Science.gov

Sample records for fm chirp waveforms

  1. Generating nonlinear FM chirp waveforms for radar.

    SciTech Connect

    Doerry, Armin Walter

    2006-09-01

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

  2. SAR processing with non-linear FM chirp waveforms.

    SciTech Connect

    Doerry, Armin Walter

    2006-12-01

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

  3. Multiplexed chirp waveform synthesizer

    DOEpatents

    Dudley, Peter A.; Tise, Bert L.

    2003-09-02

    A synthesizer for generating a desired chirp signal has M parallel channels, where M is an integer greater than 1, each channel including a chirp waveform synthesizer generating at an output a portion of a digital representation of the desired chirp signal; and a multiplexer for multiplexing the M outputs to create a digital representation of the desired chirp signal. Preferably, each channel receives input information that is a function of information representing the desired chirp signal.

  4. Coherent ladar imaging of the SEASAT satellite retro-reflector array using linear-FM chirp waveforms and pulse-compression

    NASA Astrophysics Data System (ADS)

    Youmans, Douglas G.

    2007-04-01

    Coherent ladar imaging of satellite retro-reflector arrays is analyzed to determine some of the potential capabilities of coherent ladar systems for long range imaging. The satellites are at mega-meters of slant range and are basically angularly unresolved assuming a nominal one meter telescope used at a laser wavelength of 1.064 μm corresponding to a 281,625 GHz center-frequency. A coherent ladar may have a selectable waveform ranging from single nanosecond pulses through tone-pulses, but the imaging waveform considered here is the linear-FM chirp pulse-compression ladar waveform, which consists of a series of frequency chirps over a long period of time. The linear-FM chirp return is pulse compressed digitally using several possible approaches. Image reconstruction follows basic ISAR algorithms in forming a "range-resolved Doppler and intensity" (RRDI) image. A retro-reflector ring on the SEASAT satellite is used to illustrate the ladar's capability, although we spin the satellite faster than the true rotation rate to demonstrate waveform resolution. Several other useful algorithms as (multi-chirp) range-time-intensity (RTI matrix) range-bin summation and segmented-spectrum frequency-bin summation are also discussed. A covariance matrix calculation is applied to the RTI matrix and also to the segmented-spectrum matrix for the extraction of additional target information.

  5. Pulse compression of an FM chirped CO(2) laser.

    PubMed

    Halmos, M J; Henderson, D M; Duvall Iii, R L

    1989-09-01

    A CO(2) laser has been FM chirp modulated by a CdTe intracavity modulator. A frequency deviation-of-100 MHz in 2 micros was attained in this fashion. Following heterodyne detection the chirped pulse was compressed to 15 ns using a surface acoustic wave compression filter. This corresponded to a compression factor of 130. The suppression of unwanted sidelobes with a weighting filter was demonstrated. We have explored the use of this technique for laser radar systems and described an electrooptically FM modulated CO(2) waveguide laser with postdetection pulse compression by a surface acoustic wave compressive filter. To our knowledge this is the first report of the successful operation of this important system. PMID:20555743

  6. Short-range harmonic radar: chirp waveform, electronic targets

    NASA Astrophysics Data System (ADS)

    Mazzaro, Gregory J.; Gallagher, Kyle A.; Martone, Anthony F.; Sherbondy, Kelly D.; Narayanan, Ram M.

    2015-05-01

    Radio-frequency (RF) electronic targets, such as man-portable electronics, cannot be detected by traditional linear radar because the radar cross section of those targets is much smaller than that of nearby clutter. One technology that is capable of separating RF electronic targets from naturally-occurring clutter is nonlinear radar. Presented in this paper is the evolution of nonlinear radar at the United States Army Research Laboratory (ARL) and recent results of short-range over-the-air harmonic radar tests there. For the present implementation of ARL's nonlinear radar, the transmit waveform is a chirp which sweeps one frequency at constant amplitude over an ultra-wide bandwidth (UWB). The receiver captures a single harmonic of this entire chirp. From the UWB received harmonic, a nonlinear frequency response of the radar environment is constructed. An inverse Fourier Transform of this nonlinear frequency response reveals the range to the nonlinear target within the environment. The chirped harmonic radar concept is validated experimentally using a wideband horn antenna and commercial off-the-shelf electronic targets.

  7. Generating nonlinear FM chirp radar signals by multiple integrations

    DOEpatents

    Doerry, Armin W.

    2011-02-01

    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.

  8. Photonic generation of low phase noise arbitrary chirped microwave waveforms with large time-bandwidth product.

    PubMed

    Xie, Weilin; Xia, Zongyang; Zhou, Qian; Shi, Hongxiao; Dong, Yi; Hu, Weisheng

    2015-07-13

    We present a photonic approach for generating low phase noise, arbitrary chirped microwave waveforms based on heterodyne beating between high order correlated comb lines extracted from frequency-agile optical frequency comb. Using the dual heterodyne phase transfer scheme, extrinsic phase noises induced by the separate optical paths are efficiently suppressed by 42-dB at 1-Hz offset frequency. Linearly chirped microwave waveforms are achieved within 30-ms temporal duration, contributing to a large time-bandwidth product. The linearity measurement leads to less than 90 kHz RMS frequency error during the entire chirp duration, exhibiting excellent linearity for the microwave and sub-THz waveforms. The capability of generating arbitrary waveforms up to sub-THz band with flexible temporal duration, long repetition period, broad bandwidth, and large time-bandwidth product is investigated and discussed. PMID:26191866

  9. Ultrafast chirped optical waveform recorder using a time microscope

    DOEpatents

    Bennett, Corey Vincent

    2015-04-21

    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. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

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

    DOEpatents

    Bennett, Corey Vincent

    2011-11-22

    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.

  11. Ultrafast chirped optical waveform recording using referenced heterodyning and a time microscope

    DOEpatents

    Bennett, Corey Vincent

    2010-06-15

    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.

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

    SciTech Connect

    Bielek, T.P.

    1990-11-01

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

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

    PubMed

    Niebauer, T M

    2013-03-20

    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(θ), 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

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  15. SAR impulse response with residual chirps.

    SciTech Connect

    Doerry, Armin Walter

    2009-06-01

    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.

  16. 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...

  17. Complex heterodyne for undersampled chirped sinusoidal signals.

    PubMed

    Niebauer, T M; Schiel, A; van Westrum, D

    2006-11-10

    We describe a method for analyzing frequency-chirped sinusoidal signals using a complex heterodyne, sometimes also known as complex demodulation on the digitized waveform. This method allows one to use prior knowledge of the signal to reduce the effective bandwidth of the signal. The method can be used to extract a frequency-chirped signal even when it is sampled well below the Nyquist criterion. Accordingly, the method facilitates the use of less-expensive data acquisition and signal processing hardware than has traditionally been used for these applications. This technique is particularly useful for high-precision (parts in 10(9)) interferometer applications in which there exists a differential acceleration between the two arms (commonly found in absolute gravity meters or gradiometers). PMID:17068577

  18. Complex heterodyne for undersampled chirped sinusoidal signals

    NASA Astrophysics Data System (ADS)

    Niebauer, T. M.; Schiel, A.; van Westrum, D.

    2006-11-01

    We describe a method for analyzing frequency-chirped sinusoidal signals using a complex heterodyne, sometimes also known as complex demodulation on the digitized waveform. This method allows one to use prior knowledge of the signal to reduce the effective bandwidth of the signal. The method can be used to extract a frequency-chirped signal even when it is sampled well below the Nyquist criterion. Accordingly, the method facilitates the use of less-expensive data acquisition and signal processing hardware than has traditionally been used for these applications. This technique is particularly useful for high-precision (parts in 109) interferometer applications in which there exists a differential acceleration between the two arms (commonly found in absolute gravity meters or gradiometers).

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

    PubMed

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

    2012-11-01

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

  20. Carrier Modulation Via Waveform Probability Density Function

    NASA Technical Reports Server (NTRS)

    Williams, Glenn L.

    2006-01-01

    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.

  1. Carrier Modulation Via Waveform Probability Density Function

    NASA Technical Reports Server (NTRS)

    Williams, Glenn L.

    2004-01-01

    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.

  2. Excitation Waveform Design for Lamb Wave Pulse Compression.

    PubMed

    Lin, Jing; Hua, Jiadong; Zeng, Liang; Luo, Zhi

    2016-01-01

    Most ultrasonic guided wave methods focus on tone burst excitation to reduce the effect of dispersion so as to facilitate signal interpretation. However, the resolution of the output cannot attain a very high value because time duration of the excitation waveform cannot be very small. To overcome this limitation, a pulse compression technique is introduced to Lamb wave propagation to achieve a δ-like correlation so as to obtain a high resolution for inspection. Ideal δ-like correlation is impossible as only a finite frequency bandwidth can propagate. The primary purpose of this paper is to design a proper excitation waveform for Lamb wave pulse compression, which shortens the correlation as close as possible to a δ function. To achieve this purpose, the performance of some typical signals is discussed in pulse compression, which include linear chirp (L-Chirp) signal, nonlinear chirp (NL-Chirp) signal, Barker code (BC), and Golay complementary code (GCC). In addition, how the excitation frequency range influences inspection resolution is investigated. A strategy for the frequency range determination is established subsequently. Finally, an experiment is carried out on an aluminum plate where these typical signals are used as excitations at different frequency ranges. The quantitative comparisons of the pulse compression responses validate the theoretical findings. By utilizing the experimental data, the improvement of pulse compression in resolution compared with tone burst excitation is also validated, and the robustness of the waveform design method to inaccuracies in the dispersion compensation is discussed as well. PMID:26571520

  3. Moving target indication of FM-CW radar for clutter rejection

    NASA Astrophysics Data System (ADS)

    Yang, Jian-Yu; Huang, Shun-Ji

    The moving target indication technique of FM-CW radar with symmetric triangular waveform frequency-modulated transmitted signal is proposed in this paper. The derivation of this technique is presented, and a 35 GHz FM-CW radar with 500 MHz frequency sweep bandwidth is developed to realize this technique.

  4. Chirped-pulse terahertz spectroscopy for broadband trace gas sensing.

    PubMed

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

    2011-04-25

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

  5. Optimal time and frequency domain waveform design for target detection

    NASA Astrophysics Data System (ADS)

    Hamschin, Brandon; Loughlin, Patrick

    2010-04-01

    Some marine mammals as well as bats are known to emit sophisticated waveforms while searching for objects or hunting prey. Some dolphins have been observed to change their sonar pulse depending on the environment. Incorporating these strategies into sonar waveform and receiver design has become an active area of research. In this paper, we explore the application of an optimal waveform design scheme recently given by Kay, to the detection of elastic objects. We examine the benefits of optimal waveform design versus transmitting a linear FM waveform, as well as performance loss suffered by assuming a point target. The optimization approach designs the magnitude spectrum of the transmit waveform and, accordingly, there is an unlimited number of "optimal" transmit waveforms with the same magnitude spectrum. We propose a time domain optimization criterion to obtain the transmit waveform with the optimal magnitude spectrum and the smallest possible duration, as well as the waveform with the optimal magnitude spectrum and the longest possible duration. The former waveform allows for higher ping rates, but necessarily has higher time domain peak power, while the latter waveform has lower time domain peak power and lower ping rates. A method to obtain waveforms that are a blend of these two extremes is also presented, allowing a smooth trade-off between ping rate and peak power.

  6. Transionospheric chirp event classifier

    SciTech Connect

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

    1995-09-01

    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.

  7. Waveform design for detection of weapons based on signature exploitation

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  8. First results of a deep tow CHIRP sonar seafloor imaging system

    USGS Publications Warehouse

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

    1993-01-01

    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. 

  9. Frequency-chirped subwavelength nanoantennas.

    PubMed

    Yaacobi, Ami; Watts, Michael R

    2012-12-01

    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

  10. Generation of isolated sub-40-attosecond pulse with a multicycle chirped laser and a static electric field

    NASA Astrophysics Data System (ADS)

    Mohebbi, Masoud

    2016-02-01

    We numerically investigate the high-order harmonic generation and isolated attosecond pulse generation in a waveform that linearly produced by chirped laser pulse, chirp-free laser pulse, and static electric field. When a chirp-free laser pulse is added to the produced field of the chirped driving pulse and the static electric field, the plateau harmonic yield is enhanced by two orders. The spectral modulation is also significantly decreased, and the bandwidth of XUV spectrum is further broadened. An intense and a clean isolated 38-as pulse can be produced from the intense broadband XUV supercontinuum. After proper phase compensation, an isolated sub-8-attosecond pulse can be obtained. Furthermore, quantum time-frequency analysis reveals that the selection of the short quantum path can be achieved in this scheme.

  11. The IT Vision in FM.

    ERIC Educational Resources Information Center

    NeSmith, Jerry

    2002-01-01

    Provides a forward-looking vision, including goals, objectives, and principles, of information technology (IT) use within facilities management (FM). This vision includes the evolution of the FM/IT organization from an operational role to a strategic role--from an FM divisional role to an enterprise role. (EV)

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

    PubMed Central

    Karunakaran, Chandra P; Oelze, Michael L

    2013-01-01

    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

  13. Hybrid chirped pulse amplification system

    DOEpatents

    Barty, Christopher P.; Jovanovic, Igor

    2005-03-29

    A hybrid chirped pulse amplification system wherein a short-pulse oscillator generates an oscillator pulse. The oscillator pulse is stretched to produce a stretched oscillator seed pulse. A pump laser generates a pump laser pulse. The stretched oscillator seed pulse and the pump laser pulse are directed into an optical parametric amplifier producing an optical parametric amplifier output amplified signal pulse and an optical parametric amplifier output unconverted pump pulse. The optical parametric amplifier output amplified signal pulse and the optical parametric amplifier output laser pulse are directed into a laser amplifier producing a laser amplifier output pulse. The laser amplifier output pulse is compressed to produce a recompressed hybrid chirped pulse amplification pulse.

  14. Subcarrier placement in a PCM-FM-FM/FM modulation scheme

    NASA Astrophysics Data System (ADS)

    Moser, Juliette L.

    PCM-FM-FM/FM modulation scheme with pulse-code-modulated (PCM) signals and FM subcarrier modulated signals are described in terms of the interference power of the PCM signal that is passed by the subcarrier signals' bandpass filters. The effect of the interference power can be reduced when the subcarrier frequencies are chosen to coincide with the zero-crossing frequencies of the PCM signal. It will be shown that this choice results in a lower interference power than when the subcarrier frequencies come between the zero crossings. The PCM signal used in this study is of polar nonreturn-to-zero format.

  15. An MSK Radar Waveform

    NASA Technical Reports Server (NTRS)

    Quirk, Kevin J.; Srinivasan, Meera

    2012-01-01

    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.

  16. Prediction of downhole waveforms

    SciTech Connect

    Long, J.W.; Sabisch, K.A.; Stearns, S.D.; Vortman, L.J.

    1983-03-01

    A least-squares linear prediction method using an optimum finite impulse response filter was used to predict a downhole velocity waveform. A filter was determined from surface and downhole velocity waveforms from several underground nuclear test events at each of several locations. Separate filters were determined for vertical, radial, and tangential components. Filters for each component for several events were averaged. Then the measured surface velocity waveform for a different event was used with the filter to predict the downhole velocity waveform for that event. Then the predicted or simulated downhole waveform was compared with the downhole velocity waveform measured on that event. The coherence between the measured and predicted velocity waveforms was evaluated using a normalized mean squared error. The method was applied to velocity waveforms generated by test events on Pahute Mesa and in Yucca Flat. Coherence was generally better for the vertical component than for radial and tangential components. Coherence was good for the surface/downhole pair at the station in the Climax granite pluton. It was especially poor for the pair in Rainier Mesa and for Dome Mountain and Fortymile Canyon (not a true surface/downhole pair) where topographic effects affected the horizontal components. The Climax granite pluton was found to rotate in a north-south direction regardless of whether the motion came from the south (Yucca Flat) or the west (Pahute Mesa). There is insufficient data to date from a recently installed surface/downhole pair in Yucca Mountain to apply the method as it was applied to other pairs. There is a similarity in geology of Yucca Mountain and Rainier Mesa. Therefore, the average filter from Rainier Mesa was applied to the surface velocity waveforms at Yucca Mountain from one event to predict the downhole waveform.

  17. Nuclear fission of Fm isotopes

    SciTech Connect

    Asano, T.; Wada, T.; Ohta, M.; Chiba, S.

    2010-06-01

    Multi-modal fission has been systematically investigated for the series of isotopes of Fm and Cf. The multi-dimensional Langevin-type stochastic differential equation is used for the dynamical calculation. The primary fission mode changes from mass-asymmetric fission to mass-symmetric fission with the increase of neutron numbers for both Fm and Cf cases.

  18. Improved PLL For FM Demodulator

    NASA Technical Reports Server (NTRS)

    Kirkham, Harold; Jackson, Shannon P.

    1992-01-01

    Phase-locked loop (PLL) for frequency demodulator contains improved frequency-to-voltage converter producing less ripple than conventional phase detector. In improved PLL, phase detector replaced by state estimator, implemented by ramp/sample-and-hold circuit. Intended to reduce noise in receiver of frequency-modulated (FM) telemetry link without sacrificing bandwidth. Also applicable to processing received FM signals.

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

    DOEpatents

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

    1997-09-09

    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.

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

    DOEpatents

    Dong, Qiujie; Jenkins, Michael V.; Bernadas, Salvador R.

    1997-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Chassande-Mottin, Éric; Pai, Archana

    2006-02-01

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

  2. Detection and frequency tracking of chirping signals

    SciTech Connect

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

    1990-08-01

    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.

  3. Population inversion by chirped pulses

    SciTech Connect

    Lu Tianshi

    2011-09-15

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

  4. Chirp signal generator feasibility study

    NASA Astrophysics Data System (ADS)

    Chomiki, M.; Genauzeau, F.

    1983-03-01

    The feasibility of a signal generator with 100 microsec temporal dispersion, and 330 MHz frequency dispersion, for the ERS-1 (ESA satellite) radar altimeter, with a solid state transmitter, is demonstrated. Two surface wave dispersive filters (20 and 80 microsec dispersion) are cascaded with a frequency multiplier to give a 900 MHz output signal. The first filter receives an impulse which ensures an output signal to noise ratio 20 dB. The chirp signal output level is 0 dBm; amplitude fluctuation 2 dBcc, phase error compared with theory 10 deg rms; short term jitter 100 psec. The generator model occupies 0.5 l, and consumes 7 W.

  5. Surrogate waveform models

    NASA Astrophysics Data System (ADS)

    Blackman, Jonathan; Field, Scott; Galley, Chad; Scheel, Mark; Szilagyi, Bela; Tiglio, Manuel

    2015-04-01

    With the advanced detector era just around the corner, there is a strong need for fast and accurate models of gravitational waveforms from compact binary coalescence. Fast surrogate models can be built out of an accurate but slow waveform model with minimal to no loss in accuracy, but may require a large number of evaluations of the underlying model. This may be prohibitively expensive if the underlying is extremely slow, for example if we wish to build a surrogate for numerical relativity. We examine alternate choices to building surrogate models which allow for a more sparse set of input waveforms. Research supported in part by NSERC.

  6. Altimeter waveform software design

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  7. High resolution 95 GHz FM-CW solid state radar

    NASA Astrophysics Data System (ADS)

    Brookshire, S. P.; Eaves, J. L.

    1985-10-01

    A new state-of-the-art 95 GHz instrumentation radar designated HIRES-95 has been developed. It is designed specifically for full polarization scattering matrix measurements and characterization applications. The transmission waveform, the system polarization, and the range and angular resolutions are selectable from a variety of operational modes. For example, the system can operate with CW, FM-CW or pulsed waveforms including coherent pulse-to-pulse frequency agility; it can operate in either a coherent or a noncoherent mode; the system is dual polarized and has pulse-to-pulse (or transmissin to transmission) polarization agility; it can operate with either linear polarization or circular polarization; both the angular and range resolutions are continuously selectable to a maximum resolution of approximately one foot in each dimension.

  8. Full Waveform Inversion Using Waveform Sensitivity Kernels

    NASA Astrophysics Data System (ADS)

    Schumacher, Florian; Friederich, Wolfgang

    2013-04-01

    We present a full waveform inversion concept for applications ranging from seismological to enineering contexts, in which the steps of forward simulation, computation of sensitivity kernels, and the actual inversion are kept separate of each other. We derive waveform sensitivity kernels from Born scattering theory, which for unit material perturbations are identical to the Born integrand for the considered path between source and receiver. The evaluation of such a kernel requires the calculation of Green functions and their strains for single forces at the receiver position, as well as displacement fields and strains originating at the seismic source. We compute these quantities in the frequency domain using the 3D spectral element code SPECFEM3D (Tromp, Komatitsch and Liu, 2008) and the 1D semi-analytical code GEMINI (Friederich and Dalkolmo, 1995) in both, Cartesian and spherical framework. We developed and implemented the modularized software package ASKI (Analysis of Sensitivity and Kernel Inversion) to compute waveform sensitivity kernels from wavefields generated by any of the above methods (support for more methods is planned), where some examples will be shown. As the kernels can be computed independently from any data values, this approach allows to do a sensitivity and resolution analysis first without inverting any data. In the context of active seismic experiments, this property may be used to investigate optimal acquisition geometry and expectable resolution before actually collecting any data, assuming the background model is known sufficiently well. The actual inversion step then, can be repeated at relatively low costs with different (sub)sets of data, adding different smoothing conditions. Using the sensitivity kernels, we expect the waveform inversion to have better convergence properties compared with strategies that use gradients of a misfit function. Also the propagation of the forward wavefield and the backward propagation from the receiver into the medium (here realized by Green functions) can be done independently of each other. In comparison with the adjoint method, this can reduce the necessary number of wave propagation simulations, depending on the number of involved sources and receivers. One challenge, however, is that in order to calculate the kernels in the volume of interest, wavefields and strains have to be stored throughout that volume, which typically demands a large amount of storage capacity.

  9. Transionospheric signal detection with chirped wavelets

    SciTech Connect

    Doser, A.B.; Dunham, M.E.

    1997-11-01

    Chirped wavelets are utilized to detect dispersed signals in the joint time scale domain. Specifically, pulses that become dispersed by transmission through the ionosphere and are received by satellites as nonlinear chirps are investigated. Since the dispersion greatly lowers the signal to noise ratios, it is difficult to isolate the signals in the time domain. Satellite data are examined with discrete wavelet expansions. Detection is accomplished via a template matching threshold scheme. Quantitative experimental results demonstrate that the chirped wavelet detection scheme is successful in detecting the transionospheric pulses at very low signal to noise ratios.

  10. Low frequency AC waveform generator

    DOEpatents

    Bilharz, Oscar W.

    1986-01-01

    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.

  11. Adaptive Chirp Beamforming for Direction-of-Arrival Estimation of Wideband Chirp Signals in Sensor Arrays

    NASA Astrophysics Data System (ADS)

    Kim, Jeong-Soo; Choi, Byung-Woong; Bae, Eun-Hyon; Lee, Kyun-Kyung

    An adaptive chirp beamforming method is proposed to solve the bias problem in the direction-of-arrival (DOA) estimation of wideband chirp signals that have identical time-frequency parameters yet emanate from different directions. The proposed method, based on the steered minimum variance (STMV) method, exploits the time-frequency structure of a chirp signal to improve the DOA estimation performance by effectively suppressing the wideband chirp interferences causing the bias. Simulations are performed to demonstrate the effectiveness of the proposed method.

  12. Optical chirped beam amplification and propagation

    DOEpatents

    Barty, Christopher P.

    2004-10-12

    A short pulse laser system uses dispersive optics in a chirped-beam amplification architecture to produce high peak power pulses and high peak intensities without the potential for intensity dependent damage to downstream optical components after amplification.

  13. A chirp modem incorporating interference excision

    NASA Astrophysics Data System (ADS)

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

    1992-08-01

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

  14. Nonlinear waveform generation.

    PubMed

    Goldstein, L J; Rypins, E B

    1990-01-01

    We developed three analog logic SPICE (Simulation Program with Integrated Circuit Emphasis, developed at the University of California, Berkeley, CA) subcircuits, a voltage comparator and a nonlinear waveform generator to compliment the previously derived functions (Goldstein and Rypins, Comput. Methods Programs Biomed. 29 (1989) 161-172) that simplify modeling of physiologic systems. The logic elements are the 'AND', 'OR' and 'NOT' Boolean functions. In addition, we derived a voltage comparator for use in our composite waveform generator. All the circuits are analog so they can be incorporated into existing analog circuits while performing digital functions. PMID:2364683

  15. Low frequency ac waveform generator

    DOEpatents

    Bilharz, O.W.

    1983-11-22

    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.

  16. Adaptive chirp-Fourier transform for chirp estimation with applications in ISAR imaging of maneuvering targets

    NASA Astrophysics Data System (ADS)

    Xia, Xiang-Gen; Wang, Genyuan; Chen, Victor C.

    2001-03-01

    This paper first reviews some basic properties of the discrete chirp-Fourier transform and then present an adaptive chirp- Fourier transform, a generalization of the amplitude and phase estimation of sinusoids (APES) algorithm proposed by Li and Stoica for sinusoidal signals. We finally applied it to the ISAR imaging of maneuvering targets.

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

    SciTech Connect

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

    2007-01-03

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

  18. Efficient Formation of Ultracold Molecules with Chirped Nanosecond Pulses.

    PubMed

    Carini, J L; Kallush, S; Kosloff, R; Gould, P L

    2016-05-19

    We describe experiments and associated quantum simulations involving the production of ultracold (87)Rb2 molecules with nanosecond pulses of frequency-chirped light. With appropriate chirp parameters, the formation is dominated by coherent processes. For a positive chirp, excited molecules are produced by photoassociation early in the chirp, and then transferred into high vibrational levels of the lowest triplet state by stimulated emission later in the chirp. Generally good agreement is seen between the data and the simulations. Shaping of the chirp can lead to a significant enhancement of the formation rate. Further improvements using higher intensities and different intermediate states are predicted. PMID:26652642

  19. Optical waveform generation using a directly modulated laser

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  20. Noise analysis for near field 3-D FM-CW radar imaging systems

    SciTech Connect

    Sheen, David M.

    2015-06-19

    Near field radar imaging systems are used for several applications including concealed weapon detection in airports and other high-security venues. Despite the near-field operation, phase noise and thermal noise can limit the performance in several ways including reduction in system sensitivity and reduction of image dynamic range. In this paper, the effects of thermal noise, phase noise, and processing gain are analyzed in the context of a near field 3-D FM-CW imaging radar as might be used for concealed weapon detection. In addition to traditional frequency domain analysis, a time-domain simulation is employed to graphically demonstrate the effect of these noise sources on a fast-chirping FM-CW system.

  1. Optimal chirped probe pulse length for terahertz pulse measurement.

    PubMed

    Peng, Xiao-Yu; Willi, Oswald; Chen, Min; Pukhov, Alexander

    2008-08-01

    A detailed analysis of the relationship between the duration of the chirped probe pulse and the bipolar terahertz (THz) pulse length in the spectral encoding technique is carried out. We prove that there is an optimal chirped probe pulse length (or an optimal chirp rate of the chirped probe pulse) matched to the input THz pulse length and derive a rigorous relationship between them. We find that only under this restricted condition the THz signal can be correctly retrieved. PMID:18679511

  2. High precision triangular waveform generator

    DOEpatents

    Mueller, Theodore R.

    1983-01-01

    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.

  3. Cr4+ : YAG chirped-pulse oscillator

    PubMed Central

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

    2010-01-01

    We demonstrate chirped-pulse operation of a Cr : YAG passively mode-locked laser. Different operation regimes of the laser are extensively investigated in the vicinity of zero dispersion both experimentally and numerically. It is shown that for a given laser configuration, transition to the positive dispersion regime allows a 5-fold increase in the output pulse energy, which is otherwise limited by the onset of the multipulsing or ‘chaotic’ mode-locking. The output pulses have 1.4 ps duration and are compressible down to 120 fs in a 3 m piece of silica fiber, enabling supercontinuum generation in a nonlinear fiber. The spectrum shape and operation stability of the chirped-pulse regime depend strongly on the amount and shape of the intracavity dispersion. The numerical model predicts the existence of the minimum amount of the positive dispersion, above which the chirped-pulse regime can be realized. Once located, the chirped-pulse regime can be reliably reproduced and is sufficiently stable for applications. PMID:21151831

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

    SciTech Connect

    Xu Junjie; Zeng Bin; Yu Yongli

    2010-11-15

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

  5. SXS Catalog of Gravitational Waveforms

    NASA Astrophysics Data System (ADS)

    Hemberger, Daniel; SXS Collaboration

    2015-04-01

    Many aspects of gravitational-wave astronomy rely on numerical relativity for accurate models of gravitational waveforms. In recent years, several numerical relativity groups have built catalogs of numerical waveforms from binary black hole systems. I will report on the status of the Simulating Extreme Spacetimes (SXS) waveform catalog, which comprises simulations performed with the Spectral Einstein Code (SpEC). I will describe our approach for assessing numerical errors and convergence. Finally, I will discuss future plans to increase parameter space coverage of the catalog and to improve waveform accuracy.

  6. FM/CW radar system

    NASA Technical Reports Server (NTRS)

    Brey, H.; Geise, P. E., Jr. (Inventor)

    1978-01-01

    An FM/CW radar system is presented with improved noise discrimination in which the received signal is multiplied by a sample of the transmitted signal, and the product signal is employed to deflect a laser beam as a function of frequency. The position of the beam is thus indicative of a discrete frequency, and it is detected by the frequency encoded positions of an array of photodiodes. The outputs of the photodiodes are scanned, then threshold detected, and used to obtain the range and velocity of a target.

  7. Time reversed photonic beamforming of arbitrary waveform ladar arrays

    NASA Astrophysics Data System (ADS)

    Cox, Joseph L.; Zmuda, Henry; Bussjaeger, Rebecca J.; Erdmann, Reinhard K.; Fanto, Michael L.; Hayduk, Michael J.; Malowicki, John E.

    2007-04-01

    Herein is described a novel approach of performing adaptive photonic beam forming of an array of optical fibers with the expressed purpose of performing laser ranging. The beam forming technique leverages the concepts of time reversal, previously implemented in the sonar community, and wherein photonic implementation has recently been described for use by beamforming of ultra-wideband radar arrays. Photonic beam forming is also capable of combining the optical output of several fiber lasers into a coherent source, exactly phase matched on a pre-determined target. By implementing electro-optically modulated pulses from frequency chirped femtosecond-scale laser pulses, ladar waveforms can be generated with arbitrary spectral and temporal characteristics within the limitations of the wide-band system. Also described is a means of generating angle/angle/range measurements of illuminated targets.

  8. The Climate Hazards group InfraRed Precipitation (CHIRP) with Stations (CHIRPS): Development and Validation

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    CHIRP and CHIRPS are new quasi-global precipitation products with daily to seasonal time scales, a 0.05° resolution, and a 1981 to near real-time period of record. Developed by the Climate Hazards Group at UCSB and scientists at the U.S. Geological Survey Earth Resources Observation and Science Center specifically for drought early warning and environmental monitoring, CHIRPS provides moderate latency precipitation estimates that place observed hydrologic extremes in their historic context. Three main types of information are used in the CHIRPS: (1) global 0.05° precipitation climatologies, (2) time-varying grids of satellite-based precipitation estimates, and (3) in situ precipitation observations. CHIRP: The global grids of long-term (1980-2009) average precipitation were estimated for each month based on station data, averaged satellite observations, and physiographic parameters. 1981-present time-varying grids of satellite precipitation were derived from spatially varying regression models based on pentadal cold cloud duration (CCD) values and TRMM V7 training data. The CCD time-series were derived from the CPC and NOAA B1 datasets. Pentadal CCD-percent anomaly values were multiplied by pentadal climatology fields to produce low bias pentadal precipitation estimates. CHIRPS: The CHG station blending procedure uses the satellite-observed spatial covariance structure to assign relative weights to neighboring stations and the CHIRP values. The CHIRPS blending procedure is based on the expected correlation between precipitation at a given target location and precipitation at the locations of the neighboring observation stations. These correlations are estimated using the CHIRP fields. The CHG has developed an extensive archive of in situ daily, pentadal and monthly precipitation totals. The CHG database has over half a billion daily rainfall observations since 1980 and another half billion before 1980. Most of these observations come from four sets of global climate observations: the monthly Global Historical Climate Network version 2 archive, the daily Global Historical Climate Network archive, the Global Summary of the Day dataset (GSOD), and the daily Global Telecommunication System (GTS) archive provided by NOAA's Climate Prediction Center (CPC). A screening procedure was developed to flag and remove potential false zeros from the daily data, since these potentially spurious data can artificially suppress rainfall totals. Validation: Our validation focused on precipitation products with global coverage, long periods of record and near real-time availability: CHIRP, CHIRPS, CPC-Unified, CFS Reanalysis and ECMWF datasets were compared to GPCC and high quality datasets from Uganda, Colombia and the Sahel. The CHIRP and CHIRPS are shown to have low systematic errors (bias) and low mean absolute errors. Analyses in Uganda, Colombia and the Sahel indicate that the ECMWF, CPC-Unified and CFS-Reanalysis have large inhomogeneities, making them unsuitable for drought monitoring. The CHIRPS performance appears quite similar to research quality products like the GPCC and GPCP, but with higher resolution and lower latency.

  9. Waveform Sampler CAMAC Module

    SciTech Connect

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

    1985-09-01

    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.

  10. STRS Compliant FPGA Waveform Development

    NASA Technical Reports Server (NTRS)

    Nappier, Jennifer; Downey, Joseph; Mortensen, Dale

    2008-01-01

    The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. The extension of STRS to the SSP hardware will promote easier waveform reconfiguration and reuse. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. A FPGA-based transmit waveform implementation of the proposed standard interfaces on a laboratory breadboard SDR will be discussed.

  11. 4-bit Bipolar Triangle Voltage Waveform Generator Using Single-Flux-Quantum Circuit

    NASA Astrophysics Data System (ADS)

    Watanabe, Tomoki; Takahashi, Yoshitaka; Shimada, Hiroshi; Maezawa, Masaaki; Mizugaki, Yoshinao

    SFQ digital-to-analog converters (DACs) are one of the candidates for AC voltage standards. We have proposed SFQ-DACs based on frequency modulation (FM). Bipolar output is required for applications of AC voltage standards, while our previous SFQ-DACs generated only positive voltages. In this paper, we present our design of a 4-bit bipolar triangle voltage waveform generator comprising an SFQ-DAC. The waveform generator has two output ports. Synthesized half-period waveforms are alternately generated in one of the output ports. The bipolar output is realized by observing the differential voltage between the ports. We confirmed a 72-μVPP bipolar triangle voltage waveform at the frequency of 35.7 Hz.

  12. Coherent control of ultracold collisions with chirped light: Direction matters

    SciTech Connect

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

    2007-05-15

    We demonstrate the ability to coherently control ultracold atomic Rb collisions using frequency-chirped light on the nanosecond time scale. For certain center frequencies of the chirp, the rate of inelastic trap-loss collisions induced by negatively chirped light is dramatically suppressed compared to the case of a positive chirp. We attribute this to a fundamental asymmetry in the system: an excited wave packet moves inward on the attractive molecular potential. For a positive chirp, the resonance condition moves outward in time, while for a negative chirp, it moves inward, in the same direction as the excited wave packet; this allows multiple interactions between the wave packet and the light, enabling the wave packet to be returned coherently to the ground state. Classical and quantum calculations support this interpretation.

  13. Simulated lidar waveforms for understanding factors affecting waveform shape

    NASA Astrophysics Data System (ADS)

    Kim, Angela M.; Olsen, Richard C.

    2011-06-01

    Full-waveform LIDAR is a technology which enables the analysis of the 3-D structure and arrangement of objects. An in-depth understanding of the factors that affect the shape of the full-waveform signal is required in order to extract as much information as possible from the signal. A simple model of LIDAR propagation has been created which simulates the interaction of LIDAR energy with objects in a scene. A 2-dimensional model tree allows controlled manipulation of the geometric arrangement of branches and leaves with varying spectral properties. Results suggest complex interactions of the LIDAR energy with the tree canopy, including the occurrence of multiple bounces for energy reaching the ground under the canopy. Idealized sensor instrument response functions incorporated in the simulation illustrate a large impact on waveform shape. A waveform recording laser rangefinder has been built which will allow validation or model results; preliminary collection results are presented here.

  14. Mechanism of electron acceleration by chirped laser pulse

    SciTech Connect

    Wu, X. Y.; Wang, P. X.; Kawata, S.

    2012-05-28

    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.

  15. Radar/sonar acceleration estimation with linear-period modulated waveforms

    NASA Astrophysics Data System (ADS)

    Altes, Richard A.

    1990-11-01

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

  16. Wavelet approximations for computationally efficient FM demodulation

    NASA Astrophysics Data System (ADS)

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

    2001-03-01

    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.

  17. Spontaneous fission of /sup 259/Fm

    SciTech Connect

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

    1980-03-01

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

  18. SAR processing with stepped chirps and phased array antennas.

    SciTech Connect

    Doerry, Armin Walter

    2006-09-01

    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.

  19. Tapered and linearly chirped fiber Bragg gratings with co-directional and counter-directional resultant chirps

    NASA Astrophysics Data System (ADS)

    Osuch, Tomasz

    2016-05-01

    A method of spectral width tailoring of tapered fiber Bragg gratings is theoretically analyzed and experimentally verified. This concept is based on inscription grating structures in which synthesis of chirps comes from both taper profile and a linearly chirped phase mask used for grating inscription. It is shown that under UV exposure and depending on the orientation of the optical fiber taper relative to the variable-pitch phase mask, tapered and linearly chirped fiber Bragg gratings (TCFBG) with resultant co-directional or counter-directional chirps are achieved. Thus, both effects, those of reduction and enhancement of the grating chirp, as well as their influence on the grating spectral response, are presented. In particular, using the above approach TCFBG with significantly narrowed spectral width are shown. Moreover, fused tapered chirped FBG with relatively large waist diameter are shown having broad spectrum, something that prior to now was not attainable using previously developed techniques.

  20. Zeptosecond high harmonic keV x-ray waveforms driven by midinfrared laser pulses.

    PubMed

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

    2013-07-19

    We demonstrate theoretically that the temporal structure of high harmonic x-ray pulses generated with midinfrared lasers differs substantially from those generated with near-infrared pulses, especially at high photon energies. In particular, we show that, although the total width of the x-ray bursts spans femtosecond time scales, the pulse exhibits a zeptosecond structure due to the interference of high harmonic emission from multiple reencounters of the electron wave packet with the ion. Properly filtered and without any compensation of the chirp, regular subattosecond keV waveforms can be produced. PMID:23909315

  1. STRS Compliant FPGA Waveform Development

    NASA Technical Reports Server (NTRS)

    Nappier, Jennifer; Downey, Joseph

    2008-01-01

    The Space Telecommunications Radio System (STRS) Architecture Standard describes a standard for NASA space software defined radios (SDRs). It provides a common framework that can be used to develop and operate a space SDR in a reconfigurable and reprogrammable manner. One goal of the STRS Architecture is to promote waveform reuse among multiple software defined radios. Many space domain waveforms are designed to run in the special signal processing (SSP) hardware. However, the STRS Architecture is currently incomplete in defining a standard for designing waveforms in the SSP hardware. Therefore, the STRS Architecture needs to be extended to encompass waveform development in the SSP hardware. A transmit waveform for space applications was developed to determine ways to extend the STRS Architecture to a field programmable gate array (FPGA). These extensions include a standard hardware abstraction layer for FPGAs and a standard interface between waveform functions running inside a FPGA. Current standards were researched and new standard interfaces were proposed. The implementation of the proposed standard interfaces on a laboratory breadboard SDR will be presented.

  2. A Segmented Chirped-Pulse Fourier Transform Mm-Wave Spectrometer (260-295 Ghz) with Real-Time Signal Averaging Capability

    NASA Astrophysics Data System (ADS)

    Harris, Brent J.; Steber, Amanda L.; Pate, Brooks H.

    2013-06-01

    The design and performance of a 260-295 GHz segmented chirped-pulse Fourier transform mm-wave spectrometer is presented. The spectrometer uses an arbitrary waveform generator to create an excitation and detection waveform. The excitation waveform is a series of chirped pulses with 720 MHz bandwidth at mm-wave and about 200 ns pulse duration. The excitation pulses are produced using an x24 active multiplier chain with a peak power of 30 mW. Following a chirped pulse excitation, the molecular emission from all transitions in the excitation bandwidth is detected using heterodyne detection. The free induction decay (FID) is collected for about 1.5 microseconds and each segment measurement time period is 2 microseconds. The local oscillator for the detection in each segment is also created from the arbitrary waveform generator. The full excitation waveform contains 50 segments that scan the chirped pulse frequency and LO frequency across the 260-295 GHz frequency range in a total measurement time of 100 microseconds. The FID from each measurement segment is digitized at 4 GSamples/s, for a record length of 400 kpts. Signal averaging is performed by accumulating the FID signals from each sweep through the spectrum in a 32-bit FPGA. This allows the acquisition of 16 million sequential 260-295 GHz spectra in real time. The final spectrum is produced from fast Fourier transform of the FID in each measurement segment with the frequency calculated using the segment's LO frequency. The agility of the arbitrary waveform generator light source makes it possible to perform several coherent spectroscopic measurements to speed the analysis of the spectrum. In particular, high-sensitivity double-resonance measurements can be performed by applying a "pi-pulse" to a selected molecular transition and observing the changes to all other transitions in the 260-295 GHz frequency range of the spectrometer. In this mode of operation, up to 50 double-resonance frequencies can be used in each segment with the double-resonance signal collection taking place in real time.

  3. Chirped optical solitons in single-mode birefringent fibers

    NASA Astrophysics Data System (ADS)

    Mahmood, M. F.

    1996-12-01

    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.

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

    PubMed Central

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

    2008-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  6. Detector For FM Voice Or Digital Signals

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz

    1989-01-01

    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.

  7. Chirped fiber Bragg grating detonation velocity sensing.

    PubMed

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

    2013-01-01

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

  8. Over-modulated AM-FM decomposition

    NASA Astrophysics Data System (ADS)

    Li, Qin; Atlas, Les E.

    2004-10-01

    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.

  9. A broadband Fourier transform microwave spectrometer based on chirped pulse excitation.

    PubMed

    Brown, Gordon G; Dian, Brian C; Douglass, Kevin O; Geyer, Scott M; Shipman, Steven T; Pate, Brooks H

    2008-05-01

    Designs for a broadband chirped pulse Fourier transform microwave (CP-FTMW) spectrometer are presented. The spectrometer is capable of measuring the 7-18 GHz region of a rotational spectrum in a single data acquisition. One design uses a 4.2 Gsampless arbitrary waveform generator (AWG) to produce a 1 mus duration chirped pulse with a linear frequency sweep of 1.375 GHz. This pulse is sent through a microwave circuit to multiply the bandwidth of the pulse by a factor of 8 and upconvert it to the 7.5-18.5 GHz range. The chirped pulse is amplified by a traveling wave tube amplifier and broadcast inside the spectrometer by using a double ridge standard gain horn antenna. The broadband molecular free induction decay (FID) is received by a second horn antenna, downconverted, and digitized by a 40 Gsampless (12 GHz hardware bandwidth) digital oscilloscope. The second design uses a simplified pulse generation and FID detection scheme, employing current state-of-the-art high-speed digital electronics. In this spectrometer, a chirped pulse with 12 GHz of bandwidth is directly generated by using a 20 Gsampless AWG and upconverted in a single step with an ultrabroadband mixer. The amplified molecular emission is directly detected by using a 50 Gsampless digital oscilloscope with 18 GHz bandwidth. In both designs, fast Fourier transform of the FID produces the frequency domain rotational spectrum in the 7-18 GHz range. The performance of the CP-FTMW spectrometer is compared to a Balle-Flygare-type cavity-FTMW spectrometer. The CP-FTMW spectrometer produces an equal sensitivity spectrum with a factor of 40 reduction in measurement time and a reduction in sample consumption by a factor of 20. The CP-FTMW spectrometer also displays good intensity accuracy for both sample number density and rotational transition moment. Strategies to reduce the CP-FTMW measurement time by another factor of 90 while simultaneously reducing the sample consumption by a factor of 30 are demonstrated. PMID:18513057

  10. Chirped-Superlattice, Blocked-Intersubband QWIP

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath; Ting, David; Bandara, Sumith

    2004-01-01

    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.

  11. 47 CFR 73.295 - FM subsidiary communications services.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM subsidiary communications services. 73.295... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.295 FM subsidiary communications services. (a) Subsidiary communication services are those transmitted on a subcarrier within the FM baseband signal, but...

  12. 47 CFR 73.293 - Use of FM multiplex subcarriers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Use of FM multiplex subcarriers. 73.293 Section 73.293 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.293 Use of FM multiplex subcarriers. Licensees of FM...

  13. 47 CFR 73.295 - FM subsidiary communications services.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM subsidiary communications services. 73.295... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.295 FM subsidiary communications services. (a) Subsidiary communication services are those transmitted on a subcarrier within the FM baseband signal, but...

  14. 47 CFR 73.295 - FM subsidiary communications services.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM subsidiary communications services. 73.295... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.295 FM subsidiary communications services. (a) Subsidiary communication services are those transmitted on a subcarrier within the FM baseband signal, but...

  15. 47 CFR 73.293 - Use of FM multiplex subcarriers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Use of FM multiplex subcarriers. 73.293 Section 73.293 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.293 Use of FM multiplex subcarriers. Licensees of FM...

  16. 47 CFR 73.293 - Use of FM multiplex subcarriers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Use of FM multiplex subcarriers. 73.293 Section 73.293 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.293 Use of FM multiplex subcarriers. Licensees of FM...

  17. 47 CFR 73.295 - FM subsidiary communications services.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM subsidiary communications services. 73.295... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.295 FM subsidiary communications services. (a) Subsidiary communication services are those transmitted on a subcarrier within the FM baseband signal, but...

  18. 47 CFR 73.293 - Use of FM multiplex subcarriers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Use of FM multiplex subcarriers. 73.293 Section 73.293 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.293 Use of FM multiplex subcarriers. Licensees of FM...

  19. 47 CFR 73.297 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM stereophonic sound broadcasting. 73.297... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.297 FM stereophonic sound broadcasting. (a) An FM..., quadraphonic, etc.) sound programs upon installation of stereophonic sound transmitting equipment under...

  20. 47 CFR 73.297 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM stereophonic sound broadcasting. 73.297... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.297 FM stereophonic sound broadcasting. (a) An FM..., quadraphonic, etc.) sound programs upon installation of stereophonic sound transmitting equipment under...

  1. 47 CFR 73.297 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM stereophonic sound broadcasting. 73.297... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.297 FM stereophonic sound broadcasting. (a) An FM..., quadraphonic, etc.) sound programs upon installation of stereophonic sound transmitting equipment under...

  2. 47 CFR 73.297 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM stereophonic sound broadcasting. 73.297... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.297 FM stereophonic sound broadcasting. (a) An FM..., quadraphonic, etc.) sound programs upon installation of stereophonic sound transmitting equipment under...

  3. 47 CFR 73.297 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM stereophonic sound broadcasting. 73.297... RADIO BROADCAST SERVICES FM Broadcast Stations § 73.297 FM stereophonic sound broadcasting. (a) An FM..., quadraphonic, etc.) sound programs upon installation of stereophonic sound transmitting equipment under...

  4. 47 CFR 73.293 - Use of FM multiplex subcarriers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Use of FM multiplex subcarriers. 73.293 Section 73.293 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.293 Use of FM multiplex subcarriers. Licensees of FM...

  5. Altimetry Waveform Inversion over Antarctica

    NASA Astrophysics Data System (ADS)

    Blumstein, D.; Nino, F.; Berthier, E.; Remy, F.; Fleury, S.; Steunou, N.; Picot, N.

    2014-12-01

    Measurement provided by radar altimeters is much richer than the fewparameters traditionnally used in the applications (mainly ground altitudeand backscatter). Indeed, the whole history of the radar return is available,this is called radar waveforms.By a careful analysis of sequences of consecutive waveforms, it is possible toretrieve crucial information about the nature of the soil backscatter as wellas details about the topography at a resolution much better than the footprintof the altimeter. In particular the shape of the waveforms allows us todiscriminate the power return by the surface from the return by the subsurface.These parameters can then be used to provide information about geophysicalcharacteristics of the terrain (snow grain size, etc) and its temporalevolution through the analysis of the penetration of the radar wave in thesnow.This presentation will describe the technics we have developped to performwaveforms inversions through the use of an accurate waveform simulation modelthat is able to handle the Envisat mission (Ku band, 13.6 GHz) as well as thenew AltiKa mission from CNES/ISRO that provides measurements in Ka band(35.75 GHz) on the same orbit.We will also show how we can use good high resolution DEM, e.g. fromthe Spirit projet (CNES/SPOT IMAGE), in order to improve the retrievalsin regions which are notoriously difficult for radar altimetry(near the coast).Finally we will show results obtained on a few places of theAntarctica icesheet.

  6. Evolution of chirped laser pulses in a magnetized plasma channel

    SciTech Connect

    Jha, Pallavi; Hemlata,; Mishra, Rohit Kumar

    2014-12-15

    The propagation of intense, short, sinusoidal laser pulses in a magnetized plasma channel has been studied. The wave equation governing the evolution of the radiation field is set up and a variational technique is used to obtain the equations describing the evolution of the laser spot size, pulse length and chirp parameter. Numerical methods are used to analyze the simultaneous evolution of these parameters. The effect of the external magnetic field on initially chirped as well as unchirped laser pulses on the spot size, pulse length and chirping has been analyzed.

  7. Evolution of chirped laser pulses in a magnetized plasma channel

    NASA Astrophysics Data System (ADS)

    Jha, Pallavi; Hemlata; Mishra, Rohit Kumar

    2014-12-01

    The propagation of intense, short, sinusoidal laser pulses in a magnetized plasma channel has been studied. The wave equation governing the evolution of the radiation field is set up and a variational technique is used to obtain the equations describing the evolution of the laser spot size, pulse length and chirp parameter. Numerical methods are used to analyze the simultaneous evolution of these parameters. The effect of the external magnetic field on initially chirped as well as unchirped laser pulses on the spot size, pulse length and chirping has been analyzed.

  8. Sandia's Arbitrary Waveform MEMO Actuator

    Energy Science and Technology Software Center (ESTSC)

    2003-08-07

    SAMA is a multichannel, arbitrary waveform generator program for driving microelectromechanical systems (MEMS). It allows the user to piece together twelve available wave parts, thereby permitting the user to create practically any waveform, or upload a previously constructed signal. The waveforms (bundled together as a signal) may simultaneously be output through four different channels to actuate MEMS devices, and the number of output channels may be increased depending on the DAQ card or instrument utilized.more » Additionally, real-time changes may be made to the frequency and amplitude. The signal may be paused temporarily. The waveform may be saved to file for future uploading. Recent work for this version has focused on modifications that will allow loading previously generated arbitrary waveforms, independent channel waveform amplification, adding a pause function, separating the "modify waveform: and "end program" functions, and simplifying the user interface by adding test blocks with statements to help the user program and output the desired signals. The program was developed in an effort to alleviate some of the limitations of Micro Driver. For example, Micro Driver will not allow the user to select a segment of a sine wave, but rather the user is limited to choosing either a whole or half sine wave pattern. It therefore becomes quite difficult ot construct partial sine wave patterns out of a "ramp" waveparts for several reasons. First, one must determine on paper how many data points each ramp will cover, and what the slopes of these ramps will be. Second, from what was observed, Micro Driver has difficulty processing more than six distinct waveparts during sequencing. The program will allow the user to input the various waves into the desired sequence; however, it will not allow the user to compile them (by clicking "ok" and returning to the main screen). Third, should the user decide that they want to increase the amplitute of the output signal, they must go through each wavepart individually, recalculate slopes, and modify the ramps accordingly. This is certainly not a problem for single wavepart signals (i.e., the half-sine TRA signal), but for a ramp-created partial sine wave pattern, quick changes to the amplitude require quite a bit of thought and modification time. Finally, the five-ramp molded partial sine wave pattern is not a peace-wise smooth curve, which may or may not be a problem. Given the recent modifications that have been added to SAMS in this second version, Micro Driver may be replaced by this program.« less

  9. Chirped pulse amplification: Present and future

    SciTech Connect

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

    1988-01-01

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

  10. Dispersion compensation in chirped pulse amplification systems

    SciTech Connect

    Bayramian, Andrew James; Molander, William A.

    2014-07-15

    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.

  11. ABCD-matrix elements for a chirped diffraction grating

    NASA Astrophysics Data System (ADS)

    April, Alexandre; McCarthy, Nathalie

    2007-03-01

    The ABCD-matrix elements for a chirped diffraction grating, used at an arbitrary angle of incidence and in an arbitrary diffraction order, are derived both for the tangential and sagittal planes. The derivation is based on the notion of optical path difference and assumes a spherical chirped grating used in reflection in air or vacuum, but the results apply to transmission grating as well. The matrix elements are then employed to establish the effective focal length of the chirped grating and the position of its cardinal points. In this paper, by chirped gratings (also called varied line-space gratings or varied pitch gratings), it is meant gratings whose grooves are straight and parallel but not equally spaced.

  12. Chirp and polarization control of femtosecond molecular fragmentation

    PubMed Central

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

    2013-01-01

    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

  13. FM-cw radar for imaging applications

    NASA Astrophysics Data System (ADS)

    Bjornholt, John E.; Wilson, Terry B.

    1998-10-01

    FM-CW radars operating in the millimeter wave or upper microwave bands can provide low cost, low power solutions for many applications requiring the resolution of targets separated by one meter or less in range. Range resolution of this quality is obtained by sweeping the radar output frequency over several hundred megahertz of bandwidth using modern techniques to achieve extremely good linearity. Because of the short wavelengths at millimeter bands, relatively good angular resolution is achievable with moderately sized antennas. Applications for FM-CW radar sensors include automotive collision warning systems, traffic monitoring, height profiling, terrain profiling, autonomous vehicle navigation, surveillance and site security systems where high resolution is required.

  14. Control of Ultracold Collisions with Frequency-Chirped Light

    SciTech Connect

    Wright, M.J.; Gould, P.L.; Gensemer, S.D.; Vala, J.; Kosloff, R.

    2005-08-05

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

  15. Single attosecond pulse generation from multicycle nonlinear chirped pulses

    SciTech Connect

    Niu Yueping; Qi Yihong; Gong Shangqing; Xiang Yang

    2009-12-15

    We present a method of producing single attosecond pulses by high-order harmonic generation with multicycle nonlinear chirped driver laser pulses. The symmetry of the laser field in several optical cycles near the pulse center is broken, and then the photons near the cutoff burst only in half optical cycle. By selecting out the harmonics near the cutoff, an isolated attosecond pulse could be obtained. The results are almost independent of the length and chirp form of the driver laser pulse.

  16. Chirping for efficiency enhancement of the free-electron laser

    SciTech Connect

    Moore, G.T.; Goldstein, J.C.

    1988-01-01

    One-dimensional numerical studies have been made of free-electron laser oscillators in which the incident electron energy varies (chirps) as a function of time over each micropulse. Optical radiation resonant with such micropulses is chirped in frequency. Highest calculated efficiency (up to 8.1% for wavelengths near 10 ..mu..m) has been obtained in cases where the optical pulse at saturation is short compared to the slippage. 8 refs., 7 figs., 1 tab.

  17. Iterative direction-of-arrival estimation with wideband chirp signals

    NASA Astrophysics Data System (ADS)

    Wang, Genyuan; Xia, Xiang-Gen; Chen, Victor C.

    1999-11-01

    Amin et. al. recently developed a time-frequency MUSIC algorithm with narrow band models for the estimation of direction of arrival (DOA) when the source signals are chirps. In this research, we consider wideband models. The joint time-frequency analysis is first used to estimate the chirp rates of the source signals and then the DOA is estimated by the MUSIC algorithm with an iterative approach.

  18. Sampled chirped fiber gratings as distributed pressure sensors

    NASA Astrophysics Data System (ADS)

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

    2004-09-01

    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.

  19. Broadband spectroscopy of dynamic impedances with short chirp pulses.

    PubMed

    Min, M; Land, R; Paavle, T; Parve, T; Annus, P; Trebbels, D

    2011-07-01

    An impedance spectrum of dynamic systems is time dependent. Fast impedance changes take place, for example, in high throughput microfluidic devices and in operating cardiovascular systems. Measurements must be as short as possible to avoid significant impedance changes during the spectrum analysis, and as long as possible for enlarging the excitation energy and obtaining a better signal-to-noise ratio (SNR). The authors propose to use specific short chirp pulses for excitation. Thanks to the specific properties of the chirp function, it is possible to meet the needs for a spectrum bandwidth, measurement time and SNR so that the most accurate impedance spectrogram can be obtained. The chirp wave excitation can include thousands of cycles when the impedance changes slowly, but in the case of very high speed changes it can be shorter than a single cycle, preserving the same excitation bandwidth. For example, a 100 kHz bandwidth can be covered by the chirp pulse with durations from 10 s to 1 s; only its excitation energy differs also 10(5) times. After discussing theoretical short chirp properties in detail, the authors show how to generate short chirps in the microsecond range with a bandwidth up to a few MHz by using digital synthesis architectures developed inside a low-cost standard field programmable gate array. PMID:21646703

  20. Excitation of chirping whistler waves in a laboratory plasma

    NASA Astrophysics Data System (ADS)

    An, Xin

    2015-11-01

    Whistler mode chorus emissions with a characteristic frequency chirp largely control the dynamic variability of the Earth's outer radiation belt. They are responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Here, we report on the first laboratory experiment where whistler waves exhibiting fast frequency chirping have been artificially produced using a gyrating beam of energetic electrons injected into a cold plasma. It is shown that there is an optimal beam density for frequency chirps, which indicates the existence of optimum wave amplitude for the generation of chirps. Also, frequency chirps only occur for a very narrow range of ratio of fpe /fce , similar to that observed in space. Strong magnetic field gradient, which prohibits the formation of phase space electron hole, disrupts frequency chirps as expected. Broadband whistler waves similar to magnetospheric hiss are also observed at relatively high plasma density. Their mode structures are identified by the phase-correlation technique. It is demonstrated that broadband whistlers are excited through Landau resonance, cyclotron resonance and anomalous cyclotron resonance. Wave growth rate and wave normal angle given by linear theory are consistent with experimental results in general. Preliminary particle-in-cell simulation captures the linear theory prediction of broadband whistlers and also gives important information on the evolution of electron distribution function. Supported by NSF/DOE Plasma Partnership grant DE-SC0010578.

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

    SciTech Connect

    Du Hongchuan; Hu Bitao

    2011-08-15

    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.

  2. Automated Analysis, Classification, and Display of Waveforms

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  3. Noise analysis for near-field 3D FM-CW radar imaging systems

    NASA Astrophysics Data System (ADS)

    Sheen, David M.

    2015-05-01

    Near field radar imaging systems are used for demanding security applications including concealed weapon detection in airports and other high-security venues. Despite the near-field operation, phase noise and thermal noise can limit performance in several ways. Practical imaging systems can employ arrays with low gain antennas and relatively large signal distribution networks that have substantial losses which limit transmit power and increase the effective noise figure of the receiver chain, resulting in substantial thermal noise. Phase noise can also limit system performance. The signal coupled from transmitter to receiver is much larger than expected target signals. Phase noise from this coupled signal can set the system noise floor if the oscillator is too noisy. Frequency modulated continuous wave (FM-CW) radar transceivers used in short range systems are relatively immune to the effects of the coupled phase noise due to range correlation effects. This effect can reduce the phase-noise floor such that it is below the thermal noise floor for moderate performance oscillators. Phase noise is also manifested in the range response around bright targets, and can cause smaller targets to be obscured. Noise in synthetic aperture imaging systems is mitigated by the processing gain of the system. In this paper, the effects of thermal noise, phase noise, and processing gain are analyzed in the context of a near field 3-D FM-CW imaging radar as might be used for concealed weapon detection. In addition to traditional frequency domain analysis, a time-domain simulation is employed to graphically demonstrate the effect of these noise sources on a fast-chirping FM-CW system.

  4. Measuring Exocytosis in Neurons Using FM Labeling

    PubMed Central

    Newton, Jamila; Murthy, Venkatesh

    2006-01-01

    The ability to measure the kinetics of vesicle release can help provide insight into some of the basics of neurotransmission. Here we used real-time imaging of vesicles labeled with FM dye to monitor the rate of presynaptic vesicle release. FM4-64 is a red fluorescent amphiphilic styryl dye that embeds into the membranes of synaptic vesicles as endocytosis is stimulated. Lipophilic interactions cause the dye to greatly increase in fluorescence, thus emitting a bright signal when associated with vesicles and a nominal one when in the extracellular fluid. After a wash step is used to help remove external dye within the plasma membrane, the remaining FM is concentrated within the vesicles and is then expelled when exocytosis is induced by another round of electrical stimulation. The rate of vesicles release is measured from the resulting decrease in fluorescence. Since FM dye can be applied external and transiently, it is a useful tool for determining rates of exocytosis in neuronal cultures, especially when comparing the rates between transfected synapses and neighboring control boutons. PMID:18704189

  5. Improving FM transmitter power and efficiency

    NASA Technical Reports Server (NTRS)

    Honnell, M. A.

    1977-01-01

    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.

  6. FY05 FM Dial Summary Report

    SciTech Connect

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

    2005-12-01

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

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

    PubMed

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

    2008-02-01

    High-frequency ultrasound (HFU, > 15 MHz) is an effective means of obtaining fine-resolution images of biological tissues for applications such as opthalmologic, dermatologic, and small animal imaging. HFU has two inherent drawbacks. First, HFU images have a limited depth of field (DOF) because of the short wavelength and the low fixed F-number of conventional HFU transducers. Second, HFU can be used to image only a few millimeters deep into a tissue because attenuation increases with frequency. In this study, a five-element annular array was used in conjunction with a synthetic-focusing algorithm to extend the DOF. The annular array had an aperture of 10 mm, a focal length of 31 mm, and a center frequency of 17 MHz. To increase penetration depth, 8-micros, chirp-coded signals were designed, input into an arbitrary waveform generator, and used to excite each array element. After data acquisition, the received signals were linearly filtered to restore axial resolution and increase the SNR. To compare the chirpcoded imaging method with conventional impulse imaging in terms of resolution, a 25-microm diameter wire was scanned and the -6-dB axial and lateral resolutions were computed at depths ranging from 20.5 to 40.5 mm. The results demonstrated that chirp-coded excitation did not degrade axial or lateral resolution. A tissue-mimicking phantom containing 10-microm glass beads was scanned, and backscattered signals were analyzed to evaluate SNR and penetration depth. Finally, ex vivo ophthalmic images were formed and chirpcoded images showed features that were not visible in conventional impulse images. PMID:18334358

  8. FD-CHIRP: hosted payload system engineering lessons

    NASA Astrophysics Data System (ADS)

    Schueler, Carl F.

    2012-10-01

    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.

  9. A Joint Viterbi Algorithm to Separate Cochannel FM Signals

    NASA Technical Reports Server (NTRS)

    Hamkins, J.

    1998-01-01

    This paper presents a method for separating cochannel FM signals. We show that the Viterbi algorithm, traditionally limited to estimation of digital quantities, can jointly track analog FM signals by quantizing the derivative of their instantaneous frequencies.

  10. Lightning current waveform measuring system

    NASA Technical Reports Server (NTRS)

    Wojtasinski, R. J.; Fuchs, J. C.; Grove, C. H. (Inventor)

    1978-01-01

    An apparatus is described for monitoring current waveforms produced by lightning strikes which generate currents in an elongated cable. These currents are converted to voltages and to light waves for being transmitted over an optical cable to a remote location. At the remote location, the waves are reconstructed back into electrical waves for being stored into a memory. The information is stored within the memory with a timing signal so that only different signals need be stored in order to reconstruct the wave form.

  11. Cancer versus FM radio polarization types.

    PubMed

    Hallberg, Örjan

    2016-07-01

    In 2002, a detailed analysis of skin melanoma in 289 Swedish municipalities showed a strong association with the number of horizontally polarized main FM transmitters covering a municipality. Basic antenna theory says that body-resonance and standing waves cannot appear above a metal spring mattress unless the electric field is horizontally polarized. To test the hypothesis that body-resonant radiation can cause increased cancer risk in other European countries, I collected and analysed reported data from 24 countries, among which six were using vertical polarization. The results showed a strong association between cancer risk and the use of horizontally polarized FM broadcasting radiation, whereas vertical polarization seemed to cause no health effects. This information should form the basis for initiating relevant corrective actions by responsible authorities. PMID:26954356

  12. Detailed spectroscopy of {sup 249}Fm

    SciTech Connect

    Lopez-Martens, A.; Hauschild, K.; Briancon, Ch.; Korichi, A.; 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.; Curien, D.; Dorvaux, O.; Gall, B.; Khalfallah, F.

    2006-10-15

    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.

  13. 47 CFR 73.599 - NCE-FM engineering charts.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.599 NCE-FM engineering charts....

  14. 47 CFR 73.599 - NCE-FM engineering charts.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.599 NCE-FM engineering charts....

  15. 47 CFR 73.599 - NCE-FM engineering charts.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.599 NCE-FM engineering charts....

  16. 47 CFR 73.599 - NCE-FM engineering charts.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.599 NCE-FM engineering charts....

  17. 47 CFR 73.319 - FM multiplex subcarrier technical standards.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM multiplex subcarrier technical standards. 73.319 Section 73.319 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.319 FM multiplex subcarrier technical standards. (a) The technical specifications in...

  18. 47 CFR 73.319 - FM multiplex subcarrier technical standards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM multiplex subcarrier technical standards. 73.319 Section 73.319 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.319 FM multiplex subcarrier technical standards. (a) The technical specifications in...

  19. 47 CFR 73.310 - FM technical definitions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM technical definitions. 73.310 Section 73.310 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.310 FM technical definitions. (a) Frequency modulation. Antenna height above average terrain (HAAT). HAAT...

  20. 47 CFR 73.310 - FM technical definitions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM technical definitions. 73.310 Section 73.310 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.310 FM technical definitions. (a) Frequency modulation. Antenna height above average terrain (HAAT). HAAT...

  1. 47 CFR 73.315 - FM transmitter location.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM transmitter location. 73.315 Section 73.315 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.315 FM transmitter location. (a) The transmitter location shall be chosen so...

  2. 47 CFR 73.315 - FM transmitter location.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM transmitter location. 73.315 Section 73.315 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.315 FM transmitter location. (a) The transmitter location shall be chosen so...

  3. 47 CFR 73.515 - NCE FM transmitter location.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false NCE FM transmitter location. 73.515 Section 73.515 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.515 NCE FM transmitter location....

  4. 47 CFR 73.515 - NCE FM transmitter location.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false NCE FM transmitter location. 73.515 Section 73.515 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.515 NCE FM transmitter location....

  5. 47 CFR 73.515 - NCE FM transmitter location.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false NCE FM transmitter location. 73.515 Section 73.515 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.515 NCE FM transmitter location....

  6. 47 CFR 73.515 - NCE FM transmitter location.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false NCE FM transmitter location. 73.515 Section 73.515 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.515 NCE FM transmitter location....

  7. 47 CFR 73.597 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM stereophonic sound broadcasting. 73.597... RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.597 FM stereophonic sound..., transmit stereophonic sound programs upon installation of stereophonic sound transmitting equipment...

  8. 47 CFR 73.322 - FM stereophonic sound transmission standards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM stereophonic sound transmission standards... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.322 FM stereophonic sound transmission... modulation levels apply: (i) When a signal exists in only one channel of a two channel (biphonic)...

  9. 47 CFR 73.322 - FM stereophonic sound transmission standards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM stereophonic sound transmission standards... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.322 FM stereophonic sound transmission... modulation levels apply: (i) When a signal exists in only one channel of a two channel (biphonic)...

  10. 47 CFR 73.597 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM stereophonic sound broadcasting. 73.597... RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.597 FM stereophonic sound..., transmit stereophonic sound programs upon installation of stereophonic sound transmitting equipment...

  11. 47 CFR 73.597 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM stereophonic sound broadcasting. 73.597... RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.597 FM stereophonic sound..., transmit stereophonic sound programs upon installation of stereophonic sound transmitting equipment...

  12. 47 CFR 73.322 - FM stereophonic sound transmission standards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM stereophonic sound transmission standards... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.322 FM stereophonic sound transmission... modulation levels apply: (i) When a signal exists in only one channel of a two channel (biphonic)...

  13. 47 CFR 73.597 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM stereophonic sound broadcasting. 73.597... RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.597 FM stereophonic sound..., transmit stereophonic sound programs upon installation of stereophonic sound transmitting equipment...

  14. 47 CFR 73.597 - FM stereophonic sound broadcasting.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM stereophonic sound broadcasting. 73.597... RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.597 FM stereophonic sound..., transmit stereophonic sound programs upon installation of stereophonic sound transmitting equipment...

  15. 47 CFR 73.322 - FM stereophonic sound transmission standards.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM stereophonic sound transmission standards... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.322 FM stereophonic sound transmission... modulation levels apply: (i) When a signal exists in only one channel of a two channel (biphonic)...

  16. 47 CFR 73.322 - FM stereophonic sound transmission standards.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM stereophonic sound transmission standards... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.322 FM stereophonic sound transmission... modulation levels apply: (i) When a signal exists in only one channel of a two channel (biphonic)...

  17. 75 FR 13236 - FM Table of Allotments, Port Angeles, Washington

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-19

    ... applications. See 73 FR 75631, published December 12, 2008. In the first application (File No. BPH-20080710AJA... COMMISSION 47 CFR Part 73 FM Table of Allotments, Port Angeles, Washington AGENCY: Federal Communications... KSWW(FM), Montesano, Washington, to substitute FM Channel 271A for vacant Channel 229A at Port...

  18. 47 CFR 73.515 - NCE FM transmitter location.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false NCE FM transmitter location. 73.515 Section 73.515 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.515 NCE FM transmitter location....

  19. 47 CFR 73.315 - FM transmitter location.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM transmitter location. 73.315 Section 73.315 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.315 FM transmitter location. (a) The transmitter location shall be chosen so...

  20. 75 FR 43897 - FM TABLE OF ALLOTMENTS, GRANTS PASS, OREGON

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-27

    ... COMMISSION 47 CFR Part 73 FM TABLE OF ALLOTMENTS, GRANTS PASS, OREGON AGENCY: Federal Communications Commission ACTION: Proposed rule. SUMMARY: This document sets forth a proposal to amend the FM Table of.... 73.202 Amended 2. Section 73.202(b), the Table of FM Allotments under Oregon, is amended by...

  1. 75 FR 27977 - FM Table of Allotments, Fairbanks, Alaska

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-19

    ... COMMISSION 47 CFR Part 73 FM Table of Allotments, Fairbanks, Alaska AGENCY: Federal Communications Commission ACTION: Proposed rule. SUMMARY: This document sets forth a proposal to amend the FM Table of Allotments.... 73.202 Amended 2. Section 73.202(b), the Table of FM Allotments under Alaska, is amended by...

  2. 47 CFR 73.317 - FM transmission system requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM transmission system requirements. 73.317 Section 73.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.317 FM transmission system requirements. (a)...

  3. 47 CFR 73.317 - FM transmission system requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM transmission system requirements. 73.317 Section 73.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.317 FM transmission system requirements. (a)...

  4. 47 CFR 73.317 - FM transmission system requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM transmission system requirements. 73.317 Section 73.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.317 FM transmission system requirements. (a)...

  5. 47 CFR 73.317 - FM transmission system requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM transmission system requirements. 73.317 Section 73.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.317 FM transmission system requirements. (a)...

  6. 47 CFR 73.317 - FM transmission system requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM transmission system requirements. 73.317 Section 73.317 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.317 FM transmission system requirements. (a)...

  7. 47 CFR 73.295 - FM subsidiary communications services.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM subsidiary communications services. 73.295 Section 73.295 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.295 FM subsidiary communications services....

  8. 47 CFR 73.315 - FM transmitter location.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM transmitter location. 73.315 Section 73.315 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.315 FM transmitter location. (a) The transmitter location shall be chosen so...

  9. 47 CFR 73.316 - FM antenna systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM antenna systems. 73.316 Section 73.316 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.316 FM antenna systems. (a) It shall be standard to employ horizontal polarization; however, circular...

  10. 47 CFR 73.599 - NCE-FM engineering charts.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false NCE-FM engineering charts. 73.599 Section 73.599 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.599 NCE-FM engineering charts....

  11. Automatic frequency control for FM transmitter

    NASA Technical Reports Server (NTRS)

    Honnell, M. A. (Inventor)

    1974-01-01

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

  12. Graphs for Isotopes of 100-Fm (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides a graphic representation of nucleon separation energies and residual interaction parameters for isotopes of the chemical element 100-Fm (Fermium, atomic number Z = 100).

  13. High-precision triangular-waveform generator

    DOEpatents

    Mueller, T.R.

    1981-11-14

    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.

  14. Analysis of Q burst waveforms

    NASA Astrophysics Data System (ADS)

    Ogawa, Toshio; Komatsu, Masayuki

    2007-04-01

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

  15. Phase-locked loop FM demodulator

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  16. Excitation of Chirping Whistler Waves in a Laboratory Plasma

    NASA Astrophysics Data System (ADS)

    Van Compernolle, B.; An, X.; Bortnik, J.; Thorne, R. M.; Pribyl, P.; Gekelman, W.

    2015-06-01

    Whistler mode chorus emissions with a characteristic frequency chirp are important magnetospheric waves, responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Here, we report on the first laboratory experiment where whistler waves exhibiting fast frequency chirping have been artificially produced using a beam of energetic electrons launched into a cold plasma. Frequency chirps are only observed for a narrow range of plasma and beam parameters, and show a strong dependence on beam density, plasma density, and magnetic field gradient. Broadband whistler waves similar to magnetospheric hiss are also observed, and the parameter ranges for each emission are quantified.

  17. Excitation of Chirping Whistler Waves in a Laboratory Plasma.

    PubMed

    Van Compernolle, B; An, X; Bortnik, J; Thorne, R M; Pribyl, P; Gekelman, W

    2015-06-19

    Whistler mode chorus emissions with a characteristic frequency chirp are important magnetospheric waves, responsible for the acceleration of outer radiation belt electrons to relativistic energies and also for the scattering loss of these electrons into the atmosphere. Here, we report on the first laboratory experiment where whistler waves exhibiting fast frequency chirping have been artificially produced using a beam of energetic electrons launched into a cold plasma. Frequency chirps are only observed for a narrow range of plasma and beam parameters, and show a strong dependence on beam density, plasma density, and magnetic field gradient. Broadband whistler waves similar to magnetospheric hiss are also observed, and the parameter ranges for each emission are quantified. PMID:26196981

  18. Thomson scattering in high-intensity chirped laser pulses

    NASA Astrophysics Data System (ADS)

    Holkundkar, Amol R.; Harvey, Chris; Marklund, Mattias

    2015-10-01

    We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.

  19. Effects of collisions on energetic particle-driven chirping bursts

    SciTech Connect

    Lesur, M.

    2013-05-15

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

  20. Time-frequency signature sparse reconstruction using chirp dictionary

    NASA Astrophysics Data System (ADS)

    Nguyen, Yen T. H.; Amin, Moeness G.; Ghogho, Mounir; McLernon, Des

    2015-05-01

    This paper considers local sparse reconstruction of time-frequency signatures of windowed non-stationary radar returns. These signals can be considered instantaneously narrow-band, thus the local time-frequency behavior can be recovered accurately with incomplete observations. The typically employed sinusoidal dictionary induces competing requirements on window length. It confronts converse requests on the number of measurements for exact recovery, and sparsity. In this paper, we use chirp dictionary for each window position to determine the signal instantaneous frequency laws. This approach can considerably mitigate the problems of sinusoidal dictionary, and enable the utilization of longer windows for accurate time-frequency representations. It also reduces the picket fence by introducing a new factor, the chirp rate α. Simulation examples are provided, demonstrating the superior performance of local chirp dictionary over its sinusoidal counterpart.

  1. Chirped pulse inverse free-electron laser vacuum accelerator

    DOEpatents

    Hartemann, Frederic V.; Baldis, Hector A.; Landahl, Eric C.

    2002-01-01

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

  2. 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

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Interference to the input signals of FM translator or FM booster stations. 73.827 Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) §...

  3. 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

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Interference to the input signals of FM translator or FM booster stations. 73.827 Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) §...

  4. 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

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Interference to the input signals of FM translator or FM booster stations. 73.827 Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) §...

  5. 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

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Interference to the input signals of FM translator or FM booster stations. 73.827 Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) §...

  6. 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

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Interference to the input signals of FM translator or FM booster stations. 73.827 Section 73.827 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) §...

  7. Experimental investigation of chirp properties induced by signal amplification in quantum-dot semiconductor optical amplifiers.

    PubMed

    Matsuura, Motoharu; Ohta, Hiroaki; Seki, Ryota

    2015-03-15

    We experimentally show the dynamic frequency chirp properties induced by signal amplification in a quantum-dot semiconductor optical amplifier (QD-SOA) for the first time. We also compare the red and blue chirp peak values and temporal chirp changes while changing the gain and injected signal powers of the QD-SOA with those of a common SOA. PMID:25768145

  8. Temperature insensitive accelerometer based on a strain-chirped FBG

    NASA Astrophysics Data System (ADS)

    Zhou, Wenjun; Dong, Xinyong; Ni, Kai; Chan, C. C.; Shum, P.

    2009-10-01

    A novel accelerometer based on a strain-chirped optical fiber Bragg grating (FBG) is proposed. The FBG is glued in a slanted direction onto the lateral side of a right-angled triangle cantilever beam with a mass bonded on its free end. Vertical acceleration applied to the cantilever beam leads to a uniform bending along the beam length. As a result, the FBG is chirped and its reflection bandwidth changes linearly with the applied acceleration. A high sensitivity of 0.684 nm/g has been achieved in the experiment. This sensor is temperature insensitive, owning to the temperatureindependence nature of reflection bandwidth of the FBG.

  9. Ultrabroadband optical chirp linearization for precision metrology applications.

    PubMed

    Roos, Peter A; Reibel, Randy R; Berg, Trenton; Kaylor, Brant; Barber, Zeb W; Babbitt, Wm Randall

    2009-12-01

    We demonstrate precise linearization of ultrabroadband laser frequency chirps via a fiber-based self-heterodyne technique to enable extremely high-resolution, frequency-modulated cw laser-radar (LADAR) and a wide range of other metrology applications. Our frequency chirps cover bandwidths up to nearly 5 THz with frequency errors as low as 170 kHz, relative to linearity. We show that this performance enables 31-mum transform-limited LADAR range resolution (FWHM) and 86 nm range precisions over a 1.5 m range baseline. Much longer range baselines are possible but are limited by atmospheric turbulence and fiber dispersion. PMID:19953164

  10. Dense Monoenergetic Proton Beams from Chirped Laser-Plasma Interaction

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    Interaction of a frequency-chirped laser pulse with single protons and a hydrogen gas target is studied analytically and by means of particle-in-cell simulations, respectively. The feasibility of generating ultraintense (107 particles per bunch) and phase-space collimated beams of protons (energy spread of about 1%) is demonstrated. Phase synchronization of the protons and the laser field, guaranteed by the appropriate chirping 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 1021W/cm2.

  11. Goldstone Solar System Radar Waveform Generator

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  12. Waveform digitizing at 500 MHz

    SciTech Connect

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

    1988-01-01

    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.

  13. Gaussian and click noise in an FM/FM multiplex receiver.

    NASA Technical Reports Server (NTRS)

    Stochel, N. H.; Schilling, D. L.

    1972-01-01

    An FM/FM system is one in which the signal information frequency modulates a subcarrier, which, in turn, frequency modulates a main carrier for transmission. The detection process then involves two frequency demodulators in sequence. Using Rice's click model for both FM demodulators, we obtain the average click rate and an approximate output spectrum that include the effect of the impulses generated by the carrier demodulator on the subcarrier demodulation at and below threshold. We then focus on the threshold behavior of these systems and the proportioning of their modulation parameters so as to provide certain desired characteristics. We find that due to the filtering action of the second demodulator, the number of output clicks from carrier generated spikes can be orders of magnitude smaller, yet their contribution to the output noise can be much greater than that produced by the first demodulation.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  15. SPIDYAN, a MATLAB library for simulating pulse EPR experiments with arbitrary waveform excitation.

    PubMed

    Pribitzer, Stephan; Doll, Andrin; Jeschke, Gunnar

    2016-02-01

    Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations. PMID:26773526

  16. SPIDYAN, a MATLAB library for simulating pulse EPR experiments with arbitrary waveform excitation

    NASA Astrophysics Data System (ADS)

    Pribitzer, Stephan; Doll, Andrin; Jeschke, Gunnar

    2016-02-01

    Frequency-swept chirp pulses, created with arbitrary waveform generators (AWGs), can achieve inversion over a range of several hundreds of MHz. Such passage pulses provide defined flip angles and increase sensitivity. The fact that spectra are not excited at once, but single transitions are passed one after another, can cause new effects in established pulse EPR sequences. We developed a MATLAB library for simulation of pulse EPR, which is especially suited for modeling spin dynamics in ultra-wideband (UWB) EPR experiments, but can also be used for other experiments and NMR. At present the command line controlled SPin DYnamics ANalysis (SPIDYAN) package supports one-spin and two-spin systems with arbitrary spin quantum numbers. By providing the program with appropriate spin operators and Hamiltonian matrices any spin system is accessible, with limits set only by available memory and computation time. Any pulse sequence using rectangular and linearly or variable-rate frequency-swept chirp pulses, including phase cycling can be quickly created. To keep track of spin evolution the user can choose from a vast variety of detection operators, including transition selective operators. If relaxation effects can be neglected, the program solves the Liouville-von Neumann equation and propagates spin density matrices. In the other cases SPIDYAN uses the quantum mechanical master equation and Liouvillians for propagation. In order to consider the resonator response function, which on the scale of UWB excitation limits bandwidth, the program includes a simple RLC circuit model. Another subroutine can compute waveforms that, for a given resonator, maintain a constant critical adiabaticity factor over the excitation band. Computational efficiency is enhanced by precomputing propagator lookup tables for the whole set of AWG output levels. The features of the software library are discussed and demonstrated with spin-echo and population transfer simulations.

  17. A fine resolution multifrequency polarimetric FM radar

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  18. Electron heating enhancement by frequency-chirped laser pulses

    SciTech Connect

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

    2014-09-14

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

  19. Fiber dispersion measurement using chirped laser dispersion spectroscopy technique.

    PubMed

    Plant, Genevieve; Hangauer, Andreas; Wang, Ting; Wysocki, Gerard

    2015-11-20

    Utilizing the fundamentals of chirped laser dispersion spectroscopy, an alternative method of fiber dispersion measurement is presented. The dispersion of the device under test is probed through the interaction of copropagating electromagnetic waves and subsequent heterodyne detection and frequency demodulation. Measurement of the dispersion parameter, D, is possible with this direct measurement scheme. PMID:26836547

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

    PubMed

    Raupach, Sebastian M F; Grosche, Gesine

    2014-06-01

    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

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

    SciTech Connect

    Afhami, Saeedeh; Eslami, Esmaeil

    2014-06-15

    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.

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

    SciTech Connect

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

    1988-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Unruh, Wesley P.; Wolf, Michael A.; Bluestein, Howard B.

    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.

  4. Magnetoresistance and Anti-Ferromagnetic Coupling in FM-Graphene-FM Trilayers

    NASA Astrophysics Data System (ADS)

    Cobas, Enrique D.; van't Erve, Olaf M. J.; Cheng, Shu-Fan; Jonker, Berend T.

    Both high-magnetoresistance(MR) minority spin filtering and anti-ferromagnetic (AFM) coupling have been predicted for FM|Graphene|FM vertical heterostructures. Our previous experiments demonstrated ordinary magnetoresistance in NiFe-Graphene-Co heterostructures and no evident AFM coupling. Here we present experimental results that confirm both MR minority spin filtering and AFM coupling in high-quality FM|Graphene|FM heterostructures. The heterostructures were fabricated by a combination of sputtering, chemical vapor deposition and electron beam evaporation. The stack was patterned into symmetric cross-bar structures using Ar ion milling. Measurements show negative magnetoresistance in excess of 10 percent, confirming spin-filtering, and weak anti-ferromagnetic coupling throughout the temperature range 15K to 300K. The temperature dependence of the MR was studied and found consistent with thermal excitation of spin waves in the ferromagnetic electrodes. Junction resistance-area products are in the range of 10 Ωcm2. These heterostructures provide a fast and low-power magnetic field sensor in the sub-100 Oe range and are a step towards high-MR low RA-product MRAM junctions.

  5. Waveform Fingerprinting for Efficient Seismic Signal Detection

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  6. Attosecond control of optical waveforms

    NASA Astrophysics Data System (ADS)

    Fuji, Takao; Rauschenberger, Jens; Gohle, Christoph; Apolonski, Alexander; Udem, Thomas; Yakovlev, Vladislav S.; Tempea, Gabriel; Hänsch, Theodor W.; Krausz, Ferenc

    2005-05-01

    A new, monolithic scheme for stabilizing the phase between the carrier wave and the envelope (CE phase) in a train of few-cycle laser pulses is demonstrated. Self-phase modulation and second-harmonic generation or difference-frequency generation in a single periodically poled lithium niobate crystal, that transmits the main laser beam, allows for the CE-phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE-phase control, coupling into microstructured fibre, as well as separation and recombination of spectral components. As a result, the CE-phase error integrated over the spectral range of 0.2 mHz 35 MHz is as small as 0.016 × 2π rad. This implies that the phase of the field oscillations (λ ~ 830 nm) with respect to the pulse peak is locked to within 44 attoseconds, resulting in optical waveform control with subhundred attosecond fidelity for the first time.

  7. Elliptic waveforms for inspiralling compact binaries

    NASA Astrophysics Data System (ADS)

    Mikóczi, Balázs

    2010-03-01

    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.

  8. Quantum cascade laser FM spectroscopy of explosives

    NASA Astrophysics Data System (ADS)

    Gutmann, Zach; Clasp, Trocia; Lue, Chris; Johnson, Tiffani; Ingle, Taylor; Jamison, Janet; Buchanan, Roger; Reeve, Scott

    2013-05-01

    Polyisobutylene is an industrial polymer that is widely used in a number of applications including the manufacture of military grade explosives. We have examined the vapor emanating from a series of different molecular weight samples of polyisobutylene using high resolution Quantum Cascade Laser FM spectroscopy. The vapor phase spectra all exhibit a rovibrational structure similar to that for the gas phase isobutylene molecule. We have assigned the structure in the 890 cm-1 and 1380 cm-1 regions to the isobutylene ν28 and ν7 fundamental bands respectively. These spectroscopic signatures may prove useful for infrared sensing applications. Here we will present the infrared signatures along with recent GCMS data from a sample of C4, utilizing solid-phase microextraction vapor collection fibers, which confirm the presence of isobutylene as one of the volatile bouquet species in RDX-based explosives.

  9. What FM can offer DFCS design

    NASA Technical Reports Server (NTRS)

    Rushby, John

    1990-01-01

    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.

  10. Superfluid dynamics of 258Fm fission

    NASA Astrophysics Data System (ADS)

    Scamps, Guillaume; Simenel, Cédric; Lacroix, Denis

    2015-07-01

    The theoretical description of nuclear fission remains one of the major challenges of quantum many-body dynamics. The motion through the fission barrier is followed by a fast, nonadiabatic descent of the potential between the fragments. The latter stage is crucial as it generates most of the excitation energy in the fragments. The superfluid dynamics in the latter stage of fission is obtained from 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 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 and quasiparticle picture is emphasized and qualitatively studied.

  11. Seismic waveform viewer, processor and calculator

    Energy Science and Technology Software Center (ESTSC)

    2015-02-15

    SWIFT is a computer code that is designed to do research level signal analysis on seismic waveforms, including visualization, filtering and measurement. LLNL is using this code, amplitude and global tomography efforts.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  13. High-Voltage, Asymmetric-Waveform Generator

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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).

  14. GRC GSFC TDRSS Waveform Metrics Report

    NASA Technical Reports Server (NTRS)

    Mortensen, Dale J.

    2013-01-01

    The report presents software metrics and porting metrics for the GGT Waveform. The porting was from a ground-based COTS SDR, the SDR-3000, to the CoNNeCT JPL SDR. The report does not address any of the Operating Environment (OE) software development, nor the original TDRSS waveform development at GSFC for the COTS SDR. With regard to STRS, the report presents compliance data and lessons learned.

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  17. Optical chirp z-transform processor with a simplified architecture.

    PubMed

    Ngo, Nam Quoc

    2014-12-29

    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

  18. Time Resolved Optical Nonlinearities Using Long Chirped Pulses

    NASA Astrophysics Data System (ADS)

    Sutherland, R. L.; Tang, N.; Fleitz, P. A.; McLean, D. G.

    1997-03-01

    We have developed a novel technique for resolving optical nonlinearities with response time much shorter than the interrogating laser pulse. The method employs a simple two- wave mixing geometry in a time-delayed pump-probe scheme using chirped pulses. Although the pulse width is long compared to the material response time, the pulse chirp magnifies the time scale of the material response and allows measurement of very fast mechanisms. The transmission of the probe pulse as a function of delay time exhibits a Lorentzian dispersion-like curve. The time difference between the peak and valley yields the time response of the medium, while the peak-to-valley swing gives the refractive nonlinearity, and the deviation of the mean transmission from unity gives the two-photon absorption coefficient. We illustrate our technique by measuring nonlinearities in molten diphenyl butadiene referenced to carbon disulfide.

  19. Hyper dispersion pulse compressor for chirped pulse amplification systems

    SciTech Connect

    Barty, Christopher P. J.

    2011-11-29

    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.

  20. Multimodal nonlinear Raman microspectroscopy with ultrashort chirped laser pulses

    NASA Astrophysics Data System (ADS)

    Lanin, A. A.; Stepanov, E. A.; Tikhonov, R. A.; Sidorov-Biryukov, D. A.; Fedotov, A. B.; Zheltikov, A. M.

    2015-05-01

    We demonstrate the physical principles of multimodal nonlinear optical microspectroscopy, integrating methods of coherent and stimulated Raman scattering of ultrashort chirped laser pulses in a single optical scheme. Nonlinear phase distortions of ultrashort laser pulses are accurately compensated within a broad spectral range in this scheme to enable a high-spectral-resolution laser microspectroscopy that can reliably resolve groups of fingerprint molecular vibrations with close frequencies, thus facilitating an analysis of complex multicomponent systems.

  1. Optical fringe reduction technique for FM laser spectroscopy

    NASA Technical Reports Server (NTRS)

    Chou, Nee-Yin; Sachse, Glen W.; Wang, Liang-Guo; Gallagher, Thomas F.

    1989-01-01

    A simple fringe reduction method for FM diode laser spectroscopy is discussed. The fringes can be effectively suppressed by using a modulation frequency that is an integral multiple of the free spectral range of the fringes. The technique is experimentally confirmed by two-tone FM spectroscopy of water vapor absorption lines. A factor of 20 fringe reduction is observed.

  2. Preparing Students to Take SOA/CAS Exam FM/2

    ERIC Educational Resources Information Center

    Marchand, Richard J.

    2014-01-01

    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…

  3. ES8 Aqua-FM3 Ed3

    Atmospheric Science Data Center

    2016-05-11

    ES8 Aqua-FM3 Ed3 Project Title:  CERES Discipline:  ... 3 Level:  L2 Platform:  Aqua Instrument:  FM3 Spatial Coverage:  (-90, ...  The latest CERES data products (Edition3 for Terra and Aqua; Edition2 for TRMM) are approved for science publications. ...

  4. 47 CFR 73.319 - FM multiplex subcarrier technical standards.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ....319 Section 73.319 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.319 FM multiplex subcarrier technical... by more than 10%. (4) Total modulation of the carrier wave during transmission of...

  5. 47 CFR 73.319 - FM multiplex subcarrier technical standards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ....319 Section 73.319 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.319 FM multiplex subcarrier technical... by more than 10%. (4) Total modulation of the carrier wave during transmission of...

  6. 47 CFR 73.319 - FM multiplex subcarrier technical standards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ....319 Section 73.319 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.319 FM multiplex subcarrier technical... by more than 10%. (4) Total modulation of the carrier wave during transmission of...

  7. FM: Clinically Meaningful Rorschach Index with Minority Children?

    ERIC Educational Resources Information Center

    Scott, Ralph

    1981-01-01

    Uses a case vignette to consider the possibility that the Rorschach FM index may be a forerunner of abstract thinking. Data support the major finding that FM may enable educational diagnosticians to more accurately estimate the intellectual capabilities of some preschool minority and other culturally disadvantaged children. (Author/JAC)

  8. 47 CFR 73.4017 - Application processing: Commercial FM stations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Application processing: Commercial FM stations. 73.4017 Section 73.4017 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST... processing: Commercial FM stations. See Report and Order, MM Docket 84-750, FCC 85-125, adopted March 4,...

  9. 47 CFR 73.4108 - FM transmitter site map submissions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM transmitter site map submissions. 73.4108 Section 73.4108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4108 FM transmitter site...

  10. 47 CFR 73.4104 - FM assignment policies and procedures.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM assignment policies and procedures. 73.4104 Section 73.4104 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4104 FM assignment policies...

  11. 47 CFR 73.4017 - Application processing: Commercial FM stations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Application processing: Commercial FM stations. 73.4017 Section 73.4017 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST... processing: Commercial FM stations. See Report and Order, MM Docket 84-750, FCC 85-125, adopted March 4,...

  12. 47 CFR 73.4108 - FM transmitter site map submissions.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM transmitter site map submissions. 73.4108 Section 73.4108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4108 FM transmitter site...

  13. 47 CFR 73.4108 - FM transmitter site map submissions.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false FM transmitter site map submissions. 73.4108 Section 73.4108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4108 FM transmitter site...

  14. 47 CFR 73.4104 - FM assignment policies and procedures.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false FM assignment policies and procedures. 73.4104 Section 73.4104 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4104 FM assignment policies...

  15. 47 CFR 73.4104 - FM assignment policies and procedures.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM assignment policies and procedures. 73.4104 Section 73.4104 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4104 FM assignment policies...

  16. 47 CFR 73.4017 - Application processing: Commercial FM stations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Application processing: Commercial FM stations. 73.4017 Section 73.4017 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST... processing: Commercial FM stations. See Report and Order, MM Docket 84-750, FCC 85-125, adopted March 4,...

  17. 47 CFR 73.4017 - Application processing: Commercial FM stations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Application processing: Commercial FM stations. 73.4017 Section 73.4017 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST... processing: Commercial FM stations. See Report and Order, MM Docket 84-750, FCC 85-125, adopted March 4,...

  18. 47 CFR 73.4104 - FM assignment policies and procedures.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false FM assignment policies and procedures. 73.4104 Section 73.4104 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4104 FM assignment policies...

  19. 47 CFR 73.4108 - FM transmitter site map submissions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM transmitter site map submissions. 73.4108 Section 73.4108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4108 FM transmitter site...

  20. 47 CFR 73.4017 - Application processing: Commercial FM stations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Application processing: Commercial FM stations. 73.4017 Section 73.4017 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST... processing: Commercial FM stations. See Report and Order, MM Docket 84-750, FCC 85-125, adopted March 4,...

  1. 47 CFR 73.4104 - FM assignment policies and procedures.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false FM assignment policies and procedures. 73.4104 Section 73.4104 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4104 FM assignment policies...

  2. Pulsed FM mode locking of a Nd:BEL laser

    NASA Astrophysics Data System (ADS)

    Godil, A. A.; Li, K. D.; Bloom, D. M.

    1991-08-01

    A novel pulsed FM mode locker for a diode-pumped Nd:BEL laser is described. Fast electrical pulses from a comb generator drive a LiNbO3 crystal, which produces pulsed electrooptic phase modulation in the laser cavity. The pulsed FM mode locking produced stable pulses of 7.5-ps duration at a repetition rate of 250 MHz.

  3. 75 FR 41766 - FM Table of Allotments, Amboy, California

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-19

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 FM Table of Allotments, Amboy, California AGENCY: Federal Communications Commission... 0 2. Section 73.202(b), the Table of FM Allotments under California, is amended by adding...

  4. 75 FR 41092 - FM TABLE OF ALLOTMENTS, Kingsland, Texas

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-15

    ... From the Federal Register Online via the Government Publishing Office FEDERAL COMMUNICATIONS COMMISSION 47 CFR Part 73 FM TABLE OF ALLOTMENTS, Kingsland, Texas AGENCY: Federal Communications Commission..., 303, 334, 336. Sec. 73.202 Amended 0 2. Section 73.202(b), the Table of FM Allotments under Texas,...

  5. 75 FR 4037 - FM TABLE OF ALLOTMENTS, BRACKETTVILLE, TX

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-26

    ... Proceedings, 63 FR 24121 (1988). Electronic Filers: Comments may be filed electronically using the Internet by... COMMISSION 47 CFR Part 73 FM TABLE OF ALLOTMENTS, BRACKETTVILLE, TX AGENCY: Federal Communications Commission.... 73.202 2. Section 73.202(b), the Table of FM Allotments under Texas, is amended by...

  6. FM-CW radar performance in a lossy layered medium

    NASA Astrophysics Data System (ADS)

    Deng, Ruili; Liu, Ce

    1999-08-01

    FM-CW radar is capable of detecting subsurface anomalies by using linear sweep frequency transmission of a periodically repetitive continuous FM signal. Due to the continuous-wave nature, the peak power of the FM-CW radar is usually in the range of hundreds of milliwatts. In cases where high resolution is necessary, the FM-CW radar is preferred because of the simple hardware structure and the availability of low-power components. The distance from the antenna to an anomaly can be determined by FM-CW radar in lossless media. In this paper, we present both analytical and numerical methods for modelling FM-CW radar performance in lossless and lossy layered formations for 1D and 2D cases. The FM-CW operating frequency is set in the range of 1-2 GHz, and the sweep periods are 10 ms and 2 ms, respectively. An inversion formulation is discussed to invert the distance and dielectric constant simultaneously from the spectrum of the received signal by using FFT and the `range equation'. The spatial resolution is about one-third of the center wavelength and the depth of penetration is about 4 m in a medium having a conductivity less than 1 mS/m. The FM-CW radar technique cannot be used in a lossy medium having conductivity more than 30 mS/m. The spectrum and images of multilayer formations is also studied.

  7. Preparing Students to Take SOA/CAS Exam FM/2

    ERIC Educational Resources Information Center

    Marchand, Richard J.

    2014-01-01

    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

  8. 47 CFR 73.4108 - FM transmitter site map submissions.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false FM transmitter site map submissions. 73.4108 Section 73.4108 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.4108 FM transmitter site...

  9. Platform for Postprocessing Waveform-Based NDE

    NASA Technical Reports Server (NTRS)

    Roth, Don

    2008-01-01

    Taking advantage of the similarities that exist among all waveform-based non-destructive evaluation (NDE) methods, a common software platform has been developed containing multiple- signal and image-processing techniques for waveforms and images. The NASA NDE Signal and Image Processing software has been developed using the latest versions of LabVIEW, and its associated Advanced Signal Processing and Vision Toolkits. The software is useable on a PC with Windows XP and Windows Vista. The software has been designed with a commercial grade interface in which two main windows, Waveform Window and Image Window, are displayed if the user chooses a waveform file to display. Within these two main windows, most actions are chosen through logically conceived run-time menus. The Waveform Window has plots for both the raw time-domain waves and their frequency- domain transformations (fast Fourier transform and power spectral density). The Image Window shows the C-scan image formed from information of the time-domain waveform (such as peak amplitude) or its frequency-domain transformation at each scan location. The user also has the ability to open an image, or series of images, or a simple set of X-Y paired data set in text format. Each of the Waveform and Image Windows contains menus from which to perform many user actions. An option exists to use raw waves obtained directly from scan, or waves after deconvolution if system wave response is provided. Two types of deconvolution, time-based subtraction or inverse-filter, can be performed to arrive at a deconvolved wave set. Additionally, the menu on the Waveform Window allows preprocessing of waveforms prior to image formation, scaling and display of waveforms, formation of different types of images (including non-standard types such as velocity), gating of portions of waves prior to image formation, and several other miscellaneous and specialized operations. The menu available on the Image Window allows many further image processing and analysis operations, some of which are found in commercially-available image-processing software programs (such as Adobe Photoshop), and some that are not (removing outliers, Bscan information, region-of-interest analysis, line profiles, and precision feature measurements).

  10. Combining Full Waveform Inversion and Traveltime Tomography

    NASA Astrophysics Data System (ADS)

    Sager, K.; Fichtner, A.; Afanasiev, M.; Rawlinson, N.; Ritsema, J.

    2014-12-01

    By alternating full waveform inversion and traveltime tomography we attempt to merge their complementary merits and produce models of the European continent that explain both waveform and traveltime data sets. Technological developments and advances in theoretical and numerical seismology allow us to assimilate complete waveforms for the solution of full waveform tomographic problems. On regional to continental scales, however, full waveform inversion is still and will also in the long term be limited to an intermediate period band because of computational limitations. Valuable information contained in high-frequency P and S wave traveltimes cannot be exploited. Since mainly surface waves can be observed in the period range that is technically feasible, full waveform inversion yields excellent results in the upper 300 km, where surface wave sensitivity is large. At greater depth S velocity anomalies are less well resolved and generally P velocity heterogeneities are not well constrained at all. In contrast, classical traveltime tomography intrinsically incorporates information from high-frequency body waves. However, traveltime methods are deficient for longer periods due to the commonly used infinite frequency approximation of the wave equation. To combine their complementary assets and extend the spectrum of exploited information, we develop an inversion scheme, where full waveform inversion and ray tomography alternate, thereby avoiding an explicit coupling of both methods and data sets. We put special emphasis on its ability to produce 3D models that explain both waveform and traveltime data sets. We start with a full waveform inversion model and machinery of Europe and Western Asia in conjunction with the traveltime tomography package FMTOMO. For the traveltime update we use the teleseismic data set that constrains the global model S40RTS, complemented with measurements distributed by the International Seismological Centre. Avoiding difficulties in modeling the complexities in the crust and upper mantle, the traveltime update primarily introduces information in deeper parts of the model. After alternating both methods the resulting model finally incorporates information from traveltime measurements and from waveform data, thus proving the compatibility of both approaches.

  11. Auditory brainstem responses to chirps delivered by an insert earphone with equalized frequency response

    PubMed Central

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

    2012-01-01

    Recently it has been demonstrated that auditory brainstem responses, ABRs, to chirps are larger with the ER-2 than with the ER-3A insert earphone due to differences between the corresponding amplitude-frequency responses. Therefore a modified chirp, which equalizes the amplitude-frequency response of the ER-3A, is constructed and subsequently compared to the unmodified chirp. ABRs are recorded from 20 normal-hearing subjects in response to the two chirps delivered by the ER-3A earphone at a wide range of levels. The results confirm that the modified chirp generates significantly larger ABRs than the unmodified chirp at levels below 60 dB nHL. PMID:22894314

  12. Chirped pulse control of CsI fragmentation: an experimental possibility

    NASA Astrophysics Data System (ADS)

    Amstrup, Bjarne; Szabó, Gábor; Sauerbrey, Roland A.; Lörincz, András

    1994-10-01

    The strength of chirped pulse optimal control as an experimental possibility is demonstrated in this paper. The suggested experiment is a pump-dump experiment that first creates an unstable - dissociating - molecule on a repulsive level and then stops fragmentation. The experiment is envisioned by using a start pulse (a doubled green pulse) that inverts the population. The control pulse - that stops the fragmentation - is the chirp optimized green pulse itself. Optimization includes second and third order chirp expansion terms. Optimization is made for the weak and strong field limits with the help of the simulated annealing method. Weak field optimization shows the expected red chirp results. Strong field optimization, on the other hand, gives rise to blue chirp as optimal solution. It is argued, that the blue chirp is the consequence of the need for locking the upper and lower state wavefunctions for efficient population inversion.

  13. Chirped pulse Raman amplification in warm plasma: towards controlling saturation.

    PubMed

    Yang, X; Vieux, G; Brunetti, E; Ersfeld, B; Farmer, J P; Hur, M S; Issac, R C; Raj, G; Wiggins, S M; Welsh, G H; Yoffe, S R; Jaroszynski, D A

    2015-01-01

    Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10's - 100's fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies. PMID:26290153

  14. Shear wave speed and dispersion measurements using crawling wave chirps.

    PubMed

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

    2014-10-01

    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

  15. Chirped pulse Raman amplification in warm plasma: towards controlling saturation

    PubMed Central

    Yang, X.; Vieux, G.; Brunetti, E.; Ersfeld, B.; Farmer, J. P.; Hur, M. S.; Issac, R. C.; Raj, G.; Wiggins, S. M.; Welsh, G. H.; Yoffe, S. R.; Jaroszynski, D. A.

    2015-01-01

    Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10’s – 100’s fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies. PMID:26290153

  16. Coherent chirped pulse laser network with Mickelson phase conjugator.

    PubMed

    Okulov, A Yu

    2014-04-10

    The mechanisms of nonlinear phase-locking of a large fiber amplifier array are analyzed. The preference is given to the most suitable configuration for a coherent coupling of thousands of fundamental spatial mode fiber beams into a single smooth beam ready for chirped pulse compression. It is shown that a Michelson phase-conjugating configuration with double passage through an array of fiber amplifiers has the definite advantage compared to a one-way fiber array coupled in a Mach-Zehnder configuration. Regardless of the amount of synchronized fiber amplifiers, the Michelson phase-conjugating interferometer is expected to do a perfect compensation of the phase-piston errors and collimation of backwardly amplified fiber beams on an entrance/output beam splitter. In both configurations, the nonlinear transformation of the stretched pulse envelope, due to gain saturation, is capable of randomizing the position of chirp inside an envelope; thus it may reduce the visibility of the interference pattern at an output beam splitter. Certain advantages are inherent to the sech-form temporal envelope because of the exponential precursor and self-similar propagation in gain medium. The Gaussian envelope is significantly compressed in a deep gain saturation regime, and the frequency chirp position inside pulse envelope is more deformed. PMID:24787398

  17. Chirp Z-transform spectral zoom optimization with MATLAB.

    SciTech Connect

    Martin, Grant D.

    2005-11-01

    The MATLAB language has become a standard for rapid prototyping throughout all disciplines of engineering because the environment is easy to understand and use. Many of the basic functions included in MATLAB are those operations that are necessary to carry out larger algorithms such as the chirp z-transform spectral zoom. These functions include, but are not limited to mathematical operators, logical operators, array indexing, and the Fast Fourier Transform (FFT). However, despite its ease of use, MATLAB's technical computing language is interpreted and thus is not always capable of the memory management and performance of a compiled language. There are however, several optimizations that can be made within the chirp z-transform spectral zoom algorithm itself, and also to the MATLAB implementation in order to take full advantage of the computing environment and lower processing time and improve memory usage. To that end, this document's purpose is two-fold. The first demonstrates how to perform a chirp z-transform spectral zoom as well as an optimization within the algorithm that improves performance and memory usage. The second demonstrates a minor MATLAB language usage technique that can reduce overhead memory costs and improve performance.

  18. A 32x32 pixel focal plane array ladar system using chirped amplitude modulation

    NASA Astrophysics Data System (ADS)

    Stann, Barry L.; Aliberti, Keith; Carothers, Daniel; Dammann, John; Dang, Gerard; Giza, Mark M.; Lawler, William B.; Redman, Brian C.; Simon, Deborah R.

    2004-09-01

    The Army Research Laboratory is researching system architectures and components required to build a 32x32 pixel scannerless ladar breadboard. The 32x32 pixel architecture achieves ranging based on a frequency modulation/continuous wave (FM/cw) technique implemented by directly amplitude modulating a near-IR diode laser transmitter with a radio frequency (RF) subcarrier that is linearly frequency modulated (i.e. chirped amplitude modulation). The backscattered light is focused onto an array of metal-semiconductor-metal (MSM) detectors where it is detected and mixed with a delayed replica of the laser modulation signal that modulates the responsivity of each detector. The output of each detector is an intermediate frequency (IF) signal (a product of the mixing process) whose frequency is proportional to the target range. Pixel read-out is achieved using code division multiple access techniques as opposed to the usual time-multiplexed techniques to attain high effective frame rates. The raw data is captured with analog-to-digital converters and fed into a PC to demux the pixel data, compute the target ranges, and display the imagery. Last year we demonstrated system proof-of-principle for the first time and displayed an image of a scene collected in the lab that was somewhat corrupted by pixel-to-pixel cross-talk. This year we report on system modifications that reduced pixel-to-pixel cross-talk and new hardware and display codes that enable near real-time stereo display of imagery on the ladar's control computer. The results of imaging tests in the laboratory will also be presented.

  19. Spectral characteristics of draw-tower step-chirped fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Idrisov, Ravil F.; Varzhel, Sergey V.; Kulikov, Andrey V.; Meshkovskiy, Igor K.; Rothhardt, Manfred; Becker, Martin; Schuster, Kay; Bartelt, Hartmut

    2016-06-01

    This paper presents research results on the spectral properties of step-chirped fiber Bragg grating arrays written during the fiber drawing process into a birefringent optical fiber with an elliptical stress cladding. The dependences of resonance shift of the step-chirped fiber Bragg grating on bending, on applied tensile stress and on temperature have been investigated. A usage of such step-chirped fiber Bragg gratings in fiber-optic sensing elements creation has been considered.

  20. Tunable-chirp pulse compression in quasi-phase-matched second-harmonic generation.

    PubMed

    Schober, A M; Imeshev, G; Fejer, M M

    2002-07-01

    We demonstrate continuously tunable compensation of linear chirp on a first-harmonic pump pulse to produce a near-transform-limited second-harmonic output pulse through the use of a chirped, fanned, periodically poled lithium niobate quasi-phase-matching grating. Compensation of positive and negative chirps is possible through reversal of device orientation. The device is simple and monolithic and can be applied to compensation of a higher-order phase with minor modification. PMID:18026383

  1. 47 CFR 74.1233 - Processing FM translator and booster station applications.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Processing FM translator and booster station... SERVICES FM Broadcast Translator Stations and FM Broadcast Booster Stations § 74.1233 Processing FM translator and booster station applications. (a) Applications for FM translator and booster stations...

  2. 47 CFR 74.1233 - Processing FM translator and booster station applications.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Processing FM translator and booster station... SERVICES FM Broadcast Translator Stations and FM Broadcast Booster Stations § 74.1233 Processing FM translator and booster station applications. (a) Applications for FM translator and booster stations...

  3. Compression and collisions of chirped pulses in a dense two-level medium

    NASA Astrophysics Data System (ADS)

    Novitsky, Denis V.

    2016-01-01

    Using numerical simulations, we study propagation of linearly-chirped optical pulses in a homogeneously broadened two-level medium. We pay attention to the three main topics - validity of the rotating-wave approximation (RWA), pulse compression, and collisions of counter-propagating pulses. The cases of long and single-cycle pulses are considered and compared with each other. We show that the RWA does not give a correct description of chirped pulse interaction with the medium. The compression of the chirp-free single-cycle pulse is stronger than of the chirped one, while the opposite is true for long pulses. We demonstrate that the influence of chirp on the collisions of the long pulses allows us to control the state of the transmitted radiation: the transmission of the chirp-free pulse can be dramatically changed under collision with the chirped counter-propagating one, in sharp contrast to the case when both pulses are chirped. On the other hand, the collisions of the chirped single-cycle pulses can be used for precise control of medium excitation in a narrow spatial region.

  4. Transit time of chirped pulses through one-dimensional, nonabsorbing barriers.

    PubMed

    D'Aguanno, G; Centini, M; Bloemer, M J; Myneni, K; Scalora, M; Bowden, C M; Sibilia, C; Bertolotti, M

    2002-02-01

    Experiments show that the transit times of chirped, narrow-band pulses that move across nonabsorbing, one-dimensional barriers are modified dramatically by the interplay between the chirp and the transmission function of the sample. In an experiment we monitored 0.9-ns chirped, nearly Gaussian pulses as they traversed a 450-mum GaAs etalon. At certain wavelengths pulse transit times can be superluminal or even negative. To explain these phenomena we have proposed a generalization of the transit time for chirped pulses that is still meaningful even when the transit times are superluminal or negative. Our predictions agree well with the experimental results. PMID:18007747

  5. SCA Waveform Development for Space Telemetry

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  6. Gaussian Decomposition of Laser Altimeter Waveforms

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  7. Wavelet analysis of the impedance cardiogram waveforms

    NASA Astrophysics Data System (ADS)

    Podtaev, S.; Stepanov, R.; Dumler, A.; Chugainov, S.; Tziberkin, K.

    2012-12-01

    Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt)max) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.

  8. STEREO database of interplanetary Langmuir electric waveforms

    NASA Astrophysics Data System (ADS)

    Briand, C.; Henri, P.; Génot, V.; Lormant, N.; Dufourg, N.; Cecconi, B.; Nguyen, Q. N.; Goetz, K.

    2016-02-01

    This paper describes a database of electric waveforms that is available at the Centre de Données de la Physique des Plasmas (CDPP, http://cdpp.eu/). This database is specifically dedicated to waveforms of Langmuir/Z-mode waves. These waves occur in numerous kinetic processes involving electrons in space plasmas. Statistical analysis from a large data set of such waves is then of interest, e.g., to study the relaxation of high-velocity electron beams generated at interplanetary shock fronts, in current sheets and magnetic reconnection region, the transfer of energy between high and low frequencies, the generation of electromagnetic waves. The Langmuir waveforms were recorded by the Time Domain Sampler (TDS) of the WAVES radio instrument on board the STEREO mission. In this paper, we detail the criteria used to identify the Langmuir/Z-mode waves among the whole set of waveforms of the STEREO spacecraft. A database covering the November 2006 to August 2014 period is provided. It includes electric waveforms expressed in the normalized frame (B,B × Vsw,B × (B × Vsw)) with B and Vsw the local magnetic field and solar wind velocity vectors, and the local magnetic field in the variance frame, in an interval of ±1.5 min around the time of the Langmuir event. Quicklooks are also provided that display the three components of the electric waveforms together with the spectrum of E∥, together with the magnitude and components of the magnetic field in the 3 min interval, in the variance frame. Finally, the distribution of the Langmuir/Z-mode waves peak amplitude is also analyzed.

  9. The Waveform Suite: A robust platform for accessing and manipulating seismic waveforms in MATLAB

    NASA Astrophysics Data System (ADS)

    Reyes, C. G.; West, M. E.; McNutt, S. R.

    2009-12-01

    The Waveform Suite, developed at the University of Alaska Geophysical Institute, is an open-source collection of MATLAB classes that provide a means to import, manipulate, display, and share waveform data while ensuring integrity of the data and stability for programs that incorporate them. Data may be imported from a variety of sources, such as Antelope, Winston databases, SAC files, SEISAN, .mat files, or other user-defined file formats. The waveforms being manipulated in MATLAB are isolated from their stored representations, relieving the overlying programs from the responsibility of understanding the specific format in which data is stored or retrieved. The waveform class provides an object oriented framework that simplifies manipulations to waveform data. Playing with data becomes easier because the tedious aspects of data manipulation have been automated. The user is able to change multiple waveforms simultaneously using standard mathematical operators and other syntactically familiar functions. Unlike MATLAB structs or workspace variables, the data stored within waveform class objects are protected from modification, and instead are accessed through standardized functions, such as get and set; these are already familiar to users of MATLAB’s graphical features. This prevents accidental or nonsensical modifications to the data, which in turn simplifies troubleshooting of complex programs. Upgrades to the internal structure of the waveform class are invisible to applications which use it, making maintenance easier. We demonstrate the Waveform Suite’s capabilities on seismic data from Okmok and Redoubt volcanoes. Years of data from Okmok were retrieved from Antelope and Winston databases. Using the Waveform Suite, we built a tremor-location program. Because the program was built on the Waveform Suite, modifying it to operate on real-time data from Redoubt involved only minimal code changes. The utility of the Waveform Suite as a foundation for large developments is demonstrated with the Correlation Toolbox for MATLAB. This mature package contains 50+ codes for carrying out various type of waveform correlation analyses (multiplet analysis, clustering, interferometry, …) This package is greatly strengthened by delegating numerous book-keeping and signal processing tasks to the underlying Waveform Suite. The Waveform Suite’s built-in tools for searching arbitrary directory/file structures is demonstrated with matched video and audio from the recent eruption of Redoubt Volcano. These tools were used to find subsets of photo images corresponding to specific seismic traces. Using Waveform’s audio file routines, matched video and audio were assembled to produce outreach-quality eruption products. The Waveform Suite is not designed as a ready-to-go replacement for more comprehensive packages such as SAC or AH. Rather, it is a suite of classes which provide core time series functionality in a MATLAB environment. It is designed to be a more robust alternative to the numerous ad hoc MATLAB formats that exist. Complex programs may be created upon the Waveform Suite’s framework, while existing programs may be modified to take advantage of the Waveform Suites capabilities.

  10. Surface and liquid-crystalline properties of FmHnFm triblock semifluorinated n-alkanes.

    PubMed

    Chachaj-Brekiesz, Anna; Górska, Natalia; Osiecka, Natalia; Makyła-Juzak, Katarzyna; Dynarowicz-Łątka, Patrycja

    2016-05-01

    A series of triblock semifluorinated n-alkanes of the general formula: F(CF2)m(CH2)n(CF2)mF, (in short FmHnFm), where m=10, 12, and n=6, 8, and 12 have been synthesized and employed for liquid crystalline studies and Langmuir monolayer characterization. Differential scanning calorimetry (DSC) measurements together with texture observation with polarizing microscope (POM) revealed the presence of liquid crystalline smectic phases for all the investigated homologs. The behavior of the studied molecules spread at the free water surface has also been investigated. Our results show for the first time that these unusual film-forming materials, which are completely hydrophobic in nature and do not possess any polar group in their structure, are surface active and form insoluble (Langmuir) monolayers at the air/water interface. Due to the fact that these molecules are chemically inert and, similar to the semifluorinated diblocks, are not toxic, they may be destined for biomedical uses as gas carriers and contrast agents, as well as in drug delivery systems. PMID:26952494

  11. Role of spin polarization in FM/Al/FM trilayer film at low temperature

    NASA Astrophysics Data System (ADS)

    Lu, Ning; Webb, Richard

    2014-03-01

    Measurements of electronic transport in diffusive FM/normal metal/FM trilayer film are performed at temperature ranging from 2K to 300K to determine the behavior of the spin polarized current in normal metal under the influence of quantum phase coherence and spin-orbital interaction. Ten samples of Hall bar with length of 200 micron and width of 20 micron are fabricated through e-beam lithography followed by e-gun evaporation of Ni0.8Fe0.2, aluminum and Ni0.8Fe0.2 with different thickness (5nm to 45nm) in vacuum. At low temperature of 4.2K, coherent backscattering, Rashba spin-orbital interaction and spin flip scattering of conduction electrons contribute to magnetoresistance at low field. Quantitative analysis of magnetoresistance shows transition between weak localization and weak anti-localization for samples with different thickness ratio, which indicates the spin polarization actually affects the phase coherence length and spin-orbital scattering length. However, at temperature between 50K and 300K, only the spin polarization dominates the magnetoresistance.

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

    NASA Astrophysics Data System (ADS)

    Evans, J. W.

    1985-12-01

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

  13. Auditory brainstem responses to chirps delivered by different insert earphones

    PubMed Central

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

    2012-01-01

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

  14. Chirped Pulse Microwave Spectroscopy in Pulsed Uniform Supersonic Flows

    NASA Astrophysics Data System (ADS)

    Abeysekera, Chamara; Oldham, James; Prozument, Kirill; Joalland, Baptiste; Park, Barratt; Field, Robert W.; Sims, Ian; Suits, Arthur; Zack, Lindsay

    2014-06-01

    We present preliminary results describing the development of a new instrument that combines two powerful techniques: Chirped Pulse-Fourier Transform MicroWave (CP-FTMW) 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. We have constructed a new high-power K_a-band, 26-40 GHz, chirped pulse spectrometer with sub-MHz resolution, analogous to the revolutionary CP-FTMW spectroscopic technique developed in the Pate group at University of Virginia. In order to study smaller molecules, the E-band, 60-90 GHz, CP capability was added to our spectrometer. A novel strategy for generating uniform supersonic flow through a Laval nozzle is introduced. High throughput pulsed piezo-valve is used to produce cold (30 K) uniform flow with large volumes of 150 cm^3 and densities of 1014 molecules/cm3 with modest pumping facilities. The uniform flow conditions for a variety of noble gases extend as far as 20 cm from the Laval nozzle and a single compound turbo-molecular pump maintains the operating pressure. Two competing design considerations are critical to the performance of the system: a low temperature flow is needed to maximize the population difference between rotational levels, and high gas number densities are needed to ensure rapid cooling to achieve the uniform flow conditions. At the same time, collision times shorter than the chirp duration will give inaccurate intensities and reduced signal levels due to collisional dephasing of free induction decay. Details of the instrument and future directions and challenges will be discussed.

  15. Effect of pulse profile and chirp on a laser wakefield generation

    SciTech Connect

    Zhang Xiaomei; Shen Baifei; Ji Liangliang; Wang Wenpeng; Xu Jiancai; Yu Yahong; Yi Longqing; Wang Xiaofeng; Hafz, Nasr A. M.; Kulagin, V.

    2012-05-15

    A laser wakefield driven by an asymmetric laser pulse with/without chirp is investigated analytically and through two-dimensional particle-in-cell simulations. For a laser pulse with an appropriate pulse length compared with the plasma wavelength, the wakefield amplitude can be enhanced by using an asymmetric un-chirped laser pulse with a fast rise time; however, the growth is small. On the other hand, the wakefield can be greatly enhanced for both positively chirped laser pulse having a fast rise time and negatively chirped laser pulse having a slow rise time. Simulations show that at the early laser-plasma interaction stage, due to the influence of the fast rise time the wakefield driven by the positively chirped laser pulse is more intense than that driven by the negatively chirped laser pulse, which is in good agreement with analytical results. At a later time, since the laser pulse with positive chirp exhibits opposite evolution to the one with negative chirp when propagating in plasma, the wakefield in the latter case grows more intensely. These effects should be useful in laser wakefield acceleration experiments operating at low plasma densities.

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

    SciTech Connect

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

    1986-12-01

    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.

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

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

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

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

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

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

  19. Diode-quad bridge for reactive transducers and FM discriminators

    NASA Technical Reports Server (NTRS)

    Harrison, D. R.; Dimeff, J.

    1972-01-01

    Diode-quad bridge circuit was developed for use with pressure-sensitive capacitive transducers, liquid-level measuring devices, proximity deflection sensors, and inductive displacement sensors. It may also be used as FM discriminator and as universal impedance bridge.

  20. 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

  1. 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

  2. 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

  3. 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

  4. Chirped nonlinear cavity for digital quantum state readout without switching

    NASA Astrophysics Data System (ADS)

    Naaman, Ofer; Aumentado, José.; Friedland, Lazar; Wurtele, Jonathan; Siddiqi, Irfan

    2009-03-01

    We observe a new phase-locking effect in a high-Q cavity embedding a Josephson junction driven with a chirped microwave signal. Above a critical drive amplitude, the cavity phase-locks to the drive and its oscillation amplitude grows with time. Below threshold, the cavity dephases from the drive and its amplitude remains small. The transition to phase-locking is associated with a sharp threshold sensitive to the junction I0, and can be used for digital detection of quantum states. This detector smoothly evolves into one oscillation state or the other without relying on any switching process.

  5. Attenuated total reflectance spectroscopy with chirped-pulse upconversion.

    PubMed

    Shirai, Hideto; Duchesne, Constance; Furutani, Yuji; Fuji, Takao

    2014-12-01

    Chirped-pulse upconversion technique has been applied to attenuated total reflectance (ATR) infrared spectroscopy. An extremely broadband infrared pulse was sent to an ATR diamond prism and the reflected pulse was converted to the visible by using four-wave mixing in krypton gas. Absorption spectra of liquids in the range from 200 to 5500 cm(-1) were measured with a visible spectrometer on a single-shot basis. The system was applied to observe the dynamics of exchanging process of two solvents, water and acetone, which give clear vibrational spectral contrast. We observed that the exchange was finished within ∼ 10 ms. PMID:25606893

  6. Chirped-Pulse Microwave Spectroscopy in the Undergraduate Chemistry Curriculum

    NASA Astrophysics Data System (ADS)

    Gaster, Sydney A.; Hall, Taylor M.; Arnold, Sean; Brown, Gordon G.

    2015-06-01

    The use of chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy as a tool for training undergraduates will be discussed. Coker College's inexpensive, versatile CP-FTMW spectrometer has been applied both in the undergraduate teaching laboratory and the undergraduate research laboratory. In both cases, the education of the students is a central priority of the project. The study of 3-iodopyridine, a project recently completed by Coker undergraduate students, will be discussed. Details of the Coker CP-FTMW spectrometer will also be presented.

  7. Optimal control of quantum systems by chirped pulses

    NASA Astrophysics Data System (ADS)

    Amstrup, B.; Doll, J. D.; Sauerbrey, R. A.; Szabó, G.; Lorincz, A.

    1993-11-01

    Research on optimal control of quantum systems has been severely restricted by the lack of experimentally feasible control pulses. Here, to overcome this obstacle, optimal control is considered with the help of chirped pulses. Simulated annealing is used as the optimizing procedure. The examples treated are pulsed population inversion between electronic levels, and optimization of vibronic excitation in the presence of another electronic level. In the problem of population inversion effective potentials of displaced harmonic oscillators are used. For optimizing vibronic excitation the CsI model potential is used.

  8. High-order dispersion in chirped-pulse oscillators.

    PubMed

    Kalashnikov, Vladimir L; Fernández, Alma; Apolonski, Alexander

    2008-03-17

    The effects of high-order dispersion on a chirped-pulse oscillator operating in the positive dispersion regime were studied both theoretically and experimentally. It was found that odd and negative even high-order dispersions impair the oscillator stability owing to resonance with the dispersion waves, but can broaden the spectrum as in the case of continuum generation in the fibers. Positive fourth-order dispersion enhances the stability and shifts the stability range into negative dispersion. The destabilization mechanism was found to be a parametrical instability which causes noisy mode locking around zero dispersion. PMID:18542516

  9. Plasma absorption evidence via chirped pulse spectral transmission measurements

    SciTech Connect

    Jedrkiewicz, Ottavia; Minardi, Stefano; Couairon, Arnaud; Jukna, Vytautas; Selva, Marco; Di Trapani, Paolo

    2015-06-08

    This work aims at highlighting the plasma generation dynamics and absorption when a Bessel beam propagates in glass. We developed a simple diagnostics allowing us to retrieve clear indications of the formation of the plasma in the material, thanks to transmission measurements in the angular and wavelength domains. This technique featured by the use of a single chirped pulse having the role of pump and probe simultaneously leads to results showing the plasma nonlinear absorption effect on the trailing part of the pulse, thanks to the spectral-temporal correspondence in the measured signal, which is also confirmed by numerical simulations.

  10. A transformer of closely spaced pulsed waveforms

    NASA Technical Reports Server (NTRS)

    Niedra, J.

    1970-01-01

    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.

  11. ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

    SciTech Connect

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

    2008-06-17

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

  12. A multi-channel waveform digitizer system

    SciTech Connect

    Bieser, F.; Muller, W.F.J. )

    1990-04-01

    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.

  13. Tailored Voltage Waveform Capacitively-Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Booth, Jean-Paul; Lafleur, Trevor; Delattre, Pierre-Alexandre; Johnson, Erik

    2012-10-01

    A major limitation of large-area capacitively-coupled plasmas for materials processing is the inability to increase plasma density without increasing ion bombardment energy. Heil et al. (J. Phys. D 41. 165202, (2008)) demonstrated that for a driving voltage comprising one frequency, f, and it's harmonic 2f, the symmetry of the sheaths can be broken (the Electrical Asymmetry Effect, EAE). We have investigated large-area plasmas (50cm dia) in Ar driven by arbitrary voltage waveforms. Specifically we studied waveforms comprising sharp positive pulses (10-20ns wide, 15MHz repetition frequency). The voltage waveform was measured by an HV probe close to the powered electrode edge, the electron density was measured with a microwave hairpin resonator, the ion flux was measured by an array of planar ion flux probes in the grounded counter-electrode, and the power absorbed was determined from the current and voltage waveforms measured by a derivative probe. As well as the expected EAE observed in the electrode self-bias, we were able to demonstrate a dramatic increase in electron density (and concomitant increased power absorption) with reduced pulse-width at constant amplitude, in qualitative agreement with recent PIC simulations (Lafleur et al, APL 100, 194101(2012)).

  14. Waveform Selectivity at the Same Frequency

    PubMed Central

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

    2015-01-01

    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 circuit elements are then combined to absorb or transmit specific waveforms in between. This waveform selectivity gives us another degree of freedom to control electromagnetic waves in various fields including wireless communications, as our simulation reveals that the metasurfaces are capable of varying bit error rates in response to different waveforms. PMID:25866071

  15. Analysis of an impulse noise suppressor for FM demodulators

    NASA Technical Reports Server (NTRS)

    James, S. N.

    1974-01-01

    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.

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

    SciTech Connect

    Afhami, Saeedeh; Eslami, Esmaeil

    2014-08-15

    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.

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

    SciTech Connect

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

    2012-05-01

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

  18. Control of Brillouin short-pulse seed amplification by chirping the pump pulse

    SciTech Connect

    Lehmann, G.; Spatschek, K. H.

    2015-04-15

    Seed amplification via Brillouin backscattering of a long pump pulse is considered. Similar to Raman amplification, several obstructive effects may occur during short-pulse Brillouin amplification. One is the spontaneous Raman backscattering of the pump before interacting with the seed. Preforming the plasma and/or chirping the pump will reduce unwanted pump backscattering. Optimized regions for low-loss pump propagation were proposed already in conjunction with Raman seed amplification. Hence, the influence of the chirp of the pump during Brillouin interaction with the seed becomes important and will be considered here. Both, the linear as well as the nonlinear evolution phases of the seed caused by Brillouin amplification under the action of a chirped pump are investigated. The amplification rate as well as the seed profiles are presented as function of the chirping rate. Also the dependence of superradiant scaling rates on the chirp parameter is discussed.

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

    SciTech Connect

    Xu Junjie

    2011-03-15

    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.

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

    SciTech Connect

    Pronin, E. A.; Starace, Anthony F.; Peng Liangyou

    2011-07-15

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

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

    PubMed Central

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

    2009-01-01

    We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H3+ and C5H5+ in the case of negatively chirped pulses and C6H5+ in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth. PMID:19696899

  2. Enhancement of proton acceleration by frequency-chirped laser pulse in radiation pressure mechanism

    NASA Astrophysics Data System (ADS)

    Vosoughian, H.; Riazi, Z.; Afarideh, H.; Yazdani, E.

    2015-07-01

    The transition from hole-boring to light-sail regime of radiation pressure acceleration by frequency-chirped laser pulses is studied using particle-in-cell simulation. The penetration depth of laser into the plasma with ramped density profile increases when a negatively chirped laser pulse is applied. Because of this induced transparency, the laser reflection layer moves deeper into the target and the hole-boring stage would smoothly transit into the light-sail stage. An optimum chirp parameter which satisfies the laser transparency condition, a 0 ≈ π n e l / n c λ , is obtained for each ramp scale length. Moreover, the efficiency of conversion of laser energy into the kinetic energy of particles is maximized at the obtained optimum condition. A relatively narrow proton energy spectrum with peak enhancement by a factor of 2 is achieved using a negatively chirped pulse compared with the un-chirped pulse.

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

    We present the effect of chirping a femtosecond laser pulse on the fragmentation of n-propyl benzene. An enhancement of an order of magnitude for the relative yields of C3H 3 + and C5H 5 + in the case of negatively chirped pulses and C6H 5 + in the case of positively chirped pulses with respect to the transform-limited pulse indicates that in some fragmentation channel, coherence of the laser field plays an important role. For the relative yield of all other heavier fragment ions, resulting from the interaction of the intense laser field with the molecule, there is no such enhancement effect with the sign of chirp, within experimental errors. The importance of the laser phase is further reinforced through a direct comparison of the fragmentation results with the second harmonic of the chirped laser pulse with identical bandwidth.

  4. JTRS/SCA and Custom/SDR Waveform Comparison

    NASA Technical Reports Server (NTRS)

    Oldham, Daniel R.; Scardelletti, Maximilian C.

    2007-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    1981-01-01

    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.

  6. Chirped CPMG for well-logging NMR applications.

    PubMed

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

    2014-05-01

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

  7. Modification of chirped laser pulses via delayed rotational nonlinearity

    NASA Astrophysics Data System (ADS)

    Romanov, D. A.; Odhner, J. H.; Levis, R. J.

    2016-03-01

    To interpret single-shot measurements of rotational revival patterns in molecular gases excited by an ultrashort laser pulse, an analytical description of the probe pulse modulation by the impulsively excited medium is developed. A femtosecond pump laser pulse prepares a rotational wavepacket in a gas-phase sample, and the resulting periodic revivals are mapped into the frequency domain by using a substantially chirped continuum probe pulse. Since the standard approximate descriptions of probe pulse propagation are inapplicable (such as the slowly varying envelope approximation and the slowly evolving wave approximation), we propose an approach capable of incorporating both the substantial chirp of the pulse and the temporal dispersion of the medium response. Theory is presented for the case where the frequency change of the probe during the probe pulse duration is comparable with the carrier frequency. Analytical expressions are obtained for the probe signal modulation over the pump-probe interaction region and for the resulting heterodyned transient birefringence spectra. The approach is illustrated using the case of nitrogen gas.

  8. Photodissociation of D2 (+) induced by linearly chirped laser pulses.

    PubMed

    Csehi, Andrs; Halsz, Gbor J; Cederbaum, Lorenz S; Vibk, gnes

    2015-07-01

    Recently, it has been revealed that so-called light-induced conical intersections (LICIs) can be formed both by standing or by running laser waves even in diatomic molecules. Due to the strong nonadiabatic couplings, the existence of such LICIs has significant impact on the dynamical properties of a molecular system. In our former studies, the photodissociation process of the D2 (+) molecule was studied initiating the nuclear dynamics both from individual vibrational levels and from the superposition of all the vibrational states produced by ionizing D2. In the present work, linearly chirped laser pulses were used for initiating the dissociation dynamics of D2 (+). In contrast to the constant frequency (transform limited) laser fields, the chirped pulses give rise to LICIs with a varying position according to the temporal frequency change. To demonstrate the impact of these LICIs on the dynamical properties of diatomics, the kinetic energy release spectra, the total dissociation probabilities, and the angular distributions of the D2 (+) photofragments were calculated and discussed. PMID:26156481

  9. Chirped CPMG for well-logging NMR applications

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  10. Modification of chirped laser pulses via delayed rotational nonlinearity.

    PubMed

    Romanov, D A; Odhner, J H; Levis, R J

    2016-03-28

    To interpret single-shot measurements of rotational revival patterns in molecular gases excited by an ultrashort laser pulse, an analytical description of the probe pulse modulation by the impulsively excited medium is developed. A femtosecond pump laser pulse prepares a rotational wavepacket in a gas-phase sample, and the resulting periodic revivals are mapped into the frequency domain by using a substantially chirped continuum probe pulse. Since the standard approximate descriptions of probe pulse propagation are inapplicable (such as the slowly varying envelope approximation and the slowly evolving wave approximation), we propose an approach capable of incorporating both the substantial chirp of the pulse and the temporal dispersion of the medium response. Theory is presented for the case where the frequency change of the probe during the probe pulse duration is comparable with the carrier frequency. Analytical expressions are obtained for the probe signal modulation over the pump-probe interaction region and for the resulting heterodyned transient birefringence spectra. The approach is illustrated using the case of nitrogen gas. PMID:27036454

  11. Characterization and compensation of the residual chirp in a Mach-Zehnder-type electro-optical intensity modulator.

    PubMed

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

    2010-01-18

    We utilize various techniques to characterize the residual phase modulation of a waveguide-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement. PMID:20173940

  12. Characterization and compensation of the residual chirp in a Mach-Zehnder-type electro-optical intensity modulator

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

    We utilize various techniques to characterize the residual phase modulation of a fiber-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement.

  13. 47 CFR 73.809 - Interference protection to full service FM stations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Interference protection to full service FM... RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) § 73.809 Interference protection to full service FM stations. (a) If a full service commercial or NCE FM facility application...

  14. 47 CFR 73.809 - Interference protection to full service FM stations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Interference protection to full service FM... RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) § 73.809 Interference protection to full service FM stations. (a) If a full service commercial or NCE FM facility application...

  15. 47 CFR 73.201 - Numerical designation of FM broadcast channels.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Numerical designation of FM broadcast channels... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.201 Numerical designation of FM broadcast channels. The FM broadcast band consists of that portion of the radio frequency spectrum between 88 MHz...

  16. 47 CFR 73.809 - Interference protection to full service FM stations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Interference protection to full service FM... RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) § 73.809 Interference protection to full service FM stations. (a) If a full service commercial or NCE FM facility application...

  17. 47 CFR 73.809 - Interference protection to full service FM stations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Interference protection to full service FM... RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) § 73.809 Interference protection to full service FM stations. (a) If a full service commercial or NCE FM facility application...

  18. FM Technologies: Enhancing Language and Learning in Home and School Environments.

    ERIC Educational Resources Information Center

    Flexer, Carol

    2000-01-01

    This article discusses why FM technologies and a remote microphone should be used to assist students with hearing impairments in inclusive classrooms, lists factors governing the selection of FM coupling arrangements and performance, and describes types of FM systems. Cochlear implants and FM technology are also addressed. (Contains six references…

  19. 47 CFR 73.809 - Interference protection to full service FM stations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Interference protection to full service FM... RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) § 73.809 Interference protection to full service FM stations. (a) If a full service commercial or NCE FM facility application...

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

    NASA Astrophysics Data System (ADS)

    Gao, Yan; Yu, Yanguang; Xi, Jiangtao

    2012-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  2. Waveforms Measured in Confined Thermobaric Explosion

    SciTech Connect

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

    2007-05-04

    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.

  3. Bazhen Fm matured reservoir evaluation (West Siberia, Russia)

    NASA Astrophysics Data System (ADS)

    Parnachev, S.; Skripkin, A.; Baranov, V.; Zakharov, S.

    2015-02-01

    The depletion of the traditional sources of hydrocarbons leads to the situation when the biggest players of the oil and gas production market turn to unconventional reserves. Commercial shale oil and gas production levels in the USA have largely determined world prospects for oil and gas industry development. Russia takes one of the leading place in the world in terms of shale oil resources. The main source rock of the West Siberia, the biggest oil and gas basin in Russia under development, the Bazhen Fm and its stratigraphic and lithologic analogs, is located in the territory of over 1,000,000 square kilometers. Provided it has similar key properties (organic carbon content, porosity, permeability) with the deposits of the Bakken Fm and Green River Fm, USA, it is still extremely poorly described with laboratory methods. We have performed the laboratory analysis of core samples from a well drilled in Bazhen Fm deposits with matured organic matter (Tmax>435 °C). It was demonstrated the applicability of the improved steady-state gas flow method to evaluate the permeability of nanopermeable rocks. The role of natural fracturing in forming voids was determided that allows regarding potential Bazhen Fm reservoirs as systems with dual porosity and dual permeability.

  4. Waveform Generation of Time-Limited Pseudo-Random Signals

    SciTech Connect

    Zhou, Ning; Pierre, John W.

    2006-09-29

    A time-limited pseudo-random signal is an important component in perturbation signals during a system identification procedure. In this paper, a finite-time duration pseudo-random waveform with desired continuous spectral features is generated using an extended time-frequency domain swapping algorithm. Impulse responses of Finite Impulse Response (FIR) filters are used as initial waveforms. Through iterations, the waveform is polished to achieve a desired smaller crest factor while maintaining major spectral features. A comparison with the commonly used filtered Gaussian white noise waveform shows that the new waveform generated with the proposed algorithm has a much flatter spectrum and sharp transient as being desired.

  5. Binary Black Holes: Mergers, Dynamics, and Waveforms

    NASA Astrophysics Data System (ADS)

    Centrella, Joan

    2007-04-01

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

  6. Acoustofluidic Chemical Waveform Generator and Switch

    PubMed Central

    2015-01-01

    Eliciting a cellular response to a changing chemical microenvironment is central to many biological processes including gene expression, cell migration, differentiation, apoptosis, and intercellular signaling. The nature and scope of the response is highly dependent upon the spatiotemporal characteristics of the stimulus. To date, studies that investigate this phenomenon have been limited to digital (or step) chemical stimulation with little control over the temporal counterparts. Here, we demonstrate an acoustofluidic (i.e., fusion of acoustics and microfluidics) approach for generating programmable chemical waveforms that permits continuous modulation of the signal characteristics including the amplitude (i.e., sample concentration), shape, frequency, and duty cycle, with frequencies reaching up to 30 Hz. Furthermore, we show fast switching between multiple distinct stimuli, wherein the waveform of each stimulus is independently controlled. Using our device, we characterized the frequency-dependent activation and internalization of the β2-adrenergic receptor (β2-AR), a prototypic G-protein coupled receptor (GPCR), using epinephrine. The acoustofluidic-based programmable chemical waveform generation and switching method presented herein is expected to be a powerful tool for the investigation and characterization of the kinetics and other dynamic properties of many biological and biochemical processes. PMID:25405550

  7. Tunable optoelectronic oscillator based on a chirped Mach-Zehnder modulator

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  8. Dynamic chirp control and pulse compression for attosecond high-order harmonic emission.

    PubMed

    Zheng, Yinghui; Zeng, Zhinan; Zou, Pu; Zhang, Li; Li, Xiaofang; Liu, Peng; Li, Ruxin; Xu, Zhizhan

    2009-07-24

    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. PMID:19659355

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

    SciTech Connect

    Zheng Yinghui; Zeng Zhinan; Zou Pu; Zhang Li; Li Xiaofang; Liu Peng; Li Ruxin; Xu Zhizhan

    2009-07-24

    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.

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

    SciTech Connect

    Song, Q.; Wu, X. Y.; Wang, J. X.; Kawata, S.; Wang, P. X.

    2014-05-15

    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.

  11. High-order-harmonic generation driven by pulses with angular spatial chirp

    NASA Astrophysics Data System (ADS)

    Hernández-García, Carlos; Jaron-Becker, Agnieszka; Hickstein, Daniel D.; Becker, Andreas; Durfee, Charles G.

    2016-02-01

    We present and analyze a technique to drive high-order harmonics by laser pulses with an angular spatial chirp. Results of our numerical simulations show that each harmonic is emitted with an angular chirp which scales inversely with the harmonic order and leads to additional control of the spatial and temporal resolution of the spectrum. In particular, the use of angular chirp leads to separation of the harmonics in two dimensions where (i) high spectral resolution can be achieved and (ii) the temporal periodicity of the harmonic pulse trains can be controlled. We show that this technique does not require carrier-envelope-phase stabilization when using few-cycle laser pulses.

  12. Positive and negative chirping of laser pulses shorter than 100 fsec in a saturable absorber

    SciTech Connect

    Miranda, R.S.; Jacobovitz, G.R.; Brito Cruz, C.H.; Scarparo, M.A.F.

    1986-04-01

    We present a calculation of the chirp generated in laser pulses shorter than 100 fsec on propagation through a saturable absorber (DODCI in ethylene glycol). The calculation takes into account the absorber saturation and the solvent nonlinear refractive index. At pulse energies greater than 10 nJ the chirp tends to be predominantly positive, and it increases rapidly as the pulse duration becomes shorter than 50 fsec. At pulse energies in the 1--7-nJ range the chirp is mostly negative for pulses longer than 30 fsec.

  13. Rate equation analysis of frequency chirp in optically injection-locked quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Wang, C.; Grillot, F.; Kovanis, V. I.; Bodyfelt, J. D.; Even, J.

    2014-03-01

    The frequency chirp characteristics of an optically injection-locked quantum cascade laser are theoretically investigated. The key parameter chirp-to-power ratio (CPR) is analytically derived from a full rate equation model. The CPR value can be efficiently reduced by increasing optical injection strength, especially at modulation frequencies less than 10 GHz. In contrast to interband lasers, both positive and negative frequency detuning increase the CPR. Since the frequency detuning is also predicted to enhance the intensity modulation response, a trade-off is required in the optical injection to simultaneously obtain a large modulation bandwidth and low frequency chirp.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    We study the two-photon double-ionization process of the helium atom by solving numerically the nonrelativistic, time-dependent Schrödinger 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.

  15. Intrinsic chirp of attosecond pulses: Single-atom model versus experiment

    SciTech Connect

    Kazamias, S.; Balcou, Ph.

    2004-06-01

    We demonstrate and evaluate the importance of an intrinsic chirp inherent to attosecond pulse creation accompanying high-order harmonic generation in recently published experimental data by Dinu et al. [Phys. Rev. Lett. 91, 063901 (2003)]. We present an analytical model, from which the atomic origin of the harmonic chirp is clearly understood. Moreover, the behavior of the chirp as a function of experimental parameters such as laser intensity is inferred. The comparison between our model and the experimental data provides us with useful information about the conditions in which the high-order harmonics is generated.

  16. Processing Aftershock Sequences Using Waveform Correlation

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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.

  17. Design of AM/FM mobile telephone triband antenna

    NASA Astrophysics Data System (ADS)

    Egashira, Shigeru; Tanaka, Takayuki; Sakitani, Akihide

    1994-04-01

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

  18. Neutron multiplicity measurements of Cf and Fm isotopes

    SciTech Connect

    Hoffman, D.C.; Ford, G.P.; Balagna, J.P.; Veeser, L.R.

    1980-02-01

    Prompt neutrons in coincidence with the fission fragments from the spontaneous fission of /sup 250,252,254/Cf and /sup 257/Fm were measured inside a 75-cm-diameter, Gd-loaded liquid scintillation counter having a neutron-detection efficiency of about 78%. Measurements for /sup 256/Fm were done just outside the counter with an efficiency of 31%. The kinetic energies of both fission fragments and the number of neutrons for each fission event were recorded. From these data, the fragment kinetic energies and masses and the neutron multiplicity distributions were determined for /sup 250,252,254/Cf and /sup 257/Fm. Variances of neutron multiplicity distributions as a function of total fragment kinetic energy and the ratio of fragment masses have been calculated and are presented for all the nuclides studied.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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 40μm and 34μm respectively. It proved that ZFFT-CZT has a small amount of calculation, which can meet the requirement of high precision frequency extraction.

  20. Experimental demonstration of fiber optical parametric chirped-pulse amplification

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

    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.

  1. Compression of chirp pulses from a femtosecond fiber based amplifier

    NASA Astrophysics Data System (ADS)

    Ito, Rumi; Takiuchi, Ken-ichi; Tei, Kazuyoku; Yamaguchi, Shigeru; Enokidani, Jyun; Sumida, Shin

    2015-03-01

    We demonstrate a single mode fiber based master oscillator power amplifier (MOPA) with a single polarization and a fully monolithic design. We have built a passive mode-locked polarization maintaining Yb doped fiber as the master oscillator contains a semiconductor saturable absorber mirror and a chirped fiber Bragg grating for the dispersion management. The net intracavity dispersion was managed to be slightly anomalous. The oscillator generates the 150 fs (sech2) pulses at the center wavelength of 1065 nm, and the repetition rate of 42 MHz. The oscillator output was amplified to 1.4 W from 80 mW in the single stage fiber amplifier which results in pulse shape distortion. The pulse shaping with a band pass filter and a compressor was applied to the amplified pulses. The shaping pulses have the pulse width of 90 fs and the pulse energy of 16 nJ.

  2. Femtosecond Chirp-Free Transient Absorption Method And Apparatus

    DOEpatents

    McBranch, Duncan W.; Klimov, Victor I.

    2001-02-20

    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.

  3. Synchronously pumped femtosecond optical parametric oscillator with broadband chirped mirrors

    NASA Astrophysics Data System (ADS)

    Stankevičiūte, Karolina; Melnikas, Simas; Kičas, Simonas; Trišauskas, Lukas; Vengelis, Julius; Grigonis, Rimantas; Vengris, Mikas; Sirutkaitis, Valdas

    2015-05-01

    We present results obtained during investigation of synchronously pumped optical parametric oscillator (SPOPO) with broadband complementary chirped mirror pairs (CMP). The SPOPO based on β-BBO nonlinear crystal is pumped by second harmonic of femtosecond Yb:KGW laser and provides signal pulses tunable over spectral range from 625 to 980 nm. More than 500 mW are generated in the signal beam, giving up to 27 % pump power to signal power conversion efficiency. The plane SPOPO cavity mirror pairs were specially designed to provide 99 % reflection in broad spectral range corresponding to signal wavelength tuning (630-1030 nm) and to suppress group delay dispersion (GDD) oscillations down to +/-10 fs2. Dispersion properties of designed mirrors were tested with white light interferometer (WLI) and attributed to the SPOPO tuning behaviour.

  4. Active stabilization for optically synchronized optical parametric chirped pulse amplification.

    PubMed

    Schwarz, Alexander; Ueffing, Moritz; Deng, Yunpei; Gu, Xun; Fattahi, Hanieh; Metzger, Thomas; Ossiander, Marcus; Krausz, Ferenc; Kienberger, Reinhard

    2012-02-27

    The development of new high power laser sources tends toward optical parametric chirped pulse amplification (OPCPA) in recent years. One of the difficulties in OPCPA is the the temporal overlap between pump and seed pulses. In this work we characterize our timing jitter on a single-shot basis using spectrally resolved cross-correlation in combination with a position sensitive detector. A commercial beam stabilization is adapted to actively enhance temporal overlap. This delay-stabilizer reduces the RMS jitter from σ = 127 fs down to σ = 24 fs. The enhanced temporal overlap is demonstrated in our frontend and we propose the scheme to be applicable in many optically synchronized high-repetition-rate OPCPA systems. PMID:22418362

  5. 9-Fluorenylmethyl (Fm) Disulfides: Biomimetic Precursors for Persulfides.

    PubMed

    Park, Chung-Min; Johnson, Brett A; Duan, Jicheng; Park, Jeong-Jin; Day, Jacob J; Gang, David; Qian, Wei-Jun; Xian, Ming

    2016-03-01

    The development of a functional disulfide, FmSSPy-A (Fm = 9-fluorenylmethyl; Py = pyridinyl), is reported. It can effectively convert small molecule and protein thiols (-SH) to form -S-SFm adducts under mild conditions. This method allows for a H2S-free and biomimetic protocol to generate highly reactive persulfides (in their anionic forms). The high nucleophilicity of persulfides toward a number of thiol-blocking reagents is also demonstrated. The method holds promise for further understanding the chemical biology of persulfides and S-sulfhydration. PMID:26870874

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

    PubMed

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

    1995-05-01

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

  7. Coherent Decomposition of Fully Polarimetric FM-CW Radar Data

    NASA Astrophysics Data System (ADS)

    Nakamura, Jun; Aoyama, Kazuyasu; Ikarashi, Muneyuki; Yamaguchi, Yoshio; Yamada, Hiroyoshi

    This paper presents a coherent decomposition scheme for polarimetric SAR data. Coherent decomposition means the decomposition is applied to a single or a few scattering matrix data. Based on the scattering matrix acquired with an FM-CW polarimetric SAR system, we have devised a simple decomposition technique using the coherency matrix for the purpose of identifying scatterers. This paper presents the decomposition technique and some decomposition results obtained by a fully polarimetric FM-CW radar. It is shown the scattering mechanisms are well recovered and the orientation angles of wire scatterer are precisely measured.

  8. Giant magnetoimpedance in FM/SiO 2/Cu/SiO 2/FM films at GHz frequencies

    NASA Astrophysics Data System (ADS)

    Corrêa, M. A.; Bohn, F.; Viegas, A. D. C.; Carara, M. A.; Schelp, L. F.; Sommer, R. L.

    We study the magnetic properties at high frequency of new structures of the tri-layer samples. The magnetoimpedance effect was analyzed in FM/i/Cu/i/FM sandwiched layers, where the ferromagnetic layer (FM) is, in fact, a multilayered film [F (10 nm)+Cu (1 nm)]×50 and F is the amorphous ferromagnetic alloy Fe 73.5Cu 1Nb 3Si 13.5B 9 and i is an isolating layer produced by magnetron sputtering. The effect of, both, the probe current frequency (in the range 10 MHz-1.8 GHz) and the dimensions of the magnetic and non-magnetic layers of the MI response were investigated. A comparison between samples with and without the isolating layer is discussed. MI ratios of 220% were obtained for samples at 180 MHz with a ferromagnetic and Cu width layers of 2 and 1 mm, respectively.

  9. Light-charged-particle emission in the spontaneous fission of /sup 250/Cf, /sup 256/Fm, and /sup 257/Fm

    SciTech Connect

    Wild, J.F.; Baisden, P.A.; Dougan, R.J.; Hulet, E.K.; Lougheed, R.W.; Landrum, J.H.

    1985-08-01

    We have measured the energy spectra for the emission of long-range ..cap alpha.. particles from the spontaneous fission of /sup 250/Cf, /sup 256/Fm, and /sup 257/Fm, and for tritons and protons from the spontaneous fission of /sup 250/Cf and /sup 256/Fm. We have determined ..cap alpha.., triton, and proton emission probabilities and estimated total light-particle emission probabilities for these nuclides. We compare these and known emission probabilities for five other spontaneously fissioning nuclides with the deformation energy available at scission and show that there is a possible correlation that is consistent with a one-body dissipation mechanism for transferring release energy to particle clusters.

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

    SciTech Connect

    Polli, D.; Lanzani, G.; Brida, D.; Cerullo, G.; Mukamel, S.

    2010-11-15

    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.

  11. 5 Hz, >250 mJ Optical Parametric Chirped-Pulse Amplifier at 1053 nm

    SciTech Connect

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

    2005-07-15

    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.

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

    SciTech Connect

    Peng Liangyou; Tan Fang; Gong Qihuang; Pronin, Evgeny A.; Starace, Anthony F.

    2009-07-15

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

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

    PubMed Central

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

    2007-01-01

    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

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

    SciTech Connect

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

    2005-09-30

    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.

  15. Nonlinear chirped-pulse propagation and supercontinuum generation in photonic crystal fibers.

    PubMed

    Hu, Xiaohong; Wang, Yishan; Zhao, Wei; Yang, Zhi; Zhang, Wei; Li, Cheng; Wang, Hushan

    2010-09-10

    Based on the generalized nonlinear Schrödinger equation and waveguiding properties typical of the photonic crystal fiber structure, nonlinear chirped-pulse propagation and supercontinua generation in the femtosecond and picosecond regimes are investigated numerically. The simulation results indicate that an input chirp parameter mainly affects the initial stage of spectral broadening caused by the self-phase modulation (SPM) effect. In the femtosecond regime where the SPM effect plays an important role in the process of spectral broadening, an input positive chirp can enhance the supercontinuum bandwidth through a modified pulse compression phase and a decreased propagation distance required by soliton fission. In the picosecond regime, where the SPM effect contributes less to the continuum bandwidth and four-wave mixing process or modulational instability dominates the initial stage of spectral and temporal evolution, the output spectral shape and bandwidths are less sensitive to the input chirp parameters. PMID:20830188

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  17. Quantum dynamics of a two-state system induced by a chirped zero-area pulse

    NASA Astrophysics Data System (ADS)

    Lee, Han-gyeol; Song, Yunheung; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

    2016-02-01

    It is well known that area pulses make Rabi oscillation and chirped pulses in the adiabatic interaction regime induce complete population inversion of a two-state system. Here we show that chirped zero-area pulses could engineer an interplay between the adiabatic evolution and Rabi-like rotations. In a proof-of-principle experiment utilizing spectral chirping of femtosecond laser pulses with a resonant spectral hole, we demonstrate that the chirped zero-area pulses could induce, for example, complete population inversion and return of the cold rubidium atom two-state system. Experimental result agrees well with the theoretically considered overall dynamics, which could be approximately modeled to a Ramsey-like three-pulse interaction, where the x and z rotations are driven by the hole and the main pulse, respectively.

  18. Magnetostriction of FM/TbFe (FM=Fe, Py-permalloy, FeCo) coupled bilayer

    NASA Astrophysics Data System (ADS)

    Li, Jianjun

    2012-04-01

    Choosing TbFe as the magnetostrictive layer and using soft ferromagnetic materials (FM=Fe, Py-permalloy, FeCo) as the inductive layer, we report the magnetization and magnetostriction of the S/FM(10 nm)/TbFe(10 nm) coupled bilayer (S-glass substrate). The magnetization of the coupled bilayer is attributed to the soft ferromagnetic layer and there is no contribution from the TbFe layer. Interfacial exchange interaction plays an important role in determining the magnetostriction of the coupled bilayer. The effect coming from the deposition Argon pressure on the magnetostriction of the coupled bilayer was also investigated.

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

    PubMed

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

    2009-11-15

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

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

    SciTech Connect

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

    1989-01-01

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

  1. Seismic waveform inversion using neural networks

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  2. Insights Into GLAS Waveforms Using Google Earth

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    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.

  3. Weigh-In-Motion Waveform Capture Systems

    Energy Science and Technology Software Center (ESTSC)

    2007-09-01

    Input data is generated from multiple weight sensor signals embedded in a thin weighing pad. This information is then reduced to total weight and position of a wheel rolling over the pad. This produces a signal which includes both the wheel weight and it inertial effects due to vehicle bounce, engine noise, and other mechanical vibrations. In order to extract accurate weight information of the wheel from the extraneous information, it is necessary to firstmore » capture the waveform and then perform a form of modal analysis. This program captures the above data and formats it into a useable form for analysis.« less

  4. Narrowband photon pair generation and waveform reshaping

    NASA Astrophysics Data System (ADS)

    Chen, J. F.; Du, Shengwang

    2012-10-01

    In this article, we review on narrowband photon pairs produced in nonlinear crystals, and especially in atomic ensembles. In atomic ensembles, "write-read" process in pulse mode and spontaneous four-wave mixing process (SFWM) in continuous mode are two popular photon pair generation schemes. We specifically discuss the experimental works with continuous SFWM scheme in cold atomic ensembles. Photon pairs produced in these systems are characteristic of controllable long coherence time, and therefore are accessible with direct temporal modulation. We elaborate on the recent techniques on modulation and waveform reshaping of narrow-band paired photons.

  5. 75 FR 30756 - FM Table of Allotments, Pacific Junction, Iowa

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-02

    ... added to the FM Table of Allotment in 2000. See 65 FR 41377, published July 5, 2000. However, the allotment was later removed as a result of MB Docket 05-210. See 71 FR 76208, published December 20, 2006... copies. See Electronic Filing of Documents in Rulemaking Proceedings, 63 FR 24121 (1988)....

  6. 47 CFR 73.310 - FM technical definitions.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM.... The term “center frequency” means: (1) The average frequency of the emitted wave when modulated by a sinusoidal signal. (2) The frequency of the emitted wave without modulation. Composite antenna pattern....

  7. 47 CFR 73.310 - FM technical definitions.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES FM.... The term “center frequency” means: (1) The average frequency of the emitted wave when modulated by a sinusoidal signal. (2) The frequency of the emitted wave without modulation. Composite antenna pattern....

  8. Principles and Limitations of Ultra-Wideband FM Communications Systems

    NASA Astrophysics Data System (ADS)

    Gerrits, John F. M.; Kouwenhoven, Michiel H. L.; van der Meer, Paul R.; Farserotu, John R.; Long, John R.

    2005-12-01

    This paper presents a novel UWB communications system using double FM: a low-modulation index digital FSK followed by a high-modulation index analog FM to create a constant-envelope UWB signal. FDMA techniques at the subcarrier level are exploited to accommodate multiple users. The system is intended for low (1-10 kbps) and medium (100-1000 kbps) bit rate, and short-range WPAN systems. A wideband delay-line FM demodulator that is not preceded by any limiting amplifier constitutes the key component of the UWBFM receiver. This unusual approach permits multiple users to share the same RF bandwidth. Multipath, however, may limit the useful subcarrier bandwidth to one octave. This paper addresses the performance with AWGN and multipath, the resistance to narrowband interference, as well as the simultaneous detection of multiple FM signals at the same carrier frequency. SPICE and Matlab simulation results illustrate the principles and limitations of this new technology. A hardware demonstrator has been realized and has allowed the confirmation of theory with practical results.

  9. Laser noise limitations on an acousto-optic FM demodulator

    NASA Astrophysics Data System (ADS)

    Brooks, Paul; Reeve, Christopher D.

    1994-06-01

    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.

  10. Frequency Response Characteristics of FM Mini-Loop Auditory Trainers.

    ERIC Educational Resources Information Center

    Van Tasell, Dianne; Landin, Deborah P.

    1980-01-01

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

  11. 47 CFR 73.316 - FM antenna systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Broadcast Stations § 73.316 FM antenna systems. (a) It shall be standard to employ horizontal polarization; however, circular or elliptical polarization may be employed if desired. Clockwise or counterclockwise... or elliptical polarization shall in no event exceed the effective radiated power authorized....

  12. 47 CFR 73.3573 - Processing FM broadcast station applications.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... groups: (1) In the first group are applications for new stations or for major changes of authorized stations. A major change in ownership is any change where the original party or parties to the application... case of a Class D or an NCE FM reserved band channel station, a major facility change is any change...

  13. FM Systems: A Good Idea That Keeps Getting Better.

    ERIC Educational Resources Information Center

    Lewis, Dawna E.

    1995-01-01

    Examines the current technological benefits and limitations of individual frequency-modulated (FM) systems for students with hearing impairments in the typical classroom setting. Recent technological advances such as diminished size and increased battery power that may alleviate current limitations are also discussed. (Author/DB)

  14. Pocket-sized tone-modulated FM transmitter

    NASA Technical Reports Server (NTRS)

    Couvillon, L. A.

    1969-01-01

    Pressure of a button on a crystal-controlled transmitter causes generation of a tone. The tone modulates the FM transmitter which in turn radiates by way of the enclosed loop antenna, through the radio-frequency-transparent wall of the transmitters case to the receiver.

  15. Frequency Response Characteristics of FM Mini-Loop Auditory Trainers.

    ERIC Educational Resources Information Center

    Van Tasell, Dianne; Landin, Deborah P.

    1980-01-01

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

  16. 47 CFR 73.3573 - Processing FM broadcast station applications.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Processing FM broadcast station applications... for major modifications will be accepted only during the appropriate filing period or “window.” Applications submitted prior to the window opening date identified in the Public Notice will be returned...

  17. An Inexpensive Group FM Amplification System for the Classroom.

    ERIC Educational Resources Information Center

    Worner, William A.

    1988-01-01

    An inexpensive FM amplification system was developed to enhance auditory learning in classrooms for the hearing impaired. Evaluation indicated that the system equalizes the sound pressure level throughout the room, with the increased sound pressure level falling in the range of 70 to 73 decibels. (Author/DB)

  18. 47 CFR 73.316 - FM antenna systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... educational stations operating on Channels 201 through 220 must show that the 60 dBu contour covers at least a... immediate vicinity (i.e. 60 meters or less) of other FM or TV broadcast antennas must include a showing...

  19. Evaluating auditory brainstem responses to different chirp stimuli at three levels of stimulation

    PubMed Central

    Elberling, Claus; Callø, Johannes; Don, Manuel

    2010-01-01

    Auditory brainstem responses (ABRs) are recorded in ten normal-hearing adults (20 ears) in response to a standard 100 μs click and five chirps having different durations (sweeping rates). The chirps are constructed from five versions of a power function model of the cochlear-neural delay that is based on derived-band ABR latencies from N=81 normal-hearing adults [Elberling, C., and Don, M. (2008). J. Acoust. Soc. Am. 124, 3022–3037]. The click and the chirps have identical amplitude spectra and, in general, for each of the three stimulus levels 60, 40, and 20 dB nHL, the ABRs to the chirps are significantly larger than the ABRs to the click. However, the shorter chirps are the most efficient at higher levels of stimulation whereas the longer chirps are the most efficient at lower levels. It is suggested that two different mechanisms are responsible for these observed changes with stimulus level—(1) upward spread of excitation at higher levels, and (2) an increased change of the cochlear-neural delay with frequency at lower levels. PMID:20649217

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  1. Spectral property of ultrashort chirped pulsed Gaussian beams diffracted by Gaussian aperture in dispersive media

    NASA Astrophysics Data System (ADS)

    Zou, Qihui; Hu, Qianhuan; Guo, Jie; Duan, Xi; Tong, Shihong

    2015-10-01

    Based on the Fresnel-Kirchhoff diffraction integral and Fourier transform, the propagation equation and its Fourier spectrum for ultra-short chirped pulsed Gaussian beams diffracted by Gaussian aperture are derived in dispersive medium, and the frequency-domain analytical electric field are presented. The effects of relative aperture, transmission distance and chirp parameter on the axial spectral properties are illustrated with numerical calculation results, and the variations of off-axis power spectrum with relative aperture, transmission distance and off-axis radius are given. It is found that the axial power spectrum of ultra-short chirped pulsed Gaussian increases with increasing relative aperture, the axial spectral blue-shift increases and approaches an asymptotic value associated with chirp parameter and propagation distance. The axial spectra of ultra-short chirped pulsed Gaussian become broadened with increasing the absolute value of the chirp parameter. With increasing off-axis radius, the off-axis power spectrum reduce rapidly, and the distribution of spectra shifts to the left. The off-axis spectral redshift increases with increasing off-axis radius.

  2. Combining harmonic generation and laser chirping to achieve high spectral density in Compton sources

    DOE PAGESBeta

    Terzić, Balša; Reeves, Cody; Krafft, Geoffrey A.

    2016-04-25

    Recently various laser-chirping schemes have been investigated with the goal of reducing or eliminating ponderomotive line broadening in Compton or Thomson scattering occurring at high laser intensities. Moreover, as a next level of detail in the spectrum calculations, we have calculated the line smoothing and broadening expected due to incident beam energy spread within a one-dimensional plane wave model for the incident laser pulse, both for compensated (chirped) and unchirped cases. The scattered compensated distributions are treatable analytically within three models for the envelope of the incident laser pulses: Gaussian, Lorentzian, or hyperbolic secant. We use the new results tomore » demonstrate that the laser chirping in Compton sources at high laser intensities: (i) enables the use of higher order harmonics, thereby reducing the required electron beam energies; and (ii) increases the photon yield in a small frequency band beyond that possible with the fundamental without chirping. We found that this combination of chirping and higher harmonics can lead to substantial savings in the design, construction and operational costs of the new Compton sources. This is of particular importance to the widely popular laser-plasma accelerator based Compton sources, as the improvement in their beam quality enters the regime where chirping is most effective.« less

  3. Speech Processing Applications Using AN Am-Fm Modulation Model.

    NASA Astrophysics Data System (ADS)

    Potamianos, Alexandros

    1995-01-01

    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.

  4. Focal waveforms for various source waveforms driving a prolate-spheroidal impulse radiating antenna (IRA)

    NASA Astrophysics Data System (ADS)

    Altunc, Serhat; Baum, Carl E.; Christodoulou, Christos G.; Schamiloglu, Edl; Buchenauer, C. Jerald

    2008-08-01

    Impulse radiating antennas (IRAs) are designed to radiate very fast pulses in a narrow beam with low dispersion and high field amplitude. For this reason they have been used in a variety of applications. IRAs have been developed for use in the transient far-field region using parabolic reflectors. However, in this paper we focus in the near field region and develop the field waveform at the second focus of a prolate-spheroidal IRA. Certain skin cancers can be killed by the application of a high-amplitude electric field pulse. This can be accomplished by either inserting electrodes near the skin cancer or by applying fast, high-electric field pulses without direct contact. We investigate a new manifestation of an IRA, in which we use a prolate spheroid as a reflector instead of a parabolic reflector and focus in the near-field region instead of the far-field region. This technique minimizes skin damage associated with inserting electrodes near the tumor. Analytical and experimental behaviors for the focal waveforms of two and four-feed arm prolate-spheroidal IRAs are explored. With appropriate choice of the driving waveform we maximize the impulse field at the second focus. The focal waveform of a prolate-spheroidal IRA has been explained theoretically and verified experimentally.

  5. Constructing binary black hole template banks using numerical relativity waveforms

    NASA Astrophysics Data System (ADS)

    Kumar, Prayush

    2013-04-01

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

  6. Waveform Freezing of Sonic Booms Revisited

    NASA Technical Reports Server (NTRS)

    Cleveland, Robin O.; Blackstock, David T.

    1996-01-01

    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).

  7. ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

    SciTech Connect

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

    2007-12-10

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

  8. ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

    SciTech Connect

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

    2009-01-27

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

  9. Target discrimination technique utilizing noise waveforms

    NASA Astrophysics Data System (ADS)

    Woodington, Gordon; DeLuca, Mark; Moro, Richard; Lemus, Daniel; Vela, Russell; Narayanan, Ram

    2011-06-01

    Noise waveforms generated using low cost diodes are a simple way for radars to transmit a wideband (> 4 GHz) multi-bit pseudorandom code for use in a cross correlation receiver. This type of waveform also has the advantage of being difficult to intercept and is less prone to interfere with adjacent systems. Radar designed to operate over this wide frequency range can take advantage of unique target Radar Cross Section (RCS) ripple versus frequency for objects of different materials and sizes. Specifically the periodicity and amplitude of the ripple is dependent on the shape and size of a target. Since background clutter does not display this variation, RCS variation determines whether a known target is present in a return. This paper will present the radar hardware and signal processing techniques used to maximize a target's unique spectral response against a cluttered background. The system operates CW over a 4-8 GHz bandwidth requiring the need to address issues regarding range resolution and far out undesired returns. Lessons learned from field observations and mitigation techniques incorporated in the system are included. This paper also deals with the signal processing technique used for detection, then discrimination. Detection thresholds are set and triggered by a simple correlation peak level. Discrimination involves inspection of the spectral return. A comparison performed in real time to a stored library value determines the presence of known objects. Measured data provided demonstrates the ability of the radar to discriminate multiple targets against multiple backgrounds.

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

    SciTech Connect

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

    2011-06-15

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

  11. AM/FM development for a small electric utility or form partnerships to minimize AM/FM development costs

    SciTech Connect

    Hahne, R.

    1996-08-01

    Chelan County Public Utility District is a 32,000 customer electric utility in central Washington State. Being a small utility presents unique problems in developing a complex AM/FM system. With only a small staff assigned part-time to this project, partnering and outsourcing became essential for developing an AM/FM system. An incremental approach was also necessary. Our project started in 1992 in partnership with Chelan County and the City of Wenatchee for the development of a common landbase in ARC/INFO. For our AM/FM system, a purchased solution was much more feasible than in-house development. We decided against a big requirements definition phase or a formal RFP, and instead looked at available AM/FM systems to decide what was feasible for us. This paper shares the basics of our partnering strategy and outlines how our approach will allow the project to be completed in a fast-track of 40 months at a minimal cost to the Chelan P.U.D. ratepayers.

  12. Performance improvement of plasma actuators using asymmetric high voltage waveforms

    NASA Astrophysics Data System (ADS)

    Kotsonis, M.; Ghaemi, S.

    2012-02-01

    An experimental study is conducted on high voltage waveforms used to power plasma actuators. Shapes that present an asymmetry between the two half cycles are investigated by means of induced thrust and velocity measurements. A parametric study is performed based on thrust measurements in order to find the optimum shape within the tested range. An asymmetric waveform which is made as a combination of sinusoidal and square shapes is found to increase produced thrust by almost 30% compared with the conventional sinusoidal waveform. The asymmetric waveform is further analysed using time-resolved particle image velocimetry in order to reveal the forcing mechanism governed by the shape differences. It is shown that the shape of the waveform has a significant effect on the performance of the actuator. Push and pull events occur within the actuation period and their respective strength and duration closely correlates with the shape of the waveform. It is found that the pull event is significantly weakened for the case of the optimized asymmetric waveform in comparison with the sinusoidal shape. This effectively increases the net momentum transfer and an improvement of approximately 40% in maximum induced velocity is achieved compared with sine waveform. Power consumption due to the asymmetric waveform is marginally increased which provides a significant increase in the actuator's relative efficiency.

  13. Pervasive post-Eocene faulting and folding in unconsolidated sediments of the Mississippi River, Central U.S. as imaged by high-resolution CHIRP seismic data

    NASA Astrophysics Data System (ADS)

    Fave, X. J.; Magnani, M.; Waldron, B. A.; McIntosh, K. D.; Saustrup, S.; Guo, L.

    2010-12-01

    Despite being located in the stable continental interior of the North American plate, in 1811-1812 the New Madrid Seismic Zone (NMSZ) experienced among the largest magnitude historical earthquakes that ever occurred in the U.S. Paleoseismological evidence shows that large earthquakes have been occurring every 500 yr in the region for the past few thousand years, and historical and instrumental seismicity demonstrate that the NMSZ fault system is actively deforming today. By contrast, motion rates emerging from almost twenty years of geodetic observations substantiate a very slow rate of deformation across the NMSZ faults, suggesting that present velocities are not representative of the long-term deformation rate of the NMSZ fault system, and that deformation has likely been accommodated along structures additional to the NMSZ. In the summer of 2010, a high-resolution marine seismic reflection survey was carried out along the Mississippi River as part of a multi-year cooperative effort to investigate the spatial and temporal distribution of deformation in the Mississippi Embayment. Coincident to the seismic reflection profile, the survey also acquired ~300 km of CHIRP (Edgetech SB-512i) data from Cape Girardeau, MO to Caruthersville, MO. The CHIRP used a 0.7-1.2 kHz source pulse and recorded to a depth of 5-50 m sub-bottom. Here we present the preliminary interpretation of part of the CHIRP profile along the Mississippi River north of Hickman, KY, where the survey imaged a highly reflective sedimentary package down to a depth of ~50 m. The sedimentary sequence is about 20 m thick and appears to be bounded at the top and at the bottom by angular unconformities. The package is mildly folded and pervasively faulted, in some cases by extensional faults that exhibit up to 2 m of displacement and that reach the riverbed. Based on exposure of Eocene deposits 7 km to the east of the study area, and on the correlation of electric and gamma logs of nearby oil, gas and water wells, projected from 12 km to the west and which penetrated the Eocene units at a depth of 67 m, we determined that the reflective package corresponds to one of the elements of the Jackson Fm, (i.e. the top of the Eocene and of the Tertiary sequences), sealed at the top by the basal unconformity of the Mississippi River Quaternary alluvium and at the bottom by the Claiborne Group deposits. ¬

  14. Chromatin Isolation by RNA Purification (ChIRP)

    PubMed Central

    Chu, Ci; Quinn, Jeffrey; Chang, Howard Y.

    2012-01-01

    Long noncoding RNAs are key regulators of chromatin states for important biological processes such as dosage compensation, imprinting, and developmental gene expression 1,2,3,4,5,6,7. The recent discovery of thousands of lncRNAs in association with specific chromatin modification complexes, such as Polycomb Repressive Complex 2 (PRC2) that mediates histone H3 lysine 27 trimethylation (H3K27me3), suggests broad roles for numerous lncRNAs in managing chromatin states in a gene-specific fashion 8,9. While some lncRNAs are thought to work in cis on neighboring genes, other lncRNAs work in trans to regulate distantly located genes. For instance, Drosophila lncRNAs roX1 and roX2 bind numerous regions on the X chromosome of male cells, and are critical for dosage compensation 10,11. However, the exact locations of their binding sites are not known at high resolution. Similarly, human lncRNA HOTAIR can affect PRC2 occupancy on hundreds of genes genome-wide 3,12,13, but how specificity is achieved is unclear. LncRNAs can also serve as modular scaffolds to recruit the assembly of multiple protein complexes. The classic trans-acting RNA scaffold is the TERC RNA that serves as the template and scaffold for the telomerase complex 14; HOTAIR can also serve as a scaffold for PRC2 and a H3K4 demethylase complex 13. Prior studies mapping RNA occupancy at chromatin have revealed substantial insights 15,16, but only at a single gene locus at a time. The occupancy sites of most lncRNAs are not known, and the roles of lncRNAs in chromatin regulation have been mostly inferred from the indirect effects of lncRNA perturbation. Just as chromatin immunoprecipitation followed by microarray or deep sequencing (ChIP-chip or ChIP-seq, respectively) has greatly improved our understanding of protein-DNA interactions on a genomic scale, here we illustrate a recently published strategy to map long RNA occupancy genome-wide at high resolution 17. This method, Chromatin Isolation by RNA Purification (ChIRP) (Figure 1), is based on affinity capture of target lncRNA:chromatin complex by tiling antisense-oligos, which then generates a map of genomic binding sites at a resolution of several hundred bases with high sensitivity and low background. ChIRP is applicable to many lncRNAs because the design of affinity-probes is straightforward given the RNA sequence and requires no knowledge of the RNA's structure or functional domains. PMID:22472705

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

    PubMed Central

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

    2013-01-01

    We describe a new approach to analyze chirp syllables of free-tailed bats from two regions of Texas in which they are predominant: Austin and College Station. Our goal is to characterize any systematic regional differences in the mating chirps and assess whether individual bats have signature chirps. The data are analyzed by modeling spectrograms of the chirps as responses in a Bayesian functional mixed model. Given the variable chirp lengths, we compute the spectrograms on a relative time scale interpretable as the relative chirp position, using a variable window overlap based on chirp length. We use 2D wavelet transforms to capture correlation within the spectrogram in our modeling and obtain adaptive regularization of the estimates and inference for the regions-specific spectrograms. Our model includes random effect spectrograms at the bat level to account for correlation among chirps from the same bat, and to assess relative variability in chirp spectrograms within and between bats. The modeling of spectrograms using functional mixed models is a general approach for the analysis of replicated nonstationary time series, such as our acoustical signals, to relate aspects of the signals to various predictors, while accounting for between-signal structure. This can be done on raw spectrograms when all signals are of the same length, and can be done using spectrograms defined on a relative time scale for signals of variable length in settings where the idea of defining correspondence across signals based on relative position is sensible. PMID:23997376

  16. ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

    SciTech Connect

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

    2008-10-17

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

  17. Optimization and characterization of dual-chirped optical parametric amplification

    NASA Astrophysics Data System (ADS)

    Fu, Yuxi; Takahashi, Eiji J.; Zhang, Qingbin; Lu, Peixiang; Midorikawa, Katsumi

    2015-12-01

    We report optimization and characterization of a dual-chirped optical parametric amplification (DC-OPA) scheme (2011 Opt. Express 19 7190). By increasing a pump pulse energy to 100 mJ, a total (signal + idler) output energy exceeding 30 mJ was recorded with higher than 30% conversion efficiency. The feasibility of further increasing the output energy to a higher scale using the DC-OPA scheme was confirmed by a proof-of-principle experiment, in which 30%-40% conversion efficiency was observed. The signal pulse with the center wavelength of 1.4 μm was compressed to 27 fs (FWHM), which was very close to a transform-limited pulse duration of 25 fs. Since the DC-OPA scheme is efficient for generating high-energy infrared (IR) pulses with excellent scaling ability, the design parameters for obtaining hundred-mJ-level and even joule-level IR pulses are discussed and presented in detail. Invited contribution to the special issue on optical parametric processes.

  18. Mismatch characteristics of optical parametric chirped pulse amplification

    NASA Astrophysics Data System (ADS)

    Novák, O.; Turčičová, H.; Divoký, M.; Huynh, J.; Straka, P.

    2014-02-01

    The stability of an optical parametric chirped pulse amplifier (OPCPA) is influenced by time and the angular matching of the input beams. We derived the Gaussian dependence of the monochromatic signal gain on the small mismatch between the signal and pump beams. Gain characteristics were also calculated for polychromatic amplification and the impact of different beam mismatches and interaction geometries was explained. The asymmetry of the energy gain, and the square root dependence of the phase matched wavelength on beam angles were found. The predicted dependences were verified in a noncollinear OPCPA system with LBO and KDP crystal amplifying pulses of a Ti:sapphire laser around a central wavelength of 800 nm, pumped by the third harmonic frequency of an iodine gas laser at a wavelength of 438 nm. The widths of the gain curves in the dependence on both the pump-signal or the phase matching angles varied from several tenths to a few milliradians. The gain curve widths dependent on the pump-signal pulse delay were about two thirds of the pump pulse width for moderate pumping and about a half of the pump pulse width for pumping on the order of GW cm-2. A stable gain output is achieved if angular and temporal fluctuations are fractions of the measured gain curve widths, and when the signal direction is between the pump and the crystal principal axis (i.e. in the psz geometry).

  19. Inverse synthetic aperture radar imaging of targets with complex motions based on modified chirp rate-quadratic chirp rate distribution for cubic phase signal

    NASA Astrophysics Data System (ADS)

    Yanyan, Li; Tao, Su; Jibin, Zheng

    2015-01-01

    For targets with complex motions, the time-varying Doppler frequency deteriorates inverse synthetic aperture radar (ISAR) images. After range alignment and phase adjustment, azimuth echoes in a range cell can be modeled as multicomponent cubic phase signals (CPSs). The chirp rate and the quadratic chirp rate of the CPS are identified as the causes of the time-varying Doppler frequency; thus, it is necessary to estimate these two parameters correctly to obtain a well-focused ISAR image. The parameter-estimation algorithm based on the modified chirp rate-quadratic chirp rate distribution (M-CRQCRD) is proposed for the CPS and applied to the ISAR imaging of targets with complex motions. The computational cost of M-CRQCRD is low, because it can be implemented by the fast Fourier transform (FFT) and the nonuniform FFT easily. Compared to two representative parameter-estimation algorithms, the M-CRQCRD can acquire a higher antinoise performance due to the introduction of an optimal lag-time. Through simulations and analyses for the synthetic radar data, the effectiveness of the M-CRQCRD and the imaging algorithm based on the M-CRQCRD are verified.

  20. 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)

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

    2012-06-01

    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.

  1. Waveform Synthesizer For Imaging And Ranging Applications

    DOEpatents

    DUDLEY, PETER A.; [et al

    2004-11-30

    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.

  2. Waveform Synthesizer For Imaging And Ranging Applications

    DOEpatents

    Dubbert, Dale F.; Dudley, Peter A.; Doerry, Armin W.; Tise, Bertice L.

    2004-12-28

    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.

  3. Binary black hole merger dynamics and waveforms

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  4. Waveform encoding of voiceband data signals

    NASA Astrophysics Data System (ADS)

    Oneal, J. B., Jr.

    1980-02-01

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

  5. Using waveform information in nonlinear data assimilation

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  6. Flagellar waveform analysis of swimming algal cells

    NASA Astrophysics Data System (ADS)

    Kurtuldu, Huseyin; Johnson, Karl; Gollub, Jerry

    2011-11-01

    The twin flagella of the green alga Chlamydomas reinhardtii are driven by dynein molecular motors to oscillate at about 50-60 Hz in a breaststroke motion. For decades, Chlamydomas has been used as a model organism for studies of flagellar motility, and of genetic disorders of ciliary motion. However, little is known experimentally about the flagellar waveforms, and the resulting time-dependent force distribution along the 250 nm diameter flagella. Here, we study flagellar dynamics experimentally by confining cells in quasi-2D liquid films. From simultaneous measurements of the cell body velocity and the time-dependent velocities along the center lines of the two flagella, we determine the drag coefficients, and estimate the power expended by the body and the flagella, comparing our findings with measurements based on the induced fluid flow field. We contrast the results for the quite different beating patterns of synchronous and asynchronous flagella, respectively. Supported by NSF Grant DMR-0803153.

  7. New FM Detection Techniques for Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Kobayashi, Dai; Kawai, Shigeki; Kawakatsu, Hideki

    2004-07-01

    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.

  8. Software Reception of AM & FM Broadcast Using Frequency Domain Samples

    NASA Astrophysics Data System (ADS)

    Sakabe, Takuji; Kimbara, Masato; Egami, Shunichiro

    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.

  9. Simultaneous occupational exposure to FM and UHF transmitters.

    PubMed

    Valič, Blaž; Kos, Bor; Gajšek, Peter

    2012-01-01

    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

  10. 47 CFR 73.201 - Numerical designation of FM broadcast channels.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Numerical designation of FM broadcast channels... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.201 Numerical designation of FM broadcast... numerical designations which are shown in the table below: Frequency (Mc/s) Channel No. 88.1 201 88.3 202...

  11. 47 CFR 73.201 - Numerical designation of FM broadcast channels.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Numerical designation of FM broadcast channels... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.201 Numerical designation of FM broadcast... numerical designations which are shown in the table below: Frequency (Mc/s) Channel No. 88.1 201 88.3 202...

  12. 47 CFR 73.201 - Numerical designation of FM broadcast channels.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Numerical designation of FM broadcast channels... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.201 Numerical designation of FM broadcast... numerical designations which are shown in the table below: Frequency (Mc/s) Channel No. 88.1 201 88.3 202...

  13. 47 CFR 73.201 - Numerical designation of FM broadcast channels.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Numerical designation of FM broadcast channels... SERVICES RADIO BROADCAST SERVICES FM Broadcast Stations § 73.201 Numerical designation of FM broadcast... numerical designations which are shown in the table below: Frequency (Mc/s) Channel No. 88.1 201 88.3 202...

  14. 75 FR 51812 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-23

    ...The following applicants filed AM or FM proposals to change the community of license: BRYAN BROADCASTING CORPORATION, Station KWBC, Facility ID 40912, BP-20100712ABU, From NAVASOTA, TX, To COLLEGE STATION, TX; CUMULUS LICENSING LLC, Station KNRQ-FM, Facility ID 12501, BMPH-20100805AKO, From TUALATIN, OR, To ALOHA, OR; IORIO BROADCASTING, INC., Station WNAE-FM, Facility ID 164188,......

  15. 47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Classes of noncommercial educational FM...) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.506 Classes of noncommercial educational FM stations and channels. (a) Noncommercial educational...

  16. 47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Noncommercial educational FM stations operating... (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.513 Noncommercial educational FM stations operating on unreserved channels. (a)...

  17. 47 CFR 73.7002 - Fair distribution of service on reserved band FM channels.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... FM channels. 73.7002 Section 73.7002 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...-Reserved Channels § 73.7002 Fair distribution of service on reserved band FM channels. (a) If timely filed applications for full service stations on reserved FM channels are determined to be mutually exclusive,...

  18. 77 FR 57086 - Radio Broadcasting Services; AM or FM Proposals To Change The Community of License.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-17

    ... COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change The Community of License. AGENCY: Federal Communications Commission. ACTION: Notice. SUMMARY: The following applicants filed AM or FM proposals to change the community of license: ALEXANDRA COMMUNICATIONS, INC., Station KRKZ- FM, Facility...

  19. 47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Noncommercial educational FM stations operating... (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.513 Noncommercial educational FM stations operating on unreserved channels. (a)...

  20. 47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Classes of noncommercial educational FM...) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.506 Classes of noncommercial educational FM stations and channels. (a) Noncommercial educational...

  1. 77 FR 24954 - Radio Broadcasting Services; AM or FM Proposals to Change the Community of License

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-26

    ... COMMISSION Radio Broadcasting Services; AM or FM Proposals to Change the Community of License AGENCY: Federal Communications Commission. ACTION: Notice. SUMMARY: The following applicants filed AM or FM proposals to change... 17227, BPH-20120327ALB, From HUDSON, IA, To EVANSDALE; HOG RADIO, INC., Station KLYR-FM, Facility...

  2. 47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Classes of noncommercial educational FM...) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.506 Classes of noncommercial educational FM stations and channels. (a) Noncommercial educational...

  3. 75 FR 13761 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-23

    ... COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community of License AGENCY: Federal Communications Commission. ACTION: Notice. SUMMARY: The following applicants filed AM or FM proposals to change... BROADCASTING CORPORATION, Station KFFF-FM, Facility ID 6417, BPH-20100126AGR, From BOONE, IA, To JOHNSTON,...

  4. 47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Classes of noncommercial educational FM...) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.506 Classes of noncommercial educational FM stations and channels. (a) Noncommercial educational...

  5. 47 CFR 73.7002 - Fair distribution of service on reserved band FM channels.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... FM channels. 73.7002 Section 73.7002 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...-Reserved Channels § 73.7002 Fair distribution of service on reserved band FM channels. (a) If timely filed applications for full service stations on reserved FM channels are determined to be mutually exclusive,...

  6. 75 FR 20597 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-20

    ... COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community of License AGENCY: Federal Communications Commission. ACTION: Notice. SUMMARY: The following applicants filed AM or FM proposals to change..., From RESERVE, NM, To CONCHO, AZ; DAILEY CORPORATION, Station WETZ-FM, Facility ID 18534,...

  7. 47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Noncommercial educational FM stations operating... (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.513 Noncommercial educational FM stations operating on unreserved channels. (a)...

  8. 47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Noncommercial educational FM stations operating... (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.513 Noncommercial educational FM stations operating on unreserved channels. (a)...

  9. 47 CFR 73.7002 - Fair distribution of service on reserved band FM channels.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... FM channels. 73.7002 Section 73.7002 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...-Reserved Channels § 73.7002 Fair distribution of service on reserved band FM channels. (a) If timely filed applications for full service stations on reserved FM channels are determined to be mutually exclusive,...

  10. 47 CFR 73.7002 - Fair distribution of service on reserved band FM channels.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... FM channels. 73.7002 Section 73.7002 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...-Reserved Channels § 73.7002 Fair distribution of service on reserved band FM channels. (a) If timely filed applications for full service stations on reserved FM channels are determined to be mutually exclusive,...

  11. 77 FR 75434 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-20

    ... COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community of License AGENCY: Federal Communications Commission. ACTION: Notice. SUMMARY: The following applicants filed AM or FM proposals to change... ABERDEEN, WA; MCC RADIO, LLC, Station KDUX-FM, Facility ID 52676, BPH-20121114AGF, From ABERDEEN, WA,...

  12. 47 CFR 73.513 - Noncommercial educational FM stations operating on unreserved channels.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Noncommercial educational FM stations operating... (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.513 Noncommercial educational FM stations operating on unreserved channels. (a)...

  13. 47 CFR 73.506 - Classes of noncommercial educational FM stations and channels.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Classes of noncommercial educational FM...) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Noncommercial Educational FM Broadcast Stations § 73.506 Classes of noncommercial educational FM stations and channels. (a) Noncommercial educational...

  14. 75 FR 6395 - Radio Broadcasting Services; AM or FM Proposals To Change the Community of License

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-09

    ... COMMISSION Radio Broadcasting Services; AM or FM Proposals To Change the Community of License AGENCY: Federal Communications Commission. ACTION: Notice. SUMMARY: The following applicants filed AM or FM proposals to change..., WY; COMMANDER COMMUNICATIONS CORPORATION, Station WRTM- FM, Facility ID 19864, BPH-20100107AAB,...

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

    ERIC Educational Resources Information Center

    Early, L. F.

    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…

  16. Resonant tunneling and the bimodal symmetric fission of sup 258 Fm

    SciTech Connect

    Bhandari, B.S. )

    1991-02-25

    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.

  17. E-Learning Readiness in Medicine: Turkish Family Medicine (FM) Physicians Case

    ERIC Educational Resources Information Center

    Parlakkiliç, Alaattin

    2015-01-01

    This research investigates e-learning readiness level of family medicine physicians (FM) in Turkey. The study measures the level of e-learning readiness of Turkish FM physicians by an online e-learning readiness survey. According to results five areas are ready at Turkish FM physicians but need a few improvements:…

  18. Statistical Sampling Enabled Full Waveform Inversion

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  19. Analytical Approaches to Guide SLS Fault Management (FM) Development

    NASA Technical Reports Server (NTRS)

    Patterson, Jonathan D.

    2012-01-01

    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).

  20. Optical processing of pulsed Doppler and FM stepped radar signals.

    PubMed

    Casasent, D; Casasayas, F

    1975-06-01

    A real-time radar processor with an electron beam addressed KD(2)PO(4) light valve as the input electrical-to-optical transducer is described. The input format, output plane pattern, and the required optical processing of pulsed Doppler and FM stepped radar data on this system are discussed. Experimental output plane patterns with actual radar data are presented. Although these data are processed off-line, the processing is performed at real-time data rates. PMID:20154832

  1. Level structure of sup 256 Fm: Experiment vs theory

    SciTech Connect

    Bunker, M.E.; Starner, J.W.

    1990-01-01

    The amount of experimental data on intrinsic states in the even-even isotopes of the transcurium elements is rather limited, providing only a few tests of theoretical models in this region. Thus, it is of interest to determine to what extent the recent results on levels in {sup 256}Fm compare with existing theoretical calculations, such as those of Ivanova et al. 4 refs., 1 fig., 1 tab.

  2. 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

    2010-10-01

    ....24′ W. long.; and (29) 34°08.40′ N. lat., 120°33.78′ W. long. (d) The 50 fm (91 m) depth contour.... long.; and (18) 33°28.01′ N. lat., 118°37.42′ W. long. (f) The 60-fm (110-m) depth contour used between....83′ N. lat., 120°25.61′ W. long. (h) The 60 fm (110 m) depth contour around San Clemente Island...

  3. 50 CFR 660.72 - Latitude/longitude coordinates defining the 50 fm (91 m) through 75 fm (137 m) depth contours.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ....59′ N. lat., 117°17.89′ W. long. (b) The 50-fm (91-m) depth contour around the Swiftsure Bank and... connecting back to 48°30.15′ N. lat., 124°56.12′ W. long. (c) The 50 fm (91 m) depth contour around the...°03.73′ N. lat., 118°36.98′ W. long. (e) The 50 fm (91 m) depth contour around Santa Catalina...

  4. Uniform spectral amplitude windowing for hyperbolic frequency modulated waveforms

    NASA Astrophysics Data System (ADS)

    Drumheller, David M.

    1994-07-01

    The hyperbolic frequency-modulated (HFM) waveform has been used in experimental and scientific low-frequency sonar systems because it possesses the pulse compression property and is Doppler-tolerant. This report presents a class of HFM waveforms that possess a flat spectrum, and as such is useful for the direct measurement of a target frequency response and the development of classification algorithms.

  5. Method and apparatus for resonant frequency waveform modulation

    DOEpatents

    Taubman, Matthew S [Richland, WA

    2011-06-07

    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.

  6. Altimeter waveform parameters retrieval using Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Swain, Debadatta; Sasamal, S. K.

    2012-07-01

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

  7. Multiscale AM-FM Methods for Diabetic Retinopathy Lesion Detection

    PubMed Central

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

    2010-01-01

    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 40×40 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

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

    SciTech Connect

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

    1986-01-01

    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.

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

    SciTech Connect

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

    1980-10-01

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

  10. Design of a 9-loop quasi-exponential waveform generator.

    PubMed

    Banerjee, Partha; Shukla, Rohit; Shyam, Anurag

    2015-12-01

    We know in an under-damped L-C-R series circuit, current follows a damped sinusoidal waveform. But if a number of sinusoidal waveforms of decreasing time period, generated in an L-C-R circuit, be combined in first quarter cycle of time period, then a quasi-exponential nature of output current waveform can be achieved. In an L-C-R series circuit, quasi-exponential current waveform shows a rising current derivative and thereby finds many applications in pulsed power. Here, we have described design and experiment details of a 9-loop quasi-exponential waveform generator. In that, design details of magnetic switches have also been described. In the experiment, output current of 26 kA has been achieved. It has been shown that how well the experimentally obtained output current profile matches with the numerically computed output. PMID:26724051

  11. Design of a 9-loop quasi-exponential waveform generator

    NASA Astrophysics Data System (ADS)

    Banerjee, Partha; Shukla, Rohit; Shyam, Anurag

    2015-12-01

    We know in an under-damped L-C-R series circuit, current follows a damped sinusoidal waveform. But if a number of sinusoidal waveforms of decreasing time period, generated in an L-C-R circuit, be combined in first quarter cycle of time period, then a quasi-exponential nature of output current waveform can be achieved. In an L-C-R series circuit, quasi-exponential current waveform shows a rising current derivative and thereby finds many applications in pulsed power. Here, we have described design and experiment details of a 9-loop quasi-exponential waveform generator. In that, design details of magnetic switches have also been described. In the experiment, output current of 26 kA has been achieved. It has been shown that how well the experimentally obtained output current profile matches with the numerically computed output.

  12. Analysis of orthogonal waveform for spaceborne MIMO-GMTI radar

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

  13. Validation of a high-resolution precipitation database (CHIRPS) over Cyprus for a 30-year period

    NASA Astrophysics Data System (ADS)

    Katsanos, Dimitrios; Retalis, Adrianos; Michaelides, Silas

    2016-03-01

    A study for a 30-year period (1981-2010) for a new precipitation database is performed over the island of Cyprus. Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) is a more than 30-year quasi-global rainfall dataset, spanning 50°S-50°N (and all longitudes). Starting in 1981 to near-present, CHIRPS incorporates 0.05° resolution satellite imagery with in situ station data to create gridded rainfall time series. In this study, CHIRPS database is firstly compared to other precipitation databases over the Mediterranean basin. In the following, this study focuses over Cyprus, where a dense and reliable network of rain gauges is available. CHIRPS data are compared for the first time with in situ measurements in this area, for the aforementioned 30-year period. Monthly and annual comparisons are presented for each of the 0.05 × 0.05 degree cells overlaying the island of Cyprus. Results showed good correlation between CHIRPS values and recorded precipitation, although an overestimation of the in situ rainfall data has been noted during the last decade.

  14. Characteristics of nonlinear imaging of broadband laser stacked by chirped pulses

    NASA Astrophysics Data System (ADS)

    Wang, Youwen; You, Kaiming; Chen, Liezun; Lu, Shizhuan; Dai, Zhiping; Ling, Xiaohui

    2014-11-01

    Nanosecond-level pulses of specific shape is usually generated by stacking chirped pulses for high-power inertial confinement fusion driver, in which nonlinear imaging of scatterers may damage precious optical elements. We present a numerical study of the characteristics of nonlinear imaging of scatterers in broadband laser stacked by chirped pulses to disclose the dependence of location and intensity of images on the parameters of the stacked pulse. It is shown that, for sub-nanosecond long sub-pulses with chirp or transform-limited sub-pulses, the time-mean intensity and location of images through normally dispersive and anomalously dispersive self-focusing medium slab are almost identical; While for picosecond-level short sub-pulses with chirp, the time-mean intensity of images for weak normal dispersion is slightly higher than that for weak anomalous dispersion through a thin nonlinear slab; the result is opposite to that for strong dispersion in a thick nonlinear slab; Furthermore, for given time delay between neighboring sub-pulses, the time-mean intensity of images varies periodically with chirp of the sub-pulse increasing; for a given pulse width of sub-pulse, the time-mean intensity of images decreases with the time delay between neighboring sub-pulses increasing; additionally, there is a little difference in the time-mean intensity of images of the laser stacked by different numbers of sub-pulses. Finally, the obtained results are also given physical explanations.

  15. Frequency Correction for MIRO Chirp Transformation Spectroscopy Spectrum

    NASA Technical Reports Server (NTRS)

    Lee, Seungwon

    2012-01-01

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

  16. Comparison of rectangular and bisinusoidal waveforms in a miniature planar high-field asymmetric waveform ion mobility spectrometer.

    PubMed

    Prieto, Marilyn; Tsai, Chia-Wei; Boumsellek, Said; Ferran, Robert; Kaminsky, Ilya; Harris, Scott; Yost, Richard A

    2011-12-15

    High-field asymmetric waveform ion mobility spectrometry (FAIMS) separates ions by utilizing the mobility differences of ions at high and low fields. The shape of the waveform is one of the essential features affecting the resolution, transmission, and separation of FAIMS. Due to practical circuitry advantages, sinusoidal asymmetric waveforms are typically used in FAIMS, whereas theoretical studies indicate that square asymmetric waveforms improve ion separation, resolution, and sensitivity. Results from FAIMS using square and sinusoidal waveforms are presented, and effects of the waveforms on ion separation are discussed. A FAIMS system interfaced with a quadrupole ion trap mass spectrometer was used in this study. FAIMS spectra were generated by scanning the compensation voltage (CV) while operating the mass spectrometer in total ion mode. The identification of ions was accomplished through mass spectra acquired at fixed values of ions' CVs. Square waveform evaluation was done by acquiring data at three frequencies and six duty cycles of the square waveform generator. The performance of FAIMS using square and sinusoidal waveforms at 250, 333, and 500 kHz frequencies was compared, and trends were identified. For all frequencies, the best response of FAIMS was achieved at the lower amplitudes and under the lower duty cycles of the square waveform generator. The separation of FAIMS was better at the higher frequencies. These results demonstrate the potential to incorporate square-wave FAIMS into the design of a miniature device for detection of explosives in the field. SIMION version 8.0, the ion trajectory modeling program, was utilized to optimize the performance of the miniature FAIMS cell and to validate experimental results. PMID:22017325

  17. A direct approach for the design of chirp stimuli used for the recording of auditory brainstem responses

    PubMed Central

    Elberling, Claus; Don, Manuel

    2010-01-01

    A recent study evaluates auditory brainstem responses (ABRs) evoked by chirps of different durations (sweeping rates) [Elberling et al. (2010). J. Acoust. Soc. Am. 128, 215–223]. The study demonstrates that shorter chirps are most efficient at higher levels of stimulation whereas longer chirps are most efficient at lower levels. Mechanisms other than the traveling wave delay, in particular, upward spread of excitation and changes in cochlear-neural delay with level, are suggested to be responsible for these findings. As a consequence, delay models based on estimates of the traveling wave delay are insufficient for the design of chirp stimuli, and another delay model based on a direct approach is therefore proposed. The direct approach uses ABR-latencies from normal-hearing subjects in response to octave-band chirps over a wide range of levels. The octave-band chirps are constructed by decomposing a broad-band chirp, and constitute a subset of the chirp. The delay compensations of the proposed model are similar to those found in the previous experimental study, which thus verifies the results of the proposed model. PMID:21110591

  18. Frequency chirped light at large detuning with an injection-locked diode laser

    SciTech Connect

    Teng, K.; Disla, M.; Dellatto, J.; Limani, A.; Kaufman, B.; Wright, M. J.

    2015-04-15

    We have developed a laser system to generate frequency-chirped light at rapid modulation speeds (∼100 MHz) with a large frequency offset. Light from an external cavity diode laser with its frequency locked to an atomic resonance is passed through a lithium niobate electro-optical phase modulator. The phase modulator is driven by a ∼6 GHz signal whose frequency is itself modulated with a RF MHz signal (<200 MHz). A second injection locked diode laser is used to filter out all of the light except the frequency-chirped ±1 order by more than 30 dB. Using this system, it is possible to generate a 1 GHz frequency chirp in 5 ns.

  19. Attosecond XUV sources generation from polarized gating two-color chirped pulse

    NASA Astrophysics Data System (ADS)

    Feng, Liqiang; Liu, Hang; Chu, Tianshu

    2015-07-01

    A promising method to generate the attosecond XUV sources from the high-order harmonic has been theoretically presented by controlling the polarized gating two-color chirped pulse. The results show that with the introduction of the chirps, the harmonic has been remarkably extended. Moreover, the harmonic interferences are very sensitive to the polarization angle between the two lasers. Particularly, when the polarization angle is equal to 0.2π, the supercontinuum with a single quantum path contribution is achieved, and a series of isolated attosecond pulses with the duration of 33 as are directly obtained. Further, by testing the influences of other laser parameters on the supercontinuum, we found that this polarized two-color chirped scheme can also be achieved in the multi-cycle pulse region, which is much better for experimental realization.

  20. Note: Directly measuring the direct digital synthesizer frequency chirp-rate for an atom interferometer

    SciTech Connect

    Tao, Juan-Juan; Zhou, Min-Kang E-mail: zmk@hust.edu.cn; Zhang, Qiao-Zhen; Cui, Jia-Feng; Duan, Xiao-Chun; Shao, Cheng-Gang; Hu, Zhong-Kun E-mail: zmk@hust.edu.cn

    2015-09-15

    During gravity measurements with Raman type atom interferometry, the frequency of the laser used to drive Raman transition is scanned by chirping the frequency of a direct digital synthesizer (DDS), and the local gravity is determined by precisely measuring the chip rate α of DDS. We present an effective method that can directly evaluate the frequency chirp rate stability of our DDS. By mixing a pair of synchronous linear sweeping signals, the chirp rate fluctuation is precisely measured with a frequency counter. The measurement result shows that the relative α instability can reach 5.7 × 10{sup −11} in 1 s, which is neglectable in a 10{sup −9} g level atom interferometry gravimeter.

  1. Low chirp and high-speed operation of transverse coupled cavity VCSEL

    NASA Astrophysics Data System (ADS)

    Hu, Shanting; Ahmed, Moustafa; Bakry, Ahmed; Koyama, Fumio

    2015-09-01

    We present the modeling on the modulation bandwidth and frequency chirp of transverse-coupled-cavity vertical-cavity surface-emitting lasers (VCSELs), which enable us to tailor the transfer function of intensity and frequency modulations thanks to an optical feedback effect. The simulation shows the 3-dB-modulation bandwidth can be doubled and the chirp can be reduced by a factor of more than three. These improvements could be explained by an increase in differential net gain in coupled cavities. The result shows a possibility of high-speed and low-chirp operations of transverse coupled cavity VCSELs for higher data rates and longer link lengths of single-mode fiber transmissions.

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

    SciTech Connect

    Kopyciuk, T.; Parzynski, R.

    2007-05-15

    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.

  3. Precise linearization of broadband frequency chirp for coherent optical frequency domain reflectometry

    NASA Astrophysics Data System (ADS)

    Qin, Jie; Shi, Hongxiao; Xie, Weilin; Zhou, Qian; Dong, Yi; Hu, Weisheng

    2015-08-01

    Optical frequency domain reflectometry is a suitable and promising measurement technique for optical network components characterization; however its performance is severely limited by sweep nonlinearity of the laser chirp. We demonstrate precise linearization of broadband optical frequency chirp using optoelectronic feedback loop. The sweep rate and the laser chirp shape is locked to and determined by the frequency of a reference electronic signal, an agile, high coherence swept-frequency semiconductor laser source with a bandwidth of 66GHz in 100ms is achieved. The laser source is applied to a coherent optical frequency domain reflectometry; a transform-limited spatial resolution of 1.5mm at a distance of 200 meters is demonstrated.

  4. Period-chirped gratings fabricated by laser interference lithography with a concave Lloyd's mirror.

    PubMed

    Kim, Hanbit; Jung, Hyunho; Lee, Dong-Hyun; Lee, Kyu Back; Jeon, Heonsu

    2016-01-10

    We developed a laser interference lithography (LIL) system for fabrication of period-chirped gratings, which would be useful for sophisticated optical components. Despite its simplicity, the developed LIL system, based on a Lloyd's mirror interferometer with a cylindrically concave mirror, can generate chirped gratings, yet over a large area at high throughput owing to the nature of LIL. We have derived exact theoretical equations needed for system design, built the LIL system, and subsequently realized period-chirped gratings. A fabricated sample whose center period is Λ≈600  nm exhibits a continuous period variation of ΔΛ=92  nm across 17 mm width. PMID:26835772

  5. Self-deflecting plasmonic lattice solitons and surface modes in chirped plasmonic arrays.

    PubMed

    Li, Chunyan; Cui, Ran; Ye, Fangwei; Kartashov, Yaroslav V; Torner, Lluis; Chen, Xianfeng

    2015-03-15

    We show that chirped metal-dielectric waveguide arrays with focusing cubic nonlinearity can support plasmonic lattice solitons that undergo self-deflection in the transverse plane. Such lattice solitons are deeply subwavelength self-sustained excitations, although they cover several periods of the array. Upon propagation, the excitations accelerate in the transverse plane and follow trajectories curved in the direction in which the separation between neighboring metallic layers decreases, a phenomenon that yields considerable deflection angles. The deflection angle can be controlled by varying the array chirp. We also reveal the existence of surface modes at the boundary of truncated plasmonic chirped array that form even in the absence of nonlinearity. PMID:25768141

  6. Control of the two-Photon Double Ionization of Helium with Intense Chirped Attosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Barmaki, Samira; Laulan, Stephane

    2014-05-01

    We study the two-photon double ionization process of the helium atom by solving numerically the nonrelativistic time-dependent Schrödinger equation in its full dimensionality. We investigate with an intense chirped attosecond laser pulse of central carrier frequency that corresponds to the 29th harmonic of a Ti-sapphire laser the direct and sequential processes in helium. We show how it is possible by adjusting the chirp parameter to control the dominance of one process over the other within the atom. 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.

  7. Frequency chirped light at large detuning with an injection-locked diode laser.

    PubMed

    Teng, K; Disla, M; Dellatto, J; Limani, A; Kaufman, B; Wright, M J

    2015-04-01

    We have developed a laser system to generate frequency-chirped light at rapid modulation speeds (∼100 MHz) with a large frequency offset. Light from an external cavity diode laser with its frequency locked to an atomic resonance is passed through a lithium niobate electro-optical phase modulator. The phase modulator is driven by a ∼6 GHz signal whose frequency is itself modulated with a RF MHz signal (<200 MHz). A second injection locked diode laser is used to filter out all of the light except the frequency-chirped ±1 order by more than 30 dB. Using this system, it is possible to generate a 1 GHz frequency chirp in 5 ns. PMID:25933848

  8. Direct space-to-time pulse shaping for ultrafast optical waveform generation

    NASA Astrophysics Data System (ADS)

    Leaird, Daniel E.

    The high-speed photonic network industry, driven by the demands of enormous growth of network data traffic, has grown to be a multi-billion dollar entity. The availability of increased data traffic has come about due to the growth in bandwidth transmitted over optical fiber. This growth is primarily due to research in two areas-time-division-multiplexed (TDM), and wavelength-division-multiplexed (WDM) photonic network schemes. A key bottleneck in these high-speed photonic networks is the optical-electronic (OE) interface. Currently, multiple laser sources and/or multiple serial optoelectronic modulators are used to implement the OE interface in both photonic network schemes. In this thesis, an apparatus will be demonstrated that could act as a relatively simple OE interface for these high-speed photonic networks. The optical system, a direct space-to-time (DST) pulse shaper, converts a 1-D spatially patterned short optical pulse directly into a serial ultrafast time-domain waveform in a configuration compatible with the use of high-speed reflection modulator arrays. The space-to-time conversion properties, chirp compensation/cancellation, and potential for multiple spatially separated but wavelength shifted outputs will be examined theoretically and experimentally. Integrated optic implementations of the DST pulse shaper, based on a common high-speed WDM network component, will be investigated as well. Work on the bulk optics implementation of the DST shaper provides considerable insight into the operation of the integrated optics implementations. The space-to-time mapping, and multiple output channel characteristics of the bulk optics DST are shown to function similarly in the integrated optics implementations. These integrated optic versions of the DST pulse shaper may play a significant role in future high-speed photonic networks.

  9. Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening.

    PubMed

    Kamimura, H A S; Wang, S; Wu, S-Y; Karakatsani, M E; Acosta, C; Carneiro, A A O; Konofagou, E E

    2015-10-01

    Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n  =  15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5–1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were mm3, mm3and mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were V.s, V.s and V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue. PMID:26394091

  10. Variations in recorded acoustic gunshot waveforms generated by small firearms.

    PubMed

    Beck, Steven D; Nakasone, Hirotaka; Marr, Kenneth W

    2011-04-01

    Analysis of recorded acoustic gunshot signals to determine firearm waveform characteristics requires an understanding of the impulsive signal events, how the waveforms vary among different sources, and how the waveforms are affected by the environment and the recording system. This paper presents empirical results from waveforms produced by different small firearms and an analysis of their variations under different and controlled conditions. Acoustic signals were generated using multiple firearm makes and models firing different ammunition types. Simultaneous recordings from the microphones located at different distances from the source and at different azimuth angles (from the line-of-fire) were used to study source characteristics and sound propagation effects. The results indicate that recorded gunshot waveforms generally consist of multiple acoustic events, and these are observable depending on the received distance and azimuth angle. The source blast size, microphone distance, and microphone azimuth angle are the primary factors affecting the recorded muzzle blast characteristics. Ground or object reflections and ballistic shockwaves and their reflections can interfere with the muzzle blast waveform and its measurements. This experiment confirmed and quantified the wide range of correlation results between waveforms recorded from different source, microphone distance, and microphone angle configurations. PMID:21476632

  11. Design and implementation of a hospital wide waveform capture system.

    PubMed

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

    2015-06-01

    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 10 month 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 11 MB of data. The average single day data collection consisted of 8.6 GB 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

  12. Waveform Inversion by One-way Wavefield Extrapolation

    NASA Astrophysics Data System (ADS)

    Shragge, J. C.

    2006-12-01

    Forward modeling in frequency-domain waveform inversion is often implemented using finite difference (FD) methods. However, the cost of FD modeling remains too expensive for typical 3D seismic data volumes. One- way wavefield extrapolation is one alternative strategy considerably cheaper to implement. This approach, though, comes with caveats that typically include lower accuracy at steep propagation angles in laterally varying media, a difficulty for incorporating source radiation patterns, and an inability to propagate turning or multiply reflected waves. Each of these factors can play a role in determining the success or failure of a waveform inversion analysis. This study examines the potential for using one-way Riemannian wavefield extrapolation (RWE) operators in the forward modeling component of frequency-domain waveform inversion. RWE is carried out on computational meshes designed to conform to the general direction of turning-wave propagation, which enables the calculation of the direct arrivals, wide-angle reflections and refractions important for a successful waveform inversion. The waveform inversion procedure otherwise closely resembles the frequency-domain approach of Pratt. Forward modeling test results indicate that RWE waveforms match fairly well with those generated by FD modeling fairly at wider offsets. Preliminary tests of the RWE waveform inversion scheme demonstrate its ability to invert FD-generated synthetic data for moderate (10%) 1D velocity perturbations.

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

    SciTech Connect

    Feng, Liqiang; Chu, Tianshu

    2011-11-15

    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.

  14. The symmetry in a chirp filter and its application to LPI communication

    NASA Astrophysics Data System (ADS)

    Lam, Larry

    The even phase symmetry property of a chirp filter is discussed. It is known that significant spectral lines are produced at the output when a binary-phase-shift keyed (BPSK) signal is applied to a squaring circuit (SC) or a delay-and-multiply circuit. These spectral lines can be suppressed by using an even phase symmetric filter. One application of a chirp filter is to transform a conventional direct-sequence-spread-spectrum (DS-SS) low probability of intercept (LPI) signal into a form that is more difficult to detect. Computer simulation results are presented to show the effectiveness of the proposed technique.

  15. Ultrashort-attosecond-pulse generation by reducing harmonic chirp with a spatially inhomogeneous electric field

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Chen, Gao; Li, Su-Yu; Ding, Da-Jun; Chen, Ji-Gen; Guo, Fu-Ming; Yang, Yu-Jun

    2015-09-01

    We theoretically study high-order harmonic generation from an inhomogeneous field originated by the interaction between an ultrashort laser pulse and a gold nanostructure and demonstrate that ultrashort isolated attosecond pulses can be generated by reducing the harmonic chirp with the spatially inhomogeneous electric field. It can be found that the instants of ionized electrons coming back to the core are highly concentrated in the case of the spatially inhomogeneous electric field and a broadband supercontinuum harmonic spectrum with less chirp can be produced. Then an isolated 127-as pulse close to the Fourier transform limit can be directly generated without phase compensation.

  16. Control of the Atomic Ionization with Short and Intense Chirped Laser Pulses

    NASA Astrophysics Data System (ADS)

    Hennani, Salima; Laulan, Stephane; Barmaki, Samira

    2014-05-01

    We investigate a two-photon ionization process in a real hydrogen atom by short and intense chirped laser pulses. Our simulation of the laser-atom interaction consists on numerically solving the three-dimensional time-dependent Schrödinger equation with a spectral method. The unperturbed wave functions and electronic energies of the atomic system were found by using an accurate L2 discretization technique based on the expansion of the wave functions on B-spline functions. We show the efficiency of chirped laser pulses to control the ionization yield and the transfer of the population to the 2 p bound state involved in the ionization path.

  17. Ultrashort pulse chirp measurement via transverse second-harmonic generation in strontium barium niobate crystal

    SciTech Connect

    Trull, J.; Wang, B.; Parra, A.; Vilaseca, R.; Cojocaru, C.; Sola, I.; Sheng, Y.

    2015-06-01

    Pulse compression in dispersive strontium barium niobate crystal with a random size and distribution of the anti-parallel orientated nonlinear domains is observed via transverse second harmonic generation. The dependence of the transverse width of the second harmonic trace along the propagation direction allows for the determination of the initial chirp and duration of pulses in the femtosecond regime. This technique permits a real-time analysis of the pulse evolution and facilitates fast in-situ correction of pulse chirp acquired in the propagation through an optical system.

  18. Some refractometric features of dual-core chirped microstructured optical fibers

    NASA Astrophysics Data System (ADS)

    Velasquez-Botero, Fabian; Reyes-Vera, Erick; Torres, Pedro

    2015-09-01

    Refractometric features of dual-core transversally chirped microstructured optical fibers (MOF) are evaluated. It is shown from numerical results that the chirped MOF could act as a structure with decoupled cores, forming a Mach- Zehnder interferometer in which the analyte directly modulates the device transmittance by its differential influence on the effective refractive index of each core mode. We investigate the influence of the MOF parameters and the analyte refractive index on sensor performance. This novel structure is suitable for measuring refractive indices in the 1.33-1.44 range.

  19. Photodissociation of Methyl Isothiocyanate Studied Using Chirped Pulse Uniform Flow Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ariyasingha, Nuwandi M.; Zack, Lindsay N.; Abeysekera, Chamara; Joalland, Baptiste; Suits, Arthur

    2015-06-01

    Chirped-Pulse Fourier-transform microwave spectroscopy has been applied in a uniform supersonic flow (Chirped-pulse/Uniform flow, CPUF) to study the 193 nm photodissociation of methyl isothiocyanate (MITC). Several products (CH3NC, NCS, H2CS, HCN and HNC) were identified via their pure rotational spectra. Observation of CH3NC and NCS are consistent with previous studies of this system, however it is the first detection of H2CS and HCN/HNC. Branching ratios were obtained from these data and will be discussed.

  20. Control of spectral aberrations in a monochromator using a chirped grating

    NASA Astrophysics Data System (ADS)

    April, A.; McCarthy, N.

    2008-06-01

    A method is proposed to minimize the impact of spectral aberrations in a monochromator based on a rectilinear translation of a plane chirped grating. The chirped grating, that has a spatially variable groove spacing, is used to diffract and to spectrally focus the radiation. The expression of the width of the instrument line shape due to aberrations have been developed in order to obtain the optimal rectilinear trajectory required to operate the monochromator without significant spectral aberrations. Experimental measurements of the emission spectrum of a five-wavelength Helium-Neon laser are presented, as well as the sensitivity of the monochromator performance to different geometrical parameters.

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

    SciTech Connect

    Hamdalla, Taymour A.

    2012-09-06

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

  2. a Low-Cost Chirped-Pulse Fourier Transform Microwave Spectrometer for Undergraduate Physical Chemistry Lab

    NASA Astrophysics Data System (ADS)

    Carroll, Brandon; Finneran, Ian; Blake, Geoffrey

    2014-06-01

    We present the design and construction of a simple and low-cost waveguide chirped pulse Fourier transform microwave (CP-FTMW) spectrometer suitable for gas-phase rotational spectroscopy experiments in undergraduate physical chemistry labs as well as graduate level research. The spectrometer operates with modest bandwidth, using phased locked loop (PLL) microwave sources and a direct digital synthesis (DDS) chirp source, making it an affordable for undergraduate labs. The performance of the instrument is benchmarked by acquiring the pure rotational spectrum of the J = 1 - 0 transition OCS and its isotopologues from 11-12.5 GHz.

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

    SciTech Connect

    Yang Xihua; Zhang Zhenhua; Yan Xiaona; Li Chunfang

    2010-03-15

    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.

  4. 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. ...

  5. Waveform synthesis for imaging and ranging applications

    DOEpatents

    Doerry, Armin W.; Dudley, Peter A.; Dubert, Dale F.; Tise, Bertice L.

    2004-12-07

    Frequency dependent corrections are provided for quadrature imbalance and Local Oscillator (LO) feed-through. An operational procedure filters imbalance and 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 and/or 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 LO feed-through and 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.

  6. Femtosecond Nanofocusing with Full Optical Waveform Control

    SciTech Connect

    Berweger, Samuel; Atkin, Joanna M.; Xu, Xiaoji G.; Olmon, Robert L.; Raschke, Markus Bernd

    2011-10-12

    The simultaneous nanometer spatial confinement and femtosecond temporal control of an optical excitation has been a long-standing challenge in optics. Previous approaches using surface plasmon polariton (SPP) resonant nanostructures or SPP waveguides have suffered from, for example, mode mismatch, or possible dependence on the phase of the driving laser field to achieve spatial localization. Here we take advantage of the intrinsic phase- and amplitude-independent nanofocusing ability of a conical noble metal tip with weak wavelength dependence over a broad bandwidth to achieve a 10 nm spatially and few-femtosecond temporally confined excitation. In combination with spectral pulse shaping and feedback on the second-harmonic response of the tip apex, we demonstrate deterministic arbitrary optical waveform control. In addition, the high efficiency of the nanofocusing tip provided by the continuous micro- to nanoscale mode transformation opens the door for spectroscopy of elementary optical excitations in matter on their natural length and time scales and enables applications from ultrafast nano-opto-electronics to single molecule quantum coherent control.

  7. ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

    SciTech Connect

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

    2009-04-30

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

  8. Gravitational radiation reaction and inspiral waveforms in the adiabatic limit.

    PubMed

    Hughes, Scott A; Drasco, Steve; Flanagan, Eanna E; Franklin, Joel

    2005-06-10

    We describe progress evolving an important limit of binaries in general relativity: stellar mass compact objects spiraling into much larger black holes. Such systems are of great observational interest. We have developed tools to compute for the first time the radiation from generic orbits. Using global conservation laws, we find the orbital evolution and waveforms for special cases. For generic orbits, inspirals and waveforms can be found by augmenting our approach with an adiabatic self-force rule due to Mino. Such waveforms should be accurate enough for gravitational-wave searches. PMID:16090377

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

    NASA Technical Reports Server (NTRS)

    Briones, Janette C.; Shalkhauser, Mary Jo

    2014-01-01

    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.

  10. A 10 tesla table-top controlled waveform magnet

    NASA Astrophysics Data System (ADS)

    Roy Choudhury, Aditya N.; Venkataraman, V.

    2012-06-01

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

  11. Fast construction of FM-index for long sequence reads

    PubMed Central

    2014-01-01

    Summary: We present a new method to incrementally construct the FM-index for both short and long sequence reads, up to the size of a genome. It is the first algorithm that can build the index while implicitly sorting the sequences in the reverse (complement) lexicographical order without a separate sorting step. The implementation is among the fastest for indexing short reads and the only one that practically works for reads of averaged kilobases in length. Availability and implementation: https://github.com/lh3/ropebwt2 Contact: hengli@broadinstitute.org PMID:25107872

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

    NASA Astrophysics Data System (ADS)

    D'Emilia, Giulio

    1996-11-01

    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.

  13. Multi channel FM reflection profiler for buried pipeline surveying

    SciTech Connect

    Schock, S.G.; LeBlanc, L.R.

    1996-12-31

    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.

  14. Atomic Mass and Nuclear Binding Energy for Fm-291 (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-291 (Fermium, atomic number Z = 100, mass number A = 291).

  15. Atomic Mass and Nuclear Binding Energy for Fm-333 (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-333 (Fermium, atomic number Z = 100, mass number A = 333).

  16. Atomic Mass and Nuclear Binding Energy for Fm-262 (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-262 (Fermium, atomic number Z = 100, mass number A = 262).

  17. Atomic Mass and Nuclear Binding Energy for Fm-294 (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-294 (Fermium, atomic number Z = 100, mass number A = 294).

  18. Atomic Mass and Nuclear Binding Energy for Fm-293 (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-293 (Fermium, atomic number Z = 100, mass number A = 293).

  19. Atomic Mass and Nuclear Binding Energy for Fm-281 (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-281 (Fermium, atomic number Z = 100, mass number A = 281).

  20. Atomic Mass and Nuclear Binding Energy for Fm-330 (Fermium)

    NASA Astrophysics Data System (ADS)

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

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides atomic mass, mass excess, nuclear binding energy, nucleon separation energies, Q-values, and nucleon residual interaction parameters for atomic nuclei of the isotope Fm-330 (Fermium, atomic number Z = 100, mass number A = 330).