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1

Generating nonlinear FM chirp waveforms for radar.  

SciTech Connect

Nonlinear FM waveforms offer a radar matched filter output with inherently low range sidelobes. This yields a 1-2 dB advantage in Signal-to-Noise Ratio over the output of a Linear FM waveform with equivalent sidelobe filtering. This report presents design and implementation techniques for Nonlinear FM waveforms.

Doerry, Armin Walter

2006-09-01

2

SAR processing with non-linear FM chirp waveforms.  

SciTech Connect

Nonlinear FM (NLFM) waveforms offer a radar matched filter output with inherently low range sidelobes. This yields a 1-2 dB advantage in Signal-to-Noise Ratio over the output of a Linear FM (LFM) waveform with equivalent sidelobe filtering. This report presents details of processing NLFM waveforms in both range and Doppler dimensions, with special emphasis on compensating intra-pulse Doppler, often cited as a weakness of NLFM waveforms.

Doerry, Armin Walter

2006-12-01

3

Simplified Homodyne Detection for FM Chirped Lidar  

E-print Network

The investigation of global warming requires more sensitive altimeters to better map the global ice reserves. A homodyne detection scheme for FM chirped lidar is developed in which dechirping is performed in the optical domain, simplifying both...

Adany, Peter

2007-12-14

4

Linear FM chirp pulse compression ladar receiver operating characteristic  

Microsoft Academic Search

The linear frequency-modulation chirp pulse compression technique of classical microwave radar is examined in the context of coherent laser radar. A coherent CO2 laser radar may operate near 9.115 micrometers and 33,000 GHz. Because of this short wavelength, a large target Doppler-spread is realizable in a single ladar measurement. In addition, target surface roughness with respect to wavelength causes the

Douglas G. Youmans; David U. Fluckiger

1997-01-01

5

Waveform error analysis for bistatic synthetic aperture radar systems  

NASA Astrophysics Data System (ADS)

The signal phase histories at the transmitter, receiver, and radar signal processor in bistatic SAR systems are described. The fundamental problem of mismatches in the waveform generators for the illuminating and receiving radar systems is analyzed. The effects of errors in carrier frequency and chirp slope are analyzed for bistatic radar systems which use linear FM waveforms. It is shown that the primary effect of a mismatch in carrier frequencies is an azimuth displacement of the image.

Adams, J. W.; Schifani, T. M.

6

Synthetic aperture acoustic imaging of canonical targets with a 2-15 kHz linear FM chirp  

NASA Astrophysics Data System (ADS)

Synthetic aperture image reconstruction applied to outdoor acoustic recordings is presented. Acoustic imaging is an alternate method having several military relevant advantages such as being immune to RF jamming, superior spatial resolution, capable of standoff side and forward-looking scanning, and relatively low cost, weight and size when compared to 0.5 - 3 GHz ground penetrating radar technologies. Synthetic aperture acoustic imaging is similar to synthetic aperture radar, but more akin to synthetic aperture sonar technologies owing to the nature of longitudinal or compressive wave propagation in the surrounding acoustic medium. The system's transceiver is a quasi mono-static microphone and audio speaker pair mounted on a rail 5meters in length. Received data sampling rate is 80 kHz with a 2- 15 kHz Linear Frequency Modulated (LFM) chirp, with a pulse repetition frequency (PRF) of 10 Hz and an inter-pulse period (IPP) of 50 milliseconds. Targets are positioned within the acoustic scene at slant range of two to ten meters on grass, dirt or gravel surfaces, and with and without intervening metallic chain link fencing. Acoustic image reconstruction results in means for literal interpretation and quantifiable analyses. A rudimentary technique characterizes acoustic scatter at the ground surfaces. Targets within the acoustic scene are first digitally spotlighted and further processed, providing frequency and aspect angle dependent signature information.

Vignola, Joseph F.; Judge, John A.; Good, Chelsea E.; Bishop, Steven S.; Gugino, Peter M.; Soumekh, Mehrdad

2011-06-01

7

Amplitude-modulation chirp imaging for contrast detection.  

PubMed

We propose an amplitude-modulation chirp imaging method for contrast detection with high-frequency ultrasound. Our proposed method detects microbubbles by extracting and then selectively compressing the component of the backscattered chirp signal modulated by changes in the radii of microbubbles at their resonance frequency. Microbubbles are sonicated simultaneously with a narrowband, low-frequency pumping signal at their resonance frequency and a wideband, high-frequency imaging chirp signal. Changes in the radii of the resonant microbubbles result in periodic changes in their acoustic cross section that modulate the amplitude of the backscattered imaging chirp signal, forming pumping and imaging frequency sum-and-difference chirp terms. The frequency-sum or -difference chirp component is then extracted by a bandpass filter (BPF). Because a long imaging pulse duration is required to obtain a sufficient modulation depth on the chirp for contrast detection and to facilitate frequency-sum-and-difference signal extraction with the BPF, a chirp with a longer-than-usual waveform is used so pulse compression of the extracted chirp signal can then be performed to maintain the axial resolution, and even further improve the signal-to-noise ratio and contrast-to-tissue ratio. Experiments performed on flow phantoms with and without a speckle-generating background were performed to demonstrate the efficacy of the proposed technique. These results indicate that our proposed method can potentially provide high-resolution contrast detection in the microvasculature. PMID:20800180

Li, Meng-Lin; Kuo, Yu-Chen; Yeh, Chih-Kuang

2010-09-01

8

Propagation compensation by waveform predistortion  

NASA Astrophysics Data System (ADS)

Certain modifications of the Cobra Dane radar are considered, particularly modernization of the waveform generator. For wideband waveforms, the dispersive effects of the ionosphere become increasingly significant. The technique of predistorting the transmitted waveform so that a linear chirp is received after two-way passage is one way to overcome that dispersion. This approach is maintained for the modified system, but with a specific predistortion waveform well suited to the modification. The appropriate form of predistortion was derived in an implicit form of time as a function of frequency. The exact form was approximated by Taylor series and pseudo-Chebyshev approximation. The latter proved better, as demonstrated by the resulting smaller loss in detection sensitivity, less coarsening of range resolution, and a lower peak sidelobe. The effects of error in determining the plasma delay constant were determined and are given in graphical form. A suggestion for in-place determination of the plasma delay constant is given.

Halpin, Thomas F.; Urkowitz, Harry; Maron, David E.

9

The Theta Laser A Low Noise Chirped Pulse Laser  

E-print Network

Coherence Tomography ( Medical ) Laser Ranging ( Millitary ) #12;6 Outline · Applications of frequency sweptThe Theta Laser A Low Noise Chirped Pulse Laser Dimitrios Mandridis dmandrid@creol.ucf.edu April 29, 2011 CREOL Affiliates Day 2011 #12;2 Objective: Frequency Swept (FM) Mode-locked Laser · Develop

Van Stryland, Eric

10

A New Approach of Extended Chirp Scaling Algorithm for High Squint Missile-Borne SAR Data Processing  

Microsoft Academic Search

In the traditional extended chirp scaling (ECS) algorithm, after RCMC in the range signal\\/Doppler domain, targets in the same range gate will have different FM rates for difference of the slant ranges. In the paper, a novel approach for high squint missile-borne SAR data processing using a modified extended chirp scaling algorithm is proposed. A non-linear chirp perturbation function (CPF)

Qiang Zhou; Changwen Qu; Feng Su; Ying Wang

2008-01-01

11

UTILIZING A CHIRP SONAR TO ACCURATELY CHARACTERIZE NEWLY DEPOSITED MATERIAL AT THE CALCASIEU OCEAN DREDGED MATERIAL DISPOSAL SITE, LOUISIANA  

EPA Science Inventory

The distribution of dredged sediments is measured at the Calcasieu Ocean Dredged Material Disposal Site (ODMDS) using a chirp sonar immediately after disposal and two months later. ubbottom reflection data, generated by a chirp sonar transmitting a 4 to 20 kHz FM sweep, is proces...

12

Coded multiple chirp spread spectrum system and overlay service  

NASA Astrophysics Data System (ADS)

An asynchronous spread-spectrum system called coded multiple chirp is proposed, and the possible spread-spectrum overlay over an analog FM-TV signal is investigated by computer simulation. Multiple single-sloped up and down chirps are encoded by a pseudonoise code and decoded by dechirpers (pulse-compression filters) followed by a digital code correlator. The performance of the proposed system, expressed in terms of in probability of bit error and code miss probability, is similar to that of FSK (frequency shift keying) using codewords if sufficient compression gain is used. When chirp is used to overlay an FM-TV channel, two chirp signals with data rate up to 25 kb/s could be overlaid in a 36-MHz satellite transponder without significant mutual interference. Performance estimates for a VSAT (very small aperture terminal) earth station operating at C-band show that a 2.4-m antenna and 300-mW transmitter could send a 2.4-kb/s signal to a large central earth station over an occupied channel.

Kim, Junghwan; Pratt, Timothy; Ha, Tri T.

13

Coded multiple chirp spread spectrum system and overlay service  

NASA Technical Reports Server (NTRS)

An asynchronous spread-spectrum system called coded multiple chirp is proposed, and the possible spread-spectrum overlay over an analog FM-TV signal is investigated by computer simulation. Multiple single-sloped up and down chirps are encoded by a pseudonoise code and decoded by dechirpers (pulse-compression filters) followed by a digital code correlator. The performance of the proposed system, expressed in terms of in probability of bit error and code miss probability, is similar to that of FSK (frequency shift keying) using codewords if sufficient compression gain is used. When chirp is used to overlay an FM-TV channel, two chirp signals with data rate up to 25 kb/s could be overlaid in a 36-MHz satellite transponder without significant mutual interference. Performance estimates for a VSAT (very small aperture terminal) earth station operating at C-band show that a 2.4-m antenna and 300-mW transmitter could send a 2.4-kb/s signal to a large central earth station over an occupied channel.

Kim, Junghwan; Pratt, Timothy; Ha, Tri T.

1988-01-01

14

Chirped pulse Raman amplifier  

NASA Astrophysics Data System (ADS)

All modern terawatt- and petawatt-class laser systems are based on the principle of chirped-pulse amplification (CPA). In this work, a compact subsystem that shifts a micro-joule portion of the chirped pulse energy to a new wavelength outside its original bandwidth, then amplifies it to millijoule energy without adding pump lasers, and without compromising the output of the fundamental CPA system in any significant way, has been developed and integrated into a standard terawatt-class CPA system. In this chirped pulse Raman amplifier sub-system, a 30 mJ portion of a chirped 800 nm fundamental pulse within the CPA system was split into two unequal portions, each of which impinged on a Raman-active barium nitrate, or Ba(NO3)2, crystal of length 5 cm. The weaker portion created a weak (15 J) first Stokes pulse (873 nm) by Stimulated Raman Scattering (SRS) in the first crystal, which then seeded a non-collinear four-wave-mixing process driven by the stronger portion of the split-off CPA pulse in the second crystal. The latter process amplified the first Stokes seed pulse to several millijoules with excellent beam quality. A study of Raman gain as a function of time delay between pump and Stokes pulse in the second crystal revealed a sharply peaked narrow interval (3 ps FWHM) of high gain and a wider interval (50 ps) of low gain. The amplified, chirped first Stokes pulse was successfully compressed to 100 fs duration using a grating pair of different line density than in the main CPA system, based on a comprehensive dispersion analysis of the optical path of the first Stokes pulse. The possibility of generating higher-order Stokes and anti-Stokes sidebands of the CPA pulse is also demonstrated. Further amplification of the sideband pulse by conventional methods, using an additional pump laser, appears straightforward. The chirped pulse Raman amplifier provides temporally synchronized fundamental and Raman sideband pulses for performing two-color, high-intensity laser experiments, some of which are briefly discussed. It can be integrated into any standard CPA system, and provides significant new versatility for high-intensity laser sources.

Grigsby, Franklin Bhogaraju

15

Business critical FM  

Microsoft Academic Search

FM's failure management to capture its cherished place in the business support pantheon has been subject of much recent comment. This paper presents an overview of how that contribution might be expressed drawing on research-based evidence from offices, universities, hospitals and retail facilities. Only in a business that conceives itself as running a facility will FM approach a core competence,

Ilfryn Price

2004-01-01

16

Gravitational waveforms for 2- and 3-body gravitating systems  

E-print Network

Different numbers of self-gravitating particles (in different types of periodic motion) are most likely to generate very different shapes of gravitational waves, some of which, however, can be accidentally almost the same. One such example is a binary and a three-body system for Lagrange's solution. To track the evolution of these similar waveforms, we define a chirp mass to the triple system. Thereby, we show that the quadrupole waveforms cannot distinguish the sources. It is suggested that waveforms with higher $\\ell$-th multipoles will be important for classification of them (with a conjecture of $\\ell \\leq N$ for N particles).

Yuji Torigoe; Keisuke Hattori; Hideki Asada

2009-06-08

17

Chirped-pulse terahertz spectroscopy for broadband trace gas sensing.  

PubMed

We report the first demonstration of a broadband trace gas sensor based on chirp-pulse terahertz spectroscopy. The advent of newly developed solid state sources and sensitive heterodyne detectors for the terahertz frequency range have made it possible to generate and detect precise arbitrary waveforms at THz frequencies with ultra-low phase noise. In order to maximize sensitivity, the sample gas is first polarized using sub-?s chirped THz pulses and the free inductive decays (FIDs) are then detected using a heterodyne receiver. This approach allows for a rapid broadband multi-component sensing with low parts in 10(9) (ppb) sensitivities and spectral frequency accuracy of <20 kHz in real-time. Such a system can be configured into a portable, easy to use, and relatively inexpensive sensing platform. PMID:21643150

Gerecht, Eyal; Douglass, Kevin O; Plusquellic, David F

2011-04-25

18

Super-resolution processing for multi-functional LPI waveforms  

NASA Astrophysics Data System (ADS)

Super-resolution (SR) is a radar processing technique closely related to the pulse compression (or correlation receiver). There are many super-resolution algorithms developed for the improved range resolution and reduced sidelobe contaminations. Traditionally, the waveforms used for the SR have been either phase-coding (such as LKP3 code, Barker code) or the frequency modulation (chirp, or nonlinear frequency modulation). There are, however, an important class of waveforms which are either random in nature (such as random noise waveform), or randomly modulated for multiple function operations (such as the ADS-B radar signals in [1]). These waveforms have the advantages of low-probability-of-intercept (LPI). If the existing SR techniques can be applied to these waveforms, there will be much more flexibility for using these waveforms in actual sensing missions. Also, SR usually has great advantage that the final output (as estimation of ground truth) is largely independent of the waveform. Such benefits are attractive to many important primary radar applications. In this paper the general introduction of the SR algorithms are provided first, and some implementation considerations are discussed. The selected algorithms are applied to the typical LPI waveforms, and the results are discussed. It is observed that SR algorithms can be reliably used for LPI waveforms, on the other hand, practical considerations should be kept in mind in order to obtain the optimal estimation results.

Li, Zhengzheng; Zhang, Yan; Wang, Shang; Cai, Jingxiao

2014-05-01

19

*FM 10-52-1 FM 10-52-1  

E-print Network

of the raw water source will dictate the amount of water each purifier can produce. The total daily water#12;*FM 10-52-1 i #12;FM 10-52-1 i i #12;FM 10-52-1 Preface PURPOSE This manual describes water deals with water supply point operations. It includes information on quality control; ground and air

US Army Corps of Engineers

20

Frequency-chirped subwavelength nanoantennas.  

PubMed

Herein we propose, theoretically investigate, and numerically demonstrate the first use to our knowledge of frequency chirping to achieve broadband, efficient subwavelength vertical emission from a dielectric waveguide. We demonstrate this unique and effective approach in the telecom C band in a nanophotonic frequency-chirped dipole antenna. The structure utilizes a plasmonic antenna placed above an Si3N4 waveguide and a ground plane to enhance emission efficiency. Three-dimensional finite-difference time-domain simulations reveal up to 55% vertical emission efficiency, and a bandwidth of 500 nm is possible in a structure less than half a wavelength long. The design methodology and theoretical underpinnings of frequency-chirped nanophotonic antennas coupled to dielectric waveguides are presented. PMID:23202110

Yaacobi, Ami; Watts, Michael R

2012-12-01

21

The effect of amplitude modulation on subharmonic imaging with chirp excitation.  

PubMed

Subharmonic generation from ultrasound contrast agents depends on the spectral and temporal properties of the excitation signal. The subharmonic response can be improved by using wideband and long-duration signals. However, for sinusoidal tone-burst excitation, the effective bandwidth of the signal is inversely proportional to the signal duration. Linear frequency-modulated (LFM) and nonlinear frequency-modulated (NLFM) chirp excitations allow independent control over the signal bandwidth and duration; therefore, in this study LFM and NLFM signals were used for the insonation of microbubble populations. The amplitude modulation of the excitation waveform was achieved by applying different window functions. A customized window was designed for the NLFM chirp excitation by focusing on reducing the spectral leakage at the subharmonic frequency and increasing the subharmonic generation from microbubbles. Subharmonic scattering from a microbubble population was measured for various excitation signals and window functions. At a peak negative pressure of 600 kPa, the generated subharmonic energy by ultrasound contrast agents was 15.4 dB more for NLFM chirp excitation with 40% fractional bandwidth when compared with tone-burst excitation. For this reason, the NLFM chirp with a customized window was used as an excitation signal to perform subharmonic imaging in an ultrasound flow phantom. Results showed that the NLFM waveform with a customized window improved the subharmonic contrast by 4.35 0.42 dB on average over a Hann-windowed LFM excitation. PMID:24297019

Harput, Sevan; Arif, Muhammad; McLaughlan, James; Cowell, David M J; Freear, Steven

2013-12-01

22

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave spectroscopy  

Microsoft Academic Search

The rotational spectrum of epifluorohydrin measured by chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy is presented. A new CP-FTMW spectrometer capable of measuring the entire 7.518.5GHz spectrum with a single polarizing pulse is described briefly. The CP-FTMW spectrometer takes advantage of recent advances in digital electronics by utilizing a 4.2GS\\/s arbitrary waveform generator as a frequency source and a 12GHz digital

Gordon G. Brown; Brian C. Dian; Kevin O. Douglass; Scott M. Geyer; Brooks H. Pate

2006-01-01

23

The interlaced chirp Z transform  

Microsoft Academic Search

In this paper we introduce the interlaced chirp Z transform (Interlaced CZT). It is based on the computation of several carefully staggered CZT that are progressively interlaced to result in a spectrum that has denser frequency samples where needed. This simple modification of the CZT is shown to result in significant computational savings over the regular CZT, as well as

Indranil Sarkar; Adly T. Fam

2006-01-01

24

FM 6-22 (FM 22-100) Army Leadership  

E-print Network

;Foreword Competent leaders of character are necessary for the Army to meet the challenges in the dangerous. It establishes leadership doctrine and fundamental principles for all officers, noncommissioned officers and Doctrine Digital Library at (www.train.army.mil). #12;*FM 6-22 (FM 22-100) Distribution Restriction

US Army Corps of Engineers

25

Basic characteristics of FM-CW radar systems  

NASA Astrophysics Data System (ADS)

Due to rapid technological progress in real-time signal processing, FM-CW radar systems are expected to become a more serious competitor to pulse radar systems. This paper deals with basic radar principles such as modulating waveforms and ambiguity functions characteristics. Advantages and disadvantages of FM-CW radar systems are compared to pulse radar systems. The inherent signal processing used in FM-CW radar systems allows a flexible choice of system parameters. In this context aspects like sensitivity, range and velocity resolution are discussed. It is elucidated that the use of digital processors for signal processing (frequency determination, filtering, etc.) offers the possibility to exchange dedicated hardware solutions with software implementations. Attention is paid to equipment like the antennas, diplexer, transmitter and receiver, and to isolation problems between transmitter and receiver. Results of an experimental FM-CW research radar are shown. In addition, the future prospects of FM-CW radar, with the aerial and solid-state R.F. head-end integrated, are indicated.

Ligthart, L. P.; Nieuwkerk, L. R.; Vansinttruyen, J. S.

1986-07-01

26

Waveform: Acoustics/Electroacoustics  

NSDL National Science Digital Library

This webpage from the Handbook for Acoustic Ecology provides a description of waveform, a pattern of sound pressure variation. Information includes linked explanations of numerous related terms like sound pressure, amplitude, and the law of superposition. Also incorporated into the site are sound clips of various waveforms such as sine, sawtooth, and triangle waves.

2006-07-14

27

Spacevariant Fourier Analysis: the Exponential Chirp Transform  

E-print Network

of the fast exponential chirp algorithm on a data­base of images in a template matching task, and also­Variant Image Processing, Fourier Analysis, Non­Uniform Sampling, Real­Time Imaging, Warped Template Matching to the Mellin­ Transform) provides a fast exponential chirp transform. This provides size and rotation

Schwartz, Eric L.

28

Frequency chirped differential absorption LIDAR  

NASA Astrophysics Data System (ADS)

We present a novel concept design of a differential absorption LIDAR for open path trace gas sensing in the atmosphere. To perform a range-resolved gas sensing we propose to arrange a set of retroreflectors in the laser beam path to measure a differential absorption in adjacent sections. In validation experiments we used a pulsed DFB quantum cascade laser fabricated by Alpes Lasers. The laser was excited with 200-ns current pulses with a repetition rate of 10 kHz. The frequency chirp rate was found to increase from 7.7 to 1.0 cm -1/?s as peak injection current was increased from 7.1, to 7.8 A. We utilized the frequency chirp at laser substrate temperature of 24.0 C to scan the 967.0 - 968.5 cm -1 spectral interval containing the absorption lines of CO II and NH3. We detected ~ 0.25 ppmv of NH 3 in nitrogen at atmospheric pressure using a double-pass gas cell with an effective absorption path of 2.4 m. Digital filtering of the spectra was shown to be effective in eliminating a high-frequency noise. To demonstrate range-resolved capabilities of the sensor we used two retroreflectors inserted into the laser beam. A differential absorption of CO II at 967.7 cm -1 was measured with the gas cell placed in one of the sections. Our experiments indicate that the frequency chirped LIDAR can be used for open path spectroscopy of NH 3 over the ranges up to ~ 1 km with a spatial resolution of ~ 30 m and detection limit of ~ 20 ppbv per a 30-m section.

Lytkine, A.; Jger, W.; Tulip, J.

2006-09-01

29

Population inversion by chirped pulses  

SciTech Connect

In this paper, we analyze the condition for complete population inversion by a chirped pulse over a finite duration. The nonadiabatic transition probability is mapped in the two-dimensional parameter space of coupling strength and detuning amplitude. Asymptotic forms of the probability are derived by the interference of nonadiabatic transitions for sinusoidal and triangular pulses. The qualitative difference between the maps for the two types of pulses is accounted for. The map is used for the design of stable inversion pulses under specific accuracy thresholds.

Lu Tianshi [Department of Mathematics and Statistics, Wichita State University, Wichita, Kansas 67260-0033 (United States)

2011-09-15

30

MATLAB simulation of a Distributed Feedback (DFB) laser with chirp effects  

NASA Astrophysics Data System (ADS)

A model of a distributed feedback (DFB) laser was implemented in MATLAB and SIMULINK. Using the laser rate equation, the model was simulated to obtain general characteristics of the chirp of the lasers frequency. The simulations were controlled by using different drive current waveforms, based on various bit patterns, data rates, and drive current values (threshold current and the extinction ratio). Once created, the laser drive current was passed to the SIMULINK DFB laser model. The output of a simulation provided frequency chirp, laser power emitted, photon density, and carrier density data. Two sets of simulations were conducted. The first set of simulations focused on the data rates and bit patterns. From these simulations it was determined that the transition from a ZERO bit to a ONE bit caused the greatest frequency excursions. Also, as the data rate increases the maximum frequency excursion increases. Finally, the first set of simulations revealed that the predictability of the chirp decreases as the data rate increases and as the complexity of the bit pattern increases. The second set of simulations examined the effect of the extinction ratio on frequency chirp. By plotting the maximum frequency excursion against its respective extinction ratio, it was determined that in some cases the maximum frequency excursions in a system could be minimized.

Espe, Burt L.

1994-12-01

31

Altimeter waveform software design  

NASA Technical Reports Server (NTRS)

Techniques are described for preprocessing raw return waveform data from the GEOS-3 radar altimeter. Topics discussed include: (1) general altimeter data preprocessing to be done at the GEOS-3 Data Processing Center to correct altimeter waveform data for temperature calibrations, to convert between engineering and final data units and to convert telemetered parameter quantities to more appropriate final data distribution values: (2) time "tagging" of altimeter return waveform data quantities to compensate for various delays, misalignments and calculational intervals; (3) data processing procedures for use in estimating spacecraft attitude from altimeter waveform sampling gates; and (4) feasibility of use of a ground-based reflector or transponder to obtain in-flight calibration information on GEOS-3 altimeter performance.

Hayne, G. S.; Miller, L. S.; Brown, G. S.

1977-01-01

32

ISRO's programmable digital waveform generator  

Microsoft Academic Search

One of the major and common requirements for all active microware sensors is generation of the transmit modulation signal-like chirp\\/LFM signal, MSK, etc., which can be generated by analog or digital means. With the increasing demands of side bandwidth, longer duration chirp signals in radar systems, digital signal generation, and processing has emerged as a preferred alternative. Design and development

S. Gangele; N. M. Desai; R. Senthil Kumar; J. G. Vachhani; V. R. Gujraty

2008-01-01

33

Improved transmission performance resulting from the reduced chirp of a semiconductor laser coupled to an external high-Q resonator  

Microsoft Academic Search

The improvement in the receiver sensitivity due to the reduced chirp is examined for NRZ and RZ intensity modulation, direct detection systems operating in the 1.55-?m wavelength region with conventional single-mode optical fiber. The methodology involves (a) solving modified rate equations numerically for the optical power and phase of the external resonator laser in response to an injected current waveform,

J. C. Cartledge

1990-01-01

34

Detection performance improvement of chirped amplitude modulation ladar based on Gieger-mode avalanche photoelectric detector.  

PubMed

This paper presents an improved system structure of photon-counting chirped amplitude modulation (AM) ladar based on the Geiger-mode avalanche photoelectric detector (GmAPD). The error-pulse probability is investigated with statistical method. The research shows that most of the error pulses that are triggered by noise are distributed in the intensity troughs of the chirped AM waveform. The error-pulse probability is lowered with the sliding window and the threshold. With the average intensity of noise and signal being 0.3 count/sample and 1 count/sample, respectively, the probability of error pulses is reduced from 12% to 1.0%, and the SNR is improved by 2.2 dB in the improved system. PMID:22193131

Zhang, Zijing; Wu, Long; Zhang, Yu; Zhao, Yuan; Sun, Xiudong

2011-12-10

35

FM 4-20.07(FM 42-424) QUARTERMASTER FORCE PROVIDER  

E-print Network

FM 4-20.07(FM 42-424) QUARTERMASTER FORCE PROVIDER COMPANY AUGUST 2008 DISTRIBUTION RESTRICTION and Doctrine Digital Library at (www.train.army.mil). #12;*FM 4-20.07 (FM 42-424) Distribution Restriction: Approved for public release; distribution is unlimited. *This publication supersedes FM 42-424, dated 6

US Army Corps of Engineers

36

Low frequency AC waveform generator  

DOEpatents

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Bilharz, Oscar W. (Scotia, NY)

1986-01-01

37

CHIRP  

Cancer.gov

Skip to Main Content Headlines Pediatric Oncology Branch Home > Pediatric Psycho-Oncology Professionals > Training Headline Title Pediatric Psycho-Oncology Professionals Pediatric Psychology Postdoctoral Fellowship University of Louisville School of

38

Chaotic chirped-pulse oscillators.  

PubMed

We present results of experimental investigation of the chaotic and quasi-periodic regime in the chirped-pulsed (dissipative soliton) Cr:ZnS and Cr:ZnSe mid-IR oscillators with significant third-order dispersion. The instability develops when the spectrum edge approaches resonance with a linear wave either due to power increase or by dispersion adjustment. In practice, this occurs when the spectrum edge reaches zero dispersion wavelength. The analysis suggests a three-oscillator chaos model, which is confirmed by numerical simulations. The regime is long-term stable and can be easily overlooked in similar systems. We show that chaotic regime is accompanied by a characteristic spectral shape and can be reliably recognized by using wavelength-skewed filters and by second-harmonic or two-photon absorption detectors. PMID:24514508

Sorokin, Evgeni; Tolstik, Nikolai; Kalashnikov, Vladimir L; Sorokina, Irina T

2013-12-01

39

Terahertz surface plasmon on chirped groove grating  

Microsoft Academic Search

The excitation of terahertz surface plasmon on metallized chirped groove gratings is studied in time- and frequency-domain. These gratings have a potential to launch and decouple broadband terahertz surface plasmon necessary for integrated optical circuits.

M. Martl; J. Darmo; K. Unterrainer; E. Gornik

2008-01-01

40

Low frequency ac waveform generator  

DOEpatents

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Bilharz, O.W.

1983-11-22

41

FM use of BM PPT  

E-print Network

Brady (LB to attend Core Team forum) Core Operational Team (decision makers) Paul Thompson ? FM Manager Tony Jones ? CTS M&E Team Leader Andy Schilling ? LOR M&E Lead George Hughes ? NG Bailey Tom Young ? Commissioning Manager (Fortnightly... Review Forum) LOR Support to Core Team ?NG Bailey ?Lateral Commissioning Team. ?Granfen ?ADT ?Specialist sub contractors ?Wider supply chain. ?Arup fire ?BIM Team (AR) ?Dragonfly (Journey plans) ?CDMC ?Etc? MCC Support to Core Team...

Brady, L.

2012-01-01

42

Optical waveform generation using a directly modulated laser  

NASA Astrophysics Data System (ADS)

The capability of a directly modulated laser (DML) can be dramatically enhanced through precise control of the drive current waveform based on digital signal processing (DSP) and a digital-to-analog convertor (DAC). In this paper, a novel method to pre-compensate fiber dispersion for metro and regional networks is described for a bit rate of 10.709 Gb/s using a DML. A look-up table (LUT) for the drive current is optimized for dispersion mitigation. The entries of the LUT are determined based on the effects of the DML adiabatic and transient chirp on pulse propagation, the nonlinear mapping between the input current and the output optical power, and the bandwidth of the DML package. A DAC operating at 2 samples per bit (21.418 GSa/s with 6 bit resolution) converts the digital samples at the output of the LUT to an analog current waveform driving the DML. Experimental results for a bit rate of 10.709 Gb/s and on-off keying demonstrate a transmission reach of 252 km using a DML intended for 2.5 Gb/s operation and 608 km using a chirp managed laser intended for 10 Gb/s operation. Using this approach (DSP + DAC), the generation of 10.709 Gb/s differential phase shift keying (DPSK) and 56 Gb/s 16-ary quadrature amplitude modulation, sub-carrier multiplexed (QAM SCM) optical signals using the direct modulation of a passive feedback laser is also presented. 6-bit DACs operating at sampling rates of 21.418 GSa/s and 28 GSa/s, respectively, was used to generate the requisite analog current waveform.

Cartledge, John C.; Karar, Abdullah S.; Roberts, Kim

2013-10-01

43

Quantum optical waveform conversion  

E-print Network

Currently proposed architectures for long-distance quantum communication rely on networks of quantum processors connected by optical communications channels [1,2]. The key resource for such networks is the entanglement of matter-based quantum systems with quantum optical fields for information transmission. The optical interaction bandwidth of these material systems is a tiny fraction of that available for optical communication, and the temporal shape of the quantum optical output pulse is often poorly suited for long-distance transmission. Here we demonstrate that nonlinear mixing of a quantum light pulse with a spectrally tailored classical field can compress the quantum pulse by more than a factor of 100 and flexibly reshape its temporal waveform, while preserving all quantum properties, including entanglement. Waveform conversion can be used with heralded arrays of quantum light emitters to enable quantum communication at the full data rate of optical telecommunications.

D Kielpinski; JF Corney; HM Wiseman

2010-10-11

44

Sampled chirped fiber gratings as distributed pressure sensors  

Microsoft Academic Search

Fiber gratings have been studied for their applications in sensing and communications. Many sensing applications of the uniform fiber Bragg grating, chirped fiber grating and long period grating have been studied, proposed and commercialized. Sampled chirped gratings have been studied for multichannel dispersion compensation in DWDM systems. In this paper, we show that the sampled chirped fiber grating can be

Swee Chuan Tjin; Lipi Mohanty; Nam Quoc Ngo

2004-01-01

45

Enhancement of sound in chirped sonic crystals  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate a mechanism of sound wave concentration based on soft reflections in chirped sonic crystals. The reported controlled field enhancement occurs at around particular (bright) planes in the crystal and is related to a progressive slowing down of the sound wave as it propagates along the material. At these bright planes, a substantial concentration of the energy (with a local increase up to 20 times) was obtained for a linear chirp and for frequencies around the first band gap. A simple couple mode theory is proposed that interprets and estimates the observed effects. Wave concentration energy can be applied to increase the efficiency of detectors and absorbers.

Romero-Garca, V.; Pic, R.; Cebrecos, A.; Snchez-Morcillo, V. J.; Staliunas, K.

2013-03-01

46

High precision triangular waveform generator  

DOEpatents

An ultra-linear ramp generator having separately programmable ascending and descending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

Mueller, Theodore R. (Oak Ridge, TN)

1983-01-01

47

Compression of amplified chirped optical pulses  

Microsoft Academic Search

A system is reported which transposes a short-pulse amplification technique employed in radar to the optical regime and that, in principle, should be capable of producing short (1 pc or less) pulses with energies at the Joule level. The technique involves stretching a chirped optical pulse and then amplifying it before recompression. To date, 2-ps pulses with an energy of

D. Strickland; G. Mourou

1985-01-01

48

FM 2-22.3 (FM 34-52) HUMAN INTELLIGENCE  

E-print Network

FM 2-22.3 (FM 34-52) HUMAN INTELLIGENCE COLLECTOR OPERATIONS HEADQUARTERS, DEPARTMENT OF THE ARMY Washington, DC, 6 September 2006 Human Intelligence Collector Operations Contents Page PREFACE...................................................................................................1-1 Intelligence Battlefield Operating System

US Army Corps of Engineers

49

Waveforms from colliding black holes  

Microsoft Academic Search

A new field of astrophysics is beginning to form. The advent of very large gravitational radiation detectors will soon make it possible to study the physics of distant catastrophic phenomena by the gravitational radiation that is emitted. However, before any physical interpretations can be extracted from the waveforms, there must be a way of associating particular features in the waveforms

Yosef Eliyahu Zlochower

2002-01-01

50

Analysis of the ambiguity function for an FM signal derived from the Lorenz chaotic flow  

NASA Astrophysics Data System (ADS)

In prior work, we showed that any one of the state variables of the Lorenz chaotic flow can be used effectively as the instantaneous frequency of an FM signal. We further investigated a method to improve chaotic-wideband FM signals for high resolution radar applications by introducing a compression factor to the Lorenz flow equations and by varying two control parameters, namely ? and ?, to substantially increase the bandwidth of the signal. In this paper, we obtain an empirical quadratic relationship between these two control parameters that yields a high Lyapunov exponent which allows the Lorenz flow to quickly diverge from its initial state. This, in turn, results in an FM signal with an agile center frequency that is also chaotic. A time-frequency analysis of the FM signal shows that variable time-bandwidth products of the order of 105 and wide bandwidths of approximately 10 GHz are achievable over short segments of the signal. Next, we compute the average ambiguity function for a large number of short segments of the signal with positive range-Doppler coupling. The resulting ambiguity surface is shaped as a set of mountain ridges that align with multiple range-Doppler coupling lines with low self-noise surrounding the peak response. Similar results are achieved for segments of the signal with negative range-Doppler coupling. The characteristics of the ambiguity surface are directly attributed to the frequency agility of the FM signal which could be potentially used to counteract electronic counter measures aimed at traditional chirp radars.

Pappu, Chandra S.; Flores, Benjamin C.; deBroux, Patrick

2012-06-01

51

Radar/sonar acceleration estimation with linear-period modulated waveforms  

NASA Astrophysics Data System (ADS)

Doppler and acceleration tolerance of wideband LPM/HFM (linear period-modulated, hyperbolic frequency-modulated) and linear FM signals are compared. A bank of filters matched to frequency-shifted versions of a wideband LPM/HFM transmission system yields a joint maximum-likelihood estimate of range and acceleration and avoids acceleration-induced degradation in detection performance. Analytical and neurophysiological results suggest that such processing can be used in bat echolocation for detection and classification of insect wing motion, since wideband LFM waveforms are much less Doppler-tolerant than HFM waveforms but have greater acceleration tolerance.

Altes, Richard A.

1990-11-01

52

47 CFR 73.322 - FM stereophonic sound transmission standards.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false FM stereophonic sound transmission standards. 73.322 Section 73... 73.322 FM stereophonic sound transmission standards. (a) An FM broadcast...the stereophonic pilot frequency in a transmission system meeting the following...

2011-10-01

53

47 CFR 73.322 - FM stereophonic sound transmission standards.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false FM stereophonic sound transmission standards. 73.322 Section 73... 73.322 FM stereophonic sound transmission standards. (a) An FM broadcast...the stereophonic pilot frequency in a transmission system meeting the following...

2010-10-01

54

47 CFR 73.322 - FM stereophonic sound transmission standards.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false FM stereophonic sound transmission standards. 73.322 Section 73... 73.322 FM stereophonic sound transmission standards. (a) An FM broadcast...the stereophonic pilot frequency in a transmission system meeting the following...

2012-10-01

55

47 CFR 73.297 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false FM stereophonic sound broadcasting. 73.297 Section 73...Stations 73.297 FM stereophonic sound broadcasting. (a) An FM broadcast...stereophonic (biphonic, quadraphonic, etc.) sound programs upon installation of...

2011-10-01

56

47 CFR 73.297 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false FM stereophonic sound broadcasting. 73.297 Section 73...Stations 73.297 FM stereophonic sound broadcasting. (a) An FM broadcast...stereophonic (biphonic, quadraphonic, etc.) sound programs upon installation of...

2012-10-01

57

47 CFR 73.297 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false FM stereophonic sound broadcasting. 73.297 Section 73...Stations 73.297 FM stereophonic sound broadcasting. (a) An FM broadcast...stereophonic (biphonic, quadraphonic, etc.) sound programs upon installation of...

2013-10-01

58

47 CFR 73.297 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false FM stereophonic sound broadcasting. 73.297 Section 73...Stations 73.297 FM stereophonic sound broadcasting. (a) An FM broadcast...stereophonic (biphonic, quadraphonic, etc.) sound programs upon installation of...

2010-10-01

59

Fourier-transform electron spin resonance with bandwidth-compensated chirp pulses.  

PubMed

Electron spin echo experiments using chirp pulses at X-band around 9GHz have been performed with a home-built spectrometer based on an arbitrary waveform generator. Primary echoes without phase dispersion were obtained by employing the Bhlen-Bodenhausen scheme with the refocusing pulse being half as long as the coherence-generating pulse. To account for physical bandwidth limitation by the resonator, the instantaneous sweep rate of the chirps was adapted to the spectrometer's frequency response function, which can be recorded from the sample under study within a few minutes. Such bandwidth-compensated chirp pulses are experimentally shown to achieve an almost uniform excitation bandwidth that exceeds the resonator bandwidth. This uniform excitation allows for computing frequency-domain spectra by Fourier-transformation (FT) of the echo signal. For a nitroxide in dilute solid solution with a spectral width of 200MHz, the FT EPR spectrum agrees remarkably well with a field-swept echo-detected EPR spectrum. The overall spectral perturbation for operation far beyond the resonator bandwidth was characterized by acquiring a 700MHz wide spectral range of a copper (II) EPR spectrum with nearly uniform amplitude with excitation and refocusing pulses of 200 and 100ns, respectively. Furthermore, peculiarities were observed in solid-state FT EPR spectra of disordered systems. To understand these peculiarities two-dimensional data sets were acquired that correlate the FT EPR spectrum to inversion recovery or nuclear modulation. The echo envelope modulation experiments reveal echo decay rates increased by enhanced instantaneous diffusion and passage-specific effects in the nuclear modulations. The latter effect can be suppressed by nuclear modulation averaging. Apparent longitudinal relaxation times for a given subset of orientations are influenced by nuclear modulation effects. Proper extraction of orientation-dependent relaxation times thus requires an experimental setup that minimizes the modulations. PMID:25063952

Doll, Andrin; Jeschke, Gunnar

2014-09-01

60

Enlightening News and Views FM Employees  

E-print Network

in August with 22 years of service at Memorial. A retirement social was held for Joan at Squires House where contributed to the Campus Food Bank. #12;FM Light 2 Toys for Kids Since 2002, Campus Enforcement and Patrol

deYoung, Brad

61

Detector For FM Voice Or Digital Signals  

NASA Technical Reports Server (NTRS)

Frequency-modulation (FM) detector operates with either analog audio (usually voice) signals or digital signals sent by differential minimum-shift keying (DMSK). Performance expected similar to conventional limiter/discriminator FM detectors. Detector operates at baseband, obviating need for band-pass filtering at intermediate frequency. Baseband version made in very-large-scale integrated circuit. New detector useful in mobile communications, where trend is toward integrated voice and data service.

Davarian, Faramaz

1989-01-01

62

Point Response Characteristics for the CERES/EOS-PM, FM3 & FM4 instruments.  

NASA Technical Reports Server (NTRS)

This paper describes the point source functions (PSF s) of the Clouds and the Earth s Radiant Energy System (CERES,) Earth Observing System (EOS,) afternoon platform (PM,) Flight Model 3 (FM3,) and Flight Model 4 (FM4) scanning instruments. The PSF (also known as the Point Response Function, or PRF) is vital to the accurate geo-location of the remotely sensed radiance measurements acquired by the instrument. This paper compares the characteristics of the FM3 and FM4 instruments with the earlier Proto Flight Model (PFM) on the Tropical Rainfall Measuring Mission (TRMM) platform, and the FM1 and FM2 Models on the EOS morning orbiting (AM) platform, which has recently been renamed "Terra". All of the PSF s were found to be quite comparable, and the previously noted "spreading" characteristic of the window (water vapor) channel PSF is analyzed Keywords: PSF, PRF, CERES, TRMM, EOS, Earth Radiation Budget

Paden, Jack; Smith, G. Louis; Lee, Robert B., III; Pandey, Dhirendra K.; Priestley, Kory J.; Thomas, Susan; Wilson, Robert S.

1999-01-01

63

Online waveform processing for demanding target situations  

NASA Astrophysics Data System (ADS)

RIEGL LIDAR instruments are based on echo digitization and provide point cloud data by online waveform processing or full waveform data for external full waveform analysis or both. The advantages of online waveform processing of being fast and highly accurate for most typical target situation are made up by full waveform processing for demanding echo signal shapes when employing sophisticated algorithms. It is investigated how online waveform processing performs in turbid media and where the limitations are by analyzing experimental results when measuring in a fog chamber. An algorithm is proposed to determine the visibility range from the echo waveforms return of the medium.

Pfennigbauer, Martin; Wolf, Clifford; Weinkopf, Josef; Ullrich, Andreas

2014-06-01

64

Chirped fiber Bragg grating sensor for pressure and position sensing  

Microsoft Academic Search

We present a chirped fiber Bragg grating sensor that should be suitable for esophageal motility studies. The device uses the time-dependent group delay response of a chirped fiber Bragg grating to measure the peristaltic pressure wave that propagates down the esophagus with the transport of a bolus to the stomach. In contrast to existing transducers that only measure at discrete

Pieter L. Swart; Beatrys M. Lacquet; Anatolii A. Chtcherbakov

2005-01-01

65

Chirped optical solitons in single-mode birefringent fibers  

NASA Astrophysics Data System (ADS)

The trapping behavior of two chirped solitons forming a bound state in a single-mode birefringent fiber is investigated on the basis of a model of coupled nonlinear Schroedinger equations. The positive initial chirp plays an important role in controlling the threshold amplitude for soliton trapping without causing excessive pulse broadening.

Mahmood, M. F.

1996-12-01

66

Distributed nonlinear fiber chirped-pulse amplifier system  

E-print Network

Distributed nonlinear fiber chirped-pulse amplifier system Marc Hanna,* Dimitris Papadopoulos-stage fiber-based femtosecond amplification system is presented, based on chirped-pulse amplification. 2009 Optical Society of America OCIS codes: (060.2320) Fiber optics amplifiers and oscillators; (140

Paris-Sud XI, Université de

67

Sampled chirped fiber gratings as distributed pressure sensors  

Microsoft Academic Search

Fiber gratings have been studied for their applications in sensing and communications. Many sensing applications of the uniform fiber Bragg grating, chirped fiber grating and long period grating have been studied, proposed and commercialized. Sampled chirped gratings have been studied for multichannel dispersion compensation in DWDM systems. In this paper, we show that the sampled chi rped fiber grating can

Swee Chuan Tjin; Lipi Mohanty; Nam Quoc Ngo

68

Chirp on Crickets: Teaching Compilers Using an Embedded Robot Controller  

E-print Network

Chirp on Crickets: Teaching Compilers Using an Embedded Robot Controller Li Xu Department into the simple yet versatile Handy Cricket educational robot con- troller. As a compiler, the Chirp design with code generation for the Cricket controller. They will test their work on both phys- ical Cricket

69

Hyperspectral Imaging with Stimulated Raman Scattering by Chirped Femtosecond Lasers  

E-print Network

Hyperspectral Imaging with Stimulated Raman Scattering by Chirped Femtosecond Lasers Dan Fu, Gary imaging system using chirped femtosecond lasers to achieve rapid Raman spectra acquisition while retaining laser beams with an energy difference tuned to the vibrational frequency of the molecule of interest

Xie, Xiaoliang Sunney

70

FM 4-01.502 (FM 55-502) Army Watercraft Safety  

E-print Network

is available at Army Knowledge Online (www.us.army.mil) and General Dennis J. Reimer Training and DoctrineFM 4-01.502 (FM 55-502) Army Watercraft Safety May 2008 Distribution Restriction: Approved for public release; distribution is unlimited. Headquarters, Department of the Army #12;This publication

US Army Corps of Engineers

71

HEADQUARTERS FM 3-23.35 (FM 23-35) DEPARTMENT OF THE ARMY  

E-print Network

publication is available at Army Knowledge Online (www.us.army.mil) and General Dennis J. Reimer Training National Guard, and U.S. Army Reserve: To be distributed in accordance with the initial distribution numberHEADQUARTERS FM 3-23.35 (FM 23-35) DEPARTMENT OF THE ARMY COMBAT TRAINING WITH PISTOLS, M9 AND M11

US Army Corps of Engineers

72

Chirped fiber Bragg grating detonation velocity sensing.  

PubMed

An all optical-fiber-based approach to measuring high explosive detonation front position and velocity is described. By measuring total light return using an incoherent light source reflected from a linearly chirped fiber Bragg grating sensor in contact with the explosive, dynamic mapping of the detonation front position and velocity versus time is obtained. We demonstrate two calibration procedures and provide several examples of detonation front measurements: PBX 9502 cylindrical rate stick, radial detonation front in PBX 9501, and PBX 9501 detonation along curved meridian line. In the cylindrical rate stick measurement, excellent agreement with complementary diagnostics (electrical pins and streak camera imaging) is achieved, demonstrating accuracy in the detonation front velocity to below the 0.3% level when compared to the results from the pin data. Finally, an estimate on the linear spatial and temporal resolution of the system shows that sub-mm and sub-?s levels are attainable with proper consideration of the recording speed, detection sensitivity, spectrum, and chirp properties of the grating. PMID:23387683

Rodriguez, G; Sandberg, R L; McCulloch, Q; Jackson, S I; Vincent, S W; Udd, E

2013-01-01

73

Chirped fiber Bragg grating detonation velocity sensing  

NASA Astrophysics Data System (ADS)

An all optical-fiber-based approach to measuring high explosive detonation front position and velocity is described. By measuring total light return using an incoherent light source reflected from a linearly chirped fiber Bragg grating sensor in contact with the explosive, dynamic mapping of the detonation front position and velocity versus time is obtained. We demonstrate two calibration procedures and provide several examples of detonation front measurements: PBX 9502 cylindrical rate stick, radial detonation front in PBX 9501, and PBX 9501 detonation along curved meridian line. In the cylindrical rate stick measurement, excellent agreement with complementary diagnostics (electrical pins and streak camera imaging) is achieved, demonstrating accuracy in the detonation front velocity to below the 0.3% level when compared to the results from the pin data. Finally, an estimate on the linear spatial and temporal resolution of the system shows that sub-mm and sub-?s levels are attainable with proper consideration of the recording speed, detection sensitivity, spectrum, and chirp properties of the grating.

Rodriguez, G.; Sandberg, R. L.; McCulloch, Q.; Jackson, S. I.; Vincent, S. W.; Udd, E.

2013-01-01

74

Advanced analysis of FM-reception systems with antenna diversity  

Microsoft Academic Search

Objective comparisons of different FM-reception systems with FM-antenna diversity systems are important for optimization and development. An advanced analyzing and evaluation system for FM-antenna diversity systems is introduced. With the possibility to record real FM-signals and the preprocessing of FM-signals, which takes into account the influence of the reception scenario and the diversity antennas, objective and reproducible comparisons of different

S. Treinies; J. Hopf; S. Lindenmeier

2011-01-01

75

Frequency specificity of chirp-evoked auditory brainstem responses  

NASA Astrophysics Data System (ADS)

This study examines the usefulness of the upward chirp stimulus developed by Dau et al. [J. Acoust. Soc. Am. 107, 1530-1540 (2000)] for retrieving frequency-specific information. The chirp was designed to produce simultaneous displacement maxima along the cochlear partition by compensating for frequency-dependent traveling-time differences. In the first experiment, auditory brainstem responses (ABR) elicited by the click and the broadband chirp were obtained in the presence of high-pass masking noise, with cutoff frequencies of 0.5, 1, 2, 4, and 8 kHz. Results revealed a larger wave-V amplitude for chirp than for click stimulation in all masking conditions. Wave-V amplitude for the chirp increased continuously with increasing high-pass cutoff frequency while it remains nearly constant for the click for cutoff frequencies greater than 1 kHz. The same two stimuli were tested in the presence of a notched-noise masker with one-octave wide spectral notches corresponding to the cutoff frequencies used in the first experiment. The recordings were compared with derived responses, calculated offline, from the high-pass masking conditions. No significant difference in response amplitude between click and chirp stimulation was found for the notched-noise responses as well as for the derived responses. In the second experiment, responses were obtained using narrow-band stimuli. A low-frequency chirp and a 250-Hz tone pulse with comparable duration and magnitude spectrum were used as stimuli. The narrow-band chirp elicited a larger response amplitude than the tone pulse at low and medium stimulation levels. Overall, the results of the present study further demonstrate the importance of considering peripheral processing for the formation of ABR. The chirp might be of particular interest for assessing low-frequency information.

Wegner, Oliver; Dau, Torsten

2002-03-01

76

Three-Dimensional Analysis of Frequency-Chirped FELs  

SciTech Connect

Frequency-chirped free-electron lasers (FELs) are useful to generate a large photon bandwidth or a shorter x-ray pulse duration. In this paper, we present a three-dimensional analysis of a high-gain FEL driven by the energy-chirped electron beam. We show that the FEL eigenmode equation is the same for a frequency-chirped FEL as for an undulator-tapered FEL. We study the transverse effects of such FELs including mode properties and transverse coherence.

Huang, Z.

2010-09-14

77

FM Clerkship Update Helping Students do well  

E-print Network

the learning objectives of the STFM Family Medicine Clerkship Curriculum. Cases build clinical competency, fill educational gaps, and help instill the core values and attitudes of family medicine. fm and is acceptable for up to 60 Prescribed credits by the AAFP. Each Family Medicine Case is approved for up to 1

Maxwell, Bruce D.

78

FM radio: family interplay with sonic mementos  

Microsoft Academic Search

Digital mementos are increasingly problematic, as people acquire large amounts of digital belongings that are hard to access and often forgotten. Based on fieldwork with 10 families, we designed a new type of embodied digital memento, the FM Radio. It allows families to access and play sonic mementos of their previous holidays. We describe our underlying design motivation where recordings

Daniela Petrelli; Nicolas Villar; Vaiva Kalnikait; Lina Dib; Steve Whittaker

2010-01-01

79

FM wide band panel dipole antenna  

Microsoft Academic Search

It is very common that when a broadcaster needs to install an FM transmitting antenna within a large metropolitan area he places it on the tallest structure or building available. When the rooftop is already occupied by a large number of other types of transmitting and receiving antennas, the panel dipole antenna should be chosen. This antenna is secured to

Valentn Trainotti; N. Dalmas Di Giovanni

2002-01-01

80

Enlightening News and Views FM Employees  

E-print Network

event held in FM on Kindness Friday was a Children's Book Drive. A total of 407 books was collected, all Kindness Friday Soup Day and Book DriveIn This Issue Kindness Friday Book Drive Lotto Winner Green Tip Branch 1 on Blackmarsh Road at 7 pm on Friday, December 9. NAPE 7801 Children's Party will be held

deYoung, Brad

81

Waveform optimizations for ultrawideband radio systems  

Microsoft Academic Search

Solutions are presented for various optimizations of transient waveforms and signals used in ultrawideband radio systems. These include the transmit antenna generator waveform required to maximize receive antenna voltage amplitude (with bounded input energy), the transmit antenna generator waveform that provides the \\

David M. Pozar

2003-01-01

82

Fission modes of 256Fm and 258Fm in a microscopic approach  

E-print Network

A static microscopic study of potential-energy surfaces within the Skyrme-Hartree-Fock-plus-BCS model is carried out for the 256Fm and 258Fm isotopes with the goal of deducing some properties of spontaneous fission. The calculated fission modes are found to be in agreement with the experimentaly observed asymmetric-to-symmetric transition in the fragment-mass distributions and with the high- and low-total-kinetic-energy modes experimentally observed in 258Fm. Most of the results are similar to those obtained in macroscopic-microscopic models as well as in recent Hartree-Fock-Bogolyubov calculations with the Gogny interaction, with a few differences in their interpretations. In particular an alternative explanation is proposed for the low-energy fission mode of 258Fm.

L. Bonneau

2006-04-04

83

Control of Ultracold Collisions with Frequency-Chirped Light  

SciTech Connect

We report on ultracold atomic collision experiments utilizing frequency-chirped laser light. A rapid chirp below the atomic resonance results in adiabatic excitation to an attractive molecular potential over a wide range of internuclear separation. This leads to a transient inelastic collision rate which is large compared to that obtained with fixed-frequency excitation. The combination of high efficiency and temporal control demonstrates the benefit of applying the techniques of coherent control to the ultracold domain.

Wright, M.J.; Gould, P.L. [Department of Physics, U-3046, University of Connecticut, Storrs, Connecticut 06269 (United States); Gensemer, S.D. [Van der Waals-Zeeman Institut, Universiteit van Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands); Vala, J. [Department of Chemistry and Pitzer Center for Theoretical Chemistry, University of California, Berkeley, California 94720 (United States); Kosloff, R. [Department of Physical Chemistry and the Fritz Haber Research Center for Molecular Dynamics, the Hebrew University, 91094 Jerusalem (Israel)

2005-08-05

84

Low chirp observed in directly modulated quantum dot lasers  

Microsoft Academic Search

We have examined the dynamic properties of high-aspect-ratio InAs-quantum-dot (QD) lasers at room temperature. A novel characteristic of low chirp in the lasing wavelength under 1-GHz current modulation was found in the quantum dot lasers. This is more than one order of magnitude less than the typical chirp (0.2-nm) found in a conventional quantum well laser that we used as

Hideaki Saito; Kenichi Nishi; Akio Kamei; Shigeo Sugou

2000-01-01

85

Dense Monoenergetic Proton Beams from Chirped Laser-Plasma Interaction  

Microsoft Academic Search

Interaction of a frequency-chirped laser pulse with single protons and a hydrogen gas target is studied analytically and by means of particle-in-cell simulations, respectively. The feasibility of generating ultraintense (107 particles per bunch) and phase-space collimated beams of protons (energy spread of about 1%) is demonstrated. Phase synchronization of the protons and the laser field, guaranteed by the appropriate chirping

Benjamin J. Galow; Yousef I. Salamin; Tatyana V. Liseykina; Zoltn Harman; Christoph H. Keitel

2011-01-01

86

Versatile Dual-Channel Waveform Generator  

NASA Technical Reports Server (NTRS)

Programmable waveform generator synthesizes two independent waveforms simultaneously at frequencies up to 250 MHz. Can be in phase or out of phase with each other. Use of commercial integrated circuits helps keep cost low. Operation governed by BASIC source code enabling any user equipped with suitable personal computer to specify waveforms. User can modify source code to satisfy special needs. Other applications include simulation of Doppler waveforms for radar, and of video signals for testing color displays and computer monitors. With eventual substitution of gallium arsenide integrated circuits for its present silicon integrated circuits, instrument able to generate waveforms with 14-bit precision and sample rates as high as 2 GHz.

Staples, Edward J.; Lie, Sen; Ching, Michael; Budinger, James M.

1994-01-01

87

Sampled chirped fiber gratings as distributed pressure sensors  

NASA Astrophysics Data System (ADS)

Fiber gratings have been studied for their applications in sensing and communications. Many sensing applications of the uniform fiber Bragg grating, chirped fiber grating and long period grating have been studied, proposed and commercialized. Sampled chirped gratings have been studied for multichannel dispersion compensation in DWDM systems. In this paper, we show that the sampled chirped fiber grating can be used as a distributed pressure sensor. The chirp provides ease of manufacture of many gratings. The sampling results in many small, uniform grating-like structures. This fact can be used to simulate a distributed sensor over the length of the sampled chirped grating. When a surface comes into contact with the sensor, the distribution of the pressure determines the shift in central wavelength of the various sub-gratings. The sub-grating that experiences the maximum pressure will show maximum wavelength shift whereas adjacent sub-gratings will show less shift. This can also give the location of the pressure. The sensor design comprises of a sampled chirped grating embedded in unidirectional fiber-reinforced composite prepreg. The prepreg enhances the mechanical strength and the unidirectional embedding reduces birefringence. The number of layers in the prepreg stack varies the sensitivity. Such distributed pressure sensors can be applied in robotics, ergonomics, and in the biomedical field.

Tjin, Swee Chuan; Mohanty, Lipi; Ngo, Nam Quoc

2004-09-01

88

47 CFR 73.597 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false FM stereophonic sound broadcasting. 73.597 Section 73...Stations 73.597 FM stereophonic sound broadcasting. A noncommercial educational...authority from the FCC, transmit stereophonic sound programs upon installation of...

2013-10-01

89

47 CFR 73.597 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false FM stereophonic sound broadcasting. 73.597 Section 73...Stations 73.597 FM stereophonic sound broadcasting. A noncommercial educational...authority from the FCC, transmit stereophonic sound programs upon installation of...

2012-10-01

90

47 CFR 73.597 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false FM stereophonic sound broadcasting. 73.597 Section 73...Stations 73.597 FM stereophonic sound broadcasting. A noncommercial educational...authority from the FCC, transmit stereophonic sound programs upon installation of...

2011-10-01

91

47 CFR 73.322 - FM stereophonic sound transmission standards.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false FM stereophonic sound transmission standards. 73.322 Section...Stations 73.322 FM stereophonic sound transmission standards. (a) An...one channel of a two channel (biphonic) sound transmission, modulation of the...

2013-10-01

92

47 CFR 73.597 - FM stereophonic sound broadcasting.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false FM stereophonic sound broadcasting. 73.597 Section 73...Stations 73.597 FM stereophonic sound broadcasting. A noncommercial educational...authority from the FCC, transmit stereophonic sound programs upon installation of...

2010-10-01

93

A modified adaptive algorithm of dealing with the high chirp when chirped pulses propagating in optical fiber  

NASA Astrophysics Data System (ADS)

In this paper, we propose a modified adaptive algorithm (MAA) of dealing with the high chirp to efficiently simulate the propagation of chirped pulses along an optical fiber for the propagation distance shorter than the "temporal focal length". The basis of the MAA is that the chirp term of initial pulse is treated as the rapidly varying part by means of the idea of the slowly varying envelope approximation (SVEA). Numerical simulations show that the performance of the MAA is validated, and that the proposed method can decrease the number of sampling points by orders of magnitude. In addition, the computational efficiency of the MAA compared with the time-domain beam propagation method (BPM) can be enhanced with the increase of the chirp of initial pulse.

Wu, Lianglong; Fu, Xiquan; Guo, Xing

2013-03-01

94

Automatic frequency control for FM transmitter  

NASA Technical Reports Server (NTRS)

An automatic frequency control circuit for an FM television transmitter is described. The frequency of the transmitter is sampled during what is termed the back porch portion of the horizontal synchronizing pulse which occurs during the retrace interval, the frequency sample compared with the frequency of a reference oscillator, and a correction applied to the frequency of the transmitter during this portion of the retrace interval.

Honnell, M. A. (inventor)

1974-01-01

95

FM Receiving System for Endoradiosonde Techniques  

Microsoft Academic Search

The receiver detects FM signals with frequency deviations up to 30 kc in the 300-400-kc band. The drift is less than 20 cps per day. The receiver operates satisfactorily with field strength variations of 1:30,000. To prevent erroneous recordings when the signal strength varies abruptly with changes in the mutual direction of the transmitting and receiving antennas, a nondirectional receiving

B. Jacobson; B. Lindberg

1960-01-01

96

(Formerly FM 19-4) MILITARY POLICE LEADERS'  

E-print Network

FM 3-19.4 (Formerly FM 19-4) MILITARY POLICE LEADERS' HANDBOOK HEADQUARTERS, DEPARTMENT OF THE ARMY Police Leaders' Handbook 1. Change FM 3-19.4, 4 March 2002 as follows: Remove Old Pages Insert New Pages March 2002 Military Police Leaders' Handbook Contents Page PREFACE

US Army Corps of Engineers

97

Armstrong's invention of noise-suppressing FM [History of Communications  

Microsoft Academic Search

Edwin H. Armstrong is well known as the inventor of wide-deviation or wideband FM. His patent on this invention was granted December 26, 1933, followed soon thereafter by demonstrations of his system before engineers, papers on the subject of wideband frequency modulation (FM) and its noise-suppression property, and eventually, of course, after World War II, widespread acceptance of FM by

MISCHA SCHWARTZ

2009-01-01

98

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following Figures 1 and...

2012-10-01

99

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following Figures 1 and...

2011-10-01

100

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following Figures 1 and...

2013-10-01

101

Sound Reproduction Using Evolutionary Methods: A Comparison of FM Models  

Microsoft Academic Search

In this study a genetic algorithm is used to op- timize the parameters of a sound synthesizer in order to reproduce a given sound. Three synthesis methods, based on frequency modu- lation, are discussed: double FM, nested FM and asymmetrical FM. These are tested on (1) their influence on the optimization process per- formed by the genetic algorithm and (2)

L. J. S. M. Alberts

102

Phase-locked loop FM demodulator  

NASA Technical Reports Server (NTRS)

A conventional phase-locked loop is improved by replacing its phase detector with one comprising a linear ramp generator and a sample-and-hold circuit, thus eliminating the need for a lowpass loop filter, although the output of the sample-and-hold circuit may be filtered in the case of a very low level modulating signal on the incoming FM signal, but then filtering is not a difficult problem as in a conventional phase-locked loop. The result is FM demodulation by zero-order estimation. For FM demodulation by first-order estimation, the arithmetic difference between adjacent samples is formed, and using a second sample-and-hold circuit an arithmetic difference signal is produced as an input to a second ramp generator that is reset after each sampling cycle to generate a ramp the slope of which is a function of the arithmetic difference signal stored in the second sample-and-hold circuit. The ramp thus generated by the second ramp generator is arithmetically summed with the zero-estimation signal from the first sample-and-hold circuit to form a first-order estimation signal. Filtering such a first-order estimation signal is less of a problem than filtering a zero-order estimation signal.

Kirkham, Harold (Inventor); Jackson, Shannon P. (Inventor)

1992-01-01

103

47 CFR 73.827 - Interference to the input signals of FM translator or FM booster stations.  

Code of Federal Regulations, 2011 CFR

...Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.827 Interference to the input signals of FM...

2011-10-01

104

47 CFR 73.827 - Interference to the input signals of FM translator or FM booster stations.  

Code of Federal Regulations, 2013 CFR

...Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.827 Interference to the input signals of FM...

2013-10-01

105

47 CFR 73.827 - Interference to the input signals of FM translator or FM booster stations.  

Code of Federal Regulations, 2010 CFR

...Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.827 Interference to the input signals of FM...

2010-10-01

106

47 CFR 73.827 - Interference to the input signals of FM translator or FM booster stations.  

Code of Federal Regulations, 2012 CFR

...Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.827 Interference to the input signals of FM...

2012-10-01

107

Optically tunable chirped fiber Bragg grating.  

PubMed

This work presents an optically tunable chirped fiber Bragg grating (CFBG). The CFBG is obtained by a side-polished fiber Bragg grating (SPFBG) whose thickness of the residual cladding layer in the polished area (D(RC)) varies with position along the length of the grating, which is coated with a photoresponsive liquid crystal (LC) overlay. The reflection spectrum of the CFBG is tuned by refractive index (RI) modulation, which comes from the phase transition of the overlaid photoresponsive LC under ultraviolet (UV) light irradiation. The broadening in the reflection spectrum and corresponding shift in the central wavelength are observed with UV light irradiation density of 0.64mW/mm. During the phase transition of the photoresponsive LC, the RI increase of the overlaid LC leads to the change of the CFBG reflection spectrum and the change is reversible and repeatable. The optically tunable CFBGs have potential use in optical DWDM system and an all-fiber telecommunication system. PMID:22565706

Li, Zhen; Chen, Zhe; Hsiao, V K S; Tang, Jie-Yuan; Zhao, Fuli; Jiang, Shao-Ji

2012-05-01

108

High-precision triangular-waveform generator  

DOEpatents

An ultra-linear ramp generator having separately programmable ascending and decending ramp rates and voltages is provided. Two constant current sources provide the ramp through an integrator. Switching of the current at current source inputs rather than at the integrator input eliminates switching transients and contributes to the waveform precision. The triangular waveforms produced by the waveform generator are characterized by accurate reproduction and low drift over periods of several hours. The ascending and descending slopes are independently selectable.

Mueller, T.R.

1981-11-14

109

Effects of collisions on energetic particle-driven chirping bursts  

SciTech Connect

In the presence of an energetic particle population in a dissipative plasma, self-trapped structures in phase-space (holes and clumps) emerge from nonlinear wave-particle interactions. Their dynamics can lead to a nonlinear continuous shifting of the wave frequency (chirping). The effects of collisions on chirping characteristics are investigated, with a one-dimensional kinetic model. Existing analytic theory is extended to account for Krook-like collisions, which quantitatively explains a significant departure from widely accepted square-root time dependency. Relaxation oscillations, associated with chirping bursts, are investigated in the presence of dynamical friction and velocity-diffusion. The period increases with decreasing drag and weakly increases with decreasing diffusion. The mechanism is clarified with a simple semi-analytic model of hole/clump pair, which satisfies a Fokker-Planck equation. The model shows that the linear growth rate cannot be obtained simply by fitting an exponential to the amplitude time-series.

Lesur, M. [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga, Kasuga Koen 6-1, Fukuoka 816-8580 (Japan)] [Itoh Research Center for Plasma Turbulence, Kyushu University, Kasuga, Kasuga Koen 6-1, Fukuoka 816-8580 (Japan)

2013-05-15

110

Beam energy chirp effects in seeded free-electron lasers  

NASA Astrophysics Data System (ADS)

Seeded free-electron lasers (FELs) hold great promise for generating high brilliance radiation pulses with a narrow bandwidth, which typically requires an electron bunch with relatively uniform energy distribution. However, it has been pointed out that the beam energy curvature generated in the acceleration process may degrade the output radiation pulse quality of seeded FELs. In this paper, we studied the beam energy chirp effects in various seeded FEL configurations. The theoretical and simulation results show that the performance degradation of high gain harmonic generation scheme is proportional to the beam energy chirp, while the advanced seeding schemes, e.g. echo-enabled harmonic generation and phase merging enhanced harmonic generation, are capable of eliminating the effect of the electron beam energy chirp.

Wang, Guanglei; Feng, Chao; Deng, Haixiao; Zhang, Tong; Wang, Dong

2014-07-01

111

Rainbow trapping using chirped all-dielectric periodic structures  

NASA Astrophysics Data System (ADS)

We report a numerical investigation of rainbow trapping (light of different wavelengths) at different spatial locations in a newly designed two-dimensional photonic structure that is formed using chirping parameters in two-dimensional photonic crystals. Chirped parameters ensure trapping of certain light wavelengths inside these structures. To achieve broadband electromagnetic wave trapping, we properly adjust and chirp the position and dielectric filling factor of each unit cell within a photonic crystal structure. The low group velocity regions of the dielectric continuum bands at the Brillouin zone edge enable different wavelengths to be slowed and stopped along the propagation direction. The all-dielectric transparent material nature of the proposed structure realizes light trapping in different electromagnetic regions by spatially varying the effective refractive index of the structure.

Kurt, H.; Yilmaz, D.

2013-03-01

112

Chirped Gaussian laser beam parameters in paraxial approximation  

NASA Astrophysics Data System (ADS)

In this paper, new expressions for spot size, radius of curvature, and Rayleigh length of a linearly and negatively chirped Gaussian beam are presented in paraxial approximation self-consistently. It is shown that there is a slight modification in those relations in comparison to that of used in literatures. These modifications change the tailored parameters in some laser beam interactions such as laser electron vacuum acceleration. At propagation distances much grater than the Rayleigh length, the modifications indicate that the temporal shape of the chirped laser beam will be changed. This effect indicates an asymmetric pulse with a slowly increasing front part and a suddenly dropping tail. For propagation distances less than the Rayleigh length, the change in laser pulse shape is not considerable. Finally, the modifications are employed in modeling of a single electron acceleration by the chirped Gaussian laser pulse.

Sohbatzadeh, F.; Mirzanejhad, S.; Aku, H.; Ashouri, S.

2010-08-01

113

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer  

NASA Astrophysics Data System (ADS)

Chirped pulse Fourier transform microwave (CP-FTMW) spectrometers have become the instrument of choice for acquiring rotational spectra, due to their high sensitivity, fast acquisition rate, and large bandwidth. Here we present the design and capabilities of a recently constructed CP-FTMW spectrometer using direct digital synthesis (DDS) as a new method for chirped pulse generation, through both a suite of extensive microwave characterizations and deep averaging of the 10-14 GHz spectrum of jet-cooled acetone. The use of DDS is more suited for in situ applications of CP-FTMW spectroscopy, as it reduces the size, weight, and power consumption of the chirp generation segment of the spectrometer all by more than an order of magnitude, while matching the performance of traditional designs. The performance of the instrument was further improved by the use of a high speed digitizer with dedicated signal averaging electronics, which facilitates a data acquisition rate of 2.1 kHz.

Finneran, Ian A.; Holland, Daniel B.; Carroll, P. Brandon; Blake, Geoffrey A.

2013-08-01

114

High-spectral-resolution multiplex CARS spectroscopy using chirped pulses  

NASA Astrophysics Data System (ADS)

A novel technique for achieving high spectral resolution with a femtosecond laser system is presented. Transform-limited 800 nm, 90 femtosecond (fs) pulses pass off two gratings, stretching the pulse in time to a pulse width of several picoseconds due to an induced linear temporal chirp directly proportional to the grating separation. This chirped pulse is the degenerate pump (?P) and probe (?p) pulse for the CARS experiment. When overlapped in time with the 1050 nm, 90 fs transform-limited Stokes (?S) pulse, only a fraction of the chirped ?p pulse generates the CARS signal, thereby creating a temporal slit that defines the spectral resolution of the technique. Spectra for liquid methanol and liquid isooctane are presented, with ~6 cm-1 spectral resolution achieved for isooctane. Resonance enhancement and the mechanism of achieving high spectral resolution are shown by adjusting the ?S wavelength and ?p delay relative to the ?S pulse.

Knutsen, Kelly P.; Johnson, Justin C.; Miller, Abigail E.; Petersen, Poul B.; Saykally, Richard J.

2004-06-01

115

Project Summary MRI: Development of a Chirped-Pulse, Fourier-Transform mm-Wave Pulsed  

E-print Network

Project Summary MRI: Development of a Chirped-Pulse, Fourier-Transform mm-Wave Pulsed Uniform technologies: chirped-pulse Fourier-transform mm-wave spectroscopy and pulsed uniform supersonic flows: The instrument will leverage the ultra-broadband Chirped-pulse Fourier-transform Microwave (CP

Baskaran, Mark

116

Multiple mechanisms shape FM sweep rate selectivity: complementary or redundant?  

PubMed Central

Auditory neurons in the inferior colliculus (IC) of the pallid bat have highly rate selective responses to downward frequency modulated (FM) sweeps attributable to the spectrotemporal pattern of their echolocation call (a brief FM pulse). Several mechanisms are known to shape FM rate selectivity within the pallid bat IC. Here we explore how two mechanisms, stimulus duration and high-frequency inhibition (HFI), can interact to shape FM rate selectivity within the same neuron. Results from extracellular recordings indicated that a derived duration-rate function (based on tonal response) was highly predictive of the shape of the FM rate response. Longpass duration selectivity for tones was predictive of slowpass rate selectivity for FM sweeps, both of which required long stimulus durations and remained intact following iontophoretic blockade of inhibitory input. Bandpass duration selectivity for tones, sensitive to only a narrow range of tone durations, was predictive of bandpass rate selectivity for FM sweeps. Conversion of the tone duration response from bandpass to longpass after blocking inhibition was coincident with a change in FM rate selectivity from bandpass to slowpass indicating an active inhibitory component to the formation of bandpass selectivity. Independent of the effect of duration tuning on FM rate selectivity, the presence of HFI acted as a fastpass FM rate filter by suppressing slow FM sweep rates. In cases where both mechanisms were present, both had to be eliminated, by removing inhibition, before bandpass FM rate selectivity was affected. It is unknown why the auditory system utilizes multiple mechanisms capable of shaping identical forms of FM rate selectivity though it may represent distinct but convergent modes of neural signaling directed at shaping response selectivity for important biologically relevant sounds. PMID:22912604

Williams, Anthony J.; Fuzessery, Zoltan M.

2012-01-01

117

A portable CW/FM-CW Doppler radar for local investigation of severe storms  

SciTech Connect

During the 1987 spring storm season we used a portable 1-W X-band CW Doppler radar to probe a tornado, a funnel cloud, and a wall cloud in Oklahoma and Texas. This same device was used during the spring storm season in 1988 to probe a wall cloud in Texas. The radar was battery powered and highly portable, and thus convenient to deploy from our chase vehicle. The device separated the receding and approaching Doppler velocities in real time and, while the radar was being used, it allowed convenient stereo data recording for later spectral analysis and operator monitoring of the Doppler signals in stereo headphones. This aural monitoring, coupled with the ease with which an operator can be trained to recognize the nature of the signals heard, made the radar very easy to operate reliably and significantly enhanced the quality of the data being recorded. At the end of the 1988 spring season, the radar was modified to include FM-CW ranging and processing. These modifications were based on a unique combination of video recording and FM chirp generation, which incorporated a video camera and recorder as an integral part of the radar. After modification, the radar retains its convenient portability and the operational advantage of being able to listen to the Doppler signals directly. The original mechanical design was unaffected by these additions. During the summer of 1988, this modified device was used at the Langmuir Laboratory at Socorro, New Mexico in an attempt to measure vertical convective flow in a thunderstorm. 2 refs., 2 figs.

Unruh, W.P.; Wolf, M.A.; Bluestein, H.B.

1988-01-01

118

High spectral resolution multiplex CARS spectroscopy using chirped pulses  

NASA Astrophysics Data System (ADS)

A simple technique for achieving high spectral resolution coherent anti-Stokes Raman scattering (CARS) spectra with a femtosecond laser system is presented. A linearly chirped and stretched (10 ps) pump pulse generates CARS signal only when overlapped in time with the Stokes pulse (90 fs), creating a `temporal slit' that defines the spectral resolution of the technique. Multiplex CARS spectra for liquid methanol and liquid isooctane are presented, demonstrating a spectral resolution of better than 5 cm -1. This new chirped (c-CARS) technique should prove useful for chemically-selective imaging applications, as it significantly reduces the non-resonant background contribution.

Knutsen, K. P.; Johnson, J. C.; Miller, A. E.; Petersen, P. B.; Saykally, R. J.

2004-04-01

119

Waveform digitizing at 500 MHz  

SciTech Connect

Experiment E787 at Brookhaven National Laboratory is designed to study the decay K/sup +/ ..-->.. ..pi../sup +/..nu../bar /nu// to a sensitivity of 2 /times/ 10/sup /minus/10/. To achieve acceptable muon rejection it is necessary to couple traditional methods (range/energy/momentum correlation) with observation of the ..pi../sup +/ ..-->.. ..mu../sup +/ ..-->.. e/sup +/..nu../bar /nu// decay sequence in scintillator. We report on the design and construction of over 200 channels of relatively low cost solid state waveform digitizers. The distinguishing features are: 8 bits dynamic range, 500 MHz sampling, zero suppression on the fly, deep memory (up to .5 msec), and fast readout time (100 ..mu..sec for the entire system). We report on data obtained during the February--May 1988 run showing performance of the system for the observation of the above decay. 9 figs.

Atiya, M.; Ito, M.; Haggerty, J.; Ng, C.; Sippach, F.W.

1988-01-01

120

AM-FM separation using auditory-motivated filters  

Microsoft Academic Search

An approach to the joint estimation of sine-wave amplitude modulation (AM) and frequency modulation (FM) is described based on the transduction of frequency modulation into amplitude modulation by linear filters, being motivated by the hypothesis that the auditory system uses a similar transduction mechanism in measuring sine-wave FM. An AM-FM estimation algorithm is described that uses the amplitude envelope of

Thomas F. Quatieri; Thomas E. Hanna; G. C. O'Leary

1997-01-01

121

FINDR: Low-Cost Indoor Positioning Using FM Radio  

NASA Astrophysics Data System (ADS)

This paper presents an indoor positioning system based on FM radio. The system is built upon commercially available, short-range FM transmitters. The features of the FM radio which make it distinct from other localisation technologies are discussed. Despite the low cost and off-the-shelf components, the performance of the FM positioning is comparable to that of other positioning technologies (such as Wi-Fi). From our experiments, the median accuracy of the system is around 1.3 m and in 95% of cases the error is below 4.5 m.

Papliatseyeu, Andrei; Kotilainen, Niko; Mayora, Oscar; Osmani, Venet

122

Spectral selectivity of FM-FM neurons in the auditory cortex of the echolocating bat, Myotis lucifugus  

Microsoft Academic Search

1.Spectral sensitivity was examined in delaysensitive neurons in the auditory cortex of the awake FM bat, Myotis lucifugus. FM stimuli sweeping 60 kHz downward in 4 ms were used as simulated pulse-echo pairs to measure delay-dependent responses. At each neuron's best delay, the pulse and\\/or echo were divided into 4 FM quarters (Ist, IInd, IIIrd, and IVth), each sweeping 15

Masao Maekawa; Donald Wong; William G. Paschal

1992-01-01

123

Ultra-wideband WDM transmission using cascaded chirped fiber gratings  

Microsoft Academic Search

We demonstrate 32 channel WDM transmission at a per-channel rate of 10 Gb\\/s over 375 km (five amplified fiber spans) of conventional fiber. Chirped-fiber-grating modules provide dispersion compensation over an 18-nm bandwidth, and a swept-frequency measurement confirms continuous good performance across the entire band

L. D. Garrett; A. H. Gnauck; R. W. Tkach; B. Agogliati; L. Arcangeli; D. Scarano; V. Gusmeroli; C. Tosetti; G. Di Maio; F. Forghieri

1999-01-01

124

High Squint SAR Processing Using Modified Extended Chirp Scaling  

Microsoft Academic Search

This paper proposes a novel approach for high squint missile borne SAR raw data processing using a modified extended chirp scaling algorithm to accommodate the condition of high squint and short wave wavelength. Compared with the tradition synthesis aperture radar (SAR), the missile borne SAR has important characteristics including high flight speed, non-straight movement with non-constant velocity and big squint

Duan Shizhong; Li Junxian

2006-01-01

125

Electron heating enhancement by frequency-chirped laser pulses  

NASA Astrophysics Data System (ADS)

Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic field is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a0 = 5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about ne ? 6nc, where nc is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.

Yazdani, E.; Sadighi-Bonabi, R.; Afarideh, H.; Riazi, Z.; Hora, H.

2014-09-01

126

Aggressive Signal in ``Courtship'' Chirps of a Gregarious Cricket  

Microsoft Academic Search

Unlike other known species of crickets, Amphiacusta maya in Central America mates in groups. Experimentally silenced males experience reduced mating success, not owing to decreased receptivity by females, but owing to increased time spent fighting with other males that persistently interrupt silent courtships. Thus, the data indicate that ``courtship'' chirping functions as a warning to other males, rather than as

Christine R. B. Boake; Robert R. Capranica

1982-01-01

127

Spectral analysis using the CCD Chirp Z-transform  

NASA Technical Reports Server (NTRS)

The charge coupled device (CCD) Chirp Z transformation (CZT) spectral analysis techniques were reviewed and results on state-of-the-art CCD CZT technology are presented. The CZT algorithm was examined and the advantages of CCD implementation are discussed. The sliding CZT which is useful in many spectral analysis applications is described, and the performance limitations of the CZT are studied.

Eversole, W. L.; Mayer, D. J.; Bosshart, P. W.; Dewit, M.; Howes, C. R.; Buss, D. D.

1978-01-01

128

Length requirements for numerical-relativity waveforms  

E-print Network

One way to produce complete inspiral-merger-ringdown gravitational waveforms from black-hole-binary systems is to connect post-Newtonian (PN) and numerical-relativity (NR) results to create "hybrid" waveforms. Hybrid waveforms are central to the construction of some phenomenological models for GW search templates, and for tests of GW search pipelines. The dominant error source in hybrid waveforms arises from the PN contribution, and can be reduced by increasing the number of NR GW cycles that are included in the hybrid. Hybrid waveforms are considered sufficiently accurate for GW detection if their mismatch error is below 3% (i.e., a fitting factor about 0.97). We address the question of the length requirements of NR waveforms such that the final hybrid waveforms meet this requirement, considering nonspinning binaries with q = M_2/M_1 \\in [1,4] and equal-mass binaries with \\chi = S_i/M_i^2 \\in [-0.5,0.5]. We conclude that for the cases we study simulations must contain between three (in the equal-mass nonspinning case) and ten (the \\chi = 0.5 case) orbits before merger, but there is also evidence that these are the regions of parameter space for which the least number of cycles will be needed.

Mark Hannam; Sascha Husa; Frank Ohme; P. Ajith

2010-08-17

129

Comparison of monophasic and biphasic defibrillating pulse waveforms for transthoracic cardioversion. Biphasic Waveform Defibrillation Investigators.  

PubMed

All transthoracic defibrillators on the US market use nominally monophasic shock waveforms. However, biphasic waveforms have a lower defibrillation threshold than monophasic waveforms for transthoracic defibrillation of animals and for defibrillation of humans by implantable cardioverter defibrillators. The relative efficacies of Edmark monophasic and Gurvich biphasic transthoracic cardioversion waveforms (200 J into 50 omega) were compared for transthoracic cardioversion in 171 patients undergoing electrophysiologic study for evaluation of ventricular arrhythmias. Patients were randomized in a blinded fashion to receive either a monophasic or a biphasic waveform for the initial shock for conversion of induced ventricular arrhythmias (ventricular fibrillation [VF] = 53, monomorphic ventricular tachycardia [VT] = 80, polymorphic VT = 30, ventricular flutter = 8). Delivered energies for the Edmark and Gurvich waveforms were 215 +/- 11 and 171 +/- 11 J, respectively. There were no significant differences in patient characteristics, use of antiarrhythmic agents, arrhythmia cycle length, or duration of arrhythmia prior to shock for monophasic and biphasic waveform groups. The first shock for all arrhythmias was successful in 75 of 88 patients (85.2%) for the monophasic waveform compared with 81 of 83 patients (97.6%) for the biphasic waveform, p = 0.0054. The first shock for VF was successful in 22 of 28 patients (78.6%) for the monophasic waveform compared with 25 of 25 (100%) for the biphasic waveform, p = 0.0241. The Gurvich biphasic waveforms delivering a mean of 171 J were superior to Edmark monophasic waveforms delivering a mean of 215 J for transthoracic cardioversion of arrhythmias of short duration. This finding may have important implications for the development of future transthoracic defibrillators. PMID:7762500

Greene, H L; DiMarco, J P; Kudenchuk, P J; Scheinman, M M; Tang, A S; Reiter, M J; Echt, D S; Chapman, P D; Jazayeri, M R; Chapman, F W

1995-06-01

130

The Ames waveform digitizer module user guide  

SciTech Connect

This document describes a waveform digitizer module developed for the DELPHI experiment at the CERN Laboratory in Geneva, Switzerland. The Ames Waveform Digitizer is a single electronics board conforming to the FASTBUS standard (IEEE-960) which digitizes 32 channels of analog waveforms, removes data values below a settable threshold, and can reformat the data and perform fast analysis using an on-board microprocessor. This guide is intended to help the user install and use the modules in a data acquisition system. The technical details necessary for repair or modification will be available in a separate Technical Manual. 10 refs., 12 figs., 16 tabs.

Crawley, H.B.; Gorbics, M.S.; Homer, J.F. Jr.; McKay, R.; Meyer, W.T.; Rosenberg, E.I.; Thomas, W.D.

1989-02-01

131

75 FR 65521 - FM Approvals; Expansion of Recognition  

Federal Register 2010, 2011, 2012, 2013

...final notice to grant FM's expansion application...requirements of 29 CFR 1910.7 for expansion of its recognition, subject...Limitation OSHA limits the expansion of FM's recognition to testing...Room Air Conditioners UL 521 Heat Detectors for Fire...

2010-10-25

132

High-energy half-cycle cutoffs in high harmonic and rescattered electron spectra using waveform-controlled few-cycle infrared pulses  

NASA Astrophysics Data System (ADS)

We developed a few-cycle waveform-controlled light source for infrared pulses at 1.6 ? m that is based on optical chirped-pulse amplification in Bi{{B}3}{{O}6} (BIBO) crystals pumped by Ti:sapphire lasers. Using this source, we observe soft x-ray high harmonics that extend up to a photon energy of ? 320 eV, as well as high-energy photoelectrons up to ? 1 keV. The spectra of the high harmonics and photoelectrons have clear signatures of half-cycle cutoffs that can be used to extract electronic and molecular dynamics on an attosecond time scale.

Geiseler, H.; Ishii, N.; Kaneshima, K.; Kitano, K.; Kanai, T.; Itatani, J.

2014-10-01

133

Flat optical frequency comb generation and its application for optical waveform generation  

NASA Astrophysics Data System (ADS)

We demonstrate the generation of a flat optical frequency comb (OFC) using an electro absorption modulator (EAM) and two cascaded phase modulators (PM). Compared with previous flat OFC generation schemes using a Mach-Zehnder modulator (MZM) for amplitude gating of the phase modulated light, an EAM creates much shorter time window for amplitude gating, and more flattened OFC spectrum is obtained using EAM as an amplitude gate. In our experiment, a very flat OFC having 11 lines within 3-dB bandwidth (3.8 nm), and 40 GHz comb line spacing is generated. Besides the excellent spectral flatness, the strong time-domain linear-chirp of the generated OFC can be simply compensated by a dispersion compensation fiber (DCF) link, which is preferred for optical waveform generation based on spectral manipulation. In this paper, we also demonstrate the OFC application for generation of several optical waveforms by manipulating the amplitude and phase of the comb lines. High repetition-rate optical cosine pulse, optical pulse burst, optical square and triangle pulses are successfully generated.

Zhang, Fangzheng; Wu, Jian; Li, Yan; Lin, Jintong

2013-03-01

134

First Results Of The New Goldstone Delay-Doppler Radar Chirp Imaging System  

NASA Astrophysics Data System (ADS)

We report the first results of a new delay-Doppler radar chirp waveform system at Goldstone, which improves the range resolution by a factor of five from 18.75-m to 3.75-m. We successfully tested the new system on near-Earth asteroids (NEAs) 2010 AL30 and 2009 UN3 in January and February 2010. 2010 AL30 was a target-of-opportunity observed only three days after its discovery by LINEAR on January 10. During 2.3 hours of observations, 2010 AL30 moved between 1.0 to 0.8 lunar distances from Earth en route to a close approach of only 0.34 lunar distances. Due to this short round-trip light-travel time, the observations were bistatic with transmissions at the 70-m DSS-14 antenna and reception at the 34-m DSS-13 antenna. 2010 AL30 has a very faint absolute magnitude of 27.2, suggesting a diameter of less than 20 meters. We imaged 2010 AL30 at resolutions as high as 3.75-m, which reveal a somewhat elongated shape roughly 15-m in diameter, making 2010 AL30 the smallest NEA spatially resolved at Goldstone to date. The sequence of images shows obvious rotation that is consistent with the period of about 9 minutes reported by W. Ryan. (pers. comm.). 2009 UN3 was discovered in October 2009 by the Siding Spring Survey and approached within 0.037 AU (14 lunar distances) on February 9. We observed 2009 UN3 monostatically at Goldstone on February 8 and 9. Due to its moderate SNRs, we used chirp imaging at 15-m and 30-m resolutions, and binary-phase-coded imaging with 37.5-m resolution. The images reveal an irregular, elongated object close to 700-m in diameter. For future research, the new 3.75-m-resolution capability at Goldstone offers significant scientific potential to reveal much more detailed surface features than previously possible, to yield more detailed 3D shapes, and to substantially improve NEA orbits and long-term orbit prediction.

Slade, Martin A.; Lee, C. G.; Jao, J. S.; Benner, L. A. M.; Brozovic, M.; Giorgini, J. D.; Busch, M. W.

2010-10-01

135

LISA Parameter Estimation using Numerical Merger Waveforms  

NASA Technical Reports Server (NTRS)

Coalescing supermassive black holes are expected to provide the strongest sources for gravitational radiation detected by LISA. Recent advances in numerical relativity provide a detailed description of the waveforms of such signals. We present a preliminary study of LISA's sensitivity to waveform parameters using a hybrid numerical/analytic waveform describing the coalescence of two equal-mass, nonspinning black holes. The Synthetic LISA software package is used to simulate the instrument response and the Fisher information matrix method is used to estimate errors in the waveform parameters. Initial results indicate that inclusion of the merger signal can significantly improve the precision of some parameter estimates. For example, the median parameter errors for an ensemble of systems with total redshifted mass of 10(exp 6) deg M solar mass at a redshift of z is approximately 1 were found to decrease by a factor of slightly more than two when the merger was included.

Thorpe, J. I.; McWilliams, S.; Baker, J.

2008-01-01

136

Video compression transmission via FM radio  

NASA Astrophysics Data System (ADS)

At this moment of technology, video still represents the most effective communication in the world. In recent study from Dr. Charles Hsu and Dr. Harold Szu, the video can be compressed highly using feature-preserving but lossy discrete wavelet transform (DWT) technology. The processes of DWT technology are to improve the video compression level, storage capacity, filtering, and restoration techniques. This technology would allow running real time video through radio with fairly quality performance due to their compression and computational complexity techniques. After the compression, the video can be stored and transmitted at 16kbps through any reliable media and still retain a reasonable video quality. Hsu and Szu have done serious simulations and successfully implemented in the brassboards. The main objective of this paper is to present how to transmit this highly compressed video to the users via FM radio link interactively by using special technique. This application can enable many radio users receive video through their radio receiver box. This application has more interested in developing countries where television transmission is hardly afforded for education, distance learning, telemedicine, low cost sports, one-way videoconference and entertainment broadcasting.

Do, Chat C.; Szu, Harold H.

2001-03-01

137

Modeling measured glottal volume velocity waveforms.  

PubMed

The source-filter theory of speech production describes a glottal energy source (volume velocity waveform) that is filtered by the vocal tract and radiates from the mouth as phonation. The characteristics of the volume velocity waveform, the source that drives phonation, have been estimated, but never directly measured at the glottis. To accomplish this measurement, constant temperature anemometer probes were used in an in vivo canine constant pressure model of phonation. A 3-probe array was positioned supraglottically, and an endoscopic camera was positioned subglottically. Simultaneous recordings of airflow velocity (using anemometry) and glottal area (using stroboscopy) were made in 3 animals. Glottal airflow velocities and areas were combined to produce direct measurements of glottal volume velocity waveforms. The anterior and middle parts of the glottis contributed significantly to the volume velocity waveform, with less contribution from the posterior part of the glottis. The measured volume velocity waveforms were successfully fitted to a well-known laryngeal airflow model. A noninvasive measured volume velocity waveform holds promise for future clinical use. PMID:12597284

Verneuil, Andrew; Berry, David A; Kreiman, Jody; Gerratt, Bruce R; Ye, Ming; Berke, Gerald S

2003-02-01

138

Interaction of strongly chirped pulses with two-level atoms  

SciTech Connect

We study the effect of ultrachirped pulses on the population inversion of two-level atoms. Ultrachirped pulses are defined as those for which the frequency chirp is of the order of the transition frequency of the two-level atom. When the chirp is large enough, the resonance may be crossed twice, for positive and negative frequencies. In fact the decomposition of the field into amplitude and phase factors, and the corresponding definition of the instantaneous frequency, are not unique. The interaction pictures for different decomposition are strictly equivalent, but only as long as approximations are not applied. The domain of validity of the formal rotating wave approximation is dramatically enhanced by a suitable choice, the so-called analytic signal representation.

Ibanez, S.; Peralta Conde, A.; Muga, J. G. [Departamento de Quimica Fisica, Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Apdo. 644, Bilbao (Spain); Guery-Odelin, D. [Laboratoire Collisions Agregats Reactivite, CNRS UMR 5589, IRSAMC, Universite Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse CEDEX 4 (France)

2011-07-15

139

Dense monoenergetic proton beams from chirped laser-plasma interaction  

E-print Network

Interaction of a frequency-chirped laser pulse with single protons and a hydrogen plasma cell is studied analytically and by means of particle-in-cell simulations, respectively. Feasibility of generating ultra-intense (10^7 particles per bunch) and phase-space collimated beams of protons (energy spread of about 1 %) is demonstrated. Phase synchronization of the protons and the laser field, guaranteed by the appropriate chirping of the laser pulse, allows the particles to gain sufficient kinetic energy (around 250 MeV) required for such applications as hadron cancer therapy, from state-of-the-art laser systems of intensities of the order of 10^21 W/cm^2.

Galow, Benjamin J; Liseykina, Tatyana V; Harman, Zoltan; Keitel, Christoph H

2011-01-01

140

Chirped fiber Bragg grating sensor for pressure and position sensing  

NASA Astrophysics Data System (ADS)

We present a chirped fiber Bragg grating sensor that should be suitable for esophageal motility studies. The device uses the time-dependent group delay response of a chirped fiber Bragg grating to measure the peristaltic pressure wave that propagates down the esophagus with the transport of a bolus to the stomach. In contrast to existing transducers that only measure at discrete points, the output of this device is a continuous function of length along the esophagus. This paper presents ex-vivo experimental results. There is a linear relation between the wavelength location of the maximum phase perturbation and the position along the sensor where the perturbation occurred. The maximum phase change itself is directly proportional to the magnitude of the applied load at a specific position.

Swart, Pieter L.; Lacquet, Beatrys M.; Chtcherbakov, Anatolii A.

2005-05-01

141

An adaptive algorithm for strongly chirped pulses propagating in optical fibers  

NASA Astrophysics Data System (ADS)

Chirp, especially strong chirp, can be used to control the pulses in optical fibers, but it makes numerical simulation difficult by using the time-domain beam propagation method (TD-BPM) because of more sampling data requirements. In this paper, we present a modified beam propagation method (M-BPM) to efficiently simulate the propagation of strongly chirped pulses along an optical fiber. The validity of the M-BPM is demonstrated both theoretically and numerically. Numerical simulations show that the number of samples in time necessary to simulate the chirped pulse propagation by the TD-BPM varies linearly with the initial chirp parameter, but that of the M-BPM is the same one would need to simulate the propagation of the envelope without the initial chirp. In addition, the closer the propagation distance is to the temporal focal length, the more efficient the M-BPM comparing with the TD-BPM is.

Wu, Lianglong; Fu, Xiquan; Guo, Xing; Li, Huai

2012-07-01

142

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2010 CFR

...designation of FM broadcast channels. 73.201 Section 73...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...designation of FM broadcast channels. The FM broadcast band...MHz. It is divided into 100 channels of 200 kHz each....

2010-10-01

143

Hyper dispersion pulse compressor for chirped pulse amplification systems  

DOEpatents

A grating pulse compressor configuration is introduced for increasing the optical dispersion for a given footprint and to make practical the application for chirped pulse amplification (CPA) to quasi-narrow bandwidth materials, such as Nd:YAG. The grating configurations often use cascaded pairs of gratings to increase angular dispersion an order of magnitude or more. Increased angular dispersion allows for decreased grating separation and a smaller compressor footprint.

Barty, Christopher P. J. (Hayward, CA)

2011-11-29

144

Development of a Reduced-Cost Chirped Pulse Microwave Spectrometer  

NASA Astrophysics Data System (ADS)

Chirped pulse Fourier transform microwave (CP-FTMW) spectroscopy has become a ubiquitous technique in the high-resolution molecular spectroscopy community. Unfortunately, many components of CP-FTMW spectrometers are extremely expensive. Here we report of the development of an inexpensive microwave circuit and we present spectra of tetrahydrofuran and methanol collected between 8-16 GHz. Possible applications in remote sensing will also be discussed.

Finneran, Ian A.; Holland, Daniel B.; Carroll, P. Brandon; Blake, Geoffrey A.

2013-06-01

145

Identification of biological tissue using chirped probe THz imaging  

Microsoft Academic Search

We consider the application of pulsed THz imaging systems in biomedical diagnostics and mail\\/packaging inspection. The sub-millimetre spectroscopic measurements obtained from T-ray systems contain a wealth of information about the sample under test. We demonstrate that different types of tissue can be classified based on their terahertz response measured with the chirped probe pulse technique. We demonstrate the performance of

B. Ferguson; S. Wang; D. Gray; D. Abbott; X.-C Zhang

2002-01-01

146

Generalized chirp-like polyphase sequences with optimum correlation properties  

Microsoft Academic Search

A new general class of polyphase sequences with ideal periodic autocorrelation function is presented. The new class of sequences is based on the application of Zadoff-Chu polyphase sequences of length N=sm2, where s and m are any positive integers. It is shown that the generalized chirp-like sequences of odd length have the optimum crosscorrelation function under certain conditions. Finally, recently

Branislav M. Popovic

1992-01-01

147

Quantum Phenomena in a Chirped Parametric Anharmonic Oscillator  

NASA Astrophysics Data System (ADS)

Parametric ladder climbing and the quantum saturation of the threshold for the classical parametric autoresonance due to the zero point fluctuations at low temperatures are discussed. The probability for capture into the chirped parametric resonance is found by solving the Schrdinger equation in the energy basis and the associated resonant phase-space dynamics is illustrated via the Wigner distribution. The numerical threshold for capture into the resonance is compared with the classical and quantum theories in different parameter regimes.

Barth, I.; Friedland, L.

2014-07-01

148

Quantum phenomena in a chirped parametric anharmonic oscillator.  

PubMed

Parametric ladder climbing and the quantum saturation of the threshold for the classical parametric autoresonance due to the zero point fluctuations at low temperatures are discussed. The probability for capture into the chirped parametric resonance is found by solving the Schrdinger equation in the energy basis and the associated resonant phase-space dynamics is illustrated via the Wigner distribution. The numerical threshold for capture into the resonance is compared with the classical and quantum theories in different parameter regimes. PMID:25105601

Barth, I; Friedland, L

2014-07-25

149

An improved processing sequence for uncorrelated Chirp sonar data  

NASA Astrophysics Data System (ADS)

Chirp sonar systems can be used to obtain high resolution seismic reflection images of the sub-seafloor during marine surveys. The exact knowledge of the Chirp signature allows the use of deterministic algorithms to process the data, similarly to that applied to Vibroseis data on land. Here, it is described an innovative processing sequence to be applied to uncorrelated Chirp data, which can improve vertical and lateral resolution compared to conventional methods. It includes application of a Wiener filter to transform a frequency-modulated sweep into a minimum-phase pulse sequence. In this way, the data become causal and can undergo predictive deconvolution to reduce ringing and enhance vertical resolution. Afterwards, FX-deconvolution and Stolt migration can be applied to obtain an improved imaging of the subsurface. The result of this procedure is a seismic reflection image with higher resolution than traditional ones, which are normally represented using the envelope function of the signal. This technique can be particularly useful for engineering-geotechnical surveys and archaeological investigations that require a fine detail imaging of the uppermost meters of the sub-seafloor.

Baradello, Luca

2014-03-01

150

Auditory brainstem responses to chirps delivered by different insert earphones.  

PubMed

The frequency response and sensitivity of the ER-3A and ER-2 insert earphones are measured in the occluded-ear simulator using three ear canal extensions. Compared to the other two extensions, the DB 0370 (Bru?el & Kjr), which is recommended by the international standards, introduces a significant resonance peak around 4500 Hz. The ER-3A has an amplitude response like a band-pass filter (1400 Hz, 6 dB/octave -4000 Hz, -36 dB/octave), and a group delay with "ripples" of up to 0.5 ms, while the ER-2 has an amplitude response, and a group delay which are flat and smooth up to above 10000 Hz. Both earphones are used to record auditory brainstem responses, ABRs, from 22 normal-hearing ears in response to two chirps and a click at levels from 20 to 80 dB nHL. While the click-ABRs are slightly larger for ER-2 than for ER-3A, the chirp-ABRs are much larger for ER-2 than for ER-3A at levels below 60 dB nHL. With a simulated amplitude response of the ER-3A and the smooth group delay of the ER-2 it is shown that the increased chirp-ABR amplitude with the ER-2 is caused by its broader amplitude response and not by its smoother group delay. PMID:22423705

Elberling, Claus; Kristensen, Sinnet G B; Don, Manuel

2012-03-01

151

Progress Towards Chirped-Pulse Fourier Transform Thz Spectroscopy  

NASA Astrophysics Data System (ADS)

New opportunities are provided by the development of higher power THz frequency multiplier sources, the development of a broadband Chirped-Pulse FTMW spectroscopy technique at microwave and mm Wave frequencies, and recently demonstrated heterodyne hot electron bolometer detection technology in the THz frequency region with near quantum noise-limited performance and high spectral resolution. Combining these three technologies and extending the chirped-pulse technique to 0.85 THz enables a host of new applications. NIST is currently pursing applications as a point sensor for greenhouse gases, volatile organic compounds, and potentially human breath. The generation and detection of phase stable chirped pulses at 850 GHz will be demonstrated. A description of the experimental setup and preliminary data will be presented for nitrous oxide. G.G. Brown, B.C. Dian, K.O. Douglass, S.M. Geyer, S. Shipman and B.H. Pate, Rev.Sci.Instrum. 79 (2008) 053103. E. Gerecht, D. Gu, L. You, K.S. Yngvesson, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES. 56, (2008) 1083.

Douglass, Kevin O.; Plusquellic, David F.; Gerecht, Eyal

2010-06-01

152

Active stabilization of a rapidly chirped laser by an optoelectronic digital servo-loop control.  

PubMed

We propose and demonstrate a novel active stabilization scheme for wide and fast frequency chirps. The system measures the laser instantaneous frequency deviation from a perfectly linear chirp, thanks to a digital phase detection process, and provides an error signal that is used to servo-loop control the chirped laser. This way, the frequency errors affecting a laser scan over 10 GHz on the millisecond timescale are drastically reduced below 100 kHz. This active optoelectronic digital servo-loop control opens new and interesting perspectives in fields where rapidly chirped lasers are crucial. PMID:17392895

Gorju, G; Jucha, A; Jain, A; Crozatier, V; Lorger, I; Le Gout, J-L; Bretenaker, F; Colice, M

2007-03-01

153

Chirped holographic grating used as the dispersive element in an optical spectrometer  

SciTech Connect

We have developed a new design of optical spectrometer based on the use of a chirped holographic grating inscribed on a flat substrate. This type of grating has a surface modulation with a spatially varying period. The ability of the chirped grating to focus a beam is exploited to reduce significantly the physical dimensions of the instrument. Wavelength selection is achieved by a pure translation of the chirped grating. The properties of the chirped grating spectrometer have been characterized with different lasers and arc lamps and compared with those of two commercial spectrometers. A performance parameter has been defined, enabling the various instruments to be compared.

Fortin, Gilles; McCarthy, Nathalie

2005-08-10

154

Reduction of damage threshold in dielectric materials induced by negatively chirped laser pulses  

SciTech Connect

The threshold fluence for laser induced damage in wide band gap dielectric materials, fused silica and MgF{sub 2}, is observed to be lower by up to 20% for negatively (down) chirped pulses than for positively (up) chirped, at pulse durations ranging from 60 fs to 1 ps. This behavior of the threshold fluence for damage on the chirp direction was not observed in semiconductors (silicon and GaAs). Based on a model including electron generation in the conduction band and Joule heating, it is suggested that the decrease in the damage threshold for negatively chirped pulse is related to the dominant role of multiphoton ionization in wide gap materials.

Louzon, E.; Henis, Z.; Pecker, S.; Ehrlich, Y.; Fisher, D.; Fraenkel, M.; Zigler, A. [Soreq NRC, Yavne 81800 (Israel); Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)

2005-12-12

155

Chirped-pulse millimeter-wave spectroscopy: Spectrum, dynamics, and manipulation of Rydberg-Rydberg transitions  

SciTech Connect

We apply the chirped-pulse millimeter-wave (CPmmW) technique to transitions between Rydberg states in calcium atoms. The unique feature of Rydberg-Rydberg transitions is that they have enormous electric dipole transition moments ({approx}5 kiloDebye at n*{approx} 40, where n* is the effective principal quantum number), so they interact strongly with the mm-wave radiation. After polarization by a mm-wave pulse in the 70-84 GHz frequency region, the excited transitions re-radiate free induction decay (FID) at their resonant frequencies, and the FID is heterodyne-detected by the CPmmW spectrometer. Data collection and averaging are performed in the time domain. The spectral resolution is {approx}100 kHz. Because of the large transition dipole moments, the available mm-wave power is sufficient to polarize the entire bandwidth of the spectrometer (12 GHz) in each pulse, and high-resolution survey spectra may be collected. Both absorptive and emissive transitions are observed, and they are distinguished by the phase of their FID relative to that of the excitation pulse. With the combination of the large transition dipole moments and direct monitoring of transitions, we observe dynamics, such as transient nutations from the interference of the excitation pulse with the polarization that it induces in the sample. Since the waveform produced by the mm-wave source may be precisely controlled, we can populate states with high angular momentum by a sequence of pulses while recording the results of these manipulations in the time domain. We also probe the superradiant decay of the Rydberg sample using photon echoes. The application of the CPmmW technique to transitions between Rydberg states of molecules is discussed.

Colombo, Anthony P.; Zhou Yan; Prozument, Kirill; Coy, Stephen L.; Field, Robert W. [Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2013-01-07

156

Gaussian Decomposition of Laser Altimeter Waveforms  

NASA Technical Reports Server (NTRS)

We develop a method to decompose a laser altimeter return waveform into its Gaussian components assuming that the position of each Gaussian within the waveform can be used to calculate the mean elevation of a specific reflecting surface within the laser footprint. We estimate the number of Gaussian components from the number of inflection points of a smoothed copy of the laser waveform, and obtain initial estimates of the Gaussian half-widths and positions from the positions of its consecutive inflection points. Initial amplitude estimates are obtained using a non-negative least-squares method. To reduce the likelihood of fitting the background noise within the waveform and to minimize the number of Gaussians needed in the approximation, we rank the "importance" of each Gaussian in the decomposition using its initial half-width and amplitude estimates. The initial parameter estimates of all Gaussians ranked "important" are optimized using the Levenburg-Marquardt method. If the sum of the Gaussians does not approximate the return waveform to a prescribed accuracy, then additional Gaussians are included in the optimization procedure. The Gaussian decomposition method is demonstrated on data collected by the airborne Laser Vegetation Imaging Sensor (LVIS) in October 1997 over the Sequoia National Forest, California.

Hofton, Michelle A.; Minster, J. Bernard; Blair, J. Bryan

1999-01-01

157

SCA Waveform Development for Space Telemetry  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center is investigating and developing suitable reconfigurable radio architectures for future NASA missions. This effort is examining software-based open-architectures for space based transceivers, as well as common hardware platform architectures. The Joint Tactical Radio System's (JTRS) Software Communications Architecture (SCA) is a candidate for the software approach, but may need modifications or adaptations for use in space. An in-house SCA compliant waveform development focuses on increasing understanding of software defined radio architectures and more specifically the JTRS SCA. Space requirements put a premium on size, mass, and power. This waveform development effort is key to evaluating tradeoffs with the SCA for space applications. Existing NASA telemetry links, as well as Space Exploration Initiative scenarios, are the basis for defining the waveform requirements. Modeling and simulations are being developed to determine signal processing requirements associated with a waveform and a mission-specific computational burden. Implementation of the waveform on a laboratory software defined radio platform is proceeding in an iterative fashion. Parallel top-down and bottom-up design approaches are employed.

Mortensen, Dale J.; Kifle, Multi; Hall, C. Steve; Quinn, Todd M.

2004-01-01

158

Waveform methods for ordinary differential equations  

SciTech Connect

The traditional approach for solving large dynamical systems is time consuming. Waveform method, an iterative technique for solving systems of differential equations, can be used to reduce the processing time. Waveform method has been shown to converge superlinearly on finite intervals. In this thesis, a measure of speed of convergence is defined and is used to compare the value of different waveform methods. This measure is the rate of increase of order of accuracy. The speed of the waveform Gauss-Seidel method depends on the numbering of the equations. The numbering of the equations corresponds to a numbering of the directed graph specifying the coupling relations among all equations. We show how to compute the rate of order increase from the structure of the numbered graph and hence the optimum numbering, that is, the one which maximizes the speed of convergence. Finally, in a variety of numerical experiments, conducted on a Sun 3/60, we demonstrate that the different speeds of convergence correspond to different numberings and the effectiveness of the waveform Gauss-Seidel method for large sparse systems. 17 refs.

Juang, Fen-Lien.

1990-01-01

159

FM 4-02.19 DENTAL SERVICE SUPPORT OPERATIONS  

E-print Network

FM 4-02.19 July 2009 DENTAL SERVICE SUPPORT OPERATIONS DISTRIBUTION RESTRICTION: Approved of the Army Washington, DC, 31 July 2009 Dental Service Support Operations Contents Page PREFACE .............................................................................................................iv Chapter 1 OVERVIEW OF DENTAL SERVICE SUPPORT............................................... 1

US Army Corps of Engineers

160

47 CFR 73.319 - FM multiplex subcarrier technical standards.  

Code of Federal Regulations, 2010 CFR

...multiplex subcarrier technical standards. 73...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...multiplex subcarrier technical standards. (a...to comply with the technical provisions for FM broadcast...interference to other communication services, the...

2010-10-01

161

FM 7-15, C3 Change No. 3 Headquarters  

E-print Network

collective tasks and current intelligence doctrine as a result of the recently published FM 2-0. 2. A bar.2.6 Cross a Danger Area ...................................................................... 1-18 ART 1

US Army Corps of Engineers

162

Horizontal Branch stars as AmFm/HgMn stars  

E-print Network

Recent observations and models for horizontal branch stars are briefly described and compared to models for AmFm stars. The limitations of those models are emphasized by a comparison to observations and models for HgMn stars.

G. Michaud; J. Richer

2008-02-12

163

75 FR 43897 - FM TABLE OF ALLOTMENTS, GRANTS PASS, OREGON  

Federal Register 2010, 2011, 2012, 2013

...AGENCY: Federal Communications Commission...allotment of FM Channel 257A as the...which involve channel allotments...the Federal Communications Commission...Grants Pass, Channel 257A. Federal Communications...

2010-07-27

164

75 FR 19338 - FM TABLE OF ALLOTMENTS, Milford, Utah  

Federal Register 2010, 2011, 2012, 2013

...AGENCY: Federal Communications Commission. ACTION...Station KCLS(FM), Channel 269C2, Pioche...amended by removing Channel 285C at Milford and by adding Channel 288C at Milford. Federal Communications Commission....

2010-04-14

165

75 FR 41766 - FM Table of Allotments, Amboy, California  

Federal Register 2010, 2011, 2012, 2013

...FEDERAL COMMUNICATIONS COMMISSION 47...AGENCY: Federal Communications Commission ACTION...LLC, allots FM Channel 284A at Amboy...amended by adding Channel 284A to Amboy. Federal Communications Commission....

2010-07-19

166

Biphoton waveform: Space-to-time mapping  

E-print Network

We study narrow-band biphoton generation from spontaneous four-wave mixing with electro-magnetically induced transparency in a laser cooled atomic ensemble. We extend the theoretical formalism accounting the non-uniformity in atomic density and the driving laser fields in both the interaction and Heisenberg pictures. We find that for a fixed optical depth the two-photon waveform is independent of the atomic density distribution. However, the spatial profiles of the two driving laser beams have a significant effect on the biphoton temporal waveform at a high optical depth (> 100). Under such a condition, the modulation of the laser beams in space domain can shape the waveform in time domain.

Zhao, Luwei; Du, Shengwang

2014-01-01

167

Ion-beam sputtering deposition and magnetoelectric properties of layered heterostructures (FM/PZT/FM)n, where FM - Co or Ni78Fe22  

NASA Astrophysics Data System (ADS)

Magnetoelectric properties of layered heterostructures (FM/PZT/FM)n (n? 3) obtained by ion-beam sputtering deposition of ferromagnetic metal (FM), where FM is the cobalt (Co) or permalloy Ni78Fe22, onto ferroelectric ceramic based on lead zirconate titanate (PZT) have been studied. The polished ferroelectric plates in thickness from 400 to 20 ?m were subjected to finished treatment by ion-beam sputtering. After plasma activation they were covered by the ferromagnetic films from 1 to 6 ?m in thickness. Enhanced characteristics of these structures were reached by means of both the thickness optimization of ferroelectric and ferromagnetic layers and obtaining of ferromagnetic/ferroelectric interfaces being free from defects and foreign impurities. Assuming on the basis of analysis of elastic stresses in the ferromagnetic film that the magnetoelectric effect forms within ferromagnetic/ferroelectric interface, the structures with 2-3 ferromagnetic layers were obtained. In layered heterostructure (Py/PZT/Py)3, the optimal thickness of ferromagnetic film was 2 ?m, and outer and inner ferroelectric layers had 20 ?m and 80 ?m in thickness, respectively. For such structure the maximal magnetoelectric voltage coefficient of 250 mV/(cm Oe) was reached at a frequency 100 Hz in magnetic field of 0.25 T at room temperature. The structures studied can serve as energy-independent elements detecting the change of magnetic or electric fields in electronic devices based on magnetoelectric effect.

Stognij, Alexander; Novitskii, Nikolai; Sazanovich, Andrei; Poddubnaya, Nadezhda; Sharko, Sergei; Mikhailov, Vladimir; Nizhankovski, Viktor; Dyakonov, Vladimir; Szymczak, Henryk

2013-08-01

168

Chirped fiber-optic Bragg grating interrogator in a multiplexed Bragg grating sensor configuration  

Microsoft Academic Search

This paper presents a chirped grating interrogator for fiber Bragg grating sensors. The interrogator uses the wavelength dependence of the phase group-delay response of a chirped fiber Bragg grating to determine the Bragg wavelength of the sensor. The sensitivity of the interrogator is determined by the selection of the grating length and the bandwidth. The experimental results demonstrated strain measurements

Anatoli A. Chtcherbakov; Pieter L. Swart

2004-01-01

169

Effects of Energy Chirp on Echo-Enabled Harmonic Generation Free-Electron Lasers  

SciTech Connect

We study effects of energy chirp on echo-enabled harmonic generation (EEHG). Analytical expressions are compared with numerical simulations for both harmonic and bunching factors. We also discuss the EEHG free-electron laser bandwidth increase due to an energy-modulated beam and its pulse length dependence on the electron energy chirp.

Huang, Z.; Ratner, D.; Stupakov, G.; Xiang, D.; /SLAC

2009-02-23

170

Analytical Expressions for Small-Signal and Saturation Processes of Optical Parametric Chirped-Pulse Amplification  

NASA Astrophysics Data System (ADS)

Analytical expressions corresponding to the small-signal and saturation processes of optical parametric chirped-pulse amplification are derived from the elliptic integration obtained by nonlinear-wave equations. The analytical expressions are simple and practical for the optimization of optical parametric chirped-pulse amplification even under the saturation process.

Harimoto, Tetsuo; Yamakawa, Koichi

2009-09-01

171

Design, fabrication, and analysis of chirped multilayer mirrors for reflection of extreme-ultraviolet attosecond pulses  

Microsoft Academic Search

Chirped Mo\\/Si multilayer coatings have been designed, fabricated, and characterized for use in extreme-ultraviolet attosecond experiments. By numerically simulating the reflection of the attosecond pulse from a multilayer mirror during the optimization procedure based on a genetic algorithm, we obtain optimized layer designs. We show that normal incidence chirped multilayer mirrors capable of reflecting pulses of approximately 100 attoseconds (as)

A. Wonisch; U. Neuhaeusler; N. M. Kabachnik; T. Uphues; M. Uiberacker; V. Yakovlev; F. Krausz; M. Drescher; U. Kleineberg; U. Heinzmann

2006-01-01

172

A completely integrated thirty-two-point chirp Z transform [CCD IC realisation  

Microsoft Academic Search

A monolithic 32-point DFT using the chirp Z transform (CZT) algorithm has been designed and fabricated using an n-channel two-level polysilicon coplanar electrode process. The detailed design and operation of this first fully integrated CCD chirp Z transform are discussed, and some spectral analysis applications for a CCD CZT are described.

WILLIAM L. EVERSOLE; DALE J. MAYER; PATRICK W. BOSSHART; M. De Wit; C. R. Hewes; D. D. Buss

1978-01-01

173

Simple measurement of fiber dispersion and of chirp parameter of intensity modulated light emitter  

Microsoft Academic Search

We report a novel method to measure two important parameters for optical fiber intensity modulated transmission systems: dispersion of optical fibers and chirp parameter of modulated light emitters. The method is easy, quick, and accurate for chirp parameter in the -10-to-10 range

F. Devaux; Y. Sorel; J. F. Kerdiles

1993-01-01

174

Spectral and synchrony differences in auditory brainstem responses evoked by chirps of varying durations.  

PubMed

The chirp-evoked ABR has been termed a more synchronous response, referring to the fact that rising-frequency chirp stimuli theoretically compensate for temporal dispersions down the basilar membrane. This compensation is made possible by delaying the higher frequency content of the stimulus until the lower frequency traveling waves are closer to the cochlea apex. However, it is not yet clear how sensitive this temporal compensation is to variation in the delay interval. This study analyzed chirp- and click-evoked ABRs at low intensity, using a variety of tools in the time, frequency, and phase domains, to measure synchrony in the response. Additionally, this study also examined the relationship between chirp sweep rate and response synchrony by varying the delay between high- and low-frequency portions of chirp stimuli. The results suggest that the chirp-evoked ABRs in this study exhibited more synchrony than the click-evoked ABRs and that slight gender-based differences exist in the synchrony of chirp-evoked ABRs. The study concludes that a tailoring of chirp parameters to gender may be beneficial in pathologies that severely affect neural synchrony, but that such a customization may not be necessary in routine clinical applications. PMID:20968361

Petoe, Matthew A; Bradley, Andrew P; Wilson, Wayne J

2010-10-01

175

Chirped Pulse Adiabatic Passage in CARS for Imaging of Biological Structure and Dynamics  

SciTech Connect

We propose the adiabatic passage control scheme implementing chirped femtosecond laser pulses to maximize coherence in a predetermined molecular vibrational mode using two-photon Raman transitions. We investigate vibrational energy relaxation and collisional dephasing as factors of coherence loss, and demonstrate the possibility for preventing decoherence by the chirped pulse train. The proposed method may be used to advance noninvasive biological imaging techniques.

Malinovskaya, Svetlana A. [Department of Physics and Engineering Physics, Stevens Institute of Technology Hoboken, NJ 07030 (United States)

2007-12-26

176

Helicopter-borne SAR Imaging Processing of Chirp-stepped Signal  

Microsoft Academic Search

In this paper, the processing algorithm of high resolution range profile of chirp-stepped signal is studied in the view of system, and the process of chirp-stepped signal SAR imaging on helicopter platform is analyzed. Furthermore, technology difficulties of helicopter-borne SAR imaging are showed, and imaging results are presented by experimental data

Hong Xiangru Zhang Tao; Du Zicheng

2006-01-01

177

Measuring error propagation in waveform relaxation algorithms  

Microsoft Academic Search

A new analysis tool is introduced that characterizes and measures subcircuit coupling and error attenuation in waveform relaxation (WR) circuit simulation algorithms with full dimensionality. Unlike current methods that use heuristics to calculate scalar coupling, this method captures all of the effects of error attenuation over time and space. The new method characterizes the propagation of errors in the solution

George Diedrich Gristede; Charles Albert Zukowski; Albert E. Ruehli

1999-01-01

178

Parameter Estimation using Numerical Merger Waveforms  

NASA Technical Reports Server (NTRS)

Results: Developed parameter estimation model integrating complete waveforms and improved instrumental models. Initial results for equal-mass non-spinning systems indicate moderate improvement in most parameters, significant improvement in some Near-term improvement: a) Improved statistics; b) T-channel; c) Larger parameter space coverage. Combination with other results: a) Higher harmonics; b) Spin precession; c) Instrumental effects.

Thorpe, J. I.; McWilliams, S.; Kelly, B.; Fahey, R.; Arnaud, K.; Baker, J.

2008-01-01

179

Efficient waveform recall in absorbing media  

Microsoft Academic Search

We have found that highly efficient waveform recall is possible in coherent transient systems in which the storage is optically thick. Coherent transients may be used in a variety of information storage and processing applications with advantages over traditional electronic methods. However, it is believed that a serious problem in application of photon echoes in practical systems is the relatively

Carrie S. Cornish; Mohammad Azadeh; W. Randall Babbitt; Leung Tsang

1998-01-01

180

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

SciTech Connect

Earthquake source parameters underpin several aspects of nuclear explosion monitoring. Such aspects are: calibration of moment magnitudes (including coda magnitudes) and magnitude and distance amplitude corrections (MDAC); source depths; discrimination by isotropic moment tensor components; and waveform modeling for structure (including waveform tomography). This project seeks to improve methods for and broaden the applicability of estimating source parameters from broadband waveforms using the Cut-and-Paste (CAP) methodology. The CAP method uses a library of Greens functions for a one-dimensional (1D, depth-varying) seismic velocity model. The method separates the main arrivals of the regional waveform into 5 windows: Pnl (vertical and radial components), Rayleigh (vertical and radial components) and Love (transverse component). Source parameters are estimated by grid search over strike, dip, rake and depth and seismic moment or equivalently moment magnitude, MW, are adjusted to fit the amplitudes. Key to the CAP method is allowing the synthetic seismograms to shift in time relative to the data in order to account for path-propagation errors (delays) in the 1D seismic velocity model used to compute the Greens functions. The CAP method has been shown to improve estimates of source parameters, especially when delay and amplitude biases are calibrated using high signal-to-noise data from moderate earthquakes, CAP+.

Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

2008-06-17

181

A multi-channel waveform digitizer system  

SciTech Connect

The authors report on the design and performance of a multichannel waveform digitizer system for use with the Multiple Sample Ionization Chamber (MUSIC) Detector at the Bevalac. 128 channels of 20 MHz Flash ADC plus 256 word deep memory are housed in a single crate. Digital thresholds and hit pattern logic facilitate zero suppression during readout which is performed over a standard VME bus.

Bieser, F.; Muller, W.F.J. (Lawrence Berkeley Lab., CA (USA))

1990-04-01

182

Parameters Determination of Oscillatory Impulse Current Waveform  

NASA Astrophysics Data System (ADS)

This paper proposes numerical techniques to distil waveform parameters out of digitally measured data of oscillatory impulse current. The first method, to be used for liner circuit, based on a curve-fitting technique in which a smooth analytical curve is defined to fit the noise-superposed measured data. The waveform parameters are derived from the curve. The algorithm is examined its performance using a measured waveform data which is obtained from a circuit composed of linear elements only. It is not rare when impulse current is measured in a circuit with non-linear element, namely an arrester. After carefully observed behaviours of the circuit current when the non-linear element turns on and off, authors developed two algorithms capable to determine the parameters from the recorded data obtained from a circuit having a ZnO arrester. The developed algorithm processed the waveform data generated by TDG which is to be issued in 2009 as a part of IEC 61083-2. The details of the algorithm are to be demonstrated in the paper.

Sato, Shuji; Nishimura, Seisuke; Seki, Shingo

183

Matter effects on binary neutron star waveforms  

E-print Network

Using an extended set of equations of state and a multiple-group multiple-code collaborative effort to generate waveforms, we improve numerical-relativity-based data-analysis estimates of the measurability of matter effects in neutron-star binaries. We vary two parameters of a parameterized piecewise-polytropic equation of state (EOS) to analyze the measurability of EOS properties, via a parameter {\\Lambda} that characterizes the quadrupole deformability of an isolated neutron star. We find that, to within the accuracy of the simulations, the departure of the waveform from point-particle (or spinless double black-hole binary) inspiral increases monotonically with {\\Lambda}, and changes in the EOS that did not change {\\Lambda} are not measurable. We estimate with two methods the minimal and expected measurability of {\\Lambda} in second- and third- generation gravitational-wave detectors. The first estimate, using numerical waveforms alone, shows two EOS which vary in radius by 1.3km are distinguishable in mergers at 100Mpc. The second estimate relies on the construction of hybrid waveforms by matching to post-Newtonian inspiral, and estimates that the same EOS are distinguishable in mergers at 300Mpc. We calculate systematic errors arising from numerical uncertainties and hybrid construction, and we estimate the frequency at which such effects would interfere with template-based searches.

Jocelyn S. Read; Luca Baiotti; Jolien D. E. Creighton; John L. Friedman; Bruno Giacomazzo; Koutarou Kyutoku; Charalampos Markakis; Luciano Rezzolla; Masaru Shibata; Keisuke Taniguchi

2013-06-18

184

Simulating distributed elements with asymptotic waveform evaluation  

Microsoft Academic Search

A novel method for simulating distributed elements is described. The asymptotic waveform evaluation (AWE) technique is used to compute a low-order approximation to the admittance matrix for a system of coupled lossy lines. The Y-matrix can serve as a macromodel for the lines, so that they can be simulated together with arbitrary (nonlinear) terminations. A major advantage of the proposed

J. Eric Bracken; V. Raghavan; Ronald A. Rohrer

1992-01-01

185

Exploiting Partitioning In Asymptotic Waveform Evaluation (AWE)  

Microsoft Academic Search

Asymptotic Waveform Evaluation (AWE) is an efficient technique for simulating linear(ized) circuits. AWE is typically orders of magnitude faster than traditional methods. In this paper, partitioning techniques for AWE are presented that allow it to handle circuits in partitioned form. Partitions can be handled either at the moment level before AWE'S Pad6 approximation, or afterwards, at the pole level. These

M. M. Alaybeyi; J. E. Bracken; J. Y. Lee; V. Raghavan; R. J. Trihy; R. A. Rohrer

1992-01-01

186

Interconnect simulation with asymptotic waveform evaluation (AWE)  

Microsoft Academic Search

The interconnect analysis problem is treated in a general fashion, exploiting the efficiency and accuracy of asymptotic waveform evaluation (AWE) for the linear interconnect portion of the circuit while using the SPICE simulator for the nonlinear portions. An algorithm that allows the use of partitioned circuit solution techniques in conjunction with AWE is described. A special technique for determining the

J. Eric Bracken; Vivek Raghavan; Ronald A. Rohrer

1992-01-01

187

A transformer of closely spaced pulsed waveforms  

NASA Technical Reports Server (NTRS)

Passive circuit, using diodes, transistors, and magnetic cores, transforms the voltage of repetitive positive or negative pulses. It combines a pulse transformer with switching devices to effect a resonant flux reset and can transform various pulsed waveforms that have a nonzero average value and are relatively cosely spaced in time.

Niedra, J.

1970-01-01

188

Frequency agile stepped OFDM waveform for HRR  

Microsoft Academic Search

High range resolution (HRR) is an important feature for radar, aiming at target classification. The range resolution is inversely proportional to the bandwidth of the transmitted signal. Pulse burst waveforms can achieve HRR at low expenses when the carrier frequency increases from one pulse to the next, stepping and synthesizing the wide bandwidth. In such a stepped frequency approach the

Gabriel Lellouch; Radmila Pribic; Piet van Genderen

2009-01-01

189

JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 29, NO. 9, MAY 1, 2011 1239 Real-Time Interrogation of a Linearly Chirped  

E-print Network

of a Linearly Chirped Fiber Bragg Grating Sensor Based on Chirped Pulse Compression With Improved Resolution to interrogating in real time a lin- early chirped fiber Bragg grating (LCFBG) sensor based on spec- tral, fiber Bragg grating (FBG), wavelength-to-time mapping. I. INTRODUCTION F IBER BRAGG grating (FBG

Yao, Jianping

190

Chirped pulse enhancement of multiphoton absorption in molecular iodine Vladislav V. Yakovlev, Christopher J. Bardeen, Jianwe Che, Jianshu Cao,  

E-print Network

are observed for chirped pulses with respect to transform-limited, zero chirp pulses. Theoretical a negatively chirped pulse has the opposite ordering. A transform-limited pulse is of the shortest possible relative to the shortest, transform- limited pulse. Preliminary calculations suggest that this en

Cao, Jianshu

191

Raman chirped adiabatic passage probed by X-ray spectroscopy.  

PubMed

We report a theoretical study of the selective vibrational excitation of a HCl molecule achieved by Raman chirped adiabatic passage (RCAP) and probed by X-ray photoelectron spectroscopy (XPS). It is demonstrated that HCl can be prepared in any vibrational level up to ? = 9 with nearly complete population inversion. We explore the effects of both the rotation of the molecule and of the temperature on the RCAP process, which is proved to be very robust. Furthermore, we emphasize that XPS spectra at the chlorine K-shell threshold show characteristic signatures of the populated vibrational level, allowing us to follow the RCAP process. PMID:23550700

Engin, Selma; Sisourat, Nicolas; Selles, Patricia; Taeb, Richard; Carniato, Stphane

2013-08-29

192

Spatial filtering of light by chirped photonic crystals  

SciTech Connect

We propose an efficient method for spatial filtering of light beams by propagating them through two-dimensional (also three dimensional) chirped photonic crystals, i.e., through the photonic structures with fixed transverse lattice period and with the longitudinal lattice period varying along the direction of the beam propagation. We prove the proposed idea by numerically solving the paraxial propagation equation in refraction-index-modulated media and we evaluate the efficiency of the process by harmonic-expansion analysis. The technique can be also applied for filtering (for cleaning) of the packages of atomic waves (Bose condensates), also to improve the directionality of acoustic and mechanical waves.

Staliunas, Kestutis [ICREA, Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa, Barcelona (Spain); Sanchez-Morcillo, Victor J. [Instituto de Investigacion para la Gestion Integrada de Zonas Costeras, Universidad Politecnica de Valencia, Ctra. Natzaret-Oliva S/N, 46730 Grao de Gandia (Spain)

2009-05-15

193

JTRS/SCA and Custom/SDR Waveform Comparison  

NASA Technical Reports Server (NTRS)

This paper compares two waveform implementations generating the same RF signal using the same SDR development system. Both waveforms implement a satellite modem using QPSK modulation at 1M BPS data rates with one half rate convolutional encoding. Both waveforms are partitioned the same across the general purpose processor (GPP) and the field programmable gate array (FPGA). Both waveforms implement the same equivalent set of radio functions on the GPP and FPGA. The GPP implements the majority of the radio functions and the FPGA implements the final digital RF modulator stage. One waveform is implemented directly on the SDR development system and the second waveform is implemented using the JTRS/SCA model. This paper contrasts the amount of resources to implement both waveforms and demonstrates the importance of waveform partitioning across the SDR development system.

Oldham, Daniel R.; Scardelletti, Maximilian C.

2007-01-01

194

Radar altimeter waveform modeled parameter recovery. [SEASAT-1 data  

NASA Technical Reports Server (NTRS)

Satellite-borne radar altimeters include waveform sampling gates providing point samples of the transmitted radar pulse after its scattering from the ocean's surface. Averages of the waveform sampler data can be fitted by varying parameters in a model mean return waveform. The theoretical waveform model used is described as well as a general iterative nonlinear least squares procedures used to obtain estimates of parameters characterizing the modeled waveform for SEASAT-1 data. The six waveform parameters recovered by the fitting procedure are: (1) amplitude; (2) time origin, or track point; (3) ocean surface rms roughness; (4) noise baseline; (5) ocean surface skewness; and (6) altitude or off-nadir angle. Additional practical processing considerations are addressed and FORTRAN source listing for subroutines used in the waveform fitting are included. While the description is for the Seasat-1 altimeter waveform data analysis, the work can easily be generalized and extended to other radar altimeter systems.

1981-01-01

195

Flagellar waveform dynamics of freely swimming algal cells  

E-print Network

We present quantitative measurements of time-dependent flagellar waveforms for freely swimming biflagellated algal cells, for both synchronous and asynchronous beating. We use the waveforms in conjunction with resistive ...

Kurtuldu, H.

196

Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam  

SciTech Connect

Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.

Thangaraj, J.; Ruan, J.; Johnson, A.S.; Thurman-Keup, R.; Lumpkin, A.H.; Santucci, J.; Sun, Y.-E; Maxwell, T.; Edwards, H.; /Fermilab

2012-05-01

197

Effect of nonlinear chirped Gaussian laser pulse on plasma wake field generation  

NASA Astrophysics Data System (ADS)

An ultrashort laser pulse propagating in plasma can excite a nonlinear plasma wake field which can accelerate charged particles up to GeV energies within a compact space compared to the conventional accelerator devices. In this paper, the effect of different kinds of nonlinear chirped Gaussian laser pulse on wake field generation is investigated. The numerical analysis of our results depicts that the excitation of plasma wave with large and highly amplitude can be accomplished by nonlinear chirped pulses. The maximum amplitude of excited wake in nonlinear chirped pulse is approximately three times more than that of linear chirped pulse. In order to achieve high wake field generation, chirp parameters and functions should be set to optimal values.

Afhami, Saeedeh; Eslami, Esmaeil

2014-08-01

198

Waveform Optimizations for Ultra-Wideband Radio Systems  

Microsoft Academic Search

Solutions are presented for various optimizations of transient waveforms and signals used in ultra-wideband radio systems. These include the transmit antenna generator waveform required to maximize receive antenna voltage amplitude (with bounded input energy), the transmit antenna generator waveform that provides the \\

David M. Pozar

199

A pulse-foot-seeking algorithm for Doppler ultrasound waveforms  

Microsoft Academic Search

A simple algorithm for detecting and flagging the start of the systolic upstroke or 'pulse foot' of Doppler ultrasound waveforms is described. It operates in three stages. It first locates the true maximum of each waveform, it then works back to the point of maximum gradient on the upslope of the waveform, and finally works back to the maximum rate

D H Evans

1988-01-01

200

50 CFR 660.73 - Latitude/longitude coordinates defining the 100 fm (183 m) through 150 fm (274 m) depth contours.  

Code of Federal Regulations, 2013 CFR

...The 100 fm (183 m) depth contour around Santa Catalina Island off the state...The 125 fm (229 m) depth contour around Santa Catalina Island off the state...150 fm (274 m) depth contour used around Santa Catalina Island off the...

2013-10-01

201

Chirped fiber Brillouin frequency-domain distributed sensing  

NASA Astrophysics Data System (ADS)

A frequency-domain distributed temperature/strain sensor based on a longitudinally graded optical fiber (LGF) is proposed and evaluated. In an LGF, the Brillouin scattering frequency, ?, changes (i.e., is chirped) lengthwise monotonically and thus every position along the fiber has a unique ?. Any change locally (at some position) in the fiber environment will result in a measurable change in the shape of the Brillouin gain spectrum (BGS) near the frequency component mapped to that position. This is demonstrated via measurements and modeling for an LGF with local heating. The LGF is one with 100 MHz Brillouin frequency gradient over 16.7 m, with 1.1 and 1.7 m segments heated up to 40 K above ambient. A measurement of the BGS can enable the determination of a thermal (or strain) distribution along a sensor fiber, thus rendering the system one that is in the frequency domain. A sensitivity analysis is also presented for both coherent and pump-probe BGS measurement schemes. The modeling results suggest that the frequency-domain systems based on fibers with a chirped Brillouin frequency are highly suited as inexpensive event sensors (alarms) and have the potential to reach submeter position determination with sub-1-K temperature accuracies at >1 kHz sampling rates. Limitations to the technique are discussed.

Dragic, Peter D.; Mangognia, Anthony; Ballato, John

2014-05-01

202

Chirped CPMG for well-logging NMR applications.  

PubMed

In NMR well-logging, the measurement apparatus typically consists of a permanent magnet which is inserted into a bore, and the sample is the rock surrounding the borehole. When compared to the conditions of standard NMR experiments, this application is thus challenged by relatively weak and invariably inhomogeneous B0 and B1 fields. Chemical shift information is not generally obtained in these measurements. Instead, diffusivity, porosity and permeability information is collected from multi-echo decay measurements - most often using a Carr-Purcell Meiboom-Gill (CPMG) pulse sequence to enhance the experiment's limited sensitivity. In this work, we explore the consequences of replacing the hard square pulses used in a typical CPMG sequence with chirped pulses sweeping a range of frequencies. The greater bandwidths that for a maximum B1 level can be excited by chirped pulses translates into marked expansion of the detection volume, and thus significant signal-to-noise improvements when compared to standard CPMG acquisitions using hard pulses. This improvement, usually amounting to signal enhancements ?3, can be used to reduce the experimental time of NMR well-logging measurements, for measuring T2 even when B0 and B1 inhomogenieties complicate the measurements, and opening new opportunities in the determination of diffusional properties. PMID:24674888

Casabianca, Leah B; Mohr, Daniel; Mandal, Soumyajit; Song, Yi-Qiao; Frydman, Lucio

2014-05-01

203

1340 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 23, NO. 18, SEPTEMBER 15, 2011 Real-Time Interrogation of a Linearly Chirped Fiber  

E-print Network

of a Linearly Chirped Fiber Bragg Grating Sensor for Simultaneous Measurement of Strain and Temperature Weilin. Index Terms--Chirped fiber Bragg grating (CFBG), chirped mi- crowave pulse, interrogation, sensor-birefringence linearly chirped fiber Bragg grating (Hi-Bi LCFBG) for simultaneous measure- ment of strain and temperature

Yao, Jianping

204

Waveforms Measured in Confined Thermobaric Explosion  

SciTech Connect

Experiments with 1.5-g Shock-Dispersed-Fuel (SDF) charges have been conducted in six different chambers. Both flake Aluminum and TNT were used as the fuel. Static pressure gauges on the chamber wall were the main diagnostic. Waveforms for explosions in air were significantly larger than those in nitrogen - thereby demonstrating a strong thermobaric (combustion) effect. This effect increases as the confinement volume decreases and the mixture richness approaches 1.

Reichenbach, H; Neuwald, P; Kuhl, A L

2007-05-04

205

Digital Encoder for RF Transmit Waveform Synthesizer  

Microsoft Academic Search

We are designing an encoder for conversion of a Nyquist-rate N-bit digital word into a high frequency stream of single-bit data, to enable a novel architecture for a digital waveform synthesizer. The multi-bit to single-bit data conversion is performed by a new encoding scheme called the ldquostaggered thermometer code.rdquo Similar to the delta-sigma code, the staggered thermometer code also pushes

Amol Inamdar; Deepnarayan Gupta; Saad Sarwana; Anubhav Sahu; Alan M. Kadin

2007-01-01

206

Noise and distortion in transient waveform recorders  

Microsoft Academic Search

A data-acquisition system that measures transient waveform recorder (TWR) performance and has self-test capability is described. It uses an HP9836 desktop computer with 2 megabytes of RAM storage, a 30-megabyte hard disc and two floppy discs, a ten-bit TWR interfaced on an HPIB interface, and a CAMAC crate capable of housing up to four 12-bit 20-MHz TWRs. A sinewave curve-fit

R. Gorton

1988-01-01

207

Satellite and Instrument Influences on ICESat Waveforms  

NASA Astrophysics Data System (ADS)

The White Sands Space Harbor (WSSH) has served as the principal ground calibration site throughout the Ice, Cloud and land Elevation Satellite (ICESat) mission. The Center for Space Research (CSR) at the University of Texas at Austin continues to conduct various experiments designed to validate the timing, geolocation and geometric characteristics of individual laser footprints on the surface. In addition, two airborne lidar surveys of the calibration site and surrounding area were conducted during the mission, first in 2003 and again in 2007. Chosen for its limited surface roughness and topographic flatness, this area has been targeted 3-4 times in each of the 12 ICESat mapping campaigns to date, yielding a significant altimetry data set. The derived surface elevations are compared with those from the airborne lidar surveys, as well as those obtained by the Shuttle Radar Topography Mission (SRTM). Furthermore, the Geoscience Laser Altimetry System (GLAS) onboard ICESat records a digitized waveform for each laser pulse returned from the surface. The two methods currently used to fit such signals in ICESat data processing are examined and compared for the WSSH waveforms. The first fits up to two distinct Gaussians and provides a surface elevation at the location of the maximum peak. The second fits up to six overlapping Gaussians and provides a surface elevation at the centroid of the pulse. Observed differences in the reported elevations are discussed in terms of the satellite's off-nadir targeting geometry, the laser energy, and the skewness of the returned waveforms.

Webb, C. E.; Urban, T. J.; Neuenschwander, A. L.; Gutierrez, R.; Schutz, B. E.

2007-12-01

208

Binary Black Holes: Mergers, Dynamics, and Waveforms  

NASA Astrophysics Data System (ADS)

The final merger of two black holes is expected to be the strongest gravitational wave source for ground-based interferometers such as LIGO, VIRGO, and GEO600, as well as the space-based interferometer LISA. Observing these sources with gravitational wave detectors requires that we know the radiation waveforms they emit. Since these mergers take place in regions of extreme gravity, we need to solve Einstein's equations of general relativity on a computer in order to calculate these waveforms. For more than 30 years, scientists have tried to compute black hole mergers using the methods of numerical relativity. The resulting computer codes have been plagued by instabilities, causing them to crash well before the black holes in the binary could complete even a single orbit. Within the past few years, however, this situation has changed dramatically, with a series of remarkable breakthroughs. This talk will focus on new simulations that are revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, data analysis, and astrophysics.

Centrella, Joan

2007-04-01

209

Quantifying infrared target signature evolution using AM-FM features  

Microsoft Academic Search

In this paper we combine a new method of measuring infrared target signature evolution with current research and developmental tracking algorithms. Thermal images are decomposed by a set of Gabor filters and demodulated to produce a set of spatiospectrally localized AM-FM functions corresponding to oriented texture regions from within the original image. Critical updates are detected and issued to a

Mark Shook; John Junger; Nick Mould; Joseph P. Havlicek

2010-01-01

210

College of Medicine FM Family and Community Medicine  

E-print Network

College of Medicine FM Family and Community Medicine KEY: # = new course * = course changed, FAMILY MEDICINE. (1-3) With the advice and approval of his or her faculty adviser, the first-year student may choose approved electives offered by the Department of Family and Community Medicine. The intent

MacAdam, Keith

211

FM Analysis/Synthesis Based Audio Coding Bondhan Winduratna  

E-print Network

, the frequency of a sine wave (carrier) is modulated by another sine wave (modulator) to generate a complex/s. The achieved sound quality, however, decreases at lower bit rates, in particular for speech and single was in musical sound synthesis. This FM synthesis offers the advantage, that it is capable to model audio signals

212

FM HALFTONING VIA BLOCK ERROR DIFFUSION Niranjan Damera-Venkata  

E-print Network

size and shape using block quantization and a block lter in the feedback loop. We call this modi ed halftoning may be classi ed into three categories AM amplitude modulation, FM frequency modulation and AM physical printer imperfections such as dot gain 6 . Dot gain is caused from the increase in printed dot

Evans, Brian L.

213

FM 7-15, C5 Change No. 5 Headquarters  

E-print Network

The Army Universal Task List 1. Change 5 to FM 7-15, 27 February 2009, updates the tasks with chemical replaces Chapter 6, ART 6.0: The Protection Warfighting Function. 3. A not-equal-to symbol () marks new of the Army Washington, DC, 27 February 2009 The Army Universal Task List Contents Page PREFACE

US Army Corps of Engineers

214

Control of optical properties of hybrid materials with chirped femtosecond laser pulses under strong coupling conditions.  

PubMed

The interaction of chirped femtosecond laser pulses with hybrid materials--materials comprised of plasmon sustaining structures and resonant molecules--is scrutinized using a self-consistent model of coupled Maxwell-Bloch equations. The optical properties of such systems are examined with the example of periodic sinusoidal gratings. It is shown that under strong coupling conditions one can control light transmission using chirped pulses in a spatiotemporal manner. The temporal origin of control relies on chirps non-symmetric in time while the space control is achieved via spatial localization of electromagnetic energy due to plasmon resonances. PMID:25173035

Sukharev, Maxim

2014-08-28

215

Tunable optoelectronic oscillator based on a chirped Mach-Zehnder modulator  

NASA Astrophysics Data System (ADS)

Realization of a wideband tunable optoelectronic oscillator based on a chirped Mach-Zehnder modulator (MZM) and a chirped fiber Bragg grating is proposed and demonstrated. By simply adjusting the direct-current bias of the chirped MZM, the frequency of the oscillating signal is tuned. A theoretical model is established, then verified by an experiment. A high-purity microwave signal with a tunable frequency from 5.8 to 11.8 GHz is generated. The single-sideband phase noise of the generated signal is -112.6 dBc/Hz at a frequency offset of 10 kHz.

Wei, Zhihu; Pan, Shilong; Wang, Rong; Pu, Tao; Fang, Tao; Sun, Guodan; Zheng, Jilin

2013-05-01

216

Processing Aftershock Sequences Using Waveform Correlation  

NASA Astrophysics Data System (ADS)

For most event monitoring systems, the objective is to keep up with the flow of incoming data, producing a bulletin with some modest, relatively constant, time delay after present time, often a period of a few hours or less. Because the association problem scales exponentially and not linearly with the number of detections, a dramatic increase in seismicity due to an aftershock sequence can easily cause the bulletin delay time to increase dramatically. In some cases, the production of a bulletin may cease altogether, until the automatic system can catch up. For a nuclear monitoring system, the implications of such a delay could be dire. Given the expected similarity between a mainshock and aftershocks, it has been proposed that waveform correlation may provide a powerful means to simultaneously increase the efficiency of processing aftershock sequences, while also lowering the detection threshold and improving the quality of the event solutions. However, many questions remain unanswered. What are the key parameters for achieving the best correlations between waveforms (window length, filtering, etc.), and are they sequence-dependent? What is the overall percentage of similar events in an aftershock sequence, i.e. what is the maximum level of efficiency that a waveform correlation could be expected to achieve? Finally, how does this percentage of events vary among sequences? Using data from the aftershock sequence for the December 26, 2004 Mw 9.1 Sumatra event, we investigate these issues by building and testing a prototype waveform correlation event detection system that automatically expands its library of known events as new signatures are indentified in the aftershock sequence (by traditional signal detection and event processing). Our system tests all incoming data against this dynamic library, thereby identify any similar events before traditional processing takes place. In the region surrounding the Sumatra event, the NEIC EDR contains 4997 events in the 9 months following the mainshock, and only 265 events during the same period for the previous year, so this sequence represents a formidable challenge for any automatic processing system. Preliminary results suggest that a waveform correlation-based system can detect on the order of 10% or more of the aftershocks for this event. Results published in the recent literature suggest that significantly larger proportions may be achievable for other aftershock sequences with smaller fault ruptures; we investigate and report encouraging results from one such sequence. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04- 94AL85000.

Resor, M. E.; Procopio, M. J.; Young, C. J.; Carr, D. B.

2008-12-01

217

Three-dimensional waveform sensitivity kernels  

NASA Astrophysics Data System (ADS)

The sensitivity of intermediate-period (~10-100s) seismic waveforms to the lateral heterogeneity of the Earth is computed using an efficient technique based upon surface-wave mode coupling. This formulation yields a general, fully fledged 3-D relationship between data and model without imposing smoothness constraints on the lateral heterogeneity. The calculations are based upon the Born approximation, which yields a linear relation between data and model. The linear relation ensures fast forward calculations and makes the formulation suitable for inversion schemes; however, higher-order effects such as wave-front healing are neglected. By including up to 20 surface-wave modes, we obtain Frchet, or sensitivity, kernels for waveforms in the time frame that starts at the S arrival and which includes direct and surface-reflected body waves. These 3-D sensitivity kernels provide new insights into seismic-wave propagation, and suggest that there may be stringent limitations on the validity of ray-theoretical interpretations. Even recently developed 2-D formulations, which ignore structure out of the source-receiver plane, differ substantially from our 3-D treatment. We infer that smoothness constraints on heterogeneity, required to justify the use of ray techniques, are unlikely to hold in realistic earth models. This puts the use of ray-theoretical techniques into question for the interpretation of intermediate-period seismic data. The computed 3-D sensitivity kernels display a number of phenomena that are counter-intuitive from a ray-geometrical point of view: (1) body waves exhibit significant sensitivity to structure up to 500km away from the source-receiver minor arc; (2) significant near-surface sensitivity above the two turning points of the SS wave is observed; (3) the later part of the SS wave packet is most sensitive to structure away from the source-receiver path; (4) the sensitivity of the higher-frequency part of the fundamental surface-wave mode is wider than for its faster, lower-frequency part; (5) delayed body waves may considerably influence fundamental Rayleigh and Love waveforms. The strong sensitivity of waveforms to crustal structure due to fundamental-mode-to-body-wave scattering precludes the use of phase-velocity filters to model body-wave arrivals. Results from the 3-D formulation suggest that the use of 2-D and 1-D techniques for the interpretation of intermediate-period waveforms should seriously be reconsidered.

Marquering, Henk; Nolet, Guust; Dahlen, F. A.

1998-03-01

218

Seed laser chirping for enhanced backward Raman amplification in plasmas  

NASA Astrophysics Data System (ADS)

Backward Raman compression in plasma enables pulse compression to intensities not available using material gratings. Mediating the compression with higher density plasma (moderately undercritical plasmas) generally produces shorter and therefore more intense output pulses. However, very high density plasma, even if sufficiently tenuous to be transparent to the laser, also produces group velocity dispersion of the amplified pulse, deleteriously affecting the interaction. Nevertheless the seed dispersion can be used advantageously, by chirping the seed pulse, the length to reach the highest intensity is considerably reduced. The fact that the plasma length is reduced has considerable advantages: first, there is less distance over which deleterious instabilities can develop, such as forward Raman amplification; second, there is less radiative loss through inverse bremsstrahlung; and, third, less plasma is needed in the first place, requiring less input pump energy.

Toroker, Z.; Malkin, V. M.; Fisch, N. J.

2012-10-01

219

Femtosecond Chirp-Free Transient Absorption Method And Apparatus  

DOEpatents

A method and apparatus for femtosecond transient absorption comprising phase-sensitive detection, spectral scanning and simultaneous controlling of a translation stage to obtain TA spectra information having at least a sensitivity two orders of magnitude higher than that for single-shot methods, with direct, simultaneous compensation for chirp as the data is acquired. The present invention includes a amplified delay translation stage which generates a splittable frequency-doubled laser signal at a predetermined frequency f, a controllable means for synchronously modulating one of the laser signals at a repetition rate of f/2, applying the laser signals to a material to be sample, and acquiring data from the excited sample while simultaneously controlling the controllable means for synchronously modulating.

McBranch, Duncan W. (Santa Fe, NM); Klimov, Victor I. (White Rock, NM)

2001-02-20

220

Effect of linear chirp on femtosecond two-photon processes in solution  

PubMed Central

Coherent control via linear chirping a femtosecond laser pulse holds the promise of a potent spectroscopic tool in the study of two-photon processes in condensed phase. Here, we show modulation in the two-photon absorption and fluorescence of several common dyes in solution by simple phase ordering of femtosecond laser pulse into a linearly frequency chirped pulse. However, the modulation is dependent on associated solvent properties as the coherence is lost rapidly in the solution phase. Also, systematic effects are mostly seen only over a limited range of chirp since it is an interplay of two opposing effects on two-photon processeslinear chirp enhancing it while the associated pulse broadening reducing it. PMID:24364002

Nag, Amit; Goswami, Debabrata

2013-01-01

221

The use of chirped pulse millimeter-wave spectroscopy in chemical dynamics and kinetics  

E-print Network

.Chirped-pulse millimeter wave (CPmmW) spectroscopy is a revolutionary technique that has taken advantage of advances in electronics to give high signal to noise broadband rotational spectra in a very short period of time ...

Shaver, Rachel Glyn

2013-01-01

222

Individual acoustic variation in Belding's ground squirrel alarm chirps in the High Sierra Nevada  

NASA Astrophysics Data System (ADS)

The acoustic structure of calls within call types can vary as function of individual identity, sex, and social group membership and is important in kin and social group recognition. Belding's ground squirrels (Spermophilus beldingi) produce alarm chirps that function in predator avoidance but little is known about the acoustic variability of these alarm chirps. The purpose of this preliminary study was to analyze the acoustic structure of alarm chirps with respect to individual differences (e.g., signature information) from eight Belding's ground squirrels from four different lakes in the High Sierra Nevada. Results demonstrate that alarm chirps are individually distinctive, and that acoustic similarity among individuals may correspond to genetic similarity and thus dispersal patterns in this species. These data suggest, on a preliminary basis, that the acoustic structure of calls might be used as a bioacoustic tool for tracking individuals, dispersal, and other population dynamics in Belding's ground squirrels, and perhaps other vocal species.

McCowan, Brenda; Hooper, Stacie L.

2002-03-01

223

Fourier Transforms of Finite Chirps Peter G. Casazza and Matthew Fickus  

E-print Network

is altered whenever the wave is emanating from or reflecting off a moving body. As such, chirps have-Fourier transform is introduced. Chirplets have been used in image processing for over a decade [5]. For that matter

Casazza, Pete

224

Chirped-pulse millimeter-wave spectroscopy, dynamics, and manipulation of Rydberg-Rydberg Transitions  

E-print Network

The chirped-pulse millimeter-wave (CPmmW) technique is applied to transitions between Rydberg states, and calcium atoms are used as the initial test system. The unique feature of Rydberg{Rydberg transitions is that they ...

Colombo, Anthony P. (Anthony Paul)

2013-01-01

225

Chirped-pulse millimeter-wave spectroscopy: Spectrum, dynamics, and manipulation of RydbergRydberg transitions  

E-print Network

We apply the chirped-pulse millimeter-wave (CPmmW) technique to transitions between Rydberg states in calcium atoms. The unique feature of RydbergRydberg transitions is that they have enormous electric dipole transition ...

Colombo, Anthony P.

2013-01-01

226

Interrogation Using Bandpass Filters with Chirped Fiber Bragg Gratings for Fiber Bragg Grating Sensor  

Microsoft Academic Search

Wavelength interrogation based on bandpass filters with an array of chirped fiber Bragg gratings has been investigated. Single-passband filters have been fabricated by the concatenation method with chirped fiber Bragg gratings. The reflected wavelength by a fiber Bragg grating sensor can be precisely interrogated by this system. This technique potentially offers a low-cost compact and high-performance solution for the interrogation

Kiyoshi Nakagawa

2008-01-01

227

Design of a 3D Chirp Sub-bottom Imaging System  

Microsoft Academic Search

Chirp sub-bottom profilers are marine acoustic devices that use a known and repeatable source signature (1-24 kHz) to produce decimetre vertical resolution cross-sections of the sub-seabed. Here the design and development of the first true 3D Chirp system is described. When developing the design, critical factors that had to be considered included spatial aliasing, and precise positioning of sources and

Jonathan M. Bull; Martin Gutowski; Justin K. Dix; Timothy J. Henstock; Peter Hogarth; Timothy G. Leighton; Paul R. White

2005-01-01

228

3D CHIRP SUB-BOTTOM IMAGING SYSTEM: DESIGN AND FIRST 3D VOLUME  

Microsoft Academic Search

Chirp sub-bottom profilers are marine acoustic devices that use a known and repeatable source signature (1 - 24 kHz) to produce decimetre vertical resolution cross- sections of the sub-seabed. Here the design and development of the first true 3D Chirp system is described. When developing the design, critical factors that had to be considered included spatial aliasing, and precise positioning

Jonathan M. Bull; Martin Gutowski; Justin K. Dix; Timothy J. Henstock; Peter Hogarth; Timothy G. Leighton; Paul R. White

229

Generation and direct measurement of giant chirp in a passively mode-locked laser.  

PubMed

We evaluate the shape and chirp of nanosecond pulses from a fiber laser passively mode locked with a nanotube-based saturable absorber by using a synchronously scanning streak camera and a monochromator to directly measure the pulse spectrogram. We show that the stable sech(2) output pulse possesses a predominantly linear chirp, with a residual quartic phase and low noise. Comparison with analytical mode-locking theory shows a good quantitative agreement with the master equation mode-locking model. PMID:19927199

Kelleher, E J R; Travers, J C; Ippen, E P; Sun, Z; Ferrari, A C; Popov, S V; Taylor, J R

2009-11-15

230

Comparison of binaural auditory brainstem responses and the binaural dierence potential evoked by chirps and clicks  

E-print Network

auditory brainstem responses were recorded for clicks and chirps for levels from 10 to 60 dB nHL in steps and 40 dB nHL. Both the binaurally evoked potential and the binaural difference potential exhibit steeper growth functions for chirps than for clicks for levels up to 40 dB nHL. For higher stimulation levels

Oldenburg, Carl von Ossietzky, Universität

231

75 FR 9439 - FM Approvals: Application for Expansion of Recognition; Wyle Laboratories: Voluntary Modification...  

Federal Register 2010, 2011, 2012, 2013

...test standards for the expansion. FM seeks expansion of its recognition for...Conditioners UL 521 Heat Detectors for Fire Protective...Utility Signaling FM 3210 Heat Detectors for Automatic...acceptable request for expansion of its recognition...

2010-03-02

232

Enabling Pervasive Mobile Applications with the FM Radio Broadcast Data System  

E-print Network

. Independent content may be data services, e.g. news, weather, traffic, job postings, or large scale queries, e or independent from the broadcasted FM radio program. Supplemental content could enhance the FM radio program

Zhong, Lin

233

47 CFR 73.4154 - Network/AM, FM station affiliation agreements.  

Code of Federal Regulations, 2013 CFR

...Telecommunication 4 2013-10-01 2013-10-01 false Network/AM, FM station affiliation agreements. 73.4154 Section... Rules Applicable to All Broadcast Stations 73.4154 Network/AM, FM station affiliation agreements. See...

2013-10-01

234

47 CFR 73.4154 - Network/AM, FM station affiliation agreements.  

Code of Federal Regulations, 2010 CFR

...Telecommunication 4 2010-10-01 2010-10-01 false Network/AM, FM station affiliation agreements. 73.4154 Section... Rules Applicable to All Broadcast Stations 73.4154 Network/AM, FM station affiliation agreements. See...

2010-10-01

235

47 CFR 73.4154 - Network/AM, FM station affiliation agreements.  

Code of Federal Regulations, 2011 CFR

...Telecommunication 4 2011-10-01 2011-10-01 false Network/AM, FM station affiliation agreements. 73.4154 Section... Rules Applicable to All Broadcast Stations 73.4154 Network/AM, FM station affiliation agreements. See...

2011-10-01

236

47 CFR 73.4154 - Network/AM, FM station affiliation agreements.  

Code of Federal Regulations, 2012 CFR

...Telecommunication 4 2012-10-01 2012-10-01 false Network/AM, FM station affiliation agreements. 73.4154 Section... Rules Applicable to All Broadcast Stations 73.4154 Network/AM, FM station affiliation agreements. See...

2012-10-01

237

47 CFR 73.7002 - Fair distribution of service on reserved band FM channels.  

Code of Federal Regulations, 2010 CFR

...on reserved band FM channels. 73.7002 Section...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...Noncommercial Educational Channels, and for Certain...stations on reserved FM channels are determined...section 307(b) of the Communications Act, 47...

2010-10-01

238

47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.  

Code of Federal Regulations, 2010 CFR

...educational FM stations and channels. 73.506 Section 73...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...educational FM stations and channels. (a) Noncommercial educational stations operating on the channels specified in 73.501...

2010-10-01

239

Discussant response to 'Does the acoustic waveform mirror the voice?'.  

PubMed

The acoustic waveform that reaches the two ears of a listener can convey the intended message. Over the telephone, this waveform is the only source of information from the speaker, since the listener is out of visual contact; indeed, in this situation the acoustic waveform itself is restricted in its frequency content. Whilst the listener can infer much about the speaker from the acoustic waveform, including the speaker's age, gender, nationality, dialect, and emotional state, the issue under consideration here is the extent to which quantitative analysis of the acoustic waveform can provide useful information about a speaker's voice. This paper was presented as an Invited Discussant Response, at the Pan-European Voice Conference (PEVOC6) in London, to the question posed in Ternstrm's Invited Keynote Lecture 1: Does the acoustic waveform mirror the voice? PMID:16287649

Howard, David M

2005-01-01

240

Plunge waveforms from inspiralling binary black holes  

E-print Network

We study the coalescence of non-spinning binary black holes from near the innermost stable circular orbit down to the final single rotating black hole. We use a technique that combines the full numerical approach to solve Einstein equations, applied in the truly non-linear regime, and linearized perturbation theory around the final distorted single black hole at later times. We compute the plunge waveforms which present a non negligible signal lasting for $t\\sim 100M$ showing early non-linear ringing, and we obtain estimates for the total gravitational energy and angular momentum radiated.

J. Baker; B. Bruegmann; M. Campanelli; C. O. Lousto; R. Takahashi

2001-02-09

241

Anisotropy effects on 3D waveform inversion  

NASA Astrophysics Data System (ADS)

In the recent years 3D waveform inversion has become achievable procedure for seismic data processing. A number of datasets has been inverted and presented (Warner el al 2008, Ben Hadj at all, Sirgue et all 2010) using isotropic 3D waveform inversion. However the question arises will the results be affected by isotropic assumption. Full-wavefield inversion techniques seek to match field data, wiggle-for-wiggle, to synthetic data generated by a high-resolution model of the sub-surface. In this endeavour, correctly matching the travel times of the principal arrivals is a necessary minimal requirement. In many, perhaps most, long-offset and wide-azimuth datasets, it is necessary to introduce some form of p-wave velocity anisotropy to match the travel times successfully. If this anisotropy is not also incorporated into the wavefield inversion, then results from the inversion will necessarily be compromised. We have incorporated anisotropy into our 3D wavefield tomography codes, characterised as spatially varying transverse isotropy with a tilted axis of symmetry - TTI anisotropy. This enhancement approximately doubles both the run time and the memory requirements of the code. We show that neglect of anisotropy can lead to significant artefacts in the recovered velocity models. We will present inversion results of inverting anisotropic 3D dataset by assuming isotropic earth and compare them with anisotropic inversion result. As a test case Marmousi model extended to 3D with no velocity variation in third direction and with added spatially varying anisotropy is used. Acquisition geometry is assumed as OBC with sources and receivers everywhere at the surface. We attempted inversion using both 2D and full 3D acquisition for this dataset. Results show that if no anisotropy is taken into account although image looks plausible most features are miss positioned in depth and space, even for relatively low anisotropy, which leads to incorrect result. This may lead to misinterpretation of results. However if correct physics is used results agree with correct model. Our algorithm is relatively affordable and runs on standard pc clusters in acceptable time. Refferences: H. Ben Hadj Ali, S. Operto and J. Virieux. Velocity model building by 3D frequency-domain full-waveform inversion of wide-aperture seismic data, Geophysics (Special issue: Velocity Model Building), 73(6), P. VE101-VE117 (2008). L. Sirgue, O.I. Barkved, J. Dellinger, J. Etgen, U. Albertin, J.H. Kommedal, Full waveform inversion: the next leap forward in imaging at Valhall, First Brake April 2010 - Issue 4 - Volume 28 M. Warner, I. Stekl, A. Umpleby, Efficient and Effective 3D Wavefield Tomography, 70th EAGE Conference & Exhibition (2008)

Stekl, I.; Warner, M.; Umpleby, A.

2010-12-01

242

Multiscale AM-FM Methods for Diabetic Retinopathy Lesion Detection  

Microsoft Academic Search

In this paper, we propose the use of multiscale amplitude-modulation-frequency-modulation (AM-FM) methods for discriminating between normal and pathological retinal images. The method presented in this paper is tested using standard images from the early treatment diabetic retinopathy study. We use 120 regions of 40 ?? 40 pixels containing four types of lesions commonly associated with diabetic retinopathy (DR) and two

Carla Agurto; Vctor Murray; Eduardo S. Barriga; Sergio Murillo; Marios S. Pattichis; Herbert Davis; Stephen R. Russell; Michael D. Abrmoff; Peter Soliz

2010-01-01

243

Observation of Partial Discharge Current Waveform under Inverter Surge Application  

NASA Astrophysics Data System (ADS)

The partial discharge (PD) generated by the surge voltage is an issue in inverter-fed motor for the reliability of the electrical insulation. The measurement of PD waveform with a wide frequency range is one way to investigate this PD. However, measurement of the PD waveform under inverter surge voltage is not easy, because of the rapid rising time of the applied voltage. In this paper, the detecting circuit and the analysis method were studied to construct a novel analysis system for the PD current waveform with wide frequency range under the application of rapid rising voltage. A detecting circuit containing a detecting resistance, a coupling capacitor and a resistance for suppressing the ringing brought appropriate current waveform under a surge voltage application. It is also recognized that the PD current waveform is only extracted from the detected current waveform using a transfer function calculated by a voltage and current waveforms without PD. Furthermore, this system on the PD analysis may further be useful to clarify the PD mechanism under a surge voltage application because the PD current waveform, which contains information on PD mechanism, was extracted without waveform change.

Murakami, Yoshinobu; Takino, Takahiro; Hozumi, Naohiro; Nagao, Masayuki

244

F68-4 F.M. RADIO STATION Legislative History  

E-print Network

F68-4 F.M. RADIO STATION Legislative History: Document dated November 21, 1968. At its meeting by Dr. Frederic Weed, Chairman of the Ad Hoc F.M. Radio Policy Committee, (amended November 18, 1968): ACTION BY COLLEGE PRESIDENT: "Approved." Signed: Robert D. Clark, December 6, 1968. F.M. RADIO STATION

Gleixner, Stacy

245

Development of DARC decoding LSI for high-speed FM subcarrier system  

Microsoft Academic Search

Expectations have been running high for a new generation of FM broadcasting systems targeted at mobile FM reception, notably in cars. The DARC (data radio channel) is an FM multiplex broadcasting system designed to address these expectations. When compared with the RDS (radio data system) and the RBDS (radio broadcast data system) which have already gone into service in Europe

M. Suka; Y. Hirakoso; Y. Takahashi; T. Kuroda; M. Takada; M. Fujiwara; Y. Tomida; S. Okada

1994-01-01

246

Automatic Calibration of Modified FM Synthesis to Harmonic Sounds using Genetic Algorithms  

E-print Network

Automatic Calibration of Modified FM Synthesis to Harmonic Sounds using Genetic Algorithms Matthieu scheme. Genetic algorithms (GA) have been used rather exten- sively for this purpose, and in particular to further explore its modified counterpart, Modified FM (ModFM), which has not been used as widely, and its

Smyth, Tamara

247

MICRO SYNTHETIC APERTURE RADAR USING FM/CW Ryan L. Smith  

E-print Network

MICRO SYNTHETIC APERTURE RADAR USING FM/CW TECHNOLOGY by Ryan L. Smith A thesis submitted;ABSTRACT MICRO SYNTHETIC APERTURE RADAR USING FM/CW TECHNOLOGY Ryan L. Smith Department of Electrical of gener- ating high quality images using frequency modulated, continuous wave (FM/CW) technology and it

Long, David G.

248

Multiscale AM-FM Methods for Diabetic Retinopathy Lesion Detection  

PubMed Central

We propose the use of multiscale amplitude-modulation frequency-modulation (AM-FM) methods for discriminating between normal and pathological retinal images. The method presented in this paper is tested using standard images from the Early Treatment Diabetic Retinopathy Study (ETDRS). We use 120 regions of 4040 pixels containing 4 types of lesions commonly associated with diabetic retinopathy (DR) and two types of normal retinal regions that were manually selected by a trained analyst. The region types included: microaneurysms, exudates, neovascularization on the retina, hemorrhages, normal retinal background, and normal vessels patterns. The cumulative distribution functions of the instantaneous amplitude, the instantaneous frequency magnitude, and the relative instantaneous frequency angle from multiple scales are used as texture features vectors. We use distance metrics between the extracted feature vectors to measure interstructure similarity. Our results demonstrate a statistical differentiation of normal retinal structures and pathological lesions based on AM-FM features. We further demonstrate our AM-FM methodology by applying it to classification of retinal images from the MESSIDOR database. Overall, the proposed methodology shows significant capability for use in automatic DR screening. PMID:20129850

Murray, Victor; Barriga, Eduardo; Murillo, Sergio; Pattichis, Marios; Davis, Herbert; Russell, Stephen; Abrmoff, Michael; Soliz, Peter

2010-01-01

249

Lidar compressive sensing using chaotic waveform  

NASA Astrophysics Data System (ADS)

Full waveform Lidar systems have the ability of recording the complete signal reflected from the illuminated target. Therefore, more detail information can be obtained compared to conventional Lidar systems. The problem that is faced in using full waveform Lidar is the acquisition of high volume data, a solution proposed to solve this problem is compressive sensing. By using a compressive sensing approach we can reduce the sampling rate and still be able to recover the signal. The reduction is incorporated in the acquisition hardware, where we perform sensing of the signal with compression. In this paper we propose to use a deterministic compressive sensing approach by using a chaotic signal as the sensing matrix. The proposed approach gives the range profile information without the requirement of further processing techniques. For comparison we used two different types of transmitted signals: chaotic and Linear Frequency Modulated (LFM) signals. Simulations demonstrate that chaotic signals give better results than the LFM signals. By using a chaotic signal we can obtain the impulse response of the target by using less than 20 percent of the samples.

Verdin, B.; von Borries, R.

2014-05-01

250

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

SciTech Connect

Abstract We conduct a detailed test of a recently developed technique, CAPloc, in recovering source parameters from a few stations against results from a large broadband network in Southern California. The method uses a library of 1D Greens functions which are broken into segments and matched to waveform observations with adjustable timing shifts. These shifts can be established by calibration against a distribution of well-located earthquakes and assembled in tomographic images for predicting various phase-delays. Synthetics generated from 2D cross-sections through these models indicates that 1D synthetic waveforms are sufficient in modeling but simply shifted in time for most hard-rock sites. This simplification allows the source inversion for both mechanism and location to easily obtain by grid search. We test one-station mechanisms for 160 events against the array for both PAS and GSC which have data since 1960. While individual solutions work well (about 90%), joint solutions produce more reliable and defensible results. Inverting for both mechanism and location also works well except for certain complex paths across deep basins and along mountain ridges.

Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

2009-01-27

251

The Marriage of Spectroscopy and Dynamics: Chirped-Pulse Fourier-Transform Mm-Wave Cp-Ft Spectroscopy in Pulsed Uniform Supersonic Flows  

NASA Astrophysics Data System (ADS)

A new experimental scheme is presented that combines two powerful emerging technologies: chirped-pulse Fourier-transform mm-Wave spectroscopy and pulsed uniform supersonic flows. It promises a nearly universal detection method that can deliver quantitative isomer, conformer, and vibrational level specific detection, characterization of unstable reaction products and intermediates, and perform unique spectroscopic, kinetics, and dynamics measurements. Chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy, pioneered by Pate and coworkers, allows rapid acquisition of broadband microwave spectrum through advancements in waveform generation and oscilloscope technology. This revolutionary approach has successfully been adapted to higher frequencies by the Field group at MIT. Our new apparatus will exploit amplified chirped pulses in the range of 26-40 GHz, in combination with a pulsed uniform supersonic flow from a Laval nozzle. This nozzle source, pioneered by Rowe, Sims, and Smith for low temperature kinetics studies, produces thermalized reactants at high densities and low temperatures perfectly suitable for reaction dynamics experiments studied using the CP-mmW approach. This combination of techniques shall enhance the thousand-fold improvement in data acquisition rate achieved in the CP method by a further 2-3 orders of magnitude. A pulsed flow alleviates the challenges of continuous uniform flow, e.g. large gas loads and reactant consumption rates. In contrast to other pulsed Laval systems currently in use, we will use a fast piezo valve and small chambers to achieve the desired pressures while minimizing the gas load, so that a 10 Hz repetition rate can be achieved with one turbomolecular pump. The proposed technique will be suitable for many diverse fields, including fundamental studies in spectroscopy and reaction dynamics, reaction kinetics, combustion, atmospheric chemistry, and astrochemistry. We expect a significant advancement in the ability to detect absolute populations of complex reaction products under near-nascent conditions, providing the powerful method of reaction dynamics with a universal spectroscopic probe capable of capturing the details of complex chemistry for specific product isomers and conformers.

Abeysekera, Chamara; Oldham, James M.; Suits, Arthur G.; Park, G. Barratt; Field, Robert W.

2012-06-01

252

Fast prediction and evaluation of gravitational waveforms using surrogate models  

E-print Network

[Abridged] We propose a solution to the problem of quickly and accurately predicting gravitational waveforms within any given physical model. The method is relevant for both real-time applications and in more traditional scenarios where the generation of waveforms using standard methods can be prohibitively expensive. Our approach is based on three offline steps resulting in an accurate reduced-order model that can be used as a surrogate for the true/fiducial waveform family. First, a set of m parameter values is determined using a greedy algorithm from which a reduced basis representation is constructed. Second, these m parameters induce the selection of m time values for interpolating a waveform time series using an empirical interpolant. Third, a fit in the parameter dimension is performed for the waveform's value at each of these m times. The cost of predicting L waveform time samples for a generic parameter choice is of order m L + m c_f online operations where c_f denotes the fitting function operation count and, typically, m << L. We generate accurate surrogate models for Effective One Body (EOB) waveforms of non-spinning binary black hole coalescences with durations as long as 10^5 M, mass ratios from 1 to 10, and for multiple harmonic modes. We find that these surrogates are three orders of magnitude faster to evaluate as compared to the cost of generating EOB waveforms in standard ways. Surrogate model building for other waveform models follow the same steps and have the same low online scaling cost. For expensive numerical simulations of binary black hole coalescences we thus anticipate large speedups in generating new waveforms with a surrogate. As waveform generation is one of the dominant costs in parameter estimation algorithms and parameter space exploration, surrogate models offer a new and practical way to dramatically accelerate such studies without impacting accuracy.

Scott E. Field; Chad R. Galley; Jan S. Hesthaven; Jason Kaye; Manuel Tiglio

2013-08-16

253

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

SciTech Connect

This quarter, we have focused on several tasks: (1) Building a high-quality catalog of earthquake source parameters for the Middle East and East Asia. In East Asia, we computed source parameters using the CAP method for a set of events studied by Herrman et al., (MRR, 2006) using a complete waveform technique. Results indicated excellent agreement with the moment magnitudes in the range 3.5 -5.5. Below magnitude 3.5 the scatter increases. For events with more than 2-3 observations at different azimuths, we found good agreement of focal mechanisms. Depths were generally consistent, although differences of up to 10 km were found. These results suggest that CAP modeling provides estimates of source parameters at least as reliable as complete waveform modeling techniques. However, East Asia and the Yellow Sea Korean Paraplatform (YSKP) region studied are relatively laterally homogeneous and may not benefit from the CAP methods flexibility to shift waveform segments to account for path-dependent model errors. A more challenging region to study is the Middle East where strong variations in sedimentary basin, crustal thickness and crustal and mantle seismic velocities greatly impact regional wave propagation. We applied the CAP method to a set of events in and around Iran and found good agreement between estimated focal mechanisms and those reported by the Global Centroid Moment Tensor (CMT) catalog. We found a possible bias in the moment magnitudes that may be due to the thick low-velocity crust in the Iranian Plateau. (2) Testing Methods on a Lifetime Regional Data Set. In particular, the recent 2/21/08 Nevada Event and Aftershock Sequence occurred in the middle of USArray, producing over a thousand records per event. The tectonic setting is quite similar to Central Iran and thus provides an excellent testbed for CAP+ at ranges out to 10, including extensive observations of crustal thinning and thickening and various Pnl complexities. Broadband modeling in 1D, 2D, and 3D will be presented. (3) Shallow Crustal Structure and Sparse Network Source Inversions for Southern California. We conducted a detailed test of a recently developed technique, CAPloc, in recovering source parameters including location and depth based on tomographic maps. We tested two-station solutions against 160 well determined events which worked well except for paths crossing deep basins and along mountain ridges.

Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

2008-10-17

254

Ultrafast control of the internuclear distance with parabolic chirped pulses.  

PubMed

Recently, control over the bond length of a diatomic molecule with the use of parabolic chirped pulses was predicted on the basis of numerical calculations [Chang; et al. Phys. Rev. A 2010, 82, 063414]. To achieve the required bond elongation, a laser scheme was proposed that implies population inversion and vibrational trapping in a dissociative state. In this work we identify two regimes where the scheme works, called the strong and the weak adiabatic regimes. We define appropriate parameters to identify the thresholds where the different regimes operate. The strong adiabatic regime is characterized by a quasi-static process that requires longer pulses. The molecule is stabilized at a bond distance and at a time directly controlled by the pulse in a time-symmetrical way. In this work we analyze the degree of control over the period and elongation of the bond as a function of the pulse bandwidth. The weak adiabatic regime implies dynamic deformation of the bond, which allows for larger bond stretch and the use of shorter pulses. The dynamics is anharmonic and not time-symmetrical and the final state is a wave packet in the ground potential. We show how the vibrational energy of the wave packet can be controlled by changing the pulse duration. PMID:22082170

Chang, Bo Y; Shin, Seokmin; Santamaria, Jesus; Sola, Ignacio R

2012-03-22

255

Optimal discrete pulse modulation waveforms for resonant link inverters  

Microsoft Academic Search

The advent of zero-voltage-switching resonant link inverters has raised the question of modulation strategies that satisfy the regular sampling constraints of such systems. An easy and elegant approach to the synthesis of optimal discrete pulse modulation waveforms is presented. Utilizing the finiteness of the set of possible waveforms, an exhaustive search algorithm is deployed to derive a set of optimum

M. H. Kheraluwala; D. M. Divan

1988-01-01

256

A Marked Point Process for Modeling Lidar Waveforms  

Microsoft Academic Search

Lidar waveforms are 1-D signals representing a train of echoes caused by reflections at different targets. Modeling these echoes with the appropriate parametric function is useful to retrieve information about the physical characteristics of the targets. This paper presents a new probabilistic model based upon a marked point process which reconstructs the echoes from recorded discrete waveforms as a sequence

Clment Mallet; Florent Lafarge; Michel Roux; Uwe Soergel; Frdric Bretar; Christian Heipke

2010-01-01

257

Multiharmonic Waveform Fitting of Periodic Signals using Genetic Algorithms  

Microsoft Academic Search

A genetic algorithm is used to estimate the parameters of periodic signals in multiharmonic waveform fitting. This algorithm is used to find the fundamental frequency which can then be used in a multiple linear least-squares (LS) waveform fitting algorithm. This procedure is applied to different multiharmonic signals with very good results. The main advantage of genetic algorithms when compared with

Fernando M. Janeiro; P. M. Ramos

2007-01-01

258

Altimeter waveform parameters retrieval using Artificial Neural Networks  

NASA Astrophysics Data System (ADS)

Waveform retracking and analysis methods form an integral part of any altimeter data processing to derive useable information. This is significant owing to the strong heterogeneity in the waveforms resulting of returns of altimeter pulses from uneven geographical features. The waveforms consisting of altimeter return pulses follow the Brown model over the deep oceans. However, the waveforms become rather complex when received over coastal and land regions owing to large scale inhomogeneities. The present work attempts to characterize altimeter return pulses (consisting of slope, amplitude and range) on the basis of the surface responsible for the echo followed by estimation of these waveform parameters based on an Artificial Neural Network Technique (ANN). An ANN is a non-linear parallel-distributed computer model highly effective for classification type of problems. ANNs are widely applied for pattern recognition since their non-linear characteristics makes them very suitable for application to processes with internal inhomogeneities. To demonstrate the technique, we have utilized JASON-2 high resolution waveform data over multiple passes spanning varied geographical topography covering open ocean, coasts, and in-land water bodies. The ANN model is formulated by first training and testing with data sets identified for various topography classifications. Following this, the model estimations are validated with actual altimeter returns forming the waveform, and that have not been used during the ANN model formulation process. The work aims to demonstrate the ANN technique for high resolution altimeter waveform analysis.

Swain, Debadatta; Sasamal, S. K.

2012-07-01

259

Gravitational waveforms from the evaporating ACO cosmic string loop  

E-print Network

The linearly polarized gravitational waveforms from a certain type of rotating, evaporating cosmic string - the Allen-Casper-Ottewill loop - are constructed and plotted over the lifetime of the loop. The formulas for the waveforms are simple and exact, and describe waves which attenuate self-similarly, with the amplitude and period of the waves falling off linearly with time.

Malcolm Anderson

2009-03-28

260

Joint Dynamic Resource Allocation and Waveform Adaptation for Cognitive Networks  

Microsoft Academic Search

This paper investigates the issue of dynamic re- source allocation (DRA) in the context of multi-user cognitive radio networks. We present a general framework adopting gen- eralized signal expansion functions for representation of physical- layer radio resources as well as for synthesis of transmitter and receiver waveforms, which allow us to join DRA with waveform adaptation, two procedures that are

Zhi Tian; Geert Leus; Vincenzo Lottici

2011-01-01

261

Harmonic minimization waveforms for modulated heating experiments at HAARP  

E-print Network

Harmonic minimization waveforms for modulated heating experiments at HAARP G. Jin,1 M. Spasojevic,1), Harmonic minimization waveforms for modulated heating experiments at HAARP, J. Geophys. Res., 117, A11315 and Stubbe [1984], and Milikh et al. [1999]. The High Fre- quency Active Auroral Research Program (HAARP

262

ECG beats classification using waveform similarity and RR interval  

E-print Network

1 ECG beats classification using waveform similarity and RR interval Ahmad Khoureich Ka Abstract--This paper present an electrocardiogram (ECG) beat classification method based on waveform similarity and RR. Heart beats of 128 samples data centered on the R peak are extracted from the ECG signal and thence

Boyer, Edmond

263

Simulation of waveform interactions for interference analysis of military networks  

Microsoft Academic Search

Efficient use of spectrum requires an accurate determination of interference effects. In this paper, we introduce a radio to radio (R2R) factor that quantifies the interference effects of one radio waveform on another based on multiple waveform properties instead of solely on intermediate frequency (IF) signal power. The R2R factor is formulated as a dimensionless correction term in the victims

Chrysanthos Chrysanthou; Jeffrey Boksiner; Michael Zankel; Glenn Minko; Douglas S. Pfeil; John Kountouriotis; Jeffrey Wildman; Matthew Garfield; Timothy P. Kurzweg; Kapil R. Dandekar; Moshe Kam

2009-01-01

264

Coupled Waveform Analysis in Dynamic Characterization of Lossy Solids  

E-print Network

Coupled Waveform Analysis in Dynamic Characterization of Lossy Solids Bojan B. Guzina, M.ASCE,1-infinite solid, a rational analytical and computational framework is developed for nonintrusive, wave; Damping; Viscoelasticity; Solids. Introduction Inverse analysis of the waveforms stemming from a surficial

Guzina, Bojan

265

Modeling lidar waveforms in heterogeneous and discrete canopies  

Microsoft Academic Search

This study explores the relationship between laser waveforms and canopy structure parameters and the effects of the spatial arrangement of canopy structure on this relationship through a geometric optical model. Studying laser waveforms for such plant canopies is needed for the advanced retrieval of three-dimensional (3D) canopy structure parameters from the vegetation canopy lidar (VCL) mission. For discontinuous plant canopies,

Wenge Ni-Meister; David L. B. Jupp; Ralph Dubayah

2001-01-01

266

A CCD-BASED WAVEFORM GENERATOR FOR DRIVING CCD CIRCUITS  

E-print Network

A CCD-BASED WAVEFORM GENERATOR FOR DRIVING CCD CIRCUITS S.E. Kemeny and E.R. Fossum Center for charge-coupled device (CCD) circuits is described. The method utilizes four parallel-in, serial-out CCD in CCD circuits of generating complex waveforms on-chip with minimum power and maximum flexibility. #12

Fossum, Eric R.

267

A procedure to Estimate the Fractal Dimension of Waveforms  

E-print Network

A method is described for calculating the approximate fractal dimension from a set of N values y sampled from a waveform between time zero and t. The waveform was subjected to a double linear transformation that maps it into a unit square.

Carlos Sevcik

2010-03-27

268

Cognitive radio - an adaptive waveform with spectral sharing capability  

Microsoft Academic Search

The growth of wireless applications and spectral limitations are serious concerns for both the military and civilian communities. Cognitive radio (CR) technologies expand spectrum efficiency using elements of space, time and frequency diversity that up to now have not been exploited. An adaptive waveform (AW) generation technique is presented which adapts to the changing electromagnetic environment and synthesizes waveform features

Vasu D. Chakravarthy; A. K. Shaw; Michael A. Temple; James P. Stephens

2005-01-01

269

Wideband Waveform Optimization with Energy Detector Receiver in Cognitive Radio  

E-print Network

Wideband Waveform Optimization with Energy Detector Receiver in Cognitive Radio Zhen Hu Department investigates the transmitted waveform optimization issues for wideband cognitive radio with energy detector receiver. The motivation is to provide a cheap cognitive radio network with simple and cheap cognitive

Qiu, Robert Caiming

270

Fast bus waveform estimation at the presence of coupling noise  

Microsoft Academic Search

With the technology scaling and shrinking feature sizes, coupling noise has become one of the most critical concerns in today's interconnect-centric design, especially for long global buses. A very common consequence of coupling is that the output signal waveform becomes non-monotonic. Traditionally, only through circuit simulation can the output waveform can be precisely acquired. However, this method suffers from low

Jingye Xu; Pervez Khaled; Masud H. Chowdhury

2008-01-01

271

Method and apparatus for resonant frequency waveform modulation  

DOEpatents

A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.

Taubman, Matthew S [Richland, WA

2011-06-07

272

Waveform encoding of voiceband data signals  

NASA Astrophysics Data System (ADS)

This is a tutorial paper on encoding the waveform of voiceband data signals into digital form for digital transmission. The encoding algorithms covered are PCM, DPCM, and DM with and without quantizer adaptation. Coder bit rates from 16 to 64 kb/s are considered. Most digital Codec's on voiceband channels are designed primarily for speech and their performance with speech is well known. However, since many voiceband channels may contain other signals such as voiceband data, adequate performance with such signals is a necessity. Much of the paper is a summary and an interpretation of previous work in encoding data signals. Some new perspectives and material are presented, especially for DPCM. Topics covered include the sampling phase effect, fast and slow acting quantizer adaptation of algorithms, comparison between speech and data performance, dual-mode coders, network considerations, and the effect of quantizing noise on the phase integrity of data signals.

Oneal, J. B., Jr.

1980-02-01

273

Statistical Sampling Enabled Full Waveform Inversion  

NASA Astrophysics Data System (ADS)

Full-waveform Inversion has recently emerged as a promising method for refining seismic velocity models to achieve enhanced imaging. The algorithm involves iteratively updating the velocity model to improve the match between the recorded seismic data and the simulated waveforms, with the goal of estimating the true velocity structure. Each iteration typically requires multiple wavefield extrapolations. As a result the technique places significant computational burdens on even the largest computers when applied to commercial three-dimensional surface seismic datasets. This computational cost has been attacked previously by combining the processing of multiple physical shots into a single ';encoded-shot', using random encoding techniques (Krebs et al, 2009). The encoding can be based upon time shifts, polarity reversal or convolution with a short random series any of which may be changed between iterations. While this technique works well for geometries with fixed receiver arrays (e.g. ocean-bottom cables) additional steps are usually required when applied to moving arrays both because the area occupied by the encoded shot grows in comparison to a single shot, and because not every receiver registers data from every shot in the recorded data. This paper discusses an alternative approach using concepts from statistical sampling, proposed by van Leeuwen & Hermann 2012. Rather than using every shot, or encoding multiple shots, at each iteration we randomly select a different subset of shots as input to the inversion algorithm. The method promises a reduction in the computational costs while still ensuring that all the information in the data is utilized during the inversion. Furthermore, the method is applicable without modification to both fixed and moving geometries. Results are shown for a synthetic model and a real marine data set acquired with a multi-vessel coil geometry. Both examples show significant computational savings, compared to the conventional algorithm, without any detectable reduction in quality.

Jiao, K.; Huang, W.; Schiemenz, A. R.; Coates, R. T.

2013-12-01

274

Analysis of orthogonal waveform for spaceborne MIMO-GMTI radar  

NASA Astrophysics Data System (ADS)

The application of MIMO (Multiple input multiple output) techniques to spaceborne multichannel radar offers a number of advantages, including target detection, parameter estimation, and so on. Based on two kinds of waveforms presented in MIMO radar, a concise definition of synthetical ISLR is proposed. Through analysis of synthetical ISLR for two kinds of waveforms, it concludes that compared with orthogonal frequency division waveform, the crosscorrelation of orthogonal code waveform badly weakens the performance of spaceborne MIMO radar in GMTI (Ground moving target indication). Thus, by adopting orthogonal frequency division waveform, the basic principle of space-time-frequency adaptive processing is studied. Simulation results demonstrate the superiority of frequency division orthogonal MIMO radar in improving clutter suppression and GMTI performance.

Zou, Bo; Dong, Zhen; Du, Xiang-yu

2011-10-01

275

50 CFR 660.71 - Latitude/longitude coordinates defining the 10-fm (18-m) through 40-fm (73-m) depth contours.  

Code of Federal Regulations, 2011 CFR

...W. long. (j) The 30 fm (55 m) depth contour around Santa Catalina Island off the state of California is defined...W. long. (n) The 40 fm (73 m) depth contour around Santa Catalina Island off the state of California is...

2011-10-01

276

50 CFR 660.71 - Latitude/longitude coordinates defining the 10-fm (18-m) through 40-fm (73-m) depth contours.  

Code of Federal Regulations, 2012 CFR

...W. long. (j) The 30 fm (55 m) depth contour around Santa Catalina Island off the state of California is defined...W. long. (n) The 40 fm (73 m) depth contour around Santa Catalina Island off the state of California is...

2012-10-01

277

DIODE LASER MEASUREMENTS OF HF CONCENTRATIONS PRODUCED FROM HEPTANE/AIR PAN FIRES EXTINGUISHED BY FE-36, FM-200, FE-36 PLUS APP, AND FM-200 PLUS APP  

EPA Science Inventory

Tunable diode laser absorption spectroscopy (TDLAS) is used to measure the time evolution of hydrogen fluoride (HF) concentrations produced from a series of enclosed heptane/air pan fires extinguished by FE-36, FM-200, FE-35 plus ammonium polyphosphate (APP), or FM-200 plus APP. ...

278

Atomic Mass and Nuclear Binding Energy for Fm-223 (Fermium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Brnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-223 (Fermium, atomic number Z = 100, mass number A = 223).

Sukhoruchkin, S. I.; Soroko, Z. N.

279

Atomic Mass and Nuclear Binding Energy for Fm-227 (Fermium)  

NASA Astrophysics Data System (ADS)

This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Brnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-227 (Fermium, atomic number Z = 100, mass number A = 227).

Sukhoruchkin, S. I.; Soroko, Z. N.

280

Comparison of chirp versus click and tone pip stimulation for cervical vestibular evoked myogenic potentials.  

PubMed

The current study explored differences among cervical vestibular evoked myogenic potentials (cVEMP) that were evoked by CE-chirp and click and tone pip in healthy controls, and tried to explain the differences of cVEMP between the three of them. Thirty normal volunteers were used as subjects for CE-chirp and click and tone-pip (Blackman pip) stimuli. The latency of P1, N1, peak-to-peak P1-N1 amplitude, and cVEMP interaural difference were obtained and analyzed. The response rates of cVEMP were 93% for click and 100% for both Blackman pip and CE-chirp, respectively. The P1 and N1 latencies of cVEMP evoked by CE-chirp were the shortest, followed by click, with Blackman pip the longest (F=6,686.852, P<0.001). All indices of cVEMP evoked by the three stimuli showed no significant difference between the left and right earsor between genders. cVEMP responses were significantly different between the three stimuli. Compared with the currently used stimulus, CE-chirp can evoke cVEMP with shorter latencies and demonstrates increased speed and reliability. PMID:24178551

Wang, Bo-Chen; Liang, Yong; Liu, Xiao-Long; Zhao, Jing; Liu, You-Li; Li, Yan-Fei; Zhang, Wei; Li, Qi

2014-12-01

281

Stimulated Brillouin scattering suppression with a chirped laser seed: comparison of dynamical model to experimental data  

NASA Astrophysics Data System (ADS)

When scaling CW single-mode fiber amplifiers to high power, the first nonlinear limitation that appears for narrowlinewidth seed lasers is stimulated Brillouin scattering (SBS). We present a dynamical simulation of Brillouin scattering in a Yb-doped fiber amplifier that numerically solves the differential equations in z and t describing the laser, Stokes and pump waves, the inversion, and the density fluctuations that seed the scattering process. We compare the model to experimental data, and show that a linearly chirped seed laser is an efficient form of SBS suppression; especially for long delivery fibers. The frequency chirp decreases the interaction length by chirping through the Brillouin resonance in a time that is short compared to the fiber transit time. The seed has a highly linear chirp of 1014 - 1016 Hz/s at 1064 nm which preserves a well-defined phase relationship in time. This method of SBS suppression retains a long effective coherence length for purposes of coherent combining, while at high chirps appears to the SBS as a large linewidth, increasing the threshold. An increase in fiber length increases the laser bandwidth as seen by the SBS, leading to a fiberlength- independent SBS threshold.

Petersen, Eliot; Yang, Zhi; White, Jeffrey O.; Rakuljic, George; Satyan, Naresh; Vasilyev, Arseny; Yariv, Amnon

2014-03-01

282

Fast Prediction and Evaluation of Gravitational Waveforms Using Surrogate Models  

NASA Astrophysics Data System (ADS)

We propose a solution to the problem of quickly and accurately predicting gravitational waveforms within any given physical model. The method is relevant for both real-time applications and more traditional scenarios where the generation of waveforms using standard methods can be prohibitively expensive. Our approach is based on three offline steps resulting in an accurate reduced order model in both parameter and physical dimensions that can be used as a surrogate for the true or fiducial waveform family. First, a set of m parameter values is determined using a greedy algorithm from which a reduced basis representation is constructed. Second, these m parameters induce the selection of m time values for interpolating a waveform time series using an empirical interpolant that is built for the fiducial waveform family. Third, a fit in the parameter dimension is performed for the waveform's value at each of these m times. The cost of predicting L waveform time samples for a generic parameter choice is of order O(mL+mcfit) online operations, where cfit denotes the fitting function operation count and, typically, m ?L. The result is a compact, computationally efficient, and accurate surrogate model that retains the original physics of the fiducial waveform family while also being fast to evaluate. We generate accurate surrogate models for effective-one-body waveforms of nonspinning binary black hole coalescences with durations as long as 105M, mass ratios from 1 to 10, and for multiple spherical harmonic modes. We find that these surrogates are more than 3 orders of magnitude faster to evaluate as compared to the cost of generating effective-one-body waveforms in standard ways. Surrogate model building for other waveform families and models follows the same steps and has the same low computational online scaling cost. For expensive numerical simulations of binary black hole coalescences, we thus anticipate extremely large speedups in generating new waveforms with a surrogate. As waveform generation is one of the dominant costs in parameter estimation algorithms and parameter space exploration, surrogate models offer a new and practical way to dramatically accelerate such studies without impacting accuracy. Surrogates built in this paper, as well as others, are available from GWSurrogate, a publicly available python package.

Field, Scott E.; Galley, Chad R.; Hesthaven, Jan S.; Kaye, Jason; Tiglio, Manuel

2014-07-01

283

Frequency Correction for MIRO Chirp Transformation Spectroscopy Spectrum  

NASA Technical Reports Server (NTRS)

This software processes the flyby spectra of the Chirp Transform Spectrometer (CTS) of the Microwave Instrument for Rosetta Orbiter (MIRO). The tool corrects the effect of Doppler shift and local-oscillator (LO) frequency shift during the flyby mode of MIRO operations. The frequency correction for CTS flyby spectra is performed and is integrated with multiple spectra into a high signal-to-noise averaged spectrum at the rest-frame RF frequency. This innovation also generates the 8 molecular line spectra by dividing continuous 4,096-channel CTS spectra. The 8 line spectra can then be readily used for scientific investigations. A spectral line that is at its rest frequency in the frame of the Earth or an asteroid will be observed with a time-varying Doppler shift as seen by MIRO. The frequency shift is toward the higher RF frequencies on approach, and toward lower RF frequencies on departure. The magnitude of the shift depends on the flyby velocity. The result of time-varying Doppler shift is that of an observed spectral line will be seen to move from channel to channel in the CTS spectrometer. The direction (higher or lower frequency) in the spectrometer depends on the spectral line frequency under consideration. In order to analyze the flyby spectra, two steps are required. First, individual spectra must be corrected for the Doppler shift so that individual spectra can be superimposed at the same rest frequency for integration purposes. Second, a correction needs to be applied to the CTS spectra to account for the LO frequency shifts that are applied to asteroid mode.

Lee, Seungwon

2012-01-01

284

Estimation of multiple accelerated motions using chirp-Fourier transform and clustering.  

PubMed

Motion estimation in the spatiotemporal domain has been extensively studied and many methodologies have been proposed, which, however, cannot handle both time-varying and multiple motions. Extending previously published ideas, we present an efficient method for estimating multiple, linearly time-varying motions. It is shown that the estimation of accelerated motions is equivalent to the parameter estimation of superpositioned chirp signals. From this viewpoint, one can exploit established signal processing tools such as the chirp-Fourier transform. It is shown that accelerated motion results in energy concentration along planes in the 4-D space: spatial frequencies-temporal frequency-chirp rate. Using fuzzy c-planes clustering, we estimate the plane/motion parameters. The effectiveness of our method is verified on both synthetic as well as real sequences and its advantages are highlighted. PMID:17283773

Alexiadis, Dimitrios S; Sergiadis, George D

2007-01-01

285

Experimental demonstration of energy-chirp compensation by a tunable dielectric-based structure.  

PubMed

A tunable energy-chirp compensator was used to remove a correlated energy chirp from the 60-MeV beam at the Brookhaven National Laboratory Accelerator Test Facility. The compensator operates through the interaction of the wakefield of the electron bunch with itself and consists of a planar structure comprised of two alumina bars with copper-plated backs separated by an adjustable beam aperture. By changing the gap size, the correlated energy chirp of the electron bunch was completely removed. Calculations show that this device, properly scaled to account for the electron bunch charge and length, can be used to remove residual correlated energy spread at the end of the linacs used for free-electron lasers. The experimental results are shown to be in good agreement with numerical simulations. Application of this technique can significantly simplify linac design and improve free-electron lasers performance. PMID:24702378

Antipov, S; Baturin, S; Jing, C; Fedurin, M; Kanareykin, A; Swinson, C; Schoessow, P; Gai, W; Zholents, A

2014-03-21

286

Chirp control of a single-mode, good beam quality, zigzag dye laser  

SciTech Connect

The authors report a substantial reduction of frequency chirp of a single-mode laser-pumped zigzag dye laser. A linear optical cavity using counterpropagating orthogonally polarized waves was injection-seeded at 568 nm and operated with a laser output of about 1 J. The chirp was controlled by an intracavity Pockels cell that was configured to add optical density at a rate which counterbalanced the decrease in optical density due to dye-solvent heating during the {approximately}1-{micro}s laser pulse. Heterodyne measurements were used to determine that the bandwidth was near the transform limit and chirp rate of {approximately}1 MHz/{micro}s. The beam quality of the laser was measured at 10 Hz as 1.7 XDL.

Mandl, A.; Zavriyev, A.; Klimek, D.E. [Textron Systems Div., Wilmington, MA (United States)] [Textron Systems Div., Wilmington, MA (United States)

1997-03-01

287

Control of chirped pulse trains: a speedway for free-optimization experiments  

NASA Astrophysics Data System (ADS)

Complex phase-only shaping of intense ultrashort laser pulses is applied to generate highly flexible pulse structures with regular envelopes. By incorporating the linear chirp as additional free parameter into the technique of colored pulses, trains of chirped pulses are produced, capable of independent and simultaneous modulation of relative intensity ratio, optical delay, and individual chirp. Such pulses might find applications in multi-parameter scans or closed-loop feedback measurements. For the latter, we demonstrate that with use of these tailored pulse trains, adaptive feedback control experiments quickly converge. They provide near-optimal solutions, already revealing key features of the system under study. Moreover, seeding standard free-optimization routines with these temporary solutions largely accelerates the search for the closest-possible optimum.

Truong, N. X.; Tiggesbumker, J.; Meiwes-Broer, K.-H.

2011-11-01

288

Reliability of complete gravitational waveform models for compact binary coalescences  

E-print Network

With recent advances in post-Newtonian (PN) theory and numerical relativity (NR) it has become possible to construct inspiral-merger-ringdown waveforms by combining both descriptions into one hybrid signal. While addressing the reliability of such waveforms, previous studies have identified the PN contribution as the dominant source of error, which can be reduced by incorporating longer NR simulations. Here we overcome the two outstanding issues that make it difficult to determine the minimum NR simulation length necessary to produce suitably accurate hybrids: (1) the criteria for a GW search is the mismatch between the true waveform and a set of model waveforms, optimized over all waveforms in the model, but for discrete hybrids this optimization was not yet possible. (2) these calculations typically require that numerical waveforms already exist, while we develop an algorithm to estimate hybrid mismatches errors without numerical data. Our procedure relies on combining supposedly equivalent PN models at highest available order with common data in the NR regime, and their difference serves as a measure of the uncertainty assumed in each waveform. Contrary to some earlier studies, we estimate that ~10 NR orbits before merger should allow for the construction of waveform families that are accurate enough for detection in a broad range of parameters, only excluding highly spinning, unequal-mass systems. Nonspinning systems, even with high mass-ratio (q>=20) are well modeled for astrophysically reasonable component masses. The parameter bias is only of the order of 1% for total mass and symmetric mass-ratio and less than 0.1 for the dimensionless spin magnitude. We take the view that similar NR waveform lengths will remain the state of the art in the advanced detector era, and begin to assess the limits of the science that can be done with them.

Frank Ohme; Mark Hannam; Sascha Husa

2011-07-05

289

Evaluation of chirp reversal power modulation sequence for contrast agent imaging  

NASA Astrophysics Data System (ADS)

Over the last decade, significant research effort has been focused on the use of chirp for contrast agent imaging because chirps are known to significantly increase imaging contrast-to-noise ratio (CNR). New imaging schemes, such as chirp reversal (CR), have been developed to improve contrast detection by increasing non-linear microbubble responses. In this study we evaluated the contrast enhancement efficiency of various chirped imaging sequences in combination with well-established imaging schemes such as power modulation (PM) and pulse inversion (PI). The imaging schemes tested were implemented on a fully programmable open scanner and evaluated by ultrasonically scanning (excitation frequency of 2.5?MHz amplitude of 350?kPa) a tissue-mimicking flow phantom comprising a 4?mm diameter tube through which aqueous dispersions (dilution fraction of 1/2000) of the commercial ultrasound contrast agent, SonoVue were continuously circulated. The recovery of non-linear microbubble responses after chirp compression requires the development and the optimization of a specific filter. A compression filter was therefore designed and used to compress and extract several non-linear components from the received microbubble responses. The results showed that using chirps increased the image CNR by approximately 10?dB, as compared to conventional Gaussian apodized sine burst excitation but degraded the axial resolution by a factor of 1.4, at -3?dB. We demonstrated that the highest CNR and contrast-to-noise ratio (CTR) were achievable when CR was combined with PM as compared to other imaging schemes such as PI.

Novell, A.; Sennoga, CA; Escoffre, JM; Chaline, J.; Bouakaz, A.

2014-09-01

290

HfO2/SiO2 chirped mirrors manufactured by electron beam evaporation.  

PubMed

A HfO2/SiO2 chirped mirror was manufactured by electron beam evaporation to increase the laser resistance. The hybrid monitoring strategy utilizing both monochromatic monitoring and quartz crystal monitoring was applied to the deposition compared to the single optical monitoring method. The coatings were characterized by transmission spectrophotometer and white light interferometry, and the experimental results showed that the chirped mirror monitored with the hybrid strategy possessed high reflectivity (>99.7%) and tolerable group delay dispersion oscillation (-5020?fs2) in the spectra range of 740-860?nm. PMID:21460969

Jinlong, Zhang; Xinbin, Cheng; Zhanshan, Wang; Hongfei, Jiao; Tao, Ding

2011-03-20

291

Dual-Chirped Optical Parametric Amplification for Generating High-Power Infrared Pulses  

NASA Astrophysics Data System (ADS)

We propose and calculate a novel OPA method for obtaining an ultrafast high-power infrared pulse source, called dual-chirped OPA (DC-OPA), based on a Ti:sapphire laser system in a collinear configuration. By chirping both pump and seed pulses in an optimized way, high-energy pump pulses can be utilized for a DC-OPA process without exceeding the damage threshold of BBO crystals, and broadband signal and idler pulses can be generated with a total conversion efficiency approaching 40%. Furthermore, the few-cycle idler pulses with a passively stabilized carrier-envelope phase (CEP) can be generated by the difference frequency generation (DFG) process.

Zhang, Q.; Takahashi, E. J.; Mcke, O. D.; Lu, P.; Midorikawa, K.

292

Effect of input pulse chirp on nonlinear energy deposition and plasma excitation in water  

NASA Astrophysics Data System (ADS)

We analyze numerically and experimentally the effect of the input pulse chirp on the nonlinear energy deposition from $5\\ \\mu$J fs-pulses at $800$ nm to water. Numerical results are also shown for pulses at $400$ nm, where linear losses are minimized, and for different focusing geometries. Input chirp is found to have a big impact on the deposited energy and on the plasma distribution around focus, thus providing a simple and effective mechanism to tune the electron density and energy deposition. We identify three relevant ways in which plasma features may be tuned.

Milin, Carles; Jarnac, Amlie; Brelet, Yohann; Jukna, Vytautas; Houard, Aurlien; Mysyrowicz, Andr; Couairon, Arnaud

2014-11-01

293

Quasi-phase-matching high-harmonic radiation using chirped THz pulses  

E-print Network

High-order harmonic generation in the presence of a chirped THz pulse is investigated numerically with a complete 3D non-adiabatic model. The assisting THz pulse illuminates the HHG gas cell laterally inducing quasi-phase-matching. We demonstrate that it is possible to compensate the phase mismatch during propagation and extend the macroscopic cutoff of a propagated strong IR pulse to the single-dipole cutoff. We obtain two orders of magnitude increase in the harmonic efficiency of cutoff harmonics ($\\approx$170 eV) using a THz pulse of constant wavelength, and a further factor of 3 enhancement when a chirped THz pulse is used.

Kovcs, Katalin; Hebling, Jnos; Tosa, Valer; Varj, Katalin

2014-01-01

294

High-Fidelity Adiabatic Passage by Composite Sequences of Chirped Pulses  

SciTech Connect

We present a method for optimization of the technique of adiabatic passage between two quantum states by composite sequences of frequency-chirped pulses with specific relative phases: composite adiabatic passage (CAP). By choosing the composite phases appropriately the nonadiabatic losses can be canceled to any desired order with sufficiently long sequences, regardless of the nonadiabatic coupling. The values of the composite phases are universal for they do not depend on the pulse shapes and the chirp. The accuracy of the CAP technique and its robustness against parameter variations make CAP suitable for high-fidelity quantum information processing.

Torosov, Boyan T. [Department of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria); Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR CNRS 5209, BP 47870, F-21078 Dijon (France); Guerin, Stephane [Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR CNRS 5209, BP 47870, F-21078 Dijon (France); Vitanov, Nikolay V. [Department of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria)

2011-06-10

295

Design of a 3D Chirp Sub-bottom Imaging System  

Microsoft Academic Search

Chirp sub-bottom profilers are marine acoustic devices that use a known and repeatable source signature (124kHz) to produce\\u000a decimetre vertical resolution cross-sections of the sub-seabed. Here the design and development of the first true 3D Chirp\\u000a system is described. When developing the design, critical factors that had to be considered included spatial aliasing, and\\u000a precise positioning of sources and receivers.

Jonathan M. Bull; Martin Gutowski; Justin K. Dix; Timothy J. Henstock; Peter Hogarth; Timothy G. Leighton; Paul R. White

2005-01-01

296

Prepulse suppression and optimization of backward Raman amplification with a chirped pump laser beam.  

PubMed

Two-dimensional particle-in-cell (PIC) simulations have been performed to demonstrate how chirping the pump laser beam can make the seed backward Raman amplification more efficient. The PIC code ocean is detailed and validated with theoretical analysis of the three-wave coupling. Particular attention is devoted to the impact of numerical noise on Raman scattering. Once the numerical parameters are set, one- and two-dimensional simulations exhibit the ability to suppress the pedestal pulse preceding the amplified seed laser beam and lower the spontaneous Raman scattering by appropriately choosing the pump chirp value. PMID:23679532

Nuter, R; Tikhonchuk, V

2013-04-01

297

Chirped pulse formation dynamics in ultra-long mode-locked fiber lasers.  

PubMed

By modeling giant chirped pulse formation in ultra-long, normally dispersive, mode-locked fiber lasers, we verify convergence to a steady-state consisting of highly chirped and coherent, nanosecond-scale pulses, which is in good agreement with recent experimental results. Numerical investigation of the transient dynamics reveals the existence of dark soliton-like structures within the envelope of the initial noisy pulse structure. Quasi-stationary dark solitons can persist throughout a large part of the evolution from noise to a stable dissipative soliton solution of the mode-locked laser cavity. PMID:24690797

Kelleher, E J R; Travers, J C

2014-03-15

298

Two-photon ladder climbing and transition to autoresonance in a chirped oscillator  

NASA Astrophysics Data System (ADS)

The two-photon ladder climbing (successive two-photon Landau-Zener-type transitions) in a chirped quantum nonlinear oscillator and its classical limit (subharmonic autoresonance) are discussed. An isomorphism between the chirped one- and two-photon resonances in the system is used in calculating the threshold for the phase-locking transition in both the classical and quantum limits. The theory is tested by solving the Schrdinger equation in the energy basis and illustrated via the Wigner function in phase space.

Barth, I.; Friedland, L.

2013-05-01

299

Modelling chirp as a function of reflectivity in electroabsorption modulated lasers (EML)  

NASA Astrophysics Data System (ADS)

We present a theoretical analysis of the chirp caused by the reflection of light from the Electro-Absorption Modulator (EAM) facet back into the laser. The work is modelled on our Essex Distributed Time Domain Model (eDTDM) (S. P. Higgins and A. J. Vickers, Proc SPIE Phys. and Simulations of Opto-Electron. Devices X11, 5349, 435 (2004) [1]; A. J. Vickers and S. P. Higgins, A new model for complex dynamic laser modelling, IEEE J Quantum Electron., 2005, awaiting publication [2]). A novel method of determining the chirp within the simulation is presented.

Higgins, S. P.; Vickers, A. J.

2006-03-01

300

Dynamics of surface solitons at the edge of chirped optical lattices  

NASA Astrophysics Data System (ADS)

We address soliton formation at the edge of chirped optical lattices imprinted in Kerr-type nonlinear media. We find families of power thresholdless surface waves that do not exist at other types of lattice interfaces. Such solitons form due to combined action of internal reflection at the interface, distributed Bragg-type reflection, and focusing nonlinearity. Remarkably, we discover that surfaces of chirped lattices are soliton attractors: Below an energy threshold, solitons launched well within the lattice self-bend toward the interface, and then stick to it.

Kartashov, Yaroslav V.; Vysloukh, Victor A.; Torner, Lluis

2007-07-01

301

Prepulse suppression and optimization of backward Raman amplification with a chirped pump laser beam  

NASA Astrophysics Data System (ADS)

Two-dimensional particle-in-cell (PIC) simulations have been performed to demonstrate how chirping the pump laser beam can make the seed backward Raman amplification more efficient. The PIC code ocean is detailed and validated with theoretical analysis of the three-wave coupling. Particular attention is devoted to the impact of numerical noise on Raman scattering. Once the numerical parameters are set, one- and two-dimensional simulations exhibit the ability to suppress the pedestal pulse preceding the amplified seed laser beam and lower the spontaneous Raman scattering by appropriately choosing the pump chirp value.

Nuter, R.; Tikhonchuk, V.

2013-04-01

302

Monaural and binaural processing of complex waveforms  

NASA Astrophysics Data System (ADS)

Data were collected concerning the amount of comodulation masking release (CMR) obtained when coherent envelope information is presented successively rather than simultaneously. It was determined that off-frequency information, which produces a CMR, can provide only a small release from masking when presented prior and subsequent to the temporal interval containing the signal. Three papers were published and a fourth is undergoing revision. One assessed sensitivity to interaural correlation of the envelope of high-frequency waveforms and whether such sensitivity might account for detectability in an MLD paradigm. Another showed sensitivity to antiphasic sinusoids added only to the envelopes of high-frequency bands of noise as a function of the frequency of the sinusoid and the bandwidth of the masker. A third, with Dr. R. M. Stem, depicts how straightness weighting can be accomplished by a second, physiologically demonstrated, stage of neural processing. The complex, cross-correlation-based model was extended to account for how interaural insensitive disparities in combination with interaural temporal disparities affects lateralization. Software was written for experiments concerning effects of forward masking fringes on the high-frequency MLD and to perform the theoretical analyses of stimuli used in the successive CMR paradigm.

Trahiotis, Constantine; Bernstein, Leslie R.

1993-01-01

303

Full Waveform Inversion of Solar Interior Flows  

E-print Network

The inference of flows of material in the interior of the Sun is a subject of major interest in helioseismology. Here we apply techniques of Full Waveform Inversion (FWI) to synthetic data to test flow inversions. In this idealized setup, we do not model seismic realization noise, training the focus entirely on the problem of whether a chosen supergranulation flow model can be seismically recovered. We define the misfit functional as a sum of L_2 norm deviations in travel times between prediction and observation, as measured using short-distance f and p_1 filtered and large-distance unfiltered $p$ modes. FWI allows for the introduction of measurements of choice and iteratively improving the background model, while monitoring the evolution of the misfit in all desired categories. Although the misfit is seen to uniformly reduce in all categories, convergence to the true model is very slow, possibly because it is trapped in a local minimum. The primary source of error is inaccurate depth localization, which, owi...

Hanasoge, Shravan M

2014-01-01

304

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

SciTech Connect

High-Resolution Source Parameters using Calibration from Ambient Seismic Noise (ASN) Zhongwen Zhan, Shengji Wei, Sidao Ni, and Don V. Helmberger Abstract Several new methods have been developed to retrieve local Green's functions based on the cross-correlation of ambient seismic noise (station-to-station) and conventional (source-to-station) inversions. The latter methods provide the most broadband results but require accurate source parameters for phase-delay recovery which depends on the starting model. Considerable progress is being made in providing such information from 3D modeling, Tape et al. (2008), using Adjoint Tomography. But to match waveforms for the recent Chino Hills event still requires shifting synthetics to align on data. This means that it is difficult to use 3D simulations to refine source locations in near-real time. We can avoid the 3D problems by applying the CAP method and storing shifts from past events, Tan (2006), and/or using ASN, Shapiro et al. (2005), to predict lags for surface waves. Here, we directly compare results from CAP predictions with ASN results using stations near the Chino Hills event. We use the same SC seismic model as used in the Library of Earthquakes to generate Green's functions for noise (single force) for comparison with ASN correlations and allow Cap delays. We apply these delays or corrections to determine precise Centroid locations.

Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

2009-04-30

305

One Chip Digital FM\\/AM Frequency and Clock Indicator Using Improved In2 Technology  

Microsoft Academic Search

A one-chip digital frequency and clock indicator (T1400) has been developed using improved I2L technology which enables the integration of ECL and LED driver circuits on the same chip. The LSI is suitable for use in FM\\/AM radio receivers and displays time of days or FM\\/AM tuning frequencies on a four digit LED display. An ECL prescaler circuit for FM

K. Kanzaki; K. Ichinose; K. Aoki; A. Furukawa; M. Taguchi; Y. Tokumaru; M. Nakai; N. Miura; J. Sano

1979-01-01

306

Consistency of post-Newtonian waveforms with numerical relativity.  

PubMed

General relativity predicts the gravitational wave signatures of coalescing binary black holes. Explicit waveform predictions for such systems, required for optimal analysis of observational data, have so far been achieved primarily using the post-Newtonian (PN) approximation. The quality of this treatment is unclear, however, for the important late-inspiral portion. We derive late-inspiral waveforms via a complementary approach, direct numerical simulation of Einstein's equations. We compare waveform phasing from simulations of the last approximately 14 cycles of gravitational radiation from equal-mass, nonspinning black holes with the corresponding 2.5PN, 3PN, and 3.5PN orbital phasing. We find phasing agreement consistent with internal error estimates for either approach, suggesting that PN waveforms for this system are effective until the last orbit prior to final merger. PMID:17995394

Baker, John G; van Meter, James R; McWilliams, Sean T; Centrella, Joan; Kelly, Bernard J

2007-11-01

307

In silico estimates of cell electroporation by electrical incapacitation waveforms  

E-print Network

We use a system model of a cell and approximate magnitudes of electrical incapacitation (EI) device waveforms to estimate conditions that lead to responses with or without electroporation (EP) of cell membranes near ...

Weaver, James C.

308

A UNIFIED METHODOLOGY FOR SEISMIC WAVEFORM ANALYSIS AND INVERSION  

E-print Network

(sebastien.chevrot@cnes.fr). Other data analysis and inversion tools were developed using Python (http://www.python....................................................36 2.4.1 Effects of Windowing and Narrow-band Filtering on Target Waveform

Chen, Po

309

Acoustic Waveform Logging - Advances In Theory And Application  

E-print Network

Full-waveform acoustic logging has made significant advances in both theory and application in recent years, and these advances have greatly increased the capability of log analysts to measure the physical properties of ...

Cheng, C. H.

310

Effects of surface scattering in full-waveform inversion  

E-print Network

In full-waveform inversion of seismic body waves, often the free surface is ignored on grounds of computational efficiency. A synthetic study was performed to investigate the effects of this simplification. In terms of ...

Rondenay, Stephane

311

Detection, Synchronization, and Doppler Scale Estimation with Multicarrier Waveforms in  

E-print Network

method enables online receiver operation. I. INTRODUCTION Offline data processing based on recorded Acoustic Communication Sean Mason, Christian R. Berger, Shengli Zhou, and Peter Willett Department acoustic communication using orthogonal frequency division multiplex (OFDM) waveforms. The method involves

Zhou, Shengli

312

Subpicosecond single-shot waveform measurement using temporal imaging  

SciTech Connect

Experimental results from a new single-transient optical recorder with < 300 fs resolution are presented. The system uses a 103x temporal imaging system to expand the waveform which is then recorded with a streak camera.

Bennett, C V; Kolner, B H

1999-07-19

313

Optimization of loading pressure waveforms for piston driven isentropic compression  

NASA Astrophysics Data System (ADS)

Smooth ramp loading with higher pressure amplitude is usually preferred in the isentropic compression experiment (ICE) of condensed materials. Optimizing the pressure waveforms of ICE is important in avoiding any shock wave propagating during ramp loading and raising the peak pressure as high as possible. Most reports on shaping ICE waveforms mainly focused on magnetohydrodynamic numerical simulations; a few used the hydrodynamic theory of isentropic flow. However, some points can be improved. Based on one-dimensional planar isentropic flow theory and regarding the ICE loading pressure exerted on the sample's surface as a time-dependent piston boundary condition, a condition for the ramp-to-shock transition as a compression wave propagates in the sample materials, has been derived that forms a necessary condition to avoid such transitions and determines ICE loading pressure waveforms with shorter rise time. A comparison of results is presented for samples of the maximum thickness and for optimized current waveforms obtained in magnetically driven ICEs.

Jin, Yunsheng; Sun, Chengwei; Zhao, Jianheng; Wang, Guiji; Tan, Fuli

2014-06-01

314

Continuous real time endotracheal tube cuff pressure waveform.  

PubMed

Endotracheal tube cuff pressure monitoring is one of the standard degrees of care afforded to anesthetized patients in the operative theater. Traditional pressure transducer when used to monitor cuff pressure provides real time continuous sine wave pressure waveform which has not been described in literature so far. This unique waveform needs to be further processed and evaluated to check its utility in airway pressure monitoring. PMID:24838549

Ganigara, Anuradha; Ramavakoda, Chandrika Y

2014-08-01

315

A STOCHASTIC APPROACH FOR MODELLING AIRBORNE LIDAR WAVEFORMS  

Microsoft Academic Search

In contrast to conventional airborne multi-echo laser scanner systems, full-waveform (FW) lidar systems are able to record the entire emitted and backscattered signals of each laser pulse. Instead of clouds of individual 3D points, FW devices provide 1D profiles of the 3D scene, which allows gaining additional and more detailed observations of the illuminated surfaces. Indeed, lidar waveforms are signals

Florent Lafarge; Fred eric Bretar; Michel Roux; Uwe Soergel; Christian Heipke

2009-01-01

316

Regional waveform calibration in the Pamir-Hindu Kush region  

Microsoft Academic Search

Twelve moderate-magnitude earthquakes (mb 4-5.5) in the Pamir-Hindu Kush region are investigated to determine their focal mechanisms and to relocate them using their regional waveform records at two broadband arrays, the Kyrgyzstan Regional Network (KNET), and the 1992 Pakistan Himalayas seismic experiment array (PAKH) in northern Pakistan. We use the ``cut-and-paste'' source estimation technique to invert the whole broadband waveforms

Lupei Zhu; Donald V. Helmberger; Chandan K. Saikia; Bradley B. Woods

1997-01-01

317

Transthoracic defibrillation threshold of sine and trapezoidal waveforms in defibrillation.  

PubMed

The transthoracic defibrillation threshold of trapezoidal (2.5-, 5-, 10-, 15-, 20-, 40-, and 55-msec duration) and damped sine waveforms were established in groups of anesthetized greyhounds. Of the seven trapezoidal waveforms, the threshold current was lowest for the 20-msec pulse but was not significantly different for the 5-20-msec pulses (p greater than 0.05). The threshold delivered energy was not significantly different for the 2.5-20-msec waveforms. The 40- and 55-msec pulses had significantly greater delivered energies than the shorter pulses (p less than 0.01). The transthoracic defibrillation threshold of two trapezoidal (5- and 20-msec) and three damped sine waves (Lown, Edmark, and Belfast) showed that the threshold transthoracic current and energy were not significantly different for the 5-msec trapezoid and three sine waves (p greater than 0.05). The threshold transthoracic energy for the 20-msec trapezoid was significantly greater than that of the four other waveforms. The threshold current for the 20-msec trapezoid was significantly less than that of the Belfast and Edmark waveforms only. Thus, none of the three damped sine waveforms was superior, with the 5-msec trapezoid producing similar results. Although the 20-msec trapezoid had the lowest threshold current, it had the highest delivery energy. PMID:2760559

Wilson, C M; Bailey, A; Allen, J D; Anderson, J; Adgey, A A

1989-07-01

318

Estimation of airway obstruction using oximeter plethysmograph waveform data  

PubMed Central

Background Validated measures to assess the severity of airway obstruction in patients with obstructive airway disease are limited. Changes in the pulse oximeter plethysmograph waveform represent fluctuations in arterial flow. Analysis of these fluctuations might be useful clinically if they represent physiologic perturbations resulting from airway obstruction. We tested the hypothesis that the severity of airway obstruction could be estimated using plethysmograph waveform data. Methods Using a closed airway circuit with adjustable inspiratory and expiratory pressure relief valves, airway obstruction was induced in a prospective convenience sample of 31 healthy adult subjects. Maximal change in airway pressure at the mouthpiece was used as a surrogate measure of the degree of obstruction applied. Plethysmograph waveform data and mouthpiece airway pressure were acquired for 60 seconds at increasing levels of inspiratory and expiratory obstruction. At each level of applied obstruction, mean values for maximal change in waveform area under the curve and height as well as maximal change in mouth pressure were calculated for sequential 7.5 second intervals. Correlations of these waveform variables with mouth pressure values were then performed to determine if the magnitude of changes in these variables indicates the severity of airway obstruction. Results There were significant relationships between maximal change in area under the curve (P < .0001) or height (P < 0.0001) and mouth pressure. Conclusion The findings suggest that mathematic interpretation of plethysmograph waveform data may estimate the severity of airway obstruction and be of clinical utility in objective assessment of patients with obstructive airway diseases. PMID:15985171

Arnold, Donald H; Spiro, David M; Desmond, Renee' A; Hagood, James S

2005-01-01

319

Design and Testing of Space Telemetry SCA Waveform  

NASA Technical Reports Server (NTRS)

A Software Communications Architecture (SCA) Waveform for space telemetry is being developed at the NASA Glenn Research Center (GRC). The space telemetry waveform is implemented in a laboratory testbed consisting of general purpose processors, field programmable gate arrays (FPGAs), analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). The radio hardware is integrated with an SCA Core Framework and other software development tools. The waveform design is described from both the bottom-up signal processing and top-down software component perspectives. Simulations and model-based design techniques used for signal processing subsystems are presented. Testing with legacy hardware-based modems verifies proper design implementation and dynamic waveform operations. The waveform development is part of an effort by NASA to define an open architecture for space based reconfigurable transceivers. Use of the SCA as a reference has increased understanding of software defined radio architectures. However, since space requirements put a premium on size, mass, and power, the SCA may be impractical for today s space ready technology. Specific requirements for an SCA waveform and other lessons learned from this development are discussed.

Mortensen, Dale J.; Handler, Louis M.; Quinn, Todd M.

2006-01-01

320

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

SciTech Connect

The recent Nevada Earthquake (M=6) produced an extraordinary set of crustal guided waves. In this study, we examine the three-component data at all the USArray stations in terms of how well existing models perform in predicting the various phases, Rayleigh waves, Love waves, and Pnl waves. To establish the source parameters, we applied the Cut and Paste Code up to distance of 5 for an average local crustal model which produced a normal mechanism (strike=35,dip=41,rake=-85) at a depth of 9 km and Mw=5.9. Assuming this mechanism, we generated synthetics at all distances for a number of 1D and 3D models. The Pnl observations fit the synthetics for the simple models well both in timing (VPn=7.9km/s) and waveform fits out to a distance of about 5. Beyond this distance a great deal of complexity can be seen to the northwest apparently caused by shallow subducted slab material. These paths require considerable crustal thinning and higher P-velocities. Small delays and advances outline the various tectonic province to the south, Colorado Plateau, etc. with velocities compatible with that reported on by Song et al.(1996). Five-second Rayleigh waves (Airy Phase) can be observed throughout the whole array and show a great deal of variation ( up to 30s). In general, the Love waves are better behaved than the Rayleigh waves. We are presently adding higher frequency to the source description by including source complexity. Preliminary inversions suggest rupture to northeast with a shallow asperity. We are, also, inverting the aftershocks to extend the frequencies to 2 Hz and beyond following the calibration method outlined in Tan and Helmberger (2007). This will allow accurate directivity measurements for events with magnitude larger than 3.5. Thus, we will address the energy decay with distance as s function of frequency band for the various source types.

Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

2008-04-15

321

WCEDS: A waveform correlation event detection system  

SciTech Connect

We have developed a working prototype of a grid-based global event detection system based on waveform correlation. The algorithm comes from a long-period detector but we have recast it in a full matrix formulation which can reduce the number of multiplications needed by better than two orders of magnitude for realistic monitoring scenarios. The reduction is made possible by eliminating redundant multiplications in the original formulation. All unique correlations for a given origin time are stored in a correlation matrix (C) which is formed by a full matrix product of a Master Image matrix (M) and a data matrix (D). The detector value at each grid point is calculated by following a different summation path through the correlation matrix. Master Images can be derived either empirically or synthetically. Our testing has used synthetic Master Images because their influence on the detector is easier to understand. We tested the system using the matrix formulation with continuous data from the IRIS (Incorporate Research Institutes for Seismology) broadband global network to monitor a 2 degree evenly spaced surface grid with a time discretization of 1 sps; we successfully detected the largest event in a two hour segment from October 1993. The output at the correct gridpoint was at least 33% larger than at adjacent grid points, and the output at the correct gridpoint at the correct origin time was more than 500% larger than the output at the same gridpoint immediately before or after. Analysis of the C matrix for the origin time of the event demonstrates that there are many significant ``false`` correlations of observed phases with incorrect predicted phases. These false correlations dull the sensitivity of the detector and so must be dealt with if our system is to attain detection thresholds consistent with a Comprehensive Test Ban Treaty (CTBT).

Young, C.J.; Beiriger, J.I.; Trujillo, J.R. [Sandia National Labs., Albuquerque, NM (United States); Withers, M.M.; Aster, R.C. [New Mexico Inst. of Mining and Technology, NM (United States); Astiz, L.; Shearer, P.M. [California Univ., San Diego, CA (United States)

1995-08-01

322

50 CFR 660.393 - Latitude/longitude coordinates defining the 100 fm (183 m) through 150 fm (274 m) depth contours.  

Code of Federal Regulations, 2010 CFR

...m) through 150 fm (274 m) depth contours. 660.393 Section 660.393 Wildlife and Fisheries FISHERY CONSERVATION AND...COAST STATES West Coast Groundfish Fisheries 660.393 Latitude/longitude coordinates defining the...

2010-10-01

323

Chirped-pulse Raman amplification for two-color high-intensity laser experiments  

NASA Astrophysics Data System (ADS)

We report generation and compression of millijoule-level first Stokes sideband (873nm) of 800nm TW pulses by inserting a multi-stage barium nitrate Raman shifter-amplifier into a conventional Ti:sapphire chirped pulse amplification system.

Dong, Peng; Grigsby, Franklin; Downer, Mike

324

Wideband and low dispersion slow light by chirped photonic crystal coupled waveguide  

E-print Network

Wideband and low dispersion slow light by chirped photonic crystal coupled waveguide Daisuke Mori coupled waveguide, which allows more robust slow light with lower loss. For this device, unique photonic, and J. Yonekura, "Observation of light propagation in photonic crystal optical waveguides with bends

Baba, Toshihiko

325

Individual acoustic variation in Belding's ground squirrel alarm chirps in the High Sierra Nevada (L)  

E-print Network

Individual acoustic variation in Belding's ground squirrel alarm chirps in the High Sierra Nevada (L) Brenda McCowan and Stacie L. Hooper Behavioral Biology Laboratory, Veterinary Medicine Teaching membership and is important in kin and social group recognition. Belding's ground squirrels Spermophilus

Patricelli, Gail

326

Chirps on finite cyclic groups Peter G. Casazzaa and Matthew Fickusb  

E-print Network

, the phenomenon by which the perceived frequency of a wave is altered whenever the wave is emanating from or reflecting off a moving body. As such, chirps have historically been of great interest in applications-Fourier transform,8 and chirplets have been used in image processing for over a decade.5 For that matter, discrete

Casazza, Pete

327

Design, fabrication, and analysis of chirped multilayer mirrors for reflection of extreme-ultraviolet attosecond pulses.  

PubMed

Chirped Mo/Si multilayer coatings have been designed, fabricated, and characterized for use in extreme-ultraviolet attosecond experiments. By numerically simulating the reflection of the attosecond pulse from a multilayer mirror during the optimization procedure based on a genetic algorithm, we obtain optimized layer designs. We show that normal incidence chirped multilayer mirrors capable of reflecting pulses of approximately 100 attoseconds (as) duration can be designed by enhancing the reflectivity bandwidth and optimizing the phase-shift behavior. The chirped multilayer coatings have been fabricated by electron-beam evaporation in an ultrahigh vacuum in combination with ion-beam polishing of the interfaces and in situ reflectivity measurement for layer thickness control. To analyze the aperiodic layer structure by hard-x-ray reflectometry, we have developed an automatic fitting procedure that allows us to determine the individual layer thicknesses with an error of less than 0.05 nm. The fabricated chirped mirror may be used for production of 150-160 as pulses. PMID:16761058

Wonisch, A; Neuhusler, U; Kabachnik, N M; Uphues, T; Uiberacker, M; Yakovlev, V; Krausz, F; Drescher, M; Kleineberg, U; Heinzmann, U

2006-06-10

328

Design, fabrication, and analysis of chirped multilayer mirrors for reflection of extreme-ultraviolet attosecond pulses  

SciTech Connect

Chirped Mo/Si multilayer coatings have been designed, fabricated, and characterized for use in extreme-ultraviolet attosecond experiments. By numerically simulating the reflection of the attosecond pulse from a multilayer mirror during the optimization procedure based on a genetic algorithm, we obtain optimized layer designs. We show that normal incidence chirped multilayer mirrors capable of reflecting pulses of approximately 100 attoseconds (as) duration can be designed by enhancing the reflectivity bandwidth and optimizing the phase-shift behavior. The chirped multilayer coatings have been fabricated by electron-beam evaporation in an ultrahigh vacuum in combination with ion-beam polishing of the interfaces and in situ reflectivity measurement for layer thickness control. To analyze the aperiodic layer structure by hard-x-ray reflectometry, we have developed an automatic fitting procedure that allows us to determine the individual layer thicknesses with an error of less than 0.05 nm. The fabricated chirped mirror may be used for production of 150-160 as pulses.

Wonisch, A.; Neuhaeusler, U.; Kabachnik, N. M.; Uphues, T.; Uiberacker, M.; Yakovlev, V.; Krausz, F.; Drescher, M.; Kleineberg, U.; Heinzmann, U

2006-06-10

329

Powerful femtosecond pulse generation by chirped and stretched pulse parametric amplification in BBO crystal  

Microsoft Academic Search

Chirped pulses have been parametrically amplified by a factor of ~2104 without bandwidth limitation in BBO crystal. Pulses were compressed down to 70 fs, and ~0.9 GW output power has been obtained. A special technique to match temporal profiles of signal and pump pulses was used.

A. Dubietis; G. Jonusauskas; A. Piskarskas

1992-01-01

330

A novel sensor interrogation technique using chirped fiber grating based Sagnac loop  

Microsoft Academic Search

We demonstrate a novel and simple sensor interrogation scheme for fiber Bragg grating (FBG) based sensing systems. In this scheme, a chirped FBG based Sagnac loop is used as a wavelength-dependent receiver, and a stable and linear readout response is realised. It is a significant advantage of this scheme that the sensitivity and the measurement wavelength range can be easily

Donghui Zhao; Xuewen Shu; Lin Zhang; Ian Bennion

2002-01-01

331

CHIRP SUB-BOTTOM PROFILER SOURCE SIGNATURE DESIGN AND FIELD TESTING  

E-print Network

signature. A 3D chirp system is currently being developed at the Southampton Oceanography Centre and as part@soc.soton.ac.uk § GeoAcoustics Ltd., Shuttleworth Close, Gapton Hall Industrial Estate, Great Yarmouth, Norfolk, NR31 0 of this development we developed and tested a number of alternative source sweeps to optimise the vertical resolution

National Oceanography Centre Southampton

332

Tunable dispersion using linearly chirped polymer optical fiber Bragg gratings with fixed center wavelength  

Microsoft Academic Search

We propose a new scheme for tunable dispersion using linearly chirped polymer optical fiber Bragg gratings made in fiber tapers. The simple tension and uniform heating to the fiber gratings act as the adjustment and control process. Dispersion is tuned by the applied tensile strain. Owing to the unusually large and negative thermooptic coefficient of polymer fiber, the center wavelength

Hongbo Liu; Huiyong Liu; Gangding Peng; Trevor W. Whitbread

2005-01-01

333

An Iterative Template Matching Algorithm Using the ChirpZ Transform for Digital Image Watermarking  

E-print Network

of the watermark. In the first part of the template matching process, the rotation and scale compensationAn Iterative Template Matching Algorithm Using the Chirp­Z Transform for Digital Image Watermarking to cropping, scaling and rotation, the idea of using an invisible template embedded in the DFT domain has also

Genève, Université de

334

The role of the FM component in shaping the number of impulses and response latency of inferior collicular neurons of Hipposideros armiger elicited by CF-FM sounds.  

PubMed

Previous studies show that when stimulated with constant frequency-frequency modulated (CF-FM) sounds, the inferior collicular neurons of the leaf-nosed bat, Hipposideros armiger, either discharge impulses only to the CF component (single-on, SO neurons) or to both CF and FM components (double-on, DO neurons). In this study, we specifically determine the role of the FM component in shaping the number of impulses and response latency of these two types of neurons in response to CF-FM sounds. Adding the FM component to the CF sounds significantly decreases the number of impulses of both SO and DO neurons but shortens the response latency of DO neurons in response to the CF component of the CF-FM sounds. The possible neural mechanisms underlying these seemingly paradoxical observations are briefly discussed based on our preliminary intracellular recording studies. Biological relevance of these findings in relation to different phases of bats' hunting is also discussed. PMID:24915297

Fu, Zi-Ying; Xu, Na; Wang, Jing; Tang, Jia; Jen, Philip Hung-Sun; Chen, Qi-Cai

2014-07-25

335

Retracking CryoSat waveforms for near-real-time ocean forecast products, platform attitude, and other applications  

NASA Astrophysics Data System (ADS)

The SIRAL altimeter on CryoSat, launched in 2010, can operate in three modes: the low-rate mode (LRM) behaves as a conventional altimeter; the SAR mode allows more precise range and more focused footprint through use of synthetic aperture radar (SAR), also known as delay-Doppler, processing; the SARIN mode, or interferometric SAR, also affords across-track slope determination from interferometry. We have been working on several CryoSat studies over this year and will present some highlights. For the conventional LRM mode, we have built a retracker that processes near-real-time (FDM: Fast Delivery Mode) and Level 1-B data at 20 Hz to yield wind speed, wave height, and sea surface height anomaly. These data are being fed to NOAA's National Centers for Environmental Prediction. The retracking also estimates the off-nadir mispointing angle of the satellite. After accounting for an effect due to orbit height variations, we find that the off-nadir angle estimates are sufficiently accurate that we have used them to calibrate biases in the pitch and roll of the spacecraft platform reported by the platform attitude control system. These biases account for mis-alignment between the star tracker bench and the antenna boresight. We have Full Bit Rate (FBR) data in SAR mode for some ocean passes, including portions crossing coastlines, both from ocean to land and from land to ocean. FBR data includes all the raw I and Q samples of the raw radar echoes, prior to the range FFT that deramps the chirp, or the azimuth FFT that initiates the delay-Doppler SAR focusing calculation. We are currently working on these data with several applications in mind: (1) We can use these data to trace exactly what happens as the instrument crosses a coastline. (2) We can use these data to derive a LRM (conventional) waveform as well as a SAR waveform, and can compare the performance of these two modes under the same conditions (sea state, propagation, etc.) (3) We can test a conjecture by J R Jensen (IEEE TGARS 1999 37(2), 651-658) that waveform sampling rates should be doubled prior to forming the summed squared power, since squaring doubles frequency. This will show whether higher resolution is potentially available from conventional altimeters. Two forthcoming altimeter satellites, Sentinel-3 and Jason-CS, will have instrument heritage from CryoSat's SIRAL. Therefore the altimeter community should be interested in these new capabilities that we can test with CryoSat.

Smith, W. H.; Scharroo, R.; Lillibridge, J. L.; Leuliette, E. W.

2011-12-01

336

Building Climate Service Capacities in Eastern Africa with CHIRP and GeoCLIM  

NASA Astrophysics Data System (ADS)

In developing countries there is a great need for capacity building within national and regional climate agencies to develop and analyze historical and real time gridded rainfall datasets. These datasets are of key importance for monitoring climate and agricultural food production at decadal and seasonal time scales, and for informing local decision makers. The Famine Early Warning Systems Network (FEWS NET), working together with the U.S. Geological Survey (USGS) and the Climate Hazards Group (CHG) of the University of California Santa Barbara, has developed an integrated set of data products and tools to support the development of African climate services. The core data product is the Climate Hazards Group Infrared Precipitation (CHIRP) dataset. The CHIRP is a new rainfall dataset resulting from the blending of satellite estimated precipitation with high resolution precipitation climatology. The CHIRP depicts rainfall on five day totals at 5km spatial resolution from 1981 to present. The CHG is developing and deploying a standalone tool - the GeoCLIM - which will allow national and regional meteorological agencies to blend the CHIRP with station observations, run simple crop water balance models, and conduct climatological, trend, and time series analysis. Blending satellite estimates and gauge data helps overcome limited in situ observing networks. Furthermore, the GeoCLIM combines rainfall, soil, and evapotranspiration data with crop hydrological requirements to calculate agricultural water balance, presented as the Water Requirement Satisfaction Index (WRSI). The WRSI is a measurement of the degree in which a crop's hydrological requirements have been satisfied by rainfall. We present the results of a training session for personnel of the East African Intergovernmental Authority on Development Climate Prediction and Applications Center. The two week training program included the use of the GeoCLIM to improve CHIRP using station data, and to calculate and analyze trends in rainfall, WRSI, and drought frequency in the region.

Pedreros, D. H.; Magadzire, T.; Funk, C. C.; Verdin, J. P.; Peterson, P.; Landsfeld, M.; Husak, G. J.

2013-12-01

337

A Question of Interference: FM Radio's Early Struggle for Survival 1934-1945.  

ERIC Educational Resources Information Center

This paper explores FM radio's struggle for survival in the 1940s, focusing primarily on the impact of Federal Communications Commission (FCC) decision making and on the influence and activities of the well-established radio corporations, primarily the Radio Corporation of America (RCA). It describes the invention of FM radio by Edwin H. Armstrong

Zenaty, Jayne W.

338

76 FR 72705 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...Services; AM or FM Proposals To Change the Community of License AGENCY...filed AM or FM proposals to change the community of license: DOUGLAS...EVANSVILLE, WY; HISPANIC TARGET MEDIA INC., Station NEW, Facility...20554 or electronically via the Media Bureau's Consolidated...

2011-11-25

339

Evidence for perception of fine echo delay and phase by the FM bat, Eptesicus fuscus  

Microsoft Academic Search

The big brown bat, Eptesicus fuscus, can perceive small changes in the delay of FM sonar echoes and shifts in echo phase, which interact with delay. Using spectral cues caused by interference, Eptesicus also can perceive the individual delays of two overlapping FM echoes at small delay separations. These results have been criticized as due to spectral artifacts caused by

J. A. Simmons

1993-01-01

340

Exploiting FM Radio Data System for Adaptive Clock Calibration in Sensor Networks  

E-print Network

Synchronization, Radio Data Sys- tem, FM Radio 1. INTRODUCTION Recent years have witnessed the widespread of low-power GPS, timekeeping radio stations, or power grid. However, high power consumption and geographicExploiting FM Radio Data System for Adaptive Clock Calibration in Sensor Networks Liqun Li1

341

(FM 9-43-2) MCRP 4-11.4A  

E-print Network

FM 4-30.31 (FM 9-43-2) MCRP 4-11.4A (FMFRP 4-34) RECOVERY AND BATTLE DAMAGE ASSESSMENT AND REPAIR-11.4A Recovery and Battle Damage Assessment and Repair Contents Page PREFACE ..............................................................................................................v Chapter 1 Introduction to Recovery and Battle Damage Assessment and Repair ..... 1-1 Recovery

US Army Corps of Engineers

342

FM Stereo and AM Stereo: Government Standard-Setting vs. the Marketplace.  

ERIC Educational Resources Information Center

The emergence of frequency modulation or FM radio signals, which arose from the desire to free broadcasting of static noise common to amplitude modulation or AM, has produced the controversial development of stereo broadcasting. The resulting enhancement of sound quality helped FM pass AM in audience shares in less than two decades. The basic

Huff, W. A. Kelly

343

75 FR 47488 - FM Table of Allotments, Boulder Town, Levan, Mount Pleasant, and Richfield, UT  

Federal Register 2010, 2011, 2012, 2013

...FM Table of Allotments, Boulder Town, Levan, Mount Pleasant, and Richfield, UT AGENCY...Communications, Inc., licensee of Station KCFM, Levan, Utah, and affirms the dismissal of Micro's...of FM Channel 229C for Channel 244C at Levan, Utah, and the modification of its...

2010-08-06

344

Applications of FM-CW laser radar to antenna contour mapping  

NASA Technical Reports Server (NTRS)

The FM-CW coherent laser radar concept, based on the FM radar principle which makes use of the coherence and lunability of injection laser diodes, is discussed. Laser radar precision/time tradeoffs, block diagrams, system performance, fiber optic system implantation, and receiver improvements are briefly described.

Slotwinski, A. R.

1989-01-01

345

Relaxed dispersion requirement in the generation of chirped RF signals based on frequency-to-time mapping  

NASA Astrophysics Data System (ADS)

Photonic generation of chirped RF signal based on frequency-to-time mapping (FTM) is investigated in this paper. A new criterion on system parameters (dispersion amounts and pulse duration) for the generation of well-shaped linearly chirped signals is given, which is proved to be less restrictive than the currently known conditions. Therefore, requirement on the dispersion amount can be relaxed, which is highly desired in practical implementation of the FTM-based system. Theoretical results are presented, the correctness of which is verified by numerical and experimental results. The reported theory is a good guidance in designing the photonic system for the generation of chirped signals based on FTM.

Xu, Yuxiao; Shi, Zhiguo; Chi, Hao; Jin, Xiaofeng; Zheng, Shilie; Zhang, Xianmin

2014-11-01

346

The role of input chirp on phase shifters based on slow and fast light effects in semiconductor optical amplifiers.  

PubMed

We experimentally investigate the initial chirp dependence of slow and fast light effects in a semiconductor optical amplifier followed by an optical filter. It is shown that the enhancement of the phase shift due to optical filtering strongly depends on the chirp of the input optical signal. We demonstrate approximately 120 degrees phase delay as well as approximately 170 degrees phase advance at a microwave frequency of 19 GHz for different optimum values of the input chirp. The experimental results are shown to be in good agreement with numerical results based on a four-wave mixing model. Finally, a simple physical explanation based on an analytical perturbative approach is presented. PMID:19188968

Xue, Weiqi; Chen, Yaohui; Ohman, Filip; Mrk, Jesper

2009-02-01

347

Doppler flow velocity waveforms in the fetal cardiac outflow tract: reproducibility of waveform recording and analysis.  

PubMed

Reproducibility of flow velocity waveform recording and analysis was studied at fetal cardiac level (ductus arteriosus, pulmonary artery and ascending aorta) in 42 normal pregnancies. The flow velocity parameters studied were the peak systolic velocity (PSV), acceleration time (ACT), acceleration velocity (ACV), average velocity (AV) and flow velocity integral (FVI). In each patient, two consecutive measurements were performed (time delay 15 min) and of each measurement two hardcopies were analysed. A high reproducibility was achieved for the PSV, AV and FVI in all vessels studied; the coefficients of variation between readings of hardcopies were less than or equal to 3%, and the coefficients of variation between tests within patients were less than or equal to 7%. A moderate reproducibility was achieved for the ACT in the ascending aorta and pulmonary artery; the variation between tests was large for the ductus arteriosus. The reproducibility of the ACV was poor. PMID:1962360

Groenenberg, I A; Hop, W C; Wladimiroff, J W

1991-01-01

348

Quantitative analysis of sensor for pressure waveform measurement  

PubMed Central

Background Arterial pressure waveforms contain important diagnostic and physiological information since their contour depends on a healthy cardiovascular system [1]. A sensor was placed at the measured artery and some contact pressure was used to measure the pressure waveform. However, where is the location of the sensor just about enough to detect a complete pressure waveform for the diagnosis? How much contact pressure is needed over the pulse point? These two problems still remain unresolved. Method In this study, we propose a quantitative analysis to evaluate the pressure waveform for locating the position and applying the appropriate force between the sensor and the radial artery. The two-axis mechanism and the modified sensor have been designed to estimate the radial arterial width and detect the contact pressure. The template matching method was used to analyze the pressure waveform. In the X-axis scan, we found that the arterial diameter changed waveform (ADCW) and the pressure waveform would change from small to large and then back to small again when the sensor was moved across the radial artery. In the Z-axis scan, we also found that the ADCW and the pressure waveform would change from small to large and then back to small again when the applied contact pressure continuously increased. Results In the X-axis scan, the template correlation coefficients of the left and right boundaries of the radial arterial width were 0.987 0.016 and 0.978 0.028, respectively. In the Z-axis scan, when the excessive contact pressure was more than 100 mm Hg, the template correlation was below 0.983. In applying force, when using the maximum amplitude as the criteria level, the lower contact pressure (r = 0.988 0.004) was better than the higher contact pressure (r = 0.976 0.012). Conclusions Although, the optimal detective position has to be close to the middle of the radial arterial, the pressure waveform also has a good completeness with a template correlation coefficient of above 0.99 when the position was within 1 mm of the middle of the radial arterial range. In applying force, using the maximum amplitude as the criteria level, the lower contact pressure was better than the higher contact pressure. PMID:20092621

2010-01-01

349

Where post-Newtonian and numerical-relativity waveforms meet  

E-print Network

We analyze numerical-relativity (NR) waveforms that cover nine orbits (18 gravitational-wave cycles) before merger of an equal-mass system with low eccentricity, with numerical uncertainties of 0.25 radians in the phase and less than 2% in the amplitude; such accuracy allows a direct comparison with post-Newtonian (PN) waveforms. We focus on one of the PN approximants that has been proposed for use in gravitational-wave data analysis, the restricted 3.5PN ``TaylorT1'' waveforms, and compare these with a section of the numerical waveform from the second to the eighth orbit, which is about one and a half orbits before merger. This corresponds to a gravitational-wave frequency range of $M\\omega = 0.0455$ to 0.1. Depending on the method of matching PN and NR waveforms, the accumulated phase disagreement over this frequency range can be within numerical uncertainty. Similar results are found in comparisons with an alternative PN approximant, 3PN ``TaylorT3''. The amplitude disagreement, on the other hand, is around 6%, but roughly constant for all 13 cycles that are compared, suggesting that only 4.5 orbits need be simulated to match PN and NR waves with the same accuracy as is possible with nine orbits. If, however, we model the amplitude up to 2.5PN order, the amplitude disagreement is roughly within numerical uncertainty up to about 11 cycles before merger.

Mark Hannam; Sascha Husa; Jose A. Gonzalez; Ulrich Sperhake; Bernd Bruegmann

2007-06-11

350

Gaussian pulse decomposition: an intuitive model of electrocardiogram waveforms.  

PubMed

This study presents a novel approach to modeling the electrocardiogram (ECG): the Gaussian pulse decomposition. Constituent waves of the ECG are decomposed into and represented by Gaussian pulses using an iterative algorithm: the chip away decomposition (ChAD) algorithm. At each iteration, a nonlinear minimization method is used to fit a portion of the ECG waveform with a single Gaussian pulse, which is then subtracted from the ECG waveform. The process iterates on the resulting residual waveform until the normalized mean square error is below an acceptable level. Three different minimization methods were compared for their applicability to the ChAD algorithm; the Nelder-Mead simplex method was found to be more noise-tolerant than the Newton-Raphson method or the steepest descent method. Using morphologically different ECG waveforms from the MIT-BIH arrhythmia database, it was demonstrated that the ChAD algorithm is capable of modeling not only normal beats, but also abnormal beats, including those exhibiting a depressed ST segment, bundle branch block, and premature ventricular contraction. An analytical expression for the spectral contributions of the constituent waves was also derived to characterize the ECG waveform in the frequency domain. The Gaussian pulse model, providing an intuitive representation of the ECG constituent waves by use of a small set of meaningful parameters, should be useful for various purposes of ECG signal processing, including signal representation and pattern recognition. PMID:9084830

Suppappola, S; Sun, Y; Chiaramida, S A

1997-01-01

351

Maintaining Stimulant Waveforms in Large Volume Microfluidic Cell Chambers  

PubMed Central

Stimulation of cells with temporal waveforms can be used to observe the frequency-dependent nature of cellular responses. The ability to produce and maintain the temporal waveforms in spite of the broadening processes that occur as the wave travels through the microfluidic system is critical for observing dynamic behaviors. Broadening of waves in microfluidic channels has been examined, but the effect that large-volume cell chambers have on the waves has not. In this report, a sinusoidal glucose wave delivered to a 1 mm diameter cell chamber using various microfluidic channel structures was simulated by finite element analysis with the goal of minimizing the broadening of the waveform in the chamber and maximizing the homogeneity of the concentration in the chamber at any given time. Simulation results indicated that increasing the flow rate was the most effective means to achieve these goals, but at a given volumetric flow rate, geometries that deliver the waveform to multiple regions in the chamber while maintaining a high linear velocity produced sufficient results. A 4-inlet geometry with a 220 ?m channel width gave the best result in the simulation and was used to deliver glucose waveforms to a population of pancreatic islets of Langerhans. The result was a stronger and more robust synchronization of the islet population as compared to when a non-optimized chamber was used. This general strategy will be useful in other microfluidic systems examining the frequency-dependence nature of cellular behavior. PMID:24244207

Zhang, Xinyu; Dhumpa, Raghuram; Roper, Michael G.

2013-01-01

352

Selection and generation of waveforms for differential mobility spectrometry  

PubMed Central

Devices based on differential mobility spectrometry (DMS) are used in a number of ways, including applications as ion prefilters for API-MS systems, as detectors or selectors in hybrid instruments (GC-DMS, DMS-IMS), and in standalone systems for chemical detection and identification. DMS ion separation is based on the relative difference between high field and low field ion mobility known as the alpha dependence, and requires the application of an intense asymmetric electric field known as the DMS separation field, typically in the megahertz frequency range. DMS performance depends on the waveform and on the magnitude of this separation field. In this paper, we analyze the relationship between separation waveform and DMS resolution and consider feasible separation field generators. We examine ideal and practical DMS separation field waveforms and discuss separation field generator circuit types and their implementations. To facilitate optimization of the generator designs, we present a set of relations that connect ion alpha dependence to DMS separation fields. Using these relationships we evaluate the DMS separation power of common generator types as a function of their waveform parameters. Optimal waveforms for the major types of DMS separation generators are determined for ions with various alpha dependences. These calculations are validated by comparison with experimental data. PMID:20192506

Krylov, Evgeny V.; Coy, Stephen L.; Vandermey, John; Schneider, Bradley B.; Covey, Thomas R.; Nazarov, Erkinjon G.

2010-01-01

353

A scalable, fast, and multichannel arbitrary waveform generator  

NASA Astrophysics Data System (ADS)

This article reports on the development of a multichannel arbitrary waveform generator that simultaneously generates arbitrary voltage waveforms on 24 independent channels with a dynamic update rate of up to 25 Msps. A real-time execution of a single waveform and/or sequence of multiple waveforms in succession, with a user programmable arbitrary sequence order is provided under the control of a stand-alone sequencer circuit implemented using a field programmable gate array. The device is operated using an internal clock and can be synced to other devices by means of transistor-transistor logic (TTL) pulses. The device can provide up to 24 independent voltages in the range of up to 9 V with a dynamic update-rate of up to 25 Msps and a power consumption of less than 35 W. Every channel can be programmed for 16 independent arbitrary waveforms that can be accessed during run time with a minimum switching delay of 160 ns. The device has a low-noise of 250 ?Vrms and provides a stable long-term operation with a drift rate below 10 ?V/min and a maximum deviation less than 300 ?Vpp over a period of 2 h.

Baig, M. T.; Johanning, M.; Wiese, A.; Heidbrink, S.; Ziolkowski, M.; Wunderlich, C.

2013-12-01

354

A Time Domain Waveform for Testing General Relativity  

E-print Network

Gravitational-wave parameter estimation is only as good as the theory the waveform generation models are based upon. It is therefore crucial to test General Relativity (GR) once data becomes available. Many previous works, such as studies connected with the ppE framework by Yunes and Pretorius, rely on the stationary phase approximation (SPA) to model deviations from GR in the frequency domain. As Fast Fourier Transform algorithms have become considerably faster and in order to circumvent possible problems with the SPA, we test GR with corrected time domain waveforms instead of SPA waveforms. Since a considerable amount of work has been done already in the field using SPA waveforms, we establish a connection between leading-order-corrected waveforms in time and frequency domain, concentrating on phase-only corrected terms. In a Markov Chain Monte Carlo study, whose results are preliminary and will only be available later, we will assess the ability of the eLISA detector to measure deviations from GR for signa...

Huwyler, Cdric; Jetzer, Philippe

2014-01-01

355

Synthesis of fiber Bragg grating for gain-narrowing compensation in high-power Nd: Glass chirped pulse amplification system  

NASA Astrophysics Data System (ADS)

We propose and analyze theoretically a method to compensate gain-narrowing effect by using the spectral shaping technology based on superstructure fiber Bragg grating (SSFBG) in high-power Nd:glass chirped pulse amplification system. The target spectrum is firstly calculated from hundreds joules amplified chirped Gaussian or super-Gaussian pulse by an inverse engineering operation. A genetic algorithm is used to design the SSFBG and obtain the index modulation distribution of grating which can transform the initial seed pulse to the target spectrum. The numerically simulations show that the spectral narrowing effect of chirped pulse amplification will be reduced largely and the ideal pulse spectrum (Gaussian or super-Gaussian) is also obtained. It is believed that this proposed method will provide a theoretical direction for the following experiment. Moreover, it will also be useful and flexible for the spectral transform in other chirped pulse application areas.

Liu, Qiong; Ye, Qing; Pan, Zhengqing; Luo, Aiping; Cai, Haiwen; Qu, Ronghui; Fang, Zujie

2011-05-01

356

Fast evaluation of asymptotic waveforms from gravitational perturbations  

E-print Network

In the context of blackhole perturbation theory, we describe both exact evaluation of an asymptotic waveform from a time series recorded at a finite radial location and its numerical approximation. From the user's standpoint our technique is easy to implement, affords high accuracy, and works for both axial (Regge-Wheeler) and polar (Zerilli) sectors. Our focus is on the ease of implementation with publicly available numerical tables, either as part of an existing evolution code or a post-processing step. Nevertheless, we also present a thorough theoretical discussion of asymptotic waveform evaluation and radiation boundary conditions, which need not be understood by a user of our methods. In particular, we identify (both in the time and frequency domains) analytical asymptotic waveform evaluation kernels, and describe their approximation by techniques developed by Alpert, Greengard, and Hagstrom. This paper also presents new results on the evaluation of far-field signals for the ordinary (acoustic) wave equa...

Benedict, Alex G; Lau, Stephen R

2012-01-01

357

Iterative Method for Predistortion of MRI Gradient Waveforms  

PubMed Central

The purpose of this work is to correct for transient gradient waveform errors in magnetic resonance imaging (MRI), whether from eddy currents, group delay, or gradient amplifier nonlinearities, which are known to affect image quality. An iterative method is proposed to minimize error between desired and measured gradient waveforms, whose success does not depend on accurate knowledge of the gradient system impulse response. The method was applied to half-pulse excitation for 2-D ultra-short echo time (UTE) imaging on a small animal MRI system and to spiral 2-D excitation on a human 7T MRI system. Predistorted gradient waveforms reduced temporal signal variation caused by excitation gradient trajectory errors in 2-D UTE, and improved the quality of excitation patterns produced by spiral excitation pulses. Iterative gradient predistortion is useful for minimizing transient gradient errors without requiring accurate characterization of the gradient system impulse response. PMID:24801945

Harkins, Kevin D.; Does, Mark D.; Grissom, William A.

2014-01-01

358

Iterative method for predistortion of MRI gradient waveforms.  

PubMed

The purpose of this work is to correct for transient gradient waveform errors in magnetic resonance imaging (MRI), whether from eddy currents, group delay, or gradient amplifier nonlinearities, which are known to affect image quality. An iterative method is proposed to minimize error between desired and measured gradient waveforms, whose success does not depend on accurate knowledge of the gradient system impulse response. The method was applied to half-pulse excitation for 2-D ultra-short echo time (UTE) imaging on a small animal MRI system and to spiral 2-D excitation on a human 7T MRI system. Predistorted gradient waveforms reduced temporal signal variation caused by excitation gradient trajectory errors in 2-D UTE, and improved the quality of excitation patterns produced by spiral excitation pulses. Iterative gradient predistortion is useful for minimizing transient gradient errors without requiring accurate characterization of the gradient system impulse response. PMID:24801945

Harkins, Kevin D; Does, Mark D; Grissom, William A

2014-08-01

359

The magnetic pumping of plasmas with sawtooth waveforms  

NASA Astrophysics Data System (ADS)

The pumping of plasmas by sawtooth-waveform magnetic induction variations is studied theoretically and by means of computer simulations. A sawtooth is a cycle waveform that is characterized by a slow increase in the magnetic induction followed by a rapid drop in the induction. Two types of sawtooth pumping are analyzed, and the types classified as to whether or not the first adiabatic invariants of the plasma particles are conserved during the rapid drops in the magnetic induction. When the invariants are conserved, the sawtooth waveforms are found to be less efficient than square waves for pumping plasmas. When the adiabatic invariations are not conserved, the pumping efficiency is found to be a slight improvement over square waves. Both types of pumping are applied to a hypothetical tokamak plasma and it is concluded that neither type of sawtooth pumping is practical for heating magnetically confined fusion plasmas.

Borovsky, Joseph E.; Hansen, Paul J.

1990-06-01

360

Analytical chirped solutions to the (3 + 1)-dimensional Gross-Pitaevskii equation for various diffraction and potential functions.  

PubMed

Analytical solutions to the (3 + 1)-dimensional Gross-Pitaevskii equation in the presence of chirp and for different diffraction and potential functions are found. We utilize a method we formulated to solve the Riccati equation for the chirp function that arises when the F-expansion technique and the homogeneous balance principle are applied to the Gross-Pitaevskii equation. Three specific examples of physical interest are considered in some detail. PMID:21867333

Al Bastami, Anas; Beli?, Milivoj R; Milovi?, Daniela; Petrovi?, Nikola Z

2011-07-01

361

Wavelet denoising for chirp-like signal in time-frequency domain and application to aircraft flight flutter testing  

Microsoft Academic Search

A novel denoising method for chirp-like signal that relies on the time-frequency analysis is described. Because the region of chirp signal in time-frequency (TF) map is well-concentrated relative to the widely distributed noise, the wavelet coefficients corresponding to the true signal can be extracted by a masking operation. And a new procedure is presented to design the mask and reconstruct

Wei Tang; Zhong-Ke Shi; Hong-Chao Li

2005-01-01

362

FM signals produce robust paradoxical latency shifts in the bat's inferior colliculus.  

PubMed

Previous studies in echolocating bats, Myotis lucifugus, showed that paradoxical latency shift (PLS) is essential for neural computation of target range and that a number of neurons in the inferior colliculus (IC) exhibit unit-specific PLS (characterized by longer first-spike latency at higher sound levels) in response to tone pulses at the unit's best frequency. The present study investigated whether or not frequency-modulated (FM) pulses that mimic the bat's echolocation sonar signals were equally effective in eliciting PLS. For two-thirds of PLS neurons in the IC, both FM and tone pulses could elicit PLS, but only FM pulses consistently produced unit-specific PLS. For the remainder of PLS neurons, only FM pulses effectively elicited PLS; these cells showed either no PLS or no response, to tone pulses. PLS neurons generally showed more pronounced PLS in response to narrow-band FM (each sweeping 20 kHz in 2 ms) pulse that contained the unit's best frequency. In addition, almost all PLS neurons showed duration-independent PLS to FM pulses, but the same units exhibited duration-dependent PLS to tone pulses. Taken together, when compared to tone pulses, FM stimuli can provide more reliable estimates of target range. PMID:17115224

Wang, Xinming; Galazyuk, Alexander V; Feng, Albert S

2007-01-01

363

Evidence for the Use of Hearing Assistive Technology by Adults: The Role of the FM System  

PubMed Central

Hearing assistive technologies include listening, alerting, and/or signaling devices that use auditory, visual, and/or tactile modalities to augment communication and/or facilitate awareness of environmental sounds. The importance of hearing assistive technologies in the management of adults with hearing loss was recently acknowledged in an evidence-based clinical practice guideline developed by the American Academy of Audiology. Most currently available evidence for hearing assistive technology use by adults focuses on frequency-modulated (FM) technology. Previous research is reviewed that demonstrates the efficacy of FM devices for adults in terms of laboratory measures of speech understanding in noise. Also reviewed are the outcomes from field trials of FM use by community-dwelling adults, which, to date, have been disappointing. Few to no individuals, in previous studies, elected to use FM devices at the end of the trial periods. Data are presented from a 1-group pretest-posttest study examining the role of extensive counseling, coaching, and instruction on FM use by adults. In addition, the potential influence of the cost of devices to the individual was eliminated by conducting the study with veterans who were eligible to receive FM systems through the Veterans Affairs National Hearing Aid Program. Positive outcomes were obtained at the end of a 6-week trial period and were found to remain 1 year after study completion. Implications for increasing the evidence base for the use of FM devices by adults are discussed. PMID:17494874

Chisolm, Theresa Hnath; Noe, Colleen M.; McArdle, Rachel; Abrams, Harvey

2007-01-01

364

Partitioned Waveform Inversion Applied to Eurasia and Northern Africa  

SciTech Connect

This report summarizes the data analysis achieved during Heather Bedle's eleven-week Technical Scholar internship at Lawrence Livermore National Labs during the early summer 2006. The work completed during this internship resulted in constraints on the crustal and upper mantle S-velocity structure in Northern Africa, the Mediterranean, the Middle East, and Europe, through the fitting of regional waveform data. This data extends current raypath coverage and will be included in a joint inversion along with data from surface wave group velocity measurements, S and P teleseismic arrival time data, and receiver function data to create an improved velocity model of the upper mantle in this region. The tectonic structure of the North African/Mediterranean/Europe/Middle Eastern study region is extremely heterogeneous. This region consists of, among others, stable cratons and platforms such as the West Africa Craton, and Baltica in Northern Europe; oceanic subduction zones throughout the Mediterranean Sea where the African and Eurasian plate collide; regions of continental collision as the Arabian Plate moves northward into the Turkish Plate; and rifting in the Red Sea, separating the Arabian and Nubian shields. With such diverse tectonic structures, many of the waveforms were difficult to fit. This is not unexpected as the waveforms are fit using an averaged structure. In many cases the raypaths encounter several tectonic features, complicating the waveform, and making it hard for the software to converge on a 1D average structure. Overall, the quality of the waveform data was average, with roughly 30% of the waveforms being discarded due to excessive noise that interfered with the frequency ranges of interest. An inversion for the 3D S-velocity structure of this region was also performed following the methodology of Partitioned Waveform Inversion (Nolet, 1990; Van der Lee and Nolet, 1997). The addition of the newly fit waveforms drastically extends the range of the model. The model now extends as far east in Africa to cover Chad and Niger, and reaches south to cover Zambia. The model is also stretched eastward to cover the eastern half of India, and northward to cover the southern portion of Scandinavia.

bedle, H; Matzel, E; Flanagan, M

2006-07-27

365

Inner core differential motion confirmed by earthquake waveform doublets.  

PubMed

We analyzed 18 high-quality waveform doublets with time separations of up to 35 years in the South Sandwich Islands region, for which the seismic signals have traversed the inner core as PKP(DF). The doublets show a consistent temporal change of travel times at up to 58 stations in and near Alaska, and they show a dissimilarity of PKP(DF) coda. Using waveform doublets avoids artifacts of earthquake mislocations and contamination from small-scale heterogeneities. Our results confirm that Earth's inner core is rotating faster than the mantle and crust at about 0.3 degrees to 0.5 degrees per year. PMID:16123296

Zhang, Jian; Song, Xiaodong; Li, Yingchun; Richards, Paul G; Sun, Xinlei; Waldhauser, Felix

2005-08-26

366

Method for waveform feature extraction from seismic signals  

SciTech Connect

A method is described for processing seismic signal data comprising: inputting seismic signal data in at least one groups of related trace signals; summing and determining average signals for a selected number of successive traces in each of the at least one groups; determining the correlation matrix for the at least one groups and constructing plural orthonormal basis waveforms; estimating the common signals of the at least one groups of a linear combination of selected ones of the orthonormal basis waveforms; and outputting the common signals as a noise reduced representation of the at least one groups of seismic signal data.

Chittineni, C.

1986-12-30

367

40 CFR Table 8 to Subpart Ggg of... - Fraction Measured (Fm) for HAP Compounds in Wastewater Streams  

...2014-07-01 false Fraction Measured (Fm) for HAP Compounds in Wastewater Streams 8 Table 8 to Subpart GGG of Part 63 Protection...Part 63Fraction Measured (Fm ) for HAP Compounds in Wastewater Streams Chemical name CAS No. a Fm Acetaldehyde...

2014-07-01

368

40 CFR Table 8 to Subpart Ggg of... - Fraction Measured (Fm) for HAP Compounds in Wastewater Streams  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Fraction Measured (Fm) for HAP Compounds in Wastewater Streams 8 Table 8 to Subpart GGG of Part 63 Protection...Part 63Fraction Measured (Fm ) for HAP Compounds in Wastewater Streams Chemical name CAS No. a Fm Acetaldehyde...

2013-07-01

369

Making ultracold molecules in a two-color pump-dump photoassociation scheme using chirped pulses  

SciTech Connect

This theoretical paper investigates the formation of ground state molecules from ultracold cesium atoms in a two-color scheme. Following previous work on photoassociation with chirped picosecond pulses [Luc-Koenig et al., Phys. Rev. A, 70, 033414 (2004)], we investigate stabilization by a second (dump) pulse. By appropriately choosing the dump pulse parameters and time delay with respect to the photoassociation pulse, we show that a large number of deeply bound molecules are created in the ground triplet state. We discuss (i) broad-bandwidth dump pulses which maximize the probability to form molecules while creating a broad vibrational distribution as well as (ii) narrow-bandwidth pulses populating a single vibrational ground state level, bound by 113 cm{sup -1}. The use of chirped pulses makes the two-color scheme robust, simple, and efficient.

Koch, Christiane P. [Laboratoire Aime Cotton, CNRS, Bat. 505, Campus d'Orsay, 91405 Orsay Cedex (France); Department of Physical Chemistry and Fritz Haber Research Center, Hebrew University, Jerusalem 91904 (Israel); Luc-Koenig, Eliane; Masnou-Seeuws, Francoise [Laboratoire Aime Cotton, CNRS, Bat. 505, Campus d'Orsay, 91405 Orsay Cedex (France)

2006-03-15

370

FEMTOSECOND X-RAY PULSES FROM A FREQUENCY CHIRPED SASE FEL.  

SciTech Connect

We discuss the temporal and spectral properties of self-amplified spontaneous emission (SASE) utilizing an energy-chirped electron beam. A short temporal pulse is generated by using a monochromator to select a narrow radiation bandwidth from the frequency chirped SASE. For the filtered radiation, the minimum pulse length is limited by the intrinsic SASE bandwidth, while the number of modes and the energy fluctuation can be controlled through the monochromator bandwidth. Two cases are considered: (1) placing the monochromator at the end of a single long undulator; (2) placing the monochromator after an initial undulator and amplifying the short-duration output in a second undulator. We analyze these cases and show that tens of femtosecond x-ray pulses may be generated for the linac coherent light source.

KRINSKY,S.HUANG,Z.

2004-01-07

371

Power limitations and pulse distortions in an Yb : KGW chirped-pulse amplification laser system  

NASA Astrophysics Data System (ADS)

We have studied self-action effects (self-focusing and self-phase modulation) and stimulated Raman scattering in an Yb : KGW chirped-pulse amplification laser system. The results demonstrate that self-focusing in combination with thermal lensing may significantly limit the chirped pulse energy in this system (down to 200 ?J) even at a relatively long pulse duration (50 ps). Nonlinear lenses in the laser crystals in combination with thermal lenses bring the regenerative amplifier cavity in the laser system to the instability zone and limit the average output power at pulse repetition rates under 50 kHz. Self-phase modulation, a manifestation of self-action, may significantly distort a recompressed femtosecond pulse at energies near the self-focusing threshold. Stimulated Raman scattering in such a laser has a weaker effect on output parameters than do self-focusing and thermal lensing, and Raman spectra are only observed in the case of pulse energy instability.

Kim, G. H.; Yang, J.; Kulik, A. V.; Sall, E. G.; Chizhov, S. A.; Yashin, V. E.; Kang, U.

2013-08-01

372

Impact of modulator chirp in 100 Gbps class optical discrete multi-tone transmission system  

NASA Astrophysics Data System (ADS)

Discrete multi-tone (DMT) technology is an attractive modulation technique for short reach optical transmission system. One of the main factors that limit the performance of the 1.5-?m band DMT system is the interplay between the chromatic dispersion of the transmission fiber and the chirp characteristic of the transmitter. We experimentally measured and compared the chirp characteristics of various modulator configurations, which are lithium-niobate Mach-Zehnder modulator, directly modulated laser, and electro-absorption modulator, by the frequency discriminator method using MZ interferometer. We also measured and compared the transmission characteristics of the transmitters using above-mentioned modulators and discuss the suitable transmitter configuration for DMT technology.

Nishihara, Masato; Tanaka, Toshiki; Takahara, Tomoo; Li, Lei; Tao, Zhenning; Rasmussen, Jens C.

2012-12-01

373

Periodic compression of chirped femtosecond pulses in silicon waveguides under fourth-order dispersion  

NASA Astrophysics Data System (ADS)

We report the analysis of the compression mechanism for chirped femtosecond pulses in silicon-on-insulator waveguides under the effect of fourth-order dispersion (FOD) using the modified variational approach that involves Rayleigh's dissipation function (RDF). Our results show that the nonlinear compression in these waveguides is input pulse dependent. Moreover, this study leads to a nearly periodic-like dynamic induced by the interplay between self-phase modulation and FOD in a normal group-velocity dispersion. In addition, when large values of the initial chirp and absorption coefficients present in these waveguides are considered, the compression mechanism is completely destroyed, with the observation of at least one pulse amplification over a short distance of propagation prior to pulse broadening.

Mandeng Mandeng, Lucien; Ibraid Fewo, Serge; Tchawoua, Clment; Crpin Kofan, Timolon

2014-08-01

374

CSR Interaction for a 2D Energy-Chirped Bunch on a General Orbit  

SciTech Connect

When an electron bunch with initial linear energy chirp traverses a bunch compression chicane, the bunch interacts with itself via coherent synchrotron radiation (CSR) and space charge force. The effective longitudinal CSR force for such kind of 2D bunch on a circular orbit has been analyzed earlier [1]. In this paper, we present the analytical results of the effective longitudinal CSR force for a 2D energy-chirped bunch going through a general orbit, which includes the entrance and exit of a circular orbit. In particular, we will show the behavior of the force in the last bend of a chicane when the bunch is under extreme compression. This is the condition when bifurcation of bunch phase space occurs in many CSR measurements. [1] R. Li, Phys. Rev. ST Accel. Beams 11, 024401 (2008)

Rui Li

2009-05-01

375

90 mJ parametric chirped pulse amplification of 10 fs pulses.  

PubMed

We demonstrate the amplification of broadband pulses from a Ti:Sapphire oscillator by non-collinear optical parametric chirped-pulse amplification technique in a type-I BBO crystal to energies of 90 mJ. Partial compression of the amplified pulses is demonstrated down to a 10 fs duration. These parameters come in combination with good spatial quality and focusability of the amplified beam. PMID:19532173

Tavella, Franz; Marcinkevicius, Andrius; Krausz, Ferenc

2006-12-25

376

Ultrahigh contrast from a frequency-doubled chirped-pulse-amplification beamline.  

PubMed

This paper describes frequency-doubled operation of a high-energy chirped-pulse-amplification beamline. Efficient type-I second-harmonic generation was achieved using a 3 mm thick 320 mm aperture KDP crystal. Shots were fired at a range of energies achieving more than 100 J in a subpicosecond, 527 nm laser pulse with a power contrast of 10(14). PMID:23842168

Hillier, David; Danson, Colin; Duffield, Stuart; Egan, David; Elsmere, Stephen; Girling, Mark; Harvey, Ewan; Hopps, Nicholas; Norman, Michael; Parker, Stefan; Treadwell, Paul; Winter, David; Bett, Thomas

2013-06-20

377

Chirped AM ladar for anti-ship missile tracking and force protection 3D imaging: update  

Microsoft Academic Search

Shipboard infrared search and track (IRST) systems can detect sea-skimming anti-ship missiles at long ranges. Since IRST systems cannot measure range and line-of-sight velocity, they have difficulty distinguishing missiles from slowly moving false targets and clutter. In a joint Army-Navy program, the Army Research Laboratory (ARL) is developing a chirped amplitude modulation ladar to provide range and velocity measurements for

Brian C. Redman; Barry Stann; William Lawler; Mark Giza; John Dammann; William Ruff; William Potter; Ronald G. Driggers; Jose Garcia; John Wilson; Keith Krapels

2006-01-01

378

Spectral broadening and self-compression of negatively chirped visible femtosecond pulses in fused silica  

SciTech Connect

This paper describes a new effect: spectral broadening and self-compression of negatively chirped visible femtosecond pulses as a result of nonlinear interaction of large-aperture beams with fused silica. We assume that the likely mechanism of the observed spectral broadening is the combined effect of self-phase modulation and four-wave mixing. (special issue devoted to the 90th anniversary of n.g. basov)

Aristov, A I; Grudtsyn, Ya V; Mikheev, L D; Polivin, A V; Stepanov, S G; Trofimov, V A; Yalovoi, V I

2012-12-31

379

Electro-optic measurement of THz field pulses with a chirped optical beam  

Microsoft Academic Search

Using a linearly chirped optical probe pulse in free-space electro-optic measurements, a temporal wave form of a co-propagating THz field is linearly encoded onto the frequency spectrum of the optical probe pulse, and then decoded by dispersing the probe beam from a grating to a detector array. We achieve acquisition of picosecond THz field pulses without using mechanical time-delay device.

Zhiping Jiang; X.-C. Zhang

1998-01-01

380

Modeling interface roughness scattering in a layered seabed for normal-incident chirp sonar signals.  

PubMed

Downward looking sonar, such as the chirp sonar, is widely used as a sediment survey tool in shallow water environments. Inversion of geo-acoustic parameters from such sonar data precedes the availability of forward models. An exact numerical model is developed to initiate the simulation of the acoustic field produced by such a sonar in the presence of multiple rough interfaces. The sediment layers are assumed to be fluid layers with non-intercepting rough interfaces. PMID:22502485

Tang, Dajun; Hefner, Brian T

2012-04-01

381

Non-collinear phase-matching geometries in optical parametric chirped-pulse amplification  

NASA Astrophysics Data System (ADS)

This study presents a full three-dimensional nonlinear pulse propagation and amplification model that includes considerations for phase-matching, diffraction, and walk-off effects. By using this model, two types of type I non-collinear phase-matching geometries in BBO based optical parametric chirped-pulse amplification are investigated theoretically and experimentally. The simulation results agree well with the experimental findings.

Guo, Xiaoyang; Xu, Yi; Zou, Xiao; Lu, Xiaoming; Li, Yanyan; Wang, Cheng; Leng, Yuxin; Li, Ruxin

2014-11-01

382

Estimation of phase derivatives using discrete chirp-Fourier-transform-based method.  

PubMed

Estimation of phase derivatives is an important task in many interferometric measurements in optical metrology. This Letter introduces a method based on discrete chirp-Fourier transform for accurate and direct estimation of phase derivatives, even in the presence of noise. The method is introduced in the context of the analysis of reconstructed interference fields in digital holographic interferometry. We present simulation and experimental results demonstrating the utility of the proposed method. PMID:19684794

Gorthi, Sai Siva; Rastogi, Pramod

2009-08-15

383

Open-path sensor for atmospheric methane based on chirped laser dispersion spectroscopy  

NASA Astrophysics Data System (ADS)

The design and characterization of a near-IR Chirped Laser Dispersion Spectroscopy (CLaDS) sensor for atmospheric methane detection are reported. The near-IR CLaDS system exhibits the benefits of the prior mid-IR CLaDS systems implemented for open-path sensing while taking advantage of the robust fiber-optic components available in the near-IR. System noise, long-term stability, and comparison with existing technology for methane detection are presented.

Nikodem, Michal; Plant, Genevieve; Sonnenfroh, David; Wysocki, Gerard

2014-10-01

384

FY07 LDRD Final Report Precision, Split Beam, Chirped-Pulse, Seed Laser Technology  

SciTech Connect

The goal of this LDRD ER was to develop a robust and reliable technology to seed high-energy laser systems with chirped pulses that can be amplified to kilo-Joule energies and recompressed to sub-picosecond pulse widths creating extremely high peak powers suitable for petawatt class physics experiments. This LDRD project focused on the development of optical fiber laser technologies compatible with the current long pulse National Ignition Facility (NIF) seed laser. New technologies developed under this project include, high stability mode-locked fiber lasers, fiber based techniques for reduction of compressed pulse pedestals and prepulses, new compact stretchers based on chirped fiber Bragg gratings (CFBGs), new techniques for manipulation of chirped pulses prior to amplification and new high-energy fiber amplifiers. This project was highly successful and met virtually all of its goals. The National Ignition Campaign has found the results of this work to be very helpful. The LDRD developed system is being employed in experiments to engineer the Advanced Radiographic Capability (ARC) front end and the fully engineered version of the ARC Front End will employ much of the technology and techniques developed here.

Dawson, J W; Messerly, M J; Phan, H H; Crane, J K; Beach, R J; Siders, C W; Barty, C J

2009-11-12

385

Cancellous bone analysis with modified least squares Prony's method and chirp filter: phantom experiments and simulation.  

PubMed

The presence of two longitudinal waves in porous media is predicted by Biot's theory and has been confirmed experimentally in cancellous bone. When cancellous bone samples are interrogated in through-transmission, these two waves can overlap in time. Previously, the Modified Least-Squares Prony's (MLSP) method was validated for estimation of amplitudes, attenuation coefficients, and phase velocities of fast and slow waves, but tended to overestimate phase velocities by up to about 5%. In the present paper, a pre-processing chirp filter to mitigate the phase velocity bias is derived. The MLSP/chirp filter (MLSPCF) method was tested for decomposition of a 500 kHz-center-frequency signal containing two overlapping components: one passing through a low-density-polyethylene plate (fast wave) and another passing through a cancellous-bone-mimicking phantom material (slow wave). The chirp filter reduced phase velocity bias from 100 m/s (5.1%) to 69 m/s (3.5%) (fast wave) and from 29 m/s (1.9%) to 10 m/s (0.7%) (slow wave). Similar improvements were found for 1) measurements in polycarbonate (fast wave) and a cancellous-bone-mimicking phantom (slow wave), and 2) a simulation based on parameters mimicking bovine cancellous bone. The MLSPCF method did not offer consistent improvement in estimates of attenuation coefficient or amplitude. PMID:20968389

Wear, Keith A

2010-10-01

386

Helium in chirped laser fields as a time-asymmetric atomic switch  

NASA Astrophysics Data System (ADS)

Tuning the laser parameters exceptional points in the spectrum of the dressed laser helium atom are obtained. The weak linearly polarized laser couples the ground state and the doubly excited P-states of helium. We show here that for specific chirped laser pulses that encircle an exceptional point one can get the time-asymmetric phenomenon, where for a negative chirped laser pulse the ground state is transformed into the doubly excited auto-ionization state, while for a positive chirped laser pulse the resonance state is not populated and the neutral helium atoms remains in the ground state as the laser pulse is turned off. Moreover, we show that the results are very sensitive to the closed contour we choose. This time-asymmetric state exchange phenomenon can be considered as a time-asymmetric atomic switch. The optimal time-asymmetric switch is obtained when the closed loop that encircles the exceptional point is large, while for the smallest loops, the time-asymmetric phenomenon does not take place. A systematic way for studying the effect of the chosen closed contour that encircles the exceptional point on the time-asymmetric phenomenon is proposed.

Kaprlov-nsk, Petra Ruth; Moiseyev, Nimrod

2014-07-01

387

Chirped-pulse four-wave Raman mixing in molecular hydrogen  

NASA Astrophysics Data System (ADS)

Four-wave Raman mixing (FWRM) in molecular hydrogen was studied using chirped pump and Stokes pulses emitting at 802 and 1,203 nm, respectively. The group delay dispersion (GDD) of the anti-Stokes pulse was examined employing a frequency-resolved optical gating system at different GDDs of the pump and Stokes pulses (0 or 1,000 fs2). As a result, the energy and the sign of GDD for the anti-Stokes pulse remained unchanged, when the pump and Stokes pulses had the GDD with the same sign. When the sign was not the same, the energy decreased and only the portion useful for resonant FWRM was converted into a Raman emission. This technique has a potential for use in compensation of dispersion by passing the negatively chirped high-order Raman sidebands through the optics with positive chirps in the spectral region from the deep-ultraviolet to the near-infrared, to generate multiple transform-limited Raman pulses and then to produce an ultrashort optical pulse by a Fourier synthesis of these Raman emissions.

Shitamichi, Osamu; Kida, Yuichiro; Imasaka, Totaro

2014-07-01

388

Wideband-adjustable reflection-suppressed rejection filters using chirped and tilted fiber gratings.  

PubMed

Wideband-adjustable band-rejection filters based on chirped and tilted fiber Bragg gratings (CTFBG) are proposed and experimentally demonstrated. The flexible chirp-rate and wide tilt-angle provide the gratings with broadband filtering functions over a large range of bandwidths (from 10 nm to 150 nm), together with a low insertion loss (less than 1dB) and a negligible back-reflection (lower than -20 dB). The slope profile of CTFBG in transmission can be easily tailored by adjusting the tilt angle, grating irradiation time and chirp rate-grating factor, and it is insensitive to the polarization state of the input light, as well as to temperature, axial strain and surrounding refractive index. Furthermore, by coating the CTFBG with a suitable polymer (whose refractive index is close to that of the cladding glass), the cladding modes no longer form weakly discrete resonances and leave a smoothly varying attenuation spectrum for high-quality band-rejection filters, edge filters and gain equalizers. PMID:25322019

Liu, Fu; Guo, Tuan; Wu, Chuang; Guan, Bai-Ou; Lu, Chao; Tam, Hwa-Yaw; Albert, Jacques

2014-10-01

389

Estimating lightning current moment waveforms from satellite optical measurements  

E-print Network

Estimating lightning current moment waveforms from satellite optical measurements Toru Adachi,1 and Duke magnetometer observed clear optical and radio signatures of 12 sprite- producing lightning events to remotely measure lightning current moment, which is critical for understanding the production of sprites

California at Berkeley, University of

390

Diversity Waveform Sets for Delay-Doppler Imaging  

Microsoft Academic Search

Properties of the ambiguity function and the un- certainty relation of Fourier transforms assert fundamental lim- itations on the ability of any single radar waveform of con- strained time-bandwidth product to distinguish two or more targets closely spaced in both time-delay (range) and Doppler- shift (radial velocity). These same mechanisms place fundamental limits on the ability radar imaging systems to

Jiann-ching Guey; Mark R. Bell

1998-01-01

391

Application of Inductive Logic Programming for Learning ECG Waveforms  

E-print Network

Application of Inductive Logic Programming for Learning ECG Waveforms Gabriella K'okai 1 , Zolt­mail: gyimi@inf.u­szeged.hu. Abstract. In this paper a learning system is presented which integrates an ECG on an attribute grammar specification of ECGs that has been transformed to Prolog. The IMPUT system combines

Alexin, Zoltán

392

Rapid development of a P25 JTRS waveform  

Microsoft Academic Search

Past disaster response experience, as well as existing terrorism threats, demands close collaboration between the military and public safety command structure in possible future operations. Establishing radio communication between military commanders, soldiers and law enforcement officers is an important enabling capability to facilitate interoperability. The JTRS program is enabling communications between military branches by implementing different military radio waveforms on

Zhongren Cao; Per Johansson; Williams Hodgkiss; Wenhua Zhao; Anthony Nwokafor; Jeffrey Cuenco; Eric Salgado; Brian Hobson

2010-01-01

393

Waveform and packet structure of lion roars W. Baumjohann1  

E-print Network

Waveform and packet structure of lion roars W. Baumjohann1 , R. A. Treumann1 , E. Georgescu1Y2 , G-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs the ®rst search-coil magnetometer observa- tions of what they called lion roars inside magnetic troughs

Paris-Sud XI, Université de

394

CLASSIFICATION OF GEOPHYSICAL ACOUSTIC WAVEFORMS USING TIMEFREQUENCY ATOMS  

E-print Network

contacts, fluid satura­ tion, volume percentages of various rocks such as sand­ stone, shale, and limestone. There are two popular approaches for estimating velocities of wave components: one is a semi­automatic tracking: A typical acoustic waveform recorded down­ hole. The surrounding subsurface formation consists of shale

Saito, Naoki

395

Optimum Waveforms for Differential Ion Mobility Spectrometry (FAIMS)  

PubMed Central

Differential mobility spectrometry or field asymmetric waveform ion mobility spectrometry (FAIMS) is a new tool for separation and identification of gas-phase ions, particularly in conjunction with mass-spectrometry. In FAIMS, ions are filtered by the difference between mobilities in gases (K) at high and low electric field intensity (E) using asymmetric waveforms. An infinite number of possible waveform profiles make maximizing the performance within engineering constraints a major issue for FAIMS technology refinement. Earlier optimizations assumed the non-constant component of mobility to scale as E2, producing the same result for all ions. Here we show that the optimum profiles are defined by the full series expansion of K(E) that includes terms beyond the 1st that is proportional to E2. For many ion/gas pairs, the first two terms have different signs, and the optimum profiles at sufficiently high E in FAIMS may differ substantially from those previously reported, improving the resolving power by up to 2.2 times. This situation arises for some ions in all FAIMS systems, but becomes more common in recent miniaturized devices that employ higher E. With realistic K(E) dependences, the maximum waveform amplitude is not necessarily optimum and reducing it by up to ?20 30% is beneficial in some cases. The present findings are particularly relevant to targeted analyses where separation depends on the difference between K(E) functions for specific ions. PMID:18585054

Shvartsburg, Alexandre A.; Smith, Richard D.

2009-01-01

396

LIDAR WAVEFORM MODELING USING A MARKED POINT PROCESS Cl  

Microsoft Academic Search

Lidar waveforms are 1D signal consisting of a train of echoes where each of them correspond to a scattering target of the Earth sur- face. Modeling these echoes with the appropriate parametric func- tion is necessary to retrieve physical information about these objects and characterize their properties. This paper presents a marked point process based model to reconstruct a lidar

Florent Lafarge; Fred eric Bretar; Uwe Soergel; Christian Heipke

397

Lidar waveform modeling using a marked point process  

Microsoft Academic Search

Lidar waveforms are 1D signal consisting of a train of echoes where each of them correspond to a scattering target of the Earth surface. Modeling these echoes with the appropriate parametric function is necessary to retrieve physical information about these objects and characterize their properties. This paper presents a marked point process based model to reconstruct a lidar signal in

Clment Mallet; Florent Lafarge; Frdric Bretar; Uwe Soergel; Christian Heipke

2009-01-01

398

Waveform inversion for Earth structure: Progress and Prospects  

NASA Astrophysics Data System (ADS)

Throughout the history of seismology, knowledge of Earth structure has advanced significantly when new techniques were applied to large datasets; the J-B model and travel-time tomography are two notable examples. Recent progress in inversion of seismic body wave waveforms appears to be another such notable instance. In this talk we mainly review and summarize work by our group. In order to realize the goal of being able to invert seismic body wave waveforms, several technical developments were necessary. First, we developed accurate and efficient methods for computing synthetic seismograms (Kawai et al., GJI, 2006 and works cited therein) and their partial derivatives (Geller and Hara, GJI, 1993). Efficient software for handling large datasets, and robust methods for making static corrections (Fuji et al., 2010, PEPI) were also necessary. Finally, methods for solving the inverse problem to obtain models with appropriate parametrization and methods for confirming the resolution and robustness of the results of the inversion were also required (Konishi et al., EPSL, 2009; Kawai and Geller, JGR, 2010). We have developed the necessary methods for waveform inversion and have applied them to determine 3-D models of S-wave velocity in the lowermost mantle (submitted for publication). We have also conducted waveform inversion for anisotropy (Kawai and Geller, EPSL, 2010) and anelasticity (Fuji et al., PEPI, 2010). In the near future prospects are bright for applying these methods to much larger datasets for obtaining high-resolution 3-D images of larger regions.

Geller, R. J.; Kawai, K.; Fuji, N.; Konishi, K.

2012-12-01

399

Consistency of Post-Newtonian Waveforms with Numerical Relativity  

NASA Technical Reports Server (NTRS)

General relativity predicts the gravitational radiation signatures of mergers of compact binaries, such as coalescing binary black hole systems. Derivations of waveform predictions for such systems are required for optimal scientific analysis of observational gravitational wave data, and have so far been achieved primarily with the aid of the post-Newtonian (PN) approximation. The quality of this treatment is unclear, however, for the important late inspiral portion. We derive late-inspiral waveforms via a complementary approach, direct numerical simulation of Einstein's equations, which has recently matured sufficiently for such applications. We compare waveform phasing from simulations covering the last approximately 14 cycles of gravitational radiation from an equal-mass binary system of nonspinning black holes with the corresponding 3PN and 3.5PN orbital phasing. We find agreement consistent with internal error estimates based on either approach at the level of one radian over approximately 10 cycles. The result suggests that PN waveforms for this system are effective roughly until the system reaches its last stable orbit just prior to the final merger/

Baker, John G.; vanMeter, James R.; McWilliams, Sean T.; Cewntrella, Joan; Kelly, Bernard J.

2006-01-01

400

Consistency of Post-Newtonian Waveforms with Numerical Relativity  

NASA Technical Reports Server (NTRS)

General relativity predicts the gravitational radiation signatures of mergers of compact binaries,such as coalescing binary black hole systems. Derivations of waveform predictions for such systems are required for optimal scientific analysis of observational gravitational wave data, and have so far been achieved primarily with the aid of the post-Newtonian (PN) approximation. The quaIity of this treatment is unclear, however, for the important late inspiral portion. We derive late-inspiral wave forms via a complementary approach, direct numerical simulation of Einstein's equations, which has recently matured sufficiently for such applications. We compare waveform phasing from simulations covering the last approximately 14 cycles of gravitational radiation from an equal-mass binary system of nonspinning black holes with corresponding 3PN and 3.5PN waveforms. We find phasing agreement consistent with internal error estimates based in either approach, at the level of one radian over approximately 10 cycles. The result suggests that PN waveforms for this system are effective roughly until the system reaches its last stable orbit just prior to the final merger.

Baker, John G.; vanMeter, James R.; McWilliams, Sean T.; Centrella, Joan; Kelly, Bernard J.

2007-01-01

401

Class-F power amplifiers with maximally flat waveforms  

Microsoft Academic Search

Class-F power amplifiers (PA's) employ harmonic-frequency resonators to shape their drain or collector waveforms to improve efficiency. Generally, the output network must present the drain with either an open or short circuit at the harmonic frequencies. At VHF and higher frequencies, the drain capacitance, lead inductance, lead length, and dispersion make implementation of reasonably ideal tuned circuits difficult. However it

Frederick H. Raab

1997-01-01

402

Gender-Related Differences in the Central Arterial Pressure Waveform  

Microsoft Academic Search

Objectives. This study investigated the effect of age and gender on central arterial hemodynamic variables derived from noninvasive tonometric carotid pressure waveforms.Background. Women have a greater age-related increase in left ventricular (LV) mass than do men and are more likely to experience symptomatic heart failure after infarction despite their higher ejection fraction. In studies of these changes, ventricular afterload is

Christopher S Hayward; Raymond P Kelly

1997-01-01

403

The Kine-Klydonograph - A Transient Waveform Recorder  

Microsoft Academic Search

The paper describes an instrument of the klydonograph type which gives a record in the form of as many as 36 different Lichtenberg figures for a given applied voltage wave. Taken in combination, these figures permit the diagnosis of the applied wave with respect to its waveform and crest amplitude. In particular, the prestrike theory 2 predicts a current spike

S. B. Griscom

1960-01-01

404

Subpicosecond Single-Shot Waveform Measurement using Temporal Imaging  

E-print Network

@leorg.ucdavis.edu Abstract Experimental results from a new single-transient optical recorder with of California, Davis, Davis, California, 95616 kolner@leorg.ucdavis.edu The recording of single-transient are presented. The system uses a 103? temporal imaging system to expand the waveform which is then recorded

Kolner, Brian H.

405

Using transient waveform recorders to measure and store beam parameters  

Microsoft Academic Search

Transient waveform digitizers are used to measure the tunes in the Stanford Linear Collider (SLC) damping rings. Since the beam injection and extraction from these rings occurs at a high rate (120 Hz) and because of the stringent extracted beam stability requirements, simpler asynchronous resonant excitation spectrum analyzer measurements are not possible. The beam position monitor signals are processed, digitized,

Robert E. Stege; R. K. Jobe; M. Ross

1993-01-01

406

ATTP 4-0.1 (FM 100-10-1) Army Theater Distribution  

E-print Network

ATTP 4-0.1 (FM 100-10-1) Army Theater Distribution May 2011 DISTRIBUTION RESTRICTION: Approved of the Army Washington, D.C., 20 May 2011 Army Theater Distribution Contents Page PREFACE .............................................................................................................iii Chapter 1 THEATER DISTRIBUTION

US Army Corps of Engineers

407

ATTP 3-39.20 (FM 3-19.50) POLICE INTELLIGENCE OPERATIONS  

E-print Network

ATTP 3-39.20 (FM 3-19.50) POLICE INTELLIGENCE OPERATIONS July 2010 DISTRIBUTION RESTRICTION Washington, DC, 29 July 2010 Police Intelligence Operations Contents Page PREFACE...................................................................................................vi Chapter 1 OPERATIONAL ENVIRONMENT AND POLICE INTELLIGENCE OPERATIONS

US Army Corps of Engineers

408

47 CFR 74.1290 - FM translator and booster station information available on the Internet.  

Code of Federal Regulations, 2011 CFR

...station information available on the Internet. 74.1290 Section 74.1290...station information available on the Internet. The Media Bureau's Audio Division provides information on the Internet regarding FM translator and...

2011-10-01

409

47 CFR 74.1290 - FM translator and booster station information available on the Internet.  

Code of Federal Regulations, 2012 CFR

...station information available on the Internet. 74.1290 Section 74.1290...station information available on the Internet. The Media Bureau's Audio Division provides information on the Internet regarding FM translator and...

2012-10-01

410

47 CFR 74.1290 - FM translator and booster station information available on the Internet.  

Code of Federal Regulations, 2013 CFR

...station information available on the Internet. 74.1290 Section 74.1290...station information available on the Internet. The Media Bureau's Audio Division provides information on the Internet regarding FM translator and...

2013-10-01

411

169. Credit FM. Remains of H.H. Noble residence, destroyed by ...  

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

169. Credit FM. Remains of H.H. Noble residence, destroyed by fire. 'Noble Castle' stood atop the ridge near Lakes Grace and Nora, overlooking Volta. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

412

The Facilities Management department (FM) saved more than $5 million by redesigning its preventive  

E-print Network

requests arise enables FM to make adjustments wherever possible. If there's not a good business reason's for expensive equipment, such as a fan that cools critical research, but let bathroom fans run until they fail

Webb, Peter

413

75 FR 20597 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...TX; MUNBILLA BROADCASTING PROPERTIES, LTD., Station KYRT, Facility ID 165378, BPH-20100312AAQ, From MASON, TX, To HUNT, TX; RINCON BROADCASTING LS LLC, Station KIST- FM, Facility ID 31434, BPH-20100301ADV, From SANTA BARBARA, CA,...

2010-04-20

414

47 CFR 73.809 - Interference protection to full service FM stations.  

Code of Federal Regulations, 2013 CFR

...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.809...interference that results from the radiation of radio frequency energy outside its assigned...

2013-10-01

415

47 CFR 73.809 - Interference protection to full service FM stations.  

Code of Federal Regulations, 2010 CFR

...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.809...interference that results from the radiation of radio frequency energy outside its assigned...

2010-10-01

416

47 CFR 73.809 - Interference protection to full service FM stations.  

Code of Federal Regulations, 2012 CFR

...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.809...interference that results from the radiation of radio frequency energy outside its assigned...

2012-10-01

417

47 CFR 73.809 - Interference protection to full service FM stations.  

Code of Federal Regulations, 2011 CFR

...COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) 73.809...interference that results from the radiation of radio frequency energy outside its assigned...

2011-10-01

418

47 CFR 73.1210 - TV/FM dual-language broadcasting in Puerto Rico.  

Code of Federal Regulations, 2013 CFR

...objectionable for broadcast exposure. (3) No television, Class A television, or FM broadcast station may devote more...presented on any given day. (4) Noncommercial educational television broadcast stations shall take all...

2013-10-01

419

47 CFR 73.1210 - TV/FM dual-language broadcasting in Puerto Rico.  

Code of Federal Regulations, 2011 CFR

...objectionable for broadcast exposure. (3) No television, Class A television, or FM broadcast station may devote more...presented on any given day. (4) Noncommercial educational television broadcast stations shall take all...

2011-10-01

420

47 CFR 73.1210 - TV/FM dual-language broadcasting in Puerto Rico.  

Code of Federal Regulations, 2012 CFR

...objectionable for broadcast exposure. (3) No television, Class A television, or FM broadcast station may devote more...presented on any given day. (4) Noncommercial educational television broadcast stations shall take all...

2012-10-01

421

47 CFR 73.1210 - TV/FM dual-language broadcasting in Puerto Rico.  

Code of Federal Regulations, 2010 CFR

...objectionable for broadcast exposure. (3) No television, Class A television, or FM broadcast station may devote more...presented on any given day. (4) Noncommercial educational television broadcast stations shall take all...

2010-10-01

422

78 FR 41062 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...MURDO, SD, To BLUNT, SD; THE MONTANA RADIO COMPANY, LLC, Station KTRO, Facility ID 183371, BPH-20130625ADB, From ROUNDUP, MT, To STANFORD, MT; WOMEN'S CIVIC IMPROVEMENT LEAGUE, INC., Station KPOV-FM, Facility ID 174895,...

2013-07-09

423

77 FR 24954 - Radio Broadcasting Services; AM or FM Proposals to Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...BROADCASTING L.L.C., Station KRSX-FM, Facility ID 2316, BPH- 20120316ABT, From TWENTYNINE PALMS, CA, To NORTH SHORE; VERMONT BROADCAST ASSOCIATES, INC, Station NEW, Facility ID 189498, BNPH- 20110630AEC, From ALBANY, VT, To...

2012-04-26

424

Effects of thienodiazepine derivatives, etizolam and clotiazepam on the appearance of Fm theta.  

PubMed

The effects of new thienodiazepine anxiolytics, etizolam and clotiazepam, on the appearance of frontal midline theta activity (Fm theta) were studied by the double-blind crossover method. The results were as follows; 1) Both clotiazepam and placebo tended to increase the Fm theta appearance in all subjects, but etizolam showed no such tendency. 2) Clotiazepam significantly increased the Fm theta appearance as compared with placebo in subjects with a high neurotic tendency (N-scale of MPI above 19). 3) Clotiazepam tended to increase the Fm theta appearance as compared with placebo and etizolam in subjects with a high anxiety level (MAS score above 14). 4) Apparently more subjects complained of drowsiness after the administration of etizolam than after clotiazepam or placebo. PMID:1363923

Nakamura, J; Mukasa, H

1992-12-01

425

Analysis and restoration of a 1960s ear vacuum tube AM-FM reflex receiver  

E-print Network

This thesis details the analysis, restoration, and evaluation of a 1960s era vacuum tube AM-FM reflex receiver. External influences such as tax laws necessitated clever designs to minimize the use of expensive vacuum tubes ...

Golden, Adam J

2004-01-01

426

75 FR 63475 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License  

Federal Register 2010, 2011, 2012, 2013

...WV; ENTRAVISION HOLDINGS, LLC, Station KVVA-FM, Facility ID 1331, BPH-20100817ABA, From APACHE JUNCTION, AZ, To SUN LAKES, AZ; MEDIA MINISTRIES, INC., Station KLIC, Facility ID 22171, BP-20100903ABU, From MONROE, LA, To...

2010-10-15

427

Complex-field measurement of ultrafast dynamic optical waveforms based on real-time spectral  

E-print Network

. Wang, S. Blais, and J. Yao, "Ultrafast and precise interrogation of fiber Bragg grating sensor based and accurate group delay ripple measurement technique for ultralong chirped fiber Bragg gratings," Opt. Lett

Jalali. Bahram

428

Manipulation of the magnetic flux in superconductor by the ferromagnetic domains in SC\\/FM hybrid  

Microsoft Academic Search

We studied magneto-optically the magnetic flux entry and exit in SC\\/FM hybrid of a ferromagnetic permalloy film sputtered on the superconducting NbSe2 single crystal. The FM film had growth induced perpendicular anisotropy and the labyrinth equilibrium domain structure. However, we could align the domain walls in a desired direction by application of a strong enough in-plane field. Thus formed stripe

Vitalii Vlasko-Vlasov; Ulrich Welp; Goran Karapetrov; Valentin Novosad; Andrei Belkin; Daniel Rosenmann; Wai Kwok

2007-01-01

429

Learning Analog Electronics Through Project-based Investigation of FM Communication Circuits  

NSDL National Science Digital Library

Since historically much of the early development of analog electronics took place in the communication field present, day students understanding of electronics can be enhanced by working with FM communication circuits. Students majoring in the electrical and computer engineering concentrations at our university are required during their junior year to take a three hour lecture course and a two-credit-hour lab course in analog electronics. By the end of the courses, students learn the theory and application of such components as diodes, Zener diodes, NPN and PNP transistors, MOSFETs, SCRs Diacs, Triacs, and optoelectronic devices.New experiments have been added to the electronics lab to enhance understanding of basic analog components. This project investigated the effects on the students learning of analog electronics by having them develop an FM transmitter and an FM receiver circuit much earlier than they are prepared to handle them. Electronic communication circuits are studied in detail a semester later in the second electronic course and RF theory is introduced a year later in the communication courses. The objective for the student was to discover how the electronic components studied in class can be placed together in an FM transmitter to work as: a signal amplifier, local oscillator, FM modulator, frequency multiplier, and power amplifier at the final output stage. In an FM receiver they see the components working as: an RF amplifier, local oscillator, FM mixer, IF amplifier, FM detector, output audio amplifier and automatic frequency control circuit. Students also learned to appreciate the modular nature of complex designs. At the end of the semester, a survey was given to determine the results on student learning concerning the concepts and applications of electronics. The results of this project may prompt the implementation of other projects that may include multidisciplinary collaboration, integration of projects between classes, projects across concentrations, and integration of a single project from the freshman to the senior year.

Leiffer, Paul; Ortiz, Oscar

2011-05-13

430

Imaging sediments in the deep, rough terrain at the Mid-Atlantic Ridge using AUV Sentry's CHIRP sub-bottom profiler  

NASA Astrophysics Data System (ADS)

AUV Sentry carries an Edgetch 2200M sub-bottom profiler, which uses a CHIRP signal (a broadband, swept waveform) in the 4 - 24 kHz range. The sub-bottom profiles obtained from AUV Sentry provide a new and exciting look at the detailed morphology of the sediments covering the deep seafloor. We obtained sub-bottom profiles on 11 Sentry dives during RV Knorr Cruise 210-05 in May-June 2013. Our study region was centered at 16.5N on the flanks of the Mid-Atlantic Ridge (MAR). Sentry flew at ~60 m above the seafloor traversing terrain that included features over 1 km in relief. The data were processed at sea using MBSystem and SeismicUnix software packages. Processing consisted of the following steps: data conversion from Edgetech jsf to SEGY format; bandpass filter to remove frequencies associated with other instruments on the vehicle; static correction according to vehicle depth; and depth conversion using a constant (water) velocity of 1500 m/s. The resulting images are excellent in quality. Sedimentary layers were identified above the acoustic basement, with thicknesses ranging from tens of centimeters to 4-5 m. Preliminary interpretation shows no evidence for reflections beneath the sediment - basement interface. We have used the high-resolution sub-bottom profiles to estimate sedimentation rate at this section of the MAR, and in combination with the other high-resolution products from Sentry we have been able to argue that some of the long-lived faults observed in the region are still active.

Yoerger, D.; Parnell-Turner, R. E.; Smith, D. K.; Cann, J. R.; Schouten, H.; Dick, H. J.; Kurras, G.; Duester, A.; Billings, A.; Kelley, S.

2013-12-01

431

Cardiac injury with damped sine and trapezoidal defibrillator waveforms.  

PubMed

To assess defibrillator-induced cardiac damage, 49 anaesthetized greyhounds received either no shocks (control group) or five shocks from a defibrillator delivering one of five waveforms (Lown, Edmark, Belfast damped sine waveforms: 5 and 20 ms trapezoidal waveforms). At 3 days the hearts of the 36 surviving dogs were examined for macroscopic damage. The Belfast and Edmark waveforms caused significantly more damage (mean 21.1 +/- SEM 2.9 g and 16.0 +/- 3.7 g) respectively than the Lown waveform (3.5 +/- 1.3 g) P less than 0.01. The 20 ms trapezoid caused significantly more damage (8.1 +/- 3.1 g) than the 5 ms pulse (0.7 +/- 1.3 g) P less than 0.05). The ventricular ectopic counts per minute were not significantly different in the three sine wave and 20 ms trapezoidal groups at 24 and 48 h (P greater than 0.05), but at 2 and 72 h were significantly greater in the Belfast and Edmark groups than in the Lown group (2 h, Belfast P less than 0.01, Edmark P less than 0.05: 72 h P less than 0.05). At 15 min there was more right chest ST-segment elevation in the Belfast than in the Lown, Edmark and 20 ms trapezoid groups (P less than 0.01), while left chest ST elevation was greater in the Belfast and Edmark than in the Lown (P less than 0.05) and 20 ms trapezoid groups (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2504609

Wilson, C M; Bailey, A; Allen, J D; Anderson, J; Adgey, A A

1989-07-01

432

Fast evaluation of asymptotic waveforms from gravitational perturbations  

E-print Network

In the context of blackhole perturbation theory, we describe both exact evaluation of an asymptotic waveform from a time series recorded at a finite radial location and its numerical approximation. From the user's standpoint our technique is easy to implement, affords high accuracy, and works for both axial (Regge-Wheeler) and polar (Zerilli) sectors. Our focus is on the ease of implementation with publicly available numerical tables, either as part of an existing evolution code or a post-processing step. Nevertheless, we also present a thorough theoretical discussion of asymptotic waveform evaluation and radiation boundary conditions, which need not be understood by a user of our methods. In particular, we identify (both in the time and frequency domains) analytical asymptotic waveform evaluation kernels, and describe their approximation by techniques developed by Alpert, Greengard, and Hagstrom. This paper also presents new results on the evaluation of far-field signals for the ordinary (acoustic) wave equation. We apply our method to study late-time decay tails at null-infinity, "teleportation" of a signal between two finite radial values, and luminosities from extreme-mass-ratio binaries. Through numerical simulations with the outer boundary as close in as r = 30M, we compute asymptotic waveforms with late-time t^{-4} decay (l = 2 perturbations), and also luminosities from circular and eccentric particle-orbits that respectively match frequency domain results to relative errors of better than 10^{-12} and 10^{-9}. Furthermore, we find that asymptotic waveforms are especially prone to contamination by spurious junk radiation.

Alex G. Benedict; Scott E. Field; Stephen R. Lau

2012-10-04

433

Advanced fiber Bragg gratings for photonic generation and processing of arbitrary microwave waveforms  

Microsoft Academic Search

Photonic generation and processing of microwave arbitrary waveforms has been a topic of interest recently. Compared with the electronic techniques, photonics techniques provide the capabilities of generating and processing high-frequency and large-bandwidth microwave waveforms which cannot be fulfilled by the electronic techniques, In this paper, techniques to generate and process microwave arbitrary waveforms in the optical domain using advanced fiber

Chao Wang; Jianping Yao

2010-01-01

434

A threshold insensitive method for locating the forest canopy top with waveform lidar  

E-print Network

A threshold insensitive method for locating the forest canopy top with waveform lidar Steven Accepted 13 July 2011 Available online xxxx Keywords: Lidar Signal start Tree height Waveform Noise Lidars in field data. This method should help improve the accuracy of waveform lidar measurements of forests

Jones, Peter JS

435

Modelling Sensor and Target effects on LiDAR Waveforms  

NASA Astrophysics Data System (ADS)

The aim of this research is to explore the influence of sensor characteristics and interactions with vegetation and terrain properties on the estimation of vegetation parameters from LiDAR waveforms. This is carried out using waveform simulations produced by the FLIGHT radiative transfer model which is based on Monte Carlo simulation of photon transport (North, 1996; North et al., 2010). The opportunities for vegetation analysis that are offered by LiDAR modelling are also demonstrated by other authors e.g. Sun and Ranson, 2000; Ni-Meister et al., 2001. Simulations from the FLIGHT model were driven using reflectance and transmittance properties collected from the Howland Research Forest, Maine, USA in 2003 together with a tree list for a 200m x 150m area. This was generated using field measurements of location, species and diameter at breast height. Tree height and crown dimensions of individual trees were calculated using relationships established with a competition index determined for this site. Waveforms obtained by the Laser Vegetation Imaging Sensor (LVIS) were used as validation of simulations. This provided a base from which factors such as slope, laser incidence angle and pulse width could be varied. This has enabled the effect of instrument design and laser interactions with different surface characteristics to be tested. As such, waveform simulation is relevant for the development of future satellite LiDAR sensors, such as NASAs forthcoming DESDynI mission (NASA, 2010), which aim to improve capabilities of vegetation parameter estimation. ACKNOWLEDGMENTS We would like to thank scientists at the Biospheric Sciences Branch of NASA Goddard Space Flight Center, in particular to Jon Ranson and Bryan Blair. This work forms part of research funded by the NASA DESDynI project and the UK Natural Environment Research Council (NE/F021437/1). REFERENCES NASA, 2010, DESDynI: Deformation, Ecosystem Structure and Dynamics of Ice. http://desdyni.jpl.nasa.gov/ (accessed May 2010). NI-MEISTER, W., JUPP, D. L. B. and DUBAYAH, R., 2001, Modeling Lidar Waveforms in Heterogeneous and Discrete Canopies. IEEE Transactions on Geoscience and Remote Sensing, 39 (9): 1943-1958. NORTH, P. R. J., 1996, Three-Dimensional Forest Light Interaction Model Using a Monte Carlo Method. IEEE Transactions on Geoscience and Remote Sensing, 34 (4): 946-956. NORTH, P. R. J., ROSETTE, J. A. B., SUREZ, J. C. and LOS, S. O., 2010, A Monte Carlo radiative transfer model of satellite waveform lidar. International Journal of Remote Sensing, 31 (5): 1343-1358. SUN, G. and RANSON, K. J., 2000, Modeling lidar returns from forest canopies. IEEE Transactions on Geoscience and Remote Sensing, 38 (6): 2617-2626.

Rosette, J.; North, P. R.; Rubio, J.; Cook, B. D.; Surez, J.

2010-12-01

436

Differential roles of GABAergic and glycinergic input on FM selectivity in the inferior colliculus of the pallid bat  

PubMed Central

Multiple mechanisms have been shown to shape frequency-modulated (FM) selectivity within the central nucleus of the inferior colliculus (IC) in the pallid bat. In this study we focus on the mechanisms associated with sideband inhibition. The relative arrival time of inhibition compared with excitation can be used to predict FM responses as measured with a two-tone inhibition paradigm. An early-arriving low-frequency inhibition (LFI) prevents responses to upward sweeps and thus shapes direction selectivity. A late-arriving high-frequency inhibition (HFI) suppresses slow FM sweeps and thus shapes rate selectivity for downward sweeps. Iontophoretic application of gabazine (GBZ) to block GABAA receptors or strychnine (Strych) to block glycine receptors was used to assess the effects of removal of inhibition on each form of FM selectivity. GBZ and Strych had a similar effect on FM direction selectivity, reducing selectivity in up to 86% of neurons when both drugs were coapplied. FM rate selectivity was more resistant to drug application with less than 38% of neurons affected. In addition, only Strych could eliminate FM rate selectivity, whereas GBZ alone was ineffective. The loss of FM selectivity was directly correlated to a loss of the respective inhibitory sideband that shapes that form of selectivity. The elimination of LFI correlated to a loss of FM direction selectivity, whereas elimination of HFI correlated to a loss of FM rate selectivity. Results indicate that 1) although the majority of FM direction selectivity is created within the IC, the majority of rate selectivity is inherited from lower levels of the auditory system, 2) a loss of LFI corresponds to a loss of FM direction selectivity and is created through either GABAergic or glycinergic input, and 3) a loss of HFI corresponds to a loss of FM rate selectivity and is created mainly through glycinergic input. PMID:21775712

Williams, Anthony J.

2011-01-01

437

Quantum optical arbitrary waveform manipulation and measurement in real time.  

PubMed

We describe a technique for dynamic quantum optical arbitrary-waveform generation and manipulation, which is capable of mode selectively operating on quantum signals without inducing significant loss or decoherence. It is built upon combining the developed tools of quantum frequency conversion and optical arbitrary waveform generation. Considering realistic parameters, we propose and analyze applications such as programmable reshaping of picosecond-scale temporal modes, selective frequency conversion of any one or superposition of those modes, and mode-resolved photon counting. We also report on experimental progress to distinguish two overlapping, orthogonal temporal modes, demonstrating over 8 dB extinction between picosecond-scale time-frequency modes, which agrees well with our theory. Our theoretical and experimental progress, as a whole, points to an enabling optical technique for various applications such as ultradense quantum coding, unity-efficiency cavity-atom quantum memories, and high-speed quantum computing. PMID:25402035

Kowligy, Abijith S; Manurkar, Paritosh; Corzo, Neil V; Velev, Vesselin G; Silver, Michael; Scott, Ryan P; Yoo, S J B; Kumar, Prem; Kanter, Gregory S; Huang, Yu-Ping

2014-11-17

438

Strategies for the characteristic extraction of gravitational waveforms  

SciTech Connect

We develop, test, and compare new numerical and geometrical methods for improving the accuracy of extracting waveforms using characteristic evolution. The new numerical method involves use of circular boundaries to the stereographic grid patches which cover the spherical cross sections of the outgoing null cones. We show how an angular version of numerical dissipation can be introduced into the characteristic code to damp the high frequency error arising form the irregular way the circular patch boundary cuts through the grid. The new geometric method involves use of the Weyl tensor component {psi}{sub 4} to extract the waveform as opposed to the original approach via the Bondi news function. We develop the necessary analytic and computational formula to compute the O(1/r) radiative part of {psi}{sub 4} in terms of a conformally compactified treatment of null infinity. These methods are compared and calibrated in test problems based upon linearized waves.

Babiuc, M. C. [Department of Physics, Marshall University, Huntington, West Virginia 25755 (United States); Bishop, N. T. [Department of Mathematical Sciences, University of South Africa, Unisa 0003 (South Africa); Szilagyi, B. [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, 14476 Golm (Germany); Theoretical Astrophysics, California Institute of Technology, Pasadena, California 91125 (United States); Winicour, J. [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, 14476 Golm (Germany); Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

2009-04-15

439

ECG beats classification using waveform similarity and RR interval  

E-print Network

This paper present an electrocardiogram (ECG) beat classification method based on waveform similarity and RR interval. The purpose of the method is to classify six types of heart beats (normal beat, atrial premature beat, paced beat, premature ventricular beat, left bundle branch block beat and right bundle branch block beat). The electrocardiogram signal is first denoised using wavelet transform based techniques. Heart beats of 128 samples data centered on the R peak are extracted from the ECG signal and thence reduced to 16 samples data to constitute a feature. RR intervals surrounding the beat are also exploited as feature. A database of annotated beats is built for the classifier for waveform comparison to unknown beats. Tested on 46 records in the MIT/BIH arrhythmia database, the method shows classification rate of 97.52%.

Ka, Ahmad Khoureich

2011-01-01

440

Sub-Nyquist Sampling and Moire-Like Waveform Distortions  

NASA Technical Reports Server (NTRS)

Investigations of aliasing effects in digital waveform sampling have revealed the existence of a mathematical field and a pseudo-alias domain lying to the left of a "Nyquist line" in a plane defining the boundary between two domains of sampling. To the right of the line lies the classic alias domain. For signals band-limited below the Nyquist limit, displayed output may show a false modulation envelope. The effect occurs whenever the sample rate and the signal frequency are related by ratios of mutually prime integers. Belying the principal of a 10:1 sampling ratio being "good enough", this distortion easily occurs in graphed one-dimensional waveforms and two-dimensional images and occurs daily on television.

Williams, Glenn L.

2000-01-01

441

Design of Waveform Generator for NBI in EAST  

NASA Astrophysics Data System (ADS)

The control system of neutral beam injector (NBI) monitors the status of NBI equipments, controls all of the power supply, realizes data acquisition and network, and provides a unified clock for all subsystems of NBI system. As an important part of NBI control system, waveform generator (WG) monitors the parameters of the experiment and displays these parameters in the waveform terminal. The WG software also can send simple experiment commands and make it easy for experiment test. The WG software develops under Windows operating system, using labview language. The design is related to many kinds of technologies, such as client/server communication, multithreading and cyclic redundancy check technology, TCP protocol and so on.

Zhao, Yuan-Zhe; Hu, Chun-Dong; Sheng, Peng; Zhang, Xiao-Dan; Wu, De-Yun; Cui, Qing-Long

2013-08-01

442

A Pilot Investigation regarding Speech-Recognition Performance in Noise for Adults with Hearing Loss in the FM+HA Listening Condition  

ERIC Educational Resources Information Center

While the concurrent use of the hearing aid (HA) microphone with frequency modulation (FM) technology can decrease speech-recognition performance, the FM+HA condition is still an important setting for users of both HA and FM technology. The primary goal of this investigation was to evaluate the effect of attenuating HA gain in the FM+HA listening

Lewis, M. Samantha; Gallun, Frederick J.; Gordon, Jane; Lilly, David J.; Crandell, Carl

2010-01-01

443

Matched filtering and parameter estimation of ringdown waveforms  

Microsoft Academic Search

Using recent results from numerical relativity simulations of nonspinning binary black hole mergers, we revisit the problem of detecting ringdown waveforms and of estimating the source parameters, considering both LISA and Earth-based interferometers. We find that Advanced LIGO and EGO could detect intermediate-mass black holes of mass up to 103M&sun; out to a luminosity distance of a few Gpc. For

Emanuele Berti; Jaime Cardoso; Vitor Cardoso; Marco Cavagli

2007-01-01

444

Matched filtering and parameter estimation of ringdown waveforms  

Microsoft Academic Search

Using recent results from numerical relativity simulations of nonspinning binary black hole mergers, we revisit the problem of detecting ringdown waveforms and of estimating the source parameters, considering both LISA and Earth-based interferometers. We find that Advanced LIGO and EGO could detect intermediate-mass black holes of mass up to 10M{sub } out to a luminosity distance of a few Gpc.

Marco Cavaglia; Vitor Cardoso; Jaime Cardoso; Emanuele Berti

2007-01-01

445

Resonant-frequency primitive waveforms and star waves in lattices  

Microsoft Academic Search

For square and triangular lattices we have found a new line-localized primitive waveform (LPW) existing at a resonant frequency. In two-dimensional (2D) case, the LPW represents a line of oscillating particles, while the lattice outside this line remains at rest. We show that: (a) A single LPW does not conduct energy; however, a band consisting of two or more neighboring

M. V. Ayzenberg-Stepanenkoa

446

Optimal storage and retrieval of single-photon waveforms.  

PubMed

We report an experimental demonstration of optimal storage and retrieval of heralded single-photon wave packets using electromagnetically induced transparency (EIT) in cold atoms at a high optical depth. We obtain an optimal storage efficiency of (49 3)% for single-photon waveforms with a temporal likeness of 96%. Our result brings the EIT quantum light-matter interface closer to practical quantum information applications. PMID:23187175

Zhou, Shuyu; Zhang, Shanchao; Liu, Chang; Chen, J F; Wen, Jianming; Loy, M M T; Wong, G K L; Du, Shengwang

2012-10-22

447

Repeatability of Electromyographic Waveforms During the Naeryo Chagi in Taekwondo  

PubMed Central

The purpose of the research was to study the repeatability of electromyographic (EMG) waveforms of major lower limb muscles during the naeryo chagi (axe kick) in taekwondo. Six male and female athletes, aged between 20 and 24 years served as volunteers. All participants were black belt holders and performed the naeryo chagi with their right leg. The electromyographic activity of rectus femoris, biceps femoris, gastrocnemius lateralis and tibialis anterior was recorded during the kick through four preamplified surface electrodes. The participants preformed 10 successive kicks to a fixed target with 1 min inter-trial interval. The electromyograms were recorded during each kick at a sampling frequency of 1000Hz. After the processing of the raw EMG data, myoelectrical activity was normalized on the time and amplitude domain. The coefficient of variation (CV), intra-class correlation coefficient (ICC) and coefficient of multiple correlation (CMC) were computed to test the repeatability of the electromyographic waveforms in each participant. The electromyographic activity during the naeryo chagi demonstrated poor repeatability. More specifically, all CVs were greater than 80%, all CMCs were lower than 0.75 and the majority of the average measure ICCs as well as all single measure ICCs were lower than 0.55. It seemed that only ensemble averages of EMG waveforms obtained from more than ten kicks may be considered as representatives of the muscle function in naeryo chagi and conclusions that have been drawn from a single trial should be reconsidered. Key points The paper is the only known paper focused on the EMG repeatability of a taekwondo kick (naeryo chagi). The paper is among the few papers of repeatability dealing with the whole EMG waveforms and not with discrete EMG parameters. Repeatability was tested using all the available statistical indices. The results suggested that conclusions drawn from a single trial in EMG studies of taekwondo kicks and probably in other sports should be treated carefully. PMID:24198696

Aggeloussis, Nickos; Gourgoulis, Vassilis; Sertsou, Maria; Giannakou, Erasmia; Mavromatis, George

2007-01-01

448

Acquisition of L2 Japanese Geminates: Training with Waveform Displays  

ERIC Educational Resources Information Center

The value of waveform displays as visual feedback was explored in a training study involving perception and production of L2 Japanese by beginning-level L1 English learners. A pretest-posttest design compared auditory-visual (AV) and auditory-only (A-only) Web-based training. Stimuli were singleton and geminate /t,k,s/ followed by /a,u/ in two

Motohashi-Saigo, Miki; Hardison, Debra M.

2009-01-01

449

Adaptive Power Spectrum Method for Processing Full Waveform Logs  

NASA Astrophysics Data System (ADS)

The power spectra of borehole mode waves like compressional and shear head waves and Stoneley waves etc., are very important information from full wave acoustic logging data analysis. Conventional power spectrum analysis based on Fourier transform cannot derive such detailed power spectra because of none resolution in time domain. We have developed a new power spectrum analysis technique for full waveform acoustic array logs. Based on local cosine packet analysis and K-L transformation, this technique can diagonalize the correlation matrix of the acoustic signal. Meanwhile for the local stationary signal, the local cosine base is the best candidate of K-L transformation base. After the correlation matrix is diagonalized, the elements at diagonal represent the power spectrum of the signal. By arranging this procedure into an optimization procedure, we can thus determine the time window for each mode adaptively while calculating each individual power spectrum at the same time. The first step of the data processing algorithm is to decompose the whole signal with local cosine packet. And then the power spectrum of each component is calculated. Finally, we will find the optimum base with the local cosine packet tree. The objective function of the optimization is composed of the norm-2 of the power under certain base. Because the full waveform of acoustic logging is not an exact local stationary signal, the compressional and shear head waves are correlated. Therefore the STC method is employed to get the arrival time of compressional and shear head waves from the array waveform data, and then the shear arrival time can be taken as a constraint for this optimization. We have applied this method to a set of field full waveform logs. Our results have shown that the individual borehole modes are separated correctly and the power spectra for each mode agree with the existing theoretical predictions.

He, F.; Tao, G.

2005-05-01

450

Regional waveform calibration in the Pamir-Hindu Kush region  

NASA Astrophysics Data System (ADS)

Twelve moderate-magnitude earthquakes (mb 4-5.5) in the Pamir-Hindu Kush region are investigated to determine their focal mechanisms and to relocate them using their regional waveform records at two broadband arrays, the Kyrgyzstan Regional Network (KNET), and the 1992 Pakistan Himalayas seismic experiment array (PAKH) in northern Pakistan. We use the "cut-and-paste" source estimation technique to invert the whole broadband waveforms for mechanisms and depths, assuming a one-dimensional velocity model developed for the adjacent Tibetan plateau. For several large events the source mechanisms obtained agree with those available from the Harvard centroid moment tensor (CMT) solutions. An advantage of using regional broadband waveforms is that focal depths can be better constrained either from amplitude ratios of Pnl to surface waves for crustal events or from time separation between the direct P and the shear-coupled P wave (sPn + sPmP) for mantle events. All the crustal events are relocated at shallower depths compared with their International Seismological Centre bulletin or Harvard CMT depths. After the focal depths are established, the events are then relocated horizontally using their first-arrival times. Only minor offsets in epicentral location are found for all mantle events and the bigger crustal events, while rather large offsets (up to 30 km) occur for the smaller crustal events. We also tested the performance of waveform inversion using only two broadband stations, one from the KNET array in the north of the region and one from the PAKH array in the south. We found that this geometry is adequate for determining focal depths and mechanisms of moderate size earthquakes in the Pamir-Hindu Kush region.

Zhu, Lupei; Helmberger, Donald V.; Saikia, Chandan K.; Woods, Bradley B.

1997-10-01

451

Monitoring fault zone environments with correlations of earthquake waveforms  

NASA Astrophysics Data System (ADS)

We develop a new technique for monitoring temporal changes in fault zone environments based on cross-correlation of earthquake waveforms recorded by pairs of stations. The method is applied to waveforms of 10 000 earthquakes observed during 100 d around the 1999 M 7.1 Duzce mainshock by a station located in the core damage zone of the North Anatolian Fault and a nearby station. To overcome clock problems, the correlation functions are realigned on a dominant peak. Consequently, the analysis focuses on measurements of coherency rather than traveltimes, and is associated with correlation coefficient of groups of events with a reference wavelet. Examination of coherency in different frequency bands reveals clear changes at a narrow band centred around 0.8 Hz. The results show a rapid drop of 1-2 per cent of the coherency at the time of the Duzce event followed by gradual recovery with several prominent oscillations over 4 d. The observed changes likely reflect evolution of permeability and fluid motion in the core damage zone of the North Anatolian Fault. Compared to noise correlation processing, our analysis of earthquake waveform correlation (i) benefits from high level of coherence with short duration recorded signals, (ii) has considerably finer temporal sampling of fault dynamics after mainshocks than is possible with noise correlation, (iii) uses the coherence level to track property variations, which may be more robust than traveltime fluctuations in the coda of noise correlations. Studies utilizing both earthquake and noise waveforms at multiple pairs of stations across fault damage zones can improve significantly the understanding of fault zone processes.

Roux, Philippe; Ben-Zion, Yehuda

2014-02-01

452

Synthesis of precision waveforms using a SINIS Josephson junction array  

Microsoft Academic Search

A synthesizer of precision ac waveforms based on a binary superconductor insulator-normal metal-insulator-superconductor (SINIS) Josephson junction array has been developed. The array segments are individually biased using a high-speed bias source which gives a switching time of approximately 250 ns between voltage steps. The accuracy limitations of the system due to limited risetime and bandwidth are discussed. Comparisons between the

Ralf Behr; Jonathan M. Williams; Pravin Patel; Theodoor J. B. M. Janssen; Torsten Funck; Manfred Klonz

2005-01-01

453

Rotating stellar core-collapse waveform decompositon: a Principal Component Analysis approach  

E-print Network

This paper introduces the use of Principal Component Analysis as a method to decompose the waveform catalogues to produce a set of orthonormal basis vectors. We apply this method to a set of supernova waveforms and compare the basis vectors obtained with those obtained through Gram-Schmidt decomposition. We observe that, for the chosen set of waveforms, the performance of the two methods are comparable for minimal match requirements up to 0.9, with 14 Gram-Schmidt basis vectors and 12 principal components required for a minimal match of 0.9. This implies that there are many common features in the chosen waveforms. Additionally, we observe the chosen waveforms have very similar features and a minimal match of 0.7 can be obtained by decomposing only one third of the entire set of waveforms in the chosen catalogue. We discuss the implications of this observation and the advantages of eigen-decomposing waveform catalogues with Principal Component Analysis.

Ik Siong Heng

2008-10-31

454

Transthoracic defibrillation of dogs with Edmark, biphasic, and quadriphasic waveforms.  

PubMed

Patients with high transthoracic impedance are reported to be at higher risk of poor outcomes when treated by present defibrillators. This study evaluates the defibrillation efficacy of biphasic truncated exponential (BTE), quadriphasic truncated exponential (QTE), and Edmark waveforms at simulated low, average, and high impedance levels. Waveforms were tested at 2 energy levels in random order in anesthetized dogs (n = 15, 16.9 +/- 1.2 kg), and a supplemental study estimated the ED50 peak current for BTE and QTE at a simulated high impedance level. Overall, BTE and QTE were equivalent, and both were superior to Edmark at equal delivered energies (P<.0001). However, in simulated high impedance patients at 24 J, QTE was superior to BTE (71% vs. 49%, P =.011 (borderline significance-see text)). Supplemental study, QTE mean ED50 peak current was lower than BTE (7.9 vs. 8.9 A, P =.0049). QTE and BTE waveforms were superior to Edmark at all studied conditions, but QTE appears to be superior to BTE in simulated high impedance patients. PMID:11786946

McDaniel, Wayne C; Magin, Thomas; Madsen, Richard W; Bonagura, John D; Schuder, John C; Curtis, Jack J

2002-01-01

455

A finite-difference algorithm for full waveform teleseismic tomography  

NASA Astrophysics Data System (ADS)

We adapt a 2-D spectral domain finite difference waveform tomography algorithm previously used in active source seismological imaging to the case of a plane wave propagating through a 2.5-D viscoelastic medium in order to recover P and S wave speed variations from body waves recorded at teleseismic distances. A transferable efficacy that permits recovery of arbitrarily heterogenous models on moderately sized computers provides the primary motivation for choosing this algorithm. Synthetic waveforms can be generated either by specifying an analytic solution for a background plane wave in a 1-D model and solving for the source distribution that would produce it, or by solving for a scattered field excited by a plane wave source and then adding the background wavefield to it. Because the former approach typically involves a concentration of sources at the free surface, the latter tends to be more stable numerically. We adapt a gradient approach to solve the inverse problem to maintain tractability; calculating the gradient does not require much more computational effort than does the forward problem. The waveform tomography algorithm can be applied in a straightforward way to perform receiver function migration and traveltime inversion.

Roecker, S.; Baker, B.; McLaughlin, J.

2010-05-01

456

Communications system using a sharply bandlimited keying waveform  

NASA Astrophysics Data System (ADS)

It is the object of this invention to transform a communications sequence in a communications system into an analog signal which is spectrally confined to the band available for the transmission within a band limited communications channel without compromising communication accuracy. Another object of this invention is to improve spectral confinement thereby allowing closer channel spacing and better electromagnetic compatibility among radar, navigation, and communications systems. These and other objects are achieved by a communication system using sharply bandlimited signals for sampled data communications wherein a sharply bandlimited waveform is computed for each sample value in a sequence of data samples. Each waveform is centered at a sample point, is weighted by the corresponding data value, and is truncated outside an appropriate time interval. Resulting data-weighted waveforms are summed in the computer for all data samples of the sequence to be communicated, and the result is converted to analog form, up-converted to the desired carrier frequency, and transmitted. Because the signal spectrum is sharply bandlimited, communication channels may be spaced more closely, permitting more channels in the same frequency band.

Waters, William M.

1995-03-01

457

Decrease of pulse-contrast in nonlinear chirped-pulse amplification systems due to high-frequency spectral phase ripples.  

PubMed

It is analytically shown that weak initial spectral phase modulations cause a pulse-contrast degradation at the output of nonlinear chirped-pulse amplification systems. The Kerr-nonlinearity causes an energy-transfer from the main pulse to side-pulses during nonlinear amplification. The relative intensities of these side-pulses can be described in terms of Bessel-functions. It is shown that the intensities of the pulses are dependent on the magnitude of the accumulated nonlinear phase-shift (i.e., the B-integral), the depth and period of the initial spectral phase-modulation and the slope of the linear stretching chirp. The results are applicable to any type of laser amplifier that is based on the technique of chirped-pulse amplification. The analytical results presented in this paper are of particular importance for high peak-power laser applications requiring high pulse-contrasts, e.g. high field physics. PMID:18545600

Schimpf, Damian; Seise, Enrico; Limpert, Jens; Tnnermann, Andreas

2008-06-01

458

High Sensitivity EMAT System using Chirp Pulse Compression and Its Application to Crater End Detection in Continuous Casting  

NASA Astrophysics Data System (ADS)

A high sensitivity EMAT system using chirp pulse compression technique was developed. The system uses a high power gated amplifier having 2kVpp output to transmit chirp waves. Pulse compression of the received signals are performed digitally in a PC after amplification and analog-to-digital conversion. A 20dB improvement of the signal-to-noise ratio was achieved by chirp pulse compression and synchronous averaging. A new surface cooling technique was also developed to improve the signal amplitude of the bulk shear wave with hot steel, and its effectiveness was demonstrated. An actual plant test of crater end detection by the developed EMAT system was conducted at a continuous caster, and clear detection by non-contact EMATs was achieved.

Iizuka, Y.; Awajiya, Y.

2014-06-01

459

Effects of Detuning on Control of Intersubband Quantum Well Transitions with Chirped Electromagnetic Pulses  

SciTech Connect

We study the interaction of a chirped electromagnetic pulse with intersubband transitions of a double semiconductor quantum well. We specifically consider the interaction of the ground and first excited subbands with the electromagnetic field and use the nonlinear density matrix equations for the description of the system dynamics. These equations are solved numerically for various values of the electron sheet density for a realistic double GaAs/AlGaAs quantum well, and the efficiency of population transfer is discussed with emphasis given to the effects of the detuning of the central frequency of the electromagnetic field from resonance.

Blekos, Konstantinos; Terzis, Andreas F. [Physics Department, School of Natural Sciences, University of Patras, Patras 265 04 (Greece); Simserides, Constantinos [Institute of Materials Science, National Center of Scientific Research Demokritos, 153 10 Athens (Greece); Paspalakis, Emmanuel [Materials Science Department, School of Natural Sciences, University of Patras, Patras 265 04 (Greece)

2010-11-10

460

Optical beam focusing by a single subwavelength metal slit surrounded by chirped dielectric surface gratings  

SciTech Connect

A method for optical beam focusing by a single subwavelength metal slit surrounded by surface gratings is proposed. In our proposed method, the period of each surface grating is chirped so that the radiation fields of surface plasmon polaritons can be controlled to make a beam spot at the desired focal length. Through our proposed method, it is numerically shown that we can make a beam spot which is located at the several times of wavelength distance from the slit, and its focal length can be controlled.

Kim, Seyoon; Lim, Yongjun; Kim, Hwi; Park, Junghyun; Lee, Byoungho [National Creative Research Center for Active Plasmonics Application Systems, Inter-University Semiconductor Research Center and School of Electrical Engineering, Seoul National University, Gwanak-Gu Sillim-Dong, Seoul 151-774 (Korea, Republic of)

2008-01-07

461

Carrier-envelope-phase stable, high-contrast, double chirped-pulse-amplification laser system.  

PubMed

We present the first carrier-envelope-phase stable chirped-pulse amplifier (CPA) featuring high temporal contrast for relativistic intensity laser-plasma interactions at 1 kHz repetition rate. The laser is based on a double-CPA architecture including cross-polarized wave (XPW) filtering technique and a high-energy grism-based compressor. The 8 mJ, 22 fs pulses feature 10? temporal contrast at -20??ps and a carrier-envelope-phase drift of 240 mrad root mean square. PMID:24978734

Jullien, Aurlie; Ricci, Aurlien; Bhle, Frederik; Rousseau, Jean-Philippe; Grabielle, Stphanie; Forget, Nicolas; Jacqmin, Hermance; Mercier, Brigitte; Lopez-Martens, Rodrigo

2014-07-01

462

High-energy noncollinear optical parametric-chirped pulse amplification in LBO at 800 nm.  

PubMed

The optical parametric-chirped pulse amplification (OPCPA) based on large-aperture nonlinear optical crystals is promising for implementation of an ultrahigh peak-power laser system of 10 PW and beyond. We demonstrated the highest energy broadband OPCPA at 800 nm, to the best of our knowledge, by using an 80 mm in diameter LiB(3)O(5)(LBO) amplifier, with an output energy of 28.68 J, a bandwidth of 80 nm (FWHM), and conversion efficiency of 25.38%. After compression, a peak power of 0.61 PW with 33.8 fs pulse duration is produced. PMID:24322145

Xu, Lu; Yu, Lianghong; Liang, Xiaoyan; Chu, Yuxi; Hu, Zhanggui; Ma, Lin; Xu, Yi; Wang, Cheng; Lu, Xiaoming; Lu, Haihe; Yue, Yinchao; Zhao, Ying; Fan, Feidi; Tu, Heng; Leng, Yuxin; Li, Ruxin; Xu, Zhizhan

2013-11-15

463

Chirped laser dispersion spectroscopy using a directly modulated quantum cascade laser  

SciTech Connect

Chirped laser dispersion spectroscopy (CLaDS) utilizing direct modulation of a quantum cascade laser (QCL) is presented. By controlling the laser bias nearly single- and dual-sideband CLaDS operation can be realized in an extremely simplified optical setup with no external optical modulators. Capability of direct single-sideband modulation is a unique feature of QCLs that exhibit a low linewidth enhancement factor. The developed analytical model shows excellent agreement with the experimental, directly modulated CLaDS spectra. This method overcomes major technical limitations of mid-infrared CLaDS systems by allowing significantly higher modulation frequencies and eliminating optical fringes introduced by external modulators.

Hangauer, Andreas, E-mail: hangauer@princeton.edu; Nikodem, Michal; Wysocki, Gerard, E-mail: gwysocki@princeton.edu [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States)] [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States); Spinner, Georg [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States) [Electrical Engineering Department, Princeton University, Princeton, New Jersey 08544 (United States); Institute for Quantum Electronics, ETH Zurich, 8093 Zurich (Switzerland)

2013-11-04

464

Experimental demonstration of distributed feedback semiconductor lasers based on reconstruction-equivalent-chirp technology.  

PubMed

In this paper we report, to the best of our knowledge, the first experimental realization of distributed feedback (DFB) semiconductor lasers based on reconstruction-equivalent-chirp (REC) technology. Lasers with different lasing wavelengths are achieved simultaneously on one chip, which shows a potential for the REC technology in combination with the photonic integrated circuits (PIC) technology to be a possible method for monolithic integration, in that its fabrication is as powerful as electron beam technology and the cost and time-consuming are almost the same as standard holographic technology. PMID:19333287

Li, Jingsi; Wang, Huan; Chen, Xiangfei; Yin, Zuowei; Shi, Yuechun; Lu, Yanqing; Dai, Yitang; Zhu, Hongliang

2009-03-30

465

Inducing changes in the bond length of diatomic molecules by time-symmetric chirped pulses  

SciTech Connect

We show numerically that it is possible to change the structure of a simple molecule, that is, a diatomic molecule, where the bond length is modified at a precise timing with symmetrically chirped laser pulses. In the adiabatic regime, the process is fully time reversible, making it possible to design slow vibrations with large bond elongations. The scheme relies on the preparation of a separable state of both nuclear and electronic degrees of freedom with predominant amplitude on the dissociative (antibonding) electronic wave function. Shorter laser pulses can be used to dynamically induce larger bond elongations, preparing a highly excited vibrational wave packet in the ground potential as the laser is switched off.

Chang, Bo Y.; Shin, Seokmin; Sola, Ignacio R. [School of Chemistry (BK21), Seoul National University, Seoul 151-747 (Korea, Republic of); Departamento de Quimica Fisica, Universidad Complutense, E-28040 Madrid (Spain)

2010-12-15

466

Self-compression controlled by the chirp of the input pulse.  

PubMed

Self-compressed (SC) pulses have been achieved through the filamentation process in air without any additional dispersion compensation, using the input pulse chirp as the control parameter. For any studied input pulse energy (3-5 mJ), we have found two opposite sign input group-delay dispersion values for which SC pulses can be achieved systematically. In addition, we have observed that the energy coupled into the inner core of the filament is always of the order of 20% of the total input pulse energy, which opens the way to a scalable technique to obtain intense short pulses directly from the filamentation process. PMID:21042379

Varela, O; Alonso, B; Sola, I J; San Romn, J; Zar, A; Mndez, C; Roso, L

2010-11-01

467

Population Transfer between Two Quantum States by Piecewise Chirping of Femtosecond Pulses: Theory and Experiment  

SciTech Connect

We propose and experimentally demonstrate the method of population transfer by piecewise adiabatic passage between two quantum states. Coherent excitation of a two-level system with a train of ultrashort laser pulses is shown to reproduce the effect of an adiabatic passage, conventionally achieved with a single frequency-chirped pulse. By properly adjusting the amplitudes and phases of the pulses in the excitation pulse train, we achieve complete and robust population transfer to the target state. The piecewise nature of the process suggests a possibility for the selective population transfer in complex quantum systems.

Zhdanovich, S. [Departments of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Laboratory for Advanced Spectroscopy and Imaging Research (LASIR), University of British Columbia, Vancouver (Canada); Shapiro, E. A. [Chemistry, University of British Columbia, Vancouver (Canada); Shapiro, M.; Hepburn, J. W.; Milner, V. [Departments of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Chemistry, University of British Columbia, Vancouver (Canada); Laboratory for Advanced Spectroscopy and Imaging Research (LASIR), University of British Columbia, Vancouver (Canada)

2008-03-14

468

Phase and intensity characterization of femtosecond pulses from a chirped-pulse amplifier by frequency-resolved optical gating  

SciTech Connect

Frequency-resolved optical gating (FROG) measurements were made to characterize pulses from a Ti:sapphire chirped-pulse amplified laser system. By characterizing both the pulse intensity and the phase, the FROG data provided the first direct observation to our knowledge of residual phase distortion in a chirped-pulse amplifier. The FROG technique was also used to measure the regenerative amplifier dispersion and to characterize an amplitude-shaped pulse. The data provide an experimental demonstration of the value of FROG for characterizing complex pulses, including tailored femtosecond pulses for quantum control.

Kohler, B.; Yakovlev, V.V.; Wilson, K.R. [Department of Chemistry, University of California, San Diego, La Jolla, California 92093-0339 (United States); Squier, J. [Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); DeLong, K.W.; Trebino, R. [Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551 (United States)

1995-03-01

469

Dependence of spectrum on pump-signal angle in BBO-I noncollinear optical-parametric chirped-pulse amplification  

Microsoft Academic Search

. A BBO-I noncollinear optical-parametric chirped-pulse amplifier pumped by a Q-switched and frequency-doubled Nd:YAG laser\\u000a has been demonstrated. At an optimal pump-signal angle, the temporally stretched chirped signal pulses with bandwidth of 36nm\\u000a (FWHM) were amplified without any distortion in spectrum. The gain bandwidth was very sensitive to the pump-signal angle.\\u000a Variation of this angle by about 1.5mrad may significantly

X. Yang; Z. Xu; Z. Zhang; Y. Leng; J. Peng; J. Wang; S. Jin; W. Zhang; R. Li

2001-01-01

470

Adaptive Waveform Correlation Detectors for Arrays: Algorithms for Autonomous Calibration  

SciTech Connect

Waveform correlation detectors compare a signal template with successive windows of a continuous data stream and report a detection when the correlation coefficient, or some comparable detection statistic, exceeds a specified threshold. Since correlation detectors exploit the fine structure of the full waveform, they are exquisitely sensitive when compared to power (STA/LTA) detectors. The drawback of correlation detectors is that they require complete knowledge of the signal to be detected, which limits such methods to instances of seismicity in which a very similar signal has already been observed by every station used. Such instances include earthquake swarms, aftershock sequences, repeating industrial seismicity, and many other forms of controlled explosions. The reduction in the detection threshold is even greater when the techniques are applied to arrays since stacking can be performed on the individual channel correlation traces to achieve significant array gain. In previous years we have characterized the decrease in detection threshold afforded by correlation detection across an array or network when observations of a previous event provide an adequate template for signals from subsequent events located near the calibration event. Last year we examined two related issues: (1) the size of the source region calibration footprint afforded by a master event, and (2) the use of temporally incoherent detectors designed to detect the gross envelope structure of the signal to extend the footprint. In Case 1, results from the PETROBAR-1 marine refraction profile indicated that array correlation gain was usable at inter-source separations out to one or two wavelengths. In Case 2, we found that incoherent detectors developed from a magnitude 6 event near Svalbard were successful at detecting aftershocks where correlation detectors derived from individual aftershocks were not. Incoherent detectors might provide 'seed' events for correlation detectors that then could extend detection to lower magnitudes. This year we addressed a problem long known to limit the acceptance of correlation detectors in practice: the labor intensive development of templates. For example, existing design methods cannot keep pace with rapidly unfolding aftershock sequences. We successfully built and tested an object-oriented framework (as described in our 2005 proposal) for autonomous calibration of waveform correlation detectors for an array. The framework contains a dynamic list of detectors of several types operating on a continuous array data stream. The list has permanent detectors: beam forming power (STA/LTA) detectors which serve the purpose of detecting signals not yet characterized with a waveform template. The framework also contains an arbitrary number of subspace detectors which are launched automatically using the waveforms from validated power detections as templates. The implementation is very efficient such that the computational cost of adding subspace detectors was low. The framework contains a supervisor that oversees the validation of power detections, and periodically halts the processing to revise the portfolio of detectors. The process of revision consists of collecting the waveforms from all detections, performing cross-correlations pairwise among all waveforms, clustering the detections using correlations as a distance measure, then creating a new subspace detector from each cluster. The collection of new subspace detectors replaces the existing portfolio and processing of the data stream resumes. This elaborate scheme was implemented to prevent proliferation of closely-related subspace detectors. The method performed very well on several simple sequences: 2005 'drumbeat' events observed locally at Mt. St. Helens, and the 2003 Orinda, CA aftershock sequence. Our principal test entailed detection of the aftershocks of the San Simeon earthquake using the NVAR array; in this case, the system automatically detected and categorized approximately 2/3 of the events above magnitude 2.8.

Ringdal, F; Harris, D B; Dodge, D; Gibbons, S J

2009-07-23

471

Evacuated FM08 Fuses Carry a Sustained Arc in a Bus over 75 VDC  

NASA Technical Reports Server (NTRS)

The FM08 style fuse is specified to interrupt an overcurrent of up to 300 A in a bus of up to 125 VDC, but this applies only when its barrel is filled with air. When placed into a space-grade vacuum, the FM08 style fuse exhausts its air within a year. Then, the probability of an enduring arc is high for all ratings when the bus is above 75 VDC, and the overcurrent is large. The arc endures until something else interrupts the current. The fuse can violently eject metal vapor or other material during the sustained arcing. The evacuated FM08 does not develop a sustained arc when interrupted in a bus of 38 VDC or less, at least when there is little inductance in the circuit. This is consistent with its successful use in many spacecraft having buses in the range 24 to 36 volts.

Leidecker, Henning; Slonaker, J.

1999-01-01

472

Thrombostatin FM compounds: direct thrombin inhibitors ? mechanism of action in vitro and in vivo  

SciTech Connect

Novel pentapeptides called Thrombostatin FM compounds consisting mostly of D-isomers and unusual amino acids were prepared based upon the stable angiotensin converting enzyme breakdown product of bradykinin - RPPGF. These peptides are direct thrombin inhibitors prolonging the thrombin clotting time, activated partial thromboplastin time, and prothrombin time at {>=}0.78, 1.6, and 1.6 {mu}m, respectively. They competitively inhibit {alpha}-thrombin-induced cleavage of a chromogenic substrate at 4.4--8.2 {mu}m. They do not significantly inhibit plasma kallikrein, factor (F) XIIa, FXIa, FIXa, FVIIa-TF, FXa, plasmin or cathepsin G. One form, FM19 [rOicPaF(p-Me)], blocks {alpha}-thrombin-induced calcium flux in fibroblasts with an IC{sub 50} of 6.9 {+-} 1.2 {mu}m. FM19 achieved 100% inhibition of threshold {alpha}- or {gamma}-thrombin-induced platelet aggregation at 8.4 {+-} 4.7 {mu}m and 16 {+-} 4 {mu}m, respectively. The crystal structure of thrombin in complex with FM19 shows that the N-terminal D-Arg retrobinds into the S1 pocket, its second residue Oic interacts with His-57, Tyr-60a and Trp-60d, and its C-terminal p-methyl Phe engages thrombin's aryl binding site composed of Ile-174, Trp-215, and Leu-99. When administered intraperitoneal, intraduodenal, or orally to mice, FM19 prolongs thrombin clotting times and delays carotid artery thrombosis. FM19, a low affinity reversible direct thrombin inhibitor, might be useful as an add-on agent to address an unmet need in platelet inhibition in acute coronary syndromes in diabetics and others who with all current antiplatelet therapy still have reactive platelets.

Nieman, M.T.; Burke, F.; Warnock, M.; Zhou, Y.; Sweigart, J.; Chen, A.; Ricketts, D.; Lucchesi, B.R.; Chen, Z.; Cera, E.Di; Hilfinger, J.; Kim, J.S.; Mosberg, H.I.; Schmaier, A.H. (Case Western); (Michigan); (TSRL); (WU-MED)

2008-04-29

473

The semantic extension and storage of EECP Hemodynamic Waveforms based on DICOM Standard.  

PubMed

Digital imaging and communications in medicine (DICOM) Standard has a detailed description on the Information Object Definition (IOD) of all kinds of medical images and waveforms. With the development and application of DICOM, all medical imaging and waveform devices will support the standard. This article describes the method and implementation on how to encapsulate the EECP Hemodynamic Waveforms data acquired from EECP device, integrating patient information, EECP physiological parameters, and diagnosis and treat information into DICOM Hemodynamic Waveform file. We define Private Data Elements to encode and represent EECP parameters which haven't been registered as Standard Data Elements. This is the semantic extension of DICOM applied in EECP. The paper introduces following parts in detail: the structure of DICOM waveform file, Data Element, Nesting of Data Sets, the Waveform IOD Modules and the specification of Private Data Element. Then the method and process of our program are analyzed in depth. According to object-oriented methodology, firstly, Data Element, Nesting of Data Sets and waveform IOD with their corresponding operations and services are respectively abstracted into classes. Then the waveforms data and other attributes are assigned to the corresponding Data Members of the waveform class. Finally, they are stored into a DICOM waveform file by invoking related functions. PMID:18266019

Xie, Shuqun; Yu, Donglan; Wei, Xianli; Wang, Kuijian

2008-04-01

474

The effect of water on the thermal expansion behavior of FM5055 carbon phenolic  

NASA Technical Reports Server (NTRS)

The effect of water on the thermal expansion behavior of FM5055 carbon phenolic is studied using a theory of mixtures approach. A partial pressure expression for the water constituent was obtained based upon certain assumptions regarding the thermodynamic state of water as it resides in the free volumes of the polymer. A simple constitutive model is used to simulate the polymer strain due to the application of the partial pressure of water. The resulting theory is applied to model the effect of moisture on the thermal expansion of FM5055 carbon phenolic specimens. The application of the theory results in calculated strains which were in close agreement with the measured strains.

Sullivan, Roy M.

1995-01-01

475

An Ascending Ramp Biphasic Waveform Has a Lower Defibrillation Threshold and Releases Less Troponin I Than a Truncated Exponential Biphasic Waveform  

PubMed Central

Background We tested the hypothesis that the shape of the shock waveform affects not only the defibrillation threshold (DFT), but also the amount of cardiac damage. Methods and Results DFTs were determined for 11 waveforms: 3 ascending ramp, 3 descending ramp, and 3 rectilinear first phase biphasic waveforms, a Gurvich waveform, and a truncated exponential biphasic waveform in 6 pigs with electrodes in the RV apex and SVC. The ascending, descending and rectilinear waveforms had 4, 8 and 16 ms 1st phases and a 3.5 ms 2nd rectilinear phase half the voltage of the 1st phase. The exponential biphasic waveform had a 60% 1st phase and a 50% 2nd phase tilt. In a second study, we attempted to defibrillate after 10 s of VF with a single ? 30 J shock (6 pigs successfully defibrillated with 8 ms ascending, 8 ms rectilinear wave and truncated exponential biphasic waveforms). Troponin I blood levels were determined before and 2 to 10 hrs after the shock. The lowest energy DFT was for the 8 ms ascending ramp (14.67.3 SD J), which was significantly less than for the truncated exponential (19.66.3 J). Six hours postshock, troponin I in ng/ml was significantly less for the ascending ramp (0.800.54) than for the truncated exponential (1.920.47) or the rectilinear waveform (1.17 0.45). Conclusions The ascending ramp has a significantly lower DFT, and at ? 30 J causes 58% less troponin I release than the truncated exponential biphasic shock. Therefore, the shock waveform affects both the DFT and the amount of cardiac damage. PMID:22865891

Huang, Jian; Walcott, Gregory P.; Ruse, Richard B.; Bohanan, Scott J.; Killingsworth, Cheryl R.; Ideker, Raymond E.

2014-01-01

476

Spin-wave storage using chirped control fields in atomic frequency comb-based quantum memory  

NASA Astrophysics Data System (ADS)

It has been shown that an inhomogeneously broadened optical transition shaped into an atomic frequency comb can store a large number of temporal modes of the electromagnetic field at the single-photon level without the need to increase the optical depth of the storage material. The readout of light modes is made efficient thanks to the rephasing of the optical-wavelength coherence similar to photon-echo-type techniques, and the reemission time is given by the comb structure. For on-demand readout and long storage times, two control fields are used to transfer the optical coherence back and forth into a spin wave. Here, we present a detailed analysis of the spin-wave storage based on chirped adiabatic control fields. In particular, we verify that chirped fields require significantly weaker intensities than ? pulses. The price to pay is a reduction of the multimode storage capacity that we quantify for realistic material parameters associated with solids doped with rare-earth-metal ions.

Min?, Ji?; Sangouard, Nicolas; Afzelius, Mikael; de Riedmatten, Hugues; Gisin, Nicolas

2010-10-01

477

Gravitational Waves from Rotating Neutron Stars and Evaluation of fast Chirp Transform Techniques  

NASA Technical Reports Server (NTRS)

X-ray observations suggest that neutron stars in low mass X-ray binaries (LMXB) are rotating with frequencies from 300 - 600 Hz. These spin rates are significantly less than the break-up rates for essentially all realistic neutron star equations of state, suggesting that some process may limit the spin frequencies of accreting neutron stars to this range. If the accretion induced spin up torque is in equilibrium with gravitational radiation losses, these objects could be interesting sources of gravitational waves. I present a brief summary of current measurements of neutron star spins in LMXBs based on the observations of high-Q oscillations during thermonuclear bursts (so called 'burst oscillations'). Further measurements of neutron star spins will be important in exploring the gravitational radiation hypothesis in more detail. To this end I also present a study of fast chirp transform (FCT) techniques as described by Jenet and Prince in the context of searching for the chirping signals observed during X-ray bursts.

Strohmayer, Tod E.; White, Nicholas E. (Technical Monitor)

2000-01-01

478

Dual-chirped optical parametric amplification for generating few hundred mJ infrared pulses.  

PubMed

An ultrafast high-power infrared pulse source employing a dual-chirped optical parametric amplification (DC-OPA) scheme based on a Ti:sapphire pump laser system is theoretically investigated. By chirping both pump and seed pulses in an optimized way, high-energy pump pulses can be utilized for a DC-OPA process without exceeding the damage threshold of BBO crystals, and broadband signal and idler pulses at 1.4 ?m and 1.87 ?m can be generated with a total conversion efficiency approaching 40%. Furthermore, few-cycle idler pulses with a passively stabilized carrier-envelope phase (CEP) can be generated by the difference frequency generation process in a collinear configuration. DC-OPA, a BBO-OPA scheme pumped by a Ti:sapphire laser, is efficient and scalable in output energy of the infrared pulses, which provides us with the design parameters of an ultrafast infrared laser system with an energy up to a few hundred mJ. PMID:21503032

Zhang, Qingbin; Takahashi, Eiji J; Mcke, Oliver D; Lu, Peixiang; Midorikawa, Katsumi

2011-04-11

479

Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses  

NASA Astrophysics Data System (ADS)

The nuclear spins in nanostructured semiconductors play a central role in quantum applications. The nuclear spins represent a useful resource for generating local magnetic fields but nuclear spin noise represents a major source of dephasing for spin qubits. Controlling the nuclear spins enhances the resource while suppressing the noise. NMR techniques are challenging: the group III and V isotopes have large spins with widely different gyromagnetic ratios; in strained material there are large atom-dependent quadrupole shifts; and nanoscale NMR is hard to detect. We report NMR on 100,000 nuclear spins of a quantum dot using chirped radiofrequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back and forth a hundred times. We demonstrate that chirped NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nanoscale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems.

Munsch, Mathieu; Wst, Gunter; Kuhlmann, Andreas V.; Xue, Fei; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.; Poggio, Martino; Warburton, Richard J.

2014-09-01

480

Compensation of high-order phase distortions in chirped-pulse amplification system  

NASA Astrophysics Data System (ADS)

Chirped-pulse amplification (CPA) technique has been widely used to generate ultra-intense femto-second pulses. In this scheme the seed pulses from an oscillator are stretched before amplification. The stretched pulses can support more energy extraction and effectively decrease the nonlinear effects in the gain media. The subsequent amplification in a CPA chain will result in a broadening of the output compressed pulses in temporal domain due to the gain narrowing and uncompensated phase distortions. In our experiment, using spectral modulation and phase pre-compensation system (Acoustic-Optics Programmable Dispersive Filter) between the oscillator and the stretcher, the effects of gain narrowing and high-order dispersions on the pulse duration in kHz chirped-pulse amplification system have been pre-compensated, and the spectral FWHM is expanded from 30nm to 50nm. The effects of GDD, TOD and FOD were investigated by scanning the four dispersion parameters respectively. By pre-compensating the high-order phase distortions with the phase measured by SPIDER, we successfully optimize the output duration from 51fs to 30fs, which is 1.07 times Fourier-transform-limitation.

Zhou, Bing; Jiang, Yong-Liang; Leng, Yu-xin; Chen, Xiao-Wei; Li, Ru-Xin; Xu, Zhi-Zhan

2007-01-01

481

Nonlinear transient chirp signal modeling of the aortic and pulmonary components of the second heart sound.  

PubMed

This paper describes a new approach based on the time-frequency representation of transient nonlinear chirp signals for modeling the aortic (A2) and the pulmonary (P2) components of the second heart sound (S2). It is demonstrated that each component is a narrow-band signal with decreasing instantaneous frequency defined by its instantaneous amplitude and its instantaneous phase. Each component is also a polynomial phase signal, the instantaneous phase of which can be accurately represented by a polynomial having an order of thirty. A dechirping approach is used to obtain the instantaneous amplitude of each component while reducing the effect of the background noise. The analysis-synthesis procedure is applied to 32 isolated A2 and 32 isolated P2 components recorded in four pigs with pulmonary hypertension. The mean +/- standard deviation of the normalized root-mean-squared error (NRMSE) and the correlation coefficient (rho) between the original and the synthesized signal components were: NRMSE = 2.1 +/- 0.3% and rho = 0.97 +/- 0.02 for A2 and NRMSE = 2.52 +/- 0.5% and rho = 0.96 +/- 0.02 for P2. These results confirm that each component can be modeled as mono-component nonlinear chirp signals of short duration with energy distributions concentrated along its decreasing instantaneous frequency. PMID:11059167

Xu, J; Durand, L G; Pibarot, P

2000-10-01

482

Study of chirping toroidicity-induced Alfvn eigenmodes in the National Spherical Torus Experiment  

NASA Astrophysics Data System (ADS)

Chirping toroidicity-induced Alfvn eigenmodes (TAEs) are destabilized during neutral beam injection on the National Spherical Torus Experiment (NSTX (Ono M. et al 2000 Nucl. Fusion 40 557)) by super-Alfvnic ions with velocities up to five times larger than the Alfvn velocity. TAEs exhibit repeated bursts in amplitude and down-chirps in frequency. Larger bursts, so-called TAE avalanches, are eventually observed and correlate with a loss of fast ions up to 30% over 1 ms. Frequency, amplitude and radial structure of TAEs are characterized via magnetic pickup coils and a multi-channel reflectometer system. The modes have a broad radial structure, which appears to be unaffected by the large frequency and amplitude variations. However, the large mode amplitude does impact the modes' dynamics by favouring the coupling among different modes. In addition, the coupling involves kink-like modes and can therefore degrade the thermal plasma confinement. In spite of the non-linear regime characterizing the TAE dynamics, the measured properties are found to be in reasonable agreement with solutions from the ideal MHD code NOVA.

Podest, M.; Bell, R. E.; Bortolon, A.; Crocker, N. A.; Darrow, D. S.; Diallo, A.; Fredrickson, E. D.; Fu, G.-Y.; Gorelenkov, N. N.; Heidbrink, W. W.; Kramer, G. J.; Kubota, S.; LeBlanc, B. P.; Medley, S. S.; Yuh, H.

2012-09-01

483

Regulation and modulation of electric waveforms in gymnotiform electric fish  

PubMed Central

Weakly electric gymnotiform fish specialize in the regulation and modulation of the action potentials that make up their multi-purpose electric signals. To produce communication signals, gymnotiform fish modulate the waveforms of their electric organ discharges (EODs) over timescales spanning ten orders of magnitude within the animal's life cycle: developmental, reproductive, circadian, and behavioral. Rapid changes lasting milliseconds to seconds are the result of direct neural control of action potential firing in the electric organ. I