Science.gov

Sample records for accessible frequency range

  1. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization

    PubMed Central

    Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris

    2015-01-01

    This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy. PMID:26263986

  2. An Ultrasonic Multiple-Access Ranging Core Based on Frequency Shift Keying Towards Indoor Localization.

    PubMed

    Segers, Laurent; Van Bavegem, David; De Winne, Sam; Braeken, An; Touhafi, Abdellah; Steenhaut, Kris

    2015-01-01

    This paper describes a new approach and implementation methodology for indoor ranging based on the time difference of arrival using code division multiple access with ultrasound signals. A novel implementation based on a field programmable gate array using finite impulse response filters and an optimized correlation demodulator implementation for ultrasound orthogonal signals is developed. Orthogonal codes are modulated onto ultrasound signals using frequency shift keying with carrier frequencies of 24.5 kHz and 26 kHz. This implementation enhances the possibilities for real-time, embedded and low-power tracking of several simultaneous transmitters. Due to the high degree of parallelism offered by field programmable gate arrays, up to four transmitters can be tracked simultaneously. The implementation requires at most 30% of the available logic gates of a Spartan-6 XC6SLX45 device and is evaluated on accuracy and precision through several ranging topologies. In the first topology, the distance between one transmitter and one receiver is evaluated. Afterwards, ranging analyses are applied between two simultaneous transmitters and one receiver. Ultimately, the position of the receiver against four transmitters using trilateration is also demonstrated. Results show enhanced distance measurements with distances ranging from a few centimeters up to 17 m, while keeping a centimeter-level accuracy. PMID:26263986

  3. Relationships between range access as monitored by radio frequency identification technology, fearfulness, and plumage damage in free-range laying hens.

    PubMed

    Hartcher, K M; Hickey, K A; Hemsworth, P H; Cronin, G M; Wilkinson, S J; Singh, M

    2016-05-01

    Severe feather-pecking (SFP), a particularly injurious behaviour in laying hens (Gallus gallus domesticus), is thought to be negatively correlated with range use in free-range systems. In turn, range use is thought to be inversely associated with fearfulness, where fearful birds may be less likely to venture outside. However, very few experiments have investigated the proposed association between range use and fearfulness. This experiment investigated associations between range use (time spent outside), fearfulness, plumage damage, and BW. Two pens of 50 ISA Brown laying hens (n=100) were fitted with radio frequency identification (RFID) transponders (contained within silicone leg rings) at 26 weeks of age. Data were then collected over 13 days. A total of 95% of birds accessed the outdoor run more than once per day. Birds spent an average duration of 6.1 h outside each day over 11 visits per bird per day (51.5 min per visit). The top 15 and bottom 15 range users (n=30), as determined by the total time spent on the range over 13 days, were selected for study. These birds were tonic immobility (TI) tested at the end of the trial and were feather-scored and weighed after TI testing. Birds with longer TI durations spent less time outside (P=0.01). Plumage damage was not associated with range use (P=0.68). The small group sizes used in this experiment may have been conducive to the high numbers of birds utilising the outdoor range area. The RFID technology collected a large amount of data on range access in the tagged birds, and provides a potential means for quantitatively assessing range access in laying hens. The present findings indicate a negative association between fearfulness and range use. However, the proposed negative association between plumage damage and range use was not supported. The relationships between range use, fearfulness, and SFP warrant further research. PMID:26593871

  4. Transponder System for High-Frequency Ranging

    NASA Technical Reports Server (NTRS)

    Lichtenberg, C. L.; Shores, P. W.; Kobayashi, H. S.

    1986-01-01

    Transponder system uses phase difference between transmitted and reflected high-frequency radio waves to measure distance to target. To suppress spurious measurements of reflections from objects near target at transmitted frequency and its harmonics, transponder at target generates return signal at half transmitted frequency. System useful in such applications as surveying, docking of ships, and short-range navigation.

  5. Frequency skewed optical pulses for range detection

    NASA Astrophysics Data System (ADS)

    Ozharar, Sarper; Gee, Sangyoun; Quinlan, Franklyn; Delfyett, Peter J., Jr.

    2007-04-01

    Frequency skewed optical pulses are generated via both a composite cavity structure in a fiberized semiconductor optical amplifier ring laser and a frequency skew loop outside the laser cavity. The composite cavity technique is similar to rational harmonic mode-locking, however it is based on cavity detuning rather than frequency detuning. These frequency skewed pulses are ideal for range detection applications since their interference results in a range dependent RF signal. The intracavity frequency skewed pulse train showed superior performance in both stability and signal quality.

  6. Active laser ranging with frequency transfer using frequency comb

    NASA Astrophysics Data System (ADS)

    Zhang, Hongyuan; Wei, Haoyun; Yang, Honglei; Li, Yan

    2016-05-01

    A comb-based active laser ranging scheme is proposed for enhanced distance resolution and a common time standard for the entire system. Three frequency combs with different repetition rates are used as light sources at the two ends where the distance is measured. Pulse positions are determined through asynchronous optical sampling and type II second harmonic generation. Results show that the system achieves a maximum residual of 379.6 nm and a standard deviation of 92.9 nm with 2000 averages over 23.6 m. Moreover, as for the frequency transfer, an atom clock and an adjustable signal generator, synchronized to the atom clock, are used as time standards for the two ends to appraise the frequency deviation introduced by the proposed system. The system achieves a residual fractional deviation of 1.3 × 10-16 for 1 s, allowing precise frequency transfer between the two clocks at the two ends.

  7. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Frequency range of measurements. 18.309 Section... MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field strength measurements: Frequency band in which device operates (MHz) Range of frequency measurements Lowest...

  8. Characteristics of different frequency ranges in scanning electron microscope images

    SciTech Connect

    Sim, K. S. Nia, M. E.; Tan, T. L.; Tso, C. P.; Ee, C. S.

    2015-07-22

    We demonstrate a new approach to characterize the frequency range in general scanning electron microscope (SEM) images. First, pure frequency images are generated from low frequency to high frequency, and then, the magnification of each type of frequency image is implemented. By comparing the edge percentage of the SEM image to the self-generated frequency images, we can define the frequency ranges of the SEM images. Characterization of frequency ranges of SEM images benefits further processing and analysis of those SEM images, such as in noise filtering and contrast enhancement.

  9. 33 CFR 86.01 - Frequencies and range of audibility.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... INLAND NAVIGATION RULES ANNEX III: TECHNICAL DETAILS OF SOUND SIGNAL APPLIANCES Whistles § 86.01 Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525..., which may include the fundamental and/or one or more higher frequencies, which lie within the...

  10. 33 CFR 86.01 - Frequencies and range of audibility.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... INLAND NAVIGATION RULES ANNEX III: TECHNICAL DETAILS OF SOUND SIGNAL APPLIANCES Whistles § 86.01 Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525..., which may include the fundamental and/or one or more higher frequencies, which lie within the...

  11. 33 CFR 86.01 - Frequencies and range of audibility.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... INLAND NAVIGATION RULES ANNEX III: TECHNICAL DETAILS OF SOUND SIGNAL APPLIANCES Whistles § 86.01 Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525..., which may include the fundamental and/or one or more higher frequencies, which lie within the...

  12. 33 CFR 86.01 - Frequencies and range of audibility.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... INLAND NAVIGATION RULES ANNEX III: TECHNICAL DETAILS OF SOUND SIGNAL APPLIANCES Whistles § 86.01 Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525..., which may include the fundamental and/or one or more higher frequencies, which lie within the...

  13. 47 CFR 15.202 - Certified operating frequency range.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Certified operating frequency range. 15.202 Section 15.202 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices that operate in a...

  14. 47 CFR 15.202 - Certified operating frequency range.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Certified operating frequency range. 15.202 Section 15.202 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices that operate in a...

  15. 47 CFR 15.202 - Certified operating frequency range.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Certified operating frequency range. 15.202 Section 15.202 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices that operate in a...

  16. 47 CFR 15.202 - Certified operating frequency range.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Certified operating frequency range. 15.202 Section 15.202 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices that operate in a...

  17. 47 CFR 15.202 - Certified operating frequency range.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Certified operating frequency range. 15.202 Section 15.202 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.202 Certified operating frequency range. Client devices that operate in a...

  18. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Frequency range of radiated measurements. 15.33 Section 15.33 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES General § 15.33 Frequency range of radiated measurements. (a) For an intentional radiator, the spectrum shall be investigated from the lowest...

  19. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Frequency range of measurements. 18.309 Section 18.309 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL INDUSTRIAL, SCIENTIFIC, AND MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field...

  20. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Frequency range of measurements. 18.309 Section 18.309 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL INDUSTRIAL, SCIENTIFIC, AND MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field...

  1. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Frequency range of measurements. 18.309 Section 18.309 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL INDUSTRIAL, SCIENTIFIC, AND MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field...

  2. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Frequency range of measurements. 18.309 Section 18.309 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL INDUSTRIAL, SCIENTIFIC, AND MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field...

  3. 33 CFR 86.01 - Frequencies and range of audibility.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Frequencies and range of audibility. 86.01 Section 86.01 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY INLAND NAVIGATION RULES ANNEX III: TECHNICAL DETAILS OF SOUND SIGNAL APPLIANCES Whistles § 86.01 Frequencies and range of audibility. The...

  4. Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species.

    PubMed

    Titze, Ingo; Riede, Tobias; Mau, Ted

    2016-06-01

    Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations. PMID:27309543

  5. Predicting Achievable Fundamental Frequency Ranges in Vocalization Across Species

    PubMed Central

    Titze, Ingo; Riede, Tobias; Mau, Ted

    2016-01-01

    Vocal folds are used as sound sources in various species, but it is unknown how vocal fold morphologies are optimized for different acoustic objectives. Here we identify two main variables affecting range of vocal fold vibration frequency, namely vocal fold elongation and tissue fiber stress. A simple vibrating string model is used to predict fundamental frequency ranges across species of different vocal fold sizes. While average fundamental frequency is predominantly determined by vocal fold length (larynx size), range of fundamental frequency is facilitated by (1) laryngeal muscles that control elongation and by (2) nonlinearity in tissue fiber tension. One adaptation that would increase fundamental frequency range is greater freedom in joint rotation or gliding of two cartilages (thyroid and cricoid), so that vocal fold length change is maximized. Alternatively, tissue layers can develop to bear a disproportionate fiber tension (i.e., a ligament with high density collagen fibers), increasing the fundamental frequency range and thereby vocal versatility. The range of fundamental frequency across species is thus not simply one-dimensional, but can be conceptualized as the dependent variable in a multi-dimensional morphospace. In humans, this could allow for variations that could be clinically important for voice therapy and vocal fold repair. Alternative solutions could also have importance in vocal training for singing and other highly-skilled vocalizations. PMID:27309543

  6. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... § 15.33 Frequency range of radiated measurements. (a) For an intentional radiator, the spectrum shall... kHz, up to at least the frequency shown in this paragraph: (1) If the intentional radiator operates... lower. (2) If the intentional radiator operates at or above 10 GHz and below 30 GHz: to the...

  7. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... § 15.33 Frequency range of radiated measurements. (a) For an intentional radiator, the spectrum shall... kHz, up to at least the frequency shown in this paragraph: (1) If the intentional radiator operates... lower. (2) If the intentional radiator operates at or above 10 GHz and below 30 GHz: to the...

  8. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... § 15.33 Frequency range of radiated measurements. (a) For an intentional radiator, the spectrum shall... kHz, up to at least the frequency shown in this paragraph: (1) If the intentional radiator operates... lower. (2) If the intentional radiator operates at or above 10 GHz and below 30 GHz: to the...

  9. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... § 15.33 Frequency range of radiated measurements. (a) For an intentional radiator, the spectrum shall... kHz, up to at least the frequency shown in this paragraph: (1) If the intentional radiator operates... lower. (2) If the intentional radiator operates at or above 10 GHz and below 30 GHz: to the...

  10. a Pre-Emphasis Technique to Broaden the Usable Frequency Range in Swept-Frequency Systems

    NASA Astrophysics Data System (ADS)

    Gammell, Paul M.; Maruvada, Subha; Liu, Yunbo; Harris, Gerald R.

    2010-02-01

    The usable frequency range of an ultrasonic swept-frequency system can be compromised because of transducer bandwidth limitations or sample frequency response and corresponding signal-to-noise (S/N) considerations. By adding a variable gain amplifier together with an arbitrary waveform generator that is synchronized with the frequency sweep, the dynamic range of the receiver can be accommodated over a wider frequency range. This pre-emphasis approach has been demonstrated for two applications: substitution calibration of hydrophones and attenuation measurements.

  11. Experimental limits on gravitational waves in the MHz frequency range

    NASA Astrophysics Data System (ADS)

    Lanza, Robert Kingman, Jr.

    This thesis presents the results of a search for gravitational waves in the 1-11MHz frequency range using dual power-recycled Michelson laser interferometers at Fermi National Accelerator Laboratory. An unprecedented level of sensitivity to gravitational waves in this frequency range has been achieved by cross-correlating the output fluctuations of two identical and co-located 40m long interferometers. This technique produces sensitivities better than two orders of magnitude below the quantum shot-noise limit, within integration times of less than 1 hour. 95% confidence level upper limits are placed on the strain amplitude of MHz frequency gravitational waves at the 10-21 Hz-1/2 level, constituting the best direct limits to date at these frequencies. For gravitational wave power distributed over this frequency range, a broadband upper limit of 2.4x10 -21Hz-1/2 at 95% confidence level is also obtained. This thesis covers the detector technology, the commissioning and calibration of the instrument, the statistical data analysis, and the gravitational wave limit results. Particular attention is paid to the end-to-end calibration of the instrument's sensitivity to differential arm length motion, and so to gravitational wave strain. A detailed statistical analysis of the data is presented as well.

  12. Improving range resolution with a frequency-hopping technique

    NASA Technical Reports Server (NTRS)

    Stitt, G. R.; Bowhill, S. A.

    1986-01-01

    Range resolution of a conventional pulsed Doppler radar is determined by the scattering volume defined by the transmitted pulse shape. To increase the resolution, the length of the pulse must be reduced. Reducing the pulse length also reduces the transmitted power and hense the signal to noise ratio unless the peak power capability of the transmitter is greatly increased. Improved range resolution may also be attained through the use of various pulse coding methods, but such methods are sometimes difficult to implement from a hardware standpoint. The frequency-hopping (F-H) technique described increases the range resolution of pulse Doppler MST (mesosphere stratosphere troposphere) radar without the need for extensive modifications to the radar transmitter. This technique consists of sending a repeated sequence of pulses, each pulse in the sequence being transmitted at a unique radio frequency that is under the control of a microcomputer. This technique is discussed along with other radar parameters.

  13. Ring current instabilities in the magnetohydrodynamic frequency range

    NASA Technical Reports Server (NTRS)

    Hasegawa, A.; Chen, L.

    1992-01-01

    This report summarizes recent theoretical developments in ring current plasma instabilities in the magnetohydrodynamic (MHD) frequency range but with the effect of finite Larmor radius, and discusses its relevance to satellite-based observations. Possible instabilities are the bounce resonant instabilities caused by a humped energy distribution, the drift mirror instability caused by an anisotropic pressure and the drift wave type instability caused by a combination of drift-bounce resonance and reduced Alfven frequency due to a high beta loading of the flux tube. Here, beta is proportional to plasma/magnetic pressures. Mechanisms leading to turbulence are also discussed.

  14. Modeling of long range frequency sweeping for energetic particle modes

    SciTech Connect

    Nyqvist, R. M.; Breizman, B. N.

    2013-04-15

    Long range frequency sweeping events are simulated numerically within a one-dimensional, electrostatic bump-on-tail model with fast particle sources and collisions. The numerical solution accounts for fast particle trapping and detrapping in an evolving wave field with a fixed wavelength, and it includes three distinct collisions operators: Drag (dynamical friction on the background electrons), Krook-type collisions, and velocity space diffusion. The effects of particle trapping and diffusion on the evolution of holes and clumps are investigated, and the occurrence of non-monotonic (hooked) frequency sweeping and asymptotically steady holes is discussed. The presented solution constitutes a step towards predictive modeling of frequency sweeping events in more realistic geometries.

  15. A broadband multifocal metalens in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Hashemi, Mahdieh; Moazami, Amin; Naserpour, Mahin; Zapata-Rodríguez, Carlos J.

    2016-07-01

    Metasurfaces, the 2D form of metamaterials with their ability in phase, amplitude and polarization manipulation are widely used in designing optical devices. Efforts to find proper photonic components in the terahertz (THz) range of frequency lead us to adopt metasurfaces as their constituent elements. Here, we conceived a broadband THz lens with an adjustable number and arrangement of focal points. To have a full control over the lens functionality, we used a metasurface with the capability of simultaneously modulating the amplitude and phase of the incident wave. C-shaped ring resonators (CSRRs) with different geometry and orientation capable of simultaneously manipulating phase and amplitude of the scattered fields, are proper choice to design the lens. We show that the introduced lens in a one-dimensional layout has a wide range of working frequencies within the THz spectrum, which can be used in a plethora of applications.

  16. Ultrasonic Multiple-Access Ranging System Using Spread Spectrum and MEMS Technology for Indoor Localization

    PubMed Central

    Segers, Laurent; Tiete, Jelmer; Braeken, An; Touhafi, Abdellah

    2014-01-01

    Indoor localization of persons and objects poses a great engineering challenge. Previously developed localization systems demonstrate the use of wideband techniques in ultrasound ranging systems. Direct sequence and frequency hopping spread spectrum ultrasound signals have been proven to achieve a high level of accuracy. A novel ranging method using the frequency hopping spread spectrum with finite impulse response filtering will be investigated and compared against the direct sequence spread spectrum. In the first setup, distances are estimated in a single-access environment, while in the second setup, two senders and one receiver are used. During the experiments, the micro-electromechanical systems are used as ultrasonic sensors, while the senders were implemented using field programmable gate arrays. Results show that in a single-access environment, the direct sequence spread spectrum method offers slightly better accuracy and precision performance compared to the frequency hopping spread spectrum. When two senders are used, measurements point out that the frequency hopping spread spectrum is more robust to near-far effects than the direct sequence spread spectrum. PMID:24553084

  17. Frequency Drives Lexical Access in Reading but Not in Speaking: The Frequency-Lag Hypothesis

    ERIC Educational Resources Information Center

    Gollan, Tamar H.; Slattery, Timothy J.; Goldenberg, Diane; Van Assche, Eva; Duyck, Wouter; Rayner, Keith

    2011-01-01

    To contrast mechanisms of lexical access in production versus comprehension we compared the effects of word frequency (high, low), context (none, low constraint, high constraint), and level of English proficiency (monolingual, Spanish-English bilingual, Dutch-English bilingual) on picture naming, lexical decision, and eye fixation times. Semantic…

  18. Long range downwind propagation of low-frequency sound

    NASA Technical Reports Server (NTRS)

    Willshire, W. L., Jr.

    1985-01-01

    The propagation of low-frequency noise outdoors was studied using as the source a large (80-m diameter) 4-megawatt horizontal axis wind turbine. Acoustic measurements were made with low-frequency microphone systems placed on the ground at five downwind sites ranging from 300 m to 10,000 m (6.3 mile) away from the wind turbine. The wind turbine fundamental was 1 Hz and the wind speed was generally 12 - 15 m/s at the hub height (80 m). The harmonic levels, when plotted versus propagation distance, exhibit a 3 dB per doubling of distance divergence. Two plausible explanations identified for this cylindrical spreading behavior were propagation of the low frequency wind turbine noise via a surface wave and downwind refraction. Surface was amplitude predictions were found to be more than 20 dB smaller than the measured levels. Ray-tracing results were used to qualitatively explain measured trends. A normal mode approach was identified as a candidate method for low-frequency acoustic refraction prediction.

  19. Ionospheric Coherence Bandwidth Measurements in the Lower VHF Frequency Range

    NASA Astrophysics Data System (ADS)

    Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

    2015-12-01

    The United States Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 820 - 1100 MHz. In this paper, we present simultaneous ionospheric coherence bandwidth and S4 scintillation index measurements in the 32 - 44 MHz frequency range collected during the ESCINT equatorial scintillation experiment. 40-MHz continuous wave (CW) and 32 - 44 MHz swept frequency signals were transmitted simultaneously to the RFProp receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in three separate campaigns during the 2014 and 2015 equinoxes. Results show coherence bandwidths as small as ~ 1 kHz for strong scintillation (S4 > 0.7) and indicate a high degree of ionospheric variability and irregularity on 10-m spatial scales. Spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities are also observed and are dominant at low elevation angles. The results are compared to previous measurements and available scaling laws.

  20. Heating by waves in the ion cyclotron frequency range

    SciTech Connect

    Koch, R.

    1996-03-01

    The main aspects of heating with the fast wave in the ion cyclotron range of frequencies (ICRF) are reviewed. First, the ion cyclotron resonance mechanism, fundamental and harmonics, is examined. Then the properties of fast wave dispersion are reviewed, and the principles of minority and higher cylcotron harmonic heating are discussed. An elementary coupling model is worked out in order to outline the computation of the electrical properties of ICRF antennas. Using the simple model, the antenna radiation pattern inside the plasma is computed and the effect of phasing on the k spectrum and on the antenna radiation properties is illustrated. The quasi linear-Fokker-Planck computation of the deformation of distribution functions due to Radio-Frequency (RF) and tail formation are briefly discussed. 11 refs., 5 figs.

  1. A wide range sigma—delta fractional-N frequency synthesizer with adaptive frequency calibration

    NASA Astrophysics Data System (ADS)

    Jianjun, Wei; Hanjun, Jiang; Lingwei, Zhang; Jingjing, Dong; Fule, Li; Zhihua, Wang; Chun, Zhang

    2013-06-01

    A wide range fractional-N frequency synthesizer in 0.18 μm RF CMOS technology is implemented. A switched-capacitors bank LC-tank VCO and an adaptive frequency calibration technique are used to expand the frequency range. A 16-bit third-order sigma—delta modulator with dither is used to randomize the fractional spur. The active area is 0.6 mm2. The experimental results show the proposed frequency synthesizer consumes 4.3 mA from a single 1.8 V supply voltage except for buffers. The frequency range is 1.44-2.11 GHz and the frequency resolution is less than 0.4 kHz. The phase noise is -94 dBc/Hz @ 100 kHz and -121 dBc/Hz @ 1 MHz at the output of the prescaler with a loop bandwidth of approximately 120 kHz. The performance meets the requirements for the multi-band and multi-mode transceiver applications.

  2. Large-orbit gyrotron operation in the terahertz frequency range.

    PubMed

    Bratman, V L; Kalynov, Yu K; Manuilov, V N

    2009-06-19

    Coherent terahertz high-harmonic radiation has been obtained in a gyrotron with an axis-encircling electron beam. An electron-optical system with a cusp gun and a following drift section of adiabatic magnetic compression with an area factor of 3000 provides the formation of an 80-keV/0.7-A beam of gyrating electrons in a wide range of voltages and magnetic fields. Stable single-mode generation with a power of 0.3-1.8 kW in microsecond pulses is detected at four frequencies in the range 0.55-1.00 THz at resonant magnetic fields 10.5-14 T. PMID:19659020

  3. Wide tracking range, auto ranging, low jitter phase lock loop for swept and fixed frequency systems

    DOEpatents

    Kerner, Thomas M.

    2001-01-01

    The present invention provides a wide tracking range phase locked loop (PLL) circuit that achieves minimal jitter in a recovered clock signal, regardless of the source of the jitter (i.e. whether it is in the source or the transmission media). The present invention PLL has automatic harmonic lockout detection circuitry via a novel lock and seek control logic in electrical communication with a programmable frequency discriminator and a code balance detector. (The frequency discriminator enables preset of a frequency window of upper and lower frequency limits to derive a programmable range within which signal acquisition is effected. The discriminator works in combination with the code balance detector circuit to minimize the sensitivity of the PLL circuit to random data in the data stream). In addition, the combination of a differential loop integrator with the lock and seek control logic obviates a code preamble and guarantees signal acquisition without harmonic lockup. An adaptive cable equalizer is desirably used in combination with the present invention PLL to recover encoded transmissions containing a clock and/or data. The equalizer automatically adapts to equalize short haul cable lengths of coaxial and twisted pair cables or wires and provides superior jitter performance itself. The combination of the equalizer with the present invention PLL is desirable in that such combination permits the use of short haul wires without significant jitter.

  4. Frequency Drives Lexical Access in Reading but not in Speaking: The Frequency-Lag Hypothesis

    PubMed Central

    Gollan, Tamar H.; Slattery, Timothy J.; Goldenberg, Diane; van Assche, Eva; Duyck, Wouter; Rayner, Keith

    2010-01-01

    To contrast mechanisms of lexical access in production versus comprehension we compared the effects of word-frequency (high, low), context (none, low-constraining, high-constraining), and level of English proficiency (monolinguals, Spanish-English bilinguals, Dutch-English bilinguals), on picture naming, lexical decision, and eye fixation times. Semantic constraint effects were larger in production than in reading. Frequency effects were larger in production than in reading without constraining context, but larger in reading than in production with constraining context. Bilingual disadvantages were modulated by frequency in production but not in eye fixation times, were not smaller in low-constraining context, and were reduced by high-constraining context only in production and only at the lowest level of English proficiency. These results challenge existing accounts of bilingual disadvantages, and reveal fundamentally different processes during lexical access across modalities, entailing a primarily semantically driven search in production, but a frequency driven search in comprehension. The apparently more interactive process in production than comprehension could simply reflect a greater number of frequency-sensitive processing stages in production. PMID:21219080

  5. Access to Strain and Other Low Frequency Geophysical Observations

    NASA Astrophysics Data System (ADS)

    Prescott, W.; Hodgkinson, K.; Neuhauser, D.; Silverman, S.; Stites, N. P.; Zuzlewski, S.

    2001-12-01

    With National Earthquake Hazards Program (NEHRP) funding, the U.S. Geological Survey (USGS ) has supported various fault monitoring efforts. In addition to monitoring at seismic frequency bands, the USGS also has supported strain, creep, water level and other instrumental systems operating at "low frequency". Principal investigators include both USGS and academic scientists. The typical observation interval for these data sets is 10 minutes (0.00167 hz). Raw data from most of these instruments are now available at the Northern California Earthquake Data Center (NCEDC). NCEDC is a joint effort of the University of California, Berkeley and the USGS. Raw low frequency data at NCEDC are stored in the SEED format, a standard format adopted for seismic data. And the raw low frequency data can be accessed with seismic querying tools. In a companion effort, the USGS is improving access to processed versions of these data. The raw low frequency data are processed to remove obvious instrumental offsets and spurious outliers. In the case of dilatometer data, the effects of air pressure variations are also removed from the time series. The resulting processed time series are available as plots (most recent week, most recent month, most recent year, and complete time series) and as downloadable files in either a tabular file or an eXtensible Markup Language (XML) file. XML is a standard format containing markup "tags" to identify the fields. The XML file contains all of the information known about the sensors as well as the observations. For example, in addition to the date, time and value, the XML file may contain investigator name and contact information, latitude, longitude, elevation, instrument manufacturer, serial number, digitizer manufacturer, serial number, orientation, and scale factors. The tabular file is a simple space-delimited file containing just the date, time and observed value fields. The XML file is large, but compresses well. For 10 minutes samples, XML

  6. Optical conductivity of warm dense matter within a wide frequency range using quantum statistical and kinetic approaches.

    PubMed

    Veysman, M; Röpke, G; Winkel, M; Reinholz, H

    2016-07-01

    Fundamental properties of warm dense matter are described by the dielectric function, which gives access to the frequency-dependent electrical conductivity; absorption, emission, and scattering of radiation; charged particles stopping; and further macroscopic properties. Different approaches to the dielectric function and the related dynamical collision frequency are compared in a wide frequency range. The high-frequency limit describing inverse bremsstrahlung and the low-frequency limit of the dc conductivity are considered. Sum rules and Kramers-Kronig relation are checked for the generalized linear response theory and the standard approach following kinetic theory. The results are discussed in application to aluminum, xenon, and argon plasmas. PMID:27575226

  7. Optical conductivity of warm dense matter within a wide frequency range using quantum statistical and kinetic approaches

    NASA Astrophysics Data System (ADS)

    Veysman, M.; Röpke, G.; Winkel, M.; Reinholz, H.

    2016-07-01

    Fundamental properties of warm dense matter are described by the dielectric function, which gives access to the frequency-dependent electrical conductivity; absorption, emission, and scattering of radiation; charged particles stopping; and further macroscopic properties. Different approaches to the dielectric function and the related dynamical collision frequency are compared in a wide frequency range. The high-frequency limit describing inverse bremsstrahlung and the low-frequency limit of the dc conductivity are considered. Sum rules and Kramers-Kronig relation are checked for the generalized linear response theory and the standard approach following kinetic theory. The results are discussed in application to aluminum, xenon, and argon plasmas.

  8. Transport induced by ion cyclotron range of frequencies waves

    SciTech Connect

    Zhang, Debing Xu, Yingfeng; Wang, Shaojie

    2014-11-15

    The Vlasov equation, which includes the effect of the ion cyclotron range of frequencies (ICRF) waves, can be written as the Fokker-Planck equation which describes the quasilinear transport in phase space by using the Lie-transform method. The radial transport fluxes of particle, energy and parallel momentum driven by ICRF waves in the slab geometry have been derived. The results show that the ICRF-induced radial redistributions of particle, energy and parallel momentum are driven by the inhomogeneity in energy of the equilibrium distribution function, and related to the correlation between the excursion in the real space and the excursion in energy. For the case with strong asymmetry of k{sub y} spectrum, the ICRF-induced radial transport driven by the energy inhomogeneity dominates the ICRF-induced radial transport driven by the spatial inhomogeneity.

  9. The technology of the ion cyclotron range of frequencies

    SciTech Connect

    Hoffman, D.J.; Barber, G.C.

    1988-01-01

    Plasma heating in the ion cyclotron range of frequencies (ICRF) is the least expensive means of accomplishing auxiliary heating in fusion experiments. RF systems comprise two major elements: the transmitter and the antenna. The state of the art for the transmitter is already at the megawatt level. The technology of the antenna is strongly coupled to the plasma character. Typically, these antennas are designed to operate at a high power density (1.2 kW/cm/sup 2/) with an efficiency of 96%. ICRF technology and options have improved over the past few years, owing to development and experiments; however, the optimal combination of options can be defined only when results from confinement experiments and test facilities are in hand. 19 refs., 5 figs., 1 tab.

  10. High precision spectroscopy and imaging in THz frequency range

    NASA Astrophysics Data System (ADS)

    Vaks, Vladimir L.

    2014-03-01

    Application of microwave methods for development of the THz frequency range has resulted in elaboration of high precision THz spectrometers based on nonstationary effects. The spectrometers characteristics (spectral resolution and sensitivity) meet the requirements for high precision analysis. The gas analyzers, based on the high precision spectrometers, have been successfully applied for analytical investigations of gas impurities in high pure substances. These investigations can be carried out both in absorption cell and in reactor. The devices can be used for ecological monitoring, detecting the components of chemical weapons and explosive in the atmosphere. The great field of THz investigations is the medicine application. Using the THz spectrometers developed one can detect markers for some diseases in exhaled air.

  11. 15 CFR 784.4 - Notification, duration and frequency of complementary access.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... of complementary access. 784.4 Section 784.4 Commerce and Foreign Trade Regulations Relating to... PROTOCOL REGULATIONS COMPLEMENTARY ACCESS § 784.4 Notification, duration and frequency of complementary access. (a) Complementary access notification. Complementary access will be provided only upon...

  12. Range and Frequency of Africanized Honey Bees in California (USA)

    PubMed Central

    Kono, Yoshiaki; Kohn, Joshua R.

    2015-01-01

    Africanized honey bees entered California in 1994 but few accounts of their northward expansion or their frequency relative to European honey bees have been published. We used mitochondrial markers and morphometric analyses to determine the prevalence of Africanized honeybees in San Diego County and their current northward progress in California west of the Sierra Nevada crest. The northernmost African mitotypes detected were approximately 40 km south of Sacramento in California’s central valley. In San Diego County, 65% of foraging honey bee workers carry African mitochondria and the estimated percentage of Africanized workers using morphological measurements is similar (61%). There was no correlation between mitotype and morphology in San Diego County suggesting Africanized bees result from bidirectional hybridization. Seventy percent of feral hives, but only 13% of managed hives, sampled in San Diego County carried the African mitotype indicating that a large fraction of foraging workers in both urban and rural San Diego County are feral. We also found a single nucleotide polymorphism at the DNA barcode locus COI that distinguishes European and African mitotypes. The utility of this marker was confirmed using 401 georeferenced honey bee sequences from the worldwide Barcode of Life Database. Future censuses can determine whether the current range of the Africanized form is stable, patterns of introgression at nuclear loci, and the environmental factors that may limit the northern range of the Africanized honey bee. PMID:26361047

  13. Fractional frequency instability in the 10{sup -14} range with a thermal beam optical frequency reference

    SciTech Connect

    McFerran, John J.; Luiten, Andre N.

    2010-02-15

    We demonstrate a means of increasing the signal-to-noise ratio in a Ramsey-Borde interferometer with spatially separated oscillatory fields on a thermal atomic beam. The {sup 1}S{sub 0}{r_reversible}{sup 3}P{sub 1} intercombination line in neutral {sup 40}Ca is used as a frequency discriminator, with an extended cavity diode laser at 423 nm probing the ground state population after a Ramsey-Borde sequence of 657 nm light-field interactions with the atoms. Evaluation of the instability of the Ca frequency reference is carried out by comparison with (i) a hydrogen-maser and (ii) a cryogenic sapphire oscillator. In the latter case the Ca reference exhibits a square-root {Lambda} variance of 9.2x10{sup -14} at 1 s and 2.0x10{sup -14} at 64 s. This is an order-of-magnitude improvement for optical beam frequency references, to our knowledge. The shot noise of the readout fluorescence produces a limiting square-root {Lambda} variance of 7x10{sup -14}/{radical}({tau}), highlighting the potential for improvement. This work demonstrates the feasibility of a portable frequency reference in the optical domain with 10{sup -14} range frequency instability.

  14. A new AC susceptibility instrument for detecting frequency dependence over a wide range of frequencies

    NASA Astrophysics Data System (ADS)

    Kodama, K.

    2008-12-01

    A unique equipment was developed for measuring low-field AC susceptibility over a frequency spectrum ranging from 10 Hz to 4 kHz. The coil system consists of a primary coil for applying an excitation field, and a set of pickup coils linked in series and wound oppositely for compensation. The number of turns for the primary coil is 6,000 and that for the pickup coils is 4,400, using 0.1 mm thick copper wire, wound around a quartz-glass tube of 36 mm in diameter, allowing to measure conventional 10cc samples. The excitation field is produced by a commercial function generator with two independent outputs, capable of generating sinusoidal current with frequencies of 0 to 10 MHz. A mutual inductor coil is connected in series, to which the wave generator supplies, through the second output, a small current that can be adjusted in phase and magnitude to compensate the out-of-balance of the pickup coils. The resulting signal output voltage is fed to a digital rock-in amplifier. The AC frequency spans practically from 10 Hz to 4 kHz due to the limitation of the lock-in amplifier, but can be swept over the entire range with a constant amplitude of the applied field, which is changeable from 0.4 to 1.0 Oe. The outputs from the lock-in amplifier, in both magnitude and phase, are transferred to a PC to obtain the frequency dependence spectrum of both real and imaginary parts of AC susceptibility. The system calibration was made using a paramagnetic Gd2O3 powder as well as several natural samples that have ever been used for inter-laboratory calibrations.

  15. The Effect of Print Access on Reading Frequency.

    ERIC Educational Resources Information Center

    McQuillan, Jeff; Au, Julie

    2001-01-01

    Examines print access in a comprehensive way to include home, school, and community resources. Finds that consistent with previous research, convenient access to reading material, regardless of these eleventh-grade students' reading ability, was associated with more frequent reading. Discusses implications for providing students with easier access…

  16. 15 CFR 784.4 - Notification, duration and frequency of complementary access.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... carried out during complementary access; (D) The time and date that complementary access is expected to... PROTOCOL REGULATIONS COMPLEMENTARY ACCESS § 784.4 Notification, duration and frequency of complementary... the Additional Protocol, the IAEA shall notify the United States Government of a complementary...

  17. 15 CFR 784.4 - Notification, duration and frequency of complementary access.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... carried out during complementary access; (D) The time and date that complementary access is expected to... PROTOCOL REGULATIONS COMPLEMENTARY ACCESS § 784.4 Notification, duration and frequency of complementary... the Additional Protocol, the IAEA shall notify the United States Government of a complementary...

  18. 15 CFR 784.4 - Notification, duration and frequency of complementary access.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... carried out during complementary access; (D) The time and date that complementary access is expected to... PROTOCOL REGULATIONS COMPLEMENTARY ACCESS § 784.4 Notification, duration and frequency of complementary... the Additional Protocol, the IAEA shall notify the United States Government of a complementary...

  19. 15 CFR 784.4 - Notification, duration and frequency of complementary access.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... carried out during complementary access; (D) The time and date that complementary access is expected to... PROTOCOL REGULATIONS COMPLEMENTARY ACCESS § 784.4 Notification, duration and frequency of complementary... the Additional Protocol, the IAEA shall notify the United States Government of a complementary...

  20. Airborne Gravity Gradiometry Resolves a Full Range of Gravity Frequencies

    NASA Astrophysics Data System (ADS)

    Mataragio, J.; Brewster, J.; Mims, J.

    2007-12-01

    Airborne Full Tensor Gradiometry (Air\\-FTGR) was flown at high altitude coincident with Airborne Gravity (AG) flown in 2003 in West Arnhem Land, Australia. A preliminary analysis of two data sets indicates that the Air\\-FTGR system has the capability of resolving intermediate to long wavelengths features that may be associated with relatively deeper geological structures. A comparison of frequency filtered slices and power spectral density (PSD) for both data sets using the short (> 5 km), intermediate (10 km) and long (20 km) wavelengths reveals that high altitude Air\\-FTGR data show greater response in high frequency anomalies than a conventional Airborne Gravity and matches well with the AG even at the longest wavelengths anomalies. The effect of line spacing and target resolution was examined between the two data sets. Reprocessed gradient and AG data at 2, 4 and 6 km line spacing suggest that Air\\-FTGR could be effectively flown at a comparatively wider line spacing to resolve similar targets the AG would resolve with tighter line spacing. Introduction Airborne Full Tensor Gradiometry (Air\\-FTGR) data have been available to the mining industry since 2002 and their use for geologic applications is well established. However, Air\\-FTGR data has been mostly considered and used in mapping and delineation of near surface geological targets. This is due to the fact that gravity gradiometer measurements are well suited to capture the high frequency signal associated with near\\-surface targets ( Li, 2001). This is possible because the gradiometer signal strength falls off with the cube of the distance to the target. Nonetheless, in recent years there has been an increasing demand from the mining, oil, and gas industry in utilizing Full Tensor Gravity Gradiometer as a mapping tool for both regional and prospect level surveys. Air\\-FTGR as a Regional Mapping Tool Several, relatively low altitude surveys have been successfully flown in Brazil, Canada and Australia

  1. Satellite range delay simulator for a matrix-switched time division multiple-access network simulator

    NASA Technical Reports Server (NTRS)

    Nagy, Lawrence A.

    1989-01-01

    The Systems Integration, Test, and Evaluation (SITE) facility at NASA Lewis Research Center is presently configured as a satellite-switched time division multiple access (SS-TDMA) network simulator. The purpose of SITE is to demonstrate and evaluate advanced communication satellite technologies, presently embodied by POC components developed under NASA contracts in addition to other hardware, such as ground terminals, designed and built in-house at NASA Lewis. Each ground terminal in a satellite communications system will experience a different aspect of the satellite's motion due mainly to daily tidal effects and station keeping, hence a different duration and rate of variation in the range delay. As a result of this and other effects such as local oscillator instability, each ground terminal must constantly adjust its transmit burst timing so that data bursts from separate ground terminals arrive at the satellite in their assigned time slots, preventing overlap and keeping the system in synchronism. On the receiving end, ground terminals must synchronize their local clocks using reference transmissions received through the satellite link. A feature of the SITE facility is its capability to simulate the varying propagation delays and associated Doppler frequency shifts that the ground terminals in the network have to cope with. Delay is achieved by means of two NASA Lewis designed and built range delay simulator (RDS) systems, each independently controlled locally with front panel switches or remotely by an experiment control and monitor (EC/M) computer.

  2. Research of polymer fibers for the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Wang, Dong

    2011-08-01

    Terahertz radiation, with wavelengths from 30 to 3000 microns, has big potential for applications such as biomedical sensing, noninvasive imaging and spectroscopy. Current researches on photonic crystal fibers as THz waveguide has been widely presented, but the sorts of waveguide usually need special fabrication technique and always be difficult to get perfect structure. We report on a new type of polymer photonic crystal fibers for low-loss guidance of THz radiation with general fabrication technique. The use of the cyclic olefin copolymer (COC) Topas, results in THz fibers with relatively low loss and low material dispersion in the THz range. We manufactured a class of THz waveguides with different structures. Then we use a THz time-domain spectroscopy system (THz- TDS) to characterize the Material loss and index of refractive of the waveguides.

  3. An optical beam frequency reference with 10{sup -14} range frequency instability

    SciTech Connect

    McFerran, J. J.; Hartnett, J. G.; Luiten, A. N.

    2009-07-20

    The authors report on a thermal beam optical frequency reference with a fractional frequency instability of 9.2x10{sup -14} at 1 s reducing to 2.0x10{sup -14} at 64 s before slowly rising. The {sup 1}S{sub 0}{r_reversible}{sup 3}P{sub 1} intercombination line in neutral {sup 40}Ca is used as a frequency discriminator. A diode laser at 423 nm probes the ground state population after a Ramsey-Borde sequence of 657 nm light-field interactions on the atoms. The measured fractional frequency instability is an order of magnitude improvement on previously reported thermal beam optical clocks. The photon shot-noise of the read-out produces a limiting square root {lambda}-variance of 7x10{sup -14}/{radical}({tau})

  4. Alleviating a form of electric vehicle range anxiety through on-demand vehicle access

    NASA Astrophysics Data System (ADS)

    King, Christopher; Griggs, Wynita; Wirth, Fabian; Quinn, Karl; Shorten, Robert

    2015-04-01

    On-demand vehicle access is a method that can be used to reduce types of range anxiety problems related to planned travel for electric vehicle owners. Using ideas from elementary queueing theory, basic quality of service (QoS) metrics are defined to dimension a shared fleet to ensure high levels of vehicle access. Using mobility data from Ireland, it is argued that the potential cost of such a system is very low.

  5. Wave Heating in Ion Cyclotron Ranges of Frequencies in RT-1

    NASA Astrophysics Data System (ADS)

    Nishiura, M.; Yoshida, Z.; Yano, Y.; Kawazura, Y.; Mushiake, T.; Saitoh, H.; Yamasaki, M.; Kashyap, A.; Takahashi, N.; Nakatsuka, M.; Fukuyama, A.

    2015-11-01

    The magnetosphere plasma device RT-1 has been developed for the studies on magnetosphere and advanced fusion plasmas. A levitated superconducting coil produces magnetic dipole fields that realize a high confinement state. The electron cyclotron resonance heating (ECRH) with 8.2 GHz and 50 kW produces the plasmas with hot electrons in a few ten keV range. We reported that the local electron beta exceeded 1 in RT-1 plasmas. In such situation, the ions still remain cold at a few ten eV. Heating ions is expected to access high ion beta state and to improve the plasma confinement theoretically. Therefore the ion cyclotron range of frequencies (ICRF) heating with 2-4 MHz and 10 kW is being prepared in RT-1. Based on the results of the TASK-WF2 code, the ∩ shape loop antenna was designed for a slow wave excitation, and was implemented in the RT-1. In the ICRF heating experiments, a base plasma was sustained by ECRH. We observed the clear increase in diamagnetic signals and impurity ion temperature (CIII) in helium plasmas at the neutral gas pressure of 3 mPa, if the ICRF power of 10 kW is comparable to the ECRH one. This result is the first time in a magnetosphere plasma device. The results related to the ICRF heating will be presented in detail. JSPS KAKENHI Grant Nos 23224014 and 24360384.

  6. An energy-efficient and elastic optical multiple access system based on coherent interleaved frequency division multiple access.

    PubMed

    Yoshida, Yuki; Maruta, Akihiro; Ishii, Kenji; Akiyama, Yuji; Yoshida, Tsuyoshi; Suzuki, Naoki; Koguchi, Kazuumi; Nakagawa, Junichi; Mizuochi, Takashi; Kitayama, Ken-ichi

    2013-05-20

    This paper proposes a novel bandwidth-elastic and energy-efficient passive optical network (PON) based on the coherent interleaved frequency division multiple access (IFDMA) scheme. We experimentally demonstrate the coherent IFDMA-PON uplink transmission up-to 30 Gbps over a 30 km standard single-mode fiber with 2 × optical network units (ONUs). A low-complexity digital carrier synchronization technique enables multiple access of the ONUs on the basis of 78.1 MHz narrow band orthogonal subcarriers without any guard-bands. PMID:23736447

  7. Range and Velocity Estimation of Moving Targets Using Multiple Stepped-frequency Pulse Trains

    PubMed Central

    Li, Gang; Meng, Huadong; Xia, Xiang-Gen; Peng, Ying-Ning

    2008-01-01

    Range and velocity estimation of moving targets using conventional stepped-frequency pulse radar may suffer from the range-Doppler coupling and the phase wrapping. To overcome these problems, this paper presents a new radar waveform named multiple stepped-frequency pulse trains and proposes a new algorithm. It is shown that by using multiple stepped-frequency pulse trains and the robust phase unwrapping theorem (RPUT), both of the range-Doppler coupling and the phase wrapping can be robustly resolved, and accordingly, the range and the velocity of a moving target can be accurately estimated.

  8. Excitation, detection, and electrostatic manipulation of terahertz-frequency range plasmons in a two-dimensional electron system

    NASA Astrophysics Data System (ADS)

    Wu, Jingbo; Mayorov, Alexander S.; Wood, Christopher D.; Mistry, Divyang; Li, Lianhe; Muchenje, Wilson; Rosamond, Mark C.; Chen, Li; Linfield, Edmund H.; Davies, A. Giles; Cunningham, John E.

    2015-10-01

    Terahertz frequency time-domain spectroscopy employing free-space radiation has frequently been used to probe the elementary excitations of low-dimensional systems. The diffraction limit, however, prevents its use for the in-plane study of individual laterally-defined nanostructures. Here, we demonstrate a planar terahertz frequency plasmonic circuit in which photoconductive material is monolithically integrated with a two-dimensional electron system. Plasmons with a broad spectral range (up to ~ 400 GHz) are excited by injecting picosecond-duration pulses, generated and detected by a photoconductive semiconductor, into a high mobility two-dimensional electron system. Using voltage modulation of a Schottky gate overlying the two-dimensional electron system, we form a tuneable plasmonic cavity, and observe electrostatic manipulation of the plasmon resonances. Our technique offers a direct route to access the picosecond dynamics of confined electron transport in a broad range of lateral nanostructures.

  9. Excitation, detection, and electrostatic manipulation of terahertz-frequency range plasmons in a two-dimensional electron system.

    PubMed

    Wu, Jingbo; Mayorov, Alexander S; Wood, Christopher D; Mistry, Divyang; Li, Lianhe; Muchenje, Wilson; Rosamond, Mark C; Chen, Li; Linfield, Edmund H; Davies, A Giles; Cunningham, John E

    2015-01-01

    Terahertz frequency time-domain spectroscopy employing free-space radiation has frequently been used to probe the elementary excitations of low-dimensional systems. The diffraction limit, however, prevents its use for the in-plane study of individual laterally-defined nanostructures. Here, we demonstrate a planar terahertz frequency plasmonic circuit in which photoconductive material is monolithically integrated with a two-dimensional electron system. Plasmons with a broad spectral range (up to ~ 400 GHz) are excited by injecting picosecond-duration pulses, generated and detected by a photoconductive semiconductor, into a high mobility two-dimensional electron system. Using voltage modulation of a Schottky gate overlying the two-dimensional electron system, we form a tuneable plasmonic cavity, and observe electrostatic manipulation of the plasmon resonances. Our technique offers a direct route to access the picosecond dynamics of confined electron transport in a broad range of lateral nanostructures. PMID:26487263

  10. Excitation, detection, and electrostatic manipulation of terahertz-frequency range plasmons in a two-dimensional electron system

    PubMed Central

    Wu, Jingbo; Mayorov, Alexander S.; Wood, Christopher D.; Mistry, Divyang; Li, Lianhe; Muchenje, Wilson; Rosamond, Mark C.; Chen, Li; Linfield, Edmund H.; Davies, A. Giles; Cunningham, John E.

    2015-01-01

    Terahertz frequency time-domain spectroscopy employing free-space radiation has frequently been used to probe the elementary excitations of low-dimensional systems. The diffraction limit, however, prevents its use for the in-plane study of individual laterally-defined nanostructures. Here, we demonstrate a planar terahertz frequency plasmonic circuit in which photoconductive material is monolithically integrated with a two-dimensional electron system. Plasmons with a broad spectral range (up to ~ 400 GHz) are excited by injecting picosecond-duration pulses, generated and detected by a photoconductive semiconductor, into a high mobility two-dimensional electron system. Using voltage modulation of a Schottky gate overlying the two-dimensional electron system, we form a tuneable plasmonic cavity, and observe electrostatic manipulation of the plasmon resonances. Our technique offers a direct route to access the picosecond dynamics of confined electron transport in a broad range of lateral nanostructures. PMID:26487263

  11. Buried Object Detection Method Using Optimum Frequency Range in Extremely Shallow Underground

    NASA Astrophysics Data System (ADS)

    Sugimoto, Tsuneyoshi; Abe, Touma

    2011-07-01

    We propose a new detection method for buried objects using the optimum frequency response range of the corresponding vibration velocity. Flat speakers and a scanning laser Doppler vibrometer (SLDV) are used for noncontact acoustic imaging in the extremely shallow underground. The exploration depth depends on the sound pressure, but it is usually less than 10 cm. Styrofoam, wood (silver fir), and acrylic boards of the same size, different size styrofoam boards, a hollow toy duck, a hollow plastic container, a plastic container filled with sand, a hollow steel can and an unglazed pot are used as buried objects which are buried in sand to about 2 cm depth. The imaging procedure of buried objects using the optimum frequency range is given below. First, the standardized difference from the average vibration velocity is calculated for all scan points. Next, using this result, underground images are made using a constant frequency width to search for the frequency response range of the buried object. After choosing an approximate frequency response range, the difference between the average vibration velocity for all points and that for several points that showed a clear response is calculated for the final confirmation of the optimum frequency range. Using this optimum frequency range, we can obtain the clearest image of the buried object. From the experimental results, we confirmed the effectiveness of our proposed method. In particular, a clear image of the buried object was obtained when the SLDV image was unclear.

  12. Estimation of ground range on the sweep frequency backscatter leading edge

    NASA Astrophysics Data System (ADS)

    Su, Fanfan; Zhao, Zhengyu; Deng, Feng; Li, Shipeng

    2011-04-01

    The high frequency management system with backscatter radar supplies the real time ionosphere channel conditions to high frequency users, which leads to the demand for the ground range between the radar location and the scatters on the distant ground. The ionosphere electron density profile is usually inversed to obtain the ground range. An inversion algorithm, with which the ground range on the leading edge of the backscatter ionograms can be obtained without electron density, is presented in this paper. The ray path geometry of the backscatter sounding and the change in the group path on the leading edge with operating frequency are used to derive the ground range. Synthesized backscatter ionogram and experimental backscatter ionograms are processed to validate the algorithm. The results indicate that the algorithm is usable for high frequency management system.

  13. Thrombolysis using multi-frequency high intensity focused ultrasound at MHz range: an in vitro study

    NASA Astrophysics Data System (ADS)

    Suo, Dingjie; Guo, Sijia; Lin, Weili; Jiang, Xiaoning; Jing, Yun

    2015-09-01

    High intensity focused ultrasound (HIFU) based thrombolysis has emerged as a promising drug-free treatment approach for ischemic stroke. The large amount of acoustic power required by this approach, however, poses a critical challenge to the future clinical translation. In this study, multi-frequency acoustic waves at MHz range (near 1.5 MHz) were introduced as HIFU excitations to reduce the required power for treatment as well as the treatment time. In vitro bovine blood clots weighing around 150 mg were treated by single-frequency and multi-frequency HIFU. The pulse length was 2 ms for all experiments except the ones where the duty cycle was changed. It was found that dual-frequency thrombolysis efficiency was statistically better than single-frequency under the same acoustic power and excitation condition. When varying the acoustic power but fixing the duty cycle at 5%, it was found that dual-frequency ultrasound can save almost 30% power in order to achieve the same thrombolysis efficiency. In the experiment where the duty cycle was increased from 0.5% to 10%, it was shown that dual-frequency ultrasound can achieve the same thrombolysis efficiency with only half of the duty cycle of single-frequency. Dual-frequency ultrasound could also accelerate the thrombolysis by a factor of 2-4 as demonstrated in this study. No significant differences were found between dual-frequencies with different frequency differences (0.025, 0.05, and 0.1 MHz) and between dual-frequency and triple-frequency. The measured cavitation doses of dual-frequency and triple-frequency excitations were at about the same level but both were significantly higher than that of single-frequency.

  14. Switched capacitor charge pump reduces hysteresis of piezoelectric actuators over a large frequency range.

    PubMed

    Huang, Liang; Ma, Yu Ting; Feng, Zhi Hua; Kong, Fan Rang

    2010-09-01

    Piezoelectric actuators exhibit large hysteresis between the applied voltage and their displacement. A switched capacitor charge pump is proposed to reduce hysteresis and linearize the movement of piezoelectric actuators. By pumping the same amount of charges into the piezoelectric actuator quantitatively, the actuator will be forced to change its length with constant step. Compared with traditional voltage and charge driving, experimental results demonstrated that the piezoelectric stack driven by the charge pump had less hysteresis over a large frequency range, especially at ultralow frequencies. A hysteresis of less than 2.01% was achieved over a frequency range of 0.01-20 Hz using the charge pump driver. PMID:20886997

  15. Full-range imaging of eye accommodation by high-speed long-depth range optical frequency domain imaging

    PubMed Central

    Furukawa, Hiroyuki; Hiro-Oka, Hideaki; Satoh, Nobuyuki; Yoshimura, Reiko; Choi, Donghak; Nakanishi, Motoi; Igarashi, Akihito; Ishikawa, Hitoshi; Ohbayashi, Kohji; Shimizu, Kimiya

    2010-01-01

    We describe a high-speed long-depth range optical frequency domain imaging (OFDI) system employing a long-coherence length tunable source and demonstrate dynamic full-range imaging of the anterior segment of the eye including from the cornea surface to the posterior capsule of the crystalline lens with a depth range of 12 mm without removing complex conjugate image ambiguity. The tunable source spanned from 1260 to 1360 nm with an average output power of 15.8 mW. The fast A-scan rate of 20,000 per second provided dynamic OFDI and dependence of the whole anterior segment change on time following abrupt relaxation from the accommodated to the relaxed status, which was measured for a healthy eye and that with an intraocular lens. PMID:21258564

  16. A novel technique of image quality objective measurement by wavelet analysis throughout the spatial frequency range

    NASA Astrophysics Data System (ADS)

    Luo, Gaoyong

    2005-01-01

    An essential determinant of the value of surrogate digital images is their quality. Image quality measurement has become crucial for most image processing applications. Over the past years , there have been many attempts to develop models or metrics for image quality that incorporate elements of human visual sensitivity. However, there is no current standard and objective definition of spectral image quality. This paper proposes a reliable automatic method for objective image quality measurement by wavelet analysis throughout the spatial frequency range. This is done by a detailed analysis of an image for a wide range of spatial frequency content, using a combination of modulation transfer function (MTF), brightness, contrast, saturation, sharpness and noise, as a more revealing metric for quality evaluation. A fast lifting wavelet algorithm is developed for computationally efficient spatial frequency analysis, where fine image detail corresponding to high spatial frequencies and image sharpness in regard to lower and mid -range spatial frequencies can be examined and compared accordingly. The wavelet frequency deconstruction is actually to extract the feature of edges in sub-band images. The technique provides a means to relate the quality of an image to the interpretation and quantification throughout the frequency range, in which the noise level is estimated in assisting with quality analysis. The experimental results of using this method for image quality measurement exhibit good correlation to subjective visual quality assessments.

  17. A novel technique of image quality objective measurement by wavelet analysis throughout the spatial frequency range

    NASA Astrophysics Data System (ADS)

    Luo, Gaoyong

    2004-10-01

    An essential determinant of the value of surrogate digital images is their quality. Image quality measurement has become crucial for most image processing applications. Over the past years , there have been many attempts to develop models or metrics for image quality that incorporate elements of human visual sensitivity. However, there is no current standard and objective definition of spectral image quality. This paper proposes a reliable automatic method for objective image quality measurement by wavelet analysis throughout the spatial frequency range. This is done by a detailed analysis of an image for a wide range of spatial frequency content, using a combination of modulation transfer function (MTF), brightness, contrast, saturation, sharpness and noise, as a more revealing metric for quality evaluation. A fast lifting wavelet algorithm is developed for computationally efficient spatial frequency analysis, where fine image detail corresponding to high spatial frequencies and image sharpness in regard to lower and mid -range spatial frequencies can be examined and compared accordingly. The wavelet frequency deconstruction is actually to extract the feature of edges in sub-band images. The technique provides a means to relate the quality of an image to the interpretation and quantification throughout the frequency range, in which the noise level is estimated in assisting with quality analysis. The experimental results of using this method for image quality measurement exhibit good correlation to subjective visual quality assessments.

  18. Multibeam single frequency synthetic aperture radar processor for imaging separate range swaths

    NASA Technical Reports Server (NTRS)

    Jain, A. (Inventor)

    1982-01-01

    A single-frequency multibeam synthetic aperture radar for large swath imaging is disclosed. Each beam illuminates a separate ""footprint'' (i.e., range and azimuth interval). The distinct azimuth intervals for the separate beams produce a distinct Doppler frequency spectrum for each beam. After range correlation of raw data, an optical processor develops image data for the different beams by spatially separating the beams to place each beam of different Doppler frequency spectrum in a different location in the frequency plane as well as the imaging plane of the optical processor. Selection of a beam for imaging may be made in the frequency plane by adjusting the position of an aperture, or in the image plane by adjusting the position of a slit. The raw data may also be processed in digital form in an analogous manner.

  19. Dielectric response of transformer oil based ferrofluid in low frequency range

    NASA Astrophysics Data System (ADS)

    Rajnak, M.; Kurimsky, J.; Dolnik, B.; Marton, K.; Tomco, L.; Taculescu, A.; Vekas, L.; Kovac, J.; Vavra, I.; Tothova, J.; Kopcansky, P.; Timko, M.

    2013-07-01

    In this article, our experimental study of the dynamic dielectric behaviour of transformer oil-based ferrofluid with magnetite nanoparticles is presented. Frequency-dependent dielectric permittivity and dissipation factor were measured within the frequency range from 20 Hz to 2 MHz by a capacitance method. The ferrofluid samples were placed in a liquid crystal cell, and experiments were carried out in an electromagnetically anechoic chamber. Two polarization processes and corresponding relaxations were revealed within the applied frequency range. Schwarz theory of electric double layer polarization is used to explain the low frequency relaxation maximum. Moreover, the shift of the maximum position towards higher frequencies is observed as the magnetic volume fraction in the ferrofluid increases. The related decrease in relaxation time due to higher counterion mobility is analysed. Reduced electric field intensity due to depolarization field, which is dependent on the particle concentration, is proposed as the reason for the maxima shift. This assumption is wholly supported by a complementary experiment.

  20. Impedance-based structural health monitoring using neural networks for autonomous frequency range selection

    NASA Astrophysics Data System (ADS)

    Min, Jiyoung; Park, Seunghee; Yun, Chung-Bang

    2010-12-01

    The impedance-based structural health monitoring (SHM) method has come to the forefront in the SHM community due to its practical potential for real applications. In the impedance-based SHM method, the selection of optimal frequency ranges plays an important role in improving the sensitivity of damage detection, since an improper frequency range can lead to erroneous damage detection results and provide false positive damage alarms. To tackle this issue, this paper proposes an innovative technique for autonomous selection of damage-sensitive frequency ranges using artificial neural networks (ANNs). First, the impedance signals are obtained in a wide frequency band, and the signals are split into multiple sub-ranges of this wide band. Then, the predefined damage index is evaluated for each sub-range by comparing impedance signals between the intact and the concurrent cases. Here, the cross correlation coefficients (CCs) are used as the predefined damage index. The ANN is constructed and trained using all CC values at multiple frequency ranges as multi-inputs and the real damage severity as the single output for various preselected damage scenarios, so that subsequent damage estimations may be carried out by selecting the governing frequency ranges autonomously. The performance of the proposed approach has been examined via a series of experimental studies to detect loose bolts and cracks induced on real steel bridge and building structures. It is found that the proposed approach autonomously determines the damage-sensitive frequency ranges and can be used for effective evaluation of damage severity in a wide variety of damage cases in real structures.

  1. Multibeam single frequency synthetic aperture radar processor for imaging separate range swaths

    NASA Technical Reports Server (NTRS)

    Jain, A. (Inventor)

    1979-01-01

    A method and apparatus are described for single frequency multibeam imaging of multiple strips of range swath at high range intervals for those applications where it is desirable to cover a range swath much greater than is possible for a given interpulse interval. Data from a single frequency synthetic aperture radar (in which beam parameters are adjusted so that the return from each successive swath is received during successive interpulse periods) are separated in Dopple frequency for the return from each beam at the frequency plane of the processor. Alternatively, the image formed by each beam may be spatially separated in the azimuth direction and successively selected by positioning an appropriate slit in the recording plane of the processor.

  2. Application of range imaging lidar for measurement of mechanical vibration and frequency mode distribution

    NASA Astrophysics Data System (ADS)

    Zhang, Hua A.; Zhu, Yonghao; He, Yun

    1993-05-01

    This article reports the application of laser range imaging radar in the measurement of mechanical vibration frequency and the mode distribution, and the periodic motion of the mechanical parts such as a piston rod. The principle of the laser range imaging radar is based on the phase shift of the reflected amplitude modulated laser beam. The mechanical vibration frequency up to 20 KHZ and the minimal retrieved amplitude (or the motion displacement) of 0.5 mm have been achieved with the laser modulating frequency of 40 MHZ. With appropriate modulating frequency, this laser range system can measure the mechanical vibration amplitude, or the moving displacement, from 10-1 mm up to 102 mm, or even higher to the order of meters, which will be useful to measure the vibration and the periodic motion of machines and their parts for field test.

  3. Numerical analysis of radio-frequency sheath-plasma interactions in the ion cyclotron range of frequencies

    SciTech Connect

    Kohno, H.; Myra, J. R.; D'Ippolito, D. A.

    2012-01-15

    A new finite element numerical scheme for analyzing self-consistent radio-frequency (RF) sheath-plasma interaction problems in the ion cyclotron range of frequencies is applied to various problems represented by simplified models for the tokamak scrape-off layer. The present code incorporates a modified boundary condition, which is called a sheath boundary condition, that couples the radio-frequency waves and sheaths at the material boundaries by treating the sheath as a thin vacuum layer. A series of numerical analyses in one- and two-dimensional domains show several important physical properties, such as the existence of multiple roots, hysteresis effects, presence and characteristics of the sheath-plasma waves, and the phase shift of a reflected slow wave, some of which are newly identified by introducing a spatially varying plasma density and background magnetic field.

  4. Single channel speech separation in modulation frequency domain based on a novel pitch range estimation method

    NASA Astrophysics Data System (ADS)

    Mahmoodzadeh, Azar; Abutalebi, Hamid Reza; Soltanian-Zadeh, Hamid; Sheikhzadeh, Hamid

    2012-12-01

    Computational Auditory Scene Analysis (CASA) has been the focus in recent literature for speech separation from monaural mixtures. The performance of current CASA systems on voiced speech separation strictly depends on the robustness of the algorithm used for pitch frequency estimation. We propose a new system that estimates pitch (frequency) range of a target utterance and separates voiced portions of target speech. The algorithm, first, estimates the pitch range of target speech in each frame of data in the modulation frequency domain, and then, uses the estimated pitch range for segregating the target speech. The method of pitch range estimation is based on an onset and offset algorithm. Speech separation is performed by filtering the mixture signal with a mask extracted from the modulation spectrogram. A systematic evaluation shows that the proposed system extracts the majority of target speech signal with minimal interference and outperforms previous systems in both pitch extraction and voiced speech separation.

  5. Measurement of the dielectric properties of dispersive materials over a wide frequency range.

    SciTech Connect

    Molina, Luis Leroy; Salazar, Robert Austin; Bacon, Larry Donald; Lehr, Jane Marie

    2003-06-01

    The propagation of electromagnetic waves through dispersive media forms the basis for a wide variety of applications. Rapid advances in materials have produced new products with tailored responses across frequency bands. Many of these new materials, such as radar absorbing material and photonic crystals, are dispersive in nature. This, in turn, has opened up the possibility for the exploitation of these dispersive dielectric properties for a variety of applications. Thus, it is desirable to know the electromagnetic properties of both man-made and natural materials across a wide frequency range. With the advent of transient pulsers with sub-nanosecond risetimes and rates of voltage rise approaching 10**16 V/s, the frequencies of interest in the transient response extend to approximately the 2 GHz range. Although a network analyzer can provide either frequency- or time-domain data (by inverse transform), common TEM cells are only rated to 0.5 to 1.5 GHz--significantly below the maximum frequency of interest. To extend the frequency range to include 2 GHz, a TEM cell was characterized and a deembedding algorithm was applied to account, in part, for the limitations of the cell. The de-embedding technique is described along with such measurement issues such as clear time and sneak around. Measurements of complex permittivity of common drinking water are shown. This frequency extension will lead to more expansive testing of dielectric materials of interest.

  6. Tracking lexical access in speech production: electrophysiological correlates of word frequency and cognate effects.

    PubMed

    Strijkers, Kristof; Costa, Albert; Thierry, Guillaume

    2010-04-01

    The present study establishes an electrophysiological index of lexical access in speech production by exploring the locus of the frequency and cognate effects during overt naming. We conducted 2 event-related potential (ERP) studies with 16 Spanish-Catalan bilinguals performing a picture naming task in Spanish (L1) and 16 Catalan-Spanish bilinguals performing a picture naming task in Spanish (L2). Behavioral results showed a clear frequency effect and an interaction between frequency and cognate status. The ERP elicited during the production of high-frequency words diverged from the low-frequency ERP between 150 and 200 ms post-target presentation and kept diverging until voice onset. The same results were obtained when comparing cognate and noncognate conditions. Positive correlations were observed between naming latencies and mean amplitude of the P2 component following the divergence, for both the lexical frequency and the cognate effects. We conclude that lexical access during picture naming begins approximately 180 ms after picture presentation. Furthermore, these results offer direct electrophysiological evidence for an early influence of frequency and cognate status in speech production. The theoretical implications of these findings for models of speech production are discussed. PMID:19679542

  7. Acoustic Treatment Design Scaling Methods. Volume 2; Advanced Treatment Impedance Models for High Frequency Ranges

    NASA Technical Reports Server (NTRS)

    Kraft, R. E.; Yu, J.; Kwan, H. W.

    1999-01-01

    The primary purpose of this study is to develop improved models for the acoustic impedance of treatment panels at high frequencies, for application to subscale treatment designs. Effects that cause significant deviation of the impedance from simple geometric scaling are examined in detail, an improved high-frequency impedance model is developed, and the improved model is correlated with high-frequency impedance measurements. Only single-degree-of-freedom honeycomb sandwich resonator panels with either perforated sheet or "linear" wiremesh faceplates are considered. The objective is to understand those effects that cause the simple single-degree-of- freedom resonator panels to deviate at the higher-scaled frequency from the impedance that would be obtained at the corresponding full-scale frequency. This will allow the subscale panel to be designed to achieve a specified impedance spectrum over at least a limited range of frequencies. An advanced impedance prediction model has been developed that accounts for some of the known effects at high frequency that have previously been ignored as a small source of error for full-scale frequency ranges.

  8. Waves guided by density ducts in magnetoplasma in the nonresonant region of the whistler frequency range

    SciTech Connect

    Es’kin, V. A.; Zaboronkova, T. M.; Kudrin, A. V. Ostafiychuk, O. M.

    2015-03-15

    Guidance of azimuthally symmetric waves by cylindrical density ducts in magnetoplasma in the nonresonant region of the whistler frequency range is investigated. It is demonstrated that eigenmodes existing at the studied frequencies in ducts with enhanced plasma density allow simplified description that makes analysis of the features of their guided propagation much easier. The results of calculation of the dispersion characteristics and field structure of the whistler modes supported by such ducts are presented.

  9. Leg stiffness of older and younger individuals over a range of hopping frequencies.

    PubMed

    Hobara, Hiroaki; Kobayashi, Yoshiyuki; Yoshida, Eiichi; Mochimaru, Masaaki

    2015-04-01

    The purpose of this study was to compare spring-mass behavior between older and younger individuals at a range of hopping frequencies. A total of 14 elderly and 14 young subjects performed in-place hopping in time with a metronome at frequencies of 2.2, 2.6, and 3.0 Hz. Using a spring-mass model, leg stiffness was calculated as the ratio of maximum ground reaction force to maximum center of mass displacement at the middle of the stance phase during ground contact. The lower extremities of both groups behaved like a simple spring-mass system at all three hopping frequencies. Further, statistical analysis revealed the existence of a significant interaction between hopping frequency and age group on leg stiffness. These results suggest that the sensitivity of leg stiffness to accommodate for variations in hopping frequency is likely to differ between elderly and young individuals. PMID:25716326

  10. Note: Digital laser frequency auto-locking for inter-satellite laser ranging.

    PubMed

    Luo, Yingxin; Li, Hongyin; Yeh, Hsien-Chi

    2016-05-01

    We present a prototype of a laser frequency auto-locking and re-locking control system designed for laser frequency stabilization in inter-satellite laser ranging system. The controller has been implemented on field programmable gate arrays and programmed with LabVIEW software. The controller allows initial frequency calibrating and lock-in of a free-running laser to a Fabry-Pérot cavity. Since it allows automatic recovery from unlocked conditions, benefit derives to automated in-orbit operations. Program design and experimental results are demonstrated. PMID:27250480

  11. An atomic magnetometer with autonomous frequency stabilization and large dynamic range.

    PubMed

    Pradhan, S; Mishra, S; Behera, R; Poornima; Dasgupta, K

    2015-06-01

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz(1/2) @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity. PMID:26133825

  12. An atomic magnetometer with autonomous frequency stabilization and large dynamic range

    SciTech Connect

    Pradhan, S. E-mail: pradhans75@gmail.com; Poornima,; Dasgupta, K.; Mishra, S.; Behera, R.

    2015-06-15

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz{sup 1/2} @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  13. UTag: Long-range Ultra-wideband Passive Radio Frequency Tags

    SciTech Connect

    Dowla, F

    2007-03-14

    Long-range, ultra-wideband (UWB), passive radio frequency (RF) tags are key components in Radio Frequency IDentification (RFID) system that will revolutionize inventory control and tracking applications. Unlike conventional, battery-operated (active) RFID tags, LLNL's small UWB tags, called 'UTag', operate at long range (up to 20 meters) in harsh, cluttered environments. Because they are battery-less (that is, passive), they have practically infinite lifetimes without human intervention, and they are lower in cost to manufacture and maintain than active RFID tags. These robust, energy-efficient passive tags are remotely powered by UWB radio signals, which are much more difficult to detect, intercept, and jam than conventional narrowband frequencies. The features of long range, battery-less, and low cost give UTag significant advantage over other existing RFID tags.

  14. TOPICAL REVIEW: Strategies for increasing the operating frequency range of vibration energy harvesters: a review

    NASA Astrophysics Data System (ADS)

    Zhu, Dibin; Tudor, Michael J.; Beeby, Stephen P.

    2010-02-01

    This review presents possible strategies to increase the operational frequency range of vibration-based micro-generators. Most vibration-based micro-generators are spring-mass-damper systems which generate maximum power when the resonant frequency of the generator matches the frequency of the ambient vibration. Any difference between these two frequencies can result in a significant decrease in generated power. This is a fundamental limitation of resonant vibration generators which restricts their capability in real applications. Possible solutions include the periodic tuning of the resonant frequency of the generator so that it matches the frequency of the ambient vibration at all times or widening the bandwidth of the generator. Periodic tuning can be achieved using mechanical or electrical methods. Bandwidth widening can be achieved using a generator array, a mechanical stopper, nonlinear (e.g. magnetic) springs or bi-stable structures. Tuning methods can be classified into intermittent tuning (power is consumed periodically to tune the device) and continuous tuning (the tuning mechanism is continuously powered). This review presents a comprehensive review of the principles and operating strategies for increasing the operating frequency range of vibration-based micro-generators presented in the literature to date. The advantages and disadvantages of each strategy are evaluated and conclusions are drawn regarding the relevant merits of each approach.

  15. On the statistical dependence of hits in frequency-hop multiple access

    NASA Astrophysics Data System (ADS)

    Frank, Colin D.; Pursley, Michael B.

    1990-09-01

    The statistical dependence of hits due to multiple-access interference in an asynchronous slow-frequency-hop packet radio network in which the radios employ memoryless hopping patterns is described. Models in which hits are conditionally independent given the number of interfering packets are investigated. It is shown that, if the conditional probability of a hit is chosen appropriately, the distribution function for the number of hits in a packet for these models can be used to compute upper and lower bounds on the true distribution function for the number of hits. Conditions are described for which these models can be used to compute upper and lower bounds on the codeword and packet error probabilities. If the ratio of the number of interfering packets to the number of frequency slots is held constant, hits in the asynchronous frequency-hop network are asymptotically independent in the limit as the number of frequency slots increases.

  16. Bendable, low-loss Topas fibers for the terahertz frequency range.

    PubMed

    Nielsen, Kristian; Rasmussen, Henrik K; Adam, Aurèle J L; Planken, Paul C; Bang, Ole; Jepsen, Peter Uhd

    2009-05-11

    We report on a new class of polymer photonic crystal fibers for low-loss guidance of THz radiation. The use of the cyclic olefin copolymer Topas, in combination with advanced fabrication technology, results in bendable THz fibers with unprecedented low loss and low material dispersion in the THz regime.We demonstrate experimentally how the dispersion may be engineered by fabricating both high- and low-dispersion fibers with zero-dispersion frequency in the regime 0.5-0.6 THz. Near-field, frequency-resolved characterization with high spatial resolution of the amplitude and phase of the modal structure proves that the fiber is single-moded over a wide frequency range, and we see the onset of higher-order modes at high frequencies as well as indication of microporous guiding at low frequencies and high porosity of the fiber. Transmission spectroscopy demonstrates low-loss propagation (< 0.1 dB/cm loss at 0.6 THz) over a wide frequency range. PMID:19434192

  17. Rolling estimations of long range dependence volatility for high frequency S&P500 index

    NASA Astrophysics Data System (ADS)

    Cheong, Chin Wen; Pei, Tan Pei

    2015-10-01

    This study evaluates the time-varying long range dependence behaviors of the S&P500 volatility index using the modified rescaled adjusted range (R/S) statistic. For better computational result, a high frequency rolling bipower variation realized volatility estimates are used to avoid possible abrupt jump. The empirical analysis findings allow us to understand better the informationally market efficiency before and after the subprime mortgage crisis.

  18. The effects of tones on speaking frequency and intensity ranges in Mandarin and Min dialects

    NASA Astrophysics Data System (ADS)

    Chen, Sheng H.

    2005-05-01

    The differences of speaking frequency and intensity in different tonal dialects has not been widely investigated. The purposes of this study were (1) to compare the speaking frequency and speaking intensity ranges of Mandarin and Min and (2) to compare the speaking frequency and intensity ranges of Mandarin and Min to those of American English. The subjects were 80 normal Taiwanese adults divided into two dialect groups, Mandarin and Min. The speaking F0, the highest speaking F0, the lowest speaking F0, the maximum range of speaking F0, and the intensity counterpart were obtained from reading in their native dialects. Statistical analysis revealed that Min speakers had a significantly greater maximum range of speaking intensity and a smaller lowest speaking intensity than Mandarin speakers, which indicated tonal effects by speakers of the Min dialect. Moreover, Mandarin and Min speakers had a greater maximum range of speaking F0 and maximum range of speaking intensity than American English speakers. The data may provide an assessment tool for Mandarin speakers and Min speakers. .

  19. Coherent terahertz-wave generation and detection over a wide frequency range using DAST crystals

    NASA Astrophysics Data System (ADS)

    Minamide, Hiroaki; Ito, Hiromasa

    2009-02-01

    Terahertz-frequency (THz) waves have shown potential for a wide range of applications. We have developed tunable THz-wave sources using nonlinear optical crystals, which have several advantages, including frequency agility, wide tunability, high output, and high coherency. We found that the organic nonlinear crystal of 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) had particular potential for ultra-wide THz-wave generation from sub-THz to mid-infrared frequencies. Using DAST, we manufactured a coherent, tunable source (1-40 THz) with frequency agility. Moreover, we demonstrated THz-wave detection through up-conversion using DAST or MgO:LiNbO3 nonlinear optical crystals, which provided a fast response, high sensitivity, and room-temperature operation.

  20. Semiannual Status Report. [excitation of electromagnetic waves in the whistler frequency range

    NASA Technical Reports Server (NTRS)

    1994-01-01

    During the last six months, we have continued our study of the excitation of electromagnetic waves in the whistler frequency range and the role that these waves will play in the acceleration of electrons and ions in the auroral region. A paper entitled 'Electron Beam Excitation of Upstream Waves in the Whistler Mode Frequency Range' was listed in the Journal of Geophysical Research. In this paper, we have shown that an anisotropic electron beam (or gyrating electron beam) is capable of generating both left-hand and right-hand polarized electromagnetic waves in the whistler frequency range. Since right-hand polarized electromagnetic waves can interact with background electrons and left-hand polarized waves can interact with background ions through cyclotron resonance, it is possible that these beam generated left-hand and right-hand polarized electromagnetic waves can accelerate either ions or electrons (or both), depending on the physical parameters under consideration. We are currently carrying out a comprehensive study of the electromagnetic whistler and lower hybrid like waves observed in the auroral zone using both wave and particle data. Our first task is to identify these wave modes and compare it with particle observations. Using both the DE-1 particle and wave measurements, we can positively identify those electromagnetics lower hybrid like waves as fast magnetosonic waves and the upper cutoff of these waves is the local lower hybrid frequency. From the upper cutoff of the frequency spectrum, one can infer the particle density and the result is in very good agreement with the particle data. Since these electromagnetic lower hybrid like waves can have frequencies extended down to the local ion cyclotron frequency, it practically confirms that they are not whistler waves.

  1. Obtaining eigensolutions for multiple frequency ranges in a single NASTRAN execution

    NASA Technical Reports Server (NTRS)

    Pamidi, P. R.; Brown, W. K.

    1990-01-01

    A novel and general procedure for obtaining eigenvalues and eigenvectors for multiple frequency ranges in a single NASTRAN execution is presented. The scheme is applicable to normal modes analyzes employing the FEER and Inverse Power methods of eigenvalue extraction. The procedure is illustrated by examples.

  2. Computerized J-H loop tracer for soft magnetic thick films in the audio frequency range

    NASA Astrophysics Data System (ADS)

    Loizos, G.; Niarchos, D.

    2014-07-01

    A computerized J-H loop tracer for soft magnetic thick films in the audio frequency range is described. It is a system built on a PXI platform combining PXI modules for control signal generation and data acquisition. The physiscal signals are digitized and the respective data strems are processed, presented and recorded in LabVIEW 7.0.

  3. Universal MOSFET gate impedance model for 200 MHz-20 GHz frequency range

    NASA Astrophysics Data System (ADS)

    Bandi, Sri Priya R.; Washburn, Clyde; Mukund, P. R.; Kolnik, Jan; Paradis, Ken; Howard, Steve; Burleson, Jeff

    2006-07-01

    The scaling of CMOS technology to 100 nm and below and the endless pursuit of higher operating frequencies drives the need to accurately model effects such as gate leakage and the deterioration of transport characteristics that dominate at those feature sizes and frequencies. Current modeling techniques are frequency limited and require different models for different frequency ranges in order to achieve accuracy goals. In the foundry world, high frequency models are typically empirical in nature and significantly lag their low frequency counterparts in terms of availability. This tends to slow the adoption of new foundry technologies for high performance applications such as extremely high data rate serializer/deserializer (SERDES) transceiver cores. However, design cycle time and time to market while transitioning between technology nodes can be reduced by incorporating a re-usable, industry-standard model. This work proposes such a model for device gate impedance that is simulator-friendly, compact, frequency-independent, and relatively portable across technology nodes. This semi-empirical gate impedance model is based on depletion in the poly-silicon gate electrode. The model performs accurately over 200 MHz-20 GHz at different bias conditions and widths and has been verified by measured data in three technology nodes. The model and model parameter behavior are consistent across technology nodes thereby enabling re-usability and portability.

  4. Cochlear implant melody recognition as a function of melody frequency range, harmonicity, and number of electrodes

    PubMed Central

    Singh, Sonya; Kong, Ying-Yee; Zeng, Fan-Gang

    2009-01-01

    Objective The primary goal of the present study was to determine how cochlear implant melody recognition was affected by the frequency range of the melodies, the harmonicity of these melodies, and the number of activated electrodes. The secondary goal was to investigate whether melody recognition and speech recognition were differentially affected by the limitations imposed by cochlear implant processing. Design Four experiments were conducted. In the first experiment, eleven cochlear implant users used their clinical processors to recognize melodies of complex harmonic tones with their fundamental frequencies being in the low (104-262 Hz), middle (207-523 Hz), and high (414-1046 Hz) ranges. In the second experiment, melody recognition with pure tones was compared to melody recognition with complex harmonic tones in 4 subjects. In the third experiment, melody recognition was measured as a function of the number of electrodes in 5 subjects. In the fourth experiment, vowel and consonant recognition were measured as a function of the number of electrodes in the same 5 subjects who participated in the third experiment. Results Frequency range significantly affected cochlear implant melody recognition with higher frequency ranges producing better performance. Pure tones produced significantly better performance than complex harmonic tones. Increasing the number of activated electrodes did not affect performance with low- and middle-frequency melodies, but produced better performance with high-frequency melodies. Large individual variability was observed for melody recognition but its source seemed to be different from the source of the large variability observed in speech recognition. Conclusion Contemporary cochlear implants do not adequately encode either temporal pitch or place pitch cues. Melody recognition and speech recognition require different signal processing strategies in future cochlear implants. PMID:19194298

  5. AC electric field induced dielectrophoretic assembly behavior of gold nanoparticles in a wide frequency range

    NASA Astrophysics Data System (ADS)

    Liu, Weiyu; Wang, Chunhui; Ding, Haitao; Shao, Jinyou; Ding, Yucheng

    2016-05-01

    In this work, we focus on frequency-dependence of pearl chain formations (PCF) of gold nanoparticles driven by AC dielectrophoresis (DEP), especially in a low field-frequency range, where induced double-layer charging effect at ideally polarizable surfaces on particle DEP behavior and surrounding liquid motion need not be negligible. As field frequency varies, grown features of DEP assembly structures ranging from low-frequency non-bridged gap to high-frequency single gold nanoparticle-made nanowires bridging the electrodes are demonstrated experimentally. Specifically, at 10 kHz, a kind of novel channel-like structure with parallel opposing banks is formed at the center of interelectrode gap. In stark contrast, at 1 MHz, thin PCF with diameter of 100 nm is created along the shortest distance of the isolation spacing. Moreover, a particular conductive path of nanoparticle chains is produced at 1 MHz in a DEP device embedded with multiple floating electrodes. A theoretical framework taking into account field-induced double-layer polarization at both the particle/electrolyte and electrode/electrolyte interface is developed to correlate these experimental observations with induced-charge electrokinetic (ICEK) phenomenon. And a RC circuit model is helpful in accounting for the formation of this particular non-bridged channel-like structure induced by a low-frequency AC voltage. As compared to thin PCF formed at high field frequency that effectively short circuits the electrode pair, though it is difficult for complete PCF bridging to occur at low frequency, the non-bridged conducting microstructure has potential to further miniaturize the size of electrode gap fabricated by standard micromachining process and may find useful application in biochemical sensing.

  6. Error correction coding for frequency-hopping multiple-access spread spectrum communication systems

    NASA Technical Reports Server (NTRS)

    Healy, T. J.

    1982-01-01

    A communication system which would effect channel coding for frequency-hopped multiple-access is described. It is shown that in theory coding can increase the spectrum utilization efficiency of a system with mutual interference to 100 percent. Various coding strategies are discussed and some initial comparisons are given. Some of the problems associated with implementing the type of system described here are discussed.

  7. The influence of flight speed on the ranging performance of bats using frequency modulated echolocation pulses

    NASA Astrophysics Data System (ADS)

    Boonman, Arjan M.; Parsons, Stuart; Jones, Gareth

    2003-01-01

    Many species of bat use ultrasonic frequency modulated (FM) pulses to measure the distance to objects by timing the emission and reception of each pulse. Echolocation is mainly used in flight. Since the flight speed of bats often exceeds 1% of the speed of sound, Doppler effects will lead to compression of the time between emission and reception as well as an elevation of the echo frequencies, resulting in a distortion of the perceived range. This paper describes the consequences of these Doppler effects on the ranging performance of bats using different pulse designs. The consequences of Doppler effects on ranging performance described in this paper assume bats to have a very accurate ranging resolution, which is feasible with a filterbank receiver. By modeling two receiver types, it was first established that the effects of Doppler compression are virtually independent of the receiver type. Then, used a cross-correlation model was used to investigate the effect of flight speed on Doppler tolerance and range-Doppler coupling separately. This paper further shows how pulse duration, bandwidth, function type, and harmonics influence Doppler tolerance and range-Doppler coupling. The influence of each signal parameter is illustrated using calls of several bat species. It is argued that range-Doppler coupling is a significant source of error in bat echolocation, and various strategies bats could employ to deal with this problem, including the use of range rate information are discussed.

  8. 24 mm depth range discretely swept optical frequency domain imaging in dentistry

    NASA Astrophysics Data System (ADS)

    Kakuma, Hideo; Choi, DongHak; Furukawa, Hiroyuki; Hiro-Oka, Hideaki; Ohbayashi, Kohji

    2009-02-01

    A large depth range is needed if optical coherence tomography (OCT) is to be used to observe multiple teeth simultaneously. A discretely swept optical frequency domain imaging system with a 24-mm depth range was made by using a superstructure-grating distributed Bragg reflector (SSG-DBR) laser as the light source and setting the frequencystep interval to be 3.13 GHz (λ ~ 0.026 nm). The swept wavelength range was 40 nm centered at 1580 nm, the resolution was 29 μm, and the A-scan rate was 1.3 kHz. Application of the OCT system to a dental phantom was demonstrated.

  9. On the slope of the equilibrium range in the frequency spectrum of wind waves

    NASA Astrophysics Data System (ADS)

    Liu, Paul C.

    1989-04-01

    An effort to empirically assess the slope of the equilibrium range in a wind wave frequency spectrum with a large number of data recorded in the Great Lakes did not serve to clarify the uncertainty between a -4 or a -5 frequency exponent representation. The uncertainty is further compounded by indications that the slope is not necessarily unique, but tends to vary with wave momentum. For sufficiently well developed wind waves the exponent appears to cluster between -3 and -4. For practical applications the f-4 equilibrium range is perhaps an effective approximation. What the correct slope is for the equilibrium range, or even whether or not a unique slope exists, remains elusive and has yet to be satisfactorily substantiated.

  10. Application of generalized Snoek's law over a finite frequency range: A case study

    NASA Astrophysics Data System (ADS)

    Rozanov, Konstantin N.; Koledintseva, Marina Y.

    2016-02-01

    Generalized Snoek's law proposed in an integral form by Acher and coauthors is a useful tool for investigation of high-frequency properties of magnetic materials. This integral law referred to as Acher's law allows for evaluating the ultimate performance of RF and microwave devices which employ magnetic materials. It may also be helpful in obtaining useful information on the structure and morphology of the materials. The key factor in practical application of Acher's law is an opportunity to employ either measured or calculated data available over a finite frequency range. The paper uses simple calculations to check the applicability of Acher's law in cases when the frequency range is limited and the magnetic loss peak is comparatively wide and has a distorted shape. The cases of large magnetic damping, pronounced skin effect, and inhomogeneity of the material are considered. It is shown that in most cases calculation of the integral through fitting of actual magnetic frequency dispersion by the Lorentzian dispersion law results in accurate estimations of the ultimate high-frequency performance of magnetic materials.

  11. Development of gyrotrons for fusion with power exceeding 1 MW over a wide frequency range

    NASA Astrophysics Data System (ADS)

    Kariya, T.; Imai, T.; Minami, R.; Numakura, T.; Eguchi, T.; Kato, T.; Endo, Y.; Ichimura, M.; Shimozuma, T.; Kubo, S.; Takahashi, H.; Yoshimura, Y.; Igami, H.; Ito, S.; Mutoh, T.; Sakamoto, K.; Idei, H.; Zushi, H.; Nagasaki, K.; Sano, F.; Ono, M.; Mitsunaka, Y.

    2015-09-01

    Megawatt-class gyrotrons covering a wide frequency range (14 GHz-300 GHz) are in increasing demand for nuclear fusion. Recent electron cyclotron heating and electron cyclotron current drive experiments highlight a requirement of megawatt-scale gyrotrons at a relatively lower frequency (14-35 GHz) range of some plasma devices, like GAMMA 10/PDX of the University of Tsukuba, QUEST of Kyushu University, NSTX-U of Princeton Plasma Physics Laboratory, and Heliotron J of Kyoto University. Collaborative studies for designing a new 28 GHz/35 GHz dual-frequency gyrotron and a 14 GHz gyrotron have commenced. Operation above 1 MW of 28 GHz/35 GHz dual oscillation was demonstrated experimentally. Further in the design of dual-frequency gyrotron, operations with 2 MW 3 s and 0.4 MW CW (continuous wave) at 28 GHz, and power exceeding 1 MW for 3 s at 34.8 GHz have been shown to be feasible. The 14 GHz gyrotron is expected to operate above 1 MW. We are also developing higher frequency gyrotrons (77-300 GHz). The joint program of National Institute for Fusion Science and the University of Tsukuba developed two new 154 GHz gyrotrons for the large helical device after the demonstration of three 77 GHz gyrotrons. The 154 GHz gyrotrons achieved a maximum output power of 1.25 MW and quasi-CW operation of 0.35 MW for 30 min.

  12. An optimal frequency range for assessing the pressure reactivity index in patients with traumatic brain injury.

    PubMed

    Howells, Tim; Johnson, Ulf; McKelvey, Tomas; Enblad, Per

    2015-02-01

    The objective of this study was to identify the optimal frequency range for computing the pressure reactivity index (PRx). PRx is a clinical method for assessing cerebral pressure autoregulation based on the correlation of spontaneous variations of arterial blood pressure (ABP) and intracranial pressure (ICP). Our hypothesis was that optimizing the methodology for computing PRx in this way could produce a more stable, reliable and clinically useful index of autoregulation status. The patients studied were a series of 131 traumatic brain injury patients. Pressure reactivity indices were computed in various frequency bands during the first 4 days following injury using bandpass filtering of the input ABP and ICP signals. Patient outcome was assessed using the extended Glasgow Outcome Scale (GOSe). The optimization criterion was the strength of the correlation with GOSe of the mean index value over the first 4 days following injury. Stability of the indices was measured as the mean absolute deviation of the minute by minute index value from 30-min moving averages. The optimal index frequency range for prediction of outcome was identified as 0.018-0.067 Hz (oscillations with periods from 55 to 15 s). The index based on this frequency range correlated with GOSe with ρ=-0.46 compared to -0.41 for standard PRx, and reduced the 30-min variation by 23%. PMID:24664812

  13. Optimal random frequency range in transcranial pulsed current stimulation indexed by quantitative electroencephalography.

    PubMed

    Morales-Quezada, Leon; Castillo-Saavedra, Laura; Cosmo, Camila; Doruk, Deniz; Sharaf, Ibrahim; Malavera, Alejandra; Fregni, Felipe

    2015-09-01

    Given the recent results provided by previous investigations on transcranial pulsed current stimulation (tPCS) demonstrating its modulatory effects on cortical connectivity; we aimed to explore the application of different random pulsed frequencies. The utility of tPCS as a neuromodulatory technique for cognition performance will come as additional frequency ranges are tested with the purpose to find optimal operational parameters for tPCS. This study was designed to analyze the effects of tPCS using the following random frequencies; 1-5, 6-10, and 11-15 Hz compared with sham on quantitative electroencephalographic changes in the spectral power and interhemispheric coherence of each electroencephalographic frequency band. This was a parallel, randomized, double-blinded, sham-controlled trial. Forty healthy individuals older than 18 years were eligible to participate. The main outcomes were differences in the spectral power analysis and interhemispheric coherence as measured by quantitative electroencephalography. Participants were randomly allocated to four groups of random frequency stimulation and received a single session of stimulation for 20 min with a current intensity of 2 mA delivered by bilateral periauricular electrode clips. We found that a random pulsed frequency between 6-10 Hz significantly increased the power and coherence in frontal and central areas for the alpha band compared with sham stimulation, while 11-15 Hz tPCS decreased the power for the alpha and theta bandwidth. Our findings corroborate the hypothesis that a random frequency ranging into the boundaries of 6-10 Hz induces changes in the naturally occurring alpha oscillatory activity, providing additional data for further studies with tPCS. PMID:26154494

  14. Observation of harmonically related solar radio zebra patterns in the 1-4 GHz frequency range

    NASA Astrophysics Data System (ADS)

    Sawant, H. S.; Karlický, M.; Fernandes, F. C. R.; Cecatto, J. R.

    2002-12-01

    A unique case of two zebra patterns related harmonically with ratio of ~ 1:2 was observed by distant radio telescopes at São José dos Campos and Ondřejov Observatories. Accompanied zebras show that the ratio of frequencies of the neighboring zebra lines is in the range of 1.009-1.037. There is a tendency of a decrease of this ratio with decreasing frequency within the specific zebra pattern. Both facts speak in favour of plasma emission models for the zebra pattern fine structure in radio burst continua.

  15. Theoretical analysis of the EAST 4-strap ion cyclotron range of frequency antenna with variational theory

    NASA Astrophysics Data System (ADS)

    Zhang, Jia-Hui; Zhang, Xin-Jun; Zhao, Yan-Ping; Qin, Cheng-Ming; Chen, Zhao; Yang, Lei; Wang, Jian-Hua

    2016-08-01

    A variational principle code which can calculate self-consistently currents on the conductors is used to assess the coupling characteristic of the EAST 4-strap ion cyclotron range of frequency (ICRF) antenna. Taking into account two layers of antenna conductors without lateral frame but with slab geometry, the antenna impedances as a function of frequency and the structure of RF field excited inside the plasma in various phasing cases are discussed in this paper. Project supported by the National Magnetic Confinement Fusion Science Program, China (Grant No. 2015GB101001) and the National Natural Science Foundation of China (Grant Nos. 11375236 and 11375235).

  16. Spectral Decay Characteristics in High Frequency Range of Observed Records from Crustal Large Earthquakes (Part 2)

    NASA Astrophysics Data System (ADS)

    Tsurugi, M.; Kagawa, T.; Irikura, K.

    2012-12-01

    Spectral decay characteristics in high frequency range of observed records from crustal large earthquakes occurred in Japan is examined. It is very important to make spectral decay characteristics clear in high frequency range for strong ground motion prediction in engineering purpose. The authors examined spectral decay characteristics in high frequency range of observed records among three events, the 2003 Miyagi-Ken Hokubu earthquake (Mw 6.1), the 2005 Fukuoka-Ken Seiho-oki earthquake (Mw 6.6), and the 2008 Iwate-Miyagi Nairiku earthquake (Mw 6.9) in previous study [Tsurugi et al.(2010)]. Target earthquakes in this study are two events shown below. *EQ No.1 Origin time: 2011/04/11 17:16, Location of hypocenter: East of Fukushima pref., Mj: 7.0, Mw: 6.6, Fault type: Normal fault *EQ No.2 Origin time: 2011/03/15 22:31, Location of hypocenter: East of Shizuoka pref., Mj: 6.4, Mw: 5.9, Fault type: Strike slip fault The borehole data of each event are used in the analysis. The Butterworth type high-cut filter with cut-off frequency, fmax and its power coefficient of high-frequency decay, s [Boore(1983)], are assumed to express the high-cut frequency characteristics of ground motions. The four parameters such as seismic moment, corner frequency, cut-off frequency and its power coefficient of high-frequency decay are estimated by comparing observed spectra at rock sites with theoretical spectra. The theoretical spectra are calculated based on the omega squared source characteristics convolved with propagation-path effects and high-cut filter shapes. In result, the fmax's of the records from the earthquakes are estimated 8.0Hz for EQ No.1 and 8.5Hz for EQ No.2. These values are almost same with those of other large crustal earthquakes occurred in Japan. The power coefficient, s, are estimated 0.78 for EQ No.1 and 1.65 for EQ No.2. The value for EQ No.2 is notably larger than those of other large crustal earthquakes. It is seems that the value of the power coefficient, s

  17. Fundamental Frequency Range in Japanese and English: The Case of Simultaneous Bilinguals.

    PubMed

    Graham, Calbert

    2014-01-01

    This article reports an experiment to test whether Japanese and English speakers vary their fundamental frequency (f0) range as a function of the language spoken. Speech samples of Japanese-(American) English simultaneous bilinguals (5 males, 5 females; all undergraduates at UC Berkeley) performing comparable reading tasks in their two native languages were analysed. The study builds on a relatively new approach to measuring f0 range that computes its high and low points from tonal targets in the intonational phonology. Unlike in most previous studies where f0 range is traditionally treated as a one-dimensional measure, f0 range in this study is measured along two quasi-independent dimensions: level and span. Findings revealed statistically significant crosslanguage differences between Japanese and English in both dimensions. This provides new insights into the relation between prosodic structure and f0 range in these two typologically different prosodic systems. PMID:25997935

  18. Noise in any frequency range can enhance information transmission in a sensory neuron

    NASA Astrophysics Data System (ADS)

    Levin, Jacob E.

    1997-05-01

    The effect of noise on the neural encoding of broadband signals was investigated in the cricket cercal system, a mechanosensory system sensitive to small near-field air particle disturbances. Known air current stimuli were presented to the cricket through audio speakers in a controlled environment in a variety of background noise conditions. Spike trains from the second layer of neuronal processing, the primary sensory interneurons, were recorded with intracellular Electrodes and the performance of these neurons characterized with the tools of information theory. SNR, mutual information rates, and other measures of encoding accuracy were calculated for single frequency, narrowband, and broadband signals over the entire amplitude sensitivity range of the cells, in the presence of uncorrelated noise background also spanning the cells' frequency and amplitude sensitivity range. Significant enhancements of transmitted information through the addition of external noise were observed regardless of the frequency range of either the signal or noise waveforms, provided both were within the operating range of the cell. Considerable improvements in signal encoding were observed for almost an entire order of magnitude of near-threshold signal amplitudes. This included sinusoidal signals embedded in broadband white noise, broadband signals in broadband noise, and even broadband signals presented with narrowband noise in a completely non-overlapping frequency range. The noise related increases in mutual information rate for broadband signals were as high as 150%, and up to 600% increases in SNR were observed for sinusoidal signals. Additionally, it was shown that the amount of information about the signal carried, on average, by each spike was INCREASED for small signals when presented with noise—implying that added input noise can, in certain situations, actually improve the accuracy of the encoding process itself.

  19. Clock signal requirement for high-frequency, high dynamic range acquisition systems

    SciTech Connect

    Viscor, Ivo; Halamek, Josef; Villa, Marco

    2005-11-15

    Analog-to-digital converters (ADC's) are increasingly replacing mixers in frequency conversion schemes. To achieve superior performances, in terms of bandwidth and dynamic range, a nearly ideal ADC clock is needed, with a spectral purity higher than the reference signal of the classical mixing scheme. These requirements of spectral purity for the ADC clock are discussed by analyzing in detail the nonuniform sampling process and by characterizing an actual acquisition system. The effect of clock phase imperfections on the output is proportional to the input frequency over sampling frequency ratio. Moreover, at the output we may have a multiple folding of the phase jitter spectrum. These effects are illustrated by three sets of measurements performed using our system: transfer of spurious clock components, aliasing of these components, and transfer of clock phase noise.

  20. A substructured Trefftz method for updating joint models in the medium-frequency range

    NASA Astrophysics Data System (ADS)

    Dorival, O.; Rouch, P.; Allix, O.

    2008-08-01

    The response of a structure to medium-frequency vibrations is highly dependent on several phenomena. One of these, the behavior of joints between substructures, is essential because it controls the distribution of the power injected into the structure and governs most of the dissipative effects. This paper introduces a new method for the identification of joint parameters from experimental vibration data, inspired by previous works on finite element model updating using the error in the constitutive relation. Since such numerical techniques are not suitable for the medium-frequency range, in which the finite element mesh must be refined, our work uses the numerical framework of the variational theory of complex rays, which is a Trefftz approach entirely dedicated to the calculation of medium-frequency vibrations at very low cost. The main scope of this paper is the presentation of the formulation and its validation against actual and numerically-simulated experimental results.

  1. Propagation in a shearing plasma. II - Turbulence and the frequency range of pulsar microstructure

    NASA Technical Reports Server (NTRS)

    Harding, A. K.; Tademaru, E.

    1980-01-01

    Numerical calculations are presented which explore the propagation of radio waves and pulses through a turbulent shearing plasma. A stochastic model is used to describe the turbulent velocity field, in which random fluctuations are superposed on a mean profile. Both Gaussian wave packets and shot-noise pulses polarized in the plane of shearing acquire quasi-periodic intensity modulations above the rest-frame plasma frequency. The frequency range over which these modulations appear is shown to depend on the spatial correlation length of the turbulent fluctuations and on their standard deviation from the mean velocity. The period of the modulations is variable from one realization of the random process to the next, and the average period is frequency dependent. The results of these calculations lend further support to a model for pulsar microstructure in which periodic micropulses are pure temporal modulations of the emitted radiation due to propagation effects in magnetospheric shearing regions. It is shown that turbulence on a scale of approximately 10 cm can produce these quasi-periodic modulations over a frequency range comparable to that of observed microstructure.

  2. Design and optimization of an ultra-wide frequency range CMOS divide-by-two circuit

    NASA Astrophysics Data System (ADS)

    Bo, Lu; Niansong, Mei; Hu, Chen; Zhiliang, Hong

    2010-11-01

    A novel toggled flip-flop (TFF) divide-by-two circuit (DTC) and its optimization method based on a large-signal analysis approach are proposed. By reducing the output RC constant in tracking mode and making it large in latching mode, compressing the internal signal swing as well as compensating the current leaked in the latching mode, the operating frequency range is greatly expanded. Implemented in a SMIC 0.13 μm RF CMOS process with a 1.2 V power supply, it can work under an ultra-wide frequency band ranging from 320 MHz to 29.6 GHz. Experimental results show that two phase-locked loops (PLLs) with the proposed DTC can achieve in-band phase noise of -94 dBc/Hz @ 10 kHz under 4224 MHz operating frequency and -84 dBc/Hz @ 10 kHz under 10 GHz operating frequency, respectively. The power consumption of the proposed DTC is reduced by almost 50% compared with the conventional counterparts.

  3. Double Brillouin frequency spaced multiwavelength Brillouin-erbium fiber laser with 50 nm tuning range

    NASA Astrophysics Data System (ADS)

    Zhao, J. F.; Liao, T. Q.; Zhang, C.; Zhang, R. X.; Miao, C. Y.; Tong, Z. R.

    2012-09-01

    A 50 nm tuning range multiwavelength Brillouin-erbium fiber laser (MWBEFL) with double Brillouin frequency spacing is presented. Two separated gain blocks with symmetrical architecture, consisted by erbium-doped fiber amplifiers (EDFAs) and Brillouin gain media, are used to generate double Brillouin frequency spacing. The wider tuning range is realized by eliminating the self-lasing cavity modes existing in conventional MWBEFLs because of the absence of the physical mirrors at the ends of the linear cavity. The Brillouin pump (BP) is preamplified by the EDFA before entering the single-mode fiber (SMF), which leads to the reduction of threshold power and the generation enhancement of Brillouin Stokes (BS) signals. Four channels with 0.176 nm spacing are achieved at 2 mW BP power and 280 mW 980 nm pump power which can be tuned from 1525 to 1575 nm.

  4. High-Resolution Group Quantization Phase Processing Method in Radio Frequency Measurement Range.

    PubMed

    Du, Baoqing; Feng, Dazheng; Tang, Yaohua; Geng, Xin; Zhang, Duo; Cai, Chaofeng; Wan, Maoquan; Yang, Zhigang

    2016-01-01

    Aiming at the more complex frequency translation, the longer response time and the limited measurement precision in the traditional phase processing, a high-resolution phase processing method by group quantization higher than 100 fs level is proposed in radio frequency measurement range. First, the phase quantization is used as a step value to quantize every phase difference in a group by using the fixed phase relationships between different frequencies signals. The group quantization is formed by the results of the quantized phase difference. In the light of frequency drift mainly caused by phase noise of measurement device, a regular phase shift of the group quantization is produced, which results in the phase coincidence of two comparing signals which obtain high-resolution measurement. Second, in order to achieve the best coincidences pulse, a subtle delay is initiatively used to reduce the width of the coincidences fuzzy area according to the transmission characteristics of the coincidences in the specific medium. Third, a series of feature coincidences pulses of fuzzy area can be captured by logic gate to achieve the best phase coincidences information for the improvement of the measurement precision. The method provides a novel way to precise time and frequency measurement. PMID:27388587

  5. High-Resolution Group Quantization Phase Processing Method in Radio Frequency Measurement Range

    NASA Astrophysics Data System (ADS)

    Du, Baoqing; Feng, Dazheng; Tang, Yaohua; Geng, Xin; Zhang, Duo; Cai, Chaofeng; Wan, Maoquan; Yang, Zhigang

    2016-07-01

    Aiming at the more complex frequency translation, the longer response time and the limited measurement precision in the traditional phase processing, a high-resolution phase processing method by group quantization higher than 100 fs level is proposed in radio frequency measurement range. First, the phase quantization is used as a step value to quantize every phase difference in a group by using the fixed phase relationships between different frequencies signals. The group quantization is formed by the results of the quantized phase difference. In the light of frequency drift mainly caused by phase noise of measurement device, a regular phase shift of the group quantization is produced, which results in the phase coincidence of two comparing signals which obtain high-resolution measurement. Second, in order to achieve the best coincidences pulse, a subtle delay is initiatively used to reduce the width of the coincidences fuzzy area according to the transmission characteristics of the coincidences in the specific medium. Third, a series of feature coincidences pulses of fuzzy area can be captured by logic gate to achieve the best phase coincidences information for the improvement of the measurement precision. The method provides a novel way to precise time and frequency measurement.

  6. High-Resolution Group Quantization Phase Processing Method in Radio Frequency Measurement Range

    PubMed Central

    Du, Baoqing; Feng, Dazheng; Tang, Yaohua; Geng, Xin; Zhang, Duo; Cai, Chaofeng; Wan, Maoquan; Yang, Zhigang

    2016-01-01

    Aiming at the more complex frequency translation, the longer response time and the limited measurement precision in the traditional phase processing, a high-resolution phase processing method by group quantization higher than 100 fs level is proposed in radio frequency measurement range. First, the phase quantization is used as a step value to quantize every phase difference in a group by using the fixed phase relationships between different frequencies signals. The group quantization is formed by the results of the quantized phase difference. In the light of frequency drift mainly caused by phase noise of measurement device, a regular phase shift of the group quantization is produced, which results in the phase coincidence of two comparing signals which obtain high-resolution measurement. Second, in order to achieve the best coincidences pulse, a subtle delay is initiatively used to reduce the width of the coincidences fuzzy area according to the transmission characteristics of the coincidences in the specific medium. Third, a series of feature coincidences pulses of fuzzy area can be captured by logic gate to achieve the best phase coincidences information for the improvement of the measurement precision. The method provides a novel way to precise time and frequency measurement. PMID:27388587

  7. PROPERTIES OF PHANTOM TISSUE-LIKE POLYMETHYLPENTENE IN THE FREQUENCY RANGE 20–70 MHZ

    PubMed Central

    Madsen, Ernest L; Deaner, Meagan E; Mehi, James

    2011-01-01

    Quantitative ultrasound (QUS) has been employed to characterize soft tissues at ordinary abdominal ultrasound frequencies (2–15 MHz) and is beginning application at high frequencies (20–70 MHz). For example, backscatter and attenuation coefficients can be estimated in vivo using a reference phantom. At high frequencies it is crucial that reverberations do not compromise the measurements. Such reverberations can occur between the phantom's scanning window and transducer components as well as within the scanning window between its surfaces. Transducers are designed to minimize reverberations between the transducer and soft tissue. Thus, the acoustic impedance of a phantom scanning window should be tissue-like; polymethylpentene (TPX) is commonly used because of its tissue-like acoustic impedance. For QUS it is also crucial to correct for the transmission coefficient of the scanning window. Computation of the latter requires knowledge of the ultrasonic properties, viz, density, speed and attenuation coefficients. This work reports values for the ultrasonic properties of two versions of TPX over the high frequency range. One form (TPX film) is used as a scanning window on high frequency phantoms, and at 40 MHz and 22°C was found to have an attenuation coefficient of 120 dB/cm and a propagation speed of 2093 m/s. PMID:21723451

  8. Serially homologous ears perform frequency range fractionation in the praying mantis, Creobroter (Mantodea, Hymenopodidae).

    PubMed

    Yager, D D

    1996-04-01

    Unlike most praying mantises that have a single region of auditory sensitivity, species in the genus Creobroter have equally sensitive hearing at 2-4 and at 25-50 kHz and and are relatively insensitivity at 10-15 kHz- they have a W-shaped audiogram. Ultrasonic sensitivity originates from an auditory organ in the ventral midline of the metathorax that closely resembles the ear of other mantises. Ablation experiments demonstrate that low frequency sensitivity derives from a serially homologous mesothoracic auditory organ. Extracellular recordings suggest that these two ears operate largely, if not entirely, independently of one another in the thorax. The low frequency response has a longer latency, more action potentials per stimulus, and different patterns of change with increasing SPL than the high frequency response. Separate interneurons mediate responses in the two frequency ranges, but our evidence suggests that they are two serially homologous sets of cells. Neither auditory organ shows any physiological evidence of directional sensitivity. Ultrasound triggers a set of behaviors in flying hymenopodid mantises much like those in other mantises, but the behavioral significance of low frequency hearing in these animals is still unknown. PMID:8847662

  9. Moment method analysis of microstrip antennas over a wide frequency range

    NASA Technical Reports Server (NTRS)

    Kwan, B. W.; Newman, E. H.

    1985-01-01

    Expressions for the self and mutual impedance between microstrip antenna modes on a grounded dielectric slab are presented. The mutual impedance between the microstrip modes and a vertical current filament in the dielectric is also presented. These are the quantities required in a method of moments analysis of the microstrip antenna. Entire domain expansion modes, suitable for representing the microstrip current over a broad frequency range, are used. Efficient methods for the evaluation of the mutual impedance elements are described.

  10. Polarization-Entangled Photon Pairs From Periodically-Poled Crystalline Waveguides Over a Range of Frequencies

    PubMed Central

    Heberle, Dylan A; Levine, Zachary H

    2013-01-01

    We propose a method to extend the frequency range of polarization entanglement in periodically poled rubidium-doped potassium titanyl phosphate (Rb:KTP) waveguides. Our calculations predict that output wavelengths from 1130 nm to 1257 nm may be achieved using Rb:KTP by the appropriate selection of a direction of propagation for the waveguide. The fidelity using a poling period of 1 mm is approximately 0.98. PMID:26401438

  11. Long range aircraft detection using high-frequency surface-wave radar

    NASA Astrophysics Data System (ADS)

    Leong, Hank

    1994-12-01

    Experimental data from a high-frequency surface-wave radar (HFSWR) operating at 1.95 MHz at Cape Bonavista, Newfoundland are analyzed to assess the capability of the radar to detect aircraft over an ocean surface. The results of the analysis show that the HFSWR could easily detect and track a low-flying CP-140 Aurora aircraft at ranges between 11 and 56 km. The radar's coverage area coincides with a trans-Atlantic international flight route, and the radar was also able to detect and track some commercial aircraft in range as far as 280 km.

  12. Low-power wide-locking-range injection-locked frequency divider for OFDM UWB systems

    NASA Astrophysics Data System (ADS)

    Jiangwei, Yin; Ning, Li; Renliang, Zheng; Wei, Li; Junyan, Ren

    2009-05-01

    This paper describes a divide-by-two injection-locked frequency divider (ILFD) for frequency synthesizers as used in multiband orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) systems. By means of dual-injection technique and other conventional tuning techniques, such as DCCA and varactor tuning, the divider demonstrates a wide locking range while consuming much less power. The chip was fabricated in the Jazz 0.18 μm RF CMOS process. The measurement results show that the divider achieves a locking range of 4.85 GHz (6.23 to 11.08 GHz) at an input power of 8 dBm. The core circuit without the test buffer consumes only 3.7 mA from a 1.8 V power supply and has a die area of 0.38 × 0.28 mm2. The wide locking range combined with low power consumption makes the ILFD suitable for its application in UWB systems.

  13. Satellite range delay simulator for a matrix-switched time division multiple-access network simulation system

    NASA Technical Reports Server (NTRS)

    Nagy, Lawrence A.

    1990-01-01

    The Systems Integration, Test, and Evaluation (SITE) facility at NASA Lewis Research Center is presently configured as a satellite-switched time division multiple access (SS-TDMA) network simulator. The purpose of SITE is to demonstrate and evaluate advanced communication satellite technologies, presently embodied by POC components developed under NASA contracts in addition to other hardware, such as ground terminals, designed and built in-house at NASA Lewis. Each ground terminal in a satellite communications system will experience a different aspect of the satellite's motion due mainly to daily tidal effects and station keeping, hence a different duration and rate of variation in the range delay. As a result of this and other effects such as local oscillator instability, each ground terminal must constantly adjust its transmit burst timing so that data bursts from separate ground terminals arrive at the satellite in their assigned time slots, preventing overlap and keeping the system in synchronism. On the receiving end, ground terminals must synchronize their local clocks using reference transmissions received through the satellite link. A feature of the SITE facility is its capability to simulate the varying propagation delays and associated Doppler frequency shifts that the ground terminals in the network have to cope with. Delay is ahcieved by means of two NASA Lewis designed and built range delay simulator (RDS) systems, each independently controlled locally with front panel switches or remotely by an experiment control and monitor (EC/M) computer.

  14. In vivo intracardiac OCT imaging through percutaneous access: towards image guided radio-frequency ablation

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Kang, Wei; Carrigan, Thomas; Bishop, Austin; Rosenthal, Noah; Arruda, Mauricio; Rollins, Andrew M.

    2012-01-01

    BACKGROUND Complete catheter-tissue contact and permanent tissue destruction are essential for efficient radio-frequency ablation (RFA) during cardiac arrhythmia treatment. Current methods of monitoring lesion formation are indirect and unreliable. We aim to develop optical coherence tomography (OCT) as an imaging guidance for RFA. OBJECTIVES The purpose of this study is to evaluate the feasibility of using OCT catheter to image endocardia wall in active beating hearts through percutaneous access. This is a critical step toward image guided RFA in a clinic setting. METHODS A cone-scanning forward-viewing OCT catheter was advanced into active beating hearts through percutaneous access in four swine. The OCT catheter was steered by an introducer to touch the endocardia wall. The images were then acquired at 10 frames per second at an axial resolution and lateral resolution of 15 μm. RESULTS We report the first in vivo intracardiac OCT imaging through percutaneous access with a thin and flexible OCT catheter. We are able to acquire high quality OCT images in active beating hearts, observe the polarization-related artifacts induced by the birefringence of myocardium and readily evaluate catheter-tissue contact. CONCLUSIONS It is feasible to acquire OCT images in beating hearts through percutaneous access. The observations indicate that OCT could be a promising technique for in vivo guidance of RFA.

  15. Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors

    NASA Technical Reports Server (NTRS)

    Erkmen, Baris I.; Barber, Zeb W.; Dahl, Jason

    2014-01-01

    Optical ranging is a problem of estimating the round-trip flight time of a phase- or amplitude-modulated optical beam that reflects off of a target. Frequency- modulated, continuous-wave (FMCW) ranging systems obtain this estimate by performing an interferometric measurement between a local frequency- modulated laser beam and a delayed copy returning from the target. The range estimate is formed by mixing the target-return field with the local reference field on a beamsplitter and detecting the resultant beat modulation. In conventional FMCW ranging, the source modulation is linear in instantaneous frequency, the reference-arm field has many more photons than the target-return field, and the time-of-flight estimate is generated by balanced difference- detection of the beamsplitter output, followed by a frequency-domain peak search. This work focused on determining the maximum-likelihood (ML) estimation algorithm when continuous-time photoncounting detectors are used. It is founded on a rigorous statistical characterization of the (random) photoelectron emission times as a function of the incident optical field, including the deleterious effects caused by dark current and dead time. These statistics enable derivation of the Cramér-Rao lower bound (CRB) on the accuracy of FMCW ranging, and derivation of the ML estimator, whose performance approaches this bound at high photon flux. The estimation algorithm was developed, and its optimality properties were shown in simulation. Experimental data show that it performs better than the conventional estimation algorithms used. The demonstrated improvement is a factor of 1.414 over frequency-domainbased estimation. If the target interrogating photons and the local reference field photons are costed equally, the optimal allocation of photons between these two arms is to have them equally distributed. This is different than the state of the art, in which the local field is stronger than the target return. The optimal

  16. Reference hearing thresholds in an extended frequency range as a function of age.

    PubMed

    Jilek, Milan; Šuta, Daniel; Syka, Josef

    2014-10-01

    The ISO 7029 (2000) standard defines normative hearing thresholds H (dB hearing level) as a function of age Y (years), given by H = α(Y - 18)(2), up to 8 kHz. The purpose of this study was to determine reference thresholds above 8 kHz. Hearing thresholds were examined using pure-tone audiometry over the extended frequency range 0.125-16 kHz, and the acquired values were used to specify the optimal approximation of the dependence of hearing thresholds on age. A sample of 411 otologically normal men and women 16-70 years of age was measured in both ears using a high-frequency audiometer and Sennheiser HDA 200 headphones. The coefficients of quadratic, linear, polynomial and power-law approximations were calculated using the least-squares fitting procedure. The approximation combining the square function H = α(Y - 18)(2) with a power-law function H = β(Y - 18)(1.5), both gender-independent, was found to be the most appropriate. Coefficient α was determined at frequencies of 9 kHz (α = 0.021), 10 kHz (α = 0.024), 11.2 kHz (α = 0.029), and coefficient β at frequencies of 12.5 kHz (β = 0.24), 14 kHz (β = 0.32), 16 kHz (β = 0.36). The results could be used to determine age-dependent normal hearing thresholds in an extended frequency range and to normalize hearing thresholds when comparing participants differing in age. PMID:25324083

  17. Accessibility

    MedlinePlus

    ... www.nlm.nih.gov/medlineplus/accessibility.html MedlinePlus Accessibility To use the sharing features on this page, ... Subscribe to RSS Follow us Disclaimers Copyright Privacy Accessibility Quality Guidelines Viewers & Players MedlinePlus Connect for EHRs ...

  18. Parallel PWMs Based Fully Digital Transmitter with Wide Carrier Frequency Range

    PubMed Central

    Zhou, Bo; Zhang, Kun; Zhou, Wenbiao; Zhang, Yanjun; Liu, Dake

    2013-01-01

    The carrier-frequency (CF) and intermediate-frequency (IF) pulse-width modulators (PWMs) based on delay lines are proposed, where baseband signals are conveyed by both positions and pulse widths or densities of the carrier clock. By combining IF-PWM and precorrected CF-PWM, a fully digital transmitter with unit-delay autocalibration is implemented in 180 nm CMOS for high reconfiguration. The proposed architecture achieves wide CF range of 2 M–1 GHz, high power efficiency of 70%, and low error vector magnitude (EVM) of 3%, with spectrum purity of 20 dB optimized in comparison to the existing designs. PMID:24223503

  19. Three-dimensional ray tracing of the Jovian magnetosphere in the low-frequency range

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Green, J. L.; Gulkis, S.; Six, F.

    1984-01-01

    Three-dimensional ray tracing of the Jovian DAM emission has been performed utilizing the O-4 magnetic field model (Acuna and Ness, 1979) and a realistic plasma model. Minimal assumptions about the emission mechanism have been made that include radiation in the right-hand extraordinary mode, propagating nearly perpendicular to the field line at source points located just above the RX cutoff frequency along Io flux tubes. Ray tracing has been performed in the frequency range from 2-35 MHz from successive Io flux tubes separated by ten degrees of central meridian longitude for a full circumference of northern hemisphere sources. The results show unusual complexity in model arc spectra that is displayed in a constant Io phase format with many similarities to the Voyager PRA data. The results suggest much of the variation in observed DAM spectral features is a result of propagation effects rather than emission process differences.

  20. Fast particles-wave interaction in the Alfven frequency range on the Joint European Torus tokamak

    SciTech Connect

    Fasoli, A.; Borba, D.; Association EURATOM Breizman, B.; Gormezano, C.; Heeter, R. F.; Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 ; Juan, A.; Mantsinen, M.; Sharapov, S.; Testa, D.

    2000-05-01

    Wave-particle interaction phenomena in the Alfven Eigenmode (AE) frequency range are investigated at the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] using active and passive diagnostic methods. Fast particles are generated by neutral beam injection, ion cyclotron resonance heating, and fusion reactions. External antennas are used to excite stable AEs and measure fast particle drive and damping separately. Comparisons with numerical calculations lead to an identification of the different damping mechanisms. The use of the active AE diagnostic system to generate control signals based on the proximity to marginal stability limits for AE and low-frequency magnetohydrodynamic (MHD) modes is explored. Signatures of the different nonlinear regimes of fast particle driven AE instabilities predicted by theory are found in the measured spectra. The diagnostic use of AE measurements to get information both on the plasma bulk and the fast particle distribution is assessed. (c) 2000 American Institute of Physics.

  1. High-frequency acoustic tracking of odontocetes at the Southern California Offshore Range (SCORE)

    NASA Astrophysics Data System (ADS)

    Hursky, Paul; Abawi, Ahmad T.; Porter, Michael B.; Hildebrand, John A.; Wiggins, Sean M.; Soldevilla, Melissa; Sauter, Allan W.

    2005-09-01

    The SCORE site, located near San Clemente Island, is known to be abundant in marine mammals, and is the site of frequent naval operations, making it an ideal site to study what impact man-made activities may have upon these creatures. In August 2004, an experiment was performed to collect both visual and acoustic observations of odontocetes at the SCORE site. Odontocete vocalizations consist of clicks and whistles. The clicks are very wideband (often 100 kHz), so times of arrival can be measured with extremely high resolution, which makes clicks attractive waveforms for multipath ranging and depth estimation. Although the whistles are narrowband, their fundamental frequency often ranges over tens of kilohertz, so these too can be processed as if they were wideband. We will present results of processing excerpts from several weeks of data recorded on a high-frequency horizontal line array deployed from the FLIP research vessel. Bearing tracks of individuals and groups from a number of different species will be correlated and compared with visual observations. In addition, we will discuss the possibilities for range and depth estimates derived from the multipath arrivals observed in the clicks and whistles.

  2. Analysis of electromagnetic fluctuations of lower hybrid frequency range in MRX

    NASA Astrophysics Data System (ADS)

    Yamada, M.; Ji, H.; Kulsrud, R. M.

    2002-05-01

    In MRX (Magnetic Reconnection Experiment), the detailed magnetic field structure and the plasma profiles of the neutral sheet have been measured and evidences for the physics beyond MHD have been obtained[1]. As the electron-ion collision frequency is reduced, the reconnection rate is observed to be significantly enhanced over the classical value. Both electrostatic and magnetic turbulence of lower hybrid frequency range has been observed in the low collisionality regime. The amplitude of magnetic fluctuation is the largest at the center of neutral sheet while the electropotential fluctuations peak at the edge of the sheath. To describe the physics of this region, much thought has been given to the `` generalized" Ohm's law where electrons and ions are separately treated to satisfy the equations of motion in the neutral sheet plasma. In this `` E-MHD" region electrons but not ions are considered to be magnetized and the lower hybrid drift wave can be connected continuously to an obliquely propagating Whistler wave[2]. In this paper we examine the entire spectrum of waves from the electron cyclotron frequency down to the ion cyclotron frequency. The electric potential fluctuations of lower hybrid frequency were measured [3] and identified as electrostatic lower hybrid drift waves [E-LHDW]. In the present study the properties of elecromagnetic waves are investigated theoretically and compared with the recent experimental data from the MRX neutral sheet plasmas[4]. Also we will discuss physical mechanisms of the enhanced resistivity induced by the electromagnetic waves including magnetic lower hybrid waves [M-LHDW] and Whistler waves. This work is supported by DoE, NASA and NSF. 1. M. Yamada et al., Phys. Plasmas, vol.7, 1781, (2000) 2. R.L. Stenzel and J.M. Urrutia, Phys. Plasmasv.7, 4450, (2000) 3. T. Carter et al., Phys. Rev. Letts. v88, 15001 (2002) 4. H. Ji et al., This meeting (2002)

  3. Radio frequency (RF) time-of-flight ranging for wireless sensor networks

    NASA Astrophysics Data System (ADS)

    Thorbjornsen, B.; White, N. M.; Brown, A. D.; Reeve, J. S.

    2010-03-01

    Position information of nodes within wireless sensor networks (WSNs) is often a requirement in order to make use of the data recorded by the sensors themselves. On deployment the nodes normally have no prior knowledge of their position and thus a locationing mechanism is required to determine their positions. In this paper, we describe a method to determine the point-to-point range between sensor nodes as part of the locationing process. A two-way time-of-flight (TOF) ranging scheme is presented using narrow-band RF. The frequency difference between the transceivers involved with the point-to-point measurement is used to obtain a sub-clock TOF phase offset measurement in order to achieve high resolution TOF measurements. The ranging algorithm has been developed and prototyped on a TI CC2430 development kit with no additional hardware being required. Performance results have been obtained for the line-of-sight (LOS), non-line-of-sight (NLOS) and indoor conditions. Accuracy is typically better than 7.0 m RMS for the LOS condition over 250.0 m and 15.8 m RMS for the NLOS condition over 120.0 m using a 100 sample average. Indoor accuracy is measured to 1.7 m RMS using a 1000 sample average over 8.0 m. Ranging error is linear and does not increase with the increased transmitter-receiver distance. Our TOA ranging scheme demonstrates a novel system where resolution and accuracy are time dependent in comparison with alternative frequency-dependent methods using narrow-band RF.

  4. Doppler imaging with dual-detection full-range frequency domain optical coherence tomography

    PubMed Central

    Meemon, Panomsak; Lee, Kye-Sung; Rolland, Jannick P.

    2010-01-01

    Most of full-range techniques for Frequency Domain Optical Coherence Tomography (FD-OCT) reported to date utilize the phase relation between consecutive axial lines to reconstruct a complex interference signal and hence may exhibit degradation in either mirror image suppression performance or detectable velocity dynamic range or both when monitoring a moving sample such as flow activity. We have previously reported a technique of mirror image removal by simultaneous detection of the quadrature components of a complex spectral interference called a Dual-Detection Frequency Domain OCT (DD-FD-OCT) [Opt. Lett. 35, 1058-1060 (2010)]. The technique enables full range imaging without any loss of acquisition speed and is intrinsically less sensitive to phase errors generated by involuntary movements of the subject. In this paper, we demonstrate the application of the DD-FD-OCT to a phase-resolved Doppler imaging without degradation in either mirror image suppression performance or detectable velocity dynamic range that were observed in other full-range Doppler methods. In order to accommodate for Doppler imaging, we have developed a fiber-based DD-FD-OCT that more efficiently utilizes the source power compared with the previous free-space DD-FD-OCT. In addition, the velocity sensitivity of the phase-resolved DD-FD-OCT was investigated, and the relation between the measured Doppler phase shift and set flow velocity of a flow phantom was verified. Finally, we demonstrate the Doppler imaging using the DD-FD-OCT in a biological sample. PMID:21258488

  5. Comments on finite Larmor radius models for ion cyclotron range of frequencies heating in tokamaks

    SciTech Connect

    Phillips, C.K.; Wilson, J.R.; Hosea, J.C.; Majeski, R. ); Smithe, D.N. )

    1994-12-01

    The accuracy of standard finite Larmor radius (FLR) models for wave propagation in the ion cyclotron range of frequencies (ICRF) is compared against full hot plasma models. For multiple ion species plasmas, the FLR model is shown to predict the presence of a spurious second harmonic ion--ion type resonance between the second harmonic cyclotron layers of two ion species. It is shown explicitly here that the spurious resonance is an artifact of the FLR models and that no absorption occurs in the plasma as a result of this resonance.''

  6. Measurements of the complex permittivity of loss ceramics at microwave frequencies and over large temperature ranges

    SciTech Connect

    Meng, B.; Booske, J.; Cooper, R.; Klein, B.

    1995-12-31

    A system has been developed for measuring the complex permittivities of low loss ceramic materials at frequencies from 2 GHz to 20 GHz and over a temperature range 20-1000{degrees}C. The measurement technique involves a, modified version of tile conventional cavity perturbation method. This extended cavity perturbation technique is presented. Details of the design and fabrication of the circular cylindrical cavity and the input and output coupling transmission lines are discussed. Data are presented for an illustrative measurement of the complex microwave dielectric properties of NaCl single crystals between 20-400{degrees}C. The experimental results are in excellent agreement with theoretical models.

  7. Comments on finite Larmor radius models for ion cyclotron range of frequencies heating in tokamaks

    SciTech Connect

    Phillips, C.K.; Wilson, J.R.; Hosea, J.C.; Majeski, R.; Smithe, D.N.

    1994-06-01

    The accuracy of standard finite Larmor radius (FLR) models for wave propagation in the ion cyclotron range of frequencies (ICRF) is compared against full hot plasma models. For multiple ion species plasmas, the FLR model is shown to predict the presence of a spurious second harmonic ion-ion type resonance between the second harmonic cyclotron layers of two ion species. It is shown explicitly here that the spurious resonance is an artifact of the FLR models and that no absorption occurs in the plasma as a result of this ``resonance.``

  8. Active modulation of refractive index by stress in the terahertz frequency range: erratum.

    PubMed

    Song, Wei; Wang, Zhiyong

    2016-03-20

    A previous paper [Appl. Opt.52, 6364 (2013)APOPAI0003-693510.1364/AO.52.006364] presented experimental work on the stress-optical effect in the terahertz frequency range. Although the theoretical model of experimental measurement is correct, there are two errors in the original version. As a result, the presented experimentally measured value of the refractive index-stress coefficient A of polytetrafluoroethylene (PTFE) is erroneous. This erratum points out the errors in the original paper and reports the correct values. PMID:27140555

  9. Missing data outside the detector range. II. Application to time-frequency entanglement

    NASA Astrophysics Data System (ADS)

    Ray, Megan R.; van Enk, S. J.

    2013-12-01

    In a previous paper, we pointed out the problem of missing data outside the detector range for continuous-variable entanglement verification and quantum key distribution, and we provided a straightforward solution based on entropic separability criteria (as those work better than variance-based criteria). We apply that solution here to the verification of time-frequency entanglement of photon pairs, particularly to the quantum key distribution scheme proposed by Nunn [Opt. ExpressOPEXFF1094-408710.1364/OE.21.015959 21, 15959 (2013)]. We find that the scheme does lead to verifiable entanglement, but that transmission noise quickly destroys the ability to verify the entanglement.

  10. Electrodynamic properties of lead Zirconate-Titanate thin films in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Komandin, G. A.; Porodinkov, O. E.; Iskhakova, L. D.; Spektor, I. E.; Volkov, A. A.; Vorotilov, K. A.; Seregin, D. S.; Sigov, A. S.

    2014-11-01

    The transmission/reflection spectra of bilayer structures consisting of thin amorphous and polycrystalline Pb(Zr0.52Ti0.48)O3 ferroelectric films deposited on dielectric substrates of magnesium oxide MgO and sapphire α-Al2O3 were measured in the frequency range of 5-4000 cm-1. Based on these spectra and using the dispersion analysis method, the spectra of complex dielectric permittivity ɛ*(ν) and dynamic conductivity σ'(ν) of the films were simulated, the electrodynamic parameters of the films were determined, and the dielectric dispersion responsible for the formation of static permittivity was found.

  11. Frequency-selective design of wireless power transfer systems for controlled access applications

    NASA Astrophysics Data System (ADS)

    Maschino, Tyler Stephen

    Wireless power transfer (WPT) has become a common way to charge or power many types of devices, ranging from cell phones to electric toothbrushes. WPT became popular through the introduction of a transmission mode known as strongly coupled magnetic resonance (SCMR). This means of transmission is non-radiative and enables mid-range WPT. Shortly after the development of WPT via SCMR, a group of researchers introduced the concept of resonant repeaters, which allows power to hop from the source to the device. These repeaters are in resonance with the WPT system, which enables them to propagate the power wirelessly with minimal losses to the environment. Resonant repeaters have rekindled the dream of ubiquitous wireless power. Inherent risks come with the realization of such a dream. One of the most prominent risks, which we set out in this thesis to address, is that of accessibility to the WPT system. We propose the incorporation of a controlled access schema within a WPT system to prevent unwarranted use of wireless power. Our thesis discusses the history of electromagnetism, examines the inception of WPT via SCMR, evaluates recent developments in WPT, and further elaborates on the controlled access schema we wish to contribute to the field.

  12. Tunable femtosecond laser in the visible range with an intracavity frequency-doubled optical parametric oscillator

    NASA Astrophysics Data System (ADS)

    Zhu, Jiang-Feng; Xu, Liang; Lin, Qing-Feng; Zhong, Xin; Han, Hai-Nian; Wei, Zhi-Yi

    2013-05-01

    We demonstrated experimentally a synchronously pumped intracavity frequency-doubled femtosecond optical parametric oscillator (OPO) using a periodically-poled lithium niobate (PPLN) as the nonlinear material in combination with a lithium triborate (LBO) as the doubling crystal. A Kerr-lens-mode-locked (KLM) Ti:sapphire oscillator at the wavelength of 790 nm was used as the pump source, which was capable of generating pulses with a duration as short as 117 fs. A tunable femtosecond laser covering the 624-672 nm range was realized by conveniently adjusting the OPO cavity length. A maximum average output power of 260 mW in the visible range was obtained at the pump power of 2.2 W, with a typical pulse duration of 205 fs assuming a sech2 pulse profile.

  13. LTP in Hippocampal Area CA1 Is Induced by Burst Stimulation over a Broad Frequency Range Centered around Delta

    ERIC Educational Resources Information Center

    Grover, Lawrence M.; Kim, Eunyoung; Cooke, Jennifer D.; Holmes, William R.

    2009-01-01

    Long-term potentiation (LTP) is typically studied using either continuous high-frequency stimulation or theta burst stimulation. Previous studies emphasized the physiological relevance of theta frequency; however, synchronized hippocampal activity occurs over a broader frequency range. We therefore tested burst stimulation at intervals from 100…

  14. Propagation and dynamics of microwaves in the ECRH frequency range for the FRC

    NASA Astrophysics Data System (ADS)

    Ceccherini, Francesco; Galeotti, Laura; Brambilla, Marco; Barnes, Daniel C.; Yang, Xiaokang; TAE Team

    2014-10-01

    A previously developed FLR code for ICRH studies has been recently upgraded to include the frequency range of interest for ECRH applications. This full wave code is able to use very fine meshes (grid spacing down to 10-3 cm on a single cpu) so that even wavelengths very short with respect to the wall radius can be resolved well. The first wave propagation scheme we have addressed - and in part used for benchmark purposes also - is given by a source placed at a few cm from the first wall with a current oscillating in the longitudinal direction and an ordinary wave propagating in the radial direction. Such a wave propagates through the plasma until the required conditions for O-X-B mode conversion are encountered. The mode-converted electrostatic wave generated at the upper hybrid frequency behaves according to the expected dispersion relation and it is studied in terms of the launched frequency. Initial results indicate that in an elongated FRC configuration under study, the possibility to satisfy all conditions required to have electron absorption in the region beyond the SOL through the O-X-B conversion process strongly depends on the plasma radial profile. Details on this scheme and different examples will be presented.

  15. Characterization of a Prototype Radio Frequency Space Environment Path Emulator for Evaluating Spacecraft Ranging Hardware

    NASA Technical Reports Server (NTRS)

    Mitchell, Jason W.; Baldwin, Philip J.; Kurichh, Rishi; Naasz, Bo J.; Luquette, Richard J.

    2007-01-01

    The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility is evolving as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation and control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, have expanded to include S-band Radio Frequency (RF) modems for interspacecraft communication and ranging. To enable realistic simulations that require RF ranging sensors for relative navigation, a mechanism is needed to buffer the RF signals exchanged between spacecraft that accurately emulates the dynamic environment through which the RF signals travel, including the effects of the medium, moving platforms, and radiated power. The Path Emulator for Radio Frequency Signals (PERFS), currently under development at NASA GSFC, provides this capability. The function and performance of a prototype device are presented.

  16. Antiferromagnetic resonance and dielectric properties of rare-earth ferroborates in the submillimeter frequency range

    SciTech Connect

    Kuz'menko, A. M.; Mukhin, A. A. Ivanov, V. Yu.; Kadomtseva, A. M.; Lebedev, S. P.; Bezmaternykh, L. N.

    2011-07-15

    The magnetoresonance and dielectric properties of a number of crystals of a new family of multiferroics, namely, rare-earth ferroborates RFe{sub 3}(BO{sub 3}){sub 4} (R = Y, Eu, Pr, Tb, Tb{sub 0.25}Er{sub 0.75}), are studied in the sub-millimeter frequency range ({nu} = 3-20 cm{sup -1}). Ferroborates with R = Y, Tb, and Eu exhibit permittivity jumps at temperatures of 375, 198, and 58 K, respectively, which are caused by the R32 {yields} P3{sub 1}21 phase transition. Antiferromagnetic resonance (AFMR) modes in the subsystem of Fe{sup 3+} ions are detected in the range of anti-ferromagnetic ordering (T < T{sub N} = 30-40 K) in all ferroborates that have either an easy-plane (Y, Eu) or easy-axis (Pr, Tb, Tb{sub 0.25}Er{sub 0.75}) magnetic structure. The AFMR frequencies are found to depend strongly on the magnetic anisotropy of a rare-earth ion and its exchange interaction with the Fe subsystem, which determine the type of magnetic structure and the sign and magnitude of an effective anisotropy constant. The basic parameters of the magnetic interactions in these ferroborates are found, and the magnetoelectric contribution to AFMR is analyzed.

  17. Signature of forty years of artificial selection in U.S. Holstein cattle identified by long-range frequency analyses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Three groups of U.S. Holstein cattle were analyzed for selection signature of artificial selection since 1964 using long-range frequency measures. The three groups included Holsteins unselected since 1964, contemporary Holsteins, and an elite line of contemporary Holsteins. Long-range frequencies in...

  18. High-resolution frequency measurement method with a wide-frequency range based on a quantized phase step law.

    PubMed

    Du, Baoqiang; Dong, Shaofeng; Wang, Yanfeng; Guo, Shuting; Cao, Lingzhi; Zhou, Wei; Zuo, Yandi; Liu, Dan

    2013-11-01

    A wide-frequency and high-resolution frequency measurement method based on the quantized phase step law is presented in this paper. Utilizing a variation law of the phase differences, the direct different frequency phase processing, and the phase group synchronization phenomenon, combining an A/D converter and the adaptive phase shifting principle, a counter gate is established in the phase coincidences at one-group intervals, which eliminates the ±1 counter error in the traditional frequency measurement method. More importantly, the direct phase comparison, the measurement, and the control between any periodic signals have been realized without frequency normalization in this method. Experimental results show that sub-picosecond resolution can be easily obtained in the frequency measurement, the frequency standard comparison, and the phase-locked control based on the phase quantization processing technique. The method may be widely used in navigation positioning, space techniques, communication, radar, astronomy, atomic frequency standards, and other high-tech fields. PMID:24158281

  19. Orthogonal frequency-division multiplexing access (OFDMA) based wireless visible light communication (VLC) system

    NASA Astrophysics Data System (ADS)

    Sung, Jiun-Yu; Yeh, Chien-Hung; Chow, Chi-Wai; Lin, Wan-Feng; Liu, Yang

    2015-11-01

    An orthogonal frequency-division multiplexing access (OFDMA) based visible light communication (VLC) system is proposed in this paper. The architecture of the proposed system is divided into several VLC cells, which is defined in this paper. The deployment and upgrade of the system involve only simple combination of the VLC cells. Hence it is economically advantageous. To guarantee smooth communication, nearly equal data rate is provided at every location within the system with no concern on the system scale. The user location monitor strategy is also discussed to solve the region division issues. The characteristics of the proposed system are analyzed in detail in this paper. A one-dimensional experiment was demonstrated with 13.6 Mb/s data rate.

  20. Performance of a Frequency-Hopped Real-Time Remote Control System in a Multiple Access Scenario

    NASA Astrophysics Data System (ADS)

    Cervantes, Frank

    A recent trend is observed in the context of the radio-controlled aircrafts and automobiles within the hobby grade category and Unmanned Aerial Vehicles (UAV) applications moving to the well-known Industrial, Scientific and Medical (ISM) band. Based on this technological fact, the present thesis evaluates an individual user performance by featuring a multiple-user scenario where several point-to-point co-located real-time Remote Control (RC) applications operate using Frequency Hopping Spread Spectrum (FHSS) as a medium access technique in order to handle interference efficiently. Commercial-off-the-shelf wireless transceivers ready to operate in the ISM band are considered as the operational platform supporting the above-mentioned applications. The impact of channel impairments and of different critical system engineering issues, such as working with real clock oscillators and variable packet duty cycle, are considered. Based on the previous, simulation results allowed us to evaluate the range of variation for those parameters for an acceptable system performance under Multiple Access (MA) environments.

  1. Frequency-hopped multiple access communications with coding and side information

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Chao, Yuying

    1992-02-01

    The authors consider frequency-hopped spread-spectrum multiple-access communications using M-ary modulation and error-correction coding. The major concerns are multiple-access interference and the network capacity in terms of the number of users that can transmit simultaneously for a given level of codeword error probability. Block coding is studied in detail. The authors first consider the use of Q-ary Reed-Solomon (RS) codes in combination with M-ary modulation with mismatched alphabets so that Q is greater than M. It is shown that the network capacity is drastically reduced in comparison with the system with matched alphabets. As a remedy, the use of matched M-ary BCH codes is proposed as an alternative to mismatched RS codes. It is shown that when the number of users in the system is large, a BCH code outperforms an RX code with a comparable code rate and decoding complexity. The authors consider the use of a robust technique for generation of reliable side information based on a ratio-threshold test. They analyze its performance in conjunction with MFSK and error-erasure correction decoding. It is shown that this nonideal ratio-threshold method can increase the network capacity in comparison with the system with perfect side information.

  2. Frequency-division multiplexing in the terahertz range using a leaky-wave antenna

    NASA Astrophysics Data System (ADS)

    Karl, Nicholas J.; McKinney, Robert W.; Monnai, Yasuaki; Mendis, Rajind; Mittleman, Daniel M.

    2015-11-01

    The idea of using radiation in the 0.1-1.0 THz range as carrier waves for free-space wireless communications has attracted growing interest in recent years, due to the promise of the large available bandwidth. Recent research has focused on system demonstrations, as well as the exploration of new components for modulation, beam steering and polarization control. However, the multiplexing and demultiplexing of terahertz signals remains an unaddressed challenge, despite the importance of such capabilities for broadband networks. Using a leaky-wave antenna based on a metal parallel-plate waveguide, we demonstrate frequency-division multiplexing and demultiplexing over more than one octave of bandwidth. We show that this device architecture offers a unique method for controlling the spectrum allocation, by variation of the waveguide plate separation. This strategy, which is distinct from those previously employed in either the microwave or optical regimes, enables independent control of both the centre frequency and bandwidth of multiplexed terahertz channels.

  3. Paternal kin recognition in the high frequency / ultrasonic range in a solitary foraging mammal

    PubMed Central

    2012-01-01

    Background Kin selection is a driving force in the evolution of mammalian social complexity. Recognition of paternal kin using vocalizations occurs in taxa with cohesive, complex social groups. This is the first investigation of paternal kin recognition via vocalizations in a small-brained, solitary foraging mammal, the grey mouse lemur (Microcebus murinus), a frequent model for ancestral primates. We analyzed the high frequency/ultrasonic male advertisement (courtship) call and alarm call. Results Multi-parametric analyses of the calls’ acoustic parameters and discriminant function analyses showed that advertisement calls, but not alarm calls, contain patrilineal signatures. Playback experiments controlling for familiarity showed that females paid more attention to advertisement calls from unrelated males than from their fathers. Reactions to alarm calls from unrelated males and fathers did not differ. Conclusions 1) Findings provide the first evidence of paternal kin recognition via vocalizations in a small-brained, solitarily foraging mammal. 2) High predation, small body size, and dispersed social systems may select for acoustic paternal kin recognition in the high frequency/ultrasonic ranges, thus limiting risks of inbreeding and eavesdropping by predators or conspecific competitors. 3) Paternal kin recognition via vocalizations in mammals is not dependent upon a large brain and high social complexity, but may already have been an integral part of the dispersed social networks from which more complex, kin-based sociality emerged. PMID:23198727

  4. Long range dependence in the high frequency USD/INR exchange rate

    NASA Astrophysics Data System (ADS)

    Kumar, Dilip

    2014-02-01

    Using high frequency data, this paper examines the long memory property in the unconditional and conditional volatility of the USD/INR exchange rate at different time scales using the Local Whittle (LW), the Exact Local Whittle (ELW) and the FIAPARCH models. Results indicate that the long memory property remains quite stable across different time scales for both unconditional and conditional volatility measures. Results from the non-overlapping moving window approach indicate that the extreme events (such as the subprime crisis and the European debt crisis) resulted in highly persistent behavior of the USD/INR exchange rate and thus lead to market inefficiency. This paper also examines the long memory property in the realized volatility based on different time scale data. Results indicate that the realized volatility measures based on different scales of the high frequency data exhibit a consistent and stable long memory property. However, the realized volatility measures based on daily data exhibit lower degree of long-range dependence. This study has implications for traders and investors (with different trading horizons) and can be helpful in predicting expected future volatility and in designing and implementing trading strategies at different time scales.

  5. Global Low Frequency Protein Motions in Long-Range Allosteric Signaling

    NASA Astrophysics Data System (ADS)

    McLeish, Tom; Rogers, Thomas; Townsend, Philip; Burnell, David; Pohl, Ehmke; Wilson, Mark; Cann, Martin; Richards, Shane; Jones, Matthew

    2015-03-01

    We present a foundational theory for how allostery can occur as a function of low frequency dynamics without a change in protein structure. Elastic inhomogeneities allow entropic ``signalling at a distance.'' Remarkably, many globular proteins display just this class of elastic structure, in particular those that support allosteric binding of substrates (long-range co-operative effects between the binding sites of small molecules). Through multi-scale modelling of global normal modes we demonstrate negative co-operativity between the two cAMP ligands without change to the mean structure. Crucially, the value of the co-operativity is itself controlled by the interactions around a set of third allosteric ``control sites.'' The theory makes key experimental predictions, validated by analysis of variant proteins by a combination of structural biology and isothermal calorimetry. A quantitative description of allostery as a free energy landscape revealed a protein ``design space'' that identified the key inter- and intramolecular regulatory parameters that frame CRP/FNR family allostery. Furthermore, by analyzing naturally occurring CAP variants from diverse species, we demonstrate an evolutionary selection pressure to conserve residues crucial for allosteric control. The methodology establishes the means to engineer allosteric mechanisms that are driven by low frequency dynamics.

  6. Fiber optic probe of free electron evanescent fields in the optical frequency range

    SciTech Connect

    So, Jin-Kyu MacDonald, Kevin F.; Zheludev, Nikolay I.

    2014-05-19

    We introduce an optical fiber platform which can be used to interrogate proximity interactions between free-electron evanescent fields and photonic nanostructures at optical frequencies in a manner similar to that in which optical evanescent fields are sampled using nanoscale aperture probes in scanning near-field microscopy. Conically profiled optical fiber tips functionalized with nano-gratings are employed to couple electron evanescent fields to light via the Smith-Purcell effect. We demonstrate the interrogation of medium energy (30–50 keV) electron fields with a lateral resolution of a few micrometers via the generation and detection of visible/UV radiation in the 700–300 nm (free-space) wavelength range.

  7. Filamentation instability of nonextensive current-driven plasma in the ion acoustic frequency range

    SciTech Connect

    Khorashadizadeh, S. M. Rastbood, E.; Niknam, A. R.

    2014-12-15

    The filamentation and ion acoustic instabilities of nonextensive current-driven plasma in the ion acoustic frequency range have been studied using the Lorentz transformation formulas. Based on the kinetic theory, the possibility of filamentation instability and its growth rate as well as the ion acoustic instability have been investigated. The results of the research show that the possibility and growth rate of these instabilities are significantly dependent on the electron nonextensive parameter and drift velocity. Besides, the increase of electrons nonextensive parameter and drift velocity lead to the increase of the growth rates of both instabilities. In addition, the wavelength region in which the filamentation instability occurs is more stretched in the presence of higher values of drift velocity and nonextensive parameter. Finally, the results of filamentation and ion acoustic instabilities have been compared and the conditions for filamentation instability to be dominant mode of instability have been presented.

  8. Virtual Acoustic Testing of Spacecraft Over a Broad Frequency Range Using FEM, BEM and Sea

    NASA Astrophysics Data System (ADS)

    Vansant, K.; Borello, G.; De Langhe, K.; Courjal, A.

    2012-07-01

    During launch, a spacecraft is exposed to high levels of structural and acoustical loading. Acceptance tests are carried out before actual launch mimicking these loading conditions to validate that vibration, force and stress levels, which could damage the payload and lead to mission failure, remain below the design envelopes. The acceptance tests themselves, carried out on the actual payload, imply a risk of overtesting. Simulation models make it possible to carry out these tests in the virtual world. They can be used to derive specifications for the desired shaker, loudspeaker or horn excitation signals and to upfront quantify the risk of overtesting. Simulation also allows to uncover and rectify flaws or sensitivities in the spacecraft design rather quickly and at a low cost. This paper will discuss several simulation models (FEM, BEM and SEA) which can be used to mimic an acoustic acceptance test for different frequency ranges of interest.

  9. Study of the dielectric properties of water in the frequency range 75-120 GHz

    NASA Astrophysics Data System (ADS)

    Furashov, N. I.; Dudin, V. E.; Sverdlov, B. A.

    2006-06-01

    We study experimentally the frequency dependences of the refractive index n and the absorption coefficient k of distilled, sea, and river water. The measurements were performed using a quasioptical device with a backward-wave oscillator as the radiation source and OAP-7 optical-acoustic receivers at a water temperature of 27°C in the cell. The quantities n and k were determined from the measured transmission and reflection coefficients of the cell with water by means of joint numerical solution of the equations for these quantities. For distilled water in the frequency range f = 75-120 GHz, we obtained n = 6.142-3.926 · 10-2f[GHz] + 1.307 · 10-4(f[GHz])2 and k = 3.607-2.101 · 10-2 f[GHz] + 5.252 · 10-5(f[GHz])2. On the whole, these data are in good agreement with the measurement results obtained by other authors at several frequencies of the indicated range and coincide with the calculation data based on the models by Meissner and Wentz and by Liebe et al. within the limits of the rms determination errors 0.05 and 0.02 for the parameters n and k, respectively. The values of n and k for different seawater samples and river water containing insoluble admixtures coincide with the values of these quantities for distilled water within the limits of the experimental measurement errors 3-5% and 1-2%, respectively. The dependences n(f) and k(f) obtained experimentally for seawater are compared with those calculated on the basis of the developed models. Measurements of the transmission spectrum of a cell with double distilled water were performed for low power density of radiation (less than µW/cm2) to reproduce the effect of water resonant transparency reported many times in the literature. Our measurements did not reveal any resonant features in the spectral behavior of the refractive index n and the absorption coefficient k of water and gave the same result as for a power density exceeding the threshold of appearance of this effect.

  10. Opto-electronic device for frequency standard generation and terahertz-range optical demodulation based on quantum interference

    DOEpatents

    Georgiades, N.P.; Polzik, E.S.; Kimble, H.J.

    1999-02-02

    An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies are disclosed. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100`s THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 {micro}m to 1.66 {micro}m for fiber optics can be accomplished with a nearly continuous frequency coverage. 7 figs.

  11. Opto-electronic device for frequency standard generation and terahertz-range optical demodulation based on quantum interference

    DOEpatents

    Georgiades, Nikos P.; Polzik, Eugene S.; Kimble, H. Jeff

    1999-02-02

    An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100's THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 .mu.m to 1.66 .mu.m for fiber optics can be accomplished with a nearly continuous frequency coverage.

  12. Speckle reduction in OCT using massively-parallel detection and frequency-domain ranging

    PubMed Central

    Desjardins, A. E.; Vakoc, B. J.; Tearney, G. J.; Bouma, B. E.

    2009-01-01

    Speckle noise significantly limits the information content provided by coherent optical imaging methods such as optical coherence tomography and its recent derivative, optical frequency-domain imaging (OFDI). In this paper, we demonstrate a novel OFDI system that simultaneously acquires hundreds of angularly resolved images, which can be compounded to reduce speckle noise. The system comprises an InGaAs line-scan camera and an interferometer, configured so that the elements of the detector array simultaneously capture light spanning a backscattering angular range of 32 degrees. On successive read-outs of the array, the wavelength of the laser source was stepped through a range of 130 nm centered at 1295 nm to concurrently generate 400 angle-resolved OFDI images. A theory of angle-resolved OFDI and the design equations of the system are presented. Incoherent averaging of the angle-resolved data is shown to yield substantial speckle reduction (as high as an 8 dB SNR improvement) in images of a tissue phantom and esophageal tissue ex vivo. PMID:19516630

  13. Expanding Hardware-in-the-Loop Formation Navigation and Control with Radio Frequency Crosslink Ranging

    NASA Technical Reports Server (NTRS)

    Mitchell, Jason W.; Barbee, Brent W.; Baldwin, Philip J.; Luquette, Richard J.

    2007-01-01

    The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility continues to evolve as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation, and control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, are reviewed with a focus on recent improvements. With the most recent improvement, in support of Technology Readiness Level (TRL) 6 testing of the Inter-spacecraft Ranging and Alarm System (IRAS) for the Magnetospheric Multiscale (MMS) mission, the FFTB has significantly expanded its ability to perform realistic simulations that require Radio Frequency (RF) ranging sensors for relative navigation with the Path Emulator for RF Signals (PERFS). The PERFS, currently under development at NASA GSFC, modulates RF signals exchanged between spacecraft. The RF signals are modified to accurately reflect the dynamic environment through which they travel, including the effects of medium, moving platforms, and radiated power.

  14. Development of a Radio Frequency Space Environment Path Emulator for Evaluating Spacecraft Ranging Hardware

    NASA Technical Reports Server (NTRS)

    Mitchell, Jason W.; Baldwin, Philip J.; Kurichh, Rishi; Naasz, Bo J.; Luquette, Richard J.

    2007-01-01

    The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility is evolving as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation and. control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, have expanded to include S-band Radio Frequency (RF) modems for inter-spacecraft communication and ranging. To enable realistic simulations that require RF ranging sensors for relative navigation, a mechanism is needed to buffer the RF signals exchanged between spacecraft that accurately emulates the dynamic environment through which the RF signals travel, including the effects of medium, moving platforms, and radiated power. The Path Emulator for RF Signals (PERFS), currently under development at NASA GSFC, provides this capability. The function and performance of a prototype device are presented.

  15. The possible meaning of the upper and lower alpha frequency ranges for cognitive and creative tasks.

    PubMed

    Petsche, H; Kaplan, S; von Stein, A; Filz, O

    1997-06-01

    This study is aimed at verifying the functional independence of two frequency bands within the alpha range. It is based on experiments that examined the role of these two hands with regard to the amount of local electrogenesis (amplitude) and the cooperation of brain areas (coherence) in mental tasks concerning: (1) visual perception and imagery; (2) listening to and composing music; (3) verbal and visual creativity; and (4) aspects of mood. In all experiments EEG were recorded for at least 1 min during each task, separated one from another by at rest periods of at least equal lengths. EEG electrodes were pasted according to the 10/20 system (averaged ear lobes as reference). After FFT power was calculated for all 19 electrodes, coherence was estimated for all possible electrode pairs (i.e. 171). This was done for six frequency ranges between 1.5 and 31.5 Hz, the alpha range having been divided into two (7.5-9 Hz and 9.5-12.5 Hz). The spectral parameters obtained during each task were compared with those of the merged EEG at rest, significant changes (P < or = 0.01-P < or = 0.05) were entered into schematic maps of the brain. Generally, fewer differences were found for amplitude than for coherence. In all four tasks concerning visual perception the clearest differences were found in single person studies. But also in group studies more or less distinct differences were found between alpha 1 and 2. Also in the series with music the two alpha bands did not behave uniformly, nor were uniform features found in the two series of musically trained and untrained subjects. Distinct discrepancies were also found in a verbal and visual imagery task. With respect to mood, only elevated mood was correlated with a decrease of coherence in alpha 2 and an increase of amplitude in alpha 1. This study though hinting at a different functional significance of these two alpha bands, however, does not allow to draw any conclusions as to their distinct functional meanings. Generally

  16. Experimental Study of High-Range-Resolution Medical Acoustic Imaging for Multiple Target Detection by Frequency Domain Interferometry

    NASA Astrophysics Data System (ADS)

    Kimura, Tomoki; Taki, Hirofumi; Sakamoto, Takuya; Sato, Toru

    2009-07-01

    We employed frequency domain interferometry (FDI) for use as a medical acoustic imager to detect multiple targets with high range resolution. The phase of each frequency component of an echo varies with the frequency, and target intervals can be estimated from the phase variance. This processing technique is generally used in radar imaging. When the interference within a range gate is coherent, the cross correlation between the desired signal and the coherent interference signal is nonzero. The Capon method works under the guiding principle that output power minimization cancels the desired signal with a coherent interference signal. Therefore, we utilize frequency averaging to suppress the correlation of the coherent interference. The results of computational simulations using a pseudoecho signal show that the Capon method with adaptive frequency averaging (AFA) provides a higher range resolution than a conventional method. These techniques were experimentally investigated and we confirmed the effectiveness of the proposed method of processing by FDI.

  17. Effective conductivity and permittivity of unsaturated porous materials in the frequency range 1 mHz–1GHz

    PubMed Central

    Revil, A

    2013-01-01

    A model combining low-frequency complex conductivity and high-frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low-frequency conductivity depends on pore water and surface conductivities. Surface conductivity is controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fp, which depends on the dynamic pore throat size Λ, the quadrature conductivity is frequency dependent. Between fp and a second critical frequency fd, the quadrature conductivity is generally well described by a plateau when clay minerals are present in the material. Clay-free porous materials with a narrow grain size distribution are described by a Cole-Cole model. The characteristic frequency fd controls the transition between double layer polarization and the effect of the high-frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponents m and n like the low-frequency electrical conductivity. The unified model is compared with various data sets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It could be therefore used to interpret induced polarization, induction-based electromagnetic methods, and ground penetrating radar data to characterize the vadose zone. PMID:23576823

  18. Multicolor photoacoustic imaging by a single transducer with piezoelectric copolymer film in a wide frequency range

    NASA Astrophysics Data System (ADS)

    Ohmori, Tsutomu; Ishihara, Miya; Tsujita, Kazuhiro; Bansaku, Isao; Kikuchi, Makoto

    2010-02-01

    We built a photoacoustic tomographic (PAT) imaging system by scanning a single detector (φ 3.5 mm) made of piezoelectric copolymer poly(vinylidene difluoride-trifluoroethylene), P(VDF-TrFE), which had been fabricated for diagnostic photoacoustic measurement of cartilage tissues in our group. The PAT images of a phantom were obtained at two excitation wavelength of 687.5 nm and 795 nm. The phantom was made of agar including a black hair and agarose gels dissolving indocyanine green (ICG) and methylene blue (MB). Laser pulses (685-900 nm) were generated from a Ti:Sappire tunable laser to excite ICG and MB molecules. The PAT image at 687.5 nm shows signals due to all absorption sources. This is good agreement with dimension of the phantom. The PAT image at 795 nm shows a strong signal due to the ICG-dyed gel and almost no signal due to the MB-dyed gel. This result indicated that absorption sources were extracted by excitation wavelength according to their absorption spectra. The signal/noise ratio of the PAT images were compared between the P(VDF-TrFE) transducer in our group and a PZT transducer (Parametrics V309, 5 MHz, φ 12.7 mm) which is commercially available. The P(VDF-TrFE) transducer was more sensitive by 9 times (120 times per area) than the PZT transducer. By using this imaging system with a P(VDF-TrFE) transducer which is highly sensitive in a wide frequency range, we will achieve frequency analysis of the PAT images to associate photoacoustic waveforms with physical properties of sample tissues.

  19. Development and Operation of the Lower Hybrid Range of Frequency System on JT-60U

    SciTech Connect

    Seki, M.; Ikeda, Y.; Maebara, S.; Moriyama, S.; Naito, O.; Anno, K.; Hiranai, S.; Shimono, M.; Shinozaki, S.; Terakado, M.; Yokokura, K.; Yamamoto, T.; Fujii, T.

    2002-09-15

    Development and operation of a lower hybrid range of frequency (LHRF) system for JT-60U are presented. The LHRF system was constructed in 1986 to study current drive and plasma heating at high injection power. Its main specifications are the total output power 24 MW with 24 high power klystrons, the frequency 1.74 to 2.23 GHz, and the injection power {approx}10 MW with three conventional antennas. To improve the antenna capabilities such as the current drive efficiency, N{sub //peak} controllability and the power injection properties, a 3-divided multi-junction type (CD1' launcher) and a 12-divided multi-junction type (CD2 launcher) are developed. The CD2 launcher can also reduce the number of the transmission lines to one fourth of the original system. The injection power {approx}7 MW is attained, and then the highest current drive efficiency 3.5 x 10{sup 19} m{sup -2}AW{sup -1} and the highest non-inductive driven current 3.6 MA are achieved. The high power klystron capable of the cathode-heater operation times more than 3000 hours is improved. The outgassing rate is estimated with the CD2 launcher as 1-10 x 10{sup -6} Pam{sup 3}/sm{sup 2}, which is sufficiently small not to need the vacuum pumping system for the launcher. Heat load onto the launcher due to the ripple enhanced banana drift loss is first observed in NBI or ICRF heating. From investigation on antenna-plasma coupling, the gas puffing improves distant coupling.

  20. The 110-GHz Electron Cyclotron Range of Frequency System on JT-60U: Design and Operation

    SciTech Connect

    Ikeda, Y.; Kasugai, A.; Moriyama, S.; Kajiwara, K.; Seki, M.; Tsuneoka, M.; Takahashi, K.; Anno, K.; Hamamatsu, K.; Hiranai, S.; Ikeda, Yu.; Imai, T.; Sakamoto, K.; Shimono, M.; Shinozaki, S.; Terakado, M.; Yamamoto, T.; Yokokura, K.; Fujii, T.

    2002-09-15

    The electron cyclotron range of frequency (ECRF) system was designed and operated on the JT-60U to locally heat and control plasmas. The frequency of 110 GHz was adopted to inject the fundamental O-mode from the low field side with an oblique injection angle. The system is composed of four 1 MW-level gyrotrons, four transmission lines, and two antennae. The gyrotron is featured by a collector potential depression (CPD) and a gaussian beam output through a diamond window. The CPD enables JAERI to drive the gyrotron under the condition of the main DC voltage of 60 kV without a thyristor regulation. The gaussian mode from the gyrotron is effectively transformed to HE{sub 11} mode in the 31.75 mm diameter corrugated waveguide. About 75% of the output power of the gyrotrons can be injected into plasmas through the waveguides about 60 m in length. There are two antennae to control the deposition position of the EC wave during a plasma discharge. One is connected with three RF lines to steer the EC beams in the poloidal direction. The other is to control the EC beam in the toroidal and poloidal directions by two steerable mirrors.On the operation in 2000, the power of 1.5 to 1.6 MW for 3 s was successfully injected into plasmas using three gyrotrons. Local profile control was demonstrated by using the antennae. This capability was devoted to improve the plasma performance such as high T{sub e} production more than 15 keV and suppression of the MHD activities. In 2001, the fourth gyrotron, whose structure was improved for long pulse operation, has been installed for a total injection power of {approx}3 MW.

  1. Blood optical properties at various glucose level values in THz frequency range

    NASA Astrophysics Data System (ADS)

    Gusev, S. I.; Borovkova, M. A.; Strepitov, M. A.; Khodzitsky, M. K.

    2015-07-01

    the patients. Most biomolecules have characteristic signature frequencies in the terahertz (THz) range, which can reveal their presence and determine the concentration. Therefore, this paper is intended to study the blood optical properties in the THz frequency range in order to determine THz radiation effect on blood. The main aim of this investigation is to determine the effect of blood glucose concentration on the blood optical properties. In the case if blood optical properties vary at different glucose concentrations having a proportional relationship between them, these results will confirm the possibility of development of non-invasive procedures for blood glucose level diagnostics.

  2. Higher-frequency extension of the gauging ranges of vector receivers in the nonuniform field of measuring chambers

    NASA Astrophysics Data System (ADS)

    Gordienko, V. A.; Goncharenko, B. I.; Zadorozhnyi, S. S.; Starkova, M. V.

    2012-09-01

    The paper discusses the frequency-dependent error of gauging acoustic receivers in the field of a standing wave and the fundamental possibility of extending the operating range of gauging of hydrophones toward high frequencies and finite-size vector receivers (acoustic pressure gradient receivers) in a vertical liquid column, oscillating in a small-volume cylindrical chamber.

  3. Fresh produce consumption and the association between frequency of food shopping, car access, and distance to supermarkets

    PubMed Central

    Gustat, Jeanette; O'Malley, Keelia; Luckett, Brian G.; Johnson, Carolyn C.

    2015-01-01

    Background Fresh fruit and vegetables are important components of a healthy diet. Distance to a supermarket has been associated with the ability to access fresh produce. Methods A randomly sampled telephone survey was conducted with the main shopper for 3000 households in New Orleans, Louisiana in 2011. Individuals were asked where and how often they shopped for groceries, frequency of consumption of a variety of foods, and whether they had access to a car. Bivariate models assessed the relationship between four outcomes: car access, distance to the store patronized by the respondent, number of monthly shopping trips, and daily servings of produce. Structural equation modeling (SEM) was used to distinguish direct and indirect effects. Results In bivariate models, car access was positively associated with number of shopping trips and produce consumption while distance was inversely associated with shopping trips. In SEM models, produce consumption was not associated with car access or distance, but to the number of monthly shopping trips. Conclusion The frequency of shopping is associated with car access but a further distance deters it. Access to stores closer to the shopper may promote more frequent shopping and consumption of produce. PMID:26844049

  4. Three dimensional ray tracing Jovian magnetosphere in the low frequency range

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.

    1982-01-01

    Ray tracing of the Jovian magnetosphere in the low frequency range (1+40 MHz) has resulted in a new understanding of the source mechanism for Io dependent decametric radiation (DAM). Our three dimensional ray tracing computer code has provided model DAM arcs at 10 deg. intervals of Io longitude source positions for the full 360 deg of Jovian system III longitude. In addition, particularly interesting arcs were singled out for detailed study and modelling. Dependent decametric radiation arcs are categorized according to curvature--the higher curvature arcs are apparently due to wave stimulation at a nonconstant wave normal angle, psi. The psi(f) relationship has a signature that is common to most of the higher curvature arcs. The low curvature arcs, on the other hand, are adequately modelled with a constant wave normal angle of close to 90 deg. These results imply that for higher curvature arcs observed for from Jupiter (to diminish spacecraft motion effects) the electrons providing the gyroemission are relativistically beamed.

  5. An Obliquely Propagating Electromagnetic Drift Instability in the Lower Hybrid Frequency Range

    SciTech Connect

    Hantao Ji; Russell Kulsrud; William Fox; Masaaki Yamada

    2005-06-10

    By employing a local two-fluid theory, we investigate an obliquely propagating electromagnetic instability in the lower hybrid frequency range driven by cross-field current or relative drifts between electrons and ions. The theory self-consistently takes into account local cross-field current and accompanying pressure gradients. It is found that the instability is caused by reactive coupling between the backward propagating whistler (fast) waves in the moving electron frame, and the forward propagating sound (slow) waves in the ion frame when the relative drifts are large. The unstable waves we consider propagate obliquely to the unperturbed magnetic field and have mixed polarization with significant electromagnetic components. A physical picture of the instability emerges in the limit of large wave number characteristic of the local approximation. The primary positive feedback mechanism is based on reinforcement of initial electron density perturbations by compression of electron fluid via induced Lorentz force. The resultant waves are qualitatively consistent with the measured electromagnetic fluctuations in reconnecting current sheet in a laboratory plasma.

  6. Observations of the radio noise background in the frequency range 150-180 kHz

    NASA Astrophysics Data System (ADS)

    Knowles, S. H.; Kelly, F. J.; Waltman, W. B.; Odenwald, S.

    1985-05-01

    Observations were made of the radio noise background in the frequency range 150-180 kHz to provide reference data for the design of the ground wave emergency network system. These observations were undertaken at Nanjemoy, Maryland, during early summer 1983 and included 41 days of data recording. The noise environment was found to be dominated by impulsive thunderstorm noise. A typical nighttime mean noise power spectral density was 1×10-15 W m-2 Hz-1 (noise factor of 107 dB above kT0), while a typical daytime level was at least 14 dB quieter. However, the daytime level was at times significantly higher, especially during the presence of a local thunderstorm front. During local thunderstorm activity, impulses with peak power spectral density of 1×10-14 W m-2 Hz-1 were observed frequently, while the most energetic pulse detected during our monitoring period had a peak power spectral density of 6.8×10-14 W m-2 Hz-1 (Fa = 125 dB). Sample amplitude probability distributions and time probability distributions are presented for day/quiet, night, and thunderstorm conditions. Agreement with the mean noise level predictions of CCIR report 322 is satisfactory within the accuracy limits of the CCIR data.

  7. Ion cyclotron range of frequencies heating and current drive in deuterium-tritium plasmas

    NASA Astrophysics Data System (ADS)

    Phillips, C. K.; Bell, M. G.; Bell, R.; Bretz, N.; Budny, R. V.; Darrow, D. S.; Grek, B.; Hammett, G.; Hosea, J. C.; Hsuan, H.; Ignat, D.; Majeski, R.; Mazzucato, E.; Nazikian, R.; Park, H.; Rogers, J. H.; Schilling, G.; Stevens, J. E.; Synakowski, E.; Taylor, G.; Wilson, J. R.; Zarnstorff, M. C.; Zweben, S. J.; Bush, C. E.; Goldfinger, R.; Jaeger, E. F.; Murakami, M.; Rasmussen, D.; Bettenhausen, M.; Lam, N. T.; Scharer, J.; Sund, R.; Sauter, O.

    1995-06-01

    The first experiments utilizing high-power radio waves in the ion cyclotron range of frequencies to heat deuterium-tritium (D-T) plasmas have been completed on the Tokamak Fusion Test Reactor [Fusion Technol. 21, 13 (1992)]. Results from the initial series of experiments have demonstrated efficient core second harmonic tritium (2ΩT) heating in parameter regimes approaching those anticipated for the International Thermonuclear Experimental Reactor [D. E. Post, Plasma Physics and Controlled Nuclear Fusion Research, Proceedings of the 13th International Conference, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 239]. Observations are consistent with modeling predictions for these plasmas. Efficient electron heating via mode conversion of fast waves to ion Bernstein waves has been observed in D-T, deuterium-deuterium (D-D), and deuterium-helium-4 (D-4He) plasmas with high concentrations of minority helium-3 (3He) (n3He/ne≳10%). Mode conversion current drive in D-T plasmas was simulated with experiments conducted in D-3He-4He plasmas. Results show a directed propagation of the mode converted ion Bernstein waves, in correlation with the antenna phasing.

  8. Ion cyclotron range of frequencies heating of plasma with small impurity production

    DOEpatents

    Ohkawa, Tihiro

    1987-01-01

    Plasma including plasma ions is magnetically confined by a magnetic field. The plasma has a defined outer surface and is intersected by resonance surfaces of respective common ion cyclotron frequency of a predetermined species of plasma ions moving in the magnetic field. A radio frequency source provides radio frequency power at a radio frequency corresponding to the ion cyclotron frequency of the predetermined species of plasma ions moving in the field at a respective said resonance surface. RF launchers coupled to the radio frequency source radiate radio frequency energy at the resonance frequency onto the respective resonance surface within the plasma from a plurality of locations located outside the plasma at such respective distances from the intersections of the respective resonance surface and the defined outer surface and at such relative phases that the resulting interference pattern provides substantially null net radio frequency energy over regions near and including substantial portions of the intersections relative to the radio frequency energy provided thereby at other portions of the respective resonance surface within the plasma.

  9. Two efficient methods for measuring hydrophone frequency response in the 100 kHz to 2 MHz range

    NASA Astrophysics Data System (ADS)

    Harris, G. R.; Maruvada, S.; Gammell, P. M.

    2004-01-01

    As new medical applications of ultrasound emerge with operating frequencies in the hundreds of kilohertz to low megahertz region, it becomes more important to have convenient calibration methods for hydrophones in this frequency range. Furthermore, short diagnostic ultrasound pulses affected by finite amplitude distortion require that the hydrophone frequency response be known well below the center frequency. National standards laboratories can provide accurate calibration data at these frequencies, but the two methods now employed, laser interferometry and three-transducer reciprocity, are both single-frequency techniques, and they can be time-consuming procedures. Therefore, two efficient methods for generating a wideband acoustic pressure spectrum have been implemented to cover this frequency range. In one method a high-voltage pulse generator was used to excite a thick piezoelectric ceramic disk, producing a plane-wave acoustic pressure transient <1 µs in duration with peak amplitude of about 40 kPa. In the other technique, time delay spectrometry (TDS), a purpose-built 1-3 piezoelectric composite source transducer weakly focused at 20 cm was swept over the 0-2 MHz range. Its transmitting voltage response at 1 MHz was 11 kPa/V. The broadband pulse technique has the advantage of being simpler to implement, but TDS has a much greater signal-to-noise ratio because of the frequency-swept narrowband filter employed.

  10. Linearization of the Frequency Sweep of a Frequency-Modulated Continuous-Wave Semiconductor Laser Radar and the Resulting Ranging Performance

    NASA Astrophysics Data System (ADS)

    Karlsson, Christer J.; Olsson, Fredrik Å. A.

    1999-05-01

    The performance of a frequency-modulated continuous-wave (FMCW) semiconductor laser radar has been examined. Frequency modulation (linear chirp) has been studied experimentally in detail. To create a linear frequency sweep, we modified the modulating function according to the measured frequency response of the laser, using an arbitrary function generator. The measurements indicate the possibility of achieving a spectral width of the signal peak that is transform limited rather than limited by the frequency modulation response of the laser, which permits the use of a narrow detection bandwidth. The narrow width results in a relatively high signal-to-noise ratio for low output power and thus also in relatively long-range and high-range accuracy. We have performed measurements of a diffuse target to determine the performance of a test laser radar system. The maximum range, range accuracy, and speed accuracy for a semiconductor laser with an output power of 10 mW and a linewidth of 400 kHz are presented. The influence of the laser s output power and coherence length on the performance of a semiconductor-laser-based FMCW laser radar is discussed.

  11. Linearization of the frequency sweep of a frequency-modulated continuous-wave semiconductor laser radar and the resulting ranging performance.

    PubMed

    Karlsson, C J; Olsson, F A

    1999-05-20

    The performance of a frequency-modulated continuous-wave (FMCW) semiconductor laser radar has been examined. Frequency modulation (linear chirp) has been studied experimentally in detail. To create a linear frequency sweep, we modified the modulating function according to the measured frequency response of the laser, using an arbitrary function generator. The measurements indicate the possibility of achieving a spectral width of the signal peak that is transform limited rather than limited by the frequency modulation response of the laser, which permits the use of a narrow detection bandwidth. The narrow width results in a relatively high signal-to-noise ratio for low output power and thus also in relatively long-range and high-range accuracy. We have performed measurements of a diffuse target to determine the performance of a test laser radar system. The maximum range, range accuracy, and speed accuracy for a semiconductor laser with an output power of 10 mW and a linewidth of 400 kHz are presented. The influence of the laser's output power and coherence length on the performance of a semiconductor-laser-based FMCW laser radar is discussed. PMID:18319935

  12. Milliwatt-level frequency combs in the 8-14 μm range via difference frequency generation from an Er:fiber oscillator.

    PubMed

    Gambetta, Alessio; Coluccelli, Nicola; Cassinerio, Marco; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca; Marangoni, Marco

    2013-04-01

    We report on the generation of mid-infrared (mid-IR) pulses with a maximum average optical power of 4 mW and wide tunability in the 8-14 μm range via difference frequency generation (DFG) in GaSe from an Er:fiber laser oscillator. The DFG process is seeded with self-frequency shifted Raman solitons that are shown to be phase coherent within the whole tuning range, from 1.76 to 1.93 μm. Interference measurements between adjacent pulses at the idler wavelengths attest coherence transfer to the mid-IR. PMID:23546275

  13. Masking of short stimuli by noises with spiked spectra: II. Time summation and frequency selectivity of hearing in a narrow frequency range

    NASA Astrophysics Data System (ADS)

    Rimskaya-Korsakova, L. K.; Lalayants, M. R.; Supin, A. Ya.; Tavartkiladze, G. A.

    2011-03-01

    The thresholds of masking of short high-frequency pulses with either different durations (1.25-25 ms) and similar central frequency or different central frequencies (3.6-4.4 kHz) but similar durations were measured to reveal manifestations of the properties of peripheral encoding in auditory perception. Noises with a spiked amplitude spectrum structure were used as maskers. The central frequency and the frequency band of a masker were 4 and 1 kHz, respectively. The central frequencies of a stimulus and a masker being equal, the noise the central frequency of which coincided with the frequency corresponding to a dip of an indented spectrum was called an off(rip)-frequency masker. Owing to the off(rip)-masker, stimuli-induced masking thresholds were formed taking into account excitation in a narrow region of a basila membrane and auditory nerve fibers with characteristic frequencies from a narrow range. High-frequency pulses with an envelope in the form of the Gaussian function and sinusoidal filling were used as stimuli. At masker levels of 30 dB above the auditory threshold, frequencies of off(rip)-masker spectra spikes of 500-2000 Hz, and a central stimulus frequency of 4 kHz, the thresholds of tonal stimuli (25 ms in duration) masking in two out of three probationers were higher than the thresholds of masking of compact stimuli (1.25 ms in duration). In the third probationer, on the contrary, the thresholds of tonal stimuli masking were lower than the thresholds of compact stimuli masking. At masker levels of 50 dB, individual threshold differences disappeared. The obtained results were interpreted in the context of implementation of different methods of auditory encoding of the intensity. The methods were based on either the average frequency of auditory nerve pulsations or the number of fibers participating in the response. The interpretation was also carried out in the context of revealing manifestations of nonlinear properties of basila membrane displacements

  14. An acoustical assessment of pitch-matching accuracy in relation to speech frequency, speech frequency range, age and gender in preschool children

    NASA Astrophysics Data System (ADS)

    Trollinger, Valerie L.

    This study investigated the relationship between acoustical measurement of singing accuracy in relationship to speech fundamental frequency, speech fundamental frequency range, age and gender in preschool-aged children. Seventy subjects from Southeastern Pennsylvania; the San Francisco Bay Area, California; and Terre Haute, Indiana, participated in the study. Speech frequency was measured by having the subjects participate in spontaneous and guided speech activities with the researcher, with 18 diverse samples extracted from each subject's recording for acoustical analysis for fundamental frequency in Hz with the CSpeech computer program. The fundamental frequencies were averaged together to derive a mean speech frequency score for each subject. Speech range was calculated by subtracting the lowest fundamental frequency produced from the highest fundamental frequency produced, resulting in a speech range measured in increments of Hz. Singing accuracy was measured by having the subjects each echo-sing six randomized patterns using the pitches Middle C, D, E, F♯, G and A (440), using the solfege syllables of Do and Re, which were recorded by a 5-year-old female model. For each subject, 18 samples of singing were recorded. All samples were analyzed by the CSpeech for fundamental frequency. For each subject, deviation scores in Hz were derived by calculating the difference between what the model sang in Hz and what the subject sang in response in Hz. Individual scores for each child consisted of an overall mean total deviation frequency, mean frequency deviations for each pattern, and mean frequency deviation for each pitch. Pearson correlations, MANOVA and ANOVA analyses, Multiple Regressions and Discriminant Analysis revealed the following findings: (1) moderate but significant (p < .001) relationships emerged between mean speech frequency and the ability to sing the pitches E, F♯, G and A in the study; (2) mean speech frequency also emerged as the strongest

  15. The Influence of Fundamental Frequency and Sound Pressure Level Range on Breathing Patterns in Female Classical Singing

    ERIC Educational Resources Information Center

    Collyer, Sally; Thorpe, C. William; Callaghan, Jean; Davis, Pamela J.

    2008-01-01

    Purpose: This study investigated the influence of fundamental frequency (F0) and sound pressure level (SPL) range on respiratory behavior in classical singing. Method: Five trained female singers performed an 8-s messa di voce (a crescendo and decrescendo on one F0) across their musical F0 range. Lung volume (LV) change was estimated, and…

  16. On the minimum electron transport coefficients in tokamaks in the range of low collision frequencies

    SciTech Connect

    Merezhkin, V. G.

    2009-06-15

    There are two close empirical scalings, namely, the T-11 and neo-Alcator ones, that provide correct estimates for the energy confinement time in tokamaks in ohmic heating regimes in the linear part of the dependence {tau}{sub E}(n-bar{sub e}) in the range of low values of n-bar{sub e} and <{nu}{sub e}{sup *}> {<=} 1. The similar character of electron energy confinement in this range, which expands with increasing magnetic field B{sub 0}, has stimulated the search for dimensionless parameters and simple physical models that would explain the experimentally observed dependences {chi}{sub e} {approx} 1/n{sub e} and {tau}{sub Ee} {approx} n-bar{sub e}. In 1987, T. Okhawa showed that the experimental data were satisfactorily described by the formula {chi}{sub eperpendicular} = (c{sup 2}/{omega}{sub pe}{sup 2}){nu}{sub e}/qR, in deriving of which the random spatial leap along the radius r on the electron trajectory was assumed to be the same as that in the coefficient of the poloidal field diffusion, while the repetition rate of these leaps was assumed to be {nu}{sub e}/qR. In 2004, J. Callen took into account the decrease in the fraction of transient electrons with increasing toroidal ratio {epsilon} = r/R and corrected the coefficient c{sup 2}/{omega}{sub pe}{sup 2} in Okhawa equation by the factor {sigma}{sub ||} {sup Sp}/{sigma}{sub ||}{sup neo}. If one takes into account this correction and assumes that the frequency of the stochastic process is equal to the reciprocal of the half-period of rotation of a trapped electron along its banana trajectory, then the resulting expression for {chi}{sub eperpendicular} will coincide with the T-11 scaling: {chi}{sub e}{sup an} {infinity} {epsilon}{sup 1.75}(T{sub e}/A{sub i}){sup 0.5}/(n{sub e}qR) at Ai = 1. If the same stochastic process also involves ions, it may result in the opening of the orbit of a trapped ion at the distance {approx}(c/{omega}{sub pe})(m{sub i}/m{sub e}){sup 1/4}. In this case, the calculated coefficient

  17. Masking of low frequency information in short-range apparent motion.

    PubMed

    Cleary, R; Braddick, O J

    1990-01-01

    When an array of random dots is displaced, the ability to report the direction of apparent motion is subject to an upper spatial limit (dmax). Using spatially low-pass filtered random dot kinematograms we show that dmax is dependent on the upper cut-off frequency of the stimulus (Fh). The extent of this dependence is critically dependent on the size of the stimulus. Our results suggest a process whereby low spatial frequency motion information is masked by the presence of high spatial frequencies in the same region of the field, analogous to phenomena occurring in the perception of static form (e.g. the Abraham Lincoln effect). The effects of stimulus size on dmax, found for broad-band stimuli by ourselves and others, result from a loss of high frequency sensitivity at increased retinal eccentricities; this loss reduces the masking effect of high frequencies, as stimulus size increases. PMID:2309465

  18. Impact of contact and access resistances in graphene field-effect transistors on quartz substrates for radio frequency applications

    SciTech Connect

    Ramón, Michael E. E-mail: hemacp@utexas.edu; Movva, Hema C. P. E-mail: hemacp@utexas.edu; Fahad Chowdhury, Sk.; Parrish, Kristen N.; Rai, Amritesh; Akinwande, Deji; Banerjee, Sanjay K.; Magnuson, Carl W.; Ruoff, Rodney S.

    2014-02-17

    High-frequency performance of graphene field-effect transistors (GFETs) has been limited largely by parasitic resistances, including contact resistance (R{sub C}) and access resistance (R{sub A}). Measurement of short-channel (500 nm) GFETs with short (200 nm) spin-on-doped source/drain access regions reveals negligible change in transit frequency (f{sub T}) after doping, as compared to ∼23% f{sub T} improvement for similarly sized undoped GFETs measured at low temperature, underscoring the impact of R{sub C} on high-frequency performance. DC measurements of undoped/doped short and long-channel GFETs highlight the increasing impact of R{sub A} for larger GFETs. Additionally, parasitic capacitances were minimized by device fabrication using graphene transferred onto low-capacitance quartz substrates.

  19. Multi-service small-cell cloud wired/wireless access network based on tunable optical frequency comb

    NASA Astrophysics Data System (ADS)

    Xiang, Yu; Zhou, Kun; Yang, Liu; Pan, Lei; Liao, Zhen-wan; Zhang, Qiang

    2015-11-01

    In this paper, we demonstrate a novel multi-service wired/wireless integrated access architecture of cloud radio access network (C-RAN) based on radio-over-fiber passive optical network (RoF-PON) system, which utilizes scalable multiple- frequency millimeter-wave (MF-MMW) generation based on tunable optical frequency comb (TOFC). In the baseband unit (BBU) pool, the generated optical comb lines are modulated into wired, RoF and WiFi/WiMAX signals, respectively. The multi-frequency RoF signals are generated by beating the optical comb line pairs in the small cell. The WiFi/WiMAX signals are demodulated after passing through the band pass filter (BPF) and band stop filter (BSF), respectively, whereas the wired signal can be received directly. The feasibility and scalability of the proposed multi-service wired/wireless integrated C-RAN are confirmed by the simulations.

  20. Spatial Release From Masking in Simulated Cochlear Implant Users With and Without Access to Low-Frequency Acoustic Hearing

    PubMed Central

    Dietz, Mathias; Hohmann, Volker; Jürgens, Tim

    2015-01-01

    For normal-hearing listeners, speech intelligibility improves if speech and noise are spatially separated. While this spatial release from masking has already been quantified in normal-hearing listeners in many studies, it is less clear how spatial release from masking changes in cochlear implant listeners with and without access to low-frequency acoustic hearing. Spatial release from masking depends on differences in access to speech cues due to hearing status and hearing device. To investigate the influence of these factors on speech intelligibility, the present study measured speech reception thresholds in spatially separated speech and noise for 10 different listener types. A vocoder was used to simulate cochlear implant processing and low-frequency filtering was used to simulate residual low-frequency hearing. These forms of processing were combined to simulate cochlear implant listening, listening based on low-frequency residual hearing, and combinations thereof. Simulated cochlear implant users with additional low-frequency acoustic hearing showed better speech intelligibility in noise than simulated cochlear implant users without acoustic hearing and had access to more spatial speech cues (e.g., higher binaural squelch). Cochlear implant listener types showed higher spatial release from masking with bilateral access to low-frequency acoustic hearing than without. A binaural speech intelligibility model with normal binaural processing showed overall good agreement with measured speech reception thresholds, spatial release from masking, and spatial speech cues. This indicates that differences in speech cues available to listener types are sufficient to explain the changes of spatial release from masking across these simulated listener types. PMID:26721918

  1. Spatial Release From Masking in Simulated Cochlear Implant Users With and Without Access to Low-Frequency Acoustic Hearing.

    PubMed

    Williges, Ben; Dietz, Mathias; Hohmann, Volker; Jürgens, Tim

    2015-01-01

    For normal-hearing listeners, speech intelligibility improves if speech and noise are spatially separated. While this spatial release from masking has already been quantified in normal-hearing listeners in many studies, it is less clear how spatial release from masking changes in cochlear implant listeners with and without access to low-frequency acoustic hearing. Spatial release from masking depends on differences in access to speech cues due to hearing status and hearing device. To investigate the influence of these factors on speech intelligibility, the present study measured speech reception thresholds in spatially separated speech and noise for 10 different listener types. A vocoder was used to simulate cochlear implant processing and low-frequency filtering was used to simulate residual low-frequency hearing. These forms of processing were combined to simulate cochlear implant listening, listening based on low-frequency residual hearing, and combinations thereof. Simulated cochlear implant users with additional low-frequency acoustic hearing showed better speech intelligibility in noise than simulated cochlear implant users without acoustic hearing and had access to more spatial speech cues (e.g., higher binaural squelch). Cochlear implant listener types showed higher spatial release from masking with bilateral access to low-frequency acoustic hearing than without. A binaural speech intelligibility model with normal binaural processing showed overall good agreement with measured speech reception thresholds, spatial release from masking, and spatial speech cues. This indicates that differences in speech cues available to listener types are sufficient to explain the changes of spatial release from masking across these simulated listener types. PMID:26721918

  2. Rapid estimation of frequency response functions by close-range photogrammetry

    NASA Technical Reports Server (NTRS)

    Tripp, J. S.

    1985-01-01

    The accuracy of a rapid method which estimates the frequency response function from stereoscopic dynamic data is computed. It is shown that reversal of the order of the operations of coordinate transformation and Fourier transformation, which provides a significant increase in computational speed, introduces error. A portion of the error, proportional to the perturbation components normal to the camera focal planes, cannot be eliminated. The remaining error may be eliminated by proper scaling of frequency data prior to coordinate transformation. Methods are developed for least squares estimation of the full 3x3 frequency response matrix for a three dimensional structure.

  3. Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency

    NASA Technical Reports Server (NTRS)

    Flock, W. L.

    1981-01-01

    When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.

  4. A self-analyzing double-loop digital controller in laser frequency stabilization for inter-satellite laser ranging.

    PubMed

    Luo, Yingxin; Li, Hongyin; Yeh, Hsien-Chi; Luo, Jun

    2015-04-01

    We present a digital controller specially designed for laser frequency stabilization in the application of inter-satellite laser ranging. The prototype of controller is developed using field programmable gate arrays programmed with National Instruments LabVIEW software. The controller is flexible, self-analyzing, and easily optimized with build-in system analysis. Application and performance of the controller to a laser frequency stabilization system designed for spaceborne scientific missions are demonstrated. PMID:25933873

  5. The influence of interlayer exchange coupling in giant-magnetoresistive devices on spin diode effect in wide frequency range

    SciTech Connect

    Ziętek, Sławomir Skowroński, Witold; Wiśniowski, Piotr; Czapkiewicz, Maciej; Stobiecki, Tomasz; Ogrodnik, Piotr; Barnaś, Józef

    2015-09-21

    Spin diode effect in a giant magnetoresistive strip is measured in a broad frequency range, including resonance and off-resonance frequencies. The off-resonance dc signal is relatively strong and also significantly dependent on the exchange coupling between magnetic films through the spacer layer. The measured dc signal is described theoretically by taking into account magnetic dynamics induced by Oersted field created by an ac current flowing through the system.

  6. Tunable optical frequency comb enabled scalable and cost-effective multiuser orthogonal frequency-division multiple access passive optical network with source-free optical network units.

    PubMed

    Chen, Chen; Zhang, Chongfu; Liu, Deming; Qiu, Kun; Liu, Shuang

    2012-10-01

    We propose and experimentally demonstrate a multiuser orthogonal frequency-division multiple access passive optical network (OFDMA-PON) with source-free optical network units (ONUs), enabled by tunable optical frequency comb generation technology. By cascading a phase modulator (PM) and an intensity modulator and dynamically controlling the peak-to-peak voltage of a PM driven signal, a tunable optical frequency comb source can be generated. It is utilized to assist the configuration of a multiple source-free ONUs enhanced OFDMA-PON where simultaneous and interference-free multiuser upstream transmission over a single wavelength can be efficiently supported. The proposed multiuser OFDMA-PON is scalable and cost effective, and its feasibility is successfully verified by experiment. PMID:23027243

  7. Oscillating two stream instability of electromagnetic pump in the ion cyclotron range of frequency in a plasma

    SciTech Connect

    Ahmad, Nafis; Tripathi, V. K.; Rafat, M.; Husain, Mudassir M.

    2009-06-15

    An analytical formalism of oscillating two stream instability of a large amplitude electromagnetic wave in the ion cyclotron range of frequency in a plasma is developed. The instability produces electrostatic ion cyclotron sidebands and a driven low frequency mode. The nonlinear coupling arises primarily due to the motion of ions and is strong when the pump frequency is close to ion cyclotron frequency and the oscillatory ion velocity is a significant fraction of acoustic speed. For propagation perpendicular to the ambient magnetic field, the X-mode pump wave produces flute type perturbation with maximum growth rate at some specific wavelengths, which are three to four times larger than the ion Larmor radius. For propagation at oblique angles to ambient magnetic field, the ion cyclotron O-mode, the growth rate increases with the wave number of the low frequency mode.

  8. High Dynamic Range Observations of Solar Coronal Transients at Low Radio Frequencies with a Spectro-correlator

    NASA Astrophysics Data System (ADS)

    Hariharan, K.; Ramesh, R.; Kathiravan, C.; Abhilash, H. N.; Rajalingam, M.

    2016-02-01

    A new antenna system with a digital spectro-correlator that provides high temporal, spectral, and amplitude resolutions has been commissioned at the Gauribidanur Observatory near Bangalore in India. Presently, it is used for observations of the solar coronal transients in the scarcely explored frequency range ≈30-15 MHz. The details of the antenna system, the associated receiver setup, and the initial observational results are reported. Some of the observed transients exhibited quasi-periodicity in their time profiles at discrete frequencies. Estimates of the associated magnetic field strength (B) indicate that B ≈ 0.06-1 G at a typical frequency such as 19.5 MHz.

  9. Wide-frequency range, dynamic matching network and power system for the “Shoelace” radio frequency antenna on the Alcator C-Mod tokamak

    SciTech Connect

    Golfinopoulos, Theodore LaBombard, Brian; Burke, William; Parker, Ronald R.; Parkin, William; Woskov, Paul

    2014-04-15

    A wide-frequency range (50–300 kHz) power system has been implemented for use with a new RF antenna – the “Shoelace” antenna – built to drive coherent plasma fluctuations in the edge of the Alcator C-Mod tokamak. A custom, dynamically tunable matching network allows two commercial 1 kW, 50-Ω RF amplifiers to drive the low-impedance, inductive load presented by the antenna. This is accomplished by a discretely variable L-match network, with 81 independently selected steps available for each of the series and parallel legs of the matching configuration. A compact programmable logic device provides a control system that measures the frequency with better than 1 kHz accuracy and transitions to the correct tuning state in less than 1 ms. At least 85% of source power is dissipated in the antenna across the operational frequency range, with a minimum frequency slew rate of 1 MHz/s; the best performance is achieved in the narrower band from 80 to 150 kHz which is of interest in typical experiments. The RF frequency can be run with open-loop control, following a pre-programmed analog waveform, or phase-locked to track a plasma fluctuation diagnostic signal in real time with programmable phase delay; the amplitude control is always open-loop. The control waveforms and phase delay are programmed remotely. These tools have enabled first-of-a-kind measurements of the tokamak edge plasma system response in the frequency range and at the wave number at which coherent fluctuations regulate heat and particle transport through the plasma boundary.

  10. Wide-frequency range, dynamic matching network and power system for the "Shoelace" radio frequency antenna on the Alcator C-Mod tokamak.

    PubMed

    Golfinopoulos, Theodore; LaBombard, Brian; Burke, William; Parker, Ronald R; Parkin, William; Woskov, Paul

    2014-04-01

    A wide-frequency range (50-300 kHz) power system has been implemented for use with a new RF antenna - the "Shoelace" antenna - built to drive coherent plasma fluctuations in the edge of the Alcator C-Mod tokamak. A custom, dynamically tunable matching network allows two commercial 1 kW, 50-Ω RF amplifiers to drive the low-impedance, inductive load presented by the antenna. This is accomplished by a discretely variable L-match network, with 81 independently selected steps available for each of the series and parallel legs of the matching configuration. A compact programmable logic device provides a control system that measures the frequency with better than 1 kHz accuracy and transitions to the correct tuning state in less than 1 ms. At least 85% of source power is dissipated in the antenna across the operational frequency range, with a minimum frequency slew rate of 1 MHz/s; the best performance is achieved in the narrower band from 80 to 150 kHz which is of interest in typical experiments. The RF frequency can be run with open-loop control, following a pre-programmed analog waveform, or phase-locked to track a plasma fluctuation diagnostic signal in real time with programmable phase delay; the amplitude control is always open-loop. The control waveforms and phase delay are programmed remotely. These tools have enabled first-of-a-kind measurements of the tokamak edge plasma system response in the frequency range and at the wave number at which coherent fluctuations regulate heat and particle transport through the plasma boundary. PMID:24784610

  11. Wide-frequency range, dynamic matching network and power system for the "Shoelace" radio frequency antenna on the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Golfinopoulos, Theodore; LaBombard, Brian; Burke, William; Parker, Ronald R.; Parkin, William; Woskov, Paul

    2014-04-01

    A wide-frequency range (50-300 kHz) power system has been implemented for use with a new RF antenna - the "Shoelace" antenna - built to drive coherent plasma fluctuations in the edge of the Alcator C-Mod tokamak. A custom, dynamically tunable matching network allows two commercial 1 kW, 50-Ω RF amplifiers to drive the low-impedance, inductive load presented by the antenna. This is accomplished by a discretely variable L-match network, with 81 independently selected steps available for each of the series and parallel legs of the matching configuration. A compact programmable logic device provides a control system that measures the frequency with better than 1 kHz accuracy and transitions to the correct tuning state in less than 1 ms. At least 85% of source power is dissipated in the antenna across the operational frequency range, with a minimum frequency slew rate of 1 MHz/s; the best performance is achieved in the narrower band from 80 to 150 kHz which is of interest in typical experiments. The RF frequency can be run with open-loop control, following a pre-programmed analog waveform, or phase-locked to track a plasma fluctuation diagnostic signal in real time with programmable phase delay; the amplitude control is always open-loop. The control waveforms and phase delay are programmed remotely. These tools have enabled first-of-a-kind measurements of the tokamak edge plasma system response in the frequency range and at the wave number at which coherent fluctuations regulate heat and particle transport through the plasma boundary.

  12. A comparison of Frequency Domain Multiple Access (FDMA) and Time Domain Multiple Access (TDMA) approaches to satellite service for low data rate Earth stations

    NASA Technical Reports Server (NTRS)

    Stevens, G.

    1983-01-01

    A technological and economic assessment is made of providing low data rate service to small earth stations by satellite at Ka-band. Various Frequency Domain Multiple Access (FDMA) and Time Domain Multiple Access (TDMA) scenarios are examined and compared on the basis of cost to the end user. Very small stations (1 to 2 meters in diameter) are found not to be viable alternatives to available terrestrial services. However, medium size (3 to 5 meters) earth stations appear to be very competitive if a minimum throughput of about 1.5 Mbs is maintained. This constrains the use of such terminals to large users and shared use by smaller users. No advantage was found to the use of FDMA. TDMA had a slight advantage from a total system viewpoint and a very significant advantage in the space segment (about 1/3 the required payload weight for an equivalent capacity).

  13. Measurements of ICRF (ion cyclotron range of frequencies) loading with a ridged waveguide coupler on PLT

    SciTech Connect

    Greene, G.J.; Wilson, J.R.; Colestock, P.L.; Fortgang, C.M.; Hosea, J.C.; Hwang, D.Q.; Nagy, A.

    1987-11-01

    An ICRF ridged waveguide coupler has been installed on PLT for measurements of plasma loading. The coupler was partially filled with TiO/sub 2/ dielectric in order to sufficiently lower the cutoff frequency and utilized a tapered ridge for improved matching. Vacuum field measurements indicated a single propagating mode in the coupler and emphasized the importance of considering the fringing fields at the mouth of the waveguide. Low power experiments were carried out at 72.6 and 95.0 MHz without any external impedance matching network. Plasma loading increased rapidly as the face of the coupler approached the plasma, and, at fixed position, increased with line-averaged plasma density. At the lower frequency, the reflection coefficient exhibited a minimum (<8%) at a particular coupler position. At both frequencies, measurements indicated efficient power coupling to the plasma. Magnetic probe signals showed evidence of dense eigenmodes suggesting excitation of the fast wave. 24 refs., 13 figs.

  14. Efficient treatment of stacked metasurfaces for optimizing and enhancing the range of accessible optical functionalities

    NASA Astrophysics Data System (ADS)

    Menzel, C.; Sperrhake, J.; Pertsch, T.

    2016-06-01

    We present, discuss, and validate an adapted S -matrix formalism for an efficient, simplified treatment of stacked homogeneous periodically structured metasurfaces operated under normally incident plane wave excitation. The proposed formalism can be applied to any material system, arbitrarily shaped metaatoms, at any frequency, and with arbitrary subwavelength periods. Circumventing the introduction of any kind of effective parameters we directly use the S parameters of the individual metasurfaces to calculate the response of an arbitrary stack. In fact, the S parameters are the complex parameters of choice fully characterizing the homogeneous metasurfaces, in particular with respect to its polarization manipulating properties. Just as effective material parameters like the permittivity and the permeability or wave parameters like the propagation constant and the impedance, the stacking based upon S matrices can be applied as long as the individual layers are decoupled with respect to their near fields. This requirement eventually sets the limits for using the optical properties of the individual layers to calculate the response of the stacked system—this being the conceptual aim for any homogeneous metasurface or metamaterial layer and therefore the essence of what is eventually possible with homogeneous metasurfaces. As simple and appealing as this approach is, it is as powerful as well: Combining structured metasurfaces with each other as well as with isotropic, anisotropic, or chiral homogeneous layers is possible by simple semianalytical S -matrix multiplication. Hence, complex stacks and resonators can be set up, accurately treated and optimized with respect to their dispersive polarization sensitive optical functionality without the need for further rigorous full-wave simulations.

  15. Dynamics of chromatin accessibility and long-range interactions in response to glucocorticoid pulsing.

    PubMed

    Stavreva, Diana A; Coulon, Antoine; Baek, Songjoon; Sung, Myong-Hee; John, Sam; Stixova, Lenka; Tesikova, Martina; Hakim, Ofir; Miranda, Tina; Hawkins, Mary; Stamatoyannopoulos, John A; Chow, Carson C; Hager, Gordon L

    2015-06-01

    Although physiological steroid levels are often pulsatile (ultradian), the genomic effects of this pulsatility are poorly understood. By utilizing glucocorticoid receptor (GR) signaling as a model system, we uncovered striking spatiotemporal relationships between receptor loading, lifetimes of the DNase I hypersensitivity sites (DHSs), long-range interactions, and gene regulation. We found that hormone-induced DHSs were enriched within ± 50 kb of GR-responsive genes and displayed a broad spectrum of lifetimes upon hormone withdrawal. These lifetimes dictate the strength of the DHS interactions with gene targets and contribute to gene regulation from a distance. Our results demonstrate that pulsatile and constant hormone stimulations induce unique, treatment-specific patterns of gene and regulatory element activation. These modes of activation have implications for corticosteroid function in vivo and for steroid therapies in various clinical settings. PMID:25677181

  16. THz-range generation frequency growth in semiconductor superlattice coupled to external high-quality resonator

    NASA Astrophysics Data System (ADS)

    Makarov, Vladimir V.; Maksimenko, Vladimir A.; Khramova, Marina V.; Pavlov, Alexey N.; Hramov, Alexander E.

    2016-03-01

    We investigate effects of a linear resonator on spatial electron dynamics in semiconductor superlattice. We have shown that coupling the external resonant system to superlattice leads to occurrence of the additional area of negative differential conductance on the current-voltage characteristic, which does not occur in autonomous system. Furthermore, this region shows great increase of generation frequency, that contains practical interest.

  17. High-Precise Spectrometry of the Terahertz Frequency Range: The Methods, Approaches and Applications

    NASA Astrophysics Data System (ADS)

    Vaks, Vladimir

    2012-01-01

    In the paper we present a high precise THz technique (frequency synthesizers and spectrometer) and its applications for noninvasive medical diagnostics and security systems. The cornerstone of the presented devices is multipliers and mixers based on quantum superlattice structures. The multipliers based on superlattice structures are shown to be more effective than Schottky diodes and provide THz radiation up to 8.1 THz.

  18. New space research frequency band proposals in the 20- to 40.5-GHz range

    NASA Technical Reports Server (NTRS)

    Bishop, D. F.

    1991-01-01

    Future space research communications systems may require spectra above 20 GHz. Frequency bands above 20 GHz are identified that are suitable for space research. The selection of the proper bands depends on consideration of interference with other radio services, adequate bandwidths, link performance, and technical requirements for practical implementation.

  19. Three dimensional ray tracing of the Jovian magnetosphere in the low frequency range

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.

    1984-01-01

    Ray tracing studies of Jovian low frequency emissions were studied. A comprehensive three-dimensional ray tracing computer code for examination of model Jovian decametric (DAM) emission was developed. The improvements to the computer code are outlined and described. The results of the ray tracings of Jovian emissions will be presented in summary form.

  20. Extended parametric gain range in photonic crystal fibers with strongly frequency-dependent field distributions.

    PubMed

    Petersen, Sidsel R; Alkeskjold, Thomas T; Olausson, Christina B; Lægsgaard, Jesper

    2014-08-15

    The parametric gain range of a degenerate four-wave mixing process is determined in the undepleted pump regime. The gain range is considered with and without taking the mode field distributions of the four-wave mixing components into account. It is found that the mode field distributions have to be included to evaluate the parametric gain correctly in dispersion-tailored speciality fibers and that mode profile engineering can provide a way to increase the parametric gain range. PMID:25121901

  1. Cryocooled terahertz photoconductive detector system with background-limited performance in 1.5–4 THz frequency range

    SciTech Connect

    Aoki, Makoto; Hiromoto, Norihisa

    2015-10-15

    We describe a 4-K-cryocooled dual-band terahertz (THz) photoconductive detector system with background-limited performance. The detector system comprises two THz photoconductive detectors covering a response in a wide frequency range from 1.5 to 4 THz, low noise amplifiers, optical low-pass filters to eliminate input radiation of higher frequencies, and a mechanical 4 K Gifford-McMahon refrigerator that provides practical and convenient operation without a liquid He container. The electrical and optical performances of the THz detector system were evaluated at a detector temperature of 4 K under 300 K background radiation. We proved that the detector system can achieve background-limited noise-equivalent-power on the order of 10{sup −14} W/Hz{sup 1/2} in the frequency range from 1.5 to 4 THz even if the vibration noise of the mechanical refrigerator is present.

  2. Cryocooled terahertz photoconductive detector system with background-limited performance in 1.5-4 THz frequency range

    NASA Astrophysics Data System (ADS)

    Aoki, Makoto; Hiromoto, Norihisa

    2015-10-01

    We describe a 4-K-cryocooled dual-band terahertz (THz) photoconductive detector system with background-limited performance. The detector system comprises two THz photoconductive detectors covering a response in a wide frequency range from 1.5 to 4 THz, low noise amplifiers, optical low-pass filters to eliminate input radiation of higher frequencies, and a mechanical 4 K Gifford-McMahon refrigerator that provides practical and convenient operation without a liquid He container. The electrical and optical performances of the THz detector system were evaluated at a detector temperature of 4 K under 300 K background radiation. We proved that the detector system can achieve background-limited noise-equivalent-power on the order of 10-14 W/Hz1/2 in the frequency range from 1.5 to 4 THz even if the vibration noise of the mechanical refrigerator is present.

  3. Cryocooled terahertz photoconductive detector system with background-limited performance in 1.5-4 THz frequency range.

    PubMed

    Aoki, Makoto; Hiromoto, Norihisa

    2015-10-01

    We describe a 4-K-cryocooled dual-band terahertz (THz) photoconductive detector system with background-limited performance. The detector system comprises two THz photoconductive detectors covering a response in a wide frequency range from 1.5 to 4 THz, low noise amplifiers, optical low-pass filters to eliminate input radiation of higher frequencies, and a mechanical 4 K Gifford-McMahon refrigerator that provides practical and convenient operation without a liquid He container. The electrical and optical performances of the THz detector system were evaluated at a detector temperature of 4 K under 300 K background radiation. We proved that the detector system can achieve background-limited noise-equivalent-power on the order of 10(-14) W/Hz(1/2) in the frequency range from 1.5 to 4 THz even if the vibration noise of the mechanical refrigerator is present. PMID:26520978

  4. Investigation of the optical properties of normal fibroblasts and fibroblasts cultured with cancer cells in terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Strepitov, E. A.; Liakhov, E. P.; Balbekin, N. S.; Khodzitsky, M. K.; Smolyanskaya, O. A.; Trulyov, A. S.; Serebryakova, M. K.

    2015-07-01

    The optical properties of normal fibroblasts and fibroblasts cultured with cancer cells were studied in the frequency range of 0.2 - 1.0 THz. The results show the possibility to distinguish healthy cells from corrupted ones using their optical parameters.

  5. Multi-pulse frequency shifted (MPFS) multiple access modulation for ultra wideband

    DOEpatents

    Nekoogar, Faranak; Dowla, Farid U.

    2012-01-24

    The multi-pulse frequency shifted technique uses mutually orthogonal short duration pulses o transmit and receive information in a UWB multiuser communication system. The multiuser system uses the same pulse shape with different frequencies for the reference and data for each user. Different users have a different pulse shape (mutually orthogonal to each other) and different transmit and reference frequencies. At the receiver, the reference pulse is frequency shifted to match the data pulse and a correlation scheme followed by a hard decision block detects the data.

  6. Ion heating in the ion cyclotron range of frequencies in the Wisconsin Tokapole II

    SciTech Connect

    Biddle, A. P.

    1980-06-01

    Ion temperatures of 75 eV, a doubling of the ohmic heating temperature in a normal discharge, have been achieved using the fast magnetosonic wave heating at the second, third, and fourth harmonics of the cyclotron frequency in a single component hydrogen plasma. The wave launching structure is a single turn, shielded, insulated loop which constitutes the inductor of the rf source tank circuit. Power levels of 800 kW have been applied to the plasma for periods of up to 1.1 milliseconds. Good agreement has been found between theory and experiment for loading and wave propagation in the plasma for m = 0 and m = +1 modes. Eigenmodes have been observed by peaking of both the rf wave amplitude and the loading of the oscillator, as well as by oscillator frequency shifts imposed by their passage.

  7. Comment on "Mode Conversion of Waves In The Ion-Cyclotron Frequency Range in Magnetospheric Plasmas"

    SciTech Connect

    Kim, Eun; Johnson, J. R.

    2014-02-01

    Recently, Kazakov and Fulop [1] studied mode conversion (MC) at the ion-ion hybrid (IIH) resonance in planetary magnetospheric plasmas by simplifying the dispersion relation of the fast wave (FW) modes to describe a cutoff-resonance (CR) pair near the IIH resonance, which can be reduced to a Budden problem. They suggested that when the IIH resonance frequency (ωS) approaches the crossover frequency (ωcr), and the parallel wavenumber (k∥) is close to the critical wavenumber k* ∥(ωS = ωcr), MC can be efficient for arbitrary heavy ion density ratios. In this Comment, we argue that (a) the FW dispersion relation cannot be simplified to the CR pair especially near ωcr because in many parameter regimes there is a cutoff-resonance-cutoff (CRC) triplet that completely changes the wave absorption; and (b) the maximum MC efficiency does not always occur near k∥ ≈ k*∥∥.

  8. Measurement of ion motional heating rates over a range of trap frequencies and temperatures

    NASA Astrophysics Data System (ADS)

    Bruzewicz, C. D.; Sage, J. M.; Chiaverini, J.

    2015-04-01

    We present measurements of the motional heating rate of a trapped ion at different trap frequencies and temperatures between ˜0.6 and 1.5 MHz and ˜4 and 295 K. Additionally, we examine the possible effect of adsorbed surface contaminants with boiling points below ˜105 ∘C by measuring the ion heating rate before and after locally baking our ion trap chip under ultrahigh vacuum conditions. We compare the heating rates presented here to those calculated from available electric-field noise models. We can tightly constrain a subset of these models based on their expected frequency and temperature scaling interdependence. Discrepancies between the measured results and predicted values point to the need for refinement of theoretical noise models in order to more fully understand the mechanisms behind motional trapped-ion heating.

  9. An objective approach to determining the weight ranges of prey preferred by and accessible to the five large African carnivores.

    PubMed

    Clements, Hayley S; Tambling, Craig J; Hayward, Matt W; Kerley, Graham I H

    2014-01-01

    Broad-scale models describing predator prey preferences serve as useful departure points for understanding predator-prey interactions at finer scales. Previous analyses used a subjective approach to identify prey weight preferences of the five large African carnivores, hence their accuracy is questionable. This study uses a segmented model of prey weight versus prey preference to objectively quantify the prey weight preferences of the five large African carnivores. Based on simulations of known predator prey preference, for prey species sample sizes above 32 the segmented model approach detects up to four known changes in prey weight preference (represented by model break-points) with high rates of detection (75% to 100% of simulations, depending on number of break-points) and accuracy (within 1.3±4.0 to 2.7±4.4 of known break-point). When applied to the five large African carnivores, using carnivore diet information from across Africa, the model detected weight ranges of prey that are preferred, killed relative to their abundance, and avoided by each carnivore. Prey in the weight ranges preferred and killed relative to their abundance are together termed "accessible prey". Accessible prey weight ranges were found to be 14-135 kg for cheetah Acinonyx jubatus, 1-45 kg for leopard Panthera pardus, 32-632 kg for lion Panthera leo, 15-1600 kg for spotted hyaena Crocuta crocuta and 10-289 kg for wild dog Lycaon pictus. An assessment of carnivore diets throughout Africa found these accessible prey weight ranges include 88±2% (cheetah), 82±3% (leopard), 81±2% (lion), 97±2% (spotted hyaena) and 96±2% (wild dog) of kills. These descriptions of prey weight preferences therefore contribute to our understanding of the diet spectrum of the five large African carnivores. Where datasets meet the minimum sample size requirements, the segmented model approach provides a means of determining, and comparing, the prey weight range preferences of any carnivore species. PMID

  10. An Objective Approach to Determining the Weight Ranges of Prey Preferred by and Accessible to the Five Large African Carnivores

    PubMed Central

    Clements, Hayley S.; Tambling, Craig J.; Hayward, Matt W.; Kerley, Graham I. H.

    2014-01-01

    Broad-scale models describing predator prey preferences serve as useful departure points for understanding predator-prey interactions at finer scales. Previous analyses used a subjective approach to identify prey weight preferences of the five large African carnivores, hence their accuracy is questionable. This study uses a segmented model of prey weight versus prey preference to objectively quantify the prey weight preferences of the five large African carnivores. Based on simulations of known predator prey preference, for prey species sample sizes above 32 the segmented model approach detects up to four known changes in prey weight preference (represented by model break-points) with high rates of detection (75% to 100% of simulations, depending on number of break-points) and accuracy (within 1.3±4.0 to 2.7±4.4 of known break-point). When applied to the five large African carnivores, using carnivore diet information from across Africa, the model detected weight ranges of prey that are preferred, killed relative to their abundance, and avoided by each carnivore. Prey in the weight ranges preferred and killed relative to their abundance are together termed “accessible prey”. Accessible prey weight ranges were found to be 14–135 kg for cheetah Acinonyx jubatus, 1–45 kg for leopard Panthera pardus, 32–632 kg for lion Panthera leo, 15–1600 kg for spotted hyaena Crocuta crocuta and 10–289 kg for wild dog Lycaon pictus. An assessment of carnivore diets throughout Africa found these accessible prey weight ranges include 88±2% (cheetah), 82±3% (leopard), 81±2% (lion), 97±2% (spotted hyaena) and 96±2% (wild dog) of kills. These descriptions of prey weight preferences therefore contribute to our understanding of the diet spectrum of the five large African carnivores. Where datasets meet the minimum sample size requirements, the segmented model approach provides a means of determining, and comparing, the prey weight range preferences of any carnivore

  11. Evaluation of range-separated hybrid density functionals for the prediction of vibrational frequencies, infrared intensities, and Raman activities†

    PubMed Central

    Jiménez-Hoyos, Carlos A.; Janesko, Benjamin G.

    2016-01-01

    We present an assessment of different density functionals, with emphasis on range-separated hybrids, for the prediction of fundamental and harmonic vibrational frequencies, infrared intensities, and Raman activities. Additionally, we discuss the basis set convergence of vibrational properties of H2O with long-range corrected hybrids. Our results show that B3LYP is the best functional for predicting vibrational frequencies (both fundamental and harmonic); the screened-PBE hybrid (HSE) density functional works best for infrared intensities, and the long-range corrected PBE (LC-ωPBE), M06-HF, and M06-L density functionals are almost as good as MP2 for predicting Raman activities. We show the predicted Raman spectrum of adenine as an example of a medium-size molecule where a DFT/Sadlej pVTZ calculation is affordable and compare our results against the experimental spectrum. PMID:18989473

  12. Optical heterodyning with a frequency difference of 1 THz in the 850-nm range.

    PubMed

    Acef, O; Nez, F; Rovera, G D

    1994-09-01

    We report our recent progress on detection of large frequency difference (up to 1.028 THz, Deltalambda = 2.5 nm) between two laser diodes at 852 nm, using a Schottky diode as harmonic mixer/detector. Using the 11th harmonic of a klystron operating at 93.5 GHz or the 991-GHz line of an optically pumped HCOOH far-infrared laser, we were able to observe a signal-to-noise ratio of 2 dB in a 1-MHz-resolution bandwidth. PMID:19855492

  13. Dielectric properties of aluminum silver alloy thin films in optical frequency range

    SciTech Connect

    Yang Guang; Sun Jingbo; Zhou Ji

    2011-06-15

    The dielectric properties of direct current (dc) magnetron sputtering aluminum silver alloy films in optical frequency have been quantitatively studied by variable angle spectroscopic ellipsometry. The structure and surface topography of the alloy films were characterized using scanning probe microscopy and x-ray diffraction. The Drude-Lorentz model was used to simulate the dielectric function of Al-Ag alloy films. Meanwhile, the effective medium theory has been utilized for the treatment of surface roughness. We found that the interband transition around 1.5 eV can be shifted through a variable annealing temperature and a changeable silver percentage of Al-Ag alloys.

  14. Motion artifacts in optical coherence tomography with frequency-domain ranging

    PubMed Central

    Yun, S. H.; Tearney, G. J.; de Boer, J. F.; Bouma, B. E.

    2009-01-01

    We describe results of theoretical and experimental investigations of artifacts that can arise in spectral-domain optical coherence tomography (SD-OCT) and optical frequency domain imaging (OFDI) as a result of sample or probe beam motion. While SD-OCT and OFDI are based on similar spectral interferometric principles, the specifics of motion effects are quite different because of distinct signal acquisition methods. These results provide an understanding of motion artifacts such as signal fading, spatial distortion and blurring, and emphasize the need for fast image acquisition in biomedical applications. PMID:19483816

  15. High resolution kilometric range optical telemetry in air by radio frequency phase measurement

    NASA Astrophysics Data System (ADS)

    Guillory, Joffray; Šmíd, Radek; García-Márquez, Jorge; Truong, Daniel; Alexandre, Christophe; Wallerand, Jean-Pierre

    2016-07-01

    We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances up to 1.2 km.

  16. High resolution kilometric range optical telemetry in air by radio frequency phase measurement.

    PubMed

    Guillory, Joffray; Šmíd, Radek; García-Márquez, Jorge; Truong, Daniel; Alexandre, Christophe; Wallerand, Jean-Pierre

    2016-07-01

    We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances up to 1.2 km. PMID:27475593

  17. Improving Processes of Mechanized Pulsed Arc Welding of Low-Frequency Range Variation of Mode Parameters

    NASA Astrophysics Data System (ADS)

    Saraev, Yu N.; Solodskiy, S. A.; Ulyanova, O. V.

    2016-04-01

    A new technology of low-frequency modulation of the arc current in MAG and MIG welding is presented. The technology provides control of thermal and crystallization processes, stabilizes the time of formation and crystallization of the weld pool. Conducting theoretical studies allowed formulating the basic criteria for obtaining strong permanent joints for high-duty structures, providing conditions for more equilibrium structure of the deposited metal and the smaller width of the HAZ. The stabilization of time of the formation and crystallization of the weld pool improves the formation of the weld and increases productivity in welding thin sheet metal.

  18. Electron beam excitation of upstream waves in the whistler mode frequency range

    NASA Technical Reports Server (NTRS)

    Wong, Hung K.; Smith, Charles W.

    1994-01-01

    We examine whistler mode instabilities arising from electron beams in interplanetary space at 1 AU. Both parallel and obliquely propagating solutions are considered. We demonstrate that the generation of two simultaneous whistler mode waves is possible, and even reasonably likely, for beam parameters frequently encountered upstream of the Earth's bow shock and at interplanetary shocks. We also explore the generation of left-hand polarized waves at whistler mode frequencies under these same conditions. We offer both parametric variations derived from numerical solutions of the various instabilities as well as an analytical treatment of the problem which succeeds in unifying the various numerical results.

  19. Plasma channel produced by femtosecond laser pulses as a medium for amplifying electromagnetic radiation of the subterahertz frequency range

    SciTech Connect

    Bogatskaya, A V; Volkova, E A; Popov, A M

    2013-12-31

    The electron energy distribution function in the plasma channel produced by a femtosecond laser pulse with a wavelength of 248 nm in atmospheric-pressure gases was considered. Conditions were determined whereby this channel may be employed for amplifying electromagnetic waves up to the terahertz frequency range over the energy spectrum relaxation time ∼10{sup -7} s. Gains were calculated as functions of time and radiation frequency. The effect of electron – electron collisions on the rate of relaxation processes in the plasma and on its ability to amplify the electromagnetic radiation was investigated. (interaction of laser radiation with matter)

  20. Study of transmission line attenuation in broad band millimeter wave frequency range

    NASA Astrophysics Data System (ADS)

    Pandya, Hitesh Kumar B.; Austin, M. E.; Ellis, R. F.

    2013-10-01

    Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.

  1. A new ionosphere-free ambiguity resolution method for long-range baseline with GNSS triple-frequency signals

    NASA Astrophysics Data System (ADS)

    Xu, Ying; Ji, Shengyue; Chen, Wu; Weng, Duojie

    2015-10-01

    New GNSS systems (i.e. GPS modernization, BeiDou, and Galileo) will provide multiple navigation signals for reliable navigation services. The triple or even multiple frequency signals are expected to bring great benefits to the ambiguity resolution (AR) over long-range baselines, which is always regarded as a huge challenge. Another issue in the long baseline AR is the unmodeled ionospheric delay, which is one of the major errors in ranging signals. A new triple-frequency, ionosphere-free technique for ambiguity resolution of long-range baseline is developed in this study. In this technique, the optimal observation combinations are chosen considering the effect of ionospheric delay. At the same time, using this technique, the double difference (DD) ionospheric delay is nullified in the ambiguity search process. The performance of the new technique is examined using the simulated GPS triple frequency data as well as the real BDS observation. Results show that the ambiguity can be fixed within 10 min for GPS and BDS long-range baselines with this new technique.

  2. Frequency and Fitness Consequences of Bacteriophage Φ6 Host Range Mutations

    PubMed Central

    Ford, Brian E.; Sun, Bruce; Carpino, James; Chapler, Elizabeth S.; Ching, Jane; Choi, Yoon; Jhun, Kevin; Kim, Jung D.; Lallos, Gregory G.; Morgenstern, Rachelle; Singh, Shalini; Theja, Sai; Dennehy, John J.

    2014-01-01

    Viruses readily mutate and gain the ability to infect novel hosts, but few data are available regarding the number of possible host range-expanding mutations allowing infection of any given novel host, and the fitness consequences of these mutations on original and novel hosts. To gain insight into the process of host range expansion, we isolated and sequenced 69 independent mutants of the dsRNA bacteriophage Φ6 able to infect the novel host, Pseudomonas pseudoalcaligenes. In total, we found at least 17 unique suites of mutations among these 69 mutants. We assayed fitness for 13 of 17 mutant genotypes on P. pseudoalcaligenes and the standard laboratory host, P. phaseolicola. Mutants exhibited significantly lower fitnesses on P. pseudoalcaligenes compared to P. phaseolicola. Furthermore, 12 of the 13 assayed mutants showed reduced fitness on P. phaseolicola compared to wildtype Φ6, confirming the prevalence of antagonistic pleiotropy during host range expansion. Further experiments revealed that the mechanistic basis of these fitness differences was likely variation in host attachment ability. In addition, using computational protein modeling, we show that host-range expanding mutations occurred in hotspots on the surface of the phage's host attachment protein opposite a putative hydrophobic anchoring domain. PMID:25409341

  3. Ion cyclotron range of frequencies heating and flow generation in deuterium{endash}tritium plasmas

    SciTech Connect

    Wilson, J.R.; Bell, R.E.; Bernabei, S.; Hill, K.; Hosea, J.C.; LeBlanc, B.; Majeski, R.; Nazikian, R.; Ono, M.; Phillips, C.K.; Schilling, G.; von Goeler, S.; Bush, C.E.; Hanson, G.R.

    1998-05-01

    Recent radio-frequency heating experiments on the Tokamak Fusion Test Reactor (TFTR) [Hawryluk {ital et al.}, Plasma Phys. Controlled Fusion {bold 33}, 1509 (1991)] have focused on developing tools for both pressure and current profile control in deuterium{endash}tritium (DT) plasmas. A new antenna was added to investigate pressure profile control utilizing direct ion Bernstein wave (IBW) heating. This was the first time direct IBW heating was explored on TFTR. Plasma heating and driven poloidal flows are observed. Previously heating and current drive via mode-converted IBW waves had been demonstrated in non-DT plasmas but efforts in DT plasmas had been unsuccessful. This lack of success had been ascribed to the presence of a small {sup 7}Li minority ion population. In the most recent experiments {sup 6}Li was used exclusively for machine conditioning and mode-conversion heating consistent with theory is now observed in DT plasmas. {copyright} {ital 1998 American Institute of Physics.}

  4. High power heating in the ion cyclotron range of frequencies in the Wisconsin Tokapole II

    SciTech Connect

    Biddle, A. P.; Sprott, J. C.

    1980-09-01

    Fast wave heating at the second, third, and fourth harmonics of the ion cyclotron resonance, and slow wave heating at the fundamental in a single ion species hydrogen plasma, are found to be in good agreement with warm plasma theory at rf power levels less than or equal to 130 kW. Ion heating is negligible off an eigenmode. Ion body temperatures are more than doubled to 75 eV from the 35 eV ohmically heated case with tails comprising 8% of the plasma at 320 eV. No deleterious effects except a non-disruptive 10% shortening of the discharge length caused by impurity influx are noted. A passive mode tracking technique allows approx. = 40% increase in power deposition in a passing eigenmode over that of a fixed frequency rf source. Ion temperatures are limited by charge exchange due to the < 50 eV central temperature and the small 13 cm radius current channel.

  5. Range-resolved interferometric signal processing using sinusoidal optical frequency modulation.

    PubMed

    Kissinger, Thomas; Charrett, Thomas O H; Tatam, Ralph P

    2015-04-01

    A novel signal processing technique using sinusoidal optical frequency modulation of an inexpensive continuous-wave laser diode source is proposed that allows highly linear interferometric phase measurements in a simple, self-referencing setup. Here, the use of a smooth window function is key to suppress unwanted signal components in the demodulation process. Signals from several interferometers with unequal optical path differences can be multiplexed, and, in contrast to prior work, the optical path differences are continuously variable, greatly increasing the practicality of the scheme. In this paper, the theory of the technique is presented, an experimental implementation using three multiplexed interferometers is demonstrated, and detailed investigations quantifying issues such as linearity and robustness against instrument drift are performed. PMID:25968772

  6. Frontside-micromachined planar piezoresistive vibration sensor: Evaluating performance in the low frequency test range

    SciTech Connect

    Zhang, Lan; Lu, Jian Takagi, Hideki; Maeda, Ryutaro

    2014-01-15

    Using a surface piezoresistor diffusion method and front-side only micromachining process, a planar piezoresistive vibration sensor was successfully developed with a simple structure, lower processing cost and fewer packaging difficulties. The vibration sensor had a large sector proof mass attached to a narrow flexure. Optimization of the boron diffusion piezoresistor placed on the edge of the narrow flexure greatly improved the sensitivity. Planar vibration sensors were fabricated and measured in order to analyze the effects of the sensor dimensions on performance, including the values of flexure width and the included angle of the sector. Sensitivities of fabricated planar sensors of 0.09–0.46 mV/V/g were measured up to a test frequency of 60 Hz. The sensor functioned at low voltages (<3 V) and currents (<1 mA) with a high sensitivity and low drift. At low background noise levels, the sensor had performance comparable to a commercial device.

  7. Dynamic shifts in the parameters of the traditional frequency range of the EEG during learning in dogs.

    PubMed

    Dumenko, V N

    1995-01-01

    The parameters of the electrical activity of various regions of the neocortex (NC) and the olfactory bulbs (OB) of dogs were studied by means of correlation-spectral analysis during the development of a food-dispenser paw pedal-pressing motor skill; a wide band of frequencies (1-100 Hz), which included both the traditional range (1-20 Hz) as well as high frequencies (HF), were used. Differences were demonstrated in the dynamics of the parameters in the NC and OB. The energy level of the potentials of the NC increased in the HF range (beta 3 and gamma), while in the OB it increased in the HF and alpha range. The coherence-phase characteristics of the NC potentials suggest that more stable (by comparison with resting wakefulness) temporal relationships between the oscillations not only within the limits of HF, but also in the alpha band, are formed in the presence of the developed skill. At the same time, greater phase shifts are characteristic for the interrelationships of the OB potentials and those of the NC, and the increase in coherence relates only to the HF range, whereas the oscillations of the traditional range are characterized by a decrease in coherence. The possible role of the alpha range (along with the HF) in the processing of information which supports appropriate behavior is stressed. PMID:8614481

  8. Beta and gamma frequency-range abnormalities in parkinsonian patients under cognitive sensorimotor task.

    PubMed

    Dushanova, Juliana; Philipova, Dolja; Nikolova, Gloria

    2010-06-15

    Parkinson's disease (PD) is a neurodegenerative disorder caused by a disruption of dopaminergic neurotransmission in the basal ganglia. Some of PD clinical symptoms are suggested to stem directly from the excessive synchrony between the basal ganglia and cortical circuits. Our present investigation explores the functional relationships between event-related desynchronization/synchronization (ERD/ERS) of beta and gamma band activity for idiopathic non-demented Parkinson's patients (PP) and control subjects (CS) during auditory discrimination tasks between two tone types (LT: 800 Hz, HT: 1000 Hz) within two post-stimulus intervals of 0-250 and 250-600 ms. Beta1 (13-20 Hz) ERD was found for both groups within both intervals more expressed in CS except for frontal beta1 synchronization in CS during the second interval. Beta2 (20-32 Hz) ERD was revealed in CS after both tones during both post-stimulus intervals. Beta2 ERS was only observed in PP. The most prominent beta2 ERS followed HT during the second interval. Gamma frequency (32-50 Hz) ERD was found in both groups except for fronto-parietal ERS for PP during the first interval after LT. During the second interval, either tone, we found prominent ERS for PP and ERD for CS everywhere except for a frontal ERS after HT. Deviations of the beta and gamma ERD/ERS for the PP compared with CS during the sensorimotor and cognitive processing are a clear evidence for disturbances in the temporal and regional integration of these frequency components and the relationships between cortical and the basal ganglia circuits in parkinsonism. PMID:20392453

  9. Low-frequency source for very long-range underwater communication.

    PubMed

    Mosca, Frédéric; Matte, Guillaume; Shimura, Takuya

    2013-01-01

    Very long-range underwater acoustic communication (UAC) is crucial for long cruising (>1000 km) autonomous underwater vehicles (AUVs). Very long-range UAC source for AUV must exhibit high electro-acoustic efficiency (>60%) and compactness. This paper describes the Janus-Hammer Bell (JHB) transducer that has been designed for this purpose and meets those requirements. The transducer works on the 450-550 Hz bandwidth and reaches source level above 200 dB (ref. 1 μPa at 1 m) with 1 kW excitation and full immersion capability. JHB source has been used for communication experiments by the Japanese institute for marine technology (Japan Agency for Marine-Earth Science and Technology) achieving a baud rate of 100 bits/s at 1000 km. PMID:23298019

  10. Transitions between various diffuse discharge modes in atmospheric-pressure helium in the medium-frequency range

    NASA Astrophysics Data System (ADS)

    Boisvert, J.-S.; Margot, J.; Massines, F.

    2016-08-01

    In this paper, we investigate DBDs in the medium frequency range (MF, 0.3–3 MHz). More precisely, for a 2 inter-dielectric gap in helium at atmospheric pressure, the frequency is varied from 1.0 to 2.7 MHz. The generated discharge shows similarities with both the low-frequency atmospheric-pressure glow discharge (APGD) and the atmospheric pressure capacitively coupled radio-frequency (CCRF) discharge. In the frequency range under investigation, two diffuse discharge modes can be observed depending on the voltage applied between the electrodes. At low applied voltage, the discharge emissions are barely visible and are concentrated in the center of the gas gap similarly to CCRF discharges in the Ω mode where the electron density is concentrated in the bulk. Ohmic heating is the main power transfer mechanism. At higher applied voltage, the discharge emissions are 10 times more intense and are closer to the dielectric surfaces similarly to the more common radio-frequency α mode. These two discharge modes can be observed in the same experimental conditions with the amplitude of the applied voltage as sole control parameter. The gas temperature obtained from N2 impurities rotational spectrum increases from room temperature to about 500 K while the power density rises from 10‑1 to 101 W cm‑3 when the applied voltage is increased. In addition, when the discharge transits back and forth from the Ω to the α mode, a hysteresis is observed. The transition from the Ω to the α mode occurs abruptly with a large RMS current increase while the transition from the α to the Ω mode is rather smooth with no significant discontinuity in the RMS current.

  11. Stroke frequency, but not swimming speed, is related to body size in free-ranging seabirds, pinnipeds and cetaceans

    PubMed Central

    Sato, Katsufumi; Watanuki, Yutaka; Takahashi, Akinori; Miller, Patrick J.O; Tanaka, Hideji; Kawabe, Ryo; Ponganis, Paul J; Handrich, Yves; Akamatsu, Tomonari; Watanabe, Yuuki; Mitani, Yoko; Costa, Daniel P; Bost, Charles-André; Aoki, Kagari; Amano, Masao; Trathan, Phil; Shapiro, Ari; Naito, Yasuhiko

    2006-01-01

    It is obvious, at least qualitatively, that small animals move their locomotory apparatus faster than large animals: small insects move their wings invisibly fast, while large birds flap their wings slowly. However, quantitative observations have been difficult to obtain from free-ranging swimming animals. We surveyed the swimming behaviour of animals ranging from 0.5 kg seabirds to 30 000 kg sperm whales using animal-borne accelerometers. Dominant stroke cycle frequencies of swimming specialist seabirds and marine mammals were proportional to mass−0.29 (R2=0.99, n=17 groups), while propulsive swimming speeds of 1–2 m s−1 were independent of body size. This scaling relationship, obtained from breath-hold divers expected to swim optimally to conserve oxygen, does not agree with recent theoretical predictions for optimal swimming. Seabirds that use their wings for both swimming and flying stroked at a lower frequency than other swimming specialists of the same size, suggesting a morphological trade-off with wing size and stroke frequency representing a compromise. In contrast, foot-propelled diving birds such as shags had similar stroke frequencies as other swimming specialists. These results suggest that muscle characteristics may constrain swimming during cruising travel, with convergence among diving specialists in the proportions and contraction rates of propulsive muscles. PMID:17476766

  12. Predicted and measured EMI shielding effectiveness of a metallic mesh coating on a sapphire window over a broad frequency range

    NASA Astrophysics Data System (ADS)

    Jacoby, Keith T.; Pieratt, Matthew W.; Halman, Jennifer I.; Ramsey, Keith A.

    2009-05-01

    Metallic mesh thin film coatings have been used for many years to provide electromagnetic interference (EMI) shielding on infrared windows and domes. The level of EMI shielding effectiveness (SE) of metallic mesh coatings when used in a high frequency application is understood and characterized. Conversely, the level of SE of these metallic mesh coatings when used in a low frequency application has been called into question. In a recent study, we applied an appropriately designed metallic mesh coating to a sapphire window, mounted that window in a fixture, and tested the SE of the window assembly over a frequency range that envelopes the various military platforms covered in MIL-STD-461 (10 kHz to 18 GHz) for a radiated emissions test. The test plan was devised in such a way as to independently assess the individual contributions of the aperture, the mounting, and the metallic mesh coating to the total shielding. The results of our testing will be described in this paper. Additionally, the test results will be compared to the predicted SE for both the aperture and the metallic mesh coated window in order to validate the predictive model. Finally, an assessment of the appropriateness of the use of metallic mesh coatings for EMI shielding in a low and/or broad range frequency application will be made.

  13. A MEMS Interface IC With Low-Power and Wide-Range Frequency-to-Voltage Converter for Biomedical Applications.

    PubMed

    Arefin, Md Shamsul; Redouté, Jean-Michel; Yuce, Mehmet Rasit

    2016-04-01

    This paper presents an interface circuit for capacitive and inductive MEMS biosensors using an oscillator and a charge pump based frequency-to-voltage converter. Frequency modulation using a differential crossed coupled oscillator is adopted to sense capacitive and inductive changes. The frequency-to-voltage converter is designed with a negative feedback system and external controlling parameters to adjust the sensitivity, dynamic range, and nominal point for the measurement. The sensitivity of the frequency-to-voltage converter is from 13.28 to 35.96 mV/MHz depending on external voltage and charging current. The sensitivity ranges of the capacitive and inductive interface circuit are 17.08 to 54.4 mV/pF and 32.11 to 82.88 mV/mH, respectively. A capacitive MEMS based pH sensor is also connected with the interface circuit to measure the high acidic gastric acid throughout the digestive tract. The sensitivity for pH from 1 to 3 is 191.4 mV/pH with 550 μV(pp) noise. The readout circuit is designed and fabricated using the UMC 0.18 μm CMOS technology. It occupies an area of 0.18 mm (2) and consumes 11.8 mW. PMID:26954843

  14. Study and development of a six port network analyzer in the 1-18 GHz frequency range

    NASA Astrophysics Data System (ADS)

    Bergeault, Eric

    A theoretical and experimental study for the realization of a six port analyzer to calibrate the components of the verification kit, used to evaluate the measurement accuracy of automated network analyzers, is presented. The detection is performed at the frequency of use, and the scattering parameters are determined in magnitude and phase by means of power measurements. The six port accuracy, realized in the 1 to 18 GHz frequency range, is limited by uncertainties in the power measurements. The detection law of the Schottky diodes used as power detectors, that relates the incident power level and the diode output voltage, is performed in situ. The characterization requires only two reference unknown test loads without any power measurement. The procedure is shown to be rather stable with frequency, so that a midband characterization is generally sufficient to provide enough accuracy in the whole frequency range. The measurement uncertainties due to the variation of the detector reflection coefficients with power, are estimated by determining the variations of the six port parameters. The principle of the six port compared to that of the heteordyne network analyzers is simpler, and it makes modeling and correcting systematic errors easier. Good agreement is found between the measurement results obtained with the dual six port and the other operating systems. Generally, the amplitude measurements are within a few thousands, while the phase measurement errors are below or around one degree for the parameters being measured.

  15. The mechanism of modulation of geoacoustic emission intensity by weak electromagnetic fields in the audio-frequency range

    NASA Astrophysics Data System (ADS)

    Gavrilov, V. A.

    2016-07-01

    We propose a physical mechanism explaining the mechanism of modulation of the geoacoustic emission intensity by an external electromagnetic field in the audio-frequency range, which was previously revealed as a result of borehole measurements at the Petropavlovsk-Kamchatskii geodynamic testing area. It was established that electric double layers (EDL) at the interface between solid and liquid phases in a fluidsaturated geological medium play a key role in the mechanism proposed.

  16. High-Power Electron Landau-Heating Experiments in the Lower Hybrid Frequency Range in a Tokamak Plasma

    NASA Astrophysics Data System (ADS)

    Porkolab, M.; Lloyd, B.; Takase, Y.; Bonoli, P.; Fiore, C.; Gandy, R.; Granetz, R.; Griffin, D.; Gwinn, D.; Lipschultz, B.; Marmar, E.; McCool, S.; Pachtman, A.; Pappas, D.; Parker, R.; Pribyl, P.; Rice, J.; Terry, J.; Texter, S.; Watterson, R.; Wolfe, S.

    1984-09-01

    The effectiveness of plasma heating by electron Landau interaction in the lower hybrid range of frequencies in tokamak plasmas is demonstrated. Upon injection of 850 kW of rf power at a density of n―e~=1.4×1014 cm-3, an electron temperature increase of 1.0 keV and an ion temperature increase of 0.8 keV was achieved. These results are compared with transport and ray-tracing code predictions.

  17. An experimental investigation of thermoacoustic lasers operating in audible frequency range

    NASA Astrophysics Data System (ADS)

    Kolhe, Sanket Anil

    Thermoacoustic lasers convert heat from a high-temperature heat source into acoustic power while rejecting waste heat to a low temperature sink. The working fluids involved can be air or noble gases which are nontoxic and environmentally benign. Simple in construction due to absence of moving parts, thermoacoustic lasers can be employed to achieve generation of electricity at individual homes, water-heating for domestic purposes, and to facilitate space heating and cooling. The possibility of utilizing waste heat or solar energy to run thermoacoustic devices makes them technically promising and economically viable to generate large quantities of acoustic energy. The research presented in this thesis deals with the effects of geometric parameters (stack position, stack length, tube length) associated with a thermoacoustic laser on the output sound wave. The effects of varying input power on acoustic output were also studied. Based on the experiments, optimum operating conditions were identified and qualitative and/or quantitative explanations were provided to justify our observations. It was observed that the maximum sound pressure level was generated for the laser with the stack positioned at a distance of quarter lengths of a resonator from the closed end. Higher sound pressure levels were recorded for the laser with longer stack lengths and longer resonator lengths. Efforts were also made to develop high-frequency thermoacoustic lasers.

  18. Occupational exposures to high frequency electromagnetic fields in the intermediate range ( >300 Hz-10 MHz).

    PubMed

    Floderus, Birgitta; Stenlund, Carin; Carlgren, Frank

    2002-12-01

    The aim of this study was to identify work situations with electromagnetic fields of 300 Hz-10 MHz and to characterize the occupational exposure. Work place investigations included descriptions of the work environment and physical measurements. We estimated electric (E) and magnetic (H) fields by spot measurements in air, by logged exposure data, and when possible, we recorded induced currents in limbs. The instruments used were Wandel and Golterman EFA-3, NARDA 8718, Holaday HI-3702. The exposure sources comprised five induction furnaces, seven induction heaters, one surface treatment equipment, four units of electronic article surveillance (EAS), and medical devices for surgery and muscle stimulation. The induction furnaces operated at 480 Hz-7 kHz, and the maximum values of logged data varied between 512-2,093 V/m (E field) and 10.5-87.3 A/m (H field). The induction heaters (3.8 kHz-1.25 MHz) also showed high maximum exposure values of both E and H fields. Three EAS units, an electromagnetic plate at a library, a luggage control unit, and an antitheft gate, showed E fields reaching 658-1,069 V/m. The H fields were comparatively lower, except for the antitheft gate (5 and 7.5 kHz) showing a maximum value of 27.2 A/m (recorded during repair). Induced currents of 5-13 mA were measured for the medical devices. The study improves the basis for an exposure assessment for epidemiological studies of long term effects of exposures to high frequency electromagnetic fields. PMID:12395411

  19. Low-frequency predictability of the Dynamical Extended-Range Forecast Experiment

    NASA Technical Reports Server (NTRS)

    Nogues-Peagle, Julia; Rodgers, Dennis A.; Mo, Kingtse C.

    1992-01-01

    The objective of the study was to analyze data from the Dynamical Extended-Range Forecast Experiment conducted from January 1986 to March 1987, and to evaluate differences between analysis and forecasts with emphasis on the tropical 30-50-day oscillation. The diagnostic toll used is the projection of analysis and forecast data onto the normal modes of a primitive equation model. Examination of zonal-wind anomalies in the tropics shows that the forecast model predicts propagation of intraseasonal variations more accurately for slow propagation rates. The forecast amplitude is generally weaker than the analyzed amplitude. Analyzed kinetic energy and error fields exhibit similar horizontal scales for internal and external modes. External Rossby-mode components maximize in the extratropics while Rossby internal modes exhibit patterns that extend over the entire globe.

  20. A Constant Energy-Per-Cycle Ring Oscillator Over a Wide Frequency Range for Wireless Sensor Nodes

    PubMed Central

    Lee, Inhee; Sylvester, Dennis; Blaauw, David

    2016-01-01

    This paper presents an energy-efficient oscillator for wireless sensor nodes (WSNs). It avoids short-circuit current by minimizing the time spent in the input voltage range from Vthn to [Vdd − |Vthp|]. A current-feeding scheme with gate voltage control enables the oscillator to operate over a wide frequency range. A test chip is fabricated in a 0.18 μm CMOS process. The measurements show that the proposed oscillator achieves a constant energy-per-cycle (EpC) of 0.8 pJ/cycle over the 21–60 MHz frequency range and is more efficient than a conventional current-starved ring oscillator (CSRO) below 300 kHz at 1.8 V supply voltage. As an application example, the proposed oscillator is implemented in a switched-capacitor DC–DC converter. The converter is 11%–56% more efficient for load power values ranging from 583 pW to 2.9 nW than a converter using a conventional CSRO. PMID:27546899

  1. Excitation of the surface flute waves in electron cyclotron frequency range by internal rotating electron beam in a coaxial waveguide

    NASA Astrophysics Data System (ADS)

    Blednov, O.; Girka, I.; Girka, V.; Pavlenko, I.; Sydora, R.

    2014-12-01

    The initial stage of interaction between a gyrating beam of electrons, which move along Larmor orbits in a narrow gap between a cylindrical plasma layer and an internal screen of a metal coaxial waveguide and electromagnetic eigen waves, is studied theoretically. These waves are extraordinary polarized ones; they propagate along the azimuthal angle across an axial external steady magnetic field in the electron cyclotron frequency range. The numerical analysis shows that the excitation process is stable enough in respect to changing plasma waveguide parameters. The wider the plasma layer, the broader the range of plasma waveguide parameters within which effective wave excitation takes place. The main influence on the excitation of these modes is performed by the applied axial magnetic field, namely: its increase leads to an increase of growth rate and a broadening of the range of the waveguide parameters within which wave excitation is effective.

  2. A reconfigurable multi-mode multi-band transmitter with integrated frequency synthesizer for short-range wireless communication

    NASA Astrophysics Data System (ADS)

    Nan, Qi; Fan, Chen; Lingwei, Zhang; Xiaoman, Wang; Baoyong, Chi

    2013-09-01

    A reconfigurable multi-mode direct-conversion transmitter (TX) with integrated frequency synthesizer (FS) is presented. The TX as well as the FS is designed with a flexible architecture and frequency plan, which helps to support all the 433/868/915 MHz ISM band signals, with the reconfigurable bandwidth from 250 kHz to 2 MHz. In order to save power and chip area, only one 1.8 GHz VCO is adopted to cover the whole frequency range. All the operation modes can be regulated in real time by configuring the integrated register-bank through an SPI interface. Implemented in 180 nm CMOS, the FS achieves a frequency coverage of 320-460 MHz and 620-920 MHz. The lowest phase noise can be -107 dBc/Hz at a 100 kHz offset and -126 dBc/Hz at a 1 MHz offset. The transmitter features a + 10.2 dBm peak output power with a +9.5 dBm 1-dB-compression point and 250 kHz/500 kHz/1 MHz/2 MHz reconfigurable signal bandwidth.

  3. Temperature and frequency characteristics of low-loss MnZn ferrite in a wide temperature range

    NASA Astrophysics Data System (ADS)

    Sun, Ke; Lan, Zhongwen; Yu, Zhong; Xu, Zhiyong; Jiang, Xiaona; Wang, Zihui; Liu, Zhi; Luo, Ming

    2011-05-01

    A low-loss Mn0.7Zn0.24Fe2.06O4 ferrite has been prepared by a solid-state reaction method. The MnZn ferrite has a high initial permeability, μi (3097), a high saturation induction, Bs (526 mT), a high Curie temperature, Tc (220 °C), and a low core loss, PL (≤ 415 kW/m3) in a wide temperature (25-120 °C) and frequency (10-100 kHz) range. As the temperature increases, an initial decrease followed by a subsequent increase of hysteresis loss, Ph, and eddy current loss, Pe is observed. Both Ph and Pe increase with increasing frequency. When f ≥ 300 kHz, a residual loss, Pr, appears. Pe increases with increasing temperature and frequency. The temperature and frequency dependence of Ph can be explained by irreversible domain wall movements, Pe by the skin effect, and Pr by domain wall resonance, respectively.

  4. In vivo intracardiac optical coherence tomography imaging through percutaneous access: toward image-guided radio-frequency ablation

    PubMed Central

    Wang, Hui; Kang, Wei; Carrigan, Thomas; Bishop, Austin; Rosenthal, Noah; Arruda, Mauricio; Rollins, Andrew M.

    2011-01-01

    Complete catheter-tissue contact and permanent tissue destruction are essential for efficient radio-frequency ablation (RFA) during cardiac arrhythmia treatment. Current methods of monitoring lesion formation are indirect and unreliable. The purpose of this study is to evaluate the feasibility of using optical coherence tomography (OCT) catheter to image endocardial wall in actively beating hearts through percutaneous access. We reported the first in vivo intracardiac OCT imaging through percutaneous access with a thin and flexible OCT catheter. This is a critical step toward image-guided RFA in a clinical setting. A cone-scanning forward-viewing OCT catheter was advanced into beating hearts through percutaneous access in four swine. The OCT catheter was steered by an introducer to touch the endocardial wall. We are able to acquire high quality OCT images in beating hearts, observe the polarization-related artifacts induced by the birefringence of myocardium, and readily evaluate catheter-tissue contact. The observations indicate that OCT could be a promising technique for in vivo guidance of RFA. PMID:22112101

  5. In vivo intracardiac optical coherence tomography imaging through percutaneous access: toward image-guided radio-frequency ablation

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Kang, Wei; Carrigan, Thomas; Bishop, Austin; Rosenthal, Noah; Arruda, Mauricio; Rollins, Andrew M.

    2011-11-01

    Complete catheter-tissue contact and permanent tissue destruction are essential for efficient radio-frequency ablation (RFA) during cardiac arrhythmia treatment. Current methods of monitoring lesion formation are indirect and unreliable. The purpose of this study is to evaluate the feasibility of using optical coherence tomography (OCT) catheter to image endocardial wall in actively beating hearts through percutaneous access. We reported the first in vivo intracardiac OCT imaging through percutaneous access with a thin and flexible OCT catheter. This is a critical step toward image-guided RFA in a clinical setting. A cone-scanning forward-viewing OCT catheter was advanced into beating hearts through percutaneous access in four swine. The OCT catheter was steered by an introducer to touch the endocardial wall. We are able to acquire high quality OCT images in beating hearts, observe the polarization-related artifacts induced by the birefringence of myocardium, and readily evaluate catheter-tissue contact. The observations indicate that OCT could be a promising technique for in vivo guidance of RFA.

  6. Frequency and Correlates of Service Access among Youth with Autism Transitioning to Adulthood

    PubMed Central

    Taylor, Julie Lounds; Henninger, Natalie A.

    2014-01-01

    This study examined service receipt and unmet service needs among youth with autism spectrum disorders (ASD) in their last year of high school, as well as the youth (intellectual disability, race/ethnicity, autism severity, comorbid psychiatric diagnoses, behavior problems, adaptive behavior) and family (income, parental health, parental depressive symptoms, parental anxiety) correlates of service access. Thirty-nine families of youth with ASD participated. Data were collected via parental interview/questionnaire and youth psychological evaluation. Results suggested that this sample was underserved relative to a nationally-representative cohort. Those with a comorbid psychiatric diagnosis and lower levels of adaptive behavior received more services. Greater unmet needs were reported for youth who were racial/ethnic minorities, who had more behavior problems, and whose parents had greater anxiety. PMID:25081594

  7. Experience using radio frequency laptops to access the electronic medical record in exam rooms.

    PubMed Central

    Dworkin, L. A.; Krall, M.; Chin, H.; Robertson, N.; Harris, J.; Hughes, J.

    1999-01-01

    Kaiser Permanente, Northwest, evaluated the use of laptop computers to access our existing comprehensive Electronic Medical Record in exam rooms via a wireless radiofrequency (RF) network. Eleven of 22 clinicians who were offered the laptops successfully adopted their use in the exam room. These clinicians were able to increase their exam room time with the patient by almost 4 minutes (25%), apparently without lengthening their overall work day. Patient response to exam room computing was overwhelmingly positive. The RF network response time was similar to the hardwired network. Problems cited by some laptop users and many of the eleven non-adopters included battery issues, different equipment layout and function, and inadequate training. IT support needs for the RF laptops were two to four times greater than for hardwired desktops. Addressing the reliability and training issues should increase clinician acceptance, making a successful general roll-out for exam room computing more likely. PMID:10566458

  8. Development of calibration techniques for ultrasonic hydrophone probes in the frequency range from 1 to 100 MHz

    PubMed Central

    Umchid, S.; Gopinath, R.; Srinivasan, K.; Lewin, P. A.; Daryoush, A. S.; Bansal, L.; El-Sherif, M.

    2009-01-01

    The primary objective of this work was to develop and optimize the calibration techniques for ultrasonic hydrophone probes used in acoustic field measurements up to 100 MHz. A dependable, 100 MHz calibration method was necessary to examine the behavior of a sub-millimeter spatial resolution fiber optic (FO) sensor and assess the need for such a sensor as an alternative tool for high frequency characterization of ultrasound fields. Also, it was of interest to investigate the feasibility of using FO probes in high intensity fields such as those employed in HIFU (High Intensity Focused Ultrasound) applications. In addition to the development and validation of a novel, 100 MHz calibration technique the innovative elements of this research include implementation and testing of a prototype FO sensor with an active diameter of about 10 μm that exhibits uniform sensitivity over the considered frequency range and does not require any spatial averaging corrections up to about 75 MHz. The results of the calibration measurements are presented and it is shown that the optimized calibration technique allows the sensitivity of the hydrophone probes to be determined as a virtually continuous function of frequency and is also well suited to verify the uniformity of the FO sensor frequency response. As anticipated, the overall uncertainty of the calibration was dependent on frequency and determined to be about ±12% (±1 dB) up to 40 MHz, ±20% (±1.5 dB) from 40 to 60 MHz and ±25% (±2 dB) from 60 to 100 MHz. The outcome of this research indicates that once fully developed and calibrated, the combined acousto-optic system will constitute a universal reference tool in the wide, 100 MHz bandwidth. PMID:19110289

  9. Vibroacoustics of the piano soundboard: (Non)linearity and modal properties in the low- and mid-frequency ranges

    NASA Astrophysics Data System (ADS)

    Ege, Kerem; Boutillon, Xavier; Rébillat, Marc

    2013-03-01

    The piano soundboard transforms the string vibration into sound and therefore, its vibrations are of primary importance for the sound characteristics of the instrument. An original vibro-acoustical method is presented to isolate the soundboard nonlinearity from that of the exciting device (here: a loudspeaker) and to measure it. The nonlinear part of the soundboard response to an external excitation is quantitatively estimated for the first time, at ≈-40 dB below the linear part at the ff nuance. Given this essentially linear response, a modal identification is performed up to 3 kHz by means of a novel high resolution modal analysis technique [K. Ege, X. Boutillon, B. David, High-resolution modal analysis, Journal of Sound and Vibration 325 (4-5) (2009) 852-869]. Modal dampings (which, so far, were unknown for the piano in this frequency range) are determined in the mid-frequency domain where FFT-based methods fail to evaluate them with an acceptable precision. They turn out to be close to those imposed by wood. A finite-element modelling of the soundboard is also presented. The low-order modal shapes and the comparison between the corresponding experimental and numerical modal frequencies suggest that the boundary conditions can be considered as blocked, except at very low frequencies. The frequency-dependency of the estimated modal densities and the observation of modal shapes reveal two well-separated regimes. Below ≈1 kHz, the soundboard vibrates more or less like a homogeneous plate. Above that limit, the structural waves are confined by ribs, as already noticed by several authors, and localised in restricted areas (one or a few inter-rib spaces), presumably due to a slightly irregular spacing of the ribs across the soundboard.

  10. Frequency interleaving towards spectrally efficient directly detected optical OFDM for next-generation optical access networks.

    PubMed

    Mehedy, Lenin; Bakaul, Masuduzzaman; Nirmalathas, Ampalavanapillai

    2010-10-25

    In this paper, we theoretically analyze and demonstrate that spectral efficiency of a conventional direct detection based optical OFDM system (DDO-OFDM) can be improved significantly using frequency interleaving of adjacent DDO-OFDM channels where OFDM signal band of one channel occupies the spectral gap of other channel and vice versa. We show that, at optimum operating condition, the proposed technique can effectively improve the spectral efficiency of the conventional DDO-OFDM system as much as 50%. We also show that such a frequency interleaved DDO-OFDM system, with a bit rate of 48 Gb/s within 25 GHz bandwidth, achieves sufficient power budget after transmission over 25 km single mode fiber to be used in next-generation time-division-multiplexed passive optical networks (TDM-PON). Moreover, by applying 64- quadrature amplitude modulation (QAM), the system can be further scaled up to 96 Gb/s with a power budget sufficient for 1:16 split TDM-PON. PMID:21164657

  11. Ultrastable optical frequency dissemination on a multi-access fibre network

    NASA Astrophysics Data System (ADS)

    Bercy, Anthony; Lopez, Olivier; Pottie, Paul-Eric; Amy-Klein, Anne

    2016-07-01

    We report a laboratory demonstration of the dissemination of an ultrastable optical frequency signal to two distant users simultaneously using a branching network. The ultrastable signal is extracted along a main fibre link; it is optically tracked by a narrow linewidth laser diode, which light is injected in a secondary link. The propagation noise of both links is actively compensated. We implement this scheme with two links of 50-km fibre spools, the extraction being set up at the mid-point of the main link. We show that the extracted signal at the end of the secondary link exhibits a fractional frequency instability of 1.4 × 10-15 at 1-s measurement time, almost equal to the 1.3 × 10-15 instability of the main link output end. The long-term instabilities are also very similar, at a level of 3-5 × 10-20 at 3 × 104-s integration time. We also show that the setting up of this extraction device, or of a simpler one, at the main link input, can test the proper functioning of the noise rejection on this main link. This work is a significant step towards a robust and flexible ultrastable network for multi-users dissemination.

  12. Rock Size-Frequency Distributions at the Mars Exploration Rover Landing Sites: Impact Hazard and Accessibility

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Matijevic, J. R.; DiMaggio, E. N.; Schroeder, R. D.

    2003-01-01

    The Viking and Mars Pathfinder landing sites and a wide variety of rocky locations on the Earth show size-frequency distributions that follow an exponential when expressed in cumulative fractional area covered by rocks of a given diameter or larger versus diameter plots. Mars lander rock distributions have been fit by an equation of the form: Fk(D) = k exp [-q(k) D], where Fk(D) is the cumulative fractional area covered by rocks of diameter D or larger, k is the total area covered by all rocks, and an exponential q(k) = 1.79 + 0.152/k, which governs how abruptly the area covered by rocks decreases with increasing diameter. These distributions form a family of noncrossing curves that flatten out at small rock diameter at a total rock abundance of 5-40%. Model rock size-frequency distributions indicate a low probability of impacting hazardous rocks during MER landing. Rocks large enough to analyze and abrade by the rover should be plentiful within an easy Sol's drive.

  13. Prediction of rain effects on earth-space communication links operating in the 10 to 35 GHz frequency range

    NASA Technical Reports Server (NTRS)

    Stutzman, Warren L.

    1989-01-01

    This paper reviews the effects of precipitation on earth-space communication links operating the 10 to 35 GHz frequency range. Emphasis is on the quantitative prediction of rain attenuation and depolarization. Discussions center on the models developed at Virginia Tech. Comments on other models are included as well as literature references to key works. Also included is the system level modeling for dual polarized communication systems with techniques for calculating antenna and propagation medium effects. Simple models for the calculation of average annual attenuation and cross-polarization discrimination (XPD) are presented. Calculation of worst month statistics are also presented.

  14. Numerical simulation of the electromagnetic fields excited by loop antennas in plasma in the whistler frequency range

    SciTech Connect

    Koldanov, V. A.; Korobkov, S. V.; Gushchin, M. E.; Kostrov, A. V.

    2011-08-15

    The electromagnetic fields excited by circular loop antennas in a magnetized plasma in the whistler frequency range are simulated by the finite-difference time-domain method. The spatial structure of quasi-monochromatic fields excited in the near- and far-field zones by an antenna with a harmonic current, as well as the dynamics of the electromagnetic field excited by an antenna with a current in the form of a single video pulse, is studied. Simulations performed for a uniform plasma and uniform ambient magnetic field agree well with the results of theoretical analysis and model laboratory experiments performed on large-scale plasma devices.

  15. Negative permittivity and permeability spectra of Cu/yttrium iron garnet hybrid granular composite materials in the microwave frequency range

    SciTech Connect

    Tsutaoka, Takanori Fukuyama, Koki; Kinoshita, Hideaki; Kasagi, Teruhiro; Yamamoto, Shinichiro; Hatakeyama, Kenichi

    2013-12-23

    The relative complex permittivity and permeability spectra of the coagulated copper and yttrium iron garnet (Cu/YIG) hybrid granular composite materials have been studied in the microwave range. The insulator to metal transition was observed at the percolation threshold of Cu particle content (φ{sub Cu} = 16.0 vol. %) in the electrical conductivity. In the percolation threshold, the low frequency plasmonic state caused by the metallic Cu particle networks was observed. The percolated Cu/YIG granular composites show simultaneous negative permittivity and permeability spectra under external magnetic fields.

  16. Wired/wireless access integrated RoF-PON with scalable generation of multi-frequency MMWs enabled by polarization multiplexed FWM in SOA.

    PubMed

    Xiang, Yu; Chen, Chen; Zhang, Chongfu; Qiu, Kun

    2013-01-14

    In this paper, we propose and demonstrate a novel integrated radio-over-fiber passive optical network (RoF-PON) system for both wired and wireless access. By utilizing the polarization multiplexed four-wave mixing (FWM) effect in a semiconductor optical amplifier (SOA), scalable generation of multi-frequency millimeter-waves (MMWs) can be provided so as to assist the configuration of multi-frequency wireless access for the wire/wireless access integrated ROF-PON system. In order to obtain a better performance, the polarization multiplexed FWM effect is investigated in detail. Simulation results successfully verify the feasibility of our proposed scheme. PMID:23389014

  17. Multiple fiber Bragg grating sensor network with a rapid response and wide spectral dynamic range using code division multiple access

    NASA Astrophysics Data System (ADS)

    Kim, Youngbok; Jeon, Sie-Wook; Park, Chang-Soo

    2011-05-01

    Fiber Bragg grating (FBG) sensor networks have been intensively researched in optical sensor area and it developed in wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies which was adopted for its interrogating many optical sensors. In particular, WDM technology can be easily employed to interrogate FBG sensor however, the number of FBG sensors is limited. On the other hand, the TDM technique can extremely expand the number of sensor because the FBG sensors have same center wavelength. However, it suffers from a reduced sensor output power due to low reflectivity of FBG sensor. In this paper, we proposed and demonstrated the FBG sensor network based on code division multiple access (CDMA) with a rapid response and wide spectral dynamic range. The reflected semiconductor optical amplifier (RSOA) as a light source was directly modulated by the generated pseudorandom binary sequence (PRBS) code and the modulated signal is amplified and goes through FBG sensors via circulator. When the modulated optical signal experienced FBG sensor array, the optical signal which was consistent with center wavelength of FBGs is reflected and added from each sensors. The added signal goes into dispersion compensating fiber (DCF) as a dispersion medium. After through the DCF, the optical signal is converted into electrical signal by using photodetector (PD). For separate individual reflected sensor signal, the sliding correlation method was used. The proposed method improves the code interference and it also has advantages such as a large number of sensors, continuously measuring individual sensors, and decreasing the complexity of the sensor network.

  18. Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5–10 GHz frequency range

    SciTech Connect

    Bonetti, Stefano Chen, Zhao; Kukreja, Roopali; Spoddig, Detlef; Schöppner, Christian; Meckenstock, Ralf; Ollefs, Katharina; Ney, Andreas; Pinto, Jude; Houanche, Richard; Frisch, Josef; Stöhr, Joachim; Dürr, Hermann A.; Ohldag, Hendrik

    2015-09-15

    We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme for studying high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes in the magnetization on short time scales and nanometer spatial dimensions is achieved by combining the excitation mechanism with single photon counting electronics that is locked to the synchrotron operation frequency. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with high spatial resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a ∼6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ∼0.1° amplitude at ∼9 GHz in a micrometer-sized cobalt strip.

  19. Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5-10 GHz frequency range

    NASA Astrophysics Data System (ADS)

    Bonetti, Stefano; Kukreja, Roopali; Chen, Zhao; Spoddig, Detlef; Ollefs, Katharina; Schöppner, Christian; Meckenstock, Ralf; Ney, Andreas; Pinto, Jude; Houanche, Richard; Frisch, Josef; Stöhr, Joachim; Dürr, Hermann A.; Ohldag, Hendrik

    2015-09-01

    We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme for studying high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes in the magnetization on short time scales and nanometer spatial dimensions is achieved by combining the excitation mechanism with single photon counting electronics that is locked to the synchrotron operation frequency. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with high spatial resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a ˜6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ˜0.1° amplitude at ˜9 GHz in a micrometer-sized cobalt strip.

  20. Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5-10 GHz frequency range.

    PubMed

    Bonetti, Stefano; Kukreja, Roopali; Chen, Zhao; Spoddig, Detlef; Ollefs, Katharina; Schöppner, Christian; Meckenstock, Ralf; Ney, Andreas; Pinto, Jude; Houanche, Richard; Frisch, Josef; Stöhr, Joachim; Dürr, Hermann A; Ohldag, Hendrik

    2015-09-01

    We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme for studying high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes in the magnetization on short time scales and nanometer spatial dimensions is achieved by combining the excitation mechanism with single photon counting electronics that is locked to the synchrotron operation frequency. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with high spatial resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a ∼6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ∼0.1° amplitude at ∼9 GHz in a micrometer-sized cobalt strip. PMID:26429444

  1. Study of the heating characteristics and mechanisms of magnetic nanoparticles over a wide range of frequencies and amplitudes of an alternating magnetic field

    NASA Astrophysics Data System (ADS)

    Seki, A.; Kita, E.; Isaka, D.; Kikuchi, Y.; Suzuki, K. Z.; Horiuchi, A.; Kishimoto, M.; Yanagihara, H.; Oda, T.; Ohkohchi, N.; Ikehata, H.; Nagano, I.

    2014-06-01

    An effective approach to gaining an understanding of the mechanism of heat generation for magnetic hyperthermia from nanomagnet suspensions is to perform heating tests over a wide frequency range. We constructed a heating test apparatus by using ferrite field cores with air gaps for low frequencies and solenoids for high frequencies. Magnetic field amplitudes up to 600 Oe (400 Oe) can be generated for frequencies lower than 500 kHz (800 kHz). Heat generation tests were performed for ferromagnetic nano-platelets and Co-doped Fe3O4 nanoparticles over a wide range of frequencies.

  2. Viscoelastic behavior over a wide range of time and frequency in tin alloys: SnCd and SnSb

    SciTech Connect

    Quackenbush, J.; Brodt, M.; Lakes, R.S.

    1996-08-01

    All materials exhibit some viscoelastic response, which can manifest itself as creep, relaxation, or, if the load is sinusoidal in time, a phase angle {delta} between stress and strain. Recently, a study of pure elements with low melting points, Cd, In, Pb, and Sn disclosed that cadmium exhibited a substantial loss tangent of 0.03 to 0.04 over much of the audio range of frequencies, combined with a moderate stiffness G = 20.7 GPa. Lead, by contrast, exhibited tan {delta} of 0.005 to 0.016 in the audio range. Indium exhibited a high loss tangent exceeding 0.1 at very low frequency. A eutectic alloy of indium and tin was found to exhibit substantial damping exceeding 0.1 below 0.1 Hz, and this alloy was used to make a composite exhibiting high stiffness and high damping. It is the purpose of this communication to present viscoelastic properties of two additional low melting point alloys, SnCd and SnSb. Both InSn and SnSb are used as solders. Although the melting point of Sb is 630.74 C, T{sub H} > 0.55 at ambient temperature for the alloy of SnSb (95 wt% Sn/5 wt% Sb) which melts near 240 C. Eutectic SnCd melts at 177 C so T{sub H} {approx} 0.65 at room temperature.

  3. Intermediate frequency band digitized high dynamic range radiometer system for plasma diagnostics and real-time Tokamak control

    SciTech Connect

    Bongers, W. A.; Beveren, V. van; Westerhof, E.; Goede, A. P. H.; Krijger, B.; Berg, M. A. van den; Graswinckel, M. F.; Schueller, F. C.; Thoen, D. J.; Nuij, P. J. W. M.; Baar, M. R. de; Donne, A. J. H.; Hennen, B. A.; Kantor, M.

    2011-06-15

    An intermediate frequency (IF) band digitizing radiometer system in the 100-200 GHz frequency range has been developed for Tokamak diagnostics and control, and other fields of research which require a high flexibility in frequency resolution combined with a large bandwidth and the retrieval of the full wave information of the mm-wave signals under investigation. The system is based on directly digitizing the IF band after down conversion. The enabling technology consists of a fast multi-giga sample analog to digital converter that has recently become available. Field programmable gate arrays (FPGA) are implemented to accomplish versatile real-time data analysis. A prototype system has been developed and tested and its performance has been compared with conventional electron cyclotron emission (ECE) spectrometer systems. On the TEXTOR Tokamak a proof of principle shows that ECE, together with high power injected and scattered radiation, becomes amenable to measurement by this device. In particular, its capability to measure the phase of coherent signals in the spectrum offers important advantages in diagnostics and control. One case developed in detail employs the FPGA in real-time fast Fourier transform (FFT) and additional signal processing. The major benefit of such a FFT-based system is the real-time trade-off that can be made between frequency and time resolution. For ECE diagnostics this corresponds to a flexible spatial resolution in the plasma, with potential application in smart sensing of plasma instabilities such as the neoclassical tearing mode (NTM) and sawtooth instabilities. The flexible resolution would allow for the measurement of the full mode content of plasma instabilities contained within the system bandwidth.

  4. Optimum rate Reed-Solomon codes for frequency-hopped spread-spectrum multiple-access communication systems

    NASA Astrophysics Data System (ADS)

    Kim, Sang W.; Stark, Wayne

    1989-02-01

    The authors consider a multiple-access frequency-hopped spread-spectrum communication system with Reed-Solomon codes. The performance measures of interest are an achieveable region and the channel throughput. The achieveable rate region is the set of all pairs of code rate and number of users for which communication is possible with error probability below a fixed value. The throughput measures the expected number of successful codeword transmissions per unit bandwidth. Two models of interference are considered. For these two models, the authors determine the optimal number of users for a given bandwidth and the optimal rate Reed-Solomon code that maximize the throughput. They also determine the achieveable region for these models.

  5. Robust rate-adaptive hybrid ARQ scheme for frequency-hopped spread-spectrum multiple-access communication systems

    NASA Astrophysics Data System (ADS)

    Bigloo, Amir M. Y.; Gulliver, T. Aaron; Wang, Q.; Bhargava, Vijay K.

    1994-06-01

    This paper considers the application of rate-adaptive coding (RAC) to a spread spectrum multiple access (SSMA) communication system. Specifically, RAC using a variable rate Reed-Solomon (RS) code with a single decoder is applied to frequency-hopped SSMA. We show that this combination can accommodate a larger number of users compared to that with conventional fixed-rate coding. This increase is a result of a reduction in the channel interference from other users. The penalty for this improvement in most cases is a slight increase in the delay (composed of propagation and decoding delay). The throughput and the undetected error probability for a Q-ary symmetric channel are analyzed, and performance results are presented.

  6. Design, performance, and grounding aspects of the International Thermonuclear Experimental Reactor ion cyclotron range of frequencies antenna

    SciTech Connect

    Durodié, F. Dumortier, P.; Vrancken, M.; Messiaen, A.; Huygen, S.; Louche, F.; Van Schoor, M.; Vervier, M.; Winkler, K.

    2014-06-15

    ITER's Ion Cyclotron Range of Frequencies (ICRF) system [Lamalle et al., Fusion Eng. Des. 88, 517–520 (2013)] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf of ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER's Vacuum Vessel (VV) ports. Each launcher is an array of 4 toroidal by 6 poloidal RF current straps specified to couple up to 20 MW in total to the plasma in the frequency range of 40 to 55 MHz but limited to a maximum system voltage of 45 kV and limits on RF electric fields depending on their location and direction with respect to, respectively, the torus vacuum and the toroidal magnetic field. A crucial aspect of coupling ICRF power to plasmas is the knowledge of the plasma density profiles in the Scrape-Off Layer (SOL) and the location of the RF current straps with respect to the SOL. The launcher layout and details were optimized and its performance estimated for a worst case SOL provided by the IO. The paper summarizes the estimated performance obtained within the operational parameter space specified by IO. Aspects of the RF grounding of the whole antenna PP to the VV port and the effect of the voids between the PP and the Blanket Shielding Modules (BSM) surrounding the antenna front are discussed. These blanket modules, whose dimensions are of the order of the ICRF wavelengths, together with the clearance gaps between them will constitute a corrugated structure which will interact with the electromagnetic waves launched by ICRF antennas. The conditions in which the grooves constituted by the clearance gaps between the blanket modules can become resonant are studied. Simple analytical models and numerical simulations show that mushroom type structures (with larger gaps at the back than at the front) can bring down the resonance frequencies, which could lead to large voltages in the gaps between the blanket modules and perturb the

  7. Design, performance, and grounding aspects of the International Thermonuclear Experimental Reactor ion cyclotron range of frequencies antenna

    NASA Astrophysics Data System (ADS)

    Durodié, F.; Dumortier, P.; Vrancken, M.; Messiaen, A.; Bamber, R.; Hancock, D.; Huygen, S.; Lockley, D.; Louche, F.; Maggiora, R.; Milanesio, D.; Nightingale, M. P. S.; Shannon, M.; Tigwell, P.; Van Schoor, M.; Vervier, M.; Wilson, D.; Winkler, K.

    2014-06-01

    ITER's Ion Cyclotron Range of Frequencies (ICRF) system [Lamalle et al., Fusion Eng. Des. 88, 517-520 (2013)] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf of ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER's Vacuum Vessel (VV) ports. Each launcher is an array of 4 toroidal by 6 poloidal RF current straps specified to couple up to 20 MW in total to the plasma in the frequency range of 40 to 55 MHz but limited to a maximum system voltage of 45 kV and limits on RF electric fields depending on their location and direction with respect to, respectively, the torus vacuum and the toroidal magnetic field. A crucial aspect of coupling ICRF power to plasmas is the knowledge of the plasma density profiles in the Scrape-Off Layer (SOL) and the location of the RF current straps with respect to the SOL. The launcher layout and details were optimized and its performance estimated for a worst case SOL provided by the IO. The paper summarizes the estimated performance obtained within the operational parameter space specified by IO. Aspects of the RF grounding of the whole antenna PP to the VV port and the effect of the voids between the PP and the Blanket Shielding Modules (BSM) surrounding the antenna front are discussed. These blanket modules, whose dimensions are of the order of the ICRF wavelengths, together with the clearance gaps between them will constitute a corrugated structure which will interact with the electromagnetic waves launched by ICRF antennas. The conditions in which the grooves constituted by the clearance gaps between the blanket modules can become resonant are studied. Simple analytical models and numerical simulations show that mushroom type structures (with larger gaps at the back than at the front) can bring down the resonance frequencies, which could lead to large voltages in the gaps between the blanket modules and perturb the RF

  8. A detailed comparison of antenna impedance measurements on ASDEX Upgrade with the ion cyclotron range of frequencies antenna code TOPICA

    NASA Astrophysics Data System (ADS)

    Stepanov, I.; Noterdaeme, J.-M.; Bobkov, V.; Faugel, H.; Coster, D.; Milanesio, D.; Maggiora, R.; Siegl, G.; Bilato, R.; Brambilla, M.; Verdoolaege, G.; Braun, F.; Fünfgelder, H.; D'Inca, R.; Suttrop, W.; Kallenbach, A.; Schweinzer, J.; Wolfrum, E.; Fischer, R.; Mlynek, A.; Nikolaeva, V.; Guimarais, L.; the ASDEX Upgrade Team

    2015-09-01

    New antenna diagnostics on the ASDEX Upgrade, in the form of voltage and current probe pairs on the feeding lines of each ion cyclotron range of frequencies antenna, close to the input ports, have made it possible to study in detail the behavior of the ASDEX Upgrade two-strap antenna under changing loading conditions, and compare these measurements with the results of simulations using the TOPICA code. The present work extends previous studies by using the input impedance (more precisely, the complex voltage reflection coefficient Γ ) on each antenna port for comparison, instead of the more commonly used loading resistance or coupled power. The electron density profiles used for the simulation were reconstructed from the deuterium-carbon-nitrogen interferometer and lithium beam emission spectroscopy measurements, edge-localized mode-synchronized and averaged over time intervals from 10 to 200 ms depending on the case; 112 cases were compared from seven ASDEX Upgrade discharges with widely different plasma parameters and two operating frequencies (30 and 36.5 MHz). Very good agreement in \\vert Γ\\vert was found with the measurements on antenna 3 (<3% averaged over a shot), and good agreement was found with antennas 1 and 2 (<10%) the code reproduced the correct trend in loading resistance {{R}\\text{L}} in a significant majority of cases, although the discrepancies in the absolute values were rather high (up to  ˜50%) due to high reflection. Sources of discrepancy are discussed.

  9. An algorithm for the calculation of 3-D ICRF (Ion Cyclotron Range of Frequencies) fields in tokamak geometry

    SciTech Connect

    Smithe, D.N.; Colestock, P.L.; Kashuba, R.J.; Kammash, T.

    1987-04-01

    A computational scheme is developed which permits tractable calculation of three-dimensional full-wave solutions to the Maxwell-Vlasov equations under typical Ion Cyclotron Range of Frequencies (ICRF) experimental conditions. The method is unique in that power deposition to the plasma is determined via the anti-Hermitian part of a truncated warm-plasma dielectric operator, rather than as the result of an assumed phenomenological collision frequency. The resulting computer code allows arbitrary variation of density, temperature, magnetic field, and minority concentration in the poloidal plane by performing a convolution of poloidal modes to produce a coupled system of differential equations in the radial variable. By assuming no inhomogeneity along the toroidal axis, an inverse transform over k/sub parallel/ is performed to yield the full three-dimensional field solutions. The application of the code to TFTR-like plasmas shows a mild resonance structure in antenna loading related to the changing number of wavelengths between antenna and the resonance layer. 48 figs.

  10. Development and Applications of High—Frequency Gyrotrons in FIR FU Covering the sub-THz to THz Range

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Sabchevski, Svilen Petrov

    2012-07-01

    Powerful sources of coherent radiation in the sub-terahertz and in the terahertz frequency range of the electromagnetic spectrum are necessary for a great and continuously expanding number of applications in the physical research and in various advanced technological processes as well as in radars, communication systems, for remote sensing and inspection etc.. In recent years, a spectacular progress in the development of various gyro-devices and in particular of the powerful high frequency (sub-terahertz and terahertz) gyrotron oscillators has demonstrated a remarkable potential for bridging the so-called terahertz power gap and stimulated many novel and prospective applications. In this review paper we outline two series of such devices, namely the Gyrotron FU Series which includes pulsed gyrotrons and Gyrotron FU CW Series which consist of tubes operated in a CW (continuous wave) or long pulse mode, both developed at the FIR FU Center. We present the most remarkable achievements of these devices and illustrate their applications by some characteristic examples. An outlook for the further extension of the Gyrotron FU CW Series is also provided.

  11. A wide-frequency range AC magnetometer to measure the specific absorption rate in nanoparticles for magnetic hyperthermia

    NASA Astrophysics Data System (ADS)

    Garaio, E.; Collantes, J. M.; Garcia, J. A.; Plazaola, F.; Mornet, S.; Couillaud, F.; Sandre, O.

    2014-11-01

    Measurement of specific absorption rate (SAR) of magnetic nanoparticles is crucial to assert their potential for magnetic hyperthermia. To perform this task, calorimetric methods are widely used. However, those methods are not very accurate and are difficult to standardize. In this paper, we present AC magnetometry results performed with a lab-made magnetometer that is able to obtain dynamic hysteresis-loops in the AC magnetic field frequency range from 50 kHz to 1 MHz and intensities up to 24 kA m-1. In this work, SAR values of maghemite nanoparticles dispersed in water are measured by AC magnetometry. The so-obtained values are compared with the SAR measured by calorimetric methods. Both measurements, by calorimetry and magnetometry, are in good agreement. Therefore, the presented AC magnetometer is a suitable way to obtain SAR values of magnetic nanoparticles.

  12. Wide-range and fast-convergence frequency offset estimator by BER-aiding for optical coherent receivers

    NASA Astrophysics Data System (ADS)

    Li, Zhiyu; Chen, Xue; Zhou, Weiqin; Zhu, Hai; Zhou, Xian; Zhang, Zhiguo

    2009-11-01

    Optical coherent detection with digital signal processing (DSP) attracts more and more interests owing to its high performance. Due to a free-running local oscillator (LO) on the receiver, a frequency offset (FO) to the optical carrier brings phase distortion with which data can not be correctly decided and decoded. All-digital feed-forward FO estimation algorithms for optical (D)QPSK coherent receivers, such as PADE, have advantages of low complexity and stable-running wide range of estimation. However, it only converges under the condition that the initialed FO is near enough to the real FO while possible FO with typical tunable lasers can be very large. In order to solve this problem, we present a novel FO estimation scheme by BER aiding. This scheme has been demonstrated to be accurate and effective to break the restriction of PADE by simulation.

  13. Computational dosimetry in embryos exposed to electromagnetic plane waves over the frequency range of 10 MHz-1.5 GHz.

    PubMed

    Kawai, Hiroki; Nagaoka, Tomoaki; Watanabe, Soichi; Saito, Kazuyuki; Takahashi, Masaharu; Ito, Koichi

    2010-01-01

    This paper presents calculated specific absorption rate (SAR) dosimetry in 4 and 8 week Japanese pregnant-woman models exposed to plane waves over the frequency range of 10 MHz-1.5 GHz. Two types of 2 mm spatial-resolution pregnant-woman models comprised a woman model, which is similar to the average-sized Japanese adult female in height and weight, with a cubic (4 week) embryo or spheroidal (8 week) one. The averaged SAR in the embryos exposed to vertically and horizontally polarized plane waves at four kinds of propagation directions are calculated from 10 MHz to 1.5 GHz. The results indicate that the maximum average SAR in the embryos exposed to plane waves is lower than 0.08 W kg(-1) when the incident power density is at the reference level of ICNIRP guideline for general public environment. PMID:20009180

  14. 750 nm 1.5 W frequency-doubled semiconductor disk laser with a 44 nm tuning range.

    PubMed

    Saarinen, Esa J; Lyytikäinen, Jari; Ranta, Sanna; Rantamäki, Antti; Sirbu, Alexei; Iakovlev, Vladimir; Kapon, Eli; Okhotnikov, Oleg G

    2015-10-01

    We demonstrate 1.5 W of output power at the wavelength of 750 nm by intracavity frequency doubling a wafer-fused semiconductor disk laser diode-pumped at 980 nm. An optical-to-optical efficiency of 8.3% was achieved using a bismuth borate crystal. The wavelength of the doubled emission could be tuned from 720 to 764 nm with an intracavity birefringent plate. The beam quality parameter M2 of the laser output was measured to be below 1.5 at all pump powers. The laser is a promising tool for biomedical applications that can take advantage of the large penetration depth of light in tissue in the 700-800 nm spectral range. PMID:26421536

  15. A solar plasma stream measured by DRVID and dual-frequency range and Doppler radio metric data

    NASA Technical Reports Server (NTRS)

    Winn, F. B.; Wu, S. C.; Komarek, T. A.; Lam, V. W.; Royden, H. N.; Yip, K. B. W.

    1977-01-01

    S- and X-band DRVID, S- and X-band dual-frequency range (SX(p)), and Doppler (SX(p)) measured a 15-fold increase in the line-of-sight electron content of the solar plasma above the normal plasma background. A general increase in the plasma electron content continued for nearly 50 hours: it started about 12:00 (GMT) on 12 March 1976 and continued to grow until 17:00 (GMT) on 14 March. For the next 55 hours, between 17:00 (GMT) on 14 March to 00:54 (GMT) on 17 March, the plasma level diminished as the background level was approached. Not only were the temporal changes and absolute level of the plasma content measured but the measurements were also used to ascertain the mean-plasma-concentration location: it was estimated to be 4.1 light minutes from earth.

  16. The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

    SciTech Connect

    Michael Klopf, J.; Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sérgio

    2014-08-10

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed 'double spectra'. Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  17. Shear Properties of Brain Tissue over a Frequency Range Relevant for Automotive Impact Situations: New Experimental Results.

    PubMed

    Nicolle, Stéphane; Lounis, Mourad; Willinger, Rémy

    2004-11-01

    This research aims at improving the definition of the shear linear material properties of brain tissue. A comparison between human and porcine white and gray matter samples was carried out over a new large frequency range associated with both traffic road and non-penetrating ballistic impacts. Oscillatory experiments were performed by using an original custom-designed oscillatory shear testing device. The findings revealed that no significant difference occured between the linear viscoelastic behavior of the porcine and the human brain tissue. On the average, the storage modulus (G') and the loss modulus (G") of the white matter increased respectively from 2.1 +/- 0.9 kPa to 16.8 +/- 2.0 kPa and from 0.4 +/- 0.2 kPa to 18.7 +/- 2.3 kPa between 0.1 and 6300 Hz at 37 degrees C. In addition, the gray and white matter behaviors seemed to be similar at small strains. The reliability of the data and the robustness of the experimental protocol were checked using a standard rheometer (Bohlin C-VOR 150). A good agreement was found between the data obtained in the frequency and time field. As a result, the linear relaxation modulus was determined over an extensive time range (from 10(-5) s to 300 s). In a first approach, the nonlinear behavior of brain tissue was studied using stress relaxation tests. Brain tissue showed significant shear softening for strains above 1% and the time relaxation behavior was independent of the applied strain. On this basis, a visco-hyperelastic model was proposed using the generalized Maxwell model and the Ogden hyperelastic model. These models respectively describe the linear relaxation modulus and the strain dependence of the shear stress. PMID:17230269

  18. The Contribution of Microbunching Instability to Solar Flare Emission in the GHz to THz Range of Frequencies

    NASA Astrophysics Data System (ADS)

    Klopf, J. Michael; Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sérgio

    2014-08-01

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed "double spectra." Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  19. Investigation of electrostatic waves in the ion cyclotron range of frequencies in L-4 and ACT-1

    SciTech Connect

    Ono, Masayuki.

    1993-05-01

    Electrostatic waves in the ion cyclotron range of frequencies (ICRF) were studied in the Princeton L-4 and ACT-1 devices for approximately ten years, from 1975 to 1985. The investigation began in the L-4 linear device, looking for the parametric excitation of electrostatic ion cyclotron waves in multi-ion-species plasmas. In addition, this investigation verified multi-ion-species effects on the electrostatic ion cyclotron wave dispersion religion including the ion-ion hybrid resonance. Finite-Larmor-radius modification of the wave dispersion relation was also observed, even for ion temperatures of T[sub i] [approx] 1/40 eV. Taking advantage of the relatively high field and long device length of L-4, the existence of the cold electrostatic ion cyclotron wave (CES ICW) was verified. With the arrival of the ACT-1 toroidal device, finite-Larmor-radius (FLR) waves were studied in a relatively collisionless warm-ion hydrogen plasma. Detailed investigations of ion Bernstein waves (IBW) included the verification of mode-transformation in their launching, their wave propagation characteristics, their absorption, and the resulting ion heating. This basic physics activity played a crucial role in developing a new reactor heating concept termed ion Bernstein wave heating. Experimental research in the lower hybrid frequency range confirmed the existence of FLR effects near the lower hybrid resonance, predicted by Stix in 1965. In a neon plasma with a carefully placed phased wave exciter, the neutralized ion Bernstein wave was observed for the first time. Using a fastwave ICRF antenna, two parasitic excitation processes for IBW -- parametric instability and density-gradient-driven excitation -- were also discovered. In the concluding section of this paper, a possible application of externally launched electrostatic waves is suggested for helium ash removal from fusion reactor plasmas.

  20. Investigation of electrostatic waves in the ion cyclotron range of frequencies in L-4 and ACT-1

    SciTech Connect

    Ono, Masayuki

    1993-05-01

    Electrostatic waves in the ion cyclotron range of frequencies (ICRF) were studied in the Princeton L-4 and ACT-1 devices for approximately ten years, from 1975 to 1985. The investigation began in the L-4 linear device, looking for the parametric excitation of electrostatic ion cyclotron waves in multi-ion-species plasmas. In addition, this investigation verified multi-ion-species effects on the electrostatic ion cyclotron wave dispersion religion including the ion-ion hybrid resonance. Finite-Larmor-radius modification of the wave dispersion relation was also observed, even for ion temperatures of T{sub i} {approx} 1/40 eV. Taking advantage of the relatively high field and long device length of L-4, the existence of the cold electrostatic ion cyclotron wave (CES ICW) was verified. With the arrival of the ACT-1 toroidal device, finite-Larmor-radius (FLR) waves were studied in a relatively collisionless warm-ion hydrogen plasma. Detailed investigations of ion Bernstein waves (IBW) included the verification of mode-transformation in their launching, their wave propagation characteristics, their absorption, and the resulting ion heating. This basic physics activity played a crucial role in developing a new reactor heating concept termed ion Bernstein wave heating. Experimental research in the lower hybrid frequency range confirmed the existence of FLR effects near the lower hybrid resonance, predicted by Stix in 1965. In a neon plasma with a carefully placed phased wave exciter, the neutralized ion Bernstein wave was observed for the first time. Using a fastwave ICRF antenna, two parasitic excitation processes for IBW -- parametric instability and density-gradient-driven excitation -- were also discovered. In the concluding section of this paper, a possible application of externally launched electrostatic waves is suggested for helium ash removal from fusion reactor plasmas.

  1. The contribution of microbunching instability to solar flare emission in the GHz to THz range of frequencies

    SciTech Connect

    Klopf, J. Michael; Kaufmann, Pierre; Raulin, Jean-Pierre; Szpigel, Sergio

    2014-07-01

    Recent solar flare observations in the sub-terahertz range have provided evidence of a new spectral component with fluxes increasing for larger frequencies, separated from the well-known microwave emission that maximizes in the gigahertz range. Suggested interpretations explain the terahertz spectral component but do not account for the simultaneous microwave component. We present a mechanism for producing the observed "double spectra." Based on coherent enhancement of synchrotron emission at long wavelengths in laboratory accelerators, we consider how similar processes may occur within a solar flare. The instability known as microbunching arises from perturbations that produce electron beam density modulations, giving rise to broadband coherent synchrotron emission at wavelengths comparable to the characteristic size of the microbunch structure. The spectral intensity of this coherent synchrotron radiation (CSR) can far exceed that of the incoherent synchrotron radiation (ISR), which peaks at a higher frequency, thus producing a double-peaked spectrum. Successful CSR simulations are shown to fit actual burst spectral observations, using typical flaring physical parameters and power-law energy distributions for the accelerated electrons. The simulations consider an energy threshold below which microbunching is not possible because of Coulomb repulsion. Only a small fraction of the radiating charges accelerated to energies above the threshold is required to produce the microwave component observed for several events. The ISR/CSR mechanism can occur together with other emission processes producing the microwave component. It may bring an important contribution to microwaves, at least for certain events where physical conditions for the occurrence of the ISR/CSR microbunching mechanism are possible.

  2. Effects of sample size and sampling frequency on studies of brown bear home ranges and habitat use

    USGS Publications Warehouse

    Arthur, Steve M.; Schwartz, Charles C.

    1999-01-01

    We equipped 9 brown bears (Ursus arctos) on the Kenai Peninsula, Alaska, with collars containing both conventional very-high-frequency (VHF) transmitters and global positioning system (GPS) receivers programmed to determine an animal's position at 5.75-hr intervals. We calculated minimum convex polygon (MCP) and fixed and adaptive kernel home ranges for randomly-selected subsets of the GPS data to examine the effects of sample size on accuracy and precision of home range estimates. We also compared results obtained by weekly aerial radiotracking versus more frequent GPS locations to test for biases in conventional radiotracking data. Home ranges based on the MCP were 20-606 km2 (x = 201) for aerial radiotracking data (n = 12-16 locations/bear) and 116-1,505 km2 (x = 522) for the complete GPS data sets (n = 245-466 locations/bear). Fixed kernel home ranges were 34-955 km2 (x = 224) for radiotracking data and 16-130 km2 (x = 60) for the GPS data. Differences between means for radiotracking and GPS data were due primarily to the larger samples provided by the GPS data. Means did not differ between radiotracking data and equivalent-sized subsets of GPS data (P > 0.10). For the MCP, home range area increased and variability decreased asymptotically with number of locations. For the kernel models, both area and variability decreased with increasing sample size. Simulations suggested that the MCP and kernel models required >60 and >80 locations, respectively, for estimates to be both accurate (change in area <1%/additional location) and precise (CV < 50%). Although the radiotracking data appeared unbiased, except for the relationship between area and sample size, these data failed to indicate some areas that likely were important to bears. Our results suggest that the usefulness of conventional radiotracking data may be limited by potential biases and variability due to small samples. Investigators that use home range estimates in statistical tests should consider the

  3. Frequency conversion of molecular gas lasers in PbIn6Te10 crystal within mid-IR range.

    PubMed

    Ionin, A A; Kinyaevskiy, I O; Klimachev, Y M; Kotkov, A A; Badikov, V V; Mitin, K V

    2016-05-15

    PbIn6Te10 is a new mid-infrared (IR) nonlinear crystal with a very wide transparency range from 1.7 up to 31 μm. Calculated phase-matching angles show possibility of frequency conversion throughout the transparency range. Sum frequency generation of multiline carbon monoxide (CO) laser and difference frequency generation when mixing CO and carbon dioxide laser radiation were experimentally studied. Laser-induced damage threshold and frequency conversion efficiency under multiline CO laser pumping were measured. PMID:27177010

  4. Medium-Range Predictability of Contrail-Cirrus Demonstrated during Experiments Ml-Cirrus and Access-Ii

    NASA Astrophysics Data System (ADS)

    Schumann, U.

    2015-12-01

    The Contrail Cirrus Prediction model CoCiP (doi:10.5194/gmd-5-543-2012) has been applied quasi operationally to predict contrails for flight planning of ML-CIRRUS (C. Voigt, DLR, et al.) in Europe and for ACCESS II in California (B. Anderson, NASA, et al.) in March-May 2014. The model uses NWP data from ECMWF and past airtraffic data (actual traffic data are used for analysis). The forecasts provided a sequence of hourly forecast maps of contrail cirrus optical depth for 3.5 days, every 12 h. CoCiP has been compared to observations before, e.g. within a global climate-aerosol-contrail model (Schumann, Penner et al., ACPD, 2015, doi:10.5194/acpd-15-19553-2015). Good predictions would allow for climate optimal routing (see, e.g., US patent by Mannstein and Schumann, US 2012/0173147 A1). The predictions are tested by: 1) Local eyewitness reports and photos, 2) satellite observed cloudiness, 3) autocorrelation analysis of predictions for various forecast periods, 4) comparisons of computed with observed optical depth from COCS (doi:10.5194/amt-7-3233-2014, 2014) by IR METEOSAT-SEVIRI observations over Europe. The results demonstrate medium-range predictability of contrail cirrus to a useful degree for given traffic, soot emissions, and high-quality NWP data. A growing set of satellite, Lidar, and in-situ data from ML-CIRRUS and ACCENT are becoming available and will be used to further test the forecast quality. The autocorrelation of optical depth predictions is near 70% for 3-d forecasts for Europe (outside times with high Sahara dust loads), and only slightly smaller for continental USA. Contrail cirrus is abundant over Europe and USA. More than 1/3 of all cirrus measured with the research aircraft HALO during ML-CIRRUS was impacted by contrails. The radiative forcing (RF) is strongly daytime and ambience dependent. The net annual mean RF, based on our global studies, may reach up to 0.08 W/m2 globally, and may well exceed 1 W/m2 regionally, with maximum over Europe

  5. Effective conductivity and permittivity of unsaturated clayey materials in the frequency range 1 mHz to 1GHz: A unified model and its appications in hydrogeophysics

    NASA Astrophysics Data System (ADS)

    Revil, A.

    2012-12-01

    A model combining low frequency complex conductivity and high frequency permittivity is developed in the frequency range from 1 mHz to 1 GHz. The low frequency conductivity depends on the pore water conductivity and a surface conductivity term that is mostly controlled by the electrical diffuse layer, the outer component of the electrical double layer coating the surface of the clay minerals. The frequency dependence of the effective quadrature conductivity shows three domains. Below a critical frequency fd that depends on the dynamic pore throat size, the quadrature conductivity is frequency dependent. Between fd and a second critical frequency fp, the quadrature conductivity is generally well described by a plateau (there are however few exception to this rule showing a well-characterized peak but still with a relatively weak frequency dependence). The characteristic frequency fd controls the transition between double layer polarization and the effect of the high frequency permittivity of the material. The Maxwell-Wagner polarization is found to be relatively negligible. For a broad range of frequencies below 1 MHz, the effective permittivity exhibits a strong dependence with the cation exchange capacity and the specific surface area. At high frequency, above the critical frequency fd, the effective permittivity reaches a high-frequency asymptotic limit that is controlled by the two Archie's exponent m and n like the low-frequency electrical conductivity. The unified model is compared with various datasets from the literature and is able to explain fairly well a broad number of observations with a very small number of textural and electrochemical parameters. It canbe therefore used to interpret induced polarization, induction-based electromagnetic methods, GPR data, and seismoelectric measurements to characterize the vadose zone.

  6. A More Precise Empirical Formula for Estimating Normalized Fog Attenuation in the Millimeter-Wave Frequency Range 30 ~ 100 GHz

    NASA Astrophysics Data System (ADS)

    Mao, Xia; Liu, Yun-Long; Chen, Li-Jiang; Xue, Yu-Li

    2013-04-01

    At millimeter wavelengths, normalized fog attenuation (NFA) in units of (dB/km)/ (g/m3) is generally calculated by the Rayleigh approximation when working wavelengths are much larger than the average diameter of fog droplets. The calculations of the Rayleigh approximation are much less than those of Mie scattering theory, but still complex and heavy. To solve the above problem and facilitate the engineering applications of the Rayleigh approximation, a new empirical formula is discussed to estimate NFA in the frequency range 30 ~ 100 GHz and the fog common temperature range -8 ~ 20 °C. The simulation results of the new formula are compared with those got by other three empirical formulae: the Altshuler empirical formula, the Liebe empirical formula and the Zhao empirical formula. Maximal absolute value of the relative errors (MAVRE) and Pearson correlation coefficient (PCC) indicate the largest deviation of estimated results and the fitting performance of an empirical formula, respectively. Comparisons show that the MAVRE of the new formula is only 4.482 %, which is much smaller than those of the other three formulae. The mean value of the Pearson correlation coefficients (PCCs) of the proposed formula is 0.999943, larger than those of other methods. Additionally, relative error (RE) curves of the four empirical formulae are given at four certain temperatures -8 °C, 0 °C, 10 °C and 20 °C.

  7. Non-inductive plasma start-up experiments on the TST-2 spherical tokamak using waves in the lower-hybrid frequency range

    NASA Astrophysics Data System (ADS)

    Shinya, T.; Takase, Y.; Wakatsuki, T.; Ejiri, A.; Furui, H.; Hiratsuka, J.; Imamura, K.; Inada, T.; Kakuda, H.; Kasahara, H.; Kumazawa, R.; Moeller, C.; Mutoh, T.; Nagashima, Y.; Nakamura, K.; Nakanishi, A.; Oosako, T.; Saito, K.; Seki, T.; Sonehara, M.; Togashi, H.; Tsuda, S.; Tsujii, N.; Yamaguchi, T.

    2015-07-01

    Non-inductive plasma current start-up and sustainment by waves in the lower-hybrid frequency range (200 MHz) have been studied on the TST-2 spherical tokamak (R0 ⩽ 0.38 m, a ⩽ 0.25 m, Bt0 ⩽ 0.3 T, Ip ⩽ 0.14 MA) using three types of antenna: the 11-element inductively-coupled combline antenna, the dielectric loaded 4-waveguide array antenna, and the 13-element capacitively-coupled combline (CCC) antenna. The maximum plasma currents of 15 kA, 10 kA and 16 kA were achieved, respectively. The highest current drive figure of merit η_CD \\equiv \\overline{n}e Ip R / P_RF was achieved by the CCC antenna. The efficiency of current drive should improve by reducing prompt orbit losses of high energy electrons by operating at higher plasma current (to improve orbit confinement) and higher toroidal magnetic field (to improve wave accessibility to the plasma core), while keeping the density high enough (to avoid excessive acceleration of electrons), but under the ‘density limit’.

  8. Microstrip Antennas with Polarization Diversity across a Wide Frequency Range and Phased Array Antennas for Radar and Satellite Communications

    NASA Astrophysics Data System (ADS)

    Ho, Kevin Ming-Jiang

    The thesis comprises of 3 projects; an L-band microstrip antenna with frequency agility and polarization diversity, X-band phased array antennas incorporating commercially packaged RFIC phased array chips, and studies for Ku/Ka-band shared aperture antenna array. The first project features the use of commercially packaged RF-MEMS SPDT switches, that boasts of high reliability, high linearity, low losses, hermetically packaged and fully compatible for SMTA processes for mass-assembly and production. Using the switches in a novel manner for the feed network, microstrip antennas with polarization diversity are presented. Frequency agility is achieved with the use of tuning diodes to provide capacitive loading to the antenna element. Additional inductance effects from surface-mounted capacitors, and its impact, is introduced. Theoretical cross-polarization of probe-fed antenna elements is presented for both linear and circular polarized microstrip antennas. Designs and measurements are presented, for microstrip antennas with polarization diversity, wide frequency tuning range, and both features. Replacement of the tuning diodes with commercially-packaged high Q RF MEMS tunable capacitors will allow for significant improvements to the radiation efficiency. In another project, multi-channel CMOS RFIC phased-array receiver chips are assembled in QFN packages and directly integrated on the same multi-layered PCB stack-up with the antenna arrays. Problems of isolation from the PCB-QFN interface, and potential performance degradation on antenna array from the use of commercial-grade laminates for assembly requirements, namely potential scan blindness and radiation efficiency, are presented. Causes for apparent drift of dielectric constant for microstrip circuits, and high conductor losses observed in measurements, are introduced. Finally, studies are performed for the design of a Ku/Ka-Band shared aperture array. Different approaches for developing dual-band shared apertures

  9. Frequency range selection method of trans-impedance amplifier for high sensitivity lock-in amplifier used in the optical sensors

    NASA Astrophysics Data System (ADS)

    Park, Chang-In; Jeon, Su-Jin; Hong, Nam-Pyo; Choi, Young-Wan

    2016-03-01

    Lock-in amplifier (LIA) has been proposed as a detection technique for optical sensors because it can measure low signal in high noise level. LIA uses synchronous method, so the input signal frequency is locked to a reference frequency that is used to carry out the measurements. Generally, input signal frequency of LIA used in optical sensors is determined by modulation frequency of optical signal. It is important to understand the noise characteristics of the trans-impedance amplifier (TIA) to determine the modulation frequency. The TIA has a frequency range in which noise is minimized by the capacitance of photo diode (PD) and the passive component of TIA feedback network. When the modulation frequency is determined in this range, it is possible to design a robust system to noise. In this paper, we propose a method for the determination of optical signal modulation frequency selection by using the noise characteristics of TIA. Frequency response of noise in TIA is measured by spectrum analyzer and minimum noise region is confirmed. The LIA and TIA circuit have been designed as a hybrid circuit. The optical sensor is modeled by the laser diode (LD) and photo diode (PD) and the modulation frequency was used as the input to the signal generator. The experiments were performed to compare the signal to noise ratio (SNR) of the minimum noise region and the others. The results clearly show that the SNR is enhanced in the minimum noise region of TIA.

  10. Frequency Allocations for Unmanned Aircraft Systems in the National Airspace. Access 5 White Paper to the WRC Advisory Committee

    NASA Technical Reports Server (NTRS)

    2006-01-01

    A critical aspect of the Access 5 program is identifying appropriate spectrum for civil and commercial purposes. However, currently, there is no spectrum allocated for the command/control link between the aircraft control station and the unmanned aircraft. Until such frequency spectrum is allocated and approved, it will be difficult for the UAS community to obtain civil airworthiness certification and operate in the NAS on a routine basis. This document provides a perspective from the UAS community on Agenda Items being considered for the upcoming World Radiocommunication Conference 2007 (WRC 07). Primarily, it supports the proposal to add Aeronautical Mobile (Route) Services (AM(R)S) to existing bands that could be used for UAS Line-of-Sight operations. It also recommends the need to identify spectrum that could be used for an Aeronautical Mobile Satellite (Route) Service (AMS(R)S) that would allow UAS to operate Beyond Line-of-Sight. If spectrum is made available to provide these services, it will then be incumbent upon the UAS community to justify their use of this spectrum as well as the assurance that they will not interfere with other users of this newly allocated spectrum.

  11. Free-Ranging Male Koalas Use Size-Related Variation in Formant Frequencies to Assess Rival Males

    PubMed Central

    Charlton, Benjamin D.; Whisson, Desley A.; Reby, David

    2013-01-01

    Although the use of formant frequencies in nonhuman animal vocal communication systems has received considerable recent interest, only a few studies have examined the importance of these acoustic cues to body size during intra-sexual competition between males. Here we used playback experiments to present free-ranging male koalas with re-synthesised bellow vocalisations in which the formants were shifted to simulate either a large or a small adult male. We found that male looking responses did not differ according to the size variant condition played back. In contrast, male koalas produced longer bellows and spent more time bellowing when they were presented with playbacks simulating larger rivals. In addition, males were significantly slower to respond to this class of playback stimuli than they were to bellows simulating small males. Our results indicate that male koalas invest more effort into their vocal responses when they are presented with bellows that have lower formants indicative of larger rivals, but also show that males are slower to engage in vocal exchanges with larger males that represent more dangerous rivals. By demonstrating that male koalas use formants to assess rivals during the breeding season we have provided evidence that male-male competition constitutes an important selection pressure for broadcasting and attending to size-related formant information in this species. Further empirical studies should investigate the extent to which the use of formants during intra-sexual competition is widespread throughout mammals. PMID:23922967

  12. Study of toroidal flow generation by ion cyclotron range of frequency minority heating in the Alcator C-Mod plasma

    NASA Astrophysics Data System (ADS)

    Murakami, S.; Itoh, K.; Zheng, L. J.; Van Dam, J. W.; Bonoli, P.; Rice, J. E.; Fiore, C. L.; Gao, C.; Fukuyama, A.

    2016-01-01

    The averaged toroidal flow of energetic minority ions during ICRF (ion cyclotron range of frequencies) heating is investigated in the Alcator C-Mod plasma by applying the GNET code, which can solve the drift kinetic equation with complicated orbits of accelerated energetic particles. It is found that a co-directional toroidal flow of the minority ions is generated in the region outside of the resonance location, and that the toroidal velocity reaches more than 40% of the central ion thermal velocity (Vtor ˜ 300 km/s with PICRF ˜ 2 MW). When we shift the resonance location to the outside of |r /a |˜0.5 , the toroidal flow immediately inside of the resonance location is reduced to 0 or changes to the opposite direction, and the toroidal velocity shear is enhanced at r/a ˜ 0.5. A radial diffusion equation for toroidal flow is solved by assuming a torque profile for the minority ion mean flow, and good agreements with experimental radial toroidal flow profiles are obtained. This suggests that the ICRF driven minority ion flow is related to the experimentally observed toroidal rotation during ICRF heating in the Alcator C-Mod plasma.

  13. Plasma waves in the range of the lower hybrid frequency - ISEE 1 and 2 observations at the earth's bow shock

    NASA Technical Reports Server (NTRS)

    Mellott, M. M.; Greenstadt, E. W.

    1988-01-01

    This report presents a characterization of plasma wave noise in the range of the lower hybrid frequency associated with 65 crossings of earth's bow shock observed by the ISEE 1 and 2 satellites. Wave growth generally becomes detectable at the upstream edge of the shock foot, increases at the upstream edge of the shock ramp, peaks within the ramp, and then quickly decays to steady downstream values. The upstream extent of the noise is on the same order as that of specularly reflected gyrating ions. Similar profiles were observed in subcritical and supercritical shocks, and no special behavior was associated with the first critical Mach number. Spectra in the foot and ramp were similar in shape, although the noise was 1 to 2 orders of magnitude more intense in the shock ramps than in the feet. Electric field intensities are positively correlated with solar wind speed and inversely related to electron beta and Mach number. Magnetic components are positively correlated with Mach number and beta. The results are generally consistent with suggestions that the noise consists of lower hybrid waves driven by reflected gyrating ions in the foot, and by additional instabilities, such as the cross-field current, in the shock ramp.

  14. Photonic approach for microwave frequency measurement with adjustable measurement range and resolution using birefringence effect in highly non-linear fiber.

    PubMed

    Feng, Danqi; Xie, Heng; Qian, Lifen; Bai, Qinhong; Sun, Junqiang

    2015-06-29

    We experimentally demonstrate a novel approach for microwave frequency measurement utilizing birefringence effect in the highly non-linear fiber (HNLF). A detailed theoretical analysis is presented to implement the adjustable measurement range and resolution. By stimulating a complementary polarization-domain interferometer pair in the HNLF, a mathematical expression that relates the microwave frequency and amplitude comparison function is developed. We carry out a proof-to-concept experiment. A frequency measurement range of 2.5-30 GHz with a measurement error within 0.5 GHz is achieved except 16-17.5 GHz. This method is all-optical and requires no high-speed electronic components. PMID:26191769

  15. What Determines the Speed of Lexical Access: Homophone or Specific-Word Frequency? A Reply to Jescheniak et al. (2003)

    ERIC Educational Resources Information Center

    Caramazza, Alfonso; Bi, Yanchao; Costa, Albert; Miozzo, Michelle

    2004-01-01

    A. Caramazza, A. Costa, M. Miozzo, and Y. Bi (2001) reported a series of experiments showing that naming latencies for homophones are determined by specific-word frequency (e.g., frequency of nun) and not homophone frequency (frequency of nun + none). J. D. Jescheniak, A. S. Meyer, and W. J. M. Levelt (2003) have challenged these studies on a…

  16. Novel wavelength division multiplex-radio over fiber-passive optical network architecture for multiple access points based on multitone generation and triple sextupling frequency

    NASA Astrophysics Data System (ADS)

    Cheng, Guangming; Guo, Banghong; Liu, Songhao; Huang, Xuguang

    2014-01-01

    An innovative wavelength division multiplex-radio over fiber-passive optical network architecture for multiple access points (AP) based on multitone generation and triple sextupling frequency is proposed and demonstrated. A dual-drive Mach-Zehnder modulator (DD-MZM) is utilized to realize the multitone generation. Even sidebands are suppressed to make the adjacent frequency separation twice the frequency of the local oscillator by adjusting the modulation voltage of the DD-MZM. Due to adopting three fiber Bragg gratings to reflect the unmodulated sidebands for uplink communications source free at optical network unit (ONU), is achieved. The system can support at least three APs at one ONU simultaneously with a 30 km single-mode fiber (SMF) transmission and 5 Gb/s data rate both for uplink and downlink communications. The theoretical analysis and simulation results show the architecture has an excellent performance and will be a promising candidate in future hybrid access networks.

  17. Efficient cryopreservation protocol enables accessibility of a broad range of ammonia-oxidizing bacteria for the scientific community.

    PubMed

    Hoefman, Sven; Pommerening-Röser, Andreas; Samyn, Emly; De Vos, Paul; Heylen, Kim

    2013-05-01

    Long-term storage of the fastidious ammonia-oxidizing bacteria has proven difficult, which limits their public availability and results in a loss of cultured biodiversity. To enable their accessibility to the scientific community, an effective protocol for cryopreservation of ammonia-oxidizing cultures at -80 °C and in liquid nitrogen was developed. Long-term storage could be achieved using 5% DMSO as cryoprotectant, preferably in a cryoprotective preservation medium containing tenfold-diluted trypticase soy broth and 1% trehalose. As such, successful activity and growth recovery was observed for a diverse set of ammonia-oxidizing cultures. PMID:23376087

  18. Ion-cyclotron range of frequencies in the scrape-off-layer: fine structure radial electric fields

    NASA Astrophysics Data System (ADS)

    Cziegler, I.; Terry, J. L.; Wukitch, S. J.; Garrett, M. L.; Lau, C.; Lin, Y.

    2012-10-01

    Gas-puff-imaging techniques are utilized to detect radial electric field structures in the scrape-off-layer (SOL) of the Alcator C-Mod tokamak via the observation of poloidal motion of advected fluctuations. When the diagnostic's field of view is magnetically connected to the ion-cyclotron range of frequencies (ICRF) active antennas, large (up to 8 km s-1) poloidal velocities are observed in a radial region encompassing both field lines terminating on and those passing in front of the antennas. The radial electric field switches sign indicating a peak in the potential profile corresponding to the transition from piercing to passing field lines. The electric field extends a few centimeters into the SOL and its local magnitude is of order Er ≈ 20-30 kV m-1. The corresponding plasma potentials scale as the square root of RF power; the poloidal structure is peaked when the field lines are connected to the top and bottom of the antenna. This structure is consistent with the presence of potential structures arising as a consequence of sheath rectification of the RF waves. The most striking result, however, is that the radial penetration λ⊥ of the potential structures is an order of magnitude larger than the basic theoretical expectation (λ⊥ ≈ 10δe, where δe is the skin depth). This substantial broadening is expected to have a strong impact on RF impurity physics. A (weak) power dependence observed in the width of the poloidal velocity features is explained as a competition between the RF induced and the background potential gradients.

  19. Face Recognition Is Affected by Similarity in Spatial Frequency Range to a Greater Degree Than Within-Category Object Recognition

    ERIC Educational Resources Information Center

    Collin, Charles A.; Liu, Chang Hong; Troje, Nikolaus F.; McMullen, Patricia A.; Chaudhuri, Avi

    2004-01-01

    Previous studies have suggested that face identification is more sensitive to variations in spatial frequency content than object recognition, but none have compared how sensitive the 2 processes are to variations in spatial frequency overlap (SFO). The authors tested face and object matching accuracy under varying SFO conditions. Their results…

  20. High-power free-electron maser with frequency multiplication operating in a shortwave part of the millimeter wave range

    NASA Astrophysics Data System (ADS)

    Bandurkin, I. V.; Kaminsky, A. K.; Perelstein, E. A.; Peskov, N. Yu.; Savilov, A. V.; Sedykh, S. N.

    2012-08-01

    The possibility of using frequency multiplication in order to obtain high-power short-wavelength radiation from a free-electron maser (FEM) with a Bragg resonator has been studied. Preliminary experiments with an LIU-3000 (JINR) linear induction accelerator demonstrate the operation of a frequency-multiplying FEM at megawatt power in the 6- and 4-mm wave bands on the second and third harmonic, respectively.

  1. Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Mod

    SciTech Connect

    Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.; Terry, J. L.; Hubbard, A.; Labombard, B.; Lau, C.; Lin, Y.; Lipschultz, B.; Miller, D.; Reinke, M. L.; Whyte, D.; Collaboration: Alcator C-Mod Team

    2013-05-15

    Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are indeed

  2. Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.; Terry, J. L.; Hubbard, A.; Labombard, B.; Lau, C.; Lin, Y.; Lipschultz, B.; Miller, D.; Reinke, M. L.; Whyte, D.; Alcator C-Mod Team

    2013-05-01

    Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%-30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are indeed

  3. Detection of a strong rfi-threat in the BI NGO frequency range due to the new Chinese satellite navigation system COMPASS at 1207.14 MHz

    NASA Astrophysics Data System (ADS)

    Monstein, Chr.

    2013-06-01

    Currently, a simple in-sensitive but cheap receiving system (which was originally designed for solar observations) is configured to receive frequencies covering BINGO frequency range from 960 MHz up to 1260 MHz. During the day the antenna tracks the sun but in the night the 5m parabolic dish is pointing to the sky to a fixed position at azimuth 180° and elevation 80°.

  4. Development of the arc attachment at HID lamp electrodes in the range from low to RF-frequencies

    NASA Astrophysics Data System (ADS)

    Reinelt, J.; Langenscheidt, O.; Westermeier, M.; Awakowicz, P.; Mentel, J.

    2008-07-01

    At cathodes of high intensity discharges two different modes of arc attachment are observed: a diffuse mode characterized by a low current density and a uniformly distributed high global temperature, and a spot mode with a high current density and a high local but low global surface temperature. For dc and low frequency operation an investigation of these different modes has already been presented. Different modes of arc attachment are shown in the case of RF operation (up to 1 MHz operation frequency) of the Bochum model lamp. Images of the arc attachment demonstrate that with increasing frequencies the occurrence of the spot mode is reduced. But it cannot be excluded that it arises accidentally at high frequencies. It is found that with increasing frequency the differences between the electrode tip temperature in the cathodic and the anodic half period are levelled and that the course of the electrode sheath voltage (ESV(t)) adjusts to the sinusoidal current waveform resulting in an increase in the average power input into the electrodes with proceeding adjustment. Moreover, it indicates a reshaping of the electrode boundary layers.

  5. High-resolution observation of field-aligned irregularities in the ionosphere using multi-frequency range imaging of VHF atmospheric radar

    NASA Astrophysics Data System (ADS)

    Chen, Jenn-Shyong; Furumoto, Jun-ichi; Su, Ching-Lun; Chu, Yen-Hsyang

    Field-aligned irregularity (FAI) in the ionosphere is a topic of interest to atmospheric radar community. In addition to the field-aligned characteristic, quasi-periodic (QP) appearance of FAI echoes has been observed frequently by very-high-frequency (VHF) atmospheric radar. The occurrence range of QP FAI echoes changes with time, and the slope of range versus time can be positive or negative, depending on occurrence time of the echoes. Several mechanisms responsible for the QP FAI echoes have been proposed, e.g., modulation in altitude by a passing atmospheric gravity wave, semidiurnal neutral-wind variation, and so on. Owing to the finite pulse length of radar in observation, the range resolution of measurement is limited within hundreds of meters. In view of this, the range imaging (RIM) using multiple frequencies has been employed to improve the range resolution of measurement. The multi-frequency technique transmits a set of slightly different frequencies sequentially during each radar pulse, and the radar returns at different transmitting frequencies are received, respectively. With adaptive retrieval algorithms for these radar returns, it is capable of resolving the echo structures at meter scale in the range direction. RIM has been employed in the lower atmosphere successfully. In this study, the performance of RIM for FAI was first carried out with the Middle and Upper atmosphere Radar (46 MHz; 34.85(°) N, 136.10(°) N; Japan) and the Chung-Li VHF radar (52 MHz; 24.9(°) N, 121.1(°) E; Taiwan). Some initial results of high-resolution FAI echoes within the range gate will be shown.

  6. Interaction of electromagnetic radiation in the 20–200 GHz frequency range with arrays of carbon nanotubes with ferromagnetic nanoparticles

    PubMed Central

    Atdayev, Agylych; Danilyuk, Alexander L

    2015-01-01

    Summary The interaction of electromagnetic radiation with a magnetic nanocomposite based on carbon nanotubes (CNT) is considered within the model of distributed random nanoparticles with a core–shell morphology. The approach is based on a system composed of a CNT conducting resistive matrix, ferromagnetic inductive nanoparticles and the capacitive interface between the CNT matrix and the nanoparticles, which form resonance resistive–inductive–capacitive circuits. It is shown that the influence of the resonant circuits leads to the emergence of specific resonances, namely peaks and valleys in the frequency dependence of the permeability of the nanocomposite, and in the frequency dependence of the reflection and transmission of electromagnetic radiation. PMID:25977874

  7. Metamaterial near-field sensor for deep-subwavelength thickness measurements and sensitive refractometry in the terahertz frequency range

    SciTech Connect

    Reinhard, Benjamin; Schmitt, Klemens M.; Neu, Jens; Wollrab, Viktoria; Beigang, Rene; Rahm, Marco

    2012-05-28

    We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16 000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance frequency on the sample material thickness and the refractive index.

  8. Particle simulations of mode conversion between slow mode and fast mode in lower hybrid range of frequencies

    NASA Astrophysics Data System (ADS)

    Jia, Guozhang; Xiang, Nong; Wang, Xueyi; Huang, Yueheng; Lin, Yu

    2016-01-01

    The propagation and mode conversion of lower hybrid waves in an inhomogeneous plasma are investigated by using the nonlinear δf algorithm in a two-dimensional particle-in-cell simulation code based on the gyrokinetic electron and fully kinetic ion (GeFi) scheme [Lin et al., Plasma Phys. Controlled Fusion 47, 657 (2005)]. The characteristics of the simulated waves, such as wavelength, frequency, phase, and group velocities, agree well with the linear theoretical analysis. It is shown that a significant reflection component emerges in the conversion process between the slow mode and the fast mode when the scale length of the density variation is comparable to the local wavelength. The dependences of the reflection coefficient on the scale length of the density variation are compared with the results based on the linear full wave model for cold plasmas. It is indicated that the mode conversion for the waves with a frequency of 2.45 GHz (ω ˜ 3ωLH, where ωLH represents the lower hybrid resonance) and within Tokamak relevant amplitudes can be well described in the linear scheme. As the frequency decreases, the modification due to the nonlinear term becomes important. For the low-frequency waves (ω ˜ 1.3ωLH), the generations of the high harmonic modes and sidebands through nonlinear mode-mode coupling provide new power channels and thus could reduce the reflection significantly.

  9. Voltage tuning of the resonance frequency of electroactive polymer membranes over a range of more than 75%

    NASA Astrophysics Data System (ADS)

    Dubois, Philippe; Rosset, Samuel; Niklaus, Muhamed; Shea, Herbert

    2009-05-01

    We report on a novel technique to control the resonance frequency of polymer membranes, without additional external actuators. An electrostatic force is used to apply compressive stress to a dielectric electroactive polymers membrane, consisting of a 25 micron thick, 1 to 4 mm diameter, polydimethylsiloxane (PDMS) film bonded onto patterned silicon or Pyrex wafers. Both sides of the membranes are rendered conductive by low-energy metal ion implantation. Ion implantation is chosen because it stiffens the membrane much less than sputtering a film of similar thickness [1][2]. The initial resonance frequency of the membrane is given by its geometry, the Young's modulus and stress of the composite film. The technique presented here allows tuning the resonance frequency from this initial value down to zero (at the buckling threshold) by adding compressive stress due to a voltage difference applied to the electrodes on both sides of the membrane. We have measured a reduction of the first mode resonance frequency of up to 77% (limited by dielectric breakdown) for ion-implanted membranes [3]. The tuning is repeatable and allows for continuous variation. Excellent agreement was found between our measurements and an analytical model we developed based on the Rayleigh-Ritz theory.

  10. Divinyl-end-functionalized polyethylenes: ready access to a range of telechelic polyethylenes through thiol-ene reactions.

    PubMed

    Norsic, Sebastien; Thomas, Coralie; D'Agosto, Franck; Boisson, Christophe

    2015-04-01

    Telechelic α,ω-iodo-vinyl-polyethylenes (Vin-PE-I) were obtained by catalytic ethylene polymerization in the presence of [(C5 Me5 )2 NdCl2 Li(OEt2 )2 ] in combination with a functionalized chain-transfer agent, namely, di(10-undecenyl)magnesium, followed by treatment of the resulting di(vinylpolyethylenyl)magnesium compounds ((vinyl-PE)2 Mg) with I2 . The iodo-functionalized vinylpolyethylenes (Vin-PE-I) were transformed into unique divinyl-functionalized polyethylenes (Vin-PE-Vin) by simple treatment with tBuOK in toluene at 95 °C. Thiol-ene reactions were then successfully performed on Vin-PE-Vin with functionalized thiols in the presence of AIBN. A range of homobifunctional telechelic polyethylenes were obtained on which a hydroxy, diol, carboxylic acid, amine, ammonium chloride, trimethoxysilyl, chloro, or fluoroalkyl group was installed quantitatively at each chain end. PMID:25688747

  11. Nonlinear frequency up-conversion of femtosecond pulses from an erbium fibre laser to the range of 0.8 - 1 {mu}m in silica fibres

    SciTech Connect

    Anashkina, E A; Andrianov, A V; Kim, A V

    2013-03-31

    We consider different mechanisms of nonlinear frequency up-conversion of femtosecond pulses emitted by an erbium fibre system ({lambda} = 1.5 {mu}m) to the range of 0.8 - 1.2 {mu}m in nonlinear silica fibres. The generation efficiency and the centre frequencies of dispersive waves are found as functions of the parameters of the fibre and the input pulse. Simple analytical estimates are obtained for the spectral distribution of the intensity and the frequency shift of a wave packet in the region of normal dispersion during the emission of a high-order soliton under phase matching conditions. In the geometrical optics approximation the frequency shifts are estimated in the interaction of dispersive waves with solitons in various regimes. (extreme light fields and their applications)

  12. Validity of segmental multiple-frequency bioelectrical impedance analysis to estimate body composition of adults across a range of body mass indexes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Objective: Compare estimates of body composition using segmental, multiple frequency bioelectrical impedance analysis (MF-BIA) with dual x-ray absorptiometry (DXA) in healthy adults across a range of body mass index (BMI). Methods: Percent body fat (%BF), fat-mass (FM), and fat-free mass (FFM) asses...

  13. Influence of temporal noise on the skin blood flow measurements performed by cooled thermal imaging camera: limit possibilities within each physiological frequency range

    NASA Astrophysics Data System (ADS)

    Sagaidachnyi, A. A.; Volkov, I. U.; Fomin, A. V.

    2016-04-01

    This paper describes limit possibilities of modern cooled thermal imaging cameras as a tool for estimation of blood flow oscillations at the surface of living body. Skin temperature oscillations, as we assumed, are a consequence of the blood flow oscillations. We considered the temperature sensitivity 0.01-0.02 °C as a typical for the most of modern cooled long wave thermal imaging cameras. Fourier filter used to investigate the temperature signal separately within endothelial, neurogenic, myogenic, respiratory and cardiac frequency ranges. The level of temporal noise has been estimated during measurements of no living body with stabilized temperature ~ 24°C. The level of temperature oscillations has been calculated for the group of healthy subjects within each frequency range. Thus, we were able to determine signal-to-noise ratio within frequency band [0.001, 1] Hz. As a result, we determine that skin temperature oscillations measured by thermal imaging camera with sensitivity 0.02°C have the upper frequency limit ~ 0.2 Hz. In other words, within the respiratory and cardiac frequency ranges of blood flow oscillations the noise level exceeds signal one, and temperature measurements at the skin surface are practically useless. The endothelial, neurogenic and myogenic components of the temperature oscillations contain ~98% of the total spectral power of the signal. We have plot the empirical extrapolated curve of sensitivity of thermal imaging camera vs. frequency of the temperature oscillations. The data analysis shows that measurements of skin temperature oscillations within respiratory and cardiac ranges require the temperature sensitivity at least ~ 0.01°C and 0.001°C, respectively.

  14. A Tale of Two Frequencies: Determining the Speed of Lexical Access for Mandarin Chinese and English Compounds

    ERIC Educational Resources Information Center

    Janssen, Niels; Bi, Yanchao; Caramazza, Alfonso

    2008-01-01

    Two picture naming experiments show that compound word production in Mandarin Chinese and in English is determined by the compound's whole-word frequency, and not by its constituent morpheme frequency. Four control experiments rule out that these results are caused by recognition or articulatory processes. These results are consistent with models…

  15. Extending the distance range accessed with continuous wave EPR with Gd3+ spin probes at high magnetic fields†

    PubMed Central

    Edwards, Devin T.; Ma, Zhidong; Meade, Thomas J.; Goldfarb, Daniella; Han, Songi

    2014-01-01

    Interspin distances between 0.8 nm and 2.0 nm can be measured through the dipolar broadening of the continuous wave (cw) EPR spectrum of nitroxide spin labels at X-band (9.4 GHz, 0.35 T). We introduce Gd3+ as a promising alternative spin label for distance measurements by cw EPR above 7 Tesla, where the |−1/2〉 to |1/2〉 transition narrows below 1 mT and becomes extremely sensitive to dipolar broadening. To estimate the distance limits of cw EPR with Gd3+, we have measured spectra of frozen solutions of GdCl3 at 8.6 T (240 GHz) and 10 K at concentrations ranging from 50 mM to 0.1 mM, covering a range of average interspin distances. These experiments show substantial dipolar broadening at distances where line broadening cannot be observed with nitroxides at X-band. This data, and its agreement with calculated dipolar-broadened lineshapes, show Gd3+ to be sensitive to distances as long as ~3.8 nm. Further, the linewidth of a bis-Gd3+ complex with a flexible ~1.6 nm bridge is strongly broadened as compared to the mono-Gd3+ complex, demonstrating the potential for application to pairwise distances. Gd-DOTA-based chelates that can be functionalized to protein surfaces display linewidths narrower than aqueous GdCl3, implying they should be even more sensitive to dipolar broadening. Therefore, we suggest that the combination of tailored Gd3+ labels and high magnetic fields can extend the longest interspin distances measurable by cw EPR from 2.0 nm to 3.8 nm. cw EPR data at 260 K demonstrate that the line broadening remains clear out to similar average interspin distances, offering Gd3+ probes as promising distance rulers at temperatures higher than possible with conventional pulsed EPR distance measurements. PMID:23732863

  16. Excitation of electrostatic waves in the electron cyclotron frequency range during magnetic reconnection in laboratory overdense plasmas

    SciTech Connect

    Kuwahata, A.; Igami, H.; Kawamori, E.; Kogi, Y.; Inomoto, M.; Ono, Y.

    2014-10-15

    We report the observation of electromagnetic radiation at high harmonics of the electron cyclotron frequency that was considered to be converted from electrostatic waves called electron Bernstein waves (EBWs) during magnetic reconnection in laboratory overdense plasmas. The excitation of EBWs was attributed to the thermalization of electrons accelerated by the reconnection electric field around the X-point. The radiative process discussed here is an acceptable explanation for observed radio waves pulsation associated with major flares.

  17. Large separations or regular technical patterns? Could data sampling mimic the frequency range of pulsating Delta Scuti stars?

    NASA Astrophysics Data System (ADS)

    Paparo, Margit; Benko, Jozsef M.; Hareter, Markus; Guzik, Joyce A.

    2015-08-01

    Asteroseismology allows unique information on the inner structure of stars. The large separation between the consecutive radial orders and the small separation of the modes with different l values are well-known and useful parameters characterizing solar-type oscillations. The large separation was derived only for a few Delta Scuti stars which are pulsating in the non-asymptotic regime. Theoretical investigations do not predict a high level of regularity of the excited modes. We carried out a search for regularity in a sample of Delta Scuti stars observed by CoRoT (91 stars). Usually the Fourier Transform or the histogram of frequency differences were used. The echelle diagrams represent the regularity when it was found. As a preliminary step we isolated set(s) of frequencies with quasi-equal spacing. Surprisingly not only a single pattern but up to six patterns were found in most of the stars. The patterns are regularly shifted with respect to each other. The echelle diagrams helped to reduce the scatter of the spacing. The derived spacing supported the better interpretation of the FT diagrams. There is no doubt of the existence of regular patterns. The interpretation is questionable: do the Delta Scuti stars behave so regularly, or we are faced with a technical pattern that obscures the real frequency pattern of the low amplitude Delta Scuti pulsation?

  18. Do speakers have access to a mental syllabary? ERP comparison of high frequency and novel syllable production.

    PubMed

    Bürki, Audrey; Cheneval, Pauline Pellet; Laganaro, Marina

    2015-11-01

    The transformation of an abstract phonological code into articulation has been hypothesized to involve the retrieval of stored syllable-sized motor plans. Accordingly, gestural scores for frequently used syllables are retrieved from memory whereas gestural scores for novel and possibly low frequency syllables are assembled on-line. The present study was designed to test this hypothesis. Participants produced disyllabic pseudowords with high frequency, low frequency and non-existent (novel) initial syllables. Behavioral results revealed slower production latencies for novel than for high frequency syllables. Event-related potentials diverged in waveform amplitudes and global topographic patterns between high frequency and low frequency/novel syllables around 170 ms before the onset of articulation. These differences indicate the recruitment of different brain networks during the production of frequent and infrequent/novel syllables, in line with the hypothesis that speakers store syllabic-sized motor programs for frequent syllables and assemble these motor plans on-line for low frequency and novel syllables. PMID:26367062

  19. Multiple Access Trade Study

    NASA Technical Reports Server (NTRS)

    Motamedi, Masoud

    1990-01-01

    The Personal Access Satellite System (PASS) strawman design uses a hybrid Time Division Multiple Access (TDMA)/Frequency Division Multiple Access (FDMA) implementation. TDMA is used for the forward direction (from Suppliers to Users), and FDMA for the return direction (from Users to Suppliers). An alternative architecture is proposed that will require minimal real time coordination and yet provide a fast access method by using random access Code Division Multiple Access (CDMA). The CDMA system issues are addressed such as connecting suppliers and users, both of whom may be located anywhere in the CONUS, when the user terminals are constrained in size and weight; and providing efficient traffic routing under highly variable traffic requirements. It is assumed that bandwidth efficiency is not of paramount importance. CDMA or Spread Spectrum Multiple Access (SSMA) communication is a method in which a group of carriers operate at the same nominal center frequency but are separable from each other by the low cross correlation of the spreading codes used. Interference and multipath rejection capability, ease of selective addressing and message screening, low density power spectra for signal hiding and security, and high resolution ranging are among the benefits of spread spectrum communications.

  20. Note: Ultra-high frequency ultra-low dc power consumption HEMT amplifier for quantum measurements in millikelvin temperature range.

    PubMed

    Korolev, A M; Shnyrkov, V I; Shulga, V M

    2011-01-01

    We have presented theory and experimentally demonstrated an efficient method for drastically reducing the power consumption of the rf/microwave amplifiers based on HEMT in unsaturated dc regime. Conceptual one-stage 10 dB-gain amplifier showed submicrowatt level of the power consumption (0.95 μW at frequency of 0.5 GHz) when cooled down to 300 mK. Proposed technique has a great potential to design the readout amplifiers for ultra-deep-cooled cryoelectronic quantum devices. PMID:21280864

  1. Loading and Asymmetry Measurements and Modeling for the National Spherical Torus Experiment Ion Cyclotron Range of Frequencies System

    SciTech Connect

    Swain, D.W.; Carter, M.D.; Wilson, J.R.; Ryan, P.M.; Wilgen, J.B.; Hosea, J.; Rosenberg, A.

    2003-06-15

    The ion cyclotron heating and current drive system on the National Spherical Torus Experiment (NSTX) has delivered over 3 MW reliably for pulse lengths over 100 ms with various phasings of the antennas. A circuit model of the system that includes the 12 coupled antennas and six radio-frequency sources has been developed that gives good agreement with vacuum measurements. When it is used to experimentally determine the S-matrix of the system under different plasma conditions, pronounced asymmetries in the off-diagonal values of the S-matrix are seen. The S-matrix in the presence of plasma has been calculated with the RANT3D code using measured edge density profiles in front of the antenna; these agree remarkably well with the measurements. The asymmetry is caused primarily by the large pitch angle of the magnetic field in front of the antenna, coupled with the gradients in the plasma edge.

  2. Loading and Asymmetry Measurements and Modeling for the National Spherical Torus Experiment Ion Cyclotron Range of Frequencies System

    SciTech Connect

    Swain, David W; Carter, Mark Dwain; Wilson, J. R.; Ryan, Philip Michael; Wilgen, John B; Hosea, J.; Rosenberg, A.

    2003-01-01

    The ion cyclotron heating and current drive system on the National Spherical Torus Experiment (NSTX) has delivered over 3 MW reliably for pulse lengths over 100 ms with various phasings of the antennas. A circuit model of the system that includes the 12 coupled antennas and six radio-frequency sources has been developed that gives good agreement with vacuum measurements. When it is used to experimentally determine the S-matrix of the system under different plasma conditions, pronounced asymmetries in the off-diagonal values of the S-matrix are seen. The S-matrix in the presence of plasma has been calculated with the RANT3D code using measured edge density profiles in front of the antenna; these agree remarkably well with the measurements. The asymmetry is caused primarily by the large pitch angle of the magnetic field in front of the antenna, coupled with the gradients in the plasma edge.

  3. Dielectric properties measurement method in the microwave frequencies range for non-polar/polar liquid mixtures characterization

    NASA Astrophysics Data System (ADS)

    Surducan, E.; Neamtu, C.; Ienciu, M.; Surducan, V.; Limare, A.; Fourel, L.

    2015-12-01

    We present a method based on dielectric properties measurements over a large spectrum of frequencies, in the microwave (MW) domain, in order to characterize a liquid mixture. The liquid mixtures consist of non-polar fluids (silicone oil, diesel fuel) and polar additives, in order to increase the specific MW absorption of the mixture for further MW power processing. We have measured the MW specific absorptions for mixtures of silicone oil with 20% and 30% (w/w) isopropanol. In both cases, the mixtures are sufficiently stable over time to allow further studies of thermal convection dynamics initiated by MW heating. For a mixture of diesel fuel with 10% (w/w) alkyl polyglycoside, the main observation was that its MW specific absorption varies over time after the mechanical mixing process.

  4. Use of radar QPE for the derivation of Intensity-Duration-Frequency curves in a range of climatic regimes

    NASA Astrophysics Data System (ADS)

    Marra, Francesco; Morin, Efrat

    2015-12-01

    Intensity-Duration-Frequency (IDF) curves are widely used in flood risk management because they provide an easy link between the characteristics of a rainfall event and the probability of its occurrence. Weather radars provide distributed rainfall estimates with high spatial and temporal resolutions and overcome the scarce representativeness of point-based rainfall for regions characterized by large gradients in rainfall climatology. This work explores the use of radar quantitative precipitation estimation (QPE) for the identification of IDF curves over a region with steep climatic transitions (Israel) using a unique radar data record (23 yr) and combined physical and empirical adjustment of the radar data. IDF relationships were derived by fitting a generalized extreme value distribution to the annual maximum series for durations of 20 min, 1 h and 4 h. Arid, semi-arid and Mediterranean climates were explored using 14 study cases. IDF curves derived from the study rain gauges were compared to those derived from radar and from nearby rain gauges characterized by similar climatology, taking into account the uncertainty linked with the fitting technique. Radar annual maxima and IDF curves were generally overestimated but in 70% of the cases (60% for a 100 yr return period), they lay within the rain gauge IDF confidence intervals. Overestimation tended to increase with return period, and this effect was enhanced in arid climates. This was mainly associated with radar estimation uncertainty, even if other effects, such as rain gauge temporal resolution, cannot be neglected. Climatological classification remained meaningful for the analysis of rainfall extremes and radar was able to discern climatology from rainfall frequency analysis.

  5. An inexpensive and versatile technique for wide frequency range surface pressure measurements: an application for the study of turbulent buffeting of a square cylinder

    NASA Astrophysics Data System (ADS)

    Carbajo Fuertes, Fernando; Cecchi, Enrico; van Beeck, Jeroen; Schram, Christophe

    2014-01-01

    This work presents the development of an inexpensive measurement technique based on miniature microphones for the measurement of pressure fluctuations in a wide frequency range, starting from infrasound up to several kilohertz. Special emphasis has been put on achieving accurate calibration of the system at very low frequencies and good agreement with reference measurements have been achieved at frequencies as low as 1 Hz, therefore opening new low-budget research possibilities in many fields of fluid mechanics. The measurement technique proposed is specially indicated when the number of simultaneous pressure measurements is high since the sensors used are inexpensive, contrarily to common research equipment. One particular area in which this technique results useful is bluff-body aerodynamics. As an example of the potential of the technique, the structural response of a finite-square cylinder immersed in a turbulent flow is studied.

  6. Experimental demonstration of a full-duplex high-speed visible light communication access network architecture based on frequency division multiplexing

    NASA Astrophysics Data System (ADS)

    Wang, Yiguang; Wang, Yuanquan; Tao, Li; Shi, Jianyang; Chi, Nan

    2014-11-01

    We propose and experimentally demonstrate a full-duplex high-speed visible light communication (VLC) access network based on star topology architecture to offer high-speed optical wireless access for a large number of users. Optical fiber is used as the backbone of the VLC network and directly connected to the light-emitting diode lamps. Frequency division multiplexing (FDM) is utilized for both the downlink and uplink. The bidirectional transmission of 32 quadrature amplitude modulation orthogonal FDM signals at an overall throughput of 4 Gb/s is successfully achieved to support four users access, and each user is offered 500 Mb/s downstream and 500 Mb/s upstream. The measured bit error rates of the downlink and uplink for all four users are <7% pre-forward error correction limit of 3.8×10-3 after a 25 km standard single-mode fiber and 65 cm free space, which clearly validates the promising potential of the proposed VLC network architecture to offer more than 10 Gb/s wireless access.

  7. Electromagnetic shielding properties of soft magnetic powder-polymer composite films for the application to suppress noise in the radio frequency range

    NASA Astrophysics Data System (ADS)

    Kim, Sang Woo; Yoon, Y. W.; Lee, S. J.; Kim, G. Y.; Kim, Y. B.; Chun, Yun Yeo; Lee, K. S.

    2007-09-01

    Electromagnetic absorption characteristics in the near- and the far-field regime were evaluated from measurements of power loss by the coaxial transmission and reflection method and the microstrip line method, respectively, for high-density soft magnetic Fe-Al-Si alloy-polymer composite films that were highly effective in the radio frequency (RF) range. The electromagnetic absorption in the near- and the far-field regime for the soft magnetic metal-polymer composite films was greatly dependent on the film density. The electromagnetic absorption in the RF range significantly increased with increasing film density, which was caused by the increase of the magnetic permeability and the electrical conductivity. As a result, the high-density soft magnetic film showed excellent electromagnetic absorption for the near- and the far-field electromagnetic shielding and was applicable as an electromagnetic absorber for high-frequency devices operated over 0.1 GHz.

  8. Theoretical and practical aspects of application of a low-energy electromagnetic radiation of the extremely high-frequency range in medicine

    NASA Astrophysics Data System (ADS)

    Lyapina, Elena P.; Chesnokov, Igor A.; Bushuev, Nikolay A.; Kuzyutkina, Svetlana E.; Shuldjakov, Andrey A.

    2006-02-01

    The questions concerning the mechanism of action of a low-energy electromagnetic radiation of the extremely high frequency range (EMR EHF) are considered. Also the features of biological effects are considered in their application as therapeutic actions. As an example the advantages of EHF treatment of patients with chronic brucellosis are shown, the algorithm of a choice of the scheme of treatment using EMR EHF is offered.

  9. Age group estimation in free-ranging African elephants based on acoustic cues of low-frequency rumbles

    PubMed Central

    Stoeger, Angela S.; Zeppelzauer, Matthias; Baotic, Anton

    2015-01-01

    Animal vocal signals are increasingly used to monitor wildlife populations and to obtain estimates of species occurrence and abundance. In the future, acoustic monitoring should function not only to detect animals, but also to extract detailed information about populations by discriminating sexes, age groups, social or kin groups, and potentially individuals. Here we show that it is possible to estimate age groups of African elephants (Loxodonta africana) based on acoustic parameters extracted from rumbles recorded under field conditions in a National Park in South Africa. Statistical models reached up to 70 % correct classification to four age groups (infants, calves, juveniles, adults) and 95 % correct classification when categorising into two groups (infants/calves lumped into one group versus adults). The models revealed that parameters representing absolute frequency values have the most discriminative power. Comparable classification results were obtained by fully automated classification of rumbles by high-dimensional features that represent the entire spectral envelope, such as MFCC (75 % correct classification) and GFCC (74 % correct classification). The reported results and methods provide the scientific foundation for a future system that could potentially automatically estimate the demography of an acoustically monitored elephant group or population. PMID:25821348

  10. HCN channels enhance spike phase coherence and regulate the phase of spikes and LFPs in the theta-frequency range.

    PubMed

    Sinha, Manisha; Narayanan, Rishikesh

    2015-04-28

    What are the implications for the existence of subthreshold ion channels, their localization profiles, and plasticity on local field potentials (LFPs)? Here, we assessed the role of hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels in altering hippocampal theta-frequency LFPs and the associated spike phase. We presented spatiotemporally randomized, balanced theta-modulated excitatory and inhibitory inputs to somatically aligned, morphologically realistic pyramidal neuron models spread across a cylindrical neuropil. We computed LFPs from seven electrode sites and found that the insertion of an experimentally constrained HCN-conductance gradient into these neurons introduced a location-dependent lead in the LFP phase without significantly altering its amplitude. Further, neurons fired action potentials at a specific theta phase of the LFP, and the insertion of HCN channels introduced large lags in this spike phase and a striking enhancement in neuronal spike-phase coherence. Importantly, graded changes in either HCN conductance or its half-maximal activation voltage resulted in graded changes in LFP and spike phases. Our conclusions on the impact of HCN channels on LFPs and spike phase were invariant to changes in neuropil size, to morphological heterogeneity, to excitatory or inhibitory synaptic scaling, and to shifts in the onset phase of inhibitory inputs. Finally, we selectively abolished the inductive lead in the impedance phase introduced by HCN channels without altering neuronal excitability and found that this inductive phase lead contributed significantly to changes in LFP and spike phase. Our results uncover specific roles for HCN channels and their plasticity in phase-coding schemas and in the formation and dynamic reconfiguration of neuronal cell assemblies. PMID:25870302

  11. Simple fabrication of an antireflective hemispherical surface structure using a self-assembly method for the terahertz frequency range.

    PubMed

    Kim, Dae-Seon; Kim, Dong-Ju; Kim, Dong-Hyun; Hwang, Sehyun; Jang, Jae-Hyung

    2012-07-01

    A hemispherical surface structure was fabricated on a sapphire substrate by utilizing a self-assembly and spin-coating process for a terahertz (THz) antireflection coating. The self-assembled glass spheres and spin-coated material led to a gradual change in the effective refractive index. The aspect ratio of the hemispherical surface structure was controlled easily by adjusting the thickness of the B-staged bisbenzocyclobutene used as a coating. The reflectance of the fabricated hemispherical surface structure, having a period of 140 μm, exhibited low reflectance and low Fabry-Perot resonance in a THz spectral range from 0.1 to 1.9 THz. PMID:22743514

  12. The effect of hair bundle shape on hair bundle hydrodynamics of non-mammalian inner ear hair cells for the full frequency range.

    PubMed

    Shatz, Lisa F

    2004-09-01

    The effect of the size and the shape of the hair bundle of a hair cell in the inner ear of non-mammals on its motion for the full range of frequencies is determined thereby extending the results of a previous analysis of hair bundle motion for high and low frequencies [Hear Res. 141 (2000) 39-50]. A hemispheroid is used to represent the hair bundle because it can represent a full range of shapes, from thin, pencil-like shapes to wide, flat, disk-like shapes. Boundary element methods are used to approximate the solution for the hydrodynamics. For physiologically relevant parameters, an excellent match is obtained between the model's predictions and measurements of hair bundle motion in the free-standing region of the basilar papilla of the alligator lizard [Aranyosi, Measuring sound-induced motions of the alligator lizard cochlea. Massachusetts Institute of Technology, PhD Thesis, 2002]. Neither in the model's predictions nor in experimental measurements is sharp tuning observed. The model predicted the low frequency region of neural tuning curves for the alligator lizard and bobtail lizard, but could not predict the sharp tuning or the high frequency region. An element that represents an active mechanism is added to the hair bundle model to predict neural tuning curves, which are sharply tuned, and an excellent match is obtained for all the characteristics of neural tuning curves for the alligator lizard, and for the low and high frequency regions for the bobtail lizard. The model does not predict well the sharp tuning of the shorter hair bundles of the bobtail lizard, possibly because it does not represent tectorial sallets. PMID:15350278

  13. Neural network interpretation of electromagnetic ellipticity data in a frequency range from 1 kHz to 32 MHz

    NASA Astrophysics Data System (ADS)

    Birken, Ralf Andreas

    A new real-time in-field interpretation and visualization scheme and software, using neural networks for the detection and localization of buried waste, and the boundaries of waste sites, has been developed. The capabilities and limitations of the high-frequency (1 kHz to 1 MHz and 31 kHz to 32 MHz) electromagnetic ellipticity systems are analyzed by numerically studying the sensitivity of the acquired 3D-ellipticity to model parameters describing the geometry of the systems and the electrical parameters of layered-earth models. Changes in ellipticity due to coil misalignment in standard operating mode are typically just 1% to 2%. Changes due to variations in layered-earth model parameters (resistivity, relative dielectric constant, and thickness) are typically at least one order of magnitude higher. Hence, it will be possible to resolve these parameters. For conductive models (resistivity <50 Omegam) it will be hard to determine the relative dielectric constant and for models with high relative dielectric constants it will be hard to determine the resistivity, especially if it is greater than 1000 Omegam. The results of the sensitivity analysis contribute considerably to the training of several neural networks to determine the electrical properties of the subsurface. The two classes of artificial neural network paradigms utilized in this study are the radial basis function and the modular neural network algorithms. One-dimensional layered-earth inversions are performed by neural networks using ellipticity data. The three-dimensional localization of metallic objects (e.g. drums) is done by visualizing the results of one particular halfspace neural network technique. Several small conductive objects have been detected by applying this technique to data collected in controlled physical modeling field experiments. Classification neural networks are trained on field data to categorize ellipticity soundings into either a target or a background class. Two environmental

  14. Functional organization of mustached bat inferior colliculus: I. Representation of FM frequency bands important for target ranging revealed by 14C-2-deoxyglucose autoradiography and single unit mapping.

    PubMed

    O'Neill, W E; Frisina, R D; Gooler, D M

    1989-06-01

    The representation in the inferior colliculus of the frequency modulated (FM) components of the first (25-30 kHz) and second (50-60 kHz) harmonic of the sonar signal of the mustached bat, which may be important for target range processing, was investigated by using the 2-deoxyglucose (2-DG) technique and single-unit mapping. In the 2-DG experiments, bats presented with second harmonic FM stimuli alone showed uptake of label in specific regions of the central nucleus and dorsal cortex of the inferior colliculus, and the nucleus of the brachium. In the central nucleus, a dorsoventrally and mediolaterally elongated slab at the caudal border of the anterolateral division was observed. Labeling in the dorsal cortex was contiguous with this band. Bats stimulated with pairs of first and second harmonic FM stimuli separated by short time delays showed similar patterns of labeling, with the addition of another dorsoventrally elongated region of uptake in the more rostral part of the anterolateral division, associated with label in the dorsal cortex. By comparison to control cases exposed to delayed pairs of first and third harmonic signals, or to a second harmonic constant-frequency tone burst at the bat's reference frequency (ca. 60 kHz), we deduced that this additional region of uptake was attributable to the first harmonic FM component. To elucidate further the details of the tonotopic organization and to correlate the frequency representation with anatomical features of the IC, fine-grained maps of single-unit best frequencies were obtained in the central nucleus. Isofrequency contours were reconstructed by computer from five bats after focal, iontophoretic injection of horseradish peroxidase to locate the penetrations and trace connections of the FM2 area. We found that the tissue volume representing FM2 frequencies (50-60 kHz) showed approximately a sixfold overrepresentation for this frequency band. This region occupied most of the caudal portion of the anterolateral

  15. Calibration of miniature medical ultrasonic hydrophones for frequencies in the range 100 to 500 kHz using an ultrasonically absorbing waveguide.

    PubMed

    Rajagopal, Srinath; Zeqiri, Bajram; Gélat, Pierre N

    2014-05-01

    Enhancements to the existing primary standard optical interferometer and narrowband tone-burst comparison calibration methods for miniature medical ultrasonic hydrophones of the membrane type over the frequency range 100 to 500 kHz are described. Improvements were realized through application of an ultrasonically absorbing waveguide made of a low-frequency-absorbing tile used in sonar applications which narrows the spatial extent of the broad acoustic field. The waveguide was employed in conjunction with a sonar multilayered polyvinylidene difluoride (PVDF) hydrophone used as a transmitting transducer covering a frequency range of 100 kHz to 1 MHz. The acoustic field emanating from the ultrasonically absorbing waveguide reduced the significance of diffracted acoustic waves from the membrane hydrophone ring and the consequent interference of this wave with the direct acoustic wave received by the active element of the hydrophone during calibration. Four membrane hydrophone make/ models with ring sizes (defined as the inner diameter of the annular mounting ring of the hydrophone) in the range 50 to 100 mm were employed along with a needle hydrophone. A reference membrane hydrophone, calibrated using the NPL primary standard optical interferometer in combination with the ultrasonically absorbing waveguide, was subsequently used to calibrate the other four hydrophones by comparison, again using the ultrasonically absorbing waveguide. In comparison to existing methods, the use of the ultrasonically absorbing waveguide enabled the low-frequency calibration limit of a membrane hydrophone with a ring diameter of 50 mm to be reduced from 400 kHz to 200 kHz. PMID:24803021

  16. High resolution, high frequency, close-range laser scanning to monitor bedrock erosion after mountain river dam removal

    NASA Astrophysics Data System (ADS)

    Cook, K. L.; Stark, C. P.

    2011-12-01

    The Chijiawan river, located in the Hsuehshan Range in central Taiwan, is a steep, coarse-grained, mixed bedrock-alluvial channel subject to heavy monsoonal rainfall, occasional typhoons and frequent floods. In May 2011, a 15m-high check dam holding back around 200,000m3 of sediment was removed. To monitor subsequent channel response, an array of instruments were deployed prior to dam removal. Given the anticipated magnitude of sediment transport and excellent empirical constraints, the Chijiawan channel is an ideal location to study fluvial incision processes into bedrock. There is abundant bedrock exposed in the river bed downstream of the dam, and we are interested in how the pulse of sediment following dam removal will impact bedrock erosion rates. We monitor erosion using repeat high resolution laser scanning at 8 sites spread along a 3 km long reach, 2 sites upstream of the dam and 6 downstream. We scan two sites with a Konica Minolta Vivid 910 scanner (with an accuracy of 1.4mm), and the remaining sites with a Faro Photon 120 scanner (with an accuracy of 2mm). Scanning at ranges of ~1m (Vivid) to ~10m (Faro), we obtain resolutions of 1 to 3mm. Based on the system developed by Wilson and Hovius (2010), reference frames for repeat surveys consist of permanent stainless steel sockets installed in 14 cm deep holes drilled into the bedrock, combined with removable targets that screw into the sockets for scanning. Vivid data are processed and 3D models are constructed using Rapidform 2004 software. Faro data is processed using Faro's Scene software. In order to compare the high resolution scanning with more traditional low-tech monitoring methods, we have also installed two sets of concrete expansion bolts. We obtain profiles between bolts with both a contour gauge and the scanners. The high accuracy and resolution of these scanners, and the system of precise benchmarks enable us to detect extremely small amounts of erosion. By repeat scanning after individual

  17. The Optoelectronic Swept-Frequency Laser and Its Applications in Ranging, Three-Dimensional Imaging, and Coherent Beam Combining of Chirped-Seed Amplifiers

    NASA Astrophysics Data System (ADS)

    Vasilyev, Arseny

    This thesis explores the design, construction, and applications of the optoelectronic swept-frequency laser (SFL). The optoelectronic SFL is a feedback loop designed around a swept-frequency (chirped) semiconductor laser (SCL) to control its instantaneous optical frequency, such that the chirp characteristics are determined solely by a reference electronic oscillator. The resultant system generates precisely controlled optical frequency sweeps. In particular, we focus on linear chirps because of their numerous applications. We demonstrate optoelectronic SFLs based on vertical-cavity surface-emitting lasers (VCSELs) and distributed-feedback lasers (DFBs) at wavelengths of 1550 nm and 1060 nm. We develop an iterative bias current predistortion procedure that enables SFL operation at very high chirp rates, up to 1016 Hz/sec. We describe commercialization efforts and implementation of the predistortion algorithm in a stand-alone embedded environment, undertaken as part of our collaboration with Telaris, Inc. We demonstrate frequency-modulated continuous-wave (FMCW) ranging and three-dimensional (3-D) imaging using a 1550 nm optoelectronic SFL. We develop the technique of multiple source FMCW (MS-FMCW) reflectometry, in which the frequency sweeps of multiple SFLs are "stitched" together in order to increase the optical bandwidth, and hence improve the axial resolution, of an FMCW ranging measurement. We demonstrate computer-aided stitching of DFB and VCSEL sweeps at 1550 nm. We also develop and demonstrate hardware stitching, which enables MS-FMCW ranging without additional signal processing. The culmination of this work is the hardware stitching of four VCSELs at 1550 nm for a total optical bandwidth of 2 THz, and a free-space axial resolution of 75 microns. We describe our work on the tomographic imaging camera (TomICam), a 3-D imaging system based on FMCW ranging that features non-mechanical acquisition of transverse pixels. Our approach uses a combination of

  18. COOMET.AUV.W-S1 supplementary comparison of free-field hydrophone calibrations in the frequency range 250 Hz to 8 kHz

    NASA Astrophysics Data System (ADS)

    Isaev, A. E.; Yi, Chen; Matveev, A. N.; Zihong, Ping

    2015-01-01

    A description is given of COOMET.AUV.W-S1 supplementary comparison of free-field hydrophone calibrations in the frequency range 250 Hz to 8 kHz between Hangzhou Applied Acoustics Research Institute—a pilot and Russian National Research Institute for Physicotechnical and Radio Engineering Measurements. Two standard hydrophones of TC 4033 and GI 55 were calibrated in this comparison. Reciprocity method, comparison methods, and their facilities were used to assess the current state of free-field hydrophone calibration in the frequency range 250 Hz to 8 kHz of China and Russia. The consistency of calibration results between two participants was confirmed, and the maximum deviation observed was 0.59 dB at frequency 400 Hz. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  19. Study of the dielectric properties of weathered granite, basalt and quartzite by means of broadband dielectric spectroscopy over a wide range of frequency and temperature.

    NASA Astrophysics Data System (ADS)

    Araujo, Steven; Delbreilh, Laurent; Antoine, Raphael; Dargent, Eric; Fauchard, Cyrille

    2016-04-01

    Broadband Dielectric Spectroscopy (BDS) allows the measurement of the complex impedance of various materials over a wide range of frequency (0.1 Hz to 2 MHz) and temperature (-150 to 400°C). Other properties can be assessed from this measurement such as permittivity and conductivity. In this study, the BDS is presented to figure out the complex behaviour of several rock parameters as a function of the temperature and frequency. Indeed, multiple processes might occur such as interfacial polarization, AC and DC conductivity. The measurements of a weathered granite, basalt and quartzite were performed. The activation energy associated to each process involved during the measurement can be calculated by following the relaxation time as a function of the temperature, taking into account the Havriliak-Négami model. The principle of the technique and the whole study is presented here and several hypothesis are advanced to explain the dielectric behaviour of rocks. Finally, as the range of frequency and temperature of the BDS method is common to several electromagnetic and electrical techniques applied in subsurface geophysics, some perspectives are proposed to better understand geophysical measurements in hydrothermal systems.

  20. Image-Guided Ultrasound Characterization of Volatile Sub-Micron Phase-Shift Droplets in the 20-40 MHz Frequency Range.

    PubMed

    Sheeran, Paul S; Daghighi, Yasaman; Yoo, Kimoon; Williams, Ross; Cherin, Emmanuel; Foster, F Stuart; Burns, Peter N

    2016-03-01

    Phase-shift perfluorocarbon droplets are designed to convert from the liquid to the gas state by the external application of acoustic or optical energy. Although droplet vaporization has been investigated extensively at ultrasonic frequencies between 1 and 10 MHz, few studies have characterized performance at the higher frequencies commonly used in small animal imaging. In this study, we use standard B-mode imaging sequences on a pre-clinical ultrasound platform to both image and activate sub-micron decafluorobutane droplet populations in vitro and in vivo at center frequencies in the range of 20-40 MHz. Results show that droplets remain stable against vaporization at low imaging pressures but are vaporized at peak negative pressures near 3.5 MPa at the three frequencies tested. This study also found that a small number of size outliers present in the distribution can greatly influence droplet performance. Removal of these outliers results in a more accurate assessment of the vaporization threshold and produces free-flowing microbubbles upon vaporization in the mouse kidney. PMID:26725168

  1. Spontaneous and forced oscillations of cell membrane of normal human erythrocytes: absence of resonance frequencies in a range of 0.03-500 Hz.

    PubMed

    Kononenko, V L; Shimkus, J K

    2000-01-01

    The spectra of natural oscillations of human erythrocyte cell membranes were studied experimentally and theoretically. The measurements were carried out at room temperature for both single normal cells and erythrocyte rouleaux in a range of 0.03-500 Hz. The spectra were measured at a resolution better than 1% using two techniques: registration of spontaneous membrane oscillations induced by thermal agitation in the surrounding medium and registration of the amplitude-frequency characteristics of the forced oscillations of erythrocyte elongation induced by a high-frequency electric field with the amplitude harmonic modulation. The spectra measured by both techniques had no resonance frequencies and decreased monotonically with the frequency increase. These results are confirmed by the theory developed for the extracellular excitation mechanisms of membrane oscillations. The spectra of active oscillatory biomechanical processes were measured for comparison. These processes are ciliary beating of human bronchial epithelium and ciliary beating and artificial periodic contractions of the cytoplasm of the ciliate Spirostomum ambiguum. The quality of the resonance lines of the order of 10-20 registered may serve as estimates for the line width in search of the resonance oscillations in erythrocytes induced by active cell processes. PMID:11368497

  2. The effect of a Lean quality improvement implementation program on surgical pathology specimen accessioning and gross preparation error frequency.

    PubMed

    Smith, Maxwell L; Wilkerson, Trent; Grzybicki, Dana M; Raab, Stephen S

    2012-09-01

    Few reports have documented the effectiveness of Lean quality improvement in changing anatomic pathology patient safety. We used Lean methods of education; hoshin kanri goal setting and culture change; kaizen events; observation of work activities, hand-offs, and pathways; A3-problem solving, metric development, and measurement; and frontline work redesign in the accessioning and gross examination areas of an anatomic pathology laboratory. We compared the pre- and post-Lean implementation proportion of near-miss events and changes made in specific work processes. In the implementation phase, we documented 29 individual A3-root cause analyses. The pre- and postimplementation proportions of process- and operator-dependent near-miss events were 5.5 and 1.8 (P < .002) and 0.6 and 0.6, respectively. We conclude that through culture change and implementation of specific work process changes, Lean implementation may improve pathology patient safety. PMID:22912352

  3. Brazing of ceramic and graphite to metal in the fabrication of ICRF (ion cyclotron range of frequencies) antenna and feedthrough components

    SciTech Connect

    Schechter, D.E.; Sluss, F.; Hoffman, D.J.

    1987-01-01

    Fabrication of some of the more critical components of ion cyclotron range of frequencies (ICRF) antenna and feedthrough assemblies has involved the brazing of alumina ceramic and graphite to various metals. Copper end pieces have been successfully brazed to alumina cylinders for use in feedthroughs for TEXTOR and in feedthroughs and capacitors for a Tokamak Fusion Test Reactor (TFTR) antenna. Copper-plated Inconel rods and tubes have been armored with graphite for construction of Faraday shields on antennas for Doublet III-D and TFTR. Details of brazing procedures and test results, including rf performance, mechanical strength, and thermal capabilities, are presented. 14 figs.

  4. The acoustic power of a vibrating clamped circular plate revisited in the wide low frequency range using expansion into the radial polynomials.

    PubMed

    Rdzanek, Wojciech P

    2016-06-01

    This study deals with the classical problem of sound radiation of an excited clamped circular plate embedded into a flat rigid baffle. The system of the two coupled differential equations is solved, one for the excited and damped vibrations of the plate and the other one-the Helmholtz equation. An approach using the expansion into radial polynomials leads to results for the modal impedance coefficients useful for a comprehensive numerical analysis of sound radiation. The results obtained are accurate and efficient in a wide low frequency range and can easily be adopted for a simply supported circular plate. The fluid loading is included providing accurate results in resonance. PMID:27369144

  5. Rapid spectrum measurement at 3  μm over 100  nm wavelength range using mid-infrared difference frequency generation source.

    PubMed

    Abe, Masashi; Nishida, Yoshiki; Tadanaga, Osamu; Tokura, Akio; Takenouchi, Hirokazu

    2016-04-01

    We demonstrate a broadband rapid scanning light source in the 3-μm region by using difference frequency generation (DFG). The DFG source consists of a module with quasi-phase-matched LiNbO3 ridge waveguides, a 1-μm-band wide swept range laser for the pump source, and a 1.5-μm continuous wave laser for the signal source. The sweep rate and the tuning bandwidth of this source are 20 kHz and 100 nm, respectively. This source enables us to evaluate the temperature dependence of absorbance of methane gas. PMID:27192241

  6. 1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

    SciTech Connect

    Sadeev, T. Arsenijević, D.; Bimberg, D.; Franke, D.; Kreissl, J.; Künzel, H.

    2015-01-19

    Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 to 300 mA leads to 30 MHz frequency tuning.

  7. Band gaps in the low-frequency range based on the two-dimensional phononic crystal plates composed of rubber matrix with periodic steel stubs

    NASA Astrophysics Data System (ADS)

    Yu, Kunpeng; Chen, Tianning; Wang, Xiaopeng

    2013-05-01

    In this paper, the numerical investigation of elastic wave propagation in two-dimensional phononic crystals composed of an array of steel stepped resonators on a thin rubber slab is presented. For the first time the rubber material is used as the matrix of the PCs. With the finite-element method, the dispersion relations of this novel PCs structure and some factors of the band structure are studied. Results show that, with the rubber material as matrix, the PC structures exhibit extremely low-frequency band gaps, in the frequency range of hundreds of Hz or even tens of Hz; the geometrical parameters and the material parameters can modulate the band gaps to different extents. Furthermore, to understand the low-frequency band gaps caused by this new structure, some resonance eigenmodes of the structure are calculated. Results show that the vibration of the unit cell of the structure can be seen as several mass-spring systems, in which the vibration of the steel stepped resonator decides the lower boundary of the first band gap and the vibration of the rubber that is not in contact with the resonator decides the upper boundary.

  8. Relationship between peak spatial-averaged specific absorption rate and peak temperature elevation in human head in frequency range of 1–30 GHz

    NASA Astrophysics Data System (ADS)

    Morimoto, Ryota; Laakso, Ilkka; De Santis, Valerio; Hirata, Akimasa

    2016-07-01

    This study investigates the relationship between the peak temperature elevation and the peak specific absorption rate (SAR) averaged over 10 g of tissue in human head models in the frequency range of 1–30 GHz. As a wave source, a half-wave dipole antenna resonant at the respective frequencies is located in the proximity of the pinna. The bioheat equation is used to evaluate the temperature elevation by employing the SAR, which is computed by electromagnetic analysis, as a heat source. The computed SAR is post-processed by calculating the peak spatial-averaged SAR with six averaging algorithms that consider different descriptions provided in international guidelines and standards, e.g. the number of tissues allowed in the averaging volume, different averaging shapes, and the consideration of the pinna. The computational results show that the SAR averaging algorithms excluding the pinna are essential when correlating the peak temperature elevation in the head excluding the pinna. In the averaging scheme considering an arbitrary shape, for better correlation, multiple tissues should be included in the averaging volume rather than a single tissue. For frequencies higher than 3–4 GHz, the correlation for peak temperature elevation in the head excluding the pinna is modest for the different algorithms. The 95th percentile value of the heating factor as well as the mean and median values derived here would be helpful for estimating the possible temperature elevation in the head.

  9. Frequency of radial artery occlusion after transradial access in patients receiving warfarin therapy and undergoing coronary angiography.

    PubMed

    Pancholy, Samir B; Ahmed, Imdad; Bertrand, Olivier F; Patel, Tejas

    2014-01-15

    The efficacy of warfarin-induced anticoagulation in reducing radial artery occlusion (RAO) after transradial access is not known. The present case-control study compared the incidence of early (24 hours) and late (30 days) RAO in patients undergoing transradial diagnostic coronary angiography during therapeutic warfarin anticoagulation (group 1) with that of a matched (3:1) cohort of patients not receiving warfarin and receiving intraprocedural heparin (group 2). All patients underwent transradial diagnostic coronary angiography using a 5F hydrophilic introducer sheath. The patients in group 2 received an intravenous heparin bolus (50 IU/kg) immediately after sheath insertion. After sheath removal, hemostasis was obtained using the TR-band (Terumo Interventional Systems, Terumo Medical, Tokyo, Japan) and a plethysmography-guided patent hemostasis technique. We included 86 patients receiving warfarin with an international normalized ratio of 2 to 4 in group 1 and 250 matched patients in group 2. No significant differences were present in the demographic and procedural variables between the 2 groups. Early RAO occurred in 18.6% of the patients in group 1 compared with 9.6% of patients in group 2 (p = 0.024). The incidence of late RAO remained significantly higher in group 1 compared with group 2 (13.9% vs 5.2%, p = 0.01). All patients with RAO remained asymptomatic. In conclusion, patients receiving chronic oral anticoagulation with warfarin and undergoing transradial coronary angiography without parenteral anticoagulation had a higher incidence of early and late RAO compared with patients receiving standard intravenous heparin therapy. PMID:24210677

  10. The effects of slight pressure oscillations in the far infrasound frequency range on the pars flaccida in gerbil and rabbit ears

    NASA Astrophysics Data System (ADS)

    Didyk, L. A.; Bogdanov, V. B.; Lysenko, V. A.; Didyk, N. P.; Gorgo, Yu P.; Dirckx, J. J. J.

    2007-01-01

    This study was designed to clarify whether the pars flaccida (PF) as a flexible part of the tympanic membrane is capable of reacting to pressure oscillations (PO) with amplitudes and frequencies typical for natural atmospheric pressure fluctuations in the far infrasound frequency range (APF). If so, the PF mechanical reactions to APF might be involved in the overall physiologic regulation processes, which make organisms susceptible to APF. The displacements of the PF in response to PO were measured in vitro in ears of gerbils and rabbits by means of laser Doppler vibrometry. The index of the PF reactivity (Ra) was determined as the ratio of the amplitude of the PF oscillations (PFO) to the amplitude of the PO. All kinds of PO applied caused PFO. The amplitude of the PFO increased when the amplitude of the PO was increased. In gerbils, a decrease in Ra with the increase in amplitude of the PO was observed. In the range of PO lowest amplitudes (4-20 Pa) Ra proved to be 1.4 times higher than in the range of highest amplitudes (90-105 Pa). Considering that the natural APF are usually within the range of ±20 Pa, this fact points to an important contribution of the PF to the pressure dynamics in the middle ear (ME) of gerbils. In rabbit ears, Ra was lower and recovery from plastic deformation was slower than in gerbils. Our findings are in line with the suggestion that the PF might play an important role in respect of adaptation to natural APF.

  11. Lower hybrid current drive and ion cyclotron range of frequencies heating experiments in H-mode plasmas in Experimental Advanced Superconducting Tokomak

    SciTech Connect

    Zhang, X. J.; Wan, B. N. Zhao, Y. P.; Ding, B. J.; Xu, G. S.; Gong, X. Z.; Li, J. G.; Lin, Y.; Wukitch, S.; Taylor, G.; Noterdaeme, J. M.; Braun, F.; Magne, R.; Litaudon, X.; Kumazawa, R.; Kasahara, H.

    2014-06-15

    An ion cyclotron range of frequencies (ICRF) system with power up to 6.0 MW and a lower hybrid current drive (LHCD) system up to 4 MW have been applied for heating and current drive experiments in Experimental Advanced Superconducting Tokomak (EAST). Significant progress has been made with ICRF heating and LHCD for realizing the H-mode plasma operation in EAST. During 2010 and 2012 experimental campaigns, ICRF heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H minority heating (H-MH) mode. The H-MH mode produced good plasma performance, and realized H-mode using ICRF power alone in 2012. In 2010, H-modes were generated and sustained by LHCD alone, where lithium coating and gas puffing near the mouth of the LH launcher were applied to improve the LHCD power coupling and penetration into the core plasmas of H-modes. In 2012, the combination of LHCD and ICRH power extended the H-mode duration up to over 30 s. H-modes with various types of edge localized modes (ELMs) have been achieved with H{sub IPB98}(y, 2) ranging from 0.7 to over unity. A brief overview of LHCD and ICRF Heating experiment and their application in achieving H-mode operation during these two campaigns will be presented.

  12. Electrodeposited thin FeCo films with highly thermal stable properties in high frequency range obtained by annealing in a strong magnetic field

    NASA Astrophysics Data System (ADS)

    Zong, B. Y.; Phuoc, N. N.; Wu, Y. P.; Ho, P.; Yang, Y.; Li, Z. W.

    2016-08-01

    The preparation of thin ferromagnetic films with thermally stable properties in the high frequency gigahertz range is crucial for applications in different advanced devices. However, it is a challenge to attain such films as the mechanism and correlation between the crystallographic structure and dynamic magnetic properties remain unclear. Herein, through an appropriate annealing process involving a temperature of 510-580 K and an applied strong magnetic field of 10 kOe along the easy-axis of electrodeposited FeCo films, magnetic properties of the films (300-450 nm) in the gigahertz range are significantly improved. Typically, the magnetic soft nanofilms display highly stable dynamic microwave properties from room temperature to 420 K, even in the presence of a high frequency of ˜1.5 GHz and a large magnetic permeability of ˜460 (the maximum value in real part). The origin of the high thermal stability is attributed to the recrystallized uniformity in crystalline orientations and larger particle sizes after the annealing, which leads to slightly increased anisotropy, stress, Curie temperature, and difference in the magnetic coercivity between the easy and hard axes for the crystalline films, thus giving rise to the steady static magnetic properties (e.g., magnetic moment of 2.02-2.05 T) against environmental temperature fluctuation. This is in contrast to conventional as-prepared thin films without annealing or annealed in a transverse applied field. This method can be applied to other ferromagnetic films to improve their thermal stability for the utilization in various high frequency devices.

  13. 1 Gbps full-duplex links for ultra-dense-WDM 6.25 GHz frequency slots in optical metro-access networks.

    PubMed

    Altabas, Jose A; Izquierdo, David; Lazaro, Jose A; Lerin, Adolfo; Sotelo, Felix; Garces, Ignacio

    2016-01-11

    1 Gbps full-duplex optical links for 6.25 GHz ultra dense WDM frequency slots are demonstrated and optimized for cost-effective metro-access networks. The OLT-ONU downlinks are based on 1 Gbps Nyquist-DPSK using MZM and single-detector heterodyne reception obtaining a sensitivity of -52 dBm. The ONU-OLT uplinks are based on 1 Gbps NRZ-DPSK by directly phase modulated DFB and also single-detector heterodyne reception obtaining same sensitivity of -52 dBm. The power budget of full-duplex link is 43 dB. These proposed links can provide service to 16 (32) users at each 100 (200) GHz WDM channel. PMID:26832286

  14. Physical-layer energy-efficient receiving method based on selective sampling in orthogonal frequency division multiplexing access passive optical network

    NASA Astrophysics Data System (ADS)

    Li, Jun; He, Hao; Bi, Meihua; Hu, Weisheng

    2014-05-01

    We propose a physical-layer energy-efficient receiving method based on selective sampling in an orthogonal frequency division multiplexing access passive optical network (OFDMA-PON). By using the special designed frame head, the receiver within an optical network unit (ONU) can identify the destination of the incoming frame. The receiver only samples at the time when the destination is in agreement with the ONU, while it stays in standby during the rest of the time. We clarify its feasibility through an experiment and analyze the downstream traffic delay by simulation. The results indicate that under limited delay conditions, ˜60% energy can be saved compared with the traditional receiving method in the OFDMA-PON system with 512 ONUs.

  15. Suppression of optical beat interference-noise in orthogonal frequency division multiple access-passive optical network link using self-homodyne balanced detection

    NASA Astrophysics Data System (ADS)

    Won, Yong-Yuk; Jung, Sang-Min; Han, Sang-Kook

    2014-08-01

    A new technique, which reduces optical beat interference (OBI) noise in orthogonal frequency division multiple access-passive optical network (OFDMA-PON) links, is proposed. A self-homodyne balanced detection, which uses a single laser for the optical line terminal (OLT) as well as for the optical network unit (ONU), reduces OBI noise and also improves the signal to noise ratio (SNR) of the discrete multi-tone (DMT) signal. The proposed scheme is verified by transmitting quadrature phase shift keying (QPSK)-modulated DMT signal over a 20-km single mode fiber. The optical signal to noise ratio (OSNR), that is required for BER of 10-5, is reduced by 2 dB in the balanced detection compared with a single channel due to the cancellation of OBI noise in conjunction with the local laser.

  16. Josephson effect due to the long-range odd-frequency triplet superconductivity in SFS junctions with Néel domain walls

    NASA Astrophysics Data System (ADS)

    Fominov, Ya. V.; Volkov, A. F.; Efetov, K. B.

    2007-03-01

    We consider a SFS Josephson junction made of two superconductors S and a multidomain ferromagnet F with an in-plane magnetization. We assume that the neighboring domains of the ferromagnet are separated by Néel domain walls. An odd-frequency triplet long-range component of superconducting correlations arises in the domain walls and spreads into the domains over a long distance of the order ξT=D/2πT , where D is the diffusion coefficient (dirty limit is implied). We calculate the contribution of this component to the Josephson current in the situation when conventional short-range components exponentially decay over the thickness of the F layer and can be neglected. In the limit when the thickness of the F layer is much smaller than the penetration length of the long-range component, we find that the junction is in the π state. We also analyze a correction to the density of states due to the long-range triplet component.

  17. Gd(III)-Gd(III) EPR distance measurements--the range of accessible distances and the impact of zero field splitting.

    PubMed

    Dalaloyan, Arina; Qi, Mian; Ruthstein, Sharon; Vega, Shimon; Godt, Adelheid; Feintuch, Akiva; Goldfarb, Daniella

    2015-07-28

    Gd(III) complexes have emerged as spin labels for distance determination in biomolecules through double-electron-electron resonance (DEER) measurements at high fields. For data analysis, the standard approach developed for a pair of weakly coupled spins with S = 1/2 was applied, ignoring the actual properties of Gd(III) ions, i.e. S = 7/2 and ZFS (zero field splitting) ≠ 0. The present study reports on a careful investigation on the consequences of this approach, together with the range of distances accessible by DEER with Gd(III) complexes as spin labels. The experiments were performed on a series of specifically designed and synthesized Gd-rulers (Gd-PyMTA-spacer-Gd-PyMTA) covering Gd-Gd distances of 2-8 nm. These were dissolved in D2O-glycerol-d8 (0.03-0.10 mM solutions) which is the solvent used for the corresponding experiments on biomolecules. Q- and W-band DEER measurements, followed by data analysis using the standard data analysis approach, used for S = 1/2 pairs gave the distance-distribution curves, of which the absolute maxima agreed very well with the expected distances. However, in the case of the short distances of 2.1 and 2.9 nm, the distance distributions revealed additional peaks. These are a consequence of neglecting the pseudo-secular term in the dipolar Hamiltonian during the data analysis, as is outlined in a theoretical treatment. At distances of 3.4 nm and above, disregarding the pseudo-secular term leads to a broadening of a maximum of 0.4 nm of the distance-distribution curves at half height. Overall, the distances of up to 8.3 nm were determined, and the long evolution time of 16 μs at 10 K indicates that a distance of up to 9.4 nm can be accessed. A large distribution of the ZFS parameter, D, as is found for most Gd(III) complexes in a frozen solution, is crucial for the application of Gd(III) complexes as spin labels for distance determination via Gd(III)-Gd(III) DEER, especially for short distances. The larger ZFS of Gd-PyMTA, in

  18. Dynamics of Flare Processes and Variety of the Fine Structure of Solar Radio Emission over a Wide Frequency Range of 30 - 7000 MHz

    NASA Astrophysics Data System (ADS)

    Chernov, Gennady; Fomichev, Valery; Tan, Baolin; Yan, Yihua; Tan, Chengming; Fu, Qijun

    2015-01-01

    Radiobursts exhibiting fine structure observed over two years during the rising phase of Cycle 24 by the Chinese Solar Broadband Radio Spectrometer (SBRS/Huairou) in the range 1 - 7.6 GHz and the spectrograph IZMIRAN in the meter range (25 - 270 MHz) are analyzed. In five events the zebra structure, various fiber bursts, and fast pulsations were observed. These observations have great importance for testing different theoretical models of fine structure formation, as, for example, only for explaining the zebra structure more than ten mechanisms have been proposed. The events on 15 and 24 February 2011 are of the greatest interest. In the course of the flare on 15 February (which occurred close to the center of disk) the zebra structure was observed during three sequential flare brightenings. The polarization changed sign in the third. This behavior of polarization combined with images of the corresponding flare brightenings, obtained in extreme ultraviolet radiation by the Solar Dynamics Observatory (SDO/AIA, 171 Å), provides important clues. The polarization of radio emission in all three cases is related to the ordinary wave mode of radio emission. The zebra structure was present at frequencies 190 - 220 MHz in the Culgoora spectrum. The event on 24 February 2011 is remarkable, as the zebra structure at frequencies of 2.6 - 3.8 GHz was not polarized and it appeared during the magnetic reconnection observed by SDO/AIA 171 Å in this limb flare. In the event on 9 August 2011, for the first time, a superfine millisecond structure was registered simultaneously in the fast pulsations and the stripes of the zebra structure. In the event on 1 August 2010 after the zebra structure two families of fibers bursts with opposite frequency drifts were observed. On 19 April 2012 the fibers against the background of type III bursts were observed by IZMIRAN and Nançay spectrographs. In the band of 42 - 52 MHz a group of nine slowly drifting narrow-band (

  19. Long-range prediction of the low-frequency mode in the low-level Indian monsoon circulation with a simple statistical method

    NASA Astrophysics Data System (ADS)

    Chen, Tsing-Chang; Yen, Ming-Cheng; Wu, Kuang-Der; Ng, Thomas

    1992-08-01

    The time evolution of the Indian monsoon is closely related to locations of the northward migrating monsoon troughs and ridges which can be well depicted with the 30 60day filtered 850-mb streamfunction. Thus, long-range forecasts of the large-scale low-level monsoon can be obtained from those of the filtered 850-mb streamfunction. These long-range forecasts were made in this study in terms of the Auto Regressive (AR) Moving-Average process. The historical series of the AR model were constructed with the 30 60day filtered 850-mb streamfunction [˜ψ (850mb)] time series of 4months. However, the phase of the last low-frequency cycle in the ˜ψ (850mb) time series can be skewed by the bandpass filtering. To reduce this phase skewness, a simple scheme is introduced. With this phase modification of the filtered 850-mb streamfunction, we performed the pilot forecast experiments of three summers with the AR forecast process. The forecast errors in the positions of the northward propagating monsoon troughs and ridges at Day 20 are generally within the range of 1~2days behind the observed, except in some extreme cases.

  20. Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2015-08-01

    Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-3He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

  1. Measurements of ion cyclotron range of frequencies mode converted wave intensity with phase contrast imaging in Alcator C-Mod and comparison with full-wave simulations

    SciTech Connect

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2012-08-15

    Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are widely used to heat tokamak plasmas. In ICRF heating schemes involving multiple ion species, the launched fast waves convert to ion cyclotron waves or ion Bernstein waves at the two-ion hybrid resonances. Mode converted waves are of interest as actuators to optimise plasma performance through current drive and flow drive. In order to describe these processes accurately in a realistic tokamak geometry, numerical simulations are essential, and it is important that these codes be validated against experiment. In this study, the mode converted waves were measured using a phase contrast imaging technique in D-H and D-{sup 3}He plasmas. The measured mode converted wave intensity in the D-{sup 3}He mode conversion regime was found to be a factor of {approx}50 weaker than the full-wave predictions. The discrepancy was reduced in the hydrogen minority heating regime, where mode conversion is weaker.

  2. Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

    SciTech Connect

    Tsujii, N.; Porkolab, M.; Bonoli, P. T.; Edlund, E. M.; Ennever, P. C.; Lin, Y.; Wright, J. C.; Wukitch, S. J.; Jaeger, E. F.; Green, D. L.; Harvey, R. W.

    2015-08-15

    Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. The phase contrast imaging (PCI) diagnostic has been used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements have been compared with full-wave simulations through a synthetic diagnostic technique. Recently, the frequency response of the PCI detector array on Alcator C-Mod was recalibrated, which greatly improved the comparison between the measurements and the simulations. In this study, mode converted waves for D-{sup 3}He and D-H plasmas with various ion species compositions were re-analyzed with the new calibration. For the minority heating cases, self-consistent electric fields and a minority ion distribution function were simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in quite reasonable agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

  3. A BIPM/CIPM key comparison covering the calibration of ultrasonic hydrophones over the frequency range 1 MHz to 15 MHz

    NASA Astrophysics Data System (ADS)

    Zeqiri, Bajram; Lee, Nigel D.

    2002-11-01

    A central objective of the Mutual Recognition Arrangement (MRA), signed by national measurement institute (NMI) directors in 1999, is the establishment of the degrees of equivalence of national measurement standards held by each institute. International comparisons, known as key comparisons, represent the sole mechanism for establishing these degrees of equivalence. In this paper we describe a key comparison, undertaken under the auspices of the BIPM/CIPM Consultative Committee for Acoustics, Ultrasound, and Vibration, related to the realization of the acoustic pascal in water at ultrasonic frequencies. This is most appropriately achieved through a comparison of calibrations of stable transfer standard hydrophones; 1 mm active element bilaminar membrane hydrophones, being chosen for this purpose. With NPL acting as the pilot laboratory, two hydrophones were calibrated using the NPL primary standard laser interferometer and circulated sequentially to participant NMI laboratories in Germany, China, The Netherlands, and Denmark. Laboratories were asked to report values for the hydrophone open-circuit free-field sensitivity over the frequency range 1 MHz to 15 MHz. The principal calibration methods used by the NMIs were optical interferometry and/or two-transducer reciprocity. The key comparison process, its results, and the analysis used to derive the key comparison reference values, are all described in detail.

  4. Investigation of dielectric behavior of water and thermally aged of XLPE/BaTiO3 composites in the low-frequency range

    NASA Astrophysics Data System (ADS)

    Madani, Lakhdar; Belkhiat, Saad; Berrag, Amine; Nemdili, Saad

    2015-10-01

    Cross-Linked Polyethylene (XLPE) is widely used as insulation in electrical engineering, especially as cable insulation sheaths. In order to improve the dielectric properties susceptible to be modified under the effects of thermal aging and water in an absorption environment, polymers are mixed with ceramics. In this paper, the influence of barium titanate (BaTiO3), on the dielectric properties of XLPE has been studied. Dielectric parameters have been measured using an impedance analyzer RLC (WAYNE KERR 6420 type). Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and X-ray diffraction were used as characterization techniques. The study has been carried out on two samples of XLPE. A pure sample of each were studied as a unloaded samples to be compared with samples of 5%wt, 10%wt, 15%wt and 20%wt. BaTiO3 loaded XLPE. Afterwards, the composites were subject to humidity and to thermal aging. The incorporation of BaTiO3 1∘C does not modify the crystallinity and morphology of the XLPE and 2∘C reduces the space charges therefore the dielectric losses. tgδ, ɛr and loss index are measured. Frequency response analysis has been followed in the frequency range (20-300 Hz). Experimental results show well that BaTiO3 as nano-filler improves the dielectric properties of XLPE but in excessive content can drive to the cracking and therefore to absorption of water.

  5. Short-range ground-based synthetic aperture radar imaging: performance comparison between frequency-wavenumber migration and back-projection algorithms

    NASA Astrophysics Data System (ADS)

    Yigit, Enes; Demirci, Sevket; Özdemir, Caner; Tekbaş, Mustafa

    2013-01-01

    Two popular synthetic aperture radar (SAR) reconstruction algorithms, namely the back-projection (BP) and the frequency wavenumber (ω-k) algorithms, were tested and compared against each other, especially for their use in ground-based (GB) SAR applications directed to foreign object debris removal. For this purpose, an experimental setup in a semi-anechoic chamber room was accomplished to obtain near-field SAR images of objects on the ground. Then, the 90 to 95 GHz scattering data were acquired by using a stepped frequency continuous-wave radar operation. The performances of the setup and the imaging algorithms were then assessed by exploiting various metrics including point spread function, signal-to-clutter ratio, integrated side-lobe ratio, and computational complexity. Results demonstrate that although both algorithms produce almost accurate images of targets, the BP algorithm is shown to be superior to the ω-k algorithm due to its some inherent advantages specifically suited for short-range GB-SAR applications.

  6. Application of the methane saturated dispersion resonance near 2.36 μm over the temperature range of 77-300 K for optical frequency standards

    NASA Astrophysics Data System (ADS)

    Tarabrin, Mikhail K.; Lazarev, Vladimir A.; Karasik, Valeriy E.; Kireev, Alexey N.; Korostelin, Yuri V.; Shelkovnikov, Alexander S.; Tuyrikov, Dmitry A.; Kozlovsky, Vladimir I.; Podmar'kov, Yuri P.; Frolov, Mikhail P.; Gubin, Mikhail A.

    2016-07-01

    New spectroscopic knowledge of the ν1 +ν4 R(2) E line of methane over the temperature range 77-300 K is reported. Theoretical calculations of the absorption coefficient and the amplitudes of saturated dispersion resonances at 4234 cm-1 were derived. The theoretical dependence on the temperature of the amplitudes of the saturated dispersion resonances was obtained. A novel setup based on a Cr2+ : ZnSe laser was used for Doppler-free spectroscopy of methane. The amplitudes of the saturated dispersion resonances of the ν1 +ν4 R(2) E line of methane were measured experimentally at different temperatures. A comparison with theoretical dependence supports the reliability of the experiment. The obtained results are of immediate interest in applications demanding laser frequency stabilization.

  7. Pulsed laser operating on the first overtone of the CO molecule in the 2.5-4.2-{mu}m range. II. Frequency-selective lasing

    SciTech Connect

    Basov, N G; Ionin, Andrei A; Kotkov, A A; Seleznev, L V; Kurnosov, A K; Napartovich, A P; Turkin, N G; McCord, J E; Hager, G D

    2000-10-31

    Lasing properties of a pulsed electroionisation CO laser operating on the first overtone of the CO molecule in the frequency-selective regime were studied experimentally and theoretically. Lasing was observed on a large number of separate vibrational-rotational transitions {nu}+2{yields}{nu} from 13{yields}11 to 38{yields}36 (more than 400 spectral lines) in the spectral range from 2.7 to 4.2 {mu}m. The specific output energy of the overtone CO laser reached {approx}3.0 J l{sup -1} amagat{sup -1}, and the electrooptical conversion was {approx}0.6 %. The formation of emission spectra from high vibrational levels in the overtone CO laser observed for the first time is discussed. The comparison of experimental and theoretical data showed the necessity of including the multiquantum exchange on high vibrational levels into the kinetic model of the active medium of the CO laser. (lasers)

  8. Annual variations of the amplitude characteristic of the noise magnetic field in the ELF frequency range based on the results of high-latitude observations

    NASA Astrophysics Data System (ADS)

    Pchelkin, V. V.

    2014-09-01

    The annual variation of a number of amplitude characteristics of the noise electromagnetic field in the frequency range near the first Schumann resonance (and in particular the mean values of the modulus of horizontal magnetic components and parameters of the distribution function of noise pulses over amplitudes) was obtained and analyzed based on the results of three-year measurements performed at the high-latitude magnetic observatory Lovozero. The summer increase in mean and median values of the magnetic component of noises associated with electrical storms and the lack of annual variations of the exponent that empirically describes the distribution of amplitudes of noise signals were found. The relationship between the seasonal (winter/summer in the northern hemisphere) increase in the mean value of the modulus of the horizontal magnetic field component and seasonal increase in the global number of lightning discharges is shown by the correlation of the results of satellite observations and measurements of the magnetic component.

  9. Frequency-resolved optical gating system with a tellurium crystal for characterizing free-electron lasers in the wavelength range of 10-30 {mu}m

    SciTech Connect

    Iijima, Hokuto; Nagai, Ryoji; Nishimori, Nobuyuki; Hajima, Ryoichi; Minehara, Eisuke J.

    2009-12-15

    A second-harmonic generation frequency-resolved optical gating (SHG-FROG) system has been developed for the complete characterization of laser pulses in the wavelength range of 10-30 {mu}m. A tellurium crystal is used so that spectrally resolved autocorrelation signals with a good signal-to-noise ratio are obtained. Pulses (wavelength {approx}22 {mu}m) generated from a free-electron laser are measured by the SHG-FROG system. The SHG intensity profile and the spectrum obtained by FROG measurements are well consistent with those of independent measurements of the pulse length and spectrum. The pulse duration and spectral width determined from the FROG trace are 0.6 ps and 5.2 THz at full width half maximum, respectively.

  10. Dielectric behavior of wild-type yeast and vacuole-deficient mutant over a frequency range of 10 kHz to 10 GHz.

    PubMed Central

    Asami, K; Yonezawa, T

    1996-01-01

    Dielectric behavior of Saccharomyces cerevisiae wild-type and vacuole-deficient mutant cells has been studied over a frequency range of 10 kHz to 10 GHz. Both types of cells harvested at the early stationary growth phase showed dielectric dispersion that was phenomenologically formulated by a sum of three separate dispersion terms: beta 1-dispersion (main dispersion) and beta 2-dispersion (additional dispersion) and gamma-dispersion due to orientation of water molecules. The beta 1-dispersion centered at a few MHz, which has been extensively studied so far, is due to interfacial polarization (or the Maxwell-Wagner effect) related to the plasma membrane. The beta 2-dispersion for the vacuole-deficient mutant centered at approximately 50 MHz was explained by taking the cell wall into account, whereas, for the wild-type cells, the beta 2-dispersion around a few tens MHz involved the contributions from the vacuole and cell wall. PMID:8889195

  11. Low-level radio-frequency interference detection algorithm based on European Centre for Medium-Range Weather Forecasting for Soil Moisture and Ocean Salinity

    NASA Astrophysics Data System (ADS)

    Lu, Hailiang; Li, Qingxia; Li, Yan; Li, Yinan; Li, Hao

    2015-01-01

    At present, the Soil Moisture and Ocean Salinity (SMOS) mission is severely affected by radio frequency interferences (RFIs), and the detection of low-level RFI-contamination brightness temperatures (BTs) is still a challenge in SMOS. A low-level RFI detection algorithm is proposed, which is based on the soil surface temperature products provided by the European Centre for Medium-Range Weather Forecasting. The algorithm is analyzed in terms of RFI-flagged snapshot, RFI-flagged probability, and localization accuracy. The performance of the algorithm is demonstrated by SMOS data. The results show this algorithm can detect and flag more low-level RFI-contamination BTs and show a better performance.

  12. An algorithm for the analysis of inductive antennas of arbitrary cross-section for heating in the ion cyclotron range of frequencies

    SciTech Connect

    Lehrman, I.S.; Colestock, P.L.

    1986-10-01

    The application of Ion Cyclotron Range of Frequency (ICRF) heating to near ignited plasmas will require launching structures that will be capable of withstanding the harsh plasma environment. The recessed antenna configuration is expected to provide sufficient protection for the structure, but to date no analysis has been done to determine if adequate coupling can be achieved in such a configuration. In this work we present a method for determining the current distribution for the antenna in the direction transverse to current flow and predict antenna loading in the presence of plasma. Antennas of arbitrary cross section are analyzed above ground planes of arbitrary shape. Results from ANDES, the ANtenna DESign code, are presented and compared to experimental results.

  13. Big Data, Small Data: Accessing and Manipulating Geoscience Data Ranging From Repositories to Student-Collected Data Sets Using GeoMapApp

    NASA Astrophysics Data System (ADS)

    Goodwillie, A. M.

    2015-12-01

    We often demand information and data to be accessible over the web at no cost, and no longer do we expect to spend time labouriously compiling data from myriad sources with frustratingly-different formats. Instead, we increasingly expect convenience and consolidation. Recent advances in web-enabled technologies and cyberinfrastructure are answering those calls by providing data tools and resources that can transform undergraduate education. By freeing up valuable classroom time, students can focus upon gaining deeper insights and understanding from real-world data. GeoMapApp (http://www.geomapapp.org) is a map-based data discovery and visualisation tool developed at Lamont-Doherty Earth Observatory. GeoMapApp promotes U-Learning by working across all major computer platforms and functioning anywhere with internet connectivity, by lowering socio-economic barriers (it is free), by seamlessly integrating thousands of built-in research-grade data sets under intuitive menus, and by being adaptable to a range of learning environments - from lab sessions, group projects, and homework assignments to in-class pop-ups. GeoMapApp caters to casual and specialist users alike. Contours, artificial illumination, 3-D displays, data point manipulations, cross-sectional profiles, and other display techniques help students better grasp the content and geospatial context of data. Layering capabilities allow easy data set comparisons. The core functionality also applies to imported data sets: Student-collected data can thus be imported and analysed using the same techniques. A new Save Session function allows educators to preserve a pre-loaded state of GeoMapApp. When shared with a class, the saved file allows every student to open GeoMapApp at exactly the same starting point from which to begin their data explorations. Examples of built-in data sets include seafloor crustal age, earthquake locations and focal mechanisms, analytical geochemistry, ocean water physical properties, US and

  14. Vibrotactile Presentation of Musical Notes to the Glabrous Skin for Adults with Normal Hearing or a Hearing Impairment: Thresholds, Dynamic Range and High-Frequency Perception.

    PubMed

    Hopkins, Carl; Maté-Cid, Saúl; Fulford, Robert; Seiffert, Gary; Ginsborg, Jane

    2016-01-01

    Presentation of music as vibration to the skin has the potential to facilitate interaction between musicians with hearing impairments and other musicians during group performance. Vibrotactile thresholds have been determined to assess the potential for vibrotactile presentation of music to the glabrous skin of the fingertip, forefoot and heel. No significant differences were found between the thresholds for sinusoids representing notes between C1 and C6 when presented to the fingertip of participants with normal hearing and with a severe or profound hearing loss. For participants with normal hearing, thresholds for notes between C1 and C6 showed the characteristic U-shape curve for the fingertip, but not for the forefoot and heel. Compared to the fingertip, the forefoot had lower thresholds between C1 and C3, and the heel had lower thresholds between C1 and G2; this is attributed to spatial summation from the Pacinian receptors over the larger contactor area used for the forefoot and heel. Participants with normal hearing assessed the perception of high-frequency vibration using 1s sinusoids presented to the fingertip and were found to be more aware of transient vibration at the beginning and/or end of notes between G4 and C6 when stimuli were presented 10dB above threshold, rather than at threshold. An average of 94% of these participants reported feeling continuous vibration between G4 and G5 with stimuli presented 10dB above threshold. Based on the experimental findings and consideration of health effects relating to vibration exposure, a suitable range of notes for vibrotactile presentation of music is identified as being from C1 to G5. This is more limited than for human hearing but the fundamental frequencies of the human voice, and the notes played by many instruments, lie within it. However, the dynamic range might require compression to avoid the negative effects of amplitude on pitch perception. PMID:27191400

  15. Developing A Low-frequency Interferometer For Detecting The Epoch Of Reionization: Correlation, Calibration, And High Dynamic-range Imaging With Paper

    NASA Astrophysics Data System (ADS)

    Parsons, Aaron; PAPER Team

    2009-01-01

    The Precision Array for Probing the Epoch of Reionization (PAPER) is a low-frequency interferometer being developed to detect cosmic reionization via fluctuations in the brightness temperature of the 21cm hyperfine transition of neutral hydrogen in the early intergalactic medium. Interfering with the direct detection of a global reionization signature are a myriad of astrophysical foregrounds, including polarized galactic synchrotron emission, continuum point-sources, and galactic/extra-galactic free-free emission. Suppression of these foregrounds will require extraordinary calibration and high dynamic-range imaging, as well as large numbers of antennas to achieve the necessary sensitivity in the region of the power spectrum where the reionization signal peaks relative to them. Addressing the challenge of correlating large numbers of antennas, we have developed a flexible correlator architecture that scales to hundreds of antennas. This correlator is based on Field-Programmable Gate Array processors connected by a 10 Gb Ethernet switch, and programmed using a parameterized signal processing library. We demonstrate how this work has dramatically decreased correlator development time, and has enabled PAPER to grow as a series of deployments of increasing size. Calibration and high dynamic-range imaging with low-frequency interferometers are exacerbated by wide bandwidths and large fields-of-view (FoV). To simplify the calibration process when an interferometer consistently has many strong sources simultaneously in its FoV, we present a fringe-rate/delay filtering technique to isolating source fluxes. This is implemented as part of Astronomical Interferometry in PYthon (AIPY), a new open-source software toolkit that facilitates exploration and algorithm development by modularizing data processing and visibility simulation. We present the application of this toolkit to various aspects of PAPER calibration. Finally, we present the first all-sky map and point source

  16. Vibrotactile Presentation of Musical Notes to the Glabrous Skin for Adults with Normal Hearing or a Hearing Impairment: Thresholds, Dynamic Range and High-Frequency Perception

    PubMed Central

    Maté-Cid, Saúl; Fulford, Robert; Seiffert, Gary; Ginsborg, Jane

    2016-01-01

    Presentation of music as vibration to the skin has the potential to facilitate interaction between musicians with hearing impairments and other musicians during group performance. Vibrotactile thresholds have been determined to assess the potential for vibrotactile presentation of music to the glabrous skin of the fingertip, forefoot and heel. No significant differences were found between the thresholds for sinusoids representing notes between C1 and C6 when presented to the fingertip of participants with normal hearing and with a severe or profound hearing loss. For participants with normal hearing, thresholds for notes between C1 and C6 showed the characteristic U-shape curve for the fingertip, but not for the forefoot and heel. Compared to the fingertip, the forefoot had lower thresholds between C1 and C3, and the heel had lower thresholds between C1 and G2; this is attributed to spatial summation from the Pacinian receptors over the larger contactor area used for the forefoot and heel. Participants with normal hearing assessed the perception of high-frequency vibration using 1s sinusoids presented to the fingertip and were found to be more aware of transient vibration at the beginning and/or end of notes between G4 and C6 when stimuli were presented 10dB above threshold, rather than at threshold. An average of 94% of these participants reported feeling continuous vibration between G4 and G5 with stimuli presented 10dB above threshold. Based on the experimental findings and consideration of health effects relating to vibration exposure, a suitable range of notes for vibrotactile presentation of music is identified as being from C1 to G5. This is more limited than for human hearing but the fundamental frequencies of the human voice, and the notes played by many instruments, lie within it. However, the dynamic range might require compression to avoid the negative effects of amplitude on pitch perception. PMID:27191400

  17. A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade.

    PubMed

    Ochoukov, R; Bobkov, V; Faugel, H; Fünfgelder, H; Noterdaeme, J-M

    2015-11-01

    A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k(//)) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k(tor)). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k(//) as strap phasing is moved away from the dipole configuration. This result is the opposite of the k(tor) trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k(//), as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue. PMID

  18. A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Ochoukov, R.; Bobkov, V.; Faugel, H.; Fünfgelder, H.; Noterdaeme, J.-M.

    2015-11-01

    A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k//) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (ktor). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k// as strap phasing is moved away from the dipole configuration. This result is the opposite of the ktor trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k//, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.

  19. Hybrid bidirectional radio-over-fiber-based orthogonal frequency division multiple access-passive optical network supporting 60/120 GHz using offset quadrate phase shift keying

    NASA Astrophysics Data System (ADS)

    Zhang, Chongfu; Chen, Chen; Qiu, Kun

    2015-09-01

    A hybrid bidirectional orthogonal frequency division multiple access-passive optical network (OFDMA-PON) based on offset quadrate phase shift keying (OQPSK) to support 60- and 120-GHz radio-over-fiber system is proposed. The system can support wired/wireless applications and enable the dynamic bandwidth allocation according to a subscriber's application. It is successfully achieved by using the millimeter waves (MMWs) generation and the carrier-reuse technique. In the proposed scheme, the MMW bands used for downlink (DL) and uplink transmissions are generated at the optical line terminal by the dual-arm Mach-Zehnder modulators. Both 60- and 120-GHz MMWs are obtained for the transmission of the high bit-rate services in source-free optical network units (ONUs), only using a single 15-GHz sinusoidal wave source. The Rayleigh backscattering effect is considered in the proposed OQPSK-based OFDMA-PON. For DL transmission over a 30-km single-mode fiber, the power penalties are less than 0.8 and 1 dB for the OQPSK-OFDM wired data at 10 Gb/s and the OQPSK-OFDM wireless data at 5 Gb/s, respectively.

  20. Forward and inverse dielectric modeling of oven-dried cement paste specimens in the frequency range of 1.02 GHz to 4.50 GHz

    NASA Astrophysics Data System (ADS)

    Owusu Twumasi, Jones; Yu, Tzuyang

    2015-04-01

    The use of radar non-destructive evaluation (NDE) technique for condition assessment of deteriorated civil infrastructure systems is an effective approach for preserving the sustainability of these systems. Radar NDE utilizes the interaction between radar signals (electromagnetic waves) and construction materials for surface and subsurface sensing based on dielectric properties and geometry. In the success of radar inspection, it is imperative to develop models capable of predicting the dielectric properties of the materials under investigation. The dielectric properties (dielectric constant and loss factor) of oven-dried cement paste specimens with water-to-cement (w/c) ratios (0.35, 0.40, 0.45, 0.50, 0.55) in the frequency range of 1.02 GHz to 4.50 GHz were studied and modeled using modified Debye's models. An open-ended coaxial probe and a network analyzer were used to measure dielectric properties. Forward models are proposed and inversed for predicting the w/c ratio of a given oven-dried cement paste specimen. Modeling results agreed with the experimental data. The proposed models can be used for predicting the dielectric properties of oven-dried cement paste specimens. Also, the modeling approach can be applied to other cementitious materials (e.g., concrete) with additional modification.

  1. Physics and technology in the ion-cyclotron range of frequency on Tore Supra and TITAN test facility: implication for ITER

    NASA Astrophysics Data System (ADS)

    Litaudon, X.; Bernard, J. M.; Colas, L.; Dumont, R.; Argouarch, A.; Bottollier-Curtet, H.; Brémond, S.; Champeaux, S.; Corre, Y.; Dumortier, P.; Firdaouss, M.; Guilhem, D.; Gunn, J. P.; Gouard, Ph.; Hoang, G. T.; Jacquot, J.; Klepper, C. C.; Kubič, M.; Kyrytsya, V.; Lombard, G.; Milanesio, D.; Messiaen, A.; Mollard, P.; Meyer, O.; Zarzoso, D.

    2013-08-01

    To support the design of an ITER ion-cyclotron range of frequency heating (ICRH) system and to mitigate risks of operation in ITER, CEA has initiated an ambitious Research & Development program accompanied by experiments on Tore Supra or test-bed facility together with a significant modelling effort. The paper summarizes the recent results in the following areas: Comprehensive characterization (experiments and modelling) of a new Faraday screen concept tested on the Tore Supra antenna. A new model is developed for calculating the ICRH sheath rectification at the antenna vicinity. The model is applied to calculate the local heat flux on Tore Supra and ITER ICRH antennas. Full-wave modelling of ITER ICRH heating and current drive scenarios with the EVE code. With 20 MW of power, a current of ±400 kA could be driven on axis in the DT scenario. Comparison between DT and DT(3He) scenario is given for heating and current drive efficiencies. First operation of CW test-bed facility, TITAN, designed for ITER ICRH components testing and could host up to a quarter of an ITER antenna. R&D of high permittivity materials to improve load of test facilities to better simulate ITER plasma antenna loading conditions.

  2. Final report on key comparison CCAUV.A-K5: pressure calibration of laboratory standard microphones in the frequency range 2 Hz to 10 kHz

    NASA Astrophysics Data System (ADS)

    Avison, Janine; Barham, Richard

    2014-01-01

    This document and the accompanying spreadsheets constitute the final report for key comparison CCAUV.A-K5 on the pressure calibration of laboratory standard microphones in the frequency range from 2 Hz to 10 kHz. Twelve national measurement institutes took part in the key comparison and the National Physical Laboratory piloted the project. Two laboratory standard microphones IEC type LS1P were circulated to the participants and results in the form of regular calibration certificates were collected throughout the project. One of the microphones was subsequently deemed to have compromised stability for the purpose of deriving a reference value. Consequently the key comparison reference value (KCRV) has been made based on the weighted mean results for sensitivity level and for sensitivity phase from just one of the microphones. Corresponding degrees of equivalence (DoEs) have also been calculated and are presented. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  3. Report on key comparison COOMET.AUV.A-K5: pressure calibration of laboratory standard microphones in the frequency range 2 Hz to 10 kHz

    NASA Astrophysics Data System (ADS)

    Dobrowolska, D.; Kosterov, A.

    2016-01-01

    This is the final report for regional key comparison COOMET.AUV.A-K5 on the pressure calibration of laboratory standard microphones in the frequency range from 2 Hz to 10 kHz. Two laboratories—Central Office of Measures (GUM)—the national metrology institute for Poland and the State Enterprise Scientific-Research Institute for Metrology of Measurement and Control Systems (DP NDI Systema)— the designated institute for acoustics in Ukraine took part in this comparison with the GUM as a pilot. One travelling type LS1P microphone was circulated to the participants and results in the form of regular calibration certificates were collected. The results of the DP NDI Systema obtained in this comparison were linked to the CCAUV.A-K5 key comparison through the joint participation of the GUM. The degrees of equivalence were computed for DP NDI Systema with respect to the CCAUV.A-K5 key comparison reference value. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  4. Performance of FeCoB based thin-film microwave noise suppressor applied to the electromagnetic interference design in the GHz frequency range

    NASA Astrophysics Data System (ADS)

    Qiu, Jing; Wen, Yumei; Li, Ping; Yang, Jin; Li, Wenli

    2014-05-01

    To develop high performance microwave noise suppressor, the microwave noise suppressors based on a microstrip line using FeCoB based magnetic thin film are presented, whose microwave noise suppression effects have been investigated. It was found that suitable low argon pressure is beneficial to the improvement of microwave noise suppression. In addition, the microwave noise suppression properties of microwave noise suppressor could be tuned by controlling the geometric dimension of FeCoB based magnetic thin film and SiO2 dielectric layer, resulted from the ferromagnetic resonance loss and eddy current loss. The maximum power loss ratio (Ploss/Pin) of thin-film microwave noise suppressor (the length, width, and thickness of FeCoNiB thin film are 25 mm, 10 mm, and 250 nm, respectively) achieves 0.75 at 3.4 GHz. These results show that the presented film noise suppressors have potential for the electromagnetic interference design in the GHz frequency range.

  5. Physics and technology in the ion-cyclotron range of frequency on Tore Supra and TITAN test facility: implication for ITER

    SciTech Connect

    Litaudon, X; Bernard, J. M.; Colas, L.; Dumont, R. J.; Argouarch, A.; Bottollier-Curtet, H.; Bremond, S.; Champeaux, S.; Corre, Y.; Dumortier, P.; Firdaouss, M.; Guilhem, D.; Gunn, J. P.; Gouard, Ph.; Hoang, G T; Jacquot, Jonathan; Klepper, C Christopher; Kubic, M.; Kyrytsya, V.; Lombard, G.; Milanesio, D.; Messiaen, A.; Mollard, P.; Meyer, O.; Zarzoso, D.

    2013-01-01

    To support the design of an ITER ion-cyclotron range of frequency heating (ICRH) system and to mitigate risks of operation in ITER, CEA has initiated an ambitious Research & Development program accompanied by experiments on Tore Supra or test-bed facility together with a significant modelling effort. The paper summarizes the recent results in the following areas: Comprehensive characterization (experiments and modelling) of a new Faraday screen concept tested on the Tore Supra antenna. A new model is developed for calculating the ICRH sheath rectification at the antenna vicinity. The model is applied to calculate the local heat flux on Tore Supra and ITER ICRH antennas. Full-wave modelling of ITER ICRH heating and current drive scenarios with the EVE code. With 20 MW of power, a current of 400 kA could be driven on axis in the DT scenario. Comparison between DT and DT(3He) scenario is given for heating and current drive efficiencies. First operation of CW test-bed facility, TITAN, designed for ITER ICRH components testing and could host up to a quarter of an ITER antenna. R&D of high permittivity materials to improve load of test facilities to better simulate ITER plasma antenna loading conditions.

  6. Specific absorption rate and temperature elevation in a subject exposed in the far-field of radio-frequency sources operating in the 10-900-MHz range.

    PubMed

    Bernardi, Paolo; Cavagnaro, Marta; Pisa, Stefano; Piuzzi, Emanuele

    2003-03-01

    The exposure of a subject in the far field of radiofrequency sources operating in the 10-900-MHz range has been studied. The electromagnetic field inside an anatomical heterogeneous model of the human body has been computed by using the finite-difference time-domain method; the corresponding temperature increase has been evaluated through an explicit finite-difference formulation of the bio-heat equation. The thermal model used, which takes into account the thermoregulatory system of the human body, has been validated through a comparison with experimental data. The results show that the peak specific absorption rate (SAR) as averaged over 10 g has about a 25-fold increase in the trunk and a 50-fold increase in the limbs with respect to the whole body averaged SAR (SARWB). The peak SAR as averaged over 1 g, instead, has a 30- to 60-fold increase in the trunk, and up to 135-fold increase in the ankles, with respect to SARWB. With reference to temperature increases, at the body resonance frequency of 40 MHz, for the ICNIRP incident power density maximum permissible value, a temperature increase of about 0.7 degrees C is obtained in the ankles muscle. The presence of the thermoregulatory system strongly limits temperature elevations, particularly in the body core. PMID:12669986

  7. A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

    SciTech Connect

    Ochoukov, R.; Bobkov, V.; Faugel, H.; Fünfgelder, H.; Noterdaeme, J.-M.

    2015-11-15

    A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k{sub //}) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k{sub tor}). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k{sub //} as strap phasing is moved away from the dipole configuration. This result is the opposite of the k{sub tor} trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k{sub //}, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas’ operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to

  8. The X-33 Extended Flight Test Range

    NASA Technical Reports Server (NTRS)

    Mackall, Dale A.; Sakahara, Robert; Kremer, Steven E.

    1998-01-01

    Development of an extended test range, with range instrumentation providing continuous vehicle communications, is required to flight-test the X-33, a scaled version of a reusable launch vehicle. The extended test range provides vehicle communications coverage from California to landing at Montana or Utah. This paper provides an overview of the approaches used to meet X-33 program requirements, including using multiple ground stations, and methods to reduce problems caused by reentry plasma radio frequency blackout. The advances used to develop the extended test range show other hypersonic and access-to-space programs can benefit from the development of the extended test range.

  9. Effects of Electromagnetic Field Over a Human Body, Sar Simulation with and Without Nanotextile in the Frequency Range 0.9-1.8GHZ

    NASA Astrophysics Data System (ADS)

    Tomovski, Boyan; Gräbner, Frank; Hungsberg, Axel; Kallmeyer, Christian; Linsel, Mario

    2011-11-01

    Within only the last decade, usage of mobile phones and many other electronic devices with high speed wireless RF connection is rapidly increasing. Modern life requires reliable, quick and high-quality information connections, which explains the widely spreading craze for electronic mobile devices of various types. The vast technological advances we are witnessing in electronics, electro-optics, and computer science have profoundly affected our everyday lives. Meanwhile, safety concerns regarding the biological effects of electromagnetic (EM) radiation have been raised, in particular at a low level of exposure which we everyday experience. A variety of waves and signals have to be considered such as different sine waves, digital signals used in radio, television, mobile phone systems and other information transfer systems. The field around us has become rather complicated and the "air space is getting more and more dense with RF. The establishing of safety recommendations, law norms and rules augmented by adequate measurements is very important and requires quite an expertise. But as many scientific researches suggest, what we are currently witnessing is very likely to generate a great public danger and a bad influence over the human body. There are many health organisations warning the public for possible development of cancer, mental and physical disorders etc [7, 8]. These suggestions are quite serious and should not be neglected by the official bodies and the test laboratories. In the following work, the effects of electromagnetic field over a virtual model of a human head have been simulated in the frequency range from 900 MHz to 1800 MHz (commonly created in the real life by mobile GSM system) with the help of the program MEFiSTo 2D Classic [1]. The created virtual models using the 2D simulation & computation software proved that the use of new high tech nanotextile materials for shielding layers around the human body can reduce the effects of EM fields

  10. Progress on radio frequency auxiliary heating system designs in ITER

    SciTech Connect

    Makowski, M.; Bosia, G.; Elio, F.

    1996-09-01

    ITER will require over 100 MW of auxiliary power for heating, on- and off-axis current drive, accessing the H-mode, and plasma shut-down. The Electron Cyclotron Range of Frequencies (ECRF) and Ion Cyclotron Range of Frequencies (ICRF) are two forms of Radio Frequency (RF) auxiliary power being developed for these applications. Design concepts for both the ECRF and ICRF systems are presented, key features and critical design issues are discussed, and projected performances outlined.

  11. Application of AWE Along with a Combined FEM/MoM Technique to Compute RCS of a Cavity-Backed Aperture in an Infinite Ground Plane Over a Frequency Range

    NASA Technical Reports Server (NTRS)

    Reddy, C.J.; Deshpande, M.D.

    1997-01-01

    A hybrid Finite Element Method (FEM)/Method of Moments (MoM) technique in conjunction with the Asymptotic Waveform Evaluation (AWE) technique is applied to obtain radar cross section (RCS) of a cavity-backed aperture in an infinite ground plane over a frequency range. The hybrid FEM/MoM technique when applied to the cavity-backed aperture results in an integro-differential equation with electric field as the unknown variable, the electric field obtained from the solution of the integro-differential equation is expanded in Taylor series. The coefficients of the Taylor series are obtained using the frequency derivatives of the integro-differential equation formed by the hybrid FEM/MoM technique. The series is then matched via the Pade approximation to a rational polynomial, which can be used to extrapolate the electric field over a frequency range. The RCS of the cavity-backed aperture is calculated using the electric field at different frequencies. Numerical results for a rectangular cavity, a circular cavity, and a material filled cavity are presented over a frequency range. Good agreement between AWE and the exact solution over the frequency range is obtained.

  12. Semantic Priming from Letter-Searched Primes Occurs for Low- but Not High-Frequency Targets: Automatic Semantic Access May Not Be a Myth

    ERIC Educational Resources Information Center

    Tse, Chi-Shing; Neely, James H.

    2007-01-01

    Letter-search (LS) within a prime often eliminates semantic priming. In 2 lexical decision experiments, the authors found that priming from LS primes occurred for low-frequency (LF) but not high-frequency (HF) targets whether the target's word frequency was manipulated between or within participants and whether the prime-target pairs were…

  13. Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for evaluation of farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency doma...

  14. Laboratory Mid-frequency (Kilohertz) Range Seismic Property Measurements and X-ray CT Imaging of Fractured Sandstone Cores During Supercritical CO2 Injection

    NASA Astrophysics Data System (ADS)

    Nakagawa, S.; Kneafsey, T. J.; Chang, C.; Harper, E.

    2014-12-01

    During geological sequestration of CO2, fractures are expected to play a critical role in controlling the migration of the injected fluid in reservoir rock. To detect the invasion of supercritical (sc-) CO2 and to determine its saturation, velocity and attenuation of seismic waves can be monitored. When both fractures and matrix porosity connected to the fractures are present, wave-induced dynamic poroelastic interactions between these two different types of rock porosity—high-permeability, high-compliance fractures and low-permeability, low-compliance matrix porosity—result in complex velocity and attenuation changes of compressional waves as scCO2 invades the rock. We conducted core-scale laboratory scCO2 injection experiments on small (diameter 1.5 inches, length 3.5-4 inches), medium-porosity/permeability (porosity 15%, matrix permeability 35 md) sandstone cores. During the injection, the compressional and shear (torsion) wave velocities and attenuations of the entire core were determined using our Split Hopkinson Resonant Bar (short-core resonant bar) technique in the frequency range of 1-2 kHz, and the distribution and saturation of the scCO2 determined via X-ray CT imaging using a medical CT scanner. A series of tests were conducted on (1) intact rock cores, (2) a core containing a mated, core-parallel fracture, (3) a core containing a sheared core-parallel fracture, and (4) a core containing a sheared, core-normal fracture. For intact cores and a core containing a mated sheared fracture, injections of scCO2 into an initially water-saturated sample resulted in large and continuous decreases in the compressional velocity as well as temporary increases in the attenuation. For a sheared core-parallel fracture, large attenuation was also observed, but almost no changes in the velocity occurred. In contrast, a sample containing a core-normal fracture exhibited complex behavior of compressional wave attenuation: the attenuation peaked as the leading edge of

  15. Medium-range objective predictions of thunderstorms on the McIDAS/CSIS interactive computer system. [Computer Interactive Data Access System/Centralized Storm Information System

    NASA Technical Reports Server (NTRS)

    Wilson, G. S.

    1982-01-01

    Until recently, all operational meteorological data has been made available to forecasters in a variety of different forms. Predictions based upon these different data formats have been complicated by the inability of forecasters to easily assimilate, in real-time, all data to provide an optimum decision regarding future weather occurrences. By March 1980, a joint NASA/NOAA effort had been initiated to develop the Centralized Storm Information System (CSIS). The primary objectives of this joint project are related to an improvement of the overall severe storm forecast and warning procedure and to a demonstration of the operational utility of techniques developed within the applied research community. CSIS is to utilize the Man Computer Interactive Data Access System (McIDAS). The present investigation is concerned with one of the first attempts to employ the CSIS system for the evaluation of a new research technique involving the prediction of thunderstorms over a forecast period of 12-48 hours.

  16. The changes of the frequency specific impedance of the human body due to the resonance in the kHz range in cancer diagnostics

    NASA Astrophysics Data System (ADS)

    Michalak, K. P.; Nawrocka-Bogusz, H.

    2011-12-01

    The frequency-specific absorption of kHz signals has been postulated for different tissues, trace elements, vitamins, toxins, pathogens, allergens etc. for low-power (μV) signals. An increase in the impedance of the human body is observed only up to the given power of the applied signal. The highest amplification of the given signal being damped by the body makes it possible to determine the intensity of the given process in the body (e.g. amount of the toxin, trace element, intensity of the allergy) being connected with a given frequency spectrum of the signal. The mechanism of frequency-specific absorption can be explained by means of the Quantum Field Theory being applied to the structure of the water. Substantially high coincidence between the frequencies of the rotation of free quasi-excited electrons in coherent domains of water and the frequencies being used in the MORA diagnostics (Med-Tronic GmbH, EN ISO 13485, EN ISO 9001) can be observed. These frequencies are located in the proximity of f = 7kHz · i (i = 1,3,5,7,...). This fact suggests that the coherent domains with the admixtures of the given substances create structure-specific coherent domains that possess frequency-specific absorption spectra. The diagnostic tool called "MORA System diagnosis" was used to investigate 102 patients with different types and stages of cancer. Many signals were observed to be absorbed by many cancer patients, e.g.: 'Cellular defense system', 'Degeneration tendencies', Manganese, Magnesium, Zinc, Selenium, Vitamin E, Glutamine, Glutathione, Cysteine, Candida albicans, Mycosis. The results confirm the role of oxidative stress, immunological system deficiency and mitochondria malfunction in the development of cancer.

  17. Self-oscillations in the laboratory periodic flow and the linear law for the dissipation rate in the single-frequency range

    NASA Astrophysics Data System (ADS)

    Batchaev, A. M.

    2016-05-01

    In this paper, a Reynolds number increase transition from self-oscillations close to single-frequency ones to the temporally chaotic regime in the flow in a cylindrical channel driven by a spatially periodic force with four half-periods is experimentally investigated. The parameter ɛ proportional to the mean rate of the kinetic energy dissipation in unit mass per unit time associated with perturbations in the fluid is used as a basic characteristic of self-oscillations. The Reynolds number dependence ɛ(Re) for single frequency self-oscillations is considered theoretically.

  18. Frequency down-conversion of solid-state laser sources to the mid-infrared spectral range using non-oxide nonlinear crystals

    NASA Astrophysics Data System (ADS)

    Petrov, Valentin

    2015-07-01

    The development of parametric devices down-converting the laser frequency to the mid-infrared (3-30 μm) based on non-oxide nonlinear optical crystals is reviewed. Such devices, pumped by solid-state laser systems operating in the near-infrared, fill in this spectral gap where no such lasers exist, on practically all time scales, from continuous-wave to femtosecond regime. All important results obtained so far with difference-frequency generation, optical parametric oscillation, generation and amplification are presented in a comparative manner, illustrating examples of recent achievements are given in more detail, and some special issues such as continuum and frequency comb generation or pulse shaping are also discussed. The vital element in any frequency-conversion process is the nonlinear optical crystal and this represents one of the major limitations for achieving high energies and average powers in the mid-infrared although the broad spectral tunability seems not to be a problem. Hence, an overview of the available non-oxide nonlinear optical materials, emphasizing new developments such as wide band-gap, engineered (mixed), and quasi-phase-matched crystals, is also included.

  19. Human exposure standards in the frequency range 1 Hz To 100 kHz: the case for adoption of the IEEE standard.

    PubMed

    Patrick Reilly, J

    2014-10-01

    Differences between IEEE C95 Standards (C95.6-2002 and C95.1-2005) in the low-frequency (1 Hz-100 kHz) and the ICNIRP-2010 guidelines appear across the frequency spectrum. Factors accounting for lack of convergence include: differences between the IEEE standards and the ICNIRP guidelines with respect to biological induction models, stated objectives, data trail from experimentally derived thresholds through physical and biological principles, selection and justification of safety/reduction factors, use of probability models, compliance standards for the limbs as distinct from the whole body, defined population categories, strategies for central nervous system protection below 20 Hz, and correspondence of environmental electric field limits with contact currents. This paper discusses these factors and makes the case for adoption of the limits in the IEEE standards. PMID:25162425

  20. Electric field of the power terrestrial sources observed by microsatellite Chibis-M in the Earth's ionosphere in frequency range 1-60 Hz

    NASA Astrophysics Data System (ADS)

    Dudkin, Fedir; Korepanov, Valery; Dudkin, Denis; Pilipenko, Vyacheslav; Pronenko, Vira; Klimov, Stanislav

    2015-07-01

    The power line emission (PLE) 50/60 Hz and the Schumann resonance (SR) harmonics were detected by the use of a compact electrical field sensor of length 0.42 m during microsatellite Chibis-M mission in years 2012-2014. The initial orbit of Chibis-M has altitude 500 km and inclination 52°. We present the space distribution of PLE and its connections with the possible overhead power lines. PLE has been recorded both in the shade and sunlit parts of the orbits as opposed to SR which have been recorded only in the nightside of the Earth. The cases of an extra long distance of PLE propagation in the Earth's ionosphere and increased value of SR Q factor have been also observed. These results should stimulate the ionosphere model refinement for ultralow frequency and extremely low frequency electromagnetic wave propagation as well as a study on new possibility of the ionosphere diagnostics.

  1. Phase noise performance of microwave analog frequency dividers: application to the characterization of oscillators up to the millimeter-wave range.

    PubMed

    Llopis, O; Regis, M; Desgrez, S; Graffeuil, J

    1999-01-01

    The phase noise performance of two different microwave analog frequency dividers is characterized and compared with the values obtained using simple theories of noise in injection-locked systems. The direct measurement of the divider noise with a low phase noise synthesizer is not accurate enough, and the residual noise technique is used. The noise levels observed using this technique, between -120 and -155 dBc/Hz at a 10 kHz offset frequency, demonstrate that this divider noise is much lower than the phase noise of most microwave free running oscillators, even if this noise is still high with respect to the residual noise of amplifiers realized with the same active devices. The down conversion of microwave sources up to 40 GHz, is proposed as an application example. PMID:18238498

  2. A new ion cyclotron range of frequency scenario for bulk ion heating in deuterium-tritium plasmas: How to utilize intrinsic impurities in our favour

    NASA Astrophysics Data System (ADS)

    Kazakov, Ye. O.; Ongena, J.; Van Eester, D.; Bilato, R.; Dumont, R.; Lerche, E.; Mantsinen, M.; Messiaen, A.

    2015-08-01

    A fusion reactor requires plasma pre-heating before the rate of deuterium-tritium fusion reactions becomes significant. In ITER, radio frequency (RF) heating of 3He ions, additionally puffed into the plasma, is one of the main options considered for increasing bulk ion temperature during the ramp-up phase of the pulse. In this paper, we propose an alternative scenario for bulk ion heating with RF waves, which requires no extra 3He puff and profits from the presence of intrinsic Beryllium impurities in the plasma. The discussed method to heat Be impurities in D-T plasmas is shown to provide an even larger fraction of fuel ion heating.

  3. The Accuracy of Measurements of the Spectral-Line Frequencies in the Studies of the Rotational Transitions of the 16O12C32S Molecule in the Millimeter and Submillimeter Wave Ranges

    NASA Astrophysics Data System (ADS)

    Golubiatnikov, G. Yu; Belov, S. P.; Lapinov, A. V.

    2016-01-01

    The absolute error of determining the center frequency of the molecule spectral line during a single measurement, which is obtained by fitting the line shape to the model profile, is usually significantly smaller than the statistical spread in the frequencies of the repeated measurements. We discuss the possible causes of the systematic errors leading to an increase in the uncertainty of measurements of the line-center frequency. For an example of the multiple spectral measurements of the rotational transitions of the 16O12C32S molecule in the millimeter- and submillimeter-wave ranges (with a frequency of up to 522 GHz), by the Lamb-dip method, we determine the absolute error of the performed measurements, which amounts to 0 .4 kHz. New precision values of the center frequencies of the rotational transitions of the 16O12C32S molecule and more accurate values of the rotational constants, which are calculated using the measured frequencies, are presented.

  4. Electromagnetic interference shielding effectiveness of composite carbon nanotube macro-film at a high frequency range of 40 GHz to 60 GHz

    NASA Astrophysics Data System (ADS)

    Wu, Zi Ping; Cheng, De Ming; Ma, Wen Jing; Hu, Jing Wei; Yin, Yan Hong; Hu, Ying Yan; Li, Ye Sheng; Yang, Jian Gao; Xu, Qian Feng

    2015-06-01

    The electromagnetic interference (EMI) shielding effectiveness (SE) of carbon nanotube (CNT) macro-film that is adhered to common cloth to maintain the light weight, silk-like quality, and smooth surface of the material for EMI shielding is investigated. The results show that a high and stable EMI SE of 48 dB to 57 dB at 40 GHz to 60 GHz was obtained by the macro-film with a thickness of only ˜4 μm. The composite CNT macro-film is easily manipulated, and its EMI property is significantly different from that of traditional electromagnetic shielding materials that show a lower EMI SE with increasing frequency. For example, the EMI SE of Cu foils decrease from 75 dB to 35 dB as frequency increases from 25 GHz to 60 GHz. Considering their stable and outstanding EMI SE and easy manipulation, the composite CNT macro-films are expected to have potential applications in shielding against millimeter waves.

  5. Investigation of broadening and shift of vapour absorption lines of H{sub 2}{sup 16}O in the frequency range 7184 – 7186 cm{sup -1}

    SciTech Connect

    Nadezhdinskii, A I; Pereslavtseva, A A; Ponurovskii, Ya Ya

    2014-10-31

    We present the results of investigation of water vapour absorption spectra in the 7184 – 7186 cm{sup -1} range that is of particular interest from the viewpoint of possible application of the data obtained for monitoring water vapour in the Earth's stratosphere. The doublet of H{sub 2}{sup 16}O near ν = 7185.596 cm{sup -1} is analysed. The coefficients of broadening and shift of water vapour lines are found in the selected range in mixtures with buffer gases and compared to those obtained by other authors. (laser spectroscopy)

  6. Intrinsic vs. spurious long-range memory in high-frequency records of environmental radioactivity - Critical re-assessment and application to indoor 222Rn concentrations from Coimbra, Portugal

    NASA Astrophysics Data System (ADS)

    Donner, Reik V.; Potirakis, Stelios M.; Barbosa, Susana M.; Matos, Jose A. O.

    2015-04-01

    The presence or absence of long-range correlations in environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas Radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental Radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor Radon concentrations from Coimbra, Portugal, each of which spans several months of continuous measurements at a high temporal resolution of five minutes. Our results reveal that at the study site, Radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between hours and one day) arising from marked periodic components probably related to tidal frequencies, and (iii) low-frequency variability indicating a true long-range dependent process, which might be dominated by a response to meteorological drivers. In the presence of such multi-scale variability, common estimators of long-range memory in time series are necessarily prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics. We emphasize that similar properties can be found in other types of geophysical time series (for

  7. A new ion cyclotron range of frequency scenario for bulk ion heating in deuterium-tritium plasmas: How to utilize intrinsic impurities in our favour

    SciTech Connect

    Kazakov, Ye. O.; Ongena, J.; Van Eester, D.; Lerche, E.; Messiaen, A.; Dumont, R.; Mantsinen, M.

    2015-08-15

    A fusion reactor requires plasma pre-heating before the rate of deuterium-tritium fusion reactions becomes significant. In ITER, radio frequency (RF) heating of {sup 3}He ions, additionally puffed into the plasma, is one of the main options considered for increasing bulk ion temperature during the ramp-up phase of the pulse. In this paper, we propose an alternative scenario for bulk ion heating with RF waves, which requires no extra {sup 3}He puff and profits from the presence of intrinsic Beryllium impurities in the plasma. The discussed method to heat Be impurities in D-T plasmas is shown to provide an even larger fraction of fuel ion heating.

  8. Accuracy analysis on C/A code and P(Y) code pseudo-range of GPS dual frequency receiver and application in point positioning

    NASA Astrophysics Data System (ADS)

    Peng, Xiuying; Fan, Shijie; Guo, Jiming

    2008-10-01

    When the Anti-Spoofing (A-S) is active, the civilian users have some difficulties in using the P(Y) code for precise navigation and positioning. Z-tracking technique is one of the effective methods to acquire the P(Y) code. In this paper, the accuracy of pseudoranges from C/A code and P(Y) code for dual frequency GPS receiver is discussed. The principle of measuring the encrypted P(Y) code is described firstly, then a large data set from IGS tracking stations is utilized for analysis and verification with the help of a precise point positioning software developed by authors. Especially, P(Y) code pseudoranges of civilian GPS receivers allow eliminating/reducing the effect of ionospheric delay and improve the precision of positioning. The point positioning experiments for this are made in the end.

  9. Development of frequency-agile high-repetition-rate CO{sub 2} DIAL systems for long range chemical remote sensing

    SciTech Connect

    Quick, C.R. Jr.; Fite, C.B.; Foy, B.R.; Jolin, J.; Mietz, D.E.

    1997-11-01

    Issues related to the development of direct detection, long-range CO{sub 2} DIAL systems for chemical detection and identification are presented and discussed including: data handling and display techniques for large, multi-{lambda} data sets, turbulence effects, slant path propagation, and speckle averaging. Data examples from various field campaigns and CO{sub 2} lidar platforms are used to illustrate the issues.

  10. Comparison of measurement standards of the acoustic pressure in air in the low frequency range: COOMET.AUV.A-K2

    NASA Astrophysics Data System (ADS)

    Chalyy, V.

    2011-01-01

    A bilateral regional comparison of national microphone standards from 2 Hz to 250 Hz was carried out between the DP NDI 'Systema' (Ukraine) and the VNIIFTRI (Russia) from July to September 2009. The comparison, COOMET.AUV.A-K2, was based on the pressure calibration of laboratory standard microphones type LSIP. The comparison results have been linked to the established key comparison reference value (KCRV) of CCAUV.A-K2. The degrees of equivalence, expressed as the deviation from the established KCRV and its expanded uncertainty (k = 2), have been determined, and the comparison result is in agreement with the KCRV within the estimated uncertainties at all employed frequencies. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

  11. Frequency doubled AlGaInP-VECSEL with high output power at 331 nm and a large wavelength tuning range in the UV

    NASA Astrophysics Data System (ADS)

    Schwarzbäck, Thomas; Kahle, Hermann; Jetter, Michael; Michler, Peter

    2012-06-01

    We present a non-resonantly pumped vertical external cavity surface-emitting laser in a compact v-shaped cavity configuration. By using intra-cavity frequency doubling in combination with a birefringent filter, a tunable high power UV laser source with an emission wavelength around 335 nm is realized. The fundamental red laser emission is based on a metal-organic vapor-phase epitaxy grown (GaxIn1-x)0.5P0.5/[(AlxGa1-x)yIn1-y]0.5P0.5 (abbr. GaInP/AlGaInP) multi-quantum-well structure. Five quantum well packages with four compressively strained quantum wells are placed in a separate confinement heterostructure in a resonant periodic gain design in strain-compensating quaternary AlGaInP barriers and cladding layers, respectively. The 3 λ cavity is fabricated on a 55 λ/4 pairs Al0.45Ga0.55As/AlAs distributed Bragg reflector. By using a beta barium borate non-linear crystal for second harmonic generation, output powers up to 150mWat a wavelength of 335 nm could be realized. Tuning of the laser resonance was accomplished with a birefringent filter. A tuning of 9 nm in the UV will be shown.

  12. Fundamental processes of fuel removal by cyclotron frequency range plasmas and integral scenario for fusion application studied with carbon co-deposits

    NASA Astrophysics Data System (ADS)

    Möller, S.; Wauters, T.; Kreter, A.; Petersson, P.; Carrasco, A. G.

    2015-08-01

    Plasma impact removal using radio frequency heated plasmas is a candidate method to control the co-deposit related tritium inventory in fusion devices. Plasma parameters evolve according to the balance of input power to losses (transport, radiation, collisions). Material is sputtered by the ion fluxes with impact energies defined by the plasma sheath. H2, D2 and 18O2 plasmas are produced in the carbon limiter tokamak TEXTOR. Pre-characterised a-C:D layers are exposed to study local removal rates. The D2 plasma exhibits the highest surface release rate of 5.7 ± 0.9 ∗ 1019 D/m2s. Compared to this the rate of the O2 plasma is 3-fold smaller due to its 11-fold lower ion flux density. Re-deposition of removed carbon is observed, indicating that pumping and ionisation are limiting the removal in TEXTOR. Presented models can explain the observations and allow tailoring removal discharges. An integral application scenario using ICWC and thermo-chemical removal is presented, allowing to remove 700 g T from a-C:DT co-deposits in 20 h with fusion compatible wall conditions using technical specifications similar to ITER.

  13. COOMET pilot comparison 473/RU-a/09: Comparison of hydrophone calibrations in the frequency range 250 Hz to 200 kHz

    NASA Astrophysics Data System (ADS)

    Yi, Chen; Isaev, A. E.; Yuebing, Wang; Enyakov, A. M.; Teng, Fei; Matveev, A. N.

    2011-01-01

    A description is given of the COOMET project 473/RU-a/09: a pilot comparison of hydrophone calibrations at frequencies from 250 Hz to 200 kHz between Hangzhou Applied Acoustics Research Institute (HAARI, China)—pilot laboratory—and Russian National Research Institute for Physicotechnical and Radio Engineering Measurements (VNIIFTRI, Designated Institute of Russia of the CIPM MRA). Two standard hydrophones, B&K 8104 and TC 4033, were calibrated and compared to assess the current state of hydrophone calibration of HAARI (China) and Russia. Three different calibration methods were applied: a vibrating column method, a free-field reciprocity method and a comparison method. The standard facilities of each laboratory were used, and three different sound fields were applied: pressure field, free-field and reverberant field. The maximum deviation of the sensitivities of two hydrophones between the participants' results was 0.36 dB. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCAUV-KCWG.

  14. The Kepler Mission: A Mission to Determine the Frequency of Inner Planets Neat the Habitable Zone of a Wide Range of Stars

    NASA Technical Reports Server (NTRS)

    Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.; Young, Richard E. (Technical Monitor)

    1997-01-01

    The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours, From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.

  15. The Kepler Mission: A Mission to Determine the Frequency of Inner Planets Near the Habitable Zone of a Wide Range of Stars

    NASA Technical Reports Server (NTRS)

    Borucki, W. J.; Koch, D. G.; Dunham, E. W.; Jenkins, J. M.

    1997-01-01

    The surprising discovery of giant planets in inner orbits around solar-like stars has brought into question our understanding of the development and evolution of planetary systems, including our solar system. To make further progress, it is critical to detect and obtain data on the frequency and characteristics of Earth-class planets. The Kepler Mission is designed to be a quick, low-cost approach to accomplish that objective. Transits by Earth-class planets produce a fractional change. in stellar brightness of 5 x 10(exp -5) to 40 x 10(exp -5) lasting for 4 to 16 hours. From the period and depth of the transits, the orbit and size of the planets can be calculated. The proposed instrument is a one-meter aperture photometer with a 12 deg. field-of-view (FOV). To obtain the required precision and to avoid interruptions caused by day-night and seasonal cycles, the photometer will be launched into a heliocentric orbit. It will continuously and simultaneously monitor the flux from 80,000 dwarf stars brighter than 14th magnitude in the Cygnus constellation. The mission tests the hypothesis that the formation of most stars produces Earth-class planets in inner orbits. Based on this assumption and the recent observations that 2% of the stars have giant planets in inner orbits, several types of results are expected from the mission: 1. From transits of Earth-class planets, about 480 planet detections and 60 cases where two or more planets are found in the same system. 2. From transits of giant planets, about 160 detections of inner-orbit planets and 24 detections of outer-orbit planets. 3. From the phase modulation of the reflected light from giant planets, about 1400 planet detections with periods less than a week, albedos for 160 of these giant planets, and densities for seven planets.

  16. Intrinsic vs. spurious long-range memory in high-frequency records of environmental radioactivity. Critical re-assessment and application to indoor 222Rn concentrations from Coimbra, Portugal

    NASA Astrophysics Data System (ADS)

    Donner, R. V.; Potirakis, S. M.; Barbosa, S. M.; Matos, J. A. O.; Pereira, A. J. S. C.; Neves, L. J. P. F.

    2015-05-01

    The presence or absence of long-range correlations in the environmental radioactivity fluctuations has recently attracted considerable interest. Among a multiplicity of practically relevant applications, identifying and disentangling the environmental factors controlling the variable concentrations of the radioactive noble gas radon is important for estimating its effect on human health and the efficiency of possible measures for reducing the corresponding exposition. In this work, we present a critical re-assessment of a multiplicity of complementary methods that have been previously applied for evaluating the presence of long-range correlations and fractal scaling in environmental radon variations with a particular focus on the specific properties of the underlying time series. As an illustrative case study, we subsequently re-analyze two high-frequency records of indoor radon concentrations from Coimbra, Portugal, each of which spans several weeks of continuous measurements at a high temporal resolution of five minutes.Our results reveal that at the study site, radon concentrations exhibit complex multi-scale dynamics with qualitatively different properties at different time-scales: (i) essentially white noise in the high-frequency part (up to time-scales of about one hour), (ii) spurious indications of a non-stationary, apparently long-range correlated process (at time scales between some hours and one day) arising from marked periodic components, and (iii) low-frequency variability indicating a true long-range dependent process. In the presence of such multi-scale variability, common estimators of long-range memory in time series are prone to fail if applied to the raw data without previous separation of time-scales with qualitatively different dynamics.

  17. Feature extraction of micro-motion frequency and the maximum wobble angle in a small range of missile warhead based on micro-Doppler effect

    NASA Astrophysics Data System (ADS)

    Li, M.; Jiang, Y. S.

    2014-11-01

    Micro-Doppler effect is induced by the micro-motion dynamics of the radar target itself or any structure on the target. In this paper, a simplified cone-shaped model for ballistic missile warhead with micro-nutation is established, followed by the theoretical formula of micro-nutation is derived. It is confirmed that the theoretical results are identical to simulation results by using short-time Fourier transform. Then we propose a new method for nutation period extraction via signature maximum energy fitting based on empirical mode decomposition and short-time Fourier transform. The maximum wobble angle is also extracted by distance approximate approach in a small range of wobble angle, which is combined with the maximum likelihood estimation. By the simulation studies, it is shown that these two feature extraction methods are both valid even with low signal-to-noise ratio.

  18. Delivering Microwave Spectroscopy to the Masses: a Design of a Low-Cost Microwave Spectrometer Operating in the 18-26 GHZ Frequency Range

    NASA Astrophysics Data System (ADS)

    Steber, Amanda; Pate, Brooks

    2014-06-01

    Advances in chip-level microwave technology in the communications field have led to the possibilities of low cost alternatives for current Fourier transform microwave (FTMW) spectrometers. Many of the large, expensive microwave components in a traditional design can now be replaced by robust, mass market monolithic microwave integrated circuits (MMICs). "Spectrometer on a board" designs are now feasible that offer dramatic cost reduction for microwave spectroscopy. These chip-level components can be paired with miniature computers to produce compact instruments that are operable through USB. A FTMW spectrometer design using the key MMIC components that drive cost reduction will be presented. Two dual channel synthesizers (Valon Technology Model 5008), a digital pattern generator (Byte Paradigm Wav Gen Xpress), and a high-speed digitizer/arbitrary waveform generator combination unit (Tie Pie HS-5 530 XM) form the key components of the spectrometer for operation in the 18-26.5 GHz range. The design performance is illustrated using a spectrometer that is being incorporated into a museum display for astrochemistry. For this instrument a user interface, developed in Python, has been developed and will be shown.

  19. Dielectric properties of porous silicon for use as a substrate for the on-chip integration of millimeter-wave devices in the frequency range 140 to 210 GHz

    PubMed Central

    2014-01-01

    In this work, the dielectric properties of porous Si for its use as a local substrate material for the integration on the Si wafer of millimeter-wave devices were investigated in the frequency range 140 to 210 GHz. Broadband electrical characterization of coplanar waveguide transmission lines (CPW TLines), formed on the porous Si layer, was used in this respect. It was shown that the dielectric parameters of porous Si (dielectric permittivity and loss tangent) in the above frequency range have values similar to those obtained at lower frequencies (1 to 40 GHz). More specifically, for the samples used, the obtained values were approximately 3.12 ± 0.05 and 0.023 ± 0.005, respectively. Finally, a comparison was made between the performance of the CPW TLines on a 150-μm-thick porous Si layer and on three other radiofrequency (RF) substrates, namely, on trap-rich high-resistivity Si (trap-rich HR Si), on a standard complementary metal-oxide-semiconductor (CMOS) Si wafer (p-type, resistivity 1 to 10 Ω.cm) and on quartz. PACS 84.40.-x; 77.22.Ch; 81.05.Rm PMID:25206316

  20. Dielectric properties of porous silicon for use as a substrate for the on-chip integration of millimeter-wave devices in the frequency range 140 to 210 GHz

    NASA Astrophysics Data System (ADS)

    Sarafis, Panagiotis; Nassiopoulou, Androula Galiouna

    2014-08-01

    In this work, the dielectric properties of porous Si for its use as a local substrate material for the integration on the Si wafer of millimeter-wave devices were investigated in the frequency range 140 to 210 GHz. Broadband electrical characterization of coplanar waveguide transmission lines (CPW TLines), formed on the porous Si layer, was used in this respect. It was shown that the dielectric parameters of porous Si (dielectric permittivity and loss tangent) in the above frequency range have values similar to those obtained at lower frequencies (1 to 40 GHz). More specifically, for the samples used, the obtained values were approximately 3.12 ± 0.05 and 0.023 ± 0.005, respectively. Finally, a comparison was made between the performance of the CPW TLines on a 150-μm-thick porous Si layer and on three other radiofrequency (RF) substrates, namely, on trap-rich high-resistivity Si (trap-rich HR Si), on a standard complementary metal-oxide-semiconductor (CMOS) Si wafer (p-type, resistivity 1 to 10 Ω.cm) and on quartz.

  1. RF-Medisys: a radio frequency identification-based electronic medical record system for improving medical information accessibility and services at point of care.

    PubMed

    Ting, Jacky S L; Tsang, Albert H C; Ip, Andrew W H; Ho, George T S

    2011-01-01

    This paper presents an innovative electronic medical records (EMR) system, RF-MediSys, which can perform medical information sharing and retrieval effectively and which is accessible via a 'smart' medical card. With such a system, medical diagnoses and treatment decisions can be significantly improved when compared with the conventional practice of using paper medical records systems. Furthermore, the entire healthcare delivery process, from registration to the dispensing or administration of medicines, can be visualised holistically to facilitate performance review. To examine the feasibility of implementing RF-MediSys and to determine its usefulness to users of the system, a survey was conducted within a multi-disciplinary medical service organisation that operates a network of medical clinics and paramedical service centres throughout Hong Kong Island, the Kowloon Peninsula and the New Territories. Questionnaires were distributed to 300 system users, including nurses, physicians and patients, to collect feedback on the operation and performance of RF-MediSys in comparison with conventional paper-based medical record systems. The response rate to the survey was 67%. Results showed a medium to high level of user satisfaction with the radiofrequency identification (RFID)-based EMR system. In particular, respondents provided high ratings on both 'user-friendliness' and 'system performance'. Findings of the survey highlight the potential of RF-MediSys as a tool to enhance quality of medical services and patient safety. PMID:21430306

  2. Absorption coefficients and frequency shifts measurement in the spectral range of 1071.88-1084.62 cm-1 vs. pressure for chlorodifluoromethane (CHClF2) using tunable CW CO2 laser

    NASA Astrophysics Data System (ADS)

    Al-Hawat, Sharif

    2013-02-01

    Infrared (IR) absorption in the spectral range of (1071.88-1084.62 cm-1) vs. pressure in chlorodifluoromethane (CFC-22, F-22, and CHClF2) was studied using a tunable continuous wave (CW) CO2 laser radiation on 9R branch lines with a maximum output power of about 2.12 W, provided with an absorber cell located outside the laser cavity. The absorption coefficients were determined vs. the gas pressure between 0.2 mbar and 170 mbar at lines from 9R branch for CFC-22. The frequency shifts of the absorption lines of CFC-22 in relative to the central frequencies of laser lines were calculated vs. the pressure on the basis of these absorption coefficients. The chosen lines were selected according to IR spectrum of the studied gas given by HITRAN cross section database. So the absorption was achieved for CFC-22 at the spectral lines of 9R branch situated from 9R (10) to 9R (30) emitted by a tunable CW CO2 laser. The absorption cross sections of CFC-22 determined in this work were compared with the relevant data given by HITRAN cross section database and a reasonable agreement was observed.

  3. Wrist range of motion and motion frequency during toy and game play with a joint-specific controller specially designed to provide neuromuscular therapy: A proof of concept study in typically developing children.

    PubMed

    Crisco, Joseph J; Schwartz, Joel B; Wilcox, Bethany; Brideau, Holly; Basseches, Benjamin; Kerman, Karen

    2015-08-20

    Upper extremities affected by hemiplegic cerebral palsy (CP) and other neuromuscular disorders have been demonstrated to benefit from therapy, and the greater the duration of the therapy, the greater the benefit. A great motivator for participating in and extending the duration of therapy with children is play. Our focus is on active motion therapy of the wrist and forearm. In this study we examine the wrist motions associated with playing with two toys and three computer games controlled by a specially-designed play controller. Twenty children (ages 5-11) with no diagnosis of a muscular disorder were recruited. The play controller was fitted to the wrist and forearm of each child and used to measure and log wrist flexion and extension. Play activity and enjoyment were quantified by average wrist range of motion (ROM), motion frequency measures, and a discrete visual scale. We found significant differences in the average wrist ROM and motion frequency among the toys and games, yet there were no differences in the level of enjoyment across all toys and games, which was high. These findings indicate which toys and games may elicit the greater number of goal-directed movements, and lay the foundation for our long-term goal to develop and evaluate innovative motion-specific play controllers that are engaging rehabilitative devices for enhancing therapy and promoting neural plasticity and functional recovery in children with CP. PMID:25935686

  4. Final report of supplementary comparison AFRIMETS.AUV.A-S1: primary pressure calibration of LS2aP microphones according to IEC 61094-2, over the frequency range 1 Hz to 31.5 kHz.

    NASA Astrophysics Data System (ADS)

    Nel, R.; Barrera-Figueroa, S.; Dobrowolska, D.; Defilippo Soares, Z. M.; Maina, A. K.; Hof, C.

    2016-01-01

    This is the final report of the AFRIMETS.AUV-S1 comparison of the pressure sensitivity, modulus and phase, of LS2aP microphones in the frequency range 1 Hz to 31.5 kHz in accordance with IEC 61094-2. Six national metrology institutes from three different regional metrology organisations participated in the comparison for which two LS2aP microphones were circulated simultaneously to all the participants in a hybrid-star configuration. The comparison reference values were calculated as the weighted mean for modulus and phase for each individual microphone. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

  5. Application of the Superslow Relaxation Model in the Description of Time Series of the Vertical Electric Field Component in the Earth's Atmospheric Boundary Layer in the Infra-Low Frequency Range

    NASA Astrophysics Data System (ADS)

    Isakevich, D. V.; Grunskaya, L. V.

    2015-12-01

    To explain the presence of spectrally localized, mutually uncorrelated the electric field components in the Earth's atmospheric boundary layer in the infra-low frequency range, it is proposed to use the model of fractionally integrated white Gaussian noise. It is shown that the uncorrelated components of the fractionally integrated (of order 0.5) white Gaussian noise have a coherence index close to that of the uncorrelated components of time series of the electric field. The energy distribution of the uncorrelated components of the fractionally integrated noise is also close to the energy distribution of the components of the electric field. To lay the basis for a physical interpretation of fractionally integrated noise, it is proposed to use the differential equation of superslow relaxation.

  6. Web Accessibility and Accessibility Instruction

    ERIC Educational Resources Information Center

    Green, Ravonne A.; Huprich, Julia

    2009-01-01

    Section 508 of the Americans with Disabilities Act (ADA) mandates that programs and services be accessible to people with disabilities. While schools of library and information science (SLIS*) and university libraries should model accessible Web sites, this may not be the case. This article examines previous studies about the Web accessibility of…

  7. SUBTLEX-UK: a new and improved word frequency database for British English.

    PubMed

    van Heuven, Walter J B; Mandera, Pawel; Keuleers, Emmanuel; Brysbaert, Marc

    2014-01-01

    We present word frequencies based on subtitles of British television programmes. We show that the SUBTLEX-UK word frequencies explain more of the variance in the lexical decision times of the British Lexicon Project than the word frequencies based on the British National Corpus and the SUBTLEX-US frequencies. In addition to the word form frequencies, we also present measures of contextual diversity part-of-speech specific word frequencies, word frequencies in children programmes, and word bigram frequencies, giving researchers of British English access to the full range of norms recently made available for other languages. Finally, we introduce a new measure of word frequency, the Zipf scale, which we hope will stop the current misunderstandings of the word frequency effect. PMID:24417251

  8. Telemetry Ranging: Concepts

    NASA Astrophysics Data System (ADS)

    Hamkins, J.; Kinman, P.; Xie, H.; Vilnrotter, V.; Dolinar, S.

    2015-11-01

    Telemetry ranging is a proposed alternative to conventional two-way ranging for determining the two-way time delay between a Deep Space Station (DSS) and a spacecraft. The advantage of telemetry ranging is that the ranging signal on the uplink is not echoed to the downlink, so that telemetry alone modulates the downlink carrier. The timing information needed on the downlink, in order to determine the two-way time delay, is obtained from telemetry frames. This article describes the phase and timing estimates required for telemetry ranging, and how two-way range is calculated from these estimates. It explains why the telemetry ranging architecture does not require the spacecraft transponder to have a high-frequency or high-quality oscillator, and it describes how a telemetry ranging system can be infused in the Deep Space Network.

  9. Open Access

    ERIC Educational Resources Information Center

    Suber, Peter

    2012-01-01

    The Internet lets us share perfect copies of our work with a worldwide audience at virtually no cost. We take advantage of this revolutionary opportunity when we make our work "open access": digital, online, free of charge, and free of most copyright and licensing restrictions. Open access is made possible by the Internet and copyright-holder…

  10. Access Denied

    ERIC Educational Resources Information Center

    Villano, Matt

    2008-01-01

    Building access control (BAC)--a catchall phrase to describe the systems that control access to facilities across campus--has traditionally been handled with remarkably low-tech solutions: (1) manual locks; (2) electronic locks; and (3) ID cards with magnetic strips. Recent improvements have included smart cards and keyless solutions that make use…

  11. Accessibility of antiretroviral therapy in Ghana: convenience of access.

    PubMed

    Addo-Atuah, Joyce; Gourley, Dick; Gourley, Greta; White-Means, Shelley I; Womeodu, Robin J; Faris, Richard J; Addo, Nii Akwei

    2012-01-01

    The convenience of accessing antiretroviral therapy (ART) is important for initial access to care and subsequent adherence to ART. We conducted a qualitative study of people living with HIV/AIDS (PLWHA) and ART healthcare providers in Ghana in 2005. The objective of this study was to explore the participants' perceived convenience of accessing ART by PLWHA in Ghana. The convenience of accessing ART was evaluated from the reported travel and waiting times to receive care, the availability, or otherwise, of special considerations, with respect to the waiting time to receive care, for those PLWHA who were in active employment in the formal sector, the frequency of clinic visits before and after initiating ART, and whether the PLWHA saw the same or different providers at each clinic visit (continuity of care). This qualitative study used in-depth interviews based on Yin's case-study research design to collect data from 20 PLWHA and 24 ART healthcare providers as study participants. • Reported travel time to receive ART services ranged from 2 to 12 h for 30% of the PLWHA. • Waiting time to receive care was from 4 to 9 h. • While known government workers, such as teachers, were attended to earlier in some of the centres, this was not a consistent practice in all the four ART centres studied. • The PLWHA corroborated the providers' description of the procedure for initiating and monitoring ART in Ghana. • PLWHA did not see the same provider every time, but they were assured that this did not compromise the continuity of their care. Our study suggests that convenience of accessing ART is important to both PLWHA and ART healthcare providers, but the participants alluded to other factors, including open provider-patient communication, which might explain the PLWHA's understanding of the constraints under which they were receiving care. The current nation-wide coverage of the ART programme in Ghana, however, calls for the replication of this study to identify

  12. Multiple Access Schemes for Lunar Missions

    NASA Technical Reports Server (NTRS)

    Deutsch, Leslie; Hamkins, Jon; Stocklin, Frank J.

    2010-01-01

    Two years ago, the NASA Coding, Modulation, and Link Protocol (CMLP) study was completed. The study, led by the authors of this paper, recommended codes, modulation schemes, and desired attributes of link protocols for all space communication links in NASA's future space architecture. Portions of the NASA CMLP team were reassembled to resolve one open issue: the use of multiple access (MA) communication from the lunar surface. The CMLP-MA team analyzed and simulated two candidate multiple access schemes that were identified in the original CMLP study: Code Division MA (CDMA) and Frequency Division MA (FDMA) based on a bandwidth-efficient Continuous Phase Modulation (CPM) with a superimposed Pseudo-Noise (PN) ranging signal (CPM/PN). This paper summarizes the results of the analysis and simulation of the CMLP-MA study and describes the final recommendations.

  13. Low frequency cultural noise

    NASA Astrophysics Data System (ADS)

    Sheen, Dong-Hoon; Shin, Jin Soo; Kang, Tae-Seob; Baag, Chang-Eob

    2009-09-01

    Abnormal cultural seismic noise is observed in the frequency range of 0.01-0.05 Hz. Cultural noise generated by human activities is generally observed in frequencies above 1 Hz, and is greater in the daytime than at night. The low-frequency noise presented in this paper exhibits a characteristic amplitude variation and can be easily identified from time domain seismograms in the frequency range of interest. The amplitude variation is predominantly in the vertical component, but the horizontal components also show variations. Low-frequency noise is markedly periodic, which reinforces its interpretation as cultural noise. Such noise is observed world-wide, but is limited to areas in the vicinity of railways. The amplitude variation in seismograms correlates strongly with railway timetables, and the waveform shows a wavelength shift associated with the Doppler effect, which indicates that the origin of seismic background noise in the frequency range 0.01-0.05 Hz is railways.

  14. Electrical properties of the electroceramic composite in the microwave frequency range: Pb(Fe0.5Nb0.5)O3 (PFN)-Cr0.75Fe1.25O3 (CRFO)

    NASA Astrophysics Data System (ADS)

    Santos, M. R. P.; Freire, F. N. A.; Sohn, R. S. T. M.; Almeida, J. S.; Sancho, E. O.; Costa, A. D. S. B.; Medeiros, A. M. L.; Sombra, A. S. B.

    2008-12-01

    In this paper, a new electroceramic composite [Pb(Fe0.5Nb0.5) O3 (PFN)]Z [Cr0.75Fe1.25O3 (CRFO)]100-Z (Z = 0, 10) is investigated in the microwave (MW) frequency range. The dielectric permittivity and loss in the region of 4-8 GHz (G and H MW bands) were studied. The performance of cylindrical resonator antennas based on CRFO100 and on PFN10 was examined. The experimental and theoretical results of the dielectric resonator antenna (DRA) such as return loss, bandwidth, input impedance and radiation patterns are in good agreement for both composites: PFN10 (10% PFN + 90% CRFO) and CRFO100 (100% CRFO). A numerical validation was made considering an air gap between the dielectric resonator and the metallic conductors. The PFN10 matrix composite PFN10 (10% PFN + 90% CRFO) presents the highest dielectric permittivity (9.9 at 4.44 GHz) and the lowest bandwidth (9.9%). The CRFO100 phase (100% CRFO) presents a dielectric permittivity of 8.35 at 4.67 GHz and a bandwidth of 11.8%. The Hakki-Coleman procedure was also used in this study. The dielectric permittivity of 8.35 (tan δ = 1 × 10-3) at 7.94 GHz was obtained for CRFO100. The PFN10 presents a dielectric permittivity of 10.17 (tan δ = 4.9 × 10-3) at 7.05 GHz. These measurements confirm the possible use of such material for small DRAs.

  15. Range Ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    After more than two hundred years, grazing remains California’s most extensive land use. The ‘Range Ecosystems’ chapter in the ‘Ecosystems of California’ sourcebook provides an integrated picture of the biophysical, social, and economic aspects of lands grazed by livestock in the state. Grazing mana...

  16. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - hemodialysis access; dialysis - hemodialysis access

  17. [Evaluation of the possibility of determining the maximum permissible intensity values for electromagnetic fields in the frequency range 0.1-10 MHz in accordance with the standards established by the COMECON Project 01.873.08.84].

    PubMed

    Aniołczyk, H; Koperski, A

    1987-01-01

    A comparative evaluation of the requirements of the draft COMECON standard for 0.1-10 MHz frequencies with the hygienic regulations currently mandatory in Poland arouses some anxiety that certain groups of high-frequency devices, meeting national requirements, may not meet the requirements of the mentioned draft standard. To evaluate the possibilities of meeting the requirements of the mentioned draft by the high-frequency devices used in Poland, an analysis of real work conditions was carried out for approx. 450 industrial and electromedical appliances, as well as radio communication devices. The number of high-frequency devices which will not meet the COMECON standard requirements was estimated. In addition, the costs to be incurred for technological and organizational undertakings to meet the e-m working conditions pursuant to the COMECON standard requirements were calculated. PMID:3444423

  18. Hemodialysis access - self care

    MedlinePlus

    Kidney failure - chronic-hemodialysis access; Renal failure - chronic-hemodialysis access; Chronic renal insufficiency - hemodialysis access; Chronic kidney failure - hemodialysis access; Chronic renal failure - ...

  19. Frequency curves

    USGS Publications Warehouse

    Riggs, H.C.

    1968-01-01

    This manual describes graphical and mathematical procedures for preparing frequency curves from samples of hydrologic data. It also discusses the theory of frequency curves, compares advantages of graphical and mathematical fitting, suggests methods of describing graphically defined frequency curves analytically, and emphasizes the correct interpretations of a frequency curve.

  20. Expanding Access

    ERIC Educational Resources Information Center

    Roach, Ronald

    2007-01-01

    There is no question that the United States lags behind most industrialized nations in consumer access to broadband Internet service. For many policy makers and activists, this shortfall marks the latest phase in the struggle to overcome the digital divide. To remedy this lack of broadband affordability and availability, one start-up firm--with…

  1. Access Denied

    ERIC Educational Resources Information Center

    Raths, David

    2012-01-01

    As faculty members add online and multimedia elements to their courses, colleges and universities across the country are realizing that there is a lot of work to be done to ensure that disabled students (and employees) have equal access to course material and university websites. Unfortunately, far too few schools consider the task a top priority.…

  2. Easy Access

    ERIC Educational Resources Information Center

    Gettelman, Alan

    2009-01-01

    School and university restrooms, locker and shower rooms have specific ADA accessibility requirements that serve the needs of staff, students and campus visitors who are disabled as a result of injury, illness or age. Taking good care of them is good for the reputation of a sensitive community institution, and fosters positive public relations.…

  3. Scaling of Yb-Fiber Frequency Combs

    NASA Astrophysics Data System (ADS)

    Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E.; Hartl, Ingmar

    2010-06-01

    Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

  4. Range and range rate system

    NASA Technical Reports Server (NTRS)

    Graham, Olin L. (Inventor); Russell, Jim K. (Inventor); Epperly, Walter L. (Inventor)

    1988-01-01

    A video controlled solid state range finding system which requires no radar, high power laser, or sophisticated laser target is disclosed. The effective range of the system is from 1 to about 200 ft. The system includes an opto-electric camera such as a lens CCD array device. A helium neon laser produces a source beam of coherent light which is applied to a beam splitter. The beam splitter applies a reference beam to the camera and produces an outgoing beam applied to a first angularly variable reflector which directs the outgoing beam to the distant object. An incoming beam is reflected from the object to a second angularly variable reflector which reflects the incoming beam to the opto-electric camera via the beam splitter. The first reflector and the second reflector are configured so that the distance travelled by the outgoing beam from the beam splitter and the first reflector is the same as the distance travelled by the incoming beam from the second reflector to the beam splitter. The reference beam produces a reference signal in the geometric center of the camera. The incoming beam produces an object signal at the camera.

  5. Hemodialysis access procedures

    MedlinePlus

    Kidney failure - chronic-dialysis access; Renal failure - chronic-dialysis access; Chronic renal insufficiency-dialysis access; Chronic kidney failure-dialysis access; Chronic renal failure-dialysis access

  6. Widening Access to Higher Education: An Evaluative Case Study of a Foundation Year Alternative to Access

    ERIC Educational Resources Information Center

    Reddy, Peter A.; Moores, Elisabeth

    2008-01-01

    Universities are encouraged to widen access to a broad range of applicants, including mature students taking Access qualifications. Admissions tutors can find it difficult to compare and choose between Access and A-level applications, and Access applicants for popular courses may be disadvantaged relative to students with good A-levels. In this…

  7. Simple sweep frequency generator

    NASA Astrophysics Data System (ADS)

    Yegorov, I.

    1985-01-01

    A sweep frequency generator is described whose center frequency can be varied from 10 kHz to 50 MHz, with seven 1 to 3 and 3 to 10 scales covering the 10 kHz to 30 MHz range and one 3 to 5 scale for the 30 to 50 MHz range. It consists of a tunable pulse generator with output voltage attenuator, a diode mixer for calibration, and a sawtooth voltage generator as a source of frequency deviation. The pulse generator is a multivibrator with two emitter coupled transistors and two diodes in the collector circuit of one. The first diode extends the tuning range and increases the frequency deviation, the second diode provides the necessary base bias to the other transistor. The pulse repetition rate is modulated either directly by the sweep voltage of the calibrating oscilloscope, this voltage being applied to the base of the transistor with the two diodes in its collector circuit through an additional attenuator or a special emitter follower, or by the separate sawtooth voltage generator. The latter is a conventional two transistor multivibrator and produces signals at any constant frequency within the 40 to 60 Hz range. The mixer receives unmodulated signals from a reference frequency source and produces different frequency signals which are sent through an RCR-filter to a calibrating oscilloscope.

  8. Reconfigurable ring filter with controllable frequency response.

    PubMed

    Ab Wahab, Norfishah; Mohd Salleh, Mohd Khairul; Ismail Khan, Zuhani; Abd Rashid, Nur Emileen

    2014-01-01

    Reconfigurable ring filter based on single-side-access ring topology is presented. Using capacitive tuning elements, the electrical length of the ring can be manipulated to shift the nominal center frequency to a desired position. A synthesis is developed to determine the values of the capacitive elements. To show the advantage of the synthesis, it is applied to the reconfigurable filter design using RF lumped capacitors. The concept is further explored by introducing varactor-diodes to continuously tune the center frequency of the ring filter. For demonstration, two prototypes of reconfigurable ring filters are realized using microstrip technology, simulated, and measured to validate the proposed concept. The reconfigured filter using lumped elements is successfully reconfigured from 2 GHz to 984.4 MHz and miniaturized by 71% compared to the filter directly designed at the same reconfigured frequency, while, for the filter using varactor-diodes, the frequency is chosen from 1.10 GHz to 1.38 GHz spreading over 280 MHz frequency range. Both designs are found to be compact with acceptable insertion loss and high selectivity. PMID:25121132

  9. Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hänsch, Theodor W.; Picqué, Nathalie

    Much of modern research in the field of atomic, molecular, and optical science relies on lasers, which were invented some 50 years ago and perfected in five decades of intense research and development. Today, lasers and photonic technologies impact most fields of science and they have become indispensible in our daily lives. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. Through the development of optical frequency comb techniques, technique a setup of the size 1 ×1 m2, good for precision measurements of any frequency, and even commercially available, has replaced the elaborate previous frequency-chain schemes for optical frequency measurements, which only worked for selected frequencies. A true revolution in optical frequency measurements has occurred, paving the way for the creation of all-optical clocks clock with a precision that might approach 10-18. A decade later, frequency combs are now common equipment in all frequency metrology-oriented laboratories. They are also becoming enabling tools for an increasing number of applications, from the calibration of astronomical spectrographs to molecular spectroscopy. This chapter first describes the principle of an optical frequency comb synthesizer. Some of the key technologies to generate such a frequency comb are then presented. Finally, a non-exhaustive overview of the growing applications is given.

  10. High-power frequency comb in the range of 2-2.15  μm based on a holmium fiber amplifier seeded by wavelength-shifted Raman solitons from an erbium-fiber laser.

    PubMed

    Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

    2014-03-15

    We demonstrate a room-temperature high-power frequency comb source covering the spectral region from 2 to 2.15 μm. The source is based on a femtosecond erbium-fiber laser operating at 1.55 μm with a repetition rate of 250 MHz, wavelength-shifted up to 2.06 μm by the solitonic Raman effect, seeding a large-mode-area holmium (Ho) fiber amplifier pumped by a thulium (Tm) fiber laser emitting at 1.94 μm. The frequency comb has an integrated power of 2 W, with overall power fluctuations as low as 0.3%. The beatnote between the comb and a high-spectral-purity, single-frequency Tm-Ho laser has a linewidth of 32 kHz over 1 ms observation time, with a signal-to-noise ratio in excess of 30 dB. PMID:24690863

  11. Photoresistance analog multiplier has wide range

    NASA Technical Reports Server (NTRS)

    Hartenstein, R. G.

    1965-01-01

    Photoactivated bridge facilitates equal performance of analog multipliers over a wide frequency range. The multiplier operates from direct current to an upper frequency limited by either the light source or the closed-loop amplifier.

  12. Generation of high-power femtosecond supercontinua in the near-IR spectral range using broadband parametric frequency conversion in LBO and DCDA crystals pumped at λ = 620 nm

    SciTech Connect

    Podshivalov, A A; Sidorov-Biryukov, D A; Potemkin, F V

    2014-09-30

    The pump wavelength of parametric amplifiers based on CLBO, DCDA and LBO crystals and pumped by the second harmonic of a femtosecond Cr : forsterite laser (620 nm) is close to optimal for broadband amplification because of the proximity of group velocities of interacting pulses. Injection of a broadband continuum into the range of the signal-wave gain in LBO and DCDA parametric amplifiers, pumped at λ = 620 nm, leads to generation of broadband femtosecond pulses with a spectrum ranging from 1050 to 1600 nm and peak powers up to 20 MW. (nonlinear optical phenomena)

  13. Generation of high-power femtosecond supercontinua in the near-IR spectral range using broadband parametric frequency conversion in LBO and DCDA crystals pumped at λ = 620 nm

    NASA Astrophysics Data System (ADS)

    Podshivalov, A. A.; Potemkin, F. V.; Sidorov-Biryukov, D. A.

    2014-09-01

    The pump wavelength of parametric amplifiers based on CLBO, DCDA and LBO crystals and pumped by the second harmonic of a femtosecond Cr : forsterite laser (620 nm) is close to optimal for broadband amplification because of the proximity of group velocities of interacting pulses. Injection of a broadband continuum into the range of the signal-wave gain in LBO and DCDA parametric amplifiers, pumped at λ = 620 nm, leads to generation of broadband femtosecond pulses with a spectrum ranging from 1050 to 1600 nm and peak powers up to 20 MW.

  14. Frequency selective terahertz retroreflectors

    NASA Astrophysics Data System (ADS)

    Williams, Richard James

    The use of novel optical structures operating at terahertz frequencies in industrial and military applications continues to grow. Some of these novel structures include gratings, frequency selective surfaces, metamaterials and metasurfaces, and retroreflectors. A retroreflector is a device that exhibits enhanced backscatter by concentrating the reflected wave in the direction of the source. Retroreflectors have applications in a variety of diverse fields such as aviation, radar systems, antenna technology, communications, navigation, passive identification, and metrology due to their large acceptance angles and frequency bandwidth. This thesis describes the design, fabrication, and characterization of a retroreflector designed for terahertz frequencies and the incorporation of a frequency selective surface in order to endow the retroreflector with narrow-band frequency performance. The radar cross section of several spherical lens reflectors operating at terahertz frequencies was investigated. Spherical lens reflectors with diameters ranging from 2 mm to 8 mm were fabricated from fused silica ball lenses and their radar cross section was measured at 100 GHz, 160 GHz, and 350 GHz. Crossed-dipole frequency selective surfaces exhibiting band-pass characteristics at 350 GHz fabricated from 12 um-thick Nickel screens were applied to the apertures of the spherical lens reflectors. The radar cross section of the frequency selective retroreflectors was measured at 160 GHz and 350 GHz to demonstrate proof-of-concept of narrow-band terahertz performance.

  15. Nonlinear Frequency Compression

    PubMed Central

    Scollie, Susan; Glista, Danielle; Seelisch, Andreas

    2013-01-01

    Frequency lowering technologies offer an alternative amplification solution for severe to profound high frequency hearing losses. While frequency lowering technologies may improve audibility of high frequency sounds, the very nature of this processing can affect the perceived sound quality. This article reports the results from two studies that investigated the impact of a nonlinear frequency compression (NFC) algorithm on perceived sound quality. In the first study, the cutoff frequency and compression ratio parameters of the NFC algorithm were varied, and their effect on the speech quality was measured subjectively with 12 normal hearing adults, 12 normal hearing children, 13 hearing impaired adults, and 9 hearing impaired children. In the second study, 12 normal hearing and 8 hearing impaired adult listeners rated the quality of speech in quiet, speech in noise, and music after processing with a different set of NFC parameters. Results showed that the cutoff frequency parameter had more impact on sound quality ratings than the compression ratio, and that the hearing impaired adults were more tolerant to increased frequency compression than normal hearing adults. No statistically significant differences were found in the sound quality ratings of speech-in-noise and music stimuli processed through various NFC settings by hearing impaired listeners. These findings suggest that there may be an acceptable range of NFC settings for hearing impaired individuals where sound quality is not adversely affected. These results may assist an Audiologist in clinical NFC hearing aid fittings for achieving a balance between high frequency audibility and sound quality. PMID:23539261

  16. High-Frequency Gated Oscillator

    NASA Technical Reports Server (NTRS)

    Berard, C. A.

    1982-01-01

    New gated oscillator generates bursts of high-frequency sine waves, square waves, and triangular waves in response to control signals. Each burst starts at zero phase, with tight tolerances on signal amplitude and frequency. Frequencies in megahertz range are made possible by using high-speed comparators and high-speed flip-flop as fast-response threshold detector.

  17. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  18. Optical Frequency Domain Imaging

    NASA Astrophysics Data System (ADS)

    Bouma, Brett E.; Tearney, Guillermo J.; Vakoc, Benjamin; Yun, Seok Hyun

    In this chapter, we discuss a frequency-domain approach, optical frequency-domain imaging (OFDI), which is based on optical frequency-domain reflectometry and uses a wavelength-swept laser and standard single-element photodetectors. The chapter begins with an overview of the fundamental aspects of the technology, including the detected signal, sensitivity, depth range, and resolution, and then goes on to discuss specific component technologies including the light source, interferometer and acquisition electronics, and image processing. The final section of the chapter provides a brief glimpse at some of the biomedical applications that most directly take advantage of the improved speed and sensitivity of OFDI.

  19. Decrease in Self-Reported Tanning Frequency among Utah Teens following the Passage of Utah Senate Bill 41: An Analysis of the Effects of Youth-Access Restriction Laws on Tanning Behaviors

    PubMed Central

    Simmons, Rebecca G.; Smith, Kristi

    2014-01-01

    Introduction. Adolescent use of indoor tanning facilities is associated with an increased risk in later development of melanoma skin cancers. States that have imposed age restrictions on access to indoor tanning generally show lower self-reported rates of indoor tanning than states with no restrictions, but currently no studies have assessed indoor tanning use before and after such restrictions. Methods. In 2013, we compared self-reported indoor tanning data collected in the Prevention Needs Assessment (PNA) survey in 2011 to PNA 2013 data. We also assessed predictors of continued tanning after passage of the bill. Results. Prior to the passage of Senate Bill 41, 12% of students reported at least one incident of indoor tanning in the past 12 months. After passage, only 7% of students reported indoor tanning in the past 12 months (P < 0.0001). Students who continued indoor tanning were more likely to be older and female and to engage in other risk behaviors, including smoking and alcohol use. Lower parental education levels were also associated with continued tanning. Conclusion. Indoor tanning restrictions showed beneficial impact on tanning rates in adolescents in Utah. Stricter restrictions may show even greater impact than restrictions that allow for parental waivers. Stronger enforcement of bans is needed to further reduce youth access. PMID:25215240

  20. Corrosion monitoring using high-frequency guided ultrasonic waves

    NASA Astrophysics Data System (ADS)

    Fromme, Paul

    2014-02-01

    Corrosion develops due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Both pitting corrosion and generalized corrosion leading to wall thickness loss can cause the degradation of the structural integrity. The nondestructive detection and monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic transducers with single sided access to the structure, guided wave modes were generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted and the wall thickness reduced by consecutive milling of the steel structure. Further measurements were conducted using accelerated corrosion in a salt water bath and the damage severity monitored. From the measured signal change due to the wave mode interference the wall thickness reduction was monitored. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

  1. Corrosion monitoring using high-frequency guided waves

    NASA Astrophysics Data System (ADS)

    Fromme, P.

    2016-04-01

    Corrosion can develop due to adverse environmental conditions during the life cycle of a range of industrial structures, e.g., offshore oil platforms, ships, and desalination plants. Generalized corrosion leading to wall thickness loss can cause the reduction of the strength and thus degradation of the structural integrity. The monitoring of corrosion damage in difficult to access areas can be achieved using high frequency guided waves propagating along the structure from accessible areas. Using standard ultrasonic wedge transducers with single sided access to the structure, guided wave modes were selectively generated that penetrate through the complete thickness of the structure. The wave propagation and interference of the different guided wave modes depends on the thickness of the structure. Laboratory experiments were conducted for wall thickness reduction due to milling of the steel structure. From the measured signal changes due to the wave mode interference the reduced wall thickness was monitored. Good agreement with theoretical predictions was achieved. The high frequency guided waves have the potential for corrosion damage monitoring at critical and difficult to access locations from a stand-off distance.

  2. Phonological activation in anaphoric lexical access (ALA).

    PubMed

    Simner, J; Smyth, R

    Simner and Smyth (1998) propose that anaphoric lexical access (ALA) occurs at an anaphor and targets the lexical entry (specifically, the lemma) of the antecedent. Since the word frequency effect (e.g., Rubenstein et al., 1970) resides at the lexeme (Jescheniak & Levelt, 1994) Simner and Smyth predict, and subsequently illustrate, that ALA exhibits no frequency effect. A problem arises, however: if ALA does not access the lexeme, how do we account for phonological priming at anaphor sites (e.g., Tanenhaus et al., 1985)? We claim that this is the result of "incidental" lemma-to-lexeme activation. Furthermore, we argue that since lexeme activation is not crucial to anaphor comprehension, anaphor reading times indicate lemma search times only (therefore there is no frequency effect). An experiment is presented demonstrating that lemma-access during ALA can cause incidental lexeme activation without invoking a frequency effect. PMID:10433737

  3. Frequency spirals

    NASA Astrophysics Data System (ADS)

    Ottino-Löffler, Bertrand; Strogatz, Steven H.

    2016-09-01

    We study the dynamics of coupled phase oscillators on a two-dimensional Kuramoto lattice with periodic boundary conditions. For coupling strengths just below the transition to global phase-locking, we find localized spatiotemporal patterns that we call "frequency spirals." These patterns cannot be seen under time averaging; they become visible only when we examine the spatial variation of the oscillators' instantaneous frequencies, where they manifest themselves as two-armed rotating spirals. In the more familiar phase representation, they appear as wobbly periodic patterns surrounding a phase vortex. Unlike the stationary phase vortices seen in magnetic spin systems, or the rotating spiral waves seen in reaction-diffusion systems, frequency spirals librate: the phases of the oscillators surrounding the central vortex move forward and then backward, executing a periodic motion with zero winding number. We construct the simplest frequency spiral and characterize its properties using analytical and numerical methods. Simulations show that frequency spirals in large lattices behave much like this simple prototype.

  4. Serial Mechanisms in Lexical Access: The Rank Hypothesis

    ERIC Educational Resources Information Center

    Murray, W. S.; Forster, K. I.

    2004-01-01

    There is general agreement that the effect of frequency on lexical access time is roughly logarithmic, although little attention has been given to the reason for this. The authors argue that models of lexical access that incorporate a frequency-ordered serial comparison or verification procedure provide an account of this effect and predict that…

  5. United States Access Board

    MedlinePlus

    ... disabilities through leadership in accessible design and the development of accessibility guidelines and standards for the built environment, transportation, communication, medical diagnostic equipment, and information technology. ...

  6. Variable frequency iteration MPPT for resonant power converters

    SciTech Connect

    Zhang, Qian; Bataresh, Issa; Chen, Lin

    2015-06-30

    A method of maximum power point tracking (MPPT) uses an MPPT algorithm to determine a switching frequency for a resonant power converter, including initializing by setting an initial boundary frequency range that is divided into initial frequency sub-ranges bounded by initial frequencies including an initial center frequency and first and second initial bounding frequencies. A first iteration includes measuring initial powers at the initial frequencies to determine a maximum power initial frequency that is used to set a first reduced frequency search range centered or bounded by the maximum power initial frequency including at least a first additional bounding frequency. A second iteration includes calculating first and second center frequencies by averaging adjacent frequent values in the first reduced frequency search range and measuring second power values at the first and second center frequencies. The switching frequency is determined from measured power values including the second power values.

  7. A Theory of Access

    ERIC Educational Resources Information Center

    Ribot, Jesse C.; Peluso, Nancy Lee

    2003-01-01

    The term "access" is frequently used by property and natural resource analysts without adequate definition. In this paper we develop a concept of access and examine a broad set of factors that differentiate access from property. We define access as "the "ability" to derive benefits from things," broadening from property's classical definition as…

  8. Small Satellite Access of the Space Network

    NASA Technical Reports Server (NTRS)

    Horan, Stephen; Minnix, Timothy O.; Vigil, J. S.

    1999-01-01

    Small satellites have been perceived as having limited access to NASA's Space Network (SN). The potential for satellite access of the space network when the design utilizes a fixed antenna configuration and low-power, coded transmission is analyzed. From the analysis, satellites using this configuration in high-inclination orbits are shown to have a daily data throughput in the 100 to 1000 Mbit range using the multiple access communications service.

  9. Mid-infrared laser phase-locking to a remote near-infrared frequency reference for high-precision molecular spectroscopy

    NASA Astrophysics Data System (ADS)

    Chanteau, B.; Lopez, O.; Zhang, W.; Nicolodi, D.; Argence, B.; Auguste, F.; Abgrall, M.; Chardonnet, C.; Santarelli, G.; Darquié, B.; Le Coq, Y.; Amy-Klein, A.

    2013-07-01

    We present a method for accurate mid-infrared frequency measurements and stabilization to a near-infrared ultra-stable frequency reference, transmitted with a long-distance fibre link and continuously monitored against state-of-the-art atomic fountain clocks. As a first application, we measure the frequency of an OsO4 rovibrational molecular line around 10 μm with an uncertainty of 8 × 10-13. We also demonstrate the frequency stabilization of a mid-infrared laser with fractional stability better than 4 × 10-14 at 1 s averaging time and a linewidth below 17 Hz. This new stabilization scheme gives us the ability to transfer frequency stability in the range of 10-15 or even better, currently accessible in the near infrared or in the visible, to mid-infrared lasers in a wide frequency range.

  10. Specifics of processing SRS lidar signals in GHz frequency range

    NASA Astrophysics Data System (ADS)

    Grishkanich, A. S.; Elizarov, V. V.; Kascheev, S. V.; Zhevlakov, A. P.; Sidorov, I. S.

    2015-12-01

    One of the highly effective methods of operative remote environmental monitoring on land and water surfaces is laser sensing. It knew that the Raman scattering cross section is very small (10-25-10-27), so in some cases radiation back into captivity to the target could be a few tens of photons. For high-speed sensing, speed of processing and ease of use lidar units required for the use of appropriate hardware and software systems used for the decision of tasks of collecting, processing, storing, organizing large amounts of data.

  11. High force vibration testing with wide frequency range

    DOEpatents

    Romero, Edward F.; Jepsen, Richard A.; Gregory, Danny Lynn

    2013-04-02

    A shaker assembly for vibration testing includes first and second shakers, where the first shaker includes a piezo-electric material for generating vibration. A support structure permits a test object to be supported for vibration of the test object by both shakers. An input permits an external vibration controller to control vibration of the shakers.

  12. PLT ion cyclotron range of frequencies heating program

    SciTech Connect

    Hosea, J.; Bell, R.; Budny, R.; Cavallo, A.; Cohen, S.; Colestock, P.; Hammett, G.; Hovey, J.; Hwang, D.; Kaita, R.

    1984-09-01

    Measurements of energetic ions, impurity influx, recycling, and Bernstein waves generated in the plasma core are described for ICRF heating in PLT. Such measurements are being used for several launchers in order to optimize rf power deposition and discharge conditions. Preparations are underway to extend operation to higher rf power levels (approx. 5 MW) for the best attainable PLT conditions to permit more reactor-relevant extrapolations.

  13. Frequency conversion system

    NASA Technical Reports Server (NTRS)

    Sanders, Steven (Inventor); Lang, Robert J. (Inventor)

    2001-01-01

    Laser diode pumped mid-IR wavelength sources include at least one high power, near-IR wavelength, injection and/or sources wherein one or both of such sources may be tunable providing a pump wave output beam to a quasi-phase matched (QPM) nonlinear frequency mixing (NFM) device. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Wavelength tuning of at least one of the sources advantageously provides the ability for optimizing pump or injection wavelengths to match the QPM properties of the NFM device enabling a broad range of mid-IR wavelength selectivity. Also, pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Raman/Brillouin amplifier or oscillator between the high power source and the NFM device. Further, polarization conversion using Raman or Brillouin wavelength shifting is provided to optimize frequency conversion efficiency in the NFM device.

  14. Performance study of hybrid spread-spectrum random-access communications

    NASA Astrophysics Data System (ADS)

    Vlachos, Theodore; Geraniotis, Evaggelos

    1991-06-01

    A numerical study of the performance of hybrid direct-sequence slow-frequency-hopped spread-spectrum random-access schemes using Reed-Solomon forward-error control coding is performed. The performance measures of interest are the maximum numbers of simultaneous transmitters that can be tolerated in the vicinity of a receiver at a desirable level of the bit (or symbol) error probability, the normalized throughput, and the packet error probability. For the case where all simultaneous signals have the same received power levels, a critical comparison of the performance of direct-sequence, frequency-hopped, and hybrid spread-spectrum systems with the same overall bandwidth expansion is conducted, and ranges of parameters, for which each system outperforms the others, are identified. Hybrid spread-spectrum random-access schemes are found to have considerably higher throughput than the uncoded nonspread-spectrum ones.

  15. Engineering Graphene Conductivity for Flexible and High-Frequency Applications.

    PubMed

    Samuels, Alexander J; Carey, J David

    2015-10-14

    Advances in lightweight, flexible, and conformal electronic devices depend on materials that exhibit high electrical conductivity coupled with high mechanical strength. Defect-free graphene is one such material that satisfies both these requirements and which offers a range of attractive and tunable electrical, optoelectronic, and plasmonic characteristics for devices that operate at microwave, terahertz, infrared, or optical frequencies. Essential to the future success of such devices is therefore the ability to control the frequency-dependent conductivity of graphene. Looking to accelerate the development of high-frequency applications of graphene, here we demonstrate how readily accessible and processable organic and organometallic molecules can efficiently dope graphene to carrier densities in excess of 10(13) cm(-2) with conductivities at gigahertz frequencies in excess of 60 mS. In using the molecule 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane (F2-HCNQ), a high charge transfer (CT) of 0.5 electrons per adsorbed molecule is calculated, resulting in p-type doping of graphene. n-Type doping is achieved using cobaltocene and the sulfur-containing molecule tetrathiafulvalene (TTF) with a CT of 0.41 and 0.24 electrons donated per adsorbed molecule, respectively. Efficient CT is associated with the interaction between the π electrons present in the molecule and in graphene. Calculation of the high-frequency conductivity shows dispersion-less behavior of the real component of the conductivity over a wide range of gigahertz frequencies. Potential high-frequency applications in graphene antennas and communications that can exploit these properties and the broader impacts of using molecular doping to modify functional materials that possess a low-energy Dirac cone are also discussed. PMID:26387636

  16. World Wide Access: Accessible Web Design.

    ERIC Educational Resources Information Center

    Washington Univ., Seattle.

    This brief paper considers the application of "universal design" principles to Web page design in order to increase accessibility for people with disabilities. Suggestions are based on the World Wide Web Consortium's accessibility initiative, which has proposed guidelines for all Web authors and federal government standards. Seven guidelines for…

  17. Parametric effects of word frequency effect in memory for mixed frequency lists

    PubMed Central

    Lohnas, Lynn J.; Kahana, Michael J.

    2013-01-01

    The word frequency paradox refers to the finding that low frequency words are better recognized than high frequency words yet high frequency words are better recalled than low frequency words. Rather than comparing separate groups of low and high frequency words, we sought to quantify the functional relation between word frequency and memory performance across the broad range of frequencies typically used in episodic memory experiments. Here we report that both low frequency and high frequency words are better recalled than mid-frequency words. In contrast, we only observe a low frequency advantage when participants were given a subsequent item recognition test. The U-shaped relation between word frequency and recall probability may help to explain inconsistent results in studies using mixed lists with separate groups of high and low frequency words. PMID:23834055

  18. Frequency agile relativistic magnetrons

    SciTech Connect

    Levine, J.S.; Harteneck, B.D.; Price, H.D.

    1995-11-01

    The authors are developing a family of frequency agile relativistic magnetrons to continuously cover the bands from 1 to 3 GHz. They have achieved tuning ranges of > 33%. The magnetrons have been operated repetitively in burst mode at rates up to 100 pps for 10 sec. Power is extracted from two resonators, and is in the range of 400--600 MW, fairly flat across the tuning bandwidth. They are using a network of phase shifters and 3-dB hybrids to combine the power into a single arm and to provide a continuously adjustable attenuator.

  19. Broadband optical serrodyne frequency shifting.

    PubMed

    Johnson, D M S; Hogan, J M; Chiow, S-w; Kasevich, M A

    2010-03-01

    We demonstrate serrodyne frequency shifting of light from 200 MHz to 1.2 GHz with an efficiency of better than 60%. The frequency shift is imparted by an electro-optic phase modulator driven by a high-frequency high-fidelity sawtooth waveform that is passively generated by a commercially available nonlinear transmission line. We also implement a push-pull configuration using two serrodyne-driven phase modulators, allowing for continuous tuning between -1.6 GHz and +1.6 GHz. Compared with competing technologies, this technique is simple and robust, and it offers the largest available tuning range in this frequency band. PMID:20195339

  20. Frequency Standards and Metrology

    NASA Astrophysics Data System (ADS)

    Maleki, Lute

    2009-04-01

    Preface / Lute Maleki -- Symposium history / Jacques Vanier -- Symposium photos -- pt. I. Fundamental physics. Variation of fundamental constants from the big bang to atomic clocks: theory and observations (Invited) / V. V. Flambaum and J. C. Berengut. Alpha-dot or not: comparison of two single atom optical clocks (Invited) / T. Rosenband ... [et al.]. Variation of the fine-structure constant and laser cooling of atomic dysprosium (Invited) / N. A. Leefer ... [et al.]. Measurement of short range forces using cold atoms (Invited) / F. Pereira Dos Santos ... [et al.]. Atom interferometry experiments in fundamental physics (Invited) / S. W. Chiow ... [et al.]. Space science applications of frequency standards and metrology (Invited) / M. Tinto -- pt. II. Frequency & metrology. Quantum metrology with lattice-confined ultracold Sr atoms (Invited) / A. D. Ludlow ... [et al.]. LNE-SYRTE clock ensemble: new [symbol]Rb hyperfine frequency measurement - spectroscopy of [symbol]Hg optical clock transition (Invited) / M. Petersen ... [et al.]. Precise measurements of S-wave scattering phase shifts with a juggling atomic clock (Invited) / S. Gensemer ... [et al.]. Absolute frequency measurement of the [symbol] clock transition (Invited) / M. Chwalla ... [et al.]. The semiclassical stochastic-field/atom interaction problem (Invited) / J. Camparo. Phase and frequency noise metrology (Invited) / E. Rubiola ... [et al.]. Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant / J. L. Flowers ... [et al.] -- pt. III. Clock applications in space. Recent progress on the ACES mission (Invited) / L. Cacciapuoti and C. Salomon. The SAGAS mission (Invited) / P. Wolf. Small mercury microwave ion clock for navigation and radioScience (Invited) / J. D. Prestage ... [et al.]. Astro-comb: revolutionizing precision spectroscopy in astrophysics (Invited) / C. E. Kramer ... [et al.]. High frequency very long baseline interferometry: frequency standards and