These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Electrical-breakdown characteristics and testing of high-voltage XLPE- and EPR-insulated cables  

NASA Astrophysics Data System (ADS)

Threshold voltages and other basic breakdown characteristics, spanning times from microseconds to cable life expectancy, were determined for cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR) cables. These results are based upon measurements of 60Hz, high frequency, impulse, and impulse with dc bias voltages. Based on the breakdown characteristics an improved, procedure for the factory testing of full-reels of polymeric insulated cables and for 2 year qualification testing of XLPE cables is proposed. This procedure can help assure proper performance of cables throughout their service life.

Bahder, G.; Sosnowski, M.; Katz, C.; Eaton, R.; Klein, K.

1982-10-01

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

Flashover and breakdown characteristics in low pressure environments  

Microsoft Academic Search

A present trend in aircraft design is the increasing use of 270-Vdc power circuitry. Also, significant voltage spikes may be superimposed on the dc level. In many situations involving unsealed equipment enclosures, electrical insulation is provided by a combination of gaseous medium and spacing between conductors. Consequently, flashover\\/breakdown characteristics of electrical wiring and printed-circuit-board traces depend upon the environment in

Dennis Grosjean; Donald Kasten; Stephen Sebo; Titus Chen; Michael Rupp; Daniel Schweickart

2011-01-01

4

Electrical breakdown gas detector featuring carbon nanotube array electrodes.  

PubMed

We demonstrate here detection of dichloro-difluoro-methane and oxygen in mixtures with helium using a carbon nanotube electrical breakdown sensor device. The sensor is comprised of an aligned array of multiwalled carbon nanotubes deposited on a nickel based super-alloy (Inconel 600) as the anode; the counter electrode is a planar nickel sheet. By monitoring the electrical breakdown characteristics of oxygen and dichloro-difluoro-methane in a background of helium, we find that the detection limit for dichloro-difluoro-methane is approximately 0.1% and the corresponding limit for oxygen is approximately 1%. A phenomenologigal model is proposed to describe the trends observed in detection of the two mixtures. These results indicate that carbon nanotube based electrical breakdown sensors show potential as end detectors in gas-chromatography devices. PMID:18468093

Kim, Seongyul; Pal, Sunil; Ajayan, Pulickel M; Borca-Tasciuc, Theodorian; Koratkar, Nikhil

2008-01-01

5

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

6

A THEORETICAL TREATMENT OF ELECTRIC BREAKDOWN IN BARIUM TITANATE  

Microsoft Academic Search

A method is developed based on an essentially rigid ion hypothesis fer ; the calculation of the electric breakdown field strength in ionic crystals. The ; basic mechanism responsible for breakdown is assumed to be an electron avalanche ; effect, and the theory rests on a calculation of the rate at which a conduction ; electron gains energy from the

Franzak

1958-01-01

7

Study on the lightning impulse breakdown characteristics of gaseous insulation media for the design of a high voltage superconducting apparatus  

NASA Astrophysics Data System (ADS)

In general, the current leads of high voltage superconducting apparatuses cooled by liquid nitrogen are exposed to gaseous insulation media. Therefore, the investigation on the electrical breakdown characteristics of gaseous insulation media should be performed to develop electrically reliable high voltage superconducting power apparatuses. In this study, the lightning impulse breakdown tests on gaseous insulation media are conducted by using sphere-to-plane electrode systems made of stainless steel. Also, the lightning impulse breakdown voltage tests on gaseous insulation media according to various pressures are performed. The experimental results show that the electrical breakdown characteristics under lightning impulse voltage are affected by the gap length between electrode systems, the size of electrodes, and the field utilization factors. From these results, the electrical insulation design criteria to estimate the electrical breakdown voltage are established. The results are expected to be applicable to the design of current leads for high voltage superconducting apparatuses.

Kang, H.; Na, J. B.; Ahn, M. C.; Bae, D. K.; Kim, Y. H.; Ko, T. K.

2010-11-01

8

Gas Temperature Effects on Electrical Breakdown in Cylindrical Electrodes  

NASA Astrophysics Data System (ADS)

One of the most important applications of atmospheric pressure plasma is in the corona discharge system, for the potential reduction of NOx and SOx gas emissions from diesel engines. However, the conventional corona discharge system for the emission control application requires a high electrical voltage (typically 45 kV or higher), making its high voltage modulator heavy and bulky with insulating material. We, therefore, investigate the influence of the gas temperature on the electrical breakdown properties in the cylindrical electrode system. A theoretical model of the electrical breakdown in a cylindrical electrode system is briefly summarized, by making use of Paschen¡¯s law. The breakdown voltage increases, reaches its peak and decreases, as the aspect ratio a/b increases from 0.01 to unity, where a and b are radii of the inner and outer electrodes, respectively. The experimental data agree remarkably well with the theoretical predictions. The breakdown voltage V in a high gas temperature Tg is given by V = (Tr/Tg)V0, where V0 is the breakdown voltage at the room temperature Tr. Obviously, the breakdown voltage decreases as the gas temperature Tg increases. The experimental data agree well with the theoretical values. It is, therefore, concluded that the breakdown voltage is inversely proportional to the gas temperature Tg as predicted from the theoretical analysis.

Uhm, Han; Jung, She

2002-11-01

9

Electric field breakdown in open-cycle disk generators  

NASA Astrophysics Data System (ADS)

Experiments have been performed in the Stanford Inflow Disk Generator facility with clean fuel and with slagging insulator walls to investigate the radial electric field breakdown phenomena. The results indicate that the presence of the magnetic field in the disk geometry has a stabilizing effect on incipient breakdown, in contrast to the previously-reported linear generator case where the B-field increases the breakdown susceptibility. The breakdown voltage threshold and insulator gap resistance both increased with time as the applied field was maintained, possibly indicating the evaporation of condensed seed material in the clean-fuel case, and the polarization and thinning of the slag layer in the coal slurry case. Insulator-initiated breakdown was the dominant breakdown mode in all cases. The plasma-initiated breakdown threshold was examined via the application of short-duration (100 ms) ramp-shaped voltage pulses and was found to be consistently higher than the insulator-initiated breakdown threshold for insulator gaps studied (3.2 mm and 6.4 mm).

Lear, W. E.; Nakamura, T.

1984-01-01

10

Electrical breakdown measurements of semicontinuous metal films  

Microsoft Academic Search

The breakdown current Ic of a percolating system is measured on real materials. We find that Ic~B-x, B is the weakly nonlinear response determined by third-harmonic generation. A new criterion for Ic is suggested, defined as the current at which a hot spot reaches the melting temperature of the metallic grains, Tm. This criterion remains valid in the presence of

Yoad Yagil; Guy Deutscher; David J. Bergman

1992-01-01

11

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

12

Fast Diagnostic For Electrical Breakdowns In Vacuum  

SciTech Connect

The design of an inexpensive, small, high bandwidth diagnostic for the study of vacuum insulator flashover is described. The diagnostic is based on the principle of capacitive coupling and is commonly referred to as a D-dot probe due to its sensitivity to the changing of the electric displacement field. The principle challenge for the design proved to be meeting the required mechanical size for the application rather than bandwidth. An array of these probes was fabricated and used in an insulator test stand. Data from the test stand with detailed analysis is presented. A highlight of the application of the probes to the test stand was the ability to detect the charging of the insulator surface by UV illumination as a prelude to the insulator flashover. The abrupt change in the insulator's surface charge during the flashover was also detected.

Houck, T L; Javedani, J B; Lahowe, D A

2008-03-25

13

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

14

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

15

Current-voltage characteristics and breakdown mechanism in one-dimensional band and mott insulators attached to electrodes  

NASA Astrophysics Data System (ADS)

The current-voltage characteristics and mechanism of bias-induced breakdown in one-dimensional models for band and Mott insulators are investigated theoretically by using nonequilibrium Green's functions. We attach the models to metallic electrodes, the effects of which are incorporated into the self-energy. For the models of both the band and the Mott insulators with lengths L C , the bias voltage induces a breakdown of the insulating state, and the breakdown mechanism shows a crossover depending on L C . When L C is smaller than the correlation length ? = W/?, the threshold is determined basically by the bias V th ˜ ?, where W and ? are the bandwidth and the energy gap, respectively. For systems with L C ? ?, the threshold is governed by the electric field, V th/ L C , which is consistent with a Landau-Zener-type breakdown V th/ L C ? ?2/ W.

Tanaka, Yasuhiro; Yonemitsu, Kenji

2013-06-01

16

INVESTIGATIONS OF THE PRESSURE DEPENDENCE OF ELECTRICAL BREAKDOWN OF PURIFIED WATER AND SALINE SOLUT  

Microsoft Academic Search

The role of ions in the electrical breakdown process of liquids is presently insufficiently understood. Ions induce local changes to the electrical properties of water as well as contribute to the conductivity. The lag time to breakdown has been measured for various solution concentrations and hydrostatic pressures. The properties of both pure liquids and electrolytic solutions and their pressure dependence

J. Messerschmitt; E. E. Kunhardt

1993-01-01

17

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

E-print Network

and stretch dependence of the electrical breakdown strength of an acrylic dielectric elastomer Jiangshui HuangThe thickness and stretch dependence of the electrical breakdown strength of an acrylic dielectric elastomer Jiangshui Huang, Samuel Shian, Roger M. Diebold, Zhigang Suo, and David R. Clarke Citation: Appl

Suo, Zhigang

18

High Voltage Breakdown and SQUID Performance for the Neutron Electric Dipole Moment Experiment  

NASA Astrophysics Data System (ADS)

A new search for a permanent electric dipole moment (EDM) of the neutron is underway at the Oak Ridge Spallation Neutron Source. A non-zero EDM would be a signal of time reversal symmetry violation and improve our understanding of the matter-antimatter asymmetry of the universe. The experiment will use a Superconducting Quantum Interference Device (SQUID) to infer the precession of ultracold neutrons held in a superfluid helium bath, in the presence of applied electric and magnetic fields. The experiment's sensitivity is proportional to the applied electric field. Neither the maximum practical size of the electric field nor the behavior of SQUIDs in proximity to this field are presently understood. Therefore we have constructed a small prototype (to decrease the cool-down time) to verify that SQUIDs can function in a high voltage environment and when exposed to RF interference. Another goal is to determine what characteristics allow us to maximize the electric field without breakdown. To do this we measure the breakdown voltage in both normal and superfluid helium at a variety of temperatures and (more uniquely) at different pressures, as well as test a variety of electrode materials.

Huffer, Craig; Liu, Chen-Yu; Long, Josh; Karcz, Maciej

2007-10-01

19

Visual and Electrical Evidence Supporting a Two-Plasma Mechanism of Vacuum Breakdown Initiation  

SciTech Connect

The energy available during vacuum breakdown between copper electrodes at high vacuum was limited using resistors in series with the vacuum gap and arresting diodes. Surviving features observed with SEM in postmortem samples were tentatively correlated with electrical signals captured during breakdown using a Rogowski coil and a high-voltage probe. The visual and electrical evidence is consistent with the qualitative model of vacuum breakdown by unipolar arc formation by Schwirzke [1, 2]. The evidence paints a picture of two plasmas of different composition and scale being created during vacuum breakdown: an initial plasma made of degassed material from the metal surface, ignites a plasma made up of the electrode material.

Castano-Giraldo, C. [University of Illinois, Urbana-Champaign; Aghazarian, Maro [ORNL; Caughman, John B [ORNL; Ruzic, D. N. [University of Illinois, Urbana-Champaign

2012-01-01

20

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

21

Stretch dependence of the electrical breakdown strength and dielectric constant of dielectric elastomers  

NASA Astrophysics Data System (ADS)

Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch dependence of the electrical breakdown strength of dielectric elastomers, and compare the electrical breakdown fields for compliant and rigid electrodes on the elastomer. We show that the electrode configuration strongly influences the electrical breakdown field strength. Further, we compare the stretch dependent dielectric function and breakdown of the acrylic elastomer VHB 4910™ from 3M™, and of the natural rubber ZruElast™ A1040™ from Zrunek rubber technology. While the dielectric permittivity of VHB decreases with increasing stretch ratio, the dielectric constant of rubber is insensitive to stretch. Our results suggest natural rubber as a versatile material for dielectric elastomer energy harvesting.

Tröls, Andreas; Kogler, Alexander; Baumgartner, Richard; Kaltseis, Rainer; Keplinger, Christoph; Schwödiauer, Reinhard; Graz, Ingrid; Bauer, Siegfried

2013-10-01

22

Locating initial breakdown pulses using electric field change network  

NASA Astrophysics Data System (ADS)

Initial breakdown pulses (IBPs) observed in the fast electric field change (E-change) at the beginning of intracloud (IC) and cloud-to-ground (CG) lightning flashes are located using a time-of-arrival technique called Position By Fast Antenna (PBFA) with data from a network of 10 E-change sensors located at Kennedy Space Center. Location errors, estimated using a Monte Carlo method, are usually less than 100 m for horizontal coordinates and several hundreds of meters for altitude, depending on distance to the sensors and altitude of the source. Comparison of PBFA source locations to locations from a VHF lightning mapping system (Lightning Detection and Ranging II (LDAR2)) shows that PBFA locates most of the "classic" IBPs while LDAR2 locates only a few percent of them. As the flash develops during the IB stage, PBFA and LDAR2 obtain similar locations when they detect the same IBPs. The overall vertical motion indicated by the PBFA positions of IBPs was downward with time for CG flashes and upward with time for IC flashes. Location of the fast pulses due to return strokes of CG flashes is also determined using PBFA. Comparison to locations from the Cloud-to-Ground Lightning Surveillance System (CGLSS) shows that PBFA reliably locates ground strokes. These results are verified using ground truth data acquired with a high-speed video camera. After cross calibration with the CGLSS data set, peak currents of return strokes are also determined.

Karunarathne, Sumedhe; Marshall, Thomas C.; Stolzenburg, Maribeth; Karunarathna, Nadeeka; Vickers, Lauren E.; Warner, Tom A.; Orville, Richard E.

2013-07-01

23

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

24

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

25

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

26

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

27

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

28

Modeling characteristics of nonequilibrium processes during breakdown of capacitive rf argon glow discharge  

SciTech Connect

A self-consistent, diffusion-drift approximated fluid model including ion and electron continuity equations and an electron energy equation is presented for simulating the nonequilibrium characteristics during breakdown of argon rf glow discharge. The nonlinear partial differential equations of the model are solved numerically by using a so-called finite volume method. The numerical results indicate that there exist two different phases on the breakdown curves, i.e., the low p{center_dot}d phase and high p{center_dot}d phase. The breakdown voltage, analyzed for three different gaps, varies little in low p{center_dot}d phase while in the high p{center_dot}d phase, it increases linearly with pressure increase. Time evolution of Ohmic heating and energy loss during breakdown are presented in detail. Analysis yields that the heating mechanisms are the dominant factors in breakdown. Moreover, the steady discharge characteristics are also studied specifically under breakdown voltage of 10 Torr. The charged particle densities are on the order of 10{sup 15}/m{sup 3} and the electron energy has two characteristic values at different rf phases.

Deng Yongfeng [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, School of Physics and Optoelectronic Technology, and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116085 (China); OXi'an Space Power Institute, Xi'an 710100 (China); Han Xianwei [OXi'an Space Power Institute, Xi'an 710100 (China); Shafiq-ur-Rehman; Liu Yue [State Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, School of Physics and Optoelectronic Technology, and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116085 (China)

2008-05-15

29

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

30

Investigation of the breakdown products produced from electrical discharge in selected CFC replacement fluids  

SciTech Connect

LLNL personnel have designed and constructed a special purpose electrical test stand to evaluate CFCs and CFC replacement fluids under simulated AC, DC, and pulsed breakdown conditions. The test stand includes an electrical diagnostic system which allows the measurement of breakdown voltage, discharge current, arc power, and energy associated with each pulse. The appropriate data that is collected in order to correlate the quantity of by-products produced with the pertinent control variables, such as voltage, current, pulse width, pulse repetition frequency, and energy. Along with the electrical test stand, LLNL has extensive chemical analysis facilities that enable us to perform gas chromatographic and gas chromatographic-mass spectrometric analysis of various fluids to identify and quantify the breakdown products formed under various scenarios of electrical energy deposition.

Hawley-Fedder, R.; Goerz, D.; Koester, C.; Wilson, M.

1996-04-01

31

Laser-induced breakdown in air in a constant electric field V. I. Fisher  

E-print Network

is discussed with allowance for drift escape and Joule heating of electrons in the constant electric field field at constant laser radiation intensity takes the form of a curve with a minimum. It follows, their heating by the constant elec- tric field, and the electrical breakdown. The electron drift velocity U

Fominov, Yakov

32

Soft breakdown characteristics of ultralow-k time-dependent dielectric breakdown for advanced complementary metal-oxide semiconductor technologies  

Microsoft Academic Search

During technology development, the study of ultralow-k (ULK) time-dependent dielectric breakdown (TDDB) is important for assuring robust reliability. As the technology advances, the increase in ULK leakage current noise level and reversible current change induced by soft breakdown (SBD) during stress has been observed. In this paper, the physical origin of SBD and reversible breakdown, and its correlation to conventional

Fen Chen; Michael Shinosky

2010-01-01

33

Microscopic scenarios for implementing a dynamic model of electric breakdown in a solid insulation system  

Microsoft Academic Search

Microscopic scenarios for electric tree initiation and propagation are developed for the case where electric breakdown occurs in a thick, homogeneous solid dielectric due to the application of a single, steep-fronted impulse. The scenarios treat the electric tree as a high-temperature, high-conductivity, gaseous region that is formed by rapid, localized, energetic dissociation of the dielectric. The scenarios provide perspective on

P. P. Budenstein; Redstone Arsenal

1990-01-01

34

AC electrical breakdown phenomena of epoxy/layered silicate nanocomposite in needle-plate electrodes.  

PubMed

Epoxy/layered silicate nanocomposite for the insulation of heavy electric equipments were prepared by dispersing 1 wt% of a layered silicate into an epoxy matrix with a homogenizing mixer and then AC electrical treeing and breakdown tests were carried out. Wide-angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) observation showed that nano-sized monolayers were exfoliated from a multilayered silicate in the epoxy matrix. When the nano-sized silicate layers were incorporated into the epoxy matrix, the breakdown rate in needle-plate electrode geometry was 10.6 times lowered than that of the neat epoxy resin under the applied electrical field of 520.9 kV/mm at 30 degrees C, and electrical tree propagated with much more branches in the epoxy/layered silicate nanocomposite. These results showed that well-dispersed nano-sized silicate layers retarded the electrical tree growth rate. The effects of applied voltage and ambient temperature on the tree initiation, growth, and breakdown rate were also studied, and it was found that the breakdown rate was largely increased, as the applied voltage and ambient temperature increased. PMID:23858862

Park, Jae-Jun; Lee, Jae-Young

2013-05-01

35

Breakdown phenomena during the growth of anodic oxide films on zirconium metal Influence of experimental parameters on electrical and mechanical breakdown  

SciTech Connect

Different aspects of the breakdown phenomena observed during the growth of anodic films on zirconium metal in aqueous solutions have been investigated. Two different mechanisms of breakdown are suggested as a result of the experimental observations. A mechanical breakdown, which is dependent upon the logarithm of the anodizing current density, has been observed in carbonate and sulfate solutions at low concentrations of salt or aci and/or low anodizing current densities. The appearance of small fissures in the ZrO/sub 2/ films is related to this type o breakdown. An electrical breakdown was observed in sulfamic acid solutions as well as in sulfate and carbonate solutions as high salt or acid concentrations and/or high current densities. In the case of electrical breakdown, the first spark voltage showed a significant dependence upon the value of current density only in carbonate and sulfate anion containing solutions. A possible explanation for this dependence is suggested in agreement with Christov's model, taking into account also the incorporation of anions into the films. The different influences of the electrolytic solutions upon both types of breakdown are presented and discussed.

Di Quarto, F.; Piazza, S.; Sunseri, C.

1984-12-01

36

Model Analysis of Self and Laser-Triggered Electrical Breakdown of Liquid Water for Pulsed-Power Applications  

Microsoft Academic Search

Electrical breakdown simulations for liquids, in response to a submicrosecond (~100-200 ns) voltage pulse, are carried out. It is shown that breakdown is initiated by field emission at the interface of preexisting microbubbles. Impact ionization within the microbubble gas then contributes to plasma development, with cathode injection having a delayed and secondary role. The model used in this paper adequately

Jun Qian; Ravindra P. Joshi; Karl H. Schoenbach; J. R. Woodworth; G. S. Sarkisov

2006-01-01

37

Explosive Electric Breakdown due to Conducting-Particle Deposition on an Insulating Substrate  

NASA Astrophysics Data System (ADS)

We introduce a theoretical model to investigate the electric breakdown of a substrate on which highly conducting particles are adsorbed and desorbed with a probability that depends on the local electric field. We find that, by tuning the relative strength q of this dependence, the breakdown can change from continuous to explosive. Precisely, in the limit in which the adsorption probability is the same for any finite voltage drop, we can map our model exactly onto the q-state Potts model and thus the transition to a jump occurs at q=4. In another limit, where the adsorption probability becomes independent of the local field strength, the traditional bond percolation model is recovered. Our model is thus an example of a possible experimental realization exhibiting a truly discontinuous percolation transition.

Oliveira, Cláudio L. N.; Araújo, Nuno A. M.; Andrade, José S.; Herrmann, Hans J.

2014-10-01

38

Field Emission Current and Electrical Breakdown by a Pointed Cathode Coated with Carbon-Nano-Tube  

Microsoft Academic Search

Feature of field emission current and electrical breakdown was experimentally investigated for very short gap in the range of 0.1mum to 3mum between a pointed cathode coated with Carbon-Nano-Tube (CNT) and a plane anode in vacuum environment. The experimental setup, which consists of the CNT coated cathode, the stainless steel anode and the precise positioning mechanisms actuated by piezoelectric devices,

Yoshinori Hirata; Masayoshi Teramoto; Mizue Mizoshiri; Ukyo Ikeda; Takayoshi Ohji; Kimihiro Ozaki

2007-01-01

39

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

40

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

41

Simulation of Spectral Characteristics of Sprites From Runaway and Conventional Breakdown Processes and Comparison to Measurements  

NASA Astrophysics Data System (ADS)

The breakdown processes that lead to sprite formation are still being debated. Are sprites formed through conventional breakdown, runaway breakdown, or a combination of both? What are the thunderstorm electrical conditions that produce one or the other or both processes? This study describes the improved two-dimensional fully electromagnetic Unified Maxwell (UNIMAX) model and an updated methodology to derive the associated optical spectra using the Physics-based Optical Emission Model (POEM). These models allow us to study the differences between conventional and runaway breakdown processes and obtain a better understanding of what information can be garnered from sprite spectral measurements. A detailed kinetic computational tool, Plume, has been developed to compute the self-consistent evolution of a seed electron population with energies from 0 to 50 MeV in the presence of a steady-state, spatially-uniform electric field (see Colman et al. abstract submitted to this meeting). This information is used to compute steady-state emission rates as a function of the applied electric field for 13 Nitrogen and 3 Oxygen band systems. These rates can be combined with the number and energy of electrons from the UNIMAX sprite model and quantum transition information from POEM to separate the band system into individual lines and generate simulated spectral images. Cascading between different bands is also included. Spectral measurements of sprites represent a temporal and spatial superposition of emissions. These emissions emanate from a wide variety of electrical and gas discharge conditions that exist along the body of the sprite and which change as a function of time. Interpretation of the spectra to obtain the properties of the gas is made difficult by this inherent averaging process and the fundamental discharge mechanism can be obscured. Thus, we fold in the properties of spectrometers (i.e. spatial and temporal averaging, slit size, atmospheric absorption, etc.) to compare with measurements and assess the effect of temporal and spatial averaging. These spectra can then be used to elucidate what would be theoretically observed separately from runaway and conventional breakdown and to suggest potential measurements that could differentiate between the different processes.

Triplett, L. A.; Roussel-Dupre, R. A.; Colman, J. J.; Symbalisty, E. M.

2004-12-01

42

DOE Task Force meeting on Electrical Breakdown of Insulating Ceramics in a High Radiation Field  

SciTech Connect

This volume contains the abstracts and presentation material from the Research Assistance Task Force Meeting Electrical Breakdown of Insulating Ceramics in a High-Radiation Field.'' The meeting was jointly sponsored by the Office of Basic Energy Sciences and the Office of Fusion Energy of the US Department of Energy in Vail, Colorado, May 28--June 1, 1991. The 26 participants represented expertise in fusion, radiation damage, electrical breakdown, ceramics, and semiconductor and electronic structures. These participants came from universities, industries, national laboratories, and government. The attendees represented eight nations. The Task Force meeting was organized in response to the recent discovery that a combination of temperature, electric field, and radiation for an extended period of time has an unexplained adverse effect in ceramics, termed radiation-enhanced electrical degradation (REED). REED occurs after an incubation period and continues to accelerate with irradiation until the ceramics can no longer be regarded as insulators. It appears that REED is irreversible and the ceramic insulators cannot be readily annealed or otherwise repaired for future services. This effect poses a serious threat for fusion reactors, which require electrical insulators in diagnostic devices, in radio frequency and neutral beam systems, and in magnetic assemblies. The problem of selecting suitable electrical insulating materials in thus far more serious than previously anticipated.

Green, P.H. (comp.) [comp.

1991-08-01

43

Thickness Dependence of Electrical Breakdown in h-BN dielectric using C-AFM microscopy  

NASA Astrophysics Data System (ADS)

For nano-scale graphene transistor applications, hexagonal boron nitride (h-BN) is a highly desirable dielectric material that is being investigated not only because of its intrinsic properties but also because of its low lattice mismatch with hexagonal graphene. Currently, SiO2 limits the carrier mobility of graphene due to substrate phonon coupling. Therefore, h-BN can be employed for mobility enhancement beyond the values achievable on standard dielectric. Decreasing the device dimensionality however, requires a more detailed understanding of electrical breakdown at the nanoscale. We will present on the intrinsic breakdown electric field (EBF) of h-BN thin films in a metal-insulator-metal (MIM) configuration. This nanoscaled MIM structure is measured using conductive-atomic-force microscopy (C-AFM). Here, C-AFM is used to extract breakdown voltage for various thicknesses of mechanically exfoliated h-BN flakes. We measure the dielectric properties of h-BN flakes that vary from 2nm to 25nm and determine the ultimate scalability of hBN dielectrics.

Nayak, Avinash; Koh, Donghyi; Akinwande, Deji

2012-02-01

44

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

45

Experimental study of electric breakdowns in liquid argon at centimeter scale  

E-print Network

In this paper we present results on measurements of the dielectric strength of liquid argon near its boiling point and cathode-anode distances in the range of 0.1 mm to 40 mm with spherical cathode and plane anode. We show that at such distances the applied electric field at which breakdowns occur is as low as 40 kV/cm. Flash-overs across the ribbed dielectric of the high voltage feed-through are observed for a length of 300 mm starting from a voltage of 55 kV. These results contribute to set reference for the breakdown-free design of ionization detectors, such as Liquid Argon Time Projection Chambers (LAr TPC).

A. Blatter; A. Ereditato; C. -C. Hsu; S. Janos; I. Kreslo; M. Luethi; C. Rudolf von Rohr; M. Schenk; T. Strauss; M. S. Weber; M. Zeller

2014-01-26

46

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

47

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

48

Dielectric breakdown via emergent nonequilibrium steady states of the electric-field-driven Mott insulator  

NASA Astrophysics Data System (ADS)

In this work, we explore the possibility of emergent nonequilibrium steady states arising from the electric-field-driven Mott insulator via the Keldysh-Floquet dynamical mean-field theory (DMFT), which can determine the fully interacting, nonequilibrium steady-state Green's functions with the noninteracting counterparts as an input to the DMFT self-consistency loop. Unlike the retarded component, obtaining the lesser Green's function for the noninteracting system presents an important obstacle since the thermalization of the noninteracting system still requires a precise understanding of the dissipation mechanism. A crucial breakthrough in this work is that the noninteracting lesser Green's function can be determined in terms of the Wannier-Stark ladder (WSL) eigenstates, which are thermalized via the standard canonical ensemble according to the Markovian quantum master equation. As a result, it is shown that the intricate interplay between strong correlation and large electric field can generate a sequence of two dielectric breakdowns with the first induced by a coherent reconstruction of the midgap state within the Mott gap and the second by an incoherent tunneling through the biased Hubbard bands. It is predicted that the reconstructed midgap state generates its own emergent WSL structure with a reduced effective electric field. The two dielectric breakdowns are mediated by a reentrant insulating phase, which is characterized by the population inversion, causing instability toward inhomogeneous current density states at weak electron-impurity scattering.

Lee, Woo-Ram; Park, Kwon

2014-05-01

49

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

50

Electrical measurements at the microscale: Air breakdown and silicon Coulomb blockade devices  

NASA Astrophysics Data System (ADS)

In this thesis I describe the work performed in two different areas of research, electrical breakdown of air for small electrode separations and measurements of silicon (Si)-based tunable-barrier single electron transistors (SETs). In this work, I describe a new method for measuring the breakdown of air for the range of electrode separation of interest. This method has several advantages compared to ones found in the literature, namely it allows for a measurement of electrode separation before each breakdown measurement; it has a parallel plate geometry and the surface roughness of the electrodes used is very small. Using the results obtained with this method I have made a quantitative comparison between the predictions of the standard theory of the field (field emission of electrons) and our data, something that has not been done before. In this thesis I describe analytically both the theory and the analysis of our data. I conclude that the standard theory used in this field fails for the range of electrode separations of interest (400 nm to 45 mum). Also, I describe electrical measurements performed on a Si-based tunable-barrier device fabricated in the group of Neil Zimmerman at the National Institute of Standards and Technology (NIST) using the fabrication facilities of Cornell University. I demonstrate that this device can be operated as an SET. I continue by describing measurements of the charge offset drift (Q 0(t)) for this device and show that it is almost 3 orders of magnitude smaller than in metal devices, and comparable to previously measured Si devices of this type. All of the previously measured devices originated from the same fabrication source, NTT, Japan. Our ability to demonstrate the same low drift in devices fabricated at Cornell, USA, indicates that the small values of Q0(t) is a robust property of Si-based devices, and not sensitive to the details of fabrication.

Hourdakis, Emmanouel Spyros

51

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

52

A sem study of stainless steel electrodes before and after electrical breakdown in ultra-high vacuum  

NASA Astrophysics Data System (ADS)

Two stainless steel needle cathodes prepared in different ways were examined in a scanning electron microscope before and after electrical breakdown in ultra-high vacuum. On one very carefully prepared cathode no protusions could be found. which could explain field enhancement factors of the order of 10 to 100, as normally occur. On the other cathode a few non-metallic protrusions were present. After a few breakdowns four types of crater were found on the cathodes, three of which were situated at places where prior to breakdown, protrusions, inclusions or scratches and holes had been detected. After many breakdowns the rims of craters can act as field enhancing projections and the erosion occurred by preference at these places.

Beukema, G. P.

1981-03-01

53

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

54

Measuring the electrical breakdown of air for very small electrode separations  

NASA Astrophysics Data System (ADS)

Understanding the basic principles of electrical breakdown in air for small electrode separations is becoming very important in the design and operation of microscale devices such as MEMS sensors and actuators. This work presents a new method [1] for measuring the value of breakdown voltage in air for electrode separations from 400 nm to 45 ?m. The method consists of bringing 2 evaporated Au electrodes on sapphire together in a parallel plate geometry. Amongst the improvements of our method are the measurement of plate separation and the very small surface roughness ( average of 6 nm ). We demonstrate the ability to deduce the value of the separation of the plates by the value of the capacitance. We analyze the data for small separations, using the theory of standard field emission and field amplification on the surface of a conductor. We come to a prediction about the geometry and size of the electrode surface protrusions that would produce the observed emission. For the first time, we look for these predicted protrusions using an AFM. We find several reasons why the standard theory does not appear to explain our data. [1] Rev. Sci. Instrum. 77, 034702 (2006)

Hourdakis, Emmanouel; Bryant, Garnett W.; Zimmerman, Neil M.

2006-10-01

55

Ignition characteristics of methane/air premixed mixture by microwave-enhanced laser-induced breakdown plasma.  

PubMed

A microwave-enhanced plasma generation technique was combined with laser-induced ignition to improve ignition characteristics. A locally intensified microwave field was formed near the laser-induced breakdown plasma. As the plasma absorbed the microwaves, the plasma emission intensity increased. The plasma lifetime could be controlled by changing the microwave oscillation duration. Furthermore, the microwave-enhanced laser-induced breakdown plasma improved the minimum ignition energy of the methane/air pre-mixture with just a small amount of absorbed microwave energy. PMID:24514928

Nishiyama, Atsushi; Moon, Ahsa; Ikeda, Yuji; Hayashi, Jun; Akamatsu, Fumiteru

2013-11-01

56

Electrical breakdown at low pressure in the presence of a weak magnetic field  

SciTech Connect

Electron trapping in crossed electric and magnetic fields is an important mechanism by which electrical discharges can develop in low pressure gases. The authors report observations of discharges produced by this mechanism around a spherical anode in two space simulation chambers, namely the Space Plasma Interaction Experiment (SPIE) at the University of Maryland, and the NASA-Lewis B-2 chamber. They have identified two types of discharges in these experiments. In the B-2 chamber, the breakdown takes the form of a runaway dischage with spherical topology, limited only by the ability of the power supply to provide the current. In the SPIE chamber this type of discharge also occurs, in addition to a low current toroidal discharge which is observed at higher magnetic fields. They present measurements of both types of discharge and show how the trapping effect of the magnetic field together with secondary electron emission by high energy ion bombardment of the chamber walls may initiate and sustains these discharges.

Alport, M.J.; Antoniades, J.A.; Boyd, D.A.; Greaves, R.G.; Ellis, R.F. (Univ. of Maryland, College Park (United States))

1990-05-01

57

Electrical breakdown of multilayer MoS2 field-effect transistors with thickness-dependent mobility.  

PubMed

We report on the experimental investigation and modeling of electrical breakdown in multilayer (a few to tens of nanometers thick) molybdenum disulfide (MoS2) field-effect transistors (FETs). By measuring MoS2 devices ranging from 5.7 nm to 77 nm in thicknesses, we achieve a breakdown current of 1.2 mA, mobility of 42 cm(2) V(-1) s(-1), and on/off current ratio IOn/IOff ? 10(7). Through measurements and simulations, we find the dependence of the breakdown current limit on MoS2 thicknesses, channel lengths and conductivities. We also explore, both experimentally and analytically, the effects of different device parameters upon carrier mobility, which is directly related to the current carrying capacity. The results suggest that, compared to single-layer devices, multilayer MoS2 FETs could be advantageous for circuit applications requiring higher carrier mobility and power handling capacities. PMID:25219778

Yang, Rui; Wang, Zenghui; Feng, Philip X-L

2014-10-01

58

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

59

Electrical breakdown of multilayer MoS2 field-effect transistors with thickness-dependent mobility  

NASA Astrophysics Data System (ADS)

We report on the experimental investigation and modeling of electrical breakdown in multilayer (a few to tens of nanometers thick) molybdenum disulfide (MoS2) field-effect transistors (FETs). By measuring MoS2 devices ranging from 5.7 nm to 77 nm in thicknesses, we achieve a breakdown current of 1.2 mA, mobility of 42 cm2 V-1 s-1, and on/off current ratio IOn/IOff ~ 107. Through measurements and simulations, we find the dependence of the breakdown current limit on MoS2 thicknesses, channel lengths and conductivities. We also explore, both experimentally and analytically, the effects of different device parameters upon carrier mobility, which is directly related to the current carrying capacity. The results suggest that, compared to single-layer devices, multilayer MoS2 FETs could be advantageous for circuit applications requiring higher carrier mobility and power handling capacities.We report on the experimental investigation and modeling of electrical breakdown in multilayer (a few to tens of nanometers thick) molybdenum disulfide (MoS2) field-effect transistors (FETs). By measuring MoS2 devices ranging from 5.7 nm to 77 nm in thicknesses, we achieve a breakdown current of 1.2 mA, mobility of 42 cm2 V-1 s-1, and on/off current ratio IOn/IOff ~ 107. Through measurements and simulations, we find the dependence of the breakdown current limit on MoS2 thicknesses, channel lengths and conductivities. We also explore, both experimentally and analytically, the effects of different device parameters upon carrier mobility, which is directly related to the current carrying capacity. The results suggest that, compared to single-layer devices, multilayer MoS2 FETs could be advantageous for circuit applications requiring higher carrier mobility and power handling capacities. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03472d

Yang, Rui; Wang, Zenghui; Feng, Philip X.-L.

2014-10-01

60

Streak investigations of the initial phase of a subnanosecond pulsed electrical breakdown of high-pressure gas gaps  

NASA Astrophysics Data System (ADS)

The initiation and the development of a breakdown of highly overvoltaged high-pressure (from 4 to 40 atm) gas gaps by voltage pulses having the risetime of 1 ns or shorter are studied experimentally and in theoretical terms. The study revealed that ionization processes leading to the breakdown start in the gas volume and not from the surface of the electrodes. The gap flashover is followed by ionization wave processes initiating in the gas volume and playing the decisive role at the first phase of the breakdown. The dynamics of the ionization waves strongly depends on the initial distribution of free electrons over the gas gap. The distribution of ionization waves is analysed when the initial electrons are distributed uniformly and nonuniformly over the gap. The calculation results are in qualitative agreement with the relevant experimental data. It is shown that the propagation of the ionization waves at the initial stage of subnanosecond pulsed electrical breakdown of gas leads to a redistribution of the electric field in the discharge gap and a region of a strong field, whose intensity is sufficient for the onset of emission processes and the generation of a short beam of fast electrons near the cathode, is formed at the cathode for a very short (up to 100 ps) time.

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

2010-08-01

61

Invasion percolation model for abnormal time-dependent dielectric breakdown characteristic of low-k dielectrics due to massive metallic diffusion  

NASA Astrophysics Data System (ADS)

With the continuing aggressive scaling of interconnect dimensions and introduction of lower k materials, back-end-of-line (BEOL) dielectric time-dependent dielectric breakdown (TDDB) reliability margin is greatly reduced. In this paper, a comprehensive investigation on abnormal low-k TDDB characteristics, a systematic degradation of Weibull slopes, and a systematic increase of field acceleration at lower stress voltages due to massive Cu diffusion were conducted for Cu interconnect with low-k dielectric. Based on data from extensive electrical and physical analysis, such abnormal TDDB characteristics were attributed to slow metallic diffusion in bulk low-k under bias and temperature stress. A TDDB model based on invasion percolation was proposed to model the observed abnormalities. Cu interconnects with robust liner and capping layer, to ensure metal free low-k film, have become important for BEOL low-k TDDB.

Chen, Fen; Shinosky, Michael; Aitken, John; Yang, Chih-Chao; Edelstein, Daniel

2012-12-01

62

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

63

The influence of the sand-dust environment on air-gap breakdown discharge characteristics of the plate-to-plate electrode  

NASA Astrophysics Data System (ADS)

The experiments of plane-plane gap discharge was carried out in an environment of artificial sandstorm. By comparing and analyzing the differences in gap breakdown voltage between the sand & dust environment and clean air, some problems were investigated, such as effects of wind speed and particle concentration on the breakdown voltage, differences of gap discharge characteristics between the dust & sand medium and the clean air medium. The results showed that compared with the clean air environment, the dust & sand environment had a decreased gap breakdown voltage. The longer the gap distance, the greater the voltage drop; the breakdown voltage decreased with the increase of particle concentration in flow. With the increase of wind speed, the breakdown voltage decreased at the beginning and rose afterwards. The results of the paper may helpful for further research regarding the unidentified flashover and external insulation characteristics of the HV power grid in the dust & sand environment.

He, Bo; Zhang, Gang; Chen, Bangfa; Gao, Naikui; Li, Yaozhong; Peng, Zongren; Jin, Haiyun

2010-03-01

64

Electric field induced avalanche breakdown and non-volatile resistive switching in the Mott Insulators AM4Q8  

NASA Astrophysics Data System (ADS)

The Mott insulator compounds AM4Q8 exhibit a new type of volatile and non volatile resistive switchings that are of interest for RRAM application. We found that above a threshold electric field ETH of the order of a few kV/cm these compounds undergo a volatile resistive switching based on an avalanche process. For electric field much higher than the threshold avalanche breakdown field, the resistive switching turns non volatile. Our EDXS and STEM analyses show that the non volatile resistive switching originating from the avalanche breakdown can neither be ascribed to local chemical modifications nor to a local phase change with symmetry breaking at a resolution better than a few nanometer. This is in strong contrast with non volatile resistive switching reported so far that are all based on chemical or structural changes. Conversely, our results suggest that the avalanche breakdown induce the collapse of the Mott insulating state at the local scale and the formation of a granular conductive filament formed by compressed metallic domains and expanded “superinsulating” domains.

Corraze, B.; Janod, E.; Cario, L.; Moreau, P.; Lajaunie, L.; Stoliar, P.; Guiot, V.; Dubost, V.; Tranchant, J.; Salmon, S.; Besland, M.-P.; Phuoc, V. Ta; Cren, T.; Roditchev, D.; Stéphant, N.; Troadec, D.; Rozenberg, M.

2013-07-01

65

Electric field induced avalanche breakdown and non-volatile resistive switching in the Mott Insulators AM4Q8  

NASA Astrophysics Data System (ADS)

The Mott insulator compounds AM4Q8 exhibit a new type of volatile and non volatile resistive switchings that are of interest for RRAM application. We found that above a threshold electric field E TH of the order of a few kV/cm these compounds undergo a volatile resistive switching based on an avalanche process. For electric field much higher than the threshold avalanche breakdown field, the resistive switching turns non volatile. Our EDXS and STEM analyses show that the non volatile resistive switching originating from the avalanche breakdown can neither be ascribed to local chemical modifications nor to a local phase change with symmetry breaking at a resolution better than a few nanometer. This is in strong contrast with non volatile resistive switching reported so far that are all based on chemical or structural changes. Conversely, our results suggest that the avalanche breakdown induce the collapse of the Mott insulating state at the local scale and the formation of a granular conductive filament formed by compressed metallic domains and expanded "superinsulating" domains.

Corraze, B.; Janod, E.; Cario, L.; Moreau, P.; Lajaunie, L.; Stoliar, P.; Guiot, V.; Dubost, V.; Tranchant, J.; Salmon, S.; Besland, M.-P.; Phuoc, V. Ta; Cren, T.; Roditchev, D.; Stéphant, N.; Troadec, D.; Rozenberg, M.

2013-07-01

66

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

67

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

68

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

69

In situ transmission electron microscopy study of dielectric breakdown of surface oxides during electric field-assisted sintering of nickel nanoparticles  

NASA Astrophysics Data System (ADS)

The removal of ultra-thin oxide surface layers on nanometric nickel particles is investigated in the framework of electric field-induced dielectric breakdown. In situ transmission electron microscopy was used to directly apply electrical biasing to agglomerates of nanoparticles during simultaneous imaging of the contact area between two adjacent particles. The applied electrical field initiated dielectric breakdown of the surface layers through percolation of oxygen vacancies and the migration of oxygen away from the particle contact, which leads to the formation of metallic necks and their subsequent growth. The experimental results represent direct evidence for surface cleaning effects during electric field-assisted sintering.

Bonifacio, Cecile S.; Rufner, Jorgen F.; Holland, Troy B.; van Benthem, Klaus

2012-08-01

70

Initiation of Electrical Breakdown by Ionic Bombardment in a Vacuum Gap after Arc Extinction  

Microsoft Academic Search

This report presents a theoretical model of development of the post-arc gap breakdown in vacuum as a result of surface processes following cathode bombardment by energetic ions flowing from residual plasma after zero arc current. The most important surface processes for this model are sputtering and secondary electron emission. For a considerable group of metals, the sputtering yield Sr and

Z. ZALUCKIAND; J. Kutzner

1985-01-01

71

The electrical characteristics of solid insulators for 154 kV class HTS transformer  

NASA Astrophysics Data System (ADS)

HTS transformer, without any loss of insulation lifetime due to the reduction in terms of size and weight, can increase the overload capacity, and have some benefits such as the improvement in efficiency, minimization of environmental pollution, and convenient spatial arrangement, which contribute a lot to electric power system operation. However, for practical insulation design of the HTS transformer, it is necessary to establish the research on electrical properties LN 2 as well as solid insulators. These solid insulators have been used as main insulations for HTS transformer. In this paper, we discussed breakdown and V- t characteristics of glass fiber reinforced plastics (GFRP) and pressboard in LN 2.

Cheon, H. G.; Choi, J. H.; Pang, M. S.; Kim, W. J.; Kim, S. H.

2011-11-01

72

Electrical Characteristics of Ozone-Oxidized HfO2 Gate Dielectrics  

NASA Astrophysics Data System (ADS)

Electrical and reliability characteristics of HfO2 gate dielectrics prepared by low-temperature ozone (O3) oxidation of ultra thin Hf metal were investigated. Compared with control HfO2 annealed in O2 ambient, HfO2 annealed in O3 ambient exhibited excellent characteristics such as lower leakage current density, lower hysteresis, lower frequency dispersion, lower degree of charge trapping (? Vg), and larger charge to breakdown (Qbd) under electrical stress. The improved electrical and reliability characteristics can be attributed to the lower density of charge trap sites which are related to nonstoichiometry and oxygen vacancy. HfO2 prepared by O3 oxidation is a promising alternative gate dielectric for future metal-oxide-semiconductor (MOS) device applications.

Sim, Hyunjun; Chang, Hyosik; Hwang, Hyunsang

2003-04-01

73

Electric field changes generated by the preliminary breakdown for the negative cloud-to-ground lightning flashes in Malaysia and Sweden  

NASA Astrophysics Data System (ADS)

We present the study of the electric field changes generated by the preliminary breakdown for negative cloud-to-ground lightning flashes in Malaysia and Sweden concerning the association of slow field changes associated in preliminary breakdown process. We examined the total of 1685 negative cloud-to-ground lightning flashes from the total of 39 thunderstorms by recording the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our results show that there is a pre-starting time, i.e. the duration between the first preliminary breakdown pulse and slow field changes starting point, which is found to be after the first preliminary breakdown pulse. The pre-starting time has the arithmetic and geometric mean range from 1.4-6.47 and 1-3.36 ms, respectively. The mean values of pre-starting time in Malaysia are greater than the values observed in Sweden by more than a factor of 3. From the two data sets it shows that the slow field changes never start before the preliminary breakdown. Furthermore, the use of single-station electric fields measurement with high resolutions of 12 bits transient recorder with several nanosecond accuracy allow one to distinguish the slow field changes generated by preliminary breakdown, which preceded the negative first return stroke, between tens to hundreds of milliseconds of pre-return stroke duration.

Baharudin, Z. A.; Fernando, M.; Ahmad, Noor Azlinda; Mäkelä, J. S.; Rahman, Mahbubur; Cooray, Vernon

2012-08-01

74

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

75

Effects of the electrical stress on the conduction characteristics of metal gate\\/MgO\\/InP stacks  

Microsoft Academic Search

The degradation dynamics and post-breakdown current–voltage (I–V) characteristics of magnesium oxide (MgO) layers grown on n and p-type indium phosphide (InP) substrates subjected to electrical stress were investigated. We show that the current–time (I–t) characteristics during degradation can be described by a power-law model I(t)=I0t??, where I0 and ? are constants. It is reported that the leakage current associated with

E. Miranda; J. Martin-Martinez; E. O’Connor; G. Hughes; P. Casey; K. Cherkaoui; S. Monaghan; R. Long; D. O’Connell; P. K. Hurley

2009-01-01

76

A study of the influence of boron diffusion sources on the material and electrical characteristics of silicon p-n junctions  

E-print Network

of Silicon F-N Junctions. (December 19~&6) Ku~w-Chun Andrew Huang, B. S. , exas ARM University Chairman of Advisory Committee: Dr. W. A. Porter Mater' al and electrical characteristics of semiconductor- . junctions formed by impurity diffusion using... characteristics measurements include: surf'ace sheet resistance, junction dep . h, impurity profile, chemical etch, X-ray topography and X-ray diffractive power measurement Electrical characteristics measurements include: forward 'oias, reverse breakdown...

Huang, Kuan-Chun Andrew

2012-06-07

77

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

PubMed

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. PMID:24387484

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

2013-12-01

78

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

79

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

80

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

81

Characteristics of solid aerosols produced by optical catapulting studied by laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Optical catapulting (OC) constitutes an effective method to transport small amounts of different materials in the form of a solid aerosol. In this report, laser-induced breakdown spectroscopy (LIBS) is used for the analysis of those aerosols produced by OC. For this purpose, materials were catapulted using a Q-switch Nd:YAG laser. A second Q-switch Nd:YAG laser was used for LIBS analysis of the ejected particles. Data processing of aerosols was conducted using conditional data analysis. Also, the standard deviation method was used for the qualitative identification of the ejected particles. Two modes of interaction in OC (OC with focused or defocused pulses) have been evaluated and discussed. LIBS demonstrates that the distribution (spreading) of the ejected particles along the propagation axis increased as a function of the interpulse delay time. The mass density and the thickness of the target also play an important role in OC-LIBS.

Fortes, F. J.; Laserna, J. J.

2010-08-01

82

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

NASA Astrophysics Data System (ADS)

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.; Radjenovi?, B.; Radmilovi?-Radjenovi?, M.

2014-10-01

83

Extrapolation of electrical breakdown currents from the laboratory to Space Station  

NASA Technical Reports Server (NTRS)

Recent experiments conducted in a plasma chamber at NASA/MSFC on anodized aluminum coatings representative of Space Station Freedom design show that if the aluminum used as a thermal control coating is biased more than 80 V negative with respect to the plasma, the anodization will experience dielectric breakdown. As the thin anodization layer creates a capacitive charge buildup, large currents are observed during the arc. How plasma generation at the arc site can support large currents and discharge the surface charge layer is investigated. The importance for Space Station Freedom is that currents similar to those observed in the laboratory can be observed on orbit.

Vaughn, Jason A.; Carruth, Melvin R., Jr.; Katz, Ira; Mandell, Myron J.; Jongeward, Gary A.

1992-01-01

84

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

85

Polarization of the terahertz radiation of uniaxially compressed p germanium at the electrical breakdown of a shallow acceptor impurity  

SciTech Connect

The spectral and polarization investigations of spontaneous terahertz radiation under the conditions of the electrical breakdown of shallow acceptors (gallium) in germanium crystals have been reported. The radiation spectra of crystals uniaxially compressed in the [111] direction at a pressure of about 3 kbar, as well as undeformed crystals, have been measured at T = 5 K using a Fourier spectrometer with step scanning. The polarization of radiation has been estimated for transitions of holes between various states of a shallow acceptor in uniaxially compressed germanium. To identify the observed radiation lines, their experimental energies and polarizations have been compared to the respective calculated values. The spectral lines corresponding to the transitions of holes from the resonance state to the excited states of acceptors have been identified.

Andrianov, A. V., E-mail: alex.andrianov@mail.ioffe.ru; Zakhar'in, A. O.; Alekseev, P. S., E-mail: pavel.alekseev@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Kagan, M. S. [Russian Academy of Sciences, Kotel'nikov Institute of Radio Engineering and Electronics (Russian Federation)

2012-12-15

86

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

87

VERY LOW FREQUENCY BREAKDOWN PROPERTIES OF ELECTRICAL INSULATION MATERIALS AT CRYOGENIC TEMPERATURES  

SciTech Connect

For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0 1 Hz) has been used for conventional cables as a way of getting around the charging current limitation For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G 10 (fiberglass reinforced plastic or FRP), Cryoflex (TM) (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0 I Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.

Sauers, I. [Oak Ridge National Laboratory (ORNL); Tuncer, E. [Oak Ridge National Laboratory (ORNL); Polizos, G. [Oak Ridge National Laboratory (ORNL); James, D. R. [Oak Ridge National Laboratory (ORNL); Ellis, A. R. [Oak Ridge National Laboratory (ORNL); Pace, M. O. [Oak Ridge National Laboratory (ORNL)

2010-01-01

88

Very Low Frequency Breakdown Properties of Electrical Insulation Materials at Cryogenic Temperatures  

NASA Astrophysics Data System (ADS)

For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex™ (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0.1 Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.

Sauers, I.; Tuncer, E.; Polizos, G.; James, D. R.; Ellis, A. R.; Pace, M. O.

2010-04-01

89

VERY LOW FREQUENCY BREAKDOWN PROPERTIES OF ELECTRICAL INSULATION MATERIALS AT CRYOGENIC TEMPERATURES  

SciTech Connect

For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0.1 Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.

Sauers, I.; Tuncer, E.; Polizos, G.; James, D. R.; Ellis, A. R.; Pace, M. O. [Applied Superconductivity Group, Fusion Energy Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2010-04-08

90

VERY LOW FREQUENCY BREAKDOWN PROPERTIES OF ELECTRICAL INSULATION MATERIALS AT CRYOGENIC TEMPERATURES  

SciTech Connect

For long cables or equipment with large capacitance it is not always possible to conduct high voltage withstand at tests at 60 Hz due to limitations in charging currents of the power supply. Very low frequency (typically at a frequency of 0.1 Hz) has been used for conventional cables as a way of getting around the charging current limitation. For superconducting grid applications the same issues apply. However there is very little data at cryogenic temperatures on how materials perform at low frequency compared to 60 Hz and whether higher voltages should be applied when performing a high voltage acceptability test. Various materials including G10 (fiberglass reinforced plastic or FRP), Cryoflex (a tape insulation used in some high temperature superconducting cables), kapton (commonly used polyimide), polycarbonate, and polyetherimide, and in liquid nitrogen alone have been tested using a step method for frequencies of 60 Hz, 0.1 Hz, and dc. The dwell time at each step was chosen so that the aging factor would be the same in both the 60 Hz and 0.1 Hz tests. The data indicated that, while there is a small frequency dependence for liquid nitrogen, there are significant differences for the solid materials studied. Breakdown data for these materials and for model cables will be shown and discussed.

Sauers, Isidor [ORNL; Tuncer, Enis [ORNL; Polyzos, Georgios [ORNL; James, David Randy [ORNL; Ellis, Alvin R [ORNL; Pace, Marshall O [ORNL

2010-01-01

91

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 ...

92

Effect of tree channel conductivity on electrical tree shape and breakdown in XLPE cable insulation samples  

Microsoft Academic Search

The results of an investigation into electrical tree growth in XLPE cable insulation using an embedded needle electrode are reported for a range of voltages from 9 kV rms to 27 kV rms. The partial discharge (PD) activity and tree structures were measured simultaneously throughout the tree growth and the trees were recorded from initiation up to and including the

Xiangrong Chen; Yang Xu; Xiaolong Cao; S. J. Dodd; L. A. Dissado

2011-01-01

93

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

94

Relationship between the structure and electrical characteristics of diamond-like carbon films  

NASA Astrophysics Data System (ADS)

To elucidate the relationship between the structure and the electrical characteristics of diamond-like carbon (DLC) films, DLC films were synthesized in a well-controlled glow discharge with the aid of photoelectrons in an argon/methane atmosphere. The dielectric constant and breakdown strength of the films exhibited opposite behaviors, depending on the total pressure during the synthesis. The product of these two values decreased monotonically as the pressure increased. The Raman spectra were analyzed with a Voigt-type formula. Based on the results, the authors propose the "sp2 cluster model" for the DLC structure. This model consists of conductive clusters of sp2 carbons surrounded by a dielectric matrix sea of sp2 carbon, sp3 carbon, and hydrogen, and indicates that the dielectric constant of the whole DLC film is determined by the balance between the dielectric constant of the matrix and the total size of the clusters, while the breakdown strength is determined by the reciprocal of the cluster size. The model suggests that a high-? DLC film can be synthesized at a middle pressure and consists of well-grown sp2 clusters and a dense matrix. A low-? DLC film can be synthesized both at low and high pressures. The sp2 cluster model explains that a low-? DLC film synthesized at low pressure consists of a dense matrix and a low density of sp2 clusters, and exhibits a high breakdown strength. On the other hand, a low-? film synthesized at high pressure consists of a coarse matrix and a high density of clusters and exhibits a low breakdown strength.

Takabayashi, Susumu; Yang, Meng; Ogawa, Shuichi; Hayashi, Hiroyuki; Ješko, Radek; Otsuji, Taiichi; Takakuwa, Yuji

2014-09-01

95

Mechanical and Electrical Characteristics of Poly-Lactic Acid which Added Plasticizer  

NASA Astrophysics Data System (ADS)

Poly-lactic acid (PLA), a biodegradable plastic, has excellent electrical insulation properties. Being a hard resin, however, PLA is difficult to apply to coated cable. In this study, we blended a plasticizer with PLA to soften it, and examined the effects of the plasticizer on the mechanical and electrical characteristics of PLA. The glass transition temperature (Tg) and the melting point (Tm) had a tendency to decrease with an increase in the amount of plasticizer. With an increase in the amount of plasticizer, the tensile strength had a tendency to decrease and the breaking elongation to increase. As described above, PLA became softer with an increase in the amount of plasticizer. At 25°C, dielectric breakdown strength (EB) was about 5 MV/cm, irrespective of the presence of the plasticizer; the plasticizer showed almost no effect on EB. At 80°C, however, EB had a tendency to increase with an increase in the amount of plasticizer.

Shinyama, Katsuyoshi; Fujita, Shigetaka

96

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

97

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

98

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

E-print Network

to the con- ventional methods to form thin Al2O3 films, i.e., by sputter- ing, electron-beam evaporation, chemical vapor deposition, or oxidation of pure Al films, the atomic-layer-deposited ALD Al2O3 is of much Al2O3. A significant enhancement on breakdown electric field up to 30 MV/cm is observed as the film

Ye, Peide "Peter"

99

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

100

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

101

A simple model of photovoltaic module electric characteristics  

Microsoft Academic Search

Power electronics is used in an increasing number of applications as connecting element between photovoltaic modules and electric loads. The design of power converters for these applications needs to consider hereby the electrical characteristics of solar cells. To support this, a behavioural model has been developed to characterise current, voltage and power of photovoltaic modules as function of solar cell

Ulrich Böke

2007-01-01

102

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

103

New approach for electric breakdown field intensity determination in insulating liquids on an electrostatic energy stored basis  

Microsoft Academic Search

The breakdown for dielectric liquids has been the study of many investigators. Also it has attained the discussion and analysis under different theories. The present approach deals with the analysis of energy stored problem at electrode interface. The sphere plane configuration is used in the present analysis. In this paper the influence of the sphere radius and external applied pressure

A. El-Zein

1994-01-01

104

IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 47, NO. 1, JANUARY 2000 121 Electrical Conduction and Dielectric Breakdown in  

E-print Network

field, casting doubt on the suit- ability of high field stressing alone to predict the long-term and Dielectric Breakdown in Aluminum Oxide Insulators on Silicon James Kolodzey, Senior Member, IEEE, Enam Ahmed of metal--aluminum oxide--silicon. The aluminum oxide was produced by thermally oxidizing AlN at 800­1100 C

Kolodzey, James

105

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

106

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

107

Electrical characteristics of thunderstorms in the Eastern part of India  

NASA Astrophysics Data System (ADS)

Measurements of surface electric field made during the Pilot experiment to STORM at Kharagpur, India have been analyzed. During period of observations, i.e., from April 15 to May 31 2006, 14, thunderstorms were observed. Some electrical characteristic features of lighting associated with these thunderstorms are presented here. The electric field pattern shows that large number of negative electric field changes occur during mature stage of thunderstorm indicating removal of negative charge from overhead. Based on the polarity of electric field changes induced by lightning and shape of recovery curves, it is concluded that the most of thunderstorms in this region have positive-dipole type charge structure. These thunderstorms generally exhibit End-Of-Storm-Oscillation (EOSO).

Gopalakrishnan, V.; Pawar, S. D.; Murugavel, P.; Johare, Kirankumar P.

2011-08-01

108

Electrical Energy Density and Discharge Characteristics of a Poly(vinylidene fluoride-chlorotrifluoroethylene)Copolymer  

Microsoft Academic Search

The high electric displacement (D>0.1 C\\/m2) and breakdown field (600 MV\\/m) in polyvinylidene fluoride based polymers suggest high electrical energy density in this class of polymers. By defect modifications which reduce or eliminate the remnant polarization in the polymer, a high electrical energy density can indeed be obtained. This paper shows that in properly prepared P(VDF-CTFE) copolymer film capacitors, an

Xin Zhou; Baojin Chu; Bret Neese; Minren Lin; Q. M. Zhang

2007-01-01

109

On the electrical characteristics of complementary metamaterial resonators  

Microsoft Academic Search

In this letter, a method to obtain the electrical characteristics of complementary split ring resonators (CSRRs) coupled to planar transmission lines is presented. CSRRs have been recently proposed by some of the authors as new constitutive elements for the synthesis of metamaterials with negative effective permittivity, and they have been applied to the fabrication of metamaterial-based circuits in planar technology.

Jordi Bonache; Marta Gil; Ignacio Gil; Joan García-García; Ferran Martín

2006-01-01

110

Basic Studies on Chaotic Characteristics of Electric Power Market Price  

NASA Astrophysics Data System (ADS)

Recently, deregulation and reform of electric power utilities have been progressing in many parts of the world. In Japan, partial deregulation has been started from generation sector since 1995 and partial deregulation of retail sector is executed through twice law revisions. Through the deregulation, because electric power is traded in the market and its price is always fluctuated, it is important for the electric power business to analyze and predict the price. Although the price data of the electric power market is time series data, it is not always proper to analyze by the linear model such as ARMA because the price sometimes changes suddenly. Therefore, in this paper, we apply the methods of chaotic time series analysis, one of non-linear analysis methods, and investigate the chaotic characteristics of the system price of JEPX.

Takeuchi, Yuya; Miyauchi, Hajime; Kita, Toshihiro

111

Improvement in electrical characteristics of high-k Al2O3 gate dielectric by field-assisted nitric oxidation  

NASA Astrophysics Data System (ADS)

The authors perform a simple technique for the improvements in both current density reliability of high-k Al2O3 gate dielectrics. An Al2O3 was prepared by chemical oxidation at an appropriate electrical field in nitric acid at room temperature then furnace annealed at 650°C in N2. The interface trap-induced capacitance was used to investigate the interfacial property between the gate dielectric Si substrate. On the other hand the stress induced leakage current (SILC) was measured for characterizing the property of bulk oxide. It was found that the electrical characteristics of bulk oxide including leakage breakdown field SILC, were much improved without sacrificing interfacial property. The improvement can be ascribed to the compensation oxidation process.

Chuang, Kai-Chieh; Hwu, Jenn-Gwo

2006-12-01

112

A possible new mechanism involved in non-uniform field breakdown in gaseous dielectrics  

SciTech Connect

The electrical breakdown of gases under uniform field conditions is fairly well understood in terms of the Townsend`s breakdown theory. In most cases involving uniform fields, the breakdown voltage can be estimated via this theory using basic electron impact parameters for molecules in their ground electronic states. In contrast, a consistent model of gaseous breakdown under nonuniform fields is not available at present although substantial progress has been made recently. We point out the possibility that electron impact processes involving high-lying electronically-excited states may play a significant role under non-uniform field conditions. Thus, such processes may need to be included in order to obtain a better understanding of non-uniform field breakdown phenomena. The general, breakdown characteristics of highly non-uniform field gaps can be illustrated by that for a point-plane geometry. It has been found that the breakdown voltage for such a gap can be calculated by a simple streamer criterion if the pressure P, is above a critical value, P{sub c}; for P < P{sub c}, the estimated breakdown voltage is found to coincide with the corona inception voltage, with the actual breakdown occurring at a higher voltage, corona discharges occur only for P < P{sub c}. In other words, the presence of corona in the pressure region below P{sub c} seems to prevent the breakdown from occurring at the predicted value. This has led to the term ``corona stabilization`` to describe the enhancement in the breakdown voltage for pressures below P{sub c}. Non-uniform field breakdown measurements in gases will be discussed. We will discuss the possibility that the ``corona stabilization`` is due to the prevention of avalanche progression by attachment of free electrons to molecules in their high-lying electronically-excited states. Information on electron attachment to electronically-excited states of molecules was not available up until the late 1980`s.

Pinnaduwage, L.A.; Christophorou, L.G.

1994-06-01

113

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

114

Low-temperature (77-300 K) current-voltage characteristics of 4H-SiC p{sup +}-p-n{sup +} diodes: Effect of impurity breakdown in the p-type base  

SciTech Connect

The effect of impurity breakdown on the low-temperature (77-300 K) current-voltage (I-V) characteristics of 4H-SiC diodes with a p-type base has been studied. Experimental samples were fabricated from CVD-grown (chemical vapor deposition) commercial p{sup +}-p-n{sup +} 4H-SiC structures. A high electric field in the p-type base was created by applying a forward bias to the diodes. It was found that, at temperatures of 136, 89, and 81 K, the commonly observed 'diode' portion of the I-V characteristics is followed by a portion in which the current grows more rapidly due to the impact ionization of frozen-out Al acceptor atoms in the ground (unexcited) state. At temperatures of 81 and 77 K, this portion is followed by one with a negative differential resistance due to the regenerative dynistor-like switching of the diode, caused by impact ionization of aluminum atoms in the excited state.

Ivanov, P. A., E-mail: Pavel.Ivanov@mail.ioffe.ru; Potapov, A. S.; Samsonova, T. P. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

2012-04-15

115

Dielectric breakdown of cell membranes.  

PubMed

With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 . 10(6) V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector voltage (or the electric field strength in the orifice) depends on the membrane composition (or the intrinsic membrane potential) as revealed by measuring the critical voltage in E. coli B harvested from the logarithmic and stationary growth phases. The critical detector voltage increased by about 30% for a given volume on reaching the stationary growth phase. PMID:4611517

Zimmermann, U; Pilwat, G; Riemann, F

1974-11-01

116

Dielectric Breakdown of Cell Membranes  

PubMed Central

With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 · 106 V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector voltage (or the electric field strength in the orifice) depends on the membrane composition (or the intrinsic membrane potential) as revealed by measuring the critical voltage in E. coli B harvested from the logarithmic and stationary growth phases. The critical detector voltage increased by about 30% for a given volume on reaching the stationary growth phase. PMID:4611517

Zimmermann, U.; Pilwat, G.; Riemann, F.

1974-01-01

117

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

118

The plasma arc torch -- its electrical and thermal characteristics  

SciTech Connect

The plasma arc torch is a very effective heating device. Plasma arc heating technology is very appropriate and essential for product manufacture and for remediating and protecting the environment. The plasma torch initiates and maintains a length of arc column, similar to a lightning bolt, and the electrically-conducting column is used in the conversion of electricity into heat energy. The format of the heat energy delivery is a low-mass, high-enthalpy gas. Heat energy is delivered by the plasma torch with a minimum of mass -- only about 2--3% of the mass delivery from a combustion heater that is delivering the same heat enthalpy. This virtually mass-less heat is ideal for promoting very rapid physical changes and chemical changes in the material being heated. It is ideal for the pyrolysis (or gasification) of organic materials and for the vitrification (or melting) of inorganic materials -- processes that are desirable for new product manufacture and for environmental remediation and protection. Plasma arc heating technology has been perfected by industry during the last 20--30 years, and the industrial sector today is employing this unique heating source in product manufacture and, lately, in environmental remediation and protection processes. It is a cost-effective industrial heat source. The primary objective of this paper is to familiarize one with plasma heaters and their operating characteristics. The essential elements of the plasma arc torch: electrodes, insulators, gas injectors, water-cooling, electrical connectors, etc., are described and the electrical and thermal characteristics of this novel heating device are highlighted. An overview of today`s employment of plasma heating technology and a sample of some of today`s applications of the technology in the industrial sector in the United States and around the world are presented.

Camacho, S.L. [Plasma Technology Corp., Raleigh, NC (United States)

1995-12-31

119

Measurement of AC electrical characteristics of SSC superconducting dipole magnets  

SciTech Connect

Experiments were conducted to measure the AC electrical characteristics of SSC superconducting dipole magnets over the frequency range of 0.1 Hz to 10 kHz. A magnet equivalent circuit representing the magnet DC inductance, eddy current losses, coil-to-ground and turn-to-turn capacitance, was synthesized from the experimental data. This magnet equivalent circuit can be used to predict the current ripple distribution along the superconducting magnet string and can provide dynamic information for the design of the collider current regulation loop.

Smedley, K M [Superconducting Super Collider Lab., Dallas, TX (United States)] [Superconducting Super Collider Lab., Dallas, TX (United States); Shafer, R E [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States)

1992-01-01

120

Basic study of transient breakdown voltage in solid dielectric cables  

NASA Astrophysics Data System (ADS)

A comprehensive review of the technical and scientific publications relating to crosslinked polyethylene (XLPE) and ethylene propylene rubber (EPR) insulated cables revealed that there is very little known with respect to the life expectancy, the final factory voltage test background and the mechanism of voltage breakdown of these cables. A new methodology for the investigation of breakdown voltages of XLPE and EPR insulated cables was developed which is based on the investigation of breakdown voltages at various voltage transients such as unipolarity pulses and dual-polarity pulses, and a.c. voltage at power and high frequency. Also, a new approach to statistical testing was developed which allows one to establish a correlation among the breakdown voltages obtained with various voltage transients. Finally, a method for the determination of threshold voltage regardless of the magnitude of apparent charge was developed. A model of breakdown and electrical aging of XLPE and EPR insulated cables was developed as well as life expectancy characteristics for high voltage stress XLPE insulated cables operated in a dry environment at room temperature and at 900 C.

Bahder, G.; Sosnowski, M.; Katz, C.

1980-09-01

121

Dielectric Breakdown Lightning Model  

NSDL National Science Digital Library

The Dielectric Breakdown Lightning Model implements a common method for modeling lightning using a grid with regions of varying electric potential to simulate the electrical charge buildup during a lightning storm. To simulate the source of the lightning in the cloud, we set the potential to zero and place a small region of negative charge near the top of the grid. Along the bottom of the grid, we set the boundary potential to one to simulate the positive charge on the ground. All other grid points are given an initial electric potential equal to 0.5. After solving Laplace's equation, we examine all the grid points that are adjacent to a negative charge. We choose one adjacent point as the new growth site for the lightning, representing a point where the air is ionized and lightning will develop. The Dielectric Breakdown Lightning Model was developed as a final project in a sophomore-level Computational Physics course (Phy 200) using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the jar file will run the program if Java is installed. You can modify this simulation if you have EJS installed by right-clicking within the map and selecting "Open Ejs Model" from the pop-up menu item.

Castle, Sam

2012-06-16

122

Improved electrical and surface characteristics of metal-oxide-semiconductor device with gate hafnium oxynitride by chemical dry etching  

NASA Astrophysics Data System (ADS)

The electrical and surface characteristics of a metal-oxide-semiconductor (MOS) device with hafnium oxynitride (HfO xN y) gate dielectric treated with chemical dry etching (CDE) were investigated. The surfaces studied in this work include HfO xN y/Si surface and contact-hole-bottom Si surface. A CDE treatment was adopted to smooth surface morphology and to reduce carbon and fluorine residue contamination for TaN/HfO xN y/Si capacitors as well as to minimize the detrimental effects induced by plasma etching at N +/P junction. MOS devices with CDE treatment possess lower gate leakage current and dispersion, smaller stress-induced leakage current (SILC), and larger time to breakdown ( Tbd). N +/P junction with a suitable depth of CDE treatment exhibits a smaller ideality factor and reverse leakage current. The possible mechanism for the improvement is also discussed.

Cheng, Chin-Lung; Chang-Liao, Kuei-Shu; Wang, Tien-Ko

2006-02-01

123

The effect of the inversion channel at the AlN/Si interface on the vertical breakdown characteristics of GaN-based devices  

NASA Astrophysics Data System (ADS)

GaN-on-Si transistors attract increasing interest for power applications. However, the breakdown behavior of such devices remains below theoretical expectations, for which the Si substrate is typically made responsible. In this work, the effect of the thickness of an aluminum nitride buffer layer on the vertical breakdown voltage, measured relative to a grounded silicon substrate, has been investigated. A voltage-polarity-dependent breakdown mechanism has been observed. It has been found that the breakdown in the positive bias voltage regime is initiated by carrier injection, for which the carriers originate from an inversion channel formed between the epitaxial layers and the p-silicon substrate. TCAD simulations have confirmed the proposed explanations, and suggest that appropriate modification of the electronic structure at the AlN/silicon interface could significantly improve the vertical breakdown voltage.

Yacoub, H.; Fahle, D.; Finken, M.; Hahn, H.; Blumberg, C.; Prost, W.; Kalisch, H.; Heuken, M.; Vescan, A.

2014-11-01

124

Time dependent breakdown in silicon dioxide films  

NASA Technical Reports Server (NTRS)

An investigation was conducted regarding the possible existence of a time-dependent breakdown mechanism in thermal oxides of the type used as gate oxide in MOS circuits. Questions of device fabrication are discussed along with details concerning breakdown measurements and the determination of C-V characteristics. A relatively large prebreakdown current observed in one of the cases is related to the time-dependent breakdown.

Svensson, C.; Shumka, A.

1975-01-01

125

Lightning Initiation by Runaway Air Breakdown  

Microsoft Academic Search

The maximum macroscopic electric fields measured in thunderstorms are generally found to exceed the threshold for runaway breakdown and lie below the threshold for initiating conventional breakdown. In order for the conventional process that has been studied extensively in the laboratory to initiate lightning discharges it is necessary therefore to invoke the existence of field enhancements (e.g. around water droplets)

R. A. Roussel-Dupré; E. M. Symbalisty; A. V. Gurevich; K. Zybin; L. Babich; I. Kutsyk

2003-01-01

126

Thermal dielectric breakdown with cylindrical electrodes  

NASA Technical Reports Server (NTRS)

Solutions to the equations of thermal breakdown are computed for cylindrial electrodes with different boundary conditions. The development of the electric field and the temperature distributions are followed as functions of time, consequent on the application of a constant interelectrode voltage. The implications for possible breakdown by modes other than thermal are briefly discussed.

Beers, B. L.; Odwyer, J. J.

1983-01-01

127

Probabilistic description of traffic breakdowns.  

PubMed

We analyze the characteristic features of traffic breakdown. To describe this phenomenon we apply the probabilistic model regarding the jam emergence as the formation of a large car cluster on a highway. In these terms, the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which enables us to confine ourselves to one cluster model. We assume that, first, the growth of the car cluster is governed by attachment of cars to the cluster whose rate is mainly determined by the mean headway distance between the car in the vehicle flow and, maybe, also by the headway distance in the cluster. Second, the cluster dissolution is determined by the car escape from the cluster whose rate depends on the cluster size directly. The latter is justified using the available experimental data for the correlation properties of the synchronized mode. We write the appropriate master equation converted then into the Fokker-Planck equation for the cluster distribution function and analyze the formation of the critical car cluster due to the climb over a certain potential barrier. The further cluster growth irreversibly causes jam formation. Numerical estimates of the obtained characteristics and the experimental data of the traffic breakdown are compared. In particular, we draw a conclusion that the characteristic intrinsic time scale of the breakdown phenomenon should be about 1 min and explain the case why the traffic volume interval inside which traffic breakdown is observed is sufficiently wide. PMID:12188801

Kühne, Reinhart; Mahnke, Reinhard; Lubashevsky, Ihor; Kaupuzs, Jevgenijs

2002-06-01

128

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

129

Electrochemical breakdown of organic pollutants  

SciTech Connect

The dependence of the degree of purification of household sewage water by the electrochemical breakdown method on the specific quantity of electricity has been studied. The process can be described by a kinetic equation of a homogeneous reaction of the first order on the pollutions and anode products.

Kuz`menko, N.A.; Srago, I.A.; Penkina, N.V. [St. Petersburg Technology Institute (Russian Federation)] [and others

1993-11-10

130

Breakdown voltage of zinc and magnesium vapours  

NASA Astrophysics Data System (ADS)

In this paper the findings of a study into the electrical breakdown of zinc and magnesium metal vapours are reported. The interest in the breakdown of these vapours lies in the fact that there is a growing interest in producing zinc-magnesium coated articles using physical vapour deposition. For commercial scale operations which require a high power input, a disturbance by electrical breakdown of the metal vapour is unacceptable. Hence, knowledge of the breakdown voltage and pressure relation of these elements is essential in the engineering of a set-up. To determine the breakdown of these metal vapours, a Knudsen effusion cell is built. It is proven that the flow through the Knudsen cell does not change the minimum breakdown voltage or location of this minimum, and is a reliable apparatus for determining the zinc and magnesium vapour data. The outcome of the experiments show that the minimum breakdown for zinc is in agreement with the reported data in the literature, around 350 V. Magnesium has a much lower minimum breakdown voltage than that found for zinc, around 110 V. Furthermore, the locations of the minimum breakdown voltages of both zinc and magnesium are found at around 4-7 Pa m and 1.5 Pa m respectively.

Zoestbergen, E.; Commandeur, C.; Maalman, T.

2014-06-01

131

Insulation breakdown characteristics of UHV-class gas insulated switchgear for lightning impulse withstand voltage test waveform - K-factor value and front time related characteristics  

Microsoft Academic Search

The lightning impulse withstand voltage test waveform for electric power equipment is specified in IEC 60060-1 “High-voltage test techniques” as revised in 2010. At present, test standards for UHV-class equipment are under study. Increasing equipment capacity and the digitization of measuring equipment are mentioned as these backgrounds. Withstand voltage test by the standard waveform specified in the previous standard had

Toshihiro Tsuboi; Genyo Ueta; Shigemitsu Okabe; Makoto Miyashita; Kiyoshi Inami

2011-01-01

132

Influence of Plasma Wake Around Satellite Body on Characteristics of Electric Field Sensor  

Microsoft Academic Search

Knowledge of the characteristics of wire antennas in magnetized plasma used as sensors for electric field observations by scientific satellites in geospace is necessary to determine the absolute intensity and the phase of the electric field wave because the observation data about electric field are available as voltage signal. Two important characteristics are the effective length and the antenna impedance.

R. Higashi; T. Imachi; S. Yagitani

2007-01-01

133

A Study of Characteristics of Water Tree Growth by Electric Field Analysis  

NASA Astrophysics Data System (ADS)

Three-dimensional electric fields analysis was applied to the tip of water trees in XLPE cable. First, pre-breakdown detection was curried out on “needle-shaped” water trees. The results were analyzed by the three-dimensional electric field F.E.M. The water tree was simplified by a spheroid in the analysis. The position of the trees, length, tip radius were read from the microphotographs. The analysis was done on all 11 examples. The test results could be explained well when the conductivity of the water tree region was assumed to be 5×10-7S/m. Next, the electric fields of tip of three kinds of water tree (“blue”, “needle-shaped” and “white” water tree) were analyzed. Three kinds of water tree were expressed by changing the conductivity of water tree region. And, a distance from water trees to inside half conductor was made to change in three kinds. These were analyzed about the cable (insulation thickness: 3, 6, 9 mm) of 6.6, 22, 66 kV respectively. It was found out that “blue” and needle-shaped tree in the 66 kV cable and “blue” tree in the 22 kV cable may cause a breakdown under the operation voltage. As for other cases, the tree may propagate without making breakdown until it bridges the insulation. And, the possibility that the growth of “white” water tree declined rapidly in 66, the 22 kV cable when it touches inner semi-conducting layer so that the tip electric fields of the tree are the same as the average electric fields of the cable was suggested.

Nakade, Masahiko; Inoue, Daisuke

134

Breakdown of thin gate silicon dioxide films—A review  

Microsoft Academic Search

The main results of many years of research in the area of degradation and breakdown of thin (5 to 20 nm) silicon dioxide films are reviewed. The principal characteristics of the phenomenon are discussed: the actual meaning of intrinsic breakdown and its relation with the degradation of the oxide, the statistical nature of breakdown, the behavior under dynamic stresses, the

M. Nafría; J. Suñé; X. Aymerich

1996-01-01

135

Neutron effects on the electrical and switching characteristics of NPN bipolar power transistors  

NASA Technical Reports Server (NTRS)

The use of nuclear reactors to generate electrical power for future space missions will require the electrical components used in the power conditioning, control, and transmission subsystem to operate in the associated radiation environments. An initial assessment of neutron irradiation on the electrical and switching characteristics of commercial high power NPN bipolar transistors was investigated. The results clearly show the detrimental effects caused by neutron irradiation on the electrical and switching characteristics of the NPN bipolar power transistor.

Frasca, Albert J.; Schwarze, Gene E.

1988-01-01

136

Electrical characteristics of amorphous molybdenum-nickel contacts to silicon  

NASA Technical Reports Server (NTRS)

The electrical characteristics of sputtered, amorphous Mo-Ni contacts have been measured on both p- and n-type Si, as functions of composition (30, 54, and 58 at. percent Mo). The contact resistivity on both p(+) and n(+) Si is in the 0.00000 ohm sq cm range. The barrier height for as-deposited samples varies between phi-bp = 0.47-0.42 V on p-type Si and between phi-bn = 0.63-0.68 V on n-type Si, as the composition of the amorphous layer goes from Ni-rich to Mo-rich. The sum phi-bp + phi-bn always equals 1.12 V, within experimental error. After thermal treatment at 500 C for 1/2 h, the contact resistivity changes by a factor of two or less, while the barrier height changes by at most approximately 0.05 V. In light of these results, the amorphous Mo-Ni film makes good ohmic contacts to silicon.

Kung, K. T.-Y.; Nicolet, M.-A.; Suni, I.

1984-01-01

137

Characteristics of thermoplastics containing electrically conducting asymmetric particles - anisotropic electrical conductivity of injection molded parts and extrusion behavior  

Microsoft Academic Search

The characteristics of compounds of acrylonitrile-butadiene-styrene and high impact polystyrene resins filled with carbon fibers, steel fibers, carbon black, and aluminum flakes have been investigated with special emphasis on electrical conductivity and flow behavior in a capillary rheometer. Compression- and injection-molded compounds were found to be highly electrically anisotropic. The components of the electrical conductivity tensor, were measured. Generally, kappa-11,

Jan Martinsson; James L. White

1986-01-01

138

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

139

Microwave gas breakdown in elliptical waveguides  

NASA Astrophysics Data System (ADS)

This paper analyzes the microwave gas discharge within elliptical waveguides excited by the fundamental mode. The Rayleigh-Ritz method has been applied to solve the continuity equation. The eigenvalue problem defined by the breakdown condition has been solved and the effective diffusion length of the elliptical waveguide has been calculated, what is used to find the corona threshold. This paper extends the microwave breakdown model developed for circular waveguides and shows the better corona withstanding capabilities of elliptical waveguides. The corona breakdown electric field threshold obtained with the variational method has been compared with the one calculated with the Finite Elements Method, showing excellent agreement.

Koufogiannis, I. D.; Sorolla, E.; Mattes, M.

2014-01-01

140

Field Induced Chemistry to Prevent RF Breakdown in Fusion Applications  

Microsoft Academic Search

It is known that microprotrusions form in metallic electrodes in times less than 15mus, due to a combination of high temperature and electric fields. Microprotrusions are field-concentration points that may induce breakdown in antennas, which can degrade performance. We are studying the possibility of using the same concentrated electric fields that cause breakdown to induce chemical reactions that can either

C. H. Castano Giraldo; D. N. Ruzic; J. B. O. Caughman

2004-01-01

141

Investigation of the thermal mechanism of interelectrode breakdown in MHD generators  

NASA Astrophysics Data System (ADS)

The paper deals with a theoretical and experimental investigation of the thermal mechanism of breakdown in open-cycle MHD electrical power generators. An approximate theory is proposed for calculating the parameters of thermal breakdown in gaps of various width. Experimental results obtained with a K-1 MHD generator correlate well with the theory at insulating-wall temperatures above 1600 K, whereas the role of the electrical breakdown increases below this temperature. The fluctuation level of the electric field is found to be a major factor of breakdown; in the presence of fluctuations, there is a substantial decrease in breakdown voltage and breakdown time.

Bystryi, A. I.; Ganefeld, R. V.; Mazur, N. I.; Miroshnichenko, A. A.; Naletov, V. V.

1980-10-01

142

The breakdown phase in a coaxial plasma gun  

Microsoft Academic Search

The electrical breakdown in a coaxial plasma gun was investigated by means of optical and electrical measurements. The optimum start and operation conditions of the gun turned out to be strongly dependent on material and length of the cylindrical insulator.

A. Donges; G. Herziger; H. Krompholz; F. Rühl; K. Schönbach

1980-01-01

143

Electromagnetic Acceleration Characteristics of Laser-Electric Hybrid Thrusters  

SciTech Connect

A fundamental study on a laser-electric hybrid thruster was conducted, in which laser-induced plasmas were generated through laser beam irradiation on to a solid target and accelerated by electrical means instead of direct acceleration using only a laser beam. As two typical cases of the hybrid propulsion systems, a feasibility study on electrostatic acceleration mode and electromagnetic acceleration mode of the laser ablation plasma were conducted including thrust performance tests with a torsion-balance, ion current measurements, and ICCD camera observations. It was confirmed that the thrust performances could be improved with electric energy inputs.

Sasaki, Koki; Takeda, Akihito; Horisawa, Hideyuki [Department of Aeronautics and Astronautics, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa, 259-1292 (Japan); Kimura, Itsuro [University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8856 (Japan)

2006-05-02

144

Characteristics of Insulating Oil for Electrical Application. Final Report.  

National Technical Information Service (NTIS)

It has been established that the supply of naphthenic type of petroleum crudes historically used for the manufacture of electrical insulating oils is diminishing, and the oil companies have recommended that the more readily available paraffinic types of c...

T. K. Sloat

1979-01-01

145

CHARACTERISTICS OF IMPULSIVE NOISE IN ELECTRICITY SUBSTATIONS Qingshan Shan1  

E-print Network

sources may be significant distances from buildings where measurement equipment can be protected against Centre for Excellence in Signal and Image Processing 2 Centre for Intelligent Dynamic Communications, 3Institute for Energy & Environment Department of Electronic & Electrical Engineering, University

Atkinson, Robert C

146

Thermal and electrical characteristics of a multilayer thermionic device  

Microsoft Academic Search

We report our recent experimental and numerical investigation into the thermal and electrical transport in GaAs-AlGaAs semiconductor multilayer structures. Electrical and thermal conduction measurements were performed on multilayer structures to determine the temperature gradient across the sample. AuGe was used for top contact metallisation, and an InGa eutectic for bottom substrate contact. Metallisation contacts were also grown directly onto the

B. C. C. Lough; S. P. Lee; Z. Dou; R. A. Lewis; C. Zhang

2002-01-01

147

Breakdown phenomena in high power klystrons  

SciTech Connect

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. 9 refs., 5 figs., 3 tabs.

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

1988-03-01

148

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

149

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

150

Electrical characteristics of spark generators for automotive ignition  

NASA Technical Reports Server (NTRS)

This paper reports the results of an extensive program of measurements on 11 ignition systems differing widely in type. The results serve primarily to give representative data on the electric and magnetic constants of such systems, and on the secondary voltage produced by them under various conditions of speed, timing, shunting resistance, etc. They also serve to confirm certain of the theoretical formulas which have been proposed to connect the performance of such systems with their electrical constants, and to indicate the extent to which certain simplified model circuits duplicate the performance of the actual apparatus.

Brode, R B; Randolph, D W; Silsbee, F B

1927-01-01

151

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

152

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

153

Effect of the levels of intrinsic defects in the CdP{sub 2} band gap on electrical characteristics of corresponding structures with the Schottky barrier  

SciTech Connect

The electrical characteristics of Schottky barriers formed on n-type cadmium diphosphide are studied. It is established that the space-charge region at the metal-semiconductor interface represents in fact a Schottky layer formed owing to a high concentration of deep-level centers. The charge transport in the conducting direction for these structures is related to the above-barrier emission of electrons and is consistent with the diffusion theory for one or two types of charge carriers. The high concentration of ionized centers in the space-charge region gives rise to the tunneling mechanism of breakdown in the blocking direction. The frequency dependences of the complex conductance are governed by the exchange of charge carriers between the conduction band and donors that specify the conductivity type of the material and also by the recharing of the centers with a large depth of levels. Good agreement between the reported results and the theory is obtained.

Stamov, I. G., E-mail: istamov51@mail.ru; Tkachenko, D. V. [Dniester State University (Moldova, Republic of)

2006-10-15

154

Influence of Pore Size on Dielectric Breakdown in Plasma-polymerized Films  

NASA Astrophysics Data System (ADS)

For solid materials with gas-filled pores, dielectric breakdown is preceded by gas-phase partial discharge. As pore size shrinks, there is a limiting pore diameter where the number of gas molecules is insufficient to support phenomena depending on multiple gas phase events. Pores are an integral part of most plasma-polymerized materials. We are investigating dielectric breakdown in three plasma-polymerized organic films: acetylene, aniline and tetrathiafulvalene (TTF). Motivation for selecting these precursor molecules includes 1) obtaining very small pore sizes, 2) presence of pi bonds in a thoroughly studied material and 3) unique light emitting molecules, respectively. Preliminary results show that dielectric breakdown voltage follows a Weibull distribution. Electrical characterization of the films includes 1) low voltage (5-50 mV) ac impedance spectroscopy, 2) high voltage (1-1,000 V) variable frequency ac measurements of partial discharge and dielectric breakdown thresholds and 3) current-voltage characteristics for voltages below dielectric breakdown. Prospective applications include organic light emitting devices, organic insulators for electronic circuits, piezoelectric copolymer films and polymer-based sensors.

Pedrow, Patrick; Chang, Jen-Ho

2004-11-01

155

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

156

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

157

Theory of Dielectric Breakdown in Randomly Inhomogeneous Materials  

NASA Astrophysics Data System (ADS)

Two models of dielectric breakdown in disordered metal-insulator composites have been developed in an attempt to explain in detail the greatly reduced breakdown electric field observed in these materials. The first model is a two dimensional model in which the composite is treated as a random array of conducting cylinders embedded in an otherwise uniform dielectric background. The two dimensional samples are generated by the Monte Carlo method and a discretized version of the integral form of Laplace's equation is solved to determine the electric field in each sample. Breakdown is modeled as a quasi-static process by which one breakdown at a time occurs at the point of maximum electric field in the system. A cascade of these local breakdowns leads to complete dielectric failure of the system after which the breakdown field can be determined. A second model is developed that is similar to the first in terms of breakdown dynamics, but uses coupled multipole expansions of the electrostatic potential centered at each particle to obtain a more computationally accurate and faster solution to the problem of determining the electric field at an arbitrary point in a random medium. This new algorithm allows extension of the model to three dimensions and treats conducting spherical inclusions as well as cylinders. Successful implementation of this algorithm relies on the use of analytical forms for off-centered expansions of cylindrical and spherical harmonics. Scaling arguments similar to those used in theories of phase transitions are developed for the breakdown field and these arguments are discussed in context with other theories that have been developed to explain the break-down behavior of random resistor and fuse networks. Finally, one of the scaling arguments is used to predict the breakdown field for some samples of solid fuel rocket propellant tested at the China Lake Naval Weapons Center and is found to compare quite well with the experimentally measured breakdown fields.

Gyure, Mark Franklin

1990-01-01

158

Non-Uniform Field Breakdown and Surface Flashover in Liquid Nitrogen Gaps for HTS Applications  

SciTech Connect

Abstract: Liquid nitrogen (LN2) is used as a coolant and electrical insulation in many High Temperature Superconducting (HTS) applications. Hence a good understanding of the breakdown characteristics of this medium under a variety of practical electrode geometries and conditions is needed for design of high voltage equipment. While there is considerable literature on breakdown of LN2 gaps for uniform (plane-plane) or quasi-uniform electric fields (sphere-plane), there is much less data available for highly non-uniform field gaps and for surface flashover along insulators. In this paper we present results on sphere-plane and cylindrical rod-plane gaps in LN2 as a function of sphere and rod diameters and radius of the rod edge at 1 bar pressure. In addition the surface flashover voltages of Fiber-Reinforced Plastic (FRP) in LN2 with these electrode arrangements will also be reported.

James, David Randy [ORNL; Sauers, Isidor [ORNL; Tuncer, Enis [ORNL; Ellis, Alvin R [ORNL; Tekletsadik, Kasegn [Consultant, SuperPower, Inc.; Hazelton, Drew [SuperPower Incorporated, Schenectady, New York

2006-01-01

159

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

160

Electrical characteristics of metal-dielectric-semiconductor systems produced on epitaxial silicon structures with various dielectrics  

Microsoft Academic Search

An experimental study was made of MDS systems with silicon as semiconductor, for the purpose of determining the dependence of their electrical characteristics on the dielectric material. Epitaxial 10 micron thick films of n-Si with electrical resistivity RHO approx 0.8-1 ohm cm were grown on p-Si substrates with resistivity RHO = 10 oh.cm, and the field electrode with a surface

O. F. Fomicheva; L. A. Otavina; A. M. Sverdlova; G. G. Kapshtal

1984-01-01

161

Optical and RF electrical characteristics of atmospheric pressure open-air hollow slot microplasmas and application to bacterial inactivation  

NASA Astrophysics Data System (ADS)

We report electrical properties of radio frequency (RF)-driven hollow slot microplasmas operating in open air but with uniform luminous discharges at RF current densities of the order of A cm-2. We employ interelectrode separations of 100-600 µm to achieve this open-air operation but because the linear slot dimension of our electrode designs are of extended length, we can achieve, for example, open-air slot shaped plasmas 30 cm in length. This creates a linear plasma source for wide area plasma driven surface treatment applications. RF voltages at frequencies of 4-60 MHz are applied to an interior electrode to both ignite and sustain the plasma between electrodes. The outer slotted electrode is grounded. Illustrative absolute emission of optical spectra from this source is presented in the region from 100 to 400 nm as well as total oxygen radical fluxes from the source. We present both RF breakdown and sustaining voltage measurements as well as impedance values measured for the microplasmas, which use flowing rare gas in the interelectrode region exiting into open air. The requirement for rare gas flow is necessary to get uniform plasmas of dimensions over 30 cm, but is a practical disadvantage. In one mode of operation we create an out-flowing afterglow plasma plume, which extends 1-3 mm from the grounded open slot allowing for treatment of work pieces placed millimetres away from the grounded electrode. This afterglow configuration also allows for lower gas temperatures impinging on substrates, than the use of active plasmas. Work pieces are not required to be part of any electrical circuit, bringing additional practical advantages. We present a crude lumped parameter equivalent circuit model to analyse the effects of changing RF sheaths with frequency of excitation and applied RF current to better understand the relative roles of sheath and bulk plasma behaviour observed in electrical characteristics. Estimates of the bulk plasma densities are also provided. Finally, we present results of afterglow plasma based bacteria inactivation studies (Escherichia coli, Bacillus atrophaeus and B. atrophaeus spores) in which we employ the flowing afterglow plume from a hollow slot microplasma device rather than the active plasma itself, which is fully contained between electrodes.

Rahul, R.; Stan, O.; Rahman, A.; Littlefield, E.; Hoshimiya, K.; Yalin, A. P.; Sharma, A.; Pruden, A.; Moore, C. A.; Yu, Z.; Collins, G. J.

2005-06-01

162

Electrical derivative characteristics of InGaAsP buried heterostructure lasers with a rectifying contact  

SciTech Connect

Results of a study of the electrical derivative chartacteristics of 1.3-..mu..m InGaAsP buried heterostructure lasers with rectifying (nonlinear) electrical contacts are presented. A physical device model and an equivalent circuit model, including a metal-semiconductor contact, have been developed. This model is also appropriate to light emitting diodes and photodiodes. Solutions for the electrical derivative characteristics, dv/di and i dv/di vs i, of the equivalent circuit model are obtained and used to calculate the characteristics of 1.3-..mu..m InGaAsP buried heterostructure lasers both with and without a rectifying contact. The calculated electrical derivative characteristics are compared to measured data for our lasers. Excellent agreement between measured and modeled characteristics is obtained and the analysis is shown to be useful for extracting detailed metal-semiconductor and p-n junction characteristics with high accuracy. The physical basis for nonlinear contacts to optoelectronic devices made from relatively wide band-gap semiconductors such as InP and InGaAsP is described. The results of this study are useful for characterization, modeling, failure mode analysis, and process control improvement of these devices.

Wright, P.D.

1987-03-01

163

Controlling reversible dielectric breakdown in metal/polymer nanocomposites.  

PubMed

Composites comprising metal nanorods encased in a polymer matrix exhibit reversible electric breakdown and can be cycled between low- and high-conductance states multiple times without permanent damage to the material. The voltage at which the breakdown occurs can be adjusted by engineering the properties of the polymeric matrix, in particular by doping the polymer with dipole-possessing additives whose role is to screen the applied electric fields. PMID:22407933

Kim, Jiwon; Grzybowski, Bartosz A

2012-04-10

164

Modeling the breakdown statistics of Al2O3/HfO2 nanolaminates grown by atomic-layer-deposition  

NASA Astrophysics Data System (ADS)

The breakdown voltage statistics of Al2O3/HfO2 nanolaminate multilayer dielectrics fabricated by atomic layer deposition (ALD) are modeled within the percolation theory. Moreover, the nanolaminate breakdown properties are predicted from the breakdown statistics of the separate materials, thus providing a reliable breakdown design framework for nanolaminates. Comparison with experimental data suggests that the electric field in each of the dielectric layers, rather than the total gate voltage, is the variable that controls the breakdown statistics.

Conde, A.; Martínez, C.; Jiménez, D.; Miranda, E.; Rafí, J. M.; Campabadal, F.; Suñé, J.

2012-05-01

165

Physical characteristics of GE (General Electric) BWR (boiling-water reactor) fuel assemblies  

SciTech Connect

The physical characteristics of fuel assemblies manufactured by the General Electric Company for boiling-water reactors are classified and described. The classification into assembly types is based on the GE reactor product line, the Characteristics Data Base (CDB) assembly class, and the GE fuel design. Thirty production assembly types are identified. Detailed physical data are presented for each assembly type in an appendix. Descriptions of special (nonstandard) fuels are also reported. 52 refs., 1 fig., 6 tabs.

Moore, R.S.; Notz, K.J.

1989-06-01

166

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

167

Separation Characteristics of Submicron Particles in an Electrostatic Precipitator with Alternating Electric Field Corona Charger  

Microsoft Academic Search

Experiments were carried out to investigate filtration characteristics of an electrostatic precipitator (ESP) with alternating and direct electric field corona charger. Potassium Sodium Tartrate Tetrahydrate as the material was used to generate polydisperse submicron aerosols by using Constant Output Atomizer. The results indicated that the aerosol penetration through the ESP decreased as applied voltage increased. The maximum collection efficiency of

Wen-Yinn Lin; Yuan-Yi Chang; Chen-Ting Lien; Churng-Wen Kuo

2011-01-01

168

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

169

Investigation of the electrical characteristics of low-temperature thermionic power generators  

Microsoft Academic Search

The effectiveness of improving the output characteristics of thermionic electrical power generators by injecting oxygen into the electrode gap was studied at emitter temperatures between 1200 and 1400 C. The electrodes were of plane geometry. Tungsten (110) single crystals were used as the emitter material, and polycrystalline molybdenum or nickel (110) single crystals for the collectors. It is shown that

N. E. Menabde; V. K. Tskhakaia; L. M. Tsakadze; V. A. Iurev; V. N. Lebedev

1978-01-01

170

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

171

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

172

Second Discharge Characteristics of Aluminum Wire Electrical Explosion Under Various Argon Pressures  

NASA Astrophysics Data System (ADS)

Electrical wire explosion is a promising method for the preparation of metal nanopowder, but the properties of metal nanopowder are affected by the second discharge process of electrical wire explosion. The second discharge characteristics of aluminum wire electrical explosion under variant argon pressures were studied in a RLC discharge circuit. The results show that the curve of the second discharge voltages versus the pressure presents a U-shape. To clarify the roles of aluminum vapor and argon in the process of the second discharge, a spectrograph and a high speed framing camera were used to study the radiation spectrum and spatial distribution of the electrical explosion plasma. It is observed that argon participates in the second discharge process under low pressure. A discharge channel develops along the surface of the aluminum vapor. Under higher pressure, a second discharge takes place in the aluminum vapor and the discharge channel is inside the aluminum vapor.

Yan, Wenyu; Zhang, Qiaogen; Zhao, Junping; Chen, Gangliang; Liu, Longchen

2014-10-01

173

Batteries for electric drive vehicles: Evaluation of future characteristics and costs through a Delphi study  

SciTech Connect

Uncertainty about future costs and operating attributes of electric drive vehicles (EVs and HEVs) has contributed to considerable debate regarding the market viability of such vehicles. One way to deal with such uncertainty, common to most emerging technologies, is to pool the judgments of experts in the field. Data from a two-stage Delphi study are used to project the future costs and operating characteristics of electric drive vehicles. The experts projected basic vehicle characteristics for EVs and HEVs for the period 2000-2020. They projected the mean EV range at 179 km in 2000, 270 km in 2010, and 358 km in 2020. The mean HEV range on battery power was projected as 145 km in 2000, 212 km in 2010, and 244 km in 2020. Experts` opinions on 10 battery technologies are analyzed and characteristics of initial battery packs for the mean power requirements are presented. A procedure to compute the cost of replacement battery packs is described, and the resulting replacement costs are presented. Projected vehicle purchase prices and fuel and maintenance costs are also presented. The vehicle purchase price and curb weight predictions would be difficult to achieve with the mean battery characteristics. With the battery replacement costs added to the fuel and maintenance costs, the conventional ICE vehicle is projected to have a clear advantage over electric drive vehicles through the projection period.

Vyas, A.D.; Ng, H.K.; Anderson, J.L.; Santini, D.J.

1997-07-01

174

Properties of preliminary breakdown processes in Scandinavian lightning  

NASA Astrophysics Data System (ADS)

Lightning flashes are usually preceded by preliminary breakdown processes (PBPs) before a stepped leader is initiated. These breakdown processes are not well understood. An early model, the so-called BIL model, has been called into question in later studies. However, we have found that the BIL model is quite successful in describing initial processes at least in high-latitude Scandinavian lightning. We present results from one summer of measurements in Finland, during which the vertical electric field was measured with a standard broadband plate antenna system. Lightning flash locations were provided by a lightning detection network and magnetic fields were measured with an experimental narrowband detection system. The relationship between the preliminary breakdown and the first return stroke (RS) is studied for 193 flashes at distances of 5-70 km. We can identify a preliminary breakdown in at least 90% of the flashes. The peak electric field of the RS is on average four times as intensive as the highest peak of the PBP. However, in 25% of the cases the PBP peak is more intensive. On the other hand, we show that this method of comparing intensities is physically arbitrary, since the PBP is continuous and the RS is impulsive. The narrowband measurement allows a physically consistent definition for intensities as the root-mean-square (RMS) sum of the most intense parts of signals. The PBP and RS are shown to have almost equal intensities at small distances. At larger distances, the PBP weakens more rapidly. This is suggested to be due to different propagation regimes, with the PBP signal changing from space-wave to ground-wave propagation with increasing distance, while the RS is predominantly ground wave at all distances. The result may have practical applications in narrowband detection of lightning. The BIL model suggests a characteristic signal in the narrowband signal, which could be used to identify the start of a lightning flash. The change in the RS-PBP ratio as a function of distance is statistically significant, but is too weak to significantly improve ranging methods.

Mäkelä, Jakke S.; Porjo, Niko; Mäkelä, Antti; Tuomi, Tapio; Cooray, Vernon

2008-12-01

175

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

176

Self-repairing characteristics in the solid-state Al2O3 film capacitors  

NASA Astrophysics Data System (ADS)

The effect of the top electrode material on electrical characteristics of Al2O3 thin film capacitors has been investigated. Compared to devices with Pt top electrodes, devices using Al as the top electrode material exhibit a significantly reduced leakage current and a much higher breakdown strength. These electrical characteristics are linked to the anodic oxidation reaction, which makes the capacitors have the capability of self-repairing the defects in a high electric field.

Hu, Baofu; Yao, Manwen; Xiao, Ruihua; Chen, Jianwen; Yao, Xi

2014-07-01

177

Lightning electrical characteristics during tropical summer thunderstorm in North-East India  

NASA Astrophysics Data System (ADS)

The preliminary results of observation of the lightning electrical characteristics during tropical summer thunderstorms locally known as "Nor-Wester", at a hilly place in North-East India (23.50°N, 91.25°E) are reported here. Some distinct peaks are observed in the VLF range between 1.5 to 6 kHz. Average cloud conductivity is found to be 8.12×10-10 S m-1. Specific characteristics of integrated field intensity of sferics (IFIS) at 14 and 17 kHz are also studied. Average enhancement of electrical activity during thunderstorms is found to be 170 dB kHz-1 compared to the normal weather sferics intensity.

Guha, A.; de, B. K.

2009-08-01

178

Electrical and photovoltaic characteristics of Al\\/n-CdS Schottky diode  

Microsoft Academic Search

In this work, we have investigated the structure of the thermally evaporated CdS thin films. The electrical characteristics, such as capacitance–voltage CV and current–voltage IV measurements, of identically prepared Al\\/n-CdS structure were studied. The values of barrier height and ionized trap like-donors concentration were obtained from the reverse bias capacitance–voltage CV measurements at 1MHz under different temperatures in the range

A. A. M. Farag; I. S. Yahia; M. Fadel

2009-01-01

179

Optical and electrical characteristics of pure and doped potassium hydrogen tartrate single crystals  

Microsoft Academic Search

The optical and electrical characteristics of pure, sodium- and lithium-doped potassium hydrogen tartrate crystals grown by the gel technique are reported. An optical absorption study conducted in the UV-Vis range of 200-800 nm reveals the transparency of these crystals in the entire visible range but not in the ultraviolet range. The optical band gap of pure potassium hydrogen tartrate crystals

I. Quasim; A. Firdous; S. K. Khosa; P. N. Kotru

2009-01-01

180

Optical and electrical characteristics of pure and doped potassium hydrogen tartrate single crystals  

Microsoft Academic Search

The optical and electrical characteristics of pure, sodium- and lithium-doped potassium hydrogen tartrate crystals grown by the gel technique are reported. An optical absorption study conducted in the UV–Vis range of 200–800 nm reveals the transparency of these crystals in the entire visible range but not in the ultraviolet range. The optical band gap of pure potassium hydrogen tartrate crystals

I Quasim; A Firdous; S K Khosa; P N Kotru

2009-01-01

181

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

182

Electrical characteristics of an electrostatic valve used for bulk transport of agricultural seeds  

SciTech Connect

In an electrostatic valve used for bulk transport of agricultural seeds, the interparticulate electroclamping forces can be established by applying electric potential gradient between a separated pair of conducting electrode grids placed perpendicularly across the flow. The flow control of particulate material is thus achieved using no moving parts. When an electric field is applied, several types of electric field forces are generated, depending on the bulk and surface resistivities of the particles, the geometry of the electrodes, the applied field, and the geometry and the conductivity of the materials used for the transport channel. In this study the current-voltage characteristics of the valve were experimentally investigated for different flow control parameters. The triboelectrification of turnip seeds caused by the frictional contact on the channel walls was investigated and compared with the valve current. A range of wall liner materials with different electrical properties conductive to insulating were tested. The materials used for the wall liner did not significantly influence the current characteristics of the electrostatic valve. The effect of pulse duration of the applied potential on charge-to-mass ratio of the level of net charge acquired by the particles could be controlled by controlling the duty cycle of the electroclamping field.

Balachandran, W.; Machowski, W. [Brunel Univ., Uxbridge (United Kingdom). Dept. of Mfg. and Engineering Systems] [Brunel Univ., Uxbridge (United Kingdom). Dept. of Mfg. and Engineering Systems; Thompson, S.A.; Law, S.E. [Univ. of Georgia, Athens, GA (United States). Dept. of Biological and Agricultural Engineering] [Univ. of Georgia, Athens, GA (United States). Dept. of Biological and Agricultural Engineering

1999-03-01

183

A method of eliminating B-mode dielectric breakdown failure in gate oxides utilizing a charging phenomenon  

Microsoft Academic Search

An investigation of the dielectric breakdown characteristics of charged samples is discussed. B-mode dielectric breakdown failure was eliminated by scrubbing gate oxide films using a brush. Various scrubbing experiments revealed that this occurred due to charging to a voltage close to the intrinsic breakdown voltage of the gate oxide film. Other characteristics such as C-V curves and time-dependent dielectric breakdown

Tsuneo Ajioka; Akihiro Nara; Yukihiro Tominaga; Takatoshi Ushikoshi; Hironori Kitabayashi

1993-01-01

184

On-line determination of nanometric and sub-micrometric particle physicochemical characteristics using spectral imaging-aided Laser-Induced Breakdown Spectroscopy coupled with a Scanning Mobility Particle Sizer  

Microsoft Academic Search

Laser-Induced Breakdown Spectroscopy has been employed to detect sodium chloride and metallic particles with sizes ranging from 40 nm up to 1 µm produced by two different particle generators. The Laser-Induced Breakdown Spectroscopy technique combined with a Scanning Mobility Particle Sizer was evaluated as a potential candidate for workplace surveillance in industries producing nanoparticle-based materials. Though research is still currently under way

Tanguy Amodeo; Christophe Dutouquet; Olivier Le Bihan; Michel Attoui; Emeric Frejafon

2009-01-01

185

Breakdown of the continuum limit approximation to the discrete scattering events and its influence on the electric field autocorrelation functions of transmitted light  

NASA Astrophysics Data System (ADS)

The complexity of modeling light propagation in turbid media can be significantly simplified if one assumes it to be diffusive. This is, however, only valid after the light has traveled a sufficient distance so that the diffusion equation can be employed. So far, there has been no reliable way to determine this distance, despite the fact that the assumption is often applied in optics. The discrete nature of scattering events plays an important role in modeling propagation of weakly scattered light, so a continuum equation such as the diffusion equation cannot be used to describe this process. Electric field autocorrelation functions g1(? ) of light transmitted through turbid colloidal samples are measured using diffusing wave spectroscopy and compared to Monte Carlo simulations in order to obtain a better estimation of the continuum limit. The two methods to calculate g1(? ) from the simulated photon trajectories are compared; the first assumes the continuum limit by using the path-length distributions of photon trajectories, while the second considers the square momentum transfers and therefore accurately calculates g1(? ) even if the detected signal is composed of weakly scattered light. The results of the two methods are used to determine the lengths of the shortest diffuse photon trajectories; they grow with the sample thickness and scattering anisotropy.

Šormaz, Miloš; Reufer, Mathias; Völker, Andreas C.; Simon, Klaus

2014-11-01

186

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

187

Dependence of delivered energy on power conditioner electrical characteristics for utility-interactive PV systems  

SciTech Connect

In a utility-interactive photovoltaic system, the electrical characteristics of the dc-to-ac power-conditioning unit (inverter) influence the quantity of electrical energy delivered by the system, and therefore, affect the user worth of the system. An analysis of the effect of relevant inverter electrical characteristics on the quantity of system-delivered energy is undertaken using computer simulations of system behavior. Significant conclusions are that: (1) the annual system performance advantage of maximum-power-point voltage tracking is small compared with fixed-dc-input voltage operation; (2) low levels of inverter ac-power consumption during times of zero insolation can significantly degrade system performance; (3) the effect of small changes in the array-to-inverter size ratio on the user worth of the system is small; and (4) most of the system energy is delivered at power levels greater than one-half of the nominal array rating, and consequently, the inverter low-power efficiency is less important than is its full-power efficiency. A formula that approximates the inverter annual throughput efficiency with only four laboratory measurements on the inverter is presented.

Rasmussen, N. E.; Branz, H. M.

1981-01-01

188

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

189

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

190

Electrical characteristics of poly(methylsilsesquioxane) thin films for non-volatile memory  

NASA Astrophysics Data System (ADS)

In this communication the electrical characteristics of poly(methylsilsesquioxane) (PMSSQ) thin films and the possibility of charge storage in the Au nanoparticle embedded PMSSQ film base memory element have been studied. PMSSQ films were sandwiched between Al and Si electrodes to fabricate metal-polymer-semiconductor (MPS) structures. The conduction mechanism in PMSSQ films has been investigated. The charge transport mechanism appears to be space charge limited current (SCLC) at the higher-voltage region. Various electrical parameters such as reverse saturation current, barrier height, ideality factor, rectification ratio, shunt and series resistance and charge carrier mobility in PMSSQ have been determined. C-V analysis is performed to confirm the memory effect for Au nanoparticles embedded MPS structures. A definite clockwise hysteresis is observed which indicates the possibility of charge storage in the Au nanoparticles embedded PMSSQ film.

Ahmad, Zubair; Ooi, P. C.; Aw, K. C.; Sayyad, M. H.

2011-02-01

191

Water film motor driven by alternating electric fields: Its dynamical characteristics  

NASA Astrophysics Data System (ADS)

The “liquid film motor,” a novel device with important implications for basic research and technology, is analyzed. It works perfectly with both direct current (dc) and alternating current (ac) fields. We develop a mathematical model describing electrohydrodynamical (EHD) motions induced by ac fields, which are more complex and have wider technological applications than those produced by dc fields. The main characteristics of these motions, derived in our paper and in full agreement with the experimental ones, are as follows: (i) Rotation of the film requires that the frequencies of the ac fields are exactly the same and their magnitudes surpass a threshold, which depends on their phase difference. (ii) Vibrations may be induced by fields with different frequencies. (iii) The EHD motions strongly depend on the polarization induced by the external electric field. However, these motions are little affected by the liquid's electrical conductivity, viscosity, dielectric constant, and density. Our model also predicts several features, which have yet to be experimentally verified.

Liu, Zhong-Qiang; Zhang, Guang-Cai; Li, Ying-Jun; Jiang, Su-Rong

2012-03-01

192

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

193

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

194

Electrical and photovoltaic characteristics of sodium copper chlorophyllin\\/n-type silicon heterojunctions  

Microsoft Academic Search

Heterojunctions of p-type sodium copper chlorophyllin (p-SCC)\\/n-type silicon (n-Si) were prepared by deposition of p-SCC film on n-Si wafers using spray-pyrolysis technique. Current–voltage and capacitance–voltage measurements of Au\\/p-SCC\\/n-Si\\/In heterojunctions were performed to discuss the electrical properties of these heterostructures. Rectifying characteristics were observed, which are definitely of the diode type. The current–voltage measurements suggest that the forward current in these

A. A. M. Farag

2009-01-01

195

Improvement of electric characteristics of lead accumulators under the action of ultrasounds  

NASA Technical Reports Server (NTRS)

Results are given of experiments conducted in order to improve the electric characteristics of lead accumulators by ultrasonic irradiation of their electrolytes. The experimental results discussed complete the research conducted on static Le2, Le3 and D. Quaiser cells whose solutions were irradiated beforehand with ultrasounds of the frequency of 1 MHz. It is demonstrated that the discharge currents and capacitances of the investigated cells keep to higher values even 1 year after ultrasonic irradiation of the electrolyte. The experimental results are discussed.

Mihu, V. P.; Gavrila, I.

1974-01-01

196

Modelling of electric characteristics of capacitively coupled discharges including nonlinear effects of sheaths  

NASA Astrophysics Data System (ADS)

Electric characteristics of capacitively coupled discharges were calculated, including their nonlinear behaviour and generation of higher harmonic frequencies of discharge current and voltage. The discharge was modelled as a series combination of the bulk plasma, two nonlinear sheaths and a radio frequency generator. Comparison of the results of the model with an experiment is discussed. The model was used for studying the waveforms of discharge current and sheath voltages and generation of higher harmonic frequencies at a wide range of discharge parameters. Coupling of higher harmonic frequencies, discharge asymmetry and discharge voltage was demonstrated. The effects of plasma-sheath resonance and other phenomena on the discharge behaviour were shown.

Dvo?ák, P.

2013-08-01

197

The Effects of Corporate and Community Characteristics on Environmental Pollution in U.S. Electrical Generating Facilities: A Multilevel Examination  

E-print Network

This dissertation uses multilevel modeling to examine the effects of corporate and community characteristics on rates of sulfur dioxide emitted by facilities in the electrical power industry. The conceptual framework draws from ecostructural theory...

Touche, George 1967-

2011-05-18

198

Land-ocean contrast on electrical characteristics of lightning discharge derived from satellite optical measurements  

NASA Astrophysics Data System (ADS)

Comparative studies on the electrical properties of oceanic and continental lightning are crucial to elucidate air discharge processes occurring under different conditions. Past studies however have primarily focused on continental lightning because of the limited coverage of ground-based instruments. Recent satellite measurements by FORMOSAT-2/ISUAL provided a new way to survey the global characteristics of lightning and transient luminous events regardless of land and ocean. In this study, we analyze ISUAL/spectrophotometer data to clarify the electrical properties of lightning on a global level. Based on the results obtained by Cummer et al. [2006] and Adachi et al. [2009], the OI-777.4nm emission intensity is used to infer lightning electrical parameters. Results show a clear land-ocean contrast on the parameters of lightning discharge: in oceanic lightning, peak luminosity is 60 % higher and the time scale of return stroke is 30 % shorter. These results suggest higher peak current in oceanic lightning, which is consistent with the fact that elves, EMP-driven phenomena, also tend to occur over the ocean [Chen et al., 2008]. Further analysis of lightning events occurring around the Caribbean Sea shows that the transition-line of lightning electrical properties is precisely located along the coastline. We suggest that the differences in these electrical properties may be due to the boundary conditions (conductivity, surface terrain, etc). In this talk, based on the calibration with NLDN and Duke magnetometer data, current moment change and charge moment change will be globally evaluated using a complete set of the ISUAL-observed lightning events.

Adachi, T.; Said, R.; Cummer, S. A.; Li, J.; Takahashi, Y.; Hsu, R.; Su, H.; Chen, A. B.; Mende, S. B.; Frey, H. U.

2010-12-01

199

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

200

Study of flow-electrical field influence on withstanding characteristics of HV suspension insulators in sandstorm circumstance  

Microsoft Academic Search

In this paper, the withstanding characteristics (differences of withstanding voltage for sub-insulator on different position, influences of electrical field and flow field on withstanding voltage, etc.) of polluted suspension insulators in the sandstorm circumstance were investigated through the simulation experiments in laboratory. The results show that both electrical field and flow field have distinct effects on pollution deposition and withstanding

Bo He; Gang Zhang; Naikui Gao; Jun Wan; Bangfa Chen; Zongren Peng

2009-01-01

201

Analysis of Machining Characteristics in Additive Mixed Electric Discharge Machining of Nickel Based Super Alloy Inconel 718  

Microsoft Academic Search

Additive mixed electric discharge machining (AEDM) is a novel innovation for enhancing the capabilities of electrical discharge machining process. The objective of present research work is to study the influence of operating process input parameters on machining characteristics of nickel based super alloy (Inconel 718) in aluminium additive mixed EDM of with copper electrode. The effectiveness of AEDM process on

Anil Kumar; Sachin Maheshwari; Chitra Sharma; Naveen Beri

2011-01-01

202

Analysis of Machining Characteristics in Additive Mixed Electric Discharge Machining of Nickel-Based Super Alloy Inconel 718  

Microsoft Academic Search

Additive mixed electric discharge machining (AEDM) is a recent innovation for enhancing the capabilities of electrical discharge machining process. The objective of present research work is to study the influence of operating process input parameters on machining characteristics of nickel-based super alloy (Inconel 718) in aluminium AEDM with copper electrode. The effectiveness of AEDM process on Inconel is evaluated in

Anil Kumar; Sachin Maheshwari; Chitra Sharma; Naveen Beri

2011-01-01

203

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

204

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

205

Growth characteristics of different heart cells on novel nanopatch substrate during electrical stimulation.  

PubMed

During a heart attack, the heart's oxygen supply is cut off, and cardiomyocytes perish. Unfortunately, once these tissues are lost, they cannot be replaced and results in cardiovascular disease-the leading cause of deaths worldwide. Advancements in medical research have been targeted to understand and combat the death of these cardiomyocytes. For example, new research (in vitro) has demonstrated that one can expand cardiomyocyte adhesion and proliferation using polylactic-co-glycolic acid (PLGA) (50:50 (weight percent)) supplemented with carbon nanofibers (CNFs) to create a cardiovascular patch. However, the examination of other cardiovascular cell types has not been investigated. Therefore, the purpose of this present in vitro study was to determine cell growth characteristics of three different important cardiovascular cell types (aortic endothelial, fibroblast and cardiomyocyte) onto the substrate. Cells were seeded onto different PLGA:CNF ratio composites to determine if CNF density has an effect on cell growth, both in static and electrically stimulated environments. During continuous electrical stimulation (rectangle, 2 nm, 5 V/cm, 1 Hz), cardiomyocyte cell density increased in comparison to its static counterparts after 24, 72 and 120 hours. A minor rise in Troponin I excretion in electrical stimulation compared to static conditions indicated nominal cardiomyocyte cell function during cell experiments. Endothelial and fibroblast cell growth experiments indicated the material hindered or stalled proliferation during both static and electrical stimulation experiments, thus supporting the growth of cardiomyocytes onto the dead tissue zone. Furthermore, the results specified that CNF density did have an effect on PLGA:CNF composite cytocompatibility properties with the best results coming from the 50:50 [PLGA:CNF (weight percent:weight percent)] composite. Therefore, this study provides further evidence that a conductive scaffold using nanotechnology should be further research for various cardiovascular applications. PMID:25226907

Stout, David A; Raimondo, Emilia; Marostica, Giuliano; Webster, Thomas J

2014-01-01

206

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

207

Runaway Breakdown and Hydrometeors in Lightning Initiation  

NASA Astrophysics Data System (ADS)

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.

Gurevich, A. V.; Karashtin, A. N.

2013-05-01

208

Effects of strained layer near SiO2-Si interface on electrical characteristics of ultrathin gate oxides  

NASA Astrophysics Data System (ADS)

Ultrathin gate oxides formed by different process technologies are investigated in detail. The following important evidence is found: the discrepant result on the two time-dependent dielectric breakdown (TDDB) lifetime measurements, the constant-current stress, and the constant-voltage stress. The discrepancy is due mainly to the difference in the oxide leakage characteristics. Apparent changes in the activation energy and the defect generation rate during the TDDB testing are also experimentally observed for the two oxides formed by different process technologies. From the analysis based on the x-ray photoelectron spectroscopy by means of the oxide etch by dilute HF and the Fourier-transform infrared attenuated total reflection method, we consider that the above phenomena are induced by the difference in the built-in compressive strain of the Si-O network near the SiO2 and Si interface.

Eriguchi, Koji; Harada, Yoshinao; Niwa, Masaaki

2000-02-01

209

On-line determination of nanometric and sub-micrometric particle physicochemical characteristics using spectral imaging-aided Laser-Induced Breakdown Spectroscopy coupled with a Scanning Mobility Particle Sizer  

NASA Astrophysics Data System (ADS)

Laser-Induced Breakdown Spectroscopy has been employed to detect sodium chloride and metallic particles with sizes ranging from 40 nm up to 1 µm produced by two different particle generators. The Laser-Induced Breakdown Spectroscopy technique combined with a Scanning Mobility Particle Sizer was evaluated as a potential candidate for workplace surveillance in industries producing nanoparticle-based materials. Though research is still currently under way to secure nanoparticle production processes, the risk of accidental release is not to be neglected. Consequently, there is an urgent need for the manufacturers to have at their command a tool enabling leak detection in-situ and in real time so as to protect workers from potential exposure. In this context, experiments dedicated to laser-induced plasma particle interaction were performed. To begin with, spectral images of the laser-induced plasma vaporizing particles were recorded to visualize the spatio-temporal evolution of the atomized matter and to infer the best recording parameters for Laser-Induced Breakdown Spectroscopy analytical purposes, taking into account our experimental set-up specificity. Then, on this basis, time-resolved spectroscopic measurements were performed to make a first assumption of the Laser-Induced Breakdown Spectroscopy potentialities. Particle size dependency on the LIBS signal was examined. Repeatability and limits of detection were assessed and discussed. All the experiments carried out with low particle concentrations point out the high time delays corresponding to the Laser-Induced Breakdown Spectroscopy signal emergence. Plasma temperature temporal evolution was found to be a key parameter to explain this peculiarity inherent to laser/plasma/particle interaction.

Amodeo, Tanguy; Dutouquet, Christophe; Le Bihan, Olivier; Attoui, Michel; Frejafon, Emeric

2009-10-01

210

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

211

A quantitative physical model for time-dependent breakdown in SiO2  

Microsoft Academic Search

A quantitative physical breakdown model for thin SiO2 is developed. The physical mechanism responsible fcor oxide breakdown has been reexamined and found to be hole trapping at localized areas. A quantitative model is built on this physical understanding of the wearout mechanism. Using this model, which considers electron injection, hole generation and charge trapping during electrical stresses and their effects

I. C. Chen; S. Holland; C. Hut

1985-01-01

212

Breakdown in high voltage, high energy density multilayer ceramic capacitors  

NASA Astrophysics Data System (ADS)

Causes of breakdown, both mechanical and electrical, in high voltage, high energy density, BaTiO3 multilayer ceramic capacitors were studied. The flexural strength of the capacitors was 96 +/- 13 MPa. Failure was due to surface defects or pores close to the surfaces of the samples. The dielectric breakdown strength of the samples was 181 kV/cm. The causes of breakdown were either field enhancements due to electrode end effects or pores between the dielectric and electrode layers. Weibull statistics were used to determine if there was a correlation between mechanical failure and dielectric breakdown. A correlation between the two types of failure was not found in the study, in contrast to earlier studies of single dielectric layer capacitor materials. The one common source of failure was porosity although it was located in different regions of the capacitors. Liquid-phase sintering can be used to eliminate porosity and therefore was chosen to improve the electrical and mechanical strengths of the capacitors. A BaO B2O3 Al2O3 SiO2 glass was selected due to it high polarizability, and therefore higher dielectric constant (˜15), as a sintering aid to improve densification behavior. The glass (4-20 vol%) was added to pure BaTiO3 and the effects on the mechanical and electrical properties were studied. The liquid-phase sintered samples reached ˜99.8% of the theoretical density and the electrical breakdown strength were found to increase over the pure material. The breakdown strength of the samples containing 20 vol% glass additions was increased by a factor of 2.8 compared to pure BaTiO3. Overall, it was shown that liquid-phase sintering could be used to successfully fabricate high voltage, high energy density multilayer ceramic capacitors.

Young, Amanda

213

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

NASA Astrophysics Data System (ADS)

The effects of 2 MeV electron irradiation on the electrical characteristics of atomic layer deposited (ALD) high permittivity (high-k) layers of Al2O3, HfO2 and a nanolaminate of them are evaluated. Metal-oxide-semiconductor capacitors with a nominal dielectric physical thickness of 10 nm were fabricated on different p-type and n-type silicon substrates. The capacitance-voltage (C-V) and current-voltage (I-V) characteristics of the different structures are analyzed as a function of electron irradiation. A progressive negative shift of the C-V characteristics is observed with increasing electron irradiation, indicating the generation of effective positive charges. Similar generation rates for effective trapped charges and interface states are obtained for all the different high-k dielectric layers studied. The hysteresis of the C-V curves after irradiation increases in the case of Al2O3 samples, for HfO2 decreases while the irradiation has little impact on the hysteresis of the nanolaminate stack. A progressive increase of the leakage current with electron irradiation dose is observed for all the studied dielectrics. The analysis of the current-voltage characteristics measured at different temperatures point to Poole-Frenkel as the dominant conduction mechanism. Under the studied conditions, no impact of electron irradiation fluence on dielectric breakdown voltage has been appreciated.

Rafí, J. M.; Campabadal, F.; Ohyama, H.; Takakura, K.; Tsunoda, I.; Zabala, M.; Beldarrain, O.; González, M. B.; García, H.; Castán, H.; Gómez, A.; Dueñas, S.

2013-01-01

214

Some characteristics of polymers in composite materials and as electrical conductors  

NASA Technical Reports Server (NTRS)

The characteristics of carbon fibers (CF) made from polyacrylonitrile (PAN) materials are discussed, together with research on conducting polymers. CF materials have better mechanical properties, chemical inertness, and higher stiffness than metallic materials but are subject to environmental instability, flammability, and delamination fatigue. Polymerization procedures for the monopolymer PAN are described, noting the use of SEM and X-ray diffraction techniques for studying the fiber structure. High modulus and strength of CF are caused by covalent sp(2) bonds in hexagonal carbon rings, which are stronger than the same links in diamonds. Details of the molecular chain structures and macroformations, stress-strain as a function of temperature, and thermosetting and glass transition temperatures of polymers are provided. Computational quantum chemistry techniques are being applied to studying electrical conductance in polymers, mainly to discover ways to stabilize the materials. Doped CH(x) has exhibited photovoltaic properties and other polymers have become superconductors at cryogenic temperatures.

Hansen, C. F.

1982-01-01

215

The characteristics of Au:VO2 nanocomposite thin film for photo-electricity applications  

NASA Astrophysics Data System (ADS)

Au nanoparticles have been fabricated on normal glass substrates using nanosphere lithography (NSL) method. Vanadium dioxide has been deposited on Au/glass by reactive radio frequency (rf) magnetron sputtering. The structure and composition were determined by X-ray diffraction and X-ray photoelectron spectroscope. Electrical and optical properties of bare VO2 and Au:VO2 nanocomposite thin films were measured. Typical hysteresis behavior and sharp phase transition were observed. Nanopartical Au could effectively reduce the transition temperature to 40 °C. The transmittance spectrum for both Au:VO2 nanocomposite thin film shows high transmittance under transition temperature and low transmittance above transition temperature. The characteristics present the Au:VO2 nanocomposite thin film can be used for applications, such as “smart window” or “laser protector”.

Zhu, Yabin; Na, Jie; He, Fan; Zhou, Yueliang

2013-08-01

216

Study of bulk and elementary screw dislocations assisted reverse breakdown in low-voltage (<250 V) 4H-SiC p{sup +}n junction diodes. Part 1: DC properties  

SciTech Connect

Given the high-density ({approximately}10{sup 4} cm{sup {minus}2}) of elementary screw dislocations (Burgers vector = 1c with no hollow core) in commercial SiC wafers and epilayers, all large current (>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 (<250 V) small-area (<5 {times} 10{sup {minus}4} cm{sup 2}) 4H-SiC p{sup +}n diodes with and without elementary screw dislocations. Diodes containing elementary screw dislocations exhibited higher pre-breakdown reverse leakage currents, softer reverse breakdown current-voltage (I-V) knees, and highly localized microplasmic breakdown current filaments compared to screw dislocation-free devices. The observed localized 4H-SiC breakdown parallels microplasmic breakdown observed in silicon and other semiconductors, in which space-charge effects limit current conduction through the local microplasma as reverse bias is increased.

Neudeck, P.G. [NASA Lewis Research Center, Cleveland, OH (United States)] [NASA Lewis Research Center, Cleveland, OH (United States); Huang, W.; Dudley, M. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering] [State Univ. of New York, Stony Brook, NY (United States). Dept. of Materials Science and Engineering

1999-03-01

217

Fractal Dimension of Dielectric Breakdown  

Microsoft Academic Search

It is shown that the simplest nontrivial stochastic model for dielectric breakdown naturally leads to fractal structures for the discharge pattern. Planar discharges are studied in detail and the results are compared with properly designed experiments.

L. Niemeyer; L. Pietronero; H. J. Wiesmann

1984-01-01

218

Water film motor driven by alternating electric fields: its dynamical characteristics.  

PubMed

The "liquid film motor," a novel device with important implications for basic research and technology, is analyzed. It works perfectly with both direct current (dc) and alternating current (ac) fields. We develop a mathematical model describing electrohydrodynamical (EHD) motions induced by ac fields, which are more complex and have wider technological applications than those produced by dc fields. The main characteristics of these motions, derived in our paper and in full agreement with the experimental ones, are as follows: (i) Rotation of the film requires that the frequencies of the ac fields are exactly the same and their magnitudes surpass a threshold, which depends on their phase difference. (ii) Vibrations may be induced by fields with different frequencies. (iii) The EHD motions strongly depend on the polarization induced by the external electric field. However, these motions are little affected by the liquid's electrical conductivity, viscosity, dielectric constant, and density. Our model also predicts several features, which have yet to be experimentally verified. PMID:22587187

Liu, Zhong-Qiang; Zhang, Guang-Cai; Li, Ying-Jun; Jiang, Su-Rong

2012-03-01

219

Predictions of Ethylene Carbonate Breakdown & Solid Electrolyte Interphase (SEI) Onset  

E-print Network

and safety of many electrochemical systems for electrical energy storage depend on a critical solid-OH edges, liquid electrolyte, and state-of-the-air (if costly) AIMD simulations ·We discover multiple chemical mechanisms of electrolyte breakdown at explicit electrode-liquid electrolyte interfaces

Rubloff, Gary W.

220

Nanocrystalline non-stoichiometric SBT: Effect of milling duration on structural and electrical characteristics  

SciTech Connect

In the present work, nanocrystalline specimens of non-stoichiometric Strontium Bismuth Tantalate (SBT) ferroelectric ceramics were synthesized by mechanical activation process using a high energy planetary ball mill. The powders were milled for different milling durations (5, 10, 20 h) keeping the milling speed fixed at 300 rpm. Microstructural characterizations have been performed using X-ray diffraction, scanning electron microscopy, electron diffraction and transmission electron microscopy. Nanocrystallites with average grain size in the range of 30-50 nm are observed to be formed. Grain size is observed to decrease with increasing milling duration. Detailed dielectric study as a function of temperature has been carried out. It is observed that dielectric constant increases and dielectric loss decreases with increasing milling duration. The observed characteristics have been explained in terms of increased number of grain boundaries due to the reduction of granular size. - Highlights: Black-Right-Pointing-Pointer In the present work nano crystalline non-stoichiometric SBT has been synthesized. Black-Right-Pointing-Pointer The technique involved is mechanical activation (high energy ball milling). Black-Right-Pointing-Pointer The milling duration has been optimized. Black-Right-Pointing-Pointer Sr0.8Bi2.2Ta2O9 milled for 20 hours exhibit enhanced electrical characteristics.

Sugandha, E-mail: miglani.sugandha@gmail.com [Thin Film and Material Science Laboratory, Department of Applied Physics, Delhi Technological University (Formerly Delhi College of Engineering), Delhi-110042 (India); Jha, A.K., E-mail: Prof.akjha@gmail.com [Thin Film and Material Science Laboratory, Department of Applied Physics, Delhi Technological University (Formerly Delhi College of Engineering), Delhi-110042 (India); Department of Applied Sciences, Ambedkar Institute of Technology, GGSIPU, Geeta Colony, Delhi-110092 (India)

2012-03-15

221

Characteristics of microstructure and electrical resistivity of inkjet-printed nanoparticle silver films annealed under ambient air  

Microsoft Academic Search

The microstructure and electrical resistivity of inkjet-printed silver (Ag) films annealed under ambient air were characterized. Analyses of the impurity amounts in the films using secondary-ion mass spectrometry showed that the decomposition temperature of the capping molecules was just below 170°C. Both the characteristics of the microstructure and electrical resistivity when annealed at low temperatures (lower than the decomposition temperature)

J.-K. Jung; S.-H. Choi; I. Kim; H. C. Jung; J. Joung; Y.-C. Joo

2008-01-01

222

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

223

Electric Field Statistics and Modulation Characteristics of Bursty Langmuir Waves Observed in the Cusp  

NASA Astrophysics Data System (ADS)

The Twin Rockets to Investigate Cusp Electrodynamics (TRICE) were launched Dec. 10, 2007, from Andoya into the active cusp over Svalbard. The high-frequency electric field waveform receiver on the higher flying payload detected Langmuir waves concentrated at 900-1145 km on the downleg. The waves occurred in bursts having durations between tens of ms and a few hundred ms. From analysis of selected sample intervals, it is estimated that the rocket encountered more than 1000 such bursts ranging in amplitude from about 1 mV/m, near the detection threshold, to nearly 1000 mV/m, though only a few bursts approached this upper bound. Waveform analysis showed that the waves were modulated at kHz to tens of kHz frequencies. The modulation was not monochromatic but consisted of many nonstationary frequency components giving rise to a complex envelope waveform. The modulated waves were sufficiently oversampled to clearly observe 180-degree phase shifts when the envelopes of the modulations passed through zero, as expected if a superposition of modulating waves is responsible. Dynamic spectra of the bursts showed that the bandwidth of each event was related to the modulation frequencies. The dynamic spectra also revealed a repeatable pattern whereby the highest Langmuir wave frequency and largest bandwidth occurred in the center of each burst, with frequency and bandwidth decreasing toward either side of each burst. For the conditions of the observations (fpe ? fce/2), Langmuir waves convert to whistler mode waves, and the observed pattern may be explained by trapping of the Langmuir/whistler waves in density enhancements. The observed wave electric fields were statistically analyzed in two ways: First, the distribution of the absolute values of all of the electric field measurements was determined, hereafter referred to as the "waveform distribution"; second, the envelope of the Langmuir waves was extracted and the distribution of this field was determined, hereafter referred to as the "envelope distribution". The waveform distribution showed a characteristic E+1 dependence at low electric fields. Bandpass-filtering the waves with progressively narrower passbands preserved the E+1 dependence but with a sharper cutoff at the high-electric field end, approaching the analytical expectation for a rectified sine wave. The envelope distribution showed a steeper power-law index at low electric fields. Averaging the waveforms by factors of 10-300 produced waveform distributions with a power index comparable to that of the envelope distribution, as expected since averaging by 10 corresponded to half the wave period so that the resulting statistics were dominated by the envelope. Averaging by factors greater than about 300, corresponding to averaging times exceeding about half of the modulation period, led to waveform distributions that appeared Gaussian although they were not well defined due to the small number of points. The relation between the waveform and envelope distributions appeared to be well explained by recent analytical predictions confirmed by numerical calculations [Cairns et al., Statistics of Waveform and Envelope Fields: Theory, Simulations and Initial Applications to TRICE Data, EOS Trans. Am. Geophys. Union, 2008, this issue]. The observed envelope distributions also appear consistent with theory [Kletzing et al., Determination of the Envelope Distribution for Langmuir Waves in the Topside Ionosphere, EOS Trans. Am. Geophys. Union, 2008, this issue].

Labelle, J.; Cairns, I. H.; Kletzing, C. A.

2008-12-01

224

An experimental study on vortex breakdown in a differentially-rotating cylindrical container  

Microsoft Academic Search

The vortex breakdown phenomenon in a closed cylindrical container with a rotating endwall disk was reproduced. Visualizations were performed to capture the prominent flow characteristics. The locations of the stagnation points of breakdown bubbles and the attendant global flow features were in excellent agreement with the preceding observations. Experiments were also carried out in a differentially-rotating cylindrical container in which

Kazuyuki Fujimura; Hide S. Koyama; Jae Min Hyun

2004-01-01

225

A method to investigate the electron scattering characteristics of ultrathin metallic films by in situ electrical resistance measurements  

SciTech Connect

In this article, a method to measure the electrical resistivity/conductivity of metallic thin films during layer growth on specific underlayers is described. The in situ monitoring of an underlayer electrical resistance, its change upon the incoming of new material atoms/molecules, and the growth of a new layer are presented. The method is easy to implement and allows obtaining in situ experimental curves of electrical resistivity dependence upon film thickness with a subatomic resolution, providing insight in film growth microstructure characteristics, specular/diffuse electron scattering surfaces, and optimum film thicknesses.

Trindade, I. G.; Sousa, J. B. [IFIMUP and IN, Rua do campo Alegre, 687, 4169-007 Porto (Portugal); Department of Physics, FCUP, Rua do Campo Alegre, 687, 4169-007 Porto (Portugal); Fermento, R. [Instituto de Microelectronica de Madrid, Isaac Newton 8, 28760 Tres Cantos, Madrid (Spain); Leitao, D. [IFIMUP and IN, Rua do campo Alegre, 687, 4169-007 Porto (Portugal)

2009-07-15

226

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

227

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

228

Effect of Pressure on Chemical Reaction in a Liquid Phase Electrical Discharge Reactor  

Microsoft Academic Search

The effects of pressure on liquid phase electrical discharge was investigated using a stainless steel high pressure reactor combined with a high voltage pulse forming network. The initiation breakdown voltage was obtained under various pressures up to 1379000 pascal (200 psi). The discharge characteristics including current and voltage waveforms as well as power per pulse were recorded. The effect of

Kai-Yuan Shih; Radu Burlica; Wright C. Finney; Bruce R. Locke

2007-01-01

229

An electromagnetic vibrator fixed on a screen initiates gas breakdown in the subcritical field of a microwave beam  

NASA Astrophysics Data System (ADS)

Results of experimental investigation of the electric breakdown of air in a quasi-optical microwave beam with a deep subcritical field level are presented. The breakdown was initiated by a linear or ?-shaped electromagnetic (EM) vibrator fixed on a screen. It is established that a vibrator positioned above the screen at a distance shorter than quarter-wavelength of the EM field can induce the electric breakdown of air at high pressures and relatively low field level. Using a ?-shaped EM vibrator, it is possible to preset the spatial region of breakdown.

Aleksandrov, K. V.; Grachev, L. P.; Esakov, I. I.; Severinov, L. G.

2014-03-01

230

High-voltage atmospheric breakdown across intervening rutile dielectrics.  

SciTech Connect

This report documents work conducted in FY13 on electrical discharge experiments performed to develop predictive computational models of the fundamental processes of surface breakdown in the vicinity of high-permittivity material interfaces. Further, experiments were conducted to determine if free carrier electrons could be excited into the conduction band thus lowering the effective breakdown voltage when UV photons (4.66 eV) from a high energy pulsed laser were incident on the rutile sample. This report documents the numerical approach, the experimental setup, and summarizes the data and simulations. Lastly, it describes the path forward and challenges that must be overcome in order to improve future experiments for characterizing the breakdown behavior for rutile.

Williamson, Kenneth Martin; Simpson, Sean; Coats, Rebecca Sue; Jorgenson, Roy Eberhardt; Hjalmarson, Harold Paul; Pasik, Michael Francis

2013-09-01

231

Correlation between the nanoscale electrical and morphological properties of crystallized hafnium oxide-based metal oxide semiconductor structures  

NASA Astrophysics Data System (ADS)

The relationship between electrical and structural characteristics of polycrystalline HfO2 films has been investigated by conductive atomic force microscopy under ultrahigh vacuum conditions. The results demonstrate that highly conductive and breakdown (BD) sites are concentrated mainly at the grain boundaries (GBs). Higher conductivity at the GBs is found to be related to their intrinsic electrical properties, while the positions of the electrical stress-induced BD sites correlate to the local thinning of the dielectric. The results indicate that variations in the local characteristics of the high-k film caused by its crystallization may have a strong impact on the electrical characteristics of high-k dielectric stacks.

Iglesias, V.; Porti, M.; Nafría, M.; Aymerich, X.; Dudek, P.; Schroeder, T.; Bersuker, G.

2010-12-01

232

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

233

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

234

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

235

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

236

Estimation of aquifer hydraulic characteristics from electrical sounding data: the case of middle Imo River basin aquifers, south- eastern Nigeria  

Microsoft Academic Search

We have used the concept of Da - Zarrouk parameters (transverse unit resistance (R) and longitudinal conductance (C)) in porous media to determine aquifer hydraulic characteristics within the middle Imo river basin. The lithostratigraphic units within the study area include: Imo formation, Bende - Ameki formation, Ogwashi Asaba formation and Benin formation. The direct current electrical resistivity method was utilized

A. C. Ekwe; N. N. Onu; K. M. Onuoha

237

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

238

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

239

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.

240

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

241

Drive Control Scheme of Electric Power Assisted Wheelchair Based on Neural Network Learning of Human Wheelchair Operation Characteristics  

NASA Astrophysics Data System (ADS)

This paper describes a novel drive control scheme of electric power assisted wheelchairs based on neural network learning of human wheelchair operation characteristics. “Electric power assisted wheelchair” which enhances the drive force of the operator by employing electric motors is expected to be widely used as a mobility support system for elderly and disabled people. However, some handicapped people with paralysis of the muscles of one side of the body cannot maneuver the wheelchair as desired because of the difference in the right and left input force. Therefore, this study proposes a neural network learning system of such human wheelchair operation characteristics and a drive control scheme with variable distribution and assistance ratios. Some driving experiments will be performed to confirm the effectiveness of the proposed control system.

Tanohata, Naoki; Seki, Hirokazu

242

Soft breakdown of hafnium oxynitride gate dielectrics  

NASA Astrophysics Data System (ADS)

A detailed study of soft breakdown modes for hafnium oxynitride (HfON) gate dielectrics under stress is investigated. Two types of soft breakdown, digital and analog modes, are observed in HfON gate dielectrics, featuring gate voltage fluctuation accompanying random telegraph noise and nonswitching 1/f noise, respectively. The dependence of gate area, oxide thickness, and stress current density on breakdown modes is also studied. Thin oxide thickness and small gate area contribute to the enhancement of charge to breakdown (Qbd). Large Joule heat damage generated under stress inducing the analog soft breakdown for thick hafnium oxynitride films is proposed to clearly understand the breakdown of HfON gate dielectrics.

Wang, Jer Chyi; Shie, De Ching; Lei, Tan Fu; Lee, Chung Len

2005-07-01

243

Electric field-induced surface transformations and experimental dynamic characteristics of dielectric elastomer membranes  

Microsoft Academic Search

Acute and tunable surface transformations of a monolithic structure by application of an electric field have immediate significance for adaptive structures, morphing concepts and optical applications. Dielectric elastomer (DE) membranes are electric field-responsive materials typically employed as large strain electrostatic actuators. In this paper, it is demonstrated that an electric field will generate several symmetric surface shapes analogous to the

J. W. Fox; N. C. Goulbourne

2009-01-01

244

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

245

LIBS vs TRELIBS - The Relative Merits Of Laser-Induced Breakdown Spectroscopy Versus Time Resolved Laser-Induced Breakdown Spectroscopy  

NASA Astrophysics Data System (ADS)

LIBS - Laser-Induced Breakdown Spectroscopy - and TRELIBS - Time REsolved Laser-Induced Breakdown Spectroscopy - are relatively new techniques for obtaining analytical emissions from solid, liquid and gaseous samples. A pulsed laser is focused on the surface of a solid or liquid sample or focused in a gaseous sample, creating a transient plasma. Sample analytes emit characteristic radiation for upwards to tens of micro-seconds. The event is monitored spectrophotometically using LIBS, where the whole event is analyzed, or by TRELIBS, where the time resolution of the plasma event is analyzed.

Cadwell, L.; Belliveau, J.; Huwell, L.; Griffin, H.

1986-07-01

246

Collision and diffusion in microwave breakdown of nitrogen gas in and around microgaps  

NASA Astrophysics Data System (ADS)

The microwave induced breakdown of N2 gas in microgaps was modeled using the collision frequency between electrons and neutral molecules and the effective electric field concept. Low pressure breakdown at the threshold electric field occurs outside the gap, but at high pressures it is found to occur inside the microgap with a large threshold breakdown electric field corresponding to a very large electron oscillation amplitude. Three distinct pressure regimes are apparent in the microgap breakdown: a low pressure multipactor branch, a mid-pressure Paschen branch, both of which occur in the space outside the microgap, and a high pressure diffusion-drift branch, which occurs inside the microgap. The Paschen and diffusion-drift branches are divided by a sharp transition and each separately fits the collision frequency model. There is evidence that considerable electron loss to the microgap faces accompanies the diffusion-drift branch in microgaps.

Campbell, J. D.; Bowman, A., III; Lenters, G. T.; Remillard, S. K.

2014-01-01

247

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

248

A theoretical estimation of the pre-breakdown-heating time in the underwater discharge acoustic source  

NASA Astrophysics Data System (ADS)

One of the common characteristics of the electrothermal breakdown in an underwater discharge acoustic source (UDAS) is the existence of a pre-breakdown-heating phase. In our experiment, two phenomena were observed: (1) the breakdown time that takes on high randomicity and obeys a “double-peak" stochastic distribution; (2) the higher salt concentration that reduces the residual voltage and causes 100% non-breakdown. The mechanism of electrothermal breakdown is analysed. To specify the end of the pre-breakdown-heating phase, a “border boiling" assumption is proposed, in which the breakdown time is assumed to be the time needed to heat the border water around the initial arc to 773 K. Based on this ‘border boiling’ assumption, the numerical simulation is performed to evaluate the effects of two heating mechanisms: the Joule heating from the ionic current, and the radiation heating from the initial arc. The simulation results verify the theoretical explanations to these two experiment phenomena: (1) the stochastic distribution of the radius of the initial arc results in the randomicity of the breakdown time; (2) the difference in efficiency between the radiation heating and the Joule heating determines that, in the case of higher salt concentration, more energy will be consumed in the pre-breakdown-heating phase.

Wang, Yi-Bo; Wang, Shang-Wu; Zeng, Xin-Wu

2012-05-01

249

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

250

Degradation and Breakdown of W-La2O3 Stack after Annealing in N2  

NASA Astrophysics Data System (ADS)

We report the effect of relatively high-voltage stressing (under substrate injection) on the stress-induced leakage current (SILC) and breakdown of W-La2O3 stacked structures. It is shown that the gate area of the metal-insulator-semiconductor (MIS) devices under evaluation influences their final degradation characteristics after stress. Once the samples reach breakdown, their post-breakdown current-voltage (I-V) characteristics suggest that leakage spots are highly localized and are caused by the accumulation of defects.

Molina, Joel; Torres, Alfonso; Calleja, Wilfrido; Kakushima, Kuniyuki; Ahmet, Parhat; Tsutsui, Kazuo; Sugii, Nobuyuki; Hattori, Takeo; Iwai, Hiroshi

2008-09-01

251

Electrical characteristics of AlxGa1-xN Schottky diodes prepared by a two-step surface treatment  

NASA Astrophysics Data System (ADS)

Near-ideal Schottky barrier contacts to n-type Al0.22Ga0.78N have been developed by a two-step surface treatment technique. Plasma etching of the AlxGa1-xN surface prior to Schottky metal deposition, combined with sequential chemical treatment of the etched surface, holds promise for developing high quality low-leakage Schottky contacts for low noise applications and for recessed gate high electron mobility transistors. In this work, the effect of postetch chemical treatment of the n-type Al0.22Ga0.78N surface on the performance of the Ni /Au based Schottky contact has been investigated. Three different types of chemical treatment: viz, reactive ion etching, reactive ion etching plus dipping in hot aqua regia, and reactive ion etching plus dipping in hot KOH, are studied. Detailed current-voltage studies of three different surface treated diodes and a comparison with as-deposited diodes reveal significant improvement in the diode characteristics. The latter surface treatment yields Ni /Au Schottky diodes with very low reverse leakage currents, breakdown voltages greater than 44V, and an ideality factor as low as 1.14.

Motayed, Abhishek; Sharma, Ashok; Jones, Kenneth A.; Derenge, Michael A.; Iliadis, Agis A.; Mohammad, S. Noor

2004-09-01

252

Effect of the design and technology factors on electrical characteristics of the Au/Ti-n-GaAs Schottky diodes  

SciTech Connect

Electrical properties of the Au/Ti-n-GaAs Schottky diodes are studied in relation to the production technology. The forward and reverse current-voltage characteristics of the diodes at low electric fields are analyzed on the basis of the mechanism of thermionic emission through the metal-semiconductor barrier. It is assumed that an increase in the reverse currents in the voltage range from 20 to 60 V can be accounted for by the Pool-Frenkel effect. The excess reverse currents at voltages higher than 60 V are caused by the phonon-assisted tunneling via deep states in the depletion region of the semiconductor.

Zakharov, D. N., E-mail: vmk@elefot.tsu.ru; Kalygina, V. M. [Kuznetsov Siberian Physicotechnical Institute at the Tomsk State University (Russian Federation); Netudykhatko, A. V. [Research Institute of Semiconductor Devices (Russian Federation); Panin, A. V. [Russian Academy of Sciences, Institute of Strength Physics and Materials Science, Siberian Division (Russian Federation)], E-mail: pav@ispms.tsu.ru

2006-06-15

253

Frequency characteristics of skate electroreceptive central neurons responding to electrical and magnetic stimulation  

Microsoft Academic Search

Responses of single neurons in the lateral lobes of the medulla to stimulation of the electroreceptive system by homogeneous sinusoidal electrical and magnetic fields were investigated in acute experiments on the skateRaja radiata. Thresholds of neuronal responses to electrical stimulation varied from 0.03 to 10 µV\\/cm. The optimal frequency ranges for electrical and magnetic reception were in the regions of

Yu. N. Andrianov; G. R. Broun; O. B. Il'inskii; V. M. Muraveiko

1984-01-01

254

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

NASA Technical Reports Server (NTRS)

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.

1982-01-01

255

Design Methodology for Wideband Electrically Small Antennas (ESA) Based on the Theory of Characteristic Modes (CM).  

E-print Network

??Emerging broadband applications with market pressures for miniaturized communication devices have encouraged the use of electrically small antennas (ESA) and highly integrated RF circuitry for… (more)

Obeidat, Khaled Ahmad

2010-01-01

256

Dynamics and pattern formation during microwave breakdown at atmospheric pressure  

NASA Astrophysics Data System (ADS)

A self-organized array of plasma filaments moving towards the source has been recently observed in microwave breakdown experiments in the millimeter range at MIT (Y. Hidaka et al., Phys. Rev. Lett. 100, 035003 (2008)). These filaments are qualitatively different from the well-known filaments observed in laser breakdown, and develop transverse to the propagation direction, along the direction of the electric field polarization. A model coupling Maxwell's equations with a simple description of the plasma dynamics has been developed and has been shown to reproduce very well the experimental observations (J.P. Boeuf et al., Phys. Rev. Lett. 104, 015002 (2010)). The propagation of the plasma toward the source is due to an ionisation-diffusion mechanism and the self-organized filamentary structure is associated with the scattered field pattern. The filaments develop in the direction of the incident field due to field enhancement by polarization at their tip and form an array with a spatial period on the order of one quarter wave length. The physics and dynamics of the filamentary plasma array will be discussed in a first part, on the basis of comparisons between model and experimental results. In a second part other aspects of microwave breakdown at atmospheric pressure will be presented, such as the development of microwave streamers (that can absorb very efficiently the microwave energy under specific, resonant conditions), the formation of complex nets of plasma filaments during breakdown in an under-critical field (breakdown is initiated next to a metallic initiator and propagates, due to thermal instabilities, in a region where the microwave field is below the critical field). The context of applications of this study (plasma aided combustion and flow control, breakdown next to an antenna) will be presented briefly.

Boeuf, Jean-Pierre

2011-11-01

257

Electrical Characteristics of NTC Thermistor Ceramics Made of Mechanically Activated Fe2O3 Powder Derived from Yarosite  

NASA Astrophysics Data System (ADS)

Electrical characteristics of ceramics for NTC thermistor made of mechanically activated Fe2O3 powder which was derived from yarosite mineral has been studied. The powder of Fe2O3 was derived from yarosite mineral by precipitation and calcination. The powder was mechanically activated by blending using an electric blending machine. The ceramics were produced by pressing the calcined and activated powders to produce pellets and sintering the pellets at 1100 °C and 1200 °C for 1 hour in air. Electrical characterization was done by measuring electrical resistivity of the ceramics at various temperatures (25 °C-100 °C). Microstructure and structural analyses were carried out by using a Scanning Electron Microscope (SEM) and X-ray diffraction (XRD), respectively. The XRD analyses showed that the sintered ceramics had crystal structure of hexagonal (hematite). The presence of second phase could not be identified from the XRD analyses. From SEM data, it was known that the ceramics from activated powder had larger grains due to small size of the activated powder. According to the electrical data, it was known that the ceramics made of the activated powder had lower thermistor constant (B) and room temperature electrical resistivity (?RT). The value of B and ?RT of the produced ceramics fitted market requirement.

Syarif, D. Gustaman; Ramelan, A.

2008-03-01

258

The Explanation of the Photon's Electric and Magnetic Fields; and its Particle and Wave Characteristics  

Microsoft Academic Search

Using the principles of the Vortex Theory, the creation of the photon's electric and magnetic components are explained: the condensed region of space is responsible for creating the photon's electric component and its particle effect; its expansion and contraction is responsible for its frequency; its motion through three dimensional space creates a wave in the surrounding space. This wave is

Russell Moon; Victor Vasiliev

2007-01-01

259

Fabrication and electrical characteristics of TFTs based on chemically deposited CdS films, using glycine as a complexing agent  

Microsoft Academic Search

In this work, we report on the fabrication and electrical characteristics of thin film transistors (TFTs) using chemically deposited cadmium sulfide (CdS) thin films as the semiconductor active layer in back-gated devices. The CdS thin films were deposited by the chemical bath deposition (CBD) technique using glycine as the complexing agent. The CdS layers were deposited on SiO2\\/Si-n substrates and

T. Mendivil-Reynoso; D. Berman-Mendoza; L. A. González; S. J. Castillo; A. Apolinar-Iribe; B. Gnade; M. A. Quevedo-López; R. Ramírez-Bon

2011-01-01

260

Electrical characteristics of scaled CMOSFET's with source\\/drain regions fabricated by 7° and 0° tilt-angle implantations  

Microsoft Academic Search

The differences of electrical characteristics in trench-isolated n-well CMOSFET's with LDD- and EPS-regions fabricated by 7° and 0° tilt-angle phosphorous implantations are measured and qualitatively explained. The CMOSFET's have channel lengths ranging from 5 to 0.4 ?m and a channel width of 10 ?m. The differences in impurity profiles due to the channeling ions by 0°-implantation cause the clear changes

Takashi Ohzone; Mariko Yamamoto; Hideyuki Iwata; Shinji Odanaka

1995-01-01

261

Rapid thermal oxidation of silicon with different thermal annealing cycles in nitrogen: Influence on surface microroughness and electrical characteristics  

Microsoft Academic Search

The influence of two different thermal annealing cycles on the microroughness of the Si-SiO2 interface and on the electrical characteristics of the Si-SiO2 system has been investigated. Experiments were performed growing oxides by rapid thermal oxidation (RTO) and post-oxidation annealing in N2 using a slow cooling ramp recipe (SCRR) or a conventional pulsed thermal annealing recipe (PTAR). Compared to PTAR,

S. G. dos Santos Filho; C. M. Hasenack; M. C. V. Lopes; V. Baranauskas

1995-01-01

262

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

263

The characteristics of electrical trees in the inner and outer layers of different voltage rating XLPE cable insulation  

NASA Astrophysics Data System (ADS)

The statistical initiation and propagation characteristics of electrical trees in cross-linked polyethylene (XLPE) cables with different voltage ratings from 66 to 500 kV were investigated under a constant test voltage of 50 Hz/7 kV (the 66 kV rating cable is from UK, the others from China). It was found that the characteristics of electrical trees in the inner region of 66 kV cable insulation differed considerably from those in the outer region under the same test conditions; however, no significant differences appeared in the 110 kV rating cable and above. The initiation time of electrical trees in both the inner and the outer regions of the 66 kV cable is much shorter than that in higher voltage rating cables; in addition the growth rate of electrical trees in the 66 kV cable is much larger than that in the higher voltage rating cables. By using x-ray diffraction, differential scanning calorimetry and thermogravimetry methods, it was revealed that besides the extrusion process, the molecular weight of base polymer material and its distribution are the prime factors deciding the crystallization state. The crystallization state and the impurity content are responsible for the resistance to electrical trees. Furthermore, it was proposed that big spherulites will cooperate with high impurity content in enhancing the initiation and growth processes of electrical trees via the 'synergetic effect'. Finally, dense and small spherulites, high crystallinity, high purity level of base polymer material and super-clean production processes are desirable for higher voltage rating cables.

Xie, Ansheng; Li, Shengtao; Zheng, Xiaoquan; Chen, George

2009-06-01

264

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

265

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

266

Time dependent dielectric breakdown at 210 Å oxides  

Microsoft Academic Search

Time-dependent dielectric breakdown (TDDB) data on 210-Å oxide films made with a 1.25-?m CMOS process using large-area test capacitors (0.3 cm2) are presented. Stress temperatures of 60°C and 150°C were used while the electric field stress was varied from near-operation conditions (3 MV\\/cm) to highly accelerated conditions (8 MV\\/cm). Approximately 14000 test capacitors have been aged. In an attempt to

K. C. Boyko; D. L. Gerlach

1989-01-01

267

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

268

Initiation of breakdown in slender compressible vortices  

NASA Technical Reports Server (NTRS)

The initiation of the breakdown process for axially symmetric compressible flows is investigated using a numerical solution of the conservation equations for mass, momentum, and energy. The vortex is isolated, with its axis parallel to the direction of the main stream, and the core radius is small compared to the breakdown length. Computations for several flowfields indicate that the breakdown of the solution is shifted further downstream with increasing Mach number until breakdown is no longer observed. In the subsonic case, the influence of the initial temperature distribution on the breakdown length of the solution is more pronounced than in the supersonic case, with heating of the core enhancing breakdown, and cooling delaying it. The breakdown of the solution is seen to always occur for nonvanishing axial velocity components.

Krause, E.; Menne, S.; Liu, C. H.

1986-01-01

269

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.

270

The role of tip leakage vortex breakdown in compressor rotor aerodynamics  

SciTech Connect

The breakdown of tip leakage vortex has been investigated on low-speed axial compressor rotor with moderate blade loadings. Effects of the breakdown on the rotor aerodynamics are elucidated by Navier-Stokes flow simulations and visualization techniques for identifying the breakdown. The simulations show that the leakage vortex breakdown occurs inside the rotor at a lower flow rate than the peak pressure rise operating condition. The breakdown is characterized by the existence of the stagnation point followed by a bubblelike recirculation region. The onset of breakdown causes significant changes in the nature of the tip leakage vortex: large expansion of the vortex and disappearance of the streamwise vorticity concentrated in the vortex. The expansion has an extremely large blockage effect extending upstream of the leading edge. The disappearance of the concentrated vorticity results in no rolling-up of the vortex downstream of the rotor and the disappearance of the pressure through on the casing. The leakage flow field downstream of the rotor is dominated by the outward radial flow, resulting from the contraction of the bubblelike structure of the breakdown region. It is found that the leakage vortex breakdown plays a major role in characteristic of rotor performance at near-stall conditions. As the flow rate is decreased from the peak pressure rise operating condition, the breakdown region grows rapidly in the streamwise, spanwise, and pitchwise directions. The growth of the breakdown causes the blockage and the loss to increase drastically. Then, the interaction of the breakdown region with the blade suction surface gives rise to the tree-dimensional separation of the suction surface boundary layer, thus leading to a sudden drop in the total pressure rise across the rotor.

Furukawa, M.; Inoue, M.; Saiki, K.; Yamada, K. [Kyushu Univ. Fukuoka (Japan). Dept. of Mechanical Science and Engineering

1999-07-01

271

The inception of pulsed discharges in air: simulations in background fields above and below breakdown  

E-print Network

We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and O$_{2}^-$ ions. When the electric field rises above the breakdown and the detachment threshold, which are similar in air, electrons can detach from O$_{2}^-$ and start ionization avalanches. These avalanches together create one large discharge, in contrast to the `double-headed' streamers found in many fluid simulations. On the other hand, in background fields below breakdown, something must enhance the field sufficiently for a streamer to form. We use a strongly ionized seed of electrons and positive ions for this, with which we observe the growth of positive streamers. Negative streamers were not observed. Below breakdown, the inclusion of electron detachment does not change the results much, and we observe similar discharge development as in fluid simulations.

Sun, Anbang; Ebert, Ute

2014-01-01

272

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

273

Effects of a parallel resistor on electrical characteristics of a piezoelectric transformer in open-circuit transient state.  

PubMed

This paper investigates electrical transient characteristics of a Rosen-type piezoelectric transformer (PT), including maximum voltages, time constants, energy losses and average powers, and their improvements immediately after turning OFF. A parallel resistor connected to both input terminals of the PT is needed to improve the transient characteristics. An equivalent circuit for the PT is first given. Then, an open-circuit voltage, involving a direct current (DC) component and an alternating current (AC) component, and its related energy losses are derived from the equivalent circuit with initial conditions. Moreover, an AC power control system, including a DC-to-AC resonant inverter, a control switch and electronic instruments, is constructed to determine the electrical characteristics of the OFF transient state. Furthermore, the effects of the parallel resistor on the transient characteristics at different parallel resistances are measured. The advantages of adding the parallel resistor also are discussed. From the measured results, the DC time constant is greatly decreased from 9 to 0.04 ms by a 10 k(omega) parallel resistance under open output. PMID:17225805

Chang, Kuo-Tsai

2007-01-01

274

Electric field modelling of DEAP material with compliant metal electrodes  

NASA Astrophysics Data System (ADS)

The main failure mode for dielectric electroactive polymer (DEAP) materials is electrical breakdown and many factors influence its occurrence, for example impurities in the dielectric, the magnitude of the electric field and environmental conditions (temperature and humidity). The electrodes that sandwich the elastomer play a key role in the electromechanical strain performance of the DEAP. Compliant metal electrode technology achieves compliance in the DEAP material by using a corrugated electrode profile. The advantages of using compliant metal electrode technology include (a) excellent conductivity, (b) 'self-healing' capability when electrical breakdown takes place and (c) unidirectional motion of the material when a voltage is applied. In this contribution, the electric field and surface charge density characteristics of a compliant metal electrode-based DEAP material are investigated. The corrugation profile used in the material is sinusoidal with a maximum strain of 33%. Modelling the electric field and surface charge density in this DEAP material provides insight into the possible influence of electrodes with a corrugation profile on electrical breakdown behaviour.

Wang, Peng; Jones, Richard W.; Lassen, Benny

2010-04-01

275

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

276

Investigations of Electrical Characteristics of the Subsurface Rock Medium in Essex County, New York.  

National Technical Information Service (NTIS)

Two vertical drill holes located in Essex County, New York were utilized for measurements to determine the electrical conductivity of the rock media below the surface. Average conductivities in the drill holes were deduced from input impedances of bare mo...

C. K. H. Tsao

1964-01-01

277

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

278

Electric field manipulation of polymer nanocomposites: processing and investigation of their physical characteristics  

E-print Network

Acceleration due to gravity ? Torque ?? Electrical torque ?V Viscous torque ? Dipole moment ? Angle between the particle axis and the electric field OM Optical microscopy SEM Scanning electron microscopy t Thickness A Area C Capacitance E? Storage... cups ............................. 5 1.2 SEM micrograph of 5 wt% MWNT-PS fracture surface ........................... 9 1.3 SEM showing uniform SWNT distribution in 1% SWNT-PMMA composite film fabricated...

Banda, Sumanth

2009-05-15

279

Head current during and blood splashes after electrical stunning in relation to characteristics of the pig's body.  

PubMed

In order to evaluate electrical stunning in relation to the incidence of blood splashes, meat quality and carcass quality parameters, 2035 pigs, heterozygous for the halothane gene, were observed during slaughter at a commercial slaughterhouse. The head current during electrical stunning is significantly higher (P<0.01) in gilts with a lower live weight (P<0.0001) or cold carcass weight (P<0.0001) and a higher lean meat percentage (P<0.0001). Also the incidence of blood splashes in the ham is significantly higher in gilts (P<0.0001) with a higher lean meat percentage (P=0.0028; odds ratio=1.11), a lower live weight (P=0.003; odds ratio=0.98) and a lower type number (P=0.0074; odds ratio=0.64). For barrows, no significant parameters were revealed. These results suggest that the variability in incidence of blood splashes can be explained by the variability of current density depending both on sex and body characteristics. Thus, electrical stunning can be improved by providing an energy level, based on the body characteristics of the pig. PMID:22061384

Lammens, V; Van de Water, G; Coenegrachts, J; Driessen, B; Peeters, E; Geers, R

2006-01-01

280

Swelling characteristics of acrylic acid polyelectrolyte hydrogel in a dc electric field  

NASA Astrophysics Data System (ADS)

A novel application of environmentally sensitive polyelectrolytes is in the fabrication of BioMEMS devices as sensors and actuators. Poly(acrylic acid) (PAA) gels are anionic polyelectrolyte networks that exhibit volume expansion in aqueous physiological environments. When an electric field is applied to PAA polyelectrolyte gels, the fixed anionic polyelectrolyte charges and the requirement of electro-neutrality in the network generate an osmotic pressure, above that in the absence of the electric field, to expand the network. The objective of this research was to investigate the effect of an externally applied dc electric field on the volume expansion of the PAA polyelectrolyte gel in a simulated physiological solution of phosphate buffer saline (PBS). For swelling studies in the electric field, two platinum-coated plates, as electrodes, were wrapped in a polyethylene sheet to protect the plates from corrosion and placed vertically in a vessel filled with PBS. The plates were placed on a rail such that the distance between the two plates could be adjusted. The PAA gel was synthesized by free radical crosslinking of acrylic acid monomer with ethylene glycol dimethacrylate (EGDMA) crosslinker. Our results demonstrate that volume expansion depends on the intensity of the electric field, the PAA network density, network homogeneity, and the position of the gel in the field relative to positive/negative electrodes. Our model predictions for PAA volume expansion, based on the dilute electrolyte concentration in the gel network, is in excellent agreement with the experimental findings in the high-electric-field regime (250-300 Newton/Coulomb).

Jabbari, Esmaiel; Tavakoli, Javad; Sarvestani, Alireza S.

2007-10-01

281

Nanopore Fabrication by Controlled Dielectric Breakdown  

PubMed Central

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 sciences interested in gaining reliable access to solid-state nanopores, but may provide a path towards manufacturing of nanopore-based biotechnologies. PMID:24658537

Tabard-Cossa, Vincent

2014-01-01

282

1D PIC-DSMC simulations of breakdown in microscale gaps  

NASA Astrophysics Data System (ADS)

An explicit electrostatic particle-in-cell (PIC) code with complex boundary conditions and direct simulation Monte Carlo (DSMC) particle collisions is utilized to investigate one dimensional direct current breakdown between two electrodes separated by air at STP. The simulation model includes Auger neutralization and cold field electron emission from the cathode as well as electron-neutral elastic, ionization, and excitation interactions. The simulated breakdown voltages at various electrode gap sizes are compared to experimental data and the Paschen curve. It is found that cold field electron emission can explain the breakdown voltage deviation from the Paschen curve measured for small gaps. Breakdown in large gaps proceeds over multiple ion transit timescales as electrons created via Auger neutralization of ions at the cathode quickly stream across the gap, creating new ions which accelerate towards the cathode and release another "pulse" of electrons. If the resultant pulse of electrons is larger than the initial pulse, then this process can build up a significant quasi-neutral plasma in the gap and the voltage drop across the gap will occur primarily across the (thin) sheath. Breakdown is accelerated if the electric field at the cathode surface is large enough for significant cold field emission flux, which increases the plasma density and decreases the Debye length and thus the sheath size, further increasing the electric field and cold field emission flux from the cathode surface. Breakdown in air pressure gaps was found to be sensitive to the differential scattering cross section for electron-neutral interactions. Isotropic scattering of elastic collisions results in lower breakdown voltages at moderate gaps (several mean free paths) and higher breakdown voltages for large gap sizes compared to when more accurate forward-biased scattering distributions are used. The dependence of breakdown voltage on the scattering distribution is due to a competition between increased backscattering resulting in a larger effective path length across the gap versus changes in the electron energy distribution function.

Moore, Chris H.; Hopkins, Matthew M.; Crozier, Paul S.; Boerner, Jeremiah J.; Musson, Lawrence C.; Hooper, Russell W.; Bettencourt, Matthew T.

2012-11-01

283

Investigation of structural properties, electrical and dielectrical characteristics of Al/Dy2O3/porous Si heterostructure  

NASA Astrophysics Data System (ADS)

This paper describes the structural properties, electrical and dielectric characteristics for the first time of the high-k Dy2O3 oxide film deposited on the porous Si substrate by electron beam deposition under ultra vacuum. Structural and morphological characterizations are investigated by a scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and X-ray diffraction measurements (XRD). The electrical and dielectric characteristics of the Al/Dy2O3/porous Si heterostructure are studied through current- voltage I (V), capacitance-voltage C (V), conductance- and capacitance-frequency dependencies (G (f) and C (f)). Therefore, the dominant conduction mechanisms for the Al/Dy2O3/porous Si heterostructure are extracted from the determining of Schottky coefficient (?SC) and Poole-Frenkel coefficient (?PF). The experimental values of ?SC and ?PF coefficients are calculated from I (V) characteristics and compared with theoretical values, thus, the appropriate model has been proposed. The C (V) characteristics at different frequencies revealed a large frequency-dispersion, indicative of a significant density of interface states. Furthermore, the G (f) characteristics were well fitted by the modified law GAC(f)=A1f+A2f and the results showed frequency dependent and evidence of two different behaviors in ac conductance i.e. the low-frequency conductivity is due to long-range ordering (frequency-independent) and high frequency conduction due to the localized orientation hopping mechanism. The Nyquist diagrams are used to identify the equivalent circuit, so, the Al/Dy2O3/porous Si heterostructure is accurately modeled at frequency ranges from 10 Hz to 1000 kHz, as a two parallel elements (RC) network placed in series.

Cherif, A.; Jomni, S.; Belgacem, W.; Hannachi, R.; Mliki, N.; Beji, L.

2014-04-01

284

CHARACTERISTICS OF TRANSVERSE ELECTRIC AND MAGNETIC FIELD TRANSMISSION CELLS AT EXTREMELY LOW FREQUENCIES  

EPA Science Inventory

Transverse electric and magnetic field cells are often designed to subject samples to electromagnetic radiation of intrinsic impedance (E/H) that is the same as in free space, 377 ohms. Earlier work has shown this value to be correct for the RF region. In the study, measurements ...

285

Thixoforming characteristics of thermo-mechanically treated AA 6061 alloy for suspension parts of electric vehicles  

Microsoft Academic Search

Thixoforming trials of AA 6061 alloy, which is a wrought aluminum alloy, were undertaken to manufacture the steering knuckles designed for suspension parts of low speed electric vehicles. The billets used as a starting material were thermo-mechanically treated to induce thixoformable fine globular microstructures during subsequent reheating process. After a slug was reheated up to the working temperature (?645°C) using

Sang-Yong Lee; Se-Il Oh

2002-01-01

286

Electrical conductivity of polyethylene aluminum nanocomposites with different particle surface chemistry characteristics  

Microsoft Academic Search

We investigated the influence of the surface modification of Al nanoparticles on the electrical conduction of polyethylene composites. Octyl-trimethoxysilane was used as a coupling agent for the treatment of Al nanoparticle. It was found that the incorporation of octyl groups onto the surface of Al nanoparticle altered the time dependence behaviors of polarization and depolarization current and increased the percolation

Xingyi Huang; Chonung Kim; Pingkai Jiang; Fei Liu; Zhe Li; Yi Yin

2008-01-01

287

Characteristics of nanopowders produced by wire electrical explosion of tinned copper conductor in argon  

Microsoft Academic Search

The end products of electrical explosion of copper wires coated with a thin tin layer were studied. Depositing tin (~1 wt.%) on the surface of the copper wire did not have a considerable effect on the relation between the sample dispersity and the input energy. When increasing the input energy, the tin content in surface and near-surface layers of the nanoparticles

Y. S. Kwon; A. P. Ilyin; D. V. Tikhonov; G. V. Yablunovsky; V. V. An

2008-01-01

288

Numerical Study of Plasma-Fluid Behavior and Generation Characteristics of the Closed Loop MHD Electrical Power Generator  

NASA Astrophysics Data System (ADS)

Time dependent r-z two-dimensional numerical simulations with LES technique have been carried out in order to clarify the plasma fluid behavior and power generation characteristics of the disk MHD generator under the rated operation conditions demonstrated in the closed loop experimental facility at Tokyo Tech. The generator currently installed could suffer from the non-uniform and low electrical conductivity, and the boundary layer separation even under the rated operation conditions. The large amount of generated electric power is consumed in the boundary layer separation region, which reduces a net output power. Reducing the back pressure and improving the inlet plasma conditions surely provide the higher generator performance. The influence of 90 degree bend downstream duct on the generator performance is found to be not marked.

Ohno, Jun; Liberati, Alessandro; Murakami, Tomoyuki; Okuno, Yoshihiro

289

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

290

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Noise Characteristics of Optocouplers on Neutron Radiation  

NASA Astrophysics Data System (ADS)

Neutron dose radiation experiment is designed to study the optocoupler's displacement effects and the noise characteristics. The burst noise is introduced in optocouplers on neutron radiation, which is indicated from experiments. With the increasing neutron radiation the displacement defects in space-charge region increase, the scattering enhances and the noise signal mutations increase. All these represent the noise time series mutations, the random pulses and the increasing noise complexity. The burst noise becomes evident, and the power spectrum density, the characteristic frequency and the fractal dimension of time series of noise greatly increase.

Li, Ying-Hui; Chen, Chun-Xia; Liu, Yong-Zhi; Jiang, Cheng; Zou, Ze-Ya; Ou, Yi; Li, Zu-An

2008-11-01

291

Electrical characteristics and optimization of extended-drain MOS transistor with dual-workfunction-gate for mixed-signal applications  

NASA Astrophysics Data System (ADS)

This paper presents the electrical characteristics of high-voltage (HV) extended-drain MOS (EDMOS) field-effect transistor with dual-workfunction-gate (DWFG) to enhance the device performance and device optimization for mixed-signal applications. For n-channel DWFG EDMOS device fabrication, the polycrystalline-silicon (poly-Si) gate on the source and drain side were doped by p+ and n+ ion implantation, respectively. The DWFG device with shorter p+ poly-Si gate length showed lower on-resistance (RON) characteristics compared to the conventional device. Therefore, the DWFG device with shorter p+ poly-Si gate length is suitable for switching applications. On the other hand, the best improvements in the drain conductance (gds) and intrinsic voltage gain (AV), which is important parameters of analog circuits, were shown in the DWFG device with identical n+ and p+ poly-Si gate length.

Baek, Ki-Ju; Na, Kee-Yeol; Kim, Yeong-Seuk

2014-10-01

292

Electric field measurements with an airplane: A solution to problems caused by emitted charge  

Microsoft Academic Search

The growth of electrical energy inthundercloud prior tolightning fish cn be studied by measuring the electric field. The use ofirplnes to measure the electric field hs beenproblem because the intense electric field of  thunderstorm cuses electric breakdown inirt sharp metallic pointsnd edges. The electrical charge produced by the breakdown cn be confused with the charge in the thunderstorm itself,

Q. Mo; A. E. Ebneter; P. Fleischhacker; W. P. Winn

1998-01-01

293

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

294

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

295

Electrical and illumination characteristics of energy-saving fluorescent lighting as a function of potential  

Microsoft Academic Search

Various combinations of F40-T12, F96-T12 and compact energy-savings fluorescent lamps with core-coil and solid-state ballasts were tested at laboratory facilities. The illumination (footcandles), the active (watts) and reactive power consumption, as well as the harmonic content (percentage of the fundamental 60 Hz frequency) of the load current, were measured as a function of varying voltage levels. The electrical parameters showed

S. A. Kalinowsky; J. J. Martello

1989-01-01

296

Stability of Electrical and Photovoltaic Characteristics of HBr Solution-Doped Polyacetylene  

Microsoft Academic Search

Polyacetylene was doped with hydrogen bromide (HBr) solution. The electrical conductivity of the solution-doped polyacetylene increased by an order of six from 5× 10-9 S\\/cm to 4× 10-3 S\\/cm. Here the stability of HBr-doped polyacetylene is discussed with respect to the changes in conductivity due to heat treatment and exposure to air, in comparison with I2-doped polyacetylene. The HBr-doped polyacetylene

M. S. Lee; J. S. Tzeng; Y. C. Chen; T. Shiramatsu

1989-01-01

297

Study on operating characteristics of fuel cell powered electric vehicle with different air feeding systems  

Microsoft Academic Search

In this paper the modeling of a fuel cell powered electric vehicle is presented. The fuel cell system consisting of a proton\\u000a exchange membrane (PEM) fuel cell stack and balance of plant (BOP) was co-simulated with a commercial vehicle simulation program.\\u000a The simulation program calculates the load of the fuel cell depending on the driving mode of the vehicle and

Junghwan Bang; Han-Sang Kim; Dong-Hun Lee; Kyoungdoug Min

2008-01-01

298

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

299

Effects of postmortem carcass electrical stimulation on goat meat quality characteristics  

Microsoft Academic Search

Electrical stimulation (ES) has been reported to improve meat quality, but the effects of postmortem ES have not been fully characterized in goats. This experiment was conducted to determine the effects of postmortem ES on meat quality in two breeds of goats. Uncastrated Spanish and crossbreds (Boer×Spanish females×Kiko male) yearlings (n=10\\/breed, body weight 31.2±2.43kg) were transported to the slaughter facility,

K. M. Gadiyaram; G. Kannan; T. D. Pringle; B. Kouakou; K. W. McMillin; Y. W. Park

2008-01-01

300

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

301

High-Current Breakdown of the Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

We have recently developed a model for the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicted that, for low-mobility samples, the critical current for breakdown should decrease linearly with temperature. This prediction was verified experimentally with the addition of a low-temperature (? 300 mK) saturation of the critical current. This saturation is consistent with quasi-elastic inter-Landau-level scattering when the maximum electric field in the sample reaches a large enough value. In this paper we extend this model to nearly integer filling factors to show how the model may account for the shape of the magnetisation signal.

Matthews, A. J.; Kavokin, K. V.; Usher, A.; Portnoi, M. E.; Gething, J. D.; Zhu, M.; Ritchie, D. A.

2005-04-01

302

High-Current Breakdown of the Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

We have recently developed a model for the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicted that, for low-mobility samples, the critical current for breakdown should decrease linearly with temperature. This prediction was verified experimentally with the addition of a low-temperature (? 300 mK) saturation of the critical current. This saturation is consistent with quasi-elastic inter-Landau-level scattering when the maximum electric field in the sample reaches a large enough value. In this paper we extend this model to nearly integer filling factors to show how the model may account for the shape of the magnetisation signal.

Matthews, A. J.; Kavokin, K. V.; Usher, A.; Portnoi, M. E.; Gething, J. D.; Zhu, M.; Ritchie, D. A.

303

High-Current Breakdown of the Quantum Hall Effect  

NASA Astrophysics Data System (ADS)

We have recently developed a model for the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicts that, for low-mobility samples, the critical current for breakdown should decrease linearly with temperature. This prediction is verified experimentally with the addition of a low-temperature (< ˜ 300 mK) saturation of the critical current. This saturation is consistent with quasi-elastic inter-Landau-level scattering when the maximum electric field in the sample reaches a large enough value. Here we extend this model to `nearly' integer filling factors to show how the model may account for the shape of the magnetisation signal.

Matthews, A. J.; Kavokin, K. V.; Usher, A.; Portnoi, M. E.; Gething, J. D.; Zhu, M.; Ritchie, D. A.

2005-06-01

304

Impacts of Various Characteristics of Electricity and Heat Demand on the Optimal Configuration of a Microgrid  

NASA Astrophysics Data System (ADS)

A methodology was developed to design the number and capacity for each piece of equipment (e.g. gas engines, batteries, thermal storage tanks) in microgrids with combined heat and power systems. We analyzed three types of microgrids; the first one consists of an office building and an apartment, the second one consists of a hospital and an apartment, the third one consists of a hotel, office and retails. In the methodology, annual cost is minimized by considering the partial load efficiency of a gas engine and its scale economy, and the optimal number and capacity of each piece of equipment and the annual operational schedule are determined by using the optimal planning method. Based on calculations using this design methodology, it is found that the optimal number of gas engines is determined by the ratio of bottom to peak of the electricity demand and the ratio of heat to electricity demand. The optimal capacity of a battery required to supply electricity for a limited time during a peak demand period is auxiliary. The thermal storage tank for space cooling and space heating is selected to minimize the use of auxiliary equipment such as a gas absorption chiller.

Bando, Shigeru; Watanabe, Hiroki; Asano, Hiroshi; Tsujita, Shinsuke

305

Electrical and Radiation Characteristics of Water in the Decimeter and Meter Range.  

National Technical Information Service (NTIS)

An examination was made of the effect of the temperature and salinity of sea water on its dielectric constants and the radiation characteristics of a smooth water surface in the 10-200 cm wavelength range. With reference to the dependence of the dielectri...

V. Y. Rayzer, Y. A. Sharkov, V. S. Etkin

1974-01-01

306

Characteristics of Langmuir electric field waveforms and power spectra exhibiting nonlinear behavior in Earth's foreshock  

E-print Network

[1979] were the first to suggest that the Langmuir waves (3­30 kHz) observed in the foreshock [Scarf et 28 June 2010; accepted 7 July 2010; published 29 October 2010. [1] Langmuir wave characteristics in the Earth's foreshock were examined to identify possible nonlinear wave behavior for two case studies

Gurnett, Donald A.

307

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

308

High voltage research (breakdown strengths of gaseous and liquid insulators) and environmental effects of dielectric gases. Semiannual report, April 1-September 30, 1981  

SciTech Connect

Electron attachment studies were performed on three perfluoroalkanes, two thioethers, n-C/sub 3/F/sub 8/, (CF/sub 3/)/sub 2/S, 1-C/sub 3/F/sub 6/, and 3,3,3-C/sub 3/F/sub 3/H/sub 3/. The attachment rates for CC1/sub 3/F were measured. The energies in dissociative electron attachment of C/sub 3/F/sub 8/, n-C/sub 4/F/sub 10/, and n-C/sub 6/F/sub 14/ were evaluated. For gases used in diffuse discharge interrupting switches, desirable characteristics and some candidate gas mixtures are discussed: The pressure effect on breakdown voltage was investigated in SF/sub 6/, N/sub 2/, and 1-C/sub 3/F/sub 6/; for the latter, (E/N)/sub lim/ increased approximately 25% from 26 kPa to 200 kPa. The breakdown voltages have been measured for SF/sub 6//1-C/sub 3/F/sub 6//moderating gas (CHF/sub 3/ or N/sub 2/) mixtures under both polarities of lightning impulse (1.2 ..mu..s rise, 50 ..mu..s fall) voltages. The effect of electrode by sparking on observed breakdown voltages were studied. The observed variations of time-to-breakdown for various mixutres are discussed. Methods for reducing the harmful effects of small conducting particles in gas-insulated apparatus were studied. The possible use of gases to form an insulating coating on offending particles, the effect of coating particles and ways to perform the coating were investigated. The immediate breakdown products of ternary mixtures containing SF/sub 6/, c-C/sub 4/F/sub 8/, and either N/sub 2/ or CHF/sub 3/ were observed. Long-term electrical and thermal stress of SF/sub 6/, c-C/sub 4/F/sub 8/ and N/sub 2/ mixtures produced no observable decomposition products. For sparking in SF/sub 6/, SF/sub 4/ was found to be a major product. The toxicity of gas mixtures before and after sparking was assessed. Nitrogen and unsparked SF/sub 6/ were found non-toxic, while sparked SF/sub 6/ and unsparked 2-C/sub 4/F/sub 6/ were found to be toxic. Studies of the effects of capacitance on the observed breakdown strengths of dielectric liquids showed that. Increased capacitance lowered the breakdown voltage, but less for external capacitance than for internal capacitance.

Christophorou, L.G.; James, D.R.; Pai, R.Y.

1982-01-01

309

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

310

Electrical characteristic signatures for non-uniformity analysis in HgCdTe photodiode arrays  

NASA Astrophysics Data System (ADS)

In this paper we present a method of analyzing the performance non-uniformity of HgCdTe photodiode arrays for infrared imaging applications. For quantifying the characteristic behavior of various photodiodes, we have parametrized the dynamic resistance verses voltage signatures in such a way that the obtained signature parameters have some relevance with different physical parameters. We also estimated the sensitivity of the proposed signatures on physical parameters using statistical technique. These characteristics signatures may be used to quantify the non-uniformity of the HgCdTe photodiodes in IR imaging arrays and its analysis. The method presented here is based on theoretical calculation of MWIR HgCdTe photodiodes. However, the method is generic and may be implemented on any other type of diode arrays for theoretical or experimental analysis of their non-uniformity.

Saxena, Raghvendra Sahai; Nokhwal, Radheshyam; Bhan, R. K.; Sharma, R. K.

2013-01-01

311

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

E-print Network

for publication 3 January 2002 We report properties of Er2O3 films deposited on silicon using electron-beam gun with the surface morphology. The obtained characteristics make the Er2O3 films a promising substitute for SiO2 of another rare-earth­ metal oxide, erbium oxide, Er2O3 . This material is rather well known as an optical

Eisenstein, Gadi

312

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

Microsoft Academic Search

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

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

2011-01-01

313

Electrical Characteristics of the Organic Field Effect Transistors Based on New Organic Semiconducting Compounds  

Microsoft Academic Search

In present study four newly synthesized organic semiconductor compounds have been used for fabrication of the organic field effect transistors. In all cases p-type channel organic field effect transistors were fabricated. I-V characteristics of the samples were investigated. The highest on\\/off ratio (up to 180) was observed in the case of the organic field effect transistors fabricated using 4-diphenylaminobenzaldehyde N-methyl-N-phenylhydrazone

Rimas GUDAITIS; Juozas Vidas GRA; Ram?nas LYGAITIS; Evaldas BURBULIS; Asta MICHALEVI?I?T?; Vytautas GETAUTIS; Tadas MALINAUSKAS

2007-01-01

314

Electrical Characteristics of WSi2 Nanocrystal Capacitors with Barrier-Engineered High-k Tunnel Layers  

NASA Astrophysics Data System (ADS)

Nanocrystal-floating gate capacitors with WSi2 nanocrystals and high-k tunnel layers were fabricated to improve the electrical properties such as retention, programming/erasing speed, and endurance. The WSi2 nanocrystals were distributed uniformly between the tunnel and control gate oxide layers. The electrical performance of the tunnel barrier with the SiO2/HfO2/Al2O3 (2/1/3 nm) (OHA) tunnel layer appeared to be better than that with the Al2O3/HfO2/Al2O3 (2/1/3 nm) (AHA) tunnel layer. When ?VFB is about 1 V after applying voltage at ±8 V, the programming/erasing speeds of AHA and OHA tunnel layers are 300 ms and 500 µs, respectively. In particular, the device with WSi2 nanocrystals and the OHA tunnel barrier showed a large memory window of about 7.76 V when the voltage swept from 10 to -10 V, and it was maintained at about 2.77 V after 104 cycles.

Lee, Hyo Jun; Lee, Dong Uk; Kim, Eun Kyu; You, Hee-Wook; Cho, Won-Ju

2011-06-01

315

Fundamental studies on passivity and passivity breakdown  

SciTech Connect

Using photoelectrochemical impedance and admittance spectroscopies, a fundamental and quantitative understanding of the mechanisms for the growth and breakdown of passive films on metal and alloy surfaces in contact with aqueous environments is being developed. A point defect model has been extended to explain the breakdown of passive films, leading to pitting and crack growth and thus development of damage due to localized corrosion.

Macdonald, D.D.; Urquidi-Macdonald, M.

1993-06-01

316

The use of the orthogonal array with grey relational analysis to optimize the electrical discharge machining process with multiple performance characteristics  

Microsoft Academic Search

In this paper a new approach for the optimization of the electrical discharge machining (EDM) process with multiple performance characteristics based on the orthogonal array with the grey relational analysis has been studied. A grey relational grade obtained from the grey relational analysis is used to solve the EDM process with the multiple performance characteristics. Optimal machining parameters can then

J. L Lin; C. L Lin

2002-01-01

317

Particle-in-cell simulations of the runaway breakdown of nitrogen  

SciTech Connect

The runaway breakdown initiated by a mono-energetic beam of runaway electrons propagating through a cathode-anode gap filled with nitrogen at atmospheric pressure is studied using the one-dimensional particle-in-cell numerical model. It is shown that the breakdown is strongly influenced by the amplitude of the beam, its duration, and the electric field in the vicinity of the cathode. In addition, the simulation results showed that, in spite of the formation of rather dense plasma inside the cathode-anode gap by runaway electrons, the electric field is not screened because of frequent electron-neutral collisions.

Levko, D.; Krasik, Ya. E. [Physics Department, Technion, Haifa 32000 (Israel)

2012-12-01

318

Effects of interface reactions on electrical characteristics of metal-GaAs contacts  

SciTech Connect

Solid-state interface reactions between metal thin films and (100) GaAs substrates at elevated temperatures are studied by conventional and heavy-ion Rutherford backscattering spectrometry, x-ray diffraction, and transmission electron microscopy. Metals investigated in this study include Pt, Pd, Ni, Co, Rh, and W. Electrical properties of the metal/n-GaAs diodes undergoing annealing treatments at various temperatures were also measured with the current-voltage dependence. Optimum diodes with maximum barrier heights as well as minimum leakage currents are obtained for diodes annealed at temperatures at which a uniform thin layer of reacted phase is observable at the interface. The barrier heights of the optimum diodes show a linear dependence on the work functions of the various metals. The range of these barrier heights is limited by nonstoichiometry related defects as suggested by a recently proposed amphoteric native defect model.

Yu, K.M.; Walukiewicz, W.; Jaklevic, J.M.; Haller, E.E.; Sands, T.

1987-07-20

319

Solar thermal electric power plants - Their performance characteristics and total social costs  

NASA Technical Reports Server (NTRS)

The central receiver (power tower) concept as a thermal conversion approach to the conversion of solar energy into electricity is compared to other solar power plant designs which feature distributed solar collection and use other types of solar collector configurations. A variety of solar thermal storage concepts are discussed and their impacts on system performance are assessed. Although a good deal of quantification is possible in a comparative study, the subjective judgments carry enormous weight in a socio-economic decision, the ultimate choice of central power plant being more a social than an economic or technical decision. Major elements of the total social cost of each type of central plant are identified as utility economic costs, R&D funds, health costs, and other relevant social impacts.

Caputo, R. S.; Truscello, V. C.

1976-01-01

320

Characteristics of electrically induced locomotion in rat in vitro brain stem-spinal cord preparation.  

PubMed

1. Electrical stimulation of two brain stem regions in the decerebrate neonatal rat brain--the mesencephalic locomotor region (MLR) and the medioventral medulla (MED)--were found to elicit rhythmic limb movements in the hind-limb-attached, in vitro, brain stem-spinal cord preparation. 2. Electromyographic (EMG) analysis revealed locomotion similar to that observed during stepping in the adult rat. The step-cycle frequency could be increased by application of higher-amplitude currents; but, unlike the adult, alternation could not be driven to a gallop. 3. Threshold currents for inducing locomotion were significantly lower for stimulation of the MED compared with the MLR. Brain stem transections carried out at midpontine levels demonstrated that the presence of the MLR was not required for the expression of MED-stimulation-induced effects. 4. Substitution of the standard artificial cerebrospinal fluid (aCSF) by magnesium-free aCSF did not affect interlimb relationships and resulted in a significant decrease of the threshold currents for inducing locomotion. 5. Fixation of the limbs during electrical stimulation of brain stem sites altered the amplitude and duration of the EMG patterns, but the basic rhythm and timing of each muscle contraction during the step cycle was not affected. 6. These studies suggest that, although peripheral afferent modulation is evident in the neonatal locomotor control system, descending projections from brain stem-locomotor regions appear capable of modulating the activity of spinal pattern generators as early as the day of birth. However, there may be ceiling to the maximal frequency of stepping possible at this early age, perhaps suggesting a later-developing mechanism for galloping. PMID:2230919

Atsuta, Y; Garcia-Rill, E; Skinner, R D

1990-09-01

321

Clinical characteristics and outcome of children with electrical status epilepticus during slow wave sleep  

PubMed Central

Background: Electrical status epilepticus in slow wave sleep (ESES) is a rare, age-related, self-limited disorder characterized as epilepsy with different seizure types, neuropsychological impairment in the form of global or selective regression of cognitive functions, motor impairment, and typical electroencephalographic (EEG) findings of continuous epileptic activity occupying 85% of nonrapid eye movement sleep. Aims: The aim is to examine the clinical and electrophysiological findings and treatment modalities of children with ESES and to evaluate the outcome of the disorder. Materials and Methods: Fourteen patients with a diagnosis of electrical status epilepticus during slow wave sleep and followed-up at least 2 years were included. Statistical Analysis: Pearson correlation test was used in the study. Results: Among the 14 patients, eight of them had normal mental development before ESES. Twelve of the patients mentioned cognitive impairment and decline in school performance during ESES. After ESES, seven patients had mental retardation in different severity. One of these patients was diagnosed with benign partial epilepsy of childhood with centrotemporal spikes and had normal intelligence quotient level prior to ESES. The diagnosis of ESES was made after newly occurred different seizure types in four of the patients while two of the previously known epileptic patients presented with only severe psychiatric impairment. Valproic acid and carbamazepine were the mostly frequently used drugs before the onset of ESES. After at least 2 years of follow-up, seven patients were seizure free, but still taking antiepileptic treatment. Five patients were seizure free, while two of them had ongoing seizures despite antiepileptic therapy. Conclusion: ESES should be kept in mind in children with unexplained regression or stagnation of development associated with seizures or not. Sleep EEGs should be performed for timely diagnosis, proper treatment and prevention of permanent cognitive impairment.

Yilmaz, Sanem; Serdaroglu, Gul; Akcay, Ayfer; Gokben, Sarenur

2014-01-01

322

A computational study on electrical characteristics of a novel band-to-band tunneling graphene nanoribbon FET  

NASA Astrophysics Data System (ADS)

In this study, a modified structure was proposed for the band-to-band tunneling field-effect transistor (BTBT-FET) mainly to suppress the ambipolar current with the assumption that the ON state characteristics, especially sub-threshold swing, must not be degraded. The proposed structure uses a dual-material gate as gate contact and a narrow lightly doped region at the drain side of the channel. Electrical characteristics of the proposed device were explored by a mode-space non-equilibrium Green’s function (NEGF) formalism in the ballistic limit. A significant reduction in the ambipolar current was seen in simulation results for different values of the drain-source voltages. The results also revealed that the ON current remained the same and the sub-threshold swing got slightly better than that of the main structure. The comparison with the main structure showed that the proposed structure benefited from improved switching characteristics such as delay, switching power-delay product and ION/IOFF ratio. Further comparison indicated that the new structure had improved hot electron effect.

Yousefi, R.; Shabani, M.; Arjmandi, M.; Ghoreishi, S. S.

2013-08-01

323

On the electrical characteristics of latent finger mark corrosion of brass  

NASA Astrophysics Data System (ADS)

Apparatus constructed to measure the variation (?V) in applied potential (V) over the surface of brass discs subject to corrosion by latent finger mark deposits is described. Results show values of ?V of up to 14 V for V = 1400 V on regions of disc coincident with the location of finger mark corrosion. Measurement of ?V for 0 V <= V <= 1400 V has revealed a non-linear relationship, which is very similar to that measured for a commercial metal-semiconductor Schottky rectifier. Further experiments have shown the corrosion product on the brass to be a p-type semiconductor with current/voltage characteristics for the brass-corrosion contact consistent with the characteristics expected for a rectifying metal-semiconductor contact. The composition of the semiconductor is discussed in terms of metal oxide corrosion products with p-type copper (I) and copper (II) oxides thought most likely to be responsible for the semiconductor behaviour of the corrosion product. A simple model is described for the galvanic corrosion of brass by finger mark deposits that is consistent with the experimental results.

Bond, J. W.

2008-06-01

324

Crossover from bias-induced to field-induced breakdown in one-dimensional band and Mott insulators attached to electrodes  

NASA Astrophysics Data System (ADS)

Nonequilibrium states induced by an applied bias voltage (V) and the corresponding current-voltage characteristics of one-dimensional models describing band and Mott insulators are investigated theoretically by using nonequilibrium Green’s functions. We attach the models to metallic electrodes, the effects of which are incorporated into the self-energy. Modulation of the electron density and the scalar potential coming from the additional long-range interaction are calculated self-consistently within the Hartree approximation. For both models of band and Mott insulators with length LC, the bias voltage induces a breakdown of the insulating state, the threshold of which shows a crossover depending on LC. It is determined basically by the bias Vth~? for LC smaller than the correlation length ?=W/?, where W denotes the bandwidth and ? denotes the energy gap. For systems with LC??, the threshold is governed by the electric field Vth/LC, which is consistent with a Landau-Zener-type breakdown Vth/LC??2/W. We demonstrate that the spatial dependence of the scalar potential is crucially important for this crossover by showing the case without the scalar potential, where the breakdown occurs at Vth~? regardless of the length LC.

Tanaka, Yasuhiro; Yonemitsu, Kenji

2011-02-01

325

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

326

Electrical Characteristics of TiSi2 Nanocrystal Nonvolatile Memory with Barrier-Engineered Tunnel Layer  

NASA Astrophysics Data System (ADS)

In this study, we fabricated TiSi2 nanocrystal nonvolatile memory devices with silicon nitride-oxide-nitride (NON) and SiO2 tunnel barriers. The TiSi2 nanocrystals with diameters of 2-5 nm and a density of 1.5 × 1012 cm-2 were formed using radio frequency magnetron sputtering in argon and a postannealing process. The memory effect of the TiSi2 nanocrystal memory device with the NON tunnel barrier was observed at about 0.7 V at 100 ms when the applied program/erase voltages were +7 V/-7 V. Also, the memory window of the NON tunnel barrier device was maintained up to 1.3 V after 103 s. These results indicate that the NON tunnel barrier provides an effective tunneling thickness for the fast program/erase speeds and an adequate physical thickness for long charge retention characteristics in nonvolatile memory devices.

Seung Jong Han,; Dong Uk Lee,; Ki Bong Seo,; Seon Pil Kim,; Eun Kyu Kim,; Jun-Seok Oh,; Won-Ju Cho,

2010-06-01

327

Electrical Characteristics of TiSi2 Nanocrystal Nonvolatile Memory with Barrier-Engineered Tunnel Layer  

NASA Astrophysics Data System (ADS)

In this study, we fabricated TiSi2 nanocrystal nonvolatile memory devices with silicon nitride-oxide-nitride (NON) and SiO2 tunnel barriers. The TiSi2 nanocrystals with diameters of 2-5 nm and a density of 1.5 ×1012 cm-2 were formed using radio frequency magnetron sputtering in argon and a postannealing process. The memory effect of the TiSi2 nanocrystal memory device with the NON tunnel barrier was observed at about 0.7 V at 100 ms when the applied program/erase voltages were +7 V/-7 V. Also, the memory window of the NON tunnel barrier device was maintained up to 1.3 V after 103 s. These results indicate that the NON tunnel barrier provides an effective tunneling thickness for the fast program/erase speeds and an adequate physical thickness for long charge retention characteristics in nonvolatile memory devices.

Jong Han, Seung; Lee, Dong Uk; Seo, Ki Bong; Kim, Seon Pil; Kim, Eun Kyu; Oh, Jun-Seok; Cho, Won-Ju

2010-06-01

328

Electric-field-induced current-voltage characteristics in electronic conducting perovskite thin films  

NASA Astrophysics Data System (ADS)

Mixed ionic-electronic conductors (MIECs) such as the (La,Sr)(Co,Fe)O3-d perovskite family are well described in their charge transport through their high temperature applications, i.e., as solid-oxide fuel cell electrodes (600-1000 °C). In this study, the current-voltage (I-V) profiles of these well-known MIEC perovskites are studied between room temperature and 150 °C under bias of ±15 V for potential applications in resistance random access memories. The impact of the metal-oxide interface on the I-V characteristics ranging from ohmic to non-linear hysteretic is discussed for metals of varying work functions and redox potentials, as well as changes in metal electrode distances and areas.

Rupp, Jennifer L. M.; Reinhard, Patrick; Pergolesi, Daniele; Ryll, Thomas; Tölke, Rene; Traversa, Enrico

2012-01-01

329

Analysis of the thickness-dependent electrical characteristics in pentacene field-effect devices  

NASA Astrophysics Data System (ADS)

n this paper, we report on the important relationship among the capacitance-voltage ( C — V ) characteristics of metal-insulator-semiconductor (MIS) capacitors, the output currents of pentacene-based organic field-effect transistors (OFETs), and the semiconductor layer's thickness. The effect of the semiconductor layer's thickness on the effective channel capacitance, when the MIS capacitors are fully accumulated with sufficient negative bias, was observed to be directly correlated with the magnitude of the saturated output current. The variation in accumulation capacitance of MIS capacitors due to changes in layer thickness is shown to indicate the existence of a channel capacitance. This determines the output currents in the saturation region. Furthermore, the accumulation capacitance appears to decrease notably when the thickness of the pentacene layer is reduced below 20 nm.

Kim, Dongwook; Shin, Hyunji; Choi, Jong Sun; Zhang, Xue; Park, Ji-Ho; Baang, Sungkeun; Park, Jaehoon

2014-07-01

330

Numerical investigations on electric field characteristics with respect to capacitive detection of free-flying droplets.  

PubMed

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 < V(drop) < 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 S(i) = 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

331

Morphological and electrical characteristics of amino acid-AuNP nanostructured two-dimensional ensembles  

NASA Astrophysics Data System (ADS)

The interaction between amino acids ( L-cysteine, L-lysine) and gold nanoparticle layers deposited on ITO glasses was investigated. The citrate capped gold nanoparticles (AuNP) were first deposited as a thin layer onto silanized ITO and subsequently linked with an amino acid, due to strong affinity of thiol and amine groups to gold. The gold nanoparticles had an elliptical shape, with size varying between 7 and 14 nm, as indicated by TEM analysis. After deposition on ITO substrate, the nanoparticles self-assembled into large aggregates with poor contact between, as revealed by AFM. After linking L-cysteine or L-lysine to the surface of nanoparticles layer, a change in morphology occured. A better contact between the gold aggregates boundary developed, which improved the conducting properties of the nanostructured layer. The electrical resistance of the AuNPs layer, obtained from I- V measurements, was very high (2.8 × 10 13 ?) and slightly decreased after linking the NPs with amino acids.

Orza, Anamaria; Olenic, Liliana; Pruneanu, Stela; Pogacean, Florina; Biris, Alexandru S.

2010-08-01

332

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

333

Electrical Characteristics of ZnO Nanowire-Based Field-Effect Transistors on Flexible Plastic Substrates  

NASA Astrophysics Data System (ADS)

ZnO nanowire field effect transistors were fabricated on flexible substrates of poly(ether sulfone) (PES) by bottom-up and photolithographic processes and their electrical characteristics were investigated. The fabrication of the flexible devices was achieved at a processing temperature of 150 °C. A representative top-gate ZnO nanowire field effect transistor (FET) on a flexible substrate exhibits a peak transconductance of 179 nS, a field effect mobility of 10.7 cm2 V-1 s-1, and an Ion/Ioff ratio of 106. When the PES substrate is bent under a strain of 0.77%, the decrement of the drain current for the FET at VGS=10 V is less than 3%.

Kang, Jeongmin; Keem, Kihyun; Jeong, Dong-Young; Kim, Sangsig

2007-09-01

334

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

335

Frequency characteristics of a nuclear spin maser for the search for the electric dipole moment of 129Xe atom  

NASA Astrophysics Data System (ADS)

Frequency characteristics of a 129Xe nuclear spin maser was studied, which is under development at Tokyo Institute of Technology for the search for a permanent electric dipole moment in diamagnetic 129Xe atom. Drifts in the solenoid current and cell temperature were found to be the most influential factors on the maser frequency. From correlation coefficient analysis, there seem to exist other origins of frequency fluctuation, such as phase drifts in the maser oscillation. In order to improve the stability of the maser frequency, the intensity of the pumping laser required to fully polarize 129Xe nuclei was evaluated. Construction of a polarization assessment system for 129Xe gas cells and development of a new scheme of current stabilization are also remarked.

Inoue, T.; Tsuchiya, M.; Furukawa, T.; Hayashi, H.; Nanao, T.; Yoshimi, A.; Uchida, M.; Matsuo, Y.; Asahi, K.

2011-01-01

336

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

337

On the electrical characteristics of Au/n-type GaAs Schottky diode  

NASA Astrophysics Data System (ADS)

The temperature dependence of the electrical properties of Au/n-type GaAs Schottky contacts have been studied using current-voltage (I-V) and capacitance-voltage (C-V) over a wide temperature range 100-300 K. In the low temperature range 100-140 K, the absence of temperature dependent tunneling parameters has been explained in terms of thermionic field emission. In the high temperature range 140-300 K, the zero-bias barrier height (?0bn) was found to decrease and the ideality factor (n) to increase with decreasing temperature. This abnormal temperature dependence of ?0bn and n is interpreted on the basis of a thermionic emission mechanism by considering the existence of the barrier height inhomogeneities (BHi) at the metal/GaAs interface. From the linear plot of the experimental Schottky barrier height (SBH) vs. 1/T based on the BHi model, the value of the homogeneous SBH (??0bn) of 1.03 eV and a zero-bias standard deviation (?0s) of 89 meV were computed. Furthermore the modified Richardson plot according to the Gaussian distribution model resulted in a homogeneous SBH (??0bn) of 1.02 eV and a Richardson constant (A*) of 7.97 A/cm2 K2, respectively. The value of A* obtained from this plot is in very close agreement with the theoretical reported value of 8.16 A/cm2 K2 for n-type GaAs.

Mamor, M.; Bouziane, K.; Tirbiyine, A.; Alhamrashdi, H.

2014-08-01

338

Silicon nanowire biologically sensitive field effect transistors: electrical characteristics and applications.  

PubMed

The interest in biologically sensitive field effect transistors (BioFETs) is growing explosively due to their potential as biosensors in biomedical, environmental monitoring and security applications. Recently, adoption of silicon nanowires in BioFETs has enabled enhancement of sensitivity, device miniaturization, decreasing power consumption and emerging applications such as the 3D cell probe. In this review, we describe the device physics and operation of the silicon nanowire BioFETs along with recent advances in the field. The silicon nanowire BioFETs are basically the same as the conventional field-effect transistors (FETs) with the exceptions of nanowire channel instead of thin film and a liquid gate instead of the conventional gate. Therefore, the silicon device physics is important to understand the operation of the BioFETs. Herein, physical characteristics of the silicon nanowire FETs are described and the operational principles of the BioFETs are classified according to the number of gates and the analysis domain of the measured signal. Even the bottom-up process has merits on low-cost fabrication; the top-down process technique is highlighted here due to its reliability and reproducibility. Finally, recent advances in the silicon nanowire BioFETs in the literature are described and key features for commercialization are discussed. PMID:24730263

Rim, Taiuk; Baek, Chang-Ki; Kim, Kihyun; Jeong, Yoon-Ha; Lee, Jeong-Soo; Meyyappan, M

2014-01-01

339

Improvement in electrical characteristics of HfO2 gate dielectrics treated by remote NH3 plasma  

NASA Astrophysics Data System (ADS)

We report the structural and electrical characteristics of hafnium oxide (HfO2) gate dielectrics treated by remote NH3 plasma under various radio-frequency (RF) powers at a low temperature. Significant increase of effective dielectric constant (keff), decrease of capacitance equivalent thickness (CET), reduction in leakage current density, and suppression of the interfacial layer thickness were observed with the increase of the RF power in the remote NH3 plasma treatment. The effects of hydrogen passivation and depassivation on the HfO2/Si interface due to the remote NH3 plasma treatment were also observed by the variation of photoluminescence (PL) intensity, indicating that the PL measurement is applicable to probe the interfacial properties. An ultrathin interfacial layer (˜0.3 nm), a high keff, (20.9), a low leakage current density (9 × 10-6 A/cm2), and a low CET (1.9 nm) in the nitrided HfO2 film were achieved, demonstrating that the nitridation process using remote NH3 plasma under a high RF power at a low temperature is a promising way to improve in electrical properties of high-K gate dielectrics.

Huang, Li-Tien; Chang, Ming-Lun; Huang, Jhih-Jie; Lin, Hsin-Chih; Kuo, Chin-Lung; Lee, Min-Hung; Liu, Chee Wee; Chen, Miin-Jang

2013-02-01

340

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

341

Electric field statistics and modulation characteristics of bursty Langmuir waves observed in the cusp  

NASA Astrophysics Data System (ADS)

HF wave receivers on the Twin Rockets to Investigate Cusp Electrodynamics (TRICE) detect numerous 20-250 ms duration Langmuir wave bursts. Investigation of 41 bursts at 967-984 km, where the gyrofrequency exceeds the plasma frequency, reveals a characteristic signature whereby the Langmuir wave bandwidth and highest frequency maximize at the center of the bursts, suggesting that bursts coincide with density enhancements. The Langmuir waveforms are modulated at frequencies up to 50 kHz, with significant modulation at frequencies <1 kHz about 10% of the time. Where amplitudes of the modulated waves pass through zero, the phase of the carrier wave shifts by 180°, consistent with a superposition of interfering waves. The corresponding wave spectrum has multiple <1 kHz bandwidth peaks separated by <1-50 kHz. For no averaging, the wave E field statistics, dominated by the carrier Langmuir wave, show an E+1 dependence at small E fields as expected for rectified sine waves. For moderate averaging, the statistics, dominated by the envelope field, show a spectral index of ? +2 at small E fields, consistent with numerical simulations of independent stochastically driven waves. The wave statistics, absence of VLF waves, lack of transition in the modulation occurrence as a function of frequency, and tendency of the spread spectrum to cut off at the ambient plasma frequency outside the density enhancement associated with the wave burst suggest that linear growth and mixing of Langmuir modes provides a more natural explanation of modulated Langmuir waves than do wave-wave processes previously proposed, at least for cusp waves encountered by TRICE.

LaBelle, J.; Cairns, Iver H.; Kletzing, C. A.

2010-10-01

342

A study of the characteristics and limitations of various platings on cylindrical electrical conductors  

NASA Astrophysics Data System (ADS)

This work explores the impedance characteristics of copper wires plated with tin, silver, or nickel, the most common type of wiring used in the computer, communications, and aerospace industries. The background of plated wires and a brief review of related research is provided. This is followed by a detailed development of the theory of plated wires, accompanied by a MAPLE code in the appendix that can be used for the numerical analysis of plated wires having two or more plating layers. The code was used to generate a series of curves predicting the impedance behavior of both solid, "pure" metals, as well as copper wire plated with silver, tin, and nickel. Additional curves are provided highlighting the very interesting impedance behavior of nickel plated copper wire. All of these curves are accompanied by a number of observations to point out the more interesting aspects of the behavior. Several impedance measurements of commonly available military specification plated wire stranded conductors are then discussed. A number of the attempted measurements were unable to resolve the very small impedances. Even so, a last attempt worked very well to demonstrate the predicted impedance behavior, as evidenced by the measured raw data curves shown in contrast to the same curves with fixture parasitics removed. Insertion loss measurements were then made of commonly available military specification plated wire twisted shielded pair that provided further confirming evidence for the predictions made from the numerical analysis. In all cases, observations and comments are provided to explain why some measurements were superior to others, and why certain steps were taken to defeat interference from clouding the results. The document closes with recommendations for future efforts and concluding remarks.

Scully, Robert C.

343

RF Breakdown in Accelerator Structures: From Plasma Spots to Surface Melting  

SciTech Connect

Plasma spots are known to form at field emission sites in regions of high dc or rf electric field. Several mechanisms for the formation of plasma spots in an rf field have been proposed, and one such mechanism which fits experimental data is presented in this paper. However, a plasma spot by itself does not produce breakdown. A single plasma spot, with a lifetime on the order of 30 ns, extracts only a negligible amount of energy from the rf field. The evidence for its existence is a small crater, on the order of 10 {micro}m in diameter, left behind on the surface. In this paper we present a model in which plasma spots act as a trigger to produce surface melting on a macroscopic scale ({approx} 0.1 mm2). Once surface melting occurs, a plasma that is capable of emitting several kiloamperes of electrons can form over the molten region. A key observation that must be explained by any theory of breakdown is that the probability of breakdown is independent of time within the rf pulse breakdown is just as likely to occur at the beginning of the pulse as toward the end. In the model presented here, the conditions for breakdown develop over many pulses until a critical threshold for breakdown is reached.

Wilson, P

2005-03-31

344

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

345

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

2014-08-01

346

Cell separation using electric fields  

NASA Technical Reports Server (NTRS)

The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

Mangano, Joseph A. (Inventor); Eppich, Henry M. (Inventor)

2003-01-01

347

Cell separation using electric fields  

NASA Technical Reports Server (NTRS)

The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.

Mangano, Joseph (Inventor); Eppich, Henry (Inventor)

2009-01-01

348

Spark gap with low breakdown voltage jitter  

DOEpatents

Novel spark gap devices and electrodes are disclosed. The novel spark gap devices and electrodes are suitable for use in a variety of spark gap device applications. The shape of the electrodes gives rise to local field enhancements and reduces breakdown voltage jitter. Breakdown voltage jitter of approximately 5% has been measured in spark gaps according the invention. Novel electrode geometries and materials are disclosed.

Rohwein, Gerald J. (Albuquerque, NM); Roose, Lars D. (Albuquerque, NM)

1996-01-01

349

Initiation of breakdown in slender compressible vortices  

NASA Technical Reports Server (NTRS)

The onset of vortex breakdown in compressible flows is investigated analytically for the case in which the flow is axially symmetric, the vortex is isolated, its axis is parallel to the main flow, and the vortex radius is small compared to the breakdown length. The conservation equations for mass, momentum, and energy are formulated and solved numerically using a finite-difference scheme, as described by Krause (1985); numerical results are presented in graphs and briefly characterized.

Krause, E.; Menne, S.; Liu, C. H.

1986-01-01

350

Dissipation process and the river formation model of the quantum Hall effect breakdown  

Microsoft Academic Search

In the river formation model recently proposed by Tsemekhman et al. [Phys. Rev. B 55 (1997) 10201] to account for the breakdown of the Quantum Hall Effect (QHE), a compressible river is formed when the Hall electric field attains a critical value. The brutal onset of the dissipation is due to the setup of a ohmic conduction process in the

C. Chaubet; F. Geniet

1998-01-01

351

Peak Power Handling limited by Microwave Breakdown in Air -Design and Validation  

E-print Network

Reduced transmission and return-loss. Increased absorption and heat Generation of O,O3,NO, NO2 In filter, corosion in silver and copper layer (green and gray) #12;4 7 Physics, modelling Modelling of the breakdown electrons are averaged and included 10 Power Handling · In the filter, the peak electric field will depend

Yu, Ming

352

Effect of surface conditions affecting voltage breakdowns  

NASA Astrophysics Data System (ADS)

The maximum power transferred by ion cyclotron range of frequency (ICRF) antennas is dependent on the breakdown threshold when operated at high voltages. The voltage that these antennas can withstand is lowered and hence breakdowns occur due to many factors. The Surface Plasma Arcs by Radiofrequency - Control Study or SPARCS facility has a 0-15kV DC power supply to deliver power to flat cathode surface and semi-spherical anode made of Cu and Al under 10-8-10-6 torr vacuum conditions. The effects of different surface conditions on the breakdown threshold were then investigated. Also, as the ICRF antennas used for heating plasmas may come into contact with contaminants from the plasma, Li was also deposited on the cathode surface through in-situ evaporation coating and its effect on the breakdown threshold was investigated. Results on surface roughness showed no significant dependence of the breakdown threshold on macroscopic surface roughness in the cathode arithmetic roughness range of ˜77-1139nm. Microscopic surface features such as grain boundaries, impurities and imperfections may play a more visible role in affecting the vacuum breakdown.

Flauta, Randolph; Aghazarian, Maro; Caughman, John; Ruzic, David

2008-11-01

353

Humidity effects on wire insulation breakdown strength.  

SciTech Connect

Methods for the testing of the dielectric breakdown strength of insulation on metal wires under variable humidity conditions were developed. Two methods, an ASTM method and the twisted pair method, were compared to determine if the twisted pair method could be used for determination of breakdown strength under variable humidity conditions. It was concluded that, although there were small differences in outcomes between the two testing methods, the non-standard method (twisted pair) would be appropriate to use for further testing of the effects of humidity on breakdown performance. The dielectric breakdown strength of 34G copper wire insulated with double layer Poly-Thermaleze/Polyamide-imide insulation was measured using the twisted pair method under a variety of relative humidity (RH) conditions and exposure times. Humidity at 50% RH and below was not found to affect the dielectric breakdown strength. At 80% RH the dielectric breakdown strength was significantly diminished. No effect for exposure time up to 140 hours was observed at 50 or 80%RH.

Appelhans, Leah

2013-08-01

354

Luminosity of initial breakdown in lightning  

NASA Astrophysics Data System (ADS)

Time correlated high-speed video and electromagnetic data for 15 cloud-to-ground and intracloud lightning flashes reveal bursts of light, bright enough to be seen through intervening cloud, during the initial breakdown (IB) stage and within the first 3 ms after flash initiation. Each sudden increase in luminosity is coincident with a CG type (12 cases) or an IC type (3 cases) IB pulse in fast electric field change records. The E-change data for 217 flashes indicate that all CG and IC flashes have IB pulses. The luminosity bursts of 14 negative CG flashes occur 11-340 ms before the first return stroke, at altitudes of 4-8 km, and at 4-41 km range from the camera. In seven cases, linear segments visibly advance away from the first light burst for 55-200 µs, then the entire length dims, then the luminosity sequence repeats along the same path. These visible initial leaders or streamers lengthen intermittently to about 300-1500 m. Their estimated 2-D speeds are 4-18 × 105 m s-1 over the first few hundred microseconds and decrease by about 50% over the first 2 ms. In other cases, only a bright spot or a broad area of diffuse light, presumably scattered by intervening cloud, is visible. The bright area grows larger over 20-60 µs before the luminosity fades in about 100 µs, then this sequence may repeat several times. In several flashes, a 1-2 ms period of little or no luminosity and small E-change is observed following the IB stage prior to stepped leader development.

Stolzenburg, M.; Marshall, T. C.; Karunarathne, S.; Karunarathna, N.; Vickers, L. E.; Warner, T. A.; Orville, R. E.; Betz, H.-D.

2013-04-01

355

Determining the feasibility of using a microcomputer for electrical trouble-shooting on underground mining machinery. Final report for 1984-85 SOMED Project  

Microsoft Academic Search

Breakdowns due to electrical component failure frequently occur with underground mining machines. These breakdowns interfere with normal production, while at the same time create potential safety hazards since repairmen must insert their hands into energized control-circuit areas to perform electrical trouble-shooting. Both the decreased productivity and safety problems associated with electrical breakdowns could possibly be reduced through using microcomputers for

T. Novak; W. E. Webb; S. K. Gupta

1985-01-01

356

A computational study of the topology of vortex breakdown  

NASA Technical Reports Server (NTRS)

A fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier-Stokes equations has been performed. Solutions to four distinct types of breakdown are identified and compared with experimental results. The computed solutions include weak helical, double helix, spiral, and bubble-type breakdowns. The topological structure of the various breakdowns as well as their interrelationship are studied. The data reveal that the asymmetric modes of breakdown may be subject to additional breakdowns as the vortex core evolves in the streamwise direction. The solutions also show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown.

Spall, Robert E.; Gatski, Thomas B.

1991-01-01

357

Effects of season (summer & winter) on electrical characteristics of skeletal muscle membranes of the spiny-tailed lizard, Uromastix hardwickii.  

PubMed

This study deals with the observation of changes with temperature variations of the seasons in the muscular electrical excitability in the reptile Uromastix hardwickii. Freshly captured adult animals of both the sexes were used in all the experiments, and the gastrocnemius (skeletal) muscles were dissected out. The muscle samples were digested with digestive fluid (pepsin & Hcl), stirred, settled and supernatant was removed, till whitish fluid having clear cells obtained for patch clamp recording of ionic currents and potentials. Resting membrane potentials and action potentials of reptilian cell membranes were measured in whole cell current mode. The glass microelectrodes, with a tip diameter 2-3 microm and tip resistance 5-6 MW (when filled with intracellular solution) were used in these experiments. The present study was carried out to investigate the electrical characteristics of the skeletal muscles of this species of Uromastix, which are not studied earlier. The average mean values of resting membrane potential, action potential and its durations showed no significant changes with the change in the season, but other components of action potential including threshold potential, after-potential and its duration were found to be increased significantly (P < 0.05) in summer as compared to winter. Temperature dependency of these parameters with seasonal variation, are studied for the first time in the gastrocnemius (skeletal) muscles of Uromastix hardwickii. Hence seasonal changes in the components of action potential are invariably associated with changes in environmental temperature, and may be responsible for changes in the activities and homeostasis of these animals; and possibly indicating underlying mechanism of hibernation. PMID:24968578

Soomro, Mohammad Saleh; Abdul Azeem, Muhammad; Kaneez, Fatima Shad; Soomro, Mohammad Naeem; Soomro, Mohammad Waseem

2013-01-01

358

Breakdown Degradation Associated with Elementary Screw Dislocations in 4H-SiC P(+)N Junction Rectifiers  

NASA Technical Reports Server (NTRS)

It is well-known that SiC wafer quality deficiencies are delaying the realization of outstandingly superior 4H-SiC power electronics. While efforts to date have centered on eradicating micropipes (i.e., hollow core super-screw dislocations with Burgers vector greater than 2c), 4H-SiC wafers and epilayers also contain elementary screw dislocations (i.e., Burgers vector = lc with no hollow core) in densities on the order of thousands per sq cm, nearly 100-fold micropipe densities. This paper describes an initial study into the impact of elementary screw dislocations on the reverse-bias current-voltage (I-V) characteristics of 4H-SiC p(+)n diodes. First, Synchrotron White Beam X-ray Topography (SWBXT) was employed to map the exact locations of elementary screw dislocations within small-area 4H-SiC p(+)n mesa diodes. Then the high-field reverse leakage and breakdown properties of these diodes were subsequently characterized on a probing station outfitted with a dark box and video camera. Most devices without screw dislocations exhibited excellent characteristics, with no detectable leakage current prior to breakdown, a sharp breakdown I-V knee, and no visible concentration of breakdown current. In contrast devices that contained at least one elementary screw dislocation exhibited a 5% to 35% reduction in breakdown voltage, a softer breakdown I-V knee, and visible microplasmas in which highly localized breakdown current was concentrated. The locations of observed breakdown microplasmas corresponded exactly to the locations of elementary screw dislocations identified by SWBXT mapping. While not as detrimental to SiC device performance as micropipes, the undesirable breakdown characteristics of elementary screw dislocations could nevertheless adversely affect the performance and reliability of 4H-SiC power devices.

Neudeck, P. G.; Huang, W.; Dudley, M.

1998-01-01

359

Acoustics of laminar boundary layers breakdown  

NASA Astrophysics Data System (ADS)

Boundary layer flow transition has long been suggested as a potential noise source in both marine (sonar-dome self noise) and aeronautical (aircraft cabin noise) applications, owing to the highly transient nature of process. The design of effective noise control strategies relies upon a clear understanding of the source mechanisms associated with the unsteady flow dynamics during transition. Due to formidable mathematical difficulties, theoretical predictions either are limited to early linear and weakly nonlinear stages of transition, or employ acoustic analogy theories based on approximate source field data, often in the form of empirical correlation. In the present work, an approach which combines direct numerical simulation of the source field with the Lighthill acoustic analogy is utilized. This approach takes advantage of the recent advancement in computational capabilities to obtain detailed information about the flow-induced acoustic sources. The transitional boundary layer flow is computed by solving the incompressible Navier-Stokes equations without model assumptions, thus allowing a direct evaluation of the pseudosound as well as source functions, including the Lighthill stress tensor and the wall shear stress. The latter are used for calculating the radiated pressure field based on the Curle-Powell solution of the Lighthill equation. This procedure allows a quantitative assessment of noise source mechanisms and the associated radiation characteristics during transition from primary instability up to the laminar breakdown stage. In particular, one is interested in comparing the roles played by the fluctuating volume Reynolds stress and the wall-shear-stresses, and in identifying specific flow processes and structures that are effective noise generators.

Wang, Meng

1994-12-01

360

Acoustics of laminar boundary layers breakdown  

NASA Technical Reports Server (NTRS)

Boundary layer flow transition has long been suggested as a potential noise source in both marine (sonar-dome self noise) and aeronautical (aircraft cabin noise) applications, owing to the highly transient nature of process. The design of effective noise control strategies relies upon a clear understanding of the source mechanisms associated with the unsteady flow dynamics during transition. Due to formidable mathematical difficulties, theoretical predictions either are limited to early linear and weakly nonlinear stages of transition, or employ acoustic analogy theories based on approximate source field data, often in the form of empirical correlation. In the present work, an approach which combines direct numerical simulation of the source field with the Lighthill acoustic analogy is utilized. This approach takes advantage of the recent advancement in computational capabilities to obtain detailed information about the flow-induced acoustic sources. The transitional boundary layer flow is computed by solving the incompressible Navier-Stokes equations without model assumptions, thus allowing a direct evaluation of the pseudosound as well as source functions, including the Lighthill stress tensor and the wall shear stress. The latter are used for calculating the radiated pressure field based on the Curle-Powell solution of the Lighthill equation. This procedure allows a quantitative assessment of noise source mechanisms and the associated radiation characteristics during transition from primary instability up to the laminar breakdown stage. In particular, one is interested in comparing the roles played by the fluctuating volume Reynolds stress and the wall-shear-stresses, and in identifying specific flow processes and structures that are effective noise generators.

Wang, Meng

1994-01-01

361

Observation of Multi-GeV Breakdown Thresholds in Dielectric Wakefield Structures  

Microsoft Academic Search

An experiment designed to test the breakdown threshold of a dielectric subjected to the GV\\/m-scale electric-fields of an intense electron-beam has been completed. In this experiment at the Final Focus Test Beam (FFTB) facility, the 28.5 GeV SLAC electron beam was focused down and propagated through short fused-silica capillary-tubes with internal diameters of as little as 100 m. The electric

M. C. Thompson; R. B. Yoder; M. J. Hogan; R. Ischebeck; N. A. Kirby; Robert H. Siemann; D. R. Walz; H. Badakov; J. B. Rosenzweig; G. Travish; A. Scott; P. Muggli

2008-01-01

362

Observation of multi-GeV breakdown thresholds in dielectric wakefield structures  

Microsoft Academic Search

An experiment designed to test the breakdown threshold of a dielectric subjected to the GV\\/m-scale electric-fields of an intense electron-beam has been completed. In this experiment at the final focus test beam (FFTB) facility, the 28.5 GeV SLAC electron beam was focused down and propagated through short fused-silica capillary-tubes with internal diameters of as little as 100 mum. The electric

M. C. Thompsonyz; H. Badakov; J. B. Rosenzweig; G. Travish; M. J. Hogan; R. Ischebeck; N. Kirby; R. Siemann; D. Walz; P. Muggli; A. Scott; R. Yoder

2007-01-01

363

Characterization of dielectric breakdown behavior by in situ transmission electron microscopy  

NASA Astrophysics Data System (ADS)

Dielectric breakdown (BD) is the loss of capacitance upheld by an insulating material through defect formation and charge trapping. Dielectric BD is well-studied in the framework of reliability physics for semiconductor applications, and presents itself as a viable mechanism during materials processing by electric field assisted sintering (EFAS). So far a mechanistic understanding of dielectric BD is incomplete due to the limitations in nanoscale defect characterization techniques. The recent development of novel in situ transmission electron microscopy (TEM) capabilities enables the atomic-scale characterization of dielectric BD mechanisms, which was the subject of this dissertation. As the technology of semiconductor devices moves toward the sub-25 nm technology the electronic properties of gate oxide layers are affected eventually leading to device failure by dielectric BD. This study aimed to provide a systematic approach of simultaneous imaging and local application of electrical stress using in situ TEM by contacting an electrically biased Scanning Tunnelling Microscopy (STM) probe directly to the TEM sample. This experimental setup therefore allows a correlation of electrical signatures with defect structure evolution. In situ TEM experiments carried out with a single SiO2-based field effect transistor resulted to catastrophic failure of the dielectric layer consistent with descriptions of soft dielectric breakdown (SBD) and hard dielectric breakdown (HBD). A variety of in situ TEM techniques was further utilized to investigate whether electric field induced dielectric breakdown may contribute to densification of metallic powder particles during EFAS. In situ heating and STM-TEM experiments were systematically applied to separately study thermal and athermal effects during densification, respectively. Nanometric metal powders used for sintering typically possess surface oxides that affect the thermodynamics and kinetics of neck formation during the initial stage of sintering. The thermal effects were found to be driven by reduction-oxidation reactions of nickel oxide with carbon. The presence of carbon promotes the removal of surface oxides at lower temperatures and, therefore, can accelerate densification. By the controlled application of electrical bias, EFAS conditions were reproduced during in situ TEM and revealed reduction of ultra-thin nickel oxide surface layers by electric field-induced dielectric breakdown. The results provide evidence for previously suggested effects of local electric field amplification at inter-particle contact areas, which, hence, triggers surface cleaning through electric field-induced dielectric breakdown.

Bonifacio, Cecile Semana

364

Breakdown tests of glass fibre reinforced polymers (GFRP) as part of improved lightning protection of wind turbine blades  

Microsoft Academic Search

This paper addresses a need for analysing the interaction between electrical discharges and GFRP. A test method for evaluating the breakdown and withstand voltages for materials used in wind turbine blades has been developed. The method is based on IEC 243-3, methods of test for electrical strength of solid insulating materials, and simulates the situation in a wind turbine blade,

S. F. Madsen; J. Holboell; M. Henriksen; F. M. Larsen; L. B. Hansen; K. Bertelsen

2004-01-01

365

Kerr electro-optic field mapping study of the effect of charge injection on the impulse breakdown strength of transformer oil  

NASA Astrophysics Data System (ADS)

The smart use of charge injection to improve breakdown strength in transformer oil is demonstrated in this paper. Hypothetically, bipolar homo-charge injection with reduced electric field at both electrodes may allow higher voltage operation without insulation failure, since electrical breakdown usually initiates at the electrode-dielectric interfaces. To find experimental evidence, the applicability and limitation of the hypothesis is first analyzed. Impulse breakdown tests and Kerr electro-optic field mapping measurements are then conducted with different combinations of parallel-plate aluminum and brass electrodes stressed by millisecond duration impulse. It is found that the breakdown voltage of brass anode and aluminum cathode is ˜50% higher than that of aluminum anode and brass cathode. This can be explained by charge injection patterns from Kerr measurements under a lower voltage, where aluminum and brass electrodes inject negative and positive charges, respectively. This work provides a feasible approach to investigating the effect of electrode material on breakdown strength.

Zhang, X.; Zahn, M.

2013-10-01

366

Reversible post-breakdown conduction in aluminum oxide-polymer capacitors  

NASA Astrophysics Data System (ADS)

Aluminum/Al2O3/polymer/metal capacitors submitted to a low-power constant current stress undergo dielectric breakdown. The post-breakdown conduction is metastable, and over time the capacitors recover their original insulating properties. The decay of the conduction with time follows a power law (1/t)?. The magnitude of the exponent ? can be raised by application of an electric field and lowered to practically zero by optical excitation of the polyspirofluorene polymer. The metastable conduction is attributed to formation of metastable pairs of oppositely charged defects across the oxide-polymer interface, and the self-healing is related to resistive switching.

Chen, Qian; Gomes, Henrique L.; Rocha, Paulo R. F.; de Leeuw, Dago M.; Meskers, Stefan C. J.

2013-04-01

367

Temperature-dependent high-current breakdown of the quantum Hall effect  

NASA Astrophysics Data System (ADS)

We have developed a model of the high-current breakdown of the integer quantum Hall effect, as measured in contactless experiments using a highly-sensitive torsion balance magnetometer. The model predicts that, for low-mobility samples, the critical current for breakdown should decrease linearly with temperature. This prediction is verified experimentally with the addition of a low-temperature (electric field in the sample reaches a large enough value.

Matthews, A. J.; Kavokin, K. V.; Usher, A.; Portnoi, M. E.; Zhu, M.; Gething, J. D.; Elliott, M.; Herrenden-Harker, W. G.; Phillips, K.; Ritchie, D. A.; Simmons, M. Y.; Sorensen, C. B.; Hansen, O. P.; Mironov, O. A.; Myronov, M.; Leadley, D. R.; Henini, M.

2004-04-01

368

Electrical Characteristics CuFe2O4 Thick Film Ceramics Made with Different Screen Size Utiizing Fe2O3 Nanopowder Derived from Yarosite for NTC Thermistor  

NASA Astrophysics Data System (ADS)

Fabrication of CuFe2O4 thick film ceramics utilizing Fe2O3 derived from yarosite using screen printing technique for NTC thermistor has been carried out. Effect of thickness variation due to different size of screen (screen 225; 300 and 375 mesh) has been studied. X-ray diffraction analyses (XRD) was done to know crystal structure and phases formation. SEM analyses was carried out to know microstructure of the films. Electrical properties characterization was done through measurement of electrical resistance at various temperatures (room temperature to 100° C). The XRD data showed that the films crystalize in tetragonal spinel. The SEM images showed that the screen with the smaller of the hole size, made the grain size was bigger. Electrical data showed that the larger the screen different size thickness variation (mesh), the larger the resistance, thermistor constant and sensitivity. From the electrical characteristics data, it was known that the electrical characteristics of the CuFe2O4 thick film ceramics followed the NTC characteristic. The value of B and RRT of the produced CuFe2O4 ceramics namely B = 3241-3484 K and RRT = 25.6-87.0 M Ohm, fitted market requirement.

Wiendartun, Syarif, Dani Gustaman

2010-10-01

369

Mechanism of Capacitance Aging under DC Electric Fields in Multilayer Ceramic Capacitors with X7R Characteristics  

NASA Astrophysics Data System (ADS)

Capacitance aging under DC electric fields has been studied on multilayer ceramic capacitors (MLCCs) with X7R characteristics. The capacitance change with time was divided into two consecutive stages. The first stage was due to the nonlinear permittivity of dielectrics and it should not be involved in the aging phenomenon. The second stage depended on the MnO content, grain size and firing conditions of the dielectrics. The aging was markedly depressed above the Curie temperature. From the behavior of the second stage, it was concluded that the capacitance aging is caused by the 90° domain switching in BaTiO3 in the core. An equation that represents the aging behavior in the second stage was presented and the mechanism that explains the capacitance aging was proposed. The first stage was due to the nonlinear permittivity and the second stage was due to the domain switching, but the domain switching was also included in the first stage if the domain walls were moved by the first application of a DC field. The change in the aging behavior with the intensity of the DC field could be explained by separating capacitance change into that due to the nonlinear permittivity and that due to the domain switching according to the mechanism proposed in this study. Finally, a methodology for handling the capacitance aging under DC fields was proposed.

Tsurumi, Takaaki; Shono, Motohiro; Kakemoto, Hirofumi; Wada, Satoshi; Saito, Kenji; Chazono, Hirokazu

2005-09-01

370

The characteristics of acupuncture-like transcutaneous electrical nerve stimulation (acupuncture-like TENS): a literature review.  

PubMed

Acupuncture-like Transcutaneous Electrical Nerve Stimulation (TENS) is used for pain relief. This study aimed to review the descriptions of the characteristics of acupuncture-like TENS reported within the published literature up to June 2011. A total of 88 items of published literature were retrieved.. 35 authors or groups provided 1 publication (Single Contributions - SC) and 10 authors or groups provided more than 1 publication (Multiple Contributions - MC). In order to gain the acupuncture-like effects of TENS, authors often characterised acupuncture-like TENS using: an intensity that caused muscle contractions (6MC, 17SC), or a sensation to tolerance threshold (3MC, 4SC); a 1-4 pulses per second (pps) pulse rate (5MC, 16SC); a 100-200 micros pulse duration (2MC, 8SC); stimulation to acupuncture points (5MC, 4SC), or myotomes (3MC, 3SC), or over the painful area (3MC, 1SC). Critically, unlike many authors included in the present review, the International Association for the Study of Pain core curriculum does not mention the triggering of muscle contractions when acupuncture-like TENS is defined. This may be an area that that they should reconsider. PMID:22443026

Francis, Richard P; Johnson, Mark I

2011-01-01

371

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

372

Influence of Structural Parameters on Electrical Characteristics of Schottky Tunneling Field-Effect Transistor and Its Scalability  

NASA Astrophysics Data System (ADS)

The influence of structural parameters, including the Schottky barrier height for electron (?Bn) and channel doping (Na), on the electrical characteristics of a scaled Schottky barrier tunneling FET (SBTFET) have been clarified by numerical device simulation. The thermionic emission current (ITH) as well as the tunneling current (ITN) have been considered as the main electron injections at the source edge. Simulation results have revealed that the main conduction is ITN in the region near and above the threshold voltage (Vth). As tunneling probability is determined by ?Bn and the width of the triangular potential barrier at the source edge, a lower ?Bn with higher Na results in a better subthreshold swing (SS) with high on-state drive current (ION) at a gate length (Lg) of 50 nm. With Lg scaling down to 10 nm, however, a lower ?Bn has shown an increased off-state leakage current (IOFF) due to the short-channel effect (SCE), while a larger ?Bn can suppress the IOFF at the cost of ION. Therefore, considering SS with ION and IOFF ratio, it can be concluded that an optimum ?Bn exists for short-channel devices. The SBTFET showed good subthreshold performance and higher ION/IOFF than the conventional silicon-on-insulator (SOI) MOSFET in 10 nm region with the Schottky barrier height optimization.

Wu, Yan; Dou, Chunmeng; Wei, Feng; Kakushima, Kuniyuki; Ohmori, Kenji; Ahmet, Parhat; Watanabe, Takanobu; Tsutsui, Kazuo; Nishiyama, Akira; Sugii, Nobuyuki; Natori, Kenji; Yamada, Keisaku; Kataoka, Yoshinori; Hattori, Takeo; Iwai, Hiroshi

2013-04-01

373

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

374

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

375

Optical, structural and electrical characteristics of aluminum oxynitride thin films deposited in an Ar-N gas mixture RF-sputtering system  

Microsoft Academic Search

The optical, structural and electrical characteristics of aluminum oxynitride thin films deposited on silicon by rf-sputtering under a fixed oxygen flow and two different Ar and N gas flows are reported. The stoichiometry of the films was studied by EDS as a function of the deposition parameters. In general, the relative oxygen content within the films was higher for a

J. J. Araiza; M. Aguilar-Frutis; C. Falcony; Ma. Jergel

2005-01-01

376

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

377

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

378

Effects of the Variation in the Dose of the Injector Implant on the Endurance Characteristics of Floating Gate Electrically Erasable Programmable Read Only Memory Devices  

Microsoft Academic Search

We have experimentally observed a dependence of the endurance characteristics of floating gate electrically erasable programmable read only memory (EEPROM) devices on the dose of the injector implant. With an increase in the implantation dose, the memory window closure is enhanced. This phenomenon is explained theoretically by calculating the change in threshold voltage and hence, the amount of charge injected

Anjan Bhattacharyya

1994-01-01

379

Ultra-Low Breakdown Voltage of Field Ionization in Atmospheric Air Based on Silicon Nanowires  

NASA Astrophysics Data System (ADS)

Classic field ionization requires extremely high positive electric fields, of the order of a few million volts per centimeter. Here we show that field ionization can occur at dramatically lower fields on the electrode of silicon nanowires (SiNWs) with dense surface states and large field enhancement factor. A field ionization structure using SiNWs as the anode has been investigated, in which the SiNWs were fabricated by improved chemical etching process. At room temperature and atmospheric pressure, breakdown of the air is reproducible with a fixed anode-to-cathode distance of 0.5 ?m. The breakdown voltage is ~38 V, low enough to be achieved by a battery-powered unit. Two reasons can be given for the low breakdown voltage. First, the gas discharge departs from the Paschen's law and the breakdown voltage decreases sharply as the gap distance falls in ?m range. The other reason is the large electric field enhancement factor (?) and the high density of surface defects, which cause a highly non-uniform electric field for field emission to occur.

Chen, Yun; Zhang, Jian

2013-11-01

380

Obstacle-induced spiral vortex breakdown  

NASA Astrophysics Data System (ADS)

An experimental investigation on vortex breakdown dynamics is performed. An adverse pressure gradient is created along the axis of a wing-tip vortex by introducing a sphere downstream of an elliptical hydrofoil. The instrumentation involves high-speed visualizations with air bubbles used as tracers and 2D Laser Doppler Velocimeter (LDV). Two key parameters are identified and varied to control the onset of vortex breakdown: the swirl number, defined as the maximum azimuthal velocity divided by the free-stream velocity, and the adverse pressure gradient. They were controlled through the incidence angle of the elliptical hydrofoil, the free-stream velocity and the sphere diameter. A single helical breakdown of the vortex was systematically observed over a wide range of experimental parameters. The helical breakdown coiled around the sphere in the direction opposite to the vortex but rotated along the vortex direction. We have observed that the location of vortex breakdown moved upstream as the swirl number or the sphere diameter was increased. LDV measurements were corrected using a reconstruction procedure taking into account the so-called vortex wandering and the size of the LDV measurement volume. This allows us to investigate the spatio-temporal linear stability properties of the flow and demonstrate that the flow transition from columnar to single helical shape is due to a transition from convective to absolute instability.

Pasche, Simon; Gallaire, François; Dreyer, Matthieu; Farhat, Mohamed

2014-08-01

381

LASER PLASMA: Interaction of laser plasmas upon optical breakdown in the normal atmosphere  

Microsoft Academic Search

The plasma front propagation regimes and the spectral characteristics of plasma emission upon laser breakdown in the normal atmosphere are experimentally investigated. The molecular emission of atmospheric gases is recorded at the initial instants of the development of the laser plasma. The behaviour of the intensities of continuous and line emission spectra is investigated upon interaction of counterpropagating plasma fronts;

O. A. Bukin; Aleksei A. Il'in; Yurii N. Kulchin; I. G. Nagornyi; A. N. Pavlov; A. V. Bulanov

2006-01-01

382

An assessment of cellulose filters as a standardized material for measuring litter breakdown in headwater streams  

EPA Science Inventory

The decay rate of cellulose filters and associated chemical and biological characteristics were compared to those of white oak (Quercus alba) leaves to determine if cellulose filters could be a suitable standardized material for measuring deciduous leaf breakdown in headwater str...

383

An Assessment of Cellulose Filters as a Standardized Material for Measuring Litter Breakdown in Headwater Streams  

EPA Science Inventory

The decay rate of cellulose filters and associated chemical and biological characteristics were compared to those of white oak (Quercus alba) leaves to determine if cellulose filters could be a suitable standardized material for measuring deciduous leaf breakdown in headwater str...

384

Breakdown Limits on Gigavolt-per-Meter Electron-Beam-Driven Wakefields in Dielectric Structures  

SciTech Connect

First measurements of the breakdown threshold in a dielectric subjected to GV/m wakefields produced by short (30-330 fs), 28.5 GeV electron bunches have been made. Fused silica tubes of 100 {micro}m inner diameter were exposed to a range of bunch lengths, allowing surface dielectric fields up to 27 GV/m to be generated. The onset of breakdown, detected through light emission from the tube ends, is observed to occur when the peak electric field at the dielectric surface reaches 13.8 {+-} 0.7 GV/m. The correlation of structure damage to beam-induced breakdown is established using an array of postexposure inspection techniques.

Thompson, M.C.; /UCLA /LLNL, Livermore; Badakov, H.; Cook, A.M.; Rosenzweig, J.B.; Tikhoplav, R.; Travish, G.; /UCLA; Blumenfeld, I.; Hogan, M.J.; Ischebeck, R.; Kirby, N.; Siemann, R.; Walz, D.; /SLAC; Muggli, P.; /Southern California U.; Scott, A.; /UC, Santa Barbara; Yoder, R.B.; /Manhattan Coll., Riverdale

2008-06-17

385

Breakdown Limits on Gigavolt-per-Meter Electron-Beam-Driven Wakefields in Dielectric Structures  

NASA Astrophysics Data System (ADS)

First measurements of the breakdown threshold in a dielectric subjected to GV/m wakefields produced by short (30 330 fs), 28.5 GeV electron bunches have been made. Fused silica tubes of 100?m inner diameter were exposed to a range of bunch lengths, allowing surface dielectric fields up to 27GV/m to be generated. The onset of breakdown, detected through light emission from the tube ends, is observed to occur when the peak electric field at the dielectric surface reaches 13.8±0.7GV/m. The correlation of structure damage to beam-induced breakdown is established using an array of postexposure inspection techniques.

Thompson, M. C.; Badakov, H.; Cook, A. M.; Rosenzweig, J. B.; Tikhoplav, R.; Travish, G.; Blumenfeld, I.; Hogan, M. J.; Ischebeck, R.; Kirby, N.; Siemann, R.; Walz, D.; Muggli, P.; Scott, A.; Yoder, R. B.

2008-05-01

386

Microwave breakdown for the TE{sub 10} mode in a rectangular waveguide  

SciTech Connect

Microwave breakdown is studied for the lowest order TE{sub 10} 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. [Plasma Waves and Particle Acceleration Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi–110 016 (India)] [Plasma Waves and Particle Acceleration Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi–110 016 (India)

2013-08-15

387

The inception of pulsed discharges in air: simulations in background fields above and below breakdown  

NASA Astrophysics Data System (ADS)

We investigate discharge inception in air, in uniform background electric fields above and below the breakdown threshold. We perform 3D particle simulations that include a natural level of background ionization in the form of positive and \\text{O}2- ions. In background fields below breakdown, we use a strongly ionized seed of electrons and positive ions to enhance the field locally. In the region of enhanced field, we observe the growth of positive streamers, as in previous simulations with 2D plasma fluid models. The inclusion of background ionization has little effect in this case. When the background field is above the breakdown threshold, the situation is very different. Electrons can then detach from \\text{O}2- and start ionization avalanches in the whole volume. These avalanches together create one extended discharge, in contrast to the ‘double-headed’ streamers found in many fluid simulations.

Sun, Anbang; Teunissen, Jannis; Ebert, Ute

2014-11-01

388

Effects of transportation during the hot season, breed and electrical stimulation on histochemical and meat quality characteristics of goat longissimus muscle.  

PubMed

The effects of transportation and electrical stimulation (90 V) on physiological, histochemical and meat quality characteristics of two breeds of Omani goats were assessed. Twenty 1-year-old male goats from each breed (Batina and Dhofari) were divided into two groups: 3 h transported during the hot season (42 degrees C day time temperature) and non-transported. Animals were blood-sampled before loading and prior to slaughter. Electrical stimulation was applied 20 min postmortem to 50% randomly selected carcasses of both breeds. Temperature and pH decline of the Longissimus was monitored. Ultimate pH, shear force, sarcomere length, myofibrillar fragmentation index, expressed juice, cooking loss and colour were measured from samples of Longissimus dorsi muscles. Electrical stimulation and transportation had a significant effect on most biochemical and meat quality characteristics of Longissimus dorsi. The transported goats had higher plasma cortisol (P < 0.01), adrenaline, nor-adrenaline and dopamine concentrations (P < 0.05) than non-transported goats. Electrical stimulation resulted in a significantly (P < 0.05) more rapid muscle pH fall during the first 12 h after slaughter. Muscles from electrically-stimulated carcasses had significantly (P < 0.05) longer sarcomeres, lower shear force value, a lighter colour (higher L* value), higher expressed juice and myofibrillar fragmentation index than those from non-stimulated ones. Meat from transported goats had significantly higher pH, expressed juice and shear force, but contained significantly lower sarcomere length and L* values than non-transported goats. The proportion of the myosin ATPase staining did not change as a function of stimulation, transportation or breed. These results indicated that subjecting goats to transportation for 3 h under high ambient temperatures can generate major physiological and muscle metabolism responses. Electrical stimulation improved quality characteristics of meat from both groups. This indicates that electrical stimulation may reduce detrimental effects of transportation on meat quality of Omani goats. PMID:20597893

Kadim, Isam T; Mahgoub, Osman; Al-Marzooqi, Waleed; Khalaf, Samera; Al-Sinawi, Shadia S H; Al-Amri, Issa

2010-06-01

389

Effect of Pressure on Discharge Initiation and Chemical Reaction in a Liquid-Phase Electrical Discharge Reactor  

Microsoft Academic Search

The effect of pressure on liquid-phase electrical discharges was investigated by using a stainless steel high-pressure reactor combined with a high-voltage pulse forming network. The initiation breakdown voltage was obtained under various pressures up to 1380 kPa (200 lb\\/in2 ). The discharge characteristics including current and voltage waveforms as well as power per pulse were determined. The effect of pressure

Kai-Yuan Shih; Radu Burlica; Wright C. Finney; Bruce R. Locke

2009-01-01

390

Study and application on the tst system for the dielectric characteristics of high-resistance powder  

NASA Astrophysics Data System (ADS)

The importance of the present study is that the dielectric characteristic of powder materials with high specific resistivity can affect the electrostatic precipitator operation, electrostatic daub, lightning strikes, etc. This paper studied and analyzed a test system for the dielectric characteristics of high-resistivity powder, including current leakage and breakdown voltage. The resistivity range of the system was from10 4?•cm to 10 14?•cm. The test voltage was from 0.5kV to 30kV (direct current), and the least leak current was 10 -9A. The test temperature was from room temperature to 300°C. The system is capable of testing and studying the resistivity and the high-voltage field intensity of electrical breakdown of industrial powders under various laboratory conditions. Results show that this system has applied widely in China and it has obtained the invent patent in China.

Yuan, Yongtao; Qi, Liqiang; Yang, Qian

2005-12-01

391

RF Breakdown Studies Using a 1.3 GHZ Test Cell  

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. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) and pressure barrier capable of operating both at high pressure and in vacuum has been designed and built, and preliminary testing has been completed. A series of detailed experiments is planned at the Argonne Wakefield Accelerator. At the same time, computer simulations of the RF Breakdown process will be carried out to help develop a consistent physics model of RF Breakdown. In order to study the effect of the radiofrequency on RF Breakdown, a second test cell will be designed, fabricated, and tested at a lower frequency, most likely 402.5 MHz.

Sah, R.; Johnson, R.P.; Neubauer, M.; /Muons Inc., Batavia; Conde, M.; Gai, W.; /Argonne; Moretti, A.; Popovic, M.; Yonehara, K.; /Fermilab; Byrd, J.; Li, D.; /LBL, Berkeley; BastaniNejad, M.; /Old Dominion U.

2009-05-01

392

RF Breakdown Studies Using a 1.3-GHz Text Cell  

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. Recent studies have shown that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas without the need for long conditioning times, because the dense gas can dramatically reduce dark currents and multipacting. In this project we use this high pressure technique to suppress effects of residual vacuum and geometry found in evacuated cavities to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. A 1.3-GHz RF test cell with replaceable electrodes (e.g. Mo, Cu, Be, W, and Nb) and pressure barrier capable of operating both at high pressure and in vacuum has been designed and built, and preliminary testing has been completed. A series of detailed experiments is planned at the Argonne Wakefield Accelerator. At the same time, computer simulations of the RF Breakdown process will be carried out to help develop a consistent physics model of RF Breakdown. In order to study the effect of the radiofrequency on RF Breakdown, a second test cell will be designed, fabricated, and tested at a lower frequency, most likely 402.5 MHz.

Sah, R.; Johnson, R. P.; Neubauer, M.; Conde, M.; Gai, W.; Moretti, A.; Popovic, M.; Yonehara, K.; Byrd, J.; Li, D.; BastaniNejad, M.; Elmustafa, M.

2009-05-04

393

Numerical analyses of fast inter-cathode break-down in open-cycle MHD generator  

NASA Astrophysics Data System (ADS)

Phenomena of interelectrode breakdown in the supersonic Faraday type MHD generator are studied through time-dependent 2D numerical analyses. The entire area of a single electrode-pair is analyzed. The dependency of electrical conductivity has been modified for the high temperature in the present analyses. No interelectrode breakdown is induced, when the channel is operated under the design condition with the averaged y-component of current density of 0.96 A/sq cm and of a Hall field of -30.4 V/cm. The intercathode breakdown alone is induced, whereas no breakdown occurs at the anode under the condition of the averaged y-component of current density of 1.91 A/sq cm and of the Hall field of -60.7 V/cm. Boundary layer separation is induced by the strong axial current between adjacent cathodes. During computations, a probable new bifurcation phenomenon has been found near cathode when the intercathode breakdown is induced.

Ishikawa, M.; Matsuura, Y.; Matsushita, Y.; Umoto, J.

1993-07-01

394

Breakdowns in Coordination Between Air Traffic Controllers  

NASA Technical Reports Server (NTRS)

This talk outlines the complexity of coordination in air traffic control, introduces the NextGen technologies, identifies common causes for coordination breakdowns in air traffic control and examines whether these causes are likely to be reduced with the introduction of NextGen technologies. While some of the common causes of breakdowns will be reduced in a NextGen environment this conclusion should be drawn carefully given the current stage of development of the technologies and the observation that new technologies often shift problems rather than reduce them.

Bearman, Chris; Orasanu, Judith; Miller, Ronald C.

2011-01-01

395

Electrical properties of commercial sheet insulation materials for cryogenic applications  

SciTech Connect

Dielectric properties of electrical insulation materials are needed for low-temperature power applications. Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. In this work we report the dielectric properties of some commercially available materials in sheet form. The selected materials are polypropylene laminated paper from Sumitomo Electric U.S.A., Inc., porous polyethylene (Tyvek\\texttrademark) from Dupont, and polyamide paper (Nomex\\texttrademark) from Dupont. The dielectric properties are characterized with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 50 to 300 K. The dielectric breakdown characteristics of the materials are measured in a liquid nitrogen bath at atmospheric pressure.

Tuncer, Enis [ORNL; Sauers, Isidor [ORNL; James, David Randy [ORNL; Ellis, Alvin R [ORNL; Pace, Marshall O [ORNL

2008-01-01

396

Grain boundary assisted degradation and breakdown study in cerium oxide gate dielectric using scanning tunneling microscopy  

NASA Astrophysics Data System (ADS)

The presence of grain boundaries (GBs) in polycrystalline high-? (HK) gate dielectric materials affects the electrical performance and reliability of advanced HK based metal-oxide-semiconductor devices. It is important to study the role of GB in stress-induced-leakage current (SILC) degradation and time-dependent dielectric breakdown of polycrystalline HK gate stacks. In this work, we present nanoscale localized electrical study and uniform stressing analysis comparing the electrical conduction properties at grain and GB locations for blanket cerium oxide (CeO2)-based HK thin films using scanning tunneling microscopy. The results clearly reveal higher SILC degradation rate at GB sites and their vulnerability to early percolation, supporting the phenomenon of GB-assisted HK gate dielectric degradation and breakdown.

Shubhakar, K.; Pey, K. L.; Kushvaha, S. S.; O'Shea, S. J.; Raghavan, N.; Bosman, M.; Kouda, M.; Kakushima, K.; Iwai, H.

2011-02-01

397

Magnetic and Electrical Characteristics of Cobalt-Based Amorphous Materials and Comparison to a Permalloy Type Polycrystalline Material  

NASA Technical Reports Server (NTRS)

Magnetic component designers are always looking for improved soft magnetic core materials to increase the efficiency, temperature rating and power density of transformers, motors, generators and alternators, and energy density of inductors. In this paper, we report on the experimental investigation of commercially available cobalt-based amorphous alloys which, in their processing, were subjected to two different types of magnetic field anneals: A longitudinal magnetic field anneal or a transverse magnetic field anneal. The longitudinal field annealed material investigated was Metglas 2714A. The electrical and magnetic characteristics of this material were investigated over the frequency range of 1 to 200 kHz and temperature range of 23 to 150 C for both sine and square wave voltage excitation. The specific core loss was lower for the square than the sine wave voltage excitation for the same maximum flux density, frequency and temperature. The transverse magnetic field annealed core materials include Metglas 2714AF and Vacuumschmelze 6025F. These two materials were experimentally characterized over the frequency range of 10 to 200 kHz for sine wave voltage excitation and 23 C only. A comparison of the 2174A to 2714AF found that 2714AF always had lower specific core loss than 2714A for any given magnetic flux density and frequency and the ratio of specific core loss of 2714A to 2714AF was dependent on both magnetic flux density and frequency. A comparison was also made of the 2714A, 2714AF, and 6025F materials to two different tape thicknesses of the polycrystalline Supermalloy material and the results show that 2714AF and 6025F have the lowest specific core loss at 100 kHz over the magnetic flux density range of 0.1 to 0.4 Tesla.

Wieserman, William R.; Schwarze, Gene E.; Niedra, Janis M.

2005-01-01

398

Comparative study on preliminary breakdown pulse trains observed in Johor, Malaysia and Florida, USA  

NASA Astrophysics Data System (ADS)

In this paper, the preliminary breakdown (PB) pulse train preceding the negative first return stroke (RS) is recorded using a broad band antenna system. These analyses were carried out in Johor Bahru, Malaysia and Florida, United States. This is a novel initiative at examining and identifying the characteristics of the PB pulse trains in the negative cloud-to-ground flashes observed in Malaysia. The arithmetic mean of the total pulse train duration is 12.3 ms and the weighted arithmetic mean of the pulse durations and interpulse intervals are 11 ?s and 152 ?s, respectively. The arithmetic mean ratio between the maximum peak amplitude of the PB pulse and the peak RS electric field was 27.8%, and the corresponding value in Florida was 29.4%. The arithmetic mean of the time duration between the most active part of the pulse train, and the RS was 57.6 ms in Malaysia and 22 ms in Florida. A qualitative comparison of our results with those obtained earlier in Sri Lanka, Sweden and Finland supports the hypothesis that the PBP/RS ratio is higher in the northern regions compared to the tropical regions.

Baharudin, Z. A.; Ahmad, Noor Azlinda; Fernando, M.; Cooray, V.; Mäkelä, J. S.

2012-11-01

399

Rapid composition analysis of compound semiconductor thin film solar cell by laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

The characteristics of laser-induced breakdown spectroscopy (LIBS) such as short measurement time and no sample preparation provide clear advantages over other analytical techniques for rapid elemental analysis at manufacturing sites where the composition of products need to be determined in real-time for process monitoring or quality control. Thin film solar cells based on CuIn1-xGaxSe2 (CIGS), polycrystalline compound semiconductor material, have unique advantages of high efficiency (>20%), long-term stability, and low manufacturing cost over other types of solar cell. The electrical and optical properties of the thin CIGS films are closely related to the concentration ratios among its major constituent elements Cu, In, Ga and Se such as Ga/(Ga + In) and Cu/(Ga + In), and thus an accurate measurement of the composition of CIGS thin films has been an issue among CIGS solar cell researchers, requiring a fast and reliable technique for composition analysis. This paper presents the results of nanosecond (ns) and femtosecond (fs) laser based LIBS analysis of thin CIGS films. The critical issues for LIBS analysis of CIGS thin films such are discussed in comparison with ns- and fs-LIBS measurement results. The calibration of LIBS signal intensity ratios with respect to reference concentration data is carried out and the results of optimal line selection for LIBS analysis, depth profiling capability, and reproducibility are discussed.

Lee, S. H.; Kim, C. K.; In, J. H.; Jeong, S. H.

2014-03-01

400

Titanium monoxide spectroscopy following laser-induced optical breakdown  

NASA Astrophysics Data System (ADS)

This work investigates Titanium Monoxide (TiO) in ablation-plasma by employing laser-induced breakdown spectroscopy (LIBS) with 1 to 10 TW/cm2 irradiance, pulsed, 13 nanosecond, Q-switched Nd:YAG laser radiation at the fundamental wavelength of 1064 nm. The analysis of TiO is based on our first accurate determination of transition line strengths for selected TiO A-X, B-X, and E-X transitions, particularly TiO A-X ? and B-X ?' bands. Electric dipole line strengths for the A3?-X3? and B3?-X3? bands of TiO are computed. The molecular TiO spectra are observed subsequent to laser-induced breakdown (LIB). We discuss analysis of diatomic molecular spectra that may occur simultaneously with spectra originating from atomic species. Gated detection is applied to investigate the development in time of the emission spectra following LIB. Collected emission spectra allow one to infer micro-plasma parameters such as temperature and electron density. Insight into the state of the micro-plasma is gained by comparing measurements with predictions of atomic and molecular spectra. Nonlinear fitting of recorded and computed diatomic spectra provides the basis for molecular diagnostics, while atomic species may overlap and are simultaneously identified. Molecular diagnostic approaches similar to TiO have been performed for diatomic molecules such as AlO, C2, CN, CH, N2, NH, NO and OH.

Parigger, Christian G.; Woods, Alexander C.; Keszler, Anna; Nemes, László; Hornkohl, James O.

2012-07-01

401

Dielectric breakdown during Cs+ sputtering of polyvinyl chloride  

NASA Astrophysics Data System (ADS)

Thin films of insulating polymers are sometimes analyzed by secondary ion mass spectrometry (SIMS) or by X-ray photoelectron spectroscopy (XPS) without the use of an electron gun. In this work, both SIMS and XPS have been used to study the chemical and structural modifications due to the charge effect during Cs+ sputtering of a thin film of polyvinyl chloride (PVC). The kinetic energy distribution study shows that at a small primary fluence ˜1015 Cs+ ions/cm2, the dielectric breakdown voltage of the PVC film is reached, i.e. the minimum voltage that causes a portion of an insulator to become electrically conductive. XPS study indicates that the conducting phase created in the PVC film after energetic Cs+ bombardment consists of graphitized carbon and metallic cesium clusters. After the dielectric breakdown of the film, the positive charge, previously accumulated on the surface, is neutralized through the conductive regions, which are created in the insulating film. During Cs+ sputtering of a PVC film, the chemical structure of the analyzed surface is completely modified and some ionic bonds such as CsC and CsCl are also created.

Wahoud, F.; Guillot, J.; Audinot, J. N.; Bertrand, P.; Delcorte, A.; Migeon, H. N.

2014-02-01

402

Modeling of time-dependent non-uniform dielectric breakdown using a clustering statistical approach  

NASA Astrophysics Data System (ADS)

We report a time-dependent clustering model for non-uniform dielectric breakdown. Its area scaling and low-percentile scaling properties are rigorously investigated. While at high percentiles non-uniform area scaling dominates, the model restores the weakest-link characteristics at low percentiles relevant for reliability projection. As a result, we develop a comprehensive methodology for the parameter extraction and projection methodology for non-uniform dielectric breakdown. Excellent agreement is obtained between the model and the experimental data of back-end-of-line low-k dielectrics and front-end-of-line gate dielectrics, suggesting a wide range of applications of this model in the field of dielectric breakdown reliability.

Wu, Ernest Y.; Li, Baozhen; Stathis, James H.

2013-10-01

403

Pulse breakdown in synchronised optical parametric oscillator  

Microsoft Academic Search

Summary form only given. Recent advances in optical parametric oscillators (OPO) design has led to increased power and extended wavelength ranges. The simple phase matching condition no longer describes the complex behavior of these novel systems. In the case of a synchronously pumped monolithic signal resonated OPO based on periodically poled LiNbO3 (PPLN) crystal we have observed spectral pulse breakdown

P. J. Phillips; M. Ebrahimzadeh; M. Mazilu; A. Miller

2001-01-01

404

Heme content and breakdown in developing chloroplasts  

SciTech Connect

Heme regulates tetrapyrrole biosynthesis in plants by inhibition of {delta}-aminolevulinic acid (ALA) synthesis, product inhibition of heme synthesis, and possibly other mechanisms. Plastid heme levels may be modulated by heme synthesis, breakdown and/or efflux. Heme breakdown may be catalyzed by a chloroplast localized heme oxygenase. Chloroplasts isolated from greening cucumber cotyledons were incubated in the presence or absence of various components thought to modulate heme breakdown. Following the incubations, the chloroplasts were broken (freeze-thaw) and then supplemented with horseradish peroxidase apoenzyme. The reconstituted peroxidase activity was used to determine the amount of free heme remaining (Thomas Weinstein (1989) Plant Physiol. 89S: 74). Chloroplasts, freshly isolated from seedlings greened for 16 hours, contained approximately 37 pmol heme/mg protein. When chloroplasts were incubated with 5 mM NADPH for 30 min, the endogenous heme dropped to unmeasurable levels. Exogenous heme was also broken down when NADPH was included in the incubation. Heme levels could be increased by the inclusion of 50 {mu}M ALA and/or p-hydroxymercuribenzoate. The increase due to exogenous ALA was blocked by levulinic acid, an inhibitor of ALA utilization. NADPH-dependent heme breakdown acid was inhibited by p-hydroxymercuribenzoate.

Thomas, J.; Weinstein, J.D. (Clemson Univ., SC (USA))

1990-05-01

405

Screening of Time-Dependent Dielectric Breakdowns  

Microsoft Academic Search

A study of screening effect on MSOS dots has shown the effect of time as well as stress on the screening of time-dependent breakdown. A model is described which is based on a reduction of allotted time-to-fail for a given area.

Eugene S. Anolick; Li-Yu Chen

1982-01-01

406

Breakdown of predictability in gravitational collapse  

Microsoft Academic Search

In this paper it is claimed that the breakdown of classical concepts of space and time is not merely a result of our ignorance of the correct theory but that it represents a fundamental limitation to our ability to predict the future, a limitation that is analogous but additional to the limitation imposed by the normal quantum-mechanical uncertainty principle. The

S. W. Hawking

1976-01-01

407

Gracefully Mitigating Breakdowns in Robotic Services  

E-print Network

impact on evaluations of the service and the robot, but forewarning and recovery strategies reduced how to mitigate breakdowns in services provided by robots. Expectancy-setting strategies forewarn people of a robot's limitations so people will expect mistakes. Recovery strategies, including apologies

Kiesler, Sara

408

Energy conversion efficiency during optical breakdown  

Microsoft Academic Search

The efficiency of optical to acoustical energy conversion during laser-induced optical breakdown has been examined. A point-explosion model has been studied to determine the value of laser-induced shock wave energy. The influence of incoming laser-pulse energy on conversion efficiency has been studied for several absorber materials.

Ladislav Grad; Janez Diaci; Janez Mozina

1991-01-01

409

Instrumental developments for in situ breakdown experiments inside a scanning electron microscope  

NASA Astrophysics Data System (ADS)

Electrical discharges in accelerating structures are one of the key issues limiting the performance of future high energy accelerators such as the Compact Linear Collider (CLIC). Fundamental understanding of breakdown phenomena is an important part of the CLIC feasibility study. The present work concerns the experimental study of breakdown using Scanning Electron Microscopes (SEMs). An SEM gives us the opportunity to achieve high electrical gradients of 1 kV/ ?m which corresponds to 1 GV/m by exciting a probe needle with a high voltage power supply and controlling the positioning of the needle with a linear piezo motor. The gap between the needle tip and the surface is controlled with sub-micron precision. A second electron microscope equipped with a Focused Ion Beam (FIB) is used to create surface corrugations and to sharpen the probe needle to a tip radius of about 50 nm. Moreover it is used to prepare cross-sections of a voltage breakdown area in order to study the geometrical surface damages as well as the elemental composition of the breakdown.

Muranaka, T.; Blom, T.; Leifer, K.; Ziemann, V.

2011-11-01

410

Aerosol measurements with laser-induced breakdown spectroscopy  

E-print Network

laser-induced breakdown spectroscopy measurements, Applied Physics Letters,by giant-pulse laser. Applied Physics Letters, vol. 3, no.Laser-Induced Breakdown Spectroscopy Measurements,” Applied Physics Letters,

Lithgow, Gregg Arthur

2007-01-01

411

Breakdown of Stokes-Einstein relation in supercooled water  

E-print Network

Water displays breakdown of the Stokes-Einstein relation at low temperatures. We hypothesize that the breakdown is a result of the structural changes and a sharp rise in dynamic heterogeneities that occurs low T upon crossing the Widom line.

Pradeep Kumar

2007-02-06

412

Engineering carbon nanotubes and nanotube circuits using electrical breakdown.  

PubMed

Carbon nanotubes display either metallic or semiconducting properties. Both large, multiwalled nanotubes (MWNTs), with many concentric carbon shells, and bundles or "ropes" of aligned single-walled nanotubes (SWNTs), are complex composite conductors that incorporate many weakly coupled nanotubes that each have a different electronic structure. Here we demonstrate a simple and reliable method for selectively removing single carbon shells from MWNTs and SWNT ropes to tailor the properties of these composite nanotubes. We can remove shells of MWNTs stepwise and individually characterize the different shells. By choosing among the shells, we can convert a MWNT into either a metallic or a semiconducting conductor, as well as directly address the issue of multiple-shell transport. With SWNT ropes, similar selectivity allows us to generate entire arrays of nanoscale field-effect transistors based solely on the fraction of semiconducting SWNTs. PMID:11326094

Collins, P G; Arnold, M S; Avouris, P

2001-04-27

413

A computational study of the taxonomy of vortex breakdown  

NASA Technical Reports Server (NTRS)

The results of a fully three-dimensional numerical simulation of vortex breakdown using the unsteady, incompressible Navier-Stokes equations are presented. The solutions show that the freestream axial velocity distribution has a significant effect on the position and type of vortex breakdown. Common features between bubble-type and spiral-type breakdown are identified and the role of flow stagnation and the critical state are discussed as complimentary ideas describing the initiation of breakdown.

Spall, Robert E.; Gatski, Thomas B.

1990-01-01

414

Laser induced breakdown spectroscopy library for the Martian environment  

NASA Astrophysics Data System (ADS)

The NASA Mars Science Laboratory rover will carry the first Laser Induced Breakdown Spectroscopy experiment in space: ChemCam. We have developed a laboratory model which mimics ChemCam's main characteristics. We used a set of target samples relevant to Mars geochemistry, and we recorded individual spectra. We propose a data reduction scheme for Laser Induced Breakdown Spectroscopy data incorporating de-noising, continuum removal, and peak fitting. Known effects of the Martian atmosphere are confirmed with our experiment: better Signal-to-Noise Ratio on Mars compared to Earth, narrower peak width, and essentially no self-absorption. The wavelength shift of emission lines from air to Mars pressure is discussed. The National Institute of Standards and Technology vacuum database is used for wavelength calibration and to identify the elemental lines. Our Martian database contains 1336 lines for 32 elements: H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ar, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Rb, Sr, Cs, Ba, and Pb. It is a subset of the National Institute of Standards and Technology database to be used for Martian geochemistry. Finally, synthetic spectra can be built from the Martian database. Correlation calculations help to distinguish between elements in case of uncertainty. This work is used to create tools and support data for the interpretation of ChemCam results.

Cousin, A.; Forni, O.; Maurice, S.; Gasnault, O.; Fabre, C.; Sautter, V.; Wiens, R. C.; Mazoyer, J.

2011-11-01

415

Effect of surface roughness on electrical characteristics in amorphous InGaZnO thin-film transistors with high-? Sm2O3 dielectrics  

NASA Astrophysics Data System (ADS)

We investigated the effect of surface roughness on the electrical characteristics in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) fabricating high-? Sm2O3 gate dielectrics, prepared under different annealing temperatures. The high-? Sm2O3 a-IGZO TFT device annealed at 200 °C exhibited better electrical characteristics, including a large field effect mobility of 6.25 cm2/V s, small threshold voltage of 0.79 V, low subthreshold swing of 354 mV/decade, and high Ion/Ioff ratio of 3.1×107. These results are attributed to the formation of smooth surface at the oxide/channel interface. Furthermore, the reliability of a Sm2O3 a-IGZO TFT device can be improved by oxygen annealing at low temperature.

Chen, Fa-Hsyang; Hung, Meng-Ning; Yang, Jui-Fu; Kuo, Shou-Yi; Her, Jim-Long; Matsuda, Yasuhiro H.; Pan, Tung-Ming

2013-04-01

416

Electrical Characteristics of InGaN/AlGaN and InGaN/GaN MQW Near UV-LEDs  

NASA Astrophysics Data System (ADS)

Electrical characteristics of In0.05Ga0.95N/Al0.07Ga0.93N and In0.05Ga0.95N/GaN multiple quantum well (MQW) ultraviolet light-emitting diodes (UV-LEDs) at 400 nm wavelength are measured. It is found that for InGaN/AlGaN MQW LEDs, both ideality factor and parallel resistance are similar to those of InGaN/GaN MQW LEDs, while series resistance is two times larger. It is suggested that the Al0.07Ga0.93N barrier layer did not change crystal quality and electrical characteristic of p-n junction either, but brought larger series resistance. As a result, InGaN/AlGaN MQW LEDs suffer more serious thermal dissipation problem although they show higher light output efficiency.

Mu, Sen; Yu, Tong-Jun; Huang, Liu-Bing; Jia, Chuan-Yu; Pan, Yao-Bo; Yang, Zhi-Jian; Chen, Zhi-Zhong; Qin, Zhi-Xin; Zhang, Guo-Yi

2007-11-01

417

Investigation of breakdown processes in automotive HID lamps  

NASA Astrophysics Data System (ADS)

HID lamps are used for applications where high lumen output levels are required. Car headlights are a special field of HID lamp application. For security reasons and lawful regulations these lamps have to have a fast run-up phase and the possibility of hot re-strike. Therefore the background gas pressure amounts to 1.5,Pa xenon. But this high background gas pressure has the disadvantage that the ignition voltage becomes quite high due to Paschen's law. For that reason this paper deals with the investigation of the breakdown process of HID lamps for automotive application. The ignition is investigated by electrical as well as optical methods. Ignition voltage and current are measured on a nanosecond time scale and correlated with simultaneous phase resolved high speed photography done by an ICCD camera. So the ignition process can be observed from the first light emission until to the formation of whole discharge channel.

Bergner, Andre; Hoebing, Thomas; Ruhrmann, Cornelia; Mentel, Juergen; Awakowicz, Peter

2011-11-01

418

Evidence for Distinct Mechanisms of Starch Granule Breakdown in Plants *  

E-print Network

The aim of this work was to understand the initial steps of starch breakdown inside chloroplasts. In the non-living endosperm of germinating cereal grains, starch breakdown is initiated by ?-amylase secreted from surrounding cells. However, loss of ?-amylase from Arabidopsis does not prevent chloroplastic starch breakdown (Yu,

Thierry Delatte; Martin Umhang; Martine Trevisan; Simona Eicke; David Thorneycroft; Steven M. Smith; Samuel C. Zeeman

419

Detection of Joule heating before dielectric breakdown in polyethylene films  

Microsoft Academic Search

Local Joule heating in polyethylene films was detected at room temperature before dielectric breakdown under DC field. When a high-temperature point appeared in a film, the conduction current increased with time. The final breakdown occurred at the point of the highest temperature. This concurrence of the breakdown point and the Joule heating point suggests that a thermal process takes part

Masayuki Nagao; Takashi Kimura; Y. Mizuno; M. Kosaki; M. Ieda

1990-01-01

420

Effects of Vibration Stress and Temperature on the Characteristics of Piezoelectric Ceramics under High Vibration Amplitude Levels Measured by Electrical Transient Responses  

Microsoft Academic Search

This paper presents a characteristic evaluation of piezoelectric ceramics at high vibration amplitude levels of resonance, based on the electrical transient response technique. Low-Q and high-Q materials are measured, and the effect of vibration stress is obtained without affecting temperature. It is revealed that for low-Q materials an increase of loss is caused mainly by the vibration stress, while for

Mikio Umeda; Kentaro Nakamura; Sadayuki Ueha

1999-01-01

421

Effects of transportation during the hot season and low voltage electrical stimulation on histochemical and meat quality characteristics of sheep longissimus muscle  

Microsoft Academic Search

The effect of transportation during the hot season (42°C) and low voltage electrical stimulation on physiological, histochemical and meat quality characteristics of Omani sheep was studied. Forty intact male sheep were divided into two equal groups: 3h transported or non-transported. The non-transported group remained in holding pens for 48h prior to slaughter, while the transported group was transported 300km (approximately

I. T. Kadim; O. Mahgoub; W. Al-Marzooqi; S. Khalaf; S. S. H. Al-Sinawi; I. S. Al-Amri

2009-01-01

422

Effects of Mg on the electrical characteristics and thermal stability of MgxZn1-xO thin film transistors  

E-print Network

of Physics. doi:10.1063/1.3567533 Recently, ZnO thin film transistors TFTs have attracted increasingEffects of Mg on the electrical characteristics and thermal stability of MgxZn1-xO thin film of MgxZn1-xO thin film transistors TFTs are investigated. The Mg0.06Zn0.94O TFT shows the smallest

Garfunkel, Eric

423

The Effect of Aging on the Breakdown Voltage of Artificially Damaged Cables.  

NASA Astrophysics Data System (ADS)

The effect of damage, and the thermal and radiation aging of damaged cable on the dielectric strength of low -voltage cable was studied. Breakdown voltages of XLPE and EPR cable were measured for both damaged and undamaged cable. For EPR cable, the following three types of artificial damage were studied: scrapes, transverse cuts, and longitudinal cuts. For XLPE, the following two types of damage were studied: scrapes and transverse cuts. For both types of cables, some were radiation aged up to 1 MGy and others were thermally aged at 130^circC for up to 50 days. For the cable used, breakdown voltage versus thickness data reveals that when the remaining insulation thickness is greater than 0.60 mm, the breakdown voltage of EPR and XLPE cable is not affected. Once damage is significant, there is a linear decrease in the breakdown voltage with decreasing thickness. Previous theoretical work related the critical electric field required for partial discharge initiation within microvoids to microvoid size. The microvoids were modeled as spherical pores. The results of this theoretical work were applied in the analysis of the data collected. The analysis of the data strongly suggests that microvoids within the insulation are the cause of electrical breakdown. Finite element analysis was used to determine the electric field at breakdown. The pore radius histogram was fitted to known distributions, and was found to have a lognormal distribution. Statistical comparisons were made between groups as based on aging and damage type. The results reveal that neither the damage nor the aging studied affects the dielectric strength of the EPR cable. This means that based on the proposed model the pore radii of EPR cable are not affected by aging or damage. From the breakdown voltage versus thickness data for XLPE cable, it was determined that transverse cuts were a more severe type of damage than scrapes; and that the insulation with transverse cuts did not endure radiation aging as well as the undamaged or scraped cable. From the statistical analysis no effects on dielectric strength were observed due to aging or scrape damage for the XLPE cable.

Hanson, Brett Allen