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1

Electrical breakdown of gases  

Microsoft Academic Search

A collection of individual works on electrical discharges is presented. Topics covered include: fundamental processes in the electrical breakdown of gases; vacuum breakdown; spark breakdown in uniform fields; corona discharge; spark breakdown in non-uniform fields; breakdown voltage characteristics; irradiation and time lags; high-frequency breakdown of gases; laser-induced electrical breakdown of gases; spark channels; and electrode phenomena. (GHT)

J. M. Meek; J. D. Craggs

1978-01-01

2

Breakdown characteristics of an isolated conducting object in a uniform electric field  

NASA Technical Reports Server (NTRS)

A laboratory experiment was conducted to determine the physical processes involved in the electrical breakdown of a particular spark gap arrangement. The gap consists of an isolated conducting ellipsoid located midway between two large flat electrodes. Gradual increase of the applied electric field, E, in the gap produces corona on the ellipsoid tips followed by flashover in a leader-arc sequence. The leader phase consists of the abrupt formation of ionized channels which partially bridge the gap and then decay prior to the arc. Measurements of dE/dt and of current were made, and photographs were taken with an image converter. Experimental parameters are listed.

Grothaus, M. G.; Trost, T. F.

1986-01-01

3

Electrical Breakdown in Water Vapor  

SciTech Connect

In this paper investigations of the voltage required to break down water vapor are reported for the region around the Paschen minimum and to the left of it. In spite of numerous applications of discharges in biomedicine, and recent studies of discharges in water and vapor bubbles and discharges with liquid water electrodes, studies of the basic parameters of breakdown are lacking. Paschen curves have been measured by recording voltages and currents in the low-current Townsend regime and extrapolating them to zero current. The minimum electrical breakdown voltage for water vapor was found to be 480 V at a pressure times electrode distance (pd) value of around 0.6 Torr cm ({approx}0.8 Pa m). The present measurements are also interpreted using (and add additional insight into) the developing understanding of relevant atomic and particularly surface processes associated with electrical breakdown.

Skoro, N.; Maric, D.; Malovic, G.; Petrovic, Z. Lj. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Graham, W. G. [Centre for Plasma Physics, School of Mathematics and Physics, Queens University Belfast, BT7 1NN (United Kingdom)

2011-11-15

4

Influence of Si/SiO 2 interface properties on electrical performance and breakdown characteristics of ultrathin stacked oxide/nitride dielectric films  

NASA Astrophysics Data System (ADS)

In this work, the influence of Si/SiO 2 interface properties, interface nitridation and remote-plasma-assisted oxidation (RPAO) thickness (<1 nm), on electrical performance and TDDB characteristics of sub-2 nm stacked oxide/nitride gate dielectrics has been investigated using a constant voltage stress (CVS). It is demonstrated that interfacial plasma nitridation improves the breakdown and electrical characteristics. In the case of PMOSFETs stressed in accumulation, interface nitridation suppresses the hole traps at the Si/SiO 2 interface evidenced by less negative Vt shifts. Interface nitridation also retards hole tunneling between the gate and drain, resulting in reduced off-state drain leakage. In addition, the RPAO thickness of stacked gate dielectrics shows a profound effect in device performance and TDDB reliability. Also, it is demonstrated that TDDB characteristics are improved for both PMOS and NMOS devices with the 0.6 nm-RPAO layer using Weibull analysis. The maximum operating voltage is projected to be improved by 0.3 V difference for a 10-year lifetime. However, physical breakdown mechanism and effective defect radius during stress appear to be independent of RPAO thickness from the observation of the Weibull slopes. A correlation between trap generation and dielectric thickness changes based on the C- V distortion and oxide thinning model is presented to clarify the trapping behavior in the RPAO and bulk nitride layer during CVS stress.

Lee, Yi-Mu; Wu, Yider

2008-05-01

5

Electrical Breakdown of Long Gaps in Sulfur Hexafluoride  

Microsoft Academic Search

The electrical discharge characteristics of SF6 are discussed theoretically in relation to the field dependence of the ionization coefficient a and the electron attachment coefficient The results are compared with the characteristics of air. A simple theoretical formulation of breakdown or corona inception voltages of gaps in SF6 is derived. The formulation has been examined by experiments on several electrode

T. Nitta; Y. Shibuya

1971-01-01

6

Origin of thickness dependent dc electrical breakdown in dielectrics  

NASA Astrophysics Data System (ADS)

A model based on space charge dynamics under high dc electric field has been proposed to explain commonly observed thickness dependent breakdown of polymeric material. The formation and dynamics of space charge will result in local electric field enhancement that has a direct impact on dielectric breakdown. The simulation results show that the breakdown depends on the sample thickness with a power index of 0.143, indicating the space charge and its dynamics are responsible for thickness dependent breakdown. The model also predicts the effect of voltage ramping rate on the electrical breakdown strength.

Chen, George; Zhao, Junwei; Li, Shengtao; Zhong, Lisheng

2012-05-01

7

Electrical breakdown of polyethylene terephthalate under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Measurements of dc dielectric breakdown strength were made on polyethylene terephthalate films of 50 micrometers in thickness at temperatures of 35, 70, and 100 C under hydrostatic pressure ranging from 50 to 500 bar. It has been found that the electrical breakdown field E(sub b) increases with pressure and decreases with temperature. It is suggested that thermal breakdown is the dominant process.

Zebouchi, N.; Essolbi, R.; Malec, D.; Giam, Hoang The; Ai, Bui; Bendaoud, M.

1994-12-01

8

Electric breakdown of thin liquid films  

NASA Astrophysics Data System (ADS)

An experimental technique is developed for assessing stability of thin liquid films by application of electrical forces and simultaneous measurement of the electric conductivity of the system. The concept involves creating a thin film at the intersection of two micro-channels etched onto a glass substrate. Once a thin film is created, a ramped DC potential difference can be applied across it. The electrical stresses developed at the film interfaces lead to its rupture above a threshold potential. The potential at which the film ruptures is used to assess the stability of the film. Small channel dimensions in this microfluidic platform allow characterization of thin films formed between micron-sized droplets at high capillary pressures, which is difficult to attain using conventional thin film characterization techniques. The results of DC potential breakdown of films show that critical potential can be considered as a measure of thin film stability. Stability measurements using this technique were in accord with Langmuir adsorption model. Furthermore, impedance spectroscopy is used to measure capacitance of the films formed using the developed microfluidic device. The capacitance measurements led to the estimation of the film area which is unknown in the microfluidic device to the vantage point along the surface of the film. The effect of drainage time and adsorption time of films is studied using impedance spectroscopy. Similar to DC measurements, capacitance measurements of the film also suggested a Langmuir adsorption trend. Moreover, capacitance measurement of films under the effect of DC potential was conducted. The results showed a dependence of capacitance to square of applied DC potential.

Karimi Mostowfi, Farshid

9

Electrical Breakdown in a Martian Gas Mixture  

NASA Technical Reports Server (NTRS)

The high probability for dust interactions during Martian dust storms and dust devils combined with the cold, dry climate of Mars most likely result in airborne dust that is highly charged. On Earth, potential gradients up to 5 kV/m have been recorded and in some cases resulted in lightning. Although the Martian atmosphere is not conducive to lightning generation, it is widely believed that electrical discharge in the form of a corona occurs. In order to understand the breakdown of gases, Paschen measurements are taken which relate the minimum potential required to spark across a gap between two electrodes. The minimum potential is plotted versus the pressure-distance value for electrodes of a given geometry. For most gases, the potential decreases as the pressure decreases. For CO2, the minimum in the curve happens to be at Mars atmospheric pressures (5-7 mm Hg) for many distances and geometries. However, a very small amount (<0.1%) of mixing gases radically changes the curve, as noted by Leach. Here, we present the first experimental results of a Paschen curve for a Mars gas mixture compared with 100% pure CO2.

Buhler, C. R.; Calle, C. I.; Nelson, E.

2003-01-01

10

Impulse Electrical Breakdown of High-Purity Water.  

NASA Astrophysics Data System (ADS)

Experiments have been conducted on the electrical breakdown of high-purity water and water mixtures. The electrical regime of interest has been carefully defined and documented to consist of electrical impulses with approximately microsecond rise time and fall time greater than 65 microseconds, on approximately 81-square-centimeter-area planar electrodes with a dielectric gap of approximately one centimeter. The results of over 25,000 shots by a Marx generator have been distilled into database form in an Excel spreadsheet and analysis performed to try to find patterns or indirect evidence into the nature of the breakdown-initiation process. An extensive review of all the experiments, which had been conducted over eight years by the Naval Surface Warfare Center and which had been designed to find the largest water-breakdown fields, was conducted with the intention of delineating the physical factors that led to breakdown. A variety of theoretical models of breakdown initiation were compared to the data, until it became clear that many of the breakdowns were dominated by impurities of various sorts. An extensive study of old and new experiments led to a more detailed understanding of the phenomenology of impurity-dominated water breakdown (such as the process of "conditioning" the electrodes and hysteresis) and the proposal of a number of new experiments to further characterize the intrinsic role of electrode materials on determining high-electric-field dielectric breakdown in water.

Gehman, Victor Herbert, Jr.

1995-01-01

11

Studies of electrical breakdown processes across vacuum gaps between metallic electrodes  

E-print Network

Studies of electrical breakdown processes across vacuum gaps between metallic electrodes L Keywords: Magnetic insulation Vacuum electrical breakdown Bacteria-induced electrical breakdown Accelerator a b s t r a c t An experimental program to elucidate the physical causes of electrical breakdown

Gilson, Erik

12

Breakdown characteristics and conditioning of carbon and refractory metal electrodes  

NASA Technical Reports Server (NTRS)

High voltage carbon and refractory metal electrodes employed in devices used in space, such as ion thrusters and traveling wave tubes, can be easily damaged by electrical breakdown and arcing events. Modification of the electrode surfaces due to these events can impact the voltage hold off capability of the surfaces, which could lead to additional arcing, further damage, and the potential for device failure. On the cathode-potential surface, the arc energy is deposited by all of the processes at the surface ultimately responsible for net electron emission, such as melting, vapor and particulate formation, sputtering, ion bombardment, etc. On the anode-potential surface, the energy is deposited from the plasma or electron stream that crosses the gap, which causes surface damage by local heating. In spite of this energy dependence on the damage, many systems that use arc discharges characterize the amount of material removed from the surfaces and the lifetime of the device for voltage hold-off by the amount of current that passes through the arc, or the 'Coulomb-rating'. The results of a series of tests that were preformed on the boltage hold off capability and damage to carbon-carbon composite surfaces and molybdenum surfaces due to induced arcing will be presented and discussed. Damage to the surfaces was characterized by the field emission performance after the arc initiation and SEM photographs for the different energy and coulomb-transfer arc conditions. Both conditioning and damage to the surfaces were observed, and will be related to the characteristics of the electrical breakdown.

Goebel, Dan M.

2004-01-01

13

Experimental Study on Electrical Breakdown for Devices with Micrometer Gaps  

NASA Astrophysics Data System (ADS)

The understanding of electrical breakdown in atmospheric air across micrometer gaps is critically important for the insulation design of micro & nano electronic devices. In this paper, planar aluminum electrodes with gaps ranging from 2 ?m to 40 ?m were fabricated by microelectromechanical system technology. The influence factors including gap width and surface dielectric states were experimentally investigated using the home-built test and measurement system. Results showed that for SiO2 layers the current sustained at 2–3 nA during most of the pre-breakdown period, and then rose rapidly to 10–30 nA just before breakdown due to field electron emission, followed by the breakdown. The breakdown voltage curves demonstrated three stages: (1) a constantly decreasing region (the gap width d < 5 ?m), where the field emission effect played an important role just near breakdown, supplying enough initial electrons for the breakdown process; (2) a plateau region with a near constant breakdown potential (5 ?m < d < 10 ?m) (3) a region for large gaps that adhered to Paschen's curve (d > 10 ?m). And the surface dielectric states including the surface resistivity and secondary electron yield were verified to be related to the propagation of discharge due to the interaction between initial electrons and dielectrics.

Meng, Guodong; Cheng, Yonghong; Dong, Chengye; Wu, Kai

2014-12-01

14

Electric breakdown in deuterium and hydrogen at low pressures  

Microsoft Academic Search

The electrical breakdown of plane parallel steel electrodes (10 cm diam) is studied in a Pyrex-walled vacuum chamber (minimum pressure less than 8Ã10⁻⁶ Torr). For clean gases, Hâ and Dâ, and with electrode gaps from 0.5 to 8 cm, the breakdown at pressures from 0.3 to 0.5 Torr is consistent with a secondary process of electron release by ion bombardment.

R. J. Armstrong; T. K. Bennett

1997-01-01

15

Electric breakdown in deuterium and hydrogen at low pressures  

Microsoft Academic Search

The electrical breakdown of plane parallel steel electrodes (10 cm diam) is studied in a Pyrex-walled vacuum chamber (minimum pressure less than 8×10?6 Torr). For clean gases, H2 and D2, and with electrode gaps from 0.5 to 8 cm, the breakdown at pressures from 0.3 to 0.5 Torr is consistent with a secondary process of electron release by ion bombardment.

R. J. Armstrong; T. K. Bennett

1997-01-01

16

The electrical breakdown of thin dielectric elastomers: thermal effects  

NASA Astrophysics Data System (ADS)

Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields. This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength. In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field. We performed numerical analysis with a quasi-steady state approximation to predict thermal runaway of dielectric elastomer films. We also studied experimentally the effect of temperature on dielectric properties of different PDMS dielectric elastomers. Different films with different percentages of silica and permittivity enhancing filler were selected for the measurements. From the modeling based on the fitting of experimental data, it is found that the electrothermal breakdown of the materials is strongly influenced by the increase in both dielectric permittivity and conductivity.

Zakaria, Shamsul; Morshuis, Peter H. F.; Benslimane, Mohamed Y.; Gernaey, Krist V.; Skov, Anne L.

2014-03-01

17

Electrical breakdown of Space Station Freedom surfaces  

NASA Technical Reports Server (NTRS)

Space Station Freedom (SSF) will be the largest and highest power spacecraft that the U.S. has put into orbit. The solar array will generate 160 volts nominal when in sunlight, and the present baseline design is for the negative end of the solar array to be tied to SSF structure. Due to the balance of leakage currents through the plasma, the structure will be driven approximately 140 volts negative of the ambient conductive ionospheric plasma. Surface materials such as anodized aluminum will have this voltage drop across a thin dielectric which may not have sufficient dielectric strength to prevent dielectric breakdown. This can lead to arcing on the exterior surfaces of Space Station.

Carruth, M. R., Jr.; Vaughn, J. A.; Bechtel, R. T.; Gray, P. A.

1992-01-01

18

Reducing bubbles in glass coatings improves electrical breakdown strength  

NASA Technical Reports Server (NTRS)

Helium reduces bubbles in glass coatings of accelerator grids for ion thrustors. Fusing the coating in a helium atmosphere creates helium bubbles in the glass. In an argon atmosphere, entrapped helium diffuses out of the glass and the bubbles collapse. The resultant coating has a substantially enhanced electrical breakdown strength.

Banks, B.

1968-01-01

19

Ionizing gas breakdown waves in strong electric fields.  

NASA Technical Reports Server (NTRS)

A previous analysis by Albright and Tidman (1972) of the structure of an ionizing potential wave driven through a dense gas by a strong electric field is extended to include atomic structure details of the background atoms and radiative effects, especially, photoionization. It is found that photoionization plays an important role in avalanche propagation. Velocities, electron densities, and temperatures are presented as a function of electric field for both negative and positive breakdown waves in nitrogen.

Klingbeil, R.; Tidman, D. A.; Fernsler, R. F.

1972-01-01

20

Studies of electrical breakdown processes across vacuum gaps between metallic electrodes  

E-print Network

Studies of electrical breakdown processes across vacuum gaps between metallic electrodes L Available online 3 June 2013 Keywords: Magnetic insulation Vacuum electrical breakdown Bacteria-induced electrical breakdown Accelerator a b s t r a c t An experimental program to elucidate the physical causes

Gilson, Erik

21

Ion manipulation device with electrical breakdown protection  

SciTech Connect

An ion manipulation method and device is disclosed. The device includes a pair of substantially parallel surfaces. An array of inner electrodes is contained within, and extends substantially along the length of, each parallel surface. The device includes a first outer array of electrodes and a second outer array of electrodes. Each outer array of electrodes is positioned on either side of the inner electrodes, and is contained within and extends substantially along the length of each parallel surface. A DC voltage is applied to the first and second outer array of electrodes. A RF voltage, with a superimposed electric field, is applied to the inner electrodes by applying the DC voltages to each electrode. Ions either move between the parallel surfaces within an ion confinement area or along paths in the direction of the electric field, or can be trapped in the ion confinement area. The surfaces are housed in a chamber, and at least one electrically insulative shield is coupled to an inner surface of the chamber for increasing a mean-free-path between two adjacent electrodes in the chamber.

Chen, Tsung-Chi; Tang, Keqi; Ibrahim, Yehia M; Smith, Richard D; Anderson, Gordon A; Baker, Erin M

2014-12-02

22

Optical characteristics of red sprites produced by runaway air breakdown  

SciTech Connect

The results of numerical calculations of intensity and spectra of optical emissions from red sprites produced by runaway air breakdown in the atmosphere are presented. It is shown that the optical emissions from red sprites consist of two components: (1) short-term (t{approx}0.3{endash}2thinspms) emissions produced as a result of dissipation of an energetic electron beam in air; (2) long-term (t{approx}2{endash}10thinspms) emissions produced by a population of low-energy electrons in an electric field. The long-term optical emissions are calculated for all low-energy electrons, including the secondary low-energy electrons produced by the relativistic electron beam, ambient background electrons, and electrons produced as a result of regular breakdown. The theoretical results are compared with observational data. {copyright} 1998 American Geophysical Union

Yukhimuk, V.; Roussel-Dupre, R.A.; Symbalisty, E.M. [Space and Atmospheric Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Space and Atmospheric Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Taranenko, Y. [Computational Science Methods, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Computational Science Methods, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)

1998-05-01

23

Electrical Conduction and Breakdown Properties of Several Biodegradable Polymers  

Microsoft Academic Search

In order to respond to soaring public concern about environmental protection, various biodegradable polymers have been developed. The present paper reports the electrical conduction and breakdown properties of various biodegradable polymers such as poly-L-lactic acid (PLLA), polyethylene terephthalate succinate (PETS), polycaprolactone butylene succinate (PCL-BS), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), and polyhydroxybutyrate\\/valerate (PHB\\/V) in comparison to those of low-density

Y. Ohki; N. Hirai

2007-01-01

24

Lightning Impulse Breakdown Characteristics and Electrodynamic Process of Insulating Vegetable Oil-Based Nanofluid  

NASA Astrophysics Data System (ADS)

Insulating vegetable oils are considered environment-friendly and fire-resistant substitutes for insulating mineral oils. This paper presents the lightning impulse breakdown characteristic of insulating vegetable oil and insulating vegetable oil-based nanofluids. It indicates that Fe3O4 nanoparticles can increase the negative lightning impulse breakdown voltages of insulating vegetable oil by 11.8% and positive lightning impulse breakdown voltages by 37.4%. The propagation velocity of streamer is reduced by the presence of nanoparticles. The propagation velocities of streamer to positive and negative lightning impulse breakdown in the insulating vegetable oil-based nanofluids are 21.2% and 14.4% lesser than those in insulating vegetable oils, respectively. The higher electrical breakdown strength and lower streamer velocity is explained by the charging dynamics of nanoparticles in insulating vegetable oil. Space charge build-up and space charge distorted filed in point-sphere gap is also described. The field strength is reduced at the streamer tip due to the low mobility of negative nanoparticles.

Li, Jian; Zhang, Zhao-Tao; Zou, Ping; Du, Bin; Liao, Rui-Jin

2012-06-01

25

Space Charge Formation and Electrical Breakdown at High Temperature Region in PVC for Electrical Wiring Assembly  

NASA Astrophysics Data System (ADS)

The Polyvinyl chloride (PVC), the most popular insulating material, is used as an insulating material of various electric products. When using an electrical wiring assembly code over the power capacity, PVC could melt by the joule heating and cause an electrical breakdown. Therefore, it is necessary to clarify the electrical breakdown phenomena near the melting point (170°C) in PVC. In this paper, space charge distribution and conduction current have been measured in PVC sheets up to the electrical breakdown in the range from room temperature to 200°C under DC electric field. The breakdown strength decreases with temperature in PVC. Small hetero-space charges are accumulated near both of the electrodes at room temperature region. At high temperature region above 100°C, it is observed that positive charges are injected from anode and move toward the cathode; the electric field is emphasized near the cathode due to the packet-like positive charge in PVC. It shows a thermal breakdown process of the electric fields due to positive charge behavior and conduction current increase with temperature near the melting point in PVC.

Miura, Masakazu; Fukuma, Masumi; Kishida, Satoru

26

Mass spectra of neutral particles released during electrical breakdown of thin polymer films  

NASA Technical Reports Server (NTRS)

A special type of time-of-flight mass spectrometer triggered from the breakdown event was developed to study the composition of the neutral particle flux released during the electrical breakdown of polymer films problem. Charge is fed onto a metal-backed polymer surface by a movable smooth platinum contact. A slowly increasing potential from a high-impedance source is applied to the contact until breakdown occurs. The breakdown characteristics is made similar to those produced by an electron beam charging system operating at similar potentials. The apparatus showed that intense instantaneous fluxes of neutral particles are released from the sites of breakdown events. For Teflon FEP films of 50 and 75 microns thickness the material released consists almost entirely of fluorocarbon fragments, some of them having masses greater than 350 atomic mass units amu, while the material released from a 50 micron Kapton film consists mainly of light hydrocarbons with masses at or below 44 amu, with additional carbon monoxide and carbon dioxide. The apparatus is modified to allow electron beam charging of the samples.

Kendall, B. R. F.

1985-01-01

27

Detection of pre-electrical breakdown of IZO/?-NPD/Alq3/Al light-emitting diodes by electric-field-induced optical second-harmonic generation measurement  

NASA Astrophysics Data System (ADS)

By using the electric-field-induced optical second-harmonic generation (EFISHG), we measured the EFISHG-time (EFISHG-t) characteristics to study pre-electrical breakdown of indium-zinc-oxide (IZO)/N,N?-di[(1-naphthyl)-N,N?-diphenyl]-(1,1?-biphenyl)-4,4?-diamine (?-NPD)/tris(8-hydroxy-quinolinato)aluminum(III) (Alq3)/Al organic light-emitting diodes (OLEDs). A series of EFISHG pulses were identified as a pre-electrical breakdown phenomenon, before OLEDs were electrically broken. Analyzing the results revealed the additional negative charge accumulation at the ?-NPD/Alq3 interface which caused by the generation of EFISHG pulses. We concluded that the EFISHG-t measurement is available as a method for detecting pre-electrical breakdown phenomena of OLEDs.

Taguchi, Dai; Nakamoto, Ryo; Manaka, Takaaki; Iwamoto, Mitsumasa

2014-01-01

28

A NEW FAILURE MECHANISM BY SCANNING ELECTRON MICROSCOPE INDUCED ELECTRICAL BREAKDOWN OF TUNGSTEN WINDOWS IN  

E-print Network

A NEW FAILURE MECHANISM BY SCANNING ELECTRON MICROSCOPE INDUCED ELECTRICAL BREAKDOWN OF TUNGSTEN..................................................................15 2.1.3 Mechanics of CVD Tungsten 2.2.2 Tungsten Corrosion

Pearton, Stephen J.

29

Enhanced electric breakdown strength and high energy density of barium titanate filled polymer nanocomposites  

NASA Astrophysics Data System (ADS)

We report improved electric breakdown strength, high energy density, and low dielectric loss of nanocomposites using surface modified BaTiO3 (BT) nanoparticles filling in poly(vinylidene fluoride) polymer matrix. Dielectric and electric breakdown properties of the nanocomposites have been investigated as a function of BT content. The electric breakdown strength of 285 MV/m has been achieved at the nanocomposite with 10 vol. % BT nanoparticles. The results indicate that functionalized and produced passivation layers on the surface of ceramic fillers can improve the homogeneity of the nanocomposites, promote space charge and interface effects, and significantly enhance electric breakdown strength of the nanocomposites.

Yu, Ke; Niu, Yujuan; Xiang, Feng; Zhou, Yongcun; Bai, Yuanyuan; Wang, Hong

2013-11-01

30

Electrical Breakdown in Lightning Arrestor Connector (LAC) Devices  

NASA Astrophysics Data System (ADS)

Lightning arrestor connector (LAC) devices protect electronic devices by providing a conductive path to ground for electrical power surges caused by lightning. Such devices consist of an insulating material between electrodes. This insulation region is composed of an air gap and a high permittivity dielectric. In this presentation, the physics of the phenomena active in the early stages of the flow of transient electrical current will be described. The conditions that lead to thermal breakdown of the dielectric will also be discussed.--Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Hjalmarson, Harold P.; Kambour, Kenneth; Pineda, Andrew C.

2011-03-01

31

Effect of temperature on the electric breakdown strength of dielectric elastomer  

NASA Astrophysics Data System (ADS)

DE (dielectric elastomer) is one of the most promising artificial muscle materials for its large strain over 100% under driving voltage. However, to date, dielectric elastomer actuators (DEAs) are prone to failure due to the temperature-dependent electric breakdown. Previously studies had shown that the electrical breakdown strength was mainly related to the temperature-dependent elasticity modulus and the permittivity of dielectric substances. This paper investigated the influence of ambient temperature on the electric breakdown strength of DE membranes (VHB4910 3M). The electric breakdown experiment of the DE membrane was conducted at different ambient temperatures and pre-stretch levels. The real breakdown strength was obtained by measuring the deformation and the breakdown voltage simultaneously. Then, we found that with the increase of the environment temperature, the electric breakdown strength decreased obviously. Contrarily, the high pre-stretch level led to the large electric breakdown strength. What is more, we found that the deformations of DEs were strongly dependent on the ambient temperature.

Liu, Lei; Chen, Hualing; Sheng, Junjie; Zhang, Junshi; Wang, Yongquan; Jia, Shuhai

2014-03-01

32

Breakdown Characteristics of In0.52Al0.48AsInP Heterojunction APDs  

E-print Network

Breakdown Characteristics of In0.52Al0.48As­InP Heterojunction APDs Oh-Hyun Kwon, Alejandro Gri (APD) are generally assessed by examining the steepness of the breakdown-probability curve to have a low operational breakdown voltage. Unfortunately, homojunction APDs that have good breakdown

Hayat, Majeed M.

33

Electrical breakdown and nanogap formation of indium oxide core/shell heterostructure nanowires.  

PubMed

We report the electrical breakdown behavior and subsequent nanogap formation of In(2)O(3)/InO(x) core/shell heterostructure nanowires with substrate-supported and suspended structures. The radial heterostructure nanowires, composed of crystalline In(2)O(3) cores and amorphous In-rich shells, are grown by chemical vapor deposition. As the nanowires broke down, they exhibited two distinct current drops in the current-voltage characteristics. The tips of the broken nanowires were found to have a cone or a volcano shape depending on the width of the nanowire. The shape, the size, and the position of the nanogap depend strongly on the device structure and the nanowire dimensions. The substrate-supported and the suspended devices exhibit distinct breakdown behavior which can be explained by the diffusive thermal transport model. The breakdown temperature of the nanowire is estimated to be about 450 K, close to the melting temperature of indium. We demonstrated the usefulness of this technique by successful fabrication of working pentacene field-effect transistors. PMID:21730682

Jung, Minkyung; Song, Woon; Sung Lee, Joon; Kim, Nam; Kim, Jinhee; Park, Jeunghee; Lee, Hyoyoung; Hirakawa, Kazuhiko

2008-12-10

34

The influence of defects on the short-term breakdown characteristics and long-term dc performance of LDPE insulation  

Microsoft Academic Search

Extruded polyethylene is used as the bulk insulation for ac HV cables because of its high electric resistivity and breakdown strength. Although the material at present has limited use in dc power cables, it is used extensively in submarine optical communication cable systems. This paper reports on the study of the short-term characteristics and long-term performance of low-density polyethylene (LDPE)

G. Chen; A. E. Davies

2000-01-01

35

The Validity of the Similarity Law for the Electrical Breakdown of SF6 Gas  

Microsoft Academic Search

The aim of this paper is to investigate the justification and the limitation of the geometrical similarity law application on the electrical breakdown of SF6 gas. For this purpose, the measurements of the dielectric breakdown voltage for similar systems insulated with SF6 gas were done. The applied dc voltage source had an 8 V\\/s rate of rise. Standard double exponential

Predrag OsmokroviTamara; Tamara Zivic; Boris Loncar; Aleksandra Vasic

2007-01-01

36

THE ONSET OF ELECTRICAL BREAKDOWN IN DUST LAYERS: II. EFFECTIVE DIELECTRIC CONSTANT AND LOCAL FIELD ENHANCEMENT  

EPA Science Inventory

Part 1 of the work has shown that electrical breakdown in dust layers obeys Paschen's Law, but occurs at applied field values which appear too small to initiate the breakdown. In this paper the authors show how an effective dielectric constant characterizing the dust layer can be...

37

THE ONSET OF ELECTRICAL BREAKDOWN IN DUST LAYERS: I. MICROSPARKING DESCRIBED BY PASCHEN'S LAW  

EPA Science Inventory

This paper describes a study of the onset of electrical breakdown in dust layers, for hand-deposited dust layers in a parallel-plate geometry. It was found that the breakdown was an ordinary electron-avalanche process originating in voids within the dust layer and obeying Paschen...

38

DC conduction and electrical breakdown of MgO\\/LDPE nanocomposite  

Microsoft Academic Search

To understand basic electric properties of nano-sized magnesium oxide (MgO) \\/ low-density polyethylene (LDPE) nanocomposite under DC voltage application, the volume resistivity, the space charge distribution and the breakdown strength were investigated. By the addition of nano-sized MgO filler, both the DC breakdown strength and the volume resistivity of LDPE increased. At the average DC electric field of about 85

Yoshinobu Murakami; Masanori Nemoto; Syunsuke Okuzumi; Suguru Masuda; Masayuki Nagao; Naohiro Hozumi; Yoitsu Sekiguchi; Yoshinao Murata

2008-01-01

39

Low electric field breakdown of thin SiO2 films under static and dynamic stress  

Microsoft Academic Search

A comprehensive study of Time-Dependent Dielectric Breakdown (TDDB) of 6.5-, 9-, 15-, and 22-nm SiO2 films under dc and pulsed bias has been conducted over a wide range of electric fields and temperatures. Very high temperatures were used at the wafer level to accelerate breakdown so tests could be conducted at electric fields as low as 4.5 MV\\/cm. New observations

John S. Suehle; Prasad Chaparala

1997-01-01

40

The Thickness And Stretch Dependence Of The Electrical Breakdown Strength Of An Acrylic Dielectric Elastomer  

NASA Astrophysics Data System (ADS)

The performance of dielectric elastomer actuators is limited by electrical breakdown. Attempts to measure this are confounded by the voltage-induced thinning of the elastomer. A test configuration is introduced that avoids this problem: A thin sheet of elastomer is stretched, crossed-wire electrodes attached, and then embedded in a stiff polymer. The applied electric field at breakdown EB,is found to depend on both the deformed thickness, h, and the stretch applied, ?. For the acrylic elastomer investigated, the breakdown field scales as EB;=;51,^,,.25,. The test configuration allows multiple individual tests to be made on the same sheet of elastomer.

Huang, Jiangshui; Suo, Zhigang; Clarke, David

2013-03-01

41

The thickness and stretch dependence of the electrical breakdown strength of an acrylic dielectric elastomer  

NASA Astrophysics Data System (ADS)

The performance of dielectric elastomer actuators is limited by electrical breakdown. Attempts to measure this are confounded by the voltage-induced thinning of the elastomer. A test configuration is introduced that avoids this problem: A thin sheet of elastomer is stretched, crossed-wire electrodes are attached, and then embedded in a stiff polymer. The applied electric field at breakdown, EB, is found to depend on both the deformed thickness, h, and the stretch applied, ?. For the acrylic elastomer investigated, the breakdown field scales as EB = 51 h - 0.25 ? 0.63. The test configuration allows multiple individual tests to be made on the same sheet of elastomer.

Huang, Jiangshui; Shian, Samuel; Diebold, Roger M.; Suo, Zhigang; Clarke, David R.

2012-09-01

42

An investigation into the cumulative breakdown process of polymethylmethacrylate in quasi-uniform electric field under nanosecond pulses  

SciTech Connect

A group of complete images on the discharge channel developed in PMMA in quasi-uniform electric field under nanosecond pulses are observed with an on-line transmission microscope. The characteristics of the cumulative breakdown process are also generalized, which include initiating from the vicinity of the cathode, developing to the anode with a branch-like shape, and taking on a wormhole appearance when final breakdown occurs. The concluded characteristics are explained by referring to the conceptions of “low density domain” and “free radical” and considering the initial discharge channel as a virtual needle. The characteristics are helpful for designers to enhance the lifetime of insulators employed on a nanosecond time scale.

Zhao, Liang; Cang Su, Jian; Bo Zhang, Xi; Feng Pan, Ya; Min Wang, Li; Peng Fang, Jin; Sun, Xu; Lui, Rui [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, P.O. Box 69 Branch 13, Xi'an 710024 (China)] [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, P.O. Box 69 Branch 13, Xi'an 710024 (China)

2013-08-15

43

An investigation into the cumulative breakdown process of polymethylmethacrylate in quasi-uniform electric field under nanosecond pulses  

NASA Astrophysics Data System (ADS)

A group of complete images on the discharge channel developed in PMMA in quasi-uniform electric field under nanosecond pulses are observed with an on-line transmission microscope. The characteristics of the cumulative breakdown process are also generalized, which include initiating from the vicinity of the cathode, developing to the anode with a branch-like shape, and taking on a wormhole appearance when final breakdown occurs. The concluded characteristics are explained by referring to the conceptions of "low density domain" and "free radical" and considering the initial discharge channel as a virtual needle. The characteristics are helpful for designers to enhance the lifetime of insulators employed on a nanosecond time scale.

Zhao, Liang; Cang Su, Jian; Bo Zhang, Xi; Feng Pan, Ya; Min Wang, Li; Peng Fang, Jin; Sun, Xu; Lui, Rui

2013-08-01

44

A novel method for investigating electrical breakdown enhancement by nm-sized features  

NASA Astrophysics Data System (ADS)

Electrical transport studies across nm-thick dielectric films can be complicated, and datasets compromised, by local electrical breakdown enhanced by nm-sized features. To avoid this problem we need to know the minimal voltage that causes the enhanced electrical breakdown, a task that usually requires numerous measurements and simulation of which is not trivial. Here we describe and use a model system, using a ``floating'' gold pad to contact Au nanoparticles, NPs, to simultaneously measure numerous junctions with high aspect ratio NP contacts, with a dielectric film, thus revealing the lowest electrical breakdown voltage of a specific dielectric-nanocontact combination. For a 48 +/- 1.5 Å SiO2 layer and a ~7 Å monolayer of organic molecules (to link the Au NPs) we show how the breakdown voltage decreases from 4.5 +/- 0.4 V for a flat contact, to 2.4 +/- 0.4 V if 5 nm Au NPs are introduced on the surface. The fact that larger Au NPs on the surface do not necessarily result in significantly higher breakdown voltages illustrates the need for combining experiments with model calculations. This combination shows two opposite effects of increasing the particle size, i.e., increase in defect density in the insulator and decrease in electric field strength. Understanding the process then explains why these systems are vulnerable to electrical breakdown as a result of spikes in regular electrical grids. Finally we use XPS-based chemically resolved electrical measurements to confirm that breakdown occurs indeed right below the nm-sized features.Electrical transport studies across nm-thick dielectric films can be complicated, and datasets compromised, by local electrical breakdown enhanced by nm-sized features. To avoid this problem we need to know the minimal voltage that causes the enhanced electrical breakdown, a task that usually requires numerous measurements and simulation of which is not trivial. Here we describe and use a model system, using a ``floating'' gold pad to contact Au nanoparticles, NPs, to simultaneously measure numerous junctions with high aspect ratio NP contacts, with a dielectric film, thus revealing the lowest electrical breakdown voltage of a specific dielectric-nanocontact combination. For a 48 +/- 1.5 Å SiO2 layer and a ~7 Å monolayer of organic molecules (to link the Au NPs) we show how the breakdown voltage decreases from 4.5 +/- 0.4 V for a flat contact, to 2.4 +/- 0.4 V if 5 nm Au NPs are introduced on the surface. The fact that larger Au NPs on the surface do not necessarily result in significantly higher breakdown voltages illustrates the need for combining experiments with model calculations. This combination shows two opposite effects of increasing the particle size, i.e., increase in defect density in the insulator and decrease in electric field strength. Understanding the process then explains why these systems are vulnerable to electrical breakdown as a result of spikes in regular electrical grids. Finally we use XPS-based chemically resolved electrical measurements to confirm that breakdown occurs indeed right below the nm-sized features. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr30620d

Shpaisman, Hagay; Cohen, Hagai; Har-Lavan, Rotem; Azulai, Daniel; Stein, Nir; Cahen, David

2012-05-01

45

A novel method for investigating electrical breakdown enhancement by nm-sized features.  

PubMed

Electrical transport studies across nm-thick dielectric films can be complicated, and datasets compromised, by local electrical breakdown enhanced by nm-sized features. To avoid this problem we need to know the minimal voltage that causes the enhanced electrical breakdown, a task that usually requires numerous measurements and simulation of which is not trivial. Here we describe and use a model system, using a "floating" gold pad to contact Au nanoparticles, NPs, to simultaneously measure numerous junctions with high aspect ratio NP contacts, with a dielectric film, thus revealing the lowest electrical breakdown voltage of a specific dielectric-nanocontact combination. For a 48 ± 1.5 Å SiO(2) layer and a ?7 Å monolayer of organic molecules (to link the Au NPs) we show how the breakdown voltage decreases from 4.5 ± 0.4 V for a flat contact, to 2.4 ± 0.4 V if 5 nm Au NPs are introduced on the surface. The fact that larger Au NPs on the surface do not necessarily result in significantly higher breakdown voltages illustrates the need for combining experiments with model calculations. This combination shows two opposite effects of increasing the particle size, i.e., increase in defect density in the insulator and decrease in electric field strength. Understanding the process then explains why these systems are vulnerable to electrical breakdown as a result of spikes in regular electrical grids. Finally we use XPS-based chemically resolved electrical measurements to confirm that breakdown occurs indeed right below the nm-sized features. PMID:22517579

Shpaisman, Hagay; Cohen, Hagai; Har-Lavan, Rotem; Azulai, Daniel; Stein, Nir; Cahen, David

2012-05-21

46

Breakdown and Voltage–Time Characteristics of Turn-to-Turn Models for an HTS Transformer  

Microsoft Academic Search

The breakdown and voltage-time characteristics of turn-to-turn models for point contact geometry and surface contact geometry using copper multiwrapped with polyimide film for a high-temperature superconducting transformer were investigated under ac and impulse voltage at 77 K. Polyimide film (Kapton) 0.025 mm thick is used for multiwrapping of the electrode. As expected, the breakdown voltages for the surface contact geometry

Seung Myeong Baek; Sang Hyun Kim

2008-01-01

47

Aromatic polythiourea dielectrics with ultrahigh breakdown field strength, low dielectric loss, and high electric energy density.  

PubMed

The promise of aromatic, amorphous, polar polymers containing high dipolar moments with very low defect levels is demonstrated for future dielectric materials with ultrahigh electric-energy density, low loss at high applied fields, and ultrahigh breakdown strengths. Specifically, aromatic polythiourea films exhibit an ultrahigh breakdown field (>1 GV m(-1)), which results in an energy density of ?22 J cm(-3), as well as a low loss. PMID:23315675

Wu, Shan; Li, Weiping; Lin, Minren; Burlingame, Quinn; Chen, Qin; Payzant, Andrew; Xiao, Kai; Zhang, Q M

2013-03-25

48

REVIEWS OF TOPICAL PROBLEMS: Runaway breakdown and electric discharges in thunderstorms  

Microsoft Academic Search

This review concerns the theory of the avalanche multiplication of high-energy (0.1 - 10 MeV) electrons in a neutral material, a newly discovered phenomenon known as runaway breakdown (RB). In atmospheric conditions RB takes place at electric fields an order of magnitude weaker than those needed for normal breakdown in air. Experimental work of the past few years has shown

Aleksandr V. Gurevich; Kirill P. Zybin

2001-01-01

49

Analytical investigation of electrical breakdown properties in a nitrogen-SF{sub 6} mixture gas  

SciTech Connect

The electrical breakdown properties in nitrogen gas mixed with SF{sub 6} are analytically investigated in this article by making use of the ionization and attachment coefficients of the mixed gas. The ionization coefficients of nitrogen and SF{sub 6} gas are obtained in terms of the electron temperature T{sub e} by assuming a Maxwellian distribution of the electron energy. The attachment coefficient of SF{sub 6} gas is also obtained in terms of the gas temperature T{sub e}. An algebraic equation is obtained, relating explicitly the electron breakdown temperature T{sub b} in terms of the SF{sub 6} mole fraction {chi}. It was found from this equation that the breakdown temperature T{sub b} increases from approximately 2 to 5.3 eV as the mole fraction {chi} increases from zero to unity. The breakdown temperature T{sub b} of the electrons increases very rapidly from a small value and then approaches 5.3 eV slowly as the SF{sub 6} mole fraction increases from zero to unity. This indicates that even a small mole fraction of SF{sub 6} in the gas dominates the electron behavior in the breakdown system. The breakdown electric field E{sub b} derived is almost linearly proportional to the breakdown electron temperature T{sub b}. The experimental data agree remarkably well with the theoretical results. Therefore, it is concluded that even a small fraction of SF{sub 6} gas dominates nitrogen in determining the breakdown field. In this context, nearly 25% of the SF{sub 6} mole fraction provides a reasonable enhancement of the breakdown field for practical applications.

Uhm, Han S. [Kwangwoon Academy of Advanced Studies, Kwangwoon University, 447-1, Wolgye-Dong, Nowon-Gu, Seoul 137-701 (Korea, Republic of); Byeon, Yong S.; Song, Ki B.; Choi, Eun H. [Department of Electrophysics, Kwangwoon University, 447-1, Wolgye-Dong, Nowon-Gu, Seoul 137-701 (Korea, Republic of); Ryu, Han-Yong; Lee, Jaimin [Agency for Defense Development, 462 Jochiwongil, Yuseong, Daejeon 305-605 (Korea, Republic of)

2010-11-15

50

The surface discharge and breakdown characteristics of HTS DC cable and stop joint box  

NASA Astrophysics Data System (ADS)

A high temperature superconducting (HTS) DC cable system consists of a HTS cable and cable joint. The HTS DC cable should be electrically connected in joint boxes because of the unit length of HTS cable is limited to several-hundred meters. In particular, the stop joint box (SJB) must be developed for a compact cooling system. Polypropylene laminated paper (PPLP) and epoxy maybe used as insulating materials for HTS DC cable and SJB. To develop a HTS DC cable, it is necessary to develop the cryogenic insulation technology, materials and the joint methods. In this paper, we will mainly discuss on the DC and impulse characteristics of epoxy and PPLP in liquid nitrogen (LN2). The surface discharge characteristics of epoxy included fillers, PPLP and epoxy with PPLP composite (epoxy + PPLP) were measured under 0.4 MPa. Also, the PPLP-insulated mini-model cable was fabricated and then DC, impulse and DC polarity reversal breakdown strength of mini-model cable under 0.4 MPa were investigated.

Kim, W. J.; Kim, H. J.; Cho, J. W.; Kim, S. H.

2014-09-01

51

Electrical breakdown in air: new experiments and statistical and numerical models  

NASA Astrophysics Data System (ADS)

The electrical breakdown and discharges in air are of great significance for science and technology due to wide applications. Besides a breakdown itself, the pre-breakdown phenomena and relaxation after the breakdown have a significant role. In this report the analysis of DC glow discharge and its relaxation processes is presented. Statistical analysis of time delay distributions is presented and the statistical model based on the mixture distribution is applied to data measured with different electrodes from which electron yield is calculated. The occurrence of mixture distributions is physically explained based on analysis of the cathode surface. Also, by analyzing the memory curve measured in synthetic air the early and late relaxation of DC discharge are discussed. The processes responsible for the memory effect are identified and corresponding rate coefficients are determined. In order to confirm that the correct particles are identified, the 2D numerical model for relaxation is developed.

Jovanovi?, A. P.

2014-12-01

52

Leakage current and breakdown electric-field studies on ultrathin atomic-layer-deposited Al2O3 on GaAs  

NASA Astrophysics Data System (ADS)

Atomic-layer deposition (ALD) provides a unique opportunity to integrate high-quality gate dielectrics on III-V compound semiconductors. We report detailed leakage current and breakdown electric-field characteristics of ultrathin Al2O3 dielectrics on GaAs grown by ALD. The leakage current in ultrathin Al2O3 on GaAs is comparable to or even lower than that of state-of-the-art SiO2 on Si, not counting the high-k dielectric properties for Al2O3. A Fowler-Nordheim tunneling analysis on the GaAs /Al2O3 barrier height is also presented. The breakdown electric field of Al2O3 is measured as high as 10MV/cm as a bulk property. A significant enhancement on breakdown electric field up to 30MV/cm is observed as the film thickness approaches to 1nm.

Lin, H. C.; Ye, P. D.; Wilk, G. D.

2005-10-01

53

Streamer formation in electric fields above and below the breakdown threshold  

NASA Astrophysics Data System (ADS)

Streamers are rapidly growing plasma filaments that can penetrate into non-ionized regions due to the electric field enhancement at their tips. They play a key role in the early stages of many atmospheric discharges, for example in lightning inception, in the streamer coronas of lightning leaders and of jets, and in sprite discharges. There are positive and negative streamers. Positive streamers propagate along the direction of the electric field, while negative streamers propagate in the opposite direction. With fully three-dimensional particle simulations, we study the combined effect of natural background ionization, electron detachment and photoionization on the formation of streamers in atmospheric air. We use adaptive grid refinement and adaptive particle management, and we have parallelized our particle code. We show that in electric fields below the breakdown threshold, positive streamers can only form if there is a strong initial seed present. Negative streamers fail to originate, at least on the time scales we have considered. In electric fields above the breakdown threshold, the situation is very different. New avalanches continuously form all over the domain. They originate from free electrons, which can be created by photoionization or by detachment from negative ions. Instead of the "double-headed" streamers that show up in most fluid models, we observe a more uniform discharge. We conclude that single elongated streamers exist only if the overall background electric field is below the breakdown value. The local field at the streamer head, of course, has to exceed the breakdown field.

Sun, Anbang; Teunissen, Jannis; Koehn, Cristoph; Ebert, Ute

2013-04-01

54

Electrical characterization of the soft breakdown failure mode in MgO layers  

NASA Astrophysics Data System (ADS)

The soft breakdown (SBD) failure mode in 20 nm thick MgO dielectric layers grown on Si substrates was investigated. We show that during a constant voltage stress, charge trapping and progressive breakdown coexist, and that the degradation dynamics is captured by a power-law time dependence. We also show that the SBD current-voltage (I-V) characteristics follow the power-law model I =aVb typical of this conduction mechanism but in a wider voltage window than the one reported in the past for SiO2. The relationship between the magnitude of the current and the normalized differential conductance was analyzed.

Miranda, E.; O'Connor, E.; Cherkaoui, K.; Monaghan, S.; Long, R.; O'Connell, D.; Hurley, P. K.; Hughes, G.; Casey, P.

2009-07-01

55

Propagation of ionizing electron shock waves in electrical breakdown  

Microsoft Academic Search

A numerical solution of a hydrodynamic second-order model shows that the propagation of the first ionizing wave arises from an overgrowth of hot electrons in the wave front in a zone of a greatly disturbed electric field. This gives rise, in the electron shock zone ahead of the wave, to a precursor phenomenon, whose effect is to accelerate the channel

P. Bayle; B. Cornebois

1985-01-01

56

Cathode plasma in electrical breakdown of high voltage vacuum devices  

Microsoft Academic Search

The production and subsequent motion of cathode plasma determine the characteristics of many high voltage vacuum devices. These devices include electron beam generators, ion beam generators, high speed switches, and a type of plasma recombination laser. A thorough understanding of the cathode plasma phenomenon is essential in designing these devices. In this thesis a detailed study is reported of the

Yen

1984-01-01

57

Mass analysis of neutral particles and ions released during electrical breakdowns on spacecraft surfaces  

NASA Technical Reports Server (NTRS)

Charged-particle fluxes from breakdown events were studied. Methods to measure mass spectra and total emitted flux of neutral particles were developed. The design and construction of the specialized mass spectrometer was completed. Electrical breakdowns were initiated by a movable blunt contact touching the insulating surface. The contact discharge apparatus was used for final development of two different high-speed recording systems and for measurements of the composition of the materials given off by the discharge. It was shown that intense instantaneous fluxes of neutral particles were released from the sites of electrical breakdown events. A laser micropulse mass analyzer showed that visible discoloration at breakdown sites were correllated with the presence of iron on the polymer side of the film, presumably caused by punch-through to the Inconel backing. Kapton samples irradiated by an oxygen ion beam were tested. The irradiated samples were free of surface hydrocarbon contamination but otherwise behaved in the same way as the Kapton samples tested earlier. Only the two samples exposed to oxygen ion bombardment were relatively clean. This indicates an additional variable that should be considered when testing spacecraft materials in the laboratory.

Kendall, B. R. F.

1985-01-01

58

Experimental and analytical study of the DC breakdown characteristics of polypropylene laminated paper with a butt gap condition considering the insulation design of superconducting cable  

NASA Astrophysics Data System (ADS)

It has been reported that the insulation design under DC stress is considered as one of the critical factors in determining the performance of high-voltage direct current (HVDC) superconducting cable. Therefore, it is fundamentally necessary to investigate the DC breakdown characteristics of the composite insulation system consisting of liquid nitrogen (LN2)/polypropylene-laminated-paper (PPLP). In particular, the insulation characteristics under DC polarity reversal condition should be verified to understand the polarity effect of the DC voltage considering the unexpected incidents taking place at line-commutated-converters (LCC) under service at a DC power grid. In this study, to examine the variation of DC electric field strength, the step voltage and polarity reversal breakdown tests are performed under DC stress. Also, we investigate the electric field distributions in a butt gap of the LN2/PPLP condition considering the DC polarity reversal by using simulation software.

Seo, In-jin; Choi, Won; Seong, Jae-gyu; Lee, Bang-wook; Koo, Ja-yoon

2014-08-01

59

Imaging the Effect of Electrical Breakdown in Multilayer Polymer Capacitor Films  

NASA Astrophysics Data System (ADS)

Multilayer polymer films show great promise as the dielectric material in high energy density capacitors. Such films show enhancement in both dielectric strength (EB) and energy density (Ud) relative to monolithic films of either source polymer. Composites are typically comprised of alternating layers of a high EB polymer and a high permittivity polymer. Here, we discuss a multilayer system based on polycarbonate (PC) interleaved with polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The dielectric properties of the PC/PVDF-HFP films are influenced by both composition and individual layer thickness. Optimized films show EB=750 kV/mm and Ud=13 J/cm^3. Further enhancements in EB and Ud are expected through optimization of the component polymers, composition, and layer structure. To guide next generation design, it is important to understand the breakdown mechanism, as it directly influences EB. To elucidate the role of the layer structure during electrical breakdown, we use a tandem focused ion beam (FIB) / scanning electron microscope (SEM) imaging technique. The technique allows us to image the internal layer structure of both `as fabricated' control films, and those subjected to high electric fields. It is therefore a powerful tool to assess film quality and analyze failure mechanisms. Specifically, the FIB is used to mill site-specific holes in a film and the resulting cross-sections are imaged via SEM. Individual layers are easily resolved down to 50 nm. For films subjected to electrical breakdown, the location and propagation of damage is tracked with sequential FIB milling and SEM imaging. Spatially resolved FIB/SEM imaging allows preparation of quasi-3D maps displaying the evolution of internal voids in areas adjacent to the breakdown location (pinhole of d = 30-80 microns). A majority of the voids are localized at the interfaces between layers and may propagate as far as 30-50 microns from the pinhole. The data suggest that the enhancement in dielectric strength arises from a barrier effect, whereby the propagation of an electrical breakdown in the direction of the applied field is impeded by the layer interfaces. We will also discuss recent TEM imaging results that are used to characterize the interfacial length scale and chemical makeup, factors that may influence breakdown.

Wolak, Mason

2013-03-01

60

Electrical breakdown strength of sulfur hexafluoride at high pressures and large interelectrode spacing  

SciTech Connect

Data are reported for a broad range of interelectrode spacings (from 0.5 to 6.0 cm) and broad range of pressures (from 0.05 to 0.8 MPa) in a homogeneous field, both with respect to breakdown voltages for sulfur hexafluoride and flashover voltages of epoxy compound support insulators. The data obtained are compared with analogous characteristics found when nitrogen and air are used. 10 refs.

Popkov, V.I.; Lyapin, A.G.; Samadashvili, A.D.

1980-01-01

61

Leakage current and breakdown electric-field studies on ultrathin atomic-layer-deposited Al2O3 on GaAs  

E-print Network

Leakage current and breakdown electric-field studies on ultrathin atomic-layer-deposited Al2O3-field characteristics of ultrathin Al2O3 dielectrics on GaAs grown by ALD. The leakage current in ultrathin Al2O3 on Ga properties for Al2O3. A Fowler-Nordheim tunneling analysis on the GaAs/Al2O3 barrier height is also presented

Ye, Peide "Peter"

62

Effects of thermal and electrical stressing on the breakdown behavior of space wiring  

NASA Technical Reports Server (NTRS)

Several failures in the electrical wiring systems of many aircraft and space vehicles have been attributed to arc tracking and damaged insulation. In some instances, these failures proved to be very costly as they have led to the loss of many aircraft and imperilment of space missions. Efforts are currently underway to develop lightweight, reliable, and arc track resistant wiring for aerospace applications. In this work, six wiring constructions were evaluated in terms of their breakdown behavior as a function of temperature. These hybrid constructions employed insulation consisting of Kapton, Teflon, and cross-linked Tefzel. The properties investigated included the 400 Hz AC dielectric strength at ambient and 200 C, and the lifetime at high temperature with an applied bias of 40, 60, and 80% of breakdown voltage level. The results obtained are discussed, and conclusions are made concerning the suitability of the wiring constructions investigated for aerospace applications.

Hammoud, Ahmad; Stavnes, Mark; Suthar, Jayant; Laghari, Javaid

1995-01-01

63

Electric field breakdown of lateral-type Schottky diodes formed on lightly doped homoepitaxial diamond  

NASA Astrophysics Data System (ADS)

The reverse current of lateral-type Schottky diodes fabricated on p-type homoepitaxial diamond was analyzed by changing the distance between Schottky and Ohmic electrodes and the metal materials in the Schottky electrodes. The maximum electric field at breakdown was 0.56 MV cm -1 for the Au Schottky contact and less than 0.26 MV cm -1 for the Al Schottky contact. The breakdown voltage depended on the electrode distance when the diamond surface was revealed in vacuum, whereas the Schottky diodes sustained the applied voltage of 500 V, corresponding to 0.69 MV cm -1, after covering of the diamond surface with an insulating liquid. Diamond surface protection is an indispensable technique for fabrication of high-voltage Schottky diodes based on diamond.

Teraji, Tokuyuki; Koizumi, Satoshi; Koide, Yasuo; Ito, Toshimichi

2008-07-01

64

Application of dynamic displacement current for diagnostics of subnanosecond breakdowns in an inhomogeneous electric field  

SciTech Connect

The breakdown of different air gaps at high overvoltages in an inhomogeneous electric field was investigated with a time resolution of up to 100 ps. Dynamic displacement current was used for diagnostics of ionization processes between the ionization wave front and a plane anode. It is demonstrated that during the generation of a supershort avalanche electron beam (SAEB) with amplitudes of {approx}10 A and more, conductivity in the air gaps at the breakdown stage is ensured by the ionization wave, whose front propagates from the electrode of small curvature radius, and by the dynamic displacement current between the ionization wave front and the plane electrode. The amplitude of the dynamic displacement current measured by a current shunt is 100 times greater than the SAEB. It is shown that with small gaps and with a large cathode diameter, the amplitude of the dynamic displacement current during a subnanosecond rise time of applied pulse voltage can be higher than 4 kA.

Shao Tao; Zhang Cheng; Yan Ping [Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Key Laboratory of Power Electronics and Electric Drive, Chinese Academy of Sciences, Beijing 100190 (China); Tarasenko, Victor F.; Burachenko, Alexandr G.; Rybka, Dmitry V.; Kostyrya, Igor' D.; Lomaev, Mikhail I.; Baksht, Evgeni Kh. [Institute of High Current Electronics, Russian Academy of Sciences, Tomsk 634055 (Russian Federation)

2013-05-15

65

Protein Preconcentration Using Nanofractures Generated by Nanoparticle-Assisted Electric Breakdown at Junction Gaps  

PubMed Central

Sample preconcentration is an important step that increases the accuracy of subsequent detection, especially for samples with extremely low concentrations. Due to the overlapping of electrical double layers in the nanofluidic channel, the concentration polarization effect can be generated by applying an electric field. Therefore, a nonlinear electrokinetic flow is induced, which results in the fast accumulation of proteins in front of the induced ionic depletion zone, the so-called exclusion-enrichment effect. Nanofractures were created in this work to preconcentrate proteins via the exclusion-enrichment effect. The protein sample was driven by electroosmotic flow and accumulated at a specific location. The preconcentration chip for proteins was fabricated using simple standard soft lithography with a polydimethylsiloxane replica. Nanofractures were formed by utilizing nanoparticle-assisted electric breakdown. The proposed method for nanofracture formation that utilizes nanoparticle deposition at the junction gap between microchannels greatly decreases the required electric breakdown voltage. The experimental results indicate that a protein sample with an extremely low concentration of 1 nM was concentrated to 1.5×104-fold in 60 min using the proposed chip. PMID:25025205

Jen, Chun-Ping; Amstislavskaya, Tamara G.; Kuo, Chen-Chi; Chen, Yu-Hung

2014-01-01

66

Protein preconcentration using nanofractures generated by nanoparticle-assisted electric breakdown at junction gaps.  

PubMed

Sample preconcentration is an important step that increases the accuracy of subsequent detection, especially for samples with extremely low concentrations. Due to the overlapping of electrical double layers in the nanofluidic channel, the concentration polarization effect can be generated by applying an electric field. Therefore, a nonlinear electrokinetic flow is induced, which results in the fast accumulation of proteins in front of the induced ionic depletion zone, the so-called exclusion-enrichment effect. Nanofractures were created in this work to preconcentrate proteins via the exclusion-enrichment effect. The protein sample was driven by electroosmotic flow and accumulated at a specific location. The preconcentration chip for proteins was fabricated using simple standard soft lithography with a polydimethylsiloxane replica. Nanofractures were formed by utilizing nanoparticle-assisted electric breakdown. The proposed method for nanofracture formation that utilizes nanoparticle deposition at the junction gap between microchannels greatly decreases the required electric breakdown voltage. The experimental results indicate that a protein sample with an extremely low concentration of 1 nM was concentrated to 1.5×10(4)-fold in 60 min using the proposed chip. PMID:25025205

Jen, Chun-Ping; Amstislavskaya, Tamara G; Kuo, Chen-Chi; Chen, Yu-Hung

2014-01-01

67

Electrical Breakdown of Anodized Structures in a Low Earth Orbital Environmental  

NASA Technical Reports Server (NTRS)

A comprehensive set of investigations involving arcing on a negatively biased anodized aluminum plate immersed in a low density argon plasma at low pressures (P(sub O), 7.5 x 10(exp -5) Torr) have been performed. These arcing experiments were designed to simulate electrical breakdown of anodized coatings in a Low Earth Orbital (LEO) environment. When electrical breakdown of an anodized layer occurs, an arc strikes, and there is a sudden flux of electrons accelerated into the ambient plasma. This event is directly followed by ejection of a quasi-neutral plasma cloud consisting of ejected material blown out of the anodized layer. Statistical analysis of plasma cloud expansion velocities have yielded a mean propagation velocity, v = (19.4 +/- 3.5) km/s. As the plasma cloud expands into the ambient plasma, energy in the form of electrical noise is generated. The radiated electromagnetic noise is detected by means of an insulated antenna immersed in the ambient plasma. The purpose of the investigations is (1) to observe and record the electromagnetic radiation spectrum resulting from the arcing process. (2) Make estimates of the travel time of the quasi-neutral plasma cloud based on fluctuations to several Langmuir probes mounted in the ambient plasma. (3) To study induced arcing between two anodized aluminum structures in close proximity.

Galofaro, J. T.; Doreswamy, C. V.; Vayner, B. V.; Snyder, D. B.; Ferguson, D. C.

1999-01-01

68

Electric breakdowns of the "plasma capacitors" occurs on insulation coating of the ISS surface  

NASA Astrophysics Data System (ADS)

High electric fields and currents are occurred in the spacecrafts plasma environment by onboard electric generators. Thus the high voltage solar array (SA) of the American segment of International Space Station (ISS) generates potential 160 V. Its negative pole is shorted to the frames of all the ISS segments. There is electric current between the SA and the frame through the plasma environment, i.e. electric discharge occurs. As a result a potential drop exists between the frames of all the ISS segments and the environmental plasma [1], which is cathode drop potential varphi _{c} defined. When ISS orbiting, the ?c varies greatly in the range 0-100 V. A large area of the ISS frames and SA surface is coated with a thin dielectric film. Because of cathode drop potential the frame surfaces accumulate ion charges and the SA surfaces accumulate electron charges. These surfaces become plasma capacitors, which accumulate much charge and energy. Micrometeorite impacts or buildup of potential drop in excess of breakdown threshold varphi_{b} (varphi _{c} > varphi _{b} = 60 V) may cause breakdowns of these capacitors. Following a breakdown, the charge collected at the surfaces disperses and transforms into a layer of dense plasma [2]. This plasma environment of the spacecraft produces great pulsed electric fields E at the frame surfaces as well as heavy currents between construction elements which in turn induce great magnetic fields H. Therefore the conductive frame and the environmental plasma is plasma inductors. We have calculated that the densities of these pulsing and high-frequency fields E and H generated in the plasma environment of the spacecraft may exceed values hazardous to human. Besides, these fields must induce large electromagnetic impulses in the space-suit and in the power supply and control circuits of onboard systems. During astronaut’s space-suit activity, these fields will penetrate the space-suit and the human body with possible hazardous effects. These effects need to be studied, and appropriate remedies are to be developed. References 1. Mikatarian, R., et al., «Electrical Charging of the International Space Station», AIAA Paper No. 2003-1079, 41th. Aerospace Sciences Meeting and Exhibit, January 2003. 2. A.G. Korsun, «Electric discharge processes intensification mechanisms on International Space Station surface». Astronautics and rocket production, ?1, 2011 (in Russian).

Homin, Taras; Korsun, Anatolii

69

Electric breakdown of longitudinally shocked Pb(Zr0.52Ti0.48)O3 ceramics  

NASA Astrophysics Data System (ADS)

Electric breakdown of longitudinally-shock-compressed Pb(Zr0.52Ti0.48)O3 (PZT 52/48) ferroelectric ceramics was experimentally investigated. It was found that a dependence of breakdown field strength, Eg, of shocked ferroelectrics on the thickness of the element, d, ranging from 0.65 to 6.5 mm is described by the Eg(d)=? .d-w law that describes the breakdown of dielectrics at ambient conditions. It follows from the experimental results that the tunnel effect is a dominant mechanism of injection of prime electrons in the shocked ferroelectric elements. It was demonstrated that electric breakdown causes significant energy losses in miniature autonomous generators based on shock depolarization of poled ferroelectric elements.

Shkuratov, Sergey I.; Talantsev, Evgueni F.; Baird, Jason

2011-07-01

70

Tether electrical characteristics design report  

SciTech Connect

The design of a tether system for use in electric and magnetic fields requires an analysis of the equivalent electrical circuit of the baboon and tether. The response of this equivalent circuit to an electric or magnetic field is dependent on the connection of the tether system to the baboon. The tether will be designed so that the currents induced in the tethered baboon are approximately the same as those induce in an untethered baboon. 6 figs., 3 tabs.

Lucas, J.H.

1989-03-24

71

Breakdown characteristics of AlGaN/GaN Schottky barrier diodes fabricated on a silicon substrate  

NASA Astrophysics Data System (ADS)

In this work, the breakdown characteristics of AlGaN/GaN planar Schottky barrier diodes (SBDs) fabricated on the silicon substrate are investigated. The breakdown voltage (BV) of the SBDs first increases as a function of the anode-to-cathode distance and then tends to saturate at larger inter-electrode spacing. The saturation behavior of the BV is likely caused by the vertical breakdown through the intrinsic GaN buffer layer on silicon, which is supported by the post-breakdown primary leakage path analysis with the emission microscopy. Surface passivation and field plate termination are found effective to suppress the leakage current and enhance the BV of the SBDs. A high BV of 601 V is obtained with a low on-resistance of 3.15 m?·cm2.

Jiang, Chao; Lu, Hai; Chen, Dun-Jun; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Dou

2014-09-01

72

Estimating the energy of electric breakdown in air gap between electrolyte and metal electrode  

NASA Astrophysics Data System (ADS)

The influence of induced electric charge (localized on the surface of a suspended copper rod) on the formation of a protrusion (Taylor cone) on the inducing liquid (aqueous solution) surface is considered. At an applied voltage of U ? 12 kV, the protrusion height in the interval of pre-breakdown voltages ( U < U P) is limited by the electric field strength. At U > U P, the growth of protrusion is terminated by an electric discharge, which drives the liquid to oscillate in a broad range of applied voltages U at almost constant multiple frequencies f = f 0 n, which are resonantly switched at certain fixed U values. By measuring the amount of evaporated liquid, the energy (27.8 × 10-3 J) and current (64.9 A) of single discharge were evaluated and the electric capacitance (7.6 × 10-10 F) of a system comprising the water surface and suspended copper electrode was estimated. Serial connection of an additional capacitor (100 ?F) to the copper electrode with induced electric charge leads to a threefold increase in these parameters.

Orlov, A. M.; Yavtushenko, I. O.; Churilov, M. V.

2010-07-01

73

Strongly Dipolar Polythiourea and Polyurea Dielectrics with High Electrical Breakdown, Low Loss, and High Electrical Energy Density  

NASA Astrophysics Data System (ADS)

Dielectric materials with high electric energy density and low loss are of great importance for applications in modern electronics and electrical systems. Strongly dipolar materials have the potential to reach relatively higher dielectric constants than the widely used non-polar or weakly dipolar polymers, as well as a much lower loss than that of nonlinear high K polymer dielectrics or polymer-ceramic composites. To realize the high energy density while maintaining the low dielectric loss, aromatic polythioureas and polyureas with high dipole moments, high dipole densities, tunable molecular structures and dielectric properties were investigated. High energy density (>24 J/cm3), high breakdown strength (>800 MV/m), and high charge-discharge efficiency (>90%) can be achieved in the new polymers. The molecular structure and film surface morphology were also studied; it is of great importance to optimize the fabrication process to make high-quality thin films.

Wu, Shan; Burlingame, Quinn; Cheng, Zhao-Xi; Lin, Minren; Zhang, Q. M.

2014-12-01

74

Strongly Dipolar Polythiourea and Polyurea Dielectrics with High Electrical Breakdown, Low Loss, and High Electrical Energy Density  

NASA Astrophysics Data System (ADS)

Dielectric materials with high electric energy density and low loss are of great importance for applications in modern electronics and electrical systems. Strongly dipolar materials have the potential to reach relatively higher dielectric constants than the widely used non-polar or weakly dipolar polymers, as well as a much lower loss than that of nonlinear high K polymer dielectrics or polymer-ceramic composites. To realize the high energy density while maintaining the low dielectric loss, aromatic polythioureas and polyureas with high dipole moments, high dipole densities, tunable molecular structures and dielectric properties were investigated. High energy density (>24 J/cm3), high breakdown strength (>800 MV/m), and high charge-discharge efficiency (>90%) can be achieved in the new polymers. The molecular structure and film surface morphology were also studied; it is of great importance to optimize the fabrication process to make high-quality thin films.

Wu, Shan; Burlingame, Quinn; Cheng, Zhao-Xi; Lin, Minren; Zhang, Q. M.

2014-09-01

75

Electrical characteristics of simulated tornadoes  

NASA Astrophysics Data System (ADS)

It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado. This research was supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA. The generous allocation of computing resources by Dr. Timothy J. Stubbs is gratefully acknowledged.

Zimmerman, M. I.; Farrell, W. M.; Barth, E. L.; Lewellen, D. C.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T.

2012-12-01

76

Effect of silane coupling agent chemistry on electrical breakdown across hybrid organic-inorganic insulating films.  

PubMed

Dielectric breakdown measurements were conducted on self-assembled monolayer (SAM)/native silicon oxide hybrid dielectrics using conductive atomic force microscopy (C-AFM). By depositing silane coupling agents (SCAs) through a diffusional barrier layer, SAM roughness was decoupled from chemistry to compare the chemical effects of exposed R-group functionality on dielectric breakdown. Using Weibull and current-voltage (I-V) analysis, the breakdown strength was observed to be independent of SCA R-group length, and the addition of a SAM was seen to improve the breakdown strength relative to native silicon oxide by up to 158%. Fluorinated SCAs were observed to suppress tunneling leakage and exhibited increased breakdown strength relative to their hydrocarbon analogs. Electron trapping, scattering, or attachment processes inherent to the fluorinated moieties are thought to be the origin of the improved breakdown properties. PMID:25010384

Diebold, Roger M; Gordon, Michael J; Clarke, David R

2014-08-13

77

Applications of LIBS for determination of ionic species (NaCl) in electrical cables for investigation of electrical breakdown  

NASA Astrophysics Data System (ADS)

The formation of water trees in high-voltage cables can wreak havoc to power systems. The water tree is produced within the high voltage cable insulator when impurities like sodium and magnesium present in the insulating material react with moist soil to form chlorides. This water tree causes electrical breakdown by short circuiting the metallic conductor and the earth. In this paper we use laser-induced breakdown spectroscopy (LIBS) to detect the potentially dangerous elements that form the water tree in the insulating cable. The LIBS system used for this work consists of the fundamental (1064 nm) of a Nd:YAG laser, four spectrometer modules that cover the visible and near-UV spectral ranges and an ICCD camera with proper delay and gating sequence. With this arrangement we were able to measure the elemental concentrations of trace metals present in the insulating cable. The concentrations measured with our LIBS system were counter checked by a standard technique like inductively coupled plasma (ICP) emission spectrometry. The maximum concentrations for ionic species such as Ba (455.40 nm), Ca (393.36 nm), Cr (267.71 nm), Fe (259.94 nm), Cl (542.3 nm), Mg (516.7 nm), Mn (257.61 nm), Na (589.59 nm) and Ti (334.18 nm) are 20.6, 43.2, 1.6, 148.4, 24.2, 22.1, 4.2, 39.56 and 4.35 ppm, respectively. The relative accuracy of our LIBS system for various elements as compared with the ICP method is in the range of 0.03-0.6 at 2.5% error confidence.

Gondal, M. A.; Shwehdi, M. H.; Khalil, A. A. I.

2011-12-01

78

Investigation on critical breakdown electric field of hot carbon dioxide for gas circuit breaker applications  

NASA Astrophysics Data System (ADS)

Sulfur hexafluoride (SF6) gas is widely used in high-voltage circuit breakers, but due to its high global warming potential, substitutes are being sought. CO2 has been investigated as a candidate based on its arc interruption performance. The hot gas in the circuit breaker after current zero, with a complicated species composition caused by the dissociation and many other reactions, will lead to the electrical breakdown, which is one of the major concerns in assessing the arc interruption performance. Despite this, little research has been reported on the dielectric strength of hot CO2. In this paper, the dielectric properties of hot CO2 related to the dielectric recovery phase of the circuit breaker were investigated in the temperature range from 300 to 4000?K and in the pressure range from 0.01 to 1.0?MPa. Under the assumptions of local thermodynamic equilibrium (LTE) and local chemical equilibrium (LCE), the equilibrium compositions of hot CO2 were obtained based on Gibbs free energy minimization. The cross sections for interactions between electrons and the species are presented. The critical reduced electric field strength of CO2 was determined by balancing electron generation and loss. These were evaluated using the electron energy distribution function (EEDF) derived from the two-term Boltzmann transport equation. The result indicates that unlike SF6 or air, in hot CO2 the reduced critical electric field strength does not change monotonically with increasing heavy-particle temperature from 300 to 4000?K. CO2 has a superior dielectric strength to pure SF6 above 2500?K at 0.5?MPa, which means it has the potential to improve the interruption performance of the circuit breakers, while reducing the global warming effect. Good agreement was found with published experimental results and calculations for CO2 at room temperature, and with previous calculations for hot CO2.

Sun, Hao; Rong, Mingzhe; Wu, Yi; Chen, Zhexin; Yang, Fei; Murphy, Anthony B.; Zhang, Hantian

2015-02-01

79

Form Characteristics of an Electric Vehicle  

Microsoft Academic Search

The shape of today's vehicles on the actual automotive market is based on the packaging design of an internal combustion engine (ICE) that is very different of that of an electric vehicle (EV). In this paper specific form characteristics that express the difference between an EV and an ICE vehicle are researched and illustrated. Based upon these determinations, three different

Dirk van Gogh; Kikuo Emoto; Hiroshi Shimizu

2004-01-01

80

Investigation on critical breakdown electric field of hot sulfur hexafluoride/carbon tetrafluoride mixtures for high voltage circuit breaker applications  

NASA Astrophysics Data System (ADS)

Sulfur hexafluoride (SF6) gas, widely used in high-voltage circuit breakers, has a high global warming potential and hence substitutes are being sought. The use of a mixture of carbon tetrafluoride (CF4) and SF6 is examined here. It is known that this reduces the breakdown voltage at room temperature. However, the electrical breakdown in a circuit breaker after arc interruption occurs in a hot gas environment, with a complicated species composition because of the occurrence of dissociation and other reactions. The likelihood of breakdown depends on the electron interactions with all these species. The critical reduced electric field strength (the field at which breakdown can occur, relative to the number density) of hot SF6/CF4 mixtures corresponding to the dielectric recovery phase of a high voltage circuit breaker is calculated in the temperature range from 300 K to 3500 K. The equilibrium compositions of hot SF6/CF4 mixtures under different mixing fractions were determined based on Gibbs free energy minimization. Full sets of improved cross sections for interactions between electrons and the species present are presented. The critical reduced electric field strength of these mixtures was obtained by balancing electron generation and loss mechanisms. These were evaluated using the electron energy distribution function derived from the Boltzmann transport equation under the two-term approximation. The result indicates that critical electric field strength decreases with increasing heavy-particle temperature from 1500 to 3500 K. Good agreement was found between calculations for pure hot SF6 and pure hot CF4 and experimental results and previous calculations. The addition of CF4 to SF6 was found to increase the critical reduced electric field strength for temperatures above 1500 K, indicating the potential of replacing SF6 by SF6/CF4 mixtures in high-voltage circuit breakers.

Wang, Weizong; Murphy, Anthony B.; Rong, Mingzhe; Looe, Hui M.; Spencer, Joseph W.

2013-09-01

81

Wind tunnel investigation of the interaction and breakdown characteristics of slender wing vortices at subsonic, transonic, and supersonic speeds  

NASA Technical Reports Server (NTRS)

The vortex dominated aerodynamic characteristics of a generic 65 degree cropped delta wing model were studied in a wind tunnel at subsonic through supersonic speeds. The lee-side flow fields over the wing-alone configuration and the wing with leading edge extension (LEX) added were observed at M (infinity) equals 0.40 to 1.60 using a laser vapor screen technique. These results were correlated with surface streamline patterns, upper surface static pressure distributions, and six-component forces and moments. The wing-alone exhibited vortex breakdown and asymmetry of the breakdown location at the subsonic and transonic speeds. An earlier onset of vortex breakdown over the wing occurred at transonic speeds due to the interaction of the leading edge vortex with the normal shock wave. The development of a shock wave between the vortex and wing surface caused an early separation of the secondary boundary layer. With the LEX installed, wing vortex breakdown asymmetry did not occur up to the maximum angle of attack in the present test of 24 degrees. The favorable interaction of the LEX vortex with the wing flow field reduced the effects of shock waves on the wing primary and secondary vortical flows. The direct interaction of the wing and LEX vortex cores diminished with increasing Mach number. The maximum attainable vortex-induced pressure signatures were constrained by the vacuum pressure limit at the transonic and supersonic speeds.

Erickson, Gary E.

1991-01-01

82

New operating limits for applications with electroactive elastomer: effect of the drift of the dielectric permittivity and the electrical breakdown  

NASA Astrophysics Data System (ADS)

Dielectric elastomer generators are a promising solution to scavenge energy from human motion, due to their lightweight, high efficiency low cost and high energy density. Performances of a dielectric elastomer used in a generator application are generally evaluated by the maximum energy which can be converted. This energy is defined by an area of allowable states and delimited by different failure modes such as: electrical breakdown, loss of tension, mechanical rupture and electromechanical instability, which depend deeply on dielectric behaviors of the material. However, there is controversy on the dielectric constant (permittivity) of usual elastomers used for these applications. This paper aims to investigate the dielectric behaviors of two popular dielectric elastomers: VHB 4910 (3M) and Polypower (Danfoss). This study is undertaken on a broad range of temperature. We focus on the influence of pre-stretch in the change of the dielectric constant. An originality of this study is related to the significant influence of the nature of compliant electrodes deposited on these elastomers. Additionally, the electrical breakdown field of these two elastomers has been studied as a function of pre-stretch and temperature. Lastly, thanks to these experiments, analytic equations have been proposed to take into account the influence of the temperature, the pre-stretch and the nature of the compliant electrodes on the permittivity. These analytic equations and the electrical breakdown field were embedded in a thermodynamic model making it possible to define new limits of operation closer to the real use of these elastomers for energy harvesting applications.

Vu-Cong, T.; Jean-Mistral, C.; Sylvestre, A.

2013-04-01

83

Effect of Space Charge on Electric Breakdown of Sulfur Hexafluoride in Nonuniform Fields  

Microsoft Academic Search

In a nonuniform field, the positive direct and 60-cycle breakdown voltages of sulfur hexafluoride (SF6) as a function of pressure pass through a pronounced maximum. In the region of this maximum, corona is present at a much lower voltage than the breakdown voltage, and the impulse ratio may be less than one. In fact, the positive impulse, i.e., 1½x40-¿sec (microsecond),

Daniel Berg

1958-01-01

84

Computational Modeling of High Pressure Gas Breakdown and Streamer Formation in External Electric Fields  

Microsoft Academic Search

Summary form only given. The development of new computational models of gas breakdown for use in particle-in-cell (PIC) codes is described. These modeling efforts include fundamental processes associated with the breakdown of high pressure gases and represent key first steps in comprehensive studies of the physics of high-pressure gas switches. Two computational algorithms are described; a Monte Carlo type collision

D. V. Rose; D. R. Welch; C. Thoma; L. K. Warne; R. Jorgenson

2007-01-01

85

Electrical resistance characteristics of starch foams  

Microsoft Academic Search

The insulative character of expanded polystyrene loose-fill packing material supports the immobile triboelectric charge on its surface, causing static cling. One beneficial property of starch-based loose-fill is its antistatic behavior, which prevents the buildup of electrostatic charges on the foam surface, resulting in no static cling. This investigation explores the electrical resistance characteristics of plasticized starch materials such as commercial

Paul D. Tatarka

1996-01-01

86

Electric field enhancement due to a saw-tooth asperity in a channel and implications on microscale gas breakdown  

NASA Astrophysics Data System (ADS)

The electric field enhancement due to an isolated saw-tooth asperity in an infinite channel is considered with the goal of providing some inputs to the choice of field enhancement factors used to describe microscale gas breakdown. The Schwarz–Christoffel transformation is used to map the interior of the channel to the upper half of the transformed plane. The expression for the electric field in the transformed plane is then used to determine the electric field distribution in the channel as well as field enhancement near the asperity. The effective field enhancement factor is determined and its dependence on operating and geometrical parameters is studied. While the effective field enhancement factor depends only weakly on the height of the asperity in comparison to the channel, it is influenced significantly by the base angles of the asperity. Due to the strong dependence of field emission current density on electric field, the effective field enhancement factor (?eff) is shown to vary rapidly with the applied electric field irrespective of the geometrical parameters. This variation is included in the analysis of microscale gas breakdown and compared with results obtained using a constant ?eff as is done traditionally. Even though results for a varying ?eff may be approximately reproduced using an equivalent constant ?eff independent of E-field, it might be important for a range of operating conditions. This is confirmed by extracting ?eff from experimental data for breakdown in argon microgaps with plane-parallel cathodes and comparing its dependence on the E-field. While the use of two-dimensional asperities is shown to be a minor disadvantage of the proposed approach in its current form, it can potentially help in developing predictive capabilities as opposed to treating ?eff as a curve-fitting parameter.

Venkattraman, Ayyaswamy

2014-10-01

87

TDDB characteristic and breakdown mechanism of ultra-thin SiO2/HfO2 bilayer gate dielectrics  

NASA Astrophysics Data System (ADS)

The characteristics of TDDB (time-dependent dielectric breakdown) and SILC (stress-induced leakage current) for an ultra-thin SiO2/HfO2 gate dielectric stack are studied. The EOT (equivalent-oxide-thickness) of the gate stack (Si/SiO2/HfO2/TiN/TiAl/TiN/W) is 0.91 nm. The field acceleration factor extracted in TDDB experiments is 1.59 s·cm/MV, and the maximum voltage is 1.06 V when the devices operate at 125 °C for ten years. A detailed study on the defect generation mechanism induced by SILC is presented to deeply understand the breakdown behavior. The trap energy levels can be calculated by the SILC peaks: one SILC peak is most likely to be caused by the neutral oxygen vacancy in the HfO2 bulk layer at 0.51 eV below the Si conduction band minimum; another SILC peak is induced by the interface traps, which are aligned with the silicon conduction band edge. Furthermore, the great difference between the two SILC peaks demonstrates that the degeneration of the high-k layer dominates the breakdown behavior of the extremely thin gate dielectric.

Fenfen, Tao; Hong, Yang; Bo, Tang; Zhaoyun, Tang; Yefeng, Xu; Jing, Xu; Qingpu, Wang; Jiang, Yan

2014-06-01

88

Influence of inert gas addition on electric breakdown using dielectric barrier discharge in oxygen  

NASA Astrophysics Data System (ADS)

This paper studies the influence of inert gas additions He, Ar, Kr and Xe on breakdown voltage within dielectric barrier discharge reactor with oxygen feed gas. The density-normalized effective ionization coefficients ?eff/N are calculated for inert gas/O2 mixtures, the critical reduced field E/Ncr is obtained where the electron ionization exactly balances the attachment. Adding inert gases would lead to the decreasing critical reduced field strength E/Ncr due to the enhancement of effective ionization coefficient. In addition, inert gas additions have shown to reduce the breakdown voltage. Moreover the numerical breakdown voltage values and the experimental data are plotted for the sake of comparison and results show that calculated results are in agreement with the experimental values. Parametric study offers substantial insight in plasma physics, as well as in ozone generation applications.

Wei, Lin-Sheng; Yuan, Ding-Kun; Zhang, Ya-Fang; Hu, Zhao-Ji; Dong, Guo-Pan

2014-07-01

89

Enhanced electric breakdown field of CaCu3Ti4O12 ceramics: tuning of grain boundary by a secondary phase  

NASA Astrophysics Data System (ADS)

The electric breakdown field of CaCu3Ti4O12 ceramics has been enhanced by one order, i.e. from the conventional 1.0-2.0 kV cm-1 to 21 kV cm-1. Such great enhancement, associated with lower and relatively flat dielectric loss at low frequency, has arisen from optimum Al2O3 addition and sintering process. It is indicated that the addition of Al2O3 can affect the grain growth and the grain boundary characteristics via the distribution of a secondary phase of CuAl2O4, which is confirmed by x-ray diffraction and electron dispersive spectroscopy. The performance of grain boundary can be described well by the Schottky barrier model. It is found that the activation energy of hopping conduction at grain boundary is increased from 0.60 to 0.81 eV due to the secondary phase, which consequently leads to enhanced breakdown field.

Li, Jianying; Jia, Ran; Tang, Xian; Zhao, Xuetong; Li, Shengtao

2013-08-01

90

On electric field induced breakdown of passive films and the mechanism of pitting corrosion  

Microsoft Academic Search

Scanning tunneling microscopy reveals that microscopic roughness inherently exists at the smoothest of metal surfaces. Mathematical modeling indicates that the passive film on the concave region of the surface is subject to higher-than-average electrostatic pressure and is, therefore, a preferred site for passive film rupture and micro pit formation. The model includes the role of Cl⁻ ion in the breakdown;

Yuan Xu; Minghua Wang; H. W. Pickering

1993-01-01

91

On Preliminary Breakdown  

NASA Astrophysics Data System (ADS)

The preliminary breakdown phase of a negative cloud-to-ground lightning flash was observed in detail. Observations were made with a Photron SA1.1 high-speed video camera operating at 9,000 frames per second, fast optical sensors, a flat-plate electric field antenna covering the SLF to MF band, and VHF and UHF radio receivers with bandwidths of 20 MHz. Bright stepwise extensions of a negative leader were observed at an altitude of 8 km during the first few milliseconds of the flash, and were coincident with bipolar electric field pulses called 'characteristic pulses'. The 2-D step lengths of the preliminary processes were in excess of 100 meters, with some 2-D step lengths in excess of 200 meters. Smaller and shorter unipolar electric field pulses were superposed onto the bipolar electric field pulses, and were coincident with VHF and UHF radio pulses. After a few milliseconds, the emerging negative stepped leader system showed a marked decrease in luminosity, step length, and propagation velocity. Details of these events will be discussed, including the possibility that the preliminary breakdown phase consists not of a single developing lightning leader system, but of multiple smaller lightning leader systems that eventually join together into a single system.

Beasley, W. H.; Petersen, D.

2013-12-01

92

The influence of the breakdown electric field in the configuration of lightning corona sheath on charge distribution in the channel  

NASA Astrophysics Data System (ADS)

A model of corona sheath that surrounds the thin core of the lightning channel has been investigated by using a generalized traveling current source return stroke model. The lightning channel is modeled by a charged corona sheath that stretches around a highly conductive central core through which the main current flows. The channel core with the negatively charged outer channel sheath forms a strong electric field, with an overall radial orientation. The return stroke process is modeled as the negative leader charge in the corona sheath being discharged by the positive charge coming from the channel core. Expressions that describe how the corona sheath radius evolves during the return stroke are obtained from the corona sheath model, which predicts charge motion within the sheath. The corona sheath model, set forth by Maslowski and Rakov (2006), Tausanovic et al. (2010), Marjanovic and Cvetic (2009), Cvetic et al. (2011) and Cvetic et al. (2012), divides the sheath onto three zones: zone 1 (surrounding the channel core with net positive charge), zone 2 (surrounding zone 1 with negative charge) and zone 3 (the outer zone, representing uncharged virgin air). In the present study, we have assumed a constant electric field inside zone 1, as suggested by experimental research of corona discharges in coaxial geometry conducted by Cooray (2000). The present investigation builds upon previous studies by Tausanovic et al. (2010) and Cvetic et al. (2012) in several ways. The value of the breakdown electric field has been varied for probing its effect on channel charge distribution prior and during the return stroke. With the aim of investigating initial space charge distribution along the channel, total electric field at the outer surface of the channel corona sheath, just before the return stroke, is calculated and compared for various return stroke models. A self-consistent algorithm is applied to the generalized traveling current source return stroke model, so that the boundary condition for total electric field is fulfilled. The new density of space charge and the new radius of channel corona envelope, immediately before the return stroke stage, are calculated. The obtained results indicate a strong dependence of channel charge distribution on the breakdown electric field value. Among the compared return stroke models, transmission-line-type models have exhibited a good agreement with the predictions of the Gauss' law regarding total breakdown electric field on the corona sheath's outer surface. The generalized lightning traveling current source return stroke model gives similar results if the adjustment of the space charge density inside the corona sheath is performed.

Ignjatovic, Milan; Cvetic, Jovan; Heidler, Fridolin; Markovic, Slavoljub; Djuric, Radivoje

2014-11-01

93

DC conduction and breakdown characteristics of Al2O3/cross-linked polyethylene nanocomposites for high voltage direct current transmission cable insulation  

NASA Astrophysics Data System (ADS)

We have discussed a cross-linked polyethylene (XLPE) nanocomposite insulating material that is able to DC voltage applications. Nanocomposites, which are composed in polymer matrix mixed with nano-fillers, have received considerable attention because of their potential benefits as dielectrics. The nano-sized alumina oxide (Al2O3)/XLPE nanocomposite was prepared, and three kinds of test, such as DC breakdown, DC polarity reversal breakdown, and volume resistivity were performed. By the addition of nano-sized Al2O3 filler, both the DC breakdown strength and the volume resistivity of XLPE were increased. A little homogeneous space charge was observed in Al2O3/XLPE nanocomposite material in the vicinity of electrode through the polarity reversal breakdown test. From these results, it is thought that the addition of Al2O3 nano-filler is effective for the improvement of DC electrical insulating properties of XLPE.

Park, Yong-Jun; Kwon, Jung-Hun; Sim, Jae-Yong; Hwang, Ju-Na; Seo, Cheong-Won; Kim, Ji-Ho; Lim, Kee-Joe

2014-08-01

94

Note: Tesla based pulse generator for electrical breakdown study of liquid dielectrics  

NASA Astrophysics Data System (ADS)

In the process of studying charge holding capability and delay time for breakdown in liquids under nanosecond (ns) time scales, a Tesla based pulse generator has been developed. Pulse generator is a combination of Tesla transformer, pulse forming line, a fast closing switch, and test chamber. Use of Tesla transformer over conventional Marx generators makes the pulse generator very compact, cost effective, and requires less maintenance. The system has been designed and developed to deliver maximum output voltage of 300 kV and rise time of the order of tens of nanoseconds. The paper deals with the system design parameters, breakdown test procedure, and various experimental results. To validate the pulse generator performance, experimental results have been compared with PSPICE simulation software and are in good agreement with simulation results.

Veda Prakash, G.; Kumar, R.; Patel, J.; Saurabh, K.; Shyam, A.

2013-12-01

95

Fractal multiplication of electron avalanches and streamers: new mechanism of electrical breakdown?  

NASA Astrophysics Data System (ADS)

Long-lasting problems concerning peculiar statistical behaviour of high populated electron avalanches have been analysed. These avalanches are precursors of streamer breakdown in gases. The present streamer theory fails in explaining severe systematic deviations from the Furry statistics that is believed to be a governing statistical law. Such a deviated behaviour of high populated avalanches seems to be a consequence of a special pre-breakdown mechanism that is rather different from that known so far in discharge physics. This analysis tends towards formulating a modified theoretical concept supplementing the streamer theory by a new statistical view of pre-streamer states. The correctness of the concept is corroborated by a series of experiments.

Ficker, T.

2007-12-01

96

Electric breakdown and ionization detection in normal liquid and superfluid 4He for the SNA nEDM experiment  

NASA Astrophysics Data System (ADS)

A new experiment to search for the neutron electric dipole moment (nEDM) is under construction at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. The SNS nEDM experiment is a national collaboration spanning over 20 universities and laboratories with more than 100 physicists and engineers contributing to the research and development. The search for a nEDM is a precision test of time reversal symmetry in particle physics, in the absence of a discovery, the SNS nEDM experiment seeks to improve the present limit on the nEDM value by two orders of magnitude. A non-zero value of the nEDM would help to explain the asym- metry between matter and anti-matter in the universe by providing an additional source of charge conjugation and parity symmetry violation, a necessary ingredient in the theory of baryogenesis in the early universe. The nEDM experiment will measure the Larmor precession frequency of neutrons by detecting scintillation from neutron capture by a dilute concentration of 3He inside a bath of superfluid 4He. Neutron capture by 3He is spin-dependent and the magnetic moments of the neutron and the 3He nucleus are comparable. A direct measurement of the precession frequency of polarized 3He and scintillation from neutron capture allows for the relative precession frequencies of 3He and the neutron to be determined. The experiment will then look for changes in the relative precession of 3He and neutrons under the influence of strong electric fields. 3He has negligible EDM and therefore any deviation due to an applied electric field would be from a nEDM. The nEDM experiment will need to apply strong electric fields inside superfluid (SF) 4He and it was necessary to investigate the ability of SF 4He to sustain electric fields. An experiment to study electric breakdown in superfluid 4He was constructed at the Indiana University Center for Exploration of Energy and Matter (CEEM). The experiment studied the electric breakdown behavior of liquid Helium throughout the pressure-temperature phase space, between 1 bar and the saturation curve and between 4.2 K and 1.7 K. A new breakdown hysteresis in liquid helium was discovered and is attributed to the suppression of heterogeneous nucleation sites inside the liquid. A phenomenological model involving the Townsend breakdown mechanism and Paschen's Law in liquid helium is proposed. In addition, the many challenges faced by efficient scintillation detection in the cryogenic environment of the nEDM experiment motivated additional studies at CEEM. To test the effect of an electric field on scintillation in superfluid, a SF test cell was constructed inside a dilution refrigerator and it was found that the scintil- lation intensity from a 241Am source in the cell, is reduced at high electric fields. Alternatives to scintillation detection for the nEDM experiment were also explored and the test cell was reconfigured to operate as a superfluid ionization chamber. The superfluid ionization chamber was tested with 241Am in pulse mode and current mode configurations. While the pulse mode in superfluid, which relies on the drift velocity of charges, is hindered by quasi-particle excitations in superfluid, results of current mode measurements appear promising. To further explore the prospect of cryogenic ionization detection, a detector cryo-stat capable of detecting neutrons using a 10B converter was also constructed at CEEM and tested at the Indiana University Low Energy Neutron Source (LENS). The neutron detector cryostat has the benefit of being able to modulate the ioniza- tion source which was not possible with the superfluid ionization chamber. Tests with argon gas led to the development of more efficient boron targets. The cryogenic test of ionization detection in current mode will be discussed.

Karcz, Maciej

97

High-Voltage Closing Switches Using Vacuum Electric Breakdown for Pulsed-Power Applications  

Microsoft Academic Search

In our previous research, a high-voltage vacuum closing switch has been proposed to synchronize the output pulses delivered from multiple parallel plasma opening switch modules to the load in a scheme of power conditioning of a generator of high-power nanosecond pulses. However, the breakdown voltage for each stage of the closing switch has to be increased to 150-300 kV to

Georgy I. Dolgachev; Andrey G. Ushakov

2007-01-01

98

Electrical conduction and dielectric breakdown in aluminum oxide insulators on silicon  

Microsoft Academic Search

Leakage currents and dielectric breakdown were studied in MIS capacitors of metal-aluminum oxide-silicon. The aluminum oxide was produced by thermally oxidizing AlN at 800-1160°C under dry O2 conditions. The AlN films were deposited by RF magnetron sputtering on p-type Si (100) substrates. Thermal oxidation produced Al 2O3 with a thickness and structure that depended on the process time and temperature.

James Kolodzey; Enam Ahmed Chowdhury; Thomas N. Adam; Guohua Qui; I. Rau; J. O. Olowolafe; J. S. Suehle; Yuan Chen

2000-01-01

99

Measurements of the volt-ampere characteristics and the breakdown voltages of direct-current helium and hydrogen discharges in microgaps  

SciTech Connect

The discharge phenomena for micro meter gap sizes include many interesting problems from engineering and physical perspectives. In this paper, the authors deal with the experimental and theoretical results of the breakdown voltage and current-voltage characteristics of the direct-current helium and hydrogen discharges. The measurements were performed at a constant pressure of around one atmosphere, while varying the gap size between two parallel plane tungsten electrodes between 1??m and 100??m. From the measured breakdown voltage curves, the effective yields and the ionization coefficients were derived for both gases. Present data for the ionization coefficients correlate with the data obtained for the breakdown voltage curves measured for fixed 100??m interelectrode separation. The current-voltage characteristics were plotted for the various gap sizes illustrating the role of the field emission effects in the microgaps. Based on the Fowler-Nordheim theory, the enhancement factors were determined. The gap spacing dependence of the field emission current can be explained by the introduction of two ideas, the first being a space charge effect by emitted electrons, and the second a change in the breakdown mechanism. Experimental results, presented here, demonstrate that Townsend phenomenology breaks down when field emission becomes the key mechanism affecting the breakdown and deforming the left hand side of the breakdown voltage curves.

Klas, M.; Matej?ik, Š. [Department of Experimental Physics, Comenius University, Mlynskadolina F2, 84248 Bratislava (Slovakia); Radjenovi?, B.; Radmilovi?-Radjenovi?, M. [Institute of Physics, University of Belgrade, P.O. Box 57, 11080 Belgrade (Serbia)

2014-10-15

100

Discharge Characteristics of SF6 in a Non-Uniform Electric Field Under Repetitive Nanosecond Pulses  

NASA Astrophysics Data System (ADS)

The characteristics of high pressure sulphur hexafluoride (SF6) discharges in a highly non-uniform electric field under repetitive nanosecond pulses are investigated in this paper. The influencing factors on discharge process, such as gas pressure, pulse repetition frequency (PRF), and number of applied pulses, are analyzed. Experimental results show that the corona intensity weakens with the increase of gas pressure and strengthens with the increase of PRF or number of applied pulses. Spark discharge images suggest that a shorter and thicker discharge plasma channel will lead to a larger discharge current. The number of applied pulses to breakdown descends with the increase of PRF and ascends with the rise of gas pressure. The reduced electric field (E/p) decreases with the increase of PRF in all circumstances. The experimental results provide significant supplements to the dielectric characteristics of strongly electronegative gases under repetitive nanosecond pulses.

Ran, Huijuan; Wang, Lei; Wang, Jue; Wang, Tao; Yan, Ping

2014-05-01

101

Impact of Organic Contaminants from the Environment on Electrical Characteristics of Thin Gate Oxides  

NASA Astrophysics Data System (ADS)

We have investigated the impact of organic contaminants from the environment on the electrical characteristics of gate oxides by evaluation of electrical characteristics of metal oxide semiconductor (MOS) capacitors and gas chromatography-mass spectrometry following thermodesorption (TD-GC/MS) analysis of organic species adsorbed on silicon surfaces. It was found that organic contaminants from the environment adsorbed on silicon surfaces deteriorate gate oxide reliability; the increase in both breakdown and infant failure of gate oxides is enhanced by organic contaminants from the environment and depends on gate oxide thickness and the kind of silicon substrate. These results are useful for clarifying the deterioration mechanism of gate oxides caused by organic contaminants on silicon surfaces.

Ogata, Tamotsu; Ban, Cozy; Ueyama, Akemi; Muranaka, Seiji; Hayashi, Tomohiko; Kobayashi, Kiyoteru; Kobayashi, Junji; Kurokawa, Hiroshi; Ohno, Yoshikazu; Hirayama, Makoto

1998-05-01

102

Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission  

PubMed Central

We demonstrate the application of non-gated laser induced breakdown spectroscopy (LIBS) for characterization and classification of organic materials with similar chemical composition. While use of such a system introduces substantive continuum background in the spectral dataset, we show that appropriate treatment of the continuum and characteristic emission results in accurate discrimination of pharmaceutical formulations of similar stoichiometry. Specifically, our results suggest that near-perfect classification can be obtained by employing suitable multivariate analysis on the acquired spectra, without prior removal of the continuum background. Indeed, we conjecture that pre-processing in the form of background removal may introduce spurious features in the signal. Our findings in this report significantly advance the prior results in time-integrated LIBS application and suggest the possibility of a portable, non-gated LIBS system as a process analytical tool, given its simple instrumentation needs, real-time capability and lack of sample preparation requirements. PMID:25084522

Dasari, Ramachandra Rao; Barman, Ishan; Gundawar, Manoj Kumar

2014-01-01

103

AN APPROACH FOR DESCRIBING ELECTRICAL CHARACTERISTICS OF PRECIPITATED DUST LAYERS  

EPA Science Inventory

The paper proposes an approach for describing the electrical characteristics of electrostatically precipitated dust layers. It describes the macroscopic electrical properties of the dust layer, by couplinag the current transport equation and Poisson's Equation. It attributes the ...

104

Mass analysis of neutral particles and ions released during electrical breakdowns on spacecraft surfaces  

NASA Technical Reports Server (NTRS)

A specialized spectrometer was designed and developed to measure the mass and velocity distributions of neutral particles (molecules and molecular clusters) released from metal-backed Teflon and Kapton films. Promising results were obtained with an insulation breakdown initiation system based on a moveable contact touching the insulated surfaces. A variable energy, high voltage pulse is applied to the contact. The resulting surface damage sites can be made similar in size and shape to those produced by a high voltage electron beam system operating at similar discharge energies. The point discharge apparatus was used for final development of several high speed recording systems and for measurements of the composition of the materials given off by the discharge. Results with this apparatus show evolution of large amounts of fluorocarbon fragments from discharge through Teflon FEP, while discharges through Kapton produce mainly very light hydrocarbon fragments at masses below about 80 a.m.u.

Kendall, B. R. F.

1983-01-01

105

Projected characteristics of hybrid-electric cars  

Microsoft Academic Search

Performance and costs are projected for future hybrid-electric cars in which a small internal-combustion engine (ICE) is added to the basic electric propulsion system to permit unlimited highway range. In most driving these hybrids would be operated in the all-electric mode without use of the ICE, thus providing most of the benefits of electric cars without their range limitation. The

W. F. Hamilton; R. L. Curtis

1979-01-01

106

Study on the Pulsed Flashover Characteristics of Solid-Solid Interface in Electrical Devices Poured by Epoxy Resin  

NASA Astrophysics Data System (ADS)

In electrical devices poured by epoxy resin, there are a lot of interfaces between epoxy resin and other solid dielectrics, i.e. solid-solid interfaces. Experiments were carried out to study the flashover characteristics of two typical solid-solid interfaces (epoxy-ceramic and epoxy-PMMA) under steep high-voltage impulse for different electrode systems (coaxial electrodes and finger electrodes) and different types of epoxy resin (neat epoxy resin, polyether modified epoxy resin and polyurethane modified epoxy resin). Results showed that, the flashover of solid-solid interface is similar to the breakdown of solid dielectric, and there are unrecoverable carbonated tracks after flashover. Under the same distance of electrodes, the electric stress of coaxial electrodes is lower than that of finger electrodes; and after the flashover, there are more severe breakdown and larger enhanced surface conductivity at interface for coaxial electrodes, as compared with the case of finger electrode. The dielectric properties are also discussed.

Li, Manping; Wu, Kai; Yang, Zhanping; Ding, Man; Liu, Xin; Cheng, Yonghong

2014-09-01

107

Structural properties and electrical characteristics of high- k Dy 2O 3 gate dielectrics  

NASA Astrophysics Data System (ADS)

This paper describes the structural properties and electrical characteristics of thin Dy2O3 dielectrics deposited on silicon substrates by means of reactive sputtering. The structural and morphological features of these films after postdeposition annealing were studied by X-ray diffraction and X-ray photoelectron spectroscopy. It is found that Dy2O3 dielectrics annealed at 700 °C exhibit a thinner capacitance equivalent thickness and better electrical properties, including the interface trap density and the hysteresis in the capacitance-voltage curves. Under constant current stress, the Weibull slope of the charge-to-breakdown of the 700 °C-annealed films is about 1.6. These results are attributed to the formation of well-crystallized Dy2O3 structure and the reduction of the interfacial SiO2 layer.

Pan, Tung-Ming; Chang, Wei-Tsung; Chiu, Fu-Chien

2011-02-01

108

Impact of thermal boundary conductances on power dissipation and electrical breakdown of carbon nanotube network transistors  

NASA Astrophysics Data System (ADS)

We study the impact of thermal boundary conductance (TBC) at carbon nanotube (CNT)-substrate interfaces and CNT junctions on power dissipation and breakdown in CNT network based thin film transistors (CN-TFTs). Comparison of our results from an electro-thermal transport model of CN-TFTs to experimental measurements of power dissipation and temperature profiles allows us to estimate the average CNT-SiO2 TBC as g ˜ 0.16 Wm-1 K-1 and the TBC at CNT junctions as GC ˜ 2.4 pWK-1. We find the peak power dissipation in CN-TFTs is more strongly correlated to the TBC of the CNT-substrate interface than to the TBC at CNT junctions. Molecular dynamics simulations of crossed CNT junctions also reveal that the top CNT is buckled over ˜30 nm lengths, losing direct contact with the substrate and creating highly localized hot-spots. Our results provide new insights into CNT network properties which can be engineered to enhance performance of CN-TFTs for macro and flexible electronics applications.

Prakash Gupta, Man; Chen, Liang; Estrada, David; Behnam, Ashkan; Pop, Eric; Kumar, Satish

2012-12-01

109

Nanostructured Carbons and Their Electrical Transport Characteristics  

NASA Astrophysics Data System (ADS)

This thesis is about the fabrication, characterization, device preparation and electrical transport properties measurements of three types of nanostructured carbons. In particular, the foci are on the 4 Angstrom carbon nanotubes embedded in zeolite crystals, bundles of double-wall carbon nanotubes, and disordered graphene. The 4 Angstrom single-wall carbon nanotubes (SWCNTs) embedded in zeolite crystals are fabricated by a new heating process which introduces ethylene gas as the carbon source. Raman characterization indicates the sample quality to be improved compared to that fabricated by the original heating process that involved converting the precursor tripropylamine. Transport measurements carried out on these newly fabricated 4 Angstrom SWCNT samples show two types of superconducting resistive transitions. The first type is one-dimensional (1D) crossover to three-dimensional (3D) superconducting transition, which was observed to initiate at 15 K, followed by a sharp, order of magnitude resistance drop at 7.5 K. The sharp transition exhibits anisotropic magnetic field dependence. And differential resistance versus current curves indicate that the establishment of coherence proceeded in stages as the temperature is lowered below 15K. In particular, the sharp resistance drop and its attendant nonlinear IV characteristics are consistent with the manifestations of a Berezinskii-Kosterlitz-Thouless (BKT) transition that establishes a quasi-long range order in the plane transverse to the c-axis of the nanotubes. The second type is quasi 1D superconducting transition, which was also observed to initiate at 15 K. But the resistance drop exhibits a smooth feature and magnetic field independence up to 11 Tesla as temperature decreases. And differential resistance increases smoothly with bias current. Specific heat and new Meissner effect measurements carried out by Prof. Rolf Lortz's group provide strong support of the superconductivity in 4 Angstrom CNTs, with detailed features that are consistent with the transport results. The double-wall carbon nanotubes (DWCNTs) are characterized by HRTEM and Raman spectroscopy. The diameters of the outer and inner tubes are measured to be around 1.54 nm and 0.83 nm, respectively. The DWCNTs are packed closely together in each bundle, forming a nearly crystal-like structure. Resonant Raman measurements reveal the chirality information of the inner and outer tubes. By using the electron-beam lithography (EBL) techniques, both single DWCNT bundle and multiple DWCNT bundles were fabricated into devices for transport measurements. Clear evidences, comprising a resistance drop as a function of temperature, magnetoresistance and a differential resistance signature of the supercurrent, indicate a range of superconducting transition temperatures within 3-18K, with a peak in the occurrences around 5-7 K. Raman characterization for one of the selective samples shows the inner tube to be metallic and the outer tube to be semiconducting in character. A broad superconducting anomaly is also observed in specific heat data of a bulk DWCNT sample, which yields a Tc distribution that correlates well with the distribution obtained from the electrical data. Pristine graphene can have a high mobility that ensures ballistic transport on submicron distances. However, the presence of disorder would limit the carrier mean free path and prevent ballistic transport. Two types of disordered graphene were fabricated and studied. One is substitutionally boron-doped grapheme, and the other is nanostructured by plasma etching. They exhibit large negative magnetoresistance behavior that differs from the pristine graphene. The preliminary graphene work presented in this thesis is for the purpose of setting the stage for the experiments to be performed in the near future.

Shi, Wu

110

Electric field mediated breakdown of thin liquid films separating microscopic emulsion droplets  

NASA Astrophysics Data System (ADS)

The authors present a microfluidic technique for electrically induced breakup of thin films formed between microscopic emulsion droplets. The method involves creating a stationary film at the intersection of two microchannels etched onto a glass substrate. After stabilizing the film, a ramped potential is applied across it. The electrical stresses developed at the film interfaces lead to its rupture above a threshold potential. The potential difference at which the film ruptures assesses the film stability. This approach is employed to demonstrate how surfactant (lecithin) adsorption imparts stability to an ultrathin oil film formed between two water droplets.

Mostowfi, Farshid; Khristov, Khristo; Czarnecki, Jan; Masliyah, Jacob; Bhattacharjee, Subir

2007-04-01

111

Electricity future market efficiency testing: the characteristics of electricity prices  

Microsoft Academic Search

The under going rapid world wide deregulation of electricity market leading to more competition, increased volatility in energy prices and exposing participants to potentially much greater risks. Along with the market deregulation, a primary derivative market has been established, within the derivative market, long and short term futures and options are being traded. The purpose of establishing the financial market

Zhe Lu; ZhaoYang Dong

2005-01-01

112

Non-Gated Laser Induced Breakdown Spectroscopy Provides a Powerful Segmentation Tool on Concomitant Treatment of Characteristic and Continuum Emission  

E-print Network

We demonstrate the application of non-gated laser induced breakdown spectroscopy (LIBS) for characterization and classification of organic materials with similar chemical composition. While use of such a system introduces ...

Myakalwar, Ashwin Kumar

113

Electrical characteristics of non-rectangular gate and transitional MOSFETS  

E-print Network

ELECTRICAL CHARACTERISTICS OF NON-RECTANGULAR GATE AND TRANSITIONAL MOSFETS A Thesis by PATRICE GRIGNOUX Submitted to the Graduate College of Texas A)M University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... August 1981 Major Subject: Electrical Engineering ELECIRICAL CHARACTERISTICS OF NON-RECTANGULAR GATE AND TRANSITIONAL MOSFETS A Thesis PATRICE GRIGNOUX Approved as to style and content by: (Chairman of Committee) (Member) (Member) (Member) (He...

Grignoux, Patrice

2012-06-07

114

The Effect of Pre-Ionization Inhomogeneities on the Dynamics of a Subnanosecond Pulsed Electrical Breakdown in Gas Gaps1  

Microsoft Academic Search

The initiation and the development of a breakdown of highly overvoltaged gas gaps by voltage pulses having the rise time of 1 ns or shorter are studied experimentally and in theoreti- cal terms. The study revealed that ionization proc- esses leading to the breakdown start in the gas vol- ume and not from the surface of the electrodes. The gap

S. N. Ivanov; V. V. Lisenkov; V. G. Shpak

115

Numerical characterization of local electrical breakdown in sub-micrometer metallized film capacitors  

NASA Astrophysics Data System (ADS)

In metallized film capacitors, there exists an air gap of about 0.2 ?m between the films, with a pressure ranging generally from 1–30 atm. Because of the created potential difference between the two films, a microdischarge is formed in this gap. In this paper, we use an implicit particle-in-cell Monte Carlo collision simulation method to study the discharge properties in this direct-current microdischarge with 0.2 ?m gap in a range of different voltages and pressures. The discharge process is significantly different from a conventional high pressure discharge. Indeed, the high electric field due to the small gap sustains the discharge by field emission. At low applied voltage (?15 V), only the electrons are generated by field emission, while both electrons and ions are generated as a stable glow discharge at medium applied voltage (?50 V). At still higher applied voltage (?100 V), the number of electrons and ions rapidly multiplies, the electric field reverses, and the discharge changes from a glow to an arc regime.

Jiang, Wei; Zhang, Ya; Bogaerts, Annemie

2014-11-01

116

Layer-by-Layer Dielectric Breakdown of Hexagonal Boron Nitride.  

PubMed

Hexagonal boron nitride (BN) is widely used as a substrate and gate insulator for two-dimensional (2D) electronic devices. The studies on insulating properties and electrical reliability of BN itself, however, are quite limited. Here, we report a systematic investigation of the dielectric breakdown characteristics of BN using conductive atomic force microscopy. The electric field strength was found to be ?12 MV/cm, which is comparable to that of conventional SiO2 oxides because of the covalent bonding nature of BN. After the hard dielectric breakdown, the BN fractured like a flower into equilateral triangle fragments. However, when the applied voltage was terminated precisely in the middle of the dielectric breakdown, the formation of a hole that did not penetrate to the bottom metal electrode was clearly observed. Subsequent I-V measurements of the hole indicated that the BN layer remaining in the hole was still electrically inactive. On the basis of these observations, layer-by-layer breakdown was confirmed for BN with regard to both physical fracture and electrical breakdown. Moreover, statistical analysis of the breakdown voltages using a Weibull plot suggested the anisotropic formation of defects. These results are unique to layered materials and unlike the behavior observed for conventional 3D amorphous oxides. PMID:25549251

Hattori, Yoshiaki; Taniguchi, Takashi; Watanabe, Kenji; Nagashio, Kosuke

2015-01-27

117

Correlation between field dependent electrical conduction and dielectric breakdown in a SiCOH based low-k (k = 2.0) dielectric  

NASA Astrophysics Data System (ADS)

The electrical conduction of a SiCOH based ultralow-k (k = 2.0) dielectric is investigated over an electric field range from 1.0 MV/cm to breakdown. Below 4.0 MV/cm, space-charge-limited current dominates the leakage. Above 5.0 MV/cm, a transition is found from trap-assisted Fowler-Nordheim (F-N) tunneling to F-N tunneling. It is hypothesized that under F-N tunneling stress, intrinsic material degradation causes positively charged defects generated in the dielectric. Moreover, this change of the dominant conduction path has a significant impact on the time dependent dielectric breakdown lifetime behavior.

Wu, C.; Li, Y.; Barbarin, Y.; Ciofi, I.; Croes, K.; Bömmels, J.; De Wolf, I.; T?kei, Zs.

2013-07-01

118

Electrical Discharge Machining (EDM) Characteristics Associated with Electrical Discharge Energy on Machining of Cemented Tungsten Carbide  

Microsoft Academic Search

In this investigation, cemented tungsten carbides graded K10 and P10 were machined by electrical discharge machining (EDM) using an electrolytic copper electrode. The machining parameters of EDM were varied to explore the effects of electrical discharge energy on the machining characteristics, such as material removal rate (MRR), electrode wear rate (EWR), and surface roughness. Moreover, the effects of the electrical

Yan-Cherng Lin; Yuan-Feng Chen; Ching-Tien Lin; Hsinn-Jyh Tzeng

2008-01-01

119

Confusion and its dynamics during device comprehension with breakdown scenarios.  

PubMed

The incidence and dynamics of confusion during complex learning and problem solving were investigated in an experiment where participants first read illustrated texts on everyday devices (e.g., an electric bell) followed by breakdown scenarios reflecting device malfunctions (e.g., "When a person rang the bell there was a short ding and then no sound was heard"). The breakdown scenarios were expected to trigger impasses and put participants in a state of cognitive disequilibrium where they would experience confusion and engage in effortful confusion resolution activities in order to restore equilibrium. The results confirmed that participants reported more confusion when presented with the breakdown scenarios compared to control scenarios that involved focusing on important device components in the absence of malfunctions. A second-by-second analysis of the dynamics of confusion yielded two characteristic trajectories that distinguished participants who partially resolved their confusion from those who remained confused. Participants who were successful in partial confusion resolution while processing the breakdowns outperformed their counterparts on knowledge assessments after controlling for scholastic aptitude, engagement, and frustration. This effect was amplified for those who were highly confused by the breakdowns. There was no direct breakdown vs. control effect on learning, but being actively engaged and partially resolving confusion during breakdown processing were positive predictors of increased learning with the breakdown compared to control scenarios. Implications of our findings for theories that highlight the role of impasses, cognitive disequilibrium, and confusion to learning are discussed. PMID:24973629

D'Mello, Sidney; Graesser, Art

2014-09-01

120

Electric field distribution characteristics of photoconductive antennas  

NASA Astrophysics Data System (ADS)

Photoexcitation of biased semiconductor photoconductive antennas by femtosecond pulses is the most common and convenient technique for generating strong terahertz (THz) pulses. In this paper, we use the three-dimensional (3D) finite-difference-time-domain (FDTD) to analyze electric field distribution of THz pulses in the near-field from a photoconductive antenna. The simulation is based on solving Maxwell's equations and the carrier rate equations simultaneously on realistic dipole antenna structures. The 3D FDTD simulation gives detailed features of THz electric field distribution in and out of the antenna. It is found that the difference of near-field distribution between the substrate and free space is considerably large. The fields of the alternating-current dipole exhibit an unsymmetrical distribution and a large deviation from those calculated using the simple Hertzian dipole theory. The magnitude of THz field in and out of the substrate attenuates rapidly while it holds the line in the gap center. The high-frequency components of THz radiation emission come only from the dipole antenna, while the low-frequency components are from both the center electrodes and coplanar stripline waveguide. This work can be used to optimize the design of antenna geometry and raise the radiation field power.

Zou, Sheng-Wu; Zhang, Tong-Yi

2012-10-01

121

RF breakdown effects in microwave power amplifiers  

E-print Network

Electrical stresses in the transistors of high-efficiency switching power amplifiers can lead to hot-electron-induced "breakdown" in these devices. This thesis explores issues related to breakdown in the Transcom TC2571 ...

Arumilli, Gautham Venkat

2007-01-01

122

Impulse breakdown delay in liquid dielectrics  

E-print Network

Theoretical images of streamers, revealing the mechanisms behind impulse breakdown in liquid dielectrics, are presented. Streamers lead to electrical breakdown by forming paths, capable of carrying large current amplitudes ...

Jadidian, Jouya

123

Analysis of electric vacuum characteristics of MCP  

NASA Astrophysics Data System (ADS)

In order to improve the electronic gain and luminance gain of low-light-level image intensifiers, microchannel plates(MCP) are adopted as the electron multiplier mechanism. According to the relevant experimental analysis, the resistance between channels is a limited value. Due to there are resistive coupling between any two adjacent channel of MCP, the electron transmission and the electron multiplication in a certain channel will be interfered by its adjacent channels, This phenomenon would affect the quality of image transmission and field of view of image intensifier. In low-light condition, the input current of MCP is small, the current gain of each channel is same, MCP has the area of linear current amplification and distortion-free image transmission. But when input current is large and close to saturation, lower current in channels has more current gain, leading to the contrast change of the image. This paper analyzes the transmission properties of electrons in the channels. It is proved that there is an electrical relationship between adjacent channels,throuht the circuit equations with relevant circuit parameters such as the resistance of secondary electron emission layer, resistance of resistive layer, the resistance between two adjacent channels, and so on. The analysis method and research results provide technical guidance for the improvement of electronic gain, luminance uniformity and preparation process of MCP.

Gao, Xiang; Shi, Feng; Cheng, Hong-chang; Yin, Lei; Miao, Zhuang; Cheng, Xing; Wang, Long; Niu, Sen

2014-09-01

124

Electrical properties and humidity sensor characteristics of lead hydroxyapatite material  

NASA Astrophysics Data System (ADS)

Crystalline lead hydroxyapatite is obtained by direct precipitation from aqueous solution, the method being easy, fast and reproducible. The synthesis route which does not involve sodium salts or sulfates makes the material suitable for applications in catalysis. The electrical characteristics of lead hydroxyapatite material treated at different temperatures, made us focus on the analysis of the influence of water vapors upon the electrical characteristics. Thus, the electrical response to humidity adsorptive processes of lead hydroxyapatite material suggested us to analyze the material characteristics in terms of its use as a humidity sensor. The hydrophilic properties of lead hydroxyapatite material are reflected especially in high sensitivity and reduced time of response of the humidity sensors but also in long time of recovery, which suggests that Pb10(PO4)6(OH)2 material can be used for humidity sensors specialized in monitoring fluctuating humidity environments.

Tudorache, Florin; Petrila, Iulian; Popa, Karin; Catargiu, Ana Maria

2014-06-01

125

Improvement of breakdown and current collapse characteristics of GaN HEMT with a polarization-graded AlGaN buffer  

NASA Astrophysics Data System (ADS)

A GaN HEMT with a polarization-graded AlGaN buffer is performed by two-dimensional analysis of drift-diffusion simulations. The bulk trap-induced current collapse of the proposed structure is effectively restrained in contrast to that of conventional HEMTs with a GaN or AlGaN buffer, resulting from the fact that the high and flat back-barrier altitude in the proposed structure prevents the two-dimensional electron gas (2DEG) from spilling over from the channel, with the reduction of hot carriers injecting into the buffer followed by trapping in deep acceptor-like levels. Simultaneously, the off-state breakdown voltage is remarkably enhanced, due to the strong electric breakdown field of the polarization-graded AlGaN buffer and the restraint of the buffer leakage current. In addition, the relationship between the off-state breakdown voltage and the thickness of the polarization-graded AlGaN buffer is analyzed.

Li, Chuanhao; Li, Zhonghui; Peng, Daqing; Ni, Jinyu; Pan, Lei; Zhang, Dongguo; Dong, Xun; Kong, Yuechan

2015-03-01

126

Statistics of electrical breakdown field in HfO2 and SiO2 films from millimeter to nanometer length scales  

NASA Astrophysics Data System (ADS)

The statistics of electrical breakdown field (Ebd) of HfO2 and SiO2 thin films has been evaluated over multiple length scales using macroscopic testing of standardized metal-oxide-semiconductor (TiN /SiO2/Si) and metal-insulator-metal (TiN/HfO2/TiN) capacitors (10-2mm2-10?m2 area) on a full 200mm wafer along with conductive-atomic-force microscopy. It is shown that Ebd follows the same Weibull distribution when the data are scaled using the testing area. This overall scaling suggests that the defect density is ˜1015cm-2 and Ebd is ˜40MV/cm for nanometer-length scales; as such, breakdown in these materials is most likely initiated by bond breaking rather than punctual defects.

Sire, Cédric; Blonkowski, Serge; Gordon, Michael J.; Baron, Thierry

2007-12-01

127

Influence of oxygen content on the structural and electrical characteristics of thin neodymium oxide gate dielectrics  

NASA Astrophysics Data System (ADS)

The structural properties and electrical characteristics of thin Nd2O3 gate oxides were deposited on silicon substrates by reactive rf sputtering. The structural and morphological features of these films were studied, as a function of the growth conditions (three various argon-to-oxygen flow ratios: 20/5, 15/10, and 12.5/12.5 and temperature from 600to800°C), by x-ray diffraction, atomic force microscopy, and x-ray photoelectron spectroscopy. It is found that Nd2O3 dielectrics with a 12.5/12.5 ratio condition annealed at 700°C exhibit a thinner capacitance equivalent thickness and excellent electrical properties, including the electric breakdown field, the interface trap density, the hysteresis, and frequency dispersion in the capacitance-voltage curves. This condition is suggested to the reduction of the interfacial SiO2 and silicate formation, and the small of surface roughness due to the optimization of oxygen in the metal oxide film.

Pan, Tung-Ming; Lee, Jian-Der; Yeh, Wen-Wei

2007-01-01

128

Gas breakdown driven by L band short-pulse high-power microwave  

NASA Astrophysics Data System (ADS)

High power microwave (HPM) driven gas breakdown is a major factor in limiting the radiation and transmission of HPM. A method that HPM driven gas breakdown could be obtained by changing the aperture of horn antenna is studied in this paper. Changing the effective aperture of horn antenna can adjust the electric field in near field zone, leading to gas breakdown. With this method, measurements of air and SF6 breakdowns are carried out on a magnetically insulated transmission-line oscillators, which is capable of generating HPM with pulse duration of 30 ns, and frequency of 1.74 GHz. The typical breakdown waveforms of air and SF6 are presented. Besides, the breakdown field strengths of the two gases are derived at different pressures. It is found that the effects of air and SF6 breakdown on the transmission of HPM are different: air breakdown mainly shortens the pulse width of HPM while SF6 breakdown mainly reduces the peak output power of HPM. The electric field threshold of SF6 is about 2.4 times larger than that of air. These differences suggest that gas properties have a great effect on the transmission characteristic of HPM in gases.

Yang, Yi-Ming; Yuan, Cheng-Wei; Qian, Bao-Liang

2012-12-01

129

A relationship between statistical time to breakdown distributions and pre-breakdown negative differential resistance at nanometric scale  

NASA Astrophysics Data System (ADS)

Using an ultra-high vacuum Conductive atomic force microscopy (C-AFM) current voltage, pre-breakdown negative differential resistance (NDR) characteristics are measured together with the time dependent dielectric breakdown (TDDB) distributions of Si/SiON (1.4 and 2.6 nm thick). Those experimental characteristics are systematically compared. The NDR effect is modelled by a conductive filament growth. It is showed that the Weibull TDDB statistic distribution scale factor is proportional to the growth rate of an individual filament and then has the same dependence on the electric field. The proportionality factor is a power law of the ratio between the surfaces of the CAFM tip and the filament's top. Moreover, it was found that, for the high fields used in those experiments, the TDDB acceleration factor as the growth rate characteristic is proportional to the Zener tunnelling probability. Those observations are discussed in the framework of possible breakdown or forming mechanism.

Foissac, R.; Blonkowski, S.; Kogelschatz, M.; Delcroix, P.

2014-07-01

130

Measuring Breakdown Voltage.  

ERIC Educational Resources Information Center

The article discusses an aspect of conductivity, one of the electrical properties subdivisions, and describes a tester that can be shop-built. Breakdown voltage of an insulation material is specifically examined. Test procedures, parts lists, diagrams, and test data form are included. (MF)

Auer, Herbert J.

1978-01-01

131

The electrical characteristics of silicon carbide alloyed with germanium  

E-print Network

The electrical characteristics of silicon carbide alloyed with germanium G. Katulkaa,* , K. Roea material for high power, high voltage applications, silicon carbide (SiC) would be more versatile without Ge. Other p-type substrates implanted with Ge that used chromium/nickel (Cr/Ni) metalization

Kolodzey, James

132

On the structure, interaction, and breakdown characteristics of slender wing vortices at subsonic, transonic, and supersonic speeds  

NASA Technical Reports Server (NTRS)

Slender wing vortex flows at subsonic, transonic, and supersonic speeds were investigated in a 6 x 6 ft wind tunnel. Test data obtained include off-body and surface flow visualizations, wing upper surface static pressure distributions, and six-component forces and moments. The results reveal the transition from the low-speed classical vortex regime to the transonic regime, beginning at a freestream Mach number of 0.60, where vortices coexist with shock waves. It is shown that the onset of core breakdown and the progression of core breakdown with the angle of attack were sensitive to the Mach number, and that the shock effects at transonic speeds were reduced by the interaction of the wing and the lead-edge extension (LEX) vortices. The vortex strengths and direct interaction of the wing and LEX cores (cores wrapping around each other) were found to diminish at transonic and supersonic speeds.

Erickson, Gary E.; Schreiner, John A.; Rogers, Lawrence W.

1989-01-01

133

Breakdown testing of wiring insulation  

NASA Technical Reports Server (NTRS)

The dielectric strength of potential wiring insulation, recommended by NASA Lewis Research Center to replace existing M81381 (polyimide), was evaluated at high temperature. Results, given in view-graph format, show that their is no dependence of breakdown strength on temperature for the constructions tested and that their was little effect of frequency on the breakdown characteristics.

Laghari, Javaid R.

1994-01-01

134

Repetitive Nanosecond-Pulse Breakdown in Tip–Plane Gaps of Air  

Microsoft Academic Search

Repetitive pulsed power is becoming an important area of high-power technology. Dielectric failure data concerning electrical insulation play a basic role, but breakdown has been inadequately studied for the repetitive nanosecond-pulse conditions. This paper is concerned with the breakdown characteristics of tip-plane gas gaps under repetitive burst conditions at variant repetition rates (rep-rates) and diverse gap distances. The relationship among

Tao Shao; Guangsheng Sun; Ping Yan; Shichang Zhang

2006-01-01

135

Electric discharge in the water: physics of formation and radiative characteristics.  

NASA Astrophysics Data System (ADS)

ELECTRIC DISCHARGE IN THE WATER: PHYSICS OF FORMATION AND RADIATIVE CHARACTERISTICS 2.10. Lighting plasmas. 2.26. Other plasma topics. A.M.Anpilov, E.M.Barkhudarov, Yu.N.Kozlov, I.A.Kossyi, V.P.Silakov and S.M.Temchin Two types of electric discharge in the water have been investigated: discharge between two electrodes and multielectrode gliding surface discharge. Results are presented from experimental studies of the prebreakdown phase of an electric discharge between the point (anode) and plane (cathode) electrodes immersed in the water with different initial conductivity. When a high-voltage pulse is applied, the induced conductivity is detected in the discharge gap. Its value is one order of magnitude higher than the initial one. It is shown that the induced conductivity increases almost linearly with initial conductivity. The induced conductivity correlates with the UV emission from the cathode surface. A qualitative analysis of the experimental results is performed. Investigations of a spectrum of radiation of discharge in water have been carried out. On the base of broadening and shifting of atomic hydrogen and oxygen lines electron density in a prebreakdown as well as breakdown stages has been determined. Results are presented from investigations of multispark electric discharge in water excited along multielectrode metal-dielectric systems with gas supply into the interelectrode gaps. The intensity distribution of discharge radiation in the region covering the biologically active soft UV (190 £l£430 nm) has been determined and the absolute number of quanta in this wavelength interval has been measured. The potentiality of the gliding surface discharge in water for its disinfection is analysed.

Anpilov, Andrei; Barkhudarov, Eduard; Kozlov, Yurii; Kossyi, Igor; Silakov, Valerii; Temchin, Savelii

2004-09-01

136

Breakdown of organic insulators  

NASA Astrophysics Data System (ADS)

Solar cells and their associated electrical interconnects and leads were encapsulated in transparent elastomeric materials. Their purpose in a photovoltaic module, one of the most important for these elastomeric encapsulation materials, is to function as electrical insulation. This includes internal insulation between adjacent solar cells, between other encapsulated electrical parts, and between the total internal electrical circuitry and external metal frames, grounded areas, and module surfaces. Catastrophic electrical breakdown of the encapsulant insulation materials or electrical current through these materials or module edges to external locations can lead to module failure and can create hazards to humans. Electrical insulation stability, advanced elastomeric encapsulation materials are developed which are intended to be intrinsically free of in-situ ionic impurities, have ultralow water absorption, be weather-stable (UV, oxygen), and have high mechanical flexibility. Efforts to develop a method of assessing the life potential of organic insulation materials in photovoltaic modules are described.

Cuddihy, E. F.

1983-11-01

137

Breakdown of organic insulators  

NASA Technical Reports Server (NTRS)

Solar cells and their associated electrical interconnects and leads were encapsulated in transparent elastomeric materials. Their purpose in a photovoltaic module, one of the most important for these elastomeric encapsulation materials, is to function as electrical insulation. This includes internal insulation between adjacent solar cells, between other encapsulated electrical parts, and between the total internal electrical circuitry and external metal frames, grounded areas, and module surfaces. Catastrophic electrical breakdown of the encapsulant insulation materials or electrical current through these materials or module edges to external locations can lead to module failure and can create hazards to humans. Electrical insulation stability, advanced elastomeric encapsulation materials are developed which are intended to be intrinsically free of in-situ ionic impurities, have ultralow water absorption, be weather-stable (UV, oxygen), and have high mechanical flexibility. Efforts to develop a method of assessing the life potential of organic insulation materials in photovoltaic modules are described.

Cuddihy, E. F.

1983-01-01

138

Task breakdown  

NASA Technical Reports Server (NTRS)

The topics concerning the Center for Space Construction (CSC) space construction breakdown structure are presented in viewgraph form. It is concluded that four components describe a task -- effecting, information gathering, analysis, and regulation; uncertainties effect the relative amount of information gathering and analysis that occurs; and that task timing requirements drive the 'location in time' of cognition.

Pavlich, Jane

1990-01-01

139

Dielectric breakdown of polymer films containing metal clusters  

SciTech Connect

Thin films of gold-containing plasma-polymerized tetrafluoroethylene were prepared in an rf glow discharge. The films thus obtained showed a wide range of conductivities from insulating ( rho>10/sup 16/ ..cap omega.. cm) to metallic ( rhoapprox.3 x 10/sup -6/ ..cap omega.. cm), depending on plasma conditions during synthesis. The synthesis of the polymer is described in detail since it presents several new aspects. The structure and composition of the films were investigated by x-ray photoelectron spectroscopy and transmission electron microscopy. Studies of current-voltage characteristics in the dielectric regime, i.e., below electrical percolation, show that the conduction is volume limited (Poole--Frenkel effect) in non-gold-containing films, and characterized by a bistable switching behavior for gold-rich films. Dielectric breakdown measurements were realized on self-healing metal-insulator-metal structures. The Weibull analysis of breakdown voltages and a statistical treatment of times to breakdown under constant stress give, respectively, the nominal breakdown field E/sub 0/ and the specific breakdown field E/sub c/. These two sets of data follow similar functional behavior as a function of metallic volume fraction in the films. Surprisingly, the breakdown-field values remain relativity high up to the percolation concentration.

Laurent, C.; Kay, E.; Souag, N.

1988-07-01

140

Quasi-breakdowns in ultrathin dielectrics  

NASA Astrophysics Data System (ADS)

In this paper, the quasi-breakdown is demonstrated to be a dominant failure mechanism in ultra-thin dielectrics with thicknesses less than 50 angstrom and should be considered as a reliability issue to avoid overestimation of dielectric breakdown. Under high stress current density (-Vg), the charge to catastrophic breakdown decreases with decreasing the oxide thickness because of dielectric breakdown in the structural transition layer existing SiO2/Si interface. But the Qbd rapidly increases again with decreasing the oxide thickness below 50 angstroms under low stress current density due to the difficulty in building up electric field to cause catastrophic breakdown through the localized conduction path induced by the quasi-breakdown prior to catastrophic breakdown. The quasi-breakdown was suppressed in NO-annealed oxide.

Min, Byoung W.; Kwong, Dim-Lee

1997-08-01

141

49 CFR 236.8 - Operating characteristics of electromagnetic, electronic, or electrical apparatus.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Operating characteristics of electromagnetic, electronic, or electrical apparatus. 236.8 Section...Systems General § 236.8 Operating characteristics of electromagnetic, electronic, or electrical apparatus. Signal...

2010-10-01

142

49 CFR 236.8 - Operating characteristics of electromagnetic, electronic, or electrical apparatus.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 false Operating characteristics of electromagnetic, electronic, or electrical apparatus. 236.8 Section...Systems General § 236.8 Operating characteristics of electromagnetic, electronic, or electrical apparatus. Signal...

2011-10-01

143

The Electrical Characteristics of a Filamentary Dielectric Barrier Discharge  

SciTech Connect

The electrical characteristics of a filamentary dielectric barrier discharge using parallel-plate electrodes geometry were statistically studied. The DBD's system was powered by a 50 Hz power supply and operated at atmospheric pressure. The influence of the air gap and position of dielectric on the discharge had been investigated. It was found that the air gap distance and position of dielectric had significant influence on the discharge current pulse. The results showed that discharge with large distance between the high voltage electrode and the dielectric would generate higher current pulses during the positive cycle. The discharge energy of single pulse was also determined.

Tay, W. H.; Yap, S. L.; Wong, C. S. [Plasma Research Laboratory, Physics Department, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2010-07-07

144

Electrical characteristics of amorphous iron-tungsten contacts on silicon  

NASA Technical Reports Server (NTRS)

The electrical characteristics of amorphous Fe-W contacts have been determined on both p-type and n-type silicon. The amorphous films were obtained by cosputtering from a composite target. Contact resistivities of 1 x 10 to the -7th and 2.8 x 10 to the -6th were measured on n(+) and p(+) silicon, respectively. These values remain constant after thermal treatment up to at least 500 C. A barrier height of 0.61 V was measured on n-type silicon.

Finetti, M.; Pan, E. T.-S.; Nicolet, M.-A.; Suni, I.

1983-01-01

145

SEMICONDUCTOR DEVICES: Structural and electrical characteristics of lanthanum oxide gate dielectric film on GaAs pHEMT technology  

NASA Astrophysics Data System (ADS)

This paper investigates the feasibility of using a lanthanum oxide thin film (La2O3) with a high dielectric constant as a gate dielectric on GaAs pHEMTs to reduce gate leakage current and improve the gate to drain breakdown voltage relative to the conventional GaAs pHEMT. An E/D mode pHEMT in a single chip was realized by selecting the appropriate La2O3 thickness. The thin La2O3 film was characterized: its chemical composition and crystalline structure were determined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. La2O3 exhibited good thermal stability after post-deposition annealing at 200, 400 and 600 °C because of its high binding-energy (835.6 eV). Experimental results clearly demonstrated that the La2O3 thin film was thermally stable. The DC and RF characteristics of Pt/La2O3/Ti/Au gate and conventional Pt/Ti/Au gate pHEMTs were examined. The measurements indicated that the transistor with the Pt/La2O3/Ti/Au gate had a higher breakdown voltage and lower gate leakage current. Accordingly, the La2O3 thin film is a potential high-k material for use as a gate dielectric to improve electrical performance and the thermal effect in high-power applications.

Chia-Song, Wu; Hsing-Chung, Liu

2009-11-01

146

Comparison of electrical characteristic between AlN/GaN and AlGaN/GaN heterostructure Schottky diodes  

NASA Astrophysics Data System (ADS)

Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated. Based on the measured current—voltage and capacitance—voltage curves, the electrical characteristics of AlN/GaN Schottky diode, such as Schottky barrier height, turn-on voltage, reverse breakdown voltage, ideal factor, and the current-transport mechanism, are analyzed and then compared with those of an AlGaN/GaN diode by self-consistently solving Schrödinger's and Poisson's equations. It is found that the dislocation-governed tunneling is dominant for both AlN/GaN and AlGaN/GaN Schottky diodes. However, more dislocation defects and a thinner barrier layer for AlN/GaN heterostructure results in a larger tunneling probability, and causes a larger leakage current and lower reverse breakdown voltage, even though the Schottky barrier height of AlN/GaN Schottky diode is calculated to be higher that of an AlGaN/GaN diode.

Lü, Yuan-Jie; Feng, Zhi-Hong; Lin, Zhao-Jun; Gu, Guo-Dong; Dun, Shao-Bo; Yin, Jia-Yun; Han, Ting-Ting; Cai, Shu-Jun

2014-02-01

147

Electrical characteristics of a millisecond pulsed glow discharge  

NASA Astrophysics Data System (ADS)

A ?s and ms pulsed argon glow discharge was investigated with respect to the breakdown condition (Paschen curve). Moreover, current-voltage profiles were acquired for different discharge frequencies, pulse durations, cathode-anode spacing and discharge pressures. The breakdown voltage was dependent on the cathode material (Cu, steel, Ti and Al). No severe change in the breakdown voltage was observed for a 1 ms pulse at different frequencies. However, the theoretical breakdown curve, calculated based on the Paschen equation did not fit the experimental data. The current plots for different cathode-anode spacing showed a maximum at intermediate distance (8-10 mm). These data were consistent with mass spectrometric data acquired using the same instrument in a GC-GD-TOFMS chemical speciation study. A higher discharge frequency with constant pulse duration leads to an increase in discharge current, probably due to a more dense plasma during the pulse. This is supported by the total emission of the plasma, which was not reaching the baseline for short delays in-between the plasma pulses. In addition, the total emission of the plasma shows that at least 2 ms is needed for the plasma to reach a stable quasi steady-state. The current-voltage (traces) for different discharge pressures show a constant relationship for different pulse durations. The current-voltage relation is pressure dependent and similar to dc-glow discharges. A fast photodiode was used for precise observation of the entire Penning ionization in the afterpeak at different pressure settings.

Fliegel, Daniel; Günther, Detlef

2008-06-01

148

Proposed RF Breakdown Studies at the AWA  

SciTech Connect

A study of breakdown mechanism has been initiated at the Argonne Wakefield Accelerator (AWA). Breakdown may include several factors such as local field enhancement, explosive electron emission, Ohmic heating, tensile stress produced by electric field, and others. The AWA is building a dedicated facility to test various models for breakdown mechanisms and to determine the roles of different factors in the breakdown. We plan to trigger breakdown events with a high-powered laser at various wavelengths (IR to UV) to determine the role of explosive electron emission in the breakdown process. Another experimental idea follows from the recent work on a Schottky-enabled photoemission in an RF photoinjector [1] that allows us to determine in situ the field enhancement factor on a cathode surface. Monitoring the field enhancement factor before and after the breakdown can shed some light on a number of observations such as the crater formation process.

Antipov, S.; Conde, M.; Gai, W.; Power, J.G.; Spentzouris, L.; Yusof, Z.; /Argonne /IIT, Chicago; Dolgashev, V.; /SLAC

2007-03-21

149

Breakdown study of DC silicon micro-discharge L Schwaederle1  

E-print Network

on silicon based micro-cavity discharge devices carried out in helium at pressure ranging from 100 to 1000Breakdown study of DC silicon micro-discharge devices L Schwaederl´e1 , M K Kulsreshath1 , L J. The influence of geometrical and operating parameters on the electrical characteristics of dc micro-cavity

Paris-Sud XI, Université de

150

Locating Initial Breakdown Pulses of Lightning Flashes  

NASA Astrophysics Data System (ADS)

Lightning flashes often begin with a series of bipolar pulses, 1-5 us in width, called initial breakdown pulses or characteristic pulses. In this presentation we show electric field change data of initial breakdown pulses collected with a network of 5 flat-plate antennas with a bandwidth of 0 - 5 MHz. These pulses were obtained at the NASA/Kennedy Space Center (KSC) during the summer of 2010. The (x, y, z, t) positions of these pulses have been determined using a time of arrival technique [Koshak and Solakiewicz, JGR, 1996] for several lightning flashes. In addition, we also collected magnetic field change data with a LINET system [e.g., Betz et al., GRL, 2004], which consisted of 7 crossed-loop sensors having a bandwidth of 5 - 200 kHz; the pulse locations detected by this system were also determined by time of arrival. The locations of the initial breakdown pulses from both systems will be compared to locations of VHF lightning sources made with the KSC LDAR2 system (with a center frequency of 63 MHz and a bandwidth of 6 MHz). Possible implications of the pulse locations derived from the three different sets of sensors on lightning initiation and propagation will be discussed.

Karunarathne, S.; Marshall, T.; Stolzenburg, M.; Betz, H.; Wieczorek, G.

2010-12-01

151

Potential of electrical resistivity tomography to infer aquifer transport characteristics from tracer studies  

E-print Network

Potential of electrical resistivity tomography to infer aquifer transport characteristics from-lapse electrical resistivity tomography (ERT), transport processes in the subsurface can be imaged and monitored of electrical resistivity tomography to infer aquifer transport characteristics from tracer studies: A synthetic

Sailhac, Pascal

152

Electrical and Sensing Properties of Single-Walled Carbon Nanotubes Network: Effect of Alignment and Selective Breakdown  

E-print Network

Full Paper Electrical and Sensing Properties of Single-Walled Carbon Nanotubes Network: Effect DOI: 10.1002/elan.200900314 1. Introduction Carbon nanotubes have many potential applications, batteries, polymer matrix composites, and nanoscale reactors [1 ­ 4]. Among these applications, the single-walled

153

On the bipolar resistive-switching characteristics of Al2O3- and HfO2-based memory cells operated in the soft-breakdown regime  

NASA Astrophysics Data System (ADS)

In this article, we investigate extensively the bipolar-switching properties of Al2O3- and HfO2-based resistive-switching memory cells operated at low current down to <1 ?A. We show that the switching characteristics differ considerably from those typically reported for larger current range (>15 ?A), which we relate as intrinsic to soft-breakdown (SBD) regime. We evidence a larger impact of the used switching-oxide in this current range, due to lower density of oxygen-vacancy (Vo) defects in the SBD regime. In this respect, deep resetting and large memory window may be achieved using the stoichiometric Al2O3 material due to efficient Vo annihilation, although no complete erasure of the conductive-filament (CF) is obtained. We finally emphasize that the conduction may be described by a quantum point-contact (QPC) model down to very low current level where only a few Vo defects compose the QPC constriction. The large switching variability inherent to this latter aspect is mitigated by CF shape tuning through adequate engineering of an Al2O3HfO2 bilayer.

Goux, L.; Raghavan, N.; Fantini, A.; Nigon, R.; Strangio, S.; Degraeve, R.; Kar, G.; Chen, Y. Y.; De Stefano, F.; Afanas'ev, V. V.; Jurczak, M.

2014-10-01

154

Electrodynamic thermal breakdown of a capacitor insulator  

NASA Astrophysics Data System (ADS)

A mechanism of the electrical breakdown is proposed for modern metal-field capacitors with the well-known property of self-healing of the breakdown strength. Upon an increase in the working voltage, the self-healing time increases to tens of microseconds, and the heating of adjacent insulator layers becomes significant. The propagating thermally activated conduction wave facilitates the enhancement of the electric field up to breakdown values. Analysis of the dynamics of electric field increase is carried out for capacitors based on polyethylene terephthalate (PET) dielectric.

Emel'Yanov, O. A.

2011-11-01

155

Effects of manufacturing technology on electrical breakdown and morphology of thin films of low density polyethylene blended with polypropylene copolymer  

Microsoft Academic Search

Extruded films prepared from blends of low-density polyethylene (LDPE) and random copolymer of ethylene and propylene (EP) with the T-die method were studied with respect to electrical properties and morphology. Comparisons with data on blown films are made. These blends are of interest as improved LDPE for making XLPE for insulated power cable. In the high temperature region (90°C), a

Chao Zhang; Tatsuo Mori; Teruyoshi Mizutani; M. Ishioka

2003-01-01

156

Impulse breakdown delay in liquid dielectrics  

NASA Astrophysics Data System (ADS)

Theoretical images of streamers, revealing the mechanisms behind impulse breakdown in liquid dielectrics, are presented. Streamers lead to electrical breakdown by forming paths, capable of carrying large current amplitudes between electrodes. Breakdown delays and terminal currents are calculated for various electrode geometries (40 ?m needle and 6.35 mm sphere) and gap distances (up to 10 mm). Modeling results indicate that the breakdown in needle-needle electrodes requires higher impulse voltage amplitudes than in needle-sphere electrodes for the same gap distances. Streamers in needle-sphere geometries are about 50% thicker than streamers propagating in needle-needle geometries under similar impulse voltage amplitudes.

Jadidian, Jouya; Zahn, Markus; Lavesson, Nils; Widlund, Ola; Borg, Karl

2012-05-01

157

Impulse breakdown of liquid water  

Microsoft Academic Search

Currently, studies of microsecond and sub-microsecond electrical breakdown in liquid water and water solutions are experiencing their renaissance period due to the development of advanced pulsed power systems and emerging technologies for environmental applications and plasma medicine. The present paper is focused on an investigation of polarity effects in sub-microsecond discharges in water. Distilled water, tap water and water based

I. V. Timoshkin; M. J. Given; M. P. Wilson; R. A. Fouracre; S. J. MacGregor

2010-01-01

158

Analysis of Electrical Characteristics of Thin Film Photovoltaic Cells  

NASA Technical Reports Server (NTRS)

Solar energy is the most abundant form of energy in many terrestrial and extraterrestrial environments. Often in extraterrestrial environments sunlight is the only readily available form of energy. Thus the ability to efficiently harness solar energy is one of the ultimate goals in the design of space power systems. The essential component that converts solar energy into electrical energy in a solar energy based power system is the photovoltaic cell. Traditionally, photovoltaic cells are based on a single crystal silicon absorber. While silicon is a well understood technology and yields high efficiency, there are inherent disadvantages to using single crystal materials. The requirements of weight, large planar surfaces, and high manufacturing costs make large silicon cells prohibitively expensive for use in certain applications. Because of silicon s disadvantages, there is considerable ongoing research into alternative photovoltaic technologies. In particular, thin film photovoltaic technologies exhibit a promising future in space power systems. While they are less mature than silicon, the better radiation hardness, reduced weight, ease of manufacturing, low material cost, and the ability to use virtually any exposed surface as a substrate makes thin film technologies very attractive for space applications. The research group lead by Dr. Hepp has spent several years researching copper indium disulfide as an absorber material for use in thin film photovoltaic cells. While the group has succeeded in developing a single source precursor for CuInS2 as well as a unique method of aerosol assisted chemical vapor deposition, the resulting cells have not achieved adequate efficiencies. While efficiencies of 11 % have been demonstrated with CuInS2 based cells, the cells produced by this group have shown efficiencies of approximately 1 %. Thus, current research efforts are turning towards the analysis of the individual layers of these cells, as well as the junctions between them, to determine the cause of the poor yields. As a student of electrical engineering with some material science background, my role in this research is to develop techniques for analyzing the electrical characteristics of the CuInS2 cells. My first task was to design a shadow mask to be used to place molybdenum contacts under a layer of CuInS;! in order to analyze the contact resistance between the materials. In addition, I have also analyzed evaporated aluminum top contacts and have tested various methods of increasing their thicknesses in order to decrease series resistance. More recently I have worked with other members of the research group in reviving a vertical cold-wall reactor for experimentation with CuInS2 quantum dots. As part of that project, I have improved the design for a variable frequency and pulse width square wave generator to be used in driving the precursor injection process. My task throughout the remainder of my tenure is to continue to analyze and develop tools for the analysis of electrical properties of the CuInS2 cells with the ultimate goal of discovering ways to improve the efficiency of our photovoltaic cells. Traditionally, photovoltaic cells are based on a single crystal silicon absorber. While The research group lead by Dr. Hepp has spent several years researching copper indium

Kasick, Michael P.

2004-01-01

159

Microwave propagation with the gas breakdown  

NASA Astrophysics Data System (ADS)

By combining the microwave propagation theory and the gas breakdown theory, the microwave propagation with the gas breakdown is analyzed theoretically. Particle-in-cell/Monte Carlo collision (PIC/MCC) simulations are carried out to verify the theoretical results. Based on this theoretical method, the breakdown phenomenon of the pulse microwave is analyzed. The results show that the product values of the initial electron density and the propagation length are the criterion to distinguish the pulse peak decline breakdown and the pulse width reduction breakdown. Furthermore, the energy transmission is also studied, which shows that the total output energy is approximately independent of the input electric field if the electric field is not extremely large.

Wang, Hui-Hui; Liu, Da-Gang; Liu, La-Qun; Meng, Lin

2014-11-01

160

Nanolaminates: increasing dielectric breakdown strength of composites.  

PubMed

Processable, low-cost, high-performance hybrid dielectrics are enablers for a vast array of green technologies, including high-temperature electrical insulation and pulsed power capacitors for all-electric transportation vehicles. Maximizing the dielectric breakdown field (E(BD)), in conjunction with minimization of leakage current, directly impacts system performance because of the field's quadratic relationship with electrostatic energy storage density. On the basis of the extreme internal interfacial area and ultrafine morphology, polymer-inorganic nanocomposites (PNCs) have demonstrated modest increases in E(BD) at very low inorganic loadings, but because of insufficient control of the hierarchal morphology of the blend, have yielded a precipitous decline in E(BD) at intermediate and high inorganic volume fractions. Here in, we demonstrate that E(BD) can be increased up to these intermediate inorganic volume fractions by creating uniform one-dimensional nanocomposites (nanolaminates) rather than blends of spherical inorganic nanoparticles and polymers. Free standing nanolaminates of highly aligned and dispersed montmorillonite in polyvinyl butyral exhibited enhancements in E(BD) up to 30 vol % inorganic (70 wt % organically modified montmorillonite). These relative enhancements extend up to five times the inorganic fraction observed for random nanoparticle dispersions, and are anywhere from two to four times greater than observed at comparable volume fraction of nanoparticles. The breakdown characteristics of this model system suggested a trade-off between increased path tortuosity and polymer-deficient structural defects. This implies that an idealized PNC morphology to retard the breakdown cascade perpendicular to the electrodes will occur at intermediate volume fractions and resemble a discotic nematic phase where highly aligned, high-aspect ratio nanometer thick plates are uniformly surrounded by nanoscopic regions of polymer. PMID:22301841

Fillery, Scott P; Koerner, Hilmar; Drummy, Lawrence; Dunkerley, Erik; Durstock, Michael F; Schmidt, Daniel F; Vaia, Richard A

2012-03-01

161

Analysis of the electrical characteristics of a Westinghouse variable speed generating system for wind turbine applications  

Microsoft Academic Search

Variable speed electric generating technology can enhance the general use of wind energy in electric utility applications. This enhancement results from two characteristic properties of variable speed wind turbine generators: an improvement in drive train damping characteristics, which results in reduced structural loading on the entire wind turbine system, and an improvement in the overall efficiency by using a more

J. I. Herrera; T. W. Reddoch

1988-01-01

162

Effects of electrode layouts on electrical characteristics for unipoled step-down piezoelectric transformers  

Microsoft Academic Search

The electrical characteristics of single layer unipoled step-down piezoelectric transformers are investigated. The configuration of PT is circle-circle, where the inner circle is input and outer ring is output. The electrical characteristics simulation and performance test are focused on voltage gains and output power. Moreover, effects of input and output electrode area on voltage gains and output power are discussed.

Bai Feng-xian; Dong Wei-jie; Xu Yong-jie

2009-01-01

163

Characteristics of parallel electric fields in the downward current region of the aurora  

E-print Network

Characteristics of parallel electric fields in the downward current region of the aurora L downward current region. The observed parallel electric fields have amplitudes reaching nearly 1 V, Colorado 80309 Received 19 December 2001; accepted 7 May 2002 Direct measurements of parallel electric

California at Berkeley, University of

164

Characteristics of laser-triggered electric discharges in air  

Microsoft Academic Search

An experiment of laser-triggered electric discharges has been conducted in a uniform background electric field. By focusing the beam of a pulsed Nd-YAG laser (wavelength 532 nm, pulse duration 5 ns) in a narrow (15 mm) plane-parallel air gap exposed to a DC voltage, streamer discharges and disruptive discharges were triggered. The laser energy and the background electric field strength

Mose Akyuz; Mahbubur Rahman; Anders Larsson; Vernon Cooray; Axel Franke

2005-01-01

165

Penetration electric fields: Efficiency and characteristic time scale  

Microsoft Academic Search

Penetration of the interplanetary electric field (IEF) to the middle- and low-latitude ionosphere has been investigated for nearly four decades. Most previous studies focused on the correlation between the interplanetary and ionospheric electric field perturbations. Very little attention has been paid to a quantitative relationship except for a recent case analysis by Kelley et al. [2003. Penetration of the solar

Chao-Song Huang; Stanislav Sazykin; Jorge L. Chau; Naomi Maruyama; Michael C. Kelley

2007-01-01

166

Vortex breakdown incipience: Theoretical considerations  

NASA Technical Reports Server (NTRS)

The sensitivity of the onset and the location of vortex breakdowns in concentrated vortex cores, and the pronounced tendency of the breakdowns to migrate upstream have been characteristic observations of experimental investigations; they have also been features of numerical simulations and led to questions about the validity of these simulations. This behavior seems to be inconsistent with the strong time-like axial evolution of the flow, as expressed explicitly, for example, by the quasi-cylindrical approximate equations for this flow. An order-of-magnitude analysis of the equations of motion near breakdown leads to a modified set of governing equations, analysis of which demonstrates that the interplay between radial inertial, pressure, and viscous forces gives an elliptic character to these concentrated swirling flows. Analytical, asymptotic, and numerical solutions of a simplified non-linear equation are presented; these qualitatively exhibit the features of vortex onset and location noted above.

Berger, Stanley A.; Erlebacher, Gordon

1992-01-01

167

Partial discharge characteristics of polymer nanocomposite materials in electrical insulation: a review of sample preparation techniques, analysis methods, potential applications, and future trends.  

PubMed

Polymer nanocomposites have recently been attracting attention among researchers in electrical insulating applications from energy storage to power delivery. However, partial discharge has always been a predecessor to major faults and problems in this field. In addition, there is a lot more to explore, as neither the partial discharge characteristic in nanocomposites nor their electrical properties are clearly understood. By adding a small amount of weight percentage (wt%) of nanofillers, the physical, mechanical, and electrical properties of polymers can be greatly enhanced. For instance, nanofillers in nanocomposites such as silica (SiO2), alumina (Al2O3) and titania (TiO2) play a big role in providing a good approach to increasing the dielectric breakdown strength and partial discharge resistance of nanocomposites. Such polymer nanocomposites will be reviewed thoroughly in this paper, with the different experimental and analytical techniques used in previous studies. This paper also provides an academic review about partial discharge in polymer nanocomposites used as electrical insulating material from previous research, covering aspects of preparation, characteristics of the nanocomposite based on experimental works, application in power systems, methods and techniques of experiment and analysis, and future trends. PMID:24558326

Izzati, Wan Akmal; Arief, Yanuar Z; Adzis, Zuraimy; Shafanizam, Mohd

2014-01-01

168

Partial Discharge Characteristics of Polymer Nanocomposite Materials in Electrical Insulation: A Review of Sample Preparation Techniques, Analysis Methods, Potential Applications, and Future Trends  

PubMed Central

Polymer nanocomposites have recently been attracting attention among researchers in electrical insulating applications from energy storage to power delivery. However, partial discharge has always been a predecessor to major faults and problems in this field. In addition, there is a lot more to explore, as neither the partial discharge characteristic in nanocomposites nor their electrical properties are clearly understood. By adding a small amount of weight percentage (wt%) of nanofillers, the physical, mechanical, and electrical properties of polymers can be greatly enhanced. For instance, nanofillers in nanocomposites such as silica (SiO2), alumina (Al2O3) and titania (TiO2) play a big role in providing a good approach to increasing the dielectric breakdown strength and partial discharge resistance of nanocomposites. Such polymer nanocomposites will be reviewed thoroughly in this paper, with the different experimental and analytical techniques used in previous studies. This paper also provides an academic review about partial discharge in polymer nanocomposites used as electrical insulating material from previous research, covering aspects of preparation, characteristics of the nanocomposite based on experimental works, application in power systems, methods and techniques of experiment and analysis, and future trends. PMID:24558326

Izzati, Wan Akmal; Adzis, Zuraimy; Shafanizam, Mohd

2014-01-01

169

Space charge dynamics in LDPE films immediately before breakdown  

Microsoft Academic Search

Space charge dynamics in low-density polyethylene (LDPE) films were observed by the pulsed electroacoustic (PEA) method during breakdown tests at various temperatures. In order to investigate the intrinsic electrical breakdown, the applied electric field was increased to 300 kV\\/mm in 150 ms, and kept constant until breakdown of the specimens, or 300 ms at the longest. Space charge profiles were

M. Fukuma; K. Fukunaga; T. Maeno

2001-01-01

170

An Investigation of the Electrical Short Circuit Characteristics of Tin Whiskers  

NASA Technical Reports Server (NTRS)

Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has a currently unknown probability associated with it. Due to contact resistance electrical shorts may not occur at lower voltage levels. In this experiment, we study the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From this data we can estimate the probability of an electrical short, as a function of voltage, given that a free tin whisker has bridged two adjacent exposed electrical conductors. Also, three tin whiskers grown from the same Space Shuttle Orbiter card guide used in the aforementioned experiment were cross-sectioned and studied using a focused ion beam (FIB). The rare polycrystalline structure seen in the FIB cross section was confirmed using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size to determine that the tin plating on the card guides had a bright finish.

Courey, Karim J.

2008-01-01

171

Impact of electrical stress on the electrical characteristics of 2 MeV electron irradiated metal-oxide-silicon capacitors with atomic layer deposited Al2O3, HfO2 and nanolaminated dielectrics  

NASA Astrophysics Data System (ADS)

In this work, the impact of electrical stress on the electrical characteristics of 2 MeV electron irradiated metal-oxide-silicon capacitors with atomic layer deposited (ALD) high permittivity (high-k) dielectric layers of Al2O3, HfO2 and a nanolaminate of them is evaluated. The aim is to investigate the susceptibility to electrical stress of the radiation effects created in irradiated MOS structures, paying especial attention to any possible interaction between the radiation-induced damage and the subsequent electrical stress degradation. For this study, MOS capacitors with a nominal dielectric physical thickness of 10 nm (equivalent oxide thickness (EOT) between 3 nm and 7 nm) on different p-type and n-type silicon substrates were investigated. An exponentially increasing stress current was forced to flow in accumulation through the different dielectric layers, registering the evolution of gate voltage versus stress time until dielectric breakdown occurred. Capacitance-voltage characteristics of the different irradiated and non-irradiated structures are analyzed as a function of electrical stress. Different charge trapping behaviors and significant polarity dependence in interface state generation are observed for the dielectric layers subjected to substrate and gate injections. No clear interaction between radiation and electrical stress damages is noticed under substrate injection (n-type samples). However, higher negative charge trapping near the metal/dielectric interface is registered for the irradiated Al2O3 and nanolaminate layers subjected to gate injection and, in the case of the most irradiated samples, the radiation-induced interface states damage is found to dominate against the damage generated in early stages of the electrical stress.

Rafí, J. M.; González, M. B.; Takakura, K.; Tsunoda, I.; Yoneoka, M.; Beldarrain, O.; Zabala, M.; Campabadal, F.

2013-11-01

172

Comparison of the Microstructural Characteristics and Electrical Properties of Thermally Sprayed Al2O3 Coatings from Aqueous Suspensions and Feedstock Powders  

NASA Astrophysics Data System (ADS)

In this work the microstructural characteristics and electrical insulating properties of thermally sprayed alumina coatings produced by suspension-HVOF (S-HVOF) and conventional HVOF spray processes are presented. The electrical resistance at different relative air humidity (RH) levels (from 6 to 97% RH) and values of dielectric strength were investigated by direct current electrical resistance measurements, electrochemical impedance spectroscopy, and dielectric breakdown tests. Relationships between electrical properties and coating characteristics are discussed. At low humidity levels (up to 40% RH) the electrical resistivities of S-HVOF and HVOF coatings were on the same order of magnitude (1011 ?·m). At a very high humidity level (97% RH) the electrical resistivity values for the S-HVOF coatings were in the range 107-1011 ?·m, up to five orders of magnitude higher than those recorded for the HVOF coating (orders of magnitude of 106 ?·m). The better electrical resistance stability of the suspension-sprayed Al2O3 coatings can be explained by their specific microstructure and retention of a higher content of ?-Al2O3. The dielectric strength E d of suspension-sprayed coatings was found to be 19.5-26.8 kV·mm-1 for coating thicknesses ranging from 60 to 200 ?m. These values were slightly lower than those obtained for conventional HVOF coatings (up to 32 kV·mm-1). However, it seemed that the dielectric strength of conventionally sprayed coatings was more sensitive to the coating thickness (when compared with the values of E d determined for S-HVOF coatings) and varied to a greater extent (up to 10 kV·mm-1) when the coating thickness varied in the range 100-200 ?m.

Toma, Filofteia-Laura; Berger, Lutz-Michael; Scheitz, Stefan; Langner, Stefan; Rödel, Conny; Potthoff, Annegret; Sauchuk, Viktar; Kusnezoff, Mihails

2012-06-01

173

Electrical Characteristics of Simulated Tornadoes and Dust Devils  

NASA Technical Reports Server (NTRS)

It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado.

Zimmerman, Michael I.; Farrell, William M.; Barth, E. L.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T. L.

2012-01-01

174

Microwave air breakdown enhanced with metallic initiators  

SciTech Connect

We have determined X-band (9.4 GHz) electric field strengths required to obtain air breakdown at atmospheric pressure in the presence of metallic initiators, which are irradiated with repetitive (30 pulses/s) microwave pulses of 3 {mu}s duration and 200 kW peak power. Using a half-wavelength initiator, a factor of 40 reduction (compared to no initiator) was observed in the electric field required to achieve breakdown. The present measurements are compared to a previously published model for air breakdown, which was originally validated with S-band (3 GHz) frequencies and single 40 {mu}s pulses. We find good agreement between this previous model and our present measurements of breakdown with X-band frequencies and repetitive 3 {mu}s pulses.

Herring, G. C. [NASA Langley Research Center, Hampton, Virginia 23681 (United States); Popovic, S. [Department of Physics, Old Dominion University, Norfolk, Virginia 23529 (United States)

2008-03-31

175

Breakdown voltage of metal-oxide resistors in liquid argon  

E-print Network

We characterized a sample of metal-oxide resistors and measured their breakdown voltage in liquid argon by applying high voltage (HV) pulses over a 3 second period to simulate the electric breakdown in a HV-divider chain. All resistors had higher breakdown voltages in liquid argon than their vendor ratings in air at room temperature. Failure modes range from full destruction to coating damage. In cases where breakdown was not catastrophic, subsequent breakdown voltages were lower in subsequent measuring runs. One resistor type withstands 131\\,kV pulses, the limit of the test setup.

Bagby, L F; James, C C; Jones, B J P; Jostlein, H; Lockwitz, S; Naples, D; Raaf, J L; Rameika, R; Schukraft, A; Strauss, T; Weber, M S; Wolbers, S A

2014-01-01

176

Performance Characteristics of the First, State-of-the-art Electric Vehicle Implemented in Chile  

E-print Network

supplies, and a non- polluting battery charger. The car transformed to an EV was a double cabin, ChevroletPerformance Characteristics of the First, State-of-the-art Electric Vehicle Implemented in Chile, Alejandro Amaro and Eduardo Wiechmann*, Department of Electrical Engineering Catholic University of Chile

Catholic University of Chile (Universidad Católica de Chile)

177

Structural and electrical characteristics of R.F. magnetron sputtered ZnO films  

E-print Network

Structural and electrical characteristics of R.F. magnetron sputtered ZnO films D.J. Kanga , J on the physical and electrical properties of ZnO films deposited by R.F. magnetron sputtering. We found Solid Films 475 (2005) 160­165 www.elsevier.com/locate/tsf #12;magnetron sputtering using a sintered Zn

Boo, Jin-Hyo

178

Evaluating thermal aging characteristics of electric power transmission lines  

Microsoft Academic Search

Assessment of aging characteristics of conductors and other components of power transmission networks plays an important role in asset management systems. Due to adverse effects of conductor aging caused by annealing, the conductors lose their tensile strength. Although the loss of strength is gradual, it accumulates over time and increases the probability of outages and blackouts. Therefore, the most important

M. M. I. Bhuiyan; P. Musilek; J. Heckenbergerova; D. Koval

2010-01-01

179

Temporal characteristics of the pulsed electric discharges in small gaps filled with hydrocarbon oil  

NASA Astrophysics Data System (ADS)

In order to understand the role of electrode materials in electrical discharges with micro gaps (<200?µm) filled with a liquid hydrocarbon dielectric, the post-breakdown phase of low ignition voltage (100?V) and low current (<20?A) pulsed electric discharges is experimentally investigated. The electric discharge energies are selected in the range from 1 to 150?mJ. Due to the non-repetitive and transient nature of the micro-discharges, time-resolved imaging, spectroscopy and electrical analysis of single discharges are performed. The plasma–material interaction is investigated by analysing the erosion craters on anode and cathode. It is found that the electrode materials in these multiphase discharges affect the gas bubble dynamics, the transport properties of the discharge plasmas and the transition from the gaseous to metallic vapour plasma. The change in the energy fractions dissipated in the electrodes in function of the discharge time is influenced by the thermo-physical properties of the electrode materials. The simulation of craters in multiple discharge process requires consideration of the gas bubble dynamics due to different energy fractions and plasma flushing efficiencies.

Maradia, U.; Hollenstein, Ch; Wegener, K.

2015-02-01

180

Statistic Characteristic Estimations of Harmonic And Flicker on Electric Arc Furnace Feeders  

Microsoft Academic Search

This paper proposes the estimation results of the stochastic characteristics of harmonic and flicker for an AC and a DC electric arc furnace feeders. These characteristics include stationarity, normality and correlation. Besides, the statistic probability was assessed, too. The estimation and the assessment are implemented by a PC-based virtual instrumentation system. The results show that (1) most harmonic and flicker

Ming-Tang Chen; Chen-Wen Lu

2006-01-01

181

Analytical Model for a Photovoltaic Module using the Electrical Characteristics provided by the Manufacturer Data Sheet  

Microsoft Academic Search

This paper proposes an analytical model for the performance of photovoltaic modules to be used in distributed power generation. The proposed solar panel model uses the electrical characteristics provided by the manufacturer data sheet. The required characteristics are short-circuit current (Isc), open-circuit voltage (Voc ) and the temperature coefficients of Isc and Voc . The proposed model takes into consideration

Eduardo I. Ortiz-Rivera; F. Z. Peng

2005-01-01

182

Optical and electrical characteristics of ZnO/Si heterojunction  

NASA Astrophysics Data System (ADS)

Self-assembled ZnO nanorods have been synthesized on a seeded Si substrate by a simple chemical bath deposition method at a temperature of 80 °C. Room-temperature photoluminescence analysis revealed material of high optical quality with a low density of defects that can be reduced by post growth annealing. Current-voltage measurements on these devices showed excellent rectification. Junction characteristics were also studied using capacitance-voltage measurements and showed that the junction characteristics are mainly determined by the properties of the p-Si substrate. Based on the energy band diagram and possible interface states at the junction, it was suggested that the current transport in the device is predominantly determined by hopping of charge carriers between localized states through a multi-step tunneling process.

Urgessa, Z. N.; Dobson, S. R.; Talla, K.; Murape, D. M.; Venter, A.; Botha, J. R.

2014-04-01

183

Visualization of vortex breakdown on a delta wing  

NASA Technical Reports Server (NTRS)

An account is given of the results obtained by a flow visualization study of the roll-up, breakdown position, and spiral- or bubble-type breakdown characteristics of an 85-deg sweep, flat-plate delta wing at large angles-of-attack. The two different breakdown modes were noted to metamorphose into each other, with the bubble-type phenomenon appearing to prefer a more upstream location relative to the spiral mode. In those instances when the breakdown location was changing, the breakdown took the form of a bubble when moving forward, and spiral when moving aft.

Nelson, R. C.; Payne, F. M.; Ng, T. T.

1987-01-01

184

Electrical characteristics of highly reliable ultrathin hafnium oxide gate dielectric  

Microsoft Academic Search

Electrical and reliability properties of ultrathin HfO2 have been investigated. Pt electroded MOS capacitors with HfO2 gate dielectric (physical thickness ~45-135 Å and equivalent oxide thickness ~13.5-25 Å) were fabricated. HfO2 was deposited using reactive sputtering of a Hf target with O2 modulation technique. The leakage current of the 45 Å HfO2 sample was about 1×10-4 A\\/cm 2 at +1.0

Laegu Kang; Byoung Hun Lee; Wen-Jie Qi; Yongjoo Jeon; Renee Nieh; Sundar Gopalan; Katsunori Onishi; Jack C. Lee

2000-01-01

185

High frequency breakdown voltage  

SciTech Connect

This report contains information about the effect of frequency on the breakdown voltage of an air gap at standard pressure and temperature, 76 mm Hg and O{degrees}C, respectively. The frequencies of interest are 47 MHz and 60 MHz. Additionally, the breakdown in vacuum is briefly considered. The breakdown mechanism is explained on the basis of collision and ionization. The presence of the positive ions produced by ionization enhances the field in the gap, and thus determines the breakdown. When a low-frequency voltage is applied across the gap, the breakdown mechanism is the same as that caused by the DC or static voltage. However, when the frequency exceeds the first critical value f{sub c}, the positive ions are trapped in the gap, increasing the field considerably. This makes the breakdown occur earlier; in other words, the breakdown voltage is lowered. As the frequency increases two decades or more, the second critical frequency, f{sub ce}, is reached. This time the electrons start being trapped in the gap. Those electrons that travel multiple times across the gap before reaching the positive electrode result in an enormous number of electrons and positive ions being present in the gap. The result is a further decrease of the breakdown voltage. However, increasing the frequency does not decrease the breakdown voltage correspondingly. In fact, the associated breakdown field intensity is almost constant (about 29 kV/cm).The reason is that the recombination rate increases and counterbalances the production rate, thus reducing the effect of the positive ions` concentration in the gap. The theory of collision and ionization does not apply to the breakdown in vacuum. It seems that the breakdown in vacuum is primarily determined by the irregularities on the surfaces of the electrodes. Therefore, the effect of frequency on the breakdown, if any, is of secondary importance.

Chu, Thanh Duy

1992-03-01

186

Aerodynamic characteristics of sixteen electric, hybrid, and subcompact vehicles  

NASA Technical Reports Server (NTRS)

An elementary electric and hybrid vehicle aerodynamic data base was developed using data obtained on sixteen electric, hybrid, and sub-compact production vehicles tested in the Lockheed-Georgia low-speed wind tunnel. Zero-yaw drag coefficients ranged from a high of 0.58 for a boxey delivery van and an open roadster to a low of about 0.34 for a current four-passenger proto-type automobile which was designed with aerodynamics as an integrated parameter. Vehicles were tested at yaw angles up to 40 degrees and a wing weighting analysis is presented which yields a vehicle's effective drag coefficient as a function of wing velocity and driving cycle. Other parameters investigated included the effects of windows open and closed, radiators open and sealed, and pop-up headlights. Complete six-component force and moment data are presented in both tabular and graphical formats. Only limited commentary is offered since, by its very nature, a data base should consist of unrefined reference material. A justification for pursuing efficient aerodynamic design of EHVs is presented.

Kurtz, D. W.

1979-01-01

187

Role of the substrate in the electrical transport characteristics of focused ion beam fabricated nanogap electrode  

SciTech Connect

Precise metallic nanogap structure is fabricated on a glass substrate by using a 30 keV focused Ga ion beam. While investigating the I-V behavior of the nanogap structure, tunneling through the substrate has been found to play a vital role in the electrical transportation process. Substrate breakdown occurs at a certain applied voltage and a metal vapor state is initiated through intense heat generation at the nanogap region. The experimental observation confirms the role of the substrate in the explosion process. Metallic spherical particles are formed during cooling/condensation of the metal vapors or splashing of the liquid droplets showing a wide distribution of size from few tens of nanometers to few microns.

Rajput, Nitul S.; Verma, H. C. [Department of Physics, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Singh, Abhishek K. [Materials Science Programme, Indian Institute of Technology Kanpur, Kanpur 208016 (India)

2012-07-15

188

Breakdown phenomena in high power klystrons  

NASA Astrophysics Data System (ADS)

In the course of developing new high peak power klystrons at SLAC, high electric fields in several regions of these devices have become an important source of vacuum breakdown phenomena. In addition, a renewed interest in breakdown phenomena for nanosecond pulse, multi-megavolt per centimeter fields has been sparked by recent R and D work in the area of gigawatt RF sources. The most important regions of electrical breakdown are in the output cavity gap area, the RF ceramic windows, and the gun ceramic insulator. The details of the observed breakdown in these regions, experiments performed to understand the phenomena and solutions found to alleviate the problems will be discussed. Recently experiments have been performed on a new prototype R and D klystron. Peak electric fields across the output cavity gaps of this klystron exceed 2 MV/cm. The effect of peak field duration (i.e., pulse width) on the onset of breakdown have been measured. The pulse widths varied from tens of nanoseconds to microseconds. Results from these experiments will be presented. The failure of ceramic RF windows due to multipactor and puncturing was an important problem to overcome in order that our high power klystrons would have a useful life expectancy. Consequently many studies and tests were made to understand and alleviate window breakdown phenomena. Some of the results in this area, especially the effects of surface coatings, window materials and processing techniques and their effects on breakdown will be discussed. Another important source of klystron failure in the recent past at SLAC has been the puncturing of the high voltage ceramic insulator in the gun region. A way of alleviating this problem has been found although the actual cause of the puncturing is not yet clear. The practical solution to this breakdown process will be described and a possible mechanism for the puncturing will be presented.

Vlieks, A. E.; Allen, M. A.; Callin, R. S.; Fowkes, W. R.; Hoyt, E. W.; Lebacqz, J. V.; Lee, T. G.

1988-03-01

189

Magnetic control of breakdown: Toward energy-efficient hollow-cathode magnetron discharges  

SciTech Connect

Characteristics of electrical breakdown of a planar magnetron enhanced with an electromagnet and a hollow-cathode structure, are studied experimentally and numerically. At lower pressures the breakdown voltage shows a dependence on the applied magnetic field, and the voltage necessary to achieve the self-sustained discharge regime can be significantly reduced. At higher pressures, the dependence is less sensitive to the magnetic field magnitude and shows a tendency of increased breakdown voltage at the stronger magnetic fields. A model of the magnetron discharge breakdown is developed with the background gas pressure and the magnetic field used as parameters. The model describes the motion of electrons, which gain energy by passing the electric field across the magnetic field and undergo collisions with neutrals, thus generating new bulk electrons. The electrons are in turn accelerated in the electric field and effectively ionize a sufficient amount of neutrals to enable the discharge self-sustainment regime. The model is based on the assumption about the combined classical and near-wall mechanisms of electron conductivity across the magnetic field, and is consistent with the experimental results. The obtained results represent a significant advance toward energy-efficient multipurpose magnetron discharges.

Baranov, O.; Romanov, M. [National Aerospace University 'KhAI', Kharkov, 61070 (Ukraine); Kumar, S. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield NSW 2070 (Australia); Zong, X. X. [Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Ostrikov, K. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield NSW 2070 (Australia); Plasma Nanoscience - Complex Systems, School of Physics, University of Sydney, Sydney NSW 2006 (Australia)

2011-03-15

190

Structural, optical and electrical characteristics of a new NLO crystal  

NASA Astrophysics Data System (ADS)

A new nonlinear optical (NLO) organic crystal 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}amino)phenyl]ethanone (MMP) has been grown by slow evaporation technique at ambient temperature. The crystal structure of MMP was determined by single crystal X-ray diffraction. MMP crystallizes in non-centrosymmetric monoclinic system with space group P21. The FT-IR spectrum recorded for new crystal confirmed the presence of various functional groups in the material. MMP was found to be thermally stable up to 300 °C. The grown crystal was optically transparent in the wavelength range of 400-1100 nm. The second harmonic generation (SHG) efficiency of the crystal was measured by the classical powder technique using Nd:YAG laser and was found to be 4.13 times more efficient than reference material, urea. Third order nonlinear parameters were measured by employing the Z-scan technique. The laser damage threshold for MMP crystal was determined to be 4.26 GW/cm2. The Brewster angle technique was employed to measure the refractive index of the crystal and the values for green and red wavelengths were found to be 1.35 and 1.33, respectively. The dielectric and electrical measurements were carried out to study the different polarization mechanisms and conductivity of the crystal.

D'silva, E. D.; Krishna Podagatlapalli, G.; Venugopal Rao, S.; Dharmaprakash, S. M.

2012-09-01

191

Treeing Breakdown in Inorganic-filler\\/LDPE Nanocomposite Material  

Microsoft Academic Search

A nano-composite material of magnesium oxide (MgO) added to a low-density polyethylene (LDPE) was subjected to electrical tree breakdown investigation. The LDPE without nano-fillers was lower in breakdown voltage than the LDPE added with nano-fillers. The breakdown voltage was increased by increase of nano-filler concentrations in LDPE. This result much coincided with the result on tree inception voltage which was

Rudi Kurnianto; Yoshinobu Murakami; Masayuki Nagao; Naohiro Hozumi; Yoshinao Murata

2007-01-01

192

High breakdown GaN HEMT with overlapping gate structure  

Microsoft Academic Search

GaN high electron mobility transistors (HEMTs) were fabricated using an overlapping-gate technique in which the drain-side edge of the metal gate overlaps on a high breakdown and high dielectric constant dielectric. The overlapping structure reduces the electric field at the drain-side gate edge, thus increasing the breakdown of the device. A record-high three-terminal breakdown figure of 570 V was achieved

N.-Q. Zhang; S. Keller; G. Parish; S. Heikman; S. P. DenBaars; U. K. Mishra

2000-01-01

193

Modeling of Electro Optic Polymer Electrical Characteristics in a 3 layer Optical Waveguide Modulator  

NASA Technical Reports Server (NTRS)

The electrical characteristics of electro optic polymer waveguide modulators are often described by the bulk reactance of the individual layers. However, the resistance and capacitance between the layers can significantly alter the electrical performance of a waveguide modulator. These interface characteristics are related to the boundary charge density and are strongly affected by the adhesion of the layers in the waveguide stack. An electrical reactance model has been derived to investigate this phenomenon at low frequencies. The model shows the waveguide stack frequency response has no limiting effects below the microwave range and that a true DC response requires a stable voltage for over 1000 hours. Thus, reactance of the layers is the key characteristic of optimizing the voltage across the core layer, even at very low frequencies (> 10(exp -6) Hz). The results of the model are compared with experimental data for two polymer systems and show quite good correlation.

Watson, Michael D.; Ashley, Paul R.; Guenthner, Andrew J.; Abushagur, Mustafa

2004-01-01

194

Material Characteristics of Molten-metal Bridges at Electrical Contacts  

NASA Astrophysics Data System (ADS)

Steel and copper are widely used as current collecting material for power supply in electric railways. In this field experimental studies on material wear and friction phenomena are important for improving stability and reliability of current collection in service operation. However few are reported to the effect of contact bridge formation, which is caused by separation of electrodes, in the material wear and friction phenomena, especially for different materials, such as, steel and copper. In this paper, anode and cathode materials, which are made of same metal (either steel or copper), are separated with very low constant speed. to observe the bridge formation and contact surface after the bridge separation in detail. As a result, melting bridge formation of 0.5mm height was observed while steel electrodes separating. In the similar test of the identical condition of the copper electrode, the observation of the bridge formation was difficult. However, the copper bridge that grew at 0.2mm height was observed, where test was conducted with separating speed slowed down to 1/10. The molten bridge was formed at the boundary on the anode side with high brightness, and this effect was seen for both steel and copper. Although this phenomena appears for both cases of steel and copper, the anode made of steel material is damaged more seriously. Also in this paper, special strips of steel and copper, simulating the contact bridge, are studied for contact drop, contact resistance and temperature increase at contact point to melt down by increasing current slowly from zero ampere. As the result, the resistance of the copper which is a diamagnetic material rose in a smooth quadratic curve for the increase in current (temperature), and the steel which is ferromagnetic showed the rapid increase above magnetic transformation and allotropic transformation temperature. The increase of heat quantity by decreasing of specific heat due to magnetic transformation and the consequent resistance increase are the cause of the formation of large melting bridge in the steel And Thomson effect is considered as the cause of damage of anode.

Mori, Masami; Kohno, Akio

195

Analysis of the electrical characteristics of a Westinghouse variable speed generating system for wind turbine applications  

NASA Astrophysics Data System (ADS)

Variable speed electric generating technology can enhance the general use of wind energy in electric utility applications. This enhancement results from two characteristic properties of variable speed wind turbine generators: an improvement in drive train damping characteristics, which results in reduced structural loading on the entire wind turbine system, and an improvement in the overall efficiency by using a more sophisticated electrical generator. Electronic converter systems are the focus of this investigation, particularly the properties of a Westinghouse variable-speed, constant-frequency system with wound-rotor induction generator and a cycloconverter. Experience with solid-state converter systems in large wind turbines is extremely limited. This report presents measurements of electrical performances of the Westinghouse system and is limited to the terminal characteristics of the system. Variable speed generating systems working effectively in utility applications will require a satisfactory interface between the turbine-generator pair and the utility network. The electrical testing described herein focuses largely on the interface characteristics of the generating system. A MOD-0 wind turbine was connected to a very strong system; thus, the voltage distortion was low and the total harmonic distortion in the utility voltage was less than 3 percent (within the 5 percent limit required by most utilities). The largest voltage component of a frequency below 60 Hz was 40 dB down from the 60-Hz component.

Herrera, J. I.; Reddoch, T. W.

1988-02-01

196

Numerical calculation and simulation analysis of electrical field characteristics for the electrical resistance tomography system  

Microsoft Academic Search

Sensitivity field in electrical resistance tomography system is affected by the distribution of multiphase medium, and the data of sensitivity distribution which are obtained by theoretical calculation can be used as prior experimental knowledge for image reconstruction, so it is necessary to analyze the distribution of the sensitivity field to decrease error of soft field and improve the quality of

Yanjun Zhang; Deyun Chen; Lili Wang

2009-01-01

197

Electrical Characteristics of Thin-Film Transistors with Double-Active-Layer Structure  

Microsoft Academic Search

Thin-film transistors (TFTs) with a double-active-layer (DAL) structure have been proposed and found to exhibit two kinds of special electrical characteristics. One is the improvement of current drivability and transconductance as compared to the traditional structure. The other is the double-switching characteristics caused by the bi-transistor action. By means of a buried oxide separating the conduction channel into two parts,

Meng-Jin Tsai; Ping-Wei Wang; Huan-Ping Su; Huang-Chung Cheng

1995-01-01

198

Numerical calculation and simulation analysis of electrical field characteristics for the electrical resistance tomography system  

NASA Astrophysics Data System (ADS)

Sensitivity field in electrical resistance tomography system is affected by the distribution of multiphase medium, and the data of sensitivity distribution which are obtained by theoretical calculation can be used as prior experimental knowledge for image reconstruction, so it is necessary to analyze the distribution of the sensitivity field to decrease error of soft field and improve the quality of the image reconstruction. In this paper at the basis of analyzing the principle of electrical resistance tomography system, the mathematical model of sensitivity field is built by utilizing finite element method. Through study field with disperse phase, the factors affecting the distribution of the sensitivity field and rules are analyzed, the calculation of sensitivity distribution and visualized simulation are achieved The experiments show that the finite element model is right, the sensitivity field proposed is in accordance with the practice and the computation velocity is about 10seconds, which provides the basis for related image reconstruction algorithms.

Zhang, Yanjun; Chen, Deyun; Wang, Lili

2009-07-01

199

Relativistic breakdown in planetary atmospheres  

SciTech Connect

In 2003, a new electrical breakdown mechanism involving the production of runaway avalanches by positive feedback from runaway positrons and energetic photons was introduced. This mechanism, which shall be referred to as 'relativistic feedback', allows runaway discharges in gases to become self-sustaining, dramatically increasing the flux of runaway electrons, the accompanying high-energy radiation, and resulting ionization. Using detailed Monte Carlo calculations, properties of relativistic feedback are investigated. It is found that once relativistic feedback fully commences, electrical breakdown will occur and the ambient electric field, extending over cubic kilometers, will be discharged in as little as 2x10{sup -5} s. Furthermore, it is found that the flux of energetic electrons and x rays generated by this mechanism can exceed the flux generated by the standard relativistic runaway electron model by a factor of 10{sup 13}, making relativistic feedback a good candidate for explaining terrestrial gamma-ray flashes and other high-energy phenomena observed in the Earth's atmosphere.

Dwyer, J. R. [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, Florida 32901 (United States)

2007-04-15

200

Dipole Wakefield Suppression In High Phase Advance Detuned Linear Accelerators for the JLC/NLC Designed to Minimise Electrical Breakdown and Cumulative BBU  

SciTech Connect

Recent experiments at SLAC [1,2] and CERN [3] have revealed evidence of significant deformation in the form of ''pitting'' of the cells of the 1.8m series of structures DDS/RDDS (Damped Detuned Structure/Rounded Damped Detuned Structure). This pitting occurs in the high group velocity (v{sub g}/c = 0.012) end of the accelerating structure and little evidence of breakdown has been found in the lower group velocity end of the structure. Additional, albeit preliminary experimental evidence, suggests that shorter and lower group velocity structures have reduced breakdown events with increasing accelerating field strengths. Two designs are presented here, firstly a 90cm structure consisting of 83 cells with an initial v{sub g}/c = 0.0506 (known as H90VG5) and secondly, an even shorter structure of length 60cm consisting of 55 cells with an initial v{sub g}/c = 0.03 (known as H60VG3). The feasibility of using these structures to accelerate a charged beam over 10km is investigated. The particular issue focused upon is suppression of the dipole wakefields via detuning of the cell frequencies and by locally damping individual cells in order to avoid BBU (Beam Break Up). Results are presented on beam-induced dipole wakefields and on the beam dynamics encountered on tracking the progress of the beam through several thousand accelerating structures.

Jones, Roger M

2001-07-02

201

Electrical characteristics of Ta2O5 thin films deposited by electron beam gun evaporation  

E-print Network

Electrical characteristics of Ta2O5 thin films deposited by electron beam gun evaporation V films deposited by a simple electron beam gun evaporator. We describe thicknessO5 thin films deposited by a simple electron beam gun evaporator which enables versatility

Eisenstein, Gadi

202

Statistical Analysis of the Disturbance Sources characteristics on Hybrid Electric Vehicle  

Microsoft Academic Search

With the wide application of the power electronic devices in hybrid electric vehicle, the electromagnetic environment of the car is getting more and more complex. After analyzing a large amount of real vehicle experimental data, the typical waveforms of the voltage and the frequency-domain characteristics of the common-mode current can be got by the statistical method. In this paper, the

Li Yulong; Wu Zhenjun; Wang Lifang

2010-01-01

203

Evaluation of motor characteristics for hybrid electric vehicles using the hardware-in-the-loop concept  

Microsoft Academic Search

If the concept of Hardware-in-the-Loop (HIL) is applied to component testing, characteristic of component of hybrid electric vehicle in real vehicle environment can be evaluated without actually installing that component in real vehicle. In this paper, when commercially available test motor is adopted as a drivetrain of hybrid vehicle, we need to figure out which drive train configuration would be

Sung Chul Oh

2005-01-01

204

Structural properties and electrical characteristics of electron-beam gun evaporated erbium oxide films  

E-print Network

Structural properties and electrical characteristics of electron-beam gun evaporated erbium oxide of another rare-earth­ metal oxide, erbium oxide, Er2O3 . This material is rather well known as an optical it causes less of an erbium silicate in comparison with Gd2O3 and Y2O3 under similar annealing conditions

Eisenstein, Gadi

205

Plasma characteristics of repetitively-pulsed electrical discharges in saline solutions used for surgical procedures  

Microsoft Academic Search

Characteristics of plasmas formed by repetitively-pulsed electrical discharges in sodium chloride and barium chloride saline solutions are reported. Spectroscopic observations in conjunction with an analysis of the voltage and current behavior of the discharge lead to a model in which the liquid is vaporized and ionized to form a plasma containing excited water fragments H* and OH* as well as

Jean Woloszko; Kenneth R. Stalder; Ian G. Brown

2002-01-01

206

Fused Multi-Characteristic Validity Index: An Application to Reconstructed Image Evaluation in Electrical Tomography  

Microsoft Academic Search

The quality of reconstructed images is an important and direct criterion to quantitatively evaluate the effectiveness of reconstruction algorithms in electrical tomography (ET). Unfortunately, there lacks of effective and efficient approach to assessing the quality of ET images in literature and practices. Realizing the gap, we recently develop a novel index termed fused Multiple Characteristic Indices (fMCI) aiming to measure

Shihong Yue; Teresa Wu; Zhiqing Liu; Xian Zhao

2011-01-01

207

Electrical Characteristics and Testing Considerations for Gate Oxide Shorts in CMOS ICs  

Microsoft Academic Search

This paper examines the electrical characteristics and testing considerations of gate oxide shorts. Gate oxide shorts will cause increased IDD and in the majority of cases will degrade logic voltage levels and propagation delay times, but may not affect functionality. Stuck-at and functional models are therefore inadequate for testing gate oxide shorts in CMOS ICs unless they are used in

Jerry M. Soden; Charles F. Hawkins

1985-01-01

208

Pre-breakdown evaluation of gas discharge mechanisms in microgaps  

SciTech Connect

The individual contributions of various gas discharge mechanisms to total pre-breakdown current in microgaps are quantified numerically. The variation of contributions of field emission and secondary electron emission with increasing electric field shows contrasting behavior even for a given gap size. The total current near breakdown decreases rapidly with gap size indicating that microscale discharges operate in a high-current, low-voltage regime. This study provides the first such analysis of breakdown mechanisms and aids in the formulation of physics-based theories for microscale breakdown.

Semnani, Abbas; Peroulis, Dimitrios [School of Electrical and Computer Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)] [School of Electrical and Computer Engineering, Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States); Venkattraman, Ayyaswamy; Alexeenko, Alina A. [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States)] [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States)

2013-04-29

209

Electric Characteristics of Hybrid Polymer Membranes Composed of Two Lipid Species  

NASA Astrophysics Data System (ADS)

Electric characteristics of hybrid polymer membranes composed of two lipid species were studied, where one lipid species is positively charged in aqueous solution and the other is negatively charged. As a result, it was found that the hybrid membranes responded to taste substances in different ways according to the molar mixing ratio of these two kinds of lipids, and also showed different response characteristics from those of the single-lipid membranes. The membranes with the mixing ratio around 50% exhibited the largest responses to HCl (sourness) and monosodium glutamate (umami). Moreover, good quantitative agreements with the observed data on the response electric potential were obtained using a theory describing both the changes in surface electric potential and surface charge density with taste substances.

Oohira, Koji; Toko, Kiyoshi; Akiyama, Hideyuki; Yoshihara, Hiroshi; Yamafuji, Kaoru

1995-09-01

210

Modelling of the electric characteristic of type II superconductors by means of Ligurian minimization  

SciTech Connect

The electrical behavior of type II superconductors can be characterized--in a first approximation--by a strongly nonlinear (even not univocal) e-j relationship. Numerical modelling is necessary to accede to the local characteristic e-j starting from experimental data; the global characteristic U-I of the sample. Classical methods such as Newton-Raphson might fail in dealing with materials having such a characteristic as superconductors have. The authors thus use an absolutely convergent method based on convex optimization, with the Ligurian as objective function. Numerical modelling shows that the smooth U-I characteristic might be generated by a simple e-j characteristic with a well-defined critical current density. It is shown how this technique may be extended to solve complete Maxwell equations in the most general case.

Vasiliu, S.; Bouillault, F.; Degardin, A.; Kreisler, A. [ESE, Gif sur Yvette (France). Lab. de Genie Electrique de Paris] [ESE, Gif sur Yvette (France). Lab. de Genie Electrique de Paris

1996-05-01

211

The electrical and photoconductivity characteristics of donor-acceptor alternating copolymer using solution process  

NASA Astrophysics Data System (ADS)

The authors report on the electrical and photoconductivity characteristics of donor-acceptor alternating copolymer, poly(dioctyloxinapthalenediketopyrrolopyrrole) (PONDPP) with Al/PONDPP/p-Si/Al hybrid organic/inorganic Schottky diode for optoelectronic applications. The fabricated device shows ideality factor value of 2.6 and barrier height of 0.68 eV obtained from current-voltage characteristics. The high rectification ratio of 1.86 × 104 and photo-responsivity of 55 mA/W at 650 nm is achieved. From results, we found that the fine photo-response and electrical characteristics are attributed to the modified band-gap structure to have Schottky barrier at highest occupied molecular orbital to valence band of silicon and high hole mobility of PONDPP.

Woo Jeong, Shin; Back Lee, Gi; Ha, Hyeon-Jun; Kwon, Soon-Ki; Kim, Yun-Hi; Kwon Ju, Byeong

2012-12-01

212

Basic Studies of Applications of Biodegradable Polymer PLLA to Insulation of Electric Wires  

Microsoft Academic Search

We developed equipment for manufacturing a biodegradable-polymer-insulated cable with various functional properties. Using this equipment, we manufactured a poly-l-lactic acid (PLLA)-insulated electric cable and evaluated its basic electrical insulation characteristics. The mean dielectric breakdown strength of the PLLA-insulated electric cable was approximately 3.5 times that of a polyvinyl chloride-insulated electric cable (VV electric cable). The result of bending and weathering

Takuo NAKIRI; Yuuki KAWACHI; Masahiro HONDA; Kenji IMOTO; Takayuki YAMAKITA; Yoshiro TAJITSU

213

Breakdown mechanism of the charged solid dielectric during short circuit discharge  

Microsoft Academic Search

The phenomenon of PET (polyethylene terephthalate) breakdown during short circuit discharge is studied. A theoretical model for detrapping by collisional ionization is proposed for interpretation of the breakdown mechanism. The coefficient for detrapping by collisional ionization and the relation between it and the velocity of the discharging are obtained. A critical electric field of the short circuit breakdown by space

Yang Baitun; Liufu De; Tu Demin; Liu Yaonan

1991-01-01

214

Ionizing potential waves and high-voltage breakdown streamers.  

NASA Technical Reports Server (NTRS)

The structure of ionizing potential waves driven by a strong electric field in a dense gas is discussed. Negative breakdown waves are found to propagate with a velocity proportional to the electric field normal to the wavefront. This causes a curved ionizing potential wavefront to focus down into a filamentary structure, and may provide the reason why breakdown in dense gases propagates in the form of a narrow leader streamer instead of a broad wavefront.

Albright, N. W.; Tidman, D. A.

1972-01-01

215

Electrical characteristics and efficiency of organic light-emitting diodes depending on hole-injection layer  

Microsoft Academic Search

In a device structure of ITO\\/hole-injection layer\\/N,N?-biphenyl-N,N?-bis-(1-naphenyl)-[1,1?-biphthyl]4,4?-diamine(NPB)\\/tris(8-hydroxyquinoline)aluminum(Alq3)\\/Al, we investigated the effect of the hole-injection layer on the electrical characteristics and external quantum efficiency of organic light-emitting diodes. Thermal evaporation was performed to make a thickness of NPB layer with a rate of 0.5–1.0Å\\/s at a base pressure of 5×10?6Torr. We measured current–voltage characteristics and external quantum efficiency with a thickness

Y. H. Lee; W. J. Kim; T. Y. Kim; J. Jung; J. Y. Lee; H. D. Park; T. W. Kim; J. W. Hong

2007-01-01

216

The electrical characteristics of a conical horn-reflector antenna employing a corrugated horn  

Microsoft Academic Search

The electrical properties of a conical horn-reflector antenna of 2-3° beamwidth have been investigated over the frequency range of 12-18 GHz. It is shown that the employment of a corrugated horn reduces the characteristic spillover side lobe of the conical horn-reflector antenna by 15 dB and yields excellent main beam circularity over the full Ku band. This results from the

Ghassan Yassin; Martin Robson; Peter J. Duffett-Smith

1993-01-01

217

Electrical machine having controlled characteristics and its application to a wind-driven machine  

SciTech Connect

The invention provides an electrical machine having an inductor and an armature, one of which has at least two independent winding assemblies. The switching into and out of circuit of each winding assembly is controlled by a processor which receives monitoring parameters of the machine and desired value parameters, thereby controlling in real time the operating characteristics of the machine. The machine may be a winddriven generator.

Berna, M.; Kant, M.; Seger, R.; Vilain, J.P.

1983-07-26

218

Steps and spikes in current-voltage characteristics of oxide/microcrystallite-silicon/oxide diodes  

NASA Astrophysics Data System (ADS)

SiO2/microcrystallite-Si/SiO2 diodes with different contact window sizes were fabricated and studied at room temperature, 77 K, and 4.2 K. Steps were observed in the current-voltage (I-V) characteristics at all three temperatures. These steps would appear for a certain number of measurements, depending upon measurement temperature, and then were replaced by a smooth electrical breakdown I-V characteristic. Data analysis indicates that the steps in the I-V characteristics are due to local electrical breakdowns along the edge of metal contacts instead of electron resonant tunneling through the structure. Surprisingly, however, in one diode, three repeatable spikes, instead of steps, were observed at 4.2 K; this cannot be satisfactorily explained in terms of electrical breakdown, and seems rather like electron resonant tunneling.

Chou, S. Y.; Gordon, A. E.

1992-04-01

219

Analysis of the electrical characteristics and structure of Cu-Filled TSV with thermal shock test  

NASA Astrophysics Data System (ADS)

The electrical characteristics and failure of a Through-Silicon Via (TSV) were investigated using a thermal shock test. The electrical characteristics, such as resistance ( R), self-inductance ( L s ), self-capacitance ( C s ), and mutual capacitance ( C m ), were extracted using a T-equivalent circuit. A cross section of the Cu-filled via was observed by field emission-scanning electron microscopy and the electrical characteristics were measured using a commercial Agilent E4980A LCR Meter. The experimental results revealed R, L s , C s , and C m values of 3.2 m?, 29.3 pH, 12 fF, and 0.42 pF, respectively. C m occurred between the charge-holding TSVs, which changed from 0.42 pF to 0.26 pF due to a permittivity transition of the Cu ion drift. After 1,000 cycles of a thermal shock test, cracks were observed between the opening and around the side of the TSV and Si wafer due to mismatch of the coefficient of thermal expansion between the Cu-plug and Si substrate.

Jeong, Il Ho; Roh, Myong Hoon; Jung, Flora; Song, Wan Ho; Mayer, Michael; Jung, Jae Pil

2014-05-01

220

Electrical treeing studies on the Araldite LY\\/HY 5052 epoxy resin over a wide range of stressing voltage  

Microsoft Academic Search

Electrical treeing breakdown (a long-term electrical deterioration process) has been investigated in Araldite LY\\/HY 5052 epoxy resin pin-plane specimens subjected to a wide range of 50 Hz alternating current electrical stress. The full process of electrical tree initiation and growth was recorded periodically by using a digital camera. The electrical tree growth structural characteristics were examined by means of the

H.-Z. Ding; B. R. Varlow

2004-01-01

221

The prevention of electrical breakdown and electrostatic voltage problems in the space shuttle and its payloads. Part 1: Theory and phenomena  

NASA Technical Reports Server (NTRS)

An introduction to the theory of corona discharge and electrostatic phenomena is presented. The theory is mainly qualitative so that workers in the field should not have to go outside this manual for an understanding of the relevant phenomena. Some of the problems that may occur with the space shuttle in regard to electrical discharge are discussed.

Whitson, D. W.

1975-01-01

222

Physical and electrical characteristics of metal/Dy2O3/p-GaAs structure  

NASA Astrophysics Data System (ADS)

This paper describes the effect of post-deposition annealing on the physical and electrical characteristics of high-k Dy2O3 dielectric films deposited at 250 °C on p-GaAs substrate by electron beam deposition under ultra vacuum. The morphological and structural features of Dy2O3 layer before and after postdeposition annealing were studied by atomic force microscopy (AFM) and X-ray diffraction (XRD). The surface topography analysis reveals that the Dy2O3 film is granular, and contains numerous contacts between columnar grains. While investigating the electrical properties Dy2O3 oxide, the current-voltage characteristics I(V) suggest a Poole-Frenkel (PF) type mechanism of carrier transport for as-deposited and annealed layers. A deviation from the PF leakage current course was found and attributed to the current carrier trapping. The ac impedance properties of the structures have been studied in a wide frequency range at different bias voltage. The Dy2O3 annealed exhibited excellent electrical properties such as small density of interface state and low leakage current. This phenomenon is attributed to a rather crystallized Dy2O3 structure and the reduction of the defects at the oxide/GaAs interface.

Saghrouni, H.; Jomni, S.; Belgacem, W.; Hamdaoui, N.; Beji, L.

223

Nanoscale electrical and mechanical characteristics of conductive polyaniline network in polymer composite films.  

PubMed

The presence and characteristics of a connected network of polyaniline (PANI) within a composite coating based on polyester acrylate (PEA) has been investigated. The bulk electrical conductivity of the composite was measured by impedance spectroscopy. It was found that the composite films containing PANI have an electrical conductivity level in the range of semiconductors (order of 10(-3) S cm(-1)), which suggests the presence of a connected network of the conductive phase. The nanoscopic distribution of such a network within the cured film was characterized by PeakForce tunneling atomic force microscopy (AFM). This method simultaneously provides local information about surface topography and nanomechanical properties, together with electrical conductivity arising from conductive paths connecting the metallic substrate to the surface of the coating. The data demonstrates that a PEA-rich layer exists at the composite-air interface, which hinders the conductive phase to be fully detected at the surface layer. However, by exposing the internal structure of the composites using a microtome, a much higher population of a conductive network of PANI, with higher elastic modulus than the PEA matrix, was observed and characterized. Local current-voltage (I-V) spectroscopy was utilized to investigate the conduction mechanism within the nanocomposite films, and revealed non-Ohmic characteristics of the conductive network. PMID:25295701

Jafarzadeh, Shadi; Claesson, Per M; Sundell, Per-Erik; Pan, Jinshan; Thormann, Esben

2014-11-12

224

Adaptive femtosecond laser-induced breakdown spectroscopy of uranium.  

PubMed

Laser-induced breakdown spectroscopy (LIBS) is an established technique for material characterization applicable to a variety of problems in research, industry, environmental studies, and security. LIBS conducted with femtosecond laser pulses exhibits unique properties, arising from the characteristics of laser-matter interactions in this pulse width regime. The time evolution of the electric field of the pulse determines its interaction with sample materials. We present the design and performance of a femtosecond LIBS system developed to systematically optimize the technique for detection of uranium. Sample analysis can be performed in vacuum environment, and the spectral and temporal diagnostics are coupled through an adaptive feedback loop, which facilitates optimization of the signal-to-noise ratio by pulse shaping. Initial experimental results of LIBS on natural uranium are presented. PMID:23387634

Ko, P; Hartig, K C; McNutt, J P; Schur, R B D; Jacomb-Hood, T W; Jovanovic, I

2013-01-01

225

Beauty in the Breakdown  

ERIC Educational Resources Information Center

Most human beings look at erosion as the destruction of a surface, but artists can see that erosion often creates indefinable beauty. Where do you see beauty in the breakdown? In this article, the author presents an innovative lesson that would allow students to observe both human and physical nature. In this activity students will create a work…

Brisco, Nicole

2008-01-01

226

Electrical characteristics of Ta2O5 based capacitors with different gate electrodes  

NASA Astrophysics Data System (ADS)

Al, W and TiN gate stacks using reactively sputtered thin (15 35 nm) Ta2O5 as a high-k dielectric have been investigated. It has been established that the type and the deposition technique of the gate electrode strongly affect the parameters of the structures. RF sputtered tungsten has been established as the most suitable electrode material (giving a nonreactive contact) providing a low leakage current (˜10-8 A/cm2 at 1 MV/cm) through capacitors and a high dielectric constant. The application of Al gate electrodes in the advanced DRAM devices is impeded by the chemical interaction of Al with the Ta2O5 films deteriorating the performance of the structures. The radiation-induced defects during the TiN deposition increase the leakage currents for TiN/Ta2O5/Si capacitors. A modified Poole Frenkel conduction mechanism with a tendency for a reduction of the compensation level with increasing Ta2O5 thickness was found for W-gate capacitors. Schottky emission at low applied fields and modified Poole Frenkel mechanism at high fields define the J V characteristics of Al capacitors. The current through TiN capacitors is governed by ohmic and space charge limited conduction. The post metallization annealing in H2 reduces the oxide charge but deteriorates both the breakdown fields and the leakage currents for all capacitors studied. The effect is stronger for Al and TiN structures and is accompanied by a reduction of the dielectric constant.

Spassov, D.; Atanassova, E.; Virovska, D.

2006-01-01

227

Electric generators of singlet delta oxygen for an oxygen-iodine laser  

Microsoft Academic Search

Experimental and theoretical research into electric generators of singlet delta oxygen (SDO) for an oxygen-iodine laser made\\u000a at the Lebedev Physics Institute and TRINITI is discussed. Breakdown and current-voltage characteristics of self-sustained\\u000a electric discharge in SDO were studied both experimentally and theoretically, indicating that SDO and pure oxygen have quite\\u000a different electric features. The electric properties and spectroscopy of an

A. A. Ionin; A. P. Napartovich; N. N. Yuryshev

2006-01-01

228

VORTEX BREAKDOWN INCIPIENCE: THEORETICAL CONSIDERATIONS  

E-print Network

or momentum or heat exchange; or destructive, as in degradation of aerodynamic performance. Vortex breakdown interest, vortex breakdown has important technological applications, both aerodynamic and non­ aerodynamic. There is a tendency for the breakdown to migrate back and forth in the test section or on the aerodynamic surface

Erlebacher, Gordon

229

Breakdown of the pseudopotential approximation for magnetizabilities and electric multipole moments: Test calculations for Au, AuF, and Snn cluster (n ? 20)  

NASA Astrophysics Data System (ADS)

The response of the electronic wavefunction to an external electric or magnetic field is widely considered to be a typical valence property and should, therefore, be adequately described by accurately adjusted pseudopotentials, especially if a small-core definition is used within this approximation. In this paper we show for atomic Au and Au+, as well as for the molecule AuF and tin clusters, that in contrast to the case of the static electric dipole polarizability or the electric dipole moment, core contributions to the static magnetizability are non-negligible, and can therefore lead to erroneous results within the pseudopotential approximation. This error increases with increasing size of the core chosen. For tin clusters, which are of interest in ongoing molecular beam experiments currently carried out by the Darmstadt group, the diamagnetic and paramagnetic isotropic components of the magnetizability tensor almost cancel out and large-core pseudopotentials do not even predict the correct sign for this property due to erroneous results in both the diamagnetic and (more importantly) the paramagnetic terms. Hence, all-electron calculations or pseudopotentials with very small cores are required to adequately predict magnetizabilities for atoms, molecules and the solid state, making it computationally more difficult to obtain this quantity for future investigations in heavy atom containing molecules or clusters. We also demonstrate for this property that all-electron density functional calculations are quite robust and give results close to wavefunction based methods for the atoms and molecules studied here.

Schwerdtfeger, Peter; Assadollahzadeh, Behnam; Rohrmann, Urban; Schäfer, Rolf; Cheeseman, James R.

2011-05-01

230

Breakdown of the pseudopotential approximation for magnetizabilities and electric multipole moments: test calculations for Au, AuF, and Sn(n) cluster (n ? 20).  

PubMed

The response of the electronic wavefunction to an external electric or magnetic field is widely considered to be a typical valence property and should, therefore, be adequately described by accurately adjusted pseudopotentials, especially if a small-core definition is used within this approximation. In this paper we show for atomic Au and Au(+), as well as for the molecule AuF and tin clusters, that in contrast to the case of the static electric dipole polarizability or the electric dipole moment, core contributions to the static magnetizability are non-negligible, and can therefore lead to erroneous results within the pseudopotential approximation. This error increases with increasing size of the core chosen. For tin clusters, which are of interest in ongoing molecular beam experiments currently carried out by the Darmstadt group, the diamagnetic and paramagnetic isotropic components of the magnetizability tensor almost cancel out and large-core pseudopotentials do not even predict the correct sign for this property due to erroneous results in both the diamagnetic and (more importantly) the paramagnetic terms. Hence, all-electron calculations or pseudopotentials with very small cores are required to adequately predict magnetizabilities for atoms, molecules and the solid state, making it computationally more difficult to obtain this quantity for future investigations in heavy atom containing molecules or clusters. We also demonstrate for this property that all-electron density functional calculations are quite robust and give results close to wavefunction based methods for the atoms and molecules studied here. PMID:21639419

Schwerdtfeger, Peter; Assadollahzadeh, Behnam; Rohrmann, Urban; Schäfer, Rolf; Cheeseman, James R

2011-05-28

231

An estimation of the electrical characteristics of planetary shallow subsurfaces with TAPIR antennas  

NASA Astrophysics Data System (ADS)

In the frame of the NETLANDER program, we have developed the Terrestrial And Planetary Investigation by Radar (TAPIR) imaging ground-penetrating radar to explore the Martian subsurface at kilometric depths and search for potential water reservoirs. This instrument which is to operate from a fixed lander is based on a new concept which allows one to image the various underground reflectors by determining the direction of propagation of the reflected waves. The electrical parameters of the shallow subsurface (permittivity and conductivity) need to be known to correctly determine the propagation vector. In addition, these electrical parameters can bring valuable information on the nature of the materials close to the surface. The electric antennas of the radar are 35 m long resistively loaded monopoles that are laid on the ground. Their impedance, measured during a dedicated mode of operation of the radar, depends on the electrical parameters of soil and is used to infer the permittivity and conductivity of the upper layer of the subsurface. This paper presents an experimental and theoretical study of the antenna impedance and shows that the frequency profile of the antenna complex impedance can be used to retrieve the geoelectrical characteristics of the soil. Comparisons between a numerical modeling and in situ measurements have been successfully carried over various soils, showing a very good agreement.

Le Gall, A.; Reineix, A.; Ciarletti, V.; Berthelier, J. J.; Ney, R.; Dolon, F.; Corbel, C.

2006-06-01

232

Characteristics of wastes from electric and electronic equipment in Greece: results of a field survey.  

PubMed

The lifespan of electric and electronic equipment is becoming shorter and the amount of related waste is increasing. This study aimed to contribute to the knowledge about qualitative and quantitative characteristics of such wastes in Greece. Specifically, results are presented from a field survey, which took place in the city of Thessaloniki, Greece, during the year 2002. The survey was conducted with suitable questionnaires in department stores and in households of various municipalities. Household appliances were grouped as follows: (A) large (refrigerator, freezer, washing machine, clothes dryer, electric cooker, microwave oven, electric heater), (B) small (vacuum cleaner, electric iron, hair dryer), (C) information technology and telecommunication equipment (PC, laptop, printer, phone) and (D) consumer equipment (radio, TV, video, DVD, console). The analysis indicated that the lifespan of all new goods is gradually reducing (apart from refrigerators, for which the lifespan was surprisingly found to be increasing) and provided linearized functions for predicting the lifespan, according to the year of manufacture, for certain large appliances. PMID:16200988

Karagiannidis, Avraam; Perkoulidis, George; Papadopoulos, Agis; Moussiopoulos, Nicolas; Tsatsarelis, Thomas

2005-08-01

233

Neutron, gamma ray, and temperature effects on the electrical characteristics of thyristors  

NASA Technical Reports Server (NTRS)

Experimental data showing the effects of neutrons, gamma rays, and temperature on the electrical and switching characteristics of phase-control and inverter-type SCR's are presented. The special test fixture built for mounting, heating, and instrumenting the test devices is described. Four SCR's were neutron irradiated at 300 K and four at 365 K for fluences up to 3.2 x 10 exp 13 n/sq. cm, and eight were gamma irradiated at 300 K only for gamma doses up to 5.1 Mrads. The electrical measurements were made during irradiation and the switching measurements were made only before and after irradiation. Radiation induced crystal defects, resulting primarily from fast neutrons, caused the reduction of minority carrier lifetime through the generation of R-G centers. The reduction in lifetime caused increases in the on-state voltage drop and in the reverse and forward leakage currents, and decreases in the turn-off time.

Frasca, A. J.; Schwarze, G. E.

1992-01-01

234

Effect of Electrostatic Discharge on Electrical Characteristics of Discrete Electronic Components  

NASA Technical Reports Server (NTRS)

This article reports on preliminary results of a study conducted to examine how temporary electrical overstress seed fault conditions in discrete power electronic components that cannot be detected with reliability tests but impact longevity of the device. These defects do not result in formal parametric failures per datasheet specifications, but result in substantial change in the electrical characteristics when compared with pristine device parameters. Tests were carried out on commercially available 600V IGBT devices using transmission line pulse (TLP) and system level ESD stress. It was hypothesized that the ESD causes local damage during the ESD discharge which may greatly accelerate degradation mechanisms and thus reduce the life of the components. This hypothesis was explored in simulation studies where different types of damage were imposed to different parts of the device. Experimental results agree qualitatively with the simulation for a number of tests which will motivate more in-depth modeling of the damage.

Wysocki, Phil; Vashchenko, Vladislav; Celaya, Jose; Saha, Sankalita; Goebel, Kai

2009-01-01

235

Electrical and dielectric characteristics of Al/Dy2O3/p-Si heterostructure  

NASA Astrophysics Data System (ADS)

In this work we report the electrical characteristics of high-k Dy2O3 dielectric deposited on p-Si substrate by electron beam deposition under ultra vacuum. The surface morphology of Dy2O3 is investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface topography analysis reveals that the Dy2O3 film is nanograined and contains numerous contacts between columnar grains. The electrical properties of Al/Dy2O3/p-Si heterostructure are further analyzed by current-voltage (I-V), capacitance-voltage (C-V), capacitance-frequency (C-f) and conductance-frequency (G-f) measurements. The dominant conduction mechanisms which governed the Al/Dy2O3/p-Si heterostrucure are determined. The hetrostructure induces a significant value of leakage current: 1.1×10-5 A at flat-band voltage -1 V which is linked to the structural properties of the elaborated structure. The effects of grain boundaries and oxygen vacancies within the dielectric are observed in term of leakage current. Indeed, the C(V) characteristics measured at different applied voltage show a large frequency-dispersion, indicative of the presence of a continuous distribution of interface states. So, the interface state densities are determined from the C(V) characteristics to be around 1013 eV-1 cm-2. C(f) measurements elucidate that the capacitance behavior is typical of material with traps. From G(f) and C(f) measurement the trap density and relaxation time are also determined. It is suggested that the interface states series resistance are important parameters that strongly influence the electrical properties of Al/Dy2O3/p-Si heterostrucure.

Cherif, Ahlem; Jomni, Sami; Mliki, Najeh; Beji, Lotfi

2013-11-01

236

Effect of configuration and dimensions of reactor electrodes on electrical and optical corona discharge characteristics  

NASA Astrophysics Data System (ADS)

An experimental parametric study is made to investigate how the electrical corona discharge characteristics are influenced by the geometrical configuration and dimensions of the reactor and the electrode polarity of the applied voltage. Furthermore, features of the corona discharge plasma formed around the stressed electrode in some different gases are recorded photographically to provide more information on the physical mechanisms of the corona discharge in the investigated gases. The obtained results have been discussed in the light of gas discharge physics and its applications.

El-Koramy, Reda Ahmed; Yehia, Ashraf; Omer, Mohamed

2010-05-01

237

Electrical characteristics of UV photodetectors based on ZnO/diamond film structure  

NASA Astrophysics Data System (ADS)

Ultraviolet photodetectors based on ZnO/diamond film structure were fabricated. The properties of Au/ZnO contacts and effects of grain sizes on the electrical characteristics of photodetectors were discussed. Due to the bombardment with Au atoms and the annealing process, fine ohmic contacts were formed between Au electrodes and ZnO films. Dark currents and photocurrents of the photodetectors were related to sputtering time and the grain size of ZnO films. For the photodetector with a bigger grain size, a lower dark current and a higher photocurrent were obtained under 10 V bias voltage. The time-dependent photocurrent confirmed the carrier trapping effect.

Liu, Jianmin; Xia, Yiben; Wang, Linjun; Su, Qingfeng; Shi, Weimin

2007-04-01

238

Characteristics for Small Capacity Electric Energy Storage System with Batteries by Current Source Inverter  

NASA Astrophysics Data System (ADS)

We propose an electric energy storage system with batteries by a current source inverter. It is interconnected to the single-phase three-wire distribution system. In order to reduce the dc reactor capacity and change the discharging and the charging operations by signals, a set of DC-DC converters is added between the inverter and the batteries. In this paper, the proposed circuit configuration, the control scheme and the operating method are described, and then the discharging and the charging characteristics are discussed experimentally.

Ogura, Yasuhiro; Masukawa, Shigeo; Iida, Shoji

239

Spectral and Dynamic Characteristics of Helium Plasma Emission and its Effect on a Laser-Ablated Target Emission in a Double-Pulse Laser-Induced Breakdown Spectroscopy (LIBS) Experiment.  

PubMed

A systematic study has been performed on the spectral characteristics of the full spectrum of He emission lines and their time-dependent behaviors measured from the He gas plasmas generated by a nanosecond neodymium-doped yttrium aluminum garnet laser. It is shown that among the major emission lines observed, the triplet He(I) 587.6 nm emission line stands out as the most prominent and long-lasting line, associated with de-excitation of the metastable triplet (S = 1) excited state (1s(1) 3d(1)). The role of this metastable excited state is manifested in the intensity enhancement and prolonged life time of the Cu emission with narrow full width half-maximum, as demonstrated in an orthogonal double-pulse experiment using a picosecond laser for the target ablation and a nanosecond laser for the prior generation of the ambient He gas plasma. These desirable emission features are in dire contrast to the characteristics of emission spectra observed with N2 ambient gas having no metastable excited state, which exhibit an initial Stark broadening effect and rapid intensity diminution typical to thermal shock wave-induced emission. The aforementioned He metastable excited state is therefore responsible for the demonstrated favorable features. The advantage of using He ambient gas in the double-pulse setup is further confirmed by the emission spectra measured from a variety of samples. The results of this study have thus shown the potential of extending the existing laser-induced breakdown spectroscopy application to high-sensitivity and high-resolution spectrochemical analysis of wide-ranging samples with minimal destructive effect on the sample surface. PMID:25506688

Jobiliong, Eric; Suyanto, Hery; Marpaung, Alion Mangasi; Abdulmadjid, Syahrun Nur; Idris, Nasrullah; Hedwig, Rinda; Ramli, Muliadi; Pardede, Marincan; Suliyanti, Maria Margaretha; Kagawa, Kiichiro; Fukumoto, Ken-Ichi; Tjia, May On; Lie, Tjung Jie; Lie, Zener Sukra; Kurniawan, Koo Hendrik

2015-01-01

240

GPR-based evaluation of strength properties of unbound pavement material from electrical characteristics  

NASA Astrophysics Data System (ADS)

It is well known that inter-particle friction and cohesion of soil particles and aggregates deeply affect the strength and deformation properties of soils, exerting critical effects on the bearing capacity of unbound pavement materials. In that respect, considering that strength characteristics of soil are highly dependent on particle interactions, and assuming a relationship between electric properties (e.g. electric permittivity) and bulk density of materials, a good correlation between mechanical and electric characteristics of soil is expected. In this work, Ground Penetrating Radar (GPR) techniques are used to investigate this topic. Two GPR equipment with same electronic characteristics and different survey configurations are used. Each radar operates with two ground-coupled antennae at 600 MHz and 1600 MHz central frequencies. Measurements are developed using 4 channels, 2 mono-static and 2 bi-static. The received signal is sampled in the time domain at dt = 7.8125 × 10-2 ns, and in the space domain every 2.4 × 10-2 m. A semi-empirical model is proposed for predicting the resilient modulus of sub-asphalt layers from GPR-derived data. Basically, the method requires to follow two steps. Firstly, laboratory tests are carried out for calibration, with the main focus to provide consistent empirical relationships between physical (e.g. bulk density) and electric properties. The second step is focused on the in-situ validation of results through soil strength measurements retrieved by CBR tests and Light Falling Weight Deflectometer (LFWD). On the basis of traditional empirical equations used for flexible pavement design, the following expression is proposed: -m Ei = ?j?hj,i j=1 where Ei [MPa] is the ith expected resilient modulus of the surveyed soil under the line of scan, hj,i [m] is the ith thickness referred to the jth layer, and ?j is a dielectric parameter calibrated as a function of the relative electric permittivity. The experimental setting requires the use of road material, typically employed for subgrade and subbase courses. Different types of soil ranging from group A1 to A4 by AASHTO soil classification system, are analyzed. As regards the laboratory experiments, material is gradually compacted in electrically and hydraulically isolated test boxes. A large metal sheet supports the experimental boxes, so that the transmitted GPR signal is totally reflected. GPR inspections are carried out for any compaction step up to the maximum density value available. Moreover, in-situ tests are carried out on targeted types of soil, with grain size distribution and texture comparable to those analyzed in laboratory environment. The results of this study confirm a promising correlation between the electric permittivities and the strength and deformation properties of the surveyed soils. Laboratory analyses show that the relationship between the relative permittivity and the bulk density is positive: the higher the density of the compacted soil sample, the higher the electric permittivity of the medium. Analogously, in-situ validation presents a good comparison between measured and predicted data. Percentage errors less than 20% demonstrate that a reliable prediction of Young Modulus using this GPR-based approach can be achieved.

Benedetto, Andrea; D'Amico, Fabrizio; Tosti, Fabio

2013-04-01

241

Experimental study on the dielectric characteristics of liquid nitrogen with respect to various pressures  

NASA Astrophysics Data System (ADS)

The electrical breakdown characteristics of liquid nitrogen (LN 2) are required to design of high voltage superconducting machines which should have high reliability. This paper deals with the investigation to verify the relationships between the electrical breakdown characteristics of LN 2 its pressure condition. The electrical breakdown characteristics of LN 2 were measured by using sphere-plane electrode systems. The diameter of sphere electrode had five different values. The gaseous nitrogen was injected into a cryostat which contained the sphere-plane electrode system to control the pressure of LN 2 from 50 to 200 kPa. The AC dielectric tests in LN 2 were repeated 10 times in each pressure condition. The AC breakdown voltage at sparkover with 50% probability was calculated by commercialized statics tools. From finite element method simulation results, the field utilization factor which means the field uniformity was calculated between sphere and plane electrode and its relations with AC breakdown voltage with 50% probability were analyzed. Finally, these results provided a suitable design parameter of electrical insulation for high voltage superconducting machines such as superconducting fault current limiters, superconducting cables, and superconducting transformers.

Na, J. B.; Kang, H.; Chang, K. S.; Kim, Y. J.; Kim, K. J.; Lee, H. G.; Ko, T. K.

2010-11-01

242

Optical and electrical characteristics of air dielectric barrier discharges in mode transition at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Atmospheric pressure dielectric barrier discharges (DBDs) have a wide range of industrial applications, generally exhibiting either filamentary or diffuse (i.e. glow) discharges. The focus of this investigation is on the formation mechanisms of the discharge current pulse width, on the order of tens of microseconds, accompanied by a light source formation, which is called a light source (LS) mode in air DBDs at atmospheric pressure. From a macroscopic point of view, the characteristics of the discharge current in the LS mode are similar with those of the glow mode. The optical and electrical characteristics of air DBDs at atmospheric pressure are investigated in the transition from the filamentary mode to the LS mode by measuring the optical emission spectroscopy and electrical signals. It is shown that in the manual increasing voltage stage, the vibrational temperature almost never changes and the gas temperature, electron temperature, dielectric capacitance, gas voltage (Vg) and discharge power (P) increase with an increase in the applied voltage. In the automatic decreasing voltage stage, all of these parameters, except Vg and P, increase with a decrease in the voltage. But, when the voltage decreases to a minimum value corresponding to the LS mode, P reaches a maximum value. In this paper, the variations of these parameters are analyzed and discussed in detail. The formation of the LS mode originates from the secondary electrons. The formation mechanisms of the secondary electrons are also discussed.

Wang, Weiwei; Liu, Feng; Wang, Xue; Han, Haiyan; Huang, Yanbin; Liang, Rongqing

2015-04-01

243

Enhancement of the electrical characteristics of metal-free phthalocyanine films using cold isostatic pressing  

NASA Astrophysics Data System (ADS)

Spatial gaps between grains and other grains, substrates, or electrodes in organic electronic devices are one of the causes of the reduction in the electrical characteristics. In this study, we demonstrate that cold isostatic pressing (CIP) is an effective method to crush the gaps and enhance the electrical characteristics. CIP of metal-free phthalocyanine (H2PC) films induced a decrease in the film thickness by 34%-40% because of the gap crush. The connection of smaller grains into a larger grain and planarization of the film surface were also observed in the CIP film. The crystal axes of the H2PC crystallites were rearranged from the a-axis to the c-axis of the ?-phase crystal structure in a direction perpendicular to the substrate by CIP, indicating favorable hole injection and transport in this direction because of a better overlap of ? orbitals. Thermally stimulated current measurements showed that deep hole traps disappeared and the total hole-trap density decreased after CIP. These CIP-induced changes of the film thicknesses, crystal axes and the hole traps lead to a marked increase in the hole mobility of the H2PC films from 2.0 × 10-7 to 4.0 × 10-4 cm2/V s by 2000 times in the perpendicular direction. We believe that these findings are important for unveiling the underlying carrier injection and transport mechanisms of organic films and for enhancing the performance of future organic electronic devices.

Matsushima, Toshinori; Esaki, Yu; Adachi, Chihaya

2014-12-01

244

Probability characteristics of electrical noise in heterojunction light-emitting diodes  

SciTech Connect

A hardware-software complex for measurements of the characteristics of electrical and optical noise in light-emitting diodes (LEDs) in the frequency range from 1 to 40 kHz is described. The electrical noise of several types of heterojunction-based LEDs are studied; these types include red-emission LEDs with AlInGaP/GaAs quantum wells and the green- and blue-emission LEDs with AlInGaN/SiC quantum wells are studied by the method of discrete samples. The spectra of all studied LEDs in the frequency range from 1 to 10 kHz have the form 1/f{sup {gamma}}. It is noteworthy that, for red-emission LEDs, the exponent {gamma} is significantly smaller than unity; this index is close to unity for the green- and blue-emission LEDs. The characteristic time of correlation of the noise of red-emission LEDs by several times exceeds the correlation times for the blue- and green-emission LEDs. It is shown that reduced functions of the amplitude distribution of the noise voltage are close to Gaussian functions with almost the same dispersion for all LED types.

Sergeev, V. A., E-mail: sva@ulstu.ru; Frolov, I. V.; Shirokov, A. A.; Shcherbatyuk, Yu. N. [Ul'yanovsk State Technical University (Russian Federation)

2011-12-15

245

Electric Field Waveform Characteristics of Positive and Negative Lightning Return Strokes in Florida  

NASA Astrophysics Data System (ADS)

In 2007-2008, 52 positive cloud-to-ground flashes containing 63 return strokes (52 first, 10 second, and 1 third) were recorded at the Lightning Observatory in Gainesville (LOG), Florida. NLDN-reported distances from the LOG for 48 (40 first and 8 second) strokes ranged from 7.8 to 157 km. In this study, various microsecond-scale features of electric field waveforms of these positive return strokes including risetimes, characteristics of the slow-front and fast transition, zero-crossing time, opposite-polarity overshoot, and characteristics of the electric field derivative (dE/dt) pulse are examined and compared with the characteristics of negative return strokes in Florida found in the literature. Parameters of electric field waveforms produced by positive and negative first return strokes are summarized in Table 1. The AM zero-to-peak risetime and 10-90% risetime for 51 positive first return strokes were 7.9 ?s and 4.0 ?s, respectively, which are longer than the corresponding values of 4.4 ?s and 2.6 ?s for 105 first strokes in negative cloud-to-ground flashes in Florida reported by Master et al. (1984). The AM slow front duration for 51 positive first strokes was 6.1 ?s which is about a factor of two greater than that found for negative first return strokes by Master et al. For positive first return strokes examined here, the AM zero-crossing time was 58 ?s and the opposite polarity overshoot was, on average, 14% of the peak. These values are not much different from those (50 ?s and 19%) reported by Pavlick et al. (2002) for negative first return strokes in Florida. On the other hand, Haddad et al. (2012) reported the AM zero-crossing time of 96 ?s and the average opposite polarity overshoot of 23% for 48 negative first strokes recorded at the LOG at distances of 50 to 100 km. References: Haddad, M. A., V. A. Rakov et al. (2012), J. Geophys. Res., 117, D10101, doi:10.1029/2011JD017196. Krider, E. P., C. Leteinturier et al. (1996), J. Geophys. Res., 101(D1), 1589-1597. Master, M. J., M. A. Uman et al. (1984), IEEE Trans. PAS, PAS-103, pp. 2519-2529. Pavlick, A., D. E. Crawford et al. (2002), 7th International Conference on Probabilistic Methods Applied to Power Systems, Naples, Italy.Table 1. Parameters of electric field waveforms produced by positive and negative first return strokes in Floridat;

Nag, A.; Rakov, V. A.

2012-12-01

246

On Statistical Characteristics of Electric Fields of the Thunderstorm Clouds in the Atmosphere  

NASA Astrophysics Data System (ADS)

A series of features of the spectral characteristics of thunderstorm-cloud field perturbations is specified on the basis of long-term ground-based measurements of the electric field at remote locations. A significant increase in the spectral density of the electric-field variations during the thunderstorm has been observed. Maximum increase due to the pulsed field component, which is related to the lightning discharges, is observed in the fluctuation-period range from tens of seconds to several minutes. A significant increase is also observed in the range 0.5-1.5 mHz (10-30-min periods) in which the spectral density is increased by more than a factor of 104, whereas the increase factor at the lower frequencies is equal to 100 (about 10 times for the field). Quasimonochromatic components (with 10-20-min periods) in the frequency fluctuation spectra of an electric field of the powerful thunderstorm clouds, which drift by frequency at the cloud initiation, maturity, and dissipation stages are found. It is shown that presentation of the sequence of the pulsed field perturbations related to the discharges in the form of a pulse flow with independent intervals (Poisson flow) agrees with the form of the fluctuation spectrum of the observed field and leads to an estimate of 10 s for the average relaxation (regeneration) time of the field in the thunderstorm-cloud vicinity after the discharge.

Klimenko, V. V.; Mareev, E. A.; Shatalina, M. V.; Shlyugaev, Yu. V.; Sokolov, V. V.; Bulatov, A. A.; Denisov, V. P.

2014-04-01

247

Electrical and mechanical characteristics of surface AC dielectric barrier discharge plasma actuators applied to airflow control  

NASA Astrophysics Data System (ADS)

The present paper is a wide review on AC surface dielectric barrier discharge (DBD) actuators applied to airflow control. Both electrical and mechanical characteristics of surface DBD are presented and discussed. The first half of the present paper gives the last results concerning typical single plate-to-plate surface DBDs supplied by a sine high voltage. The discharge current, the plasma extension and its morphology are firstly analyzed. Then, time-averaged and time-resolved measurements of the produced electrohydrodynamic force and of the resulting electric wind are commented. The second half of the paper concerns a partial list of approaches having demonstrated a significant modification in the discharge behavior and an increasing of its mechanical performances. Typically, single DBDs can produce mean force and electric wind velocity up to 1 mN/W and 7 m/s, respectively. With multi-DBD designs, velocity up to 11 m/s has been measured and force up to 350 mN/m.

Benard, Nicolas; Moreau, Eric

2014-11-01

248

Spark breakdown of liquid hydrocarbons. I. Fast current and voltage measurements of the spark breakdown in liquid n-hexane  

NASA Astrophysics Data System (ADS)

A fast coaxial discharge line for the study of the electric breakdown of liquid hydrocarbons is described. It allows the simultaneous measurement of discharge current (up to 5 kA) and voltage (up to 50 kV) with nanosecond time resolution. The spark gap is of tip-plane geometry. A detailed frequency analysis of the discharge and measurement circuits has been performed. Examples for the spark breakdown of n-hexane under a variety of conditions are presented.

Fuhr, Jitka; Schmidt, Werner F.; Sato, Shuji

1986-06-01

249

Comparative study of electrical characteristics in (1 0 0) and (1 1 0) surface-oriented nMOSFETs with direct contact La-silicate/Si interface structure  

NASA Astrophysics Data System (ADS)

This study reports on the electrical characteristics of (1 1 0)-oriented nMOSFETs with a direct contact La-silicate/Si interface structure and the detailed comparison with (1 0 0)-oriented nMOSFETs. Precise control of oxygen partial pressure can provide the scaled EOT down to 0.73 nm on (1 1 0) orientation in common with (1 0 0) orientation. No frequency dispersion in Cgc-V characteristic for (1 1 0)-oriented nMOSFETs is successfully demonstrated at scaled EOT region, while higher amount of available bonds on (1 1 0) surface results in a larger interface state density, leading to the degradation of sub-threshold slope. High breakdown voltages of 2.85 V and 2.9 V for (1 0 0)- and (1 1 0)-oriented nMOSFETs are considered to be due to superior interfacial property. The electron mobility on (1 1 0) orientation is lower than that on (1 0 0) orientation because of the smaller energy split between fourfold valleys and twofold valleys as well as the larger density of states for lower-energy valleys in the (1 1 0) surface. Moreover, electron mobility is reduced with decreasing EOT in both (1 0 0)- and (1 1 0)-oriented nMOSFETs. It is found that threshold voltage instability by positive bias stress is mainly responsible for bulk trapping of electron even with a larger interface state density in (1 1 0) orientation and influence of surface orientation on threshold voltage instability is negligibly small.

Kawanago, T.; Kakushima, K.; Ahmet, P.; Kataoka, Y.; Nishiyama, A.; Sugii, N.; Tsutsui, K.; Natori, K.; Hattori, T.; Iwai, H.

2013-06-01

250

Electric transport of a single-crystal iron chalcogenide FeSe superconductor: Evidence of symmetry-breakdown nematicity and additional ultrafast Dirac cone-like carriers  

NASA Astrophysics Data System (ADS)

An SDW antiferromagnetic (SDW-AF) low-temperature phase transition is generally observed and the AF spin fluctuations are considered to play an important role for the superconductivity pairing mechanism in FeAs superconductors. However, a similar magnetic phase transition is not observed in FeSe superconductors, which has caused considerable discussion. We report on the intrinsic electronic states of FeSe as elucidated by electric transport measurements under magnetic fields using a high quality single crystal. A mobility spectrum analysis, an ab initio method that does not make assumptions on the transport parameters in a multicarrier system, provides very important and clear evidence that another hidden order, most likely the symmetry broken from the tetragonal C4 symmetry to the C2 symmetry nematicity associated with the selective d -orbital splitting, exists in the case of superconducting FeSe other than the AF magnetic order spin fluctuations. The intrinsic low-temperature phase in FeSe is in the almost compensated semimetallic states but is additionally accompanied by Dirac cone-like ultrafast electrons ˜104cm2(VS) -1 as minority carriers.

Huynh, K. K.; Tanabe, Y.; Urata, T.; Oguro, H.; Heguri, S.; Watanabe, K.; Tanigaki, K.

2014-10-01

251

Breakdown of model aircraft radome dielectric shell in artificial charged aerosol clouds  

NASA Astrophysics Data System (ADS)

The breakdown of a model aircraft radome dielectric shell in artificial charged aqueous aerosol clouds has been experimentally studied. It is established that, in most cases, electric breakdown of a model shell takes place without explicit discharge development between a charged aqueous aerosol cloud and a model antenna arranged under the radome shell. The probabilities of the dielectric shell breakdown have been determined for various radome models. A possible mechanism of the shell breakdown in hollow dielectric radomes interacting with charged aqueous aerosol clouds and electric discharges in these clouds is proposed that takes into account the accumulation of charges of opposite signs on the internal and external surface of the radome.

Temnikov, A. G.; Chernenskii, L. L.; Orlov, A. V.; Antonenko, S. S.

2011-10-01

252

Solar PV electricity and market characteristics: two Canadian case-studies  

Microsoft Academic Search

To determine whether solar electricity (that is, electricity generated by photovoltaics) is, on an average, more valuable—in market terms—than the electricity generated in power systems as a whole, this article investigates the extent to which solar resource availability in two Canadian locations is associated with peak electricity market demand and peak electricity market price. More specifically, solar radiation and electricity

Ian H. Rowlands

2005-01-01

253

Simulation of the Electrical Properties of ZnO-BASED Ceramic Varistors Using Continuum Theory  

NASA Astrophysics Data System (ADS)

A continuum field model describing the electrical characteristics of polycrystalline semiconductors ceramics is suggested. Taking into account the continuum theory, a static differential equation about electron level on the base of Poisson equation is established. The one-dimensional calculation is carried out using the Runge-Kutta method. The effect of grain size, temperature and donor concentration on the current-voltage characteristic and specific capacitance of the material is calculated quantitatively using ZnO ceramics as an example. The results pointed out that current and voltage characteristics divide into three regions: Linear region before breakdown field, nonlinear region near breakdown field and upturn region after breakdown field. As the applied voltage increases, the grain boundary barrier and the grain boundary capacitance in the nonlinear zone drop drastically. The results are compared with experimental data. An interesting phenomenon is that the Schottky barrier has a small offset along the direction of the applied electric field.

Fang, Chao; Zhou, Dongxiang

2012-07-01

254

Study and modeling of the breakdown voltage in semi insulating GaAs P+N, PN+, P+N+ junctions diodes presenting deep centers traps  

NASA Astrophysics Data System (ADS)

This work aims at determining the characteristic I (Breakdown voltage) of the inverse current in GaAs PN junction diode, subject to an reverse polarization while specifying the parameters that influence the Breakdown voltage of the diodes. In this work, we simulated the behavior of the ionization phenomenon by impact Breakdown by avalanche of the PN junctions, subject to an inverse polarization. Will be taken into account both the trapping model in a stationary regime in the P+N, PN+, and P+N+ structures using like material of basis the III-V compounds and mainly the GaAs semi-insulating in which the deep centers have in important densities. The study of the physical and electric behavior of the semiconductors, and notably is based on the influence of the deep center presence on the characteristic I(V) current-tension, that requires calculation the electrostatic potential, the electric field, the integral of ionization, the density of the states traps, the diffusion current of minority in the regions (1) and (3), the current thermal generation in the region (2), the leakage current in surface, and the breakdown voltage.

Resfa, A.; Menezla, Brahimi R.; Bougueneya, Mustapha

2014-08-01

255

A breakdown model for the bipolar transistor to be used with circuit simulators  

SciTech Connect

A breakdown model for the output characteristics of the bipolar transistor (bjt) has been developed. The behavioral modeling capability of PSPICE, a popular SPICE program (with Emphasis on Integrated circuits) was used to implement the macromodel. The model predicts bjt output characteristics under breakdown conditions. Experimental data was obtained to verify the macromodel. Good agreement exits between the measured and the simulated results.

Keshavarz, A.A. [Alliance Technologies, Inc., Albuquerque, NM (United States); Raney, C.W.; Campbell, D.C. [Sandia National Labs., Albuquerque, NM (United States)

1993-08-01

256

Simulating and modeling the breakdown voltage in a semi-insulating GaAs P+N junction diode  

NASA Astrophysics Data System (ADS)

This work aims to determine the characteristic I (breakdown voltage) of the inverse current in a GaAs PN junction diode, subject to a reverse polarization, while specifying the parameters that influence the breakdown voltage of the diode. In this work, we simulated the behavior of the ionization phenomenon by impact breakdown by avalanche of the PN junctions, subject to an inverse polarization. We will take into account both the trapping model in a stationary regime in the P+N structure using like material of basis the III-V compounds and mainly the GaAs semi-insulating in which the deep centers have in important densities. We are talking about the model of trapping in the space charge region (SCR) and that is the trap density donor and acceptor states. The carrier crossing the space charge region (SCR) of W thickness creates N electron—hole pairs: for every created pair, the electron and the hole are swept quickly by the electric field, each in an opposite direction, which comes back, according to an already accepted reasoning, to the crossing of the space charge region (SCR) by an electron or a hole. So the even N pair created by the initial particle provoke N2 ionizations and so forth. The study of the physical and electrical behaviour of semiconductors is based on the influence of the presence of deep centers on the characteristic I(V) current-tension, which requires the calculation of the electrostatic potential, the electric field, the integral of ionization, the density of the states traps, the diffusion current of minority in the regions (1) and (3), the current thermal generation in the region (2), the leakage current in the surface, and the breakdown voltage.

Resfa, A.; Menezla, Brahimi. R.; Benchhima, M.

2014-08-01

257

Simplified fabrication of back surface electric field silicon cells and novel characteristics of such cells.  

NASA Technical Reports Server (NTRS)

An investigation of the characteristics and behavior of 10 ohm-cm silicon cells having abnormally high open-circuit voltages was made. The cells studied were made by a new, highly simplified, contact fabrication process which creates both a contact and a thin electric field region at the cell back surface without the need for phosphorus layer removal. These cells had open-circuit voltages of about 0.58 V and their performance as a function of thickness, temperature, and 1 MeV electron irradiation is detailed. The study showed that 10 ohm-cm back-surface-field cells can have the high initial efficiencies and desirable temperature behavior of low resistivity cells. Thin back-surface-field cells were made and showed, in addition, much greater radiation damage resistance. A mechanism is proposed to explain the results.

Mandelkorn, J.; Lamneck, J. H., Jr.

1972-01-01

258

Electrical Characteristics of Pt Schottky Contacts on AlInN:Mg/GaN Heterostructures  

NASA Astrophysics Data System (ADS)

The electrical characteristics of Pt Schottky contacts on AlInN:Mg/GaN heterostructures were investigated. A barrier inhomogeneity model applied to temperature-dependent forward current-voltage (I-V) curves revealed the mean barrier height of 1.67 eV and the standard deviation of 0.22 eV. The reverse leakage current could be understood in terms of the Poole-Frenkel emission model, yielding the emission barrier height of 0.26 eV and the high-frequency relative dielectric permittivity of 5.32. On the basis of these obtained values, the continuum of electronic states could be predicted to locate 1.41 eV below the valence band.

Kim, Seongjun; Kim, Hee Jin; Choi, Suk; Ryou, Jae-Hyun; Dupuis, Russell D.; Ahn, Kwang-Soon; Kim, Hyunsoo

2013-10-01

259

Simplified fabrication of back surface electric field silicon cells and novel characteristics of such cells  

NASA Technical Reports Server (NTRS)

An investigation of the characteristics and behavior of 10 ohm-cm silicon cells having abnormally high open-circuit voltages was made. The cells studied were made by a new, highly simplified, contact fabrication process which creates both a contact and a thin electric field region at the cell back surface without the need for phosphorus layer removal. These cells had open-circuit voltages of about 0.58 V and their performance as a function of thickness, temperature, and 1 MeV electron irradiation is detailed. The study showed that 10 ohm-cm back-surface-field cells can have the high initial efficiencies and desirable temperature behavior of low resistivity cells. Thin back-surface-field cells were made and showed, in addition, much greater radiation damage resistance. A mechanism is proposed to explain the results.

Mandelkorn, J.; Lamneck, J. H., Jr.

1972-01-01

260

Electrical characteristics and interface structure of magnetic tunnel junctions with hafnium oxyfluoride barrier  

SciTech Connect

We have studied the effects of fluorine inclusion on the electrical transport characteristics and interface structure of the hafnium oxide barrier in a magnetic tunnel junction. The tunneling magnetoresistance (TMR) and resistance-area (RA) as a function of oxidation time show that the TMR ratio of the hafnium oxyfluoride barrier is higher (8.3%) than that of the hafnium oxide barrier (5.7%) at their optimum conditions, and the oxyfluoride barrier junctions maintain a high TMR ratio even when the RA product increases by three orders of magnitude. X-ray photoelectron spectroscopy analysis shows that the fluorine atoms in the oxyfluoride barrier play an important role in the formation of a barrier with uniform composition. We believe that the initial fluoride layer is causing the subsequent oxygen diffusion to slow down, resulting in the formation of a defect-free hafnium oxide layer. These results are consistent with what we have found for aluminum oxyfluoride barriers.

Yu, Y.Y.; Kim, D.S.; Char, K. [Center for Strongly Correlated Materials Research and School of Physics, Seoul National University, Seoul 151-742 (Korea, Republic of)

2004-12-01

261

Hybrid nanocomposite based on cellulose and tin oxide: growth, structure, tensile and electrical characteristics  

NASA Astrophysics Data System (ADS)

A highly flexible nanocomposite was developed by coating a regenerated cellulose film with a thin layer of tin oxide (SnO2) by liquid-phase deposition. Tin oxide was crystallized in solution and formed nanocrystal coatings on regenerated cellulose. The nanocrystalline layers did not exfoliate from cellulose. Transmission electron microscopy and energy dispersive x-ray spectroscopy suggest that SnO2 was not only deposited over the cellulose surface, but also nucleated and grew inside the cellulose film. Current-voltage characteristics of the nanocomposite revealed that its electrical resistivity decreases with deposition time, with the lowest value obtained for 24 h of deposition. The cellulose-SnO2 hybrid nanocomposite can be used for biodegradable and disposable chemical, humidity and biosensors.

Mahadeva, Suresha K.; Kim, Jaehwan

2011-10-01

262

Initiation stage of nanosecond breakdown in liquid  

NASA Astrophysics Data System (ADS)

In this paper, based on a theoretical model (Shneider and Pekker 2013 Phys. Rev. E 87 043004), it has been shown experimentally that the initial stage of development of a nanosecond breakdown in liquids is associated with the appearance of discontinuities in the liquid (cavitation) under the influence of electrostriction forces. Comparison of experimentally measured area dimensions and its temporal development were found to be in a good agreement with the theoretical calculations. This work is a continuation of the experimental and theoretical works (Dobrynin et al 2013 J. Phys. D: Appl. Phys. 46 105201, Starikovskiy 2013 Plasma Sources Sci. Technol. 22 012001, Seepersad et al 2013 J. Phys. D: Appl. Phys. 46 162001, Marinov et al 2013 Plasma Sources Sci. Technol. 22 042001, Seepersad et al 2013 J. Phys. D: Appl. Phys. 46 3555201), initiated by the work in (Shneider et al 2012 IEEE Trans. Dielectr. Electr. Insul. 19 1597-82), in which the electrostriction mechanism of breakdown was proposed.

Pekker, Mikhail; Seepersad, Yohan; Shneider, Mikhail N.; Fridman, Alexander; Dobrynin, Danil

2014-01-01

263

Optical measurements for interfacial conduction and breakdown  

NASA Astrophysics Data System (ADS)

Measurements and calculations contributing to the understanding of space and surface charges in practical insulation systems are given. Calculations are presented which indicate the size of charge densities necessary to appreciably modify the electric field from what would be calculated from geometrical considerations alone. Experimental data is also presented which locates the breakdown in an electrode system with a paper sample bridging the gap between the electrodes. It is found that with careful handling, the breakdown does not necessarily occur along the interface even if heavily contaminated oil is used. The effects of space charge in the bulk liquid are electro-optically examined in nitrobenzene and transformer oil. Several levels of contamination in transformer oil are investigated. Whereas much space charge can be observed in nitrobenzene, very little space charge, if any, can be observed in the transformer oil samples even at temperatures near 100 degrees C.

Hebner, R. E., Jr.; Kelley, E. F.; Hagler, J. N.

1983-01-01

264

Visualization on the behavior of nanoparticles in magnetic fluids under the electric field  

NASA Astrophysics Data System (ADS)

The dielectric breakdown characteristics of magnetic fluids can be influenced by the magnetic nanoparticles included because their properties should be affected by the applied electric field. Based on measuring the dielectric breakdown voltage of magnetic fluids, we found that it is higher than that of the pure transformer oil in the case of the specific volume concentrations of magnetic nanoparticles. It is known from a numerical simulation that the conductive nanoparticles might behavior as electron scavengers in the electrically stressed magnetic fluids and change fast electrons into slowly negative charged nanoparticles for the electrical breakdown. In this study, we focus on the motion of magnetic nanoparticles in the fluids under the electric field applied by the visualization using a microchannel and an optical microscope.

Lee, W.-H.; Lee, J.-C.

2013-02-01

265

Deep-level dominated electrical characteristics of Au contacts on beta-SiC  

NASA Technical Reports Server (NTRS)

Electrical characteristics of Au contacts on beta-SiC films, grown epitaxially on both nominal and off-axis (100) silicon substrates, are reported. An analysis of the logarithmic I-V plots of the Au/beta-SiC diodes revealed information pertaining to the deep states present in the materials. It was found that while the beta-SiC films grown on nominally (100) oriented substrates show the presence of two deep levels located between 0.26 and 0.38 eV below the conduction bandedge, the beta-SiC films deposited on off-axis substrates have only one deep level, located about 0.49 eV below the conduction bandedge for the 2-deg off (100) substrates and 0.57 eV for the 4-deg off (100) substrates. The presence of the shallower deep states in the beta-SiC films grown on nominal (100) substrates is attributed to the electrical activity of antiphase domain boundaries.

Das, K.; Kong, H. S.; Petit, J. B.; Bumgarner, J. W.; Davis, R. F.; Matus, L. G.

1990-01-01

266

Soluble N-Type organic thin-film transistors with enhanced electrical characteristics  

NASA Astrophysics Data System (ADS)

We fabricated and investigated soluble, organic, thin-film transistors (OTFTs) containing `[6, 6]-phenyl-C61-butyric acid methyl ester (PCBM)' as a semiconducting layer, and an organic dielectric buffer (cross-linked poly-4-vinylphenol) as a dielectric buffer-layer to improve electrical characteristics. The semiconducting layer of the devices was fabricated by the drop-casting method where PCBM was dissolved in three different solvents (odichlorobenzene, chloroform, and chlorobenzene). From the transfer and output characteristics of the PCBM OTFTs, a threshold voltage of 10 V, sub-threshold slope of 10 V/dec, on/off current ratio of 7.305 × 103, and field-effect mobility of 1.53 × 10-2 cm2/Vs were obtained; for PCBM using o-dichlorobenzene solvent and an organic dielectric buffer layer. It was also found that the hysteresis for the same device was improved conspicuously compared to the other devices, by the above-mentioned condition.

Lee, Ho Won; Lee, Seok Jae; Koo, Ja Ryong; Cho, Eou Sik; Kwon, Sang Jik; Kim, Woo Young; Park, Jaehoon; Kim, Young Kwan

2013-11-01

267

Kerr electro-optic measurements for electric field and space charge distributions using similar and dissimilar electrode pairs  

E-print Network

The electrical breakdown strength of insulating materials is a major limiting factor of reliability in electric power, medical devices, and other high electric field applications. Electrical breakdown strength increase ...

Nowocin, John Kendall

2013-01-01

268

Annealing effects on electrical characteristics of 100 MeV 28 Si implantation in GaAs  

Microsoft Academic Search

Electrical characteristics of single crystal orientation n-GaAs substrates implanted at room temperature with 100 MeV 28Si ions to a dose of 1 × 1014 ions cm-2 are reported. The room temperature electrical chracteristics of as-implanted samples and samples annealed in the temperature range of 100–1000 °C arc studied. The I–V curves show a complex behavior with annealing treatment. To understand

A. M. Narsale; A. R. Damle; Yousuf P. Ali; D. Kanjilal; B. M. Arora; A. P. Shah; S. G. Lokhre; V. P. Salvi

2000-01-01

269

Analysis of the electrical harmonic characteristics of a slip recovery variable speed generating system for wind turbine applications  

NASA Astrophysics Data System (ADS)

Variable speed electric generating technology can enhance the general use of wind energy in electric utility applications. This enhancement results from two characteristic properties of variable speed wind turbine generators: an improvement in drive train damping characteristics, which results in reduced structural loading on the entire wind turbine system, and an improvement in the overall efficiency by using a more sophisticated electrical generator. Electronic converter systems are the focus of this investigation -- in particular, the properties of a wound-rotor induction generator with the slip recovery system and direct-current link converter. Experience with solid-state converter systems in large wind turbines is extremely limited. This report presents measurements of electrical performances of the slip recovery system and is limited to the terminal characteristics of the system. Variable speed generating systems working effectively in utility applications will require a satisfactory interface between the turbine/generator pair and the utility network. The electrical testing described herein focuses largely on the interface characteristics of the generating system. A MOD-O wind turbine was connected to a very strong system; thus, the voltage distortion was low and the total harmonic distortion in the utility voltage was less than 3 percent (within the 5 percent limit required by most utilities). The largest voltage component of a frequency below 60 Hz was 40 dB down from the 60-Hz less than component.

Herrera, J. I.; Reddoch, T. W.

1988-02-01

270

Effects of nuclear radiation on a high-reliability silicon power diode. 4: Analysis of reverse bias characteristics  

NASA Technical Reports Server (NTRS)

The effects of nuclear radiation on the reverse bias electrical characteristics of one hundred silicon power diodes were investigated. On a percentage basis, the changes in reverse currents were large but, due to very low initial values, this electrical characteristic was not the limiting factor in use of these diodes. These changes were interpreted in terms of decreasing minority carrier lifetimes as related to generation-recombination currents. The magnitudes of reverse voltage breakdown were unaffected by irradiation.

Been, J. F.

1973-01-01

271

Aspects of shock wave-induced vortex breakdown  

NASA Astrophysics Data System (ADS)

In this article, we discuss supersonic vortex breakdown when sufficiently strong streamwise vortices encounter otherwise planar, normal and oblique shock fronts as well as solid surfaces placed in their passages. The dramatic destruction of a streamwise vortex during supersonic vortex interactions reveals a vortex breakdown similar in many ways to the well-documented incompressible vortex bursting. The main features of supersonic vortex breakdown include formation of a spherically blunt-nosed conical shock, and a vortex core, which upon crossing the apex of the conical shock expands into a subsonic turbulent conical region. A notable characteristic of the supersonic vortex breakdown is the formation of an entropy-shear layer separating an inner subsonic zone containing the burst structure from the surrounding supersonic flow. Numerical, experimental, and analytical studies of shock wave/vortex interactions are discussed and results from wind tunnel studies involving head-on collision of supersonic vortices with solid surfaces are presented.

Kalkhoran, Iraj M.; Smart, Michael K.

2000-01-01

272

Impact of Si substrate nitridation on electrical characteristics of Ta2O5 stack capacitors  

NASA Astrophysics Data System (ADS)

A comparison of the effect of rapid thermal nitridation (RTN) of the Si surface in N2O and NH3 ambient at different temperatures (700-850 °C) on the dielectric and electrical characteristics of thin (~20 nm) Ta2O5 stacks has been made. The electrical parameters of capacitors (film permittivity, oxide charge, densities of bulk traps, interface and slow states, leakage current) are discussed in terms of the impact of N incorporation in the interface region. The films on both types of RTN-treated Si exhibit ~100 times lower leakage current than Ta2O5 on bare Si, but among the two RTN processes NH3 nitridation is more beneficial since only it simultaneously increases also the stack permittivity. This improvement in parameters is suggested to be due to a real nitridation of Si surface which occurs under the NH3 rapid thermal process. RTN in N2O does not produce resistance to the oxidation substrate and it could explain the observed lack of stack dielectric constant improvement. The composition of the interfacial layer under NH3 RTN appears to be TaSi-oxinitride-like, while the interface region at N2O-nitrided Si seems to be SiO2-like. Each RTN process, however, modifies the Si surface and constitutes a specific interface layer different from that at the bare Si substrate. The composition of this layer defines parameters of the traps close to the substrate, the barrier height at the Ta2O5/interface layer and influences the conduction mechanisms in the stacks.

Paskaleva, A.; Spassov, D.; Atanassova, E.

2007-11-01

273

Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (less than 250 V) 4H-SiC p(+)n Junction diodes. Part 1; DC Properties  

NASA Technical Reports Server (NTRS)

Given the high density (approx. 10(exp 4)/sq cm) of elementary screw dislocations (Burgers vector = 1c with no hollow core) in commercial SiC wafers and epilayers, all appreciable current (greater than 1 A) SiC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems. This paper compares the DC-measured reverse-breakdown characteristics of low-voltage (less than 250 V) small-area (less than 5 x 10(exp -4)/sq cm) 4H-SiC p(+)n diodes with and without elementary screw dislocations. Compared to screw dislocation-free devices, diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown I-V knees, and highly localized microplasmic breakdown current filaments. The observed localized 4H-SiC breakdown parallels microplasmic breakdowns observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.

Neudeck, Philip G.; Huang, Wei; Dudley, Michael

1998-01-01

274

Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (<250 V) 4H-SiC p+n Junction Diodes - Part 1: DC Properties  

NASA Technical Reports Server (NTRS)

Given the high density (approx. 10(exp 4)/sq cm) of elementary screw dislocations (Burgers vector = lc with no hollow core) in commercial SiC wafers and epilayers, all appreciable current (greater than 1 A) SiC power devices will likely contain elementary screw dislocations for the foreseeable future. It is therefore important to ascertain the electrical impact of these defects, particularly in high-field vertical power device topologies where SiC is expected to enable large performance improvements in solid-state high-power systems. This paper compares the DC-measured reverse-breakdown characteristics of low-voltage (less than 250 V) small-area (less than 5 x 10(exp -4) sq cm) 4H-SiC p(+)n diodes with and without elementary screw dislocations. Compared to screw dislocation-free devices, diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown I-V knees, and highly localized microplasmic breakdown current filaments. The observed localized 4H-SiC breakdown parallels microplasmic breakdowns observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.

Neudeck, Philip G.; Huang, Wei; Dudley, Michael

1999-01-01

275

Electricity  

NSDL National Science Digital Library

5th Grade Electricity Try this Using Electricity Activity. Don't forget to follow the directions! Use this to learn more about electricity: Blobz Guide to Electricity Follow the directions closely! Learn more about Electricity with Electricity Tech-Topics. ...

Lerdahl, Miss

2010-02-23

276

Effects of nutrient enrichment on boreal streams: invertebrates, fungi and leaf-litter breakdown  

Microsoft Academic Search

SUMMARY 1. The effect of nutrient enrichment on structural (invertebrate indices) and functional (leaf-litter breakdown rates) characteristics of stream integrity was studied in nine boreal streams. 2. The results showed predicted changes in biotic indices and leaf-litter breakdown along a complex (principal component) nutrient gradient. Biotic indices were better correlated with nutrient effects than leaf-litter breakdown. 3. Fungal biomass and

JENNY B ERGFUR; R ICHARD K. J OHNSON; L E ONARD; S ANDIN; W ILLEM G OEDKOOP; KRISTIINA N YGREN

277

Analysis of breakdown probabilities in avalanche photodiodes using a history-dependent analytical model  

Microsoft Academic Search

The breakdown probabilities of avalanche photodiodes (APDs) working in the Geiger mode are analyzed using a history-dependent analytical impact-ionization model [R. J. McIntyre, IEEE Trans. Electron Devices 46, 1623 (1999)]. The breakdown sharpness in devices with thin and thick multiplication regions is found to follow the same trend in GaAs, InAlAs, and InP material systems. Breakdown characteristics of InP and

Shuling Wang; Feng Ma; Xiaowei Li; Gauri Karve; Xiaoguang Zheng; Joe C. Campbell

2003-01-01

278

Runaway breakdown and hydrometeors in lightning initiation.  

PubMed

The particular electric pulse discharges are observed in thunderclouds during the initiation stage of negative cloud-to-ground lightning. The discharges are quite different from conventional streamers or leaders. A detailed analysis reveals that the shape of the pulses is determined by the runaway breakdown of air in the thundercloud electric field initiated by extensive atmospheric showers (RB-EAS). The high amplitude of the pulse electric current is due to the multiple microdischarges at hydrometeors stimulated and synchronized by the low-energy electrons generated in the RB-EAS process. The series of specific pulse discharges leads to charge reset from hydrometeors to the free ions and creates numerous stretched ion clusters, both positive and negative. As a result, a wide region in the thundercloud with a sufficiently high fractal ion conductivity is formed. The charge transport by ions plays a decisive role in the lightning leader preconditioning. PMID:23683210

Gurevich, A V; Karashtin, A N

2013-05-01

279

Direct measurement of the characteristic three-body electron attachment time in the atmospheric air in direct current electric field  

SciTech Connect

We report the results of theoretical and experimental study of the characteristic time for three-body attachment of electrons produced by 100 fs UV laser pulse in the atmosphere air in the external DC electric field ranged from 0.2 to 10 kV/cm.

Shutov, A. V.; Smetanin, I. V.; Ionin, A. A.; Levchenko, A. O.; Seleznev, L. V.; Sinitsyn, D. V.; Ustinovskii, N. N.; Zvorykin, V. D. [P. N. Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991 (Russian Federation)

2013-07-15

280

Study of the effect of machining parameters on the machining characteristics in electrical discharge machining of tungsten carbide  

Microsoft Academic Search

Electrical discharge machining (EDM) is a process for shaping hard metals and forming deep and complex-shaped holes by arc erosion in all kinds of electro-conductive materials. The objective of this research is to study the influence of operating parameters of EDM of tungsten carbide on the machining characteristics. The effectiveness of the EDM process with tungsten carbide is evaluated in

S. H. Lee; X. P. Li

2001-01-01

281

Effect of electrical discharge machining on surface characteristics and machining damage of AISI D2 tool steel  

Microsoft Academic Search

In this work the electrical discharge machining (EDM) of AISI D2 tool steel was investigated. The surface characteristics and machining damage caused by EDM were studied in terms of machining parameters. Based on the experimental data, an empirical model of the tool steel was also proposed. A new damage variable was used to study the EDM damage. The workpiece surface

Y. H. Guu; H. Hocheng; C. Y. Chou; C. S. Deng

2003-01-01

282

Runaway electron mechanism of air breakdown and preconditioning during a thunderstorm  

Microsoft Academic Search

The possibility is considered of an avalanche-type increase of the number of runaway electrons leading to a new type of electric breakdown of gases. This type of breakdown could take place in the atmosphere during a thunderstorm stimulated by cosmic ray secondaries.

A. V. Gurevich; G. M. Milikh; R. Roussel-Dupre

1992-01-01

283

Kinetic theory of runaway air-breakdown  

SciTech Connect

The kinetic theory for a new air breakdown mechanism advanced in a previous paper is developed. The relevant form of the Boltzmann equation is derived and the particle orbits in both velocity space and configuration space are computed. A numerical solution of the Boltzmann equation, assuming a spatially uniform electric field, is obtained and the temporal evolution of the electron velocity distribution function is described. The results of our analysis are used to estimate the magnitude of potential x-ray emissions from discharges in thunderstorms.

Roussel-Dupre, R.A. [Los Alamos National Lab., NM (United States); Gurevich, A.V. [AN SSSR, Moscow (Russian Federation). Fizicheskij Inst.; Tunnell, T. [EG and G Energy Measurements, Inc., Los Alamos, NM (United States); Milikh, G.M. [Maryland Univ., College Park, MD (United States). Dept. of Astronomy

1993-09-01

284

Kinetic theory of runaway air breakdown  

SciTech Connect

The kinetic theory for an air breakdown mechanism advanced in a previous paper [Phys. Lett. A 165, 463 (1992)] is developed. The relevant form of the Boltzmann equation is derived and the particle orbits in both velocity space and configuration space are computed. A numerical solution of the Boltzmann equation, assuming a spatially uniform electric field, is obtained and the temporal evolution of the electron velocity distribution function is described. The results of our analysis are used to estimate the magnitude of potential x-ray emissions from discharges in thunderstorms.

Roussel-Dupre, R.A. (Space Sciences and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)); Gurevich, A.V. (P.N. Lebedev Institute of Physics, Moscow 117924 (Russian Federation)); Tunnell, T. (EG G Energy Measurements, Inc., Los Alamos, New Mexico 87544 (United States)); Milikh, G.M. (Department of Astronomy, University of Maryland, College Park, Maryland 29742 (United States))

1994-03-01

285

Metastable Electrical Characteristics of Polycrystalline Thin-Film Photovoltaic Modules upon Exposure and Stabilization: Preprint  

SciTech Connect

The significant features of a series of stabilization experiments conducted at the National Renewable Energy Laboratory (NREL) between May 2009 and the present are reported. These experiments evaluated a procedure to stabilize the measured performance of thin-film polycrystalline cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) thin-film photovoltaic (PV) modules. The current-voltage (I-V) characteristics of CdTe and CIGS thin-film PV devices and modules exhibit transitory changes in electrical performance after thermal exposure in the dark and/or bias and light exposures. We present the results of our case studies of module performance versus exposure: light-soaked at 65 degrees C; exposed in the dark under forward bias at 65 degrees C; and, finally, longer-term outdoor exposure. We find that stabilization can be achieved to varying degrees using either light-soaking or dark bias methods and that the existing IEC 61646 light-soaking interval may be appropriate for CdTe and CIGS modules with one caveat: it is likely that at least three exposure intervals are required for stabilization.

Deline, C. A.; del Cueto, J. A.; Albin, D. S.; Rummel, S. R.

2011-09-01

286

Influence of the electric characteristics of II VI semiconductor material on the electroluminescence of lanthanide complex  

NASA Astrophysics Data System (ADS)

The organic-inorganic combined structural device (ITO/PVK:Eu/ZnS/Al) is fabricated based on layered optimization scheme. II VI semiconductor material ZnS is acted as an electron function (transporting and acceleration) layer. The hot electrons which have been accelerated in the ZnS layer directly impact excitation europium ions through resonant energy transfer and then recombine with injected holes to form excitons in PVK or EuTTA2(N-HPA)Phen. Europium (Eu) ions may also be excited by intramolecular energy transfer from ligands. There are two kinds of excitation mechanisms: impacted excitation and injected recombination for the combined structural device. The electroluminescence (EL) intensity of the combined structural device is strongly improved and reaches up to 381 cd/m2 at 20 V compared with the pure organic structural device. It may be an effective method to improve the EL intensity of the lanthanide complex by using electric characteristics of inorganic semiconductor materials.

Zhang, F.-J.; Xu, Z.; Lv, Y.-G.; Zhang, J.-C.; Zhao, S. L.; Huang, J.-Z.; Wang, Y.; Yuan, G.-C.; Zhao, D.-W.; Xu, X.-R.

2006-07-01

287

Electrical switching dynamics and broadband microwave characteristics of VO2 radio frequency devices  

NASA Astrophysics Data System (ADS)

Vanadium dioxide (VO2) is a correlated electron system that features a metal-insulator phase transition (MIT) above room temperature and is of interest in high speed switching devices. Here, we integrate VO2 into two-terminal coplanar waveguides and demonstrate a large resistance modulation of the same magnitude (>103) in both electrically (i.e., by bias voltage, referred to as E-MIT) and thermally (T-MIT) driven transitions. We examine transient switching characteristics of the E-MIT and observe two distinguishable time scales for switching. We find an abrupt jump in conductivity with a rise time of the order of 10 ns followed by an oscillatory damping to steady state on the order of several ?s. We characterize the RF power response in the On state and find that high RF input power drives VO2 further into the metallic phase, indicating that electromagnetic radiation-switching of the phase transition may be possible. We measure S-parameter RF properties up to 13.5 GHz. Insertion loss is markedly flat at 2.95 dB across the frequency range in the On state, and sufficient isolation of over 25 dB is observed in the Off state. We are able to simulate the RF response accurately using both lumped element and 3D electromagnetic models. Extrapolation of our results suggests that optimizing device geometry can reduce insertion loss further and maintain broadband flatness up to 40 GHz.

Ha, Sieu D.; Zhou, You; Fisher, Christopher J.; Ramanathan, Shriram; Treadway, Jacob P.

2013-05-01

288

Mechanical and electric characteristics of vacuum impregnated no-insulation HTS coil  

NASA Astrophysics Data System (ADS)

For the conduction cooling application, epoxy impregnation is inevitable to enhance the thermal conduction. However, there have been several research results on the delamination problem with coated conductor and the main cause of the delamination is related with the different thermal contraction between epoxy, the insulation layer and the weak conductor. To avoid this problem, the amount of epoxy and insulation layer between conductors should be minimized or removed. Therefore, no insulation (NI) winding method and impregnation after dry winding can be considered to solve the problem. The NI coil winding method is very attractive due to high mechanical/thermal stability for the special purpose of DC magnets by removing the insulation layer. In this paper, the NI coil winding method and vacuum impregnation are applied to a HTS coil to avoid the delamination problem and enhance the mechanical/thermal stability for the conduction cooling application. Through the charging/discharging operation, electric/thermal characteristics are investigated at 77 K and 30 K.

Park, Heecheol; Kim, A.-rong; Kim, Seokho; Park, Minwon; Kim, Kwangmin; Park, Taejun

2014-09-01

289

Electrical characteristics and deep level traps study of Au/ZnO:H Schottky diodes  

NASA Astrophysics Data System (ADS)

The electrical characteristics and the deep level traps of Au Schottky contacts on ZnO:H films have been investigated by temperature-dependent current-voltage (I-V) and deep level transient spectroscopy (DLTS) measurements. The films were deposited with the DC-sputtering, varying the H flow rate in the Ar/H sputtering gas, so that the hydrogen per volume concentration [H2] was 0%, 20%, 33.3%, 50% and 66.6%. We found that for the Schottky diodes with [H2] = 33.3% thermionic emission is the dominant current transport process at low forward voltage, taking into consideration the lateral fluctuations of the barrier height described by a Gaussian distribution model. The domination of trap-assisted current transport mechanisms is possible in the diodes with [H2] = 0%, 20%, 50% and 66.6%. DLTS spectra revealed two electron traps, with activation energies of 0.29 and 0.21 eV, often observed in ZnO and related to intrinsic defects. The trap concentrations are significantly lower in the 33.3% H2 diodes compared to the 0% H2 ones, indicating an interaction of these traps with hydrogen.

Tsiarapas, Christos; Girginoudi, Dimitra; Georgoulas, Nikolaos

2014-11-01

290

Tunable electrical memory characteristics using polyimide:polycyclic aromatic compound blends on flexible substrates.  

PubMed

Resistance switching memory devices with the configuration of poly(ethylene naphthalate)(PEN)/Al/polyimide (PI) blend/Al are reported. The active layers of the PI blend films were prepared from different compositions of poly[4,4'-diamino-4?-methyltriphenylamine-hexafluoroisopropylidenediphthalimide] (PI(AMTPA)) and polycyclic aromatic compounds (coronene or N,N-bis[4-(2-octyldodecyloxy)phenyl]-3,4,9,10-perylenetetracarboxylic diimide (PDI-DO)). The additives of large ?-conjugated polycyclic compounds can stabilize the charge transfer complex induced by the applied electric field. Thus, the memory device characteristic changes from the volatile to nonvolatile behavior of flash and write-once-read-many times (WORM) as the additive contents increase in both blend systems. The main differences between these two blend systems are the threshold voltage values and the additive content to change the memory behavior. Due to the stronger accepting ability and higher electron affinity of PDI-DO than those of coronene, the PI(AMTPA):PDI-DO blend based memory devices show a smaller threshold voltage and change the memory behavior in a smaller additive content. Besides, the memory devices fabricated on a flexible PEN substrate exhibit an excellent durability upon the bending conditions. These tunable memory performances of the developed PI/polycyclic aromatic compound blends are advantageous for future advanced memory device applications. PMID:23646879

Yu, An-Dih; Kurosawa, Tadanori; Chou, Ying-Hsuan; Aoyagi, Koutarou; Shoji, Yu; Higashihara, Tomoya; Ueda, Mitsuru; Liu, Cheng-Liang; Chen, Wen-Chang

2013-06-12

291

Optical breakdown threshold investigation of 1064 nm laser induced air plasmas  

SciTech Connect

We present the theoretical and experimental measurements and analysis of the optical breakdown threshold for dry air by 1064 nm infrared laser radiation and the significance of the multiphoton and collisional cascade ionization process on the breakdown threshold measurements over pressures range from 10 to 2000 Torr. Theoretical estimates of the breakdown threshold laser intensities and electric fields are obtained using two distinct theories namely multiphoton and collisional cascade ionization theories. The theoretical estimates are validated by experimental measurements and analysis of laser induced breakdown processes in dry air at a wavelength of 1064 nm by focusing 450 mJ max, 6 ns, 75 MW max high-power 1064 nm IR laser radiation onto a 20 {mu}m radius spot size that produces laser intensities up to 3 - 6 TW/cm{sup 2}, sufficient for air ionization over the pressures of interest ranging from 10 to 2000 Torr. Analysis of the measured breakdown threshold laser intensities and electric fields are carried out in relation with classical and quantum theoretical ionization processes, operating pressures. Comparative analysis of the laser air breakdown results at 1064 nm with corresponding results of a shorter laser wavelength (193 nm) [M. Thiyagarajan and J. E. Scharer, IEEE Trans. Plasma Sci. 36, 2512 (2008)] and a longer microwave wavelength (10{sup 8} nm) [A. D. MacDonald, Microwave Breakdown in Gases (Wiley, New York, 1966)]. A universal scaling analysis of the breakdown threshold measurements provided a direct comparison of breakdown threshold values over a wide range of frequencies ranging from microwave to ultraviolet frequencies. Comparison of 1064 nm laser induced effective field intensities for air breakdown measurements with data calculated based on the collisional cascade and multiphoton breakdown theories is used successfully to determine the scaled collisional microwave portion. The measured breakdown threshold of 1064 nm laser intensities are then scaled to classical microwave breakdown theory after correcting for the multiphoton ionization process for different pressures and good agreement, regarding both pressure dependence and breakdown threshold electric fields, is obtained. The effect of the presence of submicron particles on the 1064 nm breakdown threshold was also investigated. The measurements show that higher breakdown field is required, especially at lower pressures, and in close agreement with classical microwave breakdown theory and measurements in air.

Thiyagarajan, Magesh; Thompson, Shane [Plasma Engineering Research Lab (PERL), College of Science and Engineering, Texas A and M University-Corpus Christi, Texas 78412 (United States)

2012-04-01

292

Dielectric breakdown induced by picosecond laser pulses  

NASA Technical Reports Server (NTRS)

The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger.

Smith, W. L.; Bechtel, J. H.; Bloembergen, N.

1976-01-01

293

Electricity  

NSDL National Science Digital Library

William J. Beaty, an Electrical Engineer at the University of Washington, has posted this website about electricity. He offers a simple answer to the question, What Is "Electricity?," identifies twenty misconceptions he has found to be barriers to understanding electricity, and then proceeds to explain various aspects of electricity. Beaty's debunking articles address common misconceptions about circuitry, doorknob sparks, voltage, and more.

Beaty, William J.

294

Propagation characteristics of a focused laser beam in a strontium barium niobate photorefractive crystal under reverse external electric field.  

PubMed

The propagation characteristics of a focused laser beam in a SBN:75 photorefractive crystal strongly depend on the signal-to-background intensity ratio (R=Is/Ib) under reverse external electric field. In the range 20>R>0.05, the laser beam shows enhanced self-defocusing behavior with increasing external electric field, while it shows self-focusing in the range 0.03>R>0.01. Spatial solitons are observed under a suitable reverse external electric field for R=0.025. A theoretical model is proposed to explain the experimental observations, which suggest a new type of soliton formation due to "enhancement" not "screening" of the external electrical field. PMID:25322227

Guo, Q L; Liang, B L; Wang, Y; Deng, G Y; Jiang, Y H; Zhang, S H; Fu, G S; Simmonds, P J

2014-10-01

295

The Relationship Between Continuing Current and Positive Breakdown  

NASA Astrophysics Data System (ADS)

Continuing currents (CCs) during negative cloud to ground discharges have long been theorized to be dependent on the associated positive breakdown activity, yet direct evidence has remained elusive. Data from the Langmuir Electric Field Array (LEFA, 0.3 Hz-50 kHz electric field change), Lightning Mapping Array (LMA, 66 MHz narrowband RF), and Continuous Digital Interferometer (Continuous DITF, 20-80 MHz broadband RF), obtained at Langmuir Laboratory, are being used to analyze the dependence of CCs on positive breakdown branching and growth. The primary flash analyzed was a bolt-from-the-blue that occurred on August 14, 2012 and had 6 return strokes (RSs), 3 of which produced CCs. We used the high time resolution of the Continuous DITF to determine when each RS ended, and the LMA data to detect positive breakdown growth subsequent to the RSs, including any CC. We found that CCs occurred only after the positive breakdown started developing multiple branches. The branches appeared to be continually developing during the CCs, hence providing the source of charge for the CC. We also found that longer CCs were associated with more positive leader channel branching and growth, implying that CC duration depends on the activity of the positive breakdown. These analyses are continuing to be applied to other flashes, yielding similar results. Ultimately, the study of CCs will improve our understanding of negative RSs, the most common form of cloud-to-ground lightning.

Lapierre, J. L.; Sonnenfeld, R. G.; Stock, M.; Edens, H. E.; Hager, W. W.; Thomas, R. J.

2013-12-01

296

Plasma Conductivity and Ionization Growth in Flame Breakdown  

Microsoft Academic Search

An investigation into the properties of flame breakdown is reported. A series of DC discharge tests were performed in a set of parallel plane electrodes bridged by flames from a bunsen burner. The experimental setup aims to reproduce the conditions found in waste-disposal reactors where the combined effect of fire and an electrical arc degrade noxious substances. The current was

Arturo Robledo-Martinez; J. Luis Hernandez

2000-01-01

297

Threshold energy effect on avalanche breakdown voltage in semiconductor junctions  

Microsoft Academic Search

The band bending for avalanche breakdown in semiconductor junctions and its temperature dependence are predicted taking account of threshold energy effects on the ionization process in semiconductors. Where experimental results exist, the theoretical predictions and experimental results are in excellent agreement. In the high electric field region inclusion of both bulk and boundary threshold energy effects is essential. The predictions

Y. Okuto; C. R. Crowell

1975-01-01

298

Ion Solid Interaction And Surface Modification At RF Breakdown In High-Gradient Linacs  

SciTech Connect

Ion solid interactions have been shown to be an important new mechanism of unipolar arc formation in high-gradient rf linear accelerators through surface self-sputtering by plasma ions, in addition to an intense surface field evaporation. We believe a non-Debye plasma is formed in close vicinity to the surface and strongly affects surface atomic migration via intense bombardment by ions, strong electric field, and high surface temperature. Scanning electron microscope studies of copper surface of an rf cavity were conducted that show craters, arc pits, and both irregular and regular ripple structures with a characteristic length of 2 microns on the surface. Strong field enhancements are characteristic of the edges, corners, and crack systems at surfaces subjected to rf breakdown.

Insepov, Zeke; Norem, Jim [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Veitzer, Seth [Tech-X Corp., 5621 Arapahoe Ave., Suite A, Boulder CO 80303 (United States)

2011-06-01

299

Effect of ultrasound waves on electrical characteristics of hollow needle to plate electrical discharge in air or in mixture of air with VOC  

NASA Astrophysics Data System (ADS)

The results of study of ultrasound waves influence on V-A characteristics of the DC hollow needle to plate electrical discharge enhanced by the flow of air or flow of the mixture of air with 2-propanol-izopropanol or n-heptane, through the needle are described. It was found that the application of ultrasound substantially influences V-A characteristics of the discharge in air. From the standpoint of application of ultrasound on the discharge in the mixture of air with VOCs the V-A characteristics can be divided into two parts: the low current region and the high current region. For the low current region the application of ultrasound for a constant current decreases the discharge voltage. On the other hand for the high current region the application of ultrasound increases for a constant current discharge voltage. This work was supported by the Grant Agency of the Czech Republic under contract 202/04/0728.

Pekarek, Stanislav; Balek, Rudolf; Pospisil, Milan

2004-09-01

300

Response of the activization of seismic processes in temporary and spectral characteristics of electric field on Tien-Shan  

NASA Astrophysics Data System (ADS)

We present results of the atmospheric electric field monitoring at the high-altitude Tien-Shan station (43.02 N, 76.56 E, 3340 m above sea level, 20 km from Almaty) and the analysis of its temporal and spectral characteristics during the activization of seismic processes in the vicinity of Almaty since 2007 till 2014. During this period the most considerable seismic activity was observed on May 1-2, 2011 and January 28, 2013. Eight events for 2 days with a magnitude of more than 4.0 occurred on May 1-2, 2011. The main shock of magnitude 5.4 occurred on May 1st at 02:31 UT, 76 km North East of Almaty. Unusual temporal variations of the electric field with amplitude achieving the values of 6-7 kV/m were recorded as during series of earthquakes, and before them (April 28, 30). The duration of the electric field disturbances were 5-12 hours (5 hours on 28.04.2011 and 12 hours on 30.04.2011). Another characteristic of the anomalous variations of the electric field was their positive polarity. The analysis of meteorological and cosmophysical conditions was carried out for the purpose of identification of disturbance sources. It is shown that characteristics of temporal anomalous variations of the electric field don't correspond to these sources of disturbances. It was concluded that the cause of anomalous variations can be sources of the lithospheric origin only. Respectively, anomalies of the electric field can be considered as precursors of earthquakes. We also registered anomalous duration temporal variations of the electric field with the amplitude achieving ±2 kV/m before of the earthquake on January 28, 2013. The main shock of magnitude 6.1 occurred at 16:38 UT, 230 km. to the East from Almaty. The earthquake was felt in Almaty with intensity 4-5 points. In this event as positive variations and with the change of the polarity were recorded. Anomalous variations of electric field before of weaker earthquakes (magnitude < 4) are recorded only for events with coordinates of the epicenter in close proximity to the detector (08.04.2009 and 27.09.2010). Spectral components of anomalous variations of electric field and features of their dynamics before earthquakes were studied. The dominating spectral peaks differing from the background were established. Thus we consider that the atmospheric quasi-static electric field variations are useful for a prediction of earthquakes.

Antonova, Valentina; Zhumabayev, Beibit

2014-05-01

301

Organizational and Individual Factors Associated with Breakdown of Residential Placements for People with Intellectual Disabilities  

ERIC Educational Resources Information Center

Background: People with intellectual disabilities (IDs) whose behaviour challenges services are at increased risk of placement breakdown. Most previous research has tended to focus on the role of individual characteristics in predicting breakdown. A small number of studies have suggested that service variables may impact on intervention…

Broadhurst, S.; Mansell, J.

2007-01-01

302

Breakdown walkout in pseudomorphic HEMT's  

Microsoft Academic Search

In this work we show for the first time evidence of gate-drain breakdown walkout due to hot electrons in pseudomorphic AlGaAs-InGaAs-GaAs HEMTs (PHEMTs). Experiments performed on passivated commercial PHEMTs show that hot electron stress cycles induce a large and permanent increase of the gate-drain breakdown voltage. Three-terminal and two-terminal stress conditions are compared, the former producing a much larger walkout

R. Menozzi; P. Cova; C. Canali; F. Fantini

1996-01-01

303

Electrical performance characteristics of high power converters for space power applications  

NASA Technical Reports Server (NTRS)

The first goal of this project was to investigate various converters that would be suitable for processing electric power derived from a nuclear reactor. The implementation is indicated of a 20 kHz system that includes a source converter, a ballast converter, and a fixed frequency converter for generating the 20 kHz output. This system can be converted to dc simply by removing the fixed frequency converter. This present study emphasized the design and testing of the source and ballast converters. A push-pull current-fed (PPCF) design was selected for the source converter, and a 2.7 kW version of this was implemented using three 900 watt modules in parallel. The characteristic equation for two converters in parallel was derived, but this analysis did not yield any experimental methods for measuring relative stability. The three source modules were first tested individually and then in parallel as a 2.7 kW system. All tests proved to be satisfactory; the system was stable; efficiency and regulation were acceptable; and the system was fault tolerant. The design of a ballast-load converter, which was operated as a shunt regulator, was investigated. The proposed power circuit is suitable for use with BJTs because proportional base drive is easily implemented. A control circuit which minimizes switching frequency ripple and automatically bypasses a faulty shunt section was developed. A nonlinear state-space-averaged model of the shunt regulator was developed and shown to produce an accurate incremental (small-signal) dynamic model, even though the usual state-space-averaging assumptions were not met. The nonlinear model was also shown to be useful for large-signal dynamic simulation using PSpice.

Stuart, Thomas A.; King, Roger J.

1989-01-01

304

Electro-Optical and Capacitive Characteristics of Stratified Polymer/Liquid Crystal Composite Devices under DC Electric Field  

NASA Astrophysics Data System (ADS)

This study focuses on the observation of distinct electro-optical and capacitive properties of a stratifiedly phase-separated polymer/liquid crystal composite film under dc electric fields with opposite polarities. The voltage-dependent transmittance and capacitance as well as time-evolved transmittance were measured for the two field-application conditions. The experimental results suggest that the dc electro-optical and electrically capacitive characteristics of the asymmetrically structured composite film sandwiched between two conductive glass substrates are sensitive to the polarity of the applied field due to the selective adsorption of positive charge by the single alignment layer of nylon 6.

Wu, Chong-Yin; Tang, Chen-Yu; Lee, Wei

2010-11-01

305

Elucidating the mechanisms behind pre-breakdown phenomena in transformer oil systems  

E-print Network

The widespread use of dielectric liquids for high voltage insulation and power apparatus cooling is due to their greater electrical breakdown strength and thermal conductivity than gaseous insulators. In addition, their ...

Hwang, Jae-Won George, 1980-

2010-01-01

306

Charge transport and breakdown physics in liquid/solid insulation systems  

E-print Network

Liquid dielectrics provide superior electrical breakdown strength and heat transfer capability, especially when used in combination with liquid-immersed solid dielectrics. Over the past half-century, there has been extensive ...

Jadidian, Jouya

2013-01-01

307

Dielectric Breakdown in Spin-Polarized Mott Insulator  

NASA Astrophysics Data System (ADS)

Nonlinear response of a Mott insulator to external electric field, corresponding to dielectric breakdown phenomenon, is studied within of a one-dimensional half-filled Hubbard model. It is shown that in the limit of nearly spin-polarized insulator the decay rate of the ground state into excited holon-doublon pair can be evaluated numerically as well to high accuracy analytically. Results show that the threshold field depends on the charge gap as Fth??3/2. Numerical results on small systems indicate on the persistence of a similar mechanism for the breakdown for decreasing magnetization down to unpolarized system.

Lenar?i?, Zala; Prelovšek, Peter

2012-05-01

308

Rf breakdown studies in copper electron linac structures  

SciTech Connect

This paper presents a summary of rf breakdown-limited electric fields observed in experimental linac structures at SLAC and a discussion of how these experiments can be interpreted against the background of existing, yet incomplete, theories. The motivation of these studies, begun in 1984, is to determine the maximum accelerating field gradients that might be used safely in future e/sup /+-// colliders, to contribute to the basic understanding of the rf breakdown mechanism, and to discover if a special surface treatment might make it possible to supersede the field limits presently reachable in room temperature copper structures. 6 refs., 4 figs., 1 tab.

Wang, J.W.; Loew, G.A.

1989-03-01

309

Dielectric breakdown in AlOx tunnelling barriers  

NASA Astrophysics Data System (ADS)

We studied the dielectric breakdown in tunnelling barriers produced by plasma-assisted oxidation of an aluminium surface. The barrier mean height, thickness and the effective tunnelling area were extracted from current versus voltage curves measured at room temperature. The effective tunnelling area ranged from 10-10 to 10-5 cm2, corresponding to less than 1% of the geometrical surface of the samples. The estimated electrical field to breakdown agreed with predictions from thermochemical models, and decreased exponentially with the effective tunnelling area.

Schaefer, D. M.; Fichtner, P. F. P.; Carara, M.; Schelp, L. F.; Dorneles, L. S.

2011-04-01

310

Nanopore Fabrication by Controlled Dielectric Breakdown  

E-print Network

Nanofabrication techniques for achieving dimensional control at the nanometer scale are generally equipment-intensive and time-consuming. The use of energetic beams of electrons or ions has placed the fabrication of nanopores in thin solid-state membranes within reach of some academic laboratories, yet these tools are not accessible to many researchers and are poorly suited for mass-production. Here we describe a fast and simple approach for fabricating a single nanopore down to 2-nm in size with sub-nm precision, directly in solution, by controlling dielectric breakdown at the nanoscale. The method relies on applying a voltage across an insulating membrane to generate a high electric field, while monitoring the induced leakage current. We show that nanopores fabricated by this method produce clear electrical signals from translocating DNA molecules. Considering the tremendous reduction in complexity and cost, we envision this fabrication strategy would not only benefit researchers from the physical and life ...

Kwok, Harold; Tabard-Cossa, Vincent

2013-01-01

311

Electrical characteristics of AlGaN\\/GaN metal-insulator semiconductor heterostructure field-effect transistors on sapphire substrates  

Microsoft Academic Search

The electrical performance of AlGaN\\/GaN metal-insulator semiconductor, heterostructure field-effect transistors (MISHFETs)\\u000a were studied and compared to passivated and unpassivated HFETs. Record MISHFET current densities up to 1,010 mA\\/mm were achieved,\\u000a and the devices exhibited stable operation at elevated temperatures up to 200C. Higher maximum-drain current, breakdown voltage,\\u000a and a lower gate-leakage current were obtained in the MISHFETs compared to unpassivated

W. S. Tan; P. A. Houston; G. Hill; R. J. Airey; P. J. Parbook

2003-01-01

312

Effect of annealing on magnetostrictive characteristics of a grain-oriented electrical steel with ordinary and refined domain structure  

NASA Astrophysics Data System (ADS)

We present the results of investigating the effect of annealing on the magnetostrictive characteristics of a grain-oriented electrical steel (GOES) with ordinary and refined domain structure. Not infrequently, the annealing of sheet samples leads to an increase in the electromagnetic induction B 100 and, simultaneously, to an enhancement in the specific electromagnetic losses P 1.7/50. In a GOES with a refined domain structure, the minimum absolute values of ?0-peak and ?peak-peak are observed before annealing. For these samples, after annealing, the magnetostrictive characteristics are impaired most severely. The mechanism for explaining this experimental fact has been suggested.

Redikul'tsev, A. A.; Korzunin, G. S.; Lobanov, M. L.; Rusakov, G. M.; Lobanova, L. V.

2014-07-01

313

Performance characteristics of an electric vehicle lead-acid battery pack at elevated temperatures  

NASA Astrophysics Data System (ADS)

Discharge testing data electric car battery pack over initial electrolyte temperature variations between 27 and 55 C are presented. The tests were conducted under laboratory conditions and then compared to detailed electric vehicle simulation models. Battery discharge capacity increased with temperature for constant current discharges, and battery energy capacity increased with temperature for constant power discharges. Dynamometer tests of the electric test vehicle showed an increase in range of 25% for the higher electrolyte temperature.

Chapman, P.

1982-04-01

314

Investigation of the dc vacuum breakdown mechanism  

NASA Astrophysics Data System (ADS)

Breakdowns occurring in rf accelerating structures will limit the ultimate performance of future linear colliders such as the Compact Linear Collider (CLIC). Because of the similarity of many aspects of dc and rf breakdown, a dc breakdown study is underway at CERN to better understand the vacuum breakdown mechanism in a simple setup. Measurements of the field enhancement factor ? show that the local breakdown field is constant and depends only on the electrode material. With copper electrodes, the local breakdown field is around 10.8GV/m, independent of the gap distance. The ? value characterizes the electrode surface state, and the next macroscopic breakdown field can be well predicted. In breakdown rate experiments, where a constant field is applied to the electrodes, clusters of consecutive breakdowns alternate with quiet periods. The occurrence and lengths of these clusters and quiet periods depend on the evolution of ?. The application of a high field can even modify the electrode surface in the absence of breakdown. Measurements of time delays to breakdown show two distinct populations, immediate and delayed breakdowns, indicating that two different mechanisms could exist. The ratio of these two populations depends on the conditioning state of the electrodes and on material. Gas release during breakdown is dominated by H2 and CO. This degassing is mainly due to electron-stimulated desorption. During the quiet periods without breakdown, gases are also released but the quantities are much smaller. All the measurements presented here emphasize the crucial role of field emission in the breakdown triggering.

Descoeudres, A.; Levinsen, Y.; Calatroni, S.; Taborelli, M.; Wuensch, W.

2009-09-01

315

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

SciTech Connect

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??m. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7??m gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

2014-03-24

316

Structural, electrical and magnetic characteristics of nickel substituted cobalt ferrite nano particles, synthesized by self combustion method  

NASA Astrophysics Data System (ADS)

Nickel-substituted cobalt ferrite nano-particles are synthesized using a self-combustion method. Aqueous metal nitrates and citric acid form the precursors. No external oxidizing agents are used to change the pH of the precursors; this resulted in a more environment friendly synthesis. Structural, magnetic and electrical characteristics of the nano ferrites are verified using X-ray diffractometer (XRD), VSM and impedance analyzer respectively. Phase formation, particle size, lattice parameter, X-ray density, saturation magnetization, coercivity, dielectric constant and electrical activation energy as function of nickel substitution in cobalt ferrite are studied. It is shown here that the magnetic and electrical properties can be tuned by varying the nickel concentration.

Sontu, Uday Bhasker; Yelasani, Vijayakumar; Musugu, Venkata Ramana Reddy

2015-01-01

317

Characteristics of Molten Slag from Hospital Waste Incineration Ash by Electric Arc Furnace  

Microsoft Academic Search

To deal with the issue of hospital solid waste (HSW) incineration ash, ash melting treatment technology was developed in combination with electric arc furnace metallurgical processes. The lab-scale melting experiment of HSW incineration ash, using 2kg DC electric arc furnace, was carried out to provide physical and chemical property analyses of molten slag from the bottom ash alone and the

Liu Han-qiao; Wei Guo-xia; Ye Hui-hua; Zhang Shu-guang

2009-01-01

318

Some Effects of Mineral Fillers on the Electrical Characteristics of Pultruded Composites  

Microsoft Academic Search

Several studies in the research literature discuss the effects of mineral fillers on the mechanical properties of pultruded composites; however, there are fewer studies that discuss the effects on dielectric\\/electrical properties. This paper will discuss some effects of mineral fillers and other constituent materials on the dielectric\\/electrical properties of pultruded composites, especially at giga- hertz frequencies. Mineral fillers including various

James G. Vaughan; Richard K. Gordon

319

Characteristic Analysis of Temperature Sensor in Dynamic Capacity Increase of High Voltage Electric Power Transmission Lines  

Microsoft Academic Search

Dynamic capacity increase in high voltage electric power transmission line is currently the most economical method for solving electric power transmission bottleneck nowadays. Temperature measurement error of the transmission line will affect the calculated current capacity of the transmission line. In this paper, conductor temperature model was applied to analyze the influence of the measurement error on the maximum current

Yuan Dai; Anqi Song; Wei Wang; Yangchun Cheng; Yongchun Liang; Jianliang Kong; Kai Xiao; Yuning Zhang

2012-01-01

320

RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES  

SciTech Connect

Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A 1.3 GHz RF test cell capable of operating both at high pressure and in vacuum with replaceable electrodes was designed, built, and power tested in preparation for testing the frequency and geometry effects of RF breakdown at Argonne National Lab. At the time of this report this cavity is still waiting for the 1.3 GHz klystron to be available at the Wakefield Test Facility. (3) Under a contract with Los Alamos National Lab, an 805 MHz RF test cavity, known as the All-Seasons Cavity (ASC), was designed and built by Muons, Inc. to operate either at high pressure or under vacuum. The LANL project to use the (ASC) was cancelled and the testing of the cavity has been continued under the grant reported on here using the Fermilab Mucool Test Area (MTA). The ASC is a true pillbox cavity that has performed under vacuum in high external magnetic field better than any other and has demonstrated that the high required accelerating gradients for many muon cooling beam line designs are possible. (4) Under ongoing support from the Muon Acceleration Program, microscopic surface analysis and computer simulations have been used to develop models of RF breakdown that apply to both pressurized and vacuum cavities. The understanding of RF breakdown will lead to better designs of RF cavities for many applications. An increase in the operating accelerating gradient, improved reliability and shorter conditioning times can generate very significant cost savings in many accelerator projects.

Johnson, Rolland

2014-09-21

321

Breakdown of silicon particle detectors under proton irradiation  

SciTech Connect

Silicon particle detectors made on Czochralski and float zone silicon materials were irradiated with 7 and 9 MeV protons at a temperature of 220 K. During the irradiations, the detectors were biased up to their operating voltage. Specific values for the fluence and flux of the irradiation were found to cause a sudden breakdown in the detectors. We studied the limits of the fluence and the flux in the breakdown as well as the behavior of the detector response function under high flux irradiations. The breakdown was shown to be an edge effect. Additionally, the buildup of an oxide charge is suggested to lead to an increased localized electric field, which in turn triggers a charge carrier multiplication. Furthermore, we studied the influences of the type of silicon material and the configuration of the detector guard rings.

Vaeyrynen, S.; Raeisaenen, J. [Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki (Finland); Kassamakov, I. [Department of Micro- and Nanosciences, Helsinki University of Technology, P.O. Box 3000, FI-02015 TKK (Finland); Tuominen, E. [Helsinki Institute of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki (Finland)

2009-11-15

322

Dielectric breakdown of polycrystalline alumina: A weakest-link failure analysis  

NASA Astrophysics Data System (ADS)

The effects of varying electrode geometry (ball and ring) and size (radius), dielectric media (castor oil and DialaRTM oil), specimen thickness, and concentration of defects on the dielectric breakdown strength of commercial-grade alumina and high-purity fine-grained (HPFG) alumina were investigated. The breakdown strength was expressed in terms of the maximum electric field in the ceramic at the breakdown voltage calculated by finite element analysis (FEA). The breakdown strength decreased systematically with increasing electrode radius and specimen thickness. The breakdown strength increased with decreasing concentration of defects. The breakdown strength was higher in the Diala RTM oil (dielectric constant, epsilonr = 2.3 +/- 0.12) as compared to the castor oil (epsilonr = 4.59 +/- 0.06). The breakdown strength was higher for the HPFG alumina as compared to the commercial- grade alumina. These effects of the electrode geometry, specimen thickness, concentration of defects, and of the dielectric media were analyzed with a weakest-link failure model employing the Laplace and Weibull distributions for a population of defects in the material. The measured size or scaling effects of the electrodes, specimen thickness, concentration of defects, and of the liquid media on breakdown strength were in better agreement with the Laplace distribution for the population. The measured concentration of surface defects was in good agreement with the concentration of surface defects estimated from the surface area scaling of the breakdown field with the Laplace distribution.

Block, Benjamin

323

Phase-field model for dielectric breakdown in solids  

NASA Astrophysics Data System (ADS)

Using an analogy between dielectric breakdown and fracture of solids, this paper develops a phase field model for the electric damage initiation and propagation in dielectric solids during breakdown. Instead of explicitly tracing the growth of a conductive channel, the model introduces a continuous phase field to characterize the degree of damage, and the conductive channel is represented by a localized region of fully damaged material. Similar as in the classic theory of fracture mechanics, an energetic criterion is taken: The conductive channel will grow only if the electrostatic energy released per unit length of the channel is greater than that dissipated through damage. Such an approach circumvents the detailed analysis on the complex microscopic processes near the tip of a conductive channel and provides a means of quantitatively predicting breakdown phenomena in materials, composites, and devices. This model is implemented into a finite-element code, and several numerical examples are solved. With randomly distributed defects, the model recovers the inverse power relation between breakdown strength and sample thickness. Finally, the effect of the layered structure in a breakdown-resistant laminate is demonstrated through a numerical example.

Chaitanya Pitike, Krishna; Hong, Wei

2014-01-01

324

Scaling law for direct current field emission-driven microscale gas breakdown  

SciTech Connect

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.

Venkattraman, A.; Alexeenko, A. A. [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States)

2012-12-15

325

The characteristics of quasistatic electric field perturbations observed by DEMETER satellite before large earthquakes  

NASA Astrophysics Data System (ADS)

This paper presents new results after processing the ULF electric field (DC-15 Hz) observed by DEMETER satellite (h = 660-710 km). Typical perturbations were picked up in quasistatic electric field around some large earthquakes in 2010 at first. And then, 27 earthquakes were selected to be analyzed on quasistatic electric field in two seismic regions of Indonesia and Chile at equatorial and middle latitude area respectively. Three-component electric field data related to earthquakes were collected along all the up-orbits (in local nighttime) in a limited distance of 2000 km to the epicenters during 9 days with 7 days before and 1 day after those cases, and totally 57 perturbations were found around them. All the results show that the amplitude of quasistatic electric field perturbations varies from 1.5 to 16 mV/m in the upper ionosphere, mostly smaller than 10 mV/m. And the perturbations were mainly located just over the epicentral area or at the end of seismic faults constructed by a series of earthquakes where electromagnetic emissions may be easily formed during preparation and development processes of seismic sequences. Among all 27 cases, there are 10 earthquakes with perturbations occurring just one day before, which demonstrates the close correlation in time domain between quasistatic electric field in ionosphere and large earthquakes. Finally, combined with in situ observation of plasma parameters, the coupling mechanism of quasistatic electric field in different earth spheres was discussed.

Zhang, X.; Shen, X.; Zhao, S.; Yao, Lu; Ouyang, X.; Qian, J.

2014-01-01

326

Performance characteristics of an electric-vehicle lead-acid battery pack at elevated temperatures  

NASA Astrophysics Data System (ADS)

Data are presented for discharge testing of an 18-Exide IV electric car battery pack over initial electrolyte temperature variations between 27 and 55 C. The tests were conducted under laboratory conditions and then compared to detailed electric vehicle simulation models. Results showed that battery discharge capacity increased with temperature for constant current discharges, and that battery energy capacity increased with temperature for constant power discharges. Dynamometer test of the GE Electric Test Vehicle showed an increase in range of 25% for the highest electrolyte temperature.

Chapman, P.

1982-04-01

327

Performance characteristics of an electric-vehicle lead-acid battery pack at elevated temperatures  

SciTech Connect

Data are presented for discharge testing of an 18-Exide IV electric car battery pack over initial electrolyte temperature variations between 27 and 55/sup 0/C. The tests were conducted under laboratory conditions and then compared to detailed electric vehicle simulation models. Results showed that battery discharge capacity increased with temperature for constant current discharges, and that battery energy capacity increased with temperature for constant power discharges. Dynamometer test of the GE Electric Test Vehicle showed an increase in range of 25% for the highest electrolyte temperature.

Chapman, P.

1982-04-01

328

Gain characteristics of THz surface plasmons in electrically pumped monolayer graphene  

NASA Astrophysics Data System (ADS)

Considering the electrically pumped monolayer graphene structures with split gates, we calculated propagation index and the imaginary part of ac conductivity, and numerically simulated the surface plasmons (SPs) frequency dependence on the absorption coefficient and the real part of the propagation index. From the simulations, the SPs gain is larger at low temperature, small gate voltage, long momentum relaxation time and high bias voltage. We compared SPs absorption coefficient and the real part of the propagation index between electrically pumped and optically pumped monolayer graphene. SPs stimulated in electrically pumped monolayer graphene have a large gain with higher bias voltage.

Zhang, Yu-Ping; Liu, Ya-Qing; Cao, Yan-Yan; Lv, Huan-Huan; Li, Tong-Tong; Huang, Xiaoyan; Zhang, Hui-Yun; Ren, Guang-Jun

2015-01-01

329

Characteristic Analysis of DC Electric Railway Systems with Superconducting Power Cables Connecting Power Substations  

NASA Astrophysics Data System (ADS)

The application of superconducting power cables to DC electric railway systems has been studied. It could leads to an effective use of regenerative brake, improved energy efficiency, effective load sharing among the substations, etc. In this study, an electric circuit model of a DC feeding system is built and numerical simulation is carried out using MATLAB-Simulink software. A modified electric circuit model with an AC power grid connection taken into account is also created to simulate the influence of the grid connection. The analyses have proved that a certain amount of energy can be conserved by introducing superconducting cables, and that electric load distribution and concentration among the substations depend on the substation output voltage distribution.

Ohsaki, H.; Matsushita, N.; Koseki, T.; Tomita, M.

2014-05-01

330

Effect of anatomical variability on electric field characteristics of electroconvulsive therapy and magnetic seizure therapy: a parametric modeling study  

PubMed Central

Electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) are conventionally applied with a fixed stimulus current amplitude, which may result in differences in the neural stimulation strength and focality across patients due to interindividual anatomical variability. The objective of this study is to quantify the effect of head anatomical variability associated with age, sex, and individual differences on the induced electric field characteristics in ECT and MST. Six stimulation modalities were modeled including bilateral and right unilateral ECT, focal electrically administered seizure therapy (FEAST), and MST with circular, cap, and double-cone coils. The electric field was computed using the finite element method in a parameterized spherical head model representing the variability in the general population. Head tissue layer thicknesses and conductivities were varied to examine the impact of interindividual anatomical differences on the stimulation strength, depth, and focality. Skull conductivity most strongly affects the ECT electric field, whereas the MST electric field is independent of tissue conductivity variation in this model but is markedly affected by differences in head diameter. Focal ECT electrode configurations such as FEAST is more sensitive to anatomical variability than that of less focal paradigms such as BL ECT. In MST, anatomical variability has stronger influence on the electric field of the cap and circular coils compared to the double-cone coil, possibly due to the more superficial field of the former. The variability of the ECT and MST electric field due to anatomical differences should be considered in the interpretation of existing studies and in efforts to improve dosing approaches for better control of stimulation strength and focality across patients, such as individualization of the current amplitude. The conventional approach to individualizing dosage by titrating the number of pulses cannot compensate for differences in the spatial extent of stimulation that result from anatomical variability. PMID:25055384

Deng, Zhi-De; Lisanby, Sarah H.; Peterchev, Angel V.

2014-01-01

331

Effect of anatomical variability on electric field characteristics of electroconvulsive therapy and magnetic seizure therapy: a parametric modeling study.  

PubMed

Electroconvulsive therapy (ECT) and magnetic seizure therapy (MST) are conventionally applied with a fixed stimulus current amplitude, which may result in differences in the neural stimulation strength and focality across patients due to interindividual anatomical variability. The objective of this study is to quantify the effect of head anatomical variability associated with age, sex, and individual differences on the induced electric field characteristics in ECT and MST. Six stimulation modalities were modeled including bilateral and right unilateral ECT, focal electrically administered seizure therapy (FEAST), and MST with circular, cap, and double-cone coils. The electric field was computed using the finite element method in a parameterized spherical head model representing the variability in the general population. Head tissue layer thicknesses and conductivities were varied to examine the impact of interindividual anatomical differences on the stimulation strength, depth, and focality. Skull conductivity most strongly affects the ECT electric field, whereas the MST electric field is independent of tissue conductivity variation in this model but is markedly affected by differences in head diameter. Focal ECT electrode configurations such as FEAST is more sensitive to anatomical variability than that of less focal paradigms such as BL ECT. In MST, anatomical variability has stronger influence on the electric field of the cap and circular coils compared to the double-cone coil, possibly due to the more superficial field of the former. The variability of the ECT and MST electric fields due to anatomical differences should be considered in the interpretation of existing studies and in efforts to improve dosing approaches for better control of stimulation strength and focality across patients, such as individualization of the current amplitude. The conventional approach to individualizing dosage by titrating the number of pulses cannot compensate for differences in the spatial extent of stimulation that result from anatomical variability. PMID:25055384

Deng, Zhi-De; Lisanby, Sarah H; Peterchev, Angel V

2015-01-01

332

Relationships between Electrical and Radar Characteristics of Thunderstorms Observed During ACES  

NASA Technical Reports Server (NTRS)

The Altus Cumulus Electrification Study (ACES) took place near Key West, Florida during August 2002. A high altitude, remotely piloted aircraft obtained optical pulse and electric field data over a number of thunderstorms during the study period. Measurements of the vertical electric field and cross sections of radar reflectivity along the flight track are shown for 2 overpasses of a thunderstorm that occurred on 10 August 2002.

Buechler, Dennis E.; Mach, Douglas M.; Blakeslee, Richard J.

2003-01-01

333

Electricity  

NSDL National Science Digital Library

Electricity is very important to our lives. This reading, part of a series about the future of energy, introduces students to the need and uses for electricity. Students review sources of electricity generation and investigate the evaluation of energy production resources. Here students review information on the generation of electric power and the infrastructure needed to transmit and distribute electricity. Thought-provoking questions afford students chances to reflect on what they've read. Web links to two PBS NewsHour energy-related articles are provided, along with a link to information on the benefits of small-scale wind projects. Copyright 2005 Eisenhower National Clearinghouse

Project, Iowa P.

2004-01-01

334

Statistical analysis of lightning electric field measured under Malaysian condition  

NASA Astrophysics Data System (ADS)

Lightning is an electrical discharge during thunderstorms that can be either within clouds (Inter-Cloud), or between clouds and ground (Cloud-Ground). The Lightning characteristics and their statistical information are the foundation for the design of lightning protection system as well as for the calculation of lightning radiated fields. Nowadays, there are various techniques to detect lightning signals and to determine various parameters produced by a lightning flash. Each technique provides its own claimed performances. In this paper, the characteristics of captured broadband electric fields generated by cloud-to-ground lightning discharges in South of Malaysia are analyzed. A total of 130 cloud-to-ground lightning flashes from 3 separate thunderstorm events (each event lasts for about 4-5 hours) were examined. Statistical analyses of the following signal parameters were presented: preliminary breakdown pulse train time duration, time interval between preliminary breakdowns and return stroke, multiplicity of stroke, and percentages of single stroke only. The BIL model is also introduced to characterize the lightning signature patterns. Observations on the statistical analyses show that about 79% of lightning signals fit well with the BIL model. The maximum and minimum of preliminary breakdown time duration of the observed lightning signals are 84 ms and 560 us, respectively. The findings of the statistical results show that 7.6% of the flashes were single stroke flashes, and the maximum number of strokes recorded was 14 multiple strokes per flash. A preliminary breakdown signature in more than 95% of the flashes can be identified.

Salimi, Behnam; Mehranzamir, Kamyar; Abdul-Malek, Zulkurnain

2014-02-01

335

Electrical characteristics of Au/n-GaAs structures with thin and thick SiO{sub 2} dielectric layer  

SciTech Connect

The aim of this study, to explain effects of the SiO{sub 2} insulator layer thickness on the electrical properties of Au/n-GaAs Shottky barrier diodes (SBDs). Thin (60 A) and thick (250 A) SiO{sub 2} insulator layers were deposited on n-type GaAs substrates using the plasma enganced chemical vapour deposition technique. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics have been carried out at room temperature. The main electrical parameters, such as ideality factor (n), zero-bias barrier height ({phi}{sub Bo}), series resistance (R{sub s}), leakage current, and interface states (N{sub ss}) for Au/SiO{sub 2}/n-GaAs SBDs have been investigated. Surface morphologies of the SiO{sub 2} dielectric layer was analyzed using atomic force microscopy. The results show that SiO{sub 2} insulator layer thickness very affects the main electrical parameters. Au/n-GaAs SBDs with thick SiO{sub 2} insulator layer have low leakage current level, small ideality factor, and low interface states. Thus, Au/n-GaAs SBDs with thick SiO{sub 2} insulator layer shows better diode characteristics than other.

Altuntas, H., E-mail: altunhalit@gmail.edu.tr [Cankiri Karatekin University, Department of Physics, Faculty of Sciences (Turkey); Altindal, S. [Gazi University, Department of Physics, Faculty of Arts and Sciences (Turkey); Corekci, S. [Kirklareli University, Department of Physics, Faculty of Arts and Sciences (Turkey); Ozturk, M. K.; Ozcelik, S. [Gazi University, Department of Physics, Faculty of Arts and Sciences (Turkey)

2011-10-15

336

Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage ( 250 V) 4H-SiC p n Junction Diodes—Part II: Dynamic Breakdown Properties  

Microsoft Academic Search

This paper outlines the dynamic reverse- breakdown characteristics of low-voltage ( 250 V) small-area cm 4H-SiC p n diodes subjected to nonadiabatic breakdown-bias pulsewidths ranging from 0.1 to 20 s. 4H-SiC diodes with and without elementary screw dislocations exhibited positive temperature coefficient of breakdown voltage and high junction failure power densities approximately five times larger than the average failure power

Philip G. Neudeck; Christian Fazi

337

Joining characteristics of titanium-based orthodontic wires connected by laser and electrical welding methods.  

PubMed

This study investigated the possibility of electrical and laser welding to connect titanium-based alloy (beta-titanium and nickel-titanium) wires and stainless-steel or cobalt-chromium alloy wires for fabrication of combination arch-wires. Four kinds of straight orthodontic rectangular wires (0.017 × 0.025 inch) were used: stainless-steel (S-S), cobalt-chromium (Co-Cr), beta-titanium alloy (?-Ti), and nickel-titanium (Ni-Ti). Homogeneous and heterogeneous end-to-end joints (15 mm long each) were made by electrical welding and laser welding. Non-welded wires (30 mm long) were also used as a control. Maximum loads at fracture (N) and elongation (%) were measured by conducting tensile test. The data (n = 10) were statistically analyzed using analysis of variance/Tukey test (P < 0.05).The S-S/S-S and Co-Cr/Co-Cr specimens showed significantly higher values of the maximum load (ML) at fracture and elongation (EL) than those of the Ni-Ti/Ni-Ti and ?-Ti/?-Ti specimens for electrical welding and those of the S-S/S-S and Co-Cr/Co-Cr specimens welded by laser. On the other hand, the laser-welded Ni-Ti/Ni-Ti and ?-Ti/?-Ti specimens exhibited higher values of the ML and EL compared to those of the corresponding specimens welded by electrical method. In the heterogeneously welded combinations, the electrically welded Ni-Ti/S-S, ?-Ti/S-S and ?-Ti/Co-Cr specimens showed significantly (P < 0.05) higher ML and EL than those of the corresponding specimens welded by laser. Electrical welding exhibited the higher values of maximum load at fracture and elongation for heterogeneously welded combinations than laser-welding. PMID:25595723

Matsunaga, Junko; Watanabe, Ikuya; Nakao, Noriko; Watanabe, Etsuko; Elshahawy, Waleed; Yoshida, Noriaki

2015-01-01

338

The structure of vortex breakdown  

NASA Technical Reports Server (NTRS)

The term 'vortex breakdown', as used in the reported investigation, refers to a disturbance characterized by the formation of an internal stagnation point on the vortex axis, followed by reversed flow in a region of limited axial extent. Two forms of vortex breakdown, which predominate, are shown in photographs. One form is called 'near-axisymmetric' (sometimes 'axisymmetric'), and the other is called 'spiral'. A survey is presented of work published since the 1972 review by Hall. Most experimental data taken since Hall's review have been in tubes, and the survey deals primarily with such cases. It is found that the assumption of axial-symmetry has produced useful results. The classification of flows as supercritical or subcritical, a step that assumes symmetry, has proved universally useful. Experiments show that vortex breakdown is always preceded by an upstream supercritical flow and followed by a subcritical wake. However, a comparison between experiments and attempts at prediction is less than encouraging. For a satisfactory understanding of the structure of vortex breakdown it is apparently necessary to take into account also aspects of asymmetry.

Leibovich, S.

1978-01-01

339

Influence of ITO, Graphene Thickness and Electrodes Buried Depth on LED Thermal-Electrical Characteristics Using Numerical Simulation  

NASA Astrophysics Data System (ADS)

Finite elements methods are used to investigate the thermal-electrical characteristics of gallium-nitride (GaN) light-emitting diodes (LEDs) with different transparent conductive layers (TCLs) and buried depths of electrodes, where the transparent conductive layers include indium tin oxide (ITO), graphene (Gr) and the combination of them (ITO/Gr). The optimal material parameters and the precision and accuracy of the simulation model are validated. Moreover, the parameters' sensitivity analysis is carried out as well. The results indicate that the LED with the TCL of a 100-nm ITO or 4-layer Gr has a good thermal-electrical performance from the viewpoint of the maximum temperature and the current density deviation of multiple quantum well (MQW), where the maximum temperature occurs at the n-Pad rather than p-Pad. The compound TCL with a 20-nm ITO and 3-layer Gr reaches a thermal-electrical performance better than that of a 100-nm ITO or 4-layer Gr. Moreover, their maximum temperatures decrease about -0.43% and 1.21%, and the current density uniformities increase up to -6.09% and 17.41%, respectively. Furthermore, when the electrode buried depth is 0.51 ?m, the thermal-electrical performance of the GaN LEDs can be further improved.

Xue, Sheng-Jie; Fang, Liang; Long, Xing-Ming; Lu, Yi; Wu, Fang; Li, Wan-Jun; Zuo, Jia-Qi; Zhang, Shu-Fang

2014-02-01

340

Dynamic response characteristics of thermoelectric generator predicted by a three-dimensional heat-electricity coupled model  

NASA Astrophysics Data System (ADS)

The practical application environments of thermoelectric generators (TEGs) always change, which make a requirement for studying the dynamic response characteristics of TEGs. This work develops a complete, three-dimensional and transient model to investigate this issue. The model couples the energy and electric potential equations. Seebeck effect, Peltier effect, Thomson effect, Joule heating and Fourier heat conduction are taken into account in this model. Dynamic output power and conversion efficiency of the TEG, which are caused by variations of the hot end temperature, cold end temperature and load current, are studied. The response hysteresis of the output power to the hot end and cold end temperatures, the overshoot or undershoot of the conversion efficiency are found and attributed to the delay of thermal diffusion. However, the output power is synchronous with the load current due to much faster electric response than thermal response.

Meng, Jing-Hui; Zhang, Xin-Xin; Wang, Xiao-Dong

2014-01-01

341

Characterization of solar cells for space applications. Volume 13: Electrical characteristics of Hughes LPE gallium arsenide solar cells as a function of intensity and temperature  

NASA Technical Reports Server (NTRS)

Electrical characteristics of Hughes Liquid phase epitaxy, P/N gallium aluminum arsenide solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature.

Anspaugh, B. E.; Beckert, D. M.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

1980-01-01

342

Test and simulation of axial flux-motor characteristics for hybrid electric vehicles  

Microsoft Academic Search

High power density is the main advantage of the axial flux motors compared to the conventional radial flux motors. Therefore, they are suitable candidates for the power train of hybrid electric vehicles. In addition, operating speed range and efficiency of axial flux motors can be improved by changing the air gap of the machine. In this paper, for each operating

Sung Chul Oh; Ali Emadi

2004-01-01

343

Electrical conductivity and current-voltage characteristics of alumina with or without neutron and electron irradiation  

E-print Network

-ku, Fukuoka 812-8581, Japan b Metals and Ceramics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak, Ibarakiken 311-1313, Japan Abstract The in situ measurement of electrical conductivity and of current) of alumina under irradiation are two of the critical issues for its application to fusion reactors. Many

Howlader, Matiar R

344

[The characteristics of the electromagnetic situation close to overhead electric power transmission lines in St. Petersburg].  

PubMed

According to task by Environmental Protection Department of St. Petersburg Municipal Administration, levels of electromagnetic fields induced by high-voltage electric power lines were measured in development lands of St. Petersburg. The authors present hygienic evaluation of electromagnetic fields intensity, match calculated and actual values of magnetic induction of occupational magnetic fields. PMID:9885493

Nikitina, V N; Marchenko, E A; Kolesnikov, G A; Naumova, T M; Shubnikova, N N; Cherniavski?, A A

1998-01-01

345

Partial discharge characteristics of enameled wire of electric machine winding under exploitation stresses  

Microsoft Academic Search

In applications where power electronic converters are used, the voltage stress has a form of fast switching pulses composing of repetitive sequences. Such conditions have influence on inception and development of partial discharges in insulating systems of electrical machines subjected to non-sinusoidal waveform. The paper presents the dependence of partial discharge parameters and partial discharge patterns upon kinds of magnet

B. Florkowska; J. Roehrich; P. Zydron; M. Florkowski

2010-01-01

346

Monte Carlo simulation of initial breakdown phase for magnetised toroidal ICRF discharges  

SciTech Connect

The radio-frequency (RF) plasma production technique in the ion cyclotron range of frequency (ICRF) attracts growing attention among fusion experts because of its high potential for solving several basic problems of reactor-oriented superconducting fusion machines, such as ICRF wall conditioning in tokamaks and stellarators (T{sub e}?=?3?5eV, n{sub e}<10{sup 12}cm{sup ?3}), ICRF-assisted tokamak start-up and target plasma production (n{sub e}?=?10{sup 13}cm{sup ?3}) in stellarators. Plasma initiation by ICRF has been studied intensively using single particle descriptions and basic analytic models. To further improve the present understanding on plasma production employing the vacuum RF field of ICRF antennas in toroidal devices in presence of the toroidal magnetic field, and its parametric dependencies a Monte Carlo code has been developed. The 1D code RFdinity1D describes the motion of electrons, accelerated by the RF field in front of the ICRF antenna, along one toroidal magnetic field line. Dependent on their individual energies and the related electron collision cross sections (ionisation, excitation and dissociation) weighted by a Monte Carlo procedure, an electron avalanche may occur. Breakdown conditions are discussed as function of RF discharge parameters (i) RF vacuum electric field strength, (ii) RF frequency and (iii) neutral pressure (H2). The slope of the exponential density increase, taken as measure for the breakdown speed, shows qualitative agreement to experimental breakdown times as found in literature and experimental data of the ASDEX upgrade and TEXTOR tokamak, and is interpreted by studying the characteristic electron velocity distribution functions.

Tripský, M. [Association Euratom-Belgian State, LPP-ERM/KMS, 1000 Brussels, Belgium and Ghent University, Department of Applied Physics, 9000 Ghent (Belgium); Wauters, T.; Lyssoivan, A.; Koch, R.; Vervier, M.; Van Schoor, M. [Association Euratom-Belgian State, LPP-ERM/KMS, 1000 Brussels (Belgium); Bobkov, V. [Association Euratom-IPP, Max-Planck Institut für Plasmaphysik, 85748 Garching (Germany); Van Oost, G. [Ghent University, Department of Applied Physics, 9000 Ghent (Belgium); Collaboration: ASDEX Upgrade Team; TEXTOR Team

2014-02-12

347

Monte Carlo simulation of initial breakdown phase for magnetised toroidal ICRF discharges  

NASA Astrophysics Data System (ADS)

The radio-frequency (RF) plasma production technique in the ion cyclotron range of frequency (ICRF) attracts growing attention among fusion experts because of its high potential for solving several basic problems of reactor-oriented superconducting fusion machines, such as ICRF wall conditioning in tokamaks and stellarators (Te = 3-5eV, ne<1012cm-3), ICRF-assisted tokamak start-up and target plasma production (ne = 1013cm-3) in stellarators. Plasma initiation by ICRF has been studied intensively using single particle descriptions and basic analytic models. To further improve the present understanding on plasma production employing the vacuum RF field of ICRF antennas in toroidal devices in presence of the toroidal magnetic field, and its parametric dependencies a Monte Carlo code has been developed. The 1D code RFdinity1D describes the motion of electrons, accelerated by the RF field in front of the ICRF antenna, along one toroidal magnetic field line. Dependent on their individual energies and the related electron collision cross sections (ionisation, excitation and dissociation) weighted by a Monte Carlo procedure, an electron avalanche may occur. Breakdown conditions are discussed as function of RF discharge parameters (i) RF vacuum electric field strength, (ii) RF frequency and (iii) neutral pressure (H2). The slope of the exponential density increase, taken as measure for the breakdown speed, shows qualitative agreement to experimental breakdown times as found in literature and experimental data of the ASDEX upgrade and TEXTOR tokamak, and is interpreted by studying the characteristic electron velocity distribution functions.

Tripský, M.; Wauters, T.; Lyssoivan, A.; Koch, R.; Bobkov, V.; Vervier, M.; van Oost, G.; van Schoor, M.; ASDEX Upgrade Team, Textor Team

2014-02-01

348

7 CFR 51.1009 - Stylar end breakdown.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Stylar end breakdown. 51.1009 Section 51.1009 Agriculture...Limes Definitions § 51.1009 Stylar end breakdown. Stylar end breakdown is a physiological breakdown starting at...

2010-01-01

349

High-power microwave bandwidth broadening by air breakdown  

NASA Astrophysics Data System (ADS)

Wideband, high-power microwave pulses are expected to have important applications in ultra-wideband radar. The wide bandwidth should generate increased information for target characterization and identification. The high power should result in increased target detection range for conventional targets and targets with reduced signatures. A way to generate wideband, high-power microwave pulses with relatively conventional technology is to tail erode high-power pulses by passage through a low pressure air cell. In this process, the tails of short (3 to 10 ns), high amplitude (greater than 1 MV/m) pulses are removed. This erosion shortens the pulses and generates transmitted pulses with broadened bandwidths. The pressure must be matched to several incident pulse characteristics to create enough electron density to cause strong tail erosion. The important pulse characteristics are amplitude, frequency, pulse length, and pulse shape. We have shown experimentally that tail erosion from air breakdown broadens the 3 dB bandwidths of 2.8608 GHz incident pulses in a rectangular waveguide at 3.5 torr. The incident pulse amplitude varied from 0.67 to 1.16 MV/m. The pulse bandwidth increased from 0.147 GHz by 0.34 to 1.4 pct. relative. The incident bandwidth was 5.12 pct. relative to the incident carrier frequency. This experimental broadening was simulated with a 2D, electromagnetic, electron fluid computer code for avalanche ionization. The simulation predicted bandwidth broadening by 0.029 to 0.13 GHz or 1.0 to 4.4 pct. relative for a peak initial electron density of 10 electrons/cu cm. Although the measured and calculated transmitted electric field envelopes were in close agreement, the calculated bandwidths exceeded those measured by 13 to 47 pct. Because the detectors were not fast enough to resolve individual cycles we presently conclude that the simulation gives better estimates of reality than do the measurements.

Mayhall, D. J.; Yee, J. H.; Alvarez, R. A.

1991-12-01

350

Criteria for Spark Breakdown in Sulfur Hexafluoride  

Microsoft Academic Search

Possible mechanisms of spark breakdown in SF6 and other electronegative gases are discussed, and quantitative criteria are derived for the Townsend type and the streamer type of breakdown in nonuniform fields. The Townsend criterion is of considerable physical interest but difficult to apply to engineering problems, whereas the semi-empirical streamer criterion, which holds for impulse breakdown, can be applied to

A. Pedersen

1970-01-01

351

Bounds for the rth characteristic frequency of a beaded string or of an electrical filter  

PubMed Central

The fundamental mode of vibration of a beaded string has a shape without change of sign. The rth higher normal mode of vibration has r changes of sign. Given any virtual shape of the string with r changes of sign, an algorithm is found that gives upper and lower bounds for the rth characteristic frequency as a function of the virtual shape. By making a certain transformation it is found that this algorithm holds for the characteristic frequencies of an inductor-capacitor network. Other transformations show that it applies to the rth eigenvalue of a Hermitian matrix. PMID:16592835

Barnsley, Michael F.; Duffin, Richard J.

1980-01-01

352

Predicting Flow Breakdown Probability and Duration in Stochastic Network Models: Impact on Travel Time Reliability  

SciTech Connect

This paper proposes a methodology to produce random flow breakdown endogenously in a mesoscopic operational model, by capturing breakdown probability and duration. Based on previous research findings that probability of flow breakdown can be represented as a function of flow rate and the duration can be characterized by a hazard model. By generating random flow breakdown at various levels and capturing the traffic characteristics at the onset of the breakdown, the stochastic network simulation model provides a tool for evaluating travel time variability. The proposed model can be used for (1) providing reliability related traveler information; (2) designing ITS (intelligent transportation systems) strategies to improve reliability; and (3) evaluating reliability-related performance measures of the system.

Dong, Jing [ORNL; Mahmassani, Hani S. [Northwestern University, Evanston

2011-01-01

353

Study of RF Breakdown Mechanisms Relevant to an ICH Antenna Environment  

NASA Astrophysics Data System (ADS)

The mechanisms that contribute to RF breakdown/arcing in an antenna environment are being studied. RF breakdown/arcing is a major power-limiting factor in antenna systems used for RF heating and current drive in fusion experiments. The factors that contribute to breakdown include gas pressure, gas type, magnetic field, materials, ultraviolet light, and local plasma density. The effects of these factors on RF breakdown are being studied in a resonant 1/4-wavelength section of vacuum transmission line terminated with an open circuit electrode structure. The electrode structure is designed to determine the role of the RF electric field strength and magnetic field orientation on the breakdown process. Changes in the electrical parameters, such as input impedance and the voltage at the electrodes, are being monitored to detect the breakdown events. Measurements of the light emission prior to and during an arc are also being made. For high vacuum conditions using copper electrodes, bright spots appear on the electrode surfaces prior to a breakdown event. An increase in the RF field results in an arc and a flash of light corresponding to copper line emission (578.2 or 521.8 nm). Analysis of the electrode surfaces show large areas of melting and formation of micron-sized rounded protrusions, especially along the sharp edges of small scratches. An increase in the chamber pressure results in a decrease in the maximum RF electric field that can be sustained without breakdown as the pressure approaches a few mTorr. The breakdown event leads to formation of a plasma in the structure, with light emission corresponding to the particular gas being used. The addition of an external magnetic field causes the formation of a plasma at lower pressures, thus limiting the amount of coupled RF power. The presence of UV light has been found to initiate multipactor under some operating conditions.

Caughman, J. B. O.; Castano-Giraldo, C.; Aghazarian, M.; Baity, F. W.; Rasmussen, D. A.; Ruzic, D. N.

2007-09-01

354

Electrical characteristics of TMAH-surface treated Ni/Au/Al2O3/GaN MIS Schottky structures  

NASA Astrophysics Data System (ADS)

The electrical characteristics and reverse leakage mechanisms of tetramethylammonium hydroxide (TMAH) surface-treated Ni/Au/Al2O3/GaN metal-insulator-semiconductor (MIS) diodes were investigated by using the current-voltage ( I-V) and capacitance-voltage ( C-V) characteristics. The MIS diode was formed on n-GaN after etching the AlGaN in the AlGaN/GaN heterostructures. The TMAH-treated MIS diode showed better Schottky characteristics with a lower ideality factor, higher barrier height and lower reverse leakage current compared to the TMAH-free MIS diode. In addition, the TMAH-free MIS diodes exhibited a transition from Poole-Frenkel emission at low voltages to Schottky emission at high voltages, whereas the TMAH-treated MIS diodes showed Schottky emission over the entire voltage range. Reasonable mechanisms for the improved device-performance characteristics in the TMAH-treated MIS diode are discussed in terms of the decreased interface state density or traps associated with an oxide material and the reduced tunneling probability.

Reddy, M. Siva Pratap; Lee, Jung-Hee; Jang, Ja-Soon

2014-03-01

355

Electrical characteristics of silicon nanowire transistors fabricated by scanning probe and electron beam lithographies.  

PubMed

Silicon nanowire (SiNW) field-effect transistors have been fabricated by oxidation scanning probes and electron beam lithographies. The analysis and comparison of the electron mobility and subthreshold swing shows that the device performance is not affected by the top-down fabrication method. The two methods produce silicon nanowire transistors with similar electrical features, although oxidation scanning probe lithography generates nanowires with smaller channel widths. The values of the electron mobility and the subthreshold swing, 200 cm(2) V(-1) s(-1) and 500 mV dec(-1), respectively, are similar to those obtained from bottom-up methods. The compatibility of top-down methods with CMOS (complementary metal-oxide-semiconductor) procedures, the good electrical properties of the nanowire devices and the potential for making sub-10 nanowires, in particular by using oxidation scanning probe lithography, make those methods attractive for device fabrication. PMID:23857981

Ryu, Yu Kyoung; Chiesa, Marco; Garcia, Ricardo

2013-08-01

356

Analysis of the electrical characteristic of linseed oil films exposed to humidity  

NASA Astrophysics Data System (ADS)

Linseed oil is a material widely used in various applications as a protecting layer for surfaces in industry, in scientific research, for medical use, and finally for artistic purpose. This natural origins substance has a particular application as a protective and smoothing layer on phenolic-melaminic laminate electrodes on Resistive Plate Chamber (RPC) detectors used in various particle physic experiments. In such electronic applications where linseed oil could be exposed to water vapours, an electrical characterization should result useful for having an overall control of the process involving the oil. In this paper, we studied the electrical behaviour towards relative humidity variations of linseed oil films deposited on interdigitated metal electrodes. Moreover, I/V characterisation both in air and vacuum, current vs. temperature and relative humidity was performed.

Palummo, Lucrezia; Bearzotti, Andrea

2009-12-01

357

Electrical isolation and characteristics of permanent magnet-actuated valves for PDMS microfluidics.  

PubMed

This paper presents a magnetically driven valve via a permanent magnet pressing a spacer against deformable polydimethylsiloxane (PDMS) to fully close a microchannel. Its ability for electrical isolation, time response, and resistance to backpressure are interrogated. Simulation of the valve closing process was commenced along with experimental verification. Effects of PDMS thickness, and dimension and aspect ratio of microchannels were characterized. Up to 10 G? electrical isolation was demonstrated, as well as 50-70 ms valve response and ?200 kPa resistible pressure. On-demand actuation for arbitrary flow patterns further quantifies its utility. With advantages of simple fabrication, flexible valving location, and no external power requirement, the on/off valve could be leveraged for proof-of-concept microfluidic devices and other applications. PMID:21132206

Chen, Chang-Yu; Chen, Chang-Hung; Tu, Ting-Yuan; Lin, Cheng-Ming; Wo, Andrew M

2011-02-21

358

Design of transducer structure parameters and materials characteristics analyses for electrical capacitance tomography system  

NASA Astrophysics Data System (ADS)

The object of this paper majors in the research of 8-electrode oil-water two-phase flow electrical capacitance tomography system. The distribution models of transducer's field are established by the finite element method for the influence of the parameters of transducer's structure on the performance of transducer. The analyses of simulation and experiment and the transducer's design optimized are done, and the measure function of transducer's design optimized is proposed based on transducer parameters. The system of 8-electrode oil-water two-phase flow electrical capacitance tomography is designed based on the results of theory and simulation analyses. The sensitivity and uniformity of sensitive field is improved and the design of the measurement circuit is easier but the data precision of sensitive field is enough for image reconstruction.

Qin, Mei

2010-01-01

359

Corona and Breakdown Voltage in HeliumOxygen Atmospheres  

Microsoft Academic Search

Helium-oxygen mixtures are being considered for use in low-pressure (3.5 to 7.5 psia) compartments of manned spacecraft. Electrical wires, cabling, and components will be required to operate in these low-pressure compartments. During extra-vehicular maneuvers the pressure could decrease to that of space vacuum. During the depressurization and pressurization periods, corona and voltage breakdown will be a significant problem. This paper

W. G. Dunbar

1970-01-01

360

A numerical model of avalanche breakdown in MOSFET's  

Microsoft Academic Search

An accurate numerical model of avalanche breakdown in MOSFET's is presented. Features of this model are a) use of an accurate electric-field distribution calculated by a two-dimensional numerical analysis, b) introduction of multiplication factors for a high-field path and the channel current path, and c) incorporation of the feedback effect of the excess substrate current induced by impact ionization into

T. Toyabe; K. Yamaguchi; S. Asai; M. S. Mock

1978-01-01

361

Characteristics of future Vertical Axis Wind Turbines (VAWTs). [to generate utility grid electric power  

NASA Technical Reports Server (NTRS)

The developing Darrieus VAWT technology whose ultimate objective is economically feasible, industry-produced, commercially marketed wind energy systems is reviewed. First-level aerodynamic, structural, and system analyses capabilities which support and evaluate the system designs are discussed. The characteristics of current technology designs are presented and their cost effectiveness is assessed. Potential improvements identified are also presented along with their cost benefits.

Kadlec, E. G.

1979-01-01

362

New phenomenology of gas breakdown in DC and RF fields  

NASA Astrophysics Data System (ADS)

This paper follows a review lecture on the new developments in the field of gas breakdown and low current discharges, usually covered by a form of Townsend's theory and phenomenology. It gives an overview of a new approach to identifying which feedback agents provide breakdown, how to model gas discharge conditions and reconcile the results with binary experiments and how to employ that knowledge in modelling gas discharges. The next step is an illustration on how to record volt-ampere characteristics and use them on one hand to obtain the breakdown voltage and, on the other, to identify the regime of operation and model the secondary electron yields. The second aspect of this section concerns understanding the different regimes, their anatomy, how those are generated and how free running oscillations occur. While temporal development is the most useful and interesting part of the new developments, the difficulty of presenting the data in a written form precludes an easy publication and discussion. Thus, we shall only mention some of the results that stem from these measurements. Most micro discharges operate in DC albeit with complex geometries. Thus, parallel plate micro discharge measurements were needed to establish that Townsend's theory, with all its recent extensions, is still valid until some very small gaps. We have shown, for example, how a long-path breakdown puts in jeopardy many experimental observations and why a flat left-hand side of the Paschen curve often does not represent good physics. We will also summarize a kinetic representation of the RF breakdown revealing a somewhat more complex picture than the standard model. Finally, we will address briefly the breakdown in radially inhomogeneous conditions and how that affects the measured properties of the discharge. This review has the goal of summarizing (rather than developing details of) the current status of the low-current DC discharges formation and operation as a discipline which, in spite of its very long history, is developing rapidly.

Petrovi?, Zoran Lj; Sivoš, Jelena; Savi?, Marija; Škoro, Nikola; Radmilovi? Radenovi?, Marija; Malovi?, Gordana; Goci?, Saša; Mari?, Dragana

2014-05-01

363

Electricity  

NSDL National Science Digital Library

This Topic In Depth explores some of what the Web has to offer on the subject of electricity.The first site from Thinkquest.org called Electricity Online (1) gives an excellent overview, with topics ranging from circuits and transformers to electricity's discovery and history. The site even contains games, activities, and quizzes. The second site, Edison's Miracle of Light (2) from PBS.org, is a companion site to a PBS special of the same name. The site explores the life and accomplishments of one of the 19th century's greatest inventors, offering a timeline, recordings, and more. From Clark Public Utilities of Clark County Washington, the next site is called Electricity (3). This Web site offers information from a public utilities perspective, with subjects like electrical safety, how electricity gets to your home, what it costs to run appliances, and so on. Next, from the US Department of Energy, is a site that offers an Overview of the Electric Power Industry (4). Here, visitors can find information, data, publications, statistics, and more relating to electric power in the US. The fifth site from ExploreScience.com is called Multimedia Activities (5) and contains just that. Geared towards students, the four interactive lessons include an introduction to electricity and magnetism, an introduction to plasma, coulomb force, and lissajous figures. The next site, provided by the BBC, is another interactive learning site, called Activity Electricity (6). Users click through a lesson about circuits and current, answering questions along the way. The site also contains a fact sheet and quiz. From NASA, the Dataset Information site (7) contains data archived and cataloged by the Global Hydrology Resource Center relating to lighting. Several datasets from varying sources are available for free and include such things as Long Range Cloud to Ground Data. The last site is offered by the Canada Science and Technology Museum and is called Background Information for Electricity (8). This Web site for kids offers simple descriptions and illustrations about electricity, who discovered it, conductors and insulators, fuses, and more. The electricity workshop link also contains lesson plans and additional student activities.

Brieske, Joel A.

2002-01-01

364

Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics  

Microsoft Academic Search

The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s-1 at heights of 1-2 mm are reached when filamentary discharges with current peaks up

Jérôme Pons; Eric Moreau; Gérard Touchard

2005-01-01

365

Electrical characteristics of GaAs implanted with 70 MeV 120Sn ions  

Microsoft Academic Search

Electrical behavior of n-GaAs substrates implanted with 70 MeV 120Sn ions has been investigated after annealing over a temperature range of 450–850°C. The resistance values are found to increase with increasing annealing temperature up to 650°C and then decrease for higher annealing temperatures. The resistance of 450°C annealed sample is dominated by defect hopping conduction below room temperature. Above room

Yousuf Pyar Ali; A. M. Narsale; Uma Bhambhani; Arun Damle; V. P. Salvi; B. M. Arora; A. P. Shah; D. Kanjilal

1996-01-01

366

Particle charging characteristics with the low-speed mixed fluid under high electric field  

NASA Astrophysics Data System (ADS)

Air pollution caused by particles with small size has been a global concern because of threats to human health. A feasible way to remove these super fine suspended particles is using electrostatic precipitation technology. Herein, the PIV was used to measure the particle velocity distribution. By analyzing the particle motion trend in high electric field, a process of particle charging loss was observed. This phenomenon cannot be explained by current particle charging theories. Our conclusions may improve the understanding of particle charging processes.

He, Bo; Li, YaDong; Ma, DongDong; Gu, Ran; Lin, Mei

2014-09-01

367

Electric double layer effect on observable characteristics of the tunnel current through a bridged electrochemical contact.  

PubMed

Scanning tunneling microscopy and electrical conductivity of redox molecules in conducting media (aqueous or other media) acquire increasing importance both as novel single-molecule science and with a view on molecular scale functional elements. Such configurations require full and independent electrochemical potential control of both electrodes involved. We provide here a general formalism for the electric current through a redox group in an electrochemical tunnel contact. The formalism applies broadly in the limits of both weak and strong coupling of the redox group with the enclosing metal electrodes. Simple approximate expressions better suited for experimental data analysis are also derived. Particular attention is given to the effects of the Debye screening of the electric potential in the narrow tunneling gap based on the limit of the linearized Poisson-Boltzmann equation. The current/overpotential relation shows a maximum at a position which depends on the ionic strength. It is shown, in particular, that the dependence of the maximum position on the bias voltage may be nonmonotonous. Approximate expressions for the limiting value of the slope of the current/overpotential dependence and the width of the maximum on the bias voltage are also given and found to depend strongly on both the Debye screening and the position of the redox group in the tunnel gap, with diagnostic value in experimental data analysis. PMID:17867770

Kuznetsov, Alexander M; Medvedev, Igor G; Ulstrup, Jens

2007-09-14

368

Electric double layer effect on observable characteristics of the tunnel current through a bridged electrochemical contact  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy and electrical conductivity of redox molecules in conducting media (aqueous or other media) acquire increasing importance both as novel single-molecule science and with a view on molecular scale functional elements. Such configurations require full and independent electrochemical potential control of both electrodes involved. We provide here a general formalism for the electric current through a redox group in an electrochemical tunnel contact. The formalism applies broadly in the limits of both weak and strong coupling of the redox group with the enclosing metal electrodes. Simple approximate expressions better suited for experimental data analysis are also derived. Particular attention is given to the effects of the Debye screening of the electric potential in the narrow tunneling gap based on the limit of the linearized Poisson-Boltzmann equation. The current/overpotential relation shows a maximum at a position which depends on the ionic strength. It is shown, in particular, that the dependence of the maximum position on the bias voltage may be nonmonotonous. Approximate expressions for the limiting value of the slope of the current/overpotential dependence and the width of the maximum on the bias voltage are also given and found to depend strongly on both the Debye screening and the position of the redox group in the tunnel gap, with diagnostic value in experimental data analysis.

Kuznetsov, Alexander M.; Medvedev, Igor G.; Ulstrup, Jens

2007-09-01

369

Microwave breakdown for the TE10 mode in a rectangular waveguide  

NASA Astrophysics Data System (ADS)

Microwave breakdown is studied for the lowest order TE10 mode in a rectangular waveguide with the help of direct variational approach via the continuity equation along with the use of ionisation and attachment frequency. We investigate the role of the ionisation, attachment of electron with neutral gas or air molecules and the diffusion on microwave breakdown threshold in the waveguide filled with air or Ar Gas. We examine the effect of different gases and microwave parameters on the diffusion length and the breakdown threshold of electric field of continuous microwave and pulsed microwave. We also employ numerical approach for obtaining the results and compare them with the ones of variational approach.

Malik, Hitendra K.; Aria, Anil K.

2013-08-01

370

Simulation of the formation of a runaway electron beam in an overvolted gas gap breakdown  

SciTech Connect

The paper reports on numerical simulation to inquire into the breakdown of a gas-filled diode in a highly inhomogeneous electric field. It is shown that early in the breakdown a runaway electron beam (RAEB) is formed in the diode and this strongly affects the rate of breakdown development. The energy gained by RAEB electrons corresponds to the electron energy gained under the same conditions in vacuum. The properties of the emission surface of the cathode determine the instant at which the beam is formed during subnanosecond voltage pulse rise time and hence the beam current and the energy spectrum of runaway electrons.

Shklyaev, V. A.; Ryzhov, V. V. [Institute of High Current Electronics SD RAS, 2/3 Akademichesky Avenue, 634055 Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30 Lenin Avenue, 634050 Tomsk (Russian Federation); Belomyttsev, S. Ya. [Institute of High Current Electronics SD RAS, 2/3 Akademichesky Avenue, 634055 Tomsk (Russian Federation)

2012-12-01

371

Effect of COOH-functionalized SWCNT addition on the electrical and photovoltaic characteristics of Malachite Green dye based photovoltaic cells  

NASA Astrophysics Data System (ADS)

We report the effect of COOH-functionalized single walled carbon nanotubes (COOH-SWCNT) on the electrical and photovoltaic characteristics of Malachite Green (MG) dye based photovoltaic cells. Two different types of photovoltaic cells were prepared, one with MG dye and another by incorporating COOH-SWCNT with this dye. Cells were characterized through different electrical and photovoltaic measurements including photocurrent measurements with pulsed radiation. From the dark current—voltage (I–V) characteristic results, we observed a certain transition voltage (Vth) for both the cells beyond which the conduction mechanism of the cells change sharply. For the MG dye, Vth is 3.9 V whereas for COOH-SWCNT mixed with this dye, Vth drops to 2.7 V. The device performance improves due to the incorporation of COOH-SWCNT. The open circuit voltage and short circuit current density change from 4.2 to 97 mV and from 108 to 965 ?A/cm2 respectively. Observations from photocurrent measurements show that the rate of growth and decay of the photocurrent are quite faster in the presence of COOH-SWCNT. This observation indicates a faster charge separation processes due to the incorporation of COOH-SWCNT in the MG dye cells. The high aspect ratio of COOH-SWCNT allows efficient conduction pathways for the generated charge carriers.

Chakraborty, S.; Manik, N. B.

2014-12-01

372

Rainfall yield characteristics of electrical storm observed in the Spanish Basque Country area during the period 1992 1996  

NASA Astrophysics Data System (ADS)

This paper is focused on the study of rainfall yield characteristics of electrical storms observed over the Northern Iberian Peninsula during 1992-1996. To this aim Principal Components Analysis (PCA) and Self-Organizing Maps (SOM) method have been used. The SOM method is a group of artificial neural networks based on the topological properties of the human brain. Results clearly suggest that there exist three different meteorological patterns that are linked to the characteristics of electrical events found in the study area. In winter, most of the electrical events are formed under oceanic advection (NW air fluxes). On these cases, mean rainfall yield estimates reach values of 700 10 4 m 3 per cloud to ground lightning flash (CG flash). During summer most frequent electrical storms are associated to local instability shooting by surface heating with advection of humidity coming from the Iberian Peninsula. Under these meteorological situations, rain is scarcer if compared with oceanic events but lightning CG counts reach the maximum values found in the area (about 10 CG counts per 20 × 20 km 2 and day) giving this way the smallest rainfall yield with a mean value of 15 10 4 m 3 per CG flash. Iberian air fluxes associated with cold air in upper parts of the atmosphere represent the third meteorological pattern found. This pattern is most common in spring and autumn but is not unusual in the rest of the seasons. In those cases mean rainfall yield in the area is about 150 10 4 m 3 per CG flash. In all electrical episodes K instability index is greater than 15 °C but in the most lightning producing events, this index reaches in the area values greater than 24 °C. PCA results pointed out that there exists a relationship between rain and CG counts expressed by the first principal component computed from standardized data. However, we must notice that no event is solely linked to this axis, since a seasonal influence which decreases lightning production when rain increases is always present. Results found are of great interest for short term forecasting of flashfloods in mountainous areas like the Spanish Basque Country region.

Ezcurra, A.; Saenz, J.; Ibarra-Berastegi, G.; Areitio, J.

2008-08-01

373

A Griffith type energy release rate model for dielectric breakdown under space charge limited conductivity  

NASA Astrophysics Data System (ADS)

An energy release rate based "fracture" model is presented, which is able to describe unstable dielectric breakdown of ceramic and polymer insulators. The electric field and electrostatic energy of an electrically conducting filament within a spheroidal surface electrode is calculated. As space charge injection is allowed the electric field singularity at the electrical conducting filament is reduced. As a consequence it is possible to solve the electrostatic problem even for filaments where the diameter is reduced to zero and the energy release rate can be formulated only as a function of the filament length. The presented energy release rate together with the formulation of a dielectric breakdown criterion allows understanding the experimentally measured one over square root sample thickness dependence and the pronounced scatter of the measured dielectric breakdown strength.

Schneider, Gerold A.

2013-01-01

374

Temperature dependent electrical characteristics of Sn/p-Si Schottky diodes  

NASA Astrophysics Data System (ADS)

Current-voltage and capacitance-voltage characteristics of Sn/p-Si Schottky diodes measured in the temperature range 80-320 K are presented and analysed. Anomalous strong temperature dependencies of the ideality factor and apparent barrier height were obtained. There was also a considerable difference between the apparent barrier heights obtained from current-voltage and capacitance-voltage characteristics. These anomalies are explained by the domination of the current by a high level of thermionic-field emission, and by the presence of deep levels near the Sn/Si interface, which yield a reduction of free hole concentration and a significant temperature dependence of the charge stored near the metal-semiconductor (MS) interface. The evaluation of temperature dependence of forward current for thermionic-field emission resulted in the following parameters: characteristic energy E00 = 9.8 meV, Schottky barrier height at zero bias ?b0 = 0.802 eV, bias coefficient of barrier height ? = 0, and effective Richardson constant A* = 37.32 A cm -2 K -2.

Ayyildiz, Enise; Cetin, Hidayet; Horváth, Zs. J.

2005-11-01

375

I-131's Rapid Breakdown  

Cancer.gov

The "active" in "radioactive" means that unstable substances produced in nuclear reactions break down and change, so that they eventually become stable and no longer release radiation. The rate of breakdown can occur quickly in some radioactive substances, often within a few days. Half of the I-131 released during each atomic bomb test was gone in about 8 days. Almost all of it was gone (less than 1 percent remained) 80 days after the test.

376

Characteristics of a magnetohydrodynamic electrical power generator using convexly divergent channel  

NASA Astrophysics Data System (ADS)

We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The slight enhancement in a MHD channel divergence upstream provides boundary layer relief in a MHD flow decelerated by a retarding Lorentz force. Despite the present approach being simple and requiring a relatively minor modification of the MHD channel profile, the quality of MHD power-generating plasma and the energy conversion efficiency are improved compared to those from a previous linearly divergent channel; an excessive increase in static pressure is suppressed and a Hall field is enhanced, whereby notably high isentropic efficiency is achieved.

Murakami, Tomoyuki; Okuno, Yoshihiro

2010-03-01

377

Electrical and structural characteristics of non-stoichiometric Cu-based delafossites  

Microsoft Academic Search

Non-stoichiometric CuxGaO2 polycrystalline ceramics were prepared using solid-state synthesis methods and their structural and electrical properties were characterized as a function of x. While single phase delafossite could only be confirmed for the stoichiometric composition, X-ray diffraction results show that the a and c lattice parameters were stable from Cu0.98GaO2 to Cu1.02GaO2. Below x = 0.97, the structure underwent a

Nathan A. Ashmore; David P. Cann

2005-01-01

378

Effect of Water Adsorption on Electrical Characteristics of Porous Silica Films  

NASA Astrophysics Data System (ADS)

The effects of water adsorption on the dielectric constant and leakage current of porous silica thin films were investigated. The films were prepared by the sol-gel method and their pore surfaces became hydrophobic with 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) or hexamethyldisilazane (HMDS) vapor phase treatment. Permittivity and leakage current were measured within the relative humidity condition range from 3 to 50%. The dielectric constant increased with increasing relative humidity, and water adsorption properties were calculated from the dielectric constant. Then, the number densities of water adsorption sites were nearly the same in the two films. Leakage current began to increase at a relative humidity of 8%. The slope of leakage current relative to electric field was described well by the Pool-Frenkel leakage current model above an electric field strength of 0.3 MV/cm. To consider the effect of water adsorption on the leakage current model, we used the Pool-Frenkel current equation for ionic conduction. This model revealed that the ionization energy of proton emission from the silanol group decreased with increasing relative humidity; thus, leakage current increased with increasing relative humidity.

Kayaba, Yasuhisa; Kohmura, Kazuo; Kikkawa, Takamaro

2008-11-01

379

Structural, electrical, and mechanical characteristics of proton beam irradiated Al5086 alloy  

NASA Astrophysics Data System (ADS)

Al5086 alloy specimens were irradiated in a vacuum ~10-6 mbar with 2 MeV proton beam (200 nA) for different exposure times in the range 10-50 min (dose range: 0.35×1015-1.75×1015 p/cm2). Surface hardness was found to increases on irradiation for 10 min, and later on it decreases with the increase in exposure time. The electrical resistivity of the specimens measured by four-point probe technique was also found to follow the same pattern. The observed behavior has been explained in terms of relative contribution of two processes, namely defects formation and heat generation due to proton-material interaction. Structural characterization of the specimens was done by X-ray diffraction technique. Both surface hardness as well as electrical resistivity of un-irradiated and irradiated specimens is found to decrease with the increase in X-ray crystallite size. Moreover, the surface hardness follows the Hall-Petch relation, which indicates that crystallite boundaries progressively impede the motion of dislocations as the crystallite size gets smaller.

Butt, M. Z.; Ali, Dilawar; Farooq, Hussain; Bashir, Farooq

2015-01-01

380

Breakdown phenomenon identification of biodegradable polyethylene film under UV-irradiation environment  

Microsoft Academic Search

Biodegradable polymers are increasingly expected for substitute of present insulating materials in the electrical and electronic devices. However, their electrical properties are not systematically confirmed and need further investigation. In this paper, biodegradable polyethylene (BDPE) films are employed as the specimens and high density polyethylene (HDPE) films are as the reference. The breakdown endurance of BDPE film is examined using

B. X. Du; Yong Liu; Y. S. Xia; B. C. Liu

2008-01-01

381

Localization of RF Breakdowns in a Standing Wave Cavity  

SciTech Connect

At SLAC, a 5-cell, normal-conducting, L-band (1.3 GHz), standing-wave (SW) cavity was built as a prototype positron capture accelerator for the ILC. The structure met the ILC gradient goal but required extensive rf processing. When rf breakdowns occurred, a large variation was observed in the decay rate of the stored energy in the cavity after the input power was shut off. It appeared that the breakdowns were isolating sections of the cavity, and that the trapped energy in those sections was then partitioned among its natural modes, producing a distinct beating pattern during the decay. To explore this phenomenon further, an equivalent circuit model of cavity was created that reproduces well its normal operating characteristics. The model was then used to compute the spectra of trapped energy for different numbers of isolated cells. The resulting modal patterns agree well with those of the breakdown data, and thus such a comparison appears to provide a means of identifying the irises on which the breakdowns occurred.

Wang, Faya; Adolphsen, Chris; /SLAC

2009-08-03

382

Electrical characteristics of metal catalyst-assisted etched rough silicon nanowire depending on the diameter size.  

PubMed

The dependence of electrical properties of rough and cylindrical Si nanowires (NWs) synthesized by diameter-controllable metal catalyst-assisted etching (MCE) on the size of the NW's diameter was demonstrated. Using a decal-printing and transfer process assisted by Al2O3 sacrificial layer, the Si NW field effect transistor (FET) embedded in a polyvinylphenol adhesive and dielectric layer were fabricated. As the diameter of Si NW increased, the mobility of FET increased from 80.51 to 170.95 cm(2)/V·s and the threshold voltage moved from -7.17 to 0 V because phonon-electron wave function overlaps, surface scattering, and defect scattering decreased and gate coupling increased as the ratio of surface-to-volume got reduced. PMID:25526518

Lee, Sang Hoon; Lee, Tae Il; Lee, Su Jeong; Lee, Sang Myung; Yun, Ilgu; Myoung, Jae Min

2015-01-14

383

Change of electrical characteristics of radio-frequency cables under thermal effect  

NASA Astrophysics Data System (ADS)

Four basic temperature dependent electrical parameters of r-f cables are described by expressions which facilitate an analysis of their sensitivity to temperature effects, these parameters being capacitance, wave impedance, attenuation factor and phase shift factor. Calculations for coaxial cables are based on an equivalent dielectric permittivity of the insulation system, including air gap between dielectric and outer conductor produced in the manufacturing process as well as the air gap between dielectric and inner conductor produced by variation of the radius of the latter. Mechanical strains affecting the system geometry are found from the solution to Lame's problem for thin walled cylinders and Hooke's law extended to a three dimensional state of stress. For illustration, numerical results are given for RK-3-28-Pr high precision cables with monolithic Teflon-4D insulation (dielectric constant epsilon = 2.03 at 20 C).

Lobanov, A. V.; Pavlov, P. P.; Khrenkov, N. N.

1985-01-01

384

Effect of annealing atmosphere on phase formation and electrical characteristics of bismuth ferrite thin films  

SciTech Connect

Bismuth ferrite thin films were deposited on Pt/Ti/SiO{sub 2}/Si substrates by a soft chemical method and spin-coating technique. The effect of annealing atmosphere (air, N{sub 2} and O{sub 2}) on the structure and electrical properties of the films are reported. X-ray diffraction analysis reveals that the film annealed in air atmosphere is a single-phase perovskite structure. The films annealed in air showed better crystallinity and the presence of a single BFO phase leading to lower leakage current density and superior ferroelectric hysteresis loops at room temperature. In this way, we reveal that BFO film crystallized in air atmosphere by the soft chemical method can be useful for practical applications, including nonvolatile digital memories, spintronics and data-storage media.

Simoes, A.Z., E-mail: alezipo@yahoo.com [Universidade Federal de Itajuba, UNIFEI - CAMPUS ITABIRA, Rua Sao Paulo, 377, Bairro Amazonas, CEP: 35900-373 Itabira, MG (Brazil); Riccardi, C.S.; Dos Santos, M.L. [Laboratorio Interdisciplinar em Ceramica, Departamento de Fisico-Quimica, Instituto de Quimica Universidade Estadual Paulista, Bairro: Quitandinha, CEP: 14800-900 Araraquara, SP (Brazil); Garcia, F. Gonzalez [Universidade Federal de Itajuba, UNIFEI - CAMPUS ITABIRA, Rua Sao Paulo, 377, Bairro Amazonas, CEP: 35900-373 Itabira, MG (Brazil); Longo, E.; Varela, J.A. [Laboratorio Interdisciplinar em Ceramica, Departamento de Fisico-Quimica, Instituto de Quimica Universidade Estadual Paulista, Bairro: Quitandinha, CEP: 14800-900 Araraquara, SP (Brazil)

2009-08-05

385

Research on the electrical characteristics of the Pt/CdS Schottky diode  

NASA Astrophysics Data System (ADS)

With the development of technology, the demand for semiconductor ultraviolet detector is increasing day by day. Compared with the traditional infrared detector in missile guidance, ultraviolet/infrared dual-color detection can significantly improve the anti-interference ability of the missile. According to the need of missile guidance and other areas of the application of ultraviolet detector, the paper introduces a manufacture of the CdS Schottky barrier ultraviolet detector. By using the radio frequency magnetron sputtering technology, a Pt thin film layer is sputtered on CdS basement to form a Schottky contact firstly. Then the indium ohmic contact electrode is fabricated by thermal evaporation method, and eventually a Pt/CdS/In Schottky diode is formed. The I-V characteristic of the device was tested at room temperature, its zero bias current and open circuit voltage is -0.578nA and 130mV, respectively. Test results show that the the Schottky contact has been formed between Pt and CdS. The device has good rectifying characteristics. According to the thermionic emission theory, the I-V curve fitting analysis of the device was studied under the condition of small voltage. The ideality factor and Schottky barrier height is 1.89 and 0.61eV, respectively. The normalized spectral responsivity at zero bias has been tested. The device has peak responsivity at 500nm, and it cutoff at 510nm.

Ding, Jia-xin; Zhang, Xiang-feng; Yao, Guansheng

2013-08-01

386

Modification of Graphene/SiO2 Interface by UV-Irradiation: Effect on Electrical Characteristics.  

PubMed

Graphene is a promising material for next-generation electronic devices. The effect of UV-irradiation on the graphene devices, however, has not been fully explored yet. Here we investigate the UV-induced change of the field effect transistor (FET) characteristics of graphene/SiO2. UV-irradiation in a vacuum gives rise to the decrease in carrier mobility and a hysteresis in the transfer characteristics. Annealing at 160 °C in a vacuum eliminates the hysteresis, recovers the mobility partially, and moves the charge neutrality point to the negative direction. Corresponding Raman spectra indicated that UV-irradiation induced D band relating with defects and the annealing at 160 °C in a vacuum removed the D band. We propose a phenomenological model for the UV-irradiated graphene, in which photochemical reaction produces dangling bonds and the weak sp(3)-like bonds at the graphene/SiO2 interface, and the annealing restores the intrinsic graphene/SiO2 interface by removal of such bonds. Our results shed light to the nature of defect formation by UV-light, which is important for the practical performance of graphene based electronics. PMID:25569142

Imamura, Gaku; Saiki, Koichiro

2015-02-01

387

Investigation of Polarimetric and Electrical Characteristics of Natural and Triggered Lightning Strikes  

NASA Astrophysics Data System (ADS)

For the past three summers, the University of Oklahoma has deployed three mobile, polarimetric radars to the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida and Langmuir Laboratory near Socorro, New Mexico for the purpose of investigating the relationship between cloud structure and the propagation of triggered and natural lightning channels. This presentation will highlight observations from select natural and triggered events at these two facilities. During the summer of 2012, University of Oklahoma radar operators made a launch recommendation to the ICLRT during the passage of Tropical Storm Debby over northeast Florida that resulted in a successful triggered flash with 11 return strokes. The trigger was attempted as precipitation streamers within the stratiform rainbands of Tropical Storm Debby approached the launch site. According to the National Lightning Detection Network (NLDN), there were no reported natural cloud-to-ground (CG) flashes within 60 km of the ICLRT 20 hours before and eight hours after the triggered flash. The recommendation was made based on previous analyses of the storm structure of trigger attempts from the ICLRT that indicated the coincidence of several successful triggers with descending regions of enhanced radar reflectivity, or descending precipitation packets (DePPs). Polarimetric data from the frequency-agile Rapid-scanning X-band Polarimetric (RaXPol) radar as well as data from the lightning mapping array (LMA) and electric field meter (EFM) networks from the ICLRT for this event will be presented. Past analyses also revealed ice alignment signatures in differential phase and specific differential phase as strong electric fields near the top of electrified clouds cause small ice particles to become vertically aligned. These signatures are especially noticeable for circularly polarized radars. Polarimetric data from the Shared Mobile Atmospheric Research & Teaching (SMART) radar and RaXPol will illustrate these effects from studies at the ICLRT, while radar data from the Polarimetric X-band (PX-1000) radar (circularly polarized) will illustrate these effects from studies at Langmuir Laboratory.

Hyland, P. T.; Biggerstaff, M. I.; Uman, M. A.; Jordan, D. M.; Hill, J. D.; Pilkey, J. T.; Ngin, T.; Blakeslee, R. J.; Krehbiel, P. R.; Rison, W.; Winn, W. P.; Eack, K.; Trueblood, J.; Edens, H. E.

2013-12-01

388

Characteristics of Retinal Reflectance Changes Induced by Transcorneal Electrical Stimulation in Cat Eyes  

PubMed Central

Transcorneal electrical stimulation (TES) activates retinal neurons leading to visual sensations. How the retinal cells are activated by TES has not been definitively determined. Investigating the reflectance changes of the retina is an established technique and has been used to determine the mechanism of retinal activation. The purpose of this study was to evaluate the reflectance changes elicited by TES in cat eyes. Eight eyes of Eight cats were studied under general anesthesia. Biphasic electrical pulses were delivered transcornealy. The fundus images observed with near-infrared light (800–880 nm) were recorded every 25 ms for 26 s. To improve the signal-to-noise ratio, the images of 10 consecutive recordings were averaged. Two-dimensional topographic maps of the reflective changes were constructed by subtracting images before from those after the TES. The effects of different stimulus parameters, e.g., current intensity, pulse duration, frequency, and stimulus duration, on the reflective changes were studied. Our results showed that after TES, the reflective changes appeared on the retinal vessels and optic disc. The intensity of reflectance changes increased as the current intensity, pulse duration, and stimulation duration increased (P<0.05 for all). The maximum intensity of the reflective change was obtained when the stimulus frequency was 20 Hz. The time course of the reflectance changes was also altered by the stimulation parameters. The response started earlier and returned to the baseline later with higher current intensities, longer pulse durations, but the time of the peak of the response was not changed. These results showed that the reflective changes were due to the activation of retinal neurons by TES and might involve the vascular changes induced by an activation of the retinal neurons. PMID:24651530

Morimoto, Takeshi; Kanda, Hiroyuki; Miyoshi, Tomomitsu; Hirohara, Yoko; Mihashi, Toshifumi; Kitaguchi, Yoshiyuki; Nishida, Kohji; Fujikado, Takashi

2014-01-01

389

Structural and electrical characteristics of nitrogen-doped nanocrystalline diamond films prepared by CVD  

NASA Astrophysics Data System (ADS)

Nitrogen-doped nanocrystalline diamond (N-NCD) films were grown using microwave plasma enhanced chemical vapour deposition method. Films were characterized by Raman spectroscopy, x-ray diffraction and scanning electron microscopy. Perfectly ohmic contacts for the N-doped NCD film and p-type Si substrate were obtained using silver (Ag). Silver deposited at a temperature of 250 °C with the pulsed laser deposition method was found to show ohmic behaviour with a high degree of reproducibility. Current-voltage (I-V) characteristics are presented for various Ag/N-NCD and Ag-Si. Rectifying I-V behaviour for the interface N-NCD/p-Si suggests that the majority carriers for N-NCD are electrons.

Hu, Qiang; Hirai, Makoto; Joshi, Rakesh K.; Kumar, Ashok

2009-01-01

390

Bonding, vibrational, and electrical characteristics of CdS nanostructures embedded in polyvinyl alcohol matrix  

SciTech Connect

CdS nanocomposites have been grown in polyvinyl alcohol matrix by a chemical synthesis process. The transmission electron micrographs of nanocomposites synthesized at 70-90 deg. C temperature showed the growth of needlelike and junctionlike nanostructures. X-ray photoelectron spectroscopy analysis revealed the growth of stoichiometric CdS without the formation of any intermediate phases at the CdS-polyvinyl alcohol interface. Raman spectra of first order longitudinal optical phonon peak has been analyzed using phonon dispersion model to detect the surface phonon modes in CdS nanoneedles and wires. The origin of negative differential resistance behavior in current-voltage characteristics for junctionlike CdS nanocomposites has been discussed.

Mondal, S. P.; Dhar, A.; Ray, S. K. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur-721 302 (India); Chakraborty, A. K. [Laboratory for Mechanical Systems Engineering EMPA, Duebendorf, Zurich, CH-8600 (Switzerland)

2009-04-15

391

Room temperature-synthesized vertically aligned InSb nanowires: electrical transport and field emission characteristics.  

PubMed

Vertically aligned single-crystal InSb nanowires were synthesized via the electrochemical method at room temperature. The characteristics of Fourier transform infrared spectrum revealed that in the syntheses of InSb nanowires, energy bandgap shifts towards the short wavelength with the occurrence of an electron accumulation layer. The current-voltage curve, based on the metal-semiconductor-metal model, showed a high electron carrier concentration of 2.0?×?1017?cm-3 and a high electron mobility of 446.42?cm2?V-1?s-1. Additionally, the high carrier concentration of the InSb semiconductor with the surface accumulation layer induced a downward band bending effect that reduces the electron tunneling barrier. Consequently, the InSb nanowires exhibit significant field emission properties with an extremely low turn-on field of 1.84?V??m-1 and an estimative threshold field of 3.36?V??m-1. PMID:23399075

Kuo, Cheng-Hsiang; Wu, Jyh-Ming; Lin, Su-Jien

2013-01-01

392

Effects of ?-irradiation on optical, electrical, and laser characteristics of pure and transition metal doped II-VI semiconductors  

NASA Astrophysics Data System (ADS)

We report a comprehensive study of gamma-irradiation on optical, electrical, and laser characteristics of pure and transition-metal doped single and polycrystalline ZnS and ZnSe. Polished pure, Cr-doped, and Ag, Au, Cu, Al, In, and Mn co-doped ZnS and ZnSe crystals after absorption and electro-conductivity characterization were gamma-irradiated at doses of 1.37x108, and 1.28x108 rad at +10 and -3°C, respectively. Dynamic RT absorption studies, electro-conductivity measurements and mid-IR lasing were performed for different exposition times of crystals at RT. Cr:ZnSe and Cr:ZnS lasers based on identical gamma-irradiated and non-irradiated crystals featured a very similar pump thresholds, slope efficiencies, and output powers.

Konak, Tetyana; Tekavec, Michael; Fedorov, Vladimir V.; Mirov, Sergey B.

2011-02-01

393

Temperature dependence of electrical characteristics of Pt/GaN Schottky diode fabricated by UHV e-beam evaporation.  

PubMed

Temperature-dependent electrical characterization of Pt/n-GaN Schottky barrier diodes prepared by ultra high vacuum evaporation has been done. Analysis has been made to determine the origin of the anomalous temperature dependence of the Schottky barrier height, the ideality factor, and the Richardson constant calculated from the I-V-T characteristics. Variable-temperature Hall effect measurements have been carried out to understand charge transport at low temperature. The modified activation energy plot from the barrier inhomogeneity model has given the value of 32.2 A/(cm2 K2) for the Richardson constant A** in the temperature range 200 to 380 K which is close to the known value of 26.4A/(cm2 K2) for n-type GaN. PMID:24229424

Kumar, Ashish; Arafin, Shamsul; Amann, Markus Christian; Singh, Rajendra

2013-01-01

394

Temperature dependence of electrical characteristics of Pt/GaN Schottky diode fabricated by UHV e-beam evaporation  

NASA Astrophysics Data System (ADS)

Temperature-dependent electrical characterization of Pt/n-GaN Schottky barrier diodes prepared by ultra high vacuum evaporation has been done. Analysis has been made to determine the origin of the anomalous temperature dependence of the Schottky barrier height, the ideality factor, and the Richardson constant calculated from the I-V-T characteristics. Variable-temperature Hall effect measurements have been carried out to understand charge transport at low temperature. The modified activation energy plot from the barrier inhomogeneity model has given the value of 32.2 A/(cm2 K2) for the Richardson constant A** in the temperature range 200 to 380 K which is close to the known value of 26.4A/(cm2 K2) for n-type GaN. PACS: 73.30. + y; 73.40.-c; 79.40. + z; 85.30.Hi

Kumar, Ashish; Arafin, Shamsul; Amann, Markus Christian; Singh, Rajendra

2013-11-01

395

Temperature dependence of electrical characteristics of Pt/GaN Schottky diode fabricated by UHV e-beam evaporation  

PubMed Central

Temperature-dependent electrical characterization of Pt/n-GaN Schottky barrier diodes prepared by ultra high vacuum evaporation has been done. Analysis has been made to determine the origin of the anomalous temperature dependence of the Schottky barrier height, the ideality factor, and the Richardson constant calculated from the I-V-T characteristics. Variable-temperature Hall effect measurements have been carried out to understand charge transport at low temperature. The modified activation energy plot from the barrier inhomogeneity model has given the value of 32.2 A/(cm2 K2) for the Richardson constant A** in the temperature range 200 to 380 K which is close to the known value of 26.4A/(cm2 K2) for n-type GaN. PMID:24229424

2013-01-01

396

IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. III. BREAKDOWN CONDITIONS FOR MINERAL CLOUDS  

SciTech Connect

Electric discharges were detected directly in the cloudy atmospheres of Earth, Jupiter, and Saturn, are debatable for Venus, and indirectly inferred for Neptune and Uranus in our solar system. Sprites (and other types of transient luminous events) have been detected only on Earth, and are theoretically predicted for Jupiter, Saturn, and Venus. Cloud formation is a common phenomenon in ultra-cool atmospheres such as in brown dwarf and extrasolar planetary atmospheres. Cloud particles can be expected to carry considerable charges which may trigger discharge events via small-scale processes between individual cloud particles (intra-cloud discharges) or large-scale processes between clouds (inter-cloud discharges). We investigate electrostatic breakdown characteristics, like critical field strengths and critical charge densities per surface, to demonstrate under which conditions mineral clouds undergo electric discharge events which may trigger or be responsible for sporadic X-ray emission. We apply results from our kinetic dust cloud formation model that is part of the DRIFT-PHOENIX model atmosphere simulations. We present a first investigation of the dependence of the breakdown conditions in brown dwarf and giant gas exoplanets on the local gas-phase chemistry, the effective temperature, and primordial gas-phase metallicity. Our results suggest that different intra-cloud discharge processes dominate at different heights inside mineral clouds: local coronal (point discharges) and small-scale sparks at the bottom region of the cloud where the gas density is high, and flow discharges and large-scale sparks near, and maybe above, the cloud top. The comparison of the thermal degree of ionization and the number density of cloud particles allows us to suggest the efficiency with which discharges will occur in planetary atmospheres.

Helling, Ch.; Jardine, M.; Stark, C. [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Diver, D., E-mail: ch@leap2010.eu [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

2013-04-20

397

Numerical Investigations on Electric Field Characteristics with Respect to Capacitive Detection of Free-Flying Droplets  

PubMed Central

In this paper a multi-disciplinary simulation of a capacitive droplet sensor based on an open plate capacitor as transducing element is presented. The numerical simulations are based on the finite volume method (FVM), including calculations of an electric field which changes according to the presence of a liquid droplet. The volume of fluid (VOF) method is applied for the simulation of the ejection process of a liquid droplet out of a dispenser nozzle. The simulations were realised using the computational fluid dynamic (CFD) software CFD ACE+. The investigated capacitive sensing principle enables to determine the volume of a micro droplet passing the sensor capacitor due to the induced change in capacity. It could be found that single droplets in the considered volume range of 5 nL < Vdrop < 100 nL lead to a linear change of the capacity up to ?Q < 30 fC. The sensitivity of the focused capacitor geometry was evaluated to be Si = 0.3 fC/nL. The simulation results are validated by experiments which exhibit good agreement. PMID:23112615

Ernst, Andreas; Mutschler, Klaus; Tanguy, Laurent; Paust, Nils; Zengerle, Roland; Koltay, Peter

2012-01-01

398

Oxidation temperature dependence of the dc electrical conduction characteristics and dielectric strength of thin Ta2O5 films on silicon  

SciTech Connect

Tantalum pentoxide thin films (60--80 nm thick) on silicon were prepared by thermal oxidation at 430--675 C of electron-beam evaporated Ta. The tantalum layers had been deposited by electron-beam evaporation onto the Si substrates held at room temperature (RT) or heated to 150 C during Ta evaporation. The dc conduction properties and the dielectic strength of the Ta2O5 films were studied employing Al/Ta2O5/Si capacitors. The smallest conductivity was found for Ta2O5 films formed from Ta deposited onto Si held at RT during evaporation and oxidized at 490 C for 1 h in dry O2. This minimum conductivity corresponds to a leakage current of 1 x 10 X A/cmS at an applied field of 1 MV/cm (Al negative on p-type Si substrates). The dc conduction characteristics can be interpreted by assuming Poole--Frenkel conduction. For Ta2O5 formed from Ta which had been deposited onto Si substrates held at 150 C during evaporation, the conductivity is smallest for a film which had been oxidized at 430 C for 1 h (lowest oxidation temperature investigated). Ta2O5 films formed from Ta deposited onto Si substrates at RT exhibit lower conductivity than Ta2O5 films formed from Ta deposited onto heated (150 C) Si substrates for a given oxidation temperature. The presence of water in the oxidizing ambient was found to greatly deteriorate the leakage characteristics of the Ta2O5 films. The dielectric strength of the Ta2O5 film for which the lowest conductivity was observed (oxidized at 490 C) ranged from 2 to 4.5 MV/cm. A maximum in the breakdown distribution was found for a breakdown strength of 3--3.5 MV/cm.

Oehrlein, G.S.

1986-03-01

399

On a criterion for vortex breakdown  

NASA Technical Reports Server (NTRS)

A criterion for the onset of vortex breakdown is proposed. Based upon previous experimental, computational, and theoretical studies, an appropriately defined local Rossby number is used to delineate the region where breakdown occurs. In addition, new numerical results are presented which further validate this criterion. A number of previous theoretical studies concentrating on inviscid standing-wave analyses for trailing wing-tip vortices are reviewed and reinterpreted in terms of the Rossby number criterion. Consistent with previous studies, the physical basis for the onset of breakdown is identified as the ability of the flow to sustain such waves. Previous computational results are reviewed and re-evaluated in terms of the proposed breakdown criterion. As a result, the cause of breakdown occurring near the inflow computational boundary, common to several numerical studies, is identified. Finally, previous experimental studies of vortex breakdown for both leading edge and trailing wing-tip vortices are reviewed and quantified in terms of the Rossby number criterion.

Spall, R. E.; Gatski, T. B.; Grosch, C. H.

1987-01-01

400

Breakdown  

ERIC Educational Resources Information Center

The multiplicity of ills facing the nation's public schools can depress even the most optimistic. In this article, the author presents her views about the school system and the negative effects that labor agreements have had on it. Her views on how to solve some seemingly intractable education problems have been informed by two experiences: her…

Moskowitz, Eva

2006-01-01

401

The effects of ion gun beam voltage on the electrical characteristics of NbCN/PbBi edge junctions  

NASA Technical Reports Server (NTRS)

The authors have succeeded in fabricating high-quality submicron NbCN edge junctions using a technique which is commonly used to make Nb edge junctions. A modified commercial ion gun was used to cut an edge in SiO2/NbCN films partially covered with photoresist. An insulating barrier was then formed on the exposed edge by reactive ion beam oxidation, and a counterelectrode of PbBi was deposited. The electrical quality of the resulting junctions was found to be strongly influenced by the ion beam acceleration voltages used to cut the edge and to oxidize it. For low ion beam voltages, the junction quality parameter was as high as Vm = 55 mV (measured at 3 mV), but higher ion beam voltages yielded strikingly poorer quality junctions. In light of the small coherence length of NbN, the dependence of the electrical characteristics on ion beam voltage is presumably due to mechanical damage of the NbCN surface. In contrast, for similar ion beam voltages, no such dependence was found for Nb edge junctions.

Lichtenberger, A. W.; Feldman, M. J.; Mattauch, R. J.; Cukauskas, E. J.

1989-01-01

402

Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics  

NASA Astrophysics Data System (ADS)

Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates [1-3]. Various approaches including optimizing morphology of the active layers [1,2], introducing new materials as the donor and acceptor [3,4], new device structures such as tandem structure [5,6] have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer [5,7].

Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

2013-03-01

403

Study of the effect of the charge transport layer in the electrical characteristics of the organic photovoltaics  

NASA Astrophysics Data System (ADS)

Significant progress in fabrication and optimization of organic photovoltaics (OPVs) has been made during the last decade. The main reason for popularity of OPVs is due to their low production cost, large area devices and compatibility with flexible substrates 1-3. Various approaches including optimizing morphology of the active layers 1, 2, introducing new materials as the donor and acceptor 3,4, new device structures such as tandem structure 5, 6 have been adapted to improve the efficiency of the organic photovoltaics. However, electrical characteristics of the OPVs do not only depend on the active layer materials or device structure. They can also be defined by the interface properties between active layers and the charge transport layers or the metal contacts. Within this paper, the effect of the thickness variation of the charge transport layer in the electrical properties of the bilayer heterojunction OPVs has been studied. Several devices with CuPc/PTCDI-C8 as the donor/acceptor layers have been fabricated with different thicknesses of electron transport layer. MoO3 and Alq3 have been used respectively as the hole transport layer (HTL) and the electron transport layer (ETL). It has been shown that the S-shape effect in the current-voltage curve is attributed to the accumulation of the charge carriers at the interface between the active layer and the charge transport layer 5, 7.

Rahimi, Ronak; Roberts, Alex; Narang, V.; Kumbham, Vamsi Krishna; Korakakis, D.

2013-09-01

404

Modified electrical characteristics of Pt/n-type Ge Schottky diode with a pyronine-B interlayer  

NASA Astrophysics Data System (ADS)

The electrical characteristics of a Pt/n-type Ge Schottky diode with a pyronine-B (PYR-B) interlayer prepared by spin coating was investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. It was observed that the barrier height of Pt/PYR-B/n-type Ge (0.65 eV) was higher than that of the conventional Pt/n-type Ge Schottky diode (0.58 eV). This is attributed to the fact that the organic interlayer increases the effective barrier height by influencing the space-charge region of Ge. The introduction of the PYR-B interlayer led to a reduction of the interface state density in the Pt Schottky contact to n-type Ge. The electric field dependence of the reverse leakage current revealed that Schottky emission and Poole-Frenkel emission mechanisms dominated the reverse current in the Pt/n-type Ge and Pt/PYR-B/n-type Ge Schottky diodes, respectively.

Jyothi, I.; Janardhanam, V.; Rajagopal Reddy, V.; Choi, Chel-Jong

2014-11-01

405

Electrical Characteristics of A1/CNT/NiPc/PEPC/Ag Surface-Type Cell  

NASA Astrophysics Data System (ADS)

The blend of nickel phthalocyanine (NiPc) (2 wt. %) poly-N-epoxypropylcarbazole (PEPC), (1 wt. %) and carbon nano-tube (CNT) powder (2 wt. %) in benzole is deposited by drop-casting on glass substrates with pre-deposited metallic electrodes to fabricate Ag/CNT/NiPc/PEPC/A1 surface type cell. It is assumed that the high nonlinearity of the I — V characteristics is related to deep traps in the nano-scale depletion region in NiPc that is observed experimentally. The values of ideality factor and barrier height are determined from the I — V curve and they are found to be 8.4 and 1.05eV, respectively. The values of mobility and conductivity are calculated to be 7.94 × 10-8 cm/Vs and 3.5 × 10-6 ?-1 cm-1. The values of ideality factor and series resistance are also calculated by using Cheung's functions, which are in good agreement with the values calculated from the I — V curve.

Mutabar, Shah; Kh., S. Karimov; Zubair, Ahmad; H. Sayyad, M.

2010-10-01

406

Graphite/CdMnTe Schottky diodes and their electrical characteristics  

NASA Astrophysics Data System (ADS)

The first Schottky diodes based on n-CdMnTe crystals with pronounced rectifying properties are investigated. It is shown that the I-V characteristics of the diodes fabricated by printing colloidal graphite can be described by the Sah-Noyce-Shockley theory of generation-recombination in the space charge region. Exponential increase of forward current with voltage is limited by a relatively low barrier height at the graphite/CdMnTe contact (˜ 0.4 eV) and a significant series resistance of the crystal bulk (˜ 106 ? at room temperature). Tunneling due to high concentration of uncompensated impurities in investigated Cd0.9Mn0.1Te crystals (7 × 1017 cm-3) does not allow increasing the reverse bias voltage to the values needed for the operation of x- and ?-ray detectors. High concentration of uncompensated donors is interpreted by the fact that a certain part of the Mn atoms does not substitute for Cd but plays a role of over-stoichiometric impurities. In the case of the presence of a thin intermediate insulator layer in the graphite/CdMnTe contact, a rapid increase in the current for both polarities of high voltage due to the Frenkel-Poole emission is observed. The obtained results shed light on the problems of technology of growing and post-processing CdMnTe crystals regarded as a prospective material for x- and ?-ray detectors.

Kosyachenko, L. A.; Yatskiv, R.; Yurtsenyuk, N. S.; Maslyanchuk, O. L.; Grym, J.

2014-01-01

407

Pulsed breakdown of 4H-SiC Schottky diodes terminated with a boron-implanted p-n junction  

SciTech Connect

Pulsed reverse current-voltage characteristics have been measured in the breakdown region for 1-kV 4H-SiC Schottky diodes terminated with a boron-implanted p-n junction. It was shown that the dynamic breakdown voltage of the diodes increases as the pulses become shorter. Owing to the homogeneous avalanche formation at the edge of the guard p-n junction and to the high differential resistance in the breakdown region, the diodes sustain without degradation a pulsed reverse voltage substantially exceeding the static breakdown threshold. Characteristic features of the pulsed breakdown are considered in relation to the specific properties of the boron-implanted guard p-n junction.

Ivanov, P. A., E-mail: Pavel.Ivanov@mail.ioffe.ru; Grekhov, I. V.; Potapov, A. S.; Samsonova, T. P. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2008-07-15

408

High breakdown-strength composites from liquid silicone rubbers  

NASA Astrophysics Data System (ADS)

In this paper we investigate the performance of liquid silicone rubbers (LSRs) as dielectric elastomer transducers. Commonly used silicones in this application include room-temperature vulcanisable (RTV) silicone elastomers and composites thereof. Pure LSRs and their composites with commercially available fillers (an anatase TiO2, a core-shell TiO2-SiO2 and a CaCu3Ti4O12 filler) are evaluated with respect to dielectric permittivity, elasticity (Young’s modulus) and electrical breakdown strength. Film formation properties are also evaluated. The best-performing formulations are those with anatase TiO2 nanoparticles, where the highest relative dielectric permittivity of 5.6 is obtained, and with STX801, a core-shell morphology TiO2-SiO2 filler from Evonik, where the highest breakdown strength of 173 V ?m-1 is obtained.

Vudayagiri, Sindhu; Zakaria, Shamsul; Yu, Liyun; Sager Hassouneh, Suzan; Benslimane, Mohamed; Ladegaard Skov, Anne

2014-10-01

409

Optical measurements for interfacial conduction and breakdown (1980)  

NASA Astrophysics Data System (ADS)

Techniques were developed to measure the fields in transformer oil using Kerr effect and to measure the surface charge at a gas-solid interface using the Pockels effects. Measurements are supplemented by calculations of the distortion produced by selected interfacial charge distributions. The relatively pure transformer oil used showed little space charge distortion of the electric field. There also was no statistically significant preference for breakdown in the vicinity of the interface. At vacuum-solid interfaces, however, interfacial breakdown was observed and surface charging was measured. As gas is introduced into the system, the surface charge is removed so that no effect of surface charging was detected at atmospheric pressure. At pressures above atmospheric, there is evidence that surface charging may again become important.

Hebner, R. E.; Kelley, E. F.; Thompson, J. E.; Sudarshan, T. S.; Jones, T. B.

1981-05-01

410

Physical mechanism of progressive breakdown in gate oxides  

NASA Astrophysics Data System (ADS)

The definition of the basic physical mechanisms of the dielectric breakdown (BD) phenomenon is still an open area of research. In particular, in advanced complementary metal-oxide-semiconductor (CMOS) circuits, the BD of gate dielectrics occurs in the regime of relatively low voltage and very high electric field; this is of enormous technological importance, and thus widely investigated but still not well understood. Such BD is characterized by a gradual, progressive growth of the gate leakage through a localized BD spot. In this paper, we report for the first time experimental data and a model which provide understanding of the main physical mechanism responsible for the progressive BD growth. We demonstrate the ability to control the breakdown growth rate of a number of gate dielectrics and provide a physical model of the observed behavior, allowing to considerably improve the reliability margins of CMOS circuits by choosing a correct combination of voltage, thickness, and thermal conductivity of the gate dielectric.

Palumbo, Felix; Lombardo, Salvatore; Eizenberg, Moshe

2014-06-01

411

Dielectric breakdown of PDMS thin films  

NASA Astrophysics Data System (ADS)

This note presents the data on the dielectric breakdown of polydimethylsiloxane (PDMS) thin films with thicknesses from 2?to 14??m between the silicon electrodes. The results demonstrate that there is a strong dependence of the breakdown field on both the electrode gap and shape. The breakdown fields range from 250 to 635 V ?m-1, depending on the electrode geometry and gap, approaching 10× the breakdown fields for air gaps of the same size. The results are critical for understanding the performance limits of PDMS thin films used in the electromechanical microsystems.

Gerratt, Aaron P.; Bergbreiter, Sarah

2013-06-01

412

Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes  

NASA Astrophysics Data System (ADS)

In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0 cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

Li, Lee; Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan

2014-07-01

413

Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes  

SciTech Connect

In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0?cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

Li, Lee, E-mail: leeli@mail.hust.edu.cn; Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, School of Electric and Electronic Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074 (China)

2014-07-15

414

Work Breakdown Structure (WBS) Handbook  

NASA Technical Reports Server (NTRS)

The purpose of this document is to provide program/project teams necessary instruction and guidance in the best practices for Work Breakdown Structure (WBS) and WBS dictionary development and use for project implementation and management control. This handbook can be used for all types of NASA projects and work activities including research, development, construction, test and evaluation, and operations. The products of these work efforts may be hardware, software, data, or service elements (alone or in combination). The aim of this document is to assist project teams in the development of effective work breakdown structures that provide a framework of common reference for all project elements. The WBS and WBS dictionary are effective management processes for planning, organizing, and administering NASA programs and projects. The guidance contained in this document is applicable to both in-house, NASA-led effort and contracted effort. It assists management teams from both entities in fulfilling necessary responsibilities for successful accomplishment of project cost, schedule, and technical goals. Benefits resulting from the use of an effective WBS include, but are not limited to: providing a basis for assigned project responsibilities, providing a basis for project schedule development, simplifying a project by dividing the total work scope into manageable units, and providing a common reference for all project communication.

2010-01-01

415

Electrical characteristics of Au/Ti/n-GaAs contacts over a wide measurement temperature range  

NASA Astrophysics Data System (ADS)

We have fabricated Au/Ti/n-GaAs/In Schottky barrier diodes using the magnetron dc sputter technique. The capacitance-temperature (C-T) measurements with bias voltage as a parameter and the current-voltage (I-V) and capacitance-voltage (C-V) measurements have been made in the temperature range of 60-300 K. The temperature-dependent capacitance measurements have been made at 1.0 MHz. The capacitance versus temperature curve at each bias voltage has four regions with slopes different from each other. The capacitance decreases with a decrease in temperature at each bias voltage. Such a temperature-dependent behavior could be attributed to modulation of the space charge region caused by the emission of deep-level impurities or interface states. The carrier concentration calculated in the -1.0 to -2.0 V range of C-2-V plots was close to the value of 7.43 × 1015 cm-3 given by the manufacturer around room temperature. The ideality factor value from the I-V characteristics has remained almost unchanged between 1.07 and 1.10 in the temperature range of 150-300 K, indicating that the current across the device obeys the thermionic emission current model quite well over the whole bias range at temperatures above 150 K. Therefore, the conventional Richardson plot in this temperature range has given a Richardson constant of 8.21 A (cm K)-2, within experimental error, which is in very close agreement with the theoretical value of 8.16 A (cm K)-2 for n-type GaAs. Again, it has been seen that the ideality factor with the values of 1.10 at 150 K and 1.22 at 60 K does not show a considerable decrease. The experimental parameters show that the Au(90 nm)/Ti(10 nm)/n-GaAs contact is a good candidate for electronic device applications.

Biyikli, Necmi; Karabulut, Abdulkerim; Efeolu, Hasan; Guzeldir, Betul; Turut, Abdulmecit

2014-09-01

416

Design of external insulation for VLF/LF bands via breakdown investigation  

NASA Astrophysics Data System (ADS)

This document reports about the role of humidity and frequency upon the breakdown of air in uniform and non-uniform electric fields for the Very Low and Low Frequency (VLF/LF) Bands (10-100 kHz), used for long distance communication. Experiments were conducted using a parallel plane configuration for a gap length range of 5-52.5 mm and a frequency range of 18-52 kHz and 60 Hz. Rod/rod and rod/plane configurations were tested at 60 Hz and 30 kHz, for a gap length range of 8-1000 mm. The results indicate that the breakdown voltage at 30 kHz is affected by humidity with varying impact based on gap configuration and length. The results show that breakdown voltage at VLF/LF decreases with humidity for uniform field gaps, opposite to that observed at 60 Hz. Short (8-45 mm) non-uniform gaps show a reduction in the breakdown voltage with humidity, while no significant variation is observed for long gaps (125-1000 mm). Breakdown voltages are observed to be markedly lower for 30 kHz when compared to the same gap at 60 Hz. The observed breakdown phenomena are explained in terms of increased space charge due to the higher frequencies. Models and humidity correction to estimate breakdown voltages at VLF/LF frequencies for uniform and non-uniform configurations were developed. Electric field simulation, space charge calculation and least squares regression were used. The models are shown to be useful for predicting breakdown voltages at VLF/LF for uniform field gap spacings up to 125 mm and nonuniform field gap spacings up to 4 m.

Rodriguez Sanabria, Doeg

417

Simulation of vortex breakdown in tubes  

NASA Technical Reports Server (NTRS)

The breakdown of a vortex flow in a tube is studied for a slightly diverging tube by means of a numerical solution of the Navier-Stokes equations for a quasi-stationary, incompressible, laminar flow. Numerical results are compared to experiments of Faler and Leibovich. The numerical data display features similar to the experimental results concerning breakdown conditions, location, and structure.

Menne, Stefan

1988-01-01

418

Pattern formation and propagation during microwave breakdown  

SciTech Connect

During microwave breakdown at atmospheric pressure, a sharp plasma front forms and propagates toward the microwave source at high velocities. Experiments show that the plasma front may exhibit a complex dynamical structure or pattern composed of plasma filaments aligned with the wave electric field and apparently moving toward the source. In this paper, we present a model of the pattern formation and propagation under conditions close to recent experiments. Maxwell's equations are solved together with plasma fluid equations in two dimensions to describe the space and time evolution of the wave field and plasma density. The simulation results are in excellent agreement with the experimental observations. The model provides a physical interpretation of the pattern formation and dynamics in terms of ionization-diffusion and absorption-reflection mechanisms. The simulations allow a good qualitative and quantitative understanding of different features such as plasma front velocity, spacing between filaments, maximum plasma density in the filaments, and influence of the discharge parameters on the development of well-defined filamentary plasma arrays or more diffuse plasma fronts.

Chaudhury, Bhaskar [Laboratoire Plasma et Conversion d'Energie (LAPLACE), INPT, UPS, Universite de Toulouse, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); Boeuf, Jean-Pierre [Laboratoire Plasma et Conversion d'Energie (LAPLACE), INPT, UPS, Universite de Toulouse, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); LAPLACE, CNRS, F-31062 Toulouse (France); Zhu, Guo Qiang [Laboratoire Plasma et Conversion d'Energie (LAPLACE), INPT, UPS, Universite de Toulouse, 118 route de Narbonne, F-31062 Toulouse Cedex 9 (France); Northwestern Polytechnique University, Xi'an 710072 (China)

2010-12-15

419

X ray photoelectron analysis of oxide-semiconductor interface after breakdown in Al2O3/InGaAs stacks  

NASA Astrophysics Data System (ADS)

In this work, the post-breakdown characteristics of metal gate/Al2O3/InGaAs structures were studied using surface analysis by x ray photoelectron spectroscopy. The results show that for dielectric breakdown under positive bias, localized filaments consisting of oxidized substrate atoms (In, Ga and As) were formed, while following breakdown under negative bias, a decrease of oxidized substrate atoms was observed. Such differences in the microstructure at the oxide-semiconductor interface after breakdown for positive and negative voltages are explained by atomic diffusion of the contact atoms into the gate dielectric in the region of the breakdown spot by the current induced electro-migration effect. These findings show a major difference between Al2O3/InGaAs and SiO2/Si interfaces, opening the way to a better understanding of the breakdown characteristics of III-V complementary-metal-oxide-semiconductor technology.

Shekhter, P.; Palumbo, F.; Cohen Weinfeld, K.; Eizenberg, M.

2014-09-01

420

Characterization of terrestrial solar cells for space applications: Electrical characteristics of thin Westinghouse dendritic web cells as a function of solar intensity, temperature, and incidence angle  

NASA Technical Reports Server (NTRS)

Electrical characteristics of thin (100- and 140-micron) Westinghouse dendritic-web N/P silicon solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature. Performance is also shown as a function of solar illlumination angle of incidence for AMO.

Stella, P. M.; Anspaugh, B. E.

1985-01-01

421

Characterization of solar cells for space applications. Volume 14: Electrical characteristics of Hughes liquid phase epitaxy gallium arsenide solar cells as a function of intensity, temperature and irradiation  

NASA Technical Reports Server (NTRS)

Electrical characteristics of liquid phase epitaxy, P/N gallium aluminum arsenide solar cells are presented in graphical and tabular format as a function of solar illumination intensity and temperature. The solar cells were exposed to 1 MeV electron fluences of, respectively, 0, one hundred trillion, one quadrillion, and ten quadrillion e/sq cm.

Anspaugh, B. E.; Downing, R. G.; Miyahira, T. F.; Weiss, R. S.

1981-01-01

422

Feasibility study for detecting copper contaminants in transformer insulation using laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

In recent times, copper sulphide (Cu2S) diffusion in the transformer insulation is a major problem reducing the life of transformers. It is therefore essential to identify a simple methodology to understand the diffusion of Cu2S into the solid insulation [oil impregnated pressboard (OIP)]. In the present work, laser-induced breakdown spectroscopy (LIBS) was adopted to study the diffusion of Cu2S into the pressboard insulation and to determine the depth of diffusion. The diffusion of Cu2S in pressboard was confirmed by electrical discharge studies. In general, flashover voltage and increase in ageing duration of pressboard insulation/Cu concentration had inverse relationship. The characteristic emission lines were also studied through optical emission spectroscopy. Based on LIBS studies with Cu powder dispersed pressboard samples, Cu I emission lines were found to be resolvable up to a lowest concentration of 5 ?g/cm2. The LIBS intensity ratio of Cu I-Ca II emission lines were found to increase with increase in the ageing duration of the OIP sample. LIBS studies with OIP samples showed an increase in the optical emission lifetime. LIBS results were in agreement with the electrical discharge studies.

Aparna, N.; Vasa, Nilesh J.; Sarathi, R.; Rajan, J. Sundara

2014-10-01

423

Effect of diameter variation on electrical characteristics of Schottky barrier indium arsenide nanowire field-effect transistors.  

PubMed

The effect of diameter variation on electrical characteristics of long-channel InAs nanowire metal-oxide-semiconductor field-effect transistors is experimentally investigated. For a range of nanowire diameters, in which significant band gap changes are observed due to size quantization, the Schottky barrier heights between source/drain metal contacts and the semiconducting nanowire channel are extracted considering both thermionic emission and thermally assisted tunneling. Nanowires as small as 10 nm in diameter were used in device geometry in this context. Interestingly, while experimental and simulation data are consistent with a band gap increase for decreasing nanowire diameter, the experimentally determined Schottky barrier height is found to be around 110 meV irrespective of the nanowire diameter. These observations indicate that for nanowire devices the density of states at the direct conduction band minimum impacts the so-called branching point. Our findings are thus distinctly different from bulk-type results when metal contacts are formed on three-dimensional InAs crystals. PMID:24848303

Razavieh, Ali; Mohseni, Parsian Katal; Jung, Kyooho; Mehrotra, Saumitra; Das, Saptarshi; Suslov, Sergey; Li, Xiuling; Klimeck, Gerhard; Janes, David B; Appenzeller, Joerg

2014-06-24

424

Current characteristic signals of aqueous solution transferring through microfluidic channel under non-continuous DC electric field  

NASA Astrophysics Data System (ADS)

The surface effect is becoming apparently significant as the miniaturization of fluidic devices. In the micro/nanochannel fluidics, the electrode surface effects have the same important influence on the current signals as the channel surface effects. In this paper, when aqueous solution are driven with non-continuous DC electric field force, the characteristics of current signals of the fluid transferring through microfluidic channel are systematically studied. Six modes of current signal are summarized, and some new significant phenomena are found, e.g. there exists a critical voltage at which the steady current value equals to zero; the absolute value of the steady current decreases at first, however, it increases with the external voltage greater than the critical voltage as the electrode area ratio of cathode and anode is 10 and 20; the critical voltage increases with the enhancing of electrode area ratio of cathode and anode and solution pH, while it decreases with the raising of ion concentration. Finally, the microscopic mechanism of the electrode surface charge effects is discussed preliminarily. The rules will be helpful for detecting and manipulating single biomolecules in the micro/nanofluidic chips and biosensors.

Ma, HongWei; Wang, KaiGe; Gao, ZeYang; Wang, HaiQing; Wang, Shuang; Zhang, Chen; Wang, GuiRen; Bai, JinTao

2014-10-01

425

Electrical and optical characteristics of diffuse nanosecond pulsed discharge plasma using a needle-array electrode in atmospheric air  

NASA Astrophysics Data System (ADS)

In this paper, a stable and diffuse dielectric barrier discharge plasma excited by bipolar nanosecond pulse is obtained under a needle-array electrode at atmospheric pressure in air. The images of the diffuse discharge, electric characteristics, and the optical emission spectra emitted from the diffuse discharge are investigated under mono and multi needle electrodes configuration. The peak value of discharge current, the average power, the power density, the emission intensity of N2 (C3?u ?B3?g, 0-0), and the gas temperature of the diffuse dielectric barrier discharge plasmas are investigated under different needle electrode numbers based on the waveforms of pulse voltage-current and the optical emission spectra. Moreover, the plasma area is obviously enlarged in the transverse direction when the needle electrode number is increased from 1 to 13. An area approximately 65 × 45 mm2 diffuse discharge plasma region under 13 needle electrodes can be obtained and the discharge plasma still keeps good uniformity, which could be used for large-area surface processing in several fields spanning from biological sterilization and plasma medicine to surface modification of materials and synthesis of functional materials.

Liu, Zhi-jie; Wang, Wen-chun; Zhang, Li; Wang, Sen; Yang, De-zheng; Zhang, Shuai; Tang, Kai

2014-05-01

426

Fundamental Characteristics of Laboratory Scale Model DC Microgrid to Exchange Electric Power from Distributed Generations installed in Residential Houses  

NASA Astrophysics Data System (ADS)

DC microgrid is a novel power system using dc distribution in order to provide a super high quality power. This dc system is suitable for dc output type distributed generations and energy storages. In this research, we assumed one type of the dc microgrids for residential houses (apartment house or housing complex). Each residence has a distributed generation such as gas engine or fuel cell. Those cogenerations are connected to the dc power line, and the electricity from the generations can be shared among the residences. The hot water from the cogeneration is used in each residence. We constructed an experimental system based on this concept in our laboratory. We have studied the fundamental characteristics and the quality of the supplied power to the loads against several fluctuations or faults. Experimental results demonstrated that the system could supply high quality power to the loads against a sudden load variation and a voltage sag of the utility grid. Afterwards, we moved the experimental system to an experimental apartment house (NEXT21). We studied the quality of the supplying power by using practical power line, and confirmed that the system was also able to supply a power to home appliances stably.

Kakigano, Hiroaki; Hashimoto, Takuya; Matsumura, Yohei; Kurotani, Takashi; Iwamoto, Wataru; Miura, Yushi; Ise, Toshifumi; Momose, Toshinari; Hayakawa, Hideki

427

Improvement of adhesion of electric vehicles using series motors. Readhesion characteristics in line with those of separately excited motor and promotion of recovery of tractive effort after readhesion  

SciTech Connect

Historically, the unit power of electric vehicles has been small in Japan, and full effort for the improvement of adhesion has not been given. As a result, the adhesion characteristics are significantly inferior to the typical European vehicles. It is well known that the best way to materialize a high adhesion vehicle is to use external excitation motors with independent control of each axle. However, the independently controlled external excitation motor is neither necessarily economical with the scale of vehicles in Japan, nor is the technical background sufficient. This paper attempts to improve the adhesion characteristics, which have been used widely in the extension of serial motor technology. The possibility of good adhesion characteristics in line with external excitation motors with serial motors controlled by fast response power electronics with choppers and controlled rectifiers is shown and a practical proposal for realistic conditions is made. This paper discusses the adhesion characteristics only with regard to the readhesion and traction recovery characteristics.

Sone, S.; Yokota, T.; Kakizoe, H.

1982-01-01

428

Kinetic modeling of the Townsend breakdown in argon  

SciTech Connect

Kinetic modeling of the Townsend breakdown in argon was performed in the “forward-back” approximation. The kinetic model was found to adequately describe the left branch of the Paschen curve, and the important role of ionization by fast ions and atoms near the cathode, as well as the increase in secondary emission coefficient in strong electric fields described in the literature, was confirmed. The modeling also showed that the electron energy distribution function develops a beam of high-energy electrons and that the runaway effect, i.e., the monotonic increase of the mean electron energy with the distance from the cathode, occurs at the left branch of the Paschen curve.

Macheret, S. O.; Shneider, M. N. [Department of Mechanical and Aerospace Engineering, Princeton University, D-414 Engineering Quadrangle, Princeton, New Jersey 08544 (United States)] [Department of Mechanical and Aerospace Engineering, Princeton University, D-414 Engineering Quadrangle, Princeton, New Jersey 08544 (United States)

2013-10-15

429

Breakdown of the Dipole Approximation in Strong-Field Ionization  

NASA Astrophysics Data System (ADS)

We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 1 013 W /cm2 . Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semiclassical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as the origin of our observations.

Ludwig, A.; Maurer, J.; Mayer, B. W.; Phillips, C. R.; Gallmann, L.; Keller, U.

2014-12-01

430

Breakdown of the dipole approximation in strong-field ionization.  

PubMed

We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10^{13}??W/cm^{2}. Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semiclassical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as the origin of our observations. PMID:25541770

Ludwig, A; Maurer, J; Mayer, B W; Phillips, C R; Gallmann, L; Keller, U

2014-12-12

431

Study of Bulk and Elementary Screw Dislocation Assisted Reverse Breakdown in Low-Voltage (< 250 V) 4H-SiC p(sup +)n Junction Diodes--Part II: Dynamic Breakdown Properties. Part 2; Dynamic Breakdown Properties  

NASA Technical Reports Server (NTRS)

This paper outlines the dynamic reverse-breakdown characteristics of low-voltage (<250 V) small-area <5 x 10(exp -4) sq cm 4H-SiC p(sup +)n diodes subjected to nonadiabatic breakdown-bias pulsewidths ranging from 0.1 to 20 microseconds. 4H-SiC diodes with and without elementary screw dislocations exhibited positive temperature coefficient of breakdown voltage and high junction failure power densities approximately five times larger than the average failure power density of reliable silicon pn rectifiers. This result indicates that highly reliable low-voltage SiC rectifiers may be attainable despite the presence of elementary screw dislocations. However, the impact of elementary screw dislocations on other more useful 4H-SiC power device structures, such as high-voltage (>1 kV) pn junction and Schottky rectifiers, and bipolar gain devices (thyristors, IGBT's, etc.) remains to be investigated.

Neudeck, Philip G.; Fazi, Christian

1999-01-01

432

Dielectric Breakdown Phenomena during Secondary Electron Emission Measurement of Sputter-Deposited MgO Films  

NASA Astrophysics Data System (ADS)

The ion-induced secondary electron emission (SEE) characteristics of sputter-deposited magnesium oxide (MgO) films have been investigated. Using an RF magnetron sputtering apparatus, MgO films of 50-200 nm thickness were deposited on Si substrates from a sintered MgO target. Under irradiation of 1 keV of Ar+ ions, secondary electrons were collected at a positively biased electrode. The secondary electron current increased as the bias voltage increased, and saturated to give an SEE coefficient of 2-2.5 in all samples. The deposition condition (gas pressure 2-20 Pa) did not strongly affect this current-voltage (I-V) characteristic of the SEE, while an increase in film thickness resulted in an increase in the voltage at which the SEE current began to rise. This rising voltage depended neither on the energy nor on the current of the primary ion beam. We concluded that the rising voltage was governed by an electric breakdown phenomenon by which the positive charge accumulating on the surface was compensated from the substrate. The field strength was estimated to be as high as 109 V/m.

Nakano, Takeo; Fujimoto, Takashi; Nakada, Daisuke; Baba, Shigeru

2006-10-01

433

Scintillation Breakdowns in Chip Tantalum Capacitors  

NASA Technical Reports Server (NTRS)

Scintillations in solid tantalum capacitors are momentarily local breakdowns terminated by a self-healing or conversion to a high-resistive state of the manganese oxide cathode. This conversion effectively caps the defective area of the tantalum pentoxide dielectric and prevents short-circuit failures. Typically, this type of breakdown has no immediate catastrophic consequences and is often considered as nuisance rather than a failure. Scintillation breakdowns likely do not affect failures of parts under surge current conditions, and so-called "proofing" of tantalum chip capacitors, which is a controllable exposure of the part after soldering to voltages slightly higher than the operating voltage to verify that possible scintillations are self-healed, has been shown to improve the quality of the parts. However, no in-depth studies of the effect of scintillations on reliability of tantalum capacitors have been performed so far. KEMET is using scintillation breakdown testing as a tool for assessing process improvements and to compare quality of different manufacturing lots. Nevertheless, the relationship between failures and scintillation breakdowns is not clear, and this test is not considered as suitable for lot acceptance testing. In this work, scintillation breakdowns in different military-graded and commercial tantalum capacitors were characterized and related to the rated voltages and to life test failures. A model for assessment of times to failure, based on distributions of breakdown voltages, and accelerating factors of life testing are discussed.

Teverovsky, Alexander

2008-01-01

434

Breakdown and critical field evaluation for porous PZT 95/5 ferroelectric ceramics under shock wave compression  

NASA Astrophysics Data System (ADS)

Bounded charges of PZT 95/5 ferroelectric ceramics with polarization can be rapidly released by shock wave loadings to form a high-power electrical energy output, which motivates pulsed power applications of ferroelectric materials. In the present paper, we first investigated experimentally the depoling current and output electric field, as well as the critical electric fields of breakdown for porous PZT 95/5 ceramics in the normal shock-wave-loaded mode by means of a gas-gun facility. By combining the output electric-field profile by shock loading with the breakdown of the quasi-static electric field, we were able to theoretically evaluate the range of the breakdown field for porous ferroelectric ceramics with different porosities under shock wave compression. Although it is a rough bound-field evaluation on breakdown of shocked porous PZT 95/5 ferroelectric ceramics suggested in the present work, it sounds reasonable and the predictions of critical field-bounds on the breakdown show good agreement with the magnitude of the experimental results. The influences of load resistance, porosity and velocity of shock wave on the lower and upper bounds of critical electric field for poled porous PZT 95/5 ceramics during the discharge process were also discussed.

Jiang, Yixuan; Wang, Xingzhe; Zhang, Fuping; He, Hongliang

2014-08-01

435

Breakdown of Benford's law for birth data  

NASA Astrophysics Data System (ADS)

Long birth time series for Romania are investigated from Benford's law point of view, distinguishing between families with a religious (Orthodox and Non-Orthodox) affiliation. The data extend from Jan. 01, 1905 till Dec. 31, 2001, i.e. over 97 years or 35 429 days. The results point to a drastic breakdown of Benford's law. Some interpretation is proposed, based on the statistical aspects due to population sizes, rather than on human thought constraints when the law breakdown is usually expected. Benford's law breakdown clearly points to natural causes.

Ausloos, M.; Herteliu, C.; Ileanu, B.

2015-02-01

436

Gas breakdown and secondary electron yields  

NASA Astrophysics Data System (ADS)

In this paper we present a systematic study of the gas breakdown potentials. An analysis of the key elementary processes in low-current low-pressure discharges is given, with an aim to illustrate how such discharges are used to determine swarm parameters and how such data may be applied to modeling discharges. Breakdown data obtained in simple parallel-plate geometry are presented for a number of atomic and molecular gases. Ionization coefficients, secondary electron yields and their influence on breakdown are analyzed, with special attention devoted to non-hydrodynamic conditions near cathode.

Mari?, Dragana; Savi?, Marija; Sivoš, Jelena; Škoro, Nikola; Radmilovi?-Radjenovi?, Marija; Malovi?, Gordana; Petrovi?, Zoran Lj.

2014-06-01

437

Streak interactions and breakdown in boundary layer flows  

NASA Astrophysics Data System (ADS)

The objective of this paper is to show that the interaction of streamwise velocity streaks of finite length can lead to turbulent breakdown in the flat-plate boundary layer flow. The work is motivated by previous numerical and experimental studies of transitional flows where the high-frequency oscillations leading to turbulence are seen to form in the region of strongest shear induced by streaks in relative motion. Therefore, a model for the interaction of steady and unsteady (i.e., slowly moving in the spanwise direction) spanwise periodic streaks is proposed. The interaction of two subsequent streaks is investigated for varying collision parameters. In particular, the relative spanwise position and angle are considered. The results show that the interaction is able to produce both a symmetric and asymmetric breakdown without the need for additional random noise from the main stream. Velocity structures characteristic of both scenarios are analyzed. Hairpin and ? vortices are found in the case of symmetric collision between a low-speed region and an incoming high-speed streak, when a region of strong wall-normal shear is induced. Alternatively, when the incoming high-momentum fluid is misaligned with the low-speed streak in front, single quasi-streamwise vortices are identified. Despite the different symmetry at the breakdown, the detrimental interaction involves for both cases the tail of a low-speed region and the head of a high-speed streak. Further, the breakdown appears in both scenarios as an instability of three-dimensional shear layers formed between the two streaks. The streak interaction scenario is suggested to be of relevance for turbulence production in wall-bounded flows.

Brandt, Luca; de Lange, H. C.

2008-02-01

438

Physical mechanisms for reduction of the breakdown voltage in the circuit of a rod lightning protector with an opening microswitch  

SciTech Connect

The effect of air gap breakdown voltage reduction in the circuit with an opening microswitch is substantiated from the physical point of view. This effect can be used to increase the efficiency of lightning protection system with a rod lightning protector. The processes which take place in the electric circuit of a lightning protector with a microswitch during a voltage breakdown are investigated. Openings of the microswitch are shown to lead to resonance overvoltages in the dc circuit and, as a result, efficient reduction in the breakdown voltage in a lightning protector-thundercloud air gap.

Bobrov, Yu. K.; Zhuravkov, I. V.; Ostapenko, E. I.; Starikov, V. V. [All-Russia Electrotechnical Institute (Russian Federation); Yurgelenas, Yu. V. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation)

2010-12-15

439

Technical Development on Partial Discharge Measurement and Electrical Insulation Techniques for Low Voltage Motors Driven by Voltage Inverters  

Microsoft Academic Search

This paper reviews the up-to-date research activities on electrical insulation techniques under repetitive surge voltages with steep wavefront for low voltage inverter-fed motors. Partial discharge (PD) inception, propagation, ageing and breakdown characteristics of magnet wires, including recently developed PD-resistant wires such as nanocomposite enameled wires, are described. PD measurement techniques under the steep-front voltages and IEC activity toward their standardization

Hitoshi Okubo; Naoki Hayakawa; Gian Carlo Montanari

2007-01-01

440

Effects of gamma-ray irradiation on dielectric surface breakdown of polybutylene polymers  

Microsoft Academic Search

Polymer materials are required to be used in radiation environments of space and nuclear power stations as insulation materials. For the use of polymer materials in such regions, it must be confirmed whether the electrical perfo