has presented computational developments by the author that allowed these demanding calculations to be performed. There are many possible choices for basis when performing an electronic structure calculation. Examples are plane waves, atomic orbitals, and real-space grids. The best choice of basis depends on the structure of the system being analyzed and the physical processes involved (e.g., laser illumination). For this reason, it was important to conduct rigorous tests of basis set performance, in terms of accuracy and computational efficiency. There are no existing benchmark calculations for field emission, but transport calculations for nanostructures are similar, and so provide a useful reference for evaluating the performance of various basis sets. Based on the results, for the purposes of studying a non-periodic nanostructure under field emission conditions, we decided to use a real-space grid basis which incorporates the Lagrange function approach. Once a basis was chosen, in this case a real-space grid, the issue of boundary conditions arose. The problem is that with a non-periodic system, field emitted electron density can experience non-physical reflections from the boundaries of the calculation volume, leading to inaccuracies. To prevent this issue, we used complex absorbing potentials (CAPs) to absorb

  8. Field emission properties of ZnO nanosheet arrays

    SciTech Connect

    Naik, Kusha Kumar; Rout, Chandra Sekhar E-mail: dj.late@ncl.res.in E-mail: csrout@iitbbs.ac.in; Khare, Ruchita; More, Mahendra A.; Chakravarty, Disha; Late, Dattatray J. E-mail: dj.late@ncl.res.in E-mail: csrout@iitbbs.ac.in; Thapa, Ranjit E-mail: dj.late@ncl.res.in E-mail: csrout@iitbbs.ac.in

    2014-12-08

    Electron emission properties of electrodeposited ZnO nanosheet arrays grown on Indium tin oxide coated glass substrates have been studied. Influence of oxygen vacancies on electronic structures and field emission properties of ZnO nanosheets are investigated using density functional theory. The oxygen vacancies produce unshared d electrons which form an impurity energy state; this causes shifting of Fermi level towards the vacuum, and so the barrier energy for electron extraction reduces. The ZnO nanosheet arrays exhibit a low turn-on field of 2.4 V/μm at 0.1 μA/cm{sup 2} and current density of 50.1 μA/cm{sup 2} at an applied field of 6.4 V/μm with field enhancement factor, β = 5812 and good field emission current stability. The nanosheet arrays grown by a facile electrodeposition process have great potential as robust high performance vertical structure electron emitters for future flat panel displays and vacuum electronic device applications.

  9. Nanotube field electron emission: principles, development, and applications.

    PubMed

    Li, Yunhan; Sun, Yonghai; Yeow, J T W

    2015-06-19

    There is a growing trend to apply field emission (FE) electron sources in vacuum electronic devices due to their fast response, high efficiency and low energy consumption compared to thermionic emission ones. Carbon nanotubes (CNTs) have been regarded as a promising class of electron field emitters since the 1990s and have promoted the development of FE technology greatly because of their high electrical and thermal conductivity, chemical stability, high aspect ratio and small size. Recent studies have shown that FE from CNTs has the potential to replace conventional thermionic emission in many areas and that it exhibits advanced features in practical applications. Consequently, FE from nanotubes and applications thereof have attracted much attention. This paper provides a comprehensive review of both recent advances in CNT field emitters and issues related to applications of CNT based FE. FE theories and principles are introduced, and the early development of field emitters is related. CNT emitter types and their FE performance are discussed. The current situation for applications based on nanotube FE is reviewed. Although challenges remain, the tremendous progress made in CNT FE over the past ten years indicates the field's development potential.

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

    PubMed

    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.

  11. Electron field emission from undoped and doped DLC films

    SciTech Connect

    Chakhovskoi, A G; Evtukh, A A; Felter, T E; Klyui, N I; Kudzinovsky, S Y; Litovchenko, V G; Litvin, Y M

    1999-06-01

    Electron field emission and electrical conductivity of undoped and nitrogen doped DLC films have been investigated. The films were grown by the PE CVD method from CH{sub 4}:H{sub 2} and CH{sub 4}:H{sub 2}:N{sub 2} gas mixtures, respectively. By varying nitrogen content in the gas mixture over the range 0 to 45%, corresponding concentrations of 0 to 8 % (atomic) could be achieved in the films. Three different gas pressures were used in the deposition chamber: 0.2, 0.6 and 0.8 Torr. Emission current measurements were performed at approximately 10{sup -6} Torr using the diode method with emitter-anode spacing set at 20 {micro}m. The current - voltage characteristics of the Si field electron emission arrays covered with DLC films show that threshold voltage (V{sub th}) varies in a complex manner with nitrogen content. As a function of nitrogen content, V{sub th} initially increases rapidly, then decreases and finally increases again for the highest concentration. Corresponding Fowler-Nordheim (F-N) plots follow F-N tunneling over a wide range. The F-N plots were used for determination of the work function, threshold voltage, field enhancement factor and effective emission area. For a qualitative explanation of experimental results, we treat the DLC film as a diamond-like (sp{sup 3} bonded) matrix with graphite-like inclusions.

  12. Pilot study to reduce emissions, improve health, and offset BC emissions through the distribution of improved cook stoves in Nepal

    NASA Astrophysics Data System (ADS)

    Banmali Pradhan, B.; Panday, A. K.; Surapipith, V.

    2013-12-01

    In most developing countries, wood and other biomass fuels are still the primary source of energy for the majority of the people, particularly the poor. It is estimated that cook stoves account for approximately 20% of global black carbon emissions. In Nepal 87% of energy is supplied from traditional biomass and 75% of households still depend on biomass as a cooking fuel. The substitution of traditional cook stoves with improved cook stoves provides an important way to reduce black carbon emissions. In 2013 the International Centre for Integrated Mountain Development (ICIMOD) has commenced a pilot study that both examines ways to effectively disseminate improved cookstoves across remote rural mountain regions, and also quantifies the resulting changes in emissions, air quality and health. The selected study area is in Bajrabarahi Village in Makawanpur district, to the southwest of Kathmandu. The study area consists of around 1600 households, which are divided into control groups and groups where the cook stove intervention is taking place. The study complements the ';Clean Cooking energy solution for all by 2017' announced by the Government of Nepal recently, and will provide insights to the government on ways to effectively reduce black carbon emissions from cook stoves. To make the study robust and sustainable, local women's group and a local medical institution are involved in the project right from the conceptualization stage. The study region has been chosen in part because the medical school Patan Academy of Health Sciences (PAHS) has already started a long term health assessment in the region, and has built up considerable local contacts. The local women's group is working on the modality of cook stove distribution through micro credit programmes in the village. We will distribute the best available manufactured, fan-assisted cook stoves that are expected to reduce BC emissions the most. Health assessments, emissions estimates, as well as measurements of

  13. Characterisation of carbon nanotube pastes for field emission using their sheet resistances

    NASA Astrophysics Data System (ADS)

    Floweri, Octia; Kim, Jihan; Seo, Yongho; Park, Jun-Young; Lee, Naesung

    2015-10-01

    Carbon nanotube (CNT) pastes for field emitters were fabricated by varying the milling speed, CNT amount and glass frit (GF) powder size. The CNTs remained agglomerated at lower milling speeds while they were damaged and shortened at higher speeds. Increasing the amount of CNTs improved the field emission properties, but excessive CNTs led to increased removal of the CNT paste with surface activation because of lower cohesion strength. Small GF particles were incorporated to provide a flat surface to the CNT paste, which improved its field emission uniformity and lifespan. The dispersion, density and milling damage characteristics of CNTs in the pastes were assessed by their sheet resistances under the assumption of equal printed thicknesses. Tape activation reduced the thickness of the CNT pastes by different amounts that depended on the cohesion strength of the paste. This reduction caused the sheet resistance to increase. For all cases in this study, the field emission properties of the CNT pastes were closely related to their sheet resistances, suggesting that sheet resistance could be used as a figure-of-merit for the evaluation of CNT pastes for field emission applications.

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

    SciTech Connect

    Jensen, Kevin L.; Shiffler, Donald A.; Tang, Wilkin; Rittersdorf, Ian M.; Lebowitz, Joel L.; Harris, John R.; Lau, Y. Y.; Petillo, John J.; Luginsland, John W.

    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.

  15. Field emission from single-crystalline HfC nanowires

    SciTech Connect

    Yuan, Jinshi; Tang, Jie; Zhang Han; Shinya, Norio; Nakajima, Kiyomi; Qin, Lu-Chang

    2012-03-12

    Single HfC nanowire field emitter/electrode structures have been fabricated using nano-assembling and electron beam induced deposition. Field ion microscopy has been applied to study the atomic arrangement of facets formed on a field evaporation-modified HfC nanowire tip. Field evaporation and crystal form studies suggest that the {l_brace}111{r_brace} and {l_brace}110{r_brace} crystal planes have lower work functions, while the {l_brace}100{r_brace}, {l_brace}210{r_brace}, and {l_brace}311{r_brace} planes have higher work functions. Field emission measurement permits us to obtain that the work function of the {l_brace}111{r_brace} crystal plane is about 3.4 eV.

  16. FIELD MEASUREMENT OF GREENHOUSE GAS EMISSION RATES AND DEVELOPMENT OF EMISSION FACTORS FOR WASTEWATER TREATMENT

    EPA Science Inventory

    The report gives results of field testing to develop more reliable green house gas (GHG) emission estimates for Wastewater treatment (WWT) lagoons. (NOTE: Estimates are available for the amount of methane (CH4) emitted from certain types of waste facilities, but there is not adeq...

  17. FIELD EVALUATION OF LOW-EMISSION COAL BURNER TECHNOLOGY ON UTILITY BOILERS VOLUME III. FIELD EVALUATIONS

    EPA Science Inventory

    The report gives results of field tests conducted to determine the emission characteristics of a Babcock and Wilcox Circular burner and Dual Register burner (DRB). The field tests were performed at two utility boilers, generally comparable in design and size except for the burner...

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

    SciTech Connect

    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.

  19. Magnetic field annealing for improved creep resistance

    DOEpatents

    Brady, Michael P.; Ludtka, Gail M.; Ludtka, Gerard M.; Muralidharan, Govindarajan; Nicholson, Don M.; Rios, Orlando; Yamamoto, Yukinori

    2015-12-22

    The method provides heat-resistant chromia- or alumina-forming Fe-, Fe(Ni), Ni(Fe), or Ni-based alloys having improved creep resistance. A precursor is provided containing preselected constituents of a chromia- or alumina-forming Fe-, Fe(Ni), Ni(Fe), or Ni-based alloy, at least one of the constituents for forming a nanoscale precipitate MaXb where M is Cr, Nb, Ti, V, Zr, or Hf, individually and in combination, and X is C, N, O, B, individually and in combination, a=1 to 23 and b=1 to 6. The precursor is annealed at a temperature of 1000-1500.degree. C. for 1-48 h in the presence of a magnetic field of at least 5 Tesla to enhance supersaturation of the M.sub.aX.sub.b constituents in the annealed precursor. This forms nanoscale M.sub.aX.sub.b precipitates for improved creep resistance when the alloy is used at service temperatures of 500-1000.degree. C. Alloys having improved creep resistance are also disclosed.

  20. Groundwater impact on methane emissions from flooded paddy fields

    NASA Astrophysics Data System (ADS)

    Rizzo, A.; Boano, F.; Revelli, R.; Ridolfi, L.

    2015-09-01

    High methane (CH4) fluxes emitted from paddy fields strongly contribute to the accumulation of greenhouse gases into the atmosphere, compromising the eco-compatibility of one of the most important world foods. A strong link exists between infiltration rates of irrigation water and CH4 emissions. Since depth to the groundwater table affects infiltration rates, a relevant groundwater impact is expected on CH4 emissions from paddy fields. In this work, a theoretical approach is adopted to investigate the aquifer effect on CH4 dynamics in paddies. Infiltration rates are strongly affected by the development of different connection states between aquifer and irrigation ponded water. A strong reduction in infiltration rates results from a water table near to the soil surface, when the system is hydraulically connected. When the groundwater level increases, the infiltration rate reduction due to the switch from disconnected to connected state promotes a relevant increase of CH4 emissions. This is due to a strong reduction of dissolved organic carbon (DOC) percolation, which leads to higher DOC availability for microbial CH4 production and, consequently, higher CH4 emissions. Our simulations show that CH4 fluxes can be reduced by up to 24% when groundwater level is decreased and the aquifer is disconnected from ponding water. In paddies with shallow aquifers, lowering the water table with a drainage system could thus represent a promising CH4 mitigation option.

  1. Multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, John P.; Friedmann, Thomas A.

    1998-01-01

    A multi-layer resistive carbon film field emitter device for cold cathode field emission applications. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced.

  2. Multi-layer carbon-based coatings for field emission

    DOEpatents

    Sullivan, J.P.; Friedmann, T.A.

    1998-10-13

    A multi-layer resistive carbon film field emitter device for cold cathode field emission applications is disclosed. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. 8 figs.

  3. Field emission of electrons from cylindrical metallic surfaces

    NASA Astrophysics Data System (ADS)

    Sodha, Mahendra Singh; Dixit, Amrit

    2008-10-01

    In this communication the authors have derived an almost exact expression for the tunneling probability of an electron through the surface potential barrier on account of a negative charge on a cylindrical metallic dust particle and have used it to obtain the field emission current density from the surface of the particle. Based on these results, a parametric analysis of the phenomenon and comparison to the results of JWKB approximation (similar to Fowler-Nordheim theory) has been presented. These results are also applicable to a number of applications based on electric field emission from a thin metallic wire surrounded by a coaxial cylindrical surface at a high electric potential with respect to the wire. The investigation is of relevance to dusty plasmas in space and laboratory and carbon nanotubes.

  4. AC Magnetic Field Frequency Dependence of Magnetoacoustic Emission

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Wincheski, B.; Fulton, J. P.; DeNale, R.

    1992-01-01

    Our recent study has proved a strong correlation between the low-frequency AC applied magnetic field amplitude dependence of the asymmetry of the magnetoacoustic emission (MAE) burst and the strength of the domain wall-defect interaction in iron-base ferromagnets. For the present study the AC magnetic field frequency dependence of the asymmetry has been investigated in the range of 1 to 200 Hz. When represented by the third moment of the rectified acoustic emission pulses, the asymmetry becomes a bell-shaped function of frequency with its center located around 25 Hz. This experiment has been performed with low carbon, high yield stress steel specimens of three different levels of domain wall-defect interaction strength. The results show that the increase in the interaction strength causes a vertical down shift of the asymmetry in the entire frequency range investigated.

  5. Influence of charge deposition in a field-emission display panel

    NASA Astrophysics Data System (ADS)

    Wei, Lei; Zhang, Xiaobing; Lou, Chaogang; Zhu, ZuoYa

    2008-01-01

    Field-emission displays (FEDs) have been studied intensively in recent years as a candidate for flat-display panels in the future. In a FED, electrons emit from field emitters. Some electrons may impinge on the insulator surface between cathode and gate electrodes and cause charging of that surface because the yield of secondary electron emission is usually not equal to one. The charging of the insulator walls between cathode and gate electrodes is one of the important factors influencing the performance of a FED. In this paper, a simulation program is used to calculate this charge deposition, electric field distribution and electron trajectories. From the change of the electric field upon charge deposition in the triode region, it is shown that the insulator surface is negatively charged at a low gate voltage, e.g. 20 V. However, positive charge is deposited when the gate voltage is high, e.g. 100 V. The simulations also show that the emission current will increase even further after coating the dielectric with a thin film of a material with a high-secondary emission coefficient such as MgO. If a cone-shaped dielectric aperture is used in a triode, the emission current will decrease after charge deposition. However, the focus performance of the electron beam is improving in this case.

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

    NASA Astrophysics Data System (ADS)

    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).

  7. Hydrocarbon emissions in the Bakken oil field in North Dakota

    NASA Astrophysics Data System (ADS)

    Mielke-Maday, I.; Petron, G.; Miller, B.; Frost, G. J.; Peischl, J.; Kort, E. A.; Smith, M. L.; Karion, A.; Dlugokencky, E. J.; Montzka, S. A.; Sweeney, C.; Ryerson, T. B.; Tans, P. P.; Schnell, R. C.

    2014-12-01

    Within the past five years, the production of oil and natural gas in the United States from tight formations has increased rapidly due to advances in technology, such as horizontal drilling and hydraulic fracturing. With the expansion of oil and natural gas extraction operations comes the need to better quantify their emissions and potential impacts on climate forcing and air quality. The Bakken formation within the Williston Basin in North Dakota has emerged as a large contributor to the recent growth in oil production and accounts for over 10% of domestic production. Close to 30% of associated gas co-produced with the oil is flared. Very little independent information is currently available to assess the oil and gas industry emissions and their impacts on regional air quality. In May 2014, an airborne field campaign was conducted by the National Oceanic and Atmospheric Administration's (NOAA) Earth System Research Laboratory and the University of Michigan to investigate hydrocarbon emissions from operations in the oil field. Here, we present results from the analysis for methane, several non-methane hydrocarbons and combustion tracers in 72 discrete air samples collected by the aircraft on nine different flights. Samples were obtained in the boundary layer upwind and downwind of the operations and in the free troposphere. We will show results of a multiple species analysis and compare them with field campaign data from other U.S. oil and gas fields, measurements from NOAA's Global Monitoring Division long-term observing network, and available bottom-up information on emissions from oil and gas operations.

  8. Peculiarities of the Field Electron Emission from Dust Grains

    SciTech Connect

    Richterova, I.; Beranek, M.; Pavlu, J.; Nemecek, Z.; Safrankova, J.

    2008-09-07

    The goal of the paper is investigation of the electron field emission that limits the attainable grain charge and can prevent electrostatic fragmentation of loosely bounded aggregates of dust grains. We have found that the effective work function of the spherical amorphous carbon grains does not depend on the relative beam energy. Preliminary results on an influence of the ion treatment/cleaning using the simultaneous electron and ion bombardments are discussed.

  9. Very stable electron field emission from strontium titanate coated carbon nanotube matrices with low emission thresholds.

    PubMed

    Pandey, Archana; Prasad, Abhishek; Moscatello, Jason P; Engelhard, Mark; Wang, Chongmin; Yap, Yoke Khin

    2013-01-22

    Novel PMMA-STO-CNT matrices were created by opened-tip vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) with conformal coatings of strontium titanate (STO) and poly(methyl methacrylate) (PMMA). Emission threshold of 0.8 V/μm was demonstrated, about 5-fold lower than that of the as-grown VA-MWCNTs. This was obtained after considering the related band structures under the perspective of work functions and tunneling width as a function of the STO thickness. We showed that there is an optimum thickness of STO coatings to effectively reduce the work function of CNTs and yet minimize the tunneling width for electron emissions. Furthermore, simulation and modeling suggest that PMMA-STO-CNT matrices have suppressed screening effects and Coulombs' repulsion forces between electrons in adjacent CNTs, leading to low emission threshold, high emission density, and prolonged emission stability. These findings are important for practical application of VA-MWCNTs in field emission devices, X-ray generation, and wave amplification.

  10. Semi-shunt field emission in electronic devices

    SciTech Connect

    Karpov, V. G.; Shvydka, Diana

    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.

  11. Synthesis and field emission properties of Cu dendritic nanostructures

    NASA Astrophysics Data System (ADS)

    Xu, Jianwen; Yu, Ke; Zhu, Ziqiang

    2010-03-01

    Cu dendritic nanostructures were synthesized on ITO glass substructure by electrochemical deposition. SEM images showed that these Cu dendritic nanostuctures revealed a clear and well-defined dendritic fractal structure with a pronounced trunk and highly ordered branches distributed on both sides of the trunk. The diffusion-limited aggregation (DLA) model was used to explain the fractal growth of Cu dendritic nanostructures. Field emission properties of these Cu dendritic nanostructures were measured, which have possessed good performance with the turn-on field of 7.5 V/μm (defined as the electric field required to be detected at a current density of 0.1 mA/cm 2) and the field enhancement factor β of 1094.

  12. Electron field emission from nanostructured cubic boron nitride islands

    SciTech Connect

    Teii, Kungen; Matsumoto, Seiichiro; Robertson, John

    2008-01-07

    Nanocrystal-assembled cubic boron nitride (cBN) islands are formed by using low-energy ({approx}20 eV) ion irradiation in an inductively coupled fluorine-containing plasma. The temporal evolution of surface morphology and roughness reveals three-dimensional island growth for initial sp{sup 2}-bonded BN and subsequent cBN, accompanied by a high frequency of renucleation. The formation of cBN islands enhances the field emission and reduces the turn-on field down to around 9 V/{mu}m due to an increase in the island-related field. The results demonstrate the high potential of cBN for field emitters, comparable to other wide band gap semiconductors.

  13. Emissive limiter bias experiment for improved confinement of tokamaks

    SciTech Connect

    Choe, W.; Ono, M.; Darrow, D.S.; Pribyl, P.A.; Liberati, J.R.; Taylor, R.J.

    1992-10-01

    Experiments have been performed in Ohmic discharges of the UCLA CCT tokamak with a LaB{sub 6} biased limiter, capable of emitting energetic electrons as a technique to improve confinement in tokamaks. To study the effects of emitted electrons, the limiter position, bias voltage, and plasma position were varied. The results have shown that the plasma positioning with respect to the emissive limiter plays an important role in obtaining H-mode plasmas. The emissive cathode must be located close to the last closed flux surface in order to charge up the plasma. As the cathode is moved closer to the wall, the positioning of the plasma becomes more critical since the plasma can easily detach from the cathode and reattach to the wall, resulting in the termination of H-mode. The emissive capability appears to be important for operating at lower bias voltage and reducing impurity levels in the plasma. With a heated cathode, transition to H-mode was observed for V{sub bias} {le} 50 V and I{sub inj} {ge} 30 A. At a lower cathode heater current, a higher bias voltage is required for the transition. Moreover, with a lower cathode heater current, the time delay for inducing H-mode becomes longer, which can be attributed to the required time for the self-heating of the cathode to reach the emissive temperature. From this result, we conclude that the capacity for emission can significantly improve the performance of limiter biasing for inducing H-mode transition. With L-mode plasmas, the injection current flowing out of the cathode was generally higher than 100 A.

  14. Fabrication and field emission properties of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Peng

    Research on the area of the fabrication of carbon nanotubes is fundamental and critical to the entire subject of carbon nanotubes. This dissertation describes an experiment to fabricate carbon nanotubes by the method of Microwave Plasma Enhanced Chemical Vapor Deposition (MPECVD) and the electron field emission properties of carbon nanotubes. A MPECVD system was built and used to fabricate the vertical aligned carbon nanotube film. Scanning electron microscope (SEM), Raman spectroscopy and transmission electron microscopy (TEM) were used to characterize the as-grown carbon nanotube samples. By using a metal-containing diblock copolymer catalyst, carbon nanotubes with a diameter of 4 to 7 nm were synthesized. The effect of growth parameters was studied and these parameters were optimized. The growth of high density (˜ 109/cm2) and large coverage area (˜ 1 cm2) carbon nanotube film on glass substrate at low growth temperature was realized. Based on a series of experiments, the effects of oxygen atoms and Ti/N underlayer on the growth were studied. A series of experiments were evaluated to characterize the field emission properties of the various carbon nanotube cathodes. A simple technique of scratching the pattern surface by a cotton swab was found effective to activate more carbon nanotubes to emit. By using the techniques of photolithography and shadow mask, various carbon nanotube patterns were achieved in order to obtain high emission current density and a low threshold electric field. The lowest threshold electric field was found to be 2.3 V/um. The highest current density was found to be 2.2 mA/cm2 when the electric field was 4.7 V/um. Our work shows that it is feasible to provide greater control over the fabrication of carbon nanotubes so that more obstacles in the broad application of carbon nanotubes can be overcome.

  15. China's CO and CO2 emissions estimated from the bottom up: Recent trends, uncertainties, and implications of improved energy efficiency and emission control

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Nielsen, C.; McElroy, M. B.

    2012-12-01

    China's emissions of anthropogenic CO and CO2 from 2005 to 2010 are estimated using a bottom-up emission inventory framework based on a detailed categorization of economic sectors and provincial economic and energy data. It includes a newly compiled database of emission factors employing the latest field study results from China. The CO emission factors for major sectors declined to varying degrees for the past years, attributed to improved energy efficiency and/or emission control regulations. The national CO emissions are estimated at 173 Tg for 2005 and have been relatively stable for subsequent years, despite fast growth of energy consumption and industrial production. While industry and transportation dominated CO emissions in developed eastern and north-central China, residential combustion played a greater role in the less developed western provinces. Total CO2 emissions are estimated to have risen from 7126 to 10152 Tg from 2005 to 2010. Recent policies to conserve energy and reduce emissions have been effective in limiting CO2 emissions from power and iron & steel plants, but have had little effect on those from cement production. The uncertainties of China's CO and CO2 emissions are quantified for the first time using Monte Carlo simulation, producing the 95% confidence intervals of -20% to +45% and -9% to +11% for emissions in 2005, respectively. Due to poor understanding of emission factors and activity levels for combustion of solid fuels, the largest uncertainties are found for emissions from the residential sector. Emission factors are identified as the most important parameters contributing to the uncertainties of CO emissions for all the sectors, while the largest contributors to uncertainties of CO2 are emission factors for most industrial sources and activity levels for power plants, transportation, and residential sources. The trends of bottom-up emissions compare reasonably to ground observations of CO2-CO correlation slopes, as shown in Table

  16. A thin film triode type carbon nanotube field emission cathode

    NASA Astrophysics Data System (ADS)

    Sanborn, Graham; Turano, Stephan; Collins, Peter; Ready, W. Jud

    2013-01-01

    The field electron emission of carbon nanotubes has been heavily studied over the past two decades for various applications, such as in display technologies, microwave amplifiers, and spacecraft propulsion. However, a commercializable lightweight and internally gated electron source has yet to be realized. This work presents the fabrication and testing of a novel internally gated carbon nanotube field electron emitter. Several specific methods are used to prevent electrical shorting of the gate layer, a common failure for internally gated devices. A unique design is explored where the etch pits extend into the silicon substrate and isotropic etching is used to create a lateral buffer zone between the gate and carbon nanotubes. Carbon nanotubes are self-aligned to and within 10 microns from the gate, which creates large electric fields at low potential inputs. Initial tests confirm high field emission performance with an anode current density (based on total area of the device) of 293 μA cm-2 and a gate current density of 1.68 mA cm-2 at 250 V.

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

    PubMed

    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.

  18. Improved Estimates of Air Pollutant Emissions from Biorefinery

    SciTech Connect

    Tan, Eric C. D.

    2015-11-13

    We have attempted to use detailed kinetic modeling approach for improved estimation of combustion air pollutant emissions from biorefinery. We have developed a preliminary detailed reaction mechanism for biomass combustion. Lignin is the only biomass component included in the current mechanism and methane is used as the biogas surrogate. The model is capable of predicting the combustion emissions of greenhouse gases (CO2, N2O, CH4) and criteria air pollutants (NO, NO2, CO). The results are yet to be compared with the experimental data. The current model is still in its early stages of development. Given the acknowledged complexity of biomass oxidation, as well as the components in the feed to the combustor, obviously the modeling approach and the chemistry set discussed here may undergo revision, extension, and further validation in the future.

  19. Experimental investigations of hard photon emission from strong crystalline fields

    NASA Astrophysics Data System (ADS)

    Medenwaldt, R.; Møller, S. P.; Jensen, B. N.; Strakhovenko, V. M.; Uggerhøj, E.; Worm, T.; Elsener, K.; Sona, P.; Connell, S. H.; Sellschop, J. P. F.; Avakian, R. O.; Avetisian, A. E.; Taroian, S. P.

    1992-05-01

    For the first time very pronounced high-energy photon peaks have been measured in the radiation emission from 70, 150 and 240 GeV electrons incident at 0.1-1.0 mrad to the axis in diamond and Si crystals. The energy of the photons in the peaks is 0.7-0.8 times the particle energy with yields of 50 times the Bethe-Heitler one (in diamond). The peaks consist of single photons and are caused by the influence of strong crystalline fields on emission of coherent bremsstrahlung, emitted when the ultrarelativistic electrons cross the rows of atoms in a crystal plane. The effect should be envisaged as a source for nearly monoenergetic photons in the multihundred GeV-region.

  20. Molecular dynamics simulations of field emission from a planar nanodiode

    SciTech Connect

    Torfason, Kristinn; Valfells, Agust; Manolescu, Andrei

    2015-03-15

    High resolution molecular dynamics simulations with full Coulomb interactions of electrons are used to investigate field emission in planar nanodiodes. The effects of space-charge and emitter radius are examined and compared to previous results concerning transition from Fowler-Nordheim to Child-Langmuir current [Y. Y. Lau, Y. Liu, and R. K. Parker, Phys. Plasmas 1, 2082 (1994) and Y. Feng and J. P. Verboncoeur, Phys. Plasmas 13, 073105 (2006)]. The Fowler-Nordheim law is used to determine the current density injected into the system and the Metropolis-Hastings algorithm to find a favourable point of emission on the emitter surface. A simple fluid like model is also developed and its results are in qualitative agreement with the simulations.

  1. Neutrino emissivity from electron-positron annihilation in hot matter in a strong magnetic field

    SciTech Connect

    Amsterdamski, P.; Haensel, P. )

    1990-10-15

    The neutrino emissivity due to electron-positron annihilation in a strong magnetic field is computed. A strong magnetic field can significantly increase the neutrino emissivity at {ital T}{similar to}10{sup 9} K.

  2. Nanowire-density-dependent field emission of n-type 3C-SiC nanoarrays

    SciTech Connect

    Wang, Lin; Gao, Fengmei; Chen, Shanliang; Yang, Weiyou; Li, Chengming

    2015-09-21

    The density of the nanowires is one of the key issues for their field emission (FE) properties of the nanoarrays, since it plays an important role on the electron emission sites and field screening effect. Here, we reported the nanowire-density-dependent FE properties of the n-type 3C-SiC nanoarrays. The highly oriented and large-scale SiC nanoarrays were grown on the 6H-SiC wafer via pyrolysis of polyureasilazane by adjusting the thicknesses of Au films used as the catalysts. The densities of the nanoarrays were tunable to be ∼2.9 × 10{sup 7}, ∼4.0 × 10{sup 7}, and ∼5.7 × 10{sup 7} nanowires/cm{sup 2} by controlling the Au film thicknesses of 50, 70, and 90 nm, respectively. The measured FE characteristics disclosed that the turn-on fields of the samples could be tailored to be of ∼1.79, 1.57, and 1.95 V/μm with the increase of the densities, suggesting that a suitable nanowire density could favor the enhanced electron emission from the SiC nanoarrays with improved emission sites and limited field screening effects.

  3. Field-emission properties of sulphur doped nanocrystalline diamonds

    NASA Astrophysics Data System (ADS)

    Baranauskas, V.; Sampaio, M. A.; Peterlevitz, A. C.; Ceragioli, H. J.; Quispe, J. C. R.

    2007-03-01

    Nanostructured diamond doped with sulphur has been prepared using a hot-filament assisted chemical vapour deposition system fed with an ethyl alcohol, carbon disulfide, hydrogen, and argon mixture. The reduction of diamond grains to the nanoscale is relevant to create a network of defective grain boundaries which may be n-type doped to facilitate the transport and injection of electrons to the diamond grains located at the vacuum interface, enhancing the electron field-emission properties of the samples. The downsizing was produced by secondary nucleation and defects induced by sulphur and argon atoms in the chemical vapour deposition surface reactions. Sulphur also acts as an n-type dopant of diamond. Raman measurements show that the samples are nanodiamonds embedded in a matrix of graphite and disordered carbon grains and the morphology, revealed by field electron scanning microscopy, shows that the grains are in the range of 10 to 30 nm. The lowest threshold achieved for field emission was 13.20 V/μm.

  4. Field emission energy distributions from individual multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Fransen, M. J.; van Rooy, Th. L.; Kruit, P.

    1999-05-01

    We measured field emission energy distributions of electrons emitted from individual multiwalled carbon nanotubes mounted on tungsten tips. The shape of the energy distribution is strongly sample dependent. Some nanotube emitters exhibit an almost metallic behaviour, while others show sharply peaked energy distributions. The smallest half-width we measured was only 0.11 eV, without correction for the broadening of the energy analyzer. A common feature of both types of carbon nanotube energy spectra is that the position of the peaks in the spectrum depends linearly on the extraction voltage, unlike metallic emitters, where the position stays in the vicinity of the Fermi level. With a small modification to the field emission theory for metals we extract the distance between the highest filled energy level of the nanotube and the vacuum potential, the field on the emitter surface, the emitter radius and the emitting area, from the energy distribution and the Fowler-Nordheim plot. The last two parameters are in good agreement with transmission electron micrographs of such samples. The sharply-peaked energy distributions from other samples indicate that resonant states can exist at the top of the nanotube.

  5. Cesiated thin-film field-emission microcathode arrays

    NASA Astrophysics Data System (ADS)

    Macaulay, J. M.; Brodie, I.; Spindt, C. A.; Holland, C. E.

    1992-08-01

    The effect of adsorbed cesium on the performance of thin-film field-emission microcathode arrays with molybdenum tips is discussed. A reduction in the voltage required to extract an average of 1 nA per tip from 50 to 15 V is reported. Cesiated arrays have exhibited stable performance when operated continuously for up to 650 h at array current densities up to 100 A/cm2, with minimal leakage current. Using the Fowler-Nordheim theory, analysis of current-voltage characteristics of a heavily cesiated emitter array gives values for the emitting area, work function, and geometrical factor.

  6. Polarization oscillations of near-field thermal emission.

    PubMed

    Machida, Manabu; Narimanov, Evgenii; Schotland, John C

    2016-06-01

    We consider the polarization of thermal emission in the near field of various materials, including dielectrics and metallic systems with resonant surface modes. We find that, at thermal equilibrium, the degree of polarization exhibits spatial oscillations with a period of approximately half the optical wavelength, independent of material composition. This result contrasts with that of Setala et al. [Phys. Rev. Lett.88, 123902 (2002)PRLTAO0031-900710.1103/PhysRevLett.88.123902], who find monotonic decay of the degree of polarization for systems in local thermal equilibrium. PMID:27409433

  7. Improved accounting of emissions from utility energy storage system operation

    SciTech Connect

    Paul Denholm; Tracey Holloway

    2005-12-01

    Several proposed utility-scale energy storage systems in the U.S. will use the spare output capacity of existing electric power systems to create the equivalent of new load-following plants that can rapidly respond to fluctuations in electricity demand and increase the flexibility of baseload generators. New energy storage systems using additional generation from existing plants can directly compete with new traditional sources of load-following and peaking electricity, yet this application of energy storage is not required to meet many of the Clean Air Act standards required of new electricity generators (e.g., coal- or gas-fired power plants). This study evaluates the total emissions that will likely result from the operation of a new energy storage facility when coupled with an average existing U.S. coal-fired power plant and estimates that the emission rates of SO{sub 2} and NOx will be considerably higher than the rate of a new plant meeting Clean Air Act standards, even accounting for the efficiency benefits of energy storage. This study suggests that improved emissions 'accounting' might be necessary to provide accurate environmental comparisons between energy storage and more traditional sources of electricity generation. 35 refs., 5 figs., 2 tabs.

  8. Improved accounting of emissions from utility energy storage system operation.

    PubMed

    Denholm, Paul; Holloway, Tracey

    2005-12-01

    Several proposed utility-scale energy storage systems in the U.S. will use the spare output capacity of existing electric power systems to create the equivalent of new load-following plants that can rapidly respond to fluctuations in electricity demand and increase the flexibility of baseload generators. New energy storage systems using additional generation from existing plants can directly compete with new traditional sources of load-following and peaking electricity, yet this application of energy storage is not required to meet many of the Clean Air Act standards required of new electricity generators (e.g., coal- or gas-fired power plants). This study evaluates the total emissions that will likely result from the operation of a new energy storage facility when coupled with an average existing U.S. coal-fired power plant and estimates that the emission rates of SO2 and NOx will be considerably higher than the rate of a new plant meeting Clean Air Act standards, even accounting for the efficiency benefits of energy storage. This study suggests that improved emissions "accounting" might be necessary to provide accurate environmental comparisons between energy storage and more traditional sources of electricity generation.

  9. The quantum mechanics of ion-enhanced field emission and how it influences microscale gas breakdown

    SciTech Connect

    Li, Yingjie; Go, David B.

    2014-09-14

    The presence of a positive gas ion can enhance cold electron field emission by deforming the potential barrier and increasing the tunneling probability of electrons—a process known as ion-enhanced field emission. In microscale gas discharges, ion-enhanced field emission produces additional emission from the cathode and effectively reduces the voltage required to breakdown a gaseous medium at the microscale (<10 μm). In this work, we enhance classic field emission theory by determining the impact of a gaseous ion on electron tunneling and compute the effect of ion-enhanced field emission on the breakdown voltage. We reveal that the current density for ion-enhanced field emission retains the same scaling as vacuum cold field emission and that this leads to deviations from traditional breakdown theory at microscale dimensions.

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

    NASA Astrophysics Data System (ADS)

    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

  11. Electron emission and fragmentation of molecules in intense laser fields

    NASA Astrophysics Data System (ADS)

    Ueda, K.; Prümper, G.; Hatamoto, T.; Okunishi, M.; Mathur, D.

    2007-06-01

    We have constructed an apparatus for high-resolution electron spectroscopy and electron-ion coincidence experiments on gas-phase molecules in intense laser fields. The apparatus comprises an electron time-of-flight (TOF) spectrometer and an ion TOF spectrometer with a position detector, placed on either side of an effusive molecular beam. The ionizing radiation is either the fundamental (800 nm wavelength) of a Ti:sapphire laser or frequency doubled 400-nm light, with pulse durations of ~ 150 fs and the repetition rate of 1 kHz. We have investigated the electron emission and fragmentation of linear alcohol molecules, methanol, ethanol and 1-propanol, in laser fields with peak intensities up to ~ 1×10 14 W/cm2. Details of our apparatus are described along with an overview of some recent results.

  12. Techniques To Improve Subharmonic Emission From Encapsulated Microbubbles

    NASA Astrophysics Data System (ADS)

    Xi, Dong Zhang Xiaoyu; Gong, Yanjun; Gong, Xiufen

    2008-06-01

    Subharmonic contrast imaging promises to improve ultrasound imaging quality by taking advantage of increased contrast to tissue signal. However, acoustic pressures beyond the subharmonic generation threshold using common ultrasound pulses may induce significant contrast microbubble destruction. In this work, we propose two techniques to improve the subharmonic emission from encapsulated microbubbles, i.e. chirp excitation technique and dual-frequency excitation techniques. For the first technique, chirp signals with center frequency 5 MHz are employed to drive microbubbles in numerical simulation and experimental studies. For the second technique, both theoretical simulation and experimental verification are also presented. The simulation uses a modified mathematical model developed by Church and experimental work uses microbubbles sonicated by dual frequencies (2 MHz and 4 MHz) superimposed to simulate a truncated saw-tooth wave.

  13. Development of an improved positron emission particle tracking system

    NASA Astrophysics Data System (ADS)

    Stellema, C. S.; Vlek, J.; Mudde, R. F.; de Goeij, J. J. M.; van den Bleek, C. M.

    1998-02-01

    An improved Positron Emission Particle Tracking (PEPT) system has been developed for the non-intrusive investigation of solids flow in a gas-solids Interconnected Fluidised Bed (IFB) reactor. This system tracks continuously the 3D location of a single positron emitting particle. This particle has the same size and density as the solids and can be made as small as 500 μm. The system performance was improved through the use of graded absorbers which enable to filter valuable information from the Compton spectrum. A radiotracer particle moving at 1 m s -1 can be located with a 3D resolution better than 15 mm in a continuous trajectory. For a velocity of 0.1 m s -1 the 3D resolution is better than 5 mm. The obtained results are presented through ensemble-averaged solids' velocity patterns.

  14. Preequilibrium neutron emission in heavy ion reaction: Mean field effect and multiple emission

    NASA Astrophysics Data System (ADS)

    Paul, Sabyasachi; Nandy, Maitreyee; Mohanty, A. K.; Gambhir, Y. K.

    2016-09-01

    Effects of nuclear mean field and of multiple preequilibrium (PEQ) emission on double differential neutron multiplicity distribution from heavy ion reactions (12C+165Ho and 20Ne+165Ho ) at 10-30 MeV/u have been investigated in the framework of the semiclassical formalism for heavy ion reaction (henceforth termed "HION") developed earlier. HION follows the equilibration of a target+projectile composite system through the kinematics of two-body scattering. In the present work nuclear density distribution in the composite system is estimated in the relativistic mean field (RMF) approach. The nucleon-nucleon collision rates and subsequently the nucleon emission probability are calculated from this density distribution. A second approach based on a semiphenomenological formalism is also used for nuclear density distribution. Energy-angle distribution of neutron multiplicities calculated with this modified HION model coupled with multiple PEQ emission could reproduce the measured data of earlier workers in the projectile energy range of 10-30 MeV/u.

  15. Development of tomographic imaging systems using carbon-nanotube-based field-emission x-ray sources

    NASA Astrophysics Data System (ADS)

    Zhang, Jian

    2005-11-01

    Conventional thermionic x-ray sources use hot filament cathodes to generate electrons for x-ray production. The thermionic technology has several inherent limitations such as high operating temperature, slow response time, and difficulty for miniaturization. On the other hand, field emission provides an alternative to generate electrons without all these limitations. The concept of field emission x-ray source has been proposed and tested in the early 1970s. Unfortunately all of the early field emission x-ray systems failed due primarily to the limitations on the electron field emitters. Carbon nanotubes (CNT) have recently emerged as a promising class of electron emissive materials and field emission x-ray source based on CNTs are expected to have significantly improved properties. We have recently developed a CNT-based field emission micro-focus x-ray source. It shows stable tube current under high operating voltage, extraordinary dynamic imaging capability, and excellent potential for miniaturization. All of these new features make it very attractive for various potential industrial and medical applications. In order to demonstrate its applications, two sets of x-ray imaging systems using this field emission x-ray source were constructed in our lab. One is a micro-computed tomographic (micro-CT) imaging system using a single field emission x-ray source for dynamic radiographic and tomographic imaging applications. It shows great potential for the future development of dynamic micro-CT scanner. The other one is a multi-beam field emission x-ray source with multiple addressable focal spots which can provide scanning x-ray beams without mechanical movement. It can lead to fast data acquisition rates for future tomographic imaging systems with a simplified experimental set-up.

  16. Coherent infrared emission from myoglobin crystals: an electric field measurement.

    PubMed

    Groot, Marie-Louise; Vos, Marten H; Schlichting, Ilme; van Mourik, Frank; Joffre, Manuel; Lambry, Jean-Christophe; Martin, Jean-Louis

    2002-02-01

    We introduce coherent infrared emission interferometry as a chi(2) vibrational spectroscopy technique and apply it to studying the initial dynamics upon photoactivation of myoglobin (Mb). By impulsive excitation (using 11-fs pulses) of a Mb crystal, vibrations that couple to the optical excitation are set in motion coherently. Because of the order in the crystal lattice the coherent oscillations of the different proteins in the crystal that are associated with charge motions give rise to a macroscopic burst of directional multi-teraHertz radiation. This radiation can be detected in a phase-sensitive way by heterodyning with a broad-band reference field. In this way both amplitude and phase of the different vibrations can be obtained. We detected radiation in the 1,000-1,500 cm(-1) frequency region, which contains modes sensitive to the structure of the heme macrocycle, as well as peripheral protein modes. Both in carbonmonoxy-Mb and aquomet-Mb we observed emission from six modes, which were assigned to heme vibrations. The phase factors of the modes contributing to the protein electric field show a remarkable consistency, taking on values that indicate that the dipoles are created "emitting" at t = 0, as one would expect for impulsively activated modes. The few deviations from this behavior in Mb-CO we propose are the result of these modes being sensitive to the photodissociation process and severely disrupted by it.

  17. Thermionic field emission in gold nitride Schottky nanodiodes

    NASA Astrophysics Data System (ADS)

    Spyropoulos-Antonakakis, N.; Sarantopoulou, E.; Kollia, Z.; Samardžija, Z.; Kobe, S.; Cefalas, A. C.

    2012-11-01

    We report on the thermionic field emission and charge transport properties of gold nitride nanodomains grown by pulsed laser deposition with a molecular fluorine laser at 157 nm. The nanodomains are sandwiched between the metallic tip of a conductive atomic force microscope and a thin gold layer forming thus a metal-semiconductor-metal junction. Although the limited existing data in the literature indicate that gold nitride was synthesized previously with low efficiency, poor stability, and metallic character; in this work, it is shown that gold nitride nanodomains exhibit semiconducting behavior and the metal-semiconductor-metal contact can be modeled with the back-to-back Schottky barrier model. From the experimental I-V curves, the main charge carrier transport process is found to be thermionic field emission via electron tunneling. The rectifying, near symmetric and asymmetric current response of nanocontacts is related to the effective contact area of the gold nitride nanodomains with the metals. A lower limit for the majority charge carriers concentration at the boundaries of nanodomains is also established using the full depletion approximation, as nanodomains with thickness as low as 6 nm were found to be conductive. Current rectification and charge memory effects are also observed in "quite small" conductive nanodomains (6-10 nm) due to stored charges. Indeed, charges near the surface are identified as inversion domains in the phase shift mapping performed with electrostatic force microscopy and are attributed to charge trapping at the boundaries of the nanodomains.

  18. Field emission property of ZnO nanowires prepared by ultrasonic spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Htay, Myo Than; Hashimoto, Yoshio

    2015-08-01

    The field emission property of cold cathode emitters utilizing the ZnO nanowires with various conditions prepared by ultrasonic spray pyrolysis technique was discussed. It is found that the emission current was enhanced in the emitters having higher aspect ratio as well as smaller sheet resistance. Applying of post-annealing process, utilization of additional Mo back electrode in the cathode, and coating of Mo on the ZnO nanowires resulted in the improvement of the emission current and lowering the threshold voltage. A threshold voltage of about 5.5 V/μm to obtain 1.0 μA/cm2 was achieved in the sample prepared at the growth temperatures varying continuously from 250 °C to 300 °C.

  19. Density functional theory for field emission from carbon nano-structures.

    PubMed

    Li, Zhibing

    2015-12-01

    Electron field emission is understood as a quantum mechanical many-body problem in which an electronic quasi-particle of the emitter is converted into an electron in vacuum. Fundamental concepts of field emission, such as the field enhancement factor, work-function, edge barrier and emission current density, will be investigated, using carbon nanotubes and graphene as examples. A multi-scale algorithm basing on density functional theory is introduced. We will argue that such a first principle approach is necessary and appropriate for field emission of nano-structures, not only for a more accurate quantitative description, but, more importantly, for deeper insight into field emission.

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

    NASA Astrophysics Data System (ADS)

    Chen, Xiangyu; Jiang, Tao; Sun, Zhuo; Ou-Yang, Wei

    2015-09-01

    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 cm2, 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.

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

    SciTech Connect

    Chen, Xiangyu E-mail: ouyangwei@phy.ecnu.edu.cn; Jiang, Tao; Sun, Zhuo; Ou-Yang, Wei E-mail: ouyangwei@phy.ecnu.edu.cn

    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. Field Emission of Wet Transferred Suspended Graphene Fabricated on Interdigitated Electrodes.

    PubMed

    Xu, Ji; Wang, Qilong; Tao, Zhi; Qi, Zhiyang; Zhai, Yusheng; Wu, Shengqi; Zhang, Xiaobing; Lei, Wei

    2016-02-10

    Suspended graphene (SG) membranes could enable strain-engineering of ballistic Dirac fermion transport and eliminate the extrinsic bulk disorder by annealing. When freely suspended without contact to any substrates, graphene could be considered as the ultimate two-dimensional (2D) morphology, leading to special field characteristics with the 2D geometrical effect and effectively utilized as an outstanding structure to explore the fundamental electronic or optoelectronic mechanism. In this paper, we report field emission characterization on an individual suspended few-layer graphene. A controllable wet transfer method is used to obtain the continuous and suspended graphene membrane on interdigitated gold electrodes. This suspended structure displays an overall field emission from the entirely surface, except for the variation in the emitting positions, acquiring a better enhancement than the exfoliated graphene on the conventional flat substrate. We also observe the transition process from space charge flow at low bias to the Fowler-Nordheim theory at high current emission regime. It could enable theoretical and experimental investigation of the typical electron emission properties of the 2D regime. Numerical simulations are also carried out to study the electrical properties of the suspended structure. Further improvement on the fabrication would realize low disorder, high quality, and large-scale suspended graphene devices. PMID:26795930

  3. Field Emission of Wet Transferred Suspended Graphene Fabricated on Interdigitated Electrodes.

    PubMed

    Xu, Ji; Wang, Qilong; Tao, Zhi; Qi, Zhiyang; Zhai, Yusheng; Wu, Shengqi; Zhang, Xiaobing; Lei, Wei

    2016-02-10

    Suspended graphene (SG) membranes could enable strain-engineering of ballistic Dirac fermion transport and eliminate the extrinsic bulk disorder by annealing. When freely suspended without contact to any substrates, graphene could be considered as the ultimate two-dimensional (2D) morphology, leading to special field characteristics with the 2D geometrical effect and effectively utilized as an outstanding structure to explore the fundamental electronic or optoelectronic mechanism. In this paper, we report field emission characterization on an individual suspended few-layer graphene. A controllable wet transfer method is used to obtain the continuous and suspended graphene membrane on interdigitated gold electrodes. This suspended structure displays an overall field emission from the entirely surface, except for the variation in the emitting positions, acquiring a better enhancement than the exfoliated graphene on the conventional flat substrate. We also observe the transition process from space charge flow at low bias to the Fowler-Nordheim theory at high current emission regime. It could enable theoretical and experimental investigation of the typical electron emission properties of the 2D regime. Numerical simulations are also carried out to study the electrical properties of the suspended structure. Further improvement on the fabrication would realize low disorder, high quality, and large-scale suspended graphene devices.

  4. A field-validated model for landfill methane emissions inclusive of seasonal methane oxidation

    NASA Astrophysics Data System (ADS)

    Bogner, J. E.; Spokas, K.; Chanton, J.

    2010-12-01

    In addition to natural wetlands, atmospheric methane (CH4) has multiple anthropogenic sources with high uncertainties, including rice production, ruminant animals, natural gas leakages, biomass burning, and landfills. For an improved IPCC Tier III methodology for landfill CH4 emissions in California, we have developed a new science-based, field-validated inventory model which decouples emissions from a historical reliance on a theoretical first order kinetic model for CH4 generation potential. The model (CALMIM, CAlifornia Landfill Methane Inventory Model) is a freely-available JAVA tool which estimates net CH4 emissions to the atmosphere for any landfill cover soil over a typical annual cycle, including (1) the effect of engineered gas extraction; (2) the physical effects of daily, intermediate, and final cover materials to retard emissions; and (3) seasonal soil moisture and temperature effects on both gaseous transport and methanotrophic CH4 oxidation. Linking site-specific data with existing globally-validated USDA models for annual climate and soil microclimate (Global TempSim; Global RainSim; Solarcalc; STM2), this model relies on 1-D diffusion as the major driver for emissions. Importantly, unlike current inventory methods based on modeled generation, the driving force for emissions (e.g., the CH4 concentration gradient) can be directly compared to field data. Methane oxidation is scaled to maximum rates over the full range of moisture and temperature conditions based on extensive supporting laboratory studies using California landfill cover soils. Field validation included meteorological data, soil moisture/temperature measurements, and seasonal (wet/dry) CH4 emissions & oxidation measurements for daily, intermediate, and final cover soils over two annual cycles at a northern (Monterey County) and southern California (Los Angeles County) landfill. The model accurately predicted soil temperature and moisture trends for individual cover materials with

  5. Improved CMOS field isolation using Germaniun/Boron implantation

    SciTech Connect

    Pfiester, J.R.; Alvis, J.R. )

    1988-08-01

    A novel germanium/boron implantation technique for improving the electrical field isolation for high-density CMOS circuits is demonstrated. Germanium implantation causes a reduction in dopant diffusion and segregation during field oxidation and is shown to increase the p-well field threshold voltage by as much as 40 percent with no significant degradation to junction or device performance. Selective germanium implantation with a blanket boron field implant can also improve the electrical field isolation behavior for CMOS circuits.

  6. Condensing economizers for thermal efficiency improvements and emissions control

    SciTech Connect

    Heaphy, J.P.; Carbonara, J.; Litzke, W.; Butcher, T.A.

    1993-12-31

    Flue gas condensing economizers improve the thermal efficiency of boilers by recovering sensible heat and water vapor latent heat from flue gas exhaust. In addition to improving thermal efficiency, condensing economizers also have the potential to act as control devices for emissions of particulates, SO{sub x}, and air toxics. Both Consolidated Edison of New York and Brookhaven National LaborAtory are currently working on condensing economizer technology with an emphasis on developing their potential for emissions control. Con Edison is currently conducting a condensing economizer demonstration at their oil-fired 74th Street Station in New York. Since installing this equipment in February of 1992 a heat rate improvement of 800 Btu/kWh has been seen. At another location, Ravenswood Station, a two stage condensing economizer has been installed in a pilot test. In this advanced configuration -the ``Integrated Flue Gas Treatment or IFGT system- two heat exchanger sections are installed and sprays of water with and without SO{sub 2} sorbents are included. Detailed studies of the removal of particulates, SO{sub 2}, SO{sub 3}, and selected air toxics have been done for a variety of operating conditions. Removal efficiencies for SO{sub 2} have been over 98% and for SO{sub 3} over 65%. Brookhaven National Laboratory`s studies involve predicting and enhancing particulate capture in condensing economizers with an emphasis on small, coal-fired applications. This work is funded by the Pittsburgh Energy Technology Center of the Department of Energy. Flyash capture efficiencies as high as 97% have been achieved to date with a single stage economizer.

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

    NASA Astrophysics Data System (ADS)

    Longtin, Rémi; Sanchez-Valencia, Juan Ramon; 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.

  8. Flexible and Transparent Field Emission Devices based on Graphene-Nanowire Hybrid Structures

    NASA Astrophysics Data System (ADS)

    Arif, Muhammad; Heo, Kwang; Lee, Byung Yang; Seo, David H.; Seo, Sunae; Jian, Jikang; Hong, Seunghun

    2011-03-01

    Recent developments in wafer scale synthesis and transfer of graphene have made it possible to fabricate electrodes for versatile flexible devices. However, a flexible and transparent graphene-based field emission device has not been explored yet. Herein, we report the fabrication of flexible and transparent field emission devices based on graphene-nanowire hybrid structures. In this work, we successfully grew vertically-aligned Au nanowires on graphene surface using an electrochemical method and utilized it as a cathode. We also utilized a graphene electrode for an anode resulting in a transparent and flexible field emission device. Our field emission devices can be bent down to 22 mm radius of curvature without any significant change in its field emission currents. This flexible and transparent field emission device based on graphene-nanowire hybrid structures will utilized for various applications such as field emission displays, x-ray tubes, and pressure sensors.

  9. Improved visualization of flow field measurements

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    1991-01-01

    A capability is proposed that makes it feasible to apply to measured flow field data the visualization tools developed to display numerical solutions for computational fluid dynamic problems. The measurement monitor surface (MMS) methodology was used for the analysis of flow field measurements within a low-aspect-ratio transonic axial-flow fan rotor acquired with two-dimensional laser anemometry. It is shown that the MMS method may be utilized to generate input for the multidimensional processing and analytical tools developed for numerical flow field simulation data. Thus an experimenter utilizing an interactive graphics program could illustrate scalar quantities such as Mach number by profiles, contour lines, carpet plots, and surfaces employing various color intensities. Also, flow directionality can be shown by the display of vector fields and particle traces.

  10. Field-effect transistor improves electrometer amplifier

    NASA Technical Reports Server (NTRS)

    Munoz, R.

    1964-01-01

    An electrometer amplifier uses a field effect transistor to measure currents of low amperage. The circuit, developed as an ac amplifier, is used with an external filter which limits bandwidth to achieve optimum noise performance.

  11. Improving lognormal models for cosmological fields

    NASA Astrophysics Data System (ADS)

    Xavier, Henrique S.; Abdalla, Filipe B.; Joachimi, Benjamin

    2016-07-01

    It is common practice in cosmology to model large-scale structure observables as lognormal random fields, and this approach has been successfully applied in the past to the matter density and weak lensing convergence fields separately. We argue that this approach has fundamental limitations which prevent its use for jointly modelling these two fields since the lognormal distribution's shape can prevent certain correlations to be attainable. Given the need of ongoing and future large-scale structure surveys for fast joint simulations of clustering and weak lensing, we propose two ways of overcoming these limitations. The first approach slightly distorts the power spectra of the fields using one of two algorithms that minimizes either the absolute or the fractional distortions. The second one is by obtaining more accurate convergence marginal distributions, for which we provide a fitting function, by integrating the lognormal density along the line of sight. The latter approach also provides a way to determine directly from theory the skewness of the convergence distribution and, therefore, the parameters for a lognormal fit. We present the public code Full-sky Lognormal Astro-fields Simulation Kit (FLASK) which can make tomographic realizations on the sphere of an arbitrary number of correlated lognormal or Gaussian random fields by applying either of the two proposed solutions, and show that it can create joint simulations of clustering and lensing with sub-per-cent accuracy over relevant angular scales and redshift ranges.

  12. 40 CFR 1065.935 - Emission test sequence for field testing.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Emission test sequence for field... Systems § 1065.935 Emission test sequence for field testing. (a) Time the start of field testing as.... Start the field test within 20 min of engine shutdown. (3) If the standard-setting part requires...

  13. 40 CFR 1065.935 - Emission test sequence for field testing.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Emission test sequence for field... Systems § 1065.935 Emission test sequence for field testing. (a) Time the start of field testing as.... Start the field test within 20 min of engine shutdown. (3) If the standard-setting part requires...

  14. 40 CFR 1065.935 - Emission test sequence for field testing.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Emission test sequence for field... Systems § 1065.935 Emission test sequence for field testing. (a) Time the start of field testing as.... Start the field test within 20 min of engine shutdown. (3) If the standard-setting part requires...

  15. 40 CFR 1065.935 - Emission test sequence for field testing.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Emission test sequence for field... Systems § 1065.935 Emission test sequence for field testing. (a) Time the start of field testing as.... Start the field test within 20 min of engine shutdown. (3) If the standard-setting part requires...

  16. Electric field induced Lyman-α emission of a hydrogen beam for electric field measurements

    SciTech Connect

    Chérigier-Kovacic, L. Doveil, F.; Ström, P.; Lejeune, A.

    2015-06-15

    Electric field induced Lyman-α emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-α radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.

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

    SciTech Connect

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

    2015-06-15

    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 I{sub D}/I{sub G} value in CNT/Al/Si film. Field emission (FE) current density of CNT/Al/Si film (∼25 mA/cm{sup 2}) is significantly higher as compared to that of CNT/Si film (∼1.6 mA/cm{sup 2}). 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.

  18. Uncertainty of oil field GHG emissions resulting from information gaps: a Monte Carlo approach.

    PubMed

    Vafi, Kourosh; Brandt, Adam R

    2014-09-01

    Regulations on greenhouse gas (GHG) emissions from liquid fuel production generally work with incomplete data about oil production operations. We study the effect of incomplete information on estimates of GHG emissions from oil production operations. Data from California oil fields are used to generate probability distributions for eight oil field parameters previously found to affect GHG emissions. We use Monte Carlo (MC) analysis on three example oil fields to assess the change in uncertainty associated with learning of information. Single factor uncertainties are most sensitive to ignorance about water-oil ratio (WOR) and steam-oil ratio (SOR), resulting in distributions with coefficients of variation (CV) of 0.1-0.9 and 0.5, respectively. Using a combinatorial uncertainty analysis, we find that only a small number of variables need to be learned to greatly improve on the accuracy of MC mean. At most, three pieces of data are required to reduce bias in MC mean to less than 5% (absolute). However, the parameters of key importance in reducing uncertainty depend on oil field characteristics and on the metric of uncertainty applied. Bias in MC mean can remain after multiple pieces of information are learned, if key pieces of information are left unknown.

  19. Field emission from optimized structure of carbon nanotube field emitter array

    NASA Astrophysics Data System (ADS)

    Chouhan, V.; Noguchi, T.; Kato, S.

    2016-04-01

    The authors report a detail study on the emission properties of field emitter array (FEA) of micro-circular emitters of multiwall carbon nanotubes (CNTs). The FEAs were fabricated on patterned substrates prepared with an array of circular titanium (Ti) islands on titanium nitride coated tantalum substrates. CNTs were rooted into these Ti islands to prepare an array of circular emitters. The circular emitters were prepared in different diameters and pitches in order to optimize their structure for acquiring a high emission current. The pitch was varied from 0 to 600 μm, while a diameter of circular emitters was kept constant to be 50 μm in order to optimize a pitch. For diameter optimization, a diameter was changed from 50 to 200 μm while keeping a constant edge-to-edge distance of 150 μm between the circular emitters. The FEA with a diameter of 50 μm and a pitch of 120 μm was found to be the best to achieve an emission current of 47 mA corresponding to an effective current density of 30.5 A/cm2 at 7 V/μm. The excellent emission current was attributed to good quality of CNT rooting into the substrate and optimized FEA structure, which provided a high electric field on a whole circular emitter of 50 μm and the best combination of the strong edge effect and CNT coverage. The experimental results were confirmed with computer simulation.

  20. Vacuum field energy and spontaneous emission in anomalously dispersive cavities

    SciTech Connect

    Bradshaw, Douglas H.; Di Rosa, Michael D.

    2011-05-15

    Anomalously dispersive cavities, particularly white-light cavities, may have larger bandwidth to finesse ratios than their normally dispersive counterparts. Partly for this reason, they have been proposed for use in laser interferometer gravitational-wave observatory (LIGO)-like gravity-wave detectors and in ring-laser gyroscopes. In this paper we analyze the quantum noise associated with anomalously dispersive cavity modes. The vacuum field energy associated with a particular cavity mode is proportional to the cavity-averaged group velocity of that mode. For anomalously dispersive cavities with group index values between 1 and 0, this means that the total vacuum field energy associated with a particular cavity mode must exceed ({h_bar}/2{pi}){omega}/2. For white-light cavities in particular, the group index approaches zero and the vacuum field energy of a particular spatial mode may be significantly enhanced. We predict enhanced spontaneous emission rates into anomalously dispersive cavity modes and broadened laser linewidths when the linewidth of intracavity emitters is broader than the cavity linewidth.

  1. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

    2006-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration' is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different spectral properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

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

    NASA Astrophysics Data System (ADS)

    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

  3. Model of the Jovian magnetic field topology constrained by the Io auroral emissions

    NASA Astrophysics Data System (ADS)

    Hess, S. L. G.; Bonfond, B.; Zarka, P.; Grodent, D.

    2011-05-01

    The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins along Io's orbit. The use of this latter constraint to determine the internal magnetic field models greatly improved the modeling of the auroral emissions, in particular the radio ones, which strongly depends on the magnetic field geometry. This constraint is, however, not sufficient for allowing a completely accurate modeling. The fact that the footprint field line should map to a longitude close to Io's was not used, so that the azimuthal component of the magnetic field could not be precisely constrained. Moreover, a recent study showed the presence of a magnetic anomaly in the northern hemisphere, which has never been included in any spherical harmonic decomposition of the internal magnetic field. We compute a decomposition of the Jovian internal magnetic field into spherical harmonics, which allows for a more accurate mapping of the magnetic field lines crossing Io, Europa, and Ganymede orbits to the satellite footprints observed in UV. This model, named VIPAL, is mostly constrained by the Io footprint positions, including the longitudinal constraint, and normalized by the Voyager and Pioneer magnetic field measurements. We show that the surface magnetic fields predicted by our model are more consistent with the observed frequencies of the Jovian radio emissions than those predicted by previous models.

  4. Model of the Jovian magnetic field topology constrained by the Io auroral emissions

    NASA Astrophysics Data System (ADS)

    Hess, S.; Bonfond, B.; Grodent, D.; Zarka, P.

    2011-10-01

    The determination of the internal magnetic field of Jupiter has been the object of many studies and publications. These models have been computed from the Pioneer, Voyager, and Ulysses measurements. Some models also use the position of the Io footprints as a constraint: the magnetic field lines mapping to the footprints must have their origins along Io's orbit. The use of this latter constraint to determine the internal magnetic field models greatly improved the modeling of the auroral emissions, in particular the radio ones, which strongly depends on the magnetic field geometry. This constraint is, however, not sufficient for allowing a completely accurate modeling. The fact that the footprint field line should map to a longitude close to Io's was not used, so that the azimuthal component of the magnetic field could not be precisely constrained. Moreover, a recent study showed the presence of a magnetic anomaly in the northern hemisphere, which has never been included in any spherical harmonic decomposition of the internal magnetic field. We compute a decomposition of the Jovian internal magnetic field into spherical harmonics, which allows for a more accurate mapping of the magnetic field lines crossing Io, Europa, and Ganymede orbits to the satellite footprints observed in UV. This model, named VIPAL, is mostly constrained by the Io footprint positions, including the longitudinal constraint, and normalized by the Voyager and Pioneer magnetic field measurements. We show that the surface magnetic fields predicted by our model are more consistent with the observed frequencies of the Jovian radio emissions than those predicted by previous models.

  5. Local field emission spectroscopy of InSb micrograins

    NASA Astrophysics Data System (ADS)

    Zhukov, N. D.; Glukhovskoy, E. G.; Mosiyash, D. S.

    2015-11-01

    Local electron density-of-state spectra and level parameters in indium antimonide (InSb) micrograins have been studied using a tunneling microscope in the field-electron emission regime. The activation energies (ψ) of electron levels and electron lifetimes (τ) on these levels have been determined based on the correspondence of current-voltage characteristics to the probabilities of emission. Several local electron levels in a near-surface region of intrinsic ( i-InSb) micrograins are identified with ψ ˜ 0.73, 1.33, 1.85, 2.15, and 5.1 eV and τ ˜ 5 × 10-8-3 × 10-7 s, respectively. A physical model is proposed, according to which "light" electrons are localized due to the Coulomb interaction and their dimensional quantization takes place in the near-surface zone as determined by the effective mass, energy, and concentration of electrons and the radius of curvature of the micrograin surface.

  6. Improved in-situ methods for determining land surface emissivity

    NASA Astrophysics Data System (ADS)

    Göttsche, Frank; Olesen, Folke; Hulley, Glynn

    2014-05-01

    misrepresented in satellite-retrieved LSEs. In-situ emissivities of dominant surface cover types at Gobabeb and Dahra were obtained with the so-called 'box method', which consists of a sequence of thermal infrared radiance measurements and employs a box with highly reflective inner walls to control the radiation from the environment. The original method was improved by continuously recording the radiance measurements at a sampling rate of one second, which allows the picking of the first undisturbed temperature after changing the box configuration. Furthermore, erroneous measurements, e.g. from incorrectly placing the box on a target, can still be identified and rejected later. In-situ LSEs are compared to emissivity spectra of soil and grass samples and to LSE retrieved from the Moderate Resolution Imaging Spectroradiometer (MODIS) on EOS-Terra.

  7. Influence of the Electric Field on Secondary Electron Emission Yield

    SciTech Connect

    Beranek, M.; Richterova, I.; Nemecek, Z.; Pavlu, J.; Safrankova, J.

    2008-09-07

    We have applied a technique based on levitation of a single charged grain in the quadrupole. We have used 3-6 micrometer spherical grains from amorphous carbon. These grains were charged by an electron beam with the energy tunable up to 10 keV and the grain charge was continuously monitored. If the grain is charged by an constant energy, its surface potential is set to the value when incident electrons are slow down to the energy where the secondary emission yield is equal to unity. Our investigations reveal that this energy changes proportionally to the grain surface field. Moreover, we have observed a shift of charging characteristics after a long-time electron bombardment.

  8. Origin of enhanced field emission characteristics postplasma treatment of multiwalled carbon nanotube array

    SciTech Connect

    Lee, Kyu; Lim, Seong Chu; Lee, Young Hee; Choi, Young Chul

    2008-08-11

    Field emission properties of chemical-vapor-deposition-grown multiwalled carbon nanotubes (MWCNTs) with plasma treatment have been investigated. Origin of the enhanced field emission current was interpreted in terms of surface morphology of MWCNTs, work function, field enhancement factor, and emission area. Contrary to the general belief, the change in the work function increased slightly with the plasma treatment time, whereas the field enhancement factor decreased. We found that the number of emittable MWCNTs played a dominant role in the current enhancement.

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

    PubMed

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

    2014-11-01

    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.

  10. Methyl bromide emissions from a covered field: II. Volatilization

    SciTech Connect

    Yates, S.R.; Gan, J.; Ernst, F.F.

    1996-01-01

    An experiment to investigate the environmental fate and transport of methyl bromide in agricultural fields is described. The methyl bromide volatilization rate was determined as a function of time for conditions where methyl bromide was applied at a rate of 843 kg in a 3.5-ha (i.e., 240 kg/ha) field covered with plastic at a depth of 25 cm. Three methods were used to estimate the methyl bromide volatilization rate, including: the aerodynamic, theoretical profile shape and integrated horizontal flux methods. The highest methyl bromide volatilization rates were at the beginning of the experiment. Within the first 24 h, approximately 36% of the applied methyl bromide mass was lost. Diurnally, the largest volatilization rates occurred during the day when temperatures were high and the atmosphere was unstable. Cooler temperatures, light winds, and neutral to stable atmospheric conditions were present at night, reducing the flux. The total emission calculated using these methods was found to be approximately 64% ({+-} 10%) of the applied mass. A mass balance was calculated using each flux estimation technique and several methods for analyzing the data. The average mass recovery using all the flux methods was 867 kg ({+-}83 kg), which was 102.8% ({+-}9.8%) of the applied (i.e., 843 kg). The range in the mass balance percent (i.e., percent of applied mass that is measured) is from 88 to 112%. The averaged mass balance percent for the aerodynamic method, which involved using the measured data directly, was approximately 100.8%. The total emission calculated using the aerodynamic method was found to be approximately 62% ({+-}11%) of the applied mass. 29 refs., 7 figs., 1 tab.

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

    NASA Astrophysics Data System (ADS)

    Jha, Arunava; Roy, Rajarshi; Sen, Dipayan; Chattopadhyay, Kalyan K.

    2016-03-01

    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.

  12. Improved visualization of flow field measurements

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    1991-01-01

    A capability was developed that makes it possible to apply to measured flow field data the visualization tools developed to display numerical solutions for computational fluid dynamic problems. The measurement monitor surface (MMS) procedure was applied to the analysis of flow field measurements within a low aspect ratio transonic axial flow fan rotor obtained with 2-D laser anemometry. The procedure generates input for the visualization tools developed to display numerical solutions for computational fluid dynamics problems. The relative Mach number contour plots obtained by this method resemble the conventional contour plots obtained by more traditional methods. The results show that the MMS procedure can be used to generate input for the multidimensional processing and analysis tools developed for data from numerical flow field simulations. They show that an experimenter can apply the MMS procedure to his data and then use an interactive graphics program to display scalar quantities like the Mach number by profiles, carpet plots, contour lines, and surfaces using various colors. Also, flow directionality can be shown by display of vector fields and particle traces.

  13. Field effect transistors improve buffer amplifier

    NASA Technical Reports Server (NTRS)

    1967-01-01

    Unity gain buffer amplifier with a Field Effect Transistor /FET/ differential input stage responds much faster than bipolar transistors when operated at low current levels. The circuit uses a dual FET in a unity gain buffer amplifier having extremely high input impedance, low bias current requirements, and wide bandwidth.

  14. Improving Field Supervision through Collaborative Supervision Institutes

    ERIC Educational Resources Information Center

    Harvey, Virginia Smith; Amador, Andria; Finer, Diana; Gotthelf, David; Hintze, John; Kruger, Lou; Li, Chieh; Lichtenstein, Bob; Rogers, Laura; Struzziero, Joan; Wandle, Caroline

    2010-01-01

    Adequate and appropriate supervision of interns is frequently identified as a significant problem by training programs while, on their part, field placement sites often indicate that training programs generate expectations for interns that are not always "in synch" with district expectations of school psychologists. As a result of an increasing…

  15. A model study of the role of workfunction variations in cold field emission from microstructures with inclusion of field enhancements

    NASA Astrophysics Data System (ADS)

    Qiu, H.; Joshi, R. P.; Neuber, A.; Dickens, J.

    2015-10-01

    An analytical study of field emission from microstructures is presented that includes position-dependent electric field enhancements, quantum corrections due to electron confinement and fluctuations of the workfunction. Our calculations, applied to a ridge microstructure, predict strong field enhancements. Though quantization lowers current densities as compared to the traditional Fowler-Nordheim process, strong field emission currents can nonetheless be expected for large emitter aspect ratios. Workfunction variations arising from changes in electric field penetration at the surface, or due to interface defects or localized screening, are shown to be important in enhancing the emission currents.

  16. Methyl bromide emission from fields partially covered with a high-density polyethylene and a virtually impermeable film

    SciTech Connect

    Wang, D.; Yates, S.R.

    1998-09-01

    Recent field studies in the interior valley of southern California have indicated that 56--73% of methyl bromide (MeBr) used in soil fumigation is lost to atmospheric emission when the fields are covered completely with a high-density polyethylene (HDPE) film. The emission can be reduced to less than 5% when a virtually impermeable film or Hytibar is used to cover the fields. This study was conducted to determine MeBr emission from bedded field plots where only the beds were covered with a HDPE or a virtually impermeable plastic film. The results provide an assessment on MeBr emission from field beds partially covered with the HDPE film and the suitability of using a virtually impermeable film for emission reduction. Methyl bromide gas was applied to replicated field beds covered with either a HDPE or the Hytibar film. The films were removed 6 days after MeBr application. Replicated soil cores were taken from different locations of the field beds, 20 days after MeBr application, for the determination of soil bromide ion concentrations. The total amount of MeBr degraded from each plot was calculated from the measured bromide ion concentrations, and the potential emission was determined as the difference between the amount of applied and that of degraded. Results indicated that the potential emission from this bedded system was about 95% for the HDPE treatment and 90% for the Hytibar-covered plots. Regardless of the small improvement with the virtually impermeable film, the experiment clearly indicates that partially covering the field with either a HDPE or a virtually impermeable film would result in unacceptably high emission losses.

  17. IMPROVE EMISSION INVENTORIES THROUGH ADVANCES IN METHODS AND MODELS

    EPA Science Inventory

    Emission inventories are the foundation of cost-effective air quality management strategies. The emission inventory must be complete, accurate, timely, transparent, and affordable. The general approach is to identify the largest uncertainties that can impact model outputs and a...

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

    NASA Astrophysics Data System (ADS)

    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

  19. Stable field emission performance of SiC-nanowire-based cathodes

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Wan; Choi, Young-Jin; Choi, Kyoung Jin; Park, Jae-Gwan; Park, Jae-Hwan; Pimenov, Sergei M.; Frolov, Vadim D.; Abanshin, Nikolay P.; Gorfinkel, Boris I.; Rossukanyi, Nikolay M.; Rukovishnikov, Alexander I.

    2008-06-01

    In this paper we report the fabrication and testing of diode-type low-voltage field emission display (FED) devices with SiC-nanowire-based cathodes. The SiC-nanowire FEDs (flat vacuum lamps) were characterized by low emission threshold fields (~2 V µm-1), high current density and stable long-term performance. The analysis of field emission data evidenced that the Schottky effect would have a considerable influence on the field emission from nanowire-based samples, leading to the true values of the field enhancement factor being significantly lower than those derived from Fowler-Nordheim plots.

  20. A Method for Studying the Electric Field Enhanced Emission of Carriers from Deep Levels

    NASA Astrophysics Data System (ADS)

    Hwang, In Duk; Choe, Byungdoo

    1986-11-01

    A spectroscopic method is proposed for studying the electric field enhanced emission of trapped carriers from deep levels. The resulting spectrum directly represents the effect of the electric field enhanced emission only, thus removing the intrinsic difficulty in treating the electric field enhanced emission from deep levels of large concentration. This method involves two steps of measurements of the ionized trap densities; in the first step the electric field pulse is applied to induce an enhanced emission, and in the second without the electric field pulse. Experimental results by this method have been given for the DX center in LPE Al068Ga0.32As:Sn.

  1. In-field greenhouse gas emissions from cookstoves in rural Mexican households

    NASA Astrophysics Data System (ADS)

    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 ( p<0.001) in rural homes during daily cooking activities (89.7±2.0%) compared to WBTs in simulated kitchens (94.2±0.5%), which results in almost a doubling of the products 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

  2. Improving dust emission characterization in dust models using dynamic high-resolution geomorphic erodibility map

    NASA Astrophysics Data System (ADS)

    Parajuli, S. P.; Yang, Z.; Kocurek, G.

    2013-12-01

    Dust is known to affect the earth radiation budget, biogeochemical cycle, precipitation, human health and visibility. Despite the increased research effort, dust emission modeling remains challenging because dust emission is affected by complex geomorphological processes. Existing dust models overestimate dust emission and rely on tuning and a static erodibility factor in order to make simulated results comparable to remote sensing and ground-based observations. In most of current models, dust emission is expressed in terms of threshold friction speed, which ultimately depends mainly upon the percentage clay content and soil moisture. Unfortunately, due to the unavailability of accurate and high resolution input data of the clay content and soil moisture, estimated threshold friction speed commonly does not represent the variability in field condition. In this work, we attempt to improve dust emission characterization by developing a high resolution geomorphic map of the Middle East and North Africa (MENA), which is responsible for more than 50% of global dust emission. We develop this geomorphic map by visually examining high resolution satellite images obtained from Google Earth Pro and ESRI base map. Albeit subjective, our technique is more reliable compared to automatic image classification technique because we incorporate knowledge of geological/geographical setting in identifying dust sources. We hypothesize that the erodibility is unique for different geomorphic landforms and that it can be quantified by the correlation between observed wind speed and satellite retrieved aerosol optical depth (AOD). We classify the study area into several key geomorphological categories with respect to their dust emission potential. Then we quantify their dust emission potential using the correlation between observed wind speed and satellite retrieved AOD. The dynamic, high-resolution geomorphic erodibility map thus prepared will help to reduce the uncertainty in current

  3. Recent Progress in Silicon-Based MEMS Field Emission Thrusters

    NASA Astrophysics Data System (ADS)

    Lenard, Roger X.; Kravitz, Stanley H.; Tajmar, Martin

    2005-02-01

    The Indium Field Emission Thruster (In-FET) is a highly characterized and space-proven device based on space-qualified liquid metal ion sources. There is also extensive experience with liquid metal ion sources for high-brightness semiconductor fabrications and inspection Like gridded ion engines, In-FETs efficiently accelerate ions through a series of high voltage electrodes. Instead of a plasma discharge to generate ions, which generates a mixture of singly and doubly charged ions as well as neutrals, indium metal is melted (157°C) and fed to the tip of a capillary tube where very high local electric fields perform more-efficient field emission ionization, providing nearly 100% singly charged species. In-FETs do not have the associated losses or lifetime concerns of a magnetically confined discharge and hollow cathode in ion thrusters. For In-FETs, propellant efficiencies ˜100% stipulate single-emitter currents ⩽10μA, perhaps as low as 5μA of current. This low emitter current results in ⩽0.5 W/emitter. Consequently, if the In-FET is to be used for future Human and Robotic missions under President Bush's Exploration plan, a mechanism to generate very high power levels is necessary. Efficient high-power operation requires many emitter/extractor pairs. Conventional fabrication techniques allow 1-10 emitters in a single module, with pain-staking precision required. Properly designed and fabricated In-FETs possess electric-to-jet efficiency >90% and a specific mass <0.25 kg/kWe. MEMS techniques allow reliable batch processing with ˜160,000 emitters in a 10×10-cm array. Developing a 1.5kW 10×10-cm module is a necessary stepping-stone for >500 kWe systems where groups of 9 or 16 modules, with a single PPU/feed system, form the building blocks for even higher-power exploration systems. In 2003, SNL and ARCS produced a MEMS-based In-FET 5×5 emitter module with individually addressable emitter/extractor pairs on a 15×15mm wafer. The first MEMS thruster

  4. IMPROVING EMISSION INVENTORIES FOR EFFECTIVE AIR-QUALITY MANAGEMENT ACROSS NORTH AMERICA - A NARSTO ASSESSMENT

    EPA Science Inventory

    The NARSTO Ozone and Particulate Matter Assessments emphasized that emission inventories are critical to the success of air quality management programs and that emissions inventories in Canada, Mexico, and the United States need improvement to meet expectations for quality, timel...

  5. IMPROVING EMISSION INVENTORIES FOR EFFECTIVE AIR-QUALITY MANAGMENT ACROSS NORTH AMERICA - A NARSTO ASSESSMENT

    EPA Science Inventory

    The NARSTO Ozone and Particulate Matter Assessments emphasized that emission inventories are critical to the success of air quality management programs and that emissions inventories in Canada, Mexico, and the United States need improvement to meet expectations for quality, timel...

  6. (AWMA) IMPROVING EMISSION INVENTORIES FOR EFFECTIVE AIR-QUALITY MANAGEMENT ACROSS NORTH AMERICA - A NARSTO ASSESSMENT

    EPA Science Inventory

    The NARSTO Ozone and Particulate Matter Assessments emphasized that emission inventories are critical to the success of air quality management programs and that emissions inventories in Canada, Mexico, and the United States need improvement to meet expectations for quality, timel...

  7. IMPROVING EMISSIONS ESTIMATES WITH COMPUTATIONAL INTELLIGENCE, DATABASE EXPANSION, AND COMPREHENSIVE VALIDATION

    EPA Science Inventory

    The report discusses an EPA investigation of techniques to improve methods for estimating volatile organic compound (VOC) emissions from area sources. Using the automobile refinishing industry for a detailed area source case study, an emission estimation method is being developed...

  8. Field Emission Characteristics of Carbon Nanotubes and Their Applications in Sensors and Devices

    NASA Astrophysics Data System (ADS)

    Vaseashta, Ashok

    2003-03-01

    FIELD EMISSION CHARACTERISTICS OF CARBON NANOTUBES AND THEIR APPLICATIONS IN SENSORS AND DEVICES A. Vaseashta, C. Shaffer, M. Collins, A. Mwuara Dept of Physics, Marshall University, Huntington, WV V. Pokropivny Institute for Materials Sciences of NASU, Kiev, Ukraine. D. Dimova-Malinovska Bulgarian Academy of Sciences, Sofia, Bulgaria. The dimensionality of a system has profound influence on its physical behavior. With advances in technology over the past few decades, it has become possible to fabricate and study reduced-dimensional systems, such as carbon nanotubes (CNTs). Carbon nanotubes are especially promising candidate for cold cathode field emitter because of their electrical properties, high aspect ratio, and small radius of curvature at the tips. Electron emission from the carbon nanotubes was investigated. Based upon the field emission investigation of carbon nanotubes, several prototype devices have been suggested that operate with low swing voltages with sufficient high current densities. Characteristics that allow improved current stability and long lifetime operation for electrical and opto-electronics devices are presented. The aim of this brief overview is to illustrate the useful characteristics of carbon nanotubes and its possible application.

  9. Sn-doped In2O3 nanowires: enhancement of electrical field emission by a selective area growth

    PubMed Central

    2012-01-01

    Selective area growth of single crystalline Sn-doped In2O3 (ITO) nanowires synthesized via vapor–liquid–solid (VLS) method at 600°C was applied to improve the field emission behavior owing to the reduction of screen effect. The enhanced field emission performance reveals the reduction of turn-on fields from 9.3 to 6.6 V μm−1 with increase of field enhancement factors (β) from 1,621 to 1,857 after the selective area growth at 3 h. Moreover, we find that the screen effect also highly depends on the length of nanowires on the field emission performance. Consequently, the turn-on fields increase from 6.6 to 13.6 V μm−1 with decreasing β values from 1,857 to 699 after the 10-h growth. The detailed screen effect in terms of electrical potential and NW density are investigated in details. The findings provide an effective way of improving the field emission properties for nanodevice application. PMID:23259411

  10. Evaluation of a Fourier transform infrared continuous emission monitor field test at a TSCA incinerator

    SciTech Connect

    Mao, Z.; Demirgian, J.C.; Reedy, G.

    1994-06-01

    A Fourier transform infrared (FTIR) spectrometer was field tested as a continuous emission monitor (CEM) at the Toxic Substances Control Act (TSCA) incinerator at K-25 in Oak Ridge, Tenn., from August 23 to September 3, 1993. This paper reports results obtained from this field test. The FTIR spectrometer and the long-path cell used for the field test were specially designed and constructed, so that optical alignment of the system can be easily performed in the field. The system was tested in the laboratory and then in the field for instrument stability and signal-to-noise ratio. Time interval required for taking a new background spectrum was determined. It appears that the system performs well both in the laboratory and in the field. The field test followed a standard operation procedure (SOP), developed for the test, based on a proposed EPA protocol for applying FTIR in emission testing. Sixteen compounds were selected as target analytes. Ethylene was used as a calibration transfer standard to ensure that spectral performance of the FTIR spectrometer in the field is consistent with that in the laboratory. Spike tests were regularly conducted with a known concentration of a mixture of six compounds and also with SF{sub 6} to check the accuracy of the monitoring system. Data sampling, processing, and reporting were automated to collect data every 10 min, and data were collected throughout the test as long as liquid nitrogen was available in the detector. The instrumentation and software performed flawlessly. Although the field test was a success, further improvement is necessary. Suggestions for revising the SOP and the proposed EPA protocol are discussed.

  11. Field emission of carbon nanotube array with normal-gate cold cathode

    NASA Astrophysics Data System (ADS)

    Dai, Jian-Feng; Mu, Xiao-Wen; Qiao, Xian-Wu; Chen, Xiao-Xing; Wang, Jun-Hong

    2010-05-01

    A hexagon pitch carbon nanotube (CNT) array vertical to the normal gate of cold cathode field emission displayer (FED) is simulated by solving the Laplace equation. The calculated results show that the normal gate causes the electric field around the CNT tops to be concentrated and the emission electron beam becomes a column. The field enhancement factor and the emission current intensity step up greatly compared with those of the diode structure. Emission current density increases rapidly with the decrease of normal-gate aperture. The gate voltage exerts a critical influence on the emission current.

  12. Oil field slim hole drilling technology improving

    SciTech Connect

    Not Available

    1992-11-23

    Recent advances in slim hole drilling technology have improved the application of this drilling technique to oil and gas exploration and development wells. These advancements include Optimization of slim hole drilling hydraulics, Application of a small particle weighing agent to improve well control and coring operations, Use of slim hole techniques to drill horizontal wells, Use of a new polycrystalline diamond compact cutter to allow economical re-entry of small diameter wells in hard rock. Slim hole continuous coring and drilling is becoming more accepted as a viable drilling method, especially as exploration budgets become smaller. Typical applications for slim hole equipment include drilling in frontier areas where logistics can be a problem and reentry operations in which the existing well has a small diameter. Typically, slim hole drilling operations use technology borrowed from the mining industry. The rigs are smaller and drill with much higher rotational speeds. Definitions of slim holes vary from a well with 90% drilled, with a diameter of less than 7 in. To a well with 70% drilled with less than 5 in. A goal of slim hole, however it is defined, is the drilling of a well with a diameter smaller than that used on conventional wells in the area. The reduced diameter helps cut rig time and cost and reduces the cost of the tubulars. Another goal of slim hole drilling is the ability to retrieve cores from the entire well during drilling.

  13. Highly efficient electron field emission from graphene oxide sheets supported by nickel nanotip arrays.

    PubMed

    Ye, Dexian; Moussa, Sherif; Ferguson, Josephus D; Baski, Alison A; El-Shall, M Samy

    2012-03-14

    Electron field emission is a quantum tunneling phenomenon whereby electrons are emitted from a solid surface due to a strong electric field. Graphene and its derivatives are expected to be efficient field emitters due to their unique geometry and electrical properties. So far, electron field emission has only been achieved from the edges of graphene and graphene oxide sheets. We have supported graphene oxide sheets on nickel nanotip arrays to produce a high density of sharp protrusions within the sheets and then applied electric fields perpendicular to the sheets. Highly efficient and stable field emission with low turn-on fields was observed for these graphene oxide sheets, because the protrusions appear to locally enhance the electric field and dramatically increase field emission. Our simple and robust approach provides prospects for the development of practical electron sources and advanced devices based on graphene and graphene oxide field emitters. PMID:22288579

  14. Flux measurements and sampling strategies: Applications to methane emissions from rice fields

    NASA Astrophysics Data System (ADS)

    Khalil, M. A. K.; Rasmussen, R. A.; Shearer, M. J.

    1998-10-01

    The emissions of methane from rice fields and other sources are often measured by placing chambers on the surface and taking sequential samples. Although static chambers pose several problems that affect the accuracy of the data, there are a few parameters that, if carefully chosen, can improve the reliability of the data and reduce the uncertainties. These parameters are the length of time the chamber is kept on the rice plants, the number of samples that are drawn to estimate the flux, the basal area and height of the chamber, the frequency of measurements during the growing season, and the number of plots sampled. In this paper we analyze a large data set to determine how these parameters can be chosen to improve data quality. The results show that, for individual flux measurements, extending the time the chambers are left on the plots improves precision more effectively than taking more sequential samples for each flux measurement. The exposure time cannot be extended too far, however, as it leads to a saturation effect so that the rate of accumulation in the chamber slows down. This can compromise the accuracy of the measurement. There is an optimum exposure time that balances these two effects. Many individual measurements are needed to characterize the emissions from the larger area of the fields and the seasonal patterns. For methane emissions from rice fields, the amplitude of the systematic seasonal cycle is usually large compared to the variability on shorter timescales. Consequently, reducing the sampling frequency increases the uncertainty of the seasonal flux very slowly. The spatial variability is large and random on the small scales of the basal area of the chambers. Reducing the number of plots sampled, therefore, has a major effect on the uncertainty of the seasonal average flux.

  15. Field Emission Electron Microprobe Analysis of Halogens in Apatite

    NASA Astrophysics Data System (ADS)

    Tacker, R. C.

    2011-12-01

    Field emission electron microprobe is capable of higher resolution and lower voltage than other microprobes, making it an ideal instrument for analysis of small accessory minerals in thin section such as apatite. In this study, the field emission electron microprobe was evaluated for analysis of fluorine and chlorine in apatite. Analysis was conducted on (001), (100) and an intermediate section of natural apatite crystals, using the JEOL JXA-8530F Hyperprobe, located at Fayetteville State University in Fayetteville, North Carolina. Conditions were beam current of 10 nanoamps, accelerating voltages from 5-20 kV, and spot sizes from 1-10 micrometers. Very short counting times were used, some as little as 2 seconds. Analytical strategies exploited the fact that excitation energies for fluorine Kα are much lower than for chlorine. Earlier studies (e.g. Stormer et al. 1993; Fialin and Chopin, 2006) documented the complex behavior of beam-driven migration, subsurface accumulation and desorption during fluorine analysis. The cumulative effect is increase and then fall of count rates with time and repeated analysis. The details of earlier studies were reproduced: (1) Apatite analysis by electron microprobe has two additional unknown variables, which are the crystallographic orientation of the unknown and of the standard. (2) The most reliable measure of fluorine cps is derived from a regression to zero time, accounting for crystal orientation; (3) Changing the analytical conditions (accelerating voltage, spot size, duration of analysis) changes only the time scale over which migration and desorption take place. New results from the JEOL Hyperprobe show that, for all crystal orientations, initial fluorine cps increase from 5 and 7 kV to 10 kV, but decrease systematically with further increases in kV, interpreted as loss of fluorine without concomitant excitation of X-rays. To date, fluorine analysis is routinely conducted at 15 and 20 kV. In contrast, chlorine initial

  16. Improve the transconductance of a graphene field-effect transistor by folding graphene into a wedge

    NASA Astrophysics Data System (ADS)

    Cao, Guiming; Liu, Weihua; Cao, Meng; Li, Xin; Zhang, Anping; Wang, Xiaoli; Chen, Bangdao

    2016-07-01

    The transport property of a graphene wedge channel is studied theoretically and its leakage current through field emission is estimated when considering the effect of the internal electric field. The transconductance of the graphene transistor is improved from 0.016 to 0.321 μS μm‑1 when the graphene is folded into a wedge (with angle of wedge π/6 and radius curvature 2.7 nm at the tip), while the wedge height is much smaller than the space between the top-gate and the channel. The improved transconductance is due to the locally enhanced electric field, which results in a potential well and causes electron accumulation at the wedge tip. The leakage current through field emission J FE shows a super-linear increase with the channel conductive current J DS, where overall the electron supply for the field emission at the wedge tip is improved by the channel bias voltage V DS.

  17. Improve the transconductance of a graphene field-effect transistor by folding graphene into a wedge

    NASA Astrophysics Data System (ADS)

    Cao, Guiming; Liu, Weihua; Cao, Meng; Li, Xin; Zhang, Anping; Wang, Xiaoli; Chen, Bangdao

    2016-07-01

    The transport property of a graphene wedge channel is studied theoretically and its leakage current through field emission is estimated when considering the effect of the internal electric field. The transconductance of the graphene transistor is improved from 0.016 to 0.321 μS μm-1 when the graphene is folded into a wedge (with angle of wedge π/6 and radius curvature 2.7 nm at the tip), while the wedge height is much smaller than the space between the top-gate and the channel. The improved transconductance is due to the locally enhanced electric field, which results in a potential well and causes electron accumulation at the wedge tip. The leakage current through field emission J FE shows a super-linear increase with the channel conductive current J DS, where overall the electron supply for the field emission at the wedge tip is improved by the channel bias voltage V DS.

  18. Supporting Field Instructors' Efforts to Help Students Improve Writing

    ERIC Educational Resources Information Center

    Kahn, Jessica M.; Holody, Richard

    2012-01-01

    Field instructors have often not felt empowered to address their concerns about a critical skill in their students' professional development: their students' writing. In this article, we explain ways that field education departments and social work faculty can support field instructors to improve their students' writing. In addition, we provide…

  19. Field emission chemical sensor for receptor/binder, such as antigen/antibody

    DOEpatents

    Panitz, John A.

    1986-01-01

    A field emission chemical sensor for specific detection of a chemical entity in a sample includes a closed chamber enclosing two field emission electrode sets, each field emission electrode set comprising (a) an electron emitter electrode from which field emission electrons can be emitted when an effective voltage is connected to the electrode set; and (b) a collector electrode which will capture said electrons emitted from said emitter electrode. One of the electrode sets is passive to the chemical entity and the other is active thereto and has an active emitter electrode which will bind the chemical entity when contacted therewith.

  20. Improved methods for fan sound field determination

    NASA Technical Reports Server (NTRS)

    Cicon, D. E.; Sofrin, T. G.; Mathews, D. C.

    1981-01-01

    Several methods for determining acoustic mode structure in aircraft turbofan engines using wall microphone data were studied. A method for reducing data was devised and implemented which makes the definition of discrete coherent sound fields measured in the presence of engine speed fluctuation more accurate. For the analytical methods, algorithms were developed to define the dominant circumferential modes from full and partial circumferential arrays of microphones. Axial arrays were explored to define mode structure as a function of cutoff ratio, and the use of data taken at several constant speeds was also evaluated in an attempt to reduce instrumentation requirements. Sensitivities of the various methods to microphone density, array size and measurement error were evaluated and results of these studies showed these new methods to be impractical. The data reduction method used to reduce the effects of engine speed variation consisted of an electronic circuit which windowed the data so that signal enhancement could occur only when the speed was within a narrow range.

  1. Developing a "Research Test Bed" to introduce innovative Emission Testing Technology to improve New Zealand's Vehicle Emission Standards

    NASA Astrophysics Data System (ADS)

    Cox, Stephen J.

    2012-05-01

    Vehicle exhaust emissions arise from the combustion of the fuel and air mixture in the engine. Exhaust emission gases generally include carbon monoxide (CO), oxides of nitrogen (NOx), hydrocarbons (HC), particulates, and the greenhouse gas carbon dioxide (CO2). In New Zealand improvements have occurred in emissions standards over the past 20 years however significant health related issues are now being discovered in Auckland as a direct effect of high vehicle emission levels. Pollution in New Zealand, especially via vehicle emissions are an increasing concern and threatens New Zealand's "clean and green" image. Unitec Institute of Technology proposes establishing a Vehicle Emissions Testing Facility, and with an understanding with Auckland University, National Institute of Water & Atmosphere Research Ltd (NIWA) this research group can work collaboratively on vehicle emissions testing. New Zealand research providers would support an application in the UK led by the University of Huddersfield to a range of European Union Structural Funds. New Zealand has an ideal "vehicle emissions research environment" supported by significant expertise in vehicle emission control technology and associated protocols at the University of Auckland, and the effects of high vehicle emissions on health at the National Institutes of Water and Atmosphere (NIWA).

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

    PubMed

    Koivisto, A J; Jensen, A C Ø; Levin, M; Kling, K I; Maso, M Dal; Nielsen, S H; Jensen, K A; Koponen, I K

    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 compared to e.g. for solvents. One way to characterize PM emission source strength is by using the material dustiness index which is scaled to correspond to industrial use by using modifying factors, such as handling energy factors. In this study we investigate how well the NF/FF model predicts PM concentration levels in a paint factory. PM concentration levels were measured during big bag and small bag powder pouring. Rotating drum dustiness indices were determined for the specific powders used and applied in the NF/FF model to predict mass concentrations. Modeled process specific concentration levels were adjusted to be similar to the measured concentration levels by adjusting the handling energy factor. The handling energy factors were found to vary considerably depending on the material and process even-though they have the same values as modifying factors in the exposure models. This suggests that the PM source characteristics and process-specific handling energies should be studied in more detail to improve the model-based exposure assessment. PMID:25407261

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

    PubMed

    Koivisto, A J; Jensen, A C Ø; Levin, M; Kling, K I; Maso, M Dal; Nielsen, S H; Jensen, K A; Koponen, I K

    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 compared to e.g. for solvents. One way to characterize PM emission source strength is by using the material dustiness index which is scaled to correspond to industrial use by using modifying factors, such as handling energy factors. In this study we investigate how well the NF/FF model predicts PM concentration levels in a paint factory. PM concentration levels were measured during big bag and small bag powder pouring. Rotating drum dustiness indices were determined for the specific powders used and applied in the NF/FF model to predict mass concentrations. Modeled process specific concentration levels were adjusted to be similar to the measured concentration levels by adjusting the handling energy factor. The handling energy factors were found to vary considerably depending on the material and process even-though they have the same values as modifying factors in the exposure models. This suggests that the PM source characteristics and process-specific handling energies should be studied in more detail to improve the model-based exposure assessment.

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

    NASA Astrophysics Data System (ADS)

    Di Bartolomeo, A.; Giubileo, F.; Iemmo, L.; Romeo, F.; Russo, S.; Unal, S.; Passacantando, M.; Grossi, V.; Cucolo, A. M.

    2016-07-01

    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 SiO2/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 SiO2 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.

  5. Low-macroscopic field emission properties of wide bandgap copper aluminium oxide nanoparticles for low-power panel applications

    NASA Astrophysics Data System (ADS)

    Narayan Banerjee, Arghya; Joo, Sang W.

    2011-09-01

    Field emission properties of CuAlO2 nanoparticles are reported for the first time, with a low turn-on field of approximately 2 V µm - 1 and field enhancement factor around 230. The field emission process follows the standard Fowler-Nordheim tunnelling of cold electron emission. The emission mechanism is found to be a combination of low electron affinity, internal nanostructure and large field enhancement at the low-dimensional emitter tips of the nanoparticles. The field emission properties are comparable to the conventional carbon-based field emitters, and thus can become alternative candidate for field emission devices for low-power panel applications.

  6. Low-macroscopic field emission properties of wide bandgap copper aluminium oxide nanoparticles for low-power panel applications.

    PubMed

    Banerjee, Arghya Narayan; Joo, Sang W

    2011-09-01

    Field emission properties of CuAlO(2) nanoparticles are reported for the first time, with a low turn-on field of approximately 2 V µm(-1) and field enhancement factor around 230. The field emission process follows the standard Fowler-Nordheim tunnelling of cold electron emission. The emission mechanism is found to be a combination of low electron affinity, internal nanostructure and large field enhancement at the low-dimensional emitter tips of the nanoparticles. The field emission properties are comparable to the conventional carbon-based field emitters, and thus can become alternative candidate for field emission devices for low-power panel applications. PMID:21841217

  7. High-resolution historical emission inventories of crop residue burning in fields in China for the period 1990-2013

    NASA Astrophysics Data System (ADS)

    Li, Jing; Li, Yaqi; Bo, Yu; Xie, Shaodong

    2016-08-01

    High-resolution historical emission inventories of crop residue burning in fields in China were developed for the period 1990-2013. More accurate time-varying statistical data and locally observed emission factors were utilized to estimate crop residue open burning emissions at provincial level. Then pollutants emissions were allocated to a high spatial resolution of 10 km × 10 km and a high temporal resolution of 1 day based on the Moderate Resolution Imaging Spectroradiometer (MODIS) Fire Product (MOD/MYD14A1). Results show that China's CO emissions have increased by 5.67 times at an annual average rate of 24% from 1.06 Tg in 1990 to 7.06 Tg in 2013; the emissions of CO2, CH4, NMVOCs, N2O, NOx, NH3, SO2, PM2.5, OC, and BC have increased by 595%, 500%, 608%, 584%, 600%, 600%, 543%, 571%, 775%, and 500%, respectively, over the past 24 years. Spatially, the regions with high emissions had been notable expanding over the years, especially in the central eastern districts, the Northeastern of China, and the Sichuan Basin. Strong temporal pattern were observed with the highest emissions in June, followed by March to May and October. This work provides a better understanding of the spatiotemporal representation of agricultural fire emissions in China and can benefit both air quality modeling and management with improved accuracy.

  8. Field Thermal Infrared Emissivity Dependence on Soil Moisture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate estimate of land surface temperature, a key parameter in surface energy balance models, requires knowledge of the surface emissivity. Emissivity dependence on soil water content has been already reported and modeled under controlled conditions at the laboratory. This study completes and ext...

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

    NASA Technical Reports Server (NTRS)

    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.

  10. Photoelectric charging of dust particles: Effect of spontaneous and light induced field emission of electrons

    SciTech Connect

    Sodha, M. S.; Dixit, A.

    2009-09-07

    The authors have analyzed the charging of dust particles in a plasma, taking into account the electron/ion currents to the particles, electron/ion generation and recombination, electric field emission, photoelectric emission and photoelectric field emission of electrons under the influence of light irradiation; the irradiance has been assumed to be at a level, which lets the particles retain the negative sign of the charge. Numerical results and discussion conclude the papers.

  11. Improving emissions factors for estimating urban natural gas leakage

    NASA Astrophysics Data System (ADS)

    Phillips, Nathan

    2013-04-01

    Emissions factors for pipeline natural gas leaks are in need of refinement. In addition to limitations from the small sample sizes of leaks that were initially used to develop emissions factors, a further limitation to emissions factors is lack of knowledge of characteristic statistical distributions of pipeline leak rates. For example, leaks were implicitly assumed to be normally distributed so that an average leak rate was used for pipelines of a given construction. Our natural gas leak data from Boston, USA, in which we found over 3,000 natural gas leaks, indicates that leaks rates are highly skewed, with relatively few leaks likely contributing disproportionately to the total. The long-tailed distribution of gas leak rates is mirrored by a similarly skewed distribution of surface methane concentrations in air. These data suggest that emissions factors should be based on correctly specified statistical distributions, and that fixing relatively few large leaks first may provide the most environmental benefit per cost.

  12. Recent progress in low-voltage cathodoluminescent materials: synthesis, improvement and emission properties.

    PubMed

    Li, Guogang; Lin, Jun

    2014-01-01

    Nowadays there are several technologies used for flat panel displays (FPDs) and the development of FPDs with enhanced energy efficiency and improved display quality is strongly required. Field emission displays (FEDs) have been considered as one of the most promising next generation flat panel display technologies due to their excellent display performance and low energy consumption. For the development of FEDs, phosphors are irreplaceable components. In the past decade, the study of highly efficient low-voltage cathodoluminescent materials, namely FED phosphors, has become the focus of enhancing energy efficiency and realizing high-quality displays. This review summaries the recent progress in the chemical synthesis and improvement of novel, rare-earth and transition metal ions activated inorganic cathodoluminescent materials in powder and thin film forms. The discussion is focused on the modification of morphology, size, surface, composition and conductivity of phosphors and the corresponding effects on their cathodoluminescent properties. Special emphases are given to the selection of host and luminescent centers, the adjustment of emission colors through doping concentration optimization, energy transfer and mono- or co-doping activator ions, the improvement of chromaticity, color stability and color gamut as well as the saturation behavior and the degradation behavior of phosphors under the excitation of a low-voltage electron beam. Finally, the research prospects and future directions of FED phosphors are discussed with recommendations to facilitate the further study of new and highly efficient low-voltage cathodoluminescent materials. PMID:24960634

  13. Recent progress in low-voltage cathodoluminescent materials: synthesis, improvement and emission properties.

    PubMed

    Li, Guogang; Lin, Jun

    2014-01-01

    Nowadays there are several technologies used for flat panel displays (FPDs) and the development of FPDs with enhanced energy efficiency and improved display quality is strongly required. Field emission displays (FEDs) have been considered as one of the most promising next generation flat panel display technologies due to their excellent display performance and low energy consumption. For the development of FEDs, phosphors are irreplaceable components. In the past decade, the study of highly efficient low-voltage cathodoluminescent materials, namely FED phosphors, has become the focus of enhancing energy efficiency and realizing high-quality displays. This review summaries the recent progress in the chemical synthesis and improvement of novel, rare-earth and transition metal ions activated inorganic cathodoluminescent materials in powder and thin film forms. The discussion is focused on the modification of morphology, size, surface, composition and conductivity of phosphors and the corresponding effects on their cathodoluminescent properties. Special emphases are given to the selection of host and luminescent centers, the adjustment of emission colors through doping concentration optimization, energy transfer and mono- or co-doping activator ions, the improvement of chromaticity, color stability and color gamut as well as the saturation behavior and the degradation behavior of phosphors under the excitation of a low-voltage electron beam. Finally, the research prospects and future directions of FED phosphors are discussed with recommendations to facilitate the further study of new and highly efficient low-voltage cathodoluminescent materials.

  14. Universal field-emission model for carbon nanotubes on a metal tip

    NASA Astrophysics Data System (ADS)

    Zhong, D. Y.; Zhang, G. Y.; Liu, S.; Sakurai, T.; Wang, E. G.

    2002-01-01

    Electron-field-emission properties have been investigated systematically for carbon nanotubes (CNTs) fabricated on a metal tip. With a vacuum gap of 0.7 mm, the threshold field is as low as 0.7 V/μm and the current density approaches 10 mA/cm2 at an electronic field of 1.0 V/μm. The emission current is quite stable with very low fluctuation. The emission behavior is in excellent agreement with Fowler-Nordheim theory and no current saturation is found even with an emission current reaching 1 A/cm2. A universal relationship 1/β=d2/d+1/β0 between the field amplification factor β and the vacuum gap d is developed within a two-region field-emission model. This relationship provides the basis for a microscopic understanding of CNT emitters and is applicable to other systems as well.

  15. Extremely stable field emission from AlZnO nanowire arrays

    NASA Astrophysics Data System (ADS)

    Xue, X. Y.; Li, L. M.; Yu, H. C.; Chen, Y. J.; Wang, Y. G.; Wang, T. H.

    2006-07-01

    Extremely stable electric field emission from well-aligned AlZnO nanowire arrays is realized. The emission current density is up to 6.5mA/cm2, and no current saturation is observed. The turn-on field is 2.9V/μm as d (distance between the nanowire emitters and anode) is 0.64mm. After aging for two days, the emission current is extremely stable with the fluctuations of ±0.4%. The high stability arises from the high crystal quality with few surface states of the nanowires and the in situ fabrication of cathodes. The field emission behaviors are in excellent agreement with Fowler-Nordheim theory, and the relationship between the field enhancement factor β and d follows a universal equation. Our results imply that AlZnO nanowire arrays are promising candidates for field emission displays.

  16. Metallic nanowire-graphene hybrid nanostructures for highly flexible field emission devices

    NASA Astrophysics Data System (ADS)

    Arif, Muhammad; Heo, Kwang; Lee, Byung Yang; Lee, Joohyung; Seo, David H.; Seo, Sunae; Jian, Jikang; Hong, Seunghun

    2011-09-01

    We report a simple but efficient method to prepare metallic nanowire-graphene (MN-G) hybrid nanostructures at a low temperature and show its application to the fabrication of flexible field emission devices. In this method, a graphene layer was transferred onto an anodic alumina oxide template, and vertically aligned Au nanowires were grown on the graphene surface via electrodeposition method. As a proof of concept, we demonstrated the fabrication of flexible field emission devices, where the MN-G hybrid nanostructures and another graphene layer on PDMS substrates were utilized as a cathode and an anode for highly flexible devices, respectively. Our field emission device exhibited stable and high field emission currents even when bent down to the radius of curvature of 25 mm. This MN-G hybrid nanostructure should prove tremendous flexibility for various applications such as bio-chemical sensors, field emission devices, pressure sensors and battery electrodes.

  17. Carbon-Coated Porous Aluminum Oxides Used as Spacer Overlayers to Reduce Secondary Electron Emission for Field Emission Display Applications

    NASA Astrophysics Data System (ADS)

    Yu, Tung-Yuan; Pan, Fu-Ming; Chen, Cheng-Li; Chen, Te-Ming; Chen, Tsung-Han; Kuo, Chih-Che; Lin, Ting-Li

    2013-07-01

    Porous surface structures can mitigate the charging effect of vacuum spacers of field-emission flat panel display due to the abundance of secondary electrons (SEs) emitted from the spacers during field emission display (FED) operation. In this study, we fabricated porous anodic aluminum oxide (AAO) overlayers on glass substrates to examine the effect of carbon deposition on the reduction of SE emissions. This paper reports that uniform AAO overlayers can be simultaneously prepared on both sides of a glass plate 2 ×10 cm2 in size. The SE emission of the AAO overlayer was examined by using an Auger electron microscope. When a small amount of carbon is evaporation-deposited on the as-prepared AAO overlayer, the SE emission efficiency is significantly decreased and the reduction in the SE emission is ascribed to the low SE yield of the carbon deposit and the suppression of SE escape from the narrowed pore channels. However, a heavy deposition of carbon results in a smaller surface roughness of the AAO overlayer, thereby increasing SE emission. The carbon-coated AAO overlayer demonstrates favorable electrical and mechanical properties, making it suitable for use in FED vacuum spacers.

  18. Enhanced field emission characteristics of boron doped diamond films grown by microwave plasma assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Koinkar, Pankaj M.; Patil, Sandip S.; Kim, Tae-Gyu; Yonekura, Daisuke; More, Mahendra A.; Joag, Dilip S.; Murakami, Ri-ichi

    2011-01-01

    Boron doped diamond films were synthesized on silicon substrates by microwave plasma chemical vapor deposition (MPCVD) technique. The effect of B 2O 3 concentration varied from 1000 to 5000 ppm on the field emission characteristics was examined. The surface morphology and quality of films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. The surface morphology obtained by SEM showed variation from facetted microcrystal covered with nanometric grains to cauliflower of nanocrystalline diamond (NCD) particles with increasing B 2O 3 concentration. The Raman spectra confirm the formation of NCD films. The field emission properties of NCD films were observed to improve upon increasing boron concentration. The values of the onset field and threshold field are observed to be as low as 0.36 and 0.08 V/μm, respectively. The field emission current stability investigated at the preset value of ˜1 μA is observed to be good, in each case. The enhanced field emission properties are attributed to the better electrical conductivity coupled with the nanometric features of the diamond films.

  19. Study of Low Temperature Baking Effect on Field Emission on Nb Samples Treated by BEP, EP, and BCP

    SciTech Connect

    Andy Wu, Song Jin, Robert Rimmer, Xiang Yang Lu, K. Zhao, Laura MacIntyre, Robert Ike

    2010-05-01

    Field emission is still one of the major obstacles facing Nb superconducting radio frequency (SRF) community for allowing Nb SRF cavities to reach routinely accelerating gradient of 35 MV/m that is required for the international linear collider. Nowadays, the well know low temperature backing at 120 oC for 48 hours is a common procedure used in the SRF community to improve the high field Q slope. However, some cavity production data have showed that the low temperature baking may induce field emission for cavities treated by EP. On the other hand, an earlier study of field emission on Nb flat samples treated by BCP showed an opposite conclusion. In this presentation, the preliminary measurements of Nb flat samples treated by BEP, EP, and BCP via our unique home-made scanning field emission microscope before and after the low temperature baking are reported. Some correlations between surface smoothness and the number of the observed field emitters were found. The observed experimental results can be understood, at least partially, by a simple model that involves the change of the thickness of the pent-oxide layer on Nb surfaces.

  20. Methane emissions from global rice fields: Magnitude, spatiotemporal patterns, and environmental controls

    NASA Astrophysics Data System (ADS)

    Zhang, Bowen; Tian, Hanqin; Ren, Wei; Tao, Bo; Lu, Chaoqun; Yang, Jia; Banger, Kamaljit; Pan, Shufen

    2016-09-01

    Given the importance of the potential positive feedback between methane (CH4) emissions and climate change, it is critical to accurately estimate the magnitude and spatiotemporal patterns of CH4 emissions from global rice fields and better understand the underlying determinants governing the emissions. Here we used a coupled biogeochemical model in combination with satellite-derived contemporary inundation area to quantify the magnitude and spatiotemporal variation of CH4 emissions from global rice fields and attribute the environmental controls of CH4 emissions during 1901-2010. Our study estimated that CH4 emissions from global rice fields varied from 18.3 ± 0.1 Tg CH4/yr (Avg. ±1 SD) under intermittent irrigation to 38.8 ± 1.0 Tg CH4/yr under continuous flooding in the 2000s, indicating that the magnitude of CH4 emissions from global rice fields is largely dependent on different water schemes. Over the past 110 years, our simulated results showed that global CH4 emissions from rice cultivation increased by 85%. The expansion of rice fields was the dominant factor for the increasing trends of CH4 emissions, followed by elevated CO2 concentration, and nitrogen fertilizer use. On the contrary, climate variability had reduced the cumulative CH4 emissions for most of the years over the study period. Our results imply that CH4 emissions from global rice fields could be reduced through optimizing irrigation practices. Therefore, the future magnitude of CH4 emissions from rice fields will be determined by the human demand for rice production as well as the implementation of optimized water management practices.

  1. Improved Algorithm For Finite-Field Normal-Basis Multipliers

    NASA Technical Reports Server (NTRS)

    Wang, C. C.

    1989-01-01

    Improved algorithm reduces complexity of calculations that must precede design of Massey-Omura finite-field normal-basis multipliers, used in error-correcting-code equipment and cryptographic devices. Algorithm represents an extension of development reported in "Algorithm To Design Finite-Field Normal-Basis Multipliers" (NPO-17109), NASA Tech Briefs, Vol. 12, No. 5, page 82.

  2. Generalized Fowler-Nordheim Theory of Field Emission of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Liang, Shi-Dong; Chen, Lu

    2008-07-01

    Based on the low-energy band structure of carbon nanotubes (CNs), we develop a generalized Fowler-Nordheim theory of the CN field emission, in which the behavior of the current-voltage (I-V) characteristics depends on the electric field and the diameter of the CNs. This formalism reveals the key differences of field emission between conventional bulk metallic emitters and low-dimensional emitters and gives a clear physical understanding of the non-Fowler-Nordheim feature of the I-V characteristics of the CN field emission.

  3. Generalized Fowler-Nordheim theory of field emission of carbon nanotubes.

    PubMed

    Liang, Shi-Dong; Chen, Lu

    2008-07-11

    Based on the low-energy band structure of carbon nanotubes (CNs), we develop a generalized Fowler-Nordheim theory of the CN field emission, in which the behavior of the current-voltage (I-V) characteristics depends on the electric field and the diameter of the CNs. This formalism reveals the key differences of field emission between conventional bulk metallic emitters and low-dimensional emitters and gives a clear physical understanding of the non-Fowler-Nordheim feature of the I-V characteristics of the CN field emission. PMID:18764229

  4. Development of Improved Oil Field Waste Injection Disposal Techniques

    SciTech Connect

    Terralog Technologies

    2002-11-25

    The goals of this project have was to: (1) assemble and analyze a comprehensive database of past waste injection operations; (2) develop improved diagnostic techniques for monitoring fracture growth and formation changes; (3) develop operating guidelines to optimize daily operations and ultimate storage capacity of the target formation; and (4) to apply these improved models and guidelines in the field.

  5. Improved Photoresist Coating for Making CNT Field Emitters

    NASA Technical Reports Server (NTRS)

    Toda, Risaku; Manohara, Harish

    2009-01-01

    An improved photoresist-coating technique has been developed for use in the fabrication of carbon-nanotube- (CNT) based field emitters is described. The improved photoresist coating technique overcomes what, heretofore, has been a major difficulty in the fabrication process.

  6. Field emission from α-Fe2O3 nanoflakes: Effect of vacuum pressure, gas adsorption and in-situ thermal treatment

    NASA Astrophysics Data System (ADS)

    Wu, J. Q.; Deng, S. Z.; Xu, N. S.; Chen, Jun

    2014-02-01

    The effects of vacuum pressure and gas adsorption on field emission current of α-Fe2O3 nanoflakes were studied. It was found that field emission current of α-Fe2O3 nanoflakes decreased with increasing pressure. The field emission current decreased when N2 or O2 was introduced into chamber, while no obvious change was observed for H2 gas. An in-situ thermal treatment was carried out to eradicate the effect of absorbed gas. After the in-situ thermal treatment, the field emission current density was largely enhanced from 60 to 500 μA/cm2 under applied electrical field of 10 MV/m and the turn on field (Eturn-on) decreased from 7.6 to 5.2 MV/m. The lowered turn-on field was attributed to the decrease of surface work function induced by surface gas desorption and reduction of α-Fe2O3 nanoflakes. Moreover, the improvement of field emission performance can be retained in high vacuum condition, which indicates the in-situ thermal treatment is an efficient method to improve field emission properties of α-Fe2O3 nanoflakes.

  7. Observation of valence band electron emission from n-type silicon field emitter arrays

    NASA Astrophysics Data System (ADS)

    Ding, Meng; Kim, Han; Akinwande, Akintunde I.

    1999-08-01

    Electron emission from the valence band of n-type Si field emitter arrays is reported. High electrostatic field at the surface of Si was achieved by reducing the radius of the emitter tip. Using oxidation sharpening, 1 μm aperture polycrystalline Si gate, n-type Si field emitter arrays with small tip radius (˜10 nm) were fabricated. Three distinct emission regions were observed: conduction band emission at low gate voltages, saturated current emission from the conduction band at intermediate voltages, and valence band plus conduction band emission at high gate voltages. Emission currents at low and high voltages obey the Fowler-Nordheim theory. The ratio of the slopes of the corresponding Fowler-Nordheim fits for these two regions is 1.495 which is in close agreement with the theoretical value of 1.445.

  8. Densification effects of the carbon nanotube pillar array on field-emission properties

    NASA Astrophysics Data System (ADS)

    Wang, Kuang-Yu; Chou, Chia-Hsin; Liao, Chan-Yu; Li, Yu-Ren; Cheng, Huang-Chung

    2016-06-01

    In this study, a simple densification method for carbon nanotube (CNT) pillars is proposed to achieve high-performance field emission characteristics and stable emission. Through capillary force during solution evaporation, the CNT density in each pillar can be increased by about six times without causing damage to the crystallinity of CNTs. The densified CNT pillars exhibit lower series resistance, sharper pillars, better contacts, higher thermal conductivity, and better mechanical stiffness than as-grown ones. Therefore, the threshold field of the field emitter with such CNT pillars of 50 µm height can be reduced to 1.98 V/µm, as compared with 2.2 V/µm for the undensified ones. Moreover, the fluctuation of field-emission current decreases from 15.5 to 9.4% after the stress tests at a field of 2 V/µm for 1800 s. These findings imply that the densified CNT pillars are promising for the field-emission applications.

  9. Greenhouse gas emissions from dairy manure management: a review of field-based studies.

    PubMed

    Owen, Justine J; Silver, Whendee L

    2015-02-01

    Livestock manure management accounts for almost 10% of greenhouse gas emissions from agriculture globally, and contributes an equal proportion to the US methane emission inventory. Current emissions inventories use emissions factors determined from small-scale laboratory experiments that have not been compared to field-scale measurements. We compiled published data on field-scale measurements of greenhouse gas emissions from working and research dairies and compared these to rates predicted by the IPCC Tier 2 modeling approach. Anaerobic lagoons were the largest source of methane (368 ± 193 kg CH4 hd(-1) yr(-1)), more than three times that from enteric fermentation (~120 kg CH4 hd(-1) yr(-1)). Corrals and solid manure piles were large sources of nitrous oxide (1.5 ± 0.8 and 1.1 ± 0.7 kg N2O hd(-1) yr(-1), respectively). Nitrous oxide emissions from anaerobic lagoons (0.9 ± 0.5 kg N2O hd(-1) yr(-1)) and barns (10 ± 6 kg N2O hd(-1) yr(-1)) were unexpectedly large. Modeled methane emissions underestimated field measurement means for most manure management practices. Modeled nitrous oxide emissions underestimated field measurement means for anaerobic lagoons and manure piles, but overestimated emissions from slurry storage. Revised emissions factors nearly doubled slurry CH4 emissions for Europe and increased N2O emissions from solid piles and lagoons in the United States by an order of magnitude. Our results suggest that current greenhouse gas emission factors generally underestimate emissions from dairy manure and highlight liquid manure systems as promising target areas for greenhouse gas mitigation.

  10. Traffic patterns and daily variability of motor vehicles emissions during the 1995 SOS Nashville/Middle Tennessee Ozone Field Study

    SciTech Connect

    Cardelino, C.; Wen-Ling Chang; Chang, M.E.

    1996-12-31

    This work describes traffic patterns and the daily variability of mobile sources in rural and urban areas in and around the Nashville Metropolitan Area. Traffic counter data, video recordings and speed data collected during the 1995 SOS Nashville/Middle Tennessee Ozone Field Study are used to analyzed the spatial and temporal distribution of traffic volume, vehicle speed, and vehicle classification. Using traffic volume as a surrogate for mobile emissions, a simple method is employed to characterize the daily variability of emissions on the different types of urban and rural roads. The method is also used to describe the daily variability of mobile emissions for the whole modeling domain. Implications of this work for the improvements of mobile emission inventories are discussed.

  11. The effect of aspect ratio and sp2/sp3 content on the field emission properties of carbon films grown by Ns-spiked PECVD

    SciTech Connect

    Tong, W.; Felter, T.E.; Pan, L.S.; Anders, S.; Cossy-Facre, A.; Stammler, T.

    1998-04-01

    The authors have deposited carbon films from mixtures of methane and N{sub 2} using Plasma Enhanced Chemical Vapor Deposition. By changing the percentage of N{sub 2} in the feed gas, they were able to produce films that have various aspect ratios and sp{sup 2}/sp{sup 3} contents. The film with the highest field emission contains spears of aspect ratio of 10:1. They also found that in their sp{sup 3}-rich films, higher sp{sup 2} content enhanced field emission. This is ascribed to improved charge transport to the field emission sites.

  12. Field emission of carbon quantum dots synthesized from a single organic solvent.

    PubMed

    Liu, Xiahui; Yang, Bingjun; Yang, Juan; Yu, Shengxue; Chen, Jiangtao

    2016-11-01

    In this paper, a facile synthesis of carbon quantum dots (CQDs) and its field emission performance are reported. The CQDs are prepared from a single N, N-dimethylformamide acting as carbon and nitrogen-doping sources simultaneously. The CQDs are investigated by photoluminescence, transmission electron microscopy and x-ray photoelectron spectroscopy. The CQDs have an average size of 3 nm and are doped with N atoms. CQD dispersion shows strong fluorescence under UV illumination. For the first time, the field emission behavior of CQDs coated on Si substrate is studied. As a candidate of cold cathode, the CQDs display good field emission performance. The CQD emitter reaches the current density of 1.1 mA cm(-2) at 7.0 V μm(-1) and exhibits good long-term emission stability, suggesting promising application in field emission devices. PMID:27671204

  13. Field emission of carbon quantum dots synthesized from a single organic solvent.

    PubMed

    Liu, Xiahui; Yang, Bingjun; Yang, Juan; Yu, Shengxue; Chen, Jiangtao

    2016-11-01

    In this paper, a facile synthesis of carbon quantum dots (CQDs) and its field emission performance are reported. The CQDs are prepared from a single N, N-dimethylformamide acting as carbon and nitrogen-doping sources simultaneously. The CQDs are investigated by photoluminescence, transmission electron microscopy and x-ray photoelectron spectroscopy. The CQDs have an average size of 3 nm and are doped with N atoms. CQD dispersion shows strong fluorescence under UV illumination. For the first time, the field emission behavior of CQDs coated on Si substrate is studied. As a candidate of cold cathode, the CQDs display good field emission performance. The CQD emitter reaches the current density of 1.1 mA cm(-2) at 7.0 V μm(-1) and exhibits good long-term emission stability, suggesting promising application in field emission devices.

  14. Field emission of carbon quantum dots synthesized from a single organic solvent

    NASA Astrophysics Data System (ADS)

    Liu, Xiahui; Yang, Bingjun; Yang, Juan; Yu, Shengxue; Chen, Jiangtao

    2016-11-01

    In this paper, a facile synthesis of carbon quantum dots (CQDs) and its field emission performance are reported. The CQDs are prepared from a single N, N-dimethylformamide acting as carbon and nitrogen-doping sources simultaneously. The CQDs are investigated by photoluminescence, transmission electron microscopy and x-ray photoelectron spectroscopy. The CQDs have an average size of 3 nm and are doped with N atoms. CQD dispersion shows strong fluorescence under UV illumination. For the first time, the field emission behavior of CQDs coated on Si substrate is studied. As a candidate of cold cathode, the CQDs display good field emission performance. The CQD emitter reaches the current density of 1.1 mA cm-2 at 7.0 V μm-1 and exhibits good long-term emission stability, suggesting promising application in field emission devices.

  15. Growth of Aligned Multiwall Carbon Nanotubes and the Effect of Adsorbates on the Field Emission Properties

    NASA Astrophysics Data System (ADS)

    Milne, W. I.; Teo, K. B. K.; Lansley, S. B.; Chhowalla, M.; Amaratunga, G. A. J.; Semet, V.; Binh, Vu Thien; Pirio, G.; Legagneux, P.

    2003-10-01

    In attempt to decipher the field emission characteristics of multiwall carbon nanotubes (MWCNTs), we have developed a fabrication method based on plasma enhanced chemical vapour deposition (PECVD) to provide utmost control of the nanotube structure such as their alignment, individual position, diameter, length and morphology. We investigated the field emission properties of these nanotubes to elucidate the effect of adsorbates on the nanotubes. Our results show that although the adsorbates cause an apparent lowering of the required turn on voltage/field of the nanotubes, the adsorbates undesirably cause a saturation of the current, large temporal fluctuations in the current, and also a deviation of the emission characteristics from Fowler-Nordheim like emission. The adsorbates are easily removed by extracting an emission current of 1 uA per nanotube or using a high applied electric field (˜25V/um).

  16. Update and improvement of the global krypton-85 emission inventory.

    PubMed

    Ahlswede, Jochen; Hebel, Simon; Ross, J Ole; Schoetter, Robert; Kalinowski, Martin B

    2013-01-01

    Krypton-85 is mainly produced in nuclear reactors by fission of uranium and plutonium and released during chopping and dissolution of spent fuel rods in nuclear reprocessing facilities. As noble gas it is suited as a passive tracer for evaluation of atmospheric transport models. Furthermore, research is ongoing to assess its quality as an indicator for clandestine reprocessing activities. This paper continues previous efforts to compile a comprehensive historic emission inventory for krypton-85. Reprocessing facilities are the by far largest emitters of krypton-85. Information on sources and calculations used to derive the annual krypton-85 emission is provided for all known reprocessing facilities in the world. In addition, the emission characteristics of two plants, Tokai (Japan) and La Hague (France), are analysed in detail using emission data with high temporal resolution. Other types of krypton-85 sources are power reactors, naval reactors and isotope production facilities. These sources contribute only little or negligible amounts of krypton-85 compared to the large reprocessing facilities. Taking the decay of krypton-85 into account, the global atmospheric inventory is estimated to about 5500 PBq at the end of 2009. The correctness if the inventory has been proven by meteorological simulations and its error is assumed to be in the range of a few percent. PMID:22858641

  17. Update and improvement of the global krypton-85 emission inventory.

    PubMed

    Ahlswede, Jochen; Hebel, Simon; Ross, J Ole; Schoetter, Robert; Kalinowski, Martin B

    2013-01-01

    Krypton-85 is mainly produced in nuclear reactors by fission of uranium and plutonium and released during chopping and dissolution of spent fuel rods in nuclear reprocessing facilities. As noble gas it is suited as a passive tracer for evaluation of atmospheric transport models. Furthermore, research is ongoing to assess its quality as an indicator for clandestine reprocessing activities. This paper continues previous efforts to compile a comprehensive historic emission inventory for krypton-85. Reprocessing facilities are the by far largest emitters of krypton-85. Information on sources and calculations used to derive the annual krypton-85 emission is provided for all known reprocessing facilities in the world. In addition, the emission characteristics of two plants, Tokai (Japan) and La Hague (France), are analysed in detail using emission data with high temporal resolution. Other types of krypton-85 sources are power reactors, naval reactors and isotope production facilities. These sources contribute only little or negligible amounts of krypton-85 compared to the large reprocessing facilities. Taking the decay of krypton-85 into account, the global atmospheric inventory is estimated to about 5500 PBq at the end of 2009. The correctness if the inventory has been proven by meteorological simulations and its error is assumed to be in the range of a few percent.

  18. Improving Dryer and Press Efficiencies Through Combustion of Hydrocarbon Emissions

    SciTech Connect

    Sujit Banerjee

    2005-10-31

    Emission control devices on dryers and presses have been legislated into the industry, and are now an integral part of the drying system. These devices consume large quantities of natural gas and electricity and down-sizing or eliminating them will provide major energy savings. The principal strategy taken here focuses on developing process changes that should minimize (and in some cases eliminate) the need for controls. A second approach is to develop lower-cost control options. It has been shown in laboratory and full-scale work that Hazardous Air Pollutants (HAPs) emerge mainly at the end of the press cycle for particleboard, and, by extension, to other prod-ucts. Hence, only the air associated with this point of the cycle need be captured and treated. A model for estimating terpene emissions in the various zones of veneer dryers has been developed. This should allow the emissions to be concentrated in some zones and minimized in others, so that some of the air could be directly released without controls. Low-cost catalysts have been developed for controlling HAPs from dryers and presses. Catalysts conventionally used for regenerative catalytic oxidizers can be used at much lower temperatures for treating press emissions. Fluidized wood ash is an especially inexpensive mate-rial for efficiently reducing formaldehyde in dryer emissions. A heat transfer model for estimating pinene emissions from hot-pressing strand for the manufacture of flakeboard has been constructed from first principles and validated. The model shows that most of the emissions originate from the 1-mm layer of wood adjoining the platen surface. Hence, a simple control option is to surface a softwood mat with a layer of hardwood prior to pressing. Fines release a disproportionate large quantity of HAPs, and it has been shown both theo-retically and in full-scale work that particles smaller than 400 µm are principally responsible. Georgia-Pacific is considering green

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

    NASA Technical Reports Server (NTRS)

    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. [Emission Inventory of Crop Residues Field Burning and Its Temporal and Spatial Distribution in Sichuan Province].

    PubMed

    He, Min; Wang, Xing-rui; Han, Li; Feng, Xiao-qiong; Mao, Xue

    2015-04-01

    Based on the collected activity data, the 2012 emission inventory of crop residues field burning in Sichuan province was developed through the emission factor approach. Besides, the temporal and spatial distribution of pollutant emissions was also analysed in this paper. The results showed that the total emissions of SO2, NO(x), NH3, CH4, NMVOC, CO, PM2.5, EC and OC from crop residues field burning in Sichuan province in the year of 2012 were 1 210, 12 185, 2 827, 20 659, 40 463, 292 671, 39 277, 1 984 and 10 215 t, respectively; The rice straw, wheat straw, corn straw and oil rape straw were four major contributors to pollutant emissions, with a total contribution about 88% - 94%; Crop residues field burning emissions were affected by agricultural harvesting. Temporally, the emissions were concentrated in July and August with a small peak in May; Spatially, the Chengdu plain, the Northern area and the Eastern area of Sichuan province were the highest emission areas, while the Western area had relatively low emissions; The key uncertain sources included emission factors and parameters used for estimating crop burning amounts.

  1. Field emission analysis of band bending in donor/acceptor heterojunction

    NASA Astrophysics Data System (ADS)

    Xing, Yingjie; Li, Shuai; Wang, Guiwei; Zhao, Tianjiao; Zhang, Gengmin

    2016-06-01

    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.

  2. Synthesis and excellent field emission properties of three-dimensional branched GaN nanowire homostructures

    NASA Astrophysics Data System (ADS)

    Li, Enling; Sun, Lihe; Cui, Zhen; Ma, Deming; Shi, Wei; Wang, Xiaolin

    2016-10-01

    Three-dimensional branched GaN nanowire homostructures have been synthesized on the Si substrate via a two-step approach by chemical vapor deposition. Structural characterization reveals that the single crystal GaN nanowire trunks have hexagonal wurtzite characteristics and grow along the [0001] direction, while the homoepitaxial single crystal branches grow in a radial direction from the six-sided surfaces of the trunks. The field emission measurements demonstrate that the branched GaN nanowire homostructures have excellent field emission properties, with low turn-on field at 2.35 V/μm, a high field enhancement factor of 2938, and long emission current stability. This indicates that the present branched GaN nanowire homostructures will become valuable for practical field emission applications.

  3. Field emission from carbon nanotubes produced using microwave plasma assisted CVD

    SciTech Connect

    Zhang, Q.; Yoon, S.F.; Ahn, J.; Gan, B.; Rusli; Yu, M.B.; Cheah, L.K.; Shi, X.

    2000-01-30

    Electron field emission from carbon nanotubes prepared using microwave plasma assisted CVD has been investigated. The nanotubes, ranging from 50 to 120 nm in diameter and a few tens of microns in length, were formed under methane and hydrogen plasma at 720 C with the aid of iron-oxide particles. The morphology and growth direction of the nanotubes are found to be strongly influenced by the flow ratio of methane to hydrogen. However, the electron field emission from these massive nanotubes show similar characteristics, i.e., high emission current at low electric fields.

  4. Enhanced electrical properties and field emission characteristics of AZO/ZnO-nanowire core-shell structures.

    PubMed

    Huang, Jheng-Ming; Tsai, Shang-You; Ku, Ching-Shun; Lin, Chih-Ming; Chen, San-Yuan; Lee, Hsin-Yi

    2016-06-01

    The electrical properties and field-emission characteristics of ZnO nanowires (ZnO-NWs) fabricated using a vapor-liquid-solid method were systematically investigated. In particular, we explored the effects of Al-doped ZnO (AZO) films (thickness 4-100 nm) deposited on ZnO-NWs using an atomic layer deposition (ALD) method on the optoelectronic properties. The results show that the sheet resistance of net-like ZnO-NW structures can be significantly improved, specifically to become ∼1/1000 of the sheet resistance of the as-grown ZnO-NWs, attaining less than 10 Ω Sq(-1). The emission current density measured at the maximum field was roughly quadrupled relative to that of the as-grown ZnO-NWs. The data of the enhanced field-emission characteristics show that, with the ALD system, the AZO films of small resistance are readily coated on a structure with a high aspect ratio and the coating radius is controlled relative to the turn-on voltage and current density. The ultrathin AZO film from a one-monolayer coating process also significantly improved emission properties through modification of the effective work function at the AZO/ZnO-NW surface. PMID:27210896

  5. Enhanced electrical properties and field emission characteristics of AZO/ZnO-nanowire core-shell structures.

    PubMed

    Huang, Jheng-Ming; Tsai, Shang-You; Ku, Ching-Shun; Lin, Chih-Ming; Chen, San-Yuan; Lee, Hsin-Yi

    2016-06-01

    The electrical properties and field-emission characteristics of ZnO nanowires (ZnO-NWs) fabricated using a vapor-liquid-solid method were systematically investigated. In particular, we explored the effects of Al-doped ZnO (AZO) films (thickness 4-100 nm) deposited on ZnO-NWs using an atomic layer deposition (ALD) method on the optoelectronic properties. The results show that the sheet resistance of net-like ZnO-NW structures can be significantly improved, specifically to become ∼1/1000 of the sheet resistance of the as-grown ZnO-NWs, attaining less than 10 Ω Sq(-1). The emission current density measured at the maximum field was roughly quadrupled relative to that of the as-grown ZnO-NWs. The data of the enhanced field-emission characteristics show that, with the ALD system, the AZO films of small resistance are readily coated on a structure with a high aspect ratio and the coating radius is controlled relative to the turn-on voltage and current density. The ultrathin AZO film from a one-monolayer coating process also significantly improved emission properties through modification of the effective work function at the AZO/ZnO-NW surface.

  6. Morphology dependent field emission characteristics of ZnS/silicon nanoporous pillar array

    NASA Astrophysics Data System (ADS)

    Wang, Ling Li; Zhao, Cheng Zhou; Kang, Li Ping; Liu, De Wei; Zhao, Hui Chun; Hao, Shan Peng; Zhang, Yuan Kai; Chen, Zhen Ping; Li, Xin Jian

    2016-10-01

    Through depositing zinc sulphide (ZnS) nanoparticals on silicon nanoporous pillar array (Si-NPA) and crater-shaped silicon nanoporous pillar array (c-Si-NPA) by chemical bath deposition (CBD) method, ZnS/Si-NPA and c-ZnS/Si-NPA were prepared and the field emission (FE) properties of them were investigated. The turn-on electric fields of were 3.8 V/mm for ZnS/Si-NPA and 5.0 V/mm for c-ZnS/Si-NPA, respectively. The lower turn-on electric fields of ZnS/Si-NPA than that of c-ZnS/Si-NPA were attributed to the different electric distribution of the field emitters causing by the different surface morphology of the two samples, which was further demonstrated via the simulated results by finite element modeling. The FN curves for the ZnS/Si-NPA showed two-slope behavior. All the results indicate that the morphology play an important role in the FE properties and designing an appropriate top morphology for the emitter is a very efficient way to improve the FE performance.

  7. Improved linac dose distributions for radiosurgery with elliptically shaped fields.

    PubMed

    Serago, C F; Lewin, A A; Houdek, P V; Gonzalez-Arias, S; Abitbol, A A; Marcial-Vega, V A; Pisciotti, V; Schwade, J G

    1991-10-01

    Stereotactic radiosurgery techniques for a linear accelerator typically use circular radiation fields to produce an essentially spherical radiation distribution with a steep dose gradient. Target volumes are frequently irregular in shape, and circular distributions may irradiate normal tissues to high dose as well as the target volume. Improvements to the dose distribution have been made using multiple target points and optimizing the dose per arc to the target. A retrospective review of 20 radiosurgery patients has suggested that the use of elliptically shaped fields may further improve the match of the radiation distribution to the intended target volume. This hypothesis has been verified with film measurements of the radiation distribution obtained using elliptical radiation beam in a head phantom. Reductions of 40% of the high dose volume have been obtained with elliptical fields compared to circular fields without compromising the dose to the target volume. PMID:1938531

  8. Growth temperature effect on field emission properties of printable carbon nanotubes cathode

    NASA Astrophysics Data System (ADS)

    Wang, Lili; Sun, Zhuo; Chen, Ting; Que, Wenxiu

    2006-05-01

    The carbon nanotubes (CNTs) were synthesized by low pressure chemical vapor deposition (CVD) in the temperature range of 500-750 °C. The dependence of field emission properties of screen-printed cathode on the CNTs growth temperatures was studied. The scanning electron microscope (SEM) images and Raman spectra showed that with the temperature increasing from 500 °C to 750 °C, the average diameter of most CNTs decreased, and the crystallinity of the nanotubes increases as shown by the narrower and more intense G peak in the Raman spectra. It is found that the higher growth temperature, the better field emission properties of the screen-printed nanotubes cathodes, i.e. lower turn-on emission field, higher emission current and more uniform emission.

  9. Characterization of field emission from carbon nanofibers on a metal tip

    NASA Astrophysics Data System (ADS)

    Sakai, Y.; Tone, D.; Nagatsu, S.; Endo, T.; Kita, S.; Okuyama, F.

    2009-08-01

    Field electron emission from carbon nanofibers (CNFs) grown on a tungsten tip has been characterized by measuring emission current-voltage (I-V) curves and observing emission patterns on a phosphor screen. CNFs were vertically grown on the tip by plasma-enhanced chemical vapor deposition. Field emission from the CNFs over 100 μA was strongly dependent on emitter-anode distance, and the dominant field electrons were emitted within an angular spread of Δθ ˜25°, indicating the electron emission took place mainly from the emitter's apex area. By analyzing the I-V curves with the aid of the Fowler-Nordheim theory, the maximum current density was estimated to be about J =2×109 A/m2.

  10. Field emission behavior of cuboid zinc oxide nanorods on zinc-filled porous silicon

    NASA Astrophysics Data System (ADS)

    Yu, Ke; Zhang, Yongsheng; Xu, Rongli; Jiang, Desheng; Luo, Laiqiang; Li, Qiong; Zhu, Ziqiang; Lu, Wei

    2005-01-01

    Single-crystalline zinc oxide (ZnO) nanorods with cuboid morphology have been prepared on the zinc-filled porous silicon substrate using a vapor phase transport method. Field-emission measurements showed that the turn-on field and threshold field of the cuboid ZnO nanorods film were about 3.2 and 8.2 V/μm respectively. From the emitter surface, a homogeneous emission image was observed with emission site density (ESD) of ˜10 4 cm -2. The better emission uniformity and the high ESD may be attributed to a large number of ZnO nanocrystallites as emitter on the surface of the nanorod end contributing to emission.

  11. High performance bulk metallic glass/carbon nanotube composite cathodes for electron field emission

    SciTech Connect

    Hojati-Talemi, Pejman; Gibson, Mark A.; East, Daniel; Simon, George P.

    2011-11-07

    We report the preparation of new nanocomposites based on a combination of bulk metallic glass and carbon nanotubes for electron field emission applications. The use of bulk metallic glass as the matrix ensures high electrical and thermal conductivity, high thermal stability, and ease of processing, whilst the well dispersed carbon nanotubes act as highly efficient electron emitters. These advantages, alongside excellent electron emission properties, make these composites one of the best reported options for electron emission applications to date.

  12. Monte Carlo simulation of near-field terahertz emission from semiconductors

    NASA Astrophysics Data System (ADS)

    Corzo-Garcia, S. C.; Hernandez-Serrano, A. I.; Castro-Camus, E.; Mitrofanov, O.

    2016-07-01

    We simulated the carrier dynamics in InGaAs after ultrafast photoexcitation. By using a finite-difference time-domain approach we were able to analyze the near terahertz field emission caused by the motion of such carriers. We found that both the current parallel and normal to the interface take a relevant role in the terahertz emission. We also found that the ballistic motion of the carriers after photoexcitation dominates the emission rather than diffusion.

  13. Modelled and field measurements of biogenic hydrocarbon emissions from a Canadian deciduous forest

    NASA Astrophysics Data System (ADS)

    Fuentes, J. D.; Wang, D.; Den Hartog, G.; Neumann, H. H.; Dann, T. F.; Puckett, K. J.

    rates by at least two-fold compared to emissions derived from field measurements. The isoprene emission algorithm proposed by Guenther et al. (1993), applied at the leaf level, provides relatively good agreement compared to measurements. Field measurements indicate that isoprene emissions change with leaf ontogeny and differ amongst tree species. Emission rates defined as function of foliage development stage and plant species need to be introduced in the hydrocarbon emission algorithms. Extensive model evaluation and more hydrocarbon emission measurement;: from different plant species are required to fully assess the appropriateness of this emission calculation approach for Canadian forests.

  14. Emissions of N2O and NO from fertilized fields: Summary of available measurement data

    NASA Astrophysics Data System (ADS)

    Bouwman, A. F.; Boumans, L. J. M.; Batjes, N. H.

    2002-12-01

    Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was summarized to assess the influence of various factors regulating emissions from mineral soils. The data indicate that there is a strong increase of both N2O and NO emissions accompanying N application rates, and soils with high organic-C content show higher emissions than less fertile soils. A fine soil texture, restricted drainage, and neutral to slightly acidic conditions favor N2O emission, while (though not significant) a good soil drainage, coarse texture, and neutral soil reaction favor NO emission. Fertilizer type and crop type are important factors for N2O but not for NO, while the fertilizer application mode has a significant influence on NO only. Regarding the measurements, longer measurement periods yield more of the fertilization effect on N2O and NO emissions, and intensive measurements (≥1 per day) yield lower emissions than less intensive measurements (2-3 per week). The available data can be used to develop simple models based on the major regulating factors which describe the spatial variability of emissions of N2O and NO with less uncertainty than emission factor approaches based on country N inputs, as currently used in national emission inventories.

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

    NASA Astrophysics Data System (ADS)

    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

  16. Field Electron Emission from Caterpillar-Like Clavae Nano-Structure Carbon Thin Films

    NASA Astrophysics Data System (ADS)

    Wang, Li-Jun; Zhu, Yu-Zhuan; Wang, Xiao-Ping; Zhang, Shi; Liu, Xin-Xin; Li, Huai-Hui; Mei, Cui-Yu; Liu, Xiao-Fei

    2010-08-01

    Nano-carbon films with large density of caterpillar-like clavae are synthesized by microwave plasma-assisted chemical vapor deposition using a mixture of methane and hydrogen gases on Mo film substrates. The films are characterized by Raman spectra, optical microscopy and field emission scanning electron microscopy. Field electron emission measurements of nano-carbon films are also carried out to show the turn-on field as low as 1.5 V/μm and the high current density of 2.2 mA/cm2 at electric field of 5.7 V/μm, the uniformly distributed emission site density from a broad well-proportioned emission area of about 4.0 cm2 is also obtained. The field-emission current density J versus macroscopic electric field E does not follow the original Fowler-Nordheim (F-N) relation since they are not well represented in the F-N plot by a straight line. A modified F-N relation is applied successfully to explain all the field-emission data observed for E < 6.0 V/μm.

  17. ABRUPT LONGITUDINAL MAGNETIC FIELD CHANGES AND ULTRAVIOLET EMISSIONS ACCOMPANYING SOLAR FLARES

    SciTech Connect

    Johnstone, B. M.; Petrie, G. J. D.; Sudol, J. J.

    2012-11-20

    We have used Transition Region and Coronal Explorer 1600 A images and Global Oscillation Network Group (GONG) magnetograms to compare ultraviolet (UV) emissions from the chromosphere to longitudinal magnetic field changes in the photosphere during four X-class solar flares. An abrupt, significant, and persistent change in the magnetic field occurred across more than 10 pixels in the GONG magnetograms for each flare. These magnetic changes lagged the GOES flare start times in all cases, showing that they were consequences and not causes of the flares. Ultraviolet emissions were spatially coincident with the field changes. The UV emissions tended to lag the GOES start times for the flares and led the changes in the magnetic field in all pixels except one. The UV emissions led the photospheric field changes by 4 minutes on average with the longest lead being 9 minutes; however, the UV emissions continued for tens of minutes, and more than an hour in some cases, after the field changes were complete. The observations are consistent with the picture in which an Alfven wave from the field reconnection site in the corona propagates field changes outward in all directions near the onset of the impulsive phase, including downward through the chromosphere and into the photosphere, causing the photospheric field changes, whereas the chromosphere emits in the UV in the form of flare kernels, ribbons, and sequential chromospheric brightenings during all phases of the flare.

  18. A multiresolution random field model for estimating fossil-fuel CO2 emissions

    NASA Astrophysics Data System (ADS)

    Ray, J.; Yadav, V.; Michalak, A. M.; Lee, J.; Lefantzi, S.; VanBloemenWaanders, B.

    2013-12-01

    We present a multiscale random field model (MsRF) that can be used for representing fossil-fuel CO2 (ffCO2) emissions. It is low-dimensional and is meant to be used in atmospheric inversions. The MsRF is constructed using wavelets. In this work, we will demonstrate a synthetic-data inversion aimed at estimating ffCO2 emissions, with 1o x 1o resolution, in the lower 48 states of the US. Measurements from 35 towers will be used. The measurements are constructed using the Vulcan inventory. The MsRF consists of a subset of Haar wavelets that can be defined in a rectangle bounding the US. By subjecting the Vulcan database to wavelet-transforms with a wide choice, the Haar wavelet was found to offer the most compressible representation. The MsRF was constructed by subjecting an image of lights at night to Haar transforms and retaining those with large weights. The lights-at-night image is correlated with ffCO2 inversions and have been used to downscale national ffCO2 aggregates when constructing spatially resolved ffCO2 emission inventories. The MsRF is then used to solve the linear inverse problem that underlies ffCO2 emission estimation. The number of parameters in the MsRF is far too large to be constrained by the measurements and thus we enforce sparsity to regularize the inverse problem. Further, we show that the transport model is only somewhat incoherent with respect to the chosen Haar bases, indicating that sparsification will be insufficient and further regularization using a prior emission model is required. This model is obtained by scaling up the nightlights to match EDGAR emissions. Finally, we present the results of the inversion and show that the resulting inversion mechanism can extract information from the observation to update and improve upon the predictive accuracy of prior model. The density of measurements dominates the accuracy of the inversion. We find that sparsification plays an important role since it removes about 50% of the wavelets in the Ms

  19. Ultralow field emission from thinned, open-ended, and defected carbon nanotubes by using microwave hydrogen plasma processing

    NASA Astrophysics Data System (ADS)

    Deng, Jian-Hua; Cheng, Lin; Wang, Fan-Jie; Yu, Bin; Li, Guo-Zheng; Li, De-Jun; Cheng, Guo-An

    2015-01-01

    Ultralow field emission is achieved from carbon nanotubes (CNTs) by using microwave hydrogen plasma processing. After the processing, typical capped CNT tips are removed, with thinned, open-ended, and defected CNTs left. Structural analyses indicate that the processed CNTs have more SP3-hybridized defects as compared to the pristine ones. The morphology of CNTs can be readily controlled by adjusting microwave powers, which change the shape of CNTs by means of hydrogen plasma etching. Processed CNTs with optimal morphology are found to have an ultralow turn-on field of 0.566 V/μm and threshold field of 0.896 V/μm, much better than 0.948 and 1.559 V/μm of the as-grown CNTs, respectively. This improved FE performance is ascribed to the structural changes of CNTs after the processing. The thinned and open-ended shape of CNTs can facilitate electron tunneling through barriers and additionally, the increased defects at tube walls can serve as new active emission sites. Furthermore, our plasma processed CNTs exhibit excellent field emission stability at a large emission current density of 10.36 mA/cm2 after being perfectly aged, showing promising prospects in applications as high-performance vacuum electron sources.

  20. “Comprehensive emission measurements from prescribed burning in Florida: field and laboratory, aerial and ground”

    EPA Science Inventory

    Simultaneous aerial- and ground-based emission sampling was conducted during prescribed burns at Eglin Air Force Base in November 2012 on a short grass/shrub field and a pine forest. Cumulative emission samples for volatile organic comounds, elemental carbon, organic carbon, ch...

  1. Comprehensive emission measurements from prescribed burning in Florida: field and laboratory, aerial and ground

    EPA Science Inventory

    Simultaneous aerial- and ground-based emission sampling was conducted during prescribed burns at Eglin Air Force Base in November 2012 on a short grass/shrub field and a pine forest. Cumulative emission samples for volatile organic compounds, elemental carbon, organic carbon, c...

  2. Planar nanosized field emission cathodes on the basis of graphene/semi-insulating silicon carbide fabricated by focused ion beam

    NASA Astrophysics Data System (ADS)

    Jityaev, L.; Ageev, O. A.; Svetlichnyi, A. M.; Kolomiytsev, A. S.; Spiridonov, O. B.

    2016-08-01

    We investigate the field emission properties of planar graphene structures with nanosized interelectrode distance. The graphene was obtained by thermal decomposition of silicon carbide in vacuum. Planar field emission structures on the basis of graphene on semiinsulating SiC were fabricated by using focused ion beam. We have performed current-voltage measurement on graphene/SiC field emission cathodes. The planar field emission structures showed a threshold voltage less than 1 V.

  3. Iterative Inverse Modeling for Reconciliation of Emission Inventories during the 2006 TexAQS Intensive Field Campaign

    NASA Astrophysics Data System (ADS)

    Xiao, X.; Cohan, D. S.

    2009-12-01

    Substantial uncertainties in current emission inventories have been detected by the Texas Air Quality Study 2006 (TexAQS 2006) intensive field program. These emission uncertainties have caused large inaccuracies in model simulations of air quality and its responses to management strategies. To improve the quantitative understanding of the temporal, spatial, and categorized distributions of primary pollutant emissions by utilizing the corresponding measurements collected during TexAQS 2006, we implemented both the recursive Kalman filter and a batch matrix inversion 4-D data assimilation (FDDA) method in an iterative inverse modeling framework of the CMAQ-DDM model. Equipped with the decoupled direct method, CMAQ-DDM enables simultaneous calculation of the sensitivity coefficients of pollutant concentrations to emissions to be used in the inversions. Primary pollutant concentrations measured by the multiple platforms (TCEQ ground-based, NOAA WP-3D aircraft and Ronald H. Brown vessel, and UH Moody Tower) during TexAQS 2006 have been integrated for the use in the inverse modeling. Firstly pseudo-data analyses have been conducted to assess the two methods, taking a coarse spatial resolution emission inventory as a case. Model base case concentrations of isoprene and ozone at arbitrarily selected ground grid cells were perturbed to generate pseudo measurements with different assumed Gaussian uncertainties expressed by 1-sigma standard deviations. Single-species inversions have been conducted with both methods for isoprene and NOx surface emissions from eight states in the Southeastern United States by using the pseudo measurements of isoprene and ozone, respectively. Utilization of ozone pseudo data to invert for NOx emissions serves only for the purpose of method assessment. Both the Kalman filter and FDDA methods show good performance in tuning arbitrarily shifted a priori emissions to the base case “true” values within 3-4 iterations even for the nonlinear

  4. Method of forming a spacer for field emission flat panel displays

    SciTech Connect

    Bernhardt, A.F.; Contolini, R.J.

    1997-08-19

    Spacers are disclosed for applications such as field emission flat panel displays and vacuum microelectronics, and which involves the application of aerogel/xerogel technology to the formation of the spacer. In a preferred approach the method uses a mold and mold release agent wherein the gel precursor is a liquid which can be applied to the mold filling holes which expose the substrate (either the baseplate or the faceplate). A release agent is applied to the mold prior to precursor application to ease removal of the mold after formation of the dielectric spacer. The shrinkage of the gel during solvent extraction also improves mold removal. The final spacer material is a good dielectric, such as silica, secured to the substrate. 3 figs.

  5. Method of forming a spacer for field emission flat panel displays

    DOEpatents

    Bernhardt, Anthony F.; Contolini, Robert J.

    1997-01-01

    Spacers for applications such as field emission flat panel displays and vacuum microelectronics, and which involves the application of aerogel/xerogel technology to the formation of the spacer. In a preferred approach the method uses a mold and mold release agent wherein the gel precursor is a liquid which can be applied to the mold filling holes which expose the substrate (either the baseplate or the faceplate). A release agent is applied to the mold prior to precursor application to ease removal of the mold after formation of the dielectric spacer. The shrinkage of the gel during solvent extraction also improves mold removal. The final spacer material is a good dielectric, such as silica, secured to the substrate.

  6. Improving continuous monitoring of VOC emissions from alternative fertilizers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Application of alternative fertilizers, such as biosolids, to agricultural fields is an environmentally beneficial practice. Biosolids provide producers with a ready source of organic matter and plant nutrients instead of using commercial fertilizers. However, concerns regarding nuisance odors cause...

  7. Fabrication of barium/strontium carbonate coated amorphous carbon nanotubes as an improved field emitter

    NASA Astrophysics Data System (ADS)

    Maity, S.; Jha, A.; Das, N. S.; Chattopadhyay, K. K.

    2013-02-01

    Amorphous carbon nanotubes (aCNTs) were synthesized by a chemical reaction between ferrocene and ammonium chloride at a temperature ˜250 ∘C in an air furnace. As-synthesized aCNTs were coated with the barium/strontium carbonate through a simple chemical process. The coating of barium/strontium carbonate was confirmed by a high resolution transmission electron microscopy, X-ray diffraction, and Fourier transformed infrared spectroscopy. Morphology of the as-prepared samples was studied by field emission scanning electron microscopy. Thermal gravimetric analysis showed that barium/strontium carbonate coated aCNTs are more stable than the pristine aCNTs. As-prepared barium/strontium carbonate coated aCNTs showed significantly improved field emission properties with a turn-on field as low as 2.5 V/μm. The variation of field emission characteristics of the barium/strontium carbonate coated aCNTs with interelectrode distances was also studied.

  8. Controlled growth and field emission properties of zinc oxide nanopyramid arrays

    NASA Astrophysics Data System (ADS)

    Chen, Hongsheng; Qi, Junjie; Zhang, Yue; Zhang, Xiaomei; Liao, Qingliang; Huang, Yunhua

    2007-09-01

    Single-crystalline, pyramidal zinc oxide nanorods have been synthesized in a large quantity on p-Si substrate via catalyst-free thermal chemical vapor deposition at low temperature. SEM investigations showed that the nanorods were vertically aligned on the substrate, with diameters ranging from 60 to 80 nm and lengths about 1.5 μm. A self-catalysis VLS growth mechanism was proposed for the formation of the ZnO nanorods. The field emission properties of the ZnO nanopyramid arrays were investigated. A turn-on field about 3.8 V/μm was obtained at a current density of 10 μA/cm 2, and the field emission data was analyzed by applying the Fowler-Nordheim theory. The stability of emission current density under a high voltage was also tested, indicating that the ZnO nanostructures are promising for an application such as field emission sources.

  9. Field Emission Study of Carbon Nanotubes: High Current Density from Nanotube Bundle Arrays

    NASA Technical Reports Server (NTRS)

    Bronikowski, Micheal J.; Manohara, Harish M.; Siegel, Peter H.; Hunt, Brian D.

    2004-01-01

    We have investigated the field emission behavior of lithographically patterned bundles of multiwalled carbon nanotubes arranged in a variety of array geometries. Such arrays of nanotube bundles are found to perform significantly better in field emission than arrays of isolated nanotubes or dense, continuous mats of nanotubes, with the field emission performance depending on the bundle diameter and inter-bundle spacing. Arrays of 2-micrometers diameter nanotube bundles spaced 5 micrometers apart (edge-to-edge spacing) produced the largest emission densities, routinely giving 1.5 to 1.8 A/cm(sup 2) at approximately 4 V/micrometer electric field, and greater than 6 A/cm(sup 2) at 20 V/micrometers.

  10. What can we learn from field experiments about the development of SOC and GHG emissions under different management practices?

    NASA Astrophysics Data System (ADS)

    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).

  11. Automated Boiler Combustion Controls for Emission Reduction and Efficiency Improvement

    SciTech Connect

    None, None

    1998-12-02

    In the late 1980s, then President Bush visited Krakow, Poland. The terrible air quality theremotivated him to initiate a USAID-funded program, managed by DOE, entitled "Krakow Clean Fossil Fuels and Energy Efficiency Program." The primary objective of this program was to encourage the formation of commercial ventures between U.S. and Polish firms to provide equipment and/or services to reduce pollution from low-emission sources in Krakow, Poland. This program led to the award of a number of cooperative agreements, including one to Control Techtronics International. The technical objective of CTI's cooperative agreement is to apply combustion controls to existing boiler plants in Krakow and transfer knowledge and technology through a joint U.S. and Polish commercial venture. CTI installed automatic combustion controls on five coal boilers for the district heating system in Krakow. Three of these were for domestic hot-water boilers, and two were for steam for industrial boilers. The following results have occurred due to the addition of CTI's combustion controls on these five existing boilers: ! 25% energy savings ! 85% reduction in particulate emissions The joint venture company CTI-Polska was then established. Eleven additional technical and costing proposals were initiated to upgrade other coal boilers in Krakow. To date, no co-financing has been made available on the Polish side. CTI-Polska continues in operation, serving customers in Russia and Ukraine. Should the market in Poland materialize, the joint venture company is established there to provide equipment and service.

  12. Estimation of light duty vehicle emissions in Islamabad and climate co-benefits of improved emission standards implementation

    NASA Astrophysics Data System (ADS)

    Shah, Izhar Hussain; Zeeshan, Muhammad

    2016-02-01

    Light Duty Vehicles (LDVs) hold a major share in Islamabad's vehicle fleet and their contribution towards air pollution has not been analyzed previously. Emissions for the base year (2014) and two optimistic 'what-if' scenarios were estimated by using the International Vehicle Emissions (IVE) model. Considering the recent implementation of Euro II as emission standard in Pakistan, scenario 1 assumed entire LDV fleet meeting at least Euro II standards while scenario 2 assumed all LDVs meeting Euro IV standards except motorcycles which would be meeting Euro III emission standards. Higher average age for all vehicles and lower share of Euro compliant vehicles was found in the base case. Low engine stress mode (lower speeds with frequent decelerations) was observed for all vehicles especially on arterials and residential roads. Highest overall emissions (59%) were observed on arterials, followed by residential roads (24%) and highways (17%) with higher emissions observed during morning (8-10 am) and evening (4-6 pm) rush hours. Composite emission factors were also calculated. Results reveal that 1094, 147, 11.1, 0.2 and 0.4 kt of CO2, CO, NOx, SO2 and PM10 respectively were emitted in 2014 by LDVs. Compared with the base year, scenario 1 showed a reduction of 9%, 69%, 73%, 13% and 31%, while scenario 2 exhibited a reduction of 5%, 92%, 90%, 92% and 81% for CO2, CO, NOx, SO2 and PM10 respectively. As compared to the base year, a 20 year CO2-equivalent Global Warming Potential (GWP) reduced by 55% and 64% under scenario 1 and 2 respectively, while a 100 year GWP reduced by 40% and 44% under scenario 1 and 2 respectively. Our results demonstrated significant co-benefits that could be achieved in emission reduction and air quality improvement in the city by vehicle technology implementation.

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

    PubMed

    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 < 0.01). Treatments T1 and T3 not only had the largest CH4 emission (0.60 and 0.88 g x m(-2)), but also had the largest N2O emission (0.20 and 0.23 g x m(-2), respectively). After the winter 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.

  14. LZIFU: IDL emission line fitting pipeline for integral field spectroscopy data

    NASA Astrophysics Data System (ADS)

    Ho, I.-Ting

    2016-07-01

    LZIFU (LaZy-IFU) is an emission line fitting pipeline for integral field spectroscopy (IFS) data. Written in IDL, the pipeline turns IFS data to 2D emission line flux and kinematic maps for further analysis. LZIFU has been applied and tested extensively to various IFS data, including the SAMI Galaxy Survey, the Wide-Field Spectrograph (WiFeS), the CALIFA survey, the S7 survey and the MUSE instrument on the VLT.

  15. PISCES field chemical emissions monitoring project: Site 102 emissions report. Final report

    SciTech Connect

    1995-12-01

    This report is one of a series sponsored by the Electric Power Research Institute in the area of trace substance emissions from fossil-fuel power plants. This report presents the results of a sampling and analytical study to characterize trace substances emissions at Site 102. Site 102 is a cyclone boiler burning a sub-bituminous coal. Site 102 employs an electrostatic precipitator for particulate control. The objective of this report is to transmit the detailed data to the US Environmental Protection Agency (EPA) to assist the Agency in evaluating utility trace chemical emissions as well as the associated health risk impacts--as mandated in Title III of the 1990 Clean Air Act Amendments. This report does not attempt to compare the results with other sites. An assessment of data from all plants that have been tested is presented in the Electric Utility Trace Substances Synthesis Report (EPRI TR-104614).

  16. Attosecond electron emission probes of ultrafast nanolocalized fields

    NASA Astrophysics Data System (ADS)

    Kling, Matthias

    2011-05-01

    Ongoing experimental and theoretical work on the temporal and spatial characterization of nanolocalized plasmonic fields will be presented. Because of their broad spectral bandwidth, plasmons in metal nanoparticles undergo ultrafast dynamics with timescales as short as a few hundred attoseconds. So far, the spatiotemporal dynamics of optical fields localized on the nanoscale has been hidden from direct access in the real space and time domain. Our ultimate goal is to characterize the nanoplasmonic fields not only on a nanometer spatial scale but also on ~100 attosecond temporal scale. Information about the nanoplasmonic fields, which are excited by few-cycle laser pulses with stable electric field waveform, can be obtained by the measurement of photoemitted electrons. We will present recent results on the large acceleration of recollision electrons in nanolocalized fields near dielectric nanoparticles following the excitation by 5-fs near-infrared laser pulses with controlled electric field waveforms. This work has been carried out in collaboration with Th. Fennel (University of Rostock), E. Ruehl (FU Berlin), and M.I. Stockman (GSU Atlanta). We acknowledge support by the DFG via Emmy-Noether program and SPP1391.

  17. Field emission characteristics of electrochemically synthesized nickel nanowires with oxygen plasma post-treatment.

    PubMed

    Joo, Jinsoo; Lee, Sun Jeong; Park, Dong Hyuk; Kim, Young Soo; Lee, Yeonhee; Lee, Cheol Jin; Lee, Seong-Rae

    2006-07-28

    The field emissive, electrical, magnetic, and structural characteristics of nickel (Ni) nanowires synthesized using the electrochemical deposition method with an alumina nanoporous template are reported. The synthesis and formation of Ni nanowires were confirmed by XRD, SEM, and HR-TEM experiments. Ferromagnetic hysteresis curves and the metallic temperature dependence of the current-voltage characteristics were observed for the Ni nanowire systems. The nanotip emitters of the field emission cells of the Ni nanowires after O(2) plasma treatment were easily patterned using the solution drop casting (SDC) method, in which the Ni nanowires were homogeneously dispersed in organic solvents, and then dropped and dried on an n-type doped Si substrate as the cathode. For the O(2) plasma treated Ni nanowires, we observed that the inhomogeneous oxidized layer on their surface was reduced, that the current density of the field emission cell increased from approximately 3.0 x 10(-9) to approximately 1.0 x 10(-3) A cm(-2) due to field emission, and that the lowest threshold electric field was approximately 4 V microm(-1). The field enhancement factor was estimated as approximately 1300 for the O(2) plasma treated Ni nanowires. The evolution of the field emission obtained from the phosphor screen was observed at different applied electric fields. PMID:19661596

  18. Process Improvement Education with Professionals in the Addiction Treatment Field

    ERIC Educational Resources Information Center

    Pulvermacher, Alice

    2006-01-01

    Continuing education is being provided to professionals in the addiction treatment field to help them develop skills in process improvement and better meet the needs and requests they encounter. Access and retention of individuals seeking addiction treatment have been two of the greatest challenges addiction treatment professionals face.…

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

    SciTech Connect

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

    2014-03-24

    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. Self-consistent density functional calculation of field emission currents from metals

    PubMed

    Gohda; Nakamura; Watanabe; Watanabe

    2000-08-21

    We have developed a fully self-consistent method which is suitable to examine field emission currents, on the basis of the density functional theory. In our method, the nearby counterelectrode is not necessary. By using this method, we have investigated field emission currents from a biased metallic surface represented by the jellium model. We have found that the energy barrier between the jellium and vacuum becomes lower than the Fermi energy under strong electric fields (e.g., 10 V/nm for r(s) = 4 bohr). In this situation, the slope of the Fowler-Nordheim plot becomes flatter than that under a weaker field.

  1. X-ray Tube Using a Graphene Flower Cloth Field Emission Cathode

    NASA Astrophysics Data System (ADS)

    Iwai, Yusuke; Muramatsu, Kazuo; Tsuboi, Shougo; Jyouzuka, Atsuo; Nakamura, Tomonori; Onizuka, Yoshihiro; Mimura, Hidenori

    2013-10-01

    We have successfully fabricated a filament-less X-ray tube using a graphene flower cloth (GFC) field emission cathode. The GFC has numerous nanoprotrusions formed by self-standing graphene structures. The field emission current and the field enhancement factor β were 500 µA and 5600, respectively. The stability of voltage defined as a variance coefficient (σ/mean) of voltage was calculated to be 0.04% while maintaining the X-ray tube current of 300 µA. We applied our X-ray tube with the GFC field emitter to the X-ray fluorescence (XRF) analysis of stainless steel.

  2. Field emission from zinc oxide nanorod bundles grown on silicon nanoporous pillar array

    NASA Astrophysics Data System (ADS)

    Wang, Ling Li; Gong, Shang Dong; Wu, Li Hong; Li, Xin Jian

    2013-04-01

    A large-area zinc oxide (ZnO) nanorod bundle array was grown on a silicon nanoporous pillar array (Si-NPA) substrate by a chemical vapor deposition method, and its field-emission properties was studied. The structural characterization disclosed that the bundles were composed of hexagonal ZnO nanorods growing along c-axis and taking roots into the silicon pillars of Si-NPA. The average diameter and length of the ZnO nanorods were ∼145 nm and ∼10 μm, respectively. The field-emission measurements showed that the turn-on field of ZnO/Si-NPA was 4.6 V/μm with an emission current density (ECD) of 1 μA/cm2, and an ECD of 420 μA/cm2 was achieved at an applied field of 8.89 V/μm. The field enhancement factor was calculated to be ∼1700 based on the Fowler-Nordheim theory. According to the obtained charge coupled device (CCD) image, the density and brightness of the emission dots increased with the applied field, and the high emission dot density was attributed to the formation of a large number of ZnO nanorod emitting tips. Our results indicated that ZnO/Si-NPA might be a promising electron emission source.

  3. Enhanced Field Emission From The Gold- Polyaniline (Au-PANI) Nanocomposite

    SciTech Connect

    Patil, Sandip S.; More, Mahendra A.; Koiry, Shankar P.; Aswal, D. K.

    2010-12-01

    The gold-polyaniline nanocomposite was synthesized by electrochemical route in two steps. In the first step polyaniline film was deposited by cyclic voltammetry on the ITO coated glass substrate, and then synthesis of gold-polyaniline nanocomposite via chronoamperometry. The synthesized gold-polyaniline nanocomposite film was characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), Ultra-violet spectroscopy (UV-vis) and Fourier Transform Infrared Spectrometry (FTIR). The SEM analysis shows well adherent gold nanoparticles on the surface of polyaniline nanofibers. The XRD and UV-Vis spectra indicate formation of gold nanoparticles. From the field emission studies, the value of the turn on field, corresponding to 1 nA emission current, is found to be 0.65 V/{mu}m and emission current density of 1 {mu}A/cm{sup 2} has been drawn at an applied field of 1.1 V/{mu}m. These values are observed to be superior than the reported ones. The field emission current stability investigated at 1 {mu}A over duration of more than four hours is found to be good. The observed field emission characteristics suggest the gold polyaniline nanocomposite as promising material for field emission based applications.

  4. Field emission and material transfer in microswitches electrical contacts

    NASA Astrophysics Data System (ADS)

    Vincent, M.; Rowe, S. W.; Poulain, C.; Mariolle, D.; Chiesi, L.; Houzé, F.; Delamare, J.

    2010-12-01

    Material transfer from one electrical contact part to the other has already been reported in microswitches operating under hot switching conditions. By using an atomic force microscope with a conductive cantilever, we highlighted that electrons are emitted from the cathode when electrode separation becomes less than a few tens of nanometers. This electronic emission proves to follow Fowler-Nordheim theory and leads to the damage of the opposite contact member (anode) by impact heating. Anode material evaporates under this extreme heating and deposits on the opposite contact member (cathode), leading to a material transfer from anode to cathode.

  5. Improving polymer injectivity at West Coyote Field, California

    SciTech Connect

    Shuler, P.J.; Kuchne, D.L.; Uhl, J.T.; Walkup, G.W.

    1987-08-01

    This paper presents a case history where laboratory and simulation results were used to model a single-well polymer injectivity field test in the West Coyote field and to improve injectivity in a subsequent field test. The polyacrylamide used in the first test exhibited low injectivity. Laboratory studies were performed to identify the causes of low injectivity and to model the field test physically. Laboratory core data and reservoir properties were used in a mathematical model to calculate the polymer injectivity, which closely matched that observed in the field. The low polymer injectivity at West Coyote was a result of formation damage caused by the polymer and low-salinity polymer makeup water and the high resistance factor developed by the polymer. These problems were overcome by using a lower-molecular-weight polyacrylamide, preshearing the polymer solution before injection, and increasing the salinity of the polymer makeup water. These improvements resulted in a 50% increase in injectivity during the second polymer injectivity field test at West Coyote.

  6. Improving polymer injectivity at West Coyote Field, California

    SciTech Connect

    Shuler, P.J.; Kuehne, D.L.; Uhl, J.T.; Walkup, G.W.

    1985-03-01

    This paper presents a case history where laboratory and simulation results were used to model a single-well polymer injectivity field test in the West Coyote Field and improve the injectivity in a subsequent field test. The polyacrylamide polymer used in the first test exhibited low injectivity. Laboratory studies were performed to identify the causes of low injectivity and physically model the field test. Laboratory core data and reservoir properties were used in a mathematical model to calculate the polymer injectivity, which closely matched that observed in the field. The low polymer injectivity at West Coyote was due to: formation damage caused by the polymer and low salinity polymer makeup water; and the high resistance factor developed by the polymer. These problems were overcome by: using a lower molecular weight polyacrylamide; preshearing the polymer solution before injection; and increasing the salinity of the polymer makeup water. These improvements resulted in a 50% increase in injectivity during the second polymer injectivity field test at West Coyote.

  7. Energy spectra of field emission electrons from a W<310> tip

    NASA Astrophysics Data System (ADS)

    Ogawa, H.; Arai, N.; Nagaoka, K.; Uchiyama, S.; Yamashita, T.; Itoh, H.; Oshima, C.

    1996-06-01

    Total energy distributions of field emission electrons from a single crystal <310>-oriented tungsten tip have been measured at temperatures of 80 and 300 K and in the emission current region from 10 -8 to 10 -6 A. We have used a high resolution field emission spectrometer computer-controlled by a low-noise power supply developed in this experiment. The main part of the observed distributions agree with the theoretical ones calculated on the basis of the Fowler-Nordheim theory, while discrepancies have been observed in two regions.

  8. Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS2

    NASA Astrophysics Data System (ADS)

    Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados del Águila, Andrés; Ballottin, Mariana V.; Christianen, Peter C. M.; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf

    2016-08-01

    We control the linear polarization of emission from the coherently emitting K+ and K- valleys (valley coherence) in monolayer WS2 with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τc=260 fs .

  9. Field-Emission from Chemically Functionalized Diamond Surfaces: Does Electron Affinity Picture Work?

    NASA Astrophysics Data System (ADS)

    Miyamoto, Yoshiyuki; Miyazaki, Takehide; Takeuchi, Daisuke; Okushi, Hideyo; Yamasaki, Satoshi

    2014-03-01

    By means of the time-dependent density functional electron dynamics, we have revisited the field-emission efficiency of chemically functionalized diamond (100) surfaces. In order to achieve high efficiency and high (chemical) stability, proper chemical species are needed to terminate diamond surfaces. Hydrogen (H) termination is well known to achieve the negative electron affinity (NEA) of diamond surface which indeed enhances field emission performance than that of clean surface with positive electron affinity (PEA). Yet, the durability of H-terminated diamond surface was concerned for long-time operation of the field-emission. Meantime, oxidation, or hydroxyl (OH) termination was considered to achieve chemical stability of the surface but presence of oxygen (O) atom should reduce the emission efficiency. Recently, H- OH-co-terminated surface is reported as NEA and was expected to achieve both emission efficiency and chemical stability. However, our simulation showed that emission efficiency of the H- OH- co-terminated surface is much lower than clean surface with PEA, thus we note that the electron affinity cannot be a unique measure to determine the emission efficiency. In this talk, we introduce necessity of new concept to understand the emission efficiency which needs to know detailed potential profile from bulk to vacuum through surface, which is strongly dependent on the surface chemical functionalization. This work was supported by ALCA project conducted by Japan Science and Technology Agency.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. The electric field effect and electromagnetic wave emission in intrinsic Josephson junctions

    NASA Astrophysics Data System (ADS)

    Koyama, T.

    2013-04-01

    We formulate a theory for the electric field effect in intrinsic Josephson junctions (IJJs). The coupled dynamical equations for the phase differences are derived in the presence of both a bias current and an applied electric field on the basis of the capacitively-coupled IJJ model. It is shown that the current-voltage characteristics of the IJJs sensitively depend on the applied electric field. The dipole emission originating from the electric field effect is also predicted.

  13. Optical field emission from resonant gold nanorods driven by femtosecond mid-infrared pulses

    SciTech Connect

    Kusa, F.; Echternkamp, K. E.; Herink, G.; Ropers, C.; Ashihara, S.

    2015-07-15

    We demonstrate strong-field photoelectron emission from gold nanorods driven by femtosecond mid-infrared optical pulses. The maximum photoelectron yield is reached at the localized surface plasmon resonance, indicating that the photoemission is governed by the resonantly-enhanced optical near-field. The wavelength- and field-dependent photoemission yield allows for a noninvasive determination of local field enhancements, and we obtain intensity enhancement factors close to 1300, in good agreement with finite-difference time domain computations.

  14. Ammonia emission time profiles based on manure transport data improve ammonia modelling across north western Europe

    NASA Astrophysics Data System (ADS)

    Hendriks, C.; Kranenburg, R.; Kuenen, J. J. P.; Van den Bril, B.; Verguts, V.; Schaap, M.

    2016-04-01

    Accurate modelling of mitigation measures for nitrogen deposition and secondary inorganic aerosol (SIA) episodes requires a detailed representation of emission patterns from agriculture. In this study the meteorological influence on the temporal variability of ammonia emissions from livestock housing and application of manure and fertilizer are included in the chemistry transport model LOTOS-EUROS. For manure application, manure transport data from Flanders (Belgium) were used as a proxy to derive the emission variability. Using improved ammonia emission variability strongly improves model performance for ammonia, mainly by a better representation of the spring maximum. The impact on model performance for SIA was negligible as explained by the limited, ammonia rich region in which the emission variability was updated. The contribution of Flemish agriculture to modelled annual mean ammonia and SIA concentrations in Flanders were quantified at respectively 7-8 and 1-2 μg/m3. A scenario study was performed to investigate the effects of reducing ammonia emissions from manure application during PM episodes by 75%, yielding a maximum reduction in modelled SIA levels of 1-3 μg/m3 during episodes. Year-to-year emission variability and a soil module to explicitly model the emission process from manure and fertilizer application are needed to further improve the modelling of the ammonia budget.

  15. Flexible field emission of nitrogen-doped carbon nanotubes/reduced graphene hybrid films.

    PubMed

    Lee, Duck Hyun; Lee, Jin Ah; Lee, Won Jong; Kim, Sang Ouk

    2011-01-01

    The outstanding flexible field emission properties of carbon hybrid films made of vertically aligned N-doped carbon nanotubes grown on mechanically compliant reduced graphene films are demonstrated. The bottom-reduced graphene film substrate enables the conformal coating of the hybrid film on flexible device geometry and ensures robust mechanical and electrical contact even in a highly deformed state. The field emission properties are precisely examined in terms of the control of the bending radius, the N-doping level, and the length or wall-number of the carbon nanotubes and analyzed with electric field simulations. This high-performance flexible carbon field emitter is potentially useful for diverse, flexible field emission devices.

  16. Marigold-like nanocrystals: controllable synthesis, field emission, and photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Song, Changqing; Yu, Ke; Yin, Haihong; Zhang, Yuanyuan; Li, Shouchuan; Wang, Yang; Zhu, Ziqiang

    2014-06-01

    Cubic marigold-like Cu2S nanostructures were synthesized from a facile hydrothermal process without using any additives or surfactants. After thermal annealed at different condition, monoclinic Cu2S and tetragonal Cu1.81S nanostructures were obtained for the first time, maintaining the marigold-like morphology undestroyed. Field emission (FE) properties of these three types of nanostructures were investigated for the first time. The results indicated that the tetragonal Cu1.81S nanostructures had excellent field emission performance with turn-on field of and threshold field of . Moreover, their photocatalytic properties of the three nanostructures were also investigated by photodegradating methylene blue (MB). The results showed that the tetragonal Cu1.81S nanostructures may be a competitive material in both field emission and photocatalytic applications.

  17. Design, Fabrication, and Characterization of Carbon Nanotube Field Emission Devices for Advanced Applications

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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.

  19. Physical properties of thin-film field emission cathodes with molybdenum cones

    NASA Technical Reports Server (NTRS)

    Spindt, C. A.; Brodie, I.; Humphrey, L.; Westerberg, E. R.

    1976-01-01

    Field emission cathodes fabricated using thin-film techniques and electron beam microlithography are described, together with effects obtained by varying the fabrication parameters. The emission originates from the tip of molybdenum cones that are about 1.5 micron tall with a tip radius around 500 A. Such cathodes have been produced in closely packed arrays containing 100 and 5000 cones as well as singly. Maximum currents in the range 50-150 microamp per cone can be drawn. Life tests with the 100-cone arrays drawing 2 mA total emission (or 3 A per sq cm) have proceeded in excess of 7000 hr with about a 10% drop in emission current. Studies are presented of the emission characteristics and current fluctuation phenomena. It is tentatively concluded that the emission arises from only one or a few atomic sites on the cone tips.

  20. Measurements of N2O emissions from different vegetable fields on the North China Plain

    NASA Astrophysics Data System (ADS)

    Diao, Tiantian; Xie, Liyong; Guo, Liping; Yan, Hongliang; Lin, Miao; Zhang, He; Lin, Jia; Lin, Erda

    2013-06-01

    Few studies have measured the N2O emission fluxes from vegetable fields. In order to identify the characteristics and the influencing factors of N2O emissions from different vegetable fields, we measured N2O emissions for a full year from four typical fields, including an open-ground vegetable field that has produced vegetables for over 20 years (OV20), a recently developed open-ground vegetable field that was converted from a maize field three years earlier (OV3), a recently developed greenhouse vegetable field that was converted from a maize field 3 years earlier (GV3) and a typical local maize field (Maize). Four different fertilization treatments were set additionally in the recently developed open-ground vegetable field. These were: no fertilizer or manure (OV3_CK), manure only (OV3_M) and the combination of manure with different rates of chemical fertilizer application (OV3_MF1 and OV3_MF3). The results showed that N2O emission fluxes fluctuated between 0.3 ± 0.1 and 912.4 ± 80.0 mg N2O-N m-2 h-1 with the highest emission peak occurring after fertilization followed by irrigation. Nitrogen application explained 64.6-84.5% of the N2O emission in the vegetable fields. The magnitude of the emission peaks depended on the nitrogen application rate and the duration of the emission peaks was mainly associated with soil temperature when appropriate irrigation was given after fertilization. The N2O emission peaks occurred later and lasted for a longer period when the soil temperature was <24 °C in May. However, emission peaks occurred earlier and lasted for a shorter period when the soil temperature was around 25-33 °C from June to August. The annual N2O emissions from the fertilized vegetable fields were 1.68-2.38 times higher than that from the maize field, which had an emission value of 2.88 ± 0.10 kg N ha-1 a-1. The N2O emission factor (EF) of manure nitrogen was 0.07% over the whole year, but was 0.11% and 0.02% in the spring cucumber season and the autumn

  1. Dark-to-arc transition in field emission dominated atmospheric microdischarges

    SciTech Connect

    Tholeti, Siva Sashank; Semnani, Abbas; Peroulis, Dimitrios; Alexeenko, Alina A.

    2015-08-15

    We study the voltage-current characteristics of gas discharges driven by field emission of electrons at the microscale. Particle-in-cell with Monte Carlo collision calculations are first verified by comparison with breakdown voltage measurements and then used to investigate atmospheric discharges in nitrogen at gaps from 1 to 10 μm. The results indicate the absence of the classical glow discharge regime because field electron emission replaces secondary electron emission as the discharge sustaining mechanism. Additionally, the onset of arcing is significantly delayed due to rarefied effects in electron transport. While field emission reduces the breakdown voltage, the power required to sustain an arc of the same density in microgaps is as much as 30% higher than at macroscale.

  2. Electric field-induced emission enhancement and modulation in individual CdSe nanowires.

    PubMed

    Vietmeyer, Felix; Tchelidze, Tamar; Tsou, Veronica; Janko, Boldizsar; Kuno, Masaru

    2012-10-23

    CdSe nanowires show reversible emission intensity enhancements when subjected to electric field strengths ranging from 5 to 22 MV/m. Under alternating positive and negative biases, emission intensity modulation depths of 14 ± 7% are observed. Individual wires are studied by placing them in parallel plate capacitor-like structures and monitoring their emission intensities via single nanostructure microscopy. Observed emission sensitivities are rationalized by the field-induced modulation of carrier detrapping rates from NW defect sites responsible for nonradiative relaxation processes. The exclusion of these states from subsequent photophysics leads to observed photoluminescence quantum yield enhancements. We quantitatively explain the phenomenon by developing a kinetic model to account for field-induced variations of carrier detrapping rates. The observed phenomenon allows direct visualization of trap state behavior in individual CdSe nanowires and represents a first step toward developing new optical techniques that can probe defects in low-dimensional materials.

  3. High brightness field emission from printed carbon nanotubes in an S-band microwave gun

    NASA Astrophysics Data System (ADS)

    Wang, Qilong; Li, Xiangkun; Di, Yusong; Yu, Cairu; Zhang, Xiaobing; Li, Ming; Lei, Wei

    2016-02-01

    Printed carbon nanotubes (CNTs) were applied as cold cathode and placed into an S-band microwave gun operating at 2856 MHz with the pulse duration of 2.8 μs. High brightness field emission was demonstrated and the current density achieves the value more than 4.2 A/cm2. The emittance of field emission beam is calculated to be nearly 21 μm based on the beam profile of emission electrons monitored via yttrium aluminum garnet screen. The infrared image of printed CNTs confirms that the emitters in the center contributed more electrons and the heat generated during the large current density field emission. The results in the paper imply that randomly distributed printed CNTs have the potential to be applied as the high brightness electron sources for free electron lasers.

  4. Stationary digital breast tomosynthesis with distributed field emission x-ray tube

    NASA Astrophysics Data System (ADS)

    Sprenger, F.; Calderon, X.; Gidcumb, E.; Lu, J.; Qian, X.; Spronk, D.; Tucker, A.; Yang, G.; Zhou, O.

    2011-03-01

    Tomosynthesis requires projection images from different viewing angles. Using a distributed x-ray source this can be achieved without mechanical motion of the source with the potential for faster image acquisition speed. A distributed xray tube has been designed and manufactured specifically for breast tomosynthesis. The x-ray tube consists of 31 field emission x-ray sources with an angular range of 30°. The total dose is up to 100mAs with an energy range between 27 and 45 kVp. We discuss the source geometry and results from the characterization of the first prototype. The x-ray tube uses field emission cathodes based on carbon nanotubes (CNT) as electron source. Prior to the manufacturing of the sealed x-ray tube extensive testing on the field emission cathodes has been performed to verify the requirements for commercial tomosynthesis systems in terms of emission current, focal spot size and tube lifetime.

  5. Nucleon-nucleon scattering in a strong external magnetic field and the neutrino emissivity

    SciTech Connect

    Bavarsad, E.; Mohammadi, R.; Haghighat, M.

    2010-11-15

    The nucleon-nucleon scattering in a large magnetic background is considered to find its potential to change the neutrino emissivity of the neutron stars. For this purpose, we consider the one-pion-exchange approximation to find the nucleon-nucleon (NN) cross section in a background field as large as 10{sup 15}-10{sup 18} G. We show that the NN cross section in neutron stars with temperatures in the range 0.1-5 MeV can be changed up to the 1 order of magnitude with respect to the one in the absence of the magnetic field. In the limit of the soft neutrino emission, the neutrino emissivity can be written in terms of the NN-scattering amplitude; therefore, the large magnetic fields can dramatically change the neutrino emissivity of the neutron stars as well.

  6. Evidence of satellite valley position in GaN by photoexcited field emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Yilmazoglu, O.; Pavlidis, D.; Hartnagel, H. L.; Evtukh, A.; Litovchenko, V.; Semenenko, N.

    2008-06-01

    GaN field emitter rods with nanometer diameter were fabricated by photoelectrochemical etching on a n+-GaN substrate. Their electron field emission properties were investigated under ultraviolet (UV) illumination. The Fowler-Nordheim plots of the emission current show different slopes for nonilluminated and UV illuminated devices. A model based on the electron emission from valleys having different specific electron affinities is proposed to explain the experimental results. In the absence of illumination, the GaN rods are almost fully depleted and emission takes place only from the lower valley. Upon UV illumination and presence of a high electric field at the emitter tip, the upper valley of the conduction band appears to be occupied by electrons generated at the valence band. The energy difference between the lower and upper valleys was determined to be 1.15eV and is in good agreement with formerly published theoretical and measured values.

  7. Influence of cluster-assembly parameters on the field emission properties of nanostructured carbon films

    NASA Astrophysics Data System (ADS)

    Ducati, C.; Barborini, E.; Piseri, P.; Milani, P.; Robertson, J.

    2002-11-01

    Supersonic cluster beam deposition has been used to produce films with different nanostructures by controlling the deposition parameters such as the film thickness, substrate temperature and cluster mass distribution. The field emission properties of cluster-assembled carbon films have been characterized and correlated to the evolution of the film nanostructure. Threshold fields ranging between 4 and 10 V/mum and saturation current densities as high as 0.7 mA have been measured for samples heated during deposition. A series of voltage ramps, i.e., a conditioning process, was found to initiate more stable and reproducible emission. It was found that the presence of graphitic particles (onions, nanotube embryos) in the films substantially enhances the field emission performance. Films patterned on a micrometer scale have been conditioned spot by spot by a ball-tip anode, showing that a relatively high emission site density can be achieved from the cluster-assembled material.

  8. An Improved Manual Method for NOx Emission Measurement.

    ERIC Educational Resources Information Center

    Dee, L. A.; And Others

    The current manual NO (x) sampling and analysis method was evaluated. Improved time-integrated sampling and rapid analysis methods were developed. In the new method, the sample gas is drawn through a heated bed of uniquely active, crystalline, Pb02 where NO (x) is quantitatively absorbed. Nitrate ion is later extracted with water and the…

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

    SciTech Connect

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

    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.

  10. Enhanced electron field emission properties of diamond/microcrystalline graphite composite films synthesized by thermal catalytic etching

    NASA Astrophysics Data System (ADS)

    Li, Shasha; Ma, Li; Long, Hangyu; Yu, Xiaoying; Luo, Hao; Wang, Yijia; Zhu, Hekang; Yu, Zhiming; Ma, Mingyang; Wei, Qiuping

    2016-03-01

    Diamond/microcrystalline graphite composite films were synthesized by thermal catalytic etching method with nickel as the catalyst. The surface morphology and composition of the composite films were examined by scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD). The results show that the etching and graphitizing degree of diamond surface increased with the rising annealing temperature and the surface of as-grown diamonds were replaced by the tips of high aspect ratios and porous foam structure. The electron field emission (EFE) properties of composite films were improved compared to the as-grown diamond. The lowest turn-on field of 9.6 V/μm has been detected for the composite film annealed at 900 °C. The field emission current stability was influenced by graphite phase formed in the etching process. Gradual increase of emission currents along with time were observed for both samples annealed at 700 °C and 800 °C. However, there was a slightly decrease for the emission current of sample annealed at 900 °C.

  11. Air quality improvements following implementation of Lisbon's Low Emission Zone

    NASA Astrophysics Data System (ADS)

    Ferreira, F.; Gomes, P.; Tente, H.; Carvalho, A. C.; Pereira, P.; Monjardino, J.

    2015-12-01

    Air pollution levels within Lisbon city limits have been exceeding the limit values established in European Union and national legislation since 2001, with the most problematic cases related to the levels of fine particles (PM10) and nitrogen dioxide (NO2), mainly originated by road traffic. With the objective of answering this public health issue, an Air Quality Action Plan was developed in 2006 and the respective Enforcement Plan was published in 2009. From the overall strategy, one of the major measures presented in this strategy was the creation of a Low Emission Zone (LEZ) in Lisbon, which has been operating since July 2011. Implemented at different stages it has progressively expanded its area, including more vehicle types and adopting more stringent requirements in terms of minimum emission standards (currently LEZ phase 2 with EURO 2 in the city center - zone 1 and EURO 1 in the rest of the LEZ area - zone 2). At the same time the road axis comprised of Marquês de Pombal square and Avenida da Liberdade was subjected to profound changes in its traffic circulation model, reducing road traffic volumes. The analysis of the air quality data before and after the LEZ phase 2 has shown positive evolution when comparing the period between 2011 (before measures) and 2013 (after measures). In 2013, there was a reduction in PM10 annual average concentration of 23% and NO2 annual average concentrations of 12%, compared with the year 2011. Although PM10 reductions were more significant inside the LEZ area, the same was not valid for NO2, suggesting that the implementation of these measures was not as effective in reducing NO2 levels as shown by results in other cities like Berlin and London. The results from road traffic characterization indicate a relevant effect on fleet renewal with an overall decrease in the relative weight of pre-EURO 2 vehicles in 2012/2013, compared with data from 2011. An important increase in the share of EURO 4 and EURO 5 vehicles was also

  12. Cosmic Rays, Magnetic Fields and Diffuse Emissions: Combining Observations from Radio to Gamma Rays

    NASA Astrophysics Data System (ADS)

    Michelson, Peter

    With the advent of WMAP, Planck, and Fermi-LAT telescopes the diffuse emission from the Milky Way has received renewed attention. Observations of the different components of the diffuse emission reveal information on Cosmic Rays (CRs), magnetic fields (B-fields) and the interstellar medium. CRs interact with the interstellar medium and the B-fields in the Milky Way, producing diffuse emission from radio to gamma rays. The fundamental problem is that CRs, B-fields, and the interstellar medium are not precisely known. In fact, despite intensive studies, the B-field intensity and topology, and CR spectra and distribution throughout the Galaxy are still uncertain. As a consequence unequivocally disentangling and describing the diffuse components simultaneously using a single wavelength domain is impossible. Our approach to disentangling and describing the diffuse emission components is to simultaneously consider the diffuse emission in multiple frequency domains. We propose to exploit the entire database of the present radio surveys, microwave observations (WMAP and Planck), X-ray observations (INTEGRAL) and gamma-ray observations (COMPTEL and Fermi-LAT) in order to analyze their diffuse emission in a combined multi-wavelength approach. We will jointly infer information on the spectra and distribution of CRs in the Galaxy, and on Galactic B-fields, with unprecedented accuracy. Finally we will be able to describe the baseline Galactic diffuse emissions and characterize Milky Way structures and their emission mechanisms, which have attracted the attention of the scientific community recently. This project is innovative and essential for maximizing the scientific return from the presently available data in a multidisciplinary view and uses novel approaches. The results will benefit NASA-related science generally and the return from the named missions specifically.

  13. Microwave snow emission model using a long-term field experiment

    NASA Astrophysics Data System (ADS)

    Munoz-Barreto, Jonathan

    Microwave remote sensing has shown great potential in estimating snowpack properties such as: snow depth and Snow Water Equivalent (SWE). However, other snow properties like density, wetness and grain size, which are variable in space and time, largely impact the microwave signal scattering, still need to be investigated and understood. With the objective to improve our understanding of the effect of changing snow characteristics (grain size, snow wetness, density, temperature) under various meteorological conditions on the microwave emission of snow, the CREST-Snow Analysis and Field Experiment (CREST-SAFE) was established at the research site of the National Weather Service office, Caribou, ME, USA. In this ground experiment, 37 and 89 GHz dual polarized microwave observations are conducted continuously, along with detailed synchronous observations of snowpack physical properties. The first part of this work provides an overview of the field experiment, the snow pack and other environmental parameters which are routinely measured at the station both automatically and manually. The measurement programme includes microwave observations, meteorological observations (air temperature, snow skin-temperature, humidity, wind speed and direction, precipitation, incoming and outgoing radiations), along with the measurements of the snow pack bulk physical properties (snow depth, grain size, shape, hardness, and density) and vertical temperature profiles. The detailed analysis of microwave observations collected during the last three years along with the observed and simulated snowpack properties are presented. The second component of this work focuses on the development of a new approach to estimate the snow wetness (liquid water content) using information on the snow grain size and temperature. The objective of these efforts is to directly assimilate the predicted snow wetness in the HUT (Helsinki University of Technology) microwave emission model. The modified version of

  14. Field Emission in CEBAF's SRF Cavities and Implications for Future Accelerators

    SciTech Connect

    Jay Benesch

    2006-02-15

    Field emission is one of the key issues in superconducting RF for particle accelerators. When present, it limits operating gradient directly or via induced heat load at 2K. In order to minimize particulate contamination of and thus field emission in the CEBAF SRF cavities during assembly, a cold ceramic RF window was placed very close to the accelerating cavity proper. As an unintended consequence of this, the window is charged by field-emitted electrons, making it possible to monitor and model field emission in the CEBAF cavities since in-tunnel operation began. From January 30, 1995, through February 10, 2003, there were 64 instances of spontaneous onset or change in cavity field emission with a drop in usable gradient averaging 1.4 ({sigma} 0.8) MV/m at each event. Fractional loss averaged 0.18 ({sigma} 0.12) of pre-event gradient. This event count corresponds to 2.4 events per century per cavity, or 8 per year in CEBAF. It is hypothesized that changes in field emission are due to adsorbed gas accumulation. The possible implications of this and other observations for the International Linear Collider (ILC) and other future accelerators will be discussed.

  15. Field emission driven direct current argon discharges and electrical breakdown mechanism across micron scale gaps

    NASA Astrophysics Data System (ADS)

    Matejčik, Štefan; Radjenović, Branislav; Klas, Matej; Radmilović-Radjenović, Marija

    2015-11-01

    In this paper results of the experimental and theoretical studies of the field emission driven direct current argon microdischarges for the gaps between 1 μm and 100 μm are presented and discussed. The breakdown voltage curves and Volt-Ampere characteristics proved to be a fertile basis providing better understanding of the breakdown phenomena in microgaps. Based on the measured breakdown voltage curves, the effective yields have been estimated confirming that the secondary electron emission due to high electric field generated in microgaps depends primarily on the electric field leading directly to the violation of the Paschen's law. Experimental data are supported by the theoretical predictions that suggest departure from the scaling law and a flattening of the Paschen curves at higher pressures confirming that Townsend phenomenology breaks down when field emission becomes the key mechanism leading to the breakdown. Field emission of electrons from the cathode, the space charge effects in the breakdown and distinction between the Fowler-Nordheim field emission and the space charge limited current density are also analyzed. Images and Volt-Ampere characteristics recorded at the electrode gap size of 20 μm indicate the existence of a discharge region similar to arc at the pressure of around 200 Torr has been observed. Contribution to the Topical Issue "Recent Breakthroughs in Microplasma Science and Technology", edited by Kurt Becker, Jose Lopez, David Staack, Klaus-Dieter Weltmann and Wei Dong Zhu.

  16. Improved Tail-Current Representation in the Rice Field Model

    NASA Astrophysics Data System (ADS)

    Naehr, S.; Toffoletto, F. R.

    2001-05-01

    The Rice Field Model (RFM) represents the magnetic field of the steady-state open magnetosphere. In order to improve the mapping of field lines in the near Earth region, the simple Harris-sheet field representing the cross-tail current is replaced near the Earth by a more flexible tail current model developed by Hilmer and Voigt In the far-tail region the tail current and expansion fan fields are modified to allow for variations in the IMF and the interconnection field down the tail. The new tail-current is completely shielded by the magnetopause current system. The effects of time-dependent IMF on the polar cap potential pattern are explored by propagating a Northward turning down the tail. To evaluate the new tail-current in the near Earth region, magnetometer data from the GOES-8 satellite (in geosynchronous orbit) for the period of March 9-17, 1998 is compared to model predictions. The combination of RFM shielding with the Hilmer-Voigt tail-current proves significantly more accurate in determining the magnetic field at GEO than either of the two models alone. Ding, C., T. W. Hill, and F. R. Toffoletto. Improvement of the Toffoletto-Hill Open Magnetospheric Model, in Physics of Space Plasmas (1995): Proceedings of the 1995 Cambridge Syposium/Workshop in Geoplasma Physics on "Multiscale Phenomena in Space Plasmas", edited by T. Chang, and J.R. Jasperse, pp. 639-644, MIT Center for Theoretical Geo/Cosmo Plasma Physics, Cambridge, Massachusetts, 1996.

  17. Enhanced field emission from ZnO nanowire arrays utilizing MgO buffer between seed layer and silicon substrate

    NASA Astrophysics Data System (ADS)

    Chen, Si; Chen, Jiangtao; Liu, Jianlin; Qi, Jing; Wang, Yuhua

    2016-11-01

    Field emitters based on ZnO nanowires and other nanomaterials are promising high-brightness electron sources for field emission display, microscopy and other applications. The performance of a ZnO nanowire field emitter is linked to the quality, conductivity and alignment of the nanowires on a substrate, therefore requiring ways to improve these parameters. Here, ZnO nanowire arrays were grown on ZnO seed layer on silicon substrate with MgO buffer between the seed layer and Si. The turn-on field and enhancement factor of these nanowire arrays are 3.79 V/μm and 3754, respectively. These properties are improved greatly compared to those of ZnO nanowire arrays grown on ZnO seed layer without MgO buffer, which are 5.06 V/μm and 1697, respectively. The enhanced field emission properties can be attributed to better electron transport in seed layer, and better nanowire alignment because of MgO buffer.

  18. Use of LEED, Auger emission spectroscopy and field ion microscopy in microstructural studies.

    NASA Technical Reports Server (NTRS)

    Ferrante, J.; Buckley, D. H.; Pepper, S. V.; Brainard, W. A.

    1972-01-01

    The studies reported were conducted to gain a fundamental understanding of adhesion and dynamic friction on an atomic or microscopic level. Fundamental aspects of low energy electron diffraction (LEED), Auger emission spectroscopy (AES), and field ion microscopy (FIM) are discussed. Typical results of studies conducted are considered, giving attention to LEED-AES experiments, pin and disk experiments, and field ion microscope investigations.

  19. Methane emissions from rice fields: Effect of plant height among several rice cultivars

    NASA Astrophysics Data System (ADS)

    Ding, A.; Willis, C. R.; Sass, R. L.; Fisher, F. M.

    The effect of rice cultivar and plant height on methane (CH4) emission from rice fields was studied from data of 8-year field experiments. Field experiments were conducted from 1989 to 1996 at the Texas A & M University Agricultural Research and Extension Center near Beaumont, Texas. Eleven rice cultivars and three soil types were involved. The results of this study showed the following: 1) Rice cultivar choice slightly influenced the day-to-day seasonal pattern of methane emission, but it had a significant effect on the seasonal total methane emission. The average seasonal methane emission is 22.8gCH4m-2 for high-emitting cultivars (Mars and Della), ranging from 8.0 to 41.0gCH4m-2 and 17.7gCH4m-2 for low-emitting cultivars (Lemont, Labelle, Lebonnet, Dawn, Katy, IR 36, Cypress, and Jasmine), ranging from 1.7 to 28.4gCH4m-2. 2) Seasonal methane emission has a positive linear correlation with postheading rice plant height. The correlation coefficient r2 is 0.736 (n=24, and p<0.05). In this paper we suggest that plant height may be a good criteria in choosing cultivars for mitigation of methane emission. More importantly, it provides a potential method for estimating methane emission from regional or global rice paddies as plant height can be evaluated by remotely sensed imagery.

  20. Field emission performance of multiwalled carbon nanotubes for a low-power spacecraft neutraliser

    NASA Astrophysics Data System (ADS)

    Aplin, K. L.; Kent, B. J.; Song, W.; Castelli, C.

    2009-05-01

    Field electron emission from aligned multiwalled carbon nanotubes has been assessed to determine if the performance, defined by power consumption, lifetime and emission current, is suitable for use in spacecraft charge neutralisation for field emission electric propulsion (FEEP). Carbon nanotubes grown by chemical vapour deposition (CVD) were mounted on a dual in line chip with a macroscopic (nickel mesh) extractor electrode mounted ˜1 mm above the tubes. The nanotubes' field emission characteristics (emission currents, electron losses and operating voltage) were measured at ˜10 -4 Pa. An endurance test of one sample, running at a software-controlled constant emission current lasted >1400 h, approaching the longest known FEEP thruster lifetime. The emission corresponds to a current density of ˜10 mA/cm 2 at a voltage of 150 V. These results, implementing mature extractor-electrode geometry, indicate that carbon nanotubes have considerable potential for development as robust, low-power, long-lived electron emitters for use in space.

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

    PubMed

    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. PMID:15707336

  2. [China's rice field greenhouse gas emission under climate change based on DNDC model simulation].

    PubMed

    Tian, Zhan; Niu, Yi-long; Sun, Lai-xiang; Li, Chang-sheng; Liu, Chun-jiang; Fan, Dong-li

    2015-03-01

    In contrast to a large body of literature assessing the impact of agriculture greenhouse gas (GHG) emissions on climate change, there is a lack of research examining the impact of climate change on agricultural GHG emissions. This study employed the DNDC v9.5, a state-of-art biogeochemical model, to simulate greenhouse gas emissions in China' s rice-growing fields during 1971-2010. The results showed that owing to temperature rising (on average 0.49 °C higher in the second 20 years than in the first 20 year) and precipitation increase (11 mm more in the second 20 years than in the first 20 years) during the rice growing season, CH4 and N2O emissions in paddy field increased by 0.25 kg C . hm-2 and 0.25 kg N . hm-2, respectively. The rising temperature accelerated CH4 emission and N2O emission increased with precipitation. These results indicated that climate change exerted impact on the mechanism of GHG emissions in paddy field.

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

    PubMed

    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.

  4. The screening effects of carbon nanotube arrays and its field emission optimum density

    SciTech Connect

    Cai, Dan Liu, Lie

    2013-12-15

    In order to investigate the field emission optimum density of carbon nanotube (CNT) array, the screening effects of CNT array have been studied. It has been shown that the electric field in the vicinity of an individual nanotube of array can be notable distorted due to the screening action of the surrounding neighbors. The optimum normalized spacing s/l(as referred to the length) for the maximum emission current is inversely proportional to aspect ratio l/r and electric field strength for CNT arrays with a fixed dimension.

  5. Elevated [CO2] magnifies isoprene emissions under heat and improves thermal resistance in hybrid aspen

    PubMed Central

    Niinemets, Ülo

    2013-01-01

    Isoprene emissions importantly protect plants from heat stress, but the emissions become inhibited by instantaneous increase of [CO2], and it is currently unclear how isoprene-emitting plants cope with future more frequent and severe heat episodes under high [CO2]. Hybrid aspen (Populus tremula x Populus tremuloides) saplings grown under ambient [CO2] of 380 μmol mol−1 and elevated [CO2] of 780 μmol mol−1 were used to test the hypothesis that acclimation to elevated [CO2] reduces the inhibitory effect of high [CO2] on emissions. Elevated-[CO2]-grown plants had greater isoprene emission capacity and a stronger increase of isoprene emissions with increasing temperature. High temperatures abolished the instantaneous [CO2] sensitivity of isoprene emission, possibly due to removing the substrate limitation resulting from curbed cycling of inorganic phosphate. As a result, isoprene emissions were highest in elevated-[CO2]-grown plants under high measurement [CO2]. Overall, elevated growth [CO2] improved heat resistance of photosynthesis, in particular, when assessed under high ambient [CO2] and the improved heat resistance was associated with greater cellular sugar and isoprene concentrations. Thus, contrary to expectations, these results suggest that isoprene emissions might increase in the future. PMID:24153419

  6. Improving the Carbon Dioxide Emission Estimates from the Combustion of Fossil Fuels in California

    SciTech Connect

    de la Rue du Can, Stephane; Wenzel, Tom; Price, Lynn

    2008-08-13

    Central to any study of climate change is the development of an emission inventory that identifies and quantifies the State's primary anthropogenic sources and sinks of greenhouse gas (GHG) emissions. CO2 emissions from fossil fuel combustion accounted for 80 percent of California GHG emissions (CARB, 2007a). Even though these CO2 emissions are well characterized in the existing state inventory, there still exist significant sources of uncertainties regarding their accuracy. This report evaluates the CO2 emissions accounting based on the California Energy Balance database (CALEB) developed by Lawrence Berkeley National Laboratory (LBNL), in terms of what improvements are needed and where uncertainties lie. The estimated uncertainty for total CO2 emissions ranges between -21 and +37 million metric tons (Mt), or -6percent and +11percent of total CO2 emissions. The report also identifies where improvements are needed for the upcoming updates of CALEB. However, it is worth noting that the California Air Resources Board (CARB) GHG inventory did not use CALEB data for all combustion estimates. Therefore the range in uncertainty estimated in this report does not apply to the CARB's GHG inventory. As much as possible, additional data sources used by CARB in the development of its GHG inventory are summarized in this report for consideration in future updates to CALEB.

  7. A novel field measurement method for determining fine particle and gas emissions from residential wood combustion

    NASA Astrophysics Data System (ADS)

    Tissari, Jarkko; Hytönen, Kati; Lyyränen, Jussi; Jokiniemi, Jorma

    Emission data from residential wood combustion are usually obtained on test stands in the laboratory but these measurements do not correspond to the operational conditions in the field because of the technological boundary conditions (e.g. testing protocol, environmental and draught conditions). The field measurements take into account the habitual practice of the operators and provide the more reliable results needed for emission inventories. In this study, a workable and compact method for measuring emissions from residential wood combustion in winter conditions was developed. The emissions for fine particle, gaseous and PAH compounds as well as particle composition in real operational conditions were measured from seven different appliances. The measurement technique worked well and was evidently suitable for winter conditions. It was easy and fast to use, and no construction scaffold was needed. The dilution of the sample with the combination of a porous tube diluter and an ejector diluter was well suited to field measurement. The results indicate that the emissions of total volatile organic carbon (TVOC) (17 g kg -1 (of dry wood burned)), carbon monoxide (CO) (120 g kg -1) and fine particle mass (PM 1) (2.7 g kg -1) from the sauna stove were higher than in the other measured appliances. In the masonry heaters, baking oven and stove, the emissions were 2.9-9 g kg -1 TVOC, 28-68 g kg -1 CO and 0.6-1.6 g kg -1 PM 1. The emission of 12 PAHs (PAH 12) from the sauna stove was 164 mg kg -1 and consisted mainly of PAHs with four benzene rings in their structure. PAH 12 emission from other appliances was, on average, 21 mg kg -1 and was dominated by 2-ring PAHs. These results indicate that despite the non-optimal operational practices in the field, the emissions did not differ markedly from the laboratory measurements.

  8. Room temperature fabrication of 1D carbon-copper composite nanostructures directly on Cu substrate and their field emission properties

    NASA Astrophysics Data System (ADS)

    Rosmi, Mohamad Saufi; Yaakob, Yazid; Mohd Yusop, Mohd Zamri; Sharma, Subash; Zulkifli, Zurita; Supee, Aizuddin; Kalita, Golap; Tanemura, Masaki

    2016-09-01

    This paper demonstrates a carbon-copper (C-Cu) composite nanostructure directly fabricated on a copper (Cu) substrate using the Ar+ ion irradiation method at room temperature. The morphology of C-Cu composite was controlled by a simultaneous carbon supply during ion irradiation. Conical protrusions formed on the surface of the Cu substrate with the low carbon supply rate (RC), whereas high RC area prominently produced nanoneedle structures. The field electron emission (FEE) tests demonstrated significant improvement between conical protrusions and nanoneedle structures, where the emission current increase from 5.70 μ Acm-2 to 4.37 mAcm-2, while the turn-on field reduced from 5.90 to 2.00 Vμ m-1 .

  9. Work function measurements by the field emission retarding potential method.

    NASA Technical Reports Server (NTRS)

    Strayer, R. W.; Mackie, W.; Swanson, L. W.

    1973-01-01

    Description of the theoretical foundation of the field electron retarding potential method, and review of its experimental application to the measurement of single crystal face work functions. The results obtained from several substrates are discussed. An interesting and useful fallout from the experimental approach described is the ability to accurately measure the elastic and inelastic reflection coefficient for impinging electrons to near zero-volt energy.

  10. Entropic and Near-Field Improvements of Thermoradiative Cells

    NASA Astrophysics Data System (ADS)

    Hsu, Wei-Chun; Tong, Jonathan K.; Liao, Bolin; Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2016-10-01

    A p-n junction maintained at above ambient temperature can work as a heat engine, converting some of the supplied heat into electricity and rejecting entropy by interband emission. Such thermoradiative cells have potential to harvest low-grade heat into electricity. By analyzing the entropy content of different spectral components of thermal radiation, we identify an approach to increase the efficiency of thermoradiative cells via spectrally selecting long-wavelength photons for radiative exchange. Furthermore, we predict that the near-field photon extraction by coupling photons generated from interband electronic transition to phonon polariton modes on the surface of a heat sink can increase the conversion efficiency as well as the power generation density, providing more opportunities to efficiently utilize terrestrial emission for clean energy. An ideal InSb thermoradiative cell can achieve a maximum efficiency and power density up to 20.4% and 327 Wm‑2, respectively, between a hot source at 500 K and a cold sink at 300 K. However, sub-bandgap and non-radiative losses will significantly degrade the cell performance.

  11. Entropic and Near-Field Improvements of Thermoradiative Cells

    PubMed Central

    Hsu, Wei-Chun; Tong, Jonathan K.; Liao, Bolin; Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2016-01-01

    A p-n junction maintained at above ambient temperature can work as a heat engine, converting some of the supplied heat into electricity and rejecting entropy by interband emission. Such thermoradiative cells have potential to harvest low-grade heat into electricity. By analyzing the entropy content of different spectral components of thermal radiation, we identify an approach to increase the efficiency of thermoradiative cells via spectrally selecting long-wavelength photons for radiative exchange. Furthermore, we predict that the near-field photon extraction by coupling photons generated from interband electronic transition to phonon polariton modes on the surface of a heat sink can increase the conversion efficiency as well as the power generation density, providing more opportunities to efficiently utilize terrestrial emission for clean energy. An ideal InSb thermoradiative cell can achieve a maximum efficiency and power density up to 20.4% and 327 Wm−2, respectively, between a hot source at 500 K and a cold sink at 300 K. However, sub-bandgap and non-radiative losses will significantly degrade the cell performance. PMID:27734902

  12. Radio Emission from particle cascades in the presence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Mulrey, Katharine

    2015-04-01

    Geomagnetic radiation from air showers is an attractive technique for detecting ultra-high energy cosmic rays. Macroscopic and microscopic models have been developed which qualitatively agreed with field observations. A controlled laboratory experiment at the SLAC National Accelerator Laboratory (SLAC) was designed to test these models. The experiment measures the radio frequency emission from cascades of secondary particles in a dense dielectric medium in the presence of a magnetic field. The cascades were induced by a ~ 4.5 GeV electron beam in a polyethylene target placed in magnetic fields up to +/-1000 G. The radio emission beam pattern was sampled in horizontal and vertical polarizations by multiple antennas with a total frequency band of 30-3000 MHz. The emission was found to be in good agreement with model predictions, including a Cerenkov-like beam pattern and linear scaling with magnetic field. Katharine Mulrey for the T-510 Collaboration.

  13. Growth and field emission of tungsten oxide nanotip arrays on ITO glass substrate

    NASA Astrophysics Data System (ADS)

    Huang, Kai; Pan, Qingtao; Yang, Feng; Ni, Shibi; He, Deyan

    2007-09-01

    High-density and uniformly aligned tungsten oxide nanotip arrays have been deposited by a conventional thermal evaporation on ITO glass substrates without any catalysts or additives. The temperature of substrate was 450-500 °C. It was shown that the tungsten oxide nanotips are single-crystal grown along [0 1 0] direction. For commercial applications, field emission of the tungsten oxide nanotip arrays was characterized in a poor vacuum at room temperature. The field emission behaviors are in agreement with Fowler-Nordheim theory. The turn-on field is 2.8 V μm -1 as d is 0.3 mm. The excellent field emission performances indicated that the tungsten oxide nanotip arrays grown by the present approach are a good candidate for application in vacuum microelectronic devices.

  14. Groups of bats improve sonar efficiency through mutual suppression of pulse emissions

    PubMed Central

    Jarvis, Jenna; Jackson, William; Smotherman, Michael

    2013-01-01

    How bats adapt their sonar behavior to accommodate the noisiness of a crowded day roost is a mystery. Some bats change their pulse acoustics to enhance the distinction between theirs and another bat's echoes, but additional mechanisms are needed to explain the bat sonar system's exceptional resilience to jamming by conspecifics. Variable pulse repetition rate strategies offer one potential solution to this dynamic problem, but precisely how changes in pulse rate could improve sonar performance in social settings is unclear. Here we show that bats decrease their emission rates as population density increases, following a pattern that reflects a cumulative mutual suppression of each other's pulse emissions. Playback of artificially-generated echolocation pulses similarly slowed emission rates, demonstrating that suppression was mediated by hearing the pulses of other bats. Slower emission rates did not support an antiphonal emission strategy but did reduce the relative proportion of emitted pulses that overlapped with another bat's emissions, reducing the relative rate of mutual interference. The prevalence of acoustic interferences occurring amongst bats was empirically determined to be a linear function of population density and mean emission rates. Consequently as group size increased, small reductions in emission rates spread across the group partially mitigated the increase in interference rate. Drawing on lessons learned from communications networking theory we show how modest decreases in pulse emission rates can significantly increase the net information throughput of the shared acoustic space, thereby improving sonar efficiency for all individuals in a group. We propose that an automated acoustic suppression of pulse emissions triggered by bats hearing each other's emissions dynamically optimizes sonar efficiency for the entire group. PMID:23781208

  15. Groups of bats improve sonar efficiency through mutual suppression of pulse emissions.

    PubMed

    Jarvis, Jenna; Jackson, William; Smotherman, Michael

    2013-01-01

    How bats adapt their sonar behavior to accommodate the noisiness of a crowded day roost is a mystery. Some bats change their pulse acoustics to enhance the distinction between theirs and another bat's echoes, but additional mechanisms are needed to explain the bat sonar system's exceptional resilience to jamming by conspecifics. Variable pulse repetition rate strategies offer one potential solution to this dynamic problem, but precisely how changes in pulse rate could improve sonar performance in social settings is unclear. Here we show that bats decrease their emission rates as population density increases, following a pattern that reflects a cumulative mutual suppression of each other's pulse emissions. Playback of artificially-generated echolocation pulses similarly slowed emission rates, demonstrating that suppression was mediated by hearing the pulses of other bats. Slower emission rates did not support an antiphonal emission strategy but did reduce the relative proportion of emitted pulses that overlapped with another bat's emissions, reducing the relative rate of mutual interference. The prevalence of acoustic interferences occurring amongst bats was empirically determined to be a linear function of population density and mean emission rates. Consequently as group size increased, small reductions in emission rates spread across the group partially mitigated the increase in interference rate. Drawing on lessons learned from communications networking theory we show how modest decreases in pulse emission rates can significantly increase the net information throughput of the shared acoustic space, thereby improving sonar efficiency for all individuals in a group. We propose that an automated acoustic suppression of pulse emissions triggered by bats hearing each other's emissions dynamically optimizes sonar efficiency for the entire group.

  16. Improving high resolution emission inventories with local proxies and urban eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Gioli, Beniamino; Gualtieri, Giovanni; Busillo, Caterina; Calastrini, Francesca; Zaldei, Alessandro; Toscano, Piero

    2015-08-01

    Emission inventories are the fundamental official data on atmospheric emissions of pollutants and greenhouse gases at a variety of spatial and temporal scales worldwide. This study makes use of direct CO2 emission measurements made with the eddy covariance technique over a completely urbanized area, with no confounding effect of vegetation, where emissions are mostly controlled by natural gas combustion processes and road traffic. Objectives are: i) to validate top-down spatially and temporally disaggregated emission inventories at yearly, monthly, weekly and hourly time scales; ii) to quantify the improvement achieved in official inventories when replacing built-in temporal disaggregation proxies with customized proxies based on local data of road traffic and natural gas consumption. We demonstrate that the overall performance of official inventory at yearly scale is rather good with an emission of 3.08 g CO2 m-2 h-1 against a measured emission of 3.21 ± 0.12 g CO2 m-2 h-1. When temporally disaggregating annual emissions, the agreement between inventory and observations always significantly improves when using local proxies, by 47% (from 0.70 to 0.37 g CO2 m-2 h-1 RMSE) at monthly scale, by 26% (from 0.58 to 0.43 g CO2 m-2 h-1 RMSE) at weekly scale, and by 32% (from 1.26 to 0.85 g CO2 m-2 h-1 RMSE), at hourly scale. The validity of this analysis goes beyond CO2 since the temporal proxies used by the inventories mimic the intensity of specific emission processes, therefore species emitted in the same processes as CO2, would benefit from the improved parameterization of temporal proxies shown here. These results indicate that effort should be put into developing improved temporal proxies based on local rather than national scale data, that can better mimic site dependent behaviors.

  17. Low energy cluster beam deposited BN films as the cascade for field emission

    NASA Astrophysics Data System (ADS)

    Song, F.; Zhang, L.; Zhu, L.; Ge, J.; Wang, G.

    2005-07-01

    The atomic deposited BN films with the thickness of nanometers (ABN) were prepared by radio frequency magnetron sputtering method and the nanostructured BN films (CBN) were prepared by Low Energy Cluster Beam Deposition. UV-Vis Absorption measurement proves the band gap of 4.27 eV and field emission of the BN films were carried out. F-N plots of all the samples give a good fitting and demonstrate the F-N tunneling of the emission process. The emission of ABN begins at the electric field of 14.6 V/μ m while that of CBN starts at 5.10 V/μ m. Emission current density of 1 mA/cm2 for ABN needs the field of 20 V/μ m while that of CBN needs only 12.1 V/μ m. The cluster-deposited BN on n-type Silicon substrate proves a good performance in terms of the lower gauge voltage, more emission sites and higher electron intensity and seems a promising substitute for the cascade of field emission.

  18. Cost-Effective Reciprocating Engine Emissions Control and Monitoring for E&P Field and Gathering Engines

    SciTech Connect

    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.

  19. A field laboratory for improved oil recovery. Final report

    SciTech Connect

    Hildebrandt, A.F.; McDonald, J.; Claridge, E.; Killough, J.

    1992-09-01

    The purpose of Annex III of the Memorandum of Understanding, undertaken by the Houston Petroleum Research Center at the University of Houston, was to develop a field laboratory for research in improved oil recovery using a Gulf Coast reservoir in Texas. The participants: (1) make a field site selection and conducted a high resolution seismic survey in the demonstration field, (2) obtained characteristics of the reservoir (3) developed an evaluation of local flood efficiency in different parts of the demonstration reservoir, (4) used diverse methodology to evaluate the potential recovery of the remaining oil in the test reservoir, (5) developed cross-well seismic tomography, and (6) will transfer the learned technologies to oil operators through publication and workshops. This abstract is an overview of these tasks.

  20. Comparison of emissions and residential exposure from traditional and improved cookstoves in Kenya

    SciTech Connect

    Ezzati, M.; Mbinda, B.M.; Kammen, D.M.

    2000-02-15

    Suspended particulate matter and carbon emissions from the combustion of biomass, in addition to their environmental consequences, have been causally associated with the incidence of respiratory and eye infections. Improved stoves offer the potential for emissions reduction. The authors compare the emissions of suspended particulate matter and carbon monoxide from traditional and improved biofuel stoves in Kenya under the actual conditions of household use. Data for analysis is from 137 14-h days of continuous real-time emission concentration monitoring in a total of 38 households. Their analysis shows that improved (ceramic) wood-burning stoves reduce daily average suspended particulate matter concentration by 48% during the active burning period and by 77% during the smoldering phase. Ceramic stoves also reduce the median and the 75th and 95th percentiles of daily emission concentration during the burning period and the 95th percentile during the smoldering phase, and therefore shift the overall emission profile downward. Improved charcoal-burning stoves also offer reductions in indoor air pollution compared to the traditional metal stove, but these are not statistically significant. The greatest reduction in emission concentration is achieved as a result of transition from wood to charcoal where mean emission concentrations drop by 87% during the burning period and by 92% when smoldering as well as large reductions in the median and 75th and 95th percentiles. These results indicate that transition to charcoal, followed by the use of improved wood stoves, are viable options for reduction of human exposure to indoor air pollution in many developing nations.

  1. An improved model for the Earth's gravity field

    NASA Technical Reports Server (NTRS)

    Tapley, B. D.; Shum, C. K.; Yuan, D. N.; Ries, J. C.; Schutz, B. E.

    1989-01-01

    An improved model for the Earth's gravity field, TEG-1, was determined using data sets from fourteen satellites, spanning the inclination ranges from 15 to 115 deg, and global surface gravity anomaly data. The satellite measurements include laser ranging data, Doppler range-rate data, and satellite-to-ocean radar altimeter data measurements, which include the direct height measurement and the differenced measurements at ground track crossings (crossover measurements). Also determined was another gravity field model, TEG-1S, which included all the data sets in TEG-1 with the exception of direct altimeter data. The effort has included an intense scrutiny of the gravity field solution methodology. The estimated parameters included geopotential coefficients complete to degree and order 50 with selected higher order coefficients, ocean and solid Earth tide parameters, Doppler tracking station coordinates and the quasi-stationary sea surface topography. Extensive error analysis and calibration of the formal covariance matrix indicate that the gravity field model is a significant improvement over previous models and can be used for general applications in geodesy.

  2. Emissions of methane, nitrous oxide, and other trace gases from rice fields in China

    NASA Astrophysics Data System (ADS)

    Khalil, M. A. K.; Rasmussen, R. A.; Shearer, M. J.; Chen, Zong-Liang; Yao, Heng; Yang, Jun

    1998-10-01

    We measured the emissions of methane, nitrous oxide, and other environmentally important trace gases from rice fields in China. The experiments were conducted near Beijing, representing temperate latitude rice agriculture, and at Guangzhou, representing tropical and subtropical agriculture. These studies complement our intensive research at Tu Zu in China (subtropical) and the work near Bogor, Indonesia, representing tropical rice agriculture. The experiments described here span 5 years between 1992 and 1996. The seasonally averaged methane emissions from Beijing were about 9 (5-16) mg m-2 h-1. Emissions from the first crop of the year at Guangzhou were about 5 (2-8) mg m-2 h-1 and about 30 (18-54) mg m-2 h-1 from the second crop. Measurements of nitrous oxide fluxes from the same rice fields show that emissions are confined to events that consist of high fluxes decaying to zero within a few days. Some of the events appear to be triggered by fertilizer applications. It is apparent that rice fields using nitrogen-based fertilizers are a source of N2O, but a robust estimate of whole season average emission rate is still not possible. The composite of all the N2O fluxes we observed gives a geometric mean of about 70 μg m-2 h-1. These rates are high enough to suggest that the rice fields could be a globally important source of N2O. As the agricultural practices change from use of organic fertilizers to nitrogen-based fertilizers, the role of N2O emissions from rice fields may become more important in its global budget. We also observed that chloroform and carbon monoxide were emitted from all fields studied. The flux of CO is not large enough to be important on the global scale, but the emissions of chloroform may be.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Vertically-Aligned Single-Crystal Nanocone Arrays: Controlled Fabrication and Enhanced Field Emission.

    PubMed

    Duan, Jing Lai; Lei, Dang Yuan; Chen, Fei; Lau, Shu Ping; Milne, William I; Toimil-Molares, M E; Trautmann, Christina; Liu, Jie

    2016-01-13

    Metal nanostructures with conical shape, vertical alignment, large ratio of cone height and curvature radius at the apex, controlled cone angle, and single-crystal structure are ideal candidates for enhancing field electron-emission efficiency with additional merits, such as good mechanical and thermal stability. However, fabrication of such nanostructures possessing all these features is challenging. Here, we report on the controlled fabrication of large scale, vertically aligned, and mechanically self-supported single-crystal Cu nanocones with controlled cone angle and enhanced field emission. The Cu nanocones were fabricated by ion-track templates in combination with electrochemical deposition. Their cone angle is controlled in the range from 0.3° to 6.2° by asymmetrically selective etching of the ion tracks and the minimum tip curvature diameter reaches down to 6 nm. The field emission measurements show that the turn-on electric field of the Cu nanocone field emitters can be as low as 1.9 V/μm at current density of 10 μA/cm(2) (a record low value for Cu nanostructures, to the best of our knowledge). The maximum field enhancement factor we measured was as large as 6068, indicating that the Cu nanocones are promising candidates for field emission applications.

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

    SciTech Connect

    Song, Meng; Xu, Peng; Wang, Xu; Wu, Huizhen; Wang, Miao E-mail: miaowang@css.zju.edu.cn; Song, Yenan; Li, Zhenhua; Zhao, Pei E-mail: miaowang@css.zju.edu.cn; Shang, Xuefu

    2015-09-15

    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/cm{sup 2}, and field enhancement factor of ∼1.3 × 10{sup 4}. 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.

  6. Microscale gas breakdown: ion-enhanced field emission and the modified Paschen’s curve

    NASA Astrophysics Data System (ADS)

    Go, D. B.; Venkattraman, A.

    2014-12-01

    Gas breakdown at microscale dimensions has been of great interest to the microelectromechanical systems (MEMS) and plasma communities for nearly 15 years as the first reports of deviations from traditional theory began to emerge. Since those first reports, a significant amount of work has investigated why gas breakdown deviates from the classic Paschen’s Law when the dimensions are in the range of 1-10 µm. Nearly universally, these deviations that form the so-called modified Paschen’s curve have been attributed to electron field emission, where electrons directly tunnel from the cathode into the gas due to the very high electric fields at microscale dimensions. Furthermore, because of ionization in the gas gap, field emission is enhanced by positive ions and thus is inherently coupled to the gas and discharge dynamics. Progress in understanding the mechanisms and physics of this process has in turn led to new ideas and devices that capitalize on the high surface-to-volume ratio in microscale dimensions and take advantage of cathode emission processes. This topical review summarizes and analyzes the numerous experimental, computational and analytical works on breakdown at microscale dimensions, discusses implications and new areas emerging in microscale devices that take advantage of field emission and presents perspectives looking ahead at new opportunities for field emission-driven microplasmas.

  7. Emission line eclipse mapping of velocity fields in dwarf nova accretion discs

    NASA Astrophysics Data System (ADS)

    Makita, M.; Mineshige, S.

    2002-01-01

    We propose a new method, emission-line eclipse mapping, to map the velocity fields in an accretion disc. We apply the usual eclipse mapping technique to the light curves at each of 12-24 wavelengths across the line center to map the region with same line-of-sight velocity, from which we are able to plot the rotational velocity as a function of radius on the assumption of axisymmetric disc. We calculate time changes of the emission line profiles, assuming Keplerian rotation fields (vvarphi propto r-1/2) and the emissivity distribution of j propto r-3/2, and reconstruct emissivity profiles. The results show typically a `two-eye' pattern for high line-of-sight velocities and we can recover the relation, vvarphi propto d-1/2, where d is the separation of two lq eyes.'

  8. Vacuum ultraviolet field emission lamp consisting of neodymium ion doped lutetium fluoride thin film as phosphor.

    PubMed

    Yanagihara, Masahiro; Tsuji, Takayuki; Yusop, Mohd Zamri; Tanemura, Masaki; Ono, Shingo; Nagami, Tomohito; Fukuda, Kentaro; Suyama, Toshihisa; Yokota, Yuui; Yanagida, Takayuki; Yoshikawa, Akira

    2014-01-01

    A vacuum ultraviolet (VUV) field emission lamp was developed by using a neodymium ion doped lutetium fluoride (Nd(3+) : 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 Nd(3+) : 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.

  9. Methane emissions estimate from airborne measurements over a western United States natural gas field

    NASA Astrophysics Data System (ADS)

    Karion, Anna; Sweeney, Colm; PéTron, Gabrielle; Frost, Gregory; Michael Hardesty, R.; Kofler, Jonathan; Miller, Ben R.; Newberger, Tim; Wolter, Sonja; Banta, Robert; Brewer, Alan; Dlugokencky, Ed; Lang, Patricia; Montzka, Stephen A.; Schnell, Russell; Tans, Pieter; Trainer, Michael; Zamora, Robert; Conley, Stephen

    2013-08-01

    (CH4) emissions from natural gas production are not well quantified and have the potential to offset the climate benefits of natural gas over other fossil fuels. We use atmospheric measurements in a mass balance approach to estimate CH4 emissions of 55 ± 15 × 103 kg h-1 from a natural gas and oil production field in Uintah County, Utah, on 1 day: 3 February 2012. This emission rate corresponds to 6.2%-11.7% (1σ) of average hourly natural gas production in Uintah County in the month of February. This study demonstrates the mass balance technique as a valuable tool for estimating emissions from oil and gas production regions and illustrates the need for further atmospheric measurements to determine the representativeness of our single-day estimate and to better assess inventories of CH4 emissions.

  10. Development of Advanced High Strength Steel for Improved Vehicle Safety, Fuel Efficiency and CO2 Emission

    NASA Astrophysics Data System (ADS)

    Kumar, Satendra; Singhai, Mrigandra; Desai, Rahul; Sam, Srimanta; Patra, Pradip Kumar

    2015-12-01

    Global warming and green house gas emissions are the major issues worldwide and their impacts are clearly visible as a record high temperatures, rising sea, and severe `flooding and droughts'. Motor vehicles considered as a major contributor on global warming due to its green house gas emissions. Hence, the automobile industries are under tremendous pressure from government and society to reduce green house gas emission to maximum possible extent. In present work, Dual Phase steel with boron as microalloying is manufactured using thermo-mechanical treatment during hot rolling. Dual phase steel with boron microalloying improved strength by near about 200 MPa than dual phase steel without boron. The boron added dual phase steel can be used for manufacturing stronger and a lighter vehicle which is expected to perform positively on green house gas emissions. The corrosion resistance behavior is also improved with boron addition which would further increase the life cycle of the vehicle even under corrosive atmosphere.

  11. Ensemble-based simultaneous emission estimates and improved forecast of radioactive pollution from nuclear power plant accidents: application to ETEX tracer experiment.

    PubMed

    Zhang, X L; Li, Q B; Su, G F; Yuan, M Q

    2015-04-01

    The accidental release of radioactive materials from nuclear power plant leads to radioactive pollution. We apply an augmented ensemble Kalman filter (EnKF) with a chemical transport model to jointly estimate the emissions of Perfluoromethylcyclohexane (PMCH), a tracer substitute for radionuclides, from a point source during the European Tracer Experiment, and to improve the forecast of its dispersion downwind. We perturb wind fields to account for meteorological uncertainties. We expand the state vector of PMCH concentrations through continuously adding an a priori emission rate for each succeeding assimilation cycle. We adopt a time-correlated red noise to simulate the temporal emission fluctuation. The improved EnKF system rapidly updates (and reduces) the excessively large initial first-guess emissions, thereby significantly improves subsequent forecasts (r = 0.83, p < 0.001). It retrieves 94% of the total PMCH released and substantially reduces transport error (>80% average reduction of the normalized mean square error).

  12. Enhancement of Laser Induced Breakdown Emission in the Presence of External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Rai, Virendra N.; Zhang, Hansheng; Yueh, Fang Y.; Singh, Jagdish P.

    2001-04-01

    Laser induced breakdown spectroscopy (LIBS) is a useful method for determining the elemental composition in solid, liquid and gaseous samples. Elemental analysis of sample is accomplished by measuring the emission of the elemental atom or ions present in the plasma from any kind of samples. The ability to form and study the plasma on unprepared sample makes LIBS a very attractive analytical technique. Various techniques have been used for enhancing the analytical characteristics of the plasma sources used for elemental analysis. Many complicated magnetic field geometries have been used earlier with various types of plasma sources to enhance the plasma emission. In this paper characterization of laser induced plasma emission from Manganese (Mn) in liquid solution is presented. The plasma was formed in between the poles of two magnets with 1200 Gauss pole strength separated by 5 mm. The effect of magnetic field on various emission properties was studied. An one and half times enhancement in the intensity of Mn emission line at 403.076, 403.307 and 403.449 nm was observed for the laser intensity below 1.5x10e12 W/cm2. The intensity of Mn line decreases at higher laser intensity in the presence of magnetic field. This decrease in the emission at higher laser intensity seems to be due to turbulence as a result of laser induced shock as well as generation of instability in the plasma in the presence of magnetic field. The calibration curve for Mn was obtained in an optimized condition in the absence and presence of magnetic field. The limit of detection for Mn in liquid was found to be 0.63 PPM in the presence of magnetic field, which is less in comparison to the absence of magnetic field ( 0.87 PPM). * Visiting Scientist from Centre for Advanced Technology, Indore-452 013 (INDIA)

  13. Measurement and Analysis of Field Emission Electrons in the LCLS Gun

    SciTech Connect

    Dowell, D.H.; Jongewaard, E.; Limborg-Deprey, C.; Schmerge, J.F.; Vlieks, A.; /SLAC

    2007-11-02

    The field emission was measured during the high-power testing of the LCLS photocathode RF gun. A careful study and analysis of the field emission electrons, or dark current is important in assessing the gun's internal surface quality in actual operation, especially those surfaces with high fields. The first indication of a good RF gun design and fabrication is short processing time to the required fields and low electron emission at high fields. The charge per 2 microsecond long RF pulse (the dark charge) was measured as a function of the peak cathode field for the 1.6 cell, 2.856GHz LCLS RF gun. Faraday cup data was taken for cathode peak RF fields up to 120MV/m producing a maximum of 0.6nC/RF pulse for a diamond-turned polycrystalline copper cathode installed in the gun. Digitized images of the dark charge were taken using a 100 micron thick YAG crystal for a range of solenoid fields to determine the location and angular distribution of the field emitters. The FN plots and emitter image analysis will be described in this paper.

  14. Vertically aligned carbon nanopillars with size and spacing control for a transparent field emission display.

    PubMed

    Lee, Seok Woo; Lee, Chang Hwa; Lee, Jung A; Lee, Seung S

    2013-01-18

    A top-down fabrication method is presented for vertically aligned carbon nanopillars (CNPs) using photolithography and pyrolysis. The modified backside exposure method of photolithography fabricates vertically aligned polymer (SU-8) nanopillars. The pyrolysis process, which transforms the polymer to amorphous carbon, reliably produces vertically aligned CNPs with widths ranging from 100 to 400 nm. The CNPs can be used as a transparent field emission cathode for a transparent display and light emission is observed.

  15. Broad band simulation of Gamma Ray Bursts (GRB) prompt emission in presence of an external magnetic field

    NASA Astrophysics Data System (ADS)

    Ziaeepour, Houri; Gardner, Brian

    2011-12-01

    The origin of prompt emission in GRBs is not yet well understood. The simplest and most popular model is Synchrotron Self-Compton (SSC) emission produced by internal shocks inside an ultra-relativistic jet. However, recent observations of a delayed high energy component by the Fermi-LAT instrument have encouraged alternative models. Here we use a recently developed formulation of relativistic shocks for GRBs to simulate light curves and spectra of synchrotron and self-Compton emissions in the framework of internal shock model. This model takes into account the evolution of quantities such as densities of colliding shells, and fraction of kinetic energy transferred to electrons and to induced magnetic field. We also extend this formulation by considering the presence of a precessing external magnetic field. These simulations are very realistic and present significant improvement with respect to previous phenomenological GRB simulations. They reproduce light curves of separate peaks of real GRBs and variety of spectral slopes at E > Epeak observed by the Fermi-LAT instrument. The high energy emission can be explained by synchrotron emission and a subdominant contribution from inverse Compton. We also suggest an explanation for extended tail emission and relate it to the screening of the magnetic field and/or trapping of accelerated electrons in the electromagnetic energy structure of the plasma in the shock front. Spectral slopes of simulated bursts at E << Epeak are consistent with theoretical prediction and at E < Epeak can be flatter if the spectrum of electrons is roughly flat or has a shallow slope at low energies. The observed flat spectra at soft gamma-ray and hard x-ray bands is the evidence that there is a significant contribution at E < Epeak from lower Lorentz factor wing of electron distribution which have a roughly random acceleration rather than being thermal. This means that the state of matter in the jet at the time of ejection is most probably

  16. Spectroscopic investigations of a field emission generated radiative zone: Mass spectroscopic measurements. Final Report

    SciTech Connect

    Mitterauer, J.

    1981-10-01

    In view of the application of liquid metal field ion sources as electric thrustors for space propulsion, the basic physical features of the field ionization mechanism were analyzed experimentally. An ultrahigh vacuum test chamber and a liquid metal ion source were built. Diagnostic methods, e.g., basic measurements of the emission characteristics, probe measurements of the ion current distribution, mass spectroscopic measurements of the particles emitted from the ion source, and spectroscopic measurements of the visible radiation accompanying field ionization, were developed. Experimental data which can be transferred to prototype field ion thrusters are presented, but experimental facilities limit conclusions regarding theoretical aspects of field ionization.

  17. Seasonal Production and Emission of Methane from Rice Fields, Final Report

    SciTech Connect

    Khalil, M. Aslam K.; Rasmussen,Reinhold A.

    2002-12-03

    B 139 - Methane (CH4) is a greenhouse gas regarded second only to carbon dioxide in its ability to cause global warming. Methane is important because of its relatively fast increase, and also because it is, per molecule, some 60 times more effective than carbon dioxide in causing global warming. The largest present anthropogenic sources of methane are rice fields, cattle and biomass burning. The global emissions from these sources are still not well known. In the middle 1980s there were few available data on methane emissions from rice fields leading to estimates of a global source between 100-280 Tg/yr. Extensive worldwide research during the last decade has shown that the global emissions from rice fields are more likely to be in the range of 30-80Tg/yr. While this work has led to a substantial reduction in the estimated emissions, the uncertainty is still quite large, and seriously affects our ability to include methane in integrated assessments for future climate change and environmental management.China dominated estimates of methane emissions from rice fields because it was, and is, the largest producer of rice, and major increases in rice production had taken place in the country over the last several decades. This report summarizes the work in Sichuan Province, China, in each of the following areas: the design of the experiment; the main results on methane emissions from rice fields, delineating the factors controlling emissions; production of methane in the soil; a survey of water management practices in sample of counties in Sichuan province; and results of ambient measurements including data from the background continental site. B139

  18. Field emission behavior of carbon nanotube yarn for micro-resolution X-ray tube cathode.

    PubMed

    Hwang, Jae Won; Mo, Chan Bin; Jung, Hyun Kyu; Ryu, Seongwoo; Hong, Soon Hyung

    2013-11-01

    Carbon nanotube (CNT) has excellent electrical and thermal conductivity and high aspect ratio for X-ray tube cathode. However, CNT field emission cathode has been shown unstable field emission and short life time due to field evaporation by high current density and detachment by electrostatic force. An alternative approach in this direction is the introduction of CNT yarn, which is a one dimensional assembly of individual carbon nanotubes bonded by the Van der Waals force. Because CNT yarn is composed with many CNTs, CNT yarns are expected to increase current density and life time for X-ray tube applications. In this research, CNT yarn was fabricated by spinning of a super-aligned CNT forest and was characterized for application to an X-ray tube cathode. CNT yarn showed a high field emission current density and a long lifetime of over 450 hours. Applying the CNT yarn field emitter to the X-ray tube cathode, it was possible to obtain micro-scale resolution images. The relationship between the field emission properties and the microstructure evolution was investigated and the unraveling effect of the CNT yarn was discussed. PMID:24245260

  19. Effect of Purity and Substrate on Field Emission Properties of Multi-walled Carbon Nanotubes

    PubMed Central

    2007-01-01

    Multi-walled carbon nanotubes (MWNT) have been synthesized by chemical vapour decomposition (CVD) of acetylene over Rare Earth (RE) based AB2(DyNi2) alloy hydride catalyst. The as-grown carbon nanotubes were purified by acid and heat treatments and characterized using powder X-ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Thermo Gravimetric Analysis and Raman Spectroscopy. Fully carbon based field emitters have been fabricated by spin coating a solutions of both as-grown and purified MWNT and dichloro ethane (DCE) over carbon paper with and without graphitized layer. The use of graphitized carbon paper as substrate opens several new possibilities for carbon nanotube (CNT) field emitters, as the presence of the graphitic layer provides strong adhesion between the nanotubes and carbon paper and reduces contact resistance. The field emission characteristics have been studied using an indigenously fabricated set up and the results are discussed. CNT field emitter prepared by spin coating of the purified MWNT–DCE solution over graphitized carbon paper shows excellent emission properties with a fairly stable emission current over a period of 4 h. Analysis of the field emission characteristics based on the Fowler–Nordheim (FN) theory reveals current saturation effects at high applied fields for all the samples. PMID:21798103

  20. Effect of Purity and Substrate on Field Emission Properties of Multi-walled Carbon Nanotubes.

    PubMed

    Rakhi, Rb; Sethupathi, K; Ramaprabhu, S

    2007-06-21

    Multi-walled carbon nanotubes (MWNT) have been synthesized by chemical vapour decomposition (CVD) of acetylene over Rare Earth (RE) based AB2(DyNi2) alloy hydride catalyst. The as-grown carbon nanotubes were purified by acid and heat treatments and characterized using powder X-ray diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, Thermo Gravimetric Analysis and Raman Spectroscopy. Fully carbon based field emitters have been fabricated by spin coating a solutions of both as-grown and purified MWNT and dichloro ethane (DCE) over carbon paper with and without graphitized layer. The use of graphitized carbon paper as substrate opens several new possibilities for carbon nanotube (CNT) field emitters, as the presence of the graphitic layer provides strong adhesion between the nanotubes and carbon paper and reduces contact resistance. The field emission characteristics have been studied using an indigenously fabricated set up and the results are discussed. CNT field emitter prepared by spin coating of the purified MWNT-DCE solution over graphitized carbon paper shows excellent emission properties with a fairly stable emission current over a period of 4 h. Analysis of the field emission characteristics based on the Fowler-Nordheim (FN) theory reveals current saturation effects at high applied fields for all the samples.

  1. Field emission behavior of carbon nanotube yarn for micro-resolution X-ray tube cathode.

    PubMed

    Hwang, Jae Won; Mo, Chan Bin; Jung, Hyun Kyu; Ryu, Seongwoo; Hong, Soon Hyung

    2013-11-01

    Carbon nanotube (CNT) has excellent electrical and thermal conductivity and high aspect ratio for X-ray tube cathode. However, CNT field emission cathode has been shown unstable field emission and short life time due to field evaporation by high current density and detachment by electrostatic force. An alternative approach in this direction is the introduction of CNT yarn, which is a one dimensional assembly of individual carbon nanotubes bonded by the Van der Waals force. Because CNT yarn is composed with many CNTs, CNT yarns are expected to increase current density and life time for X-ray tube applications. In this research, CNT yarn was fabricated by spinning of a super-aligned CNT forest and was characterized for application to an X-ray tube cathode. CNT yarn showed a high field emission current density and a long lifetime of over 450 hours. Applying the CNT yarn field emitter to the X-ray tube cathode, it was possible to obtain micro-scale resolution images. The relationship between the field emission properties and the microstructure evolution was investigated and the unraveling effect of the CNT yarn was discussed.

  2. Fabrication of field emission display prototype utilizing printed carbon nanotubes/nanofibers emitters

    NASA Astrophysics Data System (ADS)

    Guo, P. S.; Chen, T.; Chen, Y. W.; Zhang, Z. J.; Feng, T.; Wang, L. L.; Lin, L. F.; Sun, Z.; Zheng, Z. H.

    2008-06-01

    Carbon nanotubes/nanofibers (CNTs) used as emitters, diode-type field emission display (FED) prototypes of dot matrix and character images were fabricated by low-cost techniques and equipments, respectively. The technical development in the design and fabrication of the cathode, the anode, and the panel, is described. CNTs were produced by a simple, low-cost and easily-controllable thermal chemical vapor deposition. The cathode was prepared by the screen-printing method. The field emission characteristics were enhanced by a heat post-treatment in H2 gas atmosphere. The panel structure was packaged by a vacuum fluorescent display-like process and vacuum-sealed through an exhaust glass tube. The fully-sealed CNTs FED (c-FED) showed good emission properties. The brightness of 600 cd/m2 was achieved from the yellow phosphor at a relatively low applied electric field. The developed technology has a potential practical application in c-FED.

  3. Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

    NASA Astrophysics Data System (ADS)

    Dan, Cai; Lie, Liu; Jin-Chuan, Ju; Xue-Long, Zhao; Hong-Yu, Zhou; Xiao, Wang

    2016-04-01

    The carbon nanotube (CNT)-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305263 and 61401484).

  4. Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization.

    PubMed

    Van Well, Tyler L; Redshaw, Matthew; Gamage, Nadeesha D; Kandegedara, R M Eranjan B

    2016-01-01

    A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. The results of studies in which the etching current and the molarity of the NaOH solution used in the etching process were varied are presented. The investigation of the geometry of the tips, by imaging them with a scanning electron microscope, and by operating them in field emission mode is also described. The field emission tips produced are intended to be used as an electron beam source for ion production via electron impact ionization of background gas or vapor in Penning trap mass spectrometry applications. PMID:27500824

  5. Improved Fine Sun Sensor Field of View Calibration

    NASA Technical Reports Server (NTRS)

    Sedlak, J.; Hashmall, J.

    2003-01-01

    The fine Sun sensor used on many spacecraft consists of two independent single-axis sensor heads, nominally mounted perpendicularly. These detect the Sun angle over a field of view typically of +32 deg. (There is a trade-off between accuracy and size of the field of view that allows for much latitude in any numbers quoted.) The nonlinear "transfer" function that maps the telemetered counts into observed angles consists of 9 adjustable parameters for each axis (1 8 total). An augmented transfer function has previously been reported that achieves a significant accuracy improvement across the entire field of view. That function expands the parameter set to 12 coefficients per axis (24 total) and includes cross terms combining counts from both axes. To make the best use of the Sun sensor for attitude determination, it must be calibrated after launch. However, the large number of parameters and the nonlinearity of the problem make this a challenging task. The purpose of this paper is to examine ways to improve convergence of the parameter search algorithm. In particular, experience has shown that the problem should be broken down into several steps, solving for a selected subset of the parameters at each step. This approach has now been incorporated as an option in the calibration utility.

  6. Field Emission at Grain Boundaries: Modeling the Conductivity in Highly Doped Polycrystalline Semiconductors

    NASA Astrophysics Data System (ADS)

    Sommer, Nicolas; Hüpkes, Jürgen; Rau, Uwe

    2016-02-01

    In this contribution, we elaborate a conductivity model for highly doped polycrystalline semiconductors. The prominent feature of the model is the description of grain-boundary scattering by field emission, i.e., quantum-mechanical tunneling of electrons through potential barriers at grain boundaries. For this purpose, we adapt a theory of Stratton [Theory of field emission from semiconductors, Phys. Rev. 125, 67 (1962)] to double Schottky barriers at grain boundaries. We provide strong evidence that field emission rather than the predominantly applied thermionic emission is the dominant transport path across grain boundaries in semiconductors with carrier concentrations exceeding approximately 1019 cm-3 . We obtain a comprehensive conductivity model for highly doped polycrystalline semiconductors by combining field emission with two intragrain scattering mechanisms, that are ionized-impurity and electron-phonon scattering. The model is applied to a wide range of literature data in order to show its applicability and explanatory power. The literature data comprise, in particular, transparent conductive oxides with a special emphasis on aluminum-doped ZnO.

  7. Optical and field emission properties of layer-structure GaN nanowires

    SciTech Connect

    Cui, Zhen; Li, Enling; Shi, Wei; Ma, Deming

    2014-08-15

    Highlights: • The layer-structure GaN nanowires with hexagonal-shaped cross-sections are produced via a process based on the CVD method. • The diameter of the layer-structure GaN nanowire gradually decreases from ∼500 nm to ∼200 nm along the wire axis. • The layer-structure GaN nanowire film possesses good field emission property. - Abstract: A layer-structure gallium nitride (GaN) nanowires, grown on Pt-coated n-type Si (1 1 1) substrate, have been synthesized using chemical vapor deposition (CVD). The results show: (1) SEM indicates that the geometry structure is layer-structure. HRTEM indicates that GaN nanowire’s preferential growth direction is along [0 0 1] direction. (2) The room temperature PL emission spectrum of the layer-structure GaN nanowires has a peak at 375 nm, which proves that GaN nanowires have potential application in light-emitting nano-devices. (3) Field-emission measurements show that the layer-structure GaN nanowires film has a low turn-on field of 4.39 V/μm (at room temperature), which is sufficient for electron emission devices, field emission displays and vacuum nano-electronic devices. The growth mechanism for GaN nanowires has also been discussed briefly.

  8. Field studies of isoprene emissions from vegetation in the Northwest Mediterranean region

    NASA Astrophysics Data System (ADS)

    Owen, Susan M.; Boissard, C.; Hagenlocher, B.; Hewitt, C. Nicholas

    1998-10-01

    During the Biogenic Emissions in the Mediterranean Area (BEMA) project field campaigns (1993-1997), 40 native Mediterranean plant species were screened for emissions of isoprene and monoterpenes using a branch enclosure sampling method with subsequent gas chromatographic-flame ionization detector (GC-FID) and GC-mass selective detector (MS) analysis. Thirteen species emitted more than 0.5 μg (C) g-1 dw h-1 isoprene at 30°C and 1000 μmol m-2 s-1 photosynthetically active radiation (PAR), of which nine species emitted more than 20 μg (C) g-1 dw h-1. Emissions of isoprene were strongly correlated with temperature and PAR, and were reasonably well predicted by existing algorithms. There was little intraspecies and day to day variation in base emission rates. In general, median base emission rates were higher in summer compared to autumn for most species. Significant difference in aggregated habitat base emission rates was found between dunes, garrigue, woodland, and riverside sample sites. Although considerable unexplained variability in base emission rates remains to be explored, first estimates of base emission rates for Mediterranean shrublands are presented here.

  9. Interpretation of the field enhancement factor for electron emission from carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Smith, R. C.; Silva, S. R. P.

    2009-07-01

    The local electric fields in the vicinity of the tips of metallic nanotubes are calculated. The variation in the field enhancement factor as a function of internanotube separation, anode-substrate separation, and height and radius of the nanotube is reported. Calculations show that the field induced electron emission current, based on the Fowler-Nordheim theory, is reduced when the intertube separation is less than twice the height of the nanotube. The location of the anode plane is shown to be important when the anode-substrate separation is less than three times the height of the nanotube. The results also predict that the macroscopic threshold field for electron emission should decrease as the anode-substrate separation D decreases. For separations greater than three times the height of the nanotube, the threshold field becomes constant and independent of anode-cathode geometry. Conversely, the manner in which applied electric field is defined is crucial if the results are be understood better. Experimental field emission measurements made on an isolated carbon nanotube confirms the need for a new interpretation of the electric field around stand alone point emitters.

  10. Field electron and ion emission from charged surfaces: a strategic historical review of theoretical concepts.

    PubMed

    Forbes, Richard G

    2003-01-01

    The field-electron (FE) and field-ion techniques directly observe and measure atomic-level surface processes that occur in very high electric fields. In theoretical terms, the high fields put large additional terms into Hamiltonians and free energies, and significantly modify many aspects of the surface physics and chemistry, as compared with the field-free situation. This paper presents a strategic review of the fundamental science of some of these high-field surface effects and processes, as developed in the context of the field electron and ion emission techniques. It outlines the main theoretical concepts developed, notes some twists of scientific history, and suggests useful contributions made to mainstream science. Topics covered are basic aspects of FE emission, surface field ionisation, localised field adsorption, charged surfaces theory, field-ion image contrast theory and associated imaging-gas kinetics, field evaporation, and aspects of the thermodynamics of charged surfaces. Despite many years of effort, important aspects of the theory remain incomplete. Some theoretical challenges are noted.

  11. Apparatus comprising a tunable nanomechanical near-field grating and method for controlling far-field emission

    DOEpatents

    Carr, Dustin Wade; Bogart, Gregory Robert

    2007-02-06

    A tunable nanomechanical near-field grating is disclosed which is capable of varying the intensity of a diffraction mode of an optical output signal. The tunable nanomechanical near-field grating includes two sub-gratings each having line-elements with width and thickness less than the operating wavelength of light with which the grating interacts. Lateral apertures in the two sub-gratings are formed from the space between one line-element of the first sub-grating and at least one line-element of the second sub-grating. One of the sub-gratings is capable of motion such that at least one of aperture width and aperture depth changes, causing a perturbation to the near-field intensity distribution of the tunable nanomechanical near-field grating and a corresponding change to the far-field emission of thereof.

  12. Light source with carbon nanotubes field emission cathode and rare-earth doped nanocrystalline phosphors

    NASA Astrophysics Data System (ADS)

    Psuja, P.; Strek, W.

    2007-09-01

    In this work we report a new carbon nanotubes field emission (CNT-FED) light source with nanocrystalline phosphors. The nanocrystalline powders of cerium doped yttrium aluminum garnet were obtained by modified Pechini method. The phosphor has been electrophoretically deposited on ITO-glass substrates. The cathode composed of carbon nanotubes was fabricated in the same manner. A light source was assembled and tested. Low-voltage cathodoluminescent spectra and I-V characteristics of fabricated cathodes were measured. A possibility of application of Ce doped nanocrystalline YAG phosphor in the field emission displays (FEDs) was discussed.

  13. Terahertz emission from collapsing field domains during switching of a gallium arsenide bipolar transistor.

    PubMed

    Vainshtein, Sergey; Kostamovaara, Juha; Yuferev, Valentin; Knap, Wojciech; Fatimy, Abdel; Diakonova, Nina

    2007-10-26

    Broadband pulsed THz emission with peak power in the sub-mW range has been observed experimentally during avalanche switching in a gallium arsenide bipolar junction transistor at room temperature, while significantly higher total generated power is predicted in simulations. The emission is attributed to very fast oscillations in the conductivity current across the switching channels, which appear as a result of temporal evolution of the field domains generated in highly dense electron-hole plasma. This plasma is formed in turn by powerful impact ionization in multiple field domains of ultrahigh amplitude.

  14. Seeking optimal performance of multiwall carbon nanotubes in field emission: Tight-binding approach

    NASA Astrophysics Data System (ADS)

    Liang, Shi-Dong; Deng, Shao Zhi; Xu, Ning Sheng

    2006-10-01

    The field emission performance of different components of multiwall carbon nanotubes (MWCNs) is systematically studied by quantum tunneling theory with the tight-binding approach. We find that the current-voltage characteristic in field emission of MWCNs still approximately follows the Fowler-Nordheim theory. The key characteristics of all MWCNs are almost independent of the component and the layer number of MWCNs that have more three layers. The interlayer coupling of MWCNs can induce a semiconductor-metal phase transition, which leads to most MWCNs being actually metallic, and the chiral and quantum size effects disappear.

  15. Field emission in actuation pads of radio frequency microelectromechanical systems ohmic switches: A potential contamination mechanism

    NASA Astrophysics Data System (ADS)

    Koutsoureli, M.; Reig, B.; Papandreou, E.; Poulain, C.; Souchon, F.; Deborgies, F.; Papaioannou, G.

    2016-01-01

    The field emission current generated across the actuation pads in ohmic MEMS switches during ON state is shown to constitute an additional source of degradation. Switches with Au/Au and Au/Ru contacts have been subjected to 24 h continuous stress. In both cases the switch ohmic contact resistance and field emission current across actuation pads were monitored simultaneously. The experimental results revealed a negligible degradation in Au/Au contact devices while the Au/Ru contact devices show a fast degradation. The experimental results from Au/Au and Ru/Au contact switches have been compared taking into account the plasma generation in the actuation pads.

  16. Field emission characteristics of a graphite nanoneedle cathode and its application to scanning electron microscopy

    SciTech Connect

    Neo, Yoichiro; Mimura, Hidenori; Matsumoto, Takahiro

    2006-02-13

    A high-brightness electron beam of more than 10{sup 11} A sr{sup -1} m{sup -2} was achieved from a graphite nanoneedle cathode, which was fabricated by simple hydrogen plasma etching of a graphite rod. A field emission was obtained at a high residual pressure of 10{sup -6} Torr. The performance of this cold cathode was demonstrated by the fabrication of a scanning electron microscope, which was operated at a high residual pressure of 10{sup -5}-10{sup -6} Torr. The brightness of this cathode offers a convenient field electron emission source that does not require a massive ultrahigh vacuum system.

  17. Responses of nitrous oxide emissions and nitrate leaching to farm field management, climate, and soil characteristics: a meta-analysis

    NASA Astrophysics Data System (ADS)

    Heffernan, J. B.; Eagle, A.; Bernhardt, E. S.; Olander, L. P.

    2014-12-01

    Agriculture is a major source of both nitrous oxide (N2O) to the atmosphere and nitrate (NO3-) to surface and groundwaters, but synergies and tradeoffs between these nitrogen (N) loss pathways in response to agricultural practices are not well understood. We conducted a meta-analysis of both N2O emissions and NO3- leaching losses to quantify their individual responses to fertilization rate, tillage, and other practices. Overall, we assembled over 40 studies that reported fertilization rate, yield, and either N2O emissions or NO3- leaching losses over the growing season from North American corn fields. Our complete database ultimately included over 600 observations of N2O emissions or NO3- leaching. Notably, we found no individual studies that reported both NO3- leaching and N2O emissions. We used multiple regression to quantify the response of N loss pathways to fertilization rate; rotation crop and tillage practice; and climate and soil type. We also included yield as a predictor to better account for the magnitude of surplus N. We found insufficient data to address effects of fertilizer placement, timing and source. On a mass basis, NO3- losses were far greater than N2O emissions. Both NO3- leaching and N2O emissions exhibited positive relationships with fertilizer rate and surplus N, but the responses of N loss pathways to environmental conditions and to various management practices varied considerably. These results suggest that minimizing excess fertilizer application will both improve water quality and reduce greenhouse gas emissions, but that other practices such as tillage induce tradeoffs between these N loss pathways.

  18. Improving Heliospheric Field Models with Optimized Coronal Models

    NASA Astrophysics Data System (ADS)

    Jones, S. I.; Davila, J. M.; Uritsky, V. M.

    2015-12-01

    The Solar Orbiter and Solar Probe Plus missions will travel closer to the sun than any previous mission, collecting unprecedented in situ data. This data can provide insight into coronal structure, energy transport, and evolution in the inner heliosphere. However, in order to take full advantage of this data, researchers need quality models of the inner heliosphere to connect the in situ observations to their coronal and photospheric sources. Developing quality models for this region of space has proved difficult, in part because the only part of the field that is accessible for routine measurement is the photosphere. The photospheric field measurements, though somewhat problematic, are used as boundary conditions for coronal models, which often neglect or over-simplify chromospheric conditions, and these coronal models are then used as boundary conditions to drive heliospheric models. The result is a great deal of uncertainty about the accuracy and reliability of the heliospheric models. Here we present a technique we are developing for improving global coronal magnetic field models by optimizing the models to conform to the field morphology observed in coronal images. This agreement between the coronal model and the basic morphology of the corona is essential for creating accurate heliospheric models. We will present results of early tests of two implementations of this idea, and its first application to real-world data.

  19. Probing Emissions of Military Cargo Aircraft: Description of a Joint Field Measurement Program

    SciTech Connect

    Cheng, Mengdawn; Corporan, E.; DeWitt, M.; Spicer, C.; Holdren, M.; Cowen, K.; Harris, B.; Shores, R.; Hashmonay, R.; Kaganan, R.

    2008-01-01

    Direct emissions of NOx, volatile organic compounds, and particulate matter (PM) by aircraft contribute to the pollutant levels found in the atmosphere. Aircraft emissions can be injected at the ground level or directly at the high altitude in flight. Conversion of the precursor gases into secondary PM is one of the pathways for the increased atmospheric PM. Atmospheric PM interacts with solar radiation altering atmospheric radiation balance and potentially contributing to global and regional climate changes. Also, direct emissions of air toxics, ozone precursors and PM from aircraft in and around civilian airports and military air bases can worsen local air quality in non-attainment and/or maintenance areas. These emissions need to be quantified. However, the current EPA methods for particle emission measurements from such sources, modified Method 5 and Conditional Test Method 039, are gravimetric-based, and it is anticipated that these methods will not be suitable for current and future generations of aircraft turbine engines, whose particle mass emissions are low. To evaluate measurement approaches for military aircraft emissions, two complementary projects were initiated in 2005. A joint field campaign between these two programs was executed during the first week of October 2005 at the Kentucky Air National Guard (KYANG) base in Louisville, KY. This campaign represented the first in a series of field studies for each program funded by the DoD Strategic Environmental Research and Development Program (SERDP) and provided the basis for cross-comparison of the sampling approaches and measurement techniques employed by the respective program teams. This paper describes the overall programmatic of the multi-year SERDP aircraft emissions research and presents a summary of the results from the joint field campaign.

  20. ( RTP, NC ) IMPROVING EMISSION INVENTORIES FOR EFFECTIVE AIR-QUALITY MANAGEMENT ACROSS NORTH AMERICA - A NARSTO ASSESSMENT

    EPA Science Inventory

    The NARSTO Ozone and Particulate Matter Assessments emphasized that emission inventories are critical to the success of air quality management programs and that emissions inventories in Canada, Mexico, and the United States need improvement to meet expectations for quality, timel...

  1. (NEW YORK) IMPROVING EMISSION INVENTORIES FOR EFFECTIVE AIR-QUALITY MANAGEMENT ACROSS NORTH AMERICA - A NARSTO ASSESSMENT

    EPA Science Inventory

    The NARSTO Ozone and Particulate Matter Assessments emphasized that emission inventories are critical to the success of air quality management programs and that emissions inventories in Canada, Mexico, and the United States need improvement to meet expectations for quality, timel...

  2. Improved capacitive stress transducers for high-field superconducting magnets

    NASA Astrophysics Data System (ADS)

    Benson, Christopher Pete; Holik, Eddie Frank, III; Jaisle, Andrew; McInturff, A.; McIntyre, P.

    2012-06-01

    High-field (12-18 Tesla) superconducting magnets are required to enable an increase in the energy of future colliders. Such field strength requires the use of Nb3Sn superconductor, which has limited tolerance for compressive and shear strain. A strategy for stress management has been developed at Texas A&M University and is being implemented in TAMU3, a short-model 14 Tesla stress-managed Nb3Sn block dipole. The strategy includes the use of laminar capacitive stress transducers to monitor the stresses within the coil package. We have developed fabrication techniques and fixtures, which improve the reproducibility of the transducer response both at room temperature and during cryogenic operation. This is a report of the status of transducer development.

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

    PubMed

    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. PMID:24955418

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

    PubMed Central

    Xu, Shengjun; Fu, Xiaoqing; Ma, Shuanglong; 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. PMID:24955418

  5. Improved Gravitation Field Algorithm and Its Application in Hierarchical Clustering

    PubMed Central

    Zheng, Ming; Sun, Ying; Liu, Gui-xia; Zhou, You; Zhou, Chun-guang

    2012-01-01

    Background Gravitation field algorithm (GFA) is a new optimization algorithm which is based on an imitation of natural phenomena. GFA can do well both for searching global minimum and multi-minima in computational biology. But GFA needs to be improved for increasing efficiency, and modified for applying to some discrete data problems in system biology. Method An improved GFA called IGFA was proposed in this paper. Two parts were improved in IGFA. The first one is the rule of random division, which is a reasonable strategy and makes running time shorter. The other one is rotation factor, which can improve the accuracy of IGFA. And to apply IGFA to the hierarchical clustering, the initial part and the movement operator were modified. Results Two kinds of experiments were used to test IGFA. And IGFA was applied to hierarchical clustering. The global minimum experiment was used with IGFA, GFA, GA (genetic algorithm) and SA (simulated annealing). Multi-minima experiment was used with IGFA and GFA. The two experiments results were compared with each other and proved the efficiency of IGFA. IGFA is better than GFA both in accuracy and running time. For the hierarchical clustering, IGFA is used to optimize the smallest distance of genes pairs, and the results were compared with GA and SA, singular-linkage clustering, UPGMA. The efficiency of IGFA is proved. PMID:23173043

  6. Scaling law for direct current field emission-driven microscale gas breakdown

    SciTech Connect

    Venkattraman, A.; Alexeenko, A. A.

    2012-12-15

    The effects of field emission on direct current breakdown in microscale gaps filled with an ambient neutral gas are studied numerically and analytically. Fundamental numerical experiments using the particle-in-cell/Monte Carlo collisions method are used to systematically quantify microscale ionization and space-charge enhancement of field emission. The numerical experiments are then used to validate a scaling law for the modified Paschen curve that bridges field emission-driven breakdown with the macroscale Paschen law. Analytical expressions are derived for the increase in cathode electric field, total steady state current density, and the ion-enhancement coefficient including a new breakdown criterion. It also includes the effect of all key parameters such as pressure, operating gas, and field-enhancement factor providing a better predictive capability than existing microscale breakdown models. The field-enhancement factor is shown to be the most sensitive parameter with its increase leading to a significant drop in the threshold breakdown electric field and also to a gradual merging with the Paschen law. The proposed scaling law is also shown to agree well with two independent sets of experimental data for microscale breakdown in air. The ability to accurately describe not just the breakdown voltage but the entire pre-breakdown process for given operating conditions makes the proposed model a suitable candidate for the design and analysis of electrostatic microscale devices.

  7. Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets and Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Hartmann, D. H.; Hardee, P.; Hededal, C.; Mizunno, Y.; Fishman, G. J.

    2006-01-01

    We performed numerical simulations of particle acceleration, magnetic field generation, and emission from shocks in order to understand the observed emission from relativistic jets and supernova remnants. The investigation involves the study of collisionless shocks, where the Weibel instability is responsible for particle acceleration as well as magnetic field generation. A 3-D relativistic particle-in-cell (RPIC) code has been used to investigate the shock processes in electron-positron plasmas. The evolution of theWeibe1 instability and its associated magnetic field generation and particle acceleration are studied with two different jet velocities (0 = 2,5 - slow, fast) corresponding to either outflows in supernova remnants or relativistic jets, such as those found in AGNs and microquasars. Slow jets have intrinsically different structures in both the generated magnetic fields and the accelerated particle spectrum. In particular, the jet head has a very weak magnetic field and the ambient electrons are strongly accelerated and dragged by the jet particles. The simulation results exhibit jitter radiation from inhomogeneous magnetic fields, generated by the Weibel instability, which has different spectral properties than standard synchrotron emission in a homogeneous magnetic field.

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

    NASA Astrophysics Data System (ADS)

    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

  9. Modeling and computation of mean field equilibria in producers' game with emission permits trading

    NASA Astrophysics Data System (ADS)

    Zhang, Shuhua; Wang, Xinyu; Shanain, Aleksandr

    2016-08-01

    In this paper, we present a mean field game to model the production behaviors of a very large number of producers, whose carbon emissions are regulated by government. Especially, an emission permits trading scheme is considered in our model, in which each enterprise can trade its own permits flexibly. By means of the mean field equilibrium, we obtain a Hamilton-Jacobi-Bellman (HJB) equation coupled with a Kolmogorov equation, which are satisfied by the adjoint state and the density of producers (agents), respectively. Then, we propose a so-called fitted finite volume method to solve the HJB equation and the Kolmogorov equation. The efficiency and the usefulness of this method are illustrated by the numerical experiments. Under different conditions, the equilibrium states as well as the effects of the emission permits price are examined, which demonstrates that the emission permits trading scheme influences the producers' behaviors, that is, more populations would like to choose a lower rather than a higher emission level when the emission permits are expensive.

  10. The oxidized porous silicon vacuum microtriode: A revolutionary new type of field emission array

    SciTech Connect

    Smith, D.D.; Demroff, H.P.; Elliott, T.S.; Faber, J.S.; Lee, B.; Mazumdar, T.; McIntyre, P.M.; Trost, H.J.; Pang, Y.

    1997-08-01

    Yue began studying porous silicon-based vacuum microelectronic devices i n1990. Results from a device he dubbed the Oxidized Porous Silicon Field Emission Diode (OPSFED) showed that porous silicon (PS) offered an attractive alternative to standard field emission devices. Emission sites are reduced to near-atomic dimensions and site density is increased by six orders of magnitude. Yue, and later Madduri extracted electrons into the vacuum in a diode configuration, but no attempt to build a triode device had ever been successful. Using a novel metallization technique developed by Dr. R.C. Jaklevic et al. for use in STM imaging, the authors have successfully fabricated the first working PS-based vacuum microtriodes. Results are extremely encouraging. Collector currents up to 700 {micro}A were extracted across {approximately}3mm of vacuum with a pulsed DC gate bias of less than 20V. Simultaneous measurement of the gate current showed current densities to 700A/cm{sup 2}. Modulation of the emission to 5MH: was observed. Fowler-Nordheim plots show a slight curvature, as would be expected from extremely sharp emission tips, although it is stressed that the electroemissive mechanism is as yet unknown. Fowler-Nordheim plots for OPSFED`s made from the same material show an opposite curvature as predicted for emission from a large number of sites. Density of emitters approach a true two-dimensional limit, and many applications exist if the technology can be matured.

  11. Observations of improved confinement in field reversed configurations sustained by antisymmetric rotating magnetic fields

    SciTech Connect

    Guo, H.Y.; Hoffman, A.L.; Steinhauer, L.C.

    2005-06-15

    Rotating magnetic fields (RMF) have been employed to both form and sustain currents in field reversed configurations (FRC). A major concern about this method has been the fear of opening up magnetic field lines with even small ratios of vacuum RMF B{sub {omega}} to external confinement field B{sub e}. A recently proposed innovation was to use an antisymmetric arrangement of RMF, but vacuum calculations with full RMF penetration showed that very low values of B{sub {omega}}/B{sub e} would still be required to provide field-line closure. Recent comparisons of symmetric and antisymmetric RMF drive on the translation, confinement, and sustainment (TCS) facility [A. L. Hoffman, H. Y. Guo, J. T. Slough et al., Fusion Sci. Technol. 41, 92 (2002)] have shown strong improvements in the basic confinement properties of the FRCs when using antisymmetric drive, even with ratios of B{sub {omega}}/B{sub e} as high as 0.3. This is due to normal standard operation with only partial penetration of the RMF beyond the FRC separatrix. The uniform transverse RMF in vacuum is shielded by the conducting plasma, resulting in a mostly azimuthal field near the FRC separatrix with a very small radial component. Simple numerical calculations using analytical solutions for the partially penetrated antisymmetric RMF, superimposed on Grad-Shafranov solutions for the poloidal FRC fields, show good field-line closure for the TCS experimental conditions. The antisymmetric arrangement also leads to more efficient current drive and improved stabilization of rotational modes.

  12. Nitrous oxide emissions following incorporation of improved-fallow residues in the humid tropics

    NASA Astrophysics Data System (ADS)

    Millar, N.; Ndufa, J. K.; Cadisch, G.; Baggs, E. M.

    2004-03-01

    The rotation of crops with fast-growing tree, shrub, and herbaceous N2-fixing legume species (improved fallows) is a central agroforestry technology for soil fertility management in the humid tropics. Maize yields are increased following improved fallows compared with continuous maize cropping or traditional natural-fallow systems consisting of broadleaved weeds and grasses. However, the effect of these improved-fallow systems on N availability and N2O emissions following residue application has yet to be determined. Emissions from these systems not only have a detrimental effect on the environment, but are of additional concern in that they represent a potentially significant loss of N and a reduction in N-use efficiency. Emissions of N2O were measured from improved-fallow agroforestry systems in western Kenya, being characteristic of agroforestry systems in the humid tropics. Emissions were increased after incorporation of fallow residues and were higher after incorporation of improved-fallow legume residues (Sesbania sesban, Crotalaria grahamiana, Macroptilium atropurpureum) than natural-fallow residues (mainly consisting of Digitaria abyssibica, Habiscus cannabinus, Bidens pilosa, Guizotia scabra, Leonotis nepetifolia, Commelina benghalensis). Following incorporation of Sesbania and Macroptilium residues (7.4 t dry matter ha-1; 2.9% N) in a mixed fallow system, 4.1 kg N2O-N ha-1 was emitted over 84 days. The percentages of N applied emitted as N2O following residue incorporation in these tropical agroforestry systems were of the same magnitude as in temperate agricultural systems. N2O (loge) emissions were positively correlated with residue N content (r = 0.93; P < 0.05), and thus the residue composition, particularly its N content, is an important consideration when proposing management practices to mitigate N2O emissions from these systems.

  13. On the problems of stability and durability of field-emission current sources for electrovacuum devices

    NASA Astrophysics Data System (ADS)

    Yakunin, Alexander N.; Aban'shin, Nikolay P.; Akchurin, Garif G.; Akchurin, Georgy G.; Avetisyan, Yuri A.

    2016-03-01

    The results of the practical implementation of the concept of field-emission current source with high average current density of 0.1-0.3 A-cm-2 are shown. The durability of cathode samples at a level of 6000 hours is achieved under conditions of technical vacuum. A phenomenological model is suggested that describes the tunneling of both equilibrium and nonequilibrium electrons in a vacuum from the zone of concentration of electrostatic field. Conditions are discussed as the resulting increase in the emission current due to the connection mechanism of the photoelectric effect is thermodynamically favorable, that is not accompanied by an undesirable increase in the temperature of the local emission zone. It is shown that to ensure stability and durability of the cathode is also important to limit the concentration of equilibrium carriers using composite structures «DLC film on Mo substrate." This helps to reduce the criticality of the CVC. A possible alternative is to use a restrictive resistance in the cathode. However, this increases the heat losses and thus decreases assembly efficiency. The results of experimental studies of the structure showing the saturation of photoemission current component with an increase in operating voltage. This fact suggests the existence of an effective mechanism for control of emission at constant operating voltage. This is fundamentally important for the stabilization of field emission cathode, providing a reliability and durability. The single-photon processes and the small thickness DLC films (15-20 nm) provide high-speed process of control.

  14. Emissions of 1,3-Dichloropropene and Chloropicrin after Soil Fumigation under Field Conditions.

    PubMed

    Yates, Scott R; Ashworth, Daniel J; Zheng, Wei; Zhang, Qiaoping; Knuteson, James; van Wessenbeeck, Ian J

    2015-06-10

    Soil fumigation is an important agronomic practice in the production of many high-value vegetable and fruit crops, but the use of chemical fumigants can lead to excessive atmospheric emissions. A large-scale (2.9 ha) field experiment was conducted to obtain volatilization and cumulative emission rates for two commonly used soil fumigants under typical agronomic practices: 1,3-dichloropropene (1,3-D) and chloropicrin. The aerodynamic method and the indirect back-calculation method using ISCST3 and CALPUFF dispersion models were used to estimate flux loss from the treated field. Over the course of the experiment, the daily peak volatilization rates ranged from 12 to 30 μg m(-2) s(-1) for 1,3-D and from 0.7 to 2.6 μg m(-2) s(-1) for chloropicrin. Depending on the method used for quantification, total emissions of 1,3-D and chloropicrin, respectively, ranged from 16 to 35% and from 0.3 to 1.3% of the applied fumigant. A soil incubation study showed that the low volatilization rates measured for chloropicrin were due to particularly high soil degradation rates observed at this field site. Understanding and quantifying fumigant emissions from agricultural soil will help in developing best management practices to reduce emission losses, reducing adverse impacts to human and ecosystem health, and providing inputs for conducting risk assessments.

  15. Green house gas emissions from open field burning of agricultural residues in India.

    PubMed

    Murali, S; Shrivastava, Rajnish; Saxena, Mohini

    2010-10-01

    In India, about 435.98 MMT of agro-residues are produced every year, out of which 313.62 MMT are surplus. These residues are either partially utilized or un-utilised due to various constraints. To pave the way for subsequent season for agriculture activity, the excess crop residues are burnt openly in the fields, unmindful of their ill effects on the environment. The present study has been undertaken to evaluate the severity of air pollution through emission of green house gases (GHGs) due to open field burning of agro-residues in India. Open field burning of surplus agro-residues in India results in the emission of GHG. Emissions of CH4 and N2O in 1997-98 and 2006-07 have been 3.73 and 4.06 MMT CO2 equivalent, which is an increase of 8.88% over a decade. About three-fourths of GHG emissions from agro-residues burning were CH4 and the remaining one-fourth were N2O. Burning of wheat and paddy straws alone contributes to about 42% of GHGs. These GHG emissions can be avoided once the agro-residues are employed for sustainable, cost-effective and environment- friendly options like power generation.

  16. Enhanced field emission from ZnO nanowires grown on a silicon nanoporous pillar array

    NASA Astrophysics Data System (ADS)

    Xu, Hai Jun; Chan, Yu Fei; Su, Lei; Li, De Yao; Sun, Xiao Ming

    2010-12-01

    A large scale heterostructure array of ZnO nanowires/silicon nanoporous pillar array (Si-NPA) was prepared by a self-catalytic thermal evaporation and vapor-phase transport method, and an ultrahigh field emission current density of 1.55 mA cm-2 was obtained under an operating electric field of 4.0 V μm-1, with a low turn-on field of 1.65 V μm-1. The enhancement factor calculated according to the Fowler-Nordheim theory was ˜3141. The excellent field emission performance was attributed to the unique structure of ZnO/Si-NPA, especially the formation of ZnO nanowires on regular Si pillar array. Our work indicated that ZnO/Si-NPA might be an ideal candidate cathode of potential applications in flat panel displays and high brightness electron sources.

  17. Multiscale model of heat dissipation mechanisms during field emission from carbon nanotube fibers

    NASA Astrophysics Data System (ADS)

    Cahay, M.; Zhu, W.; Fairchild, S.; Murray, P. T.; Back, T. C.; Gruen, G. J.

    2016-01-01

    A multiscale model of field emission (FE) from carbon nanotube fibers (CNFs) is developed, which takes into account Joule heating within the fiber and radiative cooling and the Nottingham effect at the tip of the individual carbon nanotubes (CNTs) in the array located at the fiber tip. The model predicts the fraction of CNTs being destroyed as a function of the applied external electric field and reproduces many experimental features observed in some recently investigated CNFs, such as order of magnitude of the emission current (mA range), low turn on electric field (fraction of V/μm), deviation from pure Fowler-Nordheim behavior at large applied electric field, hysteresis of the FE characteristics, and a spatial variation of the temperature along the CNF axis with a maximum close to its tip of a few hundred °C.

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

    SciTech Connect

    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.

  19. Investigation of an electron string ion source with field emission cathode.

    PubMed

    Becker, R; Currell, F J; Donets, E D; Donets, E E; Kester, O; Quint, W; Ptitsin, V E

    2008-02-01

    The string mode of operation for an electron beam ion source uses axially oscillating electrons in order to reduce power consumption, also simplifying the construction by omitting the collector with cooling requirements and has been called electron string ion source (ESIS). We have started a project (supported by INTAS and GSI) to use Schottky field emitting cathode tips for generating the electron string. The emission from these specially conditioned tips is higher by orders of magnitude than the focused Brillouin current density at magnetic fields of some Tesla and electron energies of some keV. This may avoid the observed instabilities in the transition from axially oscillating electrons to the string state of the electron plasma, opening a much wider field of possible operating parameters for an ESIS. Besides the presentation of the basic features, we emphasize in this paper a method to avoid damaging of the field emission tip by backstreaming ions.

  20. Enhanced field emission of vertically aligned core-shelled carbon nanotubes with molybdenum oxide encapsulation

    SciTech Connect

    Yu, J.; Chua, Daniel H. C.; Sow, C. H.; Wee, Andrew T. S.

    2009-06-01

    The field emission characteristics of the core-shelled nanostructures obtained by directly coating molybdenum oxide onto vertically aligned multiwalled carbon nanotubes (MWNTs) was investigated. A metal-organic chemical vapor deposition technique was used with Mo(CO){sub 6} as the precursor and films deposited at process temperatures of 200, 400, and 700 deg. C. X-ray photoelectron spectroscopy, scanning electron microscopy, and x-ray diffraction were used to study and understand the material properties of the deposited coatings. Enhanced field emission performance was observed for molybdenum oxide coated MWNT samples at 400 deg. C with a turn-on field of 1.33 V mum{sup -1} and a field enhancement factor beta estimated to be approx7000. The enhanced performance may be due to both the shape of the coated emitters and a decrease in the effective barrier height.

  1. Improved determination of volcanic SO2 emission rates from SO2 camera images

    NASA Astrophysics Data System (ADS)

    Klein, Angelika; Lübcke, Peter; Bobrowski, Nicole; Platt, Ulrich

    2015-04-01

    SO2 cameras determine the SO2 emissions of volcanoes with a high temporal and spatial resolution. They thus visualize the plume morphology and give information about turbulence and plume dispersion. Moreover, from SO2 camera image series emission rates can be determined with high time resolution (as will be explained below), these data can help to improve our understanding of variations in the degassing regime of volcanoes. The first step to obtain emission rates is to integrate the column amount of SO2 along two different plume cross sections (ideally perpendicular to the direction of plume propagation); combined with wind speed information this allows the determination of SO2 fluxes. A popular method to determine the mean wind speed relies on estimating the time lag of the SO2 signal derived for two cross sections of the plume at different distances downwind of the source. This can be done by searching the maximum cross-correlation coefficient of the two signals. Another, more sophisticated method to obtain the wind speed is to use the optical flow technique to obtain a more detailed wind field in the plume from a series of SO2 camera images. While the cross correlation method only gives the mean wind speed between the two cross sections of the plume, the optical flow technique allows to determine the wind speed and direction for each pixel individually (in other words, a two-dimensional projection of the entire wind field in the plume is obtained). While optical flow algorithms in general give a more detailed information about the wind velocities in the volcanic plume, they may fail to determine wind speeds in homogeneous regions (i.e. regions with no spatial variation in SO2 column densities) of the plume. Usually the wind speed is automatically set to zero in those regions, which leads to an underestimation of the total SO2 emission flux. This behavior was observed more than once on a data set of SO2 camera images taken at Etna, Italy in July, 2014. For those

  2. Investigations for Heavy Metals and POPs Emission Inventory Improvement in Belarus

    NASA Astrophysics Data System (ADS)

    Kakareka, S.; Kukharchyk, T.

    2003-04-01

    polychlorinated biphenyls (PCBs) discharge into the environment; dielectric fluids with PCBs are still in use in electrical equipment. Ways forward towards uncertainty reduction were outlined: they include adoption of new reporting forms for enterprises, preparation of guidelines for heavy metals and POPs inventory at regional levels, emission factors improvement with source testing, inventory of small combustion units, improvement of wastes combustion inventory, inventory of PCB in equipment, assessment of uncontrolled burning processes, evaluation of rezervoirs and sinks detection, and in perspective - integrated inventory (considering also emissions into water, wastes and products).

  3. Finite field of view effects on inversion of limb thermal emission observations. [balloon sounding of stratosphere

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Guo, J.; Conrath, B. J.; Kunde, V. G.; Maguire, W. C.

    1985-01-01

    It is pointed out that the technique of thermal emission spectroscopy provides an effective means for remote sounding of stratospheric temperature structure and constituent distributions. One procedure for measuring the stratospheric infrared spectrum involves the conduction of observations along ray paths tangent to the stratospheric limb. Thermal emission limb tangent observations have certain advantages compared to other types of observations. The techniques for determining temperature and trace gas distributions from limb thermal emission radiances are based on the assumption that the bulk of opacity lies near the tangent point. Ideally, the field of view (FOV) of the observing instrument should be very small. The effect of a finite FOV is to reduce the spatial resolution of the retrieved temperature and constituent profiles. The present investigation is concerned with the effects of the FOV on the inversion of infrared thermal emission measurements for balloon platforms. Attention is given to a convenient method for determining the weighting functions.

  4. Observation of enhanced field emission properties of Au/TiO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Patil, Girish P.; Bagal, Vivekanand S.; Suryawanshi, Sachin R.; Late, Dattatray J.; More, Mahendra A.; Chavan, Padmakar G.

    2016-05-01

    Simple and low-cost method of thermal annealing was used to decorate Gold (Au) nanoparticles on aligned TiO2 nanotubes. The aligned TiO2 nanotubes were decorated by Au nanoparticles with an average diameter of 9, 18 and 28 nm (aligned TiO2 nanotubes referred as specimen A and TiO2 nanotubes decorated by Au nanoparticles with average diameter of 9, 18 and 28 nm are referred as specimen B, C and D, respectively). The detailed characterization such as structural, morphological and elemental analysis of TiO2 and Au/TiO2 nanocomposite have been carried out using X-ray diffraction, field emission scanning electron microscope, transmission electron microscope, X-ray photoelectron spectroscopy and Raman spectroscopy. Furthermore, the meticulous comparative field emission characteristics of the aligned TiO2 nanotubes and Au/TiO2 nanocomposite have been performed. The turn-on field defined for the current density of 10 μA/cm2 has been found to be 3.9, 2.8, 3.2 and 3.7 V/μm for specimen A, B, C and D, respectively. The observed low turn-on field of specimen B has been found to be superior than the other semiconducting nanocomposites reported in the literature. The emission current stability over a period of 3 h is found to be better for all the specimens. To the best of our knowledge, a systematic field emission study of Au/TiO2 nanocomposite has not been explored. The observed superior field emission study of Au/TiO2 nanocomposite indicates their possible use in micro/nanoelectronic devices.

  5. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers.

    PubMed

    Schellart, P; Trinh, T N G; Buitink, S; Corstanje, A; Enriquez, J E; Falcke, H; Hörandel, J R; Nelles, A; Rachen, J P; Rossetto, L; Scholten, O; Ter Veen, S; Thoudam, S; Ebert, U; Koehn, C; Rutjes, C; Alexov, A; Anderson, J M; Avruch, I M; Bentum, M J; Bernardi, G; Best, P; Bonafede, A; Breitling, F; Broderick, J W; Brüggen, M; Butcher, H R; Ciardi, B; de Geus, E; de Vos, M; Duscha, S; Eislöffel, J; Fallows, R A; Frieswijk, W; Garrett, M A; Grießmeier, J; Gunst, A W; Heald, G; Hessels, J W T; Hoeft, M; Holties, H A; Juette, E; Kondratiev, V I; Kuniyoshi, M; Kuper, G; Mann, G; McFadden, R; McKay-Bukowski, D; McKean, J P; Mevius, M; Moldon, J; Norden, M J; Orru, E; Paas, H; Pandey-Pommier, M; Pizzo, R; Polatidis, A G; Reich, W; Röttgering, H; Scaife, A M M; Schwarz, D J; Serylak, M; Smirnov, O; Steinmetz, M; Swinbank, J; Tagger, M; Tasse, C; Toribio, M C; van Weeren, R J; Vermeulen, R; Vocks, C; Wise, M W; Wucknitz, O; Zarka, P

    2015-04-24

    We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields.

  6. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers.

    PubMed

    Schellart, P; Trinh, T N G; Buitink, S; Corstanje, A; Enriquez, J E; Falcke, H; Hörandel, J R; Nelles, A; Rachen, J P; Rossetto, L; Scholten, O; Ter Veen, S; Thoudam, S; Ebert, U; Koehn, C; Rutjes, C; Alexov, A; Anderson, J M; Avruch, I M; Bentum, M J; Bernardi, G; Best, P; Bonafede, A; Breitling, F; Broderick, J W; Brüggen, M; Butcher, H R; Ciardi, B; de Geus, E; de Vos, M; Duscha, S; Eislöffel, J; Fallows, R A; Frieswijk, W; Garrett, M A; Grießmeier, J; Gunst, A W; Heald, G; Hessels, J W T; Hoeft, M; Holties, H A; Juette, E; Kondratiev, V I; Kuniyoshi, M; Kuper, G; Mann, G; McFadden, R; McKay-Bukowski, D; McKean, J P; Mevius, M; Moldon, J; Norden, M J; Orru, E; Paas, H; Pandey-Pommier, M; Pizzo, R; Polatidis, A G; Reich, W; Röttgering, H; Scaife, A M M; Schwarz, D J; Serylak, M; Smirnov, O; Steinmetz, M; Swinbank, J; Tagger, M; Tasse, C; Toribio, M C; van Weeren, R J; Vermeulen, R; Vocks, C; Wise, M W; Wucknitz, O; Zarka, P

    2015-04-24

    We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields. PMID:25955053

  7. Scalarized photon analysis of spontaneous emission in the uniform magnetic field free-electron laser

    NASA Astrophysics Data System (ADS)

    Soln, Josip

    1990-04-01

    The recently developed concept of scalarized photons (formally photons of any polarization) is used to analyze the spontaneous emission in the uniform magnetic field free-electron laser in the microwave spectral region. With the electron beam energy of up to 10 MeV and the uniform magnetic field of up to 4 Tesla, the radiation (occurring with the fundamental and higher harmonic frequencies) can easily cover a 10- to 10,000 GHz spectral region.

  8. Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS_{2}.

    PubMed

    Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados Del Águila, Andrés; Ballottin, Mariana V; Christianen, Peter C M; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf

    2016-08-12

    We control the linear polarization of emission from the coherently emitting K^{+} and K^{-} valleys (valley coherence) in monolayer WS_{2} with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τ_{c}=260  fs. PMID:27563997

  9. Tip-geometry enhanced cooling of field emission from the n-type semiconductor

    SciTech Connect

    Chung, M. S. Choi, J. Y.; Mayer, A.; Miskovsky, N. M.; Cutler, P. H.

    2014-02-24

    The cooling effect of field emission from an n-type semiconductor was theoretically investigated in quest for a solid state cooler. The vacuum potential was exactly expressed in terms of the semiconductor cathode geometry. This leaded to the more accurate configuration-dependent calculations of the energy exchange and the cooling power. It has been shown that a sharper tip of semiconductor can yield either a larger field emission current density or a larger energy exchange, according to the applied bias. For an atomic size tip, the n-Si cathode yielded the cooling power density Γ = 2.0, 75, and 713 W/cm{sup 2} at temperature T = 300, 600, and 900 K, respectively. This implies that an optimized configuration of an n-Si cathode produces a significant electron emission cooling, especially at high temperatures.

  10. Electron field emission from TiO2 nanotube arrays synthesized by hydrothermal reaction

    NASA Astrophysics Data System (ADS)

    Miyauchi, Masahiro; Tokudome, Hiromasa; Toda, Yoshitake; Kamiya, Toshio; Hosono, Hideo

    2006-07-01

    Conductive TiO2 nanotube arrays were grown on metal Ti substrates by hydrothermal reaction and subsequent postannealing in vacuum. The nanotubes were vertically grown and adhered well to the substrates. The crystal structure of the postannealed TiO2 nanotubes was identified to be oxygen-defective anatase. The nanotube arrays exhibited efficient electron field emission even at room temperature with rather low turn-on fields ˜280V per electrode distance of 100μm. The emission current density exceeded 0.15mA /cm2 at an extraction voltage of 800V. The emission current was reproducible and stable in the lower voltage (<800V) region.

  11. GAMMA-RAY BURST PROMPT EMISSION: JITTER RADIATION IN STOCHASTIC MAGNETIC FIELD REVISITED

    SciTech Connect

    Mao, Jirong; Wang Jiancheng

    2011-04-10

    We revisit the radiation mechanism of relativistic electrons in the stochastic magnetic field and apply it to the high-energy emissions of gamma-ray bursts (GRBs). We confirm that jitter radiation is a possible explanation for GRB prompt emission in the condition of a large electron deflection angle. In the turbulent scenario, the radiative spectral property of GRB prompt emission is decided by the kinetic energy spectrum of turbulence. The intensity of the random and small-scale magnetic field is determined by the viscous scale of the turbulent eddy. The microphysical parameters {epsilon}{sub e} and {epsilon}{sub B} can be obtained. The acceleration and cooling timescales are estimated as well. Due to particle acceleration in magnetized filamentary turbulence, the maximum energy released from the relativistic electrons can reach a value of about 10{sup 14} eV. The GeV GRBs are possible sources of high-energy cosmic-ray.

  12. Temporal patterns of methane emissions from wetland rice fields treated by different modes of N application

    NASA Astrophysics Data System (ADS)

    Wassmann, R.; Neue, H. U.; Lantin, R. S.; Aduna, J. B.; Alberto, M. C. R.; Andales, M. J.; Tan, M. J.; van der Gon, H. A. C. Denier; Hoffmann, H.; Papen, H.; Rennenberg, H.; Seiler, W.

    1994-08-01

    Methane emission rates from wetland rice fields were determined in Los Baños (Philippines) using an automatic system that allows continuous measurements over time. Methane emission was monitored in an irrigated Aquandic Epiaqualf planted to rice cultivar IR72. Urea fertilizer was applied using four modes: (1) broadcast 10 days after transplanting, (2) broadcast at transplanting, (3) broadcast and incorporated at final harrowing, and (4) deep placement as sulfur-coated granules. The treatments were laid out in a randomized complete block design with four replicates. Measurements were done in the 1991 wet season, 1992 dry season (four treatments), and the 1992 wet season (only treatment 3). Methane emission rates from the experimental plots showed pronounced seasonal and diel variations. The diel pattern of methane emission rates followed a consistent pattern, with highest rates observed in the early afternoon and lowest rates in the early morning. Methane emission rate was generally highest at the ripening stage. The average methane emission rate during the 1992 dry season (190 mg CH4 m-2 d-1) exceeded the average flux rates of the 1992 wet season (79 mg CH4 m-2 d-1) by a factor of 2.4. The total methane emitted from these flooded rice fields amounted to 19 g CH4 m-2 in the dry season with rice yields of 5.2-6.3 t ha-1 and 7 g CH4 m-2 in the wet season with rice yields of 2.4-3.3 t ha-1 regardless of the mode of N application. Significant amounts corresponding to 20% of the methane released under waterlogged conditions were released when the soil was drained after harvest. Emission rates increased sharply when the floodwater receded and macropores started to drain. Emission of methane stopped only when the soil became fully aerated.

  13. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    NASA Astrophysics Data System (ADS)

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-02-01

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm2 at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O2) plasma for 5 min and again field emission characteristics were measured. The O2 plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm2 at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O2 plasma treatment and the findings are being reported in this paper.

  14. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    SciTech Connect

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-02-28

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

  15. Effect of annealing in hydrogen atmosphere on ZnO films for field emission display

    NASA Astrophysics Data System (ADS)

    Zulkifli, Zurita; Sharma, Subash; Shinde, Sachin; Kalita, Golap; Tanemura, M.

    2015-11-01

    Surface morphology, crystallinity, conductivity and optical transmittance of ZnO films can be modified by annealing process. Hydrogen is one of the popular annealing gases as well as nitrogen, argon, oxygen and air which are commonly used for thin film cleaning or the removal of native oxide. In general, annealing is done at high temperatures (> 600degC) to improve the film properties. From a view point of environment, however, lower annealing temperature is preferable. In this work, low annealing process was challenged to understand the effect of annealing temperature on properties of ZnO thin films and nanostructured film grown on glass substrates for transparent field emission device applications. The annealing temperature employed was 100, 200 and 450°C at 100 sccm hydrogen flow rate. ZnO thin films were deposited by RF magnetron sputtering. The ZnO thin films were characterized by X-ray diffraction analysis (XRD), Atomic Force Microscopy (AFM), UV-VIS and Raman spectroscopy. The sheet resistances reduced about 15 kohm/sq at low annealing temperature. By contrast, the optical transmittance did not show any significant changes after annealing. The FE current density increased after the ZnO nanostructures film was annealed in 100°C. The results obtained could motivate a surface treatment for flexible ZnO thin film since the substrate is always suffered by heat.

  16. Size dependence of silica nanospheres embedded in 385 nm ultraviolet light-emitting diodes on a far-field emission pattern.

    PubMed

    Park, Young Jae; Han, Nam; Ryu, Beo Deul; Han, Min; Ko, Kang Bok; Cuong, Tran Viet; Cho, Jaehee; Suh, Eun-Kyung; Hong, Chang-Hee

    2014-10-20

    We demonstrate that the use of silica nanospheres (SNs) with sizes close to the emission wavelength of light-emitting diodes (LEDs) can enhance the light output power and manipulate the far-field emission pattern. Near-ultraviolet (NUV)-LEDs grown on a patterned sapphire substrate embedded with 300 nm SNs show a three times higher light output power than that without SNs, when measured through the top side. For far-field emission measurements, the LEDs embedded with 300 nm SNs show the significant increase of front emission due to the improved crystal quality of epitaxial films as well as the increase of Mie scattering effect of SNs. These experimental results indicate the important role of the size of embedded SNs in enhancing the light output power for NUV-LEDs.

  17. Gap size dependent transition from direct tunneling to field emission in single molecule junctions.

    PubMed

    Xiang, Dong; Zhang, Yi; Pyatkov, Feliks; Offenhäusser, Andreas; Mayer, Dirk

    2011-04-28

    I/V characteristics recorded in mechanically controllable break junctions revealed that field emission transport is enhanced in single molecule junctions as the gap size between two nanoelectrodes is reduced. This observation indicates that Fowler-Nordheim tunneling occurs not only for intermolecular but also for intramolecular electron transport driven by a reduced energy barrier at short tunneling distances.

  18. Liquid jet target x-ray tube with field emission cathode

    NASA Astrophysics Data System (ADS)

    Heid, Oliver; Polikhov, Stepan; Karpinskiy, Gennadiy; Geisler, Andreas; Bondarenko, Taras; Botyachkova, Alexandra; Frolov, Sergey; Ivanov, Vladislav

    2015-08-01

    We introduce first results of our research in a promising approach for micro focal x-ray generation. The approach combines the use of liquid metal jet target as anode and carbon based nanostructures as field emission cathode. Results of metal jet break-up CFD simulation and cold cathode performance tests are described. The planned experimental program is discussed herein as well.

  19. Field emission behaviour of manganese oxide nanorods synthesized by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Bankar, P. K.; Gavhane, D. S.; Kolhe, P. S.; Warule, S. S.; More, M. A.

    2016-05-01

    A facile, low temperature and single step hydrothermal method has been used to fabricate well defined manganese oxide (MnO2) nanorods over Si substrate. The structural and morphological studies reveal the formation of crystalline MnO2 nanostructures. The diameter of the MnO2 nanorods is estimated to be ~100 nm, with length in several micrometers. Field-emission properties of the as-synthesized MnO2 nanorods are investigated. The turn on field required to draw emission of 0.1 µA/cm2 current was observed to be ~ 3.2 V/μm and threshold field (corresponding to emission current density of 1 µA/cm2) was found to be 5.1 V/μm. The emission current was observed to be stable for more than three hours at a preset value 1 µA. These results are helpful for the design, fabrication and optimization of integrated field emitters using 1D nanostructure as cold cathode material.

  20. Electromagnetic vacuum of complex media: Dipole emission versus light propagation, vacuum energy, and local field factors

    SciTech Connect

    Donaire, M.

    2011-02-15

    We offer a unified approach to several phenomena related to the electromagnetic vacuum of a complex medium made of point electric dipoles. To this aim, we apply the linear response theory to the computation of the polarization field propagator and study the spectrum of vacuum fluctuations. The physical distinction among the local density of states which enter the spectra of light propagation, total dipole emission, coherent emission, total vacuum energy, and Schwinger-bulk energy is made clear. Analytical expressions for the spectrum of dipole emission and for the vacuum energy are derived. Their respective relations with the spectrum of external light and with the Schwinger-bulk energy are found. The light spectrum and the Schwinger-bulk energy are determined by the Dyson propagator. The emission spectrum and the total vacuum energy are determined by the polarization propagator. An exact relationship of proportionality between both propagators is found in terms of local field factors. A study of the nature of stimulated emission from a single dipole is carried out. Regarding coherent emission, it contains two components. A direct one which is transferred radiatively and directly from the emitter into the medium and whose spectrum is that of external light. And an indirect one which is radiated by induced dipoles. The induction is mediated by one (and only one) local field factor. Regarding the vacuum energy, we find that in addition to the Schwinger-bulk energy the vacuum energy of an effective medium contains local field contributions proportional to the resonant frequency and to the spectral line width.

  1. Synthesis, characterization, growth mechanism, photoluminescence and field emission properties of novel dandelion-like gallium nitride

    NASA Astrophysics Data System (ADS)

    Nabi, Ghulam; Cao, Chuanbao; Khan, Waheed S.; Hussain, Sajad; Usman, Zahid; Safdar, Muhammad; Shah, Sajjad Hussain; Khattak, Noor Abass Din

    2011-09-01

    Dandelion-like gallium nitride (GaN) microstructures were successfully synthesized via Ni catalyst assisted chemical vapor deposition method at 1200 °C under NH3 atmosphere by pre-treating precursors with aqueous ammonia. The as-synthesized product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). X-ray diffraction analysis revealed that as-synthesized dandelion-like GaN was pure and has hexagonal wurtzite structure. SEM results showed that the size of the dandelion-like GaN structure was in the range of 30-60 μm. Dandelion-like GaN microstructures exhibited reasonable field emission properties with the turn-on field of 9.65 V μm-1 (0.01 mA cm-2) and threshold field of 11.35 V μm-1 (1 mA cm-2) which is sufficient for applications of electron emission devices, field emission displays and vacuum micro electronic devices. Optical properties were studied at room temperature by using fluorescence spectrophotometer. Photoluminescence (PL) measurements of dandelion-like GaN showed a strong near-band-edge emission at 370.2 nm (3.35 eV) with blue band emission at 450.4 nm (2.75 eV) and 465.2 nm (2.66 eV) but with out yellow band emission. The room-temperature photoluminescence properties showed that it has also potential application in light-emitting devices. The tentative growth mechanism for the growth of dandelion-like GaN was also described.

  2. Simulation of nitrous oxide emissions at field scale using the SPACSYS model

    PubMed Central

    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

  3. Simulation of nitrous oxide emissions at field scale using the SPACSYS model.

    PubMed

    Wu, L; Rees, R M; Tarsitano, D; Zhang, Xubo; Jones, S K; Whitmore, A P

    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 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

  4. Vertically aligned carbon nanotubes from natural precursors by spray pyrolysis method and their field electron emission properties

    NASA Astrophysics Data System (ADS)

    Ghosh, Pradip; Soga, T.; Tanemura, M.; Zamri, M.; Jimbo, T.; Katoh, R.; Sumiyama, K.

    2009-01-01

    Vertically aligned carbon nanotubes have been synthesized from botanical hydrocarbons: Turpentine oil and Eucalyptus oil on Si(100) substrate using Fe catalyst by simple spray pyrolysis method at 700°C and at atmospheric pressure. The as-grown carbon nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Raman spectroscopy. It was observed that nanotubes grown from turpentine oil have better degree of graphitization and field emission performance than eucalyptus oil grown carbon nanotubes. The turpentine oil and eucalyptus oil grown carbon nanotubes indicated that the turn-on field of about 1.7 and 1.93 V/μm, respectively, at 10 μA/cm2. The threshold field was observed to be about 2.13 and 2.9 V/μm at 1 mA/cm2 of nanotubes grown from turpentine oil and eucalyptus oil respectively. Moreover, turpentine oil grown carbon nanotubes show higher current density in relative to eucalyptus oil grown carbon nanotubes. The maximum current density of 15.3 mA/cm2 was obtained for ˜3 V/μm corresponding to the nanotubes grown from turpentine oil. The improved field emission performance was attributed to the enhanced crystallinity, fewer defects, and greater length of turpentine oil grown carbon nanotubes.

  5. Study of the Photospheric Magnetic Field and Coronal Emission from Solar Active Regions

    NASA Astrophysics Data System (ADS)

    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

  6. Improved Fossil/Industrial CO2 Emissions Modeling for the North American Carbon Program

    NASA Astrophysics Data System (ADS)

    Gurney, K. R.; Seib, B.; Mendoza, D.; Knox, S.; Fischer, M.; Murtishaw, S.

    2006-12-01

    The quantification of fossil fuel CO2 emissions has implications for a wide variety of scientific and policy- related questions. Improvement in inverse-estimated carbon fluxes, country-level carbon budgeting, analysis of regional emissions trading systems, and targeting of observational systems are all important applications better served by improvements in understanding where and when fossil fuel/industrial CO2 is emitted. Traditional approaches to quantifying fossil/industrial CO2 emissions have relied on national sales/consumption of fossil fuels with secondary spatial footprints performed via proxies such as population. This approach has provided global spatiotemporal resolution of one degree/monthly. In recent years the need has arisen for emission estimates that not only achieve higher spatiotemporal scales but include a process- level component. This latter attribute provides dynamic linkages between energy policy/decisionmaking and emissions for use in projecting changes to energy systems and the implications these changes may have on climate change. We have embarked on a NASA-funded research strategy to construct a process-level fossil/industrial CO2 emissions model/database for North America that will resolve fossil/industrial CO2 emissions hourly and at 36 km. This project is a critical component of the North American Carbon Program. Our approach builds off of many decades of air quality monitoring for regulated pollutants such as NOx, VOCs and CO that has been performed by regional air quality managers, states, and the Environmental Protection Agency in the United States. By using the highly resolved monitoring data supplied to the EPA, we have computed CO2 emissions for residential, commercial/industrial, transportation, and biogenic sources. This effort employs a new emissions modeling system (CONCEPT) that spatially and temporally distributes the monitored emissions across the US. We will provide a description of the methodology we have employed, the

  7. Improved Fossil/Industrial CO2 Emissions Modeling for the North American Carbon Program

    NASA Astrophysics Data System (ADS)

    Gurney, K. R.; Seib, B.; Mendoza, D.; Knox, S.; Fischer, M.; Murtishaw, S.

    2005-05-01

    The quantification of fossil fuel CO2 emissions has implications for a wide variety of scientific and policy- related questions. Improvement in inverse-estimated carbon fluxes, country-level carbon budgeting, analysis of regional emissions trading systems, and targeting of observational systems are all important applications better served by improvements in understanding where and when fossil fuel/industrial CO2 is emitted. Traditional approaches to quantifying fossil/industrial CO2 emissions have relied on national sales/consumption of fossil fuels with secondary spatial footprints performed via proxies such as population. This approach has provided global spatiotemporal resolution of one degree/monthly. In recent years the need has arisen for emission estimates that not only achieve higher spatiotemporal scales but include a process- level component. This latter attribute provides dynamic linkages between energy policy/decisionmaking and emissions for use in projecting changes to energy systems and the implications these changes may have on climate change. We have embarked on a NASA-funded research strategy to construct a process-level fossil/industrial CO2 emissions model/database for North America that will resolve fossil/industrial CO2 emissions hourly and at 36 km. This project is a critical component of the North American Carbon Program. Our approach builds off of many decades of air quality monitoring for regulated pollutants such as NOx, VOCs and CO that has been performed by regional air quality managers, states, and the Environmental Protection Agency in the United States. By using the highly resolved monitoring data supplied to the EPA, we have computed CO2 emissions for residential, commercial/industrial, transportation, and biogenic sources. This effort employs a new emissions modeling system (CONCEPT) that spatially and temporally distributes the monitored emissions across the US. We will provide a description of the methodology we have employed, the

  8. Improving a plot-scale methane emission model and its performance at a northeastern Siberian tundra site

    NASA Astrophysics Data System (ADS)

    Mi, Y.; van Huissteden, J.; Parmentier, F. J. W.; Gallagher, A.; Budishchev, A.; Berridge, C. T.; Dolman, A. J.

    2014-07-01

    In order to better address the feedbacks between climate and wetland methane (CH4) emissions, we tested several mechanistic improvements to the wetland CH4 emission model Peatland-VU with a longer Arctic data set than any other model: (1) inclusion of an improved hydrological module, (2) incorporation of a gross primary productivity (GPP) module, and (3) a more realistic soil-freezing scheme. A long time series of field measurements (2003-2010) from a tundra site in northeastern Siberia is used to validate the model, and the generalized likelihood uncertainty estimation (GLUE) methodology is used to test the sensitivity of model parameters. Peatland-VU is able to capture both the annual magnitude and seasonal variations of the CH4 flux, water table position, and soil thermal properties. However, detailed daily variations are difficult to evaluate due to data limitation. Improvements due to the inclusion of a GPP module are less than anticipated, although this component is likely to become more important at larger spatial scales because the module can accommodate the variations in vegetation traits better than at plot scale. Sensitivity experiments suggest that the methane production rate factor, the methane plant oxidation parameter, the reference temperature for temperature-dependent decomposition, and the methane plant transport rate factor are the most important parameters affecting the data fit, regardless of vegetation type. Both wet and dry vegetation cover are sensitive to the minimum water table level; the former is also sensitive to the runoff threshold and open water correction factor, and the latter to the subsurface water evaporation and evapotranspiration correction factors. These results shed light on model parameterization and future improvement of CH4 modelling. However, high spatial variability of CH4 emissions within similar vegetation/soil units and data quality prove to impose severe limits on model testing and improvement.

  9. Improving a plot-scale methane emission model and its performance at a Northeastern Siberian tundra site

    NASA Astrophysics Data System (ADS)

    Mi, Y.; van Huissteden, J.; Parmentier, F. J. W.; Gallagher, A.; Budishchev, A.; Berridge, C. T.; Dolman, A. J.

    2013-12-01

    In order to better address the feedbacks between climate and wetland methane (CH4) emissions, we tested several mechanistic improvements to the wetland CH4 emission model Peatland-VU with a longer Arctic dataset than any other model: (1) inclusion of an improved hydrological module; (2) incorporation of a gross primary productivity (GPP) module; (3) a more realistic soil-freezing scheme. A long time series of field measurements (2003-2010) from a tundra site in Northeastern Siberia is used to validate the model, and the Generalized Likelihood Uncertainty Estimation (GLUE) methodology is used to test the sensitivity of model parameters. Peatland-VU is able to capture both the annual magnitude and seasonal variations of the CH4 flux, water table position and soil thermal properties. However, detailed daily variations are difficult to evaluate due to data limitation. Improvements due to the inclusion of a GPP module are less than anticipated, although this component is likely to become more important at larger spatial scales because the module can accommodate the variations in vegetation traits better than at plot-scale. Sensitivity experiments suggest that the methane production rate factor, the methane plant oxidation parameter, the reference temperature for temperature dependent decomposition, and the methane plant transport rate factor are the most important parameters affecting the data fit, regardless of vegetation type. Both wet and dry vegetation cover are sensitive to the minimum water table level, in addition to the runoff threshold and open water correction factor and the subsurface water evaporation and evapotranspiration correction factors, respectively. These results shed light on model parameterization and future improvement of CH4 modelling. However, high spatial variability of CH4 emissions within similar vegetation/soil units and data quality prove to impose severe limits on model testing and improvement.

  10. Field enhancement factor and field emission from a hemi-ellipsoidal metallic needle.

    PubMed

    Pogorelov, Evgeny G; Zhbanov, Alexander I; Chang, Yia-Chung

    2009-03-01

    We present an exact solution for the electrostatic field between a metallic hemi-ellipsoidal needle on a plate (as a cathode) and a flat anode. The basic idea is to replace the cathode by a linearly charged thread in a uniform electric field and to use a set of "image" charges to reproduce the anode. We calculate the field enhancement factor on the needle surface and ponderomotive force acting on the needle. Using the Fowler-Nordheim theory we obtain an exact analytical formula for the total current. PMID:19232831

  11. Direct current scanning field emission microscope integrated with existing scanning electron microscope

    NASA Astrophysics Data System (ADS)

    Wang, Tong; Reece, Charles E.; Sundelin, Ronald M.

    2002-09-01

    Electron field emission (FE) from broad-area metal surfaces is known to occur at much lower electric field than predicted by Fowler-Nordheim law. Although micron or submicron particles are often observed at such enhanced field emission (EFE) sites, the strength and number of emitting sites and the causes of EFE strongly depend on surface preparation and handling, and the physical mechanism of EFE remains unknown. To systematically investigate the sources of this emission, a dc scanning field emission microscope (SFEM) has been built as an extension to an existing commercial scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer for emitter characterization. In the SFEM chamber of ultrahigh vacuum (approx10-9 Torr), a sample is moved laterally in a raster pattern (2.5 mum step resolution) under a high voltage anode microtip for field emission detection and localization. The sample is then transferred under vacuum by a hermetic retractable linear transporter to the SEM chamber for individual emitter site characterization. Artificial marks on the sample surface serve as references to convert x, y coordinates of emitters in the SFEM chamber to corresponding positions in the SEM chamber with a common accuracy of plus-or-minus100-200 mum in x and y. Samples designed to self-align in sample holders are used in each chamber, allowing them to retain position registration after non-in situ processing to track interesting features. No components are installed inside the SEM except the sample holder, which does not affect the routine operation of the SEM. The apparatus is a system of low cost and maintenance and significant operational flexibility. Field emission sources from planar niobium--the material used in high-field rf superconducting cavities for particle accelerator--have been studied after different surface preparations, and significantly reduced field emitter density has been achieved by refining the preparation process based on scan

  12. Photoluminescence and field emission of 1D ZnO nanorods fabricated by thermal evaporation

    NASA Astrophysics Data System (ADS)

    Wang, B.; Jin, X.; Ouyang, Z. B.; Xu, P.

    2012-07-01

    Four kinds of new one-dimensional nanostructures, celery-shaped nanorods, needle-shaped nanorods, twist fold-shaped nanorods, and awl-shaped nanorods of ZnO, have been grown on single silicon substrates by an Au catalyst assisted thermal evaporation of ZnO and active carbon powders. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). The photoluminescence spectra (PL) analysis noted that UV emission band is the band-to-band emission peak and the emission bands in the visible range are attributed to the oxygen vacancies, Zn interstitials, or impurities. The field-emission properties of four kinds of ZnO nanorods have been invested and the awl-shaped nanorods of ZnO have preferable characteristics due to the smallest emitter radius on the nanoscale in the tip in comparison with other nanorods. The growth mechanism of the ZnO nanorods can be explained on the basis of the vapor-liquid-solid (VLS) processes.

  13. Novel thin film field emission electron source laboratory directed research and development final report

    SciTech Connect

    Walko, R.J.; Fleming, J.G.; Hubbs, J.W.

    1997-04-01

    The objective of this project was to demonstrate proof of concept of a thin film field emission electron source based on electron tunneling between discrete metal islands on an insulating substrate. An electron source of this type should be more easily fabricated permitting the use of a wider range of materials, and be less prone to damage and erratic behavior than the patterned field emitter arrays currently under development for flat panel displays and other vacuum microelectronic applications. This report describes the results of the studies of electron and light emission from such structures, and the subsequent discovery of a source of light emission from conductive paths across thin insulating gaps of the semiconductor-insulator-semiconductor (SIS) and metal-insulator-semiconductor (MIS) structures. The substrates consisted of silicon nitride and silicon dioxide on silicon wafers, Kapton{reg_sign}, quartz, and cut slabs of silica aerogels. The conductive film samples were prepared by chemical vapor deposition (CVD) and sputtering, while the MIS and SIS samples were prepared by CVD followed by cleaving, grinding, mechanical indentation, erosion by a sputter Auger beam, electrical arcing and chemical etching. Electron emission measurements were conducted in high and ultra high vacuum systems at SNL, NM as well as at SNL, CA. Optical emission measurements were made in air under an optical microscope as well as in the above vacuum environments. Sample morphology was investigated using both scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

  14. Effects of magnetic field on the low temperature emission of nitrogen vacancy centres in diamond

    NASA Astrophysics Data System (ADS)

    Mc Murtrie, Roger; Rogers, Lachlan J.; Manson, Neil B.

    2010-02-01

    Under optical illumination in the blue or green, negatively charged nitrogen vacancy centres in diamond emit in the red. The intensity of this emission varies slightly depending on spin state occupation. Optical transitions occur predominantly without change of spin projection. However, excited ms = ± 1 states can decay non-radiatively to the ground ms = 0 state via intermediary singlet states. With continuous excitation, this effect transfers most of the population to the ms = 0 state resulting in decay becoming almost entirely radiative so that optical emission is stronger than when all spin states are occupied equally. However, under optical illumination the ms = 0 polarization is reduced when an applied magnetic field induces avoided crossings between energy levels. The spin states are mixed and some population is diverted into the ms = ± 1 states with consequent reduction in optical emission. The change of emission can be calculated from a rate equation model involving the spin states of the ground and excited levels plus one singlet level [5]. The spin states of the excited levels are also affected by strain and in this work we calculate the variation in optical emission with changing magnetic field for various fixed values of strain.

  15. Microwave plasma CVD-grown graphene-CNT hybrids for enhanced electron field emission applications

    NASA Astrophysics Data System (ADS)

    Kaushik, Vishakha; Shukla, A. K.; Vankar, V. D.

    2014-12-01

    The growth and electron emission characteristics were investigated from a hybrid structure of multiwalled carbon nanotubes (MWCNTs) and multilayer layer graphene (MLG) deposited on silicon substrate coated with iron catalyst and an interlayer of aluminium. The hybrid structures were synthesized in a two-step process by microwave plasma-enhanced chemical vapour deposition technique. The formation of MWCNTs takes place by absorption and precipitation of carbon radicals into the catalyst particles. Thereafter, ample carbon forms MLG on tip of the MWCNTs resulting in a MLG-MWCNTs hybrid nanostructure. MLG was observed to grow branching out of the tips and sidewalls of the MWCNTs and is expected to attach by Van der Walls bonds. Transmission electron microscopy and micro-Raman spectroscopy confirmed the crystalline nature of the hybrid structures. Electron emission studies were carried out using a diode-type field emission setup. The enhancement factor was found to be ~3,500 for bare MWCNTs, ~4,070 to ~5,000 for hybrid structures and ~6,500 for N-doped MLG-MWCNTs hybrid structures. Modification in the defects structure and enhancement of emission sites are suggested to be responsible for the increase of the field emission characteristics.

  16. Field Emission Properties of Multi-walled Carbon Nanotubes Grown on Silicon Nanoporous Pillar Array

    NASA Astrophysics Data System (ADS)

    Jiang, Wei-fen; Li, Long-yu; Xiao, Shun-hua; Yang, Xiao-hui; Jia, Min; Li, Xin-jian

    2007-12-01

    Multi-walled carbon nanotubes (CNTs) were grown on a silicon nanoporous pillar array (Si-NPA) by thermal chemical vapor deposition. Surface morphologies and microstructure of the resultant were studied by a field emission scanning electron microscope, Raman spectrum, transmission electron microscope, and high-resolution transmission electron microscopy. The composition of samples was determined by energy dispersive X-ray spectroscopy (EDS). The results showed that a great deal of CNTs, with diameter in the range of 20-70 nm, incorporated with Si-NPA and a large scale nest array of CNTs/Si-NPA (NACNT/Si-NPA) was formed. EDS analysis showed that the composition of carbon nanotubes was carbon. Field emission measurements showed that a current density of 5 mA/cm2 was obtained at an electric field of 4.26 V/μm, with a turn-on field of 1.3 V/μm. The enhancement factor calculated according to the Fowler-Nordheim theory was ~11,000. This excellent field emission performance is attributed to the unique structure and morphology of NACNT/Si-NPA, especially the formation of a nest-shaped carbon nanotube array. A schematic drawing that illustrates the experimental configuration is given. These results indicate that NACNT/Si-NPA might be an ideal candidate cathode for potential applications in flat panel displays.

  17. Two-process model of electron field emission from nanocarbons: Temperature effect

    NASA Astrophysics Data System (ADS)

    Altman, Igor S.; Pikhitsa, Peter V.; Choi, Mansoo

    2004-09-01

    The two-process model on electron field emission from nanocarbons that we recently suggested [I. S. Altman, P. V. Pikhitsa, and M. Choi, Appl. Phys. Lett. 84, 1126 (2004)] has solved the existing experimental puzzles such as an occurrence of the sharp knee in the Fowler-Nordheim (FN) plot. Our model implies two successive processes: (1) Tunneling from the metallic region into the semiconducting region under the external macroscopic electric field and (2) tunneling from the semiconducting region into vacuum under the Coulomb field of an additional electron appearing in the first process. However, this model in its original form was inapplicable at finite temperatures. We develop the model (remaining within the framework of the two-process approach, which allows the knee occurrence in the FN plot) in order to describe temperature effects in field emission from nanocarbons. Fitting of the recent experimental data on the temperature behavior of field emission from carbon nanotubes allowed us to extract parameters corresponding to the first process in our model.

  18. Field emission properties and growth mechanism of In2O3 nanostructures

    PubMed Central

    2014-01-01

    Four kinds of nanostructures, nanoneedles, nanohooks, nanorods, and nanotowers of In2O3, have been grown by the vapor transport process with Au catalysts or without any catalysts. The morphology and structure of the prepared nanostructures are determined on the basis of field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The growth direction of the In2O3 nanoneedles is along the [001], and those of the other three nanostructures are along the [100]. The growth mechanism of the nanoneedles is the vapor-liquid–solid (VLS), and those of the other three nanostructures are the vapor-solid (VS) processes. The field emission properties of four kinds of In2O3 nanostructures have been investigated. Among them, the nanoneedles have the best field emission properties with the lowest turn-on field of 4.9 V/μm and the threshold field of 12 V/μm due to possessing the smallest emitter tip radius and the weakest screening effect. PMID:24612921

  19. Low threshold field emission from high-quality cubic boron nitride films

    NASA Astrophysics Data System (ADS)

    Teii, Kungen; Matsumoto, Seiichiro

    2012-05-01

    Field emission performance of materials with mixed sp2/sp3 phases often depends upon the phase composition at the surface. In this study, the emission performance of high-quality cubic boron nitride (cBN) films is studied in terms of phase purity. Thick cBN films consisting of micron-sized grains are prepared from boron trifluoride gas by chemical vapor deposition in a plasma jet and an inductively coupled plasma. Both the bulk and surface phase purities as well as crystallinities of cBN evaluated by visible and ultraviolet Raman spectroscopy, glancing-angle x-ray diffraction, and x-ray photoelectron spectroscopy are the highest when the film is deposited in a plasma jet under an optimized condition. The emission turn-on field decreases with increasing the phase purity, down to around 5 V/μm for the highest cBN purity, due to the larger field enhancement, while it is higher than 14 V/μm without cBN (sp2-bonded hexagonal BN only). The results indicate that the total field enhancement for the high phase purity film is governed by the internal field amplification related to the surface coverage of more conductive cBN, rather than the external one related to the surface topology or roughness.

  20. The ENSO signal in atmospheric composition fields: emission-driven versus dynamically induced changes

    NASA Astrophysics Data System (ADS)

    Inness, A.; Benedetti, A.; Flemming, J.; Huijnen, V.; Kaiser, J. W.; Parrington, M.; Remy, S.

    2015-08-01

    The El Niño-Southern Oscillation (ENSO) not only affects meteorological fields but also has a large impact on atmospheric composition. Atmospheric composition fields from the Monitoring Atmospheric Composition and Climate (MACC) reanalysis are used to identify the ENSO signal in tropospheric ozone, carbon monoxide, nitrogen oxide and smoke aerosols, concentrating on the months October to December. During El Niño years, all of these fields have increased concentrations over maritime South East Asia in October. The MACC Composition Integrated Forecasting System (C-IFS) model is used to quantify the relative magnitude of dynamically induced and emission-driven changes in the atmospheric composition fields. While changes in tropospheric ozone are a combination of dynamically induced and emission-driven changes, the changes in carbon monoxide, nitrogen oxides and smoke aerosols are almost entirely emission-driven in the MACC model. The ozone changes continue into December, i.e. after the end of the Indonesian fire season while changes in the other fields are confined to the fire season.