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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

High Resolution Pulse Compression Imaging Using Super Resolution FM-Chirp Correlation Method (SCM)  

NASA Astrophysics Data System (ADS)

This study addresses the issue of the super-resolution pulse compression technique (PCT) for ultrasound imaging. Time resolution of multiple ultrasonic echoes using the FM-Chirp PCT is limited by the bandwidth of the sweep-frequency. That is, the resolution depends on the sharpness of auto-correlation function. We propose the Super resolution FM-Chirp correlation Method (SCM) and evaluate its performance. This method is based on the multiple signal classification (MUSIC) algorithm. Our simulations were made for the model assuming multiple signals reflected from some scatterers. We confirmed that SCM detects time delay of complicated reflected signals successfully with high resolution.

Fujiwara, M.; Okubo, K.; Tagawa, N.

4

The Autocorrelation Function and Power Spectrum of PCM\\/FM with Random Binary Modulating Waveforms  

Microsoft Academic Search

This paper presents the derivation of exact expressions for the autocorrelation function and power spectrum of PCM\\/FM or FSK when the frequency modulating waveform is a random sequence of binary pulses of length T. The problem treated is that of true frequency modulation of an oscillator, a process which, except for a few special cases, generates waveforms and spectra different

M. G. Pelchat

1964-01-01

5

Design of chirp excitation waveform for dual-frequency harmonic contrast detection.  

PubMed

Tissue background suppression is essential for harmonic detection of ultrasonic contrast microbubbles. To reduce the tissue harmonic amplitude for improvement of contrast-to-tissue ratio (CTR), the method of third harmonic (3f(0)) transmit phasing uses an additional 3f(0) transmit signal to provide mutual cancellation between the frequency-sum component and the frequency-difference component of tissue harmonic signal. Chirp excitation can further improve the SNR in harmonic imaging without requiring an excessive transmit pressure and thus reduce potential bubble destruction. However, for effective suppression of tissue harmonic background in 3f(0) transmit phasing, the 3f(0) chirp waveform has to be carefully designed for the generation of spectrally matched cancellation pairs over the entire second harmonic band. In this study, we proposed a chirp waveform suitable for the method of 3f(0) transmit phasing, the different-bandwidth chirp signal (DBCS). With the DBCS waveform, the frequency-difference component of tissue harmonic signal becomes a chirp signal similar to its frequency-sum counterpart. Thus, the combination of the DBCS waveform with the 3f(0) transmit phasing can markedly suppress the tissue harmonic amplitude for CTR improvement together with effective SNR increase of contrast harmonic signal. Our results indicate that, as compared with the conventional Gaussian pulse, the DBCS waveform can provide 6-dB improvement of SNR in 3f(0) transmit phasing with a CTR increase of 3 dB. Nevertheless, the limitation of available transmit bandwidth and the frequency-dependent attenuation can degrade the performance of the DBCS waveform in tissue suppression. The design of the DBCS waveform is also applicable to other dual-frequency imaging techniques that rely on the harmonic generation at the difference frequency. PMID:19942507

Shen, Che-Chou; Chiu, Yi-Yuan

2009-10-01

6

Modified Chirp Waveforms for Cognitive Ultra Wideband Radio - Work in Progress  

Microsoft Academic Search

Cognitive Radio (CR) is an intelligent wireless communication system which is aware of its environment and can adjust its spectrum to utilize the frequency holes in the wireless environment. By this way, a highly efficient utilization of the radio resource can be achieved. We propose a novel CR modulation method that is based on the Ultra-wideband (UWB) chirp waveform in

Hanbing Shen; Weihua Zhang; Kyung Sup Kwak

2007-01-01

7

Attainable Error Probabilities in Demodulation of Random Binary PCM\\/FM Waveforms  

Microsoft Academic Search

The deviation ratio required for minimum obtainable bit-error probability for random binary PCM\\/FM waveforms is derived. The resulting minimum obtainable bit-error probabilities are calculated and compared with those obtained expenimentally and independently in two different laboratories using conventional demodulation equipment. The amplitude distribution of video noise in conventional FM receivers is investigated theoretically and experimentally in an attempt to interpret

Earl F. Smith

1962-01-01

8

Error analysis of the chirp-z transform when implemented using waveform synthesizers and FFTs  

Microsoft Academic Search

This report analyzes the effects of finite-precision arithmetic on discrete Fourier transforms (DFTs) calculated using the chirp-z transform algorithm. An introduction to the chirp-z transform is given together with a description of how the chirp-z transform is implemented in hardware. Equations for the effects of chirp rate errors, starting frequency errors, and starting phase errors on the frequency spectrum of

Bielek

1990-01-01

9

Dependence on chirp rate and spectral resolution of the terahertz field pulse waveform measured by electro-optic detection using a chirped optical pulse and a spectrometer and its effect on terahertz spectroscopy  

NASA Astrophysics Data System (ADS)

Single-shot measurement of a terahertz field pulse waveform by electro-optic sampling using a chirped optical pulse and a spectrometer was demonstrated by and Jiang and Zhang [Appl. Phys. Lett. 72, 1945 (1998)]. We have performed an experimental and theoretical investigation into the dependence of the waveform thus measured on the chirp rate and spectral resolution. It was found that the waveform exhibits multicyclic behavior at a chirp rate of -0.24 THz2, which corresponds to a chirped-pulse width of over 10 ps, for the monocyclic original terahertz field, while it approaches the monocyclic behavior with decreasing pulse width. Further, broadening of the spectral resolution of the spectrometer gives rise to a monocyclic waveform in the chirp rate range where the waveform is expected to be multicyclic. In addition, we have derived an analytical expression for the terahertz field pulse waveform thus measured without using the method of stationary phase. The theoretical results were found to be consistent with measured ones. Finally, we examined the spectral bandwidth and resolution of terahertz spectroscopy using this method.

Murakami, H.; Shimizu, K.; Katsurada, M.; Nashima, S.

2008-11-01

10

Error analysis of the chirp-z transform when implemented using waveform synthesizers and FFTs  

SciTech Connect

This report analyzes the effects of finite-precision arithmetic on discrete Fourier transforms (DFTs) calculated using the chirp-z transform algorithm. An introduction to the chirp-z transform is given together with a description of how the chirp-z transform is implemented in hardware. Equations for the effects of chirp rate errors, starting frequency errors, and starting phase errors on the frequency spectrum of the chirp-z transform are derived. Finally, the maximum possible errors in the chirp rate, the starting frequencies, and starting phases are calculated and used to compute the worst case effects on the amplitude and phase spectrums of the chirp-z transform. 1 ref., 6 figs.

Bielek, T.P.

1990-11-01

11

Effects of Range-Doppler Coupling on Chirp Radar Tracking Accuracy  

Microsoft Academic Search

Attention is called to the phenomenon of ¿range-Doppler coupling,¿ characteristic of linear FM (chirp) waveforms, and the strong effect this coupling may have on tracking accuracy. Numerical results are presented for simple three-state filters and for a realistic reentry vehicle tracking problem.

Robert Fitzgerald

1974-01-01

12

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

2011-05-01

13

CHIRP Doppler radar  

Microsoft Academic Search

The present investigation is concerned with the concept of a combination of the clinical procedure of reconstruction tomography with the radar processing for linear FM pulse compression. An approach based on such a combination is to be employed to map radar backscatter energy. Radar systems employing pulse compression of linear frequency modulated (CHIRP) pulses are considered along with the inversion

M. Bernfeld

1984-01-01

14

Best management of FM waveform by a missile-borne pulsed Doppler radar during high-manoeuvring target tracking in strong clutter environment  

Microsoft Academic Search

Referring to the application of missile-borne pulsed Doppler radars, the use of a radiofrequency HPRF-FM seeker, having a monopulse tracking processing, is considered in scenarios with a low altitude flying high-manoeuvring target. During target tracking the seeker has to solve the situations when the clutter signal occupies the target frequency positions and tracking can be lost. The algorithm that is

S. Camplani; G. Petrillo; D. Pistoia

2001-01-01

15

SAR impulse response with residual chirps.  

SciTech Connect

A Linear Frequency-Modulated (LFM) chirp is a function with unit amplitude and quadratic phase characteristic. In a focused Synthetic Aperture Radar (SAR) image, a residual chirp is undesired for targets of interest, as it coarsens the manifested resolution. However, for undesired spurious signals, a residual chirp is often advantageous because it spreads the energy and thereby diminishes its peak value. In either case, a good understanding of the effects of a residual LFM chirp on a SAR Impulse Response (IPR) is required to facilitate system analysis and design. This report presents an analysis of the effects of a residual chirp on the IPR. As reference, there is a rich body of publications on various aspects of LFM chirps. A quick search reveals a plethora of articles, going back to the early 1950s. We mention here purely as trivia one of the earlier analysis papers on this waveform by Klauder, et al.

Doerry, Armin Walter

2009-06-01

16

Real-time spectrum analysis using hardware Fourier and chirp-Z transformations  

Microsoft Academic Search

The paper emphasizes the wide variety of distinct block-schematic approaches to be adopted in analog implementations for real-time spectrum analysis by hardware Fourier and chirp-Z transformations. The discussion covers Fourier analysis by correlation, chirp-Z analysis by correlation, variants of chirp-Z correlation, chirp-Z analysis by matched filtering, matching the chirp waveform with a dispersive delay line, and some features common to

R. Benjamin

1979-01-01

17

The Development and Implementation of Chirped-Pulse Frequency Combs at Millimeter Wavelengths  

NASA Astrophysics Data System (ADS)

Technological advances in such areas as active multiplier chains and high-speed digital electronics are enabling the development of sensitive high-throughput spectroscopic instruments in the millimeter and submillimeter ranges. Recently there has been an effort to develop multiplexed direct absorption spectroscopy techniques that use frequency comb sources derived from phase-locked pulse trains (often created using ultrafast lasers). We have used a high-speed arbitrary waveform generator (AWG with 12 GHz sample rate) to create frequency combs at mm-wave wavelengths using a chirped pulse as the repeating waveform. This waveform has important advantages including 100% duty cycle for the light output and compatibility with the use of frequency multiplier chains that extend the bandwidth of the comb proportional to the frequency multiplication factor. A new spectrometer operating in the 260-290 GHz range using active multiplier chains has been constructed to test the capabilities of chirped-pulse frequency comb spectroscopy for molecular rotational spectroscopy. The spectral properties of the mm-wave combs generated following x24 frequency multiplication, methods for compressed bandwidth detection using a dual-comb approach, and frequency comb analogs of FM spectroscopy will be presented.

Steber, Amanda L.; Harris, Brent J.; Neill, Justin L.; Lehmann, Kevin K.; Pate, Brooks H.

2012-06-01

18

Analysis and Emulation of FM Radio Signals for Passive Radar  

Microsoft Academic Search

Due to its high power levels provided, and its wide coverage, FM radio could be a good opportunity transmitter for passive coherent location (PCL) radar systems. In this paper we study the effectiveness of FM signals as radar waveforms by means of simulated and real data analysis. To this purpose, an emulation of FM radio transmitter is presented, whose outputs

A. Lauri; F. Colone; R. Cardinali; C. Bongioanni; P. Lombardo

2007-01-01

19

Basic characteristics of FM-CW radar systems  

Microsoft Academic Search

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

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

1986-01-01

20

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...

21

An analysis of FM jamming and noise quality measures  

Microsoft Academic Search

This thesis provides a description of FM-by-noise jamming, both at RF and at the output of the radar receiver, in terms of spectra, time-domain waveforms, and univariate probability density of amplitude. Particular emphasis is given to the case where the peak frequency deviation of the FM modulator is sufficiently small that Woodward's Theorem does not provide a good approximation of

Timothy N. Taylor

1993-01-01

22

Chirp-encoded excitation for dual-frequency ultrasound tissue harmonic imaging.  

PubMed

Dual-frequency (DF) transmit waveforms comprise signals at two different frequencies. With a DF transmit waveform operating at both fundamental frequency (f(0)) and second-harmonic frequency (2f(0)), tissue harmonic imaging can be simultaneously performed using not only the conventional 2f(0) second-harmonic signal but also using the f(0 )frequency-difference harmonic signal. Nonetheless, when chirp excitation is incorporated into the DF transmit waveform for harmonic SNR improvement, a particular waveform design is required to maintain the bandwidth of the f(0) harmonic signal. In this study, two different DF chirp waveforms are proposed to produce equal harmonic bandwidth at both the f(0) and 2f(0) frequencies to achieve speckle reduction by harmonic spectral compounding and to increase harmonic SNR for enhanced penetration and sensitivity. The UU13 waveform comprises an up-sweeping f(0) chirp and an up-sweeping 2f(0) chirp with triple bandwidth, whereas the UD11 waveform includes an up-sweeping f(0) chirp and a down-sweeping 2f(0) chirp with equal bandwidth. Experimental results indicate that the UU13 tends to suffer from a high range side lobe level resulting from 3f(0) interference. Consequently, the 2f(0) harmonic envelopes of the UD11 and the UU13 waveforms have compression qualities of 87% and 77%, respectively, when the signal bandwidth is 30%. When the bandwidth increases to 50%, the compression quality of the 2f(0) harmonic envelope degrades to 78% and 54%, respectively, for the UD11 and the UU13 waveforms. The compression quality value of the f0 harmonic envelope remains similar between the two DF transmit waveforms for all signal bandwidths. B-mode harmonic images also show that the UD11 is less contaminated by range side lobe artifacts than is the UU13. Compared with a short pulse with equal bandwidth, the UD11 waveform not only preserves the same spatial resolution after compression but also improves the image SNR by about 10 dB. Moreover, the image contrast-to-noise ratio (CNR), defined as the ratio of the mean to the standard deviation of image intensity in the speckle region, can be increased from 1.0 to about 1.2 when DF spectral compounding is performed. Therefore, it is concluded that the UD11 waveform is a potential solution for chirp-encoded DF harmonic imaging. PMID:23192805

Shen, Che-Chou; Lin, Chin-Hsiang

2012-11-01

23

Phase-locking and coherent power combining of broadband linearly chirped optical waves.  

PubMed

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ~ 60 kHz, and a residual phase error variance of < 0.01 rad(2) between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers-where a rapidly chirping seed laser reduces stimulated Brillouin scattering-and electronic beam steering of chirped optical waves. PMID:23187338

Satyan, Naresh; Vasilyev, Arseny; Rakuljic, George; White, Jeffrey O; Yariv, Amnon

2012-11-01

24

Surface Wave Chirp Transform Correlator.  

National Technical Information Service (NTIS)

The feasibility of developing a surface wave chirp transform correlator (CTC) is evaluated. A comprehensive characterization of chirp transform (CT) signal processing is presented. A computer model for simulating CT processors is described, with numerous ...

H. M. Gerard O. W. Otto

1976-01-01

25

Surface Acoustic Wave Slanted Correlators for Linear FM Pulse-Compressors  

Microsoft Academic Search

The most commn FM chirp devices used in radar employ the conventional in-line structure. These devices have Fresnel ripple in the time domain that. unless compensated for. will degrade the compressed pulse time s idelobes. Reported ii this paper is a new structure utilizing a slanted transducer to remove unwanted interference effects including Fresnel ripple. The slanted structure is ideal

B. R. Potter; C. S. Hartmann

1977-01-01

26

Improved Chirp Transform Correlator.  

National Technical Information Service (NTIS)

This invention relates to a chirp transform correlator in which asynchronous operation is made possible by the use of a pair of paralleled signal processing channels to which the unknown signal to be correlated is applied. The two channels include sweepin...

H. M. Gerard

1983-01-01

27

47 CFR 74.1204 - Protection of FM broadcast, FM Translator and LP100 stations.  

Code of Federal Regulations, 2010 CFR

...false Protection of FM broadcast, FM Translator and LP100 stations. 74.1204 Section...DISTRIBUTIONAL SERVICES FM Broadcast Translator Stations and FM Broadcast Booster Stations...1204 Protection of FM broadcast, FM Translator and LP100 stations. (a) An...

2009-10-01

28

Chirp signal matching and signal power optimization in pulse-echo mode ultrasonic nondestructive testing  

Microsoft Academic Search

Chirp pulse compression is a signal correlation technique that uses frequency modulated pulses as transmitted signals. Usually, signals with linear frequency modulation are applied. They can be generated rather easily, but their spectra are not totally matched to the transfer function of ultrasonic systems. In pulse-echo mode operation, with signal duration and consequently the time-bandwidth product being critical parameters, waveforms

Martin Pollakowski; Helmut Ermert

1994-01-01

29

Frequency chirp stabilization in semiconductor distributed feedback lasers with external control  

NASA Astrophysics Data System (ADS)

It is well known that current modulation in diode lasers generates amplitude (AM) and optical frequency (FM) modulations. The frequency chirp under direct current modulation originates from variations in the carrier density and from the finite difference in carrier density between the laser on and off states. Modulation of the carrier density modulates the gain and the optical index causing the resonant mode to shift. This frequency chirp broadens the spectrum, which is a serious limitation for high-speed applications and optical fiber communications. At low frequencies, thermal effects also alter the frequency chirp. The aim of this paper is to show that the laser's frequency chirp can be modified using an external control technique. The chirp response is evaluated via the determination of the chirp-to-power ratio (CPR) through a Mach-Zehnder interferometer. Experiments demonstrate that when an external optical feedback is properly adjusted, the CPR can be severely decreased over a wide range of modulation frequencies as compared to the free-running case. These preliminary results obtained on quantum well distributed feedback lasers (QW DFB) with low normalized coupling coefficient (?L) demonstrate how to stabilize the CPR through the DFB facet phase effects or parameters such as the linewidth enhancement factor. In order to confirm this frequency chirp engineering, selfconsistent calculations based on the transfer matrix method are also presented.

Grillot, F.; Provost, J. G.; Kechaou, K.; Thedrez, B.; Erasme, D.

2012-02-01

30

The interlaced chirp Z transform  

Microsoft Academic Search

In this paper we introduce the Interlaced Chirp 2 Transform (Interlaced CZT). It is based on the computation of several carefully staggered Chirp Z transforms (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,

Indranil Sarkar; Adly T. Fam

2004-01-01

31

Robust chirped mirrors.  

PubMed

Optimized chirped mirrors may perform suboptimally, or completely fail to satisfy specifications, when manufacturing errors are encountered. We present a robust optimization method for designing these dispersion-compensating mirror systems that are used in ultrashort pulse lasers. Possible implementation errors in layer thickness are taken into account within an uncertainty set. The algorithm identifies worst-case scenarios with respect to reflectivity as well as group delay. An iterative update improves the robustness and warrants a high manufacturing yield, even when the encountered errors are larger than anticipated. PMID:18470259

Nohadani, Omid; Birge, Jonathan R; Kärtner, Franz X; Bertsimas, Dimitris J

2008-05-10

32

Waveform design for detection of weapons based on signature exploitation  

NASA Astrophysics Data System (ADS)

We present waveform design based on signature exploitation techniques for improved detection of weapons in urban sensing applications. A single-antenna monostatic radar system is considered. Under the assumption of exact knowledge of the target orientation and, hence, known impulse response, matched illumination approach is used for optimal target detection. For the case of unknown target orientation, we analyze the target signatures as random processes and perform signal-to-noise-ratio based waveform optimization. Numerical electromagnetic modeling is used to provide the impulse responses of an AK-47 assault rifle for various target aspect angles relative to the radar. Simulation results depict an improvement in the signal-to-noise-ratio at the output of the matched filter receiver for both matched illumination and stochastic waveforms as compared to a chirp waveform of the same duration and energy.

Ahmad, Fauzia; Amin, Moeness G.; Dogaru, Traian

2010-04-01

33

Speaker Identification using FM Features  

Microsoft Academic Search

The AM-FM modulation model of speech is a nonlinear model that has been successfully used in several branches of speech-related research. However, the significance of the AM-FM features extracted from this model has not been fully explored in applications such as speaker identification systems. This paper shows that frequency modulation (FM) features can improve speaker identification accuracy. Due to the

Tharmarajah Thiruvaran; Eliathamby Ambikairajah; Julien Epps

34

Parallelization of FM-Index  

Microsoft Academic Search

A parallel design and implementation of FM-index is presented in this paper. In applications, the performance of the FM-index is crucial, which is a self-contained, highly compressed indexing algorithm. With the popularity of multi-core processors, parallel computing allows the FM-index to run faster by performing multiple computations simultaneously when possible. Our approach works by splitting input data into overlapping blocks

Di Zhang; Yunquan Zhang; Shengfei Liu; Xiaodi Huang

2008-01-01

35

Transionospheric chirp event classifier  

SciTech Connect

In this paper we will discuss a project designed to provide computer recognition of the transionospheric chirps/pulses measured by the Blackbeard (BB) satellite, and expected to be measured by the upcoming FORTE satellite. The Blackbeard data has been perused by human means -- this has been satisfactory for the relatively small amount of data taken by Blackbeard. But with the advent of the FORTE system, which by some accounts might ``see`` thousands of events per day, it is important to provide a software/hardware method of accurately analyzing the data. In fact, we are providing an onboard DSP system for FORTE, which will test the usefulness of our Event Classifier techniques in situ. At present we are constrained to work with data from the Blackbeard satellite, and will discuss the progress made to date.

Argo, P.E.; Fitzgerald, T.J.; Freeman, M.J.

1995-09-01

36

Performance analysis of a multi-frequency FM based Passive Bistatic Radar  

Microsoft Academic Search

In this paper we evaluate the target detection performance improvement of a multi-frequency approach for FM radio based passive bistatic radar. Specifically, we consider the high diversity of the FM radio signals received over different carrier frequencies spanning the 88-108 MHz band since it represents the basis for the request of a multi-frequency operation. The joint exploitation of the waveforms

Carlo Bongioanni; Fabiola Colone; Pierfrancesco Lombardo

2008-01-01

37

FM spectral modeling and FDM\\/FM simulation programs  

Microsoft Academic Search

Frequency modulation spectral modeling and Gaussian approximation principles are analyzed and extended to develop computer simulation programs capable of providing representative FM spectra. A generalized program is developed to accommodate a variety of baseband and preemphasis characteristics, and adapted to generate FDM\\/FM telephony spectra. The program features the automatic validation and generation of the gaussian spectrum model if applicable, or

C. A. Filippi

1983-01-01

38

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

39

The FM/S/FM Trilayer: Inhomogeneous ?-Phase Superconductivity  

NASA Astrophysics Data System (ADS)

We proved that the superconductivity in the ferromagnetic metal/superconductor/ferromagnetic metal (FM/S/FM) trilayer is a superposition of the BCS pairing with constant-sign pair amplitude in the S layer and the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) pairing with the 3D oscillatory pair amplitude in the FM layers. We allow not only the indirect interaction of the FM layers magnetizations via the S layer, but also a possible existence ? phase superconducting states in such trilayers. The presence of ? magnetic states along with the ? superconducting ones allows us to explain the unexpected weak depression of superconductivity which has been found in the short period Gd/La superlattices.

Ivanovo, N.; Terentieva, L.; Sattarov, D.; Proshin, Yu.; Khusainov, M. G.

2006-09-01

40

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

Microsoft Academic Search

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

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

2010-01-01

41

Arbitrary waveform generator  

NASA Astrophysics Data System (ADS)

An arbitrary waveform generator is capable of producing pulse or continuous waveform signals. It utilizes an EPROM that sends out selected stored digital signals under control of a microprocessor and auxiliary equipment comprised of a clock and an address sequencer. A digital to analog converter receives the digital signals from the EPROM and converts them to analog signals.

Blackmon, Fletcher A.

1993-11-01

42

Altimeter waveform software design  

Microsoft Academic Search

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:

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

1977-01-01

43

Tone signal generator for producing multioperator tone signals using an operator circuit including a waveform generator, a selector and an enveloper  

DOEpatents

A frequency modulation (FM) tone signal generator for generating a FM tone signal is disclosed. The tone signal generator includes a waveform generator having a plurality of wave tables, a selector and an enveloper. The waveform generator furnishes a waveform signal in response to a phase angle address signal. Each wave table stores a different waveform. The selector selects one of the wave tables in response to a plurality of selection signals such that the selected wave table largely provides the waveform signal upon being addressed largely by the phase angle address signal. Selection of the selected wave table varies with each selection signal. The enveloper impresses an envelope signal on the waveform signal. The envelope signal is used as a carrier or modulator for generating the FM tone signal.

Dong, Qiujie (Austin, TX); Jenkins, Michael V. (Austin, TX); Bernadas, Salvador R. (Austin, TX)

1997-01-01

44

Study of a time-compression technique for TV transmission using a chirp filter and envelope detection  

NASA Astrophysics Data System (ADS)

A time-compression technique for possible application in communication signal processing is studied. The method uses a linear chirp, a linear dispersive filter realized by surface acoustic wave devices, and an envelope detector. This technique is heuristic and can be viewed as a quasi-stationary model of the FM wave involved. Numerical results show that excessive distortion is created, and its application to TV transmission is not suitable unless some kind of equalization is provided. One such form of equalization is the chirp transform processor which involves considerably more complexity. Simpler equalizations may be possible but do not seem to be straightforward.

Eng, K. Y.; Haskell, B. G.

1981-12-01

45

Best network chirplet chain: Near-optimal coherent detection of unmodeled gravitational wave chirps with a network of detectors  

NASA Astrophysics Data System (ADS)

The searches of impulsive gravitational waves (GW) in the data of the ground-based interferometers focus essentially on two types of waveforms: short unmodeled bursts from supernova core collapses and frequency modulated signals (or chirps) from inspiralling compact binaries. There is room for other types of searches based on different models. Our objective is to fill this gap. More specifically, we are interested in GW chirps “in general,” i.e., with an arbitrary phase/frequency vs time evolution. These unmodeled GW chirps may be considered as the generic signature of orbiting or spinning sources. We expect the quasiperiodic nature of the waveform to be preserved independently of the physics which governs the source motion. Several methods have been introduced to address the detection of unmodeled chirps using the data of a single detector. Those include the best chirplet chain (BCC) algorithm introduced by the authors. In the next years, several detectors will be in operation. Improvements can be expected from the joint observation of a GW by multiple detectors and the coherent analysis of their data, namely, a larger sight horizon and the more accurate estimation of the source location and the wave polarization angles. Here, we present an extension of the BCC search to the multiple detector case. This work is based on the coherent analysis scheme proposed in the detection of inspiralling binary chirps. We revisit the derivation of the optimal statistic with a new formalism which allows the adaptation to the detection of unmodeled chirps. The method amounts to searching for salient paths in the combined time-frequency representation of two synthetic streams. The latter are time series which combine the data from each detector linearly in such a way that all the GW signatures received are added constructively. We give a proof of principle for the full-sky blind search in a simplified situation which shows that the joint estimation of the source sky location and chirp frequency is possible.

Pai, Archana; Chassande-Mottin, Éric; Rabaste, Olivier

2008-03-01

46

Target detection using a pulsed linear frequency modulated noise waveform  

NASA Astrophysics Data System (ADS)

This work investigates the plausibility of target detection using a pulsed linear frequency modulated (LFM) noise waveform conglomerate. The results were generated from simulation and demonstrated that the proposed transmit waveform structure possesses the ability to successfully mask any "chirp-like" characteristic making recognition and/or corruption by unintended 2nd-party passive receivers virtually impossible. Due to the fact that the pulsed LFM noise transmit signal was digitally stored as a reference, we were able to employ classical correlation mixing techniques that enabled the target detection approach to successfully resolve targets at range in the presence of interference. In addition, the process of using various binary random signal modulation schemes for the purpose of masking conventional pulsed radar waveform is also investigated. This work describes research involving target detection using a pulsed linear frequency modulated (LFM) waveform modulated by various discrete random signals. The results include a measure of correlation assessing the effectiveness of the various random signal modulators, Monte Carlo simulations identifying the loss introduced by the random signal modulators during the transmit process, matched filter receiver analysis analytically comparing the probability of detection performance when the random signal modulators are considered, and ambiguity functions to assess the uncertainty of the transmit waveform as a function of Doppler and time.

Govoni, Mark A.; Li, Hongbin

2009-05-01

47

Extraction of Seismic Waveforms.  

National Technical Information Service (NTIS)

This report considers the effects on detectability and measurability resulting from attempts to extract seismic waveforms by application of cascaded processors and polarization filters. Previous work has shown that bandpass or Wiener filters (when cascade...

A. C. Strauss

1978-01-01

48

Influence of long-term social interaction on chirping behavior, steroid levels and neurogenesis in weakly electric fish.  

PubMed

Social interactions dramatically affect the brain and behavior of animals. Studies in birds and mammals indicate that socially induced changes in adult neurogenesis participate in the regulation of social behavior, but little is known about this relationship in fish. Here, we review studies in electric fish (Apteronotus leptorhychus) that link social stimulation, changes in electrocommunication behavior and adult neurogenesis in brain regions associated with electrocommunication. Compared with isolated fish, fish living in pairs have greater production of chirps, an electrocommunication signal, during dyadic interactions and in response to standardized artificial social stimuli. Social interaction also promotes neurogenesis in the periventricular zone, which contributes born cells to the prepacemaker nucleus, the brain region that regulates chirping. Both long-term chirp rate and periventricular cell addition depend on the signal dynamics (amplitude and waveform variation), modulations (chirps) and novelty of the stimuli from the partner fish. Socially elevated cortisol levels and cortisol binding to glucocorticoid receptors mediate, at least in part, the effect of social interaction on chirping behavior and brain cell addition. In a closely related electric fish (Brachyhypopomus gauderio), social interaction enhances cell proliferation specifically in brain regions for electrocommunication and only during the breeding season, when social signaling is most elaborate. Together, these studies demonstrate a consistent correlation between brain cell addition and environmentally regulated chirping behavior across many social and steroidal treatments and suggest a causal relationship. PMID:23761468

Dunlap, Kent D; Chung, Michael; Castellano, James F

2013-07-01

49

FM-based indoor localization  

Microsoft Academic Search

The major challenge for accurate fingerprint-based indoor localization is the design of robust and discriminative wireless signatures. Even though WiFi RSSI signatures are widely available indoors, they vary significantly over time and are susceptible to human presence, multipath, and fading due to the high operating frequency. To overcome these limitations, we propose to use FM broadcast radio signals for robust

Yin Chen; Dimitrios Lymberopoulos; Jie Liu; Bodhi Priyantha

2012-01-01

50

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

51

Path-summation waveforms  

NASA Astrophysics Data System (ADS)

In this paper, we examine an efficient, practical method to calculate approximate, finite-frequency waveforms for the early signals from a point source in 3-D acoustic media with smoothly varying velocity and constant density. In analogy to the use of Feynman path integrals in quantum physics, we obtain an approximate waveform solution for the scalar wave equation by a Monte Carlo summation of elementary signals over a representative sample of all possible paths between a source and observation point. The elementary signal is formed from the convolution of the source time function with a time derivative of the Green's function for the homogeneous problem. For each path, this elementary signal is summed into a time series at a traveltime obtained from an integral of slowness along the path. The constructive and destructive interference of these signals produces the approximate waveform response for the range of traveltimes covered by the sampled paths. We justify the path-summation technique for a smooth medium using a heuristic construction involving the Helmholtz-Kirchhoff integral theorem. The technique can be applied to smooth, but strongly varying and complicated velocity structures. The approximate waveform includes geometrical spreading, focusing, defocusing and phase changes, but does not fully account for multiple scattering. We compare path-summation waveforms with the exact solution for a 3-D geometry involving a low-velocity spherical inclusion, and with finite-difference waveforms for a 2-D structure with realistic, complicated velocity variations. In contrast to geometrical-ray methods, the path-summation approach reproduces finite-frequency wave phenomena such as diffraction and does not exhibit singular behaviour. Relative to the finite-difference numerical method, the path-summation approach requires insignificant computer memory and, depending on the number of waveforms required, up to one to two orders of magnitude less computing time. The sampled paths and associated traveltimes produced by the path summation give a relation between the medium and the signal on the waveform that is not available with finite-difference and finite-element methods. Furthermore, the speed and accuracy of the path-summation method may be sufficient to allow 3-D waveform inversion using stochastic, non-linear, global search methods.

Lomax, Anthony

1999-09-01

52

Best chirplet chain: Near-optimal detection of gravitational wave chirps  

SciTech Connect

The list of putative sources of gravitational waves possibly detected by the ongoing worldwide network of large scale interferometers has been continuously growing in the last years. For some of them, the detection is made difficult by the lack of a complete information about the expected signal. We concentrate on the case where the expected gravitational wave (GW) is a quasiperiodic frequency modulated signal i.e., a chirp. In this article, we address the question of detecting an a priori unknown GW chirp. We introduce a general chirp model and claim that it includes all physically realistic GW chirps. We produce a finite grid of template waveforms which samples the resulting set of possible chirps. If we follow the classical approach (used for the detection of inspiralling binary chirps, for instance), we would build a bank of quadrature matched filters comparing the data to each of the templates of this grid. The detection would then be achieved by thresholding the output, the maximum giving the individual which best fits the data. In the present case, this exhaustive search is not tractable because of the very large number of templates in the grid. We show that the exhaustive search can be reformulated (using approximations) as a pattern search in the time-frequency plane. This motivates an approximate but feasible alternative solution which is clearly linked to the optimal one. The time-frequency representation and pattern search algorithm are fully determined by the reformulation. This contrasts with the other time-frequency based methods presented in the literature for the same problem, where these choices are justified by 'ad hoc' arguments. In particular, the time-frequency representation has to be unitary. Finally, we assess the performance, robustness and computational cost of the proposed method with several benchmarks using simulated data.

Chassande-Mottin, Eric [CNRS, Observatoire de la Cote d'Azur, ARTEMIS, BP 4229 06304 Nice Cedex 4 (France); Pai, Archana [INFN, Sezione Roma 1-P.le Aldo Moro, 2 00185 Rome (Italy)

2006-02-15

53

Detection and frequency tracking of chirping signals  

SciTech Connect

This paper discusses several methods to detect the presence of and track the frequency of a chirping signal in broadband noise. The dynamic behavior of each of the methods is described and tracking error bounds are investigated in terms of the chirp rate. Frequency tracking and behavior in the presence of varying levels of noise are illustrated in examples. 11 refs., 29 figs.

Elliott, G.R.; Stearns, S.D.

1990-08-01

54

Frequency chirp characteristics on WDM external modulation  

Microsoft Academic Search

The paper studies the effect of frequency chirping and the Extension Ratio (ER) on the performance of optical communication system. The characteristics are obtained from the simulation using OptiSystem 7.0 on the externally modulated experimental setup. The parameter known as alpha factor (a) is used to characterize the chirp behavior and the effects of ER on Bit Error Rate (BER.

Zaiton Binti Abdul Mutalip

2010-01-01

55

Pulse Doppler radar waveforms  

Microsoft Academic Search

Modern military airborne radars are highly sophisticated, multi-mode systems which are required to detect difficult targets in all aspects and over a large range\\/velocity detection space. There are particular difficulties associated with the airborne case such as the limited antenna aperture, high platform velocity and severe clutter levels which present difficult waveform design challenges. This tutorial will consider the design

C. M. Alabaster

2010-01-01

56

Raman forward scattering of chirped laser pulses  

SciTech Connect

Raman scattering of a high-intensity, short duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatio-temporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all regimes of forward scattering, it is shown that the growth rate increases (decreases) for positive (negative) frequency chirp. The effect of chirp on the growth rate is relatively minor, i.e., a few percent chirp yields few percent changes in the growth rates. Numerical solutions based on fully nonlinear cold Maxwell-fluid model are presented which confirm analytical predictions. Relation of these results to recent experiments is discussed.

Schroeder, C.B.; Esarey, E.; Shadwick, B.A.; Leemans, W.P.

2002-12-05

57

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

58

Chirping the LCLS Electron Beam  

SciTech Connect

We explore scenarios for generating a linear time-correlated energy spread in the LCLS electron bunch, prior to the undulator, that is needed for optical (x-ray) pulse compression. The correlated energy spread (''chirp'') is formed by generating an energy gradient along the length of the electron bunch using RF phasing and/or longitudinal wakefields of the accelerating structures. The sign of the correlation is an important limitation. Excluding a complete re-design of the compression systems, the best possibility is to use ''over-compression'' to effect the required energy chirp. This is easily done with only a slight strength increase ({approx}10%) in the chicane bends of the second compressor. In this case, the bend-plane emittance dilution associated with the increased coherent synchrotron radiation (CSR) in the bunch compressor may, however, significantly compromise the electron beam density. The CSR calculations for the momentary extremely short ({approx}1 {micro}m) electron bunch during over-compression are quite subtle and an adequate confidence level may not be achievable. A practical limit in this short-pulse scenario may be to use spontaneous rather than FEL radiation. Ignoring the potential emittance growth, a FWHM electron energy spread of 2% is possible.

Emma, P.

2005-01-31

59

47 CFR 73.317 - FM transmission system requirements.  

Code of Federal Regulations, 2012 CFR

...Telecommunication 4 2012-10-01 2012-10-01 false FM transmission system requirements. 73.317 Section 73.317 Telecommunication...BROADCAST SERVICES FM Broadcast Stations § 73.317 FM transmission system requirements. (a) FM broadcast...

2012-10-01

60

Neutron Detector Waveform Digitization  

NASA Astrophysics Data System (ADS)

In the frame of a DoE Office of Nuclear Energy funded collaboration to design a next generation neutron elastic and inelastic scattering experiment, the Colorado School of Mines/Regis University group is responsible for developing and testing neutron detectors, pulse shape discrimination and read-out methods. This contribution will describe the test setup based on an n-ToF neutron selection using a ^244Cm-^13C source and the Regis Digitizer. Results on pulse shape discrimination from waveform digitization will be compared to other commercially available discrimination methods. We will also present our efforts to explore different types of algorithm for extraction of neutron assignment probabilities from the collected waveforms.

Toebbe, Jonathan; Gray, Fred; Grafil, Elliot; Greife, Uwe

2010-11-01

61

Simulation Model of Rapid TAE Chirping  

NASA Astrophysics Data System (ADS)

Spontaneous nonlinear coherent frequency chirping structures can arise due to the resonant interaction of energetic particles with a discrete toroidal Alfven eigenmode (TAE). The initial development of a coherent structure is quantitatively described by a now standard hole-clump chirping theory. However, it is still unclear what conditions are needed for the TAE chirping frequency to deviate far from the bulk plasma eigenfrequency and enter the Alfven continuum. In our model, the linear TAE controlling equation is derived from the Berk-Mett quadratic form. The interaction is studied with the linear wave with the nonlinear response of energetic particles. For the present study we simplify the wave to a single symmetric couplet while a two-dimensional distribution is used to describe the energetic particles. In order to resolve the fine structure in the phase space, the numerical scheme integrates the Vlasov equation in the Fourier transformed phase space using a method developed by Breizman and Petviashvili. The simulation results show the saturated wave amplitude and square root law of the initial chirping are in accord with previous theory. We have found conditions where the chirping signal enters the Alfven continuum and a larger amplitude and more rapidly chirping signal then develops. Plots of the phase space structure can reproduce the shape of the separatrix structure that partitions the trapped and passing particles. We attempt to relate the portrait of the phase space structure with the measured wave amplitude and chirping frequency.

Wang, Ge; Berk, H. L.

2010-11-01

62

GSSR Waveforms for Lunar Observations  

NASA Astrophysics Data System (ADS)

To increase the resolution of the Goldstone Solar System Radar (GSSR) for lunar observations, a new ranging waveform must be developed. Several candidate waveforms are identified and analytically characterized, including the existing GSSR biphase-coded (BPC) waveform; two commonly used waveforms, linear frequency modulation (LFM) and Costas frequency-hopped (Costas-FH); and a novel minimum-shift keying (MSK) type waveform developed during the course of this study. A set of requirements taking into consideration the spectrum allocation of the GSSR, the limitations of the transmit power amplifier, and the science objectives for a lunar observation were developed and used as selection criteria for the candidate waveforms. Windowed LFM, windowed Costas-FH, and MSK were identified as suitable for development consideration as a new GSSR ranging waveform for lunar observations.

Quirk, K. J.; Srinivasan, M.

2013-02-01

63

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Interference to the input signals of FM translator or FM booster...LPFM) § 73.827 Interference to the input signals of FM translator or FM booster...FM translator or FM booster station's input signal, provided that the same...

2010-10-01

64

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

65

A chirp modem incorporating interference excision  

NASA Astrophysics Data System (ADS)

The paper describes an experimental 75-baud chirp modem designed to operate at high frequency (HF), which is able to reject interference from other HF users by adaptive filtering at the receiver. It also has inherently good performance in multipath preparation and in white noise, and is thus capable of robust digital communication. The system has been tested over a 170 km point-to-point HF skywave link, in which short chirp messages (approximately 30 s duration) were alternated in time with frequency-exchange keyed (FEK) messages. The total duration of the tests was 72 hours, and included day and night operation. In these tests, the chirp system had an overall performance which was superior to that of FEK. FEK occasionally suffered from long periods (e.g., 1 hour) of severe failure, essentially due to interference, whereas the chirp modem achieved more continuous useful operation.

Darbyshire, E. P.; Gott, G. F.

1992-08-01

66

Chirp-managed directly modulated laser (CML)  

Microsoft Academic Search

We demonstrate a new highly dispersion tolerant modulation format using a chirp-managed directly modulated laser (CML) for uncompensated 10-Gb\\/s transmission over >200 km at 1.55 ?m. The CML consists of a distributed feedback (DFB) laser followed by an optical filter. We show that the combination of adiabatic chirp from the DFB and filter edge response produces high extinction ratio pulses

Yasuhiro Matsui; Daniel Mahgerefteh; Xueyan Zheng; Charlie Liao; Zhencan Frank Fan; Kevin McCallion; Parviz Tayebati

2006-01-01

67

Raman forward scattering of chirped laser pulses  

Microsoft Academic Search

Raman scattering of a high-intensity, short-duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatiotemporal regimes. This includes a previously undescribed regime of strongly coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all

C. B. Schroeder; E. Esarey; B. A. Shadwick; W. P. Leemans

2003-01-01

68

Raman forward scattering of chirped laser pulses  

Microsoft Academic Search

Raman scattering of a high-intensity, short duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatio-temporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all

C. B. Schroeder; E. Esarey; B. A. Shadwick; W. P. Leemans

2002-01-01

69

Extended delay of broadband signals in stimulated Brillouin scattering slow light using synthesized pump chirp  

NASA Astrophysics Data System (ADS)

Judicious chirping of a directly modulated pump laser is used to broaden the intrinsic linewidth of stimulated Brillouin scattering in an optical fiber. The modulation waveform is designed to obtain a spectrum with sharp edges, resulting in phase gradients stronger that those obtained for random pump modulation. The gain and phase frequency response of the slow light process are measured by a vector network analyzer, and the delays obtained for our tailored modulation are compared with the case of random direct modulation. For equal pump powers and gain bandwidths (FWHM), the tailored modulation waveform introduces 30-40% longer delays. Using this technique, pseudo random bit sequences of 5 Gb/s were successfully delayed by up to 120 ps (BER<10-5) and 80 ps (BER<10-9).

Zadok, Avi; Eyal, Avishay; Tur, Moshe

2006-09-01

70

Influence of antiferromagnetic interlayer on the exchange coupling of FM1/AFM/FM2 multilayers  

NASA Astrophysics Data System (ADS)

The effect of spin configuration of ferromagnetic (FM1)/antiferromagnetic (AFM) bilayer on the exchange bias of AFM/FM2 bilayer has been investigated in series of designed FM1/AFM/FM2 trilayers. Field cooling of the magnetic sandwich layers, with parallel or antiparallel alignment of the two FM layers, lead to a different interfacial spin configuration and internal AFM domain state. Minor magnetic hysteresis loops show that when the AFM layer is thin enough, the exchange-bias effect after field cooling with parallel and anti-parallel spin configuration is different. When the AFM layer is thick enough, it is difficult to observe the interaction between the spin configuration of FM1/AFM bilayer and the exchange-bias effect of AFM/FM2 bilayer. The AFM layer-thickness dependence on the exchange interaction of other FM layers, mediated by the AFM layer, can be interpreted by the domain state model.

Guo, S.; Liu, W.; Liu, X. H.; Gong, W. J.; Li, Bo; Feng, J. N.; Zhang, Z. D.

2013-10-01

71

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

72

Interplay of the Chirps and Chirped Pulse Compression in a High-gain Seeded Free-electron Laser  

SciTech Connect

In a seeded high-gain Free-electron Laser (FEL), where a coherent laser pulse interacts with an ultra-relativistic electron beam, the seed laser pulse can be frequency chirped, and the electron beam can be energy chirped. Besides these two chirps, the FEL interaction introduces an intrinsic frequency chirp in the FEL even if the above mentioned two chirps are absent. In this paper we examine the interplay of these three chirps. The problem is formulated as an initial value problem, and solved via a Green function approach. Besides the chirp evolution, we also give analytical expressions for the pulse duration and bandwidth of the FEL, which remains fully longitudinally coherent in the high gain exponential growth regime. Because the chirps are normally introduced for a final compression of the FEL pulse, some conceptual issues are discussed. We show that in order to get a short pulse duration, an energy chirp in the electron beam is necessary.

Wu, Juhao; /SLAC; Murphy, J.B.; /LBNL, ALS; Emma, P.J.; /SLAC; Wang, X.J.; Watanabe, T.; /LBNL, ALS; Zhong, Xinming; /Beijing Normal U.

2007-01-03

73

A digital approach to an FM exciter  

Microsoft Academic Search

A digital approach to an FM exciter is presented that provides several advantages over previous analog techniques. This approach, called direct digital frequency modulation (DDFM), is centered around a direct digital synthesis (DDS) chip which allows true digital generation of the FM signal. The DDS chip is a perfectly linear modulator with superior phase-noise characteristics over the current analog voltage-controlled

Edwin R. Twitchell

1992-01-01

74

Spontaneous fission of /sup 259/Fm  

SciTech Connect

A 1.5-s spontaneous fission activity has been produced by irradiating /sup 257/Fm with 16-MeV tritons. On the basis of formation cross sections, fission half-life systematics, and the identification of other possible products, this 1.5-s activity has been attributed to /sup 259/Fm formed by the reaction /sup 257/Fm(t,p)/sup 259/Fm. /sup 259/Fm is the heaviest known isotope of Fm and has more neutrons than any other nuclide thus far identified. This measurement of the spontaneous fission of /sup 259/Fm is the first to show a narrow, predominantly symmetric, mass division from spontaneous fission. It is accompanied by a very high kinetic energy, the most probable total kinetic energy being 242 +- 6 MeV. These features show a marked acceleration in the trend toward more symmetric mass division and higher total kinetic energies than have been observed previously for the Fm isotopes as the mass increased.

Hulet, E.K.; Lougheed, R.W.; Landrum, J.H.; Wild, J.F.; Hoffman, D.C.; Weber, J.; Wilhelmy, J.B.

1980-03-01

75

FY05 FM Dial Summary Report  

Microsoft Academic Search

Pacific Northwest National Laboratory's Infrared Sensors team is focused on developing methods for standoff detection of nuclear proliferation. In FY05, PNNL continued the development of the FM DIAL (frequency-modulated differential absorption LIDAR) experiment. Additional improvements to the FM DIAL trailer provided greater stability during field campaigns which made it easier to explore new locations for field campaigns. In addition to

Warren W. Harper; Jana D. Strasburg; Elizabeth C. Golovich; Jason S. Thompson; Timothy L. Stewart; Michael T. Batdorf

2005-01-01

76

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

2012-05-01

77

Waveform diversity for wireless sensing  

NASA Astrophysics Data System (ADS)

In active sensing systems such as radar and sensor networks, one is interested in transmitting waveforms that possess an ideal thumbtack shaped ambiguity function. However, the synthesis of waveforms with the desired ambiguity function is a difficult problem in applied mathematics and more often than not, one needs to rely on developing waveforms with an ambiguity function that is close to the desired ambiguity function in some sense. Designing waveforms with ambiguity functions that possess certain desirable properties has been a well researched problem in the field of signal analysis. In this paper, we present a methodology for designing multiantenna adaptive waveforms with autocorrelation functions that allow perfect separation at the receiver. We focus on the 4×4 case and derive the conditions that the four waveforms must satisfy in order to achieve perfect separation. Using these conditions, we show that waveforms constructed using Golay complementary sequences, barker codes and quarter-band signals through kronecker products satisfy these conditions and are therefore seperable at the receiver. We also give examples of more general wavefom families that are matched to the environment and also of waveforms that do not necessarily satisfy the conditions for perfect separation but still have good delay-Doppler ambiguity functions making them suitable for sensing environments.

Qureshi, Tariq; Zoltowski, Michael

2008-05-01

78

Coherent control of ultracold collisions with chirped light: Direction matters  

Microsoft Academic Search

We demonstrate the ability to coherently control ultracold atomic Rb\\u000acollisions using frequency-chirped light on the nanosecond time scale. For\\u000acertain center frequencies of the chirp, the rate of inelastic trap-loss\\u000acollisions induced by negatively chirped light is dramatically suppressed\\u000acompared to the case of a positive chirp. We attribute this to a fundamental\\u000aasymmetry in the system: an excited

M. J. Wright; J. A. Pechkis; J. L. Carini; S. Kallush; R. Kosloff; P. L. Gould

2007-01-01

79

Chirp coded excitation imaging with a high-frequency ultrasound annular array  

PubMed Central

High-frequency ultrasound (HFU, > 15 MHz) is an effective means of obtaining fine-resolution images of biological tissues for applications such as opthalmologic, dermatological, and small-animal imaging. HFU has two inherent drawbacks. First, HFU images have a limited depth of field (DOF) because of the short wavelength and the low fixed F-number of conventional HFU transducers. Second, HFU can be used only to image a few millimeters deep into a tissue because attenuation increases with frequency. In this study, a five-element annular array was used in conjunction with a synthetic-focusing algorithm to extend the DOF. The annular array had an aperture of 10 mm, a focal length of 31 mm, and a center frequency of 17 MHz. To increase penetration depth, 8-µs, chirp-coded signals were designed, input into an arbitrary waveform generator, and used to excite each array element. After data acquisition, the received signals were linearly filtered to restore axial resolution and increase the SNR. To compare the chirp-coded imaging method with conventional impulse imaging in terms of resolution, a 25-µm diameter wire was scanned and the ?6 dB axial and lateral resolutions were computed at depths ranging from 20.5 to 40.5 mm. The results demonstrated that chirp-coded excitation did not degrade axial or lateral resolution. A tissue-mimicking phantom containing 10-µm glass beads was scanned, and backscattered signals were analyzed to evaluate SNR and penetration depth. Finally, ex vivo ophthalmic images were formed and chirp-coded images showed features that were not visible in conventional impulse images.

Mamou, Jonathan; Ketterling, Jeffrey A.; Silverman, Ronald. H.

2009-01-01

80

Influence of Laser Frequency Chirp on the Performance of Optical Communication Systems.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. This thesis is concerned with a detailed study of laser frequency chirp and of the implications for the performance of very high bit rate direct detection optical fibre communication systems. In view of the inaccuracy and limitations of previously reported estimates of the chirp-induced penalty, a considerable part of the study is dedicated to the development of modelling and analysis techniques suitable to evaluate the performance of practical systems. In order to take into account laser dynamics, a SPICE2 equivalent-circuit model based on a set of coupled single-mode rate equations is employed, including structure-dependent electrical parasitics. Two alternative methods are considered to model the interaction between chirp and fibre dispersion: an approximate time domain technique, and a more formally based frequency domain method using a complex envelope representation of the transmitted optical field. The latter provides a rigorous description of propagation in monomode fibre, taking into account the intrinsic modulation spectrum, and is used to obtain estimates of transmission bandwidth attainable. A new method for modelling pulse distortion in monomode fibre is also presented, using an expansion of the optical signal in terms of Hermite -Gaussian functions. Pseudo-random data sequences are used to estimate the performance degradation due to chirp and patterning. Allowing for filtering at the receiver of distorted optical power waveforms, system eye-diagrams and estimates of the average error probability are obtained, and equivalent power penalties are determined. Finally, it is shown how the strategy developed may be employed to investigate overall system performance implications and design constraints.

Almeida da Silva, Henrique Jose

1988-12-01

81

Chirp Z transform based spectrum sensing via energy detection  

Microsoft Academic Search

In this study, the performance analysis of Fast Fourier Transform and Chirp Z transform based OFDM systems for cognitive radio networks with energy detector model for the spectrum sensing method is realized. Here, energy detection model for noncooperative spectrum sensing is investigated. On the other hand, the analysis is implemented by segmented Chirp z transform. In this study Chirp z

Mustafa Namdar; Baris Sahin; Haci Ilhan; Lutfiye Durak-Ata

2012-01-01

82

The Chirp Z transform with CCD and SAW technology  

Microsoft Academic Search

The Chirp Z transform (CZT) is presented as an IF process that makes use of time compression and chirp pulse compression. This allows sampled signals to be stored in CCD memory for milliseconds or more, and Z transformed by the chirp filter in microseconds. A CZT spectrum analyzer therefore has extremely high throughput and the capability to process many channels

D. MacFall; J. Collins; Sclarretta; A. Cappon

1978-01-01

83

Characterization of the chirp in semiconductor laser under modulation  

Microsoft Academic Search

In this paper we present, shortly, a study of the chirp induced in direct modulated DFB laser. Our description of the chirp is based, first on analytical resolution of the rate equations, and second on a simulation of a heterodyne system with the Optisystem software. This study enables us to visualize the chirp of a DFB laser in the RF

O. Boukari; L. Hassine; O. Latry; M. Ketata; H. Bouchriha

2008-01-01

84

Evaluation of FM-9 Antimisting Kerosene Variants.  

National Technical Information Service (NTIS)

The results of an experimental effort on evaluation of /fm-9 antimisting kerosene (AMK) variants developed by Imperial Chemical Industries (ICI) to improve the dissolution rate of mist suppression polymers in Jet A are described. Dissolution rate characte...

A. Yavrouian P. Parikh L. Bernal V. Sarohia

1986-01-01

85

Detection of a chirping electromagnetic signal  

SciTech Connect

A matched chirp transform (MCT) method for detecting a dispersive electromagnetic pulse is described. The unique feature of this transform is that it gives a distribution of signal amplitude over time rather than frequency, and thereby simplifies signal detection and identification in the case described here. In the MCT method, the incoming signal is matched to a set of signal segments that chirp in accordance with an expected model of the dispersive medium. The performance of the MCT method is compared with that of a standard periodogram method of frequency measurement. 6 refs., 5 figs.

Stearns, S.D.

1989-01-01

86

Chirped area coupled resonator optical waveguide gyroscope.  

PubMed

We study the transmission of an optical field through a rotating coupled resonator optical waveguide (CROW) in which the size of the ring resonators changes from one ring to the next. We focus on symmetric integer wavelength chirps of the circumference of the rings relative to the central ring in the array. The transfer matrix method is used to obtain the transmission as a function of the inertial rotation rate ? resulting from the Sagnac effect. Chirping increases the slope of the oscillations in the transmission as a function of ?, which can be exploited to further enhance the rotation sensitivity beyond that of a CROW with uniform resonators. PMID:21479036

Toland, John R E; Kaston, Zachary A; Sorrentino, Christopher; Search, Christopher P

2011-04-01

87

Interfacing AM/FM with distribution SCADA  

SciTech Connect

This article examines an upgrade to Union Electric's (UE's) distribution SCADA system by interfacing it with UE's automated mapping and facility management (AM/FM) system to give dispatchers a way to relate facility outages geographically with a real-time monitoring system. The topics of the article are the original SCADA system, the AM/FM system, and the new SCADA system, the man-machine and machine-machine interface, and further applications.

Horton, M.A. (Union Electric Co., St. Louis, MO (United States))

1993-01-01

88

47 CFR 73.295 - FM subsidiary communications services.  

Code of Federal Regulations, 2012 CFR

...false FM subsidiary communications services. 73...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) ...295 FM subsidiary communications services. (a...required to apply to the FCC for the...

2012-10-01

89

SCADA -- AM/FM interface: Platforms, technology  

SciTech Connect

Efficient utility operations is enhanced by close interoperation between automated mapping/facility management (AM/FM) and supervisory control and data acquisition (SCADA) systems. Important benefits of such integration are improvements in service quality and reduced maintenance costs. Development of an AM/FM -- SCADA interface to provide automatic database and display generation for SCADA through AM/FM functions is continuing by Valmet Automation. To minimize or eliminate vendor-dependence, the AM/FM-SCADA interface is compliant with the Electric Power Research Institute's (EPRI) utility communication architecture (UCA). The utility industry is changing at an unprecedented rate. To remain a leader, or even to keep pace, utilities must be flexible and innovative. Competition forces companies to become more streamlined and efficient. These forces make the requirements for automation go beyond simple SCADA. Among several developing trends in the industry is the emergence of AM/FM. Collectively, these trends indicate the need to increase efficiency in the design, operation and maintenance of the transmission and distribution system. To accomplish its mission, SCADA and AM/FM must be a highly integrated system to provide timely information to its users. Open systems, the client-server paradigm and better information integration tools facilitate meeting these needs. UCA specification provides the technological glue, to achieve application integration between heterogeneous systems.

Gilbert, R.F. (Valmet, Automation, Inc., Houston, TX (United States))

1994-05-01

90

Chirp excitation of ultrasonic probes and algorithm for filtering transit times in high-rangeability gas flow metering.  

PubMed

The signal processing used in an ultrasonic high-rangeability gas flow meter using times of flight is presented. The flow meter under discussion uses a combination of continuous wave and chirp signals to measure at low flow velocities, below 20 m/s, and chirp signals alone to measure high flow velocities, above 20 m/s. Because of the need for a pulse compression technique in the signal waveform design the technique of pulse compression and the choice of signal waveforms are discussed. The advantages and disadvantages of amplitude weighting vis-a-vis frequency domain manipulations of the waveforms are also discussed. To eliminate spurious times of flight, a special filtering technique is used, based on assessing the gradient of ascendingly ordered time series of time-of-flight measurements. A summary of user experience with high-rangeability gas flow meters in use on different offshore platforms and in refineries is given. Long-term tests that examined the accuracy of the high-rangeability flow meter are also described. PMID:18263174

Folkestad, T; Mylvaganam, K S

1993-01-01

91

Doppler-Tolerant Signal Waveforms.  

National Technical Information Service (NTIS)

When Doppler distortions of radar signals can be neglected, correlation or marched-filter processing is relatively simple. In those applications where high resolution requirements and high target speeds combine, the distortions in the waveform lead to sev...

A. W. Rihaczek

1966-01-01

92

pathChirp: Efficient Available Bandwidth Estimation for Network Paths  

SciTech Connect

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing rate within each chirp, pathChirp obtains a rich set of information from which to dynamically estimate the available bandwidth. Since it uses only packet interarrival times for estimation, pathChirp does not require synchronous nor highly stable clocks at the sender and receiver. We test pathChirp with simulations and Internet experiments and find that it provides good estimates of the available bandwidth while using only a fraction of the number of probe bytes that current state-of-the-art techniques use.

Cottrell, Les

2003-04-30

93

Extension of harmonic cutoff in a multicycle chirped pulse combined with a chirp-free pulse  

SciTech Connect

We demonstrate high-order harmonic generation in a wave form synthesized by a multicycle 800-nm chirped laser pulse and a chirp-free laser pulse. Compared with the case of using only a chirped pulse, both the harmonic cutoff and the extreme ultraviolet supercontinuum can be extended when a weak chirp-free pulse is combined with the chirped pulse. When chirp-free pulse intensity grows, the cutoff energy and bandwidth of the supercontinuum grow as well. It is found that the broad supercontinuum can be achieved for a driving pulse with long duration even though the driving pulse reaches 10 optical cycles. An isolated attosecond pulse with duration of about 59 as is obtained, and after appropriate phase compensation with a duration of about 11 as. In addition, by performing time-frequency analyses and the classical trajectory simulation, the difference in supercontinuum generation between the preceding wave form and a similar wave form synthesized by an 800-nm fundamental pulse and a 1600-nm subharmonic pulse is investigated.

Xu Junjie; Zeng Bin; Yu Yongli [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2010-11-15

94

Cr4+ : YAG chirped-pulse oscillator  

PubMed Central

We demonstrate chirped-pulse operation of a Cr : YAG passively mode-locked laser. Different operation regimes of the laser are extensively investigated in the vicinity of zero dispersion both experimentally and numerically. It is shown that for a given laser configuration, transition to the positive dispersion regime allows a 5-fold increase in the output pulse energy, which is otherwise limited by the onset of the multipulsing or ‘chaotic’ mode-locking. The output pulses have 1.4 ps duration and are compressible down to 120 fs in a 3 m piece of silica fiber, enabling supercontinuum generation in a nonlinear fiber. The spectrum shape and operation stability of the chirped-pulse regime depend strongly on the amount and shape of the intracavity dispersion. The numerical model predicts the existence of the minimum amount of the positive dispersion, above which the chirped-pulse regime can be realized. Once located, the chirped-pulse regime can be reliably reproduced and is sufficiently stable for applications.

Sorokin, Evgeni; Kalashnikov, Vladimir L; Mandon, Julien; Guelachvili, Guy; Picque, Nathalie; Sorokina, Irina T

2010-01-01

95

Wideband Chirp-Transform Adaptive Filter.  

National Technical Information Service (NTIS)

A wideband chirp-transform adaptive-filter system is described that is capable of providing both spectral monitoring and the excision of multiple narrowband signals. The 80-MHz-bandwidth system processes a wideband continuous 300-MHz center-frequency inpu...

D. R. Arsenault

1985-01-01

96

Superconductive Chirp-Transform Spectrum Analyzer.  

National Technical Information Service (NTIS)

Spectral analysis over an instantaneous bandwidth of 2.4 GHz has been demonstrated utilizing superconductive dispersive delay lines in a chirp-transform configuration. Two-tone resolution of 43 MHz and + or - 1.2 dB amplitude uniformity was achieved.

R. S. Withers S. A. Reible

1985-01-01

97

Clinical comparison of pulse and chirp excitation  

Microsoft Academic Search

Coded excitation (CE) using frequency modulated signals (chirps) combined with modified matched filtering has earlier been presented showing promising results in simulations and in-vitro. In this study an experimental ultrasound system is evaluated in a clinical setting, where image sequences are assessed by skilled medical doctors. The effect on penetration depth and image quality were measured. A modified clinical scanner

Morten H. Pedersen; Thanassis X. Misaridis; J. A. Jensen

2002-01-01

98

Zeptosecond High Harmonic keV X-Ray Waveforms Driven by Midinfrared Laser Pulses  

NASA Astrophysics Data System (ADS)

We demonstrate theoretically that the temporal structure of high harmonic x-ray pulses generated with midinfrared lasers differs substantially from those generated with near-infrared pulses, especially at high photon energies. In particular, we show that, although the total width of the x-ray bursts spans femtosecond time scales, the pulse exhibits a zeptosecond structure due to the interference of high harmonic emission from multiple reencounters of the electron wave packet with the ion. Properly filtered and without any compensation of the chirp, regular subattosecond keV waveforms can be produced.

Hernández-García, C.; Pérez-Hernández, J. A.; Popmintchev, T.; Murnane, M. M.; Kapteyn, H. C.; Jaron-Becker, A.; Becker, A.; Plaja, L.

2013-07-01

99

Nonlinear distortion free fiber-based chirped pulse amplification with self-phase modulation up to 2pi.  

PubMed

We demonstrate the removal of 2pi radians of self-phase modulation (SPM) in a fiber-based chirped pulse amplification (CPA) system. Compensation of SPM distortion is achieved in the time domain by using a LiNbO(3) electro-optic phase modulator to emulate a negative nonlinear index of refraction. By synthesizing the drive waveform to the phase modulators with two RF frequencies that are phase-locked to the repetition rate of the seed laser, we achieve large phase compensations using cost-effective narrow band electronics. Our technique is simple, robust and can be readily integrated into existing fiber CPA systems. PMID:19532489

Zhu, Guanghao; Edinberg, Joel; Xu, Chris

2007-03-01

100

FM Radio Chip Antenna using Magneto-Dielectric  

Microsoft Academic Search

This paper proposes the internal FM radio chip antenna miniaturization using magneto-dielectric. New digital multimedia broadcasting service including FM is now available with the development of VHF band and is expected to offer diverse opportunities to mobile businesses. FM radio frequency band ranges between 87.5 MHz and 108 MHz. However FM antenna is too big to fit inside mobile devices

Jae-Kwon Park; Young-Hee Cho; Jung-Min Kim; Sung-Hyun Kim; Jin-Sam Yoo

2007-01-01

101

Accuracy issues for numerical waveforms  

NASA Astrophysics Data System (ADS)

We study the convergence properties of our implementation of the moving punctures approach at very high resolutions for an equal-mass, nonspinning, black-hole binary. We find convergence of the Hamiltonian constraint on the horizons and the L2 norm of the Hamiltonian constraint in the bulk for sixth- and eighth-order finite difference implementations. The momentum constraint is more sensitive, and its L2 norm shows clear convergence for a system with consistent sixth-order finite differencing, while the momentum and Baumgarte-Shapiro-Shibata-Nakamura (BSSN) constraints on the horizons show convergence for both sixth- and eighth-order systems. We analyze the gravitational waveform error from the late inspiral, merger, and ringdown. We find that using several lower-order techniques for increasing the speed of numerical relativity simulations actually lead to apparently nonconvergent errors. Even when using standard high-accuracy techniques, rather than seeing clean convergence, where the waveform phase is a monotonic function of grid resolution, we find that the phase tends to oscillate with resolution, possibly due to stochastic errors induced by grid refinement boundaries. Our results seem to indicate that one can obtain gravitational waveform phases to within 0.05 rad. (and possibly as small as 0.015 rad), while the amplitude error can be reduced to 0.1%. We then compare with the waveforms obtained using the CCZ4 formalism. We find that the CCZ4 waveforms have larger truncation errors for a given resolution, but the Richardson extrapolation phase of the CCZ4 and BSSN waveforms agrees to within 0.01 rad, even during the ringdown.

Zlochower, Yosef; Ponce, Marcelo; Lousto, Carlos O.

2012-11-01

102

FY05 FM Dial Summary Report  

SciTech Connect

Pacific Northwest National Laboratory's Infrared Sensors team is focused on developing methods for standoff detection of nuclear proliferation. In FY05, PNNL continued the development of the FM DIAL (frequency-modulated differential absorption LIDAR) experiment. Additional improvements to the FM DIAL trailer provided greater stability during field campaigns which made it easier to explore new locations for field campaigns. In addition to the Hanford Townsite, successful experiments were conducted at the Marine Science Laboratory in Sequim, WA and the Nevada Test Site located outside Las Vegas, NV. The range of chemicals that can be detected by FM DIAL has also increased. Prior to FY05, distributed feedback quantum cascade lasers (DFB-QCL) were used in the FM DIAL experiments. With these lasers, only simple chemicals with narrow (1-2 cm-1) absorption spectra, such as CO2 and N2O, could be detected. Fabry-Perot (FP) QC lasers have much broader spectra (20-40 cm-1) which allows for the detection of larger chemicals and a wider array of chemicals that can be detected. A FP-QCL has been characterized and used during initial studies detecting DMMP (dimethyl methylphosphonate).

Harper, Warren W.; Strasburg, Jana D.; Golovich, Elizabeth C.; Thompson, Jason S.; Stewart, Timothy L.; Batdorf, Michael T.

2005-12-01

103

FM fault location on short power cables  

Microsoft Academic Search

A method was developed for determining the fault distance on electrically short power cables using swept-frequency FM techniques. The method is based upon the observation that the envelope of the composite (transmitted plus reflected) signal at the sending end of the cable has the same pattern as the magnitude of the input impedance function of the cable over the range

K. Udomkiat

1974-01-01

104

Automating seismic waveform analysis for full 3-D waveform inversions  

NASA Astrophysics Data System (ADS)

We present a semi-automatic seismic waveform selection algorithm that can be used in full 3-D waveform inversions for earthquake source parameters and/or earth structure models. The algorithm is applied on pairs of observed and synthetic seismograms. A pair of observed and synthetic seismograms are first segmented in the wavelet domain into a number of wave packets using a topological watershed algorithm. A set of user-adjustable criteria based on waveform similarities is then applied to match each wave packet obtained from the observed seismogram with the corresponding wave packet obtained from the synthetic seismogram. The selected wave packet pairs are then used for extracting frequency-dependent phase and amplitude misfit measurements, which can be used in seismic source and/or structural inversions. The algorithm takes advantage of time-frequency representations of seismograms and is able to separate seismic phases in both time and frequency domains. We demonstrate the flexibility of this algorithm using examples of full 3-D waveform inversions for earthquake centroid moment tensors and earth structure models at different geographic scales.

Lee, En-Jui; Chen, Po

2013-07-01

105

Recent EISCAT heating results using chirped ISR  

Microsoft Academic Search

The chirp technique has recently become fully operational on the EISCAT UHF radar system and has been used for daytime observations of the HF-modified ionosphere over Ramfjordmoen in November 1992 and March 1993. During certain periods the UHF observations show a difference in the frequencies of the photoelectron-enhanced plasma line and the HF-enhanced plasma line (HFPL) similar to the one

B. Isham; C. La Hoz; H. Kohl; T. Hagfors; T. B. Leyser; M. T. Rietveld

1996-01-01

106

Fabrication technologies for chirped refractive microlens arrays  

NASA Astrophysics Data System (ADS)

Conventional microlens arrays consist of a repetitive arrangement of a unit cell on a fixed pitch. In a chirped array, the inflexibility of a regular structure has been overcome. Here, the array consists of individually shaped lenses which are defined by a parametric description of the cells optical function. We propose different fabrication methods for chirped microlens arrays and present experimentally obtained data. Reflow of photoresist is an established technology for the fabrication of microlenses with superior optical performance. For the generation of a chirped microlens array the photolithographic mask for patterning the resist to be melted has to be chirped. We present an algorithm for mask generation with an example of an ultra-thin camera objective. Inherent to the reflow process stringent limitations to viable surfaces apply. For achieving more arbitrary surfaces, laser lithography and also 2-photon polymerization are employed. In both methods the structures are decomposed into pixels. In laser lithography the local height is converted into an intensity value for the exposure. This variable dose writing locally changes the solubility of the resist in the development process leading to the required surface profile. We propose a writing scheme enabling structure heights of several ten microns with sufficient height discretization. 2-photon polymerization is a rapid prototyping method. Here, a small volume of a UV-curing organic-inorganic co-polymer is hardened in the tight focus of the writing beam. The volume pixel to be exposed is addressed by piezoelectric translation stages. Experimentally obtained structures and performed tests of the optical quality are presented.

Wippermann, F. C.; Radtke, D.; Zeitner, U.; Duparré, J. W.; Tünnermann, A.; Amberg, M.; Sinzinger, S.; Reinhardt, C.; Ovsianikov, A.; Chichkov, B. N.

2006-08-01

107

Chirp Transform in the Nonlinear Tracking Performance Analysis of the LMS Adaptive Predictors.  

National Technical Information Service (NTIS)

A chirp transform is defined for the A-step LMS adaptive predictors for linearly chirped signals embedded in additive white Gaussian noise. By converting the chirped signals to stationary baseband signals, this transform provides a different approach in a...

J. Han J. R. Zeidler W. H. Ku

2001-01-01

108

pathChirp: Efficient Available Bandwidth Estimation for Network Paths  

Microsoft Academic Search

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing

Les

2003-01-01

109

Advanced digital techniques for high bandwidth chirp generation  

NASA Astrophysics Data System (ADS)

A brief summary of important digital chirp generation (DCG) techniques is provided, with emphasis on two complementary methods - systolic and parallel digital chirp generation. These techniques provide an order of magnitude improvement in performance when compared with conventional digital chirp generation techniques implemented on the same technology. When implemented on the same technology, the systolic DCG yields a threefold improvement in performance. If used in conjunction with the parallel DCG, an order of magnitude performance is readily achievable. Combining the systolic DCG with the parallel method and using the chirp generator FPGA devices with a video digital to analog converter enables sample rates of 160 MHZ to be produced.

Parkes, S. M.

110

SAR processing with stepped chirps and phased array antennas.  

SciTech Connect

Wideband radar signals are problematic for phased array antennas. Wideband radar signals can be generated from series or groups of narrow-band signals centered at different frequencies. An equivalent wideband LFM chirp can be assembled from lesser-bandwidth chirp segments in the data processing. The chirp segments can be transmitted as separate narrow-band pulses, each with their own steering phase operation. This overcomes the problematic dilemma of steering wideband chirps with phase shifters alone, that is, without true time-delay elements.

Doerry, Armin Walter

2006-09-01

111

Chirped pulse amplification with a nonlinearly chirped fiber Bragg grating matched to the Treacy compressor.  

PubMed

We demonstrate a fiber chirped pulse amplification system that uses an engineered nonlinearly chirped fiber Bragg grating stretcher dispersion matched to the Treacy compressor. The seed pulses at 1558 nm are stretched to 720 ps, amplified by more than 50 dB to 6.5-microJ energy, and recompressed to 940 fs. After almost 1000 times compression the pulses are within 30% of the bandwidth limit and have a contrast ratio of better than 30 dB. PMID:15072356

Imeshev, G; Hartl, I; Fermann, M E

2004-04-01

112

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars  

NASA Astrophysics Data System (ADS)

We examine the signal processing of both linear and sinusoidal frequency modulation (FM) coherent ladar returns from resolved and unresolved targets, which are spread in Doppler. The Doppler spread may be due to target spin, tumbling, or vibration as well as to the applied linear or sinusoidal-FM on the transmitted E-field. Monte Carlo realizations of the target surface random phasor reflector elements interact with the incident Efield producing laser speckle, and the speckled returns are analyzed in this study. The speckle signals are processed (1) using several spectrum (periodogram based) estimators, (2) the conventional "spectrogram" approach, and (3) ten joint time-frequency transforms (JTFT). We show that the Born-Jordan JTFT is superior to the other spectral estimators tested here in suppressing local oscillator laser noise and accurately estimating the target"s spectrum for signal processing under speckle target return conditions pertaining to coherent laser radar. A new algorithm which sums particular pixels of the JTFT image is introduced and is shown to be much more robust in low CNR conditions than the JTFT maxima or JTFT centroid processing when utilizing the applied linear or sinusoidal-FM modulation waveform.

Youmans, Douglas G.

2003-09-01

113

Phenomenological gravitational waveforms from spinning coalescing binaries  

Microsoft Academic Search

An accurate knowledge of the coalescing binary gravitational waveform is crucial for experimental searches as the ones performed by the LIGO-Virgo collaboration. Following an earlier paper by the same authors we refine the construction of analytical phenomenological waveforms describing the signal sourced by generically spinning binary systems. The gap between the initial inspiral part of the waveform, described by spin-Taylor

R. Sturani; S. Fischetti; L. Cadonati; G. M. Guidi; J. Healy; D. Shoemaker; A. Vicere

2010-01-01

114

CERES (FM2) field campaigns of 2008  

NASA Astrophysics Data System (ADS)

A Clouds and the Earth's Radiant Energy System instrument (FM2) on board the Terra satellite has been used in field campaigns to provide TOA radiance measurements. Using a special programmable azimuth plan scan (PAPS) mode, a scanner collects data over a specified Earth target or of a prescribed spatial orientation. This paper covers operational aspects of four field campaigns in which FM2 participated in 2008. These include the annual CERES/GERB comparison campaign carried out at the summer and winter solstices, an aerosol campaign over Beijing ran before, during and after Summer Olympics, calibration and validation of GERB radiances at the ground station in Alacar/Spain, and also a bi-weekly true long-track scan for comparison to true nadir instruments.

Szewczyk, Z. Peter; Priestley, Kory J.

2009-09-01

115

Detailed spectroscopy of {sup 249}Fm  

SciTech Connect

Excited states in {sup 249}Fm were populated via the {alpha} decay of {sup 253}No and the subsequent decay was observed with the GABRIELA detection system installed at the focal plane of the VASSILISSA recoil separator. The energies, spins, and parities of these states could be established through combined {alpha},{gamma}, and conversion-electron spectroscopy. The first members of the ground-state rotational band were identified. Their excitation energies as well as the observation of a cross-over E2 transition confirm the assignment of 7/2{sup +}624 for the ground state of {sup 249}Fm. Two excited states were also observed and their decay properties suggest that they correspond to the particle excitation 9/2{sup -}734 and hole excitation 5/2{sup +}622. The analysis suggests that the 279-keV transition de-exciting the 9/2{sup -} state has anomalous E1 conversion coefficients.

Lopez-Martens, A.; Hauschild, K.; Briancon, Ch.; Korichi, A. [CSNSM, IN2P3-CNRS, F-91405 Orsay Campus (France); Yeremin, A. V.; Belozerov, A. V.; Chelnokov, M. L.; Chepigin, V. I.; Gorshkov, V. A.; Kabachenko, A. P.; Malyshev, O. N.; Oganessian, Yu. Ts.; Popeko, A. G.; Sagaidak, R. N.; Shutov, A. V.; Svirikhin, A. I. [FLNR, JINR, Dubna (Russian Federation); Curien, D.; Dorvaux, O.; Gall, B.; Khalfallah, F. [IPHC, IN2P3-CNRS, F-67037 Strasbourg (France)] (and others)

2006-10-15

116

Interfacing AM\\/FM with distribution SCADA  

Microsoft Academic Search

Union Electric Company (UE) decided to upgrade its existing distribution SCADA system and improve dispatching\\/operating efficiencies by interfacing it with UE's automated mapping and facility management (AM\\/FM) system, thus giving the dispatchers a way to relate facility outages geographically with a real-time monitoring system. This interfaced system will improve the efficiency in the management of UE's power distribution and the

M. A. Horton

1993-01-01

117

The chirp z-transform - A CCD implementation  

Microsoft Academic Search

The chirp z-transform is a signal processing algorithm that can efficiently evaluate the z-transform of a time sampled signal when implemented using charge-coupled devices. The charge-coupled-device chirp z-transform realizes significant hardware savings over alternative approaches to perform spectral analysis and has the potential of greater signal-processing flexibility.

G. J. Mayer

1975-01-01

118

The adaptive line enhancer applied to chirp detection  

NASA Astrophysics Data System (ADS)

This paper discusses the ability of an adaptive line enhancer (ALE) driven by the least-mean-squares (LMS) algorithm to track the frequency of a chirping signal in broadband noise. The dynamic behavior of the weights is described and a weight tracking error bound is derived in terms in chirp rate. Frequency tracking and weight behavior are illustrated in examples.

Elliott, Glenn R.; Stearns, Samuel D.

1990-02-01

119

Frequency-chirped readout of spatial-spectral absorption features  

SciTech Connect

This paper examines the physical mechanisms of reading out spatial-spectral absorption features in an inhomogeneously broadened medium using linear frequency-chirped electric fields. A Maxwell-Bloch model using numerical calculation for angled beams with arbitrary phase modulation is used to simulate the chirped field readout process. The simulation results indicate that any spatial-spectral absorption feature can be read out with a chirped field with the appropriate bandwidth, duration, and intensity. Mapping spectral absorption features into temporal intensity modulations depends on the chirp rate of the field. However, when probing a spatial-spectral grating with a chirped field, a beat signal representing the grating period can be created by interfering the emitted photon echo chirped field with a reference chirped field, regardless of the chirp rate. Comparisons are made between collinear and angled readout configurations. Readout signal strength and spurious signal distortions are investigated as functions of the grating strength and the Rabi frequency of the readout pulse. Using a collinear readout geometry, distortions from optical nutation on the transmitted field and higher-order harmonics are observed, both of which are avoided in an angled beam geometry.

Chang, Tiejun; Mohan, R. Krishna; Harris, Todd L.; Merkel, Kristian D. [Spectrum Laboratory, Montana State University, Bozeman, Montana 59717 (United States); Tian Mingzhen [Physics Department, Montana State University, Bozeman, Montana 59717 (United States); Babbitt, Wm. Randall [Spectrum Laboratory, Montana State University, Bozeman, Montana 59717 (United States); Physics Department, Montana State University, Bozeman, Montana 59717 (United States)

2004-12-01

120

Design of step-chirped fibre Bragg gratings  

Microsoft Academic Search

Unapodised and apodised 10 mm and 100 mm long step-chirped fibre Bragg gratings have been theoretically modeled as a function of the number of sections for the first time. It is shown that even with a relatively few sections, the reflectivity and dispersion characteristics approach that of a continuously chirped grating, improving dramatically with apodisation. Experimental results for a 200

Raman Kashyap

1997-01-01

121

On the group delay characteristics of chirped fibre Bragg gratings  

Microsoft Academic Search

It is shown for the first time that the group delay characteristics of chirped fibre Bragg gratings show a symmetry when measured from either direction. It is shown that the dispersion of a chirped grating cannot be completely compensated by another identical grating. This has implications on the quality of apodisation required for dispersion compensation.

Raman Kashyap; Monica de Lacerda Rocha

1998-01-01

122

Chirp on crickets: teaching compilers using an embedded robot controller  

Microsoft Academic Search

Traditionally, the topics of compiler construction and language processing have been taught as an elective course in Computer Science curricula. As such, students may graduate with little understanding or experience with the useful techniques embodied in modern compiler construction.In this paper, we present the design of Chirp, a language specification and compiler implementation. As a language, Chirp is based on

Li Xu; Fred G. Martin

2006-01-01

123

Chirp on crickets: teaching compilers using an embedded robot controller  

Microsoft Academic Search

Traditionally, the topics of compiler construction and lan- guage processing have been taught as an elective course in Computer Science curricula. As such, students may gradu- ate with little understanding or experience with the useful techniques embodied in modern compiler construction. In this paper, we present the design of Chirp, a language specification and compiler implementation. As a language, Chirp

Li Xu; Fred G. Martin

2006-01-01

124

Filter characteristics of a chirped volume holographic grating  

Microsoft Academic Search

We compare and analyze the filter properties of transmission-type volume holographic gratings, especially the dispersion characteristics for uniform and chirped gratings. It is theoretically and experimentally shown that the dispersion characteristics can be controlled by introducing one-dimensional chirping to the volume grating in a photorefractive crystal. The filter response including output power and dispersion comes from a combined effect of

Seunghoon Han; Bong-Ahn Yu; Seunghwan Chung; Hwi Kim; Jungwook Paek; Byoungho Lee

2004-01-01

125

Chirp: a practical global filesystem for cluster and Grid computing  

Microsoft Academic Search

Traditional distributed £lesystem technologies designed for local and campus area networks do not adapt well to wide area grid computing environments. To address this problem, we have designed the Chirp distributed £lesystem, which is designed from the ground up to meet the needs of grid computing. Chirp is easily deployed without special privileges, provides strong andexible security mechanisms, tunable consistency

Douglas Thain; Christopher Moretti; Jeffrey Hemmes

2009-01-01

126

Raman forward scattering of high-intensity chirped laser pulses  

SciTech Connect

Raman forward scattering of a high-intensity, short-duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatio-temporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all regimes of forward scattering, it is shown that the growth rate increases (decreases) for positive (negative) frequency chirp. The effect of chirp on the growth rate is relatively minor, i.e., a few percent chirp yields few percent changes in the growth rates. Relation of these results to recent experiments is discussed.

Schroeder, C.B.; Esarey, E.; Shadwick, B.A.; Leemans, W.P.

2002-06-23

127

CHIRPED PULSE AMPLIFICATION OF HGHG-FEL FACILITY AT BNL.  

SciTech Connect

The DUV-FEL facility has been in operation in High Gain Harmonic Generation (HGHG) mode for one year producing 266 nm output from 177 MeV electrons. In this paper we present preliminary results of the Chirped Pulse Amplification (CPA) of HGHG radiation. In the normal HGHG process, a 1 ps electron beam is seeded by chirped 9 ps long 800 nm Ti:Sapphire laser. The electron beam sees only a narrow fraction of the seed laser bandwidth. However, in the CPA case the seed laser pulse length is reduced to 1 ps, and the electron beam sees the full bandwidth. We introduce an energy chirp on electron beam to match the chirp of the seed pulse, enabling the resonant condition for the whole beam. We present measurements of the spectrum bandwidth for various chirp conditions.

DOYURAN,A.ET AL.

2003-09-08

128

Photodissociation of H+2 in intense chirped laser fields  

NASA Astrophysics Data System (ADS)

Regarding an experimental measurement of proton kinetic energy spectra of H+2 with a chirped pulse [L. J. Frasinski, J. H. Posthumus, J. Plumridge, and K. Colding, Phys. Rev. Lett. 83, 3625 (1999)], we present a nonperturbative, time-dependent calculation for the photodissociation of H+2 in intense laser fields by combining three numerical techniques. The results show a finer kinetic-energy distribution structure of a proton due to the intrapulse pump-dump mechanism between two electronic states as the pulse duration and intensity change. Higher-energy peaks are also suppressed by frequency chirping of the laser field. The dissociation probabilities show that a positively chirped pulse is always more efficient for population inversion than no chirping or negatively chirped pulses, and a slight coordinate shift of the initial state could result in a significant increase of dissociation probability.

Lin, J. T.; Jiang, T. F.

2001-01-01

129

Beam homogenizers based on chirped microlens arrays.  

PubMed

Lens array arrangements are commonly used for the homogenization of highly coherent laser beams. These fly's eye condenser configurations can be used to shape almost arbitrary input intensity distributions into a top hat. Due to the periodic structure of regular arrays the output intensity distribution is modulated by equidistant sharp intensity peaks which are disturbing the homogeneity. As a new approach we apply chirped microlens arrays to the beam shaping system. These are non-regular arrays consisting of individually shaped lenses defined by a parametric description which can be derived completely from analytical functions. The advantages of the new concept and design rules are presented. PMID:19546927

Wippermann, Frank; Zeitner, Uwe-D; Dannberg, Peter; Bräuer, Andreas; Sinzinger, Stefan

2007-05-14

130

Comparison of SCARAB FM1 and SCARAB FM2 calibration performances  

NASA Astrophysics Data System (ADS)

ScaRaB is a radiometer built to observe the Earth Radiation budget at the top of the atmosphere. This instrument has been produced by means of a joint program that gathers France, Russia and Germany. SCARAB has been planned to fill the gap between the flights of NASAs instruments ERB and CERS. Thus SCARAB mission is similar to the one fulfilled by ERB and CERES. SCARAB FM1 has been launched in January 1994. At the very beginning of the flight, a critical problem occurred on-board: three calibration lamps over 6 failed and were unusable for the rest of the mission. An alternative way of calibration was found that saved the mission. This method, explained in a previous paper, and its accuracy are briefly recalled in the article. FM2 has been launched in July 1998. The first data show a perfect functioning of the on-board calibration devices. It is an opportunity to test the 3 in-flight calibration methods developed: a method using on-board lamps and black-bodies as previously planned on FM1, another one using the dependence of gains to temperature as used on FM1, and a last one using only black body-simulators. After describing more in detail these different methods, a comparison of their performances is established. These results are compared with FM1 performances. Future prospects of the calibration are given in conclusion.

Tremas, Thierry; Dinguirard, Magdeleine C.; Duvel, Jean-Philippe; Raberanto, Patrick; Sirou, Francis E.

1999-09-01

131

47 CFR 74.1233 - Processing FM translator and booster station applications.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Processing FM translator and booster station applications...DISTRIBUTIONAL SERVICES FM Broadcast Translator Stations and FM Broadcast Booster...Stations § 74.1233 Processing FM translator and booster station...

2010-10-01

132

47 CFR 74.1233 - Processing FM translator and booster station applications.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Processing FM translator and booster station applications...DISTRIBUTIONAL SERVICES FM Broadcast Translator Stations and FM Broadcast Booster...Stations § 74.1233 Processing FM translator and booster station...

2009-10-01

133

47 CFR 74.1204 - Protection of FM broadcast, FM Translator and LP100 stations.  

Code of Federal Regulations, 2011 CFR

...translators, and Class D (secondary) noncommercial...it would result in new or increased overlap... (1) Commercial Class B FM Stations (Protected...station operating on a first, second or third...authorized co-channel, first, second or third...station, including Class D (secondary)...

2011-10-01

134

Propagation of chirped laser pulses in a plasma channel  

SciTech Connect

Propagation of an initially chirped, Gaussian laser pulse in a preformed parabolic plasma channel is analyzed. A variational technique is used to obtain equations describing the evolution of the phase shift and laser spot size. The effect of initial chirp on the laser pulse length and intensity of a matched laser beam propagating in a plasma channel has been analyzed. The effective pulse length and chirp parameter of the laser pulse due to its interaction with plasma have been obtained and graphically depicted. The resultant variation in laser frequency across the laser pulse is discussed.

Jha, Pallavi; Malviya, Amita; Upadhyay, Ajay K. [Department of Physics, University of Lucknow, Lucknow 226007 (India)

2009-06-15

135

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.

Williams, Anthony J.; Fuzessery, Zoltan M.

2012-01-01

136

Analysis of Q burst waveforms  

NASA Astrophysics Data System (ADS)

The electric field changes in ELF to VLF were observed with a ball antenna in fair weather at Kochi (latitude 33.3°N, longitude 133.4°E) during 2003-2004. Some 376 Q bursts were obtained, seven examples of which are analyzed in the present study. The continuous frequency spectra of the Q bursts and the background noises from 1.0 Hz to 11 kHz are compared, and it was found that the Q bursts prevail over the background in the frequency range from 1 to 300 Hz. The surplus is 20 dB (in amplitude) near the fundamental mode frequency. The "W"-type changes found in the initial portion of the Q burst waveforms are interpreted as the combined electromagnetic waveform of direct and antipodal waves from the causative lightning strokes. From the time intervals between the two waves, the source-receiver distances are estimated as far as 19 Mm. The pulses to excite the Schumann resonances in the Q bursts are clearly identified.

Ogawa, Toshio; Komatsu, Masayuki

2007-04-01

137

Paired Photons with Controllable Waveforms  

NASA Astrophysics Data System (ADS)

The major theme of this talk is the incorporation of electromagnetically induced transparency (EIT) with nonlinear optics in atoms to achieve efficient processes at low-light levels, particularly the generation and manipulation of correlated photon pairs. Entangled photons are an ideal tool for quantum information processing; they are now routinely used in experiments on quantum measurement, quantum teleportation, and quantum information processing. Principle limitations of existing sources of paired photons are two-fold. First, the wide bandwidth of paired photons encumbers resonant interactions with atoms, which is the most promising avenue for photon storage and quantum repeaters as well as for entanglement of atomic ensembles. Second, conventional paired photons' coherence length is prohibitively short for long-distance quantum communication. An experiment requiring the transmission of a simultaneous pair of photons over many kilometers necessitates a length difference of the transmitting fibers less than the coherence length of the spontaneous parametric source (˜30 ?m for traditional paired photons created in a BBO crystal). Electromagnetically induced transparency in cold atomic ensembles enables the creation of paired photons which decisively overcome these limitations. This talk will describe experiments and theory showing the generation of counterpropagating paired photons with waveforms that are controllable by using EIT to vary the optical group velocity. Typical waveform lengths are tens of nanoseconds.

Braje, Danielle

2006-05-01

138

Yb-doped chirped pulse amplification system  

NASA Astrophysics Data System (ADS)

A very compact, all diode pumped chirped pulse amplification system was developed based on Yb-doped gain materials. A passively mode-locked Yb:KYW oscillator in combination with a photonic crystal fiber was used to seed two different regenerative amplifiers. Energies up to 10mJ at 20Hz were obtained for cryo-cooled Yb:YLF and 6.5mJ between 10Hz and 30Hz for Yb:YAG at cryogenic temperatures also. For Yb:YAG it was possible to blue shift the spectrum of the oscillator to match the wavelength of the amplifier and the seed beam without using the non-linear fiber. The entire system (oscillator-stretcher-amplifier) has a footprint of less than 2m^2. After compression it should be possible to obtain amplified pulse duration of <8ps.

Furch, Federico; Reagan, Brendan; Luther, Bradley; Rocca, Jorge

2007-10-01

139

Wide-band superconductive Chirp filters  

SciTech Connect

Chirp filters are described that consist of miniature tapped superconductive stripline. The stripline consists of 40-micron-wide niobium thin films in a spiral pattern on 125-micron-thick silicon wafers, and tapping is effected by backward-wave couplers between neighboring lines. Sophisticated fabrication and packaging techniques have led to a now mature technology. Devices with 2.6-GHz bandwidth and time-bandwidth products of 98 are routinely fabricated that exhibit amplitude errors within a few tenths of a decibel and phase errors within a fractions of a degree of theoretical. In pulse-compression tests, matched amplitude-weighted devices yield peak relative side-lobe levels of -32 dB.

DiIorio, M.S.; Withers, R.S.; Anderson, A.C.

1989-04-01

140

Chirped pulse amplification: Present and future  

SciTech Connect

Short pulses with ultrahigh peak powers have been generated in Nd: glass and Alexandrite using the Chirped Pulse Amplification (CPA) technique. This technique has been successful in producing picosecond terawatt pulses with a table-top laser system. In the near future, CPA will be applied to large laser systems such as NOVA to produce petawatt pulses (1 kJ in a 1 ps pulse) with focused intensities exceeding 10/sup /plus/21/ W/cm/sup 2/. These pulses will be associated with electric fields in excess of 100 e/a/sub o//sup 2/ and blackbody energy densities equivalent to 3 /times/ 10/sup 10/ J/cm/sup 3/. This petawatt source will have important applications in x-ray laser research and will lead to fundamentally new experiments in atomic, nuclear, solid-state, plasma, and high-energy density physics. A review of present and future designs are discussed. 17 refs., 5 figs.

Maine, P.; Strickland, D.; Pessot, M.; Squier, J.; Bado, P.; Mourou, G.; Harter, D.

1988-01-01

141

Photon Counting Chirped AM Ladar: Concept, Simulation, and Experimental Results.  

National Technical Information Service (NTIS)

The operating principles and experimental results for the Army Research Laboratory's (ARL's) patented chirped amplitude modulation (AM) ladar using linear response detectors have been presented and published previously, and will be briefly summarized here...

B. Redman M. Giza W. Ruff

2006-01-01

142

Chirp and polarization control of femtosecond molecular fragmentation  

PubMed Central

We explore the simultaneous effect of chirp and polarization as the two control parameters for non-resonant photo-dissociation of n-propyl benzene. Experiments performed over a wide range of laser intensities show that these two control knobs behave mutually exclusively. Specifically, for the coherently enhanced fragments (C3H3+, C5H5+) with negatively chirped pulses and C6H5+ with positively chirped pulses, polarization effect is the same as compared to that in the case of transform-limited pulses. Though a change in polarization affects the overall fragmentation efficiency, the fragmentation pattern of n-propyl benzene molecule remains unaffected in contrast to the chirp case.

Goswami, T; Das, D K; Kumar, S K Karthick; Goswami, D

2013-01-01

143

Raman Forward Scattering of High-Intensity Chirped Laser Pulses  

Microsoft Academic Search

Raman forward scattering of a high-intensity, short-duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatiotemporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all

C. B. Schroeder; E. Esarey; B. A. Shadwick; W. P. Leemans

2002-01-01

144

Waveform extraction for perfect reconstruction in WI coding  

Microsoft Academic Search

A signal model used in waveform interpolation (WI) coding assumes implicitly that the pitch period remains constant within a waveform to be extracted. This assumption is utilized for determining waveform boundaries and for forming the discrete Fourier transform (DFT) of the extracted waveform. Therefore, the waveforms do not describe the original signal faithfully during pitch changes even if an accurate

V. T. Ruoppila; M. Tammi; J. Saarinen

2000-01-01

145

Techniques for High-Bandwidth (?30 GHz) Chirped-Pulse Submillimeter-Wave Spectroscopy  

NASA Astrophysics Data System (ADS)

Due to the increased availability of active multiplier chains for converting microwave pulses into the millimeter/submillimeter with reasonably high power (?1 mW), chirped pulses with high phase stability and complete arbitrary waveform generator (AWG) frequency agility can be created and employed for high-sensitivity molecular spectroscopy, as demonstrated at the Symposium in the past few years. The bandwidths of multiplier chains, however, can exceed the current limitations on digitizer bandwidth. Therefore, in order to obtain ?30 GHz spectra in ~1 ms or less, techniques are being developed in which a two-channel AWG creates both the chirped pulses for molecular irradiation and a local oscillator pulse for heterodyne detection. These approaches reduce the digitizer bandwidths to 500 MHz or less to collect a high-bandwidth spectrum. A single instrument design can be used to measure both absorption and emission spectra, only requiring that the AWG pulses are changed. Due to the phase stability of the pulse generation and detection, coherent time-domain signal averaging can be performed to enhance sensitivity as desired. Preliminary results from prototype instruments designed at UVa and NIST will be presented, with sensitivity, frequency accuracy, and measurement speed comparisons to current millimeter/submillimeter-wave spectrometers. G.B. Park, A.H. Steeves, K. Kuyanov-Prozument, A.P. Colombo, R.W. Field, J.L. Neill, and B.H. Pate, RH07, 64th International Symposium on Molecular Spectroscopy (2009) K.O. Douglass, D.F. Plusquellic, and E. Gerecht, WH09, 65th International Symposium on Molecular Spectroscopy (2010).

Neill, Justin L.; Steber, Amanda L.; Harris, Brent J.; Pate, Brooks H.; Douglass, Kevin O.; Plusquellic, David F.; Gerecht, Eyal

2011-06-01

146

Propagation effects of isolated attosecond pulse generation with a multicycle chirped and chirped-free two-color field  

SciTech Connect

We present a theoretical study of isolated attosecond pulse generation with a multicycle chirped and chirped-free two-color field. We show that the bandwidth of the extreme ultraviolet supercontinuum can be extended by combining a multicycle chirped pulse and a multicycle chirped-free pulse. Also, the broadband supercontinuum can still be generated when the macroscopic effects are included. Furthermore, the macroscopic effects can ameliorate the temporal characteristic of the broadband supercontinuum of the single atom, and eliminate the modulations of the broadband supercontinuum. Thus a very smooth broadband supercontinuum and a pure isolated 102-as pulse can be directly obtained. Moreover, the structure of the broadband supercontinuum can be steadily maintained for a relative long distance after a certain distance.

Du Hongchuan; Hu Bitao [School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000 (China)

2011-08-15

147

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

148

Principal component analysis of lifting waveforms  

Microsoft Academic Search

Background. One limiting factor in lifting research design has been the inability to effectively analyze waveform data, especially when differences in body mass, height, and load magnitude influence the derived kinetic variables. The purpose of this study was to demon- strate the sensitivity of principal component analysis to quantify clinically relevant differences in kinetic lifting waveforms over three load magnitudes

Allan T. Wrigley; Wayne J. Albert; Kevin J. Deluzio; Joan M. Stevenson

2006-01-01

149

Passive Bistatic Radar (PBR) using FM radio illuminators of opportunity  

Microsoft Academic Search

We present a system characterisation of a passive bistatic radar (PBR). The system under investigation exploits dasiailluminators of opportunitypsila, which in this case are commercial, non-cooperative, VHF FM broadcast transmissions. The PBR under investigation demonstrates the detection of large passenger-jet aircraft in the airspace over greater London. FM based PBRs such as the type examined here have been shown to

D. W. O'Hagan; C. J. Baker

2008-01-01

150

Error Rates for Digital Signals Demodulated by an FM Discriminator  

Microsoft Academic Search

The calculation of the error rate resulting from the detection of binary frequency shift keyed (FSK) signals using an FM discriminator low-pass filter detector is described. An example is given using an alternating mark space sequence and the results compared with those obtained using a matched filter. The results indicate that in certain regions the FM discriminator low-pass filter detector

D. Schilling; E. Hoffman; E. Nelson

1967-01-01

151

Synthesis and pilot plant production of FM-1.  

National Technical Information Service (NTIS)

Lawrence Livermore National Laboratory (LLNL) has developed a material called FM-1, which is a liquid explosive sometimes used as a plasticizer in explosive formulations. FM-1 is comprised of three formals: FEFO (l brace)1,1(prime)-(methylenebis(oxy))bis(...

C. L. Coon E. von Holtz R. E. Whipple

1992-01-01

152

Basic examination of the FM ultrasonic flowmeter for gas  

Microsoft Academic Search

The construction of an ultrasonic gas flowmeter is difficult because the attenuation of ultrasonic waves and the effects of acoustic noises are considerably higher for gas than for liquid. The sound field of the proposed meter is stabilized by FM ultrasonic wave; however, the receiver eliminates the FM components. Therefore, the flow rate can be measured using a single frequency

T. Saitou; S. Tanisawa; H. Hirose

2002-01-01

153

Error Rate of PCM-FM Using Discriminator Detection  

Microsoft Academic Search

The probability of error is derived for a PCM-FM system that uses a discriminator as a detector. It is shown that discriminator performance is approximately 1 db poorer than optimum detection of a PCM-FM signal. The results compare favorably with experimental measurments conducted elsewhere.

PAUL D. SHAFTt

1963-01-01

154

FM Receivers in Automobiles: a Case for Deiversity Reception  

Microsoft Academic Search

The inconsistent quality of FM reception in automobiles is a major impediment to the well-deserved growth of this important medium. Although FM inherently has the potential for high- fidelity performance and has become a significant competitor to AM broad- casting to the home, it cannot hope to achieve full parity with AM until it can also successfully reach the auto-

Robert A. Finger; Emil Torick

1981-01-01

155

Wavelength-spacing-tunable multichannel filter incorporating a sampled chirped fiber Bragg grating based on a symmetrical chirp-tuning technique without center wavelength shift.  

PubMed

We propose and experimentally demonstrate a simple and flexible scheme for a wavelength-spacing-tunable multichannel filter exploiting a sampled chirped fiber Bragg grating based on a symmetrical modification of the chirp ratio. Symmetrical bending along a sampled chirped fiber Bragg grating attached to a flexible cantilever beam induces a variation of the chirp ratio and a reflection chirp bandwidth of the grating without a center wavelength shift. Accordingly, the wavelength spacing of a sampled chirped fiber Bragg grating is continuously controlled by the reflection chirp bandwidth variation of the grating corresponding to the bending direction, which allows for realization of an effective wavelength-spacing-tunable multichannel filter. Based on the proposed technique, we achieve the continuous tunability of the wavelength spacing in a range from 1.51 to 6.11 nm, depending on the bending direction of the cantilever beam. PMID:17130906

Han, Young-Geun; Dong, Xinyong; Lee, Ju Han; Lee, Sang Bae

2006-12-15

156

FD-CHIRP: hosted payload system engineering lessons  

NASA Astrophysics Data System (ADS)

The Commercially Hosted Infrared Payload (CHIRP) Flight Demonstration (FD-CHIRP) launched 21 Sept 2011 was designated a "resounding success" as the first Wide Field-of-View (WFOV) staring infrared (IR) sensor flown in geostationary earth orbit (GEO) with a primary mission of Missile Warning (MW). FD-CHIRP was an Air Force research and development project initiated in July 2008 via an unsolicited industry proposal aimed to mature and reduce the risk of WFOV sensors and ground processing technologies. Unlike the Defense Support Program (DSP) and the Space Based Infrared System (SBIRS) which were acquired via traditional integrated sensor and satellite design, FDCHIRP was developed using the "commercially hosted" approach. The FD-CHIRP host spacecraft and sensor were independently designed, creating significant development risk to the industry proposer, especially under a Firm Fixed Price contract. Yet, within 39 months of contract initiation, FD-CHIRP was launched and successfully operated in GEO to 30 June 2012 at a total cost of 111M including the 82.9M CHIRP commercial-hosting contract and a $28M sensor upgrade. The commercial-hosting contract included sensor and spacecraft modifications, integration and test, design and development of secure Mission Operations and Analysis Centers, launch, and nearly a year of GEO operations with 70 Mbps secure data acquisition. The Air Force extended the contract for six months to continue operations through the end of calendar 2012. This paper outlines system engineering challenges FD-CHIRP overcame and key lessons to smooth development of future commercially hosted missions.

Schueler, Carl F.

2012-10-01

157

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

158

Quantum fluctuations in the chirped pendulum  

NASA Astrophysics Data System (ADS)

Anharmonic oscillators, such as the pendulum, are widely used for precision measurement and to model nonlinear phenomena. Fluctuations-such as thermal or quantum mechanical noise-can excite random motion in the oscillator, ultimately imposing a bound on measurement sensitivity. In systems where equilibrium is established with the environment, noise-induced broadening scales with the intensity of fluctuations. But how does noise affect an out-of-equilibrium oscillator where the motion is varied faster than energy is exchanged with the environment? We create such a scenario by applying fast, frequency-chirped voltage pulses to a nonlinear superconducting resonator where the ring-down time is longer than the pulse duration. Under these conditions, the circuit oscillates with either small or large amplitude depending on whether the drive voltage is below or above a critical value. This phenomenon, known as autoresonance, is significant in planetary dynamics and plasmas, enables the excitation of particles in cyclotron accelerators and may even be used to detect the state of a quantum two-level system. Our results show that the amplitude of fluctuations determines the initial conditions of such a non-equilibrium oscillator and does not affect its time evolution.

Murch, K. W.; Vijay, R.; Barth, I.; Naaman, O.; Aumentado, J.; Friedland, L.; Siddiqi, I.

2011-02-01

159

Elliptic waveforms for inspiralling compact binaries  

NASA Astrophysics Data System (ADS)

The inspiral of supermassive black hole binary systems with high orbital eccentricity are the most promising sources for the gravitational wave observatories. The importance of elliptic gravitational waveforms in various physical scenarios has been emphasized by several authors (Wahlquist 1987, Moreno-Garrido, Buitrago and Mediavilla 1994, Martel and Poisson 1999). Taking into account the eccentricity of the orbit in the total waveform improves the parameter estimation for these sources, as it is shown by the construction and analyzation of the Fisher information matrix. In our work we use the Fourier-Bessel analysis of the Kepler motion and the stationary phase approximation of time-depend waveforms.

Mikóczi, Balázs

2010-03-01

160

Quantum dynamical calculations of ultracold collisions induced by nonlinearly chirped light  

NASA Astrophysics Data System (ADS)

We describe quantum dynamical calculations of ultracold 85Rb trap-loss collisions induced by pulses of light whose frequency is chirped on the nanosecond time scale. The chirped light excites the ground-state collisional wave function to the long-range attractive potential and escape from the trap is modeled by an absorbing boundary at short range. Both positive and negative chirps are considered and various chirp shapes and detunings are examined. For positive chirps, the loss rates are rather independent of the chirp shape. Negative chirps, on the other hand, show a dependence on chirp shape for detunings where collisional flux can be coherently returned to the ground state. These trends are consistent with the results of a recent experiment.

Carini, J. L.; Pechkis, J. A.; Rogers, C. E., III; Gould, P. L.; Kallush, S.; Kosloff, R.

2012-01-01

161

THE EFFECT OF ACOUSTIC SIGNALS ON THE CHIRP RHYTHM IN THE BUSH CRICKET PHOLIDOPTERA GRISEOAPTERA  

Microsoft Academic Search

SUMMARY The effect of acoustic signals on the control of chirp production has been investigated using the insect's own chirp to trigger artificial sound signals (100 msec, 7odB, 12 or 15 kHz) at predetermined phases of the chirp cycle. The signals appear to reset the phase of the chirp rhythm generator, and sig- nals given late in the cycle are

M. D. R. JONES

1974-01-01

162

Stability and Efficiency of Waveform Relaxation Methods.  

National Technical Information Service (NTIS)

We investigate the behavior of Waveform Relaxation (WR) methods for some model problems. First it is shown how convergence (of the iteration) is related to stability of some one-step integration schemes. Then we investigate the computational complexity of...

J. K. M. Jansen R. M. M. Mattheij M. T. M. Penders W. H. A. Schilders

1993-01-01

163

Developments in IRS Multi-Mode Waveforms  

NASA Astrophysics Data System (ADS)

The IRS picture [Baker et al. PRD 78:044046 (2008); Kelly et al. 84:084009 (2011)] visualises black-hole-binary late-inspiral/merger/ringdown gravitational waveforms as being generated by a single rotating source, with most important waveform angular modes being locked in phase through merger into ringdown. This led to the development of late-merger/ringdown waveform templates for the dominant modes of the binary for nonspinning black holes, and for holes with aligned (non-precessing) spins. During development of the IRS model, it was noticed that certain subdominant modes --- most notably the (3,2) mode --- suffered from non-monotonic bumps in both frequency and amplitude, indicative of some kind of mode-mixing behavior. We report on the resolution of this ``bumpy'' behavior, and of consequent developments to the IRS waveforms across multiple significant angular modes.

Kelly, Bernard; Baker, John

2013-04-01

164

Waveform Relaxation Applied to Transient Device Simulation,  

National Technical Information Service (NTIS)

This paper investigates the possibility of accelerating the transient simulation of Metal Oxide Semiconductor devices by using waveform relaxation. Standard spatial discretization techniques are used to generate a large, sparsely-connected system of algeb...

M. Reichelt J. White J. Allen F. Odeh

1988-01-01

165

Tuning of external-cavity semiconductor lasers with chirped diffraction gratings  

Microsoft Academic Search

We present a novel scheme of tunable semiconductor laser based on the use of a chirped grating in an external cavity. The chirped grating is fabricated using a simple holographic technique: two Gaussian beams having wavefronts with different radii of curvature are brought to interfere on a photoresist layer. The tuning properties of chirped gratings have been investigated with semiconductor

Marc Duval; Gilles Fortin; Michel Piché; Nathalie McCarthy

2005-01-01

166

Synchrony during acoustic interactions in the bushcricket Mecopoda ‘Chirper’ (Tettigoniidae:Orthoptera) is generated by a combination of chirp-by-chirp resetting and change in intrinsic chirp rate  

Microsoft Academic Search

In several bushcricket species, individual males synchronise their chirps during acoustic interactions. Synchrony is imperfect\\u000a with the chirps of one male leading or lagging the other by a few milliseconds. Imperfect synchrony is believed to have evolved\\u000a in response to female preferences for leading chirps. We investigated the mechanism underlying synchrony in the bushcricket\\u000a species Mecopoda ‘Chirper’ from Southern India

Vivek Nityananda; Rohini Balakrishnan

2007-01-01

167

Effects of collisions on energetic particle-driven chirping bursts  

NASA Astrophysics Data System (ADS)

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.

2013-05-01

168

Chirped-cavity dispersion-compensation filter design  

NASA Astrophysics Data System (ADS)

A new basic structure of a dispersive-compensation filter, called a chirped-cavity dispersion-compensator (CCDC) filter, was designed to offer the advantages of small ripples in both reflectance and group-delay dispersion (GDD). This filter provides a high dispersion compensation, like the Gires-Tournois interferometer (GTI) filter, and a wide working bandwidth, like the chirped mirror (CM). The structure of the CCDC is a cavity-type Fabry-Perot filter with a spacer layer (2 mH or 2 mL) and a chirped high reflector. The CCDC filter can provide a negative GDD of -50 fs2 over a bandwidth of 56 THz with half the optical thickness of the CM or the GTI.

Li, Ya-Ping; Chen, Sheng-Hui; Lee, Cheng-Chung

2006-03-01

169

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

170

Chirped Gaussian laser beam parameters in paraxial approximation  

SciTech Connect

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. [Department of Physics, Science Faculty, Mazandaran University, Babolsar, Mazandaran 47416-1467 (Iran, Islamic Republic of)

2010-08-15

171

Chirped pulse inverse free-electron laser vacuum accelerator  

DOEpatents

A chirped pulse inverse free-electron laser (IFEL) vacuum accelerator for high gradient laser acceleration in vacuum. By the use of an ultrashort (femtosecond), ultrahigh intensity chirped laser pulse both the IFEL interaction bandwidth and accelerating gradient are increased, thus yielding large gains in a compact system. In addition, the IFEL resonance condition can be maintained throughout the interaction region by using a chirped drive laser wave. In addition, diffraction can be alleviated by taking advantage of the laser optical bandwidth with negative dispersion focusing optics to produce a chromatic line focus. The combination of these features results in a compact, efficient vacuum laser accelerator which finds many applications including high energy physics, compact table-top laser accelerator for medical imaging and therapy, material science, and basic physics.

Hartemann, Frederic V. (Dublin, CA); Baldis, Hector A. (Pleasanton, CA); Landahl, Eric C. (Walnut Creek, CA)

2002-01-01

172

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

173

Measurement of interior ballistic performance using FM/FM radio telemetry techniques  

NASA Astrophysics Data System (ADS)

The continuous measurement of ballistic performance during the interior ballistic cycle of cannon launched projectiles is important to on-going research programs being conducted at the Ballistic Research Laboratory (BRL). These measurements, such as propelling gas pressure, projectile acceleration, and projectile-bore interactions, are necessary to evaluate existing weapon systems and validate newly formulated interior ballistic models. Of particular interest is the resistance to projectile motion and the behavior of the projectile during the engraving process. The measurement of forces on projectiles and projectile-bore interactions requires that transducers be located on-board the projectile. In-bore measurements of ballistic performance are made at the BRL using an FM/FM, S-band telemeter. Standard artillery projectiles are modified and instrumented with telemetry transmitting systems. These projectiles are test fired and data extracted via the real time telemetry link. The projectile systems are expendable free-flight rounds and those modified for recovery in the BRL Large Caliber Soft Recovery System (LCSRS). The instrumentation package for the recoverable rounds is configured so it can be removed from the projectile, recalibrated after exposure to the launch environment, and used on subsequent rounds.

Evans, J. W.

1985-12-01

174

Gravitational waves from inspiraling compact binaries: Parameter estimation using second-post-Newtonian waveforms  

NASA Astrophysics Data System (ADS)

The parameters of inspiraling compact binaries can be estimated using matched filtering of gravitational-waveform templates against the output of laser-interferometric gravitational-wave detectors. The estimates are most sensitive to the accuracy with which the phases of the template and signal waveforms match over the many cycles received in the detector frequency bandwidth. Using a recently calculated formula, accurate to second post-Newtonian (2PN) order [order (v/c)4, where v is the orbital velocity], for the frequency sweep (dF/dt) induced by gravitational radiation damping, we study the statistical errors in the determination of such source parameters as the ``chirp mass'' scrM, reduced mass ?, and spin parameters ? and ? (related to spin-orbit and spin-spin effects, respectively). We find that previous results using template phasing accurate to 1.5PN order actually underestimated the errors in scrM, ?, and ?. Templates with 2PN phasing yield somewhat larger measurement errors because the 2PN corrections act to suppress slightly the importance of spin-orbit contributions to the phase, thereby increasing the measurement error on ?. This, in turn, results in larger measurement errors on scrM and ? because of the strong correlations among the parameters. For two inspiraling neutron stars, the measurement errors increase by less than 16%.

Poisson, Eric; Will, Clifford M.

1995-07-01

175

Monolithic optical parametric oscillator using chirped quasi-phase matching  

NASA Astrophysics Data System (ADS)

We describe a highly efficient monolithic, Q-switched, nanosecond optical parametric oscillator based on a magnesium-oxide-doped periodically poled lithium niobate crystal and containing multiple quasi-phase-matched gratings. The crystal consisted of a single unchirped grating and five gratings containing progressively increasing amounts of longitudinal chirp. The monolithic design makes the device highly compact, stable, and robust, and it demonstrated a pump-to-signal conversion efficiency of around 50%, generating 50 ?J pulses at 1.55 ?m with a spectral bandwidth of 20 nm. Sonogram traces are presented showing the effect of crystal chirp on the temporal and spectral performance.

Tillman, Karl A.; Reid, Derryck T.

2007-06-01

176

Chirped gratings for efficient coupling into nonlinear waveguides  

NASA Astrophysics Data System (ADS)

The efficiency of chirped gratings used as couplers for nonlinear optics interactions in waveguide geometries was demonstrated. A uniform periodicity grating with a chirp rate of about 0.004 over a 2-mm-long grating was fabricated using the procedure of Xu Mai et al. (1985). Coupling efficiency for this grating illuminated with a 2-mm-diam laser beam at a wavelength of 0.515 micron showed an optimum of about 29 percent (a large value even for a linear coupler) occurring near 1500 mW input power.

Moshrefzadeh, R.; Svensson, B.; Xu, Mai; Seaton, C. T.; Stegeman, G. I.

1987-08-01

177

Effects of frequency chirp on magnetron injection locking  

SciTech Connect

The injection locking of a magnetron is theoretically analyzed when either the free running oscillator or the drive signal has a frequency chirp. It is found that complete phase locking of the signal cannot be achieved in either case. However, as long as the locking condition of Adler is well-satisfied instantaneously, a high degree of locking occurs during a major duration of the frequency chirps. The expected output phase variation is computed in terms of the noise in the free-running magnetron oscillator for the case of constant drive frequency.

Pengvanich, P.; Lau, Y. Y.; Luginsland, J. W.; Gilgenbach, R. M.; Cruz, E. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Schamiloglu, E. [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

2008-07-15

178

Chirped-pulse amplification of laser pulses with dispersive mirrors.  

PubMed

We report a novel implementation of chirped-pulse amplification (CPA) by dominantly using dispersive multilayer mirrors for chirp control. Our prototyp dispersive-mirror (DMC) compressor has been designed for a kHz Ti:sapphire amplifier and yielded--in a proof-of-concept study--millijoule-energy, sub-20-fs, 790-nm laser pulses with an overall throughput of approximately 90% and unprecedented spatio-temporal quality. Dispersive-mirror-based CPA permits a dramatic simplification of high-power lasers and affords promise for their advancement to shorter pulse durations, higher peak powers, and higher average powers with user-friendly systems. PMID:20372657

Pervak, V; Ahmad, I; Trushin, S A; Major, Zs; Apolonski, A; Karsch, S; Krausz, F

2009-10-12

179

Nanostrain measurement using chirped Bragg grating Fabry-Perot interferometer  

NASA Astrophysics Data System (ADS)

A simple nanostrain direct current (DC) measurement system based on a chirped Bragg grating Fabry-Perot (FP) structure is presented. The FP cavity, formed between the chirped fiber Bragg grating (CFBG) and the fiber end face, presents an aperiodic behavior due to the CFBG. A laser located in the fringe pattern slope is used to interrogate the sensing head. The optical power parameter is analyzed when strain is applied, for long and short period fringe pattern wavelengths, and sensitivities of -2.87 ?W/?? and -5.48 ?W/?? are respectively obtained. This configuration presents a resolution of 70 n?.

Silva, Ricardo M.; Ferreira, Marta S.; Santos, José L.; Frazão, Orlando

2012-03-01

180

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

Federal Register 2010, 2011, 2012, 2013

...SUMMARY: The Audio Division seeks comments on a petition filed by Canyon Media Group, LLC, authorized assignee of Station KCLS(FM), Channel 269C2, Pioche, Nevada, requesting the substitution of Channel 288C for vacant Channel...

2010-04-14

181

22. August, 1971. GV fm signals showing old & new ...  

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

22. August, 1971. GV fm signals showing old & new cutoff in distance-also track car. - Southern Pacific Railroad, Ogden-Lucin Cutoff Trestle, Spanning Great Salt Lake, Brigham City, Box Elder County, UT

182

Spontaneous fission of Fm isotopes in the HFB framework  

NASA Astrophysics Data System (ADS)

The multi-dimensional potential energy surface has been calculated for Fm isotopes with A=240-266 in the HFB framework. The spontaneous fission half-lives have been compared with the experimental data.

Warda, M.; Egido, J.; Robledo, L.

2006-07-01

183

75 FR 41092 - FM TABLE OF ALLOTMENTS, Kingsland, Texas  

Federal Register 2010, 2011, 2012, 2013

...right to hearing, if found by the Commission to be necessary in order to conform to the 1992 USA-Mexico FM Broadcast Agreement.'' DATES: Effective August 12, 2010. ADDRESSES: Federal Communications Commission, 445 12th Street, SW,...

2010-07-15

184

59. Credit FM. Flood waters on South Battle Creek next ...  

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

59. Credit FM. Flood waters on South Battle Creek next to powerhouse. Note height of water in relation to tailraces. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

185

47 CFR 73.310 - FM technical definitions.  

Code of Federal Regulations, 2010 CFR

... BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast...modulation where the instantaneous radio frequency varies in proportion...used) and the instantaneous radio frequency is independent of...sound broadcasting. Cross-talk. An undesired signal...

2009-10-01

186

When hearing aids go bad: an FM success story.  

PubMed

Both clinical and research findings support the effectiveness of frequency-modulated (FM) technology among individuals who continue to encounter significant communication problems despite the use of conventional hearing instruments. The use rate of FM devices throughout the nation, however, remains disappointingly low. The authors present a case of a longtime hearing aid user whose hearing aids provided decreasing benefit as his hearing impairment increased to the extent that cochlear implantation was considered. Through the establishment of patient-specific treatment goals, the provision of appropriate FM technology as verified through real-ear measurements, and careful and deliberate counseling and follow-up, this patient was able to realize significant communication benefits as reported through several self-assessment measures. The cost-benefit implications of FM technology versus cochlear implantation are discussed. PMID:16515133

McArdle, Rachel; Abrams, Harvey B; Chisolm, Theresa Hnath

187

47 CFR 73.310 - FM technical definitions.  

Code of Federal Regulations, 2010 CFR

... BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast...modulation where the instantaneous radio frequency varies in proportion...used) and the instantaneous radio frequency is independent of...sound broadcasting. Cross-talk. An undesired signal...

2010-10-01

188

47 CFR 73.310 - FM technical definitions.  

Code of Federal Regulations, 2011 CFR

...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast...operation (e.g., where tower work necessitates turning off the main...modulation where the instantaneous radio frequency varies in...

2011-10-01

189

47 CFR 73.310 - FM technical definitions.  

Code of Federal Regulations, 2012 CFR

...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast...operation (e.g., where tower work necessitates turning off the main...modulation where the instantaneous radio frequency varies in...

2012-10-01

190

76. Credit FM. Detail showing belts running from water wheel ...  

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

76. Credit FM. Detail showing belts running from water wheel to governor and from water wheel to tachometer (foreground). - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

191

Analysis in the instantaneous frequency forms of a chirped laser pulse  

SciTech Connect

We analyze two forms of the instantaneous frequency of a linearly chirped laser pulse. Using a 3D test particle simulation, numerical results are presented for electrons accelerated by a chirped laser pulse with these two linearly chirped forms of the instantaneous frequency. We summarize that the linearly chirped frequency, {omega}(t)={omega}{sub 0}[1-{alpha}(t-z/c)] is reasonable, {omega}{sub 0} is laser frequency at z=0 and t=0, and {alpha} is the frequency chirp parameter.

Yuan, C. J.; Wu, X. Y.; Wang, P. X. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education, China and Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433 (China); Wang, J. X. [State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China)

2011-10-15

192

SEASONAL AND DAILY CHIRPING CYCLES IN THE NORTHERN SPRING AND FALL FIELD CRICKETS, GRYLLUS VELETIS AND G. PENNSYLVANICU S1  

Microsoft Academic Search

In southeastern Michigan, Gryllus veletis chirps from mid-May until early August, barely or not at all overlapping with its sympatric sibling, G. pennsylvanicus, which chirps from early August until mid-November. When nights are warm, both species chirp chiefly at night; when nights are cold, they chirp solely by day. SEASONAL RELATIONSHIP OF ADULT POPULATIONS

RICHARD D. ALEXANDER; GERALD H. MERAL

193

Interpolation in waveform space: Enhancing the accuracy of gravitational waveform families using numerical relativity  

NASA Astrophysics Data System (ADS)

Matched filtering for the identification of compact object mergers in gravitational wave antenna data involves the comparison of the data stream to a bank of template gravitational waveforms. Typically the template bank is constructed from phenomenological waveform models, since these can be evaluated for an arbitrary choice of physical parameters. Recently it has been proposed that singular value decomposition (SVD) can be used to reduce the number of templates required for detection. As we show here, another benefit of SVD is its removal of biases from the phenomenological templates along with a corresponding improvement in their ability to represent waveform signals obtained from numerical relativity (NR) simulations. Using these ideas, we present a method that calibrates a reduced SVD basis of phenomenological waveforms against NR waveforms in order to construct a new waveform approximant with improved accuracy and faithfulness compared to the original phenomenological model. The new waveform family is given numerically through the interpolation of the projection coefficients of NR waveforms expanded onto the reduced basis and provides a generalized scheme for enhancing phenomenological models.

Cannon, Kipp; Emberson, J. D.; Hanna, Chad; Keppel, Drew; Pfeiffer, Harald P.

2013-02-01

194

Influence of nonideal chirped fiber grating characteristics on dispersion cancellation  

Microsoft Academic Search

The effect of nonideal dispersion and reflection characteristics of chirped fiber gratings on the performance of 10-Gb\\/s nonreturn-to-zero-transmission systems operating over standard fiber is investigated. The system penalty for different amplitude and period ripples are quantified. Analyses of an experimental grating confirm that current fabrication technology can meet the requirements for <1-dB-penalty operation

K. Ennser; M. Ibsen; M. Durkin; M. N. Zervas; R. I. Laming

1998-01-01

195

A monolithic 512 point chirp Z transform processor  

Microsoft Academic Search

A monolithic analog 512 point chirp Z transform processor which calculates the discrete time Fourier transform will be described. A 6.1 × 5.5mm N-channel MOS chip includes premultiply, convolution and postmultiplication functions. Dynamic range of 63dB with operation from 1kHz to 1.5MHz has been measured.

Robert C. Pettengill; Patrick W. Bosshart; Michiel de Wit; C. Robert Hewes

1979-01-01

196

Chirp Z-transform spectral zoom optimization with MATLAB  

Microsoft Academic Search

The MATLAB language has become a standard for rapid prototyping throughout all disciplines of engineering because the environment is easy to understand and use. Many of the basic functions included in MATLAB are those operations that are necessary to carry out larger algorithms such as the chirp z-transform spectral zoom. These functions include, but are not limited to mathematical operators,

Grant D

2005-01-01

197

Spectral analysis using the CCD Chirp Z-transform  

Microsoft Academic Search

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.

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

1978-01-01

198

High resolution Wigner distribution using chirp Z-transform analysis  

Microsoft Academic Search

The chirp Z-transform is used in the Wigner distribution for high resolution spectrum analysis. It has the capability to zoom onto the area of the signal of interest, which makes it a very useful spectral analysis tool for analyzing nonstationary time-varying signals. This capability results in a more reliable and accurate spectral analysis on the time-frequency plane

Soo-Chang Pei; Ing-Ing Yang

1991-01-01

199

Segmented chirp Z-transform and its applications  

Microsoft Academic Search

The segmented chirp Z-transform (SCZT) algorithm introduced, and its mathematical derivation is described. Only a small FFT is used to assist the implementation; hence, the algorithm can handle a very large amount of input data with very limited memory space. In an example of a frequency spectrum calculation the SCZT is able to handle 30K input data, whereas the regular

T. T. Wang

1989-01-01

200

Transform domain adaptive filtering with the chirp Z transform  

Microsoft Academic Search

The use of the chirp Z transform (CZT) is proposed to improve the rate of convergence of transform domain adaptive output error algorithms. The use of the CZT is novel and is shown to possess advantages over the DFT. Other attempts at incorporating prior knowledge of input spectra use frequency sampling structures and their generalizations. Such structures require pole-zero cancellation,

Andrew W. Hull; W. Kenneth Jenkins

1990-01-01

201

Voltage Flicker Detection Based on Chirp-z Transform  

Microsoft Academic Search

Studying of the IEC flicker meter shows that the instantaneous flicker sensation level S can be calculated directly if the spectrums of fluctuating component of voltage are known. In this paper a novel flicker measurement method is proposed. First, the square demodulation is used to obtain the fluctuating component of voltage, and then the chirp-z transform (CZT) is used to

Kang Wei; Guo Jing; Li Heming; Yan Xiangwu

2010-01-01

202

Mechanism of inverted-chirp infrasonic radiation from sprites  

Microsoft Academic Search

Farges and Blanc (2010) reported inverted-chirp infrasonic signals with high frequencies arriving before low frequencies, possibly emitted by sprite discharges and observed on the ground at close range (<100 km) from the source. In the present work a parallel version of a 2-D FDTD model of infrasound propagation in a realistic atmosphere is applied to demonstrate that the observed morphology

Sebastien de Larquier; Victor P. Pasko

2010-01-01

203

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

204

Chirped fiber Bragg grating sensor based on phase delay  

Microsoft Academic Search

A novel design of linearly chirped fiber Bragg grating (LCFBG) based sensor, operating at a single optical wavelength and avoiding the complicated interrogation, is presented and demonstrated. The LCFBG exhibits a good linear relation between the group delay and the wavelength. When a pulsed optical signal goes through the LCFBG with a fixed wavelength within the grating bandwidth, it will

Qizhen Sun; Deming Liu; Hairong Liu; Li Xia; Ping Shum

2007-01-01

205

A Novel Chirp Slope Keying Modulation Scheme for Underwater Communication  

Microsoft Academic Search

A digital modulation method using Chirp-Slope Keying (CSK) is developed for coherent underwater acoustic communications. Effective signal detection is a critical stage in the implementation of any communications system; we will see that CSK solves some significant challenges to reliable detection. This thesis is primarily based on analyzing the effectiveness of CSK through simulations using Matlab's Simulink for underwater communications.

Lastri Simanjuntak

2004-01-01

206

Experience of using the Chirp distributed file system in ATLAS  

NASA Astrophysics Data System (ADS)

Chirp is a user-level file system specifically designed for the wide area network, and developed by the University of Notre Dame CCL group. We describe the design features making it particularly suited to the Grid environment, and to ATLAS use cases. The deployment and usage within ATLAS distributed computing are discussed, together with scaling tests and evaluation for the various use cases.

Walker, Rodney; Nilsson, Paul

2012-12-01

207

Analysis of the Rayleigh-Plesset equation with chirp excitation  

NASA Astrophysics Data System (ADS)

The case of a bubble being insonified by an ultrasonic excitation in the form of a linear chirp is considered here. The dynamical equation of the bubble's motion is solved analytically and compared to a numerical solution. The analytical solution is then used to investigate the problem of maximizing the amplitude of the second harmonic with respect to the various system and signal parameters.

Barlow, Euan; Mulholland, Anthony J.; Gachagan, Anthony; Nordon, Alison; MacPherson, Kenneth

2009-02-01

208

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

209

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

210

Improving service delivery in FM: case study of a UK hospital facilities directorate  

Microsoft Academic Search

Purpose – The purpose of this paper is to describe a case study of SPICE FM implementation in the Facilities Directorate of a major UK hospital. SPICE FM is a process improvement framework for FM organisations, which was developed through university research in the UK. SPICE FM identified strengths and weaknesses of the facilities operation and provides specific guidelines for

M. Sarshar

2006-01-01

211

Performance improvement of CMA based FM multipath cancelling system in automobile application  

Microsoft Academic Search

Constant Modulus Algorithm (CMA) is widely applied to improve distorted transmitting radio signal at the receiver. FM radio is still very popular equipment for in-car entertainment. Therefore, correcting FM multipath distortion on conventional FM radio system is one of the greatly expected applications of CMA technique. In this paper, we discuss performance and improvement of the CMA based FM multipath

Masaichi Akiho; Tsuguhide Aoki; Kiyonori Takahashi; Miki Haseyama

2008-01-01

212

FM systems as primary amplification for children with profound hearing loss.  

PubMed

The use of FM systems as primary amplification for children with severe and profound hearing loss is discussed. The FM advantage for improving speech perception and for reducing the detrimental effects of distance, noise, and reverberation is described. Both hypothetical and actual cases are used to demonstrate the FM advantage. An evaluation method for selecting an appropriate FM system is described. PMID:1601190

Madell, J R

1992-04-01

213

Pharmacotherapy in fibromyalgia (FM)--implications for the underlying pathophysiology.  

PubMed

Although chronic pain states are highly prevalent, the underlying neurobiological mechanisms involved in causing pain are incompletely understood. This is especially true for the so-called chronic functional pain syndromes and pain syndromes of unknown origin, such as fibromyalgia (FM), in which no structural correlates of pain experience, in terms of a nociceptive source, can clearly be defined. In addition to limited therapeutic options and often unsatisfactory treatment, such patients often struggle with socio-medical acceptance of their pain condition. As FM has become more widely recognized, options available for treatment have grown along with our understanding of the neurobiological mechanisms underlying chronic pain experience and concomitant symptoms. The current review aims to provide an overview of existing pharmacotherapies for FM, and their implication for the underlying pathophysiology. Further we discuss some of the potential targets that have been recently identified that may hold promise for the development of novel treatments. PMID:20388527

Schmidt-Wilcke, T; Clauw, D J

2010-04-11

214

Design of AM/FM mobile telephone triband antenna  

NASA Astrophysics Data System (ADS)

In vehicles, antennas for AM/FM broadcasting (BC) and cellular mobile telephone (MT) are usually mounted on the car's body. However, a triband antenna which can be used for both AM/FM BC and MT is more desirable to decrease the number of antennas. An outline of the general design for the AM/FM MT triband antenna with coils is described. Next, the design of a new triband antenna with double sleeves instead of coils is presented. The double sleeves consist of two coaxial lines connected in series. It is shown that the triband antenna with double sleeves has good characteristics, including radiation patterns and voltage standing-wave ratio (VSWR).

Egashira, Shigeru; Tanaka, Takayuki; Sakitani, Akihide

1994-04-01

215

Waveform Moment Methods for Improved Interconnection Analysis  

Microsoft Academic Search

This paper describes a circuit analysis program aimed at quickly solving linear interconnection circuits with inductance and coupling. It computes circuit responses to varying degrees of detail, varying from a simple Elmore delay to a good waveform estimate. Allowable circuit forms are much more flexible than for existing Elmore delay algorithms. Large networks or distributed lines can be reduced to

Steven Paul Mccormick; Jonathan Allen

1990-01-01

216

Periodicity of the waveform of lunar seismograms  

NASA Astrophysics Data System (ADS)

The present analysis deals with the spectral composition of the waveform envelope of lunar seismograms, obtained at the Apollo ground station network for impacts of burnt-out rocket stages on the lunar surface. Eight impact events are studied, and curves showing the time-behavior of the squared amplitude of the envelope of seismic vibrations are given and discussed.

Galkin, I. N.; Nikolaev, A. V.; Khavroshkin, O. B.; Tsyplakov, V. V.

1980-07-01

217

Pareto-optimal radar waveform design  

Microsoft Academic Search

This paper deals with the problem of Pareto-optimal waveform design in the presence of colored Gaussian noise, under a similarity and an energy constraint. At the design stage, we determine the optimal radar code according to the following criterion: joint constrained maximization of the detection probability and constrained minimization of the Cramer Rao Lower Bound (CRLB) on the Doppler estimation

A. De Maio; M. Piezzo; A. Farina; M. Wicks

2010-01-01

218

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 Green’s 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 Green’s 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

219

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

220

Radar Waveform Optimization for Colored Noise Mitigation.  

National Technical Information Service (NTIS)

Waveform optimization is a technique that can be used to adjust any or all of the radar transmitter degrees of freedom (DoFs) based on observations of a dynamic environment caused by intentional and/or unintentional interference sources. These DoFs includ...

J. E. Don Carlos J. R. Guerci J. S. Bergin P. M. Techau

2005-01-01

221

Cognitive Radio Testbed and LPI, LPD Waveforms  

Microsoft Academic Search

This paper will introduce a cognitive radio testbed and associated technologies that have been developed by Northrop Grumman. The cognitive radio testbed is based on an internally developed hardware platform to create waveforms on demand over a broad spectral space. This advanced communication device employs a newly developed algorithm that exploits spectrum opportunities to create low-probability of interception and detection

A. J. Petrin; P. M. Markus; J. R. Pfeiffenberger; R. Palkki; D. Jaeger; P. Ring

2006-01-01

222

Neutron multiplicity at spontaneous fission of 246Fm  

NASA Astrophysics Data System (ADS)

The neutron-deficient isotope 246Fm , produced in the complete fusion reaction 40Ar + 208Pb , was investigated. The main goal of the experiment was to determine the neutron multiplicity at spontaneous fission of this isotope. For experiments aimed at the study of spontaneous fission of transfermium nuclei improvements in the focal plane detector system of recoil separator VASSILISSA have been made. A neutron detector consisting of 54 3He -filled counters has been mounted around the focal-plane detector chamber. From the experimental data the average number of neutrons per spontaneous fission of 246Fm was determined ( bar{{?}} = 3.55±0.5).

Svirikhin, A. I.; Dushin, V. N.; Chelnokov, M. L.; Chepigin, V. I.; Izosimov, I. N.; Katrasev, D. E.; Malyshev, O. N.; Minkova, A.; Popeko, A. G.; Sokol, E. A.; Yeremin, A. V.

2010-06-01

223

FM-laser operation of the Nd:YAG laser  

Microsoft Academic Search

The FM-laser or frequency-sweeping mode of laser oscillation has been demonstrated in a Nd :YAG 1.06-? laser with an intracavity LiNbO3phase modulator. The experimental results are in excellent agreement with the theoretical expressionDelta= (DeltaOmega\\/Deltanu) (delta\\/pi)where ?= peak single-pass phase retardation in the modulator,DeltaOmega= axial mode spacing,Deltanu=modulator detuning, and ?=resulting FM index of the laser output. Modulation indices as large asDelta

D. Kuizenga; A. Siegman

1970-01-01

224

FM amplification for enhancement of conversational discourse skills: case study.  

PubMed

The purpose of this single-subject pilot study was to examine the efficacy of FM amplification for enhancing the discourse skills of a 4-year-old girl with a history of speech-language impairments, otitis media with effusion (OME), and motoric delays. Over a period of several weeks, language treatment sessions were conducted with and without FM amplification, in a classroom setting. Sessions were videotaped and analyzed for the appropriateness and effectiveness of the subject's conversational turns during sessions with amplification and with no amplification. Although the number of sessions was small, more appropriate and effective conversational turns occurred during sessions with amplification. PMID:7620200

Clarke-Klein, S M; Roush, J; Roberts, J E; Davis, K; Medley, L

1995-05-01

225

Phase series echography with prior waveform distortion for evaluating posterior waveform distortion.  

PubMed

We describe a pulse-echo ultrasound method for measuring nonlinear waveform distortion. First, two artificially distorted ultrasound pulses, one of which is transformed into the other by using a linear transform, are prepared prior to the measurement. The linear relationship does not hold for nonlinear propagation. Second, different initial-phase versions of the two pulses are separately transmitted to a specimen one after another, then the echoes with the same turnaround time are placed in order of the initial phase. The placed echoes, called a phase series, have complete information on the posterior waveform distortion. We formulate a waveform distortion index by using these two techniques. The waveform distortion index has a monotonic increasing relationship with the nonlinear parameter B/A. As an example application, we performed tissue characterization of boiled eggs. As a result, egg whites and yolks were clearly distinguished. This method should be useful for biological tissue characterization. PMID:17091838

Matani, Ayumu; Shigeno, Takayuki

2006-11-01

226

Waveform calibration strategies for a small-footprint laser scanner  

NASA Astrophysics Data System (ADS)

Waveform calibration is a crucial task in the processing of full-waveform laser scanner data. In most cases, there is a non-linear relationship between the "raw" waveform data stored by the sensor system and the actual input power. However, to establish standardized methods for the post processing of waveform data, input data related linearly to the power input are required. For some commercially available systems, this problem is handled by using a look-up table (LUT) as a transfer function from the "raw" amplitude (stored by the sensor system) of the peaks of the waveforms to their actual amplitude. Since the transformation is only valid for the peaks of the waveform, the question arises how this transformation would perturbate the shape (i.e. position, width and amplitude) of a backscattered laser pulse if applied to the whole waveform. This paper discusses the effects of the use of such non-linear transfer functions on complex laser scanner waveforms.

Roncat, Andreas; Wagner, Wolfgang; Melzer, Thomas; Ullrich, Andreas

2008-10-01

227

Synchrony during acoustic interactions in the bushcricket Mecopoda 'Chirper' (Tettigoniidae:Orthoptera) is generated by a combination of chirp-by-chirp resetting and change in intrinsic chirp rate.  

PubMed

In several bushcricket species, individual males synchronise their chirps during acoustic interactions. Synchrony is imperfect with the chirps of one male leading or lagging the other by a few milliseconds. Imperfect synchrony is believed to have evolved in response to female preferences for leading chirps. We investigated the mechanism underlying synchrony in the bushcricket species Mecopoda 'Chirper' from Southern India using playback experiments and simulations of pairwise interactions. We also investigated whether intrinsic chirp period is a good predictor of leading probability during interactions between males. The mechanism underlying synchrony in this species differs from previously reported mechanisms in that it involves both a change in the oscillator's intrinsic rate and resetting on a chirp-by-chirp basis. The form of the phase response curve differs from those of previously reported firefly and bushcricket species including the closely related Malaysian species Mecopoda elongata. Simulations exploring oscillator properties showed that the outcome of pairwise interactions was independent of initial phase and alternation was not possible. Solo intrinsic chirp period was a relatively good predictor of leading probability. However, changing the intrinsic period during interactions could enable males with longer periods to lead during acoustic interactions. PMID:16983544

Nityananda, Vivek; Balakrishnan, Rohini

2006-09-16

228

ATOMIC AND MOLECULAR PHYSICS: Ionization of atoms by chirped attosecond pulses  

NASA Astrophysics Data System (ADS)

We investigate the ionization dynamics of atoms by chirped attosecond pulses using the strong field approximation method. The pulse parameters are carefully chosen in the regime where the strong field approximation method is valid. We analyse the effects of the chirp of attosecond pulses on the energy distributions and the corresponding left-right asymmetry of the ionized electrons. For a single chirped attosecond pulse, the ionized electrons can be redistributed and the left-right asymmetry shows oscillations because of the introduction of the chirp. For time-delayed double attosecond pulses at different intensities with the weaker one chirped, exchanging the order of the two pulses shows a relative shift of the energy spectra, which can be explained by the different effective time delays of different frequency components because of the chirp.

Tan, Fang; Peng, Liang-You; Gong, Qi-Huang

2009-11-01

229

Dense monoenergetic proton beams from chirped laser-plasma interaction.  

PubMed

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 (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). PMID:22107638

Galow, Benjamin J; Salamin, Yousef I; Liseykina, Tatyana V; Harman, Zoltán; Keitel, Christoph H

2011-10-27

230

Excitation of the Morse oscillator by an ultrashort chirped pulse  

SciTech Connect

The excitation of the classic Morse oscillator by an ultrashort electromagnetic pulse with a linear frequency chirp is studied theoretically. Formulas are derived for the oscillation amplitude and the radiation power averaged over a period as functions of the excitation energy for free oscillations of the Morse oscillator. Analytical expressions for describing the oscillator motion after the end of the pulse are obtained in the harmonic limit. In the general case of arbitrary parameters of the problem, the specific features of an excited Morse oscillator are analyzed numerically. Prominence is given to the effect of chirp on the excitation energy. The consideration is performed in terms of dimensionless variables, which makes it possible to apply the results obtained to a wide range of molecular systems and exciting-pulse parameters.

Astapenko, V. A., E-mail: astval@mail.ru; Romadanovskii, M. S. [Moscow Institute of Physics and Technology (Russian Federation)

2010-03-15

231

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

232

Study of chirped pulse amplification based on Raman backscattering  

NASA Astrophysics Data System (ADS)

Raman backscattering (RBS) in plasma is an attractive source of intense, ultrashort laser pulses, which has the potential asa basic for a new generation of laser amplifiers.1 Taking advantage of plasma, which can withstand extremely high power densities and can offer high efficiencies over short distances, Raman amplification in plasma could lead to significant reductions in both size and cost of high power laser systems. Chirped laser pulse amplification through RBS could be an effective way to transfer energy from a long pump pulse to a resonant counter propagating short probe pulse. The probe pulse is spectrally broadened in a controlled manner through self-phase modulation. Mechanism of chirped pulse Raman amplification has been studied, and features of supperradiant growth associated with the nonlinear stage are observed in the linear regime. Gain measurements are briefly summarized. The experimental measurements are in qualitative agreement with simulations and theoretical predictions.

Yang, X.; Vieux, G.; Lyachev, A.; Farmer, J.; Raj, G.; Ersfeld, B.; Brunetti, E.; Wiggins, M.; Issac, R.; Jaroszynski, D. A.

2009-05-01

233

Excitation of Rydberg wave packets with chirped laser pulses  

NASA Astrophysics Data System (ADS)

We study Rydberg wave packets produced by pairs of time separated femtosecond laser pulses. The time separation ranges from femtosecond to picosecond time scales. The wave packets consist predominantly of f states of principal quantum numbers n=22-32 in Li. With a direct analysis of the field ionization spectra the n-level-resolved classical orbit times are displayed. By chirping the second excitation pulse we demonstrate controlled amplitude oscillations of n-level amplitudes on femtosecond time scales.

Preclíková, J.; Kozák, M.; Fregenal, D.; Frette, Ø.; Hamre, B.; Hjertaker, B. T.; Hansen, J. P.; Kocbach, L.

2012-12-01

234

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

235

The chirp-Z transform applied to adhesively bonded structures  

Microsoft Academic Search

A signal-processing technique based on the chirp-Z transform is presented to evaluate the echo signals of longitudinal ultrasonic transducers in contact with bonded materials. Both a simulated glass-glass interface of variable thickness and a realistic double lap bonded aluminum sample were tested. The observed frequency dips and peaks in the transducer spectrum from pulse-echo and through-transmission modes were recorded and

Vinod K. Nair; Reinhold Ludwig; Robert F. Anastasi

1991-01-01

236

Development and application of a SAW Chirp-Z transformer  

Microsoft Academic Search

A development is reported in which the Chirp-z transform algorithm is truncated to perform spectral amplitude analysis. The basic process is described in relation to a unit giving in excess of one hundred resolved spectral lines with a resolution of 50kHz and a total processing time of 50 microseconds per data set. The displayed spectrum covers a dynamic range in

M. B. N. Butler

1978-01-01

237

An optimized SAW chirp -Z Transform for OFDM systems  

Microsoft Academic Search

The OFDM system that can use it combined to the Fourier transform to the OFDM signal for amount of wave of the inverse Fourier transform and received OFDM can have a definite advantage in power consumption, a super-high-speed operation processing performance be possessed, and the SAW chirp-Z transform be applied to high-speed wireless LAN and WAN. As for the SAW

Takaya Watanabe

2009-01-01

238

Application of the chirp z-transform to MRI data  

Microsoft Academic Search

A version of the chirp z-transform (CZT) enabling signal intensity and phase-preserving field-of-view scaling has been programmed. The algorithm is important for all single-point imaging sequences such as SPRITE when used with multiple data acquisition for T2? mapping or signal averaging. CZT has particular utility for SPRITE imaging of nuclei with short relaxation times such as sodium at high field.

J. Kaffanke; T. Dierkes; S. Romanzetti; M. Halse; J. Rioux; M. O. Leach; B. Balcom; N. J. Shah

2006-01-01

239

Multimillijoule chirped parametric amplification of few-cycle pulses  

Microsoft Academic Search

The concept of optical parametric chirped-pulse amplification is applied to attain pulses with energies up to 8 mJ and a bandwidth of more than 100 THz. Stretched broadband seed pulses from a Ti:sapphire oscillator are amplified in a multistage noncollinear type I phase-matched beta-barium borate parametric amplifier by use of an independent picosecond laser with lock-to-clock repetition rate synchronization. Partial

N. Ishii; L. Turi; V. S. Yakovlev; T. Fuji; F. Krausz; A. Baltuska; R. Butkus; G. Veitas; V. Smilgevicius; R. Danielius; A. Piskarskas

2005-01-01

240

Chirping a two-photon transition in a multistate ladder  

SciTech Connect

We consider a two-photon transition in a specific ladder system driven by a chirped laser pulse. In the weak field limit, we find that the excited state probability amplitude arises due to interference of multiple quantum paths which are weighted by quadratic phase factors. The excited state population has the form of a Gauss sum which plays a prominent role in number theory.

Merkel, Wolfgang; Mack, Holger; Schleich, Wolfgang P.; Lutz, Eric; Paulus, Gerhard G.; Girard, Bertrand [Institut fuer Quantenphysik, Universitaet Ulm, Albert-Einstein-Allee 11, D-89081 Ulm (Germany) and Department of Physics, Universitaet Augsburg, D-86135 Augsburg (Germany) and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States) and Laboratoire de Collisions, Agregats et Reactivite - UMR 5589, CNRS-Universite Paul Sabatier Toulouse 3, IRSAMC, Toulouse (France)

2007-08-15

241

Complete phenomenological gravitational waveforms from spinning coalescing binaries  

Microsoft Academic Search

The quest for gravitational waves from coalescing binaries is customarily performed by the LIGO-Virgo collaboration via matched filtering, which requires a detailed knowledge of the signal. Complete analytical coalescence waveforms are currently available only for the non-precessing binary systems. In this paper we introduce complete phenomenological waveforms for the dominant quadrupolar mode of generically spinning systems. These waveforms are constructed

R. Sturani; S. Fischetti; L. Cadonati; G. M. Guidi; J. Healy; D. Shoemaker; A. Viceré

2010-01-01

242

Adaptive Prony method for waveform distortion detection in power systems  

Microsoft Academic Search

IEC Standards characterize the waveform distortions in power systems with the amplitudes of harmonic and interharmonic groupings (subgroups and groups) calculated by using the waveform spectral components obtained with a 5Hz frequency resolution DFT. In some cases the power system waveforms are characterized by means of spectral signal components that the DFT with 5Hz frequency resolution is unable to capture

A. Bracale; P. Caramia; G. Carpinelli

2007-01-01

243

Reduction of energy chirp by the wake of coherent synchrotron radiation  

NASA Astrophysics Data System (ADS)

When an energy-chirped bunch is undercompressed in a magnetic chicane, the compressed bunch also has an energy chirp. The chirp may be decreased by sending the bunch through bending magnets, since the largest energy loss from the wake of coherent synchrotron radiation occurs in the tail of a typical bunch. We obtain formulas for the dechirping of a rectangular bunch by short magnets, and apply this dechirping technique in a design for a free-electron laser.

Bosch, R. A.

2010-11-01

244

Research on Cascaded Chirp Fiber Bragg Grating in Quasi-linear Optical Transmission System  

NASA Astrophysics Data System (ADS)

A Cascaded chirp fiber Bragg grating has been theoretical analyzed by using coupled mode equations and transfer matrix method. As a dispersion compensator, a wide bandwidth, big dispersion value, and low delay ripple cascaded chirp fiber Bragg grating is designed for a 200 km 8 × 160 Gbit/s high speed quasi-linear optical transmission system. The system Q value of 7.15˜8.74 demonstrates the success of the design of the cascaded chirp fiber Bragg grating.

Cai, Ju; Bai, Qiujian; Su, Xin

2013-09-01

245

Pharmacotherapy in fibromyalgia (FM) — Implications for the underlying pathophysiology  

Microsoft Academic Search

Although chronic pain states are highly prevalent, the underlying neurobiological mechanisms involved in causing pain are incompletely understood. This is especially true for the so-called chronic functional pain syndromes and pain syndromes of unknown origin, such as fibromyalgia (FM), in which no structural correlates of pain experience, in terms of a nociceptive source, can clearly be defined. In addition to

T. Schmidt-Wilcke; D. J. Clauw

2010-01-01

246

Power Spectrum of Binary FM Signal with Additional AM  

Microsoft Academic Search

Formulas are derived for the power spectral density function of a sinusoidal carrier, frequency modulated by a random baseband pulse train in which the signaling interval equalsT. The signal pulses of duration2Toverlap. In the analysis presented different shapes of the signal pulses are approximated by staircase functions. Variations of the instantaneous frequency of the binary FM signal are accompanied by

P. Szulakiewicz

1979-01-01

247

75 FR 13236 - FM Table of Allotments, Port Angeles, Washington  

Federal Register 2010, 2011, 2012, 2013

...RM-11481] FM Table of Allotments, Port Angeles, Washington AGENCY: Federal Communications...Channel 271A for vacant Channel 229A at Port Angeles, Washington. DATES: Effective March...that the channel substitution at Port Angeles serves the public interest because...

2010-03-19

248

Neutron Multiplicity At Spontaneous Fission Of 246Fm  

NASA Astrophysics Data System (ADS)

For experiments aimed at the study of spontaneous fission of transfermium nuclei improvements in the focal plane detector system of recoil separa tor VASSILISSA have been made. The neutron detector consisting of 54 3He -filled counters has been mounted around the focal plane detector chamber. The multiplicity of prompt neutrons emitted in spontaneous fission of 246 Fm was measured.

Svirikhin, A. I.; Yeremin, A. V.; Chelnokov, M. L.; Chepigin, V. I.; Izosimov, I. V.; Katrasev, D. E.; Malyshev, O. N.; Minkova, A.; Popeko, A. G.; Sokol, E. A.

2010-04-01

249

Neutron multiplicity at spontaneous fission of 246Fm  

NASA Astrophysics Data System (ADS)

For experiments aimed at the study of spontaneous fission of transfermium nuclei improvements in the focal plane detector system of recoil separator VASSILISSA have been made. The neutron detector consisting of 54 3He-filled counters has been mounted around the focal plane detector chamber. The multiplicity of prompt neutrons emitted in spontaneous fission of 246Fm was measured.

Svirikhin, A. I.; Yeremin, A. V.; Chelnokov, M. L.; Chepigin, V. I.; Izosimov, I. V.; Katrasev, D. E.; Malyshev, O. N.; Minkova, A.; Popeko, A. G.; Sokol, E. A.

2009-10-01

250

75 FR 65521 - FM Approvals; Expansion of Recognition  

Federal Register 2010, 2011, 2012, 2013

...following informational Web page: http://www.osha.gov/dts/otpca/nrtl/fm.html. OSHA recognition of an NRTL signifies...available from the Web site at http://www.osha.gov/dts/otpca/nrtl/index.html. Each NRTL's scope of...

2010-10-25

251

On radar polarimetry in FM-CW radar  

Microsoft Academic Search

This paper attempts to apply the principle of radar polarimetry to wideband synthetic aperture FM-CW radar and presents a basic polarimetric detection result of a linear target in a laboratory measurement. Although the principle of radar polarimetry has well been established for the completely polarized wave and for the monostatic case, it still needs to be extended to wideband radar

Y. Yamaguchi; T. Nishikawa; W.-M. Boerner; M. Sengoku; Hyo Joon Eom

1993-01-01

252

Frequency Response Characteristics of FM Mini-Loop Auditory Trainers.  

ERIC Educational Resources Information Center

|Five commercially available hearing aids were assessed in two settings: using hearing aid test equipment available in most audiology clinics, with the hearing aid on microphone setting; and in a public school classroom, with the hearing aid on telecoil setting and operating with an FM classroom amplification system and a personally sized…

Van Tasell, Dianne; Landin, Deborah P.

1980-01-01

253

Speech Processing Applications Using AN Am-Fm Modulation Model.  

NASA Astrophysics Data System (ADS)

In this thesis, the AM-FM modulation speech model and multiband demodulation are applied to speech analysis and coding. The AM-FM model represents the speech signal as a sum of amplitude modulated (AM) and frequency modulated (FM) signals, each AM-FM signal models a single speech resonance (formant). The model is able to describe a wide range of nonlinear and time-varying phenomena during speech production. Multiband demodulation is the proposed speech analysis method in the context of the AM-FM model. A bank of Gabor filters is used to filter the speech signal and, then, a demodulation algorithm is applied on each band to obtain the amplitude envelope and instantaneous frequency signals. The energy separation algorithm (ESA) and the Hilbert transform approach are compared for signal and speech resonance demodulation, and the ESA is found to have better time-resolution and to be computationally more efficient. Next, we apply multiband demodulation analysis (MDA) to formant and pitch tracking. Using the amplitude envelope and instantaneous frequency signals short-time estimates are proposed for the formant frequency and the fundamental frequency. The merits of the estimates are evaluated and it is concluded that the amplitude weighted mean instantaneous frequency and the short-time phase slope perform best for formant and pitch estimation respectively. Finally, decision algorithms are provided for the formant and pitch contours. Both speech analysis algorithms provide very smooth and accurate estimates and have attractive time -domain parallel implementations. Next, we use time-varying MDA for a speech coding application. A time-varying Gabor filterbank extracts four formant bands from the signal and, then, each resonance is demodulated to amplitude envelope and instantaneous frequency signals. Efficient modeling and coding schemes are proposed for the information signals that exploit the correlation between the formant bands. Finally, speech is synthesized as the sum of the reconstructed formant bands. The AM-FM analysis-synthesis system produces speech of very natural quality. Currently, the vocoder operates in the 4.8-9.6 kbits/sec range. Future applications of these modeling/coding ideas include text-to-speech synthesis and speaker identification. Overall, the AM-FM modulation model and multiband demodulation analysis are a general nonlinear approach to speech processing with a wide range of successful applications.

Potamianos, Alexandros

1995-01-01

254

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

NASA Astrophysics Data System (ADS)

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

2005-08-01

255

Uncompensated antiferromagnetic moments in Mn-Ir/FM (FM = Ni-Co, Co-Fe, Fe-Ni) bilayers: Compositional dependence and its origin  

NASA Astrophysics Data System (ADS)

Ferromagnetic (FM) material dependence of the uncompensated (UC) antiferromagnetic (AF) moments in AF/FM exchange biased bilayers has been studied using the x-ray magnetic circular dichroism technique in the AF/FM (AF = ?-Mn-Ir, FM = Ni-Co, Co-Fe, Fe-Ni) bilayers. The direction and magnitude of the UC-Mn moment change significantly when the composition of the FM layer changes. The crystal structure of the FM layer affects the magnitude of the UC-Mn moments. The UC-Mn moments and the FM moments of Fe-rich alloys prefer the anti-parallel alignment. Conversely, the UC-Mn moments align parallel to the FM moments in Co-rich or Ni-rich regions. A first-principles calculation pertaining to the L12-Mn3Ir/FM (FM = Ni4-nCon, Co4-nFen, Fe4-nNin; n = 0, 1, 2, 3) bilayer system was carried out to characterize the UC-Mn moments near the interface. It was found that the UC-Mn moments originate from the reorientation of the magnetic moments of Mn and other ferromagnetic atoms near the AF/FM interface. The calculated result for the compositional dependence of the UC-Mn moment is in good agreement with the obtained experimental data. As a result, the dependence of the UC-Mn moment on the composition of the FM layer can be explained qualitatively based on the model that the band filling fraction modifies the direction and the magnitude of exchange coupling between AF and FM atoms, depending on the crystal structure and the composition of the FM layer.

Takahashi, Hirokazu; Kota, Yohei; Tsunoda, Masakiyo; Nakamura, Tetsuya; Kodama, Kenji; Sakuma, Akimasa; Takahashi, Migaku

2011-12-01

256

Cell Membrane Electropermeabilization with Arbitrary Pulse Waveforms  

Microsoft Academic Search

(electrofusion) [5], [6]. Nowadays, these phenomena are widely used in applica-tions such as gene transfection [7]-[8], preparation of monoclonal antibodies [9], and drug delivery, especially in electrochemotherapy of tumors [10]-[12]. For optimal effectiveness of these applications, one must choose the most appropri-ate amplitude, duration, and waveform of the applied electric pulses. With 2 mm distance between plate electrodes, which is

KAREL FLISAR; MARKO PUC; TADEJ KOTNIK; DAMIJAN MIKLAVCIC

2003-01-01

257

Resolution Analysis in Full Waveform Inversion  

NASA Astrophysics Data System (ADS)

Full waveform inversion is a tomographic technique that is based on numerical wave propagation through complex media combined with adjoint or scattering integral methods for the computation of Fréchet kernels. While the tomographic method itself has advanced substantially, an essential aspect of the inverse problem has been ignored almost completely: The quantification of resolution and uncertainties. We propose a new method for the quantitative resolution analysis in full seismic waveform inversion that overcomes the limitations of synthetic inversions while being computationally more efficient and applicable to any misfit measure. The method rests on (1) the local quadratic approximation of the misfit functional in the vicinity of an optimal Earth model, (2) the parametrisation of the Hessian in terms of a parent function, and (3) the computation of the space-dependent parameters via Fourier transforms of the Hessian, calculated with the help of adjoint techniques. In the simplest case of a Gaussian approximation we can infer rigorously defined 3D distributions of direction-dependent resolution lengths and the image distortion introduced by the tomographic method. We illustrate these concepts with a realistic full waveform inversion for upper-mantle structure beneath Europe. As a corollary to the method for resolution analysis we propose several improvements to full waveform inversion techniques. These include a pre-conditioner for optimisation schemes of the conjugate-gradient type, a new family of Newton-like methods, an approach to adaptive parametrisation independent from ray theory, and a strategy for objective functional design that aims at maximising resolution. The computational requirements of our approach are less than for a typical synthetic inversion, but yield a much more complete picture of resolution and trade-offs. It allows for adaptations to exploration scenarios and other wave equation based tomography techniques that employ, for instance, georadar or microwave data.

Fichtner, A.; Trampert, J.

2011-12-01

258

Neutron spectroscopy with fast waveform digitizer  

Microsoft Academic Search

In this paper, we demonstrate the application of a fast waveform digitizer (1GHz) for neutron spectroscopy. We investigated pulse-shape discrimination between neutrons and ?-rays, timing properties and count rate capabilities of this new experimental method and compared the results with traditional techniques. The present method compares particularly well in the case of particle-type identification in the presence of pulse saturation

N. V. Kornilov; V. A. Khriatchkov; M. Dunaev; A. B. Kagalenko; N. N. Semenova; V. G. Demenkov; A. J. M. Plompen

2003-01-01

259

Congenital nystagmus waveforms and foveation strategy  

Microsoft Academic Search

Accurate eye movement recordings of sixty-five subjects with congenital nystagmus (CN) provides a firm foundation for the classification of the many types of wave-forms observed and results in objective definitions based on measurable quantities rather than subjective clinical impressions. The careful scrutiny of these records along with the utilization of laser-target retinal cinematography have yielded insights into the mechanism of

L. F. Dell'osso; R. B. Daroff

1975-01-01

260

Efficient implementation of ultrasound waveform tomography using source encoding  

NASA Astrophysics Data System (ADS)

Ultrasound waveform tomography takes wave propagation effects into account during image reconstruction, and has the potential to produce accurate estimates of the sound speeds of small breast tumors. However, waveform tomography is computationally time-consuming for large datasets acquired using a synthetic-aperture ultrasound tomography system that consists of hundreds to thousands of transducer elements. We introduce a source encoding approach to ultrasound waveform tomography to significantly improve the computational efficiency. The method simultaneously simulates ultrasound waveforms emitted from multiple transducer elements. To distinguish the effect of different sources, we apply a random phase to each source. The random phase helps eliminate the unwanted cross interferences produced by different sources. This approach greatly reduces the computational time of ultrasound waveform tomography to one tenth of that for the original waveform tomography, and makes it feasible for ultrasound waveform tomography in clinical applications.

Zhang, Zhigang; Huang, Lianjie; Lin, Youzuo

2012-02-01

261

The Waveform Server: A Web-based Interactive Seismic Waveform Interface  

NASA Astrophysics Data System (ADS)

Seismic waveform data has traditionally been displayed on machines that are either local area networked to, or directly host, a seismic networks waveform database(s). Typical seismic data warehouses allow online users to query and download data collected from regional networks passively, without the scientist directly visually assessing data coverage and/or quality. Using a suite of web-based protocols, we have developed an online seismic waveform interface that directly queries and displays data from a relational database through a web-browser. Using the Python interface to Datascope and the Python-based Twisted network package on the server side, and the jQuery Javascript framework on the client side to send and receive asynchronous waveform queries, we display broadband seismic data using the HTML Canvas element that is globally accessible by anyone using a modern web-browser. The system is used to display data from the USArray experiment, a US continent-wide migratory transportable seismic array. We are currently creating additional interface tools to create a rich-client interface for accessing and displaying seismic data that can be deployed to any system running Boulder Real Time Technology's (BRTT) Antelope Real Time System (ARTS). The software is freely available from the Antelope contributed code Git repository. Screenshot of the web-based waveform server interface

Newman, R. L.; Clemesha, A.; Lindquist, K. G.; Reyes, J.; Steidl, J. H.; Vernon, F. L.

2009-12-01

262

Investigating the Early Holocene Black Sea Flood Using Chirp Sub-bottom Seismic Reflection Profiles of the Crimean Shelf  

NASA Astrophysics Data System (ADS)

The Holocene flooding of the Black Sea with Mediterranean seawater has been attributed to either a catastrophic event or an oscillatory inundation. Features such as wave-generated seafloor morphologies and areas of onlap within the seabed may indicate the presence of past coastal beaches and sea level transgression. The oscillatory interpretation is supported by seismic data that exhibits both transgression and regression events higher on the Black Sea shelf. Evidence supporting a catastrophic event is revealed by unconformities identified in seismic data and by an early Holocene lowstand identified at greater depths. We present the results of two geophysical surveys conducted along the Crimean Shelf in the northern Black Sea in 2006 and 2008 aboard the R/V Endeavor and the USNS Pathfinder. These surveys collected multibeam bathymetry, deep-towed side scan, chirp sub-bottom seismics, and current profiling data. These geophysical data reveal many geological features including channels, hummocks, sediment waveforms and onlap. The existence of paleoshorelines from the early Holocene was interpreted based on the waveform character in seismic sections. The locations of the paleoshorelines were mapped and compared to previous studies to identify regional trends. Our preliminary interpretation does not exclusively support either inundation model but indicates deeper Holocene lowstands consistent with the catastrophic inundation. Additional data provided by core samples is necessary to further examine whether the unconformities found at these depths are from the early Holocene. We also need to investigate the water column hydrography to ensure the interpreted paleoshorelines are not the result of internal waves on the Crimean shelf.

Whitesell, D. P.; Ballard, R. D.; Pockalny, R. A.; Coleman, D. F.

2011-12-01

263

A Study of Excitation Dynamics of LT-GaAs by Chirp-Controlled Pump-Probe Technique  

NASA Astrophysics Data System (ADS)

In this work, a home made chirp-controlled pump-probe measurement system has been developed and the chirp-controlled pump-probe measurement system with temporal resolution of around 100 femtosecond and chirp parameter tuning from --350 fs^2 to +650 fs^2 was demonstrated. Meanwhile, using chirp-controlled pump-probe measurement system, ultrafast dynamics of photogenerated carrier in low-temperature growth GaAs in different chirp by was characterized. The shorter relaxation time of low-temperature growth GaAs in positive chirp pump pulse was observed and the result was explained by the Pump-Dump process in negative chirp pump pulse and similar band-filling effect in positive chirp pump pulse.

Lee, Chao-Kuei; Huang, C. K.; Liao, L. Y.

2007-03-01

264

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

265

Software Reception of AM & FM Broadcast Using Frequency Domain Samples  

NASA Astrophysics Data System (ADS)

Digital signal processing (DSP) has been widely used because it can realize variety of functions by change of software. Now, it is possible to handle practical analog or digital signal by DSP. This paper proposes a new method for reception of AM & FM broadcast signal using FFT/IFFT. Also, demultiplexing of demodulated FM signal is included. First, input signal is sampled and truncated. Then, truncated samples are transferred to frequency domain samples by FFT. Demodulation and demultiplexing are performed using both frequency domain and time domain samples. In order to process continuous signal by truncated samples, use of overlap and save method is assumed. Matlab Simulink diagram of demodulation and demultiplexing by the proposed method is also presented.

Sakabe, Takuji; Kimbara, Masato; Egami, Shunichiro

266

Simultaneous occupational exposure to FM and UHF transmitters.  

PubMed

Occupational exposure caused by large broadcasting transmitters exceeds current reference levels. As it is common for different radio and TV transmitters to share the location, we analysed combined exposure on a 40-m high mast. The frequency modulation (FM) transmitter, located between the 10th and 30th metre, had the power of 25 kW, whereas an ultra-high frequency (UHF) transmitter of 5 kW occupied the top 8 m of the mast. Measured and calculated values of the electric field strength exceeded the reference levels up to 10 times; however, the results for the specific absorption rate (SAR) values show that the reference levels are very conservative for FM exposure, i.e., basic restrictions are not exceeded even when the reference levels are exceeded 10 times. However, for UHF exposure the reference levels are not conservative; they give a good prediction of real exposure. PMID:22721535

Vali?, Blaž; Kos, Bor; Gajšek, Peter

2012-01-01

267

Frequency chirping for resonance-enhanced electron energy during laser acceleration  

NASA Astrophysics Data System (ADS)

The model given by Singh-Tripathi [Phys. Plasmas 11, 743 (2004)] for laser electron acceleration in a magnetic wiggler is revisited by including the effect of laser frequency chirping. Laser frequency chirp helps to maintain the resonance condition longer, which increases the electron energy gain. A significant enhancement in electron energy gain during laser acceleration is observed.

Gupta, D. N.; Suk, H.

2006-04-01

268

Frequency chirping for resonance-enhanced electron energy during laser acceleration  

SciTech Connect

The model given by Singh-Tripathi [Phys. Plasmas 11, 743 (2004)] for laser electron acceleration in a magnetic wiggler is revisited by including the effect of laser frequency chirping. Laser frequency chirp helps to maintain the resonance condition longer, which increases the electron energy gain. A significant enhancement in electron energy gain during laser acceleration is observed.

Gupta, D.N.; Suk, H. [Center for Advanced Accelerators, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of)

2006-04-15

269

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

270

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

271

The segmented chirp Z-transform and its application in spectrum analysis  

Microsoft Academic Search

The chirp Z-transform (CZT) algorithm is known to be more flexible than the fast Fourier transform in calculating the frequency spectrum. However, its mathematical implementation is complex, and additional memory space is required. A modified CZT algorithm called the segmented chirp Z transform (SCZT) is introduced. SCZT has the ability to handle a very large amount of input data with

T. T. Wang

1990-01-01

272

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

273

Nonlinear Dynamics of Chirped Pulse Excitation and Dissociation of Diatomic Molecules  

Microsoft Academic Search

The classical dynamics of a diatomic molecule modeled by a Morse oscillator interacting with a chirped infrared laser pulse is studied. When the chirping rate is small, the system can be described approximately in the moving frame by a time-independent Hamiltonian, which produces single-node separtrices (buckets) in phase space. Systems trapped in the buckets undergo convection to dissociation. This route

Wing-Ki Liu; Binruo Wu; Jian-Min Yuan

1995-01-01

274

Manipulating femtosecond magnetization in ferromagnets and molecular magnets through laser chirp  

NASA Astrophysics Data System (ADS)

Laser chirp has found many applications in pulse shaping, high harmonic generation, and dynamical control of the vibrational excitation. Here, we show that the laser chirp can significantly affect the amount of the magnetic moment change in the laser-induced femtosecond magnetism. Under the same laser condition, an increase in the chirp from 0 to 0.04 rad/fs2 results in the magnetic moment change from 0.4% to 5% in ferromagnetic nickel. We find that the laser pulse duration has a direct effect on the effectiveness of the chirp. For a shorter pulse of duration 12 fs, the spin change with the chirp is small. We attribute this to a shorter interaction time and consequently a smaller instantaneous photon energy. We also investigate the effect of chirp on laser-induced local-spin-switching on molecular magnets consisting of two magnetic centers (Fe, Co, and Ni) bridged by Na atoms. We find that the effect of chirping differs depending on the original switching behavior of the atom. On Fe the chirp renders the process slightly less effective, on Ni it leads to a more dramatic loss of fidelity due to quantum interference, and for Co the effect lies in-between. Our study opens a new way to manipulate spin on femtosecond time scales.

Zhang, G. P.; Lefkidis, G.; Hübner, W.; Bai, Yihua

2012-04-01

275

Time domain synchronization using Newman chirp training sequences in AWGN channels  

Microsoft Academic Search

We propose a new time-domain simultaneous fractional frequency and sampling offsets estimation algorithm using the characteristics of down-sampled chirp training signals. The training sequence is composed of one up and one down chirp symbols. We also propose a new estimation algorithm to estimate the integer timing and frequency offsets in the time domain. The algorithms use the outputs of matched

Sandrine Boumard; Aarne Mammela

2005-01-01

276

Airborne SAR processing of highly squinted data using a chirp scaling approach with integrated motion compensation  

Microsoft Academic Search

Proposes a new approach for high-resolution airborne SAR data processing, which uses a modified chirp scaling algorithm to accommodate the correction of motion errors, as well as the variations of the Doppler centroid in range and azimuth. By introducing a cubic phase term in the chirp scaling phase, data acquired with a squint angle up to 30° can be processed

A. Moreira; Yonghong Huang

1994-01-01

277

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

Microsoft Academic Search

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 coUisional 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

Svetlana A. Malinovskaya

2008-01-01

278

Chirped Fiber Grating Beamformer for Phased Array Antennas Field of the Invention.  

National Technical Information Service (NTIS)

A new fiber optic based beamforming architecture for a time steered phased array antenna based on chirped fiber gratings. All of the gratings are identical in length and period chirp so that they all have the same dispersion, thus at a given optical wavel...

J. E. Roman M. Y. Frankel R. D. Esman

1998-01-01

279

Analytical solutions for a two-level system driven by a class of chirped pulses  

SciTech Connect

We present analytical solutions for the problem of a two-level atom driven by a class of chirped pulses. The solutions are given in terms of Heun functions. By use of the appropriate chirping parameters, an enhancement of four orders of magnitude in the population transfer is obtained.

Jha, Pankaj K. [Institute for Quantum Science and Engineering and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Rostovtsev, Yuri V. [Institute for Quantum Science and Engineering and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Department of Physics, University of North Texas, 1155 Union Circle 311427, Denton, Texas 76203 (United States)

2010-07-15

280

Chirped pulse amplification of 300 fs pulses in an alexandrite regenerative amplifier  

Microsoft Academic Search

The amplification of fsec dye-laser pulses up to the 3.5-mJ level in an alexandrite regenerative amplifier is discussed. An expansion\\/compression system using different gratings allows chirped amplification techniques to be used to produce peak powers upwards of 1 GW. Limitations in the chirped pulse amplification of ultrashort pulses due to intracavity dispersive elements are discussued.

Maurice Pessot; Jeff Squier; Philippe Bado; Gerard Mourou; Donald J. Harter

1989-01-01

281

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

Federal Register 2010, 2011, 2012, 2013

...BROADCASTING, INC., Station WKOV-FM, Facility...BROADCASTING L.L.C., Station KRSX-FM, Facility...BROADCAST ASSOCIATES, INC, Station NEW, Facility ID 189498...ADDRESSES: Federal Communications Commission, 445 Twelfth...Bureau's Consolidated Data Base System,...

2012-04-26

282

76 FR 81932 - Auction of FM Broadcast Construction Permits; Revised Construction Permit Number in Auction 93  

Federal Register 2010, 2011, 2012, 2013

...DA 11-2046] Auction of FM Broadcast Construction Permits; Revised Construction Permit Number in Auction 93 AGENCY: Federal...This document announces a change to the construction permit number for one of the FM...

2011-12-29

283

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

Federal Register 2010, 2011, 2012, 2013

...Protective Signaling Systems UL 1480 Speakers for Fire Alarm, Emergency, and Commercial and Professional Use UL 1638 Visual...Utility Signaling FM 3210 Heat Detectors for Automatic Fire Alarm Signaling FM 7260 Electrostatic Finishing Equipment...

2010-03-02

284

A Power Spectral Density Analysis for Digital FM  

Microsoft Academic Search

Except for rectangular-shaped modulating pulses, the specification of the power spectral density function (psdf) for digital FM is analytically perverse and only a few results are available in the journal literature. In this paper an analysis is presented based on the selection of an appropriate duration-limited\\/level-quantized approximation for the modulating pulses and equations suitable for machine computation are subsequently developed.

G. Garrison

1975-01-01

285

FM-UWB for radar and communications in medical applications  

Microsoft Academic Search

UWB technology is an attractive technology for Wireless Body Area Networks. There are many advantages of using ultra-wideband (UWB) as both a sensing and a communication standard for biomedical applications: very low radiated power (-41.3 dBm\\/MHz), low power consumption, good coexistence with other existing wireless technologies, robustness to interference and multipath. Moreover, one specific UWB technology, namely Frequency Modulated (FM)-UWB,

Bharat Gupta; Daniela Valente; Ernestina Cianca; Ramjee Prasad

2008-01-01

286

Nuclear orientation studies of 241Am and 255Fm  

Microsoft Academic Search

Nuclei of 241Am and 255Fm were oriented in single crystals of neodymium ethylsulfate at temperatures down to 11 mK. Orientation was detected by alpha-particle angular distributions. The temperature dependences of these distributions were consistent with the lowest electronic states of these two actinide ions in the ethylsulfate lattice being similar to those of the corresponding lanthanide ions. Thus quadrupole orientation

A. J. Soinski; D. A. Shirley

1974-01-01

287

Photoionization of hydrogen by a chirped, short X-ray pulse in the presence of a laser field  

NASA Astrophysics Data System (ADS)

The ionization of hydrogen by a chirped XUV pulse in the presence of a few cycle infrared laser pulse is investigated. It is found that the combined action of the chirped pulse and the laser field brings about asymmetries in the photoelectron momentum distribution that may be exploited for obtaining information on both the chirp and XUV pulse duration.

Bivona, S.; Bonanno, G.; Burlon, R.; Leone, C.

2012-11-01

288

New fission valley for /sup 258/Fm and nuclei beyond  

SciTech Connect

Experimental results on the fission properties of nuclei close to /sup 264/Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus /sup 258/Fm, for instance, undergoes symmetric fission with a half-life of about 0.4 ms and a kinetic energy peaked at about 235 MeV whereas /sup 256/Fm undergoes asymmetric fission with a half-life of about 3 h and a kinetic energy peaked at about 200 MeV. Qualitatively, these sudden changes hve been postulated to be due to the emergence of fragment shells in symmetric fission products close to /sup 132/Sn. A quantitative calculation that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. The implications of the new fission valley on the stability of the heaviest elements is discussed. 33 refs., 12 figs.

Moeller, P.; Nix, J.R.; Swiatecki, W.J.

1986-01-01

289

Control of laser induced molecular fragmentation of n-propyl benzene using chirped femtosecond laser pulses  

PubMed Central

We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H3+ and C5H5+ in the case of negatively chirped pulses and C6H5+ in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth.

Goswami, Tapas; Karthick Kumar, S.K.; Dutta, Aveek; Goswami, Debabrata

2009-01-01

290

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

291

Female house crickets, Acheta domesticus, prefer the chirps of large males.  

PubMed

This study demonstrates that invertebrate acoustic signals can provide information about male phenotypic attributes, and that females can use this acoustic information in mate choice to select a phenotypically superior mate. I investigated the relationships between a male acoustic sexual signal, the phenotype of the signaller, and the female response to signal variation. I recorded and analysed the calling songs of male house crickets, Acheta domesticus. The analyses showed that chirps convey information about male size. With the exception of amplitude, the mean number of pulses per chirp was the best predictor of male size. I performed a laboratory tape-playback experiment to determine female preference during phonotaxis. Females preferred tapes playing the chirps of large males, specifically chirps with a greater number of pulses per chirp. Selection on the female preference is discussed.Copyright 1997 The Association for the Study of Animal Behaviour PMID:9794780

Gray

1997-12-01

292

Chirped self-similar solutions of a generalized nonlinear Schrödinger equation model.  

PubMed

Exact chirped self-similar solutions of the generalized nonlinear Schrödinger equation with varying dispersion, nonlinearity, gain or absorption, and nonlinear gain have been found. The stability of these nonlinearly chirped solutions is then demonstrated numerically by adding Gaussian white noise and by evolving from an initial chirped Gaussian pulse, respectively. It is reported that the pulse position of these chirped pulses can be precisely piloted by tailoring the dispersion profile, and that the sech-shaped solitary waves can propagate stably in the regime of beta(z)gamma(z) > 0 as well as the regime of beta(z)gamma(z) < 0 , according to the magnitude of the nonlinear chirp parameter. Our theoretical predictions are in excellent agreement with the numerical simulations. PMID:15697746

Chen, Shihua; Yi, Lin

2005-01-11

293

Directional bending sensor with temperature insensitivity using a sampled chirped fiber Bragg grating  

NASA Astrophysics Data System (ADS)

A simple and practical scheme for a directional bending sensor based on a sampled chirped fiber Bragg grating is proposed. The proposed sensing method has temperature insensitivity. The wavelength spacing in the reflection spectrum of a sampled chirped fiber Bragg grating is changed by bending because of the modification of the chirp ratio. As positive or negative bending is applied to the sampled chirped fiber Bragg grating embedded on a flexible cantilever beam, the wavelength spacing increases or decreases because of the induction of the tension and the compression strain gradient along the fiber grating. However, the wavelength spacing is not changed by the applied temperature. Since the effect of the temperature variation along the grating length remains the same, the chirp ratio is independent of the applied temperature change. Regardless of temperature change, it is therefore possible to measure the direction and the variation of bending.

Han, Young-Geun

2009-03-01

294

Perturbation-theory analysis of ionization by a chirped few-cycle attosecond pulse  

SciTech Connect

The angular distribution of electrons ionized from an atom by a chirped few-cycle attosecond pulse is analyzed using perturbation theory (PT), keeping terms in the transition amplitude up to second order in the pulse electric field. The dependence of the asymmetry in the ionized electron distributions on both the chirp and the carrier-envelope phase (CEP) of the pulse are explained using a simple analytical formula that approximates the exact PT result. This approximate formula (in which the chirp dependence is explicit) reproduces reasonably well the chirp-dependent oscillations of the electron angular distribution asymmetries found numerically by Peng et al. [Phys. Rev. A 80, 013407 (2009)]. It can also be used to determine the chirp rate of the attosecond pulse from the measured electron angular distribution asymmetry.

Pronin, E. A.; Starace, Anthony F.; Peng Liangyou [Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0299 (United States); State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871 (China)

2011-07-15

295

Quantum and classical chirps in an anharmonic oscillator.  

PubMed

We measure the state dynamics of a tunable anharmonic quantum system, the Josephson phase circuit, under the excitation of a frequency-chirped drive. At small anharmonicity, the state evolves like a wave packet-a characteristic response in classical oscillators; in this regime, we report exponentially enhanced lifetimes of highly excited states, held by the drive. At large anharmonicity, we observe sharp steps, corresponding to the excitation of discrete energy levels. The continuous transition between the two regimes is mapped by measuring the threshold of these two effects. PMID:22400784

Shalibo, Yoni; Rofe, Ya'ara; Barth, Ido; Friedland, Lazar; Bialczack, Radoslaw; Martinis, John M; Katz, Nadav

2012-01-19

296

Application of the chirp z-transform to MRI data.  

PubMed

A version of the chirp z-transform (CZT) enabling signal intensity and phase-preserving field-of-view scaling has been programmed. The algorithm is important for all single-point imaging sequences such as SPRITE when used with multiple data acquisition for T2* mapping or signal averaging. CZT has particular utility for SPRITE imaging of nuclei with short relaxation times such as sodium at high field. Here, a complete theory of the properties of CZT is given. This method operates entirely in k-space. It is compared with a conventional interpolation approach that works in image space after the application of a fast Fourier transformation. PMID:16216539

Kaffanke, J; Dierkes, T; Romanzetti, S; Halse, M; Rioux, J; Leach, M O; Balcom, B; Shah, N J

2005-10-10

297

The chirp-Z transform applied to adhesively bonded structures  

NASA Astrophysics Data System (ADS)

A signal-processing technique based on the chirp-Z transform is presented to evaluate the echo signals of longitudinal ultrasonic transducers in contact with bonded materials. Both a simulated glass-glass interface of variable thickness and a realistic double lap bonded aluminum sample were tested. The observed frequency dips and peaks in the transducer spectrum from pulse-echo and through-transmission modes were recorded and related to the condition of zero reflection coefficient at the interfacial layer. Resulting thickness predictions for different transducer center frequencies ranging from 5-20 MHz are in excellent agreement with experimental measurements.

Nair, Vinod K.; Ludwig, Reinhold; Anastasi, Robert F.

1991-08-01

298

Application of the chirp z-transform to MRI data  

NASA Astrophysics Data System (ADS)

A version of the chirp z-transform (CZT) enabling signal intensity and phase-preserving field-of-view scaling has been programmed. The algorithm is important for all single-point imaging sequences such as SPRITE when used with multiple data acquisition for T2? mapping or signal averaging. CZT has particular utility for SPRITE imaging of nuclei with short relaxation times such as sodium at high field. Here, a complete theory of the properties of CZT is given. This method operates entirely in k-space. It is compared with a conventional interpolation approach that works in image space after the application of a fast Fourier transformation.

Kaffanke, J.; Dierkes, T.; Romanzetti, S.; Halse, M.; Rioux, J.; Leach, M. O.; Balcom, B.; Shah, N. J.

2006-01-01

299

Seed laser chirping for enhanced backward Raman amplification in plasmas.  

PubMed

Backward Raman compression in plasma enables pulse compression to intensities not available using material gratings. Mediating the compression with higher density plasma 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. What is shown here is that, by chirping the seed pulse, the group velocity dispersion may in fact be used advantageously, achieving the maximum intensities over the shortest distances while minimizing unwanted effects. PMID:23002752

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

2012-08-22

300

Supercontinuum generation with a chirped-pulse oscillator.  

PubMed

We demonstrate the generation of a high power ultrabroadband supercontinuum by coupling the uncompressed pulses from a Ti:Sapphire Chirped-pulse oscillator into a photonic crystal fibre that exhibits a highly anomalous dispersion at the centre wavelength of the laser. Our simulations show that the pulses first undergo quasi-linear compression before the actual supercontinuum is generated by soliton fission dynamics. This two-step process results in an optical spectrum that is remarkably independent on the input pulse energy. Moreover, the reduced peak intensity at the input facet of the fibre mitigates damage problems and allows the generation of high power white-light radiation. PMID:19333361

Fuerbach, A; Miese, C; Koehler, W; Geissler, M

2009-03-30

301

Photonic Generation of Chirped Millimeter-Wave Pulses Based on Nonlinear Frequency-to-Time Mapping in a Nonlinearly Chirped Fiber Bragg Grating  

Microsoft Academic Search

A novel approach to optically generating chirped millimeter-wave pulses with tunable chirp rate based on spectral shaping and nonlinear frequency-to-time mapping is proposed and experimentally demonstrated. In the proposed approach, the optical power spectrum of an ultrashort pulse from a femtosecond pulsed laser is shaped by a two-tap Sagnac loop filter that has a sinusoidal frequency response. The spectrum-shaped optical

Chao Wang; Jianping Yao

2008-01-01

302

75 FR 9530 - FM TABLE OF ALLOTMENTS, French Lick, Indiana, and Irvington, Kentucky.  

Federal Register 2010, 2011, 2012, 2013

...RM-11412] FM TABLE OF ALLOTMENTS, French Lick, Indiana, and Irvington, Kentucky...modifies the license of Station WFLQ(FM), French Lick, Indiana, to specify operation...the licensee of Station WFLQ(FM), French Lick, Indiana, to show cause why...

2010-03-03

303

Efficient layering for high speed communication: the MPI over Fast Messages (FM) experience  

Microsoft Academic Search

We describe our experience of designing, implementing, and evaluating two generations of high performance communication libraries, Fast Messages (FM) for Myrinet. In FM 1, we designed a simple interface and provided guarantees of reliable and in-order delivery, and flow control. While this was a significant improvement over previous systems, it was not enough. Layering MPI atop FM 1 showed that

Mario Lauria; Scott Pakin; Andrew A. Chien

1999-01-01

304

Resonant tunneling and the bimodal symmetric fission of sup 258 Fm  

SciTech Connect

The concept of resonant tunneling is invoked to explain the sharp drop in the measured spontaneous-fission half-life when going from {sup 256}Fm to {sup 258}Fm. Various consequences of such a suggestion on the other observed characteristics of the bimodal symmetric fission of {sup 258}Fm are briefly discussed.

Bhandari, B.S. (Department of Physics, Faculty of Science, University of Garyounis, Benghazi, Libya (LY))

1991-02-25

305

A 7 GHz FM Transmitter Utilizing GaAs Power MESFETs  

Microsoft Academic Search

An FM transmitter with a power efficiency of 11.5 % was developed utilizing GaAs power MESFETs for a 7 GHz FM radio-relay equipment. The transmitter, which consists of an FM modulator and power amplifiers, provides an output power of 1 watt and transmitting capability of 960 telephone circuits.

H. Komizo; Y. Arai; T. Saito

1977-01-01

306

Insights Into GLAS Waveforms Using Google Earth  

NASA Astrophysics Data System (ADS)

The Geoscience Laser Altimeter System (GLAS) instrument aboard the Ice, Cloud, and land Elevation (ICESat) satellite was launched on 12 January 2003. The primary objective of the ICESat mission is to provide global measurements of polar ice sheet elevation to discern changes in ice volume and ice sheet mass balance over time. Secondary objectives of the mission are to measure sea ice thickness, cloud and atmospheric properties, land topography, vegetation canopy heights, ocean surface topography, and surface reflectivity. The GLAS instrument has three lasers, each of which has a 1064 nm laser channel for surface altimetry and dense cloud heights, and a 532 nm lidar channel for the vertical distribution of clouds and aerosols. The laser emits a pulse every 0.02 seconds, and receives a return signal. Laser footprints are roughly 70 meters in diameter and spaced 170 meters apart and are assigned terrestrial positions at the 10s of meters level of accuracy. As an aid to data selection we demonstrate how GLAS footprints, waveforms and quality information can be displayed in Google Earth. We represent the approximate spatial coverage of each laser shot on the Earth's surface, allowing users to assess the shot in the context of the surface characteristics gleaned from the underlying image and topography in Google Earth. Each footprint can be expanded to show the associated waveform, summarizing the detected return signal, along with numerical values for latitude and longitude, elevation, and date/time. Surface characteristics such as tree canopy, low- level dust or clouds, snow or ice cover, extreme surface roughness, have significant, easily-visible effects on the waveform. This application will provide extremely useful information, and will facilitate a detailed data preview before ordering or processing.

Fowler, D.; Khalsa, S. S.; Swick, R.; Haran, T.; Scambos, T.; Korn, D.

2008-12-01

307

Waveform acoustic impedance inversion with spectral shaping  

NASA Astrophysics Data System (ADS)

Full waveform inversion applied to surface seismic data containing only reflection data generally gives an impedance map, the background velocity being assumed known. The first iteration update does not have a spectrum close to the Earth impedance spectrum because of source wavelet and wave propagation effects. To improve the convergence, these effects can be compensated by designing a spectral shaping filter that produces a gradient of the misfit function with a spectrum similar to the Earth spectrum. Based on an asymptotic analysis of the gradient of the misfit function, we rederive the theoretical spectral shaping filter. When the observed source wavelet is known or can be estimated from the data, we retrieve that, after source deconvolution/whitening of the data, the theoretical spectral shaping is in ?-?/2 for the data or in k-? for the gradient with ? the angular frequency and k the wavenumber. ? is an exponent depending on acquisition and equal to 1 with areal (so-called 3-D) acquisition and to 2 with line (so-called 2-D) acquisition. Under acoustic assumption, this leads to a waveform acoustic impedance inversion approach. We test this approach with a small synthetic example and with a real data set. Since we did not use a priori impedance information to derive the spectral shaping, we validate the approach by comparing the spectrum of the inverted impedances with the one of the Earth impedance computed from well-log measurements. The results illustrate the relevance of the spectral shaping to improve the convergence of the waveform inversion of reflection data.

Plessix, R.-É.; Li, Y.

2013-10-01

308

Resolution analysis in full waveform inversion  

NASA Astrophysics Data System (ADS)

We propose a new method for the quantitative resolution analysis in full seismic waveform inversion that overcomes the limitations of classical synthetic inversions while being computationally more efficient and applicable to any misfit measure. The method rests on (1) the local quadratic approximation of the misfit functional in the vicinity of an optimal earth model, (2) the parametrization of the Hessian in terms of a parent function and its successive derivatives and (3) the computation of the space-dependent parameters via Fourier transforms of the Hessian, calculated with the help of adjoint techniques. In the simplest case of a Gaussian approximation, we can infer rigorously defined 3-D distributions of direction-dependent resolution lengths and the image distortion introduced by the tomographic method. We illustrate these concepts with a realistic full waveform inversion for upper-mantle structure beneath Europe. As a corollary to the method for resolution analysis, we propose several improvements to full waveform inversion techniques. These include a pre-conditioner for optimization schemes of the conjugate-gradient type, a new family of Newton-like methods, an approach to adaptive parametrization independent from ray theory and a strategy for objective functional design that aims at maximizing resolution. The computational requirements of our approach are less than for a typical synthetic inversion, but yield a much more complete picture of resolution and trade-offs. While the examples presented in this paper are rather specific, the underlying idea is very general. It allows for problem-dependent variations of the theme and for adaptations to exploration scenarios and other wave-equation-based tomography techniques that employ, for instance, georadar or microwave data.

Fichtner, Andreas; Trampert, Jeannot

2011-12-01

309

Pulse waveforms classification based on wavelet network.  

PubMed

This paper proposes a new algorithm to classify pulse waveforms based on discrete wavelet network. This paper selects 4-order discrete Daubechies wavelet as the wavelet node of this wavelet network to classify six pulse patterns distinctive in shape. 600 pulse records are used to train this wavelet network and 300 pulse records are used to test the classifier's performance. The test results show that this approach has 83% agreement rate with the experienced experts. Compared with traditional classification methods, it needs not the experience in feature extraction. PMID:17281263

Xu, L S; Wang, K Q; Wang, L

2005-01-01

310

Interferometric control of parametrically amplified waveforms  

SciTech Connect

Using atomic coherence, four-wave-mixing radiation is generated between the excited states of a ladder-type configuration in rubidium atomic vapor. By using all-optical phase control between the two frequency-swept driving beams connecting the two lower levels, the generated signal is phase modulated across its bandwidth. When homodyned with a local oscillator, such phase control looks promising for applications including waveform shaping and high-resolution metrology. Experimental observations of signal line shape symmetrization, linewidth narrowing, and bandwidth switching are demonstrated.

Khadka, Utsab; Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Zheng Huaibin [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Key Laboratory for Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049 (China)

2011-10-15

311

75 FR 61752 - Auction of FM Broadcast Construction Permits Scheduled for March 29, 2011; Comment Sought on...  

Federal Register 2010, 2011, 2012, 2013

...10-1711] Auction of FM Broadcast Construction Permits Scheduled for March 29, 2011...announces the auction of certain FM construction permits scheduled to commence on March...an auction of certain FM Broadcast construction permits. This auction, which is...

2010-10-06

312

Fragment mass and kinetic-energy distributions from spontaneous fission of the neutron-deficient isotopes, 1. 2-s /sup 246/Fm and 38-s /sup 248/Fm  

SciTech Connect

We have measured the mass and kinetic-energy distributions for fragments from the spontaneous fission of 1.2-s /sup 246/Fm and 38-s /sup 248/Fm. The mass distributions are highly asymmetric and the average total kinetic energies of 199 +- 4 MeV and 198 +- 4 MeV, respectively, are consistent with systematics for lower Z actinides. Their properties are in contrast to those of /sup 258/Fm and /sup 259/Fm, whose spontaneous fission results in narrowly symmetric mass distributions accompanied by unusually high total kinetic energies.

Hoffman, D.; Lee, D.; Ghiorso, A.; Nurmia, M.; Aleklett, K.

1980-10-01

313

Accurate analytical waveforms of coalescing binary black holes  

NASA Astrophysics Data System (ADS)

I will present analytical waveforms of gravitational-wave radiation from coalescing binary black holes generated within the analytical effective-one-body approach. These waveforms agree, within numerical errors, with waveforms generated by highly accurate numerical relativity simulations. Furthermore, in the test-particle limit, these waveforms agree with the extreme mass ratio inspiral waveforms generated by numerically solving the Teukolsky equations. I will show how this analytical approach extracts non-perturbative information contained in the numerical simulations, models the full coalescence phase, and provides a sufficiently accurate bank of waveforms to be used in matched-filtering based searches of coalescing binary black holes with ground-based gravitational-wave detectors. )

Pan, Yi

2010-02-01

314

Constructing binary black hole template banks using numerical relativity waveforms  

NASA Astrophysics Data System (ADS)

We present methods for constructing and validating template banks for gravitational waves from high mass binary black holes in advanced gravitational-wave detectors using waveforms from numerical relativity. We construct these template banks using numerical waveforms from the Simulating eXtreme Spacetimes (SXS) collaboration. We show how a template bank can be constructed using numerical waveforms for non-spinning black hole binaries and discuss how this can be extended into the aligned spin black hole binary space.

Kumar, Prayush

2013-04-01

315

Waveform-diverse moving-target spotlight SAR  

NASA Astrophysics Data System (ADS)

This paper develops the theory for waveform-diverse moving-target synthetic-aperture radar. We assume that the targets are moving linearly, but we allow an arbitrary flight path and (almost) arbitrary waveforms. We consider the monostatic case, in which a single antenna phase center is used for both transmitting and receiving. This work addresses the use of waveforms whose duration is sufficiently long that the targets and/or platform move appreciably while the data is being collected.

Cheney, Margaret; Borden, Brett

2011-05-01

316

Hepatic vein waveforms in liver cirrhosis re-evaluated  

PubMed Central

Objective There are many studies on changes in Doppler waveforms of hepatic veins in cirrhotic liver. It is postulated that dampening of phasic oscillations appears with worsening of liver function. Our aim was to reevaluate the significance of Doppler waveforms of hepatic vein in cirrhotic patients and to correlate with hepatic blood flow. Patients and method One hundred and thirty-five consecutive patients of liver cirrhosis and 60 age and sex matched non-cirrhotic controls were enrolled in this study. Doppler waveforms were obtained from right hepatic vein during normal respiration. Other parameters measured were flow volume of portal trunk, right portal vein and proper hepatic artery. Result Waveforms of the hepatic vein were classified into triphasic, biphasic and flat patterns. Flat waveform was rare and appeared in only 3% cases. There was no correlation between liver dysfunction and patterns of waveforms. Inflow, particularly to the right lobe, was significantly elevated in cases associated with the non-triphasic waveforms. Conclusion This study shows that the flat waveforms have no diagnostic value. Role of hepatic blood flow seems to be important suggesting hemodynamic changes rather than liver dysfunction as a plausible cause of change in waveforms.

Sharma, Dilip; Chataut, Saroj Prasad

2010-01-01

317

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 Green’s 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

318

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

SciTech Connect

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. The method uses a library of 1D Green’s 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 earthquake 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 hard-rock sites. This simplification allows the source inversion for both mechanism and location to be easily obtained 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 one station 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 difficult paths that cross deep basins or propagate along mountain ridges.

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

2007-12-10

319

Chirp-modulated visual evoked potential as a generalization of steady state visual evoked potential  

NASA Astrophysics Data System (ADS)

Visual evoked potentials (VEPs) are of great concern in cognitive and clinical neuroscience as well as in the recent research field of brain-computer interfaces (BCIs). In this study, a chirp-modulated stimulation was employed to serve as a novel type of visual stimulus. Based on our empirical study, the chirp stimuli visual evoked potential (Chirp-VEP) preserved frequency features of the chirp stimulus analogous to the steady state evoked potential (SSVEP), and therefore it can be regarded as a generalization of SSVEP. Specifically, we first investigated the characteristics of the Chirp-VEP in the time-frequency domain and the fractional domain via fractional Fourier transform. We also proposed a group delay technique to derive the apparent latency from Chirp-VEP. Results on EEG data showed that our approach outperformed the traditional SSVEP-based method in efficiency and ease of apparent latency estimation. For the recruited six subjects, the average apparent latencies ranged from 100 to 130 ms. Finally, we implemented a BCI system with six targets to validate the feasibility of Chirp-VEP as a potential candidate in the field of BCIs.

Tu, Tao; Xin, Yi; Gao, Xiaorong; Gao, Shangkai

2012-02-01

320

Atomic Mass and Nuclear Binding Energy for Fm-221 (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-Börnstein - 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-221 (Fermium, atomic number Z = 100, mass number A = 221).

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

321

Computer-optimised smooth-torque current waveforms for switched-reluctance motors  

Microsoft Academic Search

The paper discusses the design of current waveforms for switched-reluctance motors, which give rise to a constant (ripple-free) torque. The waveforms are optimised by computer search techniques, to give the lowest RMS current per phase consistent with producing smooth torque. Furthermore. the waveforms are constrained to be within the converter's VA rating. Current waveforms and the associated voltage waveforms are

H. C. Lovatt; J. M. Stephensoil

1997-01-01

322

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 method’s 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

323

Chirped dissipative solitons of the complex cubic-quintic nonlinear Ginzburg-Landau equation.  

PubMed

Approximate analytical chirped solitary pulse (chirped dissipative soliton) solutions of the one-dimensional complex cubic-quintic nonlinear Ginzburg-Landau equation are obtained. These solutions are stable and highly accurate under condition of domination of a normal dispersion over a spectral dissipation. The parametric space of the solitons is three-dimensional, that makes theirs to be easily traceable within a whole range of the equation parameters. Scaling properties of the chirped dissipative solitons are highly interesting for applications in the field of high-energy ultrafast laser physics. PMID:19905470

Kalashnikov, V L

2009-10-15

324

Chirp response of an active-controlled thickness-drive tunable transducer  

PubMed

The chirp response of a thickness-drive tunable transducer for wide range time-bandwidth and sweep rates chirp signals is demonstrated experimentally and computationally. The computational evaluation uses recursive digital-filter model based on the z-transform method. The model is limited to simple lossless structure with no front and backing layers. The model and experimental results show that there is no limit on the maximum sweep rate of the chirp signal but practically the limit is determined by the limitation of the circuit that generates the control voltage that simulates a variable electric load. PMID:10738791

Alwi; Carey; Smith

2000-03-01

325

Waveform Synthesizer For Imaging And Ranging Applications  

SciTech Connect

Frequency dependent corrections are provided for Local Oscillator (LO) feed-through. An operational procedure filters LO feed-through effects without prior calibration or equalization. Waveform generation can be adjusted/corrected in a synthetic aperture radar system (SAR), where a rolling phase shift is applied to the SAR's QDWS signal where it is demodulated in a receiver, unwanted energies, such as LO feed-through energy, are separated from a desired signal in Doppler; the separated energy is filtered from the receiver leaving the desired signal; and the separated energy in the receiver is measured to determine the degree of imbalance that is represented by it. Calibration methods can also be implemented into synthesis. The degree of LO feed-through can be used to determine calibration values that can then be provided as compensation for frequency dependent errors in components, such as the QDWS and SSB mixer, affecting quadrature signal quality.

Dubbert, Dale F. (Cedar Crest, NM); Dudley, Peter A. (Albuquerque, NM); Doerry, Armin W. (Albuquerque, NM); Tise, Bertice L. (Albuquerque, NM)

2004-12-28

326

LF/VLF Intracloud Waveform Classification  

NASA Astrophysics Data System (ADS)

The Los Alamos Sferic Array network of fast electric-field-change meters has geolocated well over ten million lightning events in the United States from 1998 to the present. Previous work has included the automated identification of cloud-to-ground lightning and a specific type of intracloud lightning (narrow bipolar events), including the identification of general intracloud lightning activity and leader activity preceeding cloud-to-ground discharges. In 2004, a major array hardware and software upgrade increased sensitivity. We update our work on the pre-upgrade waveform classification, detailing the improved understanding of LF/VLF radiation produced by discharge processes of intracloud lightning, narrow bipolar events, and stepped leaders gained by the increased sensitivity and event rate of the upgraded system.

Heavner, M. J.; Suszcynsky, D.; Wiens, K.; Hamlin, T.; Harlin, J.

2006-12-01

327

The Design and Construction of a DDS based Waveform Generator  

Microsoft Academic Search

A direct digital synthesis (DDS) based signal generator was designed and constructed to cover the frequency range of DC to 20 MHz. The generator is capable of producing Sine and Square waves up to 20 MHz, and can produce arbitrary waveforms whose frequency is limited by a 23 MHz low pass filter. The arbitrary waveform generator is capable of generating

Darrell Harmon

328

Non-rectangular waveforms for neural stimulation with practical electrodes  

PubMed Central

Historically the rectangular pulse waveform has been the choice for neural stimulation. The strength–duration curve is thus defined for rectangular pulses. Not much attention has been paid to alternative waveforms to determine if the pulse shape has an effect on the strength–duration relation. Similarly the charge injection capacity of neural electrodes has also been measured with rectangular pulses. In this study we questioned if non-rectangular waveforms can generate a stronger stimulation effect, when applied through practical electrodes, by minimizing the neural activation threshold and maximizing the charge injection capacity of the electrode. First, the activation threshold parameters were studied with seven different pulse shapes using computer simulations of a local membrane model. These waveforms were rectangular, linear increase and decrease, exponential increase and decrease, Gaussian, and sinusoidal. The chronaxie time was found to be longer with all the non-rectangular pulses and some provided more energy efficient stimulation than the rectangular waveform. Second, the charge injection capacity of titanium nitride microelectrodes was measured experimentally for the same waveforms. Linearly decreasing ramp provided the best charge injection for all pulse widths tested from 0.02 to 0.5 ms. Finally, the most efficient waveform that maximized the charge injection capacity of the electrode while providing the lowest threshold charge for neural activation was searched. Linear and exponential decrease, and Gaussian waveforms were found to be the most efficient pulse shapes.

Sahin, Mesut; Tie, Yanmei

2013-01-01

329

Adaptive highly localized waveform design for multiple target tracking  

NASA Astrophysics Data System (ADS)

When tracking multiple targets, radar measurements from weak targets are often masked by the ambiguity function (AF) sidelobes of the measurements from stronger targets. This results in deteriorated tracking performance and lost tracks. In this study, we consider the design of configurable waveforms whose AF sidelobes can be positioned to unmask weak targets. Specifically, we construct multicarrier phase-coded (MCPC) waveforms based on Björck constant amplitude zero-autocorrelation (CAZAC) sequences. The MCPC CAZAC waveforms exhibit wide regions in their AF surface without sidelobes and allow for selective positioning of sidelobes. We apply these waveforms in the context of a target tracker by selecting waveform parameters that minimize the expected tracking error. We show that this is accomplished by selecting the position of AF sidelobes to unmask weak targets. The target tracker is based on an independent partitions likelihood particle filter that is capable of processing the high-resolution measurements resulting from the Björck CAZAC sequences and tracks a fixed and known number of targets. Using simulations, we demonstrate the improvement in tracking performance when we adaptively select the MCPC CAZAC waveforms over tracking using non-adaptive waveform configurations or single-carrier phase-coded CAZAC waveforms.

Kyriakides, Ioannis; Morrell, Darryl; Papandreou-Suppappola, Antonia

2012-12-01

330

Zero Autocorrelation Waveforms: A Doppler Statistic and Multifunction Problems.  

National Technical Information Service (NTIS)

Constant amplitude zero autocorrelation 'off the dc component' waveforms are constructed. These are called CAZAC waveforms. In the d- dimensional case they consist of N vectors, where N is given, and N is generally greater than d. The constructions are al...

C. Shaw J. Donatelli J. Konstantinidis J. J. Benedetto

2006-01-01

331

WAVEFORM DICTIONARIES AS APPLIED TO THE AUSTRALIAN EXCHANGE RATE  

Microsoft Academic Search

This paper proposes a new method, called waveform dictionaries, to analyze the trend of the exchange rate of the Australian do llar against other currencies. Four different currencies are explored. They are the U.S. dollar, the Japanese yen, the British pound and the euro. The exchange rates can be classified as non-stationary signals. The waveform dictionaries can reduce the c

RAY ANDERSON

2006-01-01

332

TETA: transistor-level waveform evaluation for timing analysis  

Microsoft Academic Search

Static timing analysis breaks down the longest path problem into waveform analysis of paths of logic stages that are comprised of nonlinear transistors and complex RLC loads. Runtime efficiency is of the utmost importance; however, the waveform evaluation of these logic stages cannot be accelerated via timing simulation algorithms that attempt to exploit temporal or spatial latency since the simulation

Emrah Acar; Florentin Dartu; Lawrence T. Pileggi

2002-01-01

333

Ultra-wideband radar using Fourier synthesized waveforms  

Microsoft Academic Search

Traditional methods of ultra-wideband (UWB) radar signal generation suffer from several disadvantages such as low antenna radiation efficiency and lack of accurate control of signal parameters like pulse shape, pulse repetition interval (PRI), and its spectrum. UWB signals can be generated by expanding the desired radar waveform in a Fourier series and then synthesizing the waveform by generating the individual

Gurnam Singh Gill

1997-01-01

334

Adaptive Waveform Correlation Detectors for Arrays: Algorithms for Autonomous Calibration  

Microsoft Academic Search

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

Frode Ringdal; D B Harris; D Dodge; S J Gibbons

2009-01-01

335

Two-dimensional Full Waveform Inversion  

NASA Astrophysics Data System (ADS)

A two-dimensional full wavefield inversion for direct imaging of compressional wave and out-of-plane standing wave (SH) velocity distribution is developed, tested and implemented. The inversion is base on the finite difference solution of the full two-dimension scalar wave equation in the time-distance domain and operates on wide-aperture, common-shot data. The computational kernel fully utilizes the reverse-time image reconstruction principles. No travel-time picking and phase identification are required for full waveform inversion. For each shot records, gradients of misfit function (Frechét derivative) are dynamically determined by cross-correlation of the recorded forward propagating wavefield and backward propagating residual wavefield at each time step. Convergence to local minima can be avoided by gradually increasing the wavenumber bandwidth in the estimated velocity distribution and to increase the inversion resolution as iterations proceed. Synthetic examples show that the effects of the multiples, scattering, artificial boundary reflection waves, or noise do not contaminate the final results and convergences successfully to the correct solution. Using full two-way waveform approach for seismic imaging simplifies un-necessary skeleton seismic processing procedures. Furthermore, the resolution of inversion result is limited by the bandwidth of field recordings, source wavelet and dominant frequency. Convergence rate and stability of our in-house development of inversion algorithm is highly depends on step length and the complexity of subsurface structure associate with the steepest decent direction. For land data, near-surface effects including topography, lateral velocity variation, source and receiver static corrections are automatically included. For marine seismic data, multiples generated by water layer can be effectively suppressed through wavefield based seismic processing approach.

Li, K.; Chen, H.

2005-12-01

336

The evolution of featureless waveforms for LPI communications  

NASA Astrophysics Data System (ADS)

Low probability of detection (LPD), low probability of intercept (LPI), and low probability of exploitation (LPE) RF communications offer capabilities that are not available with jam resistant communications. These capabilities, reasons for LPI communications development, and jam resistant versus LPI communications requirements are described. The ideal characteristics of a LPI communications waveform and methods for detecting LPI communications transmissions are listed to form the basis for the discussion of the development of three generations of LPI communications waveforms and their capabilities. Particular attention is given to the CS3 waveform, which satisfies all the criteria for an ideal LPI communications waveform. The CS3 waveform is being implemented in prototype units which are able to be the basis of a complete LPI communications system. A typical LPI communications system configuration and a representative aircraft-to-aircraft communications application are described.

Turner, Lester

337

Modeling of current excitation waveforms for magnetic particle inspection  

NASA Astrophysics Data System (ADS)

In magnetic particle inspection, the sample is magnetized using current flow (coils) or flux flow (yoke). In both cases the excitation current may be alternating, full wave rectified, half wave rectified or pulsed. Further, these current waveforms vary significantly with current settings and time with no correlation between peak height and root mean square (rms) value. The choice of inappropriate electrical current waveforms can potentially result in missing some significant defects. This paper presents a finite element modeling study of the magnetization of a test sample due to different current waveforms. The model uses time samples of the waveform and generates magnetic flux density variations at any arbitrary point in the solution domain due to different excitation currents and peak values. The results and effects of current waveforms are presented and discussed. .

Zeng, Zhiwei; Xuan, Liang; Udpa, Lalita; Udpa, Satish

2002-05-01

338

Asymmetric light propagation in chirped photonic crystal waveguides.  

PubMed

We report numerical and experimental investigations of asymmetric light propagation in a newly designed photonic structure that is formed by creating a chirped photonic crystal (PC) waveguide. The use of a non-symmetric distribution of unit cells of PC ensures the obtaining of asymmetric light propagation. Properly designing the spatial modulation of a PC waveguide inherently modifies the band structure. That in turn induces asymmetry for the light's followed path. The investigation of the transmission characteristics of this structure reveals optical diode like transmission behavior. The amount of power collected at the output of the waveguide centerline is different for the forward and backward propagation directions in the designed configuration. The advantageous properties of the proposed approach are the linear optic concept, compact configuration and compatibility with the integrated photonics. These features are expected to hold great potential for implementing practical optical rectifier-type devices. PMID:23037111

Kurt, H; Yilmaz, D; Akosman, A E; Ozbay, E

2012-08-27

339

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

340

Chirped rectilinear core longitudinally-graded optical fibers  

NASA Astrophysics Data System (ADS)

Reported here is a straight-forward and flexible method to fabricate silica optical fibers of circular cladding cross-section and rectilinear cores whose aspect ratio and refractive index profile changes with position along the fiber in a deterministic way. Specifically, a modification to the process recently developed to produce longitudinally-graded optical fibers, LGFs [Opt. Express 20 (2012) 17394–17402], was employed. Herein reported are MCVD-derived germanosilicate fibers with rectangular cores where the aspect ratio changes by nearly 200% and the average refractive index changed by about 5%. Fiber losses were measured to be about 50 dB/km. Such rectangular core fibers are useful for a variety of telecommunication and biomedical applications and the dimensional and optical chirp provides a deterministic way to control further the modal properties of the fiber.

Evert, A.; Hawkins, T.; Stolen, R.; Dragic, P.; Rice, R.; Ballato, J.

2013-10-01

341

Few-cycle attosecond pulse chirp effects on asymmetries in ionized electron momentum distributions  

SciTech Connect

The momentum distributions of electrons ionized from H atoms by chirped few-cycle attosecond pulses are investigated by numerically solving the time-dependent Schroedinger equation. The central carrier frequency of the pulse is chosen to be 25 eV, which is well above the ionization threshold. The asymmetry (or difference) in the yield of electrons ionized along and opposite to the direction of linear laser polarization is found to be very sensitive to the pulse chirp (for pulses with fixed carrier-envelope phase), both for a fixed electron energy and for the energy-integrated yield. In particular, the larger the pulse chirp, the larger the number of times the asymmetry changes sign as a function of ionized electron energy. For a fixed chirp, the ionized electron asymmetry is found to be sensitive also to the carrier-envelope phase of the few-cycle pulse.

Peng Liangyou; Tan Fang; Gong Qihuang; Pronin, Evgeny A.; Starace, Anthony F. [Department of Physics and State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871 (China); Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588-0111 (United States)

2009-07-15

342

Chirp reduction and on/off contrast enhancement via optical injection locking and coherent carrier manipulation  

NASA Astrophysics Data System (ADS)

The most cost-effective solution for modulating data onto an optical carrier is via direct modulation of a semiconductor laser. Unfortunately, this approach suffers from high chirp. The chirp can be reduced by reducing the on/off modulation contrast ratio (i.e. by keeping the signaling laser well above threshold when generating both logical `0' and `1' bits), but the low contrast ratio itself compromises performance. Other techniques can better suppress chirp, e,g., based on selfinjection or optical injection locking of the directly-modulated laser (slave) to another laser (master) that emits CW light. However, this technique although very efficient at eliminating chirp, also requires the slave laser be operated well above threshold. We show however that the issue of the limited on/off modulation contrast can be addressed in this instance by subtraction of the carrier using a component of the master beam and an interferometric arrangement.

Slavík, Radan; Kakande, Joseph; Phelan, Richard; O'Carroll, John; Kelly, Brian; Richardson, David J.

2013-05-01

343

A fully-integrated 32-point chirp Z-transform IC  

Microsoft Academic Search

An IC to perform a complete 32-point DFT with the chirp Z-transform algorithm has been developed, using a two-level polysilicon coplanar electrode process. Chip contains CCD filters, MDACs, ROM and clock logic.

William L. Eversole; D. Mayer; P. W. Bosshart; M. deWitt; C. R. Hewes; D. Buss

1978-01-01

344

Pulse dynamic in a passively mode-locked chirped-pulse fiber laser  

Microsoft Academic Search

We report experimental and numerical results on the pulse dynamic of passively modelocked Yb-doped fiber laser operating in the chirped-pulse regime. A newly design cavity with a CFBG provides positive dispersion with negligible nonlinearity.

B. Ortac; M. Plotner; T. Schreiber; J. Limpert; A. Tunnermann

2008-01-01

345

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

346

Tuning of external-cavity semiconductor lasers with chirped diffraction gratings  

NASA Astrophysics Data System (ADS)

We present a novel scheme of tunable semiconductor laser based on the use of a chirped grating in an external cavity. The chirped grating is fabricated using a simple holographic technique: two Gaussian beams having wavefronts with different radii of curvature are brought to interfere on a photoresist layer. The tuning properties of chirped gratings have been investigated with semiconductor lasers operated with an external cavity. With this type of grating positioned in Littrow configuration, the wavelength selection can be done by translating the grating without any need to rotate it. This cavity configuration provides a tunable output beam with an angle of propagation that is independent of the wavelength. The translation of chirped gratings was shown to tune a visible diode laser and an infrared diode laser over the same spectral band as the conventional tuning scheme where an unchirped grating is rotated.

Duval, Marc; Fortin, Gilles; Piché, Michel; McCarthy, Nathalie

2005-08-01

347

Bubble-Based Acoustic Radiation Force Using Chirp Insonation to Reduce Standing Wave Effects  

PubMed Central

Bubble-based acoustic radiation force can measure local viscoelastic properties of tissue. High intensity acoustic waves applied to laser-generated bubbles induce displacements inversely proportional to local Young’s modulus. In certain instances, long pulse durations are desirable but are susceptible to standing wave artifacts, which corrupt displacement measurements. Chirp pulse acoustic radiation force was investigated as a method to reduce standing wave artifacts. Chirp pulses with linear frequency sweep magnitudes of 100, 200, and 300 kHz centered around 1.5 MHz were applied to glass beads within gelatin phantoms and laser-generated bubbles within porcine lenses. The ultrasound transducer was translated axially to vary standing wave conditions, while comparing displacements using chirp pulses and 1.5 MHz tone burst pulses of the same duration and peak rarefactional pressure. Results demonstrated significant reduction in standing wave effects using chirp pulses, with displacement proportional to acoustic intensity and bubble size.

Erpelding, Todd N.; Hollman, Kyle W.; O'Donnell, Matthew

2007-01-01

348

Highly Efficient Tabletop Optical Parametric Chirped Pulse Amplifier at 1 um(micro sign).  

National Technical Information Service (NTIS)

Optical parametric chirped pulse amplification (OPCPA) is a scalable technology, for ultrashort pulse amplification. Its major advantages include design simplicity, broad bandwidth, tunability, low B-integral, high contrast, and high beam quality. OPCPA i...

I. Jovanovic C. A. Ebbers B. J. Comaskey R. A. Bonner E. C. Morse

2001-01-01

349

Optical parametric chirped pulse amplifier at 1600 nm with all-optical synchronization  

NASA Astrophysics Data System (ADS)

We demonstrate the amplification of 1.6 ?m pulses by a KTA optical parametric chirped-pulse amplifier based on an all-optical synchronization scheme as a scalable approach to generation of high power tunable mid infrared.

Pelletier, Etienne; Leitenstorfer, Alfred; Miller, RJ Dwayne

2013-03-01

350

Longitudinal Coherence Preservation and Chirp Evolution in a High Gain Laser Seeded Free Electron Laser Amplifier  

SciTech Connect

In this letter we examine the start-up of a high gain free electron laser in which a frequency-chirped coherent seed laser pulse interacts with a relativistic electron beam. A Green function formalism is used to evaluate the initial value problem. We have fully characterized the startup and evolution through the exponential growth regime. We obtain explicit expressions for the pulse duration, bandwidth and chirp of the amplified light and show that the FEL light remains fully longitudinally coherent.

Murphy, J.B.; /BNL, NSLS; Wu, Juhao; /SLAC; Wang, X.J.; Watanabe, T.; /BNL, NSLS

2006-06-07

351

Spotlight-Mode SAR Image Formation Utilizing the Chirp Z-Transform in Two Dimensions  

Microsoft Academic Search

A new spotlight-mode synthetic aperture radar im- age formation approach is presented that directly utilizes the reflected electromagnetic returns collected on a polar grid. This approach eliminates polar-to-rectangular grid interpolation by employing chirp z-transforms in two dimensions. Since the chirp z-transform can be implemented via fast Fourier transforms (FFTs), this image formation algorithm consists almost entirely of FFTs allowing it

David A. Yocky; Daniel E. Wahl; Charles V. Jakowatz

2006-01-01

352

Study of SAW Chirp Z transform for an enhancement of OFDM\\/OFDMA systems  

Microsoft Academic Search

The surface acoustic wave has a definite advantage in the Fourier transform for distribute of OFDM that is converted into the OFDM signal and received in power consumption and has a super-high-speed operation. The operation speed of the SAW Chirp-Z transform processor composed of SAW Down Chirp Filter of bandwidth 100 MHz and N=2,048 becomes 5.5GFLOPS. The condition that the

Takaya Watanabe

2009-01-01

353

Two-dimensional chirp z-transform and its application to zoom Wigner bispectrum  

Microsoft Academic Search

In this paper, we present the 2-D chirp z-transform as an extension of the 1-D chirp z-transform. It can be used as a powerful analytic tool to emphasize any region in either the (t-f)- or the (f1-f2) planes, covering a wide variety of multidimensional distributions ranging from two-dimensional filters to higher order moment spectra (HOMS) including the Wigner distribution and

J. A. Draidi; M. A. Khasawneh; J. M. Abu-Ghalune; N. M. Ghuneinii

1996-01-01

354

Pulse multi-pass stretcher using linear chirped fiber Bragg grating  

NASA Astrophysics Data System (ADS)

A pulse stretcher using chirped fiber Bragg grating is demonstrated. Pulses from a 1053nm mode-locked fiber seed oscillator are multi-stretched by a Linear chirped grating set in a fiber regenerative amplifier structure. We have the pulse stretched from 23.6ps to 378ps after it transmits 3 loops in the stretcher. The major factors which affect the stretched pulse shape are discussed.

Zhang, Chengtao; Wang, Xiaochao; Fan, Wei; Rao, Daxing; Lin, Zunqi

2013-09-01

355

Pulse dynamics in a passively mode-locked chirped-pulse fiber laser  

NASA Astrophysics Data System (ADS)

We report experimental and numerical results on the new pulse dynamics in a passively mode-locked ytterbium-doped fiber laser operating in the chirped-pulse regime. Due to the negligible nonlinearity of added highly-positive GVD segment in the purely-normal-dispersion regime, highly-positive chirped pulses can be formed through weak intra-cavity temporal and spectral breathing. Numerical simulations reveal intra-cavity pulse evolution with local temporal stretching phenomena and pulse shaping properties.

Ortaç, B.; Plötner, M.; Limpert, J.; Tünnermann, A.

2010-04-01

356

Toward Broad Bandwidth 2-D Electronic Spectroscopy: Correction of Chirp From a Continuum Probe  

Microsoft Academic Search

Recent implementations of 2-D spectroscopy in the pump–probe geometry using a pulse-shaper demonstrate the ease with which frequency-resolved pump–probe experiments can be readily adapted to 2-D methods. Many frequency-resolved pump–probe experiments employ continuum probes to observe a broad range of electronic transitions. These continuum probes are often chirped, leading to distortions that can be postcorrected by characterizing the chirp and

Patrick A. Tekavec; Kristin L. M. Lewis; Franklin D. Fuller; Jeffrey A. Myers; Jennifer P. Ogilvie

2012-01-01

357

Performance of hybrid chirp/DS signals under Doppler and pulsed jamming  

NASA Astrophysics Data System (ADS)

The bit-error probability is evaluated for a hybrid chirp/direct sequence (DS) spread-spectrum communication system. The received signal is received in Doppler; the channel is contaminated by a pulsed barrage jammer with a varying duty factor. Moreover, the DS correlation loss due to imperfect code synchronization is taken into account. The tradeoffs involved in dividing the total RF bandwidth into the DS and chirp bandwidths to combat both the jamming and the Doppler are discussed.

Elhakeem, A. K.; Targi, Ali

358

Holocene sedimentation in the Skagerrak interpreted from chirp sonar and core data  

Microsoft Academic Search

High-resolution chirp sonar profiling in the northeastern Skagerrak shows acoustically stratified sediments draping a rough-surfaced substratum. A 32 metre long sediment core retrieved from the survey area encompasses the entire Holocene and latest Pleistocene. The uppermost seismo-acoustic units in the chirp profiles represent Holocene marine sediments. The lowermost unit is interpreted as ice-proximal glacial-marine sediments rapidly deposited during the last

Richard Gyllencreutz; Martin Jakobsson; Jan Backman

2005-01-01

359

Demonstration of a continuously variable true-time delay beamformer using a multichannel chirped fiber grating  

Microsoft Academic Search

A continuously variable true-time delay beamformer based on a multichannel chirped fiber grating (MCFG) is demonstrated. The beamformer is capable of wide-band squint-free operation and demonstrates beam steering of a four-element array over ±40°. The use of an MCFG provides a significant reduction in the length of the chirped grating required, eliminates spurious signal transmission, and utilizes narrow-band tunable laser

David B. Hunter; Michael E. Parker; James L. Dexter

2006-01-01

360

Rydberg-atom population transfer by population trapping in a chirped microwave pulse  

SciTech Connect

We demonstrate that Rydberg atoms can be transferred to states of lower principal quantum number by exposing them to a frequency chirped microwave pulse. Specifically, we have transferred n=75 atoms to n=66 with a 400-ns pulse chirped from 7.8 to 11.8 GHz. In spite of the large number of coupled levels, using a simplified model we can describe the process reasonably well as a sequence of adiabatic rapid passages.

Lambert, J.; Gallagher, T.F. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Noel, Michael W. [Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States); Department of Physics, Bryn Mawr College, Bryn Mawr, Pennysylvania 19010 (United States)

2002-11-01

361

Chirped pulse amplification of 300 fs pulses in an Alexandrite regenerative amplifier  

SciTech Connect

The authors demonstrate the amplification of femtosecond dye laser pulses up to the 3.5 mJ level in an alexandrite regenerative amplifier. An expansion/compression system using diffraction gratings allows chirped pulse amplification techniques to be used to produce peak powers upwards of 1 GW. Limitations in the chirped pulse amplification of ultrashort pulses due to intracavity dispersive elements are discussed.

Pessot, M.; Squier, J.; Bado, P.; Mourou, G. (Lab. for Laser Energetics, Univ. of Rochester, Rochester, NY (US)); Harter, D.J. (Allied Signal In., Corporate Technology, Morristown, NJ (US))

1989-01-01

362

Azimuth fractional transformation of the fractional chirp scaling algorithm (FrCSA)  

Microsoft Academic Search

The fractional chirp scaling algorithm (FrCSA) is based on the use of the fractional Fourier transform (FrFT) within the chirp scaling algorithm (CSA). In this paper, a closed-form expression for the azimuth FrFT of the FrCSA is mathematically derived and analyzed from the high-resolution synthetic aperture radar imaging point of view. The azimuth-FrFT expression of the FrCSA is compared to

Ahmed S. Amein; John J. Soraghan

2006-01-01

363

Isomeric states in 253No and 253Fm  

NASA Astrophysics Data System (ADS)

Nuclear structure and decay of isomeric states in 253No were investigated. The isotope was produced by the reaction 48Ca + 207Pb . The excitation energy of the known single-particle isomeric state ( 5/2+[622] was measured by delayed coincidences between ?-rays and implanted evaporation residues and was placed into the level scheme. In addition, decay of a high-lying multi-quasiparticle isomer in 253No was studied using e --? coincidence measurements. A rotational band populated by its de-excitation was identified in 253No . A new isomeric state in 253Fm was observed and a partial-level scheme for this isotope is suggested. In addition ? transitions from excited levels are reported for 253Md.

Antalic, S.; Heßberger, F. P.; Ackermann, D.; Heinz, S.; Hofmann, S.; Kalaninová, Z.; Kindler, B.; Khuyagbaatar, J.; Kojouharov, I.; Kuusiniemi, P.; Leino, M.; Lommel, B.; Mann, R.; Nishio, K.; Šáro, Š.; Streicher, B.; Sulignano, B.; Venhart, M.

2011-05-01

364

On chirp stimuli and neural synchrony in the suprathreshold auditory brainstem response.  

PubMed

The chirp-evoked ABR has been regarded as a more synchronous response than the click-evoked ABR, referring to the belief that the chirp stimulates lower-, mid-, and higher-frequency regions of the cochlea simultaneously. In this study a variety of tools were used to analyze the synchronicity of ABRs evoked by chirp- and click-stimuli at 40 dB HL in 32 normal hearing subjects aged 18 to 55 years (mean=24.8 years, SD=7.1 years). Compared to the click-evoked ABRs, the chirp-evoked ABRs showed larger wave V amplitudes, but an absence of earlier waves in the grand averages, larger wave V latency variance, smaller FFT magnitudes at the higher component frequencies, and larger phase variance at the higher component frequencies. These results strongly suggest that the chirp-evoked ABRs exhibited less synchrony than the click-evoked ABRs in this study. It is proposed that the temporal compensation offered by chirp stimuli is sufficient to increase neural recruitment (as measured by wave V amplitude), but that destructive phase interactions still exist along the cochlea partition, particularly in the low frequency portions of the cochlea where more latency jitter is expected. The clinical implications of these findings are discussed. PMID:20649219

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

2010-07-01

365

Influence of turbulence on the spectrum of diffracted chirped Gaussian pulsed beams  

NASA Astrophysics Data System (ADS)

The influence of turbulence on the spectrum of diffracted chirped Gaussian pulsed beams is studied in detail. By using the quadratic approximation of the Rytov’s phase structure function and the finite expansion of the aperture function, the analytical expression for the spectrum of diffracted chirped Gaussian pulsed beams propagating through atmospheric turbulence is derived. It is shown that in free space there exist the on-axis and off-axis multi-spectral switch for diffracted chirped Gaussian pulsed beams. However, the turbulence results in a decrease of the spectral transition height, and the spectral switch even disappears when the turbulence is strong enough, which is very different from the behavior of undiffracted chirped Gaussian pulsed beams. Specially, with increasing the strength of turbulence, the higher-order spectral switch disappears firstly for on-axis case, while the lower-order spectral switch disappears firstly for off-axis case. In free space the on-axis spectrum is blue-shifted after a certain propagation distance, but the on-axis spectrum is red-shifted after a shorter propagation distance when the turbulence is strong enough. The spectral transition height increases with increasing the chirp parameter and decreasing the pulse duration, and the odd number order position without spectral shift is independent of the chirp parameter and pulse duration.

Ji, Xiaoling

2008-07-01

366

Efficient layering for high speed communication: the MPI over Fast Messages (FM) experience  

Microsoft Academic Search

We describe our experience of designing, implementing, and evaluating two generations of high performance communication libraries,\\u000a Fast Messages (FM) for Myrinet. In FM 1, we designed a simple interface and provided guarantees of reliable and in-order delivery,\\u000a and flow control. While this was a significant improvement over previous systems, it was not enough. Layering MPI atop FM\\u000a 1 showed that

Mario Lauria; Scott Pakin; Andrew Chien

1999-01-01

367

Effects of Cu Interdiffusion on the Electromigration Failure of FM\\/Cu\\/FM Tri-Layers for Spin Valve Read Sensors  

Microsoft Academic Search

Electromigration-induced failure (EIF) lifetime characteristics of FM\\/Cu\\/FM (FM: NiFe or Co) tri-layers, which are currently used in GMR spin-valve read sensors, have been investigated to verify the fundamental failure mechanisms. It is found that the lifetime of NiFe\\/Cu\\/NiFe tri-layers was dramatically increased by decreasing the Cu spacer thickness. The obvious shorter lifetime of NiFe\\/Cu\\/NiFe tri-layers compared to that of Co\\/Cu\\/Co

Jing Jiang; Seongtae Bae; Sunwook Kim

2007-01-01

368

Waveform LiDAR across forest biomass gradients  

NASA Astrophysics Data System (ADS)

Detailed information on the quantity and distribution of aboveground biomass (AGB) is needed to understand how it varies across space and changes over time. Waveform LiDAR data is routinely used to derive the heights of scattering elements in each illuminated footprint, and the vertical structure of vegetation is related to AGB. Changes in LiDAR waveforms across vegetation structure gradients can demonstrate instrument sensitivity to land cover transitions. A close examination of LiDAR waveforms in footprints across a forest gradient can provide new insight into the relationship of vegetation structure and forest AGB. In this study we use field measurements of individual trees within Laser Vegetation Imaging Sensor (LVIS) footprints along transects crossing forest to non-forest gradients to examine changes in LVIS waveform characteristics at sites with low (< 50Mg/ha) AGB. We relate field AGB measurements to original and adjusted LVIS waveforms to detect the forest AGB interval along a forest - non-forest transition in which the LVIS waveform lose the ability to discern differences in AGB. Our results help identify the lower end the forest biomass range that a ~20m footprint waveform LiDAR can detect, which can help infer accumulation of biomass after disturbances and during forest expansion, and which can guide the use of LiDAR within a multi-sensor fusion biomass mapping approach.

Montesano, P. M.; Nelson, R. F.; Dubayah, R.; Sun, G.; Ranson, J.

2011-12-01

369

FM-GA and CM-GA for Gene Microarray Analysis  

Microsoft Academic Search

\\u000a In this paper, we propose two new approaches, FM-GA and CM-GA, to identify significant genes from microarray datasets. FM-GA\\u000a and CM-GA combine our innovative FM-test and CM-test with genetic algorithm (GA), respectively, and leverage the strengths\\u000a of GA. The performance of FM-GA and CM-GA was evaluated by the classification accuracy of decision trees constructed with\\u000a the selected genes. Experiments were

Lily R. Liang; Rommel A. Benites Palomino; Zhao Lu; Vinay Mandal; Deepak Kumar

370

Coherent control of ultracold {sup 85}Rb trap-loss collisions with nonlinearly frequency-chirped light  

SciTech Connect

We present results on coherent control of ultracold trap-loss collisions using 40-ns pulses of nonlinearly frequency-chirped light. The chirps, either positive or negative, sweep {approx}1 GHz in 100 ns and are centered at various detunings below the D{sub 2} line of {sup 85}Rb. At each center detuning, we compare the collisional rate constant {beta} for chirps that are linear in time, concave-down, and concave-up. For positive chirps, we find that {beta} generally depends very little on the shape of the chirp. For negative chirps, however, we find that {beta} can be enhanced by up to 50(20)% for the case of the concave-down shape. This occurs at detunings where the evolution of the wave packet is expected to be coherent. An enhancement at these detunings is also seen in quantum-mechanical simulations of the collisional process.

Pechkis, J. A. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Currently with the Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Carini, J. L.; Rogers, C. E. III; Gould, P. L. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Kallush, S. [Department of Physics and Optical Engineering, ORT Braude, P.O. Box 78, Karmiel (Israel); Kosloff, R. [Department of Physical Chemistry and the Fritz Haber Research Center for Molecular Dynamics, Hebrew University, IL-91094 Jerusalem (Israel)

2011-06-15

371

Algebraic expressions for the waveforms of sea urchin sperm flagella.  

PubMed

The waveforms of live sea urchin sperm flagella were digitized with video-digitizing apparatus. The flagellar waveforms were expressed by the coordinates of 20 points spaced 2 micron apart along the flagella. The waveforms were condensed into simple algebraic expression with four parameters. Each of these parameters showed a systematic variation with the flagellar frequency. These average trends of the parameters made it possible to define an average, idealized, waveshape as a function of the flagella frequency, in the range 8-80 Hz. PMID:3840220

Rikmenspoel, R

1985-09-01

372

Enhance cognitive radar security by designing optimal waveform  

NASA Astrophysics Data System (ADS)

In this paper, we consider cognitive radar security in the presence of interceptors. By designing waveform, the cognitive radar will spread its most power to match the target channel for estimation and remove the spectrum that matches the interception channel for security. We firstly propose the signal model of a typical scenario, and then use the mutual information criterion to guide waveform design. By solving a convex optimization problem, we can obtain a globally optimal waveform. This paper also presents numerical examples to verify effectiveness of the idea and the approaches.

Wang, Songbai; Wang, Jian; Chen, Jianshu; Shan, Xiuming

2011-10-01

373

Enhancing online waveform processing by adding new point attributes  

NASA Astrophysics Data System (ADS)

RIEGL LIDAR instruments based on echo digitization and on-line waveform processing provide valuable attributes to every detected target: calibrated amplitude, calibrated estimated target reflectance, and echo pulse deviation. Additional attributes could be provided by employing enhanced algorithms. In hydrography an estimate for the backscattering coefficient of a water column, for topographic targets an estimate of the angle of incidence of the laser beam on flat targets can be determined. We present data sets based on on-line waveform processing of RIEGL's V-Line and assess the possibility of deriving additional attributes by performing more sophisticated analysis of the waveform.

Pfennigbauer, Martin; Wolf, Clifford; Ullrich, Andreas

2013-05-01

374

A 10 tesla table-top controlled waveform magnet  

NASA Astrophysics Data System (ADS)

Controlled Waveform Magnets (CWMs) are a special class of pulsed magnets which provide semi-continuous, shape-controlled high magnetic field pulses. In this work we report a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 Tesla. Insulated Gate Bipolar Transistor (IGBT) chips were paralleled to form the high current switch. Specimen pulse shapes including flat-tops up to 10 Tesla, and linear as well as some sinusoidal-top magnetic field waveforms have been successfully generated.

Roy Choudhury, Aditya N.; Venkataraman, V.

2012-06-01

375

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

376

Extended Models in Nonlinear Seismic Waveform Inversion  

NASA Astrophysics Data System (ADS)

Most progress in seismic inverse scattering has come through use of linearization (``Born approximation''), in which the reference model is also regarded as unknown - so the problem is still nonlinear, albeit less so. The data-fitting formulations familiar from other work on inverse problems have had remarkably little influence on the development of practical solution methods for the seismic problem. Instead, industrial seismologists use an apparently ad-hoc collection of techniques dubbed velocity analysis, the effectiveness of which depends on the redundancy of seismic reflection surveys. This talk will explain how to view velocity analysis as the solution of an extended Born inverse problem. The various special techniques correspond to various extensions; Analysis shows that some of these are suitable for inversion in the presence of strong refraction, while others are not. Open problems abound, not the least of which is to get rid of the Born approximation. A natural generalization of an extended inverse formulation due originally to Claerbout combines the methodology of industrial velocity analysis with full nonlinear wavefield modeling. This presentation will describe some preliminary numerical results based on acoustic modeling, as well as a more general theory of nonlinear elastic waveform inversion.

Symes, W. W.

2004-12-01

377

Flagellar waveform analysis of swimming algal cells  

NASA Astrophysics Data System (ADS)

The twin flagella of the green alga Chlamydomas reinhardtii are driven by dynein molecular motors to oscillate at about 50-60 Hz in a breaststroke motion. For decades, Chlamydomas has been used as a model organism for studies of flagellar motility, and of genetic disorders of ciliary motion. However, little is known experimentally about the flagellar waveforms, and the resulting time-dependent force distribution along the 250 nm diameter flagella. Here, we study flagellar dynamics experimentally by confining cells in quasi-2D liquid films. From simultaneous measurements of the cell body velocity and the time-dependent velocities along the center lines of the two flagella, we determine the drag coefficients, and estimate the power expended by the body and the flagella, comparing our findings with measurementsootnotetextJ.S. Guasto et al., Phys. Rev. Lett. 105, 168102 (2010) based on the induced fluid flow field. We contrast the results for the quite different beating patterns of synchronous and asynchronous flagella, respectively.

Kurtuldu, Huseyin; Johnson, Karl; Gollub, Jerry

2011-11-01

378

Rapid Waveform Earthquake Location in Italy  

NASA Astrophysics Data System (ADS)

We present an full waveform earthquake location technique and its application to earthquakes recorded by broadband stations in Italy and in the neighbouring regions. The technique is based on the cross-correlation between pre-determined and processed Green's functions and similarly processed data. Earthquake locations are found after testing against a grid of potential points. The Green's functions can be either determined synthetically assuming a velocity-attenuation model, or empirically from small recorded earthquakes. The technique adopts and further develops a methodology introduced by Withers et al. (BSSA, 89, 657-669, 1999). The technique is applied to a set of earthquakes of various magnitudes that have occurred in Italy and that have been recorded by the Italian Digital Seismic Network and the Mediterranean Very Broadband Seismographic Network (MedNet). The results show that it is possible to locate earthquakes as low as M2.0. Our results also show that the technique is applicable to real-time data stream using current servers and it appears appealing for earthquake early warning purposes.

Maggi, A.; Michelini, A.

2009-04-01

379

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

380

Elastic electron-deuteron scattering and the electric neutron form factor at four-momentum transfers 5 fm-2 < q2 < 14 fm-2  

Microsoft Academic Search

The cross section for elastic electron-deuteron scattering was measured for ten four-momentum transfers squared in the range 5fm-2fm-2. From the measured cross sections the sum A(q2) of charge and quadrupole form factors was determined. The experimental values are compared with theoretical predictions including relativistic corrections. Different deuteron wave functions and different parametrizations for the electric neutron form factor GEN were

S. Galster; H. Klein; J. Moritz; K. H. Schmidt; D. Wegener; J. Bleckwenn

1971-01-01

381

A Study of Mexican Free-Tailed Bat Chirp Syllables: Bayesian Functional Mixed Models for Nonstationary Acoustic Time Series  

PubMed Central

We describe a new approach to analyze chirp syllables of free-tailed bats from two regions of Texas in which they are predominant: Austin and College Station. Our goal is to characterize any systematic regional differences in the mating chirps and assess whether individual bats have signature chirps. The data are analyzed by modeling spectrograms of the chirps as responses in a Bayesian functional mixed model. Given the variable chirp lengths, we compute the spectrograms on a relative time scale interpretable as the relative chirp position, using a variable window overlap based on chirp length. We use 2D wavelet transforms to capture correlation within the spectrogram in our modeling and obtain adaptive regularization of the estimates and inference for the regions-specific spectrograms. Our model includes random effect spectrograms at the bat level to account for correlation among chirps from the same bat, and to assess relative variability in chirp spectrograms within and between bats. The modeling of spectrograms using functional mixed models is a general approach for the analysis of replicated nonstationary time series, such as our acoustical signals, to relate aspects of the signals to various predictors, while accounting for between-signal structure. This can be done on raw spectrograms when all signals are of the same length, and can be done using spectrograms defined on a relative time scale for signals of variable length in settings where the idea of defining correspondence across signals based on relative position is sensible.

MARTINEZ, Josue G.; BOHN, Kirsten M.; CARROLL, Raymond J.

2013-01-01

382

Fiber-based pulse stretcher for narrowband terahertz pulse generation with a chirped-pulse beating method  

NASA Astrophysics Data System (ADS)

We theoretically show that it is possible to generate chirp-free terahertz (THz) pulses with a chirped-pulse beating method by using an optical fiber as a pulse stretcher. Proper choices of the core radius and the dopant fraction of the core material of a step-index single-mode optical fiber eliminate the third-order spectral phase of the fiber, thus giving the pump laser pulse a purely linear chirp. We also show that even a standard commercial single-mode optical fiber can give THz pulses of lower chirp than the lower limit for a grating pair. We perform experiments to verify our theory.

Yoshida, Tetsuya; Kamada, Shohei; Murata, Shuhei; Aoki, Takao

2013-10-01

383

Tracing the photodissociation probability of H{sub 2}{sup +} in intense fields using chirped laser pulses  

SciTech Connect

The temporal evolution of the dissociation probabilities for various vibrational levels of H{sub 2}{sup +} is observed in terms of shifts in the kinetic energy release dissociation spectra, induced by linearly chirped intense laser pulses. In contrast to previous observations, in which no dependence on the chirp sign was observed, the energy spectrum reported here shows peak shifts, up for negative chirp and down for positive chirp. For some vibrational levels, dissociation takes place early on in the pulse; hence, care must be taken while interpreting the effect of pulse duration in photodissociation studies. This interpretation is supported by numerical solutions of the time-dependent Schroedinger equation.

Prabhudesai, Vaibhav S.; Natan, Adi; Bruner, Barry D.; Diner, Adi; Silberberg, Yaron [Department of Physics of Complex Systems, Weizmann Institute of Science, IL-76100 Rehovot (Israel); Lev, Uri; Heber, Oded; Zajfman, Daniel [Department of Particle Physics, Weizmann Institute of Science, IL-76100 Rehovot (Israel); Strasser, Daniel [Department of Particle Physics, Weizmann Institute of Science, IL-76100 Rehovot (Israel); Institute of Chemistry, Hebrew University, IL-91904 Jerusalem (Israel); Schwalm, D. [Department of Particle Physics, Weizmann Institute of Science, IL-76100 Rehovot (Israel); Max-Planck-Institut fuer Kernphysik, D-69117 Heidelberg (Germany); Ben-Itzhak, Itzik; Hua, J. J.; Esry, B. D. [J. R. Macdonald Laboratory, Kansas State University, Manhattan, Kansas 66506 (United States)

2010-02-15

384

Consistency of Post-Newtonian Waveforms with Numerical Relativity.  

National Technical Information Service (NTIS)

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 observati...

B. J. Kelly J. Cewntrella J. G. Baker J. R. VanMeter S. T. McWilliams

2006-01-01

385

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

2007-10-29

386

Implementing a GPS Waveform Under the Software Communication Architecture.  

National Technical Information Service (NTIS)

SCA governs the structure and operation of software defined radios, enabling programmable radios to load waveforms, run applications, and network into an integrated system. Adherence to standards detailed in the SCA definition document allows hardware and...

A. Brown D. Babich L. Stricklan

2006-01-01

387

Waveform Diversity and Design for Interoperating Radar Systems.  

National Technical Information Service (NTIS)

For many years, conventional radars transmitted, received, and processed the same waveform on every pulse or burst within a coherent processing interval (CPI), independently of the environment. Now, modern radar systems have considerable flexibility in th...

M. S. Greco

2013-01-01

388

Waveform Analysis of Transmitters of Opportunity for Passive Radar.  

National Technical Information Service (NTIS)

This report investigates the suitability of a number of broadcast band transmitters of opportunity for a passive radar. Specifically, this report reviews the design of active radar waveforms, measures emissions for representative transmitters of opportuni...

M. A. Ringer G. J. Frazer S. J. Anderson

1999-01-01

389

Solving seismological problems using sgraph program: II-waveform modeling  

SciTech Connect

One of the seismological programs to manipulate seismic data is SGRAPH program. It consists of integrated tools to perform advanced seismological techniques. SGRAPH is considered a new system for maintaining and analyze seismic waveform data in a stand-alone Windows-based application that manipulate a wide range of data formats. SGRAPH was described in detail in the first part of this paper. In this part, I discuss the advanced techniques including in the program and its applications in seismology. Because of the numerous tools included in the program, only SGRAPH is sufficient to perform the basic waveform analysis and to solve advanced seismological problems. In the first part of this paper, the application of the source parameters estimation and hypocentral location was given. Here, I discuss SGRAPH waveform modeling tools. This paper exhibits examples of how to apply the SGRAPH tools to perform waveform modeling for estimating the focal mechanism and crustal structure of local earthquakes.

Abdelwahed, Mohamed F. [Geological Hazards Research Unit, King Abdulaziz University (Saudi Arabia) and National Research Institute of Astronomy and Geophysics (NRIAG), Helwan (Egypt)

2012-09-26

390

Dynamic waveform design for target tracking using MIMO radar  

Microsoft Academic Search

In this paper, we investigate waveform design for dynamic target tracking using a multiple-input, multiple-output (MIMO) radar system. The agile tracking application is based on our recently derived Cramer-Rao lower bound (CRLB) for estimating target position and velocity, that is represented in terms of the transmitted waveform parameters. Using the CRLB at high signal-to-noise ratio (SNR), we adaptively select the

Jun Zhang; B. Manjunath; G. Maalouli; A. Papandreou-Suppappola; D. Morrell

2008-01-01

391

Use and Abuse of the Model Waveform Accuracy Standards  

NASA Astrophysics Data System (ADS)

Accuracy standards have been developed to ensure that the waveforms used for gravitational-wave data analysis are good enough to serve their intended purposes. These standards place constraints on certain norms of the frequency-domain representations of the waveform errors. Examples will be presented of possible misinterpretations and misapplications of these standards, whose effect could be to vitiate the quality control they were intended to enforce. Suggestions will be given for ways to avoid these problems. )

Lindblom, Lee

2010-02-01

392

Use and abuse of the model waveform accuracy standards  

NASA Astrophysics Data System (ADS)

Accuracy standards have been developed to ensure that the waveforms used for gravitational-wave data analysis are good enough to serve their intended purposes. These standards place constraints on certain norms of the frequency-domain representations of the waveform errors. Examples are given here of possible misinterpretations and misapplications of these standards, whose effect could be to vitiate the quality control they were intended to enforce. Suggestions are given for ways to avoid these problems.

Lindblom, Lee

2009-09-01

393

Waveform effects of a metastable olivine tongue in subducting slabs  

Microsoft Academic Search

We constructed velocity models of subducting slabs with a kinetically-depressed olivine ? ?- and ?-spinel transition, and examined the effect that such structures would have on teleseismic P waveforms using a full-wave finite-difference method. These two-dimensional calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO) to

John E. Vidale; Quentin Williams; Heidi Houston

1991-01-01

394

Waveform effects of a metastable olivine tongue in subducting slabs  

Microsoft Academic Search

Velocity models of subducting slabs with a kinetically-depressed olivine to beta- and gamma-spinel transition are constructed, and the effect that such structures would have on teleseismic P waveforms are examined using a full-wave finite-difference method. These 2D calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO)

John E. Vidale; Quentin Williams; Heidi Houston

1991-01-01

395

Transmission line pulsed waveform shaping with microwave filters  

Microsoft Academic Search

Impedance mismatches in the standard transmission line pulsed (TLP) measurement system will severely distort the pulsed waveform, but use of matched microwave attenuating filters can transform the setup into a 50-Omega TLP system which produces near-ideal waveforms. In addition, passive, lossless low-pass filters can be used to vary the rise time of the pulse. Detailed measurement and microwave simulation results

Sopan Joshi; Elyse Rosenbaum

2003-01-01

396

Auditory brainstem responses with optimized chirp signals compensating basilar-membrane dispersion.  

PubMed

This study examines auditory brainstem responses (ABR) elicited by rising frequency chirps. The time course of frequency change for the chirp theoretically produces simultaneous displacement maxima by compensating for travel-time differences along the cochlear partition. This broadband chirp was derived on the basis of a linear cochlea model [de Boer, "Auditory physics. Physical principles in hearing theory I," Phys. Rep. 62, 87-174 (1980)]. Responses elicited by the broadband chirp show a larger wave-V amplitude than do click-evoked responses for most stimulation levels tested. This result is in contrast to the general hypothesis that the ABR is an electrophysiological event most effectively evoked by the onset or offset of an acoustic stimulus, and unaffected by further stimulation. The use of this rising frequency chirp enables the inclusion of activity from lower frequency regions, whereas with a click, synchrony is decreased in accordance with decreasing traveling velocity in the apical region. The use of a temporally reversed (falling) chirp leads to a further decrease in synchrony as reflected in ABR responses that are smaller than those from a click. These results are compatible with earlier experimental results from recordings of compound action potentials (CAP) [Shore and Nuttall, "High synchrony compound action potentials evoked by rising frequency-swept tonebursts," J. Acoust. Soc. Am. 78, 1286-1295 (1985)] reflecting activity at the level of the auditory nerve. Since the ABR components considered here presumably reflect neural response from the brainstem, the effect of an optimized synchronization at the peripheral level can also be observed at the brainstem level. The rising chirp may therefore be of clinical use in assessing the integrity of the entire peripheral organ and not just its basal end. PMID:10738807

Dau, T; Wegner, O; Mellert, V; Kollmeier, B

2000-03-01

397

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

398

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

399

FM1-43 reports plasma membrane phospholipid scrambling in T-lymphocytes.  

PubMed Central

We have found using imaging techniques that stimulating Jurkat human leukaemic T-cells with ionomycin in the presence of FM1-43, a dye used to monitor exocytosis and endocytosis, causes large (6--10-fold) increases in FM1-43 fluorescence. These responses are too large to be caused by exocytosis. Instead, three lines of evidence suggest that FM1-43 is responding to phospholipid scrambling. First, ionomycin also stimulates increases in the fluorescence of annexin V, a phosphatidylserine-specific probe, while thapsigargin does not stimulate fluorescence increases of either probe. Secondly, cells that exhibit FM1-43 fluorescence increases after ionomycin stimulation stain with annexin V once FM1-43 is washed out. Thirdly, ionomycin stimulates uptake of 7-nitrobenz-2-oxa-1,3-diazole-labelled phosphatidylcholine, a specific assay for scramblase activity, whereas thapsigargin does not. We find that FM1-43 reports phospholipid scrambling with 'better' kinetics than annexin V, and does require extracellular Ca(2+) to report phospholipid scrambling. We suggest that FM1-43 may be a useful probe to study the dynamics of phospholipid scrambling. The results are the first demonstration that FM1-43 can respond significantly to a biological process other than vesicular trafficking.

Zweifach, A

2000-01-01

400

47 CFR 73.4135 - Interference to TV reception by FM stations.  

Code of Federal Regulations, 2011 CFR

... 4 2011-10-01 2011-10-01 false Interference to TV reception by FM stations. 73.4135 Section 73.4135 Telecommunication...Applicable to All Broadcast Stations § 73.4135 Interference to TV reception by FM stations. See Public Notice, FCC...

2011-10-01

401

47 CFR 73.4135 - Interference to TV reception by FM stations.  

Code of Federal Regulations, 2012 CFR

... 4 2012-10-01 2012-10-01 false Interference to TV reception by FM stations. 73.4135 Section 73.4135 Telecommunication...Applicable to All Broadcast Stations § 73.4135 Interference to TV reception by FM stations. See Public Notice, FCC...

2012-10-01

402

CERES FM-5 on the NPP observatory: predicted performance and early orbit validation plans  

NASA Astrophysics Data System (ADS)

The Clouds and Earth Radiant Energy System (CERES) Flight Model FM-1 and FM-2 sensors aboard the Terra and the FM-3 and FM-4 sensors aboard the Aqua spacecraft have provided the first decade of observations of quality suitable for the Earth Radiation Climate Data Record (CDR). To assure continuity of this CDR the CERES FM-5 sensor will fly on the NPP spacecraft, scheduled for launch in October 2011. The methods for calibrating the FM-5 in orbit and validating the results so as to maintain the required level of accuracy and traceability are described. These methods include use of on-board calibration sources and a number of tests devised for FM-1 through -4. In addition, comparisons of measurement by the newly calibrated FM-5 with (nearly) coincident measurements by the older CERES instruments on Terra and Aqua provide an opportunity to investigate the effects on the instruments and the on-board calibration devices of a decade of operating in space.

Priestley, Kory; Smith, G. Lou; Thomas, Susan; Bitting, Herbert

2011-09-01

403

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars  

Microsoft Academic Search

We examine the signal processing of both linear and sinusoidal frequency modulation (FM) coherent ladar returns from resolved and unresolved targets, which are spread in Doppler. The Doppler spread may be due to target spin, tumbling, or vibration as well as to the applied linear or sinusoidal-FM on the transmitted E-field. Monte Carlo realizations of the target surface random phasor

Douglas G. Youmans

2003-01-01

404

Selecting the gain for radio microphone (FM) systems: theoretical considerations and practical limitations.  

PubMed

This paper provides theoretical estimates of the signal-to-noise (S/N) ratio advantage that can be gained from a radio microphone (FM) system used with an environmental (EV) microphone, compared with the S/N ratio delivered by a conventional hearing aid alone. These estimates show that the S/N advantage gained is a function of the speaker/listener distance and the FM/EV gain difference, the greater the distance and the closer the FM gain is to the EV gain, the greater the S/N advantage. The implications for choice of FM and EV gain when fitting FM systems are discussed. The two goals of equating the FM and EV outputs and maximizing the S/N ratio are mutually incompatible. It is concluded that the FM gain should be set to be 10dB less than the EV gain unless the situation can be closely monitored, in which case the FM gain should be set as high as possible consistent with loudness tolerance and acceptable levels of distortion. PMID:8574202

Rowson, V J; Bamford, J M

1995-06-01

405

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Network/AM, FM station affiliation agreements. 73.4154 Section 73.4154 Telecommunication...Broadcast Stations § 73.4154 Network/AM, FM station affiliation agreements. See Report, Statement of Policy, and...

2012-10-01

406

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Network/AM, FM station affiliation agreements. 73.4154 Section 73.4154 Telecommunication...Broadcast Stations § 73.4154 Network/AM, FM station affiliation agreements. See Report, Statement of Policy, and...

2011-10-01

407

Chirp-Z analysis for sol-gel transition monitoring.  

PubMed

Gelation is a complex reaction that transforms a liquid medium into a solid one: the gel. In gel state, some gel materials (DMAP) have the singular property to ring in an audible frequency range when a pulse is applied. Before the gelation point, there is no transmission of slow waves observed; after the gelation point, the speed of sound in the gel rapidly increases from 0.1 to 10 m/s. The time evolution of the speed of sound can be measured, in frequency domain, by following the frequency spacing of the resonance peaks from the Synchronous Detection (SD) measurement method. Unfortunately, due to a constant frequency sampling rate, the relative error for low speeds (0.1 m/s) is 100%. In order to maintain a low constant relative error, in the whole speed time evolution range, Chirp-Z Transform (CZT) is used. This operation transforms a time variant signal to a time invariant one using only a time dependant stretching factor (S). In the frequency domain, the CZT enables us to stretch each collected spectrum from time signals. The blind identification of the S factor gives us the complete time evolution law of the speed of sound. Moreover, this method proves that the frequency bandwidth follows the same time law. These results point out that the minimum wavelength stays constant and that it only depends on the gel. PMID:15047337

Martinez, Loïc; Caplain, Emmanuel; Serfaty, Stéphane; Griesmar, Pascal; Gouedard, Gérard; Gindre, Marcel

2004-04-01

408

Hyperspectral imaging with stimulated Raman scattering by chirped femtosecond lasers.  

PubMed

Raman microscopy is a quantitative, label-free, and noninvasive optical imaging technique for studying inhomogeneous systems. However, the feebleness of Raman scattering significantly limits the use of Raman microscopy to low time resolutions and primarily static samples. Recent developments in narrowband stimulated Raman scattering (SRS) microscopy have significantly increased the acquisition speed of Raman based label-free imaging by a few orders of magnitude, at the expense of reduced spectroscopic information. On the basis of a spectral focusing approach, we present a fast SRS hyperspectral imaging system using chirped femtosecond lasers to achieve rapid Raman spectra acquisition while retaining the full speed and image quality of narrowband SRS imaging. We demonstrate that quantitative concentration determination of cholesterol in the presence of interfering chemical species can be achieved with sensitivity down to 4 mM. For imaging purposes, hyperspectral imaging data in the C-H stretching region is obtained within a minute. We show that mammalian cell SRS hyperspectral imaging reveals the spatially inhomogeneous distribution of saturated lipids, unsaturated lipids, cholesterol, and protein. The combination of fast spectroscopy and label-free chemical imaging will enable new applications in studying biological systems and material systems. PMID:23256635

Fu, Dan; Holtom, Gary; Freudiger, Christian; Zhang, Xu; Xie, Xiaoliang Sunney

2013-01-18

409

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

2011-11-15

410

Characterization of Silicon Sulfides by Chirped-Pulse Rotational Spectroscopy  

NASA Astrophysics Data System (ADS)

Chirped-pulse Fourier transform microwave spectroscopy is used to characterize the electrical discharge products that are formed in a supersonic molecular beam through a dilute gas mixture of silane and hydrogen sulfide. The spectrum between 6 and 18 GHz is dominated by SiS: more than 175 transitions have been assigned to either its isotopic species, its vibrationally excited states, or both, on the basis of previous cavity measurements. Owing to the flat instrument response function and extensive vibrational excitation that has been observed, it is possible to derive a precise vibrational temperature for SiS, and determine the relative abundances of SiS, HSiS, and H_2SiS. Although rotational lines from more than 15 other silicon or sulfur molecules have been identified in the same discharge, more than 50% of lines that have been detected with a signal-to-noise ratio of three or greater are presently unassigned. Attempts to assign these many remaining lines, and efforts to benchmark the performance of our spectrometer will be highlighted as well.

McCarthy, Michael C.; Crabtree, Kyle N.; Martinez, Oscar; , Jr.

2013-06-01

411

MODELLING OF A SYNCHRONOUS PERMANENT MAGNET MOTOR TO ALLOW COMPARISON OF REFERENCE CURRENT WAVEFORMS  

Microsoft Academic Search

One of the challenges of optimal synchronous motor control is the determination of the reference current waveform. Traditionally these waveforms have either been square (for brushless DC) or sinu- soidal (AC synchronous), however modern electronics allow hybrid waveforms. The best waveform will achieve a balance of maximum efficiency and minimum torque ripple, while achieving the desired torque. To compare current

G. Heins; F. G. De Boer

2004-01-01

412

Remote Metrology, Mapping, and Motion Sensing of Plasma Facing Components Using FM Coherent Laser Radar  

SciTech Connect

Metrology inside a D/T burning fusion reactor must necessarily be conducted remotely since the in-vessel environment would be highly radioactive due to neutron activation of the torus walls. A technique based on frequency modulated coherent laser radar (FM CLR) for such remote metrology is described. Since the FM CLR relies on frequency shift to measure distances, the results are largely insensitive to surface reflectance characteristics. Results of measurements in TFTR and NSTX fusion devices using a prototype FM CLR unit, capable of remotely measuring distances (range) up to 22 m with better than 0.1-mm precision, are provided. These results illustrate that the FM CLR can be used for precision remote metrology as well as viewing. It is also shown that by conducting Doppler corrected range measurements using the CLR, the motion of objects can be tracked. Thus, the FM CLR has the potential to remotely measure the motion of plasma facing components (PFCs) during plasma disruptions.

Menon, M.M.; Barry, R.E.; Slotwinsky, A.; Kugel, H.W.; Skinner, C.H.

2000-09-11

413

Integrating AM/FM maps with distribution SCADA  

SciTech Connect

Distribution level power systems are characterized by a very large network of feeders, transformers, sectionalizing switches and fuses. Because of the large number of components and the relatively low power levels flowing through any particular portion of the distribution system, most of the network has no telemetering, or remote control capabilities, except, perhaps, at the distribution substations. This paper describes the implementation of full-color digital maps within a distribution SCADA system. The maps, and all the symbology they contain, originate from the client's AM/FM system where they can be updated. These maps contain special symbols that are dynamically updated with SCADA data to continuously represent the current state of the distribution system. The operator has the capability to pan to a desired point on the maps, zoom in or out on a point, with maps automatically changing from one level of detail to another at predefined zoom scales (decluttering), bring up windows containing graphics or standard SCADA crt displays that are familiar to the operator, and issue supervisory control commands.

Trudeau, D.; Hoffman, R.; Seymour, M.A. (CAE Electronics, Ltd., Montreal, Quebec (CA))

1990-04-01

414

Noncollinear parametric fluorescence by chirped quasi-phase matching for monocycle temporal entanglement.  

PubMed

Quantum entanglement of two photons created by spontaneous parametric downconversion (SPDC) can be used to probe quantum optical phenomena during a single cycle of light. Harris [Opt. Express 98, 063602 (2007)] suggested using ultrabroad parametric fluorescenc generated from a quasi-phase-matched (QPM) device whose poling period is chirped. In the Harris's original proposal, it is assumed that the photons are collinearly generated and then spatially separated by frequency filtering Here, we alternatively propose using noncollinearly generated SPDC. In our numerical calculation, to achieve 1.2 cycle temporal correlation for a 532 nm pump laser, only 10% -chirped device is sufficien when noncollinear condition is applied, while a largely chirped (50%) device is required in collinear condition. We also experimentally demonstrate an octave-spanning (790-1610 nm) noncollinear parametric fluorescenc from a 10% chirped MgSLT crystal using both a superconducting nanowire single-photon detector and photomultiplier tube as photon detectors. The observed SPDC bandwidth is 194 THz, which is the largest width achieved to date for a chirped QPM device. From this experimental result, our numerical analysis predicts that the bi-photon can be compressed to 1.2 cycles with appropriate phase compensation. PMID:23187339

Tanaka, Akira; Okamoto, Ryo; Lim, Hwan Hong; Subashchandran, Shanthi; Okano, Masayuki; Zhang, Labao; Kang, Lin; Chen, Jian; Wu, Peiheng; Hirohata, Toru; Kurimura, Sunao; Takeuchi, Shigeki

2012-11-01

415

Rotation of NMR images using the 2D chirp-z transform.  

PubMed

A quick and accurate way to rotate and shift nuclear magnetic resonance (NMR) images using the two-dimensional chirp-z transform is presented. When the desired image grid is rotated and shifted from the original grid due to patient motion, the chirp-z transform can reconstruct NMR images directly onto the ultimate grid instead of reconstructing onto the original grid and then applying interpolation to get the final real-space image in the conventional way. The rotation angle and shift distances are embedded in the parameters of the chirp-z transform. The chirp-z transform implements discrete sinc interpolation to get values at grid points that are not exactly on the original grid when applying the inverse Fourier transform. Therefore, the chirp-z transform is more accurate than methods such as linear or bicubic interpolation and is more efficient than direct implementation of sinc interpolation because the sinc interpolation is implemented at the same time as reconstruction from k-space. PMID:10080271

Tong, R; Cox, R W

1999-02-01

416

A novel method for the demodulation of fiber Bragg grating sensing system based on chirp grating  

NASA Astrophysics Data System (ADS)

In this paper, we propose a novel method of the demodulation of FBG sensing system based on chirp grating and LPG edge filter in which chirp grating is used as band filter. The measurement speed is mainly determined by the response time of the photo-detector and the convert time of AD chips. So, it can highly improve the stability and scan speed of the sensing system. In the experiment system, we use fiber Bragg grating and adjust its bandwidth to get a chirp grating.. The center wavelength of chirp grating is 1551.60nm, and the pass-band wavelength is 7nm. The LPG is written on a standard single mode fiber with microlens array. The grating has a period of 440?m and a length of 3 cm. The center wavelength of LPG is 1558nm, and the falling edge of LPG is from 1540nm to 1555nm. We investigate light power by using a monitor magnify circuit, while the reflected wavelength of FBG by using optical spectrum analyzer. This system has high linear output and the linear fitting is 0.9918. The windage is due to the non-perfect square spectral profile of the reference chirp fiber grating.

Liu, Bo; Zeng, Jian; Xiao, Chun-Xian; Kai, Gui-Yun; Dong, Xiaoyi

2004-04-01

417

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

418

Chirped moire fiber gratings operating on two-wavelength channels for use as dual-channel dispersion compensators  

Microsoft Academic Search

Long continuously chirped moire fiber gratings are demonstrated. Clean, dual-channel operation with dispersion equivalent to 100 and 200 km of standard fiber is shown from gratings of lengths 35.1 cm and 1 m. The gratings show reflection and time-delay characteristics of the same high quality as previously reported in single-channel chirped gratings

Morten Ibsen; Michael K. Durkin; Richard I. Laming

1998-01-01

419

Chirped Steady pi-pulses of Light of an Arbitrary Duration in a Lossy, Exactly Resonant Inverted Medium  

Microsoft Academic Search

It is shown that the steady ? -pulses of light in a lossy, resonant inverted medium can have an arbitrary duration greater than a critical value and are in general chirped. The non-chirped ? -pulses of fixed duration (for a given population inversion) obtained by Arecchi and Bonifacio and by Lamb is a special case of our results when the

Hari Prakash; G. S. Bhatnagar

1979-01-01

420

Responses of Neurons in Cat Primary Auditory Cortex to Bird Chirps: Effects of Temporal and Spectral Context  

Microsoft Academic Search

The responses of neurons to natural sounds and simplified natural sounds were recorded in the primary auditory cortex (AI) of halothane-anesthetized cats. Bird chirps were used as the base natural stimuli. They were first presented within the orig- inal acoustic context (at least 250 msec of sounds before and after each chirp). The first simplification step consisted of ex- tracting

Omer Bar-Yosef; Yaron Rotman; Israel Nelken

421

Theoretical and Experimental Study of the Injection-Locked TEA COâ Laser Incorporating Electron-Plasma Prepulse Chirp Phenomena  

Microsoft Academic Search

Electron-plasma-induced chirping phenomena are incorporated into a quantitative theoretical treatment of an injection-locked compact TEA COâ laser. For the first time, inferred estimates of both the magnitude and sense of the single mode detuning range asymmetry about resonance are shown to agree with experimentally derived data. Conditions for chirp-free operation are discussed and demonstrated.

A. K. Kar; R. G. Harrison; N. R. Heckenberg; D. M. Tratt

1955-01-01

422

Extended chirp scaling algorithm for air- and spaceborne SAR data processing in stripmap and ScanSAR imaging modes  

Microsoft Academic Search

Presents a generalized formulation of the extended chirp scaling (ECS) approach for high precision processing of air- and spaceborne SAR data. Based on the original chirp scaling function, the ECS algorithm incorporates a new azimuth scaling function and a subaperture approach, which allow an effective phase-preserving processing of ScanSAR data without interpolation for azimuth geometric correction. The azimuth scaling can

A. Moreira; J. Mittermayer; R. Scheiber

1996-01-01

423

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): An Ultra-Broadband Spatially Dispersed Regenerative Amplifier Free from Spatial Chirp  

NASA Astrophysics Data System (ADS)

An ultra-broadband Ti:sapphire regenerative amplifier based on spatially dispersed amplification is demonstrated experimentally Departing from previous reports, a new design of the cavity gets the amplified pulse free from spatial chirp. Utilizing this new regenerative amplifier, chirped pulses with bandwidth (FWHM) of about 80 nm are obtained, and the bandwidth is limited only by that of the incident seed pulses.

Li, Chuang; Leng, Yu-Xin; Zhang, Chun-Mei; Liang, Xiao-Yan; Li, Ru-Xin; Xu, Zhi-Zhan

2008-06-01

424

Forensic Application of FM-CW and Pulse Radar  

SciTech Connect

Ground-penetrating radar (GPR) technology has supplied vital assistance in criminal investigations. However, law enforcement personnel desire further developments such that the technology is rapidly deployable, and that it provides both a simple user interface and sophisticated target identification. To assist in the development of target identification algorithms, our efforts involve gathering background GPR data for the various site conditions and circumstances that often typify clandestine burials. For this study, forensic anthropologists established shallow-grave plots at The University of Tennessee Anthropological Research Facility (ARF) that are specific to GPR research. These plots contain donated human cadavers lying in various configurations and depths, surrounded by assorted construction material and backfill debris. We scanned the plots using two GPR technologies: (1) a multi-frequency synthetic-aperture FM-CW radar (200-700 MHz) (GPR-X) developed by the U.S. Department of Energy's (DOE) Special Technologies Laboratory (STL), Bechtel Nevada (Koppenjan et al., 2000), and (2) a commercial pulse radar (SIR-20) manufactured by Geophysical Survey Systems, Inc. (400 and 900 MHz)(GSSI). The sweep-frequency data show the large biological mass decomposing within the torso as encircled ''hot spots.'' The 400-MHz pulse radar exhibit major horizontal reflectors above the body, with shadow reflectors (horizontal multiples) occurring beneath the body at 60 cm depth. The 400-MHz antenna was able to discern the grave walls and folded tarp covering the lower body. Under these moist, clay-rich conditions, the 900-MHz antenna was able to penetrate slightly beyond 30 cm beneath the concrete layer. However, neither system was able to penetrate beyond a one meter depth in the moist, clay-rich soil (fine, mixed, thermic Typic Paleudalf). Example scans from each system are provided, along with a discussion of the survey protocol and general performance.

S. K. Koppenjan; R. S. Freeland; M. L. Miller; R. E. Yoder

2003-01-01

425

AM-FM screen design using donut filters  

NASA Astrophysics Data System (ADS)

In this paper we introduce a class of linear filters called 'donut filters' for the design of halftone screens that enable robust printing with stochastic0 clustered dots. The donut filter approach is a simple, yet efficient method to produce pleasing stochastic clustered-dot halftone patterns (a.k.a AM-FM halftones) suitable for systems with poor isolated dot reproduction and/or significant dot-gain. The radial profile of a donut filter resembles the radial cross section of a donut shape, with low impulse response at the center that rises to a peak and drops off rapidly as the pixel distance from the center is increased. A simple extension for the joint design of any number of colorant screens is given. This extension makes use of several optimal linear filters that may be treated as a single donut multi-filter having matrix-valued coefficients. A key contribution of this paper is the design of the parametric donut filters to be used at each graylevel. We show that given a desired spatial pair-correlation profile (a.k.a. spatial halftone statistics), optimum donut filters may be generated, such that the donut filter based screen design produces patterns possessing the desired profile in the maximum-likelihood sense. In fact, 'optimal green-noise' halftone screens having the spatial statistics described by Lau, Arce and Gallagher may be produced as a special case of our design. We will also demonstrate donut filter designs that do not use an 'optimum green-noise' target profile in the design and yet produce excellent stochastic clustered-dot halftone screens.

Damera-Venkata, Niranjan; Lin, Qian

2003-12-01

426

Self-referenced characterization of femtosecond laser pulses by chirp scan.  

PubMed

We investigate a variant of the d-scan technique, an intuitive pulse characterization method for retrieving the spectral phase of ultrashort laser pulses. In this variant a ramp of quadratic spectral phases is applied to the input pulses and the second harmonic spectra of the resulting pulses are measured for each chirp value. We demonstrate that a given field envelope produces a unique and unequivocal chirp-scan map and that, under some asymptotic assumptions, both the spectral amplitude and phase of the measured pulse can be retrieved analytically from only two measurements. An iterative algorithm can exploit the redundancy of the information contained in the chirp-scan map to discard experimental noise, artifacts, calibration errors and improve the reconstruction of both the spectral intensity and phase. This technique is compared to two reference characterization techniques (FROG and SRSI). Finally, we perform d-scan measurements with a simple grating-pair compressor. PMID:24150331

Loriot, Vincent; Gitzinger, Gregory; Forget, Nicolas

2013-10-21

427

High-energy, high-contrast, multiterawatt laser pulses by optical parametric chirped-pulse amplification.  

PubMed

We describe a compact, reliable, high-power, and high-contrast noncollinear optical parametric chirped-pulse amplifier system. With a broadband Ti:sapphire oscillator and grating-based stretching and compression, the chirped pulses are amplified from 0.1 nJ to 122 mJ in type I beta-barium borate optical parametric chirped-pulse amplifiers with a total gain of over 10(9) at 10 Hz repetition rate. Pulse compression down to 19-fs duration achieved after amplification indicates a peak power of 3.2 TW at an average power of 0.62 W. The prepulse contrast is measured to be less than 10(-8) on picosecond time scales. PMID:17700770

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Yamamoto, Yoichi; Tanoue, Manabu; Akutsu, Atsushi; Shimomura, Takuya; Kondo, Shuji; Kanazawa, Shuhei; Daido, Hiroyuki; Kimura, Toyoaki; Miyanaga, Noriaki

2007-08-15

428

78 FR 18582 - FM Energy Scheduling, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes...  

Federal Register 2010, 2011, 2012, 2013

...Regulatory Commission [Docket No. ER13-1107-000] FM Energy Scheduling, LLC; Supplemental Notice That Initial Market-Based Rate...notice in the above-referenced proceeding, of FM Energy Scheduling, LLC's application for market-based rate...

2013-03-27

429

78 FR 2260 - Auction of FM Broadcast Construction Permits Rescheduled for April 23, 2013; Notice of Filing...  

Federal Register 2010, 2011, 2012, 2013

...12-1865] Auction of FM Broadcast Construction Permits Rescheduled for April 23...the auction of certain FM broadcast construction permits. This document is intended...on February 6, 2013. Bidding for construction permits in Auction 94 is...

2013-01-10

430

76 FR 78645 - Auction of FM Broadcast Construction Permits Scheduled for March 27, 2012; Notice and Filing...  

Federal Register 2010, 2011, 2012, 2013

...11-1845] Auction of FM Broadcast Construction Permits Scheduled for March 27, 2012...the auction of certain FM broadcast construction permits. This document establishes...on January 12, 2012. Bidding for construction permits in Auction 93 is...

2011-12-19

431

76 FR 3892 - Auction of FM Broadcast Construction Permits Rescheduled for April 27, 2011; Notice and Filing...  

Federal Register 2010, 2011, 2012, 2013

...10-2253] Auction of FM Broadcast Construction Permits Rescheduled for April 27...upcoming auction of certain FM Broadcast construction permits. This document is intended...on February 10, 2011. Bidding for construction permits in Auction 91 is...

2011-01-21

432

Rotational spectroscopy of iodobenzene and iodobenzene-neon with a direct digital 2-8 GHz chirped-pulse Fourier transform microwave spectrometer  

NASA Astrophysics Data System (ADS)

The design of a chirped-pulse Fourier transform microwave spectrometer operating in the 2-8 GHz frequency range is presented. The linear frequency sweep is generated by an arbitrary waveform generator with a sampling rate of 20 GS/s. After amplification, the microwave pulse is broadcast into a vacuum chamber where it interacts with a supersonically expanded molecular sample. The resulting molecular free induction decay signal is amplified and digitized directly on a digital oscilloscope with a 20 GS/s sampling rate. No frequency mixing or multiplication is necessary in this spectrometer, which allows for very high pulse quality and phase stability. The performance of this spectrometer is demonstrated on the rotational spectrum of iodobenzene. All four distinct singly-substituted 13C isotopologues have been detected in natural abundance, as well as two isotopic species of a van der Waals cluster of iodobenzene with a neon atom. Spectroscopic constants and derived structural parameters for iodobenzene and for iodobenzene-Ne are reported. In addition, the use of microwave-microwave double-resonance experiments in this spectrometer to facilitate spectral assignments is presented.

Neill, Justin L.; Shipman, Steven T.; Alvarez-Valtierra, Leonardo; Lesarri, Alberto; Kisiel, Zbigniew; Pate, Brooks H.

2011-09-01

433

Generation of an isolated sub-40-as pulse using two-color laser pulses: Combined chirp effects  

SciTech Connect

In this paper, we theoretically discuss the combined chirp effects on the isolated attosecond generation when a model Ar is exposed to an intense 5-fs, 800-nm fundamental chirped pulse combined with a weak 10-fs, 1200-nm controlling chirped pulse. It shows that for the case of the chirp parameters {beta}{sub 1} = 6.1 (corresponding to the 800-nm field) and {beta}{sub 2} = 4.0 (corresponding to the 1200-nm field), both the harmonic cutoff energy and the supercontinuum can be remarkably extended resulting in a 663-eV bandwidth. Moreover, due to the introduction of the chirps, the short quantum path is selected to contribute to the harmonic spectrum. Finally, by superposing a properly selected harmonic spectrum in the supercontinuum region, an isolated pulse as short as 31 as (5 as) is generated without (with) phase compensation.

Feng, Liqiang [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023 (China); Chu, Tianshu [State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023 (China); Institute for Computational Sciences and Engineering, Laboratory of New Fiber Materials and Modern Textile, the Growing Base for State Key Laboratory, Qingdao University, Qingdao, 266071 (China)

2011-11-15

434

A simple photonic generation of linearly chirped microwave pulse with large time-bandwidth product and high compression ratio.  

PubMed

Based on the heterodyne beating between the pre-chirped optical pulse and the continuous wave (CW) light in a wideband photodetector (PD), linearly chirped microwave pulse with time duration of 3.2ns and bandwidth of 33GHz, which yields a large time-bandwidth product (TBWP) of 106 and high compression ratio of 160, is generated in our experiment. Dispersion compensation fiber (DCF) with uniform response across broad bandwidth is used for providing the original linear chirp in our method, which shows the promise to generate linearly chirped microwave pulse with bandwidth of up to THz. The flexibility of the center frequency and the stability of the time-frequency performance are demonstrated by generating different types of linearly chirped microwave pulses. The range resolution of our generated microwave pulse is also verified by off-line processing. PMID:24104226

Gao, Hongbiao; Lei, Cheng; Chen, Minghua; Xing, Fangjian; Chen, Hongwei; Xie, Shizhong

2013-10-01

435

Offset prediction for charge-balanced stimulus waveforms  

NASA Astrophysics Data System (ADS)

Functional electrical stimulation with cuff electrodes involves the controlled injection of current into an electrically excitable tissue for sensory or motor rehabilitation. Some charge injected during stimulation is 'lost' at the electrode-electrolyte interface when the charge carrier is translated from an electron to an ion in the solution. The process of charge injection through chemical reactions can reduce electrode longevity and implant biocompatibility. Conventionally, the excess charge is minimized by complex hardware solutions, which are often not appropriate for robust long-term implantable solutions. Here, we present a method of waveform design that minimizes irrecoverable charge during continuous pulsing through the use of biphasic waveforms with unequally charged phases. We developed an equivalent electrical model of the electrode-electrolyte impedance based on the electrode's surface chemistry during psuedo-bipolar stimulation conditions. Simulations with the equivalent circuit determined the uncompensated charge to be a function of stimulus parameters. In vitro stimulation experiments in saline confirmed that we could preemptively compensate for the excess charge following biphasic stimulus waveforms. As a result, there was a 92% reduction in the pre-pulse potential after a pulse train with this new waveform design when compared to stimulation with conventional biphasic waveforms.

Woods, V. M.; Triantis, I. F.; Toumazou, C.

2011-08-01

436

Offset prediction for charge-balanced stimulus waveforms.  

PubMed

Functional electrical stimulation with cuff electrodes involves the controlled injection of current into an electrically excitable tissue for sensory or motor rehabilitation. Some charge injected during stimulation is 'lost' at the electrode-electrolyte interface when the charge carrier is translated from an electron to an ion in the solution. The process of charge injection through chemical reactions can reduce electrode longevity and implant biocompatibility. Conventionally, the excess charge is minimized by complex hardware solutions, which are often not appropriate for robust long-term implantable solutions. Here, we present a method of waveform design that minimizes irrecoverable charge during continuous pulsing through the use of biphasic waveforms with unequally charged phases. We developed an equivalent electrical model of the electrode-electrolyte impedance based on the electrode's surface chemistry during psuedo-bipolar stimulation conditions. Simulations with the equivalent circuit determined the uncompensated charge to be a function of stimulus parameters. In vitro stimulation experiments in saline confirmed that we could preemptively compensate for the excess charge following biphasic stimulus waveforms. As a result, there was a 92% reduction in the pre-pulse potential after a pulse train with this new waveform design when compared to stimulation with conventional biphasic waveforms. PMID:21753229

Woods, V M; Triantis, I F; Toumazou, C

2011-07-13

437

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.

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

2010-01-01

438

Evaluation of novel stimulus waveforms for deep brain stimulation  

PubMed Central

Deep brain stimulation (DBS) is an established therapy for the treatment of a wide range of neurological disorders. Historically, DBS and other neurostimulation technologies have relied on rectangular stimulation waveforms to impose their effects on the nervous system. Recent work has suggested that non-rectangular waveforms may have advantages over the traditional rectangular pulse. Therefore, we used detailed computer models to compare a range of charge-balanced biphasic waveforms with rectangular, exponential, triangular, Gaussian, and sinusoidal stimulus pulse shapes. We explored the neural activation energy of these waveforms in both intracellular and extracellular stimulation. In the context of extracellular stimulation, we compared their effects on both axonal fibers of passage and projection neurons. Finally, we evaluated the impact of delivering the waveforms through a clinical DBS electrode, as opposed to a theoretical point source. Our results suggest that DBS with a 1 ms centered-triangular pulse can decrease energy consumption by 64 % when compared to the standard 100 ?s rectangular pulse (energy cost of 48 nJ and 133 nJ, respectively, to stimulate 50 % of a distributed population of axons) and can decrease energy consumption by 10 % when compared to the most energy efficient rectangular pulse (1.25 ms duration). In turn, there may be measureable energy savings when using appropriately designed non-rectangular pulses in clinical DBS applications, thereby warranting further experimental investigation.

Foutz, TJ; McIntyre, CC

2010-01-01

439

Selection and generation of waveforms for differential mobility spectrometry  

SciTech Connect

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.

Krylov, Evgeny V.; Coy, Stephen L.; Nazarov, Erkinjon G. [Sionex Corporation, 8-A Preston Ct., Bedford, Massachusetts 01730 (United States); Vandermey, John; Schneider, Bradley B.; Covey, Thomas R. [MDS Analytical Technologies, 71 Four Valley Drive, Concord, Ontario L4K 4V8 (Canada)

2010-02-15

440

Optimum Waveforms for Differential Ion Mobility Spectrometry (FAIMS)  

SciTech Connect

Differential mobility spectrometry or field asymmetric waveform ion mobility spectrometry (FAIMS) has emerged as a major 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 waveform profiles is possible and maximizing the performance within engineering constraints is a major issue in FAIMS technology development. 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 for either rectangular or sinusoidal-based waveforms are controlled by the full series expansion of K(E) that always includes terms beyond the 1st 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 substantially differ from those found previously, improving the resolving power by up to 2 - 2.5 times. This situation arises for some ions in all FAIMS systems, but becomes more common with recent miniaturized units that employ higher E. With realistic K(E) dependences, the maximum waveform amplitude is not necessarily best and reducing it by up to 20 - 30% is beneficial in some cases. Present findings are particularly relevant to targeted analyses where separation depends on the spread between K(E) functions of specific ions.

Shvartsburg, Alexandre A.; Smith, Richard D.

2008-09-01

441

Calcium control of waveform in isolated flagellar axonemes of chlamydomonas  

PubMed Central

The effect of Ca(++) on the waveform of reactivated, isolated axonemes of chlamydomonas flagella was investigated. Flagella were detached and isolated by the dibucaine procedure and demembranated by treatment with the detergent Nonidet; the resulting axomenes lack the flagellar membrane and basal bodies. In Ca(++)-buffered reactivation solutions containing 10(-6) M or less free Ca(++), the axonemes beat with a highly asymmetrical, predominantly planar waveform that closely resembled that of in situ flagella of forward swimming cells. In solutions containing 10(-4) M Ca(++), the axonemes beat with a symmetrical waveform that was very similar to that of in situ flagella during backward swimming. In 10(-5) M Ca(++), the axonemes were predominantly quiescent, a state that appears to be closely associated with changes in axomenal waveform or direction of beat in many organisms. Experiments in which the concentrations of free Ca(++), not CaATP(--) complex were independently varied suggested that free Ca(++), not CaATP(--), was responsible for the observed changes. Analysis of the flagellar ATPases associated with the isolated axonemes and the nonidet- soluble membrane-matrix fraction obtained during preparation of the axonemes showed that the axonemes lacked the 3.0S Ca(++)-activated ATPase, almost all of which was recovered in the membrane-matrix fraction. These results indicate that free Ca(++) binds directly to an axonemal component to alter flagellar waveform, and that neither the 3.0S CaATPase nor the basal bodies are directly involved in this change.

Bessen, M; Fay, RB; Witman, GB

1980-01-01

442

Chirped pulse shadowgraphy for single shot time resolved plasma expansion measurements  

SciTech Connect

The dynamics of ultrashort laser plasmas demand single shot temporal measurements on fast time scales. We describe a method to record the plasma expansion on picosecond (ps) timescales continuously over hundreds of ps, in single shot. The method uses the chirp of a Ti:sapphire laser as a time-resolved optical diagnostic tool. Using this technique, the evolution of the plasma expansion had been recorded with ps time resolutions, by probing with a chirped laser pulse of 200 ps duration. A peak expansion velocity of 1.8x10{sup 7} cm/s is observed and its evolution in time is obtained for approx300 ps.

Prasad, Y. B. S. R.; Barnwal, S.; Naik, P. A.; Chakera, J. A.; Khan, R. A.; Gupta, P. D. [Laser Plasma Division, RRCAT, Indore, 452 013 Madhya Pradesh (India)

2010-05-31

443

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

444

[Analysis of scatterer microstructure feature based on Chirp-Z transform cepstrum].  

PubMed

The fundamental research field of medical ultrasound has been the characterization of tissue scatterers. The signal processing method is widely used in this research field. A new method of Chirp-Z Transform Cepstrum for mean spacing estimation of tissue scatterers using ultrasonic scattered signals has been developed. By using this method together with conventional AR cepstrum method, we processed the backscattered signals of mimic tissue and pig liver in vitro. The results illustrated that the Chirp-Z Transform Cepstrum method is effective for signal analysis of ultrasonic scattering and characterization of tissue scatterers, and it can improve the resolution for mean spacing estimation of tissue scatterers. PMID:18232497

Guo, Jianzhong; Lin, Shuyu

2007-12-01

445

Pulse dynamics in a passively mode-locked chirped-pulse fiber laser  

Microsoft Academic Search

We report experimental and numerical results on the new pulse dynamics in a passively mode-locked ytterbium-doped fiber laser\\u000a operating in the chirped-pulse regime. Due to the negligible nonlinearity of added highly-positive GVD segment in the purely-normal-dispersion\\u000a regime, highly-positive chirped pulses can be formed through weak intra-cavity temporal and spectral breathing. Numerical\\u000a simulations reveal intra-cavity pulse evolution with local temporal stretching

B. Ortaç; M. Plötner; J. Limpert; A. Tünnermann

2010-01-01

446

Injection-seeded optical parametric amplifier for generating chirped nanosecond pulses.  

PubMed

We constructed an optical parametric amplifier with BiBO crystals, which was injection seeded by a phase-modulated cw beam in the 1,040-1,070 nm region. Two-stage pre-amplification by Yb-doped fibers were implemented for stable injection to the OPA. The frequency chirp in the OPA pulse was actively controlled by adjusting the RF wave for the phase modulation and its synchronization to the OPA firing. Down/up chirps with up to 500 MHz shift were demonstrated. The output pulse energy was ~40 mJ, which is sufficient for future application of frequency conversion and coherent population transfer. PMID:23482098

Miyake, Shinichirou; Ohshima, Yasuhiro

2013-03-11

447

Chirped-Pulse Millimeter-Wave Spectroscopy of Rydberg-Rydberg Transitions  

NASA Astrophysics Data System (ADS)

Transitions between Rydberg states of Ca atoms, in a pulsed, supersonic atomic beam, are directly detected by chirped-pulse millimeter-wave spectroscopy. Broadband, high-resolution spectra with accurate relative intensities are recorded instantly. Free induction decay (FID) of atoms, polarized by the chirped pulse, at their Rydberg-Rydberg transition frequencies, is heterodyne detected, averaged in the time domain, and Fourier transformed into the frequency domain. Millimeter-wave transient nutations are observed, and the possibility of FID evolving to superradiance is discussed.

Prozument, Kirill; Colombo, Anthony P.; Zhou, Yan; Park, G. Barratt; Petrovi?, Vladimir S.; Coy, Stephen L.; Field, Robert W.

2011-09-01

448

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

2013-04-22

449

Dynamics of surface solitons at the edge of chirped optical lattices  

SciTech Connect

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.; Torner, Lluis [ICFO-Institut de Ciencies Fotoniques, and Universitat Politecnica de Catalunya, Mediterranean Technology Park, 08860 Castelldefels (Barcelona) (Spain); Vysloukh, Victor A. [Departamento de Fisica y Matematicas, Universidad de las Americas - Puebla, Santa Catarina Martir, 72820, Puebla (Mexico)

2007-07-15

450

Optimal Bichromatic Two-Photon Excitation with Near-Resonant Chirped Pulses  

SciTech Connect

We investigate a method for creating complete population inversion in a three level system by using bichromatic two-photon coherent excitations with laser pulses, and study the dependence of the optimal population transfer on the chirp of the pulses. We observe that the population inversion does not monotonously decrease with increasing the time-bandwidth product, and that the excitation depends on the sign of the chirp of the individual pulses. Our results, which evidence a worthwhile strategy for coherent population transfer in three level systems, are particularized to the level structure of atomic sodium, with regard to applications in bichromatic mesospheric guide stars.

Serrat, Carles [DFEN-Universitat Politecnica de Catalunya, Colom 1, 08222 Terrassa, Barcelona (Spain); Biegert, Jens [ICREA and ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona (Spain)

2007-12-26

451

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

452

ATOMIC AND MOLECULAR PHYSICS: Lithium atom population transfer by population trapping in a chirped microwave pulse  

NASA Astrophysics Data System (ADS)

Using a time-dependent multilevel approach, we demonstrate that lithium atoms can be transferred to states of lower principle quantum number by exposing them to a frequency chirped microwave pulse. The population transfer from n = 79 to n = 70 states of lithium atoms with more than 80% efficiency is achieved by means of the sequential two-photon ?n = -1 transitions. It is shown that the coherent control of the population transfer can be accomplished by the optimization of the chirping parameters and microwave field strength. The calculation results agree well with the experimental ones and novel explanations have been given to understand the experimental results.

Jia, Guang-Rui; Zhang, Xian-Zhou; Ren, Zhen-Zhong; Wu, Su-Ling

2009-12-01

453

Reflectivity of linear and nonlinear gamma radiated apodized chirped Bragg grating under ocean  

SciTech Connect

In this paper, the effect Co{sup 60} gamma radiation is investigated on the effective refractive index of apodized chirped Bragg grating. Nine apodization profiles are considered. Comparison between the reflectivity of the gamma radiated and non radiated fiber Bragg grating has been carried out. The electric field of signals propagating through the apodized chirped fiber Bragg grating (ACFBG) is first calculated from which, new values for the refractive index are determined. The nonlinear effects appear on the ACFBG reflectivity. The effect of nonlinearity and undersea temperature and pressure on the grating is also studied.

Hamdalla, Taymour A. [Faculty of Science, Alexandria University, Alexandria (Egypt); Faculty of Science, Tabuk University, Tabuk (Saudi Arabia)

2012-09-06

454

Microjoule pulse energy from a chirped-pulse Ti:sapphire oscillator with cavity dumping.  

PubMed

We demonstrate a chirped-pulse Ti:sapphire laser oscillator with both Kerr-lens and semiconductor- saturable-absorber-mirror-assisted mode locking generating 1.1 microJ pulses at 1 MHz pulse repetition rate. The pulses are coupled out of the laser cavity by means of an acousto-optical cavity dumper, have a spectral width that supports a Fourier limit of 74 fs, and currently have a chirped-pulse duration of 5 ps. After compressing the pulses, this laser will be an ideal tool for efficient high-harmonic generation directly from a laser oscillator. PMID:19282917

Siegel, Martin; Pfullmann, Nils; Palmer, Guido; Rausch, Stefan; Binhammer, Thomas; Kovacev, Milutin; Morgner, Uwe

2009-03-15

455

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.; Mücke, O. D.; Lu, P.; Midorikawa, K.

456

Tunable chirped microwave photonic filter employing a dispersive Mach-Zehnder structure.  

PubMed

A Mach-Zehnder structure with modulation in one arm and dispersive time delay in the other is proposed to implement highly flexible single-bandpass chirped microwave photonic filters based on broadband optical sources. Both the amplitude response and the time delay slope can be fully reconfigured via control of the optical spectra and dispersion. The passband can also be widely tuned without changing the shape. A chirped filter with a bandwidth of ?4?GHz, a delay slope of ?-0.6?ns/GHz, and a tunability up to 40?GHz is demonstrated experimentally. PMID:21886263

Xue, Xiaoxiao; Zheng, Xiaoping; Zhang, Hanyi; Zhou, Bingkun

2011-09-01

457

77 FR 60690 - Auction of FM Broadcast Construction Permits Scheduled for March 26, 2013; Comment Sought on...  

Federal Register 2010, 2011, 2012, 2013

...12-1411] Auction of FM Broadcast Construction Permits Scheduled for March 26, 2013...the auction of certain FM broadcast construction permits scheduled to commence on March...an auction of certain FM broadcast construction permits and seek comment on the...

2012-10-04

458

76 FR 60830 - Auction of FM Broadcast Construction Permits Scheduled for March 27, 2012; Comment Sought on...  

Federal Register 2010, 2011, 2012, 2013

...11-1513] Auction of FM Broadcast Construction Permits Scheduled for March 27, 2012...the auction of certain FM broadcast construction permits scheduled to commence on March...an auction of certain FM broadcast construction permits and seek comment on the...

2011-09-30

459

FM-selective Networks in Human Auditory Cortex Revealed Using fMRI and Multivariate Pattern Classification  

Microsoft Academic Search

Frequency modulation (FM) is an acoustic feature of nearly all complex sounds. Directional FM sweeps are especially pervasive in speech, music, animal vocalizations, and other natural sounds. Although the existence of FM-selective cells in the auditory cortex of animals has been documented, evidence in humans remains equivocal. Here we used multivariate pattern analysis to identify cortical selectivity for direction of

I-Hui Hsieh; Paul Fillmore; Feng Rong; Gregory Hickok; Kourosh Saberi

2012-01-01

460

Digital reproduction of biopotential waveforms for neurophysiological studies.  

PubMed

A simple biological signal generator capable of reproducing complex biopotential waveforms is described. It is constructed by a combination of digital and analog circuit components and can be used under different experimental conditions, such as in calibration of biomedical instrumentation systems, or simply as a function generator providing voltage outputs of various waveforms. The biopotential waveform to be generated is sampled at a high frequency and the samples are stored sequentially in a programmable read only memory (PROM). The samples are then fed in the same sequence to a digital-to-analog (D/A) converter and the resulting output is amplified and a DC offset is added. External controls are provided to adjust the DC offset, amplitude and repetition rate of the signal generated. The reproduced voltage signals are stable and superior in quality to those produced by conventional biological signal generators. PMID:7155798

Nandedkar, S D; Ingle, F W; Sanders, D B; Kim, Y I

1982-11-11

461

A 10 tesla table-top controlled waveform magnet.  

PubMed

Controlled waveform magnets (CWMs) are a class of pulsed magnets whose pulse shape with time can be programmed by the user. With a CWM, the user gains control not only over the magnitude of the field but also over its rate of change. In this work we present a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 tesla. Insulated gate bipolar transistor chips have been paralleled to form the high current switch and paralleled chips of SiC Schottky diodes form the crowbar diode module. Sample controlled waveforms including flat-tops up to 10 tesla and some triangular magnetic field pulses have been successfully generated for 10-20 ms with a ripple <1%. PMID:22559572

Roy Choudhury, Aditya N; Venkataraman, V

2012-04-01

462

Wideband Waveform Design principles for Solid-state Weather Radars  

SciTech Connect

The use of solid-state transmitter is becoming a key part of the strategy to realize a network of low cost electronically steered radars. However, solid-state transmitters have low peak powers and this necessitates the use of pulse compression waveforms. In this paper a frequency diversity wideband waveforms design is proposed to mitigate low sensitivity of solid-state transmitters. In addition, the waveforms mitigate the range eclipsing problem associated with long pulse compression. An analysis of the performance of pulse compression using mismatched compression filters designed to minimize side lobe levels is presented. The impact of range side lobe level on the retrieval of Doppler moments are presented. Realistic simulations are performed based on CSU-CHILL radar data and Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) Integrated Project I (IP1) radar data.

Bharadwaj, Nitin; Chandrasekar, V.

2012-01-01

463

Improved time-domain accuracy standards for model gravitational waveforms  

SciTech Connect

Model gravitational waveforms must be accurate enough to be useful for detection of signals and measurement of their parameters, so appropriate accuracy standards are needed. Yet these standards should not be unnecessarily restrictive, making them impractical for the numerical and analytical modelers to meet. The work of Lindblom, Owen, and Brown [Phys. Rev. D 78, 124020 (2008)] is extended by deriving new waveform accuracy standards which are significantly less restrictive while still ensuring the quality needed for gravitational-wave data analysis. These new standards are formulated as bounds on certain norms of the time-domain waveform errors, which makes it possible to enforce them in situations where frequency-domain errors may be difficult or impossible to estimate reliably. These standards are less restrictive by about a factor of 20 than the previously published time-domain standards for detection, and up to a factor of 60 for measurement. These new standards should therefore be much easier to use effectively.

Lindblom, Lee [Theoretical Astrophysics 350-17, California Institute of Technology, Pasadena, California 91125 (United States); Baker, John G. [Gravitational Astrophysics Laboratory, NASA/GSFC, Greenbelt, Maryland 20771 (United States); Owen, Benjamin J. [Institute for Gravitation and the Cosmos, Center for Gravitational Wave Physics, Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2010-10-15

464

A 10 tesla table-top controlled waveform magnet  

NASA Astrophysics Data System (ADS)

Controlled waveform magnets (CWMs) are a class of pulsed magnets whose pulse shape with time can be programmed by the user. With a CWM, the user gains control not only over the magnitude of the field but also over its rate of change. In this work we present a table-top CWM, driven by a capacitor bank, capable of producing virtually any user-shaped magnetic field waveform up to 10 tesla. Insulated gate bipolar transistor chips have been paralleled to form the high current switch and paralleled chips of SiC Schottky diodes form the crowbar diode module. Sample controlled waveforms including flat-tops up to 10 tesla and some triangular magnetic field pulses have been successfully generated for 10-20 ms with a ripple <1%.

Roy Choudhury, Aditya N.; Venkataraman, V.

2012-04-01

465

Ultra-wideband noise radar based on optical waveform generation  

NASA Astrophysics Data System (ADS)

A microwave-photonic, ultra-wideband (UWB) noise radar system is proposed and demonstrated. The system brings together photonic generation of UWB waveforms and fiber-optic distribution. The use of UWB noise provides high ranging resolution and better immunity to interception and jamming. Distribution over fibers allows for the separation the radar-operating personnel and equipment from the location of the front-end. The noise waveforms are generated using the amplified spontaneous emission that is associated with stimulated Brillouin scattering in a standard optical fiber, or with an erbium-doped fiber amplifier. Our experiments demonstrate a proof of concept for an integrated radar system, driven by optically generated UWB noise waveforms of more than 1 GHz bandwidth that are distributed over 10 km distance. The detection of concealed metallic object and the resolving of two targets with the anticipated ranging resolution are reported.

Grodensky, Daniel; Kravitz, Daniel; Zadok, Avi

2012-05-01

466

Esophageal waveform analysis for detection and quantification of reflux episodes  

US Patent & Trademark Office Database

A system and method for automatically analyzing impedance and pH data from an esophageal probe includes a data collection system that collects and stores the output from the sensors for a certain period of time to locate reflux episodes in the waveforms. The data analysis system uses wavelet analysis to assist in locating bolus entry and exit points in the waveforms and to smooth waveforms for additional analysis. It also distinguishes between candidate acid reflux episodes and candidate non-acid reflux episodes for determining actual acid reflux episodes and non-acid reflux episodes, and it distinguishes between, and provides different signal processing for, signals from patients that have healthy esophageal tissue and those that have diseased esophageal tissue.

Stuebe; Thomas D. (Littleton, CO); Chandrasekar; Venkatachalam (Fort Collins, CO); Al-Zaben; Awad (Irbid, JO)

2010-10-19

467

The effects of electric and magnetic fields on the current spin polarization and magnetoresistance in a ferromagnetic/organic semiconductor/ferromagnetic (FM/OSC/FM) system  

NASA Astrophysics Data System (ADS)

From experimental results of spin polarized injection and transport in organic semiconductors (OSCs), we theoretically study the current spin polarization and magnetoresistance under an electric and a magnetic field in a ferromagnetic/organic semiconductor/ferromagnetic (FM/OSC/FM) sandwich structure according to the spin drift-diffusion theory and Ohm's law. From the calculations, it is found that the interfacial current spin polarization is enhanced by several orders of magnitude through tuning the magnetic and electric fields by taking into account the specific characteristics of OSC. Furthermore, the effects of the electric and magnetic fields on the magnetoresistance are also discussed in the sandwich structure.

Wang, Yu-Mei; Ren, Jun-Feng; Yuan, Xiao-Bo; Dou, Zhao-Tao; Hu, Gui-Chao

2012-10-01

468

Full waveform inversion strategy for density in the frequency domain  

NASA Astrophysics Data System (ADS)

To interpret subsurface structures properly, elastic wave propagation must be considered. Because elastic media are described by more parameters than acoustic media, elastic waveform inversion is more likely to be affected by local minima than acoustic waveform inversion. In a conventional elastic waveform inversion, P- and S-wave velocities are properly recovered, whereas density is difficult to reconstruct. For this reason, most elastic full-waveform inversion studies assume that density is fixed. Although several algorithms have been developed that attempt to describe density properly, their results are still not satisfactory. In this study, we propose a two-stage elastic waveform inversion strategy to recover density properly. The Lamé constants are first recovered while holding density fixed. While the Lamé constants and density are not correct under this assumption, the velocities obtained using these incorrect Lamé constants and constant density may be reliable. In the second stage, we simultaneously update density and Lamé constants using the wave equations expressed through velocities and density. While density is updated following the conventional method, the Lamé constants are updated using the gradient obtained by applying the chain rule. Among several parameter-selection strategies tested, only this strategy gives reliable solutions for both velocities and density. Our elastic full waveform inversion algorithm is based on the finite-element method and the backpropagation technique in the frequency domain. We demonstrate our inversion strategy for the modified Marmousi-2 model and the SEG/EAGE salt model. Numerical examples show that this new inversion strategy enhances density inversion results.

Jeong, Woodon; Lee, Ho-Yong; Min, Dong-Joo

2012-03-01

469

Interaural coherence for noise bands: Waveforms and envelopes  

PubMed Central

This paper reports the results of experiments performed in an effort to find a formulaic relationship between the interaural waveform coherence of a band of noise ?W and the interaural envelope coherence of the noise band ?E. An interdependence described by ?E=??4+(1???4)(?W)2.1 is found. This relationship holds true both in a computer experiment and for binaural measurements made in two rooms using a KEMAR manikin. Room measurements are used to derive a measure of reliability for the formula. Ultimately, a user who knows the waveform coherence can predict the envelope coherence with a small degree of uncertainty.

Aaronson, Neil L.; Hartmann, William M.

2010-01-01

470

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

471

Waveform analysis of cavitation in a globe valve.  

PubMed

Cavitation is a dynamic phenomenon occurring in fluid flows, where the local static pressure is lower than the saturated vapor pressure at working temperature. The growth and collapse of cavitation bubbles leads to corrosion and pitting of metal surfaces. Considering the fact that erosion by cavitation is still one of the current problems, it is important to detect the initiation, fully developed point of cavitation and to analyze its characteristics. In this research, an attempt is made to study acoustic waveform of cavitation in the globe valve. The waveform is transformed by Fast Fourier Transform and its important parameters such as amplitude, energy, frequency and so on are analyzed. PMID:19328513

Jazi, A Masjedian; Rahimzadeh, H

2009-02-20

472

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

473

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

474

Experiments on the mixed TDMA/FM-TV mode of transmission via the Communication Satellite (CS)  

NASA Astrophysics Data System (ADS)

It is possible that TDMA and FM-TV signals are commonly amplified by a wide band transponder such as the Medium Capacity Communication Satellite for Experimental Purposes (CS). Experiments on the mixed TDMA/FM-TV mode of transmission via the CS were conducted and the effect of the transponder nonlinearity and the operational problems were investigated. It is proved that by AM/PM conversion the bursting of the TDMA signal gives distortion to the FM-TV signal and the fluctuation of the envelope of the mixed signals degrades the BER performance of the TDMA signal. The degradation by signal suppression was also made clear. In the case of practical operation it was proved that the desired communication quality can be obtained by a slight increase in each transmitting power as compared with one signal (TDMA or FM-TV) access. But in this case, it is undesirable to operate the transponder at the saturating point.

Isobe, S.; Hamamoto, N.; Ohashi, H.; Suzuki, R.; Hashimoto, Y.

1984-09-01

475

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2012 CFR

...condition that interference is not caused to the reception of FM broadcasting stations, present or future. [28 FR 13623, Dec. 14, 1963, as amended at 30 FR 4480, Apr. 7, 1965; 52 FR 10570, Apr. 2,...

2012-10-01

476

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

Federal Register 2010, 2011, 2012, 2013

...CONCHO, AZ; DAILEY CORPORATION, Station WETZ-FM, Facility ID 18534, BPH- 20100329AFI, From NEW MARTINSVILLE, WV, To VIENNA, WV; LOUT, JAMES M, Station NEW, Facility ID 170971, BMPH-20100301ABS, From PINELAND, TX, To BROWNDELL, TX;...

2010-04-20

477

75 FR 63402 - FM Table of Allotments, Culebra, PR, Charlotte Amalie, and Christiansted, VI  

Federal Register 2010, 2011, 2012, 2013

...Culebra, PR, Charlotte Amalie, and Christiansted, VI AGENCY: Federal Communications...substituting Channel 224B for Channel 236B at Christiansted, Virgin Islands and modifying the...the licensee of Station WJKC(FM), Christiansted, for its reasonable and prudent...

2010-10-15

478

76 FR 46294 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...DEBTOR-IN-POSSESSION, Station WKRO-FM, Facility ID 5464, BPH-20110609ADM, From EDGEWATER, FL, To PORT ORANGE, FL; ETHER MINING CORPORATION, Station KPSF, Facility ID 161373, BMP-20110519AAA, From DESERT HOT SPRINGS, CA, To CATHEDRAL...

2011-08-02

479

77 FR 66839 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License  

Federal Register 2010, 2011, 2012, 2013

...FEDERAL COMMUNICATIONS COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The...BMPH-20121002ACH, From MCCALL, ID, To HUNTINGTON, OR; GATEWAY RADIO WORKS, INC., Station WKYN, Facility ID 23345,...

2012-11-07

480

75 FR 51812 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

Federal Register 2010, 2011, 2012, 2013

...CLARENDON, PA, To WATTSBURG, PA; LIFELINE MINISTRIES, INC., Station WGTI, Facility ID 173, BPH-20100804AAU, From DUCK, NC, To WINFALL, NC; LIGHT OF LIFE COMMUNITY, INC., Station WLOL-FM, Facility ID 172639, BMPED-20100722BOH,...

2010-08-23

481

Measurements of the time statistics of FMTV spectra and TV interference into FDM\\/FM carriers  

Microsoft Academic Search

A simulation approach used to 'measure' the FM power spectra of TV signals, with and without energy dispersal signals and the corresponding interference powers into the basebands of FDM\\/FM carriers are presented. Time statistics in the form of FMTV spectral masks and FDM baseband interference-power time distributions have been derived from the measured data of 1000 off-air TV frames for

Nam Nguyen; B. Mazur; S. Prasanna

1985-01-01