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Sample records for pulsed parallel current

  1. Improvements on Pulsed Current Sharing in Driving Parallel MOSFETs

    NASA Astrophysics Data System (ADS)

    Takagi, Hajime; Orihara, Masato; Yamada, Tsutomu; Yanagidaira, Takeshi

    To switch high-voltage and high-current pulses by using MOS (Metal Oxide Semiconductor) transistors, it is necessary to distribute evenly the voltage and current to each element connected in series and parallel. In parallel connection, the current flowing in each element is different depending on the series resistance and wiring inductance. We verified improvements on pulsed current sharing in parallel transistors which were arranged in line on a printed circuit board. Although Gate and Drain wirings are different in length, pulsed current was evenly distributed by using transmission line transformers. Dissipation in transistors were equalized and four transistors were driven simultaneously near the rated current.

  2. Modular, Parallel Pulse-Shaping Filter Architectures

    NASA Technical Reports Server (NTRS)

    Gray, Andrew A.

    2003-01-01

    Novel architectures based on parallel subconvolution frequency-domain filtering methods have been developed for modular processing rate reduction of discrete-time pulse-shaping filters. Such pulse-shaping is desirable and often necessary to obtain bandwidth efficiency in very-high-rate wireless communications systems. In principle, this processing could be implemented in very-large-scale integrated (VLSI) circuits. Whereas other approaches to digital pulse-shaping are based primarily on time-domain processing concepts, the theory and design rules of the architectures presented here are founded on frequency-domain processing that has advantages in certain systems.

  3. Driving parallel flashlamps with a compensated pulsed alternator

    SciTech Connect

    Carder, B.M.; Merritt, B.T.; Gagnon, W.L.; Bird, W.L.; Weldon, W.F.; Zowarka, R.C.

    1980-05-30

    Test results are given for a prototype Compensated Pulsed Alternator that was operated up to its 5400 rpm design speed. The machine has delivered approximately 140 kilojoules of energy in a single 1.3 millisecond pulse into a load comprising sixteen parallel flashlamps. The energy delivered to the lamps follows a W = (rpm/225)/sup 4/ scaling law to about 4200 rpm. Beyond that speed, eddy current losses become significant with the present design. New codes are able to model the machine parameters, and the prototype is presently being rebuilt to reduce the high speed losses predicted by the codes and verified by experiment.

  4. Global synchronization of parallel processors using clock pulse width modulation

    DOEpatents

    Chen, Dong; Ellavsky, Matthew R.; Franke, Ross L.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Jeanson, Mark J.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Littrell, Daniel; Ohmacht, Martin; Reed, Don D.; Schenck, Brandon E.; Swetz, Richard A.

    2013-04-02

    A circuit generates a global clock signal with a pulse width modification to synchronize processors in a parallel computing system. The circuit may include a hardware module and a clock splitter. The hardware module may generate a clock signal and performs a pulse width modification on the clock signal. The pulse width modification changes a pulse width within a clock period in the clock signal. The clock splitter may distribute the pulse width modified clock signal to a plurality of processors in the parallel computing system.

  5. Electromagnetic pulse-induced current measurement device

    NASA Astrophysics Data System (ADS)

    Gandhi, Om P.; Chen, Jin Y.

    1991-08-01

    To develop safety guidelines for exposure to high fields associated with an electromagnetic pulse (EMP), it is necessary to devise techniques that would measure the peak current induced in the human body. The main focus of this project was to design, fabricate, and test a portable, self-contained stand-on device that would measure and hold the peak current and the integrated change Q. The design specifications of the EMP-Induced Current Measurement Device are as follows: rise time of the current pulse, 5 ns; peak current, 20-600 A; charge Q, 0-20 microcoulombs. The device uses a stand-on parallel-plate bilayer sensor and fast high-frequency circuit that are well-shielded against spurious responses to high incident fields. Since the polarity of the incident peak electric field of the EMP may be either positive or negative, the induced peak current can also be positive or negative. Therefore, the device is designed to respond to either of these polarities and measure and hold both the peak current and the integrated charge which are simultaneously displayed on two separate 3-1/2 digit displays. The prototype device has been preliminarily tested with the EMP's generated at the Air Force Weapons Laboratory (ALECS facility) at Kirtland AFB, New Mexico.

  6. Digital parallel-to-series pulse-train converter

    NASA Technical Reports Server (NTRS)

    Hussey, J.

    1971-01-01

    Circuit converts number represented as two level signal on n-bit lines to series of pulses on one of two lines, depending on sign of number. Converter accepts parallel binary input data and produces number of output pulses equal to number represented by input data.

  7. High current high accuracy IGBT pulse generator

    SciTech Connect

    Nesterov, V.V.; Donaldson, A.R.

    1995-05-01

    A solid state pulse generator capable of delivering high current triangular or trapezoidal pulses into an inductive load has been developed at SLAC. Energy stored in a capacitor bank of the pulse generator is switched to the load through a pair of insulated gate bipolar transistors (IGBT). The circuit can then recover the remaining energy and transfer it back to the capacitor bank without reversing the capacitor voltage. A third IGBT device is employed to control the initial charge to the capacitor bank, a command charging technique, and to compensate for pulse to pulse power losses. The rack mounted pulse generator contains a 525 {mu}F capacitor bank. It can deliver 500 A at 900V into inductive loads up to 3 mH. The current amplitude and discharge time are controlled to 0.02% accuracy by a precision controller through the SLAC central computer system. This pulse generator drives a series pair of extraction dipoles.

  8. Ultrafast stimulated Raman parallel adiabatic passage by shaped pulses

    SciTech Connect

    Dridi, G.; Guerin, S.; Hakobyan, V.; Jauslin, H. R.; Eleuch, H.

    2009-10-15

    We present a general and versatile technique of population transfer based on parallel adiabatic passage by femtosecond shaped pulses. Their amplitude and phase are specifically designed to optimize the adiabatic passage corresponding to parallel eigenvalues at all times. We show that this technique allows the robust adiabatic population transfer in a Raman system with the total pulse area as low as 3{pi}, corresponding to a fluence of one order of magnitude below the conventional stimulated Raman adiabatic passage process. This process of short duration, typically picosecond and subpicosecond, is easily implementable with the modern pulse shaper technology and opens the possibility of ultrafast robust population transfer with interesting applications in quantum information processing.

  9. Adjustable direct current and pulsed circuit fault current limiter

    DOEpatents

    Boenig, Heinrich J.; Schillig, Josef B.

    2003-09-23

    A fault current limiting system for direct current circuits and for pulsed power circuit. In the circuits, a current source biases a diode that is in series with the circuits' transmission line. If fault current in a circuit exceeds current from the current source biasing the diode open, the diode will cease conducting and route the fault current through the current source and an inductor. This limits the rate of rise and the peak value of the fault current.

  10. Current Pulses Momentarily Enhance Thermoelectric Cooling

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey; Fleurial, Jean-Pierre; Caillat, Thierry; Chen, Gang; Yang, Rong Gui

    2004-01-01

    The rates of cooling afforded by thermoelectric (Peltier) devices can be increased for short times by applying pulses of electric current greater than the currents that yield maximum steady-state cooling. It has been proposed to utilize such momentary enhancements of cooling in applications in which diode lasers and other semiconductor devices are required to operate for times of the order of milliseconds at temperatures too low to be easily obtainable in the steady state. In a typical contemplated application, a semiconductor device would be in contact with the final (coldest) somewhat taller stage of a multistage thermoelectric cooler. Steady current would be applied to the stages to produce steady cooling. Pulsed current would then be applied, enhancing the cooling of the top stage momentarily. The principles of operation are straightforward: In a thermoelectric device, the cooling occurs only at a junction at one end of the thermoelectric legs, at a rate proportional to the applied current. However, Joule heating occurs throughout the device at a rate proportional to the current squared. Hence, in the steady state, the steady temperature difference that the device can sustain increases with current only to the point beyond which the Joule heating dominates. If a pulse of current greater than the optimum current (the current for maximum steady cooling) is applied, then the junction becomes momentarily cooled below its lowest steady temperature until thermal conduction brings the resulting pulse of Joule heat to the junction and thereby heats the junction above its lowest steady temperature. A theoretical and experimental study of such transient thermoelectric cooling followed by transient Joule heating in response to current pulses has been performed. The figure presents results from one of the experiments. The study established the essential parameters that characterize the pulse cooling effect, including the minimum temperature achieved, the maximum

  11. Propulsive effects of vortex coupling between parallel pulsed jets

    NASA Astrophysics Data System (ADS)

    Athanassiadis, Athanasios; Hart, Douglas

    2015-11-01

    For vehicles that use pulsed jet propulsion, nature provides inspiration for different ways to improve propulsive performance. Communities of marine invertebrates called salps improve the efficiency of cruising locomotion by aggregating into large multi-animal chains. In this process, the cylindrical animals physically connect to each other side-by-side to form an array of individual pulsed jets whose synchronous pulsing propels the entire chain forward. Some benefits of this chaining behavior can be described using existing models of pulsed jet propulsion for steady, cruising conditions. However, during unsteady conditions such as impulsive maneuvering at low speeds, it remains unclear how interactions between neighboring jets will affect the chain's propulsive performance. Using bench-top experiments, we investigate the unsteady interactions between two parallel pulsed jets. Under some conditions, the pulsed jets form vortex rings that coalesce before vortex formation is complete, coupling the hydrodynamics of the independent jets. We measure how different degrees of vortex coupling alter the energy and momentum transfer in the two-jet system. Finally, we explore the energy and momentum scalings that would guide the design of a vehicle using multi-jet maneuvering techniques. This work was supported by the Office of Naval Research.

  12. Coherent femtosecond pulse combining of multiple parallel chirped pulse fiber amplifiers.

    PubMed

    Siiman, Leo A; Chang, Wei-zung; Zhou, Tong; Galvanauskas, Almantas

    2012-07-30

    We report on femtosecond pulse combining with up to four parallel chirped-pulse fiber amplifier channels. Active phase locking is implemented using the LOCSET (Locking of Optical Coherence by Single-detector Electronic-frequency Tagging) single detector feedback technique, resulting in 96.4%, 94.0%, and 93.9% relative combining efficiency with two, three, and four channels respectively. Theoretical and experimental analysis of combining efficiency dependence on amplitude and phase noise shows convergence to a fixed value with increasing number of channels, indicating that multi-channel pulse combining with LOCSET feedback should be scalable to very large numbers of channels.

  13. Signal Preservation in Pulsing Turbidity Current Deposits

    NASA Astrophysics Data System (ADS)

    Keevil, G. M.; Dorrell, R. M.; McCaffrey, W. D.

    2014-12-01

    Recent debate has focused on the potential preservation of the signal of seismic events in the sedimentary record via the initiation of large-scale turbidity current flows. The failure of a seismic zone lying across a series of submarine canyon systems may initiate multiple linked turbidity currents from each canyon head. Such events can be distinguished from locally triggered turbidity currents by their deposits. Canyon systems may be expected to become progressively interconnected with depth. Differing run out times of each interconnected channel is expected to result in pulsing flow behavior, a key feature of such turbidity currents. Thus, cyclical waxing to waning flow behavior preserved in the rock record may be a key indicator of a large-scale seismic trigger. Novel experimental research is presented that explores the dynamics of pulsed turbidity currents. The experimental study is used to quantitatively examine controls on the time and length scale of signal preservation in pulsing density driven flows. The experiments consisted of a multi gate lock box, with the gates remotely operated by pneumatic rams. Gate timers allow for accurate experimental repeatability and a careful investigation of the effect of time spacing between flows on pulsing flow dynamics. Parameters investigated include volumes of material released, effective flow density and viscosity (as a proxy of flow mud content). Full flow field visualization was made using an array of interlinked HD cameras. Dyeing separate components of the flow different colors enabled detailed analysis of flow dynamic behavior occurring between head and tail. The secondary pulsing flow was seen to rapidly overtake the first flow. Observations of flow velocity and density suggested that due to stratification the secondary flow was travelling along the density interface between the main body of the primary flow and its turbulent wake. As the pulsing flows created in the laboratory experiments rapidly merged, it

  14. GPU-based parallel clustered differential pulse code modulation

    NASA Astrophysics Data System (ADS)

    Wu, Jiaji; Li, Wenze; Kong, Wanqiu

    2015-10-01

    Hyperspectral remote sensing technology is widely used in marine remote sensing, geological exploration, atmospheric and environmental remote sensing. Owing to the rapid development of hyperspectral remote sensing technology, resolution of hyperspectral image has got a huge boost. Thus data size of hyperspectral image is becoming larger. In order to reduce their saving and transmission cost, lossless compression for hyperspectral image has become an important research topic. In recent years, large numbers of algorithms have been proposed to reduce the redundancy between different spectra. Among of them, the most classical and expansible algorithm is the Clustered Differential Pulse Code Modulation (CDPCM) algorithm. This algorithm contains three parts: first clusters all spectral lines, then trains linear predictors for each band. Secondly, use these predictors to predict pixels, and get the residual image by subtraction between original image and predicted image. Finally, encode the residual image. However, the process of calculating predictors is timecosting. In order to improve the processing speed, we propose a parallel C-DPCM based on CUDA (Compute Unified Device Architecture) with GPU. Recently, general-purpose computing based on GPUs has been greatly developed. The capacity of GPU improves rapidly by increasing the number of processing units and storage control units. CUDA is a parallel computing platform and programming model created by NVIDIA. It gives developers direct access to the virtual instruction set and memory of the parallel computational elements in GPUs. Our core idea is to achieve the calculation of predictors in parallel. By respectively adopting global memory, shared memory and register memory, we finally get a decent speedup.

  15. Interleaved pulsed MAMBA: a new parallel slice imaging method.

    PubMed

    Paley, Martyn N J; Lee, Kuan J; Wild, James M; Whitby, Elspeth H; Griffiths, Paul D

    2002-12-01

    A method of acquiring slices in parallel is described which uses interleaved sets of pulsed B(0) field coils to generate discrete regions of uniform field within the main magnetic field known as interleaved MAMBA (multiple acquisition micro B(0) array). Simulations of a number of coil designs were performed using the Biot-Savart law. A six-step coil was built and interfaced to a 0.17 T Niche MRI system and the field steps measured using an imaging technique. Measured field steps were in good agreement with the values predicted by simulation. The coil design was then scaled up by a factor of three, interfaced to a 1.5 T whole-body MRI system, and scans of the hands and arms of volunteers were acquired from up to four field steps using standard spin and gradient echo sequences. Images were also acquired simultaneously from two field steps with no frequency encode aliasing and one excitation. The one-dimensional interleaved pulsed MAMBA step field technique shows great promise for enabling many slices to be acquired simultaneously along the axis of the coil for rapid volumetric studies without the need for multiple shot Hadamard encoding. Extension of interleaved coil design to two or three dimensions is feasible, which could provide full spatial coverage combined with ultra-rapid data acquisition. PMID:12465115

  16. Electromagnetic Enhancement of Pulsed Eddy Current Signals

    NASA Astrophysics Data System (ADS)

    Mandache, Catalin V.; Vivier Lefebvre, J. H.

    2007-03-01

    The sensitivity of pulsed eddy current (PEC) testing is increased when a layer of magnetic material is placed on the far side of the conductive test piece. This procedure ensures preservation of the lift-off point of intersection (LOI) feature, otherwise non-existent for the PEC inspections of magnetic materials. The presented method could find applications in non-destructive inspections for corrosion thinning, thickness measurement of conductive coatings over ferrous substrates, and integrity of thermally insulated pipes. Laboratory-obtained examples are given to support the method applicability.

  17. Frequency content of current pulses in slapper detonator bridges

    SciTech Connect

    Carpenter, K H

    2006-12-18

    DFT amplitudes are obtained for digital current pulse files. The frequency content of slapper detonator bridge current pulses is obtained. The frequencies are confined well within the passband of the CVR used to sample them.

  18. Current pulse effects on cylindrical damage experiments

    SciTech Connect

    Kaul, Ann M; Rousculp, Christopher L

    2009-01-01

    A series of joint experiments between LANL and VNIIEF use a VNIIEF-designed helical generator to provide currents for driving a LANL-designed cylindrical spallation experimental load. Under proper driving conditions, a cylindrical configuration allows for a natural recollection of the damaged material. In addition, the damaged material is able to come to a complete stop due to its strength, avoiding application of further forces. Thus far, experiments have provided data about failure initiation of a well-characterized material (aluminum) in a cylindrical geometry, behavior of material recollected after damage from pressures in the damage initiation regime, and behavior of material recollected after complete failure. In addition to post-shot collection of the damaged target material for subsequent metallographic analysis, dynamic in-situ experimental diagnostics include velocimetry and transverse radial radiography. This paper will focus on the effects of tailoring the driving current pulse to obtain the desired data.

  19. Efficient circuit triggers high-current, high-voltage pulses

    NASA Technical Reports Server (NTRS)

    Green, E. D.

    1964-01-01

    Modified circuit uses diodes to effectively disconnect the charging resistors from the circuit during the discharge cycle. Result is an efficient parallel charging, high voltage pulse modulator with low voltage rating of components.

  20. Current parallel I/O limitations to scalable data analysis.

    SciTech Connect

    Mascarenhas, Ajith Arthur; Pebay, Philippe Pierre

    2011-07-01

    This report describes the limitations to parallel scalability which we have encountered when applying our otherwise optimally scalable parallel statistical analysis tool kit to large data sets distributed across the parallel file system of the current premier DOE computational facility. This report describes our study to evaluate the effect of parallel I/O on the overall scalability of a parallel data analysis pipeline using our scalable parallel statistics tool kit [PTBM11]. In this goal, we tested it using the Jaguar-pf DOE/ORNL peta-scale platform on a large combustion simulation data under a variety of process counts and domain decompositions scenarios. In this report we have recalled the foundations of the parallel statistical analysis tool kit which we have designed and implemented, with the specific double intent of reproducing typical data analysis workflows, and achieving optimal design for scalable parallel implementations. We have briefly reviewed those earlier results and publications which allow us to conclude that we have achieved both goals. However, in this report we have further established that, when used in conjuction with a state-of-the-art parallel I/O system, as can be found on the premier DOE peta-scale platform, the scaling properties of the overall analysis pipeline comprising parallel data access routines degrade rapidly. This finding is problematic and must be addressed if peta-scale data analysis is to be made scalable, or even possible. In order to attempt to address these parallel I/O limitations, we will investigate the use the Adaptable IO System (ADIOS) [LZL+10] to improve I/O performance, while maintaining flexibility for a variety of IO options, such MPI IO, POSIX IO. This system is developed at ORNL and other collaborating institutions, and is being tested extensively on Jaguar-pf. Simulation code being developed on these systems will also use ADIOS to output the data thereby making it easier for other systems, such as ours, to

  1. Parallel pulse processing and data acquisition for high speed, low error flow cytometry

    DOEpatents

    Engh, G.J. van den; Stokdijk, W.

    1992-09-22

    A digitally synchronized parallel pulse processing and data acquisition system for a flow cytometer has multiple parallel input channels with independent pulse digitization and FIFO storage buffer. A trigger circuit controls the pulse digitization on all channels. After an event has been stored in each FIFO, a bus controller moves the oldest entry from each FIFO buffer onto a common data bus. The trigger circuit generates an ID number for each FIFO entry, which is checked by an error detection circuit. The system has high speed and low error rate. 17 figs.

  2. Parallel pulse processing and data acquisition for high speed, low error flow cytometry

    DOEpatents

    van den Engh, Gerrit J.; Stokdijk, Willem

    1992-01-01

    A digitally synchronized parallel pulse processing and data acquisition system for a flow cytometer has multiple parallel input channels with independent pulse digitization and FIFO storage buffer. A trigger circuit controls the pulse digitization on all channels. After an event has been stored in each FIFO, a bus controller moves the oldest entry from each FIFO buffer onto a common data bus. The trigger circuit generates an ID number for each FIFO entry, which is checked by an error detection circuit. The system has high speed and low error rate.

  3. Lipid bilayer microarray for parallel recording of transmembrane ion currents.

    PubMed

    Le Pioufle, Bruno; Suzuki, Hiroaki; Tabata, Kazuhito V; Noji, Hiroyuki; Takeuchi, Shoji

    2008-01-01

    This paper describes a multiwell biochip for simultaneous parallel recording of ion current through transmembrane pores reconstituted in planar lipid bilayer arrays. Use of a thin poly(p-xylylene) (parylene) film having micrometer-sized apertures (phi=15-50 microm, t=20 microm) led to formation of highly stable bilayer lipid membranes (BLMs) for incorporation of transmembrane pores; thus, a large number of BLMs could be arrayed without any skillful technique. We optically confirmed the simultaneous formation of BLMs in a 5x5 matrix, and in our durability test, the BLM lasted more than 15 h. Simultaneous parallel recording of alamethicin and gramicidin transmembrane pores in multiple contiguous recording sites demonstrated the feasibility of high-throughput screening of transmembrane ion currents in artificial lipid bilayers.

  4. Detailed characteristics of intermittent current pulses due to positive corona

    SciTech Connect

    Liu, Yang Cui, Xiang; Lu, Tiebing; Wang, Zhenguo; Li, Xuebao; Xiang, Yu; Wang, Xiaobo

    2014-08-15

    In order to get detailed characteristics of intermittent current pulses due to positive corona such as the repetition rate of burst-pulse trains, the peak value ratio of the primary pulse to the secondary pulse, the number of pulses per burst, and the interval of the secondary pulses, a systematic study was carried out in a coaxial conductor-cylinder electrode system with the conductor electrode being set with a discharge point. Empirical formulae for the number of pulses per burst and the interval of the secondary pulses are first presented. A theoretical model based on the motion of the space-charge clouds is proposed. Analysis with the model gives explanations to the experimental results and reveals some new insights into the physical mechanism of positive intermittent corona.

  5. Current Trends in Intense Pulsed Light

    PubMed Central

    2012-01-01

    Intense pulsed light technologies have evolved significantly since their introduction to the medical community 20 years ago. Now such devices can be used safely and effectively for the cosmetic treatment of many vascular lesions, unwanted hair, and pigmented lesions. Newer technologies often give results equal to those of laser treatments. PMID:22768357

  6. Fast initial continuous current pulses versus return stroke pulses in tower-initiated lightning

    NASA Astrophysics Data System (ADS)

    Azadifar, Mohammad; Rachidi, Farhad; Rubinstein, Marcos; Rakov, Vladimir A.; Paolone, Mario; Pavanello, Davide; Metz, Stefan

    2016-06-01

    We present a study focused on pulses superimposed on the initial continuous current of upward negative discharges. The study is based on experimental data consisting of correlated lightning current waveforms recorded at the instrumented Säntis Tower in Switzerland and electric fields recorded at a distance of 14.7 km from the tower. Two different types of pulses superimposed on the initial continuous current were identified: (1) M-component-type pulses, for which the microsecond-scale electric field pulse occurs significantly earlier than the onset of the current pulse, and (2) fast pulses, for which the onset of the field matches that of the current pulse. We analyze the currents and fields associated with these fast pulses (return-stroke type (RS-type) initial continuous current (ICC) pulses) and compare their characteristics with those of return strokes. A total of nine flashes containing 44 RS-type ICC pulses and 24 return strokes were analyzed. The median current peaks associated with RS-type ICC pulses and return strokes are, respectively, 3.4 kA and 8 kA. The associated median E-field peaks normalized to 100 km are 1.5 V/m and 4.4 V/m, respectively. On the other hand, the electric field peaks versus current peaks for the two data sets (RS-type ICC pulses and return strokes) are characterized by very similar linear regression slopes, namely, 3.67 V/(m kA) for the ICC pulses and 3.77 V/(m kA) for the return strokes. Assuming the field-current relation based on the transmission line model, we estimated the apparent speed of both the RS-type ICC pulses and return strokes to be about 1.4 × 108 m/s. A strong linear correlation is observed between the E-field risetime and the current risetime for the ICC pulses, similar to the relation observed between the E-field risetime and current risetime for return strokes. The similarity of the RS-type ICC pulses with return strokes suggests that these pulses are associated with the mixed mode of charge transfer to ground.

  7. Electrical breakdown of soil under nonlinear pulsed current spreading

    NASA Astrophysics Data System (ADS)

    Vasilyak, L. M.; Pecherkin, V. Ya; Vetchinin, S. P.; Panov, V. A.; Son, E. E.; Efimov, B. V.; Danilin, A. N.; Kolobov, V. V.; Selivanov, V. N.; Ivonin, V. V.

    2015-07-01

    Laboratory investigations on pulsed current spreading from spherical electrodes and evolution of electrical breakdown of silica sand with different water contents under a 15-20 kV voltage pulse were carried out. A sharp nonlinear decrease in the pulsed resistance of soil was observed when the current density exceeded a certain threshold value. Then ionization-overheating instability develops and leads to current contraction and plasma channel formation in the soil. The method for determination of the threshold electric field for ionization is proposed. Electrical discharge in wet sand was found to develop with a significant delay time for long discharge gaps similar to thermal breakdown.

  8. Study of the onset of the acoustic streaming in parallel plate resonators with pulse ultrasound.

    PubMed

    Castro, Angelica; Hoyos, Mauricio

    2016-03-01

    In a previous study, we introduced pulse mode ultrasound as a new method for reducing and controlling the acoustic streaming in parallel plate resonators (Hoyos and Castro, 2013). Here, by modifying other parameters such as the resonator geometry and the particle size, we have found a threshold for particle manipulation with ultrasonic standing waves in confined resonators without the influence of the acoustic streaming. We demonstrate that pulse mode ultrasound open the possibility of manipulating particles smaller than 1 μm size.

  9. Investigation of casing inspection through tubing with pulsed eddy current

    NASA Astrophysics Data System (ADS)

    Fu, Yuewen; Yu, Runqiao; Peng, Xuewen; Ren, Shangkun

    2012-12-01

    Corrosion and cracks of casing string in oil wells is a serious problem on which little research has been done when inspecting casing through tubing. In this study, inspecting casing through tubing with pulsed eddy current is investigated. Longitudinal and transverse probes are centred inside the tubing to detect wall thinnings and cracks in casing. A time slice of induced voltage in the receiving coil of the probe is used as the feature to recognise defects. The experimental results show that large area wall thinnings and long cracks in casing are detected successfully through the tubing with appropriate inspection parameters. The probe's orientation to the crack is important and a particular discovery is that the transverse probe should be parallel to the transverse crack and not be perpendicular to it when inspecting. A method based on linear regression is proposed to estimate flaws in casing while wall thinning in the tubing occurs at the same location. The method is effective for large area thinning in casing when tubing thinning is wide.

  10. Effect of an Additional, Parallel Capacitor on Pulsed Inductive Plasma Accelerator Performance

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Sivak, Amy D.; Balla, Joseph V.

    2011-01-01

    A model of pulsed inductive plasma thrusters consisting of a set of coupled circuit equations and a one-dimensional momentum equation has been used to study the effects of adding a second, parallel capacitor into the system. The equations were nondimensionalized, permitting the recovery of several already-known scaling parameters and leading to the identification of a parameter that is unique to the particular topology studied. The current rise rate through the inductive acceleration coil was used as a proxy measurement of the effectiveness of inductive propellant ionization since higher rise rates produce stronger, potentially better ionizing electric fields at the coil face. Contour plots representing thruster performance (exhaust velocity and efficiency) and current rise rate in the coil were generated numerically as a function of the scaling parameters. The analysis reveals that when the value of the second capacitor is much less than the first capacitor, the performance of the two-capacitor system approaches that of the single-capacitor system. In addition, as the second capacitor is decreased in value the current rise rate can grow to be twice as great as the rise rate attained in the single capacitor case.

  11. Characteristics of current pulses in rocket-triggered lightning

    NASA Astrophysics Data System (ADS)

    Qie, Xiushu; Jiang, Rubin; Yang, Jing

    2014-01-01

    The waveform parameters of current pulses in negative rocket-triggered lightning are analyzed statistically using recorded channel-base current during Shandong Artificially Triggered Lightning Experiment (SHATLE) from 2005 to 2011. The current pulses are divided into 3 categories, including return strokes, ICC pulses in initial continuous current (ICC) stage and M-components superimposed on the continuing current following the return stroke. The geometric mean values (GM) of peak current, risetime from 10% to 90% peak, half peak width and charge transfer for return strokes are 12.1 kA, 1.0 μs, 14.8 μs, and 0.86 C, respectively. The corresponding parameters for ICC pulses are 0.09 kA, 437 μs, 712 μs, and 0.10 C, respectively, while they are 0.28 kA, 251 μs, 242 μs and 0.10 C for M-components, respectively. There is significant fraction of larger M-components (about 10% of 63 samples) demonstrating peak current of several kilo-amperes, comparable to weak return strokes. The ICC pulses show somewhat lower current peak and slower risetime than the M-components with a difference of roughly 2-3 times, resulting from the lower charge source of ICC pulses. In general, the ICC pulses and M-components show smaller peak current and charge transfer while longer risetime and half peak width than return strokes, differing with 1-2 orders of magnitude. The charge neutralized by an individual triggered lightning flash ranged from 6.3 C to 68.1 C, while the initial stage (IS), lasted about 245 ms (GM) and lowered a GM charge of 21.2 C to the ground. The average IS current in an individual lightning discharge varies from 45.8 A to 140.6 A with a GM value of 86.7 A.

  12. Parallel line raster eliminates ambiguities in reading timing of pulses less than 500 microseconds apart

    NASA Technical Reports Server (NTRS)

    Horne, A. P.

    1966-01-01

    Parallel horizontal line raster is used for precision timing of events occurring less than 500 microseconds apart for observation of hypervelocity phenomena. The raster uses a staircase vertical deflection and eliminates ambiguities in reading timing of pulses close to the end of each line.

  13. Pulsed eddy current testing. [nondestructive tests of the external tank

    NASA Technical Reports Server (NTRS)

    Workman, G. L.

    1980-01-01

    Since a large number of the procedures used for inspecting the external tank are concerned with determining flaws in welds, there is a need to develop an inspection technique, which can be automated, to determine flaws in welds and structures with complex geometries. Techniques whereby an eddy current is generated in a metallic material and the changes in the circuit parameters due to material differences are observed, were chosen as one possible approach. Pulsed eddy current and its relationship to multifrequency techniques is discussed as well as some preliminary results obtained from observing pulsed waveforms with apparatus and algorithms currently in use for ultrasonic testing of welds. It can be shown the pulsed eddy current techniques can provide similar results, can eliminate some of the noncritical parameters affecting the eddy current signals, and can facilitate in the detection of critical parameter such as flaws, subsurface voids, and corrosion.

  14. Pulsed currents carried by whistlers. II. Excitation by biased electrodes

    SciTech Connect

    Urrutia, J.M.; Stenzel, R.L.; Rousculp, C.L. )

    1994-05-01

    The transport of time-dependent current between electrodes in contact with a large laboratory magnetoplasma is examined experimentally. Single electrodes biased with respect to the chamber wall or pairs of electrically floating electrodes are used to produce pulsed currents ([omega][sub [ital ci

  15. Contribution For Arc Temperature Affected By Current Increment Ratio At Peak Current In Pulsed Arc

    NASA Astrophysics Data System (ADS)

    Kano, Ryota; Mitubori, Hironori; Iwao, Toru

    2015-11-01

    Tungsten Inert Gas (TIG) Welding is one of the high quality welding. However, parameters of the pulsed arc welding are many and complicated. if the welding parameters are not appropriate, the welding pool shape becomes wide and shallow.the convection of driving force contributes to the welding pool shape. However, in the case of changing current waveform as the pulse high frequency TIG welding, the arc temperature does not follow the change of the current. Other result of the calculation, in particular, the arc temperature at the reaching time of peak current is based on these considerations. Thus, the accurate measurement of the temperature at the time is required. Therefore, the objective of this research is the elucidation of contribution for arc temperature affected by current increment ratio at peak current in pulsed arc. It should obtain a detail knowledge of the welding model in pulsed arc. The temperature in the case of increment of the peak current from the base current is measured by using spectroscopy. As a result, when the arc current increases from 100 A to 150 A at 120 ms, the transient response of the temperature didn't occur during increasing current. Thus, during the current rise, it has been verified by measuring. Therefore, the contribution for arc temperature affected by current increment ratio at peak current in pulsed arc was elucidated in order to obtain more knowledge of welding model of pulsed arc.

  16. A double output pulsed high current thyratron driver

    NASA Astrophysics Data System (ADS)

    Reghu, T.; Kumar, Manoj; Verma, Abrat; Mandloi, Vagesh; Kukreja, L. M.; Shrivastava, P.

    2012-11-01

    The design and development of a double output pulsed high current driver for high power multi-grid thyratron is reported. The driver generates a 100 A current pulse of 2 μs duration with a compliance voltage of 1000 V for driving grid-1. A voltage pulse of 1200 V and 1.2 μs duration, superimposed with -150 V bias has been generated for driving grid-2. A delay of 1 μs between the two drive pulses is achieved with the use of a simple circuit. The rate of rise of voltage better than 10 kV/μs and jitter of ±3 ns is achieved for grid-2 pulse. This driver module has been successfully used in a 50 kV, CX1575C thyratron switched pulsed power supply to drive a multi-joule transversely excited atmospheric CO2 laser at 100 Hz. The grid driver module can also be used for driving any high current thyratrons with minor external changes.

  17. A double output pulsed high current thyratron driver.

    PubMed

    Reghu, T; Kumar, Manoj; Verma, Abrat; Mandloi, Vagesh; Kukreja, L M; Shrivastava, P

    2012-11-01

    The design and development of a double output pulsed high current driver for high power multi-grid thyratron is reported. The driver generates a 100 A current pulse of 2 μs duration with a compliance voltage of 1000 V for driving grid-1. A voltage pulse of 1200 V and 1.2 μs duration, superimposed with -150 V bias has been generated for driving grid-2. A delay of 1 μs between the two drive pulses is achieved with the use of a simple circuit. The rate of rise of voltage better than 10 kV/μs and jitter of ±3 ns is achieved for grid-2 pulse. This driver module has been successfully used in a 50 kV, CX1575C thyratron switched pulsed power supply to drive a multi-joule transversely excited atmospheric CO(2) laser at 100 Hz. The grid driver module can also be used for driving any high current thyratrons with minor external changes.

  18. Simultaneous ballistic deficit immunity and resilience to parallel noise sources: A new pulse shaping technique

    SciTech Connect

    Fabris, Lorenzo; Becker, John A.; Goulding, Frederick S.; Madden, Norman W.

    2000-10-11

    A new and different time variant pulse processing system has been developed based on a simple CR-RC filter and two analog switches. The new pulse processing technique combines both ballistic deficit immunity and resilience to parallel noise without a significant compromise to the low energy resolution, generally considered a mutually exclusive requirement. The filter is realized by combining two different pulse-shaping techniques. One of the techniques creates a low rate of curvature at the pulse peak, which reduces ballistic deficit, while the second technique increases the tolerance to low frequency noise by modifying the noise history. Several experimental measurements are presented, including tests on a co-planar grid CdZnTe detector. Improvements on both the resolution and line shape are shown for the 662 keV line of 137Cs.

  19. High current pulse testing for ground rod integrity

    NASA Technical Reports Server (NTRS)

    Walko, Lawrence C.

    1991-01-01

    A test technique was developed to assess various grounding system concepts used for mobile facilities. The test technique involves applying a high current pulse to the grounding system with the proper waveshape and magnitude to simulate a lightning return stroke. Of concern were the step voltages present along the ground near the point of lightning strike. Step voltage is equated to how fast the current pulse is dissipated by the grounding system. The applied current pulse was produced by a high current capacitor bank with a total energy content of 80 kilojoules. A series of pulse tests were performed on two types of mobile facility grounding systems. One system consisted of an array of four 10 foot copper clad steel ground rods connected by 1/0 gauge wire. The other system was an array of 10 inch long tapered ground rods, strung on stainless steel cable. The focus here is on the pulse test technique used and its relevance to actual lightning strike conditions.

  20. Skyrmion Creation and Manipulation by Nano-Second Current Pulses

    PubMed Central

    Yuan, H. Y.; Wang, X. R.

    2016-01-01

    Easy creation and manipulation of skyrmions is important in skyrmion based devices for data storage and information processing. We show that a nano-second current pulse alone is capable of creating/deleting and manipulating skyrmions in a spin valve with a perpendicularly magnetized free layer and broken chiral symmetry. Interestingly, for an in-plane magnetized fixed layer, the free layer changes from a single domain at zero current to a Neel wall at an intermediate current density. Reverse the current polarity, the Neel wall changes to its image inversion. A properly designed nano-second current pulse, that tends to convert one type of Neel walls to its image inversion, ends up to create a stable skyrmion without assistance of external fields. For a perpendicularly magnetized fixed layer, the skyrmion size can be effectively tuned by a current density. PMID:26934954

  1. Effect of pulse magnetic field stimulation on calcium channel current

    NASA Astrophysics Data System (ADS)

    Fan, J.; Lee, Z. H.; Ng, W. C.; Khoa, W. L.; Teoh, S. H.; Soong, T. H.; Qin, Y. R.; Zhang, Z. Y.; Li, X. P.

    2012-10-01

    This study aimed to investigate the effect of low frequency and high amplitude pulse magnetic field (PMF) on Calcium ion channel current of cells. Measurements were done on the Human Embryonic Kidney 293 cells (HEK 293), which have only Calcium ion channels functioning. The whole cell current was measured by patch clamp method, with the clamped voltage ramping from -90 mV to +50 mV across the cell membrane. A PMF was generated by a 400-turn coil connected to a pulse current generator. The frequency of the pulse was 7 Hz, the width of the pulse was 3 ms, and the amplitude of the pulse, or the flux density, was ranging from 6 to 25 mT. The results showed that the profile of the whole cell Calcium channel current could be modified by the PMF. With the PMF applied, the phase shifting occurred: the onset of the channel opening took place several mili-seconds earlier than that without the PWF and correspondingly, the whole cell current reached its maximum earlier, and the current returned back to zero earlier as well. When the PWF was stopped, these effects persisted for a period of time, and then the current profile "recovered" to its original appearance. The decrease of the onset time and peak current time could be due to the local electric potential induced by the PWF and the direct interaction between PMF and ion channels/ions. The exact mechanisms of the observed effects of PMF on the cell are still unknown and need to be further studied.

  2. Comparing current cluster, massively parallel, and accelerated systems

    SciTech Connect

    Barker, Kevin J; Davis, Kei; Hoisie, Adolfy; Kerbyson, Darren J; Pakin, Scott; Lang, Mike; Sancho Pitarch, Jose C

    2010-01-01

    Currently there is large architectural diversity in high perfonnance computing systems. They include 'commodity' cluster systems that optimize per-node performance for small jobs, massively parallel processors (MPPs) that optimize aggregate perfonnance for large jobs, and accelerated systems that optimize both per-node and aggregate performance but only for applications custom-designed to take advantage of such systems. Because of these dissimilarities, meaningful comparisons of achievable performance are not straightforward. In this work we utilize a methodology that combines both empirical analysis and performance modeling to compare clusters (represented by a 4,352-core IB cluster), MPPs (represented by a 147,456-core BG/P), and accelerated systems (represented by the 129,600-core Roadrunner) across a workload of four applications. Strengths of our approach include the ability to compare architectures - as opposed to specific implementations of an architecture - attribute each application's performance bottlenecks to characteristics unique to each system, and to explore performance scenarios in advance of their availability for measurement. Our analysis illustrates that application performance is essentially unrelated to relative peak performance but that application performance can be both predicted and explained using modeling.

  3. A compact high current pulsed electron gun with subnanosecond electron pulse widths

    NASA Technical Reports Server (NTRS)

    Khakoo, M. A.; Srivastava, S. K.

    1984-01-01

    A magnetically-collimated, double-pulsed electron gun capable of generating electron pulses with a peak instantaneous current of approximately 70 microamps and a temporal width of 0.35 ns (FWHM) has been developed. Calibration is accomplished by measuring the lifetime of the well known 2(1P)-to-1(1S) transition in helium (58.4nm) at a near-threshold electron-impact energy by use of the delayed-coincidence technique.

  4. Electromagnetic pulse coupling through an aperture into a two-parallel-plate region

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Y.

    1978-01-01

    Analysis of electromagnetic-pulse (EMP) penetration via apertures into cavities is an important study in designing hardened systems. In this paper, an integral equation procedure is developed for determining the frequency and consequently the time behavior of the field inside a two-parallel-plate region excited through an aperture by an EMP. Some discussion of the numerical results is also included in the paper for completeness.

  5. Displacement Current and the Generation of Parallel Electric Fields

    SciTech Connect

    Song Yan; Lysak, Robert L.

    2006-04-14

    We show for the first time the dynamical relationship between the generation of magnetic field-aligned electric field (E{sub parallel}) and the temporal changes and spatial gradients of magnetic and velocity shears, and the plasma density in Earth's magnetosphere. We predict that the signatures of reconnection and auroral particle acceleration should have a correlation with low plasma density, and a localized voltage drop (V{sub parallel}) should often be associated with a localized magnetic stress concentration. Previous interpretations of the E{sub parallel} generation are mostly based on the generalized Ohm's law, causing serious confusion in understanding the nature of reconnection and auroral acceleration.

  6. Analysis of Ion Currents Generated with a Pulsed Laser

    SciTech Connect

    Krasa, J.; Jungwirth, K.; Krousky, E.; Laska, L.; Pfeifer, M.; Rohlena, K.; Velyhan, A.; Ullschmied, J.

    2008-03-19

    A deconvolution analysis of ion currents, which is based on the use of shifted Maxwell-Boltzmann velocity distribution, is applied to determine the temperatures and the centre-of-mass velocities of ions emitted from polyethylene and Cu targets irradiated by pulsed laser beams. This analysis can render important details in establishing the mechanisms responsible for the ion emission.

  7. Terahertz spin current pulses controlled by magnetic heterostructures.

    PubMed

    Kampfrath, T; Battiato, M; Maldonado, P; Eilers, G; Nötzold, J; Mährlein, S; Zbarsky, V; Freimuth, F; Mokrousov, Y; Blügel, S; Wolf, M; Radu, I; Oppeneer, P M; Münzenberg, M

    2013-04-01

    In spin-based electronics, information is encoded by the spin state of electron bunches. Processing this information requires the controlled transport of spin angular momentum through a solid, preferably at frequencies reaching the so far unexplored terahertz regime. Here, we demonstrate, by experiment and theory, that the temporal shape of femtosecond spin current bursts can be manipulated by using specifically designed magnetic heterostructures. A laser pulse is used to drive spins from a ferromagnetic iron thin film into a non-magnetic cap layer that has either low (ruthenium) or high (gold) electron mobility. The resulting transient spin current is detected by means of an ultrafast, contactless amperemeter based on the inverse spin Hall effect, which converts the spin flow into a terahertz electromagnetic pulse. We find that the ruthenium cap layer yields a considerably longer spin current pulse because electrons are injected into ruthenium d states, which have a much lower mobility than gold sp states. Thus, spin current pulses and the resulting terahertz transients can be shaped by tailoring magnetic heterostructures, which opens the door to engineering high-speed spintronic devices and, potentially, broadband terahertz emitters.

  8. Plasma heating and current drive using intense, pulsed microwaves

    SciTech Connect

    Cohen, B.I.; Cohen, R.H.; Nevins, W.M.; Rognlien, T.D.; Bonoli, P.T.; Porkolab, M.

    1988-01-01

    The use of powerful new microwave sources, e.g., free-electron lasers and relativistic gyrotrons, provide unique opportunities for novel heating and current-drive schemes in the electron-cyclotron and lower-hybrid ranges of frequencies. These high-power, pulsed sources have a number of technical advantages over conventional, low-intensity sources; and their use can lead to improved current-drive efficiencies and better penetration into a reactor-grade plasma in specific cases. The Microwave Tokamak Experiment at Lawrence Livermore National Laboratory will provide a test for some of these new heating and current-drive schemes. This paper reports theoretical progress both in modeling absorption and current drive for intense pulses and in analyzing some of the possible complications that may arise, e.g., parametric instabilities and nonlinear self-focusing. 22 refs., 9 figs., 1 tab.

  9. Electronic constant current and current pulse signal generator for nuclear instrumentation testing

    DOEpatents

    Brown, Roger A.

    1994-01-01

    Circuitry for testing the ability of an intermediate range nuclear instrut to detect and measure a constant current and a periodic current pulse. The invention simulates the resistance and capacitance of the signal connection of a nuclear instrument ion chamber detector and interconnecting cable. An LED flasher/oscillator illuminates an LED at a periodic rate established by a timing capacitor and circuitry internal to the flasher/oscillator. When the LED is on, a periodic current pulse is applied to the instrument. When the LED is off, a constant current is applied. An inductor opposes battery current flow when the LED is on.

  10. Electronic constant current and current pulse signal generator for nuclear instrumentation testing

    DOEpatents

    Brown, R.A.

    1994-04-19

    Circuitry is described for testing the ability of an intermediate range nuclear instrument to detect and measure a constant current and a periodic current pulse. The invention simulates the resistance and capacitance of the signal connection of a nuclear instrument ion chamber detector and interconnecting cable. An LED flasher/oscillator illuminates an LED at a periodic rate established by a timing capacitor and circuitry internal to the flasher/oscillator. When the LED is on, a periodic current pulse is applied to the instrument. When the LED is off, a constant current is applied. An inductor opposes battery current flow when the LED is on. 1 figures.

  11. Eddy current pulsed phase thermography and feature extraction

    NASA Astrophysics Data System (ADS)

    He, Yunze; Tian, GuiYun; Pan, Mengchun; Chen, Dixiang

    2013-08-01

    This letter proposed an eddy current pulsed phase thermography technique combing eddy current excitation, infrared imaging, and phase analysis. One steel sample is selected as the material under test to avoid the influence of skin depth, which provides subsurface defects with different depths. The experimental results show that this proposed method can eliminate non-uniform heating and improve defect detectability. Several features are extracted from differential phase spectra and the preliminary linear relationships are built to measure these subsurface defects' depth.

  12. Reduction of RF sheaths potentials by compensation or suppression of parallel RF currents on ICRF antennae

    NASA Astrophysics Data System (ADS)

    Mendes, A.; Colas, L.; Vulliez, K.; Argouarch, A.; Milanesio, D.

    2009-11-01

    Radio Frequency (RF) sheaths are suspected to limit the performance of present-day Ion Cyclotron Range of Frequencies (ICRF) antennae over long pulses and should be minimized in future Fusion devices. Within the simplest models, RF sheath effects are quantified by the integral VRF = ∫E//ṡdl where the parallel RF field E// is linked with the slow wave. On "long open field lines" with large toroidal extension on both sides of the antenna it was shown that VRF is excited by parallel RF currents j// flowing on the antenna structure. We thus propose two ways to reduce |VRF| by acting on j// on the antenna front face. The first method, more adapted for protruding antennae, consists in avoiding the j// circulation on the antenna structure, by slotting the antenna frame on its horizontal edges and by cutting partially the Faraday screen rods. The second method, well suited for recessed antennae, consists in compensating j// of opposite signs along long flux tubes, with parallelepiped antennae aligned with tilted flux tubes. The different concepts are assessed numerically on a 2-strap Tore Supra antenna phased [0, π] using near RF fields from the antenna code TOPICA. Simulations stress the need to suppress all current paths for j// to reduce substantially |VRF| over the whole antenna height.

  13. All-Optical Two-Dimensional Serial-to-Parallel Pulse Converter Using an Organic Film with Femtosecond Optical Response

    NASA Astrophysics Data System (ADS)

    Tatsuura, Satoshi; Wada, Osamu; Furuki, Makoto; Tian, Minquan; Sato, Yasuhiro; Iwasa, Izumi; Pu, Lyong Sun

    2001-04-01

    In this study, we introduce a new concept of all-optical two-dimensional serial-to-parallel pulse converters. Femtosecond optical pulses can be understood as thin plates of light traveling in space. When a femtosecond signal-pulse train and a single gate pulse were fed onto a material with a finite incident angle, each signal-pulse plate met the gate-pulse plate at different locations in the material due to the time-of-flight effect. Meeting points can be made two-dimensional by adding a partial time delay to the gate pulse. By placing a nonlinear optical material at an appropriate position, two-dimensional serial-to-parallel conversion of a signal-pulse train can be achieved with a single gate pulse. We demonstrated the detection of parallel outputs from a 1-Tb/s optical-pulse train through the use of a BaB2O4 crystal. We also succeeded in demonstrating 1-Tb/s serial-to-parallel operation through the use of a novel organic nonlinear optical material, squarylium-dye J-aggregate film, which exhibits ultrafast recovery of bleached absorption.

  14. Eddy current pulsed thermography for fatigue evaluation of gear

    NASA Astrophysics Data System (ADS)

    Tian, Gui Yun; Yin, Aijun; Gao, Bin; Zhang, Jishan; Shaw, Brian

    2014-02-01

    The pulsed eddy current (PEC) technique generates responses over a wide range of frequencies, containing more spectral coverage than traditional eddy current inspection. Eddy current pulsed thermography (ECPT), a newly developed non-destructive testing (NDT) technique, has advantages such as rapid inspection of a large area within a short time, high spatial resolution, high sensitivity and stand-off measurement distance. This paper investigates ECPT for the evaluation of gear fatigue tests. The paper proposes a statistical method based on single channel blind source separation to extract details of gear fatigue. The discussion of transient thermal distribution and patterns of fatigue contact surfaces as well as the non-contact surfaces have been reported. In addition, the measurement for gears with different cycles of fatigue tests by ECPTand the comparison results between ECPT with magnetic Barkhausen noise (MBN) have been evaluated. The comparison shows the competitive capability of ECPT in fatigue evaluation.

  15. Interface demarcation in GaAs by current pulsing

    NASA Technical Reports Server (NTRS)

    Matthiesen, D. H.; Kafalas, J. A.; Duchene, G. A.; Bellows, A. H.

    1990-01-01

    GTE Laboratories is currently conducting a program to investigate the effect of convection in the melt on the properties of bulk grown gallium arsenide (GaAs). In addition to extensive ground based experimentation, a Get Away Special growth system has been developed to grow two GaAs crystals aboard the Space Shuttle, each with a one inch diameter. In order to perform a complete segregation analysis of the crystals grown in space, it is necessary to measure the interface shape and growth rate as well as the spatial distribution of the selenium dopant. The techniques for interface demarcation in selenium doped GaAs by current pulsing have been developed at GTE Laboratories and successful interface demarcation has been achieved for current pulses ranging from 20 to 90 amps, in both single crystal and polycrystalline regions.

  16. Investigation on Nyquist pulse generation using a single dual-parallel Mach-Zehnder modulator.

    PubMed

    Wu, Jian; Zang, Jizhao; Li, Yan; Kong, Deming; Qiu, Jifang; Zhou, Siyuan; Shi, Jindan; Lin, Jintong

    2014-08-25

    The generation of Nyquist pulses with a dual parallel Mach-Zehnder modulator (DPMZM) driven by a single RF signal is demonstrated theoretically and experimentally. A complete theoretical analysis is developed and the limitation of the proposed scheme is also discussed. It is theoretically proved that Nyquist pulses with a spectrum of 5 flat comb lines can be generated using a single DPMZM, which is also verified with simulation. 7 flat comb lines in frequency domain can also be obtained if a large RF driving voltage is applied to DPMZM but the generated waveforms won't present a sinc-shape. This scheme is further investigated experimentally. 40 GHz Nyquist pulses with full-width-at-half-maximum (FWHM) less than 4.65 ps, signal-to-noise ratio (SNR) better than 29.5 dB, and normalized root-mean-square error (NRMSE) less than 2.4% are generated. It is found that a tradeoff exists between the insertion loss of the DPMZM and the deviation of generated pulses. The tunability of repetition rate is experimentally verified by generation of 1 GHz to 40 GHz Nyquist pulses with SNR better than 28.4 dB and NRMSE less than 6.15%.

  17. Parallel Computational Fluid Dynamics: Current Status and Future Requirements

    NASA Technical Reports Server (NTRS)

    Simon, Horst D.; VanDalsem, William R.; Dagum, Leonardo; Kutler, Paul (Technical Monitor)

    1994-01-01

    One or the key objectives of the Applied Research Branch in the Numerical Aerodynamic Simulation (NAS) Systems Division at NASA Allies Research Center is the accelerated introduction of highly parallel machines into a full operational environment. In this report we discuss the performance results obtained from the implementation of some computational fluid dynamics (CFD) applications on the Connection Machine CM-2 and the Intel iPSC/860. We summarize some of the experiences made so far with the parallel testbed machines at the NAS Applied Research Branch. Then we discuss the long term computational requirements for accomplishing some of the grand challenge problems in computational aerosciences. We argue that only massively parallel machines will be able to meet these grand challenge requirements, and we outline the computer science and algorithm research challenges ahead.

  18. Phenomenological Model of Current Sheet Canting in Pulsed Electromagnetic Accelerators

    NASA Technical Reports Server (NTRS)

    Markusic, Thomas; Choueiri, E. Y.

    2003-01-01

    The phenomenon of current sheet canting in pulsed electromagnetic accelerators is the departure of the plasma sheet (that carries the current) from a plane that is perpendicular to the electrodes to one that is skewed, or tipped. Review of pulsed electromagnetic accelerator literature reveals that current sheet canting is a ubiquitous phenomenon - occurring in all of the standard accelerator geometries. Developing an understanding of current sheet canting is important because it can detract from the propellant sweeping capabilities of current sheets and, hence, negatively impact the overall efficiency of pulsed electromagnetic accelerators. In the present study, it is postulated that depletion of plasma near the anode, which results from axial density gradient induced diamagnetic drift, occurs during the early stages of the discharge, creating a density gradient normal to the anode, with a characteristic length on the order of the ion skin depth. Rapid penetration of the magnetic field through this region ensues, due to the Hall effect, leading to a canted current front ahead of the initial current conduction channel. In this model, once the current sheet reaches appreciable speeds, entrainment of stationary propellant replenishes plasma in the anode region, inhibiting further Hall-convective transport of the magnetic field; however, the previously established tilted current sheet remains at a fairly constant canting angle for the remainder of the discharge cycle, exerting a transverse J x B force which drives plasma toward the cathode and accumulates it there. This proposed sequence of events has been incorporated into a phenomenological model. The model predicts that canting can be reduced by using low atomic mass propellants with high propellant loading number density; the model results are shown to give qualitative agreement with experimentally measured canting angle mass dependence trends.

  19. Pulsed eddy current thickness measurements of transuranic waste containers

    SciTech Connect

    O`Brien, T.K.; Kunerth, D.C.

    1995-12-31

    Thickness measurements on fifty five gallon waste drums for drum integrity purposes have been traditionally performed at the INEL using ultrasonic testing methods. Ultrasonic methods provide high resolution repeatable thickness measurements in a timely manner, however, the major drawback of using ultrasonic techniques is coupling to the drum. Areas with severe exterior corrosion, debonded paper labels or any other obstacle in the acoustic path will have to be omitted from the ultrasonic scan. We have developed a pulsed eddy current scanning system that can take thickness measurements on fifty five gallon carbon steel drums with wall thicknesses up to 65 mils. This type of measurement is not susceptible to the problems mentioned above. Eddy current measurements in the past have excluded ferromagnetic materials such as carbon steel because of the difficulty in penetrating the material and in compensating for changes in permeability from material to material. New developments in data acquisition electronics as well as advances in personal computers have made a pulsed eddy current system practical and inexpensive. Certain aspects of the pulsed eddy current technique as well as the operation of such a system and features such as real time pass/fail thresholds for overpacking identification and full scan data archiving for future evaluation will be discussed.

  20. Rarefied flow diagnostics using pulsed high-current electron beams

    NASA Technical Reports Server (NTRS)

    Wojcik, Radoslaw M.; Schilling, John H.; Erwin, Daniel A.

    1990-01-01

    The use of high-current short-pulse electron beams in low-density gas flow diagnostics is introduced. Efficient beam propagation is demonstrated for pressure up to 300 microns. The beams, generated by low-pressure pseudospark discharges in helium, provide extremely high fluorescence levels, allowing time-resolved visualization in high-background environments. The fluorescence signal frequency is species-dependent, allowing instantaneous visualization of mixing flowfields.

  1. Crack detection using pulsed eddy current stimulated thermography

    SciTech Connect

    Kostson, E.; Weekes, B.; Almond, D. P.; Wilson, J.; Tian, G. Y.

    2011-06-23

    This contribution presents results from studies investigating factors that influence the detection of surface breaking cracks using pulsed eddy current thermography. The influences of the current strength and crack orientation in both ferromagnetic and non-ferromagnetic metals have been investigated. It has been found that crack detection is far more sensitive to crack orientation in non-ferromagnetic metals than in ferromagnetic metals. The effects of crack size on detectability are presented for a large number of steel, nickel alloy and titanium samples. Results of studies comparing crack images obtained prior and after coating a nickel alloy sample with a thermal barrier coating are presented.

  2. Characterization of Magnetron Sputtered Coatings by Pulsed Eddy Current Techniques

    SciTech Connect

    Mulligan, Chris; Lee Changqing; Danon, Yaron

    2005-04-09

    A method that uses induced pulsed eddy currents for characterization of thick magnetron sputtered Nb coatings on steel is presented in this paper. The objectives of this work are to develop a system for rapid quantitative nondestructive inspection of coatings as well as to determine the correlation between coating properties, such as density and purity, and eddy current measured resistivity of coatings. A two-probe differential system having higher sensitivity and less noise than a one-probe system with 2-D scanning ability was developed.

  3. A pulsed-power generator merging inductive voltage and current adders and its switch trigger application example.

    PubMed

    Li, Lee; Yafeng, Ge; Heqin, Zhong; Bin, Yu; Longjun, Xie

    2013-07-01

    A pulsed-power generator using inductive adder technology is proposed for the case of a discharge gap. The merit of this generator is to merge the pulsed-voltage and pulsed-current adders via the dual secondary windings with special circuit. For the nonlinear impedance in any discharge gap, the standalone voltage-pulse and current-pulse can be outputted successively by this generator. The proposed generator is especially useful for the common resolution of implementing pulse discharge at less cost. As an application example, a compact trigger prototype was developed to compatibly use in the gas-insulated and vacuum switches. Experiments achieved good results that the triggered switches showed stable performance and long life. If the basic circuit of this proposed generator is regarded as a pulsed-generating unit, a certain number of such units connected in parallel can be expected to form a general device with generating greater breakdown-voltage and sustained-current pulses for discharge gaps.

  4. Numerically Modeling Pulsed-Current, Kinked Wire Experiments

    NASA Astrophysics Data System (ADS)

    Filbey, Gordon; Kingman, Pat

    1999-06-01

    The U.S. Army Research Laboratory (ARL) has embarked on a program to provide far-term land fighting vehicles with electromagnetic armor protection. Part of this work seeks to establish robust simulations of magneto-solid-mechanics phenomena. Whether describing violent rupture of a fuse link resulting from a large current pulse or the complete disruption of a copper shaped-charge jet subjected to high current densities, the simulations must include effects of intense Lorentz body forces and rapid Ohmic heating. Material models are required that describe plasticity, flow and fracture, conductivity, and equation of state (EOS) parameters for media in solid, liquid, and vapor phases. An extended version of the Eulerian wave code CTH has been used to predict the apex motion of a V-shaped (``kinked'') copper wire 3mm in diameter during a 400 kilo-amp pulse. These predictions, utilizing available material, EOS, and conductivity data for copper and the known characteristics of an existing capacitor-bank pulsed power supply, were then used to configure an experiment. The experiments were in excellent agreement with the prior simulations. Both computational and experimental results (including electrical data and flash X-rays) will be presented.

  5. Performance Effects of Adding a Parallel Capacitor to a Pulse Inductive Plasma Accelerator Powertrain

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Sivak, Amy D.; Balla, Joseph V.

    2011-01-01

    Pulsed inductive plasma accelerators are electrodeless space propulsion devices where a capacitor is charged to an initial voltage and then discharged through a coil as a high-current pulse that inductively couples energy into the propellant. The field produced by this pulse ionizes the propellant, producing a plasma near the face of the coil. Once a plasma is formed if can be accelerated and expelled at a high exhaust velocity by the Lorentz force arising from the interaction of an induced plasma current and the magnetic field. While there are many coil geometries that can be employed to inductively accelerate a plasma, in this paper the discussion is limit to planar geometries where the coil take the shape of a flat spiral. A recent review of the developmental history of planar-geometry pulsed inductive thrusters can be found in Ref. [1]. Two concepts that have employed this geometry are the Pulsed Inductive Thruster (PIT) and the Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD).

  6. Controlled motion of electrically neutral microparticles by pulsed direct current

    PubMed Central

    Zhang, Xinfang; Qin, Rongshan

    2015-01-01

    A controlled motion of electrically neutral microparticles in a conductive liquid at high temperatures has not yet been realized under the uniform direct electric current field. We propose a simple method, which employs pulsed direct current to a conductive liquid metal containing low-conductivity objects at high temperature. The electric current enables the low-conductivity particles to pass from the centre towards the various surfaces of the high-conductivity liquid metal. Most interestingly, the directionality of microparticles can be controlled and their speed can be easily regulated by adjusting pulsed current density. We find that the movement may arise from the configuration of electrical domains which generates a driving force which exceeds the force of gravity and viscous friction. All of these features are of potential benefit in separating the particles of nearly equal density but distinctly different electrical conductivities, and also offer considerable promise for the precise and selective positioning of micro-objects or the controlled motion of minute quantities of surrounding fluids. PMID:25955864

  7. Experimental study on double-pulse laser ablation of steel upon multiple parallel-polarized ultrashort-pulse irradiations

    NASA Astrophysics Data System (ADS)

    Schille, Joerg; Schneider, Lutz; Kraft, Sebastian; Hartwig, Lars; Loeschner, Udo

    2016-07-01

    In this paper, double-pulse laser processing is experimentally studied with the aim to explore the influence of ultrashort pulses with very short time intervals on ablation efficiency and quality. For this, sequences of 50 double pulses of varied energy and inter-pulse delay, as adjusted between 400 fs and 18 ns by splitting the laser beam into two optical paths of different length, were irradiated to technical-grade stainless steel. The depth and the volume of the craters produced were measured in order to evaluate the efficiency of the ablation process; the crater quality was analyzed by SEM micrographs. The results obtained were compared with craters produced with sequences of 50 single pulses and energies equal to the double pulse. It is demonstrated that double-pulse processing cannot exceed the ablation efficiency of single pulses of optimal fluence, but the ablation crater surface formed smoother if inter-pulse delay was in the range between 10 ns and 18 ns. In addition, the influence of pulse duration and energy distribution between the individual pulses of the double pulse on ablation was studied. For very short inter-pulse delay, no significant effect of energy variation within the double pulse on removal rate was found, indicating that the double pulse acts as a big single pulse of equal energy. Further, the higher removal efficiency was achieved when double-pulse processing using femtosecond pulses instead of picosecond pulses.

  8. High-Voltage Pulsed Current Electrical Stimulation in Wound Treatment

    PubMed Central

    Polak, Anna; Franek, Andrzej; Taradaj, Jakub

    2014-01-01

    Significance: A range of studies point to the efficacy of electrical stimulation (ES) in wound treatment, but the methodology of its application has not been determined to date. This article provides a critical review of the results of clinical trials published by researchers using high-voltage pulsed current (HVPC) to treat chronic wounds. In describing the methodology of the trials, the article gives special attention to electric stimulus parameters, the frequency of procedures and total treatment duration. Recent Advances: HVPC is a monophasic pulsed electric current that consists of double-peaked impulses (5–200 μs), at very high peak-current amplitude (2–2.5 A), and high voltage (up to 500 V), at a frequency of 1–125 pulses per second. HVPC can activate “skin battery” and cellular galvanotaxis, and improves blood flow and capillary density. Critical Issues: HVPC efficacy was evaluated in conservatively treated patients with diabetic foot, venous leg and pressure ulcers (PUs), and in some patients with surgically treated venous insufficiency. Future Directions: The efficacy of HVPC as one of several biophysical energies promoting venous leg ulcer (VLU) and PU healing has been confirmed. Additional studies are needed to investigate its effect on the healing of other types of soft tissue defects. Other areas that require more research include the identification of the therapeutic effect of HVPC on infected wounds, the determination of the efficacy of cathodal versus anodal stimulation, and the minimal daily/weekly duration of HVPC required to ensure optimal promotion of wound healing. PMID:24761351

  9. Subsurface Defect Detection in Metals with Pulsed Eddy Current

    SciTech Connect

    Plotnikov, Yuri A.; Bantz, Walter J.

    2005-04-09

    The eddy current (EC) method is traditionally used for open surface crack detection in metallic components. Subsurface voids in bulk metals can also be detected by the eddy current devices. Taking into consideration the skin effect in conductive materials, a lower frequency of electromagnetic excitation is used for a deeper penetration. A set of special specimens was designed and fabricated to investigate sensitivity to subsurface voids. Typically, flat bottom holes (FBHs) are used for subsurface defect simulation. This approach is not very representative of real defects for eddy current inspection because the FBH depth extends to the bottom of the specimen. Two-layer specimens with finite depth FBHs were fabricated and scanned with conventional EC of variable frequency. Sensitivity and spatial resolution of EC diminish with flaw depth. The pulsed EC approach was applied for flaw detection at variable distance under the surface. The transient response from multi-layer model was derived and compared to experiments. The multi-frequency nature of pulsed excitation provides effective coverage of a thick layer of material in one pass. Challenging aspects of subsurface flaw detection and visualization using the EC technique are discussed.

  10. Time resolved imaging of magnetization dynamics in hard disk writer yokes excited by bipolar current pulses

    SciTech Connect

    Yu, W. Keatley, P. S.; Hicken, R. J.; Gubbins, M. A.; Czoschke, P. J.; Lopusnik, R.

    2014-05-07

    A partially built hard disk writer structure with a NiFe/CoFe/Ru/NiFe/CoFe synthetic antiferromagnetic (SAF) yoke was studied by time and vector resolved scanning Kerr microscopy. All three time dependent components of the magnetization were recorded simultaneously as a bipolar current pulse with 1 MHz repetition rate was delivered to the coil. The component of magnetization parallel to the symmetry axis of the yoke was compared at the pole and above a coil winding in the centre of the yoke. The two responses are in phase as the pulse rises, but the pole piece lags the yoke as the pulse falls. The Kerr signal is smaller within the yoke than within the confluence region during pulse cycling. This suggests funneling of flux into the confluence region. Dynamic images acquired at different time delays showed that the relaxation is faster in the centre of the yoke than in the confluence region, perhaps due to the different magnetic anisotropy in these regions. Although the SAF yoke is designed to support a single domain to aid flux conduction, no obvious flux beaming was observed, suggesting the presence of a more complicated domain structure. The SAF yoke writer hence provides relatively poor flux conduction but good control of rise time compared to single layer and multi-layered yokes studied previously.

  11. Thickness Evaluation of Aluminium Plate Using Pulsed Eddy Current Technique

    NASA Astrophysics Data System (ADS)

    Singh, Gurpartap; Bapat, Harsh Madhukar; Singh, Bhanu Pratap; Bandyopadhyay, Manojit; Puri, Rakesh Kumar; Badodkar, Deepak Narayanrao

    2013-10-01

    This paper describes a pulsed eddy current (PEC) based non-destructive testing system used for detection of thickness variation in aluminium plate. A giant magneto-resistive sensor has been used instead of pick up coil for detecting resultant magnetic field. The PEC response signals obtained from 1 to 5 mm thickness change in aluminium plate were investigated. Two time domain features, namely peak value and time to peak, of PEC response were used for extracting information about thickness variation in aluminium plate. The variation of peak value and time to peak with thickness was compared. A program was developed to display the thickness variation of the tested sample.

  12. Eddy current pulsed phase thermography for subsurface defect quantitatively evaluation

    NASA Astrophysics Data System (ADS)

    He, Yunze; Pan, Mengchun; Tian, GuiYun; Chen, Dixiang; Tang, Ying; Zhang, Hong

    2013-09-01

    This Letter verified eddy current pulse phase thermography through numerical and experimental studies. During the numerical studies, two characteristic features, blind frequency and min phase, were extracted from differential phase spectra, and their monotonic relationships with defects' depth under different heating time were compared. According to the numerical studies, 100 ms was employed as heating time during the improved experimental studies. The experimental results agreed with the numerical results. Based on their linear relationship with defects' depths, both features can be used to measure the defect's depth.

  13. Hard carbon coatings deposited by pulsed high current magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Oskomov, K. V.; Solov'ev, A. A.; Rabotkin, S. V.

    2014-12-01

    Hard (up to 17 GPa) carbon coatings are deposited onto face SiC bearings used in liquid pumps by pulsed high-current magnetron sputtering of graphite. As a result, the friction coefficient is decreased from 0.43 to 0.11 and the wear rate is decreased from 26 to 0.307 μm3 N-1 m-1, which increases the service life of the bearings by approximately three times. The deposited carbon coatings have a high hardness and wear resistance due to the generation of high-density (up to 1013 cm-3) plasma.

  14. Oscillatory dependence of current-driven magnetic domain wall motion on current pulse length

    NASA Astrophysics Data System (ADS)

    Thomas, Luc; Hayashi, Masamitsu; Jiang, Xin; Moriya, Rai; Rettner, Charles; Parkin, Stuart S. P.

    2006-09-01

    Magnetic domain walls, in which the magnetization direction varies continuously from one direction to another, have long been objects of considerable interest. New concepts for devices based on such domain walls are made possible by the direct manipulation of the walls using spin-polarized electrical current through the phenomenon of spin momentum transfer. Most experiments to date have considered the current-driven motion of domain walls under quasi-static conditions, whereas for technological applications, the walls must be moved on much shorter timescales. Here we show that the motion of domain walls under nanosecond-long current pulses is surprisingly sensitive to the pulse length. In particular, we find that the probability of dislodging a domain wall, confined to a pinning site in a permalloy nanowire, oscillates with the length of the current pulse, with a period of just a few nanoseconds. Using an analytical model and micromagnetic simulations, we show that this behaviour is connected to a current-induced oscillatory motion of the domain wall. The period is determined by the wall's mass and the slope of the confining potential. When the current is turned off during phases of the domain wall motion when it has enough momentum, the domain wall is driven out of the confining potential in the opposite direction to the flow of spin angular momentum. This dynamic amplification effect could be exploited in magnetic nanodevices based on domain wall motion.

  15. Electrical and hydrodynamic characterization of a high current pulsed arc

    NASA Astrophysics Data System (ADS)

    Sousa Martins, R.; Chemartin, L.; Zaepffel, C.; Lalande, Ph; Soufiani, A.

    2016-05-01

    High current pulsed arcs are of significant industrial interest and, aiming to reduce time and cost, there is progressively more and more need for computation tools that describe and predict the behaviour of these arcs. These simulation codes need inputs and validations by experimental databases, but accurate data is missing for this category of electric discharges. The principal lack of understanding is with respect to the transient phase of the current, which can reach thousands of amperes in a few microseconds. In this paper, we present the work realized on an experimental setup that simulates in the laboratory an arc column subjected to five levels of high pulsed current, ranging from 10 kA to 100 kA, with the last one corresponding to the standard lightning current waveform used in aircraft certification processes. This device was instrumented by high speed video cameras to assess the characteristic sizes of the arc channel and to characterize the shock wave generated by the arc expansion. The arc channel radius was measured over time during the axisymmetric phase and reached 3.2 cm. The position and velocity of the shock wave was determined during the first 140 μs. The background-oriented schlieren method was used to study the shock wave and a model for the light deflection inside the shock wave was developed. The mass density profile of the shock wave was estimated and showed good agreement with Rankine-Hugoniot relations at the wave front. Electrical measurements were also used to estimate the time-dependent resistance and conductivity of the arc for times lasting up to 50 μs.

  16. Pulsed currents carried by whistlers. I - Excitation by magnetic antennas

    NASA Technical Reports Server (NTRS)

    Stenzel, R. L.; Urrutia, J. M.; Rousculp, C. L.

    1993-01-01

    Time-varying plasma currents associated with low-frequency whistlers have been investigated experimentally. Pulsed currents are induced in the uniform, boundary-free interior of a large laboratory plasma by means of insulated magnetic antennas. The time-varying magnetic field is measured in three dimensions, and the current density is calculated from del x B(r,t) = mu(0)J, where J includes the displacement current density. Typical fields B(r,t) and J(r,t) induced by a magnetic loop antenna show three-dimensional helices due to linked toroidal and solenoidal field topologies. Constant amplitude and phase surfaces assume conical shapes since the propagation speed along B0 is higher than oblique to B0. The electric field in the wave packet contains both inductive and space-charge contributions, the latter arising from the different dynamics of electrons and ions. The dominant electric field in a whistler packet is a radial space-charge field.

  17. Physical interpretation and separation of eddy current pulsed thermography

    NASA Astrophysics Data System (ADS)

    Yin, Aijun; Gao, Bin; Yun Tian, Gui; Woo, W. L.; Li, Kongjing

    2013-02-01

    Eddy current pulsed thermography (ECPT) applies induction heating and a thermal camera for non-destructive testing and evaluation (NDT&E). Because of the variation in resultant surface heat distribution, the physical mechanism that corresponds to the general behavior of ECPT can be divided into an accumulation of Joule heating via eddy current and heat diffusion. However, throughout the literature, the heating mechanisms of ECPT are not given in detail in the above two thermal phenomena and they are difficult to be separated. Nevertheless, once these two physical parameters are separated, they can be directly used to detect anomalies and predict the variation in material properties such as electrical conductivity, magnetic permeability and microstructure. This paper reports physical interpretation of these two physical phenomena that can be found in different time responses given the ECPT image sequences. Based on the phenomenon and their behaviors, the paper proposes a statistical method based on single channel blind source separation to decompose the two physical phenomena using different stages of eddy current and thermal propagation from the ECPT images. Links between mathematical models and physical models have been discussed and verified. This fundamental understanding of transient eddy current distribution and heating propagation can be applied to the development of feature extraction and pattern recognition for the quantitative analysis of ECPT measurement images and defect characterization.

  18. Repair of nonunions by electrically pulsed current stimulation.

    PubMed

    Zichner, L

    1981-01-01

    Five congenital and 52 acquired nonunions of bone were stimulated using an invasive device. The unit delivered a constant but pulsed right-angled current of positive polarity measuring 20 to 25 muAmps (voltage of 750 mV) and a frequency of 20 Hz. The power pack encapsulated in epoxy resin was implanted at the time of operative fragment stabilization. THe cathode was inserted at the site of the nonunion gap. After two to 12 months, all but two of the acquired nonunions and one of the congenital pseudarthroses healed. In the unsuccessful cases, the bone ends were often totally necrotic. Four cases required reimplantation because of broken wires or expiration of the battery, and two cases failed owing to purulent infection. Electrostimulation is an adjuvant treatment to fragment stabilization in hyporeactive and hypovascular or congenital pseudarthroses. Electrical stimuli may be assumed to simulate conditions which are essential for bone healing.

  19. Pulse width modulated push-pull driven parallel resonant converter with active free-wheel

    DOEpatents

    Reass, William A.; Schrank, Louis

    2004-06-22

    An apparatus and method for high frequency alternating power generation to control kilowatts of supplied power in microseconds. The present invention includes a means for energy storage, push-pull switching means, control electronics, transformer means, resonant circuitry and means for excess energy recovery, all in electrical communication. A push-pull circuit works synchronously with a force commutated free-wheel transistor to provide current pulses to a transformer. A change in the conduction angle of the push-pull circuit changes the amount of energy coupled into the transformer's secondary oscillating circuit, thereby altering the induced secondary resonating voltage. At the end of each pulse, the force commutated free-wheel transistor causes residual excess energy in the primary circuit to be transmitted back to the storage capacitor for later use.

  20. High current photoemission with 10 picosecond uv pulses

    SciTech Connect

    Fischer, J.; Srinivasan-Rao, T.; Tsang, T.

    1990-06-01

    The quantum efficiency and the optical damage threshold of various metals were explored with 10 ps, 266 nm, UV laser pulses. Efficiencies for Cu, Y, and Sm were: 1.4, 5, and 7 {times} 10{sup {minus}4}, with damage thresholds about 100, 10, and 30 mJ/cm{sup 2}. This would permit over 1 {mu}C/cm{sup 2} or current densities exceeding 100 kA/cm{sup 2}. High charge and current densities of up to 66 kA/cm{sup 2} were obtained on 0.25 mm diam cathodes, and 21 kA/cm{sup 2} on a 3 mm diam yttrium cathode. The maximum currents were limited by space charge and the dc field. The experiments with small area illumination indicate that the emitted electrons spread transversely due to Coulomb repulsion and their initial transverse velocity. This increases the effective area above the cathode, reduces the space charge effect and increases emission density on the cathode. The quantum efficiency can be increased substantially by enhancing the field on the surface by either a suitable electrode geometry or microstructures on it. 14 refs., 12 figs., 3 tabs.

  1. Effect of a Second, Parallel Capacitor on the Performance of a Pulse Inductive Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Balla, Joseph V.

    2010-01-01

    Pulsed inductive plasma accelerators are electrodeless space propulsion devices where a capacitor is charged to an initial voltage and is then discharged through an inductive coil that couples energy into the propellant, ionizing and accelerating it to produce thrust. A model that employs a set of circuit equations (as illustrated in Fig. 1a) coupled to a one-dimensional momentum equation has been previously used by Lovberg and Dailey [1] and Polzin et al. [2-4] to model the plasma acceleration process in pulsed inductive thrusters. In this paper an extra capacitor, inductor, and resistor are added to the system in the manner illustrated in the schematic shown in Fig. 1b. If the second capacitor has a smaller value than the initially charged capacitor, it can serve to increase the current rise rate through the inductive coil. Increasing the current rise rate should serve to better ionize the propellant. The equation of motion is solved to find the effect of an increased current rise rate on the acceleration process. We examine the tradeoffs between enhancing the breakdown process (increasing current rise rate) and altering the plasma acceleration process. These results provide insight into the performance of modified circuits in an inductive thruster, revealing how this design permutation can affect an inductive thruster's performance.

  2. Pulse-driven LED circuit with transformer-based current balance technique

    NASA Astrophysics Data System (ADS)

    Kwak, S.-S.

    2014-12-01

    Light emitting diodes (LEDs) have been gradually used for backlight modules for liquid crystal display as a substitute for cold cathode fluorescent lamps. In most of LED applications, it is required to connect several LED strings in parallel to limit the dc voltage level to be applied to the single LED string. Due to considerable current variations through each LED string with inevitable parameter deviations as well as temperature and ageing effects, techniques to balance currents flowing through LED strings are required for LED drivers. This article proposes a pulse-driven LED circuit with transformer-based current balancing scheme, which can simply regulate currents through the LED strings. The transformers are placed in series with the LED strings in such a way that the LED currents are automatically balanced. Since the developed current sharing technique employs no dissipative resistors and no linear-mode transistors, the proposed driver has high efficiency, low power dissipation and reduced thermal problems. In addition, the presented driver with no additional semiconductor devices and no additional controllers can provide a simple and a cost-effective current balancing solution, compared to conventional approaches. Thus, the proposed LED driver can feature a simple, highly efficient, reliable and cost-effective method. The presented LED driver is verified with experimental results.

  3. Effect of Pulse Current on the Tensile Deformation of SUS304 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Li, Xifeng; Wang, Shen; Zhao, Shuangjun; Ding, Wei; Chen, Jun; Wu, Guohong

    2015-12-01

    The effect of pulse current on the mechanical properties of SUS304 metastable austenitic stainless steel was studied by tension test with and without air-cooling under different current densities. The microstructural variations at different conditions were also studied by SEM, TEM, and Feritscope. A negative effect on the plasticity was observed when current pulse was applied without air-cooling. But when Joule heating resulting from current pulse was excluded by air-cooling, the elongation of SUS304 stainless steel was increased to 72.4% at a current density of 2.95 A/mm2, which is 23.3% higher than that tested without pulse current at room temperature. Pulse current can decrease the dislocation density and dislocation pile-ups. Furthermore, EP effect from pulse current can accelerate martensitic transformation and enhance TRIP effect. The mechanism of current-induced martensitic transformation was discussed from Gibbs free energy change.

  4. Low profile, highly configurable, current sharing paralleled wide band gap power device power module

    DOEpatents

    McPherson, Brice; Killeen, Peter D.; Lostetter, Alex; Shaw, Robert; Passmore, Brandon; Hornberger, Jared; Berry, Tony M

    2016-08-23

    A power module with multiple equalized parallel power paths supporting multiple parallel bare die power devices constructed with low inductance equalized current paths for even current sharing and clean switching events. Wide low profile power contacts provide low inductance, short current paths, and large conductor cross section area provides for massive current carrying. An internal gate & source kelvin interconnection substrate is provided with individual ballast resistors and simple bolted construction. Gate drive connectors are provided on either left or right size of the module. The module is configurable as half bridge, full bridge, common source, and common drain topologies.

  5. Theoretical and Experimental Study of the Primary Current Distribution in Parallel-Plate Electrochemical Reactors

    ERIC Educational Resources Information Center

    Vazquez Aranda, Armando I.; Henquin, Eduardo R.; Torres, Israel Rodriguez; Bisang, Jose M.

    2012-01-01

    A laboratory experiment is described to determine the primary current distribution in parallel-plate electrochemical reactors. The electrolyte is simulated by conductive paper and the electrodes are segmented to measure the current distribution. Experiments are reported with the electrolyte confined to the interelectrode gap, where the current…

  6. Decolorization of methylene blue in aqueous suspensions of gold nanoparticles using parallel nanosecond pulsed laser.

    PubMed

    Zong, Yan P; Liu, Xian H; Du, Xi W; Lu, Yi R; Wang, Mei Y; Wang, Guang Y

    2013-01-01

    Using 532 nm parallel nanosecond pulsed laser, the decolorization of methylene blue (MB) in aqueous suspensions of gold nanoparticles (GNPs) was studied. The effects of various experimental parameters, such as irradiation time, laser energy, and initial MB concentration on the decolorization rate were investigated. Experiments using real samples of textile dyeing wastewater were also carried out to examine the effectiveness of the method in more complex samples. From the results, the following conclusions may be drawn: (i) Under the optimum conditions (pH 7.19, 135 mJ laser energy, 4 mg/L MB concentration, and 11.6 mg/L GNP concentration), the rate of MB decolorization could reach 94% in 15 min. The decolorization follows pseudo-first-order kinetics; (ii) The amount of MB decreased rapidly during the decolorization. No intermediates of the decolorization could be detected by high-performance liquid chromatography. These observations indicate that MB was decolorized through a very rapid degradation mechanism; (iii) The rate of MB decolorization increased with the increase in laser energy (at laser energies of 0 to 135 mJ); and, (iv) The efficient decolorization of MB in real samples of textile dyeing wastewater was achieved at a decolorization rate of about 85% in 15 min.

  7. Inverse problem of pulsed eddy current field of ferromagnetic plates

    NASA Astrophysics Data System (ADS)

    Chen, Xing-Le; Lei, Yin-Zhao

    2015-03-01

    To determine the wall thickness, conductivity and permeability of a ferromagnetic plate, an inverse problem is established with measured values and calculated values of time-domain induced voltage in pulsed eddy current testing on the plate. From time-domain analytical expressions of the partial derivatives of induced voltage with respect to parameters, it is deduced that the partial derivatives are approximately linearly dependent. Then the constraints of these parameters are obtained by solving a partial linear differential equation. It is indicated that only the product of conductivity and wall thickness, and the product of relative permeability and wall thickness can be determined accurately through the inverse problem with time-domain induced voltage. In the practical testing, supposing the conductivity of the ferromagnetic plate under test is a fixed value, and then the relative variation of wall thickness between two testing points can be calculated via the ratio of the corresponding inversion results of the product of conductivity and wall thickness. Finally, this method for wall thickness measurement is verified by the experiment results of a carbon steel plate. Project supported by the National Defense Basic Technology Research Program of China (Grant No. Z132013T001).

  8. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung

    1992-12-31

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  9. A high current, short pulse electron source for wakefield accelerators

    SciTech Connect

    Ho, Ching-Hung.

    1992-01-01

    Design studies for the generation of a high current, short pulse electron source for the Argonne Wakefield Accelerator are presented. An L-band laser photocathode rf gun cavity is designed using the computer code URMEL to maximize the electric field on the cathode surface for fixed frequency and rf input power. A new technique using a curved incoming laser wavefront to minimize the space charge effect near the photocathode is studied. A preaccelerator with large iris to minimize wakefield effects is used to boost the drive beam to a useful energy of around 20 MeV for wakefield acceleration experiments. Focusing in the photocathode gun and the preaccelerator is accomplished with solenoids. Beam dynamics simulations throughout the preaccelerator are performed using particle simulation codes TBCI-SF and PARMELA. An example providing a useful set of operation parameters for the Argonne Wakefield Accelerator is given. The effects of the sagitta of the curved beam and laser amplitude and timing jitter effects are discussed. Measurement results of low rf power level bench tests and a high power test for the gun cavity are presented and discussed.

  10. Cognitive effects and autonomic responses to transcranial pulsed current stimulation.

    PubMed

    Morales-Quezada, Leon; Cosmo, Camila; Carvalho, Sandra; Leite, Jorge; Castillo-Saavedra, Laura; Rozisky, Joanna R; Fregni, Felipe

    2015-03-01

    Transcranial pulsed current stimulation (tPCS) is emerging as an option in the field of neuromodulation; however, little is known about its effects on cognition and behavior and its neurophysiological correlates as indexed by autonomic responses. Our aim was to identify the effects of tPCS on arithmetic processing and risk-taking behavior, and to further categorize physiological autonomic responses by heart rate variability (HRV) and electrodermal activity measurements before, during, and after exposure to task performance and stimulation. Thirty healthy volunteers were randomized to receive a single session of sham or active stimulation with a current intensity of 2 mA and a random frequency between 1 and 5 Hz. Our results showed that tPCS has a modest and specific effect on cognitive performance as indexed by the cognitive tasks chosen in this study. There was a modest effect of active tPCS only on performance facilitation on a complex-level mathematical task as compared to sham stimulation. On autonomic responses, we observed that HRV total power increased while LF/HF ratio decreased in the tPCS active group compared to sham. There were no group differences for adverse effects. Based on our results, we conclude that tPCS, in healthy subjects, has a modest and specific cognitive effect as shown by the facilitation of arithmetical processing on complex mathematical task. These effects are accompanied by modulation of the central autonomic network providing sympathetic-vagal balance during stressful conditions. Although behavioral results were modest, they contribute to the understanding of tPCS effects and cognitive enhancement. PMID:25479736

  11. Nonlinear MHD simulation of current drive by multi-pulsed coaxial helicity injection in spherical torus

    NASA Astrophysics Data System (ADS)

    Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro

    2011-10-01

    The dynamics of structures of magnetic field, current density, and plasma flow generated during multi-pulsed coaxial helicity injection in spherical torus is investigated by 3-D nonlinear MHD simulations. During the driven phase, the flux and current amplifications occur due to the merging and magnetic reconnection between the preexisting plasma in the confinement region and the ejected plasma from the gun region involving the n = 1 helical kink distortion of the central open flux column (COFC). Interestingly, the diamagnetic poloidal flow which tends toward the gun region is then observed due to the steep pressure gradients of the COFC generated by ohmic heating through an injection current winding around the inboard field lines, resulting in the formation of the strong poloidal flow shear at the interface between the COFC and the core region. This result is consistent with the flow shear observed in the HIST. During the decay phase, the configuration approaches the axisymmetric MHD equilibrium state without flow because of the dissipation of magnetic fluctuation energy to increase the closed flux surfaces, suggesting the generation of ordered magnetic field structure. The parallel current density λ concentrated in the COFC then diffuses to the core region so as to reduce the gradient in λ, relaxing in the direction of the Taylor state.

  12. Pulsed eddy current inspection of CF-188 inner wing spar

    NASA Astrophysics Data System (ADS)

    Horan, Peter Francis

    Royal Canadian Air Force (RCAF) CF-188 Hornet aircraft engineering authorities have stated a requirement for a Non-Destructive Evaluation (NDE) technique to detect Stress Corrosion Cracking (SCC) in the inner wing spars without fastener or composite wing skin removal. Current radiographic inspections involve significant aircraft downtime, and Pulsed Eddy Current (PEC) inspection is proposed as a solution. The aluminum inner wing spars of CF-188 Hornet aircraft may undergo stress corrosion cracking (SCC) along the spar between the fasteners that secure carbon-fiber/ epoxy composite skin to the wing. Inspection of the spar through the wing skin is required to avoid wing disassembly. The thickness of the wing skin varies between 8 and 20 mm (0.3 to 0.8 inch) and fasteners may be either titanium or ferrous. PEC generated by a probe centered over a fastener, demonstrates capability of detecting simulated cracks within spars with the wing skin present. Comparison of signals from separate sensors, mounted to either side of the excitation coil, is used to detect differences in induced eddy current fields, which arise in the presence of cracks. To overcome variability in PEC signal response due to variation in 1) skin thickness, 2) fastener material and size, and 3) centering over fasteners, a large calibration data set is acquired. Multi-dimensional scores from a Modified Principal Components Analysis (PCA) of the data are reduced to one dimension (1D) using a Discriminant Analysis method. Under inspection conditions, calibrated PCA scores combined with discriminant analysis permit rapid real time go/no-go PEC detection of cracks in CF-188 inner wing spar. Probe designs using both pickup coils and Giant Magnetoresistive (GMR) sensors were tested on samples with the same ferrous and titanium fasteners found on the CF-188. Flaws were correctly detected at lift-offs of up to 21mm utilizing a variety of insulating skin materials simulating the carbon-fibre reinforced polymer

  13. Control of the electrode metal transfer by means of the welding current pulse generator

    NASA Astrophysics Data System (ADS)

    Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Knyaz'kov, S.; Tyasto, A.

    2016-04-01

    The paper presents a generator of welding current pulses to transfer an electrode metal into the molten pool. A homogeneous artificial line is used to produce near rectangular pulses. The homogeneous artificial line provides the minimum heat input with in the pulse to transfer the electrode metal, and it significantly decreases the impact of disturbances affecting this transfer. The pulse frequency does not exceed 300 Hz, and the duration is 0.6 ÷ 0.9 ms.

  14. Electrochemical synthesis of nanosized hydroxyapatite by pulsed direct current method

    SciTech Connect

    Nur, Adrian; Rahmawati, Alifah; Ilmi, Noor Izzati; Affandi, Samsudin; Widjaja, Arief

    2014-02-24

    Synthesis of nanosized of hydroxyapatite (HA) by electrochemical pulsed direct current (PDC) method has been studied. The aim of this work is to study the influence of various PDC parameters (pH initial, electrode distance, duty cycle, frequency, and amplitude) on particle surface area of HA powders. The electrochemical synthesis was prepared in solution Ca{sup 2+}/EDTA{sup 4−}/PO{sub 4}{sup 3+} at concentration 0.25/0.25/0.15 M for 24 h. The electrochemical cell was consisted of two carbon rectangular electrodes connected to a function generator to produce PDC. There were two treatments for particles after electrosynthesized, namely without aging and aged for 2 days at 40 °C. For both cases, the particles were filtered and washed by demineralized water to eliminate the impurities and unreacted reactants. Then, the particles were dried at 100 °C for 2 days. The dried particles were characterized by X-ray diffraction, surface area analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectra and thermogravimetric and differential thermal analysis. HA particles can be produced when the initial pH > 6. The aging process has significant effect on the produced HA particles. SEM images of HA particles showed that the powders consisted of agglomerates composed of fine crystallites and have morphology plate-like and sphere. The surface area of HA particles is in the range of 25 – 91 m{sup 2}/g. The largest particle surface area of HA was produced at 4 cm electrode distance, 80% cycle duty, frequency 0.1 Hz, amplitude 9 V and with aging process.

  15. Deposition of ultrahard Ti-Si-N coatings by pulsed high-current reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Oskomov, K. V.; Zakharov, A. N.; Rabotkin, S. V.; Solov'ev, A. A.

    2016-02-01

    We report on the results of investigation of properties of ultrahard Ti-Si-N coatings deposited by pulsed high-current magnetron reactive sputtering (discharge pulse voltage is 300-900 V, discharge pulse current is up to 200 A, pulse duration is 10-100 μs, and pulse repetition rate is 20-2000 Hz). It is shown that for a short sputtering pulse (25 μs) and a high discharge current (160 A), the films exhibit high hardness (66 GPa), wear resistance, better adhesion, and a lower sliding friction coefficient. The reason is an enhancement of ion bombardment of the growing coating due to higher plasma density in the substrate region (1013 cm-3) and a manifold increase in the degree of ionization of the plasma with increasing peak discharge current (mainly due to the material being sputtered).

  16. Simple circuit produces high-speed, fixed duration pulses

    NASA Technical Reports Server (NTRS)

    Garrahan, N. M.

    1965-01-01

    Circuit generates an output pulse of fixed width from a variable width input pulse. The circuit consists of a tunnel diode in parallel with an inductance driven by a constant current generator. It is used for pulsed communication equipment design.

  17. Letter Report on 500 nA Pulsed Current from Field Ionization Source

    SciTech Connect

    Ellsworth, Jennifer L.

    2013-12-12

    We recently produced a milestone 500 nA of pulsed current using 40 Ir field ionizer electrodes in our ion source. In conclusion, we have produced the milestone pulsed current of 500 nA using 40 electrochemically etched iridium tips in a field ionization source. The pulsed current output is repeatable and scales as expected with gas fill pressure and bias voltage. We expect these current will be sufficient to produce neutral yields of 1∙107 DT n/s.

  18. Effects of imbalanced currents on large-format LiFePO4/graphite batteries systems connected in parallel

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Hu, Xiaosong; Jin, Chao; Jiang, Jiuchun; Zhang, Yanru; Yip, Tony

    2016-05-01

    With the development and popularization of electric vehicles, it is urgent and necessary to develop effective management and diagnosis technology for battery systems. In this work, we design a parallel battery model, according to equivalent circuits of parallel voltage and branch current, to study effects of imbalanced currents on parallel large-format LiFePO4/graphite battery systems. Taking a 60 Ah LiFePO4/graphite battery system manufactured by ATL (Amperex Technology Limited, China) as an example, causes of imbalanced currents in the parallel connection are analyzed using our model, and the associated effect mechanisms on long-term stability of each single battery are examined. Theoretical and experimental results show that continuously increasing imbalanced currents during cycling are mainly responsible for the capacity fade of LiFePO4/graphite parallel batteries. It is thus a good way to avoid fast performance fade of parallel battery systems by suppressing variations of branch currents.

  19. Current indications and new applications of intense pulsed light.

    PubMed

    González-Rodríguez, A J; Lorente-Gual, R

    2015-06-01

    Intense pulsed light (IPL) systems have evolved since they were introduced into medical practice 20 years ago. Pulsed light is noncoherent, noncollimated, polychromatic light energy emitted at different wavelengths that target specific chromophores. This selective targeting capability makes IPL a versatile therapy with many applications, from the treatment of pigmented or vascular lesions to hair removal and skin rejuvenation. Its large spot size ensures a high skin coverage rate. The nonablative nature of IPL makes it an increasingly attractive alternative for patients unwilling to accept the adverse effects associated with other procedures, which additionally require prolonged absence from work and social activities. In many cases, IPL is similar to laser therapy in effectiveness, and its versatility, convenience, and safety will lead to an expanded range of applications and possibilities in coming years. PMID:25638325

  20. Investigation of current transport normal and parallel to the tape plane in BSCCO/Ag tapes

    SciTech Connect

    Maley, M.P.; Cho, J.H.; Willis, J.O.; Bulaevskii, L.N.

    1995-07-01

    We have performed transport, resistivity and critical current measurements on Bi-2223/Ag and Bi-2212/Ag tapes with current directions both parallel and perpendicular to the tape plane in magnetic fields up to 7 T and 50current along the tape normal exhibits magnetic field and field orientation dependences similar to those for current flow along the tape plane. These results indicate that current flow along CuO{sub 2} planes dominates current transport even along the tape normal in highly textured tapes.

  1. Amide Proton Transfer Imaging of Diffuse Gliomas: Effect of Saturation Pulse Length in Parallel Transmission-Based Technique

    PubMed Central

    Hiwatashi, Akio; Keupp, Jochen; Yamashita, Koji; Kikuchi, Kazufumi; Yoshiura, Takashi; Yoneyama, Masami; Kruiskamp, Marijn J.; Sagiyama, Koji; Takahashi, Masaya; Honda, Hiroshi

    2016-01-01

    In this study, we evaluated the dependence of saturation pulse length on APT imaging of diffuse gliomas using a parallel transmission-based technique. Twenty-two patients with diffuse gliomas (9 low-grade gliomas, LGGs, and 13 high-grade gliomas, HGGs) were included in the study. APT imaging was conducted at 3T with a 2-channel parallel transmission scheme using three different saturation pulse lengths (0.5 s, 1.0 s, 2.0 s). The 2D fast spin-echo sequence was used for imaging. Z-spectrum was obtained at 25 frequency offsets from -6 to +6 ppm (step 0.5 ppm). A point-by-point B0 correction was performed with a B0 map. Magnetization transfer ratio (MTRasym) and ΔMTRasym (contrast between tumor and normal white matter) at 3.5 ppm were compared among different saturation lengths. A significant increase in MTRasym (3.5 ppm) of HGG was found when the length of saturation pulse became longer (3.09 ± 0.54% at 0.5 s, 3.83 ± 0.67% at 1 s, 4.12 ± 0.97% at 2 s), but MTRasym (3.5 ppm) was not different among the saturation lengths in LGG. ΔMTRasym (3.5 ppm) increased with the length of saturation pulse in both LGG (0.48 ± 0.56% at 0.5 s, 1.28 ± 0.56% at 1 s, 1.88 ± 0.56% at 2 s and HGG (1.72 ± 0.54% at 0.5 s, 2.90 ± 0.49% at 1 s, 3.83 ± 0.88% at 2 s). In both LGG and HGG, APT-weighted contrast was enhanced with the use of longer saturation pulses. PMID:27227746

  2. Effects of direct and pulse current on copper electrodeposition through photoresist molds

    NASA Astrophysics Data System (ADS)

    Quemper, Jean-Marie; Dufour-Gergam, Elisabeth; Frantz-Rodriguez, Nadège; Gilles, Jean-Paul; Grandchamp, Jean-Paul; Bosseboeuf, Alain

    2000-06-01

    In this paper, electrodeposition of copper films and copper lines with direct and pulse currents is compared. In the first step, electrical and physicochemical characterizations of the copper films are realized, and the optimized electrodeposition parameters are so determined. The use of pulse reverse current is also investigated. In the second step, these parameters are applied to micromolding. Copper lines are electro-deposited and compared in order to determine the more suitable current mode for micromolding.

  3. Cell-balancing currents in parallel strings of a battery system

    NASA Astrophysics Data System (ADS)

    Dubarry, Matthieu; Devie, Arnaud; Liaw, Bor Yann

    2016-07-01

    Lithium-ion batteries are attractive for vehicle electrification or grid modernization applications. In these applications, battery packs are required to have multiple-cell configurations and battery management system to operate properly and safely. Here, a useful equivalent circuit model was developed to simulate the spontaneous transient balancing currents among parallel strings in a battery system. The simulation results were validated with experimental data to illustrate the accuracy and validity of the model predictions. Understanding the transient behavior of such cell and string balancing in a parallel circuit configuration is very important to assess the impacts of current fluctuation and cell variability on a battery system's performance, regarding durability, reliability, safety, abuse tolerance and failure prevention, including possible short circuit or open circuit conditions. Additional features and advantages, including the ability to assessing impacts on the performance of the string assemblies from string swapping or cell/module replacement in the strings, could be realized to aid battery management, maintenance and repair.

  4. Spin-orbit torques for current parallel and perpendicular to a domain wall

    SciTech Connect

    Schulz, Tomek; Lee, Kyujoon; Karnad, Gurucharan V.; Alejos, Oscar; Martinez, Eduardo; Moretti, Simone; Garcia, Karin; Ravelosona, Dafiné; Vila, Laurent; Lo Conte, Roberto; Kläui, Mathias; Ocker, Berthold; Brataas, Arne

    2015-09-21

    We report field- and current-induced domain wall (DW) depinning experiments in Ta\\Co{sub 20}Fe{sub 60}B{sub 20}\\MgO nanowires through a Hall cross geometry. While purely field-induced depinning shows no angular dependence on in-plane fields, the effect of the current depends crucially on the internal DW structure, which we manipulate by an external magnetic in-plane field. We show depinning measurements for a current sent parallel to the DW and compare its depinning efficiency with the conventional case of current flowing perpendicularly to the DW. We find that the maximum efficiency is similar for both current directions within the error bars, which is in line with a dominating damping-like spin-orbit torque (SOT) and indicates that no large additional torques arise for currents perpendicular to the DW. Finally, we find a varying dependence of the maximum depinning efficiency angle for different DWs and pinning levels. This emphasizes the importance of our full angular scans compared with previously used measurements for just two field directions (parallel and perpendicular to the DW) to determine the real torque strength and shows the sensitivity of the SOT to the precise DW structure and pinning sites.

  5. Co-ordination of directional overcurrent protection with load current for parallel feeders

    SciTech Connect

    Wright, J.W.; Lloyd, G.; Hindle, P.J.

    1999-11-01

    Directional phase overcurrent relays are commonly applied at the receiving ends of parallel feeders or transformer feeders. Their purpose is to ensure full discrimination of main or back-up power system overcurrent protection for a fault near the receiving end of one feeder. This paper reviews this type of relay application and highlights load current setting constraints for directional protection. Such constraints have not previously been publicized in well-known text books. A directional relay current setting constraint that is suggested in some text books is based purely on thermal rating considerations for older technology relays. This constraint may not exist with modern numerical relays. In the absence of any apparent constraint, there is a temptation to adopt lower current settings with modern directional relays in relation to reverse load current at the receiving ends of parallel feeders. This paper identifies the danger of adopting very low current settings without any special relay feature to ensure protection security with load current during power system faults. A system incident recorded by numerical relays is also offered to highlight this danger. In cases where there is a need to infringe the identified constraints an implemented and testing relaying technique is proposed.

  6. Quantitative effect of initial current rise on pumping the double-pulsed copper chloride laser

    NASA Technical Reports Server (NTRS)

    Vetter, A. A.

    1977-01-01

    The laser energy at optimum time delay of a double-pulsed CuCl laser was experimentally determined to be a logarithmic function of the initial current rise of the pumping pulse over the total circuit inductance range 1 to 12 microhenrys. The minimum delay was found to decrease with initial current rise, which implies that faster rising current pulses are more efficient at pumping copper atoms from the ground state to the upper laser level because lasing threshold occurs with a higher population in the lower laser level.

  7. Strong nuclear ring currents and magnetic fields in pseudorotating OsH4 molecules induced by circularly polarized laser pulses.

    PubMed

    Barth, Ingo; Bressler, Christian; Koseki, Shiro; Manz, Jörn

    2012-06-01

    We design a circularly polarized laser pulse in the infrared frequency and femtosecond time domains, for excitation of the OsH(4) molecule in its first excited pseudorotational state of the triply-degenerate bend. The OsH(4) molecule need not be pre-oriented. After excitation, the central nucleus Os carries out pseudorotation about the axis parallel to the direction of propagation of the laser pulse. This pseudorotation causes a strong electric ring current with a value I=1.53 e fs(-1). The mean value of the radius of the ring current is very small, R=0.0031 a(0), where a(0) is the Bohr radius. According to the Biot-Savart law (|B(R=0)| ~I/R)), this nuclear ring current induces the strongest magnetic field predicted so far in molecules, with a central peak absolute value |B(R=0)| =623 T. To monitor the effect, we propose an IR-pump-X-ray-probe versus an X-ray-probe-only experiment, at the K- and L-edges of X-ray ionization. The results are based on the general quantum theory of excitations of pseudorotations in tetrahedral molecules AB(4), driven by a circularly polarized laser pulse. PMID:22389250

  8. Electronmagnetohydrodynamic response of a plasma to an external current pulse

    NASA Astrophysics Data System (ADS)

    Zhou, H. B.; Papadopoulos, K.; Sharma, A. S.; Chang, C. L.

    1996-05-01

    In this paper we examine the dynamic response of a magnetoplasma to an external time-dependent current source in the context of electronmagnetohydrodynamics (EMHD). A combined analytic and numerical technique is developed to address this problem. The set of cold electron plasma and Maxwell's equations are first solved analytically in the (k,ω) space. Inverse Laplace and three-dimensional complex Fast Fourier Transform techniques are used subsequently to numerically transform the radiation fields and plasma currents from the (k,ω) space to the (r,t) space. The results show that the electron plasma responds to a time-varying current source imposed across the magnetic field by exciting whistler/helicon waves and forming an expanding local current loop, driven by field-aligned plasma currents. The current loop consists of two antiparallel field-aligned current channels concentrated at the ends of the imposed current and a cross-field Hall current region connecting these channels. The characteristics of the current closure region are determined by the background plasma density, the magnetic field, and the time scale of the current source. The results are applied to the ionospheric generation of extremely low-frequency (ELF) and very low-frequency (VLF) radiation using amplitude modulated high-frequency heating. It is found that contrary to previous suggestions the dominant radiating moment of the ELF/VLF ionospheric source is an equivalent horizontal magnetic dipole.

  9. In situ membrane resistance measurements in polymer electrolyte fuel cells by fast auxiliary current pulses

    SciTech Connect

    Buechi, F.N.; Scherer, G.G.; Marek, A.

    1995-06-01

    A solid-state current Pulse generator for in situ membrane resistance measurements by superimposed square current pulses in polymer electrolyte fuel cells was designed and built. The choice of the measuring technique and of parameters of the instrumentation was based on a critical analysis of the relevant electrochemical and physical processes. The inductance of the current pulse path is very low ({approx}5 nH), because the last stage of the generator is directly attached to the fuel cell. This low inductance -permits the generation of 5 A pulses with extremely fast (decay time {<=}5 ns) trailing edges (accompanied by a moderate ringing), which in turn makes it possible to measure the voltage transient induced by the current decay, with gigahertz resolution. The voltage transient is analyzed in a time window of 200 to 700 ns after the end of the pulse. By measurements in this time window, it is possible to separate accurately the ohmic series resistance of the cell (membrane resistance) from the other over potentials at the electrochemical interfaces. Because the pulse current path is independent of the dc loop, the resistance can be measured independently of the dc value, i.e., at open circuit and under high current density conditions. The instrument was tested, and the results were analyzed for accuracy. Resistances down to 2 m{Omega} can be measured with an error of <5%. The influence of the pulse length and pulse amplitude on the cell voltage response was also investigated. For cell resistances in the order of few milliohms, a current pulse amplitude of 5 A is the minimum requirement for accurate measurements.

  10. Attosecond-magnetic-field-pulse generation by electronic currents in bichromatic circularly polarized UV laser fields

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2015-12-01

    Attosecond-magnetic-field-pulse generation is simulated from numerical solutions of time-dependent Schrödinger equations for oriented H2 +. Two schemes with high frequency co- and counter-rotating bichromatic ω2=2 ω1 circularly polarized UV laser pulses are investigated. Results show that comparing to single color processes, stronger induced localized magnetic fields B at the molecular center O (r =0 ) are obtained with attosecond duration. This is attributed to frequent recollision and to interference effects of two pathways in photoionization. The induced magnetic fields are shown to be sensitive to (i) the helicity of the combined laser pulses due to different recollision laser-induced electron trajectories and currents, and (ii) also the carrier envelope phases of the combined attosecond laser pulses. The sensitivity of recollision to bichromatic pulses thus allows one to control the induced magnetic-field-pulse generation.

  11. Effect of pulsed current charging on the performance of nickel-cadium cells

    NASA Technical Reports Server (NTRS)

    Bedrossian, A. A.; Cheh, H. Y.

    1977-01-01

    The effect of pulsed current charging on the charge acceptance of NiCd cells in terms of mass transfer, kinetic, and structural considerations was investigated. A systemic investigation on the performance of Ni-Cd cells by pulsed current charging was conducted under a variety of well-defined charge-discharge conditions. Experiments were carried out with half cells and film electrodes. The system behavior was studied by charge acceptance, mechanistic, and structural measurements.

  12. Nonlinear conductivity in CaRuO3 thin films measured by short current pulses

    NASA Astrophysics Data System (ADS)

    Esser, Sven; Esser, Sebastian; Stingl, Christian; Gegenwart, Philipp

    2014-06-01

    Metals near quantum critical points have been predicted to display universal out-of-equilibrium behaviour in the steady current-carrying state. We have studied the nonlinear conductivity of high-quality CaRuO3 thin films with residual resistivity ratios up to 57 using microsecond-short, high-field current pulses at low temperatures. Even for our shortest pulses, Joule heating persists, making it impossible to observe an intrinsic nonlinearity. Comparing with THz spectroscopic results, we can establish a clear window for the pulse duration needed to observe the predicted universal nonlinear conductivity.

  13. Empirical compensation function for eddy current effects in pulsed field gradient nuclear magnetic resonance experiments.

    PubMed

    Zhu, X X; Macdonald, P M

    1995-05-01

    An empirical compensation function for the correction of eddy current effects in the Stejskal-Tanner pulsed-gradient spin-echo (PGSE) nuclear magnetic resonance (NMR) experiments has been established. Eddy currents may arise as a result of the application of sharp and strong gradient pulses and may cause severe distortion of the NMR signals. In this method, the length of one gradient pulse is altered to compensate for the eddy current effects. The compensation is considered to be ideal when the position and the phase of the spin-echo maximum obtained from an aqueous solution of poly(ethylene glycol) (PEG) is the same in the presence and absence of a gradient pulse in the PGSE pulse sequence. We first characterized the functional dependence of the length of the required compensation on the three principal variables in the PGSE experiment: the gradient strength, the duration of the gradient pulse, and the interval between the two gradient pulses. Subsequently, we derived a model which successfully describes the general relationship between these variables and the size of the induced eddy current. The parameters extracted from fitting the model to the experimental compensation data may be used to predict the correct compensation for any combination of the three principal variables.

  14. Manipulation of high-current pulses for heavy-ion fusion

    SciTech Connect

    Sharp, W.M.; Callahan, D.A.; Griedman, A.; Grote, D.P.

    1996-10-28

    For efficient induction-driven heavy-ion fusion, the current profile along a pulse must be modified in a non-selfsimilar manner between the accelerator and the target. In the accelerator, the pulse should have a duration of at least 50 ns in order to make efficient use of the induction cores, and the current should by nearly uniform along the pulse to minimize the aperture. In contrast, the optimal current profile on target consists of a main pulse of about 10 ns preceded by a longer low-current `foot.` This pulse-shape manipulation must be carried out at the final pulse energy (5-10 GeV for 200 amu ions) in the presence of a large nonlinear longitudinal space-charge field. A straightforward method is presented here for doing the required pulse shaping. Induction-ceU voltages are generated using idealized beam profiles both in the accelerator and on target, and they are verified and checked for error sensitivity using the fluid/envelope code CIRCE.

  15. Design of non-selective refocusing pulses with phase-free rotation axis by gradient ascent pulse engineering algorithm in parallel transmission at 7 T

    NASA Astrophysics Data System (ADS)

    Massire, Aurélien; Cloos, Martijn A.; Vignaud, Alexandre; Le Bihan, Denis; Amadon, Alexis; Boulant, Nicolas

    2013-05-01

    At ultra-high magnetic field (⩾7 T), B1 and ΔB0 non-uniformities cause undesired inhomogeneities in image signal and contrast. Tailored radiofrequency pulses exploiting parallel transmission have been shown to mitigate these phenomena. However, the design of large flip angle excitations, a prerequisite for many clinical applications, remains challenging due the non-linearity of the Bloch equation. In this work, we explore the potential of gradient ascent pulse engineering to design non-selective spin-echo refocusing pulses that simultaneously mitigate severe B1 and ΔB0 non-uniformities. The originality of the method lays in the optimization of the rotation matrices themselves as opposed to magnetization states. Consequently, the commonly used linear class of large tip angle approximation can be eliminated from the optimization procedure. This approach, combined with optimal control, provides additional degrees of freedom by relaxing the phase constraint on the rotation axis, and allows the derivative of the performance criterion to be found analytically. The method was experimentally validated on an 8-channel transmit array at 7 T, using a water phantom with B1 and ΔB0 inhomogeneities similar to those encountered in the human brain. For the first time in MRI, the rotation matrix itself on every voxel was measured by using Quantum Process Tomography. The results are complemented with a series of spin-echo measurements comparing the proposed method against commonly used alternatives. Both experiments confirm very good performance, while simultaneously maintaining a low energy deposition and pulse duration compared to well-known adiabatic solutions.

  16. Formability of Al 5xxx Sheet Metals Using Pulsed Current for Various Heat Treatments

    SciTech Connect

    Salandro, Wesley A.; Jones, Joshua J.; McNeal, Timothy A.; Roth, John T.; Hong, Sung Tae; Smith, Mark T.

    2010-10-01

    Previous studies have shown that the presence of a pulsed electrical current, applied during the deformation process of an aluminum specimen, can significantly improve the formability of the aluminum without heating the metal above its maximum operating temperature range. The research herein extends these findings by examining the effect of electrical pulsing on 5052 and 5083 Aluminum Alloys. Two different parameter sets were used while pulsing three different heat treatments (As Is, 398°C, and 510°C) for each of the two aluminum alloys. For this research, the electrical pulsing is applied to the aluminum while the specimens are deformed, without halting the deformation process (a manufacturing technique known as Electrically-Assisted Manufacturing). The analysis focuses on establishing the effect the electrical pulsing has on the aluminum alloy’s various heat treatments by examining the displacement of the material throughout the testing region of dogbone-shaped specimens. The results from this research show that pulsing significantly increases the maximum achievable elongation of the aluminum (when compared to baseline tests conducted without electrical pulsing). Another beneficial effect produced by electrical pulsing is that the engineering flow stress within the material is considerably reduced. The electrical pulses also cause the aluminum to deform non-uniformly, such that the material exhibits a diffuse neck where the minimum deformation occurs near the ends of the specimen (near the clamps) and the maximum deformation occurs near the center of the specimen (where fracture ultimately occurs). This diffuse necking effect is similar to what can be experienced during superplastic deformation. However, when comparing the presence of a diffuse neck in this research, electrical pulsing does not create as significant of a diffuse neck as superplastic deformation. Electrical pulsing has the potential to be more efficient than traditional methods of incremental

  17. Generation and coherent control of pure spin currents via terahertz pulses

    SciTech Connect

    Schüler, Michael Berakdar, Jamal

    2014-04-21

    We inspect the time and spin-dependent, inelastic tunneling in engineered semiconductor-based double quantum well driven by time-structured terahertz pulses. An essential ingredient is an embedded spin-active structure with vibrational modes that scatter the pulse driven carriers. Due to the different time scales of the charge and spin dynamics, the spin-dependent electron-vibron coupling may result in pure net spin current (with negligible charge current). Heating the vibrational site may affect the resulting spin current. Furthermore, by controlling the charge dynamics, the spin dynamics and the generated spin current can be manipulated and switched on and off coherently.

  18. High-power pulsed-current-mode operation of an overdriven tapered amplifier.

    PubMed

    Takase, Ken; Stockton, John K; Kasevich, Mark A

    2007-09-01

    We experimentally investigate the performance of a commercial tapered amplifier diode operating in a pulsed-current mode with a peak current that is significantly higher than the specified maximum continuous current. For a tapered amplifier rated at 500 mW of continuous power, we demonstrate 2.6 W of peak optical output power with 15 mW of injection light for 200 micros, 7 A current pulses. Different failure mechanisms for the tapered amplifier, including thermal and optical damage, are identified under these conditions. PMID:17767324

  19. Double-pulse calcium channel current facilitation in adult rat sympathetic neurones.

    PubMed Central

    Ikeda, S R

    1991-01-01

    1. Double-pulse facilitation of Ca2+ channel currents in enzymatically dispersed adult rat superior cervical ganglion neurones was investigated using the whole-cell variant of the patch-clamp technique. Voltage-clamp recordings were performed at room temperature (21-24 degrees C) in solutions designed to isolate Ca2+ channel currents. 2. Ba2+ currents, elicited by a 0 mV test pulse, were increased in amplitude when preceded by a 40 ms pulse to voltages greater than 0 mV. The magnitude of facilitation was dependent on pre-pulse voltage and reached a maximum of 50% (i.e. 1.5 x the current amplitude elicited without a pre-pulse) at a pre-pulse voltage of +80 mV. Half-maximal facilitation occurred at about +25 mV. A small decrease (-6%) in test pulse amplitude was present at pre-pulse voltages between -40 and 0 mV. The magnitude of facilitation was also dependent on test pulse voltage. Facilitation was greatest between test pulse voltages of -10 and 0 mV. 3. Facilitation slowly decreased during prolonged (1 h) dialysis of the neurone even though the Ba2+ current amplitude was well maintained. 4. Increasing the pre-pulse duration over the range 0-120 ms produced an exponential increase in facilitation with a time constant of 17.3 ms. Conversely, lengthening the interpulse duration over the range 5-915 ms, while maintaining a constant pre-pulse amplitude and duration, resulted in an exponential decrease in facilitation with a time constant of 197 ms. 5. At a test potential of 0 mV, the decay of the facilitated Ba2+ current component was fitted to a double exponential function with time constants of about 25 and 150 ms. The time constants had little pre-pulse voltage dependence between +30 to +80 mV. 6. The initial rising phase of both the control and facilitated Ba2+ current were reasonably well described by a single exponential (tau rise) after a delay of 300 microseconds. The tau rise versus test pulse potential relationship was 'bell shaped' over the test pulse

  20. Terahertz pulsed photogenerated current in microdiodes at room temperature

    SciTech Connect

    Ilkov, Marjan; Torfason, Kristinn; Manolescu, Andrei Valfells, Ágúst

    2015-11-16

    Space-charge modulation of the current in a vacuum diode under photoemission leads to the formation of beamlets with time periodicity corresponding to THz frequencies. We investigate the effect of the emitter temperature and internal space-charge forces on the formation and persistence of the beamlets. We find that temperature effects are most important for beam degradation at low values of the applied electric field, whereas at higher fields, intra-beamlet space-charge forces are dominant. The current modulation is most robust when there is only one beamlet present in the diode gap at a time, corresponding to a macroscopic version of the Coulomb blockade. It is shown that a vacuum microdiode can operate quite well as a tunable THz oscillator at room temperature with an applied electric field above 10 MV/m and a diode gap of the order of 100 nm.

  1. Return current and proton emission from wire targets interacting with an intense short pulse laser

    NASA Astrophysics Data System (ADS)

    Beg, Farhat

    2004-05-01

    One of the important characteristics of short pulse high intensity laser-solid interactions is the generation of energetic charged particles, which result from the very efficient conversion of laser energy into hot electrons. Since the electrons in the electric field of the laser have relativistic quiver motions, the temperature of the hot electron distribution of the plasma produced at such extreme intensities can become very high. A large number of hot electrons (1013-1014) having an average energy of the order of 1-2 MeV can be generated as intensities exceed 1019 Wcm-2. Since the resulting beam current exceeds the Alfvén limit, a neutralizing return current of cold plasma electrons moving in the opposite direction is produced. Another source of return current is that due to the escape of very energetic electrons from the target, which then creates a large electrostatic potential due to charge separation. These return currents can cause significant ohmic heating. In addition escaping electrons establish the large electrostatic fields, accelerating a large number of protons from the target with energies of 10's of MeV. The experiments reported here were performed at the Rutherford Appleton Laboratory with the VULCAN laser facility at intensity greater than 5 x1019 Wcm-2 on wire targets. In some shots an additional wire or foil was placed nearby. The laser was blocked by the main wire target so that no laser light reached the additional wire or foil. Three main observations were made: (i) a Z-pinch was driven in the wire due to the return current, (ii) optical transition radiation (OTR) at 2w was generated and (iii) energetic proton emission was observed. The wire targets were observed to be ohmically heated and were m=0 unstable. The OTR emission is likely due to electron bunches accelerated by the ponderomotive force of the laser. The proton emission was in a form of thin disk perpendicular to the wire and centered on the wire at the laser focus. Proton

  2. Suppression of self-pulsing regime of direct current driven microplasma discharges

    NASA Astrophysics Data System (ADS)

    Mahamud, Rajib; Farouk, Tanvir

    2016-05-01

    An instability suppressor circuit for self-pulsing direct current (DC) driven microplasma discharge is proposed and experimentally tested over a range of pd values for helium feed gas. The external circuit configuration suppresses self-pulsing of the discharge, extending the normal glow regime to lower currents. The negative differential resistance (NDR) region was observed to shift further left in the voltage-current parametric space (i.e., lower current), and the slope of the NDR region was decreased substantially. In addition, the suppressor element decreased the pulsing frequency as well as the static positive resistance of the discharge in the shifted NDR region. Modeling of the discharge configuration indicated that the inductor element of the suppressor circuit increases the time lag of the plasma response, which increases the stable region of operation. A stability map in terms of the external circuit parameters is introduced.

  3. Probing Pulsed Current Gas Metal Arc Welding for Modified 9Cr-1Mo Steel

    NASA Astrophysics Data System (ADS)

    Krishnan, S.; Kulkarni, D. V.; De, A.

    2015-04-01

    Modified 9Cr-1Mo steels are commonly welded using gas tungsten arc welding process for its superior control over the rate of heat input and vaporization loss of the key alloying elements although the rate electrode deposition remains restricted. Recent developments in pulsed current gas metal arc welding have significantly improved its ability to enhance the rate of electrode deposition with a controlled heat input rate while its application for welding of modified 9Cr-1Mo steels is scarce. The present work reports a detailed experimental study on the pulsed current gas metal arc welding of modified 9Cr-1Mo steels. The effect of the shielding gas, welding current, and speed on the weld bead profile, microstructure and mechanical properties are examined. The results show that the pulsed current gas metal arc welding with appropriate welding conditions can provide acceptable bead profile and mechanical properties in welds of modified 9Cr-1Mo steels.

  4. Massively Parallel Delivery of Large-Sized Cargo into Mammalian Cells with Light Pulses

    PubMed Central

    Wu, Yi-Chien; Wu, Ting-Hsiang; Clemens, Daniel L.; Lee, Bai-Yu; Wen, Ximiao; Horwitz, Marcus A.; Teitell, Michael A.; Chiou, Pei-Yu

    2016-01-01

    We report a high-throughput platform for delivering large cargo into 100,000 cells in 1 min. An array of micro-cavitation bubbles explode in response to laser pulsing, forming pores in adjacent cell membranes, and immediately thereafter, pressurized flows drive slow diffusing cargo through these pores into cells. The platform delivers large cargo including bacteria, enzymes, antibodies, and nanoparticles into diverse cell types with high efficiency and cell viability. We used this platform to explore the intracellular lifestyle of Francisella novicida and discovered that the iglC gene is unexpectedly required for intracellular replication even after phagosome escape into the cell cytosol. PMID:25849636

  5. Reduction of RF-sheaths potentials by compensation or suppression of parallel RF currents on ICRF antennas

    NASA Astrophysics Data System (ADS)

    Mendes, A.; Colas, L.; Vulliez, K.; Ekedahl, A.; Argouarch, A.; Milanesio, D.

    2010-02-01

    Radio frequency (RF) sheaths are suspected of limiting the performance of present-day ion cyclotron range of frequencies (ICRFs) antennas over long pulses and should be minimized in future fusion devices. Within the simplest models, RF-sheath effects are quantified by the integral VRF = ∫ Epar · dl where the parallel RF field Epar is linked with the slow wave. On 'long open field lines' with large toroidal extension on both sides of the antenna it was shown that VRF is excited by parallel RF currents jpar flowing on the antenna structure. In this paper, the validity of this simple sheath theory is tested experimentally on the Tore Supra (TS) ITER-like antenna prototype (ILP), together with antenna simulation and post-processing codes developed to compute VRF. The predicted poloidal localization of high-|VRF| zones is confronted to that inferred from experimental data analysis. Surface temperature distribution on ILP front face, as well as ILP-induced modifications of RF coupling and hot spots on a magnetically connected lower hybrid current drive antenna, indicates local maxima of dc plasma potential in both the upper and lower parts of the ILP. This result, qualitatively conforming to VRF simulations, is interpreted in terms of jpar flowing on ILP frame. Once the validation is done, such reliable theoretical models and numerical codes are then employed to provide predictive results. Indeed, we propose two ways to reduce |VRF| by acting on jpar on the antenna front face. The first method, more adapted for protruding antennas, consists of avoiding the jpar circulation on the antenna structure, by slotting the antenna frame on its horizontal edges and by partially cutting the Faraday screen rods. The second method, well suited for recessed antennas, consists of compensating jpar of opposite signs along long flux tubes, with parallelepiped antennas aligned with (tilted) flux tubes. The different concepts are assessed numerically on a two-strap TS antenna phased [0

  6. FPGA implementation of current-sharing strategy for parallel-connected SEPICs

    NASA Astrophysics Data System (ADS)

    Ezhilarasi, A.; Ramaswamy, M.

    2016-01-01

    The attempt echoes to evolve an equal current-sharing algorithm over a number of single-ended primary inductance converters connected in parallel. The methodology involves the development of state-space model to predict the condition for the existence of a stable equilibrium portrait. It acquires the role of a variable structure controller to guide the trajectory, with a view to circumvent the circuit non-linearities and arrive at a stable performance through a preferred operating range. The design elicits an acceptable servo and regulatory characteristics, the desired time response and ensures regulation of the load voltage. The simulation results validated through a field programmable gate array-based prototype serves to illustrate its suitability for present-day applications.

  7. Design of long-pulse fast wave current drive antennas for DIII-D

    NASA Astrophysics Data System (ADS)

    Baity, F. W.; Batchelor, D. B.; Bills, K. C.; Fogelman, C. H.; Jaeger, E. F.; Ping, J. L.; Riemer, B. W.; Ryan, P. M.; Stallings, D. C.; Taylor, D. J.; Yugo, J. J.

    1994-10-01

    Two new long-pulse fast wave current drive (FWCD) antennas will be installed on DIII-D in early 1994. These antennas will increase the available FWCD power from 2 MW to 6 MW for pulse lengths of up to 2 s, and to 4 MW for up to 10 s. Power for the new antennas is from two ASDEX-type 30- to 120-MHz transmitters. When operated at 90° phasing into a low-density plasma (˜4×1019m-3) with hot electrons (˜10 keV), these two new antennas are predicted to drive approximately 1 MA of plasma current.

  8. High-voltage isolation transformer for sub-nanosecond rise time pulses constructed with annular parallel-strip transmission lines.

    PubMed

    Homma, Akira

    2011-07-01

    A novel annular parallel-strip transmission line was devised to construct high-voltage high-speed pulse isolation transformers. The transmission lines can easily realize stable high-voltage operation and good impedance matching between primary and secondary circuits. The time constant for the step response of the transformer was calculated by introducing a simple low-frequency equivalent circuit model. Results show that the relation between the time constant and low-cut-off frequency of the transformer conforms to the theory of the general first-order linear time-invariant system. Results also show that the test transformer composed of the new transmission lines can transmit about 600 ps rise time pulses across the dc potential difference of more than 150 kV with insertion loss of -2.5 dB. The measured effective time constant of 12 ns agreed exactly with the theoretically predicted value. For practical applications involving the delivery of synchronized trigger signals to a dc high-voltage electron gun station, the transformer described in this paper exhibited advantages over methods using fiber optic cables for the signal transfer system. This transformer has no jitter or breakdown problems that invariably occur in active circuit components.

  9. Fast pulsed operation of a small non-radioactive electron source with continuous emission current control.

    PubMed

    Cochems, P; Kirk, A T; Bunert, E; Runge, M; Goncalves, P; Zimmermann, S

    2015-06-01

    Non-radioactive electron sources are of great interest in any application requiring the emission of electrons at atmospheric pressure, as they offer better control over emission parameters than radioactive electron sources and are not subject to legal restrictions. Recently, we published a simple electron source consisting only of a vacuum housing, a filament, and a single control grid. In this paper, we present improved control electronics that utilize this control grid in order to focus and defocus the electron beam, thus pulsing the electron emission at atmospheric pressure. This allows short emission pulses and excellent stability of the emitted electron current due to continuous control, both during pulsed and continuous operations. As an application example, this electron source is coupled to an ion mobility spectrometer. Here, the pulsed electron source allows experiments on gas phase ion chemistry (e.g., ion generation and recombination kinetics) and can even remove the need for a traditional ion shutter.

  10. Fast pulsed operation of a small non-radioactive electron source with continuous emission current control

    SciTech Connect

    Cochems, P.; Kirk, A. T.; Bunert, E.; Runge, M.; Goncalves, P.; Zimmermann, S.

    2015-06-15

    Non-radioactive electron sources are of great interest in any application requiring the emission of electrons at atmospheric pressure, as they offer better control over emission parameters than radioactive electron sources and are not subject to legal restrictions. Recently, we published a simple electron source consisting only of a vacuum housing, a filament, and a single control grid. In this paper, we present improved control electronics that utilize this control grid in order to focus and defocus the electron beam, thus pulsing the electron emission at atmospheric pressure. This allows short emission pulses and excellent stability of the emitted electron current due to continuous control, both during pulsed and continuous operations. As an application example, this electron source is coupled to an ion mobility spectrometer. Here, the pulsed electron source allows experiments on gas phase ion chemistry (e.g., ion generation and recombination kinetics) and can even remove the need for a traditional ion shutter.

  11. Electrical trimming of ion-beam-sputtered polysilicon resistors by high current pulses

    NASA Astrophysics Data System (ADS)

    Das, Soumen; Lahiri, Samir K.

    1994-08-01

    Phosphorus doped polysilicon resistors have been fabricated from microcrystalline silicon films which were deposited by ion beam sputtering using an argon ion beam of diameter 3 cm, energy 1 keV and current density 7mA/cm(sup 2), with a deposition rate of 100-120 angstrom/min. The resistors, having a sheet resistance of 70 Omega /square and a carrier concentration of 7.5 x 10(sup 19)cm(sup - 3), were stressed with current pulses of width 10 mu s and duty cycle 0.6% for 5 min. There was a steady decrease of resistance with increasing pulse current density above a threshold value 5 x 10(sup 5)A/cm(sup 2). A maximum fall of 27% was observed for a 95 micron long resistor. The current-voltage characteristics were also recorded during the trimming process. The trimming characteristics were simulated using a small-signal resistivity model of Lu et al. (11) and the I-V characteristics by a large-bias conduction model (12) . A close fitting of the experimental data with the theoretical values needed an adjustment of some grain boundary parameters for the different pulse current densities used for stressing. The nature of variation of the grain boundary parameters indicates that the rapid Joule heating of the grain boundaries due to current pulses passivates the grain boundary interfaces, at lower currents above the threshold, and then, at higher values of currents, causes zone melting and gradual recrystallization of the disordered boundary layers and subsequent dopant segregation. It confirms the mechanism suggested in the physical model of Kato et al. (7) . The role played by the field-enhanced diffusivity and electromigration of dopant ions, due to the high instantaneous temperature of the grain boundaries, has also been discussed. The pulse trimming technique is simple and does not cause damage to the adjacent components on a monolithic chip.

  12. In-situ membrane resistance measurements in PEFC by fast current pulses

    SciTech Connect

    Buechi, F.N.; Scherer, G.G.; Marek, A.

    1994-12-31

    A solid-state current pulse generator for in situ membrane resistance measurements by superimposed square current pulses in polymer electrolyte fuel cells was designed and built. The choice of the measuring technique and of parameters of the instrumentation was based on a critical analysis of the relevant electrochemical and physical processes. The last stage of the generator is located in an active head directly attached to the fuel cell. This permits the generation of 5 A pulses with extremely fast and clean trailing edges (decay time {le} 5 ns), which in turn makes it possible to measure the voltage transient induced by the current decay, with GHz resolution. By measurements in this time window it is possible to accurate separate of the ohmic series resistance of the cell (membrane resistance) from the polarization of the electrochemical interfaces. Because the pulse current path is independent of the d.c. loop, the resistance can be measured independently of the d.c. value, i.e. under high current density conditions. The instrument was tested and the results analyzed for accuracy. Resistances down to 2 m{Omega} can be measured with an error of < 5%.

  13. Triangular pulse generation using a dual-parallel Mach-Zehnder modulator driven by a single-frequency radio frequency signal.

    PubMed

    Zhang, Fangzheng; Ge, Xiaozhong; Pan, Shilong

    2013-11-01

    A simple scheme for the generation of full-duty-cycle triangular pulses is proposed and experimentally demonstrated using a dual-parallel Mach-Zehnder modulator driven by a single-frequency RF signal. By properly setting the bias voltages and the RF power, even-order harmonics in the optical intensity are suppressed, and the amplitude of the first-order harmonic is 9 times of that of the third-order harmonic. A periodical triangular pulse train is obtained in the time domain. 2.5, 5, and 10 GHz triangular pulse trains are experimentally generated, which verifies the feasibility of the proposed scheme.

  14. Evidence of Spin-Injection-Induced Cooper Pair Breaking in Perovskite Ferromagnet-Insulator-Superconductor Heterostructures via Pulsed Current Measurements

    NASA Technical Reports Server (NTRS)

    Yeh, N. C.; Samoilov, A. V.; Veasquez, R. P.; Li, Y.

    1998-01-01

    The effect of spin-polarized currents on the critical current densities of cuprate superconductors is investigated in perovskite ferromagnet-insulator-superconductor heterostructures with a pulsed current technique.

  15. Diagnostic imaging, a "parallel" discipline. Can current technology provide a reliable digital diagnostic radiology department?

    PubMed

    Moore, C J; Eddleston, B

    1985-04-01

    Only recently has any detailed criticism been voiced about the practicalities of the introduction of generalised, digital, imaging complexes in diagnostic radiology. Although attendant technological problems are highlighted we argue that the fundamental causes of current difficulties are not in the generation but in the processing, filing and subsequent retrieval for display of digital image records. In the real world, looking at images is a parallel process of some complexity and so it is perhaps untimely to expect versatile handling of vast image data bases by existing computer hardware and software which, by their current nature, perform tasks serially. Successes in applying new imaging devices using digital technology, numerical methods and more easily available computing power are directing radiology towards the concept of all-digital departmental complexes. Hence a critical discussion of fundamental problems should be encouraged, to promote a thorough understanding of what may be involved (Gray et al, 1984) in following such a course. It is equally important to gain some perspective about the development possibilities for existing, commercially available equipment being offered to the medical community.

  16. Full circuit calculation for electromagnetic pulse transmission in a high current facility

    NASA Astrophysics Data System (ADS)

    Zou, Wenkang; Guo, Fan; Chen, Lin; Song, Shengyi; Wang, Meng; Xie, Weiping; Deng, Jianjun

    2014-11-01

    We describe herein for the first time a full circuit model for electromagnetic pulse transmission in the Primary Test Stand (PTS)—the first TW class pulsed power driver in China. The PTS is designed to generate 8-10 MA current into a z -pinch load in nearly 90 ns rise time for inertial confinement fusion and other high energy density physics research. The PTS facility has four conical magnetic insulation transmission lines, in which electron current loss exists during the establishment of magnetic insulation. At the same time, equivalent resistance of switches and equivalent inductance of pinch changes with time. However, none of these models are included in a commercially developed circuit code so far. Therefore, in order to characterize the electromagnetic transmission process in the PTS, a full circuit model, in which switch resistance, magnetic insulation transmission line current loss and a time-dependent load can be taken into account, was developed. Circuit topology and an equivalent circuit model of the facility were introduced. Pulse transmission calculation of shot 0057 was demonstrated with the corresponding code FAST (full-circuit analysis and simulation tool) by setting controllable parameters the same as in the experiment. Preliminary full circuit simulation results for electromagnetic pulse transmission to the load are presented. Although divergences exist between calculated and experimentally obtained waveforms before the vacuum section, consistency with load current is satisfactory, especially at the rising edge.

  17. Study of recovery phenomena in a high-current pulse-triggered vacuum switch

    SciTech Connect

    Bauville, G.; Delmas, A.; Haddad, N.; Rioux, C. , Batiment 214, 91405 Orsay )

    1989-10-01

    This paper relates to the recovery capacities of a triggered vacuum switch after the crossing of a 25-{mu}s high-current pulse. The recovery time is less than 100 {mu}s. The authors experiment with several electrodes with different gaps, and study the influence of an axial magnetic field on the switch.

  18. Periodic reverse current pulsing to form uniformly sized feed through conductors

    NASA Technical Reports Server (NTRS)

    Anthony, Thomas R. (Inventor)

    1983-01-01

    A large number of electrically conductive solid, dense feed-through paths for the high-speed low-loss transfer of electrical signals between integrated circuits of a single silicon-on-sapphire body, or between integrated circuits of several silicon-on-sapphire bodies, are provided by an electroforming method utilizing periodic reverse-current pulsing.

  19. Determination of diffusion coefficients in polypyrrole thin films using a current pulse relaxation method

    NASA Technical Reports Server (NTRS)

    Penner, Reginald M.; Vandyke, Leon S.; Martin, Charles R.

    1987-01-01

    The current pulse E sub oc relaxation method and its application to the determination of diffusion coefficients in electrochemically synthesized polypyrrole thin films is described. Diffusion coefficients for such films in Et4NBF4 and MeCN are determined for a series of submicron film thicknesses. Measurement of the double-layer capacitance, C sub dl, and the resistance, R sub u, of polypyrrole thin films as a function of potential obtained with the galvanostatic pulse method is reported. Measurements of the electrolyte concentration in reduced polypyrrole films are also presented to aid in the interpretation of the data.

  20. Pulsed-Current Electrochemical Codeposition and Heat Treatment of Ti-Dispersed Ni-Matrix Layers

    NASA Astrophysics Data System (ADS)

    Janetaisong, Pathompong; Boonyongmaneerat, Yuttanant; Techapiesancharoenkij, Ratchatee

    2016-08-01

    An electrochemical deposition is a fast and cost-efficient process to produce film or coating. In this research, Ni-Ti electrodeposition is developed by codepositing a Ti-dispersed Ni-matrix layer from a Ni-plating solution suspended with Ti particles. To enhance the coating uniformity and control the atomic composition, the pulsed current was applied to codeposit Ni-Ti layers with varying pulse duty cycles (10 to 100 pct) and frequencies (10 to 100 Hz). The microstructures and compositions of the codeposited layers were analyzed by scanning electron microscopy, X-ray diffraction, and X-ray fluorescent techniques. The pulsed current significantly improved the quality of the Ni-Ti layer as compared to a direct current. The Ni-Ti layers could be electroplated with a controlled composition within 48 to 51 at. pct of Ti. The optimal pulse duty cycle and frequency are 50 pct and 10 Hz, respectively. The standalone Ni-49Ti layers were removed from copper substrates by selective etching method and subsequently heat-treated under Ar-fed atmosphere at 1423 K (1150 °C) for 5 hours. The phase and microstructures of the post-annealed samples exhibit different Ni-Ti intermetallic compounds, including NiTi, Ni3Ti, and NiTi2. Yet, the contamination of TiN and TiO2 was also present in the post-annealed samples.

  1. Derivation of a formula describing the saturation correction of plane-parallel ionization chambers in pulsed fields with arbitrary repetition rate

    NASA Astrophysics Data System (ADS)

    Karsch, Leonhard

    2016-04-01

    Gas-filled ionization chambers are widely used radiation detectors in radiotherapy. A quantitative description and correction of the recombination effects exists for two cases, for continuous radiation exposure and for pulsed radiation fields with short single pulses. This work gives a derivation of a formula for pulsed beams with arbitrary pulse rate for which the prerequisites of the two existing descriptions are not fulfilled. Furthermore, an extension of the validity of the two known cases is investigated. The temporal evolution of idealized charge density distributions within a plane parallel chamber volume is described for pulsed beams of vanishing pulse duration and arbitrary pulse repetition rate. First, the radiation induced release, movement and collection of the charge carriers without recombination are considered. Then, charge recombination is calculated basing on these simplified charge distributions and the time dependent spatial overlap of positive and negative charge carrier distributions. Finally, a formula for the calculation of the saturation correction factor is derived by calculation and simplification of the first two terms of a Taylor expansion for small recombination. The new formula of saturation correction contains the two existing cases, descriptions for exposure by single pulses and continuous irradiation, as limiting cases. Furthermore, it is possible to determine the pulse rate range for which each of the three descriptions is applicable by comparing the dependencies of the new formula with the two existing cases. As long as the time between two pulses is lower than one third of the collection time of the chamber, the formalism for a continuous exposure can be used. The known description for single pulse irradiation is only valid if the repetition rate is less than 1.2 times the inverse collection time. For all other repetition rates in between the new formula should be used. The experimental determination by Jaffe diagrams can be

  2. Transient thermoelectric supercooling: Isosceles current pulses from a response surface perspective and the performance effects of pulse cooling a heat generating mass

    NASA Astrophysics Data System (ADS)

    Piggott, Alfred J., III

    With increased public interest in protecting the environment, scientists and engineers aim to improve energy conversion efficiency. Thermoelectrics offer many advantages as thermal management technology. When compared to vapor compression refrigeration, above approximately 200 to 600 watts, cost in dollars per watt as well as COP are not advantageous for thermoelectrics. The goal of this work was to determine if optimized pulse supercooling operation could improve cooling capacity or efficiency of a thermoelectric device. The basis of this research is a thermal-electrical analogy based modeling study using SPICE. Two models were developed. The first model, a standalone thermocouple with no attached mass to be cooled. The second, a system that includes a module attached to a heat generating mass. With the thermocouple study, a new approach of generating response surfaces with characteristic parameters was applied. The current pulse height and pulse on-time was identified for maximizing Net Transient Advantage, a newly defined metric. The corresponding pulse height and pulse on-time was utilized for the system model. Along with the traditional steady state starting current of Imax, Iopt was employed. The pulse shape was an isosceles triangle. For the system model, metrics new to pulse cooling were Qc, power consumption and COP. The effects of optimized current pulses were studied by changing system variables. Further studies explored time spacing between pulses and temperature distribution in the thermoelement. It was found net Q c over an entire pulse event can be improved over Imax steady operation but not over steady I opt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced in transient pulse operation due to the different time constants of Qc and Pin. In some cases lower performance interface materials allow more Qc and better COP during transient operation than higher performance interface materials

  3. Current pulses caused by streamers in sphere-sphere electrode system

    NASA Astrophysics Data System (ADS)

    Chirkov, V. A.; Samusenko, A. V.; Stishkov, Yu K.

    2015-10-01

    Streamer is a channel of a low temperature plasma growing due to ionization in the area of the strong electric field at the tip of the channel. Streamer investigation presents a technically highly complicated task due to fleetingness of the process: growing velocity is 106-107 m/s and characteristic duration is 10-8-10-7 s. The electric current pulse registration is a moderate method for investigating so fast process. However, the major part of streamer current investigations refers to low voltage range (about 103-104 V) and short streamers length range 10-2-10-1 cm. Also positive streamers are usually considered and there is a lack of information about current pulses caused by negative streamers. Both positive and negative streamers and their interaction are considered in the present paper. A multibranch streamer corona emerging at voltages above 250 kV and in long gaps (above 40 cm) was investigated.

  4. Measurement of positive direct current corona pulse in coaxial wire-cylinder gap

    SciTech Connect

    Yin, Han Zhang, Bo He, Jinliang Wang, Wenzhuo

    2014-03-15

    In this paper, a system is designed and developed to measure the positive corona current in coaxial wire-cylinder gaps. The characteristic parameters of corona current pulses, such as the amplitude, rise time, half-wave time, and repetition frequency, are statistically analyzed and a new set of empirical formulas are derived by numerical fitting. The influence of space charges on corona currents is tested by using three corona cages with different radii. A numerical method is used to solve a simplified ion-flow model to explain the influence of space charges. Based on the statistical results, a stochastic model is developed to simulate the corona pulse trains. And this model is verified by comparing the simulated frequency-domain responses with the measured ones.

  5. Polarization-selective vortex-core switching by tailored orthogonal Gaussian-pulse currents

    SciTech Connect

    Yu, Young-Sang; Lee, Ki-Suk; Jung, Hyunsung; Choi, Youn-Seok; Yoo, Myoung-Woo; Han, Dong-Soo; Im, Mi-Young; Fischer, Peter; Kim, Sang-Koog

    2011-05-01

    We experimentally demonstrate low-power-consumption vortex-core switching in magnetic nanodisks using tailored rotating magnetic fields produced with orthogonal and unipolar Gaussian-pulse currents. The optimal width of the orthogonal pulses and their time delay are found, from analytical and micromagnetic numerical calculations, to be determined only by the angular eigenfrequency ωD for a given vortex-state disk of polarization p, such that σ=1/ωD and Δt=π/2p/ωD. The estimated optimal pulse parameters are in good agreement with the experimental results. Finally, this work lays a foundation for energy-efficient information recording in vortex-core cross-point architecture.

  6. Radiofrequency current source (RFCS) drive and decoupling technique for parallel transmit arrays using a high-power metal oxide semiconductor field-effect transistor (MOSFET).

    PubMed

    Lee, Wonje; Boskamp, Eddy; Grist, Thomas; Kurpad, Krishna

    2009-07-01

    A radiofrequency current source (RFCS) design using a high-power metal oxide semiconductor field effect transistor (MOSFET) that enables independent current control for parallel transmit applications is presented. The design of an RFCS integrated with a series tuned transmitting loop and its associated control circuitry is described. The current source is operated in a gated class AB push-pull configuration for linear operation at high efficiency. The pulsed RF current amplitude driven into the low impedance transmitting loop was found to be relatively insensitive to the various loaded loop impedances ranging from 0.4 to 10.3 ohms, confirming current mode operation. The suppression of current induced by a neighboring loop was quantified as a function of center-to-center loop distance, and was measured to be 17 dB for nonoverlapping, adjacent loops. Deterministic manipulation of the B(1) field pattern was demonstrated by the independent control of RF phase and amplitude in a head-sized two-channel volume transmit array. It was found that a high-voltage rated RF power MOSFET with a minimum load resistance, exhibits current source behavior, which aids in transmit array design.

  7. Radiofrequency current source (RFCS) drive and decoupling technique for parallel transmit arrays using a high-power metal oxide semiconductor field-effect transistor (MOSFET).

    PubMed

    Lee, Wonje; Boskamp, Eddy; Grist, Thomas; Kurpad, Krishna

    2009-07-01

    A radiofrequency current source (RFCS) design using a high-power metal oxide semiconductor field effect transistor (MOSFET) that enables independent current control for parallel transmit applications is presented. The design of an RFCS integrated with a series tuned transmitting loop and its associated control circuitry is described. The current source is operated in a gated class AB push-pull configuration for linear operation at high efficiency. The pulsed RF current amplitude driven into the low impedance transmitting loop was found to be relatively insensitive to the various loaded loop impedances ranging from 0.4 to 10.3 ohms, confirming current mode operation. The suppression of current induced by a neighboring loop was quantified as a function of center-to-center loop distance, and was measured to be 17 dB for nonoverlapping, adjacent loops. Deterministic manipulation of the B(1) field pattern was demonstrated by the independent control of RF phase and amplitude in a head-sized two-channel volume transmit array. It was found that a high-voltage rated RF power MOSFET with a minimum load resistance, exhibits current source behavior, which aids in transmit array design. PMID:19353658

  8. Pulsed Direct Current Electrospray: Enabling Systematic Analysis of Small Volume Sample by Boosting Sample Economy.

    PubMed

    Wei, Zhenwei; Xiong, Xingchuang; Guo, Chengan; Si, Xingyu; Zhao, Yaoyao; He, Muyi; Yang, Chengdui; Xu, Wei; Tang, Fei; Fang, Xiang; Zhang, Sichun; Zhang, Xinrong

    2015-11-17

    We had developed pulsed direct current electrospray ionization mass spectrometry (pulsed-dc-ESI-MS) for systematically profiling and determining components in small volume sample. Pulsed-dc-ESI utilized constant high voltage to induce the generation of single polarity pulsed electrospray remotely. This method had significantly boosted the sample economy, so as to obtain several minutes MS signal duration from merely picoliter volume sample. The elongated MS signal duration enable us to collect abundant MS(2) information on interested components in a small volume sample for systematical analysis. This method had been successfully applied for single cell metabolomics analysis. We had obtained 2-D profile of metabolites (including exact mass and MS(2) data) from single plant and mammalian cell, concerning 1034 components and 656 components for Allium cepa and HeLa cells, respectively. Further identification had found 162 compounds and 28 different modification groups of 141 saccharides in a single Allium cepa cell, indicating pulsed-dc-ESI a powerful tool for small volume sample systematical analysis.

  9. Pulsed Direct Current Electrospray: Enabling Systematic Analysis of Small Volume Sample by Boosting Sample Economy.

    PubMed

    Wei, Zhenwei; Xiong, Xingchuang; Guo, Chengan; Si, Xingyu; Zhao, Yaoyao; He, Muyi; Yang, Chengdui; Xu, Wei; Tang, Fei; Fang, Xiang; Zhang, Sichun; Zhang, Xinrong

    2015-11-17

    We had developed pulsed direct current electrospray ionization mass spectrometry (pulsed-dc-ESI-MS) for systematically profiling and determining components in small volume sample. Pulsed-dc-ESI utilized constant high voltage to induce the generation of single polarity pulsed electrospray remotely. This method had significantly boosted the sample economy, so as to obtain several minutes MS signal duration from merely picoliter volume sample. The elongated MS signal duration enable us to collect abundant MS(2) information on interested components in a small volume sample for systematical analysis. This method had been successfully applied for single cell metabolomics analysis. We had obtained 2-D profile of metabolites (including exact mass and MS(2) data) from single plant and mammalian cell, concerning 1034 components and 656 components for Allium cepa and HeLa cells, respectively. Further identification had found 162 compounds and 28 different modification groups of 141 saccharides in a single Allium cepa cell, indicating pulsed-dc-ESI a powerful tool for small volume sample systematical analysis. PMID:26488206

  10. Measurement and Processing of Fast Pulsed Discharge Current in Plasma Focus Machines

    NASA Astrophysics Data System (ADS)

    Lee, S.; Saw, S. H.; Rawat, R. S.; Lee, P.; Verma, R.; Talebitaher, A.; Hassan, S. M.; Abdou, A. E.; Ismail, Mohamed; Mohamed, Amgad; Torreblanca, H.; Al Hawat, Sh.; Akel, M.; Chong, P. L.; Roy, F.; Singh, A.; Wong, D.; Devi, K.

    2012-04-01

    The fast pulsed electric discharge current drives all physical processes in the plasma focus device; in turn all physical processes in the focus affect the current waveform. Thus the discharge current waveform is the most important indicator of plasma focus performance. This underlies the importance of properly measuring, processing and interpreting the discharge current waveform. This paper reports the measurement of fast pulsed discharge current by the Rogowski coil, in two different modes: the current transformer, "I" mode, and current derivative, "Idot" mode. The processing and interpretation of recorded current waveform to obtain useful information about the physical processes in the plasma focus device are discussed. The current transformer with a large number of turns and a sub-1 Ohm terminator has good high frequency response, necessary for the sharp current dip region when dI/ dt exceeds 2 × 1011 A/s. However the signal is "noisy" in the current dip region. Several methods to extract the current dip from the noise are discussed and examples of how low pass filters affect the signals are shown. The dI/ dt coil, the Rogowski coil in "Idot" mode, with a few turns terminated by 50-Ohm is also described. Integrating the 1 GSa/s digital waveform does remove the high frequency noise components, yet the extracted waveform shows sharp angular features indicative of the retention of short-time features. This makes the dI/ dt coil superior to the current transformer. A 7-turn coil is tested against the Lee Model code and found to be suitable to measure the plasma focus discharge current.

  11. Effects of low frequency pulsed electrical current on keratinocytes in vitro

    SciTech Connect

    Hinsenkamp, M.; Jercinovic, A.

    1997-05-01

    The effects of low frequency pulsed electrical current on epidermal repair in vitro were examined. Charge-balanced current stimuli proposed for chronic wound treatment were tested on skin keratinocytes cultured at an air-liquid interface on dead human dermis. Results imply that the balance between proliferation and differentiation in electrically treated samples is significantly modified in favor of differentiation. More advanced differentiation, shown through epidermal histology, was obtained in cultures exposed to electrical current, whereas the culture growth, the result of keratinocyte migration and proliferation, was greater in control samples.

  12. Preparation of scanning tunneling microscopy tips using pulsed alternating current etching

    SciTech Connect

    Valencia, Victor A.; Thaker, Avesh A.; Derouin, Jonathan; Valencia, Damian N.; Farber, Rachael G.; Gebel, Dana A.; Killelea, Daniel R.

    2015-03-15

    An electrochemical method using pulsed alternating current etching (PACE) to produce atomically sharp scanning tunneling microscopy (STM) tips is presented. An Arduino Uno microcontroller was used to control the number and duration of the alternating current (AC) pulses, allowing for ready optimization of the procedures for both Pt:Ir and W tips using a single apparatus. W tips prepared using constant and pulsed AC power were compared. Tips fashioned using PACE were sharper than those etched with continuous AC power alone. Pt:Ir tips were prepared with an initial coarse etching stage using continuous AC power followed by fine etching using PACE. The number and potential of the finishing AC pulses was varied and scanning electron microscope imaging was used to compare the results. Finally, tip quality using the optimized procedures was verified by UHV-STM imaging. With PACE, at least 70% of the W tips and 80% of the Pt:Ir tips were of sufficiently high quality to obtain atomically resolved images of HOPG or Ni(111)

  13. Genomics and molecular breeding in lesser explored pulse crops: current trends and future opportunities.

    PubMed

    Bohra, Abhishek; Jha, Uday Chand; Kishor, P B Kavi; Pandey, Shailesh; Singh, Narendra P

    2014-12-01

    Pulses are multipurpose crops for providing income, employment and food security in the underprivileged regions, notably the FAO-defined low-income food-deficit countries. Owing to their intrinsic ability to endure environmental adversities and the least input/management requirements, these crops remain central to subsistence farming. Given their pivotal role in rain-fed agriculture, substantial research has been invested to boost the productivity of these pulse crops. To this end, genomic tools and technologies have appeared as the compelling supplement to the conventional breeding. However, the progress in minor pulse crops including dry beans (Vigna spp.), lupins, lablab, lathyrus and vetches has remained unsatisfactory, hence these crops are often labeled as low profile or lesser researched. Nevertheless, recent scientific and technological breakthroughs particularly the next generation sequencing (NGS) are radically transforming the scenario of genomics and molecular breeding in these minor crops. NGS techniques have allowed de novo assembly of whole genomes in these orphan crops. Moreover, the availability of a reference genome sequence would promote re-sequencing of diverse genotypes to unlock allelic diversity at a genome-wide scale. In parallel, NGS has offered high-resolution genetic maps or more precisely, a robust genetic framework to implement whole-genome strategies for crop improvement. As has already been demonstrated in lupin, sequencing-based genotyping of the representative sample provided access to a number of functionally-relevant markers that could be deployed straight away in crop breeding programs. This article attempts to outline the recent progress made in genomics of these lesser explored pulse crops, and examines the prospects of genomics assisted integrated breeding to enhance and stabilize crop yields.

  14. Investigation of a pulsed current annealing method in reusing MOSFET dosimeters for in vivo IMRT dosimetry

    SciTech Connect

    Luo, Guang-Wen; Qi, Zhen-Yu Deng, Xiao-Wu; Rosenfeld, Anatoly

    2014-05-15

    Purpose: To explore the feasibility of pulsed current annealing in reusing metal oxide semiconductor field-effect transistor (MOSFET) dosimeters forin vivo intensity modulated radiation therapy (IMRT) dosimetry. Methods: Several MOSFETs were irradiated atd{sub max} using a 6 MV x-ray beam with 5 V on the gate and annealed with zero bias at room temperature. The percentage recovery of threshold voltage shift during multiple irradiation-annealing cycles was evaluated. Key dosimetry characteristics of the annealed MOSFET such as the dosimeter's sensitivity, reproducibility, dose linearity, and linearity of response within the dynamic range were investigated. The initial results of using the annealed MOSFETs for IMRT dosimetry practice were also presented. Results: More than 95% of threshold voltage shift can be recovered after 24-pulse current continuous annealing in 16 min. The mean sensitivity degradation was found to be 1.28%, ranging from 1.17% to 1.52%, during multiple annealing procedures. Other important characteristics of the annealed MOSFET remained nearly consistent before and after annealing. Our results showed there was no statistically significant difference between the annealed MOSFETs and their control samples in absolute dose measurements for IMRT QA (p = 0.99). The MOSFET measurements agreed with the ion chamber results on an average of 0.16% ± 0.64%. Conclusions: Pulsed current annealing provides a practical option for reusing MOSFETs to extend their operational lifetime. The current annealing circuit can be integrated into the reader, making the annealing procedure fully automatic.

  15. Transient current pulses in rocket-extended wires used to trigger lightning

    NASA Astrophysics Data System (ADS)

    Biagi, C. J.; Uman, M. A.; Hill, J. D.; Rakov, V. A.; Jordan, D. M.

    2012-04-01

    We analyze current, electric field, and optical signatures of the sudden electrical breakdown processes (precursors) that occur at the top of the upward extending, grounded, Kevlar-covered copper wires used to artificially trigger lightning. For one launch, before the sustained upward positive leader initiated, we estimate that up to 10,000 precursors occurred (one every few hundred microseconds) with peak currents from 1 to more than 100 A. Luminosity at the wire tip was observed for 339 of 410 precursors examined in detail and, in seven cases, discharge channels developed to lengths of 3 to 8 m over times of several hundred microseconds. The measured propagation speeds of current pulses on the triggering wires were less than the speed of light, and decreased from about 2.8 × 108 m s-1 to about 2.3 × 108 m s-1with increasing wire-top heights from about 80 m to about 340 m. The triggering wire and its grounding system are modeled as uniform transmission lines with model predictions that are consistent with the measured wire-base precursor current signatures. The modeling shows that (1) the characteristic impedance of the triggering wire, the ratio of the propagating precursor voltage pulse to its associated current pulse, is between 600 and 800 Ω; (2) the 25 m ground rod grounding impedance for the peak precursor current is about 100 Ω, while the DC grounding resistance is 20 Ω; and (3) the current reflection coefficient at ground for peak precursor current is ˜0.9.

  16. Modeling and Dynamic Analysis of Paralleled of dc/dc Converters with Master-Slave Current Sharing Control

    NASA Technical Reports Server (NTRS)

    Rajagopalan, J.; Xing, K.; Guo, Y.; Lee, F. C.; Manners, Bruce

    1996-01-01

    A simple, application-oriented, transfer function model of paralleled converters employing Master-Slave Current-sharing (MSC) control is developed. Dynamically, the Master converter retains its original design characteristics; all the Slave converters are forced to depart significantly from their original design characteristics into current-controlled current sources. Five distinct loop gains to assess system stability and performance are identified and their physical significance is described. A design methodology for the current share compensator is presented. The effect of this current sharing scheme on 'system output impedance' is analyzed.

  17. Modeling and Dynamic Analysis of Paralleled dc/dc Converters With Master-Slave Current Sharing Control

    NASA Technical Reports Server (NTRS)

    Rajagopalan, J.; Xing, K.; Guo, Y.; Lee, F. C.; Manners, Bruce

    1996-01-01

    A simple, application-oriented, transfer function model of paralleled converters employing Master-Slave Current-sharing (MSC) control is developed. Dynamically, the Master converter retains its original design characteristics; all the Slave converters are forced to depart significantly from their original design characteristics into current-controlled current sources. Five distinct loop gains to assess system stability and performance are identified and their physical significance is described. A design methodology for the current share compensator is presented. The effect of this current sharing scheme on 'system output impedance' is analyzed.

  18. Charge and spin current oscillations in a tunnel junction induced by magnetic field pulses

    NASA Astrophysics Data System (ADS)

    Dartora, C. A.; Nobrega, K. Z.; Cabrera, G. G.

    2016-08-01

    Usually, charge and spin transport properties in tunnel junctions are studied in the DC bias regime and/or in the adiabatic regime of time-varying magnetic fields. In this letter, the temporal dynamics of charge and spin currents in a tunnel junction induced by pulsed magnetic fields is considered. At low bias voltages, energy and momentum of the conduction electrons are nearly conserved in the tunneling process, leading to the description of the junction as a spin-1/2 fermionic system coupled to time-varying magnetic fields. Under the influence of pulsed magnetic fields, charge and spin current can flow across the tunnel junction, displaying oscillatory behavior, even in the absence of DC bias voltage. A type of spin capacitance function, in close analogy to electric capacitance, is predicted.

  19. Effect of catalytic pyrolysis conditions using pulse current heating method on pyrolysis products of wood biomass.

    PubMed

    Honma, Sensho; Hata, Toshimitsu; Watanabe, Takashi

    2014-01-01

    The influence of catalysts on the compositions of char and pyrolysis oil obtained by pyrolysis of wood biomass with pulse current heating was studied. The effects of catalysts on product compositions were analyzed using GC-MS and TEM. The compositions of some aromatic compounds changed noticeably when using a metal oxide species as the catalyst. The coexistence or dissolution of amorphous carbon and iron oxide was observed in char pyrolyzed at 800 °C with Fe3O4. Pyrolysis oil compositions changed remarkably when formed in the presence of a catalyst compared to that obtained from the uncatalyzed pyrolysis of wood meal. We observed a tendency toward an increase in the ratio of polyaromatic hydrocarbons in the pyrolysis oil composition after catalytic pyrolysis at 800 °C. Pyrolysis of biomass using pulse current heating and an adequate amount of catalyst is expected to yield a higher content of specific polyaromatic compounds.

  20. Effect of Catalytic Pyrolysis Conditions Using Pulse Current Heating Method on Pyrolysis Products of Wood Biomass

    PubMed Central

    Honma, Sensho; Hata, Toshimitsu; Watanabe, Takashi

    2014-01-01

    The influence of catalysts on the compositions of char and pyrolysis oil obtained by pyrolysis of wood biomass with pulse current heating was studied. The effects of catalysts on product compositions were analyzed using GC-MS and TEM. The compositions of some aromatic compounds changed noticeably when using a metal oxide species as the catalyst. The coexistence or dissolution of amorphous carbon and iron oxide was observed in char pyrolyzed at 800°C with Fe3O4. Pyrolysis oil compositions changed remarkably when formed in the presence of a catalyst compared to that obtained from the uncatalyzed pyrolysis of wood meal. We observed a tendency toward an increase in the ratio of polyaromatic hydrocarbons in the pyrolysis oil composition after catalytic pyrolysis at 800°C. Pyrolysis of biomass using pulse current heating and an adequate amount of catalyst is expected to yield a higher content of specific polyaromatic compounds. PMID:25614894

  1. Pulsed eddy-current inspection of thin-walled stainless steel tubing

    SciTech Connect

    Dodd, C.V.; Koerner, D.W.; Deeds, W.E.; Pickett, C.A.

    1987-09-01

    A pulsed eddy-current system has been developed for production inspection of small, thin-wall, non-ferromagnetic tubing. To detect and accurately size both outer and bore-side flaws required an operating frequency higher than available from present commercial equipment. A pulsed eddy-current instrument was designed and constructed that used 3.2 MHz square waves, with a bandwidth of 20 MHz. The system is able to reliably detect flaws as small as 0.015 mm (0.6 mils) on either the inner or outer surface of the tube. A computer controls the scanning of the tube, as recording, analyzing, and plotting the data. The computer programs and instrument details are given in the report.

  2. Effect of catalytic pyrolysis conditions using pulse current heating method on pyrolysis products of wood biomass.

    PubMed

    Honma, Sensho; Hata, Toshimitsu; Watanabe, Takashi

    2014-01-01

    The influence of catalysts on the compositions of char and pyrolysis oil obtained by pyrolysis of wood biomass with pulse current heating was studied. The effects of catalysts on product compositions were analyzed using GC-MS and TEM. The compositions of some aromatic compounds changed noticeably when using a metal oxide species as the catalyst. The coexistence or dissolution of amorphous carbon and iron oxide was observed in char pyrolyzed at 800 °C with Fe3O4. Pyrolysis oil compositions changed remarkably when formed in the presence of a catalyst compared to that obtained from the uncatalyzed pyrolysis of wood meal. We observed a tendency toward an increase in the ratio of polyaromatic hydrocarbons in the pyrolysis oil composition after catalytic pyrolysis at 800 °C. Pyrolysis of biomass using pulse current heating and an adequate amount of catalyst is expected to yield a higher content of specific polyaromatic compounds. PMID:25614894

  3. Conversion of high explosive chemical energy into energy of powerful nanosecond high-current pulses

    NASA Astrophysics Data System (ADS)

    Gorbachev, K. V.; Mikhaylov, V. M.; Nesterov, E. V.; Stroganov, V. A.; Chernykh, E. V.

    2015-01-01

    This study is a contribution into the development of physicotechnical foundations for generation of powerful nanosecond high-current pulses on the basis of explosively driven magnetic flux compression generators. This problem is solved by using inductive storage of energy for matching comparatively low-voltage explosively driven magnetic flux compression generators and high-impedance loads; short forming lines and vacuum diodes. Experimental data of charging of forming lines are given.

  4. Surface modification of structural materials by low-energy high-current pulsed electron beam treatment

    SciTech Connect

    Panin, A. V. E-mail: kms@ms.tsc.ru; Kazachenok, M. S. E-mail: kms@ms.tsc.ru; Sinyakova, E. A.; Borodovitsina, O. M.; Ivanov, Yu. F.; Leontieva-Smirnova, M. V.

    2014-11-14

    Microstructure formation in surface layers of pure titanium and ferritic-martensitic steel subjected to electron beam treatment is studied. It is shown that low energy high-current pulsed electron beam irradiation leads to the martensite structure within the surface layer of pure titanium. Contrary, the columnar ferrite grains grow during solidification of ferritic-martensitic steel. The effect of electron beam energy density on the surface morphology and microstructure of the irradiated metals is demonstrated.

  5. Evaluation of conductor stresses in a pulsed high-current toroidal transformer

    SciTech Connect

    Turchi, Peter J; Rousculp, Chritopher L; Reass, William A; Oro, David M; Merrill, Frank E; Greigo, Jeffery R; Reinovsky, Robert E

    2009-01-01

    The Precision, High-Energy Density, Liner Implosion Experiment (PHELIX) pulsed power driver is currently under development at Los Alamos National Laboratory. When operational PHELIX will provide 5-10 MAmps of peak current with pulse rise-time of {approx} 5-10 ms. Crucial to the performance of PHELIX is a multi-turn primary, single-turn secondary, current step-up toroidal transformer, R{sub major} {approx} 30 cm, R{sub minor} {approx} 10 cm. The transformer lifetime should exceed 100 shots. Therefore it is essential that the design be robust enough to survive the magnetic stresses produced by high currents. In order to evaluate their design, two methods have been utilized. First, an analytical evaluation has been performed. By identifying the magnetic forces as J{sub 1}{sup 2}/2 {del}L{sub 1} + J{sub 1}J{sub 2}{del}M{sub 12}, where J{sub 1} and J{sub 2} are currents in two circuits, coupled by mutual inductance M{sub 12} and L{sub 1} is the self-inductance of the circuit carrying current J{sub 1}, analytical estimates of stress can be obtained. These results are then compared to a computational MHD model of the same system and to a full finite-element, electromagnetic simulation.

  6. Influence of current density on microstructure of pulse electrodeposited tin coatings

    SciTech Connect

    Sharma, Ashutosh; Bhattacharya, Sumit; Sen, Ranjan; Reddy, B.S.B.; Fecht, H.-J.; Das, Karabi; Das, Siddhartha

    2012-06-15

    Pulse electrodeposited tin coatings on copper substrate have been synthesized from an aqueous solution containing sodium stannate (Na{sub 2}SnO{sub 3}.3H{sub 2}O) and sodium hydroxide (NaOH). The effect of current density on surface morphology of the deposits has been investigated. As deposited coatings are characterized by X-ray diffraction, scanning electron microscopy, electron backscatter diffraction, and line profile analysis. The X-ray diffraction analysis shows that the deposits consist of tetragonal ({beta}-Sn) structure with microcrystalline grains. The deposits plated at lower current density exhibit (110) texture which decreases with increasing current densities. The effects of current density on Cu-Sn diffusion and whisker growth of the electrodeposited tin coatings are also reported here. - Highlights: Black-Right-Pointing-Pointer Pulse electrodeposition of Sn from aqueous alkaline solution without adding any organic additive. Black-Right-Pointing-Pointer Effect of current density on morphology and whisker growth in tin coatings aged for 1 year. Black-Right-Pointing-Pointer Solution bath is stable and can be operated over a wide range of current density.

  7. Efficiency of pulse high-current generator energy transfer into plasma liner energy

    NASA Astrophysics Data System (ADS)

    Oreshkin, V. I.

    2013-08-01

    The efficiency of capacitor-bank energy transfer from a high-current pulse generator into kinetic energy of a plasma liner has been analyzed. The analysis was performed using a model including the circuit equations and equations of the cylindrical shell motion. High efficiency of the energy transfer into kinetic energy of the liner is shown to be achieved only by a low-inductance generator. We considered an "ideal" liner load in which the load current is close to zero in the final of the shell compression. This load provides a high (up to 80%) efficiency of energy transfer and higher stability when compressing the liner.

  8. Electrical discharge machining (EDM) of Inconel 718 by using copper electrode at higher peak current and pulse duration

    NASA Astrophysics Data System (ADS)

    Ahmad, S.; Lajis, M. A.

    2013-12-01

    This experimental work is an attempt to investigate the performance of Copper electrode when EDM of Nickel Based Super Alloy, Inconel 718 is at higher peak current and pulse duration. Peak current, Ip and pulse duration (pulse on-time), ton are selected as the most important electrical pulse parameters. In addition, their influence on material removal rate (MRR), electrode wear rate (EWR), and surface roughness (Ra) are experimentally investigated. The ranges of 10 mm diameter of Copper electrode are used to EDM of Inconel 718. After the experiments, MRR, EWR, and Ra of the machined surfaces need to be measured in order to evaluate the performance of the EDM process. In order to obtain high MRR, higher peak current in range of 20A to 40A and pulse duration in range of 200μs to 400μs were used. Experimental results have shown that machining at a highest peak current used of 40A and the lowest pulse duration of 200μs used for the experiment yields the highest material removal rate (MRR) with value 34.94 mm3/min, whereas machining at a peak current of 20A and pulse duration of 400μs yields the lowest electrode wear rate (EWR) with value -0.0101 mm3/min. The lowest surface roughness (Ra) is 8.53 μm achieved at a lowest peak current used of 20A and pulse duration of 200μs.

  9. The effect of applied electric field on pulsed radio frequency and pulsed direct current plasma jet array

    SciTech Connect

    Hu, J. T.; Liu, X. Y.; Liu, J. H.; Xiong, Z. L.; Liu, D. W.; Lu, X. P.; Iza, F.; Kong, M. G.

    2012-06-15

    Here we compare the plasma plume propagation characteristics of a 3-channel pulsed RF plasma jet array and those of the same device operated by a pulsed dc source. For the pulsed-RF jet array, numerous long life time ions and metastables accumulated in the plasma channel make the plasma plume respond quickly to applied electric field. Its structure similar as 'plasma bullet' is an anode glow indeed. For the pulsed dc plasma jet array, the strong electric field in the vicinity of the tube is the reason for the growing plasma bullet in the launching period. The repulsive forces between the growing plasma bullets result in the divergence of the pulsed dc plasma jet array. Finally, the comparison of 309 nm and 777 nm emissions between these two jet arrays suggests the high chemical activity of pulsed RF plasma jet array.

  10. Pulse

    MedlinePlus

    ... resting for at least 10 minutes. Take the exercise heart rate while you are exercising. ... pulse rate can help determine if the patient's heart is pumping. ... rate gives information about your fitness level and health.

  11. Concordance among Measurements Obtained by Three Pulse Oximeters Currently Used by Health Professionals

    PubMed Central

    De La Rosa Hormiga, Milagros; MaríA Ramal LóPez, Josefa; DéNiz Rivero, Yasmina; Sandra Marrero Morales, MaríA

    2014-01-01

    Introduction: Oxygen saturation is considered as the 5th vital sign. Presently, there exist fixed and wireless pulse oximeters, being the latter most widely used in the last years. Some of them have no possibility of calibration. This situation leads the health staff to adopt therapeutic attitudes which can be wrong. Therefore, it is extremely important to know if these wireless oximeters show a right concordance as regards measurements, since it is of great interest in daily clinical practice. Objective: To evaluate concordance among measurements obtained by three different pulse oximeters currently used by health professionals. Materials and Methods: This is an observational, descriptive and cross-sectional study related to the concordance of the results obtained in measurements collected by three different pulse oximeters (one monitor and two wireless oximeters) which are available and in use in this hospital unit. The sample size calculation was performed for a concordance above 0.81 and an estimation error which did not exceed 0.20. The intraclass correlation index (ICI) was used to establish the concordance whereas the Landis-Koch criteria were used to interpret the results. Systematic errors were analyzed using the Bland-Altman plot. Results: The overall concordance among the three pulse oximeters analyzed resulted in 0.88, a value considered as “good” according to the Landis-Koch criteria. Conclusion: The results obtained show that in daily clinical practice both wireless pulse oximeters analyzed can be used with a certain reliability, taking into account the limitations of this research. PMID:25302228

  12. Observation of self-magnetic field relaxations in Bi2223 and Y123 HTS tapes after over-current pulse and DC current operation

    NASA Astrophysics Data System (ADS)

    Tallouli, M.; Sun, J.; Chikumoto, N.; Otabe, E. S.; Shyshkin, O.; Charfi-Kaddour, S.; Yamaguchi, S.

    2016-07-01

    The development of power transmission lines based on long-length HTS tapes requires the production of high quality tapes. Due to fault conditions, technical mistakes and human errors during the operation of a DC power transmission line, an over-current pulse, several times larger than the rated current, could occur. To study the effect of such over-current pulses on the transport current density distribution in the HTS tapes, we simulated two start-up scenarios for one BSCCO and two YBCO tapes. The first start-up scenario is an initial over-current pulse during which the transport current was turned on rapidly, rising to 900 A during the first milliseconds, then reduced to a 100 A DC current. The second start-up scenario is normal operation, and involved increasing the transport current slowly from 0 A to 100 A at a rate of 1 A/s. For both scenarios, we then measured the vertical component of the self-magnetic field by means of a Hall probe above the tape, and afterward, by solving a linear equation of the inverse problem we obtain the current density profiles. We observe a change of the self-magnetic field above the edge of the BSCCO and YBCO tapes during 30 min after the 5 ms of over-current pulse and during the normal operation. The current density profiles are peaked in the centre for over-current pulse, and more peaked around the edge of the HTS tape for normal operation, which means that the limited time over-current pulse changes the current density profiles of the HTS tapes. We observe also a loop of current for YBCO tapes and we show the role of the HTS tape stabilizer.

  13. A high current pulsed power generator CQ-3-MMAF with co-axial cable transmitting energy for material dynamics experiments.

    PubMed

    Wang, Guiji; Chen, Xuemiao; Cai, Jintao; Zhang, Xuping; Chong, Tao; Luo, Binqiang; Zhao, Jianheng; Sun, Chengwei; Tan, Fuli; Liu, Cangli; Wu, Gang

    2016-06-01

    A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films. It is composed of 32 capacitor and switch modules in parallel. The electrical parameters in short circuit are with a capacitance of 19.2 μF, an inductance of 11.7 nH, a resistance of 4.3 mΩ, and working charging voltage of 60 kV-90 kV. It can be run safely and stable when charged from 60 kV to 90 kV. The vacuum of loading chamber can be up to 10(-2) Pa, and the current waveforms can be shaped by discharging in time sequences of four groups of capacitor and switch modules. CQ-3-MMAF is an adaptive machine with lower maintenance because of its modularization design. The COMSOL Multi-physics® code is used to optimize the structure of some key components and calculate their structural inductance for designs, such as gas switches and cable connectors. Some ramp wave loading experiments were conducted to check and examine the performances of CQ-3-MMAF. Two copper flyer plates were accelerated to about 3.5 km/s in one shot when the working voltage was charged to 70 kV. The velocity histories agree very well. The dynamic experiments of some polymer bonded explosives and phase transition of tin under ramp wave loadings were also conducted. The experimental data show that CQ-3-MMAF can be used to do material dynamics experiments in high rate and low cost shots. Based on this design concept, the peak

  14. A high current pulsed power generator CQ-3-MMAF with co-axial cable transmitting energy for material dynamics experiments.

    PubMed

    Wang, Guiji; Chen, Xuemiao; Cai, Jintao; Zhang, Xuping; Chong, Tao; Luo, Binqiang; Zhao, Jianheng; Sun, Chengwei; Tan, Fuli; Liu, Cangli; Wu, Gang

    2016-06-01

    A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films. It is composed of 32 capacitor and switch modules in parallel. The electrical parameters in short circuit are with a capacitance of 19.2 μF, an inductance of 11.7 nH, a resistance of 4.3 mΩ, and working charging voltage of 60 kV-90 kV. It can be run safely and stable when charged from 60 kV to 90 kV. The vacuum of loading chamber can be up to 10(-2) Pa, and the current waveforms can be shaped by discharging in time sequences of four groups of capacitor and switch modules. CQ-3-MMAF is an adaptive machine with lower maintenance because of its modularization design. The COMSOL Multi-physics® code is used to optimize the structure of some key components and calculate their structural inductance for designs, such as gas switches and cable connectors. Some ramp wave loading experiments were conducted to check and examine the performances of CQ-3-MMAF. Two copper flyer plates were accelerated to about 3.5 km/s in one shot when the working voltage was charged to 70 kV. The velocity histories agree very well. The dynamic experiments of some polymer bonded explosives and phase transition of tin under ramp wave loadings were also conducted. The experimental data show that CQ-3-MMAF can be used to do material dynamics experiments in high rate and low cost shots. Based on this design concept, the peak

  15. A high current pulsed power generator CQ-3-MMAF with co-axial cable transmitting energy for material dynamics experiments

    NASA Astrophysics Data System (ADS)

    Wang, Guiji; Chen, Xuemiao; Cai, Jintao; Zhang, Xuping; Chong, Tao; Luo, Binqiang; Zhao, Jianheng; Sun, Chengwei; Tan, Fuli; Liu, Cangli; Wu, Gang

    2016-06-01

    A high current pulsed power generator CQ-3-MMAF (Multi-Modules Assembly Facility, MMAF) was developed for material dynamics experiments under ramp wave and shock loadings at the Institute of Fluid Physics (IFP), which can deliver 3 MA peak current to a strip-line load. The rise time of the current is 470 ns (10%-90%). Different from the previous CQ-4 at IFP, the CQ-3-MMAF energy is transmitted by hundreds of co-axial high voltage cables with a low impedance of 18.6 mΩ and low loss, and then hundreds of cables are reduced and converted to tens of cables into a vacuum chamber by a cable connector, and connected with a pair of parallel metallic plates insulated by Kapton films. It is composed of 32 capacitor and switch modules in parallel. The electrical parameters in short circuit are with a capacitance of 19.2 μF, an inductance of 11.7 nH, a resistance of 4.3 mΩ, and working charging voltage of 60 kV-90 kV. It can be run safely and stable when charged from 60 kV to 90 kV. The vacuum of loading chamber can be up to 10-2 Pa, and the current waveforms can be shaped by discharging in time sequences of four groups of capacitor and switch modules. CQ-3-MMAF is an adaptive machine with lower maintenance because of its modularization design. The COMSOL Multi-physics® code is used to optimize the structure of some key components and calculate their structural inductance for designs, such as gas switches and cable connectors. Some ramp wave loading experiments were conducted to check and examine the performances of CQ-3-MMAF. Two copper flyer plates were accelerated to about 3.5 km/s in one shot when the working voltage was charged to 70 kV. The velocity histories agree very well. The dynamic experiments of some polymer bonded explosives and phase transition of tin under ramp wave loadings were also conducted. The experimental data show that CQ-3-MMAF can be used to do material dynamics experiments in high rate and low cost shots. Based on this design concept, the peak

  16. Progress in pulsed-current Karl Fischer coulometry using diaphragm-free cells.

    PubMed

    Nordmark, U; Cedergren, A

    2000-07-01

    Factors influencing the accuracy of water determinations using diaphragm-free, pulsed current Karl Fischer (KF) coulometry were investigated with the new Metrohm 756 instrument. Results obtained with commercially available reagents from Riedel-deHaen and Merck were compared with home-made ones that were especially designed to minimize the formation of iodine-consuming reduction products generated in the cathode reaction. Positive errors in the range 2-5% were found for the commercial reagents as compared to 0.2-1% for the home-made ones which were buffered at about pH 10 containing modifiers like chloroform, hexanol or ethylene glycol. Except for the composition of the KF-reagent, the cathode current density and the titration rate were found to be critical parameters for the accuracy of the determinations. For all reagents investigated, the best results were obtained for the maximum generator current 400 mA (corresponding to a current density of 1,400 mA cm(-2)) in combination with a maximum titration rate of 2,000 microg min(-1). Surprisingly, the errors found under optimum conditions for the pulse technique were always somewhat larger than the corresponding values obtained with continuous coulometry.

  17. Current Research on Parallel Measures of Interests and Confidence for Basic Dimensions of Vocational Activity

    ERIC Educational Resources Information Center

    Betz, Nancy E.; Rottinghaus, Patrick J.

    2006-01-01

    This article begins with a rationale for and review of parallel measures of self-efficacy (confidence) and interests for basic dimensions of vocational activity. Recent development of and research on the Expanded Skills Confidence Inventory, Campbell Interest and Skills Survey, Kuder Skills Assessment, and Inventory of Work-Relevant Abilities are…

  18. Low-voltage pulsed plasma discharges inside water using a bubble self-generating parallel plate electrode with a porous ceramic

    NASA Astrophysics Data System (ADS)

    Muradia, Sonia; Nagatsu, Masaaki

    2013-04-01

    Characteristics of pulsed bubbles discharges in water were investigated using parallel punched plate electrodes with a porous thin ceramic plate inserted between two metal plates. The micro-bubbles were generated just beneath the porous ceramic plate by flowing gas through it. The transition from spiky dielectric barrier discharges to pulsed glow discharges enables efficient bubble discharges at a relatively low voltage of 1.8 ˜ 4.0 kV of the 5 kHz square-waves with a pulse-width of about 750 ns. With 80% Ar and 20% O2 mixture gas at 4.0 kV, the 50 mg/l Indigo Carmine aqueous solution was efficiently decolorized within about 3 min.

  19. High ion charge states in a high-current, short-pulse, vacuum ARC ion sources

    SciTech Connect

    Anders, A.; Brown, I.; MacGill, R.; Dickinson, M.

    1996-08-01

    Ions of the cathode material are formed at vacuum arc cathode spots and extracted by a grid system. The ion charge states (typically 1-4) depend on the cathode material and only little on the discharge current as long as the current is low. Here the authors report on experiments with short pulses (several {mu}s) and high currents (several kA); this regime of operation is thus approaching a more vacuum spark-like regime. Mean ion charge states of up to 6.2 for tungsten and 3.7 for titanium have been measured, with the corresponding maximum charge states of up to 8+ and 6+, respectively. The results are discussed in terms of Saha calculations and freezing of the charge state distribution.

  20. Laminar iridium coating produced by pulse current electrodeposition from chloride molten salt

    NASA Astrophysics Data System (ADS)

    Zhu, Li'an; Bai, Shuxin; Zhang, Hong; Ye, Yicong

    2013-10-01

    Due to the unique physical and chemical properties, Iridium (Ir) is one of the most promising oxidation-resistant coatings for refractory materials above 1800 °C in aerospace field. However, the Ir coatings prepared by traditional methods are composed of columnar grains throughout the coating thickness. The columnar structure of the coating is considered to do harm to its oxidation resistance. The laminar Ir coating is expected to have a better high-temperature oxidation resistance than the columnar Ir coating does. The pulse current electrodeposition, with three independent parameters: average current density (Jm), duty cycle (R) and pulse frequency (f), is considered to be a promising method to fabricate layered Ir coating. In this study, laminar Ir coatings were prepared by pulse current electrodeposition in chloride molten salt. The morphology, roughness and texture of the coatings were determined by scanning electron microscope (SEM), profilometer and X-ray diffraction (XRD), respectively. The results showed that the laminar Ir coatings were composed of a nucleation layer with columnar structure and a growth layer with laminar structure. The top surfaces of the laminar Ir coatings consisted of cauliflower-like aggregates containing many fine grains, which were separated by deep grooves. The laminar Ir coating produced at the deposition condition of 20 mA/cm2 (Jm), 10% (R) and 6 Hz (f) was quite smooth (Ra 1.01 ± 0.09 μm) with extremely high degree of preferred orientation of <1 1 1>, and its laminar structure was well developed with clear boundaries and uniform thickness of sub-layers.

  1. The solar wind pressure pulse as a ring current source in the disturbed magnetosphere

    NASA Astrophysics Data System (ADS)

    Kalegaev, Vladimir; Vlasova, Natalia; Nazarkov, Ilya

    2016-07-01

    The solar wind pressure and IMF are the most important factors of interplanetary medium disturbing the Earth's magnetosphere. They determine the momentum/energy transfer inside the magnetopause. The relative dynamics of solar wind pressure and IMF controls the development of the different storm-time magnetospheric currents during disturbances. While the southward turning of IMF is well-known magnetic storm source, the role of the strong pressure pulse under northward IMF is not enough studied. We present the results of studying the solar wind pressure influence on the magnetospheric structure during events on 21-22 January 2005 and 22-23 June 2015 when the main phase of geomagnetic storms developed under IMF Bz>0. Joint analysis of experimental and modeling data was carried out. Equatorial ion fluxes of 30-80 keV protons of the storm time equatorial belt (STEB) measured by low-altitude polar sun-synchronous NOAA POES satellites were used to estimate the ring current evolution. The magnetic field of the large-scale magnetospheric currents was calculated in terms of the paraboloid model of the magnetospheric geomagnetic field A2000. It was found that ring current development during the early main phase of the magnetic storms was provided not only large-scale magnetospheric convection but also by extremely strong solar wind dynamical impact. Interplanetary shock caused intensive trapped particle non-adiabatic radial motion to the lover L-shells during SSC and subsequent ring current enhancement similar to that taking place due to particle injection from the tail. The extreme solar wind pressure pulse can produce the ring current enhancement even under the northward orientation of the interplanetary magnetic field.

  2. Extreme degree of ionization in homogenous micro-capillary plasma columns heated by ultrafast current pulses.

    PubMed

    Avaria, G; Grisham, M; Li, J; Tomasel, F G; Shlyaptsev, V N; Busquet, M; Woolston, M; Rocca, J J

    2015-03-01

    Homogeneous plasma columns with ionization levels typical of megaampere discharges are created by rapidly heating gas-filled 520-μm-diameter channels with nanosecond rise time current pulses of 40 kA. Current densities of up to 0.3  GA cm^{-2} greatly increase Joule heating with respect to conventional capillary discharge Z pinches, reaching unprecedented degrees of ionization for a high-Z plasma column heated by a current pulse of remarkably low amplitude. Dense xenon plasmas are ionized to Xe^{28+}, while xenon impurities in hydrogen discharges reach Xe^{30+}. The unique characteristics of these hot, ∼300:1 length-to-diameter aspect ratio plasmas allow the observation of unexpected spectroscopic phenomena. Axial spectra show the unusual dominance of the intercombination line over the resonance line of He-like Al by nearly an order of magnitude, caused by differences in opacities in the axial and radial directions. These plasma columns could enable the development of sub-10-nm x-ray lasers. PMID:25793819

  3. Extreme Degree of Ionization in Homogenous Micro-Capillary Plasma Columns Heated by Ultrafast Current Pulses

    NASA Astrophysics Data System (ADS)

    Avaria, G.; Grisham, M.; Li, J.; Tomasel, F. G.; Shlyaptsev, V. N.; Busquet, M.; Woolston, M.; Rocca, J. J.

    2015-03-01

    Homogeneous plasma columns with ionization levels typical of megaampere discharges are created by rapidly heating gas-filled 520 -μ m -diameter channels with nanosecond rise time current pulses of 40 kA. Current densities of up to 0.3 GA cm-2 greatly increase Joule heating with respect to conventional capillary discharge Z pinches, reaching unprecedented degrees of ionization for a high-Z plasma column heated by a current pulse of remarkably low amplitude. Dense xenon plasmas are ionized to Xe28 + , while xenon impurities in hydrogen discharges reach Xe30 + . The unique characteristics of these hot, ˜300 :1 length-to-diameter aspect ratio plasmas allow the observation of unexpected spectroscopic phenomena. Axial spectra show the unusual dominance of the intercombination line over the resonance line of He-like Al by nearly an order of magnitude, caused by differences in opacities in the axial and radial directions. These plasma columns could enable the development of sub-10-nm x-ray lasers.

  4. Design and characterization of the annular cathode high current pulsed electron beam source for circular components

    NASA Astrophysics Data System (ADS)

    Jiang, Wei; Wang, Langping; Wang, Xiaofeng

    2016-08-01

    In order to irradiate circular components with high current pulsed electron beam (HCPEB), an annular cathode based on carbon fiber bunches was designed and fabricated. Using an acceleration voltage of 25 kV, the maximum pulsed irradiation current and energy of this annular cathode can reach 7.9 kA and 300 J, respectively. The irradiation current density distribution of the annular cathode HCPEB source measured along the circumferential direction shows that the annular cathode has good emission uniformity. In addition, four 9310 steel substrates fixed uniformly along the circumferential direction of a metal ring substrate were irradiated by this annular cathode HCPEB source. The surface and cross-section morphologies of the irradiated samples were characterized by scanning electron microscopy (SEM). SEM images of the surface reveal that crater and surface undulation have been formed, which hints that the irradiation energy of the HCPEB process is large enough for surface modification of 9310 steel. Meanwhile, SEM cross-section images exhibit that remelted layers with a thickness of about 5.4 μm have been obtained in all samples, which proves that a good practical irradiation uniformity can be achieved by this annular cathode HCPEB source.

  5. Microstructures and properties of zirconium-702 irradiated by high current pulsed electron beam

    NASA Astrophysics Data System (ADS)

    Yang, Shen; Cai, Jie; Lv, Peng; Zhang, Conglin; Huang, Wei; Guan, Qingfeng

    2015-09-01

    The microstructure, hardness and corrosion resistance of zirconium-702 before and after high-current pulsed electron beam (HCPEB) irradiation have been investigated. The microstructure evolution and surface morphologies of the samples were characterized by using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The experimental results indicate that the sample surface was melted after HCPEB irradiation, and martensitic phase transformation occurred. Besides, two kinds of craters as well as ultrafine structures were obtained in the melted layer. TEM observations suggest that high density dislocations and deformation twins were formed after HCPEB irradiation. With the increasing of pulses, microhardness of the irradiated samples was increased from the initial 178 Hv to 254 Hv. The corrosion resistance was tested by using electrode impedance spectroscopy (EIS) and potentiodynamic polarization curves. Electrochemical results show that, after HCPEB irradiation, all the samples had better corrosion resistance in 1 mol HNO3 solution compared to the initial one, among which the 5-pulsed sample owned the best corrosion resistance. Ultrafine structures, martensitic phase transformation, surface porosities, dislocations and deformation twins are believed to be the dominant reasons for the improvement of the hardness and corrosion resistance.

  6. Research on defects inspection of solder balls based on eddy current pulsed thermography.

    PubMed

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-10-13

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique.

  7. PULSED EDDY CURRENT THICKNESS MEASUREMENT OF SELECTIVE PHASE CORROSION ON NICKEL ALUMINUM BRONZE VALVES

    SciTech Connect

    Krause, T. W.; Harlley, D.; Babbar, V. K.; Wannamaker, K.

    2010-02-22

    Nickel Aluminum Bronze (NAB) is a material with marine environment applications that under certain conditions can undergo selective phase corrosion (SPC). SPC involves the removal of minority elements while leaving behind a copper matrix. Pulsed eddy current (PEC) was evaluated for determination of SPC thickness on a NAB valve section with access from the surface corroded side. A primarily linear response of PEC amplitude, up to the maximum available SPC thickness of 4 mm was observed. The combination of reduced conductivity and permeability in the SPC phase relative to the base NAB was used to explain the observed sensitivity of PEC to SPC thickness variations.

  8. Research on defects inspection of solder balls based on eddy current pulsed thermography.

    PubMed

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-01-01

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique. PMID:26473871

  9. Inspection of corrosion in carbody and under frame for rolling stocks using pulsed eddy current testing

    NASA Astrophysics Data System (ADS)

    Lee, C. W.; Chung, J. D.

    2011-04-01

    Under frame side sill and carbody of rolling stock structures are designed for preventing corrosion in order to meet mechanical requirements. However during long operation time more than 30 years, there are corrosion in the under frame side sill caused by environmental effect, vibration and etc. So, detection and evaluation of the corrosion in the under frame nondestructive is one of important and extending their life time. So, in this study, we have investigated performance of pulsed eddy current testing method by measuring thickness variation of fabricate of carbody and under frame for rolling stocks. And then, the process of evaluating remaining life according to testing of corrosion amount is introduced.

  10. Analysis and measurements of Eddy current effects of a beam tube in a pulsed magnet

    SciTech Connect

    Fang, S.

    1997-05-01

    The power supply design of the {gamma}{sub f} - jump system in FNAL Main Injector uses a resonant circuit. A critical design parameter is the ac losses of the beam tube in a pulsed quadrupole. This paper gives an analysis to this problem. An equivalent circuit model based on the impedance measurement was established. The measured and calculated losses are in agreement. Another effect of the eddy current is the distortion of the magnetic field inside the beam tube. A Morgan coil was used for field measurements up to 10 KHz. These results are presented in this paper.

  11. Abnormal morphology of nanocrystalline Mn-Zn ferrite sintered by pulse electric current sintering

    NASA Astrophysics Data System (ADS)

    Zhang, Jianhua; Yu, Liming; Yuan, Shujuan; Zhang, Shouhua; Zhao, Xinluo

    2009-11-01

    Nanocrystalline manganese-zinc (Mn-Zn) ferrite powders prepared by the sol-gel auto-combustion method are sintered to form bulk ferrite by pulse electric current sintering technique. The sample phase, before sintering and after sintering, is carried out by X-ray diffraction (XRD). The morphology of the sample is observed by scanning electron microscopy (SEM). The results indicate that the bulk ferrite obtained has a pure spinel structure. With special graphite die, a special morphology is observed, which is explained by pressure, temperature and induced electromagnetic field.

  12. Research on Defects Inspection of Solder Balls Based on Eddy Current Pulsed Thermography

    PubMed Central

    Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe

    2015-01-01

    In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on eddy current pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique. PMID:26473871

  13. A HIGH CURRENT, HIGH VOLTAGE SOLID-STATE PULSE GENERATOR FOR THE NIF PLASMA ELECTRODE POCKELS CELL

    SciTech Connect

    Arnold, P A; Barbosa, F; Cook, E G; Hickman, B C; Akana, G L; Brooksby, C A

    2007-07-27

    A high current, high voltage, all solid-state pulse modulator has been developed for use in the Plasma Electrode Pockels Cell (PEPC) subsystem in the National Ignition Facility. The MOSFET-switched pulse generator, designed to be a more capable plug-in replacement for the thyratron-switched units currently deployed in NIF, offers unprecedented capabilities including burst-mode operation, pulse width agility and a steady-state pulse repetition frequency exceeding 1 Hz. Capable of delivering requisite fast risetime, 17 kV flattop pulses into a 6 {Omega} load, the pulser employs a modular architecture characteristic of the inductive adder technology, pioneered at LLNL for use in acceleration applications, which keeps primary voltages low (and well within the capabilities of existing FET technology), reduces fabrication costs and is amenable to rapid assembly and quick field repairs.

  14. Desynchronization of epileptiform activity by extracellular current pulses in rat hippocampal slices.

    PubMed Central

    Durand, D M; Warman, E N

    1994-01-01

    1. A single cathodic current pulse applied in the somatic CA1 region of the hippocampus was found to induce a large decrease in the amplitude of the population spike. 2. Intracellular recordings showed intense cellular firing suggesting the amplitude decrease could not be attributed to a decrease in neuronal firing. 3. Simultaneous intracellular and extracellular potentials were recorded to analyse the synchronization of neuronal firing in the CA1 region. Action potentials were synchronized with the first population spike but this synchronization decreased with subsequent spikes. Histograms of the phase of the action potentials displayed a normal distribution. 4. Histograms of the phases of the action potentials following the application of the 'singular stimulus' (one producing a singular response) revealed a uniform distribution of the phases suggesting that the neuronal population was desynchronized. 5. This desynchronization effect of the singular stimulus was verified by double intracellular recordings. The simultaneous firing of two neurons could be desynchronized by the application of the singular stimulus. 6. These findings indicate that it is possible to desynchronize a neuronal pool with the application of a single current pulse. In addition, the results show that it is possible for a neuronal population to fire a large number of action potentials with no resulting evoked potentials in the extracellular space. Images Figure 2 Figure 4 Figure 7 Figure 8 PMID:7869266

  15. Blocking and guiding adult sea lamprey with pulsed direct current from vertical electrodes

    USGS Publications Warehouse

    Johnson, Nicholas S.; Thompson, Henry T.; Holbrook, Christopher M.; Tix, John A.

    2014-01-01

    Controlling the invasion front of aquatic nuisance species is of high importance to resource managers. We tested the hypothesis that adult sea lamprey (Petromyzon marinus), a destructive invasive species in the Laurentian Great Lakes, would exhibit behavioral avoidance to dual-frequency pulsed direct current generated by vertical electrodes and that the electric field would not injure or kill sea lamprey or non-target fish. Laboratory and in-stream experiments demonstrated that the electric field blocked sea lamprey migration and directed sea lamprey into traps. Rainbow trout (Oncorhynchus mykiss) and white sucker (Catostomus commersoni), species that migrate sympatrically with sea lamprey, avoided the electric field and had minimal injuries when subjected to it. Vertical electrodes are advantageous for fish guidance because (1) the electric field produced varies minimally with depth, (2) the electric field is not grounded, reducing power consumption to where portable and remote deployments powered by solar, wind, hydro, or a small generator are feasible, and (3) vertical electrodes can be quickly deployed without significant stream modification allowing rapid responses to new invasions. Similar dual-frequency pulsed direct current fields produced from vertical electrodes may be advantageous for blocking or trapping other invasive fish or for guiding valued fish around dams.

  16. High voltage pulsed current in collagen realignment, synthesis, and angiogenesis after Achilles tendon partial rupture

    PubMed Central

    Rampazo, Érika P.; Liebano, Richard E.; Pinfildi, Carlos Eduardo; Folha, Roberta A. C.; Ferreira, Lydia M.

    2016-01-01

    ABSTRACT Objective To verify the efficacy of high voltage pulsed current in collagen realignment and synthesis and in angiogenesis after the partial rupturing of the Achilles tendon in rats. Method Forty male Wistar rats were randomized into four groups of 10 animals each: sham, cathodic stimulation, anodic stimulation, and alternating stimulation. Their Achilles tendons were submitted to direct trauma by a free-falling metal bar. Then, the treatment was administered for six consecutive days after the injury. In the simulation group, the electrodes were positioned on the animal, but the device remained off for 30 minutes. The other groups used a frequency of 120 pps, sensory threshold, and the corresponding polarity. On the seventh day, the tendons were removed and sent for histological slide preparation for birefringence and Picrosirius Red analysis and for blood vessel quantification. Results No significant difference was observed among the groups regarding collagen realignment (types I or III collagen) or quantity of blood vessels. Conclusion High voltage pulsed current for six consecutive days was not effective in collagen realignment, synthesis, or angiogenesis after the partial rupturing of the Achilles tendon in rats. PMID:27556387

  17. Eddy Current Pulsed Thermography with Different Excitation Configurations for Metallic Material and Defect Characterization.

    PubMed

    Tian, Gui Yun; Gao, Yunlai; Li, Kongjing; Wang, Yizhe; Gao, Bin; He, Yunze

    2016-06-08

    This paper reviews recent developments of eddy current pulsed thermography (ECPT) for material characterization and nondestructive evaluation (NDE). Due to the fact that line-coil-based ECPT, with the limitation of non-uniform heating and a restricted view, is not suitable for complex geometry structures evaluation, Helmholtz coils and ferrite-yoke-based excitation configurations of ECPT are proposed and compared. Simulations and experiments of new ECPT configurations considering the multi-physical-phenomenon of hysteresis losses, stray losses, and eddy current heating in conjunction with uniform induction magnetic field have been conducted and implemented for ferromagnetic and non-ferromagnetic materials. These configurations of ECPT for metallic material and defect characterization are discussed and compared with conventional line-coil configuration. The results indicate that the proposed ECPT excitation configurations can be applied for different shapes of samples such as turbine blade edges and rail tracks.

  18. Biodiesel production from soybean oil deodorizer distillate enhanced by counter-current pulsed ultrasound.

    PubMed

    Yin, Xiulian; You, Qinghong; Ma, Haile; Dai, Chunhua; Zhang, Henan; Li, Kexin; Li, Yunliang

    2015-03-01

    Biodiesel production from soybean oil deodorizer distillate enhanced by counter-current pulsed ultrasound was studied. Effect of static probe ultrasonic enhanced transesterification (SPUE) and counter-current probe ultrasonic enhanced transesterification (CCPUE) on the biodiesel conversion were compared. The results indicated that CCPUE was a better method for enhancing transesterification. The working conditions of CCPUE were studied by single-factor experiment design and the results showed that the optimal conditions were: initial temperature 25 °C, methanol to triglyceride molar ratio 10:1, flow rate 200 mL/min, catalyst content 1.8%, ultrasound working on-time 4 s, off-time 2 s, total working time 50 min. Under these conditions, the average biodiesel conversion of three experiments was 96.1%.

  19. Eddy Current Pulsed Thermography with Different Excitation Configurations for Metallic Material and Defect Characterization.

    PubMed

    Tian, Gui Yun; Gao, Yunlai; Li, Kongjing; Wang, Yizhe; Gao, Bin; He, Yunze

    2016-01-01

    This paper reviews recent developments of eddy current pulsed thermography (ECPT) for material characterization and nondestructive evaluation (NDE). Due to the fact that line-coil-based ECPT, with the limitation of non-uniform heating and a restricted view, is not suitable for complex geometry structures evaluation, Helmholtz coils and ferrite-yoke-based excitation configurations of ECPT are proposed and compared. Simulations and experiments of new ECPT configurations considering the multi-physical-phenomenon of hysteresis losses, stray losses, and eddy current heating in conjunction with uniform induction magnetic field have been conducted and implemented for ferromagnetic and non-ferromagnetic materials. These configurations of ECPT for metallic material and defect characterization are discussed and compared with conventional line-coil configuration. The results indicate that the proposed ECPT excitation configurations can be applied for different shapes of samples such as turbine blade edges and rail tracks. PMID:27338389

  20. Biodiesel production from soybean oil deodorizer distillate enhanced by counter-current pulsed ultrasound.

    PubMed

    Yin, Xiulian; You, Qinghong; Ma, Haile; Dai, Chunhua; Zhang, Henan; Li, Kexin; Li, Yunliang

    2015-03-01

    Biodiesel production from soybean oil deodorizer distillate enhanced by counter-current pulsed ultrasound was studied. Effect of static probe ultrasonic enhanced transesterification (SPUE) and counter-current probe ultrasonic enhanced transesterification (CCPUE) on the biodiesel conversion were compared. The results indicated that CCPUE was a better method for enhancing transesterification. The working conditions of CCPUE were studied by single-factor experiment design and the results showed that the optimal conditions were: initial temperature 25 °C, methanol to triglyceride molar ratio 10:1, flow rate 200 mL/min, catalyst content 1.8%, ultrasound working on-time 4 s, off-time 2 s, total working time 50 min. Under these conditions, the average biodiesel conversion of three experiments was 96.1%. PMID:25199445

  1. Eddy Current Pulsed Thermography with Different Excitation Configurations for Metallic Material and Defect Characterization

    PubMed Central

    Tian, Gui Yun; Gao, Yunlai; Li, Kongjing; Wang, Yizhe; Gao, Bin; He, Yunze

    2016-01-01

    This paper reviews recent developments of eddy current pulsed thermography (ECPT) for material characterization and nondestructive evaluation (NDE). Due to the fact that line-coil-based ECPT, with the limitation of non-uniform heating and a restricted view, is not suitable for complex geometry structures evaluation, Helmholtz coils and ferrite-yoke-based excitation configurations of ECPT are proposed and compared. Simulations and experiments of new ECPT configurations considering the multi-physical-phenomenon of hysteresis losses, stray losses, and eddy current heating in conjunction with uniform induction magnetic field have been conducted and implemented for ferromagnetic and non-ferromagnetic materials. These configurations of ECPT for metallic material and defect characterization are discussed and compared with conventional line-coil configuration. The results indicate that the proposed ECPT excitation configurations can be applied for different shapes of samples such as turbine blade edges and rail tracks. PMID:27338389

  2. Structural and phase transformations in zinc and brass wires under heating with high-density current pulse

    NASA Astrophysics Data System (ADS)

    Pervikov, A. V.

    2016-06-01

    The work is focused on revealing the mechanism of structure and phase transformations in the metal wires under heating with a high-density current pulse (the electric explosion of wires, EEWs). It has been demonstrated on the example of brass and zinc wires that the transition of a current pulse with the density of j ≈ 3.3 × 107 A/cm2 results in homogeneous heating of the crystalline structure of the metal/alloy. It has been determined that under heating with a pulse of high-density current pulse, the electric resistance of the liquid phases of zinc and brass decreases as the temperature increases. The results obtained allow for a conclusion that the presence of the particles of the condensed phase in the expanding products of EEW is the result of overheating instabilities in the liquid metal.

  3. Analytical description of generation of the residual current density in the plasma produced by a few-cycle laser pulse

    SciTech Connect

    Silaev, A. A. Vvedenskii, N. V.

    2015-05-15

    When a gas is ionized by a few-cycle laser pulse, some residual current density (RCD) of free electrons remains in the produced plasma after the passage of the laser pulse. This quasi-dc RCD is an initial impetus to plasma polarization and excitation of the plasma oscillations which can radiate terahertz (THz) waves. In this work, the analytical model for calculation of RCD excited by a few-cycle laser pulse is developed for the first time. The dependences of the RCD on the carrier-envelope phase (CEP), wavelength, duration, and intensity of the laser pulse are derived. It is shown that maximum RCD corresponding to optimal CEP increases with the laser pulse wavelength, which indicates the prospects of using mid-infrared few-cycle laser pulses in the schemes of generation of high-power THz pulses. Analytical formulas for optimal pulse intensity and maximum efficiency of excitation of the RCD are obtained. Basing on numerical solution of the 3D time-dependent Schrödinger equation for hydrogen atoms, RCD dependence on CEP is calculated in a wide range of wavelengths. High accuracy of analytical formulas is demonstrated at the laser pulse parameters which correspond to the tunneling regime of ionization.

  4. Magnetic properties of pulse-reverse electrodeposited nanocrystalline NiFe/Cu composite wires in relation to the anodic current

    NASA Astrophysics Data System (ADS)

    Seet, H. L.; Li, X. P.; Lee, K. S.; Chia, H. Y.; Zheng, H. M.; Ng, W. C.

    2007-12-01

    Ni80Fe20/Cu composite wires were developed using the pulse-reverse electrodeposition technique with the cathodic (positive) current Ic fixed at 1 mA and the anodic (negative) current IA varied from 10 to 90% of Ic. The relationship between the magnetic properties of pulse reverse electrodeposited nanocrystalline NiFe/Cu composite wires and the anodic current was investigated. The results showed that the smaller the magnitude of the anodic current, the smaller was the average nanocrystalline grain size of the deposited material and the better was the uniformity of the surface, and consequently, the better the magnetic properties.

  5. Efficient Charging of Li‐Ion Batteries with Pulsed Output Current of Triboelectric Nanogenerators

    PubMed Central

    Pu, Xiong; Liu, Mengmeng; Li, Linxuan; Zhang, Chi; Pang, Yaokun; Jiang, Chunyan; Shao, Lihua

    2016-01-01

    The triboelectric nanogenerator (TENG) is a promising mechanical energy harvesting technology, but its pulsed output and the instability of input energy sources make associated energy‐storage devices necessary for real applications. In this work, feasible and efficient charging of Li‐ion batteries by a rotating TENG with pulsed output current is demonstrated. In‐depth discussions are made on how to maximize the power‐storage efficiency by achieving an impedance match between the TENG and a battery with appropriate design of transformers. With a transformer coil ratio of 36.7, ≈72.4% of the power generated by the TENG at 250 rpm can be stored in an LiFePO4–Li4Ti5O12 battery. Moreover, a 1 h charging of an LiCoO2–C battery by the TENG at 600 rpm delivers a discharge capacity of 130 mAh, capable of powering many smart electronics. Considering the readily scale‐up capability of the TENG, promising applications in personal electronics can be anticipated in the near future.

  6. Guiding out-migrating juvenile sea lamprey (Petromyzon marinus) with pulsed direct current

    USGS Publications Warehouse

    Johnson, Nicholas S.; Miehls, Scott M.

    2014-01-01

    Non-physical stimuli can deter or guide fish without affecting water flow or navigation and therefore have been investigated to improve fish passage at anthropogenic barriers and to control movement of invasive fish. Upstream fish migration can be blocked or guided without physical structure by electrifying the water, but directional downstream fish guidance with electricity has received little attention. We tested two non-uniform pulsed direct current electric systems, each having different electrode orientations (vertical versus horizontal), to determine their ability to guide out-migrating juvenile sea lamprey (Petromyzon marinus) and rainbow trout (Oncorhynchus mykiss). Both systems guided significantly more juvenile sea lamprey to a specific location in our experimental raceway when activated than when deactivated, but guidance efficiency decreased at the highest water velocities tested. At the electric field setting that effectively guided sea lamprey, rainbow trout were guided by the vertical electrode system, but most were blocked by the horizontal electrode system. Additional research should characterize the response of other species to non-uniform fields of pulsed DC and develop electrode configurations that guide fish over a range of water velocity.

  7. Twenty-Four-Hour Ambulatory Pulse Wave Analysis in Hypertension Management: Current Evidence and Perspectives.

    PubMed

    Omboni, Stefano; Posokhov, Igor N; Kotovskaya, Yulia V; Protogerou, Athanase D; Blacher, Jacques

    2016-10-01

    The predictive value of vascular biomarkers such as pulse wave velocity (PWV), central arterial pressure (CAP), and augmentation index (AIx), obtained through pulse wave analysis (PWA) in resting conditions, has been documented in a variety of patient groups and populations. This allowed to make appropriate recommendations in clinical practice guidelines of several scientific societies. Due to advances in technologies, largely operator-independent methods are currently available for estimating vascular biomarkers also in ambulatory conditions, over the 24 h. According to the acceptable accuracy and reproducibility of 24-h ambulatory PWA, it appears to be a promising tool for evaluating vascular biomarkers in daily life conditions. This approach may provide an opportunity to further improve the early cardiovascular screening in subjects at risk. However, concerning the clinical use of PWA over the 24 h in ambulatory conditions at the moment, there is no sufficient evidence to support its routine clinical use. In particular, long-term outcome studies are needed to show the predictive value of 24-h PWV, CAP, and AIx values, provided by these devices, over and beyond peripheral blood pressure, and to answer the many technical and clinical questions still open. To this regard, the VASOTENS Registry, an international observational prospective study recently started, will help providing answers on a large sample of hypertensive patients recruited worldwide. PMID:27659178

  8. Effect of anodal high voltage pulsed current on edema formation in frog hind limbs.

    PubMed

    Fish, D R; Mendel, F C; Schultz, A M; Gottstein-Yerke, L M

    1991-10-01

    We have recently demonstrated that some forms of cathodal high voltage pulsed current (HVPC) curb posttraumatic edema formation in frog hind limbs. The purpose of this study was to determine, by assessing the capacity of anodal HVPC to curb posttraumatic edema formation, whether polarity is an important variable. Fourteen anesthetized bullfrogs were placed on large dispersive electrodes lining body slings that maintained the frogs' limbs in a dependent position throughout data collection. The frogs' feet were traumatized by impact following initial measurement of limb volumes. At the commencement of each of four 30-minute treatments, hind limbs were immersed in separate beakers and briefly stimulated until motor threshold was determined. One limb, randomly selected, received anodal HVPC at 90% of motor threshold and 120 pulses per second; the other limb served as a control. Treatments were followed by 30-minute rests. Limb volumes were measured by water displacement immediately after trauma and following each treatment and rest period. Data were expressed as changes from pretrauma volumes in milliliters per kilogram of body weight. A repeated-measures analysis of variance was used to test for treatment effect. Despite an aggressive series of treatments, virtually symmetrical bilateral edema occurred; therefore, no treatment effect was evident. This result contrasts with treatment effects previously reported for cathodal HVPC.

  9. Dynamic analysis of the parallel-plate EMP (Electromagnetic Pulse) simulator using a wire-mesh approximation and the numerical electromagnetics code. Final report

    SciTech Connect

    Gedney, S.D.

    1987-09-01

    The electromagnetic pulse (EMP) produced by a high-altitude nuclear blast presents a severe threat to electronic systems due to its extreme characteristics. To test the vulnerability of large systems, such as airplanes, missiles, or satellites, they must be subjected to a simulated EMP environment. One type of simulator that has been used to approximate the EMP environment is the Large Parallel-Plate Bounded-Wave Simulator. It is a guided-wave simulator which has properties of a transmission line and supports a single TEM model at sufficiently low frequencies. This type of simulator consists of finite-width parallel-plate waveguides, which are excited by a wave launcher and terminated by a wave receptor. This study addresses the field distribution within a finite-width parallel-plate waveguide that is matched to a conical tapered waveguide at either end. Characteristics of a parallel-plate bounded-wave EMP simulator were developed using scattering theory, thin-wire mesh approximation of the conducting surfaces, and the Numerical Electronics Code (NEC). Background is provided for readers to use the NEC as a tool in solving thin-wire scattering problems.

  10. Cranial electrotherapy stimulation and transcranial pulsed current stimulation: a computer based high-resolution modeling study.

    PubMed

    Datta, Abhishek; Dmochowski, Jacek P; Guleyupoglu, Berkan; Bikson, Marom; Fregni, Felipe

    2013-01-15

    The field of non-invasive brain stimulation has developed significantly over the last two decades. Though two techniques of noninvasive brain stimulation--transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS)--are becoming established tools for research in neuroscience and for some clinical applications, related techniques that also show some promising clinical results have not been developed at the same pace. One of these related techniques is cranial electrotherapy stimulation (CES), a class of transcranial pulsed current stimulation (tPCS). In order to understand further the mechanisms of CES, we aimed to model CES using a magnetic resonance imaging (MRI)-derived finite element head model including cortical and also subcortical structures. Cortical electric field (current density) peak intensities and distributions were analyzed. We evaluated different electrode configurations of CES including in-ear and over-ear montages. Our results confirm that significant amounts of current pass the skull and reach cortical and subcortical structures. In addition, depending on the montage, induced currents at subcortical areas, such as midbrain, pons, thalamus and hypothalamus are of similar magnitude than that of cortical areas. Incremental variations of electrode position on the head surface also influence which cortical regions are modulated. The high-resolution modeling predictions suggest that details of electrode montage influence current flow through superficial and deep structures. Finally we present laptop based methods for tPCS dose design using dominant frequency and spherical models. These modeling predictions and tools are the first step to advance rational and optimized use of tPCS and CES.

  11. Influence of electric current pulses on the solidification of Cu-Bi-Sn immiscible alloys

    PubMed Central

    Hongxiang, Jiang; Jie, He; Jiuzhou, Zhao

    2015-01-01

    Continuous solidification experiments were carried out with Cu-Bi-Sn alloys under the effects of Electric Current Pulses (ECPs). A model describing the microstructure evolution was developed. The formation of the microstructure in the continuously solidified alloys was calculated. The calculations demonstrated that ECPs mainly affect the solidification process through changing the energy barrier for the nucleation of the minority phase droplets (MPDs). When the matrix liquid has a lower electric conductivity compared to the MPD, the ECPs lead to a decrease in the energy barrier for the nucleation of the MPDs which then promote the formation of a finely dispersed microstructure. When the matrix liquid has a higher electric conductivity compared to the MPD, the ECPs cause an increase in the energy barrier for the nucleation and lead to the formation of a phase segregated microstructure. PMID:26228180

  12. Pulsed eddy current and ultrasonic data fusion applied to stress measurement

    NASA Astrophysics Data System (ADS)

    Habibalahi, A.; Safizadeh, M. S.

    2014-05-01

    Stress measurement and its variation are key problems in the operating performance of materials. Stress can affect the material properties and the life of components. There are several destructive and nondestructive techniques that are used to measure stress. However, no single nondestructive testing (NDT) technique or method is satisfactory to fully assess stress. This paper presents an NDT data fusion method to improve stress measurement. An aluminum alloy 2024 specimen subjected to stress simulation is nondestructively inspected using pulsed eddy current and ultrasonic techniques. Following these nondestructive examinations, the information gathered from these two NDT methods has been fused using a suitable fuzzy combination operator. The results obtained with these processes are presented in this paper and their efficiency is discussed. It is shown that the fusion of NDT data with a suitable fuzzy operator can be adequate to improve the reliability of stress measurements.

  13. Influence of sulfides on the tribological properties of composites produced by pulse electric current sintering

    NASA Astrophysics Data System (ADS)

    Kim, Seung Ho

    2014-01-01

    Self-lubricating Al2O3-15wt% ZrO2 composites with sulfides, such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) serving as solid lubricants, were fabricated by using the pulse electric current sintering (PECS) technique. The coefficient of friction (COF) of the Al2O3-15wt% ZrO2 composite without/with sulfides was in the range of 0.37-0.48 and 0.27-0.49, respectively. As the amount of sulfides increased, the COF and the wear rate decreased. The reduction in COF and wear rate of the sulfide-containing composite is caused by a reduction in shear stresses between the specimen and the tribological medium due to the formation of a lubricating film resulting from the lamellar structure of sulfides located on the worn surface.

  14. Microstructure Analysis of HPb59-1 Brass Induced by High Current Pulsed Electron Beam

    NASA Astrophysics Data System (ADS)

    Lyu, Jike; Gao, Bo; Hu, Liang; Lu, Shuaidan; Tu, Ganfeng

    2016-08-01

    In this paper, the effects of high current pulsed electron beam (HCPEB) on the microstructure evolution of casting HPb59-1 (Cu 57.1 mass%, Pb 1.7 mass% and Zn balance) alloy were investigated. The results showed a "wavy" surface which was formed with Pb element existing in the forms of stacking block and microparticles on the top surface layer after treatment. Nanocrystalline structures including Pb grains and two phases (α and β) were formed on the top remelted layer and their sizes were all less than 100 nm. The disordered β phase was generated in the surface layer after HCPEB treatment, which is beneficial for the improvement of surface properties. Meanwhile, there was a large residual stress on the alloy surface, along with the appearance of microcracks, and the preferred orientations of grains also changed.

  15. Subionospheric propagation and peak currents of preliminary breakdown pulses before negative cloud-to-ground lightning discharges

    NASA Astrophysics Data System (ADS)

    Kolmašová, Ivana; Santolík, Ondřej; Farges, Thomas; Cummer, Steven A.; Lán, Radek; Uhlíř, Luděk.

    2016-02-01

    We analyze broadband electromagnetic measurements of pulse sequences occurring prior to first return strokes of negative cloud-to-ground lightning flashes. Signals generated by lightning discharges were recorded close to the thunderstorm by a magnetic field receiver and traveled up to 600 km to three distant electric field receivers. We found that amplitudes of observed preliminary breakdown pulses, as well as amplitudes of the corresponding return strokes, are attenuated approximately by 2 dB/100 km when propagating in the Earth-ionosphere waveguide over mountainous terrain. Propagation simulations show that there is a significant contribution of the sky wave signals in the waveforms observed beyond 500 km from their source. The estimated peak currents of the largest preliminary breakdown pulses reach over 60 kA. Such current pulses propagating through in-cloud lightning leader channels in a strong electric field may be able to initiate terrestrial gamma ray flashes.

  16. Use of Additional Needle Pulses Using Electrical Discharge Machining

    NASA Astrophysics Data System (ADS)

    Schulze, Hans-Peter; Juhr, Henrik; Haas, Rüdiger

    2011-05-01

    The influence exerted by the longer rectangular pulses with additional Needle Pulses. Needle pulses for the spark erosion are the fundamental of the erosion pulses with pulse durations smaller 1 μs and high current-rise-velocity (ramp unit). In this shorter pulse-duration it is possible to use higher current densities; without composition of the thermal-affected zones. The technological advantage is a higher productivity because the higher pulse energy and parallel a better quality of the processing area exist; an additional factor for the higher productivity is the smaller number of back-cuts for the finish quality of the cut.

  17. Transient-spatial pattern mining of eddy current pulsed thermography using wavelet transform

    NASA Astrophysics Data System (ADS)

    Yang, Hailong; Gao, Bin; Tian, Guiyun; Ren, Wenwei; Woo, Wai Lok

    2014-07-01

    Eddy current pulsed thermography(ECPT) is an emerging Non-destructive testing and evaluation(NDT & E) technique, which uses hybrid eddy current and thermography NDT & E techniques that enhances the detectability from their compensation. Currently, this technique is limited by the manual selection of proper contrast frames and the issue of improving the efficiency of defect detection of complex structure samples remains a challenge. In order to select a specific frame from transient thermal image sequences to maximize the contrast of thermal variation and defect pattern from complex structure samples, an energy driven approach to compute the coefficient energy of wavelet transform is proposed which has the potential of automatically selecting both optimal transient frame and spatial scale for defect detection using ECPT. According to analysis of the variation of different frequency component and the comparison study of the detection performance of different scale and wavelets, the frame at the end of heating phase is automatically selected as an optimal transient frame for defect detection. In addition, the detection capabilities of the complex structure samples can be enhanced through proper spatial scale and wavelet selection. The proposed method has successfully been applied to low speed impact damage detection of carbon fibre reinforced polymer(CFRP) composite as well as providing the guidance to improve the detectability of ECPT technique.

  18. Mechanism of formation of subnanosecond current front in high-voltage pulse open discharge

    NASA Astrophysics Data System (ADS)

    Schweigert, I. V.; Alexandrov, A. L.; Zakrevsky, Dm. E.; Bokhan, P. A.

    2014-11-01

    The mechanism of subnanosecond current front rise observed previously in the experiment in high-voltage pulse open discharge in helium is studied in kinetic particle-in-cell simulations. The Boltzmann equations for electrons, ions, and fast atoms are solved self-consistently with the Poisson equations for the electrical potential. The partial contributions to the secondary electron emission from the ions, fast atoms, photons, and electrons, bombarding the electrode, are calculated. In simulations, as in the experiment, the discharge glows between two symmetrical cathodes and the anode grid in the midplane at P =6 Torr and the applied voltage of 20 kV. The electron avalanche development is considered for two experimental situations during the last stage of breakdown: (i) with constant voltage and (ii) with decreasing voltage. For case (i), the subnanosecond current front rise is set by photons from the collisional excitation transfer reactions. For the case (ii), the energetic electrons swamp the cathode during voltage drop and provide the secondary electron emission for the subnanosecond current rise, observed in the experiment.

  19. Electrodeposition and characterization of Ni-ZrO2 nanocomposites by direct and pulse current methods.

    PubMed

    Kumar, K Arunsunai; Mohan, P; Kalaignan, G Paruthimal; Muralidharan, V S

    2012-11-01

    Direct Current (DC) and Pulse current (PC) methods were used to get nanocrystalline Ni-ZrO2 composites from tri-ammonium citrate bath. In the electrocomposite formation, the ZrO2 particles were transported to the surface by mechanical action and got entrapped in the nickel matrix. Incorporation of ZrO2 in the nickel matrix was found to increase with current densities when DC was employed. Beyond 2 A/dm2, their incorporation became saturated when PC was used. PC method offered better electrocomposites than DC method producing finer grains and uniform surface. Scanning electron micrographs (SEM) reveals that smaller grains and uniform distribution of Zirconia particles in the nickel matrix. The increased hardness of Ni-ZrO2 electrocomposite coatings is due to incorporation of ZrO2 particles in the nickel matrix and also changes in grain size. Incorporation of ZrO2 particles in Ni-matrix favoured the enhanced microhardness and corrosion resistance of the deposit.

  20. Characterization of carbon fiber polymer matrix composites subjected to simultaneous application of electric current pulse and low velocity impact

    NASA Astrophysics Data System (ADS)

    Hart, Robert James

    2011-12-01

    The use of composite materials in aerospace, electronics, and wind industries has become increasingly common, and these composite components are required to carry mechanical, electrical, and thermal loads simultaneously. A unique property of carbon fiber composites is that when an electric current is applied to the specimen, the mechanical strength of the specimen increases. Previous studies have shown that the higher the electric current, the greater the increase in impact strength. However, as current passes through the composite, heat is generated through Joule heating. This Joule heating can cause degradation of the composite and thus a loss in strength. In order to minimize the negative effects of heating, it is desired to apply a very high current for a very short duration of time. This thesis investigated the material responses of carbon fiber composite plates subjected to electrical current pulse loads of up to 1700 Amps. For 32 ply unidirectional IM7/977-3 specimens, the peak impact load and absorbed energy increased slightly with the addition of a current pulse at the time of an impact event. In 16 ply cross-ply IM7/977-2 specimens, the addition of the current pulse caused detrimental effects due to electrical arcing at the interface between the composite and electrodes. Further refinement of the experimental setup should minimize the risk of electrical arcing and should better elucidate the effects of a current pulse on the impact strength of the specimens.

  1. Column buckling of doubly parallel slender nanowires carrying electric current acted upon by a magnetic field

    NASA Astrophysics Data System (ADS)

    Kiani, Keivan

    2016-08-01

    Axial buckling of current-carrying double-nanowire-systems immersed in a longitudinal magnetic field is aimed to be explored. Each nanowire is affected by the magnetic forces resulted from the externally exerted magnetic field plus the magnetic field resulted from the passage of electric current through the adjacent nanowire. To study the problem, these forces are appropriately evaluated in terms of transverse displacements. Subsequently, the governing equations of the nanosystem are constructed using Euler-Bernoulli beam theory in conjunction with the surface elasticity theory of Gurtin and Murdoch. Using a meshless technique and assumed mode method, the critical compressive buckling load of the nanosystem is determined. In a special case, the obtained results by these two numerical methods are successfully checked. The roles of the slenderness ratio, electric current, magnetic field strength, and interwire distance on the axial buckling load and stability behavior of the nanosystem are displayed and discussed in some detail.

  2. Electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

    NASA Technical Reports Server (NTRS)

    Ganguli, G.; Palmadesso, P. J.

    1988-01-01

    The electrostatic ion instabilities are studied for oblique propagation in the presence of magnetic field-aligned currents and transverse localized electric fields in a weakly collisional plasma. The presence of transverse electric fields result in mode excitation for magnetic field aligned current values that are otherwise stable. The electron collisions enhance the growth while ion collisions have a damping effect. These results are discussed in the context of observations of low frequency ion modes in the auroral ionosphere by radar and rocket experiments.

  3. Current pulse amplifier transmits detector signals with minimum distortion and attenuation

    NASA Technical Reports Server (NTRS)

    Bush, N. E.

    1967-01-01

    Amplifier translates the square pulses generated by a boron-trifluoride neutron sensitive detector located adjacent to a nuclear reactor to slower, long exponential decay pulses. These pulses are transmitted over long coaxial cables with minimum distortion and loss of frequency.

  4. Avalanche current read-out circuit for low jitter parallel photon timing.

    PubMed

    Crotti, M; Rech, I; Gulinatti, A; Ghioni, M

    2013-08-01

    We propose a novel circuit for single photon avalanche diode (SPAD) current read-out, for photon timing applications. The circuit consists of a single transistor trans-impedance amplifier with a GHz bandwidth: the feedback loop fixes the SPAD anode voltage and allows us to obtain a high time resolution with a very high equivalent current threshold (almost 700 μA). The trans-impedance stage is followed by a low pass filter that reduces the crosstalk of other on-chip detectors and makes the designed structure suitable for multi-detector systems. The discrete components prototype presented in this letter achieves a state-of-art resolution of 34.4 ps FWHM, presents negligible crosstalk between the different pixels and opens the way for the development of an integrated structure with a large number of channels.

  5. Characterization of a high current pulsed arc using optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Sousa Martins, R.; Zaepffel, C.; Chemartin, L.; Lalande, Ph; Soufiani, A.

    2016-10-01

    In this paper, we present the investigation realized on an experimental setup that simulates an arc column subjected to the transient phase of a lightning current waveform in laboratory conditions. Optical emission spectroscopy is employed to assess space- and time-resolved properties of this high current pulsed arc. Different current peak levels are utilised in this work, ranging from 10 kA to 100 kA, with a peak time around 15 µs. Ionic lines of nitrogen and oxygen are used to determine the radial profiles of temperature and electron density of the arc channel over time from 2 µs to 36 µs. A combination of 192 N II and O II lines is considered in the calculation of the bound-bound contribution of the absorption coefficient of the plasma channel. Calculations of the optical thickness showed that self-absorption of these ionic lines in the arc column is important. To obtain temperature and electron density profiles in the arc, we solved the radiative transfer equation across the channel under an axisymmetric assumption and considering the channel formed by uniform concentric layers. For the 100 kA current peak level, the temperature reaches more than 38 000 K and the electron density reaches 5  ×  1018 cm-3. The pressure inside the channel is calculated using the air plasma composition at local thermodynamic equilibrium, and reaches 45 bar. The results are discussed and utilised to estimate the electrical conductivity of the arc channel.

  6. Electron beam dynamics in the long-pulse, high-current DARHT-II linear induction accelerator

    SciTech Connect

    Ekdahl, Carl A; Abeyta, Epifanio O; Aragon, Paul; Archuleta, Rita; Cook, Gerald; Dalmas, Dale; Esquibel, Kevin; Gallegos, Robert A; Garnett, Robert; Harrison, James F; Johnson, Jeffrey B; Jacquez, Edward B; Mccuistian, Brian T; Montoya, Nicholas A; Nath, Subrato; Nielsen, Kurt; Oro, David; Prichard, Benjamin; Rowton, Lawrence; Sanchez, Manolito; Scarpetti, Raymond; Schauer, Martin M; Seitz, Gerald; Schulze, Martin; Bender, Howard A; Broste, William B; Carlson, Carl A; Frayer, Daniel K; Johnson, Douglas E; Tom, C Y; Williams, John; Hughes, Thomas; Anaya, Richard; Caporaso, George; Chambers, Frank; Chen, Yu - Jiuan; Falabella, Steve; Guethlein, Gary; Raymond, Brett; Richardson, Roger; Trainham, C; Weir, John; Genoni, Thomas; Toma, Carsten

    2009-01-01

    The DARHT-II linear induction accelerator (LIA) now accelerates 2-kA electron beams to more than 17 MeV. This LIA is unique in that the accelerated current pulse width is greater than 2 microseconds. This pulse has a flat-top region where the final electron kinetic energy varies by less than 1% for more than 1.5 microseconds. The long risetime of the 6-cell injector current pulse is 0.5 {micro}s, which can be scraped off in a beam-head cleanup zone before entering the 68-cell main accelerator. We discuss our experience with tuning this novel accelerator; and present data for the resulting beam transport and dynamics. We also present beam stability data, and relate these to previous stability experiments at lower current and energy.

  7. Excitation of low-frequency residual currents at combination frequencies of an ionising two-colour laser pulse

    NASA Astrophysics Data System (ADS)

    Vvedenskii, N. V.; Kostin, V. A.; Laryushin, I. D.; Silaev, A. A.

    2016-05-01

    We have studied the processes of excitation of low-frequency residual currents in a plasma produced through ionisation of gases by two-colour laser pulses in laser-plasma schemes for THz generation. We have developed an analytical approach that allows one to find residual currents in the case when one of the components of a two-colour pulse is weak enough. The derived analytical expressions show that the effective generation of the residual current (and hence the effective THz generation) is possible if the ratio of the frequencies in the two-colour laser pulse is close to a rational fraction with a not very big odd sum of the numerator and denominator. The results of numerical calculations (including those based on the solution of the three-dimensional time-dependent Schrödinger equation) agree well with the analytical results.

  8. Reconstruction of stress corrosion cracks using signals of pulsed eddy current testing

    NASA Astrophysics Data System (ADS)

    Wang, Li; Xie, Shejuan; Chen, Zhenmao; Li, Yong; Wang, Xiaowei; Takagi, Toshiyuki

    2013-06-01

    A scheme to apply signals of pulsed eddy current testing (PECT) to reconstruct a deep stress corrosion crack (SCC) is proposed on the basis of a multi-layer and multi-frequency reconstruction strategy. First, a numerical method is introduced to extract conventional eddy current testing (ECT) signals of different frequencies from the PECT responses at different scanning points, which are necessary for multi-frequency ECT inversion. Second, the conventional fast forward solver for ECT signal simulation is upgraded to calculate the single-frequency pickup signal of a magnetic field by introducing a strategy that employs a tiny search coil. Using the multiple-frequency ECT signals and the upgraded fast signal simulator, we reconstructed the shape profiles and conductivity of an SCC at different depths layer-by-layer with a hybrid inversion scheme of the conjugate gradient and particle swarm optimisation. Several modelled SCCs of rectangular or stepwise shape in an SUS304 plate are reconstructed from simulated PECT signals with artificial noise. The reconstruction results show better precision in crack depth than the conventional ECT inversion method, which demonstrates the validity and efficiency of the proposed PECT inversion scheme.

  9. Pulsed remote field eddy current technique applied to non-magnetic flat conductive plates

    NASA Astrophysics Data System (ADS)

    Yang, Binfeng; Zhang, Hui; Zhang, Chao; Zhang, Zhanbin

    2013-12-01

    Non-magnetic metal plates are widely used in aviation and industrial applications. The detection of cracks in thick plate structures, such as multilayered structures of aircraft fuselage, has been challenging in nondestructive evaluation societies. The remote field eddy current (RFEC) technique has shown advantages of deep penetration and high sensitivity to deeply buried anomalies. However, the RFEC technique is mainly used to evaluate ferromagnetic tubes. There are many problems that should be fixed before the expansion and application of this technique for the inspection of non-magnetic conductive plates. In this article, the pulsed remote field eddy current (PRFEC) technique for the detection of defects in non-magnetic conducting plates was investigated. First, the principle of the PRFEC technique was analysed, followed by the analysis of the differences between the detection of defects in ferromagnetic and non-magnetic plain structures. Three different models of the PRFEC probe were simulated using ANSYS. The location of the transition zone, defect detection sensitivity and the ability to detect defects in thick plates using three probes were analysed and compared. The simulation results showed that the probe with a ferrite core had the highest detecting ability. The conclusions derived from the simulation study were also validated by conducting experiments.

  10. Enhancing pulsed eddy current for inspection of P-3 Orion lap-joint structures

    NASA Astrophysics Data System (ADS)

    Butt, D. M.; Underhill, P. R.; Krause, T. W.

    2016-02-01

    During flight, aircraft are subjected to cyclic loading. In the Lockheed P-3 Orion airframe, this cyclic loading can lead to development of fatigue cracks at steel fastener locations in the top and second layers of aluminum wing skin lap-joints. An inspection method that is capable of detecting these cracks, without fastener removal, is desirable as this can minimize aircraft downtime, while subsequently reducing the risk of collateral damage. The ability to detect second layer cracks has been demonstrated using a Pulsed Eddy Current (PEC) probe design that utilizes the ferrous fastener as a flux conduit. This allows for deeper penetration of flux into the lap-joint second layer and consequently, sensitivity to the presence of cracks. Differential pick-up coil pairs are used to sense the eddy current response due to the presence of a crack. The differential signal obtained from pick-up coils on opposing sides of the fastener is analyzed using a Modified Principal Components Analysis (MPCA). This is followed by a cluster analysis of the resulting MPCA scores to separate fastener locations with cracks from those without. Probe design features, data acquisition system parameters and signal post-processing can each have a strong impact on crack detection. Physical probe configurations and signal analysis processes, used to enhance the PEC system for detection of cracks in P-3 Orion lap-joint structures, are investigated and an enhanced probe design is identified.

  11. Hybrid monitor for both beam position and tilt of pulsed high-current beams

    SciTech Connect

    Pang, J. He, X.; Ma, C.; Zhao, L.; Li, Q.; Dai, Z.

    2014-09-15

    A Hybrid beam monitor, integrated with both azimuthal and axial B-dot probes, was designed for simultaneous measurement of both beam position and beam angle for pulsed high-current beams at the same location in beam pipe. The output signals of axial B-dot probes were found to be mixed with signals caused by transverse position deviation. In order to eliminate the unwanted signals, an elimination method was developed and its feasibility tested on a 50-Ω coaxial line test stand. By this method, a waveform, shape-like to that of input current and proportional to the tilt angle, was simulated and processed by following integration step to achieve the tilt angle. The tests showed that the measurement error of displacement and tilt angle less than 0.3 mm and 1.5 mrad, respectively. The latter error could be reduced with improved probes by reducing the inductance of the axial B-dot probe, but the improvement reached a limit due to some unknown systemic mechanism.

  12. Analysis of pulsed eddy current data using regression models for steam generator tube support structure inspection

    NASA Astrophysics Data System (ADS)

    Buck, J. A.; Underhill, P. R.; Morelli, J.; Krause, T. W.

    2016-02-01

    Nuclear steam generators (SGs) are a critical component for ensuring safe and efficient operation of a reactor. Life management strategies are implemented in which SG tubes are regularly inspected by conventional eddy current testing (ECT) and ultrasonic testing (UT) technologies to size flaws, and safe operating life of SGs is predicted based on growth models. ECT, the more commonly used technique, due to the rapidity with which full SG tube wall inspection can be performed, is challenged when inspecting ferromagnetic support structure materials in the presence of magnetite sludge and multiple overlapping degradation modes. In this work, an emerging inspection method, pulsed eddy current (PEC), is being investigated to address some of these particular inspection conditions. Time-domain signals were collected by an 8 coil array PEC probe in which ferromagnetic drilled support hole diameter, depth of rectangular tube frets and 2D tube off-centering were varied. Data sets were analyzed with a modified principal components analysis (MPCA) to extract dominant signal features. Multiple linear regression models were applied to MPCA scores to size hole diameter as well as size rectangular outer diameter tube frets. Models were improved through exploratory factor analysis, which was applied to MPCA scores to refine selection for regression models inputs by removing nonessential information.

  13. Pulsed Direct Current Electric Fields Enhance Osteogenesis in Adipose-Derived Stromal Cells

    PubMed Central

    Hammerick, Kyle E.; James, Aaron W.; Huang, Zubin; Prinz, Fritz B.

    2010-01-01

    Adipose-derived stromal cells (ASCs) constitute a promising source of cells for regenerative medicine applications. Previous studies of osteogenic potential in ASCs have focused on chemicals, growth factors, and mechanical stimuli. Citing the demonstrated role electric fields play in enhancing healing in bone fractures and defects, we investigated the ability of pulsed direct current electric fields to drive osteogenic differentiation in mouse ASCs. Employing 50 Hz direct current electric fields in concert with and without osteogenic factors, we demonstrated increased early osteoblast-specific markers. We were also able to establish that commonly reported artifacts of electric field stimulation are not the primary mediators of the observed effects. The electric fields caused marked changes in the cytoskeleton. We used atomic force microscopy–based force spectroscopy to record an increase in the cytoskeletal tension after treatment with electric fields. We abolished the increased cytoskeletal stresses with the rho-associated protein kinase inhibitor, Y27632, and did not see any decrease in osteogenic gene expression, suggesting that the pro-osteogenic effects of the electric fields are not transduced via cytoskeletal tension. Electric fields may show promise as candidate enhancers of osteogenesis of ASCs and may be incorporated into cell-based strategies for skeletal regeneration. PMID:19824802

  14. Fabrication process and electrical characterization of direct current parallel micro-discharges in helium

    NASA Astrophysics Data System (ADS)

    Mandra, M.; Dussart, R.; Lee, J.-B.; Goeckner, M.; Dufour, T.; Lefaucheux, P.; Ranson, P.; Overzet, L.

    2007-10-01

    Micro Hollow Cathode Discharges (MHCD) have been fabricated. They are round holes through 250 μm or 500 μm thick Nickel-Alumina-Nickel surfaces. The base surfaces are constructed from 7.5 X 7.5 cm alumina wafers, which are vacuum baked then coated with chromium and copper seed layers and finally patterned. Nickel film, 5-6 um thick, is then deposited on either side of the alumina wafer using the process of electroplating. Single and multi cavity micro discharges are then laser drilled with diameters ranging from 130 μm to 300 μm and spacing between the cavities ranging from 245 μm to 315 μm. Breakdown vs. pressure measurements show that smaller diameter cavities (130 μm) have higher breakdown voltages than cavities with larger diameter (300 μm). In addition, the difference between the breakdown voltage and the operating voltage is substantially larger. Current-voltage measurements for single hole MHCD devices indicates that they operate in the normal glow regime with decreasing discharge voltage as discharge current is increased.

  15. Accelerated Cardiac T2 Mapping using Breath-hold Multi-Echo Fast Spin-Echo Pulse Sequence with Compressed sensing and Parallel Imaging

    PubMed Central

    Feng, Li; Otazo, Ricardo; Jung, Hong; Jensen, Jens H.; Ye, Jong C.; Sodickson, Daniel K.; Kim, Daniel

    2010-01-01

    Cardiac T2 mapping is a promising method for quantitative assessment of myocardial edema and iron overload. We have developed a new multi-echo fast spin echo (ME-FSE) pulse sequence for breath-hold T2 mapping with acceptable spatial resolution. We propose to further accelerate this new ME-FSE pulse sequence using k-t FOCal Underdetermined System Solver (FOCUSS) adapted with a framework that utilizes both compressed sensing and parallel imaging (.e.g, GRAPPA) to achieve higher spatial resolution. We imaged twelve control subjects in mid-ventricular short-axis planes and compared the accuracy of T2 measurements obtained using ME-FSE with GRAPPA and ME-FSE with k-t FOCUSS. For image reconstruction, we used a bootstrapping two-step approach, where in the first step fast Fourier transform was used as the sparsifying transform and in the final step principal component analysis was used as the sparsifying transform. Compared with T2 measurements obtained using GRAPPA, T2 measurements obtained using k-t FOCUSS were in excellent agreement (mean difference = 0.04 ms; upper/lower 95% limits of agreement were 2.26/−2.19 ms). The proposed accelerated ME-FSE pulse sequence with k-t FOCUSS is a promising investigational method for rapid T2 measurement of the heart with relatively high spatial resolution (1.7 mm × 1.7 mm). PMID:21360737

  16. Eddy current pulsed phase thermography considering volumetric induction heating for delamination evaluation in carbon fiber reinforced polymers

    NASA Astrophysics Data System (ADS)

    Yang, Ruizhen; He, Yunze

    2015-06-01

    Anisotropy and inhomogeneity of carbon fiber reinforced polymers (CFRPs) result in that many traditional non-destructive inspection techniques are inapplicable on the delamination evaluation. This letter introduces eddy current pulsed phase thermography (ECPPT) for CFRPs evaluation considering volumetric induction heating due to small electrical conductivity, abnormal thermal wave propagation, and Fourier analysis. The proposed methods were verified through experimental studies under transmission and reflection modes. Using ECPPT, the influence of the non-uniform heating effect and carbon fiber structures can be suppressed, and then delamination detectability can be improved dramatically over eddy current pulsed thermography.

  17. Simulation of electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Ganguli, G.; Lee, Y. C.; Palmadesso, P. J.

    1989-01-01

    A spatially two-dimensional electrostatic PIC simulation code was used to study the stability of a plasma equilibrium characterized by a localized transverse dc electric field and a field-aligned drift for L is much less than Lx, where Lx is the simulation length in the x direction and L is the scale length associated with the dc electric field. It is found that the dc electric field and the field-aligned current can together play a synergistic role to enable the excitation of electrostatic waves even when the threshold values of the field aligned drift and the E x B drift are individually subcritical. The simulation results show that the growing ion waves are associated with small vortices in the linear stage, which evolve to the nonlinear stage dominated by larger vortices with lower frequencies.

  18. Current-Voltage Characteristics of Bi-dithiolbenzene in Parallel Arrangement

    SciTech Connect

    Boudjella, Aissa

    2011-03-30

    The low voltage conductance of interacting two 1,4-dithiolbenzene (DTB) molecules is investigated. The simulation results show that the electron transport can be controlled either by changing the Fermi level position E{sub f} or modifying its inter-molecular spacing d. Molecular assembly system with close interaction between DTB units, affects significantly the conductance. In addition, the position of the Fermi plays an important role in determining the current flow. Moreover, it is important to note that E{sub f} affects not only the threshold voltage V{sub th}, but also the saturation voltage V{sub sat}. When E{sub f} approaches the LUMO energy level, V{sub th} decreases, while V{sub sat} increases. To conclude, the threshold voltage and the saturation voltage depend on the Fermi level position and the inter-molecular spacing.

  19. Multiple current peaks in room-temperature atmospheric pressure homogenous dielectric barrier discharge plasma excited by high-voltage tunable nanosecond pulse in air

    SciTech Connect

    Yang, De-Zheng; Wang, Wen-Chun; Zhang, Shuai; Tang, Kai; Liu, Zhi-jie; Wang, Sen

    2013-05-13

    Room temperature homogenous dielectric barrier discharge plasma with high instantaneous energy efficiency is acquired by using nanosecond pulse voltage with 20-200 ns tunable pulse width. Increasing the voltage pulse width can lead to the generation of regular and stable multiple current peaks in each discharge sequence. When the voltage pulse width is 200 ns, more than 5 organized current peaks can be observed under 26 kV peak voltage. Investigation also shows that the organized multiple current peaks only appear in homogenous discharge mode. When the discharge is filament mode, organized multiple current peaks are replaced by chaotic filament current peaks.

  20. Test for fine defects beneath precision surface using novel magneto-optic/pulsed eddy current NDT technology

    NASA Astrophysics Data System (ADS)

    Zhou, Mu-cheng; Wang, Ya-ping

    2006-02-01

    A Magneto-Optic (MO) system is being utilized in aerospace industry for the detection of surface defects. To extend the capability of the instrument to detect and quantify sub-surface defect, we present a new Magneto-Optic (MO)/Pulsed Eddy Current (PEC) imaging system which, supported by laser, is being used for testing fine defects beneath precision surface of mental materials. The technique is based on the combination of pulsed eddy current excitation and magneto-optic sensing and imaging. In the experimental set-up, the induction of eddy currents is conventionally performed by pulsed current excitation coil over the object surface. The magnetic field induced by the pulsed eddy currents is detected by using Faraday effect. For this target, a laser beam passes through a special crystal, Faraday rotation glass (FRG), which has its easy axis of magnetization in the direction of normal magnetic fields and memory effect, integrated in the excitation coil. The polarization direction of laser beam is rotated in crystal depending on local magnetic field. The area distribution of rotation angle caused by fine defects beneath precision surface is transformed into "light" or "dark" picture using an optical set-up, which consists of a conventional microscope, a lighting, a polarimeter, and a CCD sensor. In the paper, the basic principle, configuration of the test equipment and image processing are described, and an original experimental results of fine artificial defects beneath precision surface of mental materials is presented.

  1. Design of encircling send-receive type pulsed eddy current probe

    NASA Astrophysics Data System (ADS)

    Shin, Young-Kil

    2014-02-01

    An encircling send-receive type pulsed eddy current (PEC) probe is designed for use in the tube inspection. When bare receive coils, which are located away from the exciter, are used, the peak time of the signal does not change although the distance from the exciter increases. This is because the magnetic fields from exciter coil arrive directly at the receive coil without passing through the tube. Therefore, in this work, both exciter and sensor coils are shielded to reduce the influence of direct fields from the exciter coil. Numerical simulation with the designed shielded encircling PEC probe shows the corresponding increase of peak time as the sensor distance increases. Ferrite and carbon steel shields are compared and found that the ferrite shielding results in slightly stronger peak value and quicker peak time than the carbon steel shielding. Sensitivity of peak value to defect depth variation is also investigated and found that the normalized peak value is more sensitive when the sensor is located closer to the exciter for aluminum tube. In the case of magnetic tube, however, all the characteristics are opposite to those obtained from nonmagnetic aluminum tube.

  2. Investigation of pulsed eddy current probes for detection of defects in riveted structures

    NASA Astrophysics Data System (ADS)

    Yang, Binfeng; Zhang, Hui; Kang, Zhibin; Wang, Xiaofeng

    2013-09-01

    The fatigue crack is the threat to integrity and safety of fuselage lap-joints. Quantification of fatigue cracks by designing and utilisation of an optimised electromagnetic nondestructive evaluation probe can insure the flight safety of aircrafts. In this paper, pulsed eddy current (PEC) for detection and characterisation of fatigue cracks is investigated. The principle of PEC is analysed first, from which four different models of PEC probes are simulated in ANSYS. The signal features, namely zero-crossing time, zero-crossing frequency and peak value are extracted from the time and frequency domains in an effort to qualitatively compare the crack detectability of the four models. The sensitivities of the different probes to cracks are analysed quantitatively. The difference in detectability among the probes is investigated based on the working principle. Simulation results show that the probe consisting of two horizontal detecting coils along with a magnetic field shield focusing the flux has the highest detectability. The conclusions derived from the simulation study are also validated by experiments.

  3. High current pulsed electron beam treatment of AZ31 Mg alloy

    SciTech Connect

    Gao Bo; Hao Shengzhi; Zou Jianxin; Grosdidier, Thierry; Jiang Limin; Zhou Jiyang; Dong Chuang

    2005-11-15

    This paper reports, for the first time, an analysis of the effect of High Current Pulsed Electron Beam (HCPEB) on a Mg alloy. The AZ31 alloy was HCPEB treated in order to see the potential of this fairly recent technique in modifying its wear resistance. For the 2.5 J/cm{sup 2} beam energy density used in the present work, the evaporation mode was operative and led to the formation of a ''wavy'' surface and the absence of eruptive microcraters. The selective evaporation of Mg over Al led to an Al-rich melted surface layer and precipitation hardening from the over saturated solid solution. Due to the increase in hardness of the top surface layer, the friction coefficient values were lowered by more than 20% after the HCPEB treatments, and the wear resistance was drastically (by a factor of 6) improved. The microhardness of the HCPEB samples was also increased significantly down to a depth of about 500 {mu}m, far exceeding the heat-affected zone (about 40 {mu}m). This is due to the effect of the propagation of the shockwave associated with this HCPEB treatment.

  4. Application of Hilbert-Huang transform for defect recognition in pulsed eddy current testing

    NASA Astrophysics Data System (ADS)

    Liu, Baoling; Huang, Pingjie; Hou, Dibo; Chen, Xiao; Zhang, Guangxin

    2015-07-01

    Defect recognition plays an important role in the structure integrity and health monitor of in-service equipment. However, it is difficult to recognise deep-layer defect or small-size defect in conductive structure during pulsed eddy current (PEC) testing. Aiming at the issue, this article proposes a method based on Hilbert-Huang transform which consists of two modules: data processing and defect recognition. In the data processing module, the PEC response signal is decomposed into a few of intrinsic mode functions (IMFs) using ensemble empirical mode decomposition method. The IMFs whose variance contribution rates are bigger than 1% are chosen to reconstruct signal in order to remove noise. In the defect recognition module, the features based on specific frequency components of marginal spectrum (MS) of the reconstructed signals are extracted to discriminate those defects in surface and subsurface. Furthermore, the normalisation MS energy ratio is proposed to quantify defects which cannot be distinguished using peak value in time domain. Experiments show that the proposed method can achieve better de-noising effect and defect evaluation, which contributes to the recognition of those complicated defects such as deep-layered and small-sized defect.

  5. Characterization of amorphous Co-P alloy coatings electrodeposited with pulse current using gluconate bath

    NASA Astrophysics Data System (ADS)

    Bera, Parthasarathi; Seenivasan, H.; Rajam, K. S.; William Grips, V. K.

    2012-10-01

    Co-P alloy coatings were electrodeposited with pulse current using gluconate bath and characterized by XRD, FESEM, AFM, DSC and XPS. Co-P alloy coatings are amorphous in nature as demonstrated by XRD. FESEM exhibits the “cauliflower type” morphology that is distinctive of nanocrystalline metals and alloys. Co-P alloys are found to follow instantaneous growth mechanism as revealed by AFM studies. Two exothermic peaks at 320 and 340 °C in DSC profiles of Co-P deposit correspond to the crystallization of the deposit. Detailed XPS studies of these alloy coatings have shown that as-deposited coatings consist of Co metal as well as oxidized Co species. P has mostly been present as bulk alloy on the surface as Pδ- form. Increase in the amounts of Co metal and Pδ- are observed upon intermittent sputtering. No appreciable increase in microhardness is observed with increase in the phosphorous content, but it increases with heat treatment significantly.

  6. Pulsed counter-current ultrasound-assisted extraction and characterization of polysaccharides from Boletus edulis.

    PubMed

    You, Qinghong; Yin, Xiulian; Ji, Chaowen

    2014-01-30

    Four methods for extracting polysaccharides from Boletus edulis, namely, hot-water extraction, ultrasonic clearer extraction, static probe ultrasonic extraction, and pulsed counter-current probe ultrasonic extraction (CCPUE), were studied. Results showed that CCPUE has the highest extraction efficiency among the methods studied. Under optimal CCPUE conditions, a B. edulis polysaccharide (BEP) yield of 8.21% was obtained. Three purified fractions, BEP-I, BEP-II, and BEP-III, were obtained through sequential purification by DEAE-52 and Sephadex G-75 chromatography. The average molecular weights of BEP-I, BEP-II, and BEP-III were 10,278, 23,761, and 42,736 Da, respectively. The polysaccharides were mainly composed of xylose, mannose, galactose, and glucose; of these, mannose contents were the highest. The antioxidant activities of the BEPs were further investigated by measurement of their ability to scavenge DPPH and hydroxyl radicals as well as their reducing power. The results indicated that the BEPs have good antioxidant activity. PMID:24299786

  7. Investigation of various equations of state for high current, pulsed power load modeling

    NASA Astrophysics Data System (ADS)

    Luginsland, John; Parkinson, Roland; Rigby, Fred; Toepfer, Alan

    2002-08-01

    A number of technologies utilize the increasing availability of modern pulsed power systems to produce high currents to resistively drive solid, metallic loads into the plasma state. Examples include ablation plasma deposition, circuit breakers, fuses, exploding and imploding wires, and high velocity jet disruption. One important feature in any computational model of these phenomena is the equation of state (EOS). The equations of state used in these models are typically as varied as the range of applications. In this work, using a segmented wire experiment performed at the Army Research Laboratory [1] as a benchmark, we investigate three equations of state [2-4]. We assess the merits of the EOS for both their physical accuracy and easy of use computationally. Finally, we comment on the availability of the information necessary to build the EOS, given the wide variety of materials that are used in this applied field. [1] C.E. Hollandsworth et al., J. Appl. Phys., vol. 84, no. 9, 4992-5000, 1998. [2] SESAME tables, LANL T-1 Division, Equation of State and Strength of Materials. [3] Zhukov, Demidov, and Ryabenko, Fiz. Metal. Metalloved., vol. 57, no. 2, 224-229, 1984. [4] Chittenden et al., Laser and Particle Beams, vol. 19, issue 3, 323-343, 2001, and references therein.

  8. Study on the corrosion properties of nanocrystalline nickel electrodepositied by reverse pulse current

    NASA Astrophysics Data System (ADS)

    Cheng, Wen; Ge, Wen; Yang, Qian; Qu, Xinxin

    2013-07-01

    Nanocrystalline nickel coatings were produced by the method of reverse pulse electrodepositing on the surface of steel sheets. The crystallite size of nanocrystalline nickel coatings was determined by X-ray diffraction (XRD). The effect of saccharin concentration on the crystallite size of the coatings was studied. The average crystallite sizes were diminished as a result of increasing saccharin concentration. CHI660C electrochemical workstation was used to determine the Tafel polarization curves and electrochemical impedance spectroscopy (EIS) of the coatings. The value of corrosion potential, natural corrosion current density, polarizaiton resistance and impedance was calculated, the results suggested that smaller grain size led to higher polarization resistance. EIS gave the charge transfer resistance Rct and pore resistance Rpo variation trend from beginning to 30 min. Scanning electron microscopy (SEM) examination showed the surface morphology of the nickel coatings after the neutral salt spray (NSS) test or bathing in 10% HCl. The images indicated that the corrosion behavior of nanocrystalline nickel coatings was pitting corrosion, the mechanism was also discussed.

  9. Effect of Monophasic Pulsed Current on Heel Pain and Functional Activities caused by Plantar Fasciitis

    PubMed Central

    Alotaibi, Abdullah K.; Petrofsky, Jerrold S.; Daher, Noha S.; Lohman, Everett; Laymon, Michael; Syed, Hasan M.

    2015-01-01

    Background Plantar fasciitis (PF) is a soft tissue disorder considered to be one of the most common causes of inferior heel pain. The aim of this study was to investigate the effect of monophasic pulsed current (MPC) and MPC coupled with plantar fascia-specific stretching exercises (SE) on the treatment of PF. Material/Methods Forty-four participants (22 women and 22 men, with a mean age of 49 years) diagnosed with PF were randomly assigned to receive MPC (n=22) or MPC coupled with plantar fascia-specific SE (n=22). Prior to and after 4 weeks of treatment, participants underwent baseline evaluation; heel pain was evaluated using a visual analogue scale (VAS), heel tenderness threshold was quantified using a handheld pressure algometer (PA), and functional activities level was assessed using the Activities of Daily Living subscale of the Foot and Ankle Ability Measure (ADL/FAAM). Results Heel pain scores showed a significant reduction in both groups compared to baseline VAS scores (P<0.001). Heel tenderness improved significantly in both groups compared with baseline PA scores (P<0.001). Functional activity level improved significantly in both groups compared with baseline (ADL/FAAM) scores (P<0.001). However, no significant differences existed between the 2 treatment groups in all post-intervention outcome measures. Conclusions This trial showed that MPC is useful in treating inferior heel symptoms caused by PF. PMID:25791231

  10. High voltage pulsed current stimulation of the sciatic nerve in rats: analysis by the SFI

    PubMed Central

    Leoni, Anita Sofia Leite; Mazzer, Nilton; Guirro, Rinaldo Roberto de Jesus; Jatte, Fernanda Guadallini; Chereguini, Paulo Augusto Costa; Monte-Raso, Vanessa Vilela

    2012-01-01

    Objective To analyze the efficiency of high voltage pulsed current (HVPC) with early application in three different sites, in the regeneration of the sciatic nerve in rats submitted to crush injury, the sciatic functional index (SFI) was used to assess the functional recovery. Methods After crushing of the nerve, 57 animals were submitted to cathodal HVPC at frequency of 50Hz and voltage of 100V, 20 minutes per day, 5 days per week. The rats were divided into five groups: control group; ganglion group; ganglion + muscle group; muscle group; and sham group. The SFI was determined weekly for seven weeks, from the preoperative period to the 6th postoperative week. Results Compared with the control group, the results showed a significantly better performance of group 2 for the first 3 weeks; group 3 showed significantly better performance in the third week; and group 4 showed a significantly negative performance during the 4th and 6th weeks. Conclusion Early application of HVPC had a positive effect in the treatment of the spinal cord region and the sciatic nerve root ganglion with a dispersive electrode on the contralateral lumbar region or on the gastrocnemius. However, HVPC had a negative effect in the treatment with an active electrode on the gastrocnemius and a dispersive electrode on the contralateral thigh. Level of evidence II, Prospective comparative study. PMID:24453588

  11. Parallel rendering

    NASA Technical Reports Server (NTRS)

    Crockett, Thomas W.

    1995-01-01

    This article provides a broad introduction to the subject of parallel rendering, encompassing both hardware and software systems. The focus is on the underlying concepts and the issues which arise in the design of parallel rendering algorithms and systems. We examine the different types of parallelism and how they can be applied in rendering applications. Concepts from parallel computing, such as data decomposition, task granularity, scalability, and load balancing, are considered in relation to the rendering problem. We also explore concepts from computer graphics, such as coherence and projection, which have a significant impact on the structure of parallel rendering algorithms. Our survey covers a number of practical considerations as well, including the choice of architectural platform, communication and memory requirements, and the problem of image assembly and display. We illustrate the discussion with numerous examples from the parallel rendering literature, representing most of the principal rendering methods currently used in computer graphics.

  12. Multiscale wind cycles and current pulses at the Black Sea eastern boundary

    NASA Astrophysics Data System (ADS)

    Melnikov, Vasiliy; Moskalenko, Lidija; Piotoukh, Vladimir; Zatsepin, Andrey

    2015-04-01

    quantified anomalies, associated with different frequency components of variability, such as sub-meso-scale eddies, marginal shelf waves, inertial oscillations, diurnal, semi-diurnal and short-period internal waves, long surface waves, were estimated. Based on estimates of the statistical relationships between the different parameters of hydro-meteorological system, including meteorological elements, sea level, sea temperature and flow fields, space/time scales of the observed fields variability were estimated. Several new features of the physical mechanisms of multiscale hydro-physical processes in the shelf zone of the Black Sea, have been revealed. In particular, it is shown, that there are wind self-similar cycles at different time scales, each cycle being consisted of a pair of northeast and then southeast winds, which corresponds to the alternative influences of the Azores and Siberian highs(in winter). In the range of decadal (10 years) scale and in macro space view, long-term wind cycles support basic Black Sea circulation(Rim Current).Wind cycles with a time scale of about 20 days give rise to distinct upwellings, appeared with the same frequency. Along with each upwelling, radical hydrological restructuring of the stratification is accompanied by intense advection with high velocities(up to 1 m/s). Kinetic energy is dominated by alongshore currents, the direction being reversed periodically. The vertical structure of currents is rather complicated. When the current speed exceeds some threshold value, the flow gives rise to relaxation oscillations with a period of about 24 hours with counterclockwise velocity vector rotation. All the above mentioned events and current pulses cause significant variations of air-sea fluxes. This research was jointly supported by Ministry of Education of the RF (Agreement №14.604.21.0044), Russian Academy of Sciences(Program No 23), RFBR grant 14-05-00159,contract No 10/2013 RGS-RFBR.

  13. Note: Measurement of extreme-short current pulse duration of runaway electron beam in atmospheric pressure air

    SciTech Connect

    Tarasenko, V. F.; Rybka, D. V.; Burachenko, A. G.; Lomaev, M. I.; Balzovsky, E. V.

    2012-08-15

    This note reports the time-amplitude characteristic of the supershort avalanche electron beam with up to 20 ps time resolution. For the first time it is shown that the electron beam downstream of small-diameter diaphragms in atmospheric pressure air has a complex structure which depends on the interelectrode gap width and cathode design. With a spherical cathode and collimator the minimum duration at half maximum of the supershort avalanche electron beam current pulse was shown to be {approx}25 ps. The minimum duration at half maximum of one peak in the pulses with two peaks can reach {approx}25 ps too.

  14. Investigations of current limiting properties of the MgB2 wires subjected to pulse overcurrents in the benchtop tester

    NASA Astrophysics Data System (ADS)

    Ye, Lin; Majoros, M.; Campbell, A. M.; Coombs, T.; Harrison, S.; Sargent, P.; Haslett, M.; Husband, M.

    2007-04-01

    A laboratory scale desktop test system including a cryogenic system, an AC pulse generation system and a real time data acquisition program in LabView/DAQmx, has been developed to evaluate the quench properties of MgB2 wires as an element in a superconducting fault current limiter under pulse overcurrents at 25 K in self-field conditions. The MgB2 samples started from a superconducting state and demonstrated good current limiting properties characterized by a fast transition to the normal state during the first half of the cycle and a continuously limiting effect in the subsequent cycles without burnouts. The experimental and numerical simulation results on the quench behaviour indicate the feasibility of using MgB2 for future superconducting fault current limiter (SFCL) applications. This work is supported by Rolls-Royce Plc and the UK Department of Trade & Industry (DTI).

  15. A Mechanism for Graded, Dynamically Routable Current Propagation in Pulse-Gated Synfire Chains and Implications for Information Coding

    PubMed Central

    Sornborger, Andrew T.; Wang, Zhuo; Tao, Louis

    2015-01-01

    Neural oscillations can enhance feature recognition [1], modulate interactions between neurons [2], and improve learning and memory [3]. Numerical studies have shown that coherent spiking can give rise to windows in time during which information transfer can be enhanced in neuronal networks [4–6]. Unanswered questions are: 1) What is the transfer mechanism? And 2) how well can a transfer be executed? Here, we present a pulse-based mechanism by which a graded current amplitude may be exactly propagated from one neuronal population to another. The mechanism relies on the downstream gating of mean synaptic current amplitude from one population of neurons to another via a pulse. Because transfer is pulse-based, information may be dynamically routed through a neural circuit with fixed connectivity. We demonstrate the transfer mechanism in a realistic network of spiking neurons and show that it is robust to noise in the form of pulse timing inaccuracies, random synaptic strengths and finite size effects. We also show that the mechanism is structurally robust in that it may be implemented using biologically realistic pulses. The transfer mechanism may be used as a building block for fast, complex information processing in neural circuits. We show that the mechanism naturally leads to a framework wherein neural information coding and processing can be considered as a product of linear maps under the active control of a pulse generator. Distinct control and processing components combine to form the basis for the binding, propagation, and processing of dynamically routed information within neural pathways. Using our framework, we construct example neural circuits to 1) maintain a short-term memory, 2) compute time-windowed Fourier transforms, and 3) perform spatial rotations. We postulate that such circuits, with automatic and stereotyped control and processing of information, are the neural correlates of Crick and Koch’s zombie modes. PMID:26227067

  16. Surface modification of 40CrNiMo7 steel with high current pulsed electron beam treatment

    NASA Astrophysics Data System (ADS)

    Hao, Shengzhi; Wang, Huihui; Zhao, Limin

    2016-02-01

    High current pulsed electron beam (HCPEB) treatment was conducted on 40CrNiMo7 steel with accelerating voltage 27 kV, energy density 3 J/cm2, pulse duration 2.5 μs and 1-50 pulses. The evolutions of surface microstructure were investigated by using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) techniques. It was found that the carbides in the surface remelted layer of depth ∼4 μm were dissolved gradually along with the increasing number of HCPEB pulses. Eventually, the surface microstructure of 40CrNiMo7 steel was transformed to a complex structure composed of very refined ∼150 nm austenite as the main part and a little quantity of martensite phases. After 15 pulses of HCPEB treatment, the surface microhardness was doubled to 553 HV, and the wear rate decreased to one third of the initial state correspondingly.

  17. Calculating electronic tunnel currents in networks of disordered irregularly shaped nanoparticles by mapping networks to arrays of parallel nonlinear resistors

    SciTech Connect

    Aghili Yajadda, Mir Massoud

    2014-10-21

    We have shown both theoretically and experimentally that tunnel currents in networks of disordered irregularly shaped nanoparticles (NPs) can be calculated by considering the networks as arrays of parallel nonlinear resistors. Each resistor is described by a one-dimensional or a two-dimensional array of equal size nanoparticles that the tunnel junction gaps between nanoparticles in each resistor is assumed to be equal. The number of tunnel junctions between two contact electrodes and the tunnel junction gaps between nanoparticles are found to be functions of Coulomb blockade energies. In addition, the tunnel barriers between nanoparticles were considered to be tilted at high voltages. Furthermore, the role of thermal expansion coefficient of the tunnel junction gaps on the tunnel current is taken into account. The model calculations fit very well to the experimental data of a network of disordered gold nanoparticles, a forest of multi-wall carbon nanotubes, and a network of few-layer graphene nanoplates over a wide temperature range (5-300 K) at low and high DC bias voltages (0.001 mV–50 V). Our investigations indicate, although electron cotunneling in networks of disordered irregularly shaped NPs may occur, non-Arrhenius behavior at low temperatures cannot be described by the cotunneling model due to size distribution in the networks and irregular shape of nanoparticles. Non-Arrhenius behavior of the samples at zero bias voltage limit was attributed to the disorder in the samples. Unlike the electron cotunneling model, we found that the crossover from Arrhenius to non-Arrhenius behavior occurs at two temperatures, one at a high temperature and the other at a low temperature.

  18. Calculating electronic tunnel currents in networks of disordered irregularly shaped nanoparticles by mapping networks to arrays of parallel nonlinear resistors

    NASA Astrophysics Data System (ADS)

    Aghili Yajadda, Mir Massoud

    2014-10-01

    We have shown both theoretically and experimentally that tunnel currents in networks of disordered irregularly shaped nanoparticles (NPs) can be calculated by considering the networks as arrays of parallel nonlinear resistors. Each resistor is described by a one-dimensional or a two-dimensional array of equal size nanoparticles that the tunnel junction gaps between nanoparticles in each resistor is assumed to be equal. The number of tunnel junctions between two contact electrodes and the tunnel junction gaps between nanoparticles are found to be functions of Coulomb blockade energies. In addition, the tunnel barriers between nanoparticles were considered to be tilted at high voltages. Furthermore, the role of thermal expansion coefficient of the tunnel junction gaps on the tunnel current is taken into account. The model calculations fit very well to the experimental data of a network of disordered gold nanoparticles, a forest of multi-wall carbon nanotubes, and a network of few-layer graphene nanoplates over a wide temperature range (5-300 K) at low and high DC bias voltages (0.001 mV-50 V). Our investigations indicate, although electron cotunneling in networks of disordered irregularly shaped NPs may occur, non-Arrhenius behavior at low temperatures cannot be described by the cotunneling model due to size distribution in the networks and irregular shape of nanoparticles. Non-Arrhenius behavior of the samples at zero bias voltage limit was attributed to the disorder in the samples. Unlike the electron cotunneling model, we found that the crossover from Arrhenius to non-Arrhenius behavior occurs at two temperatures, one at a high temperature and the other at a low temperature.

  19. Development of long pulse RF heating and current drive for H-mode scenarios with metallic walls in WEST

    SciTech Connect

    Ekedahl, Annika Bourdelle, Clarisse; Artaud, Jean-François; Bernard, Jean-Michel; Bufferand, Hugo; Colas, Laurent; Decker, Joan; Delpech, Léna; Dumont, Rémi; Goniche, Marc; Helou, Walid; Hillairet, Julien; Lombard, Gilles; Magne, Roland; Mollard, Patrick; Nardon, Eric; Peysson, Yves; Tsitrone, Emmanuelle

    2015-12-10

    The longstanding expertise of the Tore Supra team in long pulse heating and current drive with radiofrequency (RF) systems will now be exploited in the WEST device (tungsten-W Environment in Steady-state Tokamak) [1]. WEST will allow an integrated long pulse tokamak programme for testing W-divertor components at ITER-relevant heat flux (10-20 MW/m{sup 2}), while treating crucial aspects for ITER-operation, such as avoidance of W-accumulation in long discharges, monitoring and control of heat fluxes on the metallic plasma facing components (PFCs) and coupling of RF waves in H-mode plasmas. Scenario modelling using the METIS-code shows that ITER-relevant heat fluxes are compatible with the sustainment of long pulse H-mode discharges, at high power (up to 15 MW / 30 s at I{sub P} = 0.8 MA) or high fluence (up to 10 MW / 1000 s at I{sub P} = 0.6 MA) [2], all based on RF heating and current drive using Ion Cyclotron Resonance Heating (ICRH) and Lower Hybrid Current Drive (LHCD). This paper gives a description of the ICRH and LHCD systems in WEST, together with the modelling of the power deposition of the RF waves in the WEST-scenarios.

  20. Development of long pulse RF heating and current drive for H-mode scenarios with metallic walls in WEST

    NASA Astrophysics Data System (ADS)

    Ekedahl, Annika; Bourdelle, Clarisse; Artaud, Jean-François; Bernard, Jean-Michel; Bufferand, Hugo; Colas, Laurent; Decker, Joan; Delpech, Léna; Dumont, Rémi; Goniche, Marc; Helou, Walid; Hillairet, Julien; Lombard, Gilles; Magne, Roland; Mollard, Patrick; Nardon, Eric; Peysson, Yves; Tsitrone, Emmanuelle

    2015-12-01

    The longstanding expertise of the Tore Supra team in long pulse heating and current drive with radiofrequency (RF) systems will now be exploited in the WEST device (tungsten-W Environment in Steady-state Tokamak) [1]. WEST will allow an integrated long pulse tokamak programme for testing W-divertor components at ITER-relevant heat flux (10-20 MW/m2), while treating crucial aspects for ITER-operation, such as avoidance of W-accumulation in long discharges, monitoring and control of heat fluxes on the metallic plasma facing components (PFCs) and coupling of RF waves in H-mode plasmas. Scenario modelling using the METIS-code shows that ITER-relevant heat fluxes are compatible with the sustainment of long pulse H-mode discharges, at high power (up to 15 MW / 30 s at IP = 0.8 MA) or high fluence (up to 10 MW / 1000 s at IP = 0.6 MA) [2], all based on RF heating and current drive using Ion Cyclotron Resonance Heating (ICRH) and Lower Hybrid Current Drive (LHCD). This paper gives a description of the ICRH and LHCD systems in WEST, together with the modelling of the power deposition of the RF waves in the WEST-scenarios.

  1. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, Charles E.; Boothe, Richard W.

    1994-01-01

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

  2. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, C.E.; Boothe, R.W.

    1996-01-23

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figs.

  3. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, Charles E.; Boothe, Richard W.

    1996-01-01

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements.

  4. Ultrafast fiber lasers based on self-similar pulse evolution: a review of current progress.

    PubMed

    Chong, Andy; Wright, Logan G; Wise, Frank W

    2015-11-01

    Self-similar fiber oscillators are a relatively new class of mode-locked lasers. In these lasers, the self-similar evolution of a chirped parabolic pulse in normally-dispersive passive, active, or dispersion-decreasing fiber (DDF) is critical. In active (gain) fiber and DDF, the novel role of local nonlinear attraction makes the oscillators fundamentally different from any mode-locked lasers considered previously. In order to reconcile the spectral and temporal expansion of a pulse in the self-similar segment with the self-consistency required by a laser cavity's periodic boundary condition, several techniques have been applied. The result is a diverse range of fiber oscillators which demonstrate the exciting new design possibilities based on the self-similar model. Here, we review recent progress on self-similar oscillators both in passive and active fiber, and extensions of self-similar evolution for surpassing the limits of rare-earth gain media. We discuss some key remaining research questions and important future directions. Self-similar oscillators are capable of exceptional performance among ultrashort pulsed fiber lasers, and may be of key interest in the development of future ultrashort pulsed fiber lasers for medical imaging applications, as well as for low-noise fiber-based frequency combs. Their uniqueness among mode-locked lasers motivates study into their properties and behaviors and raises questions about how to understand mode-locked lasers more generally.

  5. Method and apparatus for improved efficiency in a pulse-width-modulated alternating current motor drive

    DOEpatents

    Konrad, C.E.; Boothe, R.W.

    1994-02-15

    A scheme for optimizing the efficiency of an AC motor drive operated in a pulse-width-modulated mode provides that the modulation frequency of the power furnished to the motor is a function of commanded motor torque and is higher at lower torque requirements than at higher torque requirements. 6 figures.

  6. Ultrafast fiber lasers based on self-similar pulse evolution: a review of current progress

    PubMed Central

    Chong, Andy; Wright, Logan G; Wise, Frank W

    2016-01-01

    Self-similar fiber oscillators are a relatively new class of mode-locked lasers. In these lasers, the self-similar evolution of a chirped parabolic pulse in normally-dispersive passive, active, or dispersion-decreasing fiber (DDF) is critical. In active (gain) fiber and DDF, the novel role of local nonlinear attraction makes the oscillators fundamentally different from any mode-locked lasers considered previously. In order to reconcile the spectral and temporal expansion of a pulse in the self-similar segment with the self-consistency required by a laser cavity's periodic boundary condition, several techniques have been applied. The result is a diverse range of fiber oscillators which demonstrate the exciting new design possibilities based on the self-similar model. Here, we review recent progress on self-similar oscillators both in passive and active fiber, and extensions of self-similar evolution for surpassing the limits of rare-earth gain media. We discuss some key remaining research questions and important future directions. Self-similar oscillators are capable of exceptional performance among ultrashort pulsed fiber lasers, and may be of key interest in the development of future ultrashort pulsed fiber lasers for medical imaging applications, as well as for low-noise fiber-based frequency combs. Their uniqueness among mode-locked lasers motivates study into their properties and behaviors and raises questions about how to understand mode-locked lasers more generally. PMID:26496377

  7. Quantum-mechanical calculations of residual current density excited during gas ionisation by an intense two-colour laser pulse

    NASA Astrophysics Data System (ADS)

    Vvedenskii, N. V.; Romanov, A. A.; Silaev, A. A.

    2016-05-01

    By solving analytically and numerically the three-dimensional time-dependent Schrödinger equation, we have studied the excitation of a residual current density during gas ionisation by a two-colour laser pulse containing a field at the fundamental frequency and an additional field at the doubled frequency. We have found the dependences of the residual current density on the phase shift between the components of the field and on the intensity of the fundamental harmonic. It is shown that the strong-field approximation taking into account the interaction of freed electrons with the parent ion yields a good quantitative agreement with the results of direct numerical simulation.

  8. The structure and properties of boron carbide ceramics modified by high-current pulsed electron-beam

    NASA Astrophysics Data System (ADS)

    Ivanov, Yuri; Tolkachev, Oleg; Petyukevich, Maria; Teresov, Anton; Ivanova, Olga; Ikonnikova, Irina; Polisadova, Valentina

    2016-01-01

    The present work is devoted to numerical simulation of temperature fields and the analysis of structural and strength properties of the samples surface layer of boron carbide ceramics treated by the high-current pulsed electron-beam of the submillisecond duration. The samples made of sintered boron carbide ceramics are used in these investigations. The problem of calculating the temperature field is reduced to solving the thermal conductivity equation. The electron beam density ranges between 8…30 J/cm2, while the pulse durations are 100…200 μs in numerical modelling. The results of modelling the temperature field allowed ascertaining the threshold parameters of the electron beam, such as energy density and pulse duration. The electron beam irradiation is accompanied by the structural modification of the surface layer of boron carbide ceramics either in the single-phase (liquid or solid) or two-phase (solid-liquid) states. The sample surface of boron carbide ceramics is treated under the two-phase state (solid-liquid) conditions of the structural modification. The surface layer is modified by the high-current pulsed electron-beam produced by SOLO installation at the Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Russia. The elemental composition and the defect structure of the modified surface layer are analyzed by the optical instrument, scanning electron and transmission electron microscopes. Mechanical properties of the modified layer are determined measuring its hardness and crack resistance. Research results show that the melting and subsequent rapid solidification of the surface layer lead to such phenomena as fragmentation due to a crack network, grain size reduction, formation of the sub-grained structure due to mechanical twinning, and increase of hardness and crack resistance.

  9. Transient analysis and control of bias magnetic state in the transformer of on-line pulse-width-modulation switching full bridge direct current-direct current converter

    NASA Astrophysics Data System (ADS)

    Chen, Jiaxin; Guo, Youguang; Zhu, Jianguo; Wei Lin, Zhi

    2012-04-01

    This paper presents a finite element analysis (FEA) based method for analyzing and controlling the bias magnetic state of the transformer of a pulse-width-modulation (PWM) switching full bridge dc-dc converter. A field-circuit indirect coupling method for predicting the transient bias magnetic state is introduced first. To increase flexibility of the proposed method, a novel transformer model which can address not only its basic input-output characteristic, but also the nonlinear magnetizing inductance, is proposed. Both the asymmetric characteristic and the variable laws of the current flowing through the two secondary windings during the period of PWM switching-off state are highlighted. Finally, the peak magnetizing current controlled method based on the on-line magnetizing current computation is introduced. Analysis results show that this method can address the magnetic saturation at winding ends, and hence many previous difficulties, such as the start-up process and asymmetry of power electronics, can be easily controlled.

  10. The production mechanisms of OH radicals in a pulsed direct current plasma jet

    SciTech Connect

    Liu, X. Y.; Pei, X. K.; Lu, X. P.; Liu, D. W.; Ostrikov, K.

    2014-09-15

    The production mechanism of OH radicals in a pulsed DC plasma jet is studied by a two-dimensional (2-D) plasma jet model and a one-dimensional (1-D) discharge model. For the plasma jet in the open air, electron-impact dissociation of H{sub 2}O, electron neutralization of H{sub 2}O{sup +}, as well as dissociation of H{sub 2}O by O(1D) are found to be the main reactions to generate the OH species. The contribution of the dissociation of H{sub 2}O by electron is more than the others. The additions of N{sub 2}, O{sub 2}, air, and H{sub 2}O into the working gas increase the OH density outside the tube slightly, which is attributed to more electrons produced by Penning ionization. On the other hand, the additions of O{sub 2} and H{sub 2}O into the working gas increase the OH density inside the tube substantially, which is attributed to the increased O (1D) and H{sub 2}O concentration, respectively. The gas flow will transport high density OH out of the tube during pulse off period. It is also shown that the plasma chemistry and reactivity can be effectively controlled by the pulse numbers. These results are supported by the laser induced fluorescence measurements and are relevant to several applications of atmospheric-pressure plasmas in health care, medicine, and materials processing.

  11. Design of a New Acceleration System for High-Current Pulsed Proton Beams from an ECR Source

    NASA Astrophysics Data System (ADS)

    Cooper, Andrew L.; Pogrebnyak, Ivan; Surbrook, Jason T.; Kelly, Keegan J.; Carlin, Bret P.; Champagne, Arthur E.; Clegg, Thomas B.

    2014-03-01

    A primary objective for accelerators at TUNL's Laboratory for Experimental Nuclear Astrophysics (LENA) is to maximize target beam intensity to ensure a high rate of nuclear events during each experiment. Average proton target currents of several mA are needed from LENA's electron cyclotron resonance (ECR) ion source because nuclear cross sections decrease substantially at energies of interest <200 keV. We seek to suppress undesired continuous environmental background by pulsing the beam and detecting events only during beam pulses. To improve beam intensity and transport, we installed a more powerful, stable microwave system for the ECR plasma, and will install a new acceleration system. This system will: reduce defocusing effects of the beam's internal space charge; provide better vacuum with a high gas conductance accelerating column; suppress bremsstrahlung X-rays produced when backstreaming electrons strike internal acceleration tube structures; and provide better heat dissipation by using deionized water to provide the current drain needed to establish the accelerating tube's voltage gradient. Details of beam optical modeling calculations, proposed accelerating tube design, and initial beam pulsing tests will be described. Work supported in part by USDOE Office of HE and Nuclear Physics.

  12. Hybrid simulations of whistler waves generation and current closure by a pulsed tether in the ionosphere

    NASA Technical Reports Server (NTRS)

    Chang, C. L.; Lipatov, A. S.; Drobot, A. T.; Papadopoulos, K.; Satya-Narayana, P.

    1994-01-01

    The dynamic response of a magnetized collisionless plasma to an externally driven, finite size, sudden switch-on current source across the magnetic field has been studied using a two dimensional hybrid code. It was found that the predominant plasma response was the excitation of whistler waves and the formation of current closure by induced currents in the plasma. The results show that the current closure path consists of: (a) two antiparallel field-aligned current channels at the end of the imposed current sheet; and (b) a cross-field current region connecting these channels. The formation of the current closure path occured in the whistler timescale much shorter than that of MHD and the closure region expanded continuously in time. The current closure process was accompanied by significant energy loss due to whistler radiation.

  13. A mechanism for graded, dynamically routable current propagation in pulse-gated synfire chains and implications for information coding.

    PubMed

    Sornborger, Andrew T; Wang, Zhuo; Tao, Louis

    2015-10-01

    Neural oscillations can enhance feature recognition (Azouz and Gray Proceedings of the National Academy of Sciences of the United States of America, 97, 8110-8115 2000), modulate interactions between neurons (Womelsdorf et al. Science, 316, 1609-01612 2007), and improve learning and memory (Markowska et al. The Journal of Neuroscience, 15, 2063-2073 1995). Numerical studies have shown that coherent spiking can give rise to windows in time during which information transfer can be enhanced in neuronal networks (Abeles Israel Journal of Medical Sciences, 18, 83-92 1982; Lisman and Idiart Science, 267, 1512-1515 1995, Salinas and Sejnowski Nature Reviews. Neuroscience, 2, 539-550 2001). Unanswered questions are: 1) What is the transfer mechanism? And 2) how well can a transfer be executed? Here, we present a pulse-based mechanism by which a graded current amplitude may be exactly propagated from one neuronal population to another. The mechanism relies on the downstream gating of mean synaptic current amplitude from one population of neurons to another via a pulse. Because transfer is pulse-based, information may be dynamically routed through a neural circuit with fixed connectivity. We demonstrate the transfer mechanism in a realistic network of spiking neurons and show that it is robust to noise in the form of pulse timing inaccuracies, random synaptic strengths and finite size effects. We also show that the mechanism is structurally robust in that it may be implemented using biologically realistic pulses. The transfer mechanism may be used as a building block for fast, complex information processing in neural circuits. We show that the mechanism naturally leads to a framework wherein neural information coding and processing can be considered as a product of linear maps under the active control of a pulse generator. Distinct control and processing components combine to form the basis for the binding, propagation, and processing of dynamically routed information within

  14. A mechanism for graded, dynamically routable current propagation in pulse-gated synfire chains and implications for information coding.

    PubMed

    Sornborger, Andrew T; Wang, Zhuo; Tao, Louis

    2015-10-01

    Neural oscillations can enhance feature recognition (Azouz and Gray Proceedings of the National Academy of Sciences of the United States of America, 97, 8110-8115 2000), modulate interactions between neurons (Womelsdorf et al. Science, 316, 1609-01612 2007), and improve learning and memory (Markowska et al. The Journal of Neuroscience, 15, 2063-2073 1995). Numerical studies have shown that coherent spiking can give rise to windows in time during which information transfer can be enhanced in neuronal networks (Abeles Israel Journal of Medical Sciences, 18, 83-92 1982; Lisman and Idiart Science, 267, 1512-1515 1995, Salinas and Sejnowski Nature Reviews. Neuroscience, 2, 539-550 2001). Unanswered questions are: 1) What is the transfer mechanism? And 2) how well can a transfer be executed? Here, we present a pulse-based mechanism by which a graded current amplitude may be exactly propagated from one neuronal population to another. The mechanism relies on the downstream gating of mean synaptic current amplitude from one population of neurons to another via a pulse. Because transfer is pulse-based, information may be dynamically routed through a neural circuit with fixed connectivity. We demonstrate the transfer mechanism in a realistic network of spiking neurons and show that it is robust to noise in the form of pulse timing inaccuracies, random synaptic strengths and finite size effects. We also show that the mechanism is structurally robust in that it may be implemented using biologically realistic pulses. The transfer mechanism may be used as a building block for fast, complex information processing in neural circuits. We show that the mechanism naturally leads to a framework wherein neural information coding and processing can be considered as a product of linear maps under the active control of a pulse generator. Distinct control and processing components combine to form the basis for the binding, propagation, and processing of dynamically routed information within

  15. Microsecond ramp compression of a metallic liner driven by a 5 MA current on the SPHINX machine using a dynamic load current multiplier pulse shaping

    NASA Astrophysics Data System (ADS)

    d'Almeida, T.; Lassalle, F.; Morell, A.; Grunenwald, J.; Zucchini, F.; Loyen, A.; Maysonnave, T.; Chuvatin, A. S.

    2013-09-01

    SPHINX is a 6 MA, 1-μs Linear Transformer Driver (LTD) operated by the CEA Gramat (France) and primarily used for imploding Z-pinch loads for radiation effects studies. Among the options that are currently being evaluated to improve the generator performances are an upgrade to a 20 MA, 1-μs LTD machine and various power amplification schemes, including a compact Dynamic Load Current Multiplier (DLCM). A method for performing magnetic ramp compression experiments, without modifying the generator operation scheme, was developed using the DLCM to shape the initial current pulse in order to obtain the desired load current profile. In this paper, we discuss the overall configuration that was selected for these experiments, including the choice of a coaxial cylindrical geometry for the load and its return current electrode. We present both 3-D Magneto-hydrodynamic and 1D Lagrangian hydrodynamic simulations which helped guide the design of the experimental configuration. Initial results obtained over a set of experiments on an aluminium cylindrical liner, ramp-compressed to a peak pressure of 23 GPa, are presented and analyzed. Details of the electrical and laser Doppler interferometer setups used to monitor and diagnose the ramp compression experiments are provided. In particular, the configuration used to field both homodyne and heterodyne velocimetry diagnostics in the reduced access available within the liner's interior is described. Current profiles measured at various critical locations across the system, particularly the load current, enabled a comprehensive tracking of the current circulation and demonstrate adequate pulse shaping by the DLCM. The liner inner free surface velocity measurements obtained from the heterodyne velocimeter agree with the hydrocode results obtained using the measured load current as the input. An extensive hydrodynamic analysis is carried out to examine information such as pressure and particle velocity history profiles or magnetic

  16. Microsecond ramp compression of a metallic liner driven by a 5 MA current on the SPHINX machine using a dynamic load current multiplier pulse shaping

    SciTech Connect

    D'Almeida, T.; Lassalle, F.; Morell, A.; Grunenwald, J.; Zucchini, F.; Loyen, A.; Maysonnave, T.; Chuvatin, A. S.

    2013-09-15

    SPHINX is a 6 MA, 1-μs Linear Transformer Driver (LTD) operated by the CEA Gramat (France) and primarily used for imploding Z-pinch loads for radiation effects studies. Among the options that are currently being evaluated to improve the generator performances are an upgrade to a 20 MA, 1-μs LTD machine and various power amplification schemes, including a compact Dynamic Load Current Multiplier (DLCM). A method for performing magnetic ramp compression experiments, without modifying the generator operation scheme, was developed using the DLCM to shape the initial current pulse in order to obtain the desired load current profile. In this paper, we discuss the overall configuration that was selected for these experiments, including the choice of a coaxial cylindrical geometry for the load and its return current electrode. We present both 3-D Magneto-hydrodynamic and 1D Lagrangian hydrodynamic simulations which helped guide the design of the experimental configuration. Initial results obtained over a set of experiments on an aluminium cylindrical liner, ramp-compressed to a peak pressure of 23 GPa, are presented and analyzed. Details of the electrical and laser Doppler interferometer setups used to monitor and diagnose the ramp compression experiments are provided. In particular, the configuration used to field both homodyne and heterodyne velocimetry diagnostics in the reduced access available within the liner's interior is described. Current profiles measured at various critical locations across the system, particularly the load current, enabled a comprehensive tracking of the current circulation and demonstrate adequate pulse shaping by the DLCM. The liner inner free surface velocity measurements obtained from the heterodyne velocimeter agree with the hydrocode results obtained using the measured load current as the input. An extensive hydrodynamic analysis is carried out to examine information such as pressure and particle velocity history profiles or magnetic

  17. Ultrashort pulse lasers for precise processing: overview on a current German research initiative

    NASA Astrophysics Data System (ADS)

    Nolte, S.

    2014-03-01

    Ultrashort laser pulses provide a powerful means of processing a wide variety of materials with highest precision and minimal damage. In order to exploit the full potential of this technology, the German Federal Ministry of Education and Research has launched an initiative with 20 Million EUR funding about two years ago. Within 9 joint research projects, different aspects from novel concepts for robust and powerful laser sources to reliable components with high damage thresholds and dynamic beam shaping and steering are investigated. Applications include eye surgery as well as the processing of semiconductors, carbon fiber reinforced plastics and metals. The paper provides an overview on the different projects and highlights first results.

  18. Evolution of the current system during solar wind pressure pulses based on aurora and magnetometer observations

    NASA Astrophysics Data System (ADS)

    Nishimura, Yukitoshi; Kikuchi, Takashi; Ebihara, Yusuke; Yoshikawa, Akimasa; Imajo, Shun; Li, Wen; Utada, Hisashi

    2016-08-01

    We investigated evolution of ionospheric currents during sudden commencements using a ground magnetometer network in conjunction with an all-sky imager, which has the advantage of locating field-aligned currents much more accurately than ground magnetometers. Preliminary (PI) and main (MI) impulse currents showed two-cell patterns propagating antisunward, particularly during a southward interplanetary magnetic field (IMF). Although this overall pattern is consistent with the Araki (solar wind sources of magnetospheric ultra-low-frequency waves. Geophysical monograph series, vol 81. AGU, Washington, DC, pp 183-200, 1994. doi: 10.1029/GM081p0183) model, we found several interesting features. The PI and MI currents in some events were highly asymmetric with respect to the noon-midnight meridian; the post-noon sector did not show any notable PI signal, but only had an MI starting earlier than the pre-noon MI. Not only equivalent currents but also aurora and equatorial magnetometer data supported the much weaker PI response. We suggest that interplanetary shocks impacting away from the subsolar point caused the asymmetric current pattern. Additionally, even when PI currents form in both pre- and post-noon sectors, they can initiate and disappear at different timings. The PI currents did not immediately disappear but coexisted with the MI currents for the first few minutes of the MI. During a southward IMF, the MI currents formed equatorward of a preexisting DP-2, indicating that the MI currents are a separate structure from a preexisting DP-2. In contrast, the MI currents under a northward IMF were essentially an intensification of a preexisting DP-2. The magnetometer and imager combination has been shown to be a powerful means for tracing evolution of ionospheric currents, and we showed various types of ionospheric responses under different upstream conditions.

  19. Reducing Current Spread by Use of a Novel Pulse Shape for Electrical Stimulation of the Auditory Nerve

    PubMed Central

    Ballestero, Jimena; Recugnat, Matthieu; Laudanski, Jonathan; Smith, Katie E.; Jagger, Daniel J.; Gnansia, Daniel

    2015-01-01

    Improving the electrode-neuron interface to reduce current spread between individual electrodes has been identified as one of the main objectives in the search for future improvements in cochlear-implant performance. Here, we address this problem by presenting a novel stimulation strategy that takes account of the biophysical properties of the auditory neurons (spiral ganglion neurons, SGNs) stimulated in electrical hearing. This new strategy employs a ramped pulse shape, where the maximum amplitude is achieved through a linear slope in the injected current. We present the theoretical framework that supports this new strategy and that suggests it will improve the modulation of SGNs’ activity by exploiting their sensitivity to the rising slope of current pulses. The theoretical consequence of this sensitivity to the slope is a reduction in the spread of excitation within the cochlea and, consequently, an increase in the neural dynamic range. To explore the impact of the novel stimulation method on neural activity, we performed in vitro recordings of SGNs in culture. We show that the stimulus efficacy required to evoke action potentials in SGNs falls as the stimulus slope decreases. This work lays the foundation for a novel, and more biomimetic, stimulation strategy with considerable potential for implementation in cochlear-implant technology. PMID:26721928

  20. Comparison of atmospheric air plasmas excited by high-voltage nanosecond pulsed discharge and sinusoidal alternating current discharge

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Wang, Wen-chun; Jiang, Peng-chao; Yang, De-zheng; Jia, Li; Wang, Sen

    2013-10-01

    In this paper, atmospheric pressure air discharge plasma in quartz tube is excited by 15 ns high-voltage nanosecond pulsed discharge (HVNPD) and sinusoidal alternating current discharge (SACD), respectively, and a comparison study of these two kinds of discharges is made through visual imaging, electrical characterization, optical detection of active species, and plasma gas temperature. The peak voltage of the power supplies is kept at 16 kV while the pulse repetition rate of nanosecond pulse power supply is 100 Hz, and the frequency of sinusoidal power supply is 10 kHz. Results show that the HVNPD is uniform while the SACD presents filamentary mode. For exciting the same cycles of discharge, the average energy consumption in HVNPD is about 1/13 of the SACD. However, the chemical active species generated by the HVNPD is about 2-9 times than that excited by the SACD. Meanwhile, the rotational and vibrational temperatures have been obtained via fitting the simulated spectrum of N2 (C3Πu → B3Πg, 0-2) with the measured one, and the results show that the plasma gas temperature in the HVNPD remains close to room temperature whereas the plasma gas temperature in the SACD is about 200 K higher than that in HVNPD in the initial phase and continually increases as discharge exposure time goes on.

  1. Real-Time Observation on Evolution of Droplets Morphology Affected by Electric Current Pulse in Al-Bi Immiscible Alloy

    NASA Astrophysics Data System (ADS)

    Zhu, Jing; Wang, Tongmin; Cao, Fei; Fu, Hongwang; Fu, Yanan; Xie, Honglan; Xiao, Tiqiao

    2013-05-01

    The evolution of Bi-rich droplets morphology in a solidifying Al-Bi immiscible alloy was directly observed using a synchrotron microradiography technique. The electric current pulse (ECP) was applied to control the solidification process of Al-Bi immiscible alloy. It was found that the electromagnetic pinch force and Marangoni force induced by ECP and temperature gradient, respectively, can significantly affect the distribution of Bi-rich droplets. The electromagnetic pinch force drove the droplets from the center to side; meanwhile, the Marangoni force lifted the droplets from the bottom to the top. As a result, the droplets finally distributed with a manner of "inverted triangle."

  2. In-situ calibration of pulsed eddy current detection of cracks at fasteners in CP-140 aircraft

    NASA Astrophysics Data System (ADS)

    Underhill, Ross; Stott, Colette; Krause, Thomas W.

    2016-02-01

    The use of the Smallest Half Volume (SHV) robust statistics method and the Mahalanobis distance to blindly distinguish fasteners with cracks from fasteners without is examined. Pulsed eddy current data obtained from CP140 Aurora wing structures is used to test the approach. It is shown that the method can achieve levels of detection very close to those obtained when the same measurement technique is applied with full knowledge of which fasteners have no cracks. The method is applicable to a broad range of similar situations when an objective hit/miss criterion is used.

  3. A behavioral model for MCT surge current analysis in pulse discharge

    NASA Astrophysics Data System (ADS)

    Chen, Wanjun; Sun, Ruize; Xiao, Kun; Zhu, Hongzhi; Peng, Chaofei; Ruan, Zhaoyang; Ruan, Jianxin; Zhang, Bo; Li, Zhaoji

    2014-09-01

    In this work, a behavioral model for MOS Controlled-Thyristor (MCT) surge current analysis is proposed together with a design criterion. In this model, the relationships between the surge current characteristics including peak current (Ipeak) and high current rising rate (di/dt) of MCT and the device resistance (R) have been discussed, and then a readily measurable parameter, critical resistance (Rc), is presented to estimate the device surge current capability. According to the analytical results, both Ipeak and di/dt of MCT have been found to remain approximately constant with increasing resistance unless its resistance approaches and exceeds this Rc. It is therefore referred to as a design criterion for guiding the device design. The accuracy of the developed model and criterion are verified by comparing the obtained results with those resulting from simulation and experiment results.

  4. Effect of Inductive Coil Geometry and Current Sheet Trajectory of a Conical Theta Pinch Pulsed Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Bonds, Kevin W.; Emsellem, Gregory D.

    2011-01-01

    Results are presented demonstrating the e ect of inductive coil geometry and current sheet trajectory on the exhaust velocity of propellant in conical theta pinch pulsed induc- tive plasma accelerators. The electromagnetic coupling between the inductive coil of the accelerator and a plasma current sheet is simulated, substituting a conical copper frustum for the plasma. The variation of system inductance as a function of plasma position is obtained by displacing the simulated current sheet from the coil while measuring the total inductance of the coil. Four coils of differing geometries were employed, and the total inductance of each coil was measured as a function of the axial displacement of two sep- arate copper frusta both having the same cone angle and length as the coil but with one compressed to a smaller size relative to the coil. The measured relationship between total coil inductance and current sheet position closes a dynamical circuit model that is used to calculate the resulting current sheet velocity for various coil and current sheet con gura- tions. The results of this model, which neglects the pinching contribution to thrust, radial propellant con nement, and plume divergence, indicate that in a conical theta pinch ge- ometry current sheet pinching is detrimental to thruster performance, reducing the kinetic energy of the exhausting propellant by up to 50% (at the upper bound for the parameter range of the study). The decrease in exhaust velocity was larger for coils and simulated current sheets of smaller half cone angles. An upper bound for the pinching contribution to thrust is estimated for typical operating parameters. Measurements of coil inductance for three di erent current sheet pinching conditions are used to estimate the magnetic pressure as a function of current sheet radial compression. The gas-dynamic contribution to axial acceleration is also estimated and shown to not compensate for the decrease in axial electromagnetic acceleration

  5. Transient interaction model of electromagnetic field generated by lightning current pulses and human body

    NASA Astrophysics Data System (ADS)

    Iváncsy, T.; Kiss, I.; Szücs, L.; Tamus, Z. Á.

    2015-10-01

    The lightning current generates time-varying magnetic field near the down- conductor and the down-conductors are mounted on the wall of the buildings where residential places might be situated. It is well known that the rapidly changing magnetic fields can generate dangerous eddy currents in the human body.The higher duration and gradient of the magnetic field can cause potentially life threatening cardiac stimulation. The coupling mechanism between the electromagnetic field and the human body is based on a well-known physical phenomena (e.g. Faradays law of induction). However, the calculation of the induced current is very complicated because the shape of the organs is complex and the determination of the material properties of living tissues is difficult, as well. Our previous study revealed that the cardiac stimulation is independent of the rising time of the lightning current and only the peak of the current counts. In this study, the authors introduce an improved model of the interaction of electromagnetic fields of lighting current near down-conductor and human body. Our previous models are based on the quasi stationer field calculations, the new improved model is a transient model. This is because the magnetic field around the down-conductor and in the human body can be determined more precisely, therefore the dangerous currents in the body can be estimated.

  6. High-temperature performance of MoS{sub 2} thin-film transistors: Direct current and pulse current-voltage characteristics

    SciTech Connect

    Jiang, C.; Samnakay, R.; Balandin, A. A.; Rumyantsev, S. L.; Shur, M. S.

    2015-02-14

    We report on fabrication of MoS{sub 2} thin-film transistors (TFTs) and experimental investigations of their high-temperature current-voltage characteristics. The measurements show that MoS{sub 2} devices remain functional to temperatures of at least as high as 500 K. The temperature increase results in decreased threshold voltage and mobility. The comparison of the direct current (DC) and pulse measurements shows that the direct current sub-linear and super-linear output characteristics of MoS{sub 2} thin-films devices result from the Joule heating and the interplay of the threshold voltage and mobility temperature dependences. At temperatures above 450 K, a kink in the drain current occurs at zero gate voltage irrespective of the threshold voltage value. This intriguing phenomenon, referred to as a “memory step,” was attributed to the slow relaxation processes in thin films similar to those in graphene and electron glasses. The fabricated MoS{sub 2} thin-film transistors demonstrated stable operation after two months of aging. The obtained results suggest new applications for MoS{sub 2} thin-film transistors in extreme-temperature electronics and sensors.

  7. Study of lower hybrid current drive towards long-pulse operation with high performance in EAST

    NASA Astrophysics Data System (ADS)

    Ding, B. J.; Li, M. H.; Li, Y. C.; Wang, M.; Shan, J. F.; Liu, F. K.; Wang, S. L.; Wei, W.; Xu, H. D.; Zhao, L. M.; Hu, H. C.; Jia, H.; Cheng, M.; Yang, Y.; Liu, L.; Xu, G. S.; Zang, Q.; Zhao, H. L.; Peysson, Y.; Decker, J.; Goniche, M.; Cesario, R.; Amicucci, L.; Tuccillo, A. A.; Baek, G. S.; Parker, R.; Bonoli, P. T.; Yang, C.; Zhao, Y. P.; Qian, J. P.; Gong, X. Z.; Hu, L. Q.; Li, J. G.; Wan, B. N.

    2015-12-01

    High density experiments with 2.45 GHz lower hybrid current drive (LHCD) in EAST are analyzed by means of simulation and modeling, showing that parametric instabilities (PI), collisional absorption and density fluctuations in the edge region could be responsible for the low CD efficiency at high density. In addition, recent LHCD results with 4.6 GHz are presented, showing that lower hybrid wave can be coupled to plasma with low reflection coefficient, drive plasma current and modify the current profile, and heat plasma effectively. The related results between two systems (2.45 GHz and 4.6 GHz) are also compared, including CD efficiency and PI behavior.

  8. Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Sun, Dali; van Schooten, Kipp J.; Kavand, Marzieh; Malissa, Hans; Zhang, Chuang; Groesbeck, Matthew; Boehme, Christoph; Valy Vardeny, Z.

    2016-08-01

    Exploration of spin currents in organic semiconductors (OSECs) induced by resonant microwave absorption in ferromagnetic substrates is appealing for potential spintronics applications. Owing to the inherently weak spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE) response is very subtle; limited by the microwave power applicable under continuous-wave (cw) excitation. Here we introduce a novel approach for generating significant ISHE signals in OSECs using pulsed ferromagnetic resonance, where the ISHE is two to three orders of magnitude larger compared to cw excitation. This strong ISHE enables us to investigate a variety of OSECs ranging from π-conjugated polymers with strong SOC that contain intrachain platinum atoms, to weak SOC polymers, to C60 films, where the SOC is predominantly caused by the curvature of the molecule’s surface. The pulsed-ISHE technique offers a robust route for efficient injection and detection schemes of spin currents at room temperature, and paves the way for spin orbitronics in plastic materials.

  9. Study on lower hybrid current drive efficiency at high density towards long-pulse regimes in Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Li, M. H.; Ding, B. J.; Zhang, J. Z.; Gan, K. F.; Wang, H. Q.; Peysson, Y.; Decker, J.; Zhang, L.; Wei, W.; Li, Y. C.; Wu, Z. G.; Ma, W. D.; Jia, H.; Chen, M.; Yang, Y.; Feng, J. Q.; Wang, M.; Xu, H. D.; Shan, J. F.; Liu, F. K.

    2014-06-01

    Significant progress on both L- and H-mode long-pulse discharges has been made recently in Experimental Advanced Superconducting Tokamak (EAST) with lower hybrid current drive (LHCD) [J. Li et al., Nature Phys. 9, 817 (2013) And B. N. Wan et al., Nucl. Fusion 53, 104006 (2013).]. In this paper, LHCD experiments at high density in L-mode plasmas have been investigated in order to explore possible methods of improving current drive (CD) efficiency, thus to extend the operational space in long-pulse and high performance plasma regime. It is observed that the normalized bremsstrahlung emission falls much more steeply than 1/ne_av (line-averaged density) above ne_av = 2.2 × 1019 m-3 indicating anomalous loss of CD efficiency. A large broadening of the operating line frequency (f = 2.45 GHz), measured by a radio frequency (RF) probe located outside the EAST vacuum vessel, is generally observed during high density cases, which is found to be one of the physical mechanisms resulting in the unfavorable CD efficiency. Collisional absorption of lower hybrid wave in the scrape off layer (SOL) may be another cause, but this assertion needs more experimental evidence and numerical analysis. It is found that plasmas with strong lithiation can improve CD efficiency largely, which should be benefited from the changes of edge parameters. In addition, several possible methods are proposed to recover good efficiency in future experiments for EAST.

  10. Effects of peak current density on the mechanical properties of nanocrystalline Ni Co alloys produced by pulse electrodeposition

    NASA Astrophysics Data System (ADS)

    Li, Yundong; Jiang, Hui; Huang, Weihua; Tian, Hui

    2008-08-01

    Cobalt content, grain size, microhardness and tensile strength of nanocrystalline Ni-Co deposits produced from a solution containing saccharin and cobalt sulfate at constant electrodeposition conditions (pulse on-time Ton at 1 ms and pulse off-time Toff at 15 ms) but varying the peak current density Jp were investigated. It is found that an increase in Jp makes the deposit Co content lower, colony-like morphology more obvious, grain size smaller, and hardness and tensile strength higher. All of the facts are believed to result from the higher overpotential and nucleation rates caused by the Jp increase. But its further increase could lead to reduction in the hardness and tensile strength. Peak current densities in the range of 100-120 A dm -2 are recommended for the preparation of nanostructured Ni-Co alloy deposits with grain sizes in the range of 15-20 nm, containing 7-8% Co, possessing hardness of 590-600 kg mm -2 and tensile strength of 1180-1200 MPa—significantly higher than the strength of pure nickel deposit which is produced by the similar method and gets similar grain size.

  11. Inverse spin Hall effect from pulsed spin current in organic semiconductors with tunable spin-orbit coupling.

    PubMed

    Sun, Dali; van Schooten, Kipp J; Kavand, Marzieh; Malissa, Hans; Zhang, Chuang; Groesbeck, Matthew; Boehme, Christoph; Valy Vardeny, Z

    2016-08-01

    Exploration of spin currents in organic semiconductors (OSECs) induced by resonant microwave absorption in ferromagnetic substrates is appealing for potential spintronics applications. Owing to the inherently weak spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE) response is very subtle; limited by the microwave power applicable under continuous-wave (cw) excitation. Here we introduce a novel approach for generating significant ISHE signals in OSECs using pulsed ferromagnetic resonance, where the ISHE is two to three orders of magnitude larger compared to cw excitation. This strong ISHE enables us to investigate a variety of OSECs ranging from π-conjugated polymers with strong SOC that contain intrachain platinum atoms, to weak SOC polymers, to C60 films, where the SOC is predominantly caused by the curvature of the molecule's surface. The pulsed-ISHE technique offers a robust route for efficient injection and detection schemes of spin currents at room temperature, and paves the way for spin orbitronics in plastic materials. PMID:27088233

  12. Finite element modeling of wall-loss sizing in a steam generator tube using a pulsed eddy current probe

    NASA Astrophysics Data System (ADS)

    Babbar, V. K.; Lepine, B.; Buck, J.; Underhill, P. R.; Morelli, J.; Krause, T. W.

    2015-03-01

    Inspection of steam generator (SG) tubes by conventional eddy current may, in general, involve analysis of indications from volumetric wall loss, cracks, fouling and support-plate degradation; however, it may be difficult to size or quantify effects from support-to-tube gap and tube tilt, especially in the presence of support plates. Pulsed eddy current (PEC) technology is being developed to investigate such complex tube and flaw geometries. The present work employs finite element modeling to investigate the effectiveness of PEC in identifying and sizing the outer diameter wall-loss in SG tubes. The signals analyzed using a modified principal components analysis (PCA) method reveal the potential success of a PEC-PCA combination to produce scores that can be used to size the wall-loss in the presence of support plates. The modeling results are in good agreement with experimental observations.

  13. Estimation of triggered-lightning dart-stepped-leader currents from close multiple-station dE/dt pulse measurements

    NASA Astrophysics Data System (ADS)

    Gamerota, W. R.; Uman, M. A.; Hill, J. D.; Ngin, T.; Pilkey, J.; Jordan, D. M.

    2015-02-01

    The modified transmission line model is used to derive the vertically propagating leader-step currents necessary to radiate measured dart-stepped-leader dE/dt pulses from triggered lightning at close range (<400 m) and low altitude (<70 m). The model-predicted dE/dt pulses were compared with measured dE/dt pulses at nine locations ranging from 27 to 391 m from the channel base for four dE/dt pulses radiated from two triggered dart-stepped leaders. The dE/dt pulses at the closest station, 27 m, were unipolar, dominated by electrostatic and induction components of the radiated dE/dt, and of opposite polarity to the more distant initial dE/dt peaks. The other, more distant, eight stations exhibited bipolar dE/dt pulses, being more or less dominated by the dE/dt radiation component. The derived leader-step current has a slow front that precedes a fast transition to peak amplitude followed by a slow decay to zero after several microseconds. For the four modeled dE/dt pulses, the estimated causative leader-step current peak amplitudes varied from 0.9 to 1.8 kA, the half-peak widths ranged from 370 to 560 ns, the charge transfers were about 1 mC, and the peak current derivatives were about 10 kA/µs. The upward propagation speeds of the leader-step current were from 1.1 to 1.5 × 108 m/s with exponential spatial current decay constants from 13 to 27 m. One dE/dt pulse is analyzed in more detail by studying changes in model-predicted waveforms versus current initiation altitude and by examining the effect of varying model input parameters.

  14. Effect of inductors to mitigate the hot-spot problem in parallel-connected superconducting thin-film fault current limiting elements

    NASA Astrophysics Data System (ADS)

    Yamasaki, H.; Furuse, M.; Kaiho, K.

    2015-06-01

    We have been developing superconducting thin-film fault current limiter (FCL) elements, in which high-resistivity Au-Ag alloy shunt layers are used to protect YBa2Cu3O7 (YBCO) thin films deposited on CeO2-buffered sapphire substrates. The high resistance of the thin films enables the element to withstand high electric fields of more than 40 Vpeak cm-1 during the current-limiting period after quenching, thus greatly reducing the amount of YBCO thin film needed and, consequently, the cost of an FCL. We have succeeded in fabricating and testing 500 V/200 A FCL modules using two 20 cm long YBCO films connected in parallel. In the present study, we performed extensive switching experiments on FCL elements, in which two YBCO films are connected in parallel to achieve higher rated currents, and confirmed the previously observed phenomenon that the hot-spot problem causing film damage just after quench initiation becomes more severe when the total critical current of the thin films is higher. We have investigated the origin of this phenomenon and found that a rapid current transfer from the first-quenched film with lower critical current to the other film causes higher current in the secondly-quenched film that sometimes leads to hot spots. It is demonstrated that the serious hot-spot problem can be mitigated by the use of inductors when the high-resistance FCL elements are connected in parallel. Based on these findings we propose an appropriate architecture of a high electric-field superconducting thin-film FCL that can be used in a real power grid.

  15. Health effects of electromagnetic field generated by lightning current pulses near down conductors

    NASA Astrophysics Data System (ADS)

    Tamus, Z. Á.; Novák, B.; Szücs, L.; Kiss, I.

    2011-06-01

    The lightning current generates a time varying magnetic field near down conductors, when lightning strikes the connected Franklin-rod. The down conductors are mounted on the wall of buildings, where residential places can be situated. It is well known that the rapidly changing magnetic fields could generate dangerous eddy currents in the human body. If the duration and the gradient of the magnetic field were high enough, the peripheral nerves are excited. In this study, the authors introduce an improved model of the interaction of electromagnetic fields of lighting current near a down conductor with the human body. The interaction model has two parts: estimation of the magnetic fields surrounding the down conductor and evaluation of health effects of rapid changing magnetic fields on the human body.

  16. Microstructural evolution of thin film vanadium oxide prepared by pulsed-direct current magnetron sputtering

    SciTech Connect

    Motyka, M. A.; Horn, M. W.; Gauntt, B. D.; Dickey, E. C.; Podraza, N. J.

    2012-11-01

    Vanadium oxide (VO{sub x}) thin films have been deposited by pulsed-DC magnetron sputtering using a metallic vanadium target in a reactive argon and oxygen environment. While the process parameters (power, total pressure, oxygen-to-argon ratio) remained constant, the deposition time was varied to produce films between 75 {+-} 6 and 2901 {+-} 30 A thick, which were then optically and electrically characterized. The complex dielectric function spectra ({epsilon} = {epsilon}{sub 1} + i{epsilon}{sub 2}) of the films from 0.75 to 5.15 eV were extracted by ex situ, multiple-angle spectroscopic ellipsometry (SE) measurements for the series of varied thickness VO{sub x} samples. Significant changes in {epsilon} and resistivity occur as a function of thickness, indicating the correlations exist between the electrical and the optical properties over this spectral range. In addition, in situ measurements via real time SE (RTSE) were made on the film grown to the largest thickness to track optical property and structural variations during growth. RTSE was also used to characterize changes in the film occurring after growth was completed, namely during post sputtering in the presence of argon and oxygen while the sample is shielded, and atmospheric exposure. RTSE indicates that the exposure of the film to the argon and oxygen environment, regardless of the shutter isolating the target, causes up to 200 A of the top surface of the deposited film to become more electrically resistive as evidenced by variations in {epsilon}. Exposure of the VO{sub x} thin film to atmospheric conditions introduces a similar change in {epsilon}, but this change occurs throughout the bulk of the film. A combination of these observations with RTSE results indicates that thinner, less ordered VO{sub x} films are more susceptible to drastic changes due to atmospheric exposure and that microstructural variations in this material ultimately control its environmental stability.

  17. Effects of Biphasic Current Pulse Frequency, Amplitude, Duration and Interphase Gap on Eye Movement Responses to Prosthetic Electrical Stimulation of the Vestibular Nerve

    PubMed Central

    Davidovics, Natan S.; Fridman, Gene Y.; Chiang, Bryce; Della Santina, Charles C.

    2011-01-01

    An implantable prosthesis that stimulates vestibular nerve branches to restore sensation of head rotation and vision-stabilizing reflexes could benefit individuals disabled by bilateral loss of vestibular (inner ear balance) function. We developed a prosthesis that partly restores normal function in animals by delivering pulse frequency modulated (PFM) biphasic current pulses via electrodes implanted in semicircular canals. Because the optimal stimulus encoding strategy is not yet known, we investigated effects of varying biphasic current pulse frequency, amplitude, duration and interphase gap on vestibulo-ocular reflex (VOR) eye movements in chinchillas. Increasing pulse frequency increased response amplitude while maintaining a relatively constant axis of rotation. Increasing pulse amplitude (range 0–325 μA) also increased response amplitude but spuriously shifted eye movement axis, probably due to current spread beyond the target nerve. Shorter pulse durations (range 28–340 μs) required less charge to elicit a given response amplitude and caused less axis shift than longer durations. Varying interphase gap (range 25–175 μs) had no significant effect. While specific values reported herein depend on microanatomy and electrode location in each case, we conclude that PFM with short duration biphasic pulses should form the foundation for further optimization of stimulus encoding strategies for vestibular prostheses intended to restore sensation of head rotation. PMID:20813652

  18. Numerical calculation and experimental research on crack arrest by detour effect and joule heating of high pulsed current in remanufacturing

    NASA Astrophysics Data System (ADS)

    Yu, Jing; Zhang, Hongchao; Deng, Dewei; Hao, Shengzhi; Iqbal, Asif

    2014-07-01

    The remanufacturing blanks with cracks were considered as irreparable. With utilization of detour effect and Joule heating of pulsed current, a technique to arrest the crack in martensitic stainless steel FV520B is developed. According to finite element theory, the finite element(FE) model of the cracked rectangular specimen is established firstly. Then, based on electro-thermo-structure coupled theory, the distributions of current density, temperature field, and stress field are calculated for the instant of energizing. Furthermore, the simulation results are verified by some corresponding experiments performed on high pulsed current discharge device of type HCPD-I. Morphology and microstructure around the crack tip before and after electro pulsing treatment are observed by optical microscope(OM) and scanning electron microscope(SEM), and then the diameters of fusion zone and heat affected zone(HAZ) are measured in order to contrast with numerical calculation results. Element distribution, nano-indentation hardness and residual stress in the vicinity of the crack tip are surveyed by energy dispersive spectrometer(EDS), scanning probe microscopy(SPM) and X-ray stress gauge, respectively. The results show that the obvious partition and refined grain around the crack tip can be observed due to the violent temperature change. The contents of carbon and oxygen in fusion zone and HAZ are higher than those in matrix, and however the hardness around the crack tip decreases. Large residual compressive stress is induced in the vicinity of the crack tip and it has the same order of magnitude for measured results and numerical calculation results that is 100 MPa. The relational curves between discharge energies and diameters of the fusion zone and HAZ are obtained by experiments. The difference of diameter of fusion zone between measured and calculated results is less than 18.3%. Numerical calculation is very useful to define the experimental parameters. An effective method

  19. Electric pulse current stimulation increases electrophysiological properties of If current reconstructed in mHCN4-transfected canine mesenchymal stem cells

    PubMed Central

    FENG, YUANYUAN; LUO, SHOUMING; YANG, PAN; SONG, ZHIYUAN

    2016-01-01

    The ‘funny’ current, also known as the If current, play a crucial role in the spontaneous diastolic depolarization of sinoatrial node cells. The If current is primarily induced by the protein encoded by the hyperpolarization-activated cyclic nucleotide-gated channel 4 (HCN4) gene. The functional If channel can be reconstructed in canine mesenchymal stem cells (cMSCs) transfected with mouse HCN4 (mHCN4). Biomimetic studies have shown that electric pulse current stimulation (EPCS) can promote cardiogenesis in cMSCs. However, whether EPCS is able to influence the properties of the If current reconstructed in mHCN4-transfected cMSCs remains unclear. The present study aimed to investigate the effects of EPCS on the If current reconstructed in mHCN4-transfected cMSCs. The cMSCs were transfected with the lentiviral vector pLentis-mHCN4-GFP. Following transfection, these cells were divided into two groups: mHCN4-transfected cMSCs (group A), and mHCN4-transfected cMSCs induced by EPCS (group B). Using a whole cell patch-clamp technique, the If current was recorded, and group A cMSCs showed significant time and voltage dependencies and sensitivity to extracellular Cs+. The half-maximal activation (V1/2) value was −101.2±4.6 mV and the time constant of activation was 324±41 msec under −160 mV. In the group B cells the If current increased obviously and activation curve moved to right. The absolute value of V1/2 increased significantly to −92.4±4.8 mV (P<0.05), and the time constant of activation diminished under the same command voltage (251±44 vs. 324±41, P<0.05). In addition, the mRNA and protein expression levels of HCN4, connexin 43 (Cx43) and Cx45 were upregulated in group B compared with group A, as determined by reverse transcription-quantitative polymerase chain reaction and western blot analyses. Transmission electron micrographs also confirmed the increased gap junctions in group B. Collectively, these results indicated that reconstructed If channels

  20. Long-lived Ar-Hg plasma in the afterglow of a high-current pulsed discharge

    SciTech Connect

    Sergeichev, K. F.; Lukina, N. A.; Fesenko, A. A.

    2013-02-15

    High-density (n > 10{sup 12} cm{sup -3}) argon-mercury plasma produced by a short (t {approx} 20 {mu}s) high-power pulsed discharge in argon with an admixture of mercury vapor at a discharge current of {approx}50 A, an argon pressure of {approx}4 mm Hg, and a mercury vapor pressure of {approx}10{sup -3} mm Hg was studied using optical spectroscopy and radio physics methods. It is found that the lifetime of this plasma after the end of the discharge pulse is up to 10{sup -2} s. It is shown that such an abnormally long lifetime of such an afterglow plasma, as compared to the plasma of an argon discharge without an admixture of mercury vapor, is related to the long residence time of atoms and ions of both argon and mercury in highly excited states due to chemi-ionization processes involving long-lived metastable argon ions. It is suggested that dissociative recombination of highly excited molecular ions of argon play an important role in the transfer of excitation to argon atoms and ions that are close to autoionization states.

  1. A comparative study of principal component analysis and independent component analysis in eddy current pulsed thermography data processing.

    PubMed

    Bai, Libing; Gao, Bin; Tian, Shulin; Cheng, Yuhua; Chen, Yifan; Tian, Gui Yun; Woo, W L

    2013-10-01

    Eddy Current Pulsed Thermography (ECPT), an emerging Non-Destructive Testing and Evaluation technique, has been applied for a wide range of materials. The lateral heat diffusion leads to decreasing of temperature contrast between defect and defect-free area. To enhance the flaw contrast, different statistical methods, such as Principal Component Analysis and Independent Component Analysis, have been proposed for thermography image sequences processing in recent years. However, there is lack of direct and detailed independent comparisons in both algorithm implementations. The aim of this article is to compare the two methods and to determine the optimized technique for flaw contrast enhancement in ECPT data. Verification experiments are conducted on artificial and thermal fatigue nature crack detection.

  2. Propagation of a surface microwave along the afterglow plasma column of a high-current pulsed discharge

    SciTech Connect

    Sergeichev, K. F.; Karfidov, D. M.

    2011-09-15

    It is demonstrated experimentally that the lifetime of the afterglow plasma of a high-current pulsed discharge in a dielectric tube filled with a mixture of argon with saturated mercury vapor is longer than 1 ms. Such a long lifetime, during which the electron density decreases from 10{sup 14} to 10{sup 12} cm{sup -3}, is explained by the chemi-ionization of mercury vapor by long-lived metastable argon atoms. During this time, the afterglow plasma can serve as a microwave waveguide for a weakly damped low-noise E{sub 0}-type axisymmetric surface mode, which allows one to use it for transmission of signals in the centimeter wavelength range.

  3. A comparative study of principal component analysis and independent component analysis in eddy current pulsed thermography data processing

    NASA Astrophysics Data System (ADS)

    Bai, Libing; Gao, Bin; Tian, Shulin; Cheng, Yuhua; Chen, Yifan; Tian, Gui Yun; Woo, W. L.

    2013-10-01

    Eddy Current Pulsed Thermography (ECPT), an emerging Non-Destructive Testing and Evaluation technique, has been applied for a wide range of materials. The lateral heat diffusion leads to decreasing of temperature contrast between defect and defect-free area. To enhance the flaw contrast, different statistical methods, such as Principal Component Analysis and Independent Component Analysis, have been proposed for thermography image sequences processing in recent years. However, there is lack of direct and detailed independent comparisons in both algorithm implementations. The aim of this article is to compare the two methods and to determine the optimized technique for flaw contrast enhancement in ECPT data. Verification experiments are conducted on artificial and thermal fatigue nature crack detection.

  4. Pulsing frequency induced change in optical constants and dispersion energy parameters of WO3 films grown by pulsed direct current magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Punitha, K.; Sivakumar, R.; Sanjeeviraja, C.

    2014-03-01

    In this work, we present the pulsing frequency induced change in the structural, optical, vibrational, and luminescence properties of tungsten oxide (WO3) thin films deposited on microscopic glass and fluorine doped tin oxide (SnO2:F) coated glass substrates by pulsed dc magnetron sputtering technique. The WO3 films deposited on SnO2:F substrate belongs to monoclinic phase. The pulsing frequency has a significant influence on the preferred orientation and crystallinity of WO3 film. The maximum optical transmittance of 85% was observed for the film and the slight shift in transmission threshold towards higher wavelength region with increasing pulsing frequency revealed the systematic reduction in optical energy band gap (3.78 to 3.13 eV) of the films. The refractive index (n) of films are found to decrease (1.832 to 1.333 at 550 nm) with increasing pulsing frequency and the average value of extinction coefficient (k) is in the order of 10-3. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (Ed) parameters, dielectric constants, plasma frequency, oscillator strength, and oscillator energy (Eo) of WO3 films were calculated and reported for the first time due to variation in pulsing frequency during deposition by pulsed dc magnetron sputtering. The Eo is change between 6.30 and 3.88 eV, while the Ed varies from 25.81 to 7.88 eV, with pulsing frequency. The Raman peak observed at 1095 cm-1 attributes the presence of W-O symmetric stretching vibration. The slight shift in photoluminescence band is attributed to the difference in excitons transition. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

  5. Development of a distributed memory parallel multiphase model for the direct numerical simulation of bottom boundary layer turbulence under combined wave-current flows

    NASA Astrophysics Data System (ADS)

    Davis, J. R.; Ozdemir, C. E.; Balachandar, S.; Hsu, T.

    2012-12-01

    Fine sediment transport and its potential to dampen turbulence under energetic waves and combined wave-current flows are critical to better understanding of the fate of terrestrial sediment particles in the river mouth and eventually, coastal morphodynamics. The unsteady nature of these oscillatory flows necessitates a computationally intense, turbulence resolving approach. Whereas a sophisticated shared memory parallel model has been successfully used to simulate these flows in the intermittently turbulent regime (Remax ~ 1000), scaling issues of shared memory computational hardware limit the applicability of the model to perform very high resolution (> 192x192x193) simulations within reasonable wall-clock times. Thus to meet the need to simulate high resolution, fully turbulent oscillatory flows, a new hybrid shared memory / distributed memory parallel model has been developed. Using OpenMP and MPI constructs, this new model implements a highly-accurate pseudo-spectral scheme in an idealized oscillatory bottom boundary layer (OBBL). Data is stored locally and transferred between computational nodes as appropriate such that FFTs used to calculate derivatives in the x and y-directions and the Chebyshev polynomials used to calculated derivatives in the z-direction are calculated completely in-processor. The model is fully configurable at compile time to support: multiple methods of operation (serial or OpenMP, MPI, OpenMP+MPI parallel), available FFT libraries (DFTI, FFTW3), high temporal resolution timing, persistent or non-persistent MPI, etc. Output is fully distributed to support both independent and shared filesystems. At run time, the model automatically selects the best performing algorithms given the computational resources and domain size. Nearly 40 Integrated test routines (derivatives, FFT transformations, eigenvalues, Poission / Helmholtz solvers, etc.) are used to validate individual components of the model. Test simulations have been performed at the

  6. Mechanism of Fast Current Interruption in p -π -n Diodes for Nanosecond Opening Switches in High-Voltage-Pulse Applications

    NASA Astrophysics Data System (ADS)

    Sharabani, Y.; Rosenwaks, Y.; Eger, D.

    2015-07-01

    Step-recovery diodes operating in the snappy recovery regime are used as opening switches for generating narrow pulses with high-voltage amplitude. Physical modeling of the switching process is complex due to the large number of parameters involved, including diode structure, the extreme physical conditions, and the effect of external driving conditions. In this work, we address the problem by using a physical device simulator for solving the coupled device and electrical driving circuit equations. This method allows deciphering of the physical processes to take place in the diode during the fast current interruption phase. Herein we analyze the complete hard (snappy) reverse recovery process in short-base devices and determine the fast-transition-phase mechanism. It was found that the fast current interruption phase is constructed of two processes; the main parameters governing the switching time duration and the prepulse magnitude are the diode's reverse current density and its base-doping concentration. We describe the dependence of the switching performance in these parameters.

  7. Influence of driving frequency on discharge modes in a dielectric-barrier discharge with multiple current pulses

    SciTech Connect

    Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2013-07-15

    A one-dimensional self-consistent fluid model was employed to investigate the effect of the driving frequency on the discharge modes in atmospheric-pressure argon discharge with multiple current pulses. The discharge mode was discussed in detail not only at current peaks but also between two adjacent peaks. The simulation results show that different transitions between the Townsend and glow modes during the discharge take place with the driving frequency increased. A complicated transition from the Townsend mode, through glow, Townsend, and glow, and finally back to the Townsend one is found in the discharge with the driving frequency of 8 kHz. There is a tendency of transition from the Townsend to glow mode for the discharge both at the current peaks and troughs with the increasing frequency. The discharge in the half period can all along operate in the glow mode with the driving frequency high enough. This is resulted from the preservation of more electrons in the gas gap and acquisition of more electron energy from the swiftly varying electric field with the increase in driving frequency. Comparison of the spatial and temporal evolutions of the electron density at different driving frequencies indicates that the increment of the driving frequency allows the plasma chemistry to be enhanced. This electrical characteristic is important for the applications, such as surface treatment and biomedical sterilization.

  8. Advances in transient (pulsed) eddy current for inspection of multi-layer aluminum structures in the presence of ferrous fasteners

    NASA Astrophysics Data System (ADS)

    Desjardins, D. R.; Vallières, G.; Whalen, P. P.; Krause, T. W.

    2012-05-01

    An experimental investigation of the electromagnetic processes underlying transient (pulsed) eddy current inspection of aircraft wing structures in the vicinity of ferrous fasteners is performed. The separate effects of transient excitation of ferrous fastener and eddy currents induced in the surrounding aluminum structure are explored using a transmit-receive configuration with transient excitation of a steel rod, an aluminum plate with a bore hole and a steel rod through the bore hole. Observations are used to interpret results from a coupled driving and differential coil sensing unit applied to detect fatigue cracks emanating from bolt holes in aluminum structures with ferrous fasteners present. In particular, it is noted that abrupt magnetization of the fastener, by the probe's central driving unit, can transfer flux and consequently, induce strong eddy current responses deep within the aluminum structure in the vicinity of the bore hole. Rotation of the probe, centered over the fastener, permits detection of subsurface discontinuities, such as cracks, by the pair of differentially connected pickup coils.

  9. A review of advanced small-scale parallel bioreactor technology for accelerated process development: current state and future need.

    PubMed

    Bareither, Rachel; Pollard, David

    2011-01-01

    The pharmaceutical and biotech industries face continued pressure to reduce development costs and accelerate process development. This challenge occurs alongside the need for increased upstream experimentation to support quality by design initiatives and the pursuit of predictive models from systems biology. A small scale system enabling multiple reactions in parallel (n ≥ 20), with automated sampling and integrated to purification, would provide significant improvement (four to fivefold) to development timelines. State of the art attempts to pursue high throughput process development include shake flasks, microfluidic reactors, microtiter plates and small-scale stirred reactors. The limitations of these systems are compared to desired criteria to mimic large scale commercial processes. The comparison shows that significant technological improvement is still required to provide automated solutions that can speed upstream process development.

  10. Parallel-beam imaging at the ESRF beamline ID19: current status and plans for the future

    NASA Astrophysics Data System (ADS)

    Weitkamp, T.; Tafforeau, P.; Boller, E.; Cloetens, P.; Valade, J.-P.; Bernard, P.; Peyrin, F.; Ludwig, W.; Helfen, L.; Baruchel, J.

    2010-06-01

    The ESRF synchrotron beamline ID19, dedicated to full-field parallel-beam imaging techniques such as phase-contrast and absorption microtomography and X-ray topography, is one of the most versatile instruments of its kind. This paper presents key characteristics of ID19 in its present form, names examples for research and development performed on the beamline, and outlines the plans for an upgrade on the beamline in coming years, to adapt to the growing needs of the user community. The technical goals envisioned include an increase in available beam size and maximum photon energy, and a substantial increase in flux density for applications using beams of small and intermediate size.

  11. Anomalous Magnetic Field Pulses, Ground Currents, and the Build-up of Stress prior to the Chi-Chi Earthquake

    NASA Astrophysics Data System (ADS)

    Hall, C. G.; Yen, H. Y.; Chen, H. C.; Takeuchi, A.; Lau, B. W.; Freund, F.

    2004-12-01

    Before the Sept. 21, 1999 Chi-Chi earthquake in Taiwan and during the period of aftershocks local magnetic field anomalies (up to 200 nT) were recorded at two stations of the Taiwan magnetometer network. The magnetic pulses each lasted for several hours. They arrived in week-long bunches and extend over more than three months. Powerful ground currents are required to generate such strong local magnetic fields, in the order of 106 Amp at peak intensity. The seismic energy released by small earthquakes (earthmurmur) during the weeks before the main shock shows a similar time-dependent evolution, which correlates with the magnetic field anomalies. This suggests that the ground currents are generated when the regional stresses increase as signaled by an increase in the frequency of small earthquakes. We have measured in the laboratory the stress-induced electrical currents generated in igneous rocks (granite and anorthosite). Our experiments show that these rocks exhibit a battery-like behavior, i.e. they produce currents, which flow out of the stressed rock volume into the surrounding unstressed rock. The charge carriers are electronic and positively charged. They are believed to be positive holes (p-holes), i.e. defect electrons in the valence band of the otherwise insulating rocks. The number of outflowing charge carriers is in the order of 106 cm-3 of stressed rock. Scaling up to the dimensions of the Chi-Chi event and assuming that the compressed rock volume was 100 x 10 x 50 km3 (length of the surface rupture in the N-S direction x thickness x width in the E-W direction) we find that the number of charge carriers activated in such a large "source volume" would suffice to produce outflow currents in the order of 106 Amps over an extended period of time.

  12. Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Ikeda, Masao; Zhou, Kun; Liu, Zongshun; Liu, Jianping; Zhang, Shuming; Yang, Hui

    2015-07-01

    Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes-like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub-nanometer scale, band filling effect (Burstein-Moss shift), and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to correlate the carrier densities with current densities, the nonradiative recombination rates were deduced experimentally by curve-fitting to the external quantum efficiencies. The transition energies in LEDs both with 15 nm quantum barriers and 5 nm quantum barriers, calculated using full strengths of theoretical macroscopic polarization given by Barnardini and Fiorentini [Phys. Status Solidi B 216, 391 (1999)] are in excellent accordance with experimental results. The LED with 5 nm barriers has been shown to exhibit a higher transition energy and a smaller blue shift than those of LED with 15 nm barriers, which is mainly caused by the smaller internal polarization field in the quantum wells.

  13. Injection current dependences of electroluminescence transition energy in InGaN/GaN multiple quantum wells light emitting diodes under pulsed current conditions

    SciTech Connect

    Zhang, Feng; Ikeda, Masao Liu, Jianping; Zhang, Shuming; Zhou, Kun; Yang, Hui; Liu, Zongshun

    2015-07-21

    Injection current dependences of electroluminescence transition energy in blue InGaN/GaN multiple quantum wells light emitting diodes (LEDs) with different quantum barrier thicknesses under pulsed current conditions have been analyzed taking into account the related effects including deformation caused by lattice strain, quantum confined Stark effects due to polarization field partly screened by carriers, band gap renormalization, Stokes-like shift due to compositional fluctuations which are supposed to be random alloy fluctuations in the sub-nanometer scale, band filling effect (Burstein-Moss shift), and quantum levels in finite triangular wells. The bandgap renormalization and band filling effect occurring at high concentrations oppose one another, however, the renormalization effect dominates in the concentration range studied, since the band filling effect arising from the filling in the tail states in the valence band of quantum wells is much smaller than the case in the bulk materials. In order to correlate the carrier densities with current densities, the nonradiative recombination rates were deduced experimentally by curve-fitting to the external quantum efficiencies. The transition energies in LEDs both with 15 nm quantum barriers and 5 nm quantum barriers, calculated using full strengths of theoretical macroscopic polarization given by Barnardini and Fiorentini [Phys. Status Solidi B 216, 391 (1999)] are in excellent accordance with experimental results. The LED with 5 nm barriers has been shown to exhibit a higher transition energy and a smaller blue shift than those of LED with 15 nm barriers, which is mainly caused by the smaller internal polarization field in the quantum wells.

  14. Comparative response of lead-acid and nickel-iron batteries to pulsed and constant-current loads

    NASA Astrophysics Data System (ADS)

    Deluca, W. H.; Tummillo, A. F.; Biwer, T. L.; Christianson, C. C.; Hornstra, F.; Yao, N. P.

    1983-06-01

    Improved lead acid and nickel iron batteries were developed for use in electric vehicles. The response of these batteries to given discharge conditions differs according to characteristics of each system. The discharge capacity of the lead acid system is reduced at increased discharge rates and its internal resistance is a function of both depth of discharge (DOD) and discharge rate. Open circuit stand times at DOD levels 50% reduce the internal resistance of the lead acid system and provide a corresponding increase in its availability capacity. The discharge capacity and internal resistance of the nickel/iron system are virtually independent of both discharge rate and open circuit stand times during discharge. With pulsed current loads, the available energy and power output of both battery systems are always less than those obtained with equivalent constant current loads due to increased internal power losses. The nickel-iron system exhibits an internal inductance that is significantly greater than that for the lead acid system thereby causing potentially damaging voltage transients. The test procedures and system employed, test data, and methods for predicting battery response are described.

  15. Microstructure and properties of Ni-Co/nano-Al 2O 3 composite coatings by pulse reversal current electrodeposition

    NASA Astrophysics Data System (ADS)

    Chang, L. M.; An, M. Z.; Guo, H. F.; Shi, S. Y.

    2006-12-01

    Ni-Co/nano-Al 2O 3 (Ni-Co/Al 2O 3) composite coatings were prepared under pulse reversal current (PRC) and direct current (dc) methods respectively. The microstructure of coatings was characterized by means of XRD, SEM and TEM. Both the Ni-Co alloy and composite coatings exhibit single phase of Ni matrix with face-centered cubic (fcc) crystal structure, and the crystal orientation of the Ni-Co/Al 2O 3 composite coating was transformed from crystal face (2 0 0) to (1 1 1) compared with alloy coatings. The hardness, anti-wear property and macro-residual stress were also investigated. The results showed that the microstructure and performance of the coatings were greatly affected by Al 2O 3 content and the electrodeposition methods. With the increasing of Al 2O 3 content, the hardness and wear resistance of the composite coatings enhanced. The PRC composite coatings exhibited compact surface, high hardness, better wear resistance and lower macro-residual stress compared with that of the dc composite coatings.

  16. PULSE GENERATOR

    DOEpatents

    Roeschke, C.W.

    1957-09-24

    An improvement in pulse generators is described by which there are produced pulses of a duration from about 1 to 10 microseconds with a truly flat top and extremely rapid rise and fall. The pulses are produced by triggering from a separate input or by modifying the current to operate as a free-running pulse generator. In its broad aspect, the disclosed pulse generator comprises a first tube with an anode capacitor and grid circuit which controls the firing; a second tube series connected in the cathode circuit of the first tube such that discharge of the first tube places a voltage across it as the leading edge of the desired pulse; and an integrator circuit from the plate across the grid of the second tube to control the discharge time of the second tube, determining the pulse length.

  17. Pulsing frequency induced change in optical constants and dispersion energy parameters of WO{sub 3} films grown by pulsed direct current magnetron sputtering

    SciTech Connect

    Punitha, K.; Sivakumar, R.; Sanjeeviraja, C.

    2014-03-21

    In this work, we present the pulsing frequency induced change in the structural, optical, vibrational, and luminescence properties of tungsten oxide (WO{sub 3}) thin films deposited on microscopic glass and fluorine doped tin oxide (SnO{sub 2}:F) coated glass substrates by pulsed dc magnetron sputtering technique. The WO{sub 3} films deposited on SnO{sub 2}:F substrate belongs to monoclinic phase. The pulsing frequency has a significant influence on the preferred orientation and crystallinity of WO{sub 3} film. The maximum optical transmittance of 85% was observed for the film and the slight shift in transmission threshold towards higher wavelength region with increasing pulsing frequency revealed the systematic reduction in optical energy band gap (3.78 to 3.13 eV) of the films. The refractive index (n) of films are found to decrease (1.832 to 1.333 at 550 nm) with increasing pulsing frequency and the average value of extinction coefficient (k) is in the order of 10{sup −3}. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion energy (E{sub d}) parameters, dielectric constants, plasma frequency, oscillator strength, and oscillator energy (E{sub o}) of WO{sub 3} films were calculated and reported for the first time due to variation in pulsing frequency during deposition by pulsed dc magnetron sputtering. The E{sub o} is change between 6.30 and 3.88 eV, while the E{sub d} varies from 25.81 to 7.88 eV, with pulsing frequency. The Raman peak observed at 1095 cm{sup −1} attributes the presence of W-O symmetric stretching vibration. The slight shift in photoluminescence band is attributed to the difference in excitons transition. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

  18. Effects of Pulse Current on Transient Liquid Phase (TLP) Diffusion Bonding of SiCp/2024Al Composites Sheet Using Mixed Al, Cu, and Ti Powder Interlayer

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Jiang, Shaosong; Zhang, Kaifeng

    2012-09-01

    The effects of pulse current on transient liquid phase (TLP) diffusion bonding of SiCp/2024Al composites sheet were investigated at 853 K (580 °C) using a mixed slurry of Al, Cu, and Ti powder interlayer. The process parameters were as follows: the pulse current density of 1.15 × 102 A/mm2, the original pressure of 0.5 MPa, the vacuum of 1.3 × 10-3 Pa, and the bonding time from 15 to 60 minutes. Moreover, the bonding mechanism in correlation with the microstructural and mechanical properties variation was analyzed.

  19. Late Holocene distal mud deposits off the Nakdong delta, SE Korea: evidence for shore-parallel sediment transport in a current-dominated setting

    NASA Astrophysics Data System (ADS)

    Chun, Jong-Hwa; Kim, Yuri; Bahk, Jang-Jun; Kim, Young Jun; Kang, Dong-Hyo; Kim, Yong Hoon; Kim, Gil Young; Ryu, Byong-Jae

    2015-12-01

    The distal mud deposits (DMDs) off the Nakdong delta represent a subaqueous delta on the inner continental shelf aligned parallel to the southeast coast of Korea and displaying a clinoform geometry. Hydrographically, the coast is characterized by a micro-tidal regime, the strong Korean Coastal Current (KCC) and the East Korean Warm Current (EKWC). Age models and sedimentary facies related to the clinoform geometries are based on high-resolution chirp subbottom profile data and have provided information on shore-parallel sediment transport and accumulation during the late Holocene sea-level highstand. The highest sedimentation rates (6.19-9.17 cm/year) produced steep foresets in the central DMDs at water depths of 35-50 m. Here, vertical burrows are repeatedly truncated by laminated mud packages displaying erosional surfaces. This region represents the main depocenter of the Nakdong subaqueous delta. The topset sediments of the southern DMD at ~40 m water depth closer to the river mouth show relatively low sedimentation rates (0.01-0.12 cm/year). Here, the muds have a predominantly mottled character. Similarly, the foreset sediments of the northern DMD at ~71-80 m water depth with sedimentation rates of 0.10-2.03 cm/year are also predominantly characterized by mottled muds. The spatial dispersal pattern of the DMDs is consistent with the coast-parallel front between the KCC and EKWC along the southeast Korean coast. In addition, the depocenter of the Nakdong subaqueous delta clinoform is affected by the near-bed turbulence generated by episodic storm events.

  20. A novel flattop current regulated energy discharge type pulsed power supply and magnet yielding 4. 4 kGauss-meter for 6 milliseconds

    SciTech Connect

    Visser, A.T.

    1989-07-01

    Most energy discharge power supplies obtain their bursts of power from the energy stored in charged capacitors when it is suddenly released into a load. This note describes the design of a similar small 800 Joules energy discharge type power supply and magnet. The magnet gap is 2 in.{times}2 in.{times}25-1/2 in. long and produces about 4.4 kGauss-meters at a rate of 12 pulses per minute. Each pulse is current regulated at the top for a duration of 6 msec. and varies less than 0.6% of set value. Current regulation at flattop is obtained by switching a resistor in and out of the discharge circuit with an IGBT at a rate of about 5 kHz. Most energy discharge systems produce half sine wave pulses, and current regulation is obtained by controlling the charge voltage at the energy storage capacitor, resulting only in a controlled peak current value of the half sine wave pulse. The current value at the top changes substantially during 6 msec. depending on the operating frequency.

  1. Dependence of synergy current driven by lower hybrid wave and electron cyclotron wave on the frequency and parallel refractive index of electron cyclotron wave for Tokamaks

    SciTech Connect

    Huang, J.; Chen, S. Y. Tang, C. J.

    2014-01-15

    The physical mechanism of the synergy current driven by lower hybrid wave (LHW) and electron cyclotron wave (ECW) in tokamaks is investigated using theoretical analysis and simulation methods in the present paper. Research shows that the synergy relationship between the two waves in velocity space strongly depends on the frequency ω and parallel refractive index N{sub //} of ECW. For a given spectrum of LHW, the parameter range of ECW, in which the synergy current exists, can be predicted by theoretical analysis, and these results are consistent with the simulation results. It is shown that the synergy effect is mainly caused by the electrons accelerated by both ECW and LHW, and the acceleration of these electrons requires that there is overlap of the resonance regions of the two waves in velocity space.

  2. Parallelized laser-direct patterning of nanocrystalline metal thin films by use of a pulsed laser-induced thermo-elastic force.

    PubMed

    Yoo, Hyeonggeun; Shin, Hyunkwon; Sim, Boyeon; Kim, Sangtae; Lee, Myeongkyu

    2009-06-17

    Thin film patterning by the conventional lithographic technique requires a number of steps including the deposition, development, and removal of the photoresist layer. Here we demonstrate that metal thin films evaporated on glass can be directly patterned by a spatially modulated pulsed Nd-YAG laser beam (wavelength = 1064 nm, pulse width = 6 ns) incident from the backside of the substrate. This method utilizes a pulsed laser-induced thermo-elastic force exerted on the film which plays a role in detaching it from the substrate. High-fidelity patterns at the micrometer scale have been fabricated over a few square centimeters by a single pulse with pulse energy of 850 mJ. This is attributed to the fact that deposited metal films are polycrystalline with nano-sized grains, and thus localized etching of the material is possible with shearing along the weakly bonded grain boundary regions. We have also developed a nano-block model to simulate the laser-direct patterning of nanocrystalline thin films. Experimental results could be well described with this simulation model. The patterning process presented here provides a simple photoresist-free route to fabricate metal thin film patterns on transparent substrates.

  3. A pulsed eddy current probe for inspection of support plates from within Alloy-800 steam generator tubes

    NASA Astrophysics Data System (ADS)

    Krause, T. W.; Babbar, V. K.; Underhill, P. R.

    2014-02-01

    Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed eddy current (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC signals to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled signal amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.

  4. High Temperature Corrosion studies on Pulsed Current Gas Tungsten Arc Welded Alloy C-276 in Molten Salt Environment

    NASA Astrophysics Data System (ADS)

    Manikandan, M.; Arivarasu, M.; Arivazhagan, N.; Puneeth, T.; Sivakumar, N.; Murugan, B. Arul; Sathishkumar, M.; Sivalingam, S.

    2016-09-01

    Alloy C-276 is widely used in the power plant environment due to high strength and corrosion in highly aggressive environment. The investigation on high- temperature corrosion resistance of the alloy C-276 PCGTA weldment is necessary for prolonged service lifetime of the components used in corrosive environments. Investigation has been carried out on Pulsed Current Gas Tungsten Arc Welding by autogenous and different filler wires (ERNiCrMo-3 and ERNiCrMo-4) under molten state of K2SO4-60% NaCl environment at 675oC under cyclic condition. Thermogravimetric technique was used to establish the kinetics of corrosion. Weight gained in the molten salt reveals a steady-state parabolic rate law while the kinetics with salt deposits displays multi-stage growth rates. PCGTA ERNiCrMo-3 shows the higher parabolic constant compared to others. The scale formed on the weldment samples upon hot corrosion was characterized by using X-ray diffraction, SEM and EDAX analysis to understand the degradation mechanisms. From the results of the experiment the major phases are identified as Cr2O3, Fe2O3, and NiCr2O4. The result showed that weld fabricated by ERNiCrMo-3 found to be more prone to degradation than base metal and ERNiCrMo-4 filler wire due to higher segregation of alloying element of Mo and W in the weldment

  5. Pulsed Current Activated Synthesis and Consolidation of Nanostructured Ti-TiC Composite and Its Mechanical Properties.

    PubMed

    Kim, Dong-Ki; Park, Na-Ra; Kim, Byung-Su; Yoon, Jin-Kook; Hong, Kyung-Tae; Shon, In-Jin

    2016-02-01

    Ti and CNT powders were milled by high energy ball milling. The milled powders were then simultaneously synthesized and consolidated using pulsed current activated sintering (PCAS) within one minute under the applied pressure of 80 MPa. The advantage of this process is not only rapid densification to near theoretical density but also to prevent grain growth in nano-structured materials The milling did not induce any reaction between the constituent powders. Meanwhile, PCAS of the Ti-CNT mixture produced a Ti-TiC composite according to the reaction (Ti + 0.06CNT --> 0.94Ti+0.06TiC, Ti+0.12CNT --> 0.88Ti+0.12TiC). Highly dense nanocrystalline Ti-TiC compos- ites with a relative density of up to 99.5% were obtained within one minute. The hardness and fracture toughness of the dense Ti-6mole% TiC and Ti-12 mole% TiC produced by PCAS were also investigated. PMID:27433696

  6. A pulsed eddy current probe for inspection of support plates from within Alloy-800 steam generator tubes

    SciTech Connect

    Krause, T. W.; Babbar, V. K.; Underhill, P. R.

    2014-02-18

    Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed eddy current (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC signals to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled signal amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.

  7. NOTE: Determination of the recombination correction factor kS for some specific plane-parallel and cylindrical ionization chambers in pulsed photon and electron beams

    NASA Astrophysics Data System (ADS)

    Bruggmoser, G.; Saum, R.; Schmachtenberg, A.; Schmid, F.; Schüle, E.

    2007-01-01

    It has been shown from an evaluation of the inverse reading of the dosemeter (1/M) against the inverse of the polarizing voltage (1/V), obtained with a number of commercially available ionization chambers, using dose per pulse values between 0.16 and 5 mGy, that a linear relationship between the recombination correction factor kS and dose per pulse (DPP) can be found. At dose per pulse values above 1 mGy the method of a general equation with coefficients dependent on the chamber type gives more accurate results than the Boag method. This method was already proposed by Burns and McEwen (1998, Phys. Med. Biol. 43 2033) and avoids comprehensive and time-consuming measurements of Jaffé plots which are a prerequisite for the application of the multi-voltage analysis (MVA) or the two-voltage analysis (TVA). We evaluated and verified the response of ionization chambers on the recombination effect in pulsed accelerator beams for both photons and electrons. Our main conclusions are: (1) The correction factor kS depends only on the DPP and the chamber type. There is no influence of radiation type and energy. (2) For all the chambers investigated there is a linear relationship between kS and DPP up to 5 mGy/pulse, and for two chambers we could show linearity up to 40 mGy/pulse. (3) A general formalism, such as that of Boag, characterizes chambers exclusively by the distance of the electrodes and gives a trend for the correction factor, and therefore (4) a general formalism has to reflect the influence of the chamber construction on the recombination by the introduction of chamber-type dependent coefficients.

  8. Pulse Voltammetry

    NASA Astrophysics Data System (ADS)

    Stojek, Zbigniew

    The idea of imposing potential pulses and measuring the currents at the end of each pulse was proposed by Barker in a little-known journal as early as in 1958 [1]. However, the first reliable trouble-free and affordable polarographs offering voltammetric pulse techniques appeared on the market only in the 1970s. This delay was due to some limitations on the electronic side. In the 1990s, again substantial progress in electrochemical pulse instrumentation took place. This was related to the introduction of microprocessors, computers, and advanced software.

  9. Saturation of light – current characteristics of high-power lasers (λ = 1.0 – 1.1 mm) in pulsed regime

    SciTech Connect

    Veselov, D A; Kapitonov, V A; Pikhtin, N A; Lyutetskiy, A V; Nikolaev, D N; Slipchenko, S O; Sokolova, Z N; Shamakhov, V V; Shashkin, I S; Tarasov, I S

    2014-11-30

    Semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with a broadened waveguide and emitting in the wavelength range 1.0 – 1.1 μm are studied. It is found that the intensity of spontaneous emission from the active region increases with increasing pump current above the lasing threshold and that this is caused by a growth in the concentration of charge carriers in the active region due to the modal gain enhancement needed to compensate for the growing internal optical loss at high pulsed pump currents. It is shown that the increase in the internal optical loss with increasing pulsed pump current is one of the main reasons for saturation of the light – current characteristics of high-power semiconductor lasers. (lasers)

  10. Parallel algorithm development

    SciTech Connect

    Adams, T.F.

    1996-06-01

    Rapid changes in parallel computing technology are causing significant changes in the strategies being used for parallel algorithm development. One approach is simply to write computer code in a standard language like FORTRAN 77 or with the expectation that the compiler will produce executable code that will run in parallel. The alternatives are: (1) to build explicit message passing directly into the source code; or (2) to write source code without explicit reference to message passing or parallelism, but use a general communications library to provide efficient parallel execution. Application of these strategies is illustrated with examples of codes currently under development.

  11. Plasma Formation and Evolution on Cu, Al, Ti, and Ni Surfaces Driven by a Mega-Ampere Current Pulse

    NASA Astrophysics Data System (ADS)

    Yates, Kevin C.

    Metal alloy mm-diameter rods have been driven by a 1-MA, 100-ns current pulse from the Zebra z-pinch. The intense current produces megagauss surface magnetic fields that diffuse into the load, ohmically heating the metal until plasma forms. Because the radius is much thicker than the skin depth, the magnetic field reaches a much higher value than around a thin-wire load. With the "barbell" load design, plasma formation in the region of interest due to contact arcing or electron avalanche is avoided, allowing for the study of ohmically heated loads. Work presented here will show first evidence of a magnetic field threshold for plasma formation in copper 101, copper 145, titanium, and nickel, and compare with previous work done with aluminum. Copper alloys 101 and 145, titanium grade II, and nickel alloy 200 form plasma when the surface magnetic field reaches 3.5, 3.0, 2.2, and 2.6 megagauss, respectively. Varying the element metal, as well as the alloy, changes multiple physical properties of the load and affects the evolution of the surface material through the multiple phase changes. Similarities and differences between these metals will be presented, giving motivation for continued work with different material loads. During the current rise, the metal is heated to temperatures that cause multiple phase changes. When the surface magnetic field reaches a threshold, the metal ionizes and the plasma becomes pinched against the underlying cooler, dense material. Diagnostics fielded have included visible light radiometry, two-frame shadowgraphy (266 and 532 nm wavelengths), time-gated EUV spectroscopy, single-frame/2ns gated imaging, and multi-frame/4ns gated imaging with an intensified CCD camera (ICCD). Surface temperature, expansion speeds, instability growth, time of plasma formation, and plasma uniformity are determined from the data. The time-period of potential plasma formation is scrutinized to understand if and when plasma forms on the surface of a heated

  12. Parallel computers

    SciTech Connect

    Treveaven, P.

    1989-01-01

    This book presents an introduction to object-oriented, functional, and logic parallel computing on which the fifth generation of computer systems will be based. Coverage includes concepts for parallel computing languages, a parallel object-oriented system (DOOM) and its language (POOL), an object-oriented multilevel VLSI simulator using POOL, and implementation of lazy functional languages on parallel architectures.

  13. Nerve-pulse interactions

    SciTech Connect

    Scott, A.C.

    1982-01-01

    Some recent experimental and theoretical results on mechanisms through which individual nerve pulses can interact are reviewed. Three modes of interactions are considered: (1) interaction of pulses as they travel along a single fiber which leads to velocity dispersion; (2) propagation of pairs of pulses through a branching region leading to quantum pulse code transformations; and (3) interaction of pulses on parallel fibers through which they may form a pulse assembly. This notion is analogous to Hebb's concept of a cell assembly, but on a lower level of the neural hierarchy.

  14. The self-consistent parallel electric field due to electrostatic ion-cyclotron turbulence in downward auroral-current regions of the Earth's magnetosphere. IV

    SciTech Connect

    Jasperse, John R.; Basu, Bamandas; Lund, Eric J.; Grossbard, Neil

    2010-06-15

    The physical processes that determine the self-consistent electric field (E{sub ||}) parallel to the magnetic field have been an unresolved problem in magnetospheric physics for over 40 years. Recently, a new multimoment fluid theory was developed for inhomogeneous, nonuniformly magnetized plasma in the guiding-center and gyrotropic approximation that includes the effect of electrostatic, turbulent, wave-particle interactions (see Jasperse et al. [Phys. Plasmas 13, 072903 (2006); ibid.13, 112902 (2006)]). In the present paper and its companion paper [Jasperse et al., Phys. Plasmas 17, 062903 (2010)], which are intended as sequels to the earlier work, a fundamental model for downward, magnetic field-aligned (Birkeland) currents for quasisteady conditions is presented. The model includes the production of electrostatic ion-cyclotron turbulence in the long-range potential region by an electron, bump-on-tail-driven ion-cyclotron instability. Anomalous momentum transfer (anomalous resistivity) by itself is found to produce a very small contribution to E{sub ||}; however, the presence of electrostatic, ion-cyclotron turbulence has a very large effect on the altitude dependence of the entire quasisteady solution. Anomalous energy transfer (anomalous heating and cooling) modifies the density, drift, and temperature altitude profiles and hence the generalized parallel-pressure gradients and mirror forces in the electron and ion momentum-balance equations. As a result, |E{sub ||}| is enhanced by nearly a factor of 40 compared to its value when turbulence is absent. The space-averaged potential increase associated with the strong double layer at the bottom of the downward-current sheet is estimated using the FAST satellite data and the multimoment fluid theory.

  15. Long-pulse production of high current negative ion beam by using actively temperature controlled plasma grid for JT-60SA negative ion source

    SciTech Connect

    Kojima, A.; Hanada, M.; Yoshida, M.; Umeda, N.; Hiratsuka, J.; Kashiwagi, M.; Tobari, H.; Watanabe, K.; Grisham, L. R.

    2015-04-08

    The temperature control system of the large-size plasma grid has been developed to realize the long pulse production of high-current negative ions for JT-60SA. By using this prototype system for the JT-60SA ion source, 15 A negative ions has been sustained for 100 s for the first time, which is three times longer than that obtained in JT-60U. In this system, a high-temperature fluorinated fluid with a high boiling point of 270 degree Celsius is circulated in the cooling channels of the plasma grids (PG) where a cesium (Cs) coverage is formed to enhance the negative ion production. Because the PG temperature control had been applied to only 10% of the extraction area previously, the prototype PG with the full extraction area (110 cm × 45 cm) was developed to increase the negative ion current in this time. In the preliminary results of long pulse productions of high-current negative ions at a Cs conditioning phase, the negative ion production was gradually degraded in the last half of 100 s pulse where the temperature of an arc chamber wall was not saturated. From the spectroscopic measurements, it was found that the Cs flux released from the wall might affect to the negative ion production, which implied the wall temperature should be kept low to control the Cs flux to the PG for the long-pulse high-current production. The obtained results of long-pulse production and the PG temperature control method contributes the design of the ITER ion source.

  16. Pulsed discharge production Ar* metastables

    NASA Astrophysics Data System (ADS)

    Han, Jiande; Heaven, Michael C.; Emmons, Daniel; Perram, Glen P.; Weeks, David E.; Bailey, William F.

    2016-03-01

    The production of relatively high densities of Ar* metastables (>1012 cm-3) in Ar/He mixtures, at total pressures close to 1 atm, is essential for the efficient operation of an optically pumped Ar* laser. We have used emission spectroscopy and diode laser absorption spectroscopy measurements to observe the production and decay of Ar* in a parallel plate pulsed discharge. With discharge pulses of 1 μs duration we find that metastable production is dominated by processes occurring within the first 100 ns of the gas break-down. Application of multiple, closely spaced discharge pulses yields insights concerning conditions that favor metastable production. This information has been combined with time-resolved measurements of voltage and current. The experimental results and preliminary modeling of the discharge kinetics are presented.

  17. Analysis and fabrication of tungsten CERMET materials for ultra-high temperature reactor applications via pulsed electric current sintering

    NASA Astrophysics Data System (ADS)

    Webb, Jonathan A.

    The optimized development path for the fabrication of ultra-high temperature W-UO2 CERMET fuel elements were explored within this dissertation. A robust literature search was conducted, which concluded that a W-UO 2 fuel element must contain a fine tungsten microstructure and spherical UO2 kernels throughout the entire consolidation process. Combined Monte Carlo and Computational Fluid Dynamics (CFD) analysis were used to determine the effects of rhenium and gadolinia additions on the performance of W-UO 2 fuel elements at refractory temperatures and in dry and water submerged environments. The computational analysis also led to the design of quasi-optimized fuel elements that can meet thermal-hydraulic and neutronic requirements A rigorous set of experiments were conducted to determine if Pulsed Electric Current Sintering (PECS) can fabricate tungsten and W-Ce02 specimens to the required geometries, densities and microstructures required for high temperature fuel elements as well as determine the mechanisms involved within the PECS consolidation process. The CeO2 acts as a surrogate for UO 2 fuel kernels in these experiments. The experiments seemed to confirm that PECS consolidation takes place via diffusional mass transfer methods; however, the densification process is rapidly accelerated due to the effects of current densities within the consolidating specimen. Fortunately the grain growth proceeds at a traditional rate and the PECS process can yield near fully dense W and W-Ce02 specimens with a finer microstructure than other sintering techniques. PECS consolidation techniques were also shown to be capable of producing W-UO2 segments at near-prototypic geometries; however, great care must be taken to coat the fuel particles with tungsten prior to sintering. Also, great care must be taken to ensure that the particles remain spherical in geometry under the influence of a uniaxial stress as applied during PECS, which involves mixing different fuel kernel sizes in

  18. Pulse doubling in zigzag-connected autotransformer-based 12-pulse ac-dc converter for power quality improvement

    NASA Astrophysics Data System (ADS)

    Abdollahi, Rohollah

    2012-12-01

    This paper presents a pulse doubling technique in a 12-pulse ac-dc converter which supplies direct torque controlled motor drives (DTCIMDs) in order to have better power quality conditions at the point of common coupling. The proposed technique increases the number of rectification pulses without significant changes in the installations and yields in harmonic reduction in both ac and dc sides. The 12-pulse rectified output voltage is accomplished via two paralleled six-pulse acdc converters each of them consisting of three-phase diode bridge rectifiers. An autotransformer is designed to supply the rectifiers. The design procedure of magnetics is in a way such that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. Independent operation of paralleled diode-bridge rectifiers, i.e. dc-ripple re-injection methodology, requires a Zero Sequence Blocking Transformer (ZSBT). Finally, a tapped interphase reactor is connected at the output of ZSBT to double the pulse numbers of output voltage up to 24 pulses. The aforementioned structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for varying loads. Furthermore, near unity power factor is obtained for a wide range of DTCIMD operation. A comparison is made between 6-pulse, 12-pulse, and proposed converters from view point of power quality indices. Results show that input current total harmonic distortion (THD) is less than 5% for the proposed topology at various loads.

  19. Propagation In Matter Of Currents Of Relativistic Electrons Beyond The Alfven Limit, Produced In Ultra-High-Intensity Short-Pulse Laser-Matter Interactions

    NASA Astrophysics Data System (ADS)

    Batani, D.; Baton, S. D.; Manclossi, M.; Amiranoff, F.; Koenig, M.; Santos, J. J.; Martinolli, E.; Gremillet, L.; Popescu, H.; Antonicci, A.; Rousseaux, C.; Rabec Le Gloahec, M.; Hall, T.; Malka, V.; Cowan, T. E.; Stephens, R.; Key, M.; King, J.; Freeman, R.

    2004-12-01

    This paper reports the results of several experiments performed at the LULI laboratory (Palaiseau, France) concerning the propagation of large relativistic currents in matter from ultra-high-intensity laser pulse interaction with target. We present our results according to the type of diagnostics used in the experiments: 1) Kα emission and Kα imaging, 2) study of target rear side emission in the visible region, 3) time resolved optical shadowgraphy.

  20. Laboratory study of the temporal evolution of the current-voltage characteristic of a probe in the wake of an object immersed in a pulsed flowing plasma

    NASA Technical Reports Server (NTRS)

    Meassick, S.; Chan, C.

    1992-01-01

    Measurements of the current-voltage characteristics of a Langmuir probe in the near wake of a disk immersed in a pulsed flowing plasma were made. A 1 cm diameter biasable sphere was placed in the ion-free near wake region of a 10 cm diameter disk immersed in a Mach 8 pulsed flowing plasma. The current-voltage characteristic of the sphere was observed as a function of time as the sphere bias was scanned from -5000 V to +1000 V. The collected current is found to be monotonically increasing with increasing positive bias voltage but exhibits a threshold voltage for current collection as the bias voltage becomes more negative. Potential measurements in the wake region were made for a sphere bias voltages below, at, and above the current collection threshold for a number of times during the wake formation period. The time evolution of the potential profile is shown to change as the sheath around the biased sphere is established. Predictions from the particle trajectory code SIMION are compared with data, showing excellent agreement in the prediction of the current collection threshold.

  1. Fast magnetic field annihilation driven by two laser pulses in underdense plasma

    SciTech Connect

    Gu, Y. J.; Kumar, D.; Weber, S.; Korn, G.; Klimo, O.; Bulanov, S. V.; Esirkepov, T. Zh.

    2015-10-15

    Fast magnetic annihilation is investigated by using 2.5-dimensional particle-in-cell simulations of two parallel ultra-short petawatt laser pulses co-propagating in underdense plasma. The magnetic field generated by the laser pulses annihilates in a current sheet formed between the pulses. Magnetic field energy is converted to an inductive longitudinal electric field, which efficiently accelerates the electrons of the current sheet. This new regime of collisionless relativistic magnetic field annihilation with a timescale of tens of femtoseconds can be extended to near-critical and overdense plasma with the ultra-high intensity femtosecond laser pulses.

  2. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Generation of currents and propagation of plasma fronts in the case of two-pulse interaction with a target in air

    NASA Astrophysics Data System (ADS)

    Barkhudarov, É. M.; Gelashvili, G. V.; Gumberidze, G. G.; Taktakishvili, M. I.

    1990-06-01

    An investigation was made of the enhancement in the efficiency of generation of currents when a target in air was subjected to two consecutive CO2 laser radiation pulses. Preliminary interaction with a low-energy (1.5-5 J) pulse increased by more than one order of magnitude the currents generated by the second pulse and this was true in a wide range of energies of the latter pulse. The energy conversion efficiency was practically unaffected. The results were in qualitative agreement with the proposed pattern of plasma formation and propagation of shock waves near a target.

  3. Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Solenoidal Magnetic Field I: Weak Magnetic Field Limit

    SciTech Connect

    Kaganovich, I. D., Startsev, E. A., Sefkow, A. B., Davidson, R. C.

    2008-10-10

    Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self- electric fields of the beam pulse, thus allowing effective control of the beam transport through the background plasma. An analytic model is developed to describe the self-magnetic field of a finite- length ion beam pulse propagating in a cold background plasma in a solenoidal magnetic field. The analytic studies show that the solenoidal magnetic field starts to infuence the self-electric and self-magnetic fields when ωce > ωpeβb, where ωce = eβ/mec is the electron gyrofrequency, ωpe is the electron plasma frequency, and βb = Vb/c is the ion beam velocity relative to the speed of light. This condition typically holds for relatively small magnetic fields (about 100G). Analytical formulas are derived for the effective radial force acting on the beam ions, which can be used to minimize beam pinching. The results of analytic theory have been verified by comparison with the simulation results obtained from two particle-in-cell codes, which show good agreement.

  4. Coherent π-electron dynamics of (P)-2,2'-biphenol induced by ultrashort linearly polarized UV pulses: Angular momentum and ring current

    NASA Astrophysics Data System (ADS)

    Mineo, H.; Lin, S. H.; Fujimura, Y.

    2013-02-01

    The results of a theoretical investigation of coherent π-electron dynamics for nonplanar (P)-2,2'-biphenol induced by ultrashort linearly polarized UV pulses are presented. Expressions for the time-dependent coherent angular momentum and ring current are derived by using the density matrix method. The time dependence of these coherences is determined by the off-diagonal density matrix element, which can be obtained by solving the coupled equations of motion of the electronic-state density matrix. Dephasing effects on coherent angular momentum and ring current are taken into account within the Markov approximation. The magnitudes of the electronic angular momentum and current are expressed as the sum of expectation values of the corresponding operators in the two phenol rings (L and R rings). Here, L (R) denotes the phenol ring in the left (right)-hand side of (P)-2,2'-biphenol. We define the bond current between the nearest neighbor carbon atoms Ci and Cj as an electric current through a half plane perpendicular to the Ci-Cj bond. The bond current can be expressed in terms of the inter-atomic bond current. The inter-atomic bond current (bond current) depends on the position of the half plane on the bond and has the maximum value at the center. The coherent ring current in each ring is defined by averaging over the bond currents. Since (P)-2,2'-biphenol is nonplanar, the resultant angular momentum is not one-dimensional. Simulations of the time-dependent coherent angular momentum and ring current of (P)-2,2'-biphenol excited by ultrashort linearly polarized UV pulses are carried out using the molecular parameters obtained by the time-dependent density functional theory (TD-DFT) method. Oscillatory behaviors in the time-dependent angular momentum (ring current), which can be called angular momentum (ring current) quantum beats, are classified by the symmetry of the coherent state, symmetric or antisymmetric. The bond current of the bridge bond linking the L and R

  5. Coherent π-electron dynamics of (P)-2,2'-biphenol induced by ultrashort linearly polarized UV pulses: angular momentum and ring current.

    PubMed

    Mineo, H; Lin, S H; Fujimura, Y

    2013-02-21

    The results of a theoretical investigation of coherent π-electron dynamics for nonplanar (P)-2,2'-biphenol induced by ultrashort linearly polarized UV pulses are presented. Expressions for the time-dependent coherent angular momentum and ring current are derived by using the density matrix method. The time dependence of these coherences is determined by the off-diagonal density matrix element, which can be obtained by solving the coupled equations of motion of the electronic-state density matrix. Dephasing effects on coherent angular momentum and ring current are taken into account within the Markov approximation. The magnitudes of the electronic angular momentum and current are expressed as the sum of expectation values of the corresponding operators in the two phenol rings (L and R rings). Here, L (R) denotes the phenol ring in the left (right)-hand side of (P)-2,2'-biphenol. We define the bond current between the nearest neighbor carbon atoms Ci and Cj as an electric current through a half plane perpendicular to the Ci-Cj bond. The bond current can be expressed in terms of the inter-atomic bond current. The inter-atomic bond current (bond current) depends on the position of the half plane on the bond and has the maximum value at the center. The coherent ring current in each ring is defined by averaging over the bond currents. Since (P)-2,2'-biphenol is nonplanar, the resultant angular momentum is not one-dimensional. Simulations of the time-dependent coherent angular momentum and ring current of (P)-2,2'-biphenol excited by ultrashort linearly polarized UV pulses are carried out using the molecular parameters obtained by the time-dependent density functional theory (TD-DFT) method. Oscillatory behaviors in the time-dependent angular momentum (ring current), which can be called angular momentum (ring current) quantum beats, are classified by the symmetry of the coherent state, symmetric or antisymmetric. The bond current of the bridge bond linking the L and R

  6. Current Status on the use of Parallel Computing in Turbulent Reacting Flow Computations Involving Sprays, Monte Carlo PDF and Unstructured Grids. Chapter 4

    NASA Technical Reports Server (NTRS)

    Raju, M. S.

    1998-01-01

    The state of the art in multidimensional combustor modeling as evidenced by the level of sophistication employed in terms of modeling and numerical accuracy considerations, is also dictated by the available computer memory and turnaround times afforded by present-day computers. With the aim of advancing the current multi-dimensional computational tools used in the design of advanced technology combustors, a solution procedure is developed that combines the novelty of the coupled CFD/spray/scalar Monte Carlo PDF (Probability Density Function) computations on unstructured grids with the ability to run on parallel architectures. In this approach, the mean gas-phase velocity and turbulence fields are determined from a standard turbulence model, the joint composition of species and enthalpy from the solution of a modeled PDF transport equation, and a Lagrangian-based dilute spray model is used for the liquid-phase representation. The gas-turbine combustor flows are often characterized by a complex interaction between various physical processes associated with the interaction between the liquid and gas phases, droplet vaporization, turbulent mixing, heat release associated with chemical kinetics, radiative heat transfer associated with highly absorbing and radiating species, among others. The rate controlling processes often interact with each other at various disparate time 1 and length scales. In particular, turbulence plays an important role in determining the rates of mass and heat transfer, chemical reactions, and liquid phase evaporation in many practical combustion devices.

  7. Huge increase in gas phase nanoparticle generation by pulsed direct current sputtering in a reactive gas admixture

    NASA Astrophysics Data System (ADS)

    Polonskyi, Oleksandr; Peter, Tilo; Mohammad Ahadi, Amir; Hinz, Alexander; Strunskus, Thomas; Zaporojtchenko, Vladimir; Biederman, Hynek; Faupel, Franz

    2013-07-01

    Using reactive DC sputtering in a gas aggregation cluster source, we show that pulsed discharge gives rise to a huge increase in deposition rate of nanoparticles by more than one order of magnitude compared to continuous operation. We suggest that this effect is caused by an equilibrium between slight target oxidation (during "time-off") and subsequent sputtering of Ti oxides (sub-oxides) at "time-on" with high power impulse.

  8. Producing nano-grained and Al-enriched surface microstructure on AZ91 magnesium alloy by high current pulsed electron beam treatment

    NASA Astrophysics Data System (ADS)

    Hao, Shengzhi; Li, Mincai

    2016-05-01

    Surface treatment of AZ91 magnesium alloy was carried out by high current pulsed electron beam (HCPEB) with accelerating voltage 27 kV and energy density 3 J/cm2. The surface microstructure and phase composition were characterized by using optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). The surface microhardness and corrosion resistance were measured. Under HCPEB treatments, the preferential evaporation of Mg element occurred intensively on irradiated surface and the initial large Mg17Al12 phases were dissolved. The nano-grained and Al-enriched surface modified layer was ultimately formed of depth ∼8 μm. According to the testing results, the surface microhardness increased from 63 to 141 HK after 30 pulses of HCPEB treatment, while the best improvement of corrosion resistance was obtained by 15 pulses of HCPEB treatment with a cathodic current density decreased by two orders of magnitude as compared with the initial AZ91 sample.

  9. Prediction of back-scatter radiations to a beam monitor chamber of medical linear accelerators by use of the digitized target-current-pulse analysis method.

    PubMed

    Suzuki, Yusuke; Hayashi, Naoki; Kato, Hideki; Fukuma, Hiroshi; Hirose, Yasujiro; Kawano, Makoto; Nishii, Yoshio; Nakamura, Masaru; Mukouyama, Takashi

    2013-01-01

    In small-field irradiation, the back-scattered radiation (BSR) affects the counts measured with a beam monitor chamber (BMC). In general, the effect of the BSR depends on the opened-jaw size. The effect is significantly large in small-field irradiation. Our purpose in this study was to predict the effect of BSR on LINAC output accurately with an improved target-current-pulse (TCP) technique. The pulse signals were measured with a system consisting of a personal computer and a digitizer. The pulse signals were analyzed with in-house software. The measured parameters were the number of pulses, the change in the waveform and the integrated signal values of the TCPs. The TCPs were measured for various field sizes with four linear accelerators. For comparison, Yu's method in which a universal counter was used was re-examined. The results showed that the variance of the measurements by the new method was reduced to approximately 1/10 of the variance by the previous method. There was no significant variation in the number of pulses due to a change in the field size in the Varian Clinac series. However, a change in the integrated signal value was observed. This tendency was different from the result of other investigations in the past. Our prediction method is able to define the cutoff voltage for the TCP acquired by digitizer. This functionality provides the capability of clearly classifying TCPs into signals and noise. In conclusion, our TCP analysis method can predict the effect of BSR on the BMC even for small-field irradiations.

  10. Parallel MR Imaging

    PubMed Central

    Deshmane, Anagha; Gulani, Vikas; Griswold, Mark A.; Seiberlich, Nicole

    2015-01-01

    Parallel imaging is a robust method for accelerating the acquisition of magnetic resonance imaging (MRI) data, and has made possible many new applications of MR imaging. Parallel imaging works by acquiring a reduced amount of k-space data with an array of receiver coils. These undersampled data can be acquired more quickly, but the undersampling leads to aliased images. One of several parallel imaging algorithms can then be used to reconstruct artifact-free images from either the aliased images (SENSE-type reconstruction) or from the under-sampled data (GRAPPA-type reconstruction). The advantages of parallel imaging in a clinical setting include faster image acquisition, which can be used, for instance, to shorten breath-hold times resulting in fewer motion-corrupted examinations. In this article the basic concepts behind parallel imaging are introduced. The relationship between undersampling and aliasing is discussed and two commonly used parallel imaging methods, SENSE and GRAPPA, are explained in detail. Examples of artifacts arising from parallel imaging are shown and ways to detect and mitigate these artifacts are described. Finally, several current applications of parallel imaging are presented and recent advancements and promising research in parallel imaging are briefly reviewed. PMID:22696125

  11. Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source for high-beta plasma experiments.

    PubMed

    Ii, Toru; Gi, Keii; Umezawa, Toshiyuki; Asai, Tomohiko; Inomoto, Michiaki; Ono, Yasushi

    2012-08-01

    We have developed a novel and economical neutral-beam injection system by employing a washer-gun plasma source. It provides a low-cost and maintenance-free ion beam, thus eliminating the need for the filaments and water-cooling systems employed conventionally. In our primary experiments, the washer gun produced a source plasma with an electron temperature of approximately 5 eV and an electron density of 5 × 10(17) m(-3), i.e., conditions suitable for ion-beam extraction. The dependence of the extracted beam current on the acceleration voltage is consistent with space-charge current limitation, because the observed current density is almost proportional to the 3/2 power of the acceleration voltage below approximately 8 kV. By optimizing plasma formation, we successfully achieved beam extraction of up to 40 A at 15 kV and a pulse length in excess of 0.25 ms. Its low-voltage and high-current pulsed-beam properties enable us to apply this high-power neutral beam injection into a high-beta compact torus plasma characterized by a low magnetic field.

  12. Design of a pulse-triggered four-channel functional electrical stimulator using complementary current source and time division multiplexing output method.

    PubMed

    Wang, Hai-Peng; Wang, Zhi-Gong; Lü, Xiao-Ying; Huang, Zong-Hao; Zhou, Yu-Xuan

    2015-08-01

    In this paper, a four-channel pulse-triggered functional electrical stimulator using complementary current source and time division output method is proposed for the research and application of functional electrical stimulation (FES). The high-voltage compliance and output impedance is increased by adopting the complementary current source, which can also realize the linear voltage-to-current conversion and high channel isolation. A high-voltage analog switch chip MAX14803, combined with a FIFO queue algorithm in the microprocessor, is used to setup the H-bridge and multiplexers for the four-channel time division multiplexing output. With this method, the size and cost of the key components are reduced greatly. The stimulating core circuit area is 30 × 50 mm(2). According to the experiments, the stimulator can achieve the four-channel charge-balanced biphasic stimulation with a current range between 0 and 60 mA and a single-phase pulse amplitude up to 60 V.

  13. Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source for high-beta plasma experiments

    NASA Astrophysics Data System (ADS)

    Ii, Toru; Gi, Keii; Umezawa, Toshiyuki; Asai, Tomohiko; Inomoto, Michiaki; Ono, Yasushi

    2012-08-01

    We have developed a novel and economical neutral-beam injection system by employing a washer-gun plasma source. It provides a low-cost and maintenance-free ion beam, thus eliminating the need for the filaments and water-cooling systems employed conventionally. In our primary experiments, the washer gun produced a source plasma with an electron temperature of approximately 5 eV and an electron density of 5 × 1017 m-3, i.e., conditions suitable for ion-beam extraction. The dependence of the extracted beam current on the acceleration voltage is consistent with space-charge current limitation, because the observed current density is almost proportional to the 3/2 power of the acceleration voltage below approximately 8 kV. By optimizing plasma formation, we successfully achieved beam extraction of up to 40 A at 15 kV and a pulse length in excess of 0.25 ms. Its low-voltage and high-current pulsed-beam properties enable us to apply this high-power neutral beam injection into a high-beta compact torus plasma characterized by a low magnetic field.

  14. Present and Future of Semiconductor Pulsed Power Generator ˜Role of Power Semiconductor Devices in Plasma Research˜ 6.High-Speed, Large-Current Power Semiconductors for Pulse Power Generation

    NASA Astrophysics Data System (ADS)

    Takata, Ikunori

    This paper describes the operation principles and limits of power semiconductors. In addition, operation mechanisms of the new pulse power devices, SOS (Semiconductor Opening Switch) and dynistors, are explained qualitatively. The fastest operating power device is the series connection of comparatively low-voltage devices. For large-current operation, a uniformly operating pin-diode structure device is essential. An SOS is constructed from dozens of medium voltage (about 3kV) special hard-recovery diodes. This can shut off 2kA current at 10kV with in 10ns. The dynistor has n+pnp+ four layers and two electrodes. Serial-connected dynistors have the potential to replace thyratrons. These new devices can endure over 10 kA/cm2 at much higher voltage than their static breakdown values in the repetitive use more than 1011 times.

  15. Self-pulsing of hollow cathode discharge in various gases

    SciTech Connect

    Qin, Y.; He, F. Jiang, X. X.; Ouyang, J. T.; Xie, K.

    2014-07-15

    In this paper, we investigate the self-pulsing phenomenon of cavity discharge in a cylindrical hollow cathode in various gases including argon, helium, nitrogen, oxygen, and air. The current-voltage characteristics of the cavity discharge, the waveforms of the self-pulsing current and voltage as well as the repetition frequency were measured. The results show that the pulsing frequency ranges from a few to tens kilohertz and depends on the averaged current and the pressure in all gases. The pulsing frequency will increase with the averaged current and decrease with the pressure. The rising time of the current pulse is nearly constant in a given gas or mixture. The self-pulsing does not depend on the external ballast but is affected significantly by the external capacitor in parallel with the discharge cell. The low-current self-pulsing in hollow cathode discharge is the mode transition between Townsend and glow discharges. It can be described by the charging-discharging process of an equivalent circuit consisting of capacitors and resistors.

  16. Modification over time of pulse wave velocity parallel to changes in aortic BP, as well as in 24-h ambulatory brachial BP.

    PubMed

    Oliveras, A; Segura, J; Suarez, C; García-Ortiz, L; Abad-Cardiel, M; Vigil, L; Gómez-Marcos, M A; Sans Atxer, L; Martell-Claros, N; Ruilope, L M; de la Sierra, A

    2016-03-01

    Arterial stiffness as assessed by carotid-femoral pulse wave velocity (cfPWV) is a marker of preclinical organ damage and a predictor of cardiovascular outcomes, independently of blood pressure (BP). However, limited evidence exists on the association between long-term variation (Δ) on aortic BP (aoBP) and ΔcfPWV. We aimed to evaluate the relationship of ΔBP with ΔcfPWV over time, as assessed by office and 24-h ambulatory peripheral BP, and aoBP. AoBP and cfPWV were evaluated in 209 hypertensive patients with either diabetes or metabolic syndrome by applanation tonometry (Sphygmocor) at baseline(b) and at 12 months of follow-up(fu). Peripheral BP was also determined by using validated oscillometric devices (office(o)-BP) and on an outpatient basis by using a validated (Spacelabs-90207) device (24-h ambulatory BP). ΔcfPWV over time was calculated as follows: ΔcfPWV=[(cfPWVfu-cfPWVb)/cfPWVb] × 100. ΔBP over time resulted from the same formula applied to BP values obtained with the three different measurement techniques. Correlations (Spearman 'Rho') between ΔBP and ΔcfPWV were calculated. Mean age was 62 years, 39% were female and 80% had type 2 diabetes. Baseline office brachial BP (mm Hg) was 143±20/82±12. Follow-up (12 months later) office brachial BP (mm Hg) was 136±20/79±12. ΔcfPWV correlated with ΔoSBP (Rho=0.212; P=0.002), Δ24-h SBP (Rho=0.254; P<0.001), Δdaytime SBP (Rho=0.232; P=0.001), Δnighttime SBP (Rho=0.320; P<0.001) and ΔaoSBP (Rho=0.320; P<0.001). A multiple linear regression analysis included the following independent variables: ΔoSBP, Δ24-h SBP, Δdaytime SBP, Δnighttime SBP and ΔaoSBP. ΔcfPWV was independently associated with Δ24-h SBP (β-coefficient=0.195; P=0.012) and ΔaoSBP (β-coefficient= 0.185; P=0.018). We conclude that changes in both 24-h SBP and aoSBP more accurately reflect changes in arterial stiffness than do office BP measurements. PMID:26108366

  17. Why Current Doppler Ultrasound Methodology Is Inaccurate in Assessing Cerebral Venous Return: The Alternative of the Ultrasonic Jugular Venous Pulse

    PubMed Central

    2016-01-01

    Assessment of cerebral venous return is growing interest for potential application in clinical practice. Doppler ultrasound (DUS) was used as a screening tool. However, three meta-analyses of qualitative DUS protocol demonstrate a big heterogeneity among studies. In an attempt to improve accuracy, several authors alternatively measured the flow rate, based on the product of the time average velocity with the cross-sectional area (CSA). However, also the quantification protocols lacked of the necessary accuracy. The reasons are as follows: (a) automatic measurement of the CSA assimilates the jugular to a circle, while it is elliptical; (b) the use of just a single CSA value in a pulsatile vessel is inaccurate; (c) time average velocity assessment can be applied only in laminar flow. Finally, the tutorial describes alternative ultrasound calculation of flow based on the Womersley method, which takes into account the variation of the jugular CSA overtime. In the near future, it will be possible to synchronize the electrocardiogram with the brain inflow (carotid distension wave) and with the outflow (jugular venous pulse) in order to nicely have a noninvasive ultrasound picture of the brain-heart axis. US jugular venous pulse may have potential use in neurovascular, neurocognitive, neurosensorial, and neurodegenerative disorders. PMID:27006525

  18. Constant potential pulse polarography

    USGS Publications Warehouse

    Christie, J.H.; Jackson, L.L.; Osteryoung, R.A.

    1976-01-01

    The new technique of constant potential pulse polarography, In which all pulses are to be the same potential, is presented theoretically and evaluated experimentally. The response obtained is in the form of a faradaic current wave superimposed on a constant capacitative component. Results obtained with a computer-controlled system exhibit a capillary response current similar to that observed In normal pulse polarography. Calibration curves for Pb obtained using a modified commercial pulse polarographic instrument are in good accord with theoretical predictions.

  19. Electrodeposition of Gold to Conformally Fill High Aspect Ratio Nanometric Silicon Grating Trenches: A Comparison of Pulsed and Direct Current Protocols

    PubMed Central

    Znati, Sami A.; Chedid, Nicholas; Miao, Houxun; Chen, Lei; Bennett, Eric E.; Wen, Han

    2016-01-01

    Filling high-aspect-ratio trenches with gold is a frequent requirement in the fabrication of x-ray optics as well as micro-electronic components and other fabrication processes. Conformal electrodeposition of gold in sub-micron-width silicon trenches with an aspect ratio greater than 35 over a grating area of several square centimeters is challenging and has not been described in the literature previously. A comparison of pulsed plating and constant current plating led to a gold electroplating protocol that reliably filled trenches for such structures. PMID:27042384

  20. Massively parallel visualization: Parallel rendering

    SciTech Connect

    Hansen, C.D.; Krogh, M.; White, W.

    1995-12-01

    This paper presents rendering algorithms, developed for massively parallel processors (MPPs), for polygonal, spheres, and volumetric data. The polygon algorithm uses a data parallel approach whereas the sphere and volume renderer use a MIMD approach. Implementations for these algorithms are presented for the Thinking Machines Corporation CM-5 MPP.

  1. High performance parallel architectures

    SciTech Connect

    Anderson, R.E. )

    1989-09-01

    In this paper the author describes current high performance parallel computer architectures. A taxonomy is presented to show computer architecture from the user programmer's point-of-view. The effects of the taxonomy upon the programming model are described. Some current architectures are described with respect to the taxonomy. Finally, some predictions about future systems are presented. 5 refs., 1 fig.

  2. Artificial intelligence in parallel

    SciTech Connect

    Waldrop, M.M.

    1984-08-10

    The current rage in the Artificial Intelligence (AI) community is parallelism: the idea is to build machines with many independent processors doing many things at once. The upshot is that about a dozen parallel machines are now under development for AI alone. As might be expected, the approaches are diverse yet there are a number of fundamental issues in common: granularity, topology, control, and algorithms.

  3. Eclipse Parallel Tools Platform

    2005-02-18

    Designing and developing parallel programs is an inherently complex task. Developers must choose from the many parallel architectures and programming paradigms that are available, and face a plethora of tools that are required to execute, debug, and analyze parallel programs i these environments. Few, if any, of these tools provide any degree of integration, or indeed any commonality in their user interfaces at all. This further complicates the parallel developer's task, hampering software engineering practices,more » and ultimately reducing productivity. One consequence of this complexity is that best practice in parallel application development has not advanced to the same degree as more traditional programming methodologies. The result is that there is currently no open-source, industry-strength platform that provides a highly integrated environment specifically designed for parallel application development. Eclipse is a universal tool-hosting platform that is designed to providing a robust, full-featured, commercial-quality, industry platform for the development of highly integrated tools. It provides a wide range of core services for tool integration that allow tool producers to concentrate on their tool technology rather than on platform specific issues. The Eclipse Integrated Development Environment is an open-source project that is supported by over 70 organizations, including IBM, Intel and HP. The Eclipse Parallel Tools Platform (PTP) plug-in extends the Eclipse framwork by providing support for a rich set of parallel programming languages and paradigms, and a core infrastructure for the integration of a wide variety of parallel tools. The first version of the PTP is a prototype that only provides minimal functionality for parallel tool integration of a wide variety of parallel tools. The first version of the PTP is a prototype that only provides minimal functionality for parallel tool integration, support for a small number of parallel architectures

  4. Some aspects of pulsed laser deposited nanocrystalline LaB(6) film: atomic force microscopy, constant force current imaging and field emission investigations.

    PubMed

    Late, Dattatray J; Date, Kalyani S; More, Mahendra A; Misra, Pankaj; Singh, B N; Kukreja, Lalit M; Dharmadhikari, C V; Joag, Dilip S

    2008-07-01

    Nanocrystalline lanthanum hexaboride (LaB(6)) films have been deposited on molybdenum foil by the pulsed laser deposition (PLD) technique. The as-deposited films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD pattern shows the cubic crystallinity of the LaB(6) film. The AFM studies reveal that the conical shaped LaB(6) nanostructures have height 60 nm, base 800 nm, and a typical radius of curvature ∼20 nm. A comparison of force and in situ current imaging AFM studies reveals that current contrast does not originate from the surface topography of the LaB(6) film. Field emission studies have been performed in the planar diode configuration. A current density of 4.4 × 10(-2) A cm(-2) is drawn from the actual emitting area. The Fowler-Nordheim plot is found to be linear, in accordance with the quantum mechanical tunneling phenomenon. The field enhancement factor is estimated to be 3585, indicating that the field emission is from LaB(6) nanocrystallites present on the emitter surface, as confirmed by the AFM. The emission current-time plots show current stability to the extent of 5% fluctuation about the average current over a period of 3 h.

  5. Thermoelectric Properties of Cu-doped Bi2Te2.85Se0.15 Prepared by Pulse-Current Sintering Under Cyclic Uniaxial Pressure

    NASA Astrophysics Data System (ADS)

    Kitagawa, Hiroyuki; Mimura, Naoki; Takimura, Kodai; Morito, Shigekazu; Kikuchi, Kotaro

    2016-03-01

    N-type Cu-doped Bi2Te2.85Se0.15 thermoelectric materials were prepared by pulse-current sintering under cyclic uniaxial pressure, and the effect of the cyclic uniaxial pressure on texture and thermoelectric properties was investigated. Cu x Bi2Te2.85Se0.15 ( x = 0-0.03) powder prepared by mechanical alloying was sintered at 673 K using pulse-current heating under 100 MPa of cyclic uniaxial pressure. X-ray diffraction patterns and electron backscattered diffraction analyses showed that the cyclic uniaxial pressure was effective for texture control. The flattened crystal grains were stacked in the thickness direction of the sintered materials and the hexagonal c-plane strongly tended to align in the direction perpendicular to the uniaxial pressure. As a result of this crystal alignment, the electrical resistivity in the direction perpendicular to the uniaxial pressure became smaller than that of equivalent samples prepared with a constant uniaxial pressure. The smaller resistivity led to a larger power factor, and the figure of merit was improved by the application of cyclic uniaxial pressure.

  6. Spatio-temporal characteristics of Trichel pulse at low pressure

    SciTech Connect

    He, Shoujie; Jing, Ha

    2014-01-15

    Trichel pulses are investigated using a needle-to-plane electrode geometry at low pressure. The evolution of current and voltage, the spatio-temporal discharge images of Trichel pulse are measured. The rising time and duration time in a pulse are about 10 μs and several tens of microseconds, respectively. One period of pulse can be divided into three stages: the stage preceding cathode breakdown, cathode glow formation, and discharge decaying process. Besides a cathode glow and a dark space, an anode glow is also observed. The emission spectra mainly originate from the C{sup 3}Π{sub u} → B{sup 3}Π{sub g} transition for nitrogen. In addition, the capacitances in parallel connected with the discharge cell have important influence on the pulsing frequency.

  7. Kinetics of the magnetization reversal in permalloy-niobium microstrips under the effect of a pulsed magnetic field and an electric current

    NASA Astrophysics Data System (ADS)

    Egorov, S. V.; Uspenskaya, L. S.

    2016-02-01

    The kinetics of magnetization reversal in bilayer permalloy-niobium microstrips under the effect of both a pulsed magnetic field and an electric current has been experimentally studied. These two cases turn out to be fundamentally different in the types of arising magnetic structures and in the dynamic characteristics of the processes. Such difference is especially striking at low temperatures. An anomalously high rate of the processes under study is observed. According to the suggested qualitative explanation, this effect is due to nonlinear excitations appearing in front of the moving domain wall if the applied electric current lowers the barriers for its motion. For achieving the final conclusions, more accurate quantitative analysis is needed.

  8. The Effect of Constant and Pulsed Current Gas Tungsten Arc Welding on Joint Properties of 2205 Duplex Stainless Steel to 316L Austenitic Stainless Steel

    NASA Astrophysics Data System (ADS)

    Neissi, R.; Shamanian, M.; Hajihashemi, M.

    2016-05-01

    In this study, dissimilar 316L austenitic stainless steel/2205 duplex stainless steel (DSS) joints were fabricated by constant and pulsed current gas tungsten arc welding process using ER2209 DSS as a filler metal. Microstructures and joint properties were characterized using optical and electron scanning microscopy, tensile, Charpy V-notch impact and micro-hardness tests, and cyclic polarization measurements. Microstructural observations confirmed the presence of chromium nitride and delta ferrite in the heat-affected zone of DSS and 316L, respectively. In addition, there was some deviation in the austenite/ferrite ratio of the surface welding pass in comparison to the root welding pass. Besides having lower pitting potential, welded joints produced by constant current gas tungsten arc welding process, consisted of some brittle sigma phase precipitates, which resulted in some impact energy reduction. The tensile tests showed high tensile strength for the weld joints in which all the specimens were broken in 316L base metal.

  9. Initial measurements of plasma current and electron density profiles using a polarimeter/interferometer (POINT) for long pulse operation in EAST (invited)

    NASA Astrophysics Data System (ADS)

    Liu, H. Q.; Qian, J. P.; Jie, Y. X.; Ding, W. X.; Brower, D. L.; Zou, Z. Y.; Li, W. M.; Lian, H.; Wang, S. X.; Yang, Y.; Zeng, L.; Lan, T.; Yao, Y.; Hu, L. Q.; Zhang, X. D.; Wan, B. N.

    2016-11-01

    A double-pass, radially viewing, far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique has been implemented for diagnosing the plasma current and electron density profiles in the Experimental Advanced Superconducting Tokamak (EAST). POINT has been operated routinely during the most recent experimental campaign and provides continuous 11 chord line-integrated Faraday effect and density measurement throughout the entire plasma discharge for all heating schemes and all plasma conditions (including ITER relevant scenario development). Reliability of both the polarimetric and interferometric measurements is demonstrated in 25 s plasmas with H-mode and 102 s long-pulse discharges. Current density, safety factor (q), and electron density profiles are reconstructed using equilibrium fitting code (EFIT) with POINT constraints for the plasma core.

  10. Radiative neutron capture as a counting technique at pulsed spallation neutron sources: a review of current progress

    NASA Astrophysics Data System (ADS)

    Schooneveld, E. M.; Pietropaolo, A.; Andreani, C.; Perelli Cippo, E.; Rhodes, N. J.; Senesi, R.; Tardocchi, M.; Gorini, G.

    2016-09-01

    Neutron scattering techniques are attracting an increasing interest from scientists in various research fields, ranging from physics and chemistry to biology and archaeometry. The success of these neutron scattering applications is stimulated by the development of higher performance instrumentation. The development of new techniques and concepts, including radiative capture based neutron detection, is therefore a key issue to be addressed. Radiative capture based neutron detectors utilize the emission of prompt gamma rays after neutron absorption in a suitable isotope and the detection of those gammas by a photon counter. They can be used as simple counters in the thermal region and (simultaneously) as energy selector and counters for neutrons in the eV energy region. Several years of extensive development have made eV neutron spectrometers operating in the so-called resonance detector spectrometer (RDS) configuration outperform their conventional counterparts. In fact, the VESUVIO spectrometer, a flagship instrument at ISIS serving a continuous user programme for eV inelastic neutron spectroscopy measurements, is operating in the RDS configuration since 2007. In this review, we discuss the physical mechanism underlying the RDS configuration and the development of associated instrumentation. A few successful neutron scattering experiments that utilize the radiative capture counting techniques will be presented together with the potential of this technique for thermal neutron diffraction measurements. We also outline possible improvements and future perspectives for radiative capture based neutron detectors in neutron scattering application at pulsed neutron sources.

  11. Radiative neutron capture as a counting technique at pulsed spallation neutron sources: a review of current progress.

    PubMed

    Schooneveld, E M; Pietropaolo, A; Andreani, C; Perelli Cippo, E; Rhodes, N J; Senesi, R; Tardocchi, M; Gorini, G

    2016-09-01

    Neutron scattering techniques are attracting an increasing interest from scientists in various research fields, ranging from physics and chemistry to biology and archaeometry. The success of these neutron scattering applications is stimulated by the development of higher performance instrumentation. The development of new techniques and concepts, including radiative capture based neutron detection, is therefore a key issue to be addressed. Radiative capture based neutron detectors utilize the emission of prompt gamma rays after neutron absorption in a suitable isotope and the detection of those gammas by a photon counter. They can be used as simple counters in the thermal region and (simultaneously) as energy selector and counters for neutrons in the eV energy region. Several years of extensive development have made eV neutron spectrometers operating in the so-called resonance detector spectrometer (RDS) configuration outperform their conventional counterparts. In fact, the VESUVIO spectrometer, a flagship instrument at ISIS serving a continuous user programme for eV inelastic neutron spectroscopy measurements, is operating in the RDS configuration since 2007. In this review, we discuss the physical mechanism underlying the RDS configuration and the development of associated instrumentation. A few successful neutron scattering experiments that utilize the radiative capture counting techniques will be presented together with the potential of this technique for thermal neutron diffraction measurements. We also outline possible improvements and future perspectives for radiative capture based neutron detectors in neutron scattering application at pulsed neutron sources. PMID:27502571

  12. Phase and Structural States Formed in Titanium Nickelide Subsurface Layers Exposed to High-Current Pulsed Electron Beams

    NASA Astrophysics Data System (ADS)

    Neyman, A. A.; Meisner, L. L.; Lotkov, A. I.; Semin, V. O.

    2015-06-01

    The behavior of the non-equilibrium states formed in the subsurface layers of a titanium nickelide-based alloy exposed to electron beams operated in the pulsed surface layer melting mode is investigated experimentally. Using methods of an x-ray diffraction analysis, and optical, scanning, and transmission electron microscopies, an 8-10 μm thick surface layer is shown to exhibit В2 phase-based structure undergoing inhomogeneous lattice microstrain. The core layer located at a depth of 10-20 μm below the irradiated surface contains a small amount (up to 5 vol.%) of a phase with В19' martensite structure along with a slightly distorted lattice and unmelted Ti2Ni phase particles. Electron beam treatment brings about changes in the chemical composition of the surface-modified layer which becomes enriched in titanium owing to the dissolution of the Ti2Ni phase particles therein. Transmission electron microscopy has not revealed martensite phases in the modified layer. The electron beam exposure of the titanium nickelide surface is assumed to give rise to nonequilibrium highly distorted bcc structure.

  13. Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure

    SciTech Connect

    Zhang, Jie; Guo, Ying; Shi, Yuncheng; Zhang, Jing; Shi, J. J.

    2015-08-15

    The atmospheric pressure glow discharges (APGD) with dual excitations in terms of pulsed voltage and pulse-modulation radio frequency (rf) power are studied experimentally between two parallel plates electrodes. Pulse-modulation applied in rf APGD temporally separates the discharge into repetitive discharge bursts, between which the high voltage pulses are introduced to ignite sub-microsecond pulsed discharge. The discharge characteristics and spatio-temporal evolution are investigated by means of current voltage characteristics and time resolved imaging, which suggests that the introduced pulsed discharge assists the ignition of rf discharge burst and reduces the maintain voltage of rf discharge burst. Furtherly, the time instant of pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.

  14. Frequency spectrum of focused broadband pulses of electromagnetic radiation generated by polarization currents with superluminally rotating distribution patterns.

    PubMed

    Ardavan, Houshang; Ardavan, Arzhang; Singleton, John

    2003-11-01

    We investigate the spectral features of the emission from a superluminal polarization current whose distribution pattern rotates (with an angular frequency omega) and oscillates (with a frequency omega > omega differing from an integral multiple of omega) at the same time. This type of polarization current is found in recent practical machines designed to investigate superluminal emission. Although all of the processes involved are linear, we find that the broadband emission contains frequencies that are higher than omega by a factor of the order of (omega/omega)2. This generation of frequencies not required for the creation of the source stems from mathematically rigorous consequences of the familiar classical expression for the retarded potential. The results suggest practical applications for superluminal polarization currents as broadband radio-frequency and infrared sources.

  15. The Galley Parallel File System

    NASA Technical Reports Server (NTRS)

    Nieuwejaar, Nils; Kotz, David

    1996-01-01

    As the I/O needs of parallel scientific applications increase, file systems for multiprocessors are being designed to provide applications with parallel access to multiple disks. Many parallel file systems present applications with a conventional Unix-like interface that allows the application to access multiple disks transparently. The interface conceals the parallelism within the file system, which increases the ease of programmability, but makes it difficult or impossible for sophisticated programmers and libraries to use knowledge about their I/O needs to exploit that parallelism. Furthermore, most current parallel file systems are optimized for a different workload than they are being asked to support. We introduce Galley, a new parallel file system that is intended to efficiently support realistic parallel workloads. We discuss Galley's file structure and application interface, as well as an application that has been implemented using that interface.

  16. Transforming dielectric coated tungsten and platinum wires to gaseous state using negative nanosecond-pulsed-current in vacuum

    SciTech Connect

    Wu, Jian; Li, Xingwen Wang, Kun; Yang, Zefeng; Shi, Zongqian; Jia, Shenli; Qiu, Aici; Li, Zhenghong

    2014-11-15

    With the help of thin dielectric coatings, corona free explosions were achieved in the region of about half a wire length (2 cm) for tungsten wires and nearly the whole wire length for platinum wires under a fast rising (46–170 A/ns) negative polarity current in vacuum. Expansion velocity of the tungsten gas was over 10 km/s. Current waveforms from exploding coated wires were similar to those from bare wires in the air including a current pause stage. Coated wires with different coating parameters had a similar joule energy deposition before voltage collapsed, but a quite different scenario in the region near the electrodes. The axial field under negative current was the main reason for the axial inhomogeneity of coated tungsten wires. Tungsten or platinum gases in the vaporized region were tightly encompassed by the dielectric coating, while gaps or probably low density gases, were observed between the coating and the edge of the dense wire core in the core-corona structure region.

  17. DIFFERENTIAL PULSE HEIGHT DISCRIMINATOR

    DOEpatents

    Test, L.D.

    1958-11-11

    Pulse-height discriminators are described, specifically a differential pulse-height discriminator which is adapted to respond to pulses of a band of amplitudes, but to reject pulses of amplitudes greater or less than tbe preselected band. In general, the discriminator includes a vacuum tube having a plurality of grids adapted to cut off plate current in the tube upon the application of sufficient negative voltage. One grid is held below cutoff, while a positive pulse proportional to the amplltude of each pulse is applled to this grid. Another grid has a negative pulse proportional to the amplitude of each pulse simultaneously applied to it. With this arrangement the tube will only pass pulses which are of sufficlent amplitude to counter the cutoff bias but not of sufficlent amplitude to cutoff the tube.

  18. Parallel pipelining

    SciTech Connect

    Joseph, D.D.; Bai, R.; Liao, T.Y.; Huang, A.; Hu, H.H.

    1995-09-01

    In this paper the authors introduce the idea of parallel pipelining for water lubricated transportation of oil (or other viscous material). A parallel system can have major advantages over a single pipe with respect to the cost of maintenance and continuous operation of the system, to the pressure gradients required to restart a stopped system and to the reduction and even elimination of the fouling of pipe walls in continuous operation. The authors show that the action of capillarity in small pipes is more favorable for restart than in large pipes. In a parallel pipeline system, they estimate the number of small pipes needed to deliver the same oil flux as in one larger pipe as N = (R/r){sup {alpha}}, where r and R are the radii of the small and large pipes, respectively, and {alpha} = 4 or 19/7 when the lubricating water flow is laminar or turbulent.

  19. Alternate drop pulse polarography

    USGS Publications Warehouse

    Christie, J.H.; Jackson, L.L.; Osteryoung, R.A.

    1976-01-01

    The new technique of alternate drop pulse polarography is presented. An experimental evaluation of alternate drop pulse polarography shows complete compensation of the capacitative background due to drop expansion. The capillary response phenomenon was studied in the absence of faradaic reaction and the capillary response current was found to depend on the pulse width to the -0.72 power. Increased signal-to-noise ratios were obtained using alternate drop pulse polarography at shorter drop times.

  20. High voltage pulse generator

    DOEpatents

    Fasching, George E.

    1977-03-08

    An improved high-voltage pulse generator has been provided which is especially useful in ultrasonic testing of rock core samples. An N number of capacitors are charged in parallel to V volts and at the proper instance are coupled in series to produce a high-voltage pulse of N times V volts. Rapid switching of the capacitors from the paralleled charging configuration to the series discharging configuration is accomplished by using silicon-controlled rectifiers which are chain self-triggered following the initial triggering of a first one of the rectifiers connected between the first and second of the plurality of charging capacitors. A timing and triggering circuit is provided to properly synchronize triggering pulses to the first SCR at a time when the charging voltage is not being applied to the parallel-connected charging capacitors. Alternate circuits are provided for controlling the application of the charging voltage from a charging circuit to be applied to the parallel capacitors which provides a selection of at least two different intervals in which the charging voltage is turned "off" to allow the SCR's connecting the capacitors in series to turn "off" before recharging begins. The high-voltage pulse-generating circuit including the N capacitors and corresponding SCR's which connect the capacitors in series when triggered "on" further includes diodes and series-connected inductors between the parallel-connected charging capacitors which allow sufficiently fast charging of the capacitors for a high pulse repetition rate and yet allow considerable control of the decay time of the high-voltage pulses from the pulse-generating circuit.

  1. [High current microsecond pulsed hollow cathode lamp excited ionic fluorescence spectrometry of alkaline earth elements in inductively coupled plasma with a Fassel-torch].

    PubMed

    Zhang, Shao-Yu; Gong, Zhen-Bin; Huang, Ben-Li

    2006-02-01

    High current microsecond pulsed hollow cathode lamp (HCMP-HCL) excited ionic fluorescence spectrometry (IFS) of alkaline earth elements in inductively coupled plasma (ICP) with a Fassel-torch has been investigated. In wide condition ranges only IFS was observed, whilst atomic fluorescence spectrometry (AFS) was not detectable. More intense ionic fluorescence signal was observed at lower observation heights and at lower incident RF powers. Without introduction of any reduction organic gases into the ICP, the limit of detection (LOD, 3sigma) of Ba was improved by 50-fold over that of a conventional pulsed (CP) HCL with the Baird sleeve-extended torch. For Ca and Sr, the LODs by HCMP-HCL-ICP-IFS and CP-HCL-ICP-AFS show no significant difference. Relative standard deviations were 0.6%-1.4% (0.1-0.2 microg x mL(-1), n = 10) for 5 ionic fluorescence lines. Preliminary studies showed that the intensity of ionic fluorescence could be depressed in the presence of K, Al and P.

  2. Scalable parallel communications

    NASA Technical Reports Server (NTRS)

    Maly, K.; Khanna, S.; Overstreet, C. M.; Mukkamala, R.; Zubair, M.; Sekhar, Y. S.; Foudriat, E. C.

    1992-01-01

    Coarse-grain parallelism in networking (that is, the use of multiple protocol processors running replicated software sending over several physical channels) can be used to provide gigabit communications for a single application. Since parallel network performance is highly dependent on real issues such as hardware properties (e.g., memory speeds and cache hit rates), operating system overhead (e.g., interrupt handling), and protocol performance (e.g., effect of timeouts), we have performed detailed simulations studies of both a bus-based multiprocessor workstation node (based on the Sun Galaxy MP multiprocessor) and a distributed-memory parallel computer node (based on the Touchstone DELTA) to evaluate the behavior of coarse-grain parallelism. Our results indicate: (1) coarse-grain parallelism can deliver multiple 100 Mbps with currently available hardware platforms and existing networking protocols (such as Transmission Control Protocol/Internet Protocol (TCP/IP) and parallel Fiber Distributed Data Interface (FDDI) rings); (2) scale-up is near linear in n, the number of protocol processors, and channels (for small n and up to a few hundred Mbps); and (3) since these results are based on existing hardware without specialized devices (except perhaps for some simple modifications of the FDDI boards), this is a low cost solution to providing multiple 100 Mbps on current machines. In addition, from both the performance analysis and the properties of these architectures, we conclude: (1) multiple processors providing identical services and the use of space division multiplexing for the physical channels can provide better reliability than monolithic approaches (it also provides graceful degradation and low-cost load balancing); (2) coarse-grain parallelism supports running several transport protocols in parallel to provide different types of service (for example, one TCP handles small messages for many users, other TCP's running in parallel provide high bandwidth

  3. Calculated fraction of an incident current pulse that will be accelerated by an electron linear accelerator and comparisons with experimental data

    SciTech Connect

    Alsmiller, R.G. Jr.; Alsmiller, F.S.; Lewis, T.A.

    1986-05-01

    In a series of previous papers, calculated results obtained using a one-dimensional ballistic model were presented to aid in the design of a prebuncher for the Oak Ridge Electron Linear Accelerator. As part of this work, a model was developed to provide limits on the fraction of an incident current pulse that would be accelerated by the existing accelerator. In this paper experimental data on this fraction are presented and the validity of the model developed previously is tested by comparing calculated and experimental data. Part of the experimental data is used to fix the physical parameters in the model and then good agreement between the calculated results and the rest of the experimental data is obtained.

  4. Stress controlled pulsed direct current co-sputtered Al1-xScxN as piezoelectric phase for micromechanical sensor applications

    NASA Astrophysics Data System (ADS)

    Fichtner, Simon; Reimer, Tim; Chemnitz, Steffen; Lofink, Fabian; Wagner, Bernhard

    2015-11-01

    Scandium alloyed aluminum nitride (Al1-xScxN) thin films were fabricated by reactive pulsed direct current co-sputtering of separate scandium and aluminum targets with x ≤ 0.37. A significant improvement of the clamped transversal piezoelectric response to strain e31,f from -1.28 C/m2 to -3.01 C/m2 was recorded, while dielectric constant and loss angle remain low. Further, the built-in stress level of Al1-xScxN was found to be tuneable by varying pressure, Ar/N2 ratio, and Sc content. The thus resulting enhancement of the expectable signal to noise ratio by a factor of 2.1 and the ability to control built-in stress make the integration of Al1-xScxN as the piezoelectric phase of micro-electro-mechanical system sensor applications highly attractive.

  5. 20 kA PFN capacitor bank with solid-state switching. [pulse forming network for plasma studies

    NASA Technical Reports Server (NTRS)

    Posta, S. J.; Michels, C. J.

    1973-01-01

    A compact high-current pulse-forming network capacitor bank using paralleled silicon controlled rectifiers as switches is described. The maximum charging voltage of the bank is 1kV and maximum load current is 20 kA. The necessary switch equalization criteria and performance with dummy load and an arc plasma generator are described.

  6. Generation of high currents of carbon ions with the use of subnanosecond near-infrared laser pulses

    SciTech Connect

    Krasa, J.; Velyhan, A.; Margarone, D.; Krousky, E.; Skala, J.; Laska, L.; Jungwirth, K.; Rohlena, K.; Ullschmied, J.

    2010-02-15

    Emission of carbon currents reaching values up to 2 A/cm{sup 2} at a distance of 1 m from the laser ion source driven by the subnanosecond Prague Asterix Laser System operated at a fundamental wavelength of 1315 nm is reported. Graphite targets were exposed to intensities up to 5x10{sup 16} W/cm{sup 2} varying both the laser energy and the position of the laser beam focus with respect to the target surface. The maximum energy gain of carbon ions was {approx_equal}1 MeV/u. At high laser intensities the shape of time-of-flight spectra is also formed by plasma outbursts, whose growth correlates with the oscillatory self-focusing of the laser beam.

  7. Simultaneous particle image velocimetry and chemiluminescence visualization of millisecond-pulsed current-voltage-induced perturbations of a premixed propane/air flame

    NASA Astrophysics Data System (ADS)

    Schmidt, Jacob; Kostka, Stanislav; Lynch, Amy; Ganguly, Biswa

    2011-09-01

    The effects of millisecond-wide, pulsed current-voltage-induced behavior in premixed laminar flames have been investigated through the simultaneous collection of particle image velocimetry (PIV) and chemiluminescence data with particular attention paid to the onset mechanisms. Disturbances caused by applied voltages of 2 kV over a 30-mm gap to a downward propagating, atmospheric pressure, premixed propane/air flame with a flow speed near 2 m/s and an equivalence ratio of 1.06 are investigated. The combined PIV and chemiluminescence-based experimental data show the observed disturbance originates only in or near the cathode fall region very close to the burner base. The data also suggest that the coupling mechanism responsible for the flame disturbance behavior is fluidic in nature, developing from the radial positive chemi-ion distribution and an ion-drift current-induced net body force that acts along the annular space discharge distribution in the reaction zone in or near the cathode fall. This net body force causes a reduction in flow speed above these near cathodic regions causing the base of the flame to laterally spread. Also, this effect seems to produce a velocity gradient leading to the transition of a laminar flame to turbulent combustion for higher applied current-voltage conditions as shown in previous work (Marcum and Ganguly in Combust Flame 143:27-36, 2005; Schmidt and Ganguly in 48th AIAA aerospace sciences meeting. Orlando, 2010).

  8. Research of Making Large Volume Atmospheric Pressure Plasma by Parallel MCS Discharge

    NASA Astrophysics Data System (ADS)

    Nagano, Kazumi; Kon, Akira; Yamazaki, Yuki; Maeyama, Mitsuaki

    We research parallel microhollow cathode sustained (MCS) discharge plasma that is generated by parallel operations of the Microhollow cathode discharge (MHCD) plasma to produce a large volume atmospheric pressure plasma. We propose the cylindrical parallel MCS discharge plasma expecting electron supply by MHCD plasma and electron trapping effects of logarithm potential. Several MHCD electrodes are placed on cylindrical surface of 19 mm in radius and a thin wire is placed at a cylinder center axis. MHCD electrodes are supplied repetitive pulse voltage and the central wire anode is supplied DC voltage. So far, 8 parallel MCS discharge plasmas could be generated at 50 kPa. In this paper, the relationship between axial distance of MHCD electrodes and number of parallel discharge electrodes, and the condition to increase power supplied to MCS discharge were studied. Axial distance of MHCD electrodes were arranged to 6 mm and 16 parallel cylindrical MCS discharge in atmospheric pressure was generated. Power supplied to MCS discharge could be increased without decreasing number of parallel discharge electrodes by reducing current limiting resistor and shortening MHCD pulse width.

  9. Femtosecond pulse spectral synthesis in coherently-spectrally combined multi-channel fiber chirped pulse amplifiers.

    PubMed

    Chang, Wei-zung; Zhou, Tong; Siiman, Leo A; Galvanauskas, Almantas

    2013-02-11

    We demonstrate coherent spectral beam combining and femtosecond pulse spectral synthesis using three parallel fiber chirped pulse amplifiers, each amplifying different ultrashort-pulse spectra. This proof-of-concept experiment opens a path to simultaneously overcome individual-amplifier energy and power limitations, as well as limitations on amplified pulse spectra due to the gain narrowing in a single fiber amplifier.

  10. High efficiency production of germ-line transgenic Japanese medaka (Oryzias latipes) by electroporation with direct current-shifted radio frequency pulses.

    PubMed

    Hostetler, Heather A; Peck, Stephanie L; Muir, William M

    2003-08-01

    Although there have been several studies showing the production of transgenic fish through electroporation techniques, success rates have been low and few studies show germ-line integration and expression. When electroporation has been successful, the device used is no longer commercially available. The goal of this experiment was to find an alternative efficient method of generating transgenic Japanese medaka (Oryzias latipes) using a commercially available electroporation device. The Gene Pulser II and RF module (Bio-Rad Laboratories, USA), along with two reporter gene constructs, were used. In contrast to other electroporation devices, which are based on a single pulse with exponential decay or square wave technology, the Gene Pulser II incorporates a direct current (DC)-shifted radio frequency (RF) signal. With this technique, over 1000 embryos can be electroporated in less than 30 min. The plasmid pCMV-SPORT-beta-gal (Invitrogen, USA) was used in the supercoiled form to optimize parameters for gene transfer into single-celled embryos, and resulted in up to 100% somatic gene transfer. Similar conditions were used to generate fish transgenic for both the pCMV-EGFP plasmid (Clontech, USA) and a cytomegalovirus (CMV) driven phytase-EGFP construct. The conditions used were a voltage of 25 V, a percent modulation of 100%, a radio frequency of 35 kHz, a burst duration of 10 ms, 3 bursts, and a burst interval of 1.0 s. Seventy percent of the embryos electroporated with the pCMV-EGFP construct survived to sexual maturity, and of those, 85% were capable of passing the transgene on to their offspring. Transgenic second generation back-crossed (BC2) fry were subjected to Southern blot analysis, which confirmed germ-line integration, and observation for green fluorescence protein, which confirmed protein expression. DC-shifted RF pulses are effective and efficient in the production of transgenic medaka, and germ-line integration and expression can be achieved without

  11. A compact nanosecond pulse modulator

    NASA Astrophysics Data System (ADS)

    Sha, Jizhang; Xue, Jianchao; Qiang, Bohan

    Two circuits of nanosecond pulse modulator which generate two different width rectangular pulses respectively are described. The basic configuration of the modulator is the Marx circuit, in which avalanche transistors are used as switching devices. In order to obtain the rectangular pulses a pulse-forming network (PFN) is introduced and fitted into the Marx. A multi-parallel arrangement of the Marx is used to satisfy the broad pulse requirement. Experiments have shown that the two different width rectangular pulses which have 130 V amplitudes and 30 and 200 ns widths respectively can be obtained at a 50 ohms load. The two pulses have steep front edges (3.6 ns and 10 ns respectively) and flat tops with less than + or - 5 percent ripples. Therefore, the modulator can meet the requirements of the nanosecond pulse radar.

  12. Parallel time integration software

    SciTech Connect

    2014-07-01

    This package implements an optimal-scaling multigrid solver for the (non) linear systems that arise from the discretization of problems with evolutionary behavior. Typically, solution algorithms for evolution equations are based on a time-marching approach, solving sequentially for one time step after the other. Parallelism in these traditional time-integrarion techniques is limited to spatial parallelism. However, current trends in computer architectures are leading twards system with more, but not faster. processors. Therefore, faster compute speeds must come from greater parallelism. One approach to achieve parallelism in time is with multigrid, but extending classical multigrid methods for elliptic poerators to this setting is a significant achievement. In this software, we implement a non-intrusive, optimal-scaling time-parallel method based on multigrid reduction techniques. The examples in the package demonstrate optimality of our multigrid-reduction-in-time algorithm (MGRIT) for solving a variety of parabolic equations in two and three sparial dimensions. These examples can also be used to show that MGRIT can achieve significant speedup in comparison to sequential time marching on modern architectures.

  13. Parallel time integration software

    2014-07-01

    This package implements an optimal-scaling multigrid solver for the (non) linear systems that arise from the discretization of problems with evolutionary behavior. Typically, solution algorithms for evolution equations are based on a time-marching approach, solving sequentially for one time step after the other. Parallelism in these traditional time-integrarion techniques is limited to spatial parallelism. However, current trends in computer architectures are leading twards system with more, but not faster. processors. Therefore, faster compute speeds mustmore » come from greater parallelism. One approach to achieve parallelism in time is with multigrid, but extending classical multigrid methods for elliptic poerators to this setting is a significant achievement. In this software, we implement a non-intrusive, optimal-scaling time-parallel method based on multigrid reduction techniques. The examples in the package demonstrate optimality of our multigrid-reduction-in-time algorithm (MGRIT) for solving a variety of parabolic equations in two and three sparial dimensions. These examples can also be used to show that MGRIT can achieve significant speedup in comparison to sequential time marching on modern architectures.« less

  14. Parallel Information Processing.

    ERIC Educational Resources Information Center

    Rasmussen, Edie M.

    1992-01-01

    Examines parallel computer architecture and the use of parallel processors for text. Topics discussed include parallel algorithms; performance evaluation; parallel information processing; parallel access methods for text; parallel and distributed information retrieval systems; parallel hardware for text; and network models for information…

  15. Parallelizing OVERFLOW: Experiences, Lessons, Results

    NASA Technical Reports Server (NTRS)

    Jespersen, Dennis C.

    1999-01-01

    The computer code OVERFLOW is widely used in the aerodynamic community for the numerical solution of the Navier-Stokes equations. Current trends in computer systems and architectures are toward multiple processors and parallelism, including distributed memory. This report describes work that has been carried out by the author and others at Ames Research Center with the goal of parallelizing OVERFLOW using a variety of parallel architectures and parallelization strategies. This paper begins with a brief description of the OVERFLOW code. This description includes the basic numerical algorithm and some software engineering considerations. Next comes a description of a parallel version of OVERFLOW, OVERFLOW/PVM, using PVM (Parallel Virtual Machine). This parallel version of OVERFLOW uses the manager/worker style and is part of the standard OVERFLOW distribution. Then comes a description of a parallel version of OVERFLOW, OVERFLOW/MPI, using MPI (Message Passing Interface). This parallel version of OVERFLOW uses the SPMD (Single Program Multiple Data) style. Finally comes a discussion of alternatives to explicit message-passing in the context of parallelizing OVERFLOW.

  16. Demonstrating Forces between Parallel Wires.

    ERIC Educational Resources Information Center

    Baker, Blane

    2000-01-01

    Describes a physics demonstration that dramatically illustrates the mutual repulsion (attraction) between parallel conductors using insulated copper wire, wooden dowels, a high direct current power supply, electrical tape, and an overhead projector. (WRM)

  17. Photoconductive circuit element pulse generator

    DOEpatents

    Rauscher, Christen

    1989-01-01

    A pulse generator for characterizing semiconductor devices at millimeter wavelength frequencies where a photoconductive circuit element (PCE) is biased by a direct current voltage source and produces short electrical pulses when excited into conductance by short laser light pulses. The electrical pulses are electronically conditioned to improve the frequency related amplitude characteristics of the pulses which thereafter propagate along a transmission line to a device under test.

  18. The Galley Parallel File System

    NASA Technical Reports Server (NTRS)

    Nieuwejaar, Nils; Kotz, David

    1996-01-01

    Most current multiprocessor file systems are designed to use multiple disks in parallel, using the high aggregate bandwidth to meet the growing I/0 requirements of parallel scientific applications. Many multiprocessor file systems provide applications with a conventional Unix-like interface, allowing the application to access multiple disks transparently. This interface conceals the parallelism within the file system, increasing the ease of programmability, but making it difficult or impossible for sophisticated programmers and libraries to use knowledge about their I/O needs to exploit that parallelism. In addition to providing an insufficient interface, most current multiprocessor file systems are optimized for a different workload than they are being asked to support. We introduce Galley, a new parallel file system that is intended to efficiently support realistic scientific multiprocessor workloads. We discuss Galley's file structure and application interface, as well as the performance advantages offered by that interface.

  19. Multiple pulse-heating experiments with different current to determine total emissivity, heat capacity, and electrical resistivity of electrically conductive materials at high temperatures.

    PubMed

    Watanabe, Hiromichi; Yamashita, Yuichiro

    2012-01-01

    A modified pulse-heating method is proposed to improve the accuracy of measurement of the hemispherical total emissivity, specific heat capacity, and electrical resistivity of electrically conductive materials at high temperatures. The proposed method is based on the analysis of a series of rapid resistive self-heating experiments on a sample heated at different temperature rates. The method is used to measure the three properties of the IG-110 grade of isotropic graphite at temperatures from 850 to 1800 K. The problem of the extrinsic heating-rate effect, which reduces the accuracy of the measurements, is successfully mitigated by compensating for the generally neglected experimental error associated with the electrical measurands (current and voltage). The results obtained by the proposed method can be validated by the linearity of measured quantities used in the property determinations. The results are in reasonably good agreement with previously published data, which demonstrate the suitability of the proposed method, in particular, to the resistivity and total emissivity measurements. An interesting result is the existence of a minimum in the emissivity of the isotropic graphite at around 1120 K, consistent with the electrical resistivity results.

  20. Stress controlled pulsed direct current co-sputtered Al{sub 1−x}Sc{sub x}N as piezoelectric phase for micromechanical sensor applications

    SciTech Connect

    Fichtner, Simon; Reimer, Tim; Chemnitz, Steffen; Wagner, Bernhard; Lofink, Fabian

    2015-11-01

    Scandium alloyed aluminum nitride (Al{sub 1−x}Sc{sub x}N) thin films were fabricated by reactive pulsed direct current co-sputtering of separate scandium and aluminum targets with x ≤ 0.37. A significant improvement of the clamped transversal piezoelectric response to strain e{sub 31,f} from −1.28 C/m{sup 2} to −3.01 C/m{sup 2} was recorded, while dielectric constant and loss angle remain low. Further, the built-in stress level of Al{sub 1−x}Sc{sub x}N was found to be tuneable by varying pressure, Ar/N{sub 2} ratio, and Sc content. The thus resulting enhancement of the expectable signal to noise ratio by a factor of 2.1 and the ability to control built-in stress make the integration of Al{sub 1−x}Sc{sub x}N as the piezoelectric phase of micro-electro-mechanical system sensor applications highly attractive.

  1. Weldability Characteristics of Sintered Hot-Forged AISI 4135 Steel Produced through P/M Route by Using Pulsed Current Gas Tungsten Arc Welding

    NASA Astrophysics Data System (ADS)

    Joseph, Joby; Muthukumaran, S.; Pandey, K. S.

    2016-01-01

    Present investigation is an attempt to study the weldability characteristics of sintered hot-forged plates of AISI 4135 steel produced through powder metallurgy (P/M) route using matching filler materials of ER80S B2. Compacts of homogeneously blended elemental powders corresponding to the above steel were prepared on a universal testing machine (UTM) by taking pre-weighed powder blend with a suitable die, punch and bottom insert assembly. Indigenously developed ceramic coating was applied on the entire surface of the compacts in order to protect them from oxidation during sintering. Sintered preforms were hot forged to flat, approximately rectangular plates, welded by pulsed current gas tungsten arc welding (PCGTAW) processes with aforementioned filler materials. Microstructural, tensile and hardness evaluations revealed that PCGTAW process with low heat input could produce weldments of good quality with almost nil defects. It was established that PCGTAW joints possess improved tensile properties compared to the base metal and it was mainly attributed to lower heat input, resulting in finer fusion zone grains and higher fusion zone hardness. Thus, the present investigation opens a new and demanding field in research.

  2. Parallel sphere rendering

    SciTech Connect

    Krogh, M.; Painter, J.; Hansen, C.

    1996-10-01

    Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the M.

  3. Mid to late Holocene strengthening of the East Greenland Current paralleled by increased Atlantic Intermediate Water outflow from the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Perner, Kerstin; Moros, Matthias; Llyod, Jeremy; Jansen, Eystein; Stein, Rüdiger

    2015-04-01

    The relatively fresh and cold East Greenland Current (EGC) connects the Arctic with the subpolar North Atlantic. Its strength and influence on the freshwater balance in the North Atlantic impacts Subpolar gyre (SPG) dynamics and deep convection in the Labrador Sea. Enhanced freshwater and sea ice expansion in the subpolar North Atlantic is suggested to modify the northward heat transport in the North Atlantic Current (NAC). High-resolution palaeoceanographic reconstructions, based on planktonic and benthic foraminifera assemblage data, from the central East Greenland shelf (Foster Bugt) reveal distinct centennial to millennial-scale oceanographic variability that relate to climatic changes during the mid to late Holocene (last c. 6.3 ka BP). Our data highlight intervals of cooling and freshening of the polar surface EGC waters that accompanies warming in the underlying subsurface Atlantic waters, which receives contribution of return Atlantic Intermediate Water (AIW) and of the Return Atlantic Current (RAC). Mid Holocene thermal optimum-like conditions prevailed until c. 4.5 ka BP. A relatively warm surface PW and strong contribution of subsurface RAC waters, alongside low drift/sea ice occurrence, suggest a relatively weak EGC during this period. Subsequently, from 4.5 to 1.4 ka BP, the surface PW layer freshened and cooled, and the water column became well stratified, indicating a strong EGC. This EGC strengthening is accompanied by increasing subsurface AIW contribution from the Arctic Ocean after c. 4.5 ka BP, which culminated in the time from 2.3 to 1.4 ka BP. Simultaneously to this maximum AIW contribution, distinct warming is also recognized in the NAC, the Irminger Current and the West Greenland Current. We relate this enhanced Arctic Ocean AIW contribution to the 'Roman Warm Period'; a warm phase whose origin is still a matter of debate. We suggest that the observed warming offshore East Greenland, centred at c. 2.0 ka BP, results from the interaction of i

  4. PulseSoar

    SciTech Connect

    Carter, P.; Peglow, S.

    1992-07-21

    This paper is an introduction to the PulseSoar concept. PulseSoar is a hypervelocity airplane that uses existing airport facilities and current technologies to fly at the very edge of space. It will be shown that PulseSoar can fly between any two points on the globe in less than two hours with fuel efficiency exceeding current state of the art commercial airliners. In addition, it will be shown that PulseSoar avoids environmental issues concerning the ozone layer and sonic booms because of its unique flight profile. All of this can be achieved with current technology. PulseSoar does not require the development of enabling technology. It is a concept which can be demonstrated today. The importance of this idea goes beyond the technical significance`s of PulseSoar in terms of feasibility and performance. PulseSoar could provide a crucial economic advantage to America`s largest export market: commercial aircraft. PulseSoar is a breakthrough concept for addressing the emerging markets of long range and high speed aircraft. Application of PulseSoar to commercial transport could provide the US Aerospace industry a substantial lead in offering high speed/long range aircraft to the world`s airlines. The rapid emergence of a US developed high speed aircraft could also be important to our competitiveness in the Pacific Rim and South American economies. A quick and inexpensive demonstration vehicle is proposed to bang the concept to reality within two years. This discussion will address all the major technical subjects encompassed by PulseSoar and identifies several near-term, and low risk, applications which may be further explored with the initial demonstration vehicle. What is PulseSoar? PulseSoar could enable high speed, high altitude and long range flight without many of the difficulties encountered by traditional hypersonic vehicles.

  5. Parallel hierarchical global illumination

    SciTech Connect

    Snell, Q.O.

    1997-10-08

    Solving the global illumination problem is equivalent to determining the intensity of every wavelength of light in all directions at every point in a given scene. The complexity of the problem has led researchers to use approximation methods for solving the problem on serial computers. Rather than using an approximation method, such as backward ray tracing or radiosity, the authors have chosen to solve the Rendering Equation by direct simulation of light transport from the light sources. This paper presents an algorithm that solves the Rendering Equation to any desired accuracy, and can be run in parallel on distributed memory or shared memory computer systems with excellent scaling properties. It appears superior in both speed and physical correctness to recent published methods involving bidirectional ray tracing or hybrid treatments of diffuse and specular surfaces. Like progressive radiosity methods, it dynamically refines the geometry decomposition where required, but does so without the excessive storage requirements for ray histories. The algorithm, called Photon, produces a scene which converges to the global illumination solution. This amounts to a huge task for a 1997-vintage serial computer, but using the power of a parallel supercomputer significantly reduces the time required to generate a solution. Currently, Photon can be run on most parallel environments from a shared memory multiprocessor to a parallel supercomputer, as well as on clusters of heterogeneous workstations.

  6. Photoelectrocatalytic decomposition of ethylene using TiO2/activated carbon fiber electrode with applied pulsed direct current square-wave potential

    NASA Astrophysics Data System (ADS)

    Ye, Sheng-ying; Zheng, Sen-hong; Song, Xian-liang; Luo, Shu-can

    2015-06-01

    Removing ethylene (C2H4) from the atmosphere of storage facilities for fruits and vegetable is one of the main challenges in their postharvest handling for maximizing their freshness, quality, and shelf life. In this study, we investigated the photoelectrocatalytic (PEC) degradation of ethylene gas by applying a pulsed direct current DC square-wave (PDCSW) potential and by using a Nafion-based PEC cell. The cell utilized a titanium dioxide (TiO2) photocatalyst or γ-irradiated TiO2 (TiO2*) loaded on activated carbon fiber (ACF) as a photoelectrode. The apparent rate constant of a pseudo-first-order reaction (K) was used to describe the PEC degradation of ethylene. Parameters of the potential applied to the PEC cell in a reactor that affect the degradation efficiency in terms of the K value were studied. These parameters were frequency, duty cycle, and voltage. Ethylene degradation by application of a constant PDCSW potential to the PEC electrode of either TiO2/ACF cell or TiO2*/ACF cell enhanced the efficiency of photocatalytic degradation and PEC degradation. Gamma irradiation of TiO2 in the electrode and the applied PDCSW potential synergistically increased the K value. Independent variables (frequency, duty cycle, and voltage) of the PEC cell fabricated from TiO2 subjected 20 kGy γ radiation were optimized to maximize the K value by using response surface methodology with quadratic rotation-orthogonal composite experimental design. Optimized conditions were as follows: 358.36 Hz frequency, 55.79% duty cycle, and 64.65 V voltage. The maximum K value attained was 4.4 × 10-4 min-1.

  7. High-voltage pulsed current stimulation enhances wound healing in diabetic rats by restoring the expression of collagen, α-smooth muscle actin, and TGF-β1.

    PubMed

    Kim, Tae Hoon; Cho, Hwi-Young; Lee, Suk Min

    2014-01-01

    Impaired wound healing is a common complication of diabetes mellitus and a major morbidity that leads to pain and severely diminished quality of life. Diabetic wounds are commonly associated with defective immune cell responses or abnormality of extracellular matrix. Various types of electrical stimulation interventions have been used to promote tissue healing. However, it is unclear whether high-voltage pulsed current stimulation (HVPCS) enhances diabetic wound healing. In this study, the effects of HVPCS on wound healing were investigated in diabetic rats. Three groups of rats (10 per group) were used: non-diabetic control, diabetic control, and diabetic rats that were administered HVPCS for 40 minutes daily for 1 week. Rats from control groups were administered sham interventions. Dorsal incision wounds were generated in all animals, and wound-healing rate was determined during one-week intervention. After interventions, we measured the relative expression levels of collagen type I (collagen-I), α-smooth muscle actin (α-SMA), and transforming growth factor-β1 (TGF-β1) mRNAs in the wounded skin. Wound closure was delayed in diabetic control rats compared to the non-diabetic control rats, and the diabetic control rats showed the reduced expression levels of collagen-I, α-SMA and TGF-β1 mRNAs. Importantly, compared to diabetic control rats, rats with HVPCS showed accelerated wound closure and healing (p < 0.01) and restored expression levels of collagen-I (p = 0.02), α-SMA (p = 0.04), and TGF-β1 (p = 0.01) mRNAs. In conclusion, HVPCS may be beneficial for enhancing the healing of diabetic wounds by restoring the expression levels of TGF-β1, collagen-I, and α-SMA. PMID:25169252

  8. Parallel Programming in the Age of Ubiquitous Parallelism

    NASA Astrophysics Data System (ADS)

    Pingali, Keshav

    2014-04-01

    Multicore and manycore processors are now ubiquitous, but parallel programming remains as difficult as it was 30-40 years ago. During this time, our community has explored many promising approaches including functional and dataflow languages, logic programming, and automatic parallelization using program analysis and restructuring, but none of these approaches has succeeded except in a few niche application areas. In this talk, I will argue that these problems arise largely from the computation-centric foundations and abstractions that we currently use to think about parallelism. In their place, I will propose a novel data-centric foundation for parallel programming called the operator formulation in which algorithms are described in terms of actions on data. The operator formulation shows that a generalized form of data-parallelism called amorphous data-parallelism is ubiquitous even in complex, irregular graph applications such as mesh generation/refinement/partitioning and SAT solvers. Regular algorithms emerge as a special case of irregular ones, and many application-specific optimization techniques can be generalized to a broader context. The operator formulation also leads to a structural analysis of algorithms called TAO-analysis that provides implementation guidelines for exploiting parallelism efficiently. Finally, I will describe a system called Galois based on these ideas for exploiting amorphous data-parallelism on multicores and GPUs

  9. Cooperative pulses

    NASA Astrophysics Data System (ADS)

    Braun, Michael; Glaser, Steffen J.

    2010-11-01

    We introduce the concept of cooperative (COOP) pulses which are designed to compensate each other's imperfections. In multi-scan experiments, COOP pulses can cancel undesired signal contributions, complementing and generalizing phase cycles. COOP pulses can be efficiently optimized using an extended version of the optimal-control-based gradient ascent pulse engineering (GRAPE) algorithm. The advantage of the COOP approach is experimentally demonstrated for broadband and band-selective pulses.

  10. Parallel asynchronous hardware implementation of image processing algorithms

    NASA Technical Reports Server (NTRS)

    Coon, Darryl D.; Perera, A. G. U.

    1990-01-01

    Research is being carried out on hardware for a new approach to focal plane processing. The hardware involves silicon injection mode devices. These devices provide a natural basis for parallel asynchronous focal plane image preprocessing. The simplicity and novel properties of the devices would permit an independent analog processing channel to be dedicated to every pixel. A laminar architecture built from arrays of the devices would form a two-dimensional (2-D) array processor with a 2-D array of inputs located directly behind a focal plane detector array. A 2-D image data stream would propagate in neuron-like asynchronous pulse-coded form through the laminar processor. No multiplexing, digitization, or serial processing would occur in the preprocessing state. High performance is expected, based on pulse coding of input currents down to one picoampere with noise referred to input of about 10 femtoamperes. Linear pulse coding has been observed for input currents ranging up to seven orders of magnitude. Low power requirements suggest utility in space and in conjunction with very large arrays. Very low dark current and multispectral capability are possible because of hardware compatibility with the cryogenic environment of high performance detector arrays. The aforementioned hardware development effort is aimed at systems which would integrate image acquisition and image processing.

  11. A compact submicrosecond, high current generator

    NASA Astrophysics Data System (ADS)

    Kovalchuk, B. M.; Kharlov, A. V.; Zorin, V. B.; Zherlitsyn, A. A.

    2009-08-01

    Pulsed current generator was developed for experiments with current carrying pulsed plasma. Main parts of the generator are capacitor bank, low inductive current driving lines, and central load part. Generator consists of four identical sections, connected in parallel to one load. Capacitor bank is assembled from 24 capacitor blocks (100 kV, 80 nF), connected in parallel. It stores 9.6 kJ at 100 kV charging voltage. Each capacitor block incorporates a multigap spark switch, which is able to commute by six parallel channels. Switches operate in dry air at atmospheric pressure. The generator was tested with an inductive load and a liner load. At 17.5 nH inductive load and 100 kV of charging voltage it provides 650 kA of current amplitude with 390 ns rise time with 0.6 Ω damping resistors in discharge circuit of each capacitor block. The net generator inductance without a load was optimized to be as low as 15 nH, which results in extremely low impedance of the generator (˜0.08 Ω). It ensures effective energy coupling with a low impedance load such as Z pinch. The generator operates reliably without any adjustments in 70-100 kV range of charging voltage. Jitter in delay between output pulse and triggering pulse is less than 5 ns at 70-100 kV charging voltage. Operation and handling are very simple, because no oil or purified gases are required for the generator. The generator has dimensions 5.24×1.2×0.18 m3 and total weight about 1400 kg, thus manifesting itself as simple, robust, and cost effective apparatus.

  12. A compact submicrosecond, high current generator.

    PubMed

    Kovalchuk, B M; Kharlov, A V; Zorin, V B; Zherlitsyn, A A

    2009-08-01

    Pulsed current generator was developed for experiments with current carrying pulsed plasma. Main parts of the generator are capacitor bank, low inductive current driving lines, and central load part. Generator consists of four identical sections, connected in parallel to one load. Capacitor bank is assembled from 24 capacitor blocks (100 kV, 80 nF), connected in parallel. It stores 9.6 kJ at 100 kV charging voltage. Each capacitor block incorporates a multigap spark switch, which is able to commute by six parallel channels. Switches operate in dry air at atmospheric pressure. The generator was tested with an inductive load and a liner load. At 17.5 nH inductive load and 100 kV of charging voltage it provides 650 kA of current amplitude with 390 ns rise time with 0.6 ohms damping resistors in discharge circuit of each capacitor block. The net generator inductance without a load was optimized to be as low as 15 nH, which results in extremely low impedance of the generator (approximately 0.08 ohms). It ensures effective energy coupling with a low impedance load such as Z pinch. The generator operates reliably without any adjustments in 70-100 kV range of charging voltage. Jitter in delay between output pulse and triggering pulse is less than 5 ns at 70-100 kV charging voltage. Operation and handling are very simple, because no oil or purified gases are required for the generator. The generator has dimensions 5.24x1.2x0.18 m(3) and total weight about 1400 kg, thus manifesting itself as simple, robust, and cost effective apparatus. PMID:19725652

  13. A compact submicrosecond, high current generator.

    PubMed

    Kovalchuk, B M; Kharlov, A V; Zorin, V B; Zherlitsyn, A A

    2009-08-01

    Pulsed current generator was developed for experiments with current carrying pulsed plasma. Main parts of the generator are capacitor bank, low inductive current driving lines, and central load part. Generator consists of four identical sections, connected in parallel to one load. Capacitor bank is assembled from 24 capacitor blocks (100 kV, 80 nF), connected in parallel. It stores 9.6 kJ at 100 kV charging voltage. Each capacitor block incorporates a multigap spark switch, which is able to commute by six parallel channels. Switches operate in dry air at atmospheric pressure. The generator was tested with an inductive load and a liner load. At 17.5 nH inductive load and 100 kV of charging voltage it provides 650 kA of current amplitude with 390 ns rise time with 0.6 ohms damping resistors in discharge circuit of each capacitor block. The net generator inductance without a load was optimized to be as low as 15 nH, which results in extremely low impedance of the generator (approximately 0.08 ohms). It ensures effective energy coupling with a low impedance load such as Z pinch. The generator operates reliably without any adjustments in 70-100 kV range of charging voltage. Jitter in delay between output pulse and triggering pulse is less than 5 ns at 70-100 kV charging voltage. Operation and handling are very simple, because no oil or purified gases are required for the generator. The generator has dimensions 5.24x1.2x0.18 m(3) and total weight about 1400 kg, thus manifesting itself as simple, robust, and cost effective apparatus.

  14. Experimental research on pulse forming based on high-temperature SMES applied in pulsed power

    NASA Astrophysics Data System (ADS)

    Zhou, Yusheng; Kuang, Jianghua; Tang, Yuejin; Song, Meng; Wei, Bin; Cheng, Shijie; Pan, Yuan

    2009-03-01

    To research the key problems of storage energy and pulse forming in pulsed power, a pulse magnet made of Bi2223/Ag high-temperature superconducting (HTS) tapes applied in pulsed power experiment was developed. After determining electromagnetic characteristics of the magnet, a pulse forming network was designed. HTS magnet was immersed in liquid nitrogen bath, experiments were carried out about discharging pulse current to resistance load based on HTS magnet energy storage (SMES). The results show that pulse current waves were obtained through adjusted circuit construction and magnet parameters by acting delay of switches in the pulse forming network. The technical schemes about pulse forming based on SMES were presented.

  15. Study of breakdown in an ablative pulsed plasma thruster

    SciTech Connect

    Huang, Tiankun; Wu, Zhiwen; Liu, Xiangyang; Xie, Kan; Wang, Ningfei; Cheng, Yue

    2015-10-15

    Breakdown in ablative pulsed plasma thrusters (APPTs) must be studied in order to design new types of APPTs and measure particular parameters. In this paper, we studied a parallel-plate ablative pulsed plasma thruster that used a coaxial semiconductor spark plug. By operating the APPT about 500 times with various capacitor voltages and electrode gaps, we measured and analyzed the voltage of the spark plug, the voltage between the electrodes, and the discharge current. These experiments revealed a time delay (∼1–10 μs) between spark plug ignition and capacitor discharge, which may affect the performance of high-pulsing-rate (>10 kHz) and double-discharge APPTs, and the measurements of some of the APPT parameters. The delay time decreased as the capacitor voltage increased, and it increased with an increasing electrode gap and increasing number of ignitions. We explain our results through a simple theoretical analysis.

  16. Pulse generator with intermediate inductive storage as a lightning simulator

    NASA Astrophysics Data System (ADS)

    Kovalchuk, B. M.; Kharlov, A. V.; Zherlytsyn, A. A.; Kumpyak, E. V.; Tsoy, N. V.

    2016-06-01

    Compact transportable generators are required for simulating a lightning current pulse for electrical apparatus testing. A bi-exponential current pulse has to be formed by such a generator (with a current rise time of about two orders of magnitude faster than the damping time). The objective of this study was to develop and investigate a compact pulse generator with intermediate inductive storage and a fuse opening switch as a simulator of lightning discharge. A Marx generator (six stages) with a capacitance of 1 μF and an output voltage of 240 kV was employed as primary storage. In each of the stages, two IK-50/3 (50 kV, 3 μF) capacitors are connected in parallel. The generator inductance is 2 μH. A test bed for the investigations was assembled with this generator. The generator operates without SF6 and without oil in atmospheric air, which is very important in practice. Straight copper wires with adjustable lengths and diameters were used for the electro-explosive opening switch. Tests were made with active-inductive loads (up to 0.1 Ω and up to 6.3 μH). The current rise time is lower than 1200 ns, and the damping time can be varied from 35 to 125 μs, following the definition of standard lightning current pulse in the IEC standard. Moreover, 1D MHD calculations of the fuse explosion were carried out self-consistently with the electric circuit equations, in order to calculate more accurately the load pulse parameters. The calculations agree fairly well with the tests. On the basis of the obtained results, the design of a transportable generator was developed for a lightning simulator with current of 50 kA and a pulse shape corresponding to the IEEE standard.

  17. Pulse generator with intermediate inductive storage as a lightning simulator.

    PubMed

    Kovalchuk, B M; Kharlov, A V; Zherlytsyn, A A; Kumpyak, E V; Tsoy, N V

    2016-06-01

    Compact transportable generators are required for simulating a lightning current pulse for electrical apparatus testing. A bi-exponential current pulse has to be formed by such a generator (with a current rise time of about two orders of magnitude faster than the damping time). The objective of this study was to develop and investigate a compact pulse generator with intermediate inductive storage and a fuse opening switch as a simulator of lightning discharge. A Marx generator (six stages) with a capacitance of 1 μF and an output voltage of 240 kV was employed as primary storage. In each of the stages, two IK-50/3 (50 kV, 3 μF) capacitors are connected in parallel. The generator inductance is 2 μH. A test bed for the investigations was assembled with this generator. The generator operates without SF6 and without oil in atmospheric air, which is very important in practice. Straight copper wires with adjustable lengths and diameters were used for the electro-explosive opening switch. Tests were made with active-inductive loads (up to 0.1 Ω and up to 6.3 μH). The current rise time is lower than 1200 ns, and the damping time can be varied from 35 to 125 μs, following the definition of standard lightning current pulse in the IEC standard. Moreover, 1D MHD calculations of the fuse explosion were carried out self-consistently with the electric circuit equations, in order to calculate more accurately the load pulse parameters. The calculations agree fairly well with the tests. On the basis of the obtained results, the design of a transportable generator was developed for a lightning simulator with current of 50 kA and a pulse shape corresponding to the IEEE standard. PMID:27370452

  18. Pulse generator with intermediate inductive storage as a lightning simulator.

    PubMed

    Kovalchuk, B M; Kharlov, A V; Zherlytsyn, A A; Kumpyak, E V; Tsoy, N V

    2016-06-01

    Compact transportable generators are required for simulating a lightning current pulse for electrical apparatus testing. A bi-exponential current pulse has to be formed by such a generator (with a current rise time of about two orders of magnitude faster than the damping time). The objective of this study was to develop and investigate a compact pulse generator with intermediate inductive storage and a fuse opening switch as a simulator of lightning discharge. A Marx generator (six stages) with a capacitance of 1 μF and an output voltage of 240 kV was employed as primary storage. In each of the stages, two IK-50/3 (50 kV, 3 μF) capacitors are connected in parallel. The generator inductance is 2 μH. A test bed for the investigations was assembled with this generator. The generator operates without SF6 and without oil in atmospheric air, which is very important in practice. Straight copper wires with adjustable lengths and diameters were used for the electro-explosive opening switch. Tests were made with active-inductive loads (up to 0.1 Ω and up to 6.3 μH). The current rise time is lower than 1200 ns, and the damping time can be varied from 35 to 125 μs, following the definition of standard lightning current pulse in the IEC standard. Moreover, 1D MHD calculations of the fuse explosion were carried out self-consistently with the electric circuit equations, in order to calculate more accurately the load pulse parameters. The calculations agree fairly well with the tests. On the basis of the obtained results, the design of a transportable generator was developed for a lightning simulator with current of 50 kA and a pulse shape corresponding to the IEEE standard.

  19. PULSE SORTER

    DOEpatents

    Wade, E.J.

    1958-07-29

    An apparatus is described for counting and recording the number of electrical pulses occurring in each of a timed sequence of groups of pulses. The particular feature of the invention resides in a novel timing circuit of the univibrator type which provides very accurately timed pulses for opening each of a series of coincidence channels in sequence. The univibrator is shown incorporated in a pulse analyzing system wherein a series of pulse counting channels are periodically opened in order, one at a time, for a predetermtned open time interval, so that only one channel will be open at the time of occurrence of any of the electrical pulses to be sorted.

  20. Emittance of short-pulsed high-current ion beams formed from the plasma of the electron cyclotron resonance discharge sustained by high-power millimeter-wave gyrotron radiation

    SciTech Connect

    Razin, S. Zorin, V.; Izotov, I.; Sidorov, A.; Skalyga, V.

    2014-02-15

    We present experimental results on measuring the emittance of short-pulsed (≤100 μs) high-current (80–100 mA) ion beams of heavy gases (Nitrogen, Argon) formed from a dense plasma of an ECR source of multiply charged ions (MCI) with quasi-gas-dynamic mode of plasma confinement in a magnetic trap of simple mirror configuration. The discharge was created by a high-power (90 kW) pulsed radiation of a 37.5-GHz gyrotron. The normalized emittance of generated ion beams of 100 mA current was (1.2–1.3) π mm mrad (70% of ions in the beams). Comparing these results with those obtained using a cusp magnetic trap, it was concluded that the structure of the trap magnetic field lines does not exert a decisive influence on the emittance of ion beams in the gas-dynamic ECR source of MCI.

  1. Special parallel processing workshop

    SciTech Connect

    1994-12-01

    This report contains viewgraphs from the Special Parallel Processing Workshop. These viewgraphs deal with topics such as parallel processing performance, message passing, queue structure, and other basic concept detailing with parallel processing.

  2. Parallel sphere rendering

    SciTech Connect

    Krogh, M.; Hansen, C.; Painter, J.; de Verdiere, G.C.

    1995-05-01

    Sphere rendering is an important method for visualizing molecular dynamics data. This paper presents a parallel divide-and-conquer algorithm that is almost 90 times faster than current graphics workstations. To render extremely large data sets and large images, the algorithm uses the MIMD features of the supercomputers to divide up the data, render independent partial images, and then finally composite the multiple partial images using an optimal method. The algorithm and performance results are presented for the CM-5 and the T3D.

  3. Highly parallel computation

    NASA Technical Reports Server (NTRS)

    Denning, Peter J.; Tichy, Walter F.

    1990-01-01

    Highly parallel computing architectures are the only means to achieve the computation rates demanded by advanced scientific problems. A decade of research has demonstrated the feasibility of such machines and current research focuses on which architectures designated as multiple instruction multiple datastream (MIMD) and single instruction multiple datastream (SIMD) have produced the best results to date; neither shows a decisive advantage for most near-homogeneous scientific problems. For scientific problems with many dissimilar parts, more speculative architectures such as neural networks or data flow may be needed.

  4. Pulse power linac

    DOEpatents

    Villa, Francesco

    1990-01-01

    A linear acceleration for charged particles is constructed of a plurality of transmission line sections that extend between a power injection region and an accelerating region. Each line section is constructed of spaced plate-like conductors and is coupled to an accelerating gap located at the accelerating region. Each gap is formed between a pair of apertured electrodes, with all of the electrode apertures being aligned along a particle accelerating path. The accelerating gaps are arranged in series, and at the injection region the line sections are connected in parallel. At the injection region a power pulse is applied simultaneously to all line sections. The line sections are graduated in length so that the pulse reaches the gaps in a coordinated sequence whereby pulse energy is applied to particles as they reach each of the gaps along the accelerating path.

  5. Pulse Oximetry

    MedlinePlus

    ... www.thoracic.org amount of gases (oxygen and carbon dioxide) that are in your blood. To get an ... Also, a pulse oximeter does not measure your carbon dioxide level. How accurate is the pulse oximeter? The ...

  6. Pulsed ultrasonic stir welding system

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  7. Scaling laws for electromagnetic pulsed plasma thrusters

    NASA Astrophysics Data System (ADS)

    Ziemer, J. K.; Choueiri, E. Y.

    2001-08-01

    The scaling laws of pulsed plasma thrusters operating in the predominantly electromagnetic acceleration mode (EM-PPT) are investigated theoretically and experimentally using gas-fed pulsed plasma thrusters. A fundamental characteristic velocity that depends on the inductance per unit length and the square root of the capacitance to the initial inductance ratio is identified. An analytical model of the discharge current predicts scaling laws in which the propulsive efficiency is proportional to the EM-PPT performance scaling number, defined here as the ratio of the exhaust velocity to the EM-PPT characteristic velocity. The importance of the effective plasma resistance in improving the propulsive performance is shown. To test the validity of the predicted scaling relations, the performance of two gas-fed pulsed plasma thruster designs (one with coaxial electrodes and the other with parallel-plate electrodes), was measured under 70 different operating conditions using an argon plasma. The measurements demonstrate that the impulse bit scales linearly with the integral of the square of the discharge current as expected for an electromagnetic accelerator. The measured performance scaling is shown to be in good agreement with the theoretically predicted scaling. Normalizing the exhaust velocity and the impulse-to-energy ratio by the EM-PPT characteristic velocity collapses almost all the measured data onto single curves that uphold the general validity of these scaling laws. [12pt]This paper is dedicated to the memory of Dr Daniel Birx

  8. Compact nanosecond pulsed power technology with applications to biomedical engineering, biology, and medicine

    NASA Astrophysics Data System (ADS)

    Gu, Xianyue

    Pulsed power refers to a technology that is suited to drive applications requiring very large power pulses in short bursts. Its recent emerging applications in biology demand compact systems with high voltage electric pulses in nanosecond time range. The required performance of a pulsed power system is enabled by the combined efforts in its design at three levels: efficient and robust devices at the component level, novel circuits and architecture at the system level, and effective interface techniques to deliver fast pulses at the application level. At the component level we are concerned with the power capability of switches and the energy storage density of capacitors. We compare semiconductor materials - Si, GaAs, GaN and SiC - for high voltage, high current, fast FET-type switches, and study the effects of their intrinsic defects on electrical characteristics. We present the fabrication of BST film capacitors on silicon substrates by pulsed laser deposition, and investigate their potential application to high voltage, high energy density capacitors. At the system level, a nanosecond pulse generator is developed for electroperturbation of biological cells. We model and design a Blumlein PFN (Pulse Forming Network) to deliver nanosecond pulses to a cuvette load. The resonant circuit employs four parallel 100 A MOSFET switches and charges the PFN to 8 kV within 350 ns. At the application level, in order to controllably deliver nanosecond electric pulses into tumors, we have designed, fabricated, and tested impulse catheter devices. Frequency responds, breakdown voltages and effective volumes of catheters are evaluated. With comparison of simulation and experimental results, we further develop dielectric dispersion models for RPMI. This thesis presents a set of strongly interdisciplinary studies based on pulsed power technology and towards biomedical applications. Addressed issues include from fundamental materials studies to application engineering designs that

  9. Coiled transmission line pulse generators

    DOEpatents

    McDonald, Kenneth Fox

    2010-11-09

    Methods and apparatus are provided for fabricating and constructing solid dielectric "Coiled Transmission Line" pulse generators in radial or axial coiled geometries. The pour and cure fabrication process enables a wide variety of geometries and form factors. The volume between the conductors is filled with liquid blends of monomers, polymers, oligomers, and/or cross-linkers and dielectric powders; and then cured to form high field strength and high dielectric constant solid dielectric transmission lines that intrinsically produce ideal rectangular high voltage pulses when charged and switched into matched impedance loads. Voltage levels may be increased by Marx and/or Blumlein principles incorporating spark gap or, preferentially, solid state switches (such as optically triggered thyristors) which produce reliable, high repetition rate operation. Moreover, these Marxed pulse generators can be DC charged and do not require additional pulse forming circuitry, pulse forming lines, transformers, or an a high voltage spark gap output switch. The apparatus accommodates a wide range of voltages, impedances, pulse durations, pulse repetition rates, and duty cycles. The resulting mobile or flight platform friendly cylindrical geometric configuration is much more compact, light-weight, and robust than conventional linear geometries, or pulse generators constructed from conventional components. Installing additional circuitry may accommodate optional pulse shape improvements. The Coiled Transmission Lines can also be connected in parallel to decrease the impedance, or in series to increase the pulse length.

  10. Dual amplitude pulse generator for radiation detectors

    DOEpatents

    Hoggan, Jerry M.; Kynaston, Ronnie L.; Johnson, Larry O.

    2001-01-01

    A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.

  11. Turbomachinery CFD on parallel computers

    NASA Technical Reports Server (NTRS)

    Blech, Richard A.; Milner, Edward J.; Quealy, Angela; Townsend, Scott E.

    1992-01-01

    The role of multistage turbomachinery simulation in the development of propulsion system models is discussed. Particularly, the need for simulations with higher fidelity and faster turnaround time is highlighted. It is shown how such fast simulations can be used in engineering-oriented environments. The use of parallel processing to achieve the required turnaround times is discussed. Current work by several researchers in this area is summarized. Parallel turbomachinery CFD research at the NASA Lewis Research Center is then highlighted. These efforts are focused on implementing the average-passage turbomachinery model on MIMD, distributed memory parallel computers. Performance results are given for inviscid, single blade row and viscous, multistage applications on several parallel computers, including networked workstations.

  12. Pulsed ultrasonic stir welding method

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  13. Parallel rendering techniques for massively parallel visualization

    SciTech Connect

    Hansen, C.; Krogh, M.; Painter, J.

    1995-07-01

    As the resolution of simulation models increases, scientific visualization algorithms which take advantage of the large memory. and parallelism of Massively Parallel Processors (MPPs) are becoming increasingly important. For large applications rendering on the MPP tends to be preferable to rendering on a graphics workstation due to the MPP`s abundant resources: memory, disk, and numerous processors. The challenge becomes developing algorithms that can exploit these resources while minimizing overhead, typically communication costs. This paper will describe recent efforts in parallel rendering for polygonal primitives as well as parallel volumetric techniques. This paper presents rendering algorithms, developed for massively parallel processors (MPPs), for polygonal, spheres, and volumetric data. The polygon algorithm uses a data parallel approach whereas the sphere and volume render use a MIMD approach. Implementations for these algorithms are presented for the Thinking Ma.chines Corporation CM-5 MPP.

  14. High current H{sub 2}{sup +} and H{sub 3}{sup +} beam generation by pulsed 2.45 GHz electron cyclotron resonance ion source

    SciTech Connect

    Xu, Yuan; Peng, Shixiang Ren, Haitao; Zhao, Jie; Chen, Jia; Zhang, Tao; Guo, Zhiyu; Zhang, Ailin; Chen, Jia'er

    2014-02-15

    The permanent magnet 2.45 GHz electron cyclotron resonance ion source at Peking University can produce more than 100 mA hydrogen ion beam working at pulsed mode. For the increasing requirements of cluster ions (H{sub 2}{sup +} and H{sub 3}{sup +}) in linac and cyclotron, experimental study was carried out to further understand the hydrogen plasma processes in the ion source for the generation of cluster ions. The constituents of extracted beam have been analyzed varying with the pulsed duration from 0.3 ms to 2.0 ms (repetition frequency 100 Hz) at different operation pressure. The fraction of cluster ions dramatically increased when the pulsed duration was lower than 0.6 ms, and more than 20 mA pure H{sub 3}{sup +} ions with fraction 43.2% and 40 mA H{sub 2}{sup +} ions with fraction 47.7% were obtained when the operation parameters were adequate. The dependence of extracted ion fraction on microwave power was also measured at different pressure as the energy absorbed by plasma will greatly influence electron temperature and electron density then the plasma processes in the ion source. More details will be presented in this paper.

  15. Current and emerging MR imaging techniques for the diagnosis and management of CSF flow disorders: a review of phase-contrast and time-spatial labeling inversion pulse.

    PubMed

    Yamada, S; Tsuchiya, K; Bradley, W G; Law, M; Winkler, M L; Borzage, M T; Miyazaki, M; Kelly, E J; McComb, J G

    2015-04-01

    This article provides an overview of phase-contrast and time-spatial labeling inversion pulse MR imaging techniques to assess CSF movement in the CNS under normal and pathophysiologic situations. Phase-contrast can quantitatively measure stroke volume in selected regions, notably the aqueduct of Sylvius, synchronized to the heartbeat. Judicious fine-tuning of the technique is needed to achieve maximal temporal resolution, and it has limited visualization of CSF motion in many CNS regions. Phase-contrast is frequently used to evaluate those patients with suspected normal pressure hydrocephalus and a Chiari I malformation. Correlation with successful treatment outcome has been problematic. Time-spatial labeling inversion pulse, with a high signal-to-noise ratio, assesses linear and turbulent motion of CSF anywhere in the CNS. Time-spatial labeling inversion pulse can qualitatively visualize whether CSF flows between 2 compartments and determine whether there is flow through the aqueduct of Sylvius or a new surgically created stoma. Cine images reveal CSF linear and turbulent flow patterns.

  16. Energy deposition in parallel-plate plasma accelerators. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Dicapua, M. S.

    1971-01-01

    To appraise the ratio of energy deposition into kinetic and thermal modes in plasma accelerators, a parallel-plate plasma accelerator has been operated in the quasi-steady mode with current pulses in the range of 10 to 100 kilo-amperes (kA), durations of the order of one millisecond, and argon mass flows up to 100 grams/sec. From photographic observations, spectroscopic measurements of velocity and electron density, and pressure measurements with a fast-rise piezoelectric transducer it is found that, for currents between 50 and 90 kA, the accelerated argon plasma is supersonic with ion velocities of 5 to 6 kilometers/sec.

  17. Pulsed spallation neutron sources

    SciTech Connect

    Carpenter, J.M.

    1996-05-01

    This paper reviews the early history of pulsed spallation neutron source development ar Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provide a few examples of applications in fundamental condensed matter physics, materials science and technology.

  18. Pulsed spallation Neutron Sources

    SciTech Connect

    Carpenter, J.M.

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  19. Computer-Aided Parallelizer and Optimizer

    NASA Technical Reports Server (NTRS)

    Jin, Haoqiang

    2011-01-01

    The Computer-Aided Parallelizer and Optimizer (CAPO) automates the insertion of compiler directives (see figure) to facilitate parallel processing on Shared Memory Parallel (SMP) machines. While CAPO currently is integrated seamlessly into CAPTools (developed at the University of Greenwich, now marketed as ParaWise), CAPO was independently developed at Ames Research Center as one of the components for the Legacy Code Modernization (LCM) project. The current version takes serial FORTRAN programs, performs interprocedural data dependence analysis, and generates OpenMP directives. Due to the widely supported OpenMP standard, the generated OpenMP codes have the potential to run on a wide range of SMP machines. CAPO relies on accurate interprocedural data dependence information currently provided by CAPTools. Compiler directives are generated through identification of parallel loops in the outermost level, construction of parallel regions around parallel loops and optimization of parallel regions, and insertion of directives with automatic identification of private, reduction, induction, and shared variables. Attempts also have been made to identify potential pipeline parallelism (implemented with point-to-point synchronization). Although directives are generated automatically, user interaction with the tool is still important for producing good parallel codes. A comprehensive graphical user interface is included for users to interact with the parallelization process.

  20. Pulsed electrodeposition of iron-nickel alloys

    SciTech Connect

    Grimmett, D.L.; Schwartz, M.; Nobe, K. )

    1990-11-01

    This paper reports on the effects of dc, pulse, and pulse reverse current waveforms on deposition of Fe-Ni alloys studied in unagitated solutions and with a rotating cylindrical electrode. A nickel sulfamate/ferrous chloride electrolyte system at pH 2 less than 2 A/dm{sup 2}. Pulse reverse plating led to a decrease in anomalous deposition at low current densities. Rotating cylindrical electrodes indicated significant mass transfer effects at high current densities. During pulse reverse plating an increase in anodic pulse magnitude decreased anomalous deposition; pulse frequency had its greatest effect in reducing anomalous deposition between 100 and 300 Hz.

  1. Pulse stretcher

    DOEpatents

    Horton, J.A.

    1994-05-03

    Apparatus for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse is disclosed. The apparatus uses a White cell having a plurality of optical delay paths of successively increasing number of passes between the field mirror and the objective mirrors. A pulse from a laser travels through a multi-leg reflective path between a beam splitter and a totally reflective mirror to the laser output. The laser pulse is also simultaneously injected through the beam splitter to the input mirrors of the optical delay paths. The pulses from the output mirrors of the optical delay paths go simultaneously to the laser output and to the input mirrors of the longer optical delay paths. The beam splitter is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output. 6 figures.

  2. Dispersion compensation in chirped pulse amplification systems

    SciTech Connect

    Bayramian, Andrew James; Molander, William A.

    2014-07-15

    A chirped pulse amplification system includes a laser source providing an input laser pulse along an optical path. The input laser pulse is characterized by a first temporal duration. The system also includes a multi-pass pulse stretcher disposed along the optical path. The multi-pass pulse stretcher includes a first set of mirrors operable to receive input light in a first plane and output light in a second plane parallel to the first plane and a first diffraction grating. The pulse stretcher also includes a second set of mirrors operable to receive light diffracted from the first diffraction grating and a second diffraction grating. The pulse stretcher further includes a reflective element operable to reflect light diffracted from the second diffraction grating. The system further includes an amplifier, a pulse compressor, and a passive dispersion compensator disposed along the optical path.

  3. Peak holding circuit for extremely narrow pulses

    NASA Technical Reports Server (NTRS)

    Oneill, R. W. (Inventor)

    1975-01-01

    An improved pulse stretching circuit comprising: a high speed wide-band amplifier connected in a fast charge integrator configuration; a holding circuit including a capacitor connected in parallel with a discharging network which employs a resistor and an FET; and an output buffer amplifier. Input pulses of very short duration are applied to the integrator charging the capacitor to a value proportional to the input pulse amplitude. After a predetermined period of time, conventional circuitry generates a dump pulse which is applied to the gate of the FET making a low resistance path to ground which discharges the capacitor. When the dump pulse terminates, the circuit is ready to accept another pulse to be stretched. The very short input pulses are thus stretched in width so that they may be analyzed by conventional pulse height analyzers.

  4. Gigawatt, femtosecond VUV pulses from a SASE FEL: Photon beam characterisation and first applications

    NASA Astrophysics Data System (ADS)

    Tiedtke, K.

    2002-11-01

    Parallel to the enormous progress in optical and conventional X-ray lasers there have also been tremendous advances in the field of Free Electron Lasers (FELs) based on the principle of Self-Amplified Spontaneous Emission (SASE). At the TESLA Test Facility (TTF FEL) at DESY, a linac-driven SASE FEL has produced short pulses with GW peak power in the wavelengths range of 80-120 nm. The radiation pulse length has been adjusted between 30 fs and 200 fs. Currently an energy upgrade of the TTF linear accelerator to 1 GeV is being prepared which will make radiation wavelengths down to 6 nm available for users.

  5. A new digital pulse power supply in heavy ion research facility in Lanzhou

    NASA Astrophysics Data System (ADS)

    Wang, Rongkun; Chen, Youxin; Huang, Yuzhen; Gao, Daqing; Zhou, Zhongzu; Yan, Huaihai; Zhao, Jiang; Shi, Chunfeng; Wu, Fengjun; Yan, Hongbin; Xia, Jiawen; Yuan, Youjin

    2013-11-01

    To meet the increasing requirements of the Heavy Ion Research Facility in Lanzhou-Cooler Storage Ring (HIRFL-CSR), a new digital pulse power supply, which employs multi-level converter, was designed. This power supply was applied with a multi H-bridge converters series-parallel connection topology. A new control model named digital power supply regulator system (DPSRS) was proposed, and a pulse power supply prototype based on DPSRS has been built and tested. The experimental results indicate that tracking error and ripple current meet the requirements of this design. The achievement of prototype provides a perfect model for HIRFL-CSR power supply system.

  6. Applied Parallel Metadata Indexing

    SciTech Connect

    Jacobi, Michael R

    2012-08-01

    The GPFS Archive is parallel archive is a parallel archive used by hundreds of users in the Turquoise collaboration network. It houses 4+ petabytes of data in more than 170 million files. Currently, users must navigate the file system to retrieve their data, requiring them to remember file paths and names. A better solution might allow users to tag data with meaningful labels and searach the archive using standard and user-defined metadata, while maintaining security. last summer, I developed the backend to a tool that adheres to these design goals. The backend works by importing GPFS metadata into a MongoDB cluster, which is then indexed on each attribute. This summer, the author implemented security and developed the user interfae for the search tool. To meet security requirements, each database table is associated with a single user, which only stores records that the user may read, and requires a set of credentials to access. The interface to the search tool is implemented using FUSE (Filesystem in USErspace). FUSE is an intermediate layer that intercepts file system calls and allows the developer to redefine how those calls behave. In the case of this tool, FUSE interfaces with MongoDB to issue queries and populate output. A FUSE implementation is desirable because it allows users to interact with the search tool using commands they are already familiar with. These security and interface additions are essential for a usable product.

  7. Pulsed welding plasma source

    NASA Astrophysics Data System (ADS)

    Knyaz'kov, A.; Pustovykh, O.; Verevkin, A.; Terekhin, V.; Shachek, A.; Tyasto, A.

    2016-04-01

    It is shown that in order to form the current pulse of a near rectangular shape, which provides conversion of the welding arc into a dynamic mode, it is rational to connect a forming element made on the basis of an artificial forming line in series to the welding DC circuit. The paper presents a diagram of a pulsed device for welding with a non-consumable electrode in argon which was developed using the forming element. The conversion of the arc into the dynamic mode is illustrated by the current and voltage oscillograms of the arc gap and the dynamic characteristic of the arc within the interval of one pulse generation time in the arc gap. The background current travels in the interpulse interval.

  8. MPP parallel forth

    NASA Technical Reports Server (NTRS)

    Dorband, John E.

    1987-01-01

    Massively Parallel Processor (MPP) Parallel FORTH is a derivative of FORTH-83 and Unified Software Systems' Uni-FORTH. The extension of FORTH into the realm of parallel processing on the MPP is described. With few exceptions, Parallel FORTH was made to follow the description of Uni-FORTH as closely as possible. Likewise, the parallel FORTH extensions were designed as philosophically similar to serial FORTH as possible. The MPP hardware characteristics, as viewed by the FORTH programmer, is discussed. Then a description is presented of how parallel FORTH is implemented on the MPP.

  9. Preference pulses without reinforcers.

    PubMed

    McLean, Anthony P; Grace, Randolph C; Pitts, Raymond C; Hughes, Christine E

    2014-05-01

    Preference pulses are thought to represent strong, short-term effects of reinforcers on preference in concurrent schedules. However, the general shape of preference pulses is substantially determined by the distributions of responses-per-visit (visit lengths) for the two choice alternatives. In several series of simulations, we varied the means and standard deviations of distributions describing visits to two concurrently available response alternatives, arranged "reinforcers" according to concurrent variable-interval schedules, and found a range of different preference pulses. Because characteristics of these distributions describe global aspects of behavior, and the simulations assumed no local effects of reinforcement, these preference pulses derive from the visit structure alone. This strongly questions whether preference pulses should continue to be interpreted as representing local effects of reinforcement. We suggest an alternative approach whereby local effects are assessed by subtracting the artifactual part, which derives from visit structure, from the observed preference pulses. This yields "residual" preference pulses. We illustrate this method in application to published data from mixed dependent concurrent schedules, revealing evidence that the delivery of reinforcers had modest lengthening effects on the duration of the current visit, a conclusion that is quantitatively consistent with early research on short-term effects of reinforcement.

  10. Results of a pilot study and a proposal to build a high current pulsed nanosecond low energy Si ion beam for the detection of trace amounts of heavy impurities in silicon

    SciTech Connect

    Jacobsen, F.M.; Zarcone, M.J.; Steski, D.; Smith, K.; Thieberger, P.; Lynn, K.G.; Throwe, J.; Cholewa, M. |

    1996-01-01

    Next generations of Very Large Scale Integrated circuits will require impurity contamination below 10{sup 8} atoms/cm. To detect such small quantities at or near the surface, new techniques have to be developed. The authors propose to build a high current nanosecond pulsed Si ion beam which can detect such small quantities of heavy impurities with a high mass resolution. A pilot study shows that the approach can be used to detect impurities in silicon below the 10{sup 7} atoms/cm{sup 2} level.

  11. Parallel Imaging Microfluidic Cytometer

    PubMed Central

    Ehrlich, Daniel J.; McKenna, Brian K.; Evans, James G.; Belkina, Anna C.; Denis, Gerald V.; Sherr, David; Cheung, Man Ching

    2011-01-01

    By adding an additional degree of freedom from multichannel flow, the parallel microfluidic cytometer (PMC) combines some of the best features of flow cytometry (FACS) and microscope-based high-content screening (HCS). The PMC (i) lends itself to fast processing of large numbers of samples, (ii) adds a 1-D imaging capability for intracellular localization assays (HCS), (iii) has a high rare-cell sensitivity and, (iv) has an unusual capability for time-synchronized sampling. An inability to practically handle large sample numbers has restricted applications of conventional flow cytometers and microscopes in combinatorial cell assays, network biology, and drug discovery. The PMC promises to relieve a bottleneck in these previously constrained applications. The PMC may also be a powerful tool for finding rare primary cells in the clinic. The multichannel architecture of current PMC prototypes allows 384 unique samples for a cell-based screen to be read out in approximately 6–10 minutes, about 30-times the speed of most current FACS systems. In 1-D intracellular imaging, the PMC can obtain protein localization using HCS marker strategies at many times the sample throughput of CCD-based microscopes or CCD-based single-channel flow cytometers. The PMC also permits the signal integration time to be varied over a larger range than is practical in conventional flow cytometers. The signal-to-noise advantages are useful, for example, in counting rare positive cells in the most difficult early stages of genome-wide screening. We review the status of parallel microfluidic cytometry and discuss some of the directions the new technology may take. PMID:21704835

  12. PULSE AMPLIFIER

    DOEpatents

    Johnstone, C.W.

    1958-06-17

    The improvement of pulse amplifiers used with scintillation detectors is described. The pulse amplifier circuit has the advantage of reducing the harmful effects of overloading cause by large signal inputs. In general the pulse amplifier circuit comprises two amplifier tubes with the input pulses applied to one amplifier grid and coupled to the second amplifier tube through a common cathode load. The output of the second amplifier is coupled from the plate circuit to a cathode follower tube grid and a diode tube in connected from grid to cathode of the cathode follower tube. Degenerative feedback is provided in the second amplifier by coupling a signal from the cathode follower cathode to the second amplifier grid. The circuit proqides moderate gain stability, and overload protection for subsequent pulse circuits.

  13. Parallel flow diffusion battery

    DOEpatents

    Yeh, H.C.; Cheng, Y.S.

    1984-01-01

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  14. Parallel flow diffusion battery

    DOEpatents

    Yeh, Hsu-Chi; Cheng, Yung-Sung

    1984-08-07

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  15. Parallel Computing in SCALE

    SciTech Connect

    DeHart, Mark D; Williams, Mark L; Bowman, Stephen M

    2010-01-01

    The SCALE computational architecture has remained basically the same since its inception 30 years ago, although constituent modules and capabilities have changed significantly. This SCALE concept was intended to provide a framework whereby independent codes can be linked to provide a more comprehensive capability than possible with the individual programs - allowing flexibility to address a wide variety of applications. However, the current system was designed originally for mainframe computers with a single CPU and with significantly less memory than today's personal computers. It has been recognized that the present SCALE computation system could be restructured to take advantage of modern hardware and software capabilities, while retaining many of the modular features of the present system. Preliminary work is being done to define specifications and capabilities for a more advanced computational architecture. This paper describes the state of current SCALE development activities and plans for future development. With the release of SCALE 6.1 in 2010, a new phase of evolutionary development will be available to SCALE users within the TRITON and NEWT modules. The SCALE (Standardized Computer Analyses for Licensing Evaluation) code system developed by Oak Ridge National Laboratory (ORNL) provides a comprehensive and integrated package of codes and nuclear data for a wide range of applications in criticality safety, reactor physics, shielding, isotopic depletion and decay, and sensitivity/uncertainty (S/U) analysis. Over the last three years, since the release of version 5.1 in 2006, several important new codes have been introduced within SCALE, and significant advances applied to existing codes. Many of these new features became available with the release of SCALE 6.0 in early 2009. However, beginning with SCALE 6.1, a first generation of parallel computing is being introduced. In addition to near-term improvements, a plan for longer term SCALE enhancement

  16. PARAVT: Parallel Voronoi tessellation code

    NASA Astrophysics Data System (ADS)

    González, R. E.

    2016-10-01

    In this study, we present a new open source code for massive parallel computation of Voronoi tessellations (VT hereafter) in large data sets. The code is focused for astrophysical purposes where VT densities and neighbors are widely used. There are several serial Voronoi tessellation codes, however no open source and parallel implementations are available to handle the large number of particles/galaxies in current N-body simulations and sky surveys. Parallelization is implemented under MPI and VT using Qhull library. Domain decomposition takes into account consistent boundary computation between tasks, and includes periodic conditions. In addition, the code computes neighbors list, Voronoi density, Voronoi cell volume, density gradient for each particle, and densities on a regular grid. Code implementation and user guide are publicly available at https://github.com/regonzar/paravt.

  17. Parallel simulation today

    NASA Technical Reports Server (NTRS)

    Nicol, David; Fujimoto, Richard

    1992-01-01

    This paper surveys topics that presently define the state of the art in parallel simulation. Included in the tutorial are discussions on new protocols, mathematical performance analysis, time parallelism, hardware support for parallel simulation, load balancing algorithms, and dynamic memory management for optimistic synchronization.

  18. Verbal and Visual Parallelism

    ERIC Educational Resources Information Center

    Fahnestock, Jeanne

    2003-01-01

    This study investigates the practice of presenting multiple supporting examples in parallel form. The elements of parallelism and its use in argument were first illustrated by Aristotle. Although real texts may depart from the ideal form for presenting multiple examples, rhetorical theory offers a rationale for minimal, parallel presentation. The…

  19. The Ranchero explosive pulsed power system

    SciTech Connect

    Goforth, J.H.; Atchison, W.L.; Bartram, D.E.

    1997-09-01

    The authors are currently developing a high explosive pulsed power system concept that they call Ranchero. Ranchero systems consist of series-parallel combinations of simultaneously initiated coaxial magnetic flux compression generators, and are intended to operate in the range from 50 MA to a few hundred MA currents. One example of a Ranchero system is shown here. The coaxial modules lend themselves to extracting the current output either from one end or along the generator midplane. They have previously published design considerations related to the different module configurations, and in this paper they concentrate on the system that they will use for their first imploding liner tests. A single module with end output. The module is 1.4-m long and expands the armature by a factor of two to reach the 30-cm OD stator. The first heavy liner implosion experiments will be conducted in the range of 40--50 MA currents. Electrical tests, to date, have employed high explosive (HE) charges 43-cm long. They have performed tests and related 1D MHD calculations at the 45-MA current level with small loads. From these results, they determine that they can deliver currents of approximately 50 MA to loads of 8 nH.

  20. Petawatt pulsed-power accelerator

    DOEpatents

    Stygar, William A.; Cuneo, Michael E.; Headley, Daniel I.; Ives, Harry C.; Ives, legal representative; Berry Cottrell; Leeper, Ramon J.; Mazarakis, Michael G.; Olson, Craig L.; Porter, John L.; Wagoner; Tim C.

    2010-03-16

    A petawatt pulsed-power accelerator can be driven by various types of electrical-pulse generators, including conventional Marx generators and linear-transformer drivers. The pulsed-power accelerator can be configured to drive an electrical load from one- or two-sides. Various types of loads can be driven; for example, the accelerator can be used to drive a high-current z-pinch load. When driven by slow-pulse generators (e.g., conventional Marx generators), the accelerator comprises an oil section comprising at least one pulse-generator level having a plurality of pulse generators; a water section comprising a pulse-forming circuit for each pulse generator and a level of monolithic triplate radial-transmission-line impedance transformers, that have variable impedance profiles, for each pulse-generator level; and a vacuum section comprising triplate magnetically insulated transmission lines that feed an electrical load. When driven by LTD generators or other fast-pulse generators, the need for the pulse-forming circuits in the water section can be eliminated.

  1. Currents Induced by Injected Charge in Junction Detectors

    PubMed Central

    Gaubas, Eugenijus; Ceponis, Tomas; Kalesinskas, Vidas

    2013-01-01

    The problem of drifting charge-induced currents is considered in order to predict the pulsed operational characteristics in photo- and particle-detectors with a junction controlled active area. The direct analysis of the field changes induced by drifting charge in the abrupt junction devices with a plane-parallel geometry of finite area electrodes is presented. The problem is solved using the one-dimensional approach. The models of the formation of the induced pulsed currents have been analyzed for the regimes of partial and full depletion. The obtained solutions for the current density contain expressions of a velocity field dependence on the applied voltage, location of the injected surface charge domain and carrier capture parameters. The drift component of this current coincides with Ramo's expression. It has been illustrated, that the synchronous action of carrier drift, trapping, generation and diffusion can lead to a vast variety of possible current pulse waveforms. Experimental illustrations of the current pulse variations determined by either the rather small or large carrier density within the photo-injected charge domain are presented, based on a study of Si detectors. PMID:24036586

  2. A generic fine-grained parallel C

    NASA Technical Reports Server (NTRS)

    Hamet, L.; Dorband, John E.

    1988-01-01

    With the present availability of parallel processors of vastly different architectures, there is a need for a common language interface to multiple types of machines. The parallel C compiler, currently under development, is intended to be such a language. This language is based on the belief that an algorithm designed around fine-grained parallelism can be mapped relatively easily to different parallel architectures, since a large percentage of the parallelism has been identified. The compiler generates a FORTH-like machine-independent intermediate code. A machine-dependent translator will reside on each machine to generate the appropriate executable code, taking advantage of the particular architectures. The goal of this project is to allow a user to run the same program on such machines as the Massively Parallel Processor, the CRAY, the Connection Machine, and the CYBER 205 as well as serial machines such as VAXes, Macintoshes and Sun workstations.

  3. Rapid thermal annealing effect on the spatial resistivity distribution of AZO thin films deposited by pulsed-direct-current sputtering for solar cells applications

    NASA Astrophysics Data System (ADS)

    Ayachi, Boubakeur; Aviles, Thomas; Vilcot, Jean-Pierre; Sion, Cathy

    2016-03-01

    Room temperature deposited aluminium-doped zinc oxide thin films on glass substrate, using pulsed-DC magnetron sputtering, have shown high optical transmittance and low electrical resistivity with high uniformity of its spatial distribution after they were exposed to a rapid thermal annealing process at 400 °C under N2H2 atmosphere. It is particularly interesting to note that such an annealing process of AZO thin films for only 30 s was sufficient, on one hand to improve their optical transmittance from 73% to 86%, on the other hand to both decrease their resistivity from 1.7 × 10-3 Ω cm to 5.1 × 10-4 Ω cm and achieve the highest uniformity spatial distribution. To understand the mechanisms behind such improvements of the optoelectronic properties, electrical, optical, structural and morphological changes as a function of annealing time have been investigated by using hall measurement, UV-visible spectrometry, X-ray diffraction and scanning electron microscope imaging, respectively.

  4. Radio-Frequency Pulse Compression for Linear Accelerators.

    NASA Astrophysics Data System (ADS)

    Nantista, Christopher Dennis

    Recent efforts to develop plans for an electron -positron linear collider with center-of-mass energy approaching a TeV have highlighted the need for sources capable of delivering hundreds of megawatts of peak rf drive power at X-band frequencies. This need has driven work in the area of rf pulse compression, which enhances the peak power available from pulsed rf tubes by compressing their output pulses in time, accumulating the available energy into shorter pulses. The classic means of rf pulse compression for linear accelerators is SLED. This technique is described, and the problem it presents for multibunch acceleration explained. Other pulse compression schemes, capable of producing suitable output pulses are explored, both theoretically and experimentally, in particular Binary Pulse Compression and SLED-II. The merits of each are considered with regard to gain, efficiency, complexity, size and cost. The development of some novel system components, along with the theory behind their design, is also discussed. The need to minimize copper losses in long waveguide runs led to the use of the circular TE_{01} propagation mode in over-moded guide, requiring much attention to mechanisms of coupling power between modes. The construction and commissioning of complete, high-power pulse compression systems is reported on, as well as their use in the testing of X-band accelerating structures, which, along with the X-band klystrons used, were developed at SLAC in parallel with the pulse compression work. The focus of the dissertation is on SLED-II, the favored scheme in some current linear accelerator designs. In addition to our experimental results, practical implementation considerations and design improvements are presented. The work to date has led to detailed plans for SLED-II systems to be used in the Next Linear Collider Test Accelerator, now under construction at SLAC. The prototype of the upgraded system is near completion. Descriptions of various rf pulse

  5. Wafer-level pulsed-DC electromigration response at very high frequencies

    SciTech Connect

    Pierce, D.G.; Snyder, E.S.; Swanson, S.E.; Irwin, L.W.

    1994-03-01

    DC and pulsed-DC electromigration tests were performed at the Wafer-Level Pulsed-DC Electromigration Response and pulsed-DC electromigration tests were performed at the wafer level using standard and self-stressing test structures. DC characterization tests over a very large temperature range (180 to 560{degrees}C) were consistent with an interface diffusion mechanism in parallel with lattice diffusion. That data allowed for extraction of the respective activation energies and the diffusion coefficient of the rapid mechanism. The ability to extract simultaneously a defect-based diffusion coefficient and activation energy is significant given the extreme difficulty in making those measurements in aluminum. The pulsed-DC experiments were conducted over a range that includes the highest frequency to date, from DC to 500 MHz. Measurements were also made as a function of duty factor from 15% to 100% at selected frequencies. The data shows that the pulsed-DC lifetime is consistent with the average current density model at high (> 10 MHz) frequencies and showed no additional effects at the highest frequency tested (500 MHz). At low frequencies, we attribute the lessened enhancement to thermal effects rather than vacancy relaxation effects. Finally, the deviation in lifetime from the expected current density dependence, characterized over 1{1/2} orders of magnitude in current density, is explained in terms of a shift in the boundary condition for electromigration as the current density is decreased.

  6. LED flicker pulsing

    NASA Astrophysics Data System (ADS)

    Johnson, Mark A.; Cote, Paul J.

    2001-08-01

    There is need to replace hazardous radioluminescent light sources with a means of illumination that is environmentally friendly. This paper describes an electronic source that was developed as a potential candidate to replace low intensity tritium in a military system. It employs an LED for illumination and a 3-volt coin cell battery as a power source. This new light source is electronically invisible, requires minimal maintenance, and provides the lowest practical illumination to preclude detection by optical means. The low intensity requires that the LED be driven at DC current levels resulting in poor luminous efficiency. Therefore, in an effort to maximize battery life, the LED is pulsed into a more optically efficient mode of operation. However, conventional pulsing techniques are not employed because of concerns the electronics could be identified by conspicuous power spectral density (PSD) components in the electromagnetic spectrum generated by a pulsed LED. Therefore, flicker noise concepts have been employed to efficiently drive the LED while generating a virtually undetectable spectral signature. Although ideally the pulse durations, magnitudes, and spacings should be random, a significant reduction in conspicuous PSD components can be achieved when imposing practical constraints. The dominant components of the power spectrum are significantly reduced using fixed pulse durations and magnitudes while varying only the pulse spacing. The mean duty cycle is set to provide the same effective illumination as DC operation while generating a PSD normally associated with natural phenomena.

  7. Pulse Data.

    ERIC Educational Resources Information Center

    Hands On!, 1998

    1998-01-01

    Presents an activity using computer software to investigate the role of the heart and blood, how the blood system responds to exercise, and how pulse rate is a good measure of physical condition. (ASK)

  8. National Combustion Code: Parallel Implementation and Performance

    NASA Technical Reports Server (NTRS)

    Quealy, A.; Ryder, R.; Norris, A.; Liu, N.-S.

    2000-01-01

    The National Combustion Code (NCC) is being developed by an industry-government team for the design and analysis of combustion systems. CORSAIR-CCD is the current baseline reacting flow solver for NCC. This is a parallel, unstructured grid code which uses a distributed memory, message passing model for its parallel implementation. The focus of the present effort has been to improve the performance of the NCC flow solver to meet combustor designer requirements for model accuracy and analysis turnaround time. Improving the performance of this code contributes significantly to the overall reduction in time and cost of the combustor design cycle. This paper describes the parallel implementation of the NCC flow solver and summarizes its current parallel performance on an SGI Origin 2000. Earlier parallel performance results on an IBM SP-2 are also included. The performance improvements which have enabled a turnaround of less than 15 hours for a 1.3 million element fully reacting combustion simulation are described.

  9. Note: A rectangular pulse generator for 50 kV voltage, 0.8 ns rise time, and 10 ns pulse width based on polymer-film switch.

    PubMed

    Wu, Hanyu; Zhang, Xinjun; Sun, Tieping; Zeng, Zhengzhong; Cong, Peitian; Zhang, Shaoguo

    2015-10-01

    In this article, we describe a rectangular pulse generator, consisting of a polymer-film switch, a tri-plate transmission line, and parallel post-shaped ceramic resistor load, for 50-kV voltage, 0.8-ns rise time, and 10-ns width. The switch and resistors are arranged in atmospheric air and the transmission line can work in atmospheric air or in transformer oil to change the pulse width from 6.7 ns to 10 ns. The fast switching and low-inductance characteristics of the polymer-film switch ensure the fast rising wavefront of <1 ns. This generator can be applied in the calibration of nanosecond voltage dividers and used for electromagnetic pulse tests as a fast-rising current injection source. PMID:26521006

  10. Pulse stretcher

    DOEpatents

    Horton, James A.

    1994-01-01

    Apparatus (20) for increasing the length of a laser pulse to reduce its peak power without substantial loss in the average power of the pulse. The apparatus (20) uses a White cell (10) having a plurality of optical delay paths (18a-18d) of successively increasing number of passes between the field mirror (13) and the objective mirrors (11 and 12). A pulse (26) from a laser (27) travels through a multi-leg reflective path (28) between a beam splitter (21) and a totally reflective mirror (24) to the laser output (37). The laser pulse (26) is also simultaneously injected through the beam splitter (21) to the input mirrors (14a-14d) of the optical delay paths (18a-18d). The pulses from the output mirrors (16a-16d) of the optical delay paths (18a-18d) go simultaneously to the laser output (37) and to the input mirrors ( 14b-14d) of the longer optical delay paths. The beam splitter (21) is 50% reflective and 50% transmissive to provide equal attenuation of all of the pulses at the laser output (37).

  11. Pulsed helium ionization detection system

    DOEpatents

    Ramsey, Roswitha S.; Todd, Richard A.

    1987-01-01

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  12. Pulsed helium ionization detection system

    DOEpatents

    Ramsey, R.S.; Todd, R.A.

    1985-04-09

    A helium ionization detection system is provided which produces stable operation of a conventional helium ionization detector while providing improved sensitivity and linearity. Stability is improved by applying pulsed dc supply voltage across the ionization detector, thereby modifying the sampling of the detectors output current. A unique pulse generator is used to supply pulsed dc to the detector which has variable width and interval adjust features that allows up to 500 V to be applied in pulse widths ranging from about 150 nsec to about dc conditions.

  13. Comparison of converter topologies for charging capacitors used in pulsed load applications

    NASA Technical Reports Server (NTRS)

    Nelms, R. M.; Schatz, J. E.; Pollard, Barry

    1991-01-01

    The authors present a qualitative comparison of different power converter topologies which may be utilized for charging capacitors in pulsed power applications requiring voltages greater than 1 kV. The operation of the converters in capacitor charging applications is described, and relevant advantages are presented. All of the converters except one may be classified in the high-frequency switching category. One of the benefits from high-frequency operation is a reduction in size and weight. The other converter discussed is a member of the command resonant changing category. The authors first describe a boost circuit which functions as a command resonant charging circuit and utilizes a single pulse of current to charge the capacitor. The discussion of high-frequency converters begins with the flyback and Ward converters. Then, the series, parallel, and series/parallel resonant converters are examined.

  14. Parallel electric fields from ionospheric winds

    NASA Technical Reports Server (NTRS)

    Nakada, M. P.

    1987-01-01

    The possible production of electric fields parallel to the magnetic field by dynamo winds in the E region is examined, using a jet stream wind model. Current return paths through the F region above the stream are examined as well as return paths through the conjugate ionosphere. The Wulf geometry with horizontal winds moving in opposite directions one above the other is also examined. Parallel electric fields are found to depend strongly on the width of current sheets at the edges of the jet stream. If these are narrow enough, appreciable parallel electric fields are produced.

  15. Switching power pulse system

    DOEpatents

    Aaland, K.

    1983-08-09

    A switching system for delivering pulses of power from a source to a load using a storage capacitor charged through a rectifier, and maintained charged to a reference voltage level by a transistor switch and voltage comparator. A thyristor is triggered to discharge the storage capacitor through a saturable reactor and fractional turn saturable transformer having a secondary to primary turn ratio N of n:l/n = n[sup 2]. The saturable reactor functions as a soaker'' while the thyristor reaches saturation, and then switches to a low impedance state. The saturable transformer functions as a switching transformer with high impedance while a load coupling capacitor charges, and then switches to a low impedance state to dump the charge of the storage capacitor into the load through the coupling capacitor. The transformer is comprised of a multilayer core having two secondary windings tightly wound and connected in parallel to add their output voltage and reduce output inductance, and a number of single turn windings connected in parallel at nodes for the primary winding, each single turn winding linking a different one of the layers of the multilayer core. The load may be comprised of a resistive beampipe for a linear particle accelerator and capacitance of a pulse forming network. To hold off discharge of the capacitance until it is fully charged, a saturable core is provided around the resistive beampipe to isolate the beampipe from the capacitance until it is fully charged. 5 figs.

  16. Parallel Power Grid Simulation Toolkit

    SciTech Connect

    Smith, Steve; Kelley, Brian; Banks, Lawrence; Top, Philip; Woodward, Carol

    2015-09-14

    ParGrid is a 'wrapper' that integrates a coupled Power Grid Simulation toolkit consisting of a library to manage the synchronization and communication of independent simulations. The included library code in ParGid, named FSKIT, is intended to support the coupling multiple continuous and discrete even parallel simulations. The code is designed using modern object oriented C++ methods utilizing C++11 and current Boost libraries to ensure compatibility with multiple operating systems and environments.

  17. Parallel digital forensics infrastructure.

    SciTech Connect

    Liebrock, Lorie M.; Duggan, David Patrick

    2009-10-01

    This report documents the architecture and implementation of a Parallel Digital Forensics infrastructure. This infrastructure is necessary for supporting the design, implementation, and testing of new classes of parallel digital forensics tools. Digital Forensics has become extremely difficult with data sets of one terabyte and larger. The only way to overcome the processing time of these large sets is to identify and develop new parallel algorithms for performing the analysis. To support algorithm research, a flexible base infrastructure is required. A candidate architecture for this base infrastructure was designed, instantiated, and tested by this project, in collaboration with New Mexico Tech. Previous infrastructures were not designed and built specifically for the development and testing of parallel algorithms. With the size of forensics data sets only expected to increase significantly, this type of infrastructure support is necessary for continued research in parallel digital forensics. This report documents the implementation of the parallel digital forensics (PDF) infrastructure architecture and implementation.

  18. PCLIPS: Parallel CLIPS

    NASA Technical Reports Server (NTRS)

    Hall, Lawrence O.; Bennett, Bonnie H.; Tello, Ivan

    1994-01-01

    A parallel version of CLIPS 5.1 has been developed to run on Intel Hypercubes. The user interface is the same as that for CLIPS with some added commands to allow for parallel calls. A complete version of CLIPS runs on each node of the hypercube. The system has been instrumented to display the time spent in the match, recognize, and act cycles on each node. Only rule-level parallelism is supported. Parallel commands enable the assertion and retraction of facts to/from remote nodes working memory. Parallel CLIPS was used to implement a knowledge-based command, control, communications, and intelligence (C(sup 3)I) system to demonstrate the fusion of high-level, disparate sources. We discuss the nature of the information fusion problem, our approach, and implementation. Parallel CLIPS has also be used to run several benchmark parallel knowledge bases such as one to set up a cafeteria. Results show from running Parallel CLIPS with parallel knowledge base partitions indicate that significant speed increases, including superlinear in some cases, are possible.

  19. Precision digital pulse phase generator

    DOEpatents

    McEwan, Thomas E.

    1996-01-01

    A timing generator comprises a crystal oscillator connected to provide an output reference pulse. A resistor-capacitor combination is connected to provide a variable-delay output pulse from an input connected to the crystal oscillator. A phase monitor is connected to provide duty-cycle representations of the reference and variable-delay output pulse phase. An operational amplifier drives a control voltage to the resistor-capacitor combination according to currents integrated from the phase monitor and injected into summing junctions. A digital-to-analog converter injects a control current into the summing junctions according to an input digital control code. A servo equilibrium results that provides a phase delay of the variable-delay output pulse to the output reference pulse that linearly depends on the input digital control code.

  20. Precision digital pulse phase generator

    DOEpatents

    McEwan, T.E.

    1996-10-08

    A timing generator comprises a crystal oscillator connected to provide an output reference pulse. A resistor-capacitor combination is connected to provide a variable-delay output pulse from an input connected to the crystal oscillator. A phase monitor is connected to provide duty-cycle representations of the reference and variable-delay output pulse phase. An operational amplifier drives a control voltage to the resistor-capacitor combination according to currents integrated from the phase monitor and injected into summing junctions. A digital-to-analog converter injects a control current into the summing junctions according to an input digital control code. A servo equilibrium results that provides a phase delay of the variable-delay output pulse to the output reference pulse that linearly depends on the input digital control code. 2 figs.

  1. Experimental and theoretical investigations concerning a frequency filter behavior of the human retina regarding electric pulse currents. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Meier-Koll, A.

    1979-01-01

    Investigation involving patients with injuries in the visual nervous system are discussed. This led to the identification of the epithelial ganglion of the retina as a frequency filter. Threshold curves of the injured visual organs were compared with threshold curves obtained with a control group as a basis for identification. A model which considers the epithelial ganglion as a homogeneous cell layer in which adjacent neurons interact is discussed. It is shown the behavior of the cells against alternating exciting currents can be explained.

  2. Improvement of critical current density and thermally assisted individual vortex depinning in pulsed-laser-deposited YBa2Cu3O7-δ thin films on SrTiO3 (100) substrate with surface modification by Ag nanodots

    NASA Astrophysics Data System (ADS)

    Li, A. H.; Liu, H. K.; Ionescu, M.; Wang, X. L.; Dou, S. X.; Collings, E. W.; Sumption, M. D.; Bhatia, M.; Lin, Z. W.; Zhu, J. G.

    2005-05-01

    YBa2Cu3O7 films were fabricated by pulsed laser deposition on SrTiO3 (100) single-crystal substrates whose surfaces were modified by the introduction of Ag nanodots. The critical current density (Jc) was found to increase with the number of Ag shots. Zero-field magnetic Jc0 at 77K increased from 8×105 up to 3.5×106A /cm2 as the number of Ag shots increased from 0 to over 150 times. Microstructure investigations indicated that the crystallinity and the ab alignment gradually improved as the number of Ag nanodots increased. Thermally activated depinning of individual vortices is suggested responsible for a field-independent Jc plateau.

  3. A modified circuit topology for inductive pulsed power supply based on HTSPPTs

    NASA Astrophysics Data System (ADS)

    Li, Haitao; Zhang, Cunshan; Wang, Teng; Gao, Mingliang; Li, Zhenmei; Zou, Guofeng

    2016-10-01

    High temperature superconducting pulsed power transformer (HTSPPT) provides an efficient method for inductive energy storage and current multiplication. The primary inductor of HTSPPT used for energy storage is made of high temperature superconducting coils, and the secondary inductor used for current pulse generation is made of normal conductor coils. In the initial circuit, the secondary inductor generates current pulse by switching out the coupled primary superconducting inductor. However, during the switching period, the leakage flux caused by imperfect coupling and the sudden change in primary current induce a voltage across the opening switch which exceeds the affordability of modern solid-state switches. In previous studies, a half-cycle oscillatory discharge circuit is proposed to mitigate these problems by using a capacitor to recapture the energy in the leakage flux and to slow down the turnoff of current in the primary. However, there are still some problems should be settled. For example, the output pulse cannot be adjusted, the residual energy cannot be recovered and the capacitor branch circuit may have an impact on the charging process. In the paper, a modified discharge circuit topology is introduced to solve these problems. A multi-module system comprising of several HTSPPTs charging in series connection and discharging in parallel is also designed and simulated. This system can be used to power an electromagnetic emission device.

  4. Parallel Lisp simulator

    SciTech Connect

    Weening, J.S.

    1988-05-01

    CSIM is a simulator for parallel Lisp, based on a continuation passing interpreter. It models a shared-memory multiprocessor executing programs written in Common Lisp, extended with several primitives for creating and controlling processes. This paper describes the structure of the simulator, measures its performance, and gives an example of its use with a parallel Lisp program.

  5. Solid state pulsed power generator

    SciTech Connect

    Tao, Fengfeng; Saddoughi, Seyed Gholamali; Herbon, John Thomas

    2014-02-11

    A power generator includes one or more full bridge inverter modules coupled to a semiconductor opening switch (SOS) through an inductive resonant branch. Each module includes a plurality of switches that are switched in a fashion causing the one or more full bridge inverter modules to drive the semiconductor opening switch SOS through the resonant circuit to generate pulses to a load connected in parallel with the SOS.

  6. Enhanced self-field critical current density of nano-composite YBa2Cu3O7 thin films grown by pulsed-laser deposition

    NASA Astrophysics Data System (ADS)

    Siraj, K.; Pedarnig, J. D.; Moser, A.; Bäuerle, D.; Babu, N. Hari; Cardwell, D. A.

    2008-06-01

    Enhanced self-field critical current density Jc of novel, high-temperature superconducting thin films is reported. Layers are deposited on (001) MgO substrates by laser ablation of YBa2Cu3O7-δ(Y-123) ceramics containing Y2Ba4CuMOx (M-2411, M=Ag, Nb, Ru, Zr) nano-particles. The Jc of films depends on the secondary-phase content of the ceramic targets, which was varied between 0 and 15 mol%. Composite layers (2 mol% of Ag-2411 and Nb-2411) exhibit Jc values at 77 K of up to 5.1 MA/cm2, which is 3 to 4 times higher than those observed in films deposited from phase pure Y-123 ceramics. Nb-2411 grows epitaxially in the composite layers and the estimated crystallite size is ~10 nm.

  7. A Method for Evaluating Electron Transport Parameters on a Pulsed Townsend Experiment

    SciTech Connect

    Ridenti, M. A.; Pascholati, P. R.; Vivaldini, T. C.; Lima, I. B.

    2010-05-21

    In this work, we present a physical model that links fundamental theory of electron kinetics on weakly ionized gases to direct measurements of induced pulsed signals in a Resistive Plate Chamber. It is also presented preliminary measurements of electron transport parameters in nitrogen obtained for reduced electric fields ranging from 129 Td up to 216 Td. These parameters were indirectly determined by fitting the proposed model to the time dependent pulse current induced on the parallel plate chamber electrodes by an electron avalanche triggered near the cathode by a N{sub 2} laser pulse. Experimental results are compared with previous measurements, Monte Carlo simulation results from Magboltz and results from classical two-term expansion Boltzmann equation solution from Bolsig+.

  8. Parallel computing works

    SciTech Connect

    Not Available

    1991-10-23

    An account of the Caltech Concurrent Computation Program (C{sup 3}P), a five year project that focused on answering the question: Can parallel computers be used to do large-scale scientific computations '' As the title indicates, the question is answered in the affirmative, by implementing numerous scientific applications on real parallel computers and doing computations that produced new scientific results. In the process of doing so, C{sup 3}P helped design and build several new computers, designed and implemented basic system software, developed algorithms for frequently used mathematical computations on massively parallel machines, devised performance models and measured the performance of many computers, and created a high performance computing facility based exclusively on parallel computers. While the initial focus of C{sup 3}P was the hypercube architecture developed by C. Seitz, many of the methods developed and lessons learned have been applied successfully on other massively parallel architectures.

  9. Totally parallel multilevel algorithms

    NASA Technical Reports Server (NTRS)

    Frederickson, Paul O.

    1988-01-01

    Four totally parallel algorithms for the solution of a sparse linear system have common characteristics which become quite apparent when they are implemented on a highly parallel hypercube such as the CM2. These four algorithms are Parallel Superconvergent Multigrid (PSMG) of Frederickson and McBryan, Robust Multigrid (RMG) of Hackbusch, the FFT based Spectral Algorithm, and Parallel Cyclic Reduction. In fact, all four can be formulated as particular cases of the same totally parallel multilevel algorithm, which are referred to as TPMA. In certain cases the spectral radius of TPMA is zero, and it is recognized to be a direct algorithm. In many other cases the spectral radius, although not zero, is small enough that a single iteration per timestep keeps the local error within the required tolerance.

  10. Massively parallel mathematical sieves

    SciTech Connect

    Montry, G.R.

    1989-01-01

    The Sieve of Eratosthenes is a well-known algorithm for finding all prime numbers in a given subset of integers. A parallel version of the Sieve is described that produces computational speedups over 800 on a hypercube with 1,024 processing elements for problems of fixed size. Computational speedups as high as 980 are achieved when the problem size per processor is fixed. The method of parallelization generalizes to other sieves and will be efficient on any ensemble architecture. We investigate two highly parallel sieves using scattered decomposition and compare their performance on a hypercube multiprocessor. A comparison of different parallelization techniques for the sieve illustrates the trade-offs necessary in the design and implementation of massively parallel algorithms for large ensemble computers.

  11. PULSE COUNTER

    DOEpatents

    Trumbo, D.E.

    1959-02-10

    A transistorized pulse-counting circuit adapted for use with nuclear radiation detecting detecting devices to provide a small, light weight portable counter is reported. The small size and low power requirements of the transistor are of particular value in this instance. The circuit provides an adjustable count scale with a single transistor which is triggered by the accumulated charge on a storage capacitor.

  12. Device for balancing parallel strings

    DOEpatents

    Mashikian, Matthew S.

    1985-01-01

    A battery plant is described which features magnetic circuit means in association with each of the battery strings in the battery plant for balancing the electrical current flow through the battery strings by equalizing the voltage across each of the battery strings. Each of the magnetic circuit means generally comprises means for sensing the electrical current flow through one of the battery strings, and a saturable reactor having a main winding connected electrically in series with the battery string, a bias winding connected to a source of alternating current and a control winding connected to a variable source of direct current controlled by the sensing means. Each of the battery strings is formed by a plurality of batteries connected electrically in series, and these battery strings are connected electrically in parallel across common bus conductors.

  13. Pulsed addressing of a dual-frequency nematic liquid crystal.

    PubMed

    Mottram, N J; Brown, C V

    2006-09-01

    A continuum theory of dielectric relaxation within liquid crystal materials is described and used to model the response of dual frequency materials to single pulse voltage waveforms. The equations governing the anisotropic axis (director) angle, electric field, and induced polarizations are solved numerically to investigate pulsed addressing of a model zenithally bistable liquid crystal device. By suitably tailoring the voltage pulse, it is found to be possible to switch between both bistable states. For short pulses the high frequency components of the leading edge of the voltage pulse excites the perpendicular polarization and forces the director to lie parallel to the cell substrates. For longer voltage pulses the constant dc component of the voltage pulse excites the parallel polarization causing the director to lie perpendicular to the substrates. It is also found that reducing rotational viscosity and increasing the achievable dielectric anisotropies (particularly the high frequency value) can significantly reduce the operating voltages of such a device.

  14. Pulsed addressing of a dual-frequency nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Mottram, N. J.; Brown, C. V.

    2006-09-01

    A continuum theory of dielectric relaxation within liquid crystal materials is described and used to model the response of dual frequency materials to single pulse voltage waveforms. The equations governing the anisotropic axis (director) angle, electric field, and induced polarizations are solved numerically to investigate pulsed addressing of a model zenithally bistable liquid crystal device. By suitably tailoring the voltage pulse, it is found to be possible to switch between both bistable states. For short pulses the high frequency components of the leading edge of the voltage pulse excites the perpendicular polarization and forces the director to lie parallel to the cell substrates. For longer voltage pulses the constant dc component of the voltage pulse excites the parallel polarization causing the director to lie perpendicular to the substrates. It is also found that reducing rotational viscosity and increasing the achievable dielectric anisotropies (particularly the high frequency value) can significantly reduce the operating voltages of such a device.

  15. Pulsed addressing of a dual-frequency nematic liquid crystal.

    PubMed

    Mottram, N J; Brown, C V

    2006-09-01

    A continuum theory of dielectric relaxation within liquid crystal materials is described and used to model the response of dual frequency materials to single pulse voltage waveforms. The equations governing the anisotropic axis (director) angle, electric field, and induced polarizations are solved numerically to investigate pulsed addressing of a model zenithally bistable liquid crystal device. By suitably tailoring the voltage pulse, it is found to be possible to switch between both bistable states. For short pulses the high frequency components of the leading edge of the voltage pulse excites the perpendicular polarization and forces the director to lie parallel to the cell substrates. For longer voltage pulses the constant dc component of the voltage pulse excites the parallel polarization causing the director to lie perpendicular to the substrates. It is also found that reducing rotational viscosity and increasing the achievable dielectric anisotropies (particularly the high frequency value) can significantly reduce the operating voltages of such a device. PMID:17025650

  16. Parallel operation of microhollow cathode discharges

    SciTech Connect

    Shi, W.; Schoenbach, K.H.

    1998-12-31

    The dc current-voltage characteristics of microhollow cathode discharges has, in certain ranges of the discharge current, a positive slope. In these current ranges it should be possible to operate multiple discharges in parallel without individual ballast, and be used as flat panel excimer lamps or large area plasma cathodes. In order to verify this hypothesis they have studied the parallel operation of two microhollow cathode discharges of 100 {micro}m hole diameter in argon at pressures from 100 Torr to 800 Torr. Stable dc operation of the two discharges, without individual ballast, was obtained if the voltage-current characteristics of the individual discharges had a positive slope greater than 10 V/mA over a voltage range of more than 5% of the sustaining voltage. Small variations in the discharge geometry generated during fabrication of cathode holes or caused by thermal effects during discharge operation are detrimental to parallel operation. Varying the distance between the discharges from twice the hole diameter to approximately five times did not affect the parallel operation. The total current was always slightly larger than the sum of the currents measured for the individual discharges, indicating coupling between the two discharges. In order to obtain parallel operation even for microhollow cathode geometries with large variations, they have studied the effect of distributed resistive ballast on the operation of such discharges.

  17. Bilingual parallel programming

    SciTech Connect

    Foster, I.; Overbeek, R.

    1990-01-01

    Numerous experiments have demonstrated that computationally intensive algorithms support adequate parallelism to exploit the potential of large parallel machines. Yet successful parallel implementations of serious applications are rare. The limiting factor is clearly programming technology. None of the approaches to parallel programming that have been proposed to date -- whether parallelizing compilers, language extensions, or new concurrent languages -- seem to adequately address the central problems of portability, expressiveness, efficiency, and compatibility with existing software. In this paper, we advocate an alternative approach to parallel programming based on what we call bilingual programming. We present evidence that this approach provides and effective solution to parallel programming problems. The key idea in bilingual programming is to construct the upper levels of applications in a high-level language while coding selected low-level components in low-level languages. This approach permits the advantages of a high-level notation (expressiveness, elegance, conciseness) to be obtained without the cost in performance normally associated with high-level approaches. In addition, it provides a natural framework for reusing existing code.

  18. The NAS parallel benchmarks

    NASA Technical Reports Server (NTRS)

    Bailey, David (Editor); Barton, John (Editor); Lasinski, Thomas (Editor); Simon, Horst (Editor)

    1993-01-01

    A new set of benchmarks was developed for the performance evaluation of highly parallel supercomputers. These benchmarks consist of a set of kernels, the 'Parallel Kernels,' and a simulated application benchmark. Together they mimic the computation and data movement characteristics of large scale computational fluid dynamics (CFD) applications. The principal distinguishing feature of these benchmarks is their 'pencil and paper' specification - all details of these benchmarks are specified only algorithmically. In this way many of the difficulties associated with conventional benchmarking approaches on highly parallel systems are avoided.

  19. SLAPP: A systolic linear algebra parallel processor

    SciTech Connect

    Drake, B.L.; Luk, F.T.; Speiser, J.M.; Symanski, J.J.

    1987-07-01

    Systolic array computer architectures provide a means for fast computation of the linear algebra algorithms that form the building blocks of many signal-processing algorithms, facilitating their real-time computation. For applications to signal processing, the systolic array operates on matrices, an inherently parallel view of the data, using numerical linear algebra algorithms that have been suitably parallelized to efficiently utilize the available hardware. This article describes work currently underway at the Naval Ocean Systems Center, San Diego, California, to build a two-dimensional systolic array, SLAPP, demonstrating efficient and modular parallelization of key matric computations for real-time signal- and image-processing problems.

  20. Parallel optical memories for very large databases

    NASA Astrophysics Data System (ADS)

    Mitkas, Pericles A.; Berra, P. B.

    1993-02-01

    The steady increase in volume of current and future databases dictates the development of massive secondary storage devices that allow parallel access and exhibit high I/O data rates. Optical memories, such as parallel optical disks and holograms, can satisfy these requirements because they combine high recording density and parallel one- or two-dimensional output. Several configurations for database storage involving different types of optical memory devices are investigated. All these approaches include some level of optical preprocessing in the form of data filtering in an attempt to reduce the amount of data per transaction that reach the electronic front-end.