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1

Cognitive Implementation of Chirp Waveform in UWB System  

NASA Astrophysics Data System (ADS)

Cognitive Radios (CR) can recognize the communication environment and switch its communication scheme to more efficiently and flexibly utilize the radio spectrum. The performance of ultra wideband (UWB) degrades if interference is not suppressed properly. We propose here a series of adaptive chirp waveforms in UWB systems. By designing waveform shaping of both linear chirp and non-linear cases, we avoid the estimated spectrum of the on-going applications without the necessity of notch filters, and thus reduce the system complexity. We evaluate system performance of the proposed scheme by simulations and verify that the proposed scheme is a candidate for cognitive UWB systems.

Shen, Hanbing; Zhang, Weihua; Kwak, Kyung Sup

2

Generating nonlinear FM chirp radar signals by multiple integrations  

DOEpatents

A phase component of a nonlinear frequency modulated (NLFM) chirp radar pulse can be produced by performing digital integration operations over a time interval defined by the pulse width. Each digital integration operation includes applying to a respectively corresponding input parameter value a respectively corresponding number of instances of digital integration.

Doerry, Armin W. (Albuquerque, NM)

2011-02-01

3

Ultrafast chirped optical waveform recorder using referenced heterodyning and a time microscope  

DOEpatents

A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

Bennett, Corey Vincent (Livermore, CA)

2011-11-22

4

Variable-chirped microwave waveform generator based on reconfigurable microwave photonic filter  

NASA Astrophysics Data System (ADS)

An optical approach to generating chirped microwave signal using a photonic microwave delay-line filter (PMDLF) with a quadratic phase response is proposed and demonstrated. In this scheme, a narrow band Gaussian pulse is used as the original signal. In order to eliminate the need for a wideband original microwave chirped-free signal, a mixer and a radio frequency signal are used to up-convert the spectrum of the original signal and the dispersion curve is tuned to minimize the attenuation caused by the fiber dispersion. Then the required frequency response can be reconstructed by a nonuniformly spaced PMDLF. Since the majority of the power of the original signal can bypass the filter, the power of the generated chirped microwave signal will be increased. A reconstruction example of a desired frequency response with a central frequency of 10 GHz is provided, and the generation of the corresponding chirped microwave signal is demonstrated by numerical simulations.

Chen, Dalei; Wang, Rong; Pu, Tao; Fang, Tao; Xiang, Peng; Zheng, Jiling; Wei, Zhihu; Xiong, Jintian

2014-09-01

5

Polyphase-Coded FM Waveform Optimization within a LINC Transmit Architecture  

E-print Network

for the Tukey window. The slight mismatch that can be seen in the linear scale is probably attributed to reflections or some components in the receiver attenuating the higher frequency portion of the waveform. Still, it is a very clean waveform sampled... ...................................................................................................................................... 7 3.2 Motivation ................................................................................................................................... 9 3.3 The Tukey Window...

Ryan, Lane

2014-05-31

6

Analytic signal demodulation of phase-modulated frequency-chirped signals.  

PubMed

Both interferometers and frequency-modulated (FM) radios create sinusoidal signals with phase information that must be recovered. Often these two applications use narrow band signals but some applications create signals with a large bandwidth. For example, accelerated mirrors in an interferometer naturally create a chirped frequency that linearly increases with time. Chirped carriers are also used for spread-spectrum, FM transmission to reduce interference or avoid detection. In both applications, it is important to recover the underlying phase modulations that are superimposed on the chirped carrier. A common way to treat a chirped waveform is to fit zero crossings of the signal. For lower signal-to-noise applications, however, it is helpful to have a technique that utilizes data over the entire waveform (not just at zero crossings). We present a technique called analytic signal demodulation (ASD), which employs a complex heterodyne of the analytic signal to fully demodulate the chirped waveform. ASD has a much higher sensitivity for recovering phase information than is possible using a chirp demodulation on the raw data. This paper introduces a phase residual function, R(?), that forms an analytic signal and provides a complex demodulation from the received signal in one step. The function defines a phase residual at each point on the chirped waveform, not just at the zero crossings. ASD allows sensitive detection of phase-modulated signals with a very small modulation index (much less than 0.01) that would otherwise be swamped by noise if the raw signal were complex demodulated. The mathematics used to analyze a phase-modulated chirped signal is quite general and can easily be extended for frequency profiles more complicated than a simple chirp. PMID:23518726

Niebauer, T M

2013-03-20

7

Digital chirp modulation  

NASA Astrophysics Data System (ADS)

A technique for digital chirp synthesis is described. The method involves storing the in-phase and quadrature components of a sampled chirp waveform in a high-speed memory element. The baseband chirp is directly applied to an IF carrier using digital-to-analog converters which in turn drive a linearized quadriphase modulator. Out-of-band alias and harmonic products are removable via a output bandpass filter, and PN chopping of both the data and carrier is performed in order to spread the carrier leakage through the quadriphase modulator hybrid. It is shown that digital chirp modulation is comparatively insensitive to the large insertion losses which are found in most analog SWD modulators. A 1-bit quantized version of the digital waveform for a 2 Delta-wide chirp from -Delta F to +Delta F is illustrated in graphic form.

Komara, M. A.; Andren, C. F.

8

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

9

Simplified Homodyne Detection for FM Chirped Lidar  

E-print Network

the optical and the RF circuits compared to heterodyne detection. Experiments show that the receiver sensitivity approaches the quantum limit and surpasses the performance of direct and heterodyne detection. In addition, the required electrical bandwidth...

Adany, Peter

2007-12-14

10

Temporal modulation transfer functions for AM and FM stimuli in cat auditory cortex. Effects of carrier type, modulating waveform and intensity.  

PubMed

For 167 single units, recorded from primary auditory cortex in 28 cats, we show that tuning to the modulation frequency (MF) of amplitude-modulated (AM) sound is strongly dependent on carrier type. In general AM noise-bursts and click-trains produce good tuning to MFs with repetition rates around 8-10 Hz. Amplitude- or frequency-modulation of tone-carriers resulted largely in low-pass temporal modulation transfer functions (tMTFs) with a best modulation frequency (BMF) around 4 Hz. Individual BMFs for noise carriers ranged from 3-26 Hz, whereas for tone carriers they were mostly below 6 Hz and rarely above 10 Hz. The sharpness of tuning for broad-band stimuli decreased with increasing duty-cycle of the modulation; it was most pronounced for clicks, next best for exponential sine-AM and broadest for sinusoidal AM. In contrast the reverse was found for tone carriers; the better modulation following was found for sinusoidal modulation and was most likely entirely due to a stronger onset response. Decreasing the modulation depth below 100% showed an increasing influence of onset transients and periodic rebounds, however, the average tMTFs for depths between 50-100% are similar. The optimal intensity level for noise carriers was usually higher than for tone carriers. Overall the modulation-sensitivity of cortical neurons regardless of carrier type and modulating waveform was in the range of modulation frequencies found in music, speech and other complex sounds. PMID:8040099

Eggermont, J J

1994-04-01

11

Amplitude-modulation chirp imaging for contrast detection.  

PubMed

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

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

2010-09-01

12

Intravascular ultrasound chirp imaging  

NASA Astrophysics Data System (ADS)

We demonstrate the feasibility of intravascular ultrasound (IVUS) chirp imaging as well as chirp reversal ultrasound contrast imaging at intravascular ultrasound frequency. Chirp excitations were emitted with a 34 MHz single crystal intravascular transducer and compared to conventional Gaussian-shaped pulses of equal acoustic pressure. The signal to noise ratio of the chirp images was increased by up to 9 dB relative to the conventional images. Imaging of contrast microbubbles was implemented by chirp reversal, achieving a contrast to tissue ratio of 12 dB. The method shows potential for intravascular imaging of structures in and beyond coronary atherosclerotic plaques including vasa vasorum.

Maresca, D.; Jansen, K.; Renaud, G.; van Soest, G.; Li, X.; Zhou, Q.; de Jong, N.; Shung, K. K.; van der Steen, A. F. W.

2012-01-01

13

FIRST-ORDER GLOBAL AM-FM DECOMPOSITION AND APPLICATION TO MUSIC ANALYSIS AND TRANSFORMATION  

E-print Network

]. A second class of approaches address the AM-FM decomposition using multiband ltering and demodulation [14FIRST-ORDER GLOBAL AM-FM DECOMPOSITION AND APPLICATION TO MUSIC ANALYSIS AND TRANSFORMATION Mahdi waveform' multiplied by the instantaneous FM signal. The variations of the global FM get expressed through

Gesbert, David

14

Agilent 33210A 10 MHz Function/Arbitrary Waveform Generator  

E-print Network

Agilent 33210A 10 MHz Function/Arbitrary Waveform Generator Data Sheet · 10 MHz Sine and Square Waveform Generator · AM, FM, and PWM modulation types · Linear & logarithmic sweeps and burst operation at an affordable price The Agilent Technologies 33210A Function/Arbitrary Waveform Generator is the latest addition

California at San Diego, University of

15

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...

16

Carrier Modulation Via Waveform Probability Density Function  

NASA Technical Reports Server (NTRS)

Beyond the classic modes of carrier modulation by varying amplitude (AM), phase (PM), or frequency (FM), we extend the modulation domain of an analog carrier signal to include a class of general modulations which are distinguished by their probability density function histogram. Separate waveform states are easily created by varying the pdf of the transmitted waveform. Individual waveform states are assignable as proxies for digital one's or zero's. At the receiver, these states are easily detected by accumulating sampled waveform statistics and performing periodic pattern matching, correlation, or statistical filtering. No fundamental physical laws are broken in the detection process. We show how a typical modulation scheme would work in the digital domain and suggest how to build an analog version. We propose that clever variations of the modulating waveform (and thus the histogram) can provide simple steganographic encoding.

Williams, Glenn L.

2006-01-01

17

Carrier Modulation Via Waveform Probability Density Function  

NASA Technical Reports Server (NTRS)

Beyond the classic modes of carrier modulation by varying amplitude (AM), phase (PM), or frequency (FM), we extend the modulation domain of an analog carrier signal to include a class of general modulations which are distinguished by their probability density function histogram. Separate waveform states are easily created by varying the pdf of the transmitted waveform. Individual waveform states are assignable as proxies for digital ONEs or ZEROs. At the receiver, these states are easily detected by accumulating sampled waveform statistics and performing periodic pattern matching, correlation, or statistical filtering. No fundamental natural laws are broken in the detection process. We show how a typical modulation scheme would work in the digital domain and suggest how to build an analog version. We propose that clever variations of the modulating waveform (and thus the histogram) can provide simple steganographic encoding.

Williams, Glenn L.

2004-01-01

18

Chirp Characterization of External Modulators With Finite Extinction Ratio Using Linear Optical Sampling  

Microsoft Academic Search

We demonstrate a network monitoring technique for the frequency chirping of external modulators based on linear optical sampling. We present ??-parameter waveforms of digital data modulation from simultaneously measured amplitude and phase. Digital data modulation was compared to sinusoidal modulation to demonstrate the measurement capabilities. The high sensitivity of our technique was used to resolve the detailed impact of a

Tasshi Dennis; Paul A. Williams

2010-01-01

19

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

20

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

21

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

22

Generation and correlation of digitally controlled coherent frequency-hopped waveforms using surface acoustic wave devices  

Microsoft Academic Search

A digitally controlled coherent frequency synthesizer is reported which uses two surface acoustic wave chirp filters to generate frequency-hopped waveforms. Attractive features are wide bandwidth and instantaneous switching between frequencies, which are selected by an external word generator. Experimental results show waveforms which hop every 2.5 s within a 12.5-MHz band. Phase coherence between pulses is demonstrated by correlating the

P.M. Grant; D. P. Morgan; J. H. Collins

1976-01-01

23

First results of a deep tow CHIRP sonar seafloor imaging system  

USGS Publications Warehouse

The latest and most innovative technology has been applied towards the development of a full-ocean depth multi-sensor sonar system using linear swept-FM (Chirp) technology. The seafloor imaging system (SIS- 7000) described herein uses Chirp sidescan sonar to provide high resolution imagery at long range, and Chirp subbottom sonar to provide high resolution profiles in both the near bottom and deeper subbottom. The tow vehicle contains a suite of full-ocean depth instrumentation for measuring various oceanographic parameters and for monitoring vehicle status. Top side systems include a sonar display and data logging system as well as real-time sensor status display and tow vehicle control system. This paper will present an overview of this system, describe its technology and capabilities, and present some initial results.

Parent, M.; Fang, Changle; O'Brien, Thomas F.; Danforth, William W.

1993-01-01

24

Amplitude modulated chirp excitation to reduce grating lobes and maintain ultrasound intensity at the focus of an array.  

PubMed

During application of high intensity focused ultrasound (HIFU) with therapy arrays, the existence of grating lobes can cause heating at unintended tissue regions. Therefore, the reduction of grating lobes in therapeutic arrays is an important goal. One way to reduce the grating lobes in therapy arrays is to excite the arrays with broadband signals (defined here as >10% fractional bandwidth). To achieve a reduction in grating lobe levels in an ultrasonic array, coded waveforms can be utilized that reduce the grating lobe levels while maintaining the spatial peak temporal average intensity. In this study, a 5-MHz, 9-element, 1.25 mm inter-elemental spacing linear array was excited by a sinusoidal waveform, a conventional linear chirp, and a modified linear chirp. Both chirps spanned the -3-dB bandwidth of the transducer. The conventional chirp was a broadband signal with a linear sweep of frequencies between 2.5 and 7.5 MHz, with all frequency components excited with equal amplitude. The modified chirp signal also swept the frequencies between 2.5 and 7.5 MHz, but the amplitude was weighted such that the edges (low and high frequencies of the band) were excited with more energy than the center of the band. In simulations, the field patterns for the sinusoidal, conventional chirp and modified chirp excitations were produced from the array using Field II and compared. For experiments, the beam pattern from a 5-MHz single-element transducer was mapped using a hydrophone for the sinusoidal, conventional chirp and modified chirp excitation. Each field from the transducer was repeated and summed to produce a field from an array of 9 elements. The difference in the time averaged intensity (in dB) in the main lobe and grating lobes were estimated for each excitation and compared. The results demonstrated that the chirp signals resulted in decreases in grating lobe levels compared to the main lobe, i.e. 10 dB down for focusing and 6 dB down for focusing and steering. A further 1 dB decrease in grating lobe levels was observed for the modified chirp excitation compared to the conventional chirp excitation, which corresponds to ~21% reduction in energy deposition at the grating lobe location. PMID:23648212

Karunakaran, Chandra P; Oelze, Michael L

2013-09-01

25

FM 6-22 (FM 22-100) Army Leadership  

E-print Network

FM 6-22 (FM 22-100) Army Leadership Competent, Confident, and Agile OCTOBER 2006 DISTRIBUTION and complex security environment we face. FM 6-22 is the Army's keystone field manual on leadership. It establishes leadership doctrine and fundamental principles for all officers, noncommissioned officers

US Army Corps of Engineers

26

WAVEFORM-AGILE SENSING FOR TRACKING MULTIPLE TARGETS IN CLUTTER Sandeep P. Sira  

E-print Network

WAVEFORM-AGILE SENSING FOR TRACKING MULTIPLE TARGETS IN CLUTTER Sandeep P. Sira , Antonia multiple targets in clutter. A number of generalized frequency modulated chirps with trapezoidal envelope- ence of clutter. 1. INTRODUCTION As sensors become increasingly capable and intelligent, it has become

Nehorai, Arye

27

Frequency-chirped subwavelength nanoantennas.  

PubMed

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

Yaacobi, Ami; Watts, Michael R

2012-12-01

28

Adaptive MIMO radar waveforms  

Microsoft Academic Search

Multiple-Input, Multiple-Output (MIMO) radars enhance performance by transmitting and receiving coded waveforms from multiple locations. To date, the theoretical literature on MIMO radar has focused largely on the use of ldquoorthogonal waveforms.rdquo Practical approaches to approximate orthogonality (e.g., via waveforms characterized by low cross-correlation and low autocorrelation sidelobe levels) have also started to emerge. We show, however, that such waveforms

Daniel J. Rabideau; Lexington MA

2008-01-01

29

SAW device provides hyperbolic chirp  

Microsoft Academic Search

The 'echo' location system employed by bats utilizes pulses whose frequency varies with time. This system is hyperbolically, rather than linearly weighted. It is pointed out that this concept of hyperbolic weighting, implemented with relatively inexpensive surface accoustic wave (SAW) devices, can be applied to torpedo guidance and satellite interception. The use of hyperbolic weighting allows the use of chirp

R. H. Johnson

1983-01-01

30

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

SciTech Connect

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, Eric; Rabaste, Olivier [Max-Planck Institut fuer Gravitationsphysik, Am Muehlenberg 1, 14476 Potsdam (Germany); CNRS, AstroParticule et Cosmologie, 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13, France and Observatoire de la Cote d'Azur, Bd de l'Observatoire, BP 4229, 06304 Nice (France); CNRS, AstroParticule et Cosmologie, 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13 (France)

2008-03-15

31

Generation of Arbitrary Frequency Chirps with a Fiber-Based Phase Modulator and Self-Injection-Locked Diode Laser  

E-print Network

We present a novel technique for producing pulses of laser light whose frequency is arbitrarily chirped. The output from a diode laser is sent through a fiber-optical delay line containing a fiber-based electro-optical phase modulator. Upon emerging from the fiber, the phase-modulated pulse is used to injection-lock the laser and the process is repeated. Large phase modulations are realized by multiple passes through the loop while the high optical power is maintained by self-injection-locking after each pass. Arbitrary chirps are produced by driving the modulator with an arbitrary waveform generator.

Rogers, C E; Carini, J L; Pechkis, J A; Gould, P L

2006-01-01

32

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. 17 figs.

Dong, Q.; Jenkins, M.V.; Bernadas, S.R.

1997-09-09

33

SAW device provides hyperbolic chirp  

NASA Astrophysics Data System (ADS)

The 'echo' location system employed by bats utilizes pulses whose frequency varies with time. This system is hyperbolically, rather than linearly weighted. It is pointed out that this concept of hyperbolic weighting, implemented with relatively inexpensive surface accoustic wave (SAW) devices, can be applied to torpedo guidance and satellite interception. The use of hyperbolic weighting allows the use of chirp by reducing the nonlinearity of the Doppler shift. The use of a hyperbolically weighted chirp (HWC) provides an approach for substantially overcoming a problem caused by the Doppler effect. The block diagram of a typical spread spectrum detection, tracking, and homing system is presented. This system uses a nonlinearly weighted SAW device as a spectrum spreader and compressor.

Johnson, R. H.

1983-11-01

34

GEORGEBUSHDR. NRD(FM2154)  

E-print Network

Green COKE GEORGEBUSHDR. BIZZELL OLDMAINDR. W LAMAR JOEROUTT HOUSTON NRD(FM2154) LEWIS LUBBOCK E LAMAR MOSHER CENTRAL LAMAR NAGLE COKE THROCKMORTON COKE THROCKMORTON STON SPENCE WELLBORNRD(FM GEORGE BUSH DR. R U SSEL CENTER GOLF CLUBHOUSE O&M BUILDINGPAVILION DUNCAN HALL COKE HART NAGLE DUNN MOSHERASTON COMMONS WELLS

Behmer, Spencer T.

35

Waveform: Acoustics/Electroacoustics  

NSDL National Science Digital Library

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

2006-07-14

36

An MSK Radar Waveform  

NASA Technical Reports Server (NTRS)

The minimum-shift-keying (MSK) radar waveform is formed by periodically extending a waveform that separately modulates the in-phase and quadrature- phase components of the carrier with offset pulse-shaped pseudo noise (PN) sequences. To generate this waveform, a pair of periodic PN sequences is each passed through a pulse-shaping filter with a half sinusoid impulse response. These shaped PN waveforms are then offset by half a chip time and are separately modulated on the in-phase and quadrature phase components of an RF carrier. This new radar waveform allows an increase in radar resolution without the need for additional spectrum. In addition, it provides self-interference suppression and configurable peak sidelobes. Compared strictly on the basis of the expressions for delay resolution, main-lobe bandwidth, effective Doppler bandwidth, and peak ambiguity sidelobe, it appears that bi-phase coded (BPC) outperforms the new MSK waveform. However, a radar waveform must meet certain constraints imposed by the transmission and reception of the modulation, as well as criteria dictated by the observation. In particular, the phase discontinuity of the BPC waveform presents a significant impediment to the achievement of finer resolutions in radar measurements a limitation that is overcome by using the continuous phase MSK waveform. The phase continuity, and the lower fractional out-of-band power of MSK, increases the allowable bandwidth compared with BPC, resulting in a factor of two increase in the range resolution of the radar. The MSK waveform also has been demonstrated to have an ambiguity sidelobe structure very similar to BPC, where the sidelobe levels can be decreased by increasing the length of the m-sequence used in its generation. This ability to set the peak sidelobe level is advantageous as it allows the system to be configured to a variety of targets, including those with a larger dynamic range. Other conventionally used waveforms that possess an even greater spectral efficiency than the MSK waveform, such as linear frequency modulation (LFM) and Costas frequency hopping, have a fixed peak sidelobe level that is therefore not configurable, and can be exceeded by high contrast targets. Furthermore, in the case of a multistatic experiment observing a target in motion, self-interference from the transmitter to the receiver is mitigated by the MSK waveform. Waveforms that have delay Doppler coupling, such as LFM, provide no such protection.

Quirk, Kevin J.; Srinivasan, Meera

2012-01-01

37

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

38

HARVEYMITCHELLPW(FM2818) RAYMOND STOTZER PW (FM 60)  

E-print Network

MEADOWLANDST UNIVERSITY DR (FM 60) LIVE OAK ST POPLAR ST LINCOLN AV WALTON DR FRANCIS DR GILCHRIST AV MOSS ST SPENCE LACY GAINER WHITE WHITELEY UTAY HARRINGTON FOUNTAIN BRIGGS HARRELL LEONARD UNDERWOOD APPELT RUDDER

39

Altimeter waveform software design  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

40

Arterial waveform analysis.  

PubMed

The bedside measurement of continuous arterial pressure values from waveform analysis has been routinely available via indwelling arterial catheterization for >50 years. Invasive blood pressure monitoring has been utilized in critically ill patients, in both the operating room and critical care units, to facilitate rapid diagnoses of cardiovascular insufficiency and monitor response to treatments aimed at correcting abnormalities before the consequences of either hypo- or hypertension are seen. Minimally invasive techniques to estimate cardiac output (CO) have gained increased appeal. This has led to the increased interest in arterial waveform analysis to provide this important information, as it is measured continuously in many operating rooms and intensive care units. Arterial waveform analysis also allows for the calculation of many so-called derived parameters intrinsically created by this pulse pressure profile. These include estimates of left ventricular stroke volume (SV), CO, vascular resistance, and during positive-pressure breathing, SV variation, and pulse pressure variation. This article focuses on the principles of arterial waveform analysis and their determinants, components of the arterial system, and arterial pulse contour. It will also address the advantage of measuring real-time CO by the arterial waveform and the benefits to measuring SV variation. Arterial waveform analysis has gained a large interest in the overall assessment and management of the critically ill and those at a risk of hemodynamic deterioration. PMID:25480767

Esper, Stephen A; Pinsky, Michael R

2014-12-01

41

Low frequency AC waveform generator  

DOEpatents

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

Bilharz, Oscar W. (Scotia, NY)

1986-01-01

42

CHIRP  

Cancer.gov

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

43

Low frequency ac waveform generator  

DOEpatents

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

Bilharz, O.W.

1983-11-22

44

Application of the effective Fisher matrix to the frequency domain inspiral waveforms  

NASA Astrophysics Data System (ADS)

The Fisher matrix (FM) has been generally used to predict the accuracy of the gravitational wave parameter estimation. Although the limitation of the FM has been well known, it is still mainly used due to its very low computational cost compared to the Monte Carlo simulations. Recently, Rodriguez et al (2013 Phys. Rev. D 88 084013) performed Markov chain Monte Carlo (MCMC) simulations using a frequency domain inspiral waveform model (TaylorF2) for nonspinning binary systems with total masses M?slant 20{{M}? }, and they found systematic differences between the predictions from FM and MCMC for M\\gt 10{{M}? }. On the other hand, an effective Fisher matrix (eFM) was recently introduced by Cho et al (2013 Phys. Rev. D 87 24004). The eFM is a semi-analytic approach to the standard FM, in which the derivative is taken of a quadratic function fitted to the local overlap surface. In this work, we apply the eFM method to the TaylorF2 waveform for nonspinning binary systems with a moderately high signal-to-noise ratio (SNR 15) and find that the eFM can reproduce the MCMC error bounds in Rodriguez et al well, even for high masses. By comparing the eFM standard deviation directly with the 1-? confidence interval of the marginalized overlap that approximates the MCMC posterior distribution, we show that the eFM can be acceptable in all mass regions for the estimation of the MCMC error bounds. We also investigate the dependence on the signal strength.

Cho, Hee-Suk; Lee, Chang-Hwan

2014-12-01

45

Local measurement validation for an intelligent chirped-FM ultrasonic range sensor  

Microsoft Academic Search

An important intelligent functionality for improving measurement systems is the validation of the returned information. To obtain this validation at the sensor level, it is essential that the sensor produces additional information for this purpose. This aspect follows directly from the measurement method. In this article, we apply these ideas to an ultrasonic range finding sensor dedicated to the navigation

Gilles Mauris; Eric Benoit; Laurent Foulloy

2000-01-01

46

WELLBORNRD(FM2154) HORTICULTURE  

E-print Network

CHERS BLEACHERS YELL COKE OLDMAINDR. W LAMAR JOEROUTT HOUSTON OLSENBLVD OLSENBLVD OLSENBLVD WELLBORNRD(FM2154) HORTICULTURE RD GEORGEBUSHDR. LEWIS CENTRALLAMAR NAGLE COKE THROCKMORTON COKE THROCKMORTON CORPSOFCADETS CENTER BEUTEL HEALTH CTR. HEEP CENTER HARRINGTON EDUCATION CENTER DUNCAN HALL REED ARENA YMCA COKE

Behmer, Spencer T.

47

Optical waveform generation using a directly modulated laser  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

48

FM use of BM PPT  

E-print Network

Management System Building Management System Maintenance Management Integration Head End Granfen Control technologies Fire, security, bookings, etc? Manchester Library Project BIM/Operational Data Architecture Sept 2012 / . Design... and Construction Laing O?Rourke BIM Data Transfer BIM Data beneficial to FM Operational life of Complex Create and maintain an accurate repository of Building assets Operational Management of the Complex Soft Landings Challenges and opportunities...

Brady, L.

2012-01-01

49

Application of the effective Fisher matrix to the frequency domain inspiral waveforms  

E-print Network

The Fisher matrix (FM) has been generally used to predict the accuracy of the gravitational wave parameter estimation. Although a limitation of the FM has been well known, it is still mainly used due to its very low computational cost compared to the Monte Carlo simulations. Recently, Rodriguez et al. [Phys. Rev. D 88, 084013 (2013)] performed Markov chain Monte Carlo (MCMC) simulations for nonspinning binary systems with total masses $M \\leq 20 M_{\\odot}$, they found systematic differences between the predictions from FM and MCMC for $M>10 M_{\\odot}$. On the other hand, an effective Fisher matrix (eFM) was recently introduced by Cho et al. [Phys. Rev. D 87, 24004 (2013)]. The eFM is a semi-analytic approach to the standard FM, in which the partial derivative is taken by a quadratic fitting function to the local overlap surface. In this work, we apply the eFM method to several nonspinning binary systems and find that the error bounds in eFM are qualitatively in good agreement with the MCMC results of Rodriguez et al. in all mass regions. In particular, we provide concrete examples showing an importance of taking into account the template-dependent frequency cutoff of the inspiral waveforms.

Hee-Suk Cho; Chang-Hwan Lee

2014-11-20

50

Probing waveform synthesis and receive filter design for active sensing systems  

NASA Astrophysics Data System (ADS)

Probing waveform synthesis and receive filter design play crucial roles in achievable performance for active sensing applications, including radar, sonar, and medical imaging. We focus herein on conventional single-input single-output (SISO) radar systems. A flexible receive filter design approach, at the costs of lower signal-to-noise ratio (SNR) and higher computational complexity, can be used to compensate for missing features of the probing waveforms. A well synthesized waveform, meaning one with good autocorrelation properties, can reduce computational burden at the receiver and improve performance. Herein, we will highlight the interplay between waveform synthesis and receiver design. We will review a novel, cyclic approach to waveform design, and then compare the merit factors of these waveforms to other well-known sequences. In our comparisons, we will consider chirp, Frank, Golomb, and P4 sequences. Furthermore, we will overview several advanced techniques for receiver design, including data-independent instrumental variables (IV) filters, a data-adaptive iterative adaptive approach (IAA), and a data-adaptive Sparse Bayesian Learning (SBL) algorithm. We will show how these designs can significantly outperform conventional matched filter (MF) techniques for range compression as well as for range-Doppler imaging.

Roberts, William; He, Hao; Tan, Xing; Xue, Ming; Vu, Duc; Li, Jian; Stoica, Petre

2009-05-01

51

Compression of amplified chirped optical pulses  

Microsoft Academic Search

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

D. Strickland; G. Mourou

1985-01-01

52

Unambiguous evaluation of a chirp measurement standard  

NASA Astrophysics Data System (ADS)

This article describes an automated evaluation method for the chirp standard. Chirp calibration standards provide a way to describe the transfer behavior of different spatial frequencies as they contain sinusoidal functions of varying wavelengths (Krger-Sehm et al 2007 chirp calibration standards for surface measuring instruments Tech. Mess. tm 74 57276 Pehnelt et al 2011 Comparative analysis of optical surface measuring systems with a chip calibration standard Tech. Mess. tm 78 45762). By introducing a new, automated evaluation method, an improvement for the application of the chirp standard can be achieved. The data-preprocessing for topography and profile measurement data and the fit of the geometric elements are described. Automated evaluation can reduce the labor required to evaluate measured data and make it easier to compare different evaluations in the course of standardization. The algorithm can be used to characterize the so-called small scale fidelity of an optical instrument. The term small scale fidelity is currently discussed in the optical group of working group no. 16 of the ISO technical committee 213.

Seewig, Jrg; Eifler, Matthias; Wiora, Georg

2014-10-01

53

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

54

Waveform diversity in distributed radar  

Microsoft Academic Search

The desire to anticipate actions before they occur is a goal within the military. Cognitive sensor and communications systems along with distributed radar systems are key enablers to meet this need. Close in sensing examples are provided showing the value of waveform diversity in distributed radar. The use of waveform diversity presents a challenge to the electromagnetic compatibility (EMC) community.

G. T. Capraro; I. Bradaric; M. C. Wicks

2009-01-01

55

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

Code of Federal Regulations, 2014 CFR

...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES EXPERIMENTAL RADIO, AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES FM Broadcast...53 or 54 channels removed from an FM radio broadcast station will not be...

2014-10-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

57

A chemical waveform synthesizer  

PubMed Central

Algorithms and methods were developed to synthesize complex chemical waveforms in open volumes by using a scanning-probe microfluidic platform. Time-dependent variations and oscillations of one or several chemical species around the scanning probe, such as formation of sine waves, damped oscillations, and generation of more complex patterns, are demonstrated. Furthermore, we show that intricate bursting and chaotic calcium oscillations found in biological microdomains can be reproduced and that a biological cell can be used as a probe to study receptor functionalities as a function of exposure to time-dependent variations of receptor activators and inhibitors. Thus, the method allows for studies of biologically important oscillatory reactions. More generally, the system allows for detailed studies of complex time-varying chemical and physical phenomena in solution or at solution/surface interfaces. PMID:15928088

Olofsson, Jessica; Bridle, Helen; Sinclair, Jon; Granfeldt, Daniel; Sahlin, Eskil; Orwar, Owe

2005-01-01

58

Waveform Sampler CAMAC Module  

SciTech Connect

A Waveform Sampler Module (WSM) for the measurement of signal shapes coming from the multi-hit drift chambers of the SLAC SLC detector is described. The module uses a high speed, high resolution analog storage device (AMU) developed in collaboration between SLAC and Stanford University. The AMU devices together with high speed TTL clocking circuitry are packaged in a hybrid which is also suitable for mounting on the detector. The module is in CAMAC format and provides eight signal channels, each recording signal amplitude versus time in 512 cells at a sampling rate of up to 360 MHz. Data are digitized by a 12-bit ADC with a 1 ..mu..s conversion time and stored in an on-board memory accessible through CAMAC.

Freytag, D.R.; Haller, G.M.; Kang, H.; Wang, J.

1985-09-01

59

Chirped incoherent scatter radar plasma line measurements  

NASA Astrophysics Data System (ADS)

The detectability of the plasma line in incoherent scatter radar experiments on the ionospheric plasma can be increased by factors in the range of 10 to 50 by chirping the transmitter frequency and the receiver local oscillator at a rate matching the linear change of plasma line frequency with height. The method of observation is explained in detail and experiments carried out at the Arecibo Observatory are described.

Birkmayer, Wolfram Siegfried

60

Mechanism of electron acceleration by chirped laser pulse  

SciTech Connect

We studied the mechanism of electron acceleration by a chirped laser pulse. We found that, because of the chirp effect, a region exists where the laser wave phase experienced by the electron varies slowly, so that the electron can be accelerated for a long time. The mechanism of chirped laser acceleration is different to that of the capture and acceleration scenario, although both of them have a main acceleration stage in which the electrons are trapped for long periods.

Wu, X. Y.; Wang, P. X. [Department of Nuclear Science and Technology, Institute of Modern Physics, Fudan University, Shanghai 200433, China and Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education (China); Kawata, S. [Department of Advanced Interdisciplinary Science, Center for Optical Research and Education, Graduate School of Engineering, Utsunomiya University, Utsunomiya 321-8585 (Japan)

2012-05-28

61

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

NASA Astrophysics Data System (ADS)

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

Doll, Andrin; Jeschke, Gunnar

2014-09-01

62

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

PubMed

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

Doll, Andrin; Jeschke, Gunnar

2014-09-01

63

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

64

Wavelet approximations for computationally efficient FM demodulation  

NASA Astrophysics Data System (ADS)

We present a framework for the use of stationary phase approximations to a Morlet wavelet transform as a device to generate computationally efficient algorithms for extracting modulation information in frequency modulated (FM) signals. Presented here are two specific FM estimators generated from this approach that may be implemented in terms of filter banks with very few filters.

Teolis, Anthony; Scheper, Richard; Frankpitt, Bernard A.

2001-03-01

65

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

66

(FM 10-500-1) AERIAL DELIVERY  

E-print Network

FM 4-20.41 (FM 10-500-1) AERIAL DELIVERY DISTRIBUTION IN THE THEATER OF OPERATIONS DISTRIBUTION-20.41 Headquarters Department of the Army Washington, DC, 29 August 2003 Aerial Delivery Distribution in the Theater.........................................................................................................III Chapter 1 AERIAL DELIVERY DISTRIBUTION ON THE BATTLEFIELD.......................1-1 Service

US Army Corps of Engineers

67

A Modified Subpulse SAR Processing Procedure Based on the Range-Doppler Algorithm for Synthetic Wideband Waveforms  

PubMed Central

Synthetic wideband waveforms (SWW) combine a stepped frequency CW waveform and a chirp signal waveform to achieve high range resolution without requiring a large bandwidth or the consequent very high sampling rate. If an efficient algorithm like the range-Doppler algorithm (RDA) is used to acquire the SAR images for synthetic wideband signals, errors occur due to approximations, so the images may not show the best possible result. This paper proposes a modified subpulse SAR processing algorithm for synthetic wideband signals which is based on RDA. An experiment with an automobile-based SAR system showed that the proposed algorithm is quite accurate with a considerable improvement in resolution and quality of the obtained SAR image.

Lim, Byoung-Gyun; Woo, Jea-Choon; Lee, Hee-Young; Kim, Young-Soo

2008-01-01

68

Incoherent-light temporal stretching of high-speed intensity waveforms.  

PubMed

We propose and demonstrate experimentally the first incoherent-light scheme for temporal imaging (magnification) of intensity waveforms. The scheme is based on a time-domain equivalent of a pinhole camera under incoherent illumination, involving two dispersive lines and temporal intensity modulation with a short gate. We report incoherent-light temporal stretching of radiofrequency waveforms by a magnification factor of 2.86, with a time-bandwidth product exceeding 160, i.e., a resolution of ~50 ps over a temporal aperture of ~8 ns, totally avoiding the use of chirp-controlled pulsed lasers. This work opens up new perspectives for realization of many critical high-speed signal-processing modules using practical incoherent light-wave schemes. PMID:25121697

Li, Bo; Azaa, Jos

2014-07-15

69

Online waveform processing for demanding target situations  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

70

chirp, 7/8/1996 BAYESIAN SPECTRUM AND CHIRP ANALYSIS y  

E-print Network

spectrum and chirp (frequency change) rate for the case that one has incomplete noisy data on values y). In that problem we estimate the spectrum of a time series (y 1 \\Delta \\Delta \\Delta y N ), from incomplete data consisting of a few autocovariances (R 0 \\Delta \\Delta \\Delta Rm ); m ! N , measured from the entire time

Rodriguez, Carlos

71

The Theta Laser A Low Noise Chirped Pulse Laser  

E-print Network

The Theta Laser A Low Noise Chirped Pulse Laser Dimitrios Mandridis dmandrid@creol.ucf.edu April 29 Applications of Uniform-Intensity Chirped-Pulse Lasers [1] Y. Han, and B. Jalali, J. Lightwave Technol., 21 Coherence Tomography ( Medical ) Laser Ranging ( Millitary ) #12;6 Outline · Applications of frequency swept

Van Stryland, Eric

72

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

73

High-spectral-resolution multiplex CARS spectroscopy using chirped pulses  

Microsoft Academic Search

A novel technique for achieving high spectral resolution with a femtosecond laser system is presented. Transform-limited 800 nm, 90 femtosecond (fs) pulses pass off two gratings, stretching the pulse in time to a pulse width of several picoseconds due to an induced linear temporal chirp directly proportional to the grating separation. This chirped pulse is the degenerate pump (omegaP) and

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

2004-01-01

74

Chirped optical solitons in single-mode birefringent fibers  

NASA Astrophysics Data System (ADS)

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

Mahmood, M. F.

1996-12-01

75

LIDAR Waveform Simulation Over Complex Targets  

NASA Astrophysics Data System (ADS)

Unlike discrete-return LIDAR system that measures the return times of some echoes, waveform LIDAR provides the full-waveform data by digitising multi-echoes. From the waveform data we can extract more information about the geometry and reflectance of the target surfaces by applying various algorithms to interpret waveform. There have been many researches about the laser beam's interaction with the illuminated surfaces and the diverse algorithms for waveform processing. The purpose of this paper is to suggest the method to simulate waveform coming from complex targets. First, we analysed the previous relevant works. And based on these we attempted to generate the simulated waveform over the complex surfaces. For the waveform simulation, we defined the sub-beams spread with a consistent interval within the beam's divergence coverage. Each sub-beam has its geometry (origin and direction) and the transmitted energy considering the laser beam's profile. Then, we searched the surfaces that intersect with sub-beams using ray-tracing algorithm, and computed the intersection points and the received energies. Using on the computed distance, the received energy and predefined pulse model, we generated the signals of echoes and put them together into a waveform. Finally, we completed the waveform simulation adding the signal noise. As a result of performing waveform simulation, we confirmed that the waveform data was successfully simulated by the proposed method. We believe that our method of the waveform simulation will be helpful to understand the waveform data and develop the algorithms for the waveform processing.

Kim, S.; Lee, I.; Lee, M.

2012-08-01

76

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; Bruer, Andreas; Sinzinger, Stefan

2007-05-14

77

Frequency chirping during a fishbone burst  

NASA Astrophysics Data System (ADS)

It is shown that frequency chirping during fishbone activity can be attributed to the reactive torque exerted on the plasma during the instability burst, which slows down plasma rotation inside the q = 1 surface and reduces the mode frequency in the lab frame. Estimates show that the peak value of this torque can exceed the neutral beam torque in modern tokamaks. The simple line-broadened quasilinear burst model (Berk et al 1995 Nucl. Fusion 35 1661), properly adapted for the fishbone case, is capable of reproducing the key features of the bursting mode.

Marchenko, V. S.; Reznik, S. N.

2011-12-01

78

LIABILITY INSURANCE University Policy No: FM5300  

E-print Network

1 LIABILITY INSURANCE University Policy No: FM5300 Classification: Financial Management Approving, its officers, employees, volunteers and certain other named insureds, Comprehensive General Liability, Errors and Omissions and other insurance policies. These policies contain certain exclusions requiring

Victoria, University of

79

Detector For FM Voice Or Digital Signals  

NASA Technical Reports Server (NTRS)

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

Davarian, Faramaz

1989-01-01

80

Over-modulated AM-FM decomposition  

NASA Astrophysics Data System (ADS)

Most previous amplitude- and frequency-modulation (AM and FM) decomposition methods assume that the AM component is non-negative. However this assumption is not always valid. Over-modulation, where the AM component has both positive and negative values, may be present in not only synthetic signals, but also in natural signals like speech and music. Assuming all non-negative values for AM in an over-modulated signal will introduce significant phase discontinuities in the FM estimate. Because of this, previous methods yield significant errors for instantaneous frequency (IF) estimation at AM zero-crossings. We propose a two-step algorithm that utilizes coherent demodulation to estimate AM and FM correctly for over-modulated signals. For synthetic signals, the algorithm produces very accurate AM and FM estimates; for band-passed speech signals, the algorithm corrects the discontinuities in the FM estimate and produces more physically reasonable results. The evaluation of source sensitivity for the algorithm shows that the estimation errors generally increase with AM and FM frequencies, but are insensitive to carrier frequency. The robustness in noise is relatively low in the over-modulation case due to very low local SNR at AM zero-crossings. Limitations of the algorithm and future work are also discussed.

Li, Qin; Atlas, Les E.

2004-10-01

81

Nonlinear frequency chirping of toroidal Alfvn eigenmodes in tokamak plasmas  

NASA Astrophysics Data System (ADS)

Nonlinear frequency chirping of toroidal Alfn eigenmodes (TAE) driven by energetic particles is investigated by kinetic simulations in toroidal plasmas. It is found that the updown symmetry of the frequency chirping of a TAE is broken due to an anisotropic pitch-angle distribution with dominant co-passing energetic particles. The nonuniform distribution of the free energy associated with the initial energetic particle distribution causes biased driving forces that result in a strongly asymmetric frequency chirping. The evolution of the perturbed distribution function in the phase space shows that a holeclump pair moves together towards the magnetic axis for the small pitch-angle parameter cases. The downward chirping of the mode frequency is associated with the negative drift of the phase island in the KAM surfaces or the resonance ?f structures in the radial direction. On the other hand, the energetic particle distribution with larger pitch-angle parameters leads to upward chirping of the TAE frequency. The upward chirping is due to the drifting of the resonance structure towards the boundary of the simulation region and overlapping of different poloidal resonances in the (?, E) phase space at the late stage. The phase space dynamics provides a key mechanism for understanding the wave chirping direction and particle transport process.

Zhu, J.; Ma, Z. W.; Fu, G. Y.

2014-12-01

82

Waveform-dependent absorbing metasurfaces  

E-print Network

We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high power pulses but not for high power continuous waves (CWs), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e. CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications.

Wakatsuchi, Hiroki; Rushton, Jeremiah J; Sievenpiper, Daniel F

2014-01-01

83

Waveform-Dependent Absorbing Metasurfaces  

NASA Astrophysics Data System (ADS)

We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high-power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high-power pulses but not for high-power continuous waves (CWs), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e., CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications.

Wakatsuchi, Hiroki; Kim, Sanghoon; Rushton, Jeremiah J.; Sievenpiper, Daniel F.

2013-12-01

84

Waveform-dependent absorbing metasurfaces.  

PubMed

We present the first use of a waveform-dependent absorbing metasurface for high-power pulsed surface currents. The new type of nonlinear metasurface, composed of circuit elements including diodes, is capable of storing high-power pulse energy to dissipate it between pulses, while allowing propagation of small signals. Interestingly, the absorbing performance varies for high-power pulses but not for high-power continuous waves (CW's), since the capacitors used are fully charged up. Thus, the waveform dependence enables us to distinguish various signal types (i.e., CW or pulse) even at the same frequency, which potentially creates new kinds of microwave technologies and applications. PMID:24483674

Wakatsuchi, Hiroki; Kim, Sanghoon; Rushton, Jeremiah J; Sievenpiper, Daniel F

2013-12-13

85

Chirped-Superlattice, Blocked-Intersubband QWIP  

NASA Technical Reports Server (NTRS)

An Al(x)Ga(1-x)As/GaAs quantum-well infrared photodetector (QWIP) of the blocked-intersubband-detector (BID) type, now undergoing development, features a chirped (that is, aperiodic) superlattice. The purpose of the chirped superlattice is to increase the quantum efficiency of the device. A somewhat lengthy background discussion is necessary to give meaning to a brief description of the present developmental QWIP. A BID QWIP was described in "MQW Based Block Intersubband Detector for Low-Background Operation" (NPO-21073), NASA Tech Briefs Vol. 25, No. 7 (July 2001), page 46. To recapitulate: The BID design was conceived in response to the deleterious effects of operation of a QWIP at low temperature under low background radiation. These effects can be summarized as a buildup of space charge and an associated high impedance and diminution of responsivity with increasing modulation frequency. The BID design, which reduces these deleterious effects, calls for a heavily doped multiple-quantum-well (MQW) emitter section with barriers that are thinner than in prior MQW devices. The thinning of the barriers results in a large overlap of sublevel wave functions, thereby creating a miniband. Because of sequential resonant quantum-mechanical tunneling of electrons from the negative ohmic contact to and between wells, any space charge is quickly neutralized. At the same time, what would otherwise be a large component of dark current attributable to tunneling current through the whole device is suppressed by placing a relatively thick, undoped, impurity-free AlxGa1 x As blocking barrier layer between the MQW emitter section and the positive ohmic contact. [This layer is similar to the thick, undoped Al(x)Ga(1-x)As layers used in photodetectors of the blocked-impurity-band (BIB) type.] Notwithstanding the aforementioned advantage afforded by the BID design, the responsivity of a BID QWIP is very low because of low collection efficiency, which, in turn, is a result of low electrostatic- potential drop across the superlattice emitter. Because the emitter must be electrically conductive to prevent the buildup of space charge in depleted quantum wells, most of the externally applied bias voltage drop occurs across the blocking-barrier layer. This completes the background discussion. In the developmental QWIP, the periodic superlattice of the prior BID design is to be replaced with the chirped superlattice, which is expected to provide a built-in electric field. As a result, the efficiency of collection of photoexcited charge carriers (and, hence, the net quantum efficiency and thus responsivity) should increase significantly.

Gunapala, Sarath; Ting, David; Bandara, Sumith

2004-01-01

86

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Interference to the input signals of FM translator...Broadcast Stations (LPFM) 73.827 Interference to the input signals of FM translator...that the LPFM station is causing actual interference to the FM translator or FM...

2012-10-01

87

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

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Interference to the input signals of FM translator...Broadcast Stations (LPFM) 73.827 Interference to the input signals of FM translator...that the LPFM station is causing actual interference to the FM translator or FM...

2011-10-01

88

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 2010-10-01 false Interference to the input signals of FM translator...Broadcast Stations (LPFM) 73.827 Interference to the input signals of FM translator...that the LPFM station is causing actual interference to the FM translator or FM...

2010-10-01

89

Response of electroexplosive devices to impulsive waveforms.  

NASA Technical Reports Server (NTRS)

The firing characteristics of insensitive electroexplosive devices to certain impulsive waveforms have been investigated. For these waveforms, energy is delivered in a time short compared to the thermal time constant and therefore cooling plays a negligible role. One waveform is a terminated capacitor discharge wherein the regular discharge of a capacitor is terminated at a preset point. Another is a half-sine wave pulse. The theory, design, and application of both impulsive waveform generators are presented together with certain limited experimental observations.

Rosenthal, L. A.; Menichelli, V. J.

1971-01-01

90

WAVEFORM ANALYSIS TECHNIQUES IN AIRBORNE LASER SCANNING  

Microsoft Academic Search

Small-footprint airborne laser scanners with waveform-digitising capabilities are becoming increasingly available. Waveform- digitising is particularly advantageous when the backscattered echo waveform is complex because it allows selecting processing algorithms adjusted to the task. In addition, waveform-digitising laser scanners depict the physical measurement process in its entire complexity. This opens the possibility to derive the backscatter cross section which is a

W. Wagner; A. Roncat; T. Melzer; A. Ullrich

2007-01-01

91

Dispersion compensation in chirped pulse amplification systems  

DOEpatents

A chirped pulse amplification system includes a laser source providing an input laser pulse along an optical path. The input laser pulse is characterized by a first temporal duration. The system also includes a multi-pass pulse stretcher disposed along the optical path. The multi-pass pulse stretcher includes a first set of mirrors operable to receive input light in a first plane and output light in a second plane parallel to the first plane and a first diffraction grating. The pulse stretcher also includes a second set of mirrors operable to receive light diffracted from the first diffraction grating and a second diffraction grating. The pulse stretcher further includes a reflective element operable to reflect light diffracted from the second diffraction grating. The system further includes an amplifier, a pulse compressor, and a passive dispersion compensator disposed along the optical path.

Bayramian, Andrew James; Molander, William A.

2014-07-15

92

Quantum Fluctuations in the Chirped Pendulum  

E-print Network

An anharmonic oscillator when driven with a fast, frequency chirped voltage pulse can oscillate with either small or large amplitude depending on whether the drive voltage is below or above a critical value-a well studied classical phenomenon known as autoresonance. Using a 6 GHz superconducting resonator embedded with a Josephson tunnel junction, we have studied for the first time the role of noise in this non-equilibrium system and find that the width of the threshold for capture into autoresonance decreases as the square root of T, and saturates below 150 mK due to zero point motion of the oscillator. This unique scaling results from the non-equilibrium excitation where fluctuations, both quantum and classical, only determine the initial oscillator motion and not its subsequent dynamics. We have investigated this paradigm in an electrical circuit but our findings are applicable to all out of equilibrium nonlinear oscillators.

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

2010-08-26

93

LPI waveforms for active sonar?  

Microsoft Academic Search

The idea of a low probability of intercept (LPI) waveform is that its form is chaotic. It can of course be recalled by the transmitter (platform), and matched to what is received; but to the target it appears only as noise, and consequently the robust target receiver can only detect a rise in energy. However, the platform pays a heavy

Peter Willett; Joshua Reinert; Robert Lynch

2004-01-01

94

Phase Detector For Rectangular Waveforms  

NASA Technical Reports Server (NTRS)

Phase detector for use with phase-locked-loops, servocontrol, and other electronic circuits designed to avoid disadvantages of other phase detectors. Used with both intermittent and continuous input signals. Circuit offers several advantages; reference signals continuous, burst of few pulses, or single pulse. Circuit "coasts" in absence of reference signal. Generates no steady-state output waveform at lock which makes filtering easier.

Dischert, Robert A.; Walter, James M.

1993-01-01

95

Chirped Incoherent Scatter Radar Plasma Line Measurements.  

NASA Astrophysics Data System (ADS)

The detectability of the plasma line in incoherent scatter radar experiments on the ionospheric plasma can be increased by factors in the range of 10 - 50 by chirping the transmitter frequency and the receiver local oscillator at a rate matching the linear change of plasma line frequency with height. The method of observation is explained in detail and experiments carried out at the Arecibo Observatory are described. The design of special equipment that had to be constructed is also discussed. Plasma line frequency versus height profiles with a frequency accuracy better than one part in 1000 were obtained with 0.4 s integration per point. The strength of the plasma line return and the point where the linear change of plasma line frequency, determined by the chirp rate, is tangent to the locally parabolic plasma line frequency profile were also determined with high accuracy. Using a nonlinear least squares fit it is possible to also determine the quadratic coefficient of a locally parabolic plasma line frequency versus height profile. In measurements of the daytime ionosphere the plasma line was found to be enhanced by about 70 times over that of thermal equilibrium. Observations during ionospheric modification experiments show that on the time scale of the 1 second integration period used the high frequency heater wave creates plasma depletions instantly. For a scale height of 51 km, a plasma line frequency of 5.1 MHz, a plasma line frequency gradient of 50 kHz/km and a HF-heater power density input of 800 kW/m('2) the heated region is depleted by 3 to 5% of its electrons. This provides the first direct evidence that the heater-induced modifications involve Langmuir waves trapped in cavities, cavitons. A number of future applications of this observation technique are discussed.

Birkmayer, Wolfram Siegfried

1987-09-01

96

Giant-chirp oscillators for short-pulse fiber amplifiers  

PubMed Central

A new regime of pulse parameters in a normal-dispersion fiber laser is identified. Dissipative solitons exist with remarkably large pulse duration and chirp, along with large pulse energy. A low-repetition-rate oscillator that generates pulses with large and linear chirp can replace the standard oscillator, stretcher, pulse-picker, and pre-amplifier in a chirped-pulse fiber amplifier. The theoretical properties of such a giant-chirp oscillator are presented. A fiber laser designed to operate in the new regime generates ~150-ps pulses at 3-MHz repetition rate. Amplification of these pulses to 1-?J energy with pulse duration as short as 670 fs demonstrates the promise of this new approach. PMID:19079529

Renninger, William H.; Chong, Andy; Wise, Frank W.

2011-01-01

97

Surface solitons in chirped photonic lattices Mario I. Molina,1,  

E-print Network

. [12] demon- strated that the soliton formation can be dramati- cally modified at the surface the surface and the critical power as a function of the lattice chirp, and also demon- strate how the lattice

98

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. PMID:24115807

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

2013-01-01

99

ECCM capabilities of an ultrawideband bandlimited random noise imaging radar  

Microsoft Academic Search

Investigated here is high-resolution imaging of targets in noisy or unfriendly radar environments through a simulation analysis of the ultrawideband (UWB) continuous-wave (CW) bandlimited random noise waveform. The linear FM chirp signal was selected as a benchmark radar waveform for comparison purposes. Simulation of the recovery of various types of target reflectivity functions (TRFs) for these waveforms were performed and

DMITRIY S. GARMATYUK; RAM M. NARAYANAN

2002-01-01

100

Narrowband pulse-enhanced upconversion of chirped broadband pulses  

Microsoft Academic Search

We propose and demonstrate an efficient sum-frequency mixing scheme based on narrowband and chirped broadband pulses. It combines the advantages of wider spectral acceptance bandwidth and of alleviating the temporal walk-off, which are both beneficial to higher conversion efficiency. Chirped sum-frequency pulses at 455 nm with energy up to 360 J, corresponding to a conversion efficiency of ~ 40%, are

Kun Zhao; Peng Yuan; Haizhe Zhong; Dongfang Zhang; Heyuan Zhu; Liezun Chen; Shuangchun Wen; Liejia Qian

2010-01-01

101

Sampled chirped fiber gratings as distributed pressure sensors  

NASA Astrophysics Data System (ADS)

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

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

2004-09-01

102

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

103

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

104

Automated Analysis, Classification, and Display of Waveforms  

NASA Technical Reports Server (NTRS)

A computer program partly automates the analysis, classification, and display of waveforms represented by digital samples. In the original application for which the program was developed, the raw waveform data to be analyzed by the program are acquired from space-shuttle auxiliary power units (APUs) at a sampling rate of 100 Hz. The program could also be modified for application to other waveforms -- for example, electrocardiograms. The program begins by performing principal-component analysis (PCA) of 50 normal-mode APU waveforms. Each waveform is segmented. A covariance matrix is formed by use of the segmented waveforms. Three eigenvectors corresponding to three principal components are calculated. To generate features, each waveform is then projected onto the eigenvectors. These features are displayed on a three-dimensional diagram, facilitating the visualization of the trend of APU operations.

Kwan, Chiman; Xu, Roger; Mayhew, David; Zhang, Frank; Zide, Alan; Bonggren, Jeff

2004-01-01

105

Improving FM transmitter power and efficiency  

NASA Technical Reports Server (NTRS)

Amplifier tracks oscillator frequency allowing narrow band high Q circuit to be used, increasing wide deviation FM transmission efficiency and power output, and suppressing spurious output frequencies system. Tracking oscillator and amplifier act like wideband circuitry with narrow-band advantages.

Honnell, M. A.

1977-01-01

106

Noise and threshold in FM systems  

Microsoft Academic Search

When investigating noise in FM receivers, Frutiger approximated experimental and numerical data. The main results are here shown to agree with Rice's rigorous analysis as extended by this author. The same applies to the threshold location, expressed here by a simple, but general, formula.

A. Wojnar

1967-01-01

107

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

108

75 FR 65521 - FM Approvals; Expansion of Recognition  

Federal Register 2010, 2011, 2012, 2013, 2014

...Conditioners UL 521 Heat Detectors for Fire Protective Signaling Systems UL 1480 Speakers for Fire Alarm, Emergency, and Commercial and Professional...Signaling FM 3210 Heat Detectors for Automatic Fire Alarm Signaling FM 7260 Electrostatic...

2010-10-25

109

Enhancement of sound by soft reflections in exponentially chirped crystals  

NASA Astrophysics Data System (ADS)

The enhancement of sound inside a two dimensional exponentially chirped crystal during the soft reflections of waves is experimentally and theoretically explored in this work. The control of this enhancement is achieved by a gradual variation of the dispersion in the system by means of a chirp of the lattice constant. The sound enhancement is produced at some planes of the crystal in which the wave is softly reflected due to a progressive slowing down of the sound wave. We find that the character of the sound enhancement depends on the function of the variation of dispersion, i.e., on the function of the chirp. A simple coupled mode theory is proposed to find the analytical solutions of the sound wave enhancement in the exponentially chirped crystal. Harmonic and time domain numerical simulations are performed to interpret the concept of the soft reflections, and to check the analytically calculated field distributions both in good agreement with experiments. Specially we obtain stronger sound enhancement than in linearly chirped crystals. This sound enhancement could motivate applications in energy harvesting, e.g., to increase the efficiency of detectors and absorbers.

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

2014-12-01

110

47 CFR 73.316 - FM antenna systems.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false FM antenna systems. 73.316 Section 73.316...FM Broadcast Stations 73.316 FM antenna systems. (a) It shall be...power authorized. (b) Directional antennas. A directional antenna is an...

2013-10-01

111

47 CFR 73.316 - FM antenna systems.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false FM antenna systems. 73.316 Section 73.316...FM Broadcast Stations 73.316 FM antenna systems. (a) It shall be...power authorized. (b) Directional antennas. A directional antenna is an...

2011-10-01

112

47 CFR 73.316 - FM antenna systems.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false FM antenna systems. 73.316 Section 73.316...FM Broadcast Stations 73.316 FM antenna systems. (a) It shall be...power authorized. (b) Directional antennas. A directional antenna is an...

2014-10-01

113

47 CFR 73.316 - FM antenna systems.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false FM antenna systems. 73.316 Section 73.316...FM Broadcast Stations 73.316 FM antenna systems. (a) It shall be...power authorized. (b) Directional antennas. A directional antenna is an...

2010-10-01

114

47 CFR 73.316 - FM antenna systems.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false FM antenna systems. 73.316 Section 73.316...FM Broadcast Stations 73.316 FM antenna systems. (a) It shall be...power authorized. (b) Directional antennas. A directional antenna is an...

2012-10-01

115

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2012 CFR

... 4 2012-10-01 2012-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following...

2012-10-01

116

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2011 CFR

... 4 2011-10-01 2011-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following...

2011-10-01

117

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2013 CFR

... 4 2013-10-01 2013-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following...

2013-10-01

118

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2010 CFR

... 4 2010-10-01 2010-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following...

2010-10-01

119

Multicomponent AM--FM Energy Demodulation with Applications to Signal  

E-print Network

Multicomponent AM--FM Energy Demodulation with Applications to Signal Processing and Communications November, 1997 Copyright c # 1997 by Balu Santhanam #12; Multicomponent AM--FM Energy Demodulation . . . . . . . . . . . . . . . . . . . . 35 3 ENERGY DEMODULATION OF MIXTURES FOR TWO--COMPONENT AM--FM SIGNAL DEMODULATION 38 3

Santhanam, Balu

120

47 CFR 73.599 - NCE-FM engineering charts.  

Code of Federal Regulations, 2014 CFR

... 4 2014-10-01 2014-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication...Educational FM Broadcast Stations 73.599 NCE-FM engineering charts. This section consists of the following...

2014-10-01

121

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

122

FM 4-20.107 (FM 10-500-7) TO 13C7-1-10  

E-print Network

FM 4-20.107 (FM 10-500-7) TO 13C7-1-10 AIRDROP DERIGGING AND RECOVERY PROCEDURES OCTOBER 2004 and Recovery Procedures Contents Page Preface ....................................................................................................... 2-3 Cargo Parachute Release Assemblies

US Army Corps of Engineers

123

Quasimonoenergic collimated electrons from the ionization of nitrogen by a chirped intense laser pulse  

SciTech Connect

A scheme is proposed for quasimonoenergic collimated GeV electrons generated during ionization of nitrogen by a chirped intense laser pulse. The electrons accelerated by a laser pulse without a frequency chirp are known for poor-quality beams. If a suitable frequency chirp is introduced, then the energy of the electrons increases significantly. It is shown that quasimonoenergic collimated GeV electrons can be produced using a right choice of laser spot size, frequency chirp, and pulse duration.

Singh, Kunwar Pal [Singh Simutech Pvt. Ltd., Bharatpur, Rajasthan 321201 (India); Sajal, Vivek [Department of Physics, Jaypee Institute of Information Technology University, Noida 201 307, Uttar Pradesh (India)

2009-04-15

124

High-precision triangular-waveform generator  

DOEpatents

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

Mueller, T.R.

1981-11-14

125

RTM-based waveform inversion  

NASA Astrophysics Data System (ADS)

Waveform inversion that determines the subsurface velocity structures can be implemented in either data domain, which compares the differences between the real data and the simulated data (Tarantola, 2005), or in image domain, which checks the coherency of the events in the CIGs (Common Image Gathers) (Symes and Kern, 1994; Chavent and Jacewitz, 1995). In the past, classic waveform inversion, as a data-domain approach, has little success in the field data experiments. We believe that one of the problems is the unknown simulation equations. The real waves will likely propagate with different kinds of wave equations at different subsurface areas. This implies that no single simulation equation can adequately describe the wave propagations underneath the earth. Because of the uncertainty of amplitudes of the waves, the objective function for classic waveform inversion that tries to compare the differences between the observed data and the simulated data will definitely hurt than help inversions. Fortunately, although waves propagate in various forms, only the amplitudes of the waves vary. The traveltime for these various forms of wave equations that are determined by the eikonal equations are more or less the same. In other words, traveltime can provide more reliable information than amplitudes. This suggests that an effective waveform inversion should emphasize on the events' traveltime or phase information and downplay the role of amplitude information. Following Chavent and Jacewitz (1995), we propose an image-domain approach that is based on the criteria that seismic data must be geometrically coherent after prestack depth migration. When the velocity is correct, the events at CIGs should be flat and therefore have maximum stack power for redundant shots. This image-domain approach relies on event coherency (traveltime) and has the effect of emphasizing more on the reliable traveltime information instead of unreliable amplitudes. Here we choose RTM (Reverse-time migration) as the migration engine. Our optimization problem is therefore defined as an image-domain semblance-like objective function, which is constrained by RTM's forward and backward two-way scalar wave equations. The gradient of the objective function that is needed for conjugate-gradient algorithm is derived by the adjoint state technique. Besides the original RTM forward/backward equations, two extra propagation equations, called adjoint equations in control theory, are introduced for this image-domain waveform inversion. These equations combined represent a demigration process that reconstructs the transmitted and reflected wavepaths for both source and receiver data respectively. The simulated reflected data that can be collected during the demigration processes also provide us with another opportunity for data-domain inversion. Finally, because of less emphasis on amplitudes, this image-domain approach may converge slower than classic waveform inversion for synthetic data, but it should be more adequate for field data experiments.

Zhou, Hongbo; Zhang, Guanquan; Ortigosa, Francisco

2010-05-01

126

Phase-locked loop FM demodulator  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

127

May4,2009May4,2009 Audio Streaming over FM bandAudio Streaming over FM band  

E-print Network

Audio streaming between USRP1 and USRP2 over FM band GNU RadioGNU Radio ­­ Used for modulation and demodulationMay4,2009May4,2009 Audio Streaming over FM bandAudio Streaming over FM band between USRP1 and USRP2FAQwww.gnuradio.org/trac/wiki/USRP2GenFAQ #12;May4,2009May4,2009 77 Audio streaming between USRP1 and USRP2 over FM band

Yu, Chansu

128

A digital dispersive matching network for SAW devices in chirp transform spectrometers  

Microsoft Academic Search

The performance of a chirp transform spectrometer can be significantly improved through a digital dispersive matching network. In this paper, we present the development of a new design, the adaptive digital chirp processor (ADCP), which generates an expander chirp signal with dispersive characteristics matching those of the surface acoustic wave filter behaving as a compressor\\/convolver. This matching signal (i.e., the

Geronimo Luis Villanueva; Paul Hartogh; Leonhard M. Reindl

2006-01-01

129

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Interference to the input signals of FM translator...Stations (LPFM) 73.827 Interference to the input signals of FM translator...FM booster stations. (a) Interference to the direct reception of...

2013-10-01

130

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

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Interference to the input signals of FM translator...Stations (LPFM) 73.827 Interference to the input signals of FM translator...FM booster stations. (a) Interference to the direct reception of...

2014-10-01

131

Chirped-cavity dispersion-compensation filter design.  

PubMed

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. PMID:16539259

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

2006-03-01

132

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

133

High-spectral-resolution multiplex CARS spectroscopy using chirped pulses  

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

134

Automatic target recognition using waveform diversity in radar sensor networks  

Microsoft Academic Search

In this paper, we perform a number of theoretical studies on constant frequency (CF) pulse waveform design and diversity in radar sensor networks (RSN): (1) the conditions for waveform co-existence, (2) interferences among waveforms in RSN, (3) waveform diversity combining in RSN. As an application example, we apply the waveform design and diversity to automatic target recognition (ATR) in RSN

Qilian Liang

2008-01-01

135

Narrowband pulse-enhanced upconversion of chirped broadband pulses  

NASA Astrophysics Data System (ADS)

We propose and demonstrate an efficient sum-frequency mixing scheme based on narrowband and chirped broadband pulses. It combines the advantages of wider spectral acceptance bandwidth and of alleviating the temporal walk-off, which are both beneficial to higher conversion efficiency. Chirped sum-frequency pulses at 455 nm with energy up to 360 J, corresponding to a conversion efficiency of ~ 40%, are obtained and the pulses can be compressed to ~ 110 fs. The sum-frequency mixing scheme may provide a promising route to the efficient generation of deep-ultraviolet femtosecond pulses.

Zhao, Kun; Yuan, Peng; Zhong, Haizhe; Zhang, Dongfang; Zhu, Heyuan; Chen, Liezun; Wen, Shuangchun; Qian, Liejia

2010-03-01

136

High spectral resolution multiplex CARS spectroscopy using chirped pulses  

NASA Astrophysics Data System (ADS)

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

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

2004-04-01

137

Goldstone Solar System Radar Waveform Generator  

NASA Technical Reports Server (NTRS)

Due to distances and relative motions among the transmitter, target object, and receiver, the time-base between any transmitted and received signal will undergo distortion. Pre-distortion of the transmitted signal to compensate for this time-base distortion allows reception of an undistorted signal. In most radar applications, an arbitrary waveform generator (AWG) would be used to store the pre-calculated waveform and then play back this waveform during transmission. The Goldstone Solar System Radar (GSSR), however, has transmission durations that exceed the available memory storage of such a device. A waveform generator capable of real-time pre-distortion of a radar waveform to a given time-base distortion function is needed. To pre-distort the transmitted signal, both the baseband radar waveform and the RF carrier must be modified. In the GSSR, this occurs at the up-conversion mixing stage to an intermediate frequency (IF). A programmable oscillator (PO) is used to generate the IF along with a time-varying phase component that matches the time-base distortion of the RF carrier. This serves as the IF input to the waveform generator where it is mixed with a baseband radar waveform whose time-base has been distorted to match the given time-base distortion function producing the modulated IF output. An error control feedback loop is used to precisely control the time-base distortion of the baseband waveform, allowing its real-time generation. The waveform generator produces IF modulated radar waveforms whose time-base has been pre-distorted to match a given arbitrary function. The following waveforms are supported: continuous wave (CW), frequency hopped (FH), binary phase code (BPC), and linear frequency modulation (LFM). The waveform generator takes as input an IF with a time varying phase component that matches the time-base distortion of the carrier. The waveform generator supports interconnection with deep-space network (DSN) timing and frequency standards, and is controlled through a 1 Gb/s Ethernet UDP/IP interface. This real-time generation of a timebase distorted radar waveform for continuous transmission in a planetary radar is a unique capability.

Quirk, Kevin J.; Patawaran, Ferze D.; Nguyen, Danh H.; Nguyen, Huy

2012-01-01

138

Digital receiver for on-board FM/FSK-FM/BPSK demodulation  

NASA Astrophysics Data System (ADS)

An all-digital demodulator FM/FSK-FM/BPSK is presented. The proposed architecture allows the 1-bit IF down-sampling technique with the hardware simplification of receiver analog section. The receiver exhibits great flexibility both in terms of signal demodulation (FSK or BPSK, subcarrier/ tone frequency, data rate) and interface capability. The demodulator is going to be realized in a VLSI chip (20 Kgate complexity). This paper describes the demodulator structure and its demodulation performances obtained with a breadboard based on programmable logic devices. The choice of a simple and effective scheme for frequency detection (FM and FSK demodulators) is suggested by system design considerations as well. Signal processing algorithms include also a Costas carrier phase recovery scheme in the case of BPSK signal and data transition tracking loop for the bit clock recovery. Test results address this solution as one of the most suitable for TT&C space application.

Boscagli, G.; Comparini, M. C.; Martone, M.

139

Digital receiver for on-board FM/FSK-FM/BPSK demodulation  

NASA Technical Reports Server (NTRS)

An all-digital demodulator FM/FSK-FM/BPSK is presented. The proposed architecture allows the 1-bit IF down-sampling technique with the hardware simplification of receiver analog section. The receiver exhibits great flexibility both in terms of signal demodulation (FSK or BPSK, subcarrier/ tone frequency, data rate) and interface capability. The demodulator is going to be realized in a VLSI chip (20 Kgate complexity). This paper describes the demodulator structure and its demodulation performances obtained with a breadboard based on programmable logic devices. The choice of a simple and effective scheme for frequency detection (FM and FSK demodulators) is suggested by system design considerations as well. Signal processing algorithms include also a Costas carrier phase recovery scheme in the case of BPSK signal and data transition tracking loop for the bit clock recovery. Test results address this solution as one of the most suitable for TT&C space application.

Boscagli, G.; Comparini, M. C.; Martone, M.

1993-01-01

140

Optical arbitrary waveform characterization using linear spectrograms  

PubMed Central

We demonstrate the first application of linear spectrogram methods based on electro-optic phase modulation to characterize optical arbitrary waveforms generated under spectral line-by-line control. This approach offers both superior sensitivity and self-referencing capability for retrieval of periodic high repetition rate optical arbitrary waveforms. PMID:21359161

Jiang, Zhi; Leaird, Daniel E.; Long, Christopher M.; Boppart, Stephen A.; Weiner, Andrew M.

2010-01-01

141

Sequential feature extraction for waveform recognition  

Microsoft Academic Search

Many practical waveform recognition problems involve a sequential structure in time. One obvious example is speech. The information in speech can be assumed to be transmitted sequentially through a phonetic structure. Other examples are seismograms, radar signals, or television signals. We will take advantage of this sequential structure to develop a means of feature extraction and recognition for waveforms. The

W. J. Steingrandt; S. S. Yau

1970-01-01

142

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

SciTech Connect

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

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

1988-01-01

143

A fine resolution multifrequency polarimetric FM radar  

NASA Technical Reports Server (NTRS)

A fine resolution polarimetric FM SAR was developed for optimization of polarimetric SARs and interpretation of SAR data via controlled experiments with surface-base sensors. The system is designed for collecting polarimetric data at 5.3 and 10 GHz over incidence angles from 0 to 60 deg. Features of the system include broad bandwidth to obtain fine range resolution, phase stabilization and linearization loop circuitry, and digital signal processing capability. The system is used in a research program to collect polarimetric backscatter data from artificial sea ice research and design trade-offs, laboratory and field evaluation, as well as results from experiments on artificial sea ice are presented.

Bredow, J.; Gogineni, S.; Leung, T.; Moore, R. K.

1988-01-01

144

Injection and acceleration of electron bunch in a plasma wakefield produced by a chirped laser pulse  

SciTech Connect

An ultrashort laser pulse propagating in plasma can excite a nonlinear plasma wakefield which can trap and accelerate charged particles up to GeV. One-dimensional analysis of electron injection, trapping, and acceleration by different chirped pulses propagating in plasma is investigated numerically. In this paper, we inject electron bunches in front of the chirped pulses. It is indicated that periodical chirped laser pulse can trap electrons earlier than other pulses. It is shown that periodical chirped laser pulses lead to decrease the minimum momentum necessary to trap the electrons. This is due to the fact that periodical chirped laser pulses are globally much efficient than nonchirped pulses in the wakefield generation. It is found that chirped laser pulses could lead to much larger electron energy than that of nonchirped pulses. Relative energy spread has a lower value in the case of periodical chirped laser pulses.

Afhami, Saeedeh; Eslami, Esmaeil, E-mail: eeslami@iust.ac.ir [Department of Physics, Iran University of Science and Technology (IUST), Narmak, Tehran 16846-13114 (Iran, Islamic Republic of)

2014-06-15

145

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

PubMed Central

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

Williams, Anthony J.; Fuzessery, Zoltan M.

2012-01-01

146

Electron heating enhancement by frequency-chirped laser pulses  

SciTech Connect

Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic field is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a{sub 0}?=?5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about n{sub e}???6n{sub c}, where n{sub c} is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.

Yazdani, E.; Afarideh, H., E-mail: hafarideh@aut.ac.ir [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir [Department of Physics, Sharif University of Technology, P.O. Box 11365-9567, Tehran (Iran, Islamic Republic of); Riazi, Z. [Physics and Accelerator School, Tehran (Iran, Islamic Republic of); Hora, H. [Department of Theoretical Physics, University of New South Wales, Sydney 2052 (Australia)

2014-09-14

147

Indoor Pseudo-ranging of Mobile Devices using Ultrasonic Chirps  

E-print Network

Introduction Location tracking on mobile devices like smart phones has already begun to revolutionize personal: building navigation (malls, factories, airports), augmented reality, location-aware pervasive computingIndoor Pseudo-ranging of Mobile Devices using Ultrasonic Chirps Patrick Lazik Anthony Rowe

Rowe, Anthony

148

Chirped frequency transfer: a tool for synchronization and time transfer.  

PubMed

We propose and demonstrate the phase-stabilized transfer of a chirped frequency as a tool for synchronization and time transfer. Technically, this is done by evaluating remote measurements of the transferred, chirped frequency. The gates of the frequency counters, here driven by a 10-MHz oscillation derived from a hydrogen maser, play a role analogous to the 1-pulse per second (PPS) signals usually employed for time transfer. In general, for time transfer, the gates consequently must be related to the external clock. Synchronizing observations based on frequency measurements, on the other hand, only requires a stable oscillator driving the frequency counters. In a proof of principle, we demonstrate the suppression of symmetrical delays, such as the geometrical path delay. We transfer an optical frequency chirped by around 240 kHz/s over a fiber link of around 149 km. We observe an accuracy and simultaneity, as well as a precision (Allan deviation, 18,000 s averaging interval) of the transferred frequency of around 2 10(-19). We apply chirped frequency transfer to remote measurements of the synchronization between two counters' gate intervals. Here, we find a precision of around 200 ps at an estimated overall uncertainty of around 500 ps. The measurement results agree with those obtained from reference measurements, being well within the uncertainty. In the present setup, timing offsets up to 4 min can be measured unambiguously. We indicate how this range can be extended further. PMID:24859656

Raupach, Sebastian M F; Grosche, Gesine

2014-06-01

149

Pulse compression on the Mark III FEL using energy chirping  

Microsoft Academic Search

We have performed preliminary simulations of the optical-pulse formation in the Mark III FEL using electron micropulses which exhibit a linear energy dependence on time, and have demonstrated optical pulses whose frequency chirps agree fairly well with those obtained analytically by assuming that the resonance condition determines the lasing wavelength during the pulse. In a typical case, we project pulse

Eric B. Szarmes; Stephen V. Benson; John M. J. Madey

1990-01-01

150

Indoor Pseudo-ranging of Mobile Devices using Ultrasonic Chirps  

E-print Network

Indoor Pseudo-ranging of Mobile Devices using Ultrasonic Chirps Patrick Lazik Anthony Rowe In this paper, we present an indoor ultrasonic location tracking system that can utilize off-the-shelf audio the human hearing frequency range where mobile devices are still sensitive. Typically transmitting data

Rowe, Anthony

151

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

152

High spectral resolution multiplex CARS spectroscopy using chirped pulses  

Microsoft Academic Search

A simple technique for achieving high spectral resolution coherent anti-Stokes Raman scattering (CARS) spectra with a femtosecond laser system is presented. A linearly chirped and stretched (?10 ps) pump pulse generates CARS signal only when overlapped in time with the Stokes pulse (90 fs), creating a `temporal slit' that defines the spectral resolution of the technique. Multiplex CARS spectra for

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

2004-01-01

153

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

154

Narrow-band FM system for television links: Interference between FM and AM television signals  

Microsoft Academic Search

The Band V FM television links used for television outside broadcasts have suffered more and more from interference as the network of UHF television broadcasting transmitters has expanded. There is also thought to be an increasing danger that Band V Links will cause interference to broadcast television reception. Experimental work was carried out to determine whether reducing the bandwidth of

N. H. C. Gilchrist; A. G. Lyner

1978-01-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

156

Waveform Fingerprinting for Efficient Seismic Signal Detection  

NASA Astrophysics Data System (ADS)

Cross-correlating an earthquake waveform template with continuous waveform data has proven a powerful approach for detecting events missing from earthquake catalogs. If templates do not exist, it is possible to divide the waveform data into short overlapping time windows, then identify window pairs with similar waveforms. Applying these approaches to earthquake monitoring in seismic networks has tremendous potential to improve the completeness of earthquake catalogs, but because effort scales quadratically with time, it rapidly becomes computationally infeasible. We develop a fingerprinting technique to identify similar waveforms, using only a few compact features of the original data. The concept is similar to human fingerprints, which utilize key diagnostic features to identify people uniquely. Analogous audio-fingerprinting approaches have accurately and efficiently found similar audio clips within large databases; example applications include identifying songs and finding copyrighted content within YouTube videos. In order to fingerprint waveforms, we compute a spectrogram of the time series, and segment it into multiple overlapping windows (spectral images). For each spectral image, we apply a wavelet transform, and retain only the sign of the maximum magnitude wavelet coefficients. This procedure retains just the large-scale structure of the data, providing both robustness to noise and significant dimensionality reduction. Each fingerprint is a high-dimensional, sparse, binary data object that can be stored in a database without significant storage costs. Similar fingerprints within the database are efficiently searched using locality-sensitive hashing. We test this technique on waveform data from the Northern California Seismic Network that contains events not detected in the catalog. We show that this algorithm successfully identifies similar waveforms and detects uncataloged low magnitude events in addition to cataloged events, while running to completion faster than a comparison waveform autocorrelation code.

Yoon, C. E.; OReilly, O. J.; Beroza, G. C.

2013-12-01

157

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

158

FINDR: Low-Cost Indoor Positioning Using FM Radio  

NASA Astrophysics Data System (ADS)

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

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

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.

Mikczi, Balzs

2010-03-01

160

What FM can offer DFCS design  

NASA Technical Reports Server (NTRS)

The results of aircrafts and spacecrafts flight tests are reported. It is shown that the problems of Digital Flight Control Systems (DFCS) are the problems of systems whose complexity has exceeded the reach of the intellectual tools employed. It is also shown that intuition, experience, and techniques derived from mechanical and analog systems are insufficient for complex, integrated, digital systems. Formal Methods (FM) of computer science can offer DFCS systematic techniques for the construction of trustworthy software, including: techniques for the precise specification of requirements and the development of designs; systematic approaches to the design and structuring of distributed and concurrent systems; fault tolerance algorithms; and systematic methods of testing and analytic methods of verification.

Rushby, John

1990-01-01

161

Superfluid dynamics of 258Fm fission  

E-print Network

Theoretical description of nuclear fission remains one of the major challenges of quantum many-body dynamics. The slow, mostly adiabatic motion through the fission barrier is followed by a fast, non-adiabatic descent of the potential between the fragments. The latter stage is essentially unexplored. However, it is crucial as it generates most of the excitation energy in the fragments. The superfluid dynamics in the latter stage of fission is obtained with the time-dependent Hartree-Fock theory including BCS dynamical pairing correlations. The fission modes of the 258Fm nucleus are studied. The resulting fission fragment characteristics show a good agreement with experimental data. Quantum shell effects are shown to play a crucial role in the dynamics and formation of the fragments. The importance of quantum fluctuations beyond the independent particle/quasi-particle picture is underlined and qualitatively studied.

Scamps, Guillaume; Lacroix, Denis

2015-01-01

162

LISA Parameter Estimation using Numerical Merger Waveforms  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

163

High-Voltage, Asymmetric-Waveform Generator  

NASA Technical Reports Server (NTRS)

The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise leave the fundamental timing signal unchanged. The buffered timing signal would be fed as input to the level shifter. The output of the level shifter would serve as a timing and control signal for the high-voltage switch, causing the switch to alternately be (1) opened, allowing the capacitive load to be charged from a high-voltage DC power supply; then (2) closed to discharge the capacitive load to ground. Hence, the output waveform would closely approximate a series of exponential charging and discharging curves (see Figure 2).

Beegle, Luther W.; Duong, Tuan A.; Duong, Vu A.; Kanik, Isik

2008-01-01

164

Analysis and Application of LIDAR Waveform Data Using a Progressive Waveform Decomposition Method  

NASA Astrophysics Data System (ADS)

Due to rich information of a full waveform of airborne LiDAR (light detection and ranging) data, the analysis of full waveform has been an active area in LiDAR application. It is possible to digitally sample and store the entire reflected waveform of small-footprint instead of only discrete point clouds. Decomposition of waveform data, a key step in waveform data analysis, can be categorized to two typical methods: 1) the Gaussian modelling method such as the Non-linear least-squares (NLS) algorithm and the maximum likelihood estimation using the Exception Maximization (EM) algorithm. 2) pulse detection method—Average Square Difference Function (ASDF). However, the Gaussian modelling methods strongly rely on initial parameters, whereas the ASDF omits the importance of parameter information of the waveform. In this paper, we proposed a fast algorithm—Progressive Waveform Decomposition (PWD) method to extract local maxims and fit the echo with Gaussian function, and calculate other parameters from the raw waveform data. On the one hand, experiments are implemented to evaluate the PWD method and the results demonstrate its robustness and efficiency. On the other hand, with the PWD parametric analysis of the full-waveform instead of a 3D point cloud, some special applications are investigated afterward.

Zhu, J.; Zhang, Z.; Hu, X.; Li, Z.

2011-09-01

165

End-to-end RMS error testing on a constant bandwidth FM/FM system  

NASA Technical Reports Server (NTRS)

End-to-end root-mean-square (rms) tests performed on a constant bandwidth FM/FM system with various settings of system parameters are reported. The testing technique employed is that of sampling, digitizing, delaying, and comparing the analog input against the sampled and digitized corresponding output. Total system error is determined by fully loading all channels with band-limited noise and conducting end-to-end rms error tests on one channel. Tests are also conducted with and without a transmission link and plots of rms errors versus receiver signal-to-noise (S/N) values are obtained. The combined effects of intermodulation, adjacent channel crosstalk, and residual system noise are determined as well as the single channel distortion of the system.

Wallace, G. R.; Salter, W. E.

1972-01-01

166

SMSE-based DSA radar waveforms  

Microsoft Academic Search

Previous communications systems research has demonstrated that the Spectrally Modulated, Spectrally Encoded (SMSE) framework is well suited to SDR platforms and operation in both contiguous and non-contiguous spectrum given its ability to generate a wide variety of multicarrier waveforms such as OFDM, NC-OFDM, MC-CDMA, NC-MC-CDMA, CI\\/MC-CDMA, NCCI\\/MC-CDMA, and TDCS. In this paper, SMSE waveforms are extended for use in sparse

John Carlson; Joe Kennedy; V. Chakravarthy

2010-01-01

167

Waveform design for compressively sampled ultrawideband radar  

NASA Astrophysics Data System (ADS)

Compressive sensing makes it possible to recover sparse target scenes from under-sampled measurements when uncorrelated random-noise waveforms are used as probing signals. The mathematical theory behind this assertion is based on the fact that Toeplitz and circulant random matrices generated from independent identically distributed (i.i.d) Gaussian random sequences satisfy the restricted isometry property. In real systems, waveforms have smooth, nonideal autocorrelation functions, thereby degrading the performance of compressive sensing algorithms. Compressive sensing requires the system matrix to have particular properties. Incorporating prior information into the target scene either to enhance imaging or to mitigate nonidealities can result in system matrices that are not suitable for compressive sensing. We can overcome this problem by designing appropriate transmit waveforms. We extend the existing theory to incorporate such nonidealities into the analysis of compressive recovery. As an example we consider the problem of tailoring waveforms to image extended targets. Extended targets make the target scene denser, causing random transmit waveforms to be suboptimal for recovery. We propose to incorporate extended targets by considering them to be sparsely representable in redundant dictionaries. We demonstrate that a low complexity algorithm to optimize the transmit waveform leads to improved performance.

Shastry, Mahesh C.; Narayanan, Ram M.; Rangaswamy, Muralidhar

2013-04-01

168

Pulse compression on the Mark III FEL using energy chirping  

NASA Astrophysics Data System (ADS)

We have performed preliminary simulations of the optical-pulse formation in the Mark III FEL using electron micropulses which exhibit a linear energy dependence on time, and have demonstrated optical pulses whose frequency chirps agree fairly well with those obtained analytically by assuming that the resonance condition determines the lasing wavelength during the pulse. In a typical case, we project pulse compression by a factor of 13.3, from an initial pulse width of 3.13 ps to a final pulse width of 236 fs, at a wavelength of 3.35 ?m and an electron energy chirp of +2% (energy increasing towards the back of the pulse). This represents an optical pulse less than half as short as the slippage length of 47 magnet periods for this wavelength.

Szarmes, Eric B.; Benson, Stephen V.; Madey, John M. J.

1990-10-01

169

Optical chirp z-transform processor with a simplified architecture.  

PubMed

Using a simplified chirp z-transform (CZT) algorithm based on the discrete-time convolution method, this paper presents the synthesis of a simplified architecture of a reconfigurable optical chirp z-transform (OCZT) processor based on the silica-based planar lightwave circuit (PLC) technology. In the simplified architecture of the reconfigurable OCZT, the required number of optical components is small and there are no waveguide crossings which make fabrication easy. The design of a novel type of optical discrete Fourier transform (ODFT) processor as a special case of the synthesized OCZT is then presented to demonstrate its effectiveness. The designed ODFT can be potentially used as an optical demultiplexer at the receiver of an optical fiber orthogonal frequency division multiplexing (OFDM) transmission system. PMID:25607197

Ngo, Nam Quoc

2014-12-29

170

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

171

Dense monoenergetic proton beams from chirped laser-plasma interaction  

E-print Network

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

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

2011-01-01

172

Preparing Students to Take SOA/CAS Exam FM/2  

ERIC Educational Resources Information Center

This paper provides suggestions for preparing students to take the actuarial examination on financial mathematics, SOA/CAS Exam FM/2. It is based on current practices employed at Slippery Rock University, a small public liberal arts university. Detailed descriptions of our Theory of Interest course and subsequent Exam FM/2 prep course are provided

Marchand, Richard J.

2014-01-01

173

47 CFR 73.4108 - FM transmitter site map submissions.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false FM transmitter site map submissions. 73.4108 Section 73.4108 Telecommunication...to All Broadcast Stations 73.4108 FM transmitter site map submissions. See Memorandum Opinion and Order and...

2010-10-01

174

Hyper dispersion pulse compressor for chirped pulse amplification systems  

DOEpatents

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

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

2011-11-29

175

Superharmonic imaging with chirp coded excitation: filtering spectrally overlapped harmonics.  

PubMed

Superharmonic imaging improves the spatial resolution by using the higher order harmonics generated in tissue. The superharmonic component is formed by combining the third, fourth, and fifth harmonics, which have low energy content and therefore poor SNR. This study uses coded excitation to increase the excitation energy. The SNR improvement is achieved on the receiver side by performing pulse compression with harmonic matched filters. The use of coded signals also introduces new filtering capabilities that are not possible with pulsed excitation. This is especially important when using wideband signals. For narrowband signals, the spectral boundaries of the harmonics are clearly separated and thus easy to filter; however, the available imaging bandwidth is underused. Wideband excitation is preferable for harmonic imaging applications to preserve axial resolution, but it generates spectrally overlapping harmonics that are not possible to filter in time and frequency domains. After pulse compression, this overlap increases the range side lobes, which appear as imaging artifacts and reduce the Bmode image quality. In this study, the isolation of higher order harmonics was achieved in another domain by using the fan chirp transform (FChT). To show the effect of excitation bandwidth in superharmonic imaging, measurements were performed by using linear frequency modulated chirp excitation with varying bandwidths of 10% to 50%. Superharmonic imaging was performed on a wire phantom using a wideband chirp excitation. Results were presented with and without applying the FChT filtering technique by comparing the spatial resolution and side lobe levels. Wideband excitation signals achieved a better resolution as expected, however range side lobes as high as -23 dB were observed for the superharmonic component of chirp excitation with 50% fractional bandwidth. The proposed filtering technique achieved >50 dB range side lobe suppression and improved the image quality without affecting the axial resolution. PMID:25389159

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

2014-11-01

176

Excitation and control of chirped nonlinear ion-acoustic waves  

NASA Astrophysics Data System (ADS)

Large-amplitude ion acoustic waves are excited and controlled by a chirped frequency driving perturbation. The process involves capturing into autoresonance (a continuous nonlinear synchronization) with the drive by passage through the linear resonance in the problem. The transition to autoresonance has a sharp threshold on the driving amplitude. The theory of this transition is developed beyond the Korteweg-de Vries limit by using the Whitham's averaged variational principle within the water bag model and compared with Vlasov-Poisson simulations.

Friedland, L.; Shagalov, A. G.

2014-05-01

177

Identification of biological tissue using chirped probe THz imaging  

Microsoft Academic Search

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

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

2002-01-01

178

A Novel Real-Time Chirp Measurement Method for Ultrashort Optical Pulses  

Microsoft Academic Search

Rapid measurements of ultrashort optical pulse chirping were realized with a newly developed real-time chirp monitor. The application of a moving coil translator and electrical filters enabled the rapid measurement and decoding of fringe-resolved second-harmonic-generation (FRSHG) autocorrelation. The prototype system displayed chirping characteristics at a repetition rate higher than a few hertz, which demonstrates the usefulness of this monitor for

Kazuo Mogi; Kazunori Naganuma; Hajime Yamada

1988-01-01

179

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 7.158.74 demonstrates the success of the design of the cascaded chirp fiber Bragg grating.

Cai, Ju; Bai, Qiujian; Su, Xin

2013-09-01

180

An improved processing sequence for uncorrelated Chirp sonar data  

NASA Astrophysics Data System (ADS)

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

Baradello, Luca

2014-12-01

181

Shear wave speed and dispersion measurements using crawling wave chirps.  

PubMed

This article demonstrates the measurement of shear wave speed and shear speed dispersion of biomaterials using a chirp signal that launches waves over a range of frequencies. A biomaterial is vibrated by two vibration sources that generate shear waves inside the medium, which is scanned by an ultrasound imaging system. Doppler processing of the acquired signal produces an image of the square of vibration amplitude that shows repetitive constructive and destructive interference patterns called "crawling waves." With a chirp vibration signal, successive Doppler frames are generated from different source frequencies. Collected frames generate a distinctive pattern which is used to calculate the shear speed and shear speed dispersion. A special reciprocal chirp is designed such that the equi-phase lines of a motion slice image are straight lines. Detailed analysis is provided to generate a closed-form solution for calculating the shear wave speed and the dispersion. Also several phantoms and an ex vivo human liver sample are scanned and the estimation results are presented. PMID:24658144

Hah, Zaegyoo; Partin, Alexander; Parker, Kevin J

2014-10-01

182

A direct digital synthesis chirped pulse Fourier transform microwave spectrometer.  

PubMed

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. PMID:24007050

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

2013-08-01

183

Progress Towards Chirped-Pulse Fourier Transform Thz Spectroscopy  

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

184

Harmonic chirp imaging method for ultrasound contrast agent.  

PubMed

Coded excitation is currently used in medical ultrasound to increase signal-to-noise ratio (SNR) and penetration depth. We propose a chirp excitation method for contrast agents using the second harmonic component of the response. This method is based on a compression filter that selectively compresses and extracts the second harmonic component from the received echo signal. Simulations have shown a clear increase in response for chirp excitation over pulse excitation with the same peak amplitude. This was confirmed by two-dimensional (2-D) optical observations of bubble response with a fast framing camera. To evaluate the harmonic compression method, we applied it to simulated bubble echoes, to measured propagation harmonics, and to B-mode scans of a flow phantom and compared it to regular pulse excitation imaging. An increase of approximately 10 dB in SNR was found for chirp excitation. The compression method was found to perform well in terms of resolution. Axial resolution was in all cases within 10% of the axial resolution from pulse excitation. Range side-lobe levels were 30 dB below the main lobe for the simulated bubble echoes and measured propagation harmonics. However, side-lobes were visible in the B-mode contrast images. PMID:15801312

Borsboom, Jerome M G; Chin, Chien Ting; Bouakaz, Ayache; Versluis, Michel; de Jong, Nico

2005-02-01

185

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

SciTech Connect

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

Fortin, Gilles; McCarthy, Nathalie

2005-08-10

186

50 CFR 660.394 - Latitude/longitude coordinates defining the 180 fm (329 m) through 250 fm (457 m) depth contours.  

Code of Federal Regulations, 2010 CFR

...Latitude/longitude coordinates defining the 180 fm (329 m) through 250 fm (457 m) depth contours. 660.394 Section 660.394 ...Latitude/longitude coordinates defining the 180 fm (329 m) through 250 fm (457 m) depth contours....

2010-10-01

187

50 CFR 660.392 - Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours.  

Code of Federal Regulations, 2010 CFR

...Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours. 660.392 Section 660.392 ...Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours....

2010-10-01

188

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

189

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

190

Design of Pulse Waveform for Waveform Division Multiple Access UWB Wireless Communication System  

PubMed Central

A new multiple access scheme, Waveform Division Multiple Access (WDMA) based on the orthogonal wavelet function, is presented. After studying the correlation properties of different categories of single wavelet functions, the one with the best correlation property will be chosen as the foundation for combined waveform. In the communication system, each user is assigned to different combined orthogonal waveform. Demonstrated by simulation, combined waveform is more suitable than single wavelet function to be a communication medium in WDMA system. Due to the excellent orthogonality, the bit error rate (BER) of multiuser with combined waveforms is so close to that of single user in a synchronous system. That is to say, the multiple access interference (MAI) is almost eliminated. Furthermore, even in an asynchronous system without multiuser detection after matched filters, the result is still pretty ideal and satisfactory by using the third combination mode that will be mentioned in the study. PMID:24672294

Yin, Zhendong; Wang, Zhirui; Liu, Xiaohui

2014-01-01

191

Design of pulse waveform for waveform division multiple access UWB wireless communication system.  

PubMed

A new multiple access scheme, Waveform Division Multiple Access (WDMA) based on the orthogonal wavelet function, is presented. After studying the correlation properties of different categories of single wavelet functions, the one with the best correlation property will be chosen as the foundation for combined waveform. In the communication system, each user is assigned to different combined orthogonal waveform. Demonstrated by simulation, combined waveform is more suitable than single wavelet function to be a communication medium in WDMA system. Due to the excellent orthogonality, the bit error rate (BER) of multiuser with combined waveforms is so close to that of single user in a synchronous system. That is to say, the multiple access interference (MAI) is almost eliminated. Furthermore, even in an asynchronous system without multiuser detection after matched filters, the result is still pretty ideal and satisfactory by using the third combination mode that will be mentioned in the study. PMID:24672294

Yin, Zhendong; Wang, Zhirui; Liu, Xiaohui; Wu, Zhilu

2014-01-01

192

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

Code of Federal Regulations, 2010 CFR

...Classes of noncommercial educational FM stations and channels. 73.506 Section 73...Noncommercial Educational FM Broadcast Stations 73.506 Classes of noncommercial educational FM stations and channels. (a)...

2010-10-01

193

The Focusing DIRC with Waveform Digitizing Electronics  

SciTech Connect

We have tested a novel Cherenkov imaging detector called the Focusing DIRC (FDIRC) with waveform digitizing electronics. The prototype's concept is based on the BaBar DIRC with several important improvements: (a) much faster, pixelated photon detectors, (b) a mirror that makes the photon detector smaller and less sensitive to background in future applications, and (c) electronics capable of measuring single photon resolution to {sigma} {approx} 150 ps, which allows for correction due to chromatic error. In this test, the prototype has been instrumented with seven Hamamatsu H-8500 MaPMTs. Waveforms from {approx}450 pixels are digitized with waveform sampling electronics based on the BLAB2 ASIC, operating at a sampling speed of {approx}2.5 GSa/s. This version of the FDIRC prototype was tested in a large cosmic ray telescope providing muon tracks with {approx}1 mrad angular resolution and a muon momentum cutoff of {ge} 1.6 GeV/c.

Ruckman, L.L.; /Hawaii U.; Nishimura, K.; /Hawaii U.; Varner, G.S.; /Hawaii U.; Vavra, J.; /SLAC; Aston, D.; /SLAC; Leith, D.W.G.S.; /SLAC; Ratcliff, B.; /SLAC

2012-06-15

194

Biphoton waveform: Space-to-time mapping  

E-print Network

We study narrow-band biphoton generation from spontaneous four-wave mixing with electromagnetically induced transparency in a laser cooled atomic ensemble. We compare two formalisms in the interaction and Heisenberg pictures, and find that they agree in the low gain regime but disagree in the high gain regime. We extend both formalisms accounting the non-uniformity in atomic density and the driving laser fields. We find that for a fixed optical depth and a weak and far-detuned pump laser beam, the two-photon waveform is independent of the atomic density distribution. However, the spatial profiles of the two driving laser beams have a significant effect on the biphoton temporal waveform. We predict that waveform shaping in time domain can be achieved by controlling the spatial profile of the driving laser fields.

Luwei Zhao; Yumian Su; Shengwang Du

2014-09-11

195

Passive coherent beam combining of two femtosecond fiber chirped-pulse amplifiers  

E-print Network

Passive coherent beam combining of two femtosecond fiber chirped-pulse amplifiers Louis Daniault,1 femtosecond chirped- pulse amplifiers. The setup consists in the use of a well-balanced amplifying Sagnac amplifiers have great advantages to amplify ultrashort femtosecond pulses. Indeed, their geometry offers

Boyer, Edmond

196

Small signal analysis of frequency chirping in injection-locked semiconductor lasers  

SciTech Connect

A theoretical and experimental investigation of frequency chirping in injection-locked semiconductor lasers under a condition of small signal modulation is presented. It shows that a substantial reduction of frequency chirping can be obtained which, however, is effective only up to modulation frequencies of the order of the locking bandwidth and is strongly dependent on the frequency detuning between master and slave.

Piazzolla, S.; Spano, P.; Tamburrini, M.

1986-12-01

197

Small signal analysis of frequency chirping in injection-locked semiconductor lasers  

Microsoft Academic Search

A theoretical and experimental investigation of frequency chirping in injection-locked semiconductor lasers under a condition of small signal modulation is presented. It shows that a substantial reduction of frequency chirping can be obtained which, however, is effective only up to modulation frequencies of the order of the locking bandwidth and is strongly dependent on the frequency detuning between master and

S. Piazzolla; P. Spano; M. Tamburrini

1986-01-01

198

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

199

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

200

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

SciTech Connect

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

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

2007-12-26

201

Low Complexity Chirp Pulsed Ultra-Wideband System with Near-Optimum Multipath Performance  

Microsoft Academic Search

This paper describes the Impulse Radio Ultra- Wideband (IR-UWB) system using linear chirp UWB pulses as symbols. The novel method of coherent or differentially coherent detection of chirp pulses in multipath channels is introduced. The method divides detection in the receiver between its analog and digital part; in the analog part of the receiver, received signal is compressed in frequency

Igor Dotlic; Ryuji Kohno

2011-01-01

202

Simulation of optical pulse compression using parabolic pulse with linear chirp  

NASA Astrophysics Data System (ADS)

It is the key of realizing high speed, large capacity fiber information transmission that achieve ultrashort optical pulse by optical pulse compression. At present, the compression method that is achieving parabolic pulse with linear chirp and compensating the linear chirp is paid more attention. Based on the two schemes for the parabolic pulse with linear chirp by the normal dispersion decreasing fiber or the fiber amplifier with a normal dispersion, more study on the characteristics of the parabolic pulse with linear chirp in the different dispersion decreasing profiles (such as cosine, Gaussian, linear, exponential and hyperbolic) is showed; the results show that, for different dispersion decreasing profiles, the good linear chirp and parabolic shapes that are good for pulse compression can be generated. Moreover, a novel scheme for the parabolic pulse, which is achieved by a dispersion decreasing fiber amplifier with a normal dispersion, is presented. Numerical simulations show that, compared with the parabolic pulses generated in the normal dispersion decreasing fiber or the fiber amplifier, the parabolic pulse generated by the novel scheme has the better linear chirp and the more pulse energy; the gain has an obviously effect on the intensity and quality of the linear chirp, which is that the output pulse has a smaller pulse width and higher pulse power after the chirp is compensated.

Wang, Zun-zhi

2013-08-01

203

Photonic generation of linearly chirped millimeter wave based on comb-spacing tunable optical frequency comb  

NASA Astrophysics Data System (ADS)

We demonstrated a photonic approach to generate a phase-continuous frequency-linear-chirped millimeter-wave (mm-wave) signal with high linearity based on continuous-wave phase modulated optical frequency comb and cascaded interleavers. Through linearly sweeping the frequency of the radio frequency (RF) driving signal, high-order frequency-linear-chirped optical comb lines are generated and then extracted by the cascaded interleavers. By beating the filtered high-order comb lines, center frequency and chirp range multiplied linear-chirp microwave signals are generated. Frequency doubled and quadrupled linear-chirp mm-wave signals of range 48.6 to 52.6 GHz and 97.2 to 105.2 GHz at chirp rates of 133.33 and 266.67 GHz/s are demonstrated with the 1st and 2nd optical comb lines, respectively, while the RF driving signal is of chirp range 24.3 to 26.3 GHz and chirp time 30 ms.

Xia, Zongyang; Xie, Weilin; Sun, Dongning; Shi, Hongxiao; Dong, Yi; Hu, Weisheng

2013-12-01

204

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

205

56. Credit FM. East elevation taken from along penstock. Note ...  

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

56. Credit FM. East elevation taken from along penstock. Note additions to the east side and the north side of the building. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

206

72. Credit FM. Overview of powerhouse from gallery. Notice cooling ...  

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

72. Credit FM. Overview of powerhouse from gallery. Notice cooling duct on generator (now removed) and spare gate valve in far corner. - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

207

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

208

68. Credit FM. Detail showing operators. Note cooling duct (now ...  

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

68. Credit FM. Detail showing operators. Note cooling duct (now removed), governor (now removed), hand-operated needle valve controls (now removed). - Battle Creek Hydroelectric System, Battle Creek & Tributaries, Red Bluff, Tehama County, CA

209

University Policy No.: FM5100 Classification: Financial Management  

E-print Network

University Policy No.: FM5100 Classification: Financial Management Approving Authority: Board of Financial Services; Manager of Financial Accounting; Manager of Treasury Services; Manager of Pension, Finance and Operations; Vice-President, Research, Executive Director of Financial Services; University

Victoria, University of

210

University Policy No.: FM5200 (1480) Classification: Financial Management  

E-print Network

1 University Policy No.: FM5200 (1480) Classification: Financial Management Approving Authority that are professionally managed externally. The funds arise from operating, research and capital project financing agencies, including DBRS, Standard & Poor's and Moody's. The portfolio manager will be responsible

Victoria, University of

211

FM 3-04.513 Aircraft Recovery Operations  

E-print Network

FM 3-04.513 Aircraft Recovery Operations July 2008 DISTRIBUTION RESTRICTION: Approved for public-04.513 Headquarters Department of the Army Washington, DC, 21 July 2008 Aircraft Recovery Operations Contents Page.............................................................................................. 1-1 Aircraft Recovery

US Army Corps of Engineers

212

Observation of a giant-chirp dissipative soliton and near chirp-free pulse in a slight-normal-dispersion fiber laser  

NASA Astrophysics Data System (ADS)

We reported a switchable giant-chirp (GC) dissipative soliton and near-chirp-free (NCF) pulse in a slight-normal-dispersion fiber laser by tuning the pump power. The GC dissipative soliton exhibits a quasi-rectangular spectrum with bandwidth of 9?nm and duration of 8?ps. The time bandwidth product (TBP) is calculated as 8.8, indicating that the dissipative soliton is highly chirped. The NCF pulse has a bandwidth of 2.5?nm and a duration of 1.8?ps, which gives a TBP of 0.55, suggesting that the pulse almost is chirp free. Our numerical simulations confirm the experimental observations, and demonstrate that the operation state of dissipative system is very sensitive to the pump strength.

Mao, D.; Jiang, B. Q.; Zhang, W. D.; Zhao, J. L.

2014-10-01

213

Analysis of an impulse noise suppressor for FM demodulators  

NASA Technical Reports Server (NTRS)

An FM click noise suppressor was evaluated by means of several experimental tests conducted to verify previous test results. The range and worst case type of operation for the suppressor were also determined. A brief theoretical justification for the existence of FM click noise near threshold conditions is presented. It is concluded that the circuit does perform click suppression, but over a limited range. Suggestions for improvement of the circuit are given.

James, S. N.

1974-01-01

214

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

SciTech Connect

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

Afhami, Saeedeh; Eslami, Esmaeil, E-mail: eeslami@iust.ac.ir [Department of Physics, Iran University of Science and Technology (IUST), Narmak, Tehran, 16846-13114 (Iran, Islamic Republic of)

2014-08-15

215

Chirp of the single attosecond pulse generated by a polarization gating  

SciTech Connect

The chirp of the xuv supercontinuum generated by a polarization gating is investigated by comparing three-dimensional nonadiabatic numerical simulations with classical calculations. The origin of the chirp is the dependence of the energy gain by an electron on the return time. The chirp is positive and its value is almost the same as that when a linearly polarized laser is used. Although the 250-eV-wide supercontinuum corresponds to a single attosecond pulse, the shortest duration of the pulse is limited by the chirp. By compensating the positive chirp with the negative group velocity dispersion of a Sn filter, it is predicted that a single 58-as pulse can be generated.

Chang Zenghu [Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States)

2005-02-01

216

Isolated short attosecond pulse generation in an orthogonally polarized multicycle chirped laser field  

SciTech Connect

We theoretically demonstrate the generation of a high-order harmonic and isolated attosecond pulse in an orthogonally polarized laser field, which is synthesized by an 800-nm chirped laser pulse and an 800-nm chirp-free laser pulse. Owing to the instantaneous frequency increasingly reducing close to the center of the driving pulse, the extreme ultraviolet supercontinuum for the chirped synthesized field is even broader than that for an orthogonal chirp-free two-color laser field. It is found that the broadband supercontinuum spectrum can be achieved for the driving pulse with ten and above optical cycles. After phase compensation an isolated attosecond pulse with a duration of {approx}16 as is produced. Furthermore, the optimization of the chirping rate parameters is investigated to achieve cutoff extension and an isolated short attosecond pulse.

Xu Junjie [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)

2011-03-15

217

Spatial filtering of light by chirped photonic crystals  

SciTech Connect

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

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

2009-05-15

218

JTRS/SCA and Custom/SDR Waveform Comparison  

NASA Technical Reports Server (NTRS)

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

Oldham, Daniel R.; Scardelletti, Maximilian C.

2007-01-01

219

Adaptive waveform scheduling in radar: an information theoretic approach  

NASA Astrophysics Data System (ADS)

In this paper, the problem of adaptively selecting radar waveforms from a pre-dened library of waveforms is addressed from an information theoretic perspective. Typically, radars transmit specic waveforms periodically, to obtain for example, the range and Doppler of a target. Although modern radars are capable of transmitting dierent waveforms during each consecutive period of transmission, it is hitherto unclear as to how these waveforms must be scheduled to best understand the dynamic radar scene. In this paper, a new information theoretic metric - directed information - is employed for waveform scheduling, and is shown to incorporate the past radar returns to eectively schedule waveforms. We formulate this waveform scheduling problem in a Gaussian framework, derive the corresponding maximization problem, and illustrate several special cases.

Setlur, Pawan; Devroye, Natasha

2012-06-01

220

Quasi-orthogonal wideband radar waveforms based on chaotic systems  

E-print Network

With the development of A/D converters possessing sufficiently high sampling rates, it is now feasible to use arbitrary, wideband waveforms in radar applications. Large sets of quasi-orthogonal, wideband waveforms can be ...

Willsey, Matt (Matt S.)

2007-01-01

221

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

NASA Technical Reports Server (NTRS)

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

1981-01-01

222

Application of arbitrary waveform generator for noise radar  

Microsoft Academic Search

The approach, when the waveforms of different types are exploited in the same radar (waveform diversity) requires new-generation sources of initial signals. For generating of different types of waveforms in the same radar we suggest using Arbitrary Waveform Generator, that allows output any type of pre-programmed signal in real time. We have carried out preliminary experimental tests of the stepped-delay

Konstantin A. Lukin; Oleg V. Zemlyaniy; Pavlo L. Vyplavin; Volodymyr P. Palamarchuk

2011-01-01

223

Waveform analysis for HF ground wave radar  

Microsoft Academic Search

According to general radar designing principles, this paper discusses the concepts and pro- cessing techniques concerning the radar waveform analysis. For the need in developing HF ground wave system, as requested by a key oceanic project in the national 863 plans, basic theories and parameter de- sign techniques on Frequency Modulated Interrupted Continuous Wave (FMICW) have been studied. This study

Wu Shi-cai; Yang Zi-jie; Wen Bi-yang; Shi Zhen-hua; Tian Jian-sheng

2001-01-01

224

A multi-channel waveform digitizer system  

SciTech Connect

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

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

1990-04-01

225

A transformer of closely spaced pulsed waveforms  

NASA Technical Reports Server (NTRS)

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

Niedra, J.

1970-01-01

226

Parameter Estimation using Numerical Merger Waveforms  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

227

Waveform Diversity in Radar Signal Processing  

Microsoft Academic Search

This article shows that suitably transmitted and processed, radar waveforms based on Golay sequences provide new primitives for adaptive transmission that enable better detection and finer resolution, while managing computational complexity at the receiver. The ability to exploit space-time adaptive processing is limited by the computational power available at the receiver, and increased flexibility on transmission only exacerbates this problem

R. Calderbank; S. Howard; B. Moran

2009-01-01

228

Responses of inferior collicular neurones to acoustic stimuli in certain FM and CF-FM paleotropical bats  

Microsoft Academic Search

1.Electrophysiological properties of auditory units of six species of paleotropical echolocating bats, including two FM bats and four CF-FM bats were studied by recording the responses to tone bursts of single units, multiple units and evoked potentials from their inferior colliculi. The orientation pulses of these bats are also described.2.The peak latency of single collicular units of these six species

Philip H.-S. Jen; Roderick A. Suthers

1982-01-01

229

Use of tsunami waveforms for earthquake source study  

Microsoft Academic Search

Tsunami waveforms recorded on tide gauges, like seismic waves recorded on seismograms, can be used to study earthquake source processes. The tsunami propagation can be accurately evaluated, since bathymetry is much better known than seismic velocity structure in the Earth. Using waveform inversion techniques, we can estimate the spatial distribution of coseismic slip on the fault plane from tsunami waveforms.

Kenji Satake; Hiroo Kanamori

1991-01-01

230

Chirped CPMG for well-logging NMR applications  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

231

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

232

Retreving alpha factor of semiconductor lasers from a self-mixing interference waveform  

NASA Astrophysics Data System (ADS)

As an active research field, the self-mixing interferometry (SMI) based on semiconductor lasers (SLs) is a highly promising and emerging technique for non-contact sensing and parameter measurement of SLs. The basic structure of an SMI system consists of an SL, a lens and an external target. When a portion of reflected light from the target travels back to the laser cavity, a new lasing field is built up leading to both amplitude and phase modulations. The modulated output power is called a self-mixing signal which carries the information of both the target and SL's feature parameters. Alpha factor, also known as linewidth enhancement factor, is one of the most important SL's feature parameters. It characterizes the characteristics of SLs, such as the linewidth, the chirp, the injection lock range and the dynamic performances. This paper presents a new method for retrieving alpha factor of SLs by making use of a self-mixing interference (SMI) waveform. According to the well-known Lang-Kobayashi (L-K) theory, the SMI waveform is shaped by multiple parameters, including the alpha, the optical feedback level factor (denoted as C) and other parameters related to the oscillation of the external target. In this work, we build a new equation based on the SMI model derived from the L-K theory, which can be used to calculate the alpha value. In the existing SMI based methods for measuring the alpha factor, the optical feedback level C is limited within a certain narrow range. The proposed method is able to relieve this limitation. The associated simulations and experiments are carried out for verifying the proposed method.

Gao, Yan; Yu, Yanguang; Xi, Jiangtao

2012-11-01

233

Noise Robust AM-FM Demodulation using Least-Squares Truncated Power Series Approximation  

E-print Network

Noise Robust AM-FM Demodulation using Least- Squares Truncated Power Series Approximation Wooi@ntu.edu.sg ABSTRACT Abstract - This paper describes a parametric approach for demodulating multicomponent AM-FM method. Keywords ­ Signal Processing, AM/FM Demodulation I. INTRODUCTION The analysis of an AM-FM signal

Goh, Wooi Boon

234

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

PubMed

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. PMID:22183443

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

2012-02-01

235

CERES ERBE-like Monthly Geographical Averages (ES-4) in HDF (CER_ES4_PFM+FM1+FM2_Edition2)  

NASA Technical Reports Server (NTRS)

The ERBE-like Monthly Geographical Averages (ES-4) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The ES-4 is also produced for combinations of scanner instruments. For each observed 2.5-degree spatial region, the daily average, the hourly average over the month, and the overall monthly average of shortwave and longwave fluxes at the Top-of-the-Atmosphere (TOA) from the CERES ES-9 product are spatially nested up from 2.5-degree regions to 5- and 10-degree regions, to 2.5-, 5-, and 10-degree zonal averages, and to global monthly averages. For each nested area, the albedo and net flux are given. For each region, the daily average flux is estimated from an algorithm that uses the available hourly data, scene identification data, and diurnal models. This algorithm is 'like' the algorithm used for the Earth Radiation Budget Experiment (ERBE). The following CERES ES4 data sets are currently available: CER_ES4_FM1+FM2_Edition1 CER_ES4_PFM+FM1+FM2_Edition1 CER_ES4_PFM+FM1+FM2_Edition2 CER_ES4_PFM+FM1_Edition1 CER_ES4_PFM+FM2_Edition1 CER_ES4_TRMM-PFM_Edition1 CER_ES4_TRMM-PFM_Edition2 CER_ES4_Terra-FM1_Edition1 CER_ES4_Terra-FM2_Edition1 CER_ES4_FM1+FM2_Edition2 CER_ES4_Terra-FM1_Edition2 CER_ES4_Terra-FM2_Edition2 CER_ES4_Aqua-FM3_Edition1 CER_ES4_Aqua-FM4_Edition1 CER_ES4_FM1+FM2+FM3+FM4_Edition1 CER_ES4_Aqua-FM3_Edition2 CER_ES4_Aqua-FM4_Edition2 CER_ES4_FM1+FM3_Edition2 CER_ES4_FM1+FM4_Edition2 CER_ES4_PFM+FM1_Edition2 CER_ES4_PFM+FM2_Edition2 CER_ES4_Aqua-FM3_Edition1-CV CER_ES4_Aqua-FM4_Edition1-CV CER_ES4_Terra-FM1_Edition1-CV CER_ES4_Terra-FM2_Edition1-CV. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2000-03-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=2.5 degree; Longitude_Resolution=2.5 degree; Horizontal_Resolution_Range=250 km - < 500 km or approximately 2.5 degrees - < 5.0 degrees; Temporal_Resolution=1 month; Temporal_Resolution_Range=Monthly - < Annual].

Wielicki, Bruce A. (Principal Investigator)

236

CERES ERBE-like Monthly Geographical Averages (ES-4) in HDF (CER_ES4_FM1+FM3_Edition2)  

NASA Technical Reports Server (NTRS)

The ERBE-like Monthly Geographical Averages (ES-4) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The ES-4 is also produced for combinations of scanner instruments. For each observed 2.5-degree spatial region, the daily average, the hourly average over the month, and the overall monthly average of shortwave and longwave fluxes at the Top-of-the-Atmosphere (TOA) from the CERES ES-9 product are spatially nested up from 2.5-degree regions to 5- and 10-degree regions, to 2.5-, 5-, and 10-degree zonal averages, and to global monthly averages. For each nested area, the albedo and net flux are given. For each region, the daily average flux is estimated from an algorithm that uses the available hourly data, scene identification data, and diurnal models. This algorithm is 'like' the algorithm used for the Earth Radiation Budget Experiment (ERBE). The following CERES ES4 data sets are currently available: CER_ES4_FM1+FM2_Edition1 CER_ES4_PFM+FM1+FM2_Edition1 CER_ES4_PFM+FM1+FM2_Edition2 CER_ES4_PFM+FM1_Edition1 CER_ES4_PFM+FM2_Edition1 CER_ES4_TRMM-PFM_Edition1 CER_ES4_TRMM-PFM_Edition2 CER_ES4_Terra-FM1_Edition1 CER_ES4_Terra-FM2_Edition1 CER_ES4_FM1+FM2_Edition2 CER_ES4_Terra-FM1_Edition2 CER_ES4_Terra-FM2_Edition2 CER_ES4_Aqua-FM3_Edition1 CER_ES4_Aqua-FM4_Edition1 CER_ES4_FM1+FM2+FM3+FM4_Edition1 CER_ES4_Aqua-FM3_Edition2 CER_ES4_Aqua-FM4_Edition2 CER_ES4_FM1+FM3_Edition2 CER_ES4_FM1+FM4_Edition2 CER_ES4_PFM+FM1_Edition2 CER_ES4_PFM+FM2_Edition2 CER_ES4_Aqua-FM3_Edition1-CV CER_ES4_Aqua-FM4_Edition1-CV CER_ES4_Terra-FM1_Edition1-CV CER_ES4_Terra-FM2_Edition1-CV. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2005-12-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=2.5 degree; Longitude_Resolution=2.5 degree; Horizontal_Resolution_Range=250 km - < 500 km or approximately 2.5 degrees - < 5.0 degrees; Temporal_Resolution=1 month; Temporal_Resolution_Range=Monthly - < Annual].

Wielicki, Bruce A. (Principal Investigator)

237

CERES ERBE-like Monthly Regional Averages (ES-9) in HDF (CER_ES9_PFM+FM1+FM2_Edition2)  

NASA Technical Reports Server (NTRS)

The ERBE-like Monthly Regional Averages (ES-9) product contains a month of space and time averaged Clouds and the Earth's Radiant Energy System (CERES) data for a single scanner instrument. The ES-9 is also produced for combinations of scanner instruments. All instantaneous shortwave and longwave fluxes at the Top-of-the-Atmosphere (TOA) from the CERES ES-8 product for a month are sorted by 2.5-degree spatial regions, by day number, and by the local hour of observation. The mean of the instantaneous fluxes for a given region-day-hour bin is determined and recorded on the ES-9 along with other flux statistics and scene information. For each region, the daily average flux is estimated from an algorithm that uses the available hourly data, scene identification data, and diurnal models. This algorithm is 'like' the algorithm used for the Earth Radiation Budget Experiment (ERBE). The ES-9 also contains hourly average fluxes for the month and an overall monthly average for each region. These average fluxes are given for both clear-sky and total-sky scenes. The following CERES ES9 data sets are currently available: CER_ES9_FM1+FM2_Edition1 CER_ES9_PFM+FM1+FM2_Edition1 CER_ES9_PFM+FM1+FM2_Edition2 CER_ES9_PFM+FM1_Edition1 CER_ES9_PFM+FM2_Edition1 CER_ES9_PFM+FM1_Edition2 CER_ES9_PFM+FM2_Edition2 CER_ES9_TRMM-PFM_Edition1 CER_ES9_TRMM-PFM_Edition2 CER_ES9_Terra-FM1_Edition1 CER_ES9_Terra-FM2_Edition1 CER_ES9_FM1+FM2_Edition2 CER_ES9_Terra-FM1_Edition2 CER_ES9_Terra-FM2_Edition2 CER_ES9_Aqua-FM3_Edition1 CER_ES9_Aqua-FM4_Edition1 CER_ES9_FM1+FM2+FM3+FM4_Edition1 CER_ES9_Aqua-FM3_Edition2 CER_ES9_Aqua-FM4_Edition2 CER_ES9_FM1+FM3_Edition2 CER_ES9_FM1+FM4_Edition2 CER_ES9_Aqua-FM3_Edition1-CV CER_ES9_Aqua-FM4_Edition1-CV CER_ES9_Terra-FM1_Edition1-CV CER_ES9_Terra-FM2_Edition1-CV. [Location=GLOBAL] [Temporal_Coverage: Start_Date=1998-01-01; Stop_Date=2000-03-31] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=2.5 degree; Longitude_Resolution=2.5 degree; Horizontal_Resolution_Range=250 km - < 500 km or approximately 2.5 degrees - < 5.0 degrees; Temporal_Resolution=hourly, daily, monthly; Temporal_Resolution_Range=Hourly - < Daily, Daily - < Weekly, Monthly - < Annual].

Wielicki, Bruce A. (Principal Investigator)

238

Research on a kind of high precision and fast signal processing algorithm for FM/CW laser radar  

NASA Astrophysics Data System (ADS)

Range accuracy and efficiency are two important indicators for Frequency modulated continuous wave (FM/CW) laser radar, improving the accuracy and efficiency of extracting beat frequency are key factors for them. Multiple Modulation Zoom Spectrum Analysis (ZFFT) and the Chirp-Z Transform (CZT) are two widely used methods for improving frequency estimation. The paper through analyze advantages and disadvantages of these methods, proposes a high accuracy and fast signal processing method which is ZFFT-CZT, it combines advantages that ZFFT can reduce data size, and CZT can zoom in frequency of any interested band. The processing of ZFFT-CZT is following: firstly ZFFT is conducted by conducting Fourier transform on short time signal to calculate amount of frequency shift, and transforming high-frequency signal into low-frequency signal of long time sampling, then CZT is conducted by choosing any interested band to continue subdividing the spectral peaks, which can reduce picket fence effect. By simulate experiment based on ZFFT-CZT method, two closed targets at distance of 50m and 50.001m are measured, and the measurement errors are 40?m and 34?m respectively. It proved that ZFFT-CZT has a small amount of calculation, which can meet the requirement of high precision frequency extraction.

Xu, Xinke; Liu, Guodong; Chen, Fengdong; Liu, Bingguo; Zhuang, Zhitao; Lu, Cheng; Gan, Yu

2014-12-01

239

Control of two-photon double ionization of helium with intense chirped attosecond laser pulses  

NASA Astrophysics Data System (ADS)

We study the two-photon double-ionization process of the helium atom by solving numerically the nonrelativistic, time-dependent Schrdinger equation in its full dimensionality. We investigate with intense chirped attosecond laser pulses of 23.5-nm wavelength the two-photon absorption near and above the sequential threshold. We show how it is possible by adjusting the chirp parameter to control the electronic transitions inside the atom, thereby reinforcing or weakening the ionization process. Attosecond chirped laser pulses offer a promising way to probe and control the two-photon double ionization of helium when compared with attosecond transform-limited pulses.

Barmaki, S.; Lanteigne, P.; Laulan, S.

2014-06-01

240

Peculiarities of laser phase behavior associated with the accelerated electron in a chirped laser pulse  

SciTech Connect

In this paper, we qualitatively analyzed peculiarities of laser phase behavior associated with the accelerated electron in a chirped laser pulse. We unveiled the relationship between the changes in the orientation of the electron trajectory and the cusps in magnitude of the phase velocity of the optical field along the electron trajectory in a chirped laser pulse. We also explained how the chirp effect induced the singular point of the phase velocity. Finally, we discussed the phase velocity and phase witnessed by the electron in the particle's moving instantaneous frame.

Song, Q.; Wu, X. Y. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education and Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433 (China); Wang, J. X. [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education and Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433 (China); State Key Laboratory of Precision Spectroscopy and Department of Physics, East China Normal University, Shanghai 200062 (China); Kawata, S. [Center for Optical Research and Education, Department of Advanced Interdisciplinary Science, Graduate School of Engineering, Utsunomiya University, Utsunomiya 321-8585 (Japan); Wang, P. X., E-mail: wpx@fudan.edu.cn [Applied Ion Beam Physics Laboratory, Key Laboratory of the Ministry of Education and Institute of Modern Physics, Department of Nuclear Science and Technology, Fudan University, Shanghai 200433 (China); Center for Optical Research and Education, Department of Advanced Interdisciplinary Science, Graduate School of Engineering, Utsunomiya University, Utsunomiya 321-8585 (Japan)

2014-05-15

241

Dynamic Chirp Control and Pulse Compression for Attosecond High-Order Harmonic Emission  

SciTech Connect

We propose a scheme to compensate dynamically the intrinsic chirp of the attosecond harmonic pulses. By adding a weak second harmonic laser field to the driving laser field, the chirp compensation can be varied from the negative to the positive continuously by simply adjusting the relative time delay between the two-color pulses. Using this technique, the compensation of the negative chirp in harmonic emission is demonstrated experimentally for the first time and the nearly transform-limited attosecond pulse trains are obtained.

Zheng Yinghui; Zeng Zhinan; Zou Pu; Zhang Li; Li Xiaofang; Liu Peng; Li Ruxin; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800 (China)

2009-07-24

242

LISA parameter estimation using numerical merger waveforms  

E-print Network

Recent advances in numerical relativity provide a detailed description of the waveforms of coalescing massive black hole binaries (MBHBs), expected to be the strongest detectable LISA sources. We present a preliminary study of LISA's sensitivity to MBHB parameters using a hybrid numerical/analytic waveform for equal-mass, non-spinning holes. The Synthetic LISA software package is used to simulate the instrument response and the Fisher information matrix method is used to estimate errors in the parameters. Initial results indicate that inclusion of the merger signal can significantly improve the precision of some parameter estimates. For example, the median parameter errors for an ensemble of systems with total redshifted mass of one million Solar masses at a redshift of one were found to decrease by a factor of slightly more than two for signals with merger as compared to signals truncated at the Schwarzchild ISCO.

J. I. Thorpe; S. T. McWilliams; B. J. Kelly; R. P. Fahey; K. Arnaud; J. G. Baker

2009-01-02

243

LISA parameter estimation using numerical merger waveforms  

NASA Astrophysics Data System (ADS)

Recent advances in numerical relativity provide a detailed description of the waveforms of coalescing massive black hole binaries (MBHBs), expected to be the strongest detectable LISA sources. We present a preliminary study of LISA's sensitivity to MBHB parameters using a hybrid numerical/analytic waveform for equal-mass, non-spinning holes. The Synthetic LISA software package is used to simulate the instrument response, and the Fisher information matrix method is used to estimate errors in the parameters. Initial results indicate that inclusion of the merger signal can significantly improve the precision of some parameter estimates. For example, the median parameter errors for an ensemble of systems with total redshifted mass of 106 Modot at a redshift of z ~ 1 were found to decrease by a factor of slightly more than two for signals with merger as compared to signals truncated at the Schwarzchild ISCO.

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

2009-05-01

244

Waveforms Measured in Confined Thermobaric Explosion  

SciTech Connect

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

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

2007-05-04

245

Waveforms Measured in Confined Thermobaric Explosion  

Microsoft Academic Search

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

H Reichenbach; P Neuwald; A L Kuhl

2007-01-01

246

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

247

Comparisons of binary black hole merger waveforms  

E-print Network

This a particularly exciting time for gravitational wave physics. Ground-based gravitational wave detectors are now operating at a sensitivity such that gravitational radiation may soon be directly detected, and recently several groups have independently made significant breakthroughs that have finally enabled numerical relativists to solve the Einstein field equations for coalescing black-hole binaries, a key source of gravitational radiation. The numerical relativity community is now in the position to begin providing simulated merger waveforms for use by the data analysis community, and it is therefore very important that we provide ways to validate the results produced by various numerical approaches. Here, we present a simple comparison of the waveforms produced by two very different, but equally successful approaches--the generalized harmonic gauge and the moving puncture methods. We compare waveforms of equal-mass black hole mergers with minimal or vanishing spins. The results show exceptional agreement for the final burst of radiation, with some differences attributable to small spins on the black holes in one case.

John G. Baker; Manuela Campanelli; Frans Pretorius; Yosef Zlochower

2007-06-05

248

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

249

Experimental demonstration of fiber optical parametric chirped-pulse amplification  

NASA Astrophysics Data System (ADS)

A fiber optical parametric chirped-pulse amplifier (FOPCPA) is experimentally demonstrated. A 1.76 ps signal at 1542 nm with a peak power of 20 mW is broadened to 40 ps, and then amplified by a 100-ps pulsed pump at 1560 nm. The corresponding idler at 1578 nm is generated as the FOPCPA output. The same medium used to stretch the signal is deployed to compress the idler to 3.8 ps, and another spool of fiber is deployed to further compress the idler to 1.87 ps. The peak power of the compressed idler is 2 W, which corresponds to a gain of 20 dB.

Zhou, Yue; Cheung, Kim K. Y.; Chui, P. C.; Wong, Kenneth K. Y.

2010-02-01

250

Femtosecond Chirp-Free Transient Absorption Method And Apparatus  

DOEpatents

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

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

2001-02-20

251

Pre-emphasis determination for an S-band constant bandwidth FM/FM station  

NASA Technical Reports Server (NTRS)

Pre-emphasis schedules are given for 11 constant-bandwidth FM subcarriers modulating an S band transmitter at three receiver signal to noise ratios (i.e., 9, 15, and 25 dB). The criterion for establishing these pre-emphasis curves is the achievement, at various receiver intermediate frequency signal to noise ratios, of equal receiver output signal to noise ratios for all channels. It is realized that these curves may not be the optimum pre-emphasis curves based on overall efficiency or maximum utilization of the allotted spectrum, but they are near-optimum for data with channels which require equal output signal to noise ratios, such as spectral densities. The empirically derived results are compared with a simplified, analytically derived schedule and the primary differences are explained. The S band pre-emphasis schedule differs from the lower frequency VHF case. Since most proportional bandwidth and constant bandwidth systems use ground based recorders and some use flight recorders (as the Saturn systems did on VHF proportional bandwidth telemetry), the effects of these recorders are discussed and a modified pre-emphasis schedule is presented showing the results of this study phase.

Wallace, G. R.; Salter, W. E.

1972-01-01

252

Photoinjector-driven chirped-pulsed free electron maser  

NASA Astrophysics Data System (ADS)

An ultra-short pulse, millimeter-wave free electron maser experiment is currently underway at UC Davis and Lawrence Livermore National Laboratory. A 8.5 kG, 30 mm period helical wiggler is used to transversally accelerate a train of one hundred 5 MeV, 0.25 nC, 1 ps duration micro bunches synchronously energized by a 20 MW, X-band photocathode RF linac. The photocathode is irradiated by a burst-mode, UV laser system which produces up to 100 pulses at 207 nm, with an energy of 10 mJ/pulse, and a pulse duration of 200 fs, at a repetition rate of 2.142 GHz. This system includes a 400 fs jitter synchronously modelocked AlGaAs semiconductor laser oscillator which is amplified by an eight-pass Ti:Al2O3 chirped pulse laser amplifier. The output of this amplifier is subsequently frequency quadrupled into the UV. Because the electron micro bunches are shorter than the radiation wavelength, the system coherently synchrotron radiates and behaves essentially as a prebunched FEM. In addition, by operating in a waveguide structure at grazing, where the bunch axial velocity in the wiggler matches the group velocity of the electromagnetic waves, one obtains output radiation pulses which are extremely short, and have greatly enhanced peak power. The device operates in the TE(sub 12) mode of a cylindrical waveguide, and will produce up to 2 MW of coherent synchrotron radiation power at 140 GHz, in a 15 ps FWHM pulse. The -3 dB instantaneous interaction bandwidth extends from 125 GHz to 225 GHz. The output pulse is chirped over the full interaction bandwidth. One of the major potential applications of such a device is an ultra-wideband millimeter-wave radar.

Lesage, G. P.; Hartemann, F. V.; Feng, H. X. C.; Fochs, S. N.; Heritage, J. P.; Luhmann, N. C., Jr.; Perry, M. D.; Westenskow, G. A.

1995-03-01

253

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

254

Fast prediction and evaluation of gravitational waveforms using surrogate models  

E-print Network

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

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

2014-02-28

255

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 Youngs 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. PMID:17306697

Erpelding, Todd N.; Hollman, Kyle W.; ODonnell, Matthew

2007-01-01

256

Multi-stage optimization of ultrabroadband high-energy optical parametric chirped pulse amplification  

E-print Network

We present a procedure for simultaneous optimization of efficiency-bandwidth product and superfluorescence noise suppression in ultrabroadband high-energy optical parametric chirped pulse amplification. Gain dependence of ...

Manzoni, Cristian

257

Effect of frequency chirp on supercontinuum generation in silicon waveguides with two zero-dispersion wavelengths  

NASA Astrophysics Data System (ADS)

The influence of initial chirp on supercontinuum generation in SOI rib waveguide with two zero-dispersion wavelengths was studied numerically, based on the generalized nonlinear Schrdinger equation (GNSE). The full-width at half-maximum (FWHM) and the peak power of the pre-chirped hyperbolic secant in the simulation are 50 fs and 50 W, respectively. The simulation results indicate that a positive initial chirp makes the energy transfer to the normal dispersion zone by affecting self-phase modulation (SPM) and four-wave mixing (FWM) processes, and therefore enhances the supercontinuum bandwidth as well as improves the spectral flatness. In particular, at the optimal initial chirp parameter of C=3, the bandwidth at -10 dB level increases to about 1620 nm (from 1140 to 2760 nm), exceeding an octave-spanning.

Cao, Yanmei; Zhang, Libin; Fei, Yonghao; Lei, Xun; Chen, Shaowu

2015-01-01

258

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

E-print Network

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

Shaver, Rachel Glyn

2013-01-01

259

Effective temporal resolution in pump-probe spectroscopy with strongly chirped pulses  

SciTech Connect

This paper introduces a general theoretical description of femtosecond pump-probe spectroscopy with chirped pulses whose joint spectral and temporal profile is expressed by Wigner spectrograms. We demonstrate that the actual experimental time resolution intimately depends on the pulse-sample interaction and that the commonly used instrumental response function needs to be replaced by a sample-dependent effective response function. We also show that, using the proper configurations in excitation and/or detection, it is possible to overcome the temporal smearing of the measured dynamics due to chirp-induced pulse broadening and recover the temporal resolution that would be afforded by the transform-limited pulses. We verify these predictions with experiments using broadband chirped pump and probe pulses. Our results allow optimization of the temporal resolution in the common case when the chirp of the pump and/or probe pulse is not corrected and may be extended to a broad range of time-resolved experiments.

Polli, D.; Lanzani, G. [IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); CNST, Istituto Italiano di Tecnologia, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Brida, D.; Cerullo, G. [IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Mukamel, S. [Chemistry Department, University of California, Irvine, Irvine, California 92697-2025 (United States)

2010-11-15

260

A Multiterawatt Laser Using a High-Contrast, Optical Parametric Chirped-Pulse Presamplifier  

SciTech Connect

A laser has been built that uses optical parametric chirped-pulse preamplification and a glass booster amplifier. We review the performance of the 5-Hz, multijoule OPCPA pump laser, the 370-mJ OPCPA, and the overall laser.

Bagnoud, V.; Puth, J.; Begishev, I.; Guardalben, M.; Zuegel, J.D.; Forget, N.; LeBlanc, C.

2005-09-30

261

5 Hz, >250 mJ Optical Parametric Chirped-Pulse Amplifier at 1053 nm  

SciTech Connect

A 250 mJ, 5 Hz repetition rate optical parametric chirped-pulse amplifier with near-Fourier-transform-limited, 430 fs pulses and a beam that can be focused to near the diffraction limit is demonstrated.

Bagnoud, V.; Begishev, I.A.; Guardalben, M.J.; Puth, J.; Zuegel, J.D.

2005-07-15

262

Spectral transmission characteristics of weakly tilted and tilted chirped fiber gratings: comparative studies  

NASA Astrophysics Data System (ADS)

In this paper the comparative study of spectral transmission characteristics of tilted Bragg gratings made using uniform phase mask and chirped phase mask are presented. Results are focused on low tilt angles with special interest on cladding modes behavior. The spectral characteristic shape for simultaneously tilted and chirped Bragg gratings point out its potential applications as amplitude discriminator in fiber sensing applications and gain flattening element for EDFA.

Osuch, Tomasz; Jurek, Tomasz; Jedrzejewski, Kazimierz

2013-10-01

263

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

264

Practical design of optical diagnostics for chirped-pulse free-electron lasers  

Microsoft Academic Search

In recent years there have been several proposals to operate rf-linac-driven FELs with chirped electron and optical micropulses for use in fast time-resolved experiments. We have been actively pursuing this application on the Mark-III infrared FEL at Duke University, and have designed and procured an apparatus to achieve broad-band compression of chirped optical pulses between roughly 2.5 mum and 4.1

Eric B. Szarmes; John M. J. Madey

1992-01-01

265

Teacher and Student Satisfaction with Freefield FM Amplification Systems.  

ERIC Educational Resources Information Center

This study surveyed teachers and students (some with hearing impairments) in 23 elementary classrooms (in Rochester, Minnesota) equipped with commercially available, narrow-band freefield FM systems. Teachers and students rated the systems very positively as helping them to understand the teacher and other students better. (DB)

Nelson, Denise Grau; Nelson, Daniel K.

1997-01-01

266

Multiple AM/FM integrations for a competitive edge  

SciTech Connect

Portland General Electric is leveraging 20 years of experience in AM/FM and data scrubbing to integrate a new AM/FM system with multiple other applications to provide improved customer service and reduce costs. The electrical distribution plant model has progressed from a geographic representation in 1985 to physical connectivity (data scrubbing at 400,000 mounts) in 1990 to electrical connectivity (batch trace of 500 circuits) in 1995. Each integration of AM/FM to another application increased information sharing and accuracy, reduced data maintenance costs, provided enhanced data for other systems and enabled competitive business process improvement initiatives. The main topics covered are: (1) First generation project history, (2) Second generation project plans, (3) Data cleanup, (4) New applications, (5) Business process paradigm resolution and simplification, (6) Additional AM/FM interfaces. The major impact on providing a competitive advantage is in the use of the distribution electrical plant model in a FRAMME/Oracle data base to support an Outage Restoration system. A competitive advantage is demonstrated by customer satisfaction via reduced PUC complaints. Interfaces to Customer, Work Management, Outage, Engineering and Accounts Receivables applications are demanding a new approach to how interfaces are analyzed.

Kruse, D.H. [Portland General Electric, Portland, OR (United States)

1996-08-01

267

Laser noise limitations on an acousto-optic FM demodulator  

NASA Astrophysics Data System (ADS)

The effect of laser noise on the frequency resolution of an acousto-optic FM demodulator is investigated. Formulae are developed which allow prediction of the demodulator's frequency resolution when affected by laser intensity noise. The limiting laser intensity SNR is calculated in order to determine the required laser SNR which will not degrade system performance.

Brooks, Paul; Reeve, Christopher D.

1994-06-01

268

Identifications of Metal-Deficient FM Stars (Bartkevicius+ 1986)  

Microsoft Academic Search

The catalog provides identifications in a variety of astronomical catalogs of 1555 metal-deficient stars from the MDSP catalog of metal-deficient F-M stars classified spectroscopically (Bartkevicius 1980) and from its first supplement, MDSPS1 (Bartkevicius 1984, Cat. ). (3 data files).

A. Bartkevicius; V.-D. Bartkeviciene; E. Jodinskiene

2000-01-01

269

Channel spacing in cellular FM mobile communication systems  

Microsoft Academic Search

This paper reports the results of a study considering channel spacing in a cellular FM mobile system. In the introduction, a short review of the subject is given and the essential quantities to be taken into account are outlined. Additionally some economic constraints will be considered. Following this, related propagation and laboratory experiments will be described. Then the relation between

B. Visser; K. Lalonde; G. Pomponi

1983-01-01

270

University Policy No.: FM5105 Classification: Financial Management  

E-print Network

University Policy No.: FM5105 Classification: Financial Management Approving Authority: Board responsive and responsible source. Purchasing and supply management functions at the University of Victoria as are determined appropriate to the efficient and effective operation of supply management services. In certain

Victoria, University of

271

University Policy No.: FM5215 Classification: Financial Management  

E-print Network

University Policy No.: FM5215 Classification: Financial Management POLICY ON SOCIAL RESPONSIBILITY of the Investment policy for Short Term investments is to achieve the "best financial interests". 2. The above goal would normally exclude adopting non-financial screens to select investment instruments. 3. Members

Victoria, University of

272

Dynamic wavelength switching of a remote nitrogen or air laser with chirped femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

We experimentally investigate the influence of the chirp of 800?nm Ti:sapphire pump laser pulses on the lasing behaviors of N2+ ions for the transitions between the excited electronic B2?u+ state (v? = 0) and the ground X2?g+ state (v = 0,1) at wavelengths of 391 and 428?nm. We found that as the chirp of the pump laser pulses varies from negative to positive, the intensities of the lasing signals at 391 and 428?nm show different chirp-dependent behaviors. Namely, the coherent emission at 391?nm reaches the maximum when the chirp of the pump pulse is transform-limited; whereas the 428?nm emission becomes strongest when the pump pulse is negatively chirped. This observation is ascribed to different self-generated seed sources produced in the plasma channel, which is verified by introducing an external seed for a pumpprobe measurement. Our finding enables switching of wavelengths of remote lasing emissions of N2+ by manipulating the chirp of the pump laser pulses.

Jing, Chenrui; Xie, Hongqiang; Li, Guihua; Zeng, Bin; Chu, Wei; Zhang, Haisu; Ni, Jielei; Yao, Jinping; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan

2015-01-01

273

Recovering strain readings from chirping fiber Bragg gratings in composite overwrapped pressure vessels  

NASA Astrophysics Data System (ADS)

This study reports on signal recovery of optical fiber Bragg gratings embedded in a carbon fiber composite overwrapped pressure vessel's (COPV) structure which have become chirped due to microcracks. COPVs are commonly used for the storage of high pressure liquids and gases. They utilize a thin metal liner to seal in contents, with a composite overwrap to strengthen the vessel with minimal additional mass. A COPV was instrumented with an array of surface mounted and embedded fiber Bragg gratings (FBGs) for structural health monitoring (SHM) via strain sensing of the material. FBGs have been studied as strain sensors for the last couple decades. Many of the embedded FBGs reflected a multi-peak, chirped response which was not able to be interpreted well by the current monitoring algorithm. Literature and this study found that the chirping correlated with microcracks. As loading increases, so does the number of chirped FBGs and microcracks. This study uses optical frequency domain reflectometry (OFDR) to demultiplex the array of FBGs, and then sub- divide individual FBGs. When a FBG is sub-divided using OFDR, the gratings' strain along its length is recovered. The sub-divided chirped FBGs have strain gradients along their length from microcracks. Applying this to all chirped gratings, nearly the entirety of the embedded sensors' readings can be recovered into a series of single peak responses, which show very large local strains throughout the structure. This study reports on this success in recovering embedded FBGs signal, and the strain gradient from microcracks.

Strutner, Scott M.; Pena, Frank; Piazza, Anthony; Parker, Allen R.; Richards, W. Lance; Carman, Gregory P.

2014-04-01

274

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

275

Effects of noise reduction on AM and FM perception.  

PubMed

The goal of noise reduction (NR) algorithms in digital hearing aid devices is to reduce background noise whilst preserving as much of the original signal as possible. These algorithms may increase the signal-to-noise ratio (SNR) in an ideal case, but they generally fail to improve speech intelligibility. However, due to the complex nature of speech, it is difficult to disentangle the numerous low- and high-level effects of NR that may underlie the lack of speech perception benefits. The goal of this study was to better understand why NR algorithms do not improve speech intelligibility by investigating the effects of NR on the ability to discriminate two basic acoustic features, namely amplitude modulation (AM) and frequency modulation (FM) cues, known to be crucial for speech identification in quiet and in noise. Here, discrimination of complex, non-linguistic AM and FM patterns was measured for normal hearing listeners using a same/different task. The stimuli were generated by modulating 1-kHz pure tones by either a two-component AM or FM modulator with patterns changed by manipulating component phases. Modulation rates were centered on 3 Hz. Discrimination of AM and FM patterns was measured in quiet and in the presence of a white noise that had been passed through a gammatone filter centered on 1 kHz. The noise was presented at SNRs ranging from -6 to +12 dB. Stimuli were left as such or processed via an NR algorithm based on the spectral subtraction method. NR was found to yield small but systematic improvements in discrimination for the AM conditions at favorable SNRs but had little effect, if any, on FM discrimination. A computational model of early auditory processing was developed to quantify the fidelity of AM and FM transmission. The model captured the improvement in discrimination performance for AM stimuli at high SNRs with NR. However, the model also predicted a relatively small detrimental effect of NR for FM stimuli in contrast with the average psychophysical data. Overall, these results suggest that the lack of benefits of NR on speech intelligibility is partly caused by the limited effect of NR on the transmission of narrowband speech modulation cues. PMID:23180229

Ives, D Timothy; Calcus, Axelle; Kalluri, Sridhar; Strelcyk, Olaf; Sheft, Stanley; Lorenzi, Christian

2013-02-01

276

Characterization of pelvic organs by Doppler sonography waveform shape.  

PubMed

The purpose was to describe blood flow waveform of pelvic organs obtained by Doppler according to their unique characteristics. A prospective study was designed and 79 premenopausal and postmenopausal women were screened. Transvaginal ultrasonography combined with color Doppler was performed. Arterial blood flow of the uterus, fallopian tubes and both ovarian center and periphery were assessed, by a unique computerized program exclusively developed for this research (MATLAB language). Waveform characterization was performed by calculating alpha and beta angles, representing upward curve of each waveform and angles of refraction gamma and delta. alpha to delta angles were found significantly different for each of the pelvic organs. Significant differences in the characteristics of Doppler waveforms were also observed between pre and postmenopausal women. Luteal and follicular phase blood flow waveforms were similar. These findings contribute to our ability to classify the origin of blood vessel by processing Doppler waveforms by a computerized method. PMID:20420968

Ronnie, Tepper; Yodfat, Shaharabany; Ron, Shiri; Hershkovitz, Reli

2010-05-01

277

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

PubMed

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

Howard, David M

2005-01-01

278

Group velocity dispersion and relativistic effects on the wakefield induced by chirped laser pulse in parabolic plasma channel  

SciTech Connect

The excitation of wake field plasma waves by a short laser pulse propagating through a parabolic plasma channel is studied. The laser pulse is assumed to be initially chirped. In this regard, the effects of initial and induced chirp on the plasma wake field as well as the laser pulse parameters are investigated. The group velocity dispersion and nonlinear relativistic effects were taken into account to evaluate the excited wake field in two dimension using source dependent expansion method. Positive, negative, and un-chirped laser pulses were employed in numerical code to evaluate the effectiveness of the initial chirp on 2-D wake field excitation. Numerical results showed that for laser irradiances exceeding 10{sup 18}W/cm{sup 2}, an intense laser pulse with initial positive chirp generates larger wake field compared to negatively and un-chirped pulses.

Sohbatzadeh, F. [Department of Atomic and Molecular Physics, Science Faculty, University of Mazandaran, Babolsar (Iran, Islamic Republic of); Akou, H. [Department of Physics, Faculty of Basic Science, Babol University of Technology, Babol 47148-71167 (Iran, Islamic Republic of)

2013-04-15

279

Seismic waveform inversion using neural networks  

NASA Astrophysics Data System (ADS)

Full waveform tomography aims to extract all available information on Earth structure and seismic sources from seismograms. The strongly non-linear nature of this inverse problem is often addressed through simplifying assumptions for the physical theory or data selection, thus potentially neglecting valuable information. Furthermore, the assessment of the quality of the inferred model is often lacking. This calls for the development of methods that fully appreciate the non-linear nature of the inverse problem, whilst providing a quantification of the uncertainties in the final model. We propose to invert seismic waveforms in a fully non-linear way by using artificial neural networks. Neural networks can be viewed as powerful and flexible non-linear filters. They are very common in speech, handwriting and pattern recognition. Mixture Density Networks (MDN) allow us to obtain marginal posterior probability density functions (pdfs) of all model parameters, conditioned on the data. An MDN can approximate an arbitrary conditional pdf as a linear combination of Gaussian kernels. Seismograms serve as input, Earth structure parameters are the so-called targets and network training aims to learn the relationship between input and targets. The network is trained on a large synthetic data set, which we construct by drawing many random Earth models from a prior model pdf and solving the forward problem for each of these models, thus generating synthetic seismograms. As a first step, we aim to construct a 1D Earth model. Training sets are constructed using the Mineos package, which computes synthetic seismograms in a spherically symmetric non-rotating Earth by summing normal modes. We train a network on the body waveforms present in these seismograms. Once the network has been trained, it can be presented with new unseen input data, in our case the body waves in real seismograms. We thus obtain the posterior pdf which represents our final state of knowledge given the information in the training set and the real data.

De Wit, R. W.; Trampert, J.

2012-12-01

280

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

281

Observation of Partial Discharge Current Waveform under Inverter Surge Application  

NASA Astrophysics Data System (ADS)

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

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

282

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

283

Plunge waveforms from inspiralling binary black holes  

E-print Network

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

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

2001-11-18

284

Anisotropy effects on 3D waveform inversion  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

285

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

Microsoft Academic Search

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

Ayumu Matani; Takayuki Shigeno

2006-01-01

286

A combined waveform relaxation: waveform relaxation newton algorithm for efficient parallel circuit simulation  

Microsoft Academic Search

This paper presents two new techniques for accelerating circuit simulation. The first technique is an improvement of the parallel Waveform Relaxation Newton (WRN) method. The computations of all the timepoints are executed concurrently. Static task partitioning is shown to be an efficient method to limit the scheduling overhead. The second technique combines in a dynamic way the efficiency of the

Patrick Odent; Luc J. M. Claesen; Hugo De Man

1990-01-01

287

Waveform Design and Diversity in Radar Sensor Networks: Theoretical Analysis and Application to Automatic Target Recognition  

Microsoft Academic Search

In this paper, we perform some theoretical studies on constant frequency (CF) pulse waveform design and diversity in radar sensor networks (RSN): (1) the conditions for waveform co-existence, (2) interferences among waveforms in RSN, (3) waveform diversity combining in RSN. As an application example, we apply the waveform design and diversity to automatic target recognition (ATR) in RSN and propose

Qilian Liang

2006-01-01

288

Revised method for forest canopy height estimation from Geoscience Laser Altimeter System waveforms  

E-print Network

Revised method for forest canopy height estimation from Geoscience Laser Altimeter System waveforms. As a result, the height of the waveform (waveform extent) is insufficient to make estimates of tree height from the waveform itself. Early work on this problem used a combination of waveform height indices

Lefsky, Michael

289

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

290

47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.  

Code of Federal Regulations, 2013 CFR

...educational FM stations operating on unreserved channels. 73.513 Section 73.513 Telecommunication...educational FM stations operating on unreserved channels. (a) Noncommercial educational...Class D (secondary) which operate on Channels 221 through 300 but which...

2013-10-01

291

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

Code of Federal Regulations, 2013 CFR

...noncommercial educational FM stations and channels. 73.506 Section 73.506 Telecommunication...noncommercial educational FM stations and channels. (a) Noncommercial educational stations operating on the channels specified in 73.501 are...

2013-10-01

292

47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.  

Code of Federal Regulations, 2010 CFR

...educational FM stations operating on unreserved channels. 73.513 Section 73.513 Telecommunication...educational FM stations operating on unreserved channels. (a) Noncommercial educational...Class D (secondary) which operate on Channels 221 through 300 but which...

2010-10-01

293

47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.  

Code of Federal Regulations, 2011 CFR

...educational FM stations operating on unreserved channels. 73.513 Section 73.513 Telecommunication...educational FM stations operating on unreserved channels. (a) Noncommercial educational...Class D (secondary) which operate on Channels 221 through 300 but which...

2011-10-01

294

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

Code of Federal Regulations, 2012 CFR

...noncommercial educational FM stations and channels. 73.506 Section 73.506 Telecommunication...noncommercial educational FM stations and channels. (a) Noncommercial educational stations operating on the channels specified in 73.501 are...

2012-10-01

295

47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.  

Code of Federal Regulations, 2012 CFR

...educational FM stations operating on unreserved channels. 73.513 Section 73.513 Telecommunication...educational FM stations operating on unreserved channels. (a) Noncommercial educational...Class D (secondary) which operate on Channels 221 through 300 but which...

2012-10-01

296

76 FR 6788 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License.  

Federal Register 2010, 2011, 2012, 2013, 2014

...FEDERAL COMMUNICATIONS COMMISSION Radio Broadcasting Services; AM or FM Proposals...From MARLOW, OK, To LAWTON, OK; FISHER RADIO REGIONAL GROUP, INC., Station KQDI-FM...FALLS, MT, To HIGHWOOD, MT; THE MONTANA RADIO COMPANY, LLC, Station KZUS,...

2011-02-08

297

Wave-formed structures and paleoenvironmental reconstruction  

USGS Publications Warehouse

Wave-formed sedimentary structures can be powerful interpretive tools because they reflect not only the velocity and direction of the oscillatory currents, but also the length of the horizontal component of orbital motion and the presence of velocity asymmetry within the flow. Several of these aspects can be related through standard wave theories to combinations of wave dimensions and water depth that have definable natural limits. For a particular grain size, threshold of particle movement and that of conversion from a rippled to flat bed indicate flow-velocity limits. The ratio of ripple spacing to grain size provides an estimate of the length of the near-bottom orbital motion. The degree of velocity asymmetry is related to the asymmetry of the bedforms, though it presently cannot be estimated with confidence. A plot of water depth versus wave height (h-H diagram) provides a convenient approach for showing the combination of wave parameters and water depths capable of generating any particular structure in sand of a given grain size. Natural limits on wave height and inferences or assumptions regarding either water depth or wave period based on geologic evidence allow refinement of the paleoenvironmental reconstruction. The assumptions and the degree of approximation involved in the different techniques impose significant constraints. Inferences based on wave-formed structures are most reliable when they are drawn in the context of other evidence such as the association of sedimentary features or progradational sequences. ?? 1984.

Clifton, H.E.; Dingler, J.R.

1984-01-01

298

Binary black hole merger dynamics and waveforms  

E-print Network

We study dynamics and radiation generation in the last few orbits and merger of a binary black hole system, applying recently developed techniques for simulations of moving black holes. Our analysis of the gravitational radiation waveforms and dynamical black hole trajectories produces a consistent picture for a set of simulations with black holes beginning on circular-orbit trajectories at a variety of initial separations. We find profound agreement at the level of one percent among the simulations for the last orbit, merger and ringdown. We are confident that this part of our waveform result accurately represents the predictions from Einstein's General Relativity for the final burst of gravitational radiation resulting from the merger of an astrophysical system of equal-mass non-spinning black holes. The simulations result in a final black hole with spin parameter a/m=0.69. We also find good agreement at a level of roughly 10 percent for the radiation generated in the preceding few orbits.

John G. Baker; Joan Centrella; Dae-Il Choi; Michael Koppitz; James van Meter

2006-02-09

299

Waveform Freezing of Sonic Booms Revisited  

NASA Technical Reports Server (NTRS)

Nonlinear distortion of sonic booms propagating in the atmosphere is strongly affected by stratification and geometrical spreading. For a downward propagating sonic boom in a standard atmosphere, stratification and spreading cause a slowing down of nonlinear distortion. In certain cases a stage is reached where no further distortion takes place. When this happens, the waveform is said to be frozen. In previous work the authors argued that for most HSCT designs and flight conditions being considered, the sonic boom is not frozen when it reaches the ground. The criterion used was the value of the distortion distance x bar is a measure of the nonlinear distortion suffered by the wave (and is closely related to Hayes's E variable). The aircraft must be at an altitude greater than 27 km (80,000 ft) for x bar at the groun be within 95% of its asymptotic value. However, work reported here demonstrates that the ground waveform is much closer to the frozen state than indicated by the previous analysis. In the new analysis, duration of the sonic boom is used as the criterion for judging closeness of approach tz frozen state. In order for the duration of the sonic boom at the ground to be within 95% of its frozen value, the flight altitude of the aircraft needs to be only 15 km (45,000 ft).

Cleveland, Robin O.; Blackstock, David T.

1996-01-01

300

Lidar compressive sensing using chaotic waveform  

NASA Astrophysics Data System (ADS)

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

Verdin, B.; von Borries, R.

2014-05-01

301

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

Code of Federal Regulations, 2012 CFR

...3) Applications for reserved band FM translator stations will be...a period for filing reserved band FM translator applications...major modifications for reserved band FM Translators will be processed...procedures set forth in subpart K of Part 73 ( 73.7000 et...

2012-10-01

302

COCHANNEL FM DEMODULATION VIA THE MULTI ANGLE-CENTERED DISCRETE FRACTIONAL FOURIER TRANSFORM  

E-print Network

COCHANNEL FM DEMODULATION VIA THE MULTI ANGLE-CENTERED DISCRETE FRACTIONAL FOURIER TRANSFORM S. L- poses of cochannel FM demodulation and also investigate its use for the demodulation of cochannel to accomplish cochannel signal separation and demodulation, where existing multicomponent AM­FM demod- ulation

Santhanam, Balu

303

Characterization of LMR Analog FM Audio Quality Using PL Tone Analysis  

E-print Network

effects of FM modulation/demodulation process (stationary chan- nelCharacterization of LMR Analog FM Audio Quality Using PL Tone Analysis Akshay Kumar Steven for characterizing the land mobile radio (LMR) analog FM audio quality using Private Line (PL) tone analysis

Ellingson, Steven W.

304

Digital and FM demodulation of a doubly-clamped single wall carbon nanotube oscillator: towards a  

E-print Network

1 Digital and FM demodulation of a doubly-clamped single wall carbon nanotube oscillator: towards experimental realization of AM, FM and digital demodulation with suspended single wall carbon nanotube in demodulation is clearly demonstrated. The FM technique is shown to lead to the suppression of unwanted

Boyer, Edmond

305

Advances in Variational Image Segmentation using AM-FM models: Regularized Demodulation and Probabilistic Cue Integration.  

E-print Network

Advances in Variational Image Segmentation using AM-FM models: Regularized Demodulation is at the feature extraction level, where we introduce a regularized approach to the demodulation of the AM-FM manner. In recent work, [18, 19] we have explored the potential of AM-FM features for driving

Paragios, Nikos

306

Phase Algorithm for Blocking Artifact Reduction in Reconstructions from Analysis-Only AM-FM Models  

E-print Network

Phase Algorithm for Blocking Artifact Reduction in Reconstructions from Analysis-Only AM-FM Models, Norman, OK 73019 USA Abstract Virtually all techniques for computing AM-FM models involve jointly reconstructions from the analysis-only models because these provide insight into the accuracy of the AM and FM

Havlicek, Joebob

307

AM-FM IMAGE FILTERS Chuong T. Nguyen and Joseph P. Havlicek  

E-print Network

AM-FM IMAGE FILTERS Chuong T. Nguyen and Joseph P. Havlicek School of Electrical and Computer Engineering, University of Oklahoma, Norman, OK, USA ABSTRACT We introduce a multicomponent invertible AM-FM image transform and use it to define new nonlinear AM-FM filters for perform- ing modulation domain

Havlicek, Joebob

308

First Results in Perceptually-Based AM-FM Image Filtering Chuong T. Nguyen,  

E-print Network

First Results in Perceptually-Based AM-FM Image Filtering Chuong T. Nguyen, Roy A. Sivley an invertible AM-FM image trans- form. For the first time, we achieve perceptually-based signal pro- cessing. In our most interesting example, a simple AM-FM filter succeeds in smoothly and naturally removing

Havlicek, Joebob

309

FM Radio; An Oral Communication Project for Migrants in Palm Beach County.  

ERIC Educational Resources Information Center

This report gives a full description of the broadcasting and operation of WHRS-FM, a FM radio station established by federal grant to serve migrant workers and their children in Palm Beach County, Florida. The goal of the project was to evaluate FM radio as a solution to the serious economic and educational problem of communicating with the

Early, L. F.

310

Object Recognition with FM Sonar; An Assistive Device for Blind and Visually-Impaired People  

Microsoft Academic Search

FM sonar sensors have been used in mobility aids for tile visually-impaired. However, previous FM sonar systems have generated continuous audio signals and rely on the user interpreting them. Our research work is carried out to solve the problem of overloading users of FM sonar sys- tem with excessive information by machine in- terpreting the audio signal. The signal is

Gordon Kao; Penny Probert; David Lee

311

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

312

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2010 CFR

...Numerical designation of FM broadcast channels. 73.201 Section 73.201 Telecommunication...Numerical designation of FM broadcast channels. The FM broadcast band consists...MHz and 108 MHz. It is divided into 100 channels of 200 kHz each. For...

2010-10-01

313

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2012 CFR

...Numerical designation of FM broadcast channels. 73.201 Section 73.201 Telecommunication...Numerical designation of FM broadcast channels. The FM broadcast band consists...MHz and 108 MHz. It is divided into 100 channels of 200 kHz each. For...

2012-10-01

314

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2011 CFR

...Numerical designation of FM broadcast channels. 73.201 Section 73.201 Telecommunication...Numerical designation of FM broadcast channels. The FM broadcast band consists...MHz and 108 MHz. It is divided into 100 channels of 200 kHz each. For...

2011-10-01

315

47 CFR 73.201 - Numerical designation of FM broadcast channels.  

Code of Federal Regulations, 2013 CFR

...Numerical designation of FM broadcast channels. 73.201 Section 73.201 Telecommunication...Numerical designation of FM broadcast channels. The FM broadcast band consists...MHz and 108 MHz. It is divided into 100 channels of 200 kHz each. For...

2013-10-01

316

78 FR 59903 - Emission Mask Requirements for Digital Technologies on 800 MHz NPSPAC Channels; Analog FM...  

Federal Register 2010, 2011, 2012, 2013, 2014

...800 MHz NPSPAC Channels; Analog FM Capability on Mutual Aid and Interoperability Channels...require equipment to have analog FM capability when operating on 800 MHz NPSPAC, VHF...NPSPAC channels and (b) have analog FM capability on public safety mutual aid and...

2013-09-30

317

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

318

New FM Detection Techniques for Scanning Probe Microscopy  

NASA Astrophysics Data System (ADS)

New FM demodulation techniques capable of detecting the fast frequency deviation of a cantilever of a noncontact atomic force microscope are proposed and their features were demonstrated by experiments. The techniques entail the frequency conversion of an input FM signal to a pair of zero-Hz-centered signals with a mutual phase difference of 90 deg, differentiation or Hilbert transformation, multiplication and subtraction. Since the center frequency and scale factor are determined by different processes, a high sensitivity, a fast response and a precise center frequency are achievable at the same time. The developed circuitry is capable of detecting a minimum frequency shift of 0.1 Hz. The maximum response bandwidth is 100 kHz.

Kobayashi, Dai; Kawai, Shigeki; Kawakatsu, Hideki

2004-07-01

319

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?, Bla; Kos, Bor; Gajek, Peter

2012-01-01

320

Analytical Approaches to Guide SLS Fault Management (FM) Development  

NASA Technical Reports Server (NTRS)

Extensive analysis is needed to determine the right set of FM capabilities to provide the most coverage without significantly increasing the cost, reliability (FP/FN), and complexity of the overall vehicle systems. Strong collaboration with the stakeholders is required to support the determination of the best triggers and response options. The SLS Fault Management process has been documented in the Space Launch System Program (SLSP) Fault Management Plan (SLS-PLAN-085).

Patterson, Jonathan D.

2012-01-01

321

Multiscale AM-FM Methods for Diabetic Retinopathy Lesion Detection  

Microsoft Academic Search

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

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

2010-01-01

322

Effect of mechanical ventilation waveforms on airway wall shear.  

PubMed

Better understanding of airway wall shear stress/strain rate is very important in order to prevent inflammation in patients undergoing mechanical ventilation due to respiratory problems in intensive-care medicine. The objective of this study was to investigate the role of mechanical ventilation waveforms on airway wall shear/strain rate using computational fluid dynamics analysis. Six different waveforms were considered to investigate the airway wall shear stress (WSS) from fluid dynamics analysis for the airway geometry of two-to-three generations. The simulation results showed that Original with Sine Inhale Waveform (OSIW) produced the highest WSS value and the Near True Sine Waveform produced the lowest WSS value. Also, the Original with Sine Inhale Waveform and the Short Sine Inhale with Long Sine Exhale Waveform (SSILSEW) produced a higher shear strain rate in comparison to the Original Waveform (OW). These results, combined with optimization, suggest that it is possible to develop a set of mechanical ventilation waveform strategies to avoid inflammation in the lung. PMID:25385315

Pidaparti, Ramana M; Swanson, John

2015-01-01

323

Performance Prediction of Ptr for Different Pressure Waveforms  

NASA Astrophysics Data System (ADS)

Many researchers have shown that pulse tube refrigerator (PTR) performance depends significantly on the pressure waveforms generated by the rotary valve in a Gifford McMahon (GM) type PTR. Some literature has shown this effect experimentally for various waveforms. The design of the rotary valve therefore is very critical in order to generate an optimum pressure waveform. However, if the optimum waveform for obtaining maximum cooling power is known, it will help the valve design significantly. In view of this, the valve design would be improved significantly if the performance of the PTR could be predicted with reasonable accuracy for any pressure waveform. The present paper aims at developing a procedure to generate such predictions of the PTR performance for different pressure waveforms. This will help to determine an optimum pressure waveform for a given PTR configuration and will be useful in a significant way for the design of the rotary valve. An isothermal model of the PTR has been developed for various operational modes viz, Basic, Orifice pulse tube refrigerator (OPTR), double inlet pulse tube refrigerator (DIPTR), and has been validated with experimental results. The model is then extended to predict the PTR performance for various pressure waveforms. The experimental data, available in literature in the form of different pressure waves for a given PTR configuration, has then been analyzed. A comparison between the experimental results and the model predictions has been presented.

Desai, S.; Desai, K. P.; Naik, H. B.; Atrey, M. D.

2008-03-01

324

On the role of waveform diversity in MIMO radar  

Microsoft Academic Search

MIMO radar employs multiple antennas to simultaneously transmit diverse waveforms, as well as multiple antennas to receive the radar returns. This paper studies the role of waveform diversity in MIMO radar as separate and distinct from the role of the multiple transmit antennas. This is done by comparing a MIMO radar system to a scanning phased-array radar which uses the

B. Friedlander

2011-01-01

325

WAVEFORM DIVERSITY FOR ADAPTIVE RADAR: AN EXPERT SYSTEM APPROACH  

Microsoft Academic Search

The focus of this paper is on the design of waveforms for efficient spatial and temporal adaptivity including the focusing of the transmitted energy on a physically-small target, so that it will be possible to synthesize waveforms in the space-time continuum for both monostatic and bistatic applications and so that they can be mission adaptive. The objective is to develop

Donald D. Weiner; Andrew L. Drozd; Pramod K. Varshney

326

Method and apparatus for resonant frequency waveform modulation  

DOEpatents

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

Taubman, Matthew S [Richland, WA

2011-06-07

327

Characterization of Shallow Water Environments and Waveform Design for Diversity  

E-print Network

to model the dispersive propagationcharacteristics of the shallow water environment. This representationCharacterization of Shallow Water Environments and Waveform Design for Diversity Ye Jiang, Hao Shen-varying system, dispersive environment, waveform diversity, shallow water acoustics. ABSTRACT In this paper, we

Nehorai, Arye

328

Prolate spheroidal wave functions induce Gaussian chip waveforms  

Microsoft Academic Search

Slepianpsilas prolate spheroidal wave function (PSWF) is optimum in energy concentration within given frequency bandwidth and time-width. However it is not employed in communications mainly because its inter-symbol interference is unfavorable. We show that introducing Markovian spreading codes makes PSWF be a strong candidate for the chip waveform in CDMA systems. For design tractability, Gaussian waveform is recommended.

Yutaka Jitsumatsu; Tohru Kohda

2008-01-01

329

Multiscale AM-FM Methods for Diabetic Retinopathy Lesion Detection  

PubMed Central

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

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

2010-01-01

330

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

331

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS  

SciTech Connect

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

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

2008-10-17

332

An automated waveform window selection algorithm based on continuous wavelet transforms  

Microsoft Academic Search

We have developed an algorithm to automatically select waveform windows by using continuous wavelet transform that allows us to analysis waveforms in time-frequency domain. The algorithm is able to select windows from different types of waveforms for full-3D waveform tomography and\\/or earthquake waveform source inversion. The algorithm has applied on different data types, including earthquake waveforms and ambient noise Green's

P. Chen; E. Lee

2010-01-01

333

Waveform Synthesizer For Imaging And Ranging Applications  

DOEpatents

Frequency dependent corrections are provided for quadrature imbalance. An operational procedure filters imbalance 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 imbalance 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 quadrature imbalance 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.

DUDLEY, PETER A.; [et al

2004-11-30

334

Waveform Synthesizer For Imaging And Ranging Applications  

DOEpatents

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

335

Waveform Selectivity at the Same Frequency  

E-print Network

Electromagnetic properties depend on the composition of materials, i.e. either angstrom scales of molecules or, for metamaterials, subwavelength periodic structures. Each material behaves differently in accordance with the frequency of an incoming electromagnetic wave due to the frequency dispersion or the resonance of the periodic structures. This indicates that if the frequency is fixed, the material always responds in the same manner unless it has nonlinearity. However, such nonlinearity is controlled by the magnitude of the incoming wave or other bias. Therefore, it is difficult to distinguish different incoming waves at the same frequency. Here we present a new concept of circuit-based metasurfaces to selectively absorb or transmit specific types of waveforms even at the same frequency. The metasurfaces, integrated with schottky diodes as well as either capacitors or inductors, selectively absorb short or long pulses, respectively. The two types of the circuit elements are then combined to absorb or tran...

Wakatsuchi, Hiroki; Rushton, Jeremiah J; Gao, Fei; Kim, Sanghoon; Sievenpiper, Daniel F

2014-01-01

336

Using waveform information in nonlinear data assimilation  

NASA Astrophysics Data System (ADS)

Information in measurements of a nonlinear dynamical system can be transferred to a quantitative model of the observed system to establish its fixed parameters and unobserved state variables. After this learning period is complete, one may predict the model response to new forces and, when successful, these predictions will match additional observations. This adjustment process encounters problems when the model is nonlinear and chaotic because dynamical instability impedes the transfer of information from the data to the model when the number of measurements at each observation time is insufficient. We discuss the use of information in the waveform of the data, realized through a time delayed collection of measurements, to provide additional stability and accuracy to this search procedure. Several examples are explored, including a few familiar nonlinear dynamical systems and small networks of Colpitts oscillators.

Rey, Daniel; Eldridge, Michael; Morone, Uriel; Abarbanel, Henry D. I.; Parlitz, Ulrich; Schumann-Bischoff, Jan

2014-12-01

337

Binary black hole merger dynamics and waveforms  

NASA Technical Reports Server (NTRS)

We apply recently developed techniques for simulations of moving black holes to study dynamics and radiation generation in the last few orbits and merger of a binary black hole system. Our analysis produces a consistent picture from the gravitational wave forms and dynamical black hole trajectories for a set of simulations with black holes beginning on circular-orbit trajectories at a variety of initial separations. We find profound agreement at the level of 1% among the simulations for the last orbit, merger and ringdown, resulting in a final black hole with spin parameter a/m = 0.69. Consequently, we are confident that this part of our waveform result accurately represents the predictions from Einstein's General Relativity for the final burst of gravitational radiation resulting from the merger of an astrophysical system of equal-mass non-spinning black holes. We also find good agreement at a level of roughly 10% for the radiation generated in the preceding few orbits.

Baker, John G.; Centrella, Joan; Choi, Dae-II; Koppitz, Michael; vanMeter, James

2006-01-01

338

A chirp spread spectrum DPSK modulator and demodulator for a time shift multiple access communication system by using SAW devices  

Microsoft Academic Search

We have developed a modulator and a demodulator for DPSK modulated chirp signals using a SAW dispersive delay line and a SAW matched filter. The SAW chirp modulator spreads the 100 MHz spectrum between every 1 bit data interval of 1.5 ?sec and provides DPSK modulation, depending upon data. The SAW demodulator demodulates data using exclusive output pulses from two

Yoshihiko Takeuchi; K. Yamanouchi

1998-01-01

339

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

340

Extension of high-order harmonic generation cutoff via coherent control of intense few-cycle chirped laser pulses  

E-print Network

We present an ab initio quantum investigation of the high-order harmonic generation (HHG) cutoff extension using intense few-cycle chirped laser pulses. For a few-cycle chirped driving laser pulse, it is shown that significant cutoff extension can...

Carrera, Juan J.; Chu, Shih-I

2007-03-16

341

Fluorescent styryl dyes FM1-43 and FM2-10 are muscarinic receptor antagonists: intravital visualization of receptor occupancy.  

PubMed

The fluorescent styryl dyes FM1-43 and FM2-10 have been used to visualize the endocytic and exocytic processes involved in neurotransmission in a variety of central and peripheral nerve preparations. Their utility is limited to some extent by a poorly understood vesicular-independent labelling of cells and tissues. We show here that one likely cause of this troublesome background labelling is that FM1-43 and FM2-10 are selective and competitive antagonists at both cloned and endogenously expressed muscarinic acetylcholine receptors. In radioligand binding studies, FM1-43 and FM2-10 bound with moderate affinity (23-220 nM) to membranes of Chinese hamster ovary (CHO) cells expressing cloned human muscarinic receptors (M1-M5). In functional studies in vitro, FM1-43 and FM2-10 inhibited electrical field stimulation (EFS) and acetylcholine-induced cholinergic contractions of guinea-pig tracheal strips (IC50: FM1-43, 0.4 +/- 0.1; FM2-10, 1.6 +/- 0.1 microM; concentration of antagonist producing a 2-fold leftward shift in the acetylcholine concentration-response curve (Kb): FM1-43, 0.3 +/- 0.1; FM2-10, 15.8 +/- 10.1 microM). Neither compound inhibited EFS-evoked, non-adrenergic non-cholinergic nerve-mediated relaxations or contractions of the airways, or contractions mediated by histamine H1 receptor or tachykinin NK2 receptor activation. Incubating freshly excised tracheal whole-mount preparations with 5 microM FM1-43 resulted in intense fluorescence labelling of the smooth muscle that was reduced by up to 90% in the presence of selective M2 and M3 receptor antagonists. The potency of the FM dyes as muscarinic receptor antagonists is within the concentration range used to study vesicular cycling at nerve terminals. Given that muscarinic receptors play a key role in the regulation of neurotransmitter release from a variety of neurones, the anticholinergic properties of FM dyes may have important implications when studying vesicular events in the nervous system. In addition, these dyes may provide a novel tool for visualizing muscarinic receptor occupancy in living tissue or cell preparations. PMID:16728454

Mazzone, Stuart B; Mori, Nanako; Burman, Miriam; Palovich, Michael; Belmonte, Kristen E; Canning, Brendan J

2006-08-15

342

Fast Prediction and Evaluation of Gravitational Waveforms Using Surrogate Models  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

343

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

344

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

PubMed

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

Alexiadis, Dimitrios S; Sergiadis, George D

2007-01-01

345

Control of Landau-Zener transition in NaI predissociation with chirped femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

We explore the control of the Landau-Zener (LZ) transition in NaI predissociation with low-intensity linearly and quadratically chirped femtosecond far-infrared laser pulses by solving the coupled time-dependent Schrdinger equations. We find that the LZ transition between the excited state and the ground state can be enhanced or be suppressed using a well-delayed control pulse with a proper linear or quadratic chirp. With instantaneously controlling the energy gap, the resonant population inversion induced by Rabi oscillation can facilitate or prohibit the molecular population transfer in the avoided-crossing region. This work provides a deep understanding of coherent control of LZ transition in molecular reaction with chirped femtosecond laser pulses.

Liu, Yuanxing; Liu, Yunquan; Gong, Qihuang

2013-03-01

346

Deexcitation of high-Rydberg-state atoms with a chirped train of half-cycle pulses  

SciTech Connect

Encouraged by the experiments on production of antihydrogen atoms in high Rydberg states we have calculated the effect of deexcitation towards lower states by a chirped train of identical unidirectional half-cycle pulses. The calculations exploit both the one-dimensional and impulse approximations providing convenient analytical formulas for the Rydberg-to-Rydberg transition amplitudes. The calculated deexcitation is shown in terms of the mean value of localization of the Rydberg wave packet in the coordinate space, the Rydberg-state population distribution, the Husimi phase-space distribution function, and the probability density distribution, each of these measures vs the length of the applied train of half-cycle pulses. The results for chirped trains are compared with those for periodic trains and examples of higher deexcitation efficiency of the chirped trains are given.

Kopyciuk, T.; Parzynski, R. [Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznan (Poland)

2007-05-15

347

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

348

Evaluation of chirp reversal power modulation sequence for contrast agent imaging  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

349

Evaluation of chirp reversal power modulation sequence for contrast agent imaging.  

PubMed

Over the last decade, significant research effort has been focused on the use of chirp for contrast agent imaging because chirps are known to significantly increase imaging contrast-to-noise ratio (CNR). New imaging schemes, such as chirp reversal (CR), have been developed to improve contrast detection by increasing non-linear microbubble responses. In this study we evaluated the contrast enhancement efficiency of various chirped imaging sequences in combination with well-established imaging schemes such as power modulation (PM) and pulse inversion (PI). The imaging schemes tested were implemented on a fully programmable open scanner and evaluated by ultrasonically scanning (excitation frequency of 2.5?MHz; amplitude of 350?kPa) a tissue-mimicking flow phantom comprising a 4?mm diameter tube through which aqueous dispersions (dilution fraction of 1/2000) of the commercial ultrasound contrast agent, SonoVue() were continuously circulated. The recovery of non-linear microbubble responses after chirp compression requires the development and the optimization of a specific filter. A compression filter was therefore designed and used to compress and extract several non-linear components from the received microbubble responses. The results showed that using chirps increased the image CNR by approximately 10?dB, as compared to conventional Gaussian apodized sine burst excitation but degraded the axial resolution by a factor of 1.4, at-3?dB. We demonstrated that the highest CNR and contrast-to-noise ratio (CTR) were achievable when CR was combined with PM as compared to other imaging schemes such as PI. PMID:25122547

Novell, A; Sennoga, C A; Escoffre, J M; Chaline, J; Bouakaz, A

2014-09-01

350

Full-3D Waveform Tomography for Southern California  

NASA Astrophysics Data System (ADS)

Our full-3D tomography (F3DT) uses 3D SCEC Community Velocity Model Version 4.0 (CVM4) in Southern California as initial model, a staggered-grid finite-difference code to simulate seismic wave propagation and the sensitivity (Frchet) kernels are calculated based on the scattering integral and adjoint methods to iteratively improve the model. We use both earthquake recordings and ambient noise Green's function data, stacking of station-to-station correlations of ambient seismic noise, in our F3DT inversions. To reduce errors of earthquake sources, the epicenters and source parameters of earthquakes used in our F3DT are inverted based on full-wave method. An automatic waveform analysis algorithm that based on continuous wavelet transforms and a topological watershed method is used to pick waveforms full-wave inversions and make frequency dependent phase and amplitude measurements. Our current model shows many features that relate to the geological structures at shallow depth and contrasting velocity values across faults. The perturbations with respect to the initial model in some regions could up to 40% and relate to some structures do not exist in the initial model, such as southern Great Valley. The waveform fittings of earthquake waveforms and ambient noise Green's function data are both improved after iterations. The earthquake waveform misfit and summation of square of ambient noise Green's function group velocity delay time between observed waveforms and updated synthetic waveforms both reduced more than 50%.

Lee, E.; Chen, P.; Jordan, T. H.; Maechling, P. J.; Denolle, M.; Beroza, G. C.

2012-12-01

351

Design and implementation of a hospital wide waveform capture system.  

PubMed

The use of telemetry and invasive monitoring is exceptionally common in modern healthcare. To date the vast majority of this information is not stored for more than a brief duration on the local monitor. This prohibits extensive investigation into waveform data. We describe a system to collect such data in a quaternary care facility. Using standardized "packet sniffing" technology along with routine manual documentation, we reverse engineered the Unity network protocol used to transmit waveform data across the University of Michigan mission critical monitor network. Data was subsequently captured using a proprietary piece of software writing waveform data to local disks. Nightly, this data is post-processed using data from the admit-discharge-transfer system into individual patient waveforms for the day regardless of location. Over a 10month period, over 2,785 individual patients had a total of 65,112 waveforms captured 15,978 from the operating rooms and 49,134 from the ICUs. The average OR case collected over 11MB of data. The average single day data collection consisted of 8.6GB of data. Entire hospital waveform data collection is possible using internally developed software enabling research on waveform data with minimal technical burden. Further research is required to determine the long-term storage and processing of such data. PMID:25224387

Blum, James M; Joo, Heyon; Lee, Henry; Saeed, Mohammed

2014-09-16

352

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

EPA Science Inventory

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

353

Noise filtering in parametric amplification by dressing the seed beam with spatial chirp.  

PubMed

We report a method for filtering out the noises produced in optical parametric chirped-pulse amplifiers by dressing the seed beam with spatial chirp. After dechirping the amplified signal with a compressor, the noises experience a spatiotemporal coupling, making themselves highly distinguishable from the compressed signal in space, and hence supporting noise filtering effectively and expediently in the spatial domain, which would otherwise not be possible. Numerical simulations performed for the proposed method show the capabilities of an order of magnitude reduction in the noise energy and several orders of magnitude enhancement in the temporal contrast. PMID:24979013

Wang, Jing; Ma, Jingui; Wang, Yongzhi; Yuan, Peng; Xie, Guoqiang; Qian, Liejia

2014-04-15

354

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

PubMed

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

Kelleher, E J R; Travers, J C

2014-03-15

355

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

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

356

Chirped pulse Raman amplification in Ba(NO3)2 crystals  

NASA Astrophysics Data System (ADS)

In this study, 35.5% conversion efficiency is obtained at the first Stokes component frequency (873 nm) upon two-stage chirped pulse Raman amplification in a Ba(NO3)2 crystal by an 8 mJ, 620 ps, 800 nm pump laser. A maximum energy of 4.22 mJ with 3.82% rms stability at the first Stokes pulse can be obtained under 35 mJ pump energy. Moreover, the chirped first Stokes pulse can be compressed to 143 fs.

Guo, Xiaoyang; Lu, Jun; Li, Wenkai; Xu, Yi; Lu, Xiaoming; Leng, Yuxin; Li, Ruxin

2015-04-01

357

Coherent XUV pulse generation using a chirped pulse combined with a unipolar pulse  

NASA Astrophysics Data System (ADS)

High-order harmonic emission and attosecond XUV source generation have been theoretically investigated using a chirped pulse combined with a unipolar pulse. It shows that the harmonic plateau is very sensitive to the chirp parameter and the intensity, pulse duration and relative position of the unipolar pulse. Further, by optimizing the laser parameters, a 714?eV supercontinuum bandwidth with a single short quantum path contribution has been obtained. Finally, by superposing the selected harmonic spectrum from the 70th to the 470th orders, an isolated attosecond pulse with a duration of 36 as can be obtained.

Feng, Liqiang; Liu, Hang

2015-01-01

358

Selective and efficient control of coherent population transfer with time-separated chirped pulses  

SciTech Connect

We propose a selective, efficient, and robust way to realize control of coherent population transfer in a {Lambda}-type four-level system with a closely spaced doublet in the final state with time-separated chirped pump pulse and Stokes pulse pair by merging stimulated Raman adiabatic passage, temporal coherent control, and chirped adiabatic passage techniques. Moreover, an arbitrary coherent superposition between the final doublet, or between the intermediate state and either of the doublets can be created. This method holds the ability to 'control with control' and has potential applications in coherent control of chemical reactions and quantum information processing.

Yang Xihua; Zhang Zhenhua; Yan Xiaona; Li Chunfang [Department of Physics, Shanghai University, Shanghai 200444 (China)

2010-03-15

359

Femtosecond laser pulse compression using angle of incidence optimization of chirped mirrors  

NASA Astrophysics Data System (ADS)

Optimal pulse compression following spectral broadening in a noble gas-filled hollow core fiber is a critical step towards producing isolated attosecond pulses. Here we present a systematic pulse shaping method based on the optimal selection of chirped mirrors and on the optimization of their angle of incidence. Feedback from second harmonic frequency resolved optical gating measurements is used to compute the optimal chirped mirror configuration of the next iteration in a genetic algorithm. Sub-5 fs pulses were achieved after a few iterations.

Marceau, C.; Gingras, G.; Toubou Bah, S.; Valle, R.; Witzel, B.

2014-06-01

360

Practical design of optical diagnostics for chirped-pulse free-electron lasers  

NASA Astrophysics Data System (ADS)

In recent years there have been several proposals to operate rf-linac-driven FELs with chirped electron and optical micropulses for use in fast time-resolved experiments. We have been actively pursuing this application on the Mark-III infrared FEL at Duke University, and have designed and procured an apparatus to achieve broad-band compression of chirped optical pulses between roughly 2.5 ?m and 4.1 ?m, with subsequent measurement of pulse widths as short as 200 fs. The principles of design for this experiment will be reviewed, and extensions of the design to other wavelengths will be considered.

Szarmes, Eric B.; Madey, John M. J.

1992-07-01

361

Nonlinear energy deposition in water from fs-laser pulses: effect of the input chirp  

NASA Astrophysics Data System (ADS)

We present numerical and experimental investigation of the effect that the input pulse chirp has on the energy transfer from 5 ?J fs-pulses at 800 nm to water. The chirp is seen to control efficiently the energy transfer and the geometrical properties of the excited plasma volumes. Agreement between simulations and experiments is obtained via a parametric study, the details of which are presented here. These results may find applications in the control of underwater bubble and sound wave formation, and also in laser surgery involving aqueous media.

Milin, C.; Jarnac, Amelie; Brelet, Y.; Jukna, V.; Houard, A.; Mysyrowicz, A.; Couairon, A.

2014-05-01

362

76 FR 28983 - Media Bureau Seeks Comment on the Economic Impact of Low-Power FM Stations on Full-Service...  

Federal Register 2010, 2011, 2012, 2013, 2014

...of Low-Power FM Stations on Full-Service Commercial FM Stations...of low-power FM stations on full-service commercial FM stations...May 10, 2011. The complete text of the document is available...low-power FM stations will have on full-service commercial FM...

2011-05-19

363

General Dynamic (GD) Launch Waveform On-Orbit Performance Report  

NASA Technical Reports Server (NTRS)

The purpose of this report is to present the results from the GD SDR on-orbit performance testing using the launch waveform over TDRSS. The tests include the evaluation of well-tested waveform modes, the operation of RF links that are expected to have high margins, the verification of forward return link operation (including full duplex), the verification of non-coherent operational models, and the verification of radio at-launch operational frequencies. This report also outlines the launch waveform tests conducted and comparisons to the results obtained from ground testing.

Briones, Janette C.; Shalkhauser, Mary Jo

2014-01-01

364

Ultrasound waveform tomography with a spatially variant regularization scheme  

NASA Astrophysics Data System (ADS)

Regularization is often needed in breast ultrasound waveform tomography to improve tomographic reconstructions. A global regularization parameter may lead to either over-regularization or under-regularization in different regions in the imaging domain. We develop a new ultrasound waveform tomography method with spatially-variant regularization. Our new method employs different regularization parameters in different regions of the breast so that each regularization parameter is optimal for the local region. Our numerical examples demonstrate the improvement of ultrasound waveform tomography using the spatially-variant modified total-variation regularization for sound-speed reconstructions of large and small breast tumors, particularly when their sizes are significantly different from one another.

Lin, Youzuo; Huang, Lianjie

2014-03-01

365

On an automatic delineator for arterial blood pressure waveforms  

Microsoft Academic Search

Arterial blood pressure waveforms contain rich pathophysiological\\u000a information; hence receive much attention in cardiovascular health\\u000a monitoring. To assist computerized analysis, an automatic delineator\\u000a was proposed for the fiducial points of arterial blood pressure\\u000a waveforms, namely their onsets, systolic peaks and dicrotic notches.\\u000a The presented delineator characterizes arterial blood pressure\\u000a waveforms in a beat-by-beat manner. It firstly seeks the pairs of

Bing Nan Li; Ming Chui Dong; Mang I. Vai

2010-01-01

366

Comparison of velocity waveforms of eye and head saccades.  

PubMed

We compared the velocity waveforms of head and eye-in-head movements during eye-head saccades over a range 5-50 degrees. The velocity waveforms of eye-in-head saccades showed a skew ratio (acceleration period/saccade duration) that varied as a function of saccade size and duration. The velocity waveforms of head saccades showed a more constant skew of approximately 0.5 for the range of movements tested. These results suggest independent system controllers for eye and head components of eye-head saccades. PMID:15827003

Liao, Ke; Kumar, Arun N; Han, Yanning H; Grammer, Victoria A; Gedeon, Brian T; Leigh, R John

2005-04-01

367

Quarter-cycle engineering of terahertz fieldwaveforms  

NASA Astrophysics Data System (ADS)

Coherent synthesis of cycle-engineered terahertz (THz) field waveforms is demonstrated using two collinear femtosecond laser pulses with a tunable delay, undergoing optical rectification in a nonlinear crystal. The output THz waveforms are tailored with sub-quarter-cycle precision by varying the delay time between the laser pulses. A straightforward scaling of this concept to THz field synthesis with multiple driver pulses suggests ways toward the ultrahigh precision of THz waveform engineering and coherent enhancement to high peak powers in the THz range.

Shu, L.; Li, Y.; Chen, L.; Shi, J.; Chai, L.; Wang, C.; Fedotov, A. B.; Zheltikov, A. M.

2014-08-01

368

A fast amplified fringe modulator and its waveform optimisation  

NASA Astrophysics Data System (ADS)

For temporally modulated fringe patterns, stellar interferometric fringe acquisition rates must generally exceed 1kHz to avoid significant atmospheric related loss of contrast and cross-talk between fringe components. Furthermore, sufficient travel and high waveform stability in the temporal phase modulation are essential to clean fringe visibility extraction. The authors present a system utilising a piezoelectric actuator that takes advantage of a resonating stage to achieve an accurate and stable high amplitude motion. Nanometre accuracy in waveform optimisation and in continuous waveform stability is demonstrated.

Thorsteinsson, Hrobjartur; Buscher, David F.

2006-06-01

369

PREFACE: Functional materials and nanotechnologies (FM&NT-2007)  

NASA Astrophysics Data System (ADS)

The International Baltic Sea Region conference Functional Materials and Nanotechnologies (FM&NT-2007) was held in Riga, 2-4 April 2007 in the Institute of Solid State Physics, University of Latvia (ISSP LU). The conference was organized in co-operation with projects ERANET 'MATERA' and EUREKA 'BIONANOCOMPOSITE'. The purpose of the conference was to bring together scientists, engineers and students from universities, research institutes and related industrial companies active in the field of advanced material science and materials technologies trends and future activities. Scientific themes covered in the conference are:

  • advanced inorganic materials for photonics, energetics and microelectronics
  • organic materials for photonics and nanoelectronics
  • advanced methods for investigation of nanostructures
  • perspective biomaterials and medicine technologies
  • development of technologies for design of nanostructured materials, nanoparticles, and thin films
  • design of functional materials and nanocomposites and development of their technologies
  • The number of registered participants from 14 countries was nearly 110. During three days of the conference 70 oral reports and 58 posters were presented, 50 papers, based on these reports, are included in this volume of Journal of Physics: Conference Series. Additional information about FM&NT-2007 is available in its homepage http://fmnt.lu.lv and http://www.fmnt.lv . The Organizing Committee would like to thank all speakers, contributors, session chairs, referees and meeting staff for their efforts in making the FM&NT-2007 successful. The local Organization Committee would like to acknowledge and thank our sponsors - Latvian Council of Science and the Institute of Solid State Physics, University of Latvia. Andris Sternberg Inta Muzikante Guest editors

    Sternberg, Andris; Muzikante, Inta

    2007-06-01

    370

    DESIGN NOTE: A linear, low cost and versatile FM demodulator  

    NASA Astrophysics Data System (ADS)

    The experimental behaviour of a low cost and versatile FM demodulator is described, designed for field applications where high linearity of the device is required in order to obtain a very low harmonic distortion of the signal to be measured. The circuit solutions which have been taken in order to reduce noise effects and to improve the dynamic range of the device are also discussed with reference to a vibration measuring system. A linearity uncertainty of less than 0957-0233/7/11/018/img1 can be attained with reference to a frequency decade with input frequency to the demodulator in the range 50 kHz to 25 MHz.

    D'Emilia, Giulio

    1996-11-01

    371

    Multi channel FM reflection profiler for buried pipeline surveying  

    SciTech Connect

    A towed multi-channel FM acoustic reflection profiler has been developed for locating and generating images of buried objects. One significant application of this sonar is buried pipeline surveying. The multi-channel reflection profiler uses 16 line arrays mounted in a towed vehicle to determine the position and burial depth of an 18 inch steel pipe filled with concrete buried under 1.5 meters of sand. This sonar will allow a survey vessel to continuously track a buried pipeline providing a continuous record of pipe burial depth and position.

    Schock, S.G.; LeBlanc, L.R. [Florida Atlantic Univ., Boca Raton, FL (United States). Dept. of Ocean Engineering

    1996-12-31

    372

    Comparison of detectability of traditional pulsed and spread spectrum radar waveforms in classic passive receivers  

    Microsoft Academic Search

    Passive receivers can be used to detect radar emissions over considerable distances. If range resolution requirements are fixed, it is of interest to compare the detectability of equal-bandwidth\\/equal-energy waveforms regardless of their time duration. Relative detection ranges are predicted, via computer simulation, for two types of transmitted waveforms: a benchmark rectangular pulse and a Welti binary coded waveform. The waveforms

    F. B. Gross; K. Chen

    2005-01-01

    373

    Efficient implementation of ultrasound waveform tomography using data blending  

    NASA Astrophysics Data System (ADS)

    Ultrasound waveform tomography is a promising tool for breast cancer characterization. However, the method is very time-consuming for large datasets acquired using a synthetic-aperture ultrasound tomography system consisting of hundreds to thousands of transducer elements. We introduce a data blending approach to ultrasound waveform tomography to greatly improves the computational efficiency. This method simultaneously simulates ultrasound waves emitted from multiple transducer elements. A random phase is applied to each source to distinguish the effect of different sources. The random phase helps eliminate the unwanted cross interference produced by different sources. This approach greatly reduces the computation time of ultrasound waveform tomography to one tenth of that for the original ultrasound waveform tomography.

    Zhang, Zhigang; Huang, Lianjie

    2014-03-01

    374

    Acoustic Waveform Logging - Advances In Theory And Application  

    E-print Network

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

    Cheng, C. H.

    375

    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

    376

    X-ray waveform monitoring for radiographic quality control.  

    PubMed

    Noninvasive monitoring of x-ray output waveforms during acceptance testing, quality of control, and troubleshooting is beneficial in an ongoing radiographic quality assurance program. The intent of waveform monitoring is to watch for abnormalities that provide additional information about the condition of the x-ray system. Because waveform monitoring is performed generally in conjunction with other quality control procedures, few, if any, additional exposures are needed and length of the testing time is affected minimally. In six years of experience with acceptance testing, quality control, and troubleshooting on more than 160 radiographic and fluoroscopic units, noninvasive waveform monitoring has detected numerous abnormalities that would have affected image quality, generator calibration, and equipment life. PMID:4059531

    Stears, J G; Gray, J E; Webbles, W E; Frank, E D

    1985-01-01

    377

    Inversion method for initial tsunami waveform reconstruction  

    NASA Astrophysics Data System (ADS)

    This paper deals with the application of r-solution method to recover the initial tsunami waveform in a tsunami source area by remote water-level measurements. Wave propagation is considered within the scope of a linear shallow-water theory. An ill-posed inverse problem is regularized by means of least square inversion using a truncated SVD approach. The properties of obtained solution are determined to a large extent by the properties of an inverse operator, which were numerically investigated. The method presented allows one to control instability of the numerical solution and to obtain an acceptable result in spite of ill-posedness of the problem. It is shown that the accuracy of tsunami source reconstruction strongly depends on the signal-to-noise ratio, the azimuthal coverage of recording stations with respect to the source area and bathymetric features along the wave path. The numerical experiments were carried out with synthetic data and various computational domains including a real bathymetry. The method proposed allows us to make a preliminary prediction of the efficiency of the inversion with a given set of the recording stations and to find out the most informative part of the existing observation system. This essential property of the method can prove to be useful in designing a monitoring system for tsunamis.

    Voronin, V. V.; Voronina, T. A.; Tcheverda, V. A.

    2014-12-01

    378

    Compression strategies for LiDAR waveform cube  

    NASA Astrophysics Data System (ADS)

    Full-waveform LiDAR data (FWD) provide a wealth of information about the shape and materials of the surveyed areas. Unlike discrete data that retains only a few strong returns, FWD generally keeps the whole signal, at all times, regardless of the signal intensity. Hence, FWD will have an increasingly well-deserved role in mapping and beyond, in the much desired classification in the raw data format. Full-waveform systems currently perform only the recording of the waveform data at the acquisition stage; the return extraction is mostly deferred to post-processing. Although the full waveform preserves most of the details of the real data, it presents a serious practical challenge for a wide use: much larger datasets compared to those from the classical discrete return systems. Atop the need for more storage space, the acquisition speed of the FWD may also limit the pulse rate on most systems that cannot store data fast enough, and thus, reduces the perceived system performance. This work introduces a waveform cube model to compress waveforms in selected subsets of the cube, aimed at achieving decreased storage while maintaining the maximum pulse rate of FWD systems. In our experiments, the waveform cube is compressed using classical methods for 2D imagery that are further tested to assess the feasibility of the proposed solution. The spatial distribution of airborne waveform data is irregular; however, the manner of the FWD acquisition allows the organization of the waveforms in a regular 3D structure similar to familiar multi-component imagery, as those of hyper-spectral cubes or 3D volumetric tomography scans. This study presents the performance analysis of several lossy compression methods applied to the LiDAR waveform cube, including JPEG-1, JPEG-2000, and PCA-based techniques. Wide ranges of tests performed on real airborne datasets have demonstrated the benefits of the JPEG-2000 Standard where high compression rates incur fairly small data degradation. In addition, the JPEG-2000 Standard-compliant compression implementation can be fast and, thus, used in real-time systems, as compressed data sequences can be formed progressively during the waveform data collection. We conclude from our experiments that 2D image compression strategies are feasible and efficient approaches, thus they might be applied during the acquisition of the FWD sensors.

    J?kw, Grzegorz; Toth, Charles; Quirk, Mihaela; Grejner-Brzezinska, Dorota

    2015-01-01

    379

    Waveform-agile tracking in heavy sea clutter  

    Microsoft Academic Search

    The detection and tracking of small targets on the ocean surface is a challenging problem due to low signal-to-clutter ratio (SCR) that results from low grazing angles and high sea state. Recent advances in sensing technologies have enabled waveform-agile schemes that tailor the sensor waveform to match the overall sensing objective. In this paper, we propose a methodology to dynamically

    Sandeep P. Sira; Antonia Papandreou-Suppappola; Darryl Morrell; Douglas Cochran

    2007-01-01

    380

    Elastic waveforms using laser generation and electromagnetic acoustic transducer detection  

    NASA Astrophysics Data System (ADS)

    A Q-switched, frequency-doubled ruby laser has been used to generate wide bandwidth ultrasonic transients in aluminum and steel plates. Both longitudinal and shear waves were generated, resultant waveforms being dependent upon the irradiation conditions. Various designs of electromagnetic acoustic transducers were then used to detect these waveforms at the opposite side of the plate. The result is a method of ultrasonic inspection with potential in noncontact applications.

    Hutchins, D. A.; Wilkins, D. E.

    1985-10-01

    381

    Use and abuse of the model waveform accuracy standards  

    SciTech Connect

    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 [Theoretical Astrophysics 350-17, California Institute of Technology, Pasadena, California 91125 (United States)

    2009-09-15

    382

    Use and Abuse of the Model Waveform Accuracy Standards  

    E-print Network

    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.

    Lee Lindblom

    2009-09-22

    383

    Use and Abuse of the Model Waveform Accuracy Standards  

    E-print Network

    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

    2009-01-01

    384

    Adaptive pulse-diverse radar\\/sonar waveform design  

    Microsoft Academic Search

    This paper devises an adaptive pulse-diverse compression waveform design method: echoes from earlier pulses of the pulse train brought back target\\/jamming\\/Doppler information of the actual battlefield environment. The present scheme allows the use of this information to assign the relative criticality of various Doppler-delay regions with respect to the waveform ambiguity function. For example, the presence of strong clutter or

    Kainam Thomas Wong

    1998-01-01

    385

    A sampling and storage system for arbitrary biomedical waveforms.  

    PubMed

    This paper describes a microcontroller based system which can sample, monitor and store, and generate biomedical waveforms. The frequency of the output waveform is controllable. The inherent advantage of this system is the programming flexibility offered by the microcontroller. Applications include patient monitoring, test signal generator for repair and maintenance of EEG or ECG monitoring equipment, and a laboratory simulation device for student educational use. PMID:8329618

    Bhaskaran, A; Ferris, C D; Sandige, R S

    1993-01-01

    386

    Single-channel broadband and multichannel narrowband filtering characteristics of linear chirped long-period fiber gratings  

    NASA Astrophysics Data System (ADS)

    Band-stop optical fiber filters based on linear chirped long-period fiber gratings (LPFGs) were investigated. The transmission characteristics of the linear chirped LPFGs were analyzed in detail with transfer matrix method. Linear chirp coefficient had a remarkable influence on the bandwidth of the transmission spectra. When the linear chirp coefficient was 10-9 and the transmission spectra corresponding to multiple cladding modes were superposed, the bandwidth of the transmission spectra could be expanded to >1000 nm. So the linear chirped LPFGs can be used for single-channel broadband band-stop filters, and the relationships between the grating parameters and the bandwidth of the transmission spectra were given. When the linear chirp coefficient is 10, several narrow and separated loss peaks appeared in the transmission spectra, which indicated that the linear chirped LPFGs can be used for multichannel narrowband filters. The variations of the grating parameters caused the shifts of the transmission spectra and the changes of the intervals between separated loss peaks. The conclusions that are significant in optimizing the fiber grating filters' design were obtained.

    Yang, Ying; Gu, Zhengtian

    2013-11-01

    387

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

    Microsoft Academic Search

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

    A. Dubietis; G. Jonusauskas; A. Piskarskas

    1992-01-01

    388

    Broadband excitation by chirped pulses: application to single electron spins in diamond  

    E-print Network

    .4. Multi-line broadband spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Conclusions 13Broadband excitation by chirped pulses: application to single electron spins in diamond I Niemeyer1 are used. If the corresponding high power is not available or not desirable, the pulses can be replaced

    Suter, Dieter

    389

    Phase control for production of high-fidelity optical pulses for chirped-pulse amplification  

    NASA Astrophysics Data System (ADS)

    We demonstrate continuous tuning of the cubic and quartic phases of the pulse stretcher in a chirped-pulse amplification laser system. We obtain near-bandwidth-limited recompression of 100-fs pulses by minimizing the total phase through fourth order.

    Sullivan, A.; White, W. E.

    1995-01-01

    390

    Quasi-Distributed Strain Sensor Incorporating a Chirped MoirÉ Fiber Bragg Grating  

    Microsoft Academic Search

    A quasi-distributed strain sensor with an average spatial resolution of 164 ?m over a length of 25 mm and a strain sensitivity of 0.80.01 pm\\/?? has been experimentally demonstrated. The sensor was formed by a chirped Moire fiber Bragg grating written into the core of single-mode optical fiber with a 244-nm continuous-wave laser.

    A. M. Gillooly; L. Zhang; I. Bennion

    2005-01-01

    391

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

    E-print Network

    Comparison of binaural auditory brainstem responses and the binaural di¡erence potential evoked that compensate for the dispersion of the travelling wave on the basilar membrane evoke larger monaural brainstem auditory brainstem responses were recorded for clicks and chirps for levels from 10 to 60 dB nHL in steps

    Oldenburg, Carl von Ossietzky, Universität

    392

    Characterization of a fiber-optic direct modulation analog link with chirp radar signals  

    Microsoft Academic Search

    This paper describes the experimental investigations carried out to evaluate the behaviour of a fiber-optic direct modulation analog link as a substitute of traditional transmission means, like coaxial cables or waveguides, for X-band chirp modulated radar signals. First of all, the link has been completely characterized, and the spurious frequency modulation has been measured in presence of pulsed signals. Afterwards,

    Rossano Pardini; Umberto Bruno; Roberto Izzo

    2009-01-01

    393

    The use of chirp overlapping properties for improved target resolution in an ultrasonic ranging system  

    Microsoft Academic Search

    The ability of many bat species to navigate, identify and capture prey has interested scientists for many years. It is known that bats possess extremely sophisticated echo location capabilities utilising chirp sequencing allied with an adaptive antenna system that enables extremely high resolution in 3D space. One particularly interesting aspect is that bats appear to resolve and locate targets with

    F. Devaud; G. Hayward; J. J. Soraghan

    2004-01-01

    394

    Simultaneous compression and characterization of ultrashort laser pulses using chirped mirrors and glass wedges  

    E-print Network

    We present a simple and robust technique to retrieve the phase of ultrashort laser pulses, based on a chirped mirror and glass wedges compressor. It uses the compression system itself as a diagnostic tool, thereby making unnecessary the use of complementary diagnostic tools. We used this technique to compress and characterize 7.1 fs laser pulses from an ultrafast laser oscillator.

    Miranda, Miguel; Arnold, Cord; L'Huillier, Anne; Crespo, Helder

    2011-01-01

    395

    Multi-kilohertz repetition rate Ti:sapphire amplifier based on down-chirped pulse  

    E-print Network

    Multi-kilohertz repetition rate Ti:sapphire amplifier based on down-chirped pulse amplification energy and capable of being operated at repetition rates exceeding 40 kHz. This ti:sapphire based system makes use of a grism based stretcher, a cryogenically cooled ti:sapphire crystal and an astigmatically

    396

    Estimation of airway obstruction using oximeter plethysmograph waveform data  

    PubMed Central

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

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

    2005-01-01

    397

    Detection and phenotyping of retinal disease using AM-FM processing for feature extraction  

    Microsoft Academic Search

    We present the application of an Amplitude-Modulation Frequency-Modulation (AM-FM) method for extracting potentially relevant features towards the classification of diseased retinas from healthy retinas. In terms of AM-FM features, we use histograms of the instantaneous amplitude, the angle of the instantaneous frequency and the magnitude of the instantaneous frequency extracted over different frequency scales. To classify the AM-FM features, we

    Carla Agurto; Sergio Murillo; Victor Murray; Marios Pattichis; Stephen Russell; Michael Abramoff; P. Soliz

    2008-01-01

    398

    Waveform Transmission Method, a New Waveform-relaxation Based Algorithm to Solve Ordinary Differential Equations in Parallel  

    E-print Network

    Waveform Relaxation method (WR) is a beautiful algorithm to solve Ordinary Differential Equations (ODEs). However, because of its poor convergence capability, it was rarely used. Virtual Transmission Method (VTM) is a new distributed algorithm to solve large sparse linear systems, with an appreciable convergence speed. In this paper, by marrying WR with VTM, a new distributed algorithm, named Waveform Transmission Method (WTM), was born. WTM has better convergence capability than the traditional WR algorithms.

    Wei, Fei

    2009-01-01

    399

    Seismic waveforms and velocity model heterogeneity: Towards a full-waveform microseismic location algorithm  

    NASA Astrophysics Data System (ADS)

    Seismic forward modeling is an integral component of microseismic location algorithms, yet there is generally no one correct approach, but rather a range of acceptable approaches that can be used. Since seismic signals are band limited, the length scale of heterogeneities can significantly influence the seismic wavefronts and waveforms. This can be especially important for borehole microseismic monitoring, where subsurface heterogeneity can be strong and/or vary on length scales equivalent to or less than the dominant source wavelength. In this paper, we show that ray-based approaches are not ubiquitously suitable for all borehole microseismic applications. For unconventional reservoir settings, ray-based algorithms may not be suitably accurate for advanced microseismic imaging. Here we focus on exploring the feasibility of using one-way wave equations as forward propagators for full waveform event location techniques. As a feasibility study, we implement an acoustic wide-angle wave equation and use a velocity model interpolation approach to explore the computational efficiency and accuracy of the solution. We compare the results with an exact solution to evaluate travel-time and amplitude errors. The results show that accurate travel-times can be predicted to within 2 ms of the true solution for modest velocity model interpolation. However, for accurate amplitude prediction or for higher dominant source frequencies, a larger number of velocity model interpolations is required.

    Angus, D. A.; Aljaafari, A.; Usher, P.; Verdon, J. P.

    2014-12-01

    400

    Chirped-pulse manipulated carrier dynamics in low-temperature molecular-beam-epitaxy grown GaAs  

    SciTech Connect

    Chirped pulse controlled carrier dynamics in low-temperature molecular-beam-epitaxy grown GaAs are investigated by degenerate pump-probe technique. Varying the chirped condition of excited pulse from negative to positive increases the carrier relaxation time so as to modify the dispersion and reshape current pulse in time domain. The spectral dependence of carrier dynamics is analytically derived and explained by Shockley-Read Hall model. This observation enables the new feasibility of controlling carrier dynamics in ultrafast optical devices via the chirped pulse excitations.

    Lee, Chao-Kuei, E-mail: chuckcklee@yahoo.com [Department of Photonics, National Sun-Yat-Sen University, Kaohsiung 80400, Taiwan (China); Lin, Yuan-Yao [Department of Electrical Engineering, Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30010, Taiwan (China); Lin, Sung-Hui [Department of Photonics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Lin, Gong-Ru [Department of Electrical Engineering, Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Roosevelt Road, Sec. 4, Taipei 10617, Taiwan (China); Pan, Ci-Ling [Department of Photonics, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Department of Physics, National Tsing Hwa University, Hsinchu 30010, Taiwan (China)

    2014-04-28

    401

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

    Code of Federal Regulations, 2014 CFR

    ...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES EXPERIMENTAL RADIO, AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES FM Broadcast...Auxiliaries) 74.603 Charges, Program Service, (Experimental...

    2014-10-01

    402

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

    Code of Federal Regulations, 2014 CFR

    ...COMMISSION (CONTINUED) BROADCAST RADIO SERVICES EXPERIMENTAL RADIO, AUXILIARY, SPECIAL BROADCAST AND OTHER PROGRAM DISTRIBUTIONAL SERVICES FM Broadcast...Each applicant's number of existing radio authorizations (licenses and...

    2014-10-01

    403

    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

    404

    FM demodulated Kelvin probe force microscopy for surface photovoltage tracking  

    NASA Astrophysics Data System (ADS)

    The surface photovoltage (SPV) of a structured semiconductor surface is deduced via detection of the contact potential difference measured with Kelvin probe force microscopy (KPFM). Our setup is based on a quantitative KPFM method complemented with modulated laser illumination in order to measure SPV. A high lateral resolution and quantitative values for the SPV are obtained by operating the KPFM in the so-called frequency modulation (FM) mode which is advantageous compared to the amplitude sensitive (AM) mode as proven by our simulations. In contrast to similar studies based on scanning tunnelling microscopy, KPFM offers the clear advantage that there is virtually no electric DC field between tip and sample and, therefore, the SPV is not affected by the presence of the tip.

    Loppacher, Christian; Zerweck, Ulrich; Teich, Sebastian; Beyreuther, Elke; Otto, Tobias; Grafstrm, Stefan; Eng, Lukas M.

    2005-03-01

    405

    FM spectroscopy in fluorescence in laser-cooled rubidium  

    NASA Astrophysics Data System (ADS)

    A novel variation of the technique of two-photon frequency modulation (FM) spectroscopy has been developed, which allows signals to be obtained from small (10 5 atoms) and dilute (10 10 cm -3) samples - in this case laser-cooled rubidium atoms. This was possible by detecting and demodulating the fluorescence signal rather than the transmission through the sample. Data are presented demonstrating the dependence of the signal on phase and frequency of the imposed modulation. Initially the atoms were held in a magneto-optic trap but, in order to eliminate line broadening due to the presence of the trapping fields, data were taken with the atoms in free fall. A similar signal, slightly shifted and broadened by the trapping fields, was obtained while the trap was on and used for long-term stabilisation of the probe laser.

    Snadden, M. J.; Clarke, R. B. M.; Riis, E.

    1998-07-01

    406

    FM 4-64 labeling of yeast vacuole membranes FM 4-64 is a lipophilic styryl dye sold by Molecular Probes (product no. T-3166;  

    E-print Network

    at room temperature (RT) 2. Aspirate supernatant; resuspend cell pellet in 50 µL YPD + 1 µL FM 4-64 *FM 4 min at RT 5. Aspirate supernatant; resuspend cell pellet in 1 mL YPD; transfer to culture tube 6. Add and spin 5 min at 5000 x g at RT 8. Aspirate supernatant and resuspend cell pellet in 1 mL sterile water 9

    Odorizzi, Greg

    407

    Chirped-beam two-stage free-electron laser for high-power femtosecond x-ray pulse generation  

    NASA Astrophysics Data System (ADS)

    A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to amplify the short-duration radiation. The radiation characteristics produced by a chirped-beam two-stage free-electron laser are calculated, and the performance of the chirped-beam two-stage option for the Linac Coherent Light Source is considered. 2002 Optical Society of America

    Schroeder, Carl B.; Pellegrini, Claudio; Reiche, Sven; Arthur, John; Emma, Paul

    2002-08-01

    408

    Quantitative analysis of sensor for pressure waveform measurement  

    PubMed Central

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

    2010-01-01

    409

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

    PubMed

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

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

    2014-07-25

    410

    Maintaining Stimulant Waveforms in Large Volume Microfluidic Cell Chambers  

    PubMed Central

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

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

    2013-01-01

    411

    A scalable, fast, and multichannel arbitrary waveform generator  

    NASA Astrophysics Data System (ADS)

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

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

    2013-12-01

    412

    Transthoracic defibrillation with chopping-modulated biphasic waveforms.  

    PubMed

    The superiority of different biphasic pulses for transthoracic defibrillation was proven by several studies. These efficient waveforms were implemented in some commercially available defibrillators. Recently we have devised and evaluated a biphasic waveform with a specially balanced ratio of the first-to-second phase voltages and with 5 kHz frequency 1:1 on-off chopping. It used less than half the energy for successful defibrillation in comparison with the 'classic' monophasic damped sinusoidal wave and showed considerably less post-shock negative effects. This experience led us to try several laws of chopping modulation. A pulse-width modulation, combining low energy with gradual upslope of the modelled transmembrane potential, proved to have better performance than the standard damped sinusoid wave and the non-chopped biphasic truncated exponential pulse. This waveform was tested in a series of animal experiments in comparison with other modulated pulses, with the non-modulated waveform and the standard damped sinusoid wave. The experiments demonstrated the superiority of the modulated waveform, assessed by combining the parameters of threshold defibrillation energy and of post-shock disturbances reduction. PMID:11601443

    Krasteva, V; Cansell, A; Daskalov, I K

    2001-01-01

    413

    Estimation of earthquake source parameters by the inversion of waveform data: synthetic waveforms  

    NASA Astrophysics Data System (ADS)

    Two methods are presented for the recovery of a time-dependent moment-tensor source from waveform data. One procedure utilizes multichannel signal-enhancement theory; in the other a multichannel vector-deconvolution approach, developed by Oldenburg (1982) and based on Backus-Gilbert inverse theory, is used. These methods have the advantage of being extremely flexible; both may be used either routinely or as research tools for studying particular earthquakes in detail. Both methods are also robust with respect to small errors in the Green's functions and may be used to refine estimates of source depth by minimizing the misfits to the data. The multichannel vector-deconvolution approach, although it requires more interaction, also allows a trade-off between resolution and accuracy, and complete statistics for the solution are obtained. The procedures have been tested using a number of synthetic body-wave data sets, including point and complex sources, with satisfactory results.

    Sipkin, Stuart A.

    1982-11-01

    414

    Simultaneous ranging and velocimetry of fast moving targets using oppositely chirped pulses from a mode-locked laser.  

    PubMed

    A lidar system based on the coherent detection of oppositely chirped pulses generated using a 20 MHz mode locked laser and chirped fiber Bragg gratings is presented. Sub millimeter resolution ranging is performed with > 25 dB signal to noise ratio. Simultaneous, range and Doppler velocity measurements are experimentally demonstrated using a target moving at > 330 km/h inside the laboratory. PMID:21716350

    Piracha, Mohammad U; Nguyen, Dat; Ozdur, Ibrahim; Delfyett, Peter J

    2011-06-01

    415

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

    Microsoft Academic Search

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

    J. A. Simmons

    1993-01-01

    416

    Audio Streaming over FM band between USRP1 and USRP2 Project Report  

    E-print Network

    Audio Streaming over FM band between USRP1 and USRP2 Phase II Project Report Kushal Shah Department is streamed over FM band from one host machine to another over a wireless channel using GNU Radio and USRPs, demodulation, etc., of the signal hardware independent. Thus, the radio system then only requires low cost

    Yu, Chansu

    417

    Air Band Scanner with Retransmission over Local FM Radio Frequencies Using a  

    E-print Network

    Air Band Scanner with Retransmission over Local FM Radio Frequencies Using a Software Defined Radio and demodulation functions that are typically implemented in the hardware portion of a radio. #12;Midterm Report it uses [4]. Despite the frequencies only being slightly higher than the FM radio frequency range, air

    Yu, Chansu

    418

    77 FR 8869 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License  

    Federal Register 2010, 2011, 2012, 2013, 2014

    ...Broadcasting Services; AM or FM Proposals To Change the Community of License AGENCY: Federal...applicants filed AM or FM proposals to change the community of license: BBC BROADCASTING...BP-20090226AAF, From FERNDALE, WA, To POINT ROBERTS, WA; CUMULUS LICENSING...

    2012-02-15

    419

    A Comparison of Common Users across Instagram and Ask.fm to Better Understand Cyberbullying  

    E-print Network

    A Comparison of Common Users across Instagram and Ask.fm to Better Understand Cyberbullying Homa social networks, Instagram and Ask.fm, that are often used for cyberbullying. An analysis increase in cyberbullying activities, especially among teenagers. Indeed, cyberbullying has become a major

    Han, Richard Y.

    420

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

    ERIC Educational Resources Information Center

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

    Huff, W. A. Kelly

    421

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

    Code of Federal Regulations, 2011 CFR

    ...2011-10-01 false TV/FM dual-language broadcasting in Puerto Rico. 73...Stations 73.1210 TV/FM dual-language broadcasting in Puerto Rico. (a) For the purpose of this section, dual-language broadcasting shall be understood...

    2011-10-01

    422

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

    Code of Federal Regulations, 2010 CFR

    ...2010-10-01 false TV/FM dual-language broadcasting in Puerto Rico. 73...Stations 73.1210 TV/FM dual-language broadcasting in Puerto Rico. (a) For the purpose of this section, dual-language broadcasting shall be understood...

    2010-10-01

    423

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

    Code of Federal Regulations, 2014 CFR

    ...Telecommunication 4 2014-10-01 2014-10-01 false Interference to TV reception by FM stations. 73.4135 Section 73...Rules Applicable to All Broadcast Stations 73.4135 Interference to TV reception by FM stations. See Public...

    2014-10-01

    424

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

    Code of Federal Regulations, 2013 CFR

    ...2013-10-01 2013-10-01 false Interference protection to full service FM stations...Broadcast Stations (LPFM) 73.809 Interference protection to full service FM stations...is protected against any condition of interference to the direct reception of its...

    2013-10-01

    425

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

    Code of Federal Regulations, 2012 CFR

    ...2012-10-01 2012-10-01 false Interference protection to full service FM stations...Broadcast Stations (LPFM) 73.809 Interference protection to full service FM stations...is protected against any condition of interference to the direct reception of its...

    2012-10-01

    426

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

    Code of Federal Regulations, 2012 CFR

    ...Telecommunication 4 2012-10-01 2012-10-01 false Interference to TV reception by FM stations. 73.4135 Section 73...Rules Applicable to All Broadcast Stations 73.4135 Interference to TV reception by FM stations. See Public...

    2012-10-01

    427

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

    Code of Federal Regulations, 2011 CFR

    ...2011-10-01 2011-10-01 false Interference protection to full service FM stations...Broadcast Stations (LPFM) 73.809 Interference protection to full service FM stations...is protected against any condition of interference to the direct reception of its...

    2011-10-01

    428

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

    Code of Federal Regulations, 2010 CFR

    ...2010-10-01 2010-10-01 false Interference protection to full service FM stations...Broadcast Stations (LPFM) 73.809 Interference protection to full service FM stations...is protected against any condition of interference to the direct reception of its...

    2010-10-01

    429

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

    Code of Federal Regulations, 2014 CFR

    ...2014-10-01 2014-10-01 false Interference protection to full service FM stations...Broadcast Stations (LPFM) 73.809 Interference protection to full service FM stations...is protected against any condition of interference to the direct reception of its...

    2014-10-01

    430

    47 CFR 73.1570 - Modulation levels: AM, FM, TV and Class A TV aural.  

    Code of Federal Regulations, 2010 CFR

    ...2010-10-01 2010-10-01 false Modulation levels: AM, FM, TV and Class...Broadcast Stations 73.1570 Modulation levels: AM, FM, TV and Class A TV aural. (a) The percentage of modulation is to be maintained at as...

    2010-10-01

    431

    47 CFR 73.1570 - Modulation levels: AM, FM, TV and Class A TV aural.  

    Code of Federal Regulations, 2012 CFR

    ...2012-10-01 2012-10-01 false Modulation levels: AM, FM, TV and Class...Broadcast Stations 73.1570 Modulation levels: AM, FM, TV and Class A TV aural. (a) The percentage of modulation is to be maintained at as...

    2012-10-01

    432

    47 CFR 73.1570 - Modulation levels: AM, FM, TV and Class A TV aural.  

    Code of Federal Regulations, 2011 CFR

    ...2011-10-01 2011-10-01 false Modulation levels: AM, FM, TV and Class...Broadcast Stations 73.1570 Modulation levels: AM, FM, TV and Class A TV aural. (a) The percentage of modulation is to be maintained at as...

    2011-10-01

    433

    47 CFR 73.1570 - Modulation levels: AM, FM, TV and Class A TV aural.  

    Code of Federal Regulations, 2013 CFR

    ...2013-10-01 2013-10-01 false Modulation levels: AM, FM, TV and Class...Broadcast Stations 73.1570 Modulation levels: AM, FM, TV and Class A TV aural. (a) The percentage of modulation is to be maintained at as...

    2013-10-01

    434

    47 CFR 73.1570 - Modulation levels: AM, FM, TV and Class A TV aural.  

    Code of Federal Regulations, 2014 CFR

    ...2014-10-01 2014-10-01 false Modulation levels: AM, FM, TV and Class...Broadcast Stations 73.1570 Modulation levels: AM, FM, TV and Class A TV aural. (a) The percentage of modulation is to be maintained at as...

    2014-10-01

    435

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

    E-print Network

    ATTP 4-0.1 (FM 100-10-1) Army Theater Distribution May 2011 DISTRIBUTION RESTRICTION: Approved for public release; distribution is unlimited. Headquarters, Department of the Army #12;This publication Digital Library at (www.train.army.mil). #12;*ATTP 4-0.1 (FM 100-10-1) Distribution Restriction: Approved

    US Army Corps of Engineers

    436

    YANG-4: "FM" --2006/9/1 --14:17 --PAGE i --#1 Computational Molecular Evolution  

    E-print Network

    : "FM" -- 2006/9/1 -- 14:17 -- PAGE ii -- #2 Oxford Series in Ecology and Evolution Edited by Paul H in Plant Evolution Donald A. Levin Living in Groups Jens Krause and Graeme Ruxton Stochastic Population#12;YANG-4: "FM" -- 2006/9/1 -- 14:17 -- PAGE i -- #1 Computational Molecular Evolution #12;YANG-4

    437

    The response of phospholipid-encapsulated microbubbles to chirp-coded excitation: Implications for high-frequency nonlinear imaging  

    PubMed Central

    The current excitation strategy for harmonic and subharmonic imaging (HI and SHI) uses short sine-bursts. However, alternate pulsing strategies may be useful for enhancing nonlinear emissions from ultrasound contrast agents. The goal of this study was to corroborate the hypothesis that chirp-coded excitation can improve the performance of high-frequency HI and SHI. A secondary goal was to understand the mechanisms that govern the response of ultrasound contrast agents to chirp-coded and sine-burst excitation schemes. Numerical simulations and acoustic measurements were conducted to evaluate the response of a commercial contrast agent (Targestar-P) to chirp-coded and sine-burst excitation (10?MHz frequency, peak pressures 290 kPa). The results of the acoustic measurements revealed an improvement in signal-to-noise ratio by 4 to 14?dB, and a two- to threefold reduction in the subharmonic threshold with chirp-coded excitation. Simulations conducted with the Marmottant model suggest that an increase in expansion-dominated radial excursion of microbubbles was the mechanism responsible for the stronger nonlinear response. Additionally, chirp-coded excitation detected the nonlinear response for a wider range of agent concentrations than sine-bursts. Therefore, chirp-coded excitation could be a viable approach for enhancing the performance of HI and SHI. PMID:23654417

    Shekhar, Himanshu; Doyley, Marvin M.

    2013-01-01

    438

    FM-dyes as experimental probes for dissecting vesicle trafficking in living plant cells.  

    PubMed

    FM-dyes are widely used to study endocytosis, vesicle trafficking and organelle organization in living eukaryotic cells. The increasing use of FM-dyes in plant cells has provoked much debate with regard to their suitability as endocytosis markers, which organelles they stain and the precise pathways they follow through the vesicle trafficking network. A primary aim of this article is to assess critically the current status of this debate in plant cells. For this purpose, background information on the important characteristics of the FM-dyes, and of optimal dye concentrations, conditions of dye storage, and staining and imaging protocols, are provided. Particular emphasis is placed on using the FM-dyes in double labelling experiments to identity specific organelles. In this way, staining of the Golgi with FM4-64 has been demonstrated for the first time. PMID:15102063

    Bolte, S; Talbot, C; Boutte, Y; Catrice, O; Read, N D; Satiat-Jeunemaitre, B

    2004-05-01

    439

    Improved Time-Domain Accuracy Standards for Model Gravitational Waveforms  

    E-print Network

    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.

    Lee Lindblom; John G. Baker; Benjamin J. Owen

    2010-08-10

    440

    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

    441

    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

    442

    Boltzmann analysis of CM waveforms using virtual instrument software.  

    PubMed

    We describe a modification to our technique for the rapid analysis of low-frequency cochlear microphonic (CM) waveforms in the basal turn of the guinea pig cochlea (Patuzzi and Moleirinho, 1998). The transfer curve relating instantaneous sound pressure in the ear canal to instantaneous receptor current through the outer hair cells (OHCs) is determined from the distorted microphonic waveform generated in the extracellular fluid near the hair cells, assuming a first-order Boltzmann activation curve. Previously, the analysis was done in real time using custom-built electronic circuitry. Here, the same task is performed numerically using virtual instrument software (National Instruments LabVIEW 4.1) running on a personal computer. The assumed theoretical function describing the CM waveform is Vcm = Voff + Vsat/[1 + exp[(Eo+Z.Po.sin(2pi f + phi(tot)))/kT

    Patuzzi, R B; O'Beirne, G A

    1999-07-01

    443

    A time-domain photonic arbitrary waveform generator.  

    PubMed

    A time domain photonic arbitrary waveform generator (PAWG) scheme based on multi-wavelength optical differential quadrature phase shift keying modulation in combination with differential detection is proposed and experimentally demonstrated. The time domain method shows advantages of large time-bandwidth product, good flexibility, fast waveform refreshing rate, and high waveform quality over the frequency domain method. In contrast with other proposed time domain PAWGs or photonic digital-to-analog converters, our PAWG proposal shows a greater dynamic range and a larger noise margin due to its bipolar output, and possesses good scalabilities both in resolution and sampling rate. Assisted with the integration technology, this PAWG presents a good prospect for broad range practical applications in future. PMID:22714250

    Liao, Jinxin; Wen, He; Zheng, Xiaoping; Zhang, Hanyi; Zhou, Bingkun

    2012-05-21

    444

    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

    2012-06-01

    445

    Stimulator with arbitrary waveform for auditory evoked potentials  

    NASA Astrophysics Data System (ADS)

    The technological improvement helps many medical areas. The audiometric exams involving the auditory evoked potentials can make better diagnoses of auditory disorders. This paper proposes the development of a stimulator based on Digital Signal Processor. This stimulator is the first step of an auditory evoked potential system based on the ADSP-BF533 EZ KIT LITE (Analog Devices Company - USA). The stimulator can generate arbitrary waveform like Sine Waves, Modulated Amplitude, Pulses, Bursts and Pips. The waveforms are generated through a graphical interface programmed in C++ in which the user can define the parameters of the waveform. Furthermore, the user can set the exam parameters as number of stimuli, time with stimulation (Time ON) and time without stimulus (Time OFF). In future works will be implemented another parts of the system that includes the acquirement of electroencephalogram and signal processing to estimate and analyze the evoked potential.

    Martins, H. R.; Romo, M.; Plcido, D.; Provenzano, F.; Tierra-Criollo, C. J.

    2007-11-01

    446

    Genetic waveform modeling for the crustal structure in Northeast Japan  

    NASA Astrophysics Data System (ADS)

    We propose a genetic algorithm (GA) search procedure for waveform modeling of local crustal earthquakes for optimal one-dimensional (1-D) crustal velocity model. Both waveforms and travel-time data are used for the structure determination. The use of travel times in model evaluation improves the waveform modeling performance in the sense of computation speed and accuracy. We applied this method to broadband waveforms of a local crustal earthquake (M 4.2) in Northeast Japan. P-wave velocities of the crustal model are found to be 4.95 0.30, 5.9 0.02, and 6.51 0.20 km/s for a surface layer, upper crust and lower crust, respectively. The surface layer thickness and the Conrad and Moho depths are found to be 3.01 0.8, 17.77 0.4 and 34.59 1.0 km, respectively. For epicentral distances <200 km, our synthetic waveforms match the observed ones generally well. Early arrivals are mainly observed at stations near the Pacific coast in the forearc area having a thinner crust. In contrast, delayed arrivals appear at stations near the volcanic front and back-arc areas where low-velocity anomalies exist due to the effect of the Pacific slab dehydration and the hot upwelling flows in the mantle wedge. In general, our results agree well with the main tectonic setting of the study area, which confirms the reliability of the proposed approach. Despite a 1-D velocity model is too simple to represent the complex crustal structure, it is still required for the conventional routine analysis of seismology, such as earthquake location and source parameter studies. The current approach is considered as a step toward the genetic full waveform modeling for the 3-D velocity model estimation.

    Abdelwahed, Mohamed F.; Zhao, Dapeng

    2014-08-01

    447

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

    NASA Astrophysics Data System (ADS)

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

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

    2012-12-01

    448

    Experimental investigation of superfocusing of plasmonic lens with chirped circular nanoslits.  

    PubMed

    A plasmonic lens with metallic chirped circular nanoslits corrugated on Au film supported on quartz substrate for the purpose of superfocusing was put forth and fabricated by means of focused ion beam direct milling technique. Topography of the lens was imaged using an atomic force microscope. After that a near-field scanning optical microscope was employed for optical characterization of focusing performance of the lens. Our experimental results verify the focusing performance and further demonstrate that they are in agreement with the theoretical calculation results. Focusing performance is significantly improved in comparison to that of the non-chirped lens. The lenses are possible to be used for the applications of bioimaging, detection, and inspection in submicron scale resolution. PMID:20389353

    Fu, Yongqi; Liu, Yu; Zhou, Xiuli; Xu, Zongwei; Fang, Fengzhou

    2010-02-15

    449

    Single sub-50-attosecond pulse generation from chirp-compensated harmonic radiation using material dispersion  

    SciTech Connect

    A method for obtaining a single sub-50-attosecond pulse using harmonic radiation is proposed. For the generation of broad harmonic radiation during a single half-optical cycle, atoms are driven by a femtosecond laser pulse with intensity above the saturation intensity for optical field ionization and hence experience a large nonadiabatic increase of the laser electric field between optical cycles. Although the chirped structure of the harmonic radiation imposes a limit on the minimum achievable pulse duration, we demonstrate that its positive chirp can be compensated by the negative group delay dispersion of an appropriately selected x-ray filter material, used also for the spectral selection, resulting in a single attosecond pulse with a duration less than 50 as.

    Kim, Kyung Taec; Kim, Chul Min; Umesh, G.; Nam, Chang Hee [Department of Physics and Coherent X-ray Research Center, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea, Republic of); Baik, Moon-Gu [Department of Physics, Kyungwon University, Seongnam, Gyeonggi-do 461-701 (Korea, Republic of)

    2004-05-01

    450

    Chirped-pulse oscillators: a route to high-power femtosecond pulses without external amplification.  

    PubMed

    We demonstrate a Kerr-lens mode-locked Ti:sapphire oscillator that generates 130-nJ, 26-fs and 220-nJ, 30-fs pulses at a repetition rate of 11 MHz. The generation of stable broadband, high-energy pulses from an extended-cavity oscillator is achieved by the use of chirped multilayer mirrors to produce a small net positive dispersion over a broad spectral range. The resultant chirped picosecond pulses are compressed by a dispersive delay line that is external to the laser cavity. The demonstrated peak powers, in excess of 5 MW, are to our knowledge the highest ever achieved from a cw-pumped laser and are expected to be scalable to tens of megawatts by an increase in the pump power and (or) a decrease in the repetition rate. The demonstrated source permits micromachining of any materials under relaxed focusing conditions. PMID:15233437

    Fernandez, A; Fuji, T; Poppe, A; Frbach, A; Krausz, F; Apolonski, A

    2004-06-15

    451

    Ultrashort electron bunch generation by an energy chirping cell attached rf gun  

    NASA Astrophysics Data System (ADS)

    We present a new design for a rf electron gun to be used in ultrashort (1 ps) electron bunch generation. Using both simulation and measurement we evaluated the principle of this new type rf gun and were able to confirm an ultrashort bunch generation. During simulation, a bunch length of less than 100 fs(rms) with a 100 pC/bunch charge was confirmed at the optimum operating condition. The principle is to produce a linearly distributed longitudinal phase space by using an attached output cell specially designed for energy chirping. Such phase space distribution can be rotated by the velocity difference in the bunch. We already fabricated an energy chirping cell attached rf gun and successfully observed 0.2 THz coherent synchrotron radiation, which corresponds to less than 500 fs bunch. Such an electron gun can be used as a compact THz light source and a new electron injector with an ultrashort bunch.

    Sakaue, K.; Koshiba, Y.; Mizugaki, M.; Washio, M.; Takatomi, T.; Urakawa, J.; Kuroda, R.

    2014-02-01

    452

    Method for tuning chirp ratio of fiber gratings without central wavelength shift  

    NASA Astrophysics Data System (ADS)

    A method for tuning the chirp ratio of a fiber grating without the central wavelength shift is proposed by using a two-fixed-end compressive beam, which induces a linear strain distribution along the grating. This technique allows dynamic control of the grating's chirp ratio by changing the displacement of the translation stage. The 3-dB bandwidth tuning range is from 6.52 to 13.5 nm when the grating is tuned in the broadening way, while the bandwidth tuning range is from 6.52 to 0.95 nm in the compressing way. The proposed method has potential applications for the dynamic dispersion compensation and the sensors of pressure and displacement, etc., by detecting the change of bandwidth information.

    Liu, Guanxiu; Feng, Dejun; Zhang, Maosen; Jia, Dongfang

    2014-12-01

    453

    Analysis of Pump-Induced Temporal Contrast Degradation in Optical Parametric Chirped-Pulse Amplification  

    SciTech Connect

    The pump-induced degradation of the temporal contrast of laser pulses amplified by optical parametric chirped-pulse amplification (OPCPA) is studied analytically. In OPCPA systems, the temporal fluctuations of the pump pulse are coupled to the spectrum of the chirped signal by the instantaneous parametric gain and lead to a reduction in the temporal contrast of the recompressed amplified signal. The intensity and shape of the induced temporal pedestal depend on the pump fluctuations and the parametric amplifier operating regime. General equations describing the contrast degradation are derived and applied to the case of sinusoidal pump-intensity modulation and pump amplified spontaneous emission. The reduction of the contrast in the amplified pulse is quantified analytically and via simulations for an OPCPA system.

    Dorrer, C,

    2007-12-12

    454

    Resonant nonlinearity in high-energy Er3+-fiber chirped-pulse-amplifiers  

    NASA Astrophysics Data System (ADS)

    We present experimental results, which show that the up-chirp of dispersively stretched femtosecond pulses decreases linearly with increasing pulse energy after amplification in Erbium-doped fibers. For 6 ?J output pulses a nonlinear dispersion of -4?106 fs? was measured. This nonlinear dispersive effect is attributable to the resonant dispersion of the Erbium-ions and the decrease of the inversion during pulse amplification and was about one order of magnitude larger than predicted by the literature. Most likely this deviation is attributable to the complex population dynamics of the Er3+-ions during pulse amplification, since in the literature the relation between the refractive index and Er3+-inversion was described for a quasi-static population distribution. Due to the high resonant dispersion the required compressor dispersion for minimum output pulse duration depends strongly on the output pulse energy in Erbium-doped fiber-based chirped-pulse-amplifier set-ups.

    Adel, P.; Engelbrecht, M.; Wandt, D.; Fallnich, C.

    2005-12-01

    455

    All optical quantum storage based on spatial chirp of the control field  

    E-print Network

    We suggest an all-optical quantum memory scheme which is based on the off-resonant Raman interaction of a signal quantum field and a strong control field in a three-level atomic medium in the case, when the control field has a spatially varying frequency across the beam, called a spatial chirp. We show that the effect of such a spatial chirp is analogous to the effect of a controllable reversible inhomogeneous broadening (CRIB) of the atomic transition used in the gradient echo memory (GEM) scheme. However, the proposed scheme does not require temporal modulation of the control field or the atomic levels, and can be realized without additional electric or magnetic fields. It means that materials demonstrating neither linear Stark nor Zeeman effects can be used and/or materials which are placed in specific external fields remain undisturbed.

    Xiwen Zhang; Alexey Kalachev; Olga Kocharovskaya

    2014-07-10

    456

    All-optical quantum storage based on spatial chirp of the control field  

    NASA Astrophysics Data System (ADS)

    We suggest an all-optical quantum memory scheme which is based on the off-resonant Raman interaction of a signal quantum field and a strong control field in a three-level atomic medium in the case where the control field has a spatially varying frequency across the beam, called a spatial chirp. We show that the effect of such a spatial chirp is analogous to the effect of a controllable reversible inhomogeneous broadening of the atomic transition used in the gradient echo memory scheme. The proposed scheme does not require temporal modulation of the control field or the atomic levels and can be realized without additional electric or magnetic fields. This means that materials demonstrating neither linear Stark nor Zeeman effects can be used and/or materials which are placed in specific external fields remain undisturbed.

    Zhang, Xiwen; Kalachev, Alexey; Kocharovskaya, Olga

    2014-11-01

    457

    Frequency chirp and pulse shape effects in self-modulated laser wakefield accelerators  

    SciTech Connect

    The effect of asymmetric laser pulses on plasma wave excitation in a self-modulated laser wakefield accelerator is examined. Laser pulse shape and frequency chirp asymmetries, controlled experimentally in the laser system through a grating pair compressor, are shown to strongly enhance measured electron yields for certain asymmetries. It is shown analytically that a positive (negative) frequency chirp enhances (suppresses) the growth rate of the Raman forward scattering and near-forward Raman sidescatter instabilities, but is of minimal importance for the experimental parameters. Temporal laser pulse shapes with fast rise times (< plasma period) are shown to generate larger wakes (compared to slow rise time pulses) which seed the growth of the plasma wave, resulting in enhanced electron yield.

    Schroeder, C.B.; Esarey, E.; Geddes, C.G.R.; Toth, Cs.; Shadwick, B.A.; van Tilborg, J.; Faure, J.; Leemans, W.P.

    2002-11-07

    458

    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. PMID:20329836

    Aaronson, Neil L.; Hartmann, William M.

    2010-01-01

    459

    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

    460

    Flagellar waveform dynamics of freely swimming algal cells  

    NASA Astrophysics Data System (ADS)

    We present quantitative measurements of time-dependent flagellar waveforms for freely swimming biflagellated algal cells, for both synchronous and asynchronous beating. We use the waveforms in conjunction with resistive force theory as well as a singularity method to predict a cell's time-dependent velocity for comparison with experiments. While net propulsion is thought to arise from asymmetry between the power and recovery strokes, we show that hydrodynamic interactions between the flagella and cell body on the return stroke make an important contribution to enhance net forward motion.

    Kurtuldu, H.; Tam, D.; Hosoi, A. E.; Johnson, K. A.; Gollub, J. P.

    2013-07-01

    461

    Investigation of the high-temporal contrast seed pulse amplification in optical parametric chirped pulse amplifier  

    NASA Astrophysics Data System (ADS)

    We theoretically and experimentally investigate the amplification of a high-temporal contrast seed pulse in an optical parametric chirped pulse amplifier. The amplified and compressed signal pulse contrast can be improved by using large seed pulse energies. And the theory model is modified for considering the seed pulse contrast and compressed pulse duration. From the modified model the calculated results agree with the experimental results better.

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

    2015-01-01

    462

    New stretcher scheme for a parametric amplifier of chirped pulses with frequency conversion  

    SciTech Connect

    The properties of hybrid prism-grating dispersion systems are studied. The scheme of a prism-grating stretcher matched to a standard compressor in the phase dispersion up to the fourth order inclusive is developed for a petawatt laser complex based on the optical parametric chirped-pulse amplification. The stretcher was used to obtain the {approx}200-TW peak power of laser radiation. (control of laser radiation parameters)

    Freidman, Gennadii I; Yakovlev, I V [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

    2007-02-28

    463

    Chirp (27 kHz) echo characters in the Ulleung Basin  

    Microsoft Academic Search

    High-resolution (Chirp, 27 kHz) reflection profiles in the Ulleung Basin (3537N) made it possible to classify the uppermost\\u000a (ca. 5070 m thick) sedimentary sequence into eleven discrete echo types. They are either (1) distinct (Echo Types IA, IB,\\u000a IC, ID, IE, and IF), (2) indistinct (Echo Types IIA, IIB, and IIC), (3) hyperbolic (Echo Type III), or (4) combined (Echo

    S. K. Chough; S. H. Lee; J. W. Kim; S. C. Park; D. G. Yoo; H. S. Han; S. H. Yoon; S. B. Oh; Y. B. Kim; G. G. Back

    1997-01-01

    464

    Diode-pumped chirped pulse amplification to the TW level using Yb:CaF2  

    NASA Astrophysics Data System (ADS)

    We present a terawatt diode-pumped chirped pulse amplifier using single-crystalline Yb:CaF2 as the gain medium. A maximum pulse energy of 420 mJ and a repetition rate of 1 Hz was obtained. After recompression, a pulse energy of 197 mJ and a pulse duration of 192 fs were achieved, corresponding to a peak power of 1 TW.

    Siebold, M.; Hornung, M.; Hein, J.; Uecker, R.; Debus, A.; Kaluza, M. C.

    2010-02-01

    465

    Application of SPICE simulation to study WDM and SCM systems using EDFAs with chirping  

    Microsoft Academic Search

    The authors have proposed an equivalent electrical circuit model of erbium-doped fiber amplifiers (EDFAs), including the chirping effect for teaching or studying the distortions and performance of lightwave transmission systems. Through the aid of a SPICE circuit simulator, its validity is demonstrated by analyzing the cross modulations of an eight-channel wavelength division multiplexing system. The intermodulations in an amplitude modulation-subcarrier

    Jau-Ji Jou; Cheng-Kuang Liu

    2002-01-01

    466

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

    NASA Astrophysics Data System (ADS)

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

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

    2014-10-01

    467

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

    Microsoft Academic Search

    The goal of this LDRD ER was to develop a robust and reliable technology to seed high-energy laser systems with chirped pulses that can be amplified to kilo-Joule energies and recompressed to sub-picosecond pulse widths creating extremely high peak powers suitable for petawatt class physics experiments. This LDRD project focused on the development of optical fiber laser technologies compatible with

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

    2009-01-01

    468

    Long-term carrier-envelope phase stability from a grating-based, chirped pulse amplifier.  

    PubMed

    We demonstrate a carrier-envelope phase (CEP) stabilized, chirped pulse laser amplifier that exhibits greatly improved intrinsic long-term CEP stability compared with that of other amplifiers. This system employs a grating-based stretcher and compressor and a cryogenically cooled laser amplifier. Single-shot carrier envelope phase noise measurements are also presented that avoid underestimation of this parameter caused by fringe averaging and represent a rigorously accurate upper limit on CEP noise. PMID:16729097

    Gagnon, Etienne; Thomann, Isabell; Paul, Ariel; Lytle, Amy L; Backus, Sterling; Murnane, Margaret M; Kapteyn, Henry C; Sandhu, Arvinder S

    2006-06-15

    469

    Tunable optical delay line in SOI implemented with step chirped Bragg gratings and serial grating arrays  

    NASA Astrophysics Data System (ADS)

    Tunable optical delay devices have numerous applications in optical communications [1] and have been successfully implemented using slow light elements and fiber or waveguide gratings. There has been considerable interest in siliconon- insulator (SOI) as a technology platform for compact integration of optical signal processing systems. SOI-based delay lines have been realized using coupled ring resonators [2], photonic crystals [3], and various Bragg grating-based configurations including single or coupled chirped sidewall gratings [4,5] as well as tapered rib waveguide gratings [6]. By linearly chirping the period in sidewall gratings, relatively small delays (a few ps) over a bandwidth of tens of nm were demonstrated [4]; with tapered waveguides, significantly larger delays (300-500 ps) were obtained, albeit over a narrower bandwidth (< 2 nm) [6]. On the other hand, some signal processing applications may require large delays (e.g., tens to hundreds of ps) over large bandwidths (several to tens of nm). Several designs have been proposed to meet these requirements, e.g., a step-chirped rib waveguide grating providing 50 ps delay over 15 nm [7] or complementary apodized sidewall gratings providing up to 275 ps over 3 nm [8], however, they have not been realized experimentally. In this paper, we demonstrate discretely tunable optical delay lines that provide tens of ps delay (up to 65 ps) in steps of 15-32 ps over bandwidths of several tens of nm (35-70 nm). The devices are fabricated on SOI using electron beam lithography and implemented through two different approaches: serial sidewall Bragg grating arrays and the step-chirped sidewall Bragg gratings.

    Spasojevic, Mina; Chen, Lawrence R.

    2013-10-01

    470

    Chirped pulses sum frequency generation for deep-UV picosecond pulse shaping  

    NASA Astrophysics Data System (ADS)

    We show by experiments and simulations that properly chirped laser pulses enable efficient and broadband sum frequency generation in nonlinear crystals. We achieved high energy, picosecond deep-UV pulses with spectral width one order of magnitude greater than the acceptance bandwidth of the nonlinear interaction. The broad spectrum supports shaping of ps flat-top deep-UV pulses with short rise- and fall-time, which are optimal for driving high brightness photocathode electron guns.

    Vicario, Carlo; Trisorio, Alexandre; Arisholm, Gunnar; Hauri, Christoph P.

    2012-03-01

    471

    Characterization of the dispersion of chirped fiber Bragg grating through Fourier transform spectrometry method  

    Microsoft Academic Search

    Introduces a Fourier transform spectrometric method for the precise characterization of dispersion of chirped FBGs(fiber Bragg grating). The measurement system is a fiber Michelson interferometer composed of a broadband EDFA (Erium doped fiber amplifier) light source, a 3db 22 fiber coupler, a pair of polarization controllers, a optical attenuator, a fiber filter, an O\\/E converter, A\\/D converter, computer and a

    Qingshan Chen; Naiguang Lu; Feng Jiang

    2008-01-01

    472

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

    Microsoft Academic Search

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

    Zhiping Jiang; X.-C. Zhang

    1998-01-01

    473

    Performance scaling via passive pulse shaping in cavity-enhanced optical parametric chirped-pulse amplification.  

    PubMed

    We show that an enhancement cavity seeded at the full repetition rate of the pump laser can automatically reshape small-signal gain across the interacting pulses in an optical parametric chirped-pulse amplifier for close-to-optimal operation, significantly increasing both the gain bandwidth and the conversion efficiency, in addition to boosting gain for high-repetition-rate amplification. Applied to a degenerate amplifier, the technique can provide an octave-spanning gain bandwidth. PMID:20548342

    Siddiqui, Aleem M; Moses, Jeffrey; Hong, Kyung-Han; Lai, Chien-Jen; Krtner, Franz X

    2010-06-15

    474

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

    NASA Astrophysics Data System (ADS)

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

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

    2014-11-01

    475

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

    Microsoft Academic Search

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

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

    2006-01-01

    476

    Multiple slow waves and relevant transverse transmission and confinement in chirped photonic crystals.  

    PubMed

    The dispersion properties of rod-type chirped photonic crystals (PhCs) and non-channeled transmission in the direction of the variation of structural parameters from one cell of such a PhC to another are studied. Two types of configurations that enable multiple slow waves but differ in the utilized chirping scheme are compared. It is demonstrated that the multiple, nearly flat bands with a group index of refraction exceeding 180 can be obtained. For these bands, transmission is characterized by multiple narrow peaks of perfect transmission, strong field enhancement inside the slab, and large values of the Q-factor. Among the bands, there are some that show negative phase velocity. Symmetry with respect to the slab mid-plane must be kept in order to obtain constructive interferences that are necessary for reflection-free transmission. It is shown that 15 and more slow wave bands can be obtained in one configuration. The corresponding transmission peaks are well separated from each other, being the only significant feature of the transmission spectrum, while the Q-factor can exceed 10?. The observed features are preserved in a wide range of the incidence angle variation. They can be used for tuning the locations and spectral widths of the transmission peaks. Some comparisons with the chirped multilayer structures have been carried out. PMID:25321556

    Serebryannikov, Andriy E; Cakmak, A Ozgur; Colak, Evrim; Caglayan, Humeyra; Kurt, Hamza; Ozbay, Ekmel

    2014-09-01

    477

    Highly depth-resolved chirped pulse photothermal radar for bone diagnostics  

    NASA Astrophysics Data System (ADS)

    A novel chirped pulse photothermal (PT) radiometric radar with improved sensitivity over the conventional harmonically modulated thermal-wave radar technique and alternative pulsed laser photothermal radiometry is introduced for the diagnosis of biological samples, especially bones with tissue and skin overlayers. The constraints imposed by the laser safety (maximum permissible exposure) ceiling on pump laser energy and the strong attenuation of thermal-wave signals in tissues significantly limit the photothermally active depth in most biological specimens to a level which is normally insufficient for practical applications (a few mm below the skin surface). A theoretical approach for improvement of signal-to-noise ratio (SNR), minimizing the static (dc) component of the photothermal signal and making use of the photothermal radiometric nonlinearity has been introduced and verified by comparing the SNR of four distinct excitation wave forms (sine-wave, square-wave, constant-width and constant duty-cycle pulses) for chirping the pump laser, under constant exposure energy. At low frequencies fixed-pulsewidth chirps of large peak power were found to be superior to all other equal-energy modalities, with an SNR improvement up to two orders of magnitude. Distinct thickness-dependent characteristic delay times in a goat bone were obtained, establishing an active depth resolution range of 2.8 mm in a layered skin-fat-bone structure, a favorable result compared to the maximum reported pulsed photothermal radiometric depth resolution <1 mm in turbid biological media.

    Kaiplavil, Sreekumar; Mandelis, Andreas

    2011-07-01

    478

    Highly depth-resolved chirped pulse photothermal radar for bone diagnostics.  

    PubMed

    A novel chirped pulse photothermal (PT) radiometric radar with improved sensitivity over the conventional harmonically modulated thermal-wave radar technique and alternative pulsed laser photothermal radiometry is introduced for the diagnosis of biological samples, especially bones with tissue and skin overlayers. The constraints imposed by the laser safety (maximum permissible exposure) ceiling on pump laser energy and the strong attenuation of thermal-wave signals in tissues significantly limit the photothermally active depth in most biological specimens to a level which is normally insufficient for practical applications (a few mm below the skin surface). A theoretical approach for improvement of signal-to-noise ratio (SNR), minimizing the static (dc) component of the photothermal signal and making use of the photothermal radiometric nonlinearity has been introduced and verified by comparing the SNR of four distinct excitation wave forms (sine-wave, square-wave, constant-width and constant duty-cycle pulses) for chirping the pump laser, under constant exposure energy. At low frequencies fixed-pulsewidth chirps of large peak power were found to be superior to all other equal-energy modalities, with an SNR improvement up to two orders of magnitude. Distinct thickness-dependent characteristic delay times in a goat bone were obtained, establishing an active depth resolution range of ~2.8 mm in a layered skin-fat-bone structure, a favorable result compared to the maximum reported pulsed photothermal radiometric depth resolution <1 mm in turbid biological media. PMID:21806220

    Kaiplavil, Sreekumar; Mandelis, Andreas

    2011-07-01

    479

    Temporal and spectral characterization of femtosecond deep-UV chirped pulses  

    NASA Astrophysics Data System (ADS)

    In contrast to the case of pulses in the infrared (IR) and visible range, the temporal characterization of deep-UV femtosecond pulses in combination with their spectral features is still a challenge, essentially due to the lack of suitable nonlinear crystals for second harmonic autocorrelation. Here we report on the characterization of 260?nm, nearly 200?fs pulses, based on two photon absorption in fused silica. 260?nm pulses are obtained as the fourth harmonic component of a near-IR fundamental which is frequency up-converted into a double beta barium borate-based harmonic generator stage. By comparing the obtained pulse duration with its Fourier limit, estimated by measuring pulse spectra, a consistent pulse chirp is retrieved. This chirp is mostly attributed to the considerable group-velocity dispersion occurring in the last doubling stage which converts the green into UV radiation. Additionally, the spectral width of the probe pulse through the fused silica window turns out to be modulated as a function of the time delay between pump and probe in the two-photon absorption setup. The observed modulation is attributed to the interplay between spectrally selective absorption, due to the chirp of the pulses, and moderate self-phase modulation just occurring at the top of the temporal autocorrelation between pump and probe.

    Valadan, Mohammadhassan; DAmbrosio, Davide; Gesuele, Felice; Velotta, Raffaele; Altucci, Carlo

    2015-02-01

    480

    Chirped-pulse four-wave Raman mixing in molecular hydrogen  

    NASA Astrophysics Data System (ADS)

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

    Shitamichi, Osamu; Kida, Yuichiro; Imasaka, Totaro

    2014-07-01

    481

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

    SciTech Connect

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

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

    2009-11-12

    482

    Trends in ultrashort and ultrahigh power laser pulses based on optical parametric chirped pulse amplification  

    NASA Astrophysics Data System (ADS)

    Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification (OPCPA) became the most promising method for the amplification of broadband optical pulses. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level. Meanwhile, the output pulse duration based on optical parametric amplification has entered the range of few-optical-cycle field. In this paper, we overview the basic principles, trends in development, and current state of the ultrashort and laser systems based on OPCPA, respectively. Project supported by the National Natural Science Foundation of China (Grant Nos. 61378030 and 11127901), the National Basic Research Program of China(Grant No. 2011CB808101), and the International S&T Cooperation Program of China (Grant No. 2011DFA11300).

    Xu, Lu; Yu, Liang-Hong; Chu, Yu-Xi; Gan, Ze-Biao; Liang, Xiao-Yan; Li, Ru-Xin; Xu, Zhi-Zhan

    2015-01-01

    483

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

    PubMed

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

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

    2014-10-01

    484

    .~ Saw-Tooth Lag Smoother with an Application to FM Demodulation. Laurence Irlicht,Vi Krishnanmrthy, J.B. Moore *  

    E-print Network

    .~ Saw-Tooth Lag Smoother with an Application to FM Demodulation. Laurence Irlicht,Vi Krishnanmrthy filter context, namely FM demodulation. The algorithm provides perfor- mance comparable to a fixed lag

    Moore, John Barratt

    485

    Absolute interferometric distance measurement using a FM-demodulation technique  

    NASA Astrophysics Data System (ADS)

    We propose an interferometric method for measuring absolute distances larger than the wavelength. A laser diode is used as a light source. The principle of operation is based on multiple-wavelength interferometry that uses a modulated light source. This method uses the fact that the wavelength of light emitted by the laser diode can be varied by means of the injection current. The modulation of the injection current in combination with the optical heterodyne technique causes a high-frequency phase-modulated detector signal. The phase deviation of the signal is a measure of the optical path difference in the interferometer. By FM demodulation of the detector output with a phase-locked loop demodulator, the optical path difference can be determined directly without the classical ambiguity problem of interferometry. The measuring range in the experiments was limited to 50 mm by the maximum travel range of the used specimen translation stage. Because of the inherent light sensitivity of the method described, the rangefinder can be used for three-dimensional profile measurements on a wide variety of objects, even on diffuse scattering surfaces.

    Fischer, Edgar; Dalhoff, Ernst; Heim, Silke; Hofbauer, Ulrich; Tiziani, Hans J.

    1995-09-01

    486

    Absolute interferometric distance measurement using a FM-demodulation technique.  

    PubMed

    We propose an interferometric method for measuring absolute distances larger than the wavelength. A laser diode is used as a light source. The principle of operation is based on multiple-wavelength interferometry that uses a modulated light source. This method uses the fact that the wavelength of light emitted by the laser diode can be varied by means of the injection current. The modulation of the injection current in combination with the optical heterodyne technique causes a high-frequency phase-modulated detector signal. The phase deviation of the signal is a measure of the optical path difference in the interferometer. By FM demodulation of the detector output with a phase-locked loop demodulator, the optical path difference can be determined directly without the classical ambiguity problem of interferometry. The measuring range in the experiments was limited to 50 mm by the maximum travel range of the used specimen translation stage. Because of the inherent light sensitivity of the method described, the rangefinder can be used for three-dimensional profile measurements on a wide variety of objects, even on diffuse scattering surfaces. PMID:21060384

    Fischer, E; Dalhoff, E; Heim, S; Hofbauer, U; Tiziani, H J

    1995-09-01

    487

    Experimental point spread function of fm pulse imaging scheme.  

    PubMed

    In this paper, we have examined the possibility of incorporating pulse compression techniques into a conventional medical B-scan imaging scheme. Linear frequency modulation fm, one form of pulse coding among many others, has been used in this study. With this approach, one can overcome current peak intensity limitations. A theoretical framework that includes medium propagation effects, transducer bandwidth and diffraction effects is presented, which could be used to examine the system point spread function under this imaging scheme. A prototype experimental set-up and signal processing are described and used for simple imaging tasks in attenuating and nonattenuating media. Analysis of the experimental point spread functions shows that resolution similar to conventional short pulse imaging can be achieved. However, the existence of large range side lobe levels usually associated with pulse compression processing can degrade contrast resolution in medical ultrasound. We have considered various different factors that can affect the range side lobe levels and examined their effect either experimentally or through simulations. The technique has the potential for improving signal-to-noise ratio (SNR), maximum penetration depth and resolution without exceeding peak intensity limitations. Some possible applications are discussed that merit further evaluation. Our work demonstrates the feasibility of this technique and presents a theoretical framework that can be used in future studies aimed at evaluating image quality, system performance, and possible artifacts under such an imaging scheme. PMID:7571207

    Rao, N A; Mehra, S; Bridges, J; Venkatraman, S

    1995-04-01

    488

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

    NASA Astrophysics Data System (ADS)

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

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

    2013-12-01

    489

    Syntax processing by auditory cortical neurons in the FM-FM area of the mustached bat Karl-Heinz Esser, Curtis J. Condon, Nobuo Suga, and Jagmeet S. Kanwal  

    E-print Network

    parnellii Syntax processing by auditory cortical neurons in the FM-FM area of the mustached bat, see: Reprints www.pnas.org/misc/reprints.shtml To order reprints, see: Notes: #12;Proc. Natl. Acad neurons in the FM­FM area of the mustached bat Pteronotus parnellii (nonspeech signals communication calls

    Allen, Jont

    490

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

    PubMed Central

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