All solid-state high power visible laser

NASA Technical Reports Server (NTRS)

Grossman, William M.

1993-01-01

The overall objective of this Phase 2 effort was to develop and deliver to NASA a high repetition rate laser-diode-pumped solid-state pulsed laser system with output in the green portion of the spectrum. The laser is for use in data communications, and high efficiency, short pulses, and low timing jitter are important features. A short-pulse 1 micron laser oscillator, a new multi-pass amplifier to boost the infrared power, and a frequency doubler to take the amplified infrared pulsed laser light into the green. This produced 1.5 W of light in the visible at a pulse repetition rate of 20 kHz in the laboratory. The pulses have a full-width at half maximum of near 1 ns. The results of this program are being commercialized.

Multipass OPCPA system at 100 kHz pumped by a CPA-free solid-state amplifier.

PubMed

Ahrens, J; Prochnow, O; Binhammer, T; Lang, T; Schulz, B; Frede, M; Morgner, U

2016-04-18

We present a compact few-cycle 100 kHz OPCPA system pumped by a CPA-free picosecond Nd:YVO₄ solid-state amplifier with all-optical synchronization to an ultra-broadband Ti:sapphire oscillator. This pump approach shows an exceptional conversion rate into the second harmonic of almost 78%. Efficient parametric amplification was realized by a two stage double-pass scheme with following chirped mirror compressor. The amount of superfluorescence was measured by an optical cross-correlation. Pulses with a duration of 8.7 fs at energies of 18 µJ are demonstrated. Due to the peak power of 1.26 GW, this simple OPCPA approach forms an ideal high repetition rate driving source for high-order harmonic generation.

All-Fiber, Directly Chirped Laser Source for Chirped-Pulse-Amplification

NASA Astrophysics Data System (ADS)

Xin, Ran

Chirped-pulse-amplification (CPA) technology is widely used to produce ultra-short optical pulses (sub picosecond to femtoseconds) with high pulse energy. A chirped pulse laser source with flexible dispersion control is highly desirable as a CPA seed. This thesis presents an all-fiber, directly chirped laser source (DCLS) that produces nanosecond, linearly-chirped laser pulses at 1053 nm for seeding high energy CPA systems. DCLS produces a frequency chirp on an optical pulse through direct temporal phase modulation. DCLS provides programmable control for the temporal phase of the pulse, high pulse energy and diffraction-limited beam performance, which are beneficial for CPA systems. The DCLS concept is first described. Its key enabling technologies are identified and their experimental demonstration is presented. These include high-precision temporal phase control using an arbitrary waveform generator, multi-pass phase modulation to achieve high modulation depth, regenerative amplification in a fiber ring cavity and a negative feedback system that controls the amplifier cavity dynamics. A few technical challenges that arise from the multi-pass architecture are described and their solutions are presented, such as polarization management and gain-spectrum engineering in the DCLS fiber cavity. A DCLS has been built and its integration into a high energy OPCPA system is demonstrated. DCLS produces a 1-ns chirped pulse with a 3-nm bandwidth. The temporal phase and group delay dispersion on the DCLS output pulse is measured using temporal interferometry. The measured temporal phase has an ˜1000 rad amplitude and is close to a quadratic shape. The chirped pulse is amplified from 0.9 nJ to 76 mJ in an OPCPA system. The amplified pulse is compressed to close to its Fourier transform limit, producing an intensity autocorrelation trace with a 1.5-ps width. Direct compressed-pulse duration control by adjusting the phase modulation drive amplitude is demonstrated. Limitation to pulse compression is investigated using numerical simulation.

Compact CH4 sensor based on difference frequency mixing of diode lasers in quasi-phasematched LiNbO3

NASA Technical Reports Server (NTRS)

Lancaster, D. G.; Weidner, R.; Richter, D.; Tittel, F. K.; Limpert, J.

2000-01-01

A compact, portable and robust room temperature CH4 sensor is reported. By difference frequency mixing a 500 mW alpha-DFB diode laser at 1066 nm and an erbium-doped fiber amplified 1574 nm DFB diode laser in periodically poled lithium niobate up to 7 (mu)W of narrowband radiation at 3.3 microns is generated. Real-time monitoring of CH4 over a 7 day period using direct absorption in an open-path multipass cell (L = 36 m) demonstrates a detection precision of +/- 14 ppb.

Spaceborne radar interferometry for coastal DEM construction

USGS Publications Warehouse

Hong, S.-H.; Lee, C.-W.; Won, J.-S.; Kwoun, Oh-Ig; Lu, Z.

2005-01-01

Topographic features in coastal regions including tidal flats change more significantly than landmass, and are characterized by extremely low slopes. High precision DEMs are required to monitor dynamic changes in coastal topography. It is difficult to obtain coherent interferometric SAR pairs especially over tidal flats mainly because of variation of tidal conditions. Here we focus on i) coherence of multi-pass ERS SAR interferometric pairs and ii) DEM construction from ERS-ENVISAT pairs. Coherences of multi-pass ERS interferograms were good enough to construct DEM under favorable tidal conditions. Coherence in sand dominant area was generally higher than that in muddy surface. The coarse grained coastal areas are favorable for multi-pass interferometry. Utilization of ERS-ENVISAT interferometric pairs is taken a growing interest. We carried out investigation using a cross-interferometric pair with a normal baseline of about 1.3 km, a 30 minutes temporal separation and the height sensitivity of about 6 meters. Preliminary results of ERS-ENVISAT interferometry were not successful due to baseline and unfavorable scattering conditions. ?? 2005 IEEE.

First results of electron temperature measurements by the use of multi-pass Thomson scattering system in GAMMA 10

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

Yoshikawa, M., E-mail: yosikawa@prc.tsukuba.ac.jp; Nagasu, K.; Shimamura, Y.

2014-11-15

A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system.

First results of electron temperature measurements by the use of multi-pass Thomson scattering system in GAMMA 10.

PubMed

Yoshikawa, M; Yasuhara, R; Nagasu, K; Shimamura, Y; Shima, Y; Kohagura, J; Sakamoto, M; Nakashima, Y; Imai, T; Ichimura, M; Yamada, I; Funaba, H; Kawahata, K; Minami, T

2014-11-01

A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system.

Using expected sequence features to improve basecalling accuracy of amplicon pyrosequencing data.

PubMed

Rask, Thomas S; Petersen, Bent; Chen, Donald S; Day, Karen P; Pedersen, Anders Gorm

2016-04-22

Amplicon pyrosequencing targets a known genetic region and thus inherently produces reads highly anticipated to have certain features, such as conserved nucleotide sequence, and in the case of protein coding DNA, an open reading frame. Pyrosequencing errors, consisting mainly of nucleotide insertions and deletions, are on the other hand likely to disrupt open reading frames. Such an inverse relationship between errors and expectation based on prior knowledge can be used advantageously to guide the process known as basecalling, i.e. the inference of nucleotide sequence from raw sequencing data. The new basecalling method described here, named Multipass, implements a probabilistic framework for working with the raw flowgrams obtained by pyrosequencing. For each sequence variant Multipass calculates the likelihood and nucleotide sequence of several most likely sequences given the flowgram data. This probabilistic approach enables integration of basecalling into a larger model where other parameters can be incorporated, such as the likelihood for observing a full-length open reading frame at the targeted region. We apply the method to 454 amplicon pyrosequencing data obtained from a malaria virulence gene family, where Multipass generates 20 % more error-free sequences than current state of the art methods, and provides sequence characteristics that allow generation of a set of high confidence error-free sequences. This novel method can be used to increase accuracy of existing and future amplicon sequencing data, particularly where extensive prior knowledge is available about the obtained sequences, for example in analysis of the immunoglobulin VDJ region where Multipass can be combined with a model for the known recombining germline genes. Multipass is available for Roche 454 data at http://www.cbs.dtu.dk/services/MultiPass-1.0 , and the concept can potentially be implemented for other sequencing technologies as well.

Correlation Between Microstructure and Low-Temperature Impact Toughness of Simulated Reheated Zones in the Multi-pass Weld Metal of High-Strength Steel

NASA Astrophysics Data System (ADS)

Kang, Yongjoon; Park, Gitae; Jeong, Seonghoon; Lee, Changhee

2018-01-01

A large fraction of reheated weld metal is formed during multi-pass welding, which significantly affects the mechanical properties (especially toughness) of welded structures. In this study, the low-temperature toughness of the simulated reheated zone in multi-pass weld metal was evaluated and compared to that of the as-deposited zone using microstructural analyses. Two kinds of high-strength steel welds with different hardenabilities were produced by single-pass, bead-in-groove welding, and both welds were thermally cycled to peak temperatures above Ac3 using a Gleeble simulator. When the weld metals were reheated, their toughness deteriorated in response to the increase in the fraction of detrimental microstructural components, i.e., grain boundary ferrite and coalesced bainite in the weld metals with low and high hardenabilities, respectively. In addition, toughness deterioration occurred in conjunction with an increase in the effective grain size, which was attributed to the decrease in nucleation probability of acicular ferrite; the main cause for this decrease changed depending on the hardenability of the weld metal.

An evaluation of multipass electrofishing for estimating the abundance of stream-dwelling salmonids

Treesearch

James T. Peterson; Russell F. Thurow; John W. Guzevich

2004-01-01

Failure to estimate capture efficiency, defined as the probability of capturing individual fish, can introduce a systematic error or bias into estimates of fish abundance. We evaluated the efficacy of multipass electrofishing removal methods for estimating fish abundance by comparing estimates of capture efficiency from multipass removal estimates to capture...

Welding arc and plasma studies using real time, multipass holographic interferometry

NASA Technical Reports Server (NTRS)

Deason, Vance

1987-01-01

Flow visualization of the plasma process in a welding arc is being studied with a multipass Argon ion interferometer. High speed movies at 10,000 frames per/sec are taken. The multipass interferometer and several interferograms of the plasma near the electrode of the welding are given. Digitization of the fringes is currently done by hand.

Regenerative Amplification of Femtosecond Pulses: Design andConstruction of a sub-100fs, muon J Laser System

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

Schumacher, Andreas B.

1996-10-01

Femtosecond lasers are a powerful tool for a wealth of applications in physics, chemistry and biology. In most cases, however, their use is fundamentally restricted to a rather narrow spectral range. This thesis deals with the construction and characterization of a femtosecond light source for spectroscopic applications which overcomes that restriction. It is demonstrated how the output of a continuously pumped Ti:sapphire femtosecond oscillator is amplified to the μJ level,while the pulse duration remains below 100 fs. A combination of continuous pumping, acousto-optic switching and Ti:Al 2O 3 as a gain medium allows amplification at high repetition rates. By focusingmore » the high energy pulses into a sapphire crystal, a broad-band continuum can be generated, extended in wavelengths over several hundred nanometers. To accomplish amplification of three orders of magnitude while maintaining the pulse length, a regenerative multipass amplifier system was built. The thesis describes theoretical design, realization and characterization of the system. Theoretical calculations and preliminary measurements were carried out and allow a critical evaluation of the final performance.« less

Interband cascade laser-based ppbv-level mid-infrared methane detection using two digital lock-in amplifier schemes

NASA Astrophysics Data System (ADS)

Song, Fang; Zheng, Chuantao; Yu, Di; Zhou, Yanwen; Yan, Wanhong; Ye, Weilin; Zhang, Yu; Wang, Yiding; Tittel, Frank K.

2018-03-01

A parts-per-billion in volume (ppbv) level mid-infrared methane (CH4) sensor system was demonstrated using second-harmonic wavelength modulation spectroscopy (2 f-WMS). A 3291 nm interband cascade laser (ICL) and a multi-pass gas cell (MPGC) with a 16 m optical path length were adopted in the reported sensor system. Two digital lock-in amplifier (DLIA) schemes, a digital signal processor (DSP)-based DLIA and a LabVIEW-based DLIA, were used for harmonic signal extraction. A limit of detection (LoD) of 13.07 ppbv with an averaging time of 2 s was achieved using the DSP-based DLIA and a LoD of 5.84 ppbv was obtained using the LabVIEW-based DLIA with the same averaging time. A rise time of 0→2 parts-per-million in volume (ppmv) and fall time of 2→0 ppmv were observed. Outdoor atmospheric CH4 concentration measurements were carried out to evaluate the sensor performance using the two DLIA schemes.

Development of SiC Nanoparticles and Second Phases Synergistically Reinforced Mg-Based Composites Processed by Multi-Pass Forging with Varying Temperatures

PubMed Central

Nie, Kaibo; Guo, Yachao; Deng, Kunkun; Wang, Xiaojun; Wu, Kun

2018-01-01

In this study, SiC nanoparticles were added into matrix alloy through a combination of semisolid stirring and ultrasonic vibration while dynamic precipitation of second phases was obtained through multi-pass forging with varying temperatures. During single-pass forging of the present composite, as the deformation temperature increased, the extent of recrystallization increased, and grains were refined due to the inhibition effect of the increasing amount of dispersed SiC nanoparticles. A small amount of twins within the SiC nanoparticle dense zone could be found while the precipitated phases of Mg17Al12 in long strips and deformation bands with high density dislocations were formed in the particle sparse zone after single-pass forging at 350 °C. This indicated that the particle sparse zone was mainly deformed by dislocation slip while the nanoparticle dense zone may have been deformed by twinning. The yield strength and ultimate tensile strength of the composites were gradually enhanced through increasing the single-pass forging temperature from 300 °C to 400 °C, which demonstrated that initial high forging temperature contributed to the improvement of the mechanical properties. During multi-pass forging with varying temperatures, the grain size of the composite was gradually decreased while the grain size distribution tended to be uniform with reducing the deformation temperature and extending the forging passes. In addition, the amount of precipitated second phases was significantly increased compared with that after multi-pass forging under a constant temperature. The improvement in the yield strength of the developed composite was related to grain refinement strengthening and Orowan strengthening resulting from synergistical effect of the externally applied SiC nanoparticles and internally precipitated second phases. PMID:29342883

Development of SiC Nanoparticles and Second Phases Synergistically Reinforced Mg-Based Composites Processed by Multi-Pass Forging with Varying Temperatures.

PubMed

Nie, Kaibo; Guo, Yachao; Deng, Kunkun; Wang, Xiaojun; Wu, Kun

2018-01-13

In this study, SiC nanoparticles were added into matrix alloy through a combination of semisolid stirring and ultrasonic vibration while dynamic precipitation of second phases was obtained through multi-pass forging with varying temperatures. During single-pass forging of the present composite, as the deformation temperature increased, the extent of recrystallization increased, and grains were refined due to the inhibition effect of the increasing amount of dispersed SiC nanoparticles. A small amount of twins within the SiC nanoparticle dense zone could be found while the precipitated phases of Mg 17 Al 12 in long strips and deformation bands with high density dislocations were formed in the particle sparse zone after single-pass forging at 350 °C. This indicated that the particle sparse zone was mainly deformed by dislocation slip while the nanoparticle dense zone may have been deformed by twinning. The yield strength and ultimate tensile strength of the composites were gradually enhanced through increasing the single-pass forging temperature from 300 °C to 400 °C, which demonstrated that initial high forging temperature contributed to the improvement of the mechanical properties. During multi-pass forging with varying temperatures, the grain size of the composite was gradually decreased while the grain size distribution tended to be uniform with reducing the deformation temperature and extending the forging passes. In addition, the amount of precipitated second phases was significantly increased compared with that after multi-pass forging under a constant temperature. The improvement in the yield strength of the developed composite was related to grain refinement strengthening and Orowan strengthening resulting from synergistical effect of the externally applied SiC nanoparticles and internally precipitated second phases.

Multipass optical device and process for gas and analyte determination

DOEpatents

Bernacki, Bruce E [Kennewick, WA

2011-01-25

A torus multipass optical device and method are described that provide for trace level determination of gases and gas-phase analytes. The torus device includes an optical cavity defined by at least one ring mirror. The mirror delivers optical power in at least a radial and axial direction and propagates light in a multipass optical path of a predefined path length.

High-efficiency cyrogenic-cooled diode-pumped amplifier with relay imaging for nanosecond pulses

NASA Astrophysics Data System (ADS)

Körner, J.; Hein, J.; Kahle, M.; Liebetrau, H.; Kaluza, M.; Siebold, M.; Loeser, M.

2011-06-01

We present temperature dependent gain measurements with different Ytterbium doped laser media, such as Yb:YAG, Yb:FP15-glass and Yb:CaF2 in a multi-pass amplifier setup. The temperature of these materials was adjusted arbitrarily between 100K and 300K, while heat removal was realized by transverse cooling. In order to obtain a good beam profile throughout the amplification process, we used an all-mirror based relay imaging setup consisting of a telescope accomplishing a 4f-imaging with a plane mirror in each image plane. The amplification beam is then coupled into the cavity and doing several round trips wandering over the surface of the spherical mirrors. Hence the laser material is placed in one of the image planes, the beam quality of the amplifier was ruled by the intensity profile of the pumping laser diodes consisting of two stacks with 2.5kW peak output power each. Due to the given damage threshold fluence, the output energy of the amplifier was limited to about 1J at a beam diameter of 4.5 mm (FWHM). The seed pulses with a duration of 6 ns were generated in a Yb:FP15-glass cavity dumped oscillator with further amplification up to the 100mJ level by a room temperature Yb:YAG multi pass amplifier. The 1 Hz repetition rate of the system was limited by the repetition rate of the front-end. With Yb:YAG for instance an output energy of 1.1 J with an record high optical to optical efficiency of more than 35% was achieved, which was further increased to 45% for 500 mJ output energy.

A cryo-cooled high-energy DPSSL system delivering ns-pulses at 10 J and 10 Hz

NASA Astrophysics Data System (ADS)

Ertel, Klaus; Banerjee, Saumyabrata; Butcher, Thomas J.; De Vido, Mariastefania; Mason, Paul D.; Phillips, P. J.; Richards, David; Shaikh, Waseem; Smith, Jodie M.; Greenhalgh, R. Justin S.; Hernandez-Gomez, Cristina; Collier, John L.

2015-02-01

Lasers generating multi-J to kJ ns-pulses are required for many types of laser-plasma interactions. Such lasers are either used directly for compressing matter to extreme densities or they serve as pump lasers for short-pulses laser chains based on large-aperture Ti:sapphire or parametric amplifiers. The thus generated high-energy fs-pulses are most useful for laser driven secondary sources of particles (electrons, protons) or photons (from THz to gamma). While proof-of-principle experiments have been carried out with flashlamp-pumped glass lasers, lasers with much higher efficiency and repetition rate are required to make this applications practically viable. We have developed a scalable new laser concept called DiPOLE (diode pumped optical laser for experiments) based on a gas-cooled ceramic Yb:YAG multi-slab architecture operating at cryogenic temperatures. While the viability of this concept has been shown earlier [1], we have now reached our target performance of 10 J pulse energy at 10 Hz repetition rate at an optical-to-optical efficiency of 21%. To the best of our knowledge, these are record values for average power and efficiency for lasers of this type. We have also upgraded the system by adding a fibre-based front-end system with arbitrary pulse shaping capability and by installing an image-relayed multipass system enabling up to eight passes of the main amplifier. We have then used this system to demonstrate frequency doubling with 65 % conversion efficiency and a long-term shot-to-shot stability of 0.5% rms over a total of nearly 2 million shots, achieved in runs extending over 4 to 6 hours.

Characterization of Microstructure and Texture of 13Cr4Ni Martensitic Stainless Steel Weld Before and After Tempering =

NASA Astrophysics Data System (ADS)

Mokhtabad Amrei, Mohsen

13Cr4Ni martensitic stainless steels are known for their outstanding performances in the hydroelectric industry, where they are mainly used in the construction of turbine components. Considering the size and geometry of turbine runners and blades, multi-pass welding procedures are commonly used in the fabrication and repair of such turbines. The final microstructure and mechanical properties of the weld are sensitive to the welding process parameters and thermal history. In the case of 13Cr4Ni steel, the thermal cycles imposed by the multi-pass welding operation have significant effects on the complex weld microstructure. Additionally, post-weld heat treatments are commonly used to reduce weld heterogeneity and improve the material's mechanical properties by tempering the microstructure and by forming a "room-temperature-stable austenite." In the first phase of this research, the microstructures and crystallographic textures of aswelded single-pass and double-pass welds were studied as a basis to studying the more complex multi-pass weld microstructure. This study found that the maximum hardness is obtained in high temperature heat affected zone inside the base metal. In particular, the results showed that the heat cycle exposed by the second pass increases the hardness of the previous pass because it produces a finer martensite microstructure. In areas of heat affected zone, a tempering effect is reported from 3 up to 6 millimeters far from the fusion line. Finding austenite phase in these areas are matter of interest and it can be indicative of the microstructure complexity of multi-pass welds. In the second phase of research, the microstructure of multi-pass welds was found to be more heterogeneous than that of single- and double-pass welds. Any individual pass in a multi-pass weld consists of several regions formed by adjacent weld passes heat cycle. Results showed that former austenite grains modification occurred in areas close to the subsequent weld passes. Furthermore, low angle interface laths were observed inside martensite sub-blocks over different regions. The hardness profile of a multi-pass weld was explained by the overlaying heat effects of surrounding passes. In some regions, a tempered matrix was observed, while in other regions a double-quenched microstructure was found. The final aspect of this study focused on the effects of post-weld heat treatments on reformed austenite and carbide formations, and evolution of hardness. The effects of tempering duration and temperature on microstructure were investigated. The study found that nanometer-sized carbides form at martensite lath interfaces and sub-block boundaries. Additionally, it was determined that for any holding duration, the maximum austenite percentage is achievable by tempering at 610 °C. Similarly, the maximum softening was reported for tempering at 610 °C, for any given holding period.

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

Bogacz, Alex

We summarize the current state of a concept for muon acceleration aimed at a future Neutrino Factory and extendable to Higgs Factory. The main thrust of these studies was to reduce the overall cost while maintaining performance by exploring the interplay between the complexity of the cooling systems and the acceptance of the accelerator complex. To ensure adequate survival for the short-lived muons, acceleration must occur at high average gradient. The need for large transverse and longitudinal acceptances drives the design of the acceleration system to an initially low RF frequency, e.g., 325 MHz, which is then increased to 650more » MHz as the transverse size shrinks with increasing energy. High-gradient normal conducting RF cavities at these frequencies require extremely high peak-power RF sources. Hence superconducting RF (SRF) cavities are chosen. We consider an SRF-efficient design based on a multi-pass (4.5) ?dogbone? RLA, extendable to multi-pass FFAG-like arcs.« less

The defects and microstructure in the fusion zone of multipass laser welded joints with Inconel 52M filler wire for nuclear power plants

NASA Astrophysics Data System (ADS)

Li, Gang; Lu, Xiaofeng; Zhu, Xiaolei; Huang, Jian; Liu, Luwei; Wu, Yixiong

2017-09-01

The defects and microstructure in the fusion zone of multipass laser welded joints with Inconel 52M filler wire are investigated for nuclear power plants. Experimental results indicate that the incomplete fusion forms as the deposited metals do not completely cover the groove during multipass laser welding. The dendritic morphologies are observed on the inner surface of the porosity in the fusion zone. Many small cellular are found in the zones near the fusion boundary. With solidification preceding, cellular gradually turn into columnar dendrites and symmetrical columnar dendrites are exhibited in the weld center of the fusion zone. The fine equiaxed grains form and columnar dendrites disappear in the remelted zone of two passes. The dendrite arm spacing in the fusion zone becomes widened with increasing welding heat input. Nb-rich carbides/carbonitrides are preferentially precipitated in the fusion zone of multipass laser welded joints. In respect to high cooling rate during multipass laser welding, element segregation could be insufficient to achieve the component of Laves phase.

Design Concept for a Compact ERL to Drive a VUV/Soft X-Ray FEL

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

Christopher Tennant ,David Douglas

2011-03-01

We explore possible upgrades of the existing Jefferson Laboratory IR/UV FEL driver to higher electron beam energy and shorter wavelength through use of multipass recirculation to drive an amplifier FEL. The system would require beam energy at the wiggler of 600 MeV with 1 mA of average current. The system must generate a high brightness beam, configure it appropriately, and preserve beam quality through the acceleration cycle ? including multiple recirculations ? and appropriately manage the phase space during energy recovery. The paper will discuss preliminary design analysis of the longitudinal match, space charge effects in the linac, and recirculatormore » design issues, including the potential for the microbunching instability. A design concept for the low energy recirculator and an emittance preserving lattice solution will be presented.« less

Demonstration of improvement in the signal-to-noise ratio of Thomson scattering signal obtained by using a multi-pass optical cavity on the Tokyo Spherical Tokamak-2

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

Togashi, H., E-mail: togashi@fusion.k.u-tokyo.ac.jp; Ejiri, A.; Nakamura, K.

2014-11-15

The multi-pass Thomson scattering (TS) scheme enables obtaining many photons by accumulating multiple TS signals. The signal-to-noise ratio (SNR) depends on the accumulation number. In this study, we performed multi-pass TS measurements for ohmically heated plasmas, and the relationship between SNR and the accumulation number was investigated. As a result, improvement of SNR in this experiment indicated similar tendency to that calculated for the background noise dominant situation.

Laser Amplifier Development for the Remote Sensing of CO2 from Space

NASA Technical Reports Server (NTRS)

Yu, Anthony W.; Abshire, James B.; Storm, Mark; Betin, Alexander

2015-01-01

Accurate global measurements of tropospheric CO2 mixing ratios are needed to study CO2 emissions and CO2 exchange with the land and oceans. NASA Goddard Space Flight Center (GSFC) is developing a pulsed lidar approach for an integrated path differential absorption (IPDA) lidar to allow global measurements of atmospheric CO2 column densities from space. Our group has developed, and successfully flown, an airborne pulsed lidar instrument that uses two tunable pulsed laser transmitters allowing simultaneous measurement of a single CO2 absorption line in the 1570 nm band, absorption of an O2 line pair in the oxygen A-band (765 nm), range, and atmospheric backscatter profiles in the same path. Both lasers are pulsed at 10 kHz, and the two absorption line regions are sampled at typically a 300 Hz rate. A space-based version of this lidar must have a much larger lidar power-area product due to the approximately x40 longer range and faster along track velocity compared to airborne instrument. Initial link budget analysis indicated that for a 400 km orbit, a 1.5 m diameter telescope and a 10 second integration time, a approximately 2 mJ laser energy is required to attain the precision needed for each measurement. To meet this energy requirement, we have pursued parallel power scaling efforts to enable space-based lidar measurement of CO2 concentrations. These included a multiple aperture approach consists of multi-element large mode area fiber amplifiers and a single-aperture approach consists of a multi-pass Er:Yb:Phosphate glass based planar waveguide amplifier (PWA). In this paper we will present our laser amplifier design approaches and preliminary results.

Three-dimensional flow characteristics of aluminum alloy in multi-pass equal channel angular pressing

NASA Astrophysics Data System (ADS)

Jin, Young-Gwan; Son, Il-Heon; Im, Yong-Taek

2010-06-01

Experiments with a square specimen made of commercially pure aluminum alloy (AA1050) were conducted to investigate deformation behaviour during a multi-pass Equal Channel Angular Pressing (ECAP) for routes A, Bc, and C up to four passes. Three-dimensional finite element numerical simulations of the multi-pass ECAP were carried out in order to evaluate the influence of processing routes and number of passes on local flow behaviour by applying a simplified saturation model of flow stress under an isothermal condition. Simulation results were investigated by comparing them with the experimentally measured data in terms of load variations and microhardness distributions. Also, transmission electron microscopy analysis was employed to investigate the microstructural changes. The present work clearly shows that the three-dimensional flow characteristics of the deformed specimen were dependent on the strain path changes due to the processing routes and number of passes that occurred during the multi-pass ECAP.

Optical Magnetometry using Multipass Cells with overlapping beams

NASA Astrophysics Data System (ADS)

McDonough, Nathaniel David; Lucivero, Vito Giovanni; Dural, Nezih; Romalis, Michael

2017-04-01

In recent years, multipass cells with cylindrical mirrors have proven to be a successful way of making highly sensitive atomic magnetometers. In such cells a small laser beam makes 40 to 100 passes within the cell without significant overlap with itself. Here we describe a new multi-pass geometry which uses spherical mirrors to reflect the probe beam multiple times over the same cell region. Such geometry reduces the effects of atomic diffusion while preserving the advantages of multi-pass cells over standing-wave cavities, namely a deterministic number of passes and absence of interference. We have fabricated several cells with this geometry and obtained good agreement between the measured and calculated levels of quantum spin noise. We will report on our effort to characterize the diffusion spin-correlation function in these cells and operation of the cell as a magnetometer. This work is supported by DARPA.

Multipass holographic interferometer improves image resolution

NASA Technical Reports Server (NTRS)

Brooks, R. E.; Heflinger, L. O.

1970-01-01

Multipass holographic interferometer forms a hologram of high diffraction efficiency, and hence provides a bright and high contrast interferogram. It is used to study any effect which changes the index of refraction and to study surface deformations of a flat reflecting surface.

Dual quantum cascade laser-based sensor for simultaneous NO and NO2 detection using a wavelength modulation-division multiplexing technique

NASA Astrophysics Data System (ADS)

Yu, Yajun; Sanchez, Nancy P.; Yi, Fan; Zheng, Chuantao; Ye, Weilin; Wu, Hongpeng; Griffin, Robert J.; Tittel, Frank K.

2017-05-01

A sensor system capable of simultaneous measurements of NO and NO2 was developed using a wavelength modulation-division multiplexing (WMDM) scheme and multi-pass absorption spectroscopy. A continuous wave (CW), distributed-feedback (DFB) quantum cascade laser (QCL) and a CW external-cavity (EC) QCL were employed for targeting a NO absorption doublet at 1900.075 cm-1 and a NO2 absorption line at 1630.33 cm-1, respectively. Simultaneous detection was realized by modulating both QCLs independently at different frequencies and demodulating the detector signals with LabView-programmed lock-in amplifiers. The sensor operated at a reduced pressure of 40 Torr and a data sampling rate of 1 Hz. An Allan-Werle deviation analysis indicated that the minimum detection limits of NO and NO2 can reach sub-ppbv concentration levels with averaging times of 100 and 200 s, respectively.

System Modeling of kJ-class Petawatt Lasers at LLNL

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

Shverdin, M Y; Rushford, M; Henesian, M A

2010-04-14

Advanced Radiographic Capability (ARC) project at the National Ignition Facility (NIF) is designed to produce energetic, ultrafast x-rays in the range of 70-100 keV for backlighting NIF targets. The chirped pulse amplification (CPA) laser system will deliver kilo-Joule pulses at an adjustable pulse duration from 1 ps to 50 ps. System complexity requires sophisticated simulation and modeling tools for design, performance prediction, and comprehension of experimental results. We provide a brief overview of ARC, present our main modeling tools, and describe important performance predictions. The laser system (Fig. 1) consists of an all-fiber front end, including chirped-fiber Bragg grating (CFBG)more » stretchers. The beam after the final fiber amplifier is split into two apertures and spatially shaped. The split beam first seeds a regenerative amplifier and is then amplified in a multi-pass Nd:glass amplifier. Next, the preamplified chirped pulse is split in time into four identical replicas and injected into one NIF Quad. At the output of the NIF beamline, each of the eight amplified pulses is compressed in an individual, folded, four-grating compressor. Compressor grating pairs have slightly different groove densities to enable compact folding geometry and eliminate adjacent beam cross-talk. Pulse duration is adjustable with a small, rack-mounted compressor in the front-end. We use non-sequential ray-tracing software, FRED for design and layout of the optical system. Currently, our FRED model includes all of the optical components from the output of the fiber front end to the target center (Fig. 2). CAD designed opto-mechanical components are imported into our FRED model to provide a complete system description. In addition to incoherent ray tracing and scattering analysis, FRED uses Gaussian beam decomposition to model coherent beam propagation. Neglecting nonlinear effects, we can obtain a nearly complete frequency domain description of the ARC beam at different stages in the system. We employ 3D Fourier based propagation codes: MIRO, Virtual Beamline (VBL), and PROP for time-domain pulse analysis. These codes simulate nonlinear effects, calculate near and far field beam profiles, and account for amplifier gain. Verification of correct system set-up is a major difficulty to using these codes. VBL and PROP predictions have been extensively benchmarked to NIF experiments, and the verified descriptions of specific NIF beamlines are used for ARC. MIRO has the added capability of treating bandwidth specific effects of CPA. A sample MIRO model of the NIF beamline is shown in Fig. 3. MIRO models are benchmarked to VBL and PROP in the narrow bandwidth mode. Developing a variety of simulation tools allows us to cross-check predictions of different models and gain confidence in their fidelity. Preliminary experiments, currently in progress, are allowing us to validate and refine our models, and help guide future experimental campaigns.« less

Resist heating effect on e-beam mask writing at 75 kV and 60 A/cm2

NASA Astrophysics Data System (ADS)

Benes, Zdenek; Deverich, Christina; Huang, Chester; Lawliss, Mark

2003-12-01

Resist heating has been known to be one of the main contributors to local CD variation in mask patterning using variable shape e-beam tools. Increasingly complex mask patterns require increased number of shapes which drives the need for higher electron beam current densities to maintain reasonable write times. As beam current density is increased, CD error resulting from resist heating may become a dominating contributor to local CD variations. In this experimental study, the IBM EL4+ mask writer with high voltage and high current density has been used to quantitatively investigate the effect of resist heating on the local CD uniformity. ZEP 7000 and several chemically amplified resists have been evaluated under various exposure conditions (single-pass, multi-pass, variable spot size) and pattern densities. Patterns were designed specifically to allow easy measurement of local CD variations with write strategies designed to maximize the effect of resist heating. Local CD variations as high as 15 nm in 18.75 × 18.75 μm sub-field size have been observed for ZEP 7000 in a single-pass writing with full 1000 nm spots at 50% pattern density. This number can be reduced by increasing the number of passes or by decreasing the maximum spot size. The local CD variation has been reduced to as low as 2 nm for ZEP 7000 for the same pattern under modified exposure conditions. The effectiveness of various writing strategies is discussed as well as their possible deficiencies. Minimal or no resist heating effects have been observed for the chemically amplified resists studied. The results suggest that the resist heating effect can be well controlled by careful selection of the resist/process system and/or writing strategy and that resist heating does not have to pose a problem for high throughput e-beam mask making that requires high voltage and high current densities.

Factors affecting the strength of multipass low-alloy steel weld metal

NASA Technical Reports Server (NTRS)

Krantz, B. M.

1972-01-01

The mechanical properties of multipass high-strength steel weld metals depend upon several factors, among the most important being: (1) The interaction between the alloy composition and weld metal cooling rate which determines the as-deposited microstructure; and (2) the thermal effects of subsequent passes on each underlying pass which alter the original microstructure. The bulk properties of a multipass weld are therefore governed by both the initial microstructure of each weld pass and its subsequent thermal history. Data obtained for a high strength low alloy steel weld metal confirmed that a simple correlation exists between mechanical properties and welding conditions if the latter are in turn correlated as weld cooling rate.

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

Bogacz, Slawomir Alex

Here, we summarize current state of concept for muon acceleration aimed at future Neutrino Factory. The main thrust of these studies was to reduce the overall cost while maintaining performance through exploring interplay between complexity of the cooling systems and the acceptance of the accelerator complex. To ensure adequate survival of the short-lived muons, acceleration must occur at high average gradient. The need for large transverse and longitudinal acceptances drives the design of the acceleration system to initially low RF frequency, e.g. 325 MHz, and then increased to 650 MHz, as the transverse size shrinks with increasing energy. High-gradient normalmore » conducting RF cavities at these frequencies require extremely high peak-power RF sources. Hence superconducting RF (SRF) cavities are chosen. Here, we considered two cost effective schemes for accelerating muon beams for a stagable Neutrino Factory: Exploration of the so-called 'dual-use' linac concept, where the same linac structure is used for acceleration of both H- and muons and alternatively, the SRF efficient design based on multi-pass (4.5) 'dogbone' RLA, extendable to multi-pass FFAG-like arcs.« less

A study of narrow gap laser welding for thick plates using the multi-layer and multi-pass method

NASA Astrophysics Data System (ADS)

Li, Ruoyang; Wang, Tianjiao; Wang, Chunming; Yan, Fei; Shao, Xinyu; Hu, Xiyuan; Li, Jianmin

2014-12-01

This paper details a new method that combines laser autogenous welding, laser wire filling welding and hybrid laser-GMAW welding to weld 30 mm thick plate using a multi-layer, multi-pass process. A “Y” shaped groove was used to create the joint. Research was also performed to optimize the groove size and the processing parameters. Laser autogenous welding is first used to create the backing weld. The lower, narrowest part of the groove is then welded using laser wire filling welding. Finally, the upper part of the groove is welded using laser-GMAW hybrid welding. Additionally, the wire feeding and droplet transfer behaviors are observed by high speed photography. The two main conclusions from this work are: the wire is often biased towards the side walls, resulting in a lack of fusion at the joint and the creation of other defects for larger groove sizes. Additionally, this results in the droplet transfer behavior becoming unstable, leading to a poor weld appearance for smaller groove sizes.

Laser multipass system with interior cell configuration.

PubMed

Borysow, Jacek; Kostinski, Alexander; Fink, Manfred

2011-10-20

We ask whether it is possible to restore a multipass system alignment after a gas cell is inserted in the central region. Indeed, it is possible, and we report on a remarkably simple rearrangement of a laser multipass system, composed of two spherical mirrors and a gas cell with flat windows in the middle. For example, for a window of thickness d and refractive index of n, adjusting the mirror separation by ≈2d(1-1/n) is sufficient to preserve the laser beam alignment and tracing. This expression is in agreement with ray-tracing computations and our laboratory experiment. Insofar as our solution corrects for spherical aberrations, it may also find applications in microscopy. © 2011 Optical Society of America

Fiber optic coupled multipass gas minicell, design assembly thereof

DOEpatents

Bond, Tiziana C.; Bora, Mihail; Engel, Michael A.; McCarrick, James F.; Moran, Bryan D.

2016-01-12

A method directs a gas of interest into a minicell and uses an emitting laser to produce laser emission light that is directed into the minicell and onto the gas of interest. The laser emission light is reflected within the cell to make multipasses through the gas of interest. After the multipasses through the gas of interest the laser light is analyzed to produces gas spectroscopy data. The minicell receives the gas of interest and a transmitting optic connected to the minicell that directs a beam into the minicell and onto the gas of interest. A receiving optic connected to the minicell receives the beam from the gas of interest and directs the beam to an analyzer that produces gas spectroscopy data.

CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

NASA Astrophysics Data System (ADS)

Nowak, K. M.; Ohta, T.; Suganuma, T.; Fujimoto, J.; Mizoguchi, H.; Sumitani, A.; Endo, A.

2013-12-01

It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers.

Multipass reconfiguration of the HELEN Nd:glass laser at the Atomic Weapons Establishment.

PubMed

Norman, Michael J; Andrew, James E; Bett, Thomas H; Clifford, Roger K; England, John E; Hopps, Nicholas W; Parker, Kenneth W; Porter, Kenneth; Stevenson, Mark

2002-06-20

The HELEN high-power Nd:glass laser has been rebuilt in a new multipass configuration that requires fewer components to maintain existing performance. This is expected to lead to greater system availability and reduced running costs. We describe the new design, discuss some of the key issues that had to be addressed, and present operational results.

High Energy, Narrow Linewidth 1572nm Eryb-Fiber Based MOPA for a Multi-Aperture CO2 Trace-Gas Laser Space Transmitter

NASA Technical Reports Server (NTRS)

Engin, Doruk; Mathason, Brian; Stephen, Mark; Yu, Anthony; Cao, He; Fouron, Jean-Luc; Storm, Mark

2016-01-01

Accurate global measurements of tropospheric CO2 mixing ratios are needed to study CO2 emissions and CO2 exchange with the land and oceans. NASA Goddard Space Flight Center (GSFC) is developing a pulsed lidar approach for an integrated path differential absorption (IPDA) lidar to allow global measurements of atmospheric CO2 column densities from space. Our group has developed, and successfully flown, an airborne pulsed lidar instrument that uses two tunable pulsed laser transmitters allowing simultaneous measurement of a single CO2 absorption line in the 1570 nm band, absorption of an O2 line pair in the oxygen A-band (765 nm), range, and atmospheric backscatter profiles in the same path. Both lasers are pulsed at 10 kHz, and the two absorption line regions are sampled at typically a 300 Hz rate. A space-based version of this lidar must have a much larger lidar power-area product due to the x40 longer range and faster along track velocity compared to airborne instrument. Initial link budget analysis indicated that for a 400 km orbit, a 1.5 m diameter telescope and a 10 second integration time, a 2 mJ laser energy is required to attain the precision needed for each measurement. To meet this energy requirement, we have pursued parallel power scaling efforts to enable space-based lidar measurement of CO2 concentrations. These included a multiple aperture approach consists of multi-element large mode area fiber amplifiers and a single-aperture approach consists of a multi-pass Er:Yb:Phosphate glass based planar waveguide amplifier (PWA). In this paper we will present our laser amplifier design approaches and preliminary results.

High time resolved electron temperature measurements by using the multi-pass Thomson scattering system in GAMMA 10/PDX.

PubMed

Yoshikawa, Masayuki; Yasuhara, Ryo; Ohta, Koichi; Chikatsu, Masayuki; Shima, Yoriko; Kohagura, Junko; Sakamoto, Mizuki; Nakashima, Yousuke; Imai, Tsuyoshi; Ichimura, Makoto; Yamada, Ichihiro; Funaba, Hisamichi; Minami, Takashi

2016-11-01

High time resolved electron temperature measurements are useful for fluctuation study. A multi-pass Thomson scattering (MPTS) system is proposed for the improvement of both increasing the TS signal intensity and time resolution. The MPTS system in GAMMA 10/PDX has been constructed for enhancing the Thomson scattered signals for the improvement of measurement accuracy. The MPTS system has a polarization-based configuration with an image relaying system. We optimized the image relaying optics for improving the multi-pass laser confinement and obtaining the stable MPTS signals over ten passing TS signals. The integrated MPTS signals increased about five times larger than that in the single pass system. Finally, time dependent electron temperatures were obtained in MHz sampling.

An Enhanced GINGERSimulation Code with Harmonic Emission and HDF5IO Capabilities

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

Fawley, William M.

GINGER [1] is an axisymmetric, polychromatic (r-z-t) FEL simulation code originally developed in the mid-1980's to model the performance of single-pass amplifiers. Over the past 15 years GINGER's capabilities have been extended to include more complicated configurations such as undulators with drift spaces, dispersive sections, and vacuum chamber wakefield effects; multi-pass oscillators; and multi-stage harmonic cascades. Its coding base has been tuned to permit running effectively on platforms ranging from desktop PC's to massively parallel processors such as the IBM-SP. Recently, we have made significant changes to GINGER by replacing the original predictor-corrector field solver with a new direct implicitmore » algorithm, adding harmonic emission capability, and switching to the HDF5 IO library [2] for output diagnostics. In this paper, we discuss some details regarding these changes and also present simulation results for LCLS SASE emission at {lambda} = 0.15 nm and higher harmonics.« less

Multipass Target Search in Natural Environments

PubMed Central

Otte, Michael W.; Sofge, Donald; Gupta, Satyandra K.

2017-01-01

Consider a disaster scenario where search and rescue workers must search difficult to access buildings during an earthquake or flood. Often, finding survivors a few hours sooner results in a dramatic increase in saved lives, suggesting the use of drones for expedient rescue operations. Entropy can be used to quantify the generation and resolution of uncertainty. When searching for targets, maximizing mutual information of future sensor observations will minimize expected target location uncertainty by minimizing the entropy of the future estimate. Motion planning for multi-target autonomous search requires planning over an area with an imperfect sensor and may require multiple passes, which is hindered by the submodularity property of mutual information. Further, mission duration constraints must be handled accordingly, requiring consideration of the vehicle’s dynamics to generate feasible trajectories and must plan trajectories spanning the entire mission duration, something which most information gathering algorithms are incapable of doing. If unanticipated changes occur in an uncertain environment, new plans must be generated quickly. In addition, planning multipass trajectories requires evaluating path dependent rewards, requiring planning in the space of all previously selected actions, compounding the problem. We present an anytime algorithm for autonomous multipass target search in natural environments. The algorithm is capable of generating long duration dynamically feasible multipass coverage plans that maximize mutual information using a variety of techniques such as ϵ-admissible heuristics to speed up the search. To the authors’ knowledge this is the first attempt at efficiently solving multipass target search problems of such long duration. The proposed algorithm is based on best first branch and bound and is benchmarked against state of the art algorithms adapted to the problem in natural Simplex environments, gathering the most information in the given search time. PMID:29099087

Noise Suppression Based on Multi-Model Compositions Using Multi-Pass Search with Multi-Label N-gram Models

NASA Astrophysics Data System (ADS)

Jitsuhiro, Takatoshi; Toriyama, Tomoji; Kogure, Kiyoshi

We propose a noise suppression method based on multi-model compositions and multi-pass search. In real environments, input speech for speech recognition includes many kinds of noise signals. To obtain good recognized candidates, suppressing many kinds of noise signals at once and finding target speech is important. Before noise suppression, to find speech and noise label sequences, we introduce multi-pass search with acoustic models including many kinds of noise models and their compositions, their n-gram models, and their lexicon. Noise suppression is frame-synchronously performed using the multiple models selected by recognized label sequences with time alignments. We evaluated this method using the E-Nightingale task, which contains voice memoranda spoken by nurses during actual work at hospitals. The proposed method obtained higher performance than the conventional method.

Muon Acceleration Concepts for NuMAX: "Dual-use" Linac and "Dogbone" RLA

DOE PAGES

Bogacz, S. A.

2018-02-01

In this paper, we summarize the current state of a concept for muon acceleration aimed at a future Neutrino Factory. The main thrust of these studies was to reduce the overall cost while maintaining performance by exploring the interplay between the complexity of the cooling systems and the acceptance of the accelerator complex. To ensure adequate survival for the short-lived muons, acceleration must occur at high average gradient. The need for large transverse and longitudinal acceptances drives the design of the acceleration system to an initially low RF frequency, e.g., 325 MHz, which is then increased to 650 MHz asmore » the transverse size shrinks with increasing energy. High-gradient normal conducting RF cavities at these frequencies require extremely high peak-power RF sources. Hence superconducting RF (SRF) cavities are chosen. Finally, we consider two cost effective schemes for accelerating muon beams for a stageable Neutrino Factory: exploration of the so-called "dual-use" linac concept, where the same linac structure is used for acceleration of both H - and muons and, alternatively, an SRF-efficient design based on a multi-pass (4.5) "dogbone" RLA, extendable to multi-pass FFAG-like arcs.« less

Application of cascade lasers to detection of trace gaseous atmospheric pollutants

NASA Astrophysics Data System (ADS)

Miczuga, Marcin; Kopczyński, Krzysztof

2016-12-01

Understanding the impact of gaseous pollutants on the earth's atmosphere, as well as more and more felt by mankind negative effects of its contamination, result in increasing the level of environmental awareness and contribute to the intensification of actions aimed at reducing the emission of harmful gases into the atmosphere. At the same time, the extensive studies are conducted in order to continuously monitor the level of air contamination with harmful gases and the industry compliance with the standards limited the amount of emitted pollutants. Over recent years, there has been increasing use of cascade lasers and multi-pass cells in optical systems detecting the gaseous atmospheric pollutants and measuring the gas concentrations. The paper presents the use of a tunable quantum cascade laser as a source of the IR radiation in an advanced detection system enabling the trace gaseous atmospheric pollutants to be identified. Apart from the laser, the main elements of the system are: a multi-pass cell, an IR detector and a module for control and analysis. Operation of the system is exemplified by measuring the level of the air pollution with ammonia, carbon oxide and nitrous oxide.

Cavity ring-down spectroscopy in the liquid phase

NASA Astrophysics Data System (ADS)

Xu, Shucheng; Sha, Guohe; Xie, Jinchun

2002-02-01

A new application for cavity ring-down spectroscopic (CRDS) technique using a pulsed polarized light source has been developed in the absorption measurement of liquids for "colorless" organic compounds using both a single sample cell and double sample cells inserted in an optical cavity at Brewster angle. At present an experimental capability of measuring absorption coefficients as small as 2-5×10-7 cm-1 has been demonstrated by measurement of the absorption baselines. The first spectra for CRDS in the liquid phase, the C-H stretching fifth vibrational overtones of benzene in the pure liquid and hexane solution are obtained. The optical absorption length for liquids in both a single sample cell and double sample cells of 1 cm length is up to 900 cm due to multipass of light within an optical cavity. Compared to the thermal lens and optoacoustic spectroscopic techniques, the sensitivity for CRDS mainly depends on the optical absorption path of the sample (single passing path of the sample times multipass times), is not determined by the laser power and the length of the sample cell. The absolute absorption coefficient and band intensity for the sample are determined directly by the spectroscopy.

Generalized design of a zero-geometric-loss, astigmatism-free, modified four-objective multipass matrix system.

PubMed

Guo, Yin; Sun, LiQun; Yang, Zheng; Liu, Zilong

2016-02-20

During this study we constructed a generalized parametric modified four-objective multipass matrix system (MMS). We used an optical system comprising four asymmetrical spherical mirrors to improve the alignment process. The use of a paraxial equation for the design of the front transfer optics yielded the initial condition for modeling our MMS. We performed a ray tracing simulation to calculate the significant aberration of the system (astigmatism). Based on the calculated meridional and sagittal focus positions, the complementary focusing mirror was easily designed to provide an output beam free of astigmatism. We have presented an example of a 108-transit multipass system (5×7 matrix arrangement) with a relatively larger numerical aperture source (xenon light source). The whole system exhibits zero theoretical geometrical loss when simulated with Zemax software. The MMS construction strategy described in this study provides an anastigmatic output beam and the generalized approach to design a controllable matrix spot pattern on the field mirrors. Asymmetrical reflective mirrors aid in aligning the whole system with high efficiency. With the generalized design strategy in terms of optics configuration and asymmetrical fabrication method in this paper, other kinds of multipass matrix system coupled with different sources and detector systems also can be achieved.

Subpicosecond thin-disk laser oscillator with pulse energies of up to 25.9 microjoules by use of an active multipass geometry.

PubMed

Neuhaus, Joerg; Bauer, Dominik; Zhang, Jing; Killi, Alexander; Kleinbauer, Jochen; Kumkar, Malte; Weiler, Sascha; Guina, Mircea; Sutter, Dirk H; Dekorsy, Thomas

2008-12-08

The pulse shaping dynamics of a diode-pumped laser oscillator with active multipass cell was studied experimentally and numerically. We demonstrate the generation of high energy subpicosecond pulses with a pulse energy of up to 25.9 microJ at a pulse duration of 928 fs directly from a thin-disk laser oscillator. These results are achieved by employing a selfimaging active multipass geometry operated in ambient atmosphere. Stable single pulse operation has been obtained with an average output power in excess of 76 W and at a repetition rate of 2.93 MHz. Self starting passive mode locking was accomplished using a semiconductor saturable absorber mirror. The experimental results are compared with numerical simulations, showing good agreement including the appearance of Kelly sidebands. Furthermore, a modified soliton-area theorem for approximating the pulse duration is presented. (c) 2008 Optical Society of America

Multi-pass light amplifier

NASA Technical Reports Server (NTRS)

Plaessmann, Henry (Inventor); Grossman, William M. (Inventor)

1997-01-01

A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A confocal resonator or White Cell resonator is provided, including two or three curvilinearly shaped mirrors facing each other along a resonator axis and an optical gain medium positioned on the resonator axis between the mirrors (confocal resonator) or adjacent to one of the mirrors (White Cell). In a first embodiment, two mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. The optical gain medium may be solid-state, liquid or gaseous medium and may be pumped longitudinally or transversely. In a second embodiment, first and second mirrors face a third mirror in a White Cell configuration, and the optical gain medium is positioned at or adjacent to one of the mirrors. Defocusing means and optical gain medium cooling means are optionally provided with either embodiment, to controllably defocus the light beam, to cool the optical gain medium and to suppress thermal lensing in the gain medium.

Spectrometer capillary vessel and method of making same

DOEpatents

Linehan, John C.; Yonker, Clement R.; Zemanian, Thomas S.; Franz, James A.

1995-01-01

The present invention is an arrangement of a glass capillary tube for use in spectroscopy. In particular, the invention is a capillary arranged in a manner permitting a plurality or multiplicity of passes of a sample material through a spectroscopic measurement zone. In a preferred embodiment, the multi-pass capillary is insertable within a standard NMR sample tube. The present invention further includes a method of making the multi-pass capillary tube and an apparatus for spinning the tube.

Microstructural Characterization of the Heat-Affected Zones in Grade 92 Steel Welds: Double-Pass and Multipass Welds

NASA Astrophysics Data System (ADS)

Xu, X.; West, G. D.; Siefert, J. A.; Parker, J. D.; Thomson, R. C.

2018-04-01

The microstructure in the heat-affected zone (HAZ) of multipass welds typical of those used in power plants and made from 9 wt pct chromium martensitic Grade 92 steel is complex. Therefore, there is a need for systematic microstructural investigations to define the different regions of the microstructure across the HAZ of Grade 92 steel welds manufactured using the traditional arc welding processes in order to understand possible failure mechanisms after long-term service. In this study, the microstructure in the HAZ of an as-fabricated two-pass bead-on-plate weld on a parent metal of Grade 92 steel has been systematically investigated and compared to a complex, multipass thick section weldment using an extensive range of electron and ion-microscopy-based techniques. A dilatometer has been used to apply controlled thermal cycles to simulate the microstructures in distinctly different regions in a multipass HAZ using sequential thermal cycles. A wide range of microstructural properties in the simulated materials were characterized and compared with the experimental observations from the weld HAZ. It has been found that the microstructure in the HAZ can be categorized by a combination of sequential thermal cycles experienced by the different zones within the complex weld metal, using the terminology developed for these regions based on a simpler, single-pass bead-on-plate weld, categorized as complete transformation, partial transformation, and overtempered.

Landing Gear/Soil Interaction Development of Criteria for Aircraft Operation on Soil During Turning and Multipass Operations

DTIC Science & Technology

1975-10-01

AFFDL-TR-75-78 LANDING GEAR/ SOIL INTERACTION DEVELOPMENT OF CRITERIA FOR AIRCRAFT "OPERATION ON SOIL DURING TURNING #"q AND MULTIPASS OPERATIONS cc...braking. Limited start-up force data were examined to determine a preliminary estimate of start-up drag ratios. A soft tire/ soil computer program was...distance, landing rollout, turning perfor nance, and number of allowable passes for a particular vehicle and select soil . .. 4 UNCLASSIFIED -i SECURITY

Spectrometer capillary vessel and method of making same

DOEpatents

Linehan, J.C.; Yonker, C.R.; Zemanian, T.S.; Franz, J.A.

1995-11-21

The present invention is an arrangement of a glass capillary tube for use in spectroscopy. In particular, the invention is a capillary arranged in a manner permitting a plurality or multiplicity of passes of a sample material through a spectroscopic measurement zone. In a preferred embodiment, the multi-pass capillary is insertable within a standard NMR sample tube. The present invention further includes a method of making the multi-pass capillary tube and an apparatus for spinning the tube. 13 figs.

Characteristics of Extra Narrow Gap Weld of HSLA Steel Welded by Single-Seam per Layer Pulse Current GMA Weld Deposition

NASA Astrophysics Data System (ADS)

Agrawal, B. P.; Ghosh, P. K.

2017-03-01

Butt weld joints are produced using pulse current gas metal arc welding process by employing the technique of centrally laid multi-pass single-seam per layer weld deposition in extra narrow groove of thick HSLA steel plates. The weld joints are prepared by using different combination of pulse parameters. The selection of parameter of pulse current gas metal arc welding is done considering a summarized influence of simultaneously interacting pulse parameters defined by a dimensionless hypothetical factor ϕ. The effect of diverse pulse parameters on the characteristics of weld has been studied. Weld joint is also prepared by using commonly used multi-pass multi-seam per layer weld deposition in conventional groove. The extra narrow gap weld joints have been found much superior to the weld joint prepared by multi-pass multi-seam per layer deposition in conventional groove with respect to its metallurgical characteristics and mechanical properties.

Development of polarization-controlled multi-pass Thomson scattering system in the GAMMA 10 tandem mirror

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

Yoshikawa, M.; Morimoto, M.; Shima, Y.

2012-10-15

In the GAMMA 10 tandem mirror, the typical electron density is comparable to that of the peripheral plasma of torus-type fusion devices. Therefore, an effective method to increase Thomson scattering (TS) signals is required in order to improve signal quality. In GAMMA 10, the yttrium-aluminum-garnet (YAG)-TS system comprises a laser, incident optics, light collection optics, signal detection electronics, and a data recording system. We have been developing a multi-pass TS method for a polarization-based system based on the GAMMA 10 YAG TS. To evaluate the effectiveness of the polarization-based configuration, the multi-pass system was installed in the GAMMA 10 YAG-TSmore » system, which is capable of double-pass scattering. We carried out a Rayleigh scattering experiment and applied this double-pass scattering system to the GAMMA 10 plasma. The integrated scattering signal was made about twice as large by the double-pass system.« less

Welding Residual Stress Analysis and Fatigue Strength Assessment at Elevated Temperature for Multi-pass Dissimilar Material Weld Between Alloy 617 and P92 Steel

NASA Astrophysics Data System (ADS)

Lee, Juhwa; Hwang, Jeongho; Bae, Dongho

2018-03-01

In this paper, welding residual stress analysis and fatigue strength assessment were performed at elevated temperature for multi-pass dissimilar material weld between Alloy 617 and P92 steel, which are used in thermal power plant. Multi-pass welding between Alloy 617 and P92 steel was performed under optimized welding condition determined from repeated pre-test welding. In particular, for improving dissimilar material weld-ability, the buttering welding technique was applied on the P92 steel side before multi-pass welding. Welding residual stress distribution at the dissimilar material weld joint was numerically analyzed by using the finite element method, and compared with experimental results which were obtained by the hole-drilling method. Additionally, fatigue strength of dissimilar material weld joint was assessed at the room temperature (R.T), 300, 500, and 700 °C. In finite element analysis results, numerical peak values; longitudinal (410 MPa), transverse (345 MPa) were higher than those of experiments; longitudinal (298 MPa), transverse (245 MPa). There are quantitatively big differences between numerical and experimental results, due to some assumption about the thermal conductivity, specific heat, effects of enforced convection of the molten pool, dilution, and volume change during phase transformation caused by actual shield gas. The low fatigue limit at R.T, 300 °C, 500 °C and 700 °C was assessed to be 368, 276, 173 and 137 MPa respectively.

Welding Residual Stress Analysis and Fatigue Strength Assessment at Elevated Temperature for Multi-pass Dissimilar Material Weld Between Alloy 617 and P92 Steel

NASA Astrophysics Data System (ADS)

Lee, Juhwa; Hwang, Jeongho; Bae, Dongho

2018-07-01

In this paper, welding residual stress analysis and fatigue strength assessment were performed at elevated temperature for multi-pass dissimilar material weld between Alloy 617 and P92 steel, which are used in thermal power plant. Multi-pass welding between Alloy 617 and P92 steel was performed under optimized welding condition determined from repeated pre-test welding. In particular, for improving dissimilar material weld-ability, the buttering welding technique was applied on the P92 steel side before multi-pass welding. Welding residual stress distribution at the dissimilar material weld joint was numerically analyzed by using the finite element method, and compared with experimental results which were obtained by the hole-drilling method. Additionally, fatigue strength of dissimilar material weld joint was assessed at the room temperature (R.T), 300, 500, and 700 °C. In finite element analysis results, numerical peak values; longitudinal (410 MPa), transverse (345 MPa) were higher than those of experiments; longitudinal (298 MPa), transverse (245 MPa). There are quantitatively big differences between numerical and experimental results, due to some assumption about the thermal conductivity, specific heat, effects of enforced convection of the molten pool, dilution, and volume change during phase transformation caused by actual shield gas. The low fatigue limit at R.T, 300 °C, 500 °C and 700 °C was assessed to be 368, 276, 173 and 137 MPa respectively.

Critical dimensional linewidth calibration using UV microscope and laser interferometry

NASA Astrophysics Data System (ADS)

Li, Qi; Gao, Si-tian; Li, Wei; Lu, Ming-zhen; Zhang, Ming-kai

2013-10-01

In order to calibrate the critical dimensional (CD) uncertainty of lithography masks in semiconductor manufacturing, NIM is building a two dimensional metrological UV microscope which has traceable measurement ability for nanometer linewidths and pitches. The microscope mainly consists of UV light receiving components, piezoelectric ceramics (PZT) driven stage and interferometer calibration framework. In UV light receiving components they include all optical elements on optical path. The UV light originates from Köhler high aperture transmit/reflect illumination sources; then goes through objective lens to UV splitting optical elements; after that, one part of light attains UV camera for large range calibration, the other part of light passes through a three dimensional adjusted pinhole and is collected by PMT for nanoscale scanning. In PZT driven stage, PZT stick actuators with closed loop control are equipped to push/pull a flexural hinge based platform. The platform has a novel designed compound flexural hinges which nest separate X, Y direction moving mechanisms within one layer but avoiding from mutual cross talk, besides this, the hinges also contain leverage structures to amplify moving distance. With these designs, the platform can attain 100 μm displacement ranges as well as 1 nm resolution. In interferometer framework a heterodyne multi-pass interferometer is mounted on the platform, which measures X-Y plane movement and Z axis rotation, through reference mirror mounted on objective lens tube and Zerodur mirror mounted on PZT platform, the displacement is traced back to laser wavelength. When development is finished, the apparatus can offer the capability to calibrate one dimensional linewidths and two dimensional pitches ranging from 200nm to 50μm with expanded uncertainty below 20nm.

Computational simulation of weld microstructure and distortion by considering process mechanics

NASA Astrophysics Data System (ADS)

Mochizuki, M.; Mikami, Y.; Okano, S.; Itoh, S.

2009-05-01

Highly precise fabrication of welded materials is in great demand, and so microstructure and distortion controls are essential. Furthermore, consideration of process mechanics is important for intelligent fabrication. In this study, the microstructure and hardness distribution in multi-pass weld metal are evaluated by computational simulations under the conditions of multiple heat cycles and phase transformation. Because conventional CCT diagrams of weld metal are not available even for single-pass weld metal, new diagrams for multi-pass weld metals are created. The weld microstructure and hardness distribution are precisely predicted when using the created CCT diagram for multi-pass weld metal and calculating the weld thermal cycle. Weld distortion is also investigated by using numerical simulation with a thermal elastic-plastic analysis. In conventional evaluations of weld distortion, the average heat input has been used as the dominant parameter; however, it is difficult to consider the effect of molten pool configurations on weld distortion based only on the heat input. Thus, the effect of welding process conditions on weld distortion is studied by considering molten pool configurations, determined by temperature distribution and history.

Bio-isolated DC operational amplifier

NASA Technical Reports Server (NTRS)

Lee, R. D.

1974-01-01

Possibility of shocks from leakage currents can be reduced by use of isolated preamplifiers. Amplifier consists of battery-powered operational amplifier coupled by means of light-emitting diodes to another amplifier which may be grounded and operated from ac power mains or separate battery supply.

Current status of Kumgang laser system

NASA Astrophysics Data System (ADS)

Kong, Hong Jin; Park, Sangwoo; Ahn, HeeKyung; Lee, Hwihyeong; Oh, Jungsuk; Kim, Jom Sool

2015-02-01

In KAIST, Kumgang laser is being developed for demonstration of the kW level coherent beam combination using stimulated Brillouin scattering phase conjugation mirrors. It will combine 4 modules of DPSSL rod amplifier which produces 1 kW output power. It is composed of the single frequency front-end, pre-amplifier module, and main amplifier. The output powers of the pre-amp and main amplifier module are 200 W (20 mJ @ 10 kHz / 10 ns) and 1.07kW (107 mJ @ 10 kHz / 10 ns), respectively.

2-micron lasing in Tm:Lu2O3 ceramic: initial operation

NASA Astrophysics Data System (ADS)

Vetrovec, John; Filgas, David M.; Smith, Carey A.; Copeland, Drew A.; Litt, Amardeep S.; Briscoe, Eldridge; Schirmer, Ernestina

2018-03-01

We report on initial lasing of Tm:Lu2O3 ceramic laser with tunable output in the vicinity of 2 μm. Tm:Lu2O3 ceramic gain materials offer a much lower saturation fluence than the traditionally used Tm:YLF and Tm:YAG materials. The gain element is pumped by 796 nm diodes via a "2-for-1" crossrelaxation energy transfer mechanism, which enables high efficiency. The high thermal conductivity of the Lu2O3 host ( 18% higher than YAG) in combination with low quantum defect of 20% supports operation at high-average power. Konoshima's ceramic fabrication process overcomes the scalability limits of single crystal sesquioxides. Tm:Lu2O3 offers wide-bandwidth amplification of ultrashort pulses in a chirped-pulse amplification (CPA) system. A laser oscillator was continuously tuned over a 230 nm range from 1890 to 2120 nm while delivering up to 43W QCW output with up to 37% efficiency. This device is intended for initial testing and later seeding of a multi-pass edge-pumped disk amplifier now being developed by Aqwest which uses composite Tm:Lu2O3 disk gain elements.

Pressure-Dependent Detection of Carbon Monoxide Employing Wavelength Modulation Spectroscopy Using a Herriott-Type Cell.

PubMed

Li, Chuanliang; Wu, Yingfa; Qiu, Xuanbing; Wei, Jilin; Deng, Lunhua

2017-05-01

Wavelength modulation spectroscopy (WMS) combined with a multipass absorption cell has been used to measure a weak absorption line of carbon monoxide (CO) at 1.578 µm. A 0.95m Herriott-type cell provides an effective absorption path length of 55.1 m. The WMS signals from the first and second harmonic output of a lock-in amplifier (WMS-1 f and 2 f, respectively) agree with the Beer-Lambert law, especially at low concentrations. After boxcar averaging, the minimum detection limit achieved is 4.3 ppm for a measurement time of 0.125 s. The corresponding normalized detection limit is 84 ppm m Hz -1/2 . If the integrated time is increased to 88 s, the minimum detectable limit of CO can reach to 0.29 ppm based on an Allan variation analysis. The pressure-dependent relationship is validated after accounting for the pressure factor in data processing. Finally, a linear correlation between the WMS-2 f amplitudes and gas concentrations is obtained at concentration ratios less than 15.5%, and the accuracy is better than 92% at total pressure less than 62.7 Torr.

Simulation of Structural Transformations in Heating of Alloy Steel

NASA Astrophysics Data System (ADS)

Kurkin, A. S.; Makarov, E. L.; Kurkin, A. B.; Rubtsov, D. E.; Rubtsov, M. E.

2017-07-01

Amathematical model for computer simulation of structural transformations in an alloy steel under the conditions of the thermal cycle of multipass welding is presented. The austenitic transformation under the heating and the processes of decomposition of bainite and martensite under repeated heating are considered. Amethod for determining the necessary temperature-time parameters of the model from the chemical composition of the steel is described. Published data are processed and the results used to derive regression models of the temperature ranges and parameters of transformation kinetics of alloy steels. The method developed is used in computer simulation of the process of multipass welding of pipes by the finite-element method.

Integrated-circuit balanced parametric amplifier

NASA Technical Reports Server (NTRS)

Dickens, L. E.

1975-01-01

Amplifier, fabricated on single dielectric substrate, has pair of Schottky barrier varactor diodes mounted on single semiconductor chip. Circuit includes microstrip transmission line and slot line section to conduct signals. Main features of amplifier are reduced noise output and low production cost.

Is there a role for amplifiers in sexual selection?

PubMed

Gualla, Filippo; Cermelli, Paolo; Castellano, Sergio

2008-05-21

The amplifier hypothesis states that selection could favour the evolution of traits in signallers that improve the ability of receivers to extract honest information from other signals or cues. We provide a formal definition of amplifiers based on the receiver's mechanisms of signal perception and we present a game-theoretical model in which males advertise their quality and females use sequential-sampling tactics to choose among prospective mates. The main effect of an amplifier on the female mating strategy is to increase her mating threshold, making the female more selective as the effectiveness of the amplifier increases. The effects of the amplifier on male advertising strategy depends both on the context and on the types of the amplifier involved. We consider two different contexts for the evolution of amplifiers (when the effect of amplifiers is on signals and when it is on cues) and two types of amplifiers (the 'neutral amplifier', when it improves quality assessment without altering male attractiveness, and the 'attractive amplifier', when it improves both quality assessment and male attractiveness). The game-theoretical model provides two main results. First, neutral and attractive amplifiers represent, respectively, a conditional and an unconditional signalling strategy. In fact, at the equilibrium, neutral amplifiers are displayed only by males whose advertising level lays above the female acceptance threshold, whereas attractive amplifiers are displayed by all signalling males, independent of their quality. Second, amplifiers of signals increase the differences in advertising levels between amplifying and not-amplifying males, but they decrease the differences within each group, so that the system converges towards an 'all-or-nothing' signalling strategy. By applying concepts from information theory, we show that the increase in information transfer at the perception level due to the amplifier of signals is contrasted by a decrease in information transfer at the emitter level due to the increased stereotypy of male advertising strategy.

Friction and wear of iron-base binary alloys in sliding contact with silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Multipass sliding friction experiments were conducted with various iron base binary alloys in contact with a single crystal silicon carbide surface in vacuum. Results indicate that the atomic size and concentration of alloy elements play important roles in controlling the transfer and friction properties of iron base binary alloys. Alloys having high solute concentration produce more transfer than do alloys having low solute concentration. The coefficient of friction during multipass sliding generally increases with an increase in the concentration of alloying element. The change of friction with succeeding passes after the initial pass also increases as the solute to iron, atomic radius ratio increases or decreases from unity.

Two antenna, two pass interferometric synthetic aperture radar

DOEpatents

Martinez, Ana; Doerry, Armin W.; Bickel, Douglas L.

2005-06-28

A multi-antenna, multi-pass IFSAR mode utilizing data driven alignment of multiple independent passes can combine the scaling accuracy of a two-antenna, one-pass IFSAR mode with the height-noise performance of a one-antenna, two-pass IFSAR mode. A two-antenna, two-pass IFSAR mode can accurately estimate the larger antenna baseline from the data itself and reduce height-noise, allowing for more accurate information about target ground position locations and heights. The two-antenna, two-pass IFSAR mode can use coarser IFSAR data to estimate the larger antenna baseline. Multi-pass IFSAR can be extended to more than two (2) passes, thereby allowing true three-dimensional radar imaging from stand-off aircraft and satellite platforms.

Generation of broadband laser by high-frequency bulk phase modulator with multipass configuration.

PubMed

Zhang, Peng; Jiang, Youen; Zhou, Shenlei; Fan, Wei; Li, Xuechun

2014-12-10

A new technique is presented for obtaining a large broadband nanosecond-laser pulse. This technique is based on multipass phase modulation of a single-frequency nanosecond-laser pulse from the integrated front-end source, and it is able to shape the temporal profile of the pulse arbitrarily, making this approach attractive for high-energy-density physical experiments in current laser fusion facilities. Two kinds of cavity configuration for multipass modulation are proposed, and the performances of both of them are discussed theoretically in detail for the first time to our knowledge. Simulation results show that the bandwidth of the generated laser pulse by this approach can achieve more than 100 nm in principle if adjustment accuracy of the time interval between contiguous passes is controlled within 0.1% of a microwave period. In our preliminary experiment, a 2 ns laser pulse with 1.35-nm bandwidth in 1053 nm is produced via this technique, which agrees well with the theoretical result. Owing to an all-solid-state structure, the energy of the pulse achieves 25 μJ. In the future, with energy compensation and spectrum filtering, this technique is expected to generate a nanosecond-laser pulse of 3 nm or above bandwidth with energy of about 100 μJ.

Multi-pass encoding of hyperspectral imagery with spectral quality control

NASA Astrophysics Data System (ADS)

Wasson, Steven; Walker, William

2015-05-01

Multi-pass encoding is a technique employed in the field of video compression that maximizes the quality of an encoded video sequence within the constraints of a specified bit rate. This paper presents research where multi-pass encoding is extended to the field of hyperspectral image compression. Unlike video, which is primarily intended to be viewed by a human observer, hyperspectral imagery is processed by computational algorithms that generally attempt to classify the pixel spectra within the imagery. As such, these algorithms are more sensitive to distortion in the spectral dimension of the image than they are to perceptual distortion in the spatial dimension. The compression algorithm developed for this research, which uses the Karhunen-Loeve transform for spectral decorrelation followed by a modified H.264/Advanced Video Coding (AVC) encoder, maintains a user-specified spectral quality level while maximizing the compression ratio throughout the encoding process. The compression performance may be considered near-lossless in certain scenarios. For qualitative purposes, this paper presents the performance of the compression algorithm for several Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and Hyperion datasets using spectral angle as the spectral quality assessment function. Specifically, the compression performance is illustrated in the form of rate-distortion curves that plot spectral angle versus bits per pixel per band (bpppb).

Microstructure and mechanical properties of China low activation martensitic steel joint by TIG multi-pass welding with a new filler wire

NASA Astrophysics Data System (ADS)

Huang, Bo; Zhang, Junyu; Wu, Qingsheng

2017-07-01

Tungsten Inner Gas (TIG) welding is employed for joining of China low activation martensitic (CLAM) steel. A new filler wire was proposed, and the investigation on welding with various heat input and welding passes were conducted to lower the tendency towards the residual of δ ferrite in the joint. With the optimized welding parameters, a butt joint by multi-pass welding with the new filler wire was prepared to investigate the microstructure and mechanical properties. The microstructure of the joint was observed by optical microscope (OM) and scanning electron microscope (SEM). The hardness, Charpy impact and tensile tests of the joint were implemented at room temperature (25 °C). The results revealed that almost full martensite free from ferrite in the joints were obtained by multipass welding with the heat input of 2.26 kJ/mm. A certain degree of softening occurred at the heat affected zone of the joint according to the results of tensile and hardness tests. The as welded joints showed brittle fracture in the impact tests. However, the joints showed toughness fracture after tempering and relatively better comprehensive performance were achieved when the joints were tempered at 740 °C for 2 h.

Far off-resonance laser frequency stabilization using multipass cells in Faraday rotation spectroscopy.

PubMed

Quan, Wei; Li, Yang; Li, Rujie; Shang, Huining; Fang, Zishan; Qin, Jie; Wan, Shuangai

2016-04-01

We propose a far off-resonance laser frequency stabilization method by using multipass cells in Rb Faraday rotation spectroscopy. Based on the detuning equation, if multipass cells with several meters optical path length are used in the conventional Faraday spectroscopy, the detuning of the lock point can be extended much further from the alkali metal resonance. A plate beam splitter was used to generate two different Faraday signals at the same time. The transmitted optical path length was L=50  mm and the reflected optical path length was 2L=100  mm. When the optical path length doubled, the detuning of the lock points moved further away from the atomic resonance. The temperature dependence of the detuning of the lock point was also analyzed. A temperature-insensitive lock point was found near resonance when the cell temperature was between 110°C and 130°C. We achieved an rms fluctuation of 0.9 MHz/23 h at a detuning of 0.5 GHz. A frequency drift of 16 MHz/h at a detuning of -5.6  GHz and 4 MHz/h at a detuning of -5.2  GHz were also obtained for the transmitted and reflected light Faraday signal.

Hybrid/Tandem Laser-Arc Welding of Thick Low Carbon Martensitic Stainless Steel Plates =

NASA Astrophysics Data System (ADS)

Mirakhorli, Fatemeh

High efficiency and long-term life of hydraulic turbines and their assemblies are of utmost importance for the hydropower industry. Usually, hydroelectric turbine components are made of thick-walled low carbon martensitic stainless steels. The assembly of large hydroelectric turbine components has been a great challenge. The use of conventional welding processes involves typical large groove design and multi-pass welding to fill the groove which exposes the weld to a high heat input creating relatively large fusion zone and heat affected zone. The newly-developed hybrid/tandem laser-arc welding technique is believed to offer a highly competitive solution to improve the overall hydro-turbine performance by combining the high energy density and fast welding speed of the laser welding technology with the good gap bridging and feeding ability of the gas metal arc welding process to increase the productivity and reduce the consumable material. The main objective of this research work is to understand different challenges appearing during hybrid laser-arc welding (HLAW) of thick gauge assemblies of low carbon 13%Cr- 4%Ni martensitic stainless steel and find a practical solution by adapting and optimizing this relatively new welding process in order to reduce the number of welding passes necessary to fill the groove gap. The joint integrity was evaluated in terms of microstructure, defects and mechanical properties in both as-welded and post-welded conditions. A special focus was given to the hybrid and tandem laser-arc welding technique for the root pass. Based on the thickness of the low carbon martensitic stainless steel plates, this work is mainly focused on the following two tasks: • Single pass hybrid laser-arc welding of 10-mm thick low carbon martensitic stainless steel. • Multi-pass hybrid/tandem laser-arc welding of 25-mm thick martensitic stainless steel.

Plastic mechanism of multi-pass double-roller clamping spinning for arc-shaped surface flange

NASA Astrophysics Data System (ADS)

Fan, Shuqin; Zhao, Shengdun; Zhang, Qi; Li, Yongyi

2013-11-01

Compared with the conventional single-roller spinning process, the double-roller clamping spinning(DRCS) process can effectively prevent the sheet metal surface wrinkling and improve the the production efficiency and the shape precision of final spun part. Based on ABAQUS/Explicit nonlinear finite element software, the finite element model of the multi-pass DRCS for the sheet metal is established, and the material model, the contact definition, the mesh generation, the loading trajectory and other key technical problems are solved. The simulations on the multi-pass DRCS of the ordinary Q235A steel cylindrical part with the arc-shaped surface flange are carried out. The effects of number of spinning passes on the production efficiency, the spinning moment, the shape error of the workpiece, and the wall thickness distribution of the final part are obtained. It is indicated definitely that with the increase of the number of spinning passes the geometrical precision of the spun part increases while the production efficiency reduces. Moreover, the variations of the spinning forces and the distributions of the stresses, strains, wall thickness during the multi-pass DRCS process are revealed. It is indicated that during the DRCS process the radical force is the largest, and the whole deformation area shows the tangential tensile strain and the radial compressive strain, while the thickness strain changes along the generatrix directions from the compressive strain on the outer edge of the flange to the tensile strain on the inner edge of the flange. Based on the G-CNC6135 NC lathe, the three-axis linkage computer-controlled experimental device for DRCS which is driven by the AC servo motor is developed. And then using the experimental device, the Q235A cylindrical parts with the arc-shape surface flange are formed by the DRCS. The simulation results of spun parts have good consistency with the experimental results, which verifies the feasibility of DRCS process and the reliability of the finite element model for DRCS.

Effect of Activated Flux on the Microstructure, Mechanical Properties, and Residual Stresses of Modified 9Cr-1Mo Steel Weld Joints

NASA Astrophysics Data System (ADS)

Maduraimuthu, V.; Vasudevan, M.; Muthupandi, V.; Bhaduri, A. K.; Jayakumar, T.

2012-02-01

A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials. The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint.

Frequency choice of eRHIC SRF linac

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

Xu, W.; Ben-Zvi, I.; Roser, T.

2016-01-05

eRHIC is a FFAG lattice-based multipass ERL. The eRHIC SRF linac has been decided to change from 422 MHz 5-cell cavity to 647 MHz 5-cell cavity. There are several considerations affecting the frequency choice for a high-current multipass-ERL: the beam structure, bunch length, energy spread, beam-break-up (BBU) threshold, SRF loss considerations. Beyond the physics considerations, cost and complexity or risk is an important consideration for the frequency choice, especially when we are designing a machine to be built in a few years. Although there are some benefits of using a 422 MHz cavity for eRHIC ERL, however, there are somemore » very critical drawbacks, including lack of facilities to fabricate a 422 MHz 5-cell cavity, very few facilities to process such a cavity and no existing facility to test the cavity anywhere. As the cavity size is big and its weight is large, it is difficult to handle it during fabrication, processing and testing, and no one has experience in this area. As the cavity size is large, the cryomodule becomes big as well. All of these considerations drive the risk of building eRHIC ERL with 422 MHz cavities to a very high level. Therefore, a decision was made to change the frequency of main linac to be 647 MHz 5-cell cavities. This note will compare these two linacs: 422MHz 5-cell cavity linac and 647Mz 5-cell cavity SRF linac, from both practical point of view and physics point of view.« less

Modeling of the static recrystallization for 7055 aluminum alloy by cellular automaton

NASA Astrophysics Data System (ADS)

Zhang, Tao; Lu, Shi-hong; Zhang, Jia-bin; Li, Zheng-fang; Chen, Peng; Gong, Hai; Wu, Yun-xin

2017-09-01

In order to simulate the flow behavior and microstructure evolution during the pass interval period of the multi-pass deformation process, models of static recovery (SR) and static recrystallization (SRX) by the cellular automaton (CA) method for the 7055 aluminum alloy were established. Double-pass hot compression tests were conducted to acquire flow stress and microstructure variation during the pass interval period. With the basis of the material constants obtained from the compression tests, models of the SR, incubation period, nucleation rate and grain growth were fitted by least square method. A model of the grain topology and a statistical computation of the CA results were also introduced. The effects of the pass interval time, temperature, strain, strain rate and initial grain size on the microstructure variation for the SRX of the 7055 aluminum alloy were studied. The results show that a long pass interval time, large strain, high temperature and large strain rate are beneficial for finer grains during the pass interval period. The stable size of the static recrystallized grain is not concerned with the initial grain size, but mainly depends on the strain rate and temperature. The SRX plays a vital role in grain refinement, while the SR has no effect on the variation of microstructure morphology. Using flow stress and microstructure comparisons of the simulated and experimental CA results, the established CA models can accurately predict the flow stress and microstructure evolution during the pass interval period, and provide guidance for the selection of optimized parameters for the multi-pass deformation process.

Nonlinear Scattering of VLF Waves in the Radiation Belts

NASA Astrophysics Data System (ADS)

Crabtree, Chris; Rudakov, Leonid; Ganguli, Guru; Mithaiwala, Manish

2014-10-01

Electromagnetic VLF waves, such as whistler mode waves, control the lifetime of trapped electrons in the radiation belts by pitch-angle scattering. Since the pitch-angle scattering rate is a strong function of the wave properties, a solid understanding of VLF wave sources and propagation in the magnetosphere is critical to accurately calculate electron lifetimes. Nonlinear scattering (Nonlinear Landau Damping) is a mechanism that can strongly alter VLF wave propagation [Ganguli et al. 2010], primarily by altering the direction of propagation, and has not been accounted for in previous models of radiation belt dynamics. Laboratory results have confirmed the dramatic change in propagation direction when the pump wave has sufficient amplitude to exceed the nonlinear threshold [Tejero et al. 2014]. Recent results show that the threshold for nonlinear scattering can often be met by naturally occurring VLF waves in the magnetosphere, with wave magnetic fields of the order of 50-100 pT inside the plasmapause. Nonlinear scattering can then dramatically alter the macroscopic dynamics of waves in the radiation belts leading to the formation of a long-lasting wave-cavity [Crabtree et al. 2012] and, when amplification is present, a multi-pass amplifier [Ganguli et al. 2012]. By considering these effects, the lifetimes of electrons can be dramatically reduced. This work is supported by the Naval Research Laboratory base program.

Electra: Repetitively Pulsed Angularly Multiplexed KrF Laser System Performance

NASA Astrophysics Data System (ADS)

Wolford, Matthew; Myers, Matthew; Giuliani, John; Sethian, John; Burns, Patrick; Hegeler, Frank; Jaynes, Reginald

2008-11-01

As in a full size fusion power plant beam line, Electra is a multistage laser amplifier system. The multistage amplifier system consists of a commercial discharge laser and two doubled sided electron beam pumped amplifiers. Angular multiplexing is used in the optical layout to provide pulse length control and to maximize laser extraction from the amplifiers. Two angularly multiplexed beams have extracted 30 J of KrF laser light with an aperture 8 x 10 cm^2, which is sufficient to extract over 500 J from the main amplifier and models agree. The main amplifier of Electra in oscillator mode has demonstrated single shot and rep-rate laser energies exceeding 700 J with 100 ns pulsewidth at 248 nm with an aperture 29 x 29 cm^2. Continuous operation of the KrF electron beam pumped oscillator has lasted for more than 2.5 hours without failure at 1 Hz and 2.5 Hz. The measured intensity and pulse energy for durations greater than thousand shots are consistent at measurable rep-rates of 1 Hz, 2.5 Hz and 5 Hz.

Towards a THz backward wave amplifier in European OPTHER project

NASA Astrophysics Data System (ADS)

Dispenza, M.; Brunetti, F.; Cojocaru, C.-S.; de Rossi, A.; Di Carlo, A.; Dolfi, D.; Durand, A.; Fiorello, A. M.; Gohier, A.; Guiset, P.; Kotiranta, M.; Krozer, V.; Legagneux, P.; Marchesin, R.; Megtert, S.; Bouamrane, F.; Mineo, M.; Paoloni, C.; Pham, K.; Schnell, J. P.; Secchi, A.; Tamburri, E.; Terranova, M. L.; Ulisse, G.; Zhurbenko, V.

2010-10-01

Within the EC funded international project OPTHER (OPtically Driven TeraHertz AmplifiERs) a considerable technological effort is being undertaken, in terms of technological development, THz device design and integration. The ultimate goal is to develop a miniaturised THz amplifier based on vacuum-tube principles The main target specifications of the OPTHER amplifier are the following: - Operating frequency: in the band 0.3 to 2 THz - Output power: > 10 mW ( 10 dBm ) - Gain: 10 to 20 dB. The project is in the middle of its duration. Design and simulations have shown that these targets can be met with a proper device configuration and careful optimization of the different parts of the amplifier. Two parallel schemes will be employed for amplifier realisation: THz Drive Signal Amplifier and Optically Modulated Beam THz Amplifier.

Fabrication of thick multilayered steel structure using A516 Grade 70 by multipass friction stir welding †

DOE PAGES

Lim, Y. C.; Sanderson, S.; Mahoney, M.; ...

2016-04-06

Here, we fabricated a thick-sectioned multilayered steel structure by multipass friction stir welding on A516 Grade 70 steel. Tensile strength of the multilayered samples was comparable to that of the base metal. Failure was located in the base metal when a defect-free sample was tested. Charpy impact toughness was higher in the stir zone and heat affected zone than in the base metal. For higher microhardness values were found in the stir zone and heat affected zone than the base metal due to grain refinement and modification of the microstructures. As a result, improved mechanical properties compared to the basemore » metal were found in the weld zones of friction stir welded A516 Grade 70 steel.« less

Multi-pass transmission electron microscopy

DOE PAGES

Juffmann, Thomas; Koppell, Stewart A.; Klopfer, Brannon B.; ...

2017-05-10

Feynman once asked physicists to build better electron microscopes to be able to watch biology at work. While electron microscopes can now provide atomic resolution, electron beam induced specimen damage precludes high resolution imaging of sensitive materials, such as single proteins or polymers. Here, we use simulations to show that an electron microscope based on a multi-pass measurement protocol enables imaging of single proteins, without averaging structures over multiple images. While we demonstrate the method for particular imaging targets, the approach is broadly applicable and is expected to improve resolution and sensitivity for a range of electron microscopy imaging modalities,more » including, for example, scanning and spectroscopic techniques. The approach implements a quantum mechanically optimal strategy which under idealized conditions can be considered interaction-free.« less

Multipass open-path Fourier-transform infrared measurements for nonintrusive monitoring of gas turbine exhaust composition.

PubMed

Schäfer, Klaus; Brockmann, Klaus; Heland, Jörg; Wiesen, Peter; Jahn, Carsten; Legras, Olivier

2005-04-10

The detection limits for NO and NO2 in turbine exhausts by nonintrusive monitoring have to be improved. Multipass mode Fourier-transform infrared (FTIR) absorption spectrometry and use of a White mirror system were found from a sensitivity study with spectra simulations in the mid-infrared to be essential for the retrieval of NO2 abundances. A new White mirror system with a parallel infrared beam was developed and tested successfully with a commercial FTIR spectrometer in different turbine test beds. The minimum detection limits for a typical turbine plume of 50 cm in diameter are approximately 6 parts per million (ppm) for NO and 9 ppm for NO2 (as well 100 ppm for CO2 and 4 ppm for CO).

Low-noise front-end electronics for detection of intermediate-frequency weak light signals

NASA Astrophysics Data System (ADS)

Lin, Cunbao; Yan, Shuhua; Du, Zhiguang; Wei, Chunhua; Wang, Guochao

2015-02-01

A novel low-noise front-end electronics was proposed for detection of light signals with intensity about 10 μW and frequency above 2.7 MHz. The direct current (DC) power supply, pre-amplifier and main-amplifier were first designed, simulated and then realized. Small-size components were used to make the power supply small, and the pre-amplifier and main-amplifier were the least capacitors to avoid the phase shift of the signals. The performance of the developed front-end electronics was verified in cross-grating diffraction experiments. The results indicated that the output peak-topeak noise of the +/-5 V DC power supply was about 2 mV, and the total output current was 1.25 A. The signal-to-noise ratio (SNR) of the output signal of the pre-amplifier was about 50 dB, and it increased to nearly 60 dB after the mainamplifier, which means this front-end electronics was especially suitable for using in the phase-sensitive and integrated precision measurement systems.

Dye laser amplifier including an improved window configuration for its dye beam

DOEpatents

O'Neil, R.W.; Davin, J.M.

1992-12-01

A dye laser amplifier in which a continuously replenished supply of dye is excited with a first light beam in order to amplify the intensity of a second different light beam passing therethrough is disclosed herein. This amplifier includes a cell though which a continuous stream of the dye is caused to pass, and means for directing the first beam into the cell while the second beam is directed into and through the same cell. There is also disclosed herein a specific improvement to this amplifier which resides in the use of a pair of particularly configured windows through which the second beam passes along fixed paths as the second beam enters and exits the dye cell. Each of these windows has a relatively thick main section which is substantially larger in dimensions transverse to its beam path than the cross section of the second beam itself, whereby to add structural integrity to the overall window. At the same time, the latter includes a second section which is disposed entirely within the confines of the main section and through which the second beam is intended to pass in its entirety. This second section is made substantially thinner than the main section in order to reduce optical distortion as the second beam passes therethrough. 4 figs.

Dye laser amplifier including an improved window configuration for its dye beam

DOEpatents

O'Neil, Richard W.; Davin, James M.

1992-01-01

A dye laser amplifier in which a continuously replenished supply of dye is excited with a first light beam in order to amplify the intensity of a second different light beam passing therethrough is disclosed herein. This amplifier includes a cell though which a continuous stream of the dye is caused to pass, and means for directing the first beam into the cell while the second beam is directed into and through the same cell. There is also disclosed herein a specific improvement to this amplifier which resides in the use of a pair of particularly configured windows through which the second beam passes along fixed paths as the second beam enters and exits the dye cell. Each of these windows has a relatively thick main section which is substantially larger in dimensions transverse to its beam path than the cross section of the second beam itself, whereby to add structural integrity to the overall window. At the same time, the latter includes a second section which is disposed entirely within the confines of the main section and through which the second beam is intended to pass in its entirety. This second section is made substantially thinner than the main section in order to reduce optical distortion as the second beam passes therethrough.

Development of cryogenic Yb:YAG ceramics amplifier for over 100 J DPSSL

NASA Astrophysics Data System (ADS)

Sekine, T.; Takeuchi, Y.; Kurita, T.; Hatano, Y.; Muramatsu, Y.; Mizuta, Y.; Kabeya, Y.; Tamaoki, Y.; Kato, Y.

2017-02-01

A high gain cryogenic Yb:YAG ceramics laser amplifier for a high energy laser amplification system has been developed. The laser system consists of a fiber oscillator and two stage LD pumped cryogenic Yb:YAG ceramic amplifiers. The preamplifier stage has a 5-pass laser amplifier head and the main amplifier stage has a 2-pass laser amplifier head, respectively. The preamplifier obtained an average stored energy density of 0.836 J/cc and small-signal gain (SSG) of 60 with 33 J of stored energy. Then about 1 μJ of input energy from the oscillator was amplified to 3.6 J. The main amplifier head had four pumping LD modules which irradiated the Yb:YAG ceramics directly. This original angular pumping scheme ideally increases irradiation intensity and homogenizes irradiation pattern on the Yb:YAG ceramics due to superposition effect of all of the LD modules. A maximum peak power of over 100 kW was generated by one LD module. When the output energy of the LD modules was 450 J, a 20 of SSG at single pass was obtained. Stored energy density was evaluated to 0.429 J/cc when 148 J energy was stored in 346 cc of Yb:YAG ceramics. As a result, a 55-J output energy with 10 ns pulse duration was demonstrated at a pumping energy of 450 J. The optical-tooptical conversion efficiency which includes transmissivity of the LD modules was 12 %. The extraction efficiency was estimated to 37%.

Spectroscopic detection of biological NO with a quantum cascade laser

NASA Technical Reports Server (NTRS)

Menzel, L.; Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.;

Assessment of delta ferrite in multipass TIG welds of 40 mm thick SS 316L: A comparative study of ferrite number (FN) prediction and measurements

NASA Astrophysics Data System (ADS)

Buddu, Ramesh Kumar; Raole, P. M.; Sarkar, B.

2017-04-01

Austenitic stainless steels are widely used in the fabrication of fusion reactor major systems like vacuum vessel, divertor, cryostat and other structural components development. Multipass welding is used for the development of thick plates for the structural components fabrication. Due to the repeated weld thermal cycles, the microstructure adversely alters owing to the presence of complex phases like austenite, ferrite and delta ferrite and subsequently influences the mechanical properties like tensile and impact toughness of joints. The present paper reports the detail analysis of delta ferrite phase in welded region of 40 mm thick SS316L plates welded by special design multipass narrow groove TIG welding process under three different heat input conditions. The correlation of delta ferrite microstructure of different type structures acicular and vermicular is observed. The chemical composition of weld samples was used to predict the Ferrite Number (FN), which is representative form of delta ferrite in welds, with Schaeffler’s, WRC-1992 diagram and DeLong techniques by calculating the Creq and Nieq ratios and compared with experimental data of FN from Feritescope measurements. The low heat input conditions (1.67 kJ/mm) have produced higher FN (7.28), medium heat input (1.72 kJ/mm) shown FN (7.04) where as high heat input (1.87 kJ/mm) conditions has shown FN (6.68) decreasing trend and FN data is compared with the prediction methods.

Effect of Multi-Pass Ultrasonic Surface Rolling on the Mechanical and Fatigue Properties of HIP Ti-6Al-4V Alloy

PubMed Central

Li, Gang; Qu, Shengguan; Xie, Mingxin; Ren, Zhaojun; Li, Xiaoqiang

2017-01-01

The main purpose of this paper was to investigate the effect of a surface plastic deformation layer introduced by multi-pass ultrasonic surface rolling (MUSR) on the mechanical and fatigue properties of HIP Ti-6Al-4V alloys. Some microscopic analysis methods (SEM, TEM and XRD) were used to characterize the modified microstructure in the material surface layer. The results indicated that the material surface layer experienced a certain extent plastic deformation, accompanied by some dense dislocations and twin generation. Moreover, surface microhardness, residual stress and roughness values of samples treated by MUSR were also greatly improved compared with that of untreated samples. Surface microhardness and compressive residual stress were increased to 435 HV and −1173 MPa, respectively. The minimum surface roughness was reduced to 0.13 μm. The maximum depth of the surface hardening layer was about 55 μm. However, the practical influence depth was about 450 μm judging from the tensile and fatigue fracture surfaces. The ultimate tensile strength of the MUSR-treated sample increased to 990 MPa from the initial 963 MPa. The fatigue strength of the MUSR-treated sample was increased by about 25% on the base of 107 cycles, and the lifetime was prolonged from two times to two orders of magnitude at the applied stress amplitudes of 650–560 MPa. The improved mechanical and fatigue properties of MUSR-treated samples should be attributed to the combined effects of the increased microhardness and compressive residual stress, low surface roughness, grain refinement and micro-pore healing in the material surface-modified layer. PMID:28772494

In Situ Magnetohydrodynamic Energy Generation for Planetary Entry Vehicles

NASA Astrophysics Data System (ADS)

Ali, H. K.; Braun, R. D.

2014-06-01

This work aims to study the suitability of multi-pass entry trajectories for harnessing of vehicle kinetic energy through magnetohydrodynamic power generation from the high temperature entry plasma. Potential mission configurations are analyzed.

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

Wojcik, Roza; Webb, Ian K.; Deng, Liulin

Understanding the biological mechanisms related to lipids and glycolipids is challenging due to the vast number of possible isomers. Mass spectrometry (MS) measurements are currently the dominant approach for studying and providing detailed information on lipid and glycolipid structures. However, difficulties in distinguishing many structural isomers (e.g. distinct acyl chain positions, double bond locations, as well as glycan isomers) inhibit the understanding of their biological roles. Here we utilized ultra-high resolution ion mobility spectrometry (IMS) separations based upon the use of traveling waves in a serpentine long path length multi-pass Structures for Lossless Manipulations (SLIM) to enhance isomer resolution. Themore » multi-pass arrangement allowed separations ranging from ~16 m (1 pass) to ~470 m (32 passes) to be investigated for the distinction of lipids and glycolipids with extremely small structural differences. Lastly, these ultra-high resolution SLIM IMS-MS analyses provide a foundation for exploring and better understanding isomer specific biological and disease processes.« less

High-speed laser anemometry based on spectrally resolved Rayleigh scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard G.

1991-01-01

Laser anemometry in unseeded flows based on the measurement of the spectrum of Rayleigh scattered laser light is reviewed. The use of molecular scattering avoids the well known problems (particle lag, biasing effects, seed generation, seed injection) of seeded flows. The fundamental limits on velocity measurement accuracy are determined using maximum likelihood methods. Measurement of the Rayleigh spectrum with scanning Fabry-Perot interferometers is analyzed and accuracy limits are established for both single pass and multipass configurations. Multipass configurations have much higher selectivity and are needed for measurements where there is a large amount of excess noise caused by stray laser light. It is shown that Rayleigh scattering is particularly useful for supersonic and hypersonic flows. The results of the analysis are compared with measurements obtained with a Rayleigh scattering diagnostic developed for study of the exhaust plume of a small hydrogen-oxygen rocket, where the velocities are in the range of 1000 to 5000 m/sec.

Oxygen-assisted multipass cutting of carbon fiber reinforced plastics with ultra-short laser pulses

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

Kononenko, T. V.; Komlenok, M. S.; Konov, V. I.

Deep multipass cutting of bidirectional and unidirectional carbon fiber reinforced plastics (CFRP) with picosecond laser pulses was investigated in different static atmospheres as well as with the assistance of an oxygen or nitrogen gas flow. The ablation rate was determined as a function of the kerf depth and the resulting heat affected zone was measured. An assisting oxygen gas flow is found to significantly increase the cutting productivity, but only in deep kerfs where the diminished evaporative ablation due to the reduced laser fluence reaching the bottom of the kerf does not dominate the contribution of reactive etching anymore. Oxygen-supportedmore » cutting was shown to also solve the problem that occurs when cutting the CFRP parallel to the fiber orientation where a strong deformation and widening of the kerf, which temporarily slows down the process speed, is revealed to be typical for processing in standard air atmospheres.« less

A Comparison between the Properties of Solid Cylinders and Tube Products in Multi-Pass Hot Radial Forging Using Finite Element Method

NASA Astrophysics Data System (ADS)

Abedian, A.; Poursina, M.; Golestanian, H.

2007-05-01

Radial forging is an open die forging process used for reducing the diameter of shafts, tubes, stepped shafts and axels, and creating internal profiles for tubes such as rifling of gun barrels. In this work, a comprehensive study of multi-pass hot radial forging of short hollow and solid products are presented using 2-D axisymmetric finite element simulation. The workpiece is modeled as an elastic-viscoplastic material. A mixture of Coulomb law and constant limit shear is used to model the die-workpiece and mandrel-workpiece contacts. Thermal effects are also taken in to account. Three-pass radial forging of solid cylinders and tube products are considered. Temperature, stress, strain and metal flow distribution are obtained in each pass through thermo-mechanical simulation. The numerical results are compared with available experimental data and are in good agreement with them.

Deceleration, precooling, and multi-pass stopping of highly charged ions in Be{sup +} Coulomb crystals

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

Schmöger, L., E-mail: lisa.schmoeger@mpi-hd.mpg.de; Schwarz, M.; Versolato, O. O.

2015-10-15

Preparing highly charged ions (HCIs) in a cold and strongly localized state is of particular interest for frequency metrology and tests of possible spatial and temporal variations of the fine structure constant. Our versatile preparation technique is based on the generic modular combination of a pulsed ion source with a cryogenic linear Paul trap. Both instruments are connected by a compact beamline with deceleration and precooling properties. We present its design and commissioning experiments regarding these two functionalities. A pulsed buncher tube allows for the deceleration and longitudinal phase-space compression of the ion pulses. External injection of slow HCIs, specificallymore » Ar{sup 13+}, into the linear Paul trap and their subsequent retrapping in the absence of sympathetic cooling is demonstrated. The latter proved to be a necessary prerequisite for the multi-pass stopping of HCIs in continuously laser-cooled Be{sup +} Coulomb crystals.« less

A multiresolution inversion for imaging the ionosphere

NASA Astrophysics Data System (ADS)

Yin, Ping; Zheng, Ya-Nan; Mitchell, Cathryn N.; Li, Bo

2017-06-01

Ionospheric tomography has been widely employed in imaging the large-scale ionospheric structures at both quiet and storm times. However, the tomographic algorithms to date have not been very effective in imaging of medium- and small-scale ionospheric structures due to limitations of uneven ground-based data distributions and the algorithm itself. Further, the effect of the density and quantity of Global Navigation Satellite Systems data that could help improve the tomographic results for the certain algorithm remains unclear in much of the literature. In this paper, a new multipass tomographic algorithm is proposed to conduct the inversion using intensive ground GPS observation data and is demonstrated over the U.S. West Coast during the period of 16-18 March 2015 which includes an ionospheric storm period. The characteristics of the multipass inversion algorithm are analyzed by comparing tomographic results with independent ionosonde data and Center for Orbit Determination in Europe total electron content estimates. Then, several ground data sets with different data distributions are grouped from the same data source in order to investigate the impact of the density of ground stations on ionospheric tomography results. Finally, it is concluded that the multipass inversion approach offers an improvement. The ground data density can affect tomographic results but only offers improvements up to a density of around one receiver every 150 to 200 km. When only GPS satellites are tracked there is no clear advantage in increasing the density of receivers beyond this level, although this may change if multiple constellations are monitored from each receiving station in the future.

Coreference analysis in clinical notes: a multi-pass sieve with alternate anaphora resolution modules.

PubMed

Jonnalagadda, Siddhartha Reddy; Li, Dingcheng; Sohn, Sunghwan; Wu, Stephen Tze-Inn; Wagholikar, Kavishwar; Torii, Manabu; Liu, Hongfang

2012-01-01

This paper describes the coreference resolution system submitted by Mayo Clinic for the 2011 i2b2/VA/Cincinnati shared task Track 1C. The goal of the task was to construct a system that links the markables corresponding to the same entity. The task organizers provided progress notes and discharge summaries that were annotated with the markables of treatment, problem, test, person, and pronoun. We used a multi-pass sieve algorithm that applies deterministic rules in the order of preciseness and simultaneously gathers information about the entities in the documents. Our system, MedCoref, also uses a state-of-the-art machine learning framework as an alternative to the final, rule-based pronoun resolution sieve. The best system that uses a multi-pass sieve has an overall score of 0.836 (average of B(3), MUC, Blanc, and CEAF F score) for the training set and 0.843 for the test set. A supervised machine learning system that typically uses a single function to find coreferents cannot accommodate irregularities encountered in data especially given the insufficient number of examples. On the other hand, a completely deterministic system could lead to a decrease in recall (sensitivity) when the rules are not exhaustive. The sieve-based framework allows one to combine reliable machine learning components with rules designed by experts. Using relatively simple rules, part-of-speech information, and semantic type properties, an effective coreference resolution system could be designed. The source code of the system described is available at https://sourceforge.net/projects/ohnlp/files/MedCoref.

Tunable lasers for water vapor measurements and other lidar applications

NASA Technical Reports Server (NTRS)

Gammon, R. W.; Mcilrath, T. J.; Wilkerson, T. D.

1977-01-01

A tunable dye laser suitable for differential absorption (DIAL) measurements of water vapor in the troposphere was constructed. A multi-pass absorption cell for calibration was also constructed for use in atmospheric DIAL measurements of water vapor.

1-MHz high power femtosecond Yb-doped fiber chirped-pulse amplifier

NASA Astrophysics Data System (ADS)

Hu, Zhong-Qi; Yang, Pei-Long; Teng, Hao; Zhu, Jiang-Feng; Wei, Zhi-Yi

2018-01-01

A practical femtosecond polarization-maintaining Yb-doped fiber amplifier enabling 153 fs transform-limited pulse duration with 32 μJ pulse energy at 1 MHz repetition rate corresponding to a peak power of 0.21 GW is demonstrated. The laser system based on chirped-pulse amplification (CPA) technique is seeded by a dispersion managed, nonlinear polarization evolution (NPE) mode-locked oscillator with spectrum bandwidth of 31 nm at 1040 nm and amplified by three fiber pre-amplifying stages and a rod type fiber main amplifying stage. The laser works with beam quality of M2 of 1.3 and power stability of 0.63% (root mean square, RMS) over 24 hours will be stable sources for industrial micromachining, medical therapy and scientific research.

Weld procedure produces quality welds for thick sections of Hastelloy-X

NASA Technical Reports Server (NTRS)

Flens, F. J.; Fletcher, C. W.; Glasier, L. F., Jr.

1967-01-01

Welding program produces premium quality, multipass welds in heavy tube sections of Hastelloy-X. It develops semiautomatic tungsten/inert gas procedures, weld wire procurement specifications material weld properties, welder-operator training, and nondestructive testing inspection techniques and procedures.

Broadband linearisation of high-efficiency power amplifiers

NASA Technical Reports Server (NTRS)

Kenington, Peter B.; Parsons, Kieran J.; Bennett, David W.

1993-01-01

A feedforward-based amplifier linearization technique is presented which is capable of yielding significant improvements in both linearity and power efficiency over conventional amplifier classes (e.g. class-A or class-AB). Theoretical and practical results are presented showing that class-C stages may be used for both the main and error amplifiers yielding practical efficiencies well in excess of 30 percent, with theoretical efficiencies of much greater than 40 percent being possible. The levels of linearity which may be achieved are required for most satellite systems, however if greater linearity is required, the technique may be used in addition to conventional pre-distortion techniques.

Performance evaluation of an architecture for the characterisation of photo-devices: design, fabrication and test on a CMOS technology

NASA Astrophysics Data System (ADS)

Castillo-Cabrera, G.; García-Lamont, J.; Reyes-Barranca, M. A.; Moreno-Cadenas, J. A.; Escobosa-Echavarría, A.

2011-03-01

In this report, the performance of a particular pixel's architecture is evaluated. It consists mainly of an optical sensor coupled to an amplifier. The circuit contains photoreceptors such as phototransistors and photodiodes. The circuit integrates two main blocks: (a) the pixel architecture, containing four p-channel transistors and a photoreceptor, and (b) a current source for biasing the signal conditioning amplifier. The generated photocurrent is integrated through the gate capacitance of the input p-channel MOS transistor, then converted to voltage and amplified. Both input transistor and current source are implemented as a voltage amplifier having variable gain (between 10dB and 32dB). Considering characterisation purposes, this last fact is relevant since it gives a degree of freedom to the measurement of different kinds of photo-devices and is not limited to either a single operating point of the circuit or one kind and size of photo-sensor. The gain of the amplifier can be adjusted with an external DC power supply that also sets the DC quiescent point of the circuit. Design of the row-select transistor's aspect ratio used in the matrix array is critical for the pixel's amplifier performance. Based on circuit design data such as capacitance magnitude, time and voltage integration, and amplifier gain, characterisation of all the architecture can be readily carried out and evaluated. For the specific technology used in this work, the spectral response of photo-sensors reveals performance differences between phototransistors and photodiodes. Good approximation between simulation and measurement was obtained.

Coreference analysis in clinical notes: a multi-pass sieve with alternate anaphora resolution modules

PubMed Central

Li, Dingcheng; Sohn, Sunghwan; Wu, Stephen Tze-Inn; Wagholikar, Kavishwar; Torii, Manabu; Liu, Hongfang

2012-01-01

Objective This paper describes the coreference resolution system submitted by Mayo Clinic for the 2011 i2b2/VA/Cincinnati shared task Track 1C. The goal of the task was to construct a system that links the markables corresponding to the same entity. Materials and methods The task organizers provided progress notes and discharge summaries that were annotated with the markables of treatment, problem, test, person, and pronoun. We used a multi-pass sieve algorithm that applies deterministic rules in the order of preciseness and simultaneously gathers information about the entities in the documents. Our system, MedCoref, also uses a state-of-the-art machine learning framework as an alternative to the final, rule-based pronoun resolution sieve. Results The best system that uses a multi-pass sieve has an overall score of 0.836 (average of B3, MUC, Blanc, and CEAF F score) for the training set and 0.843 for the test set. Discussion A supervised machine learning system that typically uses a single function to find coreferents cannot accommodate irregularities encountered in data especially given the insufficient number of examples. On the other hand, a completely deterministic system could lead to a decrease in recall (sensitivity) when the rules are not exhaustive. The sieve-based framework allows one to combine reliable machine learning components with rules designed by experts. Conclusion Using relatively simple rules, part-of-speech information, and semantic type properties, an effective coreference resolution system could be designed. The source code of the system described is available at https://sourceforge.net/projects/ohnlp/files/MedCoref. PMID:22707745

Laser removal of graffiti from Pink Morelia Quarry

NASA Astrophysics Data System (ADS)

Penide, J.; Quintero, F.; Riveiro, A.; Sánchez-Castillo, A.; Comesaña, R.; del Val, J.; Lusquiños, F.; Pou, J.

2013-11-01

Morelia is an important city sited in Mexico. Its historical center reflects most of their culture and history, especially of the colonial period; in fact, it was appointed World Heritage Site by UNESCO. Sadly, there is a serious problem with graffiti in Morelia and its historical center is the worst affected since its delicate charming is definitely damaged. Hitherto, the conventional methods employed to remove graffiti from Pink Morelia Quarry (the most used building stone in Morelia) are quite aggressive to the appearance of the monuments, so actually, they are not a very good solution. In this work, we performed a study on the removal of graffiti from Pink Morelia Quarry by high power diode laser. We carried out an extensive experimental study looking for the optimal processing parameters, and compared a single-pass with a multi-pass method. Indeed, we achieved an effective cleaning without producing serious side effects in the stone. In conclusion, the multi-pass method emitting in continuous wave was revealed as the more effective operating modes to remove the graffiti.

Lipid and glycolipid isomer analyses using ultra-high resolution ion mobility spectrometry separations

DOE PAGES

Wojcik, Roza; Webb, Ian K.; Deng, Liulin; ...

2017-01-18

Understanding the biological mechanisms related to lipids and glycolipids is challenging due to the vast number of possible isomers. Mass spectrometry (MS) measurements are currently the dominant approach for studying and providing detailed information on lipid and glycolipid structures. However, difficulties in distinguishing many structural isomers (e.g. distinct acyl chain positions, double bond locations, as well as glycan isomers) inhibit the understanding of their biological roles. Here we utilized ultra-high resolution ion mobility spectrometry (IMS) separations based upon the use of traveling waves in a serpentine long path length multi-pass Structures for Lossless Manipulations (SLIM) to enhance isomer resolution. Themore » multi-pass arrangement allowed separations ranging from ~16 m (1 pass) to ~470 m (32 passes) to be investigated for the distinction of lipids and glycolipids with extremely small structural differences. Lastly, these ultra-high resolution SLIM IMS-MS analyses provide a foundation for exploring and better understanding isomer specific biological and disease processes.« less

Effect of Multi-Pass Friction Stir Processing on Mechanical Properties for AA2024/Al2O3 Nanocomposites

PubMed Central

2017-01-01

In the present work, an aluminum metal matrix reinforced with (Al2O3) nanoparticles was fabricated as a surface composite sheet using friction stir processing (FSP). The effects of processing parameters on mechanical properties, hardness, and microstructure grain were investigated. The results revealed that multi-pass FSP causes a homogeneous distribution and good dispersion of Al2O3 in the metal matrix, and consequently an increase in the hardness of the matrix composites. A finer grain is observed in the microstructure examination in specimens subjected to second and third passes of FSP. The improvement in the grain refinement is 80% compared to base metal. The processing parameters, particularly rotational tool speed and pass number in FSP, have a major effect on strength properties and surface hardness. The ultimate tensile strength (UTS) and the average hardness are improved by 25% and 46%, respectively, due to presence of reinforcement Al2O3 nanoparticles. PMID:28885575

Ppb-level formaldehyde detection using a CW room-temperature interband cascade laser and a miniature dense pattern multipass gas cell

DOE PAGES

Dong, Lei; Yu, Yajun; Li, Chunguang; ...

2015-07-27

A ppb-level formaldehyde (H 2CO) sensor was developed using a thermoelectrically cooled (TEC), continuous-wave (CW) room temperature interband cascade laser (ICL) emitting at 3.59 μm and a miniature dense pattern multipass gas cell with >50 m optical path length. Performance of the sensor was investigated with two measurement schemes: direct absorption (DAS) and wavelength modulation spectroscopy (WMS). With an integration time of less than 1.5 second, a detection limit of ~3 ppbv for H 2CO measurement with precision of 1.25 ppbv for DAS and 0.58 ppbv for WMS, respectively, was achieved without zero air based background subtraction. An Allan-Werle variancemore » analysis indicated that the precisions can be further improved to 0.26 ppbv @ 300s for DAS and 69 pptv @ 90 s for WMS, respectively. Finally, a side-by-side comparison between two measurement schemes is also discussed in detail.« less

Numerical and experimental study on multi-pass laser bending of AH36 steel strips

NASA Astrophysics Data System (ADS)

Fetene, Besufekad N.; Kumar, Vikash; Dixit, Uday S.; Echempati, Raghu

2018-02-01

Laser bending is a process of bending of plates, small sized sheets, strips and tubes, in which a moving or stationary laser beam heats the workpiece to achieve the desired curvature due to thermal stresses. Researchers studied the effects of different process parameters related to the laser source, material and workpiece geometry on laser bending of metal sheets. The studies are focused on large sized sheets. The workpiece geometry parameters like sheet thickness, length and width also affect the bend angle considerably. In this work, the effects of width and thickness on multi-pass laser bending of AH36 steel strips were studied experimentally and numerically. Finite element model using ABAQUS® was developed to investigate the size effect on the prediction of the bend angle. Microhardness and flexure tests showed an increase in the flexural strength as well as microhardness in the scanned zone. The microstructures of the bent strips also supported the physical observations.

Highly-sensitive NO, NO 2 , and NH 3 measurements with an open-multipass cell based on mid-infrared wavelength modulation spectroscopy

NASA Astrophysics Data System (ADS)

Chen, Xiang; Yang, Chen-Guang; Hu, Mai; Shen, Jian-Kang; Niu, Er-Chao; Xu, Zhen-Yu; Fan, Xue-Li; Wei, Min; Yao, Lu; He, Ya-Bai; Liu, Jian-Guo; Kan, Rui-Feng

2018-04-01

Not Available Project supported by the National Key Scientific Instrument and Equipment Development, China (Grant No. 2014YQ060537) and the National Key Research and Development Program, China (Grant No. 2016YFC0201103).

Multi-pass light amplifier

NASA Technical Reports Server (NTRS)

Plaessmann, Henry (Inventor); Grossman, William M. (Inventor); Olson, Todd E. (Inventor)

1996-01-01

A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A resonator or a White Cell cavity is provided, including two or more mirrors (planar or curvilinearly shaped) facing each other along a resonator axis and an optical gain medium positioned on a resonator axis between the mirrors or adjacent to one of the mirrors. In a first embodiment, two curvilinear mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator. A second embodiment uses two curvilinear mirrors and one planar mirror, with a gain medium positioned in the optical path between each curvilinear mirror and the planar mirror. A third embodiment uses two curvilinear mirrors and two planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses a curvilinear mirror and three planar mirrors, with a gain medium positioned adjacent to a planar mirror. A fourth embodiment uses four planar mirrors and a focusing lens system, with a gain medium positioned between the four mirrors. A fifth embodiment uses first and second planar mirrors, a focusing lens system and a third mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the third mirror. A sixth embodiment uses two planar mirrors and a curvilinear mirror and a fourth mirror that may be planar or curvilinear, with a gain medium positioned adjacent to the fourth mirror. In a seventh embodiment, first and second mirrors face a third mirror, all curvilinear, in a White Cell configuration, and a gain medium is positioned adjacent to one of the mirrors.

Measuring system for the determination of nonlinear elastic and electromechanical properties in solids

NASA Astrophysics Data System (ADS)

Straube, U.; Beige, H.

1999-03-01

An arbitrary waveform generator was introduced to produce pulse bursts with improved time jitter for the generation of ultrasound pulses. The problem of pulse amplification was solved using a ceramic power triode driven by a power FET amplifier. The construction of these special amplifier stages is mainly considered in this paper.

Near re-entrant dense pattern optical multipass cell

NASA Technical Reports Server (NTRS)

Silver, Joel A. (Inventor)

2007-01-01

A multiple pass optical cell and method comprising providing a pair of opposed mirrors, one cylindrical and one spherical, introducing light into the cell via an entrance mechanism, and extracting light from the cell via an exit mechanism, wherein the entrance mechanism and exit mechanism are coextensive or non-coextensive.

Final EDP Ti: sapphire amplifiers for ELI project

NASA Astrophysics Data System (ADS)

Chvykov, Vladimir; Kalashnikov, Mikhail; Osvay, Károly

2015-05-01

Recently several ultrahigh intensity Chirped Pulse Amplification (CPA) laser systems have reached petawatt output powers [1, 2] setting the next milestone at tens or even hundreds petawatts for the next three to ten years [3, 4]. These remarkable results were reached when laser amplifiers (opposite to Optical Parametric Amplification (OPA) [5]) were used as final ones and from them Ti:Sapphire crystals supposed to be the working horses as well in the future design of these laser systems. Nevertheless, the main limitation that arises on the path toward ultrahigh output power and intensity is the restriction on the pumping and extraction energy imposed by Transverse Amplified Spontaneous Emission (TASE) [6] and/or transverse parasitic generation (TPG) [7] within the large aperture of the disc-shape amplifier volume.

Mode control in a high gain relativistic klystron amplifier with 3 GW output power

NASA Astrophysics Data System (ADS)

Wu, Yang; Xie, Hong-Quan; Xu, Zhou

2014-01-01

Higher mode excitation is very serious in the relativistic klystron amplifier, especially for the high gain relativistic amplifier working at tens of kilo-amperes. The mechanism of higher mode excitation is explored in the PIC simulation and it is shown that insufficient separation of adjacent cavities is the main cause of higher mode excitation. So RF lossy material mounted on the drift tube wall is adopted to suppress higher mode excitation. A high gain S-band relativistic klystron amplifier is designed for the beam current of 13 kA and the voltage of 1 MV. PIC simulation shows that the output power is 3.2 GW when the input power is only 2.8 kW.

Phase-Noise and Amplitude-Noise Measurement of Low-Power Signals

NASA Technical Reports Server (NTRS)

Rubiola, Enrico; Salik, Ertan; Yu, Nan; Maleki, Lute

2004-01-01

Measuring the phase fluctuation between a pair of low-power microwave signals, the signals must be amplified before detection. In such cases the phase noise of the amplifier pair is the main cause of 1/f background noise of the instrument. this article proposes a scheme that makes amplification possible while rejecting the close in 1/f (flicker) noise of the two amplifiers. Noise rejection, which relies upon the understanding of the amplifier noise mechanism does not require averaging. Therefore, our scheme can also be the detector of a closed loop noise reduction system. the first prototype, compared to a traditional saturated mixer system under the same condition, show a 24 dB noise reduction of the 1/f region.

Rhombic micro-displacement amplifier for piezoelectric actuator and its linear and hybrid model

NASA Astrophysics Data System (ADS)

Chen, Jinglong; Zhang, Chunlin; Xu, Minglong; Zi, Yanyang; Zhang, Xinong

2015-01-01

This paper proposes rhombic micro-displacement amplifier (RMDA) for piezoelectric actuator (PA). First, the geometric amplification relations are analyzed and linear model is built to analyze the mechanical and electrical properties of this amplifier. Next, the accurate modeling method of amplifier is studied for important application of precise servo control. The classical Preisach model (CPM) is generally implemented using a numerical technique based on the first-order reversal curves (FORCs). The accuracy of CPM mainly depends on the number of FORCs. However, it is generally difficult to achieve enough number of FORCs in practice. So, Support Vector Machine (SVM) is employed in the work to circumvent the deficiency of the CPM. Then the hybrid model, which is based on discrete CPM and SVM is developed to account for hysteresis and dynamic effects. Finally, experimental validation is carried out. The analyzed result shows that this amplifier with the hybrid model is suitable for control application.

Sub-MW peak power diffraction-limited chirped-pulse monolithic Yb-doped tapered fiber amplifier.

PubMed

Bobkov, Konstantin; Andrianov, Alexey; Koptev, Maxim; Muravyev, Sergey; Levchenko, Andrei; Velmiskin, Vladimir; Aleshkina, Svetlana; Semjonov, Sergey; Lipatov, Denis; Guryanov, Alexey; Kim, Arkady; Likhachev, Mikhail

2017-10-30

We demonstrate a novel amplification regime in a counter-pumped, relatively long (2 meters), large mode area, highly Yb-doped and polarization-maintaining tapered fiber, which offers a high peak power directly from the amplifier. The main feature of this regime is that the amplifying signal propagates through a thin part of the tapered fiber without amplification and experiences an extremely high gain in the thick part of the tapered fiber, where most of the pump power is absorbed. In this regime, we have demonstrated 8 ps pulse amplification to a peak power of up to 0.76 MW, which is limited by appearance of stimulated Raman scattering. In the same regime, 28 ps chirped pulses are amplified to a peak power of 0.35 MW directly from the amplifier and then compressed with 70% efficiency to 315 ± 10 fs, corresponding to an estimated peak power of 22 MW.

Investigation of precipitation and hardening response of maraging stainless steels 17-4 and 13-8+Mo during multi-pass welding

NASA Astrophysics Data System (ADS)

Hamlin, Robert J.

Martensitic precipitation strengthened stainless steels 17-4 and 13-8+Mo are candidate alloys for high strength military applications. These applications will require joining by fusion welding processes thus, it is necessary to develop an understanding of microstructural and mechanical property changes that occur during welding. Previous investigations on these materials have demonstrated that significant softening occurs in the heat affected zone (HAZ) during welding, due to dissolution of the strengthen precipitates. It was also observed that post weld heat treatments (PWHT's) were required to restore the properties. However, PWHT's are expensive and cannot be applied when welding on a large scale or making a repair in the field. Thus, the purpose of the current work is to gain a fundamental understanding of the precipitation kinetics in these systems so that optimized welding procedures can be developed that do not require a PWHT. Multi-pass welding provides an opportunity to restore the strengthening precipitates that dissolve during primary weld passes using the heat from secondary weld passes. Thus, a preliminary investigation was performed to determine whether the times and temperatures associated with welding thermal cycles were sufficient to restore the strength in these systems. A Gleeble thermo-mechanical simulator was used to perform multi-pass welding simulations on samples of each material using a 1000 J/mm and 2000 J/mm heat input. Additionally, base metal and weld metal samples were used as starting conditions to evaluate the difference in precipitation response between each. Hardness measurements were used to estimate the extent of precipitate dissolution and growth. Microstructures were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). It was determined that precipitate dissolution occurred during primary welding thermal cycles and that significant hardening could be achieved using secondary welding thermal cycles for both heat inputs. Additionally, it was observed that the weld metal and base metal had similar precipitation responses. The preliminary multi-pass welding simulations demonstrated that the times and temperatures associated with welding thermal cycles were sufficient to promote precipitation in each system. Furthermore, these findings indicate that controlled weld metal deposition may be a viable method for optimizing welding procedures and eliminating the need for a PWHT. Next, an in-depth Gleeble study was performed to develop a fundamental understanding of the reactions that occur in 17-4 and 13-8+Mo during exposure to times and temperatures representative of multi-pass welding. Samples of each material were subjected to a series of short isothermal holds at high temperatures and hardness measurements were recorded to investigate the dissolution behavior of each alloy. Additional secondary isothermal experiments were performed on samples that had been subjected to a high temperature primary thermal cycle and hardness measurements were recorded. Matrix microstructures were characterized by LOM and reverted austenite measurements were recorded using X-ray diffraction techniques. The hardness data from the secondary heating tests was used in combination with Avrami kinetics equations to develop a relationship between the hardness and fraction transformed of the strengthening precipitates. It was determined that the Avrami relationships provide a useful approximation of the precipitation behavior at times and temperatures representative of welding thermal cycles. Finally, an autogenous gas tungsten arc (GTA) welding study was performed to demonstrate the utility of multi-pass welding for strength restoration in these alloys. Dual-pass welds were made on samples of each material using a range of heat inputs and secondary weld pass overlap percentages. Hardness mapping was then performed to estimate the extent of precipitate growth and dissolution. It was determined that significant softening occurs after primary weld passes and that secondary weld passes, using a high heat input, restored much of the strength. Furthermore, optimal weld overlap percentages were approximated. It was concluded that controlled weld metal deposition can significantly improve the properties of 17-4 and 13-8+Mo and potentially eliminate the need for costly PWHT's.

Recent advances of mid-infrared compact, field deployable sensors: principles and applications

NASA Astrophysics Data System (ADS)

Tittel, Frank; Gluszek, Aleksander; Hudzikowski, Arkadiusz; Dong, Lei; Li, Chunguang; Patimisco, Pietro; Sampaolo, Angelo; Spagnolo, Vincenzo; Wojtas, Jacek

2016-04-01

The recent development of compact interband cascade lasers(ICLs) and quantum cascade lasers (QCLs) based trace gas sensors will permit the targeting of strong fundamental rotational-vibrational transitions in the mid-infrared which are one to two orders of magnitude more intense than transitions in the overtone and combination bands in the near-infrared. This has led to the design and fabrication of mid-infrared compact, field deployable sensors for use in the petrochemical industry, environmental monitoring and atmospheric chemistry. Specifically, the spectroscopic detection and monitoring of four molecular species, methane (CH4) [1], ethane (C2H6), formaldehyde (H2CO) [2] and hydrogen sulphide (H2S) [3] will be described. CH4, C2H6 and H2CO can be detected using two detection techniques: mid-infrared tunable laser absorption spectroscopy (TDLAS) using a compact multi-pass gas cell and quartz enhanced photoacoustic spectroscopy (QEPAS). Both techniques utilize state-of-the-art mid-IR, continuous wave (CW), distributed feedback (DFB) ICLs and QCLs. TDLAS was performed with an ultra-compact 54.6m effective optical path length innovative spherical multipass gas cell capable of 435 passes between two concave mirrors separated by 12.5 cm. QEPAS used a small robust absorption detection module (ADM) which consists of a quartz tuning fork (QTF), two optical windows, gas inlet/outlet ports and a low noise frequency pre-amplifier. Wavelength modulation and second harmonic detection were employed for spectral data processing. TDLAS and QEPAS can achieve minimum detectable absorption losses in the range from 10-8 to 10-11cm-1/Hz1/2. Several recent examples of real world applications of field deployable gas sensors will be described. For example, an ICL based TDLAS sensor system is capable of detecting CH4 and C2H6 concentration levels of 1 ppb in a 1 sec. sampling time, using an ultra-compact, robust sensor architecture. H2S detection was realized with a THz QEPAS sensor system using a custom quartz tuning fork (QTF) with a new geometry and a QCL emitting at 2.913 THz [4]. Furthermore, two new approaches aimed to achieve enhanced detection sensitivities with QEPAS based sensing can be realized. The first method will make use of a compact optical power buildup cavity, which achieves significantly lower minimum detectable trace gas concentration levels of < 10 pptv. The second approach will use custom fabricated QTFs capable of improved detection sensitivity. Acknowledgements F.K. Tittel acknowledges support by the National Science Foundation (NSF) ERC MIRTHE award, the Robert Welch Foundation (Grant C-0586) and DOE ARPA-E Monitor Proram. L. Dong acknowledges support by NSF-China (Grant #s. 61275213, 61108030), J. Wojtas acknowledges support by The National Centre for Research and Development, Poland (project ID: 179616). References [1] L. Dong, C. Li, N. P. Sanchez, A. K. Gluszek, R. Griffin and F. K. Tittel;" Compact CH4 sensor system based on a continuous-wave, low power consumption, room temperature interband cascade laser", Appl. Phys Lett. 108, 011106 (2016). [2] L. Dong, Y. Yu, C. Li, S. So, and F.K. Tittel, "Ppb-level formaldehyde detection using a CW room-temperature interband cascade laser and a miniature dense pattern multipass cell" Optics Express; 23, 19821-19830 (2015). [3] V. Spagnolo, P. Patimisco, R. Pennetta, A. Sampaolo, G. Scamarcio, M. Vitiello, and F.K. Tittel, "THz Quartz-enhanced photoacoustic sensor for H2S trace gas detection", Opt. Exp. 23, 7574-7582 (2015). [4] A. Sampaolo, P. Patimisco, L. Dong , A. Geras, S, G. Scamarcio' T. Starecki, F.K Tittel, V. Spagnolo; "Quartz-Enhanced Photoacoustic Spectroscopy exploiting tuning fork overtone modes", Appl. Phys Lett. 107, 231102 (2015).

Automated Test Case Generator for Phishing Prevention Using Generative Grammars and Discriminative Methods

ERIC Educational Resources Information Center

Palka, Sean

2015-01-01

This research details a methodology designed for creating content in support of various phishing prevention tasks including live exercises and detection algorithm research. Our system uses probabilistic context-free grammars (PCFG) and variable interpolation as part of a multi-pass method to create diverse and consistent phishing email content on…

Advances in ultrasonic testing of austenitic stainless steel welds. Towards a 3D description of the material including attenuation and optimisation by inversion

NASA Astrophysics Data System (ADS)

Moysan, J.; Gueudré, C.; Ploix, M.-A.; Corneloup, G.; Guy, Ph.; Guerjouma, R. El; Chassignole, B.

In the case of multi-pass welds, the material is very difficult to describe due to its anisotropic and heterogeneous properties. Anisotropy results from the metal solidification and is correlated with the grain orientation. A precise description of the material is one of the key points to obtain reliable results with wave propagation codes. A first advance is the model MINA which predicts the grain orientations in multi-pass 316-L steel welds. For flat position welding, good predictions of the grains orientations were obtained using 2D modelling. In case of welding in position the resulting grain structure may be 3D oriented. We indicate how the MINA model can be improved for 3D description. A second advance is a good quantification of the attenuation. Precise measurements are obtained using plane waves angular spectrum method together with the computation of the transmission coefficients for triclinic material. With these two first advances, the third one is now possible: developing an inverse method to obtain the material description through ultrasonic measurements at different positions.

A ppb level sensitive sensor for atmospheric methane detection

NASA Astrophysics Data System (ADS)

Xia, Jinbao; Zhu, Feng; Zhang, Sasa; Kolomenskii, Alexandre; Schuessler, Hans

2017-11-01

A high sensitivity sensor, combining a multipass cell and wavelength modulation spectroscopy in the near infrared spectral region was designed and implemented for trace gas detection. The effective length of the multipass cell was about 290 meters. The developed spectroscopic technique demonstrates an improved sensitivity of methane in ambient air and a relatively short detection time compared to previously reported sensors. Home-built electronics and software were employed for diode laser frequency modulation, signal lock-in detection and processing. A dual beam scheme and a balanced photo-detector were implemented to suppress the intensity modulation and noise for better detection sensitivity. The performance of the sensor was evaluated in a series of measurements ranging from three hours to two days. The average methane concentration measured in ambient air was 2.01 ppm with a relative error of ± 2.5%. With Allan deviation analysis, it was found that the methane detection limit of 1.2 ppb was achieved in 650 s. The developed sensor is compact and portable, and thus it is well suited for field measurements of methane and other trace gases.

Quantum-classical boundary for precision optical phase estimation

NASA Astrophysics Data System (ADS)

Birchall, Patrick M.; O'Brien, Jeremy L.; Matthews, Jonathan C. F.; Cable, Hugo

2017-12-01

Understanding the fundamental limits on the precision to which an optical phase can be estimated is of key interest for many investigative techniques utilized across science and technology. We study the estimation of a fixed optical phase shift due to a sample which has an associated optical loss, and compare phase estimation strategies using classical and nonclassical probe states. These comparisons are based on the attainable (quantum) Fisher information calculated per number of photons absorbed or scattered by the sample throughout the sensing process. We find that for a given number of incident photons upon the unknown phase, nonclassical techniques in principle provide less than a 20 % reduction in root-mean-square error (RMSE) in comparison with ideal classical techniques in multipass optical setups. Using classical techniques in a different optical setup that we analyze, which incorporates additional stages of interference during the sensing process, the achievable reduction in RMSE afforded by nonclassical techniques falls to only ≃4 % . We explain how these conclusions change when nonclassical techniques are compared to classical probe states in nonideal multipass optical setups, with additional photon losses due to the measurement apparatus.

High pressure homogenization vs heat treatment: safety and functional properties of liquid whole egg.

PubMed

Patrignani, Francesca; Vannini, Lucia; Sado Kamdem, Sylvain L; Hernando, Isabel; Marco-Molés, Raquel; Guerzoni, M Elisabetta; Lanciotti, Rosalba

2013-10-01

This research investigated the potential of multi-pass homogenization treatment for the inactivation of Salmonella enterica serovar Enteritidis inoculated at different levels in liquid whole egg (LWE) comparing the efficacy of this treatment with a traditional thermal one performed at 65 °C. Moreover, the effects of high pressure treatment (HPH) on structural and functional properties such as viscosity, microstructure and foaming abilities of LWE were investigated. The data obtained suggested that the multi-pass high pressure treatment at 100 MPa of S. enterica serovar Enteritidis inoculated in LWE at 7 and 4 log CFU/ml resulted in a first order inactivation kinetic, while the thermal inactivation curves of S. enterica serovar Enteritidis inoculated at 8 and 4 log CFU/ml presented a non-linear behaviour, with a marked tail after 3 min of treatment at 65 °C. Additionally, HPH treatment caused an increase in foaming capacity of LWE, with respect to the untreated samples, passing from values of 26% of the control to 50% of pressure treated samples. Copyright © 2013 Elsevier Ltd. All rights reserved.

Stacking-fault strengthening of biomedical Co-Cr-Mo alloy via multipass thermomechanical processing.

PubMed

Yamanaka, Kenta; Mori, Manami; Sato, Shigeo; Chiba, Akihiko

2017-09-07

The strengthening of metallic biomaterials, such as Co-Cr-Mo and titanium alloys, is of crucial importance to the improvement of the durability of orthopedic implants. In the present study, we successfully developed a face-centered cubic (fcc) Co-Cr-Mo alloy with an extremely high yield strength (1400 MPa) and good ductility (12%) by multipass hot-rolling, which is suitable for industrial production, and examined the relevant strengthening mechanisms. Using an X-ray diffraction line-profile analysis, we revealed that a substantial increase in the number of stacking faults (SFs) in the fcc γ-matrix occurred at a greater height reduction (r), while physical modeling demonstrated that the contribution of the accumulated SFs (i.e., the reduction in SF spacing) with an increase in r successfully explains the entire strengthening behavior of the hot-rolled alloy. The present study sheds light on the importance of the SF strengthening mechanism, and will help to guide the design and manufacturing strategy for the high-strength Co-Cr-Mo alloys used in highly durable medical devices.

Modified Welding Technique of a Hypo-Eutectic Al-Cu Alloy for Higher Mechanical Properties

NASA Astrophysics Data System (ADS)

Ghosh, B. R.; Gupta, R. K.; Biju, S.; Sinha, P. P.

GTAW process is used for welding of pressure vessels made of hypo-eutectic Al-Cu alloy AA2219 containing 6.3% Cu. As welded Yield strength of the alloy was found to be in the range of 140-150 MPa, using conventional single pass GTAW technique on both AC and DCSP modes. Interestingly, it was also found that weld-strength decreased with increase in thickness of the weld coupons. Welding metallurgy of AA2219 Al alloy was critically reviewed and factors responsible for lower properties were identified. Multipass GTAW on DCSP mode was postulated to improve the weld strength of this alloy. A systematic experimentation using 12 mm thick plates was carried out and YS of 200 MPa has been achieved in the as welded condition. Thorough characterization including optical and electron microscopy was conducted to validate the metallurgical phenomena attributable to improvement in weld strength. This paper presents the conceptual understanding of welding metallurgy of AA2219 alloy and validation by experiments, which could lead to better weld properties using multipass GTAW on DCSP mode.

Development of a Submillimeter Multipass Spectrometer for the Study of Molecular Ions

NASA Astrophysics Data System (ADS)

Carroll, A.; Rocher, B.; Laas, J. C.; Deprince, B. A.; Hays, B.; Weaver, S. L. Widicus; Lang, S.

2012-06-01

We have developed a multipass spectrometer for the submillimeter spectral region that is being used to study molecular ions through gas phase spectroscopy. The optical configuration is based on the design of Perry and coworkers that was implemented in the optical regime. To our knowledge, this is the first implementation of this optical configuration at long wavelengths. The setup involves two nearly concentric spherical mirrors that focus the multiple beam passes into a small area, or ``waist'', in the middle of the sample chamber. A supersonic molecular beam is coupled to the setup so that the molecular beam crosses the optical path at the waist. Initial studies have focused on neutral test molecules to probe the physical properties of the molecular beam under various arrangements of the molecular source relative to the optical path. Current studies focus on coupling a plasma discharge source to the setup to enable the study of molecular ions. Here we present the design of this instrument, compare the spectrometer capabilities to a traditional single pass spectrometer, and discuss the results of initial spectroscopic studies.

Precipitation behavior of σ phase in fusion zone of dissimilar stainless steel welds during multi-pass GTAW process

NASA Astrophysics Data System (ADS)

Hsieh, Chih-Chun; Chang, Tao-Chih; Lin, Dong-Yih; Chen, Ming-Che; Wu, Weite

2007-10-01

The purpose of this study is to investigate the precipitation characteristics of σ phase in the fusion zone of stainless steel welds at various welding passes during a tungsten are welding (GTAW) process. The morphology, quantity, and chemical composition of the δ-ferrite and σ phase were analyzed using optical microscopy (OM), a ferritscope (FS), a X-ray diffractometer (XRD), scanning electron microscopy (SEM), an electron probe micro-analyzer (EPMA), and a wavelength dispersive spectrometer (WDS), respectively. Massive δ-ferrite was observed in the fusion zone of the first pass welds during welding of dissimilar stainless steels. The σ phase precipitated at the inner δ-ferrite particles and decreased δ-ferrite content during the third pass welding. The σ and δ phases can be stabilized by Si element, which promoted the phase transformation of σ→ϱ+λ2 in the fusion zone of the third pass welds. It was found that the σ phase was a Fe-Cr-Si intermetallic compound found in the fusion zone of the third pass welds during multi-pass welding.

Weighted least-squares solver for determining pressure from particle image velocimetry data

NASA Astrophysics Data System (ADS)

de Kat, Roeland

2016-11-01

Currently, most approaches to determine pressure from particle image velocimetry data are Poisson approaches (e.g.) or multi-pass marching approaches (e.g.). However, these approaches deal with boundary conditions in their specific ways which cannot easily be changed-Poisson approaches enforce boundary conditions strongly, whereas multi-pass marching approaches enforce them weakly. Under certain conditions (depending on the certainty of the data or availability of reference data along the boundary) both types of boundary condition enforcement have to be used together to obtain the best result. In addition, neither of the approaches takes the certainty of the particle image velocimetry data (see e.g.) within the domain into account. Therefore, to address these shortcomings and improve upon current approaches, a new approach is proposed using weighted least-squares. The performance of this new approach is tested on synthetic and experimental particle image velocimetry data. Preliminary results show that a significant improvement can be made in determining pressure fields using the new approach. RdK is supported by a Leverhulme Trust Early Career Fellowship.

Effect of Multipass TIG and Activated TIG Welding Process on the Thermo-Mechanical Behavior of 316LN Stainless Steel Weld Joints

NASA Astrophysics Data System (ADS)

Ganesh, K. C.; Balasubramanian, K. R.; Vasudevan, M.; Vasantharaja, P.; Chandrasekhar, N.

2016-04-01

The primary objective of this work was to develop a finite element model to predict the thermo-mechanical behavior of an activated tungsten inert gas (ATIG)-welded joint. The ATIG-welded joint was fabricated using 10 mm thickness of 316LN stainless steel plates in a single pass. To distinguish the merits of ATIG welding process, it was compared with manual multipass tungsten inert gas (MPTIG)-welded joint. The ATIG-welded joint was fabricated with square butt edge configuration using an activating flux developed in-house. The MPTIG-welded joint was fabricated in thirteen passes with V-groove edge configuration. The finite element model was developed to predict the transient temperature, residual stress, and distortion of the welded joints. Also, microhardness, impact toughness, tensile strength, ferrite measurement, and microstructure were characterized. Since most of the recent publications of ATIG-welded joint was focused on the molten weld pool dynamics, this research work gives an insight on the thermo-mechanical behavior of ATIG-welded joint over MPTIG-welded joint.

A Novel Low-Power, High-Performance, Zero-Maintenance Closed-Path Trace Gas Eddy Covariance System with No Water Vapor Dilution or Spectroscopic Corrections

NASA Astrophysics Data System (ADS)

Sargent, S.; Somers, J. M.

2015-12-01

Trace-gas eddy covariance flux measurement can be made with open-path or closed-path analyzers. Traditional closed-path trace-gas analyzers use multipass absorption cells that behave as mixing volumes, requiring high sample flow rates to achieve useful frequency response. The high sample flow rate and the need to keep the multipass cell extremely clean dictates the use of a fine-pore filter that may clog quickly. A large-capacity filter cannot be used because it would degrade the EC system frequency response. The high flow rate also requires a powerful vacuum pump, which will typically consume on the order of 1000 W. The analyzer must measure water vapor for spectroscopic and dilution corrections. Open-path analyzers are available for methane, but not for nitrous oxide. The currently available methane analyzers have low power consumption, but are very large. Their large size degrades frequency response and disturbs the air flow near the sonic anemometer. They require significant maintenance to keep the exposed multipass optical surfaces clean. Water vapor measurements for dilution and spectroscopic corrections require a separate water vapor analyzer. A new closed-path eddy covariance system for measuring nitrous oxide or methane fluxes provides an elegant solution. The analyzer (TGA200A, Campbell Scientific, Inc.) uses a thermoelectrically-cooled interband cascade laser. Its small sample-cell volume and unique sample-cell configuration (200 ml, 1.5 m single pass) provide excellent frequency response with a low-power scroll pump (240 W). A new single-tube Nafion® dryer removes most of the water vapor, and attenuates fluctuations in the residual water vapor. Finally, a vortex intake assembly eliminates the need for an intake filter without adding volume that would degrade system frequency response. Laboratory testing shows the system attenuates the water vapor dilution term by more than 99% and achieves a half-power band width of 3.5 Hz.

Quantum cascade laser-based multipass absorption system for hydrogen peroxide detection

NASA Astrophysics Data System (ADS)

Cao, Yingchun; Sanchez, Nancy P.; Jiang, Wenzhe; Ren, Wei; Lewicki, Rafal; Jiang, Dongfang; Griffin, Robert J.; Tittel, Frank K.

2015-01-01

Hydrogen peroxide (H2O2) is a relevant molecular trace gas species, that is related to the oxidative capacity of the atmosphere, the production of radical species such as OH, the generation of sulfate aerosol via oxidation of S(IV) to S(VI), and the formation of acid rain. The detection of atmospheric H2O2 involves specific challenges due to its high reactivity and low concentration (ppbv to sub-ppbv level). Traditional methods for measuring atmospheric H2O2 concentration are often based on wet-chemistry methods that require a transfer from the gas- to liquid-phase for a subsequent determination by techniques such as fluorescence spectroscopy, which can lead to problems such as sampling artifacts and interference by other atmospheric constituents. A quartz-enhanced photoacoustic spectroscopy-based system for the measurement of atmospheric H2O2 with a detection limit of 75 ppb for 1-s integration time was previously reported. In this paper, an updated H2O2 detection system based on long-optical-path-length absorption spectroscopy by using a distributed feedback quantum cascade laser (DFB-QCL) will be described. A 7.73-μm CW-DFB-QCL and a thermoelectrically cooled infrared detector, optimized for a wavelength of 8 μm, are employed for theH2O2 sensor system. A commercial astigmatic Herriott multi-pass cell with an effective optical path-length of 76 m is utilized for the reported QCL multipass absorption system. Wavelength modulation spectroscopy (WMS) with second harmonic detection is used for enhancing the signal-to-noise-ratio. A minimum detection limit of 13.4 ppb is achieved with a 2 s sampling time. Based on an Allan-Werle deviation analysis the minimum detection limit can be improved to 1.5 ppb when using an averaging time of 300 s.

Feedback Augmented Sub-Ranging (FASR) Quantizer

NASA Technical Reports Server (NTRS)

Guilligan, Gerard

2012-01-01

This innovation is intended to reduce the size, power, and complexity of pipeline analog-to-digital converters (ADCs) that require high resolution and speed along with low power. Digitizers are important components in any application where analog signals (such as light, sound, temperature, etc.) need to be digitally processed. The innovation implements amplification of a sampled residual voltage in a switched capacitor amplifier stage that does not depend on charge redistribution. The result is less sensitive to capacitor mismatches that cause gain errors, which are the main limitation of such amplifiers in pipeline ADCs. The residual errors due to mismatch are reduced by at least a factor of 16, which is equivalent to at least 4 bits of improvement. The settling time is also faster because of a higher feedback factor. In traditional switched capacitor residue amplifiers, closed-loop amplification of a sampled and held residue signal is achieved by redistributing sampled charge onto a feedback capacitor around a high-gain transconductance amplifier. The residual charge that was sampled during the acquisition or sampling phase is stored on two or more capacitors, often equal in value or integral multiples of each other. During the hold or amplification phase, all of the charge is redistributed onto one capacitor in the feedback loop of the amplifier to produce an amplified voltage. The key error source is the non-ideal ratios of feedback and input capacitors caused by manufacturing tolerances, called mismatches. The mismatches cause non-ideal closed-loop gain, leading to higher differential non-linearity. Traditional solutions to the mismatch errors are to use larger capacitor values (than dictated by thermal noise requirements) and/or complex calibration schemes, both of which increase the die size and power dissipation. The key features of this innovation are (1) the elimination of the need for charge redistribution to achieve an accurate closed-loop gain of two, (2) a higher feedback factor in the amplifier stage giving a higher closed-loop bandwidth compared to the prior art, and (3) reduced requirement for calibration. The accuracy of the new amplifier is mainly limited by the sampling networks parasitic capacitances, which should be minimized in relation to the sampling capacitors.

High Intensity Mirror-Free Nanosecond Ytterbium Fiber Laser System in Master Oscillator Power Amplification

NASA Astrophysics Data System (ADS)

Chun-Lin, Louis Chang

Rare-earth-doped fiber lasers and amplifiers are relatively easy to efficiently produce a stable and high quality laser beam in a compact, robust, and alignment-free configuration. Recently, high power fiber laser systems have facilitated wide spread applications in academics, industries, and militaries in replacement of bulk solid-state laser systems. The master oscillator power amplifier (MOPA) composed of a highly-controlled seed, high-gain preamplifiers, and high-efficiency power amplifiers are typically utilized to scale up the pulse energy, peak power, or average power. Furthermore, a direct-current-modulated nanosecond diode laser in single transverse mode can simply provide a compact and highly-controlled seed to result in the flexible output parameters, such as repetition rate, pulse duration, and even temporal pulse shape. However, when scaling up the peak power for high intensity applications, such a versatile diode-seeded nanosecond MOPA laser system using rare-earth-doped fibers is unable to completely save its own advantages compared to bulk laser systems. Without a strong seeding among the amplifiers, the guided amplified spontaneous amplification is easy to become dominant during the amplification, leading to the harmful self-lasing or pulsing effects, and the difficulty of the quantitative numerical comparison. In this dissertation, we study a high-efficiency and intense nanosecond ytterbium fiber MOPA system with good beam quality and stability for high intensity applications. The all-PM-fiber structure is achieved with the output extinction ratio of >12 dB by optimizing the interconnection of high power optical fibers. The diode-seeded MOPA configuration without parasitic stimulated amplification (PAS) is implemented using the double-pass scheme to extract energy efficiently for scaling peak power. The broadband PAS was studied experimentally, which matches well with our numerical simulation. The 1064-nm nanosecond seed was a direct-current-modulated Fabry-Perot diode laser associated with a weak and pulsed noise spanning from 1045 to 1063 nm. Even though the contribution of input noise pulse is only <5%, it becomes a significant transient spike during amplification. The blue-shifted pulsed noise may be caused by band filling effect for quantum-well seed laser driven by high peak current. The study helps the development of adaptive pulse shaping for scaling peak power or energy at high efficiency. On the other hand, the broadband spike with a 3-dB bandwidth of 8.8 nm can support pulses to seed the amplifier for sub-nanosecond giant pulse generation. Because of the very weak seed laser, the design of high-gain preamplifier becomes critical. The utilization of single-mode core-pumped fiber preamplifier can not only improve the mode contrast without fiber coiling effect but also significantly suppress the fiber nonlinearity. The double-pass scheme was therefore studied both numerically and experimentally to improve energy extraction efficiency for the lack of attainable seed and core-pumped power. As a result, a record-high peak power of > 30 kW and energy of > 0.23 mJ was successfully achieved to the best of our knowledge from the output of clad-pumped power amplifier with a beam quality of M2 ˜1.1 in a diode-seeded 15-microm-core fiber MOPA system. After the power amplifier, the MOPA conversion efficiency can be dramatically improved to >56% for an energy gain of >63 dB at a moderate repetition rate of 20 kHz with a beam quality of M 2 <1.5. The output energy of >1.1 mJ with a pulse duration of ˜6.1 ns can result in a peak power up to >116 kW which is limited by fiber fuse in long-term operation. Such a condition able to generate the on-target laser intensity of > 60 GW/cm2 for applications is qualified to preliminarily create a laser-plasma light source. Moreover, the related simulation results also reveal the double-passed power amplifier can further simplify MOPA. Such an intense clad-pumped power amplifier can further become a nonlinear fiber amplifier in all-normal dispersion instead of a nonlinear passive fiber. The combination of laser amplification and nonlinear conversion together can therefore overcome the significant pump depletion during the propagation along the passive fiber for power scaling. As a result, an intense spectrum spanning from 980 to 1600 nm as a high-power nanosecond supercontinuum source can be successfully generated with a conversion efficiency of >65% and a record-high peak power of >116 kW to the best of our knowledge. Because of MOPA structure, the influence of input parameters of nonlinear fiber amplifier on supercontinuum parameters can also be studied. The onset and interplay of fiber nonlinearities can be revealed stage by stage. Such an unique and linearly-polarized light source composed of an intense pump and broad sideband seed is beneficial for efficiently driving the broadband tunable optical parametric amplification free from the bulkiness and timing jitter. Keywords: High power fiber laser and amplifier, ytterbium fiber, master oscillator power amplification, parasitic stimulated amplification, multi-pass fiber amplification, peak power/pulse energy scaling, fiber nonlinear optics, supercontinuum generation.

A Compact Operational Amplifier with Load-Insensitive Stability Compensation for High-Precision Transducer Interface.

PubMed

Yu, Zhanghao; Yang, Xi; Chung, SungWon

2018-01-29

High-resolution electronic interface circuits for transducers with nonlinear capacitive impedance need an operational amplifier, which is stable for a wide range of load capacitance. Such operational amplifier in a conventional design requires a large area for compensation capacitors, increasing costs and limiting applications. In order to address this problem, we present a gain-boosted two-stage operational amplifier, whose frequency response compensation capacitor size is insensitive to the load capacitance and also orders of magnitude smaller compared to the conventional Miller-compensation capacitor that often dominates chip area. By exploiting pole-zero cancellation between a gain-boosting stage and the main amplifier stage, the compensation capacitor of the proposed operational amplifier becomes less dependent of load capacitance, so that it can also operate with a wide range of load capacitance. A prototype operational amplifier designed in 0.13-μm complementary metal-oxide-semiconductor (CMOS) with a 400-fF compensation capacitor occupies 900- μ m 2 chip area and achieves 0.022-2.78-MHz unity gain bandwidth and over 65 ∘ phase margin with a load capacitance of 0.1-15 nF. The prototype amplifier consumes 7.6 μ W from a single 1.0-V supply. For a given compensation capacitor size and a chip area, the prototype design demonstrates the best reported performance trade-off on unity gain bandwidth, maximum stable load capacitance, and power consumption.

High energy, single-polarized, single-transverse-mode, nanosecond pulses generated by a multi-stage Yb-doped photonic crystal fiber amplifier

NASA Astrophysics Data System (ADS)

Shen, Xinglai; Zhang, Haitao; Hao, He; Li, Dan; Li, Qinghua; Yan, Ping; Gong, Mali

2015-06-01

We report the construction of a cascaded fiber amplifier where a 40-μm-core-diameter photonic crystal fiber is utilized in the main amplifier stage. Single-transverse-mode, linearly-polarized, 7.5 ns pulses with 1.5 mJ energy, 123 kW peak power and 10 nm spectral bandwidth centered at 1062 nm are generated. To our knowledge, the pulse energy we obtain is the highest from 40-μm-core-diameter photonic crystal fibers, and also the highest for long pulses (>1 ns) with linear polarization and single transverse mode.

Multi-path interferometric Josephson directional amplifier for qubit readout

NASA Astrophysics Data System (ADS)

Abdo, Baleegh; Bronn, Nicholas T.; Jinka, Oblesh; Olivadese, Salvatore; Brink, Markus; Chow, Jerry M.

2018-04-01

We realize and characterize a quantum-limited, directional Josephson amplifier suitable for qubit readout. The device consists of two nondegenerate, three-wave-mixing amplifiers that are coupled together in an interferometric scheme, embedded in a printed circuit board. Nonreciprocity is generated by applying a phase gradient between the same-frequency pumps feeding the device, which plays the role of the magnetic field in a Faraday medium. Directional amplification and reflection-gain elimination are induced via wave interference between multiple paths in the system. We measure and discuss the main figures of merit of the device and show that the experimental results are in good agreement with theory. An improved version of this directional amplifier is expected to eliminate the need for bulky, off-chip isolation stages that generally separate quantum systems and preamplifiers in high-fidelity, quantum-nondemolition measurement setups.

Effects of hot compression deformation temperature on the microstructure and properties of Al-Zr-La alloys

NASA Astrophysics Data System (ADS)

Yue, Xian-hua; Liu, Chun-fang; Liu, Hui-hua; Xiao, Su-fen; Tang, Zheng-hua; Tang, Tian

2018-02-01

The main goal of this study is to investigate the microstructure and electrical properties of Al-Zr-La alloys under different hot compression deformation temperatures. In particular, a Gleeble 3500 thermal simulator was used to carry out multi-pass hot compression tests. For five-pass hot compression deformation, the last-pass deformation temperatures were 240, 260, 300, 340, 380, and 420°C, respectively, where the first-pass deformation temperature was 460°C. The experimental results indicated that increasing the hot compression deformation temperature with each pass resulted in improved electrical conductivity of the alloy. Consequently, the flow stress was reduced after deformation of the samples subjected to the same number of passes. In addition, the dislocation density gradually decreased and the grain size increased after hot compression deformation. Furthermore, the dynamic recrystallization behavior was effectively suppressed during the hot compression process because spherical Al3Zr precipitates pinned the dislocation movement effectively and prevented grain boundary sliding.

Recent progress on monolithic fiber amplifiers for next generation of gravitational wave detectors

NASA Astrophysics Data System (ADS)

Wellmann, Felix; Booker, Phillip; Hochheim, Sven; Theeg, Thomas; de Varona, Omar; Fittkau, Willy; Overmeyer, Ludger; Steinke, Michael; Weßels, Peter; Neumann, Jörg; Kracht, Dietmar

2018-02-01

Single-frequency fiber amplifiers in MOPA configuration operating at 1064 nm (Yb3+) and around 1550 nm (Er3+ or Er3+:Yb3+) are promising candidates to fulfill the challenging requirements of laser sources of the next generation of interferometric gravitational wave detectors (GWDs). Most probably, the next generation of GWDs is going to operate not only at 1064 nm but also at 1550 nm to cover a broader range of frequencies in which gravitational waves are detectable. We developed an engineering fiber amplifier prototype at 1064 nm emitting 215 W of linearly-polarized light in the TEM00 mode. The system consists of three modules: the seed source, the pre-amplifier, and the main amplifier. The modular design ensures reliable long-term operation, decreases system complexity and simplifies repairing and maintenance procedures. It also allows for the future integration of upgraded fiber amplifier systems without excessive downtimes. We also developed and characterized a fiber amplifier prototype at around 1550 nm that emits 100 W of linearly-polarized light in the TEM00 mode. This prototype uses an Er3+:Yb3+ codoped fiber that is pumped off-resonant at 940 nm. The off-resonant pumping scheme improves the Yb3+-to-Er3+ energy transfer and prevents excessive generation of Yb3+-ASE.

Learning Strategies: Secondary LD Students in the Mainstream.

ERIC Educational Resources Information Center

D'Antoni, Alice; And Others

The paper presents four learning strategy techniques--the SQ3R method of study, the Multipass Strategy, the Advanced Study Guide Technique, and Cognitive Mapping--for use with secondary level learning disabled students. The SQ3R method involves the five steps of survey, question, read, recite, and review. An adaption of the SQ3R method, the…

Technical advantages of disk laser technology in short and ultrashort pulse processes

NASA Astrophysics Data System (ADS)

Graham, P.; Stollhof, J.; Weiler, S.; Massa, S.; Faisst, B.; Denney, P.; Gounaris, E.

2011-03-01

This paper demonstrates that disk-laser technology introduces advantages that increase efficiency and allows for high productivity in micro-processing in both the nanosecond (ns) and picosecond (ps) regimes. Some technical advantages of disk technology include not requiring good pump beam quality or special wavelengths for pumping of the disk, high optical efficiencies, no thermal lensing effects and a possible scaling of output power without an increase of pump beam quality. With cavity-dumping, the pulse duration of the disk laser can be specified between 30 and hundreds of nanoseconds, but is independent of frequency, thus maintaining process stability. TRUMPF uses this technology in the 750 watts average power laser TruMicro 7050. High intensity, along with fluency, is important for high ablation rates in thinfilm removal. Thus, these ns lasers show high removal rates, above 60 cm2/s, in thin-film solar cell production. In addition, recent results in paint-stripping of aerospace material prove the green credentials and high processing rates inherent with this technology as it can potentially replace toxic chemical processes. The ps disk technology meanwhile is used in, for example, scribing of solar cells, wafer dicing and drilling injector nozzles, as the pulse duration is short enough to minimize heat input in the laser-matter interaction. In the TruMicro Series 5000, the multi-pass regenerative amplifier stage combines high optical-optical efficiencies together with excellent output beam quality for pulse durations of only 6 ps and high pulse energies of up to 0.25 mJ.

An LMS Programming Scheme and Floating-Gate Technology Enabled Trimmer-Less and Low Voltage Flame Detection Sensor.

PubMed

Iglesias-Rojas, Juan Carlos; Gomez-Castañeda, Felipe; Moreno-Cadenas, Jose Antonio

2017-06-14

In this paper, a Least Mean Square (LMS) programming scheme is used to set the offset voltage of two operational amplifiers that were built using floating-gate transistors, enabling a 0.95 V RMS trimmer-less flame detection sensor. The programming scheme is capable of setting the offset voltage over a wide range of values by means of electron injection. The flame detection sensor consists of two programmable offset operational amplifiers; the first amplifier serves as a 26 μV offset voltage follower, whereas the second amplifier acts as a programmable trimmer-less voltage comparator. Both amplifiers form the proposed sensor, whose principle of functionality is based on the detection of the electrical changes produced by the flame ionization. The experimental results show that it is possible to measure the presence of a flame accurately after programming the amplifiers with a maximum of 35 LMS-algorithm iterations. Current commercial flame detectors are mainly used in absorption refrigerators and large industrial gas heaters, where a high voltage AC source and several mechanical trimmings are used in order to accurately measure the presence of the flame.

An LMS Programming Scheme and Floating-Gate Technology Enabled Trimmer-Less and Low Voltage Flame Detection Sensor

PubMed Central

Iglesias-Rojas, Juan Carlos; Gomez-Castañeda, Felipe; Moreno-Cadenas, Jose Antonio

2017-01-01

In this paper, a Least Mean Square (LMS) programming scheme is used to set the offset voltage of two operational amplifiers that were built using floating-gate transistors, enabling a 0.95 VRMS trimmer-less flame detection sensor. The programming scheme is capable of setting the offset voltage over a wide range of values by means of electron injection. The flame detection sensor consists of two programmable offset operational amplifiers; the first amplifier serves as a 26 μV offset voltage follower, whereas the second amplifier acts as a programmable trimmer-less voltage comparator. Both amplifiers form the proposed sensor, whose principle of functionality is based on the detection of the electrical changes produced by the flame ionization. The experimental results show that it is possible to measure the presence of a flame accurately after programming the amplifiers with a maximum of 35 LMS-algorithm iterations. Current commercial flame detectors are mainly used in absorption refrigerators and large industrial gas heaters, where a high voltage AC source and several mechanical trimmings are used in order to accurately measure the presence of the flame. PMID:28613250

Coherent combining of high brightness tapered lasers in master oscillator power amplifier configuration

NASA Astrophysics Data System (ADS)

Albrodt, P.; Hanna, M.; Moron, F.; Decker, J.; Winterfeldt, M.; Blume, G.; Erbert, G.; Crump, P.; Georges, P.; Lucas-Leclin, G.

2018-02-01

Improved diode laser beam combining techniques are in strong demand for applications in material processing. Coherent beam combining (CBC) is the only combining approach that has the potential to maintain or even improve all laser properties, and thus has high potential for future systems. As part of our ongoing studies into CBC of diode lasers, we present recent progress in the coherent superposition of high-power single-pass tapered laser amplifiers. The amplifiers are seeded by a DFB laser at λ = 976 nm, where the seed is injected into a laterally single-mode ridge-waveguide input section. The phase pistons on each beam are actively controlled by varying the current in the ridge section of each amplifier, using a sequential hill-climbing algorithm, resulting in a combined beam with power fluctuations of below 1%. The currents into the tapered sections of the amplifiers are separately controlled, and remain constant. In contrast to our previous studies, we favour a limited number of individual high-power amplifiers, in order to preserve a high extracted power per emitter in a simple, low-loss coupling arrangement. Specifically, a multi-arm interferometer architecture with only three devices is used, constructed using 6 mm-long tapered amplifiers, mounted junction up on C-mounts, to allow separate contact to single mode and amplifier sections. A maximum coherently combined power of 12.9 W is demonstrated in a nearly diffraction-limited beam, corresponding to a 65% combining efficiency, with power mainly limited by the intrinsic beam quality of the amplifiers. Further increased combined power is currently sought.

Modulation instability in high power laser amplifiers.

PubMed

Rubenchik, Alexander M; Turitsyn, Sergey K; Fedoruk, Michail P

2010-01-18

The modulation instability (MI) is one of the main factors responsible for the degradation of beam quality in high-power laser systems. The so-called B-integral restriction is commonly used as the criteria for MI control in passive optics devices. For amplifiers the adiabatic model, assuming locally the Bespalov-Talanov expression for MI growth, is commonly used to estimate the destructive impact of the instability. We present here the exact solution of MI development in amplifiers. We determine the parameters which control the effect of MI in amplifiers and calculate the MI growth rate as a function of those parameters. The safety range of operational parameters is presented. The results of the exact calculations are compared with the adiabatic model, and the range of validity of the latest is determined. We demonstrate that for practical situations the adiabatic approximation noticeably overestimates MI. The additional margin of laser system design is quantified.

III Lead ECG Pulse Measurement Sensor

NASA Astrophysics Data System (ADS)

Thangaraju, S. K.; Munisamy, K.

2015-09-01

Heart rate sensing is very important. Method of measuring heart pulse by using an electrocardiogram (ECG) technique is described. Electrocardiogram is a measurement of the potential difference (the electrical pulse) generated by a cardiac tissue, mainly the heart. This paper also reports the development of a three lead ECG hardware system that would be the basis of developing a more cost efficient, portable and easy to use ECG machine. Einthoven's Three Lead method [1] is used for ECG signal extraction. Using amplifiers such as the instrumentation amplifier AD620BN and the conventional operational amplifier Ua741 that would be used to amplify the ECG signal extracted develop this system. The signal would then be filtered from noise using Butterworth filter techniques to obtain optimum output. Also a right leg guard was implemented as a safety feature to this system. Simulation was carried out for development of the system using P-spice Program.

A Compact Operational Amplifier with Load-Insensitive Stability Compensation for High-Precision Transducer Interface

PubMed Central

Yang, Xi

2018-01-01

High-resolution electronic interface circuits for transducers with nonlinear capacitive impedance need an operational amplifier, which is stable for a wide range of load capacitance. Such operational amplifier in a conventional design requires a large area for compensation capacitors, increasing costs and limiting applications. In order to address this problem, we present a gain-boosted two-stage operational amplifier, whose frequency response compensation capacitor size is insensitive to the load capacitance and also orders of magnitude smaller compared to the conventional Miller-compensation capacitor that often dominates chip area. By exploiting pole-zero cancellation between a gain-boosting stage and the main amplifier stage, the compensation capacitor of the proposed operational amplifier becomes less dependent of load capacitance, so that it can also operate with a wide range of load capacitance. A prototype operational amplifier designed in 0.13-μm complementary metal–oxide–semiconductor (CMOS) with a 400-fF compensation capacitor occupies 900-μm2 chip area and achieves 0.022–2.78-MHz unity gain bandwidth and over 65∘ phase margin with a load capacitance of 0.1–15 nF. The prototype amplifier consumes 7.6 μW from a single 1.0-V supply. For a given compensation capacitor size and a chip area, the prototype design demonstrates the best reported performance trade-off on unity gain bandwidth, maximum stable load capacitance, and power consumption. PMID:29382183

Multipass rotary shear comminution process to produce corn stover particles

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

Dooley, James H; Lanning, David N

A process of comminution of corn stover having a grain direction to produce a mixture of corn stover, by feeding the corn stover in a direction of travel substantially randomly to the grain direction one or more times through a counter rotating pair of intermeshing arrays of cutting discs (D) arrayed axially perpendicular to the direction of corn stover travel.

SCALAR MULTI-PASS ATOMIC MAGNETOMETER

DTIC Science & Technology

2017-08-01

primarily by atomic shot noise. Furthermore, the spectrum of quantum spin noise provides information on the time correlation between the spins and...the resulting light to be shot -noise-limited both with and without the polarizer in place. Newer Vixar VCSELs with internal gratings on output...described on inside pages STINFO COPY AIR FORCE RESEARCH LABORATORY SENSORS DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7320

The interface microstructure, mechanical properties and corrosion resistance of dissimilar joints during multipass laser welding for nuclear power plants

NASA Astrophysics Data System (ADS)

Li, Gang; Lu, Xiaofeng; Zhu, Xiaolei; Huang, Jian; Liu, Luwei; Wu, Yixiong

2018-05-01

This study presents the interface microstructure, mechanical properties and corrosion resistance of dissimilar joints between Inconel 52M overlays and 316L stainless steel during multipass laser welding for nuclear power plants. The results indicate that the microstructure at the interface beside 316L stainless steel consists of cellular with the width of 30-40 μm, which also exhibits numerous Cr and Mo-rich precipitates like flocculent structure and in chains along grain boundaries as a mixed chemical solution for etching. Many dendritic structure with local melting characteristics and Nb-rich precipitates are exhibited at the interface beside Inconel 52M overlays. Such Nb-rich precipitates at the interface beside Inconel 52M overlays deteriorate the tensile strength and toughness of dissimilar joints at room temperature. The tensile strength of 316L stainless steel at 350 °C significantly decreases with the result that dissimilar joints are fractured in 316L stainless steel. The correlation between corrosion behavior and microstructure of weld metals is also discussed. The difference in high corrosion potential between Nb-rich precipitates and the matrix could result in establishing effective galvanic couples, and thus accelerating the corrosion of weld metals.

Characterization of Multilayered Multipass Friction Stir Weld on ASTM A572 G50 Steel

DOE PAGES

Lim, Yong Chae; Sanderson, Samuel; Mahoney, Murray; ...

2014-01-01

A multilayered multipass friction stir weld (MM-FSW) on ASTM A572 Grade 50 steel was characterized to understand its potential application for thick-section structures. The 15-mm-thick section was fabricated by stacking up three steel plates and then friction stir welding the plates together in a total of 5 passes. The unique butt/lap joint configuration encountered in the multilayer weld was examined to understand the effect of tool rotation direction on the joint quality especially the formation of hooking defect. Charpy V-notch impact toughness tests showed generally higher impact toughness energy for the stir zone than the base metal with a ductilemore » fracture mode. The microhardness value was measured from 195 to 220 HV in the stir zone, while the base metal showed an average value of 170 HV. The microstructure in the stir zone and the adjacent heat affected zone was quantified using Optical and Scanning Electron Microscopy (SEM) including Electron Backscatter Diffraction (EBSD). The increased toughness and hardness were correlated with the refined microstructure in stir zone, resulting from severe plastic deformation and subsequent dynamic recrystallization during friction stir welding.« less

Improved compression technique for multipass color printers

NASA Astrophysics Data System (ADS)

Honsinger, Chris

1998-01-01

A multipass color printer prints a color image by printing one color place at a time in a prescribed order, e.g., in a four-color systems, the cyan plane may be printed first, the magenta next, and so on. It is desirable to discard the data related to each color plane once it has been printed, so that data from the next print may be downloaded. In this paper, we present a compression scheme that allows the release of a color plane memory, but still takes advantage of the correlation between the color planes. The compression scheme is based on a block adaptive technique for decorrelating the color planes followed by a spatial lossy compression of the decorrelated data. A preferred method of lossy compression is the DCT-based JPEG compression standard, as it is shown that the block adaptive decorrelation operations can be efficiently performed in the DCT domain. The result of the compression technique are compared to that of using JPEG on RGB data without any decorrelating transform. In general, the technique is shown to improve the compression performance over a practical range of compression ratios by at least 30 percent in all images, and up to 45 percent in some images.

Numerical investigation on the self-induced unsteadiness in tip leakage flow of a micro-axial fan rotor

NASA Astrophysics Data System (ADS)

Chen, Jinxin; Lai, Huanxin

2015-06-01

The self-induced unsteadiness in tip leakage flow (TLF) of a micro-axial fan rotor is numerically studied by solvingReynolds-averaged Navier-Stokes equations. The micro-axial fan, which is widely used in cooling systems of electronic devices, has a tip clearance of 6% of the axial chord length of the blade. At the design rotation speed, four cases near the peak efficiency point (PEP) with self-induced unsteadiness and four steady cases which have much weaker pressure fluctuations are investigated Using the "interface" separating the incoming main flow and the TLF defined by Du et al. [1], an explanation based on the propagation of the low energy spot and its multi-passing through the high gradient zone of the relativetotal pressure, is proposed to clarify the originating mechanism of the unsteadiness. At the operating points near the PEP, the main flow is weaker than the TLF and the interface moves upstream. The low energy spot which propagates along in the close behind of the interface has opportunity to circulate in the circumferential direction and passes through the sensitive interfaces several times, a slight perturbation therefore may be magnified significantlyand develops into the self-induced unsteadiness. The explanation is demonstrated by numerical results

Evaluation of genetic diversity in Chinese kale (Brassica oleracea L. var. alboglabra Bailey) by using rapid amplified polymorphic DNA and sequence-related amplified polymorphism markers.

PubMed

Zhang, J; Zhang, L G

2014-02-14

Chinese kale is an original Chinese vegetable of the Cruciferae family. To select suitable parents for hybrid breeding, we thoroughly analyzed the genetic diversity of Chinese kale. Random amplified polymorphic DNA (RAPD) and sequence-related amplified polymorphism (SRAP) molecular markers were used to evaluate the genetic diversity across 21 Chinese kale accessions from AVRDC and Guangzhou in China. A total of 104 bands were detected by 11 RAPD primers, of which 66 (63.5%) were polymorphic, and 229 polymorphic bands (68.4%) were observed in 335 bands amplified by 17 SRAP primer combinations. The dendrogram showed the grouping of the 21 accessions into 4 main clusters based on RAPD data, and into 6 clusters based on SRAP and combined data (RAPD + SRAP). The clustering of accessions based on SRAP data was consistent with petal colors. The Mantel test indicated a poor fit for the RAPD and SRAP data (r = 0.16). These results have an important implication for Chinese kale germplasm characterization and improvement.

Measurement device for high-precision spectral transmittance of solar blind filter

NASA Astrophysics Data System (ADS)

Wang, Yan; Qian, Yunsheng; Lv, Yang; Feng, Cheng; Liu, Jian

2017-02-01

In order to measure spectral transmittance of solar-blind filter ranging from ultraviolet to visible light accurately, a high-precision filter transmittance measuring system based on the ultraviolet photomultiplier is developed. The calibration method is mainly used to measure transmittance in this system, which mainly consists of an ultraviolet photomultiplier as core of the system and a lock-in amplifier combined with an optical modulator as the aided measurement for the system. The ultraviolet photomultiplier can amplify the current signal through the filter and have the characteristics of low dark current and high luminance gain. The optical modulator and the lock-in amplifier can obtain the signal from the photomultiplier and inhibit dark noise and spurious signal effectively. Through these two parts, the low light passing through the filters can be detected and we can calculate the transmittance by the optical power detected. Based on the proposed system, the limit detection of the transmittance can reach 10-12, while the result of the conventional approach is merely 10-6. Therefore, the system can make an effective assessment of solar blind ultraviolet filters.

Phase noise in RF and microwave amplifiers.

PubMed

Boudot, Rodolphe; Rubiola, Enrico

2012-12-01

Understanding amplifier phase noise is a critical issue in many fields of engineering and physics, such as oscillators, frequency synthesis, telecommunication, radar, and spectroscopy; in the emerging domain of microwave photonics; and in exotic fields, such as radio astronomy, particle accelerators, etc. Focusing on the two main types of base noise in amplifiers, white and flicker, the power spectral density of the random phase φ(t) is Sφ(f) = b(0) + b(-1)/f. White phase noise results from adding white noise to the RF spectrum in the carrier region. For a given RF noise level, b(0) is proportional to the reciprocal of the carrier power P(0). By contrast, flicker results from a near-dc 1/f noise-present in all electronic devices-which modulates the carrier through some parametric effect in the semiconductor. Thus, b(-1) is a parameter of the amplifier, constant in a wide range of P(0). The consequences are the following: Connecting m equal amplifiers in parallel, b(-1) is 1/m times that of one device. Cascading m equal amplifiers, b(-1) is m times that of one amplifier. Recirculating the signal in an amplifier so that the gain increases by a power of m (a factor of m in decibels) as a result of positive feedback (regeneration), we find that b(-1) is m(2) times that of the amplifier alone. The feedforward amplifier exhibits extremely low b(-1) because the carrier is ideally nulled at the input of its internal error amplifier. Starting with an extensive review of the literature, this article introduces a system-oriented model which describes the phase flickering. Several amplifier architectures (cascaded, parallel, etc.) are analyzed systematically, deriving the phase noise from the general model. There follow numerous measurements of amplifiers using different technologies, including some old samples, and in a wide frequency range (HF to microwaves), which validate the theory. In turn, theory and results provide design guidelines and give suggestions for CAD and simulation. To conclude, this article is intended as a tutorial, a review, and a systematic treatise on the subject, supported by extensive experiments.

Integration & Validation of LCU with Different Sub-systems for Diacrode based amplifier

NASA Astrophysics Data System (ADS)

Rajnish, Kumar; Verma, Sriprakash; Soni, Dipal; Patel, Hriday; Suthar, Gajendra; Dalicha, Hrushikesh; Dhola, Hitesh; Patel, Amit; Upadhayay, Dishang; Jha, Akhil; Patel, Manoj; Trivedi, Rajesh; Machchhar, Harsha; Singh, Raghuraj; Mukherjee, Aparajita

2017-04-01

ITER-India is responsible to deliver nine (8+1 spare) ICH & CD Power Sources to ITER. Each power source is capable to deliver 2.5 MW at 35 to 65 MHz frequency range with a load condition up to VSWR 2:1. For remote operation of different subsystems, Local Control Unit (LCU) is developed. LCU is developed using PXI hardware and Schneider PLC with Lab VIEW-RT developmental environment. All the protection function of the amplifier is running on PXI 7841 R module that ensures hard wired protection logic. There are three level of protection function- first by power supply itself that detects overcurrent/overvoltage and trips itself and generate trip signal for further action. There are some direct hardwired signal interfaces between power supplies to protect the amplifier. Second level of protection is generated through integrated controller of amplifier i.e. Command Control Embedded (CCE) against arc and Anode over current. Third level of Protection is through LCU where different fault signals are received and processed to generate off command for different sub-systems. Before connecting different subsystem with High power RF amplifiers (Driver & Final stage), each subsystem is individually tested through LCU. All protection functions are tested before hooking up the subsystems with main amplifier and initiating RF operation.

33 Years of Continuous Solar Radio Flux Observations

NASA Astrophysics Data System (ADS)

Monstein, Christian

2015-10-01

In 1982, after development and testing of several analog receiver concepts, I started continuous solar radio flux observations at 230 MHz. My instruments for the observations were based on cheap commercial components out of consumer TV electronics. The main components included a TV-tuner (at that time analog), intermediate frequency (IF) amplifier and video-detector taken from used TV sets. The 5.5 MHz wide video signal was fed into an integrating circuit, in fact a low pass filter, followed by dc-offset circuit and dc-amplifier built with four ua741 and CA3140 operational amplifier integrated circuits. At that time the signal was recorded with a Heathkit stripchart recorder and ink pen; an example is shown in figure 1.

Dynamics of a coherently driven micromaser by the Monte Carlo wavefunction approach

NASA Astrophysics Data System (ADS)

Bonacina, L.; Casagrande, F.; Lulli, A.

2000-08-01

Using a Monte Carlo wavefunction approach we investigate the dynamics of a micromaser driven by a resonant coherent field. At steady state, for increasing interaction times, the system exhibits driven Rabi oscillations, followed by collapse as the range of micromaser trapping states is approached. The system operates in regimes ranging from a strong to a weak amplifier. In the strong-amplifier regime the cavity mode shows a preferred phase and can exhibit quadrature squeezing and sub-Poissonian photon statistics. In the weak-amplifier regime the cavity mode has no preferred phase, is super-Poissonian and is influenced by trapping effects; no revival of Rabi oscillations occurs. The main predictions can be compared with experimental measurements on the populations of atoms leaving the cavity.

Quantum Device Applications of Mesoscopic Superconductivity

NASA Astrophysics Data System (ADS)

Hakonen, P. J.

2006-08-01

A brief account is given on the possibilities of mesoscopic superconductivity in low-noise amplifier and detector applications. In particular, three devices will be described: 1) Bloch oscillating transistor (BOT), 2) Inductively-read superconducting Cooper pair transistor (L-SET), and 3) Quantum capacitive phase detector (C-SET). The BOT is a low-noise current amplifier while the L-SET and C-SET act as ultra-sensitive charge and phase detectors, respectively. The basic operating principles and the main characteristics of these devices will be reviewed and discussed.

Phasing of two amplifier channels for the coherent combining of laser beams with a total power of 60 W

NASA Astrophysics Data System (ADS)

Trikshev, A. I.; Pyrkov, Yu. N.; Tsvetkov, V. B.

2017-12-01

We have demonstrated stable operation of a system for maintaining a constant phase difference between two laser channels with a total output power of 60 W. The system is based on a two-channel fibre amplifier with phase modulators based on piezoceramic spools. At a main piezo element modulation frequency of 11 kHz, the phasing time after thermal and mechanical influences on the active medium is 100 ms.

PDF text classification to leverage information extraction from publication reports.

PubMed

Bui, Duy Duc An; Del Fiol, Guilherme; Jonnalagadda, Siddhartha

2016-06-01

Data extraction from original study reports is a time-consuming, error-prone process in systematic review development. Information extraction (IE) systems have the potential to assist humans in the extraction task, however majority of IE systems were not designed to work on Portable Document Format (PDF) document, an important and common extraction source for systematic review. In a PDF document, narrative content is often mixed with publication metadata or semi-structured text, which add challenges to the underlining natural language processing algorithm. Our goal is to categorize PDF texts for strategic use by IE systems. We used an open-source tool to extract raw texts from a PDF document and developed a text classification algorithm that follows a multi-pass sieve framework to automatically classify PDF text snippets (for brevity, texts) into TITLE, ABSTRACT, BODYTEXT, SEMISTRUCTURE, and METADATA categories. To validate the algorithm, we developed a gold standard of PDF reports that were included in the development of previous systematic reviews by the Cochrane Collaboration. In a two-step procedure, we evaluated (1) classification performance, and compared it with machine learning classifier, and (2) the effects of the algorithm on an IE system that extracts clinical outcome mentions. The multi-pass sieve algorithm achieved an accuracy of 92.6%, which was 9.7% (p<0.001) higher than the best performing machine learning classifier that used a logistic regression algorithm. F-measure improvements were observed in the classification of TITLE (+15.6%), ABSTRACT (+54.2%), BODYTEXT (+3.7%), SEMISTRUCTURE (+34%), and MEDADATA (+14.2%). In addition, use of the algorithm to filter semi-structured texts and publication metadata improved performance of the outcome extraction system (F-measure +4.1%, p=0.002). It also reduced of number of sentences to be processed by 44.9% (p<0.001), which corresponds to a processing time reduction of 50% (p=0.005). The rule-based multi-pass sieve framework can be used effectively in categorizing texts extracted from PDF documents. Text classification is an important prerequisite step to leverage information extraction from PDF documents. Copyright © 2016 Elsevier Inc. All rights reserved.

High-Throughput, Adaptive FFT Architecture for FPGA-Based Spaceborne Data Processors

NASA Technical Reports Server (NTRS)

NguyenKobayashi, Kayla; Zheng, Jason X.; He, Yutao; Shah, Biren N.

2011-01-01

Exponential growth in microelectronics technology such as field-programmable gate arrays (FPGAs) has enabled high-performance spaceborne instruments with increasing onboard data processing capabilities. As a commonly used digital signal processing (DSP) building block, fast Fourier transform (FFT) has been of great interest in onboard data processing applications, which needs to strike a reasonable balance between high-performance (throughput, block size, etc.) and low resource usage (power, silicon footprint, etc.). It is also desirable to be designed so that a single design can be reused and adapted into instruments with different requirements. The Multi-Pass Wide Kernel FFT (MPWK-FFT) architecture was developed, in which the high-throughput benefits of the parallel FFT structure and the low resource usage of Singleton s single butterfly method is exploited. The result is a wide-kernel, multipass, adaptive FFT architecture. The 32K-point MPWK-FFT architecture includes 32 radix-2 butterflies, 64 FIFOs to store the real inputs, 64 FIFOs to store the imaginary inputs, complex twiddle factor storage, and FIFO logic to route the outputs to the correct FIFO. The inputs are stored in sequential fashion into the FIFOs, and the outputs of each butterfly are sequentially written first into the even FIFO, then the odd FIFO. Because of the order of the outputs written into the FIFOs, the depth of the even FIFOs, which are 768 each, are 1.5 times larger than the odd FIFOs, which are 512 each. The total memory needed for data storage, assuming that each sample is 36 bits, is 2.95 Mbits. The twiddle factors are stored in internal ROM inside the FPGA for fast access time. The total memory size to store the twiddle factors is 589.9Kbits. This FFT structure combines the benefits of high throughput from the parallel FFT kernels and low resource usage from the multi-pass FFT kernels with desired adaptability. Space instrument missions that need onboard FFT capabilities such as the proposed DESDynl, SWOT (Surface Water Ocean Topography), and Europa sounding radar missions would greatly benefit from this technology with significant reductions in non-recurring cost and risk.

Design of high-capacity fiber-optic transport systems

NASA Astrophysics Data System (ADS)

Liao, Zhi Ming

2001-08-01

We study the design of fiber-optic transport systems and the behavior of fiber amplifiers/lasers with the aim of achieving higher capacities with larger amplifier spacing. Solitons are natural candidates for transmitting short pulses for high-capacity fiber-optic networks because of its innate ability to use two of fiber's main defects, fiber dispersion and fiber nonlinearity to balance each other. In order for solitons to retain its dynamic nature, amplifiers must be placed periodically to restore powers to compensate for fiber loss. Variational analysis is used to study the long-term stability of a periodical- amplifier system. A new regime of operation is identified which allows the use of a much longer amplifier spacing. If optical fibers are the blood vessels of an optical communication system, then the optical amplifier based on erbium-doped fiber is the heart. Optical communication systems can avoid the use of costly electrical regenerators to maintain system performance by being able to optically amplify the weakened signals. The length of amplifier spacing is largely determined by the gain excursion experienced by the solitons. We propose, model, and demonstrate a distributed erbium-doped fiber amplifier which can drastically reduce the amount of gain excursion experienced by the solitons, therefore allowing a much longer amplifier spacing and superior stability. Dispersion management techniques have become extremely valuable tools in the design of fiber-optic communication systems. We have studied in depth the advantage of different arnplification schemes (lumped and distributed) for various dispersion compensation techniques. We measure the system performance through the Q factor to evaluate the added advantage of effective noise figure and smaller gain excursion. An erbium-doped fiber laser has been constructed and characterized in an effort to develop a test bed to study transmission systems. The presence of mode-partition noise in an erbium-doped fiber laser was experimentally demonstrated. A numerical model has been developed using the Langevin rate equations and its predictions are in qualitative agreement with experimental data.

A programmable and self-adjusting class E amplifier for efficient wireless powering of biomedical implants.

PubMed

Stoecklin, S; Volk, T; Yousaf, A; Reindl, L

2015-01-01

In this paper, an enhanced approach of a class E amplifier being insensitive to coil impedance variations is presented. While state of the art class E amplifiers widely being used to supply implanted systems show a strong degradation of efficiency when powering distance, coil orientation or the implant current consumption deviate from the nominal design, the presented concept is able to detect these deviations on-line and to reconfigure the amplifier automatically. The concept is facilitated by a new approach of sensing the load impedance without interruption of the power supply to the implant, while the main components of the class E amplifier are programmable by software. Therefore, the device is able to perform dynamic impedance matching. Besides presenting the operational principle and the design equations, we show an adaptive prototype reader system which achieves a drain efficiency of up to 92% for a wide range of reflected coil impedances from 1 to 40 Ω. The integrated communication concept allows downlink data rates of up to 500 kBit/s, while the load modulation based uplink from implant to reader was verified of providing up to 1.35 MBit/s.

Wide-Temperature-Range Integrated Operational Amplifier

NASA Technical Reports Server (NTRS)

Mojarradi, Mohammad; Levanas, Greg; Chen, Yuan; Kolawa, Elizabeth; Cozy, Raymond; Blalock, Benjamin; Greenwell, Robert; Terry, Stephen

2007-01-01

A document discusses a silicon-on-insulator (SOI) complementary metal oxide/semiconductor (CMOS) integrated- circuit operational amplifier to be replicated and incorporated into sensor and actuator systems of Mars-explorer robots. This amplifier is designed to function at a supply potential less than or equal to 5.5 V, at any temperature from -180 to +120 C. The design is implemented on a commercial radiation-hard SOI CMOS process rated for a supply potential of less than or equal to 3.6 V and temperatures from -55 to +110 C. The design incorporates several innovations to achieve this, the main ones being the following: NMOS transistor channel lengths below 1 m are generally not used because research showed that this change could reduce the adverse effect of hot carrier injection on the lifetimes of transistors at low temperatures. To enable the amplifier to withstand the 5.5-V supply potential, a circuit topology including cascade devices, clamping devices, and dynamic voltage biasing was adopted so that no individual transistor would be exposed to more than 3.6 V. To minimize undesired variations in performance over the temperature range, the transistors in the amplifier are biased by circuitry that maintains a constant inversion coefficient over the temperature range.

Development of RAPD-SCAR markers for different Ganoderma species authentication by improved RAPD amplification and molecular cloning.

PubMed

Fu, J J; Mei, Z Q; Tania, M; Yang, L Q; Cheng, J L; Khan, M A

2015-05-25

The sequence-characterized amplified region (SCAR) is a valuable molecular technique for the genetic identification of any species. This method is mainly derived from the molecular cloning of the amplified DNA fragments achieved from the random amplified polymorphic DNA (RAPD). In this study, we collected DNA from 10 species of Ganoderma mushroom and amplified the DNA using an improved RAPD technique. The amplified fragments were then cloned into a T-vector, and positive clones were screened, indentified, and sequenced for the development of SCAR markers. After designing PCR primers and optimizing PCR conditions, 4 SCAR markers, named LZ1-4, LZ2-2, LZ8-2, and LZ9-15, were developed, which were specific to Ganoderma gibbosum (LZ1-4 and LZ8-2), Ganoderma sinense (LZ2-2 and LZ8-2), Ganoderma tropicum (LZ8-2), and Ganoderma lucidum HG (LZ9-15). These 4 novel SCAR markers were deposited into GenBank with the accession Nos. KM391935, KM391936, KM391937, and KM391938, respectively. Thus, in this study we developed specific SCAR markers for the identification and authentication of different Ganoderma species.

Study on ductility dip cracking susceptibility in Filler Metal 82 during welding

NASA Astrophysics Data System (ADS)

Chen, Jing-Qing; Lu, Hao; Cui, Wei

2011-06-01

In this paper, Ductility Dip Cracking (DDC) susceptibility in Inconel600 companion Filler Metal 82 (FM82) under different stress states is investigated. Inconel600 is a Ni-Cr-Fe alloy with excellent resistance to general corrosion, localized corrosion, and stress corrosion, which has been widely used in nuclear power plants. However, the companion FM82 has been shown to be susceptible to DDC in welding process. To resolve the problem, this work is mainly focused on evaluating DDC susceptibility in FM82 in welding process. First of all, Strain to Fracture (STF) test is used to achieve the DDC criterion under simple stress state, and the formation mechanism of DDC was explained. Real welding is a process with complex stress state. Later, to get the DDC susceptibility under complex stress state, models about multi-pass welding were built up by means of finite element method. According to numerical simulation results, relationship of deformation and temperature history is achieved. Moreover, susceptible locations and moments could be determined associated with STF results. The simulation results fairly agree with welding experiment from another research.

Object-oriented wavefront correction in an asymmetric amplifying high-power laser system

NASA Astrophysics Data System (ADS)

Yang, Ying; Yuan, Qiang; Wang, Deen; Zhang, Xin; Dai, Wanjun; Hu, Dongxia; Xue, Qiao; Zhang, Xiaolu; Zhao, Junpu; Zeng, Fa; Wang, Shenzhen; Zhou, Wei; Zhu, Qihua; Zheng, Wanguo

2018-05-01

An object-oriented wavefront control method is proposed aiming for excellent near-field homogenization and far-field distribution in an asymmetric amplifying high-power laser system. By averaging the residual errors of the propagating beam, smaller pinholes could be employed on the spatial filters to improve the beam quality. With this wavefront correction system, the laser performance of the main amplifier system in the Shen Guang-III laser facility has been improved. The residual wavefront aberration at the position of each pinhole is below 2 µm (peak-to-valley). For each pinhole, 95% of the total laser energy is enclosed within a circle whose diameter is no more than six times the diffraction limit. At the output of the main laser system, the near-field modulation and contrast are 1.29% and 7.5%, respectively, and 95% of the 1ω (1053 nm) beam energy is contained within a 39.8 µrad circle (6.81 times the diffraction limit) under a laser fluence of 5.8 J cm-2. The measured 1ω focal spot size and near-field contrast are better than the design values of the Shen Guang-III laser facility.

Differential CMOS Sub-Terahertz Detector with Subthreshold Amplifier.

PubMed

Yang, Jong-Ryul; Han, Seong-Tae; Baek, Donghyun

2017-09-09

We propose a differential-type complementary metal-oxide-semiconductor (CMOS) sub-terahertz (THz) detector with a subthreshold preamplifier. The proposed detector improves the voltage responsivity and effective signal-to-noise ratio (SNR) using the subthreshold preamplifier, which is located between the differential detector device and main amplifier. The overall noise of the detector for the THz imaging system is reduced by the preamplifier because it diminishes the noise contribution of the main amplifier. The subthreshold preamplifier is self-biased by the output DC voltage of the detector core and has a dummy structure that cancels the DC offsets generated by the preamplifier itself. The 200 GHz detector fabricated using 0.25 μm CMOS technology includes a low drop-out regulator, current reference blocks, and an integrated antenna. A voltage responsivity of 2020 kV/W and noise equivalent power of 76 pW/√Hz are achieved using the detector at a gate bias of 0.5 V, respectively. The effective SNR at a 103 Hz chopping frequency is 70.9 dB with a 0.7 W/m² input signal power density. The dynamic range of the raster-scanned THz image is 44.59 dB.

Differential CMOS Sub-Terahertz Detector with Subthreshold Amplifier

PubMed Central

Han, Seong-Tae; Baek, Donghyun

2017-01-01

We propose a differential-type complementary metal-oxide-semiconductor (CMOS) sub-terahertz (THz) detector with a subthreshold preamplifier. The proposed detector improves the voltage responsivity and effective signal-to-noise ratio (SNR) using the subthreshold preamplifier, which is located between the differential detector device and main amplifier. The overall noise of the detector for the THz imaging system is reduced by the preamplifier because it diminishes the noise contribution of the main amplifier. The subthreshold preamplifier is self-biased by the output DC voltage of the detector core and has a dummy structure that cancels the DC offsets generated by the preamplifier itself. The 200 GHz detector fabricated using 0.25 μm CMOS technology includes a low drop-out regulator, current reference blocks, and an integrated antenna. A voltage responsivity of 2020 kV/W and noise equivalent power of 76 pW/√Hz are achieved using the detector at a gate bias of 0.5 V, respectively. The effective SNR at a 103 Hz chopping frequency is 70.9 dB with a 0.7 W/m2 input signal power density. The dynamic range of the raster-scanned THz image is 44.59 dB. PMID:28891927

Dense Pattern Optical Multipass Cell

NASA Technical Reports Server (NTRS)

Silver, Joel A. (Inventor)

2009-01-01

A multiple pass optical cell and method comprising providing a pair of opposed cylindrical mirrors having curved axes with substantially equal focal lengths, positioning an entrance hole for introducing light into the cell and an exit hole for extracting light from the cell, wherein the entrance hole and exit hole are coextensive or non-coextensive, introducing light into the cell through the entrance hole, and extracting light from the cell through the exit hole.

Dense pattern optical multipass cell

DOEpatents

Silver, Joel A [Santa Fe, NM

2009-01-13

A multiple pass optical cell and method comprising providing a pair of opposed cylindrical mirrors having curved axes with substantially equal focal lengths, positioning an entrance hole for introducing light into the cell and an exit hole for extracting light from the cell, wherein the entrance hole and exit hole are coextensive or non-coextensive, introducing light into the cell through the entrance hole, and extracting light from the cell through the exit hole.

Determining Snow Depth Using Airborne Multi-Pass Interferometric Synthetic Aperture Radar

DTIC Science & Technology

2013-09-01

relatively low resolution 10m DEM of the survey area was obtained from the USDA NAIP and then geocorrected to match the SAR image area. Centered on...Propulsion Laboratory LiDAR Light Detection and Ranging METAR Meteorological reporting observations medivac Medical Evacuation NASA National...Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X- SAR) mission was a joint National Aeronautical and Space Administration ( NASA

High-temperature multipass cell for infrared spectroscopy of heated gases and vapors.

PubMed

Bartlome, R; Baer, M; Sigrist, M W

2007-01-01

In absorption spectroscopy, infrared spectra of heated gases or condensed samples in the vapor phase are usually recorded with a single pass heated gas cell. This device exhibits two orders of magnitude lower sensitivity than the high-temperature multipass cell presented in this article. Our device is a novel type of compact long path absorption cell that can withstand aggressive chemicals in addition to temperatures up to 723 K. The construction of the cell and its technical features are described in detail, paying special attention to the mechanisms that compensate for thermal expansion and that allow the user to vary the optical path length under any thermal or vacuum condition. The cell may be used with a laser source or implemented within a Fourier transform infrared spectrometer. Its design is compatible with optical arrangements using astigmatic mirrors or spherical mirrors in a Herriott configuration. Here we implement a homebuilt Herriott-type cell with a total optical path length of up to 35 m. In order to demonstrate the feasibility of the cell, methane and water vapor absorption lines showing dissimilar temperature effects on line intensity were recorded with the help of a mid-infrared laser source tunable between 3 and 4 microm. Emphasis is put on lines that are too weak to be recorded with a single pass cell.

Microstructure Evolution and Selective Corrosion Resistance in Underwater Multi-pass 2101 Duplex Stainless Steel Welding Joints

NASA Astrophysics Data System (ADS)

Hu, Yu; Shi, Yonghua; Shen, Xiaoqin; Wang, Zhongmin

2018-05-01

A recently developed promising material, 2101 lean duplex stainless steel, represents an alternative to 304 austenite stainless steel. In this work, multi-pass 2101 weld joints were fabricated using the flux-cored arc welding method in a hyperbaric chamber. The pressure varied from 0 to 0.75 MPa. The evolution of the welding process and microstructure was investigated. γ 2 formation in the reheated zones of the WM and HAZ was not uniform. The closer the reheated zone is to the subsequent heat source, the greater the γ 2 formation in the reheated zone. Sufficient primary austenite transformation inhibited Cr2N precipitation and the subsequent intragranular γ 2 formation in the reheated weld passes of the 0.45 MPa weld metal. The localized corrosion resistance of each zone of the 0.45 MPa DSS joint was measured using non-destructive double-loop electrochemical potentiokinetic reactivation tests. The localized corrosion was induced by γ 2 and Cr2N. The root region of the 0.45 MPa weld metal underwent two subsequent welding thermal cycles, which induced increased γ 2 formation and lower resistance to corrosion because of the decreased pitting resistance value of γ 2. The correlation between microstructure evolution and the distribution of selective corrosion was determined.

Inspection of thick welded joints using laser-ultrasonic SAFT.

PubMed

Lévesque, D; Asaumi, Y; Lord, M; Bescond, C; Hatanaka, H; Tagami, M; Monchalin, J-P

2016-07-01

The detection of defects in thick butt joints in the early phase of multi-pass arc welding would be very valuable to reduce cost and time in the necessity of reworking. As a non-contact method, the laser-ultrasonic technique (LUT) has the potential for the automated inspection of welds, ultimately online during manufacturing. In this study, testing has been carried out using LUT combined with the synthetic aperture focusing technique (SAFT) on 25 and 50mm thick butt welded joints of steel both completed and partially welded. EDM slits of 2 or 3mm height were inserted at different depths in the multi-pass welding process to simulate a lack of fusion. Line scans transverse to the weld are performed with the generation and detection laser spots superimposed directly on the surface of the weld bead. A CCD line camera is used to simultaneously acquire the surface profile for correction in the SAFT processing. All artificial defects but also real defects are visualized in the investigated thick butt weld specimens, either completed or partially welded after a given number of passes. The results obtained clearly show the potential of using the LUT with SAFT for the automated inspection of arc welds or hybrid laser-arc welds during manufacturing. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Ermelin, an endoplasmic reticulum transmembrane protein, contains the novel HELP domain conserved in eukaryotes.

PubMed

Suzuki, Akiko; Endo, Takeshi

2002-02-06

We have cloned a cDNA encoding a novel protein referred to as ermelin from mouse C2 skeletal muscle cells. This protein contained six hydrophobic amino acid stretches corresponding to transmembrane domains, two histidine-rich sequences, and a sequence homologous to the fusion peptides of certain fusion proteins. Ermelin also contained a novel modular sequence, designated as HELP domain, which was highly conserved among eukaryotes, from yeast to higher plants and animals. All these HELP domain-containing proteins, including mouse KE4, Drosophila Catsup, and Arabidopsis IAR1, possessed multipass transmembrane domains and histidine-rich sequences. Ermelin was predominantly expressed in brain and testis, and induced during neuronal differentiation of N1E-115 neuroblastoma cells but downregulated during myogenic differentiation of C2 cells. The mRNA was accumulated in hippocampus and cerebellum of brain and central areas of seminiferous tubules in testis. Epitope-tagging experiments located ermelin and KE4 to a network structure throughout the cytoplasm. Staining with the fluorescent dye DiOC(6)(3) identified this structure as the endoplasmic reticulum. These results suggest that at least some, if not all, of the HELP domain-containing proteins are multipass endoplasmic reticulum membrane proteins with functions conserved among eukaryotes.

CW EC-QCL-based sensor for simultaneous detection of H 2O, HDO, N 2O and CH 4 using multi-pass absorption spectroscopy

DOE PAGES

Yu, Yajun; Sanchez, Nancy P.; Griffin, Robert J.; ...

2016-05-03

A sensor system based on a continuous wave, external-cavity quantum-cascade laser (CW EC-QCL) was demonstrated for simultaneous detection of atmospheric H 2O, HDO, N 2O and CH 4 using a compact, dense pattern multi-pass gas cell with an effective path-length of 57.6 m. The EC-QCL with a mode-hop-free spectral range of 1225-1285 cm -1 operating at similar to 7.8 mu m was scanned covering four neighboring absorption lines, for H 2O at 1281.161 cm -1, HDO at 1281.455 cm -1, N 2O at 1281.53 cm -1 and CH 4 at 1281.61 cm -1. A first-harmonic-normalized wavelength modulation spectroscopy with second-harmonicmore » detection (WMS-2f/1f) strategy was employed for data processing. An Allan-Werle deviation analysis indicated that minimum detection limits of 1.77 ppmv for H 2O, 3.92 ppbv for HDO, 1.43 ppbv for N 2O, and 2.2 ppbv for CH 4 were achieved with integration times of 50-s, 50-s, 100-s and 129-s, respectively. In conclusion, experimental measurements of ambient air are also reported.« less

Analytical modeling of the thermomechanical behavior of ASTM F-1586 high nitrogen austenitic stainless steel used as a biomaterial under multipass deformation.

PubMed

Bernardes, Fabiano R; Rodrigues, Samuel F; Silva, Eden S; Reis, Gedeon S; Silva, Mariana B R; Junior, Alberto M J; Balancin, Oscar

2015-06-01

Precipitation-recrystallization interactions in ASTM F-1586 austenitic stainless steel were studied by means of hot torsion tests with multipass deformation under continuous cooling, simulating an industrial laminating process. Samples were deformed at 0.2 and 0.3 at a strain rate of 1.0s(-1), in a temperature range of 900 to 1200°C and interpass times varying from 5 to 80s. The tests indicate that the stress level depends on deformation temperature and the slope of the equivalent mean stress (EMS) vs. 1/T presents two distinct behaviors, with a transition at around 1100°C, the non-recrystallization temperature (Tnr). Below the Tnr, strain-induced precipitation of Z-phase (NbCrN) occurs in short interpass times (tpass<30s), inhibiting recrystallization and promoting stepwise stress build-up with strong recovery, which is responsible for increasing the Tnr. At interpass times longer than 30s, the coalescence and dissolution of precipitates promote a decrease in the Tnr and favor the formation of recrystallized grains. Based on this evidence, the physical simulation of controlled processing allows for a domain refined grain with better mechanical properties. Copyright © 2015 Elsevier B.V. All rights reserved.

Heat accumulation between scans during multi-pass cutting of carbon fiber reinforced plastics

NASA Astrophysics Data System (ADS)

Kononenko, T. V.; Freitag, C.; Komlenok, M. S.; Weber, R.; Graf, T.; Konov, V. I.

2018-02-01

Matrix evaporation caused by heat accumulation between scans (HAS) was studied in the case of multi-pass scanning of a laser beam over the surface of carbon fiber reinforced plastic (CFRP). The experiments were performed in two regimes, namely, in the process of CFRP cutting and in the regime of low-fluence irradiation avoiding ablation of carbon fibers. The feature of the ablation-free regime is that all absorbed energy remains in the material as heat, while in the cutting regime the fraction of residual heat is unknown. An analytical model based on two-dimensional (2D) heat flow was applied to predict the critical number of scans, after which the HAS effect causes a distinct growth of the matrix evaporation zone (MEZ). According to the model, the critical number of scans decreases exponentially with increasing laser power, while no dependence on the feed rate is expected. It was found that the model fits well to the experimental data obtained in the ablation-free regime where the heat input is well defined and known. In the cutting regime the measured significant reduction of the critical number of scans observed in deep grooves may be attributed to transformation of the heat flow geometry and to an expected increase of the residual heat fraction.

Beam-dynamics driven design of the LHeC energy-recovery linac

NASA Astrophysics Data System (ADS)

Pellegrini, Dario; Latina, Andrea; Schulte, Daniel; Bogacz, S. Alex

2015-12-01

The LHeC is envisioned as a natural upgrade of the LHC that aims at delivering an electron beam for collisions with the existing hadronic beams. The current baseline design for the electron facility consists of a multipass superconducting energy-recovery linac (ERL) operating in a continuous wave mode. The unprecedently high energy of the multipass ERL combined with a stringent emittance dilution budget poses new challenges for the beam optics. Here, we investigate the performances of a novel arc architecture based on a flexible momentum compaction lattice that mitigates the effects of synchrotron radiation while containing the bunch lengthening. Extensive beam-dynamics investigations have been performed with placet2, a recently developed tracking code for recirculating machines. They include the first end-to-end tracking and a simulation of the machine operation with a continuous beam. This paper briefly describes the Conceptual Design Report lattice, with an emphasis on possible and proposed improvements that emerged from the beam-dynamics studies. The detector bypass section has been integrated in the lattice, and its design choices are presented here. The stable operation of the ERL with a current up to ˜150 mA in the linacs has been validated in the presence of single- and multibunch wakefields, synchrotron radiation, and beam-beam effects.

Deformation Behavior and Microstructure Evolution of As-Cast 42CrMo Alloy in Isothermal and Non-isothermal Compression

NASA Astrophysics Data System (ADS)

Qin, Fangcheng; Li, Yongtang; Qi, Huiping; Lv, Zhenhua

2016-11-01

The isothermal and non-isothermal multi-pass compression tests of centrifugal casting 42CrMo steel were conducted on a Gleeble-3500 thermal simulation machine. The effects of compression passes and finishing temperatures on deformation behavior and microstructure evolution were investigated. It is found that the microstructure is homogeneous with equiaxed grains, and the flow stress does not show significant change with the increase in passes, while the peak softening coefficient increases first and then decreases during inter-pass. Moreover, the dominant mechanisms of controlled temperature and accumulated static recrystallization for grain refinement and its homogeneous distribution are found after 5 passes deformation. As the finishing temperature increases, the flow stress decreases gradually, but the dynamic recrystallization accelerates and softening effect increases, resulting in the larger grain size and homogeneous microstructure. The microhardness decreases sharply because the sufficient softening occurs in microstructure. When the finishing temperature is 890 °C, the carbide particles are precipitated in the vicinity of the grain boundaries, thus inhibiting the dislocation motion. Thus, the higher finishing temperature (≥970 °C) for centrifugal casting 42CrMo alloy should be avoided in non-isothermal multi-pass deformation, which is beneficial to grain refinement and properties improvement.

Highly sensitive lidar with a thumb-sized sensor-head built using an optical fiber preamplifier

NASA Astrophysics Data System (ADS)

Inoue, Daisuke; Ichikawa, Tadashi; Matsubara, Hiroyuki; Mao, Xueon; Maeda, Mitsutoshi; Nagashima, Chie; Kagami, Manabu

2011-06-01

We developed a LIDAR system with a sensor head as small as 22 cc, in spite of the inclusion of a scanning mechanism. This LIDAR system not only has a small body, but is also highly sensitive. Our LIDAR system is based on time-of-flight measurements, and it incorporates an optical fiber. The main feature of our system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enabled us to exceed the detection limit of thermal noise. In conventional LIDAR systems the detection limit is determined by thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the received signals directly. In the case of our LIDAR system, received signal is amplified by an optical fiber amplifier in front of the photo diode and the TIA. Therefore, our LIDAR system can boost the signal level before the weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode. We optimized the gain of the optical fiber amplifier and TIA in our LIDAR system such that it is capable of detecting a single photon. As a result, the detection limit of our LIDAR system is determined by shot noise. This small and highly sensitive measurement technology shows great potential for use in LIDAR with an optical preamplifier.

Development of a new photocatalytic oxidation air filter for aircraft cabin.

PubMed

Ginestet, A; Pugnet, D; Rowley, J; Bull, K; Yeomans, H

2005-10-01

A new photocatalytic oxidation air filter (PCO unit) has been designed for aircraft cabin applications. The PCO unit is designed as a regenerable VOC removal system in order to improve the quality of the recirculated air entering the aircraft cabin. The PCO was designed to be a modular unit, with four UV lamps sandwiched between two interchangeable titanium dioxide coated panels. Performances of the PCO unit has been measured in a single pass mode test rig in order to show the ability of the unit to decrease the amount of VOCs (toluene, ethanol, and acetone) entering it (VOCs are fed separately), and in a multipass mode test rig in order to measure the ability of the unit to clean the air of an experimental room polluted with the same VOCs (fed separately). Triangular cell panels have been chosen instead of the wire mesh panels because they have higher efficiency. The efficiency of the PCO unit depends on the type of VOCs that challenges it, toluene being the most difficult one to oxidise. The efficiency of the PCO unit decreases when the air flow rate increases. The multipass mode test results show that the VOCs are oxidized but additional testing time would be necessary in order to show if they can be fully oxidized. The intermediate reaction products are mainly acetaldehyde and formaldehyde whose amount depends on the challenge VOC. The intermediate reaction products are also oxidized and additional testing time would be necessary in order to show if they can be fully oxidized. The development of this new photocatalytic air filter is still going on. The VOC/odor removing adsorbers are available for only a small proportion of aircraft currently in service. The photocatalytic oxidation (PCO) technique has appeared to be a promising solution to odors problems met in aircraft. This article reports the test results of a new photocatalytic oxidation air filter (PCO unit) designed for aircraft cabin applications. The overall efficiency of the PCO unit is function of the compound (toluene, ethanol, and acetone) that challenges the unit and toluene appears to be the most difficult compound to oxidize. Test results have shown the influence of the design of the PCO unit, the air flow rate and the type of UV on the efficiency of the PCO unit. The results obtained in this study represent a first attempt on the way to design a filter for VOC removal in cabin aircraft applications. The PCO technique used by the tested prototype unit is able to partially oxidized the challenge VOCs but one has to be aware that some harmful intermediate reaction products (mainly formaldehyde and acetaldehyde) are produced during the oxidation process before being partially oxidized too.

Laser Tattoo Removal: A Clinical Update

PubMed Central

Ho, Stephanie GY; Goh, Chee Leok

2015-01-01

Techniques for tattoo removal have evolved significantly over the years. The commonly used Quality-switched (QS) ruby, alexandrite, and Nd:YAG lasers are the traditional workhorses for tattoo removal. Newer strategies using combination laser treatments, multi-pass treatments, and picosecond lasers offer promising results. The tattoo color and skin type of the patient are important considerations when choosing the appropriate laser. Standard protocols can be developed for the effective and safe treatment of tattoos. PMID:25949017

Analysis of Microstructure Refinement During Single-Pass and Multi-Pass Friction Stir Processing of Nial Propeller Bronze

DTIC Science & Technology

2010-09-01

on an Optical Micrograph of the Transverse View of Single-Pass NAB. After [5]............................................... 6 Figure 4 . Vertical...deformed and 6 elongated but does not see the same refinement that is seen inside the SZ [ 4 ]. The grain structure right outside the TMAZ will also...including grinding, polishing, and electropolishing . The first step was to grind the surface using a Buehler ECOMET 4 Variable Speed Grinder

A Low-Noise Transimpedance Amplifier for BLM-Based Ion Channel Recording.

PubMed

Crescentini, Marco; Bennati, Marco; Saha, Shimul Chandra; Ivica, Josip; de Planque, Maurits; Morgan, Hywel; Tartagni, Marco

2016-05-19

High-throughput screening (HTS) using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM) is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main challenges: (i) design of scalable microfluidic devices; (ii) design of compact ultra-low-noise transimpedance amplifiers able to detect currents in the pA range with bandwidth >10 kHz; (iii) design of compact, robust and scalable systems that integrate these two elements. This paper presents a low-noise transimpedance amplifier with integrated A/D conversion realized in CMOS 0.35 μm technology. The CMOS amplifier acquires currents in the range ±200 pA and ±20 nA, with 100 kHz bandwidth while dissipating 41 mW. An integrated digital offset compensation loop balances any voltage offsets from Ag/AgCl electrodes. The measured open-input input-referred noise current is as low as 4 fA/√Hz at ±200 pA range. The current amplifier is embedded in an integrated platform, together with a microfluidic device, for current recording from ion channels. Gramicidin-A, α-haemolysin and KcsA potassium channels have been used to prove both the platform and the current-to-digital converter.

A Low-Noise Transimpedance Amplifier for BLM-Based Ion Channel Recording

PubMed Central

Crescentini, Marco; Bennati, Marco; Saha, Shimul Chandra; Ivica, Josip; de Planque, Maurits; Morgan, Hywel; Tartagni, Marco

2016-01-01

High-throughput screening (HTS) using ion channel recording is a powerful drug discovery technique in pharmacology. Ion channel recording with planar bilayer lipid membranes (BLM) is scalable and has very high sensitivity. A HTS system based on BLM ion channel recording faces three main challenges: (i) design of scalable microfluidic devices; (ii) design of compact ultra-low-noise transimpedance amplifiers able to detect currents in the pA range with bandwidth >10 kHz; (iii) design of compact, robust and scalable systems that integrate these two elements. This paper presents a low-noise transimpedance amplifier with integrated A/D conversion realized in CMOS 0.35 μm technology. The CMOS amplifier acquires currents in the range ±200 pA and ±20 nA, with 100 kHz bandwidth while dissipating 41 mW. An integrated digital offset compensation loop balances any voltage offsets from Ag/AgCl electrodes. The measured open-input input-referred noise current is as low as 4 fA/√Hz at ±200 pA range. The current amplifier is embedded in an integrated platform, together with a microfluidic device, for current recording from ion channels. Gramicidin-A, α-haemolysin and KcsA potassium channels have been used to prove both the platform and the current-to-digital converter. PMID:27213382

Tripolar-cuff deviation from ideal model: assessment by bioelectric field simulations and saline-bath experiments.

PubMed

Triantis, Iasonas F; Demosthenous, Andreas

2008-06-01

Ideally, interference in neural measurements due to signals from nearby muscles can be completely eliminated with the use of tripolar cuffs, in combination with appropriate amplifier configurations, such as the quasi-tripole (QT) and the true-tripole (TT). The operation of these amplifiers, is based on the theoretical property of the nerve cuff to produce a linear relationship of potential versus distance along its length, internally, when external potentials appear between its ends. Thus, in principle, electroneurogram (ENG) recordings from an ideal tripolar cuff would be free from electromyogram (EMG) interference generated by nearby muscles. However, in practice the cuff exhibits non-ideal behaviour leading to "cuff imbalance". The main focus of this paper is to investigate the causes of cuff imbalance, to demonstrate that it should be incorporated as a main parameter in the theoretical ENG-recording cuff electrode model. In addition to cuff asymmetry and tissue growth, the proximity of the interference source to the cuff is shown to result in cuff imbalance. The influence of proximity imbalance on the performance of the QT and TT amplifiers is also considered. Proximity imbalance is studied using bioelectric field simulations and saline-bath experiments. Variation is observed with both distance (40 mm and 70 mm was examined) and orientation (0-180 degrees), with the latter causing a more severe effect especially when the source dipole and the cuff are vertical to each other. The simulations and measurements are in close agreement. Tissue growth imbalance and asymmetry imbalance are also investigated in vitro. Finally, the signal-to-interference ratio (SIR; ENG/EMG) of the QT and TT amplifiers is examined in the presence of cuff imbalance. It is shown that proximity imbalance results in their SIR to peak only at certain cuff orientation values. This important finding offers an insight as to why in practice ENG recordings using these amplifiers have been widely reported to be degraded by EMG interference.

Improved sensitivity via layered-double-hydroxide-uniformity-dependent chemiluminescence.

PubMed

Li, Zenghe; Wang, Dan; Yuan, Zhiqin; Lu, Chao

2016-12-01

In the last two decades nanoparticles have been widely applied to enhance chemiluminescence (CL). The morphology of nanoparticles has an important influence on nanoparticle-amplified CL. However, studies of nanoparticle-amplified CL focus mainly on the size and shape effects, and no attempt has been made to explore the influence of uniformity in nanoparticle-amplified CL processes. In this study we have investigated nanoparticle uniformity in the luminol-H 2 O 2 CL system using layered double hydroxides (LDHs) as a model material. The results demonstrated that the uniformity of LDHs played a key role in CL amplification. A possible mechanism is that LDHs with high uniformity possess abundant catalytic active sites, which results in high CL intensity. Meanwhile, the sensitivity for H 2 O 2 detection was increased by one order of magnitude (1.0 nM). Moreover, the uniform-LDH-amplified luminol CL could be applied to selective detection of glucose in human plasma samples. Furthermore, such a uniformity-dependent CL enhancement effect could adapted to other redox CL systems-for example, the peroxynitrous acid (ONOOH) CL system.

Design and Analysis of Compact DNA Strand Displacement Circuits for Analog Computation Using Autocatalytic Amplifiers.

PubMed

Song, Tianqi; Garg, Sudhanshu; Mokhtar, Reem; Bui, Hieu; Reif, John

2018-01-19

A main goal in DNA computing is to build DNA circuits to compute designated functions using a minimal number of DNA strands. Here, we propose a novel architecture to build compact DNA strand displacement circuits to compute a broad scope of functions in an analog fashion. A circuit by this architecture is composed of three autocatalytic amplifiers, and the amplifiers interact to perform computation. We show DNA circuits to compute functions sqrt(x), ln(x) and exp(x) for x in tunable ranges with simulation results. A key innovation in our architecture, inspired by Napier's use of logarithm transforms to compute square roots on a slide rule, is to make use of autocatalytic amplifiers to do logarithmic and exponential transforms in concentration and time. In particular, we convert from the input that is encoded by the initial concentration of the input DNA strand, to time, and then back again to the output encoded by the concentration of the output DNA strand at equilibrium. This combined use of strand-concentration and time encoding of computational values may have impact on other forms of molecular computation.

Gain drift compensation with no-feedback-loop developed for the X-IFU/ATHENA readout chain

NASA Astrophysics Data System (ADS)

Prêle, D.; Voisin, F.; Beillimaz, C.; Chen, S.; Goldwurm, A.

2016-07-01

The focal plane of the X-ray Integral Field Unit (X-IFU) instrument of the Athena observatory is composed of about 4000 micro-calorimeters. These sensors, based on superconducting Transition Edge Sensors, are read out through a frequency multiplexer and a base-band feedback to linearize SQUIDs. However, the loop gain of this feedback is lower than 10 in the modulated TES signal bandwidth, which is not enough to fix the gain of the full readout chain. Calibration of the instrument is planned to be done at a time scale larger than a dozen minutes and the challenging energy resolution goal of 2.5 eV at 6 keV will probably require a gain stability larger than 10-4 over a long duration. A large part of this gain is provided by a Low-Noise Amplifier (LNA) in the Warm Front-End Electronics (WFEE). To reach such gain stability over more than a dozen minutes, this non-cooled amplifier has to cope with the temperature and supply voltage variations. Moreover, mainly for noise reasons, common large loop gain with feedback can not be used. We propose a new amplifier topology using diodes as loads of a differential amplifier to provide a fixed voltage gain, independent of the temperature and of the bias fluctuations. This amplifier is designed using a 350 nm SiGe BiCMOS technology and is part of an integrated circuit developed for the WFEE. Our simulations provide the expected gain drift and noise performances of such structure. Comparison with standard resistive loaded differential pair clearly shows the advantages of the proposed amplifier topology with a gain drift decreasing by more than an order of magnitude. Performances of this diode loaded amplifier are discussed in the context of the X-IFU requirements.

Phase locking of an S-band wide-gap klystron amplifier with high power injection driven by a relativistic backward wave oscillator

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

Bai Xianchen; Zhang Jiande; Yang Jianhua

2012-12-15

Theoretical analyses and preliminary experiments on the phase-locking characteristics of an inductively loaded 2-cavity wide-gap klystron amplifier (WKA) with high power injection driven by a GW-class relativistic backward wave oscillator (RBWO) are presented. Electric power of the amplifier and oscillator is supplied by a single accelerator being capable of producing dual electron beams. The well phase-locking effect of the RBWO-WKA system requires the oscillator have good frequency reproducibility and stability from pulse to pulse. Thus, the main switch of the accelerator is externally triggered to stabilize the diode voltage and then the working frequency. In the experiment, frequency of themore » WKA is linearly locked by the RBWO. With a diode voltage of 530 kV and an input power of {approx}22 MW, an output power of {approx}230 MW with the power gain of {approx}10.2 dB is obtained from the WKA. As the main switch is triggered, the relative phase difference between the RBWO and the WKA is less than {+-}15 Degree-Sign in a single shot, and phase jitter of {+-}11 Degree-Sign is obtained within a series of shots with duration of about 40 ns.« less

Phase locking of an S-band wide-gap klystron amplifier with high power injection driven by a relativistic backward wave oscillator

NASA Astrophysics Data System (ADS)

Bai, Xianchen; Zhang, Jiande; Yang, Jianhua; Jin, Zhenxing

2012-12-01

Theoretical analyses and preliminary experiments on the phase-locking characteristics of an inductively loaded 2-cavity wide-gap klystron amplifier (WKA) with high power injection driven by a GW-class relativistic backward wave oscillator (RBWO) are presented. Electric power of the amplifier and oscillator is supplied by a single accelerator being capable of producing dual electron beams. The well phase-locking effect of the RBWO-WKA system requires the oscillator have good frequency reproducibility and stability from pulse to pulse. Thus, the main switch of the accelerator is externally triggered to stabilize the diode voltage and then the working frequency. In the experiment, frequency of the WKA is linearly locked by the RBWO. With a diode voltage of 530 kV and an input power of ˜22 MW, an output power of ˜230 MW with the power gain of ˜10.2 dB is obtained from the WKA. As the main switch is triggered, the relative phase difference between the RBWO and the WKA is less than ±15° in a single shot, and phase jitter of ±11° is obtained within a series of shots with duration of about 40 ns.

Strengthening of biomedical Ni-free Co-Cr-Mo alloy by multipass "low-strain-per-pass" thermomechanical processing.

PubMed

Mori, Manami; Yamanaka, Kenta; Sato, Shigeo; Tsubaki, Shinki; Satoh, Kozue; Kumagai, Masayoshi; Imafuku, Muneyuki; Shobu, Takahisa; Chiba, Akihiko

2015-12-01

Further strengthening of biomedical Co-Cr-Mo alloys is desired, owing to the demand for improvements to their durability in applications such as artificial hip joints, spinal rods, bone plates, and screws. Here, we present a strategy-multipass "low-strain-per-pass" thermomechanical processing-for achieving high-strength biomedical Co-Cr-Mo alloys with sufficient ductility. The process primarily consists of multipass hot deformation, which involves repeated introduction of relatively small amounts of strain to the alloy at elevated temperatures. The concept was verified by performing hot rolling of a Co-28 Cr-6 Mo-0.13N (mass%) alloy and its strengthening mechanisms were examined. Strength increased monotonically with hot-rolling reduction, eventually reaching 1,400 MPa in 0.2% proof stress, an exceptionally high value. Synchrotron X-ray diffraction (XRD) line-profile analysis revealed a drastic increase in the dislocation density with an increase in hot-rolling reduction and proposed that the significant strengthening was primarily driven by the increased dislocation density, while the contributions of grain refinement were minor. In addition, extra strengthening, which originates from contributions of planar defects (stacking faults/deformation twins), became apparent for greater hot-rolling reductions. The results obtained in this work help in reconsidering the existing strengthening strategy for the alloys, and thus, a novel feasible manufacturing route using conventional hot deformation processing, such as forging, rolling, swaging, and drawing, is realized. The results obtained in this work suggested a novel microstructural design concept/feasible manufacturing route of high-strength Co-Cr-Mo alloys using conventional hot deformation processing. The present strategy focuses on the strengthening due to the introduction of a high density of lattice defects rather than grain refinement using dynamic recrystallization (DRX). The hot-rolled samples obtained by our process exhibited exceptional strength, which is comparable to the highest strength reported for biomedical Co-Cr-Mo alloys. It was also found that the acceptable ductility can be obtained even in such highly distorted Co-Cr-Mo alloys. We described the strengthening mechanisms in detail; this will be helpful for further investigations or industrial realization of the proposed strategy. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Integrated circuits for accurate linear analogue electric signal processing

NASA Astrophysics Data System (ADS)

Huijsing, J. H.

1981-11-01

The main lines in the design of integrated circuits for accurate analog linear electric signal processing in a frequency range including DC are investigated. A categorization of universal active electronic devices is presented on the basis of the connections of one of the terminals of the input and output ports to the common ground potential. The means for quantifying the attributes of four types of universal active electronic devices are included. The design of integrated operational voltage amplifiers (OVA) is discussed. Several important applications in the field of general instrumentation are numerically evaluated, and the design of operatinal floating amplifiers is presented.

Highly sensitive LIDAR with a thumb-sized sensor-head built using an optical fiber preamplifier (3)

NASA Astrophysics Data System (ADS)

Inoue, Daisuke; Ichikawa, Tadashi; Matsubara, Hiroyuki; Kagami, Manabu

2013-05-01

We have developed a LIDAR system with a sensor head which, although it includes a scanning mechanism, is less than 20 cc in size. The system is not only small, but is also highly sensitive. Our LIDAR system is based on time-of-flight measurements, and incorporates an optical fiber. The main feature of our system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enable us to exceed the detection limit set by thermal noise. In conventional LIDAR systems the detection limit is determined by the thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the received signals directly. In the case of our LIDAR system, the received signal is amplified by an optical fiber amplifier before reaching the photo diode and the TIA. Therefore, our LIDAR system boosts the signal level before the weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode. We optimized the gains of the optical fiber amplifier and the TIA in our LIDAR system such that it would be capable of detecting a single photon. As a result, the detection limit of our system is determined by shot noise. We have previously demonstrated scanning up to a range of 80 m with this LIDAR system with a 2 mm diameter of receiving lens. We improved the optical amplifier and the peak output power of LIDAR was over 10KW. We redesigned the sensor-head and improved coupling efficiency. As a result, we succeeded in scanning over a range of 100 m. This small and highly sensitive measurement technology shows great potential for use in LIDAR.

Effects of rotation on coolant passage heat transfer. Volume 1: Coolant passages with smooth walls

NASA Technical Reports Server (NTRS)

Hajek, T. J.; Wagner, J. H.; Johnson, B. V.; Higgins, A. W.; Steuber, G. D.

1991-01-01

An experimental program was conducted to investigate heat transfer and pressure loss characteristics of rotating multipass passages, for configurations and dimensions typical of modern turbine blades. The immediate objective was the generation of a data base of heat transfer and pressure loss data required to develop heat transfer correlations and to assess computational fluid dynamic techniques for rotating coolant passages. Experiments were conducted in a smooth wall large scale heat transfer model.

Ultranarrow bandwidth spectral filtering for long-range free-space quantum key distribution at daytime.

PubMed

Höckel, David; Koch, Lars; Martin, Eugen; Benson, Oliver

2009-10-15

We describe a Fabry-Perot-based spectral filter for free-space quantum key distribution (QKD). A multipass etalon filter was built, and its performance was studied. The whole filter setup was carefully optimized to add less than 2 dB attenuation to a signal beam but block stray light by 21 dB. Simulations show that such a filter might be sufficient to allow QKD satellite downlinks during daytime with the current technology.

High sensitivity detection of trace gases at atmospheric pressure using tunable diode lasers

NASA Technical Reports Server (NTRS)

Reid, J.; Sinclair, R. L.; Grant, W. B.; Menzies, R. T.

1985-01-01

A detailed study of the detection of trace gases at atmospheric pressure using tunable diode lasers is described. The influence of multipass cells, retroreflectors and topographical targets is examined. The minimum detectable infrared absorption ranges from 0.1 percent for a pathlength of 1.2 km to 0.01 percent over short pathlengths. The factors which limit this sensitivity are discussed, and the techniques are illustrated by monitoring atmospehric CO2 and CH4.

The Quantitative Microstructural Characterization of Multipass TIG Ultra Low Carbon Bainitic Steel Weldments and Correlation with Mechanical Properties

DTIC Science & Technology

1993-09-01

in TIG weldments. The alloying elements used in ULCB steels are; Carbon (C), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Niobium (Nb), Chromium (Cr...process. 7 C. WELDING PROCESSES 1. Tungsten Inert Gas (TIG) Welding Tungsten Inert Gas (TIG) Welding (or Gas Tungsten Arc Welding ( GTAW )), produces... chromium (Cr), molybdenum (Mo), and sometimes vanadium (V). Reheat cracking occurs in the HAZ during postweld stress relieving, especially in thick

A transceiver module of the Mu radar

NASA Technical Reports Server (NTRS)

Kato, S.; Ogawa, T.; Tsuda, T.; Sato, T.; Kimura, I.; Fukao, S.

1983-01-01

The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna.

1-kW monolithic narrow linewidth linear-polarized fiber laser at 1030 nm

NASA Astrophysics Data System (ADS)

Xu, Yang; Fang, Qiang; Cui, Xuelong; Hou, Bowen; Fu, Shijie; Xie, Zhaoxin; Shi, Wei

2018-02-01

We demonstrate an all-fiberized, linear-polarized, narrow spectral linewidth laser system with kilowatts-level output power at 1030 nm in master oscillator-power amplifier (MOPA) configuration. The laser system consists of a linear-polarized, narrow linewidth ( 28 GHz) fiber laser oscillator and two stages of linear-polarized fiber amplifiers. A 925 W linear-polarized fiber laser with a polarization extinction ratio (PER) of 15.2 dB and a spectral width of 60 GHz at the central wavelength of 1030.1 nm is achieved. Owing to the setting of the appropriate parameters for the laser, no indication of Stimulate Brillouin Scattering (SBS) is observed in the system. Moreover, thanks to the excellent quantum efficiency of the laser and the thightly coiling of the active fiber in the main amplifier, the mode instability (MI) is successfully avoided. As a result, the near diffraction-limited beam quality (M2<1.3) is achieved.

Genetic and epigenetic stability of cryopreserved and cold-stored hops (Humulus lupulus L.).

PubMed

Peredo, Elena L; Arroyo-García, Rosa; Reed, Barbara M; Revilla, M Angeles

2008-12-01

Conventional cold storage and cryopreservation methods for hops (Humulus lupulus L.) are available but, to our knowledge, the genetic and epigenetic stability of the recovered plants have not been tested. This study analyzed 51 accessions of hop using the molecular techniques, Random Amplified DNA Polymorphism (RAPD) and Amplified Fragment Length Polymorphism (AFLP), revealing no genetic variation among greenhouse-grown controls and cold stored or cryopreserved plants. Epigenetic stability was evaluated using Methylation Sensitive Amplified Polymorphism (MSAP). Over 36% of the loci were polymorphic when the cold and cryo-treated plants were compared to greenhouse plants. The main changes were demethylation events and they were common to the cryopreserved and cold stored plants indicating the possible effect of the in vitro establishment process, an essential step in both protocols. Protocol-specific methylation patterns were also detected indicating that both methods produced epigenetic changes in plants following cold storage and cryopreservation.

Highly efficient X-range AlGaN/GaN power amplifier

NASA Astrophysics Data System (ADS)

Tural'chuk, P. A.; Kirillov, V. V.; Osipov, P. E.; Vendik, I. B.; Vendik, O. G.; Parnes, M. D.

2017-09-01

The development of microwave power amplifiers (PAs) based on transistors with an AlGaN/GaN heterojunction are discussed in terms of the possible enhancement of their efficiency. The main focus is on the synthesis of the transforming circuits, which ensure the reactive load at the second- and third-harmonic frequencies and complex impedance at the fundamental frequency. This makes it possible to optimize the complex operation mode of a PA; i.e., to reduce the scattering power and enhance the efficiency. A microwave PA based on the Schottky-barrier-gate field-effect transistor with 80 electrodes based on the GaN pHEMT transistor with a gate length of 0.25 nm and a gate width of 125 nm is experimentally investigated. The amplifier has a pulse output power of 35 W and a power-added efficiency of at least 50% at a working frequency of 9 GHz.

Organo-erbium systems for optical amplification at telecommunications wavelengths.

PubMed

Ye, H Q; Li, Z; Peng, Y; Wang, C C; Li, T Y; Zheng, Y X; Sapelkin, A; Adamopoulos, G; Hernández, I; Wyatt, P B; Gillin, W P

2014-04-01

Modern telecommunications rely on the transmission and manipulation of optical signals. Optical amplification plays a vital part in this technology, as all components in a real telecommunications system produce some loss. The two main issues with present amplifiers, which rely on erbium ions in a glass matrix, are the difficulty in integration onto a single substrate and the need of high pump power densities to produce gain. Here we show a potential organic optical amplifier material that demonstrates population inversion when pumped from above using low-power visible light. This system is integrated into an organic light-emitting diode demonstrating that electrical pumping can be achieved. This opens the possibility of direct electrically driven optical amplifiers and optical circuits. Our results provide an alternative approach to producing low-cost integrated optics that is compatible with existing silicon photonics and a different route to an effective integrated optics technology.

Acquisition of electrical signals using commercial electronic components for detection system of Lead ion in distilled water

NASA Astrophysics Data System (ADS)

Pujiyanto; Yasin, M.; Rusydi, F.

2018-03-01

Development of lead ion detection systems is expected to have an advantage in terms of simplicity of the device and easy for concentration analysis of a lead ion with very high performance. One important part of lead ion detection systems are electrical signal acquisition parts. The electrical signal acquisition part uses the main electronic components: non inverting op-amplifier, instrumentation amplifier, multiplier circuit and logarithmic amplifier. Here will be shown the performance of lead ion detection systems when the existing electrical signal processors use commercial electronic components. The results that can be drawn from this experimental were the lead ion sensor that has been developed can be used to detect lead ions with a sensitivity of 10.48 mV/ppm with the linearity 97.11% and had a measurement range of 0.1 ppm to 80 ppm.

A 3D Reconstruction Strategy of Vehicle Outline Based on Single-Pass Single-Polarization CSAR Data.

PubMed

Leping Chen; Daoxiang An; Xiaotao Huang; Zhimin Zhou

2017-11-01

In the last few years, interest in circular synthetic aperture radar (CSAR) acquisitions has arisen as a consequence of the potential achievement of 3D reconstructions over 360° azimuth angle variation. In real-world scenarios, full 3D reconstructions of arbitrary targets need multi-pass data, which makes the processing complex, money-consuming, and time expending. In this paper, we propose a processing strategy for the 3D reconstruction of vehicle, which can avoid using multi-pass data by introducing a priori information of vehicle's shape. Besides, the proposed strategy just needs the single-pass single-polarization CSAR data to perform vehicle's 3D reconstruction, which makes the processing much more economic and efficient. First, an analysis of the distribution of attributed scattering centers from vehicle facet model is presented. And the analysis results show that a smooth and continuous basic outline of vehicle could be extracted from the peak curve of a noncoherent processing image. Second, the 3D location of vehicle roofline is inferred from layover with empirical insets of the basic outline. At last, the basic line and roofline of the vehicle are used to estimate the vehicle's 3D information and constitute the vehicle's 3D outline. The simulated and measured data processing results prove the correctness and effectiveness of our proposed strategy.

Numerical analysis of impurity separation from waste salt by investigating the change of concentration at the interface during zone refining process

NASA Astrophysics Data System (ADS)

Choi, Ho-Gil; Shim, Moonsoo; Lee, Jong-Hyeon; Yi, Kyung-Woo

2017-09-01

The waste salt treatment process is required for the reuse of purified salts, and for the disposal of the fission products contained in waste salt during pyroprocessing. As an alternative to existing fission product separation methods, the horizontal zone refining process is used in this study for the purification of waste salt. In order to evaluate the purification ability of the process, three-dimensional simulation is conducted, considering heat transfer, melt flow, and mass transfer. Impurity distributions and decontamination factors are calculated as a function of the heater traverse rate, by applying a subroutine and the equilibrium segregation coefficient derived from the effective segregation coefficients. For multipass cases, 1d solutions and the effective segregation coefficient obtained from three-dimensional simulation are used. In the present study, the topic is not dealing with crystal growth, but the numerical technique used is nearly the same since the zone refining technique was just introduced in the treatment of waste salt from nuclear power industry because of its merit of simplicity and refining ability. So this study can show a new application of single crystal growth techniques to other fields, by taking advantage of the zone refining multipass possibility. The final goal is to achieve the same high degree of decontamination in the waste salt as in zone freezing (or reverse Bridgman) method.

Microstructure and Ductility-Dip Cracking Susceptibility of Circumferential Multipass Dissimilar Weld Between 20MND5 and Z2CND18-12NS with Ni-Base Filler Metal 52

NASA Astrophysics Data System (ADS)

Qin, Renyao; Duan, Zhaoling; He, Guo

2013-10-01

The large circumferential multipass dissimilar weld between 20MND5 steel and Z2CND18-12NS stainless steel welded with FM52 filler material was investigated in terms of the diluted composition, the grain boundary precipitation, and the ductility-dip cracking (DDC) susceptibility of the weld. The diluted composition of the weld is composed of 37 to 47 pct Ni, 21 to 24 pct Cr, and 28 to 40 pct Fe, which are inhomogeneous along the depth and over the width of the deep weld. The carbon content has a distribution in the region of the surface weld from a high level (~0.20 pct) in the zone near 20MND5 steel to a normal level (~0.03 pct) in the zone near Z2CND18-12NS stainless steel. The carbon distribution is corresponding to the grain boundary carbides. The minimum threshold strains for DDC occur in the temperature range of 1223 K to 1323 K (950 °C to 1050 °C), which are 0.5, 0.35, and 0.4 pct for the root weld, middle region, and the surface weld, respectively. The dissimilar weld has the largest susceptibility to the DDC compared to the filler metal 52 and the Inconel 690.

A novel multiplex absorption spectrometer for time-resolved studies

NASA Astrophysics Data System (ADS)

Lewis, Thomas; Heard, Dwayne E.; Blitz, Mark A.

2018-02-01

A Time-Resolved Ultraviolet/Visible (UV/Vis) Absorption Spectrometer (TRUVAS) has been developed that can simultaneously monitor absorption at all wavelengths between 200 and 800 nm with millisecond time resolution. A pulsed photolysis laser (KrF 248 nm) is used to initiate chemical reactions that create the target species. The absorption signals from these species evolve as the composition of the gas in the photolysis region changes over time. The instrument can operate at pressures over the range ˜10-800 Torr and can measure time-resolved absorbances <10-4 in the UV (300 nm) and even lower in the visible (580 nm) 2.3 × 10-5, with the peak of sensitivity at ˜500 nm. The novelty of this setup lies in the arrangement of the multipass optics. Although appearing similar to other multipass optical systems (in particular the Herriott cell), there are fundamental differences, most notably the ability to adjust each mirror to maximise the overlap between the probe beam and the photolysis laser. Another feature which aids the sensitivity and versatility of the system is the use of 2 high-throughput spectrographs coupled with sensitive line-array CCDs, which can measure absorbance from ˜200 to 800 nm simultaneously. The capability of the instrument is demonstrated via measurements of the absorption spectrum of the peroxy radical, HOCH2CH2O2, and its self-reaction kinetics.

Low-Noise MMIC Amplifiers for 120 to 180 GHz

NASA Technical Reports Server (NTRS)

Pukala, David; Samoska, Lorene; Peralta, Alejandro; Bayuk, Brian; Grundbacher, Ron; Oliver, Patricia; Cavus, Abdullah; Liu, Po-Hsin

2009-01-01

Three-stage monolithic millimeter-wave integrated-circuit (MMIC) amplifiers capable of providing useful amounts of gain over the frequency range from 120 to 180 GHz have been developed as prototype low-noise amplifiers (LNAs) to be incorporated into instruments for sensing cosmic microwave background radiation. There are also potential uses for such LNAs in electronic test equipment, passive millimeter- wave imaging systems, radar receivers, communication receivers, and systems for detecting hidden weapons. The main advantage afforded by these MMIC LNAs, relative to prior MMIC LNAs, is that their coverage of the 120-to-180-GHz frequency band makes them suitable for reuse in a wider variety of applications without need to redesign them. Each of these MMIC amplifiers includes InP transistors and coplanar waveguide circuitry on a 50- mthick chip (see Figure 1). Coplanar waveguide transmission lines are used for both applying DC bias and matching of input and output impedances of each transistor stage. Via holes are incorporated between top and bottom ground planes to suppress propagation of electromagnetic modes in the substrate. On the basis of computational simulations, each of these amplifiers was expected to operate with a small-signal gain of 14 dB and a noise figure of 4.3 dB. At the time of writing this article, measurements of noise figures had not been reported, but on-chip measurements had shown gains approaching their simulated values (see Figure 2).

Free Higher Education

ERIC Educational Resources Information Center

Reed, Jr., Adolph; Szymanski, Sharon

2004-01-01

The crisis of affordability in higher education is intensifying. Illustrations of its resonance abound: from the frequent news articles describing and amplifying the crisis and its sources to legislators' and candidates' proposed responses. Republicans' responses tend to be mainly punitive toward institutions; Democrats' proposals are more…

A Charge Sensitive Pre-Amplifier for Smart Point-of-Care Devices Employing Polymer Based Lab-on-a-Chip

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

Wang, Hanfeng; Britton, Charles; Quaiyum, Farhan

With increasing emphasis on implantable and portable medical devices, low-power, small-chip-area sensor readout system realized in lab-on-a-chip (LOC) platform is gaining more and more importance these days. The main building blocks of the LOC system include a front-end transducer that generates an electrical signal in response to the presence of an analyte of interest, signal processing electronics to process the signal to comply with a specific transmission protocol and a low-power transmitter, all realized in a single integrated circuit platform. Low power consumption and compactness of the components are essential requirements of the LOC system. This paper presents a novelmore » charge sensitive pre-amplifier developed in a standard 180-nm CMOS process suitable for implementing in an LOC platform. The pre-amplifier converts the charge generated by a pyroelectric transducer into a voltage signal, which provides a measurement of the temperature variation in biological fluids. The proposed design is capable of providing 0.8-mV/pC gain while consuming only 2.1 μW of power. Finally, the pre-amplifier composed of integrated components occupies an area of 0.038 mm 2.« less

Note: A temperature-stable low-noise transimpedance amplifier for microcurrent measurement.

PubMed

Xie, Kai; Shi, Xueyou; Zhao, Kai; Guo, Lixin; Zhang, Hanlu

2017-02-01

Temperature stability and noise characteristics often run contradictory in microcurrent (e.g., pA-scale) measurement instruments because low-noise performance requires high-value resistors with relatively poor temperature coefficients. A low-noise transimpedance amplifier with high-temperature stability, which involves an active compensation mechanism to overcome the temperature drift mainly caused by high-value resistors, is presented. The implementation uses a specially designed R-2R compensating network to provide programmable current gain with extra-fine trimming resolution. The temperature drifts of all components (e.g., feedback resistors, operational amplifiers, and the R-2R network itself) are compensated simultaneously. Therefore, both low-temperature drift and ultra-low-noise performance can be achieved. With a current gain of 10 11 V/A, the internal current noise density was about 0.4 fA/√Hz, and the average temperature coefficient was 4.3 ppm/K at 0-50 °C. The amplifier module maintains accuracy across a wide temperature range without additional thermal stabilization, and its compact size makes it especially suitable for high-precision, low-current measurement in outdoor environments for applications such as electrochemical emission supervision, air pollution particles analysis, radiation monitoring, and bioelectricity.

Characterization of transimpedance amplifier as optical to electrical converter on designing optical instrumentation

NASA Astrophysics Data System (ADS)

Hanto, D.; Ula, R. K.

2017-05-01

Optical to electrical converter is the main components for designing of the optical instrumentations. In addition, this component is also used as signal conditioning. This component usually consists of a photo detector and amplifier. In this paper, characteristics of commercial amplifiers from Thorlabs PDA50B-EC has been observed. The experiment was conducted by diode laser with power of -5 dBm and wavelength 1310 nm; the optical attenuator to vary optical power from 0 to 60 dB, optical to electrical converter from Thorlabs Amplifier PDA50B-EC; multimode optical fiber to guide the laser; and digital voltmeter to measure the output of converter. The results of the characterization indicate that each channel amplification has a non-linear correlation between optical and electrical parameter; optical conversion measurement range of 20-23 dB to full scale; and different measurement coverage area. If this converter will be used as a part component of optical instrumentation so it should be adjusted suitably with the optical power source. Then, because of the correlation equation is not linear so calculation to determine the interpretation also should be considered in addition to the transfer function of the optical sensor.

Note: A temperature-stable low-noise transimpedance amplifier for microcurrent measurement

NASA Astrophysics Data System (ADS)

Xie, Kai; Shi, Xueyou; Zhao, Kai; Guo, Lixin; Zhang, Hanlu

2017-02-01

Temperature stability and noise characteristics often run contradictory in microcurrent (e.g., pA-scale) measurement instruments because low-noise performance requires high-value resistors with relatively poor temperature coefficients. A low-noise transimpedance amplifier with high-temperature stability, which involves an active compensation mechanism to overcome the temperature drift mainly caused by high-value resistors, is presented. The implementation uses a specially designed R-2R compensating network to provide programmable current gain with extra-fine trimming resolution. The temperature drifts of all components (e.g., feedback resistors, operational amplifiers, and the R-2R network itself) are compensated simultaneously. Therefore, both low-temperature drift and ultra-low-noise performance can be achieved. With a current gain of 1011 V/A, the internal current noise density was about 0.4 fA/√Hz, and the average temperature coefficient was 4.3 ppm/K at 0-50 °C. The amplifier module maintains accuracy across a wide temperature range without additional thermal stabilization, and its compact size makes it especially suitable for high-precision, low-current measurement in outdoor environments for applications such as electrochemical emission supervision, air pollution particles analysis, radiation monitoring, and bioelectricity.

A Charge Sensitive Pre-Amplifier for Smart Point-of-Care Devices Employing Polymer Based Lab-on-a-Chip

DOE PAGES

Wang, Hanfeng; Britton, Charles; Quaiyum, Farhan; ...

2018-01-01

With increasing emphasis on implantable and portable medical devices, low-power, small-chip-area sensor readout system realized in lab-on-a-chip (LOC) platform is gaining more and more importance these days. The main building blocks of the LOC system include a front-end transducer that generates an electrical signal in response to the presence of an analyte of interest, signal processing electronics to process the signal to comply with a specific transmission protocol and a low-power transmitter, all realized in a single integrated circuit platform. Low power consumption and compactness of the components are essential requirements of the LOC system. This paper presents a novelmore » charge sensitive pre-amplifier developed in a standard 180-nm CMOS process suitable for implementing in an LOC platform. The pre-amplifier converts the charge generated by a pyroelectric transducer into a voltage signal, which provides a measurement of the temperature variation in biological fluids. The proposed design is capable of providing 0.8-mV/pC gain while consuming only 2.1 μW of power. Finally, the pre-amplifier composed of integrated components occupies an area of 0.038 mm 2.« less

Local fluctuations of ozone from 16 km to 45 km deduced from in situ vertical ozone profile

NASA Technical Reports Server (NTRS)

Moreau, G.; Robert, C.

1994-01-01

A vertical ozone profile obtained by an in situ ozone sonde from 16 km to 45 km, has allowed to observe local ozone concentration variations. These variations can be observed, thanks to a fast measurement system based on a UV absorption KrF excimer laser beam in a multipass cell. Ozone standard deviation versus altitude calculated from the mean is derived. Ozone variations or fluctuations are correlated with the different dynamic zones of the stratosphere.

Factors Influencing the Microstructure and Mechanical Properties of Ultra Low Carbon Bainitic 100 Tungsten Inert Gas Multipass Weldments

DTIC Science & Technology

1992-09-01

Optical macrograph of flat-etched sample 75B3-8 ........................ 30 Figure 4.15 Constitutional supercooling in alloy solidification ... alloying elements such as Mn, Mo, Ni and Cr are added to increase the strength and hardenability of the steel. However, substantial limitations on...0.9 Carbon Equivalent CE = C + Mn + Si + Ni + Cu + Cr + Mo + V 6 15 5 Figure 2.1 Graville Diagram (Blicharski et al, 1989, p.318) 3 B. ULTRA LOW

A Terahertz VRT spectrometer employing quantum cascade lasers

NASA Astrophysics Data System (ADS)

Cole, William T. S.; Hlavacek, Nik C.; Lee, Alan W. M.; Kao, Tsung-Yu; Hu, Qing; Reno, John L.; Saykally, Richard J.

2015-10-01

The first application of a commercial Terahertz quantum cascade laser (QCL) system for high resolution spectroscopy of supersonic beams is presented. The QCLs exhibited continuous linear voltage tuning over a 2 GHz range about a center frequency of 3.762 THz with ∼1 ppm resolution. A sensitivity of ∼1 ppm fractional absorption was measured with a single pass optical system. Multipass operation at the quantum noise limit of the stressed photoconductor detector would produce a 100-fold improvement.

Waveguide to Core: A New Approach to RF Modelling

NASA Astrophysics Data System (ADS)

Wright, John; Shiraiwa, Syunichi; Rf-Scidac Team

2017-10-01

A new technique for the calculation of RF waves in toroidal geometry enables the simultaneous incorporation of antenna geometry, plasma facing components (PFCs), the scrape off-layer (SOL) and core propagation [Shiraiwa, NF 2017]. Calculations with this technique naturally capture wave propagation in the SOL and its interactions with non-conforming PFCs permitting self-consistent calculation of core absorption and edge power loss. The main motivating insight is that the core plasma region having closed flux surfaces requires a hot plasma dielectric while the open field line region in the scrape-off layer needs only a cold plasma dielectric. Spectral approaches work well for the former and finite elements work well for the latter. The validity of this process follows directly from the superposition principle of Maxwell's equations making this technique exact. The method is independent of the codes or representations used and works for any frequency regime. Applications to minority heating in Alcator C-Mod and ITER and high harmonic heating in NSTX-U will be presented in single pass and multi-pass regimes. Support from DoE Grant Number DE-FG02-91-ER54109 (theory and computer resources) and DE-FC02-01ER54648 (RF SciDAC).

Comparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel

NASA Astrophysics Data System (ADS)

Guo, Wei; Li, Lin; Dong, Shiyun; Crowther, Dave; Thompson, Alan

2017-04-01

The microstructural characteristics and mechanical properties, including micro-hardness, tensile properties, three-point bending properties and Charpy impact toughness at different test temperatures of 8 mm thick S960 high strength steel plates were investigated following their joining by multi-pass ultra-narrow gap laser welding (NGLW) and gas metal arc welding (GMAW) techniques. It was found that the microstructure in the fusion zone (FZ) for the ultra-NGLW joint was predominantly martensite mixed with some tempered martensite, while the FZ for the GMAW joint was mainly consisted of ferrite with some martensite. The strength of the ultra-NGLW specimens was comparable to that of the base material (BM), with all welded specimens failed in the BM in the tensile tests. The tensile strength of the GMAW specimens was reduced approximately by 100 MPa when compared with the base material by a broad and soft heat affected zone (HAZ) with failure located in the soft HAZ. Both the ultra-NGLW and GMAW specimens performed well in three-point bending tests. The GMAW joints exhibited better impact toughness than the ultra-NGLW joints.

Magnet design for the splitter/combiner regions of CBETA, the Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator

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

Crittendon, J. A.; Burke, D. C.; Fuentes, Y. L.P.

2017-01-06

The Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator (CBETA) will provide a 150-MeV electron beam using four acceleration and four deceleration passes through the Cornell Main Linac Cryomodule housing six 1.3-GHz superconducting RF cavities. The return path of this 76-m-circumference accelerator will be provided by 106 fixed-field alternating-gradient (FFAG) cells which carry the four beams of 42, 78, 114 and 150 MeV. Here we describe magnet designs for the splitter and combiner regions which serve to match the on-axis linac beam to the off-axis beams in the FFAG cells, providing the path-length adjustment necessary to energy recovery for each of the four beams.more » The path lengths of the four beamlines in each of the splitter and combiner regions are designed to be adapted to 1-, 2-, 3-, and 4-pass staged operations. Design specifi- cations and modeling for the 24 dipole and 32 quadrupole electromagnets in each region are presented. The CBETA project will serve as the first demonstration of multi-pass energy recovery using superconducting RF cavities with FFAG cell optics for the return loop.« less

Impurity-induced deep centers in Tl 6SI 4

DOE PAGES

Shi, Hongliang; Lin, Wenwen; Kanatzidis, Mercouri G.; ...

2017-04-13

Tl 6SI 4 is a promising material for room-temperature semiconductor radiation detection applications. The history of the development of semiconductor radiation detection materials has demonstrated that impurities strongly affect the carrier transport and that material purification is a critically important step in improving the carrier transport and thereby the detector performance. Here, we report combined experimental and theoretical studies of impurities in Tl 6SI 4. Impurity concentrations in Tl 6SI 4 were analyzed by glow discharge mass spectrometry. Purification of the raw material by multi-pass vertical narrow zone refining was found to be effective in reducing the concentrations of mostmore » impurities. Density functional theory calculations were also performed to study the trapping levels introduced by the main impurities detected in experiments. We show that, among dozens of detected impurities, most are either electrically inactive or shallow. In the purified Tl 6SI 4 sample, only Bi has a significant concentration (0.2 ppm wt) and introduces deep electron trapping levels in the band gap. Lastly, improvement of the purification processes is expected to further reduce the impurity concentrations and their impact on carrier transport in Tl 6SI 4, leading to improved detector performance.« less

Four-Way Ka-Band Power Combiner

NASA Technical Reports Server (NTRS)

Perez, Raul; Li, Samuel

2007-01-01

A waveguide structure for combining the outputs of four amplifiers operating at 35 GHz (Ka band) is based on a similar prior structure used in the X band. The structure is designed to function with low combining loss and low total reflected power at a center frequency of 35 GHz with a 160 MHz bandwidth. The structure (see figure) comprises mainly a junction of five rectangular waveguides in a radial waveguide. The outputs of the four amplifiers can be coupled in through any four of the five waveguide ports. Provided that these four signals are properly phased, they combine and come out through the fifth waveguide port.

Investigation on microstructure and properties of narrow-gap laser welding on reduced activation ferritic/martensitic steel CLF-1 with a thickness of 35 mm

NASA Astrophysics Data System (ADS)

Wu, Shikai; Zhang, Jianchao; Yang, Jiaoxi; Lu, Junxia; Liao, Hongbin; Wang, Xiaoyu

2018-05-01

Reduced activation ferritic martensitic (RAFM) steel is chosen as a structural material for test blanket modules (TBMs) to be constructed in International Thermonuclear Experimental Reactor (ITER) and China Fusion Engineering Test Reactor (CFETR). Chinese specific RAFM steel named with CLF-1 has been developed for CFETR. In this paper, a narrow-gap groove laser multi-pass welding of CLF-1 steel with thickness of 35 mm is conduced by YLS-15000 fiber laser. Further, the microstructures of different regions in the weld joint were characterized, and tensile impact and micro-hardness tests were carried out for evaluating the mecharical properties. The results show that the butt weld joint of CLF-1 steel with a thickness of 35 mm was well-formed using the optimal narrow-gap laser filler wire welding and no obvious defects was found such as incomplete fusion cracks and pores. The microstructures of backing layer is dominated by lath martensites and the Heat-Affected Zone (HAZ) was mainly filled with two-phase hybrid structures of secondary-tempering sorbites and martensites. The filler layer is similar to the backing layer in microstructures. In tensile tests, the tensile samples from different parts of the joint all fractured at base metal (BM). The micro-hardness of weld metal (WM) was found to be higher than that of BM and the Heat-Affected Zone (HAZ) exhibited no obvious softening. After post weld heat treatment (PWHT), it can be observed that the fusion zone of the autogenous welding bead and the upper filling beads mainly consist of lath martensites which caused the lower impact absorbing energy. The HAZ mainly included two-phase hybrid structures of secondary-tempering sorbites and martensites and exhibited favorable impact toughness.

Production and genetic analysis of resynthesized Brassica napus from a B. rapa landrace from the Qinghai-Tibet Plateau and B. alboglabra.

PubMed

Liu, H D; Zhao, Z G; Du, D Z; Deng, C R; Fu, G

2016-01-08

This study aimed to reveal the genetic and epigenetic variations involved in a resynthesized Brassica napus (AACC) generated from a hybridization between a B. rapa (AA) landrace and B. alboglabra (CC). Amplified fragment length polymorphism (AFLP), methylation-sensitive amplified polymorphism, and the cDNA-AFLP technique were performed to detect changes between different generations at the genome, methylation, and transcription levels. We obtained 30 lines of resynthesized B. napus with a mean 1000-seed weight of over 7.50 g. All of the lines were self-compatible, probably because both parents were self-compatible. At the genome level, the S0 generation had the lowest frequency of variations (0.18%) and the S3 generation had the highest (6.07%). The main variation pattern was the elimination of amplified restriction fragments on the CC genome from the S0 to the S4 generations. At the methylation level, we found three loci that exhibited altered methylation patterns on the parental A genome; the variance rate was 1.35%. At the transcription level, we detected 43.77% reverse mutations and 37.56% deletion mutations that mainly occurred on the A and C genomes, respectively, in the S3 generation. Our results highlight the genetic variations that occur during the diploidization of resynthesized B. napus.

Development of pre pre-driver amplifier stage for generator of SST-1 ICRH system

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Sinh Makwana, Azad; Srinivas, Y. S. S.; Kulkarni, S. V.; ICRH-RF Group

2010-02-01

The Ion Cyclotron Resonance Heating (ICRH) system for SST1 consists mainly of the cwrf power generator to deliver 1.5MW for 1000sec duration at the frequencies 22.8, 24.3 and 45.6±1MHz, the transmission line and the antenna. This is planned to develop a independent and dedicated cwrf generator that consists of a oscillator, buffer, rf switch, modulator, rf attenuator, directional coupler, three stage solid state low power amplifier and four stage triode & tetrode based high power amplifier with specific performance at 45.6±1MHz including frequencies 22.8 and 24.3±1MHz. The pre pre-driver high power amplifier stage is fabricated about triode 3CX3000A7. The tube has sufficient margin in terms of plate dissipation and grid dissipation that makes it suitable to withstand momentarily load mismatch and to upgrade the source in terms of output power later. This indigenously developed amplifier is integrated inside a radiation resistant rack with all required biasing power supplies, cooling blower, controls, monitors and interlocks for manual or remote control operation. This grounded grid mode amplifier will be operated at plate with 3.8KV/ 800mA in class AB for 1.8KW cwrf output power rating. The input circuit is broadband and the output circuit is tunable with slide variable inductor and a vacuum variable capacitor in the frequency range of 22.8 to 45.6MHz. It is designed for a gain of about 12dB, fabrication completed and undergoing cwrf power testing. This paper presents specifications, design criteria, circuit used, operating parameters, tests conducted and the results obtained.

Gain drift compensation with no feedback-loop developed for the X-Ray Integral Field Unit/ATHENA readout chain

NASA Astrophysics Data System (ADS)

Prêle, Damien; Voisin, Fabrice; Beillimaz, Cyril; Chen, Si; Goldwurm, Andrea

2016-10-01

The focal plane of the X-Ray Integral Field Unit (X-IFU) instrument of the Advanced Telescope for High-Energy Astrophysics observatory is composed of 3840 microcalorimeters. These sensors, based on superconducting transition edge sensors (TES), are read out through a frequency multiplexer. A "base-band feedback" suppresses all the carriers of the multiplexed signal in the superconducting quantum interference devices input coil (cryogenic readout). However, the loop gain of this feedback is too small (less than 10 in the present baseline of the phase A mission) to strongly compensate the readout gain drifts. An onboard x-ray source is considered to calibrate the gain of the full instrument. However, in-flight calibration time must be minimized, which leads to a requirement on the gain stability larger than 10-4 over a long duration (between each calibration) to reach the challenging energy resolution goal of 2.5 eV at 6 keV of the X-IFU. A significant part of this gain is provided by a low-noise amplifier in the warm front-end electronics (WFEE). To reach such gain stability over more than a dozen minutes, this noncooled amplifier has to cope with the temperature and supply voltage variations. Moreover, mainly for noise reasons, a common large loop gain with feedback cannot be used. We propose a new amplifier topology using diodes as loads of a differential amplifier to provide a fixed voltage gain, independent of the temperature and of the bias fluctuations. This amplifier is designed using 350-nm SiGe BiCMOS technology and is part of an integrated circuit developed for the WFEE. Our simulations provide the expected gain and noise performances. Comparison with standard resistive loaded differential pair clearly shows the advantages of the proposed amplifier topology with a gain drift decreased by more than an order of magnitude. Performances of this diode loaded amplifier are discussed in the context of the X-IFU requirements.

Improvement of highly sensitive lidar with a thumb-sized sensor-head built using an optical fiber preamplifier

NASA Astrophysics Data System (ADS)

Inoue, Daisuke; Ichikawa, Tadashi; Matsubara, Hiroyuki; Mao, Xueon; Maeda, Mitsutoshi; Nagashima, Chie; Kagami, Manabu

2012-06-01

We have developed a LIDAR system with a sensor head which, although it includes a scanning mechanism, is less than 20 cc in size. The system is not only small, but is also highly sensitive. Our LIDAR system is based on time-of-flight measurements, and incorporates an optical fiber. The main feature of our system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enable us to exceed the detection limit set by thermal noise. In conventional LIDAR systems the detection limit is determined by the thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the received signals directly. In the case of our LIDAR system, the received signal is amplified by an optical fiber amplifier before reaching the photo diode and the TIA. Therefore, our LIDAR system boosts the signal level before the weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode. We optimized the gains of the optical fiber amplifier and the TIA in our LIDAR system such that it would be capable of detecting a single photon. As a result, the detection limit of our system is determined by shot noise. We have previously demonstrated optical pre-amplified LIDAR with a perfect co-axial optical system[1]. For this we used a variable optical attenuator to remove internal reflection from the transmission and receiving lenses. However, the optical attenuator had an insertion loss of 6dB which reduced the sensitivity of the LIDAR. We re-designed the optical system such that it was semi-co-axial and removed the variable optical attenuator. As a result, we succeeded in scanning up to a range of 80 m. This small and highly sensitive measurement technology shows great potential for use in LIDAR.

RAPD-SCAR marker and genetic relationship analysis of three Demodex species (Acari: Demodicidae).

PubMed

Zhao, Ya-E; Wu, Li-Ping

2012-06-01

For a long time, classification of Demodex mites has been mainly based on their hosts and phenotype characteristics. The study was the first to conduct molecular identification and genetic relationship analysis for six isolates of three Demodex species by random amplified polymorphic DNA (RAPD) and sequence-characterized amplified region (SCAR) marker. Totally, 239 DNA fragments were amplified from six Demodex isolates with 10 random primers in RAPD, of which 165 were polymorphic. Using a single primer, at least five fragments and at most 40 in the six isolates were amplified, whereas within a single isolate, a range of 35-49 fragments were amplified. DNA fingerprints of primers CZ 1-9 revealed intra- and interspecies difference in six Demodex isolates, whereas primer CZ 10 only revealed interspecies difference. The genetic distance and dendrogram showed the intraspecific genetic distances were closer than the interspecific genetic distances. The interspecific genetic distances of Demodex folliculorum and Demodex canis (0.7931-0.8140) were shorter than that of Demodex brevis and D. canis (0.8182-0.8987). The RAPD-SCAR marker displayed primer CZ 10 could be applied to identify the three Demodex species. The 479-bp fragment was specific for D. brevis, and the 261-bp fragment was specific for D. canis. The conclusion was that the RAPD-SCAR multi-marker was effective in molecular identification of three Demodex species. The genetic relationship between D. folliculorum and D. canis was nearer than that between D. folliculorum and D. brevis.

Multipass pumped Nd-based thin-disk lasers: continuous-wave laser operation at 1.06 and 0.9 {mu}m with intracavity frequency doubling

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

Pavel, Nicolaie; Luenstedt, Kai; Petermann, Klaus

2007-12-01

The laser performances of the 1.06 {mu}m 4F3/2 --> 4I11/2 four-level transition and of the 0.9 {mu}m 4F3/2 --> I9/24 quasi-three-level transition were investigated using multipass pumped Nd-based media in thin-disk geometry. When pumping at 0.81 {mu}m into the 4F5/2 level, continuous-wave laser operation was obtained with powers in excess of 10 W at 1.06 {mu}m, in the multiwatt region at 0.91 {mu}m in Nd:YVO4 and Nd:GdVO4, and at 0.95 {mu}m in Nd:YAG. Intracavity frequency-doubled Nd:YVO4 thin-disk lasers with output powers of 6.4 W at 532 nm and of 1.6 W at 457 nm were realized at this pumping wavelength.more » The pumping at 0.88 {mu}m, which is directed into the 4F3/2 emitting level, was also employed, and Nd:YVO4 and Nd:GdVO4 thin-disk lasers with {approx}9 W output power at 1.06 {mu}m and visible laser radiation at 0.53 {mu}m with output power in excess of 4 W were realized. Frequency-doubled Nd:vanadate thin-disk lasers with deep blue emission at 0.46 {mu}m were obtained under pumping directly into the 4F3/2 emitting level.« less

Vanadium and columbium additions in pressure vessel steels

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

Xu, P.; Somers, B.R.; Pense, A.W.

1994-09-01

A statistically designed series of vanadium and columbium microalloyed C-Mn HSLA steels was used for an investigation of heat-affected zone (HAZ) toughness in post weld heat treated (PWHT) multi-pass welds. The vanadium additions were in the range 0.005 to 0.097 Wt.% and the columbium additions were in the range 0.004 to 0.06 Wt.% GMAW processes with welding heat inputs of 3kJ/mm and 5kJ/mm and post-weld heat treatments at 620 C for 2 10 hours were employed. A degradation of the HAZ toughness with additions of microalloy elements V and Cb in the as-welded and PWHT conditions was revealed. The 50more » Joule (37 ft-lb) transition temperature (TT50J) for HAZs in all weld conditions correlated with maximum HAZ hardness. Increases in HAZ hardness and TT50J caused by PWHT were observed. Hence PWHT in some situations may not beneficial for V/Cb microalloyed HLSA steels. The randomly distributed precipitation of V and Cb carbides (V, Cb)C, including dislocation precipitation and matrix precipitation with particle sizes of 5--15 nm, is the predominant alloy carbide precipitate morphology in these steels. The crack initiation sites in Charpy specimens of HAZs tested at the approximate transition temperature are shifted from the highest stress triaxiality, mid-specimen location to an off center higher hardness location. This is found to be characteristic of fracture in the multipass HAZ of the microalloyed steel.« less

CW EC-QCL-based sensor for simultaneous detection of H₂O, HDO, N₂O and CH₄ using multi-pass absorption spectroscopy.

PubMed

Yu, Yajun; Sanchez, Nancy P; Griffin, Robert J; Tittel, Frank K

2016-05-16

A sensor system based on a continuous wave, external-cavity quantum-cascade laser (CW EC-QCL) was demonstrated for simultaneous detection of atmospheric H₂O, HDO, N₂O and CH₄ using a compact, dense pattern multi-pass gas cell with an effective path-length of 57.6 m. The EC-QCL with a mode-hop-free spectral range of 1225-1285 cm^-1 operating at ~7.8 µm was scanned covering four neighboring absorption lines, for H₂O at 1281.161 cm^-1, HDO at 1281.455 cm^-1, N₂O at 1281.53 cm^-1 and CH₄ at 1281.61 cm^-1. A first-harmonic-normalized wavelength modulation spectroscopy with second-harmonic detection (WMS-2f/1f) strategy was employed for data processing. An Allan-Werle deviation analysis indicated that minimum detection limits of 1.77 ppmv for H₂O, 3.92 ppbv for HDO, 1.43 ppbv for N₂O, and 2.2 ppbv for CH₄ were achieved with integration times of 50-s, 50-s, 100-s and 129-s, respectively. Experimental measurements of ambient air are also reported.

Integrated Circuit Design of 3 Electrode Sensing System Using Two-Stage Operational Amplifier

NASA Astrophysics Data System (ADS)

Rani, S.; Abdullah, W. F. H.; Zain, Z. M.; N, Aqmar N. Z.

2018-03-01

This paper presents the design of a two-stage operational amplifier(op amp) for 3-electrode sensing system readout circuits. The designs have been simulated using 0.13μm CMOS technology from Silterra (Malaysia) with Mentor graphics tools. The purpose of this projects is mainly to design a miniature interfacing circuit to detect the redox reaction in the form of current using standard analog modules. The potentiostat consists of several op amps combined together in order to analyse the signal coming from the 3-electrode sensing system. This op amp design will be used in potentiostat circuit device and to analyse the functionality for each module of the system.

Development of digital stethoscope for telemedicine.

PubMed

Lakhe, Aparna; Sodhi, Isha; Warrier, Jyothi; Sinha, Vineet

2016-01-01

The stethoscope is a medical acoustic device which is used to auscultate internal body sounds, mainly the heart and lungs. A digital stethoscope overcomes the limitations of a conventional stethoscope as the sound data is transformed into electrical signals which can be amplified, stored, replayed and, more importantly, sent for an expert opinion, making it very useful in telemedicine. With the above in view, a low cost digital stethoscope has been developed which is interfaceble with mobile communication devices. In this instrument sounds from various locations can be captured with the help of an electret condenser microphone. Captured sound is filtered, amplified and processed digitally using an adaptive line enhancement technique to obtain audible and distinct heart sounds.

Development of Bread Board Model of TRMM precipitation radar

NASA Astrophysics Data System (ADS)

Okamoto, Ken'ichi; Ihara, Toshio; Kumagai, Hiroshi

The active array radar was selected as a reliable candidate for the TRMM (Tropical Rainfall Measuring Mission) precipitation radar after the trade off studies performed by Communications Research Laboratory (CRL) in the US-Japan joint feasibility study of TRMM in 1987-1988. Main system parameters and block diagram for TRMM precipitation radar are shown as the result of feasibility study. CRL developed key devices for the active array precipitation radar such as 8-element slotted waveguide array antenna, the 5 bit PIN diode phase shifters, solid state power amplifiers and low noise amplifiers in 1988-1990. Integration of these key devices was made to compose 8-element Bread Board Model of TRMM precipitation radar.

Noiseless optical amplification in quasi-phase-matched bulk lithium niobate

NASA Astrophysics Data System (ADS)

Lovering, D. J.; Levenson, J. A.; Vidakovic, P.; Webjörn, J.; Russell, P. St. J.

1996-09-01

An optical parametric amplifier (OPA) has been demonstrated in bulk, periodically poled lithium niobate and is shown to operate with a noise figure well below the classical limit. In contrast to conventional OPA's, this device uses quasi-phase matching to provide the coupling between the pump and the signal. Comparison of the measured performance with that of a theoretical model reveals that the main intrinsic contribution to the output noise is due to spatial and temporal mode mixing, which arises as a consequence of tight focusing of the incident beams. Factors that affect the performance of this amplifier are identified theoretically and their relative importance investigated for both amplification and squeezing.

Progress Toward Measuring CO2 Isotopologue Fluxes in situ with the LLNL Miniature, Laser-based CO2 Sensor

NASA Astrophysics Data System (ADS)

Osuna, J. L.; Bora, M.; Bond, T.

2015-12-01

One method to constrain photosynthesis and respiration independently at the ecosystem scale is to measure the fluxes of CO2­ isotopologues. Instrumentation is currently available to makes these measurements but they are generally costly, large, bench-top instruments. Here, we present progress toward developing a laser-based sensor that can be deployed directly to a canopy to passively measure CO2 isotopologue fluxes. In this study, we perform initial proof-of-concept and sensor characterization tests in the laboratory and in the field to demonstrate performance of the Lawrence Livermore National Laboratory (LLNL) tunable diode laser flux sensor. The results shown herein demonstrate measurement of bulk CO2 as a first step toward achieving flux measurements of CO2 isotopologues. The sensor uses a Vertical Cavity Surface Emitting Laser (VCSEL) in the 2012 nm range. The laser is mounted in a multi-pass White Cell. In order to amplify the absorption signal of CO2 in this range we employ wave modulation spectroscopy, introducing an alternating current (AC) bias component where f is the frequency of modulation on the laser drive current in addition to the direct current (DC) emission scanning component. We observed a strong linear relationship (r2 = 0.998 and r2 = 0.978 at all and low CO2 concentrations, respectively) between the 2f signal and the CO2 concentration in the cell across the range of CO2 concentrations relevant for flux measurements. We use this calibration to interpret CO2 concentration of a gas flowing through the White cell in the laboratory and deployed over a grassy field. We will discuss sensor performance in the lab and in situ as well as address steps toward achieving canopy-deployed, passive measurements of CO2 isotopologue fluxes. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675788

Isoschizomers and amplified fragment length polymorphism for the detection of specific cytosine methylation changes.

PubMed

Ruiz-García, Leonor; Cabezas, Jose Antonio; de María, Nuria; Cervera, María-Teresa

2010-01-01

Different molecular techniques have been developed to study either the global level of methylated cytosines or methylation at specific gene sequences. One of them is a modification of the Amplified Fragment Length Polymorphism (AFLP) technique that has been used to study methylation of anonymous CCGG sequences in different fungi, plant and animal species. The main variation of this technique is based on the use of isoschizomers with different methylation sensitivity (such as HpaII and MspI) as a frequent cutter restriction enzyme. For each sample, AFLP analysis is performed using both EcoRI/HpaII and EcoRI/MspI digested samples. Comparative analysis between EcoRI/HpaII and EcoRI/MspI fragment patterns allows the identification of two types of polymorphisms: (1) "Methylation-insensitive polymorphisms" that show common EcoRI/HpaII and EcoRI/MspI patterns but are detected as polymorphic amplified fragments among samples; and (2) "Methylation-sensitive polymorphisms" that are associated with amplified fragments differing in their presence or absence or in their intensity between EcoRI/HpaII and EcoRI/MspI patterns. This chapter describes a detailed protocol of this technique and discusses modifications that can be applied to adjust the technology to different species of interest.

Analysis of DNA Cytosine Methylation Patterns Using Methylation-Sensitive Amplification Polymorphism (MSAP).

PubMed

Guevara, María Ángeles; de María, Nuria; Sáez-Laguna, Enrique; Vélez, María Dolores; Cervera, María Teresa; Cabezas, José Antonio

2017-01-01

Different molecular techniques have been developed to study either the global level of methylated cytosines or methylation at specific gene sequences. One of them is the methylation-sensitive amplified polymorphism technique (MSAP) which is a modification of amplified fragment length polymorphism (AFLP). It has been used to study methylation of anonymous CCGG sequences in different fungi, plants, and animal species. The main variation of this technique resides on the use of isoschizomers with different methylation sensitivity (such as HpaII and MspI) as a frequent-cutter restriction enzyme. For each sample, MSAP analysis is performed using both EcoRI/HpaII- and EcoRI/MspI-digested samples. A comparative analysis between EcoRI/HpaII and EcoRI/MspI fragment patterns allows the identification of two types of polymorphisms: (1) methylation-insensitive polymorphisms that show common EcoRI/HpaII and EcoRI/MspI patterns but are detected as polymorphic amplified fragments among samples and (2) methylation-sensitive polymorphisms which are associated with the amplified fragments that differ in their presence or absence or in their intensity between EcoRI/HpaII and EcoRI/MspI patterns. This chapter describes a detailed protocol of this technique and discusses the modifications that can be applied to adjust the technology to different species of interest.

Alloying Elements Transition Into the Weld Metal When Using an Inventor Power Source

NASA Astrophysics Data System (ADS)

Mamadaliev, R. A.; Kuskov, V. N.; Popova, A. A.; Valuev, D. V.

2016-04-01

The temperature distribution over the surface of the welded 12Kh18N10T steel plates using the inventor power source ARC-200 has been calculated. In order to imitate multipass welding when conducting the thermal analysis the initial temperature was changed from 298K up to 798K in 100K increments. It has been determined that alloying elements transition into the weld metal depends on temperature. Using an inventor power source facilitates a uniform distribution of alloying elements along the length and height of the weld seam.

Compact TDLAS based sensor design using interband cascade lasers for mid-IR trace gas sensing

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

Dong, Lei; Tittel, Frank K.; Li, Chunguang

2016-02-25

Two compact TDLAS sensor systems based on different structural optical cores were developed. The two optical cores combine two recent developments, gallium antimonide (GaSb)-based ICL and a compact multipass gas cell (MPGC) with the goal to create compact TDLAS based sensors for the mid-IR gas detection with high detection sensitivity and low power consumption. The sensors achieved minimum detection limits of ~5 ppbv and ~8 ppbv, respectively, for CH 4 and C 2H 6 concentration measurements with a 3.7-W power consumption.

Face pumping of thin, solid-state slab lasers with laser diodes.

PubMed

Faulstich, A; Baker, H J; Hall, D R

1996-04-15

A new technique for face pumping of slab lasers uses transfer of light from 10 quasi-cw laser diode bars through a slotted mirror into a rectangular, highly ref lective pump chamber, giving efficient multipass pumping of a thin Nd:glass slab laser. A slope efficiency of 28% and a maximum pulse energy of 65 mJ have been obtained, and gain and loss measurements with thickness t = 0.45-1.04 mm have confirmed the 1/t scaling of gain in thin slabs and the high efficiency of pump light transfer.

Switch device having a non-linear transmission line

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

Elizondo-Decanini, Juan M.

Switching devices are provided. The switching devices include an input electrode, having a main electrode and a trigger electrode, and an output electrode. The main electrode and the trigger electrode are separated from the output electrode by a main gap and a trigger gap, respectively. During operation, the trigger electrode compresses and amplifies a trigger voltage signal causing the trigger electrode to emit a pulse of energy. This pulse of energy form plasma near the trigger electrode, either by arcing across the trigger gap, or by arcing from the trigger electrode to the main electrode. This plasma decreases the breakdownmore » voltage of the main gap. Simultaneously, or near simultaneously, a main voltage signal propagates through the main electrode. The main voltage signal emits a main pulse of energy that arcs across the main gap while the plasma formed by the trigger pulse is still present.« less

Distortion cancellation performance of miniature delay filters for feed-forward linear power amplifiers.

PubMed

Roy, Manas K

2002-11-01

The technique of feed-forward amplitude control has been widely used in the linearization of power amplifiers for wireless communication systems. In this technique, an error signal due to third order intermodulation distortion (IMD) is extracted, amplified, and used to correct the delayed main line distorted signal. For example, a miniature prototype base station for the Global System for Mobile Communications/Code Division Multiple Access (GSM/CDMA) cellular system uses feed-forward amplifiers with bulky and expensive coaxial cables, about 20 feet in length, to provide about 25 ns of delay. This paper shows alternate space-saving approaches of achieving these delays using three different types of delay filters: electromagnetic interdigital/lumped (<2.5"), ceramic (<1.8"), and ladder-type surface acoustic wave (SAW) (0.15"). The delay lines introduce phase and amplitude imbalance and delay mismatch in the linearization loop due to fabrication tolerances. These adversely affect the IMD cancellation. Using an RF system simulation tool, this paper critically compares the IMD cancellation performance achieved using the three technologies. Simulation results show that the optimization of delay mismatch can achieve the desired cancellation more easily than other parameters. It is shown that, if the critical system parameter (phase deviation from linearity), is maintained at <2.5 degrees peak-to-peak over a 20 MHz bandwidth in the frequency range 855 MHz to 875 MHz, one can achieve 25 dB of IMD cancellation performance. This paper concludes with the suggestion of a set of realistic specifications for a miniature delay filter for the low power loop of the feed-forward amplifier.

P300 speller BCI with a mobile EEG system: comparison to a traditional amplifier

NASA Astrophysics Data System (ADS)

De Vos, Maarten; Kroesen, Markus; Emkes, Reiner; Debener, Stefan

2014-06-01

Objective. In a previous study, we presented a low-cost, small and wireless EEG system enabling the recording of single-trial P300 amplitudes in a truly mobile, outdoor walking condition (Debener et al (2012 Psychophysiology 49 1449-53)). Small and wireless mobile EEG systems have substantial practical advantages as they allow for brain activity recordings in natural environments, but these systems may compromise the EEG signal quality. In this study, we aim to evaluate the EEG signal quality that can be obtained with the mobile system. Approach. We compared our mobile 14-channel EEG system with a state-of-the-art wired laboratory EEG system in a popular brain-computer interface (BCI) application. N = 13 individuals repeatedly performed a 6 × 6 matrix P300 spelling task. Between conditions, only the amplifier was changed, while electrode placement and electrode preparation, recording conditions, experimental stimulation and signal processing were identical. Main results. Analysis of training and testing accuracies and information transfer rate (ITR) revealed that the wireless mobile EEG amplifier performed as good as the wired laboratory EEG system. A very high correlation for testing ITR between both amplifiers was evident (r = 0.92). Moreover the P300 topographies and amplitudes were very similar for both devices, as reflected by high degrees of association (r > = 0.77). Significance. We conclude that efficient P300 spelling with a small, lightweight and quick to set up mobile EEG amplifier is possible. This technology facilitates the transfer of BCI applications from the laboratory to natural daily life environments, one of the key challenges in current BCI research.

Design of an amplifier model accounting for thermal effect in fully aperiodic large pitch fibers

NASA Astrophysics Data System (ADS)

Tragni, K.; Molardi, C.; Poli, F.; Dauliat, R.; Leconte, B.; Darwich, D.; du Jeu, R.; Malleville, M. A.; Jamier, R.; Selleri, S.; Roy, P.; Cucinotta, A.

2018-02-01

Yb-doped Photonic Crystal Fibers (PCFs) have triggered a significant power scaling into fiber-based lasers. However thermally-induced effects, like mode instability, can compromise the output beam quality. PCF design with improved Higher Order Mode (HOM) delocalization and effective thermal resilience can contain the problem. In particular, Fully- Aperiodic Large-Pitch Fibers (FA-LPFs) have shown interesting properties in terms of resilience to thermal effects. In this paper the performances of a Yb-doped FA-LPF amplifier are experimentally and numerically investigated. Modal properties and gain competition between Fundamental Mode (FM) and first HOM have been calculated, in presence of thermal effects. The main doped fiber characteristics have been derived by comparison between experimental and numerical results.

Soft x-ray plasma-based seeded multistage amplification chain.

PubMed

Oliva, Eduardo; Fajardo, Marta; Li, Lu; Sebban, Stephane; Ros, David; Zeitoun, Philippe

2012-10-15

To date, plasma-based soft x-ray lasers have demonstrated experimentally 1 μJ, 1 ps (1 MW) pulses. This Letter reports extensive study using time-dependant Maxwell-Bloch code of seeding millimeter scale plasmas that store more than 100 mJ in population inversion. Direct seeding of these plasmas has to overcome very strong amplified spontaneous emission (ASE) as well as prevent wake-field amplification. Below 100 nJ injected energy, seed produces pulses with picosecond duration. To overcome this limitation, a new scheme has been studied, taking advantage of a plasma preamplifier that dramatically increases the seed energy prior to entering the main plasma amplifier leading to ASE and wake-free, fully coherent 21.6 μJ, 80 fs pulses (0.27 GW).

Amplified spontaneous emission properties of semiconducting organic materials.

PubMed

Calzado, Eva M; Boj, Pedro G; Díaz-García, María A

2010-06-18

This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature.

Amplified Spontaneous Emission Properties of Semiconducting Organic Materials

PubMed Central

Calzado, Eva M.; Boj, Pedro G.; Díaz-García, María A.

2010-01-01

This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature. PMID:20640167

Ambient measurement of ammonia and formaldehyde: Open path vs. extractive approach.

NASA Astrophysics Data System (ADS)

Rajamäki, Timo

2017-04-01

Ammonia NH3 and formaldehyde CH2O are some of the most critical chemicals for air quality. Reliable online measurement of these gases is one of the key operations for air quality and safety monitoring, in indoor, outdoor and process applications alike. Ammonia and formaldehyde are reactive compounds and they are harmful, even in very low ppb level concentrations. This means challenges for measurement system in all of its critical aspects: sampling, calibration and sensitivity. We are applying techniques so far successfully used to measure reactive inorganic compounds like ammonia NH3 and hydrogen fluoride HF to tackle these challenges. Now a novel setup based on direct laser absorption with cavity enhancement employing fundamental vibration level excitations of ammonia and formaldehyde molecules is constructed in connection with new mechanics and algorithms optimized for gas exchange and sampling in the case of these reactive molecules easily sticking to surfaces. An aberration corrected multipass sample cell in vacuum pressure is used in parallel with an open path multipass setup. The CH2O and NH3 calibration gases necessary for system calibration are dynamically generated using traceable standards and components. We compare these two approaches with special emphasis on the system's response time, robustness, sensitivity, usability in field conditions, maintenance need and long term stability. A further coal is to enable the use of the same setups also for simultaneous measurement of other reactive compounds often encountered in air quality monitoring. This would make possible more comprehensive and also economic monitoring of these compounds with a single device.

Decomposition of ferrite in commercial superduplex stainless steel weld metals; microstructural transformations above 700 °C

NASA Astrophysics Data System (ADS)

Gregori, A.; Nilsson, J.-O.

2002-04-01

The microstructural stability at temperatures above 700 °C of weld metal of type 29Cr-8Ni-2Mo-0.39N and weld metal of type 25Cr-10Ni-4Mo-0.28N has been compared. Multipass welding was employed using the gas tungsten arc welding technique with a shielding gas of Ar+2 pct N2. The quantitative assessment of the intermetallic phase was performed using automatic image analysis in the light optical microscope (LOM). Detailed microanalysis was also performed using scanning and transmission electron microscopy. A computer program developed by the authors was used to calculate a continuous cooling-temperature (CCT) diagram on the basis of the experimentally determined time-temperature-transformation (TTT) diagram. Thermodynamic calculations for estimating phase stabilities and for interpreting experimental observations were performed. It was found that weld metal of type 29Cr-8Ni-2Mo-0.39N was microstructurally more stable than weld metal of type 25Cr-10Ni-4Mo-0.28N. A lower molybdenum concentration and a higher nitrogen concentration in the former alloy could explain the higher stability with respect to the intermetallic phase. The higher nitrogen concentration also provides a rationale for the higher stability against the formation of secondary austenite in weld metal of type 29Cr-8Ni-2Mo-0.39N. This effect, which is associated with a lower thermodynamic driving force for precipitation of secondary austenite during multipass welding, can be explained by nitrogen-enhanced primary austenite formation.

Interferometric detection of freeze-thaw displacements of Alaskan permafrost using ERS-1 data

NASA Technical Reports Server (NTRS)

Werner, Charles L.; Gabriel, Andrew K.

1993-01-01

The possibility of making large scale (50 km) measurements of motions of the earth's surface with high resolution (10 m) and very high accuracy (1 cm) from multipass SAR interferometry was established in 1989. Other experiments have confirmed the viability and usefulness of the method. Work is underway in various groups to measure displacements from volcanic activity, seismic events, glacier motion, and in the present study, freeze-thaw cycles in Alaskan permafrost. The ground is known to move significantly in these cycles, and provided that freezing does not cause image decorrelation, it should be possible to measure both ground swelling and subsidence. The authors have obtained data from multiple passes of ERS-1 over the Toolik Lake region of northern Alaska of suitable quality for interferometry. The data are processed into images, and single interferograms are formed in the usual manner. Phase unwrapping is performed, and the multipass baselines are estimated from the images using both orbit ephemerides and scene tie points. The phases are scaled by the baseline ratio, and a double-difference interferogram (DDI) is formed. It is found that there is a residual 'saddle-shape' phase error across the image, which is postulated to be caused by a small divergence (10(exp -2) deg.) in the orbits. A simulation of a DDI from divergent orbits confirms the shape and magnitude of the error. A two-dimensional least squares fit to the error is performed, which is used to correct the DDI. The final, corrected DDI shows significant phase (altitude) changes over the period of the observation.

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

Bogacz, Alex; Bruning, Oliver; Cruz-Alaniz, E.

Unprecedently high luminosity of 10 34 cm -2 s -1, promised by the LHeC accelerator complex poses several beam dynamics and lattice design challenges. As part of accelerator design process, exploration of innovative beam dynamics solutions and their lattice implementations is the key to mitigating performance limitations due to fundamental beam phenomena, such as: synchrotron radiation and collective instabilities. This article will present beam dynamics driven approach to accelerator design, which in particular, addresses emittance dilution due to quantum excitations and beam breakup instability in a large scale, multi-pass Energy Recovery Linac (ERL). The use of ERL accelerator technology tomore » provide improved beam quality and higher brightness continues to be the subject of active community interest and active accelerator development of future Electron Ion Colliders (EIC). Here, we employ current state of though for ERLs aiming at the energy frontier EIC. We will follow conceptual design options recently identified for the LHeC. The main thrust of these studies was to enhance the collider performance, while limiting overall power consumption through exploring interplay between emittance preservation and efficiencies promised by the ERL technology. Here, this combined with a unique design of the Interaction Region (IR) optics gives the impression that luminosity of 10 34 cm -2 s -1 is indeed feasible.« less

Novel Lattice Solutions for the LHeC

DOE PAGES

Bogacz, Alex; Bruning, Oliver; Cruz-Alaniz, E.; ...

2017-08-01

Unprecedently high luminosity of 10 34 cm -2 s -1, promised by the LHeC accelerator complex poses several beam dynamics and lattice design challenges. As part of accelerator design process, exploration of innovative beam dynamics solutions and their lattice implementations is the key to mitigating performance limitations due to fundamental beam phenomena, such as: synchrotron radiation and collective instabilities. This article will present beam dynamics driven approach to accelerator design, which in particular, addresses emittance dilution due to quantum excitations and beam breakup instability in a large scale, multi-pass Energy Recovery Linac (ERL). The use of ERL accelerator technology tomore » provide improved beam quality and higher brightness continues to be the subject of active community interest and active accelerator development of future Electron Ion Colliders (EIC). Here, we employ current state of though for ERLs aiming at the energy frontier EIC. We will follow conceptual design options recently identified for the LHeC. The main thrust of these studies was to enhance the collider performance, while limiting overall power consumption through exploring interplay between emittance preservation and efficiencies promised by the ERL technology. Here, this combined with a unique design of the Interaction Region (IR) optics gives the impression that luminosity of 10 34 cm -2 s -1 is indeed feasible.« less

Technology Advancement for Active Remote Sensing of Carbon Dioxide from Space Using the ASCENDS CarbonHawk Experiment Simulator: First Results

NASA Technical Reports Server (NTRS)

Obland, Michael D.; Nehrir, Amin R.; Lin, Bing; Harrison, F. Wallace; Kooi, Susan; Choi, Yonghoon; Plant, James; Yang, Melissa; Antill, Charles; Campbell, Joel;

Numerical simulation of incoherent optical wave propagation in nonlinear fibers

NASA Astrophysics Data System (ADS)

Fernandez, Arnaud; Balac, Stéphane; Mugnier, Alain; Mahé, Fabrice; Texier-Picard, Rozenn; Chartier, Thierry; Pureur, David

2013-11-01

The present work concerns the study of pulsed laser systems containing a fiber amplifier for boosting optical output power. In this paper, this fiber amplification device is included into a MOPFA laser, a master oscillator coupled with fiber amplifier, usually a cladding-pumped high-power amplifier often based on an ytterbium-doped fiber. An experimental study has established that the observed nonlinear effects (such as Kerr effect, four waves mixing, Raman effect) could behave very differently depending on the characteristics of the optical source emitted by the master laser. However, it has not yet been possible to determine from the experimental data if the statistics of the photons is alone responsible for the various nonlinear scenarios observed. Therefore, we have developed a numerical simulation software for solving the generalized nonlinear Schrödinger equation with a stochastic source term in order to validate the hypothesis that the coherence properties of the master laser are mainly liable for the behavior of the observed nonlinear effects. Contribution to the Topical Issue "Numelec 2012", Edited by Adel Razek.

Fourier transform spectroscopy of the nu3 band of the N3 radical

NASA Technical Reports Server (NTRS)

Brazier, C. R.; Bernath, P. F.; Burkholder, James B.; Howard, Carleton J.

1988-01-01

The nu3 transitions of N3 radicals produced by HN3-Cl reactions in a multipass cell (effective path length 100 m) are investigated experimentally using a Fourier-transform spectrometer with maximum resolution 0.004/cm. A total of 176 rotation-vibration lines are listed in a table and used, in combination with published data on 240 optical lines (Douglas and Jones, 1965), to determine the nu3 molecular constants. The lower-than-expected value of the nu3 fundamental frequency (1644.6784/cm) is attributed to the vibronic interaction discussed by Kawaguchi et al. (1981).

Brewster-plate spoiler - A novel method for reducing the amplitude of interference fringes that limit tunable-laser absorption sensitivities

NASA Technical Reports Server (NTRS)

Webster, C. R.

1985-01-01

A simple method is described for substantially reducing the amplitude of interference fringes that limit the sensitivities of tunable-laser high-resolution absorption spectrometers. A lead-salt diode laser operating in the 7-micron region is used with a single Brewster-plate spoiler to reduce the fringe amplitude by a factor of 30 and also to allow the detection of absorptances 0.001 percent in a single laser scan without subtraction techniques, without complex frequency modulation, and without distortion of the molecular line-shape signals. Application to multipass-cell spectrometers is described.

Latest developments for low-power infrared laser-based trace gas sensors for sensor networks

NASA Astrophysics Data System (ADS)

So, Stephen; Thomazy, David; Wang, Wen; Marchat, Oscar; Wysocki, Gerard

2011-09-01

Academic and industrial researchers require ultra-low power, compact laser based trace-gas sensor systems for the most demanding environmental and space-borne applications. Here the latest results from research projects addressing these applications will be discussed: 1) an ultra-compact CO2 sensor based on a continuous wave quantum cascade laser, 2) an ultra-sensitive Faraday rotation spectrometer for O2 detection, 3) a fully ruggedized compact and low-power laser spectrometer, and 4) a novel non-paraxial nonthin multipass cell. Preliminary tests and projection for performance of future sensors based on this technology is presented.

Wear particles of single-crystal silicon carbide in vacuum

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Buckley, D. H.

1980-01-01

Sliding friction experiments, conducted in vacuum with silicon carbide /000/ surface in contact with iron based binary alloys are described. Multiangular and spherical wear particles of silicon carbide are observed as a result of multipass sliding. The multiangular particles are produced by primary and secondary cracking of cleavage planes /000/, /10(-1)0/, and /11(-2)0/ under the Hertzian stress field or local inelastic deformation zone. The spherical particles may be produced by two mechanisms: (1) a penny shaped fracture along the circular stress trajectories under the local inelastic deformation zone, and (2) attrition of wear particles.

Quantum cascade laser-based analyzer for hydrogen sulfide detection at sub-parts-per-million levels

NASA Astrophysics Data System (ADS)

Nikodem, Michal; Krzempek, Karol; Stachowiak, Dorota; Wysocki, Gerard

2018-01-01

Due to its high toxicity, monitoring of hydrogen sulfide (H2S) concentration is essential in many industrial sites (such as natural gas extraction sites, petroleum refineries, geothermal power plants, or waste water treatment facilities), which require sub-parts-per-million sensitivities. We report on a quantum cascade laser-based spectroscopic system for detection of H2S in the midinfrared at ˜7.2 μm. We present a sensor design utilizing Herriott multipass cell and a wavelength modulation spectroscopy to achieve a detection limit of 140 parts per billion for 1-s integration time.

Multi-passes warm rolling of AZ31 magnesium alloy, effect on evaluation of texture, microstructure, grain size and hardness

NASA Astrophysics Data System (ADS)

Kamran, J.; Hasan, B. A.; Tariq, N. H.; Izhar, S.; Sarwar, M.

2014-06-01

In this study the effect of multi-passes warm rolling of AZ31 magnesium alloy on texture, microstructure, grain size variation and hardness of as cast sample (A) and two rolled samples (B & C) taken from different locations of the as-cast ingot was investigated. The purpose was to enhance the formability of AZ31 alloy in order to help manufacturability. It was observed that multi-passes warm rolling (250°C to 350°C) of samples B & C with initial thickness 7.76mm and 7.73 mm was successfully achieved up to 85% reduction without any edge or surface cracks in ten steps with a total of 26 passes. The step numbers 1 to 4 consist of 5, 2, 11 and 3 passes respectively, the remaining steps 5 to 10 were single pass rolls. In each discrete step a fixed roll gap is used in a way that true strain per step increases very slowly from 0.0067 in the first step to 0.7118 in the 26th step. Both samples B & C showed very similar behavior after 26th pass and were successfully rolled up to 85% thickness reduction. However, during 10th step (27th pass) with a true strain value of 0.772 the sample B experienced very severe surface as well as edge cracks. Sample C was therefore not rolled for the 10th step and retained after 26 passes. Both samples were studied in terms of their basal texture, microstructure, grain size and hardness. Sample C showed an equiaxed grain structure after 85% total reduction. The equiaxed grain structure of sample C may be due to the effective involvement of dynamic recrystallization (DRX) which led to formation of these grains with relatively low misorientations with respect to the parent as cast grains. The sample B on the other hand showed a microstructure in which all the grains were elongated along the rolling direction (RD) after 90 % total reduction and DRX could not effectively play its role due to heavy strain and lack of plastic deformation systems. The microstructure of as cast sample showed a near-random texture (mrd 4.3), with average grain size of 44 & micro-hardness of 52 Hv. The grain size of sample B and C was 14μm and 27μm respectively and mrd intensity of basal texture was 5.34 and 5.46 respectively. The hardness of sample B and C came out to be 91 and 66 Hv respectively due to reduction in grain size and followed the well known Hall-Petch relationship.

Effect of white pine blister rust (Cronartium ribicola) and rust-resistance breeding on genetic variation in western white pine Pinus monticola)

Treesearch

M. -S. Kim; S. J. Brunsfeld; G. I. McDonald; N. B. Klopfenstein

2003-01-01

Western white pine (Pinus monticola) is an economically and ecologically important species from western North America that has declined over the past several decades mainly due to the introduction of blister rust (Cronartium ribicola) and reduced opportunities for regeneration. Amplified fragment length polymorphism (AFLP) was used...

RESONANT CAVITY EXCITATION SYSTEM

DOEpatents

Baker, W.R.

1959-08-01

A cavity excitation circuit is described for rapidly building up and maintaining high-level oscillations in a resonant cavity. The circuit overcomes oscillation buildup slowing effects such as ion locking in the cavity by providing for the selective application of an amplified accelerating drive signal to the main cavity exciting oscillator during oscillation buildup and a direct drive signal to the oscillator thereafter.

Computational analysis of the amplified spontaneous emission in quantum dot doped plastic optical fibers

NASA Astrophysics Data System (ADS)

Peng, Xuefeng; Wu, Pinghui; Han, Yinxia; Hu, Guoqiang

2014-11-01

The properties of amplified spontaneous emission (ASE) in CdSe/ZnS quantum dot (QD) doped step-index polymer optical fibers (POFs) were computationally analyzed in this paper. A theoretical model based on the rate equations between two main energy levels of CdSe/ZnS QD was built in terms of time (t), distance traveled by light (z) and wavelength (λ), which can describe the ASE successfully. Through analyzing the spectral evolution with distance of the pulses propagating along the CdSe/ZnS QD doped POFs, dependences of the ASE threshold and the slope efficiency on the numerical aperture were obtained. Compared to the ASE in common dye-doped POFs, the pump threshold was just about 1/1000, but the slope efficiency was much higher.

Acid generation mechanism in anion-bound chemically amplified resists used for extreme ultraviolet lithography

NASA Astrophysics Data System (ADS)

Komuro, Yoshitaka; Yamamoto, Hiroki; Kobayashi, Kazuo; Ohomori, Katsumi; Kozawa, Takahiro

2015-03-01

Extreme ultraviolet (EUV) lithography is the most promising candidate for the high-volume production of semiconductor devices with half-pitches of sub 10nm. An anion-bound polymer(ABP), in which at the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, the acid generation mechanism in ABP films was investigated using γ and EUV radiolysis. On the basis of experimental results, the acid generation mechanism in anion-bound chemically amplified resists was proposed. The protons of acids are considered to be mainly generated through the reaction of phenyl radicals with diphenylsulfide radical cations that are produced through the hole transfer to the decomposition products of onium salts.

Testing the Dependence of Airborne Gravity Results on Three Variables in Kinematic GPS Processing

NASA Astrophysics Data System (ADS)

Weil, C.; Diehl, T. M.

2011-12-01

The National Geodetic Survey's Gravity for the Redefinition of the American Vertical Datum (GRAV-D) program plans to collect airborne gravity data across the entire U.S. and its holdings over the next decade. The goal is to build a geoid accurate to 1-2 cm, for which the airborne gravity data is key. The first phase is underway, with > 13% of data collection completed in: parts of Alaska, parts of California, most of the Gulf Coast, Puerto Rico, and the Virgin Islands. Obtaining accurate airborne gravity survey results depends on the quality of the GPS/IMU position solution used in the processing. There are many factors that could have an influence on the positioning results. First, we will investigate how an increased data sampling rate for the GPS/IMU affects the position solution and accelerations derived from those positions. Second we will test the hypothesis that, for differential kinematic processing a better solution is obtained using both a base and a rover GPS unit that contain an additional rubidium clock that is reported to sync better with GPS time. Finally, we will look at a few different GPS+IMU processing methods available in commercial software. This includes comparing GPS-only solutions with loosely coupled GPS/IMU solutions from the Applanix POSAV-510 system and tightly coupled solutions with our newly-acquired NovAtel SPAN system (micro-IRS IMU). Differential solutions are compared with PPP (Precise Point Positioning) solutions along with multi-pass and advanced tropospheric corrections available with the NovAtel Inertial Explorer software. Based on preliminary research, we expect that the tightly-coupled solutions with either better troposphere and/or multi-pass solutions will provide superior position (and gravity) results.

Stress Corrosion Cracking Behavior of Multipass TIG-Welded AA2219 Aluminum Alloy in 3.5 wt pct NaCl Solution

NASA Astrophysics Data System (ADS)

Venugopal, A.; Sreekumar, K.; Raja, V. S.

2012-09-01

The stress corrosion cracking (SCC) behavior of the AA2219 aluminum alloy in the single-pass (SP) and multipass (MP) welded conditions was examined and compared with that of the base metal (BM) in 3.5 wt pct NaCl solution using a slow-strain-rate technique (SSRT). The reduction in ductility was used as a parameter to evaluate the SCC susceptibility of both the BM and welded joints. The results showed that the ductility ratio ( ɛ NaCl/( ɛ air) was 0.97 and 0.96, respectively, for the BM and MP welded joint, and the same was marginally reduced to 0.9 for the SP welded joint. The fractographic examination of the failed samples revealed a typical ductile cracking morphology for all the base and welded joints, indicating the good environmental cracking resistance of this alloy under all welded conditions. To understand the decrease in the ductility of the SP welded joint, preexposure SSRT followed by microstructural observations were made, which showed that the decrease in ductility ratio of the SP welded joint was caused by the electrochemical pitting that assisted the nucleation of cracks in the form of corrosion induced mechanical cracking rather than true SCC failure of the alloy. The microstructural examination and polarization tests demonstrated a clear grain boundary (GB) sensitization of the PMZ, resulting in severe galvanic corrosion of the SP weld joint, which initiated the necessary conditions for the localized corrosion and cracking along the PMZ. The absence of PMZ and a refined fusion zone (FZ) structure because of the lesser heat input and postweld heating effect improved the galvanic corrosion resistance of the MP welded joint greatly, and thus, failure occurred along the FZ.

Sieve-based coreference resolution enhances semi-supervised learning model for chemical-induced disease relation extraction.

PubMed

Le, Hoang-Quynh; Tran, Mai-Vu; Dang, Thanh Hai; Ha, Quang-Thuy; Collier, Nigel

2016-07-01

The BioCreative V chemical-disease relation (CDR) track was proposed to accelerate the progress of text mining in facilitating integrative understanding of chemicals, diseases and their relations. In this article, we describe an extension of our system (namely UET-CAM) that participated in the BioCreative V CDR. The original UET-CAM system's performance was ranked fourth among 18 participating systems by the BioCreative CDR track committee. In the Disease Named Entity Recognition and Normalization (DNER) phase, our system employed joint inference (decoding) with a perceptron-based named entity recognizer (NER) and a back-off model with Semantic Supervised Indexing and Skip-gram for named entity normalization. In the chemical-induced disease (CID) relation extraction phase, we proposed a pipeline that includes a coreference resolution module and a Support Vector Machine relation extraction model. The former module utilized a multi-pass sieve to extend entity recall. In this article, the UET-CAM system was improved by adding a 'silver' CID corpus to train the prediction model. This silver standard corpus of more than 50 thousand sentences was automatically built based on the Comparative Toxicogenomics Database (CTD) database. We evaluated our method on the CDR test set. Results showed that our system could reach the state of the art performance with F1 of 82.44 for the DNER task and 58.90 for the CID task. Analysis demonstrated substantial benefits of both the multi-pass sieve coreference resolution method (F1 + 4.13%) and the silver CID corpus (F1 +7.3%).Database URL: SilverCID-The silver-standard corpus for CID relation extraction is freely online available at: https://zenodo.org/record/34530 (doi:10.5281/zenodo.34530). © The Author(s) 2016. Published by Oxford University Press.

Multipass haemodialysis: a novel dialysis modality

PubMed Central

Heaf, James Goya; Axelsen, Mette; Pedersen, Robert Smith

2013-01-01

Introduction Most home haemodialysis (HD) modalities are limited to home use since they are based on a single-pass (SP) technique, which requires preparation of large amounts of dialysate. We present a new dialysis method, which requires minimal dialysate volumes, continuously recycled during treatment [multipass HD (MPHD)]. Theoretical calculations suggest that MPHD performed six times weekly for 8 h/night, using a dialysate bath containing 50% of the calculated body water, will achieve urea clearances equivalent to conventional HD 4 h thrice weekly, and a substantial clearance of higher middle molecules. Methods Ten stable HD patients were dialyzed for 4 h using standard SPHD (dialysate flow 500 mL/min). Used dialysate was collected. One week later, an 8-h MPHD was performed. The dialysate volume was 50% of the calculated water volume, the dialysate inflow 500 mL/min−0.5 × ultrafiltration/min and the outflow 500 mL/min + 0.5 × ultrafiltration/min. Elimination rates of urea, creatinine, uric acid, phosphate and β2-microglobulin (B2M) and dialysate saturation were determined hourly. Results Three hours of MPHD removed 49, 54, 50, 51 and 57%, respectively, of the amounts of urea, creatinine, uric acid, phosphate and B2M that were removed by 4 h conventional HD. The corresponding figures after 8 h MPHD were 63, 78, 74, 78 and 111%. Conclusions Clearance of small molecules using MPHD 6 × 8 h/week will exceed traditional HD 3 × 4 h/week. Similarly, clearance of large molecules will significantly exceed traditional HD and HD 5 × 2.5 h/week. This modality will increase patients' freedom of movement compared with traditional home HD. The new method can also be used in the intensive care unit and for automated peritoneal dialysis. PMID:23136214

Refinement of Ferrite Grain Size near the Ultrafine Range by Multipass, Thermomechanical Compression

NASA Astrophysics Data System (ADS)

Patra, S.; Neogy, S.; Kumar, Vinod; Chakrabarti, D.; Haldar, A.

2012-11-01

Plane-strain compression testing was carried out on a Nb-Ti-V microalloyed steel, in a GLEEBLE3500 simulator using a different amount of roughing, intermediate, and finishing deformation over the temperature range of 1373 K to 1073 K (1100 °C to 800 °C). A decrease in soaking temperature from 1473 K to 1273 K (1200 °C to 1000 °C) offered marginal refinement in the ferrite ( α) grain size from 7.8 to 6.6 μm. Heavy deformation using multiple passes between A e3 and A r3 with true strain of 0.8 to 1.2 effectively refined the α grain size (4.1 to 3.2 μm) close to the ultrafine size by dynamic-strain-induced austenite ( γ) → ferrite ( α) transformation (DSIT). The intensities of microstructural banding, pearlite fraction in the microstructure (13 pct), and fraction of the harmful "cube" texture component (5 pct) were reduced with the increase in finishing deformation. Simultaneously, the fractions of high-angle (>15 deg misorientation) boundaries (75 to 80 pct), beneficial gamma-fiber (ND//<111>) texture components, along with {332}<133> and {554}<225> components were increased. Grain refinement and the formation of small Fe3C particles (50- to 600-nm size) increased the hardness of the deformed samples (184 to 192 HV). For the same deformation temperature [1103 K (830 °C)], the difference in α-grain sizes obtained after single-pass (2.7 μm) and multipass compression (3.2 μm) can be explained in view of the static- and dynamic-strain-induced γ → α transformation, strain partitioning between γ and α, dynamic recovery and dynamic recrystallization of the deformed α, and α-grain growth during interpass intervals.

A Mixed Mode Cochlear Amplifier Including Neural Feedback

NASA Astrophysics Data System (ADS)

Flax, Matthew R.; Holmes, W. Harvey

2011-11-01

The mixed mode cochlear amplifier (MMCA) model is derived from the physiology of the cochlea. It is comprised of three main elements of the peripheral hearing system: the cochlear mechanics, hair cell motility, and neurophysiology. This model expresses both active compression wave and active traveling wave modes of operation. The inclusion of a neural loop with a time delay, and a new paradigm for the mechanical response of the outer hair cells, are believed to be unique features of the MMCA. These elements combine to form an active feedback loop to constitute the cochlear amplifier, whose input is a passive traveling wave vibration. The result is a cycle-by-cycle amplifier with nonlinear response. This system can assume an infinite number of different operating states. The stable state and the first few amplitude-limited unstable (Hopf-bifurcated) states are significant in describing the operation of the peripheral hearing system. A hierarchy of models can be constructed from this concept, depending on the amount of detail included. The simplest model of the MMCA is a nonlinear delay line resonator. It was found that even this simple MMCA version can explain a large number of hearing phenomena, at least qualitatively. This paper concentrates on explaining the fractional octave shift from the living to postmortem response in terms of the new model. Other mechanical, hair cell and neurological phenomena can also be accounted for by the MMCA, including two-tone suppression behavior, distortion product responses, otoacoustic emissions and neural spontaneous rates.

Identification, genetic localization, and allelic diversity of selectively amplified microsatellite polymorphic loci in lettuce and wild relatives (Lactuca spp.).

PubMed

Witsenboer, H; Michelmore, R W; Vogel, J

1997-12-01

Selectively amplified microsatellite polymorphic locus (SAMPL) analysis is a method of amplifying microsatellite loci using generic PCR primers. SAMPL analysis uses one AFLP primer in combination with a primer complementary to microsatellite sequences. SAMPL primers based on compound microsatellite sequences provided the clearest amplification patterns. We explored the potential of SAMPL analysis in lettuce to detect PCR-based codominant microsatellite markers. Fifty-eight SAMPLs were identified and placed on the genetic map. Seventeen were codominant. SAMPLs were dispersed with RFLP markers on 11 of the 12 main linkage groups in lettuce, indicating that they have a similar genomic distribution. Some but not all fragments amplified by SAMPL analysis were confirmed to contain microsatellite sequences by Southern hybridization. Forty-five cultivars of lettuce and five wild species of Lactuca were analyzed to determine the allelic diversity for codominant SAMPLs. From 3 to 11 putative alleles were found for each SAMPL; 2-6 alleles were found within Lactuca sativa and 1-3 alleles were found among the crisphead genotypes, the most genetically homogeneous plant type of L. sativa. This allelic diversity is greater than that found for RFLP markers. Numerous new alleles were observed in the wild species; however, there were frequent null alleles. Therefore, SAMPL analysis is more applicable to intraspecific than to interspecific comparisons. A phenetic analysis based on SAMPLs resulted in a dendrogram similar to those based on RFLP and AFLP markers.

Hot electron generation under large-signal radio frequency operation of GaN high-electron-mobility transistors

NASA Astrophysics Data System (ADS)

Latorre-Rey, Alvaro D.; Sabatti, Flavio F. M.; Albrecht, John D.; Saraniti, Marco

2017-07-01

In order to assess the underlying physical mechanisms of hot carrier-related degradation such as defect generation in millimeter-wave GaN power amplifiers, we have simulated the electron energy distribution function under large-signal radio frequency conditions in AlGaN/GaN high-electron-mobility transistors. Our results are obtained through a full band Monte Carlo particle-based simulator self-consistently coupled to a harmonic balance circuit solver. At lower frequency, simulations of a Class AB power amplifier at 10 GHz show that the peak hot electron generation is up to 43% lower under RF drive than it is under DC conditions, regardless of the input power or temperature of operation. However, at millimeter-wave operation up to 40 GHz, RF hot carrier generation reaches that from DC biasing and even exceeds it up to 75% as the amplifier is driven into compression. Increasing the temperature of operation also shows that degradation of DC and RF characteristics are tightly correlated and mainly caused by increased phonon scattering. The accurate determination of the electron energy mapping is demonstrated to be a powerful tool for the extraction of compact models used in lifetime and reliability analysis.

A new cultivation independent approach to detect and monitor common Trichoderma species in soils.

PubMed

Hagn, Alexandra; Wallisch, Stefanie; Radl, Viviane; Charles Munch, Jean; Schloter, Michael

2007-04-01

A set of primers was developed for the detection, identification and quantification of common Trichoderma species in soil samples. Based on a broad range master alignment primers were derived to amplify an approximate 540 bp fragment comprising the internal transcribed spacer region 1 (ITS 1), 5.8S rDNA and internal transcribed spacer region 2 (ITS 2) from all taxonomic Clades of the genus Trichoderma. The primer set was applied to test strains as well as community DNA isolated from arable and forest soil. For all tested isolates the corresponding internal transcribed spacer regions of Trichoderma spp. strains were amplified, but none of non-Trichoderma origin. PCR with community DNA from soil yielded products of the expected size. Analysis of a clone library established for an arable site showed that all amplified sequences originated exclusively from Trichoderma species mainly being representatives of the Clades Hamatum, Harzianum and Pachybasioides and comprising most of the species known for biocontrol ability. In a realtime PCR approach the primer set uTf/uTr also proved to be a suitable system to quantify DNA of Trichoderma spp. in soils.

DNA methylation levels analysis in four tissues of sea cucumber Apostichopus japonicus based on fluorescence-labeled methylation-sensitive amplified polymorphism (F-MSAP) during aestivation.

PubMed

Zhao, Ye; Chen, Muyan; Storey, Kenneth B; Sun, Lina; Yang, Hongsheng

2015-03-01

DNA methylation plays an important role in regulating transcriptional change in response to environmental stimuli. In the present study, DNA methylation levels of tissues of the sea cucumber Apostichopus japonicus were analyzed by the fluorescence-labeled methylation-sensitive amplified polymorphism (F-MSAP) technique over three stages of the aestivation cycle. Overall, a total of 26,963 fragments were amplified including 9112 methylated fragments among four sea cucumber tissues using 18 pairs of selective primers. Results indicated an average DNA methylation level of 33.79% for A. japonicus. The incidence of DNA methylation was different across tissue types in the non-aestivation stage: intestine (30.16%), respiratory tree (27.61%), muscle (27.94%) and body wall (56.25%). Our results show that hypermethylation accompanied deep-aestivation in A. japonicus, which suggests that DNA methylation may have an important role in regulating global transcriptional suppression during aestivation. Further analysis indicated that the main DNA modification sites were focused on intestine and respiratory tree tissues and that full-methylation but not hemi-methylation levels exhibited significant increases in the deep-aestivation stage. Copyright © 2014 Elsevier Inc. All rights reserved.

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

Litvinenko,V.; Yakimenko, V.

We propose undertaking a demonstration experiment on suppressing spontaneous undulator radiation from an electron beam at BNL's Accelerator Test Facility (ATF). We describe the method, the proposed layout, and a possible schedule. There are several advantages in strongly suppressing shot noise in the electron beam, and the corresponding spontaneous radiation. The self-amplified spontaneous (SASE) emission originating from shot noise in the electron beam is the main source of noise in high-gain FEL amplifiers. It may negatively affect several HG FEL applications ranging from single- to multi-stage HGHG FELs. SASE saturation also imposes a fundamental hard limit on the gain ofmore » an FEL amplifier in a coherent electron-cooling scheme. A novel active method for suppressing shot noise in relativistic electron beams by many orders-of-magnitude was recently proposed. While theoretically such strong suppression appears feasible, the performance and applicability of this novel method must be evaluated experimentally. Several practical questions about the proposed noise suppressor, such as 3D effects and/or sensitivity to the e-beam parameters also require experimental clarification. To do this, we propose here a proof-of-principle experiment using elements of the VISA FEL at BNL's Accelerator Test Facility.« less

Patterning highly ordered arrays of complex nanofeatures through EUV directed polarity switching of non chemically amplified photoresist

PubMed Central

Ghosh, Subrata; Satyanarayana, V. S. V.; Pramanick, Bulti; Sharma, Satinder K.; Pradeep, Chullikkattil P.; Morales-Reyes, Israel; Batina, Nikola; Gonsalves, Kenneth E.

2016-01-01

Given the importance of complex nanofeatures in the filed of micro-/nanoelectronics particularly in the area of high-density magnetic recording, photonic crystals, information storage, micro-lens arrays, tissue engineering and catalysis, the present work demonstrates the development of new methodology for patterning complex nanofeatures using a recently developed non-chemically amplified photoresist (n-CARs) poly(4-(methacryloyloxy)phenyl)dimethylsulfoniumtriflate) (polyMAPDST) with the help of extreme ultraviolet lithography (EUVL) as patterning tool. The photosensitivity of polyMAPDST is mainly due to the presence of radiation sensitive trifluoromethanesulfonate unit (triflate group) which undergoes photodegradation upon exposure with EUV photons, and thus brings in polarity change in the polymer structure. Integration of such radiation sensitive unit into polymer network avoids the need of chemical amplification which is otherwise needed for polarity switching in the case of chemically amplified photoresists (CARs). Indeed, we successfully patterned highly ordered wide-raging dense nanofeatures that include nanodots, nanowaves, nanoboats, star-elbow etc. All these developed nanopatterns have been well characterized by FESEM and AFM techniques. Finally, the potential of polyMAPDST has been established by successful transfer of patterns into silicon substrate through adaptation of compatible etch recipes. PMID:26975782

Electronic amplifiers: A compilation

NASA Technical Reports Server (NTRS)

1971-01-01

Several types of amplifiers and amplifier systems are considered. These include preamplifiers, high power amplifiers, buffer and isolation amplifiers, amplifier circuits, and general purpose amplifiers.

Design update and recent results of the Apollon 10 PW facility

NASA Astrophysics Data System (ADS)

Le Garrec, B.; Papadopoulos, D. N.; Le Blanc, C.; Zou, J. P.; Chériaux, G.; Georges, P.; Druon, F.; Martin, L.; Fréneaux, L.; Beluze, A.; Lebas, N.; Mathieu, F.; Audebert, P.

2017-05-01

In this paper we are giving a summary of the Apollon 10 PW facility laser design together with updated laser performance. The Apollon facility is currently under construction in France. The APOLLON laser system is a laser designed for delivering pulses as short as 15 fs (10-15 s) with an energy exceeding 150 Joules on target. The peak power delivered by this laser system will be 10 Petawatts (1016W). The Apollon laser system will be delivering 4 beams: one 10 PW beam (F1 beam 400 mm diameter), one 1 PW beam (F2 beam 140 mm diameter) and two additional probe beams (F3 and F4) at a repetition rate of 1 shot per minute. The laser system is based on Ti-sapphire amplifiers pumped by frequency doubled solid-state lasers. The repetition rate of the high energy part will be 1 shot per minute. The main beam at the output of the last amplifier will be split and dispatched to two experimental areas. The main laser beam is delivering 30 J before compression at a repetition rate of 1 shot per minute and we are currently increasing to get 100J.

Design and status of the detector block for the ISO-SWS

NASA Technical Reports Server (NTRS)

Luinge, W.; Beintema, D. A.; Haser, L.; Katterloher, R.; Ploeger, G.

1989-01-01

The Short Wave Spectrometer (SWS) is one of the two spectrometers for the Infrared Space Observatory (ISO). It consists of a pair of grating spectrometers and a Fabry-Perot interferometer. Together, the grating spectrometers cover the wavelength range 2.4 to 45 microns, at a resolution between 1000 and 2000. The Fabry-Perot interferometer, in series with one of the grating spectrometers, provides a resolution of about 20,000 at the wavelengths between 15 and 35 microns. The SWS is being built by the Space Research Organization of the Netherlands and the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. The spectrometer has 52 discrete detectors, most of which are bulk detectors. In the design of the spectrometer, the main emphasis is on the sensitivity of the individual channels, rather than on the number of detectors. This was one of the main reasons to select non-destructive read-out circuits, with a separate heated-JFET pre-amplifier for each individual detector. The signals are amplified and filtered in parallel. The engineering tests on the SWS detector block have not yet been completed. The design of the detector block is described and the present problem areas are indicated.

Method and apparatus for linear low-frequency feedback in monolithic low-noise charge amplifiers

DOEpatents

DeGeronimo, Gianluigi

2006-02-14

A charge amplifier includes an amplifier, feedback circuit, and cancellation circuit. The feedback circuit includes a capacitor, inverter, and current mirror. The capacitor is coupled across the signal amplifier, the inverter is coupled to the output of the signal amplifier, and the current mirror is coupled to the input of the signal amplifier. The cancellation circuit is coupled to the output of the signal amplifier. A method of charge amplification includes providing a signal amplifier; coupling a first capacitor across the signal amplifier; coupling an inverter to the output of the signal amplifier; coupling a current mirror to the input of the signal amplifier; and coupling a cancellation circuit to the output of the signal amplifier. A front-end system for use with radiation sensors includes a charge amplifier and a current amplifier, shaping amplifier, baseline stabilizer, discriminator, peak detector, timing detector, and logic circuit coupled to the charge amplifier.

Ping-pong auto-zero amplifier with glitch reduction

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

Larson, Mark R

A ping-pong amplifier with reduced glitching is described. The ping-pong amplifier includes a nulling amplifier coupled to a switching network. The switching network is used to auto-zero a ping amplifier within a ping-pong amplifier. The nulling amplifier drives the output of a ping amplifier to a proper output voltage level during auto-zeroing of the ping amplifier. By being at a proper output voltage level, glitches associated with transitioning between a ping amplifier and a pong amplifier are reduced or eliminated.

Optimized radiation-hardened erbium doped fiber amplifiers for long space missions

NASA Astrophysics Data System (ADS)

Ladaci, A.; Girard, S.; Mescia, L.; Robin, T.; Laurent, A.; Cadier, B.; Boutillier, M.; Ouerdane, Y.; Boukenter, A.

2017-04-01

In this work, we developed and exploited simulation tools to optimize the performances of rare earth doped fiber amplifiers (REDFAs) for space missions. To describe these systems, a state-of-the-art model based on the rate equations and the particle swarm optimization technique is developed in which we also consider the main radiation effect on REDFA: the radiation induced attenuation (RIA). After the validation of this tool set by confrontation between theoretical and experimental results, we investigate how the deleterious radiation effects on the amplifier performance can be mitigated following adequate strategies to conceive the REDFA architecture. The tool set was validated by comparing the calculated Erbium-doped fiber amplifier (EDFA) gain degradation under X-rays at ˜300 krad(SiO2) with the corresponding experimental results. Two versions of the same fibers were used in this work, a standard optical fiber and a radiation hardened fiber, obtained by loading the previous fiber with hydrogen gas. Based on these fibers, standard and radiation hardened EDFAs were manufactured and tested in different operating configurations, and the obtained data were compared with simulation data done considering the same EDFA structure and fiber properties. This comparison reveals a good agreement between simulated gain and experimental data (<10% as the maximum error for the highest doses). Compared to our previous results obtained on Er/Yb-amplifiers, these results reveal the importance of the photo-bleaching mechanism competing with the RIA that cannot be neglected for the modeling of the radiation-induced gain degradation of EDFAs. This implies to measure in representative conditions the RIA at the pump and signal wavelengths that are used as input parameters for the simulation. The validated numerical codes have then been used to evaluate the potential of some EDFA architecture evolutions in the amplifier performance during the space mission. Optimization of both the fiber length and the EDFA pumping scheme allows us to strongly reduce its radiation vulnerability in terms of gain. The presented approach is a complementary and effective tool for hardening by device techniques and opens new perspectives for the applications of REDFAs and lasers in harsh environments.

A narrow-band injection-seeded pulsed titanium:sapphire oscillator-amplifier system with on-line chirp analysis for high-resolution spectroscopy.

PubMed

Hannemann, S; van Duijn, E-J; Ubachs, W

2007-10-01

A narrow-band tunable injection-seeded pulsed titanium:sapphire laser system has been developed for application in high-resolution spectroscopic studies at the fundamental wavelengths in the near infrared as well as in the ultraviolet, deep ultraviolet, and extreme ultraviolet after upconversion. Special focus is on the quantitative assessment of the frequency characteristics of the oscillator-amplifier system on a pulse-to-pulse basis. Frequency offsets between continuous-wave seed light and the pulsed output are measured as well as linear chirps attributed mainly to mode pulling effects in the oscillator cavity. Operational conditions of the laser are found in which these offset and chirp effects are minimal. Absolute frequency calibration at the megahertz level of accuracy is demonstrated on various atomic and molecular resonance lines.

RESONANT CAVITY EXCITATION SYSTEM

DOEpatents

Baker, W.R.; Kerns, Q.A.; Riedel, J.

1959-01-13

An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

Analysis of Dual-Order Backward Pumping Schemes in Distributed Raman Amplification System

NASA Astrophysics Data System (ADS)

Singh, Kulwinder; Patterh, Manjeet Singh; Bhamrah, Manjit Singh

2018-04-01

Backward pumping in fiber Raman amplifiers has been investigated in this paper in terms of on-off Raman gain, noise figure and optical signal-to-noise ratio. The results exhibit that with four first-order pumps and one second-order pump scheme can be employed to achieve 8.2 dB noise figure in 64 channel fiber optic communication system. It has also been reported that 2.65 dB gain ripple, 0.87 dB noise figure tilt and 2.02 dB OSNR tilt can be attained with the second-order pumping in fiber Raman amplifiers. The main advantage of the scheme is that only 50 mW second-order pump shows appreciable improvement in the system performance. It shows that further increase in first-order and second-order pump powers increase system noise implications.

No detection of SV40 DNA in mesothelioma tissues from a high incidence area in Sweden.

PubMed

Lundstig, Annika; Dejmek, Annika; Eklund, Carina; Filinic, Ivo; Dillner, Joakim

2007-01-01

Simian virus 40 (SV40), a polyoma virus of the rhesus macaque was discovered in 1960 as a contaminant of human polio vaccines produced in monkey cells. A number of studies have reported the detection of SV40 nucleotide sequences in human tumors, mainly mesotheliomas, but the reports have not been consistent. The presence of SV40 in 26 consecutive cases of malignant mesothelioma of biphasic type was investigated using a SV40 quantitative real time polymerase chain reaction (PCR) with a sensitivity of 10 copies of viral DNA per sample. All the samples were also tested for amplifiability using a real-time PCR for the beta-globin gene. Eighteen tumors were amplifiable, but none contained SV40 DNA. The results do not support an association between mesothelioma and SV40.

High power RF solid state power amplifier system

NASA Technical Reports Server (NTRS)

Sims, III, William Herbert (Inventor); Chavers, Donald Gregory (Inventor); Richeson, James J. (Inventor)

2011-01-01

A high power, high frequency, solid state power amplifier system includes a plurality of input multiple port splitters for receiving a high-frequency input and for dividing the input into a plurality of outputs and a plurality of solid state amplifier units. Each amplifier unit includes a plurality of amplifiers, and each amplifier is individually connected to one of the outputs of multiport splitters and produces a corresponding amplified output. A plurality of multiport combiners combine the amplified outputs of the amplifiers of each of the amplifier units to a combined output. Automatic level control protection circuitry protects the amplifiers and maintains a substantial constant amplifier power output.

High strength, low carbon, dual phase steel rods and wires and process for making same

DOEpatents

Thomas, Gareth; Nakagawa, Alvin H.

1986-01-01

A high strength, high ductility, low carbon, dual phase steel wire, bar or rod and process for making the same is provided. The steel wire, bar or rod is produced by cold drawing to the desired diameter in a single multipass operation a low carbon steel composition characterized by a duplex microstructure consisting essentially of a strong second phase dispersed in a soft ferrite matrix with a microstructure and morphology having sufficient cold formability to allow reductions in cross-sectional area of up to about 99.9%. Tensile strengths of at least 120 ksi to over 400 ksi may be obtained.

Contribution of precipitate on migrated grain boundaries to ductility-dip cracking in Alloy 625 weld joints

NASA Astrophysics Data System (ADS)

Lee, Dong Jin; Kim, Youn Soo; Shin, Yong Taek; Jeon, Eon Chan; Lee, Sang Hwa; Lee, Hyo-Jong; Lee, Sung Keun; Lee, Jun Hee; Lee, Hae Woo

2010-10-01

We investigated the crack properties in Alloy 625 weld metals and their characteristics using experimentally designed filler wires fabricated by varying the niobium and manganese contents in the flux with the shield metal arc welding (SMAW) process. The fast diffusivity of niobium on the migrated grain boundary (MGB) under strong restraint tensile stress, which was induced by the hardened matrix in weld metal containing high niobium and manganese, accelerated the growth of niobium carbide (NbC) in multipass deposits. Coalescence of microvoids along with incoherent NbC and further propagation induced ductility-dip cracking (DDC) on MGB.

A Controlled-Environment Chamber for Atmospheric Chemistry Studies Using FT-IR Spectroscopy

DTIC Science & Technology

1990-06-01

necessary and identify by block number) FELD GROUP SUB-GROUP i >Chamber, controlled environment; long-path cell ; 07 04 FT-IR; Hydrazine decay...modification doubles the useable path length of the original multipass cell described by White (Reference 8). The pattern of images formed on the nesting...system is shown in Figure 13. 24 z C C02, Ibm, El4 944 C3 ta) caC E-4- 252 14 $4 41) 41) 0. 0 04 04 4 41) ~0 to 0.0 V-4 (A q14 0~ 1% 4-r4 $4 0 u P416 4 4

Multi-pass cooling for turbine airfoils

DOEpatents

Liang, George [Palm City, FL

2011-06-28

An airfoil for a turbine vane of a gas turbine engine. The airfoil includes an outer wall having pressure and suction sides, and a radially extending cooling cavity located between the pressure and suction sides. A plurality of partitions extend radially through the cooling cavity to define a plurality of interconnected cooling channels located at successive chordal locations through the cooling cavity. The cooling channels define a serpentine flow path extending in the chordal direction. Further, the cooling channels include a plurality of interconnected chambers and the chambers define a serpentine path extending in the radial direction within the serpentine path extending in the chordal direction.

Cavity enhanced atomic magnetometry

PubMed Central

Crepaz, Herbert; Ley, Li Yuan; Dumke, Rainer

2015-01-01

Atom sensing based on Faraday rotation is an indispensable method for precision measurements, universally suitable for both hot and cold atomic systems. Here we demonstrate an all-optical magnetometer where the optical cell for Faraday rotation spectroscopy is augmented with a low finesse cavity. Unlike in previous experiments, where specifically designed multipass cells had been employed, our scheme allows to use conventional, spherical vapour cells. Spherical shaped cells have the advantage that they can be effectively coated inside with a spin relaxation suppressing layer providing long spin coherence times without addition of a buffer gas. Cavity enhancement shows in an increase in optical polarization rotation and sensitivity compared to single-pass configurations. PMID:26481853

The Effect of Multi-pass Equal-Channel Angular Pressing (ECAP) for Consolidation of Aluminum-Nano Alumina Composite Powder on Wear Resistance

NASA Astrophysics Data System (ADS)

Derakhshandeh-Haghighi, Reza; Jenabali Jahromi, Seyed Ahmad

2016-02-01

The wear behavior of aluminum matrix composite powder with varying concentration of nano alumina particles, which was consolidated by equal-channel angular pressing (ECAP) at different passes, was determined by applying, 10 and 46 N loads, using a pin-on-disk machine. Optical and electronic microscopy, EDX analysis, and hardness measurement were performed in order to characterize the worn samples. The relative density of the samples after each pass of ECAP was determined using Archimedes principle. Within the studied range of loads, the wear loss decreased by increasing the number of ECAP passes.

Piercing mandrel strengthening by surfacing with nickel aluminide-based alloy

NASA Astrophysics Data System (ADS)

Zorin, I. V.; Dubtsov, Yu N.; Sokolov, G. N.; Artem'ev, A. A.; Lysak, V. I.; Elsukov, S. N.

2017-02-01

Electrode composite wire (CW) was used for argon-arc surfacing of a thermal-resisting nickel aluminide-based alloy (Ni-Al-Cr-W-Mo-Ta system) on the butt-end surface of the non-water-cooled piercing mandrel. It was shown that multipassing surfacing forms a defect-free deposited metal based on the γ’-Ni3Al phase of various structural origins. Using high-temperature sclerometry and thermal fatigue testing methods, the metal deposited with CW containing ultrafine particle of 0.3-0.4 % wt. WC carbide features increased resistance to thermal and force effects at temperatures up to 1200 °C.

Tunable infrared laser detection of pyrolysis products of explosives in soils

NASA Astrophysics Data System (ADS)

Wormhoudt, J.; Shorter, J. H.; McManus, J. B.; Kebabian, P. L.; Zahniser, M. S.; Kolb, Charles E.; Davis, W. M.; Cespedes, E. R.

1996-07-01

A research program involving two applications of tunable infrared laser differential absorption spectroscopy (TILDAS) with multipass, long-path absorption cells to the detection of explosives contamination in soils is reported. In the first application, sensitive, specific real-time species concentration measurements by TILDAS have led to new understanding of the processes involved in explosives detection by the heating of contaminated soils and the quantification of the resulting pyrolysis gases. In the second, we present results of our calculations of the properties of astigmatic off-axis resonator absorption cells, which show that useful TILDAS path lengths can be achieved inside a cone penetrometer probe.

LongISLND: in silico sequencing of lengthy and noisy datatypes

PubMed Central

Lau, Bayo; Mohiyuddin, Marghoob; Mu, John C.; Fang, Li Tai; Bani Asadi, Narges; Dallett, Carolina; Lam, Hugo Y. K.

2016-01-01

Summary: LongISLND is a software package designed to simulate sequencing data according to the characteristics of third generation, single-molecule sequencing technologies. The general software architecture is easily extendable, as demonstrated by the emulation of Pacific Biosciences (PacBio) multi-pass sequencing with P5 and P6 chemistries, producing data in FASTQ, H5, and the latest PacBio BAM format. We demonstrate its utility by downstream processing with consensus building and variant calling. Availability and Implementation: LongISLND is implemented in Java and available at http://bioinform.github.io/longislnd Contact: hugo.lam@roche.com Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27667791

Vertical transportation systems embedded on shuffled frog leaping algorithm for manufacturing optimisation problems in industries.

PubMed

Aungkulanon, Pasura; Luangpaiboon, Pongchanun

2016-01-01

Response surface methods via the first or second order models are important in manufacturing processes. This study, however, proposes different structured mechanisms of the vertical transportation systems or VTS embedded on a shuffled frog leaping-based approach. There are three VTS scenarios, a motion reaching a normal operating velocity, and both reaching and not reaching transitional motion. These variants were performed to simultaneously inspect multiple responses affected by machining parameters in multi-pass turning processes. The numerical results of two machining optimisation problems demonstrated the high performance measures of the proposed methods, when compared to other optimisation algorithms for an actual deep cut design.

Analysis method for Thomson scattering diagnostics in GAMMA 10/PDX.

PubMed

Ohta, K; Yoshikawa, M; Yasuhara, R; Chikatsu, M; Shima, Y; Kohagura, J; Sakamoto, M; Nakasima, Y; Imai, T; Ichimura, M; Yamada, I; Funaba, H; Minami, T

2016-11-01

We have developed an analysis method to improve the accuracies of electron temperature measurement by employing a fitting technique for the raw Thomson scattering (TS) signals. Least square fitting of the raw TS signals enabled reduction of the error in the electron temperature measurement. We applied the analysis method to a multi-pass (MP) TS system. Because the interval between the MPTS signals is very short, it is difficult to separately analyze each Thomson scattering signal intensity by using the raw signals. We used the fitting method to obtain the original TS scattering signals from the measured raw MPTS signals to obtain the electron temperatures in each pass.

Post-weld Tempered Microstructure and Mechanical Properties of Hybrid Laser-Arc Welded Cast Martensitic Stainless Steel CA6NM

NASA Astrophysics Data System (ADS)

Mirakhorli, Fatemeh; Cao, Xinjin; Pham, Xuan-Tan; Wanjara, Priti; Fihey, Jean-Luc

2016-12-01

Manufacturing of hydroelectric turbine components involves the assembly of thick-walled stainless steels using conventional multi-pass arc welding processes. By contrast, hybrid laser-arc welding may be an attractive process for assembly of such materials to realize deeper penetration depths, higher production rates, narrower fusion, and heat-affected zones, and lower distortion. In the present work, single-pass hybrid laser-arc welding of 10-mm thick CA6NM, a low carbon martensitic stainless steel, was carried out in the butt joint configuration using a continuous wave fiber laser at its maximum power of 5.2 kW over welding speeds ranging from 0.75 to 1.2 m/minute. The microstructures across the weldment were characterized after post-weld tempering at 873 K (600 °C) for 1 hour. From microscopic examinations, the fusion zone was observed to mainly consist of tempered lath martensite and some residual delta-ferrite. The mechanical properties were evaluated in the post-weld tempered condition and correlated to the microstructures and defects. The ultimate tensile strength and Charpy impact energy values of the fully penetrated welds in the tempered condition were acceptable according to ASTM, ASME, and industrial specifications, which bodes well for the introduction of hybrid laser-arc welding technology for the manufacturing of next generation hydroelectric turbine components.

Increasing feasibility of the field-programmable gate array implementation of an iterative image registration using a kernel-warping algorithm

NASA Astrophysics Data System (ADS)

Nguyen, An Hung; Guillemette, Thomas; Lambert, Andrew J.; Pickering, Mark R.; Garratt, Matthew A.

2017-09-01

Image registration is a fundamental image processing technique. It is used to spatially align two or more images that have been captured at different times, from different sensors, or from different viewpoints. There have been many algorithms proposed for this task. The most common of these being the well-known Lucas-Kanade (LK) and Horn-Schunck approaches. However, the main limitation of these approaches is the computational complexity required to implement the large number of iterations necessary for successful alignment of the images. Previously, a multi-pass image interpolation algorithm (MP-I2A) was developed to considerably reduce the number of iterations required for successful registration compared with the LK algorithm. This paper develops a kernel-warping algorithm (KWA), a modified version of the MP-I2A, which requires fewer iterations to successfully register two images and less memory space for the field-programmable gate array (FPGA) implementation than the MP-I2A. These reductions increase feasibility of the implementation of the proposed algorithm on FPGAs with very limited memory space and other hardware resources. A two-FPGA system rather than single FPGA system is successfully developed to implement the KWA in order to compensate insufficiency of hardware resources supported by one FPGA, and increase parallel processing ability and scalability of the system.

Major results from the first plasma campaign of the Wendelstein 7-X stellarator

DOE PAGES

Wolf, R. C.; Ali, A.; Alonso, A.; ...

2017-07-27

Here, after completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreedmore » for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 × 10 19 m –3, central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre.« less

Cell-Free Systems Based on CHO Cell Lysates: Optimization Strategies, Synthesis of “Difficult-to-Express” Proteins and Future Perspectives

PubMed Central

Thoring, Lena; Wüstenhagen, Doreen A.; Borowiak, Maria; Stech, Marlitt; Sonnabend, Andrei; Kubick, Stefan

2016-01-01

Nowadays, biotechnological processes play a pivotal role in target protein production. In this context, Chinese Hamster Ovary (CHO) cells are one of the most prominent cell lines for the expression of recombinant proteins and revealed as a safe host for nearly 40 years. Nevertheless, the major bottleneck of common in vivo protein expression platforms becomes obvious when looking at the production of so called “difficult-to-express” proteins. This class of proteins comprises in particular several ion channels and multipass membrane proteins as well as cytotoxic proteins. To enhance the production of “difficult-to-express” proteins, alternative technologies were developed, mainly based on translationally active cell lysates. These so called “cell-free” protein synthesis systems enable an efficient production of different classes of proteins. Eukaryotic cell-free systems harboring endogenous microsomal structures for the synthesis of functional membrane proteins and posttranslationally modified proteins are of particular interest for future applications. Therefore, we present current developments in cell-free protein synthesis based on translationally active CHO cell extracts, underlining the high potential of this platform. We present novel results highlighting the optimization of protein yields, the synthesis of various “difficult-to-express” proteins and the cotranslational incorporation of non-standard amino acids, which was exemplarily demonstrated by residue specific labeling of the glycoprotein Erythropoietin and the multimeric membrane protein KCSA. PMID:27684475

Major results from the first plasma campaign of the Wendelstein 7-X stellarator

NASA Astrophysics Data System (ADS)

Wolf, R. C.; Ali, A.; Alonso, A.; Baldzuhn, J.; Beidler, C.; Beurskens, M.; Biedermann, C.; Bosch, H.-S.; Bozhenkov, S.; Brakel, R.; Dinklage, A.; Feng, Y.; Fuchert, G.; Geiger, J.; Grulke, O.; Helander, P.; Hirsch, M.; Höfel, U.; Jakubowski, M.; Knauer, J.; Kocsis, G.; König, R.; Kornejew, P.; Krämer-Flecken, A.; Krychowiak, M.; Landreman, M.; Langenberg, A.; Laqua, H. P.; Lazerson, S.; Maaßberg, H.; Marsen, S.; Marushchenko, M.; Moseev, D.; Niemann, H.; Pablant, N.; Pasch, E.; Rahbarnia, K.; Schlisio, G.; Stange, T.; Pedersen, T. Sunn; Svensson, J.; Szepesi, T.; Trimino Mora, H.; Turkin, Y.; Wauters, T.; Weir, G.; Wenzel, U.; Windisch, T.; Wurden, G.; Zhang, D.; Abramovic, I.; Äkäslompolo, S.; Aleynikov, P.; Aleynikova, K.; Alzbutas, R.; Anda, G.; Andreeva, T.; Ascasibar, E.; Assmann, J.; Baek, S.-G.; Banduch, M.; Barbui, T.; Barlak, M.; Baumann, K.; Behr, W.; Benndorf, A.; Bertuch, O.; Biel, W.; Birus, D.; Blackwell, B.; Blanco, E.; Blatzheim, M.; Bluhm, T.; Böckenhoff, D.; Bolgert, P.; Borchardt, M.; Borsuk, V.; Boscary, J.; Böttger, L.-G.; Brand, H.; Brandt, Ch.; Bräuer, T.; Braune, H.; Brezinsek, S.; Brunner, K.-J.; Brünner, B.; Burhenn, R.; Buttenschön, B.; Bykov, V.; Calvo, I.; Cannas, B.; Cappa, A.; Carls, A.; Carraro, L.; Carvalho, B.; Castejon, F.; Charl, A.; Chernyshev, F.; Cianciosa, M.; Citarella, R.; Ciupiński, Ł.; Claps, G.; Cole, M.; Cole, M. J.; Cordella, F.; Cseh, G.; Czarnecka, A.; Czermak, A.; Czerski, K.; Czerwinski, M.; Czymek, G.; da Molin, A.; da Silva, A.; Dammertz, G.; Danielson, J.; de la Pena, A.; Degenkolbe, S.; Denner, P.; Dhard, D. P.; Dostal, M.; Drevlak, M.; Drewelow, P.; Drews, Ph.; Dudek, A.; Dundulis, G.; Durodie, F.; van Eeten, P.; Effenberg, F.; Ehrke, G.; Endler, M.; Ennis, D.; Erckmann, E.; Esteban, H.; Estrada, T.; Fahrenkamp, N.; Feist, J.-H.; Fellinger, J.; Fernandes, H.; Fietz, W. H.; Figacz, W.; Fontdecaba, J.; Ford, O.; Fornal, T.; Frerichs, H.; Freund, A.; Führer, M.; Funaba, T.; Galkowski, A.; Gantenbein, G.; Gao, Y.; García Regaña, J.; Garcia-Munoz, M.; Gates, D.; Gawlik, G.; Geiger, B.; Giannella, V.; Gierse, N.; Gogoleva, A.; Goncalves, B.; Goriaev, A.; Gradic, D.; Grahl, M.; Green, J.; Grosman, A.; Grote, H.; Gruca, M.; Guerard, C.; Haiduk, L.; Han, X.; Harberts, F.; Harris, J. H.; Hartfuß, H.-J.; Hartmann, D.; Hathiramani, D.; Hein, B.; Heinemann, B.; Heitzenroeder, P.; Henneberg, S.; Hennig, C.; Hernandez Sanchez, J.; Hidalgo, C.; Hölbe, H.; Hollfeld, K. P.; Hölting, A.; Höschen, D.; Houry, M.; Howard, J.; Huang, X.; Huber, M.; Huber, V.; Hunger, H.; Ida, K.; Ilkei, T.; Illy, S.; Israeli, B.; Ivanov, A.; Jablonski, S.; Jagielski, J.; Jelonnek, J.; Jenzsch, H.; Junghans, P.; Kacmarczyk, J.; Kaliatka, T.; Kallmeyer, J.-P.; Kamionka, U.; Karalevicius, R.; Kasahara, H.; Kasparek, W.; Kenmochi, N.; Keunecke, M.; Khilchenko, A.; Kinna, D.; Kleiber, R.; Klinger, T.; Knaup, M.; Kobarg, Th.; Köchl, F.; Kolesnichenko, Y.; Könies, A.; Köppen, M.; Koshurinov, J.; Koslowski, R.; Köster, F.; Koziol, R.; Krämer, M.; Krampitz, R.; Kraszewsk, P.; Krawczyk, N.; Kremeyer, T.; Krings, Th.; Krom, J.; Krzesinski, G.; Ksiazek, I.; Kubkowska, M.; Kühner, G.; Kurki-Suonio, T.; Kwak, S.; Lang, R.; Langish, S.; Laqua, H.; Laube, R.; Lechte, C.; Lennartz, M.; Leonhardt, W.; Lewerentz, L.; Liang, Y.; Linsmeier, Ch.; Liu, S.; Lobsien, J.-F.; Loesser, D.; Loizu Cisquella, J.; Lore, J.; Lorenz, A.; Losert, M.; Lubyako, L.; Lücke, A.; Lumsdaine, A.; Lutsenko, V.; Majano-Brown, J.; Marchuk, O.; Mardenfeld, M.; Marek, P.; Massidda, S.; Masuzaki, S.; Maurer, D.; McCarthy, K.; McNeely, P.; Meier, A.; Mellein, D.; Mendelevitch, B.; Mertens, Ph.; Mikkelsen, D.; Mishchenko, O.; Missal, B.; Mittelstaedt, J.; Mizuuchi, T.; Mollen, A.; Moncada, V.; Mönnich, T.; Morizaki, T.; Munk, R.; Murakami, S.; Musielok, F.; Náfrádi, G.; Nagel, M.; Naujoks, D.; Neilson, H.; Neubauer, O.; Neuner, U.; Ngo, T.; Nocentini, R.; Nührenberg, C.; Nührenberg, J.; Obermayer, S.; Offermanns, G.; Ogawa, K.; Ongena, J.; Oosterbeek, J. W.; Orozco, G.; Otte, M.; Pacios Rodriguez, L.; Pan, W.; Panadero, N.; Panadero Alvarez, N.; Panin, A.; Papenfuß, D.; Paqay, S.; Pavone, A.; Pawelec, E.; Pelka, G.; Peng, X.; Perseo, V.; Peterson, B.; Pieper, A.; Pilopp, D.; Pingel, S.; Pisano, F.; Plaum, B.; Plunk, G.; Povilaitis, M.; Preinhaelter, J.; Proll, J.; Puiatti, M.-E.; Sitjes, A. Puig; Purps, F.; Rack, M.; Récsei, S.; Reiman, A.; Reiter, D.; Remppel, F.; Renard, S.; Riedl, R.; Riemann, J.; Rimkevicius, S.; Riße, K.; Rodatos, A.; Röhlinger, H.; Romé, M.; Rong, P.; Roscher, H.-J.; Roth, B.; Rudischhauser, L.; Rummel, K.; Rummel, T.; Runov, A.; Rust, N.; Ryc, L.; Ryosuke, S.; Sakamoto, R.; Samartsev, A.; Sanchez, M.; Sano, F.; Satake, S.; Satheeswaran, G.; Schacht, J.; Schauer, F.; Scherer, T.; Schlaich, A.; Schlüter, K.-H.; Schmitt, J.; Schmitz, H.; Schmitz, O.; Schmuck, S.; Schneider, M.; Schneider, W.; Scholz, M.; Scholz, P.; Schrittwieser, R.; Schröder, M.; Schröder, T.; Schroeder, R.; Schumacher, H.; Schweer, B.; Shanahan, B.; Shikhovtsev, I. V.; Sibilia, M.; Sinha, P.; Sipliä, S.; Skodzik, J.; Slaby, C.; Smith, H.; Spiess, W.; Spong, D. A.; Spring, A.; Stadler, R.; Standley, B.; Stephey, L.; Stoneking, M.; Stridde, U.; Sulek, Z.; Surko, C.; Suzuki, Y.; Szabó, V.; Szabolics, T.; Szökefalvi-Nagy, Z.; Tamura, N.; Terra, A.; Terry, J.; Thomas, J.; Thomsen, H.; Thumm, M.; von Thun, C. P.; Timmermann, D.; Titus, P.; Toi, K.; Travere, J. M.; Traverso, P.; Tretter, J.; Tsuchiya, H.; Tsujimura, T.; Tulipán, S.; Turnyanskiy, M.; Unterberg, B.; Urban, J.; Urbonavicius, E.; Vakulchyk, I.; Valet, S.; van Millingen, B.; Vela, L.; Velasco, J.-L.; Vergote, M.; Vervier, M.; Vianello, N.; Viebke, H.; Vilbrandt, R.; Vorkörper, A.; Wadle, S.; Wagner, F.; Wang, E.; Wang, N.; Warmer, F.; Wegener, L.; Weggen, J.; Wei, Y.; Wendorf, J.; Werner, A.; Wiegel, B.; Wilde, F.; Winkler, E.; Winters, V.; Wolf, S.; Wolowski, J.; Wright, A.; Xanthopoulos, P.; Yamada, H.; Yamada, I.; Yasuhara, R.; Yokoyama, M.; Zajac, J.; Zarnstorff, M.; Zeitler, A.; Zhang, H.; Zhu, J.; Zilker, M.; Zimbal, A.; Zocco, A.; Zoletnik, S.; Zuin, M.

2017-10-01

After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3  ×  1019 m-3, central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre.

Major results from the first plasma campaign of the Wendelstein 7-X stellarator

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

Wolf, R. C.; Ali, A.; Alonso, A.

Here, after completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreedmore » for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 × 10 19 m –3, central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre.« less

Real Time Calibration Method for Signal Conditioning Amplifiers

NASA Technical Reports Server (NTRS)

Medelius, Pedro J. (Inventor); Mata, Carlos T. (Inventor); Eckhoff, Anthony (Inventor); Perotti, Jose (Inventor); Lucena, Angel (Inventor)

2004-01-01

A signal conditioning amplifier receives an input signal from an input such as a transducer. The signal is amplified and processed through an analog to digital converter and sent to a processor. The processor estimates the input signal provided by the transducer to the amplifier via a multiplexer. The estimated input signal is provided as a calibration voltage to the amplifier immediately following the receipt of the amplified input signal. The calibration voltage is amplified by the amplifier and provided to the processor as an amplified calibration voltage. The amplified calibration voltage is compared to the amplified input signal, and if a significant error exists, the gain and/or offset of the amplifier may be adjusted as necessary.

SMART Rotor Development and Wind Tunnel Test

DTIC Science & Technology

2009-09-01

amplifier and control system , and data acquisition, processing, and display systems . Boeing�s LRTS (Fig. 2), consists of a sled structure that...Support Test Stand Sled Tail Sting Outrigger Arm Figure 2: System integration test at whirl tower Port Rotor Balance Main Strut Flap Tail...demonstrated. Finally, the reliability of the flap actuation system was successfully proven in more than 60 hours of wind tunnel testing

Rail-to-rail differential input amplification stage with main and surrogate differential pairs

DOEpatents

Britton, Jr., Charles Lanier; Smith, Stephen Fulton

2007-03-06

An operational amplifier input stage provides a symmetrical rail-to-rail input common-mode voltage without turning off either pair of complementary differential input transistors. Secondary, or surrogate, transistor pairs assume the function of the complementary differential transistors. The circuit also maintains essentially constant transconductance, constant slew rate, and constant signal-path supply current as it provides rail-to-rail operation.

Whole-body direct 4D parametric PET imaging employing nested generalized Patlak expectation-maximization reconstruction

PubMed Central

Karakatsanis, Nicolas A.; Casey, Michael E.; Lodge, Martin A.; Rahmim, Arman; Zaidi, Habib

2016-01-01

Whole-body (WB) dynamic PET has recently demonstrated its potential in translating the quantitative benefits of parametric imaging to the clinic. Post-reconstruction standard Patlak (sPatlak) WB graphical analysis utilizes multi-bed multi-pass PET acquisition to produce quantitative WB images of the tracer influx rate Ki as a complimentary metric to the semi-quantitative standardized uptake value (SUV). The resulting Ki images may suffer from high noise due to the need for short acquisition frames. Meanwhile, a generalized Patlak (gPatlak) WB post-reconstruction method had been suggested to limit Ki bias of sPatlak analysis at regions with non-negligible 18F-FDG uptake reversibility; however, gPatlak analysis is non-linear and thus can further amplify noise. In the present study, we implemented, within the open-source Software for Tomographic Image Reconstruction (STIR) platform, a clinically adoptable 4D WB reconstruction framework enabling efficient estimation of sPatlak and gPatlak images directly from dynamic multi-bed PET raw data with substantial noise reduction. Furthermore, we employed the optimization transfer methodology to accelerate 4D expectation-maximization (EM) convergence by nesting the fast image-based estimation of Patlak parameters within each iteration cycle of the slower projection-based estimation of dynamic PET images. The novel gPatlak 4D method was initialized from an optimized set of sPatlak ML-EM iterations to facilitate EM convergence. Initially, realistic simulations were conducted utilizing published 18F-FDG kinetic parameters coupled with the XCAT phantom. Quantitative analyses illustrated enhanced Ki target-to-background ratio (TBR) and especially contrast-to-noise ratio (CNR) performance for the 4D vs. the indirect methods and static SUV. Furthermore, considerable convergence acceleration was observed for the nested algorithms involving 10–20 sub-iterations. Moreover, systematic reduction in Ki % bias and improved TBR were observed for gPatlak vs. sPatlak. Finally, validation on clinical WB dynamic data demonstrated the clinical feasibility and superior Ki CNR performance for the proposed 4D framework compared to indirect Patlak and SUV imaging. PMID:27383991

Nonlinear VLF Wave Physics in the Radiation Belts

NASA Astrophysics Data System (ADS)

Crabtree, C. E.; Tejero, E. M.; Ganguli, G.; Mithaiwala, M.; Rudakov, L.; Hospodarsky, G. B.; Kletzing, C.

2014-12-01

Electromagnetic VLF waves, such as whistler mode waves, both control the lifetime of trapped electrons in the radiation belts by pitch-angle scattering and are responsible for the energization of electrons during storms. Traditional approaches to understanding the influence of waves on trapped electrons have assumed that the wave characteristics (frequency spectrum, wave-normal angle distribution, etc.) were both stationary in time and amplitude independent from event to event. In situ data from modern satellite missions, such as the Van Allen probes, are showing that this assumption may not be justified. In addition, recent theoretical results [Crabtree et al. 2012] show that the threshold for nonlinear wave scattering can often be met by naturally occurring VLF waves in the magnetosphere, with wave magnetic fields of the order of 50-100 pT inside the plasmapause. Nonlinear wave scattering (Nonlinear Landau Damping) is an amplitude dependent mechanism that can strongly alter VLF wave propagation [Ganguli et al. 2010], primarily by altering the direction of propagation. Laboratory results have confirmed the dramatic change in propagation direction when the pump wave has sufficient amplitude to exceed the nonlinear threshold [Tejero et al. 2014]. Nonlinear scattering can alter the macroscopic dynamics of waves in the radiation belts leading to the formation of a long-lasting wave-cavity [Crabtree et al. 2012] and, when amplification is present, a multi-pass amplifier [Ganguli et al., 2012]. Such nonlinear wave effects can dramatically reduce electron lifetimes. Nonlinear wave dynamics such as these occur when there are more than one wave present, such a condition necessarily violates the assumption of traditional wave-normal analysis [Santolik et al., 2003] which rely on the plane wave assumption. To investigate nonlinear wave dynamics using modern in situ data we apply the maximum entropy method [Skilling and Bryan, 1984] to solve for the wave distribution function [Storey and Lefeuvre, 1979] to yield the power distribution as a function of wave-normal angle and local azimuthal angle. We have validated this technique in the NRL space chamber and applied this methodology to Van Allen probe data to demonstrate that traditional wave-normal analaysis can give misleading results when multiple waves are present.

Whole-body direct 4D parametric PET imaging employing nested generalized Patlak expectation-maximization reconstruction

NASA Astrophysics Data System (ADS)

Karakatsanis, Nicolas A.; Casey, Michael E.; Lodge, Martin A.; Rahmim, Arman; Zaidi, Habib

2016-08-01

Whole-body (WB) dynamic PET has recently demonstrated its potential in translating the quantitative benefits of parametric imaging to the clinic. Post-reconstruction standard Patlak (sPatlak) WB graphical analysis utilizes multi-bed multi-pass PET acquisition to produce quantitative WB images of the tracer influx rate K i as a complimentary metric to the semi-quantitative standardized uptake value (SUV). The resulting K i images may suffer from high noise due to the need for short acquisition frames. Meanwhile, a generalized Patlak (gPatlak) WB post-reconstruction method had been suggested to limit K i bias of sPatlak analysis at regions with non-negligible 18F-FDG uptake reversibility; however, gPatlak analysis is non-linear and thus can further amplify noise. In the present study, we implemented, within the open-source software for tomographic image reconstruction platform, a clinically adoptable 4D WB reconstruction framework enabling efficient estimation of sPatlak and gPatlak images directly from dynamic multi-bed PET raw data with substantial noise reduction. Furthermore, we employed the optimization transfer methodology to accelerate 4D expectation-maximization (EM) convergence by nesting the fast image-based estimation of Patlak parameters within each iteration cycle of the slower projection-based estimation of dynamic PET images. The novel gPatlak 4D method was initialized from an optimized set of sPatlak ML-EM iterations to facilitate EM convergence. Initially, realistic simulations were conducted utilizing published 18F-FDG kinetic parameters coupled with the XCAT phantom. Quantitative analyses illustrated enhanced K i target-to-background ratio (TBR) and especially contrast-to-noise ratio (CNR) performance for the 4D versus the indirect methods and static SUV. Furthermore, considerable convergence acceleration was observed for the nested algorithms involving 10-20 sub-iterations. Moreover, systematic reduction in K i % bias and improved TBR were observed for gPatlak versus sPatlak. Finally, validation on clinical WB dynamic data demonstrated the clinical feasibility and superior K i CNR performance for the proposed 4D framework compared to indirect Patlak and SUV imaging.

A new driving method for piezo deformable mirrors: open loop control and MOAO made easy

NASA Astrophysics Data System (ADS)

Ouattara, Issa; Gach, Jean-Luc; Amram, Philippe

2016-07-01

This paper presents the design and the realisation of a technique to attenuate the hysteresis nonlinear phenomenon of piezoelectric actuators. Piezoelectric actuator are widely utilised for deformable mirrors used for MOAO and power laser beam shaping techniques. The nonlinearities of piezo are usually iteratively compensa- ted using closed-loop set-ups. In open-loop control, the hysteresis and the creep of the piezo cannot be corrected, thus this nonlinearities must be removed or at least minimised. The concept has been demonstrated on high displacement Amplified Piezoelectric Actuators (APA) mounted in a Fabry-Perot interferometer. The hysteresis attenuation technique aims to assist the Fabry-Perots nano-positioning control system to attain its main scientific specification. In such system, each APA has a maximum stroke of 270 μm within a 170 V (-20 V to +150 V) range and is used to position a high reflective mirror plate. The Fabry-Perots nano-positioning control system is specified to limit the APAs positioning steady-state noise to 3nm rms, but the hysteresis limits the positioning accuracy. In order to attenuate hysteresis, a hybrid amplifier circuit built with a high power operational amplifier has been designed and applied for each APA. The experiments results show that the hysteresis effect has almost been eliminated, and consequently the positioning steady-state noise can significantly been reduced. Because of the excellent results of this hybrid amplifier, a patent application has been introduced in June 12, 2015 under number No.1555381 and is being reviewed now.

Markovian Dynamics of Josephson Parametric Amplification

NASA Astrophysics Data System (ADS)

Kaiser, Waldemar; Haider, Michael; Russer, Johannes A.; Russer, Peter; Jirauschek, Christian

2017-09-01

In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA). The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

Single Cell Total RNA Sequencing through Isothermal Amplification in Picoliter-Droplet Emulsion.

PubMed

Fu, Yusi; Chen, He; Liu, Lu; Huang, Yanyi

2016-11-15

Prevalent single cell RNA amplification and sequencing chemistries mainly focus on polyadenylated RNAs in eukaryotic cells by using oligo(dT) primers for reverse transcription. We develop a new RNA amplification method, "easier-seq", to reverse transcribe and amplify the total RNAs, both with and without polyadenylate tails, from a single cell for transcriptome sequencing with high efficiency, reproducibility, and accuracy. By distributing the reverse transcribed cDNA molecules into 1.5 × 10 5 aqueous droplets in oil, the cDNAs are isothermally amplified using random primers in each of these 65-pL reactors separately. This new method greatly improves the ease of single-cell RNA sequencing by reducing the experimental steps. Meanwhile, with less chance to induce errors, this method can easily maintain the quality of single-cell sequencing. In addition, this polyadenylate-tail-independent method can be seamlessly applied to prokaryotic cell RNA sequencing.

Integrated all-optical programmable logic array based on semiconductor optical amplifiers.

PubMed

Dong, Wenchan; Huang, Zhuyang; Hou, Jie; Santos, Rui; Zhang, Xinliang

2018-05-01

The all-optical programmable logic array (PLA) is one of the most important optical complex logic devices that can implement combinational logic functions. In this Letter, we propose and experimentally demonstrate an integrated all-optical PLA at the operation speed of 40 Gb/s. The PLA mainly consists of a delay interferometer (DI) and semiconductor optical amplifiers (SOAs) of different lengths. The DI is used to pre-code the input signals and improve the reconfigurability of the scheme. The longer SOAs are nonlinear media for generating canonical logic units (CLUs) using four-wave mixing. The shorter SOAs are used to select the appropriate CLUs by changing the working states; then reconfigurable logic functions can be output directly. The results show that all the CLUs are realized successfully, and the optical signal-to-noise ratios are above 22 dB. The exclusive NOR gate and exclusive OR gate are experimentally demonstrated based on output CLUs.

Serologic and Molecular Characterization of Vibrio parahaemolyticus Strains Isolated from Seawater and Fish Products of the Gulf of Mexico

PubMed Central

Cabrera-García, María Eugenia; Vázquez-Salinas, Carlos; Quiñones-Ramírez, Elsa Irma

2004-01-01

The thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH) are the main virulence factors of Vibrio parahaemolyticus. We isolated V. parahaemolyticus from seawater, fish, and oysters obtained from the Pueblo Viejo Lagoon in Veracruz, determined the serogroups, phenotypically and genotypically characterized TDH and TRH, and investigated the presence of the toxR gene. A total of 46 V. parahaemolyticus strains were isolated, and all of them amplified the 368-bp toxR gene fragment. The trh gene was not identified in any of the strains; 4 of the 46 strains were Kanagawa phenomenon (KP) positive and amplified the 251-bp tdh gene fragment. The most frequent serogroup was serogroup O3. This is the first report of the presence of KP-positive tdh-positive environmental V. parahaemolyticus strains in Mexico. PMID:15528498

Project Echo: 960-Megacycle, 10-Kilowatt Transmitter

NASA Technical Reports Server (NTRS)

Schafer, J. P.; Brandt, R. H.

1961-01-01

A 10-kw transmitter operating at 960 to 961 Mc was used at the eastern terminus of the Project Echo communications experiment. This transmitter is located on Crawford's Hill near Holmdel, New Jersey. The 10-kw output feeds into a waveguide line leading to a 60-foot dish antenna. Exciter-driver units are available to drive the power amplifier with various modulations, such as wide-deviation FM, low-index phase modulation, single-sideband or double-sideband modulation with or without carrier, 960.05 or 961.05 Mc constant-frequency CW, and radar on-off pulses at 961.05 Mc. The main output amplifier consists primarily of a four-stage, externally-tuned-cavity, water-cooled klystron, operating at a beam voltage of 16 to 18 kv. The transmitter has been operated during many Moonbounce, tropospheric scatter, and Echo I tests with very satisfactory results. This paper describes its use before March 1, 1961.

Genetic relatedness of Trichoderma isolates antagonistic against Fusarium oxysporum f.sp. dianthi inflicting carnation wilt.

PubMed

Shanmugam, V; Sharma, Vivek; Ananthapadmanaban

2008-01-01

Twenty-eight isolates of Trichoderma belonging to four different species were screened in vitro for their antagonistic ability against Fusarium oxysporum f.sp. dianthi causing carnation wilt. Three different levels of antagonism observed in dual plate assay were further confirmed by cell-free culture filtrate experiments. Isolates showing class I level of antagonism produced maximum lytic enzymes, chitinases and beta-1,3-glucanases. Genetic variability of 25 selected isolates was assessed by random amplified polymorphic DNA technique and the amplified products were correlated for their level of antagonism. Unweighed pair-group method with arithmetical averages cluster analysis revealed prominent inter-and intraspecific genetic variation among the isolates. Based on their genetic relationship, the isolates were mainly distributed into 3 major groups representing T. atroviride, T. pseudokoningii and T. harzianum, with 20-35% interspecific dissimilarity. However, the polymorphism shown by the isolates did not correlate to their level of antagonism.

The hybrid photonic planar integrated receiver with a polymer optical waveguide

NASA Astrophysics Data System (ADS)

Busek, Karel; Jerábek, Vitezslav; Armas Arciniega, Julio; Prajzler, Václav

2008-11-01

This article describes design of the photonic receiver composed of the system polymer planar waveguides, InGaAs p-i-n photodiode and integrated HBT amplifier on a low loss composite substrate. The photonic receiver was the main part of the hybrid integrated microwave optoelectronic transceiver TRx (transciever TRx) for the optical networks PON (passive optical networks) with FTTH (fiber-to-the-home) topology. In this article are presented the research results of threedimensional field between output facet of a optical waveguide and p-i-n photodiode. In terms of our research, there was optimized the optical coupling among the facet waveguide and pi-n photodiode and the electrical coupling among p-i-n photodiode and input of HBT amplifier. The hybrid planar lightwave circuit (PLC) of the transceiver TRx will be composed from a two parts - polymer optical waveguide including VHGT filter section and a optoelectronic microwave section.

Phytomonas: analysis of polymorphism and genetic relatedness between isolates from plants and phytophagous insects from different geographic regions by RAPD fingerprints and synapomorphic markers.

PubMed

Serrano, M G; Camargo, E P; Teixeira, M M

1999-01-01

The random amplification of polymorphic DNA was used for easy, quick and sensitive assessment of genetic polymorphism within Phytomonas to discriminate isolates and determine genetic relationships within the genus. We examined 48 Phytomonas spp., 31 isolates from plants and 17 from insects, from different geographic regions. Topology of the dendrogram based on randomly amplified polymorphic DNA fingerprints segregated the Phytomonas spp. into 5 main clusters, despite the high genetic variability within this genus. Similar clustering could also be obtained by both visual and cross-hybridization analysis of randomly amplified synapomorphic DNA fragments. There was some concordance between the genetic relationship of isolates and their plant tissue tropism. Moreover, Phytomonas spp. from plants and insects were grouped according to geographic origin, thus revealing a complex structure of this taxon comprising several clusters of very closely related organisms.

Sequence analysis of a few species of termites (Order: Isoptera) on the basis of partial characterization of COII gene.

PubMed

Sobti, Ranbir Chander; Kumari, Mamtesh; Sharma, Vijay Lakshmi; Sodhi, Monika; Mukesh, Manishi; Shouche, Yogesh

2009-11-01

The present study was aimed to get the nucleotide sequences of a part of COII mitochondrial gene amplified from individuals of five species of Termites (Isoptera: Termitidae: Macrotermitinae). Four of them belonged to the genus Odontotermes (O. obesus, O. horni, O. bhagwatii and Odontotermes sp.) and one to Microtermes (M. obesi). Partial COII gene fragments were amplified by using specific primers. The sequences so obtained were characterized to calculate the frequencies of each nucleotide bases and a high A + T content was observed. The interspecific pairwise sequence divergence in Odontotermes species ranged from 6.5% to 17.1% across COII fragment. M. obesi sequence diversity ranged from 2.5 with Odontotermes sp. to 19.0% with O. bhagwatii. Phylogenetic trees drawn on the basis of distance neighbour-joining method revealed three main clades clustering all the individuals according to their genera and families.

Polarization independent thermally tunable erbium-doped fiber amplifier gain equalizer using a cascaded Mach-Zehnder coupler.

PubMed

Sahu, P P

2008-02-10

A thermally tunable erbium-doped fiber amplifier (EDFA) gain equalizer filter based on compact point symmetric cascaded Mach-Zehnder (CMZ) coupler is presented with its mathematical model and is found to be polarization dependent due to stress anisotropy caused by local heating for thermo-optic phase change from its mathematical analysis. A thermo-optic delay line structure with a stress releasing groove is proposed and designed for the reduction of polarization dependent characteristics of the high index contrast point symmetric delay line structure of the device. It is found from thermal analysis by using an implicit finite difference method that temperature gradients of the proposed structure, which mainly causes the release of stress anisotropy, is approximately nine times more than that of the conventional structure. It is also seen that the EDFA gain equalized spectrum by using the point symmetric CMZ device based on the proposed structure is almost polarization independent.

Genetic relatedness between oral and intestinal isolates of Porphyromonas endodontalis by analysis of random amplified polymorphic DNA.

PubMed

Gonçalves, R B; Väisänen, M L; Van Steenbergen, T J; Sundqvist, G; Mouton, C

1999-01-01

Genomic fingerprints from the DNA of 27 strains of Porphyromonas endodontalis from diverse clinical and geographic origins were generated as random amplified polymorphic DNA (RAPD) using the technique of PCR amplification with a single primer of arbitrary sequence. Cluster analysis of the combined RAPD data obtained with three selected 9- or 10-mer-long primers identified 25 distinct RAPD types which clustered as three main groups identifying three genogroups. Genogroups I and II included exclusively P. endodontalis isolates of oral origin, while 7/9 human intestinal strains of genogroup III which linked at a similarity level of 52% constituted the most homogeneous group in our study. Genotypic diversity within P. endodontalis, as shown by RAPD analysis, suggests that the taxon is composed of two oral genogroups and one intestinal genogroup. This hypothesis remains to be confirmed.

Hybrid chirped pulse amplification system

DOEpatents

Barty, Christopher P.; Jovanovic, Igor

2005-03-29

A hybrid chirped pulse amplification system wherein a short-pulse oscillator generates an oscillator pulse. The oscillator pulse is stretched to produce a stretched oscillator seed pulse. A pump laser generates a pump laser pulse. The stretched oscillator seed pulse and the pump laser pulse are directed into an optical parametric amplifier producing an optical parametric amplifier output amplified signal pulse and an optical parametric amplifier output unconverted pump pulse. The optical parametric amplifier output amplified signal pulse and the optical parametric amplifier output laser pulse are directed into a laser amplifier producing a laser amplifier output pulse. The laser amplifier output pulse is compressed to produce a recompressed hybrid chirped pulse amplification pulse.

Development of a cryogenic DC-low noise amplifier for SQuID-based readout electronics

NASA Astrophysics Data System (ADS)

Macculi, C.; Torrioli, G.; Di Giorgio, A.; Spinoglio, L.; Piro, Luigi

2014-07-01

We present the preliminary results of the design and test activities for a DC cryogenic low noise amplifier for the SAFARI imaging spectrometer, planned to be onboard the SPICA mission, necessary not only to drive, as usual, the voltage signal produced by the SQuID but also to boost such signals over about 7 meter of path towards the warm feedback electronics. This development has been done in the framework of the mission preparation studies, within the European Consortium for the development of the SAFARI instrument. The actual configuration of the SAFARI focal plane assembly (FPA), indeed, foresees a long distance to the warm back end electronics. It is therefore mandatory to boost the faint electric signal coming from the SQuID device by keeping under control both power dissipation and noise: this is the main role of the designed Cryogenic Low Noise Amplifier (LNA). Working at 136K, it has a differential input gain-stage, and a differential balanced voltage buffer output stage, running at few mW target overall power. At present the design is based on the use of Heterojunction Si:Ge transistors, the required bandwidth is DC-4MHz and the required noise lower than 1 nV/rtHz.

Evaluation damage threshold of optical thin-film using an amplified spontaneous emission source

NASA Astrophysics Data System (ADS)

Zhou, Qiong; Sun, Mingying; Zhang, Zhixiang; Yao, Yudong; Peng, Yujie; Liu, Dean; Zhu, Jianqiang

2014-10-01

An accurate evaluation method with an amplified spontaneous emission (ASE) as the irradiation source has been developed for testing thin-film damage threshold. The partial coherence of the ASE source results in a very smooth beam profile in the near-field and a uniform intensity distribution of the focal spot in the far-field. ASE is generated by an Nd: glass rod amplifier in SG-II high power laser facility, with pulse duration of 9 ns and spectral width (FWHM) of 1 nm. The damage threshold of the TiO2 high reflection film is 14.4J/cm2 using ASE as the irradiation source, about twice of 7.4 J/cm2 that tested by a laser source with the same pulse duration and central wavelength. The damage area induced by ASE is small with small-scale desquamation and a few pits, corresponding to the defect distribution of samples. Large area desquamation is observed in the area damaged by laser, as the main reason that the non-uniformity of the laser light. The ASE damage threshold leads to more accurate evaluations of the samples damage probability by reducing the influence of hot spots in the irradiation beam. Furthermore, the ASE source has a great potential in the detection of the defect distribution of the optical elements.

2 micron femtosecond fiber laser

DOEpatents

Liu, Jian; Wan, Peng; Yang, Lihmei

2014-07-29

Methods and systems for generating femtosecond fiber laser pulses are disclose, including generating a signal laser pulse from a seed laser oscillator; using a first amplifier stage comprising an input and an output, wherein the signal laser pulse is coupled into the input of the first stage amplifier and the output of the first amplifier stage emits an amplified and stretched signal laser pulse; using an amplifier chain comprising an input and an output, wherein the amplified and stretched signal laser pulse from the output of the first amplifier stage is coupled into the input of the amplifier chain and the output of the amplifier chain emits a further amplified, stretched signal laser pulse. Other embodiments are described and claimed.

Genetic diversity and structure of western white pine (Pinus monticola) in North America: A baseline study for conservation, restoration, and addressing impacts of climate change

Treesearch

Mee-Sook Kim; Bryce A. Richardson; Geral I. McDonald; Ned B. Klopfenstein

2010-01-01

Western white pine (Pinus monticola) is an economically and ecologically important species in western North America that has declined in prominence over the past several decades, mainly due to the introduction of Cronartium ribicola (cause of white pine blister rust) and reduced opportunities for regeneration. Amplified fragment length polymorphism (AFLP) markers were...

Why we forget our dreams: Acetylcholine and norepinephrine in wakefulness and REM sleep.

PubMed

Becchetti, Andrea; Amadeo, Alida

2016-01-01

The ascending fibers releasing norepinephrine and acetylcholine are highly active during wakefulness. In contrast, during rapid-eye-movement sleep, the neocortical tone is sustained mainly by acetylcholine. By comparing the different physiological features of the norepinephrine and acetylcholine systems in the light of the GANE (glutamate amplifies noradrenergic effects) model, we suggest how to interpret some functional differences between waking and rapid-eye-movement sleep.

Physician cooperation in outpatient cancer care. An amplified secondary analysis of qualitative interview data.

PubMed

Engler, J; Güthlin, C; Dahlhaus, A; Kojima, E; Müller-Nordhorn, J; Weißbach, L; Holmberg, C

2017-11-01

The importance of outpatient cancer care services is increasing due to the growing number of patients having or having had cancer. However, little is known about cooperation among physicians in outpatient settings. To understand what inter- and multidisciplinary care means in community settings, we conducted an amplified secondary analysis that combined qualitative interview data with 42 general practitioners (GPs), 21 oncologists and 21 urologists that mainly worked in medical practices in Germany. We compared their perspectives on cooperation relationships in cancer care. Our results indicate that all participants regarded cooperation as a prerequisite for good cancer care. Oncologists and urologists mainly reported cooperating for tumour-specific treatment tasks, while GPs' reasoning for cooperation was more patient-centred. While oncologists and urologists reported experiencing reciprocal communication with other physicians, GPs had to gather the information they needed. GPs seldom reported engaging in formal cooperation structures, while for specialists, participation in formal spaces of cooperation, such as tumour boards, facilitated a more frequent and informal discussion of patients, for instance on the phone. Further research should focus on ways to foster GPs' integration in cancer care and evaluate if this can be reached by incorporating GPs in formal cooperation structures such as tumour boards. © 2017 John Wiley & Sons Ltd.

SQUARE WAVE AMPLIFIER

DOEpatents

Leavitt, M.A.; Lutz, I.C.

1958-08-01

An amplifier circuit is described for amplifying sigmals having an alternating current component superimposed upon a direct current component, without loss of any segnnent of the alternating current component. The general circuit arrangement includes a vibrator, two square wave amplifiers, and recombination means. The amplifier input is connected to the vibrating element of the vibrator and is thereby alternately applied to the input of each square wave amplifier. The detailed circuitry of the recombination means constitutes the novelty of the annplifier and consists of a separate, dual triode amplifier coupled to the output of each square wave amplifier with a recombination connection from the plate of one amplifier section to a grid of one section of the other amplifier. The recombination circuit has provisions for correcting distortion caused by overlapping of the two square wave voltages from the square wave amplifiers.

NASA developments in solid state power amplifiers

NASA Technical Reports Server (NTRS)

Leonard, Regis F.

1990-01-01

Over the last ten years, NASA has undertaken an extensive program aimed at development of solid state power amplifiers for space applications. Historically, the program may be divided into three phases. The first efforts were carried out in support of the advanced communications technology satellite (ACTS) program, which is developing an experimental version of a Ka-band commercial communications system. These first amplifiers attempted to use hybrid technology. The second phase was still targeted at ACTS frequencies, but concentrated on monolithic implementations, while the current, third phase, is a monolithic effort that focusses on frequencies appropriate for other NASA programs and stresses amplifier efficiency. The topics covered include: (1) 20 GHz hybrid amplifiers; (2) 20 GHz monolithic MESFET power amplifiers; (3) Texas Instruments' (TI) 20 GHz variable power amplifier; (4) TI 20 GHz high power amplifier; (5) high efficiency monolithic power amplifiers; (6) GHz high efficiency variable power amplifier; (7) TI 32 GHz monolithic power amplifier performance; (8) design goals for Hughes' 32 GHz variable power amplifier; and (9) performance goals for Hughes' pseudomorphic 60 GHz power amplifier.

PULSE AMPLIFIER

DOEpatents

Johnstone, C.W.

1958-06-17

The improvement of pulse amplifiers used with scintillation detectors is described. The pulse amplifier circuit has the advantage of reducing the harmful effects of overloading cause by large signal inputs. In general the pulse amplifier circuit comprises two amplifier tubes with the input pulses applied to one amplifier grid and coupled to the second amplifier tube through a common cathode load. The output of the second amplifier is coupled from the plate circuit to a cathode follower tube grid and a diode tube in connected from grid to cathode of the cathode follower tube. Degenerative feedback is provided in the second amplifier by coupling a signal from the cathode follower cathode to the second amplifier grid. The circuit proqides moderate gain stability, and overload protection for subsequent pulse circuits.

Determination of the Order of Passes of AN Austenitic Weld by Optimization of AN Inversion Process of Ultrasound Data

NASA Astrophysics Data System (ADS)

Gueudré, C.; Marrec, L. Le; Chekroun, M.; Moysan, J.; Chassignole, B.; Corneloup, G.

2011-06-01

Multipass welds made in austenitic stainless steel, in the primary circuit of nuclear power plants with pressurized water reactors, are characterized by an anisotropic and heterogeneous structure that disturbs the ultrasonic propagation and challenge the ultrasonic non-destructive testing. The simulation in this type of structure is now possible thanks to the MINA code which allows the grain orientation modeling taking into account the welding process, and the ATHENA code to exactly simulate the ultrasonic propagation. We propose studying the case where the order of the passes is unknown to estimate the possibility of reconstructing this important parameter by ultrasound measures. The first results are presented.

Highly efficient end-side-pumped Nd:YAG solar laser by a heliostat-parabolic mirror system.

PubMed

Almeida, J; Liang, D; Vistas, C R; Guillot, E

2015-03-10

We report a large improvement in the collection and slope efficiency of an Nd:YAG solar laser pumped by a heliostat-parabolic mirror system. A conical fused silica lens was used to further concentrate the solar radiation from the focal zone of a 2 m diameter primary concentrator to a Nd:YAG single-crystal rod within a conical pump cavity, which enabled multipass pumping to the active medium. A 56 W cw laser power was measured, corresponding to 21.1  W/m2 record-high solar laser collection efficiency with the heliostat-parabolic mirror system. 4.9% slope efficiency was calculated, corresponding to 175% enhancement over our previous result.

Apparatus for maintaining alignment of a shrinking weld joint in an electron-beam welding operation

DOEpatents

Trent, Jett B.; Murphy, Jimmy L.

1981-01-01

The present invention is directed to an apparatus for automatically maintaining a shrinking weld joint in alignment with an electron beam during an electron-beam multipass-welding operation. The apparatus utilizes a biasing device for continually urging a workpiece-supporting face plate away from a carriage mounted base that rotatably supports the face plate. The extent of displacement of the face plate away from the base is indicative of the shrinkage occuring in the weld joint area. This displacement is measured and is used to move the base on the carriage a distance equal to one-half the displacement for aligning the weld joint with the electron beam during each welding pass.

Apparatus for maintaining aligment of a shrinking weld joint in an electron-beam welding operation

DOEpatents

Trent, J.B.; Murphy, J.L.

1980-01-03

The invention is directed to an apparatus for automatically maintaining a shrinking weld joint in alignement with an electron beam during an electron-beam multipass-welding operation. The apparatus utilizes a bias means for continually urging a workpiece-supporting face plate away from a carriage mounted base that rotatably supports the face plate. The extent of displacement of the face plate away from the base in indicative of the shrinkage occuring in the weld joint area. This displacement is measured and is used to move the base on the carriage a distance equal to one-half the displacement for aligning the weld joint with the electron beam during each welding pass.

Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

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

Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

2016-02-13

A rapidly-swept external cavity quantum cascade laser (ECQCL) system for fast open-path quantification of multiple chemicals and mixtures is presented. The ECQCL system is swept over its entire tuning range (>100 cm-1) at frequencies up to 200 Hz. At 200 Hz the wavelength tuning rate and spectral resolution are 2x104 cm-1/sec and < 0.2 cm-1, respectively. The capability of the current system to quantify changes in chemical concentrations on millesecond timescales is demonstrated at atmospheric pressure using an open-path multi-pass cell. The detection limits for chemicals ranged from ppb to ppm levels depending on the absorption cross-section.

Fiber optic gas detection system for health monitoring of oil-filled transformer

NASA Astrophysics Data System (ADS)

Ho, H. L.; Ju, J.; Jin, W.

2009-10-01

This paper reports the development of a fiber-optic gas detection system capable of detecting three types of dissolved fault gases in oil-filled power transformers or equipment. The system is based on absorption spectroscopy and the target gases include acetylene (C2H2), methane (CH4) and ethylene (C2H4). Low-cost multi-pass sensor heads using fiber coupled micro-optic cells are employed for which the interaction length is up to 4m. Also, reference gas cells made of photonic bandgap (PBG) fiber are implemented. The minimum detectable gas concentrations for methane, acetylene and ethylene are 5ppm, 2ppm and 50ppm respectively.

A field-deployable compound-specific isotope analyzer based on quantum cascade laser and hollow waveguide

NASA Astrophysics Data System (ADS)

Wu, Sheng; Deev, Andrei

2013-01-01

A field deployable Compound Specific Isotope Analyzer (CSIA) coupled with capillary chromatogrpahy based on Quantum Cascade (QC) lasers and Hollow Waveguide (HWG) with precision and chemical resolution matching mature Mass Spectroscopy has been achieved in our laboratory. The system could realize 0.3 per mil accuracy for 12C/13C for a Gas Chromatography (GC) peak lasting as short as 5 seconds with carbon molar concentration in the GC peak less than 0.5%. Spectroscopic advantages of HWG when working with QC lasers, i.e. single mode transmission, noiseless measurement and small sample volume, are compared with traditional free space and multipass spectroscopy methods.

LongISLND: in silico sequencing of lengthy and noisy datatypes.

PubMed

Lau, Bayo; Mohiyuddin, Marghoob; Mu, John C; Fang, Li Tai; Bani Asadi, Narges; Dallett, Carolina; Lam, Hugo Y K

2016-12-15

LongISLND is a software package designed to simulate sequencing data according to the characteristics of third generation, single-molecule sequencing technologies. The general software architecture is easily extendable, as demonstrated by the emulation of Pacific Biosciences (PacBio) multi-pass sequencing with P5 and P6 chemistries, producing data in FASTQ, H5, and the latest PacBio BAM format. We demonstrate its utility by downstream processing with consensus building and variant calling. LongISLND is implemented in Java and available at http://bioinform.github.io/longislnd CONTACT: hugo.lam@roche.comSupplementary information: Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press.

Schemes for efficient QW pumping of AlGaInP disk lasers

NASA Astrophysics Data System (ADS)

Brauch, Uwe; Mateo, Cherry May N.; Kahle, Hermann; Bek, Roman; Jetter, Michael; Abdou Ahmed, Marwan; Michler, Peter; Graf, Thomas

2017-02-01

Keys to high-power operation of disk lasers are a thin active layer, a small Stokes shift and an efficient cooling, best realized with a limited number of QWs which are pumped close to the laser wavelength and which are in close contact with one or two diamond heat sinks. To get sufficient pump absorption many passes of the pump radiation are needed. This can be realized either by taking advantage of intrinsic resonances (designed for the pump radiation) or by an external multi-pass optics (known from Yb disk lasers) or a combination of both. The various options will be discussed and some results for AlGaInP disk lasers will be presented.

212-Angstrom neonlike zinc laser of LULI

NASA Astrophysics Data System (ADS)

Jamelot, Gerard; Jaegle, Pierre; Rus, Bedrich; Carillon, Antoine; Klisnick, Annie; Nantel, Marc; Sebban, Stephane; Albert, F.; Zeitoun, Philippe; Plankl, E.; Sirgand, A.; Lewis, Ciaran L. S.; MacPhee, Andrew G.; Tallents, Gregory J.; Krishnan, J.; Holden, M.

1995-09-01

The main feature of x-ray laser research at LULI is the development of a saturated laser at 212 angstrom with a relatively small pump laser of 0.4 kJ in 600 ps. The laser works with the 3p- 3s J equals O yields 1 transition of neon-like zinc, by using the double-pass of amplified radiation in the active medium. Plasma parameters (temperature, density, homogeneity), and x-ray laser emission properties (intensity, pointing angle, divergence, and coherence) have been studied. Lasing action needs the main laser pulse to be preceded by a ten-prepulse train (contrast ratio less than 103) due to the remnant oscillator. The effect of a single prepulse was investigated as a function of contrast ratio and delay between the prepulse and the main pulse.

Biologically relevant effects of mRNA amplification on gene expression profiles.

PubMed

van Haaften, Rachel I M; Schroen, Blanche; Janssen, Ben J A; van Erk, Arie; Debets, Jacques J M; Smeets, Hubert J M; Smits, Jos F M; van den Wijngaard, Arthur; Pinto, Yigal M; Evelo, Chris T A

2006-04-11

Gene expression microarray technology permits the analysis of global gene expression profiles. The amount of sample needed limits the use of small excision biopsies and/or needle biopsies from human or animal tissues. Linear amplification techniques have been developed to increase the amount of sample derived cDNA. These amplified samples can be hybridised on microarrays. However, little information is available whether microarrays based on amplified and unamplified material yield comparable results. In the present study we compared microarray data obtained from amplified mRNA derived from biopsies of rat cardiac left ventricle and non-amplified mRNA derived from the same organ. Biopsies were linearly amplified to acquire enough material for a microarray experiment. Both amplified and unamplified samples were hybridized to the Rat Expression Set 230 Array of Affymetrix. Analysis of the microarray data showed that unamplified material of two different left ventricles had 99.6% identical gene expression. Gene expression patterns of two biopsies obtained from the same parental organ were 96.3% identical. Similarly, gene expression pattern of two biopsies from dissimilar organs were 92.8% identical to each other.Twenty-one percent of reporters called present in parental left ventricular tissue disappeared after amplification in the biopsies. Those reporters were predominantly seen in the low intensity range. Sequence analysis showed that reporters that disappeared after amplification had a GC-content of 53.7+/-4.0%, while reporters called present in biopsy- and whole LV-samples had an average GC content of 47.8+/-5.5% (P <0.001). Those reporters were also predicted to form significantly more (0.76+/-0.07 versus 0.38+/-0.1) and longer (9.4+/-0.3 versus 8.4+/-0.4) hairpins as compared to representative control reporters present before and after amplification. This study establishes that the gene expression profile obtained after amplification of mRNA of left ventricular biopsies is representative for the whole left ventricle of the rat heart. However, specific gene transcripts present in parental tissues were undetectable in the minute left ventricular biopsies. Transcripts that were lost due to the amplification process were not randomly distributed, but had higher GC-content and hairpins in the sequence and were mainly found in the lower intensity range which includes many transcription factors from specific signalling pathways.

Biologically relevant effects of mRNA amplification on gene expression profiles

PubMed Central

van Haaften, Rachel IM; Schroen, Blanche; Janssen, Ben JA; van Erk, Arie; Debets, Jacques JM; Smeets, Hubert JM; Smits, Jos FM; van den Wijngaard, Arthur; Pinto, Yigal M; Evelo, Chris TA

2006-01-01

Background Gene expression microarray technology permits the analysis of global gene expression profiles. The amount of sample needed limits the use of small excision biopsies and/or needle biopsies from human or animal tissues. Linear amplification techniques have been developed to increase the amount of sample derived cDNA. These amplified samples can be hybridised on microarrays. However, little information is available whether microarrays based on amplified and unamplified material yield comparable results. In the present study we compared microarray data obtained from amplified mRNA derived from biopsies of rat cardiac left ventricle and non-amplified mRNA derived from the same organ. Biopsies were linearly amplified to acquire enough material for a microarray experiment. Both amplified and unamplified samples were hybridized to the Rat Expression Set 230 Array of Affymetrix. Results Analysis of the microarray data showed that unamplified material of two different left ventricles had 99.6% identical gene expression. Gene expression patterns of two biopsies obtained from the same parental organ were 96.3% identical. Similarly, gene expression pattern of two biopsies from dissimilar organs were 92.8% identical to each other. Twenty-one percent of reporters called present in parental left ventricular tissue disappeared after amplification in the biopsies. Those reporters were predominantly seen in the low intensity range. Sequence analysis showed that reporters that disappeared after amplification had a GC-content of 53.7+/-4.0%, while reporters called present in biopsy- and whole LV-samples had an average GC content of 47.8+/-5.5% (P <0.001). Those reporters were also predicted to form significantly more (0.76+/-0.07 versus 0.38+/-0.1) and longer (9.4+/-0.3 versus 8.4+/-0.4) hairpins as compared to representative control reporters present before and after amplification. Conclusion This study establishes that the gene expression profile obtained after amplification of mRNA of left ventricular biopsies is representative for the whole left ventricle of the rat heart. However, specific gene transcripts present in parental tissues were undetectable in the minute left ventricular biopsies. Transcripts that were lost due to the amplification process were not randomly distributed, but had higher GC-content and hairpins in the sequence and were mainly found in the lower intensity range which includes many transcription factors from specific signalling pathways. PMID:16608515

Auto-Zero Differential Amplifier

NASA Technical Reports Server (NTRS)

Quilligan, Gerard T. (Inventor); Aslam, Shahid (Inventor)

2017-01-01

An autozero amplifier may include a window comparator network to monitor an output offset of a differential amplifier. The autozero amplifier may also include an integrator to receive a signal from a latched window comparator network, and send an adjustment signal back to the differential amplifier to reduce an offset of the differential amplifier.

Automatic alignment of double optical paths in excimer laser amplifier

NASA Astrophysics Data System (ADS)

Wang, Dahui; Zhao, Xueqing; Hua, Hengqi; Zhang, Yongsheng; Hu, Yun; Yi, Aiping; Zhao, Jun

2013-05-01

A kind of beam automatic alignment method used for double paths amplification in the electron pumped excimer laser system is demonstrated. In this way, the beams from the amplifiers can be transferred along the designated direction and accordingly irradiate on the target with high stabilization and accuracy. However, owing to nonexistence of natural alignment references in excimer laser amplifiers, two cross-hairs structure is used to align the beams. Here, one crosshair put into the input beam is regarded as the near-field reference while the other put into output beam is regarded as the far-field reference. The two cross-hairs are transmitted onto Charge Coupled Devices (CCD) by image-relaying structures separately. The errors between intersection points of two cross-talk images and centroid coordinates of actual beam are recorded automatically and sent to closed loop feedback control mechanism. Negative feedback keeps running until preset accuracy is reached. On the basis of above-mentioned design, the alignment optical path is built and the software is compiled, whereafter the experiment of double paths automatic alignment in electron pumped excimer laser amplifier is carried through. Meanwhile, the related influencing factors and the alignment precision are analyzed. Experimental results indicate that the alignment system can achieve the aiming direction of automatic aligning beams in short time. The analysis shows that the accuracy of alignment system is 0.63μrad and the beam maximum restoration error is 13.75μm. Furthermore, the bigger distance between the two cross-hairs, the higher precision of the system is. Therefore, the automatic alignment system has been used in angular multiplexing excimer Main Oscillation Power Amplification (MOPA) system and can satisfy the requirement of beam alignment precision on the whole.

Gain and noise figure enhancement of Er+3/Yb+3 co-doped fiber/Raman hybrid amplifier

NASA Astrophysics Data System (ADS)

Mahran, O.

2016-02-01

An Er/Yb co-doped fiber/Raman hybrid amplifier (HA) is proposed and studied theoretically and analytically to improve the gain and noise figure of optical amplifiers. The calculations are performed under a uniform dopant and steady-state conditions. The initial energy transfer efficiency for Er/Yb co-doped fiber amplifier (EYDFA) is introduced, while the amplified spontaneous emission (ASE) is neglected. The glass fiber used for both Er/Yb and Raman amplifiers is phosphate. Different pump powers are used for both EYDFA and RA with 1 μW input signal power, 1 m length of Er/Yb amplifier and 25 km length of Raman amplifier (RA). The proposed model is validated for Er/Yb co-doped amplifier and Raman amplifier separately by comparing the calculating results with the experimental data. A high gain and low noise figure at 200 mW Raman pump power and 500 mW Er/Yb pump power are obtained for the proposed HA as compared with the experimental results of EYDFA, Raman amplifier and the EDFA/Raman hybrid amplifier.

Pressure-Transducer Simulator

NASA Technical Reports Server (NTRS)

Simon, Richard A.

1987-01-01

Simulation circuit operates under remote, automatic, or manual control to produce electrical outputs similar to pressure transducer. Specific circuit designed for simulations of Space Shuttle main engine. General circuit concept adaptable to other simulation and control systems involving several operating modes. Switches and amplifiers respond to external control signals and panel control settings to vary differential excitation of resistive bridge. Output voltage or passive terminal resistance made to equal pressure transducer in any of four operating modes.

Large-Signal Code TESLA: Current Status and Recent Development

DTIC Science & Technology

2008-04-01

K.Eppley, J.J.Petillo, “ High - power four cavity S - band multiple- beam klystron design”, IEEE Trans. Plasma Sci. , vol. 32, pp. 1119-1135, June 2004. 4...advances in the development of the large-signal code TESLA, mainly used for the modeling of high - power single- beam and multiple-beam klystron ...amplifiers. Keywords: large-signal code; multiple-beam klystrons ; serial and parallel versions. Introduction The optimization and design of new high power

Programmable differential capacitance-to-voltage converter for MEMS accelerometers

NASA Astrophysics Data System (ADS)

Royo, G.; Sánchez-Azqueta, C.; Gimeno, C.; Aldea, C.; Celma, S.

2017-05-01

Capacitive MEMS sensors exhibit an excellent noise performance, high sensitivity and low power consumption. They offer a huge range of applications, being the accelerometer one of its main uses. In this work, we present the design of a capacitance-to-voltage converter in CMOS technology to measure the acceleration from the capacitance variations. It is based on a low-power, fully-differential transimpedance amplifier with low input impedance and a very low input noise.

[Research progress of molecular genetic analysis in Schistosoma variation].

PubMed

Zheng, Su-Yue; Li, Fei

2014-02-01

The development of molecular biology techniques makes important contributions to the researches of heritable variation of Schistosoma. In recent years, the molecular genetic analysis in the Schistosoma variation researches mainly includes the restriction fragment length polymorphism (RFLP), random amplified polymorphism technology (RAPD), microsatellite anchored PCR (SSR-PCR), and polymerase reaction single-strand conformation polymorphism (PCR-SSCP). This article reviews the research progress of molecular genetic analysis in Schistosoma variation in recent years.

MSFC Skylab experimenter's reference

NASA Technical Reports Server (NTRS)

1974-01-01

The methods and techniques for experiment development and integration that evolved during the Skylab Program are described to facilitate transferring this experience to experimenters in future manned space programs. Management responsibilities and the sequential process of experiment evolution from initial concept through definition, development, integration, operation and postflight analysis are outlined in the main text and amplified, as appropriate, in appendixes. Emphasis is placed on specific lessons learned on Skylab that are worthy of consideration by future programs.

Screening and Characterization of RAPD Markers in Viscerotropic Leishmania Parasites

PubMed Central

Mkada–Driss, Imen; Talbi, Chiraz; Guerbouj, Souheila; Driss, Mehdi; Elamine, Elwaleed M.; Cupolillo, Elisa; Mukhtar, Moawia M.; Guizani, Ikram

2014-01-01

Visceral leishmaniasis (VL) is mainly due to the Leishmania donovani complex. VL is endemic in many countries worldwide including East Africa and the Mediterranean region where the epidemiology is complex. Taxonomy of these pathogens is under controversy but there is a correlation between their genetic diversity and geographical origin. With steady increase in genome knowledge, RAPD is still a useful approach to identify and characterize novel DNA markers. Our aim was to identify and characterize polymorphic DNA markers in VL Leishmania parasites in diverse geographic regions using RAPD in order to constitute a pool of PCR targets having the potential to differentiate among the VL parasites. 100 different oligonucleotide decamers having arbitrary DNA sequences were screened for reproducible amplification and a selection of 28 was used to amplify DNA from 12 L. donovani, L. archibaldi and L. infantum strains having diverse origins. A total of 155 bands were amplified of which 60.65% appeared polymorphic. 7 out of 28 primers provided monomorphic patterns. Phenetic analysis allowed clustering the parasites according to their geographical origin. Differentially amplified bands were selected, among them 22 RAPD products were successfully cloned and sequenced. Bioinformatic analysis allowed mapping of the markers and sequences and priming sites analysis. This study was complemented with Southern-blot to confirm assignment of markers to the kDNA. The bioinformatic analysis identified 16 nuclear and 3 minicircle markers. Analysis of these markers highlighted polymorphisms at RAPD priming sites with mainly 5′ end transversions, and presence of inter– and intra– taxonomic complex sequence and microsatellites variations; a bias in transitions over transversions and indels between the different sequences compared is observed, which is however less marked between L. infantum and L. donovani. The study delivers a pool of well-documented polymorphic DNA markers, to develop molecular diagnostics assays to characterize and differentiate VL causing agents. PMID:25313833

Application of Multi-Input Multi-Output Feedback Control for F-16 Ventral Fin Buffet Alleviation Using Piezoelectric Actuators

DTIC Science & Technology

2012-03-22

Power Amplifier (7). A power amplifier was required to drive the actuators. For this research a Trek , Inc. Model PZD 700 Dual Channel Amplifier was used...while the flight test amplifier was being built. The Trek amplifier was capable of amplifying 32 Figure 3.19: dSpace MicroAutoBox II Digital...averaging of 25% was used to reduce the errors caused by noise but still maintain accuracy. For the laboratory Trek amplifier, a 100 millivolt input

Studies on Creep Deformation and Rupture Behavior of 316LN SS Multi-Pass Weld Joints Fabricated with Two Different Electrode Sizes

NASA Astrophysics Data System (ADS)

Vijayanand, V. D.; Kumar, J. Ganesh; Parida, P. K.; Ganesan, V.; Laha, K.

2017-02-01

Effect of electrode size on creep deformation and rupture behavior has been assessed by carrying out creep tests at 923 K (650 °C) over the stress range 140 to 225 MPa on 316LN stainless steel weld joints fabricated employing 2.5 and 4 mm diameter electrodes. The multi-pass welding technique not only changes the morphology of delta ferrite from vermicular to globular in the previous weld bead region near to the weld bead interface, but also subjects the region to thermo-mechanical heat treatment to generate appreciable strength gradient. Electron backscatter diffraction analysis revealed significant localized strain gradients in regions adjoining the weld pass interface for the joint fabricated with large electrode size. Larger electrode diameter joint exhibited higher creep rupture strength than the smaller diameter electrode joint. However, both the joints had lower creep rupture strength than the base metal. Failure in the joints was associated with microstructural instability in the fusion zone, and the vermicular delta ferrite zone was more prone to creep cavitation. Larger electrode diameter joint was found to be more resistant to failure caused by creep cavitation than the smaller diameter electrode joint. This has been attributed to the larger strength gradient between the beads and significant separation between the cavity prone vermicular delta ferrite zones which hindered the cavity growth. Close proximity of cavitated zones in smaller electrode joint facilitated their faster coalescence leading to more reduction in creep rupture strength. Failure location in the joints was found to depend on the electrode size and applied stress. The change in failure location has been assessed on performing finite element analysis of stress distribution across the joint on incorporating tensile and creep strengths of different constituents of joints, estimated by ball indentation and impression creep testing techniques.

Static magnetic Faraday rotation spectroscopy combined with a differential scheme for OH detection

NASA Astrophysics Data System (ADS)

Zhao, Weixiong; Deng, Lunhua; Qian, Xiaodong; Fang, Bo; Gai, Yanbo; Chen, Weidong; Gao, Xiaoming; Zhang, Weijun

2015-04-01

The hydroxyl (OH) radical plays a critical role in atmospheric chemistry due to its high reactivity with volatile organic compounds (VOCs) and other trace gaseous species. Because of its very short life time and very low concentration in the atmosphere, interference-free high sensitivity in-situ OH monitoring by laser spectroscopy represents a real challenge. Faraday rotation spectroscopy (FRS) relies on the particular magneto-optic effect observed for paramagnetic species, which makes it capable of enhancing the detection sensitivity and mitigation of spectral interferences from diamagnetic species in the atmosphere. When an AC magnetic field is used, the Zeeman splitting of the molecular absorption line (and thus the magnetic circular birefringence) is modulated. This provides an 'internal modulation' of the sample, which permits to suppress the external noise like interference fringes. An alternative FRS detection scheme is to use a static magnetic field (DC-field) associated with laser wavelength modulation to effectively modulate the Zeeman splitting of the absorption lines. In the DC field case, wavelength modulation of the laser frequency can provide excellent performance compared to most of the sensing systems based on direct absorption and wavelength modulation spectroscopy. The dimension of the DC solenoid is not limited by the resonant frequency of the RLC circuit, which makes large dimension solenoid coil achievable and the absorption base length could be further increased. By employing a combination of the environmental photochemical reactor or smog chamber with multipass absorption cell, one can lower the minimum detection limit for high accuracy atmospheric chemistry studies. In this paper, we report on the development of a DC field based FRS in conjunction with a balanced detection scheme for OH radical detection at 2.8 μm and the construction of OH chemistry research platform which combined a large dimension superconducting magnetic coil with the multipass cell and photochemical reactor chamber for real time in-situ measurement of OH radical concentration in the chamber.

A numerical study of the supercritical CO2 plate heat exchanger subject to U-type, Z-type, and multi-pass arrangements

NASA Astrophysics Data System (ADS)

Zhu, Chen-Xi; Wang, Chi-Chuan

2018-01-01

This study proposes a numerical model for plate heat exchanger that is capable of handling supercritical CO2 fluid. The plate heat exchangers under investigation include Z-type (1-pass), U-type (1-pass), and 1-2 pass configurations. The plate spacing is 2.9 mm with a plate thickness of 0.8 mm, and the size of the plate is 600 mm wide and 218 mm in height with 60 degrees chevron angle. The proposed model takes into account the influence of gigantic change of CO2 properties. The simulation is first compared with some existing data for water-to-water plate heat exchangers with good agreements. The flow distribution, pressure drop, and heat transfer performance subject to the supercritical CO2 in plate heat exchangers are then investigated. It is found that the flow velocity increases consecutively from the entrance plate toward the last plate for the Z-type arrangement, and this is applicable for either water side or CO2 side. However, the flow distribution of the U-type arrangement in the water side shows opposite trend. Conversely, the flow distribution for U-type arrangement of CO2 depends on the specific flow ratio (C*). A lower C* like 0.1 may reverse the distribution, i.e. the flow velocity increases moderately alongside the plate channel like Z-type while a large C* of 1 would resemble the typical distribution in water channel. The flow distribution of CO2 side at the first and last plate shows a pronounced drop/surge phenomenon while the channels in water side does not reveal this kind of behavior. The performance of 2-pass plate heat exchanger, in terms of heat transfer rate, is better than that of 1-pass design only when C* is comparatively small (C* < 0.5). Multi-pass design is more effective when the dominant thermal resistance falls in the CO2 side.

Multi-Pass Quadrupole Mass Analyzer

NASA Technical Reports Server (NTRS)

Prestage, John D.

2013-01-01

Analysis of the composition of planetary atmospheres is one of the most important and fundamental measurements in planetary robotic exploration. Quadrupole mass analyzers (QMAs) are the primary tool used to execute these investigations, but reductions in size of these instruments has sacrificed mass resolving power so that the best present-day QMA devices are still large, expensive, and do not deliver performance of laboratory instruments. An ultra-high-resolution QMA was developed to resolve N2 +/CO+ by trapping ions in a linear trap quadrupole filter. Because N2 and CO are resolved, gas chromatography columns used to separate species before analysis are eliminated, greatly simplifying gas analysis instrumentation. For highest performance, the ion trap mode is used. High-resolution (or narrow-band) mass selection is carried out in the central region, but near the DC electrodes at each end, RF/DC field settings are adjusted to allow broadband ion passage. This is to prevent ion loss during ion reflection at each end. Ions are created inside the trap so that low-energy particles are selected by low-voltage settings on the end electrodes. This is beneficial to good mass resolution since low-energy particles traverse many cycles of the RF filtering fields. Through Monte Carlo simulations, it is shown that ions are reflected at each end many tens of times, each time being sent back through the central section of the quadrupole where ultrahigh mass filtering is carried out. An analyzer was produced with electrical length orders of magnitude longer than its physical length. Since the selector fields are sized as in conventional devices, the loss of sensitivity inherent in miniaturizing quadrupole instruments is avoided. The no-loss, multi-pass QMA architecture will improve mass resolution of planetary QMA instruments while reducing demands on the RF electronics for high-voltage/high-frequency production since ion transit time is no longer limited to a single pass. The QMA-based instrument will thus give way to substantial reductions of the mass of flight instruments.

A Novel Method of Measuring the Phase Behavior and Rheology of Polyethylene Solutions Using a Multi-Pass Rheometer

NASA Astrophysics Data System (ADS)

Lee, Karen; Lacombe, Y.; Cheluget, E.

2008-07-01

The Advanced SCLAIRTECH™ Technology process is used to manufacture Linear Low Density Polyethylene using solution polymerization. In this process ethylene is polymerized in an inert solvent, which is subsequently evaporated and recycled. The reactor effluent in the process is a polymer solution containing the polyethylene product, which is separated from the solvent and unconverted ethylene/co-monomer before being extruded and pelletized. The design of unit operations in this process requires a detailed understanding of the thermophysical properties, phase behaviour and rheology of polymer containing streams at high temperature and pressure, and over a wide range of composition. This paper describes a device used to thermo-rheologically characterize polymer solutions under conditions prevailing in polymerization reactors, downstream heat exchangers and attendant phase separation vessels. The downstream processing of the Advanced SCLAIRTECH™ Technology reactor effluent occurs at temperatures and pressures near the critical point of the solvent and co-monomer mixture. In addition, the process trajectory encompasses regions of liquid-liquid and liquid-liquid-vapour co-existence, which are demarcated by a `cloud point' curve. Knowing the location of this phase boundary is essential for the design of downstream devolatilization processes and for optimizing operating conditions in existing plants. In addition, accurate solution rheology data are required for reliable equipment sizing and design. At NOVA Chemicals, a robust high-temperature and high-pressure-capable version of the Multi-Pass Rheometer (MPR) is used to provide data on solution rheology and phase boundary location. This sophisticated piece of equipment is used to quantify the effects of solvent types, comonomer, and free ethylene concentration on the properties of the reactor effluent. An example of the experimental methodology to characterize a polyethylene solution with hexane solvent, and the ethylene dosing technique developed for the MPR will be described. ™Advanced SCLAIRTECH is a trademark of NOVA Chemicals.

Towards a Narrowband Photonic Sigma-Delta Digital Antenna

DTIC Science & Technology

2012-02-01

High Speed Photodiode/ Amplifier 26 G no amplifier 50 k transimpedance amplifier N/A 12 ps rise time 50 Ω output impedance HP 8447A Amplifier ......Response for the optical amplifier as a function of input drive current

Low noise tuned amplifier

NASA Technical Reports Server (NTRS)

Kleinberg, L. L. (Inventor)

1984-01-01

A bandpass amplifier employing a field effect transistor amplifier first stage is described with a resistive load either a.c. or directly coupled to the non-inverting input of an operational amplifier second stage which is loaded in a Wien Bridge configuration. The bandpass amplifier may be operated with a signal injected into the gate terminal of the field effect transistor and the signal output taken from the output terminal of the operational amplifier. The operational amplifier stage appears as an inductive reactance, capacitive reactance and negative resistance at the non-inverting input of the operational amplifier, all of which appear in parallel with the resistive load of the field effect transistor.

Matched wideband low-noise amplifiers for radio astronomy.

PubMed

Weinreb, S; Bardin, J; Mani, H; Jones, G

2009-04-01

Two packaged low noise amplifiers for the 0.3-4 GHz frequency range are described. The amplifiers can be operated at temperatures of 300-4 K and achieve noise temperatures in the 5 K range (<0.1 dB noise figure) at 15 K physical temperature. One amplifier utilizes commercially available, plastic-packaged SiGe transistors for first and second stages; the second amplifier is identical except it utilizes an experimental chip transistor as the first stage. Both amplifiers use resistive feedback to provide input reflection coefficient S11<-10 dB over a decade bandwidth with gain over 30 dB. The amplifiers can be used as rf amplifiers in very low noise radio astronomy systems or as i.f. amplifiers following superconducting mixers operating in the millimeter and submillimeter frequency range.

Relation of raw and cooked vegetable consumption to blood pressure: the INTERMAP Study.

PubMed

Chan, Q; Stamler, J; Brown, I J; Daviglus, M L; Van Horn, L; Dyer, A R; Oude Griep, L M; Miura, K; Ueshima, H; Zhao, L; Nicholson, J K; Holmes, E; Elliott, P

2014-06-01

Inverse associations have been reported of overall vegetable intake to blood pressure (BP); whether such relations prevail for both raw and cooked vegetables has not been examined. Here we report cross-sectional associations of vegetable intakes with BP for 2195 Americans ages 40-59 in the International Study of Macro/Micronutrients and Blood Pressure (INTERMAP) using four standardized multi-pass 24-h dietary recalls and eight BP measurements. Relations to BP of raw and cooked vegetables consumption, and main individual constituents were assessed by multiple linear regression. Intakes of both total raw and total cooked vegetables considered separately were inversely related to BP in multivariate-adjusted models. Estimated average systolic BP differences associated with two s.d. differences in raw vegetable intake (68 g per 1000 kcal) and cooked vegetable intake (92 g per 1000 kcal) were -1.9 mm Hg (95% confidence interval (CI): -3.1, -0.8; P=0.001) and -1.3 mm Hg (95% CI: -2.5, -0.2; P=0.03) without body mass index (BMI) in the full model; -1.3 mm Hg (95% CI: -2.4, -0.2; P=0.02) and -0.9 mm Hg (95% CI: -2.0, 0.2; P=0.1) with additional adjustment for BMI. Among commonly consumed individual raw vegetables, tomatoes, carrots, and scallions related significantly inversely to BP. Among commonly eaten cooked vegetables, tomatoes, peas, celery, and scallions related significantly inversely to BP.

Power-Amplifier Module for 145 to 165 GHz

NASA Technical Reports Server (NTRS)

Samoska, Lorene; Peralta, Alejandro

2007-01-01

A power-amplifier module that operates in the frequency range of 145 to 165 GHz has been designed and constructed as a combination of (1) a previously developed monolithic microwave integrated circuit (MMIC) power amplifier and (2) a waveguide module. The amplifier chip was needed for driving a high-electron-mobility-transistor (HEMT) frequency doubler. While it was feasible to connect the amplifier and frequency-doubler chips by use of wire bonds, it was found to be much more convenient to test the amplifier and doubler chips separately. To facilitate separate testing, it was decided to package the amplifier and doubler chips in separate waveguide modules. Figure 1 shows the resulting amplifier module. The amplifier chip was described in "MMIC HEMT Power Amplifier for 140 to 170 GHz" (NPO-30127), NASA Tech Briefs, Vol. 27, No. 11, (November 2003), page 49. To recapitulate: This is a three-stage MMIC power amplifier that utilizes HEMTs as gain elements. The amplifier was originally designed to operate in the frequency range of 140 to 170 GHz. The waveguide module is based on a previously developed lower frequency module, redesigned to support operation in the frequency range of 140 to 220 GHz. Figure 2 presents results of one of several tests of the amplifier module - measurements of output power and gain as functions of input power at an output frequency of 150 GHz. Such an amplifier module has many applications to test equipment for power sources above 100 GHz.

Essais de fissuration a froid appliques aux metaux d'apport inoxydables martensitiques 410NiMo

NASA Astrophysics Data System (ADS)

Paquin, Mathieu

Martensitic stainless steels have represented since few years a material of choice for the manufacture of mechanical parts such as hydroelectric turbines. The development of the alloy has led to grades with very low amount of carbon giving them a good weldability. The assembly of these parts, made by autogenous welding, requires the use of materials with low transformation temperature (LTT) such as 410NiMo. These filler metals are also used for assembly by heterogeneous welding of steel parts susceptible to cold cracking. The transformation of austenite to martensite occurring at low temperature, residual stresses from single-pass welding operation are different from those normally found and reduce the risk of cracking. By cons, industrial experience shows that in situation of multipass welding, the risks of cold cracking are still present. This project aimed to determine a cracking test for assessing susceptibility to cold cracking of 13%Cr-4%Ni stainless steel according to the welding procedure, in autogenous welding situation. Literature contains much information about cold cracking phenomena. That phenomena occurs under three conditions. These conditions are: a high diffusible hydrogen level, significant residual stresses and a brittle microstructure. It seems that despite the low mass ratio of carbon (0.022%C) and the low diffusible hydrogen level (< 3 ml/100g) risks of cold cracking remain present during multipass deposits. Use of cracking tests was necessary to assess the sensitivity to cracking of the martensitic stainless steel. Before the work preliminary tests have been made or tested Tekken GBOP and testing to determine that to obtain the most representative of the industrial reality results. Then they have been modified to reverse the compression stress in the seam test to tension by the addition of a second weld. This inversion occurs in multipass welding and has been targeted as an important factor in the occurrence of cold cracking phenomenon. The results of these tests show that Tekken test is not suitable for LTT testing. It was also demonstrated that GBOP test with two juxtaposed seams configuration gave results consistent with the industrial observations. The second stage of the project was to study the cracking test selected. Acoustic emission tests were done during welding and cooling of GBOP test. These tests were conducted in order to detect when the cracking of the test occurred and to validate the method of inspection. This inspection is done after separation of the specimen, by observation of the fracture surface. Usually, cliveage zone on the fracture surface can be associated with cold cracking and dimple zones can be associated with the specimen separation. Through these tests, it was possible to validate this assertion. Then the relevance of the addition of a second weld has been validated by studying the residual stress by the contour method. It was possible to observe an area of the first bead in tension, promoting cracking of the test. Finally, some test runs were made with various filler metals in order to confirm that the utilization of the modified GBOP test for 13%Cr-4%Ni was adequate. A fractographic study of some sample was also made.

Industrial universal electrometer

DOEpatents

Cordaro, Joseph V [Martinez, GA; Wood, Michael B [Aiken, SC

2012-07-03

An electrometer for use in measuring current is provided. The electrometer includes an enclosure capable of containing various components of the electrometer. A pre-amplifier is present and is one of the components of the electrometer. The pre-amplifier is contained by the enclosure. The pre-amplifier has a pre-amplifier enclosure that contains the pre-amplifier and provides radio frequency shielding and magnetic shielding to the pre-amplifier.

Limit circuit prevents overdriving of operational amplifier

NASA Technical Reports Server (NTRS)

Openshaw, F. L.

1967-01-01

Cutoff-type high gain amplifier coupled by a diode prevents overdriving of operational amplifier. An amplified feedback signal offsets the excess input signal that tends to cause the amplifier to exceed its preset limit. The output is, therfore, held to the set clamp level.

Method to amplify variable sequences without imposing primer sequences

DOEpatents

Bradbury, Andrew M.; Zeytun, Ahmet

2006-11-14

The present invention provides methods of amplifying target sequences without including regions flanking the target sequence in the amplified product or imposing amplification primer sequences on the amplified product. Also provided are methods of preparing a library from such amplified target sequences.

21 CFR 882.1835 - Physiological signal amplifier.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Physiological signal amplifier. 882.1835 Section... signal amplifier. (a) Identification. A physiological signal amplifier is a general purpose device used to electrically amplify signals derived from various physiological sources (e.g., the...

21 CFR 882.1835 - Physiological signal amplifier.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Physiological signal amplifier. 882.1835 Section... signal amplifier. (a) Identification. A physiological signal amplifier is a general purpose device used to electrically amplify signals derived from various physiological sources (e.g., the...

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

2010-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

2011-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Hybrid matrix amplifier

DOEpatents

Martens, J.S.; Hietala, V.M.; Plut, T.A.

1995-01-03

The present invention comprises a novel matrix amplifier. The matrix amplifier includes an active superconducting power divider (ASPD) having N output ports; N distributed amplifiers each operatively connected to one of the N output ports of the ASPD; and a power combiner having N input ports each operatively connected to one of the N distributed amplifiers. The distributed amplifier can included M stages of amplification by cascading superconducting active devices. The power combiner can include N active elements. The resulting (N[times]M) matrix amplifier can produce signals of high output power, large bandwidth, and low noise. 6 figures.

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Aoki, Ichiro (Inventor); Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor)

2013-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

Hybrid matrix amplifier

DOEpatents

Martens, Jon S.; Hietala, Vincent M.; Plut, Thomas A.

1995-01-01

The present invention comprises a novel matrix amplifier. The matrix amplifier includes an active superconducting power divider (ASPD) having N output ports; N distributed amplifiers each operatively connected to one of the N output ports of the ASPD; and a power combiner having N input ports each operatively connected to one of the N distributed amplifiers. The distributed amplifier can included M stages of amplification by cascading superconducting active devices. The power combiner can include N active elements. The resulting (N.times.M) matrix amplifier can produce signals of high output power, large bandwidth, and low noise.

Cross-differential amplifier

NASA Technical Reports Server (NTRS)

Hajimiri, Seyed-Ali (Inventor); Kee, Scott D. (Inventor); Aoki, Ichiro (Inventor)

2008-01-01

A cross-differential amplifier is provided. The cross-differential amplifier includes an inductor connected to a direct current power source at a first terminal. A first and second switch, such as transistors, are connected to the inductor at a second terminal. A first and second amplifier are connected at their supply terminals to the first and second switch. The first and second switches are operated to commutate the inductor between the amplifiers so as to provide an amplified signal while limiting the ripple voltage on the inductor and thus limiting the maximum voltage imposed across the amplifiers and switches.

A Methodological Approach for Assessing Amplified Reflection Distributed Denial of Service on the Internet of Things

PubMed Central

Costa Gondim, João José; de Oliveira Albuquerque, Robson; Clayton Alves Nascimento, Anderson; García Villalba, Luis Javier; Kim, Tai-Hoon

2016-01-01

Concerns about security on Internet of Things (IoT) cover data privacy and integrity, access control, and availability. IoT abuse in distributed denial of service attacks is a major issue, as typical IoT devices’ limited computing, communications, and power resources are prioritized in implementing functionality rather than security features. Incidents involving attacks have been reported, but without clear characterization and evaluation of threats and impacts. The main purpose of this work is to methodically assess the possible impacts of a specific class–amplified reflection distributed denial of service attacks (AR-DDoS)–against IoT. The novel approach used to empirically examine the threat represented by running the attack over a controlled environment, with IoT devices, considered the perspective of an attacker. The methodology used in tests includes that perspective, and actively prospects vulnerabilities in computer systems. This methodology defines standardized procedures for tool-independent vulnerability assessment based on strategy, and the decision flows during execution of penetration tests (pentests). After validation in different scenarios, the methodology was applied in amplified reflection distributed denial of service (AR-DDoS) attack threat assessment. Results show that, according to attack intensity, AR-DDoS saturates reflector infrastructure. Therefore, concerns about AR-DDoS are founded, but expected impact on abused IoT infrastructure and devices will be possibly as hard as on final victims. PMID:27827931

A Methodological Approach for Assessing Amplified Reflection Distributed Denial of Service on the Internet of Things.

PubMed

Costa Gondim, João José; de Oliveira Albuquerque, Robson; Clayton Alves Nascimento, Anderson; García Villalba, Luis Javier; Kim, Tai-Hoon

2016-11-04

Concerns about security on Internet of Things (IoT) cover data privacy and integrity, access control, and availability. IoT abuse in distributed denial of service attacks is a major issue, as typical IoT devices' limited computing, communications, and power resources are prioritized in implementing functionality rather than security features. Incidents involving attacks have been reported, but without clear characterization and evaluation of threats and impacts. The main purpose of this work is to methodically assess the possible impacts of a specific class-amplified reflection distributed denial of service attacks (AR-DDoS)-against IoT. The novel approach used to empirically examine the threat represented by running the attack over a controlled environment, with IoT devices, considered the perspective of an attacker. The methodology used in tests includes that perspective, and actively prospects vulnerabilities in computer systems. This methodology defines standardized procedures for tool-independent vulnerability assessment based on strategy, and the decision flows during execution of penetration tests (pentests). After validation in different scenarios, the methodology was applied in amplified reflection distributed denial of service (AR-DDoS) attack threat assessment. Results show that, according to attack intensity, AR-DDoS saturates reflector infrastructure. Therefore, concerns about AR-DDoS are founded, but expected impact on abused IoT infrastructure and devices will be possibly as hard as on final victims.

High power, high contrast hybrid femtosecond laser systems

NASA Astrophysics Data System (ADS)

Dabu, Razvan

2017-06-01

For many research applications a very high laser intensity of more than 1022 W/cm2 in the focused beam is required. If a laser intensity of about 1011W/cm2 is reached on the target before the main laser pulse, the generated pre-plasma disturbs the experiment. High power femtosecond lasers must be tightly focused to get high intensity and in the same time must have a high enough intensity contrast of the temporally compressed amplified pulses. Reaching an intensity contrast in the range of 1012 represents a challenging task for a Ti:sapphire CPA laser. Hybrid femtosecond lasers combine optical parametric chirped pulsed amplification (OPCPA) in nonlinear crystals with the chirped pulse amplification (CPA) in laser active media. OPCPA provides large amplification spectral bandwidth and improves the intensity contrast of the amplified pulses. A key feature of these systems consists in the adaptation of the parametric amplification phase-matching bandwidth of nonlinear crystals to the spectral gain bandwidth of laser amplifying Ti:sapphire crystals. OPCPA in BBO crystals up to mJ energy level in the laser Front-End, followed by CPA up to ten/hundred Joules in large aperture Ti:sapphire crystals, represents a suitable solution for PW-class femtosecond lasers. The configuration and expected output beam characteristics of the hybrid amplification 2 × 10 PW ELI-NP laser are described.

Excitation of parasitic waves in forward-wave amplifiers with weak guiding fields.

PubMed

Nusinovich, G S; Romero-Talamás, C A; Han, Y

2012-12-01

To produce high-power coherent electromagnetic radiation at frequencies from microwaves up to terahertz, the radiation sources should have interaction circuits of large cross sections, i.e., the sources should operate in high-order modes. In such devices, the excitation of higher-order parasitic modes near cutoff where the group velocity is small and, hence, start currents are low can be a serious problem. The problem is especially severe in the sources of coherent, phase-controlled radiation, i.e., the amplifiers or phase-locked oscillators. This problem was studied earlier [Nusinovich, Sinitsyn, and Antonsen, Phys. Rev. E 82, 046404 (2010)] for the case of electron focusing by strong guiding magnetic fields. For many applications it is desirable to minimize these focusing fields. Therefore in this paper we analyze the problem of excitation of parasitic modes near cutoff in forward-wave amplifiers with weak focusing fields. First, we study the large-signal operation of such a device with a signal wave only. Then, we analyze the self-excitation conditions of parasitic waves near cutoff in the presence of the signal wave. It is shown that the main effect is the suppression of the parasitic wave in large-signal regimes. At the same time, there is a region of device parameters where the presence of signal waves can enhance excitation of parasitic modes. The role of focusing fields in such effects is studied.

A 1-W, 30-ghz, CPW Amplifier for ACTS Small Terminal Uplink

NASA Technical Reports Server (NTRS)

Taub, Susan R.; Simons, Rainee N.

1992-01-01

The progress is described of the development of a 1 W, 30 GHz, coplanar waveguide (CPW) amplifier for the Advanced Communication Technology Satellite (ACTS)Small Terminal Uplink. The amplifier is based on Texas Instruments' monolithic microwave integrated circuit (MMIC) amplifiers; a three stage, low power amplifier, and a single stage, high power amplifier. The amplifiers have a power output of 190 mW and 0.710 W, gain of 23 and 4.2 dB, and efficiencies of 30.2 and 24 percent for the three stage and one stage amplifiers, respectively. The chips are to be combined via a CPW power divider/combiner circuit to yield the desired 1 W of output power.

Improved Grid-Array Millimeter-Wave Amplifier

NASA Technical Reports Server (NTRS)

Rosenberg, James J.; Rutledge, David B.; Smith, R. Peter; Weikle, Robert

1993-01-01

Improved grid-array amplifiers operating at millimeter and submillimeter wavelengths developed for use in communications and radar. Feedback suppressed by making input polarizations orthogonal to output polarizations. Amplifier made to oscillate by introducing some feedback. Several grid-array amplifiers concatenated to form high-gain beam-amplifying unit.

Nearly noiseless amplification of microwave signals with a Josephson parametric amplifier

NASA Astrophysics Data System (ADS)

Castellanos-Beltran, Manuel

2009-03-01

A degenerate parametric amplifier transforms an incident coherent state by amplifying one of its quadrature components while deamplifying the other. This transformation, when performed by an ideal parametric amplifier, is completely deterministic and reversible; therefore the amplifier in principle can be noiseless. We attempt to realize a noiseless amplifier of this type at microwave frequencies with a Josephson parametric amplifier (JPA). To this end, we have built a superconducting microwave cavity containing many dc-SQUIDs. This arrangement creates a non-linear medium in a cavity and it is closely analogous to an optical parametric amplifier. In my talk, I will describe the current performance of this circuit, where I show I can amplify signals with less added noise than a quantum-limited amplifier that amplifies both quadratures. In addition, the JPA also squeezes the electromagnetic vacuum fluctuations by 10 dB. Finally, I will discuss our effort to put two such amplifiers in series in order to undo the first stage of squeezing with a second stage of amplification, demonstrating that the amplification process is truly reversible.[4pt] M. A. Castellanos-Beltran, K. D. Irwin, G. C. Hilton, L. R. Vale and K. W. Lehnert, Nature Physics, published on line, http://dx.doi.org/10.1038/nphys1090 (2008).

High frequency inductive lamp and power oscillator

DOEpatents

Kirkpatrick, Douglas A.; Gitsevich, Aleksandr

2005-09-27

An oscillator includes an amplifier having an input and an output, a feedback network connected between the input of the amplifier and the output of the amplifier, the feedback network being configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and a tuning circuit connected to the input of the amplifier, wherein the tuning circuit is continuously variable and consists of solid state electrical components with no mechanically adjustable devices including a pair of diodes connected to each other at their respective cathodes with a control voltage connected at the junction of the diodes. Another oscillator includes an amplifier having an input and an output, a feedback network connected between the input of the amplifier and the output of the amplifier, the feedback network being configured to provide suitable positive feedback from the output of the amplifier to the input of the amplifier to initiate and sustain an oscillating condition, and transmission lines connected to the input of the amplifier with an input pad and a perpendicular transmission line extending from the input pad and forming a leg of a resonant "T", and wherein the feedback network is coupled to the leg of the resonant "T".

Genetic diversity of rice tungro spherical virus in tungro-endemic provinces of the Philippines and Indonesia.

PubMed

Azzam, O; Yambao, M L; Muhsin, M; McNally, K L; Umadhay, K M

2000-01-01

The two adjacent genes of coat protein 1 and 2 of rice tungro spherical virus (RTSV) were amplified from total RNA extracts of serologically indistinguishable field isolates from the Philippines and Indonesia, using reverse transcriptase polymerase chain reaction (RT-PCR). Digestion with HindIII and BstYI restriction endonucleases differentiated the amplified DNA products into eight distinct coat protein genotypes. These genotypes were then used as indicators of virus diversity in the field. Inter- and intra-site diversities were determined over three cropping seasons. At each of the sites surveyed, one or two main genotypes prevailed together with other related minor or mixed genotypes that did not replace the main genotype over the sampling time. The cluster of genotypes found at the Philippines sites was significantly different from the one at the Indonesia sites, suggesting geographic isolation for virus populations. Phylogenetic studies based on the nucleotide sequences of 38 selected isolates confirm the spatial distribution of RTSV virus populations but show that gene flow may occur between populations. Under the present conditions, rice varieties do not seem to exert selective pressure on the virus populations. Based on the selective constraints in the coat protein amino acid sequences and the virus genetic composition per site, a negative selection model followed by random-sampling events due to vector transmissions is proposed to explain the inter-site diversity observed.

Amplified fragment length polymorphism of Streptococcus suis strains correlates with their profile of virulence-associated genes and clinical background.

PubMed

Rehm, Thomas; Baums, Christoph G; Strommenger, Birgit; Beyerbach, Martin; Valentin-Weigand, Peter; Goethe, Ralph

2007-01-01

Amplified fragment length polymorphism (AFLP) typing was applied to 116 Streptococcus suis isolates with different clinical backgrounds (invasive/pneumonia/carrier/human) and with known profiles of virulence-associated genes (cps1, -2, -7 and -9, as well as mrp, epf and sly). A dendrogram was generated that allowed identification of two clusters (A and C) with different subclusters (A1, A2, C1 and C2) and two heterogeneous groups of strains (B and D). For comparison, three strains from each AFLP subcluster and group were subjected to multilocus sequence typing (MLST) analysis. The closest relationship and lowest diversity were found for patterns clustering within AFLP subcluster A1, which corresponded with sequence type (ST) complex 1. Strains within subcluster A1 were mainly invasive cps1 and mrp+ epf+ (or epf*) sly+ cps2+ strains of porcine or human origin. A new finding of this study was the clustering of invasive mrp* cps9 isolates within subcluster A2. MLST analysis suggested that A2 correlates with a single ST complex (ST87). In contrast to A1 and A2, subclusters C1 and C2 contained mainly pneumonia isolates of genotype cps7 or cps2 and epf- sly-. In conclusion, this study demonstrates that AFLP allows identification of clusters of S. suis strains with clinical relevance.

Molecular Determination of Fasciola Spp. Isolates from Domestic Ruminants Fecal Samples in the Northwest of Iran

PubMed Central

IMANI BARAN, Abbas; CHERAGHI SARAY, Habib; KATIRAEE, Farzad

2017-01-01

Background: Fasciola species are the main causes for fascioliasis with great financial losses and are among the most important food/water-borne parasites worldwide. The basic proceedings such as epidemiology and effective control of fascioliasis rely mainly on precise identification of Fasciola species. The present study was conducted to determine the Fasciola species in ruminant fecal samples from East Azerbaijan Province in Iran. Methods: Overall, 2012 fecal samples were collected and processed initially for microscopic examination of Fasciola eggs in 2014–15. Then, recovered eggs were subjected to molecular identification. A fragment of 618 bp of the 28S rRNA gene pertaining to Fasciola genus was amplified under PCR. The amplified fragment was restricted by fast digest Ava II enzyme in order to a Restriction Fragment Length Polymorphism. Results: Based on microscopic examination, 72 samples were infected, from which, 10 and 62 cases pertained to cattle and sheep samples respectively. Based on RFLP, the PCR products restricted by the Ava II restriction enzyme produced 529 bp fragments only. According to the positive controls, all restriction patterns were related to Fasciola hepatica, while no restriction patterns were linked to F. gigantica. Conclusion: Based on PCR-RFLP, F. hepatica was dominant species in animals of the studied areas and no evidence of F. gigantica was observed. Therefore, further field studies to verify these results are suggested. PMID:28761485

High-power broadband plasma maser with magnetic self-insulation

NASA Astrophysics Data System (ADS)

Litvin, Vitaliy O.; Loza, Oleg T.

2018-01-01

Presented in this paper are the results of a particle-in-cell modelling of a novel high-power microwave (HPM) source which combines the properties of two devices. The first prototype is a magnetically insulated transmission line oscillator (MILO), an HPM self-oscillator which does not need an external magnetic field and irradiates a narrow spectrum depending on its iris-loaded slow-wave structure. The second prototype is a plasma maser, a Cherenkov HPM amplifier driven by a high-current relativistic electron beam propagating in a strong external magnetic field in plasma which acts as a slow-wave structure. The radiation frequency of plasma masers mainly depends on an easily variable plasma concentration; hence, their spectrum may overlap a few octaves. The plasma-based HPM device described in this paper operates without an external magnetic field: it looks like an MILO in which the iris-loaded slow-wave structure is substituted by a hollow plasma tube. The small pulse duration of ˜1.5 ns prevents a feedback rise in the 20-cm long generation section so that the device operates as a noise amplifier. Unlike conventional ultra wideband generators, the spectrum depends not only on the pulse duration but mainly on plasma, so the operation frequency of the device ranges within 12 GHz. For irradiated frequencies above 2 GHz, the total pulse energy efficiency of 7% is demonstrated at the HPM power level ˜1 GW.

Low-Noise Band-Pass Amplifier

NASA Technical Reports Server (NTRS)

Kleinberg, L.

1982-01-01

Circuit uses standard components to overcome common limitation of JFET amplifiers. Low-noise band-pass amplifier employs JFET and operational amplifier. High gain and band-pass characteristics are achieved with suitable choice of resistances and capacitances. Circuit should find use as low-noise amplifier, for example as first stage instrumentation systems.

Applications of Optical Coherent Transient Technology to Pulse Shaping, Spectral Filtering, Arbitrary Waveform Generation and RF Beamforming

DTIC Science & Technology

2006-04-15

was amplified by injection locking of a high power diode laser and further amplified to -300 mW with a semiconductor optical amplifier. This light...amplifiers at 793nm, cascaded injection locked amplifiers at 793nm, and frequency chirped lasers at 793nm. 15. SUBJECT TERMS Optical Coherent Transients...injection- locking for broadband optical signal amplification ................. 34 2.10. Tapered semiconductor optical amplifier

Visual neurophysiology: a field-effect amplifier designed and built by R. L. De Valois.

PubMed

Albrecht, Duane G; Creeger, Carl P; Crane, Alison M

2005-10-01

In the middle of the last century, R. L. De Valois designed and built a unique and effective amplifier based on the newly developed field-effect transistor (FET). This amplifier has many beneficial qualities for amplifying the signals of neurons with minimal disturbance. We have used this amplifier successfully for more than three decades. We describe the circuitry of the De Valois amplifier and provide performance specifications. The FET amplifier is one of De Valois's contributions to visual neurophysiology; we share the design in his honor, with the hope that it might prove useful to others.

Amplifier for measuring low-level signals in the presence of high common mode voltage

NASA Technical Reports Server (NTRS)

Lukens, F. E. (Inventor)

1985-01-01

A high common mode rejection differential amplifier wherein two serially arranged Darlington amplifier stages are employed and any common mode voltage is divided between them by a resistance network. The input to the first Darlington amplifier stage is coupled to a signal input resistor via an amplifier which isolates the input and presents a high impedance across this resistor. The output of the second Darlington stage is transposed in scale via an amplifier stage which has its input a biasing circuit which effects a finite biasing of the two Darlington amplifier stages.

ULTRA-STABILIZED D. C. AMPLIFIER

DOEpatents

Hartwig, E.C.; Kuenning, R.W.; Acker, R.C.

1959-02-17

An improved circuit is described for stabilizing the drift and minimizing the noise and hum level of d-c amplifiers so that the output voltage will be zero when the input is zero. In its detailed aspects, the disclosed circuit incorporates a d-c amplifier having a signal input, a second input, and an output circuit coupled back to the first input of the amplifier through inverse feedback means. An electronically driven chopper having a pair of fixed contacts and a moveable contact alternately connects the two inputs of a difference amplifier to the signal input. The A. E. error signal produced in the difference amplifier is amplified, rectified, and applied to the second input of the amplifier as the d-c stabilizing voltage.

High-power piezo drive amplifier for large stack and PFC applications

NASA Astrophysics Data System (ADS)

Clingman, Dan J.; Gamble, Mike

2001-08-01

This paper describes the continuing development of Boeing High Power Piezo Drive Amplifiers. Described is the development and testing of a 1500 Vpp, 8 amp switching amplifier. This amplifier is used to drive a piezo stack driven rotor blade trailing edge flap on a full size helicopter. Also discuss is a switching amplifier designed to drive a Piezo Fiber Composite (PFC) active twist rotor blade. This amplifier was designed to drive the PFC material at 2000 Vpp and 0.5 amps. These amplifiers recycle reactive energy, allowing for a power and weight efficient amplifier design. This work was done in conjunction with the DARPA sponsored Phase II Smart Rotor Blade program and the NASA Langley Research Center sponsored Active Twist Rotor (ATR) blade program.

Portable musical instrument amplifier

DOEpatents

Christian, David E.

1990-07-24

The present invention relates to a musical instrument amplifier which is particularly useful for electric guitars. The amplifier has a rigid body for housing both the electronic system for amplifying and processing signals from the guitar and the system's power supply. An input plug connected to and projecting from the body is electrically coupled to the signal amplifying and processing system. When the plug is inserted into an output jack for an electric guitar, the body is rigidly carried by the guitar, and the guitar is operatively connected to the electrical amplifying and signal processing system without use of a loose interconnection cable. The amplifier is provided with an output jack, into which headphones are plugged to receive amplified signals from the guitar. By eliminating the conventional interconnection cable, the amplifier of the present invention can be used by musicians with increased flexibility and greater freedom of movement.

A 0.1-1.4 GHz inductorless low-noise amplifier with 13 dBm IIP3 and 24 dBm IIP2 in 180 nm CMOS

NASA Astrophysics Data System (ADS)

Guo, Benqing; Chen, Jun; Chen, Hongpeng; Wang, Xuebing

2018-01-01

An inductorless noise-canceling CMOS low-noise amplifier (LNA) with wideband linearization technique is proposed. The complementary configuration by stacked NMOS/PMOS is employed to compensate second-order nonlinearity of the circuit. The third-order distortion of the auxiliary stage is also mitigated by that of the weak inversion transistors in the main path. The bias and scaling size combined by digital control words are further tuned to obtain enhanced linearity over the desired band. Implemented in a 0.18 μm CMOS process, simulated results show that the proposed LNA provides a voltage gain of 16.1 dB and a NF of 2.8-3.4 dB from 0.1 GHz to 1.4 GHz. The IIP3 and IIP2 of 13-18.9 and 24-40 dBm are obtained, respectively. The circuit core consumes 19 mW from a 1.8 V supply.

2.36 J, 50 Hz nanosecond pulses from a diode side-pumped Nd:YAG MOPA system

NASA Astrophysics Data System (ADS)

Li, Chaoyang; Lu, Chengqiang; Li, Chuan; Yang, Ning; Li, Ye; Yang, Zhen; Han, Song; Shi, Junfeng; Zhou, Zewu

2017-07-01

We report on a high-energy high-repetition-rate nanosecond Nd:YAG main oscillator power amplifier (MOPA) system. Maximum output pulse energy of 2.36 J with duration of 9.4 ns at 50 Hz has been achieved. The master oscillator was a LD side-pumped electro-optical Q-switched Nd:YAG rod laser adopting unstable cavity with variable reflectivity mirror (VRM). It delivered a pulse train with energy up to 180 mJ and pulse duration of 10.7 ns. The near-field pattern demonstrated a nearly super Gaussian flat top profile. In the amplification stage, the pulse was boosted via double-pass two Nd:YAG rod amplifiers. Maximum pulse energy was obtained at the peak pump power of 37.5 kW, corresponding to an optical-optical conversion efficiency of 25.2%. The correlative peak power was deduced to be 251 MW. We also presented the result of 100 Hz nanosecond laser with average output power of >100 W.

What Would Happen to Superstorm Sandy Under the Influence of a Substantially Warmer Atlantic Ocean?

NASA Technical Reports Server (NTRS)

Lau, William K. M.; Shi, J. J.; Tao, W. K.; Kim, K. M.

2016-01-01

Based on ensemble numerical simulations, we find that possible responses of Sandy-like superstorms under the influence of a substantially warmer Atlantic Ocean bifurcate into two groups. In the first group, storms are similar to present-day Sandy from genesis to extratropical transition, except they are much stronger, with peak Power Destructive Index (PDI) increased by 50-80%, heavy rain by 30-50%, and maximum storm size (MSS) approximately doubled. In the second group, storms amplify substantially over the interior of the Atlantic warm pool, with peak PDI increased by 100-160%, heavy rain by 70-180%, and MSS more than tripled compared to present-day Superstorm Sandy. These storms when exiting the warm pool, recurve northeastward out to sea, subsequently interact with the developing midlatitude storm by mutual counterclockwise rotation around each other and eventually amplify into a severe Northeastern coastal storm, making landfall over the extreme northeastern regions from Maine to Nova Scotia.

The sludge loading rate regulates the growth and release of heterotrophic bacteria resistant to six types of antibiotics in wastewater activated sludge.

PubMed

Yuan, Qing-Bin; Guo, Mei-Ting; Yang, Jian

2015-01-01

Wastewater treatment plants are considered as hot reservoirs of antimicrobial resistance. However, the fates of antibiotic-resistant bacteria during biological treatment processes and relevant influencing factors have not been fully understood. This study evaluated the effects of the sludge loading rate on the growth and release of six kinds of antibiotic-resistant bacteria in an activated sludge system. The results indicated that higher sludge loading rates amplified the growth of all six types of antibiotic resistant bacteria. The release of most antibiotic-resistant bacteria through both the effluent and biosolids was amplified with increased sludge loading rate. Biosolids were the main pattern for all antibiotic-resistant bacteria release in an activated sludge system, which was determined primarily by their growth in the activated sludge. A higher sludge loading rate reactor tended to retain more antibiotic resistance. An activated sludge system with lower sludge loading rates was considered more conducive to the control of antibiotic resistance.

Suppression of shot noise and spontaneous radiation in electron beams

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

Litvinenko,V.

2009-08-23

Shot noise in the electron beam distribution is the main source of noise in high-gain FEL amplifiers, which may affect applications ranging from single- and multi-stage HGHG FELs to an FEL amplifier for coherent electron cooling. This noise also imposes a fundamental limit of about 10{sup 6} on FEL gain, after which SASE FELs saturate. There are several advantages in strongly suppressing this shot noise in the electron beam, and the corresponding spontaneous radiation. For more than a half-century, a traditional passive method has been used successfully in practical low-energy microwave electronic devices to suppress shot noise. Recently, it wasmore » proposed for this purpose in FELs. However, being passive, the method has some significant limitations and is hardly suitable for the highly inhomogeneous beams of modern high-gain FELs. I present a novel active method of suppressing, by many orders-of-magnitude, the shot noise in relativistic electron beams. I give a theoretical description of the process, and detail its fundamental limitation.« less

[Analysis of genomic DNA methylation level in radish under cadmium stress by methylation-sensitive amplified polymorphism technique].

PubMed

Yang, Jin-Lan; Liu, Li-Wang; Gong, Yi-Qin; Huang, Dan-Qiong; Wang, Feng; He, Ling-Li

2007-06-01

The level of cytosine methylation induced by cadmium in radish (Raphanus sativus L.) genome was analysed using the technique of methylation-sensitive amplified polymorphism (MSAP). The MSAP ratios in radish seedling exposed to cadmium chloride at the concentration of 50, 250 and 500 mg/L were 37%, 43% and 51%, respectively, and the control was 34%; the full methylation levels (C(m)CGG in double strands) were at 23%, 25% and 27%, respectively, while the control was 22%. The level of increase in MSAP and full methylation indicated that de novo methylation occurred in some 5'-CCGG sites under Cd stress. There was significant positive correlation between increase of total DNA methylation level and CdCl(2) concentration. Four types of MSAP patterns: de novo methylation, de-methylation, atypical pattern and no changes of methylation pattern were identified among CdCl(2) treatments and the control. DNA methylation alteration in plants treated with CdCl(2) was mainly through de novo methylation.

Do aphid colonies amplify their emission of alarm pheromone?

PubMed

Hatano, Eduardo; Kunert, Grit; Bartram, Stefan; Boland, Wilhelm; Gershenzon, Jonathan; Weisser, Wolfgang W

2008-09-01

When aphids are attacked by natural enemies, they emit alarm pheromone to alert conspecifics. For most aphids tested, (E)-beta-farnesene (EBF) is the main, or only, constituent of the alarm pheromone. In response to alarm pheromone, alerted aphids drop off the plant, walk away, or attempt to elude predators. However, under natural conditions, EBF concentration might be low due to the low amounts emitted, to rapid air movement, or to oxidative degradation. To ensure that conspecifics are warned, aphids might conceivably amplify the alarm signal by emitting EBF in response to EBF emitted by other aphids. To examine whether such amplification occurs, we synthesized deuterated EBF (DEBF), which allowed us to differentiate between applied and aphid-derived chemical. Colonies of Acyrthosiphon pisum were treated with DEBF, and headspace volatiles were collected and analyzed for evidence of aphid-derived EBF. No aphid-derived EBF was detected, suggesting that amplification of the alarm signal does not occur. We discuss the disadvantages of alarm signal reinforcement.

Performance Analysis of Amplify-and-Forward Systems with Single Relay Selection in Correlated Environments.

PubMed

Van Nguyen, Binh; Kim, Kiseon

2016-09-11

In this paper, we consider amplify-and-forward (AnF) cooperative systems under correlated fading environments. We first present a brief overview of existing works on the effect of channel correlations on the system performance. We then focus on our main contribution which is analyzing the outage probability of a multi-AnF-relay system with the best relay selection (BRS) scheme under a condition that two channels of each relay, source-relay and relay-destination channels, are correlated. Using lower and upper bounds on the end-to-end received signal-to-noise ratio (SNR) at the destination, we derive corresponding upper and lower bounds on the system outage probability. We prove that the system can achieve a diversity order (DO) equal to the number of relays. In addition, and importantly, we show that the considered correlation form has a constructive effect on the system performance. In other words, the larger the correlation coefficient, the better system performance. Our analytic results are corroborated by extensive Monte-Carlo simulations.

Amplification of the concept of erroneous meaning in psychodynamic science and in the consulting room.

PubMed

Brookes, Crittenden E

2007-01-01

Previous papers dealt with the concept of psyche as that dynamic field which underlies the subjective experience of mind. A new paradigm, psychodynamic science, was suggested for dealing with subjective data. The venue of the psychotherapeutic consulting room is now brought directly into science, expanding the definition of psychotherapy to include both humanistic and scientific elements. Certain concepts were introduced to amplify this new scientific model, including psyche as hypothetical construct, the concept of meaning as replacement for operational validation in scientific investigation, the synonymity of meaning and insight, and the concept of synchronicity, together with the meaning-connected affect of numinosity. The presence of unhealthy anxiety as the conservative ego attempts to preserve its integrity requires a deeper look at the concept of meaning. This leads to a distinction between meaning and erroneous meaning. The main body of this paper amplifies that distinction, and introduces the concept of intolerance of ambiguity in the understanding of erroneous meanings and their connection with human neurosis.

The MSAT spacecraft of Telesat Mobile, Inc.

NASA Astrophysics Data System (ADS)

Bertenyi, E.

The Canadian MSAT system will offer a mobile telephone, radio, and data services. The last two will be offered via feederlink earth stations. The earth stations will use a 13 GHz Ku-band uplink and an L-band for downlink from the satellite to mobile earth terminals. User access will be controlled by a network control center. The basic service area of MSAT includes the part of Canada which is accessible from the geostationary orbit of 106.5 deg W as well as the continental USA. The satellite will have a minimum service life of ten years. The main elements of the communication subsystem are the antennas which include two large unfurlable L-band reflectors and their feed elements, the cross-polarized Ku-band antenna, the L-band and Ku-band receivers, the up-down converters each serving one antennal beam, and the Ku-band travelling wave tube amplifiers and L-band solid state power amplifiers. Voice and data services are expected to be available in 1994.

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

Hand, L.N.

Some proposed techniques for using laser beams to accelerate charged particles are reviewed. Two specific ideas for 'grating-type' accelerating structures are discussed. Speculations are presented about how a successful laser accelerator could be used in a 'multi-pass collider', a type of machine which would have characteristics intermediate between those of synchrotrons and linear (single-pass) colliders. No definite conclusions about practical structures for laser accelerators are reached, but it is suggested that a serious effort be made to design a small prototype machine. Achieving a reasonable luminosity demands that the accelerator either be a cw machine or that laser peak powermore » requirements be much higher than those presently available. Use of superconducting gratings requires a wavelength in the sub-millimeter range.« less

The laser accelerator-another unicorn in the garden

NASA Astrophysics Data System (ADS)

Hand, L. N.

1981-07-01

Some proposed techniques for using laser beams to accelerate charged particles was reviewed. Two specific ideas for grating type accelerating structures are discussed. Speculations are presented about how a successful laser accelerator could be used in a multipass collider; a type of machine which would have characteristics intermediate between those of synchrotrons and linear (single pass) colliders. No definite conclusions about practical structures for laser accelerators are reached, but it is suggested that a serious effort be made to design a small prototype machine. Achieving a reasonable luminosity demands that the accelerator either be a cw machine or that laser peak power requirements to be much higher than those presently available. Use of superconducting gratings requires a wavelength in the sub-millimeter range.

High-extinction virtually imaged phased array-based Brillouin spectroscopy of turbid biological media

NASA Astrophysics Data System (ADS)

Fiore, Antonio; Zhang, Jitao; Shao, Peng; Yun, Seok Hyun; Scarcelli, Giuliano

2016-05-01

Brillouin microscopy has recently emerged as a powerful technique to characterize the mechanical properties of biological tissue, cell, and biomaterials. However, the potential of Brillouin microscopy is currently limited to transparent samples, because Brillouin spectrometers do not have sufficient spectral extinction to reject the predominant non-Brillouin scattered light of turbid media. To overcome this issue, we combined a multi-pass Fabry-Perot interferometer with a two-stage virtually imaged phased array spectrometer. The Fabry-Perot etalon acts as an ultra-narrow band-pass filter for Brillouin light with high spectral extinction and low loss. We report background-free Brillouin spectra from Intralipid solutions and up to 100 μm deep within chicken muscle tissue.

Illustrative visualization of 3D city models

NASA Astrophysics Data System (ADS)

Doellner, Juergen; Buchholz, Henrik; Nienhaus, Marc; Kirsch, Florian

2005-03-01

This paper presents an illustrative visualization technique that provides expressive representations of large-scale 3D city models, inspired by the tradition of artistic and cartographic visualizations typically found in bird"s-eye view and panoramic maps. We define a collection of city model components and a real-time multi-pass rendering algorithm that achieves comprehensible, abstract 3D city model depictions based on edge enhancement, color-based and shadow-based depth cues, and procedural facade texturing. Illustrative visualization provides an effective visual interface to urban spatial information and associated thematic information complementing visual interfaces based on the Virtual Reality paradigm, offering a huge potential for graphics design. Primary application areas include city and landscape planning, cartoon worlds in computer games, and tourist information systems.

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

Juffmann, Thomas; Koppell, Stewart A.; Klopfer, Brannon B.

Feynman once asked physicists to build better electron microscopes to be able to watch biology at work. While electron microscopes can now provide atomic resolution, electron beam induced specimen damage precludes high resolution imaging of sensitive materials, such as single proteins or polymers. Here, we use simulations to show that an electron microscope based on a multi-pass measurement protocol enables imaging of single proteins, without averaging structures over multiple images. While we demonstrate the method for particular imaging targets, the approach is broadly applicable and is expected to improve resolution and sensitivity for a range of electron microscopy imaging modalities,more » including, for example, scanning and spectroscopic techniques. The approach implements a quantum mechanically optimal strategy which under idealized conditions can be considered interaction-free.« less

Method for optical pumping of thin laser media at high average power

DOEpatents

Zapata, Luis E [Livermore, CA; Beach, Raymond J [Livermore, CA; Honea, Eric C [Sunol, CA; Payne, Stephen A [Castro Valley, CA

2004-07-13

A thin, planar laser material is bonded to a light guide of an index-matched material forming a composite disk. Diode array or other pump light is introduced into the composite disk through the edges of the disk. Pump light trapped within the composite disk depletes as it multi-passes the laser medium before reaching an opposing edge of the disk. The resulting compound optical structure efficiently delivers concentrated pump light and to a laser medium of minimum thickness. The external face of the laser medium is used for cooling. A high performance cooler attached to the external face of the laser medium rejects heat. Laser beam extraction is parallel to the heat flux to minimize optical distortions.

Application of a broadly tunable SG-DBR QCL for multi-species trace gas spectroscopy.

PubMed

Diba, Abdou S; Xie, Feng; Gross, Barry; Hughes, Lawrence C; Zah, Chung-en; Moshary, Fred

2015-10-19

Feasibility of using a mid-Infrared tunable sampled-grating distributed Bragg reflectors quantum cascade laser for high resolution multicomponent trace gas spectroscopy is demonstrated. By controlling the driving currents to the front and back sections of the laser, we were able to tune a pulsed 4.55 µm laser over a frequency range a of 30 cm(-1) with high resolution, accuracy and repeatability. The laser was applied to absorption spectroscopy of ambient and reduced pressure (150 Torr) air in a 205 meters multi-pass Herriott cell, and by using standard LSQ fitting to a spectral database of these trace gases (HITRAN), the concentrations of nitrous oxide, carbon monoxide, and water vapor were retrieved.

Gated frequency-resolved optical imaging with an optical parametric amplifier

DOEpatents

Cameron, S.M.; Bliss, D.E.; Kimmel, M.W.; Neal, D.R.

1999-08-10

A system for detecting objects in a turbid media utilizes an optical parametric amplifier as an amplifying gate for received light from the media. An optical gating pulse from a second parametric amplifier permits the system to respond to and amplify only ballistic photons from the object in the media. 13 figs.

Gated frequency-resolved optical imaging with an optical parametric amplifier

DOEpatents

Cameron, Stewart M.; Bliss, David E.; Kimmel, Mark W.; Neal, Daniel R.

1999-01-01

A system for detecting objects in a turbid media utilizes an optical parametric amplifier as an amplifying gate for received light from the media. An optical gating pulse from a second parametric amplifier permits the system to respond to and amplify only ballistic photons from the object in the media.

Study of beam aberrations in a germanium XXIII XUV laser amplifier

NASA Astrophysics Data System (ADS)

Smith, C. G.; Key, M. H.; Cairns, G.; Dwivedi, L.; Krishnan, J.; Lewis, C. L. S.; MacPhee, A. G.; Neely, D.; Ramsden, S. A.; Tallents, G.

1996-02-01

A beam of amplified spontaneous emission at {23.2}/{23.6}nm from a GeXXIII XUV laser has been injected into a separate amplifier plasma and the astigmatic aberrations introduced by plasma density gradients in the amplifier have been estimated from analysis of images of the amplified beam.

S-band low noise amplifier and 40 kW high power amplifier subsystems of Japanese Deep Space Earth Station

NASA Astrophysics Data System (ADS)

Honma, K.; Handa, K.; Akinaga, W.; Doi, M.; Matsuzaki, O.

This paper describes the design and the performance of the S-band low noise amplifier and the S-band high power amplifier that have been developed for the Usuda Deep Space Station of the Institute of Space and Astronautical Science (ISAS), Japan. The S-band low noise amplifier consists of a helium gas-cooled parametric amplifier followed by three-stage FET amplifiers and has a noise temperature of 8 K. The high power amplifier is composed of two 28 kW klystrons, capable of transmitting 40 kW continuously when two klystrons are combined. Both subsystems are operating quite satisfactorily in the tracking of Sakigake and Suisei, the Japanese interplanetary probes for Halley's comet exploration, launched by ISAS in 1985.

A low-noise current-sensitive amplifier-discriminator system for beta particle counting.

PubMed

Sephton, J P; Johansson, L C; Williams, J M

2008-01-01

NPL has developed a low-noise current amplifier/discriminator system for radionuclides that emit low-energy electrons and X-rays. The new beta amplifier is based on the low-noise Amptek A-250 operational amplifier. The design has been configured for optimum signal to noise ratio. The new amplifier is described and results obtained using primarily electron-capture decaying radionuclides are presented. The new amplifier gives rise to higher particle detection efficiency than the previously used Atomic Energy of Canada Limited-designed amplifier. This is shown by measurements of (54)Mn and (65)Zn. The counting plateaux are significantly longer and have reduced gradients.

Low phase noise oscillator using two parallel connected amplifiers

NASA Technical Reports Server (NTRS)

Kleinberg, Leonard L.

1987-01-01

A high frequency oscillator is provided by connecting two amplifier circuits in parallel where each amplifier circuit provides the other amplifier circuit with the conditions necessary for oscillation. The inherent noise present in both amplifier circuits causes the quiescent current, and in turn, the generated frequency, to change. The changes in quiescent current cause the transconductance and the load impedance of each amplifier circuit to vary, and this in turn results in opposing changes in the input susceptance of each amplifier circuit. Because the changes in input susceptance oppose each other, the changes in quiescent current also oppose each other. The net result is that frequency stability is enhanced.

The warm, rich sound of valve guitar amplifiers

NASA Astrophysics Data System (ADS)

Keeports, David

2017-03-01

Practical solid state diodes and transistors have made glass valve technology nearly obsolete. Nevertheless, valves survive largely because electric guitar players much prefer the sound of valve amplifiers to the sound of transistor amplifiers. This paper discusses the introductory-level physics behind that preference. Overdriving an amplifier adds harmonics to an input sound. While a moderately overdriven valve amplifier produces strong even harmonics that enhance a sound, an overdriven transistor amplifier creates strong odd harmonics that can cause dissonance. The functioning of a triode valve explains its creation of even and odd harmonics. Music production software enables the examination of both the wave shape and the harmonic content of amplified sounds.

Multifrequency Raman amplifiers

NASA Astrophysics Data System (ADS)

Barth, Ido; Fisch, Nathaniel J.

2018-03-01

In its usual implementation, the Raman amplifier features only one pump carrier frequency. However, pulses with well-separated frequencies can also be Raman amplified while compressed in time. Amplification with frequency-separated pumps is shown to hold even in the highly nonlinear, pump-depletion regime, as derived through a fluid model, and demonstrated via particle-in-cell simulations. The resulting efficiency is similar to single-frequency amplifiers, but, due to the beat-wave waveform of both the pump lasers and the amplified seed pulses, these amplifiers feature higher seed intensities with a shorter spike duration. Advantageously, these amplifiers also suffer less noise backscattering, because the total fluence is split between the different spectral components.

Effect of mid-term drought on Quercus pubescens BVOCs' emission seasonality and their dependency on light and/or temperature

NASA Astrophysics Data System (ADS)

Saunier, Amélie; Ormeño, Elena; Boissard, Christophe; Wortham, Henri; Temime-Roussel, Brice; Lecareux, Caroline; Armengaud, Alexandre; Fernandez, Catherine

2017-06-01

Biogenic volatile organic compounds (BVOCs) emitted by plants represent a large source of carbon compounds released into the atmosphere, where they account for precursors of tropospheric ozone and secondary organic aerosols. Being directly involved in air pollution and indirectly in climate change, understanding what factors drive BVOC emissions is a prerequisite for modeling their emissions and predict air pollution. The main algorithms currently used to model BVOC emissions are mainly light and/or temperature dependent. Additional factors such as seasonality and drought also influence isoprene emissions, especially in the Mediterranean region, which is characterized by a rather long drought period in summer. These factors are increasingly included in models but only for the principal studied BVOC, namely isoprene, but there are still some discrepancies in estimations of emissions. In this study, the main BVOCs emitted by Quercus pubescens - isoprene, methanol, acetone, acetaldehyde, formaldehyde, MACR, MVK and ISOPOOH (these three last compounds detected under the same m/z) - were monitored with a PTR-ToF-MS over an entire seasonal cycle during both in situ natural and amplified drought, which is expected with climate change. Amplified drought impacted all studied BVOCs by reducing emissions in spring and summer while increasing emissions in autumn. All six BVOCs monitored showed daytime light and temperature dependencies while three BVOCs (methanol, acetone and formaldehyde) also showed emissions during the night despite the absence of light under constant temperature. Moreover, methanol and acetaldehyde burst in the early morning and formaldehyde deposition and uptake were also punctually observed, which were not assessed by the classical temperature and light models.

Bio-isolated dc operational amplifier. [for bioelectric measurements

NASA Technical Reports Server (NTRS)

Lee, R. D. (Inventor)

1974-01-01

A bio-isolated dc operational amplifier is described for use in making bioelectrical measurements of a patient while providing isolation of the patient from electrical shocks. The circuit contains a first operational amplifier coupled to the patient with its output coupled in a forward loop through a first optic coupler to a second operational amplifier. The output of the second operational amplifier is coupled to suitable monitoring circuitry via a feedback circuit including a second optic coupler to the input of the first operational amplifier.

Direct Current Amplifier. Report No. 92; AMPLIFICADOR DE CORRIENTE CONTINUA. Informe No. 92

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

Marazzi, C.

1963-01-01

A direct-current amplifier with low zero current and solid-state chopper for input is described. This amplifier can be used in control circuits and for general applications such as temperature measurement in thermocouples, amplifier for a photo-sensitive element, or zero amplifier in control systems. The input impedance is relatively low, serving principally as current amplifier. It is possible to obtain a symmetry characteristic for positive and negative values of the output voltage with respect to the input. (tr-auth)

Laser amplifier chain

DOEpatents

Hackel, Richard P.

1992-01-01

A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1985-01-01

This semiannual progress report covers the period from April 1, 1985 to Sept. 30, 1985 under NASA grant NAS1-441 entitled direct solar pumped iodine laser amplifier. During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator was carried out before the amplifier studies. The amplifier studies are postponed to the extended period following completion of the parametric studies. In addition, the kinetic modeling of a solar pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) the radiation characteristics of solar simulator and the parametric characteristics of photodissociation iodine laser continuously pumped by a Vortek solar simulator; (2) kinetic modeling of a solar pumped iodine laser amplifier; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

High temperature charge amplifier for geothermal applications

DOEpatents

Lindblom, Scott C.; Maldonado, Frank J.; Henfling, Joseph A.

2015-12-08

An amplifier circuit in a multi-chip module includes a charge to voltage converter circuit, a voltage amplifier a low pass filter and a voltage to current converter. The charge to voltage converter receives a signal representing an electrical charge and generates a voltage signal proportional to the input signal. The voltage amplifier receives the voltage signal from the charge to voltage converter, then amplifies the voltage signal by the gain factor to output an amplified voltage signal. The lowpass filter passes low frequency components of the amplified voltage signal and attenuates frequency components greater than a cutoff frequency. The voltage to current converter receives the output signal of the lowpass filter and converts the output signal to a current output signal; wherein an amplifier circuit output is selectable between the output signal of the lowpass filter and the current output signal.

Multifrequency Raman amplifiers

DOE PAGES

Barth, Ido; Fisch, Nathaniel J.

2018-03-08

In its usual implementation, the Raman amplifier features only one pump carrier frequency. However, pulses with well-separated frequencies can also be Raman amplified while compressed in time. Amplification with frequency-separated pumps is shown to hold even in the highly nonlinear, pump-depletion regime, as derived through a fluid model, and demonstrated via particle-in-cell (PIC) simulations. The resulting efficiency is similar to single-frequency amplifiers, but, due to the beat-wave waveform of both the pump lasers and the amplified seed pulses, these amplifiers feature higher seed intensities with a shorter spike duration. Advantageously, these amplifiers also suffer less noise backscattering, because the totalmore » fluence is split between the different spectral components.« less

Multifrequency Raman amplifiers

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

Barth, Ido; Fisch, Nathaniel J.

In its usual implementation, the Raman amplifier features only one pump carrier frequency. However, pulses with well-separated frequencies can also be Raman amplified while compressed in time. Amplification with frequency-separated pumps is shown to hold even in the highly nonlinear, pump-depletion regime, as derived through a fluid model, and demonstrated via particle-in-cell (PIC) simulations. The resulting efficiency is similar to single-frequency amplifiers, but, due to the beat-wave waveform of both the pump lasers and the amplified seed pulses, these amplifiers feature higher seed intensities with a shorter spike duration. Advantageously, these amplifiers also suffer less noise backscattering, because the totalmore » fluence is split between the different spectral components.« less

Simple two-electrode biosignal amplifier.

PubMed

Dobrev, D; Neycheva, T; Mudrov, N

2005-11-01

A simple, cost effective circuit for a two-electrode non-differential biopotential amplifier is proposed. It uses a 'virtual ground' transimpedance amplifier and a parallel RC network for input common mode current equalisation, while the signal input impedance preserves its high value. With this innovative interface circuit, a simple non-inverting amplifier fully emulates high CMRR differential. The amplifier equivalent CMRR (typical range from 70-100 dB) is equal to the open loop gain of the operational amplifier used in the transimpedance interface stage. The circuit has very simple structure and utilises a small number of popular components. The amplifier is intended for use in various two-electrode applications, such as Holter-type monitors, defibrillators, ECG monitors, biotelemetry devices etc.

Mushu, a free- and open source BCI signal acquisition, written in Python.

PubMed

Venthur, Bastian; Blankertz, Benjamin

2012-01-01

The following paper describes Mushu, a signal acquisition software for retrieval and online streaming of Electroencephalography (EEG) data. It is written, but not limited, to the needs of Brain Computer Interfacing (BCI). It's main goal is to provide a unified interface to EEG data regardless of the amplifiers used. It runs under all major operating systems, like Windows, Mac OS and Linux, is written in Python and is free- and open source software licensed under the terms of the GNU General Public License.

The ISEE-C plasma wave investigation

NASA Technical Reports Server (NTRS)

Scarf, F. L.; Fredricks, R. W.; Gurnett, D. A.; Smith, E. J.

1978-01-01

The ISEE-C plasma wave investigation is designed to provide comprehensive information on interplanetary wave-particle interactions. Three spectrum analyzers with a total of 19 bandpass channels cover the frequency range 0.3 Hz to 100 kHz. The main analyzer, which uses 16 continuously active amplifiers, gives two complete spectral scans per second in each of 16 filter channels. The instrument sensors include a high-sensitivity magnetic search coil, and electric antennas with effective lengths of 0.6 and 45 m.

Distinct transcriptional MYCN/c-MYC activities are associated with spontaneous regression or malignant progression in neuroblastomas

PubMed Central

Westermann, Frank; Muth, Daniel; Benner, Axel; Bauer, Tobias; Henrich, Kai-Oliver; Oberthuer, André; Brors, Benedikt; Beissbarth, Tim; Vandesompele, Jo; Pattyn, Filip; Hero, Barbara; König, Rainer; Fischer, Matthias; Schwab, Manfred

2008-01-01

Background Amplified MYCN oncogene resulting in deregulated MYCN transcriptional activity is observed in 20% of neuroblastomas and identifies a highly aggressive subtype. In MYCN single-copy neuroblastomas, elevated MYCN mRNA and protein levels are paradoxically associated with a more favorable clinical phenotype, including disseminated tumors that subsequently regress spontaneously (stage 4s-non-amplified). In this study, we asked whether distinct transcriptional MYCN or c-MYC activities are associated with specific neuroblastoma phenotypes. Results We defined a core set of direct MYCN/c-MYC target genes by applying gene expression profiling and chromatin immunoprecipitation (ChIP, ChIP-chip) in neuroblastoma cells that allow conditional regulation of MYCN and c-MYC. Their transcript levels were analyzed in 251 primary neuroblastomas. Compared to localized-non-amplified neuroblastomas, MYCN/c-MYC target gene expression gradually increases from stage 4s-non-amplified through stage 4-non-amplified to MYCN amplified tumors. This was associated with MYCN activation in stage 4s-non-amplified and predominantly c-MYC activation in stage 4-non-amplified tumors. A defined set of MYCN/c-MYC target genes was induced in stage 4-non-amplified but not in stage 4s-non-amplified neuroblastomas. In line with this, high expression of a subset of MYCN/c-MYC target genes identifies a patient subtype with poor overall survival independent of the established risk markers amplified MYCN, disease stage, and age at diagnosis. Conclusions High MYCN/c-MYC target gene expression is a hallmark of malignant neuroblastoma progression, which is predominantly driven by c-MYC in stage 4-non-amplified tumors. In contrast, moderate MYCN function gain in stage 4s-non-amplified tumors induces only a restricted set of target genes that is still compatible with spontaneous regression. PMID:18851746

Log amplifier with pole-zero compensation

DOEpatents

Brookshier, William

1987-01-01

A logarithmic amplifier circuit provides pole-zero compensation for improved stability and response time over 6-8 decades of input signal frequency. The amplifier circuit includes a first operational amplifier with a first feedback loop which includes a second, inverting operational amplifier in a second feedback loop. The compensated output signal is provided by the second operational amplifier with the log elements, i.e., resistors, and the compensating capacitors in each of the feedback loops having equal values so that each break point or pole is offset by a compensating break point or zero.

Laser amplifier chain

DOEpatents

Hackel, R.P.

1992-10-20

A laser amplifier chain has a plurality of laser amplifiers arranged in a chain to sequentially amplify a low-power signal beam to produce a significantly higher-power output beam. Overall efficiency of such a chain is improved if high-gain, low efficiency amplifiers are placed on the upstream side of the chain where only a very small fraction of the total pumped power is received by the chain and low-gain, high-efficiency amplifiers are placed on the downstream side where a majority of pumping energy is received by the chain. 6 figs.

Characterization of a Common-Gate Amplifier Using Ferroelectric Transistors

NASA Technical Reports Server (NTRS)

Hunt, Mitchell; Sayyah, Rana; MacLeod, Todd C.; Ho, Fat D.

2011-01-01

In this paper, the empirical data collected through experiments performed using a FeFET in the common-gate amplifier circuit is presented. The FeFET common-gate amplifier was characterized by varying all parameters in the circuit, such as load resistance, biasing of the transistor, and input voltages. Due to the polarization of the ferroelectric layer, the particular behavior of the FeFET common-gate amplifier presents interesting results. Furthermore, the differences between a FeFET common-gate amplifier and a MOSFET common-gate amplifier are examined.

Application of a three-lens slit spatial filter in high power lasers

NASA Astrophysics Data System (ADS)

Xiong, Han

2018-07-01

Combined with partial parameters in National Ignition Facility, the conceptual design of off-axial four-pass main laser optical system with a three-lens slit spatial filter has been discussed. Since the three-lens slit spatial filter can decline the focal intensity by about 3 orders of magnitudes than that in NIF system, the cutoff frequency in main amplifier cavity can be reduced from 51 × DL to 39 × DL for better beam quality. The main laser system for single beam line can be shortened from 174.7 m to 155.7 m and the spatial filter in high vacuum becomes 60 m instead of the original 83.5 m. Additionally, the pinhole closure could be avoided since the declining of focal intensity in slit spatial filter and the absence of pinhole aperture in the other (pinhole) spatial filter, which provides new ideas for the future high-power lasers.

Amplifiers in the radio-electronic equipment of aircraft

NASA Astrophysics Data System (ADS)

Khol'Nyi, Vladimir Ia.

The applications, classification, and technical specifications of airborne electronic amplifiers are discussed. Particular attention is given to the general design and principles of operation of single amplification cascades and multicascade amplifiers, including dc, audio, and video amplifiers used as part of the radio-electronic equipment of modern aircraft. The discussion also covers the principal technical and performance characteristics of various amplifiers, their operating conditions, service, and repair.

Multistaged stokes injected Raman capillary waveguide amplifier

DOEpatents

Kurnit, Norman A.

1980-01-01

A multistaged Stokes injected Raman capillary waveguide amplifier for providing a high gain Stokes output signal. The amplifier uses a plurality of optically coupled capillary waveguide amplifiers and one or more regenerative amplifiers to increase Stokes gain to a level sufficient for power amplification. Power amplification is provided by a multifocused Raman gain cell or a large diameter capillary waveguide. An external source of CO.sub.2 laser radiation can be injected into each of the capillary waveguide amplifier stages to increase Raman gain. Devices for injecting external sources of CO.sub.2 radiation include: dichroic mirrors, prisms, gratings and Ge Brewster plates. Alternatively, the CO.sub.2 input radiation to the first stage can be coupled and amplified between successive stages.

Note: Development of a wideband amplifier for cryogenic scanning tunneling microscopy.

PubMed

Zhang, Chao; Jeon, Hoyeon; Oh, Myungchul; Lee, Minjun; Kim, Sungmin; Yi, Sunwouk; Lee, Hanho; Zoh, Inhae; Yoo, Yongchan; Kuk, Young

2017-06-01

A wideband cryogenic amplifier has been developed for low temperature scanning tunneling microscopy. The amplifier consisting of a wideband complementary metal oxide semiconductor field effect transistors operational amplifier together with a feedback resistor of 100 kΩ and a capacitor is mounted within a 4 K Dewar. This amplifier has a wide bandwidth and is successfully applied to scanning tunneling microscopy applications at low temperatures down to ∼7 K. The quality of the designed amplifier is validated by high resolution imaging. More importantly, the amplifier has also proved to be capable of performing scanning tunneling spectroscopy measurements, showing the detection of the Shockley surface state of the Au(111) surface and the superconducting gap of Nb(110).

Note: Development of a wideband amplifier for cryogenic scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Zhang, Chao; Jeon, Hoyeon; Oh, Myungchul; Lee, Minjun; Kim, Sungmin; Yi, Sunwouk; Lee, Hanho; Zoh, Inhae; Yoo, Yongchan; Kuk, Young

2017-06-01

A wideband cryogenic amplifier has been developed for low temperature scanning tunneling microscopy. The amplifier consisting of a wideband complementary metal oxide semiconductor field effect transistors operational amplifier together with a feedback resistor of 100 kΩ and a capacitor is mounted within a 4 K Dewar. This amplifier has a wide bandwidth and is successfully applied to scanning tunneling microscopy applications at low temperatures down to ˜7 K. The quality of the designed amplifier is validated by high resolution imaging. More importantly, the amplifier has also proved to be capable of performing scanning tunneling spectroscopy measurements, showing the detection of the Shockley surface state of the Au(111) surface and the superconducting gap of Nb(110).

High-efficiency solid state power amplifier

NASA Technical Reports Server (NTRS)

Wallis, Robert E. (Inventor); Cheng, Sheng (Inventor)

2005-01-01

A high-efficiency solid state power amplifier (SSPA) for specific use in a spacecraft is provided. The SSPA has a mass of less than 850 g and includes two different X-band power amplifier sections, i.e., a lumped power amplifier with a single 11-W output and a distributed power amplifier with eight 2.75-W outputs. These two amplifier sections provide output power that is scalable from 11 to 15 watts without major design changes. Five different hybrid microcircuits, including high-efficiency Heterostructure Field Effect Transistor (HFET) amplifiers and Monolithic Microwave Integrated Circuit (MMIC) phase shifters have been developed for use within the SSPA. A highly efficient packaging approach enables the integration of a large number of hybrid circuits into the SSPA.

Ferroelectric Field-Effect Transistor Differential Amplifier Circuit Analysis

NASA Technical Reports Server (NTRS)

Phillips, Thomas A.; MacLeod, Todd C.; Ho, Fat D.

2008-01-01

There has been considerable research investigating the Ferroelectric Field-Effect Transistor (FeFET) in memory circuits. However, very little research has been performed in applying the FeFET to analog circuits. This paper investigates the use of FeFETs in a common analog circuit, the differential amplifier. The two input Metal-Oxide-Semiconductor (MOS) transistors in a general MOS differential amplifier circuit are replaced with FeFETs. Resistors are used in place of the other three MOS transistors. The FeFET model used in the analysis has been previously reported and was based on experimental device data. Because of the FeFET hysteresis, the FeFET differential amplifier has four different operating modes depending on whether the FeFETs are positively or negatively polarized. The FeFET differential amplifier operation in the different modes was analyzed by calculating the amplifier voltage transfer and gain characteristics shown in figures 2 through 5. Comparisons were made between the FeFET differential amplifier and the standard MOS differential amplifier. Possible applications and benefits of the FeFET differential amplifier are discussed.

Characterization of hydrocortisone bioconversion and 16S RNA gene in Synechococcus nidulans cultures.

PubMed

Rasoul-Amini, S; Ghasemi, Y; Morowvat, M H; Ghoshoon, M B; Raee, M J; Mosavi-Azam, S B; Montazeri-Najafabady, N; Nouri, F; Parvizi, R; Negintaji, N; Khoubani, S

2010-01-01

A unicellular cyanobacterium, Synechococcus nidulans (Pringsheim) Komárek, was isolated from paddy-fields and applied in the biotransformation experiment of hydrocortisone (1). This strain has not been previously tested for steroid bioconversion. Fermentation was carried out in BG-11 medium supplemented with 0.05% substrate at 25 degrees C for 14 days of incubation. The obtained products were chromatographically purified followed by their characterization using spectroscopic methods. 11beta,17beta-dihydroxyandrost-4-en-3-one (2), 11beta-hydroxyandrost-4-en-3,17-dione (3), and androst-4-ene-3,17-dione (4) were the main bioproducts in the hydrocortisone bioconversion. The observed bioreaction characteristics were the side chain degradation of the substrate to prepare compounds (2) and (3) following the 11beta-dehydroxylation for accumulation of the compound (4). Time course study showed the accumulation of the product (2) from the second day of the fermentation and compounds (3) and (4) from the third day. All the metabolites reached their maximum concentration in seven days. Cyanobacterial 16S rRNA gene was also amplified by PCR. Sequences were amplified using the universal prokaryotic primers which amplify a approximately 400-bp region of the 16S rRNA gene. PCR products were sequenced to confirm their authenticity as 16S rRNA gene of cyanobacteria. The result of PCR blasted with other sequenced cyanobacteria in NCBI showed 99% identity to the 16S small subunit rRNA of seven Synechococcus species.

The development and progress of XeCl Excimer laser system

NASA Astrophysics Data System (ADS)

Zhang, Yongsheng; Ma, Lianying; Wang, Dahui; Zhao, Xueqing; Zhu, Yongxiang; Hu, Yun; Qian, Hang; Shao, Bibo; Yi, Aiping; Liu, Jingru

2015-05-01

A large angularly multiplexed XeCl Excimer laser system is under development at the Northwest Institute of Nuclear Technology (NINT). It is designed to explore the technical issues of uniform and controllable target illumination. Short wavelength, uniform and controllable target illumination is the fundamental requirement of high energy density physics research using large laser facility. With broadband, extended light source and multi-beam overlapping techniques, rare gas halide Excimer laser facility will provide uniform target illumination theoretically. Angular multiplexing and image relay techniques are briefly reviewed and some of the limitations are examined to put it more practical. The system consists of a commercial oscillator front end, three gas discharge amplifiers, two electron beam pumped amplifiers and the optics required to relay, encode and decode the laser beam. An 18 lens array targeting optics direct and focus the laser in the vacuum target chamber. The system is operational and currently undergoing tests. The total 18 beams output energy is more than 100J and the pulse width is 7ns (FWHM), the intensities on the target will exceed 1013W/cm2. The aberration of off-axis imaging optics at main amplifier should be minimized to improve the final image quality at the target. Automatic computer controlled alignment of the whole system is vital to efficiency and stability of the laser system, an array of automatic alignment model is under test and will be incorporated in the system soon.

HERMES travels by CAN bus

NASA Astrophysics Data System (ADS)

Waller, Lewis G.; Shortridge, Keith; Farrell, Tony J.; Vuong, Minh; Muller, Rolf; Sheinis, Andrew I.

2014-07-01

The new HERMES spectrograph represents the first foray by AAO into the use of commercial off-the-shelf industrial field bus technology for instrument control, and we regard the final system, with its relatively simple wiring requirements, as a great success. However, both software and hardware teams had to work together to solve a number of problems integrating the chosen CANopen/CAN bus system into our normal observing systems. A Linux system running in an industrial PC chassis ran the HERMES control software, using a PCI CAN bus interface connected to a number of distributed CANopen/CAN bus I/O devices and servo amplifiers. In the main, the servo amplifiers performed impressively, although some experimentation with homing algorithms was required, and we hit a significant hurdle when we discovered that we needed to disable some of the encoders used during observations; we learned a lot about how servo amplifiers respond when their encoders are turned off, and about how encoders react to losing power. The software was based around a commercial CANopen library from Copley Controls. Early worries about how this heavily multithreaded library would work with our standard data acquisition system led to the development of a very low-level CANopen software simulator to verify the design. This also enabled the software group to develop and test almost all the control software well in advance of the construction of the hardware. In the end, the instrument went from initial installation at the telescope to successful commissioning remarkably smoothly.

Automatic quadrature control and measuring system

NASA Technical Reports Server (NTRS)

Hamlet, J. F.

1973-01-01

Quadrature is separated from amplified signal by use of phase detector, with phase shifter providing appropriate reference. Output of phase detector is further amplified and filtered by dc amplifier. Output of dc amplifier provides signal to neutralize quadrature component of transducer signal.

Measurements of the Low Frequency Gain Fluctuations of a 30 GHz High-Electron-Mobility-Transistor Cryogenic Amplifier

NASA Technical Reports Server (NTRS)

Jarosik, Norman

1994-01-01

Low frequency gain fluctuations of a 30 GHz cryogenic HEMT amplifier have been measured with the input of the amplifier connected to a 15 K load. Effects of fluctuations of other components of the test set-up were eliminated by use of a power-power correlation technique. Strong correlation between output power fluctuations of the amplifier and drain current fluctuations of the transistors comprising the amplifier are observed. The existence of these correlations introduces the possibility of regressing some of the excess noise from the HEMT amplifier's output using the measured drain currents.

Successful isolation of Leishmania infantum from Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) collected from naturally infected dogs.

PubMed

Medeiros-Silva, Viviane; Gurgel-Gonçalves, Rodrigo; Nitz, Nadjar; Morales, Lucia Emilia D' Anduraim; Cruz, Laurício Monteiro; Sobral, Isabele Gonçalves; Boité, Mariana Côrtes; Ferreira, Gabriel Eduardo Melim; Cupolillo, Elisa; Romero, Gustavo Adolfo Sierra

2015-10-09

The main transmission route of Leishmania infantum is through the bites of sand flies. However, alternative mechanisms are being investigated, such as through the bites of ticks, which could have epidemiological relevance. The objective of this work was to verify the presence of Leishmania spp. in Rhipicephalus sanguineus sensu lato collected from naturally infected dogs in the Federal District of Brazil. Ticks were dissected to remove their intestines and salivary glands for DNA extraction and the subsequent amplification of the conserved region of 120 bp of kDNA and 234 bp of the hsp70 gene of Leishmania spp. The amplified kDNA products were digested with endonucleases HaeIII and BstUI and were submitted to DNA sequencing. Isolated Leishmania parasites from these ticks were analyzed by multilocus enzyme electrophoresis, and the DNA obtained from this culture was subjected to microsatellite analyses. Overall, 130 specimens of R. sanguineus were collected from 27 dogs. Leishmania spp. were successfully isolated in culture from five pools of salivary glands and the intestines of ticks collected from four dogs. The amplified kDNA products from the dog blood samples and from the tick cultures, when digested by HaeIII and BstUI, revealed the presence of L. braziliensis and L. infantum. One strain was cultivated and characterized as L. infantum by enzyme electrophoresis. The amplified kDNA products from the blood of one dog showed a sequence homology with L. braziliensis; however, the amplified kDNA from the ticks collected from this dog showed a sequence homology to L. infantum. The results confirm that the specimens of R. sanguineus that feed on dogs naturally infected by L. infantum contain the parasite DNA in their intestines and salivary glands, and viable L. infantum can be successfully isolated from these ectoparasites.

High power green lasers for gamma source

NASA Astrophysics Data System (ADS)

Durand, Magali; Sevillano, Pierre; Alexaline, Olivier; Sangla, Damien; Casanova, Alexis; Aubourg, Adrien; Saci, Abdelhak; Courjaud, Antoine

2018-02-01

A high intensity Gamma source is required for Nuclear Spectroscopy, it will be delivered by the interaction between accelerated electron and intense laser beams. Those two interactions lasers are based on a multi-stage amplification scheme that ended with a second harmonics generation to deliver 200 mJ, 5 ps pulses at 515 nm and 100 Hz. A t-Pulse oscillator with slow and fast feedback loop implemented inside the oscillator cavity allows the possibility of synchronization to an optical reference. A temporal jitter of 120 fs rms is achieved, integrated from 10 Hz to 10 MHz. Then a regenerative amplifier, based on Yb:YAG technology, pumped by fiber-coupled QCW laser diodes, delivers pulses up to 30 mJ. The 1 nm bandwidth was compressed to 1.5 ps with a good spatial quality: M2 of 1.1. This amplifier is integrated in a compact sealed housing (750 x 500 x 150 mm), which allows a pulse-pulse stability of 0.1 % rms, and a long-term stability of 1,9 % over 100 hours (with +/-1°C environment). The main amplification stage uses a cryocooled Yb:YAG crystal in an active mirror configuration. The crystal is cooled at 130 K via a compact and low-vibration cryocooler, avoiding any additional phase noise contribution, 340 mJ in a six pass scheme was achieved, with 0.9 of Strehl ratio. The trade off to the gain of a cryogenic amplifier is the bandwidth reduction, however the 1030 nm pulse was compressed to 4.4 ps. As for the regenerative amplifier a long-term stability of 1.9 % over 30 hours was achieved in an environment with +/-1°C temperature fluctuations The compression and Second Harmonics Generation Stages have allowed the conversion of 150 mJ of uncompressed infrared beam into 60 mJ at 515 nm.

Millimeter-Wave GaN MMIC Integration with Additive Manufacturing

NASA Astrophysics Data System (ADS)

Coffey, Michael

This thesis addresses the analysis, design, integration and test of microwave and millimeter-wave monolithic microwave integrated circuits (MMIC or MMICs). Recent and ongoing progress in semiconductor device fabrication and MMIC processing technology has pushed the upper limit in MMIC frequencies from millimeter-wave (30-300 GHz) to terahertz (300-3000 GHz). MMIC components operating at these frequencies will be used to improve the sensitivity and performance of radiometers, receivers for communication systems, passive remote sensing systems, transceivers for radar instruments and radio astronomy systems. However, a serious hurdle in the utilization of these MMIC components, and a main topic presented in this thesis, is the development and reliable fabrication of practical packaging techniques. The focus of this thesis is the investigation of first, the design and analysis of microwave and millimeter-wave GaN MMICs and second, the integration of those MMICs into usable waveguide components. The analysis, design and testing of various X-band (8-12 GHz) thru H-band (170-260 GHz) GaN MMIC power amplifier (PA or PAs), including a V-band (40-75 GHz) voltage controlled oscillator, is the majority of this work. Several PA designs utilizing high-efficiency techniques are analyzed, designed and tested. These examples include a 2nd harmonic injection amplifier, a Class-E amplifier fabricated with a GaN-on-SiC 300 GHz fT process, and an example of the applicability of supply-modulation with a Doherty power amplifier, all operating at 10 GHz. Two H-band GaN MMIC PAs are designed, one with integrated CPW-to-waveguide transitions for integration. The analysis of PA stability is especially important for wideband, high- fT devices and a new way of analyzing stability is explored and experimentally validated. Last, the challenges of integrating MMICs operating at millimeter-wave frequencies are discussed and assemblies using additive and traditional manufacturing are demonstrated.

Three-beam coherent combination experiments based on segmented mirrors and measure of phase characteristics of beams passing through Yb-doped fiber amplifier

NASA Astrophysics Data System (ADS)

Yang, Ping; Yang, Ruo fu; Shen, Feng; Ao, Mingwu; Jiang, Wenhan

2009-05-01

Coherent combination is one of the most promising ways to realize high power laser output. A three- laser-beam coherent combination system based on adaptive optics (AO) technique has been set up in our laboratory. In this system, three 1064nm laser beams are placed side-by-side and compressed by two reflective mirrors. An active segmented deformable mirror (DM) is used to compensate the optical path difference (OPD) among three laser beams. The beams are overlapped onto a 2900Hz CCD camera to form an interference pattern while the peak intensity of the interference pattern is taken as the cost function to optimize by a stochastic parallel gradient descent (SPGD) algorithm. SPGD algorithm is realized on a RT-Linux dual-core industrial computer. A series of experiments have been accomplished and experimental results show that both static distorted aberrations in the beams and active distorted aberrations (which are brought in by a hot iron and the frequency is about 5Hz) can be compensated successfully when the gain coefficients and the perturbation amplitude of SPGD are chosed appropriately, thereby three beams can be well combined. For controlling the phase of fiber lasers, the phase characteristics of beams passing through Yb-doped dual-clad fiber amplifier are measured by means of investigating the interference pattern under different output power through experiments. The frequency of phase fluctuation is evaluated through analyzing the fluctuation of power within a 90um aperture of far-field focal spot. Experimental results show that the phase fluctuation frequencies of laser beam transmitted through fiber amplifier are mainly in the range of 100~1500Hz. As a result, to control the phase fluctuation of beams passing through fiber amplifier, the bandwidth of any potential phase control scheme must be greater than 1.5 kilohertz.

Angle amplifier based on multiplexed volume holographic gratings

NASA Astrophysics Data System (ADS)

Cao, Liangcai; Zhao, Yifei; He, Qingsheng; Jin, Guofan

2008-03-01

Angle amplifier of laser beam scanner is a widely used device in optical systems. Volume holographic optical elements can be applied in the angle amplifier. Compared with the traditional angle amplifier, it has the advantages of high angle resolution, high diffraction efficiency, small size, and high angle magnification and flexible design. Bragg anglewavelength- compensating recording method is introduced. Because of the Bragg compensatory relation between angle and wavelength, this device could be recorded at another wavelength. The design of the angle amplifier recording at the wavelength of 514.2nm for the working wavelength of 632.8nm is described. An optical setup for recording the angle amplifier device is designed and discussed. Experimental results in the photorefractive crystal Fe:LiNbO 3 demonstrate the feasibility of the angle amplifier scheme.

Controlling the 1 μm spontaneous emission in Er/Yb co-doped fiber amplifiers.

PubMed

Sobon, Grzegorz; Kaczmarek, Pawel; Antonczak, Arkadiusz; Sotor, Jaroslaw; Abramski, Krzysztof M

2011-09-26

In this paper we present our experimental studies on controlling the amplified spontaneous emission (ASE) from Yb(3+) ions in Er/Yb co-doped fiber amplifiers. We propose a new method of controlling the Yb-ASE by stimulating a laser emission at 1064 nm in the amplifier, by providing a positive 1 μm signal feedback loop. The results are discussed and compared to a conventional amplifier setup without 1 μm ASE control and to an amplifier with auxiliary 1064 nm seeding. We have shown, that applying a 1064 nm signal loop in an Er/Yb amplifier can increase the output power at 1550 nm and provide stable operation without parasitic lasing at 1 μm. © 2011 Optical Society of America

LOGARITHMIC AMPLIFIER

DOEpatents

De Shong, J.A. Jr.

1957-12-31

A logarithmic current amplifier circuit having a high sensitivity and fast response is described. The inventor discovered the time constant of the input circuit of a system utilizing a feedback amplifier, ionization chamber, and a diode, is inversely proportional to the input current, and that the amplifier becomes unstable in amplifying signals in the upper frequency range when the amplifier's forward gain time constant equals the input circuit time constant. The described device incorporates impedance networks having low frequency response characteristic at various points in the circuit to change the forward gain of the amplifler at a rate of 0.7 of the gain magnitude for every two times increased in frequency. As a result of this improvement, the time constant of the input circuit is greatly reduced at high frequencies, and the amplifier response is increased.

X-Band, 17-Watt Solid-State Power Amplifier

NASA Technical Reports Server (NTRS)

Mittskus, Anthony; Stone, Ernest; Boger, William; Burgess, David; Honda, Richard; Nuckolls, Carl

2005-01-01

An advanced solid-state power amplifier that can generate an output power of as much as 17 W at a design operating frequency of 8.4 GHz has been designed and constructed as a smaller, lighter, less expensive alternative to traveling-wave-tube X-band amplifiers and to prior solid-state X-band power amplifiers of equivalent output power. This amplifier comprises a monolithic microwave integrated circuit (MMIC) amplifier module and a power-converter module integrated into a compact package (see Figure 1). The amplifier module contains an input variable-gain amplifier (VGA), an intermediate driver stage, a final power stage, and input and output power monitors (see Figure 2). The VGA and the driver amplifier are 0.5-m GaAs-based metal semiconductor field-effect transistors (MESFETs). The final power stage contains four parallel high-efficiency, GaAs-based pseudomorphic high-electron-mobility transistors (PHEMTs). The gain of the VGA is voltage-variable over a range of 10 to 24 dB. To provide for temperature compensation of the overall amplifier gain, the gain-control voltage is generated by an operational-amplifier circuit that includes a resistor/thermistor temperature-sensing network. The driver amplifier provides a gain of 14 dB to an output power of 27 dBm to drive the four parallel output PHEMTs, each of which is nominally capable of putting out as much as 5 W. The driver output is sent to the input terminals of the four parallel PHEMTs through microstrip power dividers; the outputs of these PHEMTs are combined by microstrip power combiners (which are similar to the microstrip power dividers) to obtain the final output power of 17 W.

Bias-Voltage Stabilizer for HVHF Amplifiers in VHF Pulse-Echo Measurement Systems.

PubMed

Choi, Hojong; Park, Chulwoo; Kim, Jungsuk; Jung, Hayong

2017-10-23

The impact of high-voltage-high-frequency (HVHF) amplifiers on echo-signal quality is greater with very-high-frequency (VHF, ≥100 MHz) ultrasound transducers than with low-frequency (LF, ≤15 MHz) ultrasound transducers. Hence, the bias voltage of an HVHF amplifier must be stabilized to ensure stable echo-signal amplitudes. We propose a bias-voltage stabilizer circuit to maintain stable DC voltages over a wide input range, thus reducing the harmonic-distortion components of the echo signals in VHF pulse-echo measurement systems. To confirm the feasibility of the bias-voltage stabilizer, we measured and compared the deviations in the gain of the HVHF amplifier with and without a bias-voltage stabilizer. Between -13 and 26 dBm, the measured gain deviations of a HVHF amplifier with a bias-voltage stabilizer are less than that of an amplifier without a bias-voltage stabilizer. In order to confirm the feasibility of the bias-voltage stabilizer, we compared the pulse-echo responses of the amplifiers, which are typically used for the evaluation of transducers or electronic components used in pulse-echo measurement systems. From the responses, we observed that the amplitudes of the echo signals of a VHF transducer triggered by the HVHF amplifier with a bias-voltage stabilizer were higher than those of the transducer triggered by the HVHF amplifier alone. The second, third, and fourth harmonic-distortion components of the HVHF amplifier with the bias-voltage stabilizer were also lower than those of the HVHF amplifier alone. Hence, the proposed scheme is a promising method for stabilizing the bias voltage of an HVHF amplifier, and improving the echo-signal quality of VHF transducers.

Bias-Voltage Stabilizer for HVHF Amplifiers in VHF Pulse-Echo Measurement Systems

PubMed Central

Choi, Hojong; Park, Chulwoo; Kim, Jungsuk; Jung, Hayong

2017-01-01

The impact of high-voltage–high-frequency (HVHF) amplifiers on echo-signal quality is greater with very-high-frequency (VHF, ≥100 MHz) ultrasound transducers than with low-frequency (LF, ≤15 MHz) ultrasound transducers. Hence, the bias voltage of an HVHF amplifier must be stabilized to ensure stable echo-signal amplitudes. We propose a bias-voltage stabilizer circuit to maintain stable DC voltages over a wide input range, thus reducing the harmonic-distortion components of the echo signals in VHF pulse-echo measurement systems. To confirm the feasibility of the bias-voltage stabilizer, we measured and compared the deviations in the gain of the HVHF amplifier with and without a bias-voltage stabilizer. Between −13 and 26 dBm, the measured gain deviations of a HVHF amplifier with a bias-voltage stabilizer are less than that of an amplifier without a bias-voltage stabilizer. In order to confirm the feasibility of the bias-voltage stabilizer, we compared the pulse-echo responses of the amplifiers, which are typically used for the evaluation of transducers or electronic components used in pulse-echo measurement systems. From the responses, we observed that the amplitudes of the echo signals of a VHF transducer triggered by the HVHF amplifier with a bias-voltage stabilizer were higher than those of the transducer triggered by the HVHF amplifier alone. The second, third, and fourth harmonic-distortion components of the HVHF amplifier with the bias-voltage stabilizer were also lower than those of the HVHF amplifier alone. Hence, the proposed scheme is a promising method for stabilizing the bias voltage of an HVHF amplifier, and improving the echo-signal quality of VHF transducers. PMID:29065526

Two and Three Beam Pumped Optical Parametric Amplifier of Chirped Pulses

NASA Astrophysics Data System (ADS)

Ališauskas, S.; Butkus, R.; Pyragaitė, V.; Smilgevičius, V.; Stabinis, A.; Piskarskas, A.

2010-04-01

We present two and three beam pumped optical parametric amplifier of broadband chirped pulses. The seed pulses from Ti:sapphire oscillator were stretched and amplified in a non-collinear geometry pumping with up to three beams derived from independent laser amplifiers. The signal with ˜90 nm bandwidth was amplified up to 0.72 mJ. The conversion efficiency dependence on intersection angles of pump beams is also revealed.

Effect of Cold-rolling on Mechanical Properties and Microstructure of an Al-12%Si-0.2%Mg Alloy

NASA Astrophysics Data System (ADS)

Liao, Hengcheng; Cai, Mingdong; Jing, Qiumin; Ding, Ke

2011-11-01

Effect of multi-pass cold-rolling on the mechanical properties and microstructure of a near-eutectic Al-12%Si-0.2%Mg casting alloy was investigated. Optical microscopy, SEM, and TEM were employed to resolve the as-rolled microstructure, and the microstructure of samples after aging treatment. It has been found that Brinell hardness increases considerably with rolling reduction ratio; and further annealing leads to a remarkable drop in hardness. Two mechanisms, namely precipitation hardening and recovery softening, were found to develop simultaneously in the subsequent aging treatment following cold rolling. In contrast, recovery softening dominated the aging of cold-rolled specimen with prior intermediate annealing. Tensile properties were also performed to measure the effect of cold rolling and subsequent aging treatment.

Graphene-gold supercapacitor as a voltage controlled saturable absorber for femtosecond pulse generation.

PubMed

Baylam, Isinsu; Balci, Osman; Kakenov, Nurbek; Kocabas, Coskun; Sennaroglu, Alphan

2016-03-01

We report, for the first time to the best of our knowledge, use of a graphene-gold supercapacitor as a voltage controlled fast saturable absorber for femtosecond pulse generation. The unique design involving only one graphene electrode lowers the insertion loss of the device, in comparison with capacitor designs with two graphene electrodes. Furthermore, use of the high-dielectric electrolyte allows reversible, adjustable control of the absorption level up to the visible region with low bias voltages of only a few volts (0-2 V). The fast saturable absorber action of the graphene-gold supercapacitor was demonstrated inside a multipass-cavity Cr:forsterite laser to generate nearly transform-limited, sub-100 fs pulses at a pulse repetition rate of 4.51 MHz at 1.24 μm.

A survey of compiler development aids. [concerning lexical, syntax, and semantic analysis

NASA Technical Reports Server (NTRS)

Buckles, B. P.; Hodges, B. C.; Hsia, P.

1977-01-01

A theoretical background was established for the compilation process by dividing it into five phases and explaining the concepts and algorithms that underpin each. The five selected phases were lexical analysis, syntax analysis, semantic analysis, optimization, and code generation. Graph theoretical optimization techniques were presented, and approaches to code generation were described for both one-pass and multipass compilation environments. Following the initial tutorial sections, more than 20 tools that were developed to aid in the process of writing compilers were surveyed. Eight of the more recent compiler development aids were selected for special attention - SIMCMP/STAGE2, LANG-PAK, COGENT, XPL, AED, CWIC, LIS, and JOCIT. The impact of compiler development aids were assessed some of their shortcomings and some of the areas of research currently in progress were inspected.

FTIR studies of low temperature sulfuric acid aerosols

NASA Technical Reports Server (NTRS)

Anthony, S. E.; Tisdale, R. T.; Disselkamp, R. S.; Tolbert, M. A.; Wilson, J. C.

1995-01-01

Sub-micrometer sized sulfuric acid H2SO4 particles were generated using a constant output atomizer source. The particles were then exposed to water vapor before being injected into a low temperature cell. Multipass transmission Fourier Transformation Infrared (FTIR) spectroscopy was used to determine the phase and composition of the aerosols as a function of time for periods of up to five hours. Binary H2SO4H2O aerosols with compositions from 35 to 95 wt % H2SO4 remained liquid for over 3 hours at room temperatures ranging from 189-240 K. These results suggest that it is very difficut to freeze SSAs via homogeneous nucleation. Attempts to form aerosols more dilute than 35 wt % H2SO4 resulted in ice formation.

Aluminum U-groove weld enhancement based on experimental stress analyses

NASA Technical Reports Server (NTRS)

Verderaime, V.; Vaughan, R.

1995-01-01

Though butt-welds are among the most preferred joining methods in aerostructures because of their sealing and assembly integrity and general elastic performance; their inelastic mechanics are generally the least understood. This study investigated experimental strain distributions across a thick aluminum U-grooved weld and identified two weld process considerations for improving the multipass weld strength. The extreme thermal expansion and contraction gradient of the fusion heat input across the tab thickness between the grooves produce severe peaking, which induces bending moment under uniaxial loading. The filler strain hardening decreased with increasing filler pass sequence. These combined effects reduce the weld strength, and a depeaking index model was developed to select filler pass thicknesses, pass numbers, and sequences to improve the welding process results over the current normal weld schedule.

The effect of thermomechanical processing on second phase particle redistribution in U-10 wt%Mo

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

Hu, Xiaohua; Wang, Xiaowo; Joshi, Vineet V.

2018-03-01

The multi-pass hot-rolling process of an annealed uranium-10 wt% molybdenum coupon was studied by plane-strain compression finite element modeling. Two point correlation function (2PCF) was used to analyze the carbide particle distribution after each rolling reduction. The hot rolling simulation results show that the alignment of UC particles along grain boundaries will rotate during rolling until it is parallel to the rolling direction, to form stringer-like distributions which are typically observed in rolled products that contain inclusions. 2PCF analysis of simulation shows that the interparticle spacing shrinks along the normal direction. The number of major peaks of 2PCF along NDmore » decreases after large reduction. The locations of major peaks indicate the inter-stringer distances.« less

Meter circuit for tuning RF amplifiers

NASA Technical Reports Server (NTRS)

Longthorne, J. E.

1973-01-01

Circuit computes and indicates efficiency of RF amplifier as inputs and other parameters are varied. Voltage drop across internal resistance of ammeter is amplified by operational amplifier and applied to one multiplier input. Other input is obtained through two resistors from positive terminal of power supply.

High-gain cryogenic amplifier assembly employing a commercial CMOS operational amplifier.

PubMed

Proctor, J E; Smith, A W; Jung, T M; Woods, S I

2015-07-01

We have developed a cryogenic amplifier for the measurement of small current signals (10 fA-100 nA) from cryogenic optical detectors. Typically operated with gain near 10(7) V/A, the amplifier performs well from DC to greater than 30 kHz and exhibits noise level near the Johnson limit. Care has been taken in the design and materials to control heat flow and temperatures throughout the entire detector-amplifier assembly. A simple one-board version of the amplifier assembly dissipates 8 mW to our detector cryostat cold stage, and a two-board version can dissipate as little as 17 μW to the detector cold stage. With current noise baseline of about 10 fA/(Hz)(1/2), the cryogenic amplifier is generally useful for cooled infrared detectors, and using blocked impurity band detectors operated at 10 K, the amplifier enables noise power levels of 2.5 fW/(Hz)(1/2) for detection of optical wavelengths near 10 μm.

Assessment of commercial optical amplifiers for potential use in space applications

NASA Astrophysics Data System (ADS)

Barbero, Juan; Sotom, Michel; Benazet, Benoit; Esquivias, Ignacio; López Hernández, Francisco José

2017-11-01

This paper describes the activities and results of an ESA-funded project concerned with the assessment of optical amplifier technologies and products for applications in fiber optic subsystems of future satellite payloads. On-board applications are briefly introduced, together with associated system-level requirements. Optical amplifier technologies, research achievements and products are reviewed. They are compared in terms of current performance, perspectives and suitability for the target space applications. Optical fibre amplifiers, not limited to Erbium-doped amplifiers, Erbium-doped waveguide amplifiers and Semiconductor Optical Amplifiers are covered. The review includes analysis and trade-off of all performance parameters including saturation output power, noise figure, polarisation maintaining capability, wall-plug efficiency, and mass and size. A selection of optical amplifier products for further evaluation and testing is presented. Results of extensive testing covering both functional performance and environmental behaviour (mechanical, thermal vacuum, radiations) aspects are reported. Most of the work has been completed, but an extension has been proposed for checking and comparing the behaviour of doped fibers under gamma radiation.

Isolated thermocouple amplifier system for stirred fixed-bed gasifier

DOEpatents

Fasching, George E.

1992-01-01

A sensing system is provided for determining the bed temperature profile of the bed of a stirred, fixed-bed gasifier including a plurality of temperature sensors for sensing the bed temperature at different levels, a transmitter for transmitting data based on the outputs of the sensors to a remote operator's station, and a battery-based power supply. The system includes an isolation amplifier system comprising a plurality of isolation amplifier circuits for amplifying the outputs of the individual sensors. The isolation amplifier circuits each comprise an isolation operational amplifier connected to a sensor; a first "flying capacitor" circuit for, in operation, controlling the application of power from the power supply to the isolation amplifier; an output sample and hold circuit connected to the transmitter; a second "flying capacitor" circuit for, in operation, controlling the transfer of the output of the isolation amplifier to the sample and hold circuit; and a timing and control circuit for activating the first and second capacitor circuits in a predetermined timed sequence.

Design of an Auto-zeroed, Differential, Organic Thin-film Field-effect Transistor Amplifier for Sensor Applications

NASA Technical Reports Server (NTRS)

Binkley, David M.; Verma, Nikhil; Crawford, Robert L.; Brandon, Erik; Jackson, Thomas N.

2004-01-01

Organic strain gauge and other sensors require high-gain, precision dc amplification to process their low-level output signals. Ideally, amplifiers would be fabricated using organic thin-film field-effect transistors (OTFT's) adjacent to the sensors. However, OTFT amplifiers exhibit low gain and high input-referred dc offsets that must be effectively managed. This paper presents a four-stage, cascaded differential OTFT amplifier utilizing switched capacitor auto-zeroing. Each stage provides a nominal voltage gain of four through a differential pair driving low-impedance active loads, which provide common-mode output voltage control. p-type pentacence OTFT's are used for the amplifier devices and auto-zero switches. Simulations indicate the amplifier provides a nominal voltage gain of 280 V/V and effectively amplifies a 1-mV dc signal in the presence of 500-mV amplifier input-referred dc offset voltages. Future work could include the addition of digital gain calibration and offset correction of residual offsets associated with charge injection imbalance in the differential circuits.

GLASS: The Grism Lens-Amplified Survey From Space. HST Grism Spectroscopy of the Frontier Fields

NASA Astrophysics Data System (ADS)

Schmidt, Kasper B.; Schmidt

The Grism Lens-Amplified Survey From Space (GLASS) is a 140 orbit spectroscopic survey of 10 massive galaxy clusters, including the six Hubble Frontier Fields. GLASS has observed the cluster cores with the HST-WFC3 G102 and G141 grisms providing a wide wavelength coverage in the near-infrared from roughly 0.8-1.7μm. The parallel fields were observed through the optical ACS G800L grism. Taking advantage of the lensing magnification of the clusters, GLASS reaches intrinsic spectroscopic 1σ flux limits of roughly 10-18erg/s/cm2 and improved spatial resolution for lensed sources behind the clusters. These features are particularly useful for the three main science drivers of GLASS which are, I) exploring the universe at the epoch of reionization, II) describe how metals cycle in and out of galaxies, and III) asses the environmental dependence of galaxy evolution. The former two benefit highly from the improved depth and increased resolution provided by the cluster lensing. Apart from the main science drivers, a slew of ancillary science has been enabled by the survey, including improving cluster lens modeling and searches for supernovae. Here we present the survey and the GLASS data releases, which are continuously being made available to the community through https://archive.stsci.edu/prepds/glass/. For further information we refer to Schmidt et al. (2014), Treu et al. (2015), and http://glass.physics.ucsb.edu.

A Model-Based Fast Protection System for High-Power RF Tube Amplifiers Used at the European XFEL Accelerator

NASA Astrophysics Data System (ADS)

Butkowski, Łukasz; Vogel, Vladimir; Schlarb, Holger; Szabatin, Jerzy

2017-06-01

The driving engine of the superconducting accelerator of the European X-ray free electron laser (XFEL) is a set of 27 radio frequency (RF) stations. Each of the underground RF stations consists of a multibeam horizontal klystron that can provide up to 10 MW of power at 1.3 GHz. Klystrons are sensitive devices with a limited lifetime and a high mean time between failures. In real operation, the lifetime of the tube can be significantly reduced because of failures. The special fast protection klystron lifetime management (KLM) system has been developed to minimize the influence of service conditions on the lifetime of klystrons. The main task of this system is to detect all events which can destroy the tube as quickly as possible, and switch off the driving RF signal or the high voltage. Detection of events is based on a comparison of the value of the real signal obtained at the system output with the value estimated on the basis of a high-power RF amplifier model and input signals. The KLM system has been realized in field-programmable gate array (FPGA) and implemented in XFEL. Implementation is based on the standard low-level RF micro telecommunications computing architecture (MTCA.4 or xTCA). The main part of the paper focuses on an estimation of the klystron model and the implementation of KLM in FPGA. The results of the performance of the KLM system will also be presented.

Picosecond laser system with 30-W average power via cavity dumping and amplifying

NASA Astrophysics Data System (ADS)

Fu, J.; Pang, Q. S.; Chang, L.; Bai, Z. A.; Ai, Q. K.; Chen, L. Y.; Chen, M.; Li, G.; Ma, Y. F.; Fan, Z. W.; Niu, G.; Yu, J.; Liu, Y.; Zhang, X.; Kang, W. Y.; He, K.

2011-06-01

We present a picosecond laser system with high energy by technologies of cavity dumping and amplifying. Firstly, pulses with 10 ps and ˜520 nJ were obtained by cavity-dumped mode-locked laser at 10 kHz repetition rate. Secondly those pulses were seeded into a side-pumped regenerative amplifier (RA). Then pulses output from the regenerative amplifier were amplified by two four-pass post amplifiers. From the laser system pulses with an average power of 30 W corresponding to 3 mJ pulse energy were achieved with the pulse-width of 25.4 ps at repetition rate of 10 kHz.

Segmented amplifier configurations for laser amplifier

DOEpatents

Hagen, Wilhelm F.

1979-01-01

An amplifier system for high power lasers, the system comprising a compact array of segments which (1) preserves high, large signal gain with improved pumping efficiency and (2) allows the total amplifier length to be shortened by as much as one order of magnitude. The system uses a three dimensional array of segments, with the plane of each segment being oriented at substantially the amplifier medium Brewster angle relative to the incident laser beam and with one or more linear arrays of flashlamps positioned between adjacent rows of amplifier segments, with the plane of the linear array of flashlamps being substantially parallel to the beam propagation direction.

Note: A high dynamic range, linear response transimpedance amplifier.

PubMed

Eckel, S; Sushkov, A O; Lamoreaux, S K

2012-02-01

We have built a high dynamic range (nine decade) transimpedance amplifier with a linear response. The amplifier uses junction-gate field effect transistors (JFETs) to switch between three different resistors in the feedback of a low input bias current operational amplifier. This allows for the creation of multiple outputs, each with a linear response and a different transimpedance gain. The overall bandwidth of the transimpedance amplifier is set by the bandwidth of the most sensitive range. For our application, we demonstrate a three-stage amplifier with transimpedance gains of approximately 10(9)Ω, 3 × 10(7)Ω, and 10(4)Ω with a bandwidth of 100 Hz.