Production of atmospheric pressure diffuse nanosecond pulsed dielectric barrier discharge using the array needles-plate electrode in air

NASA Astrophysics Data System (ADS)

Yang, De-zheng; Wang, Wen-chun; Jia, Li; Nie, Dong-xia; Shi, Heng-chao

2011-04-01

In this paper, a bidirectional high pulse voltage with 20 ns rising time is employed to generate an atmospheric pressure diffuse dielectric barrier discharge using the array needles-plate electrode configuration. Both double needle and multiple needle electrode configurations nanosecond pulsed dielectric barrier discharges are investigated. It is found that a diffuse discharge plasma with low gas temperature can be obtained, and the plasma volume increases with the increase of the pulse peak voltage, but remains almost constant with the increase of the pulse repetition rate. In addition to showing the potential application on a topographically nonuniform surface treatment of the discharge, the multiple needle-plate electrode configuration with different needle-plate electrode gaps are also employed to generate diffuse discharge plasma.

The gelatinous extracellular matrix facilitates transport studies in kelp: visualization of pressure-induced flow reversal across sieve plates

PubMed Central

Knoblauch, Jan; Peters, Winfried S.; Knoblauch, Michael

2016-01-01

Background and Aims In vascular plants, important questions regarding phloem function remain unanswered due to problems with invasive experimental procedures in this highly sensitive tissue. Certain brown algae (kelps; Laminariales) also possess sieve tubes for photoassimilate transport, but these are embedded in large volumes of a gelatinous extracellular matrix which isolates them from neighbouring cells. Therefore, we hypothesized that kelp sieve tubes might tolerate invasive experimentation better than their analogues in higher plants, and sought to establish Nereocystis luetkeana as an experimental system. Methods The predominant localization of cellulose and the gelatinous extracellular matrix in N. luetkeana was verified using specific fluorescent markers and confocal laser scanning microscopy. Sieve tubes in intact specimens were loaded with fluorescent dyes, either passively (carboxyfluorescein diacetate; CFDA) or by microinjection (rhodamine B), and the movement of the dyes was monitored by fluorescence microscopy. Key Results Application of CFDA demonstrated source to sink bulk flow in N. luetkeana sieve tubes, and revealed the complexity of sieve tube structure, with branches, junctions and lateral connections. Microinjection into sieve elements proved comparatively easy. Pulsed rhodamine B injection enabled the determination of flow velocity in individual sieve elements, and the direct visualization of pressure-induced reversals of flow direction across sieve plates. Conclusions The reversal of flow direction across sieve plates by pressurizing the downstream sieve element conclusively demonstrates that a critical requirement of the Münch theory is satisfied in kelp; no such evidence exists for tracheophytes. Because of the high tolerance of its sieve elements to experimental manipulation, N. luetkeana is a promising alternative to vascular plants for studying the fluid mechanics of sieve tube networks. PMID:26929203

The gelatinous extracellular matrix facilitates transport studies in kelp: visualization of pressure-induced flow reversal across sieve plates.

PubMed

Knoblauch, Jan; Peters, Winfried S; Knoblauch, Michael

2016-04-01

In vascular plants, important questions regarding phloem function remain unanswered due to problems with invasive experimental procedures in this highly sensitive tissue. Certain brown algae (kelps; Laminariales) also possess sieve tubes for photoassimilate transport, but these are embedded in large volumes of a gelatinous extracellular matrix which isolates them from neighbouring cells. Therefore, we hypothesized that kelp sieve tubes might tolerate invasive experimentation better than their analogues in higher plants, and sought to establish Nereocystis luetkeana as an experimental system. The predominant localization of cellulose and the gelatinous extracellular matrix in N. luetkeana was verified using specific fluorescent markers and confocal laser scanning microscopy. Sieve tubes in intact specimens were loaded with fluorescent dyes, either passively (carboxyfluorescein diacetate; CFDA) or by microinjection (rhodamine B), and the movement of the dyes was monitored by fluorescence microscopy. Application of CFDA demonstrated source to sink bulk flow in N. luetkeana sieve tubes, and revealed the complexity of sieve tube structure, with branches, junctions and lateral connections. Microinjection into sieve elements proved comparatively easy. Pulsed rhodamine B injection enabled the determination of flow velocity in individual sieve elements, and the direct visualization of pressure-induced reversals of flow direction across sieve plates. The reversal of flow direction across sieve plates by pressurizing the downstream sieve element conclusively demonstrates that a critical requirement of the Münch theory is satisfied in kelp; no such evidence exists for tracheophytes. Because of the high tolerance of its sieve elements to experimental manipulation, N. luetkeana is a promising alternative to vascular plants for studying the fluid mechanics of sieve tube networks. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Time change of perceptual reversal of ambiguous figures by rTMS.

PubMed

Nojima, K; Ge, S; Katayama, Y; Iramina, K

2010-01-01

The aim of this study was to investigate the effect of stimulus frequency and number of pulses during rTMS (repetitive transcranial magnetic stimulation) on the phenomenon of perceptual reversal. Particularly, we focused on the temporal dynamics of perceptual reversal in the right SPL (superior parietal lobule), using the spinning wheel illusion. We measured the IRT (inter-reversal time) of perceptual reversal. To investigate whether stimulus frequency or the number of pulses is critical for the rTMS effect, we applied the following schedules over the right SPL and the right PTL (posterior temporal lobe): 0.25Hz 60 pulses, 0.25Hz 120pulses, 0.5Hz 120 pulses, and 1Hz 120 pulses biphasic rTMS at 90% of the resting motor threshold. As a control, we included a No-TMS condition. The results showed that rTMS with 0.25Hz 60 pulses over the right SPL caused shorter IRT. There were no significant differences between IRTs for rTMS with 0.25Hz 120 pulses, 0.5Hz 120 pulses or 1Hz 120 pulses over the right SPL. Comparing these results with those of a previous study, we found that an rTMS condition with 60 pulses causes shorter IRT; 240 pulses causes longer IRT; and 120 pulses does not change IRT. Therefore, when applying rTMS over the right SPL, the IRT of perceptual reversal is primarily affected by the number of pulses.

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.

Effect of the stimulus frequency and pulse number of repetitive transcranial magnetic stimulation on the inter-reversal time of perceptual reversal on the right superior parietal lobule

NASA Astrophysics Data System (ADS)

Nojima, Kazuhisa; Ge, Sheng; Katayama, Yoshinori; Ueno, Shoogo; Iramina, Keiji

2010-05-01

The aim of this study is to investigate the effect of the stimulus frequency and pulses number of repetitive transcranial magnetic stimulation (rTMS) on the inter-reversal time (IRT) of perceptual reversal on the right superior parietal lobule (SPL). The spinning wheel illusion was used as the ambiguous figures stimulation in this study. To investigate the rTMS effect over the right SPL during perceptual reversal, 0.25 Hz 60 pulse, 1 Hz 60 pulse, 0.5 Hz 120 pulse, 1 Hz 120 pulse, and 1 Hz 240 pulse biphasic rTMS at 90% of resting motor threshold was applied over the right SPL and the right posterior temporal lobe (PTL), respectively. As a control, a no TMS was also conducted. It was found that rTMS on 0.25 Hz 60 pulse and 1 Hz 60 pulse applied over the right SPL caused shorter IRT. In contrast, it was found that rTMS on 1 Hz 240-pulse applied over the right SPL caused longer IRT. On the other hand, there is no significant difference between IRTs when the rTMS on 0.5 Hz 120 pulse and 1 Hz 120 pulse were applied over the right SPL. Therefore, the applying of rTMS over the right SPL suggests that the IRT of perceptual reversal is effected by the rTMS conditions such as the stimulus frequency and the number of pulses.

Hardening parts by chrome plating in manufacture and repair

NASA Astrophysics Data System (ADS)

Astanin, V. K.; Pukhov, E. V.; Stekolnikov, Y. A.; Emtsev, V. V.; Golikova, O. A.

2018-03-01

In the engineering industry, galvanic coatings are widely used to prolong the service life of the machines, which contribute to the increase in the strength of the parts and their resistance to environmental influences, temperature and pressure drops, wear and fretting corrosion. Galvanic coatings have been widely applied in engineering, including agriculture, aircraft building, mining, construction, and electronics. The article focuses on the manufacturing methods of new agricultural machinery parts and the repair techniques of worn parts by chrome plating. The main attention is paid to the unstable methods of chromium deposition (in pulsed and reversing modes) in low-concentration electrolytes, which makes it possible to increase the reliability and durability of the hardened parts operation by changing the conditions of electrocrystallization, that is, directed formation of the structure and texture, thickness, roughness and microhardness of chromium plating. The practical recommendations are given on the current and temperature regimes of chromium deposition and composition of baths used for the restoration and hardening of the machine parts. Moreover, the basic methods of machining allowances removal are analysed.

Effect of Current Density and Plating Time on Cu Electroplating in TSV and Low Alpha Solder Bumping

NASA Astrophysics Data System (ADS)

Jung, Do-Hyun; Sharma, Ashutosh; Kim, Keong-Heum; Choo, Yong-Chul; Jung, Jae-Pil

2015-03-01

In this study, copper filling in through-silicon via (TSV) by pulse periodic reverse electroplating and low alpha solder bumping on Cu-filled TSVs was investigated. The via diameter and depth of TSV were 60 and 120 µm, respectively. The experimental results indicated that the thickness of electrodeposited copper layer increased with increasing cathodic current density and plating time. The electroplated Cu in TSV showed a typical bottom-up filling. A defectless, complete, and fast 100% Cu-filled TSV was achieved at cathodic and anodic current densities of -8 and 16 mA/cm2 for a plating time of 4 h, respectively. A sound low alpha solder ball, Sn-1.0 wt.% Ag-0.5 wt.% Cu (SAC 105) with a diameter of 83 µm and height of 66 µm was reflow processed at 245 °C on Cu-filled TSV. The Cu/solder joint interface was subjected to high temperature aging at 85 °C for 150 h, which showed an excellent bonding characteristic with minimum Cu-Sn intermetallic compounds growth.

Lightweight Portable Plasma Medical Device - Plasma Engineering Research Laboratory

DTIC Science & Technology

2015-12-01

Wang, W. Zheng, and Y. N. Wang, "Optical study of radicals (OH, O, H, N) in a needle-plate negative pulsed streamer corona discharge ," Plasma...needle- plate bi-directional pulsed corona discharge ," European Physical Journal D, vol. 38, pp. 515-522, Jun 2006. 155 [35] W. Wang, S. Wang...F. Liu, W. Zheng, and D. Wang, "Optical study of OH radical in a wire-plate pulsed corona discharge ," Spectrochimica Acta Part A: Molecular and

Few-cycle Optical Parametric Chirped Pulse Amplification

DTIC Science & Technology

2007-01-08

silicon - 150mm suprasi1300 Figure 10. Stretcher-compressor unit: group delay 5 -45mm TeO2 (ordinary) (GD) of 30mm silicon, 150mm suprasil300, 45mm CL 0...cycle pulse characterization: 840 -Measured raw 2DSI 20 °OA- traces for pulse (a) before 02. -and (b) after dispersion D 0 by glass plate; (c) so...fused silica plateJ19] see Fig. 15(a), along with the extracted spectral group delays. The chirp introduced by the glass plate is reflected in the

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, Emanuel M.

1987-01-01

A high-power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime.

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, E.M.

1984-06-05

A high power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elizondo-Decanini, Juan M.

Short pulse neutron generators are described herein. In a general embodiment, the short pulse neutron generator includes a Blumlein structure. The Blumlein structure includes a first conductive plate, a second conductive plate, a third conductive plate, at least one of an inductor or a resistor, a switch, and a dielectric material. The first conductive plate is positioned relative to the second conductive plate such that a gap separates these plates. A vacuum chamber is positioned in the gap, and an ion source is positioned to emit ions in the vacuum chamber. The third conductive plate is electrically grounded, and themore » switch is operable to electrically connect and disconnect the second conductive plate and the third conductive plate. The at least one of the resistor or the inductor is coupled to the first conductive plate and the second conductive plate.« less

Method and apparatus for jetting, manufacturing and attaching uniform solder balls

DOEpatents

Yost, F.G.; Frear, D.R.; Schmale, D.T.

1999-01-05

An apparatus and process are disclosed for jetting molten solder in the form of balls directly onto all the metallized interconnects lands for a ball grid array package in one step with no solder paste required. Molten solder is jetted out of a grid of holes using a piston attached to a piezoelectric crystal. When voltage is applied to the crystal it expands forcing the piston to extrude a desired volume of solder through holes in the aperture plate. When the voltage is decreased the piston reverses motion creating an instability in the molten solder at the aperture plate surface and thereby forming spherical solder balls that fall onto a metallized substrate. The molten solder balls land on the substrate and form a metallurgical bond with the metallized lands. The size of the solder balls is determined by a combination of the size of the holes in the aperture plate, the duration of the piston pulse, and the displacement of the piston. The layout of the balls is dictated by the location of the hooks in the grid. Changes in ball size and layout can be easily accomplished by changing the grid plate. This invention also allows simple preparation of uniform balls for subsequent supply to BGA users. 7 figs.

Method and apparatus for jetting, manufacturing and attaching uniform solder balls

DOEpatents

Yost, Frederick G.; Frear, Darrel R.; Schmale, David T.

1999-01-01

An apparatus and process for jetting molten solder in the form of balls directly onto all the metallized interconnects lands for a ball grid array package in one step with no solder paste required. Molten solder is jetted out of a grid of holes using a piston attached to a piezoelectric crystal. When voltage is applied to the crystal it expands forcing the piston to extrude a desired volume of solder through holes in the aperture plate. When the voltage is decreased the piston reverses motion creating an instability in the molten solder at the aperture plate surface and thereby forming spherical solder balls that fall onto a metallized substrate. The molten solder balls land on the substrate and form a metallurgical bond with the metallized lands. The size of the solder balls is determined by a combination of the size of the holes in the aperture plate, the duration of the piston pulse, and the displacement of the piston. The layout of the balls is dictated by the location of the hooks in the grid. Changes in ball size and layout can be easily accomplished by changing the grid plate. This invention also allows simple preparation of uniform balls for subsequent supply to BGA users.

Method and apparatus for sputtering utilizing an apertured electrode and a pulsed substrate bias

NASA Technical Reports Server (NTRS)

Przybyszewski, J. S.; Shaltens, R. K. (Inventor)

1973-01-01

The method and equipment used for sputtering by use of an apertured electrode and a pulsed substrate bias are discussed. The technique combines the advantages of ion plating with the versatility of a radio frequency sputtered source. Electroplating is accomplished by passing a pulsed high voltage direct current to the article being plated during radio frequency sputtering.

Modeling and Simulation of a 5.8kV SiC PiN Diode for Inductive Pulsed Plasma Thruster Applications

NASA Technical Reports Server (NTRS)

Toftul, Alexandra; Hudgins, Jerry L.; Polzin, Kurt A.; Martin, Adam K.

2014-01-01

Current ringing in an Inductive Pulsed Plasma Thruster (IPPT) can lead to reduced energy efficiency, excess heating, and wear on circuit components such as capacitors and solid state devices. Clamping off the current using a fast turn-off power diode is an effective way to reduce current ringing and increase energy efficiency. A diode with a shorter reverse recovery time will allow the least amount of current to ring back through the circuit, as well as minimize switching losses. The reverse recovery response of a new 5.8 kilovolt SiC PiN diode from Cree, Inc. in the IPPT plasma drive circuit is investigated using a physicsbased Simulink model, and compared with that of a 5SDF 02D6004 5.5 kilovolt fast-switching Si diode from ABB. Parameter extraction was carried out for each diode using both datasheet specifications and experimental waveforms, in order to most accurately adapt the model to the specific device. Further experimental data will be discussed using a flat-plate IPPT developed at NASA Marshall Space Flight Center and used to verify the simulation results. A final quantitative measure of circuit efficiency will be described for both the Si and SiC diode configuration.

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, E.M.

1987-02-10

A high-power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime. 10 figs.

Linear optical pulse compression based on temporal zone plates.

PubMed

Li, Bo; Li, Ming; Lou, Shuqin; Azaña, José

2013-07-15

We propose and demonstrate time-domain equivalents of spatial zone plates, namely temporal zone plates, as alternatives to conventional time lenses. Both temporal intensity zone plates, based on intensity-only temporal modulation, and temporal phase zone plates, based on phase-only temporal modulation, are introduced and studied. Temporal zone plates do not exhibit the limiting tradeoff between temporal aperture and frequency bandwidth (temporal resolution) of conventional linear time lenses. As a result, these zone plates can be ideally designed to offer a time-bandwidth product (TBP) as large as desired, practically limited by the achievable temporal modulation bandwidth (limiting the temporal resolution) and the amount of dispersion needed in the target processing systems (limiting the temporal aperture). We numerically and experimentally demonstrate linear optical pulse compression by using temporal zone plates based on linear electro-optic temporal modulation followed by fiber-optics dispersion. In the pulse-compression experiment based on temporal phase zone plates, we achieve a resolution of ~25.5 ps over a temporal aperture of ~5.77 ns, representing an experimental TBP larger than 226 using a phase-modulation amplitude of only ~0.8π rad. We also numerically study the potential of these devices to achieve temporal imaging of optical waveforms and present a comparative analysis on the performance of different temporal intensity and phase zone plates.

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.

Pulse cleaning flow models and numerical computation of candle ceramic filters.

PubMed

Tian, Gui-shan; Ma, Zhen-ji; Zhang, Xin-yi; Xu, Ting-xiang

2002-04-01

Analytical and numerical computed models are developed for reverse pulse cleaning system of candle ceramic filters. A standard turbulent model is demonstrated suitably to the designing computation of reverse pulse cleaning system from the experimental and one-dimensional computational result. The computed results can be used to guide the designing of reverse pulse cleaning system, which is optimum Venturi geometry. From the computed results, the general conclusions and the designing methods are obtained.

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.

Ultra-fast magnetic vortex core reversal by a local field pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rückriem, R.; Albrecht, M., E-mail: manfred.albrecht@physik.uni-augsburg.de; Schrefl, T.

2014-02-03

Magnetic vortex core reversal of a 20-nm-thick permalloy disk with a diameter of 100 nm was studied by micromagnetic simulations. By applying a global out-of-plane magnetic field pulse, it turned out that the final core polarity is very sensitive to pulse width and amplitude, which makes it hard to control. The reason for this phenomenon is the excitation of radial spin waves, which dominate the reversal process. The excitation of spin waves can be strongly suppressed by applying a local field pulse within a small area at the core center. With this approach, ultra-short reversal times of about 15 ps weremore » achieved, which are ten times faster compared to a global pulse.« less

Additive-free size-controlled synthesis of gold square nanoplates using photochemical reaction in dynamic phase-separating media.

PubMed

Kajimoto, Shinji; Shirasawa, Daisuke; Horimoto, Noriko Nishizawa; Fukumura, Hiroshi

2013-05-14

Ultrafast phase separation of water and 2-butoxyethanol mixture was induced by nanosecond IR laser pulse irradiation. After a certain delay time, a UV laser pulse was introduced to induce photoreduction of aurate ions, which led to the formation of gold nanoparticles in dynamic phase-separating media. The structure and size of the nanoparticles varied depending on the delay time between the IR and UV pulses. For a delay time of 5 and 6 μs, gold square plates having edge lengths of 150 and 100 nm were selectively obtained, respectively. With a delay time of 3 μs, on the other hand, the size of the square plates varied widely from 100 nm to a few micrometers. The size of the gold square plates was also varied by varying the total irradiation time of the IR and UV pulses. The size distribution of the square plates obtained under different conditions suggests that the growth process of the square plates was affected by the size of the nanophases during phase separation. Electron diffraction patterns of the synthesized square plates showed that the square plates were highly crystalline with a Au(100) surface. These results showed that the nanophases formed during laser-induced phase separation can provide detergent-free reaction fields for size-controlled nanomaterial synthesis.

Dynamic characteristics of 4H-SiC drift step recovery diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, P. A., E-mail: Pavel.Ivanov@mail.ioffe.ru; Kon’kov, O. I.; Samsonova, T. P.

The dynamic characteristics of 4H-SiC p{sup +}–p–n{sub 0}–n{sup +} diodes are experimentally studied in the pulsed modes characteristic of the operation of drift step recovery diodes (DSRD-mode). The effect of the subnanosecond termination of the reverse current maintained by electron-hole plasma preliminarily pumped by a forward current pulse is analyzed in detail. The influence exerted on the DSRD effect by the amplitude of reverse-voltage pulses, the amplitude and duration of forward-current pulses, and the time delay between the forward and reverse pulses is demonstrated and accounted for.

Single electron counting using a dual MCP assembly

NASA Astrophysics Data System (ADS)

Yang, Yuzhen; Liu, Shulin; Zhao, Tianchi; Yan, Baojun; Wang, Peiliang; Yu, Yang; Lei, Xiangcui; Yang, Luping; Wen, Kaile; Qi, Ming; Heng, Yuekun

2016-09-01

The gain, pulse height resolution and peak-to-valley ratio of single electrons detected by using a Chevron configured Microchannel Plate (MCP) assembly are studied. The two MCPs are separated by a 280 μm gap and are biased by four electrodes. The purpose of the study is to determine the optimum bias voltage arrangements for single electron counting. By comparing the results of various bias voltage combinations, we conclude that good performance for the electron counting can be achieved by operating the MCP assembly in saturation mode. In addition, by applying a small reverse bias voltage across the gap while adjusting the bias voltages of the MCPs, optimum performance of electron counting can be obtained.

Compact neutron imaging system using axisymmetric mirrors

DOEpatents

Khaykovich, Boris; Moncton, David E; Gubarev, Mikhail V; Ramsey, Brian D; Engelhaupt, Darell E

2014-05-27

A dispersed release of neutrons is generated from a source. A portion of this dispersed neutron release is reflected by surfaces of a plurality of nested, axisymmetric mirrors in at least an inner mirror layer and an outer mirror layer, wherein the neutrons reflected by the inner mirror layer are incident on at least one mirror surface of the inner mirror layer N times, wherein N is an integer, and wherein neutrons reflected by the outer mirror are incident on a plurality of mirror surfaces of the outer layer N+i times, where i is a positive integer, to redirect the neutrons toward a target. The mirrors can be formed by a periodically reversed pulsed-plating process.

Characterization of pulsed (plasma focus) neutron source with image plate and application to neutron radiography

NASA Astrophysics Data System (ADS)

Andola, Sanjay; Niranjan, Ram; Shaikh, A. M.; Rout, R. K.; Kaushik, T. C.; Gupta, S. C.

2013-02-01

Plasma focus device of Mather type developed in house has been used first time for neutron radiography of different objects. The device gives (1.2±0.3) ×109 neutrons per pulse produced by D-D fusion reaction with a pulse width of 50±5 ns. The method involves exposing sample to be radiographed to thermalized D-D neutrons and recording the image on Fuji-film BAS-ND image plates. The thermal neutron component of the moderated beam was estimated using two image plates: a conventional IP for X-rays and gamma rays, and an IP doped with Gd for detecting neutrons.

Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser

NASA Astrophysics Data System (ADS)

Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira

A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.

Quasisubharmonic vibrations in metal plates excited by high-power ultrasonic pulses

NASA Astrophysics Data System (ADS)

Chen, Zhao-jiang; Zhang, Shu-yi; Zheng, Kai; Kuo, Pao-kuang

2009-07-01

Strongly nonlinear vibration phenomena in metal plates excited by high-power ultrasonic pulses in different conditions are studied experimentally and theoretically. The experimental conditions for generating quasisubharmonics and subharmonics are found and discussed. The plate vibrations are characterized by waveforms, frequency spectra, pseudostate portraits, and Poincaré maps. Then, a three-degree-of-freedom vibroimpact-dynamic model is presented to explore the generation mechanisms of the quasisubharmonic and subharmonic vibrations in the plates. According to the model, the intermittent contact-impact forces caused by the interactions between the transducer horn tip and the plate are considered as the main source for generating the complex nonlinear vibration in the plate. The numerical calculation results can explain reasonably the observed experimental phenomena.

The outcome of unstable proximal femoral fracture treated with reverse LISS plates.

PubMed

Lin, Shih-Jie; Huang, Kuo-Chin; Chuang, Po-Yao; Lee, Chien-Yin; Huang, Tsan-Wen; Lee, Mel S; Hsu, Robert Wen-Wei

2016-10-01

The Russel-Taylor type 2B fractures compromised the trochanteric region and medial buttress of proximal femur. This fracture pattern limits the choice of implants and raises the risk of adverse outcomes. We aimed to (i) determine the outcome of Russel-Taylor type 2B fractures treated using reverse less invasive stabilization system plates (LISS-DF) and to (ii) learn what factors affected outcomes after osteosynthesis with reverse LISS plates. A retrospective study SETTING: The study was conducted at a Level III trauma center in Taiwan. Twenty-five consecutive patients presenting with a Russel-Taylor type 2B fracture were enrolled. All cases were treated with reverse LISS plates. A Modified Radiographic Union Scale for Femur (RUSF), Radiographic parameters, functional scores, and complications were assessed. Union occurred in 21 cases at an average of 18.8 weeks. The average immediate postoperative neck-shaft angle was 130° (range: 122-135°) compared with 139° (range: 135-141°, p=0.05) on the contralateral side. Two cases had complications of proximal screws cutting out and two cases had broken implants. Finally, all 4 cases required repeated surgeries (16%). Malunion occurred in 4 patients and early mechanical failure (proximal screws cut out) occurred in 2. There was a significant difference in the purchase index of the proximal screws between cases with redisplacement and those without (26.4mm and 98.6mm, p=0.01). The use of reverse LISS plate appeared to be an alternative procedure for the specific pattern in the present study. We recommend using this reverse locking plate to treat unstable proximal femoral fractures with meticulous techniques of placing plates. Adequate purchase of the proximal locking screws might decrease the risks of complications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Wavefront reversal technique for self-referencing collimation testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hii, King Ung; Kwek, Kuan Hiang

2010-02-01

We present a wavefront reversal technique to produce a dual-field fringe pattern for self-referencing collimation testing in wedge-plate lateral-shear interferometry. The method requires only a suitably placed cubic beam splitter to produce two replicas of the fringe field formed by the wedge-plate lateral-shear interferometer. One of the replicas has a fringe pattern that is the reverse of the other. With these two fringe fields, the collimation testing has a built-in reference, and the detection sensitivity is twice that of a single-wedge-plate technique.

Fiber optic mounted laser driven flyer plates

DOEpatents

Paisley, Dennis L.

1991-01-01

A laser driven flyer plate where the flyer plate is deposited directly onto the squared end of an optical fiber. The plasma generated by a laser pulse drives the flyer plate toward a target. In another embodiment, a first metal layer is deposited onto the squared end of an optical fiber, followed by a layer of a dielectric material and a second metal layer. The laser pulse generates a plasma in the first metal layer, but the plasma is kept away from the second metal layer by the dielectric layer until the pressure reaches the point where shearing occurs.

METHOD AND APPARATUS FOR PULSING A CHARGED PARTICLE BEAM

DOEpatents

Aaland, K.; Kuenning, R.W.; Harmon, R.K.

1961-05-01

A system is offered for pulsing a continuous beam of charged particles to form beam pulses that are consistently rectangular and of precise time durations which may be varied over an extremely wide range at a widely variable range of repetition rates. The system generally comprises spaced deflection plates on opposite sides of a beam axis in between which a unidirectional bias field is established to deflect the beam for impingement on an off-axis collector. The bias field is periodically neutralized by the application of fast rise time substantially rectangular pulses to one of the deflection plates in opposition to the bias field and then after a time delay to the other deflection plate in aiding relation to the bias field and during the flat crest portion of the bias opposing pulses. The voltage distribution of the resulting deflection field then includes neutral or zero portions which are of symmetrical substantially rectangular configuration relative to time and during which the beam axially passes the collector in the form of a substantially rectangular beam pulse.

Characterization of pulsed (plasma focus) neutron source with image plate and application to neutron radiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andola, Sanjay; Niranjan, Ram; Rout, R. K.

Plasma focus device of Mather type developed in house has been used first time for neutron radiography of different objects. The device gives (1.2{+-}0.3) Multiplication-Sign 10{sup 9} neutrons per pulse produced by D-D fusion reaction with a pulse width of 50{+-}5 ns. The method involves exposing sample to be radiographed to thermalized D-D neutrons and recording the image on Fuji-film BAS-ND image plates. The thermal neutron component of the moderated beam was estimated using two image plates: a conventional IP for X-rays and gamma rays, and an IP doped with Gd for detecting neutrons.

Study of high performance alloy electroforming

NASA Technical Reports Server (NTRS)

Malone, G. A.

1985-01-01

More panels electroformed with intentional variations of pulse plating parameters are being made. Pulse plating frequency was noted to have a significant effect regarding mechanical properties. The use of a high pulse frequency (assuming fixed duty cycles) results in an increase in ductility and a decrease in ultimate and yield strengths. Electroforming to intermediate frequencies is being done to obtain the best possible combination of ductility and strength. Results of some tests from high frequency specimens are tabulated.

Splash flow from a metal plate hit by an electron beam pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia, M., LLNL

1997-09-01

When a pulsed electron beam hits a metal plate with sufficient energy a volume of the metal becomes hot fluid that subsequently sprays out of the plate. A second pulse of electrons traveling toward the plate would scatter and degrade before impacting the solid plate because of its encounter with the diffuse material of the initial splash. People designing electron beam machines for use as pulsed radiation sources wish to eliminate the interaction between the electrons and the splash because they want sharp radiation pulses emitted from the solid plate. This report presents a compressible fluid model of this splashmore » flow and compares specific cases with experiments and comprehensive calculations performed by B. DeVolder and others at the Los Alamos National Laboratory, see reference (1). My aim was to develop as simple a theory as possible to calculate the speed and density of the splash flow. I have used both simplifying assumptions and mathematical approximations to develop convenient formulas. As I wished to make a clear and interesting presentation of this work to a diverse audience that includes people outside the specialty of fluid dynamics, some of my descriptions may seem wordier than necessary. The plan of the report is as follows. In the section called ``energy deposition`` I describe how an electron beam deposits energy in a solid plate, converting some of the material into a hot fluid. The initial temperature of this fluid is the key parameter in determining the nature of the subsequent flow; an explicit formula is shown. Flow occurs in two regions: along a streamtube within the metal plate and as an expanding plume outside the metal plate. Flow within the plate is described in the section called ``isentropic flow.`` This flow occurs as expansion waves move at the speed of sound through the streamtube. The analysis of this flow provides a formula for the mass flow over time from the plate into the external splash. The section called ``centered expansion`` elaborates on the nature of certain approximations I have made in treating the wave phenomena in both the streamtube and splash flows. The section called ``splash flow`` presents a formula to describe the material density as a function of space and time outside the plate. This formula depends on the time- dependent material density at the plate, which was found during the streamtube analysis. The section called ``examples`` shows the results of specific calculations and a comparison to computational and experimental results described in reference (1). The final section, ``possible future work,`` poses new questions.« less

PIC simulations of post-pulse field reversal and secondary ionization in nanosecond argon discharges

NASA Astrophysics Data System (ADS)

Kim, H. Y.; Gołkowski, M.; Gołkowski, C.; Stoltz, P.; Cohen, M. B.; Walker, M.

2018-05-01

Post-pulse electric field reversal and secondary ionization are investigated with a full kinetic treatment in argon discharges between planar electrodes on nanosecond time scales. The secondary ionization, which occurs at the falling edge of the voltage pulse, is induced by charge separation in the bulk plasma region. This process is driven by a reverse in the electric field from the cathode sheath to the formerly driven anode. Under the influence of the reverse electric field, electrons in the bulk plasma and sheath regions are accelerated toward the cathode. The electron movement manifests itself as a strong electron current generating high electron energies with significant electron dissipated power. Accelerated electrons collide with Ar molecules and an increased ionization rate is achieved even though the driving voltage is no longer applied. With this secondary ionization, in a single pulse (SP), the maximum electron density achieved is 1.5 times higher and takes a shorter time to reach using 1 kV 2 ns pulse as compared to a 1 kV direct current voltage at 1 Torr. A bipolar dual pulse excitation can increase maximum density another 50%–70% above a SP excitation and in half the time of RF sinusoidal excitation of the same period. The first field reversal is most prominent but subsequent field reversals also occur and correspond to electron temperature increases. Targeted pulse designs can be used to condition plasma density as required for fast discharge applications.

A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests.

PubMed

Forquin, Pascal; Zinszner, Jean-Luc

2017-01-28

Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the 'wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, 'wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

A pulse-shaping technique to investigate the behaviour of brittle materials subjected to plate-impact tests

NASA Astrophysics Data System (ADS)

Forquin, Pascal; Zinszner, Jean-Luc

2017-01-01

Owing to their significant hardness and compressive strengths, ceramic materials are widely employed for use with protective systems subjected to high-velocity impact loadings. Therefore, their mechanical behaviour along with damage mechanisms need to be significantly investigated as a function of loading rates. However, the classical plate-impact testing procedures produce shock loadings in the brittle sample material which cause unrealistic levels of loading rates. Additionally, high-pulsed power techniques and/or functionally graded materials used as flyer plates to smooth the loading pulse remain costly, and are generally difficult to implement. In this study, a shockless plate-impact technique based on the use of either a wavy-machined flyer plate or buffer plate that can be produced by chip-forming is proposed. A series of numerical simulations using an explicit transient dynamic finite-element code have been performed to design and validate the experimental testing configuration. The calculations, conducted in two-dimensional (2D) plane-strain or in 2D axisymmetric modes, prove that the `wavy' contact surface will produce a pulse-shaping effect, whereas the buffer plate will produce a homogenizing effect of the stress field along the transverse direction of the sample. In addition, `wavy-shape' geometries of different sizes provide an easy way to change the level of loading rate and rise time in an experimentally tested ceramic specimen. Finally, when a shockless compression loading method is applied to the sample, a Lagrangian analysis of data is made possible by considering an assemblage of ceramic plates of different thicknesses in the target, so the axial stress-strain response of the brittle sample material can be provided. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

Idiopathic scoliosis, growth zones, magnetic therapy.

PubMed

Arsenev, A; Dudin, M; Lednev, V; Belova, N; Mikhailov, V; Sokolov, G

2012-01-01

The study has been performed to investigate the influence of pulsed magnetic field on the bone growth plates to get new grounds of magneto therapy in AIS treatment. Were used methods of "strong" and "weak" pulsed magnetic fields influence. Application of pulsed magnetic field causes an authentic inhibition of chondrocytes' active proliferation processes, decreases the index of labeled nuclei, indicating the suppression of DNA synthesis, takes place an increase in the unit weight of the more "mature" differentiated chondrocytes. The final result of these effects is the accelerated synostosis of bones' growth plates. Regardless of the reasons that cause growth infringements, the operating organ in the chain is the body's growth plate. Therefore, the appliance of magnetic fields in AIS treatment can be considered as a perspective one concerning growth plates' functional activity local management. To our point of view, the potential of magneto therapy methods in child's orthopedic treatment is significantly higher compared with modern practice.

Time-reversing light pulses by adiabatic coupling modulation in coupled-resonator optical waveguides

NASA Astrophysics Data System (ADS)

Wang, Chao; Martini, Rainer; Search, Christopher P.

2012-12-01

We introduce a mechanism to time reverse short optical pulses in coupled resonator optical waveguides (CROWs) by direct modulation of the coupling coefficients between microresonators. The coupling modulation is achieved using phase modulation of a Mach-Zehnder interferometer coupler. We demonstrate that by adiabatic modulation of the coupling between resonators we can time reverse or store light pulses with bandwidths up to a few hundred GHz. The large pulse bandwidths, small device footprint, robustness with respect to resonator losses, and easy tuning process of the coupling coefficients make this method more practical than previous proposals.

Nd:YAG Pulsed Laser based flaw imaging techniques for noncontact NDE of an aluminum plate

NASA Astrophysics Data System (ADS)

Park, Woong-Ki; Lee, Changgil; Park, Seunghee

2012-04-01

Recently, the longitudinal, shear and surface waves have been very widely used as a kind of ultrasonic wave exploration methods to identify internal defects of metallic structures. The ultrasonic wave-based non-destructive testing (NDT) is one of main non-destructive inspection techniques for a health assessment about nuclear power plant, aircraft, ships, and/or automobile manufacturing. In this study, a noncontact pulsed laser-based flaw imaging NDT technique is implemented to detect the damage of a plate-like structure and to identify the location of the damage. To achieve this goal, the Nd:YAG pulsed laser equipment is used to generate a guided wave and scans a specific area to find damage location. The Nd: YAG pulsed laser is used to generate Lamb wave and piezoelectric sensors are installed to measure structural responses. Ann aluminum plate is investigated to verify the effectiveness and the robustness of the proposed NDT approach. A notch is a target to detect, which is inflicted on the surface of an aluminum plate. The damagesensitive features are extracted by comparing the time of flight of the guided wave obtained from an acoustic emission (AE) sensor and make use of the flaw imaging techniques of the aluminum plate.

An all-reflective polarization rotator

NASA Astrophysics Data System (ADS)

Bohus, J.; Budai, Judit; Kalashnikov, M.; Osvay, K.

2017-05-01

The conceptual design and proof of principle experimental results of a polarization rotator based on mirrors are presented. The device is suitable for any-angle, online rotation of the plane of polarization of high peak intensity ultrashort laser pulses. Controllable rotation of the polarization vector of short laser pulses with a broad bandwidth requires achromatic retarding plates which have a limited scalability and the substantial plate thickness can lead to pulse broadening and inaccurate polarization rotation. Polarization rotators based on reflective optical elements are preferable alternatives to wave plates especially when used in high average power or high peak intensity ultra-short laser systems. The control of the polarization state is desirable in many laser-matter interaction experiments e.g., high harmonic and attosecond pulse generation, electron, proton and ion acceleration, electron-positron pair creating, vacuum nonlinear polarization effect. The device can also serve as a beam attenuator, in combination with a linear polarizer.

Pulse-Shape Discrimination of Alpha Particles of Different Specific Energy-Loss With Parallel-Plate Avalanche Counters

NASA Astrophysics Data System (ADS)

Nakhostin, M.; Baba, M.

2014-06-01

Parallel-plate avalanche counters have long been recognized as timing detectors for heavily ionizing particles. However, these detectors suffer from a poor pulse-height resolution which limits their capability to discriminate between different ionizing particles. In this paper, a new approach for discriminating between charged particles of different specific energy-loss with avalanche counters is demonstrated. We show that the effect of the self-induced space-charge in parallel-plate avalanche counters leads to a strong correlation between the shape of output current pulses and the amount of primary ionization created by the incident charged particles. The correlation is then exploited for the discrimination of charged particles with different energy-losses in the detector. The experimental results obtained with α-particles from an 241Am α-source demonstrate a discrimination capability far beyond that achievable with the standard pulse-height discrimination method.

Lightweight Portable Plasma Medical Device - Plasma Engineering Research Laboratory

DTIC Science & Technology

2014-10-01

34Optical study of radicals (OH, O, H, N) in a needle- plate negative pulsed streamer corona discharge ," Plasma Chemistry and Plasma Processing, vol. 26...pulsed corona discharge ," European Physical Journal D, vol. 38, pp. 515-522, Jun 2006. [35] W. Wang, S. Wang, F. Liu, W. Zheng, and D. Wang, "Optical...study of OH radical in a wire-plate pulsed corona discharge ," Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 63, pp. 477

A coaxial-output capacitor-loaded annular pulse forming line.

PubMed

Li, Rui; Li, Yongdong; Su, Jiancang; Yu, Binxiong; Xu, Xiudong; Zhao, Liang; Cheng, Jie; Zeng, Bo

2018-04-01

A coaxial-output capacitor-loaded annular pulse forming line (PFL) is developed in order to reduce the flat top fluctuation amplitude of the forming quasi-square pulse and improve the quality of the pulse waveform produced by a Tesla-pulse forming network (PFN) type pulse generator. A single module composed of three involute dual-plate PFNs is designed, with a characteristic impedance of 2.44 Ω, an electrical length of 15 ns, and a sustaining voltage of 60 kV. The three involute dual-plate PFNs connected in parallel have the same impedance and electrical length. Due to the existed small inductance and capacitance per unit length in each involute dual-plate PFN, the upper cut-off frequency of the PFN is increased. As a result, the entire annular PFL has better high-frequency response capability. Meanwhile, the three dual-plate PFNs discharge in parallel, which is much closer to the coaxial output. The series connecting inductance between adjacent two modules is significantly reduced when the annular PFL modules are connected in series. The pulse waveform distortion is reduced when the pulse transfers along the modules. Finally, the shielding electrode structure is applied on both sides of the module. The electromagnetic field is restricted in the module when a single module discharges, and the electromagnetic coupling between the multi-stage annular PFLs is eliminated. Based on the principle of impedance matching between the multi-stage annular PFL and the coaxial PFL, the structural optimization design of a mixed PFL in a Tesla type pulse generator is completed with the transient field-circuit co-simulation method. The multi-stage annular PFL consists of 18 stage annular PFL modules in series, with the characteristic impedance of 44 Ω, the electrical length of 15 ns, and the sustaining voltage of 1 MV. The mixed PFL can generate quasi-square electrical pulses with a pulse width of 43 ns, and the fluctuation ratio of the pulse flat top is less than 8% when the pulse rise time is about 5 ns.

A coaxial-output capacitor-loaded annular pulse forming line

NASA Astrophysics Data System (ADS)

Li, Rui; Li, Yongdong; Su, Jiancang; Yu, Binxiong; Xu, Xiudong; Zhao, Liang; Cheng, Jie; Zeng, Bo

2018-04-01

A coaxial-output capacitor-loaded annular pulse forming line (PFL) is developed in order to reduce the flat top fluctuation amplitude of the forming quasi-square pulse and improve the quality of the pulse waveform produced by a Tesla-pulse forming network (PFN) type pulse generator. A single module composed of three involute dual-plate PFNs is designed, with a characteristic impedance of 2.44 Ω, an electrical length of 15 ns, and a sustaining voltage of 60 kV. The three involute dual-plate PFNs connected in parallel have the same impedance and electrical length. Due to the existed small inductance and capacitance per unit length in each involute dual-plate PFN, the upper cut-off frequency of the PFN is increased. As a result, the entire annular PFL has better high-frequency response capability. Meanwhile, the three dual-plate PFNs discharge in parallel, which is much closer to the coaxial output. The series connecting inductance between adjacent two modules is significantly reduced when the annular PFL modules are connected in series. The pulse waveform distortion is reduced when the pulse transfers along the modules. Finally, the shielding electrode structure is applied on both sides of the module. The electromagnetic field is restricted in the module when a single module discharges, and the electromagnetic coupling between the multi-stage annular PFLs is eliminated. Based on the principle of impedance matching between the multi-stage annular PFL and the coaxial PFL, the structural optimization design of a mixed PFL in a Tesla type pulse generator is completed with the transient field-circuit co-simulation method. The multi-stage annular PFL consists of 18 stage annular PFL modules in series, with the characteristic impedance of 44 Ω, the electrical length of 15 ns, and the sustaining voltage of 1 MV. The mixed PFL can generate quasi-square electrical pulses with a pulse width of 43 ns, and the fluctuation ratio of the pulse flat top is less than 8% when the pulse rise time is about 5 ns.

Comparison between Trichel pulse in negative corona and self-pulsing in other configurations

NASA Astrophysics Data System (ADS)

Xia, Qing; Zhang, Yu; He, Feng; Qin, Yu; Jiang, Zhaorui; Ouyang, Jiting

2018-02-01

We present here a comparison study on self-pulsing phenomena in negative corona, hollow cathode discharges (HCD) and parallel-plate discharge in air. The voltage-current (V-I) curve, the waveforms of self-pulsed currents, and the time-resolved images of the pulsed discharge are measured under various operating conditions. It is experimentally evidenced that the Trichel pulse in a negative corona and the self-pulsing in HCD and/or parallel-plate discharge have similar features as well as spatial-temporal developing process. It is suggested that they should have a similar mechanism that the pulsing reflects the mode transition of discharge between the low-current Townsend and the high-current normal glow. The pulse rising corresponds to the breakdown and formation of temporal glow discharge in a background of low-current Townsend discharge, while the decay edge relates to the transition back to Townsend discharge. The pulse interval is the re-building process of the space charge layer of high density to ensure the glow breakdown.

Influence of Voltage Rise Time for Oxidation Treatment of NO in Simulated Exhausted Gas by Polarity-Reversed Pulse Discharge

NASA Astrophysics Data System (ADS)

Shinmoto, Kazuya; Kadowaki, Kazunori; Nishimoto, Sakae; Kitani, Isamu

This paper describes experimental study on NO removal from a simulated exhausted-gas using repetitive surface discharge on a glass barrier subjected to polarity-reversed voltage pulses. The very fast polarity-reversal with a rise time of 20ns is caused by direct grounding of a charged coaxial cable of 10m in length. Influence of voltage rise time on energy efficiency for NO removal is studied. Results of NO removal using a barrier-type plasma reactor with screw-plane electrode system indicates that the energy efficiency for the very fast polarity reversal caused by direct grounding becomes higher than that for the slower polarity reversal caused by grounding through an inductor at the cable end. The energy efficiency for the direct grounding is about 80g/kWh for 50% NO removal ratio and is about 60g/kWh for 100% NO removal ratio. Very intense discharge light is observed at the initial time of 10ns for the fast polarity reversal, whereas the intensity in the initial discharge light for the slower polarity reversal is relatively small. To confirm the effectiveness of the polarity-reversed pulse application, comparison of the energy efficiency between the polarity-reversed voltage pulse and ac 60Hz voltage will be presented.

Reverse Evolution of Armor Plates in the Threespine Stickleback

USGS Publications Warehouse

Kitano, J.; Bolnick, D.I.; Beauchamp, D.A.; Mazur, M.M.; Mori, S.; Nakano, T.; Peichel, C.L.

2008-01-01

Faced with sudden environmental changes, animals must either adapt to novel environments or go extinct. Thus, study of the mechanisms underlying rapid adaptation is crucial not??only for the understanding of natural evolutionary processes but also for the understanding of human-induced evolutionary change, which is an increasingly important problem [1-8]. In the present study, we demonstrate that the frequency of completely plated threespine stickleback fish (Gasterosteus aculeatus) has increased in an urban freshwater lake (Lake Washington, Seattle, Washington) within the last 40 years. This is a dramatic example of "reverse evolution," [9] because the general evolutionary trajectory is toward armor-plate reduction in freshwater sticklebacks [10]. On the basis of our genetic studies and simulations, we propose that the most likely cause of reverse evolution is increased selection for the completely plated morph, which we suggest could result from higher levels of trout predation after a sudden increase in water transparency during the early 1970s. Rapid evolution was facilitated by the existence of standing allelic variation in Ectodysplasin (Eda), the gene that underlies the major plate-morph locus [11]. The Lake Washington stickleback thus provides a novel example of reverse evolution, which is probably caused by a change in allele frequency at the major plate locus in response to a changing predation regime. ?? 2008 Elsevier Ltd. All rights reserved.

Aortic Blood Flow Reversal Determines Renal Function: Potential Explanation for Renal Dysfunction Caused by Aortic Stiffening in Hypertension.

PubMed

Hashimoto, Junichiro; Ito, Sadayoshi

2015-07-01

Aortic stiffness determines the glomerular filtration rate (GFR) and predicts the progressive decline of the GFR. However, the underlying pathophysiological mechanism remains obscure. Recent evidence has shown a close link between aortic stiffness and the bidirectional (systolic forward and early diastolic reverse) flow characteristics. We hypothesized that the aortic stiffening-induced renal dysfunction is attributable to altered central flow dynamics. In 222 patients with hypertension, Doppler velocity waveforms were recorded at the proximal descending aorta to calculate the reverse/forward flow ratio. Tonometric waveforms were recorded to measure the carotid-femoral (aortic) and carotid-radial (peripheral) pulse wave velocities, to estimate the aortic pressure from the radial waveforms, and to compute the aortic characteristic impedance. In addition, renal hemodynamics was evaluated by duplex ultrasound. The estimated GFR was inversely correlated with the aortic pulse wave velocity, reverse/forward flow ratio, pulse pressure, and characteristic impedance, whereas it was not correlated with the peripheral pulse wave velocity or mean arterial pressure. The association between aortic pulse wave velocity and estimated GFR was independent of age, diabetes mellitus, hypercholesterolemia, and antihypertensive medication. However, further adjustment for the aortic reverse/forward flow ratio and pulse pressure substantially weakened this association, and instead, the reverse/forward flow ratio emerged as the strongest determinant of estimated GFR (P=0.001). A higher aortic reverse/forward flow ratio was also associated with lower intrarenal forward flow velocities. These results suggest that an increase in aortic flow reversal (ie, retrograde flow from the descending thoracic aorta toward the aortic arch), caused by aortic stiffening and impedance mismatch, reduces antegrade flow into the kidney and thereby deteriorates renal function. © 2015 American Heart Association, Inc.

Broadband spectral shaping in regenerative amplifier based on modified polarization-encoded chirped pulse amplification

NASA Astrophysics Data System (ADS)

Wang, Xinliang; Lu, Xiaoming; Liu, Yanqi; Xu, Yi; Wang, Cheng; Li, Shuai; Yu, Linpeng; Liu, Xingyan; Liu, Keyang; Xu, Rongjie; Leng, Yuxin

2018-06-01

We present an intra-cavity spectral shaping method to suppress the spectral narrowing in a Ti:sapphire (Ti:Sa) regenerative amplifier. The spectral shaping is realized by manipulating the stored energies of two Ti:Sa crystals with orthogonal c-axes, changing the length of a quartz plate, and rotating a broadband achromatic half-wave plate. Using this method, in our proof-of-concept experiment, an 84-nm-(FWHM)-broadband amplified pulse with an energy gain larger than 106 is obtained, which supports a 17.8 fs Fourier-transform-limited pulse duration. The pulse is compressed to 18.9 fs.

Oxidation of ammonium sulfite by a multi-needle-to-plate gas phase pulsed corona discharge reactor

NASA Astrophysics Data System (ADS)

Ren, Hua; Lu, Na; Shang, Kefeng; Li, Jie; Wu, Yan

2013-03-01

The oxidation of ammonium sulfite in the ammonia-based flue gas desulfurization (FGD) process was investigated in a multi-needle-to-plate gas phase pulsed corona discharge reactor in this paper. The effect of several parameters, including capacitance and peak pulse voltage of discharge system, electrode gap and bubbling gas flow rate on the oxidation rate of ammonium sulfite was reviewed. The oxidation rate of ammonium sulfite could reach 47.2% at the capacitance, the peak pulse voltage, electrode gap and bubbling gas flow rate equal to 2 nF, -24.6 k V, 35 mm and 4 L min-1 within treatment time of 40 min The experimental results indicate that the gas phase pulsed discharge system with a multi-needle-to-plate electrode can oxide the ammonium sulfite. The oxidation rate increased with the applied capacitance and peak pulse voltage and decreased with the electrode gap. As the bubbling gas flow rate increased, the oxidation rate increased first and then tended to reach a stationary value. These results would be important for the process optimization of the (NH4)2SO3 to (NH4)2SO4 oxidation.

High-speed multi-frame dynamic transmission electron microscope image acquisition system with arbitrary timing

DOEpatents

Reed, Bryan W.; DeHope, William J.; Huete, Glenn; LaGrange, Thomas B.; Shuttlesworth, Richard M.

2016-02-23

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system ("laser"). The laser produces a train of temporally-shaped laser pulses each being of a programmable pulse duration, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has a plurality of plates. A control system having a digital sequencer controls the laser and a plurality of switching components, synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to enable programmable pulse durations and programmable inter-pulse spacings.

Current sheet characteristics of a parallel-plate electromagnetic plasma accelerator operated in gas-prefilled mode

NASA Astrophysics Data System (ADS)

Liu, Shuai; Huang, Yizhi; Guo, Haishan; Lin, Tianyu; Huang, Dong; Yang, Lanjun

2018-05-01

The axial characteristics of a current sheet in a parallel-plate electromagnetic plasma accelerator operated in gas-prefilled mode are reported. The accelerator is powered by a fourteen stage pulse forming network. The capacitor and inductor in each stage are 1.5 μF and 300 nH, respectively, and yield a damped oscillation square wave of current with a pulse width of 20.6 μs. Magnetic probes and photodiodes are placed at various axial positions to measure the behavior of the current sheet. Both magnetic probe and photodiode signals reveal a secondary breakdown when the current reverses the direction. An increase in the discharge current amplitude and a decrease in pressure lead to a decrease in the current shedding factor. The current sheet velocity and thickness are nearly constant during the run-down phase under the first half-period of the current. The current sheet thicknesses are typically in the range of 25 mm to 40 mm. The current sheet velocities are in the range of 10 km/s to 45 km/s when the discharge current is between 10 kA and 55 kA and the gas prefill pressure is between 30 Pa and 800 Pa. The experimental velocities are about 75% to 90% of the theoretical velocities calculated with the current shedding factor. One reason for this could be that the idealized snowplow analysis model ignores the surface drag force.

The influence of laser pulse waveform on laser-TIG hybrid welding of AZ31B magnesium alloy

NASA Astrophysics Data System (ADS)

Song, Gang; Luo, Zhimin

2011-01-01

By dividing laser pulse duration into two parts, three kinds of laser waveforms are designed, including a high power density pulse (HPDP) laser in a short duration set at the beginning of the laser waveform. This paper aims to find out the laser pulse waveform and idiographic critical values of HPDP, which can affect the magnesium penetration in laser-tungsten inert gas (TIG) hybrid welding. Results show that when the laser pulse duration of HPDP is not more than 0.4 ms, the welding penetration values of lasers with HPDP are larger than otherwise. Also, the welding penetration values of laser with HPDP have increased by up to 26.1%. It has been found that with HPDP, the laser can form the keyhole more easily because the interaction between laser and the plate is changed, when the TIG arc preheats the plate. Besides, the laser with high power density and short duration strikes on the plates so heavily that the corresponding background power can penetrate into the bottom of the keyhole and maintain the keyhole open, which facilitates the final welding penetration.

Generating high-power short terahertz electromagnetic pulses with a multifoil radiator.

PubMed

Vinokurov, Nikolay A; Jeong, Young Uk

2013-02-08

We describe a multifoil cone radiator capable of generating high-field short terahertz pulses using short electron bunches. Round flat conducting foil plates with successively decreasing radii are stacked, forming a truncated cone with the z axis. The gaps between the foil plates are equal and filled with some dielectric (or vacuum). A short relativistic electron bunch propagates along the z axis. At sufficiently high particle energy, the energy losses and multiple scattering do not change the bunch shape significantly. When passing by each gap between the foil plates, the electron bunch emits some energy into the gap. Then, the radiation pulses propagate radially outward. For transverse electromagnetic waves with a longitudinal (along the z axis) electric field and an azimuthal magnetic field, there is no dispersion in these radial lines; therefore, the radiation pulses conserve their shapes (time dependence). At the outer surface of the cone, we have synchronous circular radiators. Their radiation field forms a conical wave. Ultrashort terahertz pulses with gigawatt-level peak power can be generated with this device.

Study of axial mixing, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column using radiotracer technique.

PubMed

Ghiyas Ud Din; Imran Rafiq Chughtai; Hameed Inayat, Mansoor; Hussain Khan, Iqbal

2009-01-01

Axial mixing, holdup and slip velocity of dispersed phase which are parameters of fundamental importance in the design and operation of liquid-liquid extraction pulsed sieve plate columns have been investigated. Experiments for residence time distribution (RTD) analysis have been carried out for a range of pulsation frequency and amplitude in a liquid-liquid extraction pulsed sieve plate column with water as dispersed and kerosene as continuous phase using radiotracer technique. The column was operated in emulsion region and (99m)Tc in the form of sodium pertechnetate eluted from a (99)Mo/(99m)Tc generator was used to trace the dispersed phase. Axial dispersed plug flow model with open-open boundary condition and two points measurement method was used to simulate the hydrodynamics of dispersed phase. It has been observed that the axial mixing and holdup of dispersed phase increases with increase in pulsation frequency and amplitude until a maximum value is achieved while slip velocity decreases with increase in pulsation frequency and amplitude until it approaches a minimum value. Short lived and low energy radiotracer (99m)Tc in the form of sodium pertechnetate was found to be a good water tracer to study the hydrodynamics of a liquid-liquid extraction pulsed sieve plate column operating with two immiscible liquids, water and kerosene. Axial dispersed plug flow model with open-open boundary condition was found to be a suitable model to describe the hydrodynamics of dispersed phase in the pulsed sieve plate extraction column.

Preliminary results with microchannel array plates employing curved microchannels to inhibit ion feedback. [for photon counters

NASA Technical Reports Server (NTRS)

Timothy, J. G.; Bybee, R. L.

1977-01-01

Up to now, microchannel array plates (MCPs) have been constructed with microchannels having a straight geometry and hence have been prone to ion-feedback instabilities at high operating potentials and high ambient pressures. This paper describes the performances of MCPs with curved (J and C configuration) microchannels to inhibit ion feedback. Plates with curved microchannels have demonstrated performances comparable to those of conventional channel electron multipliers with saturated output pulse-height distributions and modal gain values in excess of 10 to the 6th electrons/pulse.

Novel technique to ensure battery reliability in 42-V PowerNets for new-generation automobiles

NASA Astrophysics Data System (ADS)

Lam, L. T.; Haigh, N. P.; Phyland, C. G.; Huynh, T. D.

The proposed 42-V PowerNet in automobiles requires the battery to provide a large number of shallow discharge-charge cycles at a high rate. High-rate discharge is necessary for engine cranking, while high-rate charge is associated with regenerative braking. The battery will therefore operate at these high rates in a partial-state-of-charge condition — 'HRPSoC duty'. Under simulated HRPSoC duty, it is found that the valve-regulated lead-acid (VRLA) battery fails prematurely due to the progressive accumulation of lead sulfate mainly on the surfaces of the negative plates. This is because the lead sulfate layer cannot be converted efficiently back to sponge lead during charging either from the engine or from the regenerative braking. Eventually, this layer of lead sulfate develops to such extent that the effective surface area of the plate is reduced markedly and the plate can no longer deliver the high-cranking current demanded by the automobile. The objective of this study is to develop and optimize a pulse-generation technique to minimize the development of lead sulfate layers on negative plates of VRLA batteries subjected to HRPSoC duty. The technique involves the application of sets of charging pulses of different frequency. It is found that the cycle-life performance of VRLA batteries is enhanced markedly when d.c. pulses of high frequency are used. For example, battery durability is raised from ˜10 600 cycles (no pulses) to 32 000 cycles with pulses of high frequency. Two key factors contribute to this improvement. The first factor is localization of the charging current on the surfaces of the plates — the higher the frequency, the greater is the amount of current concentrated on the plate surface. This phenomenon is known as the 'skin effect' as only the outer 'skin' of the plate is effectively carrying the current. The second factor is delivery of sufficient charge to the Faradaic resistance of the plate to compensate for the energy loss to inductance and double-layer capacitance effects. The Faradaic resistance represents the electrochemical reaction, i.e., conversion of lead sulfate to lead. The inductance simply results from the connection either between the cables and the terminals of the battery or between the terminals, bus-bars, and the lugs of the plates. The capacitance arises from the double layer which exists at the interface between the plate and the electrolyte solution. These findings have provided a demonstration and a scientific explanation of the benefit of superimposed pulsed current charging in suppressing the sulfation of negative plates in VRLA batteries operated under 42-V PowerNet and hybrid electric vehicle duties. A Novel Pulse™ device has been developed by the CSIRO. This device has the capability to be programmable to suite various applications and can be miniaturized to be encapsulated in the battery cover.

Plate-shaped Yb:LuPO4 crystal for efficient CW and passively Q-switched microchip lasers

NASA Astrophysics Data System (ADS)

Liu, Junhai; Wang, Lisha; Han, Wenjuan; Xu, Honghao; Zhong, Degao; Teng, Bing

2016-10-01

It is demonstrated that plate-shaped crystals of Yb:LuPO4, which are grown from spontaneous nucleation by high-temperature solution method, can be utilized to make microchip lasers operating in continuous-wave (CW) or passively Q-switched mode. Efficient operation of such a microchip laser, which is built with a 0.3 mm thick crystal plate in a 2 mm long plane-parallel cavity, is realized at room temperature. With 2.37 W of pump power absorbed, 1.45 W of CW output power is generated with a slope efficiency of 73%. When passively Q-switched with a Cr4+:YAG crystal plate as saturable absorber, the laser produces a maximum pulsed output power of 0.53 W at 1013.3 nm, at a pulse repetition rate of 23.8 kHz, the resulting pulse energy, duration, and peak power are 22.3 μJ, 4.0 ns, and 5.6 kW, respectively.

Pulsed, high-current, in-line reversal electron attachment detector

NASA Technical Reports Server (NTRS)

Bernius, Mark T.; Chutjian, Ara

1989-01-01

A new, pulsed, high-current, in-line reversal electron attachment ionizer/detector is described. The ionizer is capable of delivering a beam of electrons into an electrostatic mirror field to form a planar wall of electrons having zero kinetic energy. Electron attachment to a molecular target at the reversal point produces either parent or fragment negative ions through a zero-energy (s-wave) state. The atomic or molecular ion is pulsed out of the attachment region approximately 2 microsec after the electrons are pulsed off, and focused onto the entrance plane of a quadrupole mass analyzer. The sensitivity of the apparatus is preliminarily assessed, and its higher-energy behavior with regard to molecular attachment and ionization is described.

Pulse power applications of silicon diodes in EML capacitive pulsers

NASA Astrophysics Data System (ADS)

Dethlefsen, Rolf; McNab, Ian; Dobbie, Clyde; Bernhardt, Tom; Puterbaugh, Robert; Levine, Frank; Coradeschi, Tom; Rinaldi, Vito

1993-01-01

Crowbar diodes are used for increasing the energy transfer from capacitive pulse forming networks. They also prevent voltage reversal on the energy storage capacitors. 52 mm diameter diodes with a 5 kV reverse blocking voltage, rated 40 kA were successfully used for the 32 MJ SSG rail gun. An uprated diode with increased current capability and a 15 kV reverse blocking voltage has been developed. Transient thermal analysis has predicted the current ratings for different pulse length. Analysis verification is obtained from destructive testing.

An Investigation of Ionic Flows in a Sphere-Plate Electrode Gap

NASA Astrophysics Data System (ADS)

Z. Alisoy, H.; Alagoz, S.; T. Alisoy, G.; B. Alagoz, B.

2013-10-01

This paper presents analyses of ion flow characteristics and ion discharge pulses in a sphere-ground plate electrode system. As a result of variation in electric field intensity in the electrode gap, the ion flows towards electrodes generate non-uniform discharging pulses. Inspection of these pulses provides useful information on ionic stream kinetics, the effective thickness of ion cover around electrodes, and the timing of ion clouds discharge pulse sequences. A finite difference time domain (FDTD) based space-charge motion simulation is used for the numerical analysis of the spatio-temporal development of ionic flows following the first Townsend avalanche, and the simulation results demonstrate expansion of the positive ion flow and compression of the negative ion flow, which results in non-uniform discharge pulse characteristics.

Direct micromachining of quartz glass plates using pulsed laser plasma soft x-rays

NASA Astrophysics Data System (ADS)

Makimura, Tetsuya; Miyamoto, Hisao; Kenmotsu, Youichi; Murakami, Kouichi; Niino, Hiroyuki

2005-03-01

We have investigated direct micromachining of quartz glass, using pulsed laser plasma soft x-rays (LPSXs) having a potential capability of nanomachining because the diffraction limit is ˜10nm. The LPSX's were generated by irradiation of a Ta target with 532nm laser light from a conventional Q switched Nd :YAG laser at 700mJ/pulse. In order to achieve a sufficient power density of LPSX's beyond the ablation threshold, we developed an ellipsoidal mirror to obtain efficient focusing of LPSXs at around 10nm. It was found that quartz glass plates are smoothly ablated at 45nm/shot using the focused and pulsed LPSX's.

Femtosecond laser spectroscopy of the rhodopsin photochromic reaction: a concept for ultrafast optical molecular switch creation (ultrafast reversible photoreaction of rhodopsin).

PubMed

Smitienko, Olga; Nadtochenko, Victor; Feldman, Tatiana; Balatskaya, Maria; Shelaev, Ivan; Gostev, Fedor; Sarkisov, Oleg; Ostrovsky, Mikhail

2014-11-11

Ultrafast reverse photoreaction of visual pigment rhodopsin in the femtosecond time range at room temperature is demonstrated. Femtosecond two-pump probe experiments with a time resolution of 25 fs have been performed. The first рump pulse at 500 nm initiated cis-trans photoisomerization of rhodopsin chromophore, 11-cis retinal, which resulted in the formation of the primary ground-state photoproduct within a mere 200 fs. The second pump pulse at 620 nm with a varying delay of 200 to 3750 fs relative to the first рump pulse, initiated the reverse phototransition of the primary photoproduct to rhodopsin. The results of this photoconversion have been observed on the differential spectra obtained after the action of two pump pulses at a time delay of 100 ps. It was found that optical density decreased at 560 nm in the spectral region of bathorhodopsin absorption and increased at 480 nm, where rhodopsin absorbs. Rhodopsin photoswitching efficiency shows oscillations as a function of the time delay between two рump pulses. The quantum yield of reverse photoreaction initiated by the second pump pulse falls within the range 15%±1%. The molecular mechanism of the ultrafast reversible photoreaction of visual pigment rhodopsin may be used as a concept for the development of an ultrafast optical molecular switch.

High-speed multiframe dynamic transmission electron microscope image acquisition system with arbitrary timing

DOEpatents

Reed, Bryan W.; DeHope, William J.; Huete, Glenn; LaGrange, Thomas B.; Shuttlesworth, Richard M.

2015-10-20

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system ("laser"). The laser produces a train of temporally-shaped laser pulses of a predefined pulse duration and waveform, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has two pairs of plates arranged perpendicular to one another. A control system controls the laser and a plurality of switching components synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to be provided with an independently set duration and independently set inter-pulse spacings.

High-speed multiframe dynamic transmission electron microscope image acquisition system with arbitrary timing

DOEpatents

Reed, Bryan W.; Dehope, William J; Huete, Glenn; LaGrange, Thomas B.; Shuttlesworth, Richard M

2016-06-21

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system ("laser"). The laser produces a train of temporally-shaped laser pulses of a predefined pulse duration and waveform, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has two pairs of plates arranged perpendicular to one another. A control system controls the laser and a plurality of switching components synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to be provided with an independently set duration and independently set inter-pulse spacings.

Ultrafast Reverse Recovery Time Measurement for Wide-Bandgap Diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauch, Daniel L.; Zutavern, Fred J.; Delhotal, Jarod J.

A system is presented that is capable of measuring sub-nanosecond reverse recovery times of diodes in wide-bandgap materials over a wide range of forward biases (0 – 1 A) and reverse voltages (0 – 10 kV). The system utilizes the step recovery technique and comprises a cable pulser based on a silicon (Si) Photoconductive Semiconductor Switch (PCSS) triggered with an Ultra Short Pulse Laser (USPL), a pulse charging circuit, a diode biasing circuit, and resistive and capacitive voltage monitors. The PCSS based cable pulser transmits a 130 ps rise time pulse down a transmission line to a capacitively coupled diode,more » which acts as the terminating element of the transmission line. The temporal nature of the pulse reflected by the diode provides the reverse recovery characteristics of the diode, measured with a high bandwidth capacitive probe integrated into the cable pulser. Furthermore, this system was used to measure the reverse recovery times (including the creation and charging of the depletion region) for two Avogy gallium nitride (GaN) diodes; the initial reverse recovery time was found to be 4 ns and varied minimally over reverse biases of 50 – 100 V and forward current of 1 – 100 mA.« less

Ultrafast Reverse Recovery Time Measurement for Wide-Bandgap Diodes

DOE PAGES

Mauch, Daniel L.; Zutavern, Fred J.; Delhotal, Jarod J.; ...

2017-03-01

A system is presented that is capable of measuring sub-nanosecond reverse recovery times of diodes in wide-bandgap materials over a wide range of forward biases (0 – 1 A) and reverse voltages (0 – 10 kV). The system utilizes the step recovery technique and comprises a cable pulser based on a silicon (Si) Photoconductive Semiconductor Switch (PCSS) triggered with an Ultra Short Pulse Laser (USPL), a pulse charging circuit, a diode biasing circuit, and resistive and capacitive voltage monitors. The PCSS based cable pulser transmits a 130 ps rise time pulse down a transmission line to a capacitively coupled diode,more » which acts as the terminating element of the transmission line. The temporal nature of the pulse reflected by the diode provides the reverse recovery characteristics of the diode, measured with a high bandwidth capacitive probe integrated into the cable pulser. Furthermore, this system was used to measure the reverse recovery times (including the creation and charging of the depletion region) for two Avogy gallium nitride (GaN) diodes; the initial reverse recovery time was found to be 4 ns and varied minimally over reverse biases of 50 – 100 V and forward current of 1 – 100 mA.« less

Hybrid pulse anodization for the fabrication of porous anodic alumina films from commercial purity (99%) aluminum at room temperature.

PubMed

Chung, C K; Zhou, R X; Liu, T Y; Chang, W T

2009-02-04

Most porous anodic alumina (PAA) or anodic aluminum oxide (AAO) films are fabricated using the potentiostatic method from high-purity (99.999%) aluminum films at a low temperature of approximately 0-10 degrees C to avoid dissolution effects at room temperature (RT). In this study, we have demonstrated the fabrication of PAA film from commercial purity (99%) aluminum at RT using a hybrid pulse technique which combines pulse reverse and pulse voltages for the two-step anodization. The reaction mechanism is investigated by the real-time monitoring of current. A possible mechanism of hybrid pulse anodization is proposed for the formation of pronounced nanoporous film at RT. The structure and morphology of the anodic films were greatly influenced by the duration of anodization and the type of voltage. The best result was obtained by first applying pulse reverse voltage and then pulse voltage. The first pulse reverse anodization step was used to form new small cells and pre-texture concave aluminum as a self-assembled mask while the second pulse anodization step was for the resulting PAA film. The diameter of the nanopores in the arrays could reach 30-60 nm.

Reverse Less Invasive Stabilization System (LISS) Plating for Proximal Femur Fractures in Poliomyelitis Survivors: A Report of Two Cases.

PubMed

Yao, Chen; Jin, Dongxu; Zhang, Changqing

2017-11-15

BACKGROUND Poliomyelitis is a neuromuscular disease which causes muscle atrophy, skeletal deformities, and disabilities. Treatment of hip fractures on polio-affect limbs is unique and difficult, since routine fixation methods like nailing may not be suitable due to abnormal skeletal structures. CASE REPORT We report one femoral neck fracture and one subtrochanteric fracture in polio survivors successfully treated with reverse less invasive stabilization system (LISS) plating technique. Both fractures were on polio-affected limbs with significant skeletal deformities and low bone density. A contralateral femoral LISS plate was applied upside down to the proximal femur as an internal fixator after indirect or direct reduction. Both patients had uneventful bone union and good functional recovery. CONCLUSIONS Reverse LISS plating is a safe and effective technique to treat hip fractures with skeletal deformities caused by poliomyelitis.

Processing and Probability Analysis of Pulsed Terahertz NDE of Corrosion under Shuttle Tile Data

NASA Technical Reports Server (NTRS)

Anastasi, Robert F.; Madaras, Eric I.; Seebo, Jeffrey P.; Ely, Thomas M.

2009-01-01

This paper examines data processing and probability analysis of pulsed terahertz NDE scans of corrosion defects under a Shuttle tile. Pulsed terahertz data collected from an aluminum plate with fabricated corrosion defects and covered with a Shuttle tile is presented. The corrosion defects imaged were fabricated by electrochemically etching areas of various diameter and depth in the plate. In this work, the aluminum plate echo signal is located in the terahertz time-of-flight data and a threshold is applied to produce a binary image of sample features. Feature location and area are examined and identified as corrosion through comparison with the known defect layout. The results are tabulated with hit, miss, or false call information for a probability of detection analysis that is used to identify an optimal processing threshold.

Pulsed ultrasonic comb filtering effect and its applications in the measurement of sound velocity and thickness of thin plates.

PubMed

Liu, Jingfei; Declercq, Nico F

2017-03-01

An analytical and experimental study of the pulsed ultrasonic comb filtering effect is presented in this work intending to provide a fundamental tool for data analysis and phenomenon understanding in pulsed ultrasonics. The basic types of comb filter, feedforward and feedback filters, are numerically simulated and demonstrated. The characteristic features of comb filters, which include the formula for determining the locations of the spectral peaks or notches and the relationship between its temporal characteristics (relative time delay between constituent pulses) and its spectral characteristics (frequency interval between peaks or notches), are theoretically derived. To demonstrate the applicability of the comb filtering effect, it is applied to measuring the sound velocities and thickness of a thin plate sample. It is proven that the comb filtering effect based method not only is capable of accurate measurements, but also has advantages over the conventional time-of-flight based method in thin plate measurements. Furthermore, the principles developed in this study have potential applications in any pulsed ultrasonic cases where the output signal shows comb filter features. Copyright © 2016 Elsevier B.V. All rights reserved.

Penetration Effects of the Compound Vortex in Gas Metal-Arc Welding

DTIC Science & Technology

1988-05-01

steel plate using constant current GMAW equipment and argon + 2;. oxygen shielding gas. After welding, the plates were cut, ground, polished and etched...49 14. Typical time plot of current used in pulsed GMAW ..... 51 15. The experimental apparatus ........................... 54 16. Plot...this phenomenon could be employed in some manner to yield high penetration welds with low average current. 2. Pulsed GMAW . KolodziejczaK [26] studied

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.

Carrier-envelope phase control by a composite plate.

PubMed

Ell, Richard; Birge, Jonathan R; Araghchini, Mohammad; Kärtner, Franz X

2006-06-12

We demonstrate a new concept to vary the carrier-envelope phase of a mode-locked laser by a composite plate while keeping all other pulse parameters practically unaltered. The effect is verified externally in an interferometric autocorrelator, as well as inside the cavity of an octave-spanning femtosecond oscillator. The carrier-envelope frequency can be shifted by half the repetition rate with negligible impact on pulse spectrum and energy.

Cirrus Dopant Nano-Composite Coatings

DTIC Science & Technology

2014-11-01

100 200 300 400 500 600 HARDNESS (HV) MICROHARDNESS - ELECTROPLATED NICKEL STANDARD DC PLATED DOPED DC PLATED DOPED PULSE PLATED ↑48% 10...STANDARD COATING HARDNESS (HV) DOPED COATING MICROHARDNESS - ELECTROPLATED ZN NI ↑32% DC ZnNi Cirrus ZnNi Current Test Applications cirrus nano

Control of reversible magnetization switching by pulsed circular magnetic field in glass-coated amorphous microwires

NASA Astrophysics Data System (ADS)

Chizhik, Alexander; Zhukov, Arkady; Gonzalez, Julian; Stupakiewicz, Andrzej

2018-02-01

Magnetization reversal in magnetic microwires was studied in the presence of external mechanical stress and helical magnetic fields using the magneto-optical Kerr effect. It was found that a combination of tuned magnetic anisotropy and a direct current or pulsed circular magnetic field activated different types of magnetization reversal scenarios. The application of the pulsed magnetic field of 10 ns time duration induced a transient controlling action to switch the magnetic states without activating a domain wall motion. This created a promising method for tuning the giant magneto-impedance effect.

Intrinsic subpicosecond magnetization reversal driven by femtosecond laser pulses in GdFeCo amorphous films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Shufa; Gao, Ruixin; Cheng, Chuyuan

2013-12-09

Ultrafast magnetization dynamics in GdFeCo films triggered by femtosecond laser pulses with and without an external field applied is studied experimentally for different excitation fluence. It is found that subpicosecond magnetization reversal occurs simultaneously in the ultrafast dynamics of both saturation and remnant magnetization states and almost identical within 13 ps, whereas relatively slow magnetization reversal across compensation point appears only in the dynamics of saturation magnetization state. It shows the subpicosecond magnetization reversal is external field independent, and originates from intrinsic magnetic evolution in ferrimagnetic system. The intrinsic subpicosecond reversal is qualitatively explained by linear reversal.

Preparation and application of reversed phase chromatorotor for the isolation of natural products by centrifugal preparative chromatography

USDA-ARS?s Scientific Manuscript database

A method of preparation of Chromatorotor or plates with a reversed phase (RP) solid silica gel sorbent layer has been developed for preparative centrifugal chromatography. The RP-rotor plates consist of binder free RP solid SiO2 sorbent layers of different thicknesses paked between two supported cir...

On the boundary flow using pulsed nanosecond DBD plasma actuators

NASA Astrophysics Data System (ADS)

Zhao, Zi-Jie; Cui, Y. D.; Li, Jiun-Ming; Zheng, Jian-Guo; Khoo, B. C.

2018-05-01

Our previous studies in quiescent air environment [Z. J. Zhao et al., AIAA J. 53(5) (2015) 1336; J. G. Zheng et al., Phys. Fluids 26(3) (2014) 036102] reveal experimentally and numerically that the shock wave generated by the nanosecond pulsed plasma is fundamentally a microblast wave. The shock-induced burst perturbations (overpressure and induced velocity) are found to be restricted to a very narrow region (about 1 mm) behind the shock front and last only for a few microseconds. These results indicate that the pulsed nanosecond dielectric barrier discharge (DBD) plasma actuator has stronger local effects in time and spatial domain. In this paper, we further investigate the effects of pulsed plasma on the boundary layer flow over a flat plate. The present investigation reveals that the nanosecond pulsed plasma actuator generates intense perturbations and tends to promote the laminar boundary over a flat plate to turbulent flow. The heat effect after the pulsed plasma discharge was observed in the external flow, lasting a few milliseconds for a single pulse and reaching a quasi-stable state for multi-pulses.

38. VIEW OF COTTRELL MAGNETIC IMPULSE GENERATOR ADJACENT TO SIX ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

38. VIEW OF COTTRELL MAGNETIC IMPULSE GENERATOR ADJACENT TO SIX GAP ROTARY RECTIFIER. THIS UNIT GENERATED A MAGNETIC PULSE WHICH WAS TRANSMITTED TO THE COLLECTION PLATES IN THE ELECTROSTATIC PRECIPITATOR CHAMBER. THESE PERIODIC PULSES VIBRATE THE PLATES AND CAUSE PRECIPITATED ARTICLES OF SMOKE AND FLY ASH TO FALL TO THE BOTTOM OF THE PRECIPITATOR CHAMBER. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT

Electrospark Deposition for the Repair of Army Main Battle Tank Components

DTIC Science & Technology

2006-07-01

Inconel 718, and Inconel 625 were deposited onto low-alloy carbon steel and Inconel 718 substrates. 6.2 ESD Procedure Development (M1A1... Inconel 625 Inconel 718 Inconel 718 Inconel 718 Electrode diameter (in) 0.125 0.125 0.125 .125 0.125 0.125 Pulse rate (Hz) 400 400 400 400 400 400...coating Chrome plating Chrome plating Chrome plating Chrome plating Chrome plating Chrome plating Electrode alloy Inconel 718 Inconel

Analysis of deformation of aluminum plates under the influence of nano- and microsecond laser pulses

NASA Astrophysics Data System (ADS)

Jach, K.; Świerczyński, R.; Ostrowski, R.; Rycyk, A.; CzyŻ, K.; Strzelec, M.; Sarzyński, A.

2017-10-01

The paper presents numerical modeling of interaction of strong laser radiation with conventional aluminum sheets, similar to those used in military technology. The theoretical model uses equations of continuum mechanics (equations of hydrodynamics and the equations of mechanics of solid bodies in a cylindrical coordinates r, z), enriched with equations describing the typical effects of high temperature, such as absorption of laser radiation within the Al shield, electronic and radiative thermal conductivity, and energy loss on phase transitions (melting, evaporation, ionization). Semiempirical equations of state were used to describe the properties of material in the conditions of large deformation and the Johnson-Cook's model. The equations were solved using the method of free points developed by one of the authors. Two kinds od laser pulses were considered: microsecond pulse with duration of 200 μs and a low peak power of 10 kW/cm2 (CW laser), and nanosecond pulse with duration of 10 ns and high peak power of 5 GW/cm2 (pulsed laser). The aim of this study was to determine the shapes and temperatures of Al plates under the influence of these pulses for the comparison of the numerical results with future experiments and to verify the possibility to determine the distribution of the energy density of the laser beam on the basis of the plate deformation.

Selective Mode Focusing in a Plate of Arbitrary Shape Applying Time Reversal Mirrors

DOE PAGES

Payan, Cedric; Remillieux, Marcel C.; Bas, Pierre-Yves Le; ...

2017-11-01

In this study, a time reversal mirror is used to remotely focus symmetric or antisymmetric modes in a plate of arbitrary shape without the need of precise knowledge about material properties and geometry. The addition or subtraction of the forward motions recorded by two laser beams located on both sides of the plate allows, respectively, to focus a symmetric or an antisymmetric mode. The concept is validated using experimental and numerical analysis on an aluminum plate of complex machined geometry which exhibits various thicknesses as well as a bi-materials zone. Finally, the limitations and possible ways to overcome them aremore » then presented.« less

Selective Mode Focusing in a Plate of Arbitrary Shape Applying Time Reversal Mirrors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Payan, Cedric; Remillieux, Marcel C.; Bas, Pierre-Yves Le

In this study, a time reversal mirror is used to remotely focus symmetric or antisymmetric modes in a plate of arbitrary shape without the need of precise knowledge about material properties and geometry. The addition or subtraction of the forward motions recorded by two laser beams located on both sides of the plate allows, respectively, to focus a symmetric or an antisymmetric mode. The concept is validated using experimental and numerical analysis on an aluminum plate of complex machined geometry which exhibits various thicknesses as well as a bi-materials zone. Finally, the limitations and possible ways to overcome them aremore » then presented.« less

Damage imaging in a laminated composite plate using an air-coupled time reversal mirror

DOE PAGES

Le Bas, P. -Y.; Remillieux, M. C.; Pieczonka, L.; ...

2015-11-03

We demonstrate the possibility of selectively imaging the features of a barely visible impact damage in a laminated composite plate by using an air-coupled time reversal mirror. The mirror consists of a number of piezoelectric transducers affixed to wedges of power law profiles, which act as unconventional matching layers. The transducers are enclosed in a hollow reverberant cavity with an opening to allow progressive emission of the ultrasonic wave field towards the composite plate. The principle of time reversal is used to focus elastic waves at each point of a scanning grid spanning the surface of the plate, thus allowingmore » localized inspection at each of these points. The proposed device and signal processing removes the need to be in direct contact with the plate and reveals the same features as vibrothermography and more features than a C-scan. More importantly, this device can decouple the features of the defect according to their orientation, by selectively focusing vector components of motion into the object, through air. For instance, a delamination can be imaged in one experiment using out-of-plane focusing, whereas a crack can be imaged in a separate experiment using in-plane focusing. As a result, this capability, inherited from the principle of time reversal, cannot be found in conventional air-coupled transducers.« less

Multi-operational tuneable Q-switched mode-locking Er fibre laser

NASA Astrophysics Data System (ADS)

Qamar, F. Z.

2018-01-01

A wavelength-spacing tuneable, Q-switched mode-locking (QML) erbium-doped fibre laser based on non-linear polarization rotation controlled by four waveplates and a cube polarizer is proposed. A mode-locked pulse train using two quarter-wave plates and a half-wave plate (HWP) is obtained first, and then an extra HWP is inserted into the cavity to produce different operation regimes. The evolutions of temporal and spectral dynamics with different orientation angles of the extra HWP are investigated. A fully modulated stable QML pulse train is observed experimentally. This is, to the author’s best knowledge, the first experimental work reporting QML operation without adding an extra saturable absorber inside the laser cavity. Multi-wavelength pulse laser operation, multi-pulse train continuous-wave mode-locking operation and pulse-splitting operations are also reported at certain HWP angles. The observed operational dynamics are interpreted as a mutual interaction of dispersion, non-linear effect and insertion loss. This work provides a new mechanism for fabricating cheap tuneable multi-wavelength lasers with QML pulses.

Structural controls on the hydrogeology of the Costa Rica subduction thrust NW of the Osa Peninisula (Invited)

NASA Astrophysics Data System (ADS)

Bangs, N. L.; McIntosh, K. D.; Silver, E. A.; Kluesner, J.; Ranero, C. R.

2013-12-01

Three-dimensional seismic reflection data from the Costa Rica margin NW of the Osa peninsula have enabled us to map the subduction megathrust from the trench to ~12 km subseafloor beneath the shelf. The subduction thrust has a large, abrupt downdip transition in seismic reflection amplitude from very high to low amplitude 6 km subseafloor beneath the upper slope. This transition broadly corresponds with an increase in concentration of microseismic earthquakes potentially due to a significant increase in plate coupling (Bangs et al., 2012, AGU Fall Meeting, T13A-2587), thus linking seismic reflection amplitude to fluid content and mechanical coupling along the fault. A detailed look at the overriding plate reflectivity shows numerous high-amplitude, continuous seismic reflections through the upper plate, many of which are clearly reversed-polarity from the seafloor reflection and are thus likely active fluid conduits through the overriding margin wedge, the slope cover sediment, and the seafloor. Broadly, the structural grain of the margin wedge trends E-W and dips landward across the lower slope and onto the shelf, presumably due to stress imparted by subducting ridges. However, directly above the abrupt high-to-low plate-boundary reflection amplitude transition, structures within the overlying margin wedge reverse dip, steepen, and change strike to an ESE direction. Within this zone we interpret a set of parallel reflections with small offsets and reverse-polarity as high-angle reverse faults that act as fluid conduits leading directly into shallow fluid migration systems described by Bangs et al., 2012 (AGU Fall Meeting, T13A-2587) and Kluesner et al. [this meeting]. The coincidence between the plate-boundary reflection amplitude patterns and the change in structure implies that the fluid migration pathways that drain the plate interface are locally disrupted by overriding plate structure in two possible ways: 1) by focusing up dip fluid migration along the plate interface into a thinner but richer fluid zone along the subduction thrust, or 2) by creating a more direct, nearly vertical route along high-angle reverse faults through the overlying margin wedge to the seafloor (possibly shortened by a factor of two) and draining deeper portions of the plate-boundary more efficiently.

Pulsed Corona Discharge Generated By Marx Generator

NASA Astrophysics Data System (ADS)

Sretenovic, G. B.; Obradovic, B. M.; Kovacevic, V. V.; Kuraica, M. M.; Puric J.

2010-07-01

The pulsed plasma has a significant role in new environmental protection technologies. As a part of a pulsed corona system for pollution control applications, Marx type repetitive pulse generator was constructed and tested in arrangement with wire-plate corona reactor. We performed electrical measurements, and obtained voltage and current signals, and also power and energy delivered per pulse. Ozone formation by streamer plasma in air was chosen to monitor chemical activity of the pulsed corona discharge.

Indirect ignition of energetic materials with laser-driven flyer plates.

PubMed

Dean, Steven W; De Lucia, Frank C; Gottfried, Jennifer L

2017-01-20

The impact of laser-driven flyer plates on energetic materials CL-20, PETN, and TATB has been investigated. Flyer plates composed of 25 μm thick Al were impacted into the energetic materials at velocities up to 1.3 km/s. The flyer plates were accelerated by means of an Nd:YAG laser pulse. The laser pulse generates rapidly expanding plasma between the flyer plate foil and the substrate to which it is adhered. As the plasma grows, a section of the metal foil is ejected at high speed, forming the flyer plate. The velocity of the flyer plate was determined using VISAR, time of flight, and high-speed video. The response of the energetic material to impact was determined by light emission recorded by an infrared-sensitive photodiode. Following post-impact analysis of the impacted energetic material, it was hypothesized that the light emitted by the material after impact is not due to the impact of the flyer itself but rather is caused by the decomposition of energetic material ejected (via the shock of flyer plate impact) into a cloud of hot products generated during the launch of the flyer plate. This hypothesis was confirmed through schlieren imaging of a flyer plate launch, clearly showing the ejection of hot gases and particles from the region surrounding the flyer plate launch and the burning of the ejected energetic material particles.

Laser-induced selective copper plating of polypropylene surface

NASA Astrophysics Data System (ADS)

Ratautas, K.; Gedvilas, M.; Stankevičiene, I.; JagminienÄ--, A.; Norkus, E.; Li Pira, N.; Sinopoli, S.; Emanuele, U.; Račiukaitis, G.

2016-03-01

Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals. In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.

Pulsed laser generation of ultrasound in a metal plate between the melting and ablation thresholds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Every, A. G., E-mail: arthur.every@wits.ac.za; Utegulov, Z. N., E-mail: zhutegulov@nu.edu.kz; Veres, I. A., E-mail: istvan.veres@recendt.at

2015-03-31

The generation of ultrasound in a metal plate exposed to nanosecond pulsed laser heating, sufficient to cause melting but not ablation, is treated. Consideration is given to the spatial and temporal profiles of the laser pulse, penetration of the laser beam into the sample, the evolution of the melt pool, and thermal conduction in the melt and surrounding solid. The excitation of the ultrasound takes place over a few nanoseconds, and occurs predominantly within the thermal diffusion length of a micron or so beneath the surface. Because of this, the output of the thermal simulations can be represented as axiallymore » symmetric transient radial and normal surface force distributions. The epicentral displacement response at the opposite surface to these forces is obtained by two methods, the one based on the elastodynamic Green’s functions for plate geometry determined by the Cagniard generalized ray method, and the other using a finite element numerical method. The two approaches are in very close agreement. Numerical simulations are reported of the epicentral displacement response of a 3.12mm thick tungsten plate irradiated with a 4 ns pulsed laser beam with Gaussian spatial profile, at intensities below and above the melt threshold. Comparison is made between results obtained using available temperature dependent thermophysical data, and room temperature materials constants except near the melting point.« less

High-Field Fast-Risetime Pulse Failures in 4H- and 6H-SiC pn Junction Diodes

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.; Fazi, Christian

1996-01-01

We report the observation of anomalous reverse breakdown behavior in moderately doped (2-3 x 10(exp 17 cm(exp -3)) small-area micropipe-free 4H- and 6H-SiC pn junction diodes. When measured with a curve tracer, the diodes consistently exhibited very low reverse leakage currents and sharp repeatable breakdown knees in the range of 140-150 V. However, when subjected to single-shot reverse bias pulses (200 ns pulsewidth, 1 ns risetime), the diodes failed catastrophically at pulse voltages of less than 100 V. We propose a possible mechanism for this anomalous reduction in pulsed breakdown voltage relative to dc breakdown voltage. This instability must be removed so that SiC high-field devices can operate with the same high reliability as silicon power devices.

A cross correlation PIV technique using electro-optical image separation

NASA Astrophysics Data System (ADS)

Wirth, M.; Baritaud, T. A.

1996-11-01

A new approach for 2-dimensional flow field investigation by PIV has been developed for measurements with high spatial resolution without the well known directional ambiguity. This feature of the technique is especially important for measurements in flows with reversal regions or strong turbulent motion as in-cylinder engine measurements. The major aim of the work was to achieve the benefits of cross correlation PIV image evaluation at reasonable cost and under application of common single wavelength double pulsed laser systems as they are mainly used for PIV experiments. The development of the technique is based on polarization rotation of the light scattered by the seeding particles by means of a ferroelectric liquid crystal half wave plate (FLC). Measurement samples from low turbulent jets and the flow in the wake of a cylinder are being presented.

A Baseline-Free Defect Imaging Technique in Plates Using Time Reversal of Lamb Waves

NASA Astrophysics Data System (ADS)

Hyunjo, Jeong; Sungjong, Cho; Wei, Wei

2011-06-01

We present an analytical investigation for a baseline-free imaging of a defect in plate-like structures using the time-reversal of Lamb waves. We first consider the flexural wave (A0 mode) propagation in a plate containing a defect, and reception and time reversal process of the output signal at the receiver. The received output signal is then composed of two parts: a directly propagated wave and a scattered wave from the defect. The time reversal of these waves recovers the original input signal, and produces two additional sidebands that contain the time-of-flight information on the defect location. One of the side-band signals is then extracted as a pure defect signal. A defect localization image is then constructed from a beamforming technique based on the time-frequency analysis of the side band signal for each transducer pair in a network of sensors. The simulation results show that the proposed scheme enables the accurate, baseline-free imaging of a defect.

Monitoring of ultraviolet pulse rate dependent photomechanical actuation in carbon nanotubes using fiber Bragg gratings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shivananju, B. N.; Suri, Ashish; Asokan, S.

2014-01-06

In this Letter, we present a non-contact method of controlling and monitoring photomechanical actuation in carbon nanotubes (CNT) by exposing it to ultra-violet radiation at different pulse rates (10 to 200 Hz). This is accomplished by imparting a reversible photo induced strain (5–330 με) on CNT coated fibre Bragg gratings; CNT undergoes an internal reversible structural change due to cyclic photon absorption that leads to the development of mechanical strain, which in turn allows reversible switching of the Bragg wavelength. The results also reveal an interesting pulse rate dependent rise and fall times of photomechanical actuation in CNT.

Novel MCP-Based Electron Source Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haughey, M.; Shiltsev V., Shiltsev V.; Stancari, G.

Microchannel plates (MCPs) were recently proposed as novel type of cathodes for electron guns [1], suitable for applications in design of electron lenses. We report results of the first systematic study of microchannel plate based photomultiplier time response and maximum cur-rent density tests using different sources of light pulses. The Burle 85011-501 MCP-PMT is found to have good time response properties being capable of producing na-nosecond long pulses with modest maximum current density and performance strongly dependent on magnetic field strength.

Real time determination of the laser ablated mass by means of electric field-perturbation measurement

NASA Astrophysics Data System (ADS)

Pacheco, P.; Álvarez, J.; Sarmiento, R.; Bredice, F.; Sánchez-Aké, C.; Villagrán-Muniz, M.; Palleschi, V.

2018-04-01

A Nd:YAG ns-pulsed laser was used to ablate Al, Cd and Zn targets, which were placed between the plates of a planar charged capacitor. The plasma generates a transient redistribution of the electrical charges on the plates that can be measured as a voltage drop across a resistor connected to the ground plate. This signal is proportional to the capacitor applied voltage, the distance between the plates and the total number of ions produced in the ablation process which in turn is related to the laser energy and the ablated mass. After a series of pulses, the targets were weighed on a thermogravimetric balance to measure the ablated mass. Our results show that the electrical signal measured on the resistor is univocally related to the ablated mass from the target. Therefore, after a proper calibration depending on the material and the experimental geometry, the electrical signal can be used for real time quantitative measurement of the ablated mass in pulsed laser generated plasma experiments. The experiments were repeated on an aluminum target, with and without the presence of the external electric field in order to determine the possible influence of the applied electric field on the ablated mass.

Characterization of reticulated vitreous carbon foam using a frisch-grid parallel-plate ionization chamber

NASA Astrophysics Data System (ADS)

Edwards, Nathaniel S.; Conley, Jerrod C.; Reichenberger, Michael A.; Nelson, Kyle A.; Tiner, Christopher N.; Hinson, Niklas J.; Ugorowski, Philip B.; Fronk, Ryan G.; McGregor, Douglas S.

2018-06-01

The propagation of electrons through several linear pore densities of reticulated vitreous carbon (RVC) foam was studied using a Frisch-grid parallel-plate ionization chamber pressurized to 1 psig of P-10 proportional gas. The operating voltages of the electrodes contained within the Frisch-grid parallel-plate ionization chamber were defined by measuring counting curves using a collimated 241Am alpha-particle source with and without a Frisch grid. RVC foam samples with linear pore densities of 5, 10, 20, 30, 45, 80, and 100 pores per linear inch were separately positioned between the cathode and anode. Pulse-height spectra and count rates from a collimated 241Am alpha-particle source positioned between the cathode and each RVC foam sample were measured and compared to a measurement without an RVC foam sample. The Frisch grid was positioned in between the RVC foam sample and the anode. The measured pulse-height spectra were indiscernible from background and resulted in negligible net count rates for all RVC foam samples. The Frisch grid parallel-plate ionization chamber measurement results indicate that electrons do not traverse the bulk of RVC foam and consequently do not produce a pulse.

Ultrasonic detection of plate cracks in railway wheels

DOT National Transportation Integrated Search

1976-07-31

The results of experimental efforts established the feasibility of the detection of railway wheel plate cracks by an ultrasonic pulse echo testing technique from the tread surface. Feasibility and test sensitivities were established using artificial ...

Time-of-flight direct recoil ion scattering spectrometer

DOEpatents

Krauss, A.R.; Gruen, D.M.; Lamich, G.J.

1994-09-13

A time-of-flight direct recoil and ion scattering spectrometer beam line is disclosed. The beam line includes an ion source which injects ions into pulse deflection regions and separated by a drift space. A final optics stage includes an ion lens and deflection plate assembly. The ion pulse length and pulse interval are determined by computerized adjustment of the timing between the voltage pulses applied to the pulsed deflection regions. 23 figs.

A high voltage pulse generator based on silicon-controlled rectifier for field-reversed configuration experiment.

PubMed

Lin, Munan; Liu, Ming; Zhu, Guanghui; Wang, Yanpeng; Shi, Peiyun; Sun, Xuan

2017-08-01

A high voltage pulse generator based on a silicon-controlled rectifier has been designed and implemented for a field reversed configuration experiment. A critical damping circuit is used in the generator to produce the desired pulse waveform. Depending on the load, the rise time of the output trigger signal can be less than 1 μs, and the peak amplitudes of trigger voltage and current are up to 8 kV and 85 A in a single output. The output voltage can be easily adjusted by changing the voltage on a capacitor of the generator. In addition, the generator integrates an electrically floating heater circuit so it is capable of triggering either pseudosparks (TDI-type hydrogen thyratron) or ignitrons. Details of the circuits and their implementation are described in the paper. The trigger generator has successfully controlled the discharging sequence of the pulsed power supply for a field reversed configuration experiment.

A high voltage pulse generator based on silicon-controlled rectifier for field-reversed configuration experiment

NASA Astrophysics Data System (ADS)

Lin, Munan; Liu, Ming; Zhu, Guanghui; Wang, Yanpeng; Shi, Peiyun; Sun, Xuan

2017-08-01

A high voltage pulse generator based on a silicon-controlled rectifier has been designed and implemented for a field reversed configuration experiment. A critical damping circuit is used in the generator to produce the desired pulse waveform. Depending on the load, the rise time of the output trigger signal can be less than 1 μs, and the peak amplitudes of trigger voltage and current are up to 8 kV and 85 A in a single output. The output voltage can be easily adjusted by changing the voltage on a capacitor of the generator. In addition, the generator integrates an electrically floating heater circuit so it is capable of triggering either pseudosparks (TDI-type hydrogen thyratron) or ignitrons. Details of the circuits and their implementation are described in the paper. The trigger generator has successfully controlled the discharging sequence of the pulsed power supply for a field reversed configuration experiment.

Status of Pulsed Inductive Thruster Research

NASA Technical Reports Server (NTRS)

Hrbud, Ivana; LaPointe, Michael; Vondra, Robert; Lovberg, Ralph; Dailey, C. Lee; Schafer, Charles (Technical Monitor)

2002-01-01

The TRW Pulsed Inductive Thruster (PIT) is an electromagnetic propulsion system that can provide high thrust efficiency over a wide range of specific impulse values. In its basic form, the PIT consists of a flat spiral coil covered by a thin dielectric plate. A pulsed gas injection nozzle distributes a thin layer of gas propellant across the plate surface at the same time that a pulsed high current discharge is sent through the coil. The rising current creates a time varying magnetic field, which in turn induces a strong azimuthal electric field above the coil. The electric field ionizes the gas propellant and generates an azimuthal current flow in the resulting plasma. The current in the plasma and the current in the coil flow in opposite directions, providing a mutual repulsion that rapidly blows the ionized propellant away from the plate to provide thrust. The thrust and specific impulse can be tailored by adjusting the discharge power, pulse repetition rate, and propellant mass flow, and there is minimal if any erosion due to the electrodeless nature of the discharge. Prior single-shot experiment,; performed with a Diameter diameter version of the PIT at TRW demonstrated specific impulse values between 2,000 seconds and 8,000 seconds, with thruster efficiencies of about 52% for ammonia. This paper outlines current and planned activities to transition the single shot device into a multiple repetition rate thruster capable of supporting NASA strategic enterprise missions.

Reversible, high-voltage square-wave pulse generator for triggering spark gaps.

PubMed

Robledo-Martinez, A; Vega, R; Cuellar, L E; Ruiz-Meza, A; Guzmán, E

2007-05-01

A design is presented for a reversible, square-pulse generator that employs coaxial cables for charge storage and pulse formation and a thyratron as the switch. The generator has a nominal output voltage of 5-30 kV and a pulse duration determined by the cable's physical length. Two variations are presented: (1) a single-stage one consisting of cable that is charged via its shield on one end and discharged with a thyratron on the opposite end and (2) a two-stage one having an inverting circuit that uses a coaxial cable to reverse the polarity of the pulse. The generator operates with "flying shields," i.e., high-voltage pulses also propagate on the outside of the cables; this calls for a dedicated insulation that avoids breakdown between sections of the cable's shield. The rise time obtained is mostly dictated by the switching time of the thyratron; with the one we used in the tests, rise times in the range of 30-40 ns were obtained. We present the results obtained in the implementation of the generators as well as its application to fire a large Marx generator.

Needle-array to Plate DBD Plasma Using Sine AC and Nanosecond Pulse Excitations for Purpose of Improving Indoor Air Quality

PubMed Central

Zhang, Li; Yang, Dezheng; Wang, Wenchun; Wang, Sen; Yuan, Hao; Zhao, Zilu; Sang, Chaofeng; Jia, Li

2016-01-01

In this study, needle-array to plate electrode configuration was employed to generate an atmospheric air diffuse discharge using both nanosecond pulse and sine AC voltage as excitation voltage for the purpose of improving indoor air quality. Different types of voltage sources and electrode configurations are employed to optimize electrical field distribution and improve discharge stability. Discharge images, electrical characteristics, optical emission spectra, and plasma gas temperatures in both sine AC discharge and nanosecond pulse discharge were compared and the discharge stability during long operating time were discussed. Compared with the discharge excited by sine AC voltage, the nanosecond pulsed discharge is more homogenous and stable, besides, the plasma gas temperature of nanosecond pulse discharge is much lower. Using packed-bed structure, where γ- Al2O3 pellets are filled in the electrode gap, has obvious efficacy in the production of homogenous discharge. Furthermore, both sine AC discharge and nanosecond pulse discharge were used for removing formaldehyde from flowing air. It shows that nanosecond pulse discharge has a significant advantage in energy cost. And the main physiochemical processes for the generation of active species and the degradation of formaldehyde were discussed. PMID:27125663

Time-of-flight direct recoil ion scattering spectrometer

DOEpatents

Krauss, Alan R.; Gruen, Dieter M.; Lamich, George J.

1994-01-01

A time of flight direct recoil and ion scattering spectrometer beam line (10). The beam line (10) includes an ion source (12) which injects ions into pulse deflection regions (14) and (16) separated by a drift space (18). A final optics stage includes an ion lens and deflection plate assembly (22). The ion pulse length and pulse interval are determined by computerized adjustment of the timing between the voltage pulses applied to the pulsed deflection regions (14) and (16).

Cheap streak camera based on the LD-S-10 intensifier tube

NASA Astrophysics Data System (ADS)

Dashevsky, Boris E.; Krutik, Mikhail I.; Surovegin, Alexander L.

1992-01-01

Basic properties of a new streak camera and its test results are reported. To intensify images on its screen, we employed modular G1 tubes, the LD-A-1.0 and LD-A-0.33, enabling magnification of 1.0 and 0.33, respectively. If necessary, the LD-A-0.33 tube may be substituted by any other image intensifier of the LDA series, the choice to be determined by the size of the CCD matrix with fiber-optical windows. The reported camera employs a 12.5- mm-long CCD strip consisting of 1024 pixels, each 12 X 500 micrometers in size. Registered radiation was imaged on a 5 X 0.04 mm slit diaphragm tightly connected with the LD-S- 10 fiber-optical input window. Electrons escaping the cathode are accelerated in a 5 kV electric field and focused onto a phosphor screen covering a fiber-optical plate as they travel between deflection plates. Sensitivity of the latter was 18 V/mm, which implies that the total deflecting voltage was 720 V per 40 mm of the screen surface, since reversed-polarity scan pulses +360 V and -360 V were applied across the deflection plate. The streak camera provides full scan times over the screen of 15, 30, 50, 100, 250, and 500 ns. Timing of the electrically or optically driven camera was done using a 10 ns step-controlled-delay (0 - 500 ns) circuit.

An Examination of Adaptive Reversion in Saccharomyces Cerevisiae

PubMed Central

Steele, D. F.; Jinks-Robertson, S.

1992-01-01

Reversion to Lys(+) prototrophy in a haploid yeast strain containing a defined lys2 frameshift mutation has been examined. When cells were plated on synthetic complete medium lacking only lysine, the numbers of Lys(+) revertant colonies accumulated in a time-dependent manner in the absence of any detectable increase in cell number. An examination of the distribution of the numbers of early appearing Lys(+) colonies from independent cultures suggests that the mutations to prototrophy occurred randomly during nonselective growth. In contrast, an examination of the distribution of late appearing Lys(+) colonies indicates that the underlying reversion events occurred after selective plating. No accumulation of Lys(+) revertants occurred when cells were starved for tryptophan, leucine or both lysine and tryptophan prior to plating selectively for Lys(+) revertants. These results indicate that mutations accumulate more frequently when they confer a selective advantage, and are thus consistent with the occurrence of adaptive mutations in yeast. PMID:1398066

A Highly Reversible Room-Temperature Sodium Metal Anode.

PubMed

Seh, Zhi Wei; Sun, Jie; Sun, Yongming; Cui, Yi

2015-11-25

Owing to its low cost and high natural abundance, sodium metal is among the most promising anode materials for energy storage technologies beyond lithium ion batteries. However, room-temperature sodium metal anodes suffer from poor reversibility during long-term plating and stripping, mainly due to formation of nonuniform solid electrolyte interphase as well as dendritic growth of sodium metal. Herein we report for the first time that a simple liquid electrolyte, sodium hexafluorophosphate in glymes (mono-, di-, and tetraglyme), can enable highly reversible and nondendritic plating-stripping of sodium metal anodes at room temperature. High average Coulombic efficiencies of 99.9% were achieved over 300 plating-stripping cycles at 0.5 mA cm(-2). The long-term reversibility was found to arise from the formation of a uniform, inorganic solid electrolyte interphase made of sodium oxide and sodium fluoride, which is highly impermeable to electrolyte solvent and conducive to nondendritic growth. As a proof of concept, we also demonstrate a room-temperature sodium-sulfur battery using this class of electrolytes, paving the way for the development of next-generation, sodium-based energy storage technologies.

Imaging of a Defect in Thin Plates Using the Time Reversal of Single Mode Lamb Waves

NASA Astrophysics Data System (ADS)

Jeong, Hyunjo; Lee, Jung-Sik; Bae, Sung-Min

2011-06-01

This paper presents an analytical investigation for a baseline-free imaging of a defect in plate-like structures using the time-reversal of Lamb waves. We first consider the flexural wave (A0 mode) propagation in a plate containing a defect, and reception and time reversal process of the output signal at the receiver. The received output signal is then composed of two parts: a directly propagated wave and a scattered wave from the defect. The time reversal of these waves recovers the original input signal, and produces two additional sidebands that contain the time-of-flight information on the defect location. One of the side band signals is then extracted as a pure defect signal. A defect localization image is then constructed from a beamforming technique based on the time-frequency analysis of the side band signal for each transducer pair in a network of sensors. The simulation results show that the proposed scheme enables the accurate, baseline-free detection of a defect, so that experimental studies are needed to verify the proposed method and to be applied to real structure.

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Calculation of mass transfer in the remote cutting of metals by radiation of a high-power repetitively pulsed CO2 laser

NASA Astrophysics Data System (ADS)

Gladush, G. G.; Rodionov, N. B.

2002-01-01

The mechanism of remote cutting of steel plates by radiation of a high-power repetitively pulsed CO2 laser is theoretically studied. The models of melt removal by the gravity force and the recoil pressure of material vapour are proposed and the sufficient conditions for the initiation of cutting are determined. A numerical model of a thermally thin plate was employed to describe the cutting for large focal spots.

Analysis of short pulse laser altimetry data obtained over horizontal path

NASA Technical Reports Server (NTRS)

Im, K. E.; Tsai, B. M.; Gardner, C. S.

1983-01-01

Recent pulsed measurements of atmospheric delay obtained by ranging to the more realistic targets including a simulated ocean target and an extended plate target are discussed. These measurements are used to estimate the expected timing accuracy of a correlation receiver system. The experimental work was conducted using a pulsed two color laser altimeter.

New hybrid reverse differential pulse position width modulation scheme for wireless optical communication

NASA Astrophysics Data System (ADS)

Liao, Renbo; Liu, Hongzhan; Qiao, Yaojun

2014-05-01

In order to improve the power efficiency and reduce the packet error rate of reverse differential pulse position modulation (RDPPM) for wireless optical communication (WOC), a hybrid reverse differential pulse position width modulation (RDPPWM) scheme is proposed, based on RDPPM and reverse pulse width modulation. Subsequently, the symbol structure of RDPPWM is briefly analyzed, and its performance is compared with that of other modulation schemes in terms of average transmitted power, bandwidth requirement, and packet error rate over ideal additive white Gaussian noise (AWGN) channels. Based on the given model, the simulation results show that the proposed modulation scheme has the advantages of improving the power efficiency and reducing the bandwidth requirement. Moreover, in terms of error probability performance, RDPPWM can achieve a much lower packet error rate than that of RDPPM. For example, at the same received signal power of -28 dBm, the packet error rate of RDPPWM can decrease to 2.6×10-12, while that of RDPPM is 2.2×10. Furthermore, RDPPWM does not need symbol synchronization at the receiving end. These considerations make RDPPWM a favorable candidate to select as the modulation scheme in the WOC systems.

Active and long-lived permanent forearc deformation driven by the subduction seismic cycle

NASA Astrophysics Data System (ADS)

Aron Melo, Felipe Alejandro

I have used geological, geophysical and engineering methods to explore mechanisms of upper plate, brittle deformation at active forearc regions. My dissertation particularly addresses the permanent deformation style experienced by the forearc following great subduction ruptures, such as the 2010 M w8.8 Maule, Chile and 2011 Mw9.0 Tohoku, Japan earthquakes. These events triggered large, shallow seismicity on upper plate normal faults above the rupture reaching Mw7.0. First I present new structural data from the Chilean Coastal Cordillera over the rupture zone of the Maule earthquake. The study area contains the Pichilemu normal fault, which produced the large crustal aftershocks of the megathrust event. Normal faults are the major neotectonic structural elements but reverse faults also exist. Crustal seismicity and GPS surface displacements show that the forearc experiences pulses of rapid coseismic extension, parallel to the heave of the megathrust, and slow interseismic, convergence-parallel shortening. These cycles, over geologic time, build the forearc structural grain, reactivating structures properly-oriented respect to the deformation field of each stage of the interplate cycle. Great subduction events may play a fundamental role in constructing the crustal architecture of extensional forearc regions. Static mechanical models of coseismic and interseismic upper plate deformation are used to explore for distinct features that could result from brittle fracturing over the two stages of the interplate cycle. I show that the semi-elliptical outline of the first-order normal faults along the Coastal Cordillera may define the location of a characteristic, long-lived megathrust segment. Finally, using data from the Global CMT catalog I analyzed the seismic behavior through time of forearc regions that have experienced great subduction ruptures >Mw7.7 worldwide. Between 61% and 83% of the cases where upper plate earthquakes exhibited periods of increased seismicity above background levels occurred contemporaneous to megathrust ruptures. That correlation is stronger for normal fault events than reverse or strike-slip crustal earthquakes. More importantly, for any given megathrust the summation of the Mw accounted by the forearc normal fault aftershocks appears to have a positive linear correlation with the Mw of the subduction earthquake -- the larger the megathrust the larger the energy released by forearc events.

Cold pulse and rotation reversals with turbulence spreading and residual stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hariri, F.; Naulin, V.; Juul Rasmussen, J.

2016-05-15

Transport modeling based on inclusion of turbulence spreading and residual stresses shows internal rotation reversals and polarity reversal of cold pulses, with a clear indication of nonlocal transport effects due to fast spreading in the turbulence intensity field. The effects of turbulence spreading and residual stress are calculated from the gradient of the turbulence intensity. In the model presented in this paper, the flux is carried by the turbulence intensity field, which in itself is subject to radial transport effects. The pulse polarity inversion and the rotation profile reversal positions are close to the radial location of the stable/unstable transition.more » Both effects have no direct explanation within the framework of classical transport modeling, where the fluxes are related directly to the linear growth rates, the turbulence intensity profile is not considered and the corresponding residual stress is absent. Our simulations are in qualitative agreement with measurements from ohmically heated plasmas. Rotation reversal at a finite radius is found in situations not displaying saturated confinement, which we identify as situations where the plasma is nearly everywhere unstable. As an additional and new effect, the model predicts a perturbation of the velocity profile following a cold pulse from the edge. This allows direct experimental confirmation of both the existence of residual stress caused by turbulence intensity profiles and fundamental ideas of transport modeling presented here.« less

Photonic microwave waveforms generation based on pulse carving and superposition in time-domain

NASA Astrophysics Data System (ADS)

Xia, Yi; Jiang, Yang; Zi, Yuejiao; He, Yutong; Tian, Jing; Zhang, Xiaoyu; Luo, Hao; Dong, Ruyang

2018-05-01

A novel photonic approach for various microwave waveforms generation based on time-domain synthesis is theoretically analyzed and experimentally investigated. In this scheme, two single-drive Mach-Zehnder modulators are used for pulses shaping. After shifting the phase and implementing envelopes superposition of the pulses, desired waveforms can be achieved in time-domain. The theoretic analysis and simulations are presented. In the experimental demonstrations, a triangular waveform, square waveform, and half duty cycle sawtooth (or reversed-sawtooth) waveform are generated successfully. By utilizing time multiplexing technique, a frequency-doubled sawtooth (or reversed-sawtooth) waveform with 100% duty cycle can be obtained. In addition, a fundamental frequency sawtooth (or reversed-sawtooth) waveform with 100% duty cycle can also be achieved by the superposition of square waveform and frequency-doubled sawtooth waveform.

Unsteady laminar boundary-layer calculations on oscillating configurations including backflow. Part 1: Flat plate, oscillating in its own plane

NASA Technical Reports Server (NTRS)

Geissler, W.

1983-01-01

A finite difference method has been developed to calculate the unsteady boundary layer over an oscillating flat plate. Low- and high frequency approximations were used for comparison with numerical results. Special emphasis was placed on the behavior of the flow and on the numerical calculation procedure as soon as reversed flow has occurred over part of the oscillation cycle. The numerical method displayed neither problems nor singular behavior at the beginning of or within the reversed flow region. Calculations, however, came to a limit where the back-flow region reached the plate's leading edge in the case of high oscillation amplitudes. It is assumed that this limit is caused by the special behavior of the flow at the plate's leading edge where the boundary layer equations are not valid.

Ultrafast magnetization reversal by picosecond electrical pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Yang; Wilson, Richard B.; Gorchon, Jon

The field of spintronics involves the study of both spin and charge transport in solid-state devices. Ultrafast magnetism involves the use of femtosecond laser pulses to manipulate magnetic order on subpicosecond time scales. Here, we unite these phenomena by using picosecond charge current pulses to rapidly excite conduction electrons in magnetic metals. We observe deterministic, repeatable ultrafast reversal of the magnetization of a GdFeCo thin film with a single sub–10-ps electrical pulse. The magnetization reverses in ~10 ps, which is more than one order of magnitude faster than any other electrically controlled magnetic switching, and demonstrates a fundamentally new electricalmore » switching mechanism that does not require spin-polarized currents or spin-transfer/orbit torques. The energy density required for switching is low, projecting to only 4 fJ needed to switch a (20 nm) 3 cell. This discovery introduces a new field of research into ultrafast charge current–driven spintronic phenomena and devices.« less

A Superfluid Pulse Tube Refrigerator Without Moving Parts for Sub-Kelvin Cooling

NASA Technical Reports Server (NTRS)

Miller, Franklin K.

2012-01-01

A report describes a pulse tube refrigerator that uses a mixture of He-3 and superfluid He-4 to cool to temperatures below 300 mK, while rejecting heat at temperatures up to 1.7 K. The refrigerator is driven by a novel thermodynamically reversible pump that is capable of pumping the He-3 He-4 mixture without the need for moving parts. The refrigerator consists of a reversible thermal magnetic pump module, two warm heat exchangers, a recuperative heat exchanger, two cold heat exchangers, two pulse tubes, and an orifice. It is two superfluid pulse tubes that run 180 out of phase. All components of this machine except the reversible thermal pump have been demonstrated at least as proof-of-concept physical models in previous superfluid Stirling cycle machines. The pump consists of two canisters packed with pieces of gadolinium gallium garnet (GGG). The canisters are connected by a superleak (a porous piece of VYCOR glass). A superconducting magnetic coil surrounds each of the canisters.

Ultrafast magnetization reversal by picosecond electrical pulses

DOE PAGES

Yang, Yang; Wilson, Richard B.; Gorchon, Jon; ...

2017-11-03

The field of spintronics involves the study of both spin and charge transport in solid-state devices. Ultrafast magnetism involves the use of femtosecond laser pulses to manipulate magnetic order on subpicosecond time scales. Here, we unite these phenomena by using picosecond charge current pulses to rapidly excite conduction electrons in magnetic metals. We observe deterministic, repeatable ultrafast reversal of the magnetization of a GdFeCo thin film with a single sub–10-ps electrical pulse. The magnetization reverses in ~10 ps, which is more than one order of magnitude faster than any other electrically controlled magnetic switching, and demonstrates a fundamentally new electricalmore » switching mechanism that does not require spin-polarized currents or spin-transfer/orbit torques. The energy density required for switching is low, projecting to only 4 fJ needed to switch a (20 nm) 3 cell. This discovery introduces a new field of research into ultrafast charge current–driven spintronic phenomena and devices.« less

Methods And System Suppressing Clutter In A Gain-Block, Radar-Responsive Tag System

DOEpatents

Ormesher, Richard C.; Axline, Robert M.

2006-04-18

Methods and systems reduce clutter interference in a radar-responsive tag system. A radar transmits a series of linear-frequency-modulated pulses and receives echo pulses from nearby terrain and from radar-responsive tags that may be in the imaged scene. Tags in the vicinity of the radar are activated by the radar's pulses. The tags receive and remodulate the radar pulses. Tag processing reverses the direction, in time, of the received waveform's linear frequency modulation. The tag retransmits the remodulated pulses. The radar uses a reversed-chirp de-ramp pulse to process the tag's echo. The invention applies to radar systems compatible with coherent gain-block tags. The invention provides a marked reduction in the strength of residual clutter echoes on each and every echo pulse received by the radar. SAR receiver processing effectively whitens passive-clutter signatures across the range dimension. Clutter suppression of approximately 14 dB is achievable for a typical radar system.

Areal Mass Oscillations in Planar Targets Due to Feedout: Theory and Simulations.

NASA Astrophysics Data System (ADS)

Velikovich, A. L.; Schmitt, A. J.; Karasik, M.; Obenschain, S. P.; Serlin, V.; Pawley, C. J.; Gardner, J. H.; Aglitskiy, Y.; Metzler, N.

2001-10-01

When a planar shock wave breaks out at a rippled rear surface of a laser-driven target, the lateral pressure gradient in a rippled rarefaction wave propagating back to the front surface causes a lateral mass redistribution that reverses the phase of mass variation. If the driving laser pulse has no foot, then the RT growth, starting when the rarefaction wave reaches the front surface, causes the second phase reversal of mass variation, and continues at the initial phase, as consistently observed in feedout experiments on Nike. A foot of the laser pulse can cause an early phase reversal of mass variation, making the strong shock wave driven by the main pulse interact with a density variation in a rippled rarefaction wave rather than with static rear surface ripples. Theory and simulations predict that this interaction can make the phase of mass variation reverse one or three times. Then the phase of the RT growing mode would be opposite to that of the initial mass variation.

Non-Contact Determination of Antisymmetric Plate Wave Velocity in Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Kautz, Harold E.

1996-01-01

A 13 mJ NdYAG 1064 nm, 4 ns, laser pulse was employed to produce ultrasonic plate waves in 20 percent porous SiC/SiC composite tensile specimens of three different architectures. An air coupled 0.5 MHz transducer was used to detect and collect the waveforms which contained first antisymmetric plate wave pulses for determining the shear wave velocity (VS). These results were compared to VS values determined on the same specimens with 0.5 MHz ultrasonic transducers with contact coupling. Averages of four noncontact determinations on each of 18 specimens were compared to averages of four contact values. The noncontact VS's fall in the same range as the contact. The standard deviations for the noncontact VS's averaged 2.8 percent. The standard deviations for the contact measurements averaged 2.3 percent, indicating similar reproducibility. Repeated laser pulsing at the same location always lead to deterioration of the ulu-"nic signal. The signal would recover in about 24 hr in air however, indicating that no permanent damage was produced.

Modeling of a microchannel plate working in pulsed mode

NASA Astrophysics Data System (ADS)

Secroun, Aurelia; Mens, Alain; Segre, Jacques; Assous, Franck; Piault, Emmanuel; Rebuffie, Jean-Claude

1997-05-01

MicroChannel Plates (MCPs) are used in high speed cinematography systems such as MCP framing cameras and streak camera readouts. In order to know the dynamic range or the signal to noise ratio that are available in these devices, a good knowledge of the performances of the MCP is essential. The point of interest of our simulation is the working mode of the microchannel plate--that is light pulsed mode--, in which the signal level is relatively high and its duration can be shorter than the time needed to replenish the wall of the channel, when other papers mainly studied night vision applications with weak continuous and nearly single electron input signal. Also our method allows the simulation of saturation phenomena due to the large number of electrons involved, whereas the discrete models previously used for simulating pulsed mode might not be properly adapted. Here are presented the choices made in modeling the microchannel, more specifically as for the physics laws, the secondary emission parameters and the 3D- geometry. In a last part first results are shown.

Measurement of OH Radicals in Pulsed Corona and Pulsed Dielectric Barrier Discharge

NASA Astrophysics Data System (ADS)

Ono, Ryo; Oda, Tetsuji

OH radicals are measured in a pulsed corona or a pulsed dielectric barrier discharge (DBD) using laserinduced fluorescence (LIF) method. The pulsed discharges occur in nitrogen-oxygen mixture with 2.4% water vapor at atmospheric pressure. The pulse width is 100ns and the peak voltage is 35kV. The electrode configuration is a needle to plate electrode with 16-mm gap for corona discharge, and with 5-mm gap for DBD where the barrier is 2mm thick glass plate. It is shown that OH density is approximately proportional to the energy consumed by the discharge. The OH density per the discharge energy is about 2-4×1014cm-3/mJ for both discharges in H2O(2.4%)/N2 mixture. It is shown that OH density increases with oxygen content in DBD, whereas OH density reaches a maximum at 3% oxygen content in corona discharge. The existence of oxygen accelerates OH decay rate in both discharges. A trace amount of trichloroethylene (TCE) is added to the ambient gas. It is shown that the addition of 100ppm TCE to corona discharge reduces discharge current by about 50%. That leads to decrease of OH production.

High-damage-threshold antireflection coatings on diamond for CW and pulsed CO2 lasers

NASA Astrophysics Data System (ADS)

Komlenok, M. S.; Pivovarov, P. A.; Volodkin, B. O.; Pavelyev, V. S.; Anisimov, V. I.; Butuzov, V. V.; Sorochenko, V. R.; Nefedov, S. M.; Mineev, A. P.; Soifer, V. A.; Konov, V. I.

2018-03-01

A multilayer antireflection coating for diamond optics that allows work in the infrared spectral range of 8 -12 µm with minimal optical losses is developed. The optical transmittance of a chemical vapour deposition diamond plate coated with this film on both sides exceeds 94% over the whole specified wavelength range. The coatings deposited on the diamond plate were damage-tested by coherent-wave and pulsed (τ  =  90 ns) CO2 lasers. Results of the tests demonstrated that the coating can withstand prolonged radiation loads with intensity above 3 MW cm-2 in a continuous-mode laser exposure. In the case of a nanosecond pulsed action, destruction of the coating begins at intensities greater than 50 MW cm-2.

Finding Platinum-Coating Gaps On Titanium Anodes

NASA Technical Reports Server (NTRS)

Bodemeijer, Ronnald; Flowers, Cecil E.

1990-01-01

Simple procedure makes gaps visible to eye. New gap-detection method consists of plating thin layer of non-silver-colored metal like copper or gold on anode. Contrast in color between plated metal and bare anode material makes gaps stand out. If anode passes inspection, copper or gold plate removable by reversal of test-plating current. Remains to be determined whether test plating and removal damages anode. New method simpler and more economical than previous attempts to identify gaps in platinum.

Laser-launched flyer plate and confined laser ablation for shock wave loading: validation and applications.

PubMed

Paisley, Dennis L; Luo, Sheng-Nian; Greenfield, Scott R; Koskelo, Aaron C

2008-02-01

We present validation and some applications of two laser-driven shock wave loading techniques: laser-launched flyer plate and confined laser ablation. We characterize the flyer plate during flight and the dynamically loaded target with temporally and spatially resolved diagnostics. With transient imaging displacement interferometry, we demonstrate that the planarity (bow and tilt) of the loading induced by a spatially shaped laser pulse is within 2-7 mrad (with an average of 4+/-1 mrad), similar to that in conventional techniques including gas gun loading. Plasma heating of target is negligible, in particular, when a plasma shield is adopted. For flyer plate loading, supported shock waves can be achieved. Temporal shaping of the drive pulse in confined laser ablation allows for flexible loading, e.g., quasi-isentropic, Taylor-wave, and off-Hugoniot loading. These techniques can be utilized to investigate such dynamic responses of materials as Hugoniot elastic limit, plasticity, spall, shock roughness, equation of state, phase transition, and metallurgical characteristics of shock-recovered samples.

Investigation of Temperature Change under Influence of Ultrashort Laser Pulses Taking into Account Relaxation Properties of Materials

NASA Astrophysics Data System (ADS)

Eremin, A. V.; Kudinov, V. A.; Stefanyuk, E. V.; Kudinov, I. V.

2018-03-01

By using the modified Fourier law’s formula considering the relaxation of heat flow and temperature gradient, a mathematical model of the local non-equilibrium process of plate heating with ultrashort laser pulses was developed. The research showed that consideration of non-locality results in the delayed plate heat up irrespective of the laser radiation flow intensity. It was also shown that in consideration of the relaxation phenomena, the boundary conditions may not be fulfilled immediately – they may be set only within a definite range of the initial time.

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

Laser processing of polymer constructs from poly(3-hydroxybutyrate).

PubMed

Volova, T G; Tarasevich, A A; Golubev, A I; Boyandin, A N; Shumilova, A A; Nikolaeva, E D; Shishatskaya, E I

2015-01-01

CO2 laser radiation was used to process poly(3-hydroxybutyrate) constructs - films and 3D pressed plates. Laser processing increased the biocompatibility of unperforated films treated with moderate uniform radiation, as estimated by the number and degree of adhesion of NIH 3T3 mouse fibroblast cells. The biocompatibility of perforated films modified in the pulsed mode did not change significantly. At the same time, pulsed laser processing of the 3D plates produced perforated scaffolds with improved mechanical properties and high biocompatibility with bone marrow-derived multipotent, mesenchymal stem cells, which show great promise for bone regeneration.

Reduction in the write error rate of voltage-induced dynamic magnetization switching using the reverse bias method

NASA Astrophysics Data System (ADS)

Ikeura, Takuro; Nozaki, Takayuki; Shiota, Yoichi; Yamamoto, Tatsuya; Imamura, Hiroshi; Kubota, Hitoshi; Fukushima, Akio; Suzuki, Yoshishige; Yuasa, Shinji

2018-04-01

Using macro-spin modeling, we studied the reduction in the write error rate (WER) of voltage-induced dynamic magnetization switching by enhancing the effective thermal stability of the free layer using a voltage-controlled magnetic anisotropy change. Marked reductions in WER can be achieved by introducing reverse bias voltage pulses both before and after the write pulse. This procedure suppresses the thermal fluctuations of magnetization in the initial and final states. The proposed reverse bias method can offer a new way of improving the writing stability of voltage-driven spintronic devices.

Nonlinear Time-Reversal in a Wave Chaotic System

NASA Astrophysics Data System (ADS)

Frazier, Matthew; Taddese, Biniyam; Ott, Edward; Antonsen, Thomas; Anlage, Steven

2012-02-01

Time reversal mirrors are particularly simple to implement in wave chaotic systems and form the basis for a new class of sensors [1-3]. These sensors work by applying the quantum mechanical concepts of Loschmidt echo and fidelity decay to classical waves. The sensors make explicit use of time-reversal invariance and spatial reciprocity in a wave chaotic system to remotely measure the presence of small perturbations to the system. The underlying ray chaos increases the sensitivity to small perturbations throughout the volume explored by the waves. We extend our time-reversal mirror to include a discrete element with a nonlinear dynamical response. The initially injected pulse interacts with the nonlinear element, generating new frequency components originating at the element. By selectively filtering for and applying the time-reversal mirror to the new frequency components, we focus a pulse only onto the element, without knowledge of its location. Furthermore, we demonstrate transmission of arbitrary patterns of pulses to the element, creating a targeted communication channel to the exclusion of 'eavesdroppers' at other locations in the system. [1] Appl. Phys. Lett. 95, 114103 (2009) [2] J. Appl. Phys. 108, 1 (2010) [3] Acta Physica Polonica A 112, 569 (2007)

Wave propagation in a plate after impact by a projectile

NASA Technical Reports Server (NTRS)

El-Raheb, M.; Wagner, P.

1987-01-01

The wave propagation in a circular plate after impact by a cylindrical projectile is studied. In the vicinity of impact, the pressure is computed numerically. An intense pressure pulse is generated that peaks 0.2 microns after impact, then drops sharply to a plateau. The response of the plate is determined adopting a modal solution of Mindlin's equations. Velocity and acceleration histories display both propagating and dispersive features.

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.

Simulation of the Transverse Injection of a Pulsed Jet from the Surface of a Flat Plate into a Supersonic Flow

NASA Astrophysics Data System (ADS)

Volkov, K. N.; Emelyanov, V. N.; Yakovchuk, M. S.

2017-11-01

The transverse injection of a pulsed jet into a supersonic flow for thrust vectoring in solid rocket motors is investigated. The gas flow through the injection nozzle is controlled by a piston which performs reciprocating motion. Reynolds-averaged Navier-Stokes equations and the ( k- ɛ) turbulence model equations are discretized using the finite volume method and moving grids. The pressure distributions on the plate surface obtained using various approaches to the description of the flow field and difference schemes are compared. The solution obtained for the case of injection of a pulsed jet is compared with the solution for the case where a valve prevents gas flow through the injection nozzle. The dependence of the control force produced by gas injection on time is investigated.

A novel laser ranging system for measurement of ground-to-satellite distances

NASA Technical Reports Server (NTRS)

Golden, K. E.; Kind, D. E.; Leonard, S. L.; Ward, R. C.

1973-01-01

A technique was developed for improving the precision of laser ranging measurements of ground-to-satellite distances. The method employs a mode-locked laser transmitter and utilizes an image converter tube equipped with deflection plates in measuring the time of flight of the laser pulse to a distant retroreflector and back. Samples of the outgoing and returning light pulses are focussed on the photocathode of the image converter tube, whose deflection plates are driven by a high-voltage 120 MHz sine wave derived from a very stable oscillator. From the relative positions of the images produced at the output phosphor by the two light pulses, it is possible to make a precise determination of the fractional amount by which the time of flight exceeds some large integral multiple of the period of the deflection sinusoid.

Particle image velocimetry based on wavelength division multiplexing

NASA Astrophysics Data System (ADS)

Tang, Chunxiao; Li, Enbang; Li, Hongqiang

2018-01-01

This paper introduces a technical approach of wavelength division multiplexing (WDM) based particle image velocimetry (PIV). It is designed to measure transient flows with different scales of velocity by capturing multiple particle images in one exposure. These images are separated by different wavelengths, and thus the pulse separation time is not influenced by the frame rate of the camera. A triple-pulsed PIV system has been created in order to prove the feasibility of WDM-PIV. This is demonstrated in a sieve plate extraction column model by simultaneously measuring the fast flow in the downcomer and the slow vortices inside the plates. A simple displacement/velocity field combination method has also been developed. The constraints imposed by WDM-PIV are limited wavelength choices of available light sources and cameras. The usage of WDM technique represents a feasible way to realize multiple-pulsed PIV.

Pulse plating of Pt on n-GaAs ( 1 0 0 ) wafer surfaces: Synchrotron induced photoelectron spectroscopy and XPS of wet fabrication processes

NASA Astrophysics Data System (ADS)

Ensling, D.; Hunger, R.; Kraft, D.; Mayer, Th.; Jaegermann, W.; Rodriguez-Girones, M.; Ichizli, V.; Hartnagel, H. L.

2003-01-01

Preparation steps of Pt/n-GaAs Schottky contacts as applied in the fabrication process of varactor diode arrays for THz applications are analysed by photoelectron spectroscopy. Pulsed cathodic deposition of Pt onto GaAs (1 0 0) wafer surfaces from acidic solution has been studied by core level photoelectron spectroscopy using different excitation energies. A laboratory AlKα source as well as synchrotron radiation of hν=130 and 645 eV at BESSY was used. Chemical analyses and semiquantitative estimates of layer thickness are given for the natural oxide of an untreated wafer surface, a surface conditioning NH 3 etching step, and stepwise pulse plating of Pt. The structural arrangement of the detected species and interface potentials are considered.

Blade Sections in Streamwise Oscillations into Reverse Flow

DTIC Science & Technology

2015-05-07

NC 27709-2211 Reverse Flow, Oscillating Airfoils , Oscillating Freesteam REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR...plate or bluff body rather than an airfoil . Reverse flow operation requires investigation and quantification to accurately capture these Submitted for... airfoil integrated quantities (lift, drag, moment) in reverse flow and developed new algorithms for comprehensive codes, reducing errors from 30 %–50

TEMPS (Transportable EMP Simulator) Final Report. Volume 2. Appendixes

DTIC Science & Technology

1973-08-01

Electromagnetic pulse Pulser system Pulse generator 20. ASSTRPACT (Confirma an reverse ese It neessary and IdmntSIy by Weeck pmbff) This report...Research Institute I>, PIFR-372 A.1 INTRODUCTION The Transportable Electromagnetic Pulse Simulator (TEMPS) was built for the Harry Diamond Laboratories

Temporal development and chemical efficiency of positive streamers in a large scale wire-plate reactor as a function of voltage waveform parameters

NASA Astrophysics Data System (ADS)

Winands, G. J. J.; Liu, Z.; Pemen, A. J. M.; van Heesch, E. J. M.; Yan, K.; van Veldhuizen, E. M.

2006-07-01

In this paper a large-scale pulsed corona system is described in which pulse parameters such as pulse rise-time, peak voltage, pulse width and energy per pulse can be varied. The chemical efficiency of the system is determined by measuring ozone production. The temporal and spatial development of the discharge streamers is recorded using an ICCD camera with a shortest exposure time of 5 ns. The camera can be triggered at any moment starting from the time the voltage pulse arrives on the reactor, with an accuracy of less than 1 ns. Measurements were performed on an industrial size wire-plate reactor. The influence of pulse parameters like pulse voltage, DC bias voltage, rise-time and pulse repetition rate on plasma generation was monitored. It was observed that for higher peak voltages, an increase could be seen in the primary streamer velocity, the growth of the primary streamer diameter, the light intensity and the number of streamers per unit length of corona wire. No significant separate influence of DC bias voltage level was observed as long as the total reactor voltage (pulse + DC bias) remained constant and the DC bias voltage remained below the DC corona onset. For those situations in which the plasma appearance changed (e.g. different streamer velocity, diameter, intensity), a change in ozone production was also observed. The best chemical yields were obtained for low voltage (55 kV), low energetic pulses (0.4 J/pulse): 60 g (kWh)-1. For high voltage (86 kV), high energetic pulses (2.3 J/pulse) the yield decreased to approximately 45 g (kWh)-1, still a high value for ozone production in ambient air (RH 42%). The pulse repetition rate has no influence on plasma generation and on chemical efficiency up to 400 pulses per second.

Treatment of chromium contaminated plating shop rinsewater streams by reverse osmosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, J.F.; Brown, C.H. Jr.; Wilson, J.H.

1988-01-01

Wastewater is discharged to the local sanitary sewer, which is regulated by a Metropolitan Sewer District (MSD). The MSD has established discharge limits and reports have indicated that the major source of wastewater and primary area of concern is the discharge from the industrial plating shop within the plant complex. This plating shop generates /approximately/1100 m/sup 3/ (300,000 gal) of wastewater per day. Because construction of a new plating shop is currently planned, a complete renovation of the existing plating shop is not economically feasible. The sponsor demonstrated the use of innovative wastewater treatment technologies that will minimize the amountmore » of wastewater generated from the plating processes and maintain compliance with MSD discharge limits until the new plating shop is constructed. The problems at the facility have been analyzed and a treatment system utilizing reverse osmosis (RO), with volume reduction of the RO concentrate by evaporation, has been recommended. The utilization of RO meets the specification for the demonstration of innovative technology. This paper discusses the problem analysis at the plant as well as the results of a pilot scale RO test program currently being conducted. The installation of the full scale unit is dependent on the successful completion of the RO pilot tests. 1 ref., 6 figs., 3 tabs.« less

Late Miocene Pacific plate kinematic change explained with coupled global models of mantle and lithosphere dynamics

NASA Astrophysics Data System (ADS)

Stotz, I. L.; Iaffaldano, G.; Davies, D. R.

2017-07-01

The timing and magnitude of a Pacific plate motion change within the past 10 Ma remains enigmatic, due to the noise associated with finite-rotation data. Nonetheless, it has been hypothesized that this change was driven by the arrival of the Ontong Java Plateau (OJP) at the Melanesian arc and the consequent subduction polarity reversal. The uncertainties associated with the timing of this event, however, make it difficult to quantitatively demonstrate a dynamical association. Here, we first reconstruct the Pacific plate's absolute motion since the mid-Miocene (15 Ma), at high-temporal resolution, building on previous efforts to mitigate the impact of finite-rotation data noise. We find that the largest change in Pacific plate-motion direction occurred between 10 and 5 Ma, with the plate rotating clockwise. We subsequently develop and use coupled global numerical models of the mantle/lithosphere system to test hypotheses on the dynamics driving this change. These indicate that the arrival of the OJP at the Melanesian arc, between 10 and 5 Ma, followed by a subduction polarity reversal that marked the initiation of subduction of the Australian plate underneath the Pacific realm, were the key drivers of this kinematic change.

A novel method to study single-particle dynamics by the resistive pulse technique

NASA Astrophysics Data System (ADS)

Berge, L. I.; Feder, J.; Jøssang, T.

1989-08-01

We have developed a new method, a pressure-reversal technique, which extends the uses of the resistive pulse (Coulter counter) technique to single-particle dynamics. The resistive pulse technique measures the increase in resistance when particles suspended in an electrolyte are transported through a current-carrying aperture. By the new method, the pressure is reversed when a particle exits the pore. A trigger signal, derived from the particle pulses, is used to activate two miniature solenoid valves which serve as pressure switches. In this way, the particle reenters the pore. A single particle flowing back and forth may be studied over a long period of time. The time the particle spends outside the pore between reversals is variable from a few milliseconds to several seconds. We have so far used pore diameters in the range of 3-30 μm. The new technique enables us to study single-particle dissolution and single-particle flow dynamics. The experimental arrangement and the details of the new method are described together with some illustrative measurements.

How to Drive CARS in Reverse

DTIC Science & Technology

2013-11-07

pulse . This pulse is then used to drive a coherent anti-Stokes Raman scattering scheme, resulting in a strong chemically specific signal propagating...generation of a backward propagating stimulated Raman pulse . This pulse is then used to drive a coherent anti-Stokes Raman scattering scheme, resulting in a...proposed to re- motely generate a spatially coherent backward propagating pulse . The first uses the impurities in air as a lasing medium [2]. Two photon

Improving Plating by Use of Intense Acoustic Beams

NASA Technical Reports Server (NTRS)

Oeftering, Richard C.; Denofrio, Charles

2003-01-01

An improved method of selective plating of metals and possibly other materials involves the use of directed high-intensity acoustic beams. The beams, typically in the ultrasonic frequency range, can be generated by fixed-focus transducers (see figure) or by phased arrays of transducers excited, variously, by continuous waves, tone bursts, or single pulses. The nonlinear effects produced by these beams are used to alter plating processes in ways that are advantageous.

Tunable time-reversal cavity for high-pressure ultrasonic pulses generation: A tradeoff between transmission and time compression

NASA Astrophysics Data System (ADS)

Arnal, Bastien; Pernot, Mathieu; Fink, Mathias; Tanter, Mickael

2012-08-01

This Letter presents a time reversal cavity that has both a high reverberation time and a good transmission factor. A multiple scattering medium has been embedded inside a fluid-filled reverberating cavity. This allows creating smart ultrasonic sources able to generate very high pressure pulses at the focus outside the cavity with large steering capabilities. Experiments demonstrate a 25 dB gain in pressure at the focus. This concept will enable us to convert conventional ultrasonic imaging probes driven by low power electronics into high power probes for therapeutic applications requiring high pressure focused pulses, such as histotripsy or lithotripsy.

Gas composition sensing using carbon nanotube arrays

NASA Technical Reports Server (NTRS)

Li, Jing (Inventor); Meyyappan, Meyya (Inventor)

2008-01-01

A method and system for estimating one, two or more unknown components in a gas. A first array of spaced apart carbon nanotubes (''CNTs'') is connected to a variable pulse voltage source at a first end of at least one of the CNTs. A second end of the at least one CNT is provided with a relatively sharp tip and is located at a distance within a selected range of a constant voltage plate. A sequence of voltage pulses {V(t.sub.n)}.sub.n at times t=t.sub.n (n=1, . . . , N1; N1.gtoreq.3) is applied to the at least one CNT, and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of a curve I(t.sub.n) for current or a curve e(t.sub.n) for electric charge transported from the at least one CNT to the constant voltage plate. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas.

Comparison of continuous versus pulsed photodynamic antimicrobial therapy for inhibition of fungal keratitis isolates in vitro (Conference Presentation)

NASA Astrophysics Data System (ADS)

Nolan, Nicholas; Durkee, Heather A.; Aguilar, Mariela C.; Arboleda, Alejandro; Relhan, Nidhi; Martinez, Anna; Rowaan, Cornelis; Gonzalez, Alex; Alawa, Karam A.; Amescua, Guillermo; Flynn, Harry W.; Miller, Darlene; Parel, Jean-Marie A.

2017-02-01

Fungal keratitis can lead to pain and impaired vision. Current treatment options include antifungal agents and therapeutic penetrating keratoplasty. An emerging option for the management of keratitis is photodynamic antimicrobial therapy (PDAT) which uses a photosensitizer rose bengal activated with green light. Utilizing a pulsed irradiation, rather than the standard continuous irradiation may have a similar antimicrobial effect with less total energy. This study is to compare pulsed and continuous rose bengal mediated PDAT for inhibition of six fungal isolates on agar plates: Fusarium solani, Fusarium keratoplasticum, Aspergillus fumigatus, Candida albicans, Paecilomyces variotti, and Pseudoallescheria boydii. Isolates were mixed with 0.1% rose bengal and exposed to three irradiation conditions: (1) 30-minute continuous (10.8J/cm2), (2) 15-minute continuous (5.4J/cm2), (3) 30-minute pulsed (5.4J/cm2). Plates were photographed at 72 hours and analyzed with custom software. At 72 hours, 30-minute continuous rose bengal mediated PDAT inhibited all six fungal species. Fungal inhibition was analogous between 30-minute continuous and 30-minute pulsed test groups, with the exception of A. fumigatus. The 15-minute continuous irradiation was less effective when compared to both 30-minute continuous and 30-minute pulsed groups. These in vitro results demonstrate the potential strength of pulsed rose bengal mediated PDAT as an adjunct treatment modality for fungal keratitis.

Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

NASA Astrophysics Data System (ADS)

Furukawa, Yuki; Sakata, Ryoichi; Konishi, Kazuki; Ono, Koki; Matsuoka, Shusaku; Watanabe, Kota; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji

2016-06-01

By pairing femtosecond laser pulses (duration ˜40 fs and central wavelength ˜810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm2 and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm2, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

PULSE COLUMN

DOEpatents

Grimmett, E.S.

1964-01-01

This patent covers a continuous countercurrent liquidsolids contactor column having a number of contactor states each comprising a perforated plate, a layer of balls, and a downcomer tube; a liquid-pulsing piston; and a solids discharger formed of a conical section at the bottom of the column, and a tubular extension on the lowest downcomer terminating in the conical section. Between the conical section and the downcomer extension is formed a small annular opening, through which solids fall coming through the perforated plate of the lowest contactor stage. This annular opening is small enough that the pressure drop thereacross is greater than the pressure drop upward through the lowest contactor stage. (AEC)

Shot H3837: Darht's first dual-axis explosive experiment

NASA Astrophysics Data System (ADS)

Harsh, James F.; Hull, Lawrence; Mendez, Jacob; McNeil, Wendy Vogan

2012-03-01

Test H3837 was the first explosive shot performed in front of both flash x-ray axes at the Los Alamos Dual Axis Radiographic Hydrodynamic Test (DARHT) facility. Executed in November 2009, the shot was an explosively-driven metal flyer plate in a series of experiments designed to explore equation-of-state properties of shocked materials. Imaging the initial shock wave traveling through the flyer plate, DARHT Axis II captured the range of motion from the shock front emergence in the flyer to breakout at the free surface; the Axis I pulse provided a perpendicular perspective of the shot at a time coinciding with the third pulse of Axis II.

Carbon-assisted flyer plates

DOEpatents

Stahl, D.B.; Paisley, D.L.

1994-04-12

A laser driven flyer plate is described utilizing an optical fiber connected to a laser. The end of the optical fiber has a layer of carbon and a metal layer deposited onto it. The carbon layer provides the laser induced plasma which is superior to the plasma produced from most metals. The carbon layer plasma is capable of providing a flatter flyer plate, converting more of the laser energy to driving plasma, promoting a higher flyer plate acceleration, and providing a more uniform pulse behind the plate. In another embodiment, the laser is in optical communication with a substrate onto which a layer of carbon and a layer of metal have been deposited. 2 figures.

Plasma-Based Detector of Outer-Space Dust Particles

NASA Technical Reports Server (NTRS)

Tsurutani, Bruce; Brinza, David E.; Henry, Michael D.; Clay, Douglas R.

2006-01-01

A report presents a concept for an instrument to be flown in outer space, where it would detect dust particles - especially those associated with comets. The instrument would include a flat plate that would intercept the dust particles. The anticipated spacecraft/dust-particle relative speeds are so high that the impingement of a dust particle on the plate would generate a plasma cloud. Simple electric dipole sensors located equidistantly along the circumference of the plate would detect the dust particle indirectly by detecting the plasma cloud. The location of the dust hit could be estimated from the timing of the detection pulses of the different dipoles. The mass and composition of the dust particle could be estimated from the shapes and durations of the pulses from the dipoles. In comparison with other instruments for detecting hypervelocity dust particles, the proposed instrument offers advantages of robustness, large collection area, and simplicity.

Parameters influencing focalization spot in time reversal of acoustic waves

NASA Astrophysics Data System (ADS)

Zophoniasson, Harald; Bolzmacher, Christian; Hafez, Moustafa

2015-05-01

Time reversal is an approach that can be used to focus acoustic waves in a particular location on a surface, allowing a multitouch tactile feedback interaction. The spatial resolution in this case depends on several parameters, such as geometrical parameters, frequency used and material properties, described by the Lamb wave theory. This paper highlights the impact of frequency, geometrical parameters such as plate thickness and transducer's surface on the focused spot dimensions. In this paper a study of the influence of the plate's thickness and the frequency bandwidth used in the focusing process is presented. It is also shown that the dimension of the piezoelectric diaphragms used has little influence on the spatial resolution. Resonant behavior of the plate and its implication on focus point dimension and focalization contrast were investigated.

Characterisation of a Zn / Ni Plating Bath

DTIC Science & Technology

2009-09-03

accelerated corrosion in the first stages which is then slowed down by its own product of corrosion, Zn(OH)212. Zinc hydroxide dehydrates in time to form ZnO ... Electrochemistry , 1991, 21, 642 [5] – Alfantasi, A.M., A study on the synthesis, characterization ans properties of pulse-plated ultrafine- grained Zn-Ni alloy

Electric field measurements in nanosecond pulse discharges in air over liquid water surface

NASA Astrophysics Data System (ADS)

Simeni Simeni, Marien; Baratte, Edmond; Zhang, Cheng; Frederickson, Kraig; Adamovich, Igor V.

2018-01-01

Electric field in nanosecond pulse discharges in ambient air is measured by picosecond four-wave mixing, with absolute calibration by a known electrostatic field. The measurements are done in two geometries, (a) the discharge between two parallel cylinder electrodes placed inside quartz tubes, and (b) the discharge between a razor edge electrode and distilled water surface. In the first case, breakdown field exceeds DC breakdown threshold by approximately a factor of four, 140 ± 10 kV cm-1. In the second case, electric field is measured for both positive and negative pulse polarities, with pulse durations of ˜10 ns and ˜100 ns, respectively. In the short duration, positive polarity pulse, breakdown occurs at 85 kV cm-1, after which the electric field decreases over several ns due to charge separation in the plasma, with no field reversal detected when the applied voltage is reduced. In a long duration, negative polarity pulse, breakdown occurs at a lower electric field, 30 kV cm-1, after which the field decays over several tens of ns and reverses direction when the applied voltage is reduced at the end of the pulse. For both pulse polarities, electric field after the pulse decays on a microsecond time scale, due to residual surface charge neutralization by transport of opposite polarity charges from the plasma. Measurements 1 mm away from the discharge center plane, ˜100 μm from the water surface, show that during the voltage rise, horizontal field component (Ex ) lags in time behind the vertical component (Ey ). After breakdown, Ey is reduced to near zero and reverses direction. Further away from the water surface (≈0.9 mm), Ex is much higher compared to Ey during the entire voltage pulse. The results provide insight into air plasma kinetics and charge transport processes near plasma-liquid interface, over a wide range of time scales.

Study on the Shielding Effectiveness of an Arc Thermal Metal Spraying Method against an Electromagnetic Pulse

PubMed Central

Lee, Han-Seung; Choe, Hong-Bok; Baek, In-Young

2017-01-01

An electromagnetic pulse (EMP) explodes in real-time and causes critical damage within a short period to not only electric devices, but also to national infrastructures. In terms of EMP shielding rooms, metal plate has been used due to its excellent shielding effectiveness (SE). However, it has difficulties in manufacturing, as the fabrication of welded parts of metal plates and the cost of construction are non-economical. The objective of this study is to examine the applicability of the arc thermal metal spraying (ATMS) method as a new EMP shielding method to replace metal plate. The experimental parameters, metal types (Cu, Zn-Al), and coating thickness (100–700 μm) used for the ATMS method were considered. As an experiment, a SE test against an EMP in the range of 103 to 1010 Hz was conducted. Results showed that the ATMS coating with Zn-Al had similar shielding performance in comparison with metal plate. In conclusion, the ATMS method is judged to have a high possibility of actual application as a new EMP shielding material. PMID:28976931

Study on the Shielding Effectiveness of an Arc Thermal Metal Spraying Method against an Electromagnetic Pulse.

PubMed

Lee, Han-Seung; Choe, Hong-Bok; Baek, In-Young; Singh, Jitendra Kumar; Ismail, Mohamed A

2017-10-04

An electromagnetic pulse (EMP) explodes in real-time and causes critical damage within a short period to not only electric devices, but also to national infrastructures. In terms of EMP shielding rooms, metal plate has been used due to its excellent shielding effectiveness (SE). However, it has difficulties in manufacturing, as the fabrication of welded parts of metal plates and the cost of construction are non-economical. The objective of this study is to examine the applicability of the arc thermal metal spraying (ATMS) method as a new EMP shielding method to replace metal plate. The experimental parameters, metal types (Cu, Zn-Al), and coating thickness (100-700 μm) used for the ATMS method were considered. As an experiment, a SE test against an EMP in the range of 103 to 1010 Hz was conducted. Results showed that the ATMS coating with Zn-Al had similar shielding performance in comparison with metal plate. In conclusion, the ATMS method is judged to have a high possibility of actual application as a new EMP shielding material.

Unsplit bipolar pulse forming line

DOEpatents

Rhodes, Mark A [Pleasanton, CA

2011-05-24

A bipolar pulse forming transmission line module and system for linear induction accelerators having first, second, third, and fourth planar conductors which form a sequentially arranged interleaved stack having opposing first and second ends, with dielectric layers between the conductors. The first and second planar conductors are connected to each other at the first end, and the first and fourth planar conductors are connected to each other at the second end via a shorting plate. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short at the first end a high voltage from the third planar conductor to the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

Investigation of nanosecond pulsed dielectric barrier discharge using plate-to-plate electrode with asymmetric dielectric arrangement in airflow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qi, Haicheng; School of Physics Science and Technology, Anshan Normal University, Anshan 114005; Fan, Zhihui

Atmospheric pressure dielectric barrier discharge plasma is produced in airflow by applying nanosecond high voltage pulses with peak voltage about 35 kV and rising time about 40 ns on a plate-to-plate electrode arrangement. The effects of airflow rate (0–50 m/s) on the discharge characteristics are investigated under different barrier conditions (the bare anode case and the bare cathode case). For both cases, the breakdown voltage and the time lag increase distinctly and the discharge intensity decreases sharply when the airflow rate increases from 0 to 30 m/s, and then keep almost constant until the airflow rate is further increased to 50 m/s. For the baremore » anode case (the cathode is covered by dielectric plate), the discharge mode transforms gradually from filamentary to diffuse discharge with the increasing airflow rate. While for the bare cathode case, some micro-discharge channels are still excited, though the discharge becomes more diffuse when the airflow rate is higher than 30 m/s. By acquiring the time-resolved images of the discharge, it is proved that it is the primary discharge which becomes diffuse when airflow is introduced and the following two discharges of the same voltage pulse occur principally at the positions where the primary discharge is more intense. And in both cases, the plasma temperatures are reduced, but the degree is different. All the phenomena can be explained mainly by the variation of the space charge distribution when the airflow is introduced into the discharge gap. And it is indicated that the bare anode case has an advantage in obtaining diffuse discharge.« less

Blast Loading of Epoxy Panels Using a Shock Tube

NASA Technical Reports Server (NTRS)

Pankow, Mark; Waas, Anthony M.; Bednarcyk, Brett

2010-01-01

The high strain rate mechanical response of thin polymer plates has been studied using a modified shock tube. Diagnostics include the pressure-time history of the incident and reflected pulses and the use of digital image correlation (DIC) techniques to extract the time-history of the out-of-plane displacement distribution. Additionally, finite element models have been developed to understand the plate response and to validate and modify plate material constitutive models that have been proposed.

Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furukawa, Yuki; Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-8502; Advanced Research Center for Beam Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011

By pairing femtosecond laser pulses (duration ∼40 fs and central wavelength ∼810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm{sup 2} and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm{sup 2}, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

Post-rift deformation of the Red Sea Arabian margin

NASA Astrophysics Data System (ADS)

Zanoni, Davide; Schettino, Antonio; Pierantoni, Pietro Paolo; Rasul, Najeeb

2017-04-01

Starting from the Oligocene, the Red Sea rift nucleated within the composite Neoproterozoic Arabian-Nubian shield. After about 30 Ma-long history of continental lithosphere thinning and magmatism, the first pulse of oceanic spreading occurred at around 4.6 Ma at the triple junction of Africa, Arabia, and Danakil plate boundaries and propagated southward separating Danakil and Arabia plates. Ocean floor spreading between Arabia and Africa started later, at about 3 Ma and propagated northward (Schettino et al., 2016). Nowadays the northern part of the Red Sea is characterised by isolated oceanic deeps or a thinned continental lithosphere. Here we investigate the deformation of thinned continental margins that develops as a consequence of the continental lithosphere break-up induced by the progressive oceanisation. This deformation consists of a system of transcurrent and reverse faults that accommodate the anelastic relaxation of the extended margins. Inversion and shortening tectonics along the rifted margins as a consequence of the formation of a new segment of ocean ridge was already documented in the Atlantic margin of North America (e.g. Schlische et al. 2003). We present preliminary structural data obtained along the north-central portion of the Arabian rifted margin of the Red Sea. We explored NE-SW trending lineaments within the Arabian margin that are the inland continuation of transform boundaries between segments of the oceanic ridge. We found brittle fault zones whose kinematics is consistent with a post-rift inversion. Along the southernmost transcurrent fault (Ad Damm fault) of the central portion of the Red Sea we found evidence of dextral movement. Along the northernmost transcurrent fault, which intersects the Harrat Lunayyir, structures indicate dextral movement. At the inland termination of this fault the evidence of dextral movement are weaker and NW-SE trending reverse faults outcrop. Between these two faults we found other dextral transcurrent systems that locally are associated with metre-thick reverse fault zones. Along the analysed faults there is evidence of tectonic reworking. Relict kinematic indicators or the sense of asymmetry of sigmoidal Miocene dykes may suggest that a former sinistral movement was locally accommodated by these faults. This evidence of inversion of strike-slip movement associated with reverse structures, mostly found at the inland endings of these lineaments, suggests an inversion tectonics that could be related to the progressive and recent oceanisation of rift segments. Schettino A., Macchiavelli C., Pierantoni P.P., Zanoni D. & Rasul N. 2016. Recent kinematics of the tectonic plates surrounding the Red Sea and Gulf of Aden. Geophysical Journal International, 207, 457-480. Schlische R.W., Withjack M.O. & Olsen P.E., 2003. Relative timing of CAMP, rifting, continental breakup, and basin inversion: tectonic significance, in The Central Atlantic Magmatic Province: Insights from Fragments of Pangea, eds Hames W., Mchone J.G., Renne P. & Ruppel C., American Geophysical Union, 33-59.

High power solid state laser modulator

DOEpatents

Birx, Daniel L.; Ball, Don G.; Cook, Edward G.

2004-04-27

A multi-stage magnetic modulator provides a pulse train of .+-.40 kV electrical pulses at a 5-7 kHz repetition rate to a metal vapor laser. A fractional turn transformer steps up the voltage by a factor of 80 to 1 and magnetic pulse compression is used to reduce the pulse width of the pulse train. The transformer is fabricated utilizing a rod and plate stack type of construction to achieve a high packing factor. The pulses are controlled by an SCR stack where a plurality of SCRs are electrically connected in parallel, each SCR electrically connected to a saturable inductor, all saturable inductors being wound on the same core of magnetic material for enhanced power handling characteristics.

Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jie; College of Science, Donghua University, Shanghai 201620; Guo, Ying

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 ofmore » pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.« less

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.

Optically reconfigurable metasurfaces and photonic devices based on phase change materials

NASA Astrophysics Data System (ADS)

Wang, Qian; Rogers, Edward T. F.; Gholipour, Behrad; Wang, Chih-Ming; Yuan, Guanghui; Teng, Jinghua; Zheludev, Nikolay I.

2016-01-01

Photonic components with adjustable parameters, such as variable-focal-length lenses or spectral filters, which can change functionality upon optical stimulation, could offer numerous useful applications. Tuning of such components is conventionally achieved by either micro- or nanomechanical actuation of their constituent parts, by stretching or by heating. Here, we report a novel approach for making reconfigurable optical components that are created with light in a non-volatile and reversible fashion. Such components are written, erased and rewritten as two-dimensional binary or greyscale patterns into a nanoscale film of phase-change material by inducing a refractive-index-changing phase transition with tailored trains of femtosecond pulses. We combine germanium-antimony-tellurium-based films with a diffraction-limited resolution optical writing process to demonstrate a variety of devices: visible-range reconfigurable bichromatic and multi-focus Fresnel zone plates, a super-oscillatory lens with subwavelength focus, a greyscale hologram, and a dielectric metamaterial with on-demand reflection and transmission resonances.

Study of Ni-Mo electrodeposition in direct and pulse-reverse current

NASA Astrophysics Data System (ADS)

Stryuchkova, Yu M.; Rybin, N. B.; Suvorov, D. V.; Gololobov, G. P.; Tolstoguzov, A. B.; Tarabrin, D. Yu; Serpova, M. A.; Korotchenko, V. A.; Slivkin, E. V.

2017-05-01

Process of electrochemical deposition of the coating based on a binary nickel-molybdenum alloy onto a nickel substrate under pulse mode with current reverse within the range of current density change from 2 to 9 A/dm2 has been researched. Coating structure and its surface morphology have been studied. Method of X-ray energy dispersive spectroscopy has determined a percentage ratio of alloy components in the coating. Mode to obtain the densest and smoothest deposits has been identified under considered terms.

Thin-layer chromatography and colorimetric analysis of multi-component explosive mixtures

DOEpatents

Pagoria, Philip F.; Mitchell, Alexander R.; Whipple, Richard E.; Carman, M. Leslie

2014-08-26

A thin-layer chromatography method for detection and identification of common military and peroxide explosives in samples includes the steps of provide a reverse-phase thin-layer chromatography plate; prepare the plate by marking spots on which to deposit the samples by touching the plate with a marker; spot one micro liter of a first standard onto one of the spots, spot one micro liter of a second standard onto another of the spots, and spot samples onto other of spots producing a spotted plate; add eluent to a developing chamber; add the spotted plate to the developing chamber; remove the spotted plate from the developing chamber producing a developed plate; place the developed plate in an ultraviolet light box; add a visualization agent to a dip tank; dip the developed plate in the dip tank and remove the developed plate quickly; and detect explosives by viewing said developed plate.

Pulse mitigation and heat transfer enhancement techniques. Volume 3: Liquid sodium heat transfer facility and transient response of sodium heat pipe to pulse forward and reverse heat load

NASA Astrophysics Data System (ADS)

Chow, L. C.; Hahn, O. J.; Nguyen, H. X.

1992-08-01

This report presents the description of a liquid sodium heat transfer facility (sodium loop) constructed to support the study of transient response of heat pipes. The facility, consisting of the loop itself, a safety system, and a data acquisition system, can be safely operated over a wide range of temperature and sodium flow rate. The transient response of a heat pipe to pulse heat load at the condenser section was experimentally investigated. A 0.457 m screen wick, sodium heat pipe with an outer diameter of 0.127 m was tested under different heat loading conditions. A major finding was that the heat pipe reversed under a pulse heat load applied at the condenser. The time of reversal was approximately 15 to 25 seconds. The startup of the heat pipe from frozen state was also studied. It was found that during the startup process, at least part of the heat pipe was active. The active region extended gradually down to the end of the condenser until all of the working fluid in the heat pipe was molten.

Analysis of rectangular resonant cavities in terahertz parallel-plate waveguides.

PubMed

Astley, Victoria; McCracken, Blake; Mendis, Rajind; Mittleman, Daniel M

2011-04-15

We describe an experimental and theoretical characterization of rectangular resonant cavities integrated into parallel-plate waveguides, using terahertz pulses. When the waveguide is excited with the lowest-order transverse-electric mode, these cavities exhibit resonances with narrow linewidths. Broadband transmission spectra are compared with the results of mode-matching calculations, for various cavity dimensions.

Nanocrystalline Cobalt-Phosphorous Electroplating as an Alternative to Hard Chromium Electroplating

DTIC Science & Technology

2012-08-01

Validate pulsed electrodeposition of Nanocrystalline Cobalt-Phosphorous (nCoP) alloy coatings as a Hard Chrome electroplating alternative for DoD...limits Cr+6  Cathode Efficiency Cr Plating *Co PEL is 20 µg/m3  ≈5X faster than Chrome plating  Increased throughput  One nCo-P tank can...replace several hard chrome tanks  Bath is Stable nCoP Plating Approaches 100% Efficiency  Process Comparison CoP Technical Approach

High-speed off-axis holographic cinematography with a copper-vapor-pumped dye laser.

PubMed

Lauterborn, W; Judt, A; Schmitz, E

1993-01-01

A series of coherent light pulses is generated by pumping a dye laser with the pulsed output of a copper-vapor laser at rates of as much as 20 kHz. Holograms are recorded at this pulse rate on a rotating holographic plate. This technique of high-speed holographic cinematography is demonstrated by viewing the bubble filaments that appear in water under the action of a sound field of high intensity.

Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module

DTIC Science & Technology

2015-02-01

executed with SolidWorks Flow Simulation , a computational fluid-dynamics code. The graph in Fig. 2 shows the timing and amplitudes of power pulses...defined a convective flow of air perpendicular to the bottom surface of the mounting plate, with a velocity of 10 ft/s. The thermal simulations were...Thermal Simulation of Switching Pulses in an Insulated Gate Bipolar Transistor (IGBT) Power Module by Gregory K Ovrebo ARL-TR-7210

Searching for U-235m produced by Nuclear Excitation by Electronic Transition

NASA Astrophysics Data System (ADS)

Chodash, Perry; Norman, Eric; Burke, Jason; Wilks, Scott; Casperson, Robert

2014-09-01

Nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that is predicted to occur in numerous isotopes, including U-235. When a nuclear transition matches the energy and the multipolarity of an electronic transition, there is a possibility that NEET will occur. If NEET were to occur in U-235, the nucleus would be excited to its 1/2 + isomeric state that subsequently decays by internal conversion with a decay energy of 77 eV and a half-life of 26 minutes. Theory predicts that NEET can occur in partially ionized uranium plasma with a charge state of 23 +. A pulsed Nd:YAG laser operating at 1064 nm with a pulse energy of 780 mJ and a pulse width of 9 ns was used to generate the uranium plasma. The laser was focused on small samples of both depleted uranium and highly enriched uranium. The plasma conditions created by the intense laser pulse were varied by changing the spot size of the laser on the target. The resulting plasma was collected on a plate and the internal conversion electrons were focused onto a microchannel plate detector by a series of electrostatic lenses. First results will be presented. Nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that is predicted to occur in numerous isotopes, including U-235. When a nuclear transition matches the energy and the multipolarity of an electronic transition, there is a possibility that NEET will occur. If NEET were to occur in U-235, the nucleus would be excited to its 1/2 + isomeric state that subsequently decays by internal conversion with a decay energy of 77 eV and a half-life of 26 minutes. Theory predicts that NEET can occur in partially ionized uranium plasma with a charge state of 23 +. A pulsed Nd:YAG laser operating at 1064 nm with a pulse energy of 780 mJ and a pulse width of 9 ns was used to generate the uranium plasma. The laser was focused on small samples of both depleted uranium and highly enriched uranium. The plasma conditions created by the intense laser pulse were varied by changing the spot size of the laser on the target. The resulting plasma was collected on a plate and the internal conversion electrons were focused onto a microchannel plate detector by a series of electrostatic lenses. First results will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. The U.S. DHS, UC Berkeley, the NNIS fellowship and the NSSC further supported this work.

Self-seeding ring optical parametric oscillator

DOEpatents

Smith, Arlee V [Albuquerque, NM; Armstrong, Darrell J [Albuquerque, NM

2005-12-27

An optical parametric oscillator apparatus utilizing self-seeding with an external nanosecond-duration pump source to generate a seed pulse resulting in increased conversion efficiency. An optical parametric oscillator with a ring configuration are combined with a pump that injection seeds the optical parametric oscillator with a nanosecond duration, mJ pulse in the reverse direction as the main pulse. A retroreflecting means outside the cavity injects the seed pulse back into the cavity in the direction of the main pulse to seed the main pulse, resulting in higher conversion efficiency.

Ultra-short pulse generator

DOEpatents

McEwan, T.E.

1993-12-28

An inexpensive pulse generating circuit is disclosed that generates ultra-short, 200 picosecond, and high voltage 100 kW, pulses suitable for wideband radar and other wideband applications. The circuit implements a nonlinear transmission line with series inductors and variable capacitors coupled to ground made from reverse biased diodes to sharpen and increase the amplitude of a high-voltage power MOSFET driver input pulse until it causes non-destructive transit time breakdown in a final avalanche shock wave diode, which increases and sharpens the pulse even more. 5 figures.

Ultra-short pulse generator

DOEpatents

McEwan, Thomas E.

1993-01-01

An inexpensive pulse generating circuit is disclosed that generates ultra-short, 200 picosecond, and high voltage 100 kW, pulses suitable for wideband radar and other wideband applications. The circuit implements a nonlinear transmission line with series inductors and variable capacitors coupled to ground made from reverse biased diodes to sharpen and increase the amplitude of a high-voltage power MOSFET driver input pulse until it causes non-destructive transit time breakdown in a final avalanche shockwave diode, which increases and sharpens the pulse even more.

Giant reversible anisotropy changes at room temperature in a (La,Sr)MnO3/Pb(Mg,Nb,Ti)O3 magneto-electric heterostructure.

PubMed

Chopdekar, Rajesh Vilas; Buzzi, Michele; Jenkins, Catherine; Arenholz, Elke; Nolting, Frithjof; Takamura, Yayoi

2016-06-08

In a model artificial multiferroic system consisting of a (011)-oriented ferroelectric Pb(Mg,Nb,Ti)O3 substrate intimately coupled to an epitaxial ferromagnetic (La,Sr)MnO3 film, electric field pulse sequences of less than 6 kV/cm induce large, reversible, and bistable remanent strains. The magnetic anisotropy symmetry reversibly switches from a highly anisotropic two-fold state to a more isotropic one, with concomitant changes in resistivity. Anisotropy changes at the scale of a single ferromagnetic domain were measured using X-ray microscopy, with electric-field dependent magnetic domain reversal showing that the energy barrier for magnetization reversal is drastically lowered. Free energy calculations confirm this barrier lowering by up to 70% due to the anisotropic strain changes generated by the substrate. Thus, we demonstrate that an electric field pulse can be used to 'set' and 'reset' the magnetic anisotropy orientation and resistive state in the film, as well as to lower the magnetization reversal barrier, showing a promising route towards electric-field manipulation of multifunctional nanostructures at room temperature.

An advanced selective liquid-metal plating technique for stretchable biosensor applications.

PubMed

Li, Guangyong; Lee, Dong-Weon

2017-10-11

This paper presents a novel stretchable pulse sensor fabricated by a selective liquid-metal plating process (SLMP), which can conveniently attach to the human skin and monitor the patient's heartbeat. The liquid metal-based stretchable pulse sensor consists of polydimethylsiloxane (PDMS) thin films and liquid metal functional circuits with electronic elements that are embedded into the PDMS substrate. In order to verify the utility of the fabrication process, various complex liquid-metal patterns are achieved by using the selective wetting behavior of the reduced liquid metal on the Cu patterns of the PDMS substrate. The smallest liquid-metal pattern is approximately 2 μm in width with a uniform surface. After verification, a transparent flowing LED light with programmed circuits is realized and exhibits stable mechanical and electrical properties under various deformations (bending, twisting and stretching). Finally, based on SLMP, a wireless pulse measurement system is developed which is composed of the liquid metal-based stretchable pulse sensor, a Bluetooth module, an Arduino development board, a laptop computer and a self-programmed visualized software program. The experimental results reveal that the portable non-invasive pulse sensor has the potential to reduce costs, simplify biomedical diagnostic procedures and help patients to improve their life in the future.

Femtosecond pulse laser-oriented recording on dental prostheses: a trial introduction.

PubMed

Ichikawa, Tetsuo; Hayasaki, Yoshio; Fujita, Keiji; Nagao, Kan; Murata, Masayo; Kawano, Takanori; Chen, JianRong

2006-12-01

The purpose of this study was to evaluate the feasibility of using a femtosecond pulse laser processing technique to store information on a dental prosthesis. Commercially pure titanium plates were processed by a femtosecond pulse laser system. The processed surface structure was observed with a reflective illumination microscope, scanning electron microscope, and atomic force microscope. Processed area was an almost conical pit with a clear boundary. When laser pulse energy was 2 microJ, the diameter and depth were approximately 10microm and 0.2 microm respectively--whereby both increased with laser pulse energy. Further, depth of pit increased with laser pulse number without any thermal effect. This study showed that the femtosecond pulse processing system was capable of recording personal identification and optional additional information on a dental prosthesis.

PULSE AMPLITUDE ANALYZER

DOEpatents

Greenblatt, M.H.

1958-03-25

This patent pertains to pulse amplitude analyzers for sorting and counting a serles of pulses, and specifically discloses an analyzer which ls simple in construction and presents the puise height distribution visually on an oscilloscope screen. According to the invention, the pulses are applied to the vertical deflection plates of an oscilloscope and trigger the horizontal sweep. Each pulse starts at the same point on the screen and has a maximum amplitude substantially along the same vertical line. A mask is placed over the screen except for a slot running along the line where the maximum amplitudes of the pulses appear. After the slot has been scanned by a photocell in combination with a slotted rotating disk, the photocell signal is displayed on an auxiliary oscilloscope as vertical deflection along a horizontal time base to portray the pulse amplitude distribution.

Electric field detection of phase-locked near-infrared pulses using photoconductive antenna.

PubMed

Katayama, I; Akai, R; Bito, M; Matsubara, E; Ashida, M

2013-07-15

We have demonstrated that a photoconductive antenna gated with 5-fs ultrashort laser pulses can detect electric field transients of near-infrared pulses at least up to 180 THz. Measured sensitivity spectrum of the antenna shows a good agreement with a simple calculation, demonstrating the promising capability of the antenna to near infrared spectroscopy. Using this setup, near-infrared time-domain spectroscopy and characterization of phase controlled near-infrared pulses are demonstrated. Observed absorption spectrum of a polystyrene film and complex refractive index dispersion of a fused silica plate both agree well with those obtained by the conventional methods.

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.

Short infrared laser pulses block action potentials in neurons

NASA Astrophysics Data System (ADS)

Walsh, Alex J.; Tolstykh, Gleb P.; Martens, Stacey L.; Ibey, Bennett L.; Beier, Hope T.

2017-02-01

Short infrared laser pulses have many physiological effects on cells including the ability to stimulate action potentials in neurons. Here we show that short infrared laser pulses can also reversibly block action potentials. Primary rat hippocampal neurons were transfected with the Optopatch2 plasmid, which contains both a blue-light activated channel rhodopsin (CheRiff) and a red-light fluorescent membrane voltage reporter (QuasAr2). This optogenetic platform allows robust stimulation and recording of action potential activity in neurons in a non-contact, low noise manner. For all experiments, QuasAr2 was imaged continuously on a wide-field fluorescent microscope using a Krypton laser (647 nm) as the excitation source and an EMCCD camera operating at 1000 Hz to collect emitted fluorescence. A co-aligned Argon laser (488 nm, 5 ms at 10Hz) provided activation light for CheRiff. A 200 mm fiber delivered infrared light locally to the target neuron. Reversible action potential block in neurons was observed following a short infrared laser pulse (0.26-0.96 J/cm2; 1.37-5.01 ms; 1869 nm), with the block persisting for more than 1 s with exposures greater than 0.69 J/cm2. Action potential block was sustained for 30 s with the short infrared laser pulsed at 1-7 Hz. Full recovery of neuronal activity was observed 5-30s post-infrared exposure. These results indicate that optogenetics provides a robust platform for the study of action potential block and that short infrared laser pulses can be used for non-contact, reversible action potential block.

A new lead-acid battery for high pulse power applications

NASA Technical Reports Server (NTRS)

Rowlette, J. J.; Attia, A. I.

1987-01-01

The development of new electronically conductive materials which can withstand the environment of the positive plates has made possible the construction of a high pulse power sealed bipolar lead-acid battery. The new battery is described and its advantages over other electrochemical systems are outlined. Performance projections show that the peak specific power of the battery can be as high as 90 kW/kg, and that a specific power of 5 kW/kg can be sustained over several thousand pulses.

Temperature Histories of Ti-6Al-4V Pulsed-Mode Laser Welds Calculated Using Multiple Constraints

DTIC Science & Technology

2015-08-12

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--15-9621 Temperature Histories of Ti-6Al-4V Pulsed-Mode Laser Welds Calculated Using...b. ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Temperature Histories of Ti-6Al-4V Pulsed-Mode Laser Welds Calculated Using...plate structures. The results of the case studies provide parametric representations of weld temperature histories that can be adopted as input data to

Multiscale modelling and experimentation of hydrogen embrittlement in aerospace materials

NASA Astrophysics Data System (ADS)

Jothi, Sathiskumar

Pulse plated nickel and nickel based superalloys have been used extensively in the Ariane 5 space launcher engines. Large structural Ariane 5 space launcher engine components such as combustion chambers with complex microstructures have usually been manufactured using electrodeposited nickel with advanced pulse plating techniques with smaller parts made of nickel based superalloys joined or welded to the structure to fabricate Ariane 5 space launcher engines. One of the major challenges in manufacturing these space launcher components using newly developed materials is a fundamental understanding of how different materials and microstructures react with hydrogen during welding which can lead to hydrogen induced cracking. The main objective of this research has been to examine and interpret the effects of microstructure on hydrogen diffusion and hydrogen embrittlement in (i) nickel based superalloy 718, (ii) established and (iii) newly developed grades of pulse plated nickel used in the Ariane 5 space launcher engine combustion chamber. Also, the effect of microstructures on hydrogen induced hot and cold cracking and weldability of three different grades of pulse plated nickel were investigated. Multiscale modelling and experimental methods have been used throughout. The effect of microstructure on hydrogen embrittlement was explored using an original multiscale numerical model (exploiting synthetic and real microstructures) and a wide range of material characterization techniques including scanning electron microscopy, 2D and 3D electron back scattering diffraction, in-situ and ex-situ hydrogen charged slow strain rate tests, thermal spectroscopy analysis and the Varestraint weldability test. This research shows that combined multiscale modelling and experimentation is required for a fundamental understanding of microstructural effects in hydrogen embrittlement in these materials. Methods to control the susceptibility to hydrogen induced hot and cold cracking and to improve the resistance to hydrogen embrittlement in aerospace materials are also suggested. This knowledge can play an important role in the development of new hydrogen embrittlement resistant materials. A novel micro/macro-scale coupled finite element method incorporating multi-scale experimental data is presented with which it is possible to perform full scale component analyses in order to investigate hydrogen embrittlement at the design stage. Finally, some preliminary and very encouraging results of grain boundary engineering based techniques to develop alloys that are resistant to hydrogen induced failure are presented. Keywords: Hydrogen embrittlement; Aerospace materials; Ariane 5 combustion chamber; Pulse plated nickel; Nickel based super alloy 718; SSRT test; Weldability test; TDA; SEM/EBSD; Hydrogen induced hot and cold cracking; Multiscale modelling and experimental methods.

A Kinetic Study of the Reaction of Ch3 02 with N02. Volume I,

DTIC Science & Technology

1980-01-01

Ravishankara F.L. Eisele IP.H. Wine ABSTRACT The technique of pulsed laser photolysis-long path laser aborption is employed to study the kinetics of the...Inrad Corp.) which was housed in a gold plated copper block. This copper block was in snug contact with a gold plated pedestal which was backed by a

Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic impedance measurements

DOEpatents

Langlois, Gary N.

1983-09-13

Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material.

Locating interfaces in vertically-layered materials and determining concentrations in mixed materials utilizing acoustic impedance measurements

DOEpatents

Langlois, G.N.

1983-09-13

Measurement of the relative and actual value of acoustic characteristic impedances of an unknown substance, location of the interfaces of vertically-layered materials, and the determination of the concentration of a first material mixed in a second material are disclosed. A highly damped ultrasonic pulse is transmitted into one side of a reference plate, such as a tank wall, where the other side of the reference plate is in physical contact with the medium to be measured. The amplitude of a return signal, which is the reflection of the transmitted pulse from the interface between the other side of the reference plate and the medium, is measured. The amplitude value indicates the acoustic characteristic impedance of the substance relative to that of the reference plate or relative to that of other tested materials. Discontinuities in amplitude with repeated measurements for various heights indicate the location of interfaces in vertically-layered materials. Standardization techniques permit the relative acoustic characteristic impedance of a substance to be converted to an actual value. Calibration techniques for mixtures permit the amplitude to be converted to the concentration of a first material mixed in a second material. 6 figs.

Biocompatibility of hydroxyapatite coatings deposited by pulse electrodeposition technique on the Nitinol superelastic alloy.

PubMed

Marashi-Najafi, F; Khalil-Allafi, J; Etminanfar, M R

2017-07-01

The present study deals with pulse electrochemical deposition of HA on NiTi alloy and in vitro evaluation of coatings. At first step, a thermo-chemical surface modification process was applied to control the Ni release of the alloy. The electrochemical deposition of CaP coatings was examined at both dilute and concentrated solutions. The morphology and the composition of coatings were studied using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Plate like and needle like morphologies were formed for dilute and concentrated solution respectively and HA phase was formed by increasing the pulse current density for both electrolyte. The thickness of the samples was measured using cross sectioning technique. Fibroblast cell culture test on the coated samples revealed that the HA coating obtained by dilute solution shows the best biocompatibility. Also, MTT assay showed the highest cell density and cell proliferation after 5days for the HA coating of dilute solution. The contact angle of samples was measured and the coated samples showed a hydrophilic surface. Soaking the sample in SBF revealed that the crystallization rate of calcium-phosphate compounds is higher on the plate like HA coating as compared to the needle like morphology. The P release of the HA coated samples was measured in a physiological saline solution and the results show that the ions releasing in the plate like coating are less than the needle like coating. It seems that the stability of the plate like coating in biological environments is responsible for the better biocompatibility of the coating. Copyright © 2017 Elsevier B.V. All rights reserved.

High-current-density electrodeposition using pulsed and constant currents to produce thick CoPt magnetic films on silicon substrates

NASA Astrophysics Data System (ADS)

Ewing, Jacob; Wang, Yuzheng; Arnold, David P.

2018-05-01

This paper investigates methods for electroplating thick (>20 μm), high-coercivity CoPt films using high current densities (up to 1 A/cm2) and elevated bath temperatures (70 °C). Correlations are made tying current-density and temperature process parameters with plating rate, elemental ratio and magnetic properties of the deposited CoPt films. It also investigates how pulsed currents can increase the plating rate and film to substrate adhesion. Using 500 mA/cm2 and constant current, high-quality, dense CoPt films were successfully electroplated up to 20 μm thick in 1 hr on silicon substrates (0.35 μm/min plating rate). After standard thermal treatment (675°C, 30 min) to achieve the ordered L10 crystalline phase, strong magnetic properties were measured: coercivities up 850 kA/m, remanences >0.5 T, and maximum energy products up to 46 kJ/m3.

Optimization of the performance of a tandem microchannel plate detector as a function of interplate spacing and voltage

NASA Technical Reports Server (NTRS)

Rogers, D.; Malina, R. F.

1982-01-01

The effect of varying the size of the gap voltage and spacing on the performance of a tandem pair of microchannel plates (MCP) is investigated. Results show that increasing the voltage in the gap increases the gain of the pair and also produces a narrower Gaussian pulse-height distribution, although beyond a critical voltage the gain of the channel plate pair is found to plateau. A model is developed which explains the nonlinear gain behavior of individual microchannels and the behavior of the electron cloud emitted from the first MCP as it spreads out between the two MCPs and hits the surface of the second. The model calculates the plateau voltage as a function of the gap size, the gain of each MCP, and the diameter of the channels, and is found to show good agreement with the observed results. It is concluded that interplate gaps of up to several millimeters can be accommodated without a significant degradation in pulse-height distribution.

Fluorescence lifetime plate reader: Resolution and precision meet high-throughput

PubMed Central

Petersen, Karl J.; Peterson, Kurt C.; Muretta, Joseph M.; Higgins, Sutton E.; Gillispie, Gregory D.; Thomas, David D.

2014-01-01

We describe a nanosecond time-resolved fluorescence spectrometer that acquires fluorescence decay waveforms from each well of a 384-well microplate in 3 min with signal-to-noise exceeding 400 using direct waveform recording. The instrument combines high-energy pulsed laser sources (5–10 kHz repetition rate) with a photomultiplier and high-speed digitizer (1 GHz) to record a fluorescence decay waveform after each pulse. Waveforms acquired from rhodamine or 5-((2-aminoethyl)amino) naphthalene-1-sulfonic acid dyes in a 384-well plate gave lifetime measurements 5- to 25-fold more precise than the simultaneous intensity measurements. Lifetimes as short as 0.04 ns were acquired by interleaving with an effective sample rate of 5 GHz. Lifetime measurements resolved mixtures of single-exponential dyes with better than 1% accuracy. The fluorescence lifetime plate reader enables multiple-well fluorescence lifetime measurements with an acquisition time of 0.5 s per well, suitable for high-throughput fluorescence lifetime screening applications. PMID:25430092

Pc-based car license plate reading

NASA Astrophysics Data System (ADS)

Tanabe, Katsuyoshi; Marubayashi, Eisaku; Kawashima, Harumi; Nakanishi, Tadashi; Shio, Akio

1994-03-01

A PC-based car license plate recognition system has been developed. The system recognizes Chinese characters and Japanese phonetic hiragana characters as well as six digits on Japanese license plates. The system consists of a CCD camera, vehicle sensors, a strobe unit, a monitoring center, and an i486-based PC. The PC includes in its extension slots: a vehicle detector board, a strobe emitter board, and an image grabber board. When a passing vehicle is detected by the vehicle sensors, the strobe emits a pulse of light. The light pulse is synchronized with the time the vehicle image is frozen on an image grabber board. The recognition process is composed of three steps: image thresholding, character region extraction, and matching-based character recognition. The recognition software can handle obscured characters. Experimental results for hundreds of outdoor images showed high recognition performance within relatively short performance times. The results confirmed that the system is applicable to a wide variety of applications such as automatic vehicle identification and travel time measurement.

Capacitive proximity sensor

DOEpatents

Kronberg, James W.

1994-01-01

A proximity sensor based on a closed field circuit. The circuit comprises a ring oscillator using a symmetrical array of plates that creates an oscillating displacement current. The displacement current varies as a function of the proximity of objects to the plate array. Preferably the plates are in the form of a group of three pair of symmetric plates having a common center, arranged in a hexagonal pattern with opposing plates linked as a pair. The sensor produces logic level pulses suitable for interfacing with a computer or process controller. The proximity sensor can be incorporated into a load cell, a differential pressure gauge, or a device for measuring the consistency of a characteristic of a material where a variation in the consistency causes the dielectric constant of the material to change.

Design for the optical retardation in broadband zero-order half-wave plates.

PubMed

Liu, Jin; Cai, Yi; Chen, Hongyi; Zeng, Xuanke; Zou, Da; Xu, Shixiang

2011-04-25

This paper presents a novel design for broadband zero-order half-wave plates to eliminate the first-order or up to second-order wavelength-dependent birefringent phase retardation (BPR) with 2 or 3 different birefringent materials. The residual BPRs of the plates increase monotonously with the wavelength deviation from a selected wavelength, so the plates are applicable to the broadband light pulses which gather most of the light energy around their central wavelengths. The model chooses the materials by the birefringent dispersion coefficient and evaluates the performances of the plates by the weighted average of the absolute value of residual BPR in order to emphasize the contributions of the incident spectral components whose possess higher energies.

Design of a bounded wave EMP (Electromagnetic Pulse) simulator

NASA Astrophysics Data System (ADS)

Sevat, P. A. A.

1989-06-01

Electromagnetic Pulse (EMP) simulators are used to simulate the EMP generated by a nuclear weapon and to harden equipment against the effects of EMP. At present, DREO has a 1 m EMP simulator for testing computer terminal size equipment. To develop the R and D capability for testing larger objects, such as a helicopter, a much bigger threat level facility is required. This report concerns the design of a bounded wave EMP simulator suitable for testing large size equipment. Different types of simulators are described and their pros and cons are discussed. A bounded wave parallel plate type simulator is chosen for it's efficiency and the least environmental impact. Detailed designs are given for 6 m and 10 m parallel plate type wire grid simulators. Electromagnetic fields inside and outside the simulators are computed. Preliminary specifications for a pulse generator required for the simulator are also given. Finally, the electromagnetic fields radiated from the simulator are computed and discussed.

High accuracy electronic material level sensor

DOEpatents

McEwan, T.E.

1997-03-11

The High Accuracy Electronic Material Level Sensor (electronic dipstick) is a sensor based on time domain reflectometry (TDR) of very short electrical pulses. Pulses are propagated along a transmission line or guide wire that is partially immersed in the material being measured; a launcher plate is positioned at the beginning of the guide wire. Reflected pulses are produced at the material interface due to the change in dielectric constant. The time difference of the reflections at the launcher plate and at the material interface are used to determine the material level. Improved performance is obtained by the incorporation of: (1) a high accuracy time base that is referenced to a quartz crystal, (2) an ultrawideband directional sampler to allow operation without an interconnect cable between the electronics module and the guide wire, (3) constant fraction discriminators (CFDs) that allow accurate measurements regardless of material dielectric constants, and reduce or eliminate errors induced by triple-transit or ``ghost`` reflections on the interconnect cable. These improvements make the dipstick accurate to better than 0.1%. 4 figs.

High accuracy electronic material level sensor

DOEpatents

McEwan, Thomas E.

1997-01-01

The High Accuracy Electronic Material Level Sensor (electronic dipstick) is a sensor based on time domain reflectometry (TDR) of very short electrical pulses. Pulses are propagated along a transmission line or guide wire that is partially immersed in the material being measured; a launcher plate is positioned at the beginning of the guide wire. Reflected pulses are produced at the material interface due to the change in dielectric constant. The time difference of the reflections at the launcher plate and at the material interface are used to determine the material level. Improved performance is obtained by the incorporation of: 1) a high accuracy time base that is referenced to a quartz crystal, 2) an ultrawideband directional sampler to allow operation without an interconnect cable between the electronics module and the guide wire, 3) constant fraction discriminators (CFDs) that allow accurate measurements regardless of material dielectric constants, and reduce or eliminate errors induced by triple-transit or "ghost" reflections on the interconnect cable. These improvements make the dipstick accurate to better than 0.1%.

Bipolar pulse forming line

DOEpatents

Rhodes, Mark A.

2008-10-21

A bipolar pulse forming transmission line module for linear induction accelerators having first, second, third, fourth, and fifth planar conductors which form an interleaved stack with dielectric layers between the conductors. Each conductor has a first end, and a second end adjacent an acceleration axis. The first and second planar conductors are connected to each other at the second ends, the fourth and fifth planar conductors are connected to each other at the second ends, and the first and fifth planar conductors are connected to each other at the first ends via a shorting plate adjacent the first ends. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short a high voltage from the first end of the third planar conductor to the first end of the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

Comparison of the lowest-order transverse-electric (TE1) and transverse-magnetic (TEM) modes of the parallel-plate waveguide for terahertz pulse applications.

PubMed

Mendis, Rajind; Mittleman, Daniel M

2009-08-17

We present a comprehensive experimental study comparing the propagation characteristics of the virtually unknown TE(1) mode to the well-known TEM mode of the parallel-plate waveguide (PPWG), for THz pulse applications. We demonstrate that it is possible to overcome the undesirable effects caused by the TE(1) mode's inherent low-frequency cutoff, making it a viable THz wave-guiding option, and that for certain applications, the TE(1) mode may even be more desirable than the TEM mode. This study presents a whole new dimension to the THz technological capabilities offered by the PPWG, via the possible use of the TE(1) mode. (c) 2009 Optical Society of America

Pulsed Plasma Thruster Plume Study: Symmetry and Impact on Spacecraft Surfaces

NASA Technical Reports Server (NTRS)

Arrington, Lynn A.; Marrese, Colleen M.; Blandino, John J.

2000-01-01

Twenty-four witness plates were positioned on perpendicular arrays near a breadboard Pulsed Plasma Thruster (PPT) to collect plume constituents for analysis. Over one million shots were fired during the experiment at 43 J using fluorocarbon polymer propellant. The asymmetry of the film deposition on the witness plates was investigated with mass and thickness measurements and correlated with off-axis thrust vector measurements. The composition of the films was determined. The transmittance and reflectance of the films were measured and the absorption coefficients were calculated in the wavelength range from 350 to 1200 mn. These data were applied to calculate the loss in signal intensity through the films, which will impact the visibility of spaceborne interferometer systems positioned by these thrusters.

Lead-acid battery construction

NASA Technical Reports Server (NTRS)

Rowlette, John J. (Inventor)

1988-01-01

The power characteristics of a lead-acid battery are improved by incorporating a dispersion of 1 to 10% by weight of a thermodynamically stable conductivity additive, such as conductive tin oxide coated glass fibers (34) of filamentary glass wool (42) in the positive active layer (32) carried on the grid (30) of the positive plate (16). The avoiding of positive plate reversal to prevent reduction of the tin oxide is accomplished by (a) employing an oversized positive plate and pre-charging it; (b) by pre-discharging the negative plate; and/or (c) by placing a circuit breaker (26) in combination with the plates (16, 18) and terminals (22, 24) to remove the load when the voltage of the positive plate falls below a pre-selected level.

Normal and Reversed-Phase Thin Layer Chromatography of Green Leaf Extracts

ERIC Educational Resources Information Center

Sjursnes, Birte Johanne; Kvittingen, Lise; Schmid, Rudolf

2015-01-01

Introductory experiments of chromatography are often conducted by separating colored samples, such as inks, dyes, and plant extracts, using filter paper, chalk, or thin layer chromatography (TLC) plates with various solvent systems. Many simple experiments have been reported. The relationship between normal chromatography and reversed-phase…

Pulse compression and prepulse suppression apparatus

DOEpatents

Dane, Clifford B.; Hackel, Lloyd A.; George, Edward V.; Miller, John L.; Krupke, William F.

1993-01-01

A pulse compression and prepulse suppression apparatus (10) for time compressing the output of a laser (14). A pump pulse (46) is separated from a seed pulse (48) by a first polarized beam splitter (20) according to the orientation of a half wave plate (18). The seed pulse (48) is directed into an SBS oscillator (44) by two plane mirrors (22, 26) and a corner mirror (24), the corner mirror (24) being movable to adjust timing. The pump pulse (46) is directed into an SBS amplifier 34 wherein SBS occurs. The seed pulse (48), having been propagated from the SBS oscillator (44), is then directed through the SBS amplifier (34) wherein it sweeps the energy of the pump pulse (46) out of the SBS amplifier (34) and is simultaneously compressed, and the time compressed pump pulse (46) is emitted as a pulse output (52). A second polarized beam splitter (38) directs any undepleted pump pulse 58 away from the SBS oscillator (44).

Pulse compression and prepulse suppression apparatus

DOEpatents

Dane, C.B.; Hackel, L.A.; George, E.V.; Miller, J.L.; Krupke, W.F.

1993-11-09

A pulse compression and prepulse suppression apparatus (10) for time compressing the output of a laser (14). A pump pulse (46) is separated from a seed pulse (48) by a first polarized beam splitter (20) according to the orientation of a half wave plate (18). The seed pulse (48) is directed into an SBS oscillator (44) by two plane mirrors (22, 26) and a corner mirror (24), the corner mirror (24) being movable to adjust timing. The pump pulse (46) is directed into an SBS amplifier 34 wherein SBS occurs. The seed pulse (48), having been propagated from the SBS oscillator (44), is then directed through the SBS amplifier (34) wherein it sweeps the energy of the pump pulse (46) out of the SBS amplifier (34) and is simultaneously compressed, and the time compressed pump pulse (46) is emitted as a pulse output (52). A second polarized beam splitter (38) directs any undepleted pump pulse 58 away from the SBS oscillator (44).

Reduction of B-integral accumulation in lasers

DOEpatents

Meyerhofer, David D.; Konoplev, Oleg A.

2000-01-01

A pulsed laser is provided wherein the B-integral accumulated in the laser pulse is reduced using a semiconductor wafer. A laser pulse is generated by a laser pulse source. The laser pulse passes through a semiconductor wafer that has a negative nonlinear index of refraction. Thus, the laser pulse accumulates a negative B-integral. The laser pulse is then fed into a laser amplification medium, which has a positive nonlinear index of refraction. The laser pulse may make a plurality of passes through the laser amplification medium and accumulate a positive B-integral during a positive non-linear phase change. The semiconductor and laser pulse wavelength are chosen such that the negative B-integral accumulated in the semiconductor wafer substantially cancels the positive B-integral accumulated in the laser amplification medium. There may be additional accumulation of positive B-integral if the laser pulse passes through additional optical mediums such as a lens or glass plates. Thus, the effects of self-phase modulation in the laser pulse are substantially reduced.

Influence of laser-target interaction regime on composition and properties of surface layers grown by laser treatment of Ti plates

NASA Astrophysics Data System (ADS)

Lavisse, L.; Berger, P.; Cirisan, M.; Jouvard, J. M.; Bourgeois, S.; de Lucas, M. C. Marco

2009-12-01

Surface laser treatment of commercially pure titanium plates was performed in air using two different Nd : YAG sources delivering pulses of 5 and 35 ns. The laser fluence conditions were set to obtain with each source either yellow or blue surface layers. Nuclear reaction analysis (NRA) was used to quantify the amount of light elements in the formed layers. Titanium oxinitrides, containing different amounts of oxygen and nitrogen, were mainly found, except in the case of long pulses and high laser fluence, which led to the growth of titanium dioxide. The structure of the layers was studied by x-ray diffraction and Raman spectroscopy. In addition, reflectance spectra showed the transition from a metal-like behaviour to an insulating TiO2-like behaviour as a function of the treatment conditions. Modelling of the laser-target interaction on the basis of the Semak model was performed to understand the different compositions and properties of the layers. Numerical calculations showed that vaporization dominates in the case of short pulses, whereas a liquid-ablation regime is achieved in the case of 35 ns long pulses.

Measurement of plasma momentum exerted on target by a small helicon plasma thruster and comparison with direct thrust measurement.

PubMed

Takahashi, Kazunori; Komuro, Atsushi; Ando, Akira

2015-02-01

Momentum, i.e., force, exerted from a small helicon plasma thruster to a target plate is measured simultaneously with a direct thrust measurement using a thrust balance. The calibration coefficient relating a target displacement to a steady-state force is obtained by supplying a dc to a calibration coil mounted on the target, where a force acting to a small permanent magnet located near the coil is directly measured by using a load cell. As the force exerted by the plasma flow to the target plate is in good agreement with the directly measured thrust, the validity of the target technique is demonstrated under the present operating conditions, where the thruster is operated in steady-state. Furthermore, a calibration coefficient relating a swing amplitude of the target to an impulse bit is also obtained by pulsing the calibration coil current. The force exerted by the pulsed plasma, which is estimated from the measured impulse bit and the pulse width, is also in good agreement with that obtained for the steady-state operation; hence, the thrust assessment of the helicon plasma thruster by the target is validated for both the steady-state and pulsed operations.

Cyp26b1 within the growth plate regulates bone growth in juvenile mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minegishi, Yoshiki; Department of Plastic and Reconstructive Surgery, University of Fukui Hospital, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1193; Department of Plastic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871

Highlights: • Retinoic acid and Cyp26b1 were oppositely localized in growth plate cartilage. • Cyp26b1 deletion in chondrocytes decreased bone growth in juvenile mice. • Cyp26b1 deletion reduced chondrocyte proliferation and growth plate height. • Vitamin A-depletion partially reversed growth plate abnormalities caused by Cyp26b1 deficiency. • Cyp26b1 regulates bone growth by controlling chondrocyte proliferation. - Abstract: Retinoic acid (RA) is an active metabolite of vitamin A and plays important roles in embryonic development. CYP26 enzymes degrade RA and have specific expression patterns that produce a RA gradient, which regulates the patterning of various structures in the embryo. However, itmore » has not been addressed whether a RA gradient also exists and functions in organs after birth. We found localized RA activities in the diaphyseal portion of the growth plate cartilage were associated with the specific expression of Cyp26b1 in the epiphyseal portion in juvenile mice. To disturb the distribution of RA, we generated mice lacking Cyp26b1 specifically in chondrocytes (Cyp26b1{sup Δchon} cKO). These mice showed reduced skeletal growth in the juvenile stage. Additionally, their growth plate cartilage showed decreased proliferation rates of proliferative chondrocytes, which was associated with a reduced height in the zone of proliferative chondrocytes, and closed focally by four weeks of age, while wild-type mouse growth plates never closed. Feeding the Cyp26b1 cKO mice a vitamin A-deficient diet partially reversed these abnormalities of the growth plate cartilage. These results collectively suggest that Cyp26b1 in the growth plate regulates the proliferation rates of chondrocytes and is responsible for the normal function of the growth plate and growing bones in juvenile mice, probably by limiting the RA distribution in the growth plate proliferating zone.« less

Synergistic Combination of Electrolysis and Electroporation for Tissue Ablation.

PubMed

Stehling, Michael K; Guenther, Enric; Mikus, Paul; Klein, Nina; Rubinsky, Liel; Rubinsky, Boris

2016-01-01

Electrolysis, electrochemotherapy with reversible electroporation, nanosecond pulsed electric fields and irreversible electroporation are valuable non-thermal electricity based tissue ablation technologies. This paper reports results from the first large animal study of a new non-thermal tissue ablation technology that employs "Synergistic electrolysis and electroporation" (SEE). The goal of this pre-clinical study is to expand on earlier studies with small animals and use the pig liver to establish SEE treatment parameters of clinical utility. We examined two SEE methods. One of the methods employs multiple electrochemotherapy-type reversible electroporation magnitude pulses, designed in such a way that the charge delivered during the electroporation pulses generates the electrolytic products. The second SEE method combines the delivery of a small number of electrochemotherapy magnitude electroporation pulses with a low voltage electrolysis generating DC current in three different ways. We show that both methods can produce lesion with dimensions of clinical utility, without the need to inject drugs as in electrochemotherapy, faster than with conventional electrolysis and with lower electric fields than irreversible electroporation and nanosecond pulsed ablation.

Synergistic Combination of Electrolysis and Electroporation for Tissue Ablation

PubMed Central

Mikus, Paul; Klein, Nina; Rubinsky, Liel; Rubinsky, Boris

2016-01-01

Electrolysis, electrochemotherapy with reversible electroporation, nanosecond pulsed electric fields and irreversible electroporation are valuable non-thermal electricity based tissue ablation technologies. This paper reports results from the first large animal study of a new non-thermal tissue ablation technology that employs “Synergistic electrolysis and electroporation” (SEE). The goal of this pre-clinical study is to expand on earlier studies with small animals and use the pig liver to establish SEE treatment parameters of clinical utility. We examined two SEE methods. One of the methods employs multiple electrochemotherapy-type reversible electroporation magnitude pulses, designed in such a way that the charge delivered during the electroporation pulses generates the electrolytic products. The second SEE method combines the delivery of a small number of electrochemotherapy magnitude electroporation pulses with a low voltage electrolysis generating DC current in three different ways. We show that both methods can produce lesion with dimensions of clinical utility, without the need to inject drugs as in electrochemotherapy, faster than with conventional electrolysis and with lower electric fields than irreversible electroporation and nanosecond pulsed ablation. PMID:26866693

Laser-induced reversion of δ' precipitates in an Al-Li alloy: Study on temperature rise in pulsed laser atom probe.

PubMed

Khushaim, Muna; Gemma, Ryota; Al-Kassab, Talaat

2016-08-01

The influence of tuning the laser pulse energy during the analyses on the resulting microstructure in a specimen utilizing an ultra-fast laser assisted atom probe was demonstrated by a case study of a binary Al-Li alloy. The decomposition parameters, such as the size, number density, volume fraction, and composition of δ' precipitates, were carefully monitored after each analysis. A simple model was employed to estimate the corresponding specimen temperature for each value of the laser energy. The results indicated that the corresponding temperatures for the laser pulse energy in the range of 10 to 80 pJ are located inside the miscibility gap of the binary Al-Li phase diagram and fall into the metastable equilibrium field. In addition, the corresponding temperature for a laser pulse energy of 100 pJ was in fairly good agreement with reported range of  δ' solvus temperature, suggesting a result of reversion upon heating due to laser pulsing. Microsc. Res. Tech. 79:727-737, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

High resolution reconstructions of Southwest Indian Ridge plate motions during the Neogene: Comparison to GPS estimates and implications for global plate motion estimates

NASA Astrophysics Data System (ADS)

DeMets, C.; Merkouriev, S.; Sauter, D.; Calais, E.

2013-12-01

Plate kinematic data from the slow-spreading Southwest Indian Ridge (SWIR) are the primary source of information about relative movements between Antarctica and Africa over geologic time and are critical for linking the movements of plates in the Atlantic and Indian Ocean basins. We describe the first high-resolution model of SWIR plate kinematics from the present to 20 Ma, consisting of rotations based on 21 magnetic reversals with ~1 million-year spacing. The new rotations, which are derived from 4822 identifications of magnetic reversals C1n to C6no and 6000 crossings of 21 fracture zones and transform faults, describe in detail the ultra-slow motions of the Nubia, Lwandle, and Somalia plates north of the SWIR relative to the Antarctic plate. A search for the Nubia-Lwandle-Antarctic triple junction with all data since C5n.2 (11.0 Ma) gives a best location at the Andrew Bain transform fault (~32E), in accord with previous work. Plate kinematic data from the SWIR east of the Andrew Bain fracture zone support the existence of the previously proposed Lwandle plate at high confidence level. The likely diffuse Lwandle-Somalia plate boundary north of the SWIR is however only loosely constrained to 45E-52E. After calibrating the new rotations for the biasing effects of finite-width magnetic polarity transition zones (i.e. outward displacement), the new rotations reveal that SWIR plate motion has remained steady from the present back to 7.5 Ma, but was modestly faster (~25%) from 19.6 Ma to 7.5 Ma. GPS estimates of present SWIR plate motions based on more than 100 continuous GPS sites on the Antarctic, Nubia, and Somalia plates are remarkably consistent with SWIR velocities determined with the new geological reconstructions. The superb agreement between the two independent plate motion estimates validates both sets of estimates and our calibration for outward displacement. Implications of the new estimates, including evidence for anomalously wide outward displacement across parts of the SWIR, will be discussed

Biomechanical outcome of proximal femoral nail antirotation is superior to proximal femoral locking compression plate for reverse oblique intertrochanteric fractures: a biomechanical study of intertrochanteric fractures.

PubMed

Ma, Jian-Xiong; Wang, Jie; Xu, Wei-Guo; Yu, Jing-Tao; Yang, Yang; Ma, Xin-Long

2015-01-01

Reverse obliquity intertrochanteric fractures are a challenge for orthopedic surgeons. The optimal internal fixation for repairing this type of unstable intertrochanteric fractures remains controversial. This study aimed to compare the biomechanical properties in axial load and cyclical axial load of proximal femoral nail antirotation (PFNA) and proximal femoral locking compression plate (PFLCP) for fixation of reverse obliquity intertrochanteric fractures. Sixteen embalmed cadaver femurs were sawed to simulate reverse obliquity intertrochanteric fracture and instrumented with PFNA or PFLCP. Axial loads and axial cyclic loads were applied to the femoral head by an Instron tester. If the implant-femur constructs did not fail, axial failure load was added to the remaining implant-femur constructs. Mean axial stiffness for PFNA was 21.10% greater than that of PFLCP. Cyclic axial loading caused significantly less (p=0.022) mean irreversible deformation in PFNA (3.43 mm) than in PFLCP (4.34 mm). Significantly less (p=0.002) mean total deformation was detected in PFNA (6.16 mm) than in PFLCP (8.67 mm). For fixing reverse obliquity intertrochanteric fractures, PFNA is superior to PFLCP under axial load.

Pulse analysis of acoustic emission signals. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Houghton, J. R.

1976-01-01

A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio are examined in the frequency domain analysis, and pulse shape deconvolution is developed for use in the time domain analysis. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameters values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emissions associated with: (1) crack propagation, (2) ball dropping on a plate, (3) spark discharge and (4) defective and good ball bearings.

Phosphoric acid as an electrolyte additive for lead/acid batteries in electric-vehicle applications

NASA Astrophysics Data System (ADS)

Meissner, E.

The influence of the addition of phosphoric acid to the electrolyte on the performance of gelled lead/acid electric-vehiicle batteries is investigated. This additive reduces the reversible capacity decay of the positive electrode significantly which is observed upon extended cycling when recharge of the battery is performed at low initial rate. This is important when low-rate on-board chargers are used. Pulsed discharge, typical for electric-vehicle application, induces reversible capacity decay more than constant-current discharge at a same depth-of-discharge, as well with as without the addition of phosphoric acid. By contrast, hindrance in presence of H 3PO 4 for both the recharge and the discharge reaction helps to homogenize the state of many individual cells during cycling in long battery strings. Reversible capacity loss, which occurs after extended cycling and when pulsed discharge is applied, can be recovered by a single discharge at very low rate with batteries with and without the addition of phosphoric acid. The discharge-rate dependency of the capacity is significantly reduced when phosphoric acid is added. The pulse discharge behaviour may be better, even if the nominal capacity is reduced. The experimental findings of the influence of phosphoric acid addition is discussed in terms of the aggregate-of-spheres model of reversible capacity decay.

Three phase AC motor controller

DOEpatents

Vuckovich, Michael; Wright, Maynard K.; Burkett, John P.

1984-03-20

A motor controller for a three phase AC motor (10) which is adapted to operate bidirectionally from signals received either from a computer (30) or a manual control (32). The controller is comprised of digital logic circuit means which implement a forward and reverse command signal channel (27, 29) for the application of power through the forward and reverse power switching relays (16, 18, 20, 22). The digital logic elements are cross coupled to prevent activation of both channels simultaneously and each includes a plugging circuit (65, 67) for stopping the motor upon the removal of control signal applied to one of the two channels (27, 29) for a direction of rotation desired. Each plugging circuit (65, 67) includes a one-shot pulse signal generator (88, 102) which outputs a single pulse signal of predetermined pulsewidth which is adapted to inhibit further operation of the application of power in the channel which is being activated and to apply a reversal command signal to the other channel which provides a reversed phase application of power to the motor for a period defined by the pulse-width output of the one-shot signal generator to plug the motor (10) which will then be inoperative until another rotational command signal is applied to either of the two channels.

Episodicity of Orogeny Revisited

NASA Astrophysics Data System (ADS)

Condie, K. C.; Aster, R. C.

2008-12-01

Although it is well established that orogeny is episodic, the duration, correlation and geographic distribution of orogenic episodes is not well constrained. Using large numbers of concordant U/Pb zircon ages from subduction-related granitoids (> 7000), it is now possible to better constrain these variables. Monte Carlo simulation probabilistic histograms of zircon age spectra remove questionable and spurious age peaks, yet allow resolution of peaks with >10 My duration with the data sets. Orogenic episodes with durations < 20 My, herein called pulses, are generally of regional geographic extent, whereas long-lived events (100-250 My), herein called periods, may be of regional or global extent. Orogenic periods comprise several to many pulses. Most orogenic pulses reflect geographic variations in intensity of subduction or/and plate collisions as for instance recorded around the perimeter of the Pacific basin in the last 100 My. Neither of the widely recognized pulses at 2.7 nor 1.9 Ga is global in extent. Orogenic pulses at 2700 and 2680 Ma occur on four continents each (2700: Superior, Hearne-Rae, Nain, North China; 2680: Yilgarn, Africa, Slave, Wyoming). Likewise, an orogenic pulse at 1880 is found on four continents (Laurentia, Baltica, East Asia, South America), and another pulse at 1860 Ma occurs on three continents (Africa, Siberia, Australia). Some orogenic pulses track lateral continental growth, such as 2730, 2715, and 2700 Ma pulses in the Abitibi greenstone belt, and 850, 800 and 750 Ma pulses in the Arabian-Nubian shield. Major orogenic periods are recognized at 2750-2650, 1900-1650, and 1250-1000 Ma and each of these is associated with supercontinent formation. Orogenic periods at 2600-2500 (China and India) and 2150-2050 Ma (West Africa, Amazonia, Rio de la Plata) may be associated with the formation of small supercontinents. Our results suggest that orogenic periods with intervening gaps may not require sudden and short-lived changes in mantle behavior, but may be associated primarily with the supercontinent cycle, and thus be a characteristic feature of planets with plate tectonics.

F14A System Safety Program Plan

DTIC Science & Technology

1981-09-03

by block number) Electromagnetic Pulse (EMP) Safety Plans Test Program EMP Testing F14 Aircraft Plans 20 ABSTRACT (Continue on reverse side if...compromising completion of the required experimental tasks. This document addresses the safety aspect of performing an Electromagnetic Pulse (EMP) test

Seismotectonics of New Guinea: a Model for Arc Reversal Following Arc-Continent Collision

NASA Astrophysics Data System (ADS)

Cooper, Patricia; Taylor, Brian

1987-02-01

The structure and evolution of the northern New Guinea collision zone is deduced from International Seismological Center (ISC) seismicity (1964-1985), new and previously published focal mechanisms and a reexamination of pertinent geological data. A tectonic model for the New Guinea margin is derived which illustrates the sequential stages in the collision and suturing of the Bewani-Toricelli-Adelbert-Finisterre-Huon-New Britain arc to central New Guinea followed by subduction polarity reversal in the west. East of 149°E, the Solomon plate is being subducted both to the north and south; bringing the New Britain and Trobriand forearcs toward collision. West of 149°E the forearcs have collided, and together they override a fold in the doubly subducted Solomon plate lithosphere, which has an axis that is parallel to the strike of the Ramu-Markham suture and that plunges westward at an angle of 5° beneath the coast ranges of northern New Guinea. Active volcanism off the north coast of New Guinea is related to subduction of the Solomon plate beneath the Bismarck plate. Active volcanism of the Papuan peninsula and Quaternary volcanism of the New Guinea highlands are related to slow subduction of the Solomon plate beneath the Indo-Australian plate along the Trobriand Trough and the trough's former extension to the west, respectively. From 144°-148°E, seismicity and focal mechanisms reveal that convergence between the sutured Bismarck and Indo-Australian plates is accommodated by thrusting within the Finisterre and Adelbert ranges and compression of the New Guinea orogenic belt, together with basement-involved foreland folding and thrusting to the south. The Finisterre block overthrusts the New Guinea orogenic belt, whereas the Adelbert block is sutured to New Guinea and overthrusts the oceanic lithosphere of the Bismarck Sea. Along the New Guinea Trench, west of 144°E, seismicity defines a southward dipping Wadati-Benioif zone, and focal mechanisms indicate oblique subduction. Only this oldest, westernmost portion of the collision has progressed past suturing to a full reversal in subduction polarity.

A possible propellantless propulsion system

NASA Astrophysics Data System (ADS)

Goodwin, David P.

2001-02-01

A newly developed high power solid state switch might have enabled a propellantless propulsion system (PPS), based on the Lenz's Law interactions of a very rapidly pulsed magnet. Although only limited propulsion would be provided with each pulse, and then only during the 100-nanosecond ramp-up of the pulse, the newly developed switch produces 400,000 high power pulses per second. A PPS of this type would consist of an electrical power supply, the switch, and a solenoid with a plate on one end to produce an asymmetry in the magnetic field. Other applications might include propulsion with reduced thermal and acoustical signatures, and a means to dampen inertia. .

Characterization of x-ray framing cameras for the National Ignition Facility using single photon pulse height analysis.

PubMed

Holder, J P; Benedetti, L R; Bradley, D K

2016-11-01

Single hit pulse height analysis is applied to National Ignition Facility x-ray framing cameras to quantify gain and gain variation in a single micro-channel plate-based instrument. This method allows the separation of gain from detectability in these photon-detecting devices. While pulse heights measured by standard-DC calibration methods follow the expected exponential distribution at the limit of a compound-Poisson process, gain-gated pulse heights follow a more complex distribution that may be approximated as a weighted sum of a few exponentials. We can reproduce this behavior with a simple statistical-sampling model.

Giant reversible anisotropy changes at room temperature in a (La,Sr)MnO3/Pb(Mg,Nb,Ti)O3 magneto-electric heterostructure

PubMed Central

Chopdekar, Rajesh Vilas; Buzzi, Michele; Jenkins, Catherine; Arenholz, Elke; Nolting, Frithjof; Takamura, Yayoi

2016-01-01

In a model artificial multiferroic system consisting of a (011)-oriented ferroelectric Pb(Mg,Nb,Ti)O3 substrate intimately coupled to an epitaxial ferromagnetic (La,Sr)MnO3 film, electric field pulse sequences of less than 6 kV/cm induce large, reversible, and bistable remanent strains. The magnetic anisotropy symmetry reversibly switches from a highly anisotropic two-fold state to a more isotropic one, with concomitant changes in resistivity. Anisotropy changes at the scale of a single ferromagnetic domain were measured using X-ray microscopy, with electric-field dependent magnetic domain reversal showing that the energy barrier for magnetization reversal is drastically lowered. Free energy calculations confirm this barrier lowering by up to 70% due to the anisotropic strain changes generated by the substrate. Thus, we demonstrate that an electric field pulse can be used to ‘set’ and ‘reset’ the magnetic anisotropy orientation and resistive state in the film, as well as to lower the magnetization reversal barrier, showing a promising route towards electric-field manipulation of multifunctional nanostructures at room temperature. PMID:27271984

Two-fluid dynamo relaxation and momentum transport induced by CHI on HIST

NASA Astrophysics Data System (ADS)

Nagata, Masayoshi; Hirono, Hidetoshi; Hanao, Takafumi; Hyobu, Takahiro; Ito, Kengo; Matsumoto, Keisuke; Nakayama, Takashi; Oki, Nobuharu; Kikuchi, Yusuke; Fukumoto, Naoyuki

2013-10-01

Non-inductive current drive by using Multi-pulsing coaxial helicity injection was studied on HIST. In the double-pulsing CHI experiment, we have examined two-fluid effects by reversing polarity of the bias poloidal coil current. In the ST magnetic configurations with the right-handed magnetic field (positive CHI), there are a diamagnetic structure in the open flux column region and a paramagnetic structure in the closed flux region. It is naturally understood that the direction of the poloidal magnetic field (toroidal current) is reversed in reversing the polarity of the bias flux from positive to negative. However, the poloidal current is surprisingly reversed in reversing the magnetic helicity polarity. The direction of the poloidal current is opposite in the each region. The toroidal flow is reversed, but a shear profile of the poloidal flow is not changed significantly. In this configuration, the diamagnetic structure appears in the closed flux region. Thus, not only Jt×Bp but also Jp×Bt force contributes on pressure balance leading to a higher beta. We are studying a more general helicity conservation that constrains the interaction between flows and magnetic fields and momentum transport in the two-fluid framework.

Giant reversible anisotropy changes at room temperature in a (La,Sr)MnO 3/Pb(Mg,Nb,Ti)O 3 magneto-electric heterostructure

DOE PAGES

Chopdekar, Rajesh Vilas; Buzzi, Michele; Jenkins, Catherine; ...

2016-06-08

In a model artificial multiferroic system consisting of a (011)-oriented ferroelectric Pb(Mg,Nb,Ti)O 3 substrate intimately coupled to an epitaxial ferromagnetic (La,Sr)MnO 3 film, electric field pulse sequences of less than 6 kV/cm induce large, reversible, and bistable remanent strains. The magnetic anisotropy symmetry reversibly switches from a highly anisotropic two-fold state to a more isotropic one, with concomitant changes in resistivity. Anisotropy changes at the scale of a single ferromagnetic domain were measured using X-ray microscopy, with electric-field dependent magnetic domain reversal showing that the energy barrier for magnetization reversal is drastically lowered. Free energy calculations confirm this barrier loweringmore » by up to 70% due to the anisotropic strain changes generated by the substrate. Thus, we demonstrate that an electric field pulse can be used to 'set' and 'reset' the magnetic anisotropy orientation and resistive state in the film, as well as to lower the magnetization reversal barrier, showing a promising route towards electric-field manipulation of multifunctional nanostructures at room temperature.« less

Optimization of process parameters of pulsed TIG welded maraging steel C300

NASA Astrophysics Data System (ADS)

Deepak, P.; Jualeash, M. J.; Jishnu, J.; Srinivasan, P.; Arivarasu, M.; Padmanaban, R.; Thirumalini, S.

2016-09-01

Pulsed TIG welding technology provides excellent welding performance on thin sections which helps to increase productivity, enhance weld quality, minimize weld costs, and boost operator efficiency and this has drawn the attention of the welding society. Maraging C300 steel is extensively used in defence and aerospace industry and thus its welding becomes an area of paramount importance. In pulsed TIG welding, weld quality depends on the process parameters used. In this work, Pulsed TIG bead-on-plate welding is performed on a 5mm thick maraging C300 plate at different combinations of input parameters: peak current (Ip), base current (Ib) and pulsing frequency (HZ) as per box behnken design with three-levels for each factor. Response surface methodology is utilized for establishing a mathematical model for predicting the weld bead depth. The effect of Ip, Ib and HZ on the weld bead depth is investigated using the developed model. The weld bead depth is found to be affected by all the three parameters. Surface and contour plots developed from regression equation are used to optimize the processing parameters for maximizing the weld bead depth. Optimum values of Ip, Ib and HZ are obtained as 259 A, 120 A and 8 Hz respectively. Using this optimum condition, maximum bead depth of the weld is predicted to be 4.325 mm.

Pulsed operation of Tm-doped fiber lasers using piezoelectric-driven microbend applied to elliptical coating fibers

NASA Astrophysics Data System (ADS)

Sakata, H.; Kimpara, K.; Komori, K.; Tomiki, M.

2014-05-01

We report Q-switched pulse generation in Tm-doped fiber lasers by introducing piezoelectric-driven microbend into an elliptical coating fiber in a fiber ring resonator. Compared with the untreated circular fiber having a diameter of 240 μm, the elliptical coating fiber was flattened to have a major axis diameter of about 300 μm. We employed a pair of comblike plates attached on the piezoelectric actuators in order to bend the fiber from both sides. The output pulse power is improved by optimizing the tooth-width and spatial period of the comb-like plates, so that the elliptical coating fiber is easily bent and the propagation mode is efficiently coupled to radiation modes around λ = 1.9 μm. The Tm-doped fiber is pumped by a laser diode emitting at 1.63 μm and the pump light is introduced to the fiber ring resonator via the wavelength division multiplexing coupler. The emission spectra showed that the center oscillation wavelength was typically 1.92 μm. When the pump power was increased to 156 mW, the output pulse showed a peak power of 42.5 W with a pulse width of 1.06 μs. We expect that the in-fiber Q-switching technique will provide simple laser systems for environmental sensing and medical applications.

Speeding up NMR by in Situ Photo-Induced Reversible Acceleration of T1 -Relaxation (PIRAT).

PubMed

Stadler, Eduard; Dommaschk, Marcel; Frühwirt, Philipp; Herges, Rainer; Gescheidt, Georg

2018-03-05

Increasing the signal-to-noise ratio is one of the major goals in the field of NMR spectroscopy. In this proof of concept, we accelerate relaxation during an NMR pulse sequence using photo-generated paramagnetic states of an inert sensitizer. For the follow-up acquisition period, the system is converted to a diamagnetic state. The reversibility of the photo-induced switching allows extensive repetition required for multidimensional NMR. We thus eliminate the obstacle of line-broadening by the presence of paramagnetic species. In this contribution, we show how cycling of synchronized light/pulse sequences leads to an enhanced efficiency in multidimensional NMR. Our approach utilizes a molecular spin switch reversibly altering between a paramagnetic and diamagnetic state. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Time Reversed Electromagnetics as a Novel Method for Wireless Power Transfer

NASA Astrophysics Data System (ADS)

Challa, Anu; Anlage, Steven M.; Tesla Team

Taking advantage of ray-chaotic enclosures, time reversal has been shown to securely transmit information via short-wavelength waves between two points, yielding noise at all other sites. In this presentation, we propose a method to adapt the signal-focusing technique to electromagnetic signals in order to transmit energy to portable devices. Relying only on the time-reversal invariance properties of waves, the technique is unencumbered by the inversely-proportional-to-distance path loss or precise orientation requirements of its predecessors, making it attractive for power transfer applications. We inject a short microwave pulse into a complex, wave-chaotic chamber and collect the resulting long time-domain signal at a designated transceiver. The signal is then time reversed and emitted from the collection site, collapsing as a time-reversed replica of the initial pulse at the injection site. When amplified, this reconstruction is robust, as measured through metrics of peak-to-peak voltage and energy transfer ratio. We experimentally demonstrate that time reversed collapse can be made on a moving target, and propose a way to selectively target devices through nonlinear time-reversal. University of Maryland Gemstone Team TESLA: Frank Cangialosi, Anu Challa, Tim Furman, Tyler Grover, Patrick Healey, Ben Philip, Brett Potter, Scott Roman, Andrew Simon, Liangcheng Tao, Alex Tabatabai.

Multi-parametric studies of electrically-driven flyer plates

NASA Astrophysics Data System (ADS)

Neal, William; Bowden, Michael; Explosive Trains; Devices Collaboration

2015-06-01

Exploding foil initiator (EFI) detonators function by the acceleration of a flyer plate, by the electrical explosion of a metallic bridge, into an explosive pellet. The length, and therefore time, scales of this shock initation process is dominated by the magnitude and duration of the imparted shock pulse. To predict the dynamics of this initiation, it is critical to further understand the velocity, shape and thickness of this flyer plate. This study uses multi-parametric diagnostics to investigate the geometry and velocity of the flyer plate upon impact including the imparted electrical energy: photon Doppler velocimetry (PDV), dual axis imaging, time-resolved impact imaging, voltage and current. The investigation challenges the validity of traditional assumptions about the state of the flyer plate at impact and discusses the improved understanding of the process.

Capacitive proximity sensor

DOEpatents

Kronberg, J.W.

1994-05-31

A proximity sensor based on a closed field circuit is disclosed. The circuit comprises a ring oscillator using a symmetrical array of plates that creates an oscillating displacement current. The displacement current varies as a function of the proximity of objects to the plate array. Preferably the plates are in the form of a group of three pair of symmetric plates having a common center, arranged in a hexagonal pattern with opposing plates linked as a pair. The sensor produces logic level pulses suitable for interfacing with a computer or process controller. The proximity sensor can be incorporated into a load cell, a differential pressure gauge, or a device for measuring the consistency of a characteristic of a material where a variation in the consistency causes the dielectric constant of the material to change. 14 figs.

High average power magnetic modulator for metal vapor lasers

DOEpatents

Ball, Don G.; Birx, Daniel L.; Cook, Edward G.; Miller, John L.

1994-01-01

A three-stage magnetic modulator utilizing magnetic pulse compression designed to provide a 60 kV pulse to a copper vapor laser at a 4.5 kHz repetition rate is disclosed. This modulator operates at 34 kW input power. The circuit includes a step up auto transformer and utilizes a rod and plate stack construction technique to achieve a high packing factor.

Mass spectrometer calibration of Cosmic Dust Analyzer

NASA Astrophysics Data System (ADS)

Ahrens, Thomas J.; Gupta, Satish C.; Jyoti, G.; Beauchamp, J. L.

2003-02-01

The time-of-flight (TOF) mass spectrometer (MS) of the Cosmic Dust Analyzer (CDA) instrument aboard the Cassini spacecraft is expected to be placed in orbit about Saturn to sample submicrometer-diameter ring particles and impact ejecta from Saturn's satellites. The CDA measures a mass spectrum of each particle that impacts the chemical analyzer sector of the instrument. Particles impact a Rh target plate at velocities of 1-100 km/s and produce some 10-8 to 10-5 times the particle mass of positive valence, single-charged ions. These are analyzed via a TOF MS. Initial tests employed a pulsed N2 laser acting on samples of kamacite, pyrrhotite, serpentine, olivine, and Murchison meteorite induced bursts of ions which were detected with a microchannel plate and a charge sensitive amplifier (CSA). Pulses from the N2 laser (1011 W/cm2) are assumed to simulate particle impact. Using aluminum alloy as a test sample, each pulse produces a charge of ~4.6 pC (mostly Al+1), whereas irradiation of a stainless steel target produces a ~2.8 pC (Fe+1) charge. Thus the present system yields ~10-5% of the laser energy in resulting ions. A CSA signal indicates that at the position of the microchannel plate, the ion detector geometry is such that some 5% of the laser-induced ions are collected in the CDA geometry. Employing a multichannel plate detector in this MS yields for Al-Mg-Cu alloy and kamacite targets well-defined peaks at 24 (Mg+1), 27(Al+1), and 64 (Cu+1) and 56 (Fe+1), 58 (Ni+1), and 60 (Ni+1) dalton, respectively.

Plate Margin Deformation and Active Tectonics Along the Northern Edge of the Yakutat Terrane in the Saint Elias Orogen, Alaska and Yukon, Canada

NASA Technical Reports Server (NTRS)

Bruhn, Ronald L.; Sauber, Jeanne; Cotton, Michele M.; Pavlis, Terry L.; Burgess, Evan; Ruppert, Natalia; Forster, Richard R.

2012-01-01

The northwest directed motion of the Pacific plate is accompanied by migration and collision of the Yakutat terrane into the cusp of southern Alaska. The nature and magnitude of accretion and translation on upper crustal faults and folds is poorly constrained, however, due to pervasive glaciation. In this study we used high-resolution topography, geodetic imaging, seismic, and geologic data to advance understanding of the transition from strike-slip motion on the Fairweather fault to plate margin deformation on the Bagley fault, which cuts through the upper plate of the collisional suture above the subduction megathrust. The Fairweather fault terminates by oblique-extensional splay faulting within a structural syntaxis, allowing rapid tectonic upwelling of rocks driven by thrust faulting and crustal contraction. Plate motion is partly transferred from the Fairweather to the Bagley fault, which extends 125 km farther west as a dextral shear zone that is partly reactivated by reverse faulting. The Bagley fault dips steeply through the upper plate to intersect the subduction megathrust at depth, forming a narrow fault-bounded crustal sliver in the obliquely convergent plate margin. Since . 20 Ma the Bagley fault has accommodated more than 50 km of dextral shearing and several kilometers of reverse motion along its southern flank during terrane accretion. The fault is considered capable of generating earthquakes because it is linked to faults that generated large historic earthquakes, suitably oriented for reactivation in the contemporary stress field, and locally marked by seismicity. The fault may generate earthquakes of Mw <= 7.5.

Free energy gap laws for the pulse-induced and stationary fluorescence quenching by reversible charge transfer in polar solutions.

PubMed

Khokhlova, Svetlana S; Burshtein, Anatoly I

2011-01-21

The Stern-Volmer constants for either pulse-induced or stationary fluorescence being quenched by a contact charge transfer are calculated and their free energy dependencies (the free energy gap laws) are specified. The reversibility of charge transfer is taken into account as well as spin conversion in radical ion pairs, followed by their recombination in either singlet or triplet neutral products. The natural decay of triplets as well as their impurity quenching by ionization are accounted for when estimating the fluorescence quantum yield and its free energy dependence.

Development of reverse biased p-n junction electron emission

NASA Technical Reports Server (NTRS)

Fowler, P.; Muly, E. C.

1971-01-01

A cold cathode emitter of hot electrons for use as a source of electrons in vacuum gauges and mass spectrometers was developed using standard Norton electroluminescent silicon carbide p-n diodes operated under reverse bias conditions. Continued development including variations in the geometry of these emitters was carried out such that emitters with an emission efficiency (emitted current/junction current) as high as 3 x 10-0.00001 were obtained. Pulse measurements of the diode characteristics were made and showed that higher efficiency can be attained under pulse conditions probably due to the resulting lower temperatures resulting from such operation.

Effects of pulse ON and OFF time and electrode types on the material removal rate and tool wear rate of the Ti-6Al-4V Alloy using EDM machining with reverse polarity

NASA Astrophysics Data System (ADS)

Praveen, L.; Geeta Krishna, P.; Venugopal, L.; Prasad, N. E. C.

2018-03-01

Electrical Discharge Machining (EDM) is an unconventional metal removal process that is extensively used for removing the difficult-to-machine metal such as Ti alloys, super alloys and metal matrix composites. This paper investigates the effects of pulse (ON/OFF) time on EDM machining characteristics of Ti-6Al-4V alloy using copper and graphite as electrodes in reverse polarity condition. Full factorial design method was used to design the experiments. Two variables (Pulse On and OFF) with three levels are considered. The output variables are the tool wear rate and the material removal rate. The important findings from the present work are: (1) the material removal rate (MRR) increases gradually with an increase of the Pulse ON time whereas the change is insignificant with an increase of the Pulse OFF time, (2) Between copper and graphite electrodes, the copper electrode is proved to be good in terms of MRR, (3) a combination of high pulse ON time and OFF time is desirable for high MRR rate in the Cu electrode whereas for the graphite electrode, a combination of high pulse ON time and low pulse OFF time is desirable for high MRR rate, (4) the tool wear rate (TWR) reduces with the Pulse On or OFF time, the rate of TWR is uniform for the graphite electrode in contrast to abrupt decrease from 25 to 50 μs (pulse ON time) in the copper electrode, (5) In order to keep the TWR as minimum possible, it is desirable to have a combination of high pulse ON time and OFF time for both the copper and the graphite electrode.

System for phase-contrast x-ray radiography using X pinch radiation and a method thereof

DOEpatents

Chandler, Katherine; Chelkovenko, Tatiana; Hammer, David; Pikuz, Sergei; Sinars, Daniel; Song, Byungmoo

2007-11-06

A radiograph system with an anode plate, a cathode plate, and a power source coupled to said anode plate and the cathode plate. At least two wires coupled between the anode plate and the cathode plate provide a configuration to form an X-pinch having a photon source size of less than five microns at energies above 2.5 keV. Material at the configuration forming the X-pinch vaporizes upon application of a suitable current to the wires forming a dense hot plasma and emitting a single x-ray pulse with sufficient photons having energies in the range of from about 2.5 keV to about 20 keV to provide a phase contrast image of an object in the path of the photons. Multiple simultaneous images may be formed of a plurality of objects. Suitable filters and x-ray detectors are provided.

Pulsed differential holographic measurements of vibration modes of high temperature panels

NASA Technical Reports Server (NTRS)

Evensen, D. A.; Aprahamian, R.; Overoye, K. R.

1972-01-01

Holography is a lensless imaging technique which can be applied to measure static or dynamic displacements of structures. Conventional holography cannot be readily applied to measure vibration modes of high-temperature structures, due to difficulties caused by thermal convection currents. The present report discusses the use of pulsed differential holography, which is a technique for recording structural motions in the presence of random fluctuations such as turbulence. An analysis of the differential method is presented, and demonstration experiments were conducted using heated stainless steel plates. Vibration modes were successfully recorded for the heated plates at temperatures of 1000, 1600, and 2000 F. The technique appears promising for such future measurments as vibrations of the space shuttle TPS panels or recording flutter of aeroelastic models in a wind-tunnel.

A new approach to large area microchannel plate manufacture

NASA Technical Reports Server (NTRS)

1986-01-01

Methods of manufacture of twisted single elements as the base for producing microchannel plates (MCP) are discussed. Initial evaluations validated the off-axis channel concept and no technological roadblocks were identified which would prevent fabrication of high gain, high spatial resolution, large format MCP's using this technique. The first MP's have operated at stable gains of 3 million with pulse height resolution superior to results obtained by standard chevron MCP's.

Laser damage resistant nematic liquid crystal cell

NASA Astrophysics Data System (ADS)

Raszewski, Z.; Piecek, W.; Jaroszewicz, L.; Soms, L.; Marczak, J.; Nowinowski-Kruszelnicki, E.; Perkowski, P.; Kedzierski, J.; Miszczyk, E.; Olifierczuk, M.; Morawiak, P.; Mazur, R.

2013-08-01

There exists a problem in diagnostics of a dense plasma (so-called Thomson diagnostics). For this purpose, the plasma is illuminated by series of high energy laser pulses. Such pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along an exactly the same optical path. In this case, the energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, several independent lasers have to be used. To form optical path with λ = 1.064 μm and absolute value of the energy of laser pulse through of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell (NLCC) of type LCNP2 with switching on time τON smaller than 5 μs might be applied. High laser damage resistance of NLCC and short τON can be fulfilled by preparation of liquid crystal cells with Liquid Crystal Mixture (LCM), well tuned to twisted nematic electro-optical effect, and well tuned all optical interfaces (Air - Antireflection - Quartz Plate - Electrode - Blocking Film - Aligning Layer - LCM - Aligning Layer - Blocking Film - Electrode - Quartz Plate - Antireflection - Air). In such LCNP2 cell, the transmission is higher than 97% at λ = 1.064 μm, as it is presented by Gooch and Tarry [J. Phys. D: Appl. Phys. 8, 1575 (1975)]. The safe laser density energy is about 0.6 J/cm2 for a train of laser pulses (λ = 1.064 μm, pulse duration 10 ns FWHM, pulse repetition rate 100 pps, train duration 10 s), so the area of liquid crystal cell tolerating 3 J through it shall be as large as 5 cm2. Due to the presence of two blocking film layers between electrodes, LCNP2 can be driven by high voltages. Switching on time smaller than τON = 5 μs was obtained under 200 V switching voltage.

Maximizing energy deposition by shaping few-cycle laser pulses

NASA Astrophysics Data System (ADS)

Gateau, Julien; Patas, Alexander; Matthews, Mary; Hermelin, Sylvain; Lindinger, Albrecht; Kasparian, Jérôme; Wolf, Jean-Pierre

2018-07-01

We experimentally investigate the impact of pulse shape on the dynamics of laser-generated plasma in rare gases. Fast-rising triangular pulses with a slower decay lead to early ionization of the gas and depose energy more efficiently than their temporally reversed counterparts. As a result, in both argon and krypton, the induced shockwave as well as the plasma luminescence are stronger. This is due to an earlier availability of free electrons to undergo inverse Bremsstrahlung on the pulse trailing edge. Our results illustrate the ability of adequately tailored pulse shapes to optimize the energy deposition in gas plasmas.

The Behavior of Thin Dielectrics Under Electron Irradiation

DTIC Science & Technology

1980-03-01

one of the principal surface materials used in satellites. As such, their behavior is of concern in SGEMP (system- generated electromagnetic pulse ), which...is time-reversible. 4 B. Goplen, R. E. Clark, and B. Fishbine, "MAD2 - A Computer Code for Systems-Generated Electromagnetic Pulse (SGEMP

Phase conjugation and time reversal in acoustics

NASA Astrophysics Data System (ADS)

Fink, Mathias

2000-07-01

This paper compares the different approaches used in acoustics to time reverse or to phase conjugate a wavefield. The basic principle of a time reversal mirror is an extension for broadband pulsed waves to the optical phase conjugated mirror designed for monochromatic waves. However, this equivalence is only valid mathematically and there are some fundamental differences between these two techniques that will be described in this paper.

Damping of collective modes and the echo effect in a confined Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Kuklov, A. B.; Chencinski, N.

1998-04-01

We discuss the reversible nature of two mechanisms of the apparent damping of the collective modes of a confined Bose-Einstein condensate -- Landau Damping (LD) and a dephasing caused by thermal fluctuations of the normal component. The reversibility of the damping in both cases can be tested by the echo effect, when two consecutive external pulses modulate the potential trapping the condensate and induce a third pulse -- the echo -- at the time approximately equal to twice the time interval between the first two pulses. This effect is similar to the phonon echo in powders (Koji Kajimura in Physical Acoustics), ed. W.P. Mason, V.XVI, Academic Press, NY, Toronto 1982.. Parameters of the echo for the isotropic condensate are calculated analytically in the adiabatic approximation for the case of the small external pulses. Numerical simulations for the arbitrary pulses are also presented. The echo in an anisotropic condensate, where the adaibatic approximation is not valid because of the LD, is described in terms of the model of a single oscillator interacting with a quasi-continuum of modes which constitutes the normal component. In both cases in the weak echo limit the echo amplitude turns out to be proportional to the amplitudes of the external pulses. We suggest to test these predictions experimentally.

The physics of transverse mode instability-induced nonlinear phase distortions in large area optical fiber amplifiers and their mitigation with applications in scaling of pulsed and continuous wave high-energy lasers

DTIC Science & Technology

2016-12-13

plate and novel all-fiber fused coupler. Such work has laid the platform to demonstrate the mitigation of thermal mode instability through vortex beam...at IIT Madras to experimentally validate the above results as well as to explore the generation of vortex modes through a spiral phase plate and...modes through spiral phase plates and novel all-fiber fused couplers. We have demonstrated the excitation of a vortex mode with charge 1 through a

Reversing flow causes passive shark scale actuation in a separating turbulent boundary layer

NASA Astrophysics Data System (ADS)

Lang, Amy; Gemmell, Bradford; Motta, Phil; Habegger, Laura; Du Clos, Kevin; Devey, Sean; Stanley, Caleb; Santos, Leo

2017-11-01

Control of flow separation by shortfin mako skin in experiments has been demonstrated, but the mechanism is still poorly understood yet must be to some extent Re independent. The hypothesized mechanisms inherent in the shark skin for controlling flow separation are: (1) the scales, which are capable of being bristled only by reversing flow, inhibit flow reversal events from further development into larger-scale separation and (2) the cavities formed when scales bristle induces mixing of high momentum flow towards the wall thus energizing the flow close to the surface. Two studies were carried out to measure passive scale actuation caused by reversing flow. A small flow channel induced an unsteady, wake flow over the scales prompting reversing flow events and scale actuation. To resolve the flow and scale movements simultaneously we used specialized optics at high magnification (1 mm field of view) at 50,000 fps. In another study, 3D printed models of shark scales, or microflaps (bristling capability up to 50 degrees), were set into a flat plate. Using a tripped, turbulent boundary layer grown over the long flat plate and a localized adverse pressure gradient, a separation bubble was generated within which the microflaps were placed. Passive flow actuation of both shark scales and microflaps by reversing flow was observed. Funding from Army Research Office and NSF REU site Grant.

PULSE AMPLITUDE ANALYZER

DOEpatents

Gray, G.W.; Jensen, A.S.

1957-10-22

A pulse-height analyzer system of improved design for sorting and counting a series of pulses, such as provided by a scintillation detector in nuclear radiation measurements, is described. The analyzer comprises a main transmission line, a cathode-ray tube for each section of the line with its deflection plates acting as the line capacitance; means to bias the respective cathode ray tubes so that the beam strikes a target only when a prearranged pulse amplitude is applied, with each tube progressively biased to respond to smaller amplitudes; pulse generating and counting means associated with each tube to respond when the beam is deflected; a control transmission line having the same time constant as the first line per section with pulse generating means for each tube for initiating a pulse on the second transmission line when a pulse triggers the tube of corresponding amplitude response, the former pulse acting to prevent successive tubes from responding to the pulse under test. This arrangement permits greater deflection sensitivity in the cathode ray tube and overcomes many of the disadvantages of prior art pulse-height analyzer circuits.

Achievement of radiative feedback control for long-pulse operation on EAST

NASA Astrophysics Data System (ADS)

Wu, K.; Yuan, Q. P.; Xiao, B. J.; Wang, L.; Duan, Y. M.; Chen, J. B.; Zheng, X. W.; Liu, X. J.; Zhang, B.; Xu, J. C.; Luo, Z. P.; Zang, Q.; Li, Y. Y.; Feng, W.; Wu, J. H.; Yang, Z. S.; Zhang, L.; Luo, G.-N.; Gong, X. Z.; Hu, L. Q.; Hu, J. S.; Li, J.

2018-05-01

The active feedback control of radiated power to prevent divertor target plates overheating during long-pulse operation has been developed and implemented on EAST. The radiation control algorithm, with impurity seeding via a supersonic molecular beam injection (SMBI) system, has shown great success in both reliability and stability. By seeding a sequence of short neon (Ne) impurity pulses with the SMBI from the outer mid-plane, the radiated power of the bulk plasma can be well controlled, and the duration of radiative control (feedforward and feedback) is 4.5 s during a discharge of 10 s. Reliable control of the total radiated power of bulk plasma has been successfully achieved in long-pulse upper single null (USN) discharges with a tungsten divertor. The achieved control range of {{f}rad} is 20%–30% in L-mode regimes and 18%–36% in H-mode regimes. The temperature of the divertor target plates was maintained at a low level during the radiative control phase. The peak particle flux on the divertor target was decreased by feedforward Ne injection in the L-mode discharges, while the Ne pulses from the SMBI had no influence on the peak particle flux because of the very small injecting volume. It is shown that although the radiated power increased, no serious reduction of plasma-stored energy or confinement was observed during the control phase. The success of the radiation control algorithm and current experiments in radiated power control represents a significant advance for steady-state divertor radiation and heat flux control on EAST for near-future long-pulse operation.

Study of a plate-electrode XeCl laser with a pulse repetition rate up to 5 kHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voevodin, Denis D; Vysotskii, Andrei V; Lazhintsev, Boris V

2012-11-30

The results of the study of a repetitively pulsed XeCl laser with a high rate of pulse repetition and the electrode assembly based on a multi-section discharge gap with inductance-capacitance stabilisation of the discharge are presented. The multi-section discharge gap is formed by 25 pairs of anode - cathode plates. The discharge formed in the interelectrode gap had the dimensions 250 Multiplication-Sign 12 Multiplication-Sign 2 mm. The studies were performed using the HCl - Xe - Ne laser mixture at the total pressure up to 3.5 atm. The limit value of the radiation pulse repetition rate was equal to 5more » kHz. The meansquare deviation of the pulse energy increased from 0.8 % to 1.6 % in the range of repetition rates from 1 to 4.5 kHz and did not exceed 2.4 % at the frequency 5 kHz. The maximal energy of the laser pulse and the efficiency coefficient were equal to 7.9 mJ and 1.6 %, respectively. The maximal power of laser radiation (31 W) was obtained at the repetition rate 5 kHz. A new technique of measuring the gas flow velocity in the interelectrode gap is proposed. The velocity of gas circulation at the maximal pressure of the mixture did not exceed 18 m s{sup -1}. Optical inhomogeneities were observed, caused by a high concentration of electrons in the discharge plasma, by the acoustic wave, arising in the discharge gap, and by the heating of the gas in the discharge. (lasers)« less

Hybrid Ion-Detector/Data-Acquisition System for a TOF-MS

NASA Technical Reports Server (NTRS)

Burton, William D., Jr.; Schultz, J. Albert; Vaughn, Valentine; McCully, Michael; Ulrich, Steven; Egan, Thomas F.

2006-01-01

A modified ion-detector/data-acquisition system has been devised to increase the dynamic range of a time-of-flight mass spectrometer (TOF-MS) that, previously, included a microchannel-plate detector and a data-acquisition system based on counting pulses and time-tagging them by use of a time-to-digital converter (TDC). The dynamic range of the TOF-MS was limited by saturation of the microchannel plate detector, which can handle no more than a few million counts per second. The modified system includes (1) a combined microchannel plate/discrete ion multiplier and (2) a hybrid data-acquisition system that simultaneously performs analog current or voltage measurements and multianode single-ion-pulse-counting time-of-flight measurements to extend the dynamic range of a TDC into the regime in which a mass peak comprises multiple ions arriving simultaneously at the detector. The multianode data are used to determine, in real time, whether the detector is saturated. When saturation is detected, the data-acquisition system selectively enables circuitry that simultaneously determines the ion-peak intensity by measuring the time profile of the analog current or voltage detector-output signal.

High-speed microstrip multi-anode multichannel plate detector system

NASA Astrophysics Data System (ADS)

Riedo, Andreas; Tulej, Marek; Rohner, Urs; Wurz, Peter

2017-04-01

High-speed detector systems with high dynamic range and pulse width characteristics in the sub-nanosecond regime are mandatory for high resolution and highly sensitive time-of-flight mass spectrometers. Typically, for a reasonable detector area, an impedance-matched anode design is necessary to transmit the registered signal fast and distortion-free from the anode to the signal acquisition system. In this report, a high-speed microstrip multi-anode multichannel plate detector is presented and discussed. The anode consists of four separate active concentric anode segments allowing a simultaneous readout of signal with a dynamic range of about eight orders of magnitude. The impedance matched anode segments show pulse width of about 250 ps, measured at full width at half maximum, and rise time of ˜170 ps, measured with an oscilloscope with a sampling rate of 20 GS/s and 4 GHz analogue bandwidth. The usage of multichannel plates as signal amplifier allowed the design of a lightweight, low power consuming, and compact detector system, suitable, e.g., for the integration into space instrumentation or portable systems where size, weight, and power consumption are limited parameters.

Effect of sequential isoproturon pulse exposure on Scenedesmus vacuolatus.

PubMed

Vallotton, Nathalie; Eggen, Rik Ilda Lambertus; Chèvre, Nathalie

2009-04-01

Aquatic organisms are typically exposed to fluctuating concentrations of herbicides in streams. To assess the effects on algae of repeated peak exposure to the herbicide isoproturon, we subjected the alga Scenedesmus vacuolatus to two sequential pulse exposure scenarios. Effects on growth and on the inhibition of the effective quantum yield of photosystem II (PSII) were measured. In the first scenario, algae were exposed to short, 5-h pulses at high isoproturon concentrations (400 and 1000 microg/l), each followed by a recovery period of 18 h, while the second scenario consisted of 22.5-h pulses at lower concentrations (60 and 120 microg/l), alternating with short recovery periods (1.5 h). In addition, any changes in the sensitivity of the algae to isoproturon following sequential pulses were examined by determining the growth rate-EC(50) prior to and following exposure. In both exposure scenarios, we found that algal growth and its effective quantum yield were systematically inhibited during the exposures and that these effects were reversible. Sequential pulses to isoproturon could be considered a sequence of independent events. Nevertheless, a consequence of inhibited growth during the repeated exposures is the cumulative decrease in biomass production. Furthermore, in the second scenario, when the sequence of long pulses began to approach a scenario of continuous exposure, a slight increase in the tolerance of the algae to isoproturon was observed. These findings indicated that sequential pulses do affect algae during each pulse exposure, even if algae recover between the exposures. These observations could support an improved risk assessment of fluctuating exposures to reversibly acting herbicides.

Reversal of progressive necrotizing vasculitis with intravenous pulse cyclophosphamide and methylprednisolone.

PubMed

Fort, J G; Abruzzo, J L

1988-09-01

We describe a patient with polyarteritis nodosa who, despite therapy with daily doses of oral prednisone and cyclophosphamide, developed acute renal failure. Renal histopathologic examination demonstrated crescentic glomerulonephritis. Treatment with intravenous pulse cyclophosphamide and methylprednisolone resulted in clinical improvement and significant recovery of renal function.

Subpicosecond pulses from a neodymium-glass laser with a solid-liquid phototropic shutter

NASA Astrophysics Data System (ADS)

Altshuler, G. B.; Dulneva, E. G.; Karasev, V. B.; Okishev, A. V.; Telegin, L. S.

1985-02-01

Subpicosecond, spectrally limited pulses were generated in a mode-locked silicate-Nd-glass laser by means of a phototropic shutter. The shutter featured molecules of an organic dye added to a matrix composed of an isobutyl alcohol-filled quartz micropore glass plate. A coating on the inner surface of one of the cell windows was 0.99 reflective at the lasing wavelength. Single pulses with 0.5-1 psec length were generated, validating the use of a solid-liquid shutter for producing subpicosecond pulses with a Nd-glass laser. Furthermore, the liquid component permitted output powers of up to 5 W/sq cm without eliciting thermooptical effects.

Combined multiphoton imaging and automated functional enucleation of porcine oocytes using femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Kuetemeyer, Kai; Lucas-Hahn, Andrea; Petersen, Bjoern; Lemme, Erika; Hassel, Petra; Niemann, Heiner; Heisterkamp, Alexander

2010-07-01

Since the birth of ``Dolly'' as the first mammal cloned from a differentiated cell, somatic cell cloning has been successful in several mammalian species, albeit at low success rates. The highly invasive mechanical enucleation step of a cloning protocol requires sophisticated, expensive equipment and considerable micromanipulation skill. We present a novel noninvasive method for combined oocyte imaging and automated functional enucleation using femtosecond (fs) laser pulses. After three-dimensional imaging of Hoechst-labeled porcine oocytes by multiphoton microscopy, our self-developed software automatically identified the metaphase plate. Subsequent irradiation of the metaphase chromosomes with the very same laser at higher pulse energies in the low-density-plasma regime was used for metaphase plate ablation (functional enucleation). We show that fs laser-based functional enucleation of porcine oocytes completely inhibited the parthenogenetic development without affecting the oocyte morphology. In contrast, nonirradiated oocytes were able to develop parthenogenetically to the blastocyst stage without significant differences to controls. Our results indicate that fs laser systems have great potential for oocyte imaging and functional enucleation and may improve the efficiency of somatic cell cloning.

Analogue saturation limit of single and double 10 mm microchannel plate photomultiplier tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milnes, J. S., E-mail: james.milnes@photek.co.uk; Conneely, T. M.; Horsfield, C. J.

Photek are a well-established supplier of microchannel plate (MCP) photomultiplier tubes (PMTs) to the inertial confinement fusion community. The analogue signals produced at the major inertial confinement fusion facilities cover many orders of magnitude, therefore understanding the upper saturation limit of MCP-PMTs to large low rate signals takes on a high importance. Here we present a study of a single and a double MCP-PMT with 10 mm diameter active area. The saturation was studied for a range of optical pulse widths from 4 ns to 100 ns and at a range of electron gain values: 10{sup 3} to 10{sup 4}more » for the single and 10{sup 4} to 10{sup 6} for the double. We have shown that the saturation level of ∼1.2 nC depends only on the integrated charge of the pulse and is independent of pulse width and gain over this range, but that the level of charge available in deep saturation is proportional to the operating gain.« less

HIGH POWER PULSED OSCILLATOR

DOEpatents

Singer, S.; Neher, L.K.

1957-09-24

A high powered, radio frequency pulse oscillator is described for generating trains of oscillations at the instant an input direct voltage is impressed, or immediately upon application of a light pulse. In one embodiment, the pulse oscillator comprises a photo-multiplier tube with the cathode connected to the first dynode by means of a resistor, and adjacent dynodes are connected to each other through adjustable resistors. The ohmage of the resistors progressively increases from a very low value for resistors adjacent the cathode to a high value adjacent the plate, the last dynode. Oscillation occurs with this circuit when a high negative voltage pulse is applied to the cathode and the photo cathode is bombarded. Another embodiment adds capacitors at the resistor connection points of the above circuit to increase the duration of the oscillator train.

The effect of laser pulse tailored welding of Inconel 718

NASA Technical Reports Server (NTRS)

Mccay, T. Dwayne; Mccay, Mary Helen; Sharp, C. Michael; Womack, Michael G.

1990-01-01

Pulse tailored laser welding has been applied to wrought, wrought grain grown, and cast Inconel 718 using a CO2 laser. Prior to welding, the material was characterized metallographically and the solid state transformation regions were identified using Differential Scanning Calorimetry and high temperature x-ray diffraction. Bead on plate welds (restrained and unrestrained) were then produced using a matrix of pulse duty cycles and pulsed average power. Subsequent characterization included heat affected zone width, penetration and underbead width, the presence of cracks, microfissures and porosity, fusion zone curvature, and precipitation and liquated region width. Pedigree welding on three selected processing conditions was shown by microstructural and dye penetrant analysis to produce no microfissures, a result which strongly indicates the viability of pulse tailored welding for microfissure free IN 718.

AFRL’s HP3 60mm Powder Gun

DTIC Science & Technology

2012-08-08

reminiscent of wood -grain. It is unknown what effect the different construction techniques will have on the material’s suitability as a projectile...large plastic bar and mounts on the rear of the target plate are the interferometry probe holder (and probe). 11 Distribution Statement A. Approval...required to extrude the tapered boot through the tapering cone of the orifice plate, the breech pressure pulse shape (how long the high pressures are

Effect of the combination of different welding parameters on melting characteristics of grade 1 titanium with a pulsed Nd-Yag laser.

PubMed

Bertrand, C; Laplanche, O; Rocca, J P; Le Petitcorps, Y; Nammour, S

2007-11-01

The laser is a very attractive tool for joining dental metallic alloys. However, the choice of the setting parameters can hardly influence the welding performances. The aim of this research was to evaluate the impact of several parameters (pulse shaping, pulse frequency, focal spot size...) on the quality of the microstructure. Grade 1 titanium plates have been welded with a pulsed Nd-Yag laser. Suitable power, pulse duration, focal spot size, and flow of argon gas were fixed by the operator. Five different pulse shapes and three pulse frequencies were investigated. Two pulse shapes available on this laser unit were eliminated because they considerably hardened the metal. As the pulse frequency rose, the metal was more and more ejected, and a plasma on the surface of the metal increased the oxygen contamination in the welded area. Frequencies of 1 or 2 Hz are optimum for a dental use. Three pulse shapes can be used for titanium but the rectangular shape gives better results.

Synaptic transistor with a reversible and analog conductance modulation using a Pt/HfOx/n-IGZO memcapacitor

NASA Astrophysics Data System (ADS)

Yang, Paul; Kim, Hyung Jun; Zheng, Hong; Beom, Geon Won; Park, Jong-Sung; Kang, Chi Jung; Yoon, Tae-Sik

2017-06-01

A synaptic transistor emulating the biological synaptic motion is demonstrated using the memcapacitance characteristics in a Pt/HfOx/n-indium-gallium-zinc-oxide (IGZO) memcapacitor. First, the metal-oxide-semiconductor (MOS) capacitor with Pt/HfOx/n-IGZO structure exhibits analog, polarity-dependent, and reversible memcapacitance in capacitance-voltage (C-V), capacitance-time (C-t), and voltage-pulse measurements. When a positive voltage is applied repeatedly to the Pt electrode, the accumulation capacitance increases gradually and sequentially. The depletion capacitance also increases consequently. The capacitances are restored by repeatedly applying a negative voltage, confirming the reversible memcapacitance. The analog and reversible memcapacitance emulates the potentiation and depression synaptic motions. The synaptic thin-film transistor (TFT) with this memcapacitor also shows the synaptic motion with gradually increasing drain current by repeatedly applying the positive gate and drain voltages and reversibly decreasing one by applying the negative voltages, representing synaptic weight modulation. The reversible and analog conductance change in the transistor at both the voltage sweep and pulse operations is obtained through the memcapacitance and threshold voltage shift at the same time. These results demonstrate the synaptic transistor operations with a MOS memcapacitor gate stack consisting of Pt/HfOx/n-IGZO.

Synaptic transistor with a reversible and analog conductance modulation using a Pt/HfOx/n-IGZO memcapacitor.

PubMed

Yang, Paul; Jun Kim, Hyung; Zheng, Hong; Won Beom, Geon; Park, Jong-Sung; Jung Kang, Chi; Yoon, Tae-Sik

2017-06-02

A synaptic transistor emulating the biological synaptic motion is demonstrated using the memcapacitance characteristics in a Pt/HfOx/n-indium-gallium-zinc-oxide (IGZO) memcapacitor. First, the metal-oxide-semiconductor (MOS) capacitor with Pt/HfOx/n-IGZO structure exhibits analog, polarity-dependent, and reversible memcapacitance in capacitance-voltage (C-V), capacitance-time (C-t), and voltage-pulse measurements. When a positive voltage is applied repeatedly to the Pt electrode, the accumulation capacitance increases gradually and sequentially. The depletion capacitance also increases consequently. The capacitances are restored by repeatedly applying a negative voltage, confirming the reversible memcapacitance. The analog and reversible memcapacitance emulates the potentiation and depression synaptic motions. The synaptic thin-film transistor (TFT) with this memcapacitor also shows the synaptic motion with gradually increasing drain current by repeatedly applying the positive gate and drain voltages and reversibly decreasing one by applying the negative voltages, representing synaptic weight modulation. The reversible and analog conductance change in the transistor at both the voltage sweep and pulse operations is obtained through the memcapacitance and threshold voltage shift at the same time. These results demonstrate the synaptic transistor operations with a MOS memcapacitor gate stack consisting of Pt/HfOx/n-IGZO.

High-resolution estimates of Southwest Indian Ridge plate motions, 20 Ma to present

NASA Astrophysics Data System (ADS)

DeMets, C.; Merkouriev, S.; Sauter, D.

2015-12-01

We present the first estimates of Southwest Indian Ridge (SWIR) plate motions at high temporal resolution during the Quaternary and Neogene based on nearly 5000 crossings of 21 magnetic reversals out to C6no (19.72 Ma) and the digitized traces of 17 fracture zones and transform faults. Our reconstructions of this slow-spreading mid-ocean ridge reveal several unexpected results with notable implications for regional and global plate reconstructions since 20 Ma. Extrapolations of seafloor opening distances to zero-age seafloor based on reconstructions of reversals C1n (0.78 Ma) through C3n.4 (5.2 Ma) reveal evidence for surprisingly large outward displacement of 5 ± 1 km west of 32°E, where motion between the Nubia and Antarctic plates occurs, but 2 ± 1 km east of 32°E, more typical of most mid-ocean ridges. Newly estimated SWIR seafloor spreading rates are up to 15 per cent slower everywhere along the ridge than previous estimates. Reconstructions of the numerous observations for times back to 11 Ma confirm the existence of the hypothesized Lwandle plate at high confidence level and indicate that the Lwandle plate's western and eastern boundaries respectively intersect the ridge near the Andrew Bain transform fault complex at 32°E and between ˜45°E and 52°E, in accord with previous results. The Nubia-Antarctic, Lwandle-Antarctic and Somalia-Antarctic rotation sequences that best fit many magnetic reversal, fracture zone and transform fault crossings define previously unknown changes in the Neogene motions of all three plate pairs, consisting of ˜20 per cent slowdowns in their spreading rates at 7.2^{+0.9 }_{ -1.4} Ma if we enforce a simultaneous change in motion everywhere along the SWIR and gradual 3°-7° anticlockwise rotations of the relative slip directions. We apply trans-dimensional Bayesian analysis to our noisy, best-fitting rotation sequences in order to estimate less-noisy rotation sequences suitable for use in future global plate reconstructions and geodynamic studies. Notably, our new Nubia-Antarctic reconstruction of C5n.2 (11.0 Ma) predicts 20 per cent less opening than do two previous estimates, with important implications for motion that is estimated between the Nubia and Somalia plates. A Nubia-Somalia rotation determined from our Nubia-Antarctic and Somalia-Antarctic plate rotations for C5n.2 (11.0 Ma) predicts cumulative opening of 45 ± 4 km (95 per cent uncertainty) across the northernmost East Africa rift since 11.0 Ma, 70 per cent less than a recent 129 ± 62 km opening estimate based on a now-superseded interpretation of Anomaly 5 along the western portion of the SWIR.

A halochromic stimuli-responsive reversible fluorescence switching 3, 4, 9, 10-perylene tetracarboxylic acid dye for fabricating rewritable platform

NASA Astrophysics Data System (ADS)

Hariharan, P. S.; Pitchaimani, J.; Madhu, Vedichi; Anthony, Savarimuthu Philip

2017-02-01

3, 4, 9, 10-perylene tetracarboxylic acid (PTCA), a strongly fluorescent water soluble dye with halochromic functionality showed pH dependent reversible fluorescence switching. The strong fluorescence of PTCA (Φf = 0.67) in basic medium was completely quenched upon acidification. The fluorescent PTCA has been transferred on to a solid substrate (filter paper and glass plate) that also showed reversible off-on fluorescence switching by acid/base and drying/water vapor exposure. The reversible fluorescence switching of PTCA could be of potential interest for fabricating rewritable fluorescent medium.

Internal polarization dynamics of vector dissipative-soliton-resonance pulses in normal dispersion fiber lasers.

PubMed

Li, Daojing; Shen, Deyuan; Li, Lei; Tang, Dingyuan; Su, Lei; Zhao, Luming

2018-03-15

Internal polarization dynamics of vector dissipative-soliton-resonance (DSR) pulses in a mode-locked fiber laser are investigated. By utilizing a wave plate analyzer configuration to analyze the special structure of a DSR pulse, we find that polarization state is not uniform across a resonant dissipative soliton. Specifically, although the central plane wave of the resonant dissipative soliton acquires nearly a single fixed polarization, the dissipative fronts feature polarization states that are different and spatially varying. This distinct polarization distribution is maintained while the whole soliton extends with increasing gain. Numerical simulation further confirms the experimental observations.

Energy Losses Estimation During Pulsed-Laser Seam Welding

NASA Astrophysics Data System (ADS)

Sebestova, Hana; Havelkova, Martina; Chmelickova, Hana

2014-06-01

The finite-element tool SYSWELD (ESI Group, Paris, France) was adapted to simulate pulsed-laser seam welding. Besides temperature field distribution, one of the possible outputs of the welding simulation is the amount of absorbed power necessary to melt the required material volume including energy losses. Comparing absorbed or melting energy with applied laser energy, welding efficiencies can be calculated. This article presents achieved results of welding efficiency estimation based on the assimilation both experimental and simulation output data of the pulsed Nd:YAG laser bead on plate welding of 0.6-mm-thick AISI 304 stainless steel sheets using different beam powers.

A compact 300 kV solid-state high-voltage nanosecond generator for dielectric wall accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Yi; Wang, Wei; Liu, Yi

2015-05-15

Compact solid-state system is the main development trend in pulsed power technologies. A compact solid-state high-voltage nanosecond pulse generator with output voltage of 300 kV amplitude, 10 ns duration (FWHM), and 3 ns rise-time was designed for a dielectric wall accelerator. The generator is stacked by 15 planar-plate Blumlein pulse forming lines (PFL). Each Blumlein PFL consists of two solid-state planar transmission lines, a GaAs photoconductive semiconductor switch, and a laser diode trigger. The key components of the generator and the experimental results are reported in this paper.

Rise time measurement for ultrafast X-ray pulses

DOEpatents

Celliers, Peter M [Berkeley, CA; Weber, Franz A [Oakland, CA; Moon, Stephen J [Tracy, CA

2005-04-05

A pump-probe scheme measures the rise time of ultrafast x-ray pulses. Conventional high speed x-ray diagnostics (x-ray streak cameras, PIN diodes, diamond PCD devices) do not provide sufficient time resolution to resolve rise times of x-ray pulses on the order of 50 fs or less as they are being produced by modern fast x-ray sources. Here, we are describing a pump-probe technique that can be employed to measure events where detector resolution is insufficient to resolve the event. The scheme utilizes a diamond plate as an x-ray transducer and a p-polarized probe beam.

Rise Time Measurement for Ultrafast X-Ray Pulses

DOEpatents

Celliers, Peter M.; Weber, Franz A.; Moon, Stephen J.

2005-04-05

A pump-probe scheme measures the rise time of ultrafast x-ray pulses. Conventional high speed x-ray diagnostics (x-ray streak cameras, PIN diodes, diamond PCD devices) do not provide sufficient time resolution to resolve rise times of x-ray pulses on the order of 50 fs or less as they are being produced by modern fast x-ray sources. Here, we are describing a pump-probe technique that can be employed to measure events where detector resolution is insufficient to resolve the event. The scheme utilizes a diamond plate as an x-ray transducer and a p-polarized probe beam.

Grain Refinement of AZ31 Magnesium Alloy Weldments by AC Pulsing Technique

NASA Astrophysics Data System (ADS)

Kishore Babu, N.; Cross, C. E.

2012-11-01

The current study has investigated the influence of alternating current pulsing on the structure and mechanical properties of AZ31 magnesium alloy gas tungsten arc (GTA) weldments. Autogenous full penetration bead-on-plate GTA welds were made under a variety of conditions including variable polarity (VP), variable polarity mixed (VPM), alternating current (AC), and alternating current pulsing (ACPC). AC pulsing resulted in significant refinement of weld metal when compared with the unpulsed conditions. AC pulsing leads to relatively finer and more equiaxed grain structure in GTA welds. In contrast, VP, VPM, and AC welding resulted in predominantly columnar grain structures. The reason for this grain refinement may be attributed to the periodic variations in temperature gradient and solidification rate associated with pulsing as well as weld pool oscillation observed in the ACPC welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, tensile strength, and ductility.

Spectral modification of the laser emission of a terahertz quantum cascade laser induced by broad-band double pulse injection seeding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Markmann, Sergej, E-mail: sergej.markmann@ruhr-uni-bochum.de; Nong, Hanond, E-mail: nong.hanond@ruhr-uni-bochum.de; Hekmat, Negar

2015-09-14

We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.

Simulations of nanosecond-pulsed dielectric barrier discharges in atmospheric pressure air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soo Bak, Moon; Cappelli, Mark A.

2013-03-21

This paper describes simulations of nanosecond pulse plasma formation between planer electrodes covered by dielectric barriers in air at atmospheric pressure and 340 K. The plasma formation process starts as electrons detach from negative ions of molecular oxygen that are produced from the previous discharge pulse. An ionization front is found to form close to the positively biased electrode and then strengthens and propagates towards the grounded electrode with increasing gap voltage. Charge accumulation and secondary emission from the grounded electrode eventually lead to sheath collapse. One interesting feature is a predicted reversal in gap potential due to the accumulatedmore » charge, even when there is no reversal in applied potential. The simulation results are compared to recent measurement of mid-gap electric field under the same discharge conditions [Ito et al., Phys. Rev. Lett. 107, 065002 (2011)].« less

Infrared light excites cells by changing their electrical capacitance

PubMed Central

Shapiro, Mikhail G.; Homma, Kazuaki; Villarreal, Sebastian; Richter, Claus-Peter; Bezanilla, Francisco

2012-01-01

Optical stimulation has enabled important advances in the study of brain function and other biological processes, and holds promise for medical applications ranging from hearing restoration to cardiac pace making. In particular, pulsed laser stimulation using infrared wavelengths >1.5 μm has therapeutic potential based on its ability to directly stimulate nerves and muscles without any genetic or chemical pre-treatment. However, the mechanism of infrared stimulation has been a mystery, hindering its path to the clinic. Here we show that infrared light excites cells through a novel, highly general electrostatic mechanism. Infrared pulses are absorbed by water, producing a rapid local increase in temperature. This heating reversibly alters the electrical capacitance of the plasma membrane, depolarizing the target cell. This mechanism is fully reversible and requires only the most basic properties of cell membranes. Our findings underscore the generality of pulsed infrared stimulation and its medical potential. PMID:22415827

DIODE STEERED MANGETIC-CORE MEMORY

DOEpatents

Melmed, A.S.; Shevlin, R.T.; Laupheimer, R.

1962-09-18

A word-arranged magnetic-core memory is designed for use in a digital computer utilizing the reverse or back current property of the semi-conductor diodes to restore the information in the memory after read-out. In order to ob tain a read-out signal from a magnetic core storage unit, it is necessary to change the states of some of the magnetic cores. In order to retain the information in the memory after read-out it is then necessary to provide a means to return the switched cores to their states before read-out. A rewrite driver passes a pulse back through each row of cores in which some switching has taken place. This pulse combines with the reverse current pulses of diodes for each column in which a core is switched during read-out to cause the particular cores to be switched back into their states prior to read-out. (AEC)

Improvement of rolling 6 mm thin plates in plate rolling mill PT. Krakatau Posco

NASA Astrophysics Data System (ADS)

Pujiyanto, Hamdani

2017-01-01

A 6-mm thin plate is difficult to produce especially if the product requires wide size and high strength. Flatness is the main quality issue in rolling 6-mm plate using a 4-high reversing mill which use ±1100-mm work roll. Thus some methods are applied to overcome such issue in order to comply to customer quality requirement. Pre-rolling, rolling, and post-rolling conditions have to be considered comprehensively. Roll unit management will be the key factor before rolling condition. The roll unit itself has a significant impact on work roll crown wearness in relation with work roll intial crown and thermal crown. Work roll crown along with the modification of hydraulic gap control (HGC) could directly alter the flatness of the plate.

Spatiotemporal characterization of ultrashort optical vortex pulses

NASA Astrophysics Data System (ADS)

Miranda, Miguel; Kotur, Marija; Rudawski, Piotr; Guo, Chen; Harth, Anne; L'Huillier, Anne; Arnold, Cord L.

2017-12-01

We use a spiral phase plate to generate few-cycle optical vortices from an ultrafast titanium:sapphire oscillator and characterize them in the spatiotemporal domain with a recently introduced technique based on spatially resolved Fourier transform spectrometry. The performance of this simple approach to the generation of optical vortices is analysed from a wavelength-dependent perspective as well as in the spatiotemporal domain, allowing us to characterize ultrashort vortex pulses in space, frequency and time.

Pulsed gas laser

DOEpatents

Anderson, Louis W.; Fitzsimmons, William A.

1978-01-01

A pulsed gas laser is constituted by Blumlein circuits wherein space metal plates function both as capacitors and transmission lines coupling high frequency oscillations to a gas filled laser tube. The tube itself is formed by spaced metal side walls which function as connections to the electrodes to provide for a high frequency, high voltage discharge in the tube to cause the gas to lase. Also shown is a spark gap switch having structural features permitting a long life.

Optical reversible programmable Boolean logic unit.

PubMed

Chattopadhyay, Tanay

2012-07-20

Computing with reversibility is the only way to avoid dissipation of energy associated with bit erase. So, a reversible microprocessor is required for future computing. In this paper, a design of a simple all-optical reversible programmable processor is proposed using a polarizing beam splitter, liquid crystal-phase spatial light modulators, a half-wave plate, and plane mirrors. This circuit can perform 16 logical operations according to three programming inputs. Also, inputs can be easily recovered from the outputs. It is named the "reversible programmable Boolean logic unit (RPBLU)." The logic unit is the basic building block of many complex computational operations. Hence the design is important in sense. Two orthogonally polarized lights are defined here as two logical states, respectively.

Flaw growth behavior in thick welded plates of 2219-T87 aluminum at room and cryogenic temperatures

NASA Technical Reports Server (NTRS)

Forman, R. G.; Glorioso, S. V.; Medlock, J. D.

1973-01-01

Axial load fatigue and fracture tests were conducted on thick welded plates of 2219-T87 aluminum alloy to determine the tensile strength properties and the flaw growth behavior in electron beam, gas metal arc, and pulse current gas tungsten arc welds for plates 6.35 centimeters (2.5 in.) thick. The tests were conducted in room temperature air and in liquid nitrogen environments. Specimens were tested in both the as-welded and the aged after welding conditions. The experimental crack growth rate were correlated with theoretical crack growth rate predictions for semielliptical surface flaws.

Crack detection in fastener holes using surface acoustic wave

NASA Astrophysics Data System (ADS)

Bao, Xiao-Qi; Varadan, Vasundara V.; Varadan, Vijay K.

1995-05-01

This paper presents an investigation of the monitoring of cracks at the edge of fastener holes on plates using an ultrasonic pulse-echo technique. Our studies show that, if the surface of the plate surrounding the hold is free, an acoustic wave on the surface of the plate is able to detect the cracks located in an arc of 60 degree(s). When the inner surface of the hole is free, surface acoustic waves on the inner surface are alternate choices. For the case when all these surfaces are in tight contact with other parts, hence unavailable for mounting transducers, a particular type of Lamb wave mode is presented.

Microchannel plate EUV detectors for the Extreme Ultraviolet Explorer

NASA Technical Reports Server (NTRS)

Siegmund, O. H. W.; Malina, R. F.; Coburn, K.; Werthimer, D.

1984-01-01

The design and operating characteristics of the prototype imaging microchannel plate (MCP) detector for the Extreme Ultraviolet Explorer (EUVE) Satellite are discussed. It is shown that this detector has achieved high position resolution performance (greater than 512 x 512 pixels) and has low (less than one percent) image distortion. In addition, the channel plate scheme used has tight pulse height distributions (less than 40 percent FWHM) for UV radiation and displays low (less than 0.2 cnt/sq cm-s) dark background counting rates. Work that has been done on EUV filters in relation to the envisaged filter and photocathode complement is also described.

Influence of cooling rate in planar thermally assisted magnetic random access memory: Improved writeability due to spin-transfer-torque influence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chavent, A.; CNRS, INAC-SPINTEC, F-38000 Grenoble; CEA, INAC-SPINTEC, F-38000 Grenoble

This paper investigates the effect of a controlled cooling rate on magnetic field reversal assisted by spin transfer torque (STT) in thermally assisted magnetic random access memory. By using a gradual linear decrease of the voltage at the end of the write pulse, the STT decays more slowly or at least at the same rate as the temperature. This condition is necessary to make sure that the storage layer magnetization remains in the desired written direction during cooling of the cell. The influence of the write current pulse decay rate was investigated on two exchange biased synthetic ferrimagnet (SyF) electrodes.more » For a NiFe based electrode, a significant improvement in writing reproducibility was observed using a gradual linear voltage transition. The write error rate decreases by a factor of 10 when increasing the write pulse fall-time from ∼3 ns to 70 ns. For comparison, a second CoFe/NiFe based electrode was also reversed by magnetic field assisted by STT. In this case, no difference between sharp and linear write pulse fall shape was observed. We attribute this observation to the higher thermal stability of the CoFe/NiFe electrode during cooling. In real-time measurements of the magnetization reversal, it was found that Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling in the SyF electrode vanishes for the highest pulse voltages that were used due to the high temperature reached during write. As a result, during the cooling phase, the final state is reached through a spin-flop transition of the SyF storage layer.« less

Interactions between rewarding lateral hypothalamic and aversive nucleus reticularis gigantocellularis stimulation.

PubMed

Diotte, M; Miguelez, M; Miliaressis, E; Bielajew, C

2000-12-05

The interaction between rewarding and aversive consequences of brain stimulation were assessed in two studies. In the first, the frequency threshold for 300 ms trains of combined lateral hypothalamic (LH) and nucleus reticularis gigantocellularis (Gi) stimulation, in which each LH pulse was followed 2 ms later by the Gi one, was determined for one month. Compared to the threshold for trains of single LH pulses, combined LH-Gi stimulation initially increased the frequency threshold; however, this effect reversed within one session and was subsequently maintained for the duration of the study. The aversion produced by Gi stimulation, as measured by latency to escape, was abolished following a single session of LH-Gi pairs. In the second study, a subset of animals received both presentations of combined pulses, LH followed by Gi, and the reverse; the interval between pulses was varied from 0.2 to 6.4 ms. The effectiveness of combined stimulation, determined by the ratio of LH frequency thresholds to that of the LH-Gi ranged from 0 to 50% across animals but the individual effectiveness functions within animals did not vary with different intervals. In addition, the order of presentation of pulses was of no consequence. Thus, not only did exposure to LH stimulation appear to obliterate Gi aversion, but the combination of LH and Gi pulses added to the rewarding effect produced by LH stimulation alone.

Pulse analysis of acoustic emission signals

NASA Technical Reports Server (NTRS)

Houghton, J. R.; Packman, P. F.

1977-01-01

A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameter values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emission associated with (a) crack propagation, (b) ball dropping on a plate, (c) spark discharge, and (d) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train is shown to be the region in which the significant signatures of the acoustic emission event are to be found.

Pulse analysis of acoustic emission signals

NASA Technical Reports Server (NTRS)

Houghton, J. R.; Packman, P. F.

1977-01-01

A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis, and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameters values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emissions associated with: (1) crack propagation, (2) ball dropping on a plate, (3) spark discharge and (4) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train are shown to be the region in which the significant signatures of the acoustic emission event are to be found.

Mechanical Evolution and Dynamics of Decollement Slip in Contractional Systems: Correlating Macro- and Micro-Scale Processes in Particle Dynamics Simulation

NASA Astrophysics Data System (ADS)

Morgan, J. K.

2014-12-01

Particle-based numerical simulations allow detailed investigations of small-scale processes and mechanisms associated with fault initiation and slip, which emerge naturally in such models. This study investigates the evolving mechanical conditions and associated micro-mechanisms during transient slip on a weak decollement propagating beneath a growing contractional wedge (e.g., accretionary prism, fold and thrust belt). The models serve as analogs of the seismic cycle, although lacking full earthquake dynamics. Nonetheless, the mechanical evolution of both decollement and upper plate can be monitored, and correlated with the particle-scale physical and contact properties, providing insights into changes that accompany such stick-slip behavior. In this study, particle assemblages consolidated under gravity and bonded to impart cohesion, are pushed at a constant velocity above a weak, unbonded decollement surface. Forward propagation of decollement slip occurs in discrete pulses, modulated by heterogeneous stress conditions (e.g., roughness, contact bridging) along the fault. Passage of decollement slip resets the stress along this horizon, producing distinct patterns: shear stress is enhanced in front of the slipped decollement due to local contact bridging and fault locking; shear stress minima occur immediately above the tip, denoting local stress release and contact reorganization following slip; more mature portions of the fault exhibit intermediate shear stress, reflecting more stable contact force distributions and magnitudes. This pattern of shear stress pre-conditions the decollement for future slip events, which must overcome the high stresses at the fault tip. Long-term slip along the basal decollement induces upper plate contraction. When upper plate stresses reach critical strength conditions, new thrust faults break through the upper plate, relieving stresses and accommodating horizontal shortening. Decollement activity retreats back to the newly formed thrust fault. The cessation of upper plate fault slip causes gradual increases in upper plate stresses, rebuilding shear stresses along the decollement and enabling renewed pulses of decollement slip. Thus, upper plate deformation occurs out of phase with decollement propagation.

Improved field localization in transcranial magnetic stimulation of the brain with the utilization of a conductive shield plate in the stimulator.

PubMed

Kim, Dong-Hun; Georghiou, George E; Won, Chulho

2006-04-01

In this paper, a carefully designed conductive shield plate is presented, which helps to improve localization of the electric field distribution induced by transcranial magnetic stimulation for neuron stimulation. The shield plate is introduced between a figure-of-eight coil and the head. In order to accurately predict the field distribution inside the brain and to examine the effects of the shield plate, a realistic head model is constructed from magnetic resonance image data with the help of image processing tools and the finite-element method in three dimensions is employed. Finally, to show the improvements obtained, the results are compared with two conventional coil designs. It is found that an incorporation of the shield plate into the coil, effectively improves the induced field localization by more than 50%, and prevents other parts of the brain from exposure to high pulsed magnetic fields.

AUTOMATIC COUNTER

DOEpatents

Robinson, H.P.

1960-06-01

An automatic counter of alpha particle tracks recorded by a sensitive emulsion of a photographic plate is described. The counter includes a source of mcdulated dark-field illumination for developing light flashes from the recorded particle tracks as the photographic plate is automatically scanned in narrow strips. Photoelectric means convert the light flashes to proportional current pulses for application to an electronic counting circuit. Photoelectric means are further provided for developing a phase reference signal from the photographic plate in such a manner that signals arising from particle tracks not parallel to the edge of the plate are out of phase with the reference signal. The counting circuit includes provision for rejecting the out-of-phase signals resulting from unoriented tracks as well as signals resulting from spurious marks on the plate such as scratches, dust or grain clumpings, etc. The output of the circuit is hence indicative only of the tracks that would be counted by a human operator.

REDISTRIBUTOR FOR LIQUID-LIQUID EXTRACTION COLUMNS

DOEpatents

Bradley, J.G.

1957-10-29

An improved baffle plate construction to intimately mix immiscible liquid solvents for solvent extraction processes in a liquid-liquid pulse column is described. To prevent the light and heavy liquids from forming separate continuous homogeneous vertical channels through sections of the column, a baffle having radially placed rectangular louvers with deflection plates opening upon alternate sides of the baffle is placed in the column, normal to the axis. This improvement substantially completely reduces strippiig losses due to poor mixing.

Efficacy of tourniquets exposed to the afghanistan combat environment stored in individual first aid kits versus on the exterior of plate carriers.

PubMed

Weppner, Justin; Lang, Michael; Sunday, Robert; Debiasse, Nicholas

2013-03-01

Between February and May 2010, 1st Battalion, 6th Marines reported a 10% (10/92) breakage rate for tourniquets. One theory suggested was that tourniquets were weakened by exposure to the Afghan environment. Our study was designed to compare three groups of Afghanistan-exposed tourniquets to unexposed tourniquets. The three experimental arms were: (1) Afghan-exposed tourniquets worn on the plate carrier, (2) Afghan-exposed tourniquets carried in the Individual First Aid Kit (IFAK) and wrapped in manufacturer plastic wrapping, and (3) Afghan-exposed tourniquets carried in the IFAK with the manufacturer plastic wrapping removed. The outcome measures of this study were efficacy, breakage, and number of turns required to successfully stop the distal pulse. Tourniquets worn on the plate carrier had an efficacy of 57%, which was significantly lower than the control efficacy rate of 95.2%. When compared to the control arm, there were no significant differences in efficacy between the tourniquets stored in the IFAK with or without manufacturing packaging. No control tourniquets or tourniquets stored in IFAKs broke; however, 46 (12%) of the plate carrier-exposed tourniquets did break. No statistically significant differences were found between the four groups with regard to the median number of turns required to stop the distal pulse. Reprint & Copyright © 2013 Association of Military Surgeons of the U.S.

Pulse-burst laser systems for fast Thomson scattering (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Den Hartog, D. J.; Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706; Ambuel, J. R.

2010-10-15

Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to ''pulse-burst'' capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinchmore » to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.« less

Pulsed x-ray imaging of high-density objects using a ten picosecond high-intensity laser driver

NASA Astrophysics Data System (ADS)

Rusby, D. R.; Brenner, C. M.; Armstrong, C.; Wilson, L. A.; Clarke, R.; Alejo, A.; Ahmed, H.; Butler, N. M. H.; Haddock, D.; Higginson, A.; McClymont, A.; Mirfayzi, S. R.; Murphy, C.; Notley, M.; Oliver, P.; Allott, R.; Hernandez-Gomez, C.; Kar, S.; McKenna, P.; Neely, D.

2016-10-01

Point-like sources of X-rays that are pulsed (sub nanosecond), high energy (up to several MeV) and bright are very promising for industrial and security applications where imaging through large and dense objects is required. Highly penetrating X-rays can be produced by electrons that have been accelerated by a high intensity laser pulse incident onto a thin solid target. We have used a pulse length of 10ps to accelerate electrons to create a bright x-ray source. The bremsstrahlung temperature was measured for a laser intensity from 8.5-12×1018 W/cm2. These x-rays have sequentially been used to image high density materials using image plate and a pixelated scintillator system.

Preparation of metastable CoFeNi alloys with ultra-high magnetic saturation (Bs = 2.4-2.59 T) by reverse pulse electrodeposition

NASA Astrophysics Data System (ADS)

Tabakovic, Ibro; Venkatasamy, Venkatram

2018-04-01

The results of reverse pulse electrodeposition of CoFeNi films with ultra-high magnetic saturation, i.e. Bs values between 2.4 and 2.59 T, are presented in this work. Based on valence-bond theory (Hund's rule) it was assumed that the electronic configuration of MOH obtained by one electron reduction of electroactive intermediate (MOH+ads + e → MOHads) or oxidation of metal (M - e + HOH → MOH + H+) would result with larger number of spins per atom for each of transition metals in MOH-precipitated in CoFeNi deposit- with one more spin than their respective neutral metal in the order: Fe > Co > Ni. The experimental results showed that the increase of Bs value above Slater-Pauling curve was not observed for CoFe alloys, thus FeOH and CoOH compounds were not present in deposit. However, the increase of the Bs values above the Slater-Pauling curve (Bs = 2.4-2.59 T) was observed, for CoFeNi films obtained by reverse pulse electrodeposition. Therefore, NiOH as a stable compound is probably formed in a one-electron oxidation step during anodic pulse oxidation reaction precipitated presumably at the grain boundaries, giving rise to the ultra-high magnetic saturation of CoFeNi films. The effects of experimental conditions on elemental composition, magnetic properties, crystal structure, and thermal stability of CoFeNi films were studied.

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.

Integrating solids and gases for attosecond pulse generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammond, T. J.; Monchoce, Sylvain; Zhang, Chunmei

Here, control of the field of few-cycle optical pulses has had an enormous impact on attosecond science. Subcycle pulses open the potential for non-adiabatic phase matching while concentrating the electric field so it can be used most efficiently. However, subcycle field transients have been difficult to generate. We exploit the perturbative response of a sub-100 µm thick monocrystalline quartz plate irradiated by an intense few-cycle 1.8 µm pulse, which creates a phase-controlled supercontinuum spectrum. Within the quartz, the pulse becomes space–time coupled as it generates a parallel second harmonic. Vacuum propagation naturally leads to a subcycle electric-field transient whose envelopemore » is sculpted by the carrier envelope phase of the incident radiation. We show that a second medium (either gas or solid) can generate isolated attosecond pulses in the extreme ultraviolet region. With no optical elements between the components, the process is scalable to very high energy pulses and allows the use of diverse media.« less

Integrating solids and gases for attosecond pulse generation

DOE PAGES

Hammond, T. J.; Monchoce, Sylvain; Zhang, Chunmei; ...

2017-08-21

Here, control of the field of few-cycle optical pulses has had an enormous impact on attosecond science. Subcycle pulses open the potential for non-adiabatic phase matching while concentrating the electric field so it can be used most efficiently. However, subcycle field transients have been difficult to generate. We exploit the perturbative response of a sub-100 µm thick monocrystalline quartz plate irradiated by an intense few-cycle 1.8 µm pulse, which creates a phase-controlled supercontinuum spectrum. Within the quartz, the pulse becomes space–time coupled as it generates a parallel second harmonic. Vacuum propagation naturally leads to a subcycle electric-field transient whose envelopemore » is sculpted by the carrier envelope phase of the incident radiation. We show that a second medium (either gas or solid) can generate isolated attosecond pulses in the extreme ultraviolet region. With no optical elements between the components, the process is scalable to very high energy pulses and allows the use of diverse media.« less

Absolute Calibration of Image Plate for electrons at energy between 100 keV and 4 MeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, H; Back, N L; Eder, D C

2007-12-10

The authors measured the absolute response of image plate (Fuji BAS SR2040) for electrons at energies between 100 keV to 4 MeV using an electron spectrometer. The electron source was produced from a short pulse laser irradiated on the solid density targets. This paper presents the calibration results of image plate Photon Stimulated Luminescence PSL per electrons at this energy range. The Monte Carlo radiation transport code MCNPX results are also presented for three representative incident angles onto the image plates and corresponding electron energies depositions at these angles. These provide a complete set of tools that allows extraction ofmore » the absolute calibration to other spectrometer setting at this electron energy range.« less

Flow reversal, convection, and modeling in the DIII-D divertor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boedo, J.A.; Porter, G.D.; Schaffer, M.J.

1998-12-01

Measurements of the parallel Mach number of background plasma in the DIII-D tokamak divertor [M. A. Mahdavi {ital et al.} in {ital Proceedings, 16th International Conference}, Montreal, 1996 (International Atomic Energy Agency, Vienna, 1997) Vol. I, p. 397] were performed using a fast scanning Mach probe. The parallel particle flow shows evidence of complex behavior such as reverse flow, i.e., flow away from the target plate, stagnant flow, and large scale convection. For detached discharges, measurements confirm predictions of convective flow towards the divertor target plate at near sound speed over large regions in the divertor. The resulting convected heatmore » flux is a dominant heat transport mechanism in the divertor. For attached discharges with high recycling, particle flow reversal in a thin region at or near the outer separatrix, thereby confirming the existence of a mechanism by which impurities can be transported away from the divertor target plates. Modeling results from the two-dimensional fluid code UEDGE [G. D. Porter and the DIII-D Team, {open_quotes}Divertor characterization experiments and modelling in DIII-D,{close_quotes} in {ital Proceedings of the 23rd European Conference on Controlled Fusion and Plasma Physics}, 24{endash}28 June 1996, Kiev, Ukraine (European Physical Society, Petit-Lancy, Switzerland, 1996), Vol. 20C, Part II, p. 699] can reproduce the main features of the experimental observations. {copyright} {ital 1998 American Institute of Physics.}« less

Non-equilibrium dynamic reversal of in-plane ferromagnetic elliptical disk

NASA Astrophysics Data System (ADS)

Kim, June-Seo; Hwang, Hee-Kyeong; You, Chun-Yeol

2018-01-01

The ultrafast switching mechanism of an in-plane magnetized elliptical magnetic disk by applying dynamic out-of-plane magnetic field pulses is investigated by performing micromagnetic simulations. For the in-plane magnetized nanostructures, the out-of-plane magnetic field is able to rotate the direction of magnetization when the precession torque overcomes the shape anisotropy of the system. This type magnetization reversal is one of non-equilibrium dynamic within a certain transition time util the precession torque is equivalent to the damping torque. By controlling the rise time or fall times of dynamic out-of-plane field pulses, the transition time can be also successively tuned and then an ultrafast switching of an elliptical magnetic nano-disk is clearly achieved by controlling the precessional torque. As another reversal approach, sinusoidal magnetic fields in gigahertz range are applied to the system. Consequently, the thresholds of switching fields are drastically decreased. We also reveal that the ferromagnetic resonance frequencies at the center and the edge of the elliptical disk are most important for microwave sinusoidal out-of-plane magnetic field induced magnetization reversal.

Acoustic Reverse Time Migration of the Cascadia Subduction Zone Dataset

NASA Astrophysics Data System (ADS)

Jia, L.; Mallick, S.

2017-12-01

Reverse time migration (RTM) is a wave-equation based migration method, which provides more accurate images than ray-based migration methods, especially for the structures in deep areas, making it an effective tool for imaging the subduction plate boundary. In this work, we extend the work of Fortin (2015) and applied acoustic finite-element RTM on the Cascadia Subduction Zone (CSZ) dataset. The dataset was acquired by Cascadia Open-Access Seismic Transects (COAST) program, targeting the megathrust in the central Cascadia subduction zone (Figure 1). The data on a 2D seismic reflection line that crosses the Juan de Fuca/North American subduction boundary off Washington (Line 5) were pre-processed and worked through Kirchhoff prestack depth migration (PSDM). Figure 2 compares the depth image of Line 5 of the CSZ data using Kirchhoff PSDM (top) and RTM (bottom). In both images, the subducting plate is indicated with yellow arrows. Notice that the RTM image is much superior to the PSDM image by several aspects. First, the plate boundary appears to be much more continuous in the RTM image than the PSDM image. Second, the RTM image indicates the subducting plate is relatively smooth on the seaward (west) side between 0-50 km. Within the deformation front of the accretionary prism (50-80 km), the RTM image shows substantial roughness in the subducting plate. These features are not clear in the PSDM image. Third, the RTM image shows a lot of fine structures below the subducting plate which are almost absent in the PSDM image. Finally, the RTM image indicates that the plate is gently dipping within the undeformed sediment (0-50 km) and becomes steeply dipping beyond 50 km as it enters the deformation front of the accretionary prism. Although the same conclusion could be drawn from the discontinuous plate boundary imaged by PSDM, RTM results are far more convincing than the PSDM.

Ultrafast Magnetization Manipulation Using Single Femtosecond Light and Hot-Electron Pulses.

PubMed

Xu, Yong; Deb, Marwan; Malinowski, Grégory; Hehn, Michel; Zhao, Weisheng; Mangin, Stéphane

2017-11-01

Current-induced magnetization manipulation is a key issue for spintronic applications. This manipulation must be fast, deterministic, and nondestructive in order to function in device applications. Therefore, single- electronic-pulse-driven deterministic switching of the magnetization on the picosecond timescale represents a major step toward future developments of ultrafast spintronic systems. Here, the ultrafast magnetization dynamics in engineered Gd x [FeCo] 1- x -based structures are studied to compare the effect of femtosecond laser and hot-electron pulses. It is demonstrated that a single femtosecond hot-electron pulse causes deterministic magnetization reversal in either Gd-rich and FeCo-rich alloys similarly to a femtosecond laser pulse. In addition, it is shown that the limiting factor of such manipulation for perpendicular magnetized films arises from the formation of a multidomain state due to dipolar interactions. By performing time-resolved measurements under various magnetic fields, it is demonstrated that the same magnetization dynamics are observed for both light and hot-electron excitation, and that the full magnetization reversal takes place within 40 ps. The efficiency of the ultrafast current-induced magnetization manipulation is enhanced due to the ballistic transport of hot electrons before reaching the GdFeCo magnetic layer. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Passive fetal monitoring sensor

NASA Astrophysics Data System (ADS)

Zuckerwar, Allan J.; Hall, Earl T.; Baker, Donald A.; Bryant, Timothy D.

1992-08-01

An ambulatory, passive sensor for use in a fetal monitoring system is discussed. The invention is comprised of a piezoelectric polymer film, combined with a metallic mounting plate fastened to a belt, and electrically connected to a signal processing unit by means of a shielded cable. The purpose of the sensor is to receive pressure pulses emitted by a fetus inside an expectant mother. Additionally, the monitor will filter out pressure pulses arising from other sources, such as the maternal heart.

Passive fetal monitoring sensor

NASA Astrophysics Data System (ADS)

1990-07-01

The invention is an ambulatory, passive sensor for use in a fetal monitoring system. The invention incorporates piezoelectric polymer film combined with a metallic mounting plate fastened to a belt and electrically connected to a signal processing unit by means of a shielded cable. The purpose of the sensor is to receive pressure pulses emitted from a fetus inside an expectant mother and to provide means for filtering out pressure pulses arising from other sources, such as the maternal heart.

Passive fetal monitoring sensor

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J. (Inventor); Hall, Earl T. (Inventor); Baker, Donald A. (Inventor); Bryant, Timothy D. (Inventor)

1992-01-01

An ambulatory, passive sensor for use in a fetal monitoring system is discussed. The invention is comprised of a piezoelectric polymer film, combined with a metallic mounting plate fastened to a belt, and electrically connected to a signal processing unit by means of a shielded cable. The purpose of the sensor is to receive pressure pulses emitted by a fetus inside an expectant mother. Additionally, the monitor will filter out pressure pulses arising from other sources, such as the maternal heart.

Controlled Bending of a Thin Mirror to Regain Figure after Warping due to Edge-Cutting

NASA Astrophysics Data System (ADS)

Humphries, C. M.

1990-03-01

A thin circular Cer-Vit mirror, diameter 1.3 m, that had been polished flat was cut along 10 edges to form a 12-sided pseudo-elliptical plate. As a result of the edge-cutting, the mirror distorted and an experiment that investigated the effect of reverse stressing to counteract the distortion is described and analysed. The configuration adopted for stressing the mirror when installed as a driven coudé flat in the UK Infrared Telescope is also described. The reverse stressing results can be understood in terms of thin plate theory for pure bending and, in general, if the distortion is toroidal (including the case of a sphere) an orthogonal pair of bending moments can be chosen that will remove the undesired curvatures.

Control of magnetization reversal in oriented strontium ferrite thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, Debangsu, E-mail: debangsu@physics.iisc.ernet.in; Anil Kumar, P. S.

2014-02-21

Oriented Strontium Ferrite films with the c axis orientation were deposited with varying oxygen partial pressure on Al{sub 2}O{sub 3}(0001) substrate using Pulsed Laser Deposition technique. The angle dependent magnetic hysteresis, remanent coercivity, and temperature dependent coercivity had been employed to understand the magnetization reversal of these films. It was found that the Strontium Ferrite thin film grown at lower (higher) oxygen partial pressure shows Stoner-Wohlfarth type (Kondorsky like) reversal. The relative importance of pinning and nucleation processes during magnetization reversal is used to explain the type of the magnetization reversal with different oxygen partial pressure during growth.

Characteristics of the Secondary Divertor on DIII-D

NASA Astrophysics Data System (ADS)

Watkins, J. G.; Lasnier, C. J.; Leonard, A. W.; Evans, T. E.; Pitts, R.; Stangeby, P. C.; Boedo, J. A.; Moyer, R. A.; Rudakov, D. L.

2009-11-01

In order to address a concern that the ITER secondary divertor strike plates may be insufficiently robust to handle the incident pulses of particles and energy from ELMs, we performed dedicated studies of the secondary divertor plasma and scrape-off layer (SOL). Detailed measurements of the ELM energy and particle deposition footprint on the secondary divertor target plates were made with a fast IR camera and Langmuir probes and SOL profile and transport measurements were made with reciprocating probes. The secondary divertor and SOL conditions depended on changes in the magnetic balance and the core plasma density. Larger density resulted in smaller ELMs and the magnetic balance affected how many ELM particles coupled to the secondary SOL and divertor. Particularly striking are the images from a new fast IR camera that resolve ELM heat pulses and show spiral patterns with multiple peaks during ELMs in the secondary divertor.

Shot H3837: Darht's First Dual-Axis Explosive Experiment

NASA Astrophysics Data System (ADS)

Mendez, Jacob; McNeil, Wendy Vogan; Harsh, James; Hull, Lawrence

2011-06-01

Test H3837 was the first explosive shot performed in front of both flash x-ray axes at the Los Alamos Dual Axis Radiographic HydroTest (DARHT) facility. Executed in November 2009, the shot was an explosively-driven metal flyer plate in a series of experiments designed to explore equation-of-state properties of shocked materials. Imaging the initial shock wave traveling through the flyer plate, DARHT Axis II captured the range of motion from the shock front emergence in the flyer to breakout at the free surface; the Axis I pulse provided a perpendicular perspective of the shot at a time coinciding with the third pulse of Axis II. Since the days of the Manhattan Project, penetrating radiography with multiple frames from different viewing angles has remained a high-profile goal at the Laboratory. H3837 is merely the beginning of a bright future for two-axis penetrating radiography.

Laser engineering of microbial systems

NASA Astrophysics Data System (ADS)

Yusupov, V. I.; Gorlenko, M. V.; Cheptsov, V. S.; Minaev, N. V.; Churbanova, E. S.; Zhigarkov, V. S.; Chutko, E. A.; Evlashin, S. A.; Chichkov, B. N.; Bagratashvili, V. N.

2018-06-01

A technology of laser engineering of microbial systems (LEMS) based on the method of laser-induced transfer of heterogeneous mixtures containing microorganisms (laser bioprinting) is described. This technology involves laser printing of soil microparticles by focusing near-infrared laser pulses on a specially prepared gel/soil mixture spread onto a gold-coated glass plate. The optimal range of laser energies from the point of view of the formation of stable jets and droplets with minimal negative impact on living systems of giant accelerations, laser pulse irradiation, and Au nanoparticles was found. Microsamples of soil were printed on glucose-peptone-yeast agar plates to estimate the LEMS process influence on structural and morphological microbial diversity. The obtained results were compared with traditionally treated soil samples. It was shown that LEMS technology allows significantly increasing the biodiversity of printed organisms and is effective for isolating rare or unculturable microorganisms.

Axial dispersion, holdup and slip velocity of dispersed phase in a pulsed sieve plate extraction column by radiotracer residence time distribution analysis.

PubMed

Din, Ghiyas Ud; Chughtai, Imran Rafiq; Inayat, Mansoor Hameed; Khan, Iqbal Hussain

2008-12-01

Axial dispersion, holdup and slip velocity of dispersed phase have been investigated for a range of dispersed and continuous phase superficial velocities in a pulsed sieve plate extraction column using radiotracer residence time distribution (RTD) analysis. Axial dispersion model (ADM) was used to simulate the hydrodynamics of the system. It has been observed that increase in dispersed phase superficial velocity results in a decrease in its axial dispersion and increase in its slip velocity while its holdup increases till a maximum asymptotic value is achieved. An increase in superficial velocity of continuous phase increases the axial dispersion and holdup of dispersed phase until a maximum value is obtained, while slip velocity of dispersed phase is found to decrease in the beginning and then it increases with increase in superficial velocity of continuous phase.

Measurements of a Newly Designed BPM for the Tevatron Electron Lens 2

NASA Astrophysics Data System (ADS)

Scarpine, V. E.; Kamerdzhiev, V.; Fellenz, B.; Olson, M.; Kuznetsov, G.; Kamerdzhiev, V.; Shiltsev, V. D.; Zhang, X. L.

2006-11-01

Fermilab has developed a second electron lens (TEL-2) for beam-beam compensation in the Tevatron as part of its Run II upgrade program. Operation of the beam position monitors (BPMs) in the first electron lens (TEL-1) showed a systematic transverse position difference between short proton bunches (2 ns sigma) and long electron pulses (˜1 us) of up to ˜1.5 mm. This difference was attributed to frequency dependence in the BPM system. The TEL-2 BPMs utilize a new, compact four-plate design with grounding strips between plates to minimize crosstalk. In-situ measurements of these new BPMs are made using a stretched wire pulsed with both proton and electron beam formats. In addition, longitudinal impedance measurements of the TEL-2 are presented. Signal processing algorithm studies indicate that the frequency-dependent transverse position offset may be reduced to ˜0.1 mm for the beam structures of interest.

Pulse design for multilevel systems by utilizing Lie transforms

NASA Astrophysics Data System (ADS)

Kang, Yi-Hao; Chen, Ye-Hong; Shi, Zhi-Cheng; Huang, Bi-Hua; Song, Jie; Xia, Yan

2018-03-01

We put forward a scheme to design pulses to manipulate multilevel systems with Lie transforms. A formula to reverse construct a control Hamiltonian is given and is applied in pulse design in the three- and four-level systems as examples. To demonstrate the validity of the scheme, we perform numerical simulations, which show the population transfers for cascaded three-level and N -type four-level Rydberg atoms can be completed successfully with high fidelities. Therefore, the scheme may benefit quantum information tasks based on multilevel systems.

Enhanced Reverse Saturable Absorption and Optical Limiting in Heavy-Atom Substituted Phthalocyanines

NASA Technical Reports Server (NTRS)

Perry, J. W.; Mansour, K.; Marder, S. R.; Alvarez, D., Jr.; Perry, K. J.; Choong, I.

1994-01-01

The reverse saturable absorption and optical limiting response of metal phthalocyaninies can be enhanced by using the heavy-atom effect. Phthalocyanines containing heavy metal atoms, such as In, Sn, and Pb show nearly a factor of two enhancement in the ratio of effective excited-state to ground-state absorption cross sections compared to those containing lighter atoms, such as Al and Si. In an f/8 optical geometry, homogeneous solutions of heavy metal phthalocyanines, at 30% linear transmission, limit 8-ns, 532-nm laser pulses to less than or equal to 3 (micro)J (the energy for 50% probability of eye damage) for incident pulses up to 800 (micro)J.

Pulsed Eddy Current Probe Design Based on Transient Circuit Analysis

NASA Astrophysics Data System (ADS)

Cadeau, Trevor J.; Krause, Thomas W.

2009-03-01

Probe design parameters affecting depth of penetration of pulsed eddy currents in multi-layer aluminum 2024-T3 were examined. Several probe designs were evaluated for their ability to detect a discontinuity at the bottom of a stack of aluminum plates. The reflection type probes, consisting of pick-up coil and encircling drive coil, were characterized based on their transient response to a square pulse excitation. Probes with longer fundamental time constants, equivalent to a lower driving frequency, generated greater depth of penetration. However, additional factors such as inductive and resistive load, and excessive coil heating were also factors that limited signal-to-noise response with increasing layer thickness.

Reverse distal femoral locking compression plate a salvage option in nonunion of proximal femoral fractures.

PubMed

Dumbre Patil, Sampat S; Karkamkar, Sachin S; Patil, Vaishali S Dumbre; Patil, Shailesh S; Ranaware, Abhijeet S

2016-01-01

When primary fixation of proximal femoral fractures with implants fails, revision osteosynthesis may be challenging. Tracts of previous implants and remaining insufficient bone stock in the proximal femur pose unique problems for the treatment. Intramedullary implants like proximal femoral nail (PFN) or surface implants like Dynamic Condylar Screw (DCS) are few of the described implants for revision surgery. There is no evidence in the literature to choose one implant over the other. We used the reverse distal femur locking compression plate (LCP) of the contralateral side in such cases undergoing revision surgery. This implant has multiple options of fixation in proximal femur and its curvature along the length matches the anterior bow of the femur. We aimed to evaluate the efficacy of this implant in salvage situations. Twenty patients of failed primary proximal femoral fractures who underwent revision surgery with reverse distal femoral locking plate from February 2009 to November 2012 were included in this retrospective study. There were 18 subtrochanteric fractures and two ipsilateral femoral neck and shaft fractures, which exhibited delayed union or nonunion. The study included 14 males and six females. The mean patient age was 43.6 years (range 22-65 years) and mean followup period was 52.1 months (range 27-72 months). Delayed union was considered when clinical and radiological signs of union failed to progress at the end of four months from initial surgery. All fractures exhibited union without any complications. Union was assessed clinically and radiologically. One case of ipsilateral femoral neck and shaft fracture required bone grafting at the second stage for delayed union of the femoral shaft fracture. Reverse distal femoral LCP of the contralateral side can be used as a salvage option for failed fixation of proximal femoral fractures exhibiting nonunion.

Vibration Mitigation for a Cryogen-Free Dilution Refrigerator for the AMoRE-Pilot Experiment

NASA Astrophysics Data System (ADS)

Lee, C.; Jo, H. S.; Kang, C. S.; Kim, G. B.; Kim, I.; Kim, Y. H.; Lee, H. J.; So, J. H.

2018-06-01

The Advanced Mo-based Rare process Experiment utilizes a cryogen-free dilution refrigerator to operate its low-temperature detectors. Mechanical vibration originating from its pulse tube refrigerator can affect the detector performance. A mechanical filter system has been installed between the 4K and still plates with eddy current dampers in addition to a spring-loaded damping system previously installed below the mixing chamber plate of the cryostat. The filters significantly mitigated vibrations and improved the detector signals.

The geometry of the forisome-sieve element-sieve plate complex in the phloem of Vicia faba L. leaflets.

PubMed

Peters, Winfried S; van Bel, Aart J E; Knoblauch, Michael

2006-01-01

Forisomes are contractile protein bodies that appear to control flux rates in the phloem of faboid legumes by reversibly plugging the sieve tubes. Plugging is triggered by Ca(2+) which induces an anisotropic deformation of forisomes, consisting of a longitudinal contraction and a radial expansion. By conventional light microscopy and confocal laser-scanning microscopy, the three-dimensional geometry of the forisome-sieve element-sieve plate complex in intact sieve tubes of leaflets of Vicia faba L. was reconstructed. Forisomes were mostly located close to sieve plates, and occasionally were observed drifting unrestrainedly along the sieve element, suggesting that they might be utilized as internal markers of flow direction. The diameter of forisomes in the resting state correlated with the diameter of their sieve elements, supporting the idea that radial expansion of forisomes is the geometric basis of reversible sieve tube plugging. Comparison of the present results regarding forisome geometry in situ with previously published data on forisome reactivity in vitro makes it questionable, however, whether forisomes are capable of completely sealing sieve tubes in V. faba leaves.

Cross-Sectional Associations of Flow Reversal, Vascular Function, and Arterial Stiffness in the Framingham Heart Study.

PubMed

Bretón-Romero, Rosa; Wang, Na; Palmisano, Joseph; Larson, Martin G; Vasan, Ramachandran S; Mitchell, Gary F; Benjamin, Emelia J; Vita, Joseph A; Hamburg, Naomi M

2016-12-01

Experimental studies link oscillatory flow accompanied by flow reversal to impaired endothelial cell function. The relation of flow reversal with vascular function and arterial stiffness remains incompletely defined. We measured brachial diastolic flow patterns along with vasodilator function in addition to tonometry-based central and peripheral arterial stiffness in 5708 participants (age 47±13 years, 53% women) in the Framingham Heart Study Offspring and Third Generation cohorts. Brachial artery diastolic flow reversal was present in 35% of the participants. In multivariable regression models, the presence of flow reversal was associated with lower flow-mediated dilation (3.9±0.2 versus 5.0±0.2%; P<0.0001) and reactive hyperemic flow velocity (50±0.99 versus 57±0.93 cm/s; P<0.0001). The presence of flow reversal (compared with absence) was associated with higher central aortic stiffness (carotid-femoral pulse wave velocity 9.3±0.1 versus 8.9±0.1 m/s), lower muscular artery stiffness (carotid-radial pulse wave velocity 9.6±0.1 versus 9.8±0.1 m/s), and higher forearm vascular resistance (5.32±0.03 versus 4.66±0.02 log dyne/s/cm 5 ; P<0.0001). The relations of diastolic flow velocity with flow-mediated dilation, aortic stiffness, and forearm vascular resistance were nonlinear, with a steeper decline in vascular function associated with increasing magnitude of flow reversal. In our large, community-based sample, brachial artery flow reversal was common and associated with impaired vasodilator function and higher aortic stiffness. Our findings are consistent with the concept that flow reversal may contribute to vascular dysfunction. © 2016 American Heart Association, Inc.

Decomposition of mixed malodorants in a wire-plate pulse corona reactor.

PubMed

Shi, Y; Ruan, J; Wang, X; Li, W; Tan, T

2005-09-01

Decomposition characteristics of two groups of representative mixed malodorants (1, ethanethiol + hydrogen sulfide; 2, ethanethiol + ammonia) in air were investigated employing a wire-plate pulse corona reactor. A new type of high-voltage pulse generator with a thyratron switch and a Blumlein pulse-forming network (BPFN) was used in our experiments. The experiments were conducted at a gas-flow rate of 13 m3/h. Important parameters, including peak voltage, chemical structures of malodorants, pulse frequency, and initial concentration, which influenced the removal efficiency, were investigated. The results showed that the mixed malodorants could be treated effectively by pulse corona. The removal efficiencies of 200 mg/m3 C2H5SH and 200 mg/m3 H2S for group 1 were 95.6% and 100%, respectively, which were almost equal to those of the two pollutants separately. The energy cost was about 65.1-81.4 J/L, which was 31.5-45.2% lower than for treating pollutants alone. The removal efficiencies of 105 mg/m3 C2HsSH and 40 mg/m3 NH3 for group 2 were 93.1% and almost 100%, and the energy cost was 65.1 J/L, 55.6% lower than that which was treated separately. In the case of two groups of mixed malodorants removal, NOx, 03, SO2, CO2, and CO were all observed. Moreover, some sulfur and white crystal ammonium nitrates were discovered adhering to the corona wires in the removal of groups 1 and 2, respectively. A dynamics model was developed to describe the relation of the removal efficiency with specific energy density and initial concentration. In the case of group 1 removal,the decomposition rate constants decreased as compared to the single treating. As for group 2 removal, the decomposition rate constants increased, especially for NH3. According to the results, the optimization design for the reactor and the matching of high pulse voltage source can be reckoned.

Functional enucleation of porcine oocytes for somatic cell nuclear transfer using femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Kuetemeyer, K.; Lucas-Hahn, A.; Petersen, B.; Hassel, P.; Lemme, E.; Niemann, H.; Heisterkamp, A.

2010-02-01

Cloning of several mammalian species has been achieved by somatic cell nuclear transfer over the last decade. However, this method still results in very low efficiencies originating from biological and technical aspects. The highly-invasive mechanical enucleation belongs to the technical aspects and requires considerable micromanipulation skill. In this paper, we present a novel non-invasive method for combined oocyte imaging and automated functional enucleation using femtosecond (fs) laser pulses. After three-dimensional imaging of Hoechst-labeled porcine oocytes by multiphoton microscopy, our self-developed software automatically determined the metaphase plate position and shape. Subsequent irradiation of this volume with the very same laser at higher pulse energies in the low-density-plasma regime was used for metaphase plate ablation. We show that functional fs laser-based enucleation of porcine oocytes completely inhibited further embryonic development while maintaining intact oocyte morphology. In contrast, non-irradiated oocytes were able to develop to the blastocyst stage without significant differences to control oocytes. Our results indicate that fs laser systems offer great potential for oocyte imaging and enucleation as a fast, easy to use and reliable tool which may improve the efficiency of somatic cell clone production.

[Spectroscopic Diagnosis of Two-Dimensional Distribution of OH Radicals in Wire-Plate Pulsed Corona Discharge Reactor].

PubMed

Jiang, Jian-ping; Luo, Zhong-yang; Xuan, Jian-yong; Zhao, Lei; Fang, Meng-xiang; Gao, Xiang

2015-10-01

Pulsed corona discharge in atmosphere has been widely regarded as an efficient flue gas treatment technology for the generation of active radical species, such as the OH radicals. The spatial distribution of OH radicals generated by pulsed corona discharge plays an important role in decomposing pollutants. The two-dimensional (2-D) distribution of OH radicals of positive wire--plate pulsed corona discharge was detected using laser-induced fluorescence (LIF). The influence of relative humidity (RH) and oxygen concentration on the 2-D distribution of OH radicals were investigated. The results indicated that the 2-D distribution of OH radicals was characterized by a fan-shaped distribution from the wire electrode to plate electrode, and both the maximum values of vertical length and horizontal width of the fan area was less than 1 cm. The 2-D distribution area of OH radicals increased significantly with increasing the RH and the optimum condition was 65% RH. The optimal level of the oxygen concentration for the 2-D distribution area of OH radicals was 2%. The process of OH radical generation and 2-D distribution area of OH radicals were significantly interfered when the oxygen concentration was larger than 15%. The total quenching rate coefficients for different RH values and oxygen concentration in this study were used to calculate the fluorescence yield of OH radical. The fluorescence yield, which is the ratio between the emission rate (Einstein coefficient) and the sum of the emission rate and quenching rate, was used to normalize the 2-D distribution area of OH radicals. The fluorescence yield of OH radical decreased with increasing the RH and oxygen concentration linearly and rapidly. It was also found that compared with the RH, the influence of the oxygen concentration had more notable effect on the fluorescence yield of OH radical and 2-D distribution area of OH radicals.

Three-dimensional structure determination protocol for noncrystalline biomolecules using x-ray free-electron laser diffraction imaging.

PubMed

Oroguchi, Tomotaka; Nakasako, Masayoshi

2013-02-01

Coherent and intense x-ray pulses generated by x-ray free-electron laser (XFEL) sources are paving the way for structural determination of noncrystalline biomolecules. However, due to the small scattering cross section of electrons for x rays, the available incident x-ray intensity of XFEL sources, which is currently in the range of 10(12)-10(13) photons/μm(2)/pulse, is lower than that necessary to perform single-molecule diffraction experiments for noncrystalline biomolecules even with the molecular masses of megadalton and submicrometer dimensions. Here, we propose an experimental protocol and analysis method for visualizing the structure of those biomolecules by the combined application of coherent x-ray diffraction imaging and three-dimensional reconstruction methods. To compensate the small scattering cross section of biomolecules, in our protocol, a thin vitreous ice plate containing several hundred biomolecules/μm(2) is used as sample, a setup similar to that utilized by single-molecule cryoelectron microscopy. The scattering cross section of such an ice plate is far larger than that of a single particle. The images of biomolecules contained within irradiated areas are then retrieved from each diffraction pattern, and finally provide the three-dimensional electron density model. A realistic atomic simulation using large-scale computations proposed that the three-dimensional structure determination of the 50S ribosomal subunit embedded in a vitreous ice plate is possible at a resolution of 0.8 nm when an x-ray beam of 10(16) photons/500×500 nm(2)/pulse is available.

Observation of Reverse Saturable Absorption of an X-ray Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, B. I.; Cho, M. S.; Kim, M.

A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K-absorption edge of aluminum, and the x-ray intensity ranges are 10more » 16 –10 17 W=cm 2. It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray freeelectron laser pulses.« less

Observation of Reverse Saturable Absorption of an X-ray Laser

DOE PAGES

Cho, B. I.; Cho, M. S.; Kim, M.; ...

2017-08-16

A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K-absorption edge of aluminum, and the x-ray intensity ranges are 10more » 16 –10 17 W=cm 2. It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray freeelectron laser pulses.« less

Actively dewatering fluid-rich zones along the Costa Rica plate boundary fault

NASA Astrophysics Data System (ADS)

Bangs, N. L.; McIntosh, K. D.; Silver, E. A.; Kluesner, J. W.; Ranero, C. R.; von Huene, R.

2012-12-01

New 3D seismic reflection data reveal distinct evidence for active dewatering above a 12 km wide segment of the plate boundary fault within the Costa Rica subduction zone NW of the Osa Peninsula. In the spring of 2011 we acquired a 11 x 55 km 3D seismic reflection data set on the R/V Langseth using four 6,000 m streamers and two 3,300 in3 airgun arrays to examine the structure of the Costa Rica margin from the trench into the seismogenic zone. We can trace the plate-boundary interface from the trench across our entire survey to where the plate-boundary thrust lies > 10 km beneath the margin shelf. Approximately 20 km landward of the trench beneath the mid slope and at the updip edge of the seismogenic zone, a 12 km wide zone of the plate-boundary interface has a distinctly higher-amplitude seismic reflection than deeper or shallower segments of the fault. Directly above and potentially directly connected with this zone are high-amplitude, reversed-polarity fault-plane reflections that extend through the margin wedge and into overlying slope sediment cover. Within the slope cover, high-amplitude reversed-polarity reflections are common within the network of closely-spaced nearly vertical normal faults and several broadly spaced, more gently dipping thrust faults. These faults appear to be directing fluids vertically toward the seafloor, where numerous seafloor fluid flow indicators, such as pockmarks, mounds and ridges, and slope failure features, are distinct in multibeam and backscatter images. There are distinctly fewer seafloor and subsurface fluid flow indicators both updip and downdip of this zone. We believe these fluids come from a 12 km wide fluid-rich segment of the plate-boundary interface that is likely overpressured and has relatively low shear stress.

Interpreting the Effects of Pulse Remagnetization on Animal Behavior

NASA Astrophysics Data System (ADS)

Kirschvink, J. L.; Wang, C. X.; Golash, H. N.; Hilburn, I. A.; Wu, D. A.; Crucilla, S. J.; Badal, Y. D.; Shimojo, S.

2017-12-01

Observations of geomagnetic sensitivity by migratory and homing animals have puzzled biophysicists for over 70 years. Widely dismissed as biophysically implausible due to the lack of physiological ferromagnetic materials [e.g., D.R. Griffin, 1944, 1952], clear and reproducible responses to earth-strength magnetic fields is now firmly established in organisms ranging from Bacteria, Protists, and Animals from numerous phyla, including mollusks, arthropods, and the chordates. Behavior demands sensory transduction, as external stimuli only `get into the nervous system' through sensory cells specialized to transduce the physical stimulus into a modulated stream of action potentials in neurons. Three basic biophysical mechanisms could plausibly explain the biophysical transduction of geomagnetic cues, including electrical induction, hyperfine magnetic field effects on photo-activated free radicals (the `Quantum Compass'), or receptor cells containing biologically-precipitated crystals of a ferromagnetic mineral like magnetite (Fe3O4). The definitive test of a ferromagnetic receptor is the pulse-remagnetization experiment, in which you apply a brief, unidirectional magnetic pulse of about 1 mS in duration, configured to exceed the coercive force of the SD particles and reverse the orientation of the magnetic moment wrt to the crystal axis (typically, a pulse few tens of mT is adequate). A pulse configured in this fashion can be well below the dB/dt level needed to fire a sensory nerve through the induced electric fields. The pulse produces a permanent flip in magnetization direction, the same way information is coded on magnetic tape. Magnetotactic bacteria, exposed to such a pulse, reverse their magnetic swimming directions passively. There are now over 16 peer-reviewed papers in which this experiment has been applied to animals, including birds, all of which show clear and long-lasting effects of the pulse. Such a pulse would have no lasting effect on a quantum compass. Initial experiments with a magnetic pulse of 70 mT on a large primate show a clear effect, although the results are … complex!

Surface Modification of Micro-Alloyed High-Strength Low-Alloy Steel by Controlled TIG Arcing Process

NASA Astrophysics Data System (ADS)

Ghosh, P. K.; Kumar, Ravindra

2015-02-01

Surface modification of micro-alloyed HSLA steel plate has been carried out by autogenous conventional and pulse current tungsten inert gas arcing (TIGA) processes at different welding parameters while the energy input was kept constant. At a given energy input the influence of pulse parameters on the characteristics of surface modification has been studied in case of employing single and multi-run procedure. The role of pulse parameters has been studied by considering their summarized influence defined by a factor Φ. The variation in Φ and pulse frequency has been found to significantly affect the thermal behavior of fusion and accordingly the width and penetration of the modified region along with its microstructure, hardness and wear characteristics. It is found that pulsed TIGA is relatively more advantageous over the conventional TIGA process, as it leads to higher hardness, improved wear resistance, and a better control over surface characteristics.

Pulse energy dependence of refractive index change in lithium niobium silicate glass during femtosecond laser direct writing.

PubMed

Cao, Jing; Poumellec, Bertrand; Brisset, François; Lancry, Matthieu

2018-03-19

Femtosecond laser-induced refractive index changes in lithium niobium silicate glass were explored at high repetition rate (300 fs, 500 kHz) by polarized light microscopy, full-wave retardation plate, quantitative birefringence microscopy, and digital holographic microscopy. We found three regimes on energy increase. The first one corresponds to isotropic negative refractive index change (for pulse energy ranging 0.4-0.8 μJ/pulse, 0.6 NA, 5μm/s, 650μm focusing depth in the glass). The second one (0.8-1.2 μJ/pulse) corresponds to birefringence with well-defined slow axis orientation. The third one (above 1.2 μJ/pulse) is related to birefringence direction fluctuation. Interestingly, these regimes are consistent with crystallization ones. In addition, an asymmetric orientational writing effect has been detected on birefringence. These topics extend the possibility of controlling refractive index change in multi-component glasses.

MULTI-PLATE IONIZATION CHAMBER FOR THE DETECTION OF SLOW NEUTRONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bubzanowski, A.; Grotowski, K.

1957-01-01

A description is given of an ionization chamber, the electrodes of which are coated with a layer of natural boron of thickness 3 mg/cm/sup 2/. Each electrode of the chamber consists of three disks, placed between plates of the other electrodes. The capacitance between the electrodes does not exceed 15 micromicrofarads. The technology of coating the layer is as follows: the boron is mixed with alcohol and a small amount of Canada balsam and is coated in the form of an emulsion on the plates. The chamber efficiency is approximately 2%. The filler is argon at atmospheric pressure. The durationmore » of the output pulses after forming is approximately 5 microseconds.« less

Low pressure spark gap triggered by an ion diode

DOEpatents

Prono, Daniel S.

1985-01-01

Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.

Low-pressure spark gap triggered by an ion diode

DOEpatents

Prono, D.S.

1982-08-31

Spark gap apparatus for use as an electric switch operating at high voltage, high current and high repetition rate. Mounted inside a housing are an anode, cathode and ion plate. An ionizable fluid is pumped through the chamber of the housing. A pulse of current to the ion plate causes ions to be emitted by the ion plate, which ions move into and ionize the fluid. Electric current supplied to the anode discharges through the ionized fluid and flows to the cathode. Current stops flowing when the current source has been drained. The ionized fluid recombines into its initial dielectric ionizable state. The switch is now open and ready for another cycle.

Earthquake-driven fluid flow rates inferred from borehole temperature measurements within the Japan Trench plate boundary fault zone

NASA Astrophysics Data System (ADS)

Fulton, P. M.; Brodsky, E. E.

2016-12-01

Using borehole sub-seafloor temperature measurements, we have recently identified signatures suggestive of earthquake-driven fluid pulses within the Japan Trench plate boundary fault zone during a major aftershock sequence. Here we use numerical models to show that these signatures are consistent with time-varying fluid flow rates out of permeable zones within the formation into the borehole annulus. In addition, we also identify an apparent time-varying sensitivity of whether suspected fluid pulses occur in response to earthquakes of a given magnitude and distance. The results suggest a damage and healing process and therefore provides a mechanism to allow for a disproportionate amount of heat and chemical transport in the short time frame after an earthquake. Our observations come from an observatory installed across the main plate boundary fault as part of IODP's Japan Trench Fast Drilling Project (JFAST) following the March 2011 Mw 9.0 Tohoku-oki earthquake. It operated from July 2012 - April 2013 during which a Mw 7.3 earthquake and numerous aftershocks occurred. High-resolution temperature time series data reveal spatially correlated transients in response to earthquakes with distinct patterns interpreted to reflect advection by transient pulses of fluid flow from permeable zones into the borehole annulus. Typical transients involve perturbations over 12 m with increases of 10 mK that build over 0.1 days at shallower depths and decreases at deeper depths. They are consistently centered around 792.5 m below seafloor (mbsf) where a secondary fault and permeable zone have been independently identified within the damage zone above the main plate boundary fault at 820 mbsf . Model simulations suggest transient flow rates of up to 10-3m/s from the formation that quickly decrease. Comparison of characteristics of earthquakes identified in nearby ocean bottom pressure measurements suggest there is not a clear relationship between fluid pulses and static strain. There does appear to be a time-varying sensitivity likely from dynamic stresses suggestive of a damage process followed by healing over 1 month time. The transient redistribution of fluid pressures and fluid flow within fault zones inferred here is a potential mechanism for earthquake triggering and episodic heat and chemical transport.

14. 'ANNISQUAM POINT JAN. 4, 1898.' Photocopy of photograph ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

14. 'ANNISQUAM POINT -- JAN. 4, 1898.' Photocopy of photograph (original glass plate negative #T86 in the collection of the Annisquam Historical Society, Annisquam, Massachusetts). Photographer: Martha Harvey (1862-1949). (The handwritten legend along the top edge of the photograph is scratched in the emulsion of the original glass plate negative. Consequently it reads in reverse when printed.) - Annisquam Bridge, Spanning Lobster Cove between Washington & River Streets, Gloucester, Essex County, MA

BLIPPED (BLIpped Pure Phase EncoDing) high resolution MRI with low amplitude gradients

NASA Astrophysics Data System (ADS)

Xiao, Dan; Balcom, Bruce J.

2017-12-01

MRI image resolution is proportional to the maximum k-space value, i.e. the temporal integral of the magnetic field gradient. High resolution imaging usually requires high gradient amplitudes and/or long spatial encoding times. Special gradient hardware is often required for high amplitudes and fast switching. We propose a high resolution imaging sequence that employs low amplitude gradients. This method was inspired by the previously proposed PEPI (π Echo Planar Imaging) sequence, which replaced EPI gradient reversals with multiple RF refocusing pulses. It has been shown that when the refocusing RF pulse is of high quality, i.e. sufficiently close to 180°, the magnetization phase introduced by the spatial encoding magnetic field gradient can be preserved and transferred to the following echo signal without phase rewinding. This phase encoding scheme requires blipped gradients that are identical for each echo, with low and constant amplitude, providing opportunities for high resolution imaging. We now extend the sequence to 3D pure phase encoding with low amplitude gradients. The method is compared with the Hybrid-SESPI (Spin Echo Single Point Imaging) technique to demonstrate the advantages in terms of low gradient duty cycle, compensation of concomitant magnetic field effects and minimal echo spacing, which lead to superior image quality and high resolution. The 3D imaging method was then applied with a parallel plate resonator RF probe, achieving a nominal spatial resolution of 17 μm in one dimension in the 3D image, requiring a maximum gradient amplitude of only 5.8 Gauss/cm.

Thin film beam splitter multiple short pulse generation for enhanced Ni-like Ag x-ray laser emission.

PubMed

Cojocaru, Gabriel V; Ungureanu, Razvan G; Banici, Romeo A; Ursescu, Daniel; Delmas, Olivier; Pittman, Moana; Guilbaud, Olivier; Kazamias, Sophie; Cassou, Kevin; Demailly, Julien; Neveu, Olivier; Baynard, Elsa; Ros, David

2014-04-15

An alternative, novel multiple pulse generation scheme was implemented directly after the optical compressor output of an x-ray pump laser. The new method uses a polarization sensitive thin film beam splitter and a half-wavelength wave plate for tuning the energy ratio in the multiple short pulses. Based on this method, an extensive study was made of the running parameters for a grazing incidence pumped silver x-ray laser (XRL) pumped with a long pulse of 145 mJ in 6 ns at 532 nm and up to 1.45 J in few picoseconds at 810 nm. Fivefold enhancement in the emission of the silver XRL was demonstrated using the new pump method.

Ultra-wideband horn antenna with abrupt radiator

DOEpatents

McEwan, Thomas E.

1998-01-01

An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna.

Crack Detection in Plates Using Coupled Rayleigh-Like Waves

NASA Astrophysics Data System (ADS)

Masserey, B.; Fromme, P.

2008-02-01

The use of coupled Rayleigh-like waves in aluminum plates with a view towards the non-destructive inspection of aircraft structures has been investigated experimentally and theoretically. Rayleigh-like waves transfer energy between both plate surfaces with a characteristic distance called the beatlength. A simple, analytical model and finite difference calculations are used to describe the reflection of Rayleigh-like waves at surface defects. Good agreement has been achieved with experimental results using either standard pulse-echo or laser interferometer measurements. The sensitivity for the detection and localization of small defects on both plate surfaces has been found to be very good. Selecting appropriate excitation frequency and position, a significant part of the energy of the Rayleigh-like wave can be transmitted past surface features, allowing the remote detection of defects in areas where access is restricted.

VCSEL End-Pumped Passively Q-Switched Nd:YAG Laser with Adjustable Pulse Energy

DTIC Science & Technology

2011-02-28

entire VCSEL array. Neglecting lens aberrations, the focused spot diameter is given by focal length of the lens times the full divergence angle of the...pump intensity distribution generated by a pump-light-focusing lens . ©2011 Optical Society of America OCIS codes: (140.3530) Lasers Neodymium...Passive Q-Switch and Brewster Plate in a Pulsed Nd: YAG Laser,” IEEE J. Quantum Electron. 31(10), 1738–1741 (1995). 6. G. Xiao, and M. Bass, “A

High rate lithium/thionyl chloride bipolar battery development

NASA Technical Reports Server (NTRS)

Russell, Philip G.; Goebel, F.

1994-01-01

Presented in viewgraph format are results and accomplishments on the development of lithium/thionyl chloride bipolar batteries. Results include the development of manufacturing capability for producing large quantities of uniform cathodes and bipolar plates; the development of assembly, sealing, and activation procedures for fabrication of battery modules containing up to 150 cells in bipolar configuration; and the successful demonstration of a 10.7 kW 150-cell module with constant power pulse discharge, 20 second pulse, and 10 percent duty cycle.

Fast scan control for deflection type mass spectrometers

NASA Technical Reports Server (NTRS)

Yeager, P. R.; Gaetano, G.; Hughes, D. B. (Inventor)

1974-01-01

A high speed scan device is reported that allows most any scanning sector mass spectrometer to measure preselected gases at a very high sampling rate. The device generates a rapidly changing staircase output which is applied to the accelerator of the spectrometer and it also generates defocusing pulses that are applied to one of the deflecting plates of the spectrometer which when shorted to ground deflects the ion beam away from the collector. A defocusing pulse occurs each time there is a change in the staircase output.

Characteristics of Extra Narrow Gap Weld of HSLA Steel Welded by Single-Seam per Layer Pulse Current GMA Weld Deposition

NASA Astrophysics Data System (ADS)

Agrawal, B. P.; Ghosh, P. K.

2017-03-01

Butt weld joints are produced using pulse current gas metal arc welding process by employing the technique of centrally laid multi-pass single-seam per layer weld deposition in extra narrow groove of thick HSLA steel plates. The weld joints are prepared by using different combination of pulse parameters. The selection of parameter of pulse current gas metal arc welding is done considering a summarized influence of simultaneously interacting pulse parameters defined by a dimensionless hypothetical factor ϕ. The effect of diverse pulse parameters on the characteristics of weld has been studied. Weld joint is also prepared by using commonly used multi-pass multi-seam per layer weld deposition in conventional groove. The extra narrow gap weld joints have been found much superior to the weld joint prepared by multi-pass multi-seam per layer deposition in conventional groove with respect to its metallurgical characteristics and mechanical properties.

Laser-excited pulse propagation in a crystallized complex plasma

NASA Astrophysics Data System (ADS)

Nosenko, V.; Nunomura, S.; Goree, J.

2000-10-01

A complex plasma, so-called in analogy with complex fluids, is an ionized gas containing small solid particles. This medium is also called a dusty plasma. The particles acquire a large negative electric charge. In an experiment, polymer microspheres were shaken into a parallel-plate rf plasma. The particles were levitated by the electric field in the sheath above the lower electrode. The particles settled in a single horizontal layer, and were arranged in a hexagonal lattice. They were imaged using a video camera to record the particle motion. Like any crystal, this so-called ``plasma crystal'' sustains compressional sound waves, which can be launched as a pulse. By modulating an argon laser beam directed tangentially at the lattice, we launched a pulsed wave in the lattice. We evaluated the pulse shape and propagation speed, while varying the pulse power and duration. This allowed a test for dispersion and nonlinearity, as well as a test of whether the pulse has the properties of a shock.

Time Reversal Methods for Structural Health Monitoring of Metallic Structures Using Guided Waves

DTIC Science & Technology

2011-09-01

measure elastic properties of thin isotropic materials and laminated composite plates. Two types of waves propagate a symmetric wave and antisymmetric...compare it to the original signal. In this time reversal procedure wave propagation from point-A to point-B and can be modeled as a convolution ...where * is the convolution operator and transducer transmit and receive transfer function are neglected for simplification. In the frequency

Anatomy of a Plate Boundary at Shallow Crustal Levels: a Composite Section from the Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Barth, N. C.; Toy, V. G.; Boulton, C. J.; Carpenter, B. M.

2010-12-01

New Zealand's Alpine Fault is mostly a moderately SE-dipping dextral reverse plate boundary structure, but at its southern end, strike-slip-normal motion is indicated by offset of recent surfaces, juxtaposition of sediments, and both brittle and ductile shear sense indicators. At the location of uplift polarity reversal fault rocks exhumed from both the hangingwall Pacific and footwall Australian Plates are juxtaposed, offering a remarkably complete cross section of the plate boundary at shallow crustal levels. We describe Alpine Fault damage zone and fault core structures overprinted on Pacific and Australian plate mylonites of a variety of compositions, in a fault-strike perpendicular composite section spanning the reversal in dip-slip polarity. The damage zone is asymmetric; on the Australian Plate 160m of quartzose paragneiss-derived mylonites are overprinted by brittle faults and fractures that increase in density towards the principal slip surface (PSS). This damage zone fabric consists of 1-10m-spaced, moderately to steeply-dipping, 1-20cm-thick gouge-filled faults, overprinted on and sub-parallel to a mylonitic foliation sub-parallel to the PSS. On the Pacific Plate, only 40m of the 330m section of volcaniclastic-derived mylonites have brittle damage in the form of unhealed fractures and faults, as well as a pervasive greenschist facies hydrothermal alteration absent in the footwall. These damage-related structures comprise a network of small-offset faults and fractures with increasing density and intensity towards the PSS. The active Pacific Plate fault core is composed of ~1m of cataclasite grading into folded protocataclasite that is less folded and fractured with increasing distance from the PSS. The active Australian Plate fault core is <1.5m wide and consists of 3 distinct foliated clay gouges, as well as a 4cm thick brittle ultracataclasite immediately adjacent to the active PSS. The Australian Plate foliated clay gouge contains stringers of quartz that become less continuous and more sigmoidal toward the PSS, indicating a strain gradient across the gouge zone. Gouge textures are consistent with deformation by pressure solution. Intact wafers from one of the gouges, experimentally -sheared in a biaxial configuration under true-triaxial loading at σn’= 31MPa and Pf = 10MPa, yielded a friction coefficient, μss = 0.32 and displayed velocity strengthening behavior. No significant re-strengthening was observed during hold periods of slide-hold tests. Well-cemented glacial till (~8000 years old), which caps many outcrops, is a marker that shows that the damage zone is not active in the near-surface, but most of the fault core is. The active near-surface damage zone here is <40m wide and the active fault core is <2.5m wide. Both overprint a much wider, inactive damage zone. The combination of rheologically-weak Australian Plate fault rocks with surface rupture traces indicates distinctly different coseismic and interseismic behaviors along the southern strike-slip-normal segment of the Alpine Fault.

On the discrimination between nucleation and propagation in nanomagnetic logic devices

NASA Astrophysics Data System (ADS)

Ziemys, Grazvydas; Csaba, Gyorgy; Becherer, Markus

2018-05-01

In this paper we present the extensive nucleation and propagation characterization of fabricated nanomagnets by applying ns-range magnetic field pulses. For that, an artificial nucleation center (ANC) is created by focused ion beam irradiation (FIB) of a 50 x 50 nm area at the side of a Co/Pt island as typically used in Nanomagnetic Logic with perpendicular anisotropy (pNML). Laser-Kerr Microscope is applied for statistical evaluation of the switching probability of the whole magnet, while the wide-field-Kerr microscopy is employed to discriminate between the nucleation process (which takes place at the irradiated ANC area) and the domain wall propagation process along the magnet. We show that the nanomagnet can be treated as a single Stoner-Wolfhart particle above 100 ns field-pulse width, as the whole magnetization is switched during the field-pulse. By contrary, for field-pulse width below 100 ns, the domain wall (DW) motion is the limiting process hindering full magnetization reversal on that time-scale. However, the nucleation still follows the Arrhenius law. The results allow precise understanding of the reversal process and highlight the need for faster DW speed in pNML materials.

Influence of High Speed Repetition of Pulsed Streamer Discharge Produced by Polarity-Reversed Traveling Wave on NO Oxidation

NASA Astrophysics Data System (ADS)

Matsuda, Eiji; Kadowaki, Kazunori; Nishimoto, Sakae; Kitani, Isamu

This paper describes experimental results of NO removal from a simulated exhausted gas using a barrier-type plasma reactor subjected to reciprocal traveling wave voltage pulses. A pulse-forming cable was charged and then grounded at one end without any resistance, so that a traveling wave reciprocated along the cable with a change in its polarity because the traveling wave was negatively reflected at the grounded-end. Transient discharge light between point-plane electrodes with a glass barrier was observed using a gated image-intensifier. Photographs of the transient discharge light indicated that many streamer channels extended widely in the gap at the initial stage in the voltage oscillation, while only an intense discharge channel was observed at the latter stage. NO removal tests were carried out using the reciprocal pulse generator and a coaxial plasma reactor with a cylindrical glass-barrier. Results indicated that the discharges at the first and the second polarity reversals contributed largely to the oxidation reaction from NO into NO2, whereas the contribution of the subsequent discharges in the latter stage to NO removal was small.

Direct control of transitions between different mode-locking states of a fiber laser

NASA Astrophysics Data System (ADS)

Ilday, Fatih; Teamir, Tesfay; Iegorov, Roman; Makey, Ghaith

Mode-locking corresponds to a far-from-equilibrium steady state of a laser, whereby extremely short pulses can be produced. Capability to directly control mode-locking states can be used to improve laser performance with numerous applications, as well as shed light on their far-from-equilibrium physics using the laser as an experimental platform. Here, we demonstrate direct control of the mode-locking state using spectral pulse shaping by incorporating a spatial light modulator at a Fourier plane inside the cavity of an Yb-doped fiber laser. We show that we can halt and restart mode-locking, suppress instabilities, induce controlled reversible and irreversible transitions between mode-locking states, and perform advanced pulse shaping on pulses as short as 40 fs. This capability can be used to experimentally investigate bifurcations, reversible and irreversible transitions, by selecting, steering, and even competing various mode-locking states. Such studies can explore collective dynamics of dissipative soliton molecules, and ultimately test emerging theories about far-from-equilibrium physics, where there is an acute lack of experimental systems that are sufficiently well controlled. ERC CoG 617521, TUBITAK 113F319.

Optimization of spin-torque switching using AC and DC pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunn, Tom; Kamenev, Alex; Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, Minnesota 55455

2014-06-21

We explore spin-torque induced magnetic reversal in magnetic tunnel junctions using combined AC and DC spin-current pulses. We calculate the optimal pulse times and current strengths for both AC and DC pulses as well as the optimal AC signal frequency, needed to minimize the Joule heat lost during the switching process. The results of this optimization are compared against numeric simulations. Finally, we show how this optimization leads to different dynamic regimes, where switching is optimized by either a purely AC or DC spin-current, or a combination AC/DC spin-current, depending on the anisotropy energies and the spin-current polarization.

Regeneration of Airy pulses in fiber-optic links with dispersion management of the two leading dispersion terms of opposite signs

NASA Astrophysics Data System (ADS)

Driben, R.; Meier, T.

2014-04-01

Dispersion management of periodically alternating fiber sections with opposite signs of two leading dispersion terms is applied for the regeneration of self-accelerating truncated Airy pulses. It is demonstrated that for such a dispersion management scheme, the direction of the acceleration of the pulse is reversed twice within each period. In this scheme the system features light hot spots in the center of each fiber section, where the energy of the light pulse is tightly focused in a short temporal slot. Comprehensive numerical studies demonstrate a long-lasting propagation also under the influence of a strong fiber Kerr nonlinearity.

Ultrafast magnetization switching by spin-orbit torques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garello, Kevin, E-mail: kevin.garello@mat.ethz.ch; Avci, Can Onur; Baumgartner, Manuel

2014-11-24

Spin-orbit torques induced by spin Hall and interfacial effects in heavy metal/ferromagnetic bilayers allow for a switching geometry based on in-plane current injection. Using this geometry, we demonstrate deterministic magnetization reversal by current pulses ranging from 180 ps to ms in Pt/Co/AlO{sub x} dots with lateral dimensions of 90 nm. We characterize the switching probability and critical current I{sub c} as a function of pulse length, amplitude, and external field. Our data evidence two distinct regimes: a short-time intrinsic regime, where I{sub c} scales linearly with the inverse of the pulse length, and a long-time thermally assisted regime, where I{sub c} variesmore » weakly. Both regimes are consistent with magnetization reversal proceeding by nucleation and fast propagation of domains. We find that I{sub c} is a factor 3–4 smaller compared to a single domain model and that the incubation time is negligibly small, which is a hallmark feature of spin-orbit torques.« less

Two-photon interference of weak coherent laser pulses recalled from separate solid-state quantum memories

NASA Astrophysics Data System (ADS)

Jin, Jeongwan; Slater, Joshua A.; Saglamyurek, Erhan; Sinclair, Neil; George, Mathew; Ricken, Raimund; Oblak, Daniel; Sohler, Wolfgang; Tittel, Wolfgang

2013-08-01

Quantum memories allowing reversible transfer of quantum states between light and matter are central to quantum repeaters, quantum networks and linear optics quantum computing. Significant progress regarding the faithful transfer of quantum information has been reported in recent years. However, none of these demonstrations confirm that the re-emitted photons remain suitable for two-photon interference measurements, such as C-NOT gates and Bell-state measurements, which constitute another key ingredient for all aforementioned applications. Here, using pairs of laser pulses at the single-photon level, we demonstrate two-photon interference and Bell-state measurements after either none, one or both pulses have been reversibly mapped to separate thulium-doped lithium niobate waveguides. As the interference is always near the theoretical maximum, we conclude that our solid-state quantum memories, in addition to faithfully mapping quantum information, also preserve the entire photonic wavefunction. Hence, our memories are generally suitable for future applications of quantum information processing that require two-photon interference.

Two-photon interference of weak coherent laser pulses recalled from separate solid-state quantum memories.

PubMed

Jin, Jeongwan; Slater, Joshua A; Saglamyurek, Erhan; Sinclair, Neil; George, Mathew; Ricken, Raimund; Oblak, Daniel; Sohler, Wolfgang; Tittel, Wolfgang

2013-01-01

Quantum memories allowing reversible transfer of quantum states between light and matter are central to quantum repeaters, quantum networks and linear optics quantum computing. Significant progress regarding the faithful transfer of quantum information has been reported in recent years. However, none of these demonstrations confirm that the re-emitted photons remain suitable for two-photon interference measurements, such as C-NOT gates and Bell-state measurements, which constitute another key ingredient for all aforementioned applications. Here, using pairs of laser pulses at the single-photon level, we demonstrate two-photon interference and Bell-state measurements after either none, one or both pulses have been reversibly mapped to separate thulium-doped lithium niobate waveguides. As the interference is always near the theoretical maximum, we conclude that our solid-state quantum memories, in addition to faithfully mapping quantum information, also preserve the entire photonic wavefunction. Hence, our memories are generally suitable for future applications of quantum information processing that require two-photon interference.

Homogeneous dielectric barrier discharges in atmospheric air and its influencing factor

NASA Astrophysics Data System (ADS)

Ran, Junxia; Li, Caixia; Ma, Dong; Luo, Haiyun; Li, Xiaowei

2018-03-01

The stable homogeneous dielectric barrier discharge (DBD) is obtained in atmospheric 2-3 mm air gap. It is generated using center frequency 1 kHz high voltage power supply between two plane parallel electrodes with specific alumina ceramic plates as the dielectric barriers. The discharge characteristics are studied by a measurement of its electrical discharge parameters and observation of its light emission phenomena. The results show that a large single current pulse of about 200 μs duration appearing in each voltage pulse, and its light emission is radially homogeneous and covers the entire surface of the two electrodes. The homogeneous discharge generated is a Townsend discharge during discharge. The influences of applied barrier, its thickness, and surface roughness on the transition of discharge modes are studied. The results show that it is difficult to produce a homogeneous discharge using smooth plates or alumina plate surface roughness Ra < 100 nm even at a 1 mm air gap. If the alumina plate is too thin, the discharge also transits to filamentary discharge. If it is too thick, the discharge is too weak to observe. With the increase of air gap distance and applied voltage, the discharge can also transit from a homogeneous mode to a filamentary mode. In order to generate stable and homogeneous DBD at a larger air gap, proper dielectric material, dielectric thickness, and dielectric surface roughness should be used, and proper applied voltage amplitude and frequency should also be used.

Series-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, Emanuel M.

1986-01-01

A high-power series-counterpulse repetitive-pulse inductive energy storage and transfer circuit includes an opening switch, a main energy storage coil, and a counterpulse capacitor. The load pulse is initiated simultaneously with the initiation of the counterpulse which is used to turn the opening switch off. There is no delay from command to output pulse. During the load pulse, the counterpulse capacitor is first discharged and then recharged in the opposite polarity with sufficient energy to accomplish the load counterpulse which terminates the load pulse and turns the load switch off. When the main opening switch is triggered closed again to terminate the load pulse, the counterpulse capacitor discharges in the reverse direction through the load switch and through the load, causing a rapid, sharp cutoff of the load pulse as well as recovering any energy remaining in the load inductance. The counterpulse capacitor is recharged to its original condition by the main energy storage coil after the load pulse is over, not before it begins.

An Investigation into the Application of Generalized Differential Quadrature Method to Bending Analysis of Composite Sandwich Plates

NASA Astrophysics Data System (ADS)

Ghassemi, Aazam; Yazdani, Mostafa; Hedayati, Mohamad

2017-12-01

In this work, based on the First Order Shear Deformation Theory (FSDT), an attempt is made to explore the applicability and accuracy of the Generalized Differential Quadrature Method (GDQM) for bending analysis of composite sandwich plates under static loading. Comparative studies of the bending behavior of composite sandwich plates are made between two types of boundary conditions for different cases. The effects of fiber orientation, ratio of thickness to length of the plate, the ratio of thickness of core to thickness of the face sheet are studied on the transverse displacement and moment resultants. As shown in this study, the role of the core thickness in deformation of these plates can be reversed by the stiffness of the core in comparison with sheets. The obtained graphs give very good results due to optimum design of sandwich plates. In Comparison with existing solutions, fast convergent rates and high accuracy results can be achieved by the GDQ method.

Collision processes at the northern margin of the Black Sea

NASA Astrophysics Data System (ADS)

Gobarenko, V. S.; Murovskaya, A. V.; Yegorova, T. P.; Sheremet, E. E.

2016-07-01

Extended along the Crimea-Caucasus coast of the Black Sea, the Crimean Seismic Zone (CSZ) is an evidence of active tectonic processes at the junction of the Scythian Plate and Black Sea Microplate. A relocation procedure applied to weak earthquakes (mb ≤ 3) recorded by ten local stations during 1970-2013 helped to determine more accurately the parameters of hypocenters in the CSZ. The Kerch-Taman, Sudak, Yuzhnoberezhnaya (South Coast), and Sevastopol subzones have also been recognized. Generalization of the focal mechanisms of 31 strong earthquakes during 1927-2013 has demonstrated the predominance of reverse and reverse-normal-faulting deformation regimes. This ongoing tectonic process occurs under the settings of compression and transpression. The earthquake foci with strike-slip component mechanisms concentrate in the west of the CSZ. Comparison of deformation modes in the western and eastern Crimean Mountains according to tectonophysical data has demonstrated that the western part is dominated by strike-slip and normal- faulting, while in the eastern part, reverse-fault and strike-slip deformation regimes prevail. Comparison of the seismicity and gravity field and modes of deformation suggests underthusting of the East Black Sea Microplate with thin suboceanic crust under the Scythian Plate. In the Yuzhnoberezhnaya Subzone, this process is complicated by the East Black Sea Microplate frontal part wedging into the marginal part of the Scythian Plate crust. The indentation mechanism explains the strong gravity anomaly in the Crimean Mountains and their uplift.

Improved Intrapulse Raman Scattering Control via Asymmetric Airy Pulses

NASA Astrophysics Data System (ADS)

Hu, Yi; Tehranchi, Amirhossein; Wabnitz, Stefan; Kashyap, Raman; Chen, Zhigang; Morandotti, Roberto

2015-02-01

We experimentally demonstrate the possibility of tuning the frequency of a laser pulse via the use of an Airy pulse-seeded soliton self-frequency shift. The intrinsically asymmetric nature of Airy pulses, typically featured by either leading or trailing oscillatory tails (relatively to the main lobe), is revealed through the nonlinear generation of both a primary and a secondary Raman soliton self-frequency shift, a phenomenon which is driven by the soliton fission processes. The resulting frequency shift can be carefully controlled by using time-reversed Airy pulses or, alternatively, by applying an offset to the cubic phase modulation used to generate the pulses. When compared with the use of conventional chirped Gaussian pulses, our technique brings about unique advantages in terms of both efficient frequency tuning and feasibility, along with the generation and control of multicolor Raman solitons with enhanced tunability. Our theoretical analysis agrees well with our experimental observations.

Microturbulence studies of pulsed poloidal current drive discharges in the reversed field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmody, D., E-mail: dcarmody@wisc.edu; Pueschel, M. J.; Anderson, J. K.

2015-01-15

Experimental discharges with pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed field pinch are investigated using a semi-analytic equilibrium model in the gyrokinetic turbulence code GENE. PPCD cases, with plasma currents of 500 kA and 200 kA, exhibit a density-gradient-driven trapped electron mode (TEM) and an ion temperature gradient mode, respectively. Relative to expectations of tokamak core plasmas, the critical gradients for the onset of these instabilities are found to be greater by roughly a factor of the aspect ratio. A significant upshift in the nonlinear TEM transport threshold, previously found for tokamaks, is confirmed in nonlinear reversed fieldmore » pinch simulations and is roughly three times the threshold for linear instability. The simulated heat fluxes can be brought in agreement with measured diffusivities by introducing a small, resonant magnetic perturbation, thus modeling the residual fluctuations from tearing modes. These fluctuations significantly enhance transport.« less

PUMPS

DOEpatents

Thornton, J.D.

1959-03-24

A pump is described for conveving liquids, particure it is not advisable he apparatus. The to be submerged in the liquid to be pumped, a conduit extending from the high-velocity nozzle of the injector,and means for applying a pulsating prcesure to the surface of the liquid in the conduit, whereby the surface oscillates between positions in the conduit. During the positive half- cycle of an applied pulse liquid is forced through the high velocity nozzle or jet of the injector and operates in the manner of the well known water injector and pumps liquid from the main intake to the outlet of the injector. During the negative half-cycle of the pulse liquid flows in reverse through the jet but no reverse pumping action takes place.

Stereo multiplexed holographic particle image velocimeter

DOEpatents

Adrian, Ronald J.; Barnhart, Donald H.; Papen, George A.

1996-01-01

A holographic particle image velocimeter employs stereoscopic recording of particle images, taken from two different perspectives and at two distinct points in time for each perspective, on a single holographic film plate. The different perspectives are provided by two optical assemblies, each including a collecting lens, a prism and a focusing lens. Collimated laser energy is pulsed through a fluid stream, with elements carried in the stream scattering light, some of which is collected by each collecting lens. The respective focusing lenses are configured to form images of the scattered light near the holographic plate. The particle images stored on the plate are reconstructed using the same optical assemblies employed in recording, by transferring the film plate and optical assemblies as a single integral unit to a reconstruction site. At the reconstruction site, reconstruction beams, phase conjugates of the reference beams used in recording the image, are directed to the plate, then selectively through either one of the optical assemblies, to form an image reflecting the chosen perspective at the two points in time.

Stereo multiplexed holographic particle image velocimeter

DOEpatents

Adrian, R.J.; Barnhart, D.H.; Papen, G.A.

1996-08-20

A holographic particle image velocimeter employs stereoscopic recording of particle images, taken from two different perspectives and at two distinct points in time for each perspective, on a single holographic film plate. The different perspectives are provided by two optical assemblies, each including a collecting lens, a prism and a focusing lens. Collimated laser energy is pulsed through a fluid stream, with elements carried in the stream scattering light, some of which is collected by each collecting lens. The respective focusing lenses are configured to form images of the scattered light near the holographic plate. The particle images stored on the plate are reconstructed using the same optical assemblies employed in recording, by transferring the film plate and optical assemblies as a single integral unit to a reconstruction site. At the reconstruction site, reconstruction beams, phase conjugates of the reference beams used in recording the image, are directed to the plate, then selectively through either one of the optical assemblies, to form an image reflecting the chosen perspective at the two points in time. 13 figs.

Rarefaction Effects in Hypersonic Aerodynamics

NASA Astrophysics Data System (ADS)

Riabov, Vladimir V.

2011-05-01

The Direct Simulation Monte-Carlo (DSMC) technique is used for numerical analysis of rarefied-gas hypersonic flows near a blunt plate, wedge, two side-by-side plates, disk, torus, and rotating cylinder. The role of various similarity parameters (Knudsen and Mach numbers, geometrical and temperature factors, specific heat ratios, and others) in aerodynamics of the probes is studied. Important kinetic effects that are specific for the transition flow regime have been found: non-monotonic lift and drag of plates, strong repulsive force between side-by-side plates and cylinders, dependence of drag on torus radii ratio, and the reverse Magnus effect on the lift of a rotating cylinder. The numerical results are in a good agreement with experimental data, which were obtained in a vacuum chamber at low and moderate Knudsen numbers from 0.01 to 10.

On the efficiency and reversibility of active ligand transport induced by alternating rectangular electric pulses.

PubMed Central

Chen, Y; Tsong, T Y

1994-01-01

The stationary-state kinetic properties of a simplified two-state electro-conformational coupling model (ECC) in the presence of alternating rectangular electric potential pulses are derived analytically. Analytic expressions for the transport flux, the rate of electric energy dissipation, and the efficiency of the transducing system are obtained as a function of the amplitude and frequency of the oscillation. These formulas clarify some fundamental concept of the ECC model and are directly applicable to the interpretation and design of experiments. Based on these formulas, the reversibility and the degree of coupling of the system can be studied quantitatively. It is found that the oscillation-induced free energy transduction is reversible and tight-coupled only when the amplitude of the oscillating electric field is infinitely large. In general, the coupling is not tight when the amplitude of the electric field is finite. Furthermore, depending on the kinetic parameters of the model, there may exist a "critical" electric field amplitude, below which free energy transduction is not reversible. That is, energy may be transduced from the electric to the chemical, but not from the chemical to the electric. PMID:8075348

Stability of the mode-locking regime in tapered quantum-dot lasers

NASA Astrophysics Data System (ADS)

Bardella, P.; Drzewietzki, L.; Rossetti, M.; Weber, C.; Breuer, S.

2018-02-01

We study numerically and experimentally the role of the injection current and reverse bias voltage on the pulse stability of tapered, passively mode-locked, Quantum Dot (QD) lasers. By using a multi-section delayed differential equation and introducing in the model the QD inhomogenous broadening, we are able to predict the onset of leading and trailing edge instabilities in the emitted pulse trains and to identify specific trends of stability in dependence on the laser biasing conditions. The numerical results are confirmed experimentally trough amplitude and timing stability analysis of the pulses.

Giant-pulse Nd:YVO4 microchip laser with MW-level peak power by emission cross-sectional control.

PubMed

Kausas, Arvydas; Taira, Takunori

2016-02-22

We present a giant-pulse generation laser realized by the emission cross-section control of a gain medium in a passively Q-switched Nd:YVO4 microchip laser with a Cr4+:YAG saturable absorber. Up to 1.17 MW peak power and 1.03 mJ pulse energy were obtained with a 100 Hz repetition rate. By combining the Nd:YVO4 crystal with a Sapphire plate, lower temperature difference between a pump region in the gain crystal and a crystal holder was obtained which helped to keep the cavity in stability zone at elevated temperatures and allowed the achievement of the high peak power for this laser system.

The stress distribution in pin-loaded orthotropic plates

NASA Technical Reports Server (NTRS)

Klang, E. C.; Hyer, M. W.

1985-01-01

The performance of mechanically fastened composite joints was studied. Specially, a single-bolt connector was modeled as a pin-loaded, infinite plate. The model that was developed used two dimensional, complex variable, elasticity techniques combined with a boundary collocation procedure to produce solutions for the problem. Through iteration, the boundary conditions were satisfied and the stresses in the plate were calculated. Several graphite epoxy laminates were studied. In addition, parameters such as the pin modulus, coefficient of friction, and pin-plate clearance were varied. Conclusions drawn from this study indicate: (1) the material properties (i.e., laminate configuration) of the plate alter the stress state and, for highly orthotropic materials, the contact stress deviates greatly from the cosinusoidal distribution often assumed; (2) friction plays a major role in the distribution of stresses in the plate; (3) reversing the load direction also greatly effects the stress distribution in the plate; (4) clearance (or interference) fits change the contact angle and thus the location of the peak hoop stress; and (5) a rigid pin appears to be a good assumption for typical material systems.

A new back-and-forth iterative method for time-reversed convection modeling: Implications for the Cenozoic evolution of 3-D structure and dynamics of the mantle

NASA Astrophysics Data System (ADS)

Glišović, Petar; Forte, Alessandro M.

2016-06-01

The 3-D distribution of buoyancy in the convecting mantle drives a suite of convection-related manifestations. Although seismic tomography is providing increasingly resolved images of the present-day mantle heterogeneity, the distribution of mantle density variations in the geological past is unknown, and, by implication, this is true for the convection-related observables. The one major exception is tectonic plate motions, since geologic data are available to estimate their history and they currently provide the only available constraints on the evolution of 3-D mantle buoyancy in the past. We developed a new back-and-forth iterative method for time-reversed convection modeling with a procedure for matching plate velocity data at different instants in the past. The crucial aspect of this reconstruction methodology is to ensure that at all times plates are driven by buoyancy forces in the mantle and not vice versa. Employing tomography-based retrodictions over the Cenozoic, we estimate the global amplitude of the following observables: dynamic surface topography, the core-mantle boundary ellipticity, the free-air gravity anomalies, and the global divergence rates of tectonic plates. One of the major benefits of the new data assimilation method is the stable recovery of much shorter wavelength changes in heterogeneity than was possible in our previous work. We now resolve what appears to be two-stage subduction of the Farallon plate under the western U.S. and a deeply rooted East African Plume that is active under the Ethiopian volcanic fields during the Early Eocene.

Evaluation of a new baseplate in reverse total shoulder arthroplasty - comparison of biomechanical testing of stability with roentgenological follow up criteria.

PubMed

Irlenbusch, U; Kohut, G

2015-04-01

To minimize notching problem associated with reversed prostheses, inferior positioning of base plate is recommended. This reduces the risk of notching, but does not eliminate it completely. Both polyethylene/PE-induced osteolysis and implant-to-bone or implant-to-implant contact may still occur, contributing to the risk of screw-breakage and resulting long-term failure. Therefore, the stability and integration of a newly developed base plate without inferior screw and inversion of bearing materials was investigated. Biomechanical assessment of primary stability of the two types of glenoid baseplate (1- and 2-pegged) was carried out according to ASTM F-2028-02 (American Society for Testing and Materials). Patients with a follow-up period of at least 2 years were clinically (n=78) and for most of them radiologically (n=61) examined. The X-rays were evaluated for loosening and scapular notching. The mean values of micromotions after 100,000 cycles showed no relevant differences between the 2-peg and the 1-peg base plates (47 μm for the 2-peg design and 43 μm for the 1-peg design), i.e. both were below the borderline for secure Osseointegration of 150 μm. Radiologically, no signs of loosening or radiolucent lines/RLL were found for both base plates. The mean incidence of inferior scapular notching was 23.6% (42 mm glenoid sphere: 15.8%). Only grade 1 and grade 2 notching was observed. Additionally as result of absence of PE-induced osteolysis shape, size, borderline and location of notching differed from those observed with conventional reverse total shoulder arthroplasty bearing materials. In combination with modified inferior operating technique, the newly designed implant has the potential to reduce the incidence of scapular notching and to avoid both PE-induced osteolysis and metal-screw contact. The new design did not compromise stability of the base plate in any way during the investigation period, as demonstrated both by the data from the biomechanical investigation and also by the radiological follow-up. Level III, case-control study. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Control of DC gas flow in a single-stage double-inlet pulse tube cooler

NASA Astrophysics Data System (ADS)

Wang, C.; Thummes, G.; Heiden, C.

The use of double-inlet mode in the pulse tube cooler opens up a possibility of DC gas flow circulating around the regenerator and pulse tube. Numerical analysis shows that effects of DC flow in a single-stage pulse tube cooler are different in some aspects from that in a 4 K pulse tube cooler. For highest cooler efficiency, DC flow should be compensated to a small value, i.e. DC flow over average AC flow at regenerator inlet should be in the range -0.0013 to +0.00016. Dual valves with reversed asymmetric geometries were used for the double-inlet bypass to control the DC flow in this paper. The experiment, performed in a single-stage double-inlet pulse tube cooler, verified that the cooler performance can be significantly improved by precisely controlling the DC flow.

Using a short-pulse diffraction-limited laser beam to probe filamentation of a random phase plate smoothed beam.

PubMed

Kline, J L; Montgomery, D S; Flippo, K A; Johnson, R P; Rose, H A; Shimada, T; Williams, E A

2008-10-01

A short pulse (few picoseconds) laser probe provides high temporal resolution measurements to elucidate details of fast dynamic phenomena not observable with typical longer laser pulse probes and gated diagnostics. Such a short pulse laser probe (SPLP) has been used to measure filamentation of a random phase plate (RPP) smoothed laser beam in a gas-jet plasma. The plasma index of refraction due to driven density and temperature fluctuations by the RPP beam perturbs the phase front of a SPLP propagating at a 90 degree angle with respect to the RPP interaction beam. The density and temperature fluctuations are quasistatic on the time scale of the SPLP (approximately 2 ps). The transmitted near-field intensity distribution from the SPLP provides a measure of the phase front perturbation. At low plasma densities, the transmitted intensity pattern is asymmetric with striations across the entire probe beam in the direction of the RPP smoothed beam. As the plasma density increases, the striations break up into smaller sizes along the direction of the RPP beam propagation. The breakup of the intensity pattern is consistent with self-focusing of the RPP smoothed interaction beam. Simulations of the experiment using the wave propagation code, PF3D, are in qualitative agreement demonstrating that the asymmetric striations can be attributed to the RPP driven density fluctuations. Quantification of the beam breakup measured by the transmitted SPLP could lead to a new method for measuring self-focusing of lasers in underdense plasmas.

Holographic Cinematography With The Help Of A Pulse YAG Laser

NASA Astrophysics Data System (ADS)

Smigielski, P.; Fagot, H.; Albe, F.

1985-02-01

For many years opticists have tried to achieve 3D-cinematography with the help of holography. The term "cineholography" has been introduced in 1965. At that time the method consisted in superimposing on the same photographic plate various holograms recorded at different times. The image separation was achieved by rotating either the plate in its plane or the reference beam during both the recording and reconstructing processes. The number of views was limited by the principle itself, but a high repetition rate (100 kHz) has been obtained with a pulsed ruby laser. Then other experiments have been conducted by different authors, mainly in the Soviet Unions and in the United States of America, by using the principle of classical cinematography in which the image separation is obtained by translating the film. With this method we have recorded the first French holographic movies on 35 mm Agfa films with the help of a pulsed YAG laser built in our laboratory. This frequency doubled laser (X = 0.532 pm) delivers pulses of 20 ns with an energy of 30 HO at a repetition rate of 24 Hz. The experimental arrangements are described and some images of diffuse moving objects are presented. The volume of the recording scene is greater than one cubic meter. The coherence length of the laser is higher than one meter and remains steady during the recording process. Results are discussed and an outlook on the future is given with special respect to high repetition rate techniques.

Controlled generation of a single Trichel pulse and a series of single Trichel pulses in air

NASA Astrophysics Data System (ADS)

Mizeraczyk, Jerzy; Berendt, Artur; Akishev, Yuri

2018-04-01

In this paper, a simple method for the controlled generation of a single Trichel pulse or a series of single Trichel pulses of a regulated repetition frequency in air is proposed. The concept of triggering a single Trichel pulse or a series of such pulses is based on the precise controlling the voltage inception of the negative corona, which can be accomplished through the use of a ramp voltage pulse or a series of such pulses with properly chosen ramp voltage pulse parameters (rise and fall times, and ramp voltage pulse repetition frequency). The proposal has been tested in experiments using a needle-to-plate electrode arrangement in air, and reproducible Trichel pulses (single or in a series) were obtained by triggering them with an appropriately designed voltage waveform. The proposed method and results obtained have been qualitatively analysed. The analysis provides guidance for designing the voltage ramp pulse in respect of the generation of a single Trichel pulse or a series of single Trichel pulses. The controlled generation of a single Trichel pulse or a series of such pulses would be a helpful research tool for the refined studies of the fundamental processes in a negative corona discharge in a single- (air is an example) and multi-phase gaseous fluids. The controlled generation of a single Trichel pulse or a series of Trichel pulses can also be attractive for those corona treatments which need manipulation of the electric charge and heat portions delivered by the Trichel pulses to the object.

Electrical Switching of Perovskite Thin-Film Resistors

NASA Technical Reports Server (NTRS)

Liu, Shangqing; Wu, Juan; Ignatiev, Alex

2010-01-01

Electronic devices that exploit electrical switching of physical properties of thin films of perovskite materials (especially colossal magnetoresistive materials) have been invented. Unlike some related prior devices, these devices function at room temperature and do not depend on externally applied magnetic fields. Devices of this type can be designed to function as sensors (exhibiting varying electrical resistance in response to varying temperature, magnetic field, electric field, and/or mechanical pressure) and as elements of electronic memories. The underlying principle is that the application of one or more short electrical pulse(s) can induce a reversible, irreversible, or partly reversible change in the electrical, thermal, mechanical, and magnetic properties of a thin perovskite film. The energy in the pulse must be large enough to induce the desired change but not so large as to destroy the film. Depending on the requirements of a specific application, the pulse(s) can have any of a large variety of waveforms (e.g., square, triangular, or sine) and be of positive, negative, or alternating polarity. In some applications, it could be necessary to use multiple pulses to induce successive incremental physical changes. In one class of applications, electrical pulses of suitable shapes, sizes, and polarities are applied to vary the detection sensitivities of sensors. Another class of applications arises in electronic circuits in which certain resistance values are required to be variable: Incorporating the affected resistors into devices of the present type makes it possible to control their resistances electrically over wide ranges, and the lifetimes of electrically variable resistors exceed those of conventional mechanically variable resistors. Another and potentially the most important class of applications is that of resistance-based nonvolatile-memory devices, such as a resistance random access memory (RRAM) described in the immediately following article, Electrically Variable Resistive Memory Devices (MFS-32511-1).

Evaluating the potential of a novel dual heat-pulse sensor to measure volumetric water use in grapevines under a range of flow conditions

USDA-ARS?s Scientific Manuscript database

The aim of this study was to validate dual sap flow sensors that combine two heat pulse techniques to measure volumetric water use over the full range of sap flows found in grapevines. The heat ratio method (HRM), which works well at measuring low and reverse flows, was combined with the compensati...

Circadian Rhythm in the Expression of the mRNA Coding for the Apoprotein of the Light-Harvesting Complex of Photosystem II 1

PubMed Central

Tavladoraki, Paraskevi; Kloppstech, Klaus; Argyroudi-Akoyunoglou, Joan

1989-01-01

The mRNA coding for light-harvesting complex of PSII (LHC-II) apoprotein is present in etiolated bean (Phaseolus vulgaris L.) leaves; its level is low in 5-day-old leaves, increases about 3 to 4 times in 9- to 13-day-old leaves, and decreases thereafter. A red light pulse induces an increase in LHC-II mRNA level, which is reversed by far red light, in all ages of the etiolated tissue tested. The phytochrome-controlled initial increase of LHC-II mRNA level is higher in 9- and 13-day-old than in 5- and 17-day-old bean leaves. The amount of LHC-II mRNA, accumulated in the dark after a red light pulse, oscillates rhythmically with a period of about 24 hours. This rhythm is also observed in continuous white light and in the dark following exposure to continuous white light, and persists for at least 70 hours. A second red light pulse, applied 36 hours after initiation of the rhythm, induces a phase-shift, which is prevented by far red light immediately following the second red light pulse. A persistent, but gradually reduced, far red reversibility of the red light-induced increase in LHC-II mRNA level is observed. In contrast, far red reversibility of the red light-induced clock setting is only observed when far red follows immediately the red light. It is concluded that (a) the light-induced LHC-II mRNA accumulation follows an endogenous, circadian rhythm, for the appearance of which a red light pulse is sufficient, (b) the circadian oscillator is under phytochrome control, and (c) a stable Pfr form, which exists for several hours, is responsible for sustaining LHC-II gene transcription. Images Figure 1 Figure 2 Figure 8 PMID:16666825

Effects of 1-MeV gamma radiation on a multi-anode microchannel array detector tube

NASA Technical Reports Server (NTRS)

Timothy, J. G.; Bybee, R. L.

1979-01-01

A multianode microchannel array (MAMA) detector tube without a photocathode was exposed to a total dose of 1,000,000 rads of 1-MeV gamma radiation from a Co-60 source. The high-voltage characteristic of the microchannel array plate, average dark count, gain, and resolution of pulse height distribution characteristics showed no degradation after this total dose. In fact, the degassing of the microchannels induced by the high radiation flux had the effect of cleaning up the array plate and improving its characteristics.

SFD-261 Crossed-Field Amplifier Manufacturing Technology Program.

DTIC Science & Technology

1979-09-28

microwave amplifier used to increase tet pow--rlel of pulses of energy by a factor of 20. It is used in the Aegis A4/SPY1V DD 1473 ECIIOwOF I MOV 65...transmitter. A single ship.,; complement without spares is seventy-six. Its internal parts are made from high purity copper and many are complex and...23 Cathode Support 39 24 Mounting Plate ’i 25 Support Plate 42 26 Tubing Support 43 27 SFD-261 High Voltage Can End 45 b 28 Comparison of MT Tube

Development and test of photon-counting microchannel plate detector arrays for use on space telescopes

NASA Technical Reports Server (NTRS)

Timothy, J. G.

1976-01-01

The full sensitivity, dynamic range, and photometric stability of microchannel array plates(MCP) are incorporated into a photon-counting detection system for space operations. Components of the system include feedback-free MCP's for high gain and saturated output pulse-height distribution with a stable response; multi-anode readout arrays mounted in proximity focus with the output face of the MCP; and multi-layer ceramic headers to provide electrical interface between the anode array in a sealed detector tube and the associated electronics.

Observation of a spark channel generated in water with shock wave assistance in plate-to-plate electrode configuration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stelmashuk, V., E-mail: vitalij@ipp.cas.cz

2014-01-15

When a high voltage pulse with an amplitude of 30 kV is applied to a pair of disk electrodes at a time when a shock wave is passing between them, an electrical spark is generated. The dynamic changes in the spark morphology are studied here using a high-speed framing camera. The primary result of this work is the provision of experimental evidence of plasma instability that was observed in the channel of the electric spark.

Performance of low resistance microchannel plate stacks

NASA Technical Reports Server (NTRS)

Siegmund, O. H. W.; Stock, J.

1991-01-01

Results are presented from an evaluation of three sets of low resistance microchannel plate (MCP) stacks; the tests encompassed gain, pulse-height distribution, background rate, event rate capacity as a function of illuminated area, and performance changes due to high temperature bakeout and high flux UV scrub. The MCPs are found to heat up, requiring from minutes to hours to reach stabilization. The event rate is strongly dependent on the size of the area being illuminated, with larger areas experiencing a gain drop onset at lower rates than smaller areas.

High precision electric gate for time-of-flight ion mass spectrometers

NASA Technical Reports Server (NTRS)

Sittler, Edward C. (Inventor)

2011-01-01

A time-of-flight mass spectrometer having a chamber with electrodes to generate an electric field in the chamber and electric gating for allowing ions with a predetermined mass and velocity into the electric field. The design uses a row of very thin parallel aligned wires that are pulsed in sequence so the ion can pass through the gap of two parallel plates, which are biased to prevent passage of the ion. This design by itself can provide a high mass resolution capability and a very precise start pulse for an ion mass spectrometer. Furthermore, the ion will only pass through the chamber if it is within a wire diameter of the first wire when it is pulsed and has the right speed so it is near all other wires when they are pulsed.

Method to reduce damage to backing plate

DOEpatents

Perry, Michael D.; Banks, Paul S.; Stuart, Brent C.

2001-01-01

The present invention is a method for penetrating a workpiece using an ultra-short pulse laser beam without causing damage to subsequent surfaces facing the laser. Several embodiments are shown which place holes in fuel injectors without damaging the back surface of the sack in which the fuel is ejected. In one embodiment, pulses from an ultra short pulse laser remove about 10 nm to 1000 nm of material per pulse. In one embodiment, a plasma source is attached to the fuel injector and initiated by common methods such as microwave energy. In another embodiment of the invention, the sack void is filled with a solid. In one other embodiment, a high viscosity liquid is placed within the sack. In general, high-viscosity liquids preferably used in this invention should have a high damage threshold and have a diffusing property.

Ultra-wideband horn antenna with abrupt radiator

DOEpatents

McEwan, T.E.

1998-05-19

An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna. 8 figs.

DNA electrotransfer into the skin using a combination of one high- and one low-voltage pulse.

PubMed

Pavselj, N; Préat, V

2005-09-02

Electroporation is an effective alternative to viral methods to significantly improve DNA transfection after intradermal and topical delivery. The aim of the study was to check whether a combination of a short high-voltage pulse (HV) to permeabilize the skin cells and a long low-voltage pulse (LV) to transfer DNA by electrophoresis was more efficient to enhance DNA expression than conventional repeated HV or LV pulses alone after intradermal injection of DNA plasmid. GFP and luciferase expressions in the skin were enhanced by HV+LV protocol as compared to HV or LV pulses alone. The expression lasted for up to 10 days. Consistently, HV+LV protocol induced a higher Th2 immune response against ovalbumin than HV or LV pulses. Standard methods were used to assess the effect of electric pulses on skin: the application of a combination of HV and LV pulses on rat skin fold delivered by plate electrodes was well tolerated. These data demonstrate that a combination of one HV (700 to 1000 V/cm; 100 micros) followed by one LV (140 to 200 V/cm; 400 ms) is an efficient electroporation protocol to enhance DNA expression in the skin.

Study and Construction of Electrostatic Biprisms Useful in Corpuscular Optics; ETUDE ET REALISATION DE BIPRISMES ELECTROSTATIQUES UTILISABLES EN OPTIQUE CORPUSCULAIRE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Septier, A.

1960-03-01

In the simultaneous injection of two beams identical except in direction in an FFAG cyclotron, two beams of equal intensity and energy are needed. The two beams can be produced either by alternating the direction of a single beam by very short, rectangular, high-voltage pulses fed to a deflector, or by chopping the beam with a static apparatus. The second method was investigated because of its simplicity. The principles and properties of the electrostatic biprism are presented. Three cases are then considered: a wire stretched between two plates, a grid between two plates, and a plate between two flat conductors.more » (T.R.H.)« less

Remote defect imaging for plate-like structures based on the scanning laser source technique

NASA Astrophysics Data System (ADS)

Hayashi, Takahiro; Maeda, Atsuya; Nakao, Shogo

2018-04-01

In defect imaging with a scanning laser source technique, the use of a fixed receiver realizes stable measurements of flexural waves generated by laser at multiple rastering points. This study discussed the defect imaging by remote measurements using a laser Doppler vibrometer as a receiver. Narrow-band burst waves were generated by modulating laser pulse trains of a fiber laser to enhance signal to noise ratio in frequency domain. Averaging three images obtained at three different frequencies suppressed spurious distributions due to resonance. The experimental system equipped with these newly-devised means enabled us to visualize defects and adhesive objects in plate-like structures such as a plate with complex geometries and a branch pipe.

Design and Modelling of a Microfluidic Electro-Lysis Device with Controlling Plates

NASA Technical Reports Server (NTRS)

Jenkins, A.; Chen, C. P.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-01-01

Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell-lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a-Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two "control plates" are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (gladwater) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

Design and Modelling of a Microfluidic Electro-Lysis Device with Controlling Plates

NASA Astrophysics Data System (ADS)

Jenkins, A.; Chen, C. P.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-04-01

Many Lab-on-Chip applications require sample pre-treatment systems. Using electric fields to perform cell lysis in bio-MEMS systems has provided a powerful tool which can be integrated into Lab-on-a- Chip platforms. The major design considerations for electro-lysis devices include optimal geometry and placement of micro-electrodes, cell concentration, flow rates, optimal electric field (e.g. pulsed DC vs. AC), etc. To avoid electrolysis of the flowing solution at the exposed electrode surfaces, magnitudes and the applied voltages and duration of the DC pulse, or the AC frequency of the AC, have to be optimized for a given configuration. Using simulation tools for calculation of electric fields has proved very useful, for exploring alternative configurations and operating conditions for achieving electro cell-lysis. To alleviate the problem associated with low electric fields within the microfluidics channel and the high voltage demand on the contact electrode strips, two ''control plates'' are added to the microfluidics configuration. The principle of placing the two controlling plate-electrodes is based on the electric fields generated by a combined insulator/dielectric (glass/water) media. Surface charges are established at the insulator/dielectric interface. This paper discusses the effects of this interface charge on the modification of the electric field of the flowing liquid/cell solution.

5.8kV SiC PiN Diode for Switching of High-Efficiency Inductive Pulsed Plasma Thruster Circuits

NASA Technical Reports Server (NTRS)

Toftul, Alexandra; Polzin, Kurt A.; Hudgins, Jerry L.

2014-01-01

Inductive Pulsed Plasma Thruster (IPPT) pulse circuits, such as those needed to operate the Pulsed Inductive Thruster (PIT), are required to quickly switch capacitor banks operating at a period of µs while conducting current at levels on the order of at least 10 kA. [1,2] For all iterations of the PIT to date, spark gaps have been used to discharge the capacitor bank through an inductive coil. Recent availability of fast, high-power solid state switching devices makes it possible to consider the use of semiconductor switches in modern IPPTs. In addition, novel pre-ionization schemes have led to a reduction in discharge energy per pulse for electric thrusters of this type, relaxing the switching requirements for these thrusters. [3,4] Solid state switches offer the advantage of greater controllability and reliability, as well as decreased drive circuit dimensions and mass relative to spark gap switches. The use of solid state devices such as Integrated Gate Bipolar Transistors (IGBTs), Gate Turn-off Thyristors (GTOs) and Silicon-Controlled Rectifiers (SCRs) often involves the use of power diodes. These semiconductor devices may be connected antiparallel to the switch for protection from reverse current, or used to reduce power loss in a circuit by clamping off current ringing. In each case, higher circuit efficiency may be achieved by using a diode that is able to transition, or 'switch,' from the forward conducting state ('on' state) to the reverse blocking state ('off' state) in the shortest amount of time, thereby minimizing current ringing and switching losses. Silicon Carbide (SiC) PiN diodes offer significant advantages to conventional fast-switching Silicon (Si) diodes for high power and fast switching applications. A wider band gap results in a breakdown voltage 10 times that of Si, so that a SiC device may have a thinner drift region for a given blocking voltage. [5] This leads to smaller, lighter devices for high voltage applications, as well as reduced forward conduction losses, faster reverse recovery time (faster turn-off), and lower-magnitude reverse recovery current. In addition, SiC devices have lower leakage current as compared to their Si counterparts, and a high thermal conductivity, potentially allowing the former to operate at higher temperatures with a smaller, lighter heatsink (or no heatsink at all).

Negative DC corona discharge current characteristics in a flowing two-phase (air + suspended smoke particles) fluid

NASA Astrophysics Data System (ADS)

Berendt, Artur; Domaszka, Magdalena; Mizeraczyk, Jerzy

2017-04-01

The electrical characteristics of a steady-state negative DC corona discharge in a two-phase fluid (air with suspended cigarette smoke particles) flowing along a chamber with a needle-to-plate electrode arrangement were experimentally investigated. The two-phase flow was transverse in respect to the needle-to-plate axis. The velocity of the transverse two-phase flow was limited to 0.8 m/s, typical of the electrostatic precipitators. We found that three discharge current modes of the negative corona exist in the two-phase (air + smoke particles) fluid: the Trichel pulses mode, the "Trichel pulses superimposed on DC component" mode and the DC component mode, similarly as in the corona discharge in air (a single-phase fluid). The shape of Trichel pulses in the air + suspended particles fluid is similar to that in air. However, the Trichel pulse amplitudes are higher than those in "pure" air while their repetition frequency is lower. As a net consequence of that the averaged corona discharge current in the two-phase fluid is lower than in "pure" air. It was also found that the average discharge current decreases with increasing suspended particle concentration. The calculations showed that the dependence of the average negative corona current (which is a macroscopic corona discharge parameter) on the particle concentration can be explained by the particle-concentration dependencies of the electric charge of Trichel pulse and the repetition frequency of Trichel pulses, both giving a microscopic insight into the electrical phenomena in the negative corona discharge. Our investigations showed also that the average corona discharge current in the two-phase fluid is almost unaffected by the transverse fluid flow up to a velocity of 0.8 m/s. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

An approximate theoretical treatment of ion transfer processes at asymmetric microscopic and nanoscopic liquid-liquid interfaces: Single and double potential pulse techniques

NASA Astrophysics Data System (ADS)

Molina, A.; Laborda, E.; Compton, R. G.

2014-03-01

Simple theory for the electrochemical study of reversible ion transfer processes at micro- and nano-liquid|liquid interfaces supported on a capillary is presented. Closed-form expressions are obtained for the response in normal pulse and differential double pulse voltammetries, which describe adequately the particular behaviour of these systems due to the ‘asymmetric’ ion diffusion inside and outside the capillary. The use of different potential pulse techniques for the determination of the formal potential and diffusion coefficients of the ion is examined. For this, very simple analytical expressions are presented for the half-wave potential in NPV and the peak potential in DDPV.

Noncontact Determination of Antisymmetric Plate Wave Velocity in Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Kautz, Harold E.

1998-01-01

High-temperature materials are of increasing importance in the development of more efficient engines and components for the aeronautics industry. In particular, ceramic matrix composite (CMC) and metal matrix composite (MMC) structures are under active development for these applications. The acousto-ultrasonic (AU) method has been shown to be useful for assessing mechanical properties in composite structures. In particular, plate wave analysis can characterize composites in terms of their stiffness moduli. It is desirable to monitor changes in mechanical properties that occur during thermomechanical testing and to monitor the health of components whose geometry or position make them hard to reach with conventional ultrasonic probes. In such applications, it would be useful to apply AU without coupling directly to the test surface. For a number of years, lasers have been under investigation as remote ultrasonic input sources and ultrasound detectors. The use of an ultrasonic transducer coupled through an air gap has also been under study. So far at the NASA Lewis Research Center, we have been more successful in using lasers as ultrasonic sources than as output devices. On the other hand, we have been more successful in using an air-coupled piezoelectric transducer as an output device than as an input device. For this reason, we studied the laser in/air-coupled-transducer out combination-using a pulsed NdYAG laser as the ultrasonic source and an air-coupled-transducer as the detector. The present work is focused on one of the AU parameters of interest, the ultrasonic velocity of the antisymmetric plate-wave mode. This easily identified antisymmetric pulse can be used to determine shear and flexure modulus. It was chosen for this initial work because the pulse arrival times are likely to be the most precise. The following schematic illustrates our experimental arrangement for using laser in/air-transducer out on SiC/SiC composite tensile specimens. The NdYAG pulse was directed downward by a 90 infrared prism to the top of the specimen, but at the edge of one end. An energy sensor measured a single pulse at 13 millijoules (mJ) before it passed through the prism, which attenuated 15 percent of its energy. It also provided an output trigger for the waveform time-delay synthesizer.

Search for Nuclear Excitation by Electronic Transition in U-235

NASA Astrophysics Data System (ADS)

Chodash, P. A.; Norman, E. B.; Burke, J. T.; Wilks, S. C.; Casperson, R. J.; Swanberg, E. L.; Wakeling, M. A.; Cordeiro, T. J.

2013-10-01

Nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that is predicted to occur in numerous isotopes, including U-235. When a nuclear transition matches the energy and the multipolarity of an electronic transition, there is a possibility that NEET will occur. If NEET were to occur in U-235, the nucleus would be excited to its 1/2 + isomeric state that subsequently decays by internal conversion with a decay energy of 77 eV and a half-life of 26 minutes. Theory predicts that NEET can occur in partially ionized uranium plasma with a charge state of 23 +. A pulsed Nd:YAG laser operating at 1064 nm with a pulse energy of 780 mJ and a pulse width of 9 ns was used to generate the uranium plasma. The plasma was collected on a plate and the internal conversion electrons were focused onto a microchannel plate detector by a series of electrostatic lenses. Depleted uranium and highly enriched uranium samples were used for the experiment. Preliminary results will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. This work was further supported by the U.S. DHS, UC Berkeley, and the NNIS Fellowship.

Production of field-reversed mirror plasma with a coaxial plasma gun

DOEpatents

Hartman, Charles W.; Shearer, James W.

1982-01-01

The use of a coaxial plasma gun to produce a plasma ring which is directed into a magnetic field so as to form a field-reversed plasma confined in a magnetic mirror. Plasma thus produced may be used as a target for subsequent neutral beam injection or other similarly produced and projected plasma rings or for direct fusion energy release in a pulsed mode.

Production of field-reversed mirror plasma with a coaxial plasma gun

DOEpatents

Hartman, C.W.; Shearer, J.W.

The use of a coaxial plasma gun to produce a plasma ring which is directed into a magnetic field so as to form a field-reversed plasma confined in a magnetic mirror. Plasma thus produced may be used as a target for subsequent neutral beam injection or other similarly produced and projected plasma rings or for direct fusion energy release in a pulsed mode.

13. 'WAITING AT THE DRAWBRIDGE.' THE COAL SCHOONER LUCY MAY ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

13. 'WAITING AT THE DRAWBRIDGE.' THE COAL SCHOONER LUCY MAY WAITING AT THE DRAW, JUNE 19, 1896. Photocopy of photograph (original glass plate negative #T89 in the collection of the Annisquam Historical Society, Annisquam, Massachusetts). Photographer: Martha Harvey (1862-1949). (The handwritten legend along the top edge of the photograph is scratched in the emulsion of the original glass plate negative. Consequently it reads in reverse when printed.) - Annisquam Bridge, Spanning Lobster Cove between Washington & River Streets, Gloucester, Essex County, MA

Assessing earthquake hazards with fault trench and LiDAR maps in the Puget Lowland, Washington, USA (Invited)

NASA Astrophysics Data System (ADS)

Nelson, A. R.; Bradley, L.; Personius, S. F.; Johnson, S. Y.

2010-12-01

Deciphering the earthquake histories of faults over the past few thousands of years in tectonically complex forearc regions relies on detailed site-specific as well as regional geologic maps. Here we present examples of site-specific USGS maps used to reconstruct earthquake histories for faults in the Puget Lowland. Near-surface faults and folds in the Puget Lowland accommodate 4-7 mm/yr of north-south shortening resulting from northward migration of forearc blocks along the Cascadia convergent margin. The shortening has produced east-trending uplifts, basins, and associated reverse faults that traverse urban areas. Near the eastern and northern flanks of the Olympic Mountains, complex interactions between north-south shortening and mountain uplift are reflected by normal, oblique-slip, and reverse surface faults. Holocene oblique-slip movement has also been mapped on Whidbey Island and on faults in the foothills of the Cascade Mountains in the northeastern lowland. The close proximity of lowland faults to urban areas may pose a greater earthquake hazard there than do much longer but more distant plate-boundary faults. LiDAR imagery of the densely forested lowland flown over the past 12 years revealed many previously unknown 0.5-m to 6-m-high scarps showing Holocene movement on upper-plate faults. This imagery uses two-way traveltimes of laser light pulses to detect as little as 0.2 m of relative relief on the forest floor. The returns of laser pulses with the longest travel times yield digital elevation models of the ground surface, which we vertically exaggerate and digitally shade from multiple directions at variable transparencies to enhance identification of scarps. Our maps include imagery at scales of 1:40,000 to 1:2500 with contour spacings of 100 m to 0.5 m. Maps of the vertical walls of fault-scarp trenches show complex stratigraphies and structural relations used to decipher the histories of large surface-rupturing earthquakes. These logs (field mapping at 1:8 to 1:20 scales) of 25 trenches are included in five published (and one in preparation) maps along with lithologic descriptions of stratigraphic units and tables of 14C, structural, and stratigraphic data. Maps include soil profile data, topographic profiles across scarps, structural orientation data, or photographs of trench sites or trench walls. Stratigraphy and 14C ages suggest that earthquake recurrence varies from less than a century to many thousands of years. Interpretation and synthesis of such data are reserved for journal papers, which commonly cannot accommodate the detailed, large-format information shown on the maps. Many thanks to Brian Sherrod, Harvey Kelsey, Jason Buck, Ray Wells, Liz Schermer, Rob Witter, Rich Koehler, Rich Briggs, Robert Bogar, Gary Henley, Dave Harding, Koji Okumura, Silvio Pezzopane, Bob Bucknam, Zeb Maharrey, Bill Laprade, Ralph Haugerud, Lee Liberty, Michael Polenz, Eliza Nemser, Trenton Cladouhos, and many others for days to many weeks of effort in our trenches over the past 12 years.

Femtosecond laser based enucleation of porcine oocytes for somatic cell nuclear transfer

NASA Astrophysics Data System (ADS)

Kütemeyer, K.; Lucas-Hahn, A.; Petersen, B.; Hassel, P.; Lemme, E.; Niemann, H.; Heisterkamp, A.

2009-07-01

Cloning of several mammalian species has been achieved by somatic cell nuclear transfer (SCNT) in recent years. However, this method still results in very low efficiencies around 1% which originate from suboptimal culture conditions and highly invasive techniques for oocyte enucleation and injection of the donor cell using micromanipulators. In this paper, we present a new minimal invasive method for oocyte imaging and enucleation based on the application of femtosecond (fs) laser pulses. After imaging of the oocyte with multiphoton microscopy, ultrashort pulses are focused onto the metaphase plate of MII-oocytes in order to ablate the DNA molecules. We show that fs laser based enucleation of porcine oocytes completely inhibits the first mitotic cleavage after parthenogenetic activation while maintaining intact oocyte morphology in most cases. In contrast, control groups without previous irradiation of the metaphase plate are able to develop to the blastocyst stage. Further experiments have to clarify the suitability of fs laser based enucleated oocytes for SCNT.

Arc plasma generator of atomic driver for steady-state negative ion source.

PubMed

Ivanov, A A; Belchenko, Yu I; Davydenko, V I; Ivanov, I A; Kolmogorov, V V; Listopad, A A; Mishagin, V V; Putvinsky, S V; Shulzhenko, G I; Smirnov, A

2014-02-01

The paper reviews the results of development of steady-state arc-discharge plasma generator with directly heated LaB6 cathode. This arc-discharge plasma generator produces a plasma jet which is to be converted into an atomic one after recombination on a metallic plate. The plate is electrically biased relative to the plasma in order to control the atom energies. Such an intensive jet of hydrogen atoms can be used in negative ion sources for effective production of negative ions on a cesiated surface of plasma grid. All elements of the plasma generator have an augmented water cooling to operate in long pulse mode or in steady state. The thermo-mechanical stresses and deformations of the most critical elements of the plasma generator were determined by simulations. Magnetic field inside the discharge chamber was optimized to reduce the local power loads. The first tests of the steady-state arc plasma generator prototype have performed in long-pulse mode.

The influence of process parameters on porosity formation in hybrid LASER-GMA welding of AA6082 aluminum alloy

NASA Astrophysics Data System (ADS)

Ascari, Alessandro; Fortunato, Alessandro; Orazi, Leonardo; Campana, Giampaolo

2012-07-01

This paper deals with an experimental campaign carried out on AA6082 8 mm thick plates in order to investigate the role of process parameters on porosity formation in hybrid LASER-GMA welding. Bead on plate weldments were obtained on the above mentioned aluminum alloy considering the variation of the following process parameters: GMAW current (120 and 180 A for short-arc mode, 90 and 130 A for pulsed-arc mode), arc transfer mode (short-arc and pulsed-arc) and mutual distance between arc and LASER sources (0, 3 and 6 mm). Porosities occurring in the fused zone were observed by means of X-ray inspection and measured exploiting an image analysis software. In order to understand the possible correlation between process parameters and porosity formation an analysis of variance statistical approach was exploited. The obtained results pointed out that GMAW current is significant on porosity formation, while the distance between the sources do not affect this aspect.

Estimation of current plate motions in Papua New Guinea from Global Positioning System observations

NASA Astrophysics Data System (ADS)

Tregoning, Paul; Lambeck, Kurt; Stolz, Art; Morgan, Peter; McClusky, Simon C.; van der Beek, Peter; McQueen, Herbert; Jackson, Russell J.; Little, Rodney P.; Laing, Alex; Murphy, Brian

1998-06-01

Plate tectonic motions have been estimated in Papua New Guinea from a 20 station network of Global Positioning System sites that has been observed over five campaigns from 1990 to 1996. The present velocities of the sites are consistent with geological models in which the South Bismarck, Woodlark, and Solomon Sea Plates form the principal tectonic elements between the Pacific and Australian Plates in this region. Active spreading is observed on the Woodlark Basin Spreading Centre but at a rate that is about half the rate determined from magnetic reversals. The other major motions observed are subduction on the New Britain Trench, seafloor spreading across the Bismarck Sea Seismic Lineation, convergence across the Ramu-Markham Fault and left-lateral strike slip across the Papuan Peninsula. These motions are consistent with a 8.2° Myr-1 clockwise rotation of the South Bismarck Plate about a pole in the Huon Gulf and a rotation of the Woodlark Plate away from the Australian Plate. Second order deformation may also be occurring; in particular, Manus Island and northern New Ireland may be moving northward relative to the Pacific Plate at ˜5-8 mm yr-1 (significant at the 95% but not at the 99% confidence level) which may suggest the existence of a North Bismarck Plate.

Visualization of vortex flow field around a flat plate with noncircular hole

NASA Astrophysics Data System (ADS)

Manigandan, S.; Gunasekar, P.; Sruthisree, N.; Aich, Kaushali; Sathya, K.; Selvan, Alice; Nithya, S.

2018-02-01

In this paper we study the numerical three dimensional simulation of laminar incompressible viscous flow over a flat plate with circular and noncircular hole. The hole is located at the center of the plate. The aim of this paper is to visualize the steady and unsteady vortex dynamics using immersed boundary method. This method takes three variables, viz. velocity, vortices and the pressure to solve the flow field over a specimen. The plate considered is of 0.01 m length and the air is used as the flow medium and hole is made of same area. The analysis are done both circular hole plate and non-circular hole to examine the difference in the force and wake at the trailing part of the flat plate. In this study we measure the magnitude of vortices behind a flat plate and we also study the physical backdrop of how vortex strength is depend on the inner profile of the body. From the results it is evident that the reverse flow is stronger in non circular profile however the strength of vortex is higher in circular holed plate. It’s also found that velocity is inversely proportional to strength of vortices in flat plate with noncircular hole.

Survey of simulation methods for modeling pulsed sieve-plate extraction columns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burkhart, L.

1979-03-01

The report first considers briefly the use of liquid-liquid extraction in nuclear fuel reprocessing and then describes the operation of the pulse column. Currently available simulation models of the column are reviewed, and followed by an analysis of the information presently available from which the necessary parameters can be obtained for use in a model of the column. Finally, overall conclusions are given regarding the information needed to develop an accurate model of the column for materials accountability in fuel reprocessing plants. 156 references.

OH radicals generated by DC corona discharge for improving the pulsed discharge desulfuration efficiency.

PubMed

Li, Jie; Li, Guo-feng; Wu, Yan; Wang, Ning-hui; Huang, Qiu-nan

2004-01-01

Positive DC corona discharge is formed with needle-plate electrode configuration, in which the water vapor is ejected though the needle points. The purpose is to increase the numbers of the water-based radicals, ionize the water molecule and improve the desulfuration efficiency of pulsed corona reactor. The water ions were determined by four stages molecular beam mass spectrometer and diagnose the water-based radicals by emission spectrograph. A conclusion on formation of ions and radicals with DC corona discharges can be drawn.

Marble Ageing Characterization by Acoustic Waves

NASA Astrophysics Data System (ADS)

Boudani, Mohamed El; Wilkie-Chancellier, Nicolas; Martinez, Loïc; Hébert, Ronan; Rolland, Olivier; Forst, Sébastien; Vergès-Belmin, Véronique; Serfaty, Stéphane

In cultural heritage, statue marble characterization by acoustic waves is a well-known non-destructive method. Such investigations through the statues by time of flight method (TOF) point out sound speeds decrease with ageing. However for outdoor stored statues as the ones in the gardens of Chateau de Versailles, ageing affects mainly the surface of the Carrara marble. The present paper proposes an experimental study of the marble acoustic properties variations during accelerated laboratory ageing. The surface degradation of the marble is reproduced in laboratory for 29 mm thick marble samples by using heating/cooling thermal cycles on one face of a marble plate. Acoustic waves are generated by 1 MHz central frequency contact transducers excited by a voltage pulse placed on both sides of the plate. During the ageing and by using ad hoc transducers, the marble samples are characterized in transmission, along their volume by shear, compressional TOF measurements and along their surface by Rayleigh waves measurements. For Rayleigh waves, both TOF by transducers and laser vibrometry methods are used to detect the Rayleigh wave. The transmission measurements point out a deep decrease of the waves speeds in conjunction with a dramatic decrease of the maximum frequency transmitted. The marble acts as a low pass filter whose characteristic frequency cut decreases with ageing. This pattern occurs also for the Rayleigh wave surface measurements. The speed change in conjunction with the bandwidth translation is shown to be correlated to the material de-structuration during ageing. With a similar behavior but reversed in time, the same king of phenomena have been observed trough sol-gel materials during their structuration from liquid to solid state (Martinez, L. et all (2004). "Chirp-Z analysis for sol-gel transition monitoring". Ultrasonics, 42(1), 507-510.). A model is proposed to interpret the acoustical measurements

Understanding of self-terminating pulse generation using silicon controlled rectifier and RC load

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chris, E-mail: chrischang81@gmail.com; Karunasiri, Gamani, E-mail: karunasiri@nps.edu; Alves, Fabio, E-mail: falves@alionscience.com

2016-01-15

Recently a silicon controlled rectifier (SCR)-based circuit that generates self-terminating voltage pulses was employed for the detection of light and ionizing radiation in pulse mode. The circuit consisted of a SCR connected in series with a RC load and DC bias. In this paper, we report the investigation of the physics underlying the pulsing mechanism of the SCR-based. It was found that during the switching of SCR, the voltage across the capacitor increased beyond that of the DC bias, thus generating a reverse current in the circuit, which helped to turn the SCR off. The pulsing was found to bemore » sustainable only for a specific range of RC values depending on the SCR’s intrinsic turn-on/off times. The findings of this work will help to design optimum SCR based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.« less

Design of a pulsed-mode fluidic pump using a venturi-like reverse flow diverter. [With no packing glands, mechanical seals or moving parts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, G.V.; Lewis, B.E.

1987-02-01

This report presents a design procedure for pulsed-mode, venturi-like reverse flow diverter (RFD) pumping systems. Design techniques are presented for systems in which the output line area is allowed to vary proportionally with the throat area of the RFD as well as situations in which the output line area is held constant. The results show that for cases in which the output line area is allowed to vary, an optimum RFD throat area exists for a given input pressure. For situations in which the output line area is held constant, the average output flow decreases in almost a linear fashionmore » with increasing RFD throat area. 6 refs., 8 figs.« less

Reversed Cherenkov emission of terahertz waves from an ultrashort laser pulse in a sandwich structure with nonlinear core and left-handed cladding.

PubMed

Bakunov, M I; Mikhaylovskiy, R V; Bodrov, S B; Luk'yanchuk, B S

2010-01-18

We propose a scheme for an experimental verification of the reversed Cherenkov effect in left-handed media. The scheme uses optical-to-terahertz conversion in a planar sandwichlike structure that consists of a nonlinear core cladded with a material that exhibits left-handedness at terahertz frequencies. The focused into a line femtosecond laser pulse propagates in the core and emits Cherenkov wedge of terahertz waves in the cladding. We developed a theory that describes terahertz generation in such a structure and calculated spatial distribution of the generated terahertz field, its energy spectrum, and optical-to-terahertz conversion efficiency. The proposed structure can be a useful tool for characterization of the electromagnetic properties of metamaterials in the terahertz frequency range.

Suppressing relaxation in superconducting qubits by quasiparticle pumping.

PubMed

Gustavsson, Simon; Yan, Fei; Catelani, Gianluigi; Bylander, Jonas; Kamal, Archana; Birenbaum, Jeffrey; Hover, David; Rosenberg, Danna; Samach, Gabriel; Sears, Adam P; Weber, Steven J; Yoder, Jonilyn L; Clarke, John; Kerman, Andrew J; Yoshihara, Fumiki; Nakamura, Yasunobu; Orlando, Terry P; Oliver, William D

2016-12-23

Dynamical error suppression techniques are commonly used to improve coherence in quantum systems. They reduce dephasing errors by applying control pulses designed to reverse erroneous coherent evolution driven by environmental noise. However, such methods cannot correct for irreversible processes such as energy relaxation. We investigate a complementary, stochastic approach to reducing errors: Instead of deterministically reversing the unwanted qubit evolution, we use control pulses to shape the noise environment dynamically. In the context of superconducting qubits, we implement a pumping sequence to reduce the number of unpaired electrons (quasiparticles) in close proximity to the device. A 70% reduction in the quasiparticle density results in a threefold enhancement in qubit relaxation times and a comparable reduction in coherence variability. Copyright © 2016, American Association for the Advancement of Science.

Different centre of pressure patterns within the golf stroke II: group-based analysis.

PubMed

Ball, K A; Best, R J

2007-05-01

Although the golf coaching literature stresses the importance of weight transfer during the swing, research has been conflicting or lacking statistical support. A potential problem with previous studies is that no attempt was made to account for different movement strategies in the golf swing. This study evaluated the relationship between centre of pressure measures and club head velocity within two previously identified swing styles, the "Front Foot" and "Reverse" styles. Thirty-nine Front Foot golfers and 19 Reverse golfers performed swings with a driver while standing on two force plates. From the force plate data, centre of pressure displacement, velocity, range, and timing parameters were calculated. Correlation and regression analysis indicated that a larger range of centre of pressure and a more rapid centre of pressure movement in the downswing was associated with a larger club head velocity at ball contact for the Front Foot group. For the Reverse golfers, positioning the centre of pressure further from the back foot at late backswing and a more rapid centre of pressure transfer towards the back foot at ball contact was associated with a larger club head velocity at ball contact. This study has highlighted the importance of identifying different movement strategies before evaluating performance measures, as different parameters were found to be important for the Front Foot and Reverse styles.

Pulse Phase Dependence of Low Energy Emission Lines in an X-ray pulsar 4U 1626-67 during its spin-up and spin-down phase

NASA Astrophysics Data System (ADS)

Beri, Aru; Paul, Biswajit; Dewangan, Gulab Chand

2016-07-01

We will present the results obtained from the new observation of an ultra-compact X-ray binary pulsar 4U 1626-67, carried out with the XMM-Newton observatory. 4U 1626-67, a unique accretion powered pulsar underwent two torque reversals since its discovery in 1977. Pulse phase resolved spectroscopy of this source performed using the data from the XMM-Newton observatory during its spin-down phase revealed the dependence of the emission lines on the pulse phase. O VII emission line at 0.569 keV showed the maximum variation by factor of 4. These variations were interpreted due to warps in the accretion disk (Beri et al. 2015). Radiation pressure induced warping is also believed to be the cause for spin-down. In light of this possible explanation for spin-down torque reversal we expect different line variability during the spin-up phase. We will discuss the implications of the results obtained after performing pulse phase resolved spectroscopy using data from the EPIC-pn during the current spin-up phase. Detailed study of the prominent Neon and Oxygen line complexes with the high resolution Reflection Grating Spectrometer (RGS) on-board XMM-Newton will also be presented.

Highly Efficient Vector-Inversion Pulse Generators

NASA Technical Reports Server (NTRS)

Rose, Franklin

2004-01-01

Improved transmission-line pulse generators of the vector-inversion type are being developed as lightweight sources of pulsed high voltage for diverse applications, including spacecraft thrusters, portable x-ray imaging systems, impulse radar systems, and corona-discharge systems for sterilizing gases. In this development, more than the customary attention is paid to principles of operation and details of construction so as to the maximize the efficiency of the pulse-generation process while minimizing the sizes of components. An important element of this approach is segmenting a pulse generator in such a manner that the electric field in each segment is always below the threshold for electrical breakdown. One design of particular interest, a complete description of which was not available at the time of writing this article, involves two parallel-plate transmission lines that are wound on a mandrel, share a common conductor, and are switched in such a manner that the pulse generator is divided into a "fast" and a "slow" section. A major innovation in this design is the addition of ferrite to the "slow" section to reduce the size of the mandrel needed for a given efficiency.

Monitoring of Pre-Load on Rock Bolt Using Piezoceramic-Transducer Enabled Time Reversal Method.

PubMed

Huo, Linsheng; Wang, Bo; Chen, Dongdong; Song, Gangbing

2017-10-27

Rock bolts ensure structural stability for tunnels and many other underground structures. The pre-load on a rock bolt plays an important role in the structural reinforcement and it is vital to monitor the pre-load status of rock bolts. In this paper, a rock bolt pre-load monitoring method based on the piezoceramic enabled time reversal method is proposed. A lead zirconate titanate (PZT) patch transducer, which works as an actuator to generate stress waves, is bonded onto the anchor plate of the rock bolt. A smart washer, which is fabricated by sandwiching a PZT patch between two metal rings, is installed between the hex nut and the anchor plate along the rock bolt. The smart washer functions as a sensor to detect the stress wave. With the increase of the pre-load values on the rock bolt, the effective contact surface area between the smart washer and the anchor plate, benefiting the stress wave propagation crossing the contact surface. With the help of time reversal technique, experimental results reveal that the magnitude of focused signal clearly increases with the increase of the pre-load on a rock bolt before the saturation which happens beyond a relatively high value of the pre-load. The proposed method provides an innovative and real time means to monitor the pre-load level of a rock bolt. By employing this method, the pre-load degradation process on a rock bolt can be clearly monitored. Please note that, currently, the proposed method applies to only new rock bolts, on which it is possible to install the PZT smart washer.

Properties of the welded joints of manganese steel made by low-frequency pulsed arc welding

NASA Astrophysics Data System (ADS)

Saraev, Yu. N.; Bezborodov, V. P.; Gladovskii, S. V.; Golikov, N. I.

2017-04-01

The structure, the mechanical properties, the impact toughness, and the fracture mechanisms of the welded joints made of steel 09G2S plates by direct current welding and pulsed arc welding with a modulated arc current in the frequency range 0.25-5.0 Hz are studied. The application of low-frequency pulsed arc welding allowed us to form welded joints with a fine-grained structure in the weld metal and the heat-affected zone and to achieve a higher impact toughness and a longer cyclic fatigue life as compared to the welded joints fabricated by direct current welding. The achieved effect manifests itself over the entire testing range from 20 to-60°C.

Q-switched Nd:YAG optical vortex lasers.

PubMed

Kim, D J; Kim, J W; Clarkson, W A

2013-12-02

Q-switched operation of a high-quality Nd:YAG optical vortex laser with the first order Laguerre-Gaussian mode and well-determined helical wavefronts using a fiber-based pump beam conditioning scheme is reported. A simple two-mirror resonator incorporating an acousto-optic Q-switch was employed, along with an etalon and a Brewster plate to enforce the particular helicity of the output. The laser yielded Q-switched pulses with ~250 μJ pulse energy and ~33 ns pulse duration (FWHM) at a 0.1 kHz repetition rate for 5.1 W of absorbed pump power. The handedness of the helical wavefronts was preserved regardless of the repetition rates. The prospects of further power scaling and improved laser performance are discussed.

Core-pumped mode-locked ytterbium-doped fiber laser operating around 980 nm

NASA Astrophysics Data System (ADS)

Zhou, Yue; Dai, Yitang; Li, Jianqiang; Yin, Feifei; Dai, Jian; Zhang, Tian; Xu, Kun

2018-07-01

In this letter, we first demonstrate a core-pumped passively mode-locked all-normal-dispersion ytterbium-doped fiber oscillator based on nonlinear polarization evolution operating around 980 nm. The dissipative soliton fiber laser pulse can be compressed down to 250 fs with 1 nJ pulse energy, and the slope efficiency of the oscillator can be as high as 19%. To improve the dissipative soliton laser output spectrum smoothness, we replace the birefringent plate based intracavity filter with a diffraction-grating based filter. The output pulse duration can then be further compressed down to 180 fs with improved spectral-smoothness. These schemes have potential applications in seeding cryogenic Yb:YLF amplifiers and underwater exploration of marine resources.

Algae inhibition experiment and load characteristics of the algae solution

NASA Astrophysics Data System (ADS)

Xiong, L.; Gao, J. X.; Zhang, Y. X.; Yang, Z. K.; Zhang, D. Q.; He, W.

2016-08-01

It is necessary to inhibit microbial growth in an industrial cooling water system. This paper has developed a Monopolar/Bipolar polarity high voltage pulser with load adaptability for an algal experimental study. The load characteristics of the Chlorella pyrenoidosa solution were examined, and it was found that the solution load is resistive. The resistance is related to the plate area, concentration, and temperature of the solution. Furthermore, the pulser's treatment actually inhibits the algae cell growth. This article also explores the influence of various parameters of electric pulses on the algal effect. After the experiment, the optimum pulse parameters were determined to be an electric field intensity of 750 V/cm, a pulse width per second of 120μs, and monopolar polarity.

Estimation of Tegaserod Maleate by Differential Pulse Polarography

PubMed Central

Rajput, S. J.; Raj, H. A.

2009-01-01

A highly sensitive differential pulse polarographic method has been developed for the estimation of tegaserod maleate after treating it with hydrogen peroxide solution. The oxidation of tegaserod maleate is a reversible process as the oxidized product could be reduced at hanging mercury drop electrode in a quantitative manner using differential pulse polarography mode. The limit of quantification was 0.1ng/ml. The voltametric peak was obtained at -1.05 volts in presence of 0.1M potassium chloride as supporting electrolyte. The technique could be used successfully to analyze tegaserod maleate in its tablet formulation. PMID:20177456

Moment tensor solutions for the Iberian-Maghreb region during the IberArray deployment (2009-2013)

NASA Astrophysics Data System (ADS)

Martín, R.; Stich, D.; Morales, J.; Mancilla, F.

2015-11-01

We perform regional moment tensor inversion for 84 earthquakes that occurred in the Iberian-Maghreb region during the second and third leg of IberArray deployment (2009-2013). During this period around 300 seismic broadband stations were operating in the area, reducing the interstation spacing to ~ 50 km over extended areas. We use the established processing sequence of the IAG moment tensor catalogue, increasing to 309 solutions with this update. New moment tensor solutions present magnitudes ranging from Mw 3.2 to 6.3 and source depths from 2 to 620 km. Most solutions correspond to Northern Algeria, where a compressive deformation pattern is consolidated. The Betic-Rif sector shows a progression of faulting styles from mainly shear faulting in the east via predominantly extension in the central sector to reverse and strike-slip faulting in the west. At the SW Iberia margin, the predominance of strike-slip and reverse faulting agrees with the expected transpressive character of the Eurasian-Nubia plate boundary. New strike-slip and oblique reverse solutions in the Trans-Alboran Shear Zone reflect its left-lateral regime. The most significant improvement corresponds to the Atlas Mountains and the surroundings of the Gibraltar Arc with scarce previous solutions. Reverse and strike-slip faulting solutions in the Atlas System display the accommodation of plate convergence by shortening in the belt. At the Gibraltar Arc, several new solutions were obtained at lower crustal and subcrustal depths. These mechanisms show substantial heterogeneity, covering the full range of faulting styles with highly variable orientations of principal stress axes, including opposite strike slip faulting solutions at short distance. The observations are not straightforward to explain by a simple geodynamic scenario and suggest the interplay of different processes, among them plate convergence in old oceanic lithospheric with large brittle thickness at the SW Iberia margin, as well as delamination of thickened continental lithosphere beneath the Betic-Rif arc.

Biomechanical strength of the Peri-Loc proximal tibial plate: a comparison of all-locked versus hybrid locked/nonlocked screw configurations.

PubMed

Estes, Chris; Rhee, Peter; Shrader, M Wade; Csavina, Kristine; Jacofsky, Marc C; Jacofsky, David J

2008-01-01

The purpose of this study was to compare the biomechanical properties of a contoured locking plate instrumented with either an all-locked or hybrid locked/nonlocked screw construct in a proximal metaphyseal fracture of the tibia (AO 41-A3.2). A standardized proximal metaphyseal wedge osteotomy (AO 41-A3.2) was created in five pairs of cadaveric tibia. Each pair was randomly instrumented with either an all-locked or combination locked/nonlocked screw construct using a locked contoured periarticular plate (Peri-Loc periarticular locked plating system, Smith & Nephew, Memphis, TN). Vertical subsidence (irreversible deformation) and deflection (reversible deformation) in each pair were analyzed and compared. Load to failure, defined by complete fracture gap closure, was also determined. There was no statistically significant difference in vertical subsidence (P = 0.19) or deflection (P = 0.19) of the proximal tibia between the all-locked and combination locked/nonlocked screw construct with increasing levels of cyclical axial load from 200 to 1200 N. Failure occurred at a mean value of 2160 N in the locked group and 1760 N in the hybrid group (P = 0.19); the failure mode was plate bending in all specimens. The results indicate that the use of compression screws with locked screws in this particular construct allows a similar amount of irreversible and reversible deformation in response to an axial load when compared to an all-locked screw construct. This suggests that there is no statistically significant difference in the stability in fixation between the two methods, allowing the surgeon the freedom to choose the appropriate screw combination unique to each fracture.

Microcomponents manufacturing for precise devices by copper vapor laser

NASA Astrophysics Data System (ADS)

Gorny, Sergey; Nikonchuk, Michail O.; Polyakov, Igor V.

2001-06-01

This paper presents investigation results of drilling of metal microcomponents by copper vapor laser. The laser consists of master oscillator - spatial filter - amplifier system, electronics switching with digital control of laser pulse repetition rate and quantity of pulses, x-y stage with computer control system. Mass of metal, removed by one laser pulse, is measured and defined by means of diameter and depth of holes. Interaction of next pulses on drilled material is discussed. The difference between light absorption and metal evaporation processes is considered for drilling and cutting. Efficiency of drilling is estimated by ratio of evaporation heat and used laser energy. Maximum efficiency of steel cutting is calculated with experimental data of drilling. Applications of copper vapor laser for manufacturing is illustrated by such microcomponents as pin guide plate for printers, stents for cardio surgery, encoded disks for security systems and multiple slit masks for spectrophotometers.

Study of Pulsed Columns with the System. Uranyl Nitrate-Nitric Acid-Water- Tributylphosphate; ETUDE DES COLONNES A PULSATIONS A L'AIDE DU SYSTEME NITRATE D'URANYLE-ACIDE NITRIQUEEAU-TRIBUTYLPHOSPHATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durandet, J.; Defives, D.; Choffe, B.

1959-10-31

The performsnce of a pulsed column with perforated plates was studied with the aid of a uranyl nitrate-nitric acid --water --tributyl phosphate system. The extraction of uranium from an aqueous acidic solution by an organic solvent and the extraction of uranium from organic solutions by water were the two cases investigated. The variation of the efficiency and the capacity of the pulsed column was determined as a function of the pulse amplitude and frequency, of the total flow rate, of the diameter of the holes, and of the choice of dispersed phase. The results showed that for a given amplitudemore » and total flow rate the efficiency has a maximum with an increase in frequency. (J.S.R.)« less

Implementation of a SVWP-based laser beam shaping technique for generation of 100-mJ-level picosecond pulses.

PubMed

Adamonis, J; Aleknavičius, A; Michailovas, K; Balickas, S; Petrauskienė, V; Gertus, T; Michailovas, A

2016-10-01

We present implementation of the energy-efficient and flexible laser beam shaping technique in a high-power and high-energy laser amplifier system. The beam shaping is based on a spatially variable wave plate (SVWP) fabricated by femtosecond laser nanostructuring of glass. We reshaped the initially Gaussian beam into a super-Gaussian (SG) of the 12th order with efficiency of about 50%. The 12th order of the SG beam provided the best compromise between large fill factor, low diffraction on the edges of the active media, and moderate intensity distribution modification during free-space propagation. We obtained 150 mJ pulses of 532 nm radiation. High-energy, pulse duration of 85 ps and the nearly flat-top spatial profile of the beam make it ideal for pumping optical parametric chirped pulse amplification systems.

High Mobility Flexible Amorphous IGZO Thin-Film Transistors with a Low Thermal Budget Ultra-Violet Pulsed Light Process.

PubMed

Benwadih, M; Coppard, R; Bonrad, K; Klyszcz, A; Vuillaume, D

2016-12-21

Amorphous, sol-gel processed, indium gallium zinc oxide (IGZO) transistors on plastic substrate with a printable gate dielectric and an electron mobility of 4.5 cm 2 /(V s), as well as a mobility of 7 cm 2 /(V s) on solid substrate (Si/SiO 2 ) are reported. These performances are obtained using a low temperature pulsed light annealing technique. Ultraviolet (UV) pulsed light system is an innovative technique compared to conventional (furnace or hot-plate) annealing process that we successfully implemented on sol-gel IGZO thin film transistors (TFTs) made on plastic substrate. The photonic annealing treatment has been optimized to obtain IGZO TFTs with significant electrical properties. Organic gate dielectric layers deposited on this pulsed UV light annealed films have also been optimized. This technique is very promising for the development of amorphous IGZO TFTs on plastic substrates.

Laser-excited pulses in a crystallized dusty plasma

NASA Astrophysics Data System (ADS)

Nosenko, V.; Nunomura, S.; Goree, J.

2000-10-01

A dusty plasma is an ionized gas containing small particles of solid matter. These particles acquire a large negative electric charge. Polymer microspheres were shaken into a capacitively-coupled parallel-plate rf plasma. The particles were levitated by the electric field in the sheath above the lower electrode. The particles settled in a single horizontal layer, arranged in a hexagonal lattice. They were imaged using a video camera, to record the particle motion. Like any crystal, this so-called ``plasma crystal'' sustains compressional sound waves, which can be launched as a pulse. There are several ways these waves can be excited, including applying a force from the radiation pressure of a laser beam. By chopping an argon laser beam that is directed at the lattice, it is possible to launch a pulsed wave in the lattice. We evaluate the pulse's shape and propagation speed, and test whether it has the properties of a shock.

Rate constant for the H˙ + H2O → ˙OH + H2 reaction at elevated temperatures measured by pulse radiolysis.

PubMed

Muroya, Y; Yamashita, S; Lertnaisat, P; Sanguanmith, S; Meesungnoen, J; Jay-Gerin, J-P; Katsumura, Y

2017-11-22

Maintaining the structural integrity of materials in nuclear power plants is an essential issue associated with safe operation. Hydrogen (H 2 ) addition or injection to coolants is a powerful technique that has been widely applied such that the reducing conditions in the coolant water avoid corrosion and stress corrosion cracking (SCC). Because the radiation-induced reaction of ˙OH + H 2 → H˙ + H 2 O plays a crucial role in these systems, the rate constant has been measured at operation temperatures of the reactors (285-300 °C) by pulse radiolysis, generating sufficient data for analysis. The reverse reaction H˙ + H 2 O → ˙OH + H 2 is negligibly slow at ambient temperature; however, it accelerates considerably quickly at elevated temperatures. Although the reverse reaction reduces the effectiveness of H 2 addition, reliable rate constants have not yet been measured. In this study, the rate constants have been determined in a temperature range of 250-350 °C by pulse radiolysis in an aqueous I - solution.

High-voltage lateral double-implanted MOSFETs implemented on high-purity semi-insulating 4H-SiC substrates with gate field plates

NASA Astrophysics Data System (ADS)

Seok, Ogyun; Kim, Hyoung Woo; Moon, Jeong Hyun; Lee, Hyun-Su; Bahng, Wook

2018-06-01

Lateral double-implanted MOSFETs (LDIMOSFETs) fabricated on on-axis high-purity semi-insulating (HPSI) 4H-SiC substrates with gate field plates have been demonstrated for the enhancement of reverse blocking capability. The effects of gate field plate on LDIMOSFET were analyzed by simulation and experimental methods. The electric field concentration at the gate edge was successfully suppressed by a gate field plate. A high breakdown voltage of 934 V and a figure of merit of 14.6 MW/cm2 were achieved at L FP of 2 µm and L drift of 15 µm, while those of the conventional device without a gate field plate were 744 V and 13.3 MW/cm2, respectively. Also, the fabricated device shows stable blocking characteristics at a high temperature of 250 °C. The drain leakage was increased by only 22% at 250 °C compared with that at room temperature.

Heat transfer and flow friction correlations for perforated plate matrix heat exchangers

NASA Astrophysics Data System (ADS)

Ratna Raju, L.; Kumar, S. Sunil; Chowdhury, K.; Nandi, T. K.

2017-02-01

Perforated plate matrix heat exchangers (MHE) are constructed of high conductivity perforated plates stacked alternately with low conductivity spacers. They are being increasingly used in many cryogenic applications including Claude cycle or Reversed Brayton cycle cryo-refrigerators and liquefiers. Design of high NTU (number of (heat) transfer unit) cryogenic MHEs requires accurate heat transfer coefficient and flow friction factor. Thermo-hydraulic behaviour of perforated plates strongly depends on the geometrical parameters. Existing correlations, however, are mostly expressed as functions of Reynolds number only. This causes, for a given configuration, significant variations in coefficients from one correlation to the other. In this paper we present heat transfer and flow friction correlations as functions of all geometrical and other controlling variables. A FluentTM based numerical model has been developed for heat transfer and pressure drop studies over a stack of alternately arranged perforated plates and spacers. The model is validated with the data from literature. Generalized correlations are obtained through regression analysis over a large number of computed data.

Reconstructing plate-motion changes in the presence of finite-rotations noise.

PubMed

Iaffaldano, Giampiero; Bodin, Thomas; Sambridge, Malcolm

2012-01-01

Understanding lithospheric plate motions is of paramount importance to geodynamicists. Much effort is going into kinematic reconstructions featuring progressively finer temporal resolution. However, the challenge of precisely identifying ocean-floor magnetic lineations, and uncertainties in geomagnetic reversal timescales result in substantial finite-rotations noise. Unless some type of temporal smoothing is applied, the scenario arising at the native temporal resolution is puzzling, as plate motions vary erratically and significantly over short periods (<1 Myr). This undermines our ability to make geodynamic inferences, as the rates at which forces need to be built upon plates to explain these kinematics far exceed the most optimistic estimates. Here we show that the largest kinematic changes reconstructed across the Atlantic, Indian and South Pacific ridges arise from data noise. We overcome this limitation using a trans-dimensional hierarchical Bayesian framework. We find that plate-motion changes occur on timescales no shorter than a few million years, yielding simpler kinematic patterns and more plausible dynamics.

The influence of climatically-driven surface loading variations on continental strain and seismicity

NASA Astrophysics Data System (ADS)

Craig, Tim; Calais, Eric; Fleitout, Luce; Bollinger, Laurent; Scotti, Oona

2016-04-01

In slowly deforming regions of plate interiors, secondary sources of stress and strain can result in transient deformation rates comparable to, or greater than, the background tectonic rates. Highly variable in space and time, these transients have the potential to influence the spatio-temporal distribution of seismicity, interfering with any background tectonic effects to either promote or inhibit the failure of pre-existing faults, and potentially leading to a clustered, or 'pulse-like', seismic history. Here, we investigate the ways in which the large-scale deformation field resulting from climatically-controlled changes in surface ice mass over the Pleistocene and Holocene may have influenced not only the seismicity of glaciated regions, but also the wider seismicity around the ice periphery. We first use a set of geodynamic models to demonstrate that a major pulse of seismic activity occurring in Fennoscandia, coincident with the time of end-glaciation, occurred in a setting where the contemporaneous horizontal strain-rate resulting from the changing ice mass, was extensional - opposite to the reverse sense of coseismic displacement accommodated on these faults. Therefore, faulting did not release extensional elastic strain that was building up at the time of failure, but compressional elastic strain that had accumulated in the lithosphere on timescales longer than the glacial cycle, illustrating the potential for a non-tectonic trigger to tap in to the background tectonic stress-state. We then move on to investigate the more distal influence that changing ice (and ocean) volumes may have had on the evolving strain field across intraplate Europe, how this is reflected in the seismicity across intraplate Europe, and what impact this might have on the paleoseismic record.

The effects of a picosecond pulsed electric field on angiogenesis in the cervical cancer xenograft models.

PubMed

Wu, Limei; Yao, Chenguo; Xiong, Zhengai; Zhang, Ruizhe; Wang, Zhiliang; Wu, Yutong; Qin, Qin; Hua, Yuanyuan

2016-04-01

The application of picosecond pulsed electric field (psPEF) is a new biomedical engineering technique used in cancer therapy. However, its effects on cervical cancer angiogenesis are not clear. Therefore, the aim of the present study is to investigate the effects of psPEF on angiogenesis in cervical cancer xenograft models. Xenograft tumors were created by subcutaneously inoculating nude mice (athymic BALB/c nu/nu mice) with HeLa cells, then were placed closely between tweezer-type plate electrodes and subjected to psPEF with a gradually increased electric field intensity (0kV/cm, 50kV/cm, 60kV/cm, 70kV/cm). The direct effect on tumor tissue was observed by hematoxylin and eosin (H&E) staining and transmission electron microscopy (TEM). The changes of blood vessels and oxygen saturation (sO2) of tumors were monitored in vivo by photoacoustic tomography (PAT). The microvessel density (MVD), vascular endothelial growth factor (VEGF) and hypoxia-inducible transcription factors (HIF-1α and HIF-2α) were detected by immunohistochemical technique (IHC). Their protein expressions and gene transcription levels were evaluated using western blot (WB) and quantitative reverse transcription and polymerase chain reaction (RT-PCR). PsPEF induced obvious necrosis of cervical cancer tissue; with the increasing of electric field intensity, the MVD, vascular PA signal and sO2 values declined significantly. The protein expression and gene transcription levels of VEGF, HIF1α and HIF2α were significantly decreased at the same time. PsPEF exhibited dramatic anti-tumor and anti-angiogenesis effects in cervical cancer xenograft models by exerting direct effect on cancer cells and vascular endothelial cells and indirect effect on tumor angiogenesis-related factors. Copyright © 2016 Elsevier Inc. All rights reserved.

Identification and discrimination of Pseudomonas aeruginosa bacteria grown in blood and bile by laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Rehse, Steven J.; Diedrich, Jonathan; Palchaudhuri, Sunil

2007-10-01

Pseudomonas aeruginosa bacteria colonies have been analyzed by laser-induced breakdown spectroscopy using nanosecond laser pulses. LIBS spectra were obtained after transferring the bacteria from a nutrient-rich culture medium to a nutrient-free agar plate for laser ablation. To study the dependence of the LIBS spectrum on growth and environmental conditions, colonies were cultured on three different nutrient media: a trypticase soy agar (TSA) plate, a blood agar plate, and a medium chosen deliberately to induce bacteria membrane changes, a MacConkey agar plate containing bile salts. Nineteen atomic and ionic emission lines in the LIBS spectrum, which was dominated by inorganic elements such as calcium, magnesium and sodium, were used to identify and classify the bacteria. A discriminant function analysis was used to discriminate between the P. aeruginosa bacteria and two strains of E. coli: a non-pathogenic environmental strain and the pathogenic strain enterohemorrhagic E. coli 0157:H7 (EHEC). Nearly identical spectra were obtained from P. aeruginosa grown on the TSA plate and the blood agar plate, while the bacteria grown on the MacConkey plate exhibited easily distinguishable differences from the other two. All P. aeruginosa samples, independent of initial growth conditions, were readily discriminated from the two E. coli strains.

Seismicity and Structure of the Incoming Pacific Plate Subducting into the Japan Trench off Miyagi

NASA Astrophysics Data System (ADS)

Obana, K.; Fujie, G.; Kodaira, S.; Takahashi, T.; Yamamoto, Y.; Sato, T.; Yamashita, M.; Nakamura, Y.; Miura, S.

2015-12-01

Stresses within the oceanic plate in trench axis and outer-rise region have been characterized by shallow extension and deep compression due to the bending of the plate subducting into the trench. The stress state within the incoming/subducting oceanic plate is an important factor not only for the occurrence of shallow intraplate normal-faulting earthquakes in the trench-outer rise region but also the hydration of the oceanic plate through the shallow normal faults cutting the oceanic lithosphere. We investigate seismic velocity structure and stress state within the incoming/subducting Pacific Plate in the Japan Trench based on the OBS aftershock observations for the December 2012 intraplate doublet, which consists of a deep reverse faulting (Mw 7.2) and a shallow normal faulting (Mw 7.2) earthquake, in the Japan Trench off Miyagi. Hypocenter locations and seismic velocity structures were estimated from the arrival time data of about 3000 earthquakes by using double-difference tomography method (Zhang and Thurber, 2003). Also, focal mechanisms were estimated from first motion polarities by using the program HASH by Hardebeck and Shearer (2002). The results show that the earthquakes occurred mainly within the oceanic crust and the uppermost mantle. The deepest event was located at a depth of about 60 km. Focal mechanisms of the earthquakes shallower than a depth of 40 km indicate normal-faulting with T-axis normal to the trench. On the other hand, first motion polarities of the events at depths between 50 and 60 km can be explained a reverse faulting. The results suggest that the neutral plane of the stress between shallow extension and deep compression locates at 40 to 50 km deep. Seismic velocity structures indicate velocity decrease in the oceanic mantle toward the trench. Although the velocity decrease varies with locations, the results suggest the bending-related structure change could extend to at least about 15 km below the oceanic Moho in some locations.

Experiments on Maxwell's fish-eye dynamics in elastic plates

NASA Astrophysics Data System (ADS)

Lefebvre, Gautier; Dubois, Marc; Beauvais, Romain; Achaoui, Younes; Ing, Ros Kiri; Guenneau, Sébastien; Sebbah, Patrick

2015-01-01

We experimentally demonstrate that a Duraluminium thin plate with a thickness profile varying radially in a piecewise constant fashion as h ( r ) = h ( 0 ) ( 1 + (r / R max ) 2 ) 2 , with h(0) = 0.5 mm, h(Rmax) = 2 mm, and Rmax = 10 cm, behaves in many ways as Maxwell's fish-eye lens in optics. Its imaging properties for a Gaussian pulse with central frequencies 30 kHz and 60 kHz are very similar to those predicted by ray trajectories (great circles) on a virtual sphere (rays emanating from the North pole meet at the South pole). However, the refocusing time depends on the carrier frequency as a direct consequence of the dispersive nature of flexural waves in thin plates. Importantly, experimental results are in good agreement with finite-difference-time-domain simulations.

Sensitive far uv spectrograph with a multispectral element microchannel plate detector for rocket-borne astronomy.

PubMed

Weiser, H; Vitz, R C; Moos, H W; Weinstein, A

1976-12-01

An evacuated high transmission prism spectrograph using a microchannel plate detection system with resistive strip readout was flown behind a precision pointing telescope on a sounding rocket. The construction, preparation, flight performance, and calibration stability of the system are discussed. Despite the adverse environmental conditions associated with sounding rocket flights, the microchannel detector system performed well. Far uv spectra (1160-1750 A) of stellar and planetary objects were obtained; spectral features with fluxes as low as 0.06 photons cm(-2) sec(-1) were detectable. This was achieved by operating the plates at lower than normal gains, using sensitive pulse counting electronics with both upper and lower limit discriminators, and maintaining the spectrograph and detector at a pressure of ~10(-6) Torr until reaching altitude.

Raman q-plates for Singular Atom Optics

NASA Astrophysics Data System (ADS)

Schultz, Justin T.; Hansen, Azure; Murphree, Joseph D.; Jayaseelan, Maitreyi; Bigelow, Nicholas P.

2016-05-01

We use a coherent two-photon Raman interaction as the atom-optic equivalent of a birefringent optical q-plate to facilitate spin-to-orbital angular momentum conversion in a pseudo-spin-1/2 BEC. A q-plate is a waveplate with a fixed retardance but a spatially varying fast axis orientation angle. We derive the time evolution operator for the system and compare it to a Jones matrix for an optical waveplate to show that in our Raman q-plate, the equivalent orientation of the fast axis is described by the relative phase of the Raman beams and the retardance is determined by the pulse area. The charge of the Raman q-plate is determined by the orbital angular momentum of the Raman beams, and the beams contain umbilic C-point polarization singularities which are imprinted into the condensate as spin singularities: lemons, stars, spirals, and saddles. By tuning the optical beam parameters, we can create a full-Bloch BEC, which is a coreless vortex that contains every possible superposition of two spin states, that is, it covers the Bloch sphere.

Electric-field-driven magnetization reversal in square-shaped nanomagnet-based multiferroic heterostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Ren-Ci; Nan, Ce-Wen, E-mail: jzw12@psu.edu, E-mail: cwnan@tsinghua.edu.cn; Wang, J. J., E-mail: jzw12@psu.edu, E-mail: cwnan@tsinghua.edu.cn

Based on phase field modeling and thermodynamic analysis, purely electric-field-driven magnetization reversal was shown to be possible in a multiferroic heterostructure of a square-shaped amorphous Co{sub 40}Fe{sub 40}B{sub 20} nanomagnet on top of a ferroelectric layer through electrostrain. The reversal is made possible by engineering the mutual interactions among the built-in uniaxial magnetic anisotropy, the geometry-dependent magnetic configuration anisotropy, and the magnetoelastic anisotropy. Particularly, the incorporation of the built-in uniaxial anisotropy made it possible to reverse magnetization with one single unipolar electrostrain pulse, which is simpler than previous designs involving the use of bipolar electrostrains and may alleviate ferroelectric fatigue.more » Critical conditions for triggering the magnetization reversal are identified.« less

Nano- and femtosecond UV laser pulses to immobilize biomolecules onto surfaces with preferential orientation

NASA Astrophysics Data System (ADS)

Lettieri, S.; Avitabile, A.; Della Ventura, B.; Funari, R.; Ambrosio, A.; Maddalena, P.; Valadan, M.; Velotta, R.; Altucci, C.

2014-10-01

By relying on the photonic immobilization technique of antibodies onto surfaces, we realized portable biosensors for light molecules based on the use of quartz crystal microbalances, given the linear dependence of the method on the laser pulse intensity. Here, we compare the quality of the anchoring method when using nanosecond (260 nm, 25 mJ/pulse, 5 ns, 10 Hz rep. rate) and femtosecond (258 nm, 25 μJ/pulse, 150 fs, 10 kHz rep. rate) laser source, delivering the same energy to the sample with the same average power. As a reference, we also tethered untreated antibodies by means of the passive adsorption. The results are striking: When the antibodies are irradiated with the femtosecond pulses, the deposition on the gold plate is much more ordered than in the other two cases. The effects of UV pulses irradiation onto the antibodies are also analyzed by measuring absorption and fluorescence and suggest the occurrence of remarkable degradation when nanosecond pulses are used likely induced by a larger thermal coupling. In view of the high average power required to activate the antibodies for the achievement of the photonic immobilization technique, we conclude that femtosecond rather than nanosecond laser pulses have to be used.

NO Removal with Repetitive Discharges Caused by Reciprocal Traveling Wave Voltage Pulse in a Coaxial Cable

NASA Astrophysics Data System (ADS)

Yamaga, Keisuke; Kadowaki, Kazunori; Nishimoto, Sakae; Kitani, Isamu

This paper describes experimental results of NO removal using barrier discharges produced by a reciprocal pulse generator. When a coaxial cable is charged and then grounded at one end of the cable without any resistance, a reciprocal traveling voltage pulse is repeatedly applied to a barrier-type reactor at the opposite end with a change in its polarity. 50% streamer initiation voltage for the reciprocal pulse generator was much smaller than that with the self-matched pulse generator having a matching resistance. The reason for the low initiation voltage in the reciprocal pulse was that space charges which accumulated on the barrier surface during cable charging had an effect on field enhancement in the reactor after the first polarity reversal. High speed photographs of discharge light produced by the reciprocal pulse showed that the voltage oscillation caused by one switching induced alternate propagation of positive and negative streamers with a very high frequency. In measurements of NO concentration, the reciprocal pulse generator gave a better performance for NO removal ratio than the self-matched pulse generator even though the stored energy in the recipocal pulse generator was very low.

Scatterometer-Calibrated Stability Verification Method

NASA Technical Reports Server (NTRS)

McWatters, Dalia A.; Cheetham, Craig M.; Huang, Shouhua; Fischman, Mark A.; CHu, Anhua J.; Freedman, Adam P.

2011-01-01

The requirement for scatterometer-combined transmit-receive gain variation knowledge is typically addressed by sampling a portion of the transmit signal, attenuating it with a known-stable attenuation, and coupling it into the receiver chain. This way, the gain variations of the transmit and receive chains are represented by this loop-back calibration signal, and can be subtracted from the received remote radar echo. Certain challenges are presented by this process, such as transmit and receive components that are outside of this loop-back path and are not included in this calibration, as well as the impracticality for measuring the transmit and receive chains stability and post fabrication separately, without the resulting measurement errors from the test set up exceeding the requirement for the flight instrument. To cover the RF stability design challenge, the portions of the scatterometer that are not calibrated by the loop-back, (e.g., attenuators, switches, diplexers, couplers, and coaxial cables) are tightly thermally controlled, and have been characterized over temperature to contribute less than 0.05 dB of calibration error over worst-case thermal variation. To address the verification challenge, including the components that are not calibrated by the loop-back, a stable fiber optic delay line (FODL) was used to delay the transmitted pulse, and to route it into the receiver. In this way, the internal loopback signal amplitude variations can be compared to the full transmit/receive external path, while the flight hardware is in the worst-case thermal environment. The practical delay for implementing the FODL is 100 s. The scatterometer pulse width is 1 ms so a test mode was incorporated early in the design phase to scale the 1 ms pulse at 100-Hz pulse repetition interval (PRI), by a factor of 18, to be a 55 s pulse with 556 s PRI. This scaling maintains the duty cycle, thus maintaining a representative thermal state for the RF components. The FODL consists of an RF-modulated fiber-optic transmitter, 20 km SMF- 28 standard single-mode fiber, and a photodetector. Thermoelectric cooling and insulating packaging are used to achieve high thermal stability of the FODL components. The chassis was insulated with 1-in. (.2.5-cm) thermal isolation foam. Nylon rods support the Micarta plate, onto which are mounted four 5-km fiber spool boxes. A copper plate heat sink was mounted on top of the fiber boxes (with thermal grease layer) and screwed onto the thermoelectric cooler plate. Another thermal isolation layer in the middle separates the fiberoptics chamber from the RF electronics components, which are also mounted on a copper plate that is screwed onto another thermoelectric cooler. The scatterometer subsystem fs overall stability was successfully verified to be calibratable to within 0.1 dB error in thermal vacuum (TVAC) testing with the fiber-optic delay line, while the scatterometer temperature was ramped from 10 to 30 C, which is a much larger temperature range than the worst-case expected seasonal variations.

Time reversal of optically carried radiofrequency signals in the microsecond range.

PubMed

Linget, H; Morvan, L; Le Gouët, J-L; Louchet-Chauvet, A

2013-03-01

The time-reversal (TR) protocol we implement in an erbium-doped YSO crystal is based on photon echoes but avoids the storage of the signal to be processed. Unlike other approaches implying digitizing or highly dispersive optical fibers, the proposed scheme reaches the μs range and potentially offers high bandwidth, both required for RADAR applications. In this Letter, we demonstrate faithful reversal of arbitrary pulse sequences with 6 μs duration and 10 MHz bandwidth. To the best of our knowledge, this is the first demonstration of TR via linear filtering in a programmable material.

Reverse slapper detonator

DOEpatents

Weingart, Richard C.

1990-01-01

A reverse slapper detonator (70), and methodology related thereto, are provided. The detonator (70) is adapted to be driven by a pulse of electric power from an external source (80). A conductor (20) is disposed along the top (14), side (18), and bottom (16) surfaces of a sheetlike insulator (12). Part of the conductor (20) comprises a bridge (28), and an aperture (30) is positioned within the conductor (20), with the bridge (28) and the aperture (30) located on opposite sides of the insulator (12). A barrel (40) and related explosive charge (50) are positioned adjacent to and in alignment with the aperture (30), and the bridge (28) is buttressed with a backing layer (60). When the electric power pulse vaporizes the bridge (28), a portion of the insulator (12) is propelled through the aperture (30) and barrel (40), and against the explosive charge (50), thereby detonating it.

Pulse-reverse electrodeposition for mesoporous metal films: combination of hydrogen evolution assisted deposition and electrochemical dealloying.

PubMed

Cherevko, Serhiy; Kulyk, Nadiia; Chung, Chan-Hwa

2012-01-21

Hydrogen evolution assisted electrodeposition is a new bottom-up technique allowing the fast and simple synthesis of nanometals. Electrochemical dealloying is a top-down approach with the same purpose. In this work, we show that a combination of these two methods in sequence by pulse-reverse electrodeposition can be used to prepare high-surface-area nanostructured metals. Highly porous adherent platinum is obtained by the deposition of CuPt alloy during the cathodic cycles and the selective dissolution of copper during the anodic cycles. The convection created by the movement of the hydrogen bubbles increases the deposition rate and removes the dissolved copper ions from the diffusion layer, which ensures the deposition of a film with the same stoichiometry throughout the whole process. Due to the relatively high ratio of copper atoms on the surface in the as-deposited layer, it is proposed that the dealloying kinetics is significantly higher than that usually observed during the dealloying process in a model system. The proposed approach has several advantages over other methods, such as a very high growth rate and needlessness of any post-treatment processes. A detailed analysis of the effect of pulse-reverse waveform parameters on the properties of the films is presented. Mesoporous platinum with pores and ligaments having characteristic sizes of less than 10 nm, an equivalent surface area of up to ca. 220 m(2) cm(-3), and a roughness factor of more than 1000 is fabricated.

SLAC pulsed X-ray facility

NASA Astrophysics Data System (ADS)

Ipe, N. E.; McCall, R. C.; Baker, E. D.

1986-05-01

The Stanford Linear Accelerator Center (SLAC) operates a high energy (up to 33 GeV) linear accelerator delivering pulses up to a few microseconds wide. The pulsed nature of the electron beam creates problems in the detection and measurement of radiation both from the accelerator beam and the klystrons that provide the RF power for the accelerator. Hence, a pulsed X-ray facility has been built at SLAC mainly for the purpose of testing the response of different radiation detection instruments to pulsed radiation fields. The X-ray tube consists of an electron gun with a control grid. This provides a stream of pulsed electrons that can be accelerated towards a confined target-window. The window is made up of aluminum 0.051 cm (20 mils) thick, plated on the vacuum side with a layer of gold 0.0006 cm (1/4 mil) thick. The frequency of electron pulses can be varied by an internal pulser from 60 to 360 pulses per second with pulse widths of 360 ns to 5 ms. The pulse amplitude can be varied over a wide range of currents. An external pulser can be used to obtain other frequencies or special pulse shapes. The voltage across the gun can be varied from 0 to 100 kV. The major part of the X-ray tube is enclosed in a large walk-in-cabinet made of 1.9 cm (3/4 in) plywood and lined with 0.32 cm (1/8 in) lead to make a very versatile facility.

A Visualization Method for Corrosion Damage on Aluminum Plates Using an Nd:YAG Pulsed Laser Scanning System

PubMed Central

Lee, Inbok; Zhang, Aoqi; Lee, Changgil; Park, Seunghee

2016-01-01

This paper proposes a non-contact nondestructive evaluation (NDE) technique that uses laser-induced ultrasonic waves to visualize corrosion damage in aluminum alloy plate structures. The non-contact, pulsed-laser ultrasonic measurement system generates ultrasonic waves using a galvanometer-based Q-switched Nd:YAG laser and measures the ultrasonic waves using a piezoelectric (PZT) sensor. During scanning, a wavefield can be acquired by changing the excitation location of the laser point and measuring waves using the PZT sensor. The corrosion damage can be detected in the wavefield snapshots using the scattering characteristics of the waves that encounter corrosion. The structural damage is visualized by calculating the logarithmic values of the root mean square (RMS), with a weighting parameter to compensate for the attenuation caused by geometrical spreading and dispersion of the waves. An intact specimen is used to conduct a comparison with corrosion at different depths and sizes in other specimens. Both sides of the plate are scanned with the same scanning area to observe the effect of the location where corrosion has formed. The results show that the damage can be successfully visualized for almost all cases using the RMS-based functions, whether it formed on the front or back side. Also, the system is confirmed to have distinguished corroded areas at different depths. PMID:27999252

A Visualization Method for Corrosion Damage on Aluminum Plates Using an Nd:YAG Pulsed Laser Scanning System.

PubMed

Lee, Inbok; Zhang, Aoqi; Lee, Changgil; Park, Seunghee

2016-12-16

This paper proposes a non-contact nondestructive evaluation (NDE) technique that uses laser-induced ultrasonic waves to visualize corrosion damage in aluminum alloy plate structures. The non-contact, pulsed-laser ultrasonic measurement system generates ultrasonic waves using a galvanometer-based Q-switched Nd:YAG laser and measures the ultrasonic waves using a piezoelectric (PZT) sensor. During scanning, a wavefield can be acquired by changing the excitation location of the laser point and measuring waves using the PZT sensor. The corrosion damage can be detected in the wavefield snapshots using the scattering characteristics of the waves that encounter corrosion. The structural damage is visualized by calculating the logarithmic values of the root mean square (RMS), with a weighting parameter to compensate for the attenuation caused by geometrical spreading and dispersion of the waves. An intact specimen is used to conduct a comparison with corrosion at different depths and sizes in other specimens. Both sides of the plate are scanned with the same scanning area to observe the effect of the location where corrosion has formed. The results show that the damage can be successfully visualized for almost all cases using the RMS-based functions, whether it formed on the front or back side. Also, the system is confirmed to have distinguished corroded areas at different depths.

Passive control of coherent structures in a modified backwards-facing step flow

NASA Astrophysics Data System (ADS)

Ormonde, Pedro C.; Cavalieri, André V. G.; Silva, Roberto G. A. da; Avelar, Ana C.

2018-05-01

We study a modified backwards-facing step flow, with the addition of two different plates; one is a baseline, impermeable plate and the second a perforated one. An experimental investigation is carried out for a turbulent reattaching shear layer downstream of the two plates. The proposed setup is a model configuration to study how the plate characteristics affect the separated shear layer and how turbulent kinetic energies and large-scale coherent structures are modified. Measurements show that the perforated plate changes the mean flow field, mostly by reducing the intensity of reverse flow close to the bottom wall. Disturbance amplitudes are significantly reduced up to five step heights downstream of the trailing edge of the plate, more specifically in the recirculation region. A loudspeaker is then used to introduce phase-locked, low-amplitude perturbations upstream of the plates, and phase-averaged measurements allow a quantitative study of large-scale structures in the shear-layer. The evolution of such coherent structures is evaluated in light of linear stability theory, comparing the eigenfunction of the Kelvin-Helmholtz mode to the experimental results. We observe a close match of linear-stability eigenfunctions with phase-averaged amplitudes for the two tested Strouhal numbers. The perforated plate is found to reduce the amplitude of the Kelvin-Helmholtz coherent structures in comparison to the baseline, impermeable plate, a behavior consistent with the predicted amplification trends from linear stability.

Development towards a fast ion loss detector for the reversed field pinch.

PubMed

Bonofiglo, P J; Anderson, J K; Almagri, A F; Kim, J; Clark, J; Capecchi, W; Sears, S H; Egedal, J

2016-11-01

A fast ion loss detector has been constructed and implemented on the Madison Symmetric Torus (MST) to investigate energetic ion losses and transport due to energetic particle and MHD instabilities. The detector discriminates particle orbits solely on pitch and consists of two thin-foil, particle collecting plates that are symmetric with respect to the device aperture. One plate collects fast ion signal, while the second aids in the minimization of background and noise effects. Initial measurements are reported along with suggestions for the next design phase of the detector.

High-gradient compact linear accelerator

DOEpatents

Carder, B.M.

1998-05-26

A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter. 10 figs.

High-gradient compact linear accelerator

DOEpatents

Carder, Bruce M.

1998-01-01

A high-gradient linear accelerator comprises a solid-state stack in a vacuum of five sets of disc-shaped Blumlein modules each having a center hole through which particles are sequentially accelerated. Each Blumlein module is a sandwich of two outer conductive plates that bracket an inner conductive plate positioned between two dielectric plates with different thicknesses and dielectric constants. A third dielectric core in the shape of a hollow cylinder forms a casing down the series of center holes, and it has a dielectric constant different that the two dielectric plates that sandwich the inner conductive plate. In operation, all the inner conductive plates are charged to the same DC potential relative to the outer conductive plates. Next, all the inner conductive plates are simultaneously shorted to the outer conductive plates at the outer diameters. The signal short will propagate to the inner diameters at two different rates in each Blumlein module. A faster wave propagates quicker to the third dielectric core across the dielectric plates with the closer spacing and lower dielectric constant. When the faster wave reaches the inner extents of the outer and inner conductive plates, it reflects back outward and reverses the field in that segment of the dielectric core. All the field segments in the dielectric core are then in unipolar agreement until the slower wave finally propagates to the third dielectric core across the dielectric plates with the wider spacing and higher dielectric constant. During such unipolar agreement, particles in the core are accelerated with gradients that exceed twenty megavolts per meter.

Effect of bioparticle size on dispersion and retention in monolithic and perfusive beds

PubMed Central

Trilisky, Egor I.; Lenhoff, Abraham M.

2010-01-01

Single-component pulse response studies were used to compare the retention and transport behavior of small molecules, proteins, and a virus on commercially available monolithic and perfusive ion-exchangers. Temporal distortion and extra-column effects were corrected for using a simple algorithm based on the method of moments. It was found that temporal distortion is inversely related to the number of theoretical plates. With increasing bioparticle size, retention increased and the transition from a non-eluting to a non-adsorbing state with increasing ionic strength became more abrupt. Both of these observations are qualitatively explained by calculations of particle-surface electrostatic attractive energy. Calculations also show that, for sufficiently large bioparticles, such as viruses or cells, hydrodynamic drag can promote elution. Under non-adsorbing conditions, plate height increased only weakly with flow rate and the skew remained unchanged. With increasing retention, plate height increased dramatically for proteins. Plate height was scaled by permeability rather than bead diameter to enable comparison among different stationary phases. PMID:20951383

ELECTRICAL CIRCUITS USING COLD-CATHODE TRIODE VALVES

DOEpatents

Goulding, F.S.

1957-11-26

An electrical circuit which may be utilized as a pulse generator or voltage stabilizer is presented. The circuit employs a cold-cathode triode valve arranged to oscillate between its on and off stages by the use of selected resistance-capacitance time constant components in the plate and trigger grid circuits. The magnitude of the d-c voltage applied to the trigger grid circuit effectively controls the repetition rate of the output pulses. In the voltage stabilizer arrangement the d-c control voltage is a portion of the supply voltage and the rectified output voltage is substantially constant.

The Effects of Pulse Current Plating on the Mechanical Properties of Cobalt and Cobalt-Al2O3

DTIC Science & Technology

1977-04-01

258. Branson cobalt deposits as a function ol cu rrent pulses superImposed on Ultrasonic Corp.) was used tominimi,eAl ..0 agglomeration in a back...intens ify nucleation and growth processes leading to a Iheauthors wishtot hank Mr. Richard Carte rforprepar ingthe re finement in grain structure...i N BOX CM , I)UKE STATION ATTN : A~.1\\5T..SD ATTN : RI)Rl)- IP L 220 “III SIR E !~T N .E . Du RHAM , NC 27706 C1LARI U l’Tl Sv ILI.I. , VA 22901 Cl)R

Report on the lunar ranging at McDonald Observatory. [spark gap configuration and photomultiplier system

NASA Technical Reports Server (NTRS)

Silverberg, E. C.

1977-01-01

Range measurements to an accuracy of 5 cm were achieved following improvements in the laser oscillator configuration and the photomultiplier system. Modifications to the laser include a redesigned pockel cell mount to eliminate stressing of the cell crystal; an improved electrically triggered spark gap for sharpening the electrical pulse; the use of a brewster plate in the cavity to eliminate pre-pulsing; improved alignment for the oscillator system; and increased cavity lifetime through thin film polarizer technology. Laser calibration data are presented along with the lunar laser operations log for June to October 1977.

Degradation of Acid Orange 7 Dye in Two Hybrid Plasma Discharge Reactors

NASA Astrophysics Data System (ADS)

Shen, Yongjun; Lei, Lecheng; Zhang, Xingwang; Ding, Jiandong

2014-11-01

To get an optimized pulsed electrical plasma discharge reactor and to increase the energy utilization efficiency in the removal of pollutants, two hybrid plasma discharge reactors were designed and optimized. The reactors were compared via the discharge characteristics, energy transfer efficiency, the yields of the active species and the energy utilization in dye wastewater degradation. The results showed that under the same AC input power, the characteristics of the discharge waveform of the point-to-plate reactor were better. Under the same AC input power, the two reactors both had almost the same peak voltage of 22 kV. The peak current of the point-to-plate reactor was 146 A, while that of the wire-to-cylinder reactor was only 48.8 A. The peak powers of the point-to-plate reactor and the wire-to-cylinder reactor were 1.38 MW and 1.01 MW, respectively. The energy per pulse of the point-to-plate reactor was 0.2221 J, which was about 29.4% higher than that of the wire-to-cylinder reactor (0.1716 J). To remove 50% Acid Orange 7 (AO7), the energy utilizations of the point-to-plate reactor and the wire-to-cylinder reactor were 1.02 × 10-9 mol/L and 0.61 × 10-9 mol/L, respectively. In the point-to-plate reactor, the concentration of hydrogen peroxide in pure water was 3.6 mmol/L after 40 min of discharge, which was higher than that of the wire-to-cylinder reactor (2.5 mmol/L). The concentration of liquid phase ozone in the point-to-plate reactor (5.7 × 10-2 mmol/L) was about 26.7% higher than that in the wire-to-cylinder reactor (4.5 × 10-2 mmol/L). The analysis results of the variance showed that the type of reactor and reaction time had significant impacts on the yields of the hydrogen peroxide and ozone. The main degradation intermediates of AO7 identified by gas chromatography and mass spectrometry (GCMS) were acetic acid, maleic anhydride, p-benzoquinone, phenol, benzoic acid, phthalic anhydride, coumarin and 2-naphthol. Proposed degradation pathways were elucidated in light of the analyzed degradation products.

Copper extraction from ammoniacal medium in a pulsed sieve-plate column with LIX 84-I.

PubMed

Gameiro, M Lurdes F; Machado, Remígio M; Ismael, M Rosinda C; Reis, M Teresa A; Carvalho, Jorge M R

2010-11-15

This article reports on a study of copper removal from ammoniacal aqueous solution (1.0 kg m(-3) Cu, pH 9.5) by liquid-liquid extraction using a pulsed sieve-plate column. The extractant tested was the hydroxyoxime LIX 84-I (2-hydroxy-5-nonylacetophenone oxime) in the aliphatic diluent Shellsol D-70. The results of the pilot plant experiments demonstrated the feasibility of operating the extraction process in this type of column, with efficiencies of copper removal in the range of 90.5-99.5%. Several effects on the column performance were examined, namely the aqueous and organic flow rates and the pulse velocity. The axial dispersion model was applied to simulate the concentration profiles, which reasonably predicted the experimental data. The overall mass transfer coefficient was evaluated from the experimental data and was found to be between 9×10(-6) and 1.2×10(-5) m s(-1). These data were compared with the ones obtained from the resistances in series model, which indicated that the resistance due to chemical reaction was 84-91% of the overall resistance to mass transfer. The extraction using a hollow fiber contactor was also carried out to compare the membrane process performance with the one of conventional process. Copyright © 2010 Elsevier B.V. All rights reserved.

Eyeballing oscillators for pulsed Doppler radar

NASA Astrophysics Data System (ADS)

Goldman, S.

1985-03-01

The visibility of small targets to a Doppler radar system in the presence of large targets is limited by phase noise. Such limitations occur when an airborne radar searches the ground for a mobile vehicle. Under these conditions, the performance of the Doppler radar depends greatly on the specifications of its phased-locked oscillator. Goldman (1984) has discussed the steps required to evaluate the noise resulting from a pulsed Doppler radar system. In the present investigation, these techniques are applied in reverse to determine system specifications for oscillator noise. A 95-GHz pulsed Doppler radar system is used as an example of specifying system phase noise.

Interfacing superconducting qubits and telecom photons via a rare-earth-doped crystal.

PubMed

O'Brien, Christopher; Lauk, Nikolai; Blum, Susanne; Morigi, Giovanna; Fleischhauer, Michael

2014-08-08

We propose a scheme to couple short single photon pulses to superconducting qubits. An optical photon is first absorbed into an inhomogeneously broadened rare-earth doped crystal using controlled reversible inhomogeneous broadening. The optical excitation is then mapped into a spin state using a series of π pulses and subsequently transferred to a superconducting qubit via a microwave cavity. To overcome the intrinsic and engineered inhomogeneous broadening of the optical and spin transitions in rare-earth doped crystals, we make use of a special transfer protocol using staggered π pulses. We predict total transfer efficiencies on the order of 90%.

Multi-frame acquisition scheme for efficient energy-dispersive X-ray magnetic circular dichroism in pulsed high magnetic fields at the Fe K-edge

PubMed Central

Strohm, Cornelius; Perrin, Florian; Dominguez, Marie-Christine; Headspith, Jon; van der Linden, Peter; Mathon, Olivier

2011-01-01

Using a fast silicon strip detector, a multi-frame acquisition scheme was implemented to perform energy-dispersive X-ray magnetic circular dichroism at the iron K-edge in pulsed high magnetic fields. The acquisition scheme makes use of the entire field pulse. The quality of the signal obtained from samples of ferrimagnetic erbium iron garnet allows for quantitative evaluation of the signal amplitude. Below the compensation point, two successive field-induced phase transitions and the reversal of the net magnetization of the iron sublattices in the intermediate phase were observed. PMID:21335909

Analysis of reliable sub-ns spin-torque switching under transverse bias magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

D'Aquino, M., E-mail: daquino@uniparthenope.it; Perna, S.; Serpico, C.

2015-05-07

The switching process of a magnetic spin-valve nanosystem subject to spin-polarized current pulses is considered. The dependence of the switching probability on the current pulse duration is investigated. The further application of a transverse field along the intermediate anisotropy axis of the particle is used to control the quasi-random relaxation of magnetization to the reversed magnetization state. The critical current amplitudes to realize the switching are determined by studying the phase portrait of the Landau-Lifshtz-Slonczewski dynamics. Macrospin numerical simulations are in good agreement with the theoretical prediction and demonstrate reliable switching even for very short (below 100 ps) current pulses.

Eocene extension in Idaho generated massive sediment floods into Franciscan trench and into Tyee, Great Valley, and Green River basins

USGS Publications Warehouse

Dumitru, Trevor A.; Ernst, W.G.; Wright, James E.; Wooden, Joseph L.; Wells, Ray E.; Farmer, Lucia P.; Kent, Adam J.R.; Graham, Stephan A.

2013-01-01

The Franciscan Complex accretionary prism was assembled during an ∼165-m.y.-long period of subduction of Pacific Ocean plates beneath the western margin of the North American plate. In such fossil subduction complexes, it is generally difficult to reconstruct details of the accretion of continent-derived sediments and to evaluate the factors that controlled accretion. New detrital zircon U-Pb ages indicate that much of the major Coastal belt subunit of the Franciscan Complex represents a massive, relatively brief, surge of near-trench deposition and accretion during Eocene time (ca. 53–49 Ma). Sediments were sourced mainly from the distant Idaho Batholith region rather than the nearby Sierra Nevada. Idaho detritus also fed the Great Valley forearc basin of California (ca. 53–37 Ma), the Tyee forearc basin of coastal Oregon (49 to ca. 36 Ma), and the greater Green River lake basin of Wyoming (50–47 Ma). Plutonism in the Idaho Batholith spanned 98–53 Ma in a contractional setting; it was abruptly superseded by major extension in the Bitterroot, Anaconda, Clearwater, and Priest River metamorphic core complexes (53–40 Ma) and by major volcanism in the Challis volcanic field (51–43 Ma). This extensional tectonism apparently deformed and uplifted a broad region, shedding voluminous sediments toward depocenters to the west and southeast. In the Franciscan Coastal belt, the major increase in sediment input apparently triggered a pulse of massive accretion, a pulse ultimately controlled by continental tectonism far within the interior of the North American plate, rather than by some tectonic event along the plate boundary itself.

Pilot Production of Large Area Microchannel Plates and Picosecond Photodetectors

NASA Astrophysics Data System (ADS)

Minot, M.; Adams, B.; Abiles, M.; Bond, J.; Craven, C.; Cremer, T.; Foley, M.; Lyashenko, A.; Popecki, M.; Stochaj, M.; Worstell, W.; Elam, J.; Mane, A.; Siegmund, O.; Ertley, C.

2016-09-01

Pilot production performance is reported for large area atomic layer deposition (ALD) coated microchannel plates (ALD-GCA-MCPs) and for Large Area Picosecond Photodetectors (LAPPD™) which incorporate them. "Hollowcore" glass capillary array (GCA) substrates are coated with ALD resistive and emissive layers to form the ALDGCA- MCPs, an approach that facilitates independent selection of glass substrates that are mechanically stronger and that have lower levels of radioactive alkali elements compared to conventional MCP lead glass, reducing background noise[1,2,3,4]. ALD-GCA-MCPs have competitive gain ( 104 each or 107 for a chevron pair ), enhanced lifetime and gain stability (7 C cm-2 of charge extraction), reduced background levels (0.028 events cm-2 sec-1) and low gamma-ray detection efficiency. They can be fabricated in large area (20cm X 20 cm) planar and curved formats suitable for use in high radiation environment applications, including astronomy, space instrumentation, and remote night time sensing. The LAPPD™ photodetector incorporates these ALD-GCA-MCPs in an all-glass hermetic package with top and bottom plates and sidewalls made of borosilicate float glass. Signals are generated by a bi-alkali Na2KSb photocathode, amplified with a stacked chevron pair of ALD-GCA-MCPs. Signals are collected on RF strip-line anodes integrated into to the bottom plates which exit the detector via pin-free hermetic seals under the side walls [5]. Tests show that LAPPDTMs have electron gains greater than 107, submillimeter spatial resolution for large (multiphoton) pulses and several mm for single photons, time resolution less than 50 picoseconds for single photons, predicted resolution less than 5 picoseconds for large pulses, high stability versus charge extraction[6], and good uniformity for applications including astrophysics, neutron detection, high energy physics Cherenkov light detection, and quantum-optical photon-correlation experiments.

Altered ion channel conductance and ionic selectivity induced by large imposed membrane potential pulse.

PubMed Central

Chen, W; Lee, R C

1994-01-01

The effects of large magnitude transmembrane potential pulses on voltage-gated Na and K channel behavior in frog skeletal muscle membrane were studied using a modified double vaseline-gap voltage clamp. The effects of electroconformational damage to ionic channels were separated from damage to lipid bilayer (electroporation). A 4 ms transmembrane potential pulse of -600 mV resulted in a reduction of both Na and K channel conductivities. The supraphysiologic pulses also reduced ionic selectivity of the K channels against Na+ ions, resulting in a depolarization of the membrane resting potential. However, TTX and TEA binding effects were unaltered. The kinetics of spontaneous reversal of the electroconformational damage of channel proteins was found to be dependent on the magnitude of imposed membrane potential pulse. These results suggest that muscle and nerve dysfunction after electrical shock may be in part caused by electroconformational damage to voltage-gated ion channels. PMID:7948676

Control of nitromethane photoionization efficiency with shaped femtosecond pulses.

PubMed

Roslund, Jonathan; Shir, Ofer M; Dogariu, Arthur; Miles, Richard; Rabitz, Herschel

2011-04-21

The applicability of adaptive femtosecond pulse shaping is studied for achieving selectivity in the photoionization of low-density polyatomic targets. In particular, optimal dynamic discrimination (ODD) techniques exploit intermediate molecular electronic resonances that allow a significant increase in the photoionization efficiency of nitromethane with shaped near-infrared femtosecond pulses. The intensity bias typical of high-photon number, nonresonant ionization is accounted for by reference to a strictly intensity-dependent process. Closed-loop adaptive learning is then able to discover a pulse form that increases the ionization efficiency of nitromethane by ∼150%. The optimally induced molecular dynamics result from entry into a region of parameter space inaccessible with intensity-only control. Finally, the discovered pulse shape is demonstrated to interact with the molecular system in a coherent fashion as assessed from the asymmetry between the response to the optimal field and its time-reversed counterpart.

Flux-trapping during the formation of field-reversed configurations

NASA Astrophysics Data System (ADS)

Armstrong, W. T.; Harding, D. G.; Crawford, E. A.; Hoffman, A. L.

1981-10-01

Optimized trapping of bias flux during the early formation phases of a Field Reversed Configuration was studied experimentally on the field reversed theta pinch TRX-1. An annular z-pinch preionizer was employed to permit ionization at high values of initial reverse bias flux. Octopole barrier fields are pulsed during field reversal to minimize plasma/wall contact and associated loss of reverse flux. Also, second half cycle operation was examined in obtaining very high values of reverse flux. Flux loss is generally observed to be governed by resistive diffusion through a current sheath at the plasma boundary, rather than flux convection to the plasma boundary. Trapped reverse flux at the time of field reversal, as well as after the radial implosion, is observed to increase with the applied bias field. This increase is greatest, and in fact nearly linear with bias field, when barrier fields are employed. Barrier fields also appear to broaden the current sheath, which results in some flux loss and a less dynamic radial implosion. A general model and one dimensional simulation of flux loss is described and correlated with experimental results.

Measurement and significance of the reversal potential for the pace-maker current (iK2) in sheep Purkinje fibres.

PubMed

DiFrancesco, D; Ohba, M; Ojeda, C

1979-12-01

1. The apparent reversal potential (Erev) of the pace-maker current (iK2) is found to depend on the experimental protocol used for its measurement. Evidence is presented showing that depolarizing (hyperpolarizing) pulses given before a test hyperpolarization used to determine Erev, shift Erev to more negative (positive) values. These shifts are opposite to those expected if the only effect of pre-pulses were to change the concentration of potassium in extracellular clefts ([K]c) via accumulation and depletion processes. 2. This effect is shown to be due to the fact that Erev is dependent on s0, the degree of activation of iK2 at the start of the test hyperpolarization. 3. When a suitable protocol is used, depletion of cleft K can be demonstrated to take place during a large hyperpolarization. Changes in the level of [K]c induced by pre-pulses must therefore also affect the Erev determination. 4. A simplified three-compartment model has been used to investigate how K accumulation and depletion can affect the time course of iK2, with particular reference to the problem of Erev determination. Computed examples show that the model is able to reproduce the main features of the time course of iK2 recorded near its reversal potential and the changes induced by pre-pulses on Erev measuremnet. By contrast, simulation on a linear cable model rules out the possibility that such results are due to voltage non-uniformity. 5. The three-compartment model predicts that the measured value of Erev differs from EK2 for two reasons: (1) when the recorded current trace is flat iK2 is still outward and decaying, and (2) the K equilibrium potential shifts to more negative values while the test hyperpolarization is applied. 6. The finding that Erev is directly affected by changes in s at the beginning of the test pulse is discussed in relation to the action of agents (such as Ca2+, H+, salicylate, adrenaline and ouabain) which are found to shift both the s00 curve and Erev.

Fluid pathways from mantle wedge up to forearc seafloor in the coseismic slip area of the 2011 Tohoku earthquake

NASA Astrophysics Data System (ADS)

Park, J. O.; Tsuru, T.; Fujie, G.; Kagoshima, T.; Sano, Y.

2017-12-01

A lot of fluids at subduction zones are exchanged between the solid Earth and ocean, affecting the earthquake and tsunami generation. New multi-channel seismic reflection and sub-bottom profiling data reveal normal and reverse faults as the fluid pathways in the coseismic slip area of the 2011 Tohoku earthquake (M9.0). Based on seismic reflection characteristics and helium isotope anomalies, we recognize variations in fluid pathways (i.e., faults) from the mantle wedge up to forearc seafloor in the Japan Trench margin. Some fluids are migrated from the mantle wedge along plate interface and then normal or reverse faults cutting through the overriding plate. Others from the mantle wedge are migrated directly up to seafloor along normal faults, without passing through the plate interface. Locations of the normal faults are roughly consistent with aftershocks of the 2011 Tohoku earthquake, which show focal mechanism of normal faulting. It is noticeable that landward-dipping normal faults developing down into Unit C (Cretaceous basement) from seafloor are dominant in the middle slope region where basal erosion is inferred to be most active. A high-amplitude, reverse-polarity reflection of the normal faults within Unit C suggests that the fluids are locally trapped along the faults in high pore pressures. The 2011 Tohoku mainshock and subsequent aftershocks could lead the pre-existing normal faults to be reactive and more porous so that the trapped fluids are easily transported up to seafloor through the faults. Elevated fluid pressures can decrease the effective normal stress for the fault plane, allowing easier slip of the landward-dipping normal fault and also enhancing its tsunamigenic potential.

Laser-Launched Flyer Plates and Direct Laser Shocks for Dynamic Material Property Measurements

NASA Astrophysics Data System (ADS)

Paisley, D. L.; Swift, D. C.; Johnson, R. P.; Kopp, R. A.; Kyrala, G. A.

2002-07-01

The Trident laser at Los Alamos was used to impart known and controlled shocks in various materials by launching flyer plates or by irradiating the sample directly. Materials investigated include copper, gold, NiTi, SS316, and other metals and alloys. Tensile spall strength, elastic-plastic transition, phase boundaries, and equation of state can be determined with small samples. Using thin samples (0.1 - 1.0 mm thick) as targets, high pressure gradients can be generated with relatively low pressures, resulting in high tensile strain rates (105 to 108 s-1). Free surface and interface velocities are recorded with point- and line-imaging VISARs. The flexible spatial and temporal pulse profiles of Trident, coupled with the use of laser-launched flyer plates, provides capabilities which complement experiments conducted using gas guns and tensile bars.

Graphene-gold supercapacitor as a voltage controlled saturable absorber for femtosecond pulse generation.

PubMed

Baylam, Isinsu; Balci, Osman; Kakenov, Nurbek; Kocabas, Coskun; Sennaroglu, Alphan

2016-03-01

We report, for the first time to the best of our knowledge, use of a graphene-gold supercapacitor as a voltage controlled fast saturable absorber for femtosecond pulse generation. The unique design involving only one graphene electrode lowers the insertion loss of the device, in comparison with capacitor designs with two graphene electrodes. Furthermore, use of the high-dielectric electrolyte allows reversible, adjustable control of the absorption level up to the visible region with low bias voltages of only a few volts (0-2 V). The fast saturable absorber action of the graphene-gold supercapacitor was demonstrated inside a multipass-cavity Cr:forsterite laser to generate nearly transform-limited, sub-100 fs pulses at a pulse repetition rate of 4.51 MHz at 1.24 μm.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies

NASA Astrophysics Data System (ADS)

Ji, Q.; Seidl, P. A.; Waldron, W. L.; Takakuwa, J. H.; Friedman, A.; Grote, D. P.; Persaud, A.; Barnard, J. J.; Schenkel, T.

2016-02-01

The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ˜1 eV using intense, short pulses (˜1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He+ ions leads to more uniform energy deposition of the target material than Li+ ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li+ ions from a hot plate type ion source. He+ beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.