Science.gov

Sample records for rate pulse operation

  1. Investigation of component failure rates for pulsed versus steady state tokamak operation

    SciTech Connect

    Cadwallader, L.C.

    1992-07-01

    This report presents component failure rate data sources applicable to magnetic fusion systems, and defines multiplicative factors to adjust these data for specific use on magnetic fusion experiment designs. The multipliers address both long pulse and steady state tokamak operation. Thermal fatigue and radiation damage are among the leading reasons for large multiplier values in pulsed operation applications. Field failure rate values for graphite protective tiles are presented, and beryllium tile failure rates in laboratory testing are also given. All of these data can be used for reliability studies, safety analyses, design tradeoff studies, and risk assessments.

  2. Characteristics of a velvet cathode under high repetition rate pulse operation

    SciTech Connect

    Xun Tao; Zhang Jiande; Yang Hanwu; Zhang Zicheng; Fan Yuwei

    2009-10-15

    As commonly used material for cold cathodes, velvet works well in single shot and low repetition rate (rep-rate) high-power microwave (HPM) sources. In order to determine the feasibility of velvet cathodes under high rep-rate operation, a series of experiments are carried out on a high-power diode, driven by a {approx}300 kV, {approx}6 ns, {approx}100 {omega}, and 1-300 Hz rep-rate pulser, Torch 02. Characteristics of vacuum compatibility and cathode lifetime under different pulse rep-rate are focused on in this paper. Results of time-resolved pressure history, diode performance, shot-to-shot reproducibility, and velvet microstructure changes are presented. As the rep-rate increases, the equilibrium pressure grows hyperlinearly and the velvet lifetime decreases sharply. At 300 Hz, the pressure in the given diode exceeded 1 Pa, and the utility shots decreased to 2000 pulses for nonstop mode. While, until the velvet begins to degrade, the pulse-to-pulse instability of diode voltage and current is quite small, even under high rep-rate conditions. Possible reasons for the operation limits are discussed, and methods to improve the performance of a rep-rate velvet cathode are also suggested. These results may be of interest to the repetitive HPM systems with cold cathodes.

  3. Dentin bond strength after ablation using a CO2 laser operating at high pulse repetition rates

    NASA Astrophysics Data System (ADS)

    Hedayatollahnajafi, Saba; Staninec, Michal; Watanabe, Larry; Lee, Chulsung; Fried, Daniel

    2009-02-01

    Pulsed CO2 lasers show great promise for the rapid and efficient ablation of dental hard tissues. Our objective was to demonstrate that CO2 lasers operated at high repetition rates can be used for the rapid removal of dentin without excessive thermal damage and without compromising adhesion to restorative materials. Human dentin samples (3x3mm2) were rapidly ablated with a pulsed CO2 laser operating at a wavelength of 9.3-µm, pulse repetition rate of 300-Hz and an irradiation intensity of 18-J/cm2. The bond strength to composite was determined by the modified single plane shear test. There were 8 test groups each containing 10 blocks: negative control (non-irradiated non-etched), positive control (non-irradiated acid-etched), and six laser treated groups (three etched and three non-etched sets). The first and second etched and non-etched sets were ablated at a speed of 25 mm/sec and 50 mm/sec with water, respectively. The third set was also ablated at 50 mm/sec without application of water during laser irradiation. Minimal thermal damage was observed on the dentin surfaces for which water cooling was applied. Bond strengths exceeded 20 MPa for laser treated surfaces that were acid-etched after ablation (25-mm/sec: 29.9-MPa, 50-mm/sec: 21.3-MPa). The water-cooled etched laser groups all produced significantly stronger bonds than the negative control (p<0.001) and a lower bond strength than the positive control (p<0.05). These measurements demonstrate that dentin surfaces can be rapidly ablated by a CO2 lasers with minimal peripheral thermal damage. Additional studies are needed to determine if a lower bond strength than the acid-etched control samples is clinically significant where durability of these bonded restoration supersedes high bond strength.

  4. PULSE RATE DIVIDER

    DOEpatents

    McDonald, H.C. Jr.

    1962-12-18

    A compact pulse-rate divider circuit affording low impedance output and high input pulse repetition rates is described. The circuit features a single secondary emission tube having a capacitor interposed between its dynode and its control grid. An output pulse is produced at the anode of the tube each time an incoming pulse at the control grid drives the tube above cutoff and the duration of each output pulse corresponds to the charging time of the capacitor. Pulses incoming during the time the grid bias established by the discharging capacitor is sufficiently negative that the pulses are unable to drive the tube above cutoff do not produce output pulses at the anode; these pulses are lost and a dividing action is thus produced by the circuit. The time constant of the discharge path may be vanied to vary in turn the division ratio of the circuit; the time constant of the charging circuit may be varied to vary the width of the output pulses. (AEC)

  5. All about Heart Rate (Pulse)

    MedlinePlus

    ... Pressure High Blood Pressure Tools & Resources Stroke More All About Heart Rate (Pulse) Updated:Apr 19,2016 ... Sodium and Salt 3 Low Blood Pressure 4 All About Heart Rate (Pulse) 5 How to Eat ...

  6. Third-generation megahertz-rate pulse burst laser system.

    PubMed

    Thurow, Brian S; Satija, Aman; Lynch, Kyle

    2009-04-10

    The design and performance of a third-generation megahertz-rate pulse burst laser system is described. The third-generation system incorporates two distinct design changes that distinguish it from earlier-generation systems. The first is that pulse slicing is now achieved by using an economical acousto-optic modulator (AOM), and the second is the use of a variable pulse duration flashlamp driver that provides relatively uniform gain over a ~700 mus window. The use of an AOM for pulse slicing permits flexible operation such as pulse-on-demand operation with variable pulse durations ranging from 10 ns to DC. The laser described here is capable of producing a burst of laser pulses at repetition rates as high as 50 MHz and peak powers of 10 kW. Second-harmonic conversion efficiency using a type II KTP crystal is also demonstrated.

  7. Nova pulse power design and operational experience

    NASA Astrophysics Data System (ADS)

    Whitham, K.; Larson, D.; Merritt, B.; Christie, D.

    1987-01-01

    Nova is a 100 TW Nd++ solid state laser designed for experiments with laser fusion at Lawrence Livermore National Laboratory (LLNL). The pulsed power for Nova includes a 58 MJ capacitor bank driving 5336 flashlamps with millisecond pulses and subnanosecond high voltages for electro optics. This paper summarizes the pulsed power designs and the operational experience to date.

  8. Heart-rate pulse-shift detector

    NASA Technical Reports Server (NTRS)

    Anderson, M.

    1974-01-01

    Detector circuit accurately separates and counts phase-shift pulses over wide range of basic pulse-rate frequency, and also provides reasonable representation of full repetitive EKG waveform. Single telemeter implanted in small animal monitors not only body temperature but also animal movement and heart rate.

  9. Diode-pumped short pulse passively Q-switched 912 nm Nd:GdVO4/Cr:YAG laser at high repetition rate operation

    NASA Astrophysics Data System (ADS)

    Chen, F.; Yu, X.; Wang, C.; Yan, R. P.; Li, X. D.; Gao, J.; Zhang, Z. H.; Yu, J. H.

    2010-06-01

    A diode-end-pumped passively Q-switched 912 nm Nd:GdVO4/Cr:YAG laser is demonstrated for the first time. In a concave-piano cavity, pulsed 912 nm laser performance is investigated using two kinds of Cr:YAG crystal with different unsaturated transmission ( T U) of 95% and 90% at 912 nm as the saturable absorbers. When the T U = 90% Cr:YAG is used, as much as 2.6 W average output power for short pulsed 912 nm laser is achieved at an absorbed pump power of 34.0 W, corresponding to an optical efficiency of 7.6% and a slope efficiency of 20.3%. Moreover, 10.5 ns duration pulses and up to 2.3 kW peak power is obtained at the repetition rate around 81.6 kHz.

  10. Note: Emittance measurements of intense pulsed proton beam for different pulse length and repetition rate

    SciTech Connect

    Miracoli, R.; Gammino, S.; Celona, L.; Mascali, D.; Castro, G.; Gobin, R.; Delferriere, O.; Adroit, G.; Senee, F.; Ciavola, G.

    2012-05-15

    The high intensity ion source (SILHI), in operation at CEA-Saclay, has been used to produce a 90 mA pulsed proton beam with pulse length and repetition rates suitable for the European Spallation Source (ESS) linac. Typical r-r{sup '} rms normalized emittance values smaller than 0.2{pi} mm mrad have been measured for operation in pulsed mode (0.01 < duty cycle < 0.15 and 1 ms < pulse duration < 10 ms) that are relevant for the design update of the Linac to be used at the ESS in Lund.

  11. Stably operating pulse combustor and method

    DOEpatents

    Zinn, B.T.; Reiner, D.

    1990-05-29

    A pulse combustor apparatus is described which is adapted to burn either a liquid fuel or a pulverized solid fuel within a preselected volume of the combustion chamber. The combustion process is substantially restricted to an optimum combustion zone in order to attain effective pulse combustion operation. 4 figs.

  12. Stably operating pulse combustor and method

    DOEpatents

    Zinn, Ben T.; Reiner, David

    1990-01-01

    A pulse combustor apparatus adapted to burn either a liquid fuel or a pulverized solid fuel within a preselected volume of the combustion chamber. The combustion process is substantially restricted to an optimum combustion zone in order to attain effective pulse combustion operation.

  13. High Rate Pulse Processing Algorithms for Microcalorimeters

    NASA Astrophysics Data System (ADS)

    Tan, Hui; Breus, Dimitry; Hennig, Wolfgang; Sabourov, Konstantin; Collins, Jeffrey W.; Warburton, William K.; Bertrand Doriese, W.; Ullom, Joel N.; Bacrania, Minesh K.; Hoover, Andrew S.; Rabin, Michael W.

    2009-12-01

    It has been demonstrated that microcalorimeter spectrometers based on superconducting transition-edge-sensors can readily achieve sub-100 eV energy resolution near 100 keV. However, the active volume of a single microcalorimeter has to be small in order to maintain good energy resolution, and pulse decay times are normally on the order of milliseconds due to slow thermal relaxation. Therefore, spectrometers are typically built with an array of microcalorimeters to increase detection efficiency and count rate. For large arrays, however, as much pulse processing as possible must be performed at the front end of readout electronics to avoid transferring large amounts of waveform data to a host computer for post-processing. In this paper, we present digital filtering algorithms for processing microcalorimeter pulses in real time at high count rates. The goal for these algorithms, which are being implemented in readout electronics that we are also currently developing, is to achieve sufficiently good energy resolution for most applications while being: a) simple enough to be implemented in the readout electronics; and, b) capable of processing overlapping pulses, and thus achieving much higher output count rates than those achieved by existing algorithms. Details of our algorithms are presented, and their performance is compared to that of the "optimal filter" that is currently the predominantly used pulse processing algorithm in the cryogenic-detector community.

  14. Recycle Rate in a Pulsed, Optically Pumped Rubidium Laser

    SciTech Connect

    Miller, Wooddy S.; Sulham, Clifford V.; Holtgrave, Jeremy C.; Perram, Glen P.

    2010-10-08

    A pulsed, optically pumped rubidium laser operating in analogy to the diode pumped alkali laser (DPAL) system at pump intensities as high as 750 kW/cm{sup 2} has been demonstrated with output energies of up to 13 {mu}J/pulse. Output energy is dramatically limited by spin-orbit relaxation rates under these high intensity pump conditions. More than 250 photons are available for every rubidium atom in the pumped volume, requiring a high number of cycles per atom during the 2-8 ns duration of the pump pulse. At 550 Torr of ethane, the spin-orbit relaxation rate is too slow to effectively utilize all the incident pump photons. Indeed, a linear dependence of output energy on pump pulse duration for fixed pump energy is demonstrated.

  15. An Experiment on Repetitive Pulse Operation of Microwave Rocket

    SciTech Connect

    Oda, Yasuhisa; Shibata, Teppei; Komurasaki, Kimiya; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi

    2008-04-28

    Microwave Rocket was operated with repetitive pulses. The microwave rocket model with forced breathing system was used. The pressure history in the thruster was measured and the thrust impulse was deduced. As a result, the impulse decreased at second pulse and impulses at latter pulses were constant. The dependence of the thrust performance on the partial filling rate of the thruster was compared to the thrust generation model based on the shock wave driven by microwave plasma. The experimental results showed good agreement to the predicted dependency.

  16. Pulse transducer with artifact signal attenuator. [heart rate sensors

    NASA Technical Reports Server (NTRS)

    Cash, W. H., Jr.; Polhemus, J. T. (Inventor)

    1980-01-01

    An artifact signal attenuator for a pulse rate sensor is described. The circuit for attenuating background noise signals is connected with a pulse rate transducer which has a light source and a detector for light reflected from blood vessels of a living body. The heart signal provided consists of a modulated dc signal voltage indicative of pulse rate. The artifact signal resulting from light reflected from the skin of the body comprises both a constant dc signal voltage and a modulated dc signal voltage. The amplitude of the artifact signal is greater and the frequency less than that of the heart signal. The signal attenuator circuit includes an operational amplifier for canceling the artifact signal from the output signal of the transducer and has the capability of meeting packaging requirements for wrist-watch-size packages.

  17. Comparative investigation of three dose rate meters for their viability in pulsed radiation fields.

    PubMed

    Gotz, M; Karsch, L; Pawelke, J

    2015-06-01

    Pulsed radiation fields, characterized by microsecond pulse duration and correspondingly high pulse dose rates, are increasingly used in therapeutic, diagnostic and research applications. Yet, dose rate meters which are used to monitor radiation protection areas or to inspect radiation shielding are mostly designed, characterized and tested for continuous fields and show severe deficiencies in highly pulsed fields. Despite general awareness of the problem, knowledge of the specific limitations of individual instruments is very limited, complicating reliable measurements. We present here the results of testing three commercial dose rate meters, the RamION ionization chamber, the LB 1236-H proportional counter and the 6150AD-b scintillation counter, for their response in pulsed radiation fields of varied pulse dose and duration. Of these three the RamION proved reliable, operating in a pulsed radiation field within its specifications, while the other two instruments were only able to measure very limited pulse doses and pulse dose rates reliably. PMID:25978117

  18. Count rate limitations in pulsed accelerator fields

    SciTech Connect

    Justus, Alan L

    2010-12-15

    This paper discusses various concepts involved in the counting losses of pulse-counting health physics instrumentation when used within the pulsed radiation environments of typical accelerator fields, in order to pre-establish appropriate limitations in use. Discussed are the 'narrow' pulse and the 'wide' pulse cases, the special effect of neutron moderating assemblies, and the effect of pulse microstructure on the counting losses of the pulse-counting instrumentation. Examples are provided which highlight the various concepts and limitations.

  19. Modeling of Multi-Tube Pulse Detonation Engine Operation

    NASA Technical Reports Server (NTRS)

    Ebrahimi, Houshang B.; Mohanraj, Rajendran; Merkle, Charles L.

    2001-01-01

    The present paper explores some preliminary issues concerning the operational characteristics of multiple-tube pulsed detonation engines (PDEs). The study is based on a two-dimensional analysis of the first-pulse operation of two detonation tubes exhausting through a common nozzle. Computations are first performed to assess isolated tube behavior followed by results for multi-tube flow phenomena. The computations are based on an eight-species, finite-rate transient flow-field model. The results serve as an important precursor to understanding appropriate propellant fill procedures and shock wave propagation in multi-tube, multi-dimensional simulations. Differences in behavior between single and multi-tube PDE models are discussed, The influence of multi-tube geometry and the preferred times for injecting the fresh propellant mixture during multi-tube PDE operation are studied.

  20. Acousto-optic pulse picking scheme with carrier-frequency-to-pulse-repetition-rate synchronization.

    PubMed

    de Vries, Oliver; Saule, Tobias; Plötner, Marco; Lücking, Fabian; Eidam, Tino; Hoffmann, Armin; Klenke, Arno; Hädrich, Steffen; Limpert, Jens; Holzberger, Simon; Schreiber, Thomas; Eberhardt, Ramona; Pupeza, Ioachim; Tünnermann, Andreas

    2015-07-27

    We introduce and experimentally validate a pulse picking technique based on a travelling-wave-type acousto-optic modulator (AOM) having the AOM carrier frequency synchronized to the repetition rate of the original pulse train. As a consequence, the phase noise characteristic of the original pulse train is largely preserved, rendering this technique suitable for applications requiring carrier-envelope phase stabilization. In a proof-of-principle experiment, the 1030-nm spectral part of an 74-MHz, carrier-envelope phase stable Ti:sapphire oscillator is amplified and reduced in pulse repetition frequency by a factor of two, maintaining an unprecedentedly low carrier-envelope phase noise spectral density of below 68 mrad. Furthermore, a comparative analysis reveals that the pulse-picking-induced additional amplitude noise is minimized, when the AOM is operated under synchronicity. The proposed scheme is particularly suitable when the down-picked repetition rate is still in the multi-MHz-range, where Pockels cells cannot be applied due to piezoelectric ringing. PMID:26367616

  1. Pulse Rate Research: Students Follow the Steps of Inquiry To Compare Carotid and Artery Pulse Rates.

    ERIC Educational Resources Information Center

    Landsman, Robert E.

    2002-01-01

    Presents an inquiry-based science activity on pulse rate. Includes observations; developing a research question; constructing the hypothesis; designing the study; collecting, summarizing, and analyzing data; and interpretation stages in the activity. Presents information on how to use standards and benchmarks in this activity. (YDS)

  2. Properties of water surface discharge at different pulse repetition rates

    SciTech Connect

    Ruma,; Yoshihara, K.; Hosseini, S. H. R. Sakugawa, T.; Akiyama, H.; Akiyama, M.; Lukeš, P.

    2014-09-28

    The properties of water surface discharge plasma for variety of pulse repetition rates are investigated. A magnetic pulse compression (MPC) pulsed power modulator able to deliver pulse repetition rates up to 1000 Hz, with 0.5 J per pulse energy output at 25 kV, was used as the pulsed power source. Positive pulse with a point-to-plane electrode configuration was used for the experiments. The concentration and production yield of hydrogen peroxide (H₂O₂) were quantitatively measured and orange II organic dye was treated, to evaluate the chemical properties of the discharge reactor. Experimental results show that the physical and chemical properties of water surface discharge are not influenced by pulse repetition rate, very different from those observed for under water discharge. The production yield of H₂O₂ and degradation rate per pulse of the dye did not significantly vary at different pulse repetition rates under a constant discharge mode on water surface. In addition, the solution temperature, pH, and conductivity for both water surface and underwater discharge reactors were measured to compare their plasma properties for different pulse repetition rates. The results confirm that surface discharge can be employed at high pulse repetition rates as a reliable and advantageous method for industrial and environmental decontamination applications.

  3. Assessment of pulse rate variability by the method of pulse frequency demodulation

    PubMed Central

    Hayano, Junichiro; Barros, Allan Kardec; Kamiya, Atsunori; Ohte, Nobuyuki; Yasuma, Fumihiko

    2005-01-01

    Background Due to its easy applicability, pulse wave has been proposed as a surrogate of electrocardiogram (ECG) for the analysis of heart rate variability (HRV). However, its smoother waveform precludes accurate measurement of pulse-to-pulse interval by fiducial-point algorithms. Here we report a pulse frequency demodulation (PFDM) technique as a method for extracting instantaneous pulse rate function directly from pulse wave signal and its usefulness for assessing pulse rate variability (PRV). Methods Simulated pulse wave signals with known pulse interval functions and actual pulse wave signals obtained from 30 subjects with a trans-dermal pulse wave device were analyzed by PFDM. The results were compared with heart rate and HRV assessed from simultaneously recorded ECG. Results Analysis of simulated data revealed that the PFDM faithfully demodulates source interval function with preserving the frequency characteristics of the function, even when the intervals fluctuate rapidly over a wide range and when the signals include fluctuations in pulse height and baseline. Analysis of actual data revealed that individual means of low and high frequency components of PRV showed good agreement with those of HRV (intraclass correlation coefficient, 0.997 and 0.981, respectively). Conclusion The PFDM of pulse wave signal provides a reliable assessment of PRV. Given the popularity of pulse wave equipments, PFDM may open new ways to the studies of long-term assessment of cardiovascular variability and dynamics. PMID:16259639

  4. Working group summary report on effects of pulsed operation

    SciTech Connect

    Gabriel, T.A.; Ni, L.

    1996-06-01

    In a short pulsed spallation neutron source, extremely high energy ({approx_gt}1 GeV) proton beam pulses are injected into a liquid metal target in a very short period of time ({approximately}1 {mu}sec) at a high repetition rate ({approximately}50 Hertz). The beam energy will be deposited in the target materials (such as mercury or lead) and converted into heat. It causes a sudden temperature rise and resulting pressure wave. This pressure wave travels through the liquid, reaches the steel container wall and may possibly lead to material damage due to induced stress. Almost all participants agreed that the shock problem due to the short pulse operation in the liquid metal target could be serious and could present a challenging problem. It was determined that the following points need to be addressed: (1) equation of state for mercury (2) code validation and benchmark experiments (3) shock effects on the entire target system (4) two phase flow by gas injection. All these investigations should be carried out in the framework of international cooperation. Two small scaled Hg pressure pulse tests are planned at ORNL to provide insight into the pressure wave propagation and thermal shock effects. One experiment will use exploding wires to generate the pulse pressure, the other the electron beam at ORELA. Also PSI, LANL, CERN (ISOLDE facility), INR and IPPE could contribute to the experimental methods for producing shock. The necessary R&D for bubble injection might be performed at PSI, RIGA, ORNL or Ben-Gurion University. All of the above experiments can possibly yield benchmarking data which is absolutely necessary for code validation.

  5. Recouping etch rates in pulsed inductively coupled plasmas

    SciTech Connect

    Agarwal, Ankur; Stout, Phillip J.; Banna, Samer; Rauf, Shahid; Collins, Ken

    2011-01-15

    Pulsed rf plasmas are increasingly being employed for plasma etching at future technological nodes. Although the plasma uniformity usually improves with pulsing, the lower time-averaged power decreases the etch rate and the lower throughput is undesirable. It is therefore important to evaluate different strategies to restore higher etch rates while retaining the advantages of pulsed plasmas. In this work, the impact of varying pulsing modes in an inductively coupled plasma on plasma characteristics and feature profile evolution are discussed using the results from a two-dimensional reactor scale plasma model coupled to a Monte Carlo based feature profile model. Results are discussed for poly-Si etching in an Ar/Cl{sub 2} gas mixture. The consequences of source-only and bias-only pulsing modes on discharge characteristics, ion energy distributions (IEDs) to the wafer, and feature profile evolution are discussed. Although the etch depth rates were found to be higher for source-only pulsing compared to the synchronized (source and bias) pulsing mode, the higher ion energies in the afterglow period during source-only pulsing may also increase ion bombardment damage. Compensation of power may allow for increased etch depth rates while retaining the benefits of synchronized pulsing. Further, power compensation level can be varied to achieve fine tuning of the IEDs to the wafer.

  6. Pen harvester for powering a pulse rate sensor

    NASA Astrophysics Data System (ADS)

    Bedekar, Vishwas; Oliver, Josiah; Priya, Shashank

    2009-05-01

    Rapid developments in the area of micro-sensors for various applications such as structural health monitoring, bio-chemical sensors and pressure sensors have increased the demand for portable, low cost, high efficiency energy harvesting devices. In this paper, we describe the scheme for powering a pulse rate sensor with a vibration energy harvester integrated inside a pen commonly carried by humans in the pocket close to the heart. Electromagnetic energy harvesting was selected in order to achieve high power at lower frequencies. The prototype pen harvester was found to generate 3 mW at 5 Hz and 1 mW at 3.5 Hz operating under displacement amplitude of 16 mm (corresponding to an acceleration of approximately 1.14 grms at 5 Hz and 0.56 grms at 3.5 Hz, respectively). A comprehensive mathematical modelling and simulations were performed in order to optimize the performance of the vibration energy harvester. The integrated pen harvester prototype was found to generate continuous power of 0.46-0.66 mW under normal human actions such as jogging and jumping which is enough for a small scale pulse rate sensor.

  7. Radiation measuring apparatus employing variable rate pulse sampling control

    SciTech Connect

    Kakegawa, M.; Kumano, N.; Nohara, N.; Tanaka, E.; Tomitani, T.

    1980-01-29

    A scintillation type radiation-measuring apparatus comprising a radiation-detecting scintillator is described. A scintillation given off from the scintillator is converted into current by a photomultiplier tube. A current amplifier generates a plurality of pulses each proportional to the intensity of said converted current. The pulses have the width clipped by a clipped pulse generating circuit. The clipped form of the pulses is delayed by a delay circuit and integrated by an integrator; the wave height value of the outputs from the integrator is sampled by a sampling circuit to provide a sampled output. Means are provided to supply instructions to start and reset the operation of the integrator and to commence the operation of the sampling circuit in accordance with the interval between successively detected current pulses.

  8. Widely tunable repetition-rate and pulse-duration nanosecond pulses from two spectral beam combined fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Hu, Man; Zheng, Ye; Yang, Yifeng; Chen, Xiaolong; Zhao, Chun; Liu, Kai; Wang, Jianhua; Qi, Yunfeng; He, Bing; Zhou, Jun

    2016-10-01

    Nanosecond pulses with a widely tunable repetition-rate and pulse-duration at 1 μm wavelength are obtained by spectrally combining two pulse fiber amplifiers using a home-made polarization-independent multilayer dielectric reflective diffraction grating. The width of the combined pulses can be tuned from 4 ns to 800 ns, and the pulse repetition-rate can be ranged from 1 MHz to 200 MHz. Thanks to the spectral beam combining system, the maximum repetition-rate and pulse-duration of the combined pulses are doubled, compared to the single pulse fiber amplifier, by setting a proper temporal delay between the two pulse channels.

  9. Cryogenic pellet production developments for long-pulse plasma operation

    NASA Astrophysics Data System (ADS)

    Meitner, S. J.; Baylor, L. R.; Combs, S. K.; Fehling, D. T.; McGill, J. M.; Duckworth, R. C.; McGinnis, W. D.; Rasmussen, D. A.

    2014-01-01

    Long pulse plasma operation on large magnetic fusion devices require multiple forms of cryogenically formed pellets for plasma fueling, on-demand edge localized mode (ELM) triggering, radiative cooling of the divertor, and impurity transport studies. The solid deuterium fueling and ELM triggering pellets can be formed by extrusions created by helium cooled, twin-screw extruder based injection system that freezes deuterium in the screw section. A solenoid actuated cutter mechanism is activated to cut the pellets from the extrusion, inserting them into the barrel, and then fired by the pneumatic valve pulse of high pressure gas. Fuel pellets are injected at a rate up to 10 Hz, and ELM triggering pellets are injected at rates up to 20 Hz. The radiative cooling and impurity transport study pellets are produced by introducing impurity gas into a helium cooled section of a pipe gun where it deposits in-situ. A pneumatic valve is opened and propellant gas is released downstream where it encounters a passive punch which initially accelerates the pellet before the gas flow around the finishes the pellet acceleration. This paper discusses the various cryogenic pellet production techniques based on the twin-screw extruder, pipe gun, and pellet punch designs.

  10. Cryogenic pellet production developments for long-pulse plasma operation

    SciTech Connect

    Meitner, S. J.; Baylor, L. R.; Combs, S. K.; Fehling, D. T.; McGill, J. M.; Duckworth, R. C.; McGinnis, W. D.; Rasmussen, D. A.

    2014-01-29

    Long pulse plasma operation on large magnetic fusion devices require multiple forms of cryogenically formed pellets for plasma fueling, on-demand edge localized mode (ELM) triggering, radiative cooling of the divertor, and impurity transport studies. The solid deuterium fueling and ELM triggering pellets can be formed by extrusions created by helium cooled, twin-screw extruder based injection system that freezes deuterium in the screw section. A solenoid actuated cutter mechanism is activated to cut the pellets from the extrusion, inserting them into the barrel, and then fired by the pneumatic valve pulse of high pressure gas. Fuel pellets are injected at a rate up to 10 Hz, and ELM triggering pellets are injected at rates up to 20 Hz. The radiative cooling and impurity transport study pellets are produced by introducing impurity gas into a helium cooled section of a pipe gun where it deposits in-situ. A pneumatic valve is opened and propellant gas is released downstream where it encounters a passive punch which initially accelerates the pellet before the gas flow around the finishes the pellet acceleration. This paper discusses the various cryogenic pellet production techniques based on the twin-screw extruder, pipe gun, and pellet punch designs.

  11. Innovative phase shifter for pulse tube operating below 10 K

    NASA Astrophysics Data System (ADS)

    Duval, Jean-Marc; Charles, Ivan; Daniel, Christophe; André, Jérôme

    2016-09-01

    Stirling type pulse tubes are classically based on the use of an inertance phase shifter to optimize their cooling power. The limitations of the phase shifting capabilities of these inertances have been pointed out in various studies. These limitations are particularly critical for low temperature operation, typically below about 50 K. An innovative phase shifter using an inertance tube filled with liquid, or fluid with high density or low viscosity, and separated by a sealed metallic diaphragm has been conceived and tested. This device has been characterized and validated on a dedicated test bench. Operation on a 50-80 K pulse tube cooler and on a low temperature (below 8 K) pulse tube cooler have been demonstrated and have validated the device in operation. These developments open the door for efficient and compact low temperature Stirling type pulse tube coolers. The possibility of long life operation has been experimentally verified and a design for space applications is proposed.

  12. Performance scaling of inductive pulsed plasma thrusters with coil angle and pulse rate

    NASA Astrophysics Data System (ADS)

    Martin, A. K.

    2016-01-01

    A circuit model for an inductive pulsed plasma thruster was developed in order to investigate the performance of thrusters with conical coils; the model can accommodate cone-angles from 0° (a straight theta-pinch coil) to 90° (a planar coil). The plasma is treated as a deformable slug that moves both radially and axially in response to the force applied by the coil. The radial equation of motion includes a restoring force due to the plasma pressure, which is derived under the assumption that the electron population is isothermal, while the ions are isothermal, adiabatic, or shock-heated depending on the magnitude and sign of the radial velocity. The inductance of the coil and the plasma slug, and their mutual inductance, was determined using QuickField. A local maximum in efficiency and specific impulse was found for angles less than 90° however the absolute maximum for both these quantities occurs at 90°. High pulse-rate operation was found to yield dynamic efficiencies (excluding ionization cost) as high as 60-70% for I SP in the range of 3000-5000 s, even for a device with modest jet-power (5 kW). This mode of operation also permits elimination of the pulsed gas valve, which would be a significant system-level simplification. An alternate mode of inductive recapture, in which the current is interrupted at the second zero-crossing, was found to result in a sacrifice of only 1-2% in efficiency, while offering other significant system-level benefits for this kind of thruster.

  13. Study of potassium DPAL operation in pulsed and CW mode

    NASA Astrophysics Data System (ADS)

    Zhdanov, Boris V.; Rotondaro, Matthew D.; Schaffer, Michael K.; Knize, Randall J.

    2014-10-01

    This paper presents the results of our experiments on development of the efficient hydrocarbon free Diode Pumped Alkali Laser based on potassium vapor buffered by He gas at 600 Torr. We studied the performance of this laser operating in pulsed mode with pulses up to 5 ms long at different pulse energies and cell temperatures. A slope efficiency of more than 50% was demonstrated with total optical efficiency about 30% for the pump pulses with duration about 30 μs. For the longer pump pulses the DPAL efficiency degraded in time with a characteristic time in the range from 0.5 ms to 4.5 ms depending on the pump pulse energy and cell temperature. The recorded spectrum of the side fluorescence indicates that multi-photon excitation, energy pooling collisions and ionization may be strong candidates for explaining the observed performance degradation.

  14. Plant N capture from pulses: effects of pulse size, growth rate, and other soil resources.

    PubMed

    James, J J; Richards, J H

    2005-08-01

    In arid ecosystems, the ability to rapidly capture nitrogen (N) from brief pulses is expected to influence plant growth, survival, and competitive ability. Theory and data suggest that N capture from pulses should depend on plant growth rate and availability of other limiting resources. Theory also predicts trade-offs in plant stress tolerance and ability to capture N from different size pulses. We injected K15NO3, to simulate small and large N pulses at three different times during the growing season into soil around the co-dominant Great Basin species Sarcobatus vermiculatus, Chrysothamnus nauseosus ssp. consimilis, and Distichlis spicata. Soils were amended with water and P in a partial factorial design. As predicted, all study species showed a comparable decline in N capture from large pulses through the season as growth rates slowed. Surprisingly, however, water and P availability differentially influenced the ability of these species to capture N from pulses. Distichlis N capture increased up to tenfold with water addition while Chrysothamnus N capture increased up to threefold with P addition. Sarcobatus N capture was not affected by water or P availability. Opposite to our prediction, Sarcobatus, the most stress tolerant species, captured less N from small pulses but more N from large pulses relative to the other species. These observations suggest that variation in N pulse timing and size can interact with variable soil water and P supply to determine how N is partitioned among co-existing Great Basin species.

  15. SETI Pulse Detection Algorithm: Analysis of False-alarm Rates

    NASA Technical Reports Server (NTRS)

    Levitt, B. K.

    1983-01-01

    Some earlier work by the Search for Extraterrestrial Intelligence (SETI) Science Working Group (SWG) on the derivation of spectrum analyzer thresholds for a pulse detection algorithm based on an analysis of false alarm rates is extended. The algorithm previously analyzed was intended to detect a finite sequence of i periodically spaced pulses that did not necessarily occupy the entire observation interval. This algorithm would recognize the presence of such a signal only if all i-received pulse powers exceeded a threshold T(i): these thresholds were selected to achieve a desired false alarm rate, independent of i. To simplify the analysis, it was assumed that the pulses were synchronous with the spectrum sample times. This analysis extends the earlier effort to include infinite and/or asynchronous pulse trains. Furthermore, to decrease the possibility of missing an extraterrestrial intelligence signal, the algorithm was modified to detect a pulse train even if some of the received pulse powers fall below the threshold. The analysis employs geometrical arguments that make it conceptually easy to incorporate boundary conditions imposed on the derivation of the false alarm rates. While the exact results can be somewhat complex, simple closed form approximations are derived that produce a negligible loss of accuracy.

  16. Pulsed interrupter and method of operation

    DOEpatents

    Drake, Joel Lawton; Kratz, Robert

    2015-06-09

    Some embodiments provide interrupter systems comprising: a first electrode; a second electrode; a piston movably located at a first position and electrically coupled with the first and second electrodes establishing a closed state, the piston comprises an electrical conductor that couples with the first and second electrodes providing a conductive path; an electromagnetic launcher configured to, when activated, induce a magnetic field pulse causing the piston to move away from the electrical coupling with the first and second electrodes establishing an open circuit between the first and second electrodes; and a piston control system comprising a piston arresting system configured to control a deceleration of the piston following the movement of the piston induced by the electromagnetic launcher such that the piston is not in electrical contact with at least one of the first electrode and the second electrode when in the open state.

  17. A long-pulse repetitive operation magnetically insulated transmission line oscillator

    SciTech Connect

    Fan, Yu-Wei; Zhong, Hui-Huang; Zhang, Jian-De; Shu, Ting; Liu, Jin Liang

    2014-05-15

    The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube. It has allowed us to generate 3.1 GW pulse of 40 ns duration in the single-pulse operation and 500 MW pulse of 25 ns duration in the repetition rate operation. However, because of the severe impedance mismatch, the power conversion efficiency is only about 4% in the repetition rate operation. In order to eliminate the impedance mismatch and obtain repetitive long-pulse high-power microwave (HPM), a series of experiments are carried out and the recent progress is presented in this paper. In the single-pulse operation, when the diode voltage is 466 kV and current is 41.6 kA, the radiated microwave power is above 2.2 GW, the pulse duration is above 102 ns, the microwave frequency is about 1.74 GHz, and the power conversion efficiency is about 11.5%. In the repetition rate operation, under the condition of the diode voltage about 400 kV, beam current about 38 kA, the radiated microwave power is about 1.0 GW, the pulse duration is about 85 ns. Moreover, the radiated microwave power and the pulse duration decline little by little when the shot numbers increase gradually. The experimental results show that the impedance matching is a vital factor for HPM systems and one of the major technical challenges is to improve the cathode for the repetition rate operation MILO.

  18. A long-pulse repetitive operation magnetically insulated transmission line oscillator.

    PubMed

    Fan, Yu-Wei; Zhong, Hui-Huang; Zhang, Jian-De; Shu, Ting; Liu, Jin Liang

    2014-05-01

    The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube. It has allowed us to generate 3.1 GW pulse of 40 ns duration in the single-pulse operation and 500 MW pulse of 25 ns duration in the repetition rate operation. However, because of the severe impedance mismatch, the power conversion efficiency is only about 4% in the repetition rate operation. In order to eliminate the impedance mismatch and obtain repetitive long-pulse high-power microwave (HPM), a series of experiments are carried out and the recent progress is presented in this paper. In the single-pulse operation, when the diode voltage is 466 kV and current is 41.6 kA, the radiated microwave power is above 2.2 GW, the pulse duration is above 102 ns, the microwave frequency is about 1.74 GHz, and the power conversion efficiency is about 11.5%. In the repetition rate operation, under the condition of the diode voltage about 400 kV, beam current about 38 kA, the radiated microwave power is about 1.0 GW, the pulse duration is about 85 ns. Moreover, the radiated microwave power and the pulse duration decline little by little when the shot numbers increase gradually. The experimental results show that the impedance matching is a vital factor for HPM systems and one of the major technical challenges is to improve the cathode for the repetition rate operation MILO.

  19. High-gradient, pulsed operation of superconducting niobium cavities

    SciTech Connect

    Campisi, I.E.; Farkas, Z.D.

    1984-02-01

    Tests performed on several Niobium TM/sub 010/ cavities at frequencies of about 2856 MHz using a high-power, pulsed method indicate that, at the end of the charging pulse, peak surface magnetic fields of up to approx. 1300 Oe, corresponding to a peak surface electric field of approx. 68 MV/m, can be reached at 4.2/sup 0/K without appreciable average losses. Further studies of the properties of superconductors under pulsed operation might shed light on fundamental properties of rf superconductivity, as well as lead to the possibility of applying the pulse method to the operation of high-gradient linear colliders. 7 references, 30 figures, 2 tables.

  20. Ultrashort pulse high repetition rate laser system for biological tissue processing

    DOEpatents

    Neev, Joseph; Da Silva, Luiz B.; Matthews, Dennis L.; Glinsky, Michael E.; Stuart, Brent C.; Perry, Michael D.; Feit, Michael D.; Rubenchik, Alexander M.

    1998-01-01

    A method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment.

  1. Ultrashort pulse high repetition rate laser system for biological tissue processing

    DOEpatents

    Neev, J.; Da Silva, L.B.; Matthews, D.L.; Glinsky, M.E.; Stuart, B.C.; Perry, M.D.; Feit, M.D.; Rubenchik, A.M.

    1998-02-24

    A method and apparatus are disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment. 8 figs.

  2. Rotation Operator Propagators for Time-varying Radiofrequency Pulses in NMR Spectroscopy: Applications to Shaped Pulses and Pulse Trains

    PubMed Central

    Li, Ying; Rance, Mark; Palmer, Arthur G.

    2014-01-01

    The propagator for trains of radiofrequency pulses can be directly integrated numerically or approximated by average Hamiltonian approaches. The former provides high accuracy and the latter, in favorable cases, convenient analytical formula. The Euler-angle rotation operator factorization of the propagator provides insights into performance that are not as easily discerned from either of these conventional techniques. This approach is useful in determining whether a shaped pulse can be represented over some bandwidth by a sequence τ1—Rϕ(β)—τ2, in which Rϕ(β) is a rotation by an angle β around an axis with phase ϕ in the transverse plane and τ1 and τ2 are time delays, allowing phase evolution during the pulse to be compensated by adjusting time periods prior or subsequent to the pulse. Perturbation theory establishes explicit formulas for τ1 and τ2 as proportional to the average transverse magnetization generated during the shaped pulse. The Euler-angle representation of the propagator also is useful in iterative reduction of pulse-interrupted-free precession schemes. Application to Carr-Purcell-Meiboom-Gill sequences identifies an eight-pulse phase-alternating scheme that generates a propagator nearly equal to the identity operator. PMID:25442779

  3. Improvement in the statistical operation of a Blumlein pulse forming line in bipolar pulse mode

    SciTech Connect

    Pushkarev, A. I. Isakova, Y. I.; Khaylov, I. P.

    2014-07-15

    The paper presents the results of studies on shot-to-shot performance of a water Blumlein pulse forming line of 1–1.2 kJ of stored energy. The experiments were carried using the TEMP-4M pulsed ion beam accelerator during its operation in both unipolar pulse mode (150 ns, 250–300 kV) and bipolar-pulse mode with the first negative (300–600 ns, 100–150 kV) followed by a second positive (120 ns, 250–300 kV) pulse. The analysis was carried out for two cases when the Blumlein was terminated with a resistive load and with a self-magnetically insulated ion diode. It was found that in bipolar pulse mode the shot-to-shot variation in breakdown voltage of a preliminary spark gap is small, the standard deviation (1σ) does not exceed 2%. At the same time, the shot-to-shot variation in the breakdown voltage of the main spark gap in both bipolar-pulse and unipolar pulse mode is 3–4 times higher than that for the preliminary spark gap. To improve the statistical performance of the main spark gap we changed the regime of its operation from a self-triggered mode to an externally triggered mode. In the new arrangement the first voltage pulse at the output of Blumlein was used to trigger the main spark gap. The new trigatron-type regime of the main spark gap operation showed a good stability of breakdown voltage and thus allowed to stabilize the duration of the first pulse. The standard deviation of the breakdown voltage and duration of the first pulse did not exceed 2% for a set of 50 pulses. The externally triggered mode of the main gap operation also allowed for a decrease in the charging voltage of the Blumlein to a 0.9–0.95 of self-breakdown voltage of the main spark gap while the energy stored in Marx generator was decreased from 4 kJ to 2.5 kJ. At the same time the energy stored in Blumlein remained the same.

  4. Influence of design and operation parameters on bag-cleaning performance of pulse-jet baghouse

    SciTech Connect

    Lu, H.C.; Tsai, C.J.

    1999-06-01

    In this study, a filter test system with clean new fabric bags was used to measure the pulse pressure and acceleration of the filter bag. Fabric acceleration and pulse pressure were used as an index of bag-cleaning intensity. The jet pump curves, which relate the flow rate through the venturi to the average developed pressure by the venturi, were determined by the similar system. The intersection of the jet pump curve and the bag operating line, which relates the pressure drop to flow rate across the bag during pulse-jet cleaning, is the system operating point that was used to predict the average pulse pressure can be achieved without the venturi at the top of the bag for bag materials with low resistance coefficient. For bags with higher resistance coefficients, higher pulse pressure is obtained with a venturi installed at the top of the bag. The predicted pressure values are in good agreement with experimental data. Dimensional analysis for jet pump performance was developed to reduce the experimental data. The results show that the jet pump curves obtained under different operating conditions can be reduced to the same nondimensional curve, which can be used to facilitate the design and operation of a pulse-jet cleaning system.

  5. Dose rate effect on micronuclei induction in human blood lymphocytes exposed to single pulse and multiple pulses of electrons.

    PubMed

    Acharya, Santhosh; Bhat, N N; Joseph, Praveen; Sanjeev, Ganesh; Sreedevi, B; Narayana, Y

    2011-05-01

    The effects of single pulses and multiple pulses of 7 MV electrons on micronuclei (MN) induction in cytokinesis-blocked human peripheral blood lymphocytes (PBLs) were investigated over a wide range of dose rates per pulse (instantaneous dose rate). PBLs were exposed to graded doses of 2, 3, 4, 6, and 8 Gy of single electron pulses of varying pulse widths at different dose rates per pulse, ranging from 1 × 10(6) Gy s(-1) to 3.2 × 10(8) Gy s(-1). Different dose rates per pulse were achieved by changing the dose per electron pulse by adjusting the beam current and pulse width. MN yields per unit absorbed dose after irradiation with single electron pulses were compared with those of multiple pulses of electrons. A significant decrease in the MN yield with increasing dose rates per pulse was observed, when dose was delivered by a single electron pulse. However, no reduction in the MN yield was observed when dose was delivered by multiple pulses of electrons. The decrease in the yield at high dose rates per pulse suggests possible radical recombination, which leads to decreased biological damage. Cellular response to the presence of very large numbers of chromosomal breaks may also alter the damage.

  6. Dose rate in brachytherapy using after-loading machine: pulsed or high-dose rate?

    PubMed

    Hannoun-Lévi, J-M; Peiffert, D

    2014-10-01

    Since February 2014, it is no longer possible to use low-dose rate 192 iridium wires due to the end of industrial production of IRF1 and IRF2 sources. The Brachytherapy Group of the French society of radiation oncology (GC-SFRO) has recommended switching from iridium wires to after-loading machines. Two types of after-loading machines are currently available, based on the dose rate used: pulsed-dose rate or high-dose rate. In this article, we propose a comparative analysis between pulsed-dose rate and high-dose rate brachytherapy, based on biological, technological, organizational and financial considerations.

  7. Pulse

    MedlinePlus

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

  8. VARIABLE FIRING RATE OIL BURNER USING PULSE FUEL FLOW CONTROL.

    SciTech Connect

    KRISHNA,C.R.; BUTCHER,T.A.; KAMATH,B.R.

    2004-10-01

    problem is to develop a burner, which can operate at two firing rates, with the lower rate being significantly lower than 0.5 gallons per hour. This paper describes the initial results of adopting this approach through a pulsed flow nozzle. It has been shown that the concept of flow modulation with a small solenoid valve is feasible. Especially in the second configuration tested, where the Lee valve was integrated with the nozzle, reasonable modulation in flow of the order of 1.7 could be achieved. For this first prototype, the combustion performance is still not quite satisfactory. Improvements in operation, for example by providing a sharp and positive shut-off so that there is no flow under low pressures with consequent poor atomization could lead to better combustion performance. This could be achieved by using nozzles that have shut off or check valves for example. It is recommended that more work in cooperation with the valve manufacturer could produce a technically viable system. Marketability is of course a far more complex problem to be addressed once a technically viable product is available.

  9. Long pulse and steady state operation activities at KSTAR

    NASA Astrophysics Data System (ADS)

    Bae, Young-Soon; KSTAR Team; KAERI Collaboration; JAEA Collaboration; PPPL Collaboration; SNU Collaboration

    2014-10-01

    The mission of Korea Superconducting Tokamak Advanced Research (KSTAR) is to develop a steady state capable advanced tokamak (AT) operation. The original AT operation mode at KSTAR is a reversed shear scenario with the plasma current of 2 MA, the toroidal magnetic field of 3.5 T, βN of 5, safety factor q95 of 3.7. Recently, the stationary long pulse H-mode discharge is sustained for maximum pulse duration of 20 s using heating of 2.5-MW NBI and 0.7-MW, X3 170 GHz ECH with low density level ~ 0.3 × 1020/m3. The main activities of long pulse and steady state operation in KSTAR are the density feedback control, optimization of plasma shape and vertical control, real-time β control, and steady state capable heating upgrade. For the longer pulse H-mode discharge at the increased plasma current upcoming KSTAR campaign, there have been improvements in plasma control system and upgraded heating systems. Meanwhile, steady state operation scenario in KSTAR next 4-year is being investigated using time-dependent integrated transport simulation code with possible heating upgrade-schemes. The promising steady state scenario near future is a reversed shear using a new 4 MW off-axis neutral beam injector for broad pressure profile peaked at off-axis, and using ECH for local current profile control aiming at βN > 3 with Ip ~ 1 MA. This paper present activities and plan for steady state operation in KSTAR as well as the long pulse H-mode discharge results in the recent KSTAR campaign.

  10. Pulsed Operation of a Compact Fusion Neutron Source Using a High-Voltage Pulse Generator Developed for Landmine Detection

    SciTech Connect

    Yamauchi, Kunihito; Watanabe, Masato; Okino, Akitoshi; Kohno, Toshiyuki; Hotta, Eiki; Yuura, Morimasa

    2005-05-15

    Preliminary experimental results of pulsed neutron source based on a discharge-type beam fusion called Inertial Electrostatic Confinement Fusion (IECF) for landmine detection are presented. In Japan, a research and development project for constructing an advanced anti-personnel landmine detection system by using IECF, which is effective not only for metal landmines but also for plastic ones, is now in progress. This project consists of some R and D topics, and one of them is R and D of a high-voltage pulse generator system specialized for landmine detection, which can be used in the severe environment such as that in the field in Afghanistan. Thus a prototype of the system for landmine detection was designed and fabricated in consideration of compactness, lightness, cooling performance, dustproof and robustness. By using this prototype pulse generator system, a conventional IECF device was operated as a preliminary experiment. As a result, it was confirmed that the suggested pulse generator system is suitable for landmine detection system, and the results follow the empirical law obtained by the previous experiments. The maximum neutron production rate of 2.0x10{sup 8} n/s was obtained at a pulsed discharge of -51 kV, 7.3 A.

  11. Pulsed Operation of Microhollow Cathode Discharge Excimer Sources

    NASA Astrophysics Data System (ADS)

    Moselhy, M.; El-Habachi, A.; Schoenbach, K. H.

    1999-10-01

    Spatially resolved measurements on DC microhollow cathode discharges showed that the average radiant emittance of the xenon excimer source increases superlinearly with pressure [1]. At a current of 3 mA and a pressure of 750 Torr, the radiant emittance is approximately 20 W/cm2. For DC operation the current was limited to 8 mA to avoid thermal damage. Pulsed operation at 700 microseconds pulse width allowed us to extend the current range to 80 mA before the discharge became unstable. Pulsing the discharge allowed us also to explore its temporal development and the current dependence of the radiative power at high currents. The results showed that the time to reach a steady-state is about 200 microseconds, independent of pressure and current, in the parameter range of up to 1 atm and 80 mA, respectively. For operation at 80 mA, and 200 V, at 250 Torr the electrical power is 16 W; the optical power, assuming the same efficiency as for DC operation (8linear dependence of the intensity on current allows to generate excimer point sources which can easily be controlled electrically over a wide optical power range. This work is supported by the U.S. Department of Energy (DoE), Advanced Energy Division, and the National Science Foundation (NSF). [1] A. El-Habachi, M. Moselhy and K. H. Schoenbach, this conference.

  12. Efficient potassium diode pumped alkali laser operating in pulsed mode.

    PubMed

    Zhdanov, Boris V; Rotondaro, Matthew D; Shaffer, Michael K; Knize, Randall J

    2014-07-14

    This paper presents the results of our experiments on the development of an efficient hydrocarbon free diode pumped alkali laser based on potassium vapor buffered by He gas at 600 Torr. A slope efficiency of more than 50% was demonstrated with a total optical conversion efficiency of 30%. This result was achieved by using a narrowband diode laser stack as the pump source. The stack was operated in pulsed mode to avoid limiting thermal effects and ionization.

  13. Role of the optical pulse repetition rate in the efficiency of terahertz emitters

    NASA Astrophysics Data System (ADS)

    Reklaitis, Antanas

    2016-07-01

    Excitation of n-GaAs and p-InAs terahertz emitters by the series of optical pulses is studied by ensemble Monte Carlo simulations. It is found that the spatial separation of photoexcited electrons and holes dramatically reduces the recombination intensity in n-GaAs emitter, the operation of which is based on the surface field effect. The spatial separation of carriers does not affect the recombination intensity in p-InAs emitter, the operation of which is based on the photo-Dember effect. Therefore, the recovery time of equilibrium state after optical pulse in n-GaAs emitter significantly exceeds the corresponding recovery time in p-InAs emitter. This fact leads to a substantial reduction of photocurrent amplitude in n-GaAs emitter excited by the optical pulse series at high repetition rate.

  14. Rapid vaporization of kidney stones, ex vivo, using a Thulium fiber laser at pulse rates up to 500 Hz with a stone basket

    NASA Astrophysics Data System (ADS)

    Hardy, Luke A.; Wilson, Christopher R.; Irby, Pierce B.; Fried, Nathaniel M.

    2014-03-01

    The Holmium:YAG laser (λ = 2120 nm) is currently the preferred laser for fragmenting kidney stones in the clinic. However, this laser has some limitations, including operation at low pulse rates and a multimode spatial beam profile which prohibits its use with smaller, more flexible optical fibers. Our laboratory is studying the Thulium fiber laser (λ = 1908 nm) as an alternative lithotripter. The TFL has several advantages, including lower stone ablation thresholds, use with smaller and more flexible fibers, and operation at arbitrary pulse lengths and pulse rates. Previous studies have reported increased stone ablation rates with TFL operation at higher pulse rates, however, stone retropulsion remains an obstacle to even more efficient stone ablation. This study explores TFL operation at high pulse rates in combination with a stone stabilization device (e.g. stone basket) for improved efficiency. A TFL beam with pulse energy of 35 mJ, pulse duration of 500-μs, and pulse rates of 10-500 Hz was coupled into 100-μm-core, low-OH, silica fibers, in contact mode with uric acid and calcium oxalate monohydrate stones, ex vivo. TFL operation at 500 Hz produced UA and COM stone ablation rates up to 5.0 mg/s and 1.3 mg/s, respectively. High TFL pulse rates produced increased stone ablation rates sufficient for use in the clinic.

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

    PubMed

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

    2007-09-01

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

  16. Cellular response to high pulse repetition rate nanosecond pulses varies with fluorescent marker identity.

    PubMed

    Steelman, Zachary A; Tolstykh, Gleb P; Beier, Hope T; Ibey, Bennett L

    2016-09-23

    Nanosecond electric pulses (nsEP's) are a well-studied phenomena in biophysics that cause substantial alterations to cellular membrane dynamics, internal biochemistry, and cytoskeletal structure, and induce apoptotic and necrotic cell death. While several studies have attempted to measure the effects of multiple nanosecond pulses, the effect of pulse repetition rate (PRR) has received little attention, especially at frequencies greater than 100 Hz. In this study, uptake of Propidium Iodide, FM 1-43, and YO-PRO-1 fluorescent dyes in CHO-K1 cells was monitored across a wide range of PRRs (5 Hz-500 KHz) using a laser-scanning confocal microscope in order to better understand how high frequency repetition rates impact induced biophysical changes. We show that frequency trends depend on the identity of the dye under study, which could implicate transmembrane protein channels in the uptake response due to their chemical selectivity. Finally, YO-PRO-1 fluorescence was monitored in the presence of Gadolinium (Gd(3+)), Ruthenium Red, and in calcium-free solution to elucidate a mechanism for its unique frequency trend. PMID:27553279

  17. Microcalorimeter Spectroscopy at High Pulse Rates: A Multi-pulse Fitting Technique

    NASA Astrophysics Data System (ADS)

    Fowler, J. W.; Alpert, B. K.; Doriese, W. B.; Fischer, D. A.; Jaye, C.; Joe, Y. I.; O'Neil, G. C.; Swetz, D. S.; Ullom, J. N.

    2015-08-01

    Transition Edge Sensor microcalorimeters can measure X-ray and gamma-ray energies with very high energy resolution and high photon-collection efficiency. For this technology to reach its full potential in future X-ray observatories, each sensor must be able to measure hundreds or even thousands of photon energies per second. Current “optimal filtering” approaches to achieve the best possible energy resolution work only for photons that are well isolated in time, a requirement which is in direct conflict with the need for high-rate measurements. We describe a new analysis procedure to allow fitting for the pulse height of all photons even in the presence of heavy pulse pile-up. In the limit of isolated pulses, the technique reduces to standard optimal filtering with long records. We employ reasonable approximations to the noise covariance function in order to render this procedure computationally viable even for very long data records. The technique is employed to analyze X-ray emission spectra at 600 eV and 6 keV at rates up to 250 counts s-1 in microcalorimeters having exponential signal decay times of approximately 1.2 ms.

  18. MICROCALORIMETER SPECTROSCOPY AT HIGH PULSE RATES: A MULTI-PULSE FITTING TECHNIQUE

    SciTech Connect

    Fowler, J. W.; Alpert, B. K.; Doriese, W. B.; Joe, Y. I.; O’Neil, G. C.; Swetz, D. S.; Ullom, J. N.; Fischer, D. A.; Jaye, C.

    2015-08-15

    Transition Edge Sensor microcalorimeters can measure X-ray and gamma-ray energies with very high energy resolution and high photon-collection efficiency. For this technology to reach its full potential in future X-ray observatories, each sensor must be able to measure hundreds or even thousands of photon energies per second. Current “optimal filtering” approaches to achieve the best possible energy resolution work only for photons that are well isolated in time, a requirement which is in direct conflict with the need for high-rate measurements. We describe a new analysis procedure to allow fitting for the pulse height of all photons even in the presence of heavy pulse pile-up. In the limit of isolated pulses, the technique reduces to standard optimal filtering with long records. We employ reasonable approximations to the noise covariance function in order to render this procedure computationally viable even for very long data records. The technique is employed to analyze X-ray emission spectra at 600 eV and 6 keV at rates up to 250 counts s{sup −1} in microcalorimeters having exponential signal decay times of approximately 1.2 ms.

  19. Mid-infrared pulsed fiber lasers operating at 3μm region

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Li, Jianfeng; Yu, Luohong; Zhang, Zhiyao; Li, Heping; Zhou, Xiaojun

    2014-11-01

    Mid-infrared pulsed fiber laser with centered wavelength from 2 to 5 μm have attracted substantial attention owing to their potential applications in defence, laser microsurgery, material processing, nonlinear frequency conversion, etc. We demonstrated our recent achievements at 3 μm pulsed fiber lasers by utilizing Q-switching method. Firstly, a cascaded dual wavelength actively Q-switched Ho3+-doped ZBLAN fiber was reported by inserting an external electrically driven acoustic-optical modulator (AOM) into the cavity. The 3.0 μm and 2.07 μm pulse trains were achieved with a μs level time delay corresponding to the pulse energy of 29 μJ and 7 μJ, pulse duration of 380 ns and 260 ns, respectively. The narrower pulse width in this case compared to that in passively Q-switched fiber lasers can be attributed to the much higher modulation depth of AOM. Using a reversely designed semiconductor saturable mirror (SESAM) as the saturable absorber (SA), we presented a passively Q-switched Ho3+-doped ZBLAN fiber laser operating at ~2971 nm, the obtained maximum pulse energy of 6.65 μJ only limited by the maximum pump power was also the highest level from passively Q-switched fiber lasers at this wavelength range, and corresponding pulse repetition rate and duration were 47.6 kHz and 1.68 μs, respectively. Then using a Fe2+: ZnSe crystal with an initial transmission of 69 % as the SA, a passively Q-switched Ho3+-doped ZBLAN fiber laser operating at 2970.3 nm was also achieved. The obtained pulse duration and repetition rate were 1.92 μs and 62.74 kHz, respectively with an output power of 266 mW and a pulse energy of 4.24 μJ. The further performance improvements were possible because they were just limited by the maximum pump power. To sum up, the above achievements would be beneficial for further development of mid-infrared pulsed fiber lasers.

  20. Pulse wave transit time for monitoring respiration rate.

    PubMed

    Johansson, A; Ahlstrom, C; Lanne, T; Ask, P

    2006-06-01

    In this study, we investigate the beat-to-beat respiratory fluctuations in pulse wave transit time (PTT) and its subcomponents, the cardiac pre-ejection period (PEP) and the vessel transit time (VTT) in ten healthy subjects. The three transit times were found to fluctuate in pace with respiration. When applying a simple breath detecting algorithm, 88% of the breaths seen in a respiration air-flow reference could be detected correctly in PTT. Corresponding numbers for PEP and VTT were 76 and 81%, respectively. The performance during hypo- and hypertension was investigated by invoking blood pressure changes. In these situations, the error rates in breath detection were significantly higher. PTT can be derived from signals already present in most standard monitoring set-ups. The transit time technology thus has prospects to become an interesting alternative for respiration rate monitoring.

  1. Effects of frame rate and image resolution on pulse rate measured using multiple camera imaging photoplethysmography

    NASA Astrophysics Data System (ADS)

    Blackford, Ethan B.; Estepp, Justin R.

    2015-03-01

    Non-contact, imaging photoplethysmography uses cameras to facilitate measurements including pulse rate, pulse rate variability, respiration rate, and blood perfusion by measuring characteristic changes in light absorption at the skin's surface resulting from changes in blood volume in the superficial microvasculature. Several factors may affect the accuracy of the physiological measurement including imager frame rate, resolution, compression, lighting conditions, image background, participant skin tone, and participant motion. Before this method can gain wider use outside basic research settings, its constraints and capabilities must be well understood. Recently, we presented a novel approach utilizing a synchronized, nine-camera, semicircular array backed by measurement of an electrocardiogram and fingertip reflectance photoplethysmogram. Twenty-five individuals participated in six, five-minute, controlled head motion artifact trials in front of a black and dynamic color backdrop. Increasing the input channel space for blind source separation using the camera array was effective in mitigating error from head motion artifact. Herein we present the effects of lower frame rates at 60 and 30 (reduced from 120) frames per second and reduced image resolution at 329x246 pixels (one-quarter of the original 658x492 pixel resolution) using bilinear and zero-order downsampling. This is the first time these factors have been examined for a multiple imager array and align well with previous findings utilizing a single imager. Examining windowed pulse rates, there is little observable difference in mean absolute error or error distributions resulting from reduced frame rates or image resolution, thus lowering requirements for systems measuring pulse rate over sufficient length time windows.

  2. Development of a KSTAR ICRF antenna for long pulse operation

    NASA Astrophysics Data System (ADS)

    Bae, Y. D.; Kwak, J. G.; Kim, S. K.; Yoon, J. S.; Hong, B. G.; Hwang, C. K.; Wang, S. J.; Jeong, S. U.

    2003-09-01

    A prototype ion cyclotron range of frequency (ICRF) antenna with RF power of 6 MW has been developed for the long pulse (300 s), high power operation in the Korea superconducting tokamak advanced research (KSTAR) tokamak. Cooling paths in the antenna were carefully designed to remove the dissipated RF power loss. An RF power test has been performed to estimate the standoff capability of the antenna. A high power RF test at a frequency of 30 MHz gives a standoff voltage of 30.5 kVp for 60 s and 23.2 kVp for 300 s (without cooling). During the RF pulse, the peak voltage, forward/reflected powers, temperature of the antenna, and gas pressure are measured. A vacuum feedthrough of 1 MW RF power has been developed, which has two alumina ceramic cylinders and an O-ring seal. For cooling of the ceramic parts, dry air is injected into the ceramic surface through two outer nozzles. Independent cooling water channels are installed to cool the inner conductor of the feedthrough. RF high voltage tests show that stable operation is possible, with a peak voltage of 28.9 kVp for 300 s, without any severe damage.

  3. Residual gas analysis for long-pulse, advanced tokamak operation.

    PubMed

    Klepper, C C; Hillis, D L; Bucalossi, J; Douai, D; Oddon, P; Vartanian, S; Colas, L; Manenc, L; Pégourié, B

    2010-10-01

    A shielded residual gas analyzer (RGA) system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This "diagnostic RGA" has been used in long-pulse (up to 6 min) discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H(2)/D(2) isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H(2) injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses (>4 min) absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H(2) could increase due to thermodesorption of overheated plasma facing components.

  4. Residual gas analysis for long-pulse, advanced tokamak operation

    SciTech Connect

    Klepper, C. C.; Hillis, D. L.; Bucalossi, J.; Douai, D.; Oddon, P.; Vartanian, S.; Colas, L.; Manenc, L.; Pegourie, B.

    2010-10-15

    A shielded residual gas analyzer (RGA) system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This ''diagnostic RGA'' has been used in long-pulse (up to 6 min) discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H{sub 2}/D{sub 2} isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H{sub 2} injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses (>4 min) absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H{sub 2} could increase due to thermodesorption of overheated plasma facing components.

  5. Residual Gas Analysis for Long-Pulse, Advanced Tokamak Operation

    SciTech Connect

    Klepper, C Christopher; Hillis, Donald Lee; Bucalossi, J.; Douai, D.; OddonCEA, IRFM, P.; VartanianCEA-Cadarach, S.; Colas, L.; Manenc, L.; Pegourie, B.

    2010-01-01

    A shielded residual gas analyzer RGA system on Tore Supra can function during plasma operation and is set up to monitor the composition of the neutral gas in one of the pumping ducts of the toroidal pumped limited. This diagnostic RGA has been used in long-pulse up to 6 min discharges for continuous monitoring of up to 15 masses simultaneously. Comparison of the RGA-measured evolution of the H2 /D2 isotopic ratio in the exhaust gas to that measured by an energetic neutral particle analyzer in the plasma core provides a way to monitor the evolution of particle balance. RGA monitoring of corrective H2 injection to maintain proper minority heating is providing a database for improved ion cyclotron resonance heating, potentially with RGA-base feedback control. In very long pulses 4 min absence of significant changes in the RGA-monitored, hydrocarbon particle pressures is an indication of proper operation of the actively cooled, carbon-based plasma facing components. Also H2 could increase due to thermodesorption of overheated plasma facing components. 2010 American Institute of Physics.

  6. Comparison of pulse rate variability with heart rate variability during obstructive sleep apnea.

    PubMed

    Khandoker, Ahsan H; Karmakar, Chandan K; Palaniswami, Marimuthu

    2011-03-01

    We investigate whether pulse rate variability (PRV) extracted from finger photo-plethysmography (Pleth) waveforms can be the substitute of heart rate variability (HRV) from RR intervals of ECG signals during obstructive sleep apnea (OSA). Simultaneous measurements (ECG and Pleth) were taken from 29 healthy subjects during normal (undisturbed sleep) breathing and 22 patients with OSA during OSA events. Highly significant (p<0.01) correlations (1.0>r>0.95) were found between heart rate (HR) and pulse rate (PR). Bland-Altman plot of HR and PR shows good agreement (<5% difference). Comparison of 2 min recording epochs demonstrated significant differences (p<0.01) in time, frequency domains and complexity analysis, between normal and OSA events using PRV as well as HRV measures. Results suggest that both HRV and PRV indices could be used to distinguish OSA events from normal breathing during sleep. However, several variability measures (SDNN, RMSSD, HF power, LF/HF and sample entropy) of PR and HR were found to be significantly (p<0.01) different during OSA events. Therefore, we conclude that PRV provides accurate inter-pulse variability to measure heart rate variability under normal breathing in sleep but does not precisely reflect HRV in sleep disordered breathing.

  7. High Repetition Rate Grazing Incidence Pumped X-ray Laser operating at 18.9 nm

    SciTech Connect

    Keenan, R; Dunn, J; Patel, P K; Price, D F; Smith, R F; Shlyaptsev, V N

    2004-05-11

    We have demonstrated a 10 Hz Ni-like Mo X-ray laser operating at 18.9 nm with 150 mJ total pump energy by employing a novel pumping scheme. The grazing incidence scheme is described, where a picosecond pulse is incident at a grazing angle to a Mo plasma column produced by a slab target irradiated by a 200 ps laser pulse. This scheme uses refraction of the short pulse at a pre-determined electron density to increase absorption to pump a specific gain region. The high efficiency inherent to this scheme allows a reduction in the pump energy where 70 mJ long pulse energy and 80 mJ short pulse energy are sufficient to produce lasing at a 10 Hz repetition rate. Under these conditions and by optimizing the delay between the pulses, we achieve strong amplification and saturation for 4 mm long targets.

  8. Count rate limitations for pulse-counting instrumentation in pulsed accelerator fields.

    PubMed

    Justus, Alan L

    2012-01-01

    This paper discusses various concepts involved in the counting losses of pulse-counting health physics instrumentation when used within the pulsed radiation environments of typical accelerator fields in order to preestablish appropriate limitations in use. Discussed are the "narrow" pulse and the "wide" pulse cases, the special effect of neutron moderating assemblies, and the effect of pulse fine microstructure on the counting losses of the pulse-counting instrumentation. In the narrow-pulse case, the accelerator pulse width is less than or equal to the instrument's dead time; whereas in the wide-pulse case, the accelerator pulse width is significantly longer than the instrument's dead time. Examples are provided that highlight the various concepts and limitations.

  9. Constrained independent component analysis approach to nonobtrusive pulse rate measurements

    NASA Astrophysics Data System (ADS)

    Tsouri, Gill R.; Kyal, Survi; Dianat, Sohail; Mestha, Lalit K.

    2012-07-01

    Nonobtrusive pulse rate measurement using a webcam is considered. We demonstrate how state-of-the-art algorithms based on independent component analysis suffer from a sorting problem which hinders their performance, and propose a novel algorithm based on constrained independent component analysis to improve performance. We present how the proposed algorithm extracts a photoplethysmography signal and resolves the sorting problem. In addition, we perform a comparative study between the proposed algorithm and state-of-the-art algorithms over 45 video streams using a finger probe oxymeter for reference measurements. The proposed algorithm provides improved accuracy: the root mean square error is decreased from 20.6 and 9.5 beats per minute (bpm) for existing algorithms to 3.5 bpm for the proposed algorithm. An error of 3.5 bpm is within the inaccuracy expected from the reference measurements. This implies that the proposed algorithm provided performance of equal accuracy to the finger probe oximeter.

  10. Neodymium glass laser with a pulse energy of 220 J and a pulse repetition rate of 0.02 Hz

    SciTech Connect

    Kuzmin, A A; Kulagin, O V; Khazanov, Efim A; Shaykin, A A

    2013-07-31

    A compact neodymium glass laser with a pulse energy of 220 J and a record-high pulse repetition rate of 0.02 Hz (pulse duration 30 ns) is developed. Thermally induced phase distortions are compensated using wave phase conjugation. The integral depolarisation of radiation is decreased to 0.4% by using linear compensation schemes. The second harmonic of laser radiation can be used for pumping Ti : sapphire multipetawatt complexes. (letters)

  11. Improved pen harvester for powering a pulse rate sensor

    NASA Astrophysics Data System (ADS)

    Marin, Anthony; Heitzmann, Patrick; Twiefel, Jens; Priya, Shashank

    2012-04-01

    With the continued advancement in electronics the power requirement for micro-sensors has been decreasing opening the possibility for incorporating on-board energy harvesting devices to create self-powered sensors. The requirement for the energy harvesters are small size, light weight and the possibility of a low-budget mass production. In this study, we focus on developing an energy harvester for powering a pulse rate sensor. We propose to integrate an inductive energy harvester within a commonly available pen to harvest vibration energy from normal human motions like jogging and jumping. An existing prototype was reviewed which consists of a magnet wedged between two mechanical springs housed within a cylindrical shell. A single copper coil surrounds the cylindrical shell which harvests energy through Faraday's effect during magnet oscillation. This study reports a design change to the previous prototype providing a significant reduction in the device foot print without causing major losses in power generation. By breaking the single coil in the previous prototype into three separate coils an increase in power density was achieved. Several pulse rate sensors were evaluated to determine a target power requirement of 0.3 mW. To evaluate the prototype as a potential solution, the harvester was excited at various frequencies and accelerations typically produced through jogging and jumping motion. The improved prototype generated 0.043 mW at 0.56 grms and 3 Hz; and 0.13 mW at 1.14 grms at 5 Hz. The design change allowed reduction in total volume from 8.59 cm3 to 1.31 cm3 without significant losses in power generation.

  12. Noncontact imaging photoplethysmography to effectively access pulse rate variability

    NASA Astrophysics Data System (ADS)

    Sun, Yu; Hu, Sijung; Azorin-Peris, Vicente; Kalawsky, Roy; Greenwald, Stephen

    2013-06-01

    Noncontact imaging photoplethysmography (PPG) can provide physiological assessment at various anatomical locations with no discomfort to the patient. However, most previous imaging PPG (iPPG) systems have been limited by a low sample frequency, which restricts their use clinically, for instance, in the assessment of pulse rate variability (PRV). In the present study, plethysmographic signals are remotely captured via an iPPG system at a rate of 200 fps. The physiological parameters (i.e., heart and respiration rate and PRV) derived from the iPPG datasets yield statistically comparable results to those acquired using a contact PPG sensor, the gold standard. More importantly, we present evidence that the negative influence of initial low sample frequency could be compensated via interpolation to improve the time domain resolution. We thereby provide further strong support for the low-cost webcam-based iPPG technique and, importantly, open up a new avenue for effective noncontact assessment of multiple physiological parameters, with potential applications in the evaluation of cardiac autonomic activity and remote sensing of vital physiological signs.

  13. Operation and beam profiling of an up to 200 kHz pulse-burst laser for Thomson scattering

    SciTech Connect

    Young, W. C. Den Hartog, D. J.

    2014-11-15

    A new, high-repetition rate laser is in development for use on the Thomson scattering diagnostic on the Madison Symmetric Torus. The laser has been tested at a rate of 200 kHz in a pulse-burst operation, producing bursts of 5 pulses above 1.5 J each, while capable of bursts of 17 pulses at 100 kHz. A master oscillator-power amplifier architecture is used with a Nd:YVO{sub 4} oscillator, four Nd:YAG amplifiers, and a Nd:glass amplifier. A radial profile over the pulse sequence is measured by using a set of graphite apertures and an energy meter, showing a change in beam quality over a pulsing sequence.

  14. Operation and beam profiling of an up to 200 kHz pulse-burst laser for Thomson scattering

    NASA Astrophysics Data System (ADS)

    Young, W. C.; Den Hartog, D. J.

    2014-11-01

    A new, high-repetition rate laser is in development for use on the Thomson scattering diagnostic on the Madison Symmetric Torus. The laser has been tested at a rate of 200 kHz in a pulse-burst operation, producing bursts of 5 pulses above 1.5 J each, while capable of bursts of 17 pulses at 100 kHz. A master oscillator-power amplifier architecture is used with a Nd:YVO4 oscillator, four Nd:YAG amplifiers, and a Nd:glass amplifier. A radial profile over the pulse sequence is measured by using a set of graphite apertures and an energy meter, showing a change in beam quality over a pulsing sequence.

  15. Pulsed magnetic field-electron cyclotron resonance ion source operation

    SciTech Connect

    Muehle, C.; Ratzinger, U.; Joest, G.; Leible, K.; Schennach, S.; Wolf, B.H.

    1996-03-01

    The pulsed magnetic field (PuMa)-electron cyclotron resonance (ECR) ion source uses a pulsed coil to improve the peak current by opening the magnetic bottle along the beam axis. After demonstration of the principle of the pulsed magnetic extraction, the ion source was tested with different gases. We received promising results from helium to krypton. The influence of the current in the pulsed coil on the analyzed ion current was measured. With increased current levels within the pulsed coil not only the pulse height of the PuMa pulse, but the pulse length can also be controlled. By using the pulsed coil the maximum of the charge state distribution can be shifted to higher charge states. {copyright} {ital 1996 American Institute of Physics.}

  16. Pulsed magnetic field-electron cyclotron resonance ion source operation

    NASA Astrophysics Data System (ADS)

    Mühle, C.; Ratzinger, U.; Jöst, G.; Leible, K.; Schennach, S.; Wolf, B. H.

    1996-03-01

    The pulsed magnetic field (PuMa)-electron cyclotron resonance (ECR) ion source uses a pulsed coil to improve the peak current by opening the magnetic bottle along the beam axis. After demonstration of the principle of the pulsed magnetic extraction, the ion source was tested with different gases. We received promising results from helium to krypton. The influence of the current in the pulsed coil on the analyzed ion current was measured. With increased current levels within the pulsed coil not only the pulse height of the PuMa pulse, but the pulse length can also be controlled. By using the pulsed coil the maximum of the charge state distribution can be shifted to higher charge states.

  17. Repetitively rated plasma relativistic microwave oscillator with a controllable frequency in every pulse

    SciTech Connect

    Bogdankevich, I. L.; Grishin, D. M.; Gunin, A. V.; Ivanov, I. E.; Korovin, S. D.; Loza, O. T.; Mesyats, G. A.; Pavlov, D. A.; Rostov, V. V.; Strelkov, P. S.; Ul'yanov, D. K.

    2008-10-15

    A repetitively rated microwave oscillator whose frequency can be varied electronically from pulse to pulse in a predetermined manner is created for the first time. The microwave oscillator has a power on the order of 10{sup 8} W and is based on the Cherenkov interaction of a high-current relativistic electron beam with a plasma preformed before each pulse. Electronic control over the plasma properties allows one to arbitrarily vary the microwave frequency from pulse to pulse at a pulse repetition rate of up to 50 Hz.

  18. High energy pulsed inductive thruster modeling operating with ammonia propellant

    NASA Astrophysics Data System (ADS)

    Mikellides, Pavlos G.; Villarreal, James K.

    2007-11-01

    Numerical modeling of the pulsed inductive thruster operating with ammonia propellant at high energy levels, utilized a time-dependent, two-dimensional, and axisymmetric magnetohydrodynamics code to provide bilateral validation of experiment and theory and offer performance insights for improved designs. The power circuit model was augmented by a plasma voltage algorithm that accounts for the propellant's time-dependent resistance and inductance to properly account for plasma dynamics and was verified using available analytic solutions of two idealized plasma problems. Comparisons of the predicted current waveforms to experimental data exhibited excellent agreement for the initial half-period, essentially capturing the dominant acceleration phase. Further validation proceeded by comparisons of the impulse for three different energy levels, 2592, 4050, and 4608J and a wide range of propellant mass values. Predicted impulse captured both trends and magnitudes measured experimentally for nominal operation. Interpretation of the modeling results in conjunction to experimental observations further confirm the critical mass phenomenon beyond which efficiency degrades due to elevated internal energy mode deposition and anomalous operation.

  19. Theory and Practice in ICRF Antennas for Long Pulse Operation

    SciTech Connect

    Colas, L.; Bremond, S.; Mitteau, R.; Chantant, M.; Goniche, M.; Basiuk, V.; Bosia, G.; Gunn, J.P.

    2005-09-26

    Long plasma discharges on the Tore Supra (TS) tokamak were extended in 2004 towards higher powers and plasma densities by combined Lower Hybrid (LH) and Ion Cyclotron Range of Frequencies (ICRF) waves. RF pulses of 20sx8MW and 60sx4MW were produced. TS is equipped with 3 ICRF antennas, whose front faces are ready for CW operation. This paper reports on their behaviour over high power long pulses, as observed with infrared (IR) thermography and calorimetric measurements. Edge parasitic losses, although modest, are concentrated on a small surface and can raise surface temperatures close to operational limits. A complex hot spot pattern was revealed with at least 3 physical processes involved : convected power, electron acceleration in the LH near field, and a RF-specific phenomenon compatible with RF sheaths. LH coupling was also perturbed in the antenna shadow. This was attributed to RF-induced DC ExB0 convection. This motivated sheath modelling in two directions. First, the 2D topology of RF potentials was investigated in relation with the RF current distribution over the antenna, via a Green's function formalism and full-wave calculation using the ICANT code. In front of phased arrays of straps, convective cells were interpreted using the RF current profiles of strip line theory. Another class of convective cells, specific to antenna box corners, was evidenced for the first time. Within 1D sheath models assuming independent flux tubes, RF and rectified DC potentials are proportional. 2D fluid models couple nearby flux tubes via transverse polarisation currents. Unexpectedly this does not necessarily smooth RF potential maps. Peak DC potentials can even be enhanced. The experience gained on TS and the numerical tools are valuable for designing steady state high power antennas for next step devices. General rules to reduce RF potentials as well as concrete design options are discussed.

  20. A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    NASA Astrophysics Data System (ADS)

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; van den Ende, Daan A.; Groen, Wilhelm A.; Janssen, Maurice H. M.

    2009-11-01

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4×1022 particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5×10-6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv /v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever

  1. A short pulse (7 {mu}s FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams

    SciTech Connect

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; Janssen, Maurice H. M.; Ende, Daan A. van den; Groen, Wilhelm A.

    2009-11-15

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 {mu}s have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 {mu}m nozzle releases about 10{sup 16} particles/pulse and the beam brightness was estimated to be 4x10{sup 22} particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5x10{sup -6} Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow ({Delta}v/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas

  2. A short pulse (7 micros FWHM) and high repetition rate (dc-5 kHz) cantilever piezovalve for pulsed atomic and molecular beams.

    PubMed

    Irimia, Daniel; Dobrikov, Dimitar; Kortekaas, Rob; Voet, Han; van den Ende, Daan A; Groen, Wilhelm A; Janssen, Maurice H M

    2009-11-01

    In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 micros have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 microm nozzle releases about 10(16) particles/pulse and the beam brightness was estimated to be 4x10(22) particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5x10(-6) Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Delta v/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the

  3. Daily changes in oxygen saturation and pulse rate associated with particulate air pollution and barometric pressure.

    PubMed

    Dockery, D W; Pope, C A; Kanner, R E; Martin Villegas, G; Schwartz, J

    1999-01-01

    Epidemiologic studies have linked fine particulate air pollution with increases in morbidity and mortality rates from cardiopulmonary complications. Although the underlying biologic mechanisms responsible for this increase remain largely unknown, potential pathways include transient declines in blood oxygenation and changes in pulse rate following exposures to particulate air pollution episodes. This study evaluated potential associations between daily measures of respirable particulate matter (PM) with pulse rate and oxygen saturation of the blood. Pulse rate and oxygen saturation (Spo2) using pulse oximetry were measured daily in 90 elderly subjects living near air pollution monitors during the winter of 1995-96 in Utah Valley. We also evaluated potential associations of oxygen saturation and pulse rate with barometric pressure. Small but statistically significant positive associations between day-to-day changes in Spo2 and barometric pressure were observed. Pulse rate was inversely associated with barometric pressure. Exposure to particulate pollution was not significantly associated with Spo2 except in male participants 80 years of age or older. Increased daily pulse rate, as well as the odds of having a pulse rate 5 or 10 beats per minute (bpm) above normal (normal is defined as the individual's mean pulse rate throughout the study period), were significantly associated with exposure to particulate pollution on the previous 1 to 5 days. The medical or biologic relevance of these increases in pulse rate following exposure to particulate air pollution requires further study.

  4. Daily changes in oxygen saturation and pulse rate associated with particulate air pollution and barometric pressure.

    PubMed

    Dockery, D W; Pope, C A; Kanner, R E; Martin Villegas, G; Schwartz, J

    1999-01-01

    Epidemiologic studies have linked fine particulate air pollution with increases in morbidity and mortality rates from cardiopulmonary complications. Although the underlying biologic mechanisms responsible for this increase remain largely unknown, potential pathways include transient declines in blood oxygenation and changes in pulse rate following exposures to particulate air pollution episodes. This study evaluated potential associations between daily measures of respirable particulate matter (PM) with pulse rate and oxygen saturation of the blood. Pulse rate and oxygen saturation (Spo2) using pulse oximetry were measured daily in 90 elderly subjects living near air pollution monitors during the winter of 1995-96 in Utah Valley. We also evaluated potential associations of oxygen saturation and pulse rate with barometric pressure. Small but statistically significant positive associations between day-to-day changes in Spo2 and barometric pressure were observed. Pulse rate was inversely associated with barometric pressure. Exposure to particulate pollution was not significantly associated with Spo2 except in male participants 80 years of age or older. Increased daily pulse rate, as well as the odds of having a pulse rate 5 or 10 beats per minute (bpm) above normal (normal is defined as the individual's mean pulse rate throughout the study period), were significantly associated with exposure to particulate pollution on the previous 1 to 5 days. The medical or biologic relevance of these increases in pulse rate following exposure to particulate air pollution requires further study. PMID:10192116

  5. 500 MW peak power degenerated optical parametric amplifier delivering 52 fs pulses at 97 kHz repetition rate.

    PubMed

    Rothhardt, J; Hädrich, S; Röser, F; Limpert, J; Tünnermann, A

    2008-06-01

    We present a high peak power degenerated parametric amplifier operating at 1030 nm and 97 kHz repetition rate. Pulses of a state-of-the art fiber chirped-pulse amplification (FCPA) system with 840 fs pulse duration and 410 microJ pulse energy are used as pump and seed source for a two stage optical parametric amplifier. Additional spectral broadening of the seed signal in a photonic crystal fiber creates enough bandwidth for ultrashort pulse generation. Subsequent amplification of the broadband seed signal in two 1 mm BBO crystals results in 41 microJ output pulse energy. Compression in a SF 11 prism compressor yields 37 microJ pulses as short as 52 fs. Thus, pulse shortening of more than one order of magnitude is achieved. Further scaling in terms of average power and pulse energy seems possible and will be discussed, since both concepts involved, the fiber laser and the parametric amplifier have the reputation to be immune against thermo-optical effects.

  6. Radiobiological influence of megavoltage electron pulses of ultra-high pulse dose rate on normal tissue cells.

    PubMed

    Laschinsky, Lydia; Karsch, Leonhard; Leßmann, Elisabeth; Oppelt, Melanie; Pawelke, Jörg; Richter, Christian; Schürer, Michael; Beyreuther, Elke

    2016-08-01

    Regarding the long-term goal to develop and establish laser-based particle accelerators for a future radiotherapeutic treatment of cancer, the radiobiological consequences of the characteristic short intense particle pulses with ultra-high peak dose rate, but low repetition rate of laser-driven beams have to be investigated. This work presents in vitro experiments performed at the radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance). This accelerator delivered 20-MeV electron pulses with ultra-high pulse dose rate of 10(10) Gy/min either at the low pulse frequency analogue to previous cell experiments with laser-driven electrons or at high frequency for minimizing the prolonged dose delivery and to perform comparison irradiation with a quasi-continuous electron beam analogue to a clinically used linear accelerator. The influence of the different electron beam pulse structures on the radiobiological response of the normal tissue cell line 184A1 and two primary fibroblasts was investigated regarding clonogenic survival and the number of DNA double-strand breaks that remain 24 h after irradiation. Thereby, no considerable differences in radiation response were revealed both for biological endpoints and for all probed cell cultures. These results provide evidence that the radiobiological effectiveness of the pulsed electron beams is not affected by the ultra-high pulse dose rates alone. PMID:27193178

  7. Error rate performance of pulse position modulation schemes for indoor wireless optical communication

    NASA Astrophysics Data System (ADS)

    Azzam, Nazmy; Aly, Moustafa H.; AboulSeoud, A. K.

    2009-06-01

    Error rate performance of pulse position modulation (PPM) schemes for indoor wireless optical communication (WOC) applications is investigated. These schemes include traditional PPM and multiple PPM (MPPM). Study is unique in presenting and evaluating symbol error behaviour under wide range of design parameters such symbol length (L), number of chips per symbol (n), number of chips forms optical pulse (w). Effect of signal to noise ratio levels and operating bitrates on symbol error performance is also discussed. A comparison between studying modulation schemes is done. Relation with IrDA and IEEE 802.11 indoor WOC standardization is also investigated. Results indicate that PPM achieve great symbol error performance at reasonable signal to noise ratio and high bitrates with large symbol length.

  8. An Operational Wake Vortex Sensor Using Pulsed Coherent Lidar

    NASA Technical Reports Server (NTRS)

    Barker, Ben C., Jr.; Koch, Grady J.; Nguyen, D. Chi

    1998-01-01

    more recently, including a system developed by the MIT Lincoln Laboratory. This lidar has been used for detailed measurements of wake vortex velocities in support of wake vortex model validation. The first measurements of wake vortices using a pulsed, lidar were made by Coherent Technologies, Inc. (CTI) using a 2 micron solid-state, flashlamp-pumped system operating at 5 Hz. This system was first deployed at Denver's Stapleton Airport. Pulsed lidar has been selected as the baseline technology for an operational sensor due to its longer range capability.

  9. Narrow-linewidth megahertz-rate pulse-burst laser for high-speed flow diagnostics.

    PubMed

    Thurow, Brian; Jiang, Naibo; Samimy, Mo; Lempert, Walter

    2004-09-10

    A second-generation pulse-burst laser system for high-speed flow diagnostics is described in detail. The laser can produce a burst of high-energy pulses (of the order of hundreds of millijoules per pulse) with individual pulse durations of less than 10 ns and pulse separations as short as 1 micros. A key improvement is the addition of a phase-conjugate mirror, which effectively isolates the high-intensity, short-duration pulses from the low-intensity, long-duration background illumination. It allows for more-efficient amplification and harmonic generation, with efficiencies exceeding 50% for second-harmonic and 40% for third-harmonic generation. Characteristics of the laser system, including gain narrowing, pulse-burst energy distribution, pulse narrowing, and overall pulse-burst energy, are described. In addition, the applicability of the laser for spectroscopic-based flow diagnostics is demonstrated through the presentation of megahertz-rate planar Doppler velocimetry results.

  10. 14 CFR 33.7 - Engine ratings and operating limitations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...) Rated 2-minute OEI Power; (ix) Rated 30-second OEI power; and (x) Auxiliary power unit (APU) mode of...— (i) Rated maximum continuous power (relating to unsupercharged operation or to operation in each supercharger mode as applicable); and (ii) Rated takeoff power (relating to unsupercharged operation or...

  11. 14 CFR 33.7 - Engine ratings and operating limitations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) Rated 2-minute OEI Power; (ix) Rated 30-second OEI power; and (x) Auxiliary power unit (APU) mode of...— (i) Rated maximum continuous power (relating to unsupercharged operation or to operation in each supercharger mode as applicable); and (ii) Rated takeoff power (relating to unsupercharged operation or...

  12. High Repetition Rate Pulsed 2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Uprendra N.; Bai, Yingxin; Yu, Jirong; Petros, Mulugeta; Petzar, Paul J.; Trieu, Bo C.; Lee, Hyung

    2009-01-01

    A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed at NASA Langley Research Center. Such a laser transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of approximately 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. The measured standard deviation of the laser frequency jitter is about 3 MHz.

  13. Improving Reliability of High Power Quasi-CW Laser Diode Arrays Operating in Long Pulse Mode

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.

    2006-01-01

    Operating high power laser diode arrays in long pulse regime of about 1 msec, which is required for pumping 2-micron thulium and holmium-based lasers, greatly limits their useful lifetime. This paper describes performance of laser diode arrays operating in long pulse mode and presents experimental data of the active region temperature and pulse-to-pulse thermal cycling that are the primary cause of their premature failure and rapid degradation. This paper will then offer a viable approach for determining the optimum design and operational parameters leading to the maximum attainable lifetime.

  14. Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

    NASA Astrophysics Data System (ADS)

    Prasetyaningrum, A.; Ratnawati, Jos, B.

    2015-12-01

    Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O3) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

  15. Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

    SciTech Connect

    Prasetyaningrum, A. Ratnawati,; Jos, B.

    2015-12-29

    Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O{sub 3}) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

  16. Speech perception performance as a function of stimulus pulse rate and processing strategy preference for the Cochlear Nucleus CI24RE device: relation to perceptual threshold and loudness comfort profiles.

    PubMed

    Battmer, Rolf-Dieter; Dillier, Norbert; Lai, Wai Kong; Begall, Klaus; Leypon, Elisabeth Estrada; González, Juan C Falcón; Manrique, Manuel; Morera, Constantino; Müller-Deile, Joachim; Wesarg, Thomas; Zarowski, Andrzej; Killian, Matthijs J; von Wallenberg, Ernst; Smoorenburg, Guido F

    2010-09-01

    Current cochlear implants can operate at high pulse rates. The effect of increasing pulse rate on speech performance is not yet clear. Habituation to low rates may affect the outcome. This paper presents the results of three subsequent studies using different experimental paradigms, applying the Nucleus CI24RE device, and conducted by ten European implant teams. Pulse rate per channel varied from 500 to 3500 pulses per second with ACE and from 1200 to 3500 pps with CIS strategy. The results showed that the first rate presented had little effect on the finally preferred rate. Lower rates were preferred. The effect of pulse rate on word scores of post-linguistic implantees was small; high rates tended to give lower scores. However, there were no significant differences between the word scores across subjects if collected at the individually preferred pulse rate. High pulse rates were preferred when the post-implantation threshold was low.

  17. Using a Calculated Pulse Rate with an Artificial Neural Network to Detect Irregular Interbeats.

    PubMed

    Yeh, Bih-Chyun; Lin, Wen-Piao

    2016-03-01

    Heart rate is an important clinical measure that is often used in pathological diagnosis and prognosis. Valid detection of irregular heartbeats is crucial in the clinical practice. We propose an artificial neural network using the calculated pulse rate to detect irregular interbeats. The proposed system measures the calculated pulse rate to determine an "irregular interbeat on" or "irregular interbeat off" event. If an irregular interbeat is detected, the proposed system produces a danger warning, which is helpful for clinicians. If a non-irregular interbeat is detected, the proposed system displays the calculated pulse rate. We include a flow chart of the proposed software. In an experiment, we measure the calculated pulse rates and achieve an error percentage of < 3% in 20 participants with a wide age range. When we use the calculated pulse rates to detect irregular interbeats, we find such irregular interbeats in eight participants. PMID:26643078

  18. 14 CFR 35.5 - Propeller ratings and operating limitations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Propeller ratings and operating limitations... AIRCRAFT AIRWORTHINESS STANDARDS: PROPELLERS General § 35.5 Propeller ratings and operating limitations. (a) Propeller ratings and operating limitations must: (1) Be established by the applicant and approved by...

  19. 14 CFR 35.5 - Propeller ratings and operating limitations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Propeller ratings and operating limitations... AIRCRAFT AIRWORTHINESS STANDARDS: PROPELLERS General § 35.5 Propeller ratings and operating limitations. (a) Propeller ratings and operating limitations must: (1) Be established by the applicant and approved by...

  20. 14 CFR 35.5 - Propeller ratings and operating limitations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Propeller ratings and operating limitations... AIRCRAFT AIRWORTHINESS STANDARDS: PROPELLERS General § 35.5 Propeller ratings and operating limitations. (a) Propeller ratings and operating limitations must: (1) Be established by the applicant and approved by...

  1. 14 CFR 35.5 - Propeller ratings and operating limitations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Propeller ratings and operating limitations... AIRCRAFT AIRWORTHINESS STANDARDS: PROPELLERS General § 35.5 Propeller ratings and operating limitations. (a) Propeller ratings and operating limitations must: (1) Be established by the applicant and approved by...

  2. 14 CFR 35.5 - Propeller ratings and operating limitations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Propeller ratings and operating limitations... AIRCRAFT AIRWORTHINESS STANDARDS: PROPELLERS General § 35.5 Propeller ratings and operating limitations. (a) Propeller ratings and operating limitations must: (1) Be established by the applicant and approved by...

  3. Method for generating high-energy and high repetition rate laser pulses from CW amplifiers

    DOEpatents

    Zhang, Shukui

    2013-06-18

    A method for obtaining high-energy, high repetition rate laser pulses simultaneously using continuous wave (CW) amplifiers is described. The method provides for generating micro-joule level energy in pico-second laser pulses at Mega-hertz repetition rates.

  4. Pulsed picosecond 766 nm laser source operating between 1-80 MHz with automatic pump power management

    NASA Astrophysics Data System (ADS)

    Schönau, Thomas; Siebert, Torsten; Härtel, Romano; Eckhardt, Thomas; Klemme, Dietmar; Lauritsen, Kristian; Erdmann, Rainer

    2013-03-01

    The optical amplification and frequency conversion of a gain-switched 1532 nm distributed feedback (DFB) laser diode over a wide range of repetition rates are studied. A two stage Erbium fiber amplifier setup is pumped at 976 nm and operated at 1 to 80MHz pulse repetition frequency. The seed laser repetition rate is evaluated directly inside the pumping electronics to set the optimum pump power. Second-harmonic generation to 766 nm is achieved in a periodically poled lithium niobate bulk crystal. There is a high demand of several hundred milliwatt of picosecond pulsed laser power for stimulated emission depletion (STED) microscopy.

  5. All-fiber passively mode-locked Tm-doped NOLM-based oscillator operating at 2-μm in both soliton and noisy-pulse regimes.

    PubMed

    Li, Jianfeng; Zhang, Zuxing; Sun, Zhongyuan; Luo, Hongyu; Liu, Yong; Yan, Zhijun; Mou, Chengbo; Zhang, Lin; Turitsyn, Sergei K

    2014-04-01

    A self-starting all-fiber passively mode-locked Tm(3+)-doped fiber laser based on nonlinear loop mirror (NOLM) is demonstrated. Stable soliton pulses centered at 2017.33 nm with 1.56 nm FWHM were produced at a repetition rate of 1.514 MHz with pulse duration of 2.8 ps and pulse energy of 83.8 pJ. As increased pump power, the oscillator can also operate at noise-like (NL) regime. Stable NL pulses with coherence spike width of 341 fs and pulse energy of up to 249.32 nJ was achieved at a center wavelength of 2017.24 nm with 21.33 nm FWHM. To the best of our knowledge, this is the first 2 µm region NOLM-based mode-locked fiber laser operating at two regimes with the highest single pulse energy for NL pulses. PMID:24718163

  6. Temporal compression of pulses from a 100-KHz-repetiton-rate femtosecond ytterbium laser

    NASA Astrophysics Data System (ADS)

    Didenko, N. V.; Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.; Tenyakov, S. Yu; Bryukhanov, V. V.

    2016-08-01

    We report the temporal compression a femtosecond ytterbium laser pulse at a pulse repetition rate of 100 kHz using the effect of nonlinear self-phase modulation in a gas-filled capillary. A 260-fs laser pulse is compressed down to 17 fs with an energy efficiency of 40%. An average radiation power at the compressor output is 2 W. At a second compression stage, the time contrast is increased and the pulse duration is reduced in the process of the second harmonic generation in a KDP crystal. The obtained pulses have a duration of 11 fs at an efficiency of 35%.

  7. Validation of pulse rate variability as a surrogate for heart rate variability in chronically instrumented rabbits

    PubMed Central

    Pellegrino, Peter R.; Schiller, Alicia M.

    2014-01-01

    Heart rate variability (HRV) is a function of cardiac autonomic tone that is widely used in both clinical and animal studies. In preclinical studies, HRV measures are frequently derived using the arterial pulse waveform from an implanted pressure telemetry device, termed pulse rate variability (PRV), instead of the electrocardiogram signal in accordance with clinical guidelines. The acceptability of PRV as a surrogate for HRV in instrumented animals is unknown. Using rabbits implanted with intracardiac leads and chronically implanted pressure transducers, we investigated the correlation and agreement of time-domain, frequency-domain, and nonlinear indexes of HRV and PRV at baseline. We also investigated the effects of ventricular pacing and autonomic blockade on both measures. At baseline, HRV and PRV time- and frequency-domain parameters showed robust correlations and moderate to high agreement, whereas nonlinear parameters showed slightly weaker correlations and varied agreement. Ventricular pacing almost completely eliminated HRV, and spectral analysis of the PRV signal revealed a HRV-independent rhythm. After cardiac autonomic blockade with atropine or metoprolol, the changes in time- and non-normalized frequency-domain measures of PRV continued to show strong correlations and moderate to high agreement with corresponding changes in HRV measures. Blockade-induced changes in nonlinear PRV indexes correlated poorly with HRV changes and showed weak agreement. These results suggest that time- and frequency-domain measures of PRV are acceptable surrogates for HRV even in the context of changing cardiac autonomic tone, but caution should be used when nonlinear measures are a primary end point or when HRV is very low as HRV-independent rhythms may predominate. PMID:24791786

  8. Comparison of heart rate variability and pulse rate variability detected with photoplethysmography

    NASA Astrophysics Data System (ADS)

    Rauh, Robert; Limley, Robert; Bauer, Rainer-Dieter; Radespiel-Troger, Martin; Mueck-Weymann, Michael

    2004-08-01

    This study compares ear photoplethysmography (PPG) and electrocardiogram (ECG) in providing accurate heart beat intervals for use in calculations of heart rate variability (HRV, from ECG) or of pulse rate variability (PRV, from PPG) respectively. Simultaneous measurements were taken from 44 healthy subjects at rest during spontaneous breathing and during forced metronomic breathing (6/min). Under both conditions, highly significant (p > 0.001) correlations (1.0 > r > 0.97) were found between all evaluated common HRV and PRV parameters. However, under both conditions the PRV parameters were higher than HRV. In addition, we calculated the limits of agreement according to Bland and Altman between both techniques and found good agreement (< 10% difference) for heart rate and standard deviation of normal-to-normal intervals (SDNN), but only moderate (10-20%) or even insufficient (> 20%) agreement for other standard HRV and PRV parameters. Thus, PRV data seem to be acceptable for screening purposes but, at least at this state of knowledge, not for medical decision making. However, further studies are needed before more certain determination can be made.

  9. Optically controlled in-line graphene saturable absorber for the manipulation of pulsed fiber laser operation.

    PubMed

    Gene, Jinhwa; Park, Nam Hun; Jeong, Hwanseong; Choi, Sun Young; Rotermund, Fabian; Yeom, Dong-Il; Kim, Byoung Yoon

    2016-09-19

    We demonstrate an optically tunable graphene saturable absorber to manipulate the laser operation in pulsed fiber laser system. Owing to the strongly enhanced evanescent field interaction with monolayer graphene, we could realize an efficient control of modulation depth in the graphene saturable absorber by optical means through cross absorption modulation method. By integrating the tunable graphene saturable absorber into the fiber laser system, we could switch the laser operation from Q-switching through Q-switched mode-locking to continuous wave mode-locking by adjusting only the optical power of the control beam. In addition, we realized a hybrid Q-switching of fiber laser by periodical modulation of the absorption of the graphene saturable absorber, where we observed that the repetition rate of the Q-switched laser could be continuously tuned according to the modulation frequency of the applied external signal. PMID:27661873

  10. Apparatus for and method of operating a cylindrical pulsed induction mass launcher

    DOEpatents

    Cowan, M. Jr.; Duggin, B.W.; Widner, M.M.

    1992-06-30

    An electromagnetic cylindrical projectile mass launcher and a method of operation is provided which includes a cylindrical projectile having a conducting armature, a cylindrical barrel in which the armature is received, a plurality of electromagnetic drive coil stages, a plurality of pulse energy sources, and a pulsed power arrangement for generating magnetic pulses forming a pulsed magnetic wave along the length of the launcher barrel. The pulsed magnetic wave provides a propelling force on the projectile along the drive coil. The pulsed magnetic wave of the drive coil stages is advanced along the armature faster than the projectile to thereby generate an induced current wave in the armature. The pulsed generation of the magnetic wave minimizes electromagnetic heating of the projectile and provides for smooth acceleration of the projectile through the barrel of the launcher. 2 figs.

  11. Apparatus for and method of operating a cylindrical pulsed induction mass launcher

    DOEpatents

    Cowan, Jr., Maynard; Duggin, Billy W.; Widner, Melvin M.

    1992-01-01

    An electromagnetic cylindrical projectile mass launcher and a method of operation is provided which includes a cylindrical projectile having a conducting armature, a cylindrical barrel in which the armature is received, a plurality of electromagnetic drive coil stages, a plurality of pulse energy sources, and a pulsed power arrangement for generating magnetic pulses forming a pulsed magnetic wave along the length of the launcher barrel. The pulsed magnetic wave provides a propelling force on the projectile along the drive coil. The pulsed magnetic wave of the drive coil stages is advanced along the armature faster than the projectile to thereby generate an induced current wave in the armature. The pulsed generation of the magnetic wave minimizes electromagnetic heating of the projectile and provides for smooth acceleration of the projectile through the barrel of the launcher.

  12. Operating characteristics of a three-stage Stirling pulse tube cryocooler operating around 5 K

    NASA Astrophysics Data System (ADS)

    Qiu, L. M.; Cao, Q.; Zhi, X. Q.; Han, L.; Gan, Z. H.; Yu, Y. B.; Liu, Y.; Zhang, X. J.; Pfotenhauer, J. M.

    2012-07-01

    A Stirling pulse tube cryocooler (SPTC) operating at the liquid-helium temperatures represents an excellent prospect for satisfying the requirements of space applications because of its compactness, high efficiency and reliability. However, the working mechanism of a 4 K SPTC is more complicated than that of the Gifford McMahon (GM) PTC that operates at the relatively low frequency of 1-2 Hz, and has not yet been well understood. In this study, the primary operating parameters, including frequency, charge pressure, input power and precooling temperature, are systematically investigated in a home-developed separate three-stage SPTC. The investigation demonstrates that the frequency and precooling temperature are closely coupled via phase shift. In order to improve the cooling capacity it is important to lower the frequency and the precooling temperature simultaneously. In contrast to the behavior predicted by previous studies, the pressure dependence of the gas properties results in an optimized pressure that decreases significantly as the temperature is lowered. The third stage reaches a lowest temperature of 4.97 K at 29.9 Hz and 0.91 MPa. A cooling power of 25 mW is measured at 6.0 K. The precooling temperature is 23.7 K and the input power is 100 W.

  13. Fast Back Propagation Learning Using Optimization of Learning Rate for Pulsed Neural Networks

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kenji; Koakutsu, Seiichi; Okamoto, Takashi; Hirata, Hironori

    Neural Networks (NN) are widely applied to information processing because of its nonlinear processing capability. Digital hardware implementation of NN seems to be effective in construction of NN systems in which real-time operation and much further wide applications are possible. However, the digital hardware implementation of analogue NN is very difficult because we have to fulfill the restrictions about circuit resource, such as circuit scale, arrangement, and wiring. A technique that uses pulsed neuron model instead of analogue neuron model as a method of solving this problem has been proposed, and its effectiveness has been confirmed. To construct Pulsed Neural Networks (PNN), Back Propagation (BP) learning has been proposed. However, BP learning takes much time to construct PNN compared with the learning of analogue NN. Therefore some method to speed up BP learning of PNN is necessary. In this paper, we propose a fast BP learning using optimization of learning rate for PNN. In the proposed method, the learning rate is optimized so as to speed up the learning at every learning epoch. To evaluate the proposed method, we apply it to some pattern recognition problems, such as XOR, 3-bits parity, and digit recognition. Results of computational experiments indicate the validity of the proposed method.

  14. Operation of the TFTR Pellet Charge Exchange Diagnostic in the Pulse Counting Mode during H+ RF-minority Heating

    SciTech Connect

    Medley, S.S., PPPL

    1998-05-01

    The Pellet Charge Exchange technique on TFTR has been used primarily to obtain active charge exchange measurements using a high energy (0.5 - 4.0 MeV) neutral particle analyzer (NPA) in conjunction with impurity pellet injection (Li and B) with the scintillator-photomultiplier detector system operated in the current mode. While passive measurements using pulse counting were also obtained using this instrumentation, operation in this mode was very restrictive with pulse counting rates limited to less than {approximately}10 kHz in the absence of any significant neutron and gamma induced background signal. An upgrade to a specialized pulse counting capability which was developed by the Ioffe Institute was implemented which consisted of CsI(Tl) scintillators having features designed to minimize signals induced by background neutron and gamma rays and 16-channel pulse height analysis electronics on each of the eight NPA energy channels. Passive measurements of RF-driven energetic hydrogen minority ions which served to verify operation of the pulse counting mode are reported. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an RF power of 2 MW to 0.35 MeV at 6 MW.

  15. Digitally controlled pulse-level discriminator operates over wide voltage range

    NASA Technical Reports Server (NTRS)

    Cancro, C. A.

    1966-01-01

    Low power drain discriminator circuit generates an output pulse when an input pulse exceeds a discrete digitally controlled threshold voltage. The discriminator operates over a wide linear or nonlinear range of threshold levels. It uses several amplifier stages ahead of a fixed-reference threshold detector.

  16. 615 fs pulses with 17 mJ energy generated by an Yb:thin-disk amplifier at 3 kHz repetition rate.

    PubMed

    Fischer, Jonathan; Heinrich, Alexander-Cornelius; Maier, Simon; Jungwirth, Julian; Brida, Daniele; Leitenstorfer, Alfred

    2016-01-15

    A combination of Er/Yb:fiber and Yb:thin-disk technology produces 615 fs pulses at 1030 nm with an average output power of 72 W. The regenerative amplifier allows variation of the repetition rate between 3 and 5 kHz with pulse energies from 13 to 17 mJ. A broadband and intense seed provided by the compact and versatile fiber front-end minimizes gain narrowing. The resulting sub-ps performance is ideal for nonlinear frequency conversion and pulse compression. Operating in the upper branch of a bifurcated pulse train, the system exhibits exceptional noise performance and stability.

  17. Octave-spanning OPCPA system delivering CEP-stable few-cycle pulses and 22 W of average power at 1 MHz repetition rate.

    PubMed

    Rothhardt, Jan; Demmler, Stefan; Hädrich, Steffen; Limpert, Jens; Tünnermann, Andreas

    2012-05-01

    We report on an OPCPA system delivering CEP-stable pulses with a pulse duration of only 1.7 optical cycles at 880 nm wavelength. This pulse duration is achieved by the generation, optical parametric amplification and compression of a full optical octave of bandwidth. The system is pumped by a high average power Yb-fiber laser system, which allows for operation of the OPCPA at up to 1 MHz repetition rate and 22 W of average output power. Further scaling towards single-cycle pulses, higher energy and output power is discussed. PMID:22565712

  18. High repetition rate tunable femtosecond pulses and broadband amplification from fiber laser pumped parametric amplifier.

    PubMed

    Andersen, T V; Schmidt, O; Bruchmann, C; Limpert, J; Aguergaray, C; Cormier, E; Tünnermann, A

    2006-05-29

    We report on the generation of high energy femtosecond pulses at 1 MHz repetition rate from a fiber laser pumped optical parametric amplifier (OPA). Nonlinear bandwidth enhancement in fibers provides the intrinsically synchronized signal for the parametric amplifier. We demonstrate large tunability extending from 700 nm to 1500 nm of femtosecond pulses with pulse energies as high as 1.2 muJ when the OPA is seeded by a supercontinuum generated in a photonic crystal fiber. Broadband amplification over more than 85 nm is achieved at a fixed wavelength. Subsequent compression in a prism sequence resulted in 46 fs pulses. With an average power of 0.5 W these pulses have a peak-power above 10 MW. In particular, the average power and pulse energy scalability of both involved concepts, the fiber laser and the parametric amplifier, will enable easy up-scaling to higher powers.

  19. Apparatus and method for tuned unsteady flow purging of high pulse rate spark gaps

    DOEpatents

    Thayer, III, William J.

    1990-01-01

    A spark gap switch apparatus is disclosed which is capable of operating at a high pulse rate which comprises an insulated housing; a pair of spaced apart electrodes each having one end thereof within a first bore formed in the housing and defining a spark gap therebetween; a pressure wave reflector in the first bore in the housing and spaced from the spark gap and capable of admitting purge flow; and a second enlarged bore contiguous with the first bore and spaced from the opposite side of the spark gap; whereby pressure waves generated during discharge of a spark across the spark gap will reflect off the wave reflector and back from the enlarged bore to the spark gap to clear from the spark gap hot gases residues generated during the discharge and simultaneously restore the gas density and pressure in the spark gap to its initial value.

  20. Low-intensity pulsed ultrasound treatment improved the rate of autograft peripheral nerve regeneration in rat

    PubMed Central

    Jiang, Wenli; Wang, Yuexiang; Tang, Jie; Peng, Jiang; Wang, Yu; Guo, Quanyi; Guo, Zhiyuan; Li, Pan; Xiao, Bo; Zhang, Jinxing

    2016-01-01

    Low intensity pulsed ultrasound (LIPUS) has been widely used in clinic for the treatment of repairing pseudarthrosis, bone fractures and of healing in various soft tissues. Some reports indicated that LIPUS accelerated peripheral nerve regeneration including Schwann cells (SCs) and injured nerves. But little is known about its appropriate intensities on autograft nerves. This study was to investigate which intensity of LIPUS improved the regeneration of gold standard postsurgical nerves in experimental rat model. Sprague-Dawley rats were made into 10 mm right side sciatic nerve reversed autologous nerve transplantation and randomly treated with 250 mW/cm2, 500 mW/cm2 or 750 mW/cm2 LIPUS for 2–12 weeks after operation. Functional and pathological results showed that LIPUS of 250 mW/cm2 significantly induced faster rate of axonal regeneration. This suggested that autograft nerve regeneration was improved. PMID:27102358

  1. Reliability of High Power Laser Diode Arrays Operating in Long Pulse Mode

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.

    2006-01-01

    Reliability and lifetime of quasi-CW laser diode arrays are greatly influenced by their thermal characteristics. This paper examines the thermal properties of laser diode arrays operating in long pulse duration regime.

  2. Improving Switching Performance of Power MOSFETs Used in High Rep-Rate, Short Pulse, High-Power Pulsers

    SciTech Connect

    Cook, E G

    2006-09-19

    As their switching and power handling characteristics improve, solid-state devices are finding new applications in pulsed power. This is particularly true of applications that require fast trains of short duration pulses. High voltage (600-1200V) MOSFETs are especially well suited for use in these systems, as they can switch at significant peak power levels and are easily gated on and off very quickly. MOSFET operation at the shortest pulse durations is not constrained by the intrinsic capabilities of the MOSFET, but rather by the capabilities of the gate drive circuit and the system physical layout. This project sought to improve MOSFET operation in a pulsed power context by addressing these issues. The primary goal of this project is to improve the switching performance of power MOSFETs for use in high rep-rate, short pulse, high-power applications by improving the design of the gate drive circuits and the circuit layouts used in these systems. This requires evaluation of new commercial gate drive circuits and upgrading the designs of LLNL-developed circuits. In addition, these circuits must be tested with the fastest available high-voltage power MOSFETs.

  3. A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power.

    PubMed

    Binh, P H; Trong, V D; Renucci, P; Marie, X

    2013-08-01

    We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power.

  4. Self-mode-locked all-fibre erbium laser with a low repetition rate and high pulse energy

    SciTech Connect

    Denisov, Vladimir I; Nyushkov, B N; Pivtsov, V S

    2010-01-31

    Self-starting mode locking is demonstrated for the first time in an all-fibre erbium laser with a cavity length above 1 km and high positive (normal) intracavity dispersion. The unconventional cavity design, with polarisation instability compensation, ensures stable operation and good frequency stability. The laser generates pulses with a record low repetition rate (82.4 kHz) and record high energy (564.3 nJ). (lasers)

  5. Evaluation of catalyst for closed cycle operation of high energy pulsed CO2 lasers

    NASA Technical Reports Server (NTRS)

    Rogowski, R. S.; Miller, I. M.; Wood, G.; Schryer, D. R.; Hess, R. V.; Upchurch, B. T.

    1983-01-01

    Several catalyst materials have been tested for efficiency of converting CO and O2 to CO2 for use in a high energy CO2 laser. The composition of the gas mixtures was monitored by mass spectrometry and gas chromatography. A copper/copper oxide catalyst and a platinum/tin oxide catalyst were used for closed cycle operation of a CO2 laser (0.7 joules/pulse), operating at 10 pulses/sec.

  6. Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers

    NASA Astrophysics Data System (ADS)

    Lindberg, Robert; Zeil, Peter; Malmström, Mikael; Laurell, Fredrik; Pasiskevicius, Valdas

    2016-10-01

    A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrödinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement.

  7. Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers

    PubMed Central

    Lindberg, Robert; Zeil, Peter; Malmström, Mikael; Laurell, Fredrik; Pasiskevicius, Valdas

    2016-01-01

    A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrödinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement. PMID:27713496

  8. Optical pulse dynamics for quantum-dot logic operations in a photonic-crystal waveguide

    SciTech Connect

    Ma, Xun; John, Sajeev

    2011-11-15

    We numerically demonstrate all-optical logic operations with quantum dots (QDs) embedded in a bimodal photonic-crystal waveguide using Maxwell-Bloch equations in a slowly varying envelope approximation (SVEA). The two-level QD excitation level is controlled by one or more femtojoule optical driving pulses passing through the waveguide. Specific logic operations depend on the relative pulse strengths and their detunings from an inhomogeneouslly broadened (about 1% for QD transitions centered at 1.5 {mu}m) QD transition. This excitation controlled two-level medium then determines passage of subsequent probe optical pulses. Envelope equations for electromagnetic waves in the linear dispersion and cutoff waveguide modes are derived to simplify solution of the coupled Maxwell-Bloch equations in the waveguide. These determine the quantum mechanical evolution of the QD excitation and its polarization, driven by classical electromagnetic (EM) pulses near a sharp discontinuity in the EM density of states of the bimodal waveguide. Different configurations of the driving pulses lead to distinctive relations between driving pulse strength and probe pulse passage, representing all-optical logic and, or, and not operations. Simulation results demonstrate that such operations can be done on picosecond time scales and within a waveguide length of about 10 {mu}m in a photonic-band-gap (PBG) optical microchip.

  9. Fuzzy entropy based motion artifact detection and pulse rate estimation for fingertip photoplethysmography.

    PubMed

    Paradkar, Neeraj; Chowdhury, Shubhajit Roy

    2014-01-01

    The paper presents a fingertip photoplethysmography (PPG) based technique to estimate the pulse rate of the subject. The PPG signal obtained from a pulse oximeter is used for the analysis. The input samples are corrupted with motion artifacts due to minor motion of the subjects. Entropy measure of the input samples is used to detect the motion artifacts and estimate the pulse rate. A three step methodology is adapted to identify and classify signal peaks as true systolic peaks or artifact. CapnoBase database and CSL Benchmark database are used to analyze the technique and pulse rate estimation was performed with positive predictive value and sensitivity figures of 99.84% and 99.32% respectively for CapnoBase and 98.83% and 98.84% for CSL database respectively.

  10. Pulse-by-pulse multi-beam-line operation for x-ray free-electron lasers

    NASA Astrophysics Data System (ADS)

    Hara, Toru; Fukami, Kenji; Inagaki, Takahiro; Kawaguchi, Hideaki; Kinjo, Ryota; Kondo, Chikara; Otake, Yuji; Tajiri, Yasuyuki; Takebe, Hideki; Togawa, Kazuaki; Yoshino, Tatsuya; Tanaka, Hitoshi; Ishikawa, Tetsuya

    2016-02-01

    The parallel operation of plural undulator beam lines is an important means of improving the efficiency and usability of x-ray free-electron laser facilities. After the installation of a second undulator beam line (BL2) at SPring-8 Angstrom compact free-electron laser (SACLA), pulse-by-pulse switching between two beam lines was tested using kicker and dc twin-septum magnets. To maintain a compact size, all undulator beam lines at SACLA are designed to be placed within the same undulator hall located downstream of the accelerator. In order to ensure broad tunability of the laser wavelength, the electron bunches are accelerated to different beam energies optimized for the wavelengths of each beam line. In the demonstration, the 30 Hz electron beam was alternately deflected to two beam lines and simultaneous lasing was achieved with 15 Hz at each beam line. Since the electron beam was deflected twice by 3° in a dogleg to BL2, the coherent synchrotron radiation (CSR) effects became non-negligible. Currently in a wavelength range of 4-10 keV, a laser pulse energy of 100 - 150 μ J can be obtained with a reduced peak current of around 1 kA by alleviating the CSR effects. This paper reports the results and operational issues related to the multi-beam-line operation of SACLA.

  11. Rate discrimination at low pulse rates in normal-hearing and cochlear implant listeners: Influence of intracochlear stimulation site.

    PubMed

    Stahl, Pierre; Macherey, Olivier; Meunier, Sabine; Roman, Stéphane

    2016-04-01

    Temporal pitch perception in cochlear implantees remains weaker than in normal hearing listeners and is usually limited to rates below about 300 pulses per second (pps). Recent studies have suggested that stimulating the apical part of the cochlea may improve the temporal coding of pitch by cochlear implants (CIs), compared to stimulating other sites. The present study focuses on rate discrimination at low pulse rates (ranging from 20 to 104 pps). Two experiments measured and compared pulse rate difference limens (DLs) at four fundamental frequencies (ranging from 20 to 104 Hz) in both CI and normal-hearing (NH) listeners. Experiment 1 measured DLs in users of the (Med-El CI, Innsbruck, Austria) device for two electrodes (one apical and one basal). In experiment 2, DLs for NH listeners were compared for unresolved harmonic complex tones filtered in two frequency regions (lower cut-off frequencies of 1200 and 3600 Hz, respectively) and for different bandwidths. Pulse rate discrimination performance was significantly better when stimulation was provided by the apical electrode in CI users and by the lower-frequency tone complexes in NH listeners. This set of data appears consistent with better temporal coding when stimulation originates from apical regions of the cochlea. PMID:27106306

  12. Rate discrimination at low pulse rates in normal-hearing and cochlear implant listeners: Influence of intracochlear stimulation site.

    PubMed

    Stahl, Pierre; Macherey, Olivier; Meunier, Sabine; Roman, Stéphane

    2016-04-01

    Temporal pitch perception in cochlear implantees remains weaker than in normal hearing listeners and is usually limited to rates below about 300 pulses per second (pps). Recent studies have suggested that stimulating the apical part of the cochlea may improve the temporal coding of pitch by cochlear implants (CIs), compared to stimulating other sites. The present study focuses on rate discrimination at low pulse rates (ranging from 20 to 104 pps). Two experiments measured and compared pulse rate difference limens (DLs) at four fundamental frequencies (ranging from 20 to 104 Hz) in both CI and normal-hearing (NH) listeners. Experiment 1 measured DLs in users of the (Med-El CI, Innsbruck, Austria) device for two electrodes (one apical and one basal). In experiment 2, DLs for NH listeners were compared for unresolved harmonic complex tones filtered in two frequency regions (lower cut-off frequencies of 1200 and 3600 Hz, respectively) and for different bandwidths. Pulse rate discrimination performance was significantly better when stimulation was provided by the apical electrode in CI users and by the lower-frequency tone complexes in NH listeners. This set of data appears consistent with better temporal coding when stimulation originates from apical regions of the cochlea.

  13. 14 CFR 33.7 - Engine ratings and operating limitations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Engine ratings and operating limitations. 33.7 Section 33.7 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION...) Rated 2-minute OEI Power; (ix) Rated 30-second OEI power; and (x) Auxiliary power unit (APU) mode...

  14. 14 CFR 33.7 - Engine ratings and operating limitations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Engine ratings and operating limitations. 33.7 Section 33.7 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION...) Rated 2-minute OEI Power; (ix) Rated 30-second OEI power; and (x) Auxiliary power unit (APU) mode...

  15. Operability of an Ejector Enhanced Pulse Combustor in a Gas Turbine Environment

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.; Dougherty, Kevin

    2008-01-01

    A pressure-gain combustor comprised of a mechanically valved, liquid fueled pulsejet, an ejector, and an enclosing shroud, was coupled to a small automotive turbocharger to form a self-aspirating, thrust producing gas turbine engine. The system was constructed in order to investigate issues associated with the interaction of pulsed combustion devices and turbomachinery. Installed instrumentation allowed for sensing of distributed low frequency pressure and temperature, high frequency pressure in the shroud, fuel flow rate, rotational speed, thrust, and laboratory noise. The engine ran successfully and reliably, achieving a sustained thrust of 5 to 6 lbf, and maintaining a rotor speed of approximately 90,000 rpm, with a combustor pressure gain of approximately 4 percent. Numerical simulations of the system without pressure-gain combustion indicated that the turbocharger would not operate. Thus, the new combustor represented a substantial improvement in system performance. Acoustic measurements in the shroud and laboratory indicated turbine stage sound pressure level attenuation of 20 dB. This is consistent with published results from detonative combustion experiments. As expected, the mechanical reed valves suffered considerable damage under the higher pressure and thermal loading characteristics of this system. This result underscores the need for development of more robust valve systems for this application. The efficiency of the turbomachinery components did not appear to be significantly affected by unsteadiness associated with pulsed combustion, though the steady component efficiencies were already low, and thus not expected to be particularly sensitive.

  16. Respiratory rate derived from smartphone-camera-acquired pulse photoplethysmographic signals.

    PubMed

    Lázaro, Jesús; Nam, Yunyoung; Gil, Eduardo; Laguna, Pablo; Chon, Ki H

    2015-11-01

    A method for deriving respiratory rate from smartphone-camera-acquired pulse photoplethysmographic (SCPPG) signal is presented. Our method exploits respiratory information by examining the pulse wave velocity and dispersion from the SCPPG waveform and we term these indices as the pulse width variability (PWV). A method to combine information from several derived respiration signals is also presented and it is used to combine PWV information with other methods such as pulse amplitude variability (PAV), pulse rate variability (PRV), and respiration-induced amplitude and frequency modulations (AM and FM) in SCPPG signals.Evaluation is performed on a database containing SCPPG signals recorded from 30 subjects during controlled respiration experiments at rates from 0.2 to 0.6 Hz with an increment of 0.1 Hz, using three different devices: iPhone 4S, iPod 5, and HTC One M8. Results suggest that spontaneous respiratory rates (0.2-0.4 Hz) can be estimated from SCPPG signals by the PWV- and PRV-based methods with low relative error (median of order 0.5% and interquartile range of order 2.5%). The accuracy can be improved by combining PWV and PRV with other methods such as PAV, AM and/or FM methods. Combination of these methods yielded low relative error for normal respiratory rates, and maintained good performance at higher rates (0.5-0.6 Hz) when using the iPhone 4S or iPod 5 devices.

  17. Respiratory rate derived from smartphone-camera-acquired pulse photoplethysmographic signals.

    PubMed

    Lázaro, Jesús; Nam, Yunyoung; Gil, Eduardo; Laguna, Pablo; Chon, Ki H

    2015-11-01

    A method for deriving respiratory rate from smartphone-camera-acquired pulse photoplethysmographic (SCPPG) signal is presented. Our method exploits respiratory information by examining the pulse wave velocity and dispersion from the SCPPG waveform and we term these indices as the pulse width variability (PWV). A method to combine information from several derived respiration signals is also presented and it is used to combine PWV information with other methods such as pulse amplitude variability (PAV), pulse rate variability (PRV), and respiration-induced amplitude and frequency modulations (AM and FM) in SCPPG signals.Evaluation is performed on a database containing SCPPG signals recorded from 30 subjects during controlled respiration experiments at rates from 0.2 to 0.6 Hz with an increment of 0.1 Hz, using three different devices: iPhone 4S, iPod 5, and HTC One M8. Results suggest that spontaneous respiratory rates (0.2-0.4 Hz) can be estimated from SCPPG signals by the PWV- and PRV-based methods with low relative error (median of order 0.5% and interquartile range of order 2.5%). The accuracy can be improved by combining PWV and PRV with other methods such as PAV, AM and/or FM methods. Combination of these methods yielded low relative error for normal respiratory rates, and maintained good performance at higher rates (0.5-0.6 Hz) when using the iPhone 4S or iPod 5 devices. PMID:26450762

  18. An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

    SciTech Connect

    Höppner, H.; Tanikawa, T.; Schulz, M.; Riedel, R.; Teubner, U.; Faatz, B.; Tavella, F.

    2015-05-15

    High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to many hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.

  19. Application of a nanosecond laser pulse to evaluate dynamic hardness under ultra-high strain rate

    NASA Astrophysics Data System (ADS)

    Radziejewska, Joanna

    2016-04-01

    The paper presents results of experimental tests of plastic metals deformation generated by a shock wave induced by laser pulse. Tests were carried out on the Nd:YAG laser with a wavelength of 1064 nm and the laser pulse of 10 ns duration. The shock wave generate by the laser pulse was used to induced local plastic deformation of the material surface. The study examined the possibility of application the process to develop a new method of measuring the dynamic hardness of materials under ultra-high strain rate. It has been shown that the shock wave induced by the laser pulse with an energy of 0.35-1.22 J causes a repeatable plastic deformation of surface of commercially available metals and alloys without thermal effects on the surfaces. Based on the knowledge of an imprint geometry, it is possible to evaluate the dynamic hardness of materials at strain rate in the range of 107 s-1.

  20. Adjustable high-repetition-rate pulse trains in a passively-mode-locked fiber laser

    NASA Astrophysics Data System (ADS)

    Si Fodil, Rachid; Amrani, Foued; Yang, Changxi; Kellou, Abdelhamid; Grelu, Ph.

    2016-07-01

    We experimentally investigate multipulse regimes obtained within a passively-mode-locked fiber laser that includes a Mach-Zehnder (MZ) interferometer. By adjusting the time delay imbalance of the MZ, ultrashort pulse trains at multi-GHz repetition rates are generated. We compare the observed dynamics with high-harmonic mode locking, and show that the multi-GHz pulse trains display an inherent instability, which has been overlooked. By using a recirculation loop containing the MZ, we demonstrate a significant improvement of the pulse train stability.

  1. Study on the steady operating state of a micro-pulse electron gun.

    PubMed

    Kui, Zhou; Xiangyang, Lu; Shengwen, Quan; Jifei, Zhao; Xing, Luo; Ziqin, Yang

    2014-09-01

    Micro-pulse electron gun (MPG) employs the basic concept of multipacting to produce high-current and short-pulse electron beams from a radio-frequency (RF) cavity. The concept of MPG has been proposed for more than two decades. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady operating state of a micro-pulse electron gun with theory and experiments. The requirements for the steady operating state are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed, constructed, and tested. Some primary experiments have been finished. Both the unstable and stable operating states of the MPG have been observed. The stable output beam current has been detected at about 3.8 mA. Further experimental study is under way now.

  2. Study on the steady operating state of a micro-pulse electron gun

    SciTech Connect

    Kui, Zhou; Xing, Luo; Xiangyang, Lu; Shengwen, Quan; Jifei, Zhao; Ziqin, Yang

    2014-09-15

    Micro-pulse electron gun (MPG) employs the basic concept of multipacting to produce high-current and short-pulse electron beams from a radio-frequency (RF) cavity. The concept of MPG has been proposed for more than two decades. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady operating state of a micro-pulse electron gun with theory and experiments. The requirements for the steady operating state are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed, constructed, and tested. Some primary experiments have been finished. Both the unstable and stable operating states of the MPG have been observed. The stable output beam current has been detected at about 3.8 mA. Further experimental study is under way now.

  3. Study on the steady operating state of a micro-pulse electron gun.

    PubMed

    Kui, Zhou; Xiangyang, Lu; Shengwen, Quan; Jifei, Zhao; Xing, Luo; Ziqin, Yang

    2014-09-01

    Micro-pulse electron gun (MPG) employs the basic concept of multipacting to produce high-current and short-pulse electron beams from a radio-frequency (RF) cavity. The concept of MPG has been proposed for more than two decades. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady operating state of a micro-pulse electron gun with theory and experiments. The requirements for the steady operating state are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed, constructed, and tested. Some primary experiments have been finished. Both the unstable and stable operating states of the MPG have been observed. The stable output beam current has been detected at about 3.8 mA. Further experimental study is under way now. PMID:25273716

  4. Multi-pulse operation of a super-radiant backward-wave oscillator

    SciTech Connect

    Bandurkin, I. V.; Savilov, A. V.

    2014-08-15

    Theory of a backward-wave electron oscillator operating in the non-stationary regime of super-radiation of short powerful rf pulses is developed. It is shown that there exist multi-frequency regimes of generation of either two-peak or three-peak output signal with different characteristic frequencies in every peak. The use of such regimes allows increasing the duration, the peak power, and the total energy of the output super-radiation rf pulse.

  5. A study of high repetition rate pulse generation and all-optical add/drop multiplexing

    NASA Astrophysics Data System (ADS)

    Chen, Hongmin

    Ultra high-speed optical time-division-multiplexed (OTDM) transmission technologies are essential for the construction of ultra high-speed all-optical networks needed in the information era. In this Ph. D thesis dissertation, essential mechanisms associated with ultra high speed OTDM transmission systems, such as, high speed ultra short pulse generation, all optical demultiplexing and all optical add/drop multiplexing, have been studied. Both experimental demonstrations and numerical simulations have been performed. In order to realize high-speed optical TDM systems, high repetition rate, ultra short pulses are needed. A rational harmonic mode-locked ring fiber laser has been used to produce ultrashort pulses, the pulse jitter will be eliminated using a Phase-Locked-Loop (PLL), and the self-pulsation has been suppressed using a semiconductor optical amplifier (SOA). Sub pico-second pulses are very important for all optical sampling in the ultrahigh-speed OTDM transmission system. In this thesis, a two stage compression scheme utilizing the nonlinearity and dispersion of the optical fibers has been constructed and used to compress the gain switched DFB laser pulses. Also a nonlinear optical loop mirror has been constructed to suppress the wings associated with nonlinear compression. Pedestal free, transform-limited pulses with pulse widths in range of 0.2 to 0.4 ps have been generated. LiNbO3 modulators play a very important role in fiber optical communication systems. In this thesis, LiNbO3 modulators have been used to perform high repetition rate pulse generation, all optical demultiplexing and all optical add/drop for the TDM transmission system.

  6. Long Pulse Operation on Tore-Supra: Towards Steady State

    SciTech Connect

    Moreau, P.; Bucalossi, J.; Brosset, C.; Dufour, E.; Loarer, T.; Monier-Garbet, P.; Pegourie, B.; Tsitrone, E.; Basiuk, V.; Bremond, S.; Chantant, M.; Colas, L.; Commaux, N.; Geraud, A.; Guirlet, R.; Gunn, J.; Hertout, P.; Hoang, G. T.; Kazarian, F.; Mazon, D.

    2006-01-15

    The experimental programme of Tore Supra is devoted to the study of technology and physics issues associated to long-duration high performance discharges. This new domain of operation requires simultaneously and in steady state: heat removal capability, particle exhaust, fully non-inductive current drive, advanced technology integration and real time plasma control. The long discharge allows for addressing new time scale physic such as the wall particle retention and erosion. Moreover, the physics of fully non-inductive discharges is full of novelty, namely: the MHD stability, the slow spontaneous oscillation of the central electron temperature or the outstanding inward particle pinch.

  7. A new sealed RF-excited CO2 laser for enamel ablation operating at 9.4μm with pulse duration of 26 μs

    NASA Astrophysics Data System (ADS)

    Chan, Kenneth H.; Jew, Jamison M.; Fried, Daniel

    2016-02-01

    Several studies over the past 20 years have identified that carbon dioxide lasers operating at wavelengths between 9.3 and 9.6-μm with pulse durations near 20-µs are ideal for hard tissue ablation. Those wavelengths are coincident with the peak absorption of the mineral phase and the pulse duration is close to the thermal relaxation time of the deposited energy of a few microseconds to minimize peripheral thermal damage and long enough to minimize plasma shielding effects to allow efficient ablation at practical rates. The desired pulse duration near 20-μs has been difficult to achieve since it is too long for TEA lasers and too short for RF-excited lasers for efficient operation. Recently, Coherent Inc. (Santa Clara, CA) developed the J5-V laser for microvia drilling which can produce laser pulses greater than 100 mJ in energy at 9.4-μm with a pulse duration of 26-µs and it can achieve pulse repetition rates of 3 KHz. We report the first results using this laser to ablate enamel and dentin. The onset of plasma shielding does not occur until the fluence exceeds 100 J/cm2 allowing efficient ablation at rates exceeding 50-μm per pulse. This laser is ideally suited for the selective ablation of carious lesions.

  8. Investigation of pulsed mode operation with the frequency tuned CAPRICE ECRIS

    NASA Astrophysics Data System (ADS)

    Maimone, F.; Tinschert, K.; Endermann, M.; Hollinger, R.; Kondrashev, S.; Lang, R.; Mäder, J.; Patchakui, P. T.; Spädtke, P.

    2016-02-01

    In order to increase the intensity of the highly charged ions produced by the Electron Cyclotron Resonance Ion Sources (ECRISs), techniques like the frequency tuning and the afterglow mode have been developed and in this paper the effect on the ion production is shown for the first time when combining both techniques. Recent experimental results proved that the tuning of the operating frequency of the ECRIS is a promising technique to achieve higher ion currents of higher charge states. On the other hand, it is well known that the afterglow mode of the ECRIS operation can provide more intense pulsed ion beams in comparison with the continuous wave (cw) operation. These two techniques can be combined by pulsing the variable frequency signal driving the traveling wave tube amplifier which provides the high microwave power to the ECRIS. In order to analyze the effect of these two combined techniques on the ion source performance, several experiments were carried out on the pulsed frequency tuned CAPRICE (Compacte source A Plusiers Résonances Ionisantes Cyclotron Electroniques)-type ECRIS. Different waveforms and pulse lengths have been investigated under different settings of the ion source. The results of the pulsed mode have been compared with those of cw operation.

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

    SciTech Connect

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

    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.

  10. Field Intensity Detection of Individual Terahertz Pulses at 80 MHz Repetition Rate

    NASA Astrophysics Data System (ADS)

    Rettich, F.; Vieweg, N.; Cojocari, O.; Deninger, A.

    2015-07-01

    We present a new approach to detect the intensity of individual terahertz pulses at repetition rates as high as 80 MHz. Our setup comprises a femtosecond fiber laser, an InGaAs-based terahertz emitter, a zero-bias Schottky detector, and a high-speed data acquisition unit. The detected pulses consist of two lobes with half-widths of 1-2 ns, which is much shorter than the inverse repetition rate of the laser. The system lends itself for high-speed terahertz transmission measurements, e.g., to study wetting dynamics in real time.

  11. Operation of a Wideband Terahertz Superconducting Bolometer Responding to Quantum Cascade Laser Pulses

    NASA Astrophysics Data System (ADS)

    Cibella, S.; Beck, M.; Carelli, P.; Castellano, M. G.; Chiarello, F.; Faist, J.; Leoni, R.; Ortolani, M.; Sabbatini, L.; Scalari, G.; Torrioli, G.; Turcinkova, D.

    2012-06-01

    We make use of a niobium film to produce a micrometric vacuum-bridge superconducting bolometer responding to THz frequency. The bolometer works anywhere in the temperature range 2-7 K, which can be easily reached in helium bath cryostats or closed-cycle cryocoolers. In this work the bolometer is mounted on a pulse tube refrigerator and operated to measure the equivalent noise power (NEP) and the response to fast (μs) terahertz pulses. The NEP above 100 Hz equals that measured in a liquid helium cryostat showing that potential drawbacks related to the use of a pulse tube refrigerator (like mechanical and thermal oscillations, electromagnetic interference, noise) are irrelevant. At low frequency, instead, the pulse tube expansion-compression cycles originate lines at 1 Hz and harmonics in the noise spectrum. The bolometer was illuminated with THz single pulses coming either from a Quantum Cascade Laser operating at liquid nitrogen temperature or from a frequency-multiplied electronic oscillator. The response of the bolometer to the single pulses show that the device can track signals with a rise time as fast as about 450 ns.

  12. Q-switched operation of a pulsed-laser-deposited Yb:Y(2)O(3) waveguide using graphene as a saturable absorber.

    PubMed

    Choudhary, Amol; Dhingra, Shonali; D'Urso, Brian; Parsonage, Tina L; Sloyan, Katherine A; Eason, Robert W; Shepherd, David P

    2014-08-01

    The first, to the best of our knowledge, Q-switched operation of a pulsed-laser-deposited waveguide laser is presented. A clad Yb:Y(2)O(3) waveguide was Q-switched using an output coupling mirror coated with a single layer of graphene deposited by atmospheric pressure chemical vapor deposition. During continuous-wave operation, a maximum power of 83 mW at a slope efficiency of 25% was obtained. During Q-switched operation, pulses as short as 98 ns were obtained at a repetition rate of 1.04 MHz and a central wavelength of 1030.8 nm.

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

    PubMed

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

    2015-06-01

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

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

    SciTech Connect

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

    2015-06-15

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

  15. [Changes of pulse rate caused by sonic bomms during sleep (author's transl)].

    PubMed

    Griefahn, B

    1975-12-01

    In two experimental series (19 resp. 53 nights, 2 different persons in each series, test-time 10.30 p.m. to 3.00 a.m.) pulse rate after sonic booms had been recorded during sleep. In the first 3 nights the subjects slept undisturbed by noise. In the following 11 resp. 30 nights sonic booms were applied alternately 2 or 4 times. In the main series after 10 more nights without any noise 4 nights with 8 and 16 sonic booms alternately followed. The last 6 undisturbed nights in both series were used as comparison phase. The interval between two sonic booms was 40 min in nights with 2 booms, 20 min in nights with 4 sonic booms and in the nights with 8 and 16 sonic booms 8.6 resp. 4.6 min. Sound level of the sonic booms ranged from 0.48 mbar to 1.45 mbar, 1 mbar [83.5 dB (A)] in the average. The first sonic boom was applied if one of the two subjects had entered the deepest stage of sleep. Sonic booms induced a biphasic reaction in pulse rate. After an initial increase in frequency with a maximum in the 4th sec pulse rate decreased below the value before sonic boom; it was followed by a slow increase towards the baseline value. This reaction was analysed with special regard to the following factors: 1. Intensity. Due to very fast increase of noise intensity there was no significant correlation between the intensity of sonic boom and the pulse reaction. 2. Exogenic variables. There is no significant connection between postboom pulse rate and noiseless time before the sonic boom, the duration of the test series and the ambient temperature. 3. Endogenic variables. No correlation could be found between the stage of sleep and the reaction. On the contrary a very significant correlation was found between the maximum of postboom increase of pulse rate and the pulse rate before boom. With increasing pulse rate the extent of reaction becomes smaller. PMID:1201745

  16. Characterization of pulse amplitude and pulse rate modulation for a human vestibular implant during acute electrical stimulation

    NASA Astrophysics Data System (ADS)

    Nguyen, T. A. K.; DiGiovanna, J.; Cavuscens, S.; Ranieri, M.; Guinand, N.; van de Berg, R.; Carpaneto, J.; Kingma, H.; Guyot, J.-P.; Micera, S.; Perez Fornos, A.

    2016-08-01

    Objective. The vestibular system provides essential information about balance and spatial orientation via the brain to other sensory and motor systems. Bilateral vestibular loss significantly reduces quality of life, but vestibular implants (VIs) have demonstrated potential to restore lost function. However, optimal electrical stimulation strategies have not yet been identified in patients. In this study, we compared the two most common strategies, pulse amplitude modulation (PAM) and pulse rate modulation (PRM), in patients. Approach. Four subjects with a modified cochlear implant including electrodes targeting the peripheral vestibular nerve branches were tested. Charge-equivalent PAM and PRM were applied after adaptation to baseline stimulation. Vestibulo-ocular reflex eye movement responses were recorded to evaluate stimulation efficacy during acute clinical testing sessions. Main results. PAM evoked larger amplitude eye movement responses than PRM. Eye movement response axes for lateral canal stimulation were marginally better aligned with PRM than with PAM. A neural network model was developed for the tested stimulation strategies to provide insights on possible neural mechanisms. This model suggested that PAM would consistently cause a larger ensemble firing rate of neurons and thus larger responses than PRM. Significance. Due to the larger magnitude of eye movement responses, our findings strongly suggest PAM as the preferred strategy for initial VI modulation.

  17. Use of a prototype pulse oximeter for time series analysis of heart rate variability

    NASA Astrophysics Data System (ADS)

    González, Erika; López, Jehú; Hautefeuille, Mathieu; Velázquez, Víctor; Del Moral, Jésica

    2015-05-01

    This work presents the development of a low cost pulse oximeter prototype consisting of pulsed red and infrared commercial LEDs and a broad spectral photodetector used to register time series of heart rate and oxygen saturation of blood. This platform, besides providing these values, like any other pulse oximeter, processes the signals to compute a power spectrum analysis of the patient heart rate variability in real time and, additionally, the device allows access to all raw and analyzed data if databases construction is required or another kind of further analysis is desired. Since the prototype is capable of acquiring data for long periods of time, it is suitable for collecting data in real life activities, enabling the development of future wearable applications.

  18. A fast rise-rate, adjustable-mass-bit gas puff valve for energetic pulsed plasma experiments.

    PubMed

    Loebner, Keith T K; Underwood, Thomas C; Cappelli, Mark A

    2015-06-01

    A fast rise-rate, variable mass-bit gas puff valve based on the diamagnetic repulsion principle was designed, built, and experimentally characterized. The ability to hold the pressure rise-rate nearly constant while varying the total overall mass bit was achieved via a movable mechanical restrictor that is accessible while the valve is assembled and pressurized. The rise-rates and mass-bits were measured via piezoelectric pressure transducers for plenum pressures between 10 and 40 psig and restrictor positions of 0.02-1.33 cm from the bottom of the linear restrictor travel. The mass-bits were found to vary linearly with the restrictor position at a given plenum pressure, while rise-rates varied linearly with plenum pressure but exhibited low variation over the range of possible restrictor positions. The ability to change the operating regime of a pulsed coaxial plasma deflagration accelerator by means of altering the valve parameters is demonstrated. PMID:26133835

  19. A fast rise-rate, adjustable-mass-bit gas puff valve for energetic pulsed plasma experiments.

    PubMed

    Loebner, Keith T K; Underwood, Thomas C; Cappelli, Mark A

    2015-06-01

    A fast rise-rate, variable mass-bit gas puff valve based on the diamagnetic repulsion principle was designed, built, and experimentally characterized. The ability to hold the pressure rise-rate nearly constant while varying the total overall mass bit was achieved via a movable mechanical restrictor that is accessible while the valve is assembled and pressurized. The rise-rates and mass-bits were measured via piezoelectric pressure transducers for plenum pressures between 10 and 40 psig and restrictor positions of 0.02-1.33 cm from the bottom of the linear restrictor travel. The mass-bits were found to vary linearly with the restrictor position at a given plenum pressure, while rise-rates varied linearly with plenum pressure but exhibited low variation over the range of possible restrictor positions. The ability to change the operating regime of a pulsed coaxial plasma deflagration accelerator by means of altering the valve parameters is demonstrated.

  20. A fast rise-rate, adjustable-mass-bit gas puff valve for energetic pulsed plasma experiments

    NASA Astrophysics Data System (ADS)

    Loebner, Keith T. K.; Underwood, Thomas C.; Cappelli, Mark A.

    2015-06-01

    A fast rise-rate, variable mass-bit gas puff valve based on the diamagnetic repulsion principle was designed, built, and experimentally characterized. The ability to hold the pressure rise-rate nearly constant while varying the total overall mass bit was achieved via a movable mechanical restrictor that is accessible while the valve is assembled and pressurized. The rise-rates and mass-bits were measured via piezoelectric pressure transducers for plenum pressures between 10 and 40 psig and restrictor positions of 0.02-1.33 cm from the bottom of the linear restrictor travel. The mass-bits were found to vary linearly with the restrictor position at a given plenum pressure, while rise-rates varied linearly with plenum pressure but exhibited low variation over the range of possible restrictor positions. The ability to change the operating regime of a pulsed coaxial plasma deflagration accelerator by means of altering the valve parameters is demonstrated.

  1. A fast rise-rate, adjustable-mass-bit gas puff valve for energetic pulsed plasma experiments

    SciTech Connect

    Loebner, Keith T. K. Underwood, Thomas C.; Cappelli, Mark A.

    2015-06-15

    A fast rise-rate, variable mass-bit gas puff valve based on the diamagnetic repulsion principle was designed, built, and experimentally characterized. The ability to hold the pressure rise-rate nearly constant while varying the total overall mass bit was achieved via a movable mechanical restrictor that is accessible while the valve is assembled and pressurized. The rise-rates and mass-bits were measured via piezoelectric pressure transducers for plenum pressures between 10 and 40 psig and restrictor positions of 0.02-1.33 cm from the bottom of the linear restrictor travel. The mass-bits were found to vary linearly with the restrictor position at a given plenum pressure, while rise-rates varied linearly with plenum pressure but exhibited low variation over the range of possible restrictor positions. The ability to change the operating regime of a pulsed coaxial plasma deflagration accelerator by means of altering the valve parameters is demonstrated.

  2. Initial operation of high power ICRF system for long pulse in EAST

    SciTech Connect

    Qin, C. M. Zhao, Y. P.; Zhang, X. J.; Wan, B. N.; Gong, X. Z.; Mao, Y. Z.; Yuan, S.; Chen, G.

    2015-12-10

    The ICRF heating system on EAST upgraded by active cooling aims for long pulse operation. In this paper, the main technical features of the ICRF system are described. One of a major challenges for long pulse operation is RF-edge interactions induced impurity production and heat loading. In EAST, ICRF antenna protections and Faraday screen bars damaged due to LH electron beam are found. Preliminary results for the analysis of the interaction between LHCD and ICRF antenna are discussed. Increase of metal impurities in the plasma during RF pulse and in a larger core radiation are also shown. These RF-edge interactions at EAST and some preliminary results for the optimizing RF performance will be presented.

  3. Operative delivery rates following induction of labour for obstetric cholestasis.

    PubMed

    Webster, Jessica R; Chappell, Lucy; Cheng, Floria; Breeze, Andrew C G; Lucas, Nuala; Plaat, Felicity; Williamson, Catherine

    2011-06-01

    The aim of this study was to determine whether women induced for obstetric cholestasis (OC) have increased rates of operative delivery compared with women without OC who are induced. This retrospective case-control study included 64 women with OC (singleton pregnancies), who had labour induced compared with two control groups (matched for parity and gestational week at delivery). The majority of women were induced at 37 weeks. We found no significant increase in the rate of operative or assisted delivery in OC cases compared with either control group. Women with OC who are induced between 36 and 40 weeks gestation do not have increased rates of assisted or operative delivery compared with induced controls. PMID:27582856

  4. Effect of the pulse repetition rate on fiber-assisted tissue ablation

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook

    2016-07-01

    The effect of the pulse repetition rate on ablation performance was evaluated ex vivo at various fiber sweeping speeds for an effective 532-nm laser prostatectomy. Three pulse repetition rates (7.5, 15, and 30 kHz) at 100 W were delivered to bovine liver tissue at three sweeping speeds (2, 4, and 6 mm/s) to achieve bulky tissue removal. Ablation performance was quantitatively compared in terms of the ablation volume and the coagulation thickness. The lowest pulse repetition rate of 7.5 kHz attained the highest ablation volume (101.5 ± 12.0 mm3) and the thinnest coagulation (0.7 ± 0.1 mm) along with superficial carbonization. The highest pulse repetition rate of 30 kHz was associated with the least tissue removal (65.8 ± 5.0 mm3) and the deepest thermal denaturation (1.1 ± 0.2 mm). Quantitative evaluations of laser parameters can be instrumental in facilitating ablation efficiency and maintaining hemostatic coagulation during treatment of large-sized benign prostate hyperplasia.

  5. Precipitation pulse size and frequency controls on dryland litter decomposition rates

    NASA Astrophysics Data System (ADS)

    Kurupas, K. L.; Throop, H.

    2014-12-01

    Drylands are an important component of the global carbon (C) cycle, accounting for 40% of the land area and 20% of the soil organic C globally. Litter decomposition is a key biogeochemical process, controlling C and nutrient cycling. While simple decomposition models successfully predict decomposition rates in many systems based on climate variables, there is a disconnect between the modeled and measured rates decomposition in drylands. This disconnect may stem from abiotic factors of importance in drylands, such as photodegradation and soil-litter mixing, not being taken into account. Soil-litter mixing can accelerate decomposition, but the underlying mechanisms are poorly understood. Potential mechanisms include microclimate buffering, physical abrasion, and enhanced microbial colonization. Recent work suggests that litter decomposition is remarkably insensitive to climate variables, at least when variables are presented as long temporal-scale values (e.g., annual precipitation). We hypothesized that decomposition would be more strongly affected by litter moisture content than total precipitation (PPT) alone. Thus, frequent, small PPT pulses would accelerate decomposition more than larger, but infrequent pulses. Furthermore, soil-litter mixing would enhance decomposition by buffering litter moisture content. To test the combined influence of soil-litter mixing and PPT pulses on decomposition, we incubated litter and soil in a semi-controlled greenhouse which simulated dryland summer temperatures. Two litter types (grass and shrub) were incubated under two levels of soil-litter mixing (no mixing and complete soil-litter mixing) and with 16 different PPT treatments (a factorial combination of four PPT pulses sizes and four PPT frequencies). We measured instantaneous CO2 flux throughout the 30 day incubation and mass loss at the end of the incubation. Shrub litter decomposed faster than grass litter. Flux rates generally peaked at day 8 and declined thereafter. CO2

  6. Minimum operational performance standards for airborne weather and ground mapping pulsed radars

    NASA Astrophysics Data System (ADS)

    1980-11-01

    Minimum operational performance standards for airborne weather and ground mapping pulsed radars, including both air carrier and large aircraft-type radar systems, are described. Those requirements and technologies pertinent to general aviation, where limitations on space and/or weight may apply are taken into account.

  7. Radioactivity computation of steady-state and pulsed fusion reactors operation

    SciTech Connect

    Attaya, H.

    1994-11-01

    The International Thermonuclear Report (ITER) is expected to operate in a pulsed operational mode. Accurate radioactivity calculations, that take into account this mode of operation, are required in order to determine precisely the different safety aspects of ITER. The authors previous examined analytically the effect of pulsed operation in ITER and showed how it depends on the burn time, the dwell time, and the half-lives. That analysis showed also that for ITER`s low duty factor, using the continuous operation assumption would considerably overestimate the radioactivities, for a wide range of half-lives. At the same time, the large improvements in the quality and the quantity of the decay and the cross-section data libraries has considerably increased the computation times of the radioactivity calculations. For both reasons it is imperative to seek different methods of solution that reduce the computational time and can be easily adopted to the treatment of the pulsed operation. In this work, they have developed algorithms based on several mathematical methods that were chosen based on their generality, reliability, stability, accuracy, and efficiency. These methods are the matrix Schuer decomposition, the eigenvector decomposition, and the Pade approximation for the matrix exponential functions.

  8. Ozone generation in a kHz-pulsed He-O2 capillary dielectric barrier discharge operated in ambient air

    NASA Astrophysics Data System (ADS)

    Sands, Brian L.; Ganguly, Biswa N.

    2013-12-01

    The generation of reactive oxygen species using nonequilibrium atmospheric pressure plasma jet devices has been a subject of recent interest due to their ability to generate localized concentrations from a compact source. To date, such studies with plasma jet devices have primarily utilized radio-frequency excitation. In this work, we characterize ozone generation in a kHz-pulsed capillary dielectric barrier discharge configuration comprised of an active discharge plasma jet operating in ambient air that is externally grounded. The plasma jet flow gas was composed of helium with an admixture of up to 5% oxygen. A unipolar voltage pulse train with a 20 ns pulse risetime was used to drive the discharge at repetition rates between 2-25 kHz. Using UVLED absorption spectroscopy centered at 255 nm near the Hartley-band absorption peak, ozone was detected over 1 cm from the capillary axis. We observed roughly linear scaling of ozone production with increasing pulse repetition rate up to a "turnover frequency," beyond which ozone production steadily dropped and discharge current and 777 nm O(5P→5S°) emission sharply increased. The turnover in ozone production occurred at higher pulse frequencies with increasing flow rate and decreasing applied voltage with a common energy density of 55 mJ/cm3 supplied to the discharge. The limiting energy density and peak ozone production both increased with increasing O2 admixture. The power dissipated in the discharge was obtained from circuit current and voltage measurements using a modified parallel plate dielectric barrier discharge circuit model and the volume-averaged ozone concentration was derived from a 2D ozone absorption measurement. From these measurements, the volume-averaged efficiency of ozone production was calculated to be 23 g/kWh at conditions for peak ozone production of 41 mg/h at 11 kV applied voltage, 3% O2, 2 l/min flow rate, and 13 kHz pulse repetition rate, with 1.79 W dissipated in the discharge.

  9. Influence of the Pulse Duration onto the Material Removal Rate and Machining Quality for Different Types of Steel

    NASA Astrophysics Data System (ADS)

    Lauer, Benjamin; Jäggi, Beat; Neuenschwander, Beat

    When high requirements concerning machining quality are demanded, ultra short pulsed lasers with pulse durations from a few 100fs to 10ps may be the tool of choice. For these pulses it is known that the removal rate and machining quality slightly increases with shorter pulse duration. But as cost-effectiveness is also a key factor for a successful transfer of a technology to industrial applications, these systems compete against more cost effective systems with pulse durations from several 10ps to a few ns. It was found in previous work that the removal rate for metals strongly depends on the pulse duration. For steel also the composition and microstructure will influence the ablation processes. A systematic study of the removal rate and the machining quality for different types of steel and for pulse durations of several 100 fs to few ns will be presented.

  10. Dependence of diode sensitivity on the pulse rate of delivered radiation

    SciTech Connect

    Jursinic, Paul A.

    2013-02-15

    Purpose: It has been reported that diode sensitivity decreases by as much as 2% when the average dose rate set at the accelerator console was decreased from 600 to 40 MU/min. No explanation was given for this effect in earlier publications. This work is a detailed investigation of this phenomenon: the change of diode sensitivity versus the rate of delivery of dose pulses in the milliseconds and seconds range. Methods: X-ray beams used in this work had nominal energies of 6 and 15 MV and were generated by linear accelerators. The average dose rate was varied from 25 to 600 MU/min, which corresponded to time between microsecond-long dose pulses of 60-2.7 ms, respectively. The dose-per-pulse, dpp, was changed by positioning the detector at different source-to-detector distance. A variety of diodes fabricated by a number of manufacturers were tested in this work. Also, diodes in three different MapCHECKs (Sun Nuclear, Melbourne, FL) were tested. Results: For all diodes tested, the diode sensitivity decreases as the average dose rate is decreased, which corresponds to an increase in the pulse period, the time between radiation pulses. A sensitivity decrease as large as 5% is observed for a 60-ms pulse period. The diode sensitivity versus the pulse period is modeled by an empirical exponential function. This function has a fitting parameter, t{sub eff}, defined as the effective lifetime. The values of t{sub eff} were found to be 1.0-14 s, among the various diodes. For all diodes tested, t{sub eff} decreases as the dpp decreases and is greater for 15 MV than for 6 MV x rays. The decrease in diode sensitivity after 20 s without radiation can be reversed by as few as 60 radiation pulses. Conclusions: A decrease in diode sensitivity occurs with a decrease in the average dose rate, which corresponds to an increase in the pulse period of radiation. The sensitivity decrease is modeled by an empirical exponential function that decreases with an effective lifetime, t{sub eff}, of

  11. Multi-pulse operation of a dissipative soliton fibre laser based on nonlinear polarisation rotation

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Wang, X. L.; Zhou, P.; Chen, J. B.

    2016-03-01

    We report an experimental observation of multiple dissipative soliton (DS) operation states in an all-normal-dispersion passively mode-locked Yb-doped fibre laser, including DS bound and oscillating states. In the bound state, multiple DSs up to 11 can coexist in the cavity. In the oscillating state, the DSs' movements are not purely random and three typical states are generalised and illustrated. A single-pulse mode-locked state is established at a high pump power by carefully adjusting the polarisation controllers. The broad spectrum indicates that it may be noise-like pulses, which can serve as a pump to generate a supercontinuum.

  12. Pulsed-mode operation and performance of a ferromagnetic shape memory alloy actuator

    NASA Astrophysics Data System (ADS)

    Asua, E.; García-Arribas, A.; Etxebarria, V.; Feuchtwanger, J.

    2014-02-01

    The actuation capabilities and positioning performance of a single crystal ferromagnetic shape memory alloy (FSMA) operated in pulsed mode are evaluated in a prototype device. It consists of two orthogonal coil pairs that produce the magnetic fields necessary for the non-contact deformation of the material. The position of the top of the crystal after actuation is measured by a capacitive sensor. A specifically designed power module drives the discharge of a set of capacitors through the coils, producing fast current pulses of large amplitudes (about 250 A), the coil pairs are driven independently to control the direction of actuation. Open-loop experiments demonstrate that successive pulses of increasing magnitude successfully produced the desired expansion and contraction of the crystal, depending on the pair of coils that is activated. The deformation achieved is maintained after the pulses, highlighting the advantageous set-and-forget operation of the device. Closed-loop experiments are performed using a double proportional-integral-derivative controller, designed to take advantage of the energy-saving quality of the set-and-forget operation. Despite the nonlinear response and hysteric response of FSMA materials, a reference position can be reached and maintained with a maximum error of 0.5 μm.

  13. Development of a wideband pulse quaternary modulation system. [for an operational 400 Mbps baseband laser communication system

    NASA Technical Reports Server (NTRS)

    Federhofer, J. A.

    1974-01-01

    Laboratory data verifying the pulse quaternary modulation (PQM) theoretical predictions is presented. The first laboratory PQM laser communication system was successfully fabricated, integrated, tested and demonstrated. System bit error rate tests were performed and, in general, indicated approximately a 2 db degradation from the theoretically predicted results. These tests indicated that no gross errors were made in the initial theoretical analysis of PQM. The relative ease with which the entire PQM laboratory system was integrated and tested indicates that PQM is a viable candidate modulation scheme for an operational 400 Mbps baseband laser communication system.

  14. Single-pulse picking at kHz repetition rates using a Ge plasma switch at the free-electron laser FELBE

    SciTech Connect

    Schmidt, J. Helm, M.; Winnerl, S.; Seidel, W.; Schneider, H.; Bauer, C.; Gensch, M.

    2015-06-15

    We demonstrate a system for picking of mid-infrared and terahertz (THz) radiation pulses from the free-electron laser (FEL) FELBE operating at a repetition rate of 13 MHz. Single pulses are reflected by a dense electron-hole plasma in a Ge slab that is photoexcited by amplified near-infrared (NIR) laser systems operating at repetition rates of 1 kHz and 100 kHz, respectively. The peak intensity of picked pulses is up to 400 times larger than the peak intensity of residual pulses. The required NIR fluence for picking pulses at wavelengths in the range from 5 μm to 30 μm is discussed. In addition, we show that the reflectivity of the plasma decays on a time scale from 100 ps to 1 ns dependent on the wavelengths of the FEL and the NIR laser. The plasma switch enables experiments with the FEL that require high peak power but lower average power. Furthermore, the system is well suited to investigate processes with decay times in the μs to ms regime, i.e., much longer than the 77 ns long pulse repetition period of FELBE.

  15. Two-photon polymerization with variable repetition rate bursts of femtosecond laser pulses.

    PubMed

    Baldacchini, Tommaso; Snider, Scott; Zadoyan, Ruben

    2012-12-31

    We describe fabrication of microstructures by two-photon polymerization using bursts of femtosecond laser pulses. With the aid of an acousto-optic modulator driven by a function generator, two-photon polymerization is performed at variable burst repetition rates. We investigate how the time between the bursts of laser pulses influences the ultimate dimensions of lines written in a photosensitive resin. We observe that when using the same laser fluence, polymer lines fabricated at different burst repetition rates have different dimensions. In particular, the widths of two-photon polymerized lines become smaller with decreasing burst repetition rates. Based on the thermal properties of the resin and experimental writing conditions, we attribute this effect to localized heat accumulation. PMID:23388815

  16. Cesium dynamics in long pulse operation of negative hydrogen ion sources for fusion

    SciTech Connect

    Fantz, U.; Wimmer, C.

    2012-02-15

    Large scale negative hydrogen ion sources operating stable for 1 h (cw mode) are required for the neutral beam heating system of the fusion experiment ITER. The formation of negative hydrogen ions relies on the surface effect for which cesium is evaporated into the source. In order to monitor the cesium dynamics the laser absorption spectroscopy technique is applied to the long pulse test facility MANITU. In the vacuum phase, without plasma operation the evaporation of cesium and the built-up of the cesium in the source are measured. Typical neutral cesium densities are 10{sup 15} m{sup -3}. During plasma operation and after the plasma phase a high cesium dynamics is observed, showing also depletion of cesium during long pulses with low cesium amount. The co-extracted electron current decreases with the cesium amount to a certain level whereas the ion current indicates an optimum density range.

  17. Reducing error rates in straintronic multiferroic nanomagnetic logic by pulse shaping

    NASA Astrophysics Data System (ADS)

    Munira, Kamaram; Xie, Yunkun; Nadri, Souheil; Forgues, Mark B.; Salehi Fashami, Mohammad; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo; Ghosh, Avik W.

    2015-06-01

    Dipole-coupled nanomagnetic logic (NML), where nanomagnets (NMs) with bistable magnetization states act as binary switches and information is transferred between them via dipole-coupling and Bennett clocking, is a potential replacement for conventional transistor logic since magnets dissipate less energy than transistors when they switch in a logic circuit. Magnets are also ‘non-volatile’ and hence can store the results of a computation after the computation is over, thereby doubling as both logic and memory—a feat that transistors cannot achieve. However, dipole-coupled NML is much more error-prone than transistor logic at room temperature (\\gt 1%) because thermal noise can easily disrupt magnetization dynamics. Here, we study a particularly energy-efficient version of dipole-coupled NML known as straintronic multiferroic logic (SML) where magnets are clocked/switched with electrically generated mechanical strain. By appropriately ‘shaping’ the voltage pulse that generates strain, we show that the error rate in SML can be reduced to tolerable limits. We describe the error probabilities associated with various stress pulse shapes and discuss the trade-off between error rate and switching speed in SML.The lowest error probability is obtained when a ‘shaped’ high voltage pulse is applied to strain the output NM followed by a low voltage pulse. The high voltage pulse quickly rotates the output magnet’s magnetization by 90° and aligns it roughly along the minor (or hard) axis of the NM. Next, the low voltage pulse produces the critical strain to overcome the shape anisotropy energy barrier in the NM and produce a monostable potential energy profile in the presence of dipole coupling from the neighboring NM. The magnetization of the output NM then migrates to the global energy minimum in this monostable profile and completes a 180° rotation (magnetization flip) with high likelihood.

  18. A three-stage Stirling pulse tube cryocooler operating below the critical point of helium-4

    NASA Astrophysics Data System (ADS)

    Qiu, L. M.; Cao, Q.; Zhi, X. Q.; Gan, Z. H.; Yu, Y. B.; Liu, Y.

    2011-10-01

    Precooled phase shifters can significantly enhance the phase shift effect and further improve the performance of pulse tube cryocoolers. A separate three-stage Stirling pulse tube cryocooler (SPTC) with a cold inertance tube was designed and fabricated. Helium-4 instead of the rare helium-3 was used as the working fluid. The cryocooler reached a bottom temperature of 4.97 K with a net cooling power of 25 mW at 6.0 K. The operating frequency was 29.9 Hz and the charging pressure was 0.91 MPa. It is the first time a refrigeration temperature below the critical point of helium-4 was obtained in a three-stage Stirling pulse tube cryocooler.

  19. Lead extraction by selective operation of a nanosecond-pulsed 355nm laser

    NASA Astrophysics Data System (ADS)

    Herzog, Amir; Bogdan, Stefan; Glikson, Michael; Ishaaya, Amiel A.; Love, Charles

    2016-03-01

    Lead extraction (LE) is necessary for patients who are suffering from a related infection, or in opening venous occlusions that prevent the insertion of additional lead. In severe cases of fibrous encapsulation of the lead within a vein, laser-based cardiac LE has become one of the foremost methods of removal. In cases where the laser radiation (typically at 308 nm wavelength) interacts with the vein wall rather than with the fibrotic lesion, severe injury and subsequent bleeding may occur. Selective tissue ablation was previously demonstrated by a laser operating in the UV regime; however, it requires the use of sensitizers (e.g.: tetracycline). In this study, we present a preliminary examination of efficacy and safety aspects in the use of a nanosecond-pulsed solid-state laser radiation, at 355 nm wavelength, guided in a catheter consisting of optical fibers, in LE. Specifically, we demonstrate a correlation between the tissue elasticity and the catheter advancement rate, in ex-vivo experiments. Our results indicate a selectivity property for specific parameters of the laser radiation and catheter design. The selectivity is attributed to differences in the mechanical properties of the fibrotic tissue and a normal vein wall, leading to a different photomechanical response of the tissue's extracellular matrix. Furthermore, we performed successful in-vivo animal trials, providing a basic proof of concept for using the suggested scheme in LE. Selective operation using a 355 nm laser may reduce the risk of blood vessel perforation as well as the incidence of major adverse events.

  20. An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

    DOE PAGES

    Höppner, H.; Hage, A.; Tanikawa, T.; Schulz, M.; Riedel, R.; Teubner, U.; Prandolini, M. J.; Faatz, B.; Tavella, F.

    2015-05-15

    High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to manymore » hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.« less

  1. Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

    NASA Astrophysics Data System (ADS)

    Liu, Ji-Cai; Berrah, Nora; Cederbaum, Lorenz S.; Cryan, James P.; Glownia, James M.; Schafer, Kenneth J.; Buth, Christian

    2016-04-01

    We study theoretically the quantum dynamics of nitrogen molecules (N2) exposed to intense and ultrafast x-rays at a wavelength of 1.1 {{nm}} (1100 {{eV}} photon energy) from the Linac Coherent Light Source (LCLS) free electron laser. Molecular rate equations are derived to describe the intertwined photoionization, decay, and dissociation processes occurring for N2. This model complements our earlier phenomenological approaches, the single-atom, symmetric-sharing, and fragmentation-matrix models of 2012 (J. Chem. Phys. 136 214310). Our rate-equations are used to obtain the effective pulse energy at the sample and the time scale for the dissociation of the metastable dication {{{N}}}22+. This leads to a very good agreement between the theoretically and experimentally determined ion yields and, consequently, the average charge states. The effective pulse energy is found to decrease with shortening pulse duration. This variation together with a change in the molecular fragmentation pattern and frustrated absorption—an effect that reduces absorption of x-rays due to (double) core hole formation—are the causes for the drop of the average charge state with shortening LCLS pulse duration discovered previously.

  2. Rate equations for nitrogen molecules in ultrashort and intense x-ray pulses

    DOE PAGES

    Liu, Ji -Cai; Berrah, Nora; Cederbaum, Lorenz S.; Cryan, James P.; Glownia, James M.; Schafer, Kenneth J.; Buth, Christian

    2016-03-16

    Here, we study theoretically the quantum dynamics of nitrogen molecules (N2) exposed to intense and ultrafast x-rays at a wavelength ofmore » $$1.1\\;{\\rm{nm}}$$ ($$1100\\;{\\rm{eV}}$$ photon energy) from the Linac Coherent Light Source (LCLS) free electron laser. Molecular rate equations are derived to describe the intertwined photoionization, decay, and dissociation processes occurring for N2. This model complements our earlier phenomenological approaches, the single-atom, symmetric-sharing, and fragmentation-matrix models of 2012 (J. Chem. Phys. 136 214310). Our rate-equations are used to obtain the effective pulse energy at the sample and the time scale for the dissociation of the metastable dication $${{\\rm{N}}}_{2}^{2+}$$. This leads to a very good agreement between the theoretically and experimentally determined ion yields and, consequently, the average charge states. The effective pulse energy is found to decrease with shortening pulse duration. This variation together with a change in the molecular fragmentation pattern and frustrated absorption—an effect that reduces absorption of x-rays due to (double) core hole formation—are the causes for the drop of the average charge state with shortening LCLS pulse duration discovered previously.« less

  3. Ultrafast XUV Pulses at High Repetition Rate for Time Resolved Photoelectron Spectroscopy of Surface Dynamics

    NASA Astrophysics Data System (ADS)

    Corder, Christopher; Zhao, Peng; Li, Xinlong; Muraca, Amanda R.; Kershis, Matthew D.; White, Michael G.; Allison, Thomas K.

    2016-05-01

    Ultrafast photoelectron studies of surface dynamics are often limited by low repetition rates. At Stony Brook we have built a cavity-enhanced high-harmonic generation XUV source that delivers ultrafast pulses to a surface science apparatus for photoelectron spectroscopy. We begin with a Ytterbium fiber laser at a repetition rate of 78 MHz and up to 90 W of average power. After compression the pulses have μJ's of energy with < 180 fs pulse width. We then use an enhancement cavity with a finesse of a few hundred to build up to the peak intensity required for high harmonic generation. The enhancement cavity is a six mirror double folded bow-tie geometry with a focus of 15 μm at a Krypton gas jet, followed by a Sapphire crystal at Brewster's angle for the fundamental to allow outcoupling of the harmonics. A single harmonic is selected using a time-preserving monochromator to maintain the short pulses, and is sent to an ultra high vacuum chamber with sample preparation and diagnostic tools as well as an electron energy spectrometer. This allows us to study the electronic dynamics of semiconductor surfaces and their interfaces with adsorbed molecules which enable various charge transfer effects. Supported by AFOSR.

  4. a Thermoacoustically-Driven Pulse Tube Cryocryocooler Operating around 300HZ

    NASA Astrophysics Data System (ADS)

    Yu, G. Y.; Zhu, S. L.; Dai, W.; Luo, E. C.

    2008-03-01

    High frequency operation of the thermoacoustic cryocooler system, i.e. pulse tube cryocooler driven by thermoacoustic engine, leads to reduced size, which is quite attractive to small-scale cryogenic applications. In this work, a no-load coldhead temperature of 77.8 K is achieved on a 292 Hz pulse tube cryocooler driven by a standing-wave thermoacoustic engine with 3.92 MPa helium gas and 1750 W heat input. To improve thermal efficiency, a high frequency thermoacoustic-Stirling heat engine is also built to drive the same pulse tube cryocooler, and a no-load temperature of 109 K was obtained with 4.38 MPa helium gas, 292 Hz working frequency and 400W heating power. Ideas such as tapered resonators, acoustic amplifier tubes and simple thin tubes without reservoir are used to effectively suppress harmonic modes, amplify the acoustic pressure wave available to the pulse tube cryocooler and provide desired acoustic impedance for the pulse tube cryocooler, respectively. Comparison of systems with different thermoacoustic engines is made. Numerical simulations based on the linear thermoacoustic theory have also been done for comparison with experimental results, which shows reasonable agreement.

  5. Estimation of heart rate and heart rate variability from pulse oximeter recordings using localized model fitting.

    PubMed

    Wadehn, Federico; Carnal, David; Loeliger, Hans-Andrea

    2015-08-01

    Heart rate variability is one of the key parameters for assessing the health status of a subject's cardiovascular system. This paper presents a local model fitting algorithm used for finding single heart beats in photoplethysmogram recordings. The local fit of exponentially decaying cosines of frequencies within the physiological range is used to detect the presence of a heart beat. Using 42 subjects from the CapnoBase database, the average heart rate error was 0.16 BPM and the standard deviation of the absolute estimation error was 0.24 BPM. PMID:26737125

  6. Polarization-operator approach to pair creation in short laser pulses

    NASA Astrophysics Data System (ADS)

    Meuren, Sebastian; Hatsagortsyan, Karen Z.; Keitel, Christoph H.; Di Piazza, Antonino

    2015-01-01

    Short-pulse effects are investigated for the nonlinear Breit-Wheeler process, i.e. the production of an electron-positron pair induced by a gamma photon inside an intense plane-wave laser pulse. To obtain the total pair-creation probability we verify (to leading-order) the cutting rule for the polarization operator in the realm of strong-field QED by an explicit calculation. Using a double-integral representation for the leading-order contribution to the polarization operator, compact expressions for the total pair-creation probability inside an arbitrary plane-wave background field are derived. Correspondingly, the photon wave function including leading-order radiative corrections in the laser field is obtained via the Schwinger-Dyson equation in the quasistatic approximation. Moreover, the influence of the carrier-envelope phase and of the laser pulse shape on the total pair-creation probability in a linearly polarized laser pulse is investigated, and the validity of the (local) constant-crossed field approximation analyzed. It is shown that with presently available technology pair-creation probabilities of the order of ten percent could be reached for a single gamma photon.

  7. Safety Aspects of Pulsed Dose Rate Brachytherapy: Analysis of Errors in 1,300 Treatment Sessions

    SciTech Connect

    Koedooder, Kees Wieringen, Niek van; Grient, Hans N.B. van der; Herten, Yvonne R.J. van; Pieters, Bradley R.; Blank, Leo

    2008-03-01

    Purpose: To determine the safety of pulsed-dose-rate (PDR) brachytherapy by analyzing errors and technical failures during treatment. Methods and Materials: More than 1,300 patients underwent treatment with PDR brachytherapy, using five PDR remote afterloaders. Most patients were treated with consecutive pulse schemes, also outside regular office hours. Tumors were located in the breast, esophagus, prostate, bladder, gynecology, anus/rectum, orbit, head/neck, with a miscellaneous group of small numbers, such as the lip, nose, and bile duct. Errors and technical failures were analyzed for 1,300 treatment sessions, for which nearly 20,000 pulses were delivered. For each tumor localization, the number and type of occurring errors were determined, as were which localizations were more error prone than others. Results: By routinely using the built-in dummy check source, only 0.2% of all pulses showed an error during the phase of the pulse when the active source was outside the afterloader. Localizations treated using flexible catheters had greater error frequencies than those treated with straight needles or rigid applicators. Disturbed pulse frequencies were in the range of 0.6% for the anus/rectum on a classic version 1 afterloader to 14.9% for orbital tumors using a version 2 afterloader. Exceeding the planned overall treatment time by >10% was observed in only 1% of all treatments. Patients received their dose as originally planned in 98% of all treatments. Conclusions: According to the experience in our institute with 1,300 PDR treatments, we found that PDR is a safe brachytherapy treatment modality, both during and outside of office hours.

  8. Serum lipids and apolipoprotein B values, blood pressure and pulse rate in anorexia nervosa.

    PubMed

    Sánchez-Muniz, F J; Marcos, A; Varela, P

    1991-01-01

    Some risk factors associated with coronary heart disease (CHD) were evaluated in patients with different types of anorexia nervosa (AN). Anthropometric parameters, serum cholesterol, triglycerides and apoprotein (apo) B values, blood pressure and pulse rate were tested in 29 young female patients and 16 controls. Cholesterol, triglycerides and apo B were higher at the acute period of the illness (AN1), whereas at the chronic period the values of these parameters tended to normalize. Triglycerides were higher in patients who binge ate (bulimarexia). Systolic blood pressure decreased in all types of AN, while diastolic blood pressure decreased only in AN1; pulse rate was not altered. According to cholesterol and apo B values, AN patients may be at risk of CHD if they remain at low body weight. PMID:1855497

  9. How to improve rate of penetration in field operations

    SciTech Connect

    Fear, M.J.

    1999-03-01

    A method has been developed to identify which factors are controlling rate of penetration (ROP) in a particular group of bit runs. The method uses foot-based mud logging data, geological information, and drill bit characteristics, to produce numerical correlations between ROP and applied drilling parameters or other attributes of drilling conditions. These correlations are then used to generate recommendations for maximizing ROP in drilling operations.

  10. Feedback threshold control extends pulse rate measurements into the pileup region

    SciTech Connect

    Valentine, K.H.; Kopp, M.K.; Williams, J.A.

    1986-01-01

    By using feedback control of the discrimination threshold we have added 4 to 6 decades to the useful range of otherwise conventional pulse counting systems. The additional range is obtained at the high end by retarding saturation of the output count rate with higher threshold levels. We have implemented the method with low-power microcircuits that provide a 9-decade range (10/sup -5/ to 10/sup 4/ R/h) without the need for range or mode switching.

  11. High-rate dead-time corrections in a general purpose digital pulse processing system.

    PubMed

    Abbene, Leonardo; Gerardi, Gaetano

    2015-09-01

    Dead-time losses are well recognized and studied drawbacks in counting and spectroscopic systems. In this work the abilities on dead-time correction of a real-time digital pulse processing (DPP) system for high-rate high-resolution radiation measurements are presented. The DPP system, through a fast and slow analysis of the output waveform from radiation detectors, is able to perform multi-parameter analysis (arrival time, pulse width, pulse height, pulse shape, etc.) at high input counting rates (ICRs), allowing accurate counting loss corrections even for variable or transient radiations. The fast analysis is used to obtain both the ICR and energy spectra with high throughput, while the slow analysis is used to obtain high-resolution energy spectra. A complete characterization of the counting capabilities, through both theoretical and experimental approaches, was performed. The dead-time modeling, the throughput curves, the experimental time-interval distributions (TIDs) and the counting uncertainty of the recorded events of both the fast and the slow channels, measured with a planar CdTe (cadmium telluride) detector, will be presented. The throughput formula of a series of two types of dead-times is also derived. The results of dead-time corrections, performed through different methods, will be reported and discussed, pointing out the error on ICR estimation and the simplicity of the procedure. Accurate ICR estimations (nonlinearity < 0.5%) were performed by using the time widths and the TIDs (using 10 ns time bin width) of the detected pulses up to 2.2 Mcps. The digital system allows, after a simple parameter setting, different and sophisticated procedures for dead-time correction, traditionally implemented in complex/dedicated systems and time-consuming set-ups.

  12. High-rate dead-time corrections in a general purpose digital pulse processing system

    PubMed Central

    Abbene, Leonardo; Gerardi, Gaetano

    2015-01-01

    Dead-time losses are well recognized and studied drawbacks in counting and spectroscopic systems. In this work the abilities on dead-time correction of a real-time digital pulse processing (DPP) system for high-rate high-resolution radiation measurements are presented. The DPP system, through a fast and slow analysis of the output waveform from radiation detectors, is able to perform multi-parameter analysis (arrival time, pulse width, pulse height, pulse shape, etc.) at high input counting rates (ICRs), allowing accurate counting loss corrections even for variable or transient radiations. The fast analysis is used to obtain both the ICR and energy spectra with high throughput, while the slow analysis is used to obtain high-resolution energy spectra. A complete characterization of the counting capabilities, through both theoretical and experimental approaches, was performed. The dead-time modeling, the throughput curves, the experimental time-interval distributions (TIDs) and the counting uncertainty of the recorded events of both the fast and the slow channels, measured with a planar CdTe (cadmium telluride) detector, will be presented. The throughput formula of a series of two types of dead-times is also derived. The results of dead-time corrections, performed through different methods, will be reported and discussed, pointing out the error on ICR estimation and the simplicity of the procedure. Accurate ICR estimations (nonlinearity < 0.5%) were performed by using the time widths and the TIDs (using 10 ns time bin width) of the detected pulses up to 2.2 Mcps. The digital system allows, after a simple parameter setting, different and sophisticated procedures for dead-time correction, traditionally implemented in complex/dedicated systems and time-consuming set-ups. PMID:26289270

  13. 3D thermal analysis of rectangular microscale inorganic light-emitting diodes in a pulsed operation

    NASA Astrophysics Data System (ADS)

    Cui, Y.; Bian, Z.; Li, Y.; Xing, Y.; Song, J.

    2016-10-01

    Microscale inorganic light-emitting diodes (µ-ILEDs) have attracted much attention due to their excellent performance in biointegrated applications such as optogenetics. The thermal behaviors of µ-ILEDs are critically important since a certain temperature increase may degrade the LED performance and cause tissue lesion. The µ-ILEDs in a pulsed operation offer an advantage in thermal management. In this paper, a 3D analytic model, as validated by finite element analysis, is developed to study the thermal response of rectangular µ-ILEDs in a pulsed operation. A scaling law for the maximum normalized temperature increase of rectangular µ-ILEDs in terms of non-dimensional parameters is established. The influences of geometric (i.e. shape factor) and loading parameters (e.g. duty cycle and period) on the temperature increase are systematically investigated. These results are very helpful in designing µ-ILEDs by providing guidelines to avoid adverse thermal effects.

  14. Thermal properties of microscale inorganic light-emitting diodes in a pulsed operation

    NASA Astrophysics Data System (ADS)

    Li, Yuhang; Shi, Yan; Song, Jizhou; Lu, Chaofeng; Kim, Tae-il; Rogers, John A.; Huang, Yonggang

    2013-04-01

    Light-emitting diodes (LEDs) in a pulsed operation offer combined characteristics in efficiency, thermal management, and communication, which make them attractive for many applications such as backlight unit, optical communication, and optogenetics. In this paper, an analytic model, validated by three dimensional finite element analysis and experiments, is developed to study the thermal properties of micro-scale inorganic LEDs (μ-ILED) in a pulsed operation. A simple scaling law for the μ-ILED temperature after saturation is established in terms of the material and geometrical parameters of μ-ILED systems, peak power, and duty cycle. It shows that the normalized maximum temperature increase only depends on two non-dimensional parameters: normalized μ-ILED area and duty cycle. This study provides design guidelines for minimizing adverse thermal effects of μ-ILEDs.

  15. Nonlinear absorption of SWNT film and its effects to the operation state of pulsed fiber laser.

    PubMed

    Li, Xiaohui; Wang, Yonggang; Wang, Yishan; Zhao, Wei; Yu, Xuechao; Sun, Zhipei; Cheng, Xueping; Yu, Xia; Zhang, Ying; Wang, Qi Jie

    2014-07-14

    We study a single-wall carbon nanotube (SWNT) Polyvinyl alcohol (PVA) composite as a saturable absorber (SA) for pulse generation in Yb-doped fiber lasers. The saturable absorption and optical limiting (OL) characteristics of the SWNT device are investigated. By combing these two nonlinear effects, we find out for the first time, to the best of our knowledge, that mode-locking can be obtained in the dissipative soliton regime at low pumping followed by Q-switching at high pumping, which is quite different from conventional pulse dynamic evolutions. The Q-switched state operating at higher pump powers is due to the OL effect. The inverted operating fiber laser can be applied in various potential applications such as versatile material processing, optical communication and radar system etc.

  16. Binaural jitter improves interaural time-difference sensitivity of cochlear implantees at high pulse rates.

    PubMed

    Laback, Bernhard; Majdak, Piotr

    2008-01-15

    Interaural time difference (ITD) arises whenever a sound outside of the median plane arrives at the two ears. There is evidence that ITD in the rapidly varying fine structure of a sound is most important for sound localization and for understanding speech in noise. Cochlear implants (CIs), neural prosthetic devices that restore hearing in the profoundly deaf, are increasingly implanted to both ears to provide implantees with the advantages of binaural hearing. CI listeners have been shown to be sensitive to fine structure ITD at low pulse rates, but their sensitivity declines at higher pulse rates that are required for speech coding. We hypothesize that this limitation in electric stimulation is at least partially due to binaural adaptation associated with periodic stimulation. Here, we show that introducing binaurally synchronized jitter in the stimulation timing causes large improvements in ITD sensitivity at higher pulse rates. Our experimental results demonstrate that a purely temporal trigger can cause recovery from binaural adaptation. Thus, binaurally jittered stimulation may improve several aspects of binaural hearing in bilateral recipients of neural auditory prostheses. PMID:18182489

  17. Dual axis operation of a micromachined rate gyroscope

    SciTech Connect

    Juneau, T.; Pisano, A.P.; Smith, J.

    1997-04-01

    Since micromachining technology has raised the prospect of fabricating high performance sensors without the associated high cost and large size, many researchers have investigated micromachined rate gyroscopes. The vast majority of research has focused on single input axis rate gyroscopes, but this paper presents work on a dual input axis micromachined rate gyroscope. The key to successful simultaneous dual axis operation is the quad symmetry of the circular oscillating rotor design. Untuned gyroscopes with mismatched modes yielded random walk as low as 10{degrees}/{radical}hour with cross sensitivity ranging from 6% to 16%. Mode frequency matching via electrostatic tuning allowed performance better than 2{degrees}/{radical}hour, but at the expense of excessive cross sensitivity.

  18. Optical Parameter Variability in Laser Nerve Stimulation: A Study of Pulse Duration, Repetition Rate, and Wavelength

    PubMed Central

    Walsh, Joseph T.; Jansen, E. Duco; Bendett, Mark; Webb, Jim; Ralph, Heather; Richter, Claus-Peter

    2012-01-01

    Pulsed lasers can evoke neural activity from motor as well as sensory neurons in vivo. Lasers allow more selective spatial resolution of stimulation than the conventional electrical stimulation. To date, few studies have examined pulsed, mid-infrared laser stimulation of nerves and very little of the available optical parameter space has been studied. In this study, a pulsed diode laser, with wavelength between 1.844–1.873 μm, was used to elicit compound action potentials (CAPs) from the auditory system of the gerbil. We found that pulse durations as short as 35 μs elicit a CAP from the cochlea. In addition, repetition rates up to 13 Hz can continually stimulate cochlear spiral ganglion cells for extended periods of time. Varying the wavelength and, therefore, the optical penetration depth, allowed different populations of neurons to be stimulated. The technology of optical stimulation could significantly improve cochlear implants, which are hampered by a lack of spatial selectivity. PMID:17554829

  19. Kinetic instabilities in pulsed operation mode of a 14 GHz electron cyclotron resonance ion source.

    PubMed

    Tarvainen, O; Kalvas, T; Koivisto, H; Komppula, J; Kronholm, R; Laulainen, J; Izotov, I; Mansfeld, D; Skalyga, V

    2016-02-01

    The occurrence of kinetic plasma instabilities is studied in pulsed operation mode of a 14 GHz A-electron cyclotron resonance type electron cyclotron resonance ion source. It is shown that the temporal delay between the plasma breakdown and the appearance of the instabilities is on the order of 10-100 ms. The most important parameters affecting the delay are magnetic field strength and neutral gas pressure. It is demonstrated that kinetic instabilities limit the high charge state ion beam production in the unstable operating regime. PMID:26931919

  20. Ytterbium fiber-based, 270 fs, 100 W chirped pulse amplification laser system with 1 MHz repetition rate

    NASA Astrophysics Data System (ADS)

    Zhao, Zhigang; Kobayashi, Yohei

    2016-01-01

    A 100 W Yb-doped, fiber-based, femtosecond, chirped pulse amplification laser system was developed with a repetition rate of 1 MHz, corresponding to a pulse energy of 100 µJ. Large-scale, fused-silica transmission gratings were used for both the pulse stretcher and compressor, with a compression throughput efficiency of ∼85%. A pulse duration of 270 fs was measured by second harmonic generation frequency-resolved optical gating (SHG-FROG). To the best of our knowledge, this is the shortest pulse duration ever achieved by a 100-W-level fiber chirped pulse amplification laser system at a repetition rate of few megahertz, without any special post-compression manipulation.

  1. Development of Recuperator for 4 K Pulse Tube Refrigerators Operating at Opposite Phases

    NASA Astrophysics Data System (ADS)

    Jung, Jeheon; Jeong, Sangkwon

    2004-06-01

    A 4 K pulse tube refrigerator can be constructed with a recuperator as the second stage regenerator and two pulse tubes operating at opposite phases in the second stage. The recuperator would be the critical component in this configuration, as is the second stage regenerator in typical 4 K cryocoolers. The required condition of this recuperative pulse tube refrigerator for efficient performance is that the recuperator should excel or at least equal the typical second stage regenerator. The recuperator has to have lower pressure drop, lager heat transfer area and smaller void volume. Practically the major difficulty encountered in adapting the recuperator to pulse tube refrigerator is the fact that small void volume is not easily achieved in the recuperator. In order to fulfill such requirement, the recuperator has to be constructed with very narrow channels. The way of constructing narrow channels which is recommended in this paper is forming the metal sheet-porous spacer-metal sheet layers. If the recuperator is constructed in the recommend way in the flat rectangular form, the configuration of placing ports at the four corners with the flow across is revealed to have the optimal performance.

  2. Slow and Go: Pulsing Slip Rates on the Creeping Section of the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Turner, R. C.; Shirzaei, M.; Nadeau, R. M.; Burgmann, R.

    2014-12-01

    Rising and falling slip rates on the creeping section of the San Andreas Fault have been inferred from variations of recurrence intervals of repeating micro-earthquakes, but this observation has not previously been confirmed using modern geodetic data. Here, we report on observations of this 'pulsing' slip obtained from advanced multi-temporal Interferometric Synthetic Aperture Radar (InSAR) data. The surface deformation time series show a strong correlation to the previously documented slip rate variations derived from repeating earthquakes on the fault interface, at various spatial and temporal scales. Time series analysis reveals a quasi-periodic pulsing with approximately 2-year-long intervals along some sections of the fault in both InSAR and repeating earthquake datasets, with the earthquakes on the fault interface lagging behind the far-field deformation by about six months. This suggests a temporal delay between the pulsing crustal strain generated by deep-seated shear and the time-variable slip on the shallow fault interface, and that at least in some places this process may be cyclical.

  3. Slow and Go: Pulsing slip rates on the creeping section of the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Turner, Ryan C.; Shirzaei, Manoochehr; Nadeau, Robert M.; Bürgmann, Roland

    2015-08-01

    Rising and falling slip rates on the creeping section of the San Andreas Fault have been inferred from variations of recurrence intervals of characteristically repeating microearthquakes, but this observation has not previously been confirmed using modern geodetic data. Here we report on observations of this "pulsing" slip obtained from advanced multitemporal interferometric synthetic aperture radar (InSAR) data, confirmed using continuous GPS sites of the Plate Boundary Observatory. The surface deformation time series show a strong correlation to the previously documented slip rate variations derived from repeating earthquakes on the fault interface, at various spatial and temporal scales. Time series and spectral analyses of repeating earthquake and InSAR data reveal a quasiperiodic pulsing with a roughly 2 year period along some sections of the fault, with the earthquakes on the fault interface lagging behind the far-field deformation by about 6 months. This suggests a temporal delay between the pulsing crustal strain generated by deep-seated shear and the time-variable slip on the shallow fault interface, and that at least in some places this process may be cyclical. There exist potential impacts for time-dependent seismic hazard forecasting in California and, as it becomes better validated in the richly instrumented natural laboratory of the central San Andreas Fault, the process used here will be even more helpful in characterizing hazard and fault zone rheology in areas without California's geodetic infrastructure.

  4. Effects of cochlear-implant pulse rate and inter-channel timing on channel interactions and thresholds

    NASA Astrophysics Data System (ADS)

    Middlebrooks, John C.

    2004-07-01

    Interactions among the multiple channels of a cochlear prosthesis limit the number of channels of information that can be transmitted to the brain. This study explored the influence on channel interactions of electrical pulse rates and temporal offsets between channels. Anesthetized guinea pigs were implanted with 2-channel scala-tympani electrode arrays, and spike activity was recorded from the auditory cortex. Channel interactions were quantified as the reduction of the threshold for pulse-train stimulation of the apical channel by sub-threshold stimulation of the basal channel. Pulse rates were 254 or 4069 pulses per second (pps) per channel. Maximum threshold reductions averaged 9.6 dB when channels were stimulated simultaneously. Among nonsimultaneous conditions, threshold reductions at the 254-pps rate were entirely eliminated by a 1966-μs inter-channel offset. When offsets were only 41 to 123 μs, however, maximum threshold shifts averaged 3.1 dB, which was comparable to the dynamic ranges of cortical neurons in this experimental preparation. Threshold reductions at 4069 pps averaged up to 1.3 dB greater than at 254 pps, which raises some concern in regard to high-pulse-rate speech processors. Thresholds for various paired-pulse stimuli, pulse rates, and pulse-train durations were measured to test possible mechanisms of temporal integration.

  5. Input/output pulse operation of ZnO nanowire threshold integrators.

    PubMed

    White, Richard; Colli, Alan; Li, Hongwei; Kivioja, Jani

    2011-01-14

    Integrating more functionality into individual nano-components is a key step to exploit alternative architectures for energy-efficient computation, such as, for instance, neuromorphic computing. Here, we show how to configure ZnO nanowire field-effect transistors as light pulse integrators with programmable threshold. We demonstrate that these single-component devices can be operated as both synchronous and asynchronous neuron-like structures, where the firing threshold and the form of the output signal, either step-like or spiked, can be controlled by using several operational parameters, including the environment in which the device operates. A detailed study showing how environmental variables, such as relative humidity, ambient light and temperature, affect device operation is presented.

  6. High power pulsed magnetron sputtering: A method to increase deposition rate

    SciTech Connect

    Raman, Priya McLain, Jake; Ruzic, David N; Shchelkanov, Ivan A.

    2015-05-15

    High power pulsed magnetron sputtering (HPPMS) is a state-of-the-art physical vapor deposition technique with several industrial applications. One of the main disadvantages of this process is its low deposition rate. In this work, the authors report a new magnetic field configuration, which produces deposition rates twice that of conventional magnetron's dipole magnetic field configuration. Three different magnet pack configurations are discussed in this paper, and an optimized magnet pack configuration for HPPMS that leads to a higher deposition rate and nearly full-face target erosion is presented. The discussed magnetic field produced by a specially designed magnet assembly is of the same size as the conventional magnet assembly and requires no external fields. Comparison of deposition rates with different power supplies and the electron trapping efficiency in complex magnetic field arrangements are discussed.

  7. Performance of large aperture tapered fiber phase conjugate mirror with high pulse energy and 1-kHz repetition rate.

    PubMed

    Zhao, Zhigang; Dong, Yantao; Pan, Sunqiang; Liu, Chong; Chen, Jun; Tong, Lixin; Gao, Qingsong; Tang, Chun

    2012-01-16

    A large aperture fused silica tapered fiber phase conjugate mirror is presented with a maximum 70% stimulated Brillouin scattering (SBS) reflectivity, which is obtained with 1 kHz repetition rate, 15 ns pulse width and 38 mJ input pulse energy. To the best of our knowledge, this is the highest SBS reflectivity ever reported by using optical fiber as a phase conjugate mirror for such high pulse repetition rate (1 kHz) and several tens of millijoule (mJ) input pulse energy. The influences of fiber end surface quality and pump pulse widths on SBS reflectivity are investigated experimentally. The results show that finer fiber end surface quality and longer input pulse widths are preferred for obtaining higher SBS reflectivity with higher input pulse energy. Double passing amplification experiments are also performed. 52 mJ pulse energy is achieved at 1 kHz repetition rate, with a reflected SBS pulse width of 1.5 ns and a M(2) factor of 2.3. The corresponding peak power reaches 34.6 MW. Obvious beam quality improvement is observed. PMID:22274534

  8. Operation Mode on Pulse Modulation in Atmospheric Radio Frequency Glow Discharges

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Guo, Ying; Huang, Xiaojiang; Zhang, Jing; Shi, Jianjun

    2016-10-01

    The discharge operation regime of pulse modulated atmospheric radio frequency (RF) glow discharge in helium is investigated on the duty cycle and frequency of modulation pulses. The characteristics of radio frequency discharge burst in terms of breakdown voltage, alpha(α)-gamma(γ) mode transition voltage and current are demonstrated by the discharge current voltage characteristics. The minimum breakdown voltage of RF discharge burst was obtained at the duty cycle of 20% and frequency of 400 kHz, respectively. The α-γ mode transition of RF discharge burst occurs at higher voltage and current by reducing the duty cycle and elevating the modulation frequency before the RF discharge burst evolving into the ignition phase, in which the RF discharge burst can operate stably in the γ mode. It proposes that the intensity and stability of RF discharge burst can be improved by manipulating the duty cycle and modulation frequency in pulse modulated atmospheric RF glow discharge. supported by National Natural Science Foundation of China (Nos. 11475043 and 11375042)

  9. Prototype Operational Advances for Atmospheric Radiation Dose Rate Specification

    NASA Astrophysics Data System (ADS)

    Tobiska, W. K.; Bouwer, D.; Bailey, J. J.; Didkovsky, L. V.; Judge, K.; Garrett, H. B.; Atwell, W.; Gersey, B.; Wilkins, R.; Rice, D.; Schunk, R. W.; Bell, D.; Mertens, C. J.; Xu, X.; Crowley, G.; Reynolds, A.; Azeem, I.; Wiltberger, M. J.; Wiley, S.; Bacon, S.; Teets, E.; Sim, A.; Dominik, L.

    2014-12-01

    Space weather's effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun's photons, particles, and fields. The coupling between the solar and galactic high-energy particles, the magnetosphere, and atmospheric regions can significantly affect humans and our technology as a result of radiation exposure. Space Environment Technologies (SET) has developed innovative, new space weather observations that will become part of the toolset that is transitioned into operational use. One prototype operational system for providing timely information about the effects of space weather is SET's Automated Radiation Measurements for Aerospace Safety (ARMAS) system. ARMAS will provide the "weather" of the radiation environment to improve aircraft crew and passenger safety. Through several dozen flights the ARMAS project has successfully demonstrated the operation of a micro dosimeter on commercial aviation altitude aircraft that captures the real-time radiation environment resulting from Galactic Cosmic Rays and Solar Energetic Particles. The real-time radiation exposure is computed as an effective dose rate (body-averaged over the radiative-sensitive organs and tissues in units of microsieverts per hour); total ionizing dose is captured on the aircraft, downlinked in real-time via Iridium satellites, processed on the ground into effective dose rates, compared with NASA's Langley Research Center (LaRC) most recent Nowcast of Atmospheric Ionizing Radiation System (NAIRAS) global radiation climatology model runs, and then made available to end users via the web and smart phone apps. We are extending the dose measurement domain above commercial aviation altitudes into the stratosphere with a collaborative project organized by NASA's Armstrong Flight Research Center (AFRC) called Upper-atmospheric Space and Earth Weather eXperiment (USEWX). In USEWX we will be flying on the ER-2 high altitude aircraft a micro dosimeter for

  10. Novel ultrafast sources on chip: filter driven four wave mixing lasers, from high repetition rate to burst mode operation

    NASA Astrophysics Data System (ADS)

    Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T.; Moss, Dave J.; Morandotti, Roberto

    2016-03-01

    Passive fiber mode-locked lasers enable the excitation of multiple pulses per round trip representing a potential solutions for the increasing demand of practical optical sources with repetition rates of hundreds of GHz or higher. The control of such high repetition rate regimes is however a challenge. To this purpose, linear filters have been used in an "intracavity" configuration to force the repetition rate of the laser. This design is known as dissipative four wave mixing (DFWM) but it is usually unstable and hence marginally suitable for practical applications. We explore the use of nonlinear intracavity filters, such as integrated micro-ring resonators, capable of "driving" the FWM interaction in the laser. We term this approach as Filter-Driven FWM. With a proper choice of the filter properties in terms of free spectral range (FSR) and Q factor, we could observe stable regimes over a wide range of operating conditions, from high repetition rate oscillation at a 200GHz to the formation of two stable spectral comb replicas separated by the FSR of the main cavity (65MHz). High order filters, moreover, allow achieving nonlinear operation over large passbands. With an 11th order filter we achieve low-frequency mode-locking between the main cavity modes that oscillate within each resonance of the filter, producing burst pulsed operation. A stable mode-locked pulse train at 655GHz with an envelope of 42ps at 6.45MHz is achieved.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  12. Frequency doubled high-power disk lasers in pulsed and continuous-wave operation

    NASA Astrophysics Data System (ADS)

    Weiler, Sascha; Hangst, Alexander; Stolzenburg, Christian; Zawischa, Ivo; Sutter, Dirk; Killi, Alexander; Kalfhues, Steffen; Kriegshaeuser, Uwe; Holzer, Marco; Havrilla, David

    2012-03-01

    The disk laser with multi-kW output power in infrared cw operation is widely used in today's manufacturing, primarily in the automotive industry. The disk technology combines high power (average and/or peak power), excellent beam quality, high efficiency and high reliability with low investment and operating costs. Additionally, the disk laser is ideally suited for frequency conversion due to its polarized output with negligible depolarization losses. Laser light in the green spectral range (~515 nm) can be created with a nonlinear crystal. Pulsed disk lasers with green output of well above 50 W (extracavity doubling) in the ps regime and several hundreds of Watts in the ns regime with intracavity doubling are already commercially available whereas intracavity doubled disk lasers in continuous wave operation with greater than 250 W output are in test phase. In both operating modes (pulsed and cw) the frequency doubled disk laser offers advantages in existing and new applications. Copper welding for example is said to show much higher process reliability with green laser light due to its higher absorption in comparison to the infrared. This improvement has the potential to be very beneficial for the automotive industry's move to electrical vehicles which requires reliable high-volume welding of copper as a major task for electro motors, batteries, etc.

  13. Electromagnetic Pulse (EMP) survey of the Louisiana State Emergency Operating Center, Baton Rouge, Louisiana

    SciTech Connect

    Crutcher, R.I.; Buchanan, M.E.; Jones, R.W.

    1989-08-01

    The purpose of this report is to develop an engineering design package to protect the federal Emergency Management Agency (FEMA) National Radio System (FNARS) facilities from the effects of high-altitude electromagnetic pulses (HEMP). This report refers to the Louisiana State Emergency Operating Center (EOC) in Baton Rouge, Louisiana. This report addresses electromagnetic pulse (EMP) effects only, and disregards any condition in which radiation effects may be a factor. It has been established that, except for the source region of a surface burst, EMP effects of high-altitude bursts are more severe than comparable detonations in either air or surface regions. Any system hardened to withstand the more extreme EMP environment will survive the less severe conditions. The threatening environment will therefore be limited to HEMP situations. 76 figs., 2 tabs.

  14. 948 kHz repetition rate, picosecond pulse duration, all-PM 1.03 μm mode-locked fiber laser based on nonlinear polarization evolution

    NASA Astrophysics Data System (ADS)

    Boivinet, S.; Lecourt, J.-B.; Hernandez, Y.; Fotiadi, A.; Mégret, P.

    2014-05-01

    We present in this study a PM all-fiber laser oscillator passively mode-locked (ML) at 1.03 μm. The laser is based on Nonlinear Polarization Evolution (NPE) in polarization maintaining (PM) fibers. In order to obtain the mode-locking regime, a nonlinear reflective mirror including a fibered polarizer, a long fiber span and a fibered Faraday mirror (FM) is inserted in a Fabry-Perot laser cavity. In this work we explain the principles of operation of this original laser design that permits to generate ultrashort pulses at low repetition (lower that 1MHz) rate with a cavity length of 100 m of fiber. In this experiment, the measured pulse duration is about 6 ps. To our knowledge this is the first all-PM mode-locked laser based on the NPE with a cavity of 100m length fiber and a delivered pulse duration of few picosecondes. Furthermore, the different mode-locked regimes of the laser, i.e. multi-pulse, noise-like mode-locked and single pulse, are presented together with the ways of controlling the apparition of these regimes. When the single pulse mode-locking regime is achieved, the laser delivers linearly polarized pulses in a very stable way. Finally, this study includes numerical results which are obtained with the resolution of the NonLinear Schrodinger Equations (NLSE) with the Split-Step Fourier (SSF) algorithm. This modeling has led to the understanding of the different modes of operation of the laser. In particular, the influence of the peak power on the reflection of the nonlinear mirror and its operation are studied.

  15. Pulsed Plasma Thruster (PPT) Technology: Earth Observing-1 PPT Operational and Advanced Components Being Developed

    NASA Technical Reports Server (NTRS)

    Pencil, Eric J.; Benson, Scott W.; Arrington, Lynn A.; Frus, John; Hoskins, W. Andrew; Burton, Rodney

    2003-01-01

    In 2002 the pulsed plasma thruster (PPT) mounted on the Earth Observing-1 spacecraft was operated successfully in orbit. The two-axis thruster system is fully incorporated in the attitude determination and control system and is being used to automatically counteract disturbances in the pitch axis of the spacecraft. The first tests conducted in space demonstrated the full range of PPT operation, followed by calibration of control torques from the PPT in the attitude control system. Then the spacecraft was placed in PPT control mode. To date, it has operated for about 30 hr. The PPT successfully controlled pitch momentum during wheel de-spin, solar array acceleration and deceleration during array rewind, and environmental torques in nominal operating conditions. Images collected with the Advanced Landsat Imager during PPT operation have demonstrated that there was no degradation in comparison to full momentum wheel control. In addition, other experiments have been performed to interrogate the effects of PPT operation on communication packages and light reflection from spacecraft surfaces. Future experiments will investigate the possibility of orbit-raising maneuvers, spacecraft roll, and concurrent operation with the Hyperion imager. Future applications envisioned for pulsed plasma thrusters include longer life, higher precision, multiaxis thruster configurations for three-axis attitude control systems or high-precision, formationflying systems. Advanced components, such as a "dry" mica-foil capacitor, a wear-resistant spark plug, and a multichannel power processing unit have been developed under contract with Unison Industries, General Dynamics, and C.U. Aerospace. Over the last year, evaluation tests have been conducted to determine power processing unit efficiency, atmospheric functionality, vacuum functionality, thruster performance evaluation, thermal performance, and component life.

  16. Utilization of a cryo-prober system for operation of a pulse-driven josephson junction array

    NASA Astrophysics Data System (ADS)

    Maruyama, M.; Urano, C.; Kaneko, N.; Yamamori, H.; Shoji, A.; Maezawa, M.; Hashimoto, Y.; Suzuki, H.; Nagasawa, S.; Satoh, T.; Hidaka, M.; Kiryu, S.

    2010-06-01

    We demonstrated the operation of pulse-driven Josephson junction arrays (JJAs) for AC voltage standard using a wideband cryo-prober system with a 4-K Gifford-MacMahon (GM) cooler. This unique system was originally developed for high-speed network switch applications of rapid-single-flux-quantum (RSFQ) circuits and enables wideband data transmission at bit rates of higher than 10 Gbps between room-temperature and cryogenic environments. JJA chips were fabricated using NbN-based superconductor-normal metal-superconductor (SNS) junctions. A 5-mm chip was mounted on a 16-mm chip carrier using flip-chip bonding technology for probe contact. To obtain bipolar output voltages, we tried two types of testing based on the AC coupling technique proposed by the National Institute of Standards and Technology (NIST). A pulse pattern generator (PPG) with a large memory of 134 Mbit was used for covering a wide frequency range of output signals. As a result, we succeeded in bipolar operation of the JJA, generating waveforms at frequencies from 60 Hz to several tens of kilo hertz. The maximum rms voltage obtained for a single array was 12.7 mV. The observed spurious level was lower than -93 dBc at 16 kHz.

  17. Double-pulse machining as a technique for the enhancement of material removal rates in laser machining of metals

    SciTech Connect

    Forsman, A.C.; Banks, P.S.; Perry, M.D.; Campbell, E.M.; Dodell, A.L.; Armas, M.S.

    2005-08-01

    Several nanosecond 0.53-{mu}m laser pulses separated by several tens of nanoseconds have been shown to significantly enhance (three to ten times) material removal rates while minimizing redeposition and heat-affected zones. Economic, high-quality, high-aspect ratio holes (>10:1) in metals are produced as a result. A phenomenological model whereby the second laser pulse interacts with the ejecta produced by the first laser pulse and in close proximity to the material surface is consistent with the observations. Incident laser wavelengths of 1.05 and 0.35 {mu}m also benefit from this pulse format.

  18. Fiber optic based heart-rate and pulse pressure shape monitor

    NASA Astrophysics Data System (ADS)

    Kokkinos, D.; Dehipawala, S.; Holden, T.; Cheung, E.; Musa, M.; Tremberger, G., Jr.; Schneider, P.; Lieberman, D.; Cheung, T.

    2012-01-01

    Macro-bending fiber optic based heart-rate and pulse pressure shape monitors have been fabricated and tested for non-invasive measurement. Study of fiber bending loss and its stability and variations are very important especially for sensor designs based on optical fiber bending. Wavelengths from 1300 nm to 1550 nm have been used with fabrication based on multimode fiber, single mode fiber, and photonic crystal fiber. The smallest studied curvature would demand the use of single mode standard fibers. The collected data series show high quality suitable for random series analysis. Fractal property of optically measured pulse pressure data has been observed to correlate with physical activity. Correlation to EKG signal suggests that the fabricated monitors are capable of measuring the differential time delays at wrist and leg locations. The difference in time delay could be used to formulate a velocity parameter for diagnostics. The pulse shape information collected by the fiber sensor provides additional parameters for the analysis of the fractal nature of the heart. The application to real time measurement of blood vessel stiffness with this optical non-invasive fiber sensor is discussed.

  19. Dose rate dependence of the PTW 60019 microDiamond detector in high dose-per-pulse pulsed beams

    NASA Astrophysics Data System (ADS)

    Brualla-González, Luis; Gómez, Faustino; Pombar, Miguel; Pardo-Montero, Juan

    2016-01-01

    Recombination effects can affect the detectors used for the dosimetry of radiotherapy fields. They are important when using ionization chambers, especially in liquid-filled ionization chambers, and should be corrected for. The introduction of flattening-filter-free accelerators increases the typical dose-per-pulse used in radiotherapy beams, which leads to more important recombination effects. Diamond detectors provide a good solution for the dosimetry and quality assurance of small radiotherapy fields, due to their low energy dependence and small volume. The group of Università di Roma Tor Vergata has developed a synthetic diamond detector, which is commercialized by PTW as microDiamond detector type 60019. In this work we present an experimental characterization of the collection efficiency of the microDiamond detector, focusing on high dose-per-pulse FFF beams. The collection efficiency decreases with dose-per-pulse, down to 0.978 at 2.2 mGy/pulse, following a Fowler-Attix-like curve. On the other hand, we have found no significant dependence of the collection efficiency on the pulse repetition frequency (or pulse period).

  20. Conditioned suppression, heart rate and pulse volume: effects of instructions on extinction.

    PubMed

    Bond, N W

    1979-11-01

    Two experimental groups of undergraduate volunteers received five classical aversive conditioning trials with a tone conditioned stimulus (CS) and shock unconditioned stimulus (UCS). Control groups received either the CS alone or UCS alone. Subjects from one experimental group were subsequently instructed that they would not receive further shocks, while the other experimental group received no such instructions. The CS alone was then presented once to all four groups while subjects were engaged in a button-pressing task maintained by slide reinforcement. During this latter phase rate of button pressing was measured as well as heart rate and pulse volume. The last two measures being employed as indices of autonomic arousal. The results indicated that while instructions as to the absence of the UCS completely abolished the conditioned suppression of button-pressing, they had no effect upon the pulse volume CR. A heart rate CR was not obtained. These results reflect unfavourably upon theoretical formulations of conditioned suppression that emphasize the causal interdependence of motor and autonomic events or the primacy of either one.

  1. The influence of power source dynamics on wire melting rate in pulsed GMA welding

    SciTech Connect

    Richardson, I.M. ); Bucknall, P.W. ); Stares, I. )

    1994-02-01

    The welding wire melting rate during conventional direct current (DC) gas metal arc (GMA) welding may be modeled empirically by a simple expression relating material constants, current and electrode extension. The resultant equation is found to be in good agreement when welding at moderate or high currents. In the case of pulsed GMA welding, it has already been shown that a good approximation to the observed melting behavior may be obtained by assuming that the DC equation is instantaneously valid and integrating over one pulse cycle. This article extends earlier work to consider the influence of power source dynamics on the integrated expression. Calculations have been made for two cases: an idealized trapezoidal waveform and a more representative exponential form. Predictions indicate that under certain circumstances response rate can have a significant influence over the wire melting rate at a given mean current. The validity of this prediction has been tested experimentally for the idealized trapezoidal waveform and results are presented for comparison. The significance of power source dynamics is discussed with reference to static output characteristics and the resultant influence on metal droplet detachment.

  2. Effect of pulse duration and strain rate on incipient spall fracture in copper

    SciTech Connect

    Johnson, J.N.; Gray, G.T. III; Bourne, N.K.

    1999-11-01

    Data are presented on real time (VISAR) measurements of the spall fracture of copper for various pulse durations and tensile strain rates at the spall plane. The impactors consist of Teflon, {ital Y}-cut quartz, and a tungsten heavy alloy. VISAR data are compared with finite-difference calculations employing a rate-dependent void-growth model. The data and comparisons show little dependence of the onset of void growth on either pulse duration or tensile strain rate. Also, it is shown that hydrodynamics (wave propagation properties) involving the transmission of the spall signal from the spall plane to the free surface (plane of the VISAR measurement) can mask slight differences in the void-growth or fracture response. In addition, new results are presented for the elastic description of planar wave propagation in {ital Y}-cut quartz; expressions are given for the six independent stress components to second order in infinitesimal Lagrangian strains. A discussion with regard to additional use of {ital Y}-cut quartz in impact experiments is presented. {copyright} {ital 1999 American Institute of Physics.}

  3. Power scaling of supercontinuum seeded megahertz-repetition rate optical parametric chirped pulse amplifiers.

    PubMed

    Riedel, R; Stephanides, A; Prandolini, M J; Gronloh, B; Jungbluth, B; Mans, T; Tavella, F

    2014-03-15

    Optical parametric chirped-pulse amplifiers with high average power are possible with novel high-power Yb:YAG amplifiers with kW-level output powers. We demonstrate a compact wavelength-tunable sub-30-fs amplifier with 11.4 W average power with 20.7% pump-to-signal conversion efficiency. For parametric amplification, a beta-barium borate crystal is pumped by a 140 W, 1 ps Yb:YAG InnoSlab amplifier at 3.25 MHz repetition rate. The broadband seed is generated via supercontinuum generation in a YAG crystal.

  4. Power scaling of supercontinuum seeded megahertz-repetition rate optical parametric chirped pulse amplifiers.

    PubMed

    Riedel, R; Stephanides, A; Prandolini, M J; Gronloh, B; Jungbluth, B; Mans, T; Tavella, F

    2014-03-15

    Optical parametric chirped-pulse amplifiers with high average power are possible with novel high-power Yb:YAG amplifiers with kW-level output powers. We demonstrate a compact wavelength-tunable sub-30-fs amplifier with 11.4 W average power with 20.7% pump-to-signal conversion efficiency. For parametric amplification, a beta-barium borate crystal is pumped by a 140 W, 1 ps Yb:YAG InnoSlab amplifier at 3.25 MHz repetition rate. The broadband seed is generated via supercontinuum generation in a YAG crystal. PMID:24690803

  5. Characterization of the ITER model negative ion source during long pulse operation

    SciTech Connect

    Hemsworth, R.S.; Boilson, D.; Crowley, B.; Homfray, D.; Esch, H.P.L. de; Krylov, A.; Svensson, L.

    2006-03-15

    It is foreseen to operate the neutral beam system of the International Thermonuclear Experimental Reactor (ITER) for pulse lengths extending up to 1 h. The performance of the KAMABOKO III negative ion source, which is a model of the source designed for ITER, is being studied on the MANTIS test bed at Cadarache. This article reports the latest results from the characterization of the ion source, in particular electron energy distribution measurements and the comparison between positive ion and negative ion extraction from the source.

  6. Diagrammatic analysis of the density operator for nonlinear optical calculations Pulsed and CW responses

    NASA Technical Reports Server (NTRS)

    Yee, T. K.; Gustafson, T. K.

    1978-01-01

    In the present paper a diagrammatic analysis of the density operator for the evaluation of nonlinear optical quantities is considered. The present approach extends earlier diagrammatic analysis by treating the time evolution of both the wave function and its complex conjugate. Time-ordered graphs result, each of which corresponds to a term in the density matrix. Examples involving the third-order susceptibility are discussed for both monochromatic and pulse excitation. In particular coherent rotational transient birefringence is discussed. The diagrams provide a convenient means by which nonlinear optical processes can be precisely defined and the susceptibility readily evaluated.

  7. Argon gas-puff radius optimiaztion for Saturn operating in the long-pulse mode.

    SciTech Connect

    Apruzese, John P.; Jackson, S. L.; Commisso, Robert J.; Weber, Bruce V.; Mosher, Daniel A.

    2010-06-01

    Argon gas puff experiments using the long pulse mode of Saturn (230-ns rise time) have promise to increase the coupled energy and simplify operations because the voltage is reduced in vacuum and the forward-going energy is higher for the same Marx charge. The issue addressed in this work is to determine if the 12-cm-diameter triple nozzle used in Saturn long-pulse-mode experiments to date provides maximum K-shell yield, or if a different-radius nozzle provides additional radiation. Long-pulse implosions are modeled by starting with measured density distributions from the existing 12-cm-diameter nozzle, and then varying the outer radius in an implosion-energy-conserving self-similar manner to predict the gas-puff diameter that results in the maximum K-shell yield. The snowplow-implosions and multi-zone radiation transport models used in the analysis are benchmarked against detailed measurements from the 12-cm-diameter experiments. These calculations indicate that the maximum K-shell emission is produced with very nearly the existing nozzle radius.

  8. High energy density capacitors for vacuum operation with a pulsed plasma load

    NASA Technical Reports Server (NTRS)

    Guman, W. J.

    1976-01-01

    Results of the effort of designing, fabricating, and testing of a 40 joules/lb (88.2 joules/Kg) high voltage energy storage capacitor suitable for operating a pulsed plasma thruster in a vacuum environment for millions of pulses are presented. Using vacuum brazing and heli-arc welding techniques followed by vacuum and high pressure helium leak tests it was possible to produce a hermetically sealed relatively light weight enclosure for the dielectric system. An energy density of 40 joules/lb was realized with a KF-polyvinylidene fluoride dielectric system. One capacitor was D.C. life tested at 4 KV (107.8 joules/lb) for 2,000 hours before it failed. Another exceeded 2,670 hours without failure at 38.3 joules/lb. Pulse life testing in a vacuum exceeded 300,000 discharges with testing still in progress. The D.C. life test data shows a small decrease in capacitance and an increase in dissipation factor with time. Heat transfer from the load to the capacitor must also be considered besides the self-heat generated by the capacitor.

  9. a Chirped-Pulse Fourier Transform Spectrometer Operating from 110 TO 170 GHZ

    NASA Astrophysics Data System (ADS)

    Bernier, Lauren E.; Shipman, Steven

    2014-06-01

    A chirped-pulse Fourier transform spectrometer operating from 110 - 170 GHz was constructed. The design of this spectrometer is directly adapted from that of the 260 - 295 GHz chirped-pulse spectrometer built by Steber and co-workers at the University of Virginia. In this instrument, an arbitrary waveform generator (AWG) produces a chirped pulse which is frequency shifted to a range between 9.2 and 14.1 GHz and then multiplied by a factor of 12 via an active multiplier chain to a range between 110 and 170 GHz. As in the Pate lab design, the AWG also serves as a local oscillator (LO) source; this LO is multiplied and used to downconvert the molecular emission, allowing it to be collected by a 40 GS/s digitizer. Benchmark measurements were taken for methanol at room temperature, and details of the instrument's performance will be discussed. A.L. Steber, B.J. Harris, J.L. Neill, and B.H. Pate, J. Mol. Spectrosc., 280, 3 (2012)

  10. Optimization of Pulsed-DEER Measurements for Gd-Based Labels: Choice of Operational Frequencies, Pulse Durations and Positions, and Temperature

    SciTech Connect

    Raitsimring, A.; Astashkin, A. V.; Enemark, J. H.; Kaminker, I.; Goldfarb, D.; Walter, E. D.; Song, Y.; Meade, T. J.

    2012-12-29

    In this work, the experimental conditions and parameters necessary to optimize the long-distance (≥ 60 Å) Double Electron-Electron Resonance (DEER) measurements of biomacromolecules labeled with Gd(III) tags are analyzed. The specific parameters discussed are the temperature, microwave band, the separation between the pumping and observation frequencies, pulse train repetition rate, pulse durations and pulse positioning in the electron paramagnetic resonance spectrum. It was found that: (i) in optimized DEER measurements, the observation pulses have to be applied at the maximum of the EPR spectrum; (ii) the optimal temperature range for Ka-band measurements is 14-17 K, while in W-band the optimal temperatures are between 6-9 K; (iii) W-band is preferable to Ka-band for DEER measurements. Recent achievements and the conditions necessary for short-distance measurements (<15 Å) are also briefly discussed.

  11. A novel non-linear recursive filter design for extracting high rate pulse features in nuclear medicine imaging and spectroscopy.

    PubMed

    Sajedi, Salar; Kamal Asl, Alireza; Ay, Mohammad R; Farahani, Mohammad H; Rahmim, Arman

    2013-06-01

    Applications in imaging and spectroscopy rely on pulse processing methods for appropriate data generation. Often, the particular method utilized does not highly impact data quality, whereas in some scenarios, such as in the presence of high count rates or high frequency pulses, this issue merits extra consideration. In the present study, a new approach for pulse processing in nuclear medicine imaging and spectroscopy is introduced and evaluated. The new non-linear recursive filter (NLRF) performs nonlinear processing of the input signal and extracts the main pulse characteristics, having the powerful ability to recover pulses that would ordinarily result in pulse pile-up. The filter design defines sampling frequencies lower than the Nyquist frequency. In the literature, for systems involving NaI(Tl) detectors and photomultiplier tubes (PMTs), with a signal bandwidth considered as 15 MHz, the sampling frequency should be at least 30 MHz (the Nyquist rate), whereas in the present work, a sampling rate of 3.3 MHz was shown to yield very promising results. This was obtained by exploiting the known shape feature instead of utilizing a general sampling algorithm. The simulation and experimental results show that the proposed filter enhances count rates in spectroscopy. With this filter, the system behaves almost identically as a general pulse detection system with a dead time considerably reduced to the new sampling time (300 ns). Furthermore, because of its unique feature for determining exact event times, the method could prove very useful in time-of-flight PET imaging.

  12. Effect of surface roughness on erosion rates of pure copper coupons in pulsed vacuum arc system

    NASA Astrophysics Data System (ADS)

    Rao, Lakshminarayana; Munz, Richard J.

    2007-12-01

    Vacuum arc erosion measurements were performed on copper cathodes having different surface roughness and surface patterns in 10-5 Torr vacuum (1.3324 mPa), in an external magnetic field of 0.04 T. Different surface patterns and surface roughness were created by grit blasting with alumina grits (G-cathodes) and grinding with silicon carbide emery paper (E-cathodes). The erosion rates of these cathodes were obtained by measuring the weight loss of the electrode after igniting as many as 135 arc pulses, each of which was 500 µs long at an arc current of 125 A. The erosion rates measured indicate that erosion rates decrease with decreasing roughness levels. Results obtained indicate that both surface roughness and surface patterns affect the erosion rate. Having patterns perpendicular to the direction of cathode spot movement gives lower erosion rates than having patterns parallel to arc movement. Isotropic surfaces give lower erosion rates than patterned surfaces at the same roughness.

  13. Characterization of MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces

    NASA Astrophysics Data System (ADS)

    Sivakumar, Manickam; Venkatakrishnan, Krishnan; Tan, Bo

    2011-12-01

    In this study, MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces under ambient condition were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The radiation fluence used was 0.5 J/cm2 at a pulse repetition rate of 25 MHz with 1 ms interaction time. SEM analysis of the irradiated surfaces showed self-assembled intermingled weblike nanofibrous structure in and around the laser-irradiated spots. Further TEM investigation on this nanostructure revealed that the nanofibrous structure is formed due to aggregation of Au-Si/Si nanoparticles. The XRD peaks at 32.2°, 39.7°, and 62.5° were identified as (200), (211), and (321) reflections, respectively, corresponding to gold silicide. In addition, the observed chemical shift of Au 4 f and Si 2 p lines in XPS spectrum of the irradiated surface illustrated the presence of gold silicide at the irradiated surface. The generation of Si/Au-Si alloy fibrous nanoparticles aggregate is explained by the nucleation and subsequent condensation of vapor in the plasma plume during irradiation and expulsion of molten material due to high plasma pressure.

  14. Characterization of MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces

    PubMed Central

    2011-01-01

    In this study, MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces under ambient condition were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The radiation fluence used was 0.5 J/cm2 at a pulse repetition rate of 25 MHz with 1 ms interaction time. SEM analysis of the irradiated surfaces showed self-assembled intermingled weblike nanofibrous structure in and around the laser-irradiated spots. Further TEM investigation on this nanostructure revealed that the nanofibrous structure is formed due to aggregation of Au-Si/Si nanoparticles. The XRD peaks at 32.2°, 39.7°, and 62.5° were identified as (200), (211), and (321) reflections, respectively, corresponding to gold silicide. In addition, the observed chemical shift of Au 4f and Si 2p lines in XPS spectrum of the irradiated surface illustrated the presence of gold silicide at the irradiated surface. The generation of Si/Au-Si alloy fibrous nanoparticles aggregate is explained by the nucleation and subsequent condensation of vapor in the plasma plume during irradiation and expulsion of molten material due to high plasma pressure. PMID:21711595

  15. Measurement of performance using acceleration control and pulse control in simulated spacecraft docking operations

    NASA Technical Reports Server (NTRS)

    Brody, Adam R.; Ellis, Stephen R.

    1992-01-01

    Nine commercial airline pilots served as test subjects in a study to compare acceleration control with pulse control in simulated spacecraft maneuvers. Simulated remote dockings of an orbital maneuvering vehicle (OMV) to a space station were initiated from 50, 100, and 150 meters along the station's -V-bar (minus velocity vector). All unsuccessful missions were reflown. Five way mixed analysis of variance (ANOVA) with one between factor, first mode, and four within factors (mode, bloch, range, and trial) were performed on the data. Recorded performance measures included mission duration and fuel consumption along each of the three coordinate axes. Mission duration was lower with pulse mode, while delta V (fuel consumption) was lower with acceleration mode. Subjects used more fuel to travel faster with pulse mode than with acceleration mode. Mission duration, delta V, X delta V, Y delta V., and Z delta V all increased with range. Subjects commanded the OMV to 'fly' at faster rates from further distances. These higher average velocities were paid for with increased fuel consumption. Asymmetrical transfer was found in that the mode transitions could not be predicted solely from the mission duration main effect. More testing is advised to understand the manual control aspects of spaceflight maneuvers better.

  16. High-pressure pulsed avalanche discharges: Formulas for required preionization density and rate for homogeneity

    SciTech Connect

    Brenning, N.; Axnaes, I.; Nilsson, J.O.; Eninger, J.E.

    1997-02-01

    The requirements on preionization for the formation of spatially homogeneous pulsed avalanche discharges are examined. The authors derive two formulas which apply in the case of a slowly rising electric field, one which gives the required preionization density at breakdown, and one which gives the required preionization rate. These quantities are expressed as functions of the electrochemical properties of the gas, the neutral density, and the electric field rise time. They also treat the statistical effect that the electrons tend to form groups, in contrast to being randomly distributed in space, during the prebreakdown phase. This process is found to increase the required preionization rate significantly, typically by a factor of five for a discharge at atmospheric pressure. Homogeneous high-pressure discharges have been used for laser excitation, and have also been proposed for chemical plasma processing (ozone production) because of their good scaling properties and high efficiency.

  17. Design and preliminary tests of a twin coil HTS SMES for pulse power operation

    NASA Astrophysics Data System (ADS)

    Badel, Arnaud; Tixador, Pascal; Berger, Kevin; Deleglise, Marc

    2011-05-01

    The design of a twin coil 2 × 200 kJ-1 MW pulse power high temperature superconductor (HTS) superconducting magnetic energy storage (SMES) demonstrator is presented. Its aim is to test at small scale various possibilities of electromagnetic launcher powering. The foreseen operation modes include high voltage discharge in power capacitors, sequential discharges of identical energies from two coupled coils, and XRAM current multiplication. Special attention was paid to the arrangement of the coils for the energies discharged to be equal. The coils are cooled by conduction from three cryocoolers; the thermal design was optimized in order to maintain the coils around 15 K in spite of the high number of current leads required for XRAM operation (eight). Preliminary tests of the demonstrator are also presented, showing that the thermal and electrical characteristics are in very good agreement with the design objectives.

  18. Soft X-Ray Emission Analysis Of A Pulsed Capillary Discharge Operated In Nitrogen

    NASA Astrophysics Data System (ADS)

    Valdivia, M. P.; Valenzuela, J. C.; Wyndham, E. S.; Favre, M.; Chuaqui, H.; Bhuyan, H.

    2014-05-01

    We present results from a pulsed capillary ns discharge source, operated in Nitrogen and N/He mixtures, in an alumina capillary 2.1mm long with outer diameter of 6.3mm and inner diameter of 1.6mm. The electrical energy stored is 0.5J with peak current of 6kA. Fast charging from an IGBT based pulsed power circuit allows operation at 35-600 Hz with voltages in the range of 18-24kV. Characteristic time-integrated N/He spectra were recorded and analyzed for values of 20-200 Å, with clear evidence of He-like Nitrogen emission at 28.8Å, which represents a possible source for water window soft x-ray microscopy. Filtered diode measurements reveal the influence of axial electron beams, generated by hollow cathode dynamics, on the x-ray emission in the range of 300-450 eV. We discuss optimal voltage applied and pressure conditions for soft x-ray generation. Time-integrated MCP images of a filtered slit-wire system delivered clear evidence of full wall detachment with ~500μm in radial size for the entire emission range and ~200μm for the emission in the 300-450 eV range.

  19. Collection efficiency of ultrafine particles by an electrostatic precipitator under DC and pulse operating modes

    SciTech Connect

    Zukeran, Akinori; Looy, P.C.; Chakrabarti, A.; Berezin, A.A.; Jayaram, S.; Cross, J.D.; Ito, Tairo; Chang, J.S.

    1999-10-01

    High particle collection efficiency in terms of particle weight/volume mg/m{sup 3} is well achieved by a conventional electrostatic precipitator (ESP). However, the collection efficiencies in terms of number density for the ultrafine (particle size between 0.01--0.1 {micro}m) or submicrometer particles by a conventional ESP are still relatively low. Therefore, it is necessary to improve the collection efficiency for ultrafine particles. In this paper, attempts have been made to improve the ultrafine particle collection efficiency by controlling dust loading, as well as using the short pulse energizations. The present version of the ESP consists of three sets of wire-plate-type electrodes. For the ESP under dc operation modes, experimental results show that the collection efficiency for dc applied voltage decreases with increasing dust loading when particle density is larger than 2.5 x 10{sup 10} particles/m{sup 3} due to inefficient collections of ultrafine particles. However, under pulse operating modes without dc bias, high particle collection efficiency for ultrafine particles was obtained, which is thought to be due to the enhancement of particle charging by electrons.

  20. Pulsed external magnetic fields increase the deposition rate in reactive HiPIMS while preserving stoichiometry: An application to amorphous HfO2

    NASA Astrophysics Data System (ADS)

    Ganesan, R.; Treverrow, B.; Denniss, P.; McCulloch, D. G.; McKenzie, D. R.; Bilek, M. M. M.

    2016-09-01

    We compare the use of externally applied pulsed and steady magnetic fields for the enhancement of deposition rate in reactive High Power Impulse Magnetron Sputtering (HiPIMS), using the deposition of amorphous hafnium oxide (a-HfO2) on Si as an example. The external magnetic fields were applied by a solenoidal coil, placed above the magnetron target. In the case of a steady magnetic field, a higher voltage was required to initiate the HiPIMS discharge, a longer delay time was observed for current onset, and the films became substoichiometric. For the pulsed magnetic field, film stoichiometry was maintained under all applied external magnetic field strengths. Varying the duration and delay times of the magnetic field after the application of HiPIMS voltage pulse revealed that the afterglow of the plasma between HiPIMS pulses was actively quenched by the presence of the magnetic field. Therefore, the optimum operation with the highest plasma density was obtained by applying the external magnetic field only when the plasma was established and removing it at the end of the HiPIMS pulse. A model to explain the findings is presented in which the target poisoning by oxide formation is determined by the conditions in the afterglow. We describe an approach to achieve maximum deposition rate while maintaining film stoichiometry and high film quality. Amorphous HfO2 films with leakage current through the film of less than 5 × 10-5 A/cm2 at 0.1 MV/cm were obtained at the maximum deposition rate. The refractive index, at a wavelength of 500 nm, of the film prepared with pulsed magnetic field was 2.05 with a very low extinction coefficient of 8 × 10-5.

  1. Multi-wave ultrasonic Doppler method for measuring high flow-rates using staggered pulse intervals

    NASA Astrophysics Data System (ADS)

    Muramatsu, Ei; Murakawa, Hideki; Sugimoto, Katsumi; Asano, Hitoshi; Takenaka, Nobuyuki; Furuichi, Noriyuki

    2016-02-01

    The ultrasonic pulsed Doppler method (UDM) can obtain a velocity profile along the path of an ultrasonic beam. However, the UDM measurement volume is relatively large and it is known that the measurement volume affects the measurement accuracy. In this study, the effect of the measurement volume on velocity and flow rate measurements is analytically and experimentally evaluated. The velocities measured using UDM are considered to be ensemble-averaged values over the measurement volume in order to analyze the velocity error due to the measurement volume, while the flow rates are calculated from the integration of the velocity profile across the pipe. The analytical results show that the channel width, i.e. the spatial resolution along the ultrasonic beam axis, rather than the ultrasonic beam diameter, strongly influences the flow rate measurement. To improve the accuracy of the flow rate, a novel method using a multi-wave ultrasonic transducer consisting of two piezo-electric elements with different basic frequencies is proposed to minimize the size of the measurement volume in the near-wall region of a pipe flow. The velocity profiles in the near-wall region are measured using an 8 MHz sensor with a small diameter, while those far from the transducer are measured using a hollow 2 MHz sensor in the multi-wave transducer. The applicability of the multi-wave transducer was experimentally investigated using the water flow-rate calibration facility at the National Institute of Advanced Industrial Science and Technology (AIST). As a result, the errors in the flow rate were found to be below  -1%, while the multi-wave method is shown to be particularly effective for measuring higher flow rates in a large-diameter pipe.

  2. New conditioning procedure derived from operating experience with the Common Long-Pulse Ion Source

    SciTech Connect

    Scoville, B.G.; Madruga, M.; Hong, R.M.; Phillips, J.C.

    1993-10-01

    The DIII-D neutral beam system utilizes an 80 kV version of the Common Long-Pulse Ion Source designed by Lawrence Berkeley Laboratories (LBL) and originally built by RCA. Eight of these ion sources are mounted on four beamlines to provide a total of 20 MW of injected deuterium neutral power to the DIII-D tokamak. To support the DIII-D one-shift operation, neutral beams must be readied in a relatively short period of time each day, typically one hour. During non-operating periods conditioning time for the ion sources is limited, due to the costs of associated support services and the need to perform corrective and preventive maintenance. The experience gained over a six year period has resulted in finely tuned procedures for the conditioning and operation of these ion sources. Recently, an ion source was conditioned which had been accidentally filled with water for several days, resulting in surface corrosion and deconditioning of the grids and surfaces. The method of successful recovery along with data, experience and procedures derived this event and normal operations will be detailed and discussed.

  3. Applying Hanford Tank Mixing Data to Define Pulse Jet Mixer Operation

    SciTech Connect

    Wells, Beric E.; Bamberger, Judith A.; Recknagle, Kurtis P.; Enderlin, Carl W.; Minette, Michael J.; Holton, Langdon K.

    2015-12-07

    Pulse jet mixed (PJM) process vessels are being developed for storing, blending, and chemical processing of nuclear waste slurries at the Waste Treatment and Immobilization Plant (WTP) to be built at Hanford, Washington. These waste slurries exhibit variable process feed characteristics including Newtonian to non-Newtonian rheologies over a range of solids loadings. Waste feed to the WTP from the Hanford Tank Farms will be accomplished via the Waste Feed Delivery (WFD) system which includes million-gallon underground storage double-shell tanks (DSTs) with dual-opposed jet mixer pumps. Experience using WFD type jet mixer pumps to mobilize actual Hanford waste in DSTs may be used to establish design threshold criteria of interest to pulse jet mixed process vessel operation. This paper describes a method to evaluate the pulse jet mixed vessel capability to process waste based on information obtained during mobilizing and suspending waste by the WFD system jet mixer pumps in a DST. Calculations of jet velocity and wall shear stress in a specific pulse jet mixed process vessel were performed using a commercial computational fluid dynamics (CFD) code. The CFD-modelled process vessel consists of a 4.9-m- (16-ft-) diameter tank with a 2:1 semi-elliptical head, a single, 10-cm (4-in.) downward facing 60-degree conical nozzle, and a 0.61-m (24-in.) inside diameter PJM. The PJM is located at 70% of the vessel radius with the nozzle stand-off-distance 14 cm (6 in.) above the vessel head. The CFD modeled fluid velocity and wall shear stress can be used to estimate vessel waste-processing performance by comparison to available actual WFD system process data. Test data from the operation of jet mixer pumps in the 23-m (75-ft) diameter DSTs have demonstrated mobilization, solid particles in a sediment matrix were moved from their initial location, and suspension, mobilized solid particles were moved to a higher elevation in the vessel than their initial location, of waste solids

  4. 486nm blue laser operating at 500 kHz pulse repetition frequency

    NASA Astrophysics Data System (ADS)

    Creeden, Daniel; Blanchard, Jon; Pretorius, Herman; Limongelli, Julia; Setzler, Scott D.

    2016-03-01

    Compact, high power blue light in the 470-490nm region is difficult to generate due to the lack of laser sources which are easily convertible (through parametric processes) to those wavelengths. By using a pulsed Tm-doped fiber laser as a pump source for a 2-stage second harmonic generation (SHG) scheme, we have generated ~2W of 486.5nm light at 500kHz pulse repetition frequency (PRF). To our knowledge, this is the highest PRF and output power achieved in the blue region based on a frequency converted, monolithic fiber laser. This pump laser is a pulsed Tm-doped fiber laser/amplifier which generates 12.8W of 1946nm power at 500kHz PRF with diffraction-limited output from a purely single-mode fiber. The output from this laser is converted to 973nm through second harmonic generation (SHG). The 973nm is then converted to 486.5nm via another SHG stage. This architecture operates with very low peak power, which can be challenging from a nonlinear conversion standpoint. However, the low peak power enables the use of a single-mode monolithic fiber amplifier without undergoing nonlinear effects in the fiber. This also eliminates the need for novel fiber designs, large-mode area fiber, or free-space coupling to rod-type amplifiers, improving reliability and robustness of the laser source. Higher power and conversion efficiency are possible through the addition of Tm-doped fiber amplification stages as well as optimization of the nonlinear conversion process and nonlinear materials. In this paper, we discuss the laser layout, results, and challenges with generating blue light using a low peak power approach.

  5. Radiobiological modelling of dose-gradient effects in low dose rate, high dose rate and pulsed brachytherapy

    NASA Astrophysics Data System (ADS)

    Armpilia, C.; Dale, R. G.; Sandilos, P.; Vlachos, L.

    2006-09-01

    This paper presents a generalization of a previously published methodology which quantified the radiobiological consequences of dose-gradient effects in brachytherapy applications. The methodology uses the linear-quadratic (LQ) formulation to identify an equivalent biologically effective dose (BEDeq) which, if applied uniformly to a specified tissue volume, would produce the same net cell survival as that achieved by a given non-uniform brachytherapy application. Multiplying factors (MFs), which enable the equivalent BED for an enclosed volume to be estimated from the BED calculated at the dose reference surface, have been calculated and tabulated for both spherical and cylindrical geometries. The main types of brachytherapy (high dose rate (HDR), low dose rate (LDR) and pulsed (PB)) have been examined for a range of radiobiological parameters/dimensions. Equivalent BEDs are consistently higher than the BEDs calculated at the reference surface by an amount which depends on the treatment prescription (magnitude of the prescribed dose) at the reference point. MFs are closely related to the numerical BED values, irrespective of how the original BED was attained (e.g., via HDR, LDR or PB). Thus, an average MF can be used for a given prescribed BED as it will be largely independent of the assumed radiobiological parameters (radiosensitivity and α/β) and standardized look-up tables may be applicable to all types of brachytherapy treatment. This analysis opens the way to more systematic approaches for correlating physical and biological effects in several types of brachytherapy and for the improved quantitative assessment and ranking of clinical treatments which involve a brachytherapy component.

  6. Picosecond supercontinuum light source for stroboscopic white-light interferometry with freely adjustable pulse repetition rate.

    PubMed

    Novotny, Steffen; Durairaj, Vasuki; Shavrin, Igor; Lipiäinen, Lauri; Kokkonen, Kimmo; Kaivola, Matti; Ludvigsen, Hanne

    2014-06-01

    We present a picosecond supercontinuum light source designed for stroboscopic white-light interferometry. This source offers a potential for high-resolution characterization of vibrational fields in electromechanical components with frequencies up to the GHz range. The light source concept combines a gain-switched laser diode, the output of which is amplified in a two-stage fiber amplifier, with supercontinuum generation in a microstructured optical fiber. Implemented in our white-light interferometer setup, optical pulses with optimized spectral properties and below 310 ps duration are used for stroboscopic illumination at freely adjustable repetition rates. The performance of the source is demonstrated by characterizing the surface vibration field of a square-plate silicon MEMS resonator at 3.37 MHz. A minimum detectable vibration amplitude of less than 100 pm is reached.

  7. Towards continuous monitoring of pulse rate in neonatal intensive care unit with a webcam.

    PubMed

    Mestha, Lalit K; Kyal, Survi; Xu, Beilei; Lewis, Leslie Edward; Kumar, Vijay

    2014-01-01

    We describe a novel method to monitor pulse rate (PR) on a continuous basis of patients in a neonatal intensive care unit (NICU) using videos taken from a high definition (HD) webcam. We describe algorithms that determine PR from videoplethysmographic (VPG) signals extracted from multiple regions of interest (ROI) simultaneously available within the field of view of the camera where cardiac signal is registered. We detect motion from video images and compensate for motion artifacts from each ROI. Preliminary clinical results are presented on 8 neonates each with 30 minutes of uninterrupted video. Comparisons to hospital equipment indicate that the proposed technology can meet medical industry standards and give improved patient comfort and ease of use for practitioners when instrumented with proper hardware. PMID:25570823

  8. Luminescence of black silicon fabricated by high-repetition rate femtosecond laser pulses

    SciTech Connect

    Chen Tao; Si Jinhai; Hou Xun; Kanehira, Shingo; Miura, Kiyotaka; Hirao, Kazuyuki

    2011-10-01

    We studied the photoluminescence (PL) from black silicon that was fabricated using an 800 nm, 250 kHz femtosecond laser in air. By changing the scan velocity and the fluence of the femtosecond laser, the formation of the PL band between the orange (600 nm) and red bands (near 680 nm) could be controlled. The red band PL from the photoinduced microstructures on the black silicon was observed even without annealing due to the thermal accumulation of high-repetition rate femtosecond laser pulses. The orange band PL was easily quenched under 532 nm cw laser irradiation, whereas the red band PL was more stable; this can be attributed to ''defect luminescence'' and ''quantum confinement'', respectively.

  9. Modeling and optimization of single-pass laser amplifiers for high-repetition-rate laser pulses

    SciTech Connect

    Ozawa, Akira; Udem, Thomas; Zeitner, Uwe D.; Haensch, Theodor W.; Hommelhoff, Peter

    2010-09-15

    We propose a model for a continuously pumped single-pass amplifier for continuous and pulsed laser beams. The model takes into account Gaussian shape and focusing geometry of pump and seed beam. As the full-wave simulation is complex we have developed a largely simplified numerical method that can be applied to rotationally symmetric geometries. With the tapered-shell model we treat (focused) propagation and amplification of an initially Gaussian beam in a gain crystal. The implementation can be done with a few lines of code that are given in this paper. With this code, a numerical parameter optimization is straightforward and example results are shown. We compare the results of our simple model with those of a full-wave simulation and show that they agree well. A comparison of model and experimental data also shows good agreement. We investigate in detail different regimes of amplification, namely the unsaturated, the fully saturated, and the intermediate regime. Because the amplification process is affected by spatially varying saturation and exhibits a nonlinear response against pump and seed power, no analytical expression for the expected output is available. For modeling of the amplification we employ a four-level system and show that if the fluorescence lifetime of the gain medium is larger than the inverse repetition rate of the seed beam, continuous-wave amplification can be employed to describe the amplification process of ultrashort pulse trains. We limit ourselves to this regime, which implies that if titanium:sapphire is chosen as gain medium the laser repetition rate has to be larger than a few megahertz. We show detailed simulation results for titanium:sapphire for a large parameter set.

  10. Laboratory pulse modulator uses minority carrier storage diodes

    NASA Technical Reports Server (NTRS)

    1967-01-01

    Pulse modulator is capable of continuously variable pulse width over a 10 to 1 range of 1.0 microsecond to 0.1 microsecond and operates over a wide range of pulse repetition rates. Pulse width diversity is obtained by operating step-recovery diodes in the reverse conduction mode.

  11. Architecture and operation of the Z Pulsed Power Facility vacuum system.

    SciTech Connect

    Riddle, Allen Chauncey; Petmecky, Don; Weed, John Woodruff

    2010-11-01

    The Z Pulsed Power Facility at Sandia National Laboratories in Albuquerque, New Mexico, USA is one of the world's premier high energy density physics facilities. The Z Facility derives its name from the z-pinch phenomena which is a type of plasma confinement system that uses the electrical current in the plasma to generate a magnetic field that compresses it. Z refers to the direction of current flow, the z axis in a three dimensional Cartesian coordinate system. The multiterawatt, multimegajoule electrical pulse the Facility produces is 100-400 nanoseconds in time. Research and development programs currently being conducted on the Z Facility include inertial confinement fusion, dynamic material properties, laboratory astrophysics and radiation effects. The Z Facility vacuum system consists of two subsystems, center section and load diagnostics. Dry roughing pumps and cryogenic high vacuum pumps are used to evacuate the 40,000 liter, 200 square meter center section of the facility where the experimental load is located. Pumping times on the order of two hours are required to reduce the pressure from atmospheric to 10{sup -5} Torr. The center section is cycled from atmosphere to high vacuum for each experiment. The facility is capable of conducting one to two experiments per day. Numerous smaller vacuum pumping systems are used to evacuate load diagnostics. The megajoules of energy released during an experiment causes damage to the Facility that presents numerous challenges for reliable operation of the vacuum system.

  12. Studies of Operating Frequency Effects On Ejector-based Thrust Augmentation in a Pulse Detonation Engine

    NASA Technical Reports Server (NTRS)

    Landry, K.

    2005-01-01

    Studies were performed in order to characterize the thrust augmentation potential of an ejector in a Pulse Detonation Engine application. A 49-mm diameter tube of 0.914-m length was constructed with one open end and one closed end. Ethylene, oxygen, and nitrogen were introduced into the tube at the closed end through the implementation of a fast mixing injector. The tube was completely filled with a stoichiometric mixture containing a one to one molar ratio of nitrogen to oxygen. Ethylene was selected as the fuel due to its detonation sensitivity and the molar ratio of the oxidizer was chosen for heat transfer purposes. Detonations were initiated in the tube through the use of a spark ignition system. The PDE was operated in a multi-cycle mode at frequencies ranging from 20-Hz to 50-Hz. Baseline thrust measurements with no ejector present were performed while operating the engine at various frequencies and compared to theoretical estimates. The baseline values were observed to agree with the theoretical model at low operating frequencies and proved to be increasingly lower than the predicted values as the operating frequency was increased. The baseline thrust measurements were observed to agree within 15 percent of the model for all operating frequencies. A straight 152-mm diameter ejector was installed and thrust augmentation percentages were measured. The length of the ejector was varied while the overlap percentage (percent of the ejector length which overlapped the tube) was maintained at 25 percent for all tests. In addition, the effect of ejector inlet geometry was investigated by comparing results with a straight inlet to those of a 38-mm inlet diameter. The thrust augmentation of the straight inlet ejector proved to be independent of engine operating frequency, augmenting thrust by 40 percent for the 0.914-m length ejector. In contrast, the rounded lip ejector of the same length seemed to be highly dependent on the engine operating frequency. An optimum

  13. Nocturnal Light Pulses Lower Carbon Dioxide Production Rate without Affecting Feed Intake in Geese.

    PubMed

    Huang, De-Jia; Yang, Shyi-Kuen

    2016-03-01

    This study was conducted to investigate the effect of nocturnal light pulses (NLPs) on the feed intake and metabolic rate in geese. Fourteen adult Chinese geese were penned individually, and randomly assigned to either the C (control) or NLP group. The C group was exposed to a 12L:12D photoperiod (12 h light and 12 h darkness per day), whereas the NLP group was exposed to a 12L:12D photoperiod inserted by 15-min lighting at 2-h intervals in the scotophase. The weight of the feed was automatically recorded at 1-min intervals for 1 wk. The fasting carbon dioxide production rate (CO2 PR) was recorded at 1-min intervals for 1 d. The results revealed that neither the daily feed intake nor the feed intakes during both the daytime and nighttime were affected by photoperiodic regimen, and the feed intake during the daytime did not differ from that during the nighttime. The photoperiodic treatment did not affect the time distribution of feed intake. However, NLPs lowered (p<0.05) the mean and minimal CO2 PR during both the daytime and nighttime. Both the mean and minimal CO2 PR during the daytime were significantly higher (p<0.05) than those during the nighttime. We concluded that NLPs lowered metabolic rate of the geese, but did not affect the feed intake; both the mean and minimal CO2 PR were higher during the daytime than during the nighttime. PMID:26950871

  14. High discharge rate characteristics of nickel-cadmium batteries for pulse load filtering

    NASA Technical Reports Server (NTRS)

    Gearing, G. M.; Cimino, M. B.; Fritts, D. H.; Leonard, J. F.; Terzuoli, A. J., Jr.

    1985-01-01

    Several tests of specially fabricated nickel-cadmium batteries having circular disk type electrodes were considered. These batteries were evaluated as filter elements between a constant current power supply and a five hertz pulsed load demanding approximately twice the power supply current during the load on portion of the cycle. Short tests lasting 10,000 cycles were conducted at up to a 21 C rate and an equivalent energy density of over 40 Joules per pound. In addition, two batteries were subjected to 10 to the 7 charge/discharge cycles, one at a 6.5 C rate and the other at a 13 C rate. Assuming an electrode to battery weight ratio of 0.5, these tests represent an energy density of about 7 and 14 Joules per pound respectively. Energy density, efficiency, capacitance, average voltage, and available capacity were tracked during these tests. After 10 to the 7 cycles, capacity degradation was negligible for one battery and about 20% for the other. Cadmium electrode failure may be the factor limiting lifetime at extremely low depth of discharge cycling. The output was examined and a simple equivalent circuit was proposed.

  15. High-average-power operation of a pulsed Raman fiber amplifier at 1686 nm.

    PubMed

    Yao, Weichao; Chen, Bihui; Zhang, Jianing; Zhao, Yongguang; Chen, Hao; Shen, Deyuan

    2015-05-01

    We report on high-average-power operation of a pulsed Raman fiber amplifier at ~1686 nm which cannot be covered by rare-earth-doped fiber lasers. The Raman fiber amplifier was pumped by a home-made 1565.2 nm Q-switched Er,Yb fiber laser and worked at a repetition frequency of 184 kHz. With 0.8 km Raman fiber, 4.4 W of average output power at the 1st order Stokes wavelength of 1686.5 nm was obtained for launched pump power of 16.2 W, corresponding to an optical-to-optical conversion efficiency of 27.2%. Further increasing the pump power, high-order Stokes waves grew gradually, resulting in a total output power of 6.7 W at the 19.2 W launched pump power. PMID:25969195

  16. Conceptual design of the neutral beamline for TPX long pulse operation

    SciTech Connect

    Wright, K.E.; Dahlgren, F.; Fan, H.M.; Grisham, L.R.; Hammersand, F.G.; Kamperschroer, J.H.; Lontai, L.M.; Oldaker, M.E.; Rogoff, P.

    1993-11-01

    The Tokamak Physics Experiment (TPX) will require a minimum of 8.0 megawatts of Neutral Beam beating power to be injected into the plasma for pulse lengths up to one thousand (1000) seconds to meet the experimental objectives. The Neutral Beam Injection System (NBIS) for initial operation on TPX will consist of one neutral beamline (NBL) with three Ion sources. Provisions will be made for a total of three NBLs. The NBIS will provide S.S MW of 120 keV D{sup 0} and 2.S MW of partial-energy D{sup 0} at 60 keV and 40 keV. The system also provides for measuring the neutral beam power, limits excess cold gas from entering the torus, and provides independent power, control, and protection for each individual ion source and accelerating structure. The Neutral Beam/Torus Connecting Duct (NB/TCD) includes a vacuum valve, an electrical insulating break, alignment bellows, vacuum seals, internal energy absorbing protective elements, beam diagnostics and bakeout capability. The NBL support structure will support the NBL, which will weigh approximately 80 tons at the proper elevation and withstand a seismic event. The NBIS currently operational on the Tokamak Fusion Test Reactor (TFTR) at the Princeton Plasma Physics Laboratory (PPPL) is restricted to injection pulse lengths of two (2) seconds by the limited capability of various energy absorbers. This paper describes the modifications and improvements which will be implemented for the TFTR Neutral Beamlines and the NB/TCD to satisfy the TPX requirements.

  17. Multiple-circuit pulse generator for high repetition rate rare gas halide lasers.

    PubMed

    Wang, C P

    1978-10-01

    A multiple-circuit high pulse repetition frequency (PRF) pulse generator for the pumping of rare gas halide lasers is reported. With this multiple-circuit design, high PRF can be achieved by the use of existing low PRF thyratron switches and capacitors. A two-circuit pulse generator was constructed, and its performance is described. By means of this pulse generator and a blowdown-type fast transverse-flow system, high PRF laser action in XeF was obtained, typically, 6 mJ/pulse at 1 kHz or 6 W average power. High PRF laser action in N(2) was also observed.

  18. [Design of Oxygen Saturation, Heart Rate, Respiration Rate Detection System Based on Smartphone of Android Operating System].

    PubMed

    Zhu, Mingshan; Zeng, Bixin

    2015-03-01

    In this paper, we designed an oxygen saturation, heart rate, respiration rate monitoring system based on smartphone of android operating system, physiological signal acquired by MSP430 microcontroller and transmitted by Bluetooth module. PMID:26524782

  19. [Design of Oxygen Saturation, Heart Rate, Respiration Rate Detection System Based on Smartphone of Android Operating System].

    PubMed

    Zhu, Mingshan; Zeng, Bixin

    2015-03-01

    In this paper, we designed an oxygen saturation, heart rate, respiration rate monitoring system based on smartphone of android operating system, physiological signal acquired by MSP430 microcontroller and transmitted by Bluetooth module.

  20. Optically isolated, 2 kHz repetition rate, 4 kV solid-state pulse trigger generator.

    PubMed

    Barnett, D H; Parson, J M; Lynn, C F; Kelly, P M; Taylor, M; Calico, S; Scott, M C; Dickens, J C; Neuber, A A; Mankowski, J J

    2015-03-01

    This paper presents the design and operation characteristics of a solid-state high voltage pulse generator. Its primary utilization is aimed at triggering a gaseous spark gap with high repeatability. Specifically, the trigger generator is designed to achieve a risetime on the order of 0.1 kV/ns to trigger the first stage, trigatron spark gap of a 10-stage, 500 kV Marx generator. The major design components are comprised of a 60 W constant current DC-DC converter for high voltage charging, a single 4 kV thyristor, a step-up pulse transformer, and magnetic switch for pulse steepening. A risetime of <30 ns and pulse magnitude of 4 kV is achieved matching the simulated performance of the design.

  1. Optically isolated, 2 kHz repetition rate, 4 kV solid-state pulse trigger generator

    NASA Astrophysics Data System (ADS)

    Barnett, D. H.; Parson, J. M.; Lynn, C. F.; Kelly, P. M.; Taylor, M.; Calico, S.; Scott, M. C.; Dickens, J. C.; Neuber, A. A.; Mankowski, J. J.

    2015-03-01

    This paper presents the design and operation characteristics of a solid-state high voltage pulse generator. Its primary utilization is aimed at triggering a gaseous spark gap with high repeatability. Specifically, the trigger generator is designed to achieve a risetime on the order of 0.1 kV/ns to trigger the first stage, trigatron spark gap of a 10-stage, 500 kV Marx generator. The major design components are comprised of a 60 W constant current DC-DC converter for high voltage charging, a single 4 kV thyristor, a step-up pulse transformer, and magnetic switch for pulse steepening. A risetime of <30 ns and pulse magnitude of 4 kV is achieved matching the simulated performance of the design.

  2. Improving resistance uniformity and endurance of resistive switching memory by accurately controlling the stress time of pulse program operation

    NASA Astrophysics Data System (ADS)

    Wang, Guoming; Long, Shibing; Yu, Zhaoan; Zhang, Meiyun; Ye, Tianchun; Li, Yang; Xu, Dinglin; Lv, Hangbing; Liu, Qi; Wang, Ming; Xu, Xiaoxin; Liu, Hongtao; Yang, Baohe; Suñé, Jordi; Liu, Ming

    2015-03-01

    In this letter, the impact of stress time of pulse program operation on the resistance uniformity and endurance of resistive random access memory (RRAM) is investigated. A width-adjusting pulse operation (WAPO) method which can accurately setup and measure switching time is proposed for improving the uniformity and endurance of RRAM. Different from the traditional single pulse operation (TSPO) method in which only one wide pulse is applied in each switching cycle, WAPO method utilizes a series of pulses with the width increased gradually until a set or reset switching process is completely finished and no excessive stress is produced. Our program/erase (P/E) method can exactly control the switching time and the final resistance and can significantly improve the uniformity, stability, and endurance of RRAM device. Improving resistance uniformity by WAPO compared with TSPO method is explained through the interdependence between resistance state and switching time. The endurance improvement by WAPO operation stems from the effective avoidance of the overstress-induced progressive-breakdown and even hard-breakdown to the conductive soft-breakdown path.

  3. Graphene-deposited microfiber photonic device for ultrahigh-repetition rate pulse generation in a fiber laser.

    PubMed

    Qi, You-Li; Liu, Hao; Cui, Hu; Huang, Yu-Qi; Ning, Qiu-Yi; Liu, Meng; Luo, Zhi-Chao; Luo, Ai-Ping; Xu, Wen-Cheng

    2015-07-13

    We report on the generation of a high-repetition-rate pulse in a fiber laser using a graphene-deposited microfiber photonic device (GMPD) and a Fabry-Perot filter. Taking advantage of the unique nonlinear optical properties of the GMPD, dissipative four-wave mixing effect (DFWM) could be induced at low pump power. Based on DFWM mode-locking mechanism, the fiber laser delivers a 100 GHz repetition rate pulse train. The results indicate that the small sized GMPD offers an alternative candidate of highly nonlinear optical component to achieve high-repetition rate pulses, and also opens up possibilities for the investigation of other abundant nonlinear effects or related fields of photonics. PMID:26191834

  4. Measurement verification of dose distributions in pulsed-dose rate brachytherapy in breast cancer

    PubMed Central

    Mantaj, Patrycja; Zwierzchowski, Grzegorz

    2013-01-01

    Aim The aim of the study was to verify the dose distribution optimisation method in pulsed brachytherapy. Background The pulsed-dose rate brachytherapy is a very important method of breast tumour treatment using a standard brachytheraphy equipment. The appropriate dose distribution round an implant is an important issue in treatment planning. Advanced computer systems of treatment planning are equipped with algorithms optimising dose distribution. Materials and methods The wax-paraffin phantom was constructed and seven applicators were placed within it. Two treatment plans (non-optimised, optimised) were prepared. The reference points were located at a distance of 5 mm from the applicators’ axis. Thermoluminescent detectors were placed in the phantom at suitable 35 chosen reference points. Results The dosimetry verification was carried out in 35 reference points for the plans before and after optimisation. Percentage difference for the plan without optimisation ranged from −8.5% to 1.4% and after optimisation from −8.3% to 0.01%. In 16 reference points, the calculated percentage difference was negative (from −8.5% to 1.3% for the plan without optimisation and from −8.3% to 0.8% for the optimised plan). In the remaining 19 points percentage difference was from 9.1% to 1.4% for the plan without optimisation and from 7.5% to 0.01% for the optimised plan. No statistically significant differences were found between calculated doses and doses measured at reference points in both dose distribution non-optimised treatment plans and optimised treatment plans. Conclusions No statistically significant differences were found in dose values at reference points between doses calculated by the treatment planning system and those measured by TLDs. This proves the consistency between the measurements and the calculations. PMID:24416545

  5. Reirradiation of Large-Volume Recurrent Glioma With Pulsed Reduced-Dose-Rate Radiotherapy

    SciTech Connect

    Adkison, Jarrod B.; Tome, Wolfgang; Seo, Songwon; Richards, Gregory M.; Robins, H. Ian; Rassmussen, Karl; Welsh, James S.; Mahler, Peter A.; Howard, Steven P.

    2011-03-01

    Purpose: Pulsed reduced-dose-rate radiotherapy (PRDR) is a reirradiation technique that reduces the effective dose rate and increases the treatment time, allowing sublethal damage repair during irradiation. Patients and Methods: A total of 103 patients with recurrent glioma underwent reirradiation using PRDR (86 considered to have Grade 4 at PRDR). PRDR was delivered using a series of 0.2-Gy pulses at 3-min intervals, creating an apparent dose rate of 0.0667 Gy/min to a median dose of 50 Gy (range, 20-60) delivered in 1.8-2.0-Gy fractions. The mean treatment volume was 403.5 {+-} 189.4 cm{sup 3} according to T{sub 2}-weighted magnetic resonance imaging and a 2-cm margin. Results: For the initial or upgraded Grade 4 cohort (n = 86), the median interval from the first irradiation to PRDR was 14 months. Patients undergoing PRDR within 14 months of the first irradiation (n = 43) had a median survival of 21 weeks. Those treated {>=}14 months after radiotherapy had a median survival of 28 weeks (n = 43; p = 0.004 and HR = 1.82 with a 95% CI ranging from 1.25 to 3.10). These data compared favorably to historical data sets, because only 16% of the patients were treated at first relapse (with 46% treated at the second relapse, 32% at the third or fourth relapse, and 4% at the fourth or fifth relapse). The median survival since diagnosis and retreatment was 6.3 years and 11.4 months for low-grade, 4.1 years and 5.6 months for Grade 3, and 1.6 years and 5.1 months for Grade 4 tumors, respectively, according to the initial histologic findings. Multivariate analysis revealed age at the initial diagnosis, initial low-grade disease, and Karnofsky performance score of {>=}80 to be significant predictors of survival after initiation of PRDR. Conclusion: PRDR allowed for safe retreatment of larger volumes to high doses with palliative benefit.

  6. Spallation in metallic systems: Effects of microstructure, and loading pulse shape, rate and orientation

    NASA Astrophysics Data System (ADS)

    Luo, S. N.

    2011-06-01

    The dynamic nature of spallation and the ubiquitous presence of microstructure may give rise to significant dependences on microstructure and loading, as indicated by indirect experimental observations. We present systematic, direct molecular dynamics (MD) simulations of spallation in metallic systems represented by Cu and a CuZr glass. The ``microstructure'' includes various defects in Cu, porous Cu, atomic-level inhomogeneities in the CuZr glass, and the Cu crystal -CuZr glass interfaces. We explore supported and decaying shock loading pulses, as well as different loading orientations. Tensile loading rates are changed via varying the flyer and target thicknesses in shock simulations, and more significantly (down to ~106 s-1), with accelerated MD simulations of single-void growth in Cu (mimicking shock). Our direct simulations reveal strong dependences of spallation on microstructure and loading, and quantitative dynamics of void nucleation/growth as well as mechanisms for plasticity, void nucleation and their interactions in the absence or presence of defects or interfaces. The future task of incorporating statistically the microstructure effects and their rate dependences into analytic models is of great interest to shock physics but a challenge. Work done in collaboration with T.C. Germann, D. Perez, Q. An, B. Arman, W.Z. Han, D.L. Tonks, J.E. Hammerberg, A.F. Voter, Los Alamos National Laboratory; W.A. Goddard III, Caltech; and T. Cagin, Texas A & M University.

  7. A kinetic model for estimating net photosynthetic rates of cos lettuce leaves under pulsed light.

    PubMed

    Jishi, Tomohiro; Matsuda, Ryo; Fujiwara, Kazuhiro

    2015-04-01

    Time-averaged net photosynthetic rate (P n) under pulsed light (PL) is known to be affected by the PL frequency and duty ratio, even though the time-averaged photosynthetic photon flux density (PPFD) is unchanged. This phenomenon can be explained by considering that photosynthetic intermediates (PIs) are pooled during light periods and then consumed by partial photosynthetic reactions during dark periods. In this study, we developed a kinetic model to estimate P n of cos lettuce (Lactuca sativa L. var. longifolia) leaves under PL based on the dynamics of the amount of pooled PIs. The model inputs are average PPFD, duty ratio, and frequency; the output is P n. The rates of both PI accumulation and consumption at a given moment are assumed to be dependent on the amount of pooled PIs at that point. Required model parameters and three explanatory variables (average PPFD, frequency, and duty ratio) were determined for the simulation using P n values under PL based on several combinations of the three variables. The model simulation for various PL levels with a wide range of time-averaged PPFDs, frequencies, and duty ratios further demonstrated that P n under PL with high frequencies and duty ratios was comparable to, but did not exceed, P n under continuous light, and also showed that P n under PL decreased as either frequency or duty ratio was decreased. The developed model can be used to estimate P n under various light environments where PPFD changes cyclically.

  8. Acclimatization to altitude: effects on arterial oxygen saturation and pulse rate during prolonged exercise at altitude.

    PubMed

    Stoneham, M D; Pethybridge, R J

    1993-01-01

    Changes in the arterial haemoglobin-oxygen saturation (SaO2) of the blood, in the blood pressure and in the heart rate, were monitored in subjects performing static exercise at an altitude of 3,600 metres before and after an acclimatization period of 28 days during an expedition to the Bolivian Andes. It was found that acclimatised subjects could maintain their SaO2 during prolonged exercise better than non-acclimatised subjects. The pulse rate of acclimatised subjects was consistently lower at the same work level than that of non-acclimatised subjects. Acclimatised subjects were able to reach higher levels of exercise than when they had first arrived at altitude. These data imply that acclimatization to altitude improves the delivery of oxygen to the tissues. The mechanism of this is not certain, but it may be concerned with a reduction in the degree of ventilation-perfusion inequality of the lung which occurs on exposure to high altitude.

  9. The Role of Pulse Repetition Rate in nsPEF-Induced Electroporation: A Biological and Numerical Investigation.

    PubMed

    Lamberti, Patrizia; Romeo, Stefania; Sannino, Anna; Zeni, Luigi; Zeni, Olga

    2015-09-01

    The impact of pulse repetition rate (PRR) in modulating electroporation (EP) induced by nanosecond pulsed electric fields (nsPEFs) in mammalian cells was approached here by performing both biological and numerical analysis. Plasma membrane permeabilization and viability of Jurkat cells were analyzed after exposure to 500, 1.3 MV/m, 40 ns PEFs with variable PRR (2-30 Hz). A finite-element model was used to investigate EP dynamics in a single cell under the same pulsing conditions, by looking at the time course of transmembrane voltage and pore density on the ns time scale. The biological observations showed an increased EP and reduced viability of the exposed cells at lower PRR in the considered range. The numerical analysis resulted in different dynamics of plasma membrane response when ns pulses were delivered with different PRR, consistently with a phenomenon of electrodesensitization recently hypothesized by another research group. PMID:25850084

  10. UV pulse trains by α-BBO crystal stacking for the production of THz-rap-rate electron bunches

    NASA Astrophysics Data System (ADS)

    Yan, Li-Xin; Hua, Jian-Fei; Du, Ying-Chao; Huang, Yuan-Fang; You, Yan; Wang, Dan; Huang, Wen-Hui; Tang, Chuan-Xiang; Tang

    2012-08-01

    Ultrashort electron bunch trains can be used for plasma wake field acceleration (PWFA) to overcome the limit of transformer ratio of a single electron bunch, or high-power terahertz (Thz) radiation production by various radiation mechanisms. Basic facility for high-power THz radiation development based on ultrashort electron beam has been set up at accelerator lab of TUB. Using birefringent crystal serials, ultraviolet (UV) pulse shaping for photocathode radio frequency gun to produce THz-repetition-rate pulse train was realized. Driven by such pulses, ultrashort electron bunch train with picosecond (ps) spacing was obtained for THz production. Measurement of the stacked UV pulse trains was done by difference frequency generation (DFG), and the measured group velocity mismatch of α-BBO crystal at 266.7-nm wavelength was 0.8 ps/mm. This method may also be applied to form ramped electron bunch trains for PWFA.

  11. Compatible operation of the power system for steady state and pulse modes in a magnetic torus KT-5D

    NASA Astrophysics Data System (ADS)

    Yu, Yi; Wang, Zhi-jiang; Xu, Min; Zhu, Zhen-hua; Lu, Rong-hua; Wen, Yi-zhi; Yu, Chang-xuan; Wan, Shu-de; Liu, Wan-dong; Wang, Jun; Xu, Xiao-yuan; Hu, Ling-ying

    2006-12-01

    Compatible operation of steady state mode and pulse mode is realized in the KT-5D device. New power supplies with the operation control systems for the steady state toroidal magnetic field as well as for the vertical field are added, and the rf wave injection systems for sustaining steady state plasmas are upgraded. After the modification, the device now can work not only as a tokomak with pulsed plasma currents as it was but also as a simple magnetized torus with steady state plasma discharges. It allows more flexible and efficient experimental researches on the magnetically confined plasmas to be carried on in the same device.

  12. Compatible operation of the power system for steady state and pulse modes in a magnetic torus KT-5D

    SciTech Connect

    Yu Yi; Wang Zhijiang; Xu Min; Zhu Zhenhua; Lu Ronghua; Wen Yizhi; Yu Changxuan; Wan Shude; Liu Wandong; Wang Jun; Xu Xiaoyuan; Hu Lingying

    2006-12-15

    Compatible operation of steady state mode and pulse mode is realized in the KT-5D device. New power supplies with the operation control systems for the steady state toroidal magnetic field as well as for the vertical field are added, and the rf wave injection systems for sustaining steady state plasmas are upgraded. After the modification, the device now can work not only as a tokomak with pulsed plasma currents as it was but also as a simple magnetized torus with steady state plasma discharges. It allows more flexible and efficient experimental researches on the magnetically confined plasmas to be carried on in the same device.

  13. A Real-Time Terahertz Time-Domain Polarization Analyzer with 80-MHz Repetition-Rate Femtosecond Laser Pulses

    PubMed Central

    Watanabe, Shinichi; Yasumatsu, Naoya; Oguchi, Kenichi; Takeda, Masatoshi; Suzuki, Takeshi; Tachizaki, Takehiro

    2013-01-01

    We have developed a real-time terahertz time-domain polarization analyzer by using 80-MHz repetition-rate femtosecond laser pulses. Our technique is based on the spinning electro-optic sensor method, which we recently proposed and demonstrated by using a regenerative amplifier laser system; here we improve the detection scheme in order to be able to use it with a femtosecond laser oscillator with laser pulses of a much higher repetition rate. This improvement brings great advantages for realizing broadband, compact and stable real-time terahertz time-domain polarization measurement systems for scientific and industrial applications. PMID:23478599

  14. Comparison of two techniques of interstitial pulsed dose rate boost brachytherapy in conservative treatment of breast cancer

    PubMed Central

    Tarnawska, Zofia; Blukis, Andrzej; Badzio, Andrzej; Jaskiewicz, Janusz; Jassem, Jacek

    2009-01-01

    Purpose The aim of this work is to compare selected parameters of implants and natural dose volume histograms for two techniques of interstitial pulsed dose rate brachytherapy (PDR BT) as a boost to the tumour bed in breast-conserving therapy (BCT). Material and methods Data of T1-3N0-2M0 breast cancer patients who underwent BCT with BT boost between 05.2002 and 12.2008 were analysed. Ninety two patients were implanted with rigid tubes after breast irradiation (group A) and 96 had a peri-operative BT with an intra-operative flexible tube placement and subsequent whole breast radiotherapy (group B). In both groups PDR BT of 15 Gy (1 Gy/pulse/h) was administered based on Paris system rules, and volume optimization using BT planning system PLATO. Results Three-plane implant was used in 62% and 8% of patients in group A and B, respectively, and two-plane implant in 38% of group A and in 84% of group B, with a median of 11 and 9 tubes respectively. The average volume for the prescribed dose (V100) was 42.0 ± 25.4 cc (group A) and 34.1 ± 19.7 cc (group B), respectively (p = 0.017). The individual V50 and V200 were similar. Quality index (QI) was not impacted by the technique of BT (mean QI was 1.80 ± 0.10 and 1.75 ± 0.46 for the groups A and B, respectively). Uniformity index (UI) in respective groups was 1.60 ± 0.10 and 1.52 ± 0.21 (p = 0.001). Conclusions Implant volume encompassed by prescribed dose was significantly lower with intra-operative plastic tubes placement. In respect to the QI, these two BT techniques were comparable. The target volume coverage by the dose distribution as defined by UI was better for rigid tubes.

  15. Laser beam deflection monitoring of Nd: YAG laser ablation: pulse shape and repetition rate effects

    NASA Astrophysics Data System (ADS)

    Diaci, Janez; Možina, Janez

    1993-05-01

    The laser beam deflection probe has been employed to study blast waves generated during ablation of metallic surfaces by sequences of 1.06 μm Nd:YAG laser pulses separated by less than 1μs. A fluence threshold has been found, below which the effects of individual pulses can be resolved by the laser probe. Above that, the deflection signal has a similar form as if the surface were irradiated with a single pulse. Analysis of the signals in terms of the spherical blast wave theory shows that a pulse sequence generates a weaker blast wave than a single pulse of equal total energy. On the other hand, the sequence yields a higher etch depth than the single pulse.

  16. A megawatt solid-state modulator for high repetition rate pulse generation

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Pribyl, P.; Gekelman, W.

    2016-02-01

    A novel solid-state modulator capable of generating rapid consecutive power pulses is constructed to facilitate experiments on plasma interaction with high power microwave pulses. The modulator is designed to output a 100 kHz tone burst, which consists of up to 10 pulses, each with 1 μs duration and 1 MW peak power. The pulses are formed by discharging a total of 480 μF capacitors through 24 synchronized MOSFETs and 6 step-up transformers. The highly modular design, as a replacement of an old single-pulse version used in earlier experiments which employs a pulse forming network, brings great flexibility and wide potential to its application. A systematic cost-effectiveness analysis is also presented.

  17. A megawatt solid-state modulator for high repetition rate pulse generation.

    PubMed

    Wang, Y; Pribyl, P; Gekelman, W

    2016-02-01

    A novel solid-state modulator capable of generating rapid consecutive power pulses is constructed to facilitate experiments on plasma interaction with high power microwave pulses. The modulator is designed to output a 100 kHz tone burst, which consists of up to 10 pulses, each with 1 μs duration and 1 MW peak power. The pulses are formed by discharging a total of 480 μF capacitors through 24 synchronized MOSFETs and 6 step-up transformers. The highly modular design, as a replacement of an old single-pulse version used in earlier experiments which employs a pulse forming network, brings great flexibility and wide potential to its application. A systematic cost-effectiveness analysis is also presented. PMID:26931851

  18. A megawatt solid-state modulator for high repetition rate pulse generation.

    PubMed

    Wang, Y; Pribyl, P; Gekelman, W

    2016-02-01

    A novel solid-state modulator capable of generating rapid consecutive power pulses is constructed to facilitate experiments on plasma interaction with high power microwave pulses. The modulator is designed to output a 100 kHz tone burst, which consists of up to 10 pulses, each with 1 μs duration and 1 MW peak power. The pulses are formed by discharging a total of 480 μF capacitors through 24 synchronized MOSFETs and 6 step-up transformers. The highly modular design, as a replacement of an old single-pulse version used in earlier experiments which employs a pulse forming network, brings great flexibility and wide potential to its application. A systematic cost-effectiveness analysis is also presented.

  19. Energy capability improvement of power DMOS transistors operating in pulsed conditions

    NASA Astrophysics Data System (ADS)

    Costachescu, Dragos; Pfost, Martin

    2015-01-01

    Modern power DMOS transistors greatly benefit from the continuous advances of the technology, which yield devices with very low area-specific RDS,on figures of merit and therefore allow for significantly reduced active areas. However, in many applications, where the devices must dissipate high amounts of energy and thus are subjected to significant self-heating, the active area is not dictated by RDS,on requirements, but by the energy constraints. In this paper, a simple method of improving the energy capability and reliability of power DMOS transistors operating in pulsed conditions is proposed and experimentally verified. The method consists in redistributing the power density from the hotter to the cooler device regions, hence achieving a more homogeneous temperature distribution and a reduced peak temperature. To demonstrate the principle, a simple gate offset circuit is used to redistribute the current density to the cooler DMOS parts. No technology changes are needed for the implementation, only minor changes to the driver circuit are necessary, with a minimal impact on the additional required active area. Improvements in the energy capability from 9.2% up to 39% have been measured. Furthermore, measurements have shown that the method remains effective also if the operating conditions change significantly. The simplicity and the effectiveness of the implementation makes the proposed method suitable to be used in a wide range of applications.

  20. Electromagnetic pulse (EMP) survey of the Idaho State Emergency Operating Center, Boise, Idaho

    SciTech Connect

    Crutcher, R.I.; Buchanan, M.E.; Jones, R.W.

    1992-02-01

    The purpose of this report is to develop an engineering design package to protect the Federal Emergency Management Agency (FEMA) National Radio System (FNARS) facilities from the effects of high- altitude electromagnetic pulses (HEMPs). This report was developed specifically for the Idaho State Emergency Operating Center (EOC) in Boise, Idaho. It is highly probable that there will be a heavy dependence upon high-frequency (hf) radio communications for long- haul communications following a nuclear attack on the continental United States, should one occur. To maintain the viability of the FEMA hf radio network during such a situation, steps must be taken to protect the FNARS facilities against the effects of HEMP that are likely to be created in a nuclear confrontation. The solution must than be to reduce HEMP-induced stresses on the system by means of tailored retrofit hardening measures using commercial protection devices when available. It is the intent of this report to define the particular hardening measures that will minimize the susceptibility of system components to HEMP effects. To the extent economically viable, protective actions have been recommended for implementation, along with necessary changes or additions, during the period of the FNARS upgrade program. This report addresses electromagnetic pulse (EMP) effects only and disregards any condition in which radiation effects may be a factor. It has been established that, except for the source region of a surface burst, EMP effects of high-altitude bursts are more severe than comparable detonations in either air or surface regions. Any system hardened to withstand the more extreme EMP environment will survive the less severe EMP conditions. The threatening environment will therefore be limited to HEMP situations.

  1. Spatial release from masking improves sound pattern discrimination along a biologically relevant pulse-rate continuum in gray treefrogs

    PubMed Central

    Ward, Jessica L.; Buerkle, Nathan P.; Bee, Mark A.

    2013-01-01

    Frogs form large choruses during the mating season in which males produce loud advertisement calls to attract females and repel rival males. High background noise levels in these social aggregations can impair vocal perception. In humans, spatial release from masking contributes to our ability to understand speech in noisy social groups. Here, we tested the hypothesis that spatial separation between target signals and ‘chorus-shaped noise’ improves the ability of female gray treefrogs (Hyla chrysoscelis) to perform a behavioral discrimination task based on perceiving differences in the pulsatile structure of advertisement calls. We used two-stimulus choice tests to measure phonotaxis (approach toward sound) in response to calls differing in pulse rate along a biologically relevant continuum between conspecific (50 pulses s−1) and heterospecific (20 pulses s−1) calls. Signals were presented in quiet, in colocated noise, and in spatially separated noise. In quiet conditions, females exhibited robust preferences for calls with relatively faster pulse rates more typical of conspecific calls. Behavioral discrimination between calls differing in pulse rate was impaired in the presence of colocated noise but similar between quiet and spatially separated noise conditions. Our results indicate that spatial release from energetic masking facilitates a biologically important temporal discrimination task in frogs. We discuss these results in light of previous work on spatial release from masking in frogs and other animals. PMID:24055623

  2. Data-Rate Estimation for Autonomous Receiver Operation

    NASA Technical Reports Server (NTRS)

    Tkacenko, A.; Simon, M. K.

    2005-01-01

    In this article, we present a series of algorithms for estimating the data rate of a signal whose admissible data rates are integer base, integer powered multiples of a known basic data rate. These algorithms can be applied to the Electra radio currently used in the Deep Space Network (DSN), which employs data rates having the above relationship. The estimation is carried out in an autonomous setting in which very little a priori information is assumed. It is done by exploiting an elegant property of the split symbol moments estimator (SSME), which is traditionally used to estimate the signal-to-noise ratio (SNR) of the received signal. By quantizing the assumed symbol-timing error or jitter, we present an all-digital implementation of the SSME which can be used to jointly estimate the data rate, SNR, and jitter. Simulation results presented show that these joint estimation algorithms perform well, even in the low SNR regions typically encountered in the DSN.

  3. Response elimination, reinforcement rate and resurgence of operant behavior.

    PubMed

    Cançado, Carlos R X; Lattal, Kennon A

    2013-11-01

    The effects of reinforcement rate of alternative responding on resurgence were studied in six experiments with pigeons. In Experiment 1A, key pecking was maintained on a multiple variable-interval (VI) VI schedule in the Training phase. In the Response-Elimination phase, a variable differential-reinforcement-of-other-behavior (DRO) schedule was in effect in each component. Reinforcement rates were equal and then, higher in one (rich) component, and lower in the other (lean), than in the Training phase. More resurgence occurred in the lean component, but this could have resulted from response-rate differences between components in the Training-phase. Experiment 1B was a replication of Experiment 1A, but with experimentally-naïve pigeons. Response-Elimination phase reinforcement rates were manipulated systematically in subsequent experiments: In Experiment 2, reinforcement rate was equal, in one component, and lower or higher in the other, than in the Training phase. In Experiment 3, reinforcers were discontinued before differential reinforcement rates were effected. In Experiment 4, reinforcement rates first were differential and, then, equal to those in the Training phase. In Experiments 5 and 6, differential reinforcement rates were arranged by using fixed-DROs and VIs for pecking a different key, respectively. Even though resurgence was not obtained with every pigeon, at least some small-magnitude resurgence occurred in each experiment and was not related systematically to reinforcement rates of alternative responding. Schedule differences, response topography, order of conditions and the length of each phase were not sufficient to account for these results.

  4. Expanding the Capabilities of the Pulsed Plasma Thruster for In-Space and Atmospheric Operation

    NASA Astrophysics Data System (ADS)

    Johnson, Ian Kronheim

    Of all in-space propulsion systems to date, the Pulsed Plasma Thruster (PPT) is unique in its simplicity and wide range of operational parameters. This study examined multiple uses of the thruster for in-space and atmospheric propulsion, as well as the creation of a CubeSat satellite and atmospheric airship as test beds for the thruster. The PPT was tested as a solid-propellant feed source for the High Power Helicon Thruster, a compact plasma source capable of generating order of magnitude higher plasma densities than comparable power level systems. Replacing the gaseous feed system reduced the thruster size and complexity, as well as allowing for extremely discrete discharges, minimizing the influence of wall effects. Teflon (C2F4) has been the traditional propellant for PPTs due to a high exhaust velocity and ability to ablate without surface modification over long durations. A number of alternative propellants, including minerals and metallics commonly found on asteroids, were tested for use with the PPT. Compounds with significant fractions of sulfur showed the highest performance increase, with specific thrusts double that of Teflon. A PPT with sulfur propellant designed for CubeSat operation, as well as the subsystems necessary for autonomous operation, was built and tested in the laboratory. The PPT was modified for use at atmospheric pressures where the impulse was well defined as a function of the discharge chamber volume, capacitor energy, and background pressure. To demonstrate that the air-breathing PPT was a viable concept the device was launched on two atmospheric balloon flights.

  5. Micro-processing of polymers and biological materials using high repetition rate femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ding, Li

    High repetition rate femtosecond laser micro-processing has been applied to ophthalmological hydrogel polymers and ocular tissues to create novel refractive and diffractive structures. Through the optimization of laser irradiation conditions and material properties, this technology has become feasible for future industrial applications and clinical practices. A femtosecond laser micro-processing workstation has been designed and developed. Different experimental parameters of the workstation such as laser pulse duration, focusing lens, and translational stages have been described and discussed. Diffractive gratings and three-dimensional waveguides have been fabricated and characterized in hydrogel polymers, and refractive index modifications as large as + 0.06 have been observed within the laser-irradiated region. Raman spectroscopic studies have shown that our femtosecond laser micro-processing induces significant thermal accumulation, resulting in a densification of the polymer network and increasing the localized refractive index of polymers within the laser irradiated region. Different kinds of dye chromophores have been doped in hydrogel polymers to enhance the two-photon absorption during femtosecond laser micro-processing. As the result, laser scanning speed can be greatly increased while the large refractive index modifications remain. Femtosecond laser wavelength and pulse energy as well as water and dye concentration of the hydrogels are optimized. Lightly fixed ocular tissues such as corneas and lenses have been micro-processed by focused femtosecond laser pulses, and refractive index modifications without any tissue-breakdown are observed within the stromal layer of the corneas and the cortex of the lenses. Living corneas are doped with Sodium Fluorescein to increase the two-photon absorption during the laser micro-processing, and laser scanning speed can be greatly increased while inducing large refractive index modifications. No evidence of cell death

  6. High repetition-rate neutron generation by several-mJ, 35 fs pulses interacting with free-flowing D2O

    NASA Astrophysics Data System (ADS)

    Hah, J.; Petrov, G. M.; Nees, J. A.; He, Z.-H.; Hammig, M. D.; Krushelnick, K.; Thomas, A. G. R.

    2016-10-01

    Using several-mJ energy pulses from a high-repetition rate (1/2 kHz), ultrashort (35 fs) pulsed laser interacting with a ˜ 10 μm diameter stream of free-flowing heavy water (D2O), we demonstrate a 2.45 MeV neutron flux of 105/s. Operating at high intensity (of order 1019 W/cm2), laser pulse energy is efficiently absorbed in the pre-plasma, generating energetic deuterons. These collide with deuterium nuclei in both the bulk target and the large volume of low density D2O vapor surrounding the target to generate neutrons through d ( d , n ) 3 He reactions. The neutron flux, as measured by a calibrated neutron bubble detector, increases as the laser pulse energy is increased from 6 mJ to 12 mJ. A quantitative comparison between the measured flux and the results derived from 2D-particle-in-cell simulations shows comparable neutron fluxes for laser characteristics similar to the experiment. The simulations reveal that there are two groups of deuterons. Forward moving deuterons generate deuterium-deuterium fusion reactions in the D2O stream and act as a point source of neutrons, while backward moving deuterons propagate through the low-density D2O vapor filled chamber and yield a volumetric source of neutrons.

  7. Respiratory rate and pulse oximetry derived information as predictors of hospital admission in young children in Bangladesh: a prospective observational study

    PubMed Central

    Garde, Ainara; Zhou, Guohai; Raihana, Shahreen; Dunsmuir, Dustin; Karlen, Walter; Dekhordi, Parastoo; Huda, Tanvir; Arifeen, Shams El; Larson, Charles; Kissoon, Niranjan; Dumont, Guy A; Ansermino, J Mark

    2016-01-01

    Objective Hypoxaemia is a strong predictor of mortality in children. Early detection of deteriorating condition is vital to timely intervention. We hypothesise that measures of pulse oximetry dynamics may identify children requiring hospitalisation. Our aim was to develop a predictive tool using only objective data derived from pulse oximetry and observed respiratory rate to identify children at increased risk of hospital admission. Setting Tertiary-level hospital emergency department in Bangladesh. Participants Children under 5 years (n=3374) presenting at the facility (October 2012–April 2013) without documented chronic diseases were recruited. 1-minute segments of pulse oximetry (photoplethysmogram (PPG), blood oxygen saturation (SpO2) and heart rate (HR)) and respiratory rate were collected with a mobile app. Primary outcome The need for hospitalisation based on expert physician review and follow-up. Methods Pulse rate variability (PRV) using pulse peak intervals of the PPG signal and features extracted from the SpO2 signal, all derived from pulse oximetry recordings, were studied. A univariate age-adjusted logistic regression was applied to evaluate differences between admitted and non-admitted children. A multivariate logistic regression model was developed using a stepwise selection of predictors and was internally validated using bootstrapping. Results Children admitted to hospital showed significantly (p<0.01) decreased PRV and higher SpO2 variability compared to non-admitted children. The strongest predictors of hospitalisation were reduced PRV-power in the low frequency band (OR associated with a 0.01 unit increase, 0.93; 95% CI 0.89 to 0.98), greater time spent below an SpO2 of 98% and 94% (OR associated with 10 s increase, 1.4; 95% CI 1.3 to 1.4 and 1.5; 95% CI 1.4 to 1.6, respectively), high respiratory rate, high HR, low SpO2, young age and male sex. These variables provided a bootstrap-corrected AUC of the receiver operating characteristic

  8. LN2-free Operation of the MEG Liquid Xenon Calorimeter by using a High-power Pulse Tube Cryocooler

    SciTech Connect

    Haruyama, T.; Kasami, K.; Nishiguchi, H.; Mihara, S.; Mori, T.; Otani, W.; Sawada, R.; Maruno, Y.; Nishitani, T.

    2006-04-27

    A high-power coaxial pulse tube cryocooler, originally developed in KEK and technology-transferred to Iwatani Industrial Gases Corp (IIGC), has been installed in a large liquid xenon calorimeter to evaluate liquid nitrogen-free (LN2-free) operation of the rare {mu}-particle decay experiment (MEG). Features of this pulse tube cryocooler include the cold-end heat exchanger, designed with sufficient surface area to ensure high-power cooling, and a cylindrical regenerator placed inside the pulse tube giving compact design and ease of fabrication. This production-level cryocooler provides a cooling power of {approx}200 W at 165 K, using a 6 kW Gifford-McMahon (GM)-type compressor. The paper describes the detailed configuration of the cryocooler, and the results of the continuous LN2-free operation of the large prototype liquid xenon calorimeter, which ran for more than 40 days without problems.

  9. LN2-free Operation of the MEG Liquid Xenon Calorimeter by using a High-power Pulse Tube Cryocooler

    NASA Astrophysics Data System (ADS)

    Haruyama, T.; Kasami, K.; Nishiguchi, H.; Mihara, S.; Mori, T.; Otani, W.; Sawada, R.; Maruno, Y.; Nishitani, T.

    2006-04-01

    A high-power coaxial pulse tube cryocooler, originally developed in KEK and technology-transferred to Iwatani Industrial Gases Corp (IIGC), has been installed in a large liquid xenon calorimeter to evaluate liquid nitrogen-free (LN2-free) operation of the rare μ-particle decay experiment (MEG). Features of this pulse tube cryocooler include the cold-end heat exchanger, designed with sufficient surface area to ensure high-power cooling, and a cylindrical regenerator placed inside the pulse tube giving compact design and ease of fabrication. This production-level cryocooler provides a cooling power of ˜200 W at 165 K, using a 6 kW Gifford-McMahon (GM)-type compressor. The paper describes the detailed configuration of the cryocooler, and the results of the continuous LN2-free operation of the large prototype liquid xenon calorimeter, which ran for more than 40 days without problems.

  10. Improving Pulse Rate Measurements during Random Motion Using a Wearable Multichannel Reflectance Photoplethysmograph.

    PubMed

    Warren, Kristen M; Harvey, Joshua R; Chon, Ki H; Mendelson, Yitzhak

    2016-01-01

    Photoplethysmographic (PPG) waveforms are used to acquire pulse rate (PR) measurements from pulsatile arterial blood volume. PPG waveforms are highly susceptible to motion artifacts (MA), limiting the implementation of PR measurements in mobile physiological monitoring devices. Previous studies have shown that multichannel photoplethysmograms can successfully acquire diverse signal information during simple, repetitive motion, leading to differences in motion tolerance across channels. In this paper, we investigate the performance of a custom-built multichannel forehead-mounted photoplethysmographic sensor under a variety of intense motion artifacts. We introduce an advanced multichannel template-matching algorithm that chooses the channel with the least motion artifact to calculate PR for each time instant. We show that for a wide variety of random motion, channels respond differently to motion artifacts, and the multichannel estimate outperforms single-channel estimates in terms of motion tolerance, signal quality, and PR errors. We have acquired 31 data sets consisting of PPG waveforms corrupted by random motion and show that the accuracy of PR measurements achieved was increased by up to 2.7 bpm when the multichannel-switching algorithm was compared to individual channels. The percentage of PR measurements with error ≤ 5 bpm during motion increased by 18.9% when the multichannel switching algorithm was compared to the mean PR from all channels. Moreover, our algorithm enables automatic selection of the best signal fidelity channel at each time point among the multichannel PPG data. PMID:26959034

  11. Improving Pulse Rate Measurements during Random Motion Using a Wearable Multichannel Reflectance Photoplethysmograph

    PubMed Central

    Warren, Kristen M.; Harvey, Joshua R.; Chon, Ki H.; Mendelson, Yitzhak

    2016-01-01

    Photoplethysmographic (PPG) waveforms are used to acquire pulse rate (PR) measurements from pulsatile arterial blood volume. PPG waveforms are highly susceptible to motion artifacts (MA), limiting the implementation of PR measurements in mobile physiological monitoring devices. Previous studies have shown that multichannel photoplethysmograms can successfully acquire diverse signal information during simple, repetitive motion, leading to differences in motion tolerance across channels. In this paper, we investigate the performance of a custom-built multichannel forehead-mounted photoplethysmographic sensor under a variety of intense motion artifacts. We introduce an advanced multichannel template-matching algorithm that chooses the channel with the least motion artifact to calculate PR for each time instant. We show that for a wide variety of random motion, channels respond differently to motion artifacts, and the multichannel estimate outperforms single-channel estimates in terms of motion tolerance, signal quality, and PR errors. We have acquired 31 data sets consisting of PPG waveforms corrupted by random motion and show that the accuracy of PR measurements achieved was increased by up to 2.7 bpm when the multichannel-switching algorithm was compared to individual channels. The percentage of PR measurements with error ≤ 5 bpm during motion increased by 18.9% when the multichannel switching algorithm was compared to the mean PR from all channels. Moreover, our algorithm enables automatic selection of the best signal fidelity channel at each time point among the multichannel PPG data. PMID:26959034

  12. Translational energy and desorption rate of NO from Pt(111) by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Pelak, Robert A.; Booth, M. F.; Busch, D. G.; Gao, Shiwu; Ho, Wilson

    1995-09-01

    Photodesorption of nitric oxide from Pt(111) using femtosecond laser pulses at 620 nm and 310 nm is found to result in a superlinear dependence of desorption yield on absorbed laser fluence. The translational energy distributions of the desorbed molecules are found to be nearly Maxwell-Boltzmann. For both 620 nm and 310 nm pulses with adsorbed fluences greater than 2.5 mJ/cm2, the average translational energy is found to increase linearly. At lower fluences, it is constant at 750 K, possibly suggesting a transition between DIMET and DIET desorption processes. In two pulse correlation measurements, it is found that the first pulse yield and the average translational energy have different widths as a function of delay between pulses.

  13. Influence of pressurization rate and pressure pulsing on the inactivation of Bacillus amyloliquefaciens spores during pressure-assisted thermal processing.

    PubMed

    Ratphitagsanti, Wannasawat; Ahn, Juhee; Balasubramaniam, V M; Yousef, Ahmed E

    2009-04-01

    Pressure-assisted thermal processing (PATP) is an emerging sterilization technology in which a combination of pressure (500 to 700 MPa) and temperature (90 to 120 degrees C) are used to inactivate bacterial spores. The objective of this study was to examine the role of pressurization rate and pressure pulsing in enhancing PATP lethality to the bacterial spore. Bacillus amyloliquefaciens TMW 2.479 spore suspensions were prepared in deionized water at three inoculum levels (1.1 x 10(9), 1.4 x 10(8), and 1.3 x 10(6) CFU/ml), treated at two pressurization rates (18.06 and 3.75 MPa/s), and held at 600 MPa and 105 degrees C for 0, 0.5, 1, 2, 3, and 5 min. Experiments were carried out using custom-fabricated, high-pressure microbial kinetic testing equipment. Single and double pulses with equivalent pressure-holding times (1 to 3 min) were investigated by using the spore suspension containing 1.4 x 10(8) CFU/ml. Spore survivors were enumerated by pour plating, using Trypticase soy agar after incubation at 32 degrees C for 2 days. During short pressure-holding times (< or = 2 min), PATP treatment with the slow pressurization rate provided enhanced spore reduction over that of the fast pressurization rate. However, these differences diminished with extended pressure-holding times. After a 5-min pressure-holding time, B. amyloliquefaciens population decreased about 6 log CFU/ml, regardless of pressurization rate and inoculum level. Double-pulse treatment enhanced PATP spore lethality by approximately 2.4 to 4 log CFU/ml, in comparison to single pulse for a given pressure-holding time. In conclusion, pressure pulsing considerably increases the efficacy of PATP treatment against bacterial spores. Contribution of pressurization rate to PATP spore lethality varies with duration of pressure holding.

  14. Influence of pressurization rate and pressure pulsing on the inactivation of Bacillus amyloliquefaciens spores during pressure-assisted thermal processing.

    PubMed

    Ratphitagsanti, Wannasawat; Ahn, Juhee; Balasubramaniam, V M; Yousef, Ahmed E

    2009-04-01

    Pressure-assisted thermal processing (PATP) is an emerging sterilization technology in which a combination of pressure (500 to 700 MPa) and temperature (90 to 120 degrees C) are used to inactivate bacterial spores. The objective of this study was to examine the role of pressurization rate and pressure pulsing in enhancing PATP lethality to the bacterial spore. Bacillus amyloliquefaciens TMW 2.479 spore suspensions were prepared in deionized water at three inoculum levels (1.1 x 10(9), 1.4 x 10(8), and 1.3 x 10(6) CFU/ml), treated at two pressurization rates (18.06 and 3.75 MPa/s), and held at 600 MPa and 105 degrees C for 0, 0.5, 1, 2, 3, and 5 min. Experiments were carried out using custom-fabricated, high-pressure microbial kinetic testing equipment. Single and double pulses with equivalent pressure-holding times (1 to 3 min) were investigated by using the spore suspension containing 1.4 x 10(8) CFU/ml. Spore survivors were enumerated by pour plating, using Trypticase soy agar after incubation at 32 degrees C for 2 days. During short pressure-holding times (< or = 2 min), PATP treatment with the slow pressurization rate provided enhanced spore reduction over that of the fast pressurization rate. However, these differences diminished with extended pressure-holding times. After a 5-min pressure-holding time, B. amyloliquefaciens population decreased about 6 log CFU/ml, regardless of pressurization rate and inoculum level. Double-pulse treatment enhanced PATP spore lethality by approximately 2.4 to 4 log CFU/ml, in comparison to single pulse for a given pressure-holding time. In conclusion, pressure pulsing considerably increases the efficacy of PATP treatment against bacterial spores. Contribution of pressurization rate to PATP spore lethality varies with duration of pressure holding. PMID:19435226

  15. Nonlinear measure of synchrony between blood oxygen saturation and heart rate from nocturnal pulse oximetry in obstructive sleep apnoea syndrome.

    PubMed

    Alvarez, D; Hornero, R; Abásolo, D; del Campo, F; Zamarrón, C; López, M

    2009-09-01

    This study focuses on analysis of the relationship between changes in blood oxygen saturation (SaO(2)) and heart rate (HR) recordings from nocturnal pulse oximetry (NPO) in patients suspected of suffering from obstructive sleep apnoea (OSA) syndrome. Two different analyses were developed: a classical frequency analysis based on the magnitude squared coherence (MSC) and a nonlinear analysis by means of a recently developed measure of synchrony, the cross-approximate entropy (cross-ApEn). A data set of 187 subjects was studied. We found significantly higher correlation and synchrony between oximetry signals from OSA positive patients compared with OSA negative subjects. We assessed the diagnostic ability to detect OSA syndrome of both the classical and nonlinear approaches by means of receiver operating characteristic (ROC) analyses with tenfold cross-validation. The nonlinear measure of synchrony significantly improved the results obtained with classical MSC: 69.2% sensitivity, 90.9% specificity and 78.1% accuracy were reached with MSC, whereas 83.7% sensitivity, 84.3% specificity and 84.0% accuracy were obtained with cross-ApEn. Our results suggest that the use of nonlinear measures of synchrony could provide essential information from oximetry signals, which cannot be obtained with classical spectral analysis.

  16. A rapidly-tuned, short-pulse-length, high-repetition-rate CO{sub 2} laser for IR dial

    SciTech Connect

    Zaugg, T.; Thompson, D.; Leland, W.T.; Busch, G.

    1997-08-01

    Analysis of noise sources in Differential Absorption LIDAR (DIAL) in the infrared region of the spectrum indicates that the signal-to-noise ratio for direct detection can be improved if multiple-wavelength, short-pulse-length beams are transmitted and received at high repetition rates. Atmospheric effects can be minimized, albedo can be rapidly scanned, and uncorrelated speckle can be acquired at the maximum possible rate. A compact, rugged, RF-excited waveguide laser can produce 15 nanosecond pulses at a 100 kHz rate with sufficient energy per pulse to reach the speckle limit of the signal-to-noise ratio. A high-repetition-rate laser has been procured and will be used to verify these signal and noise scaling relationships at high repetition rates. Current line-tuning devices are mechanical and are capable of switching lines at a rate up to a few hundred Hertz. Acousto-optic modulators, deflectors or tunable filters can be substituted for these mechanical devices in the resonator of a CO{sub 2} laser and used to rapidly line-tune the laser across the 9 and 10 micron bands at a rate as high as 100 kHz. Several configurations for line tuning using acousto-optic and electro-optic devices with and without gratings are presented. The merits of and constraints on each design are also discussed. A pair of large aperture, acousto-optic deflectors has been purchased and the various line-tuning designs will be evaluated in a conventional, glass tube, CO{sub 2} laser, with a view to incorporation into the high-repetition-rate, waveguide laser. A computer model of the dynamics of an RF-excited, short-pulse-length, high-repetition-rate waveguide laser has been developed. The model will be used to test the consequences of various line-tuning designs.

  17. Design and operation of the multiple-pulse driver line on the OMEGA laser

    NASA Astrophysics Data System (ADS)

    Kosc, T. Z.; Kelly, J. H.; Hill, E. M.; Waxer, L. J.

    2016-05-01

    The multiple-pulse driver line (MPD) provides on-shot co-propagation of two separately generated pulse shapes in all 60 OMEGA beams at the Laboratory for Laser Energetics. Smoothing by spectral dispersion (SSD), which increases the laser bandwidth, can be applied to either one of the two pulse shapes, thereby enabling dynamic bandwidth reduction. The design of the MPD required careful consideration of beam combination as well as the minimum pulse separation for two pulses generated by two separate seed sources. A new combined-pulse-shape diagnostic needed to be designed and installed after the last SSD grating. The capability of MPD to reduce dynamic bandwidth has been used on a series of campaigns on OMEGA and the performance data are presented.

  18. The Effects of TM on Concurrent Heart Rate, Peripheral Blood Pulse Volume, and the Alpha Wave Frequency.

    ERIC Educational Resources Information Center

    Lukas, Jerome S.

    Through observation of 26 subjects over a 3 month period, this research project measured the effects of transcendental meditation (TM) on concurrent heart rate, peripheral blood pulse volume, and the alpha wave frequency. The subjects were assigned randomly to three groups. One group practiced TM as prescribed by the International Meditation…

  19. Pioneer spacecraft operation at low and high spin rates

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The feasibility of executing major changes upward or downward from the nominal spin rate for which the Pioneer F&G spacecraft was designed was investigated along with the extent of system and subsystem modifications required to implement these mode changes in future spacecraft evolving from the baseline Pioneer F and G. Results of a previous study are re-examined and updated for an extended range of spin rate variations for missions that include outer planet orbiters, outer planet flyby and outer planet probe delivery. However, in the interest of design simplicity and cost economy, major modifications of the baseline Pioneer system and subsystem concept were avoided.

  20. Improved operation of a microwave pulse compressor with a laser-triggered high-pressure gas plasma switch

    NASA Astrophysics Data System (ADS)

    Shlapakovski, A.; Gorev, S.; Krasik, Ya. E.

    2016-08-01

    The influence of laser beam parameters on the output pulses of a resonant microwave compressor with a laser-triggered plasma switch was investigated. The S-band compressor, consisting of a rectangular waveguide-based cavity and H-plane waveguide tee with a shorted side arm, was filled with pressurized dry air and pumped by 1.8-μs-long microwave pulses of up to 450 kW power. A Nd:YAG laser was used to ignite the gas discharge in the tee side arm for output pulse extraction. The laser beam (at 213 nm or 532 nm) was directed along the RF electric field lines. It was found that the compressor operated most effectively when the laser beam was focused at the center of the switch waveguide cross-section. In this case, the power extraction efficiency reached ˜47% at an output power of ˜14 MW, while when the laser beam was not focused the maximal extraction efficiency was only ˜20% at ˜6 MW output power. Focusing the laser beam resulted also in a dramatic decrease (down to <1 ns) in the delay of the output pulses' appearance with respect to the time of the beam's entrance into the switch, and the jitter of the output pulses' appearance was minimized. In addition, the quality of the output pulses' waveform was significantly improved.

  1. Warm Spitzer: Effects of Major Operational Changes on Publication Rates

    NASA Astrophysics Data System (ADS)

    Scire, E.

    2014-05-01

    The Spitzer Space Telescope transitioned from the cryogenic mission to the warm mission in 2009. The transition involved changes to observatory operations in order to run the mission on a budget totaling less than 1/3 that of the cryogenic mission. These changes included decreasing the number of approved programs and funding to the community while removing the cap in hours for any one program. This increased the maximum program size to encourage observers to think in terms of ambitious experiments that require > 500 hours to accomplish (Exploration Science (ES) Programs). After 4 years of warm operations, this paper will discuss the how these changes have affected the way observers are publishing data in refereed journal articles.

  2. 14 CFR 33.7 - Engine ratings and operating limitations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... turbine wheel inlet gas. (5) Pressure of— (i) Fuel at the fuel inlet; and (ii) Oil at the main oil gallery... following: (1) Horsepower, torque, or thrust, r.p.m., gas temperature, and time for— (i) Rated maximum...) Fuel filtration. (10) Oil filtration. (11) Bleed air. (12) The number of start-stop stress...

  3. Operant Conditioning of Vocalization Rate of Infants with Down Syndrome.

    ERIC Educational Resources Information Center

    Poulson, Claire L.

    1988-01-01

    Parents of three Down's Syndrome infants, aged 2-8 months, provided continuous reinforcement for vocalization (CRF) and differential reinforcement of other-than-vocalization (DRO). All infants produced systematically higher vocalization rates during CRF, even though the amount of social stimulation during DRO was equal to or greater than the…

  4. CFD simulation of a miniature coaxial Stirling-type pulse tube cryocooler operating at 128 Hz

    NASA Astrophysics Data System (ADS)

    Zhao, Yibo; Dang, Haizheng

    2016-01-01

    A two-dimensional axis-symmetric CFD model of a miniature coaxial Stirling-type pulse tube cryocooler with an overall weight of 920 g operating at 128 Hz is established, and systematic simulations of the performance characteristics at different temperatures are conducted. Both thermal equilibrium and non-equilibrium mechanisms for the porous matrix are considered, and the regenerator losses including the gas and solid conduction, the pressure drop and the imperfect interfacial heat transfer are calculated, respectively. The results indicate that the pressure drop loss is dominant during the first 85% and 78% of regenerator length for the thermal equilibrium and non-equilibrium models, respectively, and it decreases monotonously from warm to cold end due to the steadily decreasing Darcy and Forchheimer terms, whereas other entropy generations share similar changing tendencies, going up gradually near the warm end, increasing dramatically from about 60% of length and then decreasing sharply near the cold end. The reasons for these entropy variations are discussed.

  5. Design and economic benefits from the operation of pulse-jet fabric filter pilot plants

    SciTech Connect

    Emerson, R.D. ); Bustard, C.J.; Holstein, D.B. )

    1992-01-01

    This paper reports that utility power plant flue gas particulate collection is generally accomplished by either electrostatic precipitation (ESP) or fabric filtration (FF). The majority of existing units use ESP's but an increase in the use of FF's occurred during the 1970's and 80's. This was partially due to advances in FF state-of-the-art technology and the tightening of regulatory requirements. Fabric filtration is usually accomplished by reverse gas (RGFF), shake and deflate (SDFF), or pulse jet (PJFF) methods. Regardless of the method, the efficiency and reliability of operation are of paramount importance, especially when six minute averaging (or similar) is required for opacity measurements. Many items enter into the efficiency and reliability of FF's with a primary one being the performance of the fabric itself. The fabric could possibly fail in a given situation and as a minimum would impact outlet emissions, cleaning frequency, and pressure drop. The fabric's performance is very much a function of the flue gas conditions and flyash characteristics.

  6. Electromagnetic pulse survey of the Kentucky State Emergency Operating Center, Frankfort, Kentucky

    SciTech Connect

    Buchanan, M.E.; Cole, O.C.; Jones, R.W.; Marshall, D.J.

    1988-09-01

    The purpose of this report is to develop an engineering design package to protect the Federal Emergency Management Agency (FEMA) National Radio System (FNARS) facilities against the effects of high-altitude electromagnetic pulses (HEMP). This report refers to the Kentucky State Emergency Operating Center (EOC) in Frankfort, Kentucky. It is highly probable that there will be a heavy dependence upon hf radio for long-haul communications following a nuclear attack on the continental United States, should one occur. To maintain the viability of the FEMA hf radio network during such a situation, the FNARS facilities must take measures to protect against the effects of HEMP that are likely to be created in a nuclear confrontation. The equipment under stress has already been designed and built so that little opportunity exists for equipment design changes that could raise the threshold levels at which malfunctions occur. The solution must then be to reduce HEMP-induced stresses on the system by means of tailored retrofit hardening measures using commercial protection devices when available. 30 figs., 2 tabs.

  7. Investigation of pulsed low dose rate radiotherapy using dynamic arc delivery techniques

    NASA Astrophysics Data System (ADS)

    Ma, C.-M.; Lin, M. H.; Dai, X. F.; Koren, Sion; Klayton, T.; Wang, L.; Li, J. S.; Chen, L.; Price, R. A.

    2012-07-01

    There has been no consensus standard of care to treat recurrent cancer patients who have previously been irradiated. Pulsed low dose rate (PLDR) external beam radiotherapy has the potential to reduce normal tissue toxicities while still providing significant tumor control for recurrent cancers. This work investigates the dosimetry feasibility of PLDR treatment using dynamic arc delivery techniques. Five treatment sites were investigated in this study including breast, pancreas, prostate, head and neck, and lung. Dynamic arc plans were generated using the Varian Eclipse system and the RapidArc delivery technique with 6 and 10 MV photon beams. Each RapidArc plan consisted of two full arcs and the plan was delivered five times to achieve a daily dose of 200 cGy. The dosimetry requirement was to deliver approximately 20 cGy/arc with a 3 min interval to achieve an effective dose rate of 6.7 cGy min-1. Monte Carlo simulations were performed to calculate the actual dose delivered to the planning target volume (PTV) per arc taking into account beam attenuation/scattering and intensity modulation. The maximum, minimum and mean doses to the PTV were analyzed together with the dose volume histograms and isodose distributions. The dose delivery for the five plans was validated using solid water phantoms inserted with an ionization chamber and film, and a cylindrical detector array. Two intensity-modulated arcs were used to efficiently deliver the PLDR plans that provided conformal dose distributions for treating complex recurrent cancers. For the five treatment sites, the mean PTV dose ranged from 18.9 to 22.6 cGy/arc. For breast, the minimum and maximum PTV dose was 8.3 and 35.2 cGy/arc, respectively. The PTV dose varied between 12.9 and 27.5 cGy/arc for pancreas, 12.6 and 28.3 cGy/arc for prostate, 12.1 and 30.4 cGy/arc for H&N, and 16.2 and 27.6 cGy/arc for lung. Advanced radiation therapy can provide superior target coverage and normal tissue sparing for PLDR

  8. Effect of Inductive Coil Geometry on the Operating Characteristics of a Pulsed Inductive Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Kimberlin, Adam C.

    2012-01-01

    Operational characteristics of two separate inductive thrusters with coils of different cone angles are explored through thrust stand measurements and time-integrated, un- filtered photography. Trends in impulse bit measurements indicate that, in the present experimental configuration, the thruster with the inductive coil possessing a smaller cone angle produced larger values of thrust, in apparent contradiction to results of a previous thruster acceleration model. Areas of greater light intensity in photographs of thruster operation are assumed to qualitatively represent locations of increased current density. Light intensity is generally greater in images of the thruster with the smaller cone angle when compared to those of the thruster with the larger half cone angle for the same operating conditions. The intensity generally decreases in both thrusters for decreasing mass ow rate and capacitor voltage. The location of brightest light intensity shifts upstream for decreasing mass ow rate of propellant and downstream for decreasing applied voltage. Recognizing that there typically exists an optimum ratio of applied electric field to gas pressure with respect to breakdown efficiency, this result may indicate that the optimum ratio was not achieved uniformly over the coil face, leading to non-uniform and incomplete current sheet formation in violation of the model assumption of immediate formation where all the injected propellant is contained in a magnetically-impermeable current sheet.

  9. Effect of Inductive Coil Geometry on the Operating Characteristics of an Inductive Pulsed Plasma Thruster

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Polzin, Kurt A.; Kimberlin, Adam C.; Perdue, Kevin A.

    2012-01-01

    Operational characteristics of two separate inductive thrusters with conical theta pinch coils of different cone angles are explored through thrust stand measurements and time- integrated, unfiltered photography. Trends in impulse bit measurements indicate that, in the present experimental configuration, the thruster with the inductive coil possessing a smaller cone angle produced larger values of thrust, in apparent contradiction to results of a previous thruster acceleration model. Areas of greater light intensity in photographs of thruster operation are assumed to qualitatively represent locations of increased current density. Light intensity is generally greater in images of the thruster with the smaller cone angle when compared to those of the thruster with the larger half cone angle for the same operating conditions. The intensity generally decreases in both thrusters for decreasing mass flow rate and capacitor voltage. The location of brightest light intensity shifts upstream for decreasing mass flow rate of propellant and downstream for decreasing applied voltage. Recognizing that there typically exists an optimum ratio of applied electric field to gas pressure with respect to breakdown efficiency, this result may indicate that the optimum ratio was not achieved uniformly over the coil face, leading to non-uniform and incomplete current sheet formation in violation of the model assumption of immediate formation where all the injected propellant is contained in a magnetically-impermeable current sheet.

  10. 7 CFR 1430.208 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Payment rate and dairy operation payment. 1430.208... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Milk Income Loss Contract Program § 1430.208 Payment rate and dairy operation payment. (a) Payments under this subpart...

  11. 7 CFR 1430.506 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 10 2011-01-01 2011-01-01 false Payment rate and dairy operation payment. 1430.506... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Dairy Market Loss Assistance Program § 1430.506 Payment rate and dairy operation payment. (a) Payments under this subpart...

  12. 7 CFR 1430.208 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Payment rate and dairy operation payment. 1430.208... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Milk Income Loss Contract Program § 1430.208 Payment rate and dairy operation payment. (a) Payments under this subpart...

  13. 7 CFR 1430.506 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Payment rate and dairy operation payment. 1430.506... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Dairy Market Loss Assistance Program § 1430.506 Payment rate and dairy operation payment. (a) Payments under this subpart...

  14. 7 CFR 1430.208 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Payment rate and dairy operation payment. 1430.208... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Milk Income Loss Contract Program § 1430.208 Payment rate and dairy operation payment. (a) Payments under this subpart...

  15. 7 CFR 1430.506 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Payment rate and dairy operation payment. 1430.506... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Dairy Market Loss Assistance Program § 1430.506 Payment rate and dairy operation payment. (a) Payments under this subpart...

  16. 7 CFR 1430.506 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Payment rate and dairy operation payment. 1430.506... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Dairy Market Loss Assistance Program § 1430.506 Payment rate and dairy operation payment. (a) Payments under this subpart...

  17. 7 CFR 1430.506 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Payment rate and dairy operation payment. 1430.506... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Dairy Market Loss Assistance Program § 1430.506 Payment rate and dairy operation payment. (a) Payments under this subpart...

  18. 7 CFR 1430.208 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Payment rate and dairy operation payment. 1430.208... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Milk Income Loss Contract Program § 1430.208 Payment rate and dairy operation payment. (a) Payments under this subpart...

  19. 7 CFR 1430.208 - Payment rate and dairy operation payment.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Payment rate and dairy operation payment. 1430.208... CORPORATION, DEPARTMENT OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS DAIRY PRODUCTS Milk Income Loss Contract Program § 1430.208 Payment rate and dairy operation payment. (a) Payments under this subpart...

  20. Different operation states of soliton pulses in an erbium-doped fibre ring laser

    NASA Astrophysics Data System (ADS)

    Zhang, Shu-Min; Lü, Fu-Yun; Gong, Yan-Dong; Yang, Xiu-Feng

    2007-07-01

    We report on the experimental observation of soliton pulses in an erbium doped fibre ring laser. The passive mode-locking is achieved using the nonlinear polarization rotation technique. By adjusting the pump power and the intracavity polarization controllers, a normal soliton, a stable 8th harmonic mode-locked pulse and a noise-like pulse have been observed in our laser. The experimental results revealed that the noise-like pulse is not suitable for the optical telecommunication, and in order to obtain the stable harmonic mode-locked soliton, a strong unstable CW laser field is necessary to mediate global soliton interaction. The formation mechanism of the harmonic mode-locked pulse has also been analysed.

  1. 14C BOMB-PULSE DATING AND STABLE ISOTOPE ANALYSIS FOR GROWTH RATE AND DIETARY INFORMATION IN BREAST CANCER?

    PubMed

    Lång, K; Eriksson Stenström, K; Rosso, A; Bech, M; Zackrisson, S; Graubau, D; Mattsson, S

    2016-06-01

    The purpose of this study was to perform an initial investigation of the possibility to determine breast cancer growth rate with (14)C bomb-pulse dating. Tissues from 11 breast cancers, diagnosed in 1983, were retrieved from a regional biobank. The estimated average age of the majority of the samples overlapped the year of collection (1983) within 3σ Thus, this first study of tumour tissue has not yet demonstrated that (14)C bomb-pulse dating can obtain information on the growth of breast cancer. However, with further refinement, involving extraction of cell types and components, there is a possibility that fundamental knowledge of tumour biology might still be gained by the bomb-pulse technique. Additionally, δ (13)C and δ (15)N analyses were performed to obtain dietary and metabolic information, and to serve as a base for improvement of the age determination.

  2. 14C BOMB-PULSE DATING AND STABLE ISOTOPE ANALYSIS FOR GROWTH RATE AND DIETARY INFORMATION IN BREAST CANCER?

    PubMed Central

    Lång, K.; Eriksson Stenström, K.; Rosso, A.; Bech, M.; Zackrisson, S.; Graubau, D.; Mattsson, S.

    2016-01-01

    The purpose of this study was to perform an initial investigation of the possibility to determine breast cancer growth rate with 14C bomb-pulse dating. Tissues from 11 breast cancers, diagnosed in 1983, were retrieved from a regional biobank. The estimated average age of the majority of the samples overlapped the year of collection (1983) within 3σ. Thus, this first study of tumour tissue has not yet demonstrated that 14C bomb-pulse dating can obtain information on the growth of breast cancer. However, with further refinement, involving extraction of cell types and components, there is a possibility that fundamental knowledge of tumour biology might still be gained by the bomb-pulse technique. Additionally, δ 13C and δ 15N analyses were performed to obtain dietary and metabolic information, and to serve as a base for improvement of the age determination. PMID:27179119

  3. Hybrid power system intelligent operation and protection involving distributed architectures and pulsed loads

    NASA Astrophysics Data System (ADS)

    Mohamed, Ahmed

    Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system. To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators. The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available

  4. Liquid-xenon detector under the intensive pulse irradiation conditions

    NASA Astrophysics Data System (ADS)

    Kirsanov, M. A.

    2016-02-01

    The effect of intense pulsed irradiation on the operation of the liquid xenon spectrometer was studied. The ionization chamber filled with liquid xenon was irradiated by bremsstrahlung pulses of the microtron. The pulse repetition rate was 400 Hz. The absorbed dose ranged from 10-7 to 0.1 Gy per pulse. Stable operation of the liquid xenon spectrometer in the intervals between the pulses of the accelerator was shown for a long time.

  5. Pulsed hall thruster system

    NASA Technical Reports Server (NTRS)

    Hruby, Vladimir J. (Inventor); Pote, Bruce M. (Inventor); Gamero-Castano, Manuel (Inventor)

    2004-01-01

    A pulsed Hall thruster system includes a Hall thruster having an electron source, a magnetic circuit, and a discharge chamber; a power processing unit for firing the Hall thruster to generate a discharge; a propellant storage and delivery system for providing propellant to the discharge chamber and a control unit for defining a pulse duration .tau.<0.1d.sup.3.rho./m, where d is the characteristic size of the thruster, .rho. is the propellant density at standard conditions, and m is the propellant mass flow rate for operating either the power processing unit to provide to the Hall thruster a power pulse of a pre-selected duration, .tau., or operating the propellant storage and delivery system to provide a propellant flow pulse of duration, .tau., or providing both as pulses, synchronized to arrive coincidentally at the discharge chamber to enable the Hall thruster to produce a discreet output impulse.

  6. Tunable short-pulse beat-wave laser source operating at 1 microm.

    PubMed

    Hankla, A K; Bullock, A B; White, W E; Squier, J A; Barty, C P

    1997-11-15

    We have demonstrated a chirped-pulse-amplification system utilizing an air-spaced etalon inside a regenerative amplifier to produce two simultaneous 2.0-ps pulses, one centered at the gain peak of Nd:phosphate glass (1052 nm) and the other centered at the gain peak of Nd:silicate (1061 nm). Autocorrelations of the resulting beat wave demonstrate a beat frequency of 2.3 THz. We achieved wavelength tunability over a 10-nm range by electronically adjusting the etalon spacing and variable pulse width by changing the etalon rotation. PMID:18188344

  7. Tunable short-pulse beat-wave laser source operating at 1 microm.

    PubMed

    Hankla, A K; Bullock, A B; White, W E; Squier, J A; Barty, C P

    1997-11-15

    We have demonstrated a chirped-pulse-amplification system utilizing an air-spaced etalon inside a regenerative amplifier to produce two simultaneous 2.0-ps pulses, one centered at the gain peak of Nd:phosphate glass (1052 nm) and the other centered at the gain peak of Nd:silicate (1061 nm). Autocorrelations of the resulting beat wave demonstrate a beat frequency of 2.3 THz. We achieved wavelength tunability over a 10-nm range by electronically adjusting the etalon spacing and variable pulse width by changing the etalon rotation.

  8. Pulse oximeter using a gain-modulated avalanche photodiode operated in a pseudo lock-in light detection mode

    NASA Astrophysics Data System (ADS)

    Miyata, Tsuyoshi; Iwata, Tetsuo; Araki, Tsutomu

    2006-01-01

    We propose a reflection-type pulse oximeter, which employs two pairs of a light-emitting diode (LED) and a gated avalanche photodiode (APD). One LED is a red one with an emission wavelength λ = 635 nm and the other is a near-infrared one with that λ = 945 nm, which are both driven with a pulse mode at a frequency f (=10 kHz). Superposition of a transistor-transistor-logic (TTL) gate pulse on a direct-current (dc) bias, which is set so as not exceeding the breakdown voltage of each APD, makes the APD work in a gain-enhanced operation mode. Each APD is gated at a frequency 2f (=20 kHz) and its output signal is fed into a laboratory-made lock-in amplifier that works in synchronous with the pulse modulation signal of each LED at a frequency f (=10 kHz). A combination of the gated APD and the lock-in like signal detection scheme is useful for the reflection-type pulse oximeter thanks to the capability of detecting a weak signal against a large background (BG) light.

  9. The midbrain central gray best suppresses chronic pain with electrical stimulation at very low pulse rates in two human cases.

    PubMed

    Hentall, Ian D; Luca, Corneliu C; Widerstrom-Noga, Eva; Vitores, Alberto; Fisher, Letitia D; Martinez-Arizala, Alberto; Jagid, Jonathan R

    2016-02-01

    Deep brain stimulation in the midbrain׳s central gray can relieve neuropathic pain in man, but for unclear reasons sometimes fails intraoperatively or in early weeks. Here we describe continuous bilateral stimulation in the central gray of two subjects with longstanding, severe neuropathic pain from spinal cord injury. Stimulation parameters were recursively adjusted over many weeks to optimize analgesia while minimizing adverse effects. In early weeks, adjustments were made in periodic office visits; subjects later selected ad libitum at home among several blinded choices while rating pain twice daily. Both subjects received significantly better pain relief when stimulus pulse rates were low. The best relief occurred with 2 Hz cycled on for 1s and off for 2s. After inferior parameters were set, pain typically climbed slowly over 1-2 days; superior parameters led to both slow and fast improvements. Over many weeks of stimulation at low pulse rates, both subjects experienced significantly less interference from pain with sleep. One subject, with major pain relief, also showed less interference with social/recreational ability and mood; the other subject, despite minor pain relief, experienced a significantly positive global impression of change. Oscillopsia, the only observed complication of stimulation, disappeared at low mean pulse rates (≤ 3/s). These subjects׳ responses are not likely to be unique even if they are uncommon. Thus daily or more frequent pain assessment, combined with slower periodic adjustment of stimulation parameters that incorporate mean pulse rates about one per second, will likely improve success with this treatment. PMID:26711853

  10. A heat-pulse flowmeter for measuring minimal discharge rates in boreholes

    USGS Publications Warehouse

    Hess, A.E.

    1982-01-01

    The U.S. Geological Survey has tested a borehole-configured heat-pulse flowmeter which has good low-velocity flow-measuring sensitivity. The flowmeter was tested in the laboratory in 51-, 102-, and 152-millimeter-diameter columns using water velocities ranging from 0.35 to 250 millimeters per second. The heat-pulse flowmeter also was tested in a 15-meter-deep granite test pit with controlled water flow, and in a 58-meter-deep borehole in sedimentary materials. The flowmeter's capability to detect and measure naturally occurring, low-velocity, thermally induced convection currents in boreholes was demonstrated. Further improvements to the heat-pulse-flowmeter system are needed to increase its reliability and improve its response through four-conductor logging cable.

  11. On the use of pulsed reduced dose rate for improvement of the therapeutic ratio

    NASA Astrophysics Data System (ADS)

    Rasmussen, Karl H., V.

    This work demonstrates three related aspects of the efficacy, delivery, and verification of pulsed reduced dose rate radiotherapy (PRDR). PRDR is a method of irradiation designed to minimize radiation-related toxicities in patients undergoing reirradiation for loco-regional reoccurrence of glioblastoma. PRDR uses 0.2GyX10fx daily doses delivered over a 30-minute time span. Under PRDR treatments, a subset of patients have had an unexpectedly positive response to treatment. It was a primary goal of this project to determine if low-dose hyper-radiosensitivity was a contributor to the increased radio-response from these patients. This was done through the use of human T98G glioma and HT29 colorectal cells, and V79.379-A Chinese hamster fibroblasts with drug inhibition of the p53 and PI3K pathways. Radiation was delivered with a medical linear accelerator in either 2Gy acute doses or through PRDR. Methods used to analyze the effect of these techniques included clonogenic assay, flow cytometry, and western blots. Comparison of survival ratios demonstrated no decrease in efficacy for either the standard T98G or HT29 cell lines when using PRDR as compared to an acute dose. T98G with PI3K inhibition and V79.397-A cells demonstrated a decreased efficacy of treatment using PRDR relative to an acute dose. These results suggest an equivalency in tumor treatment with a possible improvement in normal tissue toxicities for the PRDR method. An additional method of delivering PRDR through the use of Tomotherapy was proposed and demonstrated to be accurate. Tomotherapy planning forces the short leaf open times for individual MLC projections from low dose fractionation closed, resulting in an undeliverable plan due to the loss of a large number of usable projections. Application of a virtual grid with directional blocking allows for the output from useable segments to be above this threshold, resulting in a deliverable treatment plan. Finally, analysis was performed on a proposed QA

  12. A Technique for the Assessment of Flight Operability Characteristics of Human Rated Spacecraft

    NASA Technical Reports Server (NTRS)

    Crocker, Alan

    2010-01-01

    In support of new human rated spacecraft development programs, the Mission Operations Directorate at NASA Johnson Space Center has implemented a formal method for the assessment of spacecraft operability. This "Spacecraft Flight Operability Assessment Scale" defines six key themes of flight operability, with guiding principles and goals stated for each factor. A standardized rating technique provides feedback that is useful to the operations, design and program management communities. Applicability of this concept across the program structure and life cycle is addressed. Examples of operationally desirable and undesirable spacecraft design characteristics are provided, as is a sample of the assessment scale product.

  13. Generation of 16-fs, 10-TW pulses at a 10-Hz repetition rate with efficient Ti:sapphire amplifiers.

    PubMed

    Yamakawa, K; Aoyama, M; Matsuoka, S; Takuma, H; Barty, C P; Fittinghoff, D

    1998-04-01

    We describe a two-stage Ti:sapphire amplifier laser system that is capable of producing 16-fs pulses of 10-TW peak power at a 10-Hz repetition rate. Thin solid etalons were used to control gain narrowing and gain saturation during amplification. A cylindrical mirror expander was used to permit compensation of the dispersion of the system. An efficiency greater than 90% of the theoretical maximum for conversion of 532-nm pump light to 790-nm radiation is demonstrated.

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

    NASA Astrophysics Data System (ADS)

    Karsch, Leonhard

    2016-04-01

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

  15. Pulse pressure and heart rate in patients with metabolic syndrome across Europe: insights from the GOOD survey.

    PubMed

    Perlini, S; Naditch-Brule, L; Farsang, C; Zidek, W; Kjeldsen, S E

    2013-07-01

    The Global Cardiometabolic Risk Profile in Patients with hypertension disease (GOOD) survey investigated the global cardiometabolic risk profile in 3464 adult outpatients with hypertension across 289 sites in 12 European countries. The pulse pressure and heart rate profile of the survey population was evaluated according to the presence or absence of metabolic syndrome and/or type 2 diabetes mellitus. History and treatment of hypertension were not counted as criteria for metabolic syndrome as they applied to all patients. Out of the 3370 recruited patients, 1033 had metabolic syndrome and 1177 had neither metabolic syndrome nor diabetes. When compared with patients with no metabolic syndrome or diabetes, patients with metabolic syndrome had higher pulse pressure (59±14 vs. 55±14 mm Hg) and heart rate (75.2±11.0 vs. 72.5±10.0 beats per min) (P<0.001 for both), independent of the concomitant presence or absence of diabetes, despite a more prevalent use of β-blockers. In conclusion, in hypertensive outpatients the presence of metabolic syndrome is associated with increased heart rate and pulse pressure, which may at least in part reflect increased arterial stiffness and increased sympathetic tone. This may contribute, to some extent, to explaining the increased cardiovascular risk attributed to the presence of metabolic syndrome.

  16. High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate.

    PubMed

    Shamir, Yariv; Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Tschernajew, Maxim; Limpert, Jens; Tünnermann, Andreas

    2015-12-01

    Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed.

  17. High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate.

    PubMed

    Shamir, Yariv; Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Tschernajew, Maxim; Limpert, Jens; Tünnermann, Andreas

    2015-12-01

    Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed. PMID:26625047

  18. HydroPulse Drilling

    SciTech Connect

    J.J. Kolle

    2004-04-01

    Tempress HydroPulse{trademark} tool increases overbalanced drilling rates by generating intense suction pulses at the drill bit. This report describes the operation of the tool; results of pressure drilling tests, wear tests and downhole drilling tests; and the business case for field applications. The HydroPulse{trademark} tool is designed to operate on weighted drilling mud at conventional flow rates and pressures. Pressure drilling tests confirm that the HydroPulse{trademark} tool provides 33% to 200% increased rate of penetration. Field tests demonstrated conventional rotary and mud motor drilling operations. The tool has been operated continuous for 50 hours on weighted mud in a wear test stand. This level of reliability is the threshold for commercial application. A seismic-while-drilling version of the tool was also developed and tested. This tool was used to demonstrate reverse vertical seismic profiling while drilling an inclined test well with a PDC bit. The primary applications for the HydroPulse{trademark} tool are deep onshore and offshore drilling where rate of penetration drives costs. The application of the seismic tool is vertical seismic profiling-while-drilling and look-ahead seismic imaging while drilling.

  19. New technique of mechanical pulse jet coolant delivery system for minimal quantity lubricant (MQL) operation

    NASA Astrophysics Data System (ADS)

    Fazli, Nik; Badrul, Hamdi, M.

    2011-01-01

    Minimum quantity lubrication (MQL) machining is one of the promising solutions to decrease the cutting fluid consumption requirements. This paper describes MQL machining in a range of lubricant consumption of 2.0ml/h, which is 10-100 times smaller than the normal consumption adopted in industries. MQL machining in this range is called pulse jet coolant delivery system in this paper. A specially designed system was used for concentrating small amounts of lubricant onto the cutting interface. The performance of concentrated spraying of lubricant in pulse jet coolant delivery system design was actual simulated and compared with others systems. The concentrated spraying of lubricant with a specially designed of system was quite effective in increasing tool life in the pulse jet coolant delivery system range.

  20. Time-resolved in vivo luminescence dosimetry for online error detection in pulsed dose-rate brachytherapy

    SciTech Connect

    Andersen, Claus E.; Nielsen, Soeren Kynde; Lindegaard, Jacob Christian; Tanderup, Kari

    2009-11-15

    Purpose: The purpose of this study is to present and evaluate a dose-verification protocol for pulsed dose-rate (PDR) brachytherapy based on in vivo time-resolved (1 s time resolution) fiber-coupled luminescence dosimetry. Methods: Five cervix cancer patients undergoing PDR brachytherapy (Varian GammaMed Plus with {sup 192}Ir) were monitored. The treatments comprised from 10 to 50 pulses (1 pulse/h) delivered by intracavitary/interstitial applicators (tandem-ring systems and/or needles). For each patient, one or two dosimetry probes were placed directly in or close to the tumor region using stainless steel or titanium needles. Each dosimeter probe consisted of a small aluminum oxide crystal attached to an optical fiber cable (1 mm outer diameter) that could guide radioluminescence (RL) and optically stimulated luminescence (OSL) from the crystal to special readout instrumentation. Positioning uncertainty and hypothetical dose-delivery errors (interchanged guide tubes or applicator movements from {+-}5 to {+-}15 mm) were simulated in software in order to assess the ability of the system to detect errors. Results: For three of the patients, the authors found no significant differences (P>0.01) for comparisons between in vivo measurements and calculated reference values at the level of dose per dwell position, dose per applicator, or total dose per pulse. The standard deviations of the dose per pulse were less than 3%, indicating a stable dose delivery and a highly stable geometry of applicators and dosimeter probes during the treatments. For the two other patients, the authors noted significant deviations for three individual pulses and for one dosimeter probe. These deviations could have been due to applicator movement during the treatment and one incorrectly positioned dosimeter probe, respectively. Computer simulations showed that the likelihood of detecting a pair of interchanged guide tubes increased by a factor of 10 or more for the considered patients when

  1. Broad spectral pulse operation of 2 μm Tm:YAP laser based on reflection-type carbon nanotube absorber

    NASA Astrophysics Data System (ADS)

    Qu, Z. S.; Ma, B. M.; Fan, X. W.; Liu, J.; Wang, Y. G.

    2012-03-01

    We demonstrated the first use of reflection-type single-walled carbon nanotube (RSWCNT) as a saturable absorber in the Q-switched mode-locking (QML) of a diode pumped Tm:YAP operating at 2 μm. The spectrum of the QML laser is centered at 1.97 μm with a broad spectral region of 36 nm. At the incident pump power of 10.33 W, as high as 432 mW average output power was produced in QML laser. The repetition rate of the mode-locked pulse inside the Q-switched envelope was 158 MHz. The dependence of the operational parameters on the pump power was also investigated experimentally.

  2. Consolidated Fuel Reprocessing Program. Operating experience with pulsed-column holdup estimators

    SciTech Connect

    Ehinger, M.H.

    1986-01-01

    Methods for estimating pulsed-column holdup are being investigated as part of the Safeguards Assessment task of the Consolidated Fuel Reprocessing Program (CFRP) at the Oak Ridge National Laboratory. The CFRP was a major sponsor of test runs at the Barnwell Nuclear Fuel plant (BNFP) in 1980 and 1981. During these tests, considerable measurement data were collected for pulsed columns in the plutonium purification portion of the plant. These data have been used to evaluate and compare three available methods of holdup estimation.

  3. Thermal Spray Using a High-Frequency Pulse Detonation Combustor Operated in the Liquid-Purge Mode

    NASA Astrophysics Data System (ADS)

    Endo, T.; Obayashi, R.; Tajiri, T.; Kimura, K.; Morohashi, Y.; Johzaki, T.; Matsuoka, K.; Hanafusa, T.; Mizunari, S.

    2016-02-01

    Experiments on thermal spray by pulsed detonations at 150 Hz were conducted. Two types of pulse detonation combustors were used, one operated in the inert gas purge (GAP) mode and the other in the liquid-purge (LIP) mode. In both modes, all gases were supplied in the valveless mode. The GAP mode is free of moving components, although the explosive mixture is unavoidably diluted with the inert gas used for the purge of the hot burned gas. In the LIP mode, pure fuel-oxygen combustion can be realized, although a liquid-droplet injector must be actuated cyclically. The objective of this work was to demonstrate a higher spraying temperature in the LIP mode. First, the temperature of CoNiCrAlY particles heated by pulsed detonations was measured. As a result, the spraying temperature in the LIP mode was higher than that in the GAP mode by about 1000 K. Second, the temperature of yttria-stabilized zirconia (YSZ) particles, whose melting point was almost 2800 °C, heated by pulsed detonations in the LIP mode was measured. As a result, the YSZ particles were heated up to about 2500 °C. Finally, a thermal spray experiment using YSZ particles was conducted, and a coating with low porosity was successfully deposited.

  4. Steady slip pulses on faults with rate- and state-dependent friction and multiple thermal weakening mechanisms

    NASA Astrophysics Data System (ADS)

    Viesca, R. C.; Garagash, D.

    2012-12-01

    We present solutions for steadily propagating slip pulses whose underlying frictional evolution is dependent on both the rate of slip and the evolution of a state parameter (of a slip-law type), with strong velocity-dependent weakening of friction at high slip rates (via flash heating of asperity contacts). Additional weakening occurs by reduction of the effective normal stress by thermal pressurization of pore fluid within a shear zone of fixed nominal thickness. Such strong dynamic weakening mechanisms allow for rupture of faults under levels of a shear stress much lower than a nominal static strength. For decreasing levels of background shear stress, slip pulses become the favored mode as a critical point is reached where crack-like rupture modes may be inadmissible (Zheng and Rice, BSSA 1998). For even further decreases in shear stress, slip pulses may arrest shortly after nucleation, and our interest in characterizing steady pulse solutions lies partially in this precarious transition. The relative effect of the two thermal weakening mechanisms is determined by the relative size of the slip scales over which the flash heating and thermal pressurization evolve (Dc and Lachenbruch's δ c, respectively). Laboratory measurements of Dc and estimates for δ c indicate that Dc ≤ δ c: i.e., at the tip, weakening occurs as a cascade, which may be partially represented by tip solutions that neglect healing (Garagash and Viesca, AGU FM 2011). Considering the trailing edge, as state evolution of the slip-law type does not provide frictional restrengthening at zero slip velocity, the slip pulse heals asymptotically with distance behind the rupture tip in the absence of thermal pressurization. A robust, effective pulse length can be established in this case by setting a threshold value of the slip velocity. Allowing for TP provides a mechanism for stationary restrengthening and relocking of the fault at the trailing edge (Garagash, JGR 2012). We find relations between

  5. Radioactivity computation of steady-state and pulsed fusion reactors operation

    SciTech Connect

    Attaya, H.

    1994-06-01

    Different mathematical methods are used to calculate the nuclear transmutation in steady-state and pulsed neutron irradiation. These methods are the Schuer decomposition, the eigenvector decomposition, and the Pade approximation of the matrix exponential function. In the case of the linear decay chain approximation, a simple algorithm is used to evaluate the transition matrices.

  6. Comparison of Computed and Measured Performance of a Pulsed Inductive Thruster Operating on Argon Propellant

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Sankaran, Kameshwaran; Ritchie, Andrew G.; Peneau, Jarred P.

    2012-01-01

    Pulsed inductive plasma accelerators are electrodeless space propulsion devices where a capacitor is charged to an initial voltage and then discharged through a coil as a high-current pulse that inductively couples energy into the propellant. The field produced by this pulse ionizes the propellant, producing a plasma near the face of the coil. Once a plasma is formed if can be accelerated and expelled at a high exhaust velocity by the Lorentz force arising from the interaction of an induced plasma current and the magnetic field. A recent review of the developmental history of planar-geometry pulsed inductive thrusters, where the coil take the shape of a flat spiral, can be found in Ref. [1]. Two concepts that have employed this geometry are the Pulsed Inductive Thruster (PIT)[2, 3] and the Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)[4]. There exists a 1-D pulsed inductive acceleration model that employs a set of circuit equations coupled to a one-dimensional momentum equation. The model was originally developed and used by Lovberg and Dailey[2, 3] and has since been nondimensionalized and used by Polzin et al.[5, 6] to define a set of scaling parameters and gain general insight into their effect on thruster performance. The circuit presented in Fig. 1 provides a description of the electrical coupling between the current flowing in the thruster I1 and the plasma current I2. Recently, the model was upgraded to include an equation governing the deposition of energy into various modes present in a pulsed inductive thruster system (acceleration, magnetic flux generation, resistive heating, etc.)[7]. An MHD description of the plasma energy density evolution was tailored to the thruster geometry by assuming only one-dimensional motion and averaging the plasma properties over the spatial dimensions of the current sheet to obtain an equation for the time-evolution of the total energy. The equation set governing the dynamics of the coupled

  7. Measurement of lateral diffusion rates in membranes by pulsed magnetic field gradient, magic angle spinning-proton nuclear magnetic resonance.

    PubMed

    Gawrisch, Klaus; Gaede, Holly C

    2007-01-01

    Membrane organization, including the presence of domains, can be characterized by measuring lateral diffusion rates of lipids and membrane-bound substances. Magic angle spinning (MAS) yields well-resolved proton nuclear magnetic resonance (NMR) of lipids in biomembranes. When combined with pulsed-field gradient NMR (rendering what is called "pulsed magnetic field gradients-MAS-NMR"), it permits precise diffusion measurements on the micrometer lengths scale for any substance with reasonably well-resolved proton MAS-NMR resonances, without the need of preparing oriented samples. Sample preparation procedures, the technical requirements for the NMR equipment, and spectrometer settings are described. Additionally, equations for analysis of diffusion data obtained from unoriented samples, and a method for correcting the data for liposome curvature are provided.

  8. Review of critical flow rate, propagation of pressure pulse, and sonic velocity in two-phase media

    NASA Technical Reports Server (NTRS)

    Hsu, Y.

    1972-01-01

    For single-phase media, the critical discharge velocity, the sonic velocity, and the pressure pulse propagation velocity can be expressed in the same form by assuming isentropic, equilibria processes. In two-phase mixtures, the same concept is not valid due to the existence of interfacial transports of momentum, heat, and mass. Thus, the three velocities should be treated differently and separately for each particular condition, taking into account the various transport processes involved under that condition. Various attempts are reviewed to predict the critical discharge rate or the propagation velocities by considering slip ratio (momentum change), evaporation (mass and heat transport), flow pattern, etc. Experimental data were compared with predictions based on various theorems. The importance is stressed of the time required to achieve equilibrium as compared with the time available during the process, for example, of passing a pressure pulse.

  9. Comparison of High Rate Laser Ablation and Resulting Structures Using Continuous and Pulsed Single Mode Fiber Lasers

    NASA Astrophysics Data System (ADS)

    Knebel, T.; Streek, A.; Exner, H.

    This paper compares high rate laser ablation and resulting structures of aluminum by using both a continuous wave and a ns-pulsed single mode fiber laser of high average laser power. Two different scan technologies were applied for fast deflection of the laser beams. In this work, 2.5D laser processing was studied by using a high aperture galvanometer scanner with a maximum scan speed of 18 m/s. By contrast, considerably higher scan speeds up to 1,000 m/s were achieved by using the in-house developed polygon scanner system. The ablation rates and the processing rates per unit area were analyzed by means of the depths of line-scan ablation tracks and laser processed cavities. In addition, SEM photograph of the machining samples will be presented in order to evaluate the machining quality. Finally the feasibility of this high rate technology for industrial application is demonstrated by machining examples.

  10. Modeling and optimizing of low-repetition-rate high-energy pulse amplification in high-concentration erbium-doped fiber amplifiers

    NASA Astrophysics Data System (ADS)

    Li, Jianfeng; Dai, Zhiyong; Ou, Zhonghua; Zhang, Lixun; Liu, Yongzhi; Liu, Yong

    2009-09-01

    Starting from the modeling of isolated ions and ion-pairs, a closed form rate and power evolution equations for pulse amplification in high-concentration erbium-doped fiber amplifiers (EDFAs) are constructed. According to the equations, the effects of ion-pairs on the performance of a high-concentration EDFA in steady state including upper-state population, ASE powers without input signal are analyzed numerically. Furthermore, the effects of ion-pairs on the dynamic characteristics of low-repetition-rate pulse amplification in the EDFA including the storied energy, output pulse energy and evolution of pulse waveform distortion are systematically studied by using the finite-difference method. The results show that the presence of the ion-pairs deteriorates amplifier performance, such as the upper-state population, ASE power, storied energy, output pulse energy, and saturated gain, etc. For the high-concentration EDFA, the optimum fiber length should be modified to achieve a better performance. The relations between the evolution of pulse waveform distortion or output pulse energy and the input pulse peak power are also discussed. The results can provide important guide for the design and optimization of the low-repetition-rate pulse amplification in high-concentration EDFAs.

  11. A dealiasing method for use with ultrasonic pulsed Doppler in measuring velocity profiles and flow rates in pipes

    NASA Astrophysics Data System (ADS)

    Murakawa, Hideki; Muramatsu, Ei; Sugimoto, Katsumi; Takenaka, Nobuyuki; Furuichi, Noriyuki

    2015-08-01

    The ultrasonic pulsed Doppler method (UDM) is a powerful tool for measuring velocity profiles in a pipe. However, the maximum detectable velocity is limited by the Nyquist sampling theorem. Furthermore, the maximum detectable velocity (also called Nyquist velocity), vmax, and the maximum measurable length are related and cannot be increased at the same time. If the velocity is greater than vmax, velocity aliasing occurs. Hence, the higher velocity that occurs with a larger pipe diameter, i.e. under higher flow rate conditions, cannot be measured with the conventional UDM. To overcome these limitations, dual-pulse repetition frequency (dual PRF) and feedback methods were employed in this study to measure velocity profiles in a pipe. The velocity distributions obtained with the feedback method were found to be more accurate than those obtained with the dual PRF method. However, misdetection of the Nyquist folding number using the feedback method was found to increase with the flow velocity. A feedback method with a moving average is proposed to improve the measurement accuracy. The method can accurately measure the velocity distributions at a velocity five times greater than the maximum velocity that can be measured with the conventional UDM. The measurement volume was found to be among the important parameters that must be considered in assessing the traceability of the reflector during the pulse emission interval. Hence, a larger measurement volume is required to measure higher velocities using the dual PRF method. Integrating velocity distributions measured using the feedback method with a moving average makes it possible to accurately determine flow rates six times greater than those that can be determined using the conventional pulsed Doppler method.

  12. Operational experience of the DIII-D neutral beam 12 cm x 48 cm long pulse source

    SciTech Connect

    Hong, R.; Colleraine, A.P.; Haskovec, J.S.; Kellman, D.H.; Kim, J.; Nerem, A.; Phillips, J.C.; Sleaford, B.W.; Wight, J.J.; Vella, M.

    1987-10-01

    All four neutral beamline of the DIII-D tokamak have been converted to long pulse source operation. These common long pulse sources (CLPS) were designed for full power operation at 80 kV, 80 A, 5 sec with hydrogen. The CLPS plasma generator is equipped with cusp magnets and operates in the emission limited regime. The accelerator has an actively cooled tetrode geometry with a 10 m focus in one direction. Each new CLPS requires conditioning of the arc chamber prior to any attempt at beam extraction. It was found that the filament temperature plays an important role in the performance of the arc chamber, and that the arc operated more smoothly with the arc power supply in an unregulated mode and the filament supply in a constant voltage mode. To avoid the collapse of the voltage between the plasma and gradient grids at initial beam formation, a capacitive compensation network between the grids was added. Initial beam extraction typically started at 40 kV and progressed quickly to the full 80 kV capability with little to no degradation during shutdown periods. 4 refs., 12 figs.

  13. Dynamic absorption and scattering of water and hydrogel during high-repetition-rate (>100 MHz) burst-mode ultrafast-pulse laser ablation.

    PubMed

    Qian, Zuoming; Covarrubias, Andrés; Grindal, Alexander W; Akens, Margarete K; Lilge, Lothar; Marjoribanks, Robin S

    2016-06-01

    High-repetition-rate burst-mode ultrafast-laser ablation and disruption of biological tissues depends on interaction of each pulse with the sample, but under those particular conditions which persist from previous pulses. This work characterizes and compares the dynamics of absorption and scattering of a 133-MHz repetition-rate, burst-mode ultrafast-pulse laser, in agar hydrogel targets and distilled water. The differences in energy partition are quantified, pulse-by-pulse, using a time-resolving integrating-sphere-based device. These measurements reveal that high-repetition-rate burst-mode ultrafast-laser ablation is a highly dynamical process affected by the persistence of ionization, dissipation of plasma plume, neutral material flow, tissue tensile strength, and the hydrodynamic oscillation of cavitation bubbles. PMID:27375948

  14. Dynamic absorption and scattering of water and hydrogel during high-repetition-rate (>100 MHz) burst-mode ultrafast-pulse laser ablation

    PubMed Central

    Qian, Zuoming; Covarrubias, Andrés; Grindal, Alexander W.; Akens, Margarete K.; Lilge, Lothar; Marjoribanks, Robin S.

    2016-01-01

    High-repetition-rate burst-mode ultrafast-laser ablation and disruption of biological tissues depends on interaction of each pulse with the sample, but under those particular conditions which persist from previous pulses. This work characterizes and compares the dynamics of absorption and scattering of a 133-MHz repetition-rate, burst-mode ultrafast-pulse laser, in agar hydrogel targets and distilled water. The differences in energy partition are quantified, pulse-by-pulse, using a time-resolving integrating-sphere-based device. These measurements reveal that high-repetition-rate burst-mode ultrafast-laser ablation is a highly dynamical process affected by the persistence of ionization, dissipation of plasma plume, neutral material flow, tissue tensile strength, and the hydrodynamic oscillation of cavitation bubbles. PMID:27375948

  15. 240 GHz pedestal-free colliding-pulse mode-locked laser with a wide operation range

    NASA Astrophysics Data System (ADS)

    Hou, L.; Haji, M.; Marsh, J. H.

    2014-11-01

    A 240 GHz, sixth-harmonic monolithic ~1.55 μm colliding-pulse mode-locked laser is reported using a three-quantum-well active layer design and a passive far-field reduction layer. The device emits 0.88 ps pulses with a peak power of 65 mW and intermediate longitudinal modes suppressed by >30 dB. The device demonstrates a wide operation range compared to the conventional five-quantum-well design as well as having a low divergence angle (12.7° × 26.3°), granting a twofold improvement in butt-coupling efficiency into a flat cleaved single-mode fibre.

  16. [A project to improve the validity rate for nursing staff operating single door autoclave sterilizers].

    PubMed

    Chen, Chun-Hung; Li, Cheng-Chang; Chou, Chuan-Yu; Chen, Shu-Hwa

    2009-08-01

    This project was designed to improve the low validity rate for nurses responsible to operate single door autoclave sterilizers in the operating room. By investigating the current status, we found that the nursing staff validity rate of cognition on the autoclave sterilizer was 85%, and the practice operating check validity rate was only 80%. Such was due to a lack of in-service education. Problems with operation included: 1. Unsafe behaviors - not following standard procedure, lacking relevant operating knowledge and absence of a check form; 2. Unsafe environment - the conveying steam piping was typically not covered and lacked operation marks. Recommended improvement measures included: 1. holding in-service education; 2. generating an operation procedure flow chart; 3. implementing obstacle eliminating procedures; 4. covering piping to prevent fire and burns; 5. performing regular checks to ensure all procedures are followed. Following intervention, nursing staff cognition rose from 85% to 100%, while the operation validity rate rose from 80% to 100%. These changes ensure a safer operating room environment, and helps facilities move toward a zero accident rate in the healthcare environment.

  17. Reliability and concurrent validity of a peripheral pulse oximeter and health-app system for the quantification of heart rate in healthy adults.

    PubMed

    Losa-Iglesias, Marta Elena; Becerro-de-Bengoa-Vallejo, Ricardo; Becerro-de-Bengoa-Losa, Klark Ricardo

    2016-06-01

    There are downloadable applications (Apps) for cell phones that can measure heart rate in a simple and painless manner. The aim of this study was to assess the reliability of this type of App for a Smartphone using an Android system, compared to the radial pulse and a portable pulse oximeter. We performed a pilot observational study of diagnostic accuracy, randomized in 46 healthy volunteers. The patients' demographic data and cardiac pulse were collected. Radial pulse was measured by palpation of the radial artery with three fingers at the wrist over the radius; a low-cost portable, liquid crystal display finger pulse oximeter; and a Heart Rate Plus for Samsung Galaxy Note®. This study demonstrated high reliability and consistency between systems with respect to the heart rate parameter of healthy adults using three systems. For all parameters, ICC was > 0.93, indicating excellent reliability. Moreover, CVME values for all parameters were between 1.66-4.06 %. We found significant correlation coefficients and no systematic differences between radial pulse palpation and pulse oximeter and a high precision. Low-cost pulse oximeter and App systems can serve as valid instruments for the assessment of heart rate in healthy adults.

  18. Reliability and concurrent validity of a peripheral pulse oximeter and health-app system for the quantification of heart rate in healthy adults.

    PubMed

    Losa-Iglesias, Marta Elena; Becerro-de-Bengoa-Vallejo, Ricardo; Becerro-de-Bengoa-Losa, Klark Ricardo

    2016-06-01

    There are downloadable applications (Apps) for cell phones that can measure heart rate in a simple and painless manner. The aim of this study was to assess the reliability of this type of App for a Smartphone using an Android system, compared to the radial pulse and a portable pulse oximeter. We performed a pilot observational study of diagnostic accuracy, randomized in 46 healthy volunteers. The patients' demographic data and cardiac pulse were collected. Radial pulse was measured by palpation of the radial artery with three fingers at the wrist over the radius; a low-cost portable, liquid crystal display finger pulse oximeter; and a Heart Rate Plus for Samsung Galaxy Note®. This study demonstrated high reliability and consistency between systems with respect to the heart rate parameter of healthy adults using three systems. For all parameters, ICC was > 0.93, indicating excellent reliability. Moreover, CVME values for all parameters were between 1.66-4.06 %. We found significant correlation coefficients and no systematic differences between radial pulse palpation and pulse oximeter and a high precision. Low-cost pulse oximeter and App systems can serve as valid instruments for the assessment of heart rate in healthy adults. PMID:25038201

  19. Si nanostructures grown by picosecond high repetition rate pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Pervolaraki, M.; Komninou, Ph.; Kioseoglou, J.; Athanasopoulos, G. I.; Giapintzakis, J.

    2013-08-01

    One-step growth of n-doped Si nanostructures by picosecond ultra fast pulsed laser deposition at 1064 nm is reported for the first time. The structure and morphology of the Si nanostructures were characterized by X-ray diffraction, scanning electron microscopy and atomic force microscopy. Transmission electron microscopy studies revealed that the shape of the Si nanostructures depends on the ambient argon pressure. Fibrous networks, cauliflower formations and Si rectangular crystals grew when argon pressure of 300 Pa, 30 Pa and vacuum (10-3 Pa) conditions were used, respectively. In addition, the electrical resistance of the vacuum made material was investigated.

  20. Operation of the 118 GHz very long pulse Gyrotron for the ECRH experiment on Tore Supra

    NASA Astrophysics Data System (ADS)

    Darbos, C.; Bouquey, F.; Clary, J.; Giruzzi, G.; Jung, M.; Lennholm, M.; Magne, R.; Petit, T.; Portafaix, Ch.; Roux, D.; Segui, J. L.; Zou, X.; Giguet, E.; Lievin, Ch.; Alberti, S.; Hogge, J. P.; Thumm, M.

    2003-02-01

    An ECRH (Electron Cyclotron Resonance Heating) system capable of delivering 2.4 MW CW is presently under development at CEA (Commissariat à l'Energie Atomique) Cadarache, for the Tore Supra experiment, to provide plasma heating and current drive by Electron Cyclotron Resonance interaction. The generator is planned to consist of six gyrotrons TH 1506B developed thanks to a collaboration between TED (Thales Electron Devices) and European laboratories; the gyrotrons are specified to provide RF waves with a frequency of 118 GHz and a unit power of 400 kW (500 kW) for a pulse length up to 600 s (5 s). At present, one prototype and one series tube are installed , which were first tested on dummy loads and then on plasma, individually and together. Even though the specification was not fulfilled, a record pulse of 300 kW during 110 s was achieved by the series gyrotron; the pulse was stopped by a strong degassing within the tube, due to the overheating of the internal mirror box. This seems to be the consequence of spurious frequencies generated in the injector. New upgraded tubes will be developed by TED and the next gyrotron is planned to be delivered during summer 2003. At the end of 2001, 800 kW generated by the two existing gyrotrons were coupled to the plasma, using various polarisations and injection angles allowed by the mobile mirrors of the antenna; the power was modulated at frequencies between 2 Hz and 25 Hz, on both tubes. As a result, about 50 ECRH pulses have successfully been coupled to the plasma, leading to a first comparison of theoretical deposition profiles with the experimental profiles observed through the ECE diagnostic.

  1. Influence of selected fixed parameters on pulse-jet fabric filter operation

    NASA Astrophysics Data System (ADS)

    Hindy, K. T.

    The effect of (a) fixing the time interval between cleaning pulses or (b) fixing the maximum pressure drop at which cleaning is started, on the performance of the fabric filter was investigated. A maximum pressure drop value of 2500 Pa: (a) minimized the effect of the filter medium resistance; (b) reduced the energy consumption by the filter; (c) minimized the dust emission from the fabric filter to the surrounding atmosphere.

  2. Complex dynamics of a fiber laser in non-stationary pulsed operation.

    PubMed

    Garcia-Sanchez, E; Pottiez, O; Bracamontes-Rodriguez, Y; Lauterio-Cruz, J P; Ibarra-Villalon, H E; Hernandez-Garcia, J C; Bello-Jimenez, M; Kuzin, E A

    2016-08-22

    Conventional mode locking is characterized by the generation of a stable train of optical pulses. Even in the noise-like pulsing regime of fiber lasers, sometimes described as partial mode locking, a periodic train of waveforms is still generated. In this work we study the dynamics of a figure-eight fiber laser away from the stable noise-like pulsing regime. By analyzing sequences of time-domain measurements performed with ns resolution, we reveal a wide range of puzzling dynamics, in which sub-structures emerge and drift away from the main bunch, decay or grow in a step-like manner, before vanishing abruptly. In some cases, sub-packets also concentrate in the central part of the period, forming one or multiple wide clouds that merge or split over time scales of seconds or minutes. Spontaneous transitions between these multiple states occur in a non-periodic manner, so that no quasi-stationary behavior is found over long time scales. These results provide a dramatic illustration of the extremely rich dynamics taking place in fiber lasers at the frontier of mode locking.

  3. Complex dynamics of a fiber laser in non-stationary pulsed operation.

    PubMed

    Garcia-Sanchez, E; Pottiez, O; Bracamontes-Rodriguez, Y; Lauterio-Cruz, J P; Ibarra-Villalon, H E; Hernandez-Garcia, J C; Bello-Jimenez, M; Kuzin, E A

    2016-08-22

    Conventional mode locking is characterized by the generation of a stable train of optical pulses. Even in the noise-like pulsing regime of fiber lasers, sometimes described as partial mode locking, a periodic train of waveforms is still generated. In this work we study the dynamics of a figure-eight fiber laser away from the stable noise-like pulsing regime. By analyzing sequences of time-domain measurements performed with ns resolution, we reveal a wide range of puzzling dynamics, in which sub-structures emerge and drift away from the main bunch, decay or grow in a step-like manner, before vanishing abruptly. In some cases, sub-packets also concentrate in the central part of the period, forming one or multiple wide clouds that merge or split over time scales of seconds or minutes. Spontaneous transitions between these multiple states occur in a non-periodic manner, so that no quasi-stationary behavior is found over long time scales. These results provide a dramatic illustration of the extremely rich dynamics taking place in fiber lasers at the frontier of mode locking. PMID:27557173

  4. Power, pulse width, and repetition rate agile low-cost multi-spectral semi-active laser simulator

    NASA Astrophysics Data System (ADS)

    O'Daniel, Jason K.; Young, Preston; Golden, Eric; Barton, Robert; Snyder, Donald

    2010-04-01

    The emergence of spectrally multimode smart missiles requires hardware-in-the-loop (HWIL) facilities to simulate multiple spectral signatures simultaneously. While traditional diode-pumped solid-state (DPSS) sources provide a great basic testing source for smart missiles, they typically are bulky and provide substantially more power peak power than what is required for laboratory simulation, have fixed pulse widths, and require some external means to attenuate the output power. HWIL facilities require systems capable of high speed variability of the angular divergence and optical intensity over several orders of magnitude, which is not typically provided by basic DPSS systems. In order to meet the needs of HWIL facilities, we present a low-cost semi-active laser (SAL) simulator source using laser diode sources that emits laser light at the critical wavelengths of 1064 nm and 1550 nm, along with light in the visible for alignment, from a single fiber aperture. Fiber delivery of the multi-spectral output can provide several advantages depending on the testing setup. The SAL simulator source presented is capable of providing attenuation of greater than 70 dB with a response time of a few milliseconds and provides a means to change the angular divergence over an entire dynamic range of 0.02- 6º in less than 400 ms. Further, the SAL simulator is pulse width and pulse repetition rate agile making it capable of producing both current and any future coding format necessary.

  5. Flow rate and duty cycle effects in lysis of Chlamydomonas reinhardtii using high-energy pulsed focused ultrasound.

    PubMed

    Riesberg, Grant; Bigelow, Timothy A; Stessman, Dan J; Spalding, Martin H; Yao, Linxing; Wang, Tong; Xu, Jin

    2014-06-01

    To consider microalgae lipid biofuel as a viable energy source, it is a necessity to maximize algal cell lysis, lipid harvest, and thus biofuel production versus the energy used to lyse the cells. Previous techniques have been to use energy consumptive ultrasound waves in the 10-40 kHz range in a stationary exposure environment. This study evaluated the potential of using 1.1 MHz ultrasound pulses in a new flow through type chamber on Chlamydomonas reinhardtii as a model organism for cell breakage. The ultrasound was generated using a spherically focused transducer with a focal length of 6.34 cm and an active diameter of 6.36 cm driven by 20 cycle sine-wave tone bursts at varied pulse repetition frequencies. First, variations in flow rate were examined at a constant duty cycle of 3.6%. After assessing flow rates, the duty cycle was varied to further explore the dependence on the tone burst parameters. Cell lysis was assessed by quantifying protein and chlorophyll release into the supernatant as well as by lipid extractability. Appropriate flow rates with higher duty cycles led to statistically significant increases in cell lysis relative to controls and other exposure conditions.

  6. High-rate x-ray spectroscopy in mammography with a CdTe detector: A digital pulse processing approach

    SciTech Connect

    Abbene, L.; Gerardi, G.; Principato, F.; Del Sordo, S.; Ienzi, R.; Raso, G.

    2010-12-15

    Purpose:Direct measurement of mammographic x-ray spectra under clinical conditions is a difficult task due to the high fluence rate of the x-ray beams as well as the limits in the development of high resolution detection systems in a high counting rate environment. In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high-rate x-ray spectroscopy in mammography. Methods: The DPP system performs a digital pile-up inspection and a digital pulse height analysis of the detector signals, digitized through a 14-bit, 100 MHz digitizer, for x-ray spectroscopy even at high photon counting rates. We investigated on the response of the digital detection system both at low (150 cps) and at high photon counting rates (up to 500 kcps) by using monoenergetic x-ray sources and a nonclinical molybdenum anode x-ray tube. Clinical molybdenum x-ray spectrum measurements were also performed by using a pinhole collimator and a custom alignment device. Results: The detection system shows excellent performance up to 512 kcps with an energy resolution of 4.08% FWHM at 22.1 keV. Despite the high photon counting rate (up to 453 kcps), the molybdenum x-ray spectra, measured under clinical conditions, are characterized by a low number of pile-up events. The agreement between the attenuation curves and the half value layer values, obtained from the measured spectra, simulated spectra, and from the exposure values directly measured with an ionization chamber, also shows the accuracy of the measurements. Conclusions: These results make the proposed detection system a very attractive tool for both laboratory research and advanced quality controls in mammography.

  7. Characterization of dual-electrode CMUTs: demonstration of improved receive performance and pulse echo operation with dynamic membrane shaping.

    PubMed

    Guldiken, Rasim O; Balantekin, Mujdat; Zahorian, Jaime; Degertekin, F Levent

    2008-10-01

    A 1-D dual-electrode CMUT array for intracardiac echocardiography (ICE) with a center frequency of 8 MHz has been designed, fabricated, and used to demonstrate the potential of dual-electrode CMUTs. Using a dual-electrode CMUT, 9 dB higher receive signal level is obtained over the 6 dB fractional bandwidth as compared with a conventional CMUT with an identical center electrode biased close to its collapse voltage. Because the same device shows a 7.4 dB increase in maximum pressure output, 16.4 dB overall improvement in transduction performance has been achieved as compared with conventional CMUT. A net peak output pressure of 1.6 MPa on the dual-electrode CMUT membrane with tone burst excitation at 12 MHz is also reported. The frequency response of the dual-electrode CMUT is similar to that of a conventional CMUT with the same membrane geometry with about 15% increase in the center frequency. Monostatic operation of dual-electrode CMUTs shows that the high performance of the transducer is applicable in typical pulse-echo imaging mode of operation. With dynamic shaping of the CMUT membrane to optimize the transmit-and-receive modes of operation separately during each pulse-echo cycle, dual-electrode CMUT is a highly competitive alternative to its piezoelectric counterparts. PMID:18986882

  8. The effect of pulse duration on the growth rate of laser-induced damage sites at 351 nm on fused silica surfaces

    SciTech Connect

    Negres, R A; Norton, M A; Liao, Z M; Cross, D A; Bude, J D; Carr, C W

    2009-10-29

    Past work in the area of laser-induced damage growth has shown growth rates to be primarily dependent on the laser fluence and wavelength. More recent studies suggest that growth rate, similar to the damage initiation process, is affected by a number of additional parameters including pulse duration, pulse shape, site size, and internal structure. In this study, we focus on the effect of pulse duration on the growth rate of laser damage sites located on the exit surface of fused silica optics. Our results demonstrate, for the first time, a significant dependence of growth rate at 351 nm on pulse duration from 1 ns to 15 ns as {tau}{sup 0.3} for sites in the 50-100 {micro}m size range.

  9. A Simulation of the Effects of Varying Repetition Rate and Pulse Width of Nanosecond Discharges on Premixed Lean Methane-Air Combustion

    DOE PAGES

    Bak, Moon Soo; Cappelli, Mark A.

    2012-01-01

    Two-dimensional kinetic simulation has been carried out to investigate the effects of repetition rate and pulse width of nanosecond repetitively pulsed discharges on stabilizing premixed lean methane-air combustion. The repetition rate and pulse width are varied from 10 kHz to 50 kHz and from 9 ns to 2 ns while the total power is kept constant. The lower repetition rates provide larger amounts of radicals such as O, H, and OH. However, the effect on stabilization is found to be the same for all of the tested repetition rates. The shorter pulse width is found to favor the production of species in higher electronicmore » states, but the varying effects on stabilization are also found to be small. Our results indicate that the total deposited power is the critical element that determines the extent of stabilization over this range of discharge properties studied.« less

  10. Pulse Wave Velocity and Cardiac Output vs. Heart Rate in Patients with an Implanted Pacemaker Based on Electric Impedance Method Measurement

    NASA Astrophysics Data System (ADS)

    Soukup, Ladislav; Vondra, Vlastimil; Viščor, Ivo; Jurák, Pavel; Halámek, Josef

    2013-04-01

    The methods and device for estimation of cardiac output and measurement of pulse wave velocity simultaneously is presented here. The beat-to-beat cardiac output as well as pulse wave velocity measurement is based on application of electrical impedance method on the thorax and calf. The results are demonstrated in a study of 24 subjects. The dependence of pulse wave velocity and cardiac output on heart rate during rest in patients with an implanted pacemaker was evaluated. The heart rate was changed by pacemaker programming while neither exercise nor drugs were applied. The most important result is that the pulse wave velocity, cardiac output and blood pressure do not depend significantly on heart rate, while the stroke volume is reciprocal proportionally to the heart rate.

  11. Equipment Operator 3 and 2. NAVTRA 10640-G. Rate Training Manual.

    ERIC Educational Resources Information Center

    Bureau of Naval Personnel, Washington, DC.

    A guide for advancement and training in the Equipment Operator 3 and 2 ratings for Navy personnel is provided in this manual. The chapters outline the duties and responsibilities of the equipment operators involved with engines, fuels, lubricants, pollution control, automotive power trains and chassis, automotive vehicles, materials-handling…

  12. Proton acceleration by single-cycle laser pulses offers a novel monoenergetic and stable operating regime

    NASA Astrophysics Data System (ADS)

    Zhou, M. L.; Yan, X. Q.; Mourou, G.; Wheeler, J. A.; Bin, J. H.; Schreiber, J.; Tajima, T.

    2016-04-01

    Prompted by the possibility to produce high energy, single-cycle laser pulses with tens of Petawatt (PW) power, we have investigated laser-matter interactions in the few optical cycle and ultra relativistic intensity regimes. A particularly interesting instability-free regime for ion production was revealed leading to the efficient coherent generation of short (femtosecond; 10 - 15 s ) monoenergetic ion bunches with a peak energy greater than GeV. Of paramount importance, the interaction is absent of the Rayleigh Taylor Instabilities and hole boring that plague techniques such as target normal sheath acceleration and radiation pressure acceleration.

  13. Evaluation of the beat-to-beat detection accuracy of PulseOn wearable optical heart rate monitor.

    PubMed

    Parak, Jakub; Tarniceriu, Adrian; Renevey, Philippe; Bertschi, Mattia; Delgado-Gonzalo, Ricard; Korhonen, Ilkka

    2015-08-01

    Heart rate variability (HRV) provides significant information about the health status of an individual. Optical heart rate monitoring is a comfortable alternative to ECG based heart rate monitoring. However, most available optical heart rate monitoring devices do not supply beat-to-beat detection accuracy required by proper HRV analysis. We evaluate the beat-to-beat detection accuracy of a recent wrist-worn optical heart rate monitoring device, PulseOn (PO). Ten subjects (8 male and 2 female; 35.9±10.3 years old) participated in the study. HRV was recorded with PO and Firstbeat Bodyguard 2 (BG2) device, which was used as an ECG based reference. HRV was recorded during sleep. As compared to BG2, PO detected on average 99.57% of the heartbeats (0.43% of beats missed) and had 0.72% extra beat detection rate, with 5.94 ms mean absolute error (MAE) in beat-to-beat intervals (RRI) as compared to the ECG based RRI BG2. Mean RMSSD difference between PO and BG2 derived HRV was 3.1 ms. Therefore, PO provides an accurate method for long term HRV monitoring during sleep.

  14. Transient Flowfield Characteristics of Polycarbonate Plasma Discharge from Pulse-powered Electrothermal Gun Operation

    NASA Astrophysics Data System (ADS)

    Kim, Kyoungjin

    2008-12-01

    An electrothermal gun is the device that produces high-temperature and high-velocity plasma vapor using high current pulsed power and has a potential to be an efficient method for producing a variety of nanomaterials. Pulsed plasma discharge from the electrothermal gun into the open air has been investigated numerically, and the time-dependent inviscid gas dynamics equations are solved for the two-dimensional computational domain including electrothermal gun and the open-air space using flux-corrected transport (FCT) scheme. The modeling of the Joule heating and the mass ablation from the bore wall are incorporated in the computation. The computational results yield the details of the plasma discharge behavior inside and outside the capillary bore including choked condition at the bore exit and complex shock structure of external plasma discharge. The flow structure of freely expanding plasma discharge in the open air is essentially the highly underexpanded supersonic jet featuring Mach disk, barrel shock, contact surface, and spherical blast wave. Compared to the experiments, the numerical simulation agrees well with the experimental data such as the capillary mass ablation and shock structure of the plasma jet.

  15. Spectral broadening measurement of the lower hybrid waves during long pulse operation in Tore Supra

    NASA Astrophysics Data System (ADS)

    Berger-By, G.; Decampy, J.; Antar, G. Y.; Goniche, M.; Ekedahl, A.; Delpech, L.; Leroux, F.; Tore Supra Team

    2014-02-01

    On many tokamaks (C-Mod, EAST, FTU, JET, HT-7, TS), a decrease in current drive efficiency of the Lower Hybrid (LH) waves is observed in high electron density plasmas. The cause of this behaviour is believed to be: Parametric Instabilities (PI) and Scattering from Density Fluctuations (SDF). For the ITER LH system, our knowledge must be improved to avoid such effects and to maintain the LH current drive efficiency at high density. The ITPA IOS group coordinates this effort [1] and all experimental data are essential to validate the numerical codes in progress. Usually the broadening of the LH wave frequency spectrum is measured by a probe located in the plasma edge. For this study, the frequency spectrum of a reflected power signal from the LH antenna was used. In addition, the spectrum measurements are compared with the density fluctuations observed on RF probes located at the antenna mouth. Several plasma currents (0.6 to 1.4 MA) and densities up to 5.2 × 1019 m-3 have been realised on Tore Supra (TS) long pulses and with high injected RF power, up to 5.4 MW-30s. This allowed using a spectrum analyser to make several measurements during the plasma pulse. The side lobe amplitude, shifted by 20-30MHz with respect to the main peak, grows with increasing density. Furthermore, for an increase of plasma current at the same density, the spectra broaden and become asymmetric. Some parametric dependencies are shown in this paper.

  16. Enhancing the heralded single-photon rate from a silicon nanowire by time and wavelength division multiplexing pump pulses.

    PubMed

    Zhang, X; Jizan, I; He, J; Clark, A S; Choi, D-Y; Chae, C J; Eggleton, B J; Xiong, C

    2015-06-01

    Heralded single photons produced on a silicon chip represent an integrated photon source solution for scalable photonic quantum technologies. The key limitation of such sources is their non-deterministic nature introduced by the stochastic spontaneous four-wave mixing (SFWM) process. Active spatial and temporal multiplexing can improve this by enhancing the single-photon rate without degrading the quantum signal-to-noise ratio. Here, taking advantage of the broad bandwidth of SFWM in a silicon nanowire, we experimentally demonstrate heralded single-photon generation from a silicon nanowire pumped by time and wavelength division multiplexed pulses. We show a 90±5% enhancement on the heralded photon rate at the cost of only 14±2% reduction to the signal-to-noise ratio, close to the performance found using only time division multiplexed pulses. As single-photon events are distributed to multiple wavelength channels, this new scheme overcomes the saturation limit of avalanche single-photon detectors and will improve the ultimate performance of such photon sources. PMID:26030539

  17. Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser by sweeping the pulse repetition rate

    PubMed Central

    Lee, Keunwoo; Lee, Joohyung; Jang, Yoon-Soo; Han, Seongheum; Jang, Heesuk; Kim, Young-Jin; Kim, Seung-Woo

    2015-01-01

    Femtosecond lasers allow for simultaneous detection of multiple absorption lines of a specimen over a broad spectral range of infrared or visible light with a single spectroscopic measurement. Here, we present an 8-THz bandwidth, 0.5-GHz resolution scheme of Fourier-transform spectroscopy using an Er-doped fiber femtosecond laser. A resolving power of 1.6 × 104 about a 1560-nm center wavelength is achieved by sweeping the pulse repetition rate of the light source on a fiber Mach-Zehnder interferometer configured to capture interferograms with a 0.02-fs temporal sampling accuracy through a well-stabilized 60-m unbalance arm length. A dual-servo mechanism is realized by combining a mechanical linear stage with an electro-optic modulator (EOM) within the fiber laser cavity, enabling stable sweeping control of the pulse repetition rate over a 1.0-MHz scan range with 0.4-Hz steps with reference to the Rb clock. Experimental results demonstrate that the P-branch lines of the H13CN reference cell can be observed with a signal-to-noise ratio reaching 350 for the most intense line. PMID:26503257

  18. Library Automation Alternatives in 1996 and User Satisfaction Ratings of Library Users by Operating System.

    ERIC Educational Resources Information Center

    Cibbarelli, Pamela

    1996-01-01

    Examines library automation product introductions and conversions to new operating systems. Compares user satisfaction ratings of the following library software packages: DOS/Windows, UNIX, Macintosh, and DEC VAX/VMS. Software is rated according to documentation, service/support, training, product reliability, product capabilities, ease of use,…

  19. Effect of Buddhist meditation on serum cortisol and total protein levels, blood pressure, pulse rate, lung volume and reaction time.

    PubMed

    Sudsuang, R; Chentanez, V; Veluvan, K

    1991-09-01

    Serum cortisol and total protein levels, blood pressure, heart rate, lung volume, and reaction time were studied in 52 males 20-25 years of age practicing Dhammakaya Buddhist meditation, and in 30 males of the same age group not practicing meditation. It was found that after meditation, serum cortisol levels were significantly reduced, serum total protein level significantly increased, and systolic pressure, diastolic pressure and pulse rate significantly reduced. Vital capacity, tidal volume and maximal voluntary ventilation were significantly lower after meditation than before. There were also significant decreases in reaction time after mediation practice. The percentage decrease in reaction time during meditation was 22%, while in subjects untrained in meditation, the percentage decrease was only 7%. Results from these studies indicate that practising Dhammakaya Buddhist meditation produces biochemical and physiological changes and reduces the reaction time.

  20. Thermal damage suppression of a black phosphorus saturable absorber for high-power operation of pulsed fiber lasers.

    PubMed

    Lee, Donghyun; Park, Kichul; Debnath, Pulak C; Kim, Inho; Song, Yong-Won

    2016-09-01

    Recent studies of black phosphorus (BP) have shown its future potential in the field of photonics. We determined the optical damage threshold of BP at 21.8 dBm in a fiber ring laser cavity, and demonstrated the high-power operation capacity of an evanescent field interaction-based BP saturable absorber. The long-term stability of a passively mode-locked fiber laser with a saturable absorber operating at the optical power of 23.3 dBm was verified for 168 h without any significant performance degradation. The center wavelength, spectral width, and pulse width of the laser output are 1558.8 nm, 14.2 nm, and 805 fs, respectively. PMID:27479185

  1. Demonstrated 3600 s Integrator Operation with 5.4 μV-s Drift Error for ITER Long Pulse Applications

    NASA Astrophysics Data System (ADS)

    Miller, Kenneth; Ziemba, Timothy; Prager, James; Slobodov, Ilia

    2013-10-01

    Eagle Harbor Technologies has developed a high gain and frequency ultra-stable integrator for small scale concept experiments and long pulse ITER applications. The integrator has a 10 μs RC time with a frequency response greater than 10 MHz. The device has been operated for the 3600 s with a drift error less than 5.4 μV-s, which exceeds the ITER specification. Longer period operation has also been demonstrated (72 hours). Additionally, this integrator has an extremely large dynamic range thereby increasing the effective bit depth of a digitizer. These integrators allow for both the fast and slow magnetic/plasma dynamics to be resolved with a single diagnostic. Software has been written for fast, real-time data acquisition and processing using a field programmable gate array (FPGA). This work is supported by the DOE SBIR/STTR Program.

  2. Thermal damage suppression of a black phosphorus saturable absorber for high-power operation of pulsed fiber lasers

    NASA Astrophysics Data System (ADS)

    Lee, Donghyun; Park, Kichul; Debnath, Pulak C.; Kim, Inho; Song, Yong-Won

    2016-09-01

    Recent studies of black phosphorus (BP) have shown its future potential in the field of photonics. We determined the optical damage threshold of BP at 21.8 dBm in a fiber ring laser cavity, and demonstrated the high-power operation capacity of an evanescent field interaction-based BP saturable absorber. The long-term stability of a passively mode-locked fiber laser with a saturable absorber operating at the optical power of 23.3 dBm was verified for 168 h without any significant performance degradation. The center wavelength, spectral width, and pulse width of the laser output are 1558.8 nm, 14.2 nm, and 805 fs, respectively.

  3. The Effect of Extremely Low Frequency Pulsed Electromagnetic Field on In Vitro Fertilization Success Rate in N MRI Mice

    PubMed Central

    Hafizi, Leili; Sazgarnia, Ameneh; Mousavifar, Nezhat; Karimi, Mohammad; Ghorbani, Saleh; Kazemi, Mohammad Reza; Emami Meibodi, Neda; Hosseini, Golkoo; Mostafavi Toroghi, Hesam

    2014-01-01

    Objective: The effects of exposure to electromagnetic fields (EMF) on reproduction systems have been widely debated. In this study, we aimed to investigate whether low frequency EMF could ameliorate the in vitro fertilization success rate in Naval medical research institute (NMRI) Mice. Materials and Methods: In this randomized comparative animal study, ten NMRI mice were randomly divided into 2 equal groups (control and experimental). 10 IU of human chorionic gonadotropin (hCG) was injected intraperitoneally to both groups in order to stimulate ovulating, and ovums were then aspirated and kept in KSOM (modified version of sequential simplex optimization medium with a higher K+ concentration) culture medium. Metaphase II ovums were separated, and sperms obtained by "swim out" method were added to metaphase II ovums in the culture medium. The experimental group was exposed to 1.3 millitesla pulsed electromagnetic field at 4 kilohertz frequency for 5 hours. To assess the efficacy, we considered the identification of two-pronuclear zygote (2PN) under microscope as fertilizing criterion. Results: Total number of collected ovums in the control and experimental groups was 191 and 173, respectively, from which 58 (30.05%) and 52 (30.36%) ovums were collected from metaphase II, respectively. In vitro fertilization (IVF) success rate was 77% in extremely low frequency- pulsed electromagnetic field (ELFPEMF) for exposed group (experimental), whereas the rate was 68% for control group. Conclusion: Despite increased percentile of IVF success rate in exposed group, there was no statistically significant difference between 2 groups, but this hypothesis has still been stated as a question. Further studies with larger sample sizes and different EMF designs are suggested. PMID:24381855

  4. Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

    NASA Technical Reports Server (NTRS)

    Hallock, A. K.; Martin, A. K.; Polzin, K. A.; Kimberlin, A. C.; Eskridge, R. H.

    2013-01-01

    Impulse bits produced by conical theta-pinch inductive pulsed plasma thrusters possessing cone angles of 20deg, 38deg, and 60deg, were quantified for 500J/pulse operation by direct measurement using a hanging-pendulum thrust stand. All three cone angles were tested in single-pulse mode, with the 38deg model producing the highest impulse bits at roughly 1 mN-s operating on both argon and xenon propellants. A capacitor charging system, assembled to support repetitively-pulsed thruster operation, permitted testing of the 38deg thruster at a repetition-rate of 5 Hz at power levels of 0.9, 1.6, and 2.5 kW. The average thrust measured during multiple-pulse operation exceeded the value obtained when the single-pulse impulse bit is multiplied by the repetition rate.

  5. Open-source hardware and software and web application for gamma dose rate network operation.

    PubMed

    Luff, R; Zähringer, M; Harms, W; Bleher, M; Prommer, B; Stöhlker, U

    2014-08-01

    The German Federal Office for Radiation Protection operates a network of about 1800 gamma dose rate stations as a part of the national emergency preparedness plan. Each of the six network centres is capable of operating the network alone. Most of the used hardware and software have been developed in-house under open-source license. Short development cycles and close cooperation between developers and users ensure robustness, transparency and fast maintenance procedures, thus avoiding unnecessary complex solutions. This also reduces the overall costs of the network operation. An easy-to-expand web interface has been developed to make the complete system available to other interested network operators in order to increase cooperation between different countries. The interface is also regularly in use for education during scholarships of trainees supported, e.g. by the 'International Atomic Energy Agency' to operate a local area dose rate monitoring test network.

  6. SU-E-T-34: An in Vivo Study On Pulsed Low Dose-Rate Radiotherapy for Prostate Cancer

    SciTech Connect

    Wang, B; Cvetkovic, D; Chen, L; Ma, C; Chen, X; Zhang, P; Zhang, C

    2014-06-01

    Purpose: Re-irradiation with conventional radiotherapy techniques (CRT) may pose significant risks due to high accumulative radiation doses. Pulsed low dose-rate radiotherapy (PLDR) has been used in clinical trials for recurrent cancer treatment. In our previous studies, PLDR irradiation showed significantly lower toxicity than CRT, resulting in much longer survival of mice after PLDR total body irradiation (TBI) than conventional TBI. The purpose of this study was to investigate tumor control efficacy of PLDR treatment for prostate cancer with an animal model of prostate cancer LNCaP. Methods: We used an orthotopic murine model of LNCaP cell line for this study. LNCaP cells were implanted into immune-suppressed male nude mice via surgery. We monitored the tumor growth with MRI. The tumor-bearing mice were allocated into a PLDR(n=9), CRT(n=7), and control group(n=7) randomly. The mice in the PLDR and CRT groups were irradiated with 2Gy dose for one time. For the CRT treatment, the mice received 2Gy at a dose-rate of 300 MU/minute. For the PLDR treatment, the 2Gy dose was further divided into ten pulses of 0.2Gy at the same dose-rate with an interval of 3 minutes between the pulses. Results: Sizable tumor growth delays were observed for the PLDR and CRT groups through weekly MRI scans. The mean values of the normalized tumor volumes (± standard deviation of the mean) were 1.53±0.07, 1.53±0.14, and 1.81±0.09 at one week after treatment, 2.28±0.13, 2.19±0.16, and 3.04±0.25 at two weeks after treatment, and 3.31±0.23, 3.14±0.24 and 4.62±0.49 at three weeks after treatment, for the PLDR, CRT, and control groups, respectively. Conclusion: The PLDR and CRT treatments showed comparable tumor control rates in this study. Our in vivo results indicate that PLDR may be a viable option for treating recurrent prostate cancer due to its equivalent tumor control but low normal tissue toxocities.

  7. Spectral broadening measurement of the lower hybrid waves during long pulse operation in Tore Supra

    SciTech Connect

    Berger-By, G.; Decampy, J.; Goniche, M.; Ekedahl, A.; Delpech, L.; Leroux, F.; Antar, G. Y.; Collaboration: Tore Supra Team

    2014-02-12

    On many tokamaks (C-Mod, EAST, FTU, JET, HT-7, TS), a decrease in current drive efficiency of the Lower Hybrid (LH) waves is observed in high electron density plasmas. The cause of this behaviour is believed to be: Parametric Instabilities (PI) and Scattering from Density Fluctuations (SDF). For the ITER LH system, our knowledge must be improved to avoid such effects and to maintain the LH current drive efficiency at high density. The ITPA IOS group coordinates this effort [1] and all experimental data are essential to validate the numerical codes in progress. Usually the broadening of the LH wave frequency spectrum is measured by a probe located in the plasma edge. For this study, the frequency spectrum of a reflected power signal from the LH antenna was used. In addition, the spectrum measurements are compared with the density fluctuations observed on RF probes located at the antenna mouth. Several plasma currents (0.6 to 1.4 MA) and densities up to 5.2 × 10{sup 19} m−3 have been realised on Tore Supra (TS) long pulses and with high injected RF power, up to 5.4 MW-30s. This allowed using a spectrum analyser to make several measurements during the plasma pulse. The side lobe amplitude, shifted by 20-30MHz with respect to the main peak, grows with increasing density. Furthermore, for an increase of plasma current at the same density, the spectra broaden and become asymmetric. Some parametric dependencies are shown in this paper.

  8. 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.

  9. 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.

  10. Opportunities in pulse combustion

    SciTech Connect

    Brenchley, D.L.; Bomelburg, H.J.

    1985-10-01

    In most pulse combustors, the combustion occurs near the closed end of a tube where inlet valves operate in phase with the pressure amplitude variations. Thus, within the combustion zone, both the temperature and the pressure oscillate around a mean value. However, the development of practical applications of pulse combustion has been hampered because effective design requires the right combination of the combustor's dimensions, valve characteristics, fuel/oxidizer combination, and flow pattern. Pulse combustion has several additional advantages for energy conversion efficiency, including high combustion and thermal efficiency, high combustion intensity, and high convective heat transfer rates. Also, pulse combustion can be self-aspirating, generating a pressure boost without using a blower. This allows the use of a compact heat exchanger that may include a condensing section and may obviate the need for a chimney. In the last decade, these features have revived interest in pulse combustion research and development, which has resulted in the development of a pulse combustion air heater by Lennox, and a pulse combustion hydronic unit by Hydrotherm, Inc. To appraise this potential for energy savings, a systematic study was conducted of the many past and present attempts to use pulse combustion for practical purposes. The authors recommended areas where pulse combustion technology could possibly be applied in the future and identified areas in which additional R and D would be necessary. Many of the results of the study project derived from a special workshop on pulse combustion. This document highlights the main points of the study report, with particular emphasis on pulse combustion application in chemical engineering.

  11. Coiled transmission line pulse generators

    DOEpatents

    McDonald, Kenneth Fox

    2010-11-09

    Methods and apparatus are provided for fabricating and constructing solid dielectric "Coiled Transmission Line" pulse generators in radial or axial coiled geometries. The pour and cure fabrication process enables a wide variety of geometries and form factors. The volume between the conductors is filled with liquid blends of monomers, polymers, oligomers, and/or cross-linkers and dielectric powders; and then cured to form high field strength and high dielectric constant solid dielectric transmission lines that intrinsically produce ideal rectangular high voltage pulses when charged and switched into matched impedance loads. Voltage levels may be increased by Marx and/or Blumlein principles incorporating spark gap or, preferentially, solid state switches (such as optically triggered thyristors) which produce reliable, high repetition rate operation. Moreover, these Marxed pulse generators can be DC charged and do not require additional pulse forming circuitry, pulse forming lines, transformers, or an a high voltage spark gap output switch. The apparatus accommodates a wide range of voltages, impedances, pulse durations, pulse repetition rates, and duty cycles. The resulting mobile or flight platform friendly cylindrical geometric configuration is much more compact, light-weight, and robust than conventional linear geometries, or pulse generators constructed from conventional components. Installing additional circuitry may accommodate optional pulse shape improvements. The Coiled Transmission Lines can also be connected in parallel to decrease the impedance, or in series to increase the pulse length.

  12. Nested radiations and the pulse of angiosperm diversification: increased diversification rates often follow whole genome duplications.

    PubMed

    Tank, David C; Eastman, Jonathan M; Pennell, Matthew W; Soltis, Pamela S; Soltis, Douglas E; Hinchliff, Cody E; Brown, Joseph W; Sessa, Emily B; Harmon, Luke J

    2015-07-01

    Our growing understanding of the plant tree of life provides a novel opportunity to uncover the major drivers of angiosperm diversity. Using a time-calibrated phylogeny, we characterized hot and cold spots of lineage diversification across the angiosperm tree of life by modeling evolutionary diversification using stepwise AIC (MEDUSA). We also tested the whole-genome duplication (WGD) radiation lag-time model, which postulates that increases in diversification tend to lag behind established WGD events. Diversification rates have been incredibly heterogeneous throughout the evolutionary history of angiosperms and reveal a pattern of 'nested radiations' - increases in net diversification nested within other radiations. This pattern in turn generates a negative relationship between clade age and diversity across both families and orders. We suggest that stochastically changing diversification rates across the phylogeny explain these patterns. Finally, we demonstrate significant statistical support for the WGD radiation lag-time model. Across angiosperms, nested shifts in diversification led to an overall increasing rate of net diversification and declining relative extinction rates through time. These diversification shifts are only rarely perfectly associated with WGD events, but commonly follow them after a lag period.

  13. Laser ablation efficiency during the production of Ag nanoparticles in ethanol at a low pulse repetition rate (1-10 Hz)

    NASA Astrophysics Data System (ADS)

    Valverde-Alva, M. A.; García-Fernández, T.; Esparza-Alegría, E.; Villagrán-Muniz, M.; Sánchez-Aké, C.; Castañeda-Guzmán, R.; de la Mora, M. B.; Márquez-Herrera, C. E.; Sánchez Llamazares, J. L.

    2016-10-01

    We studied the effect of the repetition rate of laser pulses (RRLP) in the range from 1-10 Hz in the production of silver nanoparticles (Ag-NPs) by laser ablation in ethanol. Laser pulses with a duration of 7 ns, a wavelength of 1064 nm and an energy of 60 mJ were used to ablate a 99.99% pure silver target immersed in 10 ml of ethanol. Transmittance analysis and atomic absorption spectroscopy were used to study the silver concentration in the colloidal solutions. The ablation process was studied by measuring the transmission of the laser pulses through the colloid. It is shown that for a fixed number of laser pulses (NLP) the ablation efficiency, in terms of the ablated silver mass per laser pulse, increases with the RRLP. This result contradicts what had previously been established in the literature.

  14. Nitrogen and phosphorus uptake rates of different species from a coral reef community after a nutrient pulse

    NASA Astrophysics Data System (ADS)

    den Haan, Joost; Huisman, Jef; Brocke, Hannah J.; Goehlich, Henry; Latijnhouwers, Kelly R. W.; van Heeringen, Seth; Honcoop, Saskia A. S.; Bleyenberg, Tanja E.; Schouten, Stefan; Cerli, Chiara; Hoitinga, Leo; Vermeij, Mark J. A.; Visser, Petra M.

    2016-06-01

    Terrestrial runoff after heavy rainfall can increase nutrient concentrations in waters overlying coral reefs that otherwise experience low nutrient levels. Field measurements during a runoff event showed a sharp increase in nitrate (75-fold), phosphate (31-fold) and ammonium concentrations (3-fold) in waters overlying a fringing reef at the island of Curaçao (Southern Caribbean). To understand how benthic reef organisms make use of such nutrient pulses, we determined ammonium, nitrate and phosphate uptake rates for one abundant coral species, turf algae, six macroalgal and two benthic cyanobacterial species in a series of laboratory experiments. Nutrient uptake rates differed among benthic functional groups. The filamentous macroalga Cladophora spp., turf algae and the benthic cyanobacterium Lyngbya majuscula had the highest uptake rates per unit biomass, whereas the coral Madracis mirabilis had the lowest. Combining nutrient uptake rates with the standing biomass of each functional group on the reef, we estimated that the ammonium and phosphate delivered during runoff events is mostly taken up by turf algae and the two macroalgae Lobophora variegata and Dictyota pulchella. Our results support the often proposed, but rarely tested, assumption that turf algae and opportunistic macroalgae primarily benefit from episodic inputs of nutrients to coral reefs.

  15. Nitrogen and phosphorus uptake rates of different species from a coral reef community after a nutrient pulse.

    PubMed

    den Haan, Joost; Huisman, Jef; Brocke, Hannah J; Goehlich, Henry; Latijnhouwers, Kelly R W; van Heeringen, Seth; Honcoop, Saskia A S; Bleyenberg, Tanja E; Schouten, Stefan; Cerli, Chiara; Hoitinga, Leo; Vermeij, Mark J A; Visser, Petra M

    2016-01-01

    Terrestrial runoff after heavy rainfall can increase nutrient concentrations in waters overlying coral reefs that otherwise experience low nutrient levels. Field measurements during a runoff event showed a sharp increase in nitrate (75-fold), phosphate (31-fold) and ammonium concentrations (3-fold) in waters overlying a fringing reef at the island of Curaçao (Southern Caribbean). To understand how benthic reef organisms make use of such nutrient pulses, we determined ammonium, nitrate and phosphate uptake rates for one abundant coral species, turf algae, six macroalgal and two benthic cyanobacterial species in a series of laboratory experiments. Nutrient uptake rates differed among benthic functional groups. The filamentous macroalga Cladophora spp., turf algae and the benthic cyanobacterium Lyngbya majuscula had the highest uptake rates per unit biomass, whereas the coral Madracis mirabilis had the lowest. Combining nutrient uptake rates with the standing biomass of each functional group on the reef, we estimated that the ammonium and phosphate delivered during runoff events is mostly taken up by turf algae and the two macroalgae Lobophora variegata and Dictyota pulchella. Our results support the often proposed, but rarely tested, assumption that turf algae and opportunistic macroalgae primarily benefit from episodic inputs of nutrients to coral reefs. PMID:27353576

  16. Nitrogen and phosphorus uptake rates of different species from a coral reef community after a nutrient pulse

    PubMed Central

    den Haan, Joost; Huisman, Jef; Brocke, Hannah J.; Goehlich, Henry; Latijnhouwers, Kelly R. W.; van Heeringen, Seth; Honcoop, Saskia A. S.; Bleyenberg, Tanja E.; Schouten, Stefan; Cerli, Chiara; Hoitinga, Leo; Vermeij, Mark J. A.; Visser, Petra M.

    2016-01-01

    Terrestrial runoff after heavy rainfall can increase nutrient concentrations in waters overlying coral reefs that otherwise experience low nutrient levels. Field measurements during a runoff event showed a sharp increase in nitrate (75-fold), phosphate (31-fold) and ammonium concentrations (3-fold) in waters overlying a fringing reef at the island of Curaçao (Southern Caribbean). To understand how benthic reef organisms make use of such nutrient pulses, we determined ammonium, nitrate and phosphate uptake rates for one abundant coral species, turf algae, six macroalgal and two benthic cyanobacterial species in a series of laboratory experiments. Nutrient uptake rates differed among benthic functional groups. The filamentous macroalga Cladophora spp., turf algae and the benthic cyanobacterium Lyngbya majuscula had the highest uptake rates per unit biomass, whereas the coral Madracis mirabilis had the lowest. Combining nutrient uptake rates with the standing biomass of each functional group on the reef, we estimated that the ammonium and phosphate delivered during runoff events is mostly taken up by turf algae and the two macroalgae Lobophora variegata and Dictyota pulchella. Our results support the often proposed, but rarely tested, assumption that turf algae and opportunistic macroalgae primarily benefit from episodic inputs of nutrients to coral reefs. PMID:27353576

  17. Comparison of two high-repetition-rate pulsed CO/sub 2/ laser discharge geometries

    SciTech Connect

    Faszer, W.; Tulip, J.; Seguin, H.

    1980-11-01

    Two discharge geometries are commonly used for pumping high-repetition-rate transversely excited atmosphere (TEA) lasers. One uses solid electrodes with preionization provided by downstream spark pins. The other uses a solid electrode and a screen electrode with preionization provided by an auxiliary discharge behind the screen. In this study the performance of the two systems was compared. The repetition rate at which arcing occurs was found to increase linearly with flow velocity but decrease with increasing energy density. It was also dependent on system geometry and the spark pin preionized system performed better than the auxiliary discharge preionized system. Data are given for discharges in N/sub 2/, CO/sub 2/, He, and a CO/sub 2/ laser mixture.

  18. Operating modes of a hydrogen ion source based on a hollow-cathode pulsed Penning discharge.

    PubMed

    Oks, E M; Shandrikov, M V; Vizir, A V

    2016-02-01

    An ion source based on a hollow-cathode Penning discharge was switched to a high-current pulsed mode (tens of amperes and tens of microseconds) to produce an intense hydrogen ion beam. With molecular hydrogen (H2), the ion beam contained three species: H(+), H2(+), and H3(+). For all experimental conditions, the fraction of H2 (+) ions in the beam was about 10 ÷ 15% of the total ion beam current and varied little with ion source parameters. At the same time, the ratio of H(+) and H3(+) depended strongly on the discharge current, particularly on its distribution in the gap between the hollow and planar cathodes. Increasing the discharge current increased the H(+) fraction in ion beam. The maximum fraction of H(+) reached 80% of the total ion beam current. Forced redistribution of the discharge current in the cathode gap for increasing the hollow cathode current could greatly increase the H3(+) fraction in the beam. At optimum parameters, the fraction of H3(+) ions reached 60% of the total ion beam current.

  19. Influence of operating parameters on cake formation in pilot scale pulse-jet bag filter

    PubMed Central

    Saleem, Mahmood; Krammer, Gernot; Khan, Rafi Ullah; Tahir, M. Suleman

    2012-01-01

    Bag filters are commonly used for fine particles removal in off-gas purification. There dust laden gas pervades through permeable filter media starting at a lower pressure drop limit leaving dust (called filter cake) on the filter media. The filter cakeformation is influenced by many factors including filtration velocity, dust concentration, pressure drop limits, and filter media resistance. Effect of the stated parameters is investigated experimentally in a pilot scale pulse-jet bag filter test facility where lime stone dust is separated from air at ambient conditions. Results reveal that filtration velocity significantly affects filter pressure drop as well as cake properties; cake density and specific cake resistance. Cake density is slightly affected by dust concentration. Specific resistance of filter cake increases with velocity, slightly affected by dust concentration, changes inversely with the upper pressure drop limit and decreases over a prolonged use (aging). Specific resistance of filter media is independent of upper pressure drop limit and increases linearly over a prolonged use. PMID:24415802

  20. A single-stage GM-type pulse tube cryocooler operating at 10.6 K

    NASA Astrophysics Data System (ADS)

    Gan, Z. H.; Dong, W. Q.; Qiu, L. M.; Zhang, X. B.; Sun, H.; He, Y. L.; Radebaugh, R.

    2009-05-01

    In order to explore the lowest attainable refrigeration temperature and improve cooling performance at temperatures around 20 K for a single-stage G-M type pulse tube cryocooler (PTC), numerical and experimental studies were performed. The National Institute of Standards and Technology (NIST) numerical model known as REGEN was applied to the simulation of a G-M type PTC for the first time. Based on the calculation results, a single-stage G-M type PTC was designed, fabricated and tested. The performance improvement of the regenerator in the temperature range of 10-80 K was investigated. The calculations predicted a lowest temperature of 10 K. A lowest temperature of 10.6 K was achieved experimentally with an input power of 7.5 kW, which is the lowest temperature ever achieved by a single-stage PTC. Further more, the cryocooler can provide a cooling power of 20 W at 20.6 K and 39.5 W at 30 K, respectively.

  1. Operating modes of a hydrogen ion source based on a hollow-cathode pulsed Penning discharge

    NASA Astrophysics Data System (ADS)

    Oks, E. M.; Shandrikov, M. V.; Vizir, A. V.

    2016-02-01

    An ion source based on a hollow-cathode Penning discharge was switched to a high-current pulsed mode (tens of amperes and tens of microseconds) to produce an intense hydrogen ion beam. With molecular hydrogen (H2), the ion beam contained three species: H+, H2+, and H3+. For all experimental conditions, the fraction of H2+ ions in the beam was about 10 ÷ 15% of the total ion beam current and varied little with ion source parameters. At the same time, the ratio of H+ and H3+ depended strongly on the discharge current, particularly on its distribution in the gap between the hollow and planar cathodes. Increasing the discharge current increased the H+ fraction in ion beam. The maximum fraction of H+ reached 80% of the total ion beam current. Forced redistribution of the discharge current in the cathode gap for increasing the hollow cathode current could greatly increase the H3+ fraction in the beam. At optimum parameters, the fraction of H3+ ions reached 60% of the total ion beam current.

  2. Influence of operating parameters on cake formation in pilot scale pulse-jet bag filter.

    PubMed

    Saleem, Mahmood; Krammer, Gernot; Khan, Rafi Ullah; Tahir, M Suleman

    2012-07-01

    Bag filters are commonly used for fine particles removal in off-gas purification. There dust laden gas pervades through permeable filter media starting at a lower pressure drop limit leaving dust (called filter cake) on the filter media. The filter cakeformation is influenced by many factors including filtration velocity, dust concentration, pressure drop limits, and filter media resistance. Effect of the stated parameters is investigated experimentally in a pilot scale pulse-jet bag filter test facility where lime stone dust is separated from air at ambient conditions. Results reveal that filtration velocity significantly affects filter pressure drop as well as cake properties; cake density and specific cake resistance. Cake density is slightly affected by dust concentration. Specific resistance of filter cake increases with velocity, slightly affected by dust concentration, changes inversely with the upper pressure drop limit and decreases over a prolonged use (aging). Specific resistance of filter media is independent of upper pressure drop limit and increases linearly over a prolonged use.

  3. Open path atmospheric spectroscopy using room temperature operated pulsed quantum cascade laser.

    PubMed

    Taslakov, M; Simeonov, V; van den Bergh, H

    2006-04-01

    We report the application of a distributed feedback quantum cascade laser for 5.8 km long open path spectroscopic monitoring of ozone, water vapor and CO(2). The thermal chirp during a 140 or 200 ns long excitation pulse is used for fast wavelength scanning. The fast wavelength scanning has the advantage of the measured spectra not being affected by atmospheric turbulence, which is essential for long open path measurements. An almost linear tuning of about 0.6 and 1.2 cm(-1) is achieved, respectively. Lines from the nu(3) vibrational band of the ozone spectra centered at 1,031 and 1,049 cm(-1) is used for ozone detection by differential absorption. The lowest column densities (LCD) for ozone of the order of 0.3 ppmm retrieved from the absorption spectra for averaging times less than 20s are better then the LCD value of 2 ppmm measured with UV DOAS systems. The intrinsic haze immunity of mid-IR laser sources is an additional important advantage of mid-IR open path spectroscopy, compared with standard UV-vis DOAS. The third major advantage of the method is the possibility to measure more inorganic and organic atmospheric species compared to the UV-vis DOAS.

  4. Non-contact dual pulse Doppler system based respiratory and heart rates estimation for CHF patients.

    PubMed

    Tran, Vinh Phuc; Ali Al-Jumaily, Adel

    2015-01-01

    Long term continuous patient monitoring is required in many health systems for monitoring and analytical diagnosing purposes. Most of monitoring systems had shortcomings related to their functionality or patient comfortably. Non-contact continuous monitoring systems have been developed to address some of these shortcomings. One of such systems is non-contact physiological vital signs assessments for chronic heart failure (CHF) patients. This paper presents a novel automated estimation algorithm for the non-contact physiological vital signs assessments for CHF patients based on a patented novel non-contact biomotion sensor. A database consists of twenty CHF patients with New York Heart Association (NYHA) heart failure Classification Class II & III, whose underwent full Polysomnography (PSG) analysis for the diagnosis of sleep apnea, disordered sleep, or both, were selected for the study. The patients mean age is 68.89 years, with mean body weight of 86.87 kg, mean BMI of 28.83 (obesity) and mean recorded sleep duration of 7.78 hours. The propose algorithm analyze the non-contact biomotion signals and estimate the patients' respiratory and heart rates. The outputs of the algorithm are compared with gold-standard PSG recordings. Across all twenty patients' recordings, the respiratory rate estimation median accuracy achieved 92.4689% with median error of ± 1.2398 breaths per minute. The heart rate estimation median accuracy achieved 88.0654% with median error of ± 7.9338 beats per minute. Due to the good performance of the propose novel automated estimation algorithm, the patented novel non-contact biomotion sensor can be an excellent tool for long term continuous sleep monitoring for CHF patients in the home environment in an ultra-convenient fashion. PMID:26737221

  5. Hairpin resonator probes with frequency domain boxcar operation for time resolved density measurements in pulsed RF discharges

    NASA Astrophysics Data System (ADS)

    Peterson, David; Kummerer, Theresa; Coumou, David; Shannon, Steven

    2014-10-01

    In this work, microsecond time resolved electron density measurements in pulsed RF discharges are shown using an automated hairpin resonance probe using relatively low cost electronics, on par with normal Langmuir probe boxcar mode operation. A low cost signal generator is used to produce the applied microwave frequency and the reflected waveform is filtered to remove the RF component. The signal is then heterodyned with a simple frequency mixer to produce a dc signal read by an oscilloscope to determine the electron density. The applied microwave frequency is automatically shifted in small increments in a frequency boxcar routine through a Labview™program to determine the resonant frequency. A simple dc sheath correction is then easily applied since the probe is fully floating, producing low cost, high fidelity, and highly reproducible electron density measurements. The measurements are made in a capacitively coupled, parallel plate configuration in a 13.56 MHz, 50--200 W RF discharge pulsed at 500 Hz, 200 W, 50% duty cycle. The gas input ranged from 50--100 mTorr pure Ar or with 5--10% O/He mixtures.

  6. Pulsed and continuous-wave laser operation of TGT-grown Nd,Y-codoped :SrF2 single crystal

    NASA Astrophysics Data System (ADS)

    Jelínek, Michal; Kubeček, Václav; Su, Liangbi; Jiang, Dapeng; Ma, Fengkai; Zhang, Qian; Cao, Yuexin; Xu, Jun

    2014-05-01

    In this letter we present laser properties of temperature gradient technique (TGT) grown Nd,Y : SrF2 crystals with Nd3+ concentrations of 0.4, 0.65 and 0.8 at% and Y3+ concentration of 10 at%. The noncoated crystal samples, 3.1 or 5 mm long, were pumped by the 796 nm laser diode matching the Nd,Y : SrF2 absorption peak. In the pulsed pumping regime (pulse-duration 2 ms, frequency 10 Hz), maximum average output power of 75 mW (corresponding to peak power of 3.75 W) was obtained with slope efficiency as high as 51% and optical-to-optical efficiency of 42% with respect to the absorbed pump power. The output beam spatial profile was nearly Gaussian in both axes, oscillations started at the wavelength of 1057 nm. At higher pumping levels, the second emission line at 1051 nm appears corresponding to our fluorescence measurements. Wavelength tuning using a birefringent filter from 1048 to 1070 nm is probably given by the crystal-field splitting of the 4F3/2 manifold in Nd3+. True-continuous-wave laser operation was also successfully obtained at lower pumping levels with maximum output power of 380 mW and slope efficiency of 28% at the wavelength of 1057 nm.

  7. Magneto-impedance sensor for quasi-noncontact monitoring of breathing, pulse rate and activity status

    NASA Astrophysics Data System (ADS)

    Corodeanu, S.; Chiriac, H.; Radulescu, L.; Lupu, N.

    2014-05-01

    Results on the development and testing of a novel magnetic sensor based on the detection of the magneto-impedance variation due to changes in the permeability of an amorphous wire are reported. The proposed application is the quasi-noncontact monitoring of the breathing frequency and heart rate for diagnosing sleep disorders. Patient discomfort is significantly decreased by transversally placing the sensitive element onto the surface of a flexible mattress in order to detect its deformation associated with cardiorespiratory activity and body movements. The developed sensor has a great application potential in monitoring the vital signs during sleep, with special advantages for children sleep monitoring.

  8. Safety training and safe operating procedures written for PBFA (Particle Beam Fusion Accelerator) II and applicable to other pulsed power facilities

    SciTech Connect

    Donovan, G.L.; Goldstein, S.A.

    1986-12-01

    To ensure that work in advancing pulsed power technology is performed with an acceptably low risk, pulsed power research facilities at Sandia National Laboratories must satisfy general safety guidelines established by the Department of Energy, policies and formats of the Environment, Safety, and Health (ES and H) Department, and detailed procedures formulated by the Pulsed Power Sciences Directorate. The approach to safety training and to writing safe operating procedures, and the procedures presented here are specific to the Particle Beam Fusion Accelerator II (PBFA II) Facility but are applicable as guidelines to other research and development facilities which have similar hazards.

  9. The effects of perceiving color in living environment on QEEG, oxygen saturation, pulse rate, and emotion regulation in humans.

    PubMed

    Sroykham, Watchara; Wongsathikun, J; Wongsawat, Y

    2014-01-01

    Light and color have been shown to have substantial physical, psychological and sociological effects on humans. Hence, an investigation on the effect of changes in light and color to the biological signals is a challenging problem. Five participants were measured the oxygen saturation (SpO2), pulse rate, and quantitative electroencephalogram (QEEG) in six colors (white, blue, green, yellow, red and black) of living environment for 5 minutes per color. Then all participants were asked to answer the emotional questionnaire of BRUMS and color performance for each color environment. The results showed brain activity of high beta wave (25-30 Hz) that associated with alertness, agitation, mental activity, and general activation of mind and body functions (at frontal lobes and temporal lobes) in red and yellow colored rooms were higher than blue, green, white and black colored rooms, respectively. It also had the relationship with the psychological effect (BRUMS). The amplitude asymmetry of beta wave (12-25 Hz) was highly attenuated in warm color (red and yellow colored rooms), moderately attenuated in cool color (green and blue colored room) and little attenuated in white and black colored rooms. The BRUMS showed that red and yellow yielded significant effect on anger (F = 4.966, p = 0.002) and confusion (F=3.853, p=0.008). Red and green color yielded high effect on vigor. Green color did not affect the depression. Blue color yielded moderate effect on confusion, tension and fatigue. White and black colors yielded low effect on any mood, but black color had no effect on vigor. In addition, we cannot observe any significant changes of pulse rate and blood oxygen saturation in each color. The results can possibly be used as the recommendation to design the room for either normal people or patients. PMID:25571419

  10. The ethanol sensing characteristics of ZnO thin films with low operating temperatures synthesized by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Zheng, Xuejun; Zhong, Xiangli; Deng, Shuifeng

    2012-10-01

    ZnO thin films (ZTFs) are deposited on Si (1 1 1) substrates by a pulsed laser deposition (PLD) method and characterized by x-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The ethanol sensing properties of ZTFs are investigated by exposing them to different concentrations of gaseous ethanol at various temperatures. At an operating temperature of 120 °C, the ZTFs have a high response value to 5 ppm gaseous ethanol, and the detection limit can be as low as 0.1 ppm. The corresponding response and recovery times are 20 and 15 s, respectively. The results indicate that ZTFs synthesized by PLD have potential applications for fabricating high performance ethanol sensors.

  11. Influence of cloth structure on operational characteristics of pulse-jet cleaned filter bags

    SciTech Connect

    Hindy, K.T.; Sievert, J.; Loeffler, F.

    1987-01-01

    An investigation on the effect of the surface properties and the cloth structure of a filter medium on the operation of a filter bag was conducted using a pilot-scale testing device. The collection properties and the increase in the residual drop, as well as the mass of the residual dust embedded within the filter medium, were measured. Three filter media were investigated: a singed filter medium, a calendered filter medium, and one with a membrane-laminated surface. The experimental results obtained show that the operational characteristics of a filter bag is greatly influenced by the surface properties and the cloth structure of the filter medium. The calendered filter bag has an unfavorable operational quality concerning both the collection properties and the residual pressure drop. The hard thickening of the filter medium drives to the rapid clogging of the filter bag. In contrast, the other two filter media have favorable characteristics concerning the above two criteria. At the same time, it was found that after tests conducted for about 70 h each, the singed filter bag, compared with the membrane-laminated one, exhibits a lower residual pressure drop, although more particles are deposited inside. The lowest filtration cycle duration was recorded by the calendered medium, whereas the cleaning frequency by the other two media was nearly in the same range.

  12. Keeping a finger on the pulse: Cardiovascular disease rate as a measure of sustainable development.

    PubMed

    Hasan, Nazeeha

    2013-01-01

    Non-communicable diseases have been somewhat neglected as a public health issue in the past, but there is now growing international consensus that they present a significant obstacle to economic development for both high- and low-income countries. Cardiovascular disease accounts for more than half of all non-communicable disease deaths, and presents a promising target for curbing the non-communicable disease epidemic. This article explains the pressing need for non-communicable disease prevention, focusing on strategies that can be employed to decrease cardiovascular disease risk at an individual and population level, and outlines the UK's approaches to cardiovascular disease prevention in particular. Given the mounting burden of non-communicable diseases, responsible health governance and a balanced economic policy could consider the use of low cardiovascular disease rates as a measure of positive and sustainable economic development.

  13. Scattering-type scanning near-field optical microscopy with low-repetition-rate pulsed light source through phase-domain sampling

    NASA Astrophysics Data System (ADS)

    Wang, Haomin; Wang, Le; Xu, Xiaoji G.

    2016-10-01

    Scattering-type scanning near-field optical microscopy (s-SNOM) allows spectroscopic imaging with spatial resolution below the diffraction limit. With suitable light sources, s-SNOM is instrumental in numerous discoveries at the nanoscale. So far, the light sources have been limited to continuous wave or high-repetition-rate pulsed lasers. Low-repetition-rate pulsed sources cannot be used, due to the limitation of the lock-in detection mechanism that is required for current s-SNOM techniques. Here, we report a near-field signal extraction method that enables low-repetition-rate pulsed light sources. The method correlates scattering signals from pulses with the mechanical phases of the oscillating s-SNOM probe to obtain near-field signal, by-passing the apparent restriction imposed by the Nyquist-Shannon sampling theorem on the repetition rate. The method shall enable s-SNOM with low-repetition-rate pulses with high-peak-powers, such as femtosecond laser amplifiers, to facilitate investigations of strong light-matter interactions and nonlinear processes at the nanoscale.

  14. Scattering-type scanning near-field optical microscopy with low-repetition-rate pulsed light source through phase-domain sampling

    PubMed Central

    Wang, Haomin; Wang, Le; Xu, Xiaoji G.

    2016-01-01

    Scattering-type scanning near-field optical microscopy (s-SNOM) allows spectroscopic imaging with spatial resolution below the diffraction limit. With suitable light sources, s-SNOM is instrumental in numerous discoveries at the nanoscale. So far, the light sources have been limited to continuous wave or high-repetition-rate pulsed lasers. Low-repetition-rate pulsed sources cannot be used, due to the limitation of the lock-in detection mechanism that is required for current s-SNOM techniques. Here, we report a near-field signal extraction method that enables low-repetition-rate pulsed light sources. The method correlates scattering signals from pulses with the mechanical phases of the oscillating s-SNOM probe to obtain near-field signal, by-passing the apparent restriction imposed by the Nyquist–Shannon sampling theorem on the repetition rate. The method shall enable s-SNOM with low-repetition-rate pulses with high-peak-powers, such as femtosecond laser amplifiers, to facilitate investigations of strong light–matter interactions and nonlinear processes at the nanoscale. PMID:27748360

  15. System design and operation of a 100 kilovolt, 2 kilohertz pulse modulator for plasma source ion implantation

    SciTech Connect

    Reass, W.A.

    1994-07-01

    This paper describes the electrical design and operation of a high power modulator system implemented for the Los Alamos Plasma Source Ion Implantation (PSII) facility. To test the viability of the PSII process for various automotive components, the modulator must accept wide variations of load impedance. Components have varying area and composition which must be processed with different plasmas. Additionally, the load impedance may change by large factors during the typical 20 uS pulse, due to plasma displacement currents and sheath growth. As a preliminary design to test the system viability for automotive component implantation, suitable for a manufacturing environment, circuit topology must be able to directly scale to high power versions, for increased component through-put. We have chosen an evolutionary design approach with component families of characterized performance, which should Ion result in a reliable modulator system with component lifetimes. The modulator utilizes a pair of Litton L-3408 hollow beam amplifier tubes as switching elements in a ``hot-deck`` configuration. Internal to the main of planar triode hot deck, an additional pair decks, configured in a totem pole circuit, provide input drive to the L-3408 mod-anodes. The modulator can output over 2 amps average current (at 100 kV) with 1 kW of modanode drive. Diagnostic electronics monitor the load and stops pulses for 100 mS when a load arcs occur. This paper, in addition to providing detailed engineering design information, will provide operational characteristics and reliability data that direct the design to the higher power, mass production line capable modulators.

  16. System design and operation of a 100 kilovolt, 2 kilohertz pulse modulator for plasma source ion implantation

    NASA Astrophysics Data System (ADS)

    Reass, W. A.

    This paper describes the electrical design and operation of a high power modulator system implemented for the Los Alamos Plasma Source Ion Implantation (PSII) facility. To test the viability of the PSII process for various automotive components, the modulator must accept wide variations of load impedance. Components have varying area and composition which must be processed with different plasmas. Additionally, the load impedance may change by large factors during the typical 20 uS pulse, due to plasma displacement currents and sheath growth. As a preliminary design to test the system viability for automotive component implantation, suitable for a manufacturing environment, circuit topology must be able to directly scale to high power versions, for increased component through-put. We have chosen an evolutionary design approach with component families of characterized performance, which should result in a reliable modulator system with component lifetimes. The modulator utilizes a pair of Litton L-3408 hollow beam amplifier tubes as switching elements in a 'hot-deck' configuration. Internal to the main of planar triode hot deck, an additional pair decks, configured in a totem pole circuit, provide input drive to the L-3408 mod-anodes. The modulator can output over 2 amps average current (at 100 kV) with 1 kW of modanode drive. Diagnostic electronics monitor the load and stops pulses for 100 mS when a load arcs occur. This paper, in addition to providing detailed engineering design information, will provide operational characteristics and reliability data that direct the design to the higher power, mass production line capable modulators.

  17. A high repetition rate TEA CO II laser operating at λ=9.3-μm for the rapid and conservative ablation and modification of dental hard tissues

    NASA Astrophysics Data System (ADS)

    Fan, Kenneth; Fried, Daniel

    2006-02-01

    TEA CO II lasers tuned to the strong mineral absorption of hydroxyapatite near λ=9-μm are ideally suited for the efficient ablation of dental hard tissues if the laser-pulse is stretched to greater than 5-10-μs to avoid plasma shielding phenomena. Such CO II lasers are capable of operating at high repetition rates for the rapid removal of dental hard tissues. An Impact 2500 TEA CO II laser system from GSI Lumonics (Rugby, UK) custom modified by LightMachinery (Ottawa, Canada) with a repetition rate of 0-500 Hz was used for rapid tissue removal. The single pulse ablation rates through enamel were determined for incident fluence ranging from (1-160 J/cm2). Lateral incisions using a computer controlled scanning stage and water spray were produced and the crater morphology and chemical composition were measured using optical microscopy and high-resolution synchrotron radiation infrared spectromicroscopy. The transmission through 2-meter length 300, 500, 750 and 1000-μm silica hollow waveguides was measured and 80% transmission was achieved with 40-mJ per pulse. The λ=9.3-μm laser pulses efficiently removed dental enamel at rates exceeding 15-μm per pulses with minimal heat accumulation. The residual energy remaining in tooth samples was measured to be 30-40% without water cooling, significantly lower than for longer CO II laser pulses. These results suggest that high repetition rate TEA CO II laser systems operating at λ=9.3-μm with pulse durations of 10-20-μs are ideally suited for dental application.

  18. An assessment of nitrogen-based manure application rates on 39 U.S. swine operations.

    PubMed

    Lory, John A; Massey, Raymond E; Zulovich, Joseph M; Hoehne, John A; Schmidt, Amy M; Carlson, Marcia S; Fulhage, Charles D

    2004-01-01

    Water quality concerns and revised regulations are changing how confined animal feeding operations manage manure. Devising acceptable and feasible changes in manure practices requires a full understanding of the forces shaping current manure management decisions. Previous theoretical models have shown that a wide range of factors influence the lowest cost solution for manure management. We used a mechanistic model to characterize the manure management practices on 39 swine operations (20 unagitated lagoon and 19 slurry operations) in five states (Iowa, Missouri, North Carolina, Oklahoma, and Pennsylvania). Information was collected from each operation about animal numbers, feed and water use, manure handling and storage characteristics, field locations, crop rotation, fertilizer need, and equipment inventory and usage. Collected data were used as input and to validate results from a mechanistic model that determined acres required for manure application, manure application rate, time required for manure application, value of manure, and costs of manure management. The 39 farms had a mean of 984 animal units (AU) per operation, 18.2 AU ha(-1) (7.4 AU acre(-1)), and manure application costs of dollar 10.49 AU(-1) yr(-1). Significant factors affecting manure management included operation size, manure handling system, state, and ownership structure. Larger operations had lower manure management costs (r2 = 0.32). Manure value potentially exceeded manure application costs on 58% of slurry and 15% of lagoon operations. But 38% of slurry operations needed to apply manure off the farm whereas all lagoon operations had sufficient land for N-based manure management. Manure management was a higher percentage of gross income on contract operations compared with independents (P < 0.01). This research emphasized the importance of site-specific factors affecting manure management decisions and the economics of U.S. swine operations. PMID:15224950

  19. Design and implementation of a bluetooth-based band-aid pulse rate sensor

    NASA Astrophysics Data System (ADS)

    Kumar, Prashanth S.; Oh, Sechang; Rai, Pratyush; Kwon, Hyeokjun; Banerjee, Nilanjan; Varadan, Vijay K.

    2011-04-01

    Remote patient monitoring systems capable of collecting vital patient data such as blood pressure readings, Electrocardiograph (ECG) waveforms, and heart rate can obviate the need for repeated visits to the hospital. Moreover, such systems that continuously monitor the human physiology can provide valuable data to prognosticate the onset of critical health problems. The key to such remote health diagnostics is the design of minimally intrusive, low cost sensors that do not impede a patient's quotidian life but at the same time collect reliable noise free data. To this end, in this paper, we design and implement a Bluetooth-based wireless sensor system with a disposable sensor element and a reusable wireless component that can be worn as a "band-aid". The sensor is a piezoelectric polymer film placed on the wrist in proximity to the radial artery. The band-aid sized sensor allows non-intrusive monitoring of the pulsatile flow of blood in the artery. The sensor, using the Bluetooth module, can communicate with any Bluetooth enabled computer, mobile phone, or PDA. The data collected from the patient can be remotely viewed and analyzed by a physician.

  20. Maternal Ratings of Temperament and Operant Learning in Two- to Three-Month-Old Infants.

    ERIC Educational Resources Information Center

    Dunst, Carl J.; Lingerfelt, Barbara

    1985-01-01

    Relationship between maternal ratings of temperament and operant learning was examined in 18 2- to 3-month-old infants. Subjects participated in a conjugate reinforcement experiment; mothers of subjects completed the Carey and McDevitt Revised Infant Temperament Questionnaire 2 to 3 days before the learning study. Two temperament dimensions,…

  1. 42 CFR 412.62 - Federal rates for inpatient operating costs for fiscal year 1984.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... fiscal year 1984. 412.62 Section 412.62 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES... § 412.62 Federal rates for inpatient operating costs for fiscal year 1984. (a) General rule. CMS... discharge in fiscal year 1984 involving inpatient hospital services of a hospital in the United...

  2. 29 CFR 780.314 - Operations customarily * * * paid on a piece rate basis * * *.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... FAIR LABOR STANDARDS ACT Employment in Agriculture That Is Exempted From the Minimum Wage and Overtime... 29 Labor 3 2014-07-01 2014-07-01 false Operations customarily * * * paid on a piece rate basis * * *. 780.314 Section 780.314 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR...

  3. 29 CFR 780.314 - Operations customarily * * * paid on a piece rate basis * * *.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... FAIR LABOR STANDARDS ACT Employment in Agriculture That Is Exempted From the Minimum Wage and Overtime... 29 Labor 3 2013-07-01 2013-07-01 false Operations customarily * * * paid on a piece rate basis * * *. 780.314 Section 780.314 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR...

  4. 29 CFR 780.314 - Operations customarily * * * paid on a piece rate basis * * *.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... FAIR LABOR STANDARDS ACT Employment in Agriculture That Is Exempted From the Minimum Wage and Overtime... 29 Labor 3 2012-07-01 2012-07-01 false Operations customarily * * * paid on a piece rate basis * * *. 780.314 Section 780.314 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR...

  5. 29 CFR 780.314 - Operations customarily * * * paid on a piece rate basis * * *.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... FAIR LABOR STANDARDS ACT Employment in Agriculture That Is Exempted From the Minimum Wage and Overtime... 29 Labor 3 2011-07-01 2011-07-01 false Operations customarily * * * paid on a piece rate basis * * *. 780.314 Section 780.314 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR...

  6. 29 CFR 780.314 - Operations customarily * * * paid on a piece rate basis * * *.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... FAIR LABOR STANDARDS ACT Employment in Agriculture That Is Exempted From the Minimum Wage and Overtime... 29 Labor 3 2010-07-01 2010-07-01 false Operations customarily * * * paid on a piece rate basis * * *. 780.314 Section 780.314 Labor Regulations Relating to Labor (Continued) WAGE AND HOUR...

  7. 42 CFR 412.62 - Federal rates for inpatient operating costs for fiscal year 1984.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... fiscal year 1984. 412.62 Section 412.62 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES... § 412.62 Federal rates for inpatient operating costs for fiscal year 1984. (a) General rule. CMS... discharge in fiscal year 1984 involving inpatient hospital services of a hospital in the United...

  8. Nonlinear acoustic pulse propagation in dispersive sediments using fractional loss operators.

    PubMed

    Maestas, Joseph T; Collis, Jon M

    2016-03-01

    The nonlinear progressive wave equation (NPE) is a time-domain formulation of the Euler fluid equations designed to model low-angle wave propagation using a wave-following computational domain. The wave-following frame of reference permits the simulation of long-range propagation and is useful in modeling blast wave effects in the ocean waveguide. Existing models do not take into account frequency-dependent sediment attenuation, a feature necessary for accurately describing sound propagation over, into, and out of the ocean sediment. Sediment attenuation is addressed in this work by applying lossy operators to the governing equation that are based on a fractional Laplacian. These operators accurately describe frequency-dependent attenuation and dispersion in typical ocean sediments. However, dispersion within the sediment is found to be a secondary process to absorption and effectively negligible for ranges of interest. The resulting fractional NPE is benchmarked against a Fourier-transformed parabolic equation solution for a linear case, and against the analytical Mendousse solution to Burgers' equation for the nonlinear case. The fractional NPE is then used to investigate the effects of attenuation on shock wave propagation. PMID:27036279

  9. California Federal Facilities: Rate-Responsive Building Operation for Deeper Cost and Energy Savings

    SciTech Connect

    2012-05-01

    Dynamic pricing electricity tariffs, now the default for large customers in California (peak demand of 200 kW and higher for PG&E and SCE, and 20 kW and higher for SDG&E), are providing Federal facilities new opportunities to cut their electricity bills and help them meet their energy savings mandates. The U.S. Department of Energy’s (DOE) Federal Energy Management Program (FEMP) has created this fact sheet to help California federal facilities take advantage of these opportunities through “rate-responsive building operation.” Rate-responsive building operation involves designing your load management strategies around your facility’s variable electric rate, using measures that require little or no financial investment.

  10. 100-kHz-rate gas-phase thermometry using 100-ps pulses from a burst-mode laser.

    PubMed

    Roy, Sukesh; Hsu, Paul S; Jiang, Naibo; Slipchenko, Mikhail N; Gord, James R

    2015-11-01

    Temperature measurements based on gas-phase coherent anti-Stokes Raman scattering (CARS) spectroscopy are demonstrated in reacting flows at a rate of 100 kHz employing a burst-mode laser with a pulse duration of ∼100  ps. The recently developed picosecond-duration, high-energy burst-mode laser is used to pump an optical parametric generator/optical parametric amplifier that produces broadband light centered at ∼680  nm to provide the Stokes beams for excitation of the rovibrational Raman transitions of H(2). The 532-nm output of the picosecond burst-mode laser is then utilized as a pump beam for the CARS process that generates 100 single-shot spectra at a rate of 100 kHz during the 1-ms duration burst. Coherent spectroscopy-based temperature measurements at 100 kHz will significantly aid the understanding of transient and unsteady flow phenomena related to turbulent combustion, transonic and hypersonic flows, high-enthalpy flows, and the dynamics of energetic materials.

  11. Thyratron characteristics under high di/dt and high-repetition-rate operation

    SciTech Connect

    Ball, D.; Hill, J.; Kan, T.

    1981-05-11

    Power conditioning systems for high peak and average power, high repetition rate discharge excited lasers involve operation of modulator components in unconventional regimes. Reliable operation of switches and energy storage elements under high voltage and high di/dt conditions is a pacing item for laser development at the present time. To test and evaluate these components a Modulator Component Test Facility (MCTF) was constructed. The MCTF consists of a command charge system, energy storage capacitors, thyratron switch with inverse thyratron protection, and a resistive load. The modulator has initially been operated at voltages up to 60 kV at 600 Hz. Voltage, current, and calorimetric diagnostics are provided for major modulator components. Measurements of thyratron characteristics under high di/dt operation are presented. Commutation energy loss and di/dt have been measured as functions of the tube hydrogen pressure.

  12. Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

    NASA Astrophysics Data System (ADS)

    Krastelev, E. G.; Sedin, A. A.; Tugushev, V. I.

    2015-12-01

    A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80-90 ns, and a pulse repetition rate of up to 16 Hz.

  13. Nanosecond pulsed power generator for a voltage amplitude up to 300 kV and a repetition rate up to 16 Hz for fine disintegration of quartz

    SciTech Connect

    Krastelev, E. G. Sedin, A. A.; Tugushev, V. I.

    2015-12-15

    A generator of high-power high-voltage nanosecond pulses is intended for electrical discharge disintegration of mineral quartz and other nonconducting minerals. It includes a 320 kV Marx pulsed voltage generator, a high-voltage glycerin-insulated coaxial peaking capacitor, and an output gas spark switch followed by a load, an electric discharge disintegration chamber. The main parameters of the generator are as follows: a voltage pulse amplitude of up to 300 kV, an output impedance of ≈10 Ω, a discharge current amplitude of up to 25 kA for a half-period of 80–90 ns, and a pulse repetition rate of up to 16 Hz.

  14. High energy pulses generation with giant spectrum bandwidth and submegahertz repetition rate from a passively mode-locked Yb-doped fiber laser in all normal dispersion cavity

    NASA Astrophysics Data System (ADS)

    Lin, J.-H.; Wang, D.; Lin, K.-H.

    2011-01-01

    Robust passively mode-locked pulse generation with low pulse repetition rate and giant spectrum bandwidth in an all-fiber, all-normal-dispersion ytterbium-doped fiber laser has been experimentally demonstrated using nonlinear polarization evolution technique. The highest pulse energy over 20 nJ with spectrum bandwidth over 50 nm can be experimentally obtained at 175 mW pump power. The mode-locked pulses reveal broadened 3-dB pulsewidth about several nanosecond and widened pedestal in time trace that is resulted from enormous dispersion in laser cavity and gain dynamics. At certain mode-locking state, a spectrum gap around 1056 nm are observed between the three and four energy levels of Yb-doped fiber laser. By properly rotating the polarization controller, the gap can be eliminated due to four-wave mixing to produce more flattened spectrum output.

  15. An easy-to-operate portable pulse-height analysis system for area monitoring with TEPC in radiation protection

    NASA Astrophysics Data System (ADS)

    Kunz, A.; Pihet, P.; Arend, E.; Menzel, H. G.

    1990-12-01

    A portable area monitor for the measurement of dose-equivalent quantities in practical radiation-protection work has been developed. The detector applied is a low-pressure proportional counter (TEPC) used in microdosimetry. The complex analysis system required has been optimized with regard to low power consumption and small size to achieve a real operational survey meter. The newly designed electronic includes complete analog, digital and microprocessor boards. It presents the characteristic of fast pulse-height processing over a large (5 decades) dynamic range. Three original circuits have been specifically developed, consisting of: (1) a miniaturized adjustable high-voltage power supply with low ripple and high stability; (2) a double spectroscopy amplifier with constant gain ratio and common pole-zero stage; and (3) an analog-to-digital converter with quasi-logarithmic characteristics based on a flash converter using fast comparators associated in parallel. With the incorporated single-board computer, the maximal total power consumption is 5 W, enabling 40 hours operation time with batteries. With minor adaptations the equipment is proposed as a low-cost solution for various measuring problems in environmental studies.

  16. Giant-chirp oscillators for short-pulse fiber amplifiers.

    PubMed

    Renninger, William H; Chong, Andy; Wise, Frank W

    2008-12-15

    A new regime of pulse parameters in a normal-dispersion fiber laser is identified. Dissipative solitons exist with remarkably large pulse duration and chirp, along with large pulse energy. A low-repetition-rate oscillator that generates pulses with large and linear chirp can replace the standard oscillator, stretcher, pulse-picker, and preamplifier in a chirped-pulse fiber amplifier. The theoretical properties of such a giant-chirp oscillator are presented. A fiber laser designed to operate in the new regime generates approximately 150 ps pulses at a 3 MHz repetition rate. Amplification of these pulses to 1 microJ energy with pulse duration as short as 670 fs demonstrates the promise of this new approach.

  17. Pulse Data.

    ERIC Educational Resources Information Center

    Hands On!, 1998

    1998-01-01

    Presents an activity using computer software to investigate the role of the heart and blood, how the blood system responds to exercise, and how pulse rate is a good measure of physical condition. (ASK)

  18. Operant tempo varies with reinforcement rate: implications for measurement of reward efficacy.

    PubMed

    Conover, Kent L.; Fulton, Stephanie; Shizgal, Peter

    2001-11-01

    Herrnstein's melioration theory has been used to account for the hyperbolic form of the single operant matching law and to scale the effectiveness of reinforcing brain stimulation. Underlying this scaling method is the assumption that the mean rate of responding during operant bouts (the response 'tempo') is fixed and does not vary with the rate of reinforcement. The validity of this account was assessed by testing the constant-tempo assumption via a survivor analysis of the distributions of inter-response times at different variable-intervals (VIs) in rats responding for rewarding electrical stimulation of the lateral hypothalamus. Contrary to the constant-tempo assumption, response tempo was not fixed but rather decreased as the VI was lengthened. This demonstration challenges Herrnstein's account of single-operant matching and suggests that the reinforcement rate that supports a half-maximal rate of responding on a single VI schedule may not provide a valid scale for the value of brain stimulation. Possible remedies are discussed. Although the conclusions of the study are restricted to experiments on brain stimulation reward in rats, the inter-response time analysis employed can provide the basis for testing the validity of the constant-tempo assumption in other species and for other reinforcers.

  19. Numerical Simulation of a Three-Stage Stirling-Type Pulse Tube Cryocooler for 4k Operation

    NASA Astrophysics Data System (ADS)

    Hu, J. Y.; Dai, W.; Luo, E. C.; Wu, Z. H.

    2008-03-01

    The thermoacoustically driven two-stage pulse tube cooler has recently reached a lowest temperature of about 18.1K in our lab, and we are now developing a three-stage Stirling-type pulse tube cooler working at about 4K to match the thermoacoustic engine. In this paper, thermoacoustic theory is employed to simulate the three-stage pulse tube cooler. In order to decrease the cooling power losses of the second and third stage cold tips, two thermal bridges are introduced on the first and second stage cold tips to cool down the second and the third stage pulse tubes. Thus, the temperature gradients in the pulse tubes near the cold tips decrease, so do the cooling power losses through the thermal conductivity of the pulse tubes. After numerical optimization, the pulse tube cooler reaches a cooling temperature of 3.87K with 207 Watts of input acoustic power.

  20. Comparison of dose distributions around the pulsed-dose-rate Fletcher Williamson and the low-dose-rate Fletcher Suit Delclos ovoids: a Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Price, Michael J.; Gifford, Kent A.; Horton, John; Lawyer, Ann; Eifel, Patricia; Mourtada, Firas

    2006-08-01

    We performed a Monte Carlo study to compare dose distributions for a Fletcher-Suit-Delclos (FSD) ovoid used with 137Cs low-dose-rate (LDR) sources with those for a Fletcher-Williamson (FW) ovoid used with an 192Ir pulsed-dose-rate (PDR) source for intracavitary brachytherapy of cervical cancer. We recently reported on extensive validation of Monte Carlo MCNPX models of these ovoids using radiochromic film measurements. Here, we compared these models assuming identical loading of 10, 15 and 20 mgRaEq (72, 108 and 145 cGy cm2 h-1, respectively) in three dose mesh planes: one perpendicular to the ovoid long axis bisecting the ovoid, one parallel to and displaced 2 cm medially from the long axis of the ovoid, and a 'rectal' plane perpendicular to the long axis located 1 cm distal to the distal face of the ovoid cap. The FW ovoid delivered slightly higher doses (within 10%) over all loadings to regions away from the bladder and rectal shields when compared to the FSD ovoid. However, the FW ovoid delivered much higher doses (>50%) in regions near these shields. In the rectal plane, the FW ovoid delivered a slightly higher dose, but within the region directly behind the rectal shield, the FW ovoid delivered a dose ranging from +35% to -35% of the FSD dose distribution. We attribute these differences to intrinsic differences in source characteristics (radial dose function and anisotropy factors) and extrinsic factors such as the solid-angle effect between sources and shields and applicator design.

  1. Characterizing rapid capacity fade and impedance evolution in high rate pulsed discharged lithium iron phosphate cells for complex, high power loads

    NASA Astrophysics Data System (ADS)

    Wong, Derek N.; Wetz, David A.; Heinzel, John M.; Mansour, Azzam N.

    2016-10-01

    Three 26650 LiFePO4 (LFP) cells are cycled using a 40 A pulsed charge/discharge profile to study their performance in high rate pulsed applications. This profile is used to simulate naval pulsed power loads planned for deployment aboard future vessels. The LFP cells studied experienced an exponential drop in their usable high-rate recharge capacity within sixty cycles due to a rapid rise in their internal resistance. Differential capacitance shows that the voltage window for charge storage is pushed outside of the recommended voltage cutoff limits. Investigation into the state of health of the electrodes shows minimal loss of active material from the cathode to side reactions. Post-mortem examination of the anodic surface films reveals a large increase in the concentration of reduced salt compounds indicating that the pulsed profile creates highly favorable conditions for LiPF6 salt to break down into LiF. This film slows the ionic movement at the interface, affecting transfer kinetics, resulting in charge buildup in the bulk anode without successful energy storage. The results indicate that the use of these cells as a power supply for high pulsed power loads is hindered because of ionically resistant film development and not by an increasing rate of active material loss.

  2. Anthropogenic seismicity rates and operational parameters at the Salton Sea Geothermal Field.

    PubMed

    Brodsky, Emily E; Lajoie, Lia J

    2013-08-01

    Geothermal power is a growing energy source; however, efforts to increase production are tempered by concern over induced earthquakes. Although increased seismicity commonly accompanies geothermal production, induced earthquake rate cannot currently be forecast on the basis of fluid injection volumes or any other operational parameters. We show that at the Salton Sea Geothermal Field, the total volume of fluid extracted or injected tracks the long-term evolution of seismicity. After correcting for the aftershock rate, the net fluid volume (extracted-injected) provides the best correlation with seismicity in recent years. We model the background earthquake rate with a linear combination of injection and net production rates that allows us to track the secular development of the field as the number of earthquakes per fluid volume injected decreases over time.

  3. Anthropogenic seismicity rates and operational parameters at the Salton Sea Geothermal Field.

    PubMed

    Brodsky, Emily E; Lajoie, Lia J

    2013-08-01

    Geothermal power is a growing energy source; however, efforts to increase production are tempered by concern over induced earthquakes. Although increased seismicity commonly accompanies geothermal production, induced earthquake rate cannot currently be forecast on the basis of fluid injection volumes or any other operational parameters. We show that at the Salton Sea Geothermal Field, the total volume of fluid extracted or injected tracks the long-term evolution of seismicity. After correcting for the aftershock rate, the net fluid volume (extracted-injected) provides the best correlation with seismicity in recent years. We model the background earthquake rate with a linear combination of injection and net production rates that allows us to track the secular development of the field as the number of earthquakes per fluid volume injected decreases over time. PMID:23845943

  4. Connecting Anthropogenic Seismicity Rates To Operational Parameters At The Salton Sea Geothermal Field, Southern California (Invited)

    NASA Astrophysics Data System (ADS)

    Brodsky, E. E.; Lajoie, L. J.

    2013-12-01

    Geothermal power is generated at several major volcanic fields in California. As efforts to monitor seismicity increase, methods to understand the anthropogenic component need to improve. Ideally, induced earthquake rate should be forecast based on publicly-reported volumes of fluid injection or other operational parameters. At the flash facilities in the Salton Sea Geothermal Field, the total volume of fluid extracted or injected tracks the long-term evolution of seismicity. However, for recent years net fluid volume (extracted-injected) is better correlated with seismicity. After correcting for the variable aftershock rate using an Epidemic-Type Aftershock Sequence model (ETAS), we fit the background earthquake rate with a linear combination of injection and net production rate that allows us to track the secular evolution of the field. The number of earthquakes per fluid volume injected decreases gradually over time. In the Salton Sea Geothermal Field, the new analysis of induced seismicity provides a template for future evaluation of hazard directly based on measureable, controllable operational quantities. The interactions of these anthropogenic events with the larger-scale tectonic and volcanic systems remains to be investigated. Results of the linear model of seismicity based on a combination of net production and injection. (a) Example of observed seismicity rate and model prediction using the reported fluid data and the best-fit linear model. (b) Number of earthquakes triggered per net volume of fluid extracted or total fluid injection.

  5. Repetition rate operation of an improved magnetically insulated transmission line oscillator

    SciTech Connect

    Fan Yuwei; Zhong Huihuang; Li Zhiqiang; Shu Ting; Yang Hanwu; Zhou Heng; Yuan Chengwei; Zhou Weihong; Luo Ling

    2008-08-15

    In order to investigate the performances of repetition rate (rep-rate) operation of an improved magnetically insulated transmission line oscillator (MILO), a series of experiments are carried out on the improved MILO device, which is driven by a 40 {omega}, 50 ns rep-rate pulser, TORCH-01. Polymer velvet and graphite cathodes are tested, respectively, in the experiments, whose diameters and lengths are the same. The results of experimental comparison between them are presented in the paper. Both cathodes are tested at electric field strengths of about 300 kV/cm. The applied voltage has 60 ns duration with a rise time of 10 ns. This paper focuses on the performance of the voltage and current characteristics, the shot-to-shot reproducibility, the pressure evolution of the diode, and the lifetime of the cathodes, not upon the radiated microwave power. The experimental results show that the graphite cathode is superior to the velvet cathode in the lifetime and the shot-to-shot reproducibility during the rep-rate operation, and it is a promising cathode for the MILO device under the rep-rate conditions.

  6. Kinetic Rate Kernels via Hierarchical Liouville-Space Projection Operator Approach.

    PubMed

    Zhang, Hou-Dao; Yan, YiJing

    2016-05-19

    Kinetic rate kernels in general multisite systems are formulated on the basis of a nonperturbative quantum dissipation theory, the hierarchical equations of motion (HEOM) formalism, together with the Nakajima-Zwanzig projection operator technique. The present approach exploits the HEOM-space linear algebra. The quantum non-Markovian site-to-site transfer rate can be faithfully evaluated via projected HEOM dynamics. The developed method is exact, as evident by the comparison to the direct HEOM evaluation results on the population evolution. PMID:26757138

  7. Selective removal of carious human dentin using a nanosecond pulsed laser operating at a wavelength of 5.85 μ m

    NASA Astrophysics Data System (ADS)

    Ishii, Katsunori; Kita, Tetsuya; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2015-05-01

    Less invasive methods for treating dental caries are strongly desired. However, conventional dental lasers do not always selectively remove caries or ensure good bonding to the composite resin. According to our previous study, demineralized dentin might be removed by a nanosecond pulsed laser operating at wavelengths of around 5.8 μm. The present study investigated the irradiation effect of the light on carious human dentin classified into "remove," "not remove," and "unclear" categories. Under 5.85-μm laser pulses, at average power densities of 30 W/cm2 and irradiation time of 2 s, the ablation depth of "remove" and "not remove," and also the ablation depth of "unclear" and "not remove," were significantly different (p<0.01). The ablation depth was correlated with both Vickers hardness and Ca content. Thus, a nanosecond pulsed laser operating at 5.85 μm proved an effective less-invasive caries treatment.

  8. Selective removal of carious human dentin using a nanosecond pulsed laser operating at a wavelength of 5.85 μm.

    PubMed

    Ishii, Katsunori; Kita, Tetsuya; Yoshikawa, Kazushi; Yasuo, Kenzo; Yamamoto, Kazuyo; Awazu, Kunio

    2015-05-01

    Less invasive methods for treating dental caries are strongly desired. However, conventional dental lasers do not always selectively remove caries or ensure good bonding to the composite resin. According to our previous study, demineralized dentin might be removed by a nanosecond pulsed laser operating at wavelengths of around 5.8 μm . The present study investigated the irradiation effect of the light on carious human dentin classified into "remove," "not remove," and "unclear" categories. Under 5.85-μm laser pulses, at average power densities of 30 W/cm² and irradiation time of 2 s, the ablation depth of "remove" and "not remove," and also the ablation depth of "unclear" and "not remove," were significantly different (p<0.01 ). The ablation depth was correlated with both Vickers hardness and Ca content. Thus, a nanosecond pulsed laser operating at 5.85  μm proved an effective less-invasive caries treatment.

  9. Continuous high-repetition-rate operation of collisional soft-x-ray lasers with solid targets.

    PubMed

    Weith, A; Larotonda, M A; Wang, Y; Luther, B M; Alessi, D; Marconi, M C; Rocca, J J; Dunn, J

    2006-07-01

    We have generated a laser average output power of 2 microW at a wavelength of 13.9 nm by operating a tabletop laser-pumped Ni-like Ag laser at a 5 Hz repetition rate, using a solid helicoidal target that is continuously rotated and advanced to renew the target surface between shots. More than 2 x 10(4) soft-x-ray laser shots were obtained by using a single target. Similar results were obtained at 13.2 nm in Ni-like Cd with a Cd-coated target. This scheme will allow uninterrupted operation of laser-pumped tabletop collisional soft-x-ray lasers at a repetition rate of 10 Hz for a period of hours, enabling the generation of continuous high average soft-x-ray powers for applications. PMID:16770410

  10. Packet error rate analysis of digital pulse interval modulation in intersatellite optical communication systems with diversified wavefront deformation.

    PubMed

    Zhu, Jin; Wang, Dayan; Xie, Wanqing

    2015-02-20

    Diversified wavefront deformation is an inevitable phenomenon in intersatellite optical communication systems, which will decrease system performance. In this paper, we investigate the description of wavefront deformation and its influence on the packet error rate (PER) of digital pulse interval modulation (DPIM). With the wavelet method, the diversified wavefront deformation can be described by wavelet parameters: coefficient, dilation, and shift factors, where the coefficient factor represents the depth, dilation factor represents the area, and shift factor is for location. Based on this, the relationship between PER and wavelet parameters is analyzed from a theoretical viewpoint. Numerical results illustrate the validity of theoretical analysis: PER increases with the depth and area and decreases if location gets farther from the center of the optical antenna. In addition to describing diversified deformation, the advantage of the wavelet method over Zernike polynomials in computational complexity is shown via numerical example. This work provides a feasible method for the description along with influence analysis of diversified wavefront deformation from a practical viewpoint and will be helpful for designing optical systems.

  11. Accuracy of velocity and shear rate measurements using pulsed Doppler ultrasound: a comparison of signal analysis techniques.

    PubMed

    Markou, C P; Ku, D N

    1991-01-01

    An experimental investigation was instituted to evaluate the performance of Doppler ultrasound signal processing techniques for measuring fluid velocity under well-defined flow conditions using a 10-MHz multigated pulsed ultrasound instrument. Conditions of fully developed flow in a rigid, circular tube were varied over a Reynolds number range between 500 and 8000. The velocity across the tube was determined using analog and digital zero crossing detectors and three digital spectrum estimators. Determination of the Doppler frequency from analog or digital zero crossing detectors gave accurate velocity values for laminar and moderately turbulent flow away from the wall (0.969 less than or equal to r less than or equal to 0.986). Three digital spectrum estimators, Fast Fourier Transform, Burg autoregressive method, and minimum variance method, were slightly more accurate than the zero crossing detector (0.984 less than or equal to r less than or equal to 0.994), especially at points close to the walls and with higher levels of turbulence. Steep velocity gradients and transit-time-effects from high velocities produced significantly larger errors in velocity measurement. Wall shear rate estimates were most precise when calculated using the position of the wall and two velocity points. The calculated wall shears were within 20%-30% of theoretically predicted values. PMID:1808798

  12. The interaction of glottal-pulse rate and vocal-tract length in judgements of speaker size, sex, and age

    NASA Astrophysics Data System (ADS)

    Smith, David R. R.; Patterson, Roy D.

    2005-11-01

    Glottal-pulse rate (GPR) and vocal-tract length (VTL) are related to the size, sex, and age of the speaker but it is not clear how the two factors combine to influence our perception of speaker size, sex, and age. This paper describes experiments designed to measure the effect of the interaction of GPR and VTL upon judgements of speaker size, sex, and age. Vowels were scaled to represent people with a wide range of GPRs and VTLs, including many well beyond the normal range of the population, and listeners were asked to judge the size and sex/age of the speaker. The judgements of speaker size show that VTL has a strong influence upon perceived speaker size. The results for the sex and age categorization (man, woman, boy, or girl) show that, for vowels with GPR and VTL values in the normal range, judgements of speaker sex and age are influenced about equally by GPR and VTL. For vowels with abnormal combinations of low GPRs and short VTLs, the VTL information appears to decide the sex/age judgement.

  13. The effect of workplace smoking bans on heart rate variability and pulse wave velocity of non-smoking hospitality workers

    PubMed Central

    Rajkumar, Sarah; Schmidt-Trucksäss, Arno; Wellenius, Gregory A.; Bauer, Georg F.; Huynh, Cong Khanh; Moeller, Alexander; Röösli, Martin

    2014-01-01

    Objectives To investigate the effect of a change in second hand smoke (SHS) exposure on heart rate variability (HRV) and pulse wave velocity (PWV), this study utilized a quasi-experimental setting when a smoking ban was introduced. Methods HRV, a quantitative marker of autonomic activity of the nervous system, and PWV, a marker of arterial stiffness, were measured in 55 non-smoking hospitality workers before and 3 to 12 months after a smoking ban and compared to a control group that did not experience an exposure change. SHS exposure was determined with a nicotine specific badge and expressed as inhaled cigarette equivalents per day (CE/d). Results PWV and HRV parameters significantly changed in a dose dependent manner in the intervention group compared to the control group. A one CE/d decrease was associated with a 2.3% (95% CI: 0.2, 4.4; p=0.031) higher root mean square of successive differences (RMSSD), a 5.7 % (95% CI: 0.9, 10.2; p=0.02) higher high frequency component and a 0.72% (95 % CI: 0.40–1.05; p<0.001) lower PWV. Conclusions PWV and HRV significantly improved after introducing smoke-free workplaces indicating a decreased cardiovascular risk. PMID:24504155

  14. Optimization strategies for pulsed low-dose-rate IMRT of recurrent lung and head and neck cancers.

    PubMed

    Kang, Shengwei; Lang, Jinyi; Wang, Pei; Li, Jie; Lin, Muhan; Chen, Xiaoming; Guo, Ming; Chen, Fu; Chen, Lili; Ma, Charlie Ming

    2014-01-01

    Pulsed low-dose-rate radiotherapy (PLDR) has been proven to be a valid method of reirradiation. Previous studies of recurrent cancer radiotherapy were mainly based on conventional 3D CRT and VMAT delivery techniques. There are difficulties in IMRT planning using existing commercial treatment planning systems (TPS) to meet the PLDR protocol. This work focuses on PLDR using ten-field IMRT and a commercial TPS for two specific sites: recurrent lung cancers and head and neck cancers. Our PLDR protocol requires that the maximum dose to the PTV be less than 0.4 Gy and the mean dose to be 0.2 Gy per field. We investigated various planning strategies to meet the PLDR requirements for 20 lung and head and neck patients. The PTV volume for lung cases ranged from 101.7 to 919.4 cm3 and the maximum dose to the PTV ranged from 0.22 to 0.39 Gy. The PTV volume for head and neck cases ranged from 66.2 to 282.1 cm3 and the maximum dose to the PTV ranged from 0.21 to 0.39 Gy. With special beam arrangements and dosimetry parameters, it is feasible to use a commercial TPS to generate quality PLDR IMRT plans for lung and head and neck reirradiation. PMID:24892337

  15. Gas ultrasonic flow rate measurement through genetic-ant colony optimization based on the ultrasonic pulse received signal model

    NASA Astrophysics Data System (ADS)

    Hou, Huirang; Zheng, Dandan; Nie, Laixiao

    2015-04-01

    For gas ultrasonic flowmeters, the signals received by ultrasonic sensors are susceptible to noise interference. If signals are mingled with noise, a large error in flow measurement can be caused by triggering mistakenly using the traditional double-threshold method. To solve this problem, genetic-ant colony optimization (GACO) based on the ultrasonic pulse received signal model is proposed. Furthermore, in consideration of the real-time performance of the flow measurement system, the improvement of processing only the first three cycles of the received signals rather than the whole signal is proposed. Simulation results show that the GACO algorithm has the best estimation accuracy and ant-noise ability compared with the genetic algorithm, ant colony optimization, double-threshold and enveloped zero-crossing. Local convergence doesn’t appear with the GACO algorithm until -10 dB. For the GACO algorithm, the converging accuracy and converging speed and the amount of computation are further improved when using the first three cycles (called GACO-3cycles). Experimental results involving actual received signals show that the accuracy of single-gas ultrasonic flow rate measurement can reach 0.5% with GACO-3 cycles, which is better than with the double-threshold method.

  16. Generation of stable Ps, mJ pulses at high repetition rate for ultrafast diagnostic experiments: Final report

    SciTech Connect

    Mourou, G.

    1986-10-01

    Nd:Glass amplifiers have very good energy storage capabilities (5 J/cm/sup 2/), but, the energy extraction is extremely inefficient for short-pulse amplification. At relatively high peak intensities of approx. 10 GW/cm/sup 2/, nonlinear phase shifts occur, leading to beam wavefront distortion which can result in filamentation and irreversible damage. In order that the peak intensity in the amplifier remain below this damage level, a picosecond pulse can be amplified only to an energy density of approx. 10 mJ/cm/sup 2/, two orders of magnitude less than the stored energy level of 5 J/cm/sup 2/. We have developed an amplification system, which uses an optical pulse compression technique to circumvent this peak power limitation. This technique is analogous to a method developed over forty years ago for the amplification of radar pulses. Briefly: a long optical pulse is deliberately produced by stretching a short, low-energy pulse, amplified and then compressed. The frequency chirp and the temporal broadening are produced by propagating a high-intensity pulse along a single-mode fiber. At the beginning of the fiber, the pulse undergoes self-phase modulation which produces a frequncy chirp. The chirp is then linearized by the group-velocity dispersion of the fiber. This long, frequency-chirped, pulse is amplified, and then compressed to a pulsewidth approximately equal to 1/..delta..f, where ..delta..f is the chirped bandwidth. With this system, short pulses can reach the high saturation energy levels, with moderately low peak power levels being maintained in the amplifying medium.

  17. Gain-switched laser diode seeded Yb-doped fiber amplifier delivering 11-ps pulses at repetition rates up to 40-MHz

    NASA Astrophysics Data System (ADS)

    Ryser, Manuel; Neff, Martin; Pilz, Soenke; Burn, Andreas; Romano, Valerio

    2012-02-01

    Here, we demonstrate all-fiber direct amplification of 11 picosecond pulses from a gain-switched laser diode at 1063 nm. The diode was driven at a repetition rate of 40 MHz and delivered 13 μW of fiber-coupled average output power. For the low output pulse energy of 0.33 pJ we have designed a multi-stage core pumped preamplifier based on single clad Yb-doped fibers in order to keep the contribution of undesired amplified spontaneous emission as low as possible and to minimize temporal and spectral broadening. After the preamplifier we reduced the 40 MHz repetition rate to 1 MHz using a fiber coupled pulse-picker. The final amplification was done with a cladding pumped Yb-doped large mode area fiber and a subsequent Yb-doped rod-type fiber. With our setup we achieved amplification of 72 dBs to an output pulse energy of 5.7 μJ, pulse duration of 11 ps and peak power of >0.6 MW.

  18. Effects of baseline reinforcement rate on operant ABA and ABC renewal.

    PubMed

    Berry, Meredith S; Sweeney, Mary M; Odum, Amy L

    2014-10-01

    Renewal is a relapse phenomenon that occurs when the contextual stimuli present during extinction change, and consequently, an extinguished response increases in rate. Two experiments assessed extinction and renewal of key-pecking in pigeons in a two-component multiple schedule wherein baseline reinforcer rates were delivered at relatively rich or lean rates. In Experiment 1, an ABA design was used in which baseline stimuli were steady key lights (Context A). Food was then removed during extinction, and simultaneously, the context was changed by flashing the key lights (Context B). Following extinction, steady key lights were reintroduced, but food remained unavailable. Key-pecking was more resistant to extinction and recovered to a greater degree in the rich relative to the lean component. In Experiment 2, we introduced novel stimuli following extinction (ABC renewal) rather than reintroducing baseline stimuli. Similar to Experiment 1, in Experiment 2 resistance to change and renewal remained greater in the component associated with higher reinforcer rates during baseline. These findings provide additional support for the context-specificity of operant extinction, and support the prediction of behavioral momentum theory that stimuli associated with higher rates of reinforcement engender greater persistence and relapse than those associated with lower rates of reinforcement.

  19. Effects of baseline reinforcement rate on operant ABA and ABC renewal.

    PubMed

    Berry, Meredith S; Sweeney, Mary M; Odum, Amy L

    2014-10-01

    Renewal is a relapse phenomenon that occurs when the contextual stimuli present during extinction change, and consequently, an extinguished response increases in rate. Two experiments assessed extinction and renewal of key-pecking in pigeons in a two-component multiple schedule wherein baseline reinforcer rates were delivered at relatively rich or lean rates. In Experiment 1, an ABA design was used in which baseline stimuli were steady key lights (Context A). Food was then removed during extinction, and simultaneously, the context was changed by flashing the key lights (Context B). Following extinction, steady key lights were reintroduced, but food remained unavailable. Key-pecking was more resistant to extinction and recovered to a greater degree in the rich relative to the lean component. In Experiment 2, we introduced novel stimuli following extinction (ABC renewal) rather than reintroducing baseline stimuli. Similar to Experiment 1, in Experiment 2 resistance to change and renewal remained greater in the component associated with higher reinforcer rates during baseline. These findings provide additional support for the context-specificity of operant extinction, and support the prediction of behavioral momentum theory that stimuli associated with higher rates of reinforcement engender greater persistence and relapse than those associated with lower rates of reinforcement. PMID:25241305

  20. Simulation of toluene decomposition in a pulse-periodic discharge operating in a mixture of molecular nitrogen and oxygen

    SciTech Connect

    Trushkin, A. N.; Kochetov, I. V.

    2012-05-15

    The kinetic model of toluene decomposition in nonequilibrium low-temperature plasma generated by a pulse-periodic discharge operating in a mixture of nitrogen and oxygen is developed. The results of numerical simulation of plasma-chemical conversion of toluene are presented; the main processes responsible for C{sub 6}H{sub 5}CH{sub 3} decomposition are identified; the contribution of each process to total removal of toluene is determined; and the intermediate and final products of C{sub 6}H{sub 5}CH{sub 3} decomposition are identified. It was shown that toluene in pure nitrogen is mostly decomposed in its reactions with metastable N{sub 2}(A{sub 3}{Sigma}{sub u}{sup +}) and N{sub 2}(a Prime {sup 1}{Sigma}{sub u}{sup -}) molecules. In the presence of oxygen, in the N{sub 2} : O{sub 2} gas mixture, the largest contribution to C{sub 6}H{sub 5}CH{sub 3} removal is made by the hydroxyl radical OH which is generated in this mixture exclusively due to plasma-chemical reactions between toluene and oxygen decomposition products. Numerical simulation showed the existence of an optimum oxygen concentration in the mixture, at which toluene removal is maximum at a fixed energy deposition.

  1. CW and pulsed electrically detected magnetic resonance spectroscopy at 263GHz/12T on operating amorphous silicon solar cells.

    PubMed

    Akhtar, W; Schnegg, A; Veber, S; Meier, C; Fehr, M; Lips, K

    2015-08-01

    Here we describe a new high frequency/high field continuous wave and pulsed electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating at 263GHz and resonance fields between 0 and 12T. Spin dependent transport in illuminated hydrogenated amorphous silicon p-i-n solar cells at 5K and 90K was studied by in operando 263GHz CW and pEDMR alongside complementary X-band CW EDMR. Benefiting from the superior resolution at 263GHz, we were able to better resolve EDMR signals originating from spin dependent hopping and recombination processes. 5K EDMR spectra were found to be dominated by conduction and valence band tail states involved in spin dependent hopping, with additional contributions from triplet exciton states. 90K EDMR spectra could be assigned to spin pair recombination involving conduction band tail states and dangling bonds as the dominating spin dependent transport process, with additional contributions from valence band tail and triplet exciton states.

  2. CW and pulsed electrically detected magnetic resonance spectroscopy at 263GHz/12T on operating amorphous silicon solar cells.

    PubMed

    Akhtar, W; Schnegg, A; Veber, S; Meier, C; Fehr, M; Lips, K

    2015-08-01

    Here we describe a new high frequency/high field continuous wave and pulsed electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating at 263GHz and resonance fields between 0 and 12T. Spin dependent transport in illuminated hydrogenated amorphous silicon p-i-n solar cells at 5K and 90K was studied by in operando 263GHz CW and pEDMR alongside complementary X-band CW EDMR. Benefiting from the superior resolution at 263GHz, we were able to better resolve EDMR signals originating from spin dependent hopping and recombination processes. 5K EDMR spectra were found to be dominated by conduction and valence band tail states involved in spin dependent hopping, with additional contributions from triplet exciton states. 90K EDMR spectra could be assigned to spin pair recombination involving conduction band tail states and dangling bonds as the dominating spin dependent transport process, with additional contributions from valence band tail and triplet exciton states. PMID:26112328

  3. High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

    NASA Astrophysics Data System (ADS)

    Becnel, Andrew C.

    This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter

  4. Multi-color carrier-envelope-phase stabilization for high-repetition-rate multi-pulse coherent synthesis.

    PubMed

    McCracken, Richard A; Gianani, Ilaria; Wyatt, Adam S; Reid, Derryck T

    2015-04-01

    Using a zero-offset carrier-envelope locking technique, we have synthesized an octave-spanning composite frequency comb exhibiting 132-attosecond timing jitter between the constituent pulses over a one-second observation window. In the frequency domain, this composite comb has a modal structure and coherence which are indistinguishable from those of a comb that might be produced by a hypothetical single mode locked oscillator of equivalent bandwidth. The associated phase stability enables the participating multi-color pulse sequences to be coherently combined, representing an example of multi-pulse synthesis using a femtosecond oscillator.

  5. Investigations of DNA damage induction and repair resulting from cellular exposure to high dose-rate pulsed proton beams

    NASA Astrophysics Data System (ADS)

    Renis, M.; Borghesi, M.; Favetta, M.; Malfa, G.; Manti, L.; Romano, F.; Schettino, G.; Tomasello, B.; Cirrone, G. A. P.

    2013-07-01

    Studies regarding the radiobiological effects of low dose radiation, microbeam irradiation services have been developed in the world and today laser acceleration of protons and heavy ions may be used in radiation therapy. The application of different facilities is essential for studying bystander effects and relating signalling phenomena in different cells or tissues. In particular the use of ion beams results advantageous in cancer radiotherapy compared to more commonly used X-rays, since the ability of ions in delivering lethal amount of doses into the target tumour avoiding or limiting damage to the contiguous healthy tissues. At the INFN-LNS in Catania, a multidisciplinary radiobiology group is strategically structured aimed to develop radiobiological research, finalised to therapeutic applications, compatible with the use of high dose laser-driven ion beams. The characteristic non-continuous dose rates with several orders of magnitude of laser-driven ion beams makes this facility very interesting in the cellular systems' response to ultra-high dose rates with non-conventional pulse time intervals cellular studies. Our group have projected to examine the effect of high dose laser-driven ion beams on two cellular types: foetal fibroblasts (normal control cells) and DU145 (prostate cancer cells), studying the modulation of some different bio-molecular parameters, in particular cell proliferation and viability, DNA damage, redox cellular status, morphological alterations of both the cytoskeleton components and some cell organelles and the possible presence of apoptotic or necrotic cell death. Our group performed preliminary experiments with high energy (60 MeV), dose rate of 10 Gy/min, doses of 1, 2, 3 Gy and LET 1 keV/μm on human foetal fibroblasts (control cells). We observed that cell viability was not influenced by the characteristics of the beam, the irradiation conditions or the analysis time. Conversely, DNA damage was present at time 0, immediately

  6. Investigations of DNA damage induction and repair resulting from cellular exposure to high dose-rate pulsed proton beams

    SciTech Connect

    Renis, M.; Malfa, G.; Tomasello, B.; Borghesi, M.; Schettino, G.; Favetta, M.; Romano, F.; Cirrone, G. A. P.; Manti, L.

    2013-07-26

    Studies regarding the radiobiological effects of low dose radiation, microbeam irradiation services have been developed in the world and today laser acceleration of protons and heavy ions may be used in radiation therapy. The application of different facilities is essential for studying bystander effects and relating signalling phenomena in different cells or tissues. In particular the use of ion beams results advantageous in cancer radiotherapy compared to more commonly used X-rays, since the ability of ions in delivering lethal amount of doses into the target tumour avoiding or limiting damage to the contiguous healthy tissues. At the INFN-LNS in Catania, a multidisciplinary radiobiology group is strategically structured aimed to develop radiobiological research, finalised to therapeutic applications, compatible with the use of high dose laser-driven ion beams. The characteristic non-continuous dose rates with several orders of magnitude of laser-driven ion beams makes this facility very interesting in the cellular systems' response to ultra-high dose rates with non-conventional pulse time intervals cellular studies. Our group have projected to examine the effect of high dose laser-driven ion beams on two cellular types: foetal fibroblasts (normal control cells) and DU145 (prostate cancer cells), studying the modulation of some different bio-molecular parameters, in particular cell proliferation and viability, DNA damage, redox cellular status, morphological alterations of both the cytoskeleton components and some cell organelles and the possible presence of apoptotic or necrotic cell death. Our group performed preliminary experiments with high energy (60 MeV), dose rate of 10 Gy/min, doses of 1, 2, 3 Gy and LET 1 keV/μm on human foetal fibroblasts (control cells). We observed that cell viability was not influenced by the characteristics of the beam, the irradiation conditions or the analysis time. Conversely, DNA damage was present at time 0, immediately

  7. The role of gas dynamics in operation conditions of a Pulsed Microplasma Cluster Source for nanostructured thin films deposition.

    PubMed

    Tafreshi, H Vahedi; Piseri, P; Benedek, G; Milani, P

    2006-04-01

    This study intends to explain the fluid dynamic characteristics of a Pulsed Microplasma Cluster Source (PMCS). An axially symmetric steady state simulation is performed for modeling the real-life three-dimensional unsteady flow of hypersonic helium inside our PMCS. Hypersonic helium flow is simulated using Realizable k-epsilon turbulent model. We obtained the jet velocity, density, and pressure field inside our PMCS for the conditions considered and discussed them with respect to our experimental observations. We also presented a qualitative discussion on the formation-termination process of this hypersonic jet. In particular, simulation, in agreement with the experiment, indicates that the middle stage of the injection process, where the Mach disk stands close to the ablation target and at the same time the mass flow rate is relatively high, is almost the appropriate time for firing the electric discharge. We simulated the jet-electrode impingement and tracked the trajectory of the ablated carbon clusters, considered as rigid spheres, inside the PMCS. We noticed that the spatial distribution of the clusters inside PMCS is highly conserved during the free expansion of the cluster beam out of the nozzle (in the vacuum chambers) and is recognizable in the deposited carbon film. This indicates that the geometry of PMCS plays a significant role in the uniformity of the deposited film.

  8. An operational rate control scheme for H.264 with two-stage encoding

    NASA Astrophysics Data System (ADS)

    Kwon, Do-Kyoung; Shen, Mei-Yin; Kuo, C.-C. Jay

    2005-08-01

    An operational rate control (RC) scheme based on two-stage encoding is studied in this research, where frame-layer rate control with a constant bit rate to achieve constant video quality is examined. In the first encoding stage, the R-D optimized mode decision and its associated motion estimation (RDO) as well as DCT/Q, IQ/IDCT and entropy coding are performed for all macroblocks (MBs) for a target frame using an initial quantization parameter (QP), which is the QP of its previous frame. In the second encoding stage, the residual signal from the first stage is encoded using several QP values around the initial QP. Given the target bits and distortion for the current frame, the residual signal is finally encoded using the QP determined by comparing target bits and distortion with actual bits and distortion. To reduce the additional coding complexity of the two-stage encoding, upper and lower bounds around target bits and distortion are employed to reduce the number of encoding required in the second stage. Experimental results are given to show the superior performance of two proposed rate control algorithms, where one targets at the constant bit rate while the other at constant quality.

  9. Extinction under a behavioral microscope: isolating the sources of decline in operant response rate.

    PubMed

    Cheung, Timothy H C; Neisewander, Janet L; Sanabria, Federico

    2012-05-01

    Extinction performance is often used to assess underlying psychological processes without the interference of reinforcement. For example, in the extinction/reinstatement paradigm, motivation to seek drug is assessed by measuring responding elicited by drug-associated cues without drug reinforcement. However, extinction performance is governed by several psychological processes that involve motivation, memory, learning, and motoric functions. These processes are confounded when overall response rate is used to measure performance. Based on evidence that operant responding occurs in bouts, this paper proposes an analytic procedure that separates extinction performance into several behavioral components: (1-3) the baseline bout initiation rate, within-bout response rate, and bout length at the onset of extinction; (4-6) their rates of decay during extinction; (7) the time between extinction onset and the decline of responding; (8) the asymptotic response rate at the end of extinction; (9) the refractory period after each response. Data that illustrate the goodness of fit of this analytic model are presented. This paper also describes procedures to isolate behavioral components contributing to extinction performance and make inferences about experimental effects on these components. This microscopic behavioral analysis allows the mapping of different psychological processes to distinct behavioral components implicated in extinction performance, which may further our understanding of the psychological effects of neurobiological treatments. PMID:22425782

  10. Extinction under a behavioral microscope: isolating the sources of decline in operant response rate.

    PubMed

    Cheung, Timothy H C; Neisewander, Janet L; Sanabria, Federico

    2012-05-01

    Extinction performance is often used to assess underlying psychological processes without the interference of reinforcement. For example, in the extinction/reinstatement paradigm, motivation to seek drug is assessed by measuring responding elicited by drug-associated cues without drug reinforcement. However, extinction performance is governed by several psychological processes that involve motivation, memory, learning, and motoric functions. These processes are confounded when overall response rate is used to measure performance. Based on evidence that operant responding occurs in bouts, this paper proposes an analytic procedure that separates extinction performance into several behavioral components: (1-3) the baseline bout initiation rate, within-bout response rate, and bout length at the onset of extinction; (4-6) their rates of decay during extinction; (7) the time between extinction onset and the decline of responding; (8) the asymptotic response rate at the end of extinction; (9) the refractory period after each response. Data that illustrate the goodness of fit of this analytic model are presented. This paper also describes procedures to isolate behavioral components contributing to extinction performance and make inferences about experimental effects on these components. This microscopic behavioral analysis allows the mapping of different psychological processes to distinct behavioral components implicated in extinction performance, which may further our understanding of the psychological effects of neurobiological treatments.

  11. Effect of Temperature on the Aging rate of Li Ion Battery Operating above Room Temperature

    PubMed Central

    Leng, Feng; Tan, Cher Ming; Pecht, Michael

    2015-01-01

    Temperature is known to have a significant impact on the performance, safety, and cycle lifetime of lithium-ion batteries (LiB). However, the comprehensive effects of temperature on the cyclic aging rate of LiB have yet to be found. We use an electrochemistry-based model (ECBE) here to measure the effects on the aging behavior of cycled LiB operating within the temperature range of 25 °C to 55 °C. The increasing degradation rate of the maximum charge storage of LiB during cycling at elevated temperature is found to relate mainly to the degradations at the electrodes, and that the degradation of LCO cathode is larger than graphite anode at elevated temperature. In particular, the formation and modification of the surface films on the electrodes as well as structural/phase changes of the LCO electrode, as reported in the literatures, are found to be the main contributors to the increasing degradation rate of the maximum charge storage of LiB with temperature for the specific operating temperature range. Larger increases in the Warburg elements and cell impedance are also found with cycling at higher temperature, but they do not seriously affect the state of health (SoH) of LiB as shown in this work. PMID:26245922

  12. Coexistence of reward and unsupervised learning during the operant conditioning of neural firing rates.

    PubMed

    Kerr, Robert R; Grayden, David B; Thomas, Doreen A; Gilson, Matthieu; Burkitt, Anthony N

    2014-01-01

    A fundamental goal of neuroscience is to understand how cognitive processes, such as operant conditioning, are performed by the brain. Typical and well studied examples of operant conditioning, in which the firing rates of individual cortical neurons in monkeys are increased using rewards, provide an opportunity for insight into this. Studies of reward-modulated spike-timing-dependent plasticity (RSTDP), and of other models such as R-max, have reproduced this learning behavior, but they have assumed that no unsupervised learning is present (i.e., no learning occurs without, or independent of, rewards). We show that these models cannot elicit firing rate reinforcement while exhibiting both reward learning and ongoing, stable unsupervised learning. To fix this issue, we propose a new RSTDP model of synaptic plasticity based upon the observed effects that dopamine has on long-term potentiation and depression (LTP and LTD). We show, both analytically and through simulations, that our new model can exhibit unsupervised learning and lead to firing rate reinforcement. This requires that the strengthening of LTP by the reward signal is greater than the strengthening of LTD and that the reinforced neuron exhibits irregular firing. We show the robustness of our findings to spike-timing correlations, to the synaptic weight dependence that is assumed, and to changes in the mean reward. We also consider our model in the differential reinforcement of two nearby neurons. Our model aligns more strongly with experimental studies than previous models and makes testable predictions for future experiments. PMID:24475240

  13. Coexistence of reward and unsupervised learning during the operant conditioning of neural firing rates.

    PubMed

    Kerr, Robert R; Grayden, David B; Thomas, Doreen A; Gilson, Matthieu; Burkitt, Anthony N

    2014-01-01

    A fundamental goal of neuroscience is to understand how cognitive processes, such as operant conditioning, are performed by the brain. Typical and well studied examples of operant conditioning, in which the firing rates of individual cortical neurons in monkeys are increased using rewards, provide an opportunity for insight into this. Studies of reward-modulated spike-timing-dependent plasticity (RSTDP), and of other models such as R-max, have reproduced this learning behavior, but they have assumed that no unsupervised learning is present (i.e., no learning occurs without, or independent of, rewards). We show that these models cannot elicit firing rate reinforcement while exhibiting both reward learning and ongoing, stable unsupervised learning. To fix this issue, we propose a new RSTDP model of synaptic plasticity based upon the observed effects that dopamine has on long-term potentiation and depression (LTP and LTD). We show, both analytically and through simulations, that our new model can exhibit unsupervised learning and lead to firing rate reinforcement. This requires that the strengthening of LTP by the reward signal is greater than the strengthening of LTD and that the reinforced neuron exhibits irregular firing. We show the robustness of our findings to spike-timing correlations, to the synaptic weight dependence that is assumed, and to changes in the mean reward. We also consider our model in the differential reinforcement of two nearby neurons. Our model aligns more strongly with experimental studies than previous models and makes testable predictions for future experiments.

  14. Posterior consistency and convergence rates for Bayesian inversion with hypoelliptic operators

    NASA Astrophysics Data System (ADS)

    Kekkonen, Hanne; Lassas, Matti; Siltanen, Samuli

    2016-08-01

    The Bayesian approach to inverse problems is studied in the case where the forward map is a linear hypoelliptic pseudodifferential operator and measurement error is additive white Gaussian noise. The measurement model for an unknown Gaussian random variable U(x,ω ) is {M}δ (y,ω )=A (U(x,ω ))+δ \\phantom{\\rule{.2mm}{0ex}}{ E }(y,ω ), where A is a finitely many orders smoothing linear hypoelliptic operator and δ \\gt 0 is the noise magnitude. The covariance operator C U of U is smoothing of order 2r, self-adjoint, injective and elliptic pseudodifferential operator. If { E } was taking values in L 2 then in Gaussian case solving the conditional mean (and maximum a posteriori) estimate is linked to solving the minimisation problem {T}δ ({m}δ )={{arg}{min}}u\\in {Hr} \\{\\parallel {Au}-{m}δ {\\parallel }{L2}2+{δ }2\\parallel {C}U-1/2u{\\parallel }{L2}2\\}. However, Gaussian white noise does not take values in L 2 but in {H}-s where s\\gt 0 is big enough. A modification of the above approach to solve the inverse problem is presented, covering the case of white Gaussian measurement noise. Furthermore, the convergence of the conditional mean estimate to the correct solution as δ \\to 0 is proven in appropriate function spaces using microlocal analysis. Also the frequentist posterior contractions rates are studied.

  15. How to evaluate BP measurements using the oscillometric method in atrial fibrillation: the value of pulse rate variation.

    PubMed

    Wang, Xi-Xing; Shuai, Wei; Hong, Kui; Xu, Jinsong; Li, Ju-Xiang; Li, Ping; Cheng, Xiao-Shu; Su, Hai

    2016-08-01

    An oscillometric device is recommended for blood pressure (BP) measurement in atrial fibrillation (AF), but there is still controversy concerning its accuracy. Therefore, evaluation of BP values in AF patients remains a challenge. This study included 251 patients with AF and 154 participants with sinus rhythm (SR). Pulse rate (PR) and BP were measured using an oscillometric device three times. The differences between the highest and lowest PR and the systolic and diastolic BP (SBP and DBP) were calculated as ΔPR, ΔSBP and ΔDBP, respectively. AF patients were stratified with respect to ΔPR in 0-5, 6-10, 11-15 and >15 subgroups. The AF group had a greater ΔPR (12.1±8.6 vs. 4.10±3.21 b.p.m., P<0.001), ΔSBP and ΔDBP than the SR group at similar SBP and DBP. A positive correlation existed between ΔPR and ΔSBP (r=0.255, P<0.001) in AF patients, but no correlation was found in SR subjects. Meanwhile, the ΔSBP in the 0-5 and 6-10 subgroups (9.58±5.61 and 10.67±6.77 vs. 8.45±5.25 mm Hg, nonsignificant) was similar to the SR group, whereas ΔSBP in the 11-15 and >15 subgroups was significantly greater than the SR group. Regardless of ΔPR, the ΔDBP in the AF group was significantly greater than that of the SR group. The AF patients who exhibited greater variability in their PR also had a greater variability in their SBP readings. The SBP measurement for AF patients is accurate as the measurement for patients with SR if the ΔPR is of 0-10 b.p.m. in AF.

  16. The Effects of Sa-am Acupuncture Simpo-jeongkyeok Treatment on the Blood Pressure, Pulse Rate, and Body Temperature

    PubMed Central

    Choi, Woo-Jin; Cho, Yoon-Young; Sun, Seung-Ho

    2015-01-01

    Objectives: The present study evaluated the effects of sa-am acupuncture (SAA) simpo-jeongkyeok (SPJK) treatment on the blood pressure (BP), pulse rate (PR), and body temperature (BT) of patients with hwa byung (HB). Methods: This patient assessor blind, randomized, placebo controlled trial included 50 volunteers, divided randomly into two groups. The treatment group underwent SPJK (PC9, LR1, PC3, KI10) while the control (sham) group received minimal needle insertion at non acupoints. The BP in both arms, PR, and BT at several acupoints were measured before and after treatment at the 1st, 2nd, 3rd, and 4th visits and before treatment at the follow-up visit. We analyzed data by using the repeated measured analysis of variance (RM ANOVA), Mann-Whitney U, and wilcoxon signed rank tests; differences at P < 0.05 were considered significant. Results: No significant differences in the systolic blood pressure (SBP), diastolic blood pressure (DBP) and PR between the treatment and control group were observed at each visit. However, the decrease in the SBP for the treatment group before and after each visit was significantly higher than it was in the control group. The SBP in both arms in the treatment group was decreased between visits 1 and 2, 1 and 3, 1 and 4, and 1 and follow-up. The DBP in both arms and in the right arm between visits 1 and 3 in the treatment group showed decreases. A minimal BT increase for treatment at CV06 and CV12 and a minimal BT decrease for treatment at CV17 and (Ex) Yintang were found. Patients in the treatment group who visited more frequently experienced a greater decrease in the PR, but that effect was not maintained. Conclusion: The results suggest that SAA SPJK treatment has instant positive effects on the BP, PR, and BT in patients with HB, but the effects on the BP and PR are not maintained. PMID:26120486

  17. Parameters of a trigatron-driven low-pulse-repetition-rate TEA CO{sub 2} laser preionised by a surface corona discharge

    SciTech Connect

    Aram, M; Shabanzadeh, M; Mansori, F; Behjat, A

    2007-01-31

    The design of a TEA CO{sub 2} laser with UV preionisation by a surface corona discharge is described and the dependences of its average output energy on the gas-flow rate, discharge voltage and pulse repetition rate are presented. The scheme of the electric circuit and the geometry of the pre-ionisation system are considered. The electric circuit is designed to produce only impulse voltage difference between the laser electrodes. The triggering system of the trigatron is used to prevent the appearance of the arc. The dependences of the current, voltage and average output energy on the gas-mixture composition and applied voltages at a low pulse repetition rate are presented. The central output wavelength of the laser was measured with an IR spectrometer. Lasing at two adjacent vibrational-rotational transitions of the CO{sub 2} molecule was observed, which demonstrates the possibility of simultaneous lasing at several lines. (lasers)

  18. Operation logic and functionality of automatic dose rate and image quality control of conventional fluoroscopy

    SciTech Connect

    Lin, Pei-Jan Paul

    2009-05-15

    New generation of fluoroscopic imaging systems is equipped with spectral shaping filters complemented with sophisticated automatic dose rate and image quality control logic called ''fluoroscopy curve'' or ''trajectory''. Such fluoroscopy curves were implemented first on cardiovascular angiographic imaging systems and are now available on conventional fluoroscopy equipment. This study aims to investigate the control logic operations under the fluoroscopy mode and acquisition mode (equivalent to the legacy spot filming) of a conventional fluoroscopy system typically installed for upper-lower gastrointestinal examinations, interventional endoscopy laboratories, gastrointestinal laboratory, and pain clinics.

  19. A real-time pulsed photon dosimeter

    NASA Astrophysics Data System (ADS)

    Brown, David; Olsher, Richard H.; Eisen, Yosef; Rodriguez, Joseph F.

    1996-02-01

    Radiation sources producing short pulses of photon radiation are now widespread. Such sources include electron and proton linear accelerators, betatrons, synchrotrons, and field-emission impulse generators. It is often desirable to measure leakage and skyshine radiation from such sources in real time, on a single-pulse basis as low as 8.7 nGy (1 μR) per pulse. This paper describes the design and performance of a prototype, real-time, pulsed photon dosimeter (PPD) capable of single-pulse dose measurements over the range from 3.5 nGy to 3.5 μGy (0.4 to 400 μR). The PPD may also be operated in a multiple-pulse mode that integrates the dose from a train of radiation pulses over a 3-s period. A pulse repetition rate of up to 300 Hz is accommodated. The design is eminently suitable for packaging as a lightweight, portable, survey meter. The PPD uses a CdWO 4 scintillator optically coupled to a photodiode to generate a charge at the diode output. A pulse amplifier converts the charge to a voltage pulse. A digitizer circuit generates a burst of logic pulses whose number is proportional to the peak value of the voltage pulse. The digitizer output is recorded by a pulse counter and suitably displayed. A prototype PPD was built for testing and evaluation purposes. The performance of the PPD was evaluated with a variety of pulsed photon sources. The dynamic range, energy response, and response to multiple pulses were characterized. The experimental data confirm the viability of the PPD for pulsed photon dosimetry.

  20. Characteristics of a Saturated 18.9 nm Tabletop Laser Operating at 5 Hz Repetition Rate

    SciTech Connect

    Larotonda, M A; Luther, B M; Wang, Y; Liu, Y; Alessi, D; Berrill, M; Dummer, A; Brizuela, F; Menoni, C S; Marconi, M; Shlyaptsev, V N; Dunn, J; Rocca, J J

    2005-01-10

    We report the characteristics of a saturated high repetition rate Ni-like Mo laser at 18.9 nm. This table-top soft x-ray laser was pumped at 5 Hz repetition rate by 8 ps, 1 J optical laser pulses impinging at grazing incidence into a pre-created Mo plasma. The variation of the laser output intensity as a function of the grazing incidence angle of the main pump beam is reported. The maximum laser intensity was observed for an angle of 20 degrees, at which we measured a small signal gain of 65 cm{sup -1} and a gain-length product gxl > 15. Spatial coherence measurements resulting from a Young's double slit interference experiment show the equivalent incoherent source diameter is about 11 {micro}m. The peak spectral brightness is estimated to be of the order of 1 x 10{sup 24} photons s{sup -1} mm{sup -2} mrad{sup -2} within 0.01% spectral bandwidth. This type of practical, small scale, high repetition soft x-ray laser is of interest for many applications. This acts to reduce the sensitivity of burst properties to metallicity. Only the first anomalous burst in one model produces nuclei as heavy as A = 100. For the present choice of nuclear physics and accretion rates, other bursts and models make chiefly nuclei with A {approx} 64. The amount of carbon remaining after hydrogen-helium bursts is typically {approx}< 1% by mass, and decreases further as the ashes are periodically heated by subsequent bursts. For M = 3.5 x 10{sup -10} M{sub {circle_dot}} yr{sup -1} and solar metallicity, bursts are ignited in a hydrogen-free helium layer. At the base of this layer, up to 90% of the helium has already burned to carbon prior to the unstable ignition of the helium shell. These helium-ignited bursts have (a) briefer, brighter light curves with shorter tails; (b) very rapid rise times (< 0.1 s); and (c) ashes lighter than the iron group.

  1. 25 CFR 171.500 - How does BIA determine the annual operation and maintenance assessment rate for the irrigation...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... maintenance assessment rate for the irrigation facility servicing my farm unit? 171.500 Section 171.500 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER IRRIGATION OPERATION AND... annual operation and maintenance assessment rate for the irrigation facility servicing my farm unit?...

  2. 25 CFR 171.500 - How does BIA determine the annual operation and maintenance assessment rate for the irrigation...

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... maintenance assessment rate for the irrigation facility servicing my farm unit? 171.500 Section 171.500 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER IRRIGATION OPERATION AND... annual operation and maintenance assessment rate for the irrigation facility servicing my farm unit?...

  3. 25 CFR 171.500 - How does BIA determine the annual operation and maintenance assessment rate for the irrigation...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... maintenance assessment rate for the irrigation facility servicing my farm unit? 171.500 Section 171.500 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER IRRIGATION OPERATION AND... annual operation and maintenance assessment rate for the irrigation facility servicing my farm unit?...

  4. 25 CFR 171.500 - How does BIA determine the annual operation and maintenance assessment rate for the irrigation...

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... maintenance assessment rate for the irrigation facility servicing my farm unit? 171.500 Section 171.500 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER IRRIGATION OPERATION AND... annual operation and maintenance assessment rate for the irrigation facility servicing my farm unit?...

  5. 25 CFR 171.500 - How does BIA determine the annual operation and maintenance assessment rate for the irrigation...

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... maintenance assessment rate for the irrigation facility servicing my farm unit? 171.500 Section 171.500 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER IRRIGATION OPERATION AND... annual operation and maintenance assessment rate for the irrigation facility servicing my farm unit?...

  6. Detectors for alpha particles and X-rays operating in ambient air in pulse counting mode or/and with gas amplification

    NASA Astrophysics Data System (ADS)

    Charpak, G.; Benaben, P.; Breuil, P.; Peskov, V.

    2008-02-01

    Ionization chambers working in ambient air in current detection mode are attractive due to their simplicity and low cost and are widely used in several applications such as smoke detection, dosimetry, therapeutic beam monitoring and so on. The aim of this work was to investigate if gaseous detectors can operate in ambient air in pulse counting mode as well as with gas amplification which potentially offers the highest possible sensitivity in applications like alpha particle detection or high energy X-ray photon or electron detection. To investigate the feasibility of this method two types of open- end gaseous detectors were build and successfully tested. The first one was a single wire or multiwire cylindrical geometry detector operating in pulse mode at a gas gain of one (pulse ionization chamber). This detector was readout by a custom made wide -band charge sensitive amplifier able to deal with slow induced signals generated by slow motion of negative and positive ions. The multiwire detector was able to detect alpha particles with an efficiency close to 22%. The second type of an alpha detector was an innovative GEM-like detector with resistive electrodes operating in air in avalanche mode at high gas gains (up to 104). This detector can also operate in a cascaded mode or being combined with other detectors, for example with MICROMEGAS. This detector was readout by a conventional charge -sensitive amplifier and was able to detect alpha particles with 100% efficiency. This detector could also detect X-ray photons or fast electrons. A detailed comparison between these two detectors is given as well as a comparison with commercially available alpha detectors. The main advantages of gaseous detectors operating in air in a pulse detection mode are their simplicity, low cost and high sensitivity. One of the possible applications of these new detectors is alpha particle background monitors which, due to their low cost can find wide application not only in houses, but

  7. Bandwidth and repetition rate programmable Nyquist sinc-shaped pulse train source based on intensity modulators and four-wave mixing.

    PubMed

    Cordette, S; Vedadi, A; Shoaie, M A; Brès, C-S

    2014-12-01

    We propose and experimentally demonstrate an all-optical Nyquist sinc-shaped pulse train source based on intensity modulation and four-wave mixing. The proposed scheme allows for the tunability of the bandwidth and the full flexibility of the repetition rate in the limit of the electronic bandwidth of the modulators used through the flexible synthesis of rectangular frequency combs. Bandwidth up to 360 GHz at 40 GHz rate and up to 45 frequency lines at 5 GHz rate are demonstrated with 40 GHz modulators.

  8. A Miniature, High-Resolution Laser Radar Operating at Video Rates

    SciTech Connect

    SMITHPETER,COLIN L.; NELLUMS,ROBERT O.; LEBIEN,STEVEN M.; STUDOR,GEORGE

    2000-06-26

    The authors are developing a laser radar to meet the needs of NASA for a 5-lb, 150 in{sup 3} image sensor with a pixel range accuracy of 0.1-inch. NASA applications include structural dynamics measurements, navigation guidance in rendezvous and proximity operations, and space vehicle inspection. The sensor is based on the scannerless range imager architecture developed at Sandia. This architecture modulates laser floodlight illumination and a focal plane receiver to phase encode the laser time of flight (TOF) for each pixel. They believe this approach has significant advantages over architectures directly measuring TOF including high data rate, reduced detector bandwidth, and conventional FPA detection. A limitation of the phase detection technique is its periodic nature, which provides relative range information over a finite ambiguity interval. To extend the operating interval while maintaining a given range resolution, a LADAR sensor using dual modulation frequencies has been developed. This sensor also extends the relative range information to absolute range by calibrating a gating function on the receiver to the TOF. The modulation frequency values can be scaled to meet the resolution and range interval requirements of different applications. Results from the miniature NASA sensor illustrate the advantages of the dual-frequency operation and the ability to provide the range images of 640 by 480 pixels at 30 frames per second.

  9. Operation Behavior of a Multi-Candle Filter with Coupled Pressure Pulse Recleaning during Normal Operation and in the Case of a Filter Candle Failure

    SciTech Connect

    Mai, R.; Leibold, H. Seifert, H.; Heidenreich, S.; Haag, W.

    2002-09-18

    A pilot filter with the CPP recleaning system was installed and commissioned during the first half year of 2000 in ''PYDRA'', the pyrolytic rotary tube facility of the Institute for Technical Chemistry, Research Center Karlsruhe. The filter, with a rated throughput of 50 std.m{sup 3}/h, is equipped with two clusters of three filter candles each (DIA-SCHUMALITH{reg_sign} T 10-20, 1 = 1500 mm), and has been designed for a maximum operating temperature of 550 C. After commissioning, the filter was run in the stand-alone mode, first without pyrolysis, to filter sticky inorganic dust of the type which can arise in waste incineration in the temperature range above 400 C.

  10. Effect of Clearcutting Operations on the Survival Rate of a Small Mammal

    PubMed Central

    Escobar, Martín A. H.; Uribe, Sandra V.; Chiappe, Romina; Estades, Cristián F.

    2015-01-01

    Clearcutting is a common timber harvesting technique that represents a significant and abrupt change in habitat conditions for wildlife living in industrial forests. Most research on this type of impact has focused on comparing populations or communities in mature forests/plantations and the resulting clearcut stands. However, this approach does not separate the effect of changes in habitat attributes from direct mortality produced by the intensive use of heavy machinery required for cutting down trees and dragging them to a road. Because knowing the fate of individuals after a disturbance is important for modelling landscape-scale population dynamics in industrial forests, we conducted a study in South-Central Chile to understand the short-term response to clearcutting operations of the long-haired Akodont (Abrothrix longipillis), a forest specialist mouse. Between 2009 and 2013 we radiotracked a total of 51 adult male Akodonts, before, during and after the clearcutting of the pine plantations in which they lived. A minimum of 52.4% of the individuals died as a direct cause of the timbering operations, being crushed by vehicles or logs during logging operations. Our observations suggest that, instead of fleeing the area, the response of long-haired Akodonts to the approaching machinery is to hide under the forest litter or in burrows, which exposes them to a serious risk of death. The real mortality rate associated to clearcutting may be higher than that estimated by us because of some methodological biases (i.e. individuals with crushed radiotransmitters not recorded) and the fact that additional mortality sources may affect the population in the weeks following logging operations (e.g. higher exposure to predation, effects of site preparation for the new plantation, etc). PMID:25748217

  11. High-peak-power pulsed operation of 2.0 μm (AlGaIn)(AsSb) quantum-well ridge waveguide diode lasers

    NASA Astrophysics Data System (ADS)

    Eichhorn, M.; Rattunde, M.; Schmitz, J.; Kaufel, G.; Wagner, J.

    2006-03-01

    We have characterized 2.0 μm (aluminium-gallium-indium)(arsenide-antimonide) quantum-well diode lasers in pulsed operation (20-60 ns). A peak power of 1.25 W could be achieved. The near-field distribution on the output facet and the spectral output have been analyzed. Single transverse mode operation can only be maintained at low pulse currents. Above a certain current limit higher order modes occur and fluctuations between these modes have been resolved on a 10 ns time scale. The threshold for thermal and optical damage was investigated for ridge waveguide widths of 6, 8, and 16 μm. No systematic damage threshold could be determined up to current densities as high as 200 kA/cm2.

  12. Encoding of the amplitude modulation of pulsatile electrical stimulation in the feline cochlear nucleus by neurons in the inferior colliculus; effects of stimulus pulse rate

    NASA Astrophysics Data System (ADS)

    McCreery, Douglas; Han, Martin; Pikov, Victor; Yadav, Kamal; Pannu, Satinderpall

    2013-10-01

    Objectives. Persons without a functional auditory nerve cannot benefit from cochlear implants, but some hearing can be restored by an auditory brainstem implant (ABI) with stimulating electrodes implanted on the surface of the cochlear nucleus (CN). Most users benefit from their ABI, but speech recognition tends to be poorer than for users of cochlear implants. Psychophysical studies suggest that poor modulation detection may contribute to the limited performance of ABI users. In a cat model, we determined how the pulse rate of the electrical stimulus applied within or on the CN affects temporal and rate encoding of amplitude modulation (AM) by neurons in the central nucleus of the inferior colliculus (ICC). Approach. Stimulating microelectrodes were implanted chronically in and on the cats' CN, and multi-site recording microelectrodes were implanted chronically into the ICC. Encoding of AM pulse trains by neurons in the ICC was characterized as vector strength (VS), the synchrony of neural activity with the AM, and as the mean rate of neuronal action potentials (neuronal spike rate (NSR)). Main results. For intranuclear microstimulation, encoding of AM as VS was up to 3 dB greater when stimulus pulse rate was increased from 250 to 500 pps, but only for neuronal units with low best acoustic frequencies, and when the electrical stimulation was modulated at low frequencies (10-20 Hz). For stimulation on the surface of the CN, VS was similar at 250 and 500 pps, and the dynamic range of the VS was reduced for pulse rates greater than 250 pps. Modulation depth was encoded strongly as VS when the maximum stimulus amplitude was held constant across a range of modulation depth. This ‘constant maximum’ protocol allows enhancement of modulation depth while preserving overall dynamic range. However, modulation depth was not encoded as strongly as NSR. Significance. The findings have implications for improved sound processors for present and future ABIs. The performance of

  13. Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Martin, Adam; Polzin, Kurt; Kimberlin, Adam; Eskridge, Richard

    2013-01-01

    Fabricated and tested CTP IPPTs at cone angles of 20deg, 38deg, and 60deg, and performed direct single-pulse impulse bit measurements with continuous gas flow. Single pulse performance highest for 38deg angle with impulse bit of approx.1 mN-s for both argon and xenon. Estimated efficiencies low, but not unexpectedly so based on historical data trends and the direction of the force vector in the CTP. Capacitor charging system assembled to provide rapid recharging of capacitor bank, permitting repetition-rate operation. IPPT operated at repetition-rate of 5 Hz, at maximum average power of 2.5 kW, representing to our knowledge the highest average power for a repetitively-pulsed thruster. Average thrust in repetition-rate mode (at 5 kV, 75 sccm argon) was greater than simply multiplying the single-pulse impulse bit and the repetition rate.

  14. A PC-PCL-based control system for the high-voltage pulsed-power operation of the Intense Diagnostic Neutral Beam (IDNB) Experiment

    SciTech Connect

    Gribble, R.

    1993-06-01

    A stand-alone, semiautomated control system for the high-voltage pulsed-power energy sources on the Intense Diagnostic Neutral Beam Experiment at Los Alamos National Laboratory using personal computer (PC) and programmable logic controller (PLC) technology has been developed and implemented. The control system, consisting of a PC with the graphic operator interface, the network connecting the PC to the PLC, the PLC, the PLC I/O modules, fiber-optic interfaces and software, is described.

  15. Power Enhancement Cavity for Burst-Mode Laser Pulses

    SciTech Connect

    Liu, Yun

    2015-01-01

    We demonstrate a novel optical cavity scheme and locking method that can realize the power enhancement of picosecond UV laser pulses operating at a burst mode with arbitrary burst (macropulse) lengths and repetition rates.

  16. Supercontinuum generation at 1.55 μm in an all-normal dispersion photonic crystal fiber with high-repetition-rate picosecond pulses

    NASA Astrophysics Data System (ADS)

    Xu, Yong-zhao; Han, Tao; Song, Jian-xun; Ling, Dong-xiong; Li, Hong-tao

    2014-11-01

    We demonstrate the generation of supercontinuum (SC) spectrum covering S+C+L band of optical communication by injecting 1.4 ps optical pulses with center wavelength of 1 552 nm and repetition rate of 10 GHz into an all-normal dispersion photonic crystal fiber (PCF) with length of 80 m. The experimental results are in good agreement with the numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking (WB).

  17. 1 W average-power 100 MHz repetition-rate 259 nm femtosecond deep ultraviolet pulse generation from ytterbium fiber amplifier.

    PubMed

    Zhou, Xiangyu; Yoshitomi, Dai; Kobayashi, Yohei; Torizuka, Kenji

    2010-05-15

    We demonstrate 1W average-power ultraviolet (UV) femtosecond (fs) ultrashort pulse generation at a wavelength of 259 nm and a repetition rate as high as 100 MHz by quadrupling a fs ytterbium-fiber laser. A cavity-enhanced design is employed for efficient frequency doubling to the UV region. The optical-to-optical efficiency of UV output to the pump diode is 2.6%.

  18. Effect of aromatherapy with orange essential oil on salivary cortisol and pulse rate in children during dental treatment: A randomized controlled clinical trial

    PubMed Central

    Jafarzadeh, Mehdi; Arman, Soroor; Pour, Fatemeh Farahbakhsh

    2013-01-01

    Background: Essential oils have been used as an alternative and complementary treatment in medicine. Citrus fragrance has been used by aromatherapists for the treatment of anxiety symptoms. Based on this claim, the aim of present study was to investigate the effect of aromatherapy with essential oil of orange on child anxiety during dental treatment. Materials and Methods: Thirty children (10 boys, 20 girls) aged 6-9 years participated in a crossover intervention study, according to the inclusion criteria, among patients who attended the pediatric department of Isfahan Dental School in 2011. Every child underwent two dental treatment appointments including dental prophylaxis and fissure-sealant therapy under orange aroma in one session (intervention) and without any aroma (control) in another one. Child anxiety level was measured using salivary cortisol and pulse rate before and after treatment in each visit. The data were analyzed using t-test by SPSS software version 18. Results: The mean ± SD and mean difference of salivary cortisol levels and pulse rate were calculated in each group before and completion of treatment in each visit. The difference in means of salivary cortisol and pulse rate between treatment under orange odor and treatment without aroma was 1.047 ± 2.198 nmol/l and 6.73 ± 12.3 (in minutes), which was statistically significant using paired t-test (P = 0.014, P = 0.005, respectively). Conclusion: It seems that the use of aromatherapy with natural essential oil of orange could reduce salivary cortisol and pulse rate due to child anxiety state. PMID:23930255

  19. 1-J operation of monolithic composite ceramics with Yb:YAG thin layers: multi-TRAM at 10-Hz repetition rate and prospects for 100-Hz operation.

    PubMed

    Divoky, Martin; Tokita, Shigeki; Hwang, Sungin; Kawashima, Toshiyuki; Kan, Hirofumi; Lucianetti, Antonio; Mocek, Tomas; Kawanaka, Junji

    2015-03-15

    Experimental amplification of 10-ns pulses to energy of 1 J at repetition rate of 10-100 Hz in cryogenic multipass total-reflection active-mirror (TRAM) amplifier is reported for the first time. By using a monolithic multi-TRAM, which is a YAG ceramic composite with three thin Yb:YAG active layers, efficient energy extraction was achieved without parasitic lasing. A detailed measurement of output characteristics of the laser amplifier is presented; results are discussed and compared with numerical calculations.

  20. Influence of vacuum impregnation and pulsed electric field on the freezing temperature and ice propagation rates of spinach leaves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Efforts are currently directed towards improving the quality of sensitive tissues of fruits and vegetables after freezing and thawing. One of the methods under investigation is the combination of vacuum impregnation (VI) with cryoprotectants and pulsed electric field (PEF) applied to the plant tiss...