Science.gov

Sample records for accessible frequency range

  1. Exploring the accessible frequency range of phase-resolved ferromagnetic resonance detected with x-rays

    NASA Astrophysics Data System (ADS)

    Warnicke, P.; Knut, R.; Wahlström, E.; Karis, O.; Bailey, W. E.; Arena, D. A.

    2013-01-01

    We present time- and element-resolved measurements of the magnetization dynamics in a ferromagnetic trilayer structure. A pump-probe scheme was utilized with a microwave magnetic excitation field phase-locked to the photon bunches and x-ray magnetic circular dichroism in transmission geometry. Using a relatively large photon bunch length with a full width at half maximum of 650 ps, the precessional motion of the magnetization was resolved up to frequencies of 2.5 GHz, thereby enabling sampling at frequencies significantly above the inverse bunch length. By simulating the experimental data with a numerical model based on a forced harmonic oscillator, we obtain good correlation between the two. The model, which includes timing jitter analysis, is used to predict the accessible frequency range of x-ray detected ferromagnetic resonance.

  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

    2015-07-30

    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.

  3. 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

  4. Digital predistortion of 75-110 GHz W-band frequency multiplier for fiber wireless short range access systems.

    PubMed

    Zhao, Ying; Deng, Lei; Pang, Xiaodan; Yu, Xianbin; Zheng, Xiaoping; Zhang, Hanyi; Monroy, Idelfonso Tafur

    2011-12-12

    We present a W-band fiber-wireless transmission system based on a nonlinear frequency multiplier for high-speed wireless short range access applications. By implementing a baseband digital signal predistortion scheme, intensive nonlinear distortions induced in a sextuple frequency multiplier can be effectively pre-compensated. Without using costly W-band components, a transmission system with 26 km fiber and 4 m wireless transmission operating at 99.6 GHz is experimentally validated. Adjacent-channel power ratio (ACPR) improvements for IQ-modulated vector signals are guaranteed and transmission performances for fiber and wireless channels are studied. This W-band predistortion technique is a promising candidate for applications in high capacity wireless-fiber access systems.

  5. 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.

  6. Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers.

    PubMed

    Leger, Joel D; Nyby, Clara M; Varner, Clyde; Tang, Jianan; Rubtsova, Natalia I; Yue, Yuankai; Kireev, Victor V; Burtsev, Viacheslav D; Qasim, Layla N; Rubtsov, Grigory I; Rubtsov, Igor V

    2014-08-01

    A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm(-1) to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ~70 as. The anharmonicity of smaller than 10(-4) cm(-1) was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 μrad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy.

  7. Fully automated dual-frequency three-pulse-echo 2DIR spectrometer accessing spectral range from 800 to 4000 wavenumbers

    SciTech Connect

    Leger, Joel D.; Nyby, Clara M.; Varner, Clyde; Tang, Jianan; Rubtsova, Natalia I.; Yue, Yuankai; Kireev, Victor V.; Burtsev, Viacheslav D.; Qasim, Layla N.; Rubtsov, Igor V.; Rubtsov, Grigory I.

    2014-08-15

    A novel dual-frequency two-dimensional infrared instrument is designed and built that permits three-pulse heterodyned echo measurements of any cross-peak within a spectral range from 800 to 4000 cm{sup −1} to be performed in a fully automated fashion. The superior sensitivity of the instrument is achieved by a combination of spectral interferometry, phase cycling, and closed-loop phase stabilization accurate to ∼70 as. The anharmonicity of smaller than 10{sup −4} cm{sup −1} was recorded for strong carbonyl stretching modes using 800 laser shot accumulations. The novel design of the phase stabilization scheme permits tuning polarizations of the mid-infrared (m-IR) pulses, thus supporting measurements of the angles between vibrational transition dipoles. The automatic frequency tuning is achieved by implementing beam direction stabilization schemes for each m-IR beam, providing better than 50 μrad beam stability, and novel scheme for setting the phase-matching geometry for the m-IR beams at the sample. The errors in the cross-peak amplitudes associated with imperfect phase matching conditions and alignment are found to be at the level of 20%. The instrument can be used by non-specialists in ultrafast spectroscopy.

  8. 33 CFR 86.01 - Frequencies and range of audibility.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Frequencies and range of... Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525 Hz. The range of audibility of the signal from a whistle shall be determined by those...

  9. 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... Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525 Hz. The range of audibility of the signal from a whistle shall be determined by those...

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

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Frequencies and range of... Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525 Hz. The range of audibility of the signal from a whistle shall be determined by those...

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

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Frequencies and range of... Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525 Hz. The range of audibility of the signal from a whistle shall be determined by those...

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

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Frequencies and range of... Frequencies and range of audibility. The fundamental frequency of the signal shall lie within the range 70-525 Hz. The range of audibility of the signal from a whistle shall be determined by those...

  13. 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.

  14. 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...

  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, 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...

  18. 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...

  19. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... lowest frequency for which a radiated emission limit is specified, up to the frequency shown in the... level of radiated emissions within the frequency range 9 kHz to 30 MHz, such as a CB receiver or a device designed to conduct its radio frequency emissions via connecting wires or cables, e.g., a...

  20. Long range ultra-high frequency (UHF) radio frequency identification (RFID) antenna design

    NASA Astrophysics Data System (ADS)

    Reynolds, Nathan D.

    There is an ever-increasing demand for radio frequency identification (RFID) tags that are passive, long range, and mountable on multiple surfaces. Currently, RFID technology is utilized in numerous applications such as supply chain management, access control, and public transportation. With the combination of sensory systems in recent years, the applications of RFID technology have been extended beyond tracking and identifying. This extension includes applications such as environmental monitoring and healthcare applications. The available sensory systems usually operate in the medium or high frequency bands and have a low read range. However, the range limitations of these systems are being overcome by the development of RFID sensors focused on utilizing tags in the ultra-high frequency (UHF) band. Generally, RFID tags have to be mounted to the object that is being identified. Often the objects requiring identification are metallic. The inherent properties of metallic objects have substantial effects on nearby electromagnetic radiation; therefore, the operation of the tag antenna is affected when mounted on a metallic surface. This outlines one of the most challenging problems for RFID systems today: the optimization of tag antenna performance in a complex environment. In this research, a novel UHF RFID tag antenna, which has a low profile, long range, and is mountable on metallic surfaces, is designed analytically and simulated using a 3-D electromagnetic simulator, ANSYS HFSS. A microstrip patch antenna is selected as the antenna structure, as patch antennas are low profile and suitable for mounting on metallic surfaces. Matching and theoretical models of the microstrip patch antenna are investigated. Once matching and theory of a microstrip patch antenna is thoroughly understood, a unique design technique using electromagnetic band gap (EBG) structures is explored. This research shows that the utilization of an EBG structure in the patch antenna design yields

  1. 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.

  2. 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

  3. 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...

  4. 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...

  5. 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...

  6. 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...

  7. Technique for extending the frequency range of digital dividers

    NASA Technical Reports Server (NTRS)

    Long, W. C.; Middleton, J. H. (Inventor)

    1973-01-01

    A technique for extending the frequency range of a presettable digital divider is described. The conventional digital divider consists of several counter stages with the count of each stage compared to a preselected number. When the counts for all stages are equal to the preselected numbers, an output pulse is generated and all stages are reset. For high input frequencies, the least significant stage of the divider has to be reset in a very short time. This limits the frequency that can be handled by the conventional digital divider. This invention provides a technique in which the second least significant and higher stages are reset and the least significant stage is permitted to free-run. Hence, the time in which the reset operation can be performed is increased thereby extending the frequency range of the divider.

  8. A multi-frequency method for ultrasonic ranging.

    PubMed

    Queirós, Ricardo; Corrêa Alegria, Francisco; Silva Girão, Pedro; Cruz Serra, António

    2015-12-01

    This paper presents a method for ultrasonic ranging based on the cross-correlation of two multi-frequency signals. The stimulus signal is composed by multiple sine-wave bursts/segments, each containing a different frequency and an integer number of periods. The frequency of each sine-wave burst is different from that of the adjacent bursts, but it is very close to the transducer resonant frequency. The time-of-flight (TOF) is estimated by finding the maximum of the cross-correlation. Interpolation is used to increase the measurement resolution. The experimental error corresponding to two standard deviations, for a range up to 1 m, is less than 0.3 mm.

  9. Outdoor stocking density in free-range laying hens: radio-frequency identification of impacts on range use.

    PubMed

    Campbell, D L M; Hinch, G N; Dyall, T R; Warin, L; Little, B A; Lee, C

    2017-01-01

    The number and size of free-range laying hen (Gallus gallus domesticus) production systems are increasing within Australia in response to consumer demand for perceived improvement in hen welfare. However, variation in outdoor stocking density has generated consumer dissatisfaction leading to the development of a national information standard on free-range egg labelling by the Australian Consumer Affairs Ministers. The current Australian Model Code of Practice for Domestic Poultry states a guideline of 1500 hens/ha, but no maximum density is set. Radio-frequency identification (RFID) tracking technology was used to measure daily range usage by individual ISA Brown hens housed in six small flocks (150 hens/flock - 50% of hens tagged), each with access to one of three outdoor stocking density treatments (two replicates per treatment: 2000, 10 000, 20 000 hens/ha), from 22 to 26, 27 to 31 and 32 to 36 weeks of age. There was some variation in range usage across the sampling periods and by weeks 32 to 36 individual hens from the lowest stocking density on average used the range for longer each day (P<0.001), with fewer visits and longer maximum durations per visit (P<0.001). Individual hens within all stocking densities varied in the percentage of days they accessed the range with 2% of tagged hens in each treatment never venturing outdoors and a large proportion that accessed the range daily (2000 hens/ha: 80.5%; 10 000 hens/ha: 66.5%; 20 000 hens/ha: 71.4%). On average, 38% to 48% of hens were seen on the range simultaneously and used all available areas of all ranges. These results of experimental-sized flocks have implications for determining optimal outdoor stocking densities for commercial free-range laying hens but further research would be needed to determine the effects of increased range usage on hen welfare.

  10. Experimental Limits on Gravitational Waves in the MHz frequency Range

    SciTech Connect

    Lanza, Robert Jr.

    2015-03-01

    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 colocated 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 2.4 x 10-21Hz-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.

  11. 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.

  12. 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

  13. 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…

  14. Range-azimuth decouple beamforming for frequency diverse array with Costas-sequence modulated frequency offsets

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Wang, Wen-Qin; Shao, Huaizong

    2016-12-01

    Different from the phased-array using the same carrier frequency for each transmit element, the frequency diverse array (FDA) uses a small frequency offset across the array elements to produce range-angle-dependent transmit beampattern. FDA radar provides new application capabilities and potentials due to its range-dependent transmit array beampattern, but the FDA using linearly increasing frequency offsets will produce a range and angle coupled transmit beampattern. In order to decouple the range-azimuth beampattern for FDA radar, this paper proposes a uniform linear array (ULA) FDA using Costas-sequence modulated frequency offsets to produce random-like energy distribution in the transmit beampattern and thumbtack transmit-receive beampattern. In doing so, the range and angle of targets can be unambiguously estimated through matched filtering and subspace decomposition algorithms in the receiver signal processor. Moreover, random-like energy distributed beampattern can also be utilized for low probability of intercept (LPI) radar applications. Numerical results show that the proposed scheme outperforms the standard FDA in focusing the transmit energy, especially in the range dimension.

  15. Ranging with frequency-shifted feedback lasers: from μm-range accuracy to MHz-range measurement rate

    NASA Astrophysics Data System (ADS)

    Kim, J. I.; Ogurtsov, V. V.; Bonnet, G.; Yatsenko, L. P.; Bergmann, K.

    2016-12-01

    We report results on ranging based on frequency-shifted feedback (FSF) lasers with two different implementations: (1) An Ytterbium-fiber system for measurements in an industrial environment with accuracy of the order of 1 μm, achievable over a distance of the order of meters with potential to reach an accuracy of better than 100 nm; (2) A semiconductor laser system for a high rate of measurements with an accuracy of 2 mm @ 1 MHz or 75 μm @ 1 kHz and a limit of the accuracy of ≥10 μm. In both implementations, the distances information is derived from a frequency measurement. The method is therefore insensitive to detrimental influence of ambient light. For the Ytterbium-fiber system, a key feature is the injection of a single-frequency laser, phase modulated at variable frequency Ω, into the FSF-laser cavity. The frequency Ω_{max} at which the detector signal is maximal yields the distance. The semiconductor FSF-laser system operates without external injection seeding. In this case, the key feature is frequency counting that allows convenient choice of either accuracy or speed of measurements simply by changing the duration of the interval during which the frequency is measured by counting.

  16. Multimode VCSEL model for wide frequency-range RIN simulation

    NASA Astrophysics Data System (ADS)

    Perchoux, Julien; Rissons, Angélique; Mollier, Jean-Claude

    2008-01-01

    In this paper, we present an equivalent circuit model for oxide-confined AlGaAs/GaAs VCSEL with the noise contribution adapted to optomicrowave links applications. This model is derived from the multimode rate equations. In order to understand the modal competition process, we restrain our description to a two-modes rate equations system affected by the spectral hole-burning. The relative intensity noise (RIN) measurements which were achieved on a prober in Faraday cage confirm the low frequency enhancement described by the model. We validate our model for a wide frequency-range [1 MHz-10 GHz] and high bias level up to six times the threshold current.

  17. 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.

  18. [Spectral analysis of nitrofurantoin in the terahertz frequency range].

    PubMed

    Kang, Xu-Sheng; Hou, Di-Bo; Zhang, Guang-Xin; Chen, Xi-Ai; Yue, Fei-Heng; Huang, Ping-Jie; Zhou, Ze-Kui

    2012-07-01

    The present article measured the absorption coefficient spectra and refractive index spectra of nitrofurantoin original drug, which is one kind of nitrofuran drugs, in the terahertz frequency range from 0.2 to 1.8 THz using terahertz time-domain spectroscopy. The results showed that there exist a number of characteristic absorption peaks of nitrofurantoin with different intensity in the range and the absorption coefficient spectra can be used to identify nitrofurantoin. The article also simulated absorption coefficient spectra of nitrofurantoin molecule within 0.2 - 1.8 THz using density functional theory by Gaussian software, and vibrational modes of some peaks in the experimental absorption coefficient spectra were analyzed and identified. The results show that the experimental absorption peaks at 1.25 and 1.60 THz correspond with the theoretical peaks at 1.30 and 1.67 THz, and these experimental peaks were caused by intramolecular vibrational modes of nitrofurantoin.

  19. Dielectric permittivity of biological tissues in the microwave frequency range

    NASA Astrophysics Data System (ADS)

    Behari, J.; Alex, Z. C.; Zaidi, Zahid H.

    1994-09-01

    The accurate knowledge of complex dielectric behavior of biological tissues at microwave frequency is of great importance in the biomedical field for its diagnostic and therapeutic uses. This information is also essential for studying the mechanism underlying the absorption of electromagnetic energy and also the emission by tissues. In the present work, in vitro complex dielectric permittivity of liver and muscle were measured in the frequency range 0.6 GHz to 1.2 GHz using a network analyzer. An open ended coaxial cable method was used and the complex dielectric permittivity was measured from the actual terminal admittance of the sample. The system was calibrated with three standard samples. The measurements were conducted at room temperature. The calculated values of (Epsilon) ' varied from 53 to 48 for liver and from 49 to 46 for muscle. The corresponding (Epsilon) ' varied from 29 to 38 and 30 to 34 respectively. The relaxation frequency and degree of dispersion were also calculated and estimation of bound water content made in each case.

  20. 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.

  1. A Frequency Domain Approach to Pretest Analysis Model Correlation and Model Updating for the Mid-Frequency Range

    DTIC Science & Technology

    2009-02-01

    range of modal analysis and the high frequency region of statistical energy analysis , is referred to as the mid-frequency range. The corresponding...frequency range of modal analysis and the high frequency region of statistical energy analysis , is referred to as the mid-frequency range. The...predictions. The averaging process is consistent with the averaging done in statistical energy analysis for stochastic systems. The FEM will always

  2. 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.

  3. 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.

  4. 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.

  5. 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

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

    PubMed

    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.

  7. Enhanced compressive wideband frequency spectrum sensing for dynamic spectrum access

    NASA Astrophysics Data System (ADS)

    Liu, Yipeng; Wan, Qun

    2012-12-01

    Wideband spectrum sensing detects the unused spectrum holes for dynamic spectrum access (DSA). Too high sampling rate is the main challenge. Compressive sensing (CS) can reconstruct sparse signal with much fewer randomized samples than Nyquist sampling with high probability. Since survey shows that the monitored signal is sparse in frequency domain, CS can deal with the sampling burden. Random samples can be obtained by the analog-to-information converter. Signal recovery can be formulated as the combination of an L0 norm minimization and a linear measurement fitting constraint. In DSA, the static spectrum allocation of primary radios means the bounds between different types of primary radios are known in advance. To incorporate this a priori information, we divide the whole spectrum into sections according to the spectrum allocation policy. In the new optimization model, the minimization of the L2 norm of each section is used to encourage the cluster distribution locally, while the L0 norm of the L2 norms is minimized to give sparse distribution globally. Because the L2/L0 optimization is not convex, an iteratively re-weighted L2/L1 optimization is proposed to approximate it. Simulations demonstrate the proposed method outperforms others in accuracy, denoising ability, etc.

  8. A wide-frequency-range air-jet shaker

    NASA Technical Reports Server (NTRS)

    Herr, Robert W

    1957-01-01

    This paper presents a description of a simple air-jet shaker. Its force can be calibrated statically and appears to be constant with frequency. It is relatively easy to use, and it has essentially massless characteristics. This shaker is applied to define the unstable branch of a frequency-response curve obtained for a nonlinear spring with a single degree of freedom.

  9. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... frequency generated in the device or 25 MHz, whichever is lower Tenth harmonic or 1,000 MHz, whichever is... harmonic. Above 1,000 ......do Tenth harmonic or highest detectable emission. (b) For conducted...

  10. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... frequency generated in the device or 25 MHz, whichever is lower Tenth harmonic or 1,000 MHz, whichever is... harmonic. Above 1,000 ......do Tenth harmonic or highest detectable emission. (b) For conducted...

  11. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... frequency generated in the device or 25 MHz, whichever is lower Tenth harmonic or 1,000 MHz, whichever is... harmonic. Above 1,000 ......do Tenth harmonic or highest detectable emission. (b) For conducted...

  12. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... frequency generated in the device or 25 MHz, whichever is lower Tenth harmonic or 1,000 MHz, whichever is... harmonic. Above 1,000 ......do Tenth harmonic or highest detectable emission. (b) For conducted...

  13. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... frequency generated in the device or 25 MHz, whichever is lower Tenth harmonic or 1,000 MHz, whichever is... harmonic. Above 1,000 ......do Tenth harmonic or highest detectable emission. (b) For conducted...

  14. Fundamental factors affecting the optimum frequency range for SETI

    NASA Astrophysics Data System (ADS)

    Oliver, Bernard M.

    1993-08-01

    There is little doubt that confirmation of the existence of extraterrestrial intelligent life will be obtained from electromagnetic waves generated by our counterparts. The best frequency regions in which to expect such signals depends upon the free-space loss, the background noise, the spectral purity obtainable, and the power required as a function of frequency. This paper will discuss the rationale that led to the selection of the microwave window for the NASA SETI Program.

  15. Frequency-Domain Equalization for Broadband Single-Carrier Multiple Access

    NASA Astrophysics Data System (ADS)

    Adachi, Fumiyuki; Tomeba, Hiromichi; Takeda, Kazuki

    Single-carrier (SC) multiple access is a promising uplink multiple access technique because of its low peak-to-average power ratio (PAPR) property and high frequency diversity gain that is achievable through simple one-tap frequency-domain equalization (FDE) in a strong frequency-selective channel. The multiple access capability can be obtained by combining either frequency division multiple access (FDMA) or code division multiple access (CDMA) with SC transmission. In this article, we review the recent research on the SC multiple access techniques with one-tap FDE. After introducing the principle of joint FDE/antenna diversity combining, we review various SC multiple access techniques with one-tap FDE, i.e., SC-FDMA, SC-CDMA, block spread CDMA, and delay-time/CDMA.

  16. Tremor suppression orthoses for parkinson's patients: a frequency range perspective.

    PubMed

    Rahimi, Fariborz; Almeida, Quincy J; Wang, David; Janabi-Sharifi, Farrokh

    2009-01-01

    While the majority of tremor-afflicted Parkinso-nian (PD) patients suffer from rest tremors, which is not considered highly disabling, a portion of these PD patients also demonstrate action tremors that interfere with their daily lives. Two main considerations in designing an orthosis that aims at suppressing the tremor, are the frequency bands of the tremor and the joints tremor affects. Nine subjects, which included six healthy people, two PD patients with typical tremor afflictions, and a PD patient with severe tremor of not only in her fingers and wrist, but also in her elbow, participated in this study. The highly afflicted patient displayed the need for tremor suppression in action as well as when in rest. The study focuses on uncommon elbow tremors and demonstrates that, for typically afflicted patients, tremor amplitudes are comparable to healthy subjects, but the frequency distribution of the tremors are different at high levels of elbow torque. For the highly afflicted patient, both tremor amplitude and its frequency distribution are different at all levels of elbow torque. The study further investigates the tremors in two bands of frequency on both hands of the highly troubled patient before, and after medication. The two bands are those of classical Parkinsonian tremor (4-6 Hz) and physiological (or enhanced physiological) tremor (8-12 Hz). Power spectrum and tremor amplitude comparisons reveal that, for part of tremulous PD patients, both tremors coexist and, depending on the level of affliction, the designed orthosis needs to suppress tremors in both bands, even at more proximal joints, such as the elbow.

  17. Valency, Secondary Frequency, and Lexical Access: A Japanese Study.

    ERIC Educational Resources Information Center

    Yamada, Jun; Kayamoto, Yuriko

    1998-01-01

    A study examined the effects of valency (associative value representing the number of two-kanji words containing the first-positional kanji of the word) on recognition of two-kanji words in Japanese. Frequency and valency of the first constituent kanji were significant factors for word recognition, and frequency of the first constituent kanji was…

  18. 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.

  19. Fiber-based multiple-access frequency synchronization via 1f-2f dissemination

    NASA Astrophysics Data System (ADS)

    Zhu, Xi; Wang, Bo; Gao, Chao; Wang, Li-Jun

    2016-09-01

    Considering the reference frequency dissemination requirements of the Square Kilometre Array telescope (SKA) project, on the basis of the 1f-2f precision frequency synchronization scheme, we propose and demonstrate a fiber-based multiple-access frequency synchronization scheme. The dissemination reference frequency can be recovered at arbitrary nodes along the entire fiber link. It can be applied to antennas close proximity to the SKA central station, and will lead to a better SKA frequency synchronization network. As a performance test, we recover the disseminated 100-MHz reference frequency at an arbitrary node chosen as being 5 km away from the transmitting site. Relative frequency stabilities of 2.0×10-14/s and 1.6×10-16/104s are obtained. We also experimentally verify the feasibility of a frequency dissemination link with three access points. Project supported by the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2013YQ09094303).

  20. Ray-tracing studies of fast waves in the lower hybrid range of frequencies

    NASA Astrophysics Data System (ADS)

    Dittman, A.; Pinsker, R. I.

    2016-10-01

    Fast waves in the lower-hybrid range of frequencies, also referred to as `whistlers' or `helicons', will be used in the DIII-D tokamak for off-axis non-inductive current drive. Ray-tracing studies have shown that the required off-axis deposition can be achieved in target plasmas that have been recently studied in DIII-D. We wish to characterize the sensitivity of the rf power deposition profile to details of the equilibrium, and are thereby motivated to re-examine the fundamentals of ray-tracing in this regime. We have studied ray-tracing in the vicinity of regular turning points (cut-offs) and mode-coupling points in simple geometries (slab, cylinder). Later phases of the work will use the GENRAY code to study the effect of strong magnetic shear in the outer region of the plasma on the shape of the ray trajectory in that region, and on wave accessibility to the core. The usual estimate of the accessibility limit on the parallel index of refraction of the wave (n∥), based on a slab model, is inaccurate under these conditions, which could lead to improved antenna/wave coupling by utilizing a lower n∥. Work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program and under DE-FC02-04ER54698.

  1. Opportunistic Access in Frequency Hopping Cognitive Radio Networks

    DTIC Science & Technology

    2014-03-27

    adaptive BER performance as a function of ISR with orthogonal frequency-division multiplexing ( OFDM ) interference present. . . . . . . . . . 41 4.15 Non...adaptive BER performance as a function of EB/N0 with OFDM interfer- ence present...42 4.16 Adaptive BER performance as the spectrum sensing rate increases relative to the environment change rate with OFDM interference

  2. 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})

  3. Experimental demonstration of block interleaved frequency division multiple access for bidirectional visible light communications

    NASA Astrophysics Data System (ADS)

    Lin, Bangjiang; Yang, Hui; Ye, Weiping; Tang, Xuan; Ghassemlooy, Zabih

    2017-01-01

    We propose a power efficient multiple access scheme for visible light communications (VLC) based on the block interleaved frequency division multiple access (B-IFDMA) which provides large frequency-diversity, flexible bandwidth allocation, low complexity of channel equalization, and user separation. Bidirectional B-IFDMA VLC transmission is experimentally demonstrated to verify its feasibility. The impact of the number of subcarriers per block on the transmission performance under wireless optical channel is investigated.

  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. Performance analysis of single-frequency MPPSK integrated system for ranging applications.

    PubMed

    Yao, Yu; Wu, Lenan

    2014-01-01

    The dual-frequency MPPSK-MODEM is a flexible platform. When ranging accuracy request is low or platform is particularly limited by power, the platform would perform both data transmission and range measurement with single-frequency modes. In this paper, the ranging resolution of MPPSK pulse waveforms with the match filter and impacting filter processing are discussed, respectively. Also, the parameter selection of MPPSK modulator for ranging is considered. In particular, requirements that allow for employing such special parameter values for range measurements with high accuracy and high range are investigated. Moreover, high repetition frequency (HRF) biphase code MPPSK pulse train base on m sequence is presented, and the ranging accuracy of the proposed signal with the match filter processing is deduced. In addition to theoretical considerations, the paper presents system simulations and measurement results of single-frequency MPPSK integrated systems, demonstrating the high-performance of ranging applications.

  6. Performance Analysis of Single-Frequency MPPSK Integrated System for Ranging Applications

    PubMed Central

    Wu, Lenan

    2014-01-01

    The dual-frequency MPPSK-MODEM is a flexible platform. When ranging accuracy request is low or platform is particularly limited by power, the platform would perform both data transmission and range measurement with single-frequency modes. In this paper, the ranging resolution of MPPSK pulse waveforms with the match filter and impacting filter processing are discussed, respectively. Also, the parameter selection of MPPSK modulator for ranging is considered. In particular, requirements that allow for employing such special parameter values for range measurements with high accuracy and high range are investigated. Moreover, high repetition frequency (HRF) biphase code MPPSK pulse train base on m sequence is presented, and the ranging accuracy of the proposed signal with the match filter processing is deduced. In addition to theoretical considerations, the paper presents system simulations and measurement results of single-frequency MPPSK integrated systems, demonstrating the high-performance of ranging applications. PMID:25140340

  7. Numerical Analysis of Stochastic Dynamical Systems in the Medium-Frequency Range

    DTIC Science & Technology

    2003-02-01

    frequency vibration analysis such as the statistical energy analysis (SEA), the traditional modal analysis (well-suited for high and low: frequency...that the first few structural normal modes primarily constitute the total response. In the higher frequency range, the statistical energy analysis (SEA

  8. Frequency-dependent conductivity contrast for tissue characterization using a dual-frequency range conductivity mapping magnetic resonance method.

    PubMed

    Kim, Dong-Hyun; Chauhan, Munish; Kim, Min-Oh; Jeong, Woo Chul; Kim, Hyung Joong; Sersa, Igor; Kwon, Oh In; Woo, Eung Je

    2015-02-01

    Electrical conductivities of biological tissues show frequency-dependent behaviors, and these values at different frequencies may provide clinically useful diagnostic information. MR-based tissue property mapping techniques such as magnetic resonance electrical impedance tomography (MREIT) and magnetic resonance electrical property tomography (MREPT) are widely used and provide unique conductivity contrast information over different frequency ranges. Recently, a new method for data acquisition and reconstruction for low- and high-frequency conductivity images from a single MR scan was proposed. In this study, we applied this simultaneous dual-frequency range conductivity mapping MR method to evaluate its utility in a designed phantom and two in vivo animal disease models. Magnetic flux density and B(1)(+) phase map for dual-frequency conductivity images were acquired using a modified spin-echo pulse sequence. Low-frequency conductivity was reconstructed from MREIT data by the projected current density method, while high-frequency conductivity was reconstructed from MREPT data by B(1)(+) mapping. Two different conductivity phantoms comprising varying ion concentrations separated by insulating films with or without holes were used to study the contrast mechanism of the frequency-dependent conductivities related to ion concentration and mobility. Canine brain abscess and ischemia were used as in vivo models to evaluate the capability of the proposed method to identify new electrical properties-based contrast at two different frequencies. The simultaneous dual-frequency range conductivity mapping MR method provides unique contrast information related to the concentration and mobility of ions inside tissues. This method has potential to monitor dynamic changes of the state of disease.

  9. 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.

  10. 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.

  11. 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. PMID:27879769

  12. The effect of duty cycle and frequency on muscle torque production using kilohertz frequency range alternating current.

    PubMed

    Ward, Alex R; Robertson, Valma J; Ioannou, Harry

    2004-09-01

    We investigated the frequency and duty cycle dependence of maximal electrically induced torque (MEIT) of the wrist extensors. Fifty hertz burst modulated sinusoidal alternating current (AC) in the frequency range 0.5-20 kHz was used, with duty cycles ranging from a minimum (one cycle) to maximum (continuous AC). MEITs were similar at low frequencies but decreased markedly above 2.5 kHz. MEITs also decreased markedly above a 20% duty cycle. Subjective reports of discomfort were fewest at 4 kHz and at duty cycles in the range 20-25%. Our conclusion is that for maximum torque production, a frequency of 1 kHz and a duty cycle of 20% are indicated. When comfort is a major consideration, a frequency of 2.5 kHz provides an acceptable trade-off between MEIT and comfort. The findings also suggest that low duty cycle, burst modulated AC stimulation may be more effective than stimulation using conventional low-frequency pulsed current.

  13. 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

  14. Optimal frequency range for medical radar measurements of human heartbeats using body-contact radar.

    PubMed

    Brovoll, Sverre; Aardal, Øyvind; Paichard, Yoann; Berger, Tor; Lande, Tor Sverre; Hamran, Svein-Erik

    2013-01-01

    In this paper the optimal frequency range for heartbeat measurements using body-contact radar is experimentally evaluated. A Body-contact radar senses electromagnetic waves that have penetrated the human body, but the range of frequencies that can be used are limited by the electric properties of the human tissue. The optimal frequency range is an important property needed for the design of body-contact radar systems for heartbeat measurements. In this study heartbeats are measured using three different antennas at discrete frequencies from 0.1 - 10 GHz, and the strength of the received heartbeat signal is calculated. To characterize the antennas, when in contact with the body, two port S-parameters(†) are measured for the antennas using a pork rib as a phantom for the human body. The results shows that frequencies up to 2.5 GHz can be used for heartbeat measurements with body-contact radar.

  15. Dielectric Properties of Birch Wood in the High-Frequency Range

    NASA Astrophysics Data System (ADS)

    Goreshnev, M. A.; Litvishko, E. S.; Lopatin, V. V.

    2016-01-01

    Results of measurement of dielectric properties of birch wood in the radio-frequency range depending on its humidity are presented. The dependences obtained indicate strong influence of wood anisotropy especially at low frequencies. It is shown that it is irrational to use the wood for insulation if its humidity exceeds 15-20%.

  16. Simulation of polarizer based on chiral medium for terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Korolenko, S. Yu; Grebenchukov, A. N.; Masyukov, M. S.; Vozianova, A. V.; Khodzitsky, M. K.

    2016-08-01

    The work is devoted to development of the polarizer for terahertz frequency range. Chiral medium was simulated using the software package CST Microwave Studio by the method of Finite-Differences in Frequency Domain. The influence of geometry of chiral unit cell on the polarization of incident plane wave was investigated.

  17. Electron-beam buncher to operate over the frequency range 1-4 GHz

    SciTech Connect

    Goldberg, D.A.; Arthur, A.A.; Flood, W.S.; Voelker, F.

    1983-03-01

    We present a description of an electron buncher to be installed in the terminal of a Van de Graaff, which is to produce a modulated beam over the frequency range 1-4 GHz. The modulator geometry has been optimized so that the modulation amplitude should be nearly constant over the frequency ranges 1-2 GHz and 2-4 GHz. Preliminary results indicate the device works as predicted.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Range compensation for backscattering measurements in the difference-frequency nearfield of a parametric sonar.

    PubMed

    Foote, Kenneth G

    2012-05-01

    Measurement of acoustic backscattering properties of targets requires removal of the range dependence of echoes. This process is called range compensation. For conventional sonars making measurements in the transducer farfield, the compensation removes effects of geometrical spreading and absorption. For parametric sonars consisting of a parametric acoustic transmitter and a conventional-sonar receiver, two additional range dependences require compensation when making measurements in the nonlinearly generated difference-frequency nearfield: an apparently increasing source level and a changing beamwidth. General expressions are derived for range compensation functions in the difference-frequency nearfield of parametric sonars. These are evaluated numerically for a parametric sonar whose difference-frequency band, effectively 1-6 kHz, is being used to observe Atlantic herring (Clupea harengus) in situ. Range compensation functions for this sonar are compared with corresponding functions for conventional sonars for the cases of single and multiple scatterers. Dependences of these range compensation functions on the parametric sonar transducer shape, size, acoustic power density, and hydrography are investigated. Parametric range compensation functions, when applied with calibration data, will enable difference-frequency echoes to be expressed in physical units of volume backscattering, and backscattering spectra, including fish-swimbladder-resonances, to be analyzed.

  5. Ionospheric frequency spread and its relationship with range spread in mid-latitude regions

    SciTech Connect

    Bowman, G.G. )

    1991-06-01

    The distinction between range spread and frequency spread as seen on mid-latitude ionograms is discussed. A classification of these two types of spread F is proposed in terms of different arrangements of the duplicate traces which provide the basic trace structures of mid-latitude spread F ionograms. Experimental results are presented to support the idea that frequency spread results from multiple ray paths (associated with a shallow ripple structure in the isoionic contours) close to the direction of the zenith position, so that each ray path has a range approximately equal to that of its neighbor. Furthermore, a horizontal gradient of maximum electron density is an additional requirement to create frequency spread. Atmospheric conditions (involving ionospheric F{sub 2} region heights and upper atmosphere neutral particle densities) which seem to favor the generation of frequency spread are discussed.

  6. 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.

  7. Individual optimization of EEG channel and frequency ranges by means of genetic algorithm.

    PubMed

    Lee, Chungki; Jung, Jihee; Kwon, Gyuhyun; Kim, Laehyun

    2012-01-01

    It is well established that motor action/imagery provokes an event-related desynchronization (ERD) response at specific brain areas with specific frequency ranges, typically the sensory motor rhythm and beta bands. However, there are individual differences in both brain areas and frequency ranges which can be used to identify ERD. This often results in low classification accuracy of ERD, which makes it difficult to implement of BCI application such as the control of external devices and motor rehabilitation. To overcome this problem, an individually optimized solution may be desirable for enhancing the accuracy of detecting motor action/imagery with ERD rather than a global solution for all BCI users. This paper presents a method based on a genetic algorithm to find individually optimized brain areas and frequency ranges for ERD classification. To optimize these two components, we designed a chromosome consisting of 64-bit elements represented by a binary number and another 9-bit elements using 512 pre-defined frequency ranges (2^9). The average value of the significant level is set for the properties of the objective function for use in a t-test, (p < 0.01) depending on the random selection from a concurrent population. As a result, contralateral ERD responses in the spatial domain with individually optimized frequency ranges showed a significant difference between resting and motor action. The ERD responses for motor imagery, on the other hand, led to a bilateral pattern with a narrow frequency band compared to motor action. This study provides the possibility of selecting optimized electrode positions and frequency bands which can lead to high levels of ERD classification accuracy.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Method of range profile for step frequency MMW radar based on wavelet transform power spectrum estimator

    NASA Astrophysics Data System (ADS)

    Li, Yuehua; Gao, Duntang; Shen, Qinghong; Li, Xingguo

    2001-11-01

    The method of range profile for step frequency MMW radar targets based on wavelet transform power spectrum estimator is studied. We show how the Fourier power spectrum can be detected by using the wavelet function coefficients (WFC) of the DWT. This method can successfully measure the power spectrum in samples for which traditional methods often fail because the sample are finite sized, have a complex geometry, or are varyingly sampled. We demonstrate that the spectrum features, such as the power law index, the magnitude, and the typical scales can be determined by the DWT reconstructed spectrum. We apply this method to the practical step frequency MMW radar target echo signals, and on the condition of the same sampling frequency and sampling data length, it can achieve one dimensional range profile with profile"s resolution superior to FFT"s, so the one dimensional range profile of targets can be analyzed with high resolution, the detail algorithm of range profiles spectrum estimation based on wavelet transforming multirange cells is proposed. Compare with FFT algorithm, using wavelet spectrum estimator of short data series, we can achieves high resolution, high accuracy, and low SNR threshold. The Experiment results make clear that the DWT estimator is a sensitive tool in range profile of step frequency MMW radar.

  13. Experiments and error analysis of laser ranging based on frequency-sweep polarization modulation

    NASA Astrophysics Data System (ADS)

    Gao, Shuyuan; Ji, Rongyi; Li, Yao; Cheng, Zhi; Zhou, Weihu

    2016-11-01

    Frequency-sweep polarization modulation ranging uses a polarization-modulated laser beam to determine the distance to the target, the modulation frequency is swept and frequency values are measured when transmitted and received signals are in phase, thus the distance can be calculated through these values. This method gets much higher theoretical measuring accuracy than phase difference method because of the prevention of phase measurement. However, actual accuracy of the system is limited since additional phase retardation occurs in the measuring optical path when optical elements are imperfectly processed and installed. In this paper, working principle of frequency sweep polarization modulation ranging method is analyzed, transmission model of polarization state in light path is built based on the theory of Jones Matrix, additional phase retardation of λ/4 wave plate and PBS, their impact on measuring performance is analyzed. Theoretical results show that wave plate's azimuth error dominates the limitation of ranging accuracy. According to the system design index, element tolerance and error correcting method of system is proposed, ranging system is built and ranging experiment is performed. Experiential results show that with proposed tolerance, the system can satisfy the accuracy requirement. The present work has a guide value for further research about system design and error distribution.

  14. A wide-range programmable frequency synthesizer based on a finite state machine filter

    NASA Astrophysics Data System (ADS)

    Alser, Mohammed H.; Assaad, Maher M.; Hussin, Fawnizu A.

    2013-11-01

    In this article, an FPGA-based design and implementation of a fully digital wide-range programmable frequency synthesizer based on a finite state machine filter is presented. The advantages of the proposed architecture are that, it simultaneously generates a high frequency signal from a low frequency reference signal (i.e. synthesising), and synchronising the two signals (signals have the same phase, or a constant difference) without jitter accumulation issue. The architecture is portable and can be easily implemented for various platforms, such as FPGAs and integrated circuits. The frequency synthesizer circuit can be used as a part of SERDES devices in intra/inter chip communication in system-on-chip (SoC). The proposed circuit is designed using Verilog language and synthesized for the Altera DE2-70 development board, with the Cyclone II (EP2C35F672C6) device on board. Simulation and experimental results are included; they prove the synthesizing and tracking features of the proposed architecture. The generated clock signal frequency of a range from 19.8 MHz to 440 MHz is synchronized to the input reference clock with a frequency step of 0.12 MHz.

  15. Sub-frequency range stress wave factor NDE technique for assessing damage in fiber-epoxy composites

    NASA Astrophysics Data System (ADS)

    Hong, Gang

    This research aims at modifying, improving and calibrating the Stress Wave Factor Nondestructive Evaluation (SWF NDE) technique and applying it to a fiber epoxy composite material and other composite structures. In order to access the composite's integrity the Energy of SWF within a selected Sub Frequency Range (SFR) instead of the whole measured frequency range as of conventional SWF is used. This technique, introduced and examined herein and is termed the Sub Frequency Range Stress Wave Factors (SFR-SWF) and is tailored to improve the conventional SWF technique with respect to sensibility and accuracy. A series of controlled damage tests were performed, and relevant acousto-ultrasonic observations were conducted. The overall property of the composites subjected to hygrothermal degradation, the localized defects such as the surface crack and the historical damage were assessed with conventional SWF and SFR-SWF. The two methods are compared in detail. The hygrothermal degradation and surface crack experiments were also simulated using the finite element method. Dynamic numerical analysis was conducted to simulate the wave propagation process, both in time domain and frequency domain using the commercial finite element code ABAQUS. The numerical results were also evaluated via both SWF and SFR-SWF, and were compared with the results of experiments. Thus, the potential of SFR-SWF was evaluated. A general conclusion from this research is that the SFR-SWF has the better capability than that of the conventional SWF in assessing the composite's overall condition, localized defects and historical damage. Since there are still open questions regarding the physical understanding of the SWF and SFR-SWF, the finite element analysis provides confirmation for certain observed behaviors of the Acousto-Ultrasonic and SFR-SWF technique.

  16. Long-range vibration sensor based on correlation analysis of optical frequency-domain reflectometry signals.

    PubMed

    Ding, Zhenyang; Yao, X Steve; Liu, Tiegen; Du, Yang; Liu, Kun; Han, Qun; Meng, Zhuo; Chen, Hongxin

    2012-12-17

    We present a novel method to achieve a space-resolved long- range vibration detection system based on the correlation analysis of the optical frequency-domain reflectometry (OFDR) signals. By performing two separate measurements of the vibrated and non-vibrated states on a test fiber, the vibration frequency and position of a vibration event can be obtained by analyzing the cross-correlation between beat signals of the vibrated and non-vibrated states in a spatial domain, where the beat signals are generated from interferences between local Rayleigh backscattering signals of the test fiber and local light oscillator. Using the proposed technique, we constructed a standard single-mode fiber based vibration sensor that can have a dynamic range of 12 km and a measurable vibration frequency up to 2 kHz with a spatial resolution of 5 m. Moreover, preliminarily investigation results of two vibration events located at different positions along the test fiber are also reported.

  17. 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.

  18. Field of view extension using frequency division multiple access technique: numerical analysis

    NASA Astrophysics Data System (ADS)

    Kavehvash, Zahra; Mehrany, Khashayar; Bagheri, Saeed

    2011-06-01

    Integral imaging could be considered as one of the prospective methods for recording and displaying 3D images based on its distinct features. Some of the most important challenges with this approach are the field of view and resolution limitation. In this work we investigate using frequency division multiple access (FDMA) idea for solving this problem. Simulation results show an increase of more than ten percent in the performance of the 3D reconstructed images using the proposed method.

  19. UWB micro-doppler radar for human gait analysis using joint range-time-frequency representation

    NASA Astrophysics Data System (ADS)

    Wang, Yazhou; Fathy, Aly E.

    2013-05-01

    In this paper, we present a novel, standalone ultra wideband (UWB) micro-Doppler radar sensor that goes beyond simple range or micro-Doppler detection to combined range-time-Doppler frequency analysis. Moreover, it can monitor more than one human object in both line-of-sight (LOS) and through wall scenarios, thus have full human objects tracking capabilities. The unique radar design is based on narrow pulse transceiver, high speed data acquisition module, and wideband antenna array. For advanced radar post-data processing, joint range-time-frequency representation has been performed. Characteristics of human walking activity have been analyzed using the radar sensor by precisely tracking the radar object and acquiring range-time-Doppler information simultaneously. The UWB micro-Doppler radar prototype is capable of detecting Doppler frequency range from -180 Hz to +180 Hz, which allows a maximum target velocity of 9 m/s. The developed radar sensor can also be extended for many other applications, such as respiration and heartbeat detection of trapped survivors under building debris.

  20. 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.

  1. 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.

  2. 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).

  3. An impedance bridge measuring the capacitance ratio in the high frequency range up to 1 MHz

    NASA Astrophysics Data System (ADS)

    Bee Kim, Dan; Kew Lee, Hyung; Kim, Wan-Seop

    2017-02-01

    This paper describes a 2-terminal-pair impedance bridge, measuring the capacitance ratio in the high frequency range up to 1 MHz. The bridge was configured with two voltage sources and a phase control unit which enabled the bridge balance by synchronizing the voltage sources with an enhanced phase resolution. Without employing the transformers such as inductive voltage divider, injection and detection transformers, etc, the bridge system is quite simple to set up, and the balance procedure is quick and easy. Using this dual-source coaxial bridge, the 1:1 and 10:1 capacitance ratios were measured with 1 pF-1 nF capacitors in the frequency range from 1 kHz to 1 MHz. The measurement values obtained by the dual-source bridge were then compared with reference values measured using a commercial precision capacitance bridge of AH2700A, the Z-matrix method developed by ourselves, and the 4-terminal-pair coaxial bridge by the Czech Metrological Institute. All the measurements agreed within the reference uncertainty range of an order of 10-6-10-5, proving the bridge ability as a trustworthy tool for measuring the capacitance ratio in the high frequency range.

  4. 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.

  5. 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.

  6. 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.

  7. A reduced order model for dielectric elastomer actuators over a range of frequencies and prestrains

    NASA Astrophysics Data System (ADS)

    Kiser, Jillian; Manning, Michael; Adler, David; Breuer, Kenneth

    2016-09-01

    The actuation strain of an equibiaxially prestrained dielectric elastomer membrane is studied as a function of driving frequency and prestrain. Experimental data are gathered on the membrane's creep and recovery following DC actuation, as well as the steady state amplitude and phase for AC driving voltages ranging from 2 to 40 Hz. The effect of prestretch on steady state actuation was also investigated, using membranes of both 250% and 300% prestretch. A three-element generalized Kelvin-Voigt model is developed to capture the transient and steady-state actuation responses as a function of frequency and prestrain. We show that, despite its relative simplicity, this model captures the relevant timescales for the membrane behavior with good fidelity and can be used to accurately predict the actuation magnitude and phase as a function of time over a range of actuation configurations and driving conditions.

  8. Artificial Temperature Anisotropy of Crystals in X-Ray Frequency Range

    SciTech Connect

    Mkrtchyan, Vahram P.; Gasparyan, Laura G.; Balyan, Minas K.

    2010-04-06

    The effect of artificial temperature anisotropy of crystals in X-ray frequency range was observed for the first time and an effort to theoretically interpret this effect in Bragg-Laue diffraction case was made. It was established that an isotropic crystal optically turns into an artificially anisotropic one with optical axis along the direction of applied external influence as a symmetry axis, giving rise to the double refraction.

  9. Determination of the dielectric constant of GaN in the kHz frequency range

    NASA Astrophysics Data System (ADS)

    Kane, M. J.; Uren, M. J.; Wallis, D. J.; Wright, P. J.; Soley, D. E. J.; Simons, A. J.; Martin, T.

    2011-08-01

    Capacitance techniques are used to show that the dielectric constant ɛ|| of GaN in the kHz frequency range is 10.6 ± 0.3. The data allow depth information to be accurately extracted using methods such as mercury probe capacitance profiling. The measurements complement the pre-existing data which are derived from infrared reflectivity and which give a value of 10.4 ± 0.3.

  10. 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.

  11. SS433: Evolution of Radio Structure in {L} and {C} Frequency Ranges

    NASA Astrophysics Data System (ADS)

    Chuprikov, A. A.; Guirin, I. A.

    2010-02-01

    We analyze results of data processing of observations of SS433 with the VLBA during more than 10 years. Data were processed with ASL for Windows software. The Multi Frequency Synthesis method was used for reconstruction of radio maps at 18- and 6-cm wavelength ranges (L and C ranges). High-quality images of SS433 for several epochs are presented. Evolution of its radio structure is demonstrated. Astrophysical parameters of the object and their temporal changes are discussed. Polarization phenomena were not taken into account. We present results of our data processing of RR polarization for all the observing sessions.

  12. 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.

  13. 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.

  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. Low Density Parity Check Code for the Single Carrier Frequency Division Multiple Access

    NASA Astrophysics Data System (ADS)

    Islam, Mohammad Rakibul; Kim, Jinsang

    A new encoding technique for low density parity check (LDPC) code at the uplink of 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) is proposed. The concept of approximate lower triangulation (ALT) is used where the parity check matrix is preprocessed and encoded in O(n) complexity. This encoding technique is applied in the uplink of LTE system where single carrier frequency division multiple access (SC-FDMA) is used as the multiple access scheme. As the encoding is performed in a O(n) complexity, it will outperform the existing LDPC encoding which is not used in LTE uplink due to its high encoding complexity. The proposed encoding is simulated in the SCFDMA scenario and the BER curve is shown.

  16. 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

  17. MEMS - Frequency Agile High Precision Ranging under the Dual Use Applications Program (DUAP)

    NASA Astrophysics Data System (ADS)

    Bauhahn, Paul

    2001-12-01

    The objective of this program was laboratory demonstration of a low cost, jamming resistant, precision ranging system (radar) for proximity fuze and short-range measurement systems. Two approaches were envisioned: (1) The baseline-a baseband system directly radiating and detecting a random sequence of short pulses and (2) A higher risk design based on a transmitter using high-speed modulation of a micro-electromechanical (MEM) oscillator to avoid low frequency antenna radiation requirements. Size constraints drive the design toward small, single-chip monocycle pulse radar implemented in CMOS (Complementary Metal Oxide Semiconductors). This device with two external capacitors, a battery and a miniature antenna for the baseline approach is described in Figure 1-1. Triggering ranges from several inches to more than 6feet were demonstrated. Fabrication of MEM components on gallium arsenide for the second approach will require additional work. While CMOS technology is almost ideal for the long time-constant, multiple pulse integration circuits in the precision ranging receiver and most of the transmitter circuits, it is insufficient for submunition sensor final output amplifiers. The issue is the small size of the submunition antenna. Either step recovery diode circuit or higher performance output transistors are needed to generate the high frequency spectrum required for efficient radiation from these antennas. Using a 0.5-micron BiCMOS/Si(3e process, recently available for prototyping at MOSIS,' all of the required CMOS and faster output devices could be implemented with trivial modifications of the existing circuits.

  18. Acoustic Behavior of Halobacterium salinarum Gas Vesicles in the High-Frequency Range: Experiments and Modeling.

    PubMed

    Cherin, Emmanuel; Melis, Johan M; Bourdeau, Raymond W; Yin, Melissa; Kochmann, Dennis M; Foster, F Stuart; Shapiro, Mikhail G

    2017-03-01

    Gas vesicles (GVs) are a new and unique class of biologically derived ultrasound contrast agents with sub-micron size whose acoustic properties have not been fully elucidated. In this study, we investigated the acoustic collapse pressure and behavior of Halobacterium salinarum gas vesicles at transmit center frequencies ranging from 12.5 to 27.5 MHz. The acoustic collapse pressure was found to be above 550 kPa at all frequencies, nine-fold higher than the critical pressure observed under hydrostatic conditions. We illustrate that gas vesicles behave non-linearly when exposed to ultrasound at incident pressure ranging from 160 kPa to the collapse pressure and generate second harmonic amplitudes of -2 to -6 dB below the fundamental in media with viscosities ranging from 0.89 to 8 mPa·s. Simulations performed using a Rayleigh-Plesset-type model accounting for buckling and a dynamic finite-element analysis suggest that buckling is the mechanism behind the generation of harmonics. We found good agreement between the level of second harmonic relative to the fundamental measured at 20 MHz and the Rayleigh-Plesset model predictions. Finite-element simulations extended these findings to a non-spherical geometry, confirmed that the acoustic buckling pressure corresponds to the critical pressure under hydrostatic conditions and support the hypothesis of limited gas flow across the GV shell during the compression phase in the frequency range investigated. From simulations, estimates of GV bandwidth-limited scattering indicate that a single GV has a scattering cross section comparable to that of a red blood cell. These findings will inform the development of GV-based contrast agents and pulse sequences to optimize their detection with ultrasound.

  19. Free-field reciprocity calibration of microphones in ultrasonic frequency range

    NASA Astrophysics Data System (ADS)

    Bouaoua, Nourreddine; Fedtke, Thomas; Mellert, Volker

    2005-09-01

    Exposure to airborne low-frequency ultrasound occurs in many industrial applications such as cleaning, welding plastics, measuring distances in buildings, and by using consumer devices such as camera rangefinders, automatic door openers, parametric ultrasound loudspeakers, etc. Exposure to ultrasound in air may be dangerous to the hearing and may have negative bio-effects on humans. Care should be taken in its use. In order to establish appropriate limits and to measure the output of ultrasound devices, there is a need to develop a sound-pressure standard in the frequency range from 20 kHz to about 160 kHz. A calibration project for quarter-inch microphones by the reciprocity method has been started in the PTB, and a new automated measurement setup for free-field reciprocity calibration of quarter-inch microphones has been established. A procedure for a free-field reciprocity calibration of quarter-inch microphones in the frequency range 20 to 160 kHz is described. First results of free-field calibration of quarter-inch microphones are presented, giving the sensitivities and the repeatability of results. The effects of reflections and cross talk on the accuracy of the measurements will be explained.

  20. Frequency dependence of electromagnetic bias in radar altimeter sea surface range measurements

    NASA Technical Reports Server (NTRS)

    Walsh, E. J.; Jackson, F. C.; Hines, D. E.; Piazza, C.; Hevizi, L. G.; Mclaughlin, D. J.; Mcintosh, R. E.; Swift, R. N.; Scott, J. F.; Yungel, J. K.

    1991-01-01

    Range measurements made by satellite radar altimeters experience a bias toward the troughs of ocean waves. A series of aircraft flights during February-April 1989 measured this electromagnetic (EM) bias at three radar frequencies and the UV under a variety of wind and wave conditions, and provided the first airborne open-ocean measurements at the 13.6-GHz and 5.3-GHz operating frequencies of the NASA altimeter on the TOPEX/Poseidon satellite. The data suggest that the mean EM bias decreases linearly with increasing radar frequency between 5.3 and 36 GHz, according to the expression: EM bias (percent of significant wave height) = (3.0-0.0617 F)(1 +/-0.5), where F is in gigahertz. EM bias is fairly constant over a mesoscale region on a given day but can fluctuate significantly from one day to another. It shows a strong increase at all radar frequencies with increasing wind speed, although other sea state conditions, such as the wind direction relative to the wave direction, are also factors.

  1. Mechanical properties of bulk polydimethylsiloxane for microfluidics over a large range of frequencies and aging times

    NASA Astrophysics Data System (ADS)

    Placet, V.; Delobelle, P.

    2015-03-01

    The dynamic mechanical characterization of polydimethylsiloxane (PDMS) over a large range of frequencies (10-2 < f < 105 Hz) and long aging times at room temperature (4 h < tv < ~60 000 h) has been presented. Three samples with different curing conditions have been studied and three different techniques, dynamic mechanical analysis at different temperatures, nano-indentation and scanning micro-deformation microscopy, have been used. Although the three techniques work at different scales and at different frequencies all the results match the same master curve. As expected, the storage and the loss moduli greatly increase with the frequency. Moreover, these moduli moderately increase with the aging time tv depending on the curing temperature. A simple model which takes the frequency and the aging time into account, and which is based on the Havriliak-Negami model, has been presented and identified. Hence, values of the relaxed and instantaneous moduli at tv = 0 and tv = ∞ are proposed. Only the relaxed moduli depend on the curing conditions and moreover it has been shown that the tangent of the phase lag is independent of the aging time and thus of the curing process.

  2. 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.

  3. Generation of High Resolution Radar Range Profiles and Range Profile Auto-Correlation Functions Using Stepped-Frequency Pulse Train

    DTIC Science & Technology

    1984-10-18

    resulting range resolution (of both the profile and itg auto- correlation function) is determined by the total bandwidth (i.e., the fre- quency spread...contrast provided by the resulting range profiles and range profile auto-correlation functions is determined. The target-to-clutter contrast provided by the...SIMULATION RESULTS FOR RANGE-PROFILES AND RANGE-PROFILE 86 AUTO -CORRELATION FIJNCTIONS OBTAINED BY PROCESSING RETURNS FROM FR9QUENCY-STEPPED PULSE

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

    NASA Astrophysics Data System (ADS)

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

    1984-03-01

    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.

  5. 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.

  6. 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

  7. An intuitive picture of the physics underlying optical ranging using frequency shifted feedback lasers seeded by a phase-modulated field

    NASA Astrophysics Data System (ADS)

    Yatsenko, L. P.; Shore, B. W.; Bergmann, K.

    2009-06-01

    Frequency shifted feedback (FSF) lasers have been demonstrated to have interesting and useful features when used for optical ranging. The use of a phase-modulated seed to the FSF laser dramatically improves the signal-to-noise ratio, enabling distance measurements with the accuracy expected of optical interferometry. We present here an intuitively accessible description of the physics that underlies this dramatic enhancement of optical ranging signals. Unlike a free-running FSF laser, each one of the many equidistant frequency components of the seeded FSF laser spectrum (typically >104) has a definite amplitude, and a phase which varies with component number and modulation frequency Ω of the seed radiation. Suitable adjustment of Ω gives all components a common phase; the resulting constructive interference enhances the signal by orders of magnitude.

  8. Mid-frequency sound propagation through internal waves at short range with synoptic oceanographic observations.

    PubMed

    Rouseff, Daniel; Tang, Dajun; Williams, Kevin L; Wang, Zhongkang; Moum, James N

    2008-09-01

    Preliminary results are presented from an analysis of mid-frequency acoustic transmission data collected at range 550 m during the Shallow Water 2006 Experiment. The acoustic data were collected on a vertical array immediately before, during, and after the passage of a nonlinear internal wave on 18 August, 2006. Using oceanographic data collected at a nearby location, a plane-wave model for the nonlinear internal wave's position as a function of time is developed. Experimental results show a new acoustic path is generated as the internal wave passes above the acoustic source.

  9. 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.

  10. An improved energy efficient SRAM cell for access over a wide frequency range

    NASA Astrophysics Data System (ADS)

    Nayak, Debasish; Acharya, Debiprasad Priyabrata; Mahapatra, Kamalakanta

    2016-12-01

    Leakage current contribution to the power consumption cannot be ignored in the sub-100 nm technology. Drastic reduction of channel length of the modern highly scaled device enhances the leakage current significantly. Two novel 8T-SRAM cells low-leakage-current SRAM cell (LLC-SRAM cell) and low-leakage-current high-threshold-voltage SRAM cell (LLC-HVT SRAM cell) are proposed to offer high energy efficiency. The cell performances are compared with 8T NC-SRAM cell and 6T-SRAM cell. The proposed cells significantly reduce the overall power consumption. The cell array simulations are performed in spectre with a general purpose 45 nm technology library. The short-circuit current reduction during state transition helps to decrease the dynamic power consumption. In standby mode the cell operates at a voltage lower than the supply which brings down the leakage current and hence leakage power. Besides the energy prospective the stability, speed and writ-ability analysis are also performed in this work.

  11. A Robust Range Grating Lobe Suppression Method Based on Image Contrast for Stepped-Frequency SAR

    PubMed Central

    Gao, Wen-Bin; Long, Teng; Ding, Ze-Gang; Wu, Yi-Rong

    2016-01-01

    The magnitude error and phase error (MEPE) in the transfer function of a stepped-frequency synthetic aperture radar (SAR) system results in a periodic MEPE in the synthesized wideband waveform (SWW), which induces the grating lobes in the high-resolution range profile (HRRP). In this paper, a robust data-driven grating lobe suppression (GLS) method is proposed. Based on a contrast-based error estimation method and the grating lobes of the brightest scatterers in the SAR image, the periodic MEPE can be robustly estimated using the proposed method. By compensating the estimated periodic MEPE, the range grating lobes can be suppressed to the background level of the SAR image. Simulation results and real data processing have demonstrated the superiority of the proposed method. PMID:27929411

  12. Optical-fiber frequency domain interferometer with nanometer resolution and centimeter measuring range.

    PubMed

    Weng, Jidong; Tao, Tianjiong; Liu, Shenggang; Ma, Heli; Wang, Xiang; Liu, Cangli; Tan, Hua

    2013-11-01

    A new optical-fiber frequency domain interferometer (OFDI) device for accurate measurement of the absolute distance between two stationary objects, with centimeter measuring range and nanometer resolution, has been developed. Its working principle and on-line data processing method were elaborated. The new OFDI instrument was constructed all with currently available commercial communication products. It adopted the wide-spectrum amplified spontaneous emission light as the light source and optical-fiber tip as the test probe. Since this device consists of only fibers or fiber coupled components, it is very compact, convenient to operate, and easy to carry. By measuring the single-step length of a translation stage and the thickness of standard gauge blocks, its ability in implementing nanometer resolution and centimeter measuring range on-line measurements was validated.

  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. Alteration of frequency range for binaural beats in acute low-tone hearing loss.

    PubMed

    Karino, Shotaro; Yamasoba, Tatsuya; Ito, Ken; Kaga, Kimitaka

    2005-01-01

    The effect of acute low-tone sensorineural hearing loss (ALHL) on the interaural frequency difference (IFD) required for perception of binaural beats (BBs) was investigated in 12 patients with unilateral ALHL and 7 patients in whom ALHL had lessened. A continuous pure tone of 30 dB sensation level at 250 Hz was presented to the contralateral, normal-hearing ear. The presence of BBs was determined by a subjective yes-no procedure as the frequency of a loudness-balanced test tone was gradually adjusted around 250 Hz in the affected ear. The frequency range in which no BBs were perceived (FRNB) was significantly wider in the patients with ALHL than in the controls, and FRNBs became narrower in the recovered ALHL group. Specifically, detection of slow BBs with a small IFD was impaired in this limited (10 s) observation period. The significant correlation between the hearing level at 250 Hz and FRNBs suggests that FRNBs represent the degree of cochlear damage caused by ALHL.

  15. Absorption and modulus measurements in the seismic frequency and strain range on partially saturated sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Paffenholz, Josef; Burkhardt, Hans

    1989-07-01

    The absorptions 1/QE and 1/QS of partially water-saturated sedimentary rocks were determined from phase differences between stress and strain for longitudinal deformation frequencies between 0.03 and 300 Hz and torsional frequencies between 0.03 and 100 Hz. Both longitudinal and shear strain amplitudes were of the order of 10-6. For water saturation between 0 and 50%, Young's moduli and shear moduli were shown to decrease with increasing saturation. In this saturation range both 1/QE and 1/QS increased, but no distinguishable absorption maxima were observed. For saturation percentages greater than 50%, the moduli of the samples appeared independent of the water content. 1/QE increased until full saturation and showed a strong frequency dependence. 1/QS is much less affected by increasing water saturation and has no absorption maxima in general. Since the absorption and the moduli reduction show different saturation dependencies, two different mechanisms for these effects are proposed. The addition of water changes the interaction force between the molecules on opposite walls of thin cracks. This provides a mechanism for the modulus reduction. Calculations based on the Biot-Gardner theory (Gardner, 1962) indicate that part of the observed absorption may be caused by fluid flow due to the limited sample size as proposed by White (1986). Fluid-supported thermorelaxation is proposed, as a possible intrinsic absorption mechanism.

  16. Impact of high-frequency waves on the ocean altimeter range bias

    NASA Astrophysics Data System (ADS)

    Vandemark, D.; Chapron, B.; Elfouhaily, T.; Campbell, J. W.

    2005-11-01

    New aircraft observations are presented on the range determination error in satellite altimetry associated with ocean waves. Laser-based measurements of the cross correlation between the gravity wave slope and elevation are reported for the first time. These observations provide direct access to a long, O(10 m), gravity wave statistic central to nonlinear wave theory prediction of the altimeter sea state bias. Coincident Ka-band radar scattering data are used to estimate an electromagnetic (EM) range bias analogous to that in satellite altimetry. These data, along with ancillary wind and wave slope variance estimates, are used alongside existing theory to evaluate the extent of long- versus short-wave, O(cm), control of the bias. The longer wave bias contribution to the total EM bias is shown to range from 25 to as much as 100%. Moreover, on average the term is linearly related to wind speed and to the gravity wave slope variance, consistent with WNL theory. The EM bias associated with interactions between long and short waves is obtained assuming the effect is additive to the independently observed long-wave factor. This second component is also a substantial contributor, is observed to be quadratic in wind speed or wave slope, and dominates at moderate wind speeds. The behavior is shown to be consistent with EM bias prediction based in hydrodynamic modulation theory. Study implications for improved correction of the on-orbit satellite sea state bias are discussed.

  17. Impaired Neural Synchrony in the Theta Frequency Range in Adolescents at Familial Risk for Schizophrenia

    PubMed Central

    Donkers, Franc C. L.; Schwikert, Shane R.; Evans, Anna M.; Cleary, Katherine M.; Perkins, Diana O.; Belger, Aysenil

    2011-01-01

    Puberty is a critical period for the maturation of the fronto-limbic and fronto-striate brain circuits responsible for executive function and affective processing. Puberty also coincides with the emergence of the prodromal signs of schizophrenia, which may indicate an association between these two processes. Time-domain analysis and wavelet based time–frequency analysis was performed on electroencephalographic (EEG) data of 30 healthy control (HC) subjects and 24 individuals at familial risk (FR) for schizophrenia. All participants were between the ages of 13 and 18 years and were carefully matched for age, gender, ethnicity, education, and Tanner Stage. Electrophysiological recordings were obtained from 32 EEG channels while participants performed a visual oddball task, where they identified rare visual targets among standard “scrambled” images and rare aversive and neutral distracter pictures. The time-domain analysis showed that during target processing the FR group showed smaller event-related potentials in the P2 and P3 range as compared to the HC group. In addition, EEG activity in the theta (4–8 Hz) frequency range was significantly reduced during target processing in the FR group. Inefficient cortical information processing during puberty may be an early indicator of altered brain function in adolescents at FR for schizophrenia and may represent a vulnerability marker for illness onset. Longitudinal assessments will have to determine their predictive value for illness onset in populations at FR for psychotic illness. PMID:21991257

  18. 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.

  19. Frequency-Range Distribution of Boulders Around Cone Crater: Relevance to Landing Site Hazard Avoidance

    NASA Technical Reports Server (NTRS)

    Clegg-Watkins, R. N.; Jolliff, B. L.; Lawrence, S. J.

    2016-01-01

    Boulders represent a landing hazard that must be addressed in the planning of future landings on the Moon. A boulder under a landing leg can contribute to deck tilt and boulders can damage spacecraft during landing. Using orbital data to characterize boulder populations at locations where landers have safely touched down (Apollo, Luna, Surveyor, and Chang'e-3 sites) is important for determining landing hazard criteria for future missions. Additionally, assessing the distribution of boulders can address broader science issues, e.g., how far craters distribute boulders and how this distribution varies as a function of crater size and age. The availability of new Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images [1] enables the use of boulder size- and range frequency distributions for a variety of purposes [2-6]. Boulders degrade over time and primarily occur around young or fresh craters that are large enough to excavate bedrock. Here we use NAC images to analyze boulder distributions around Cone crater (340 m diameter) at the Apollo 14 site. Cone crater (CC) was selected because it is the largest crater where astronaut surface photography is available for a radial traverse to the rim. Cone crater is young (approximately 29 Ma [7]) relative to the time required to break down boulders [3,8], giving us a data point for boulder range-frequency distributions (BRFDs) as a function of crater age.

  20. 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...

  1. Wired/wireless access integrated RoF-PON with scalable generation of multi-frequency MMWs enabled by tunable optical frequency comb.

    PubMed

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

    2013-08-26

    In this paper, a novel wired/wireless access integrated radio-over-fiber passive optical network (RoF-PON) system that utilizes scalable multiple-frequency millimeter-wave (MF-MMW) generation based on tunable optical frequency comb (TOFC) is proposed. The TOFC is performed by cascading a phase modulator (PM) and two intensity modulators (IMs), and with proper selection of the peak-to-peak voltage of the PM, a flat and effective optical comb with tens of frequency lines is achieved. The MF-MMWs are generated by beating the optical comb line pairs with an interval about 60 GHz. The feasibility and scalability of the proposed wired/wireless access integrated RoF-PON scheme are confirmed by the simulations of simultaneous distribution of wired and wireless data with the proposed multiple frequency MMW generation technology.

  2. 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.

  3. 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.

  4. Radio frequency interference survey over the 1.0-10.4 GHz frequency range at the Goldstone-Venus Development Station

    NASA Technical Reports Server (NTRS)

    Gulkis, S.; Olsen, E. T.; Klein, M. J.; Jackson, E. B.

    1989-01-01

    The results of a low sensitivity Radio Frequency Interference (RFI) survey carried out at the Venus Station of the Goldstone Communications Complex are reported. The data cover the spectral range from 1 GHz to 10.4 GHz with a 10-kHz instantaneous bandwidth. Frequency and power levels were observed using a sweep-frequency spectrum analyzer connected to a 1-m diameter antenna pointed at zenith. The survey was conducted from February 16, 1987 through February 24, 1987.

  5. The Multifractal Flood Frequency Analysis to Account Long Range Dependencies and the Clustering of Extremes

    NASA Astrophysics Data System (ADS)

    Tchiguirinskaia, I.; Schertzer, D. J.; Lovejoy, S.

    2012-12-01

    The classical quantile distributions in existing flood studies often rely on two hypotheses that are questionable: stationarity and independency of the components of the time series. We discuss how to better (statistically) predict the floods by using a physically based approach that accounts long range dependencies and the clustering of extremes often resulting in fat tailed (i.e., an algebraic type) probability distributions. It established on systems that respect a scale symmetry over a wide range of space-time scales to determine the relationship between flood magnitude and return period for a wide range of aggregation periods. The results were obtained during the CEATI Project "Multifractals and physically based estimates of extreme floods". The ambition of this project was to investigate very large data sets of reasonable quality (e.g., daily stream flow data recorded for at least 20 years for several thousands of gages distributed all over Canada and the USA). The multifractal parameters such as the mean intermittency parameter and the multifractality index were estimated on 8332 time series. Obtained results demonstrate that beyond the classical sampling of the extremes and its limitations, there is the possibility to eliminate long-range dependency by uncovering a stochastic process whose fractional integration would generate the observed long-range dependent process. The results confirm the dependence of parameter estimates on the length of available data. Then developing a metric for parameter estimation error became a principal step in uncertainty evaluation with respect to the multifractal estimates. A technique for estimating confidence intervals with the help of a Bayesian approach was developed. A detailed comparison of multifractal quantile plots and paleoflood data validates the forthcoming use of the multifractal flood frequency analysis.

  6. Graphics processing unit-based dispersion encoded full-range frequency-domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wang, Ling; Hofer, Bernd; Guggenheim, Jeremy A.; Považay, Boris

    2012-07-01

    Dispersion encoded full-range (DEFR) frequency-domain optical coherence tomography (FD-OCT) and its enhanced version, fast DEFR, utilize dispersion mismatch between sample and reference arm to eliminate the ambiguity in OCT signals caused by non-complex valued spectral measurement, thereby numerically doubling the usable information content. By iteratively suppressing asymmetrically dispersed complex conjugate artifacts of OCT-signal pulses the complex valued signal can be recovered without additional measurements, thus doubling the spatial signal range to cover the full positive and negative sampling range. Previously the computational complexity and low processing speed limited application of DEFR to smaller amounts of data and did not allow for interactive operation at high resolution. We report a graphics processing unit (GPU)-based implementation of fast DEFR, which significantly improves reconstruction speed by a factor of more than 90 in respect to CPU-based processing and thereby overcomes these limitations. Implemented on a commercial low-cost GPU, a display line rate of ~21,000 depth scans/s for 2048 samples/depth scan using 10 iterations of the fast DEFR algorithm has been achieved, sufficient for real-time visualization in situ.

  7. New creep-fatigue damage model based on the frequency modified strain range method

    SciTech Connect

    Kim, Y.J.; Seok, C.S.; Park, J.J.

    1996-12-01

    For mechanical systems operating at high temperature, damage due to the interaction effect of creep and fatigue plays an important role. The objective of this paper is to propose a modified creep-fatigue damage model which separately analyzes the pure creep damage due to the hold time and the creep-fatigue interaction damage during the startup and the shutdown period. The creep damage was calculated by the general creep damage equation and the creep-fatigue interaction damage was calculated by the modified equation which is based on the frequency modified strain range method with strain rate term. In order to verify the proposed model, a series of high temperature low cycle fatigue tests were performed. The test specimens were made from Inconel-718 superalloy and the test parameters were wave form and hold time. A good agreement between the predicted lives based on the proposed model and experimentally obtained ones was obtained.

  8. 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.

  9. Stage-based frequency-modulated full-range complex Fourier-domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Bian, Haiyi; Gao, Wanrong

    2015-10-01

    We propose a simple method to modulate spatial interferogram to achieve full-range complex imaging in Fourier-domain optical coherence tomography, in which a sample stage is employed which can be adjusted to introduce a constant carrier frequency into the interference signal during the B-scan by adjusting the stage angle with respect to the normal to the object under test. An additional phase, which is linearly related to the lateral position, is then induced in the A-scan. The in vivo images of human skin were generated which demonstrate that the method proposed can generate the cross-sectional image with the same quality with that obtained with other methods and with the advantage of the simplicity in implementation.

  10. Cosmic ray scintillations in the frequency range from 0.00001 to 0.01 Hz

    NASA Technical Reports Server (NTRS)

    Gehrels, N.; Lheureux, J.

    1978-01-01

    Power spectra of the flux variations in cosmic rays of energy greater than a few GeV are presented. The data were obtained at balloon altitudes (40-45 km) from two scintillation-type detectors flown for six hours from Palestine, Texas, on November 4, 1972. The large area detectors had effective count rates up to 2000 cps setting the Poisson noise level in the power spectra of the relative fluctuations at 0.001/Hz. The analysis was made on the singles rate of each of the counters as well as on the coincidence rates between them. In all cases, the spectra between 0.0001 and 0.002 Hz are power laws in frequency of the form f to the exponent negative gamma, where gamma is between 1.5 and 2.0. No significant peaks in the range 0.0001 to 0.01 Hz are observed.

  11. Fabrication and characterization of biotissue-mimicking phantoms in the THz frequency range

    NASA Astrophysics Data System (ADS)

    Liakhov, E.; Smolyanskaya, O.; Popov, A.; Odlyanitskiy, E.; Balbekin, N.; Khodzitsky, M.

    2016-08-01

    The study revealed the most promising candidates for phantoms mimicking different biological tissues in the terahertz frequency range. Closest to biological tissues in terms of the refractive index appeared to be gelatin-based gels; in terms of the absorption coefficient they were agar-based gels. Gelatin is more stable in time, but requires special storage conditions to limit water evaporation. The dense structure of the agar-based phantom allows its use without mold and risk of damage. However, agar is a nutrient medium for bacteria and its parameters degrade even when the phantom form and water content are retained. Use of liquid suspensions of lecithin and milk powder are found to be extremely limited.

  12. Experimental study of attenuation and dispersion over a broad frequency range: 1. The apparatus

    NASA Astrophysics Data System (ADS)

    Takei, Yasuko; Fujisawa, Kazuhiro; McCarthy, Christine

    2011-09-01

    We have developed a new experimental method to investigate the anelasticity of a polycrystalline solid at high homologous temperature (T/Tm = 0.6-0.7). By using a rock analogue (borneol polycrystals) and a partially molten rock analogue (borneol + melt) having low melting and eutectic temperatures (Tm = 204.5°C, Te = 43°C), respectively, testing high homologous temperature can occur near room temperature. An apparatus is described for cyclic compressive, Young's modulus type attenuation experiments over a wide range of frequencies (10-10-4 Hz) and at small strain amplitudes (10-6-10-5). Creep tests to measure steady state viscosity can also be performed. Details of the apparatus, including its piezoelectric actuator, dual laser displacement meters and trio of load cells, are discussed. Attenuation spectra and modulus dispersion measured for aluminum, acrylic plastic, and a rock analogue are presented to illustrate the accuracy of the method.

  13. Acoustic absorption measurement of human hair and skin within the audible frequency range.

    PubMed

    Katz, B F

    2000-11-01

    Utilizing the two-microphone impedance tube method, the acoustic absorption of human skin and hair is measured in the frequency range 1-6 kHz. Various locations on a number of human subjects are measured to determine if the presence of bone or an air pocket affects the acoustic absorption of human skin. The absorption coefficient of human hair is also measured. Additional techniques are utilized to minimize errors due to sample mounting methods. Techniques are employed to minimize potential errors in sensor and sample locations. The results of these measurements are compared to relevant historical papers on similar investigations. Results for skin measurements compare well with previous work. Measured hair absorption data do not agree with previous work in the area but do coincide with expected trends, which previous works do not.

  14. 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.

  15. Harvesting Ambient Vibration Energy over a Wide Frequency Range for Self-Powered Electronics.

    PubMed

    Wang, Xiaofeng; Niu, Simiao; Yi, Fang; Yin, Yajiang; Hao, Chenglong; Dai, Keren; Zhang, Yue; You, Zheng; Wang, Zhong Lin

    2017-02-28

    Vibration is one of the most common energy sources in ambient environment. Harvesting vibration energy is a promising route to sustainably drive small electronics. This work introduces an approach to scavenge vibrational energy over a wide frequency range as an exclusive power source for continuous operation of electronics. An elastic multiunit triboelectric nanogenerator (TENG) is rationally designed to efficiently harvest low-frequency vibration energy, which can provide a maximum instantaneous output power density of 102 W·m(-3) at as low as 7 Hz and maintain its stable current outputs from 5 to 25 Hz. A self-charging power unit (SCPU) combining the TENG and a 10 mF supercapacitor gives a continuous direct current (DC) power delivery of 1.14 mW at a power management efficiency of 45.6% at 20 Hz. The performance of the SCPU can be further enhanced by a specially designed power management circuit, with a continuous DC power of 2 mW and power management efficiency of 60% at 7 Hz. Electronics such as a thermometer, hygrometer, and speedometer can be sustainably powered solely by the harvested vibration energy from a machine or riding bicycle. This approach has potential applications in self-powered systems for environment monitoring, machine safety, and transportation.

  16. 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

  17. Numerical Exposure Assessment Method for Low Frequency Range and Application to Wireless Power Transfer

    PubMed Central

    Kim, Minhyuk

    2016-01-01

    In this paper, a numerical exposure assessment method is presented for a quasi-static analysis by the use of finite-difference time-domain (FDTD) algorithm. The proposed method is composed of scattered field FDTD method and quasi-static approximation for analyzing of the low frequency band electromagnetic problems. The proposed method provides an effective tool to compute induced electric fields in an anatomically realistic human voxel model exposed to an arbitrary non-uniform field source in the low frequency ranges. The method is verified, and excellent agreement with theoretical solutions is found for a dielectric sphere model exposed to a magnetic dipole source. The assessment method serves a practical example of the electric fields, current densities, and specific absorption rates induced in a human head and body in close proximity to a 150-kHz wireless power transfer system for cell phone charging. The results are compared to the limits recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the IEEE standard guidelines. PMID:27898688

  18. Numerical Exposure Assessment Method for Low Frequency Range and Application to Wireless Power Transfer.

    PubMed

    Park, SangWook; Kim, Minhyuk

    2016-01-01

    In this paper, a numerical exposure assessment method is presented for a quasi-static analysis by the use of finite-difference time-domain (FDTD) algorithm. The proposed method is composed of scattered field FDTD method and quasi-static approximation for analyzing of the low frequency band electromagnetic problems. The proposed method provides an effective tool to compute induced electric fields in an anatomically realistic human voxel model exposed to an arbitrary non-uniform field source in the low frequency ranges. The method is verified, and excellent agreement with theoretical solutions is found for a dielectric sphere model exposed to a magnetic dipole source. The assessment method serves a practical example of the electric fields, current densities, and specific absorption rates induced in a human head and body in close proximity to a 150-kHz wireless power transfer system for cell phone charging. The results are compared to the limits recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the IEEE standard guidelines.

  19. 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.

  20. Interaction of a relativistic electron beam with radiation in the THz frequency range

    NASA Astrophysics Data System (ADS)

    Sung, Chieh

    0.5-3 THz range with a maximum of ˜2 kW of peak power in a 200 ns pulse suitable as a seed for an FEL microbuncher. These sources represent the most powerful and the most energetic narrowband THz sources currently reported using nonlinear optical technique to our knowledge. During the FEL microbunching process, the wiggling electrons in the undulator also emit radiation coherently at the resonant frequency; as a result, the THz FEL microbuncher can double as a single pass THz amplifier tunable in the 0.5-3 THz range. It is shown that when seeded with a ˜1 kW THz pulse and driven by an electron beam with a peak current of 60A, a 2 m-long undulator can amplify the radiation power to ˜20MW. The frequency range can be further expanded to up to 9 THz via the High Gain Harmonic Generation (HGHG) FEL configuration. The results of these simulations are used as a guide in designing a single-pass THz FEL microbuncher/amplifier which is currently under construction. In order to study THz microbunching and amplification, several original techniques and diagnostics were also developed. Guiding a THz pulse through a hollow waveguide, filtering a short THz pulse using a Fabry-Perot interferometer and measuring the frequency components using a diffraction grating spectrometer were demonstrated.

  1. 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.

  2. 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.

  3. Very-high-frequency dc-to-dc conversion and regulation in the low-megahertz range.

    NASA Technical Reports Server (NTRS)

    Feng, S. Y. M.; Wilson, T. G.; Sander, W. A., III

    1971-01-01

    Anticipated new mission requirements have motivated research on very-high-frequency (VHF) regulated dc-to-dc converters to operate at conversion frequencies in the low-megahertz range. State-of-the-art electronic components for VHF operation are discussed. Two different converter configurations, one using proportional control and having a conversion frequency of 0.1 MHz and the other using bistable control and having a conversion frequency of 3.8 MHz, are presented to indicate converter performance in this VHF region. Converter losses, which are of prime importance at these frequencies, are discussed and possible means of reducing these losses are suggested.

  4. Ion beam generated modes in the lower hybrid frequency range in a laboratory magnetoplasma

    NASA Astrophysics Data System (ADS)

    van Compernolle, Bart; Tripathi, Shreekrishna Kp; Gekelman, Walter; Pribyl, Patrick; Colestock, Patrick

    2012-10-01

    The interaction of a fast ion beam with a low β plasma has been studied in the laboratory. Experiments were performed at the LArge Plasma Device (LAPD) at UCLA. The experiments were done in a Helium plasma (n ˜10^12 cm-3, B0 = 1000 G - 1800 G, fpe/fce˜1 - 5, Te= 0.25 eV, vtevA). The ion beam is a Helium beam with energies ranging from 5 keV to 18 keV. The fast ion velocity is on the order of the Alfv'en velocity. The beam is injected from the end of the machine, and spirals down the linear device. Waves were observed below fci in the shear Alfv'en wave regime, and in a broad spectrum above fci in the lower hybrid frequency range, the focus of this paper. The wave spectra have distinct peaks close to ion cyclotron harmonics, extending out to the 100th harmonic in some cases. The wave generation was studied for various plasma parameters, as well as for different beam energies and pitch angles. The waves were measured with 3-axis electric and magnetic probes. Detailed measurements of the perpendicular mode structure will be shown. Langmuir probes were used to measure density and temperature evolution due to the beam-plasma interaction. Retarding field energy analyzers captured the ion beam profiles.

  5. Ion beam generated modes in the lower hybrid frequency range in a laboratory magnetoplasma

    NASA Astrophysics Data System (ADS)

    van Compernolle, Bart; Tripathi, Shreekrishna; Gekelman, Walter; Pribyl, Patrick

    2013-10-01

    The interaction of a fast ion beam with a low β plasma has been studied in the laboratory. Experiments were performed at the LArge Plasma Device (LAPD) at UCLA. The experiments were done in a Helium plasma (n ~=1012cm-3 , B0 = 1000 G - 1800 G, fpe /fce ~= 1 - 5 , Te ~= 4eV , vte <ranging from 5 keV to 18 keV. The fast ion velocity is on the order of the Alfvén velocity. The beam is injected from the end of the machine, and spirals down the linear device. Waves were observed below fci in the shear Alfvén wave regime, and in a broad spectrum above fci in the lower hybrid frequency range. The wave generation was studied for various plasma parameters, as well as for different beam energies and pitch angles. The waves were measured with 3-axis electric and magnetic probes. Detailed measurements of the 2D perpendicular mode structure will be shown. Progress on a theoretical framework of the wave generation by the ion beam will be presented along with comparisons to the measured wave properties. The work was performed at the LArge Plasma Device at the Basic Plasma Science Facility (BaPSF) at UCLA, funded by DOE/NSF.

  6. 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.

  7. 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.

  8. Frequency-range discriminations: special and general abilities in zebra finches (Taeniopygia guttata) and humans (Homo sapiens).

    PubMed

    Weisman, R; Njegovan, M; Sturdy, C; Phillmore, L; Coyle, J; Mewhort, D

    1998-09-01

    The acoustic frequency ranges in birdsongs and human speech can provide important pitch cues for recognition. Zebra finches and humans were trained to sort contiguous frequencies into 3 or 8 ranges, based on associations between the ranges and reward. The 3-range task was conducted separately in 3 spectral regions. Zebra finches discriminated 3 ranges in the medium and high spectral regions faster than in the low region and discriminated 8 ranges with precision. Humans discriminated 3 ranges in all 3 spectral regions to the same modest standard and acquired only a crude discrimination of the lowest and highest of 8 ranges. The results indicate that songbirds have a special sensitivity to the pitches in conspecific songs and, relative to humans, have a remarkable general ability to sort pitches into ranges.

  9. 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.

  10. 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

  11. 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.

  12. Gravitational Wave Track in the Electromagnetic Field of the Earth in the Infra-Low Frequency Range

    NASA Astrophysics Data System (ADS)

    Grunskaya, L. V.; Isakevich, V. V.; Isakevich, D. V.; Luk'ianov, V. E.

    2017-01-01

    Signals in the infra-low frequency range in the electric and geomagnetic fields of the Earth have been detected, corresponding to frequencies of gravitational waves (GWs) emitted by a series of binary star systems (BSS). The coherence of the detected signals has been investigated. The amplitude characteristics of signals in the electric and geomagnetic fields at GW frequencies of BSS are estimated. The estimates of the amplitudes of the detected signals are in line with model estimates.

  13. Experimentally determined attenuation and modulus in Earth analogue materials over a wide range of frequency

    NASA Astrophysics Data System (ADS)

    McCarthy, C.; Fujisawa, K.; Takei, Y.; Hiraga, T.

    2009-12-01

    Seismic observations, particularly in areas of active tectonics, show large variations and can be affected by many variables, including temperature, composition, grain size, volatile content and the presence of small quantities of melt or other fluids. The understanding and interpretation of seismic wave dispersion and attenuation data can be significantly enhanced through improved knowledge of material dynamic response at the grain scale (and smaller). The organic binary system borneol-diphenylamine is a suitable analogue of melting in the Earth’s mantle. Not only does the solid phase deform through the same deformation mechanisms (diffusion creep, dislocation creep) observed in geologic materials, but the moderate and controllable dihedral angle (40° at 316 K) exhibited by this system provides an equilibrium melt-geometry very similar to that of the olivine + basalt system [Takei, 2000]. With a eutectic melting temperature (TE = 316 K at ambient pressure) just above room temperature, borneol-diphenylamine provides an attractive chemical analogue to study the properties of solid-melt interaction, obviating the difficulties associated with high-temperature, high-pressure experimentation. We have initiated compression-compression cyclic loading experiments on single phase (borneol; TM = 477 K) and multiphase (borneol-diphenylamine) aggregates. Our newly developed apparatus is able to apply and measure very small stress and strain amplitudes with high accuracy using a piezoelectric actuator and optical displacement meters, respectively. The planned experimental conditions are P = 1 atm, T = 298 - 333 K, strain amplitude <10-5, f = 10-4 - 102 Hz, and melt fraction φ = 0 - 0.1. The combination of low (sub seismic) frequency data obtained from these forced oscillation experiments and high-frequency data (f = 102 - 106) from ultrasonic wave transmission measurements allows us to explore the dissipation and Young’s modulus over a frequency range of some ten decades

  14. 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

  15. 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.

  16. Co-analysis of Solar Microwave and Hard X-Ray Spectral Evolutions. I. In Two Frequency or Energy Ranges

    NASA Astrophysics Data System (ADS)

    Song, Qiwu; Huang, Guangli; Nakajima, Hiroshi

    2011-06-01

    Solar microwave and hard X-ray spectral evolutions are co-analyzed in the 2000 June 10 and 2002 April 10 flares, and are simultaneously observed by the Owens-Valley Solar Array in the microwave band and by Yohkoh/Hard X-ray Telescope or RHESSI in the hard X-ray band, with multiple subpeaks in their light curves. The microwave and hard X-ray spectra are fitted by a power law in two frequency ranges of the optical thin part and two photon energy ranges, respectively. Similar to an earlier event in Shao & Huang, the well-known soft-hard-soft pattern of the lower energy range changed to the hard-soft-hard (HSH) pattern of the higher energy range during the spectral evolution of each subpeak in both hard X-ray flares. This energy dependence is actually supported by a positive correlation between the overall light curves and spectral evolution in the lower energy range, while it becomes an anti-correlation in the higher energy range. Regarding microwave data, the HSH pattern appears in the spectral evolution of each subpeak in the lower frequency range, which is somewhat similar to Huang & Nakajima. However, it returns back to the well-known pattern of soft-hard-harder for the overall spectral evolution in the higher frequency range of both events. This frequency dependence is confirmed by an anti-correlation between the overall light curves and spectral evolution in the lower frequency range, but it becomes a positive correlation in the higher frequency range. The possible mechanisms are discussed, respectively, for reasons why hard X-ray and microwave spectral evolutions have different patterns in different energy and frequency intervals.

  17. Preferred Frequency Range, Technical Characteristics, and Interference Assessment for a Microwave Observatory of Subsurface and Subcanopy (MOSS) for 1 MHZ Bandwidth in the Frequency Range of 100-150 MHz

    NASA Technical Reports Server (NTRS)

    Honeycutt, Bryan L.

    2005-01-01

    This document presents rationale for the frequency band selection, technical and operational characteristics of active spaceborne sensors in the Earth Exploration-Satellite Service (active), and interference assessment for a 1 MHz bandwidth sensor in the 100-150 MHz frequency range. The active spaceborne sensors expected to be operating in the frequency range of 100-150 MHz is the synthetic aperture radar (SAR) such as the MOSS. The technical characteristics, mission objectives, orbital parameters, design parameters, antenna characteristics, and preliminary interference assessment are given for MOSS. The purpose of the document is to provide rationale for the frequency band selection, technical characteristics of the active spaceborne sensor Microwave Observatory of Subsurface and Subcanopy (MOSS) that can be used to analyze the compatibility of active spaceborne sensors and other systems of 1 MHz bandwidth in the 100-150 MHz frequency band.

  18. Ion beam generated modes in the lower hybrid frequency range in a laboratory magnetoplasma

    NASA Astrophysics Data System (ADS)

    Van Compernolle, B.; Tripathi, S.; Gekelman, W. N.; Colestock, P. L.; Pribyl, P.

    2012-12-01

    The generation of waves by ion ring distributions is of great importance in many instances in space plasmas. They occur naturally in the magnetosphere through the interaction with substorms, or they can be man-made in ionospheric experiments by photo-ionization of neutral atoms injected perpendicular to the earth's magnetic field. The interaction of a fast ion beam with a low β plasma has been studied in the laboratory. Experiments were performed at the LArge Plasma Device (LAPD) at UCLA. The experiments were done in a Helium plasma (n ≃ 1012 \\ cm-3, B0 = 1000 G - 1800 G, fpe}/f{ce ≃ 1 - 5, Te = 0.25\\ eV, vte ≤ vA). The ion beam \\cite{Tripathi_ionbeam} is a Helium beam with energies ranging from 5 keV to 18 keV. The fast ion velocity is on the order of the Alfvén velocity. The beam is injected from the end of the machine, and spirals down the linear device. Waves were observed below fci in the shear Alfvén wave regime, and in a broad spectrum above fci in the lower hybrid frequency range, the focus of this paper. The wave spectra have distinct peaks close to ion cyclotron harmonics, extending out to the 100th harmonic in some cases. The wave generation was studied for various magnetic fields and background plasma densities, as well as for different beam energies and pitch angles. The waves were measured with 3-axis electric and magnetic probes. Detailed measurements of the perpendicular mode structure will be shown. Langmuir probes were used to measure density and temperature evolution due to the beam-plasma interaction. Retarding field energy analyzers captured the ion beam profiles. The work was performed at the LArge Plasma Device at the Basic Plasma Science Facility (BaPSF) at UCLA, funded by DOE/NSF.

  19. Electromagnetic bias in sea surface range measurements at frequencies of the TOPEX/POSEIDON satellite

    SciTech Connect

    Hevizi, L.G.; McIntosh, R.E. ); Walsh, E.J.; Vandemark, D.; Hines, D.E.; Swift, R.N.; Scott, J.F. )

    1993-03-01

    Range measurements made by satellite radar altimeters experience an electromagnetic (EM) bias toward the troughs of ocean waves. This EM bias was measured at the 13.6 GHz and 5.3 GHz operating frequencies of the NASA altimeter on the TOPEX/POSEIDON satellite in a series of 11 aircraft flights from January 17, 1991, through March 4, 1991, during the Surface WAve Dynamics Experiment (SWADE). The data are consistent with an earlier set of airborne measurements and indicate that EM bias is slightly higher at 5.3 GHz than at 13.6 GHz, and that the magnitudes of both biases increase with increasing wind speed, as does their difference. With some exceptions, EM bias shows little variation over a mesoscale region on a given day or within 1 or 2 h, but it can change significantly over a 6-h period. An examination of recent tower, airborne, and satellite measurements shows a consistency in the characteristics of the wind speed dependence but suggests that there may be a height dependence in the determinations, with the bias decreasing with increasing altitude. The airborne measurements appear to be the most reasonable basis for correcting the NASA altimeter range data from the TOPEX/POSEIDON satellite. In addition, a preliminary analysis of a very limited amount of the data acquired at 20.3 m s[sup [minus]1] in Southern Ocean Waves Experiment (SOWEX) has given confidence that the quadratic models for the prelaunch EM bias corrections are more appropriate for wind speed dependence than are the linear models initially considered.

  20. 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.

  1. Discriminating low frequency components from long range persistent fluctuations in daily atmospheric temperature variability

    NASA Astrophysics Data System (ADS)

    Lanfredi, M.; Simoniello, T.; Cuomo, V.; Macchiato, M.

    2009-07-01

    This study originated from recent results reported in literature, which support the existence of long-range (power-law) persistence in atmospheric temperature fluctuations on monthly and inter-annual scales. We investigated the results of Detrended Fluctuation Analysis (DFA) carried out on twenty-two historical daily time series recorded in Europe in order to evaluate the reliability of such findings in depth. More detailed inspections emphasized systematic deviations from power-law and high statistical confidence for functional form misspecification. Rigorous analyses did not support scale-free correlation as an operative concept for Climate modelling, as instead suggested in literature. In order to understand the physical implications of our results better, we designed a bivariate Markov process, parameterised on the basis of the atmospheric observational data by introducing a slow dummy variable. The time series generated by this model, analysed both in time and frequency domains, tallied with the real ones very well. They accounted for both the deceptive scaling found in literature and the correlation details enhanced by our analysis. Our results seem to evidence the presence of slow fluctuations from another climatic sub-system such as ocean, which inflates temperature variance up to several months. They advise more precise re-analyses of temperature time series before suggesting dynamical paradigms useful for Climate modelling and for the assessment of Climate Change.

  2. Discriminating low frequency components from long range persistent fluctuations in daily atmospheric temperature variability

    NASA Astrophysics Data System (ADS)

    Lanfredi, M.; Simoniello, T.; Cuomo, V.; Macchiato, M.

    2009-02-01

    This study originated from recent results reported in literature, which support the existence of long-range (power-law) persistence in atmospheric temperature fluctuations on monthly and inter-annual scales. We investigated the results of Detrended Fluctuation Analysis (DFA) carried out on twenty-two historical daily time series recorded in Europe in order to evaluate the reliability of such findings in depth. More detailed inspections emphasized systematic deviations from power-law and high statistical confidence for functional form misspecification. Rigorous analyses did not support scale-free correlation as an operative concept for Climate modelling, as instead suggested in literature. In order to understand the physical implications of our results better, we designed a bivariate Markov process, parameterised on the basis of the atmospheric observational data by introducing a slow dummy variable. The time series generated by this model, analysed both in time and frequency domains, tallied with the real ones very well. They accounted for both the deceptive scaling found in literature and the correlation details enhanced by our analysis. Our results seem to evidence the presence of slow fluctuations from another climatic sub-system such as ocean, which inflates temperature variance up to several months. They advise more precise re-analyses of temperature time series before suggesting dynamical paradigms useful for Climate modelling and for the assessment of Climate Change.

  3. 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.

  4. Tuning the Polarization State of Light over a Broad Frequency Range with Metasurfaces

    NASA Astrophysics Data System (ADS)

    Wang, Mu; Jiang, Shang-Chi; Wang, Zheng-Han; Xiong, Xiang; Peng, Ru-Wen; Nanjing University Team

    Controlling the polarization state, the transmission direction and the phase of light within a confined space is an important issue in optics. By integrating metallic metastructure and dielectric interlayer, it is possible to realize the dispersion-free broadband device on sub-wavelength scale, where the strong response of the metallic structures helps to decrease the device size while the dielectric interlayer helps to eliminate the dispersion simultaneously in both the amplitude and the phase difference of the reflected/transmitted light. As an examples to apply this concept, a broadband quarter-wave plate and a half-wave plate are experimentally demonstrated. By carefully selecting the structural parameters, the polarization state of light can be freely tuned across a broad frequency range, and all of the polarization states on the Poincaré sphere can be realized dispersion free. Some contents of this talk can be found in the following references: [1] S.-C. Jiang, et al., High-efficiency generation of circularly polarized light via symmetry-induced anomalous reflection,Physical Review B 91, 125421 (2015), [2] S.-C. Jiang, et al., Controlling the Polarization State of Light with a Dispersion-Free Metastructure, Physical Review X 4, 021026 (2014), [3] X. Xiong, et al., Metallic stereostructured layer: an approach for broadband polarization state manipulation,Applied Physics Letters 105, 201105 (2014).

  5. Accessibility

    EPA Pesticide Factsheets

    Federal laws, including Section 508 of the Rehabilitation Act, mandate that people with disabilities have access to the same information that someone without a disability would have. 508 standards cover electronic and information technology (EIT) products.

  6. 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.

  7. 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…

  8. Accurate displacement-measuring interferometer with wide range using an I2 frequency-stabilized laser diode based on sinusoidal frequency modulation

    NASA Astrophysics Data System (ADS)

    Vu, Thanh-Tung; Higuchi, Masato; Aketagawa, Masato

    2016-10-01

    We propose the use of the sinusoidal frequency modulation technique to improve both the frequency stability of an external cavity laser diode (ECLD) and the measurement accuracy and range of a displacement-measuring interferometer. The frequency of the ECLD was modulated at 300 kHz by modulating the injection current, and it was locked to the b21 hyperfine component of the transition 6-3, P(33), 127I2 (633 nm) by the null method. A relative frequency stability of 6.5  ×  10-11 was achieved at 100 s sampling time. The stabilized ECLD was then utilized as a light source for an unbalanced Michelson interferometer. In the interferometer, the displacement and direction of the target mirror can be determined using a Lissajous diagram based on two consecutive and quadrant-phase harmonics of the interference signal. Generally, the measurement range of the interferometer by the proposed method is limited by the modulation index and the signal-to-noise ratio of the harmonics. To overcome this drawback, suitable consecutive harmonic pairs were selected for the specific measurement ranges to measure the displacement. The displacements determined in the specific ranges by the proposed method were compared with those observed by a commercial capacitive sensor. From the comparison, the proposed method has high precision to determine the displacement. The measurement range was also extended up to 10 m by selecting a suitable modulation index and suitable consecutive pairs of harmonics.

  9. A hybrid single-end-access MZI and Φ-OTDR vibration sensing system with high frequency response

    NASA Astrophysics Data System (ADS)

    Zhang, Yixin; Xia, Lan; Cao, Chunqi; Sun, Zhenhong; Li, Yanting; Zhang, Xuping

    2017-01-01

    A hybrid single-end-access Mach-Zehnder interferometer (MZI) and phase sensitive OTDR (Φ-OTDR) vibration sensing system is proposed and demonstrated experimentally. In our system, the narrow optical pulses and the continuous wave are injected into the fiber through the front end of the fiber at the same time. And at the rear end of the fiber, a frequency-shift-mirror (FSM) is designed to back propagate the continuous wave modulated by the external vibration. Thus the Rayleigh backscattering signals (RBS) and the back propagated continuous wave interfere with the reference light at the same end of the sensing fiber and a single-end-access configuration is achieved. The RBS can be successfully separated from the interference signal (IS) through digital signal process due to their different intermediate frequency based on frequency division multiplexing technique. There is no influence between these two schemes. The experimental results show 10 m spatial resolution and up to 1.2 MHz frequency response along a 6.35 km long fiber. This newly designed single-end-access setup can achieve vibration events locating and high frequency events response, which can be widely used in health monitoring for civil infrastructures and transportation.

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

    NASA Astrophysics Data System (ADS)

    Merezhkin, V. G.

    2009-06-01

    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 τ E ( bar n_e ) in the range of low values of bar n_e and <ν{/e *}> ≤ 1. The similar character of electron energy confinement in this range, which expands with increasing magnetic field B 0, has stimulated the search for dimensionless parameters and simple physical models that would explain the experimentally observed dependences χ e ˜ 1/ n e and τ Ee ˜ bar n_e . In 1987, T. Okhawa showed that the experimental data were satisfactorily described by the formula χ e⊥ = ( c 2/ω{/pe 2}) ν 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 ν e / qR. In 2004, J. Callen took into account the decrease in the fraction of transient electrons with increasing toroidal ratio ɛ = r/R and corrected the coefficient c 2/ω{/pe 2} in Okhawa equation by the factor σ{‖/Sp}/σ{‖/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 χ e⊥ will coincide with the T-11 scaling: χ{/e an} ∞ ɛ1.75( T e / A i )0.5/( n e qR) at A i = 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 ˜( c/ω pe )( m i / m e )1/4. In this case, the calculated coefficient of electron and ion diffusion D is close to D an ≈ χ{/e an}/2.

  11. 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.

  12. 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

    2015-12-30

    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.

  13. 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

  14. 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.

  15. 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.

  16. Preserving Range and Airspace Access for the Air Force Mission: Striving for a Strategic Vantage Point

    DTIC Science & Technology

    2011-01-01

    turbines on land now set aside for Air Force use, and the increasing demand for airspace to accom- modate the growth in civilian air traffic. • next...to ranges, energy development that seeks to place wind turbines on land now set aside for Air Force use, and increasing demand for sufficient... turbine towers may create a hazard to low-flying aircraft and thus preclude low-level training. Wind turbines tend to be located in gaps with higher

  17. 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.

  18. 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.

  19. HIGH DYNAMIC RANGE OBSERVATIONS OF SOLAR CORONAL TRANSIENTS AT LOW RADIO FREQUENCIES WITH A SPECTRO-CORRELATOR

    SciTech Connect

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

    2016-02-15

    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.

  20. 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).

  1. 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.

  2. 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.

  3. 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.

  4. Dielectric properties of skeletal muscle during ischemia in the frequency range from 50 Hz to 200 MHz.

    PubMed

    Schäfer, M; Kirlum, H J; Schlegel, C; Gebhard, M M

    1999-04-20

    The complex dielectric properties of canine skeletal muscles were measured at 25 degrees C during ischemia in the frequency range from 50 Hz to 200 MHz. The dielectric spectrum of skeletal muscle shows an alpha-dispersion below 1 kHz and a beta-dispersion with a relaxation frequency of about 100 kHz. The alpha-dispersion disappears between 450 and 500 min of ischemia time, the same time during which mechanical contraction was observed, and was restored later. During ischemia, the beta-dispersion is shifted continuously to higher frequencies; and at frequencies above 50 MHz, a decrease of the real part of the dielectric permittivity was measured. The dielectric loss factor decreases during ischemia at frequencies below 500 kHz, only interrupted by a short increase, coinciding with the disappearance of the alpha-dispersion. The principal processes that happen during ischemia inside the skeletal muscle tissues were studied with the help of a model especially designed to simulate membrane effects on the dielectric spectrum. The disappearance of the alpha-dispersion is explained by an increase of conductivity in the membrane of the sarcoplasmic reticulum. Shifting beta-dispersion to higher frequencies is a result of metabolically produced ions and therefore increasing conductivity of the intracellular medium. Decreasing dielectric permittivity at frequencies above 50 MHz and decreasing dielectric loss factor at low frequencies are caused by the cell edema.

  5. 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.

  6. 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.

  7. User-access-frequency statistics based hotspot adjustment in all-optically interconnected metro-embedded datacenters

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Guo, Hongxiang; Zhang, Dongxu; Wu, Jian; Cao, Xiaoyuan; Yoshikane, Noboru; Tsuritani, Takehiro; Morita, Itsuro

    2016-12-01

    Traditional datacenters are typically deployed with highly clustered resources and built-in remote areas far away from users, requiring huge floor space and power consumption. The proposed metro-embedded datacenter architecture with distributed resources spreading across the metro area close to users could be a promising solution, which exhibits lower access latency and more flexibility for service orchestration. Based on metro-embedded datacenter, we propose the conception of "follow the user" with user access location aware dynamic hotspots adjustments. By enabling service hotspots adjustment according to user access frequency statistics, the quality of service can be significantly improved in terms of reduced latency. Finally, we experimentally demonstrate low-latency service provisioning based on the proposed principle.

  8. Performances of a VLSI wide dynamic range current-to-frequency converter for strip ionization chambers

    NASA Astrophysics Data System (ADS)

    Bonazzola, G. C.; Cirio, R.; Donetti, M.; Marchetto, F.; Mazza, G.; Peroni, C.; Zampieri, A.

    1998-02-01

    In this paper we report on the design and test of a 14-channel VLSI chip to perform the current to frequency conversion for parallel plate strip ionization chambers. The chambers measure the intensity and the geometrical characteristics of a therapeutical beam.

  9. 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.

  10. Flat lensing in the visible frequency range by woodpile photonic crystals.

    PubMed

    Maigyte, L; Purlys, V; Trull, J; Peckus, M; Cojocaru, C; Gailevičius, D; Malinauskas, M; Staliunas, K

    2013-07-15

    We experimentally demonstrate full two-dimensional focalization of light beams at visible frequencies by a three-dimensional woodpile photonic crystal. The focalization (the flat lensing) with focal distances of the order of 50-70 μm is experimentally demonstrated. Experimental results are compared with numerical calculations and interpreted by harmonic expansion studies.

  11. 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.

  12. 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.

  13. [The peculiarities of the microwave in the frequency range of 51-52 GHz spectrum effects on E. coli cells].

    PubMed

    Ushakov, V L; Alipov, E D; Shcheglov, V S; Beliaev, I Ia

    2006-01-01

    The effects of microwaves on conformation of nucleoids in E. coli cells were studied by the method of anomalous viscosity time dependence (AVTD) at various frequencies in the range of 51-52 GHz and the power flux density of 100 microW/cm(2) . Linearly polarized microwaves resulted in significant effects within specific frequency windows of resonance type. The distances between frequency windows were in the range of 55-180 MHz. Only one of two possible circular polarizations, left-handed or right-handed, was shown to be effective at each frequency window. The sign of effective circular polarization alternated between frequency windows. We show that the effects of microwaves on E. coli cells as measured by the AVTD technique are not caused by adhesion of cells. The half-width of the 51.575 GHz resonance was measured to be 120+/-20 MHz. This value is very close to the half-width of the 51.755 GHz resonance as it has previously been determined at the same power flux density. The obtained data suggest similar targets for effects of microwaves at these two resonance frequencies and provide evidence for non-thermal nature of observed microwave effects.

  14. Measurement comparison among time-domain, FTIR and VNA-based spectrometers in the THz frequency range

    NASA Astrophysics Data System (ADS)

    Oberto, L.; Bisi, M.; Kazemipour, A.; Steiger, A.; Kleine-Ostmann, T.; Schrader, T.

    2017-02-01

    In this paper we present the outcome of the first international comparison in the terahertz frequency range among three different kinds of spectrometers. A Fourier-Transform infrared spectrometer, a vector network analyzer and a time-domain spectrometer have been employed for measuring the complex refractive index of three travelling standards made of selected dielectric materials in order to offer a wide enough range of parameters to be measured. The three spectrometers have been compared in terms of measurement capability and uncertainty.

  15. In vitro Neurons in Mammalian Cortical Layer 4 Exhibit Intrinsic Oscillatory Activity in the 10- to 50-Hz Frequency Range

    NASA Astrophysics Data System (ADS)

    Llinas, Rodolfo R.; Grace, Anthony A.; Yarom, Yosef

    1991-02-01

    We report here the presence of fast subthreshold oscillatory potentials recorded in vitro from neurons within layer 4 of the guinea pig frontal cortex. Two types of oscillatory neurons were recorded: (i) One type exhibited subthreshold oscillations whose frequency increased with membrane depolarization and encompassed a range of 10-45 Hz. Action potentials in this type of neuron demonstrated clear after-hyperpolarizations. (ii) The second type of neuron was characterized by narrow-frequency oscillations near 35-50 Hz. These oscillations often outlasted the initiating depolarizing stimulus. No calcium component could be identified in their action potential. In both types of cell the subthreshold oscillations were tetrodotoxin-sensitive, indicating that the depolarizing phase of the oscillation was generated by a voltage-dependent sodium conductance. The initial depolarizing phase was followed by a potassium conductance responsible for the falling phase of the oscillatory wave. In both types of cell, the subthreshold oscillation could trigger spikes at the oscillatory frequency, if the membrane was sufficiently depolarized. Combining intracellular recordings with Lucifer yellow staining showed that the narrow-frequency oscillatory activity was produced by a sparsely spinous interneuron located in layer 4 of the cortex. This neuron has extensive local axonal collaterals that ramify in layers 3 and 4 such that they may contribute to the columnar synchronization of activity in the 40- to 50-Hz range. Cortical activity in this frequency range has been proposed as the basis for the "conjunctive properties" of central nervous system networks.

  16. Multi-frequency Operation of a MEMS Vibration Energy Harvester by Accessing Five Orders of Parametric Resonance

    NASA Astrophysics Data System (ADS)

    Jia, Y.; Yan, J.; Soga, K.; Seshia, A. A.

    2013-12-01

    The mechanical amplification effect of parametric resonance has the potential to outperform direct resonance by over an order of magnitude in terms of power output. However, the excitation must first overcome the damping-dependent initiation threshold amplitude prior to accessing this more profitable region. In addition to activating the principal (1st order) parametric resonance at twice the natural frequency ω0, higher orders of parametric resonance may be accessed when the excitation frequency is in the vicinity of 2ω0/n for integer n. Together with the passive design approaches previously developed to reduce the initiation threshold to access the principal parametric resonance, vacuum packaging (< 10 torr) is employed to further reduce the threshold and unveil the higher orders. A vacuum packaged MEMS electrostatic harvester (0.278 mm3) exhibited 4 and 5 parametric resonance peaks at room pressure and vacuum respectively when scanned up to 10 g. At 5.1 ms-2, a peak power output of 20.8 nW and 166 nW is recorded for direct and principal parametric resonance respectively at atmospheric pressure; while a peak power output of 60.9 nW and 324 nW is observed for the respective resonant peaks in vacuum. Additionally, unlike direct resonance, the operational frequency bandwidth of parametric resonance broadens with lower damping.

  17. 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.

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

    DOEpatents

    Nekoogar, Faranak [San Ramon, CA; Dowla, Farid U [Castro Valley, CA

    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.

  19. 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.

  20. 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*∥∥.

  1. Influence of PDMS encapsulation on the sensitivity and frequency range of fiber-optic interferometer

    NASA Astrophysics Data System (ADS)

    Nedoma, Jan; Fajkus, Marcel; Vasinek, Vladimir

    2016-10-01

    Fiber-optic sensors are one of the dynamically developing areas of photonics and photonic applications. This group of sensors can also include fiber-optic interferometers which enable very sensitive sensing. They are entirely passive regarding power supply, and immune to electromagnetic interference. This type of sensor is dependent on the phase change. It mostly used in the field which requires high measurement accuracy. We can achieve a change of sensitivity in the order of 10-8. The fundamental problem of fiber-optic interferometry is a design and imposition (encapsulation) of the measuring arm and reference arm of the interferometer. Polydimethylsiloxane elastomer (PDMS) is one of the possibilities to encapsulation of the sensory arm. Two-component PDMS Sylgard 184 is used type. The article analyzes the effect of encapsulation into a PDMS of the measuring arm of the interferometer to frequency response and sensitivity of the Mach-Zehnder interferometer with the division of power in a ratio of 1:1 (measuring arm and reference arm). Input power set to a reference value of 1 mW, this value was constant for all performed experimental measurements. The generator of a harmonic signal with fixed amplitude signal used for analysis of the frequency characteristic of the interferometer. The application written in LabView development environment, evaluated the amplitude-frequency spectra of the signal. Repeated test of assembled prototype verified the measured results.

  2. Aerial low-frequency hearing in captive and free-ranging harbour seals (Phoca vitulina) measured using auditory brainstem responses.

    PubMed

    Lucke, Klaus; Hastie, Gordon D; Ternes, Kerstin; McConnell, Bernie; Moss, Simon; Russell, Deborah J F; Weber, Heike; Janik, Vincent M

    2016-12-01

    The hearing sensitivity of 18 free-ranging and 10 captive harbour seals (Phoca vitulina) to aerial sounds was measured in the presence of typical environmental noise through auditory brainstem response measurements. A focus was put on the comparative hearing sensitivity at low frequencies. Low- and mid-frequency thresholds appeared to be elevated in both captive and free-ranging seals, but this is likely due to masking effects and limitations of the methodology used. The data also showed individual variability in hearing sensitivity with probable age-related hearing loss found in two old harbour seals. These results suggest that the acoustic sensitivity of free-ranging animals was not negatively affected by the soundscape they experienced in the wild.

  3. Full-range swept source optical coherence tomography based on carrier frequency by transmissive dispersive optical delay line.

    PubMed

    Wu, Tong; Ding, Zhihua; Wang, Chuan; Chen, Minghui

    2011-12-01

    A high speed swept source optical coherence tomography (SS-OCT) system capable of full-range imaging is presented. Wave-number carrier frequency is introduced into the spectral interference signal by a transmissive dispersive optical delay line (TDODL). High carrier frequency in the spectral interference signal corresponding to an equivalent distance-shift is exploited to obtain full-range OCT imaging. Theoretical development is conducted with the instantaneous coherence function introduced for a complete description of a spectral interference signal. Performance advantage of the TDODL-based method over the conventional approach where only one side (positive or negative path length difference) is used for imaging to avoid overlaying mirror artifacts is confirmed by the measured envelopes of spectral interference signal. Feasibility of the proposed method for full-range imaging is validated in a custom-built SS-OCT system by in vivo imaging of a biological sample.

  4. Full-range swept source optical coherence tomography based on carrier frequency by transmissive dispersive optical delay line

    NASA Astrophysics Data System (ADS)

    Wu, Tong; Ding, Zhihua; Wang, Chuan; Chen, Minghui

    2011-12-01

    A high speed swept source optical coherence tomography (SS-OCT) system capable of full-range imaging is presented. Wave-number carrier frequency is introduced into the spectral interference signal by a transmissive dispersive optical delay line (TDODL). High carrier frequency in the spectral interference signal corresponding to an equivalent distance-shift is exploited to obtain full-range OCT imaging. Theoretical development is conducted with the instantaneous coherence function introduced for a complete description of a spectral interference signal. Performance advantage of the TDODL-based method over the conventional approach where only one side (positive or negative path length difference) is used for imaging to avoid overlaying mirror artifacts is confirmed by the measured envelopes of spectral interference signal. Feasibility of the proposed method for full-range imaging is validated in a custom-built SS-OCT system by in vivo imaging of a biological sample.

  5. Shielding properties of composite materials based on epoxy resin with graphene nanoplates in the microwave frequency range

    NASA Astrophysics Data System (ADS)

    Volynets, N. I.; Bychenok, D. S.; Lyubimov, A. G.; Kuzhir, P. P.; Maksimenko, S. A.; Baturkin, S. A.; Klochkov, A. Ya.; Mastrucci, M.; Micciulla, F.; Bellucci, S.

    2016-12-01

    Analysis of the electromagnetic properties of composite materials based on epoxy resin with the addition of 0.5 wt % graphene nanoplates in the frequency range of 26-37 GHz is performed. The influence of types of epoxy resin with different viscosities and the type of solvent used (ethanol, acetone) on the electromagnetic response in this frequency range are determined. It is established that the least viscous epoxy resin, Epikote 828, and solvent ethanol are most effective for creation of a shielding covering in the microwave range. Composite materials with optimal composition provide attenuation of the electromagnetic signal at a level at least 10 dB in power for a film thickness of 1.1 mm.

  6. Retrieving sea-wave spectra using satellite-imagery spectra in a wide range of frequencies

    NASA Astrophysics Data System (ADS)

    Bondur, V. G.; Dulov, V. A.; Murynin, A. B.; Ignatiev, V. Yu.

    2016-11-01

    A method to register sea-wave spectra using optical aerospace imagery has been developed. The method is based on the use of retrieval operators both in areas of high and low spatial frequencies, including the areas of spectral maximum. The approach to adjust and validate the method developed using sea truth data obtained by string wave recorders has been suggested. This paper presents the results of using the suggested method to study sea-wave spectra using high-resolution satellite imagery for various water areas under different conditions of wave generation.

  7. 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.

  8. SSVEP-BCI implementation for 37-40 Hz frequency range.

    PubMed

    Müller, Sandra Mara Torres; Diez, Pablo F; Bastos-Filho, Teodiano Freire; Sarcinelli-Filho, Mário; Mut, Vicente; Laciar, Eric

    2011-01-01

    This work presents a Brain-Computer Interface (BCI) based on Steady State Visual Evoked Potentials (SSVEP), using higher stimulus frequencies (>30 Hz). Using a statistical test and a decision tree, the real-time EEG registers of six volunteers are analyzed, with the classification result updated each second. The BCI developed does not need any kind of settings or adjustments, which makes it more general. Offline results are presented, which corresponds to a correct classification rate of up to 99% and a Information Transfer Rate (ITR) of up to 114.2 bits/min.

  9. 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.

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

    SciTech Connect

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

    2013-10-15

    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.

  11. Range Detection of the Extremely Low-Frequency Magnetic Field Produced by Laptop's AC Adapter

    NASA Astrophysics Data System (ADS)

    Brodić, Darko; Amelio, Alessia

    2017-02-01

    Human exposure to extremely low frequency magnetic field represents a risk to their health. This paper takes into consideration the level of an extremely low-frequency magnetic field between 30 and 300 Hz emitted by an AC laptop adapter. The experiment consists of testing 17 different AC adapters for laptops. During the testing, laptops are operated in a normal operating conditions as well as under heavy load. The magnetic field measurement is conducted in the area around the AC adapter. Obtained data is evaluated according to the critical level of the magnetic field proposed by safety standards. Furthermore, data is classified by a K-medians method in order to determine the critical levels of the magnetic field exposure in the nearby area of the AC adapter. Obtained classifications are evaluated according to safety standards, giving a critical analysis of magnetic field areas at risk. Due to emission of a very strong magnetic field in certain areas, a recommendation for safety use of the AC adapter is proposed.

  12. Inkjet Printed Wire-Grid Polarizers for the THz Frequency Range

    NASA Astrophysics Data System (ADS)

    Farid, A.; Laurita, N. J.; Tehrani, B.; Hester, J. G.; Tentzeris, M. M.; Armitage, N. P.

    2016-11-01

    We have investigated the use of inkjet printing technology for the production of THz range wire-grid polarizers using time-domain terahertz spectroscopy (TDTS). Such technology affords an inexpensive and reproducible way of quickly manufacturing THz range metamaterial structures. As a proof-of-concept demonstration, numerous thin silver-nanoparticle ink lines were printed using a Dimatix DMP-2831 printer. We investigated the optimal printing geometry of the polarizers by examining a number of samples with printed wires of varying thickness and spacing. We also investigated the polarization properties of multiply-stacked polarizers.

  13. Inkjet Printed Wire-Grid Polarizers for the THz Frequency Range

    NASA Astrophysics Data System (ADS)

    Farid, A.; Laurita, N. J.; Tehrani, B.; Hester, J. G.; Tentzeris, M. M.; Armitage, N. P.

    2017-03-01

    We have investigated the use of inkjet printing technology for the production of THz range wire-grid polarizers using time-domain terahertz spectroscopy (TDTS). Such technology affords an inexpensive and reproducible way of quickly manufacturing THz range metamaterial structures. As a proof-of-concept demonstration, numerous thin silver-nanoparticle ink lines were printed using a Dimatix DMP-2831 printer. We investigated the optimal printing geometry of the polarizers by examining a number of samples with printed wires of varying thickness and spacing. We also investigated the polarization properties of multiply-stacked polarizers.

  14. 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.

  15. 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.

  16. Optical frequency domain imaging with a rapidly swept laser in the 815-870 nm range

    NASA Astrophysics Data System (ADS)

    Lim, H.; de Boer, J. F.; Park, B. H.; Lee, E. C.; Yelin, R.; Yun, S. H.

    2006-06-01

    Optical frequency domain imaging (OFDI) in the 800-nm biological imaging window is demonstrated by using a novel wavelength-swept laser source. The laser output is tuned continuously from 815 to 870 nm at a 43.2-kHz repetition rate with 7-mW average power. Axial resolution of 10-μm in biological tissue and peak sensitivity of 96 dB are achieved. In vivo imaging of Xenopus laevis is demonstrated with an acquisition speed of 84 frames per second (512 axial lines per frame). This new imaging technique may prove useful in comprehensive retinal screening for medical diagnosis and contrast-agent-based imaging for biological investigations.

  17. 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.

  18. Impact of major and minor mode on EEG frequency range activities of music processing as a function of expertise.

    PubMed

    Jenni, Raoul; Oechslin, Mathias S; James, Clara E

    2017-04-24

    Processing western tonal music may yield distinct brain responses depending on the mode of the musical compositions. Although subjective feelings in response to major and minor mode are well described, the underlying brain mechanisms and their development with increasing expertise have not been thoroughly examined. Using high-density electroencephalography, the present study investigated neuronal activities in the frequency domain in response to polyphone musical compositions in major and minor mode in non-musicians, amateurs and experts. During active listening decrease of theta- and gamma-frequency range activities occurred with increasing expertise in right posterior regions, possibly reflecting enhanced processing efficiency. Moreover, minor and major compositions distinctively modulated synchronization of neuronal activities in high frequency ranges (beta and gamma) in frontal regions, with increased activity in response to minor compositions in musicians and in experts in particular. These results suggest that high-frequency electroencephalographic (EEG) activities carry information about musical mode, showing gradual increase of processing efficiency and sensitivity with musical expertise.

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

    PubMed

    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 o; Costa, Daniel P; Bost, Charles-André; Aoki, Kagari; Amano, Masao; Trathan, Phil; Shapiro, Ari; Naito, Yasuhiko

    2007-02-22

    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) (R(2)= 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.

  20. 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.

  1. Experimental study of attenuation and dispersion over a broad frequency range: 2. The universal scaling of polycrystalline materials

    NASA Astrophysics Data System (ADS)

    McCarthy, Christine; Takei, Yasuko; Hiraga, Takehiko

    2011-09-01

    In order to extend the range of conditions that can be obtained in experiments, we have measured the viscoelastic properties of polycrystalline organic borneol, as an analogue to mantle rock. Using a custom fabricated apparatus, the Young's modulus E and attenuation QE-1 were measured accurately over a broad frequency range (10-4 ≤ f (Hz) ≤ 2.15) and at low strain amplitude (10-5-10-6). Creep experiments were performed with the same apparatus to measure the steady state viscosity. Anelasticity and viscosity were measured at high homologous temperatures (T = 22-48°C; T/Tm = 0.61-0.67) and various grain sizes (3-22 μm), the growth of which was controlled by annealing. Using the measured viscosities η and the unrelaxed modulus EU determined from ultrasonic experiments, the frequency of the entire data set was normalized by the Maxwell frequency fM = EU/η, resulting in E and Q-1 master curves. The Q-1 data from previous studies on olivine-dominated samples also collapse onto the same curve when scaled by fM,, demonstrating the universality of anelasticity for polycrystalline materials. The similitude by the Maxwell frequency scaling indicates that the dominant mechanism for the anelasticity observed in this study and in previous studies is diffusionally accommodated grain boundary sliding. A generalized formulation for this similitude is provided to extrapolate the experimental data to velocity and attenuation of seismic shear waves.

  2. SmEdA vibro-acoustic modelling in the mid-frequency range including the effect of dissipative treatments

    NASA Astrophysics Data System (ADS)

    Hwang, H. D.; Maxit, L.; Ege, K.; Gerges, Y.; Guyader, J.-L.

    2017-04-01

    Vibro-acoustic simulation in the mid-frequency range is of interest for automotive and truck constructors. The dissipative treatments used for noise and vibration control such as viscoelastic patches and acoustic absorbing materials must be taken into account in the problem. The Statistical modal Energy distribution Analysis (SmEdA) model consists in extending Statistical Energy Analysis (SEA) to the mid-frequency range by establishing power balance equations between the modes of the different subsystems. The modal basis of uncoupled-subsystems that can be estimated by the finite element method in the mid-frequency range is used as input data. SmEdA was originally developed by considering constant modal damping factors for each subsystem. However, this means that it cannot describe the local distribution of dissipative materials. To overcome this issue, a methodology is proposed here to take into account the effect of these materials. This methodology is based on the finite element models of the subsystems that include well-known homogenized material models of dissipative treatments. The Galerkin method with subsystem normal modes is used to estimate the modal damping loss factors. Cross-modal coupling terms which appear in the formulation due to the dissipative materials are assumed to be negligible. An approximation of the energy sharing between the subsystems damped by dissipative materials is then described by SmEdA. The different steps of the method are validated experimentally by applying it to a laboratory test case composed of a plate-cavity system with different configurations of dissipative treatments. The comparison between the experimental and the simulation results shows good agreement in the mid-frequency range.

  3. Efficiency improvement of heat exchangers by the rational choice of the range of frequencies of electromagnetic water treatment

    NASA Astrophysics Data System (ADS)

    Runov, D. M.; Laptev, A. G.

    2015-05-01

    The electromagnetic water treatment is considered as one of the reagentless methods to reduce the scaling and to improve the cooling efficiency of high-temperature gas flows. It is achieved by the rational choice of the frequency range under laboratory conditions. The choice is made by the lowest particle size distribution of the precipitated particles. The time analysis of the content of hardness salts in the treated water is carried out at the input to and output of the heat exchanger.

  4. 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.

  5. An analysis of dielectric properties of synthetic ballast water at frequencies ranging from 300 to 3000 MHz.

    PubMed

    Boldor, Dorin; Ortego, Jeffrey; Rusch, Kelly A

    2008-01-01

    Ballast water presents an important vector for introduction of aquatic invasive species in the coastal waters around the world. Currently there are no established technologies proven to completely eliminate this problem due to the particularities of the ballasting and de-ballasting operations (extremely large volumes of water, efficiency at destroying macro and micro organisms, environmental issues associated with chemical treatments). Continuous microwave heating presents a potential solution to this problem, but the design of suitable applicators depends on the dielectric properties of the ballast water to be processed. The study presented in this paper is focused on the dielectric properties (dielectric constant--epsilon'; dielectric loss--epsilon") of synthetic ballast water inoculated with four organisms at seven different temperatures in the frequency range of 300 to 3000 MHz. The dielectric properties of the mixtures were determined using a network analyzer and a dielectric probe kit using the open-ended coaxial probe method. Numerical analysis was performed on data collected across all frequencies involved with an emphasis placed on F.C.C. allotted frequencies of 433, 915 and 2450 MHz. The dielectric constant was relatively independent of frequency and the organism used, but it showed a remarkable decrease with temperature. The dielectric loss showed an extreme decrease with increasing frequency, marked differences between the different organisms and between different growth stages of the same organism, and a large relatively linear increase with increasing temperature.

  6. 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.

  7. Understanding and Utilizing Waveguide Invariant Range-frequency Striations in Ocean Acoustic Waveguides

    DTIC Science & Technology

    2011-02-01

    slope of the line connecting non-SRBR modes is sig- nif cantly different than the slope of the line connecting the SRBR modes. Thus, the non-SRBR modes...maximum range that one expects to see the source. All results presented in this chapter used Eqs. (3.8) and (3.9) with r = 5000 m, c1 = 1500 m/s, and c2...present work, ∆f was determined by using Eqs. (3.21) and (3.18) with c1 = 1500 m/s, c2 = 1800 m/s, r = 1000 meters, resulting in ∆f ≈ 81 Hz. ∆r was

  8. Perception of pitch location within a speaker's range: fundamental frequency, voice quality and speaker sex.

    PubMed

    Bishop, Jason; Keating, Patricia

    2012-08-01

    How are listeners able to identify whether the pitch of a brief isolated sample of an unknown voice is high or low in the overall pitch range of that speaker? Does the speaker's voice quality convey crucial information about pitch level? Results and statistical models of two experiments that provide answers to these questions are presented. First, listeners rated the pitch levels of vowels taken over the full pitch ranges of male and female speakers. The absolute f0 of the samples was by far the most important determinant of listeners' ratings, but with some effect of the sex of the speaker. Acoustic measures of voice quality had only a very small effect on these ratings. This result suggests that listeners have expectations about f0s for average speakers of each sex, and judge voice samples against such expectations. Second, listeners judged speaker sex for the same speech samples. Again, absolute f0 was the most important determinant of listeners' judgments, but now voice quality measures also played a role. Thus it seems that pitch level judgments depend on voice quality mostly indirectly, through its information about sex. Absolute f0 is the most important information for deciding both pitch level and speaker sex.

  9. 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.

  10. Dielectric response of wurtzite gallium nitride in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Hibberd, M. T.; Frey, V.; Spencer, B. F.; Mitchell, P. W.; Dawson, P.; Kappers, M. J.; Oliver, R. A.; Humphreys, C. J.; Graham, D. M.

    2016-12-01

    We report on the characterization of the intrinsic, anisotropic, dielectric properties of wurtzite gallium nitride in the spectral range of 0.5-11 THz, using terahertz time-domain spectroscopy. The ordinary (ε˜⊥) and extraordinary (ε˜∥) components of the complex dielectric function were determined experimentally for a semi-insulating, m-plane gallium nitride single crystal, providing measurements of the refractive indices (n⊥,∥) and absorption coefficients (α⊥,∥) . These material parameters were successfully modeled by considering the contribution of the optical phonon modes, measured using Raman spectroscopy, to the dielectric function, giving values for the relative static dielectric constants of ε0⊥ = 9.22 ± 0.02 and ε0∥ = 10.32 ± 0.03 for wurtzite gallium nitride.

  11. Wide range tuning of resonant frequency for a vortex core in a regular triangle magnet.

    PubMed

    Yakata, Satoshi; Tanaka, Terumitsu; Kiseki, Kohei; Matsuyama, Kimihide; Kimura, Takashi

    2013-12-20

    A magnetic vortex structure stabilized in a micron or nano-sized ferromagnetic disk has a strong potential as a unit cell for spin-based nano-electronic devices because of negligible magnetostatic interaction and superior thermal stability. Moreover, various intriguing fundamental physics such as bloch point reversal and symmetry breaking can be induced in the dynamical behaviors in the magnetic vortex. The static and dynamic properties of the magnetic vortex can be tuned by the disk dimension and/or the separation distance between the disks. However, to realize these modifications, the preparations of other devices with different sample geometries are required. Here, we experimentally demonstrate that, in a regular-triangle Permalloy dot, the dynamic properties of a magnetic vortex are greatly modified by the application of the in-plane magnetic field. The obtained wide range tunability based on the asymmetric position dependence of the core potential provides attractive performances in the microwave spintronic devices.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Empirical dependence of acoustic transmission scintillation statistics on bandwidth, frequency, and range in New Jersey continental shelf.

    PubMed

    Andrews, Mark; Chen, Tianrun; Ratilal, Purnima

    2009-01-01

    The scintillation statistics of broadband acoustic transmissions are determined as a function of signal bandwidth B, center frequency f(c), and range with experimental data in the New Jersey continental shelf. The received signal intensity is shown to follow the Gamma distribution implying that the central limit theorem has led to a fully saturated field from independent multimodal propagation contributions. The Gamma distribution depends on the mean intensity and the number of independent statistical fluctuations or coherent cells micro of the received signal. The latter is calculated for the matched filter, the Parseval sum, and the bandpassed center frequency, all of which are standard ocean acoustic receivers. The number of fluctuations mu of the received signal is found to be an order of magnitude smaller than the time-bandwidth product TB of the transmitted signal, and to increase monotonically with relative bandwidth Bfc. A computationally efficient numerical approach is developed to predict the mean intensity and the corresponding broadband transmission loss of a fluctuating, range-dependent ocean waveguide by range and depth averaging the output of a time-harmonic stochastic propagation model. This model enables efficient and accurate estimation of transmission loss over wide areas, which has become essential in wide-area sonar imaging applications.

  18. Dynamic registration of the absorption spectrum of water in the SiO(2) nanopores in high-frequency range.

    PubMed

    Sinitsa, L N; Lugovskoy, A A

    2010-11-28

    The high-frequency region was used to record the absorption spectrum of water in nanoscale pores during vacuum pumping or injection of water. The wide spectral range, which included the vibration overtones, allowed to resolve the structure of the absorption bands with variation of water concentration in the pores of SiO(2). The absorption bands of water clusters in the 4570-5400 cm(-1) range consist of well-resolved sub-bands with interpeak intervals of up to 580 cm(-1). When the pore diameter is decreased from 11.8 to 2.6 nm, the absorption bands of clusters in this frequency range are shifted by 530 cm(-1) in the direction of the water monomer which indicates an increase of hydrogen bond strength in confined water with an increase of the pore diameter. The spectrum recorded during water pumping is extremely variable in time, and the cluster dynamics in large pores (11.8 nm) differs greatly from the dynamics in small pores (2.6 nm). While all types of water clusters are removed from small pores uniformly, in the case of large pores, the water clusters relating to strong hydrogen bonds are removed from the sample at the beginning of the vacuum pumping and the loosely coupled clusters are removed later. The rate of this process is not steady and varies throughout pumping.

  19. Human sympathetic outflows to skin and muscle target organs fluctuate concordantly over a wide range of time-varying frequencies.

    PubMed

    Bernjak, Alan; Cui, Jian; Iwase, Satoshi; Mano, Tadaaki; Stefanovska, Aneta; Eckberg, Dwain L

    2012-01-15

    Frequency-domain analyses of simultaneously recorded skin and muscle sympathetic nerve activities may yield unique information on otherwise obscure central processes governing human neural outflows. We used wavelet transform and wavelet phase coherence methods to analyse integrated skin and muscle sympathetic nerve activities and haemodynamic fluctuations, recorded from nine healthy supine young men. We tested two null hypotheses: (1) that human skin and muscle sympathetic nerve activities oscillate congruently; and (2) that whole-body heating affects these neural outflows and their haemodynamic consequences in similar ways. Measurements included peroneal nerve skin and tibial nerve muscle sympathetic activities; the electrocardiogram; finger photoplethysmographic arterial pressure; respiration (controlled at 0.25 Hz, and registered with a nasal thermistor); and skin temperature, sweating, and laser-Doppler skin blood flow. We made recordings at ∼27°C, for ∼20 min, and then during room temperature increases to ∼38°C, over 35 min. We analysed data with a wavelet transform, using the Morlet mother wavelet and wavelet phase coherence, to determine the frequencies and coherences of oscillations over time. At 27°C, skin and muscle nerve activities oscillated coherently, at ever-changing frequencies between 0.01 and the cardiac frequency (∼1 Hz). Heating significantly augmented oscillations of skin sympathetic nerve activity and skin blood flow, arterial pressure, and R-R intervals, over a wide range of low frequencies, and modestly reduced coordination between skin and muscle sympathetic oscillations. These results suggest that human skin and muscle sympathetic motoneurones are similarly entrained by external influences, including those of arterial baroreceptors, respiration, and other less well-defined brainstem oscillators. Our study provides strong support for the existence of multiple, time-varying central sympathetic neural oscillators in human subjects.

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

    NASA Astrophysics Data System (ADS)

    Umchid, Sumet

    The primary objective of this research 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 of a novel, 100 MHz calibration technique the innovative elements of this research include implementation of a prototype FO sensor with an active diameter of about 10 hum that exhibits uniform sensitivity over the considered frequency range and does not require any spatial averaging corrections up to about 75 MHz. The calibration technique provided the sensitivity of conventional, finite aperture piezoelectric hydrophone probes as a virtually continuous function of frequency and allowed the verification of 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.

  1. Increase of TCR V beta accessibility within E beta regulatory region influences its recombination frequency but not allelic exclusion.

    PubMed

    Senoo, Makoto; Wang, Lili; Suzuki, Daisuke; Takeda, Naoki; Shinkai, Yoichi; Habu, Sonoko

    2003-07-15

    Seventy percent of the murine TCRbeta locus (475 kb) was deleted to generate a large deleted TCRbeta (beta(LD)) allele to investigate a possible linkage between germline transcription, recombination frequency, and allelic exclusion of the TCR Vbeta genes. In these beta(LD/LD) mice, the TCRbeta gene locus contained only four Vbeta genes at the 5' side of the locus, and consequently, the Vbeta10 gene was located in the original Dbeta1-Jbeta1cluster within the Ebeta regulatory region. We showed that the frequency of recombination and expression of the Vbeta genes are strongly biased to Vbeta10 in these mutant mice even though the proximity of the other three 5'Vbeta genes was also greatly shortened toward the Dbeta-Jbeta cluster and the Ebeta enhancer. Accordingly, the germline transcription of the Vbeta10 gene in beta(LD/LD) mice was exceptionally enhanced in immature double negative thymocytes compared with that in wild-type mice. During double negative-to-double positive transition of thymocytes, the level of Vbeta10 germline transcription was prominently increased in beta(LD/LD) recombination activating gene 2-deficient mice receiving anti-CD3epsilon Ab in vivo. Interestingly, however, despite the increased accessibility of the Vbeta10 gene in terms of transcription, allelic exclusion of this Vbeta gene was strictly maintained in beta(LD/LD) mice. These results provide strong evidence that increase of Vbeta accessibility influences frequency but not allelic exclusion of the TCR Vbeta rearrangement if the Vbeta gene is located in the Ebeta regulatory region.

  2. 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.

  3. 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.

  4. 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.

  5. Ultra-wideband coaxial hybrid coupler for load resilient ion cyclotron range of frequency heating at fusion plasmas

    SciTech Connect

    Kim, H. J.; Bae, Y. S.; Yang, H. L.; Kwak, J.-G.; Wang, S. J.; Kim, B. K.; Choi, J. J.

    2012-06-25

    We designed a high power and ultra-wideband two-section 3 dB coaxial hybrid coupler for load resilient ion cyclotron range of frequency heating by configuring asymmetric impedance matching using a three-dimensional simulation code, hfss. By adjusting the characteristic impedances of main and coupled lines of the hybrid coupler, we realized that the bandwidth of the proposed circuit is not only wider than that of a conventional three-section coupler, but also that the bandwidth is almost twice as wide compared to the conventional two-section hybrid coupler while maintaining the identical overall size.

  6. 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.

  7. 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.

  8. 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.

  9. Plasma production and heating in a tandem mirror central cell by radio-frequency waves in the ion cyclotron frequency range

    NASA Astrophysics Data System (ADS)

    Golovato, S. N.; Brau, K.; Casey, J.; Coleman, J.; Gerver, M. J.; Guss, W.; Hallock, G.; Horne, S.; Irby, J.; Kumazawa, R.; Kesner, J.; Lane, B.; Machuzak, J.; Moran, T.; Myer, R.; Post, R. S.; Sevillano, E.; Smith, D. K.; Sullivan, J. D.; Torti, R.; Wang, L.; Yasaka, Y.; Yao, X. Z.; Zielinski, J.

    1988-12-01

    Plasma production and heating in the central cell of the Tara tandem mirror [Nucl. Fusion 22, 549 (1982); Plasma Physics and Controlled Nuclear Fusion Research, 1986, Proceedings of the 11th International Conference, Kyoto, Japan (IAEA, Vienna, 1987), Vol. 2, p. 251] have been studied. Using radio-frequency excitation by a slot antenna in the ion cyclotron frequency range (ICRF), plasmas with a peak β⊥ of 3%, density of 4×1012 cm-3, ion temperature of 800 eV, and electron temperature of 75-100 eV were routinely produced. The plasma radius decreased with increasing ICRF power, causing reduced ICRF coupling and saturation of the plasma beta. About 70% of the applied ICRF power can be accounted for in direct heating of both ions and electrons. Wave field measurements have identified the applied ICRF to be the slow, ion cyclotron wave. In operation without end plugging, the plasma parameters were limited by poor axial confinement and the requirements for maintenance of magnetohydrodynamic stability and microstability.

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

    SciTech Connect

    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

    2015-09-10

    In this study, we present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme in order to study high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes of the magnetization on short time scales and nanometer spatial dimensions is achieved by combination of the developed excitation mechanism with a single photon counting electronics that is locked to the synchrotron operation frequency. The required mechanical stability is achieved by a compact design of the microscope. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with 35 nm 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.

  11. Microwave absorption studies of Cr-doped Co-U type hexaferrites over 2-18 GHz frequency range

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep; Meena, Ram Swaroop; Chatterjee, Ratnamala

    2016-11-01

    The effect of Cr3+ ions doping on the electromagnetic (EM) properties of polycrystalline U-type hexaferrite samples: Ba4Co2-3xCr2xFe36O60 (0.0≤x≤0.60, in steps of 0.15) have been studied. The X-ray diffraction (XRD) studies confirmed the formation of single U-type hexaferrite phase in all the prepared samples. Le Bail refinement of XRD patterns was used to calculate the lattice parameters 'a' and 'c'. The room temperature M-H studies indicate that the saturation magnetization (Ms) decreases and coercivity (Hc) increases with increasing Cr3+ ions concentration. The complex permittivity (ε* = ε ‧ - i ε ″) and permeability (μ* = μ ‧ - i μ ″) measurement were carried out using vector network analyser (VNA) over 2-18 GHz frequency range. The complex permeability (μ* = μ ‧ - μ ″) spectra clearly observed the ferromagnetic resonance (FMR) phenomenon in all the prepared samples. The maximum microwave absorption (MWA) of 99.97% (or minimum reflection loss RLmin=-34.90 dB) was observed for Ba4Co1.1Cr0.6Fe36O60 sample at 8.2 GHz frequency with 1.7 mm absorber thickness. The RLmin peak was found to shift towards higher microwave (MW) frequency with increase in Cr3+ ions concentration.

  12. Frequency-based nanoparticle sensing over large field ranges using the ferromagnetic resonances of a magnetic nanodisc

    NASA Astrophysics Data System (ADS)

    Albert, Maximilian; Beg, Marijan; Chernyshenko, Dmitri; Bisotti, Marc-Antonio; Carey, Rebecca L.; Fangohr, Hans; Metaxas, Peter J.

    2016-11-01

    Using finite element micromagnetic simulations, we study how resonant magnetisation dynamics in thin magnetic discs with perpendicular anisotropy are influenced by magnetostatic coupling to a magnetic nanoparticle. We identify resonant modes within the disc using direct magnetic eigenmode calculations and study how their frequencies and spatial profiles are changed by the nanoparticle’s stray magnetic field. We demonstrate that particles can generate shifts in the resonant frequency of the disc’s fundamental mode which exceed resonance linewidths in recently studied spin torque oscillator devices. Importantly, it is shown that the simulated shifts can be maintained over large field ranges (here up to 1 T). This is because the resonant dynamics (the basis of nanoparticle detection here) respond directly to the nanoparticle stray field, i.e. detection does not rely on nanoparticle-induced changes to the magnetic ground state of the disc. A consequence of this is that in the case of small disc-particle separations, sensitivities to the particle are highly mode- and particle-position-dependent, with frequency shifts being maximised when the intense stray field localised directly beneath the particle can act on a large proportion of the disc’s spins that are undergoing high amplitude precession.

  13. 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.

  14. 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.

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

    DOE PAGES

    Bonetti, Stefano; Kukreja, Roopali; Chen, Zhao; ...

    2015-09-10

    In this study, we present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme in order to study high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes of the magnetization on short time scales and nanometer spatial dimensions is achieved by combination of the developed excitation mechanism with a single photon counting electronics that is locked to the synchrotron operation frequency. The required mechanical stability is achieved by a compact design of the microscope. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range,more » with 35 nm 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.« less

  16. Dynamic Tensile Cracking in Slopes and the Possible Existence of Seismic Rayleigh Waves in a High Frequency Range

    NASA Astrophysics Data System (ADS)

    Uenishi, K.

    2011-12-01

    In the previous investigations (Earthq. Eng. Struct. Dyn. 2000, Int. J. Geomech. 2010, Rock Mech. Rock Eng. 2010) we have shown the possibility of evaluating the mechanical characteristics of relevant seismic waves from earthquake-induced dynamic structural failure patterns. Slopes are one of the typical structures that may experience mechanical destabilization by seismic waves and thus can be used as "sensors" to detect specific properties of the waves, some of which, especially those related to high frequencies, might be difficult to be identified by using ordinary seismological recordings. One notable example is the fill slopes in the Midorigaoka area in Sendai City, Japan, where the dynamic loading associated with the 1978 Miyagi-ken-oki earthquake (Japan Meteorological Agency Magnitude Mj = 7.4) generated crack openings in the top surface along the upper edge (crest). Although the slopes were reinforced by steel pipe piles after this 1978 event, tensile cracking was induced again along the upper edge by the off the Pacific coast of Tohoku earthquake in March, 2011 (moment magnitude Mw = 9.0). Similar tensile cracks were found not only in California after the 1906 and 1957 San Francisco and the 1989 Loma Prieta earthquakes but also in the South Island along the cliff edge at Redcliffs, Sumner and Sumner Head on the occasion of the February 2011 Christchurch, New Zealand, earthquake (Mw = 6.1). In this study, using the moving particle semi-implicit (MPS) method, we perform two-dimensional numerical simulations for body or Rayleigh surface wave interaction with an archetypal linear elastic slope. The results suggest, at least from the stress point of view, that in order to systematically explain the generation mechanism of the tensile cracking, it may be more reasonable to assume the existence of Rayleigh waves in a high frequency range. That is, body waves and low-frequency Rayleigh waves may not be able to generate such failure patterns. Further analysis shows

  17. Steady-state visual evoked potentials in the low frequency range in migraine: a study of habituation and variability phenomena.

    PubMed

    de Tommaso, Marina; Stramaglia, Sebastiano; Schoffelen, Jan Mathijs; Guido, Marco; Libro, Giuseppe; Losito, Luciana; Sciruicchio, Vittorio; Sardaro, Michele; Pellicoro, Mario; Puca, Franco Michele

    2003-08-01

    Previous studies have revealed that migraine patients display an increased photic driving to flash stimuli in the medium frequency range. The aim of this study was to perform a topographic analysis of steady-state visual evoked potentials (SVEPs) in the low frequency range (3-9 Hz), evaluating the temporal behaviour of the F1 amplitude by investigating habituation and variability phenomena. The main component of SVEPs, the F1, demonstrated an increased amplitude in several channels at 3 Hz. Behaviour of F1 amplitude was rather variable over time, and the wavelet-transform standard deviation was increased in migraine patients at a low stimulus rate. The discriminative value of the F1 mean amplitude and variability index, tested by both an artificial neural network classifier and a support vector machine, were high according to both methods. The increased photic driving in migraine should be subtended by a more generic abnormality of visual reactivity instead of a selective impairment of a visual subsystem. Temporal behaviour of SVEPs is not influenced by a clear tendency to habituation, but the F1 amplitude seemed to change in a complex way, which is better described by variability phenomena. An increased variability in response to flicker stimuli in migraine patients could be interpreted as an overactive regulation mechanism, prone to instability and consequently to headache attacks, whether spontaneous or triggered.

  18. Plasma density in discharge sustained in inhomogeneous gas flow by high-power radiation in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Vodopyanov, A. V.; Glyavin, M. Yu.; Golubev, S. V.; Luchinin, A. G.; Razin, S. V.; Safronova, M. I.; Sidorov, A. V.; Fokin, A. P.

    2017-02-01

    We have measured the density of plasma (electron concentration) in discharge maintained in inhomogeneous argon flow under the action of high-power pulsed radiation of gyrotron (frequency, 0.67 THz; power 40 kW; pulse duration, 20-30 μs) in a range of background gas pressures in the discharge chamber from 10-3 to 300 Torr. The electron concentration at low pressures (10-3 to 7 Torr) was determined using Starkeffect induced broadening of the Hα atomic emission line (656.3 nm) of hydrogen present in discharge as a small impurity in residual gases. The maximum observed Stark broadening of the Hα line corresponded to a plasma density on the order of 2 × 1016 cm-3, which exceeded the critical value for the given frequency of radiation sustaining the discharge. At background pressures above 7 Torr, the plasma density was estimated from analysis of the spatiotemporal patterns and waveforms of discharge glow in the visible spectral range. These estimations gave electron concentrations on the level of (1-2) × 1015 cm-3.

  19. Optimal frequency ranges for extracting information on cardiovascular autonomic control from the blood pressure and pulse interval spectrograms in mice.

    PubMed

    Baudrie, Véronique; Laude, Dominique; Elghozi, Jean-Luc

    2007-02-01

    The analysis of blood pressure (BP) and heart rate (HR) variability by spectral methods has proven a useful tool in many animal species for the assessment of the vagal and sympathetic contributions to oscillations of BP and HR. Continuous BP measurements obtained in mice by telemetry were used to characterize the spectral bandwidths of autonomic relevance by using an approach with no a priori. The paradigm was based on the autonomic blockades obtained with conventional drugs (atropine, prazosin, atenolol). The spectral changes were estimated in all of the combinations of spectral bandwidths. The effect of hydralazine was also tested using the same systematic analysis, to detect the zones of sympathetic activation resulting reflexly from the vasodilatory action of the drug. Two zones of interest in the study of the autonomic control of BP and HR were observed. The first zone covered the 0.15-0.60 Hz range of the systolic BP spectrum and corresponds to the low-frequency zone (or Mayer waves). This zone reflects sympathetic control since the power spectral density of this zone was significantly reduced with alpha1-adrenoceptor blockade (prazosin), while it was significantly amplified as a result of a reflex sympathetic activation (hydralazine). The second zone covered the 2.5-5.0 Hz range of the pulse interval spectrum and corresponded to the high-frequency zone (respiratory sinus arrhythmia) under vagal control (blocked by atropine). These zones are recommended for testing the autonomic control of circulation in mice.

  20. High-sensitivity operation of single-beam optically pumped magnetometer in a kHz frequency range

    DOE PAGES

    Savukov, Igor Mykhaylovich; Kim, Y. J.; Shah, V.; ...

    2017-02-02

    Here, optically pumped magnetometers (OPM) can be used in various applications, from magnetoencephalography to magnetic resonance imaging and nuclear quadrupole resonance (NQR). OPMs provide high sensitivity and have the significant advantage of non-cryogenic operation. To date, many magnetometers have been demonstrated with sensitivity close to 1 fT, but most devices are not commercialized. Most recently, QuSpin developed a model of OPM that is low cost, high sensitivity, and convenient for users, which operates in a single-beam configuration. Here we developed a theory of single-beam (or parallel two-beam) magnetometers and showed that it is possible to achieve good sensitivity beyond theirmore » usual frequency range by tuning the magnetic field. Experimentally we have tested and optimized a QuSpin OPM for operation in the frequency range from DC to 1.7 kHz, and found that the performance was only slightly inferior despite the expected decrease due to deviation from the spin-exchange relaxation-free regime.« less

  1. High-sensitivity operation of single-beam optically pumped magnetometer in a kHz frequency range

    NASA Astrophysics Data System (ADS)

    Savukov, I.; Kim, Y. J.; Shah, V.; Boshier, M. G.

    2017-03-01

    Optically pumped magnetometers (OPM) can be used in various applications, from magnetoencephalography to magnetic resonance imaging and nuclear quadrupole resonance (NQR). OPMs provide high sensitivity and have the significant advantage of non-cryogenic operation. To date, many magnetometers have been demonstrated with sensitivity close to 1 fT, but most devices are not commercialized. Most recently, QuSpin developed a model of OPM that is low cost, high sensitivity, and convenient for users, which operates in a single-beam configuration. Here we developed a theory of single-beam (or parallel two-beam) magnetometers and showed that it is possible to achieve good sensitivity beyond their usual frequency range by tuning the magnetic field. Experimentally we have tested and optimized a QuSpin OPM for operation in the frequency range from DC to 1.7 kHz, and found that the performance was only slightly inferior despite the expected decrease due to deviation from the spin-exchange relaxation-free regime.

  2. The effects of sampling frequency on the climate statistics of the European Centre for Medium-Range Weather Forecasts

    SciTech Connect

    Phillips, T.J.; Gates, W.L. ); Arpe, K. )

    1992-12-20

    The effects of sampling frequency on the first- and second-moment statistics of selected European Centre for Medium-Range Weather Forecasts (ECMWF) model variables are investigated in a simulation of perpetual July' with a diurnal cycle included and with surface and atmospheric fields saved at hourly intervals. The shortest characteristic time scales are those of ground heat fluxes and temperatures, precipitation and runoff, convective processes, cloud properties, and atmospheric vertical motion, while the longest time scales are exhibited by soil temperature and moisture, surface pressure, and atmospheric specific humidity, temperature, and wind. The time scales of surface heat and momentum fluxes and of convective processes are substantially shorter over land than over oceans. An appropriate sampling frequency for each model variable is obtained by comparing the estimates of first- and second-moment statistics determined at intervals ranging from 2 to 24 hours with the best' estimates obtained from hourly sampling. Relatively accurate estimation of first- and second-moment climate statistics can be achieved by sampling a model variable at intervals that usually are longer than the bandwidth of its time series but that often are shorter than its characteristic time scale. The superior estimates of first-moment statistics are accompanied by inferior estimates of the variance of the daily means due to the presence of systematic biases, but these probably can be avoided by defining a different measure of low-frequency variability. Estimates of the intradiurnal variance of accumulated precipitation and surface runoff also are strongly impacted by the length of the storage interval. In light of these results, several alternative strategies for storage of the EMWF model variables are recommended. 20 refs., 9 figs., 1 tab.

  3. Cyclic loading experiments to measure material response over a broad frequency range: from tickling of rocks to squeezing of moons

    NASA Astrophysics Data System (ADS)

    McCarthy, C.; Takei, Y.; Cooper, R. F.; Savage, H. M.

    2014-12-01

    Seismology provides powerful methods for imaging the interior of the Earth, not only through differences in seismic velocities, but also through attenuation contrasts. As seismic waves travel through the Earth they are attenuated in accordance with the viscoelastic properties of the material through which they pass. With proper constraints, we will someday be able to use seismic attenuation data as a prospecting tool to determine the grain size, temperature, pressure, melt content, and water content of the material along the ray path. Furthermore, it should be possible to determine active deformation structure, such as crystallographic preferred orientations that form in response to far-field natural tectonic loading. Laboratory studies are striving to provide these needed constraints. Using analogues to mantle rock, we isolate and scrutinize the physics of how microstructural elements affect macroscopic properties of attenuation and steady-state viscosity. An organic analogue, borneol, was used to measure the effects of grain size, temperature, and melt content over a broad frequency range. In these experiments, grain boundary processes were found to play a major role. Polycrystalline ice, which can be considered a rock analogue, has been used to explore the effect of accumulated strain on attenuation, particularly in material that is actively deforming via dislocation creep. Here, defect concentration and substructure are important. I will discuss the use of cyclic loading experiments on borneol and on polycrystalline ice to probe material response from seismic to tidal frequencies, from 10 Hz to 10-4 Hz respectively. These experiments, then, inform our knowledge of viscoelastic behavior of geologic materials at not only seismic frequencies, but also the tidal forcing frequencies experienced by tidewater glaciers and icy satellites.

  4. 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.

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

    PubMed

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

    2011-06-01

    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.

  6. The effects of sampling frequency on the climate statistics of the European Centre for Medium-Range Weather Forecasts

    NASA Astrophysics Data System (ADS)

    Phillips, Thomas J.; Gates, W. Lawrence; Arpe, Klaus

    1992-12-01

    The effects of sampling frequency on the first- and second-moment statistics of selected European Centre for Medium-Range Weather Forecasts (ECMWF) model variables are investigated in a simulation of "perpetual July" with a diurnal cycle included and with surface and atmospheric fields saved at hourly intervals. The shortest characteristic time scales (as determined by the e-folding time of lagged autocorrelation functions) are those of ground heat fluxes and temperatures, precipitation and runoff, convective processes, cloud properties, and atmospheric vertical motion, while the longest time scales are exhibited by soil temperature and moisture, surface pressure, and atmospheric specific humidity, temperature, and wind. The time scales of surface heat and momentum fluxes and of convective processes are substantially shorter over land than over oceans. An appropriate sampling frequency for each model variable is obtained by comparing the estimates of first- and second-moment statistics determined at intervals ranging from 2 to 24 hours with the "best" estimates obtained from hourly sampling. Relatively accurate estimation of first- and second-moment climate statistics (10% errors in means, 20% errors in variances) can be achieved by sampling a model variable at intervals that usually are longer than the bandwidth of its time series but that often are shorter than its characteristic time scale. For the surface variables, sampling at intervals that are nonintegral divisors of a 24-hour day yields relatively more accurate time-mean statistics because of a reduction in errors associated with aliasing of the diurnal cycle and higher-frequency harmonics. The superior estimates of first-moment statistics are accompanied by inferior estimates of the variance of the daily means due to the presence of systematic biases, but these probably can be avoided by defining a different measure of low-frequency variability. Estimates of the intradiurnal variance of accumulated

  7. 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

  8. A wide range ultra-low power Phase-Locked Loop with automatic frequency setting in 130 nm CMOS technology for data serialisation

    NASA Astrophysics Data System (ADS)

    Firlej, M.; Fiutowski, T.; Idzik, M.; Moroń, J.; Świentek, K.

    2015-12-01

    The design and measurements results of a wide frequency range ultra-low power Phase-Locked Loop (PLL) for applications in readout systems of particle physics detectors are presented. The PLL was fabricated in a 130 nm CMOS technology. To allow the implementation of different data serialisation schemes multiple division factors (6, 8, 10, 16) were implemented in the PLL feedback loop. The main PLL block—VCO works in 16 frequency ranges/modes, switched either manually or automatically. A dedicated automatic frequency mode switching circuit was developed to allow simple frequency tuning. Although the PLL was designed and simulated for a frequency range of 30 MHz-3 GHz, due to the SLVS interface limits, the measurements were done only up to 1.3 GHz. The full PLL functionality was experimentally verified, confirming a very low and frequency scalable power consumption (0.7 mW at 1 GHz).

  9. 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.

  10. 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.

  11. Temperature-dependent Sellmeier equation at terahertz frequency range for 1 mol % MgO-doped stoichiometric lithium tantalate

    NASA Astrophysics Data System (ADS)

    Lee, Kyu-Sup; Ko, Do-Kyeong; Yu, Nan Ei

    2017-04-01

    We first examined a temperature-dependent Sellmeier equation for the extraordinary refractive index of MgO-doped stoichiometric LiTaO3 (MgO:SLT) crystal via frequency-tunable narrowband terahertz (THz) generation at 0.4–1.8 THz and at a low temperature range of 80–300 K. The mean deviation of Sellmeier equation fit was less than 0.3%, being equivalent with the predicted measurement uncertainty of 0.3%. The temperature effect (dn THz/dT) was 2.02 × 10‑3/K at 1 THz. Moreover, we showed the smaller birefringence for MgO:SLT than MgO-doped stoichiometric LiNbO3 at 300 K from THz time-domain spectroscopy. This study is crucial for material study itself and THz device engineering.

  12. Variational derivation of the dispersion relation of kinetic coherent modes in the acoustic frequency range in tokamaks

    SciTech Connect

    Nguyen, C.; Garbet, X.; Smolyakov, A. I.

    2008-11-15

    In the present paper, we compare two modes with frequencies belonging to the acoustic frequency range: the geodesic acoustic mode (GAM) and the Beta Alfven eigenmode (BAE). For this, a variational gyrokinetic energy principle coupled to a Fourier sidebands expansion is developed. High order finite Larmor radius and finite orbit width effects are kept. Their impact on the mode structures and on the Alfven spectrum is calculated and discussed. We show that in a local analysis, the degeneracy of the electrostatic GAM and the BAE dispersion relations is verified to a high order and based in particular on a local poloidal symmetry of the two modes. When a more global point of view is taken, and the full radial structures of the modes are computed, differences appear. The BAE structure is shown to have an enforced localization, and to possibly connect to a large magnetohydrodynamic structure. On the contrary, the GAM is seen to have a wavelike, nonlocalized structure, as long as standard slowly varying monotonic profiles are considered.

  13. Low-frequency sound speed and attenuation in sandy seabottom from long-range broadband acoustic measurements.

    PubMed

    Wan, Lin; Zhou, Ji-Xun; Rogers, Peter H

    2010-08-01

    A joint China-U.S. underwater acoustics experiment was conducted in the Yellow Sea with a very flat bottom and a strong and sharp thermocline. Broadband explosive sources were deployed both above and below the thermocline along two radial lines up to 57.2 km and a quarter circle with a radius of 34 km. Two inversion schemes are used to obtain the seabottom sound speed. One is based on extracting normal mode depth functions from the cross-spectral density matrix. The other is based on the best match between the calculated and measured modal arrival times for different frequencies. The inverted seabottom sound speed is used as a constraint condition to extract the seabottom sound attenuation by three methods. The first method involves measuring the attenuation coefficients of normal modes. In the second method, the seabottom sound attenuation is estimated by minimizing the difference between the theoretical and measured modal amplitude ratios. The third method is based on finding the best match between the measured and modeled transmission losses (TLs). The resultant seabottom attenuation, averaged over three independent methods, can be expressed as alpha=(0.33+/-0.02)f(1.86+/-0.04)(dB/m kHz) over a frequency range of 80-1000 Hz.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Frequency-range discriminations and absolute pitch in black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata).

    PubMed

    Lee, Tiffany T Y; Charrier, Isabelle; Bloomfield, Laurie L; Weisman, Ronald G; Sturdy, Christopher B

    2006-08-01

    The acoustic frequency ranges in birdsongs provide important absolute pitch cues for the recognition of conspecifics. Black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata) were trained to sort tones contiguous in frequency into 8 ranges on the basis of associations between response to the tones in each range and reward. All 3 species acquired accurate frequency-range discriminations, but zebra finches acquired the discrimination in fewer trials and to a higher standard than black-capped or mountain chickadees, which did not differ appreciably in the discrimination. Chickadees' relatively poorer accuracy was traced to poorer discrimination of tones in the higher frequency ranges. During transfer tests, the discrimination generalized to novel tones when the training tones were included, but not when they were omitted.

  1. Geolocation of LTE Subscriber Stations Based on the Timing Advance Ranging Parameter

    DTIC Science & Technology

    2010-12-01

    timing advance range rings (From [8]). ..................6 Figure 3. Functional commonality between SC- FDMA and OFDMA signal chains (From [14... FDMA Single Carrier Frequency Division Multiple Access SDU Service Data Unit SS Subscriber Station SVD Singular Value Decomposition TA...uplink and downlink. They are single-carrier frequency-division multiple access (SC- FDMA ) and orthogonal frequency-division multiple access (OFDMA

  2. Optically stabilized Erbium fiber frequency comb with hybrid mode-locking and a broad tunable range of repetition rate.

    PubMed

    Yang, Honglei; Wu, Xuejian; Zhang, Hongyuan; Zhao, Shijie; Yang, Lijun; Wei, Haoyun; Li, Yan

    2016-12-01

    We present an optically stabilized Erbium fiber frequency comb with a broad repetition rate tuning range based on a hybrid mode-locked oscillator. We lock two comb modes to narrow-linewidth reference lasers in turn to investigate the best performance of control loops. The control bandwidth of fast and slow piezoelectric transducers reaches 70 kHz, while that of pump current modulation with phase-lead compensation is extended to 32 kHz, exceeding laser intrinsic response. Eventually, simultaneous lock of both loops is realized to totally phase-stabilize the comb, which will facilitate precision dual-comb spectroscopy, laser ranging, and timing distribution. In addition, a 1.8-MHz span of the repetition rate is achieved by an automatic optical delay line that is helpful in manufacturing a secondary comb with a similar repetition rate. The oscillator is housed in a homemade temperature-controlled box with an accuracy of ±0.02  K, which not only keeps high signal-to-noise ratio of the beat notes with reference lasers, but also guarantees self-starting at the same mode-locking every time.

  3. Experimental investigation of ion cyclotron range of frequencies heating scenarios for ITER's half-field hydrogen phase performed in JET

    NASA Astrophysics Data System (ADS)

    Lerche, E.; Van Eester, D.; Johnson, T. J.; Hellsten, T.; Ongena, J.; Mayoral, M.-L.; Frigione, D.; Sozzi, C.; Calabro, G.; Lennholm, M.; Beaumont, P.; Blackman, T.; Brennan, D.; Brett, A.; Cecconello, M.; Coffey, I.; Coyne, A.; Crombe, K.; Czarnecka, A.; Felton, R.; Giroud, C.; Gorini, G.; Hellesen, C.; Jacquet, P.; Kiptily, V.; Knipe, S.; Krasilnikov, A.; Maslov, M.; Monakhov, I.; Noble, C.; Nocente, M.; Pangioni, L.; Proverbio, I.; Sergienko, G.; Stamp, M.; Studholme, W.; Tardocchi, M.; Vdovin, V.; Versloot, T.; Voitsekhovitch, I.; Whitehurst, A.; Wooldridge, E.; Zoita, V.; EFDA Contributors, JET

    2012-07-01

    Two ion cyclotron range of frequencies (ICRF) heating schemes proposed for the half-field operation phase of ITER in hydrogen plasmas—fundamental H majority and second harmonic 3He ICRF heating—were recently investigated in JET. Although the same magnetic field and RF frequencies (f ≈ 42 MHz and f ≈ 52 MHz, respectively) were used, the density and particularly the plasma temperature were lower than those expected in the initial phase of ITER. Unlike for the well-performing H minority heating scheme to be used in 4He plasmas, modest heating efficiencies (η = Pabsorbed/Plaunched < 40%) with dominant electron heating were found in both H plasma scenarios studied, and enhanced plasma-wall interaction manifested by high radiation losses and relatively large impurity content in the plasma was observed. This effect was stronger in the 3He ICRF heating case than in the H majority heating experiments and it was verified that concentrations as high as ˜20% are necessary to observe significant ion heating in this case. The RF acceleration of the heated ions was modest in both cases, although a small fraction of the 3He ions reached about 260 keV in the second harmonic 3He heating experiments when 5 MW of ICRF power was applied. Considerable RF acceleration of deuterium beam ions was also observed in some discharges of the 3He heating experiments (where both the second and third harmonic ion cyclotron resonance layers of the D ions are inside the plasma) whilst it was practically absent in the majority hydrogen heating scenario. While hints of improved RF heating efficiency as a function of the plasma temperature and plasma dilution (with 4He) were confirmed in the H majority case, the 3He concentration was the main handle on the heating efficiency in the second harmonic 3He heating scenario.

  4. 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

  5. Generation of difference-frequency radiation in the far- and mid-IR ranges in a two-chip laser based on gallium arsenide on a germanium substrate

    SciTech Connect

    Aleshkin, V Ya; Dubinov, A A

    2008-09-30

    The possibility of efficient generation of difference-frequency radiation in the far- and mid-IR ranges in a two-chip laser based on gallium arsenide grown on a germanium substrate is considered. It is shown that a laser with a waveguide of width 100 {mu}m emitting 1 W in the near-IR range can generate {approx}40 {mu}W at the difference frequency in the region 5-50 THz at room temperature. (nonlinear optical phenomena)

  6. 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.

  7. Updating the geographical distribution and frequency of Aedes albopictus in Brazil with remarks regarding its range in the Americas.

    PubMed

    Carvalho, Roberta Gomes; Lourenço-de-Oliveira, Ricardo; Braga, Ima Aparecida

    2014-09-01

    The geographical distribution of Aedes albopictus in Brazil was updated according to the data recorded across the country over the last eight years. Countrywide house indexes (HI) for Ae. albopictus in urban and suburban areas were described for the first time using a sample of Brazilian municipalities. This mosquito is currently present in at least 59% of the Brazilian municipalities and in 24 of the 27 federal units (i.e., 26 states and the Federal District). In 34 Brazilian municipalities, the HI values for Ae. albopictus were higher than those recorded for Ae. aegypti, reaching figures as high as HI = 7.72 in the Southeast Region. Remarks regarding the current range of this mosquito species in the Americas are also presented. Nineteen American countries are currently infested and few mainland American countries have not confirmed the occurrence of Ae. albopictus. The large distribution and high frequency of Ae. albopictus in the Americas may become a critical factor in the spread of arboviruses like chikungunya in the new world.

  8. 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.

  9. Updating the geographical distribution and frequency of Aedes albopictus in Brazil with remarks regarding its range in the Americas

    PubMed Central

    Carvalho, Roberta Gomes; Lourenço-de-Oliveira, Ricardo; Braga, Ima Aparecida

    2014-01-01

    The geographical distribution of Aedes albopictus in Brazil was updated according to the data recorded across the country over the last eight years. Countrywide house indexes (HI) for Ae. albopictus in urban and suburban areas were described for the first time using a sample of Brazilian municipalities. This mosquito is currently present in at least 59% of the Brazilian municipalities and in 24 of the 27 federal units (i.e., 26 states and the Federal District). In 34 Brazilian municipalities, the HI values for Ae. albopictus were higher than those recorded for Ae. aegypti, reaching figures as high as HI = 7.72 in the Southeast Region. Remarks regarding the current range of this mosquito species in the Americas are also presented. Nineteen American countries are currently infested and few mainland American countries have not confirmed the occurrence of Ae. albopictus. The large distribution and high frequency of Ae. albopictus in the Americas may become a critical factor in the spread of arboviruses like chikungunya in the new world. PMID:25317707

  10. Study of transmittance and reflectance spectra of the cornea and the sclera in the THz frequency range

    NASA Astrophysics Data System (ADS)

    Iomdina, Elena N.; Goltsman, Gregory N.; Seliverstov, Sergey V.; Sianosyan, Alisa A.; Teplyakova, Kseniya O.; Rusova, Anastasia A.

    2016-09-01

    An adequate water balance (hydration extent) is one of the basic factors of normal eye function, including its external shells: the cornea and the sclera. Adequate control of corneal and scleral hydration is very important for early diagnosis of a variety of eye diseases, stating indications for and contraindications against keratorefractive surgeries and the choice of contact lens correction solutions. THz systems of creating images in reflected beams are likely to become ideal instruments of noninvasive control of corneal and scleral hydration degrees. This paper reports on the results of a study involving transmittance and reflectance spectra for the cornea and the sclera of rabbit and human eyes, as well as those of the rabbit eye, in the frequency range of 0.13 to 0.32 THz. The dependence of the reflectance coefficient of these tissues on water mass percentage content was determined. The experiments were performed on three corneas, three rabbit scleras, two rabbit eyes, and three human scleras. The preliminary results demonstrate that the proposed technique, based on the use of a continuous THz radiation, may be utilized to create a device for noninvasive control of corneal and scleral hydration, which has clear potential of broad practical application.

  11. The effects of oblique incidences on the XB mode conversion in the electron cyclotron range of frequency

    NASA Astrophysics Data System (ADS)

    Jia, Guozhang; Gao, Zhe

    2017-02-01

    The linear conversion from a fast extraordinary mode to a Bernstein mode (XB) in the electron cyclotron range of frequency is revisited numerically by using a simplified kinetic model. The corresponding wave equations are solved as a standard two-point boundary value problem, where the self-consistent boundary conditions are applied and the scattering coefficients are calculated accordingly. The numerical calculation of the XB conversion efficiency is compared with the analytical formula for the normal incidence (along the direction perpendicular to the equilibrium magnetic field and parallel to the density gradient), where a reasonable agreement is found. The effects of incident angles represented by refractive indexes on the conversion efficiency are analyzed. It is shown that as the incident angle deviates from the normal incidence, the efficiency of XB conversion decreases significantly. The results also indicate that the power loss in the XB process can be ascribed to the reflected fast extraordinary mode and the reflected-converted ordinary mode. The symmetry of the conversion efficiency about the incident angle is discussed, and the rigid restriction on the scale length of the density variation for effective XB conversions can be possibly alleviated through altering the injection direction in realistic experiments.

  12. Review of recent experimental and modeling progress in the lower hybrid range of frequencies at ITER relevant parameters

    SciTech Connect

    Bonoli, Paul T.

    2014-02-12

    Progress in experiment and simulation capability in the lower hybrid range of frequencies (LHRF) at ITER relevant parameters is reviewed. Use of LH power in reactor devices is motivated in terms of its potential for efficient off-axis current profile control. Recent improvements in simulation capability including the development of full-wave field solvers, inclusion of the scrape off layer (SOL) in wave propagation codes, the use of coupled ray tracing / full-wave / 3D (r v{sub ⊥}, v{sub ∥}) Fokker Planck models, and the inclusion of nonlinear broadening effects in ray tracing / Fokker Planck codes are discussed. Experimental and modeling results are reviewed which are aimed at understanding the spectral gap problem in LH current drive (LHCD) and the density limit that has been observed in LHCD experiments. Physics mechanisms that could be operative in these experiments are discussed, including toroidally induced variations in the parallel wavenumber, nonlinear broadening of the pump wave, scattering of LH waves from density fluctuations in the SOL, and spectral broadening at the plasma edge via full-wave effects.

  13. Different Mode of Afferents Determines the Frequency Range of High Frequency Activities in the Human Brain: Direct Electrocorticographic Comparison between Peripheral Nerve and Direct Cortical Stimulation

    PubMed Central

    Kobayashi, Katsuya; Matsumoto, Riki; Matsuhashi, Masao; Usami, Kiyohide; Shimotake, Akihiro; Kunieda, Takeharu; Kikuchi, Takayuki; Mikuni, Nobuhiro; Miyamoto, Susumu; Fukuyama, Hidenao; Takahashi, Ryosuke; Ikeda, Akio

    2015-01-01

    Physiological high frequency activities (HFA) are related to various brain functions. Factors, however, regulating its frequency have not been well elucidated in humans. To validate the hypothesis that different propagation modes (thalamo-cortical vs. cortico-coritcal projections), or different terminal layers (layer IV vs. layer II/III) affect its frequency, we, in the primary somatosensory cortex (SI), compared HFAs induced by median nerve stimulation with those induced by electrical stimulation of the cortex connecting to SI. We employed 6 patients who underwent chronic subdural electrode implantation for presurgical evaluation. We evaluated the HFA power values in reference to the baseline overriding N20 (earliest cortical response) and N80 (late response) of somatosensory evoked potentials (HFASEP(N20) and HFASEP(N80)) and compared those overriding N1 and N2 (first and second responses) of cortico-cortical evoked potentials (HFACCEP(N1) and HFACCEP(N2)). HFASEP(N20) showed the power peak in the frequency above 200 Hz, while HFACCEP(N1) had its power peak in the frequency below 200 Hz. Different propagation modes and/or different terminal layers seemed to determine HFA frequency. Since HFACCEP(N1) and HFA induced during various brain functions share a similar broadband profile of the power spectrum, cortico-coritcal horizontal propagation seems to represent common mode of neural transmission for processing these functions. PMID:26087042

  14. Different Mode of Afferents Determines the Frequency Range of High Frequency Activities in the Human Brain: Direct Electrocorticographic Comparison between Peripheral Nerve and Direct Cortical Stimulation.

    PubMed

    Kobayashi, Katsuya; Matsumoto, Riki; Matsuhashi, Masao; Usami, Kiyohide; Shimotake, Akihiro; Kunieda, Takeharu; Kikuchi, Takayuki; Mikuni, Nobuhiro; Miyamoto, Susumu; Fukuyama, Hidenao; Takahashi, Ryosuke; Ikeda, Akio

    2015-01-01

    Physiological high frequency activities (HFA) are related to various brain functions. Factors, however, regulating its frequency have not been well elucidated in humans. To validate the hypothesis that different propagation modes (thalamo-cortical vs. cortico-coritcal projections), or different terminal layers (layer IV vs. layer II/III) affect its frequency, we, in the primary somatosensory cortex (SI), compared HFAs induced by median nerve stimulation with those induced by electrical stimulation of the cortex connecting to SI. We employed 6 patients who underwent chronic subdural electrode implantation for presurgical evaluation. We evaluated the HFA power values in reference to the baseline overriding N20 (earliest cortical response) and N80 (late response) of somatosensory evoked potentials (HFA(SEP(N20)) and HFA(SEP(N80))) and compared those overriding N1 and N2 (first and second responses) of cortico-cortical evoked potentials (HFA(CCEP(N1)) and HFA(CCEP(N2))). HFA(SEP(N20)) showed the power peak in the frequency above 200 Hz, while HFA(CCEP(N1)) had its power peak in the frequency below 200 Hz. Different propagation modes and/or different terminal layers seemed to determine HFA frequency. Since HFA(CCEP(N1)) and HFA induced during various brain functions share a similar broadband profile of the power spectrum, cortico-coritcal horizontal propagation seems to represent common mode of neural transmission for processing these functions.

  15. Modification of S. cerevisiae Growth Dynamics Using Low Frequency Electromagnetic Fields in the 1-2 kHz Range

    PubMed Central

    Barabáš, Ján; Radil, Roman; Malíková, Ivona

    2015-01-01

    This paper details our further experiments pertaining to the influence of low frequency electromagnetic fields (LF EMF) on the growth dynamics of two wild-type Saccharomyces cerevisiae strands. We opted to explore frequencies beyond the usual 50–60 Hz range, motivated by the ion parametric resonance theory and several studies which discovered and recorded endogenous biosignals in various Saccharomyces cerevisiae strands in the 0.4–2.0 kHz frequency range, most probably stemming from microtubules. Both yeast strands used in our experiments have been subjected to continuous 66-hour session of LF EMF exposure (frequencies 1.2, 1.4, 1.6, 1.8, and 2.0 kHz; average magnetic flux density 2.43 mT) under identical ambient conditions. Experiment results indicate a frequency-dependent proliferative response of both yeast strands. PMID:26290871

  16. Modelling the spectral induced polarization response of water-saturated sands in the intermediate frequency range (102-105 Hz) using mechanistic and empirical approaches

    NASA Astrophysics Data System (ADS)

    Kremer, Thomas; Schmutz, Myriam; Leroy, Philippe; Agrinier, Pierre; Maineult, Alexis

    2016-11-01

    The intermediate frequency range 102-105 Hz forms the transition range between the spectral induced polarization frequency domain and the dielectric spectroscopy frequency domain. Available experimental data showed that the spectral induced polarization response of sands fully saturated with water was particularly sensitive to variations of the saturating water electrical conductivity value in the intermediate frequency range. An empirical and a mechanistic model have been developed and confronted to this experimental data. This confrontation showed that the Maxwell Wagner polarization alone is not sufficient to explain the observed signal in the intermediate frequency range. The SIP response of the media was modelled by assigning relatively high dielectric permittivity values to the sand particle or high effective permittivity values to the media. Such high values are commonly observed in the dielectric spectroscopy literature when entering the intermediate frequency range. The physical origin of these high dielectric permittivity values is discussed (grain shape, electromagnetic coupling), and a preliminary study is presented which suggests that the high impedance values of the non-polarizable electrodes might play a significant role in the observed behaviour.

  17. Prediction of density and mechanical properties of human trabecular bone in vitro by using ultrasound transmission and backscattering measurements at 0.2-6.7 MHz frequency range.

    PubMed

    Hakulinen, Mikko A; Day, Judd S; Töyräs, Juha; Timonen, Matti; Kröger, Heikki; Weinans, Harrie; Kiviranta, Ilkka; Jurvelin, Jukka S

    2005-04-21

    The ultrasound (US) backscattering method has been introduced as an alternative for the through-transmission measurement of sound attenuation and speed in diagnosis of osteoporosis. Both attenuation and backscattering depend strongly on the US frequency. In this study, 20 human trabecular bone samples were measured in transmission and pulse-echo geometry in vitro. The aim of the study was to find the most sensitive frequency range for the quantitative ultrasound (QUS) analyses. Normalized broadband US attenuation (nBUA), speed of sound (SOS), broadband US backscatter (BUB) and integrated reflection coefficient (IRC) were determined for each sample. The samples were spatially scanned with five pairs of US transducers covering a frequency range of 0.2-6.7 MHz. Furthermore, mechanical properties and density of the same samples were determined. At all frequencies, SOS, BUB and IRC showed statistically significant linear correlations with the mechanical properties or density of human trabecular bone (0.51 < r < 0.82, 0.54 < r < 0.81 and 0.70 < r < 0.85, respectively). In contrast to SOS, IRC and BUB, nBUA showed statistically significant correlations with mechanical parameters or density at the centre frequency of 1 MHz only. Our results suggest that frequencies up to 5 MHz can be useful in QUS analyses for the prediction of bone mechanical properties and density. Since the use of higher frequencies provides better axial and spatial resolution, improved structural analyses may be possible. While extensive attenuation of high frequencies in trabecular bone limits the clinically feasible frequency range, selection of optimal frequency range for in vivo QUS application should be carefully considered.

  18. Neurone bioelectric activity under magnetic fields of variable frequency in the range of 0.1-80 Hz

    NASA Astrophysics Data System (ADS)

    Pérez Bruzón, R. N.; Azanza, María. J.; Calvo, Ana C.; del Moral, A.

    2004-05-01

    Intracellular recordings from single unit molluscan neurones under exposure to ELF-MF (1 mT, 0.1-80 Hz), show that neurone frequency activity, f, decreases with the applied magnetic field frequency, fM, a phenomenon which indicates a frequency-window effect for the neurone membrane response. The HMHW of the window amounts between 2-10 Hz. An explanation of this phenomenon is proposed.

  19. 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.

  20. 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…

  1. Identification and Classification of Orthogonal Frequency Division Multiple Access (OFDMA) Signals Used in Next Generation Wireless Systems

    DTIC Science & Technology

    2012-03-01

    interoperability for microwave access ZCC zero-terminating convolutional coding xv EXECUTIVE SUMMARY Many developing regions of the world that...consolidated and revised into the IEEE 802.16-2009 standard, which is the basis for mobile worldwide interoperability for microwave access (WiMAX...interoperability for microwave access (WiMAX) is based on the IEEE 802.16-2004 standard and mobile WiMAX is based on the IEEE 802.16e-2005 standard. Although

  2. 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

  3. 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

  4. 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°.

  5. 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.

  6. An investigation of electromagnetic response of composite polymer materials containing carbon nanostructures within the range of frequencies 10 MHz - 1.1 THz

    NASA Astrophysics Data System (ADS)

    Suslyaev, V. I.; Kuznetsov, V. L.; Zhuravlev, V. A.; Mazov, I. N.; Korovin, E. Yu.; Moseenkov, S. I.; Dorozhkin, K. V.

    2013-01-01

    Electromagnetic characteristics of composite polymer materials based on multilayer carbon nanotubes (MCNTs) and nano-onion carbon structures in a polymethylmethacrylate (PMMA) matrix are investigated. The purpose is to identify a functional relationship between the size, kind, type of processing, concentration of nanotubes and electromagnetic characteristics of composite materials within the frequency range 10 MHz - 1.1 THz. Use is made of the coaxial waveguide, resonator, and quasi-optical methods. The spectra of reflection and transmission coefficients are reported. The composite materials based on carbon nanostructures are shown to actively interact with electromagnetic radiation in a wide range of frequencies.

  7. Large allele frequency differences between human continental groups are more likely to have occurred by drift during range expansions than by selection.

    PubMed

    Hofer, T; Ray, N; Wegmann, D; Excoffier, L

    2009-01-01

    Several studies have found strikingly different allele frequencies between continents. This has been mainly interpreted as being due to local adaptation. However, demographic factors can generate similar patterns. Namely, allelic surfing during a population range expansion may increase the frequency of alleles in newly colonised areas. In this study, we examined 772 STRs, 210 diallelic indels, and 2834 SNPs typed in 53 human populations worldwide under the HGDP-CEPH Diversity Panel to determine to which extent allele frequency differs among four regions (Africa, Eurasia, East Asia, and America). We find that large allele frequency differences between continents are surprisingly common, and that Africa and America show the largest number of loci with extreme frequency differences. Moreover, more STR alleles have increased rather than decreased in frequency outside Africa, as expected under allelic surfing. Finally, there is no relationship between the extent of allele frequency differences and proximity to genes, as would be expected under selection. We therefore conclude that most of the observed large allele frequency differences between continents result from demography rather than from positive selection.

  8. Interaction of electromagnetic radiation in the 20-200 GHz frequency range with arrays of carbon nanotubes with ferromagnetic nanoparticles.

    PubMed

    Atdayev, Agylych; Danilyuk, Alexander L; Prischepa, Serghej L

    2015-01-01

    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.

  9. A Forced Vibration Non-Resonant Method for the Determination of Complex Modulus in the Audio Frequency Range

    DTIC Science & Technology

    1992-01-01

    water -borne sound when used in anechoic coatings1 . The frequency and temperature dependence of the viscoelastic properties of polymers is essential...strain on the sample, 8: E t11=tan 8- E’ - tanq ) [8] In this case the measured phase angle, p, is identical with 8, the angle between stress and strain

  10. Particle simulations of mode conversion between slow mode and fast mode in lower hybrid range of frequencies

    SciTech Connect

    Jia, Guozhang; Xiang, Nong; Huang, Yueheng; Wang, Xueyi; Lin, Yu

    2016-01-15

    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 ∼ 3ω{sub LH}, where ω{sub LH} 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 ∼ 1.3ω{sub LH}), 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.

  11. 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.

  12. Effects of diffraction by ionospheric electron density irregularities on the range error in GNSS dual-frequency positioning and phase decorrelation

    NASA Astrophysics Data System (ADS)

    Gherm, Vadim E.; Zernov, Nikolay N.; Strangeways, Hal J.

    2011-06-01

    It can be important to determine the correlation of different frequency signals in L band that have followed transionospheric paths. In the future, both GPS and the new Galileo satellite system will broadcast three frequencies enabling more advanced three frequency correction schemes so that knowledge of correlations of different frequency pairs for scintillation conditions is desirable. Even at present, it would be helpful to know how dual-frequency Global Navigation Satellite Systems positioning can be affected by lack of correlation between the L1 and L2 signals. To treat this problem of signal correlation for the case of strong scintillation, a previously constructed simulator program, based on the hybrid method, has been further modified to simulate the fields for both frequencies on the ground, taking account of their cross correlation. Then, the errors in the two-frequency range finding method caused by scintillation have been estimated for particular ionospheric conditions and for a realistic fully three-dimensional model of the ionospheric turbulence. The results which are presented for five different frequency pairs (L1/L2, L1/L3, L1/L5, L2/L3, and L2/L5) show the dependence of diffractional errors on the scintillation index S4 and that the errors diverge from a linear relationship, the stronger are scintillation effects, and may reach up to ten centimeters, or more. The correlation of the phases at spaced frequencies has also been studied and found that the correlation coefficients for different pairs of frequencies depend on the procedure of phase retrieval, and reduce slowly as both the variance of the electron density fluctuations and cycle slips increase.

  13. Four-frequency polarizing microscope for recording plasma images in the wavelength range 0.4-1.1 {mu}m

    SciTech Connect

    Vasin, B. L.; Mal'kova, S. V.; Osipov, M. V.; Puzyrev, V. N.; Saakyan, A. T.; Starodub, A. N.; Fedotov, S. I.; Fronya, A. A.; Shutyak, V. G.

    2010-12-15

    The optical scheme and design of a four-frequency polarizing microscope intended for simultaneous recording of plasma images in the wavelength range 0.4-1.1 {mu}m with the spatial resolution 12 {mu}m in the entire spectral range are described. The effectiveness of such a microscope in studies of plasmas produced on interaction of laser radiation with a target is demonstrated. The plasma images are obtained at the frequencies {omega}{sub 0}, (3/2){omega}{sub 0}, 2{omega}{sub 0}, and (5/2){omega}{sub 0}, where {omega}{sub 0} corresponds to the frequency of heating radiation. The transformation coefficient that characterizes the efficiency of conversion of heating radiation into the 2{omega}{sub 0}, (3/2){omega}{sub 0}, and (5/2){omega}{sub 0} harmonics generated in the plasma is determined.

  14. 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)

  15. Chromosomal dynamics predicted by an elastic network model explains genome-wide accessibility and long-range couplings.

    PubMed

    Sauerwald, Natalie; Zhang, She; Kingsford, Carl; Bahar, Ivet

    2017-03-16

    Understanding the three-dimensional (3D) architecture of chromatin and its relation to gene expression and regulation is fundamental to understanding how the genome functions. Advances in Hi-C technology now permit us to study 3D genome organization, but we still lack an understanding of the structural dynamics of chromosomes. The dynamic couplings between regions separated by large genomic distances (>50 Mb) have yet to be characterized. We adapted a well-established protein-modeling framework, the Gaussian Network Model (GNM), to model chromatin dynamics using Hi-C data. We show that the GNM can identify spatial couplings at multiple scales: it can quantify the correlated fluctuations in the positions of gene loci, find large genomic compartments and smaller topologically-associating domains (TADs) that undergo en bloc movements, and identify dynamically coupled distal regions along the chromosomes. We show that the predictions of the GNM correlate well with genome-wide experimental measurements. We use the GNM to identify novel cross-correlated distal domains (CCDDs) representing pairs of regions distinguished by their long-range dynamic coupling and show that CCDDs are associated with increased gene co-expression. Together, these results show that GNM provides a mathematically well-founded unified framework for modeling chromatin dynamics and assessing the structural basis of genome-wide observations.

  16. 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...

  17. 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.

  18. 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.

  19. Long-range measurement of Rayleigh scatter signature beyond laser coherence length based on coherent optical frequency domain reflectometry.

    PubMed

    Ohno, Shingo; Iida, Daisuke; Toge, Kunihiro; Manabe, Tetsuya

    2016-08-22

    Long-range C-OFDR measurement of fiber Rayleigh scatter signature is described. The Rayleigh scatter signature, which is an interference pattern of backscatters from the random refractive indices in fibers, is known to be applicable to fiber identification and temperature or strain sensing by measuring its repeatability and its spectral shift. However, these applications have not been realized at ranges beyond the laser coherence length since laser phase noise degrades its repeatability. This paper proposes and demonstrates a method for analyzing the optical power spectrum of local Rayleigh backscatter to overcome the limitation imposed by laser phase noise. The measurable range and spatial performance are also investigated experimentally with respect to the remaining phase noise and noise reduction by signal averaging with the proposed method. The feasibility of Rayleigh scatter signature measurement for long-range applications is confirmed.

  20. A synthesis approach for antennas with a quasi-linear gain variation over a wide frequency range

    NASA Astrophysics Data System (ADS)

    Deacu, Daniela; Tamas, Razvan; Petrescu, Teodor; Tasu, Sorin

    2016-12-01

    In this paper, we propose to extend the frequency-domain synthesis approach based on a variable slope profile for antennas with a linear variation over a fractional bandwidth in the order of 100%. In that case the inflection point on the resulting profile is no longer located at its half. Thus, the profile shape will no longer be folded at the half, but at a coordinate closer to the end, the resulting shape approaching to a bow-tie antenna than to a circular dipole antenna.

  1. Note: Ultra-high frequency ultra-low dc power consumption HEMT amplifier for quantum measurements in millikelvin temperature range

    NASA Astrophysics Data System (ADS)

    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.

  2. 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.

  3. A study of the electromagnetic shielding mechanisms in the GHz frequency range of graphene based composite layers

    NASA Astrophysics Data System (ADS)

    Drakakis, E.; Kymakis, E.; Tzagkarakis, G.; Louloudakis, D.; Katharakis, M.; Kenanakis, G.; Suchea, M.; Tudose, V.; Koudoumas, E.

    2017-03-01

    We report on the mechanisms of the electromagnetic interference shielding effect of graphene based paint like composite layers. In particular, we studied the absorption and reflection of electromagnetic radiation in the 4-20 GHz frequency of various dispersions employing different amounts of graphene nanoplatelets, polyaniline, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), special attention given on the relative contribution of each process in the shielding effect. Moreover, the influence of the composition, the thickness and the conductivity of the composite layers on the electromagnetic shielding was also examined.

  4. Maximum-Likelihood Estimation for Frequency-Modulated Continuous-Wave Laser Ranging using Photon-Counting Detectors

    DTIC Science & Technology

    2013-03-21

    instruments where frequency estimates are calcu- lated from coherently detected fields, e.g., coherent Doppler LIDAR . Our CRB results reveal that the best...wave coherent lidar using an optical field correlation detection method,” Opt. Rev. 5, 310–314 (1998). 8. H. P. Yuen and V. W. S. Chan, “Noise in...2170–2180 (2007). 13. T. J. Karr, “Atmospheric phase error in coherent laser radar,” IEEE Trans. Antennas Propag. 55, 1122–1133 (2007). 14. Throughout

  5. Maximum-Likelihood Estimation for Frequency-Modulated Continuous-Wave Laser Ranging Using Photon-Counting Detectors

    DTIC Science & Technology

    2013-01-01

    are calculated from coherently -detected fields, e.g., coherent Doppler lidar . Our CRB results reveal that the best-case mean-square error scales as 1...1088 (2001). 7. K. Asaka, Y. Hirano, K. Tatsumi, K. Kasahara, and T. Tajime, “A pseudo-random frequency modulation continuous wave coherent lidar using...multiple returns,” IEEE Trans. Pattern Anal. Mach. Intell. 29, 2170–2180 (2007). 11. T. J. Karr, “Atmospheric phase error in coherent laser radar

  6. Applying Frequency-Domain Equalization to Code-Division Multiple Access and Transform-Domain Communications Systems

    DTIC Science & Technology

    2008-03-01

    Captain, USAF AFIT/GE/ENG/08-33 DEPARTMENT OF THE AIR FORCE AIR UNIVERSITY AIR FORCE INSTITUTE OF TECHNOLOGY Wright-Patterson Air Force Base , Ohio...research examined the theory and application of using orthogonal fre- quency division multiplexing ( OFDM ), or discrete multi-tone (DMT), frequency...1 OFDM Orthogonal Frequency Division Multiplexing . . . . . . . . 4 QPSK Quadrature Phase Shift Keying . . . . . . . . . . . . . . . 4 QAM Quadrature

  7. Spatial-phase-modulation-based study of polyvinyl-alcohol/acrylamide photopolymers in the low spatial frequency range.

    PubMed

    Gallego, Sergi; Márquez, André; Méndez, David; Marini, Stephan; Beléndez, Augusto; Pascual, Inmaculada

    2009-08-01

    Photopolymers are appealing materials for the fabrication of diffractive optical elements (DOEs). We evaluate the possibilities of polyvinyl-alcohol/acrylamide-based photopolymers to store diffractive elements with low spatial frequencies. We record gratings with different spatial frequencies in the material and analyze the material behavior measuring the transmitted and the reflected orders as a function of exposition. We study two different compositions for the photopolymer, with and without a cross-linker. The values of diffraction efficiency achieved for both compositions make the material suitable to record DOEs with long spatial periods. Assuming a Fermi-Dirac-function-based profile, we fitted the diffracted intensities (up to the eighth order) to obtain the phase profile of the recorded gratings. This analysis shows that it is possible to achieve a phase shift larger than 2pi rad with steep edges in the periodic phase profile. In the case of the measurements in reflection, we have obtained information dealing with the surface profile, which show that it has a smooth shape with an extremely large phase-modulation depth.

  8. Efficient frequency downconversion at the single photon level from the red spectral range to the telecommunications C-band.

    PubMed

    Zaske, Sebastian; Lenhard, Andreas; Becher, Christoph

    2011-06-20

    We report on single photon frequency downconversion from the red part of the spectrum (738 nm) to the telecommunications C-band. By mixing attenuated laser pulses with an average photon number per pulse < 1 with a strong continuous light field at 1403 nm in a periodically poled Zn:LiNbO3 ridge waveguide an internal conversion efficiency of ∼ 73% is achieved. We further investigate the noise properties of the process by measuring the output spectrum. Our results indicate that by narrow spectral filtering a quantum interface should be feasible which bridges the wavelength gap between quantum emitters like color centers in diamond emitting in the red part of the spectrum and low-loss fiber-optic telecommunications wavelengths.

  9. 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.

  10. Coupling effect combined with incident polarization to modulate double split-ring-resonator in terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Zhu, Mei; Lin, Yu-Sheng; Lee, Chengkuo

    2014-11-01

    This work examines the coupling effect in concentric double split-ring-resonator devices in terahertz (THz) range when the inner ring changes its relative orientation to the outer ring. Through detailed analysis on the simulation results of surface current and electrical field distributions, we look into the changes of inductance and capacitance in the system caused by structural layouts, and present a set of coherent theory that is solely rooted in the inductance-capacitance circuit analogy to systematically account for the resonance change. Such coupling effect combined with polarization of the incident wave is further explored to demonstrate continuous modulation of THz resonances. A variation range of transmission intensity from 20% to 80% has been successfully achieved. These experimental results demonstrate the promise of realizing future tunable THz filters by means of rotating sub-structures of the device only.

  11. Long-range surface plasmon-induced tunable ultralow threshold optical bistability using graphene sheets at terahertz frequency.

    PubMed

    Kar, Aparupa; Goswami, Nabamita; Saha, Ardhendu

    2017-03-10

    A proposal on optical bistability at ultralow switching threshold and lower Fermi-level of graphene around 2 THz is implemented analytically through the proposed long-range surface plasmon resonance configuration by employing local field enhancement effects owing to the excitation of a graphene symmetric mode within graphene sheets. Reported threshold intensity for the optical bistability to date is 1.6  kW/cm2 within the terahertz region and 1.83  MW/cm2 at near-IR range. Whereas the proposed scheme explores the possibility of reducing this threshold down to 143.68  W/cm2, this technique proffers potential applications in nanoillumination, optical memory, and all-optical switching at an ultra-low threshold.

  12. Optimization of a Quantum Cascade Laser Operating in the Terahertz Frequency Range Using a Multiobjective Evolutionary Algorithm

    DTIC Science & Technology

    2004-06-01

    Range Using A Multiobjective Evolutionary Algorithm 1. Introduction Half of the 2000 Nobel Prize in Physics was awarded to Zhores Alferov and Herbert...Representing the Structure of an Evolutionary Algorithm [57] 3.2.1 Genetic Algorithms. The introduction of genetic algorithms occurred in Adaptation in...Highly Reliable Communications Networks.”. 22. Eiben , A. E. Evolutionary exploration of the search spaces, 178–188. Springer-Verlag, 1996. 23. Esaki, L

  13. Computation of the modified magnetostriction coefficient b' corresponding to different depth ranges in ferromagnetic specimens by using a frequency dependent model for magnetic Barkhausen emissions

    NASA Astrophysics Data System (ADS)

    Kypris, Orfeas; Nlebedim, Ikenna; Jiles, David

    2013-03-01

    We have recently shown that a linear relationship exists between the reciprocal peak voltage envelope amplitude 1 /Vpeak of the magnetic Barkhausen signal and elastic stress σ. By applying a frequency-dependent model to determine the depth of origin of the Barkhausen emissions in a uniformly stressed steel specimen, this relationship was found to be valid for different depth ranges. The linear relationship depends on a coefficient of proportionality b'. This was found to decrease with depth, indicating that the higher part of the frequency spectrum is less sensitive to changes in stress. In this study, the model equations have been applied at various depth ranges. It was found that the variation of b' with depth can be utilized in an inversion procedure to assess the stress state in ferromagnetic specimens to give stress-depth profiles. This study is useful for non-destructive characterization of stress with depth.

  14. Modulation and detection of the THz range signals using the highest harmonics of the fundamental frequency of the superlattice-based generator for biomedical applications

    NASA Astrophysics Data System (ADS)

    Makarov, Vladimir V.; Maksimenko, Vladimir A.; Ponomarenko, Vladimir I.; Khramova, Marina V.; Pavlov, Alexey N.; Prokhorov, Mikhail D.; Karavaev, Anatoly S.

    2016-04-01

    The data transmission method using the highest harmonics of semiconductor superlattice-based microwave generator has been proposed for biomedical applications. Semiconductor superlattice operated in charge domain formation regime is characterized by the rich high-harmonics power spectrum. The numerical modeling of modulation and detection of the THz range signals using the highest harmonics of the fundamental frequency of the superlattice-based generator was carried out. We have shown effectiveness of the proposed method and discussed the possible applications.

  15. 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.

  16. Linear-array-based photoacoustic imaging of human microcirculation with a range of high frequency transducer probes

    NASA Astrophysics Data System (ADS)

    Zafar, Haroon; Breathnach, Aedán; Subhash, Hrebesh M.; Leahy, Martin J.

    2015-05-01

    Photoacoustic imaging (PAI) with a linear-array-based probe can provide a convenient means of imaging the human microcirculation within its native structural context and adds functional information. PAI using a multielement linear transducer array combined with multichannel collecting system was used for in vivo volumetric imaging of the blood microcirculation, the total concentration of hemoglobin (HbT), and the hemoglobin oxygen saturation (sO2) within human tissue. Three-dimensional (3-D) PA and ultrasound (US) volumetric scans were acquired from the forearm skin by linearly translating the transducer with a stepper motor over a region of interest, while capturing two-dimensional images using 15, 21, and 40 MHz frequency transducer probes. For the microvasculature imaging, PA images were acquired at 800- and 1064-nm wavelengths. For the HbT and sO2 estimates, PA images were collected at 750- and 850-nm wavelengths. 3-D microcirculation, HbT, and sO2 maps of the forearm skin were obtained from normal subjects. The linear-array-based PAI has been found promising in terms of resolution, imaging depth, and imaging speed for in vivo microcirculation imaging within human skin. We believe that a reflection type probe, similar to existing clinical US probes, is most likely to succeed in real clinical applications. Its advantages include ease of use, speed, and familiarity for radiographers and clinicians.

  17. Excitation and propagation of an electromagnetic pulse in magnetized plasma in the low-hybrid frequency range

    NASA Astrophysics Data System (ADS)

    Shirokov, E. A.; Chugunov, Yu. V.

    2013-01-01

    We analyze specific features of slow quasi-static waves excited in the low-hybrid frequency band by a source whose dimensions are much smaller than electromagnetic wavelength. Main attention in this paper is given to an analysis of emission of harmonic signals by a dipole source in pulsed mode. First, the issue of influence of electromagnetic, thermal, and collision corrections in the dispersion equation on the field structure has been studied. Second, the structure of electric and magnetic fields near the resonant cone has been analyzed: in particular, effects of group delay and anomalous spreading of signals are considered. Thus constructed theory explains results of the OEDIPUS-C experiment, in which, for example, already at distances of order of ten wavelengths a signal delay of approximately 10-4 s was observed. Finally, we have studied some aspects of the inverse problem of electrodynamics: the role played in field formation by smoothness of charge distribution over antenna is demonstrated, and a class of smooth distributions of charge on antenna is found that form a preset field structure.

  18. On the dispersion management of fluorite whispering-gallery mode resonators for Kerr optical frequency comb generation in the telecom and mid-infrared range.

    PubMed

    Lin, Guoping; Chembo, Yanne K

    2015-01-26

    Optical whispering gallery mode (WGM) resonators have been very attracting platforms for versatile Kerr frequency comb generations. We report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above 109. Using an analytical approximation of WGM resonant frequencies in disk resonators, we investigate the effect of the geometry and transverse mode order on the total group-velocity dispersion (GVD). We demonstrate that the major radii and the radial mode indices play an important role in tailoring the GVD of WGM resonators. In particular, our study shows that in WGM disk-resonators, the polar families of modes have very similar GVD, while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude. The effect of these giant dispersion shifts are experimentally evidenced in Kerr comb generation with magnesium fluoride. From a more general perspective, this critical feature enables to push the zero-dispersion wavelength of fluorite crystals towards the mid-infrared (mid-IR) range, thereby allowing for efficient Kerr comb generation in that spectral range. We show that barium fluoride is the most interesting crystal in this regard, due to its zero dispersion wavelength (ZDW) at 1.93 μm and an optimal dispersion profile in the mid-IR regime. We expect our results to facilitate the design of different platforms for Kerr frequency comb generations in both telecommunication and mid-IR spectral ranges.

  19. Aerial perches and free-range laying hens: the effect of access to aerial perches and of individual bird parameters on keel bone injuries in commercial free-range laying hens.

    PubMed

    Donaldson, C J; Ball, M E E; O'Connell, N E

    2012-02-01

    The aim of this trial was to determine the effect of aerial perches on keel bone injuries and tibia bone characteristics in free-range laying hens. The relationship between keel bone injuries and individual bird parameters, such as weight, girth, wing:girth ratio, feather coverage, and tibia bone characteristics, was also assessed. Five commercial free-range houses, each containing between 7,000 and 8,000 birds, were used. The houses and range areas were divided in half; in half of the house, birds had access to aerial perches (P) and in the other half, they did not (NP). On 13 occasions between 17 and 70 wk of age, 20 birds per treatment were randomly selected from the slatted area and palpated for keel bone injury. At 72 wk of age, 30 birds per treatment in each of 4 houses were selected at random, weighed, and then euthanized. Girth and wing area and feather coverage were measured. The keel and left tibia bones were removed and keel bones were scored for injury. Tibia bones were weighed and diameter, length, breaking strength, and ash content recorded. Results indicated that access to aerial perches did not affect tibia bone measures (P > 0.05). Average palpated keel bone score increased with age of the hens (P < 0.001) but was not significantly affected by perch treatment (P > 0.05). There was a significant interaction between treatment and farm on keel bone injuries measured at dissection (P < 0.05), with the probability of birds having high keel-damage scores increasing in the perched treatment in some farms but not others. In general, as the keel bone injury score measured at dissection increased, the breaking strength (P < 0.001) and ash content (P < 0.05) of the tibia bone decreased. It is suggested that individual variation in bone strength contributes to differences in susceptibility to keel injury. No relationship existed between keel-injury score measured at dissection and individual parameters, such as weight, girth, or wing:girth ratio (P > 0

  20. Investigation of Multiple Frequency Ranges Using Discrete Wavelet Decomposition of Resting-State Functional Connectivity in Mild Traumatic Brain Injury Patients

    PubMed Central

    Chen, Haoxing; Roys, Steven; Zhuo, Jiachen; Varshney, Amitabh; Gullapalli, Rao P.

    2015-01-01

    Abstract The aim of this study was to investigate if discrete wavelet decomposition provides additional insight into resting-state processes through the analysis of functional connectivity within specific frequency ranges within the default mode network (DMN) that may be affected by mild traumatic brain injury (mTBI). Participants included 32 mTBI patients (15 with postconcussive syndrome [PCS+] and 17 without [PCS−]). mTBI patients received resting-state functional magnetic resonance imaging (rs-fMRI) at acute (within 10 days of injury) and chronic (6 months postinjury) time points and were compared with 31 controls (healthy control [HC]). The wavelet decomposition divides the time series into multiple frequency ranges based on four scaling factors (SF1: 0.125–0.250 Hz, SF2: 0.060–0.125 Hz, SF3: 0.030–0.060 Hz, SF4: 0.015–0.030 Hz). Within each SF, wavelet connectivity matrices for nodes of the DMN were created for each group (HC, PCS+, PCS−), and bivariate measures of strength and diversity were calculated. The results demonstrate reduced strength of connectivity in PCS+ patients compared with PCS− patients within SF1 during both the acute and chronic stages of injury, as well as recovery of connectivity within SF1 across the two time points. Furthermore, the PCS− group demonstrated greater network strength compared with controls at both time points, suggesting a potential compensatory or protective mechanism in these patients. These findings stress the importance of investigating resting-state connectivity within multiple frequency ranges; however, many of our findings are within SF1, which may overlap with frequencies associated with cardiac and respiratory activities. PMID:25808612

  1. Design and characterization of a system for exposure of cultured cells to extremely low frequency electric and magnetic fields over a wide range of field strengths.

    PubMed

    Mullins, R D; Sisken, J E; Hejase, H A; Sisken, B F

    1993-01-01

    A system is described that is capable of producing extremely low frequency (ELF) magnetic fields for relatively short-term exposure of cultured mammalian cells. The system utilizes a ferromagnetic core to contain and direct the magnetic field of a 1,000 turn solenoidal coil and can produce a range of flux densities and induced electric fields much higher than those produced by Helmholtz coils. The system can generate magnetic fields from the microtesla (microT) range up to 0.14 T with induced electric field strengths on the order of 1.0 V/m. The induced electric field can be accurately varied by changing the sample chamber configuration without changing the exposure magnetic field. This gives the system the ability to separate the bioeffects of magnetic and induced electric fields. In the frequency range of 4-100 Hz and magnetic flux density range of 0.005-0.14 T, the maximum total harmonic distortion of the induced electric field is typically less than 1.0%. The temperature of the samples is held constant to within 0.4 degrees C by constant perfusion of warmed culture medium through the sample chamber.

  2. Time constants for temperature elevation in human models exposed to dipole antennas and beams in the frequency range from 1 to 30 GHz

    NASA Astrophysics Data System (ADS)

    Morimoto, Ryota; Hirata, Akimasa; Laakso, Ilkka; Ziskin, Marvin C.; Foster, Kenneth R.

    2017-03-01

    This study computes the time constants of the temperature elevations in human head and body models exposed to simulated radiation from dipole antennas, electromagnetic beams, and plane waves. The frequency range considered is from 1 to 30 GHz. The specific absorption rate distributions in the human models are first computed using the finite-difference time-domain method for the electromagnetics. The temperature elevation is then calculated by solving the bioheat transfer equation. The computational results show that the thermal time constants (defined as the time required to reach 63% of the steady state temperature elevation) decrease with the elevation in radiation frequency. For frequencies higher than 4 GHz, the computed thermal time constants are smaller than the averaging time prescribed in the ICNIRP guidelines, but larger than the averaging time in the IEEE standard. Significant differences between the different head models are observed at frequencies higher than 10 GHz, which is attributable to the heat diffusion from the power absorbed in the pinna. The time constants for beam exposures become large with the increase in beam diameter. The thermal time constant in the brain is larger than that in the superficial tissues at high frequencies, because the brain temperature elevation is caused by the heat conduction of energy absorbed in the superficial tissue. The thermal time constant is minimized with an ideal beam with a minimum investigated diameter of 10 mm this minimal time constant is approximately 30 s and is almost independent of the radiation frequency, which is supported by analytic methods. In addition, the relation between the time constant, as defined in this paper, and ‘averaging time’ as it appears in the exposure limits is discussed, especially for short intense pulses. Similar to the laser guidelines, provisions should be included in the limits to limit the fluence for such pulses.

  3. Time constants for temperature elevation in human models exposed to dipole antennas and beams in the frequency range from 1 to 30 GHz.

    PubMed

    Morimoto, Ryota; Hirata, Akimasa; Laakso, Ilkka; Ziskin, Marvin C; Foster, Kenneth R

    2017-03-07

    This study computes the time constants of the temperature elevations in human head and body models exposed to simulated radiation from dipole antennas, electromagnetic beams, and plane waves. The frequency range considered is from 1 to 30 GHz. The specific absorption rate distributions in the human models are first computed using the finite-difference time-domain method for the electromagnetics. The temperature elevation is then calculated by solving the bioheat transfer equation. The computational results show that the thermal time constants (defined as the time required to reach 63% of the steady state temperature elevation) decrease with the elevation in radiation frequency. For frequencies higher than 4 GHz, the computed thermal time constants are smaller than the averaging time prescribed in the ICNIRP guidelines, but larger than the averaging time in the IEEE standard. Significant differences between the different head models are observed at frequencies higher than 10 GHz, which is attributable to the heat diffusion from the power absorbed in the pinna. The time constants for beam exposures become large with the increase in beam diameter. The thermal time constant in the brain is larger than that in the superficial tissues at high frequencies, because the brain temperature elevation is caused by the heat conduction of energy absorbed in the superficial tissue. The thermal time constant is minimized with an ideal beam with a minimum investigated diameter of 10 mm; this minimal time constant is approximately 30 s and is almost independent of the radiation frequency, which is supported by analytic methods. In addition, the relation between the time constant, as defined in this paper, and 'averaging time' as it appears in the exposure limits is discussed, especially for short intense pulses. Similar to the laser guidelines, provisions should be included in the limits to limit the fluence for such pulses.

  4. Frequency and Risk of Marijuana Use among Substance-Using Health Care Patients in Colorado with and without Access to State Legalized Medical Marijuana.

    PubMed

    Richmond, Melissa K; Pampel, Fred C; Rivera, Laura S; Broderick, Kerryann B; Reimann, Brie; Fischer, Leigh

    2015-01-01

    With increasing use of state legalized medical marijuana across the country, health care providers need accurate information on patterns of marijuana and other substance use for patients with access to medical marijuana. This study compared frequency and severity of marijuana use, and use of other substances, for patients with and without state legal access to medical marijuana. Data were collected from 2,030 patients who screened positive for marijuana use when seeking health care services in a large, urban safety-net medical center. Patients were screened as part of a federally funded screening, brief intervention, and referral to treatment (SBIRT) initiative. Patients were asked at screening whether they had a state-issued medical marijuana card and about risky use of tobacco, alcohol, and other illicit substances. A total of 17.4% of marijuana users had a medical marijuana card. Patients with cards had higher frequency of marijuana use and were more likely to screen at moderate than low or high risk from marijuana use. Patients with cards also had lower use of other substances than patients without cards. Findings can inform health care providers of both the specific risks of frequent, long-term use and the more limited risks of other substance use faced by legal medical marijuana users.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. On the determination of the dynamic properties of a transformer oil based ferrofluid in the frequency range 0.1-20 GHz

    NASA Astrophysics Data System (ADS)

    Fannin, P. C.; Vekas, L.; Marin, C. N.; Malaescu, I.

    2017-02-01

    Complex susceptibility measurements provide a unique and efficient means for the investigation and determination of the dynamic properties of magnetic fluids. In particular, measurement of the frequency, f(Hz), and field, H(kA/m), dependent, complex susceptibility, χ(ω, Η)= χ‧(ω, Η)-iχ″(ω, Η), of magnetic fluids has proven to be a valuable and reliable technique for investigating such properties. The experimental data presented here was obtained from measurements of a transformer oil based ferrofluid, with measurements being performed over the frequency range 0.1-20 GHz and polarising fields 0-168 kA/m. In the case of transformer oil magnetic fluids, the normal measurement emphasis has been on the investigation of their dielectric properties, including the effects which lightning may have on these properties. Little has been reported on the measurement of the corresponding magnetic susceptibility, χ(ω), of such fluids and in this paper we address this fact. Thus we consider it worthwhile, in the case of a transformer with magnetic fluid transformer oil, being affected as a result of a lightening occurrence, to have knowledge of the fluids dynamic properties, at the microwave frequencies. In the process of determining the sample susceptibility profiles, it was found that the peak value of the χ″(ω) component, was approximately constant over the frequency range 2.4-6.3 GHz. From this it was determined that the fluid was effectively operating as a wideband absorber over a bandwidth of 3.9 GHz.

  10. Interference stabilization of atoms in a strong laser field for obtaining inversion and lasing in the visible and VUV frequency ranges

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    The interference stabilization of Rydberg atoms in strong laser fields is proposed for producing a plasma channel with the inverse population. Inversion between a group of Rydberg levels and low-lying excited levels and the ground state permits amplification and lasing in the IR, visible, and VUV frequency ranges. The lasing and light amplification processes in the plasma channel are analyzed using rate equations and the efficiency of this method is compared with that in the usual method for high harmonic generation during rescattering of electrons by a parent ion.

  11. Wide-dynamic-range cantilever magnetometry using a fiber-optic interferometer and its application to high-frequency electron spin resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Takahashi, Hideyuki; Okamoto, Tsubasa; Ohmichi, Eiji; Ohta, Hitoshi

    2016-12-01

    We present a method of broadening the dynamic range of optical interferometric detection of cantilever displacement. The key idea of this method is the use of a wavelength-tunable laser source. The wavelength is subject to proportional-integral control, which is used to keep the cavity detuning constant. Under this control, the change in wavelength is proportional to the cantilever displacement. Using this technique, we can measure large displacements (>1 µm) without degrading the sensitivity. We apply this technique to high-frequency electron spin resonance spectroscopy and succeed in removing an irregular background signal that arises from the constantly varying sensitivity of the interferometer.

  12. 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.

  13. Relationship between peak spatial-averaged specific absorption rate and peak temperature elevation in human head in frequency range of 1-30 GHz.

    PubMed

    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.

  14. Lower hybrid frequency range waves generated by ion polarization drift due to electromagnetic ion cyclotron waves: Analysis of an event observed by the Van Allen Probe B

    NASA Astrophysics Data System (ADS)

    Khazanov, G. V.; Boardsen, S.; Krivorutsky, E. N.; Engebretson, M. J.; Sibeck, D.; Chen, S.; Breneman, A.

    2017-01-01

    We analyze a wave event that occurred near noon between 07:03 and 07:08 UT on 23 February 2014 detected by the Van Allen Probes B spacecraft, where waves in the lower hybrid frequency range (LHFR) and electromagnetic ion cyclotron (EMIC) waves are observed to be highly correlated, with Pearson correlation coefficient of 0.86. We assume that the correlation is the result of LHFR wave generation by the ions' polarization drift in the electric field of the EMIC waves. To check this assumption the drift velocities of electrons and H+, He+, and O+ ions in the measured EMIC wave electric field were modeled. Then the LHFR wave linear instantaneous growth rates for plasma with these changing drift velocities and different plasma compositions were calculated. The time distribution of these growth rates, their frequency distribution, and the frequency dependence of the ratio of the LHFR wave power spectral density (PSD) parallel and perpendicular to the ambient magnetic field to the total PSD were found. These characteristics of the growth rates were compared with the corresponding characteristics of the observed LHFR activity. Reasonable agreement between these features and the strong correlation between EMIC and LHFR energy densities support the assumption that the LHFR wave generation can be caused by the ions' polarization drift in the electric field of an EMIC wave.

  15. Acoustic-seismic coupling for a wide range of angles of incidence and frequencies using signals of jet-aircraft overflights

    NASA Astrophysics Data System (ADS)

    Liebsch, Mattes; Altmann, Jürgen

    2016-12-01

    We present the excitation of soil vibration at the surface and at depths to 0.6 m caused by the sound of jet-aircraft overflights. By evaluating a multitude of overflight events we show that the coupling coefficient between soil velocity and sound pressure is only dependent on the angle of incidence of the acoustic wave and the frequency and thus can be averaged over the events. While previous publications presented only pointwise measurements we present signals for a wide range of angles of incidence and frequencies. In the seismic signal we found frequency bands of increased and decreased soil velocity caused by interference of the directly excited seismic wave with waves propagating in the ground and reflected at an underground boundary and at the surface. We use this seismic response to the broadband acoustic excitation to estimate soil characteristics e.g. P-wave velocity and depth of the boundary. The behaviour at depths > 0 m can be explained by an additional reflection at the surface. Here the reflection coefficient from theory was used successfully. The reflection coefficient of the P wave at that boundary - where insufficient information is available for its derivation from theory - was estimated from amplitude ratios at the surface.

  16. 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.

  17. Peak-to-average power ratio mitigation and adaptive bit assignment in single-carrier frequency division multiplexing access via hierarchical modulation

    NASA Astrophysics Data System (ADS)

    Zhang, Lijia; Liu, Bo; Xin, Xiangjun; Wang, Yongjun

    2014-11-01

    A hierarchical modulation with multilevels is proposed for an optical single-carrier frequency division multiplexing access (SC-FDMA) system. It can mitigate the nonlinearity by reducing the peak-to-average power ratio (PAPR) of the SC-FDM signal. According to different optical signal-to-noise ratio requirements, the adaptive bit allocation can be implemented on different levels during hierarchical modulation. In the experiment, the PAPR of the hierarchical-modulated SC-FDM signal outperforms the conventional SC-FDM signal by 0.7 dB. Signals with 4- and 6-bit hierarchical modulation are successfully demodulated by the optical network unit with power penalties less than 0.2 and 0.45 dB, respectively.

  18. 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.

  19. Age dependence of dielectric properties of bovine brain and ocular tissues in the frequency range of 400 MHz to 18 GHz

    NASA Astrophysics Data System (ADS)

    Schmid, Gernot; Überbacher, Richard

    2005-10-01

    In order to identify possible age-dependent dielectric properties of brain and eye tissues in the frequency range of 400 MHz to 18 GHz, measurements on bovine grey and white matter as well as on cornea, lens (cortical) and the vitreous body were performed using a commercially available open-ended coaxial probe and a computer-controlled vector network analyser. Freshly excised tissues of 52 animals of two age groups (42 adult animals, i.e. 16-24 month old and 10 young animals, i.e. 4-6 month old calves) were examined within 8 min (brain tissue) and 15 min (eye tissue), respectively, of the animals' death. Tissue temperatures for the measurements were 32 ± 1 °C and 25 ± 1 °C for brain and eye tissues, respectively. Statistical analysis of the measured data revealed significant differences in the dielectric properties of white matter and cortical lens tissue between the adult and the young group. In the case of white matter the mean values of conductivity and permittivity of young tissue were 15%-22% and 12%-15%, respectively, higher compared to the adult tissue in the considered frequency range. Similarly, young cortical lens tissue was 25%-76% higher in conductivity and 27%-39% higher in permittivity than adult cortical lens tissue.

  20. 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

  1. 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

  2. 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

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Identification of waves in the lower-hybrid frequency range in the scrape-off layer plasma of Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Shinya, Takahiro; Gyou Baek, Seung; Wallace, Gregory M.; Shiraiwa, Syun'ichi; Takase, Yuichi; Parker, Ronald R.; Bonoli, Paul T.; Brunner, Dan; Faust, Ian; LaBombard, Brian L.; Wukitch, Steve

    2017-03-01

    Polarization resolved measurements of the parallel refractive index {{N}\\parallel}\\equiv c{{k}\\parallel}/ω of the driven RF waves in the lower hybrid (LH) range of frequencies are performed using arrays of RF magnetic probes in the scrape-off layer plasma of Alcator C-Mod. The measured {{N}\\parallel} of the RF magnetic field component parallel to the background magnetic field is about  -1.6, which corresponds to the peak of the launched LH {{N}\\parallel} spectrum. Based on the wave dispersion relationship, this wave is identified as the LH slow wave. On the other hand, the RF magnetic field component perpendicular to the magnetic field is found to have a lower {{N}\\parallel} of  -1.2, and is detected only near the last closed flux surface. This wave is identified as the LH fast wave generated by slow-fast wave mode conversion.

  6. 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.

  7. 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.

  8. 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.

  9. Rotation of Magnetization Derived from Brownian Relaxation in Magnetic Fluids of Different Viscosity Evaluated by Dynamic Hysteresis Measurements over a Wide Frequency Range.

    PubMed

    Ota, Satoshi; Kitaguchi, Ryoichi; Takeda, Ryoji; Yamada, Tsutomu; Takemura, Yasushi

    2016-09-10

    The dependence of magnetic relaxation on particle parameters, such as the size and anisotropy, has been conventionally discussed. In addition, the influences of external conditions, such as the intensity and frequency of the applied field, the surrounding viscosity, and the temperature on the magnetic relaxation have been researched. According to one of the basic theories regarding magnetic relaxation, the faster type of relaxation dominates the process. However, in this study, we reveal that Brownian and Néel relaxations coexist and that Brownian relaxation can occur after Néel relaxation despite having a longer relaxation time. To understand the mechanisms of Brownian rotation, alternating current (AC) hysteresis loops were measured in magnetic fluids of different viscosities. These loops conveyed the amplitude and phase delay of the magnetization. In addition, the intrinsic loss power (ILP) was calculated using the area of the AC hysteresis loops. The ILP also showed the magnetization response regarding the magnetic relaxation over a wide frequency range. To develop biomedical applications of magnetic nanoparticles, such as hyperthermia and magnetic particle imaging, it is necessary to understand the mechanisms of magnetic relaxation.

  10. Report on BIPM/CIPM key comparison CCAUV.U-K4: absolute calibration of medical hydrophones in the frequency range 0.5 MHz to 20 MHz

    NASA Astrophysics Data System (ADS)

    Rajagopal, S.; Fury, C. R.; Zeqiri, B.; Brandt, M.; Wilkens, V.; Koch, C.; Matsuda, Y.; Yoshioka, M.; Ping, Y.; Yan, Z.; Wenping, B.; Costa-Felix, R. P. B.; Oliveira, E. G.

    2016-01-01

    The key compariosn CCAUV.U-K4 involved measurement of end-of-cable loaded sensitivity in units of volts/pascal of two travelling standards, 1 mm element diamater medical hydrophones at medical ultrasound frequencies. This is a repetition of key comparison CCAUV.U-K2 but the scope has been extended upwards to 20 MHz and downwards to 0.5 MHz. The reduction in the lower frequency provided an overlap with the underwater acoustics key comparison CCAUV.W-K1 which covers the range 1 kHz to 0.5 MHz. The results are analysed and presented in terms of degrees of equivalence, suitable for entry in the BIPM key comparison database. 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).

  11. Effects of radio frequency fields in the lower hybrid range on temperature gradient driven drift-modes in tokamaks: Momentum and impurity transport

    NASA Astrophysics Data System (ADS)

    Das, Salil; Jhang, Hogun; Singh, R.; Nordman, H.

    2016-10-01

    The significant effect of impurities in radiation losses and plasma dilution, which result in lower fusion power, and the evaluation of the important effects of intrinsic rotation on transport barrier formation, determination of momentum pinch velocity and its theoretical basis, in tokamak performance is studied using the four-wave parametric process using an electrostatic, collisionless fluid model for ion-temperature-gradient and trapped-electron mode driven turbulence in the presence of radio frequency fields in the lower hybrid (LH) range of frequencies. The beating of the pump and the sidebands exert a ponderomotive force on electrons, modifying the eigenfrequency of the drift waves and influencing the growth rates and the turbulent transport properties. Explicit expressions for the non-linear growth rate and the associated ion thermal conductivity and effective impurity diffusivity are derived. The effects of the rf fields on the momentum and impurity transport coefficients are evaluated for key parameters like rf power, temperature gradients, and magnetic shear. Prince Georges Community College, Largo, Maryland 20774, USA.

  12. 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.

  13. Rotation of Magnetization Derived from Brownian Relaxation in Magnetic Fluids of Different Viscosity Evaluated by Dynamic Hysteresis Measurements over a Wide Frequency Range

    PubMed Central

    Ota, Satoshi; Kitaguchi, Ryoichi; Takeda, Ryoji; Yamada, Tsutomu; Takemura, Yasushi

    2016-01-01

    The dependence of magnetic relaxation on particle parameters, such as the size and anisotropy, has been conventionally discussed. In addition, the influences of external conditions, such as the intensity and frequency of the applied field, the surrounding viscosity, and the temperature on the magnetic relaxation have been researched. According to one of the basic theories regarding magnetic relaxation, the faster type of relaxation dominates the process. However, in this study, we reveal that Brownian and Néel relaxations coexist and that Brownian relaxation can occur after Néel relaxation despite having a longer relaxation time. To understand the mechanisms of Brownian rotation, alternating current (AC) hysteresis loops were measured in magnetic fluids of different viscosities. These loops conveyed the amplitude and phase delay of the magnetization. In addition, the intrinsic loss power (ILP) was calculated using the area of the AC hysteresis loops. The ILP also showed the magnetization response regarding the magnetic relaxation over a wide frequency range. To develop biomedical applications of magnetic nanoparticles, such as hyperthermia and magnetic particle imaging, it is necessary to understand the mechanisms of magnetic relaxation. PMID:28335297

  14. Individual Ranging Behaviour Patterns in Commercial Free-Range Layers as Observed through RFID Tracking

    PubMed Central

    Larsen, Hannah; Cronin, Greg M.; Gebhardt-Henrich, Sabine G.; Smith, Carolynn L.; Hemsworth, Paul H.; Rault, Jean-Loup

    2017-01-01

    Simple Summary Understanding of how free-range laying hens on commercial farms utilize the outdoor space provided is limited. In order to optimise use of the range, it is important to understand whether hens vary in their ranging behaviour, both between and within individual hens. In our study, we used individual tracking technology to assess how hens in two commercial free-range flocks used the range and whether they varied in their use of the range. We assessed use of three areas at increasing distance from the shed; the veranda [0–2.4 m], close range [2.4–11.4 m], and far range [>11.4 m]. Most hens accessed the range every day (68.6% in Flock A, and 82.2% in Flock B), and most hens that ranged accessed all three areas (73.7% in Flock A, and 84.5% in Flock B). Hens spent half of their time outside in the veranda adjacent to the shed. We found that some hens within the flocks would range consistently (similar duration and frequency) daily, whereas others would range inconsistently. Hens that were more consistent in their ranging behaviour spent more time on the range overall than those that were inconsistent. These different patterns of range use should be taken into account to assess the implications of ranging for laying hens. Abstract In this exploratory study, we tracked free-range laying hens on two commercial flocks with Radio Frequency Identification (RFID) technology with the aim to examine individual hen variation in range use. Three distinct outdoor zones were identified at increasing distances from the shed; the veranda [0–2.4 m], close range [2.4–11.4 m], and far range [>11.4 m]. Hens’ movements between these areas were tracked using radio frequency identification technology. Most of the hens in both flocks (68.6% in Flock A, and 82.2% in Flock B) accessed the range every day during the study. Of the hens that accessed the range, most hens accessed all three zones (73.7% in Flock A, and 84.5% in Flock B). Hens spent half of their time

  15. 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

  16. Individual Ranging Behaviour Patterns in Commercial Free-Range Layers as Observed through RFID Tracking.

    PubMed

    Larsen, Hannah; Cronin, Greg M; Gebhardt-Henrich, Sabine G; Smith, Carolynn L; Hemsworth, Paul H; Rault, Jean-Loup

    2017-03-09

    In this exploratory study, we tracked free-range laying hens on two commercial flocks with Radio Frequency Identification (RFID) technology with the aim to examine individual hen variation in range use. Three distinct outdoor zones were identified at increasing distances from the shed; the veranda [0-2.4 m], close range [2.4-11.4 m], and far range [>11.4 m]. Hens' movements between these areas were tracked using radio frequency identification technology. Most of the hens in both flocks (68.6% in Flock A, and 82.2% in Flock B) accessed the range every day during the study. Of the hens that accessed the range, most hens accessed all three zones (73.7% in Flock A, and 84.5% in Flock B). Hens spent half of their time outdoors in the veranda area. Within-individual consistency of range use (daily duration and frequency) varied considerably, and hens which were more consistent in their daily range use spent more time on the range overall (p < 0.001). Understanding variation within and between individuals in ranging behaviour may help elucidate the implications of ranging for laying hens.

  17. 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.

  18. 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.

  19. 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).

  20. 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).

  1. An initial measurement of a fast neutral spectrum for ion cyclotron range of frequency heated plasma using two-channel compact neutral particle analyzers in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, S. H.; Wang, S. J.; Park, M.; Kim, S. K.

    2013-11-01

    The accurate measurement of fast neutral particles from high energy ion tails is very important since it is a measure of ion cyclotron range of frequency (ICRF) or neutral beam (NB) ion heating. In KSTAR, fast neutral measurements have been carried out using a compact neutral particle analyzer based on the silicon photo diode since 2010. As a result, the fast neutral spectrum was observed consistent with the ion temperature, diamagnetic energy, and neutron flux in 2011. However, there was fast neutral count beyond the injected neutral beam energy in NB-only heating. Since it is difficult to expect the count unless the temperature is high enough to diffuse the fast ions beyond the beam energy it was required to identify what it is. During the 2012 campaign, the two-channel diode detectors with and without a particle stopper were used to distinguish fast neutral counts and other counts by a hard X-ray or neutrons. As a result, it was confirmed that the high energy component beyond the beam energy originated from a hard X-ray or neutrons. Finally, it was observed that faster neutrals are generated by ICRF heating and enhanced by electron cyclotron heating compared to NB-only heating.

  2. An initial measurement of a fast neutral spectrum for ion cyclotron range of frequency heated plasma using two-channel compact neutral particle analyzers in KSTAR

    SciTech Connect

    Kim, S. H.; Park, M.; Kim, S. K.; Wang, S. J.

    2013-11-15

    The accurate measurement of fast neutral particles from high energy ion tails is very important since it is a measure of ion cyclotron range of frequency (ICRF) or neutral beam (NB) ion heating. In KSTAR, fast neutral measurements have been carried out using a compact neutral particle analyzer based on the silicon photo diode since 2010. As a result, the fast neutral spectrum was observed consistent with the ion temperature, diamagnetic energy, and neutron flux in 2011. However, there was fast neutral count beyond the injected neutral beam energy in NB-only heating. Since it is difficult to expect the count unless the temperature is high enough to diffuse the fast ions beyond the beam energy it was required to identify what it is. During the 2012 campaign, the two-channel diode detectors with and without a particle stopper were used to distinguish fast neutral counts and other counts by a hard X-ray or neutrons. As a result, it was confirmed that the high energy component beyond the beam energy originated from a hard X-ray or neutrons. Finally, it was observed that faster neutrals are generated by ICRF heating and enhanced by electron cyclotron heating compared to NB-only heating.

  3. Paired Associative Stimulation with High-Frequency Peripheral Component Leads to Enhancement of Corticospinal Transmission at Wide Range of Interstimulus Intervals

    PubMed Central

    Shulga, Anastasia; Zubareva, Aleksandra; Lioumis, Pantelis; Mäkelä, Jyrki P.

    2016-01-01

    Background: In spinal paired associative stimulation (PAS), orthodromic and antidromic volleys elicited by transcranial magnetic stimulation (TMS) and peripheral nerve stimulation (PNS) coincide at corticomotoneuronal synapses at the spinal cord. The interstimulus interval (ISI) between TMS and PNS determines whether PAS leads to motor-evoked potential (MEP) potentiation or depression. PAS applied as a long-term treatment for neurological patients might alter conduction of neural fibers over time. Moreover, measurements of motoneuron conductance for determination of ISIs may be challenging in these patients. Results: We sought to design a PAS protocol to induce MEP potentiation at wide range of ISIs. We tested PAS consisting of high-intensity (100% stimulator output, SO) TMS and high-frequency (50 Hz) PNS in five subjects at five different ISIs. Our protocol induced potentiation of MEP amplitudes in all subjects at all tested intervals. TMS and PNS alone did not result in MEP potentiation. The variant of PAS protocol described here does not require exact adjustment of ISIs in order to achieve effective potentiation of MEPs. Conclusions: This variant of PAS might be feasible as a long-term treatment in rehabilitation of neurological patients. PMID:27721747

  4. 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.

  5. 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

  6. Prediction of density and mechanical properties of human trabecular bone in vitro by using ultrasound transmission and backscattering measurements at 0.2 6.7 MHz frequency range

    NASA Astrophysics Data System (ADS)

    Hakulinen, Mikko A.; Day, Judd S.; Töyräs, Juha; Timonen, Matti; Kröger, Heikki; Weinans, Harrie; Kiviranta, Ilkka; Jurvelin, Jukka S.

    2005-04-01

    The ultrasound (US) backscattering method has been introduced as an alternative for the through-transmission measurement of sound attenuation and speed in diagnosis of osteoporosis. Both attenuation and backscattering depend strongly on the US frequency. In this study, 20 human trabecular bone samples were measured in transmission and pulse-echo geometry in vitro. The aim of the study was to find the most sensitive frequency range for the quantitative ultrasound (QUS) analyses. Normalized broadband US attenuation (nBUA), speed of sound (SOS), broadband US backscatter (BUB) and integrated reflection coefficient (IRC) were determined for each sample. The samples were spatially scanned with five pairs of US transducers covering a frequency range of 0.2-6.7 MHz. Furthermore, mechanical properties and density of the same samples were determined. At all frequencies, SOS, BUB and IRC showed statistically significant linear correlations with the mechanical properties or density of human trabecular bone (0.51 < r < 0.82, 0.54 < r < 0.81 and 0.70 < r < 0.85, respectively). In contrast to SOS, IRC and BUB, nBUA showed statistically significant correlations with mechanical parameters or density at the centre frequency of 1 MHz only. Our results suggest that frequencies up to 5 MHz can be useful in QUS analyses for the prediction of bone mechanical properties and density. Since the use of higher frequencies provides better axial and spatial resolution, improved structural analyses may be possible. While extensive attenuation of high frequencies in trabecular bone limits the clinically feasible frequency range, selection of optimal frequency range for in vivo QUS application should be carefully considered.

  7. 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

  8. Underground statistical measurements of the world-wide magnetic-background level in the millihertz frequency range with the [SQUID]2 magnetometer

    NASA Astrophysics Data System (ADS)

    Pozzo di Borgo, E.; Marfaing, J.; Waysand, G.

    2012-04-01

    The passive ground sensor system [SQUID]2 (SQUID with Shielding QUalified for Ionosphere Detection) is a three-axis cryogenically cooled magnetometer installed within the LSBB (Laboratoire Souterrain à Bas Bruit) in the South-East of France. This permanent operating device is sheltered by a unique underground shielded cell buried under 518m of karstic rock in a low noise environment, leading to a noise level lower than 3 fT/√Hz above 40Hz. Various phenomena, mainly linked to earthquakes contributions, have been identified at the local scale through a magneto-hydrodynamic correlation or at the global ones, resulting from the Earth-ionosphere coupling. As standing waves altering the surface of the Earth, free oscillations of Earth consecutive to earthquake events can also contribute to the magnetic field variation. Because the ionosphere is a complex and nonlinear system affected by a large number of independent parameters, it appears obvious to constrain the number of sources. Investigation of the ULF magnetic pulsations detected by [SQUID]2 over very quiet seismic and ionospheric conditions allows to defined a first experimental baseline of ionosphere magnetic noise [Marfaing et al. 2009]. Here, the analysis is performed to a set of 24 magnetically quiet days in order to establish a statistical baseline for the "global minimal magnetic level" in the site. The mean magnetic spectrum obtained in the millihertz range is characterized by several pulsations of noticeable amplitude above the flicker noise. An attempt of discrimination of the seismogenic contribution has been proposed through the polarization analysis proposed by Hayakawa et al. [2007]. Some frequencies coincide with the Earth's eigenmodes with less than 1% deviation; this includes the possibility of the superposition of several interplaying signals in the spectra of ionospheric or Earth's origin, assumed by the weak turbulence theory. These results provide complementary analysis to validate the

  9. 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.

  10. 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.

  11. 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...

  12. Study on sound-speed dispersion in a sandy sediment at frequency ranges of 0.5-3 kHz and 90-170 kHz

    NASA Astrophysics Data System (ADS)

    Yu, Sheng-qi; Liu, Bao-hua; Yu, Kai-ben; Kan, Guang-ming; Yang, Zhi-guo

    2017-03-01

    In order to study the properties of sound-speed dispersion in a sandy sediment, the sound speed was measured both at high frequency (90-170 kHz) and low frequency (0.5-3 kHz) in laboratory environments. At high frequency, a sampling measurement was conducted with boiled and uncooked sand samples collected from the bottom of a large water tank. The sound speed was directly obtained through transmission measurement using single source and single hydrophone. At low frequency, an in situ measurement was conducted in the water tank, where the sandy sediment had been homogeneously paved at the bottom for a long time. The sound speed was indirectly inverted according to the traveling time of signals received by three buried hydrophones in the sandy sediment and the geometry in experiment. The results show that the mean sound speed is approximate 1710-1713 m/s with a weak positive gradient in the sand sample after being boiled (as a method to eliminate bubbles as much as possible) at high frequency, which agrees well with the predictions of Biot theory, the effective density fluid model (EDFM) and Buckingham's theory. However, the sound speed in the uncooked sandy sediment obviously decreases (about 80%) both at high frequency and low frequency due to plenty of bubbles in existence. And the sound-speed dispersion performs a weak negative gradient at high frequency. Finally, a water-unsaturated Biot model is presented for trying to explain the decrease of sound speed in the sandy sediment with plenty of bubbles.

  13. 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.

  14. 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.

  15. 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.

  16. [Characteristics of the response of animals of different typological groups to the action of electromagnetic irradiation in the high and superhigh frequency ranges].

    PubMed

    Nikitina, V N; Suvorov, N B; Minkina, N A; Shaposhnikova, E S

    1989-01-01

    Peculiarities in the response of male rats of various typological (e.g. high- and low-entropy) groups to the effect of electromagnetic radiation of high and superhigh frequencies have been investigated. Radiation intensity was 500 microW/cm2 and 500 V/m respectively. Animals of different entropy groups exhibited variations in the radiation response of their CNS and endocrine system as well as in the state of their offspring during the antenatal development.

  17. Characterization of the electromagnetic near-field absorption in layered biological tissue in the frequency range from 30 MHz to 6,000 MHz.

    PubMed

    Christ, A; Samaras, T; Klingenböck, A; Kuster, N

    2006-10-07

    Currently, standards for the compliance testing of wireless devices are being extended to cover a wider frequency band and different usage patterns of mobile phones as well as of novel body-worn and handheld devices. As a consequence, not only the head but also strongly varying tissue distributions of the body are exposed to electromagnetic radiation. Several authors have reported changes in the SAR absorption of body tissue due to the presence of a low permittivity fat layer. This paper identifies two different effects which can lead to increased SAR in layered tissue in comparison to the SAR assessed using homogeneous tissue simulating liquid: (1) for larger distances between the tissue and the antenna, standing wave effects occur depending on the frequency and fat layer thickness. (2) In the very close near-field (distances approximately lambda/40), reactive E-field components lead to high local absorption in the skin. The latter effect occurs at lower frequencies and depends on the antenna type. Modification of the parameters of the homogeneous liquids cannot compensate for these effects. However, a conservative exposure estimate can be obtained by applying a multiplication factor between 1 and 3 to the values assessed using current experimental dosimetric techniques.

  18. Multi-channel absolute distance measurement system with sub ppm-accuracy and 20 m range using frequency scanning interferometry and gas absorption cells.

    PubMed

    Dale, John; Hughes, Ben; Lancaster, Andrew J; Lewis, Andrew J; Reichold, Armin J H; Warden, Matthew S

    2014-10-06

    We present an implementation of an absolute distance measurement system which uses frequency scanning interferometry (FSI). The technique, referred to as dynamic FSI, uses two frequency scanning lasers, a gas absorption cell and a reference interferometer to determine the unknown optical path length difference (OPD) of one or many measurement interferometers. The gas absorption cell is the length reference for the measurement system and is traceable to international standards through knowledge of the frequencies of its absorption features. The OPD of the measurement interferometers can vary during the measurement and the variation is measured at the sampling rate of the system (2.77 MHz in the system described here). The system is shown to measure distances from 0.2 m to 20 m with a combined relative uncertainty of 0.41 × 10⁻⁶ at the two sigma level (k = 2). It will be shown that within a scan the change in OPD of the measurement interferometer can be determined to a resolution of 40 nm.

  19. The effect of a diet containing grasshoppers and access to free-range on carcase and meat physicochemical and sensory characteristics in broilers.

    PubMed

    Sun, T; Long, R J; Liu, Z Y

    2013-01-01

    1. Research was conducted to evaluate the impact of a diet containing grasshoppers on the carcase, physicochemical and sensory characteristics in a free-range, grassland-based broiler production system. 2. A total of 80, 28-d-old male broilers were reared on grassland containing a large population of grasshoppers (treatment PB). Control birds were reared intensively on a maize-soybean diet (treatment CB). At 91 d of age, 24 birds from each treatment were slaughtered to evaluate carcase, meat and sensory characteristics. 3. Treatment PB produced birds with significantly lower live weights, breast, wing, thigh and drum weights, and higher dressing percentage and breast percentage of carcase, compared with CB. Treatment PB produced breast meat with significantly higher redness values, shear force and protein content, and lower pH values, cooking loss, moisture and fat content compared with CB. Sensory panel results for breast and thigh meats showed no treatment effect on colour and juiciness, but significantly higher scores for chewiness, flavour, aroma and overall appreciation, and lower scores for tenderness from treatment PB compared with CB. 4. Rearing chickens on rangeland may provide an alternative way to produce poultry meat which is considered superior by modern consumers.

  20. Electric and Dielectric Properties of Au/ZnS-PVA/n-Si (MPS) Structures in the Frequency Range of 10-200 kHz

    NASA Astrophysics Data System (ADS)

    Baraz, Nalan; Yücedağ, İbrahim; Azizian-Kalandaragh, Yashar; Ersöz, Gülçin; Orak, İkram; Altındal, Şemsettin; Akbari, Bashir; Akbari, Hossein

    2017-02-01

    Pure polyvinyl alcohol (PVA) capped ZnS semiconductor nanocrystals were prepared by microwave-assisted method, and the optical and structural properties of the as-prepared materials were characterized by x-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) techniques. The XRD pattern shows the formation of ZnS nanocrystals, and the UV-Vis spectroscopy results show a blue shift of about 1.2 eV in its band gap due to the confinement of very small nanostructures. The concentration of donor atoms (N D), diffusion potential (V D), Fermi energy level (E F), and barrier height (ΦB (C-V)) values were obtained from the reverse bias C -2-V plots for each frequency. The voltage dependent profile of series resistance (R s) and surface states (N ss) were also obtained using admittance and low-high frequency methods, respectively. R s-V and N ss-V plots both have distinctive peaks in the depletion region due to the spatial distribution charge at the surface states. The effect of R s and interfacial layer on the C-V and G/ω-V characteristics was found remarkable at high frequencies. Therefore, the high frequency C-V and G/ω-V plots were corrected to eliminate the effect of R s. The real and imaginary parts of dielectric constant (ɛ' and ɛ″) and electric modulus (M' and M″), loss tangent (tan δ), and ac electrical conductivity (σ ac) were also obtained using C and G/ω data and it was found that these parameters are indeed strong functions of frequency and applied bias voltage. Experimental results confirmed that the N ss, R s , and interfacial layer of the MPS structure are important parameters that strongly influence both the electrical and dielectric properties. The low values of N ss ( 109 eV-1 cm-2) and the value of dielectric constant (ɛ' = 1.3) of ZnS-PVA interfacial layer even at 10 kHz are very suitable for electronic devices when compared with the SiO2. These results confirmed that the ZnS-PVA considerably improves the performance of Au/n-Si (MS

  1. 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)

  2. 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

  3. The direct influence of electromagnetic fields on nerve- and muscle cells of man within the frequency range of 1 Hz to 30 MHz.

    PubMed

    Bernhardt, J

    1979-01-01

    By using several biophysical approximations and considering man as free space model limiting order-of-magnitude values for external electric and magnetic field strengths which may be hazardous for human beings were calculated. Danger may occur by excitation processes below 30 kHz for field strengths exceeding these limiting values; for frequencies larger than 60 kHz, thermal effects are predominant before excitation occurs. The external electric field strength necessary for causing action potentials in the central nervous system exceeds by far the corona forming level. But excitation is possible by strong alternating magnetic fields. Furthermore, by comparing the electrically and magnetically induced currents with the naturally flowing currents in man caused by the brain's and heart's electrical activity, a "lower boundary-line" was estimated. Regarding electric or magnetic field strengths undercutting this boundary-line, direct effects on the central nervous system may be excluded. Other mechanisms should be responsible for demonstrated biological effects.

  4. 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.

  5. On a simple attack, limiting the range transmission of secret keys in a system of quantum cryptography based on coding in a sub-carrier frequency

    NASA Astrophysics Data System (ADS)

    Klimov, A. N.; Kulik, S. P.; Molotkov, S. N.; Potapova, T. A.

    2017-03-01

    In the paper by Gleim et al (2016 Opt. Express 24 2619), it was declared that the system of quantum cryptography, exploiting quantum key distribution (QKD) protocol BB84 with the additional reference state and encoding in a sub-carrier, is able to distribute secret keys at a distance of 210 km. The following shows that a simple attack realized with a beam splitter results in a loss of privacy of the keys over substantially smaller distances. It turns out that the actual length of the secret key transmission for the QKD system encoding in the sub-carrier frequency is ten times less than that declared in Gleim et al (2016 Opt. Express 24 2619). Therefore it is impossible to safely use the keys when distributed at a larger length of the communication channel than shown below. The maximum communication distance does not exceed 22 km, even in the most optimistic scenario.

  6. A 400-mV 2.4-GHz frequency-shift keying transmitter using a capacitor switch across a transformer for a wide tuning range voltage-controlled oscillator

    NASA Astrophysics Data System (ADS)

    Miyahara, Yasunori; Ishikawa, Keisuke; Kuroda, Tadahiro

    2017-04-01

    We use a simple directly modulated closed loop to develop a 2.1-mW, 2.4-GHz frequency-shift keying (FSK) transmitter that operates on 400-mV DC supply. Connecting a capacitor bank switch via a transformer in the voltage control oscillator (VCO) to the frequency-divider circuit expands the frequency tuning range without reducing VCO performance. A prototype was fabricated using the 65-nm standard CMOS process with a chip size of 1.65 × 1.85 mm2. A modulation output signal spectrum of ‑42 dBc at 1.5 MHz with ‑6 dBm at the PA buffer output terminal; moreover, a VCO phase noise of ‑101 dBc/Hz at 1 MHz is achieved. The FSK transmitter can readily use voltages supplied by harvested energy because of the low power consumption of the sensor network.

  7. 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.

  8. Access Nets: Modeling Access to Physical Spaces

    NASA Astrophysics Data System (ADS)

    Frohardt, Robert; Chang, Bor-Yuh Evan; Sankaranarayanan, Sriram

    Electronic, software-managed mechanisms using, for example, radio-frequency identification (RFID) cards, enable great flexibility in specifying access control policies to physical spaces. For example, access rights may vary based on time of day or could differ in normal versus emergency situations. With such fine-grained control, understanding and reasoning about what a policy permits becomes surprisingly difficult requiring knowledge of permission levels, spatial layout, and time. In this paper, we present a formal modeling framework, called AccessNets, suitable for describing a combination of access permissions, physical spaces, and temporal constraints. Furthermore, we provide evidence that model checking techniques are effective in reasoning about physical access control policies. We describe our results from a tool that uses reachability analysis to validate security policies.

  9. Origin of Noise in AlGaN/GaN Heterostructures in the Range of 1Hz-100 MHz and its Up-Conversion in High-Frequency Noise of Oscillators

    NASA Astrophysics Data System (ADS)

    Vitusevich, S. A.

    2007-07-01

    This paper gives an overview of our recently obtained results on investigation of noise properties in undoped AlGaN/GaN high electron mobility transistors for the development of low-noise oscillators. The features observed in the carrier transport and noise spectra in two-dimensional AlGaN/GaN conducting channels grown on sapphire substrate are explained on the basis of a model taking into account the overheating effect and dynamic redistribution of potential. The low-frequency noise investigation of AlGaN/GaN heterostructures grown on SiC substrate showed that passivation significantly decreased the level of channel noise, but the noise coming from contact regions was found to be dominant in passivated devices. For the frequency range of 10-100 MHz in the structures, the fluctuations of electron concentration on the first quantum level of the quantum well and the scattering of the electrons in the barrier have been established. The measured phase noise of the oscillator shows that the low-frequency noise of the microwave active device is up-converted into phase fluctuations of the high-frequency carrier. The up-conversion factor of the oscillator for an offset frequency of 100 kHz is only about 15 kHz/V, which results in very low oscillator phase noise of - 105 dBc/Hz.

  10. The efficacy of cerebellar vermal deep high frequency (theta range) repetitive transcranial magnetic stimulation (rTMS) in schizophrenia: A randomized rater blind-sham controlled study.

    PubMed

    Garg, Shobit; Sinha, Vinod Kumar; Tikka, Sai Krishna; Mishra, Preeti; Goyal, Nishant

    2016-09-30

    Repetitive transcranial magnetic stimulation (rTMS) is a promising therapeutic for schizophrenia. Treatment effects of rTMS have been variable across different symptom clusters, with negative symptoms showing better response, followed by auditory hallucinations. Cerebellum, especially vermis and its abnormalities (both structural and functional) have been implicated in cognitive, affective and positive symptoms of schizophrenia. rTMS to this alternate site has been suggested as a novel target for treating patients with this disorder. Hypothesizing cerebellar vermal magnetic stimulation as an adjunct to treat schizophrenia psychopathology, we conducted a double blind randomized sham controlled rTMS study. In this study, forty patients were randomly allocated (using block randomization method) to active high frequency (theta patterned) rTMS (n=20) and sham (n=20) groups. They received 10 sessions over 2 weeks. The Positive and Negative Syndrome Scale (PANSS) and Calgary Depression Scale for Schizophrenia (CDSS) scores were assessed at baseline, after last session and at 4 weeks (2 weeks post-rTMS). We found a significantly greater improvement in the group receiving active rTMS sessions, compared to the sham group on negative symptoms, and depressive symptoms. We conclude that cerebellar stimulation can be used as an effective adjunct to treat negative and affective symptoms.

  11. Quantum teleportation in space and frequency using entangled pairs of photons from a frequency comb

    NASA Astrophysics Data System (ADS)

    Song, Hongbin; Yonezawa, Hidehiro; Kuntz, Katanya B.; Heurs, Michele; Huntington, Elanor H.

    2014-10-01

    Using entangled pairs of photons from a frequency comb and wide-band frequency-resolved homodyne detection, we propose a sequential quantum teleportation protocol for continuous variables that teleports an unknown state in space and frequency. A subthreshold optical parametric oscillator (OPO) produces a comb of entangled pairs of photons separated by the free spectral range of the OPO cavity. Wide-band frequency-resolved homodyne detection enables direct access to the sum and difference of quadratures between different teeth in the comb. Such measurements are Einstein-Podolsky-Rosen nullifiers, and can be used as the basis for teleportation protocols. Our protocol for space-and-frequency teleportation effectively links arbitrary frequency channels for frequency-division multiplexing, which has applications in universal quantum computation and large-capacity quantum communication.

  12. 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.

  13. 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.

  14. Spatial proximity effects on the excitation of sheath RF voltages by evanescent slow waves in the ion cyclotron range of frequencies

    NASA Astrophysics Data System (ADS)

    Colas, Laurent; Lu, Ling-Feng; Křivská, Alena; Jacquot, Jonathan; Hillairet, Julien; Helou, Walid; Goniche, Marc; Heuraux, Stéphane; Faudot, Eric

    2017-02-01

    We investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the near RF parallel electric field E ∥ emitted by ion cyclotron (IC) wave launchers. We use a simple model of slow wave (SW) evanescence coupled with direct current (DC) plasma biasing via sheath boundary conditions in a 3D parallelepiped filled with homogeneous cold magnetized plasma. Within a ‘wide-sheath’ asymptotic regime, valid for large-amplitude near RF fields, the RF part of this simple RF  +  DC model becomes linear: the sheath oscillating voltage V RF at open field line boundaries can be re-expressed as a linear combination of individual contributions by every emitting point in the input field map. SW evanescence makes individual contributions all the larger as the wave emission point is located closer to the sheath walls. The decay of |V RF| with the emission point/sheath poloidal distance involves the transverse SW evanescence length and the radial protrusion depth of lateral boundaries. The decay of |V RF| with the emitter/sheath parallel distance is quantified as a function of the parallel SW evanescence length and the parallel connection length of open magnetic field lines. For realistic geometries and target SOL plasmas, poloidal decay occurs over a few centimeters. Typical parallel decay lengths for |V RF| are found to be smaller than IC antenna parallel extension. Oscillating sheath voltages at IC antenna side limiters are therefore mainly sensitive to E ∥ emission by active or passive conducting elements near these limiters, as suggested by recent experimental observations. Parallel proximity effects could also explain why sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallel antisymmetry of the radiated field map. They could finally justify current attempts at reducing the RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinity.

  15. Semantic priming from letter-searched primes occurs for low- but not high-frequency targets: automatic semantic access may not be a myth.

    PubMed

    Tse, Chi-Shing; Neely, James H

    2007-11-01

    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 associated symmetrically or forward asymmetrically. For the LF targets, LS priming was (a) equivalent for forward asymmetric and symmetric pairs and (b) equal to silent-read (SR) priming for forward asymmetric pairs but less than SR priming for symmetric pairs. The typical finding of greater SR priming for response times for LF than for HF targets occurred for symmetric priming but not for forward asymmetric priming, which showed the interaction for errors. The authors consider their findings' implications for various accounts of how LS affects priming and explain the findings within J. H. Neely and D. E. Keefe's (1989) 3-process model as follows: (a) LS eliminates expectancy and semantic matching but does not reduce semantic activation and (b) expectancy contributes to SR priming for HF targets but not for LF targets, whereas the opposite is so for semantic matching.

  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. Development and numerical characterization of a new standing wave ultrasonic motor operating in the 30-40kHz frequency range.

    PubMed

    Hou, Xiaoyan; Lee, Heow Pueh; Ong, Chong Jin; Lim, Siak Piang

    2013-07-01

    The purpose of this research is to present a new design of standing-wave ultrasonic motor. This motor uses three piezoelectric actuating blocks which deform appropriately when powered up. The deformations of the blocks in ultrasonic range are internally amplified via the design of the motor by about 80 times and collectively yield an elliptical trajectory for the driving head of the motor. Finite Element Analysis using ANSYS was performed for both dynamic analysis and optimization of a prototype motor. The numerical results verified that at steady state, the motor can achieve vibrations in micro-meter level and the velocity can reach decimeter scale, satisfying the fast speed requirement as a positioning actuator.

  18. 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.

  19. 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.

  20. Dose Frequency Ranging Pharmacokinetic Study of Tenofovir-Emtricitabine After Directly Observed Dosing in Healthy Volunteers to Establish Adherence Benchmarks (HPTN 066)

    PubMed Central

    Andrade, Adriana; Bumpus, Namandjé N.; Kashuba, Angela D.; Marzinke, Mark A.; Moore, Ayana; Anderson, Peter L.; Bushman, Lane R.; Fuchs, Edward J.; Wiggins, Ilene; Radebaugh, Christine; Prince, Heather A.; Bakshi, Rahul P.; Wang, Ruili; Richardson, Paul; Shieh, Eugenie; McKinstry, Laura; Li, Xin; Donnell, Deborah; Elharrar, Vanessa; Mayer, Kenneth H.; Patterson, Kristine B.

    2016-01-01

    Abstract Oral preexposure prophylaxis (PrEP) trials report disparate efficacy attributed to variable adherence. HPTN 066 was conducted to establish objective, quantitative benchmarks for discrete, regular levels of adherence using directly observed dosing of tenofovir (TFV) disoproxil fumarate (TDF)/emtricitabine (FTC). Healthy, HIV-uninfected men and women were randomized to one of four oral regimens of fixed-dose TDF 300 mg/FTC 200 mg tablet for 5 weeks with all doses observed: one tablet weekly (one/week), one tablet twice weekly (two/week), two tablets twice weekly (four/week), or one tablet daily (seven/week). Trough serum TFV and FTC, peripheral blood mononuclear cell (PBMC), and CD4+ TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP) concentrations were determined throughout dosing and 2 weeks after the last dose. Rectosigmoidal, semen, and cervicovaginal samples were collected for drug assessment at end of dosing and 2 weeks later in a subset of participants. The 49 enrolled participants tolerated the regimens well. All regimens achieved steady-state concentrations by the second dose for serum TFV/FTC and by 7 days for PBMC TFV-DP/FTC-TP. Steady-state median TFV-DP predose concentrations demonstrated dose proportionality: one/week 1.6 fmol/106 PBMCs, two/week 9.1, four/week 18.8, seven/week, 36.3. Further, TFV-DP was consistently quantifiable 2 weeks after the last dose for the ≥4/week regimens. Adherence benchmarks were identified using receiver operating characteristic curves, which had areas under the curve ≥0.93 for all analytes in serum and PBMCs. Intersubject and intrasubject coefficients of variation (%CV) ranged from 33% to 63% and 14% to 34%, respectively, for all analytes in serum and PBMCs. Steady-state PBMC TFV-DP was established earlier and at lower concentrations than predicted and was the only analyte demonstrating predose concentration dose proportionality. Steady-state daily dosing serum TFV and PBMC TFV-DP was consistent with

  1. Dose Frequency Ranging Pharmacokinetic Study of Tenofovir-Emtricitabine After Directly Observed Dosing in Healthy Volunteers to Establish Adherence Benchmarks (HPTN 066).

    PubMed

    Hendrix, Craig W; Andrade, Adriana; Bumpus, Namandjé N; Kashuba, Angela D; Marzinke, Mark A; Moore, Ayana; Anderson, Peter L; Bushman, Lane R; Fuchs, Edward J; Wiggins, Ilene; Radebaugh, Christine; Prince, Heather A; Bakshi, Rahul P; Wang, Ruili; Richardson, Paul; Shieh, Eugenie; McKinstry, Laura; Li, Xin; Donnell, Deborah; Elharrar, Vanessa; Mayer, Kenneth H; Patterson, Kristine B

    2016-01-01

    Oral preexposure prophylaxis (PrEP) trials report disparate efficacy attributed to variable adherence. HPTN 066 was conducted to establish objective, quantitative benchmarks for discrete, regular levels of adherence using directly observed dosing of tenofovir (TFV) disoproxil fumarate (TDF)/emtricitabine (FTC). Healthy, HIV-uninfected men and women were randomized to one of four oral regimens of fixed-dose TDF 300 mg/FTC 200 mg tablet for 5 weeks with all doses observed: one tablet weekly (one/week), one tablet twice weekly (two/week), two tablets twice weekly (four/week), or one tablet daily (seven/week). Trough serum TFV and FTC, peripheral blood mononuclear cell (PBMC), and CD4(+) TFV-diphosphate (TFV-DP) and FTC-triphosphate (FTC-TP) concentrations were determined throughout dosing and 2 weeks after the last dose. Rectosigmoidal, semen, and cervicovaginal samples were collected for drug assessment at end of dosing and 2 weeks later in a subset of participants. The 49 enrolled participants tolerated the regimens well. All regimens achieved steady-state concentrations by the second dose for serum TFV/FTC and by 7 days for PBMC TFV-DP/FTC-TP. Steady-state median TFV-DP predose concentrations demonstrated dose proportionality: one/week 1.6 fmol/10(6) PBMCs, two/week 9.1, four/week 18.8, seven/week, 36.3. Further, TFV-DP was consistently quantifiable 2 weeks after the last dose for the ≥4/week regimens. Adherence benchmarks were identified using receiver operating characteristic curves, which had areas under the curve ≥0.93 for all analytes in serum and PBMCs. Intersubject and intrasubject coefficients of variation (%CV) ranged from 33% to 63% and 14% to 34%, respectively, for all analytes in serum and PBMCs. Steady-state PBMC TFV-DP was established earlier and at lower concentrations than predicted and was the only analyte demonstrating predose concentration dose proportionality. Steady-state daily dosing serum TFV and PBMC TFV-DP was consistent with

  2. An in-building network based on community access television integration with quadrature phase-shift keying orthogonal frequency-division multiplexing

    NASA Astrophysics Data System (ADS)

    Chen, Chia-Yi; Lin, Ying-Pyng; Lu, Hai-Han; Wu, Po-Yi; Lin, Huang-Chang; Wu, Hsiao-Wen

    2012-07-01

    An in-building network based on cable television (CATV) integration with quadrature phase-shift keying (QPSK) orthogonal frequency-division multiplexing (OFDM) transport over a combination of single-mode fibers (SMF) and perfluorinated graded-index plastic optical fibers (GI-POF) is proposed and experimentally demonstrated. In this system, a 1558.5 nm optical signal is directly transmitted along two fiber spans (20 km SMF + 25 m GI-POF). An optimum guard band is carefully established to ensure that no very substantial signal interference is induced between the CATV and QPSK OFDM bands. Error free transmission with sufficiently low bit error rate values was achieved for 1.25 Gbps/771.5 MHz QPSK OFDM signals; also, acceptable carrier-to-noise ratio, composite second-order, and composite triple-beat performances were obtained for CATV signals. This proposed network is significant because it is economical and convenient to install.

  3. 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.

  4. Arteriovenous Access

    PubMed Central

    MacRae, Jennifer M.; Dipchand, Christine; Oliver, Matthew; Moist, Louise; Yilmaz, Serdar; Lok, Charmaine; Leung, Kelvin; Clark, Edward; Hiremath, Swapnil; Kappel, Joanne; Kiaii, Mercedeh; Luscombe, Rick; Miller, Lisa M.

    2016-01-01

    Complications of vascular access lead to morbidity and may reduce quality of life. In this module, we review both infectious and noninfectious arteriovenous access complications including neuropathy, aneurysm, and high-output access. For the challenging patients who have developed many complications and are now nearing their last vascular access, we highlight some potentially novel approaches. PMID:28270919

  5. Anomalous Behavior in the Rotational Spectra of the NU(8) = 2 and the NU(8) = 3 Vibrations for the Carbon -13 and NITROGEN-15 Tagged Isotopes of the Methyl Cyanide Molecule in the Frequency Range 17-95 GHZ

    NASA Astrophysics Data System (ADS)

    Al-Share, Mohammad Abdel Karim

    1990-01-01

    The rotational microwave spectra of the three isotopes (^{13}CH _3^{12}C^ {15}N, ^{12} CH_3^{13}C ^{15}N, and ^ {13}CH_3^{13 }C^{15}N) of the methyl cyanide molecule in the nu _8 = 3, nu_8 = 2, nu_7 = 1 and nu_4 = 1 vibrational energy levels for the rotational components 1 <=q J <=q 5 (for a range of frequency 17-95 GHz.) were experimentally and theoretically examined. Rotational components in each vibration were measured to determine the mutual interactions in each vibration between any of the vibrational levels investigated. The method of isotopic substitution was employed for internal tuning of each vibrational level by single and double substitution of ^{13} C in the two sites of the molecule. It was found that relative frequencies within each vibration with respect to another vibration were shifted in a systematic way. The results given in this work were interpreted on the basis of these energy shifts. Large departure between experimentally measured and theoretically predicted frequency for the quantum sets (J, K = +/-1, l = +/-1), K l = 1 in the nu_8 = 3 vibrational states for the ^{13 }C and ^{15}N tagged isotopes of CH_3CN showed anomalous behavior which was explained as being due to Fermi resonance. Accidentally strong resonances (ASR) were introduced to account for some departures were not explained by Fermi resonance.

  6. Equivalent magnetic noise reduction at high frequency range due to polarized direction optimization in Terfenol-D/Pb(Mg1/3Nb2/3)O3-PbTiO3 magnetoelectric laminate sensors

    NASA Astrophysics Data System (ADS)

    Fang, Cong; Ma, Jiashuai; Yao, Meng; Di, Wenning; Lin, Di; Xu, Haiqing; Wang, Wei; Luo, Haosu

    2017-02-01

    In this paper, we investigate the responsivities and output voltage noise power spectral densities of magnetoelectric (ME) laminate sensors, consisting of length magnetized Terfenol-D alloys and transverse/width poled Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) crystals (i.e. L-T mode and L-W mode respectively), which are directly integrated with custom-build low noise charge amplifier circuits. Both the theoretical analyses and experimental results prove that the L-W mode sensor with the optimized polarized direction of the PMNT plate possesses lower magnetic detection limit at the interested high frequency range of 10 kHz≤f≤50 kHz. The equivalent magnetic noise (EMN) of the L-W mode sensor is 0.78 pT/Hz1/2 at 30 kHz, which is about 1.7 times lower than the 1.35 pT/Hz1/2 for conventional L-T mode sensor. Furthermore, an effective method of using operational amplifiers with low equivalent input noise voltage and employing ME laminate composites with high voltage coefficient to reduce the EMNs of the ME laminate sensors at high frequency range has been established.

  7. 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).

  8. 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.

  9. 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…

  10. Multi-Frequency Synthesis

    NASA Astrophysics Data System (ADS)

    Sault, R. J.; Conway, J. E.

    Multi-frequency synthesis is the practice of using visibility data measured over a range of frequencies when forming a continuum image. Because observing frequency is easier to vary than antenna location, it is an effective way of filling the (u,v) plane for an observation. Here we consider the artifacts in MFS images caused by source spectral variation. For frequency ranges of about 30%, for observations where only modest dynamic range is required, the artifacts of MFS can be completely ignored. For higher dynamic range observations, some calibration techniques and deconvolution algorithms are described which minimize the artifacts.

  11. 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…

  12. 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…

  13. Central venous access.

    PubMed

    Ganeshan, Arul; Warakaulle, Dinuke R; Uberoi, Raman

    2007-01-01

    Central venous access plays an important role in the management of an ever-increasing population of patients ranging from those that are critically ill to patients with difficult clinical access. Interventional radiologists are key in delivering this service and should be familiar with the wide range of techniques and catheters now available to them. A comprehensive description of these catheters with regard to indications, technical aspects of catheterization, success rates, and associated early and late complications, as well as a review of various published guidelines on central venous catheter insertion are given in this article.

  14. 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.

  15. Equal Access.

    ERIC Educational Resources Information Center

    De Patta, Joe

    2003-01-01

    Presents an interview with Stephen McCarthy, co-partner and president of Equal Access ADA Consulting Architects of San Diego, California, about designing schools to naturally integrate compliance with the Americans with Disabilities Act (ADA). (EV)

  16. Accessibility and assistive products

    PubMed Central

    Rodríguez-Porrero, Cristina

    2009-01-01

    Introduction Accessibility and assistive products and technologies are needed to ensure the rights of persons with disabilities and older persons. Many developments have been implemented in laws, standards, markets and from the consumers perspective, at international, European and national levels. The real issue is that not all the potential users benefit from the use of assistive products or accessible measures. Discussion Innovative methods are needed to allow all potential users to have real advantage of assistive technologies and accessible and design for all facilities. Best practices will be presented and existing gaps and recommendations will be discussed. Cost-benefits aspects will also be presented. Conclusion In order to get advantages from opportunities of globalization, hard work and responsibilities of all stakeholders are needed, so that assistive products and accessibility reach a whole range of situations and environments and contribute to ensure quality of life in a society for all.

  17. Passive Ranging

    DTIC Science & Technology

    1988-08-01

    1981). 5. R. Courant and D. Hilbert, Methods of Mathematical Physics , Vol. I, English ed., * Interscience, New York, 1953. 32 32 APPENDIX A CALCULATION...K Courant and D. Hilbert, Methods of Mathematical Physics , Vol. I, English ed., * Interscience, New York, 1953. A-8 APPENDIX B * RANGING ACCURACY IN

  18. 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.

  19. Validation of soy protein estimates from a food-frequency questionnaire with repeated 24-h recalls and isoflavonoid excretion in overnight urine in a Western population with a wide range of soy intakes2

    PubMed Central

    Jaceldo-Siegl, Karen; Fraser, Gary E; Chan, Jacqueline; Franke, Adrian; Sabaté, Joan

    2013-01-01

    Background Evidence of the benefits of soy on cancer risk in Western populations is inconsistent, in part because of the low intake of soy in these groups. Objective We assessed the validity of soy protein estimates from food-frequency questionnaires (FFQs) in a sample of Adventist Health Study-2 participants with a wide range of soy intakes. Design We obtained dietary intake data from 100 men and women (43 blacks and 57 nonblacks). Soy protein estimates from FFQs were compared against repeated 24-h recalls and urinary excretion of daidzein, genistein, total isoflavonoids (TIFLs), and equol (measured by HPLC/photodiode array/mass spectrometry) as reference criteria. We calculated Pearson and Spearman correlation coefficients (with 95% CIs) for FFQ–24-h recall, 24 h-recall–urinary excretion, and FFQ–urinary excretion pairs. Results Among soy users, mean (± SD) soy protein values were 12.12 ± 10.80 g/d from 24-h recalls and 9.43 ± 7.83 g/d from FFQs. The unattenuated correlation (95% CI) between soy protein estimates from 24-h recalls and FFQs was 0.57 (0.32, 0.75). Correlation coefficients between soy protein intake from 24-h recalls and urinary isoflavonoids were 0.72 (0.43, 0.96) for daidzein, 0.67 (0.43, 0.91) for genistein, and 0.72 (0.47, 0.98) for TIFLs. Between FFQs and urinary excretion, these were 0.50 (0.32, 0.65), 0.48 (0.29, 0.61), and 0.50 (0.32, 0.64) for daidzein, genistein, and TIFLs, respectively. Conclusions Soy protein estimates from questionnaire were significantly correlated with soy protein from 24-h recalls and urinary excretion of daidzein, genistein, and TIFLs. The Adventist Health Study-2 FFQ is a valid instrument for assessing soy protein in a population with a wide range of soy intakes. PMID:18469267

  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. 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.…

  2. 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.…

  3. Accessibility in E-Assessment

    ERIC Educational Resources Information Center

    Ball, Simon

    2009-01-01

    E-assessment offers many opportunities to broaden the range of tools at the assessor's disposal and thereby improve the overall accessibility of the assessment experience. In 2006, TechDis commissioned a report, produced by Edexcel, on the state of guidance on accessibility at the various stages of the assessment process--question design,…

  4. Frequency comb swept lasers

    PubMed Central

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C.; Fujimoto, James G.

    2010-01-01

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a ~−1.2dB sensitivity roll off over ~3mm range, compared to conventional swept source and FDML lasers which have −10dB and −5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0–3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed. PMID:19997365

  5. Frequency comb swept lasers.

    PubMed

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G

    2009-11-09

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

  6. 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).

  7. Effects of lexical factors on lexical access among typical language-learning children and children with word-finding difficulties.

    PubMed

    Newman, Rochelle S; German, Diane J

    2002-09-01

    This investigation studied the influence of lexical factors, known to impact lexical access in adults, on the word retrieval of children. Participants included 320 typical and atypical (word-finding difficulties) language-learning children, ranging in age from 7 to 12 years. Lexical factors examined included word frequency, age-of-acquisition, neighborhood density, neighborhood frequency, and stress pattern. Findings indicated that these factors did influence lexical access in children. Words which were high in frequency and neighborhood frequency, low in neighborhood density and age-of-acquisition, and which contained the typical stress pattern for the language were easier to name. Further, the number of neighbors that were more frequent than the target word also had an effect on the word's ease of retrieval. Significant interactions indicated that age-of-acquisition effects decreased with maturation for typically-learning children whereas these effects continued to impact the lexical access of children with word-finding difficulties across the ages studied, suggesting that these children's difficulties in accessing words may have prevented them from developing strong access paths to these words. These findings support a view of lexical access in which access paths to words become strengthened with successful use.

  8. 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 ...

  9. Internet access to ionosondes

    NASA Astrophysics Data System (ADS)

    Galkin, I. A.; Kitrosser, D. F.; Kecic, Z.; Reinisch, B. W.

    1999-01-01

    Connecting ionosondes to the Internet gives easy access to real-time information on ionospheric conditions. Some of the ionosonde sites provide just the ionogram displays, others give in addition the scaled ionospheric characteristics directly usable for frequency management and HF channel assessment. Some sounders also store days or months of station data, which makes it possible remotely to evaluate the time history of geophysical events. The Internet link is also a convenient means for remote system maintenance and control. The paper addresses various aspects of the Internet ionosonde scenario, including data base support, WWW publishing, user interface, security, and data format. A list of Internet accessible ionosonde stations is provided with a brief description.

  10. 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…

  11. 47 CFR 15.609 - Marketing of Access BPL equipment.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Marketing of Access BPL equipment. 15.609 Section 15.609 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Access Broadband Over Power Line (Access BPL) § 15.609 Marketing of Access BPL equipment. The marketing of...

  12. Frequency discrimination of brief tonal steps as a function of frequency in the lesser bulldog bat.

    PubMed

    Roverud, R C

    1999-09-01

    In a two-alternative, forced-choice task lesser bulldog bats were trained to distinguish between a pure tone pulse and a pulse composed of a series of brief tonal steps oscillating between two different frequencies. The tone-step pulse gradually approximates the pure tone pulse as the frequency difference between the steps becomes progressively smaller. Frequency difference limens for the brief tonal frequency steps were determined for a broad range of ultrasonic frequencies. The variation in tone-step difference limens with frequency appears to be correlated to the frequency structure of the bat's short-constant-frequency/frequency-modulated echolocation sound. There was a marked decline in the value of the relative frequency difference limens (Weber ratio) over a fairly narrow range of frequencies above the constant frequency and a sharp increase in threshold above this range. The relative thresholds for frequency discrimination were small and uniform over the frequency range of the frequency-modulated sweep and increased for frequencies below the frequency-modulated sweep. Thus, the most accurate frequency-discrimination abilities occur over a narrow frequency range around the frequency of the constant-frequency component of returning echoes. Frequency discrimination over the range of frequencies of the frequency-modulated component is relatively good.

  13. 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.

  14. 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.

  15. Frequency Tuning of Collapse-Mode Capacitive Micromachined Ultrasonic Transducer.

    PubMed

    Pekař, Martin; Dittmer, Wendy U; Mihajlović, Nenad; van Soest, Gijs; de Jong, Nico

    2017-02-01

    The information in an ultrasound image depends on the frequency that is used. In a clinical examination it may therefore be beneficial to generate ultrasound images acquired at multiple frequencies, which is difficult to achieve with conventional transducers. Capacitive micromachined ultrasonic transducers (CMUTs) offer a frequency response that is tunable by the bias voltage. In this study we investigate this frequency tunability for ultrasonic imaging. We characterized a CMUT array operated at bias voltages up to three times higher than the collapse-voltage. All elements of the array were connected to a single transmit and receive channel through a bias circuit. We quantified the transmit-receive and transmit sensitivity as a function of frequency for a range of bias voltages. Impulse response measurements show that the center frequency is modifiable between 8.7MHz and 15.3MHz with an applied bias voltage of -50V to -170V. The maximum transmit sensitivity is 52kPa/V at a center frequency of 9.0MHz with an applied bias voltage of -105V. The -3dB transmit range in center frequency accessible with the variable bias voltage is 6.7-15.5MHz. This study shows that a collapse-mode CMUT can operate efficiently at multiple center frequencies when the driving pulse and the bias voltage are optimized. We demonstrate the usefulness of frequency tuning by comparing images at different optimal combinations of driving frequency and bias voltage, acquired by linearly moving the transducer across a tissue mimicking phantom.

  16. Short-range Fundamental forces

    SciTech Connect

    Antoniadis, I; Baessler, Stefan; Buechner, M; Fedorov, General Victor; Hoedl, S.; Lambrecht, A; Nesvizhevsky, V.; Pignol, G; Reynaud, S.; Sobolev, Yu.

    2011-01-01

    We consider theoretical motivations to search for extra short-range fundamental forces as well as experiments constraining their parameters. The forces could be of two types: (1) spin-independent forces; and (2) spin-dependent axion-like forces. Different experimental techniques are sensitive in respective ranges of characteristic distances. The techniques include measurements of gravity at short distances, searches for extra interactions on top of the Casimir force, precision atomic and neutron experiments. We focus on neutron constraints, thus the range of characteristic distances considered here corresponds to the range accessible for neutron experiments.

  17. 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)

  18. Measured Response of Local, Mid-range and Far-range Discontinuities of Large Metal Groundplanes using Time Domain Techniques

    NASA Astrophysics Data System (ADS)

    Schrader, T.; Münter, K.; Battermann, S.; Garbe, H.

    2005-05-01

    This work describes a method to detect and to quantify any local or mid-range discontinuity on extended flat metal planes. Often these planes are used for antenna calibration (open area test site - OATS) or the plane could be the ground of a semi-anechoic chamber used in Electromagnetic Compatibility (EMC) testing. The measurement uncertainty of antenna calibration or EMC testing depends on the groundplane's quality, which can be accessed using this method. A vector network analyzer with time-domain option is used to determine the complex-valued input scattering parameter S11,F of an aperture antenna in a monostatic setup. S;11,F contains the information desired about the discontinuities and is measured in the frequency domain with high dynamic range. But only after a linear filtering utilizing the Chirp-Z-Transform the obtained time-domain signal S11,T evidence of local and mid-range discontinuities.

  19. High-frequency broadband transformers

    NASA Astrophysics Data System (ADS)

    London, S. E.; Tomashevich, S. V.

    1981-05-01

    A systematic review of the theory and design principles of high-frequency broadband transformers is presented. It is shown that the transformers of highest performance are those whose coils consist of strips of double-wire and multiwire transmission lines. Such devices are characterized by a wide operating frequency range, and make possible operation at microwave frequencies at high levels of transmitted power.

  20. 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

  1. 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.

  2. 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.

  3. Assessment of Modeled Received Sound Pressure Levels and Movements of Satellite-Tagged Odontocetes Exposed to Mid-Frequency Active Sonar at the Pacific Missile Range Facility: February 2011 Through February 2013

    DTIC Science & Technology

    2014-05-30

    PMRF so that animal movements and diving behavior could be measured both before and during sonar use. PMRF PAM data and tag data were used in this...initial analysis to estimate exposure levels for tagged animals and determine whether any large-scale movements of these animals may have occurred in...range hydrophones), ship positions at time of transmissions (provided by PMRF) and animal locations (determined from satellite tag positions) allowed

  4. High Precision Laser Range Sensor

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge (Inventor); Lay, Oliver P. (Inventor)

    2003-01-01

    The present invention is an improved distance measuring interferometer that includes high speed phase modulators and additional phase meters to generate and analyze multiple heterodyne signal pairs with distinct frequencies. Modulation sidebands with large frequency separation are generated by the high speed electro-optic phase modulators, requiring only a single frequency stable laser source and eliminating the need for a fist laser to be tuned or stabilized relative to a second laser. The combination of signals produced by the modulated sidebands is separated and processed to give the target distance. The resulting metrology apparatus enables a sensor with submicron accuracy or better over a multi- kilometer ambiguity range.

  5. Determining the frequency, depth and velocity of preferential flow by high frequency soil moisture monitoring.

    PubMed

    Hardie, Marcus; Lisson, Shaun; Doyle, Richard; Cotching, William

    2013-01-01

    Preferential flow in agricultural soils has been demonstrated to result in agrochemical mobilisation to shallow ground water. Land managers and environmental regulators need simple cost effective techniques for identifying soil - land use combinations in which preferential flow occurs. Existing techniques for identifying preferential flow have a range of limitations including; often being destructive, non in situ, small sampling volumes, or are subject to artificial boundary conditions. This study demonstrated that high frequency soil moisture monitoring using a multi-sensory capacitance probe mounted within a vertically rammed access tube, was able to determine the occurrence, depth, and wetting front velocity of preferential flow events following rainfall. Occurrence of preferential flow was not related to either rainfall intensity or rainfall amount, rather preferential flow occurred when antecedent soil moisture content was below 226 mm soil moisture storage (0-70 cm). Results indicate that high temporal frequency soil moisture monitoring may be used to identify soil type - land use combinations in which the presence of preferential flow increases the risk of shallow groundwater contamination by rapid transport of agrochemicals through the soil profile. However use of high frequency based soil moisture monitoring to determine agrochemical mobilisation risk may be limited by, inability to determine the volume of preferential flow, difficulty observing macropore flow at high antecedent soil moisture content, and creation of artificial voids during installation of access tubes in stony soils.

  6. Determining the frequency, depth and velocity of preferential flow by high frequency soil moisture monitoring

    NASA Astrophysics Data System (ADS)

    Hardie, Marcus; Lisson, Shaun; Doyle, Richard; Cotching, William

    2013-01-01

    Preferential flow in agricultural soils has been demonstrated to result in agrochemical mobilisation to shallow ground water. Land managers and environmental regulators need simple cost effective techniques for identifying soil - land use combinations in which preferential flow occurs. Existing techniques for identifying preferential flow have a range of limitations including; often being destructive, non in situ, small sampling volumes, or are subject to artificial boundary conditions. This study demonstrated that high frequency soil moisture monitoring using a multi-sensory capacitance probe mounted within a vertically rammed access tube, was able to determine the occurrence, depth, and wetting front velocity of preferential flow events following rainfall. Occurrence of preferential flow was not related to either rainfall intensity or rainfall amount, rather preferential flow occurred when antecedent soil moisture content was below 226 mm soil moisture storage (0-70 cm). Results indicate that high temporal frequency soil moisture monitoring may be used to identify soil type - land use combinations in which the presence of preferential flow increases the risk of shallow groundwater contamination by rapid transport of agrochemicals through the soil profile. However use of high frequency based soil moisture monitoring to determine agrochemical mobilisation risk may be limited by, inability to determine the volume of preferential flow, difficulty observing macropore flow at high antecedent soil moisture content, and creation of artificial voids during installation of access tubes in stony soils.

  7. Effects of Spatial Frequencies on Word Identification by Fast and Slow Readers: Evidence from Eye Movements

    PubMed Central

    Jordan, Timothy R.; Dixon, Jasmine; McGowan, Victoria A.; Kurtev, Stoyan; Paterson, Kevin B.

    2016-01-01

    Recent research has shown that differences in the effectiveness of spatial frequencies for fast and slow skilled adult readers may be an important component of differences in reading ability in the skilled adult reading population (Jordan et al., 2016a). But the precise nature of this influence on lexical processing during reading remains to be fully determined. Accordingly, to gain more insight into the use of spatial frequencies by skilled adult readers with fast and slow reading abilities, the present study looked at effects of spatial frequencies on the processing of specific target words in sentences. These target words were of either high or low lexical frequency and each sentence was displayed as normal or filtered to contain only very low, low, medium, high, or very high spatial frequencies. Eye movement behavior for target words was closest to normal for each reading ability when text was shown in medium or higher spatial frequency displays, although reading occurred for all spatial frequencies. Moreover, typical word frequency effects (the processing advantage for words with higher lexical frequencies) were observed for each reading ability across a broad range of spatial frequencies, indicating that many different spatial frequencies provide access to lexical representations during textual reading for both fast and slow skilled adult readers. Crucially, however, target word fixations were fewer and shorter for fast readers than for slow readers for all display types, and this advantage for fast readers appeared to be similar for normal, medium, high, and very high spatial frequencies but larger for low and very low spatial frequencies. Therefore, although fast and slow skilled adult readers can both use a broad range of spatial frequencies when reading, fast readers make more effective use of these spatial frequencies, and especially those that are lower, when processing the identities of words. PMID:27733837

  8. 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.

  9. 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.

  10. Arbitrary optical frequency synthesis traced to an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Cai, Zihang; Zhang, Weipeng; Yang, Honglei; Li, Yan; Wei, Haoyun

    2016-11-01

    An arbitrary optical frequency synthesizer with a broad tuning range and high frequency accuracy is presented. The system includes an external cavity diode laser (ECDL) as the output laser, an Erbium-doped optical frequency comb being a frequency reference, and a control module. The optical frequency from the synthesizer can be continuously tuned by the large-scale trans-tooth switch and the fine intra-tooth adjustment. Robust feedback control by regulating the current and PZT voltage enables the ECDL to phase-lock to the Erbium-doped optical frequency comb, therefore to keep stable frequency output. In the meanwhile, the absolute frequency of the synthesizer is determined by the repetition rate, the offset frequency and the beat frequency. All the phase lock loops in the system are traced back to a Rubidium clock. A powerful and friendly software is developed to make the operation convenient by integrating the functions of frequency setting, tuning, tracing, locking and measuring into a LabVIEW interface. The output frequency tuning span and the uncertainty of the system are evaluated as >6 THz and <3 kHz, respectively. The arbitrary optical frequency synthesizer will be a versatile tool in diverse applications, such as synthetic wavelength based absolute distance measurement and frequency-stabilized Cavity Ring-Down Spectroscopy.

  11. High-frequency array studies of long-range Lg propagation and the causes of Lg blockage and attenuation in the Eurasian continental craton. Volume 2. Final report, 29 Sep 89-30 Jan 91

    SciTech Connect

    Baumgardt, D.R.

    1991-03-21

    An investigation was conducted of the nature of Lg propagation from the Soviet test site at Novaya Zemlya as recorded by array sensors to the south, including the new regional arrays ARCESS and NORESS, and the teleseismic Graefenburg array, located near the recently installed GERESS regional array. This study is important because of the recently announced intention of the Soviet Union to shift their underground nuclear testing activities from the test site near Semipalatinsk to Novaya Zemlya. A second study follows up earlier ones of long range Lg propagation from nuclear explosions in the continental platform and shield regions of the USSR; the present study gives geological interpretations of the efficiency of Lg propagation. The overall conclusion of these studies is that heterogeneity in the upper earth crust, sometimes referred to as the granitic layer, seems to be the primary factor in blockage of Lg. Whenever a large part of the granitic layer is replaced in a confined region as in a basin, by lower velocity sediments, such that there is a large velocity contrast between the basin sediments and the surrounding granitic rocks, Lg waves appear to be trapped in the basin and are attenuated by repeated reverberations in the basin. As a result, Lg waves are delayed, diverted, scattered, and blocked, such that their recorded amplitudes are much reduced compared with what is expected from anelastic attenuation. Effects of Lg blockages need to be taken into account whenever Lg amplitudes are used for yield estimation and event identification.

  12. Hemodialysis access procedures

    MedlinePlus

    ... returned to your body. Usually the access is put in your arm but it can also go ... A surgeon will put the access in. There are 3 types of access. Fistula: The surgeon joins an artery and vein under the ...

  13. Impacts of frequency increment errors on frequency diverse array beampattern

    NASA Astrophysics Data System (ADS)

    Gao, Kuandong; Chen, Hui; Shao, Huaizong; Cai, Jingye; Wang, Wen-Qin

    2015-12-01

    Different from conventional phased array, which provides only angle-dependent beampattern, frequency diverse array (FDA) employs a small frequency increment across the antenna elements and thus results in a range angle-dependent beampattern. However, due to imperfect electronic devices, it is difficult to ensure accurate frequency increments, and consequently, the array performance will be degraded by unavoidable frequency increment errors. In this paper, we investigate the impacts of frequency increment errors on FDA beampattern. We derive the beampattern errors caused by deterministic frequency increment errors. For stochastic frequency increment errors, the corresponding upper and lower bounds of FDA beampattern error are derived. They are verified by numerical results. Furthermore, the statistical characteristics of FDA beampattern with random frequency increment errors, which obey Gaussian distribution and uniform distribution, are also investigated.

  14. Precision optical reference frequencies

    NASA Astrophysics Data System (ADS)

    Riehle, Fritz; Schnatz, Harald; Zinner, G.; Trebst, Tilmann; Helmcke, Juergen

    1999-05-01

    Optical reference frequencies are provided by lasers of which the frequencies are stabilized to suitable absorption lines. Presently, twelve reference frequencies/wavelengths within the wavelengths range from 243 nm to 10.3 micrometers are recommended by the International Committee of Weights and Measures as references for the realization of the meter and scientific applications. As typical examples, we describe a diode-pumped, frequency doubled YAG-laser stabilized to an absorption line of molecular iodine and a Ca-stabilized laser. The latter one has been developed in two versions, a transportable system utilizing a small beam of thermal Ca atoms and a stationary standard based on laser cooled and trapped Ca atoms. The frequency of the Ca standard based on cold Ca atoms has been measured by a frequency chain allowing a phase-coherent comparison against the primary standard of time and frequency, the caesium clock. Its value is vCa equals 455 986 240 494.13 kHz with a relative standard uncertainty of 2.5 (DOT) 10-13.

  15. 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. ...

  16. Critical Access Hospitals (CAH)

    MedlinePlus

    ... use requirements for Critical Access Hospitals related to Electronic Health Records (EHRs)? Critical Access Hospital (CAH) are eligible for Electronic Health Record (EHR) incentive payments and can receive ...

  17. 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.

  18. Variable frequency iteration MPPT for resonant power converters

    DOEpatents

    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.

  19. 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…

  20. Frequency-controlled voltage regulator

    NASA Technical Reports Server (NTRS)

    Mclyman, W. T.

    1980-01-01

    Converting input ac to higher frequency reduce size and weight and makes possible unique kind of regulation. Since conversion frequency is above range of human hearing, supply generated on audible noise. It also exploits highfrequency conversion features to regulate its output voltage in novel way. Circuit is inherently short-circuit proof.