WorldWideScience

Sample records for signals simulating mid-frequency

  1. Calculation and simulation on mid-spatial frequency error in continuous polishing

    International Nuclear Information System (INIS)

    Xie Lei; Zhang Yunfan; You Yunfeng; Ma Ping; Liu Yibin; Yan Dingyao

    2013-01-01

    Based on theoretical model of continuous polishing, the influence of processing parameters on the polishing result was discussed. Possible causes of mid-spatial frequency error in the process were analyzed. The simulation results demonstrated that the low spatial frequency error was mainly caused by large rotating ratio. The mid-spatial frequency error would decrease as the low spatial frequency error became lower. The regular groove shape was the primary reason of the mid-spatial frequency error. When irregular and fitful grooves were adopted, the mid-spatial frequency error could be lessened. Moreover, the workpiece swing could make the polishing process more uniform and reduce the mid-spatial frequency error caused by the fix-eccentric plane polishing. (authors)

  2. Versatile mid-infrared frequency-comb referenced sub-Doppler spectrometer

    Science.gov (United States)

    Gambetta, A.; Vicentini, E.; Coluccelli, N.; Wang, Y.; Fernandez, T. T.; Maddaloni, P.; De Natale, P.; Castrillo, A.; Gianfrani, L.; Laporta, P.; Galzerano, G.

    2018-04-01

    We present a mid-IR high-precision spectrometer capable of performing accurate Doppler-free measurements with absolute calibration of the optical axis and high signal-to-noise ratio. The system is based on a widely tunable mid-IR offset-free frequency comb and a Quantum-Cascade-Laser (QCL). The QCL emission frequency is offset locked to one of the comb teeth to provide absolute-frequency calibration, spectral-narrowing, and accurate fine frequency tuning. Both the comb repetition frequency and QCL-comb offset frequency can be modulated to provide, respectively, slow- and fast-frequency-calibrated scanning capabilities. The characterisation of the spectrometer is demonstrated by recording sub-Doppler saturated absorption features of the CHF3 molecule at around 8.6 μm with a maximum signal-to-noise ratio of ˜7 × 103 in 10 s integration time, frequency-resolution of 160 kHz, and accuracy of less than 10 kHz.

  3. Versatile mid-infrared frequency-comb referenced sub-Doppler spectrometer

    Directory of Open Access Journals (Sweden)

    A. Gambetta

    2018-04-01

    Full Text Available We present a mid-IR high-precision spectrometer capable of performing accurate Doppler-free measurements with absolute calibration of the optical axis and high signal-to-noise ratio. The system is based on a widely tunable mid-IR offset-free frequency comb and a Quantum-Cascade-Laser (QCL. The QCL emission frequency is offset locked to one of the comb teeth to provide absolute-frequency calibration, spectral-narrowing, and accurate fine frequency tuning. Both the comb repetition frequency and QCL-comb offset frequency can be modulated to provide, respectively, slow- and fast-frequency-calibrated scanning capabilities. The characterisation of the spectrometer is demonstrated by recording sub-Doppler saturated absorption features of the CHF3 molecule at around 8.6 μm with a maximum signal-to-noise ratio of ∼7 × 103 in 10 s integration time, frequency-resolution of 160 kHz, and accuracy of less than 10 kHz.

  4. Mid-frequency Band Dynamics of Large Space Structures

    Science.gov (United States)

    Coppolino, Robert N.; Adams, Douglas S.

    2004-01-01

    High and low intensity dynamic environments experienced by a spacecraft during launch and on-orbit operations, respectively, induce structural loads and motions, which are difficult to reliably predict. Structural dynamics in low- and mid-frequency bands are sensitive to component interface uncertainty and non-linearity as evidenced in laboratory testing and flight operations. Analytical tools for prediction of linear system response are not necessarily adequate for reliable prediction of mid-frequency band dynamics and analysis of measured laboratory and flight data. A new MATLAB toolbox, designed to address the key challenges of mid-frequency band dynamics, is introduced in this paper. Finite-element models of major subassemblies are defined following rational frequency-wavelength guidelines. For computational efficiency, these subassemblies are described as linear, component mode models. The complete structural system model is composed of component mode subassemblies and linear or non-linear joint descriptions. Computation and display of structural dynamic responses are accomplished employing well-established, stable numerical methods, modern signal processing procedures and descriptive graphical tools. Parametric sensitivity and Monte-Carlo based system identification tools are used to reconcile models with experimental data and investigate the effects of uncertainties. Models and dynamic responses are exported for employment in applications, such as detailed structural integrity and mechanical-optical-control performance analyses.

  5. High-resolution mid-IR spectrometer based on frequency upconversion

    DEFF Research Database (Denmark)

    Hu, Qi; Dam, Jeppe Seidelin; Pedersen, Christian

    2012-01-01

    We demonstrate a novel approach for high-resolution spectroscopy based on frequency upconversion and postfiltering by means of a scanning Fabryx2013;Perot interferometer. The system is based on sum-frequency mixing, shifting the spectral content from the mid-infrared to the near-visible region al......-frequency 1064xA0;nm laser. We investigate water vapor emission lines from a butane burner and compare the measured results to model data. The presented method we suggest to be used for real-time monitoring of specific gas lines and reference signals....

  6. Phase Synchronization for the Mid-Frequency Square Kilometre Array Telescope

    Science.gov (United States)

    Schediwy, Sascha; Gozzard, David; Stobie, Simon; Gravestock, Charles; Whitaker, Richard; Alachkar, Bassem; Malan, Sias; Boven, Paul; Grainge, Keith

    2018-01-01

    The Square Kilometre Array (SKA) project is an international effort to build the world’s most sensitive radio telescope operating in the 50 MHz to 14 GHz frequency range. Construction of the SKA has been divided into phases, with the first phase (SKA1) accounting for the first 10% of the telescope's receiving capacity. During SKA1, a low-frequency aperture array comprising over a hundred thousand individual dipole antenna elements will be constructed in Western Australia (SKA1-low), while an array of 197 parabolic-dish antennas, incorporating the 64 dishes of MeerKAT, will be constructed in South Africa (SKA1-mid).Radio telescope arrays such as the SKA require phase-coherent reference signals to be transmitted to each antenna site in the array. In the case of the SKA1-mid, these reference signals will be generated at a central site and transmitted to the antenna sites via fiber-optic cables up to 175 km in length. Environmental perturbations affect the optical path length of the fiber and act to degrade the phase stability of the reference signals received at the antennas, which has the ultimate effect of reducing the fidelity and dynamic range of the data.Since 2011, researchers at the University of Western Australia (UWA) have led the development of an actively-stabilized phase-synchronization system designed specifically to meet the scientific needs and technical challenges of the SKA telescope. Recently this system has been select as the official phase synchronization system for the SKA1-mid telescope. The system is an evolution of Atacama Large Millimeter Array’s distributed ‘photonic local oscillator system’, incorporating key advances made by the international frequency metrology community over the last decade, as well as novel innovations developed by UWA researchers.In this presentation I will describe the technical details of the system; outline how the system's performance was tested using metrology techniques in a laboratory setting, on 186 km

  7. Generation of broadly tunable picosecond mid-infrared laser and sensitive detection of a mid-infrared signal by parametric frequency up-conversion in MgO:LiNbO3 optical parametric amplifiers

    International Nuclear Information System (INIS)

    Zhang Qiu-Lin; Zhang Jing; Qiu Kang-Sheng; Zhang Dong-Xiang; Feng Bao-Hua; Zhang Jing-Yuan

    2012-01-01

    Picosecond optical parametric generation and amplification in the near-infrared region within 1.361–1.656 μm and the mid-infrared region within 2.976–4.875 μm is constructed on the basis of bulk MgO:LiNbO 3 crystals pumped at 1.064 μm. The maximum pulse energy reaches 1.3 mJ at 1.464 μm and 0.47 mJ at 3.894 μm, corresponding to a pump-to-idler photon conversion efficiency of 25%. By seeding the hard-to-measure mid-infrared radiation as the idler in the optical parametric amplification and measuring the amplified and frequency up-converted signal in the near-infrared or even visible region, one can measure very week mid-infrared radiation with ordinary detectors, which are insensitive to mid-infrared radiation, with a very high gain. A maximum gain factor of about 7 × 10 7 is achieved at the mid-infrared wavelength of 3.374 μm and the corresponding energy detection limit is as low as about 390 aJ per pulse. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  8. Direct comparison of low- and mid-frequency Raman spectroscopy for quantitative solid-state pharmaceutical analysis.

    Science.gov (United States)

    Lipiäinen, Tiina; Fraser-Miller, Sara J; Gordon, Keith C; Strachan, Clare J

    2018-02-05

    This study considers the potential of low-frequency (terahertz) Raman spectroscopy in the quantitative analysis of ternary mixtures of solid-state forms. Direct comparison between low-frequency and mid-frequency spectral regions for quantitative analysis of crystal form mixtures, without confounding sampling and instrumental variations, is reported for the first time. Piroxicam was used as a model drug, and the low-frequency spectra of piroxicam forms β, α2 and monohydrate are presented for the first time. These forms show clear spectral differences in both the low- and mid-frequency regions. Both spectral regions provided quantitative models suitable for predicting the mixture compositions using partial least squares regression (PLSR), but the low-frequency data gave better models, based on lower errors of prediction (2.7, 3.1 and 3.2% root-mean-square errors of prediction [RMSEP] values for the β, α2 and monohydrate forms, respectively) than the mid-frequency data (6.3, 5.4 and 4.8%, for the β, α2 and monohydrate forms, respectively). The better performance of low-frequency Raman analysis was attributed to larger spectral differences between the solid-state forms, combined with a higher signal-to-noise ratio. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Simulation and theory of spontaneous TAE frequency sweeping

    International Nuclear Information System (INIS)

    Wang Ge; Berk, H.L.

    2012-01-01

    A simulation model, based on the linear tip model of Rosenbluth, Berk and Van Dam (RBV), is developed to study frequency sweeping of toroidal Alfvén eigenmodes (TAEs). The time response of the background wave in the RBV model is given by a Volterra integral equation. This model captures the properties of TAE waves both in the gap and in the continuum. The simulation shows that phase space structures form spontaneously at frequencies close to the linearly predicted frequency, due to resonant particle–wave interactions and background dissipation. The frequency sweeping signals are found to chirp towards the upper and lower continua. However, the chirping signals penetrate only the lower continuum, whereupon the frequency chirps and mode amplitude increases in synchronism to produce an explosive solution. An adiabatic theory describing the evolution of a chirping signal is developed which replicates the chirping dynamics of the simulation in the lower continuum. This theory predicts that a decaying chirping signal will terminate at the upper continuum though in the numerical simulation the hole disintegrates before the upper continuum is reached. (paper)

  10. Simulation and theory of spontaneous TAE frequency sweeping

    Science.gov (United States)

    Wang, Ge; Berk, H. L.

    2012-09-01

    A simulation model, based on the linear tip model of Rosenbluth, Berk and Van Dam (RBV), is developed to study frequency sweeping of toroidal Alfvén eigenmodes (TAEs). The time response of the background wave in the RBV model is given by a Volterra integral equation. This model captures the properties of TAE waves both in the gap and in the continuum. The simulation shows that phase space structures form spontaneously at frequencies close to the linearly predicted frequency, due to resonant particle-wave interactions and background dissipation. The frequency sweeping signals are found to chirp towards the upper and lower continua. However, the chirping signals penetrate only the lower continuum, whereupon the frequency chirps and mode amplitude increases in synchronism to produce an explosive solution. An adiabatic theory describing the evolution of a chirping signal is developed which replicates the chirping dynamics of the simulation in the lower continuum. This theory predicts that a decaying chirping signal will terminate at the upper continuum though in the numerical simulation the hole disintegrates before the upper continuum is reached.

  11. Dual-tone optical vector millimeter wave signal generated by frequency-nonupling the radio frequency 16-star quadrature-amplitude-modulation signal

    Science.gov (United States)

    Wu, Tonggen; Ma, Jianxin

    2017-12-01

    This paper proposes an original scheme to generate the photonic dual-tone optical millimeter wave (MMW) carrying the 16-star quadrature-amplitude-modulation (QAM) signal via an optical phase modulator (PM) and an interleaver with adaptive photonic frequency-nonupling without phase precoding. To enable the generated optical vector MMW signal to resist the power fading effect caused by the fiber chromatic dispersion, the modulated -5th- and +4th-order sidebands are selected from the output of the PM, which is driven by the precoding 16-star QAM signal. The modulation index of the PM is optimized to gain the maximum opto-electrical conversion efficiency. A radio over fiber link is built by simulation, and the simulated constellations and the bit error rate graph demonstrate that the frequency-nonupling 16-star QAM MMW signal has good transmission performance. The simulation results agree well with our theoretical results.

  12. Strength of forest-albedo feedback in mid-Holocene climate simulations

    Directory of Open Access Journals (Sweden)

    J. Otto

    2011-09-01

    Full Text Available Reconstructions of the mid-Holocene climate, 6000 years before present, suggest that spring temperatures were higher at high northern latitudes compared to the pre-industrial period. A positive feedback between expansion of forest and climate presumably contributed to this warming. In the presence of snow, forests have a lower albedo than grass land. Therefore, the expansion of forest likely favoured a warming in spring, counteracting the lower insolation at the mid-Holocene.

    We investigate the sensitivity of the vegetation-atmosphere interaction under mid-Holocene orbital forcing with respect to the strength of the forest-albedo feedback by using a comprehensive coupled atmosphere-vegetation model (ECHAM5/JSBACH. We perform two sets of model simulations: a first set of simulations with a relatively weak reduction of albedo of snow by forest; and a second set of simulations with a relatively strong reduction of the albedo of snow by forest.

    We show that the parameterisation of the albedo of snow leads to uncertainties in the temperature signal. Compared to the set with weak snow masking, the simulations with strong snow masking reveal a spring warming that is three times higher, by 0.34 °C north of 60° N. This warming is related to a forest expansion of only 13%.

  13. Simulation and Measurement of Through-the-Earth, Extremely Low-Frequency Signals Using Copper-Clad Steel Ground Rods

    OpenAIRE

    Damiano, Nicholas William; Yan, Lincan; Whisner, Bruce; Zhou, Chenming

    2017-01-01

    The underground mining environment can greatly affect radio signal propagation. Understanding how the earth affects signal propagation is a key to evaluating communications systems used during a mine emergency. One type of communication system is through-the-earth, which can utilize extremely low frequencies (ELF). This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating current injection...

  14. Mid-Infrared Frequency-Agile Dual-Comb Spectroscopy

    Science.gov (United States)

    Luo, Pei-Ling; Yan, Ming; Iwakuni, Kana; Millot, Guy; Hänsch, Theodor W.; Picqué, Nathalie

    2016-06-01

    We demonstrate a new approach to mid-infrared dual-comb spectroscopy. It opens up new opportunities for accurate real-time spectroscopic diagnostics and it significantly simplifies the technique of dual-comb spectroscopy. Two mid-infrared frequency combs of slightly different repetition frequencies and moderate, but rapidly tunable, spectral span are generated in the 2800-3200 cm-1 region. The generators rely on electro-optic modulators, nonlinear fibers for spectral broadening and difference frequency generation and do not involve mode-locked lasers. Flat-top frequency combs span up to 10 cm-1 with a comb line spacing of 100 MHz (3×10-3 cm-1). The performance of the spectrometer without any phase-lock electronics or correction scheme is illustrated with spectra showing resolved comb lines and Doppler-limited spectra of methane. High precision on the spectroscopic parameter (line positions and intensities) determination is demonstrated for spectra measured on a millisecond time scale and it is validated with comparison with literature data. G. Millot, S. Pitois, M. Yan, T. Hovannysyan, A. Bendahmane, T.W. Hänsch, N. Picqué, Frequency-agile dual-comb spectroscopy, Nature Photonics 10, 27-30 (2016).

  15. Generation of Mid-Infrared Frequency Combs for Spectroscopic Applications

    Science.gov (United States)

    Maser, Daniel L.

    Mid-infrared laser sources prove to be a valuable tool in exploring a vast array of phenomena, finding their way into applications ranging from trace gas detection to X-ray generation and carbon dating. Mid-infrared frequency combs, in particular, are well-suited for many of these applications, owing to their inherent low-noise and broadband nature. Frequency comb technology is well-developed in the near-infrared as a result of immense technological development by the telecommunication industry in silica fiber and the existence of readily-available glass dopants such as ytterbium and erbium that enable oscillators at 1 and 1.5 ?m. However, options become substantially more limited at longer wavelengths, as silica is no longer transparent and the components required in a mid-infrared frequency comb system (oscillators, fibers, and both fiber and free-space components) are far less technologically mature. This thesis explores several different approaches to generating frequency comb sources in the mid-infrared region, and the development of sources used in the nonlinear processes implemented to reach these wavelengths. An optical parametric oscillator, two approaches to difference frequency generation, and nonlinear spectral broadening in chip-scale waveguides are developed, characterized, and spectroscopic potential for these techniques is demonstrated. The source used for these nonlinear processes, the erbium-doped fiber amplifier, is also studied and discussed throughout the design and optimization process. The nonlinear optical processes critical to this work are numerically modeled and used to confirm and predict experimental behavior.

  16. Mid-Frequency Sonar Interactions with Beaked Whales

    National Research Council Canada - National Science Library

    Foote, Kenneth G; Feijoo, Gonzalo R; Rye, Kent; Reidenberg, Joy; Hastings, Mardi

    2007-01-01

    The top-level goal of this project is to build an interactive online modeling and visualization system, called the Virtual Beaked Whale, to enable users to predict mid-frequency sonar-induced acoustic...

  17. Application of multiple signal classification algorithm to frequency estimation in coherent dual-frequency lidar

    Science.gov (United States)

    Li, Ruixiao; Li, Kun; Zhao, Changming

    2018-01-01

    Coherent dual-frequency Lidar (CDFL) is a new development of Lidar which dramatically enhances the ability to decrease the influence of atmospheric interference by using dual-frequency laser to measure the range and velocity with high precision. Based on the nature of CDFL signals, we propose to apply the multiple signal classification (MUSIC) algorithm in place of the fast Fourier transform (FFT) to estimate the phase differences in dual-frequency Lidar. In the presence of Gaussian white noise, the simulation results show that the signal peaks are more evident when using MUSIC algorithm instead of FFT in condition of low signal-noise-ratio (SNR), which helps to improve the precision of detection on range and velocity, especially for the long distance measurement systems.

  18. Nonstationary signals phase-energy approach-theory and simulations

    CERN Document Server

    Klein, R; Braun, S; 10.1006/mssp.2001.1398

    2001-01-01

    Modern time-frequency methods are intended to deal with a variety of nonstationary signals. One specific class, prevalent in the area of rotating machines, is that of harmonic signals of varying frequencies and amplitude. This paper presents a new adaptive phase-energy (APE) approach for time-frequency representation of varying harmonic signals. It is based on the concept of phase (frequency) paths and the instantaneous power spectral density (PSD). It is this path which represents the dynamic behaviour of the system generating the observed signal. The proposed method utilises dynamic filters based on an extended Nyquist theorem, enabling extraction of signal components with optimal signal-to-noise ratio. The APE detects the most energetic harmonic components (frequency paths) in the analysed signal. Tests on simulated signals show the superiority of the APE in resolution and resolving power as compared to STFT and wavelets wave- packet decomposition. The dynamic filters also enable the reconstruction of the ...

  19. Injection-seeded tunable mid-infrared pulses generated by difference frequency mixing

    Science.gov (United States)

    Miyamoto, Yuki; Hara, Hideaki; Masuda, Takahiko; Hiraki, Takahiro; Sasao, Noboru; Uetake, Satoshi

    2017-03-01

    We report on the generation of nanosecond mid-infrared pulses having frequency tunability, a narrow linewidth, and a high pulse energy. These pulses are obtained by frequency mixing between injection-seeded near-infrared pulses in potassium titanyl arsenate crystals. A continuous-wave external cavity laser diode or a Ti:sapphire ring laser is used as a tunable seeding source for the near-infrared pulses. The typical energy of the generated mid-infrared pulses is in the range of 0.4-1 mJ/pulse. The tuning wavelength ranges from 3142 to 4806 nm. A narrow linewidth of 1.4 GHz and good frequency reproducibility of the mid-infrared pulses are confirmed by observing a rovibrational absorption line of gaseous carbon monoxide at 4587 nm.

  20. Simulation and Measurement of Through-the-Earth, Extremely Low-Frequency Signals Using Copper-Clad Steel Ground Rods.

    Science.gov (United States)

    Damiano, Nicholas William; Yan, Lincan; Whisner, Bruce; Zhou, Chenming

    2017-01-01

    The underground mining environment can greatly affect radio signal propagation. Understanding how the earth affects signal propagation is a key to evaluating communications systems used during a mine emergency. One type of communication system is through-the-earth, which can utilize extremely low frequencies (ELF). This paper presents the simulation and measurement results of recent National Institute for Occupational Safety and Health (NIOSH) research aimed at investigating current injection at ELF, and in particular, ground contact impedance. Measurements were taken at an outside surface testing location. The results obtained from modeling and measurement are characterized by electrode impedance, and the voltage received between two distant electrodes. This paper concludes with a discussion of design considerations found to affect low-frequency communication systems utilizing ground rods to inject a current into the earth.

  1. Modeling off-frequency binaural masking for short- and long-duration signals.

    Science.gov (United States)

    Nitschmann, Marc; Yasin, Ifat; Henning, G Bruce; Verhey, Jesko L

    2017-08-01

    Experimental binaural masking-pattern data are presented together with model simulations for 12- and 600-ms signals. The masker was a diotic 11-Hz wide noise centered on 500 Hz. The tonal signal was presented either diotically or dichotically (180° interaural phase difference) with frequencies ranging from 400 to 600 Hz. The results and the modeling agree with previous data and hypotheses; simulations with a binaural model sensitive to monaural modulation cues show that the effect of duration on off-frequency binaural masking-level differences is mainly a result of modulation cues which are only available in the monaural detection of long signals.

  2. Blind Compressed Sensing Parameter Estimation of Non-cooperative Frequency Hopping Signal

    Directory of Open Access Journals (Sweden)

    Chen Ying

    2016-10-01

    Full Text Available To overcome the disadvantages of a non-cooperative frequency hopping communication system, such as a high sampling rate and inadequate prior information, parameter estimation based on Blind Compressed Sensing (BCS is proposed. The signal is precisely reconstructed by the alternating iteration of sparse coding and basis updating, and the hopping frequencies are directly estimated based on the results. Compared with conventional compressive sensing, blind compressed sensing does not require prior information of the frequency hopping signals; hence, it offers an effective solution to the inadequate prior information problem. In the proposed method, the signal is first modeled and then reconstructed by Orthonormal Block Diagonal Blind Compressed Sensing (OBD-BCS, and the hopping frequencies and hop period are finally estimated. The simulation results suggest that the proposed method can reconstruct and estimate the parameters of noncooperative frequency hopping signals with a low signal-to-noise ratio.

  3. Frequency hopping signal detection based on wavelet decomposition and Hilbert-Huang transform

    Science.gov (United States)

    Zheng, Yang; Chen, Xihao; Zhu, Rui

    2017-07-01

    Frequency hopping (FH) signal is widely adopted by military communications as a kind of low probability interception signal. Therefore, it is very important to research the FH signal detection algorithm. The existing detection algorithm of FH signals based on the time-frequency analysis cannot satisfy the time and frequency resolution requirement at the same time due to the influence of window function. In order to solve this problem, an algorithm based on wavelet decomposition and Hilbert-Huang transform (HHT) was proposed. The proposed algorithm removes the noise of the received signals by wavelet decomposition and detects the FH signals by Hilbert-Huang transform. Simulation results show the proposed algorithm takes into account both the time resolution and the frequency resolution. Correspondingly, the accuracy of FH signals detection can be improved.

  4. Large signal simulation of photonic crystal Fano laser

    DEFF Research Database (Denmark)

    Zali, Aref Rasoulzadeh; Yu, Yi; Moravvej-Farshi, Mohammad Kazem

    2017-01-01

    be modulated at frequencies exceeding 1 THz which is much higher than its corresponding relaxation oscillation frequency. Large signal simulation of the Fano laser is also investigated based on pseudorandom bit sequence at 0.5 Tbit/s. It shows eye patterns are open at such high modulation frequency, verifying...

  5. Signal existence verification (SEV) for GPS low received power signal detection using the time-frequency approach.

    Science.gov (United States)

    Jan, Shau-Shiun; Sun, Chih-Cheng

    2010-01-01

    The detection of low received power of global positioning system (GPS) signals in the signal acquisition process is an important issue for GPS applications. Improving the miss-detection problem of low received power signal is crucial, especially for urban or indoor environments. This paper proposes a signal existence verification (SEV) process to detect and subsequently verify low received power GPS signals. The SEV process is based on the time-frequency representation of GPS signal, and it can capture the characteristic of GPS signal in the time-frequency plane to enhance the GPS signal acquisition performance. Several simulations and experiments are conducted to show the effectiveness of the proposed method for low received power signal detection. The contribution of this work is that the SEV process is an additional scheme to assist the GPS signal acquisition process in low received power signal detection, without changing the original signal acquisition or tracking algorithms.

  6. Detailed Analysis of Torque Ripple in High Frequency Signal Injection based Sensor less PMSM Drives

    Directory of Open Access Journals (Sweden)

    Ravikumar Setty A.

    2017-01-01

    Full Text Available High Frequency Signal Injection based techniques are robust and well proven to estimate the rotor position from stand still to low speed. However, Injected high frequency signal introduces, high frequency harmonics in the motor phase currents and results in significant Output Torque ripple. There is no detailed analysis exist in the literature, to study the effect of injected signal frequency on Torque ripple. Objective of this work is to study the Torque Ripple resulting from High Frequency signal injection in PMSM motor drives. Detailed MATLAB/Simulink simulations are carried to quantify the Torque ripple at different Signal frequencies.

  7. Time-frequency representation of a highly nonstationary signal via the modified Wigner distribution

    Science.gov (United States)

    Zoladz, T. F.; Jones, J. H.; Jong, J.

    1992-01-01

    A new signal analysis technique called the modified Wigner distribution (MWD) is presented. The new signal processing tool has been very successful in determining time frequency representations of highly non-stationary multicomponent signals in both simulations and trials involving actual Space Shuttle Main Engine (SSME) high frequency data. The MWD departs from the classic Wigner distribution (WD) in that it effectively eliminates the cross coupling among positive frequency components in a multiple component signal. This attribute of the MWD, which prevents the generation of 'phantom' spectral peaks, will undoubtedly increase the utility of the WD for real world signal analysis applications which more often than not involve multicomponent signals.

  8. A new method of hybrid frequency hopping signals selection and blind parameter estimation

    Science.gov (United States)

    Zeng, Xiaoyu; Jiao, Wencheng; Sun, Huixian

    2018-04-01

    Frequency hopping communication is widely used in military communications at home and abroad. In the case of single-channel reception, it is scarce to process multiple frequency hopping signals both effectively and simultaneously. A method of hybrid FH signals selection and blind parameter estimation is proposed. The method makes use of spectral transformation, spectral entropy calculation and PRI transformation basic theory to realize the sorting and parameter estimation of the components in the hybrid frequency hopping signal. The simulation results show that this method can correctly classify the frequency hopping component signal, and the estimated error of the frequency hopping period is about 5% and the estimated error of the frequency hopping frequency is less than 1% when the SNR is 10dB. However, the performance of this method deteriorates seriously at low SNR.

  9. Interpretation of the instantaneous frequency of phonocardiogram signals

    Science.gov (United States)

    Rey, Alexis B.

    2005-06-01

    Short-Time Fourier transforms, Wigner-Ville distribution, and Wavelet Transforms have been commonly used when dealing with non-stationary signals, and they have been known as time-frequency distributions. Also, it is commonly intended to investigate the behaviour of phonocardiogram signals as a means of prediction some oh the pathologies of the human hart. For this, this paper aims to analyze the relationship between the instantaneous frequency of a PCG signal and the so-mentioned time-frequency distributions; three algorithms using Matlab functions have been developed: the first one, the estimation of the IF using the normalized linear moment, the second one, the estimation of the IF using the periodic first moment, and the third one, the computing of the WVD. Meanwhile, the computing of the STFT spectrogram is carried out with a Matlab function. Several simulations of the spectrogram for a set of PCG signals and the estimation of the IF are shown, and its relationship is validated through correlation. Finally, the second algorithm is a better choice because the estimation is not biased, whereas the WVD is very computing-demanding and offers no benefit since the estimation of the IF by using this TFD has an equivalent result when using the derivative of the phase of the analytic signal, which is also less computing-demanding.

  10. A Signal Coordination Control Based on Traversing Empty between Mid-Block Street Crossing and Intersection

    Directory of Open Access Journals (Sweden)

    Changjiang Zheng

    2012-01-01

    Full Text Available To solve the problem in pedestrian Mid-Block street crossing, the method of signal coordination control between mid-block street crossing and intersection is researched in this paper. The paper proposes to use “distance-flow rate-time” graph as the tool for building coordination control system model which is for different situations of traffic control. Through alternating the linear optimization model, the system outputs the distribution of signal timing and system operational factors (delays in vehicles and mid-block street crossing. Finally, taking one section on the Taiping North Road in Nanjing as an example, the signal coordination control is carried out. And the results which are delays in the vehicles and mid-block street crossing are compared to those in the current distribution of signal timing.

  11. Mid-infrared frequency comb via coherent dispersive wave generation in silicon nitride nanophotonic waveguides

    Science.gov (United States)

    Guo, Hairun; Herkommer, Clemens; Billat, Adrien; Grassani, Davide; Zhang, Chuankun; Pfeiffer, Martin H. P.; Weng, Wenle; Brès, Camille-Sophie; Kippenberg, Tobias J.

    2018-06-01

    Mid-infrared optical frequency combs are of significant interest for molecular spectroscopy due to the large absorption of molecular vibrational modes on the one hand, and the ability to implement superior comb-based spectroscopic modalities with increased speed, sensitivity and precision on the other hand. Here, we demonstrate a simple, yet effective, method for the direct generation of mid-infrared optical frequency combs in the region from 2.5 to 4.0 μm (that is, 2,500-4,000 cm-1), covering a large fraction of the functional group region, from a conventional and compact erbium-fibre-based femtosecond laser in the telecommunication band (that is, 1.55 μm). The wavelength conversion is based on dispersive wave generation within the supercontinuum process in an unprecedented large-cross-section silicon nitride (Si3N4) waveguide with the dispersion lithographically engineered. The long-wavelength dispersive wave can perform as a mid-infrared frequency comb, whose coherence is demonstrated via optical heterodyne measurements. Such an approach can be considered as an alternative option to mid-infrared frequency comb generation. Moreover, it has the potential to realize compact dual-comb spectrometers. The generated combs also have a fine teeth-spacing, making them suitable for gas-phase analysis.

  12. Automated electronic intruder simulator for evaluation of odd frequency microwave detectors

    International Nuclear Information System (INIS)

    1979-01-01

    A microwave intruder simulator for testing motion detection sensors is described. This simulator can be used to evaluate a variety of microwave sensors regardless of the value of the center frequency of the signal utilized. Representative curves from the evaluation of one microwave sensor are also presented

  13. High Frequency Components Recovery in Music Signals

    Directory of Open Access Journals (Sweden)

    V. Sebesta

    1999-04-01

    Full Text Available A new technique is presented which improves the subjective quality of band-limited music by recovery of high frequency components. Sequences of harmonics are found in the band-limited signal and these sequences are expanded to the high frequency band to estimate the lost part of spectrum. High frequency signal is generated to match this estimation and is added to the band-limited signal.

  14. Numerical simulation of the manual operation of the charging/discharging machine (MID) control desk

    International Nuclear Information System (INIS)

    Doca, C; Dobre, A

    2004-01-01

    Since the year 2000 at 7th Division TAR of Institute for Nuclear Research - Pitesti continuous efforts were made to implement a software product package devoted to numerical simulation of operations at the test bench of charging/discharging machine (MID). Till now there were specified, designed, worked out and implemented on a computer the PUPITRU code, the present version fulfilling the following requirements: - graphical output specific for the computer/human operator interface: - design at a 1 : 4 scale for each of the 25 drawers of the control desk; - graphical and functional simulation of all the physical objects mounted in these drawers, namely: 12 measuring analog instruments with linear and non-linear dials (ampermeters), 21 measuring digital instruments (voltmeters), 24 two up/down settings switches, 13 switches with three up/down settings, 23 switches with two left/right hand settings, one switch with three left/right hand settings, one switch with four left/right hand settings, 2 switches with five left/right hand settings, 68, 16, 23, 53, 81 signaling lamps of white, yellow, orange, red and green light, respectively; implementation in the frame of PUPITRU code of the main notations used in the automation schemes in the execution design of the control desk, in view of a quick identification of the physical objects: switches, lamps, instruments, etc. ; - implementation in the frame of PUPITRU code of the full database (mnemonics and numerical values) used in the frame of MID tests; - implementation of over 1000 equations of numerical simulation appropriate to the situations characteristic for test bench and MID operation. At the moment, the final functional simulation for all the control desk components is finalized. In this paper a description and a demonstration run of the PUPITRU code is presented. (authors)

  15. Improved MIMO radar GMTI via cyclic-shift transmission of orthogonal frequency division signals

    Science.gov (United States)

    Li, Fuyou; He, Feng; Dong, Zhen; Wu, Manqing

    2018-05-01

    Minimum detectable velocity (MDV) and maximum detectable velocity are both important in ground moving target indication (GMTI) systems. Smaller MDV can be achieved by longer baseline via multiple-input multiple-output (MIMO) radar. Maximum detectable velocity is decided by blind velocities associated with carrier frequencies, and blind velocities can be mitigated by orthogonal frequency division signals. However, the scattering echoes from different carrier frequencies are independent, which is not good for improving MDV performance. An improved cyclic-shift transmission is applied in MIMO GMTI system in this paper. MDV performance is improved due to the longer baseline, and maximum detectable velocity performance is improved due to the mitigation of blind velocities via multiple carrier frequencies. The signal model for this mode is established, the principle of mitigating blind velocities with orthogonal frequency division signals is presented; the performance of different MIMO GMTI waveforms is analysed; and the performance of different array configurations is analysed. Simulation results by space-time-frequency adaptive processing proves that our proposed method is a valid way to improve GMTI performance.

  16. Frequency-domain interferometer simulation with higher-order spatial modes

    International Nuclear Information System (INIS)

    Freise, A; Heinzel, G; Lueck, H; Schilling, R; Willke, B; Danzmann, K

    2004-01-01

    FINESSE is a software simulation allowing one to compute the optical properties of laser interferometers used by interferometric gravitational-wave detectors today. This fast and versatile tool has already proven to be useful in the design and commissioning of gravitational-wave detectors. The basic algorithm of FINESSE numerically computes the light amplitudes inside an interferometer using Hermite-Gauss modes in the frequency domain. In addition, FINESSE provides a number of commands for easily generating and plotting the most common signals including power enhancement, error and control signals, transfer functions and shot-noise-limited sensitivities. Among the various simulation tools available to the gravitational wave community today, FINESSE provides an advanced and versatile optical simulation based on a general analysis of user-defined optical setups and is quick to install and easy to use

  17. Low frequency phase signal measurement with high frequency squeezing

    OpenAIRE

    Zhai, Zehui; Gao, Jiangrui

    2011-01-01

    We calculate the utility of high-frequency squeezed-state enhanced two-frequency interferometry for low-frequency phase measurement. To use the high-frequency sidebands of the squeezed light, a two-frequency intense laser is used in the interferometry instead of a single-frequency laser as usual. We find that the readout signal can be contaminated by the high-frequency phase vibration, but this is easy to check and avoid. A proof-of-principle experiment is in the reach of modern quantum optic...

  18. Sensibility to Changes of Vibrational Modes of Excited Electron: Sum Frequency Signals Versus Difference Frequency Signals

    International Nuclear Information System (INIS)

    Gu Anna; Liang Xianting

    2011-01-01

    In this paper, we investigate a two electronic level system with vibrational modes coupled to a Brownian oscillator bath. The difference frequency generation (DFG) signals and sum frequency generation (SFG) signals are calculated. It is shown that, for the same model, the SFG signals are more sensitive than the DFG signals to the changes of the vibrational modes of the electronic two-level system. Because the SFG conversion efficiency can be improved by using the time-delay method, the findings in this paper predict that the SFG spectrum may probe the changes of the microstructure more effectively. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  19. Numerical simulation of manual operation at MID stand control room

    International Nuclear Information System (INIS)

    Doca, C.; Dobre, A.; Predescu, D.; Mielcioiu, A.

    2003-01-01

    Since 2000 at INR Pitesti a package of software products devoted to numerical simulation of manual operations at fueling machine control room was developed. So far, specified, designed, worked out and implemented was the PUPITRU code. The following issues were solved: graphical aspects of specific computer - human operator interface; functional and graphical simulation of the whole associated equipment of the control desk components; implementation of the main notation as used in the automated schemes of the control desk in view of the fast identification of the switches, lamps, instrumentation, etc.; implementation within PUPITRU code of the entire data base used in the frame of MID tests; implementation of a number of about 1000 numerical simulation equations describing specific operational MID testing situations

  20. Direct phase-locking of a 8.6-μm quantum cascade laser to a mid-IR optical frequency comb: application to precision spectroscopy of N2O.

    Science.gov (United States)

    Gambetta, Alessio; Cassinerio, Marco; Coluccelli, Nicola; Fasci, Eugenio; Castrillo, Antonio; Gianfrani, Livio; Gatti, Davide; Marangoni, Marco; Laporta, Paolo; Galzerano, Gianluca

    2015-02-01

    We developed a high-precision spectroscopic system at 8.6 μm based on direct heterodyne detection and phase-locking of a room-temperature quantum-cascade-laser against an harmonic, 250-MHz mid-IR frequency comb obtained by difference-frequency generation. The ∼30  dB signal-to-noise ratio of the detected beat-note together with the achieved closed-loop locking bandwidth of ∼500  kHz allows for a residual integrated phase noise of 0.78 rad (1 Hz-5 MHz), for an ultimate resolution of ∼21  kHz, limited by the measured linewidth of the mid-IR comb. The system was used to perform absolute measurement of line-center frequencies for the rotational components of the ν2 vibrational band of N2O, with a relative precision of 3×10(-10).

  1. An estimation of core damage frequency of a pressurized water reactor during mid-loop operation

    International Nuclear Information System (INIS)

    Chao, C.C.; Chen, C.T.; Lee, M.

    2004-01-01

    The core damage frequency during mid-loop operation of a Westinghouse designed 3-loop Pressurizer Water Reactor (PWR) due to loss of Residual Heat Removal (RHR) events was assessed. The assessment considers two types of outages (refueling and drained maintenance), and uses failure data collected specifically for shutdown condition. Event trees were developed for five categories of loss of RHR events. Human actions to mitigate the loss of RHR events was identified and human error probabilities were quantified using HCR and THERP model. The result showed that the core damage frequency due to loss of RHR events during mid-loop operation is 3.1x10 -5 per year. The results also showed that the core damage frequency can be reduced significantly by removing a pressurizer safety valve before entering mid-loop operation. The establishment of reflux cooling, i.e. decay heat removal through steam generator secondary side also plays important role in mitigating the loss of RHR events. (author)

  2. High-coherence mid-infrared dual-comb spectroscopy spanning 2.6 to 5.2 μm

    Science.gov (United States)

    Ycas, Gabriel; Giorgetta, Fabrizio R.; Baumann, Esther; Coddington, Ian; Herman, Daniel; Diddams, Scott A.; Newbury, Nathan R.

    2018-04-01

    Mid-infrared dual-comb spectroscopy has the potential to supplant conventional Fourier-transform spectroscopy in applications requiring high resolution, accuracy, signal-to-noise ratio and speed. Until now, mid-infrared dual-comb spectroscopy has been limited to narrow optical bandwidths or low signal-to-noise ratios. Using digital signal processing and broadband frequency conversion in waveguides, we demonstrate a mid-infrared dual-comb spectrometer covering 2.6 to 5.2 µm with comb-tooth resolution, sub-MHz frequency precision and accuracy, and a spectral signal-to-noise ratio as high as 6,500. As a demonstration, we measure the highly structured, broadband cross-section of propane from 2,840 to 3,040 cm-1, the complex phase/amplitude spectra of carbonyl sulfide from 2,000 to 2,100 cm-1, and of a methane, acetylene and ethane mixture from 2,860 to 3,400 cm-1. The combination of broad bandwidth, comb-mode resolution and high brightness will enable accurate mid-infrared spectroscopy in precision laboratory experiments and non-laboratory applications including open-path atmospheric gas sensing, process monitoring and combustion.

  3. Simulating GPS radio signal to synchronize network--a new technique for redundant timing.

    Science.gov (United States)

    Shan, Qingxiao; Jun, Yang; Le Floch, Jean-Michel; Fan, Yaohui; Ivanov, Eugene N; Tobar, Michael E

    2014-07-01

    Currently, many distributed systems such as 3G mobile communications and power systems are time synchronized with a Global Positioning System (GPS) signal. If there is a GPS failure, it is difficult to realize redundant timing, and thus time-synchronized devices may fail. In this work, we develop time transfer by simulating GPS signals, which promises no extra modification to original GPS-synchronized devices. This is achieved by applying a simplified GPS simulator for synchronization purposes only. Navigation data are calculated based on a pre-assigned time at a fixed position. Pseudo-range data which describes the distance change between the space vehicle (SV) and users are calculated. Because real-time simulation requires heavy-duty computations, we use self-developed software optimized on a PC to generate data, and save the data onto memory disks while the simulator is operating. The radio signal generation is similar to the SV at an initial position, and the frequency synthesis of the simulator is locked to a pre-assigned time. A filtering group technique is used to simulate the signal transmission delay corresponding to the SV displacement. Each SV generates a digital baseband signal, where a unique identifying code is added to the signal and up-converted to generate the output radio signal at the centered frequency of 1575.42 MHz (L1 band). A prototype with a field-programmable gate array (FPGA) has been built and experiments have been conducted to prove that we can realize time transfer. The prototype has been applied to the CDMA network for a three-month long experiment. Its precision has been verified and can meet the requirements of most telecommunication systems.

  4. Time-frequency analysis of time-varying modulated signals based on improved energy separation by iterative generalized demodulation

    Science.gov (United States)

    Feng, Zhipeng; Chu, Fulei; Zuo, Ming J.

    2011-03-01

    Energy separation algorithm is good at tracking instantaneous changes in frequency and amplitude of modulated signals, but it is subject to the constraints of mono-component and narrow band. In most cases, time-varying modulated vibration signals of machinery consist of multiple components, and have so complicated instantaneous frequency trajectories on time-frequency plane that they overlap in frequency domain. For such signals, conventional filters fail to obtain mono-components of narrow band, and their rectangular decomposition of time-frequency plane may split instantaneous frequency trajectories thus resulting in information loss. Regarding the advantage of generalized demodulation method in decomposing multi-component signals into mono-components, an iterative generalized demodulation method is used as a preprocessing tool to separate signals into mono-components, so as to satisfy the requirements by energy separation algorithm. By this improvement, energy separation algorithm can be generalized to a broad range of signals, as long as the instantaneous frequency trajectories of signal components do not intersect on time-frequency plane. Due to the good adaptability of energy separation algorithm to instantaneous changes in signals and the mono-component decomposition nature of generalized demodulation, the derived time-frequency energy distribution has fine resolution and is free from cross term interferences. The good performance of the proposed time-frequency analysis is illustrated by analyses of a simulated signal and the on-site recorded nonstationary vibration signal of a hydroturbine rotor during a shut-down transient process, showing that it has potential to analyze time-varying modulated signals of multi-components.

  5. Frequency-domain method for separating signal and noise

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new method for separation of signal and noise (SSN) is put forward. Frequency is redefined according to the features of signal and its derivative in the sampl ing time interval, thus double orthogonal basis (DOB) is constructed so that a signal can be precisely signified with a linear combination of low-frequency DOB . Under joint consideration in time domain (TD) and frequency domain (FD), a method on SSN with high accuracy is derived and a matched algorithm is designed and analyzed. This method is applicable to SSN in multiple frequency bands, and convenient in applying signal characteristics in TD and FD synthetically with highe raccuracy.

  6. Frequency-domain method for separating signal and noise

    Institute of Scientific and Technical Information of China (English)

    王正明; 段晓君

    2000-01-01

    A new method for separation of signal and noise (SSN) is put forward. Frequency is redefined according to the features of signal and its derivative in the sampling time interval, thus double orthogonal basis (DOB) is constructed so that a signal can be precisely signified with a linear combination of low-frequency DOB. Under joint consideration in time domain (TD) and frequency domain (FD), a method on SSN with high accuracy is derived and a matched algorithm is designed and analyzed. This method is applicable to SSN in multiple frequency bands, and convenient in applying signal characteristics in TD and FD synthetically with higher accuracy.

  7. Investigation of non-uniform airflow signal oscillation during high frequency chest compression

    Directory of Open Access Journals (Sweden)

    Lee Jongwon

    2005-05-01

    Full Text Available Abstract Background High frequency chest compression (HFCC is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. Methods The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations. Results and discussion We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system. Conclusion We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

  8. Nanohertz frequency determination for the gravity probe B high frequency superconducting quantum interference device signal.

    Science.gov (United States)

    Salomon, M; Conklin, J W; Kozaczuk, J; Berberian, J E; Keiser, G M; Silbergleit, A S; Worden, P; Santiago, D I

    2011-12-01

    In this paper, we present a method to measure the frequency and the frequency change rate of a digital signal. This method consists of three consecutive algorithms: frequency interpolation, phase differencing, and a third algorithm specifically designed and tested by the authors. The succession of these three algorithms allowed a 5 parts in 10(10) resolution in frequency determination. The algorithm developed by the authors can be applied to a sampled scalar signal such that a model linking the harmonics of its main frequency to the underlying physical phenomenon is available. This method was developed in the framework of the gravity probe B (GP-B) mission. It was applied to the high frequency (HF) component of GP-B's superconducting quantum interference device signal, whose main frequency f(z) is close to the spin frequency of the gyroscopes used in the experiment. A 30 nHz resolution in signal frequency and a 0.1 pHz/s resolution in its decay rate were achieved out of a succession of 1.86 s-long stretches of signal sampled at 2200 Hz. This paper describes the underlying theory of the frequency measurement method as well as its application to GP-B's HF science signal.

  9. Near diffraction limited mid-IR spectromicroscopy using frequency upconversion

    DEFF Research Database (Denmark)

    Sanders, Nicolai Højer; Dam, Jeppe Seidelin; Tidemand-Lichtenberg, Peter

    2014-01-01

    morphological and spectral imaging. Recent developments in nonlinear frequency upconversion, have demonstrated the potential to perform both imaging and spectroscopy in the mid-IR range at unparalleled low levels of illumination, the low upconversion detector noise being orders of magnitude below competing...... technologies. With these applications in mind, we have incorporated microscopy optics into an image upconversion system, achieving near diffraction limited spatial resolution in the 3 μm range. Spectroscopic information is further acquired by appropriate control of the phase match condition of the upconversion...

  10. MONITORING HIGH-FREQUENCY OCEAN SIGNALS USING LOW-COST GNSS/IMU BUOYS

    Directory of Open Access Journals (Sweden)

    Y.-L. Huang

    2016-06-01

    Full Text Available In oceans there are different ocean signals covering the multi-frequencies including tsunami, meteotsunami, storm surge, as sea level change, and currents. These signals have the direct and significant impact on the economy and life of human-beings. Therefore, measuring ocean signals accurately becomes more and more important and necessary. Nowadays, there are many techniques and methods commonly used for monitoring oceans, but each has its limitation. For example, tide gauges only measure sea level relative to benchmarks and are disturbed unevenly, and satellite altimeter measurements are not continuous and inaccurate near coastal oceans. In addition, high-frequency ocean signals such as tsunami and meteotsunami cannot be sufficiently detected by 6-minutes tide gauge measurements or 10-day sampled altimetry data. Moreover, traditional accelerometer buoy is heavy, expensive and the low-frequency noise caused by the instrument is unavoidable. In this study, a small, low-cost and self-assembly autonomous Inertial Measurement Unit (IMU that independently collects continuous acceleration and angular velocity data is mounted on a GNSS buoy to provide the positions and tilts of the moving buoy. The main idea is to integrate the Differential GNSS (DGNSS or Precise Point Positioning (PPP solutions with IMU data, and then evaluate the performance by comparing with in situ tide gauges. The validation experiments conducted in the NCKU Tainan Hydraulics Laboratory showed that GNSS and IMU both can detect the simulated regular wave frequency and height, and the field experiments in the Anping Harbor, Tainan, Taiwan showed that the low-cost GNSS buoy has an excellent ability to observe significant wave heights in amplitude and frequency.

  11. Time-frequency analysis of non-stationary fusion plasma signals using an improved Hilbert-Huang transform

    International Nuclear Information System (INIS)

    Liu, Yangqing; Tan, Yi; Xie, Huiqiao; Wang, Wenhao; Gao, Zhe

    2014-01-01

    An improved Hilbert-Huang transform method is developed to the time-frequency analysis of non-stationary signals in tokamak plasmas. Maximal overlap discrete wavelet packet transform rather than wavelet packet transform is proposed as a preprocessor to decompose a signal into various narrow-band components. Then, a correlation coefficient based selection method is utilized to eliminate the irrelevant intrinsic mode functions obtained from empirical mode decomposition of those narrow-band components. Subsequently, a time varying vector autoregressive moving average model instead of Hilbert spectral analysis is performed to compute the Hilbert spectrum, i.e., a three-dimensional time-frequency distribution of the signal. The feasibility and effectiveness of the improved Hilbert-Huang transform method is demonstrated by analyzing a non-stationary simulated signal and actual experimental signals in fusion plasmas

  12. Transethnic differences in GWAS signals: A simulation study.

    Science.gov (United States)

    Zanetti, Daniela; Weale, Michael E

    2018-05-07

    Genome-wide association studies (GWASs) have allowed researchers to identify thousands of single nucleotide polymorphisms (SNPs) and other variants associated with particular complex traits. Previous studies have reported differences in the strength and even the direction of GWAS signals across different populations. These differences could be due to a combination of (1) lack of power, (2) allele frequency differences, (3) linkage disequilibrium (LD) differences, and (4) true differences in causal variant effect sizes. To determine whether properties (1)-(3) on their own might be sufficient to explain the patterns previously noted in strong GWAS signals, we simulated case-control data of European, Asian and African ancestry, applying realistic allele frequencies and LD from 1000 Genomes data but enforcing equal causal effect sizes across populations. Much of the observed differences in strong GWAS signals could indeed be accounted for by allele frequency and LD differences, enhanced by the Euro-centric SNP bias and lower SNP coverage found in older GWAS panels. While we cannot rule out a role for true transethnic effect size differences, our results suggest that strong causal effects may be largely shared among human populations, motivating the use of transethnic data for fine-mapping. © 2018 John Wiley & Sons Ltd/University College London.

  13. Decoding a combined amplitude modulated and frequency modulated signal

    DEFF Research Database (Denmark)

    2015-01-01

    The present disclosure relates to a method for decoding a combined AM/FM encoded signal, comprising the steps of: combining said encoded optical signal with light from a local oscillator configured with a local oscillator frequency; converting the combined local oscillator and encoded optical...... signal into one or more electrical signals by means of at least one opto-electrical converter having a predefined frequency bandwidth, thereby providing an amplified and encoded electrical signal having one or more encoded signal current(s), where one type of states have a higher oscillation frequency...... than other type of states; rectifying the encoded signal current(s), thereby obtaining an encoded power spectrum, wherein said power spectrum has different states, such as "0"-states and "1"-states, with different power levels such that they can be discriminated, said local oscillator frequency...

  14. TREX13: Mid-Frequency Measurements and Modeling of Scattering by Fish

    Science.gov (United States)

    2017-11-13

    508.289.2727 • Fax 508.457.2194 DISTIUBU710N STATEME tA. Approved fur p11b/ic release: d istrib11Jio11 is u11/i111/ ted . TREX13: Mid-Frequency Measurements...properties of the environment. The results will improve the ability to predict sonar perfonnance. OBJECTIVES This component. of the TR :: x 13 program

  15. Signal Processing and Neural Network Simulator

    Science.gov (United States)

    Tebbe, Dennis L.; Billhartz, Thomas J.; Doner, John R.; Kraft, Timothy T.

    1995-04-01

    The signal processing and neural network simulator (SPANNS) is a digital signal processing simulator with the capability to invoke neural networks into signal processing chains. This is a generic tool which will greatly facilitate the design and simulation of systems with embedded neural networks. The SPANNS is based on the Signal Processing WorkSystemTM (SPWTM), a commercial-off-the-shelf signal processing simulator. SPW provides a block diagram approach to constructing signal processing simulations. Neural network paradigms implemented in the SPANNS include Backpropagation, Kohonen Feature Map, Outstar, Fully Recurrent, Adaptive Resonance Theory 1, 2, & 3, and Brain State in a Box. The SPANNS was developed by integrating SAIC's Industrial Strength Neural Networks (ISNN) Software into SPW.

  16. Research and realization of signal simulation on virtual instrument

    Science.gov (United States)

    Zhao, Qi; He, Wenting; Guan, Xiumei

    2010-02-01

    In the engineering project, arbitrary waveform generator controlled by software interface is needed by simulation and test. This article discussed the program using the SCPI (Standard Commands For Programmable Instruments) protocol and the VISA (Virtual Instrument System Architecture) library to control the Agilent signal generator (Agilent N5182A) by instrument communication over the LAN interface. The program can conduct several signal generations such as CW (continuous wave), AM (amplitude modulation), FM (frequency modulation), ΦM (phase modulation), Sweep. As the result, the program system has good operability and portability.

  17. Time-domain SFG spectroscopy using mid-IR pulse shaping: practical and intrinsic advantages.

    Science.gov (United States)

    Laaser, Jennifer E; Xiong, Wei; Zanni, Martin T

    2011-03-24

    Sum-frequency generation (SFG) spectroscopy is a ubiquitous tool in the surface sciences. It provides infrared transition frequencies and line shapes that probe the structure and environment of molecules at interfaces. In this article, we apply techniques learned from the multidimensional spectroscopy community to SFG spectroscopy. We implement balanced heterodyne detection to remove scatter and the local oscillator background. Heterodyning also separates the resonant and nonresonant signals by acquiring both the real and imaginary parts of the spectrum. We utilize mid-IR pulse shaping to control the phase and delay of the mid-IR pump pulse. Pulse shaping allows phase cycling for data collection in the rotating frame and additional background subtraction. We also demonstrate time-domain data collection, which is a Fourier transform technique, and has many advantages in signal throughput, frequency resolution, and line shape accuracy over existing frequency domain methods. To demonstrate time-domain SFG spectroscopy, we study an aryl isocyanide on gold, and find that the system has an inhomogeneous structural distribution, in agreement with computational results, but which was not resolved by previous frequency-domain SFG studies. The ability to rapidly and actively manipulate the mid-IR pulse in an SFG pules sequence makes possible new experiments and more accurate spectra. © 2011 American Chemical Society

  18. Parametric Amplification Protocol for Frequency-Modulated Magnetic Resonance Force Microscopy Signals

    Science.gov (United States)

    Harrell, Lee; Moore, Eric; Lee, Sanggap; Hickman, Steven; Marohn, John

    2011-03-01

    We present data and theoretical signal and noise calculations for a protocol using parametric amplification to evade the inherent tradeoff between signal and detector frequency noise in force-gradient magnetic resonance force microscopy signals, which are manifested as a modulated frequency shift of a high- Q microcantilever. Substrate-induced frequency noise has a 1 / f frequency dependence, while detector noise exhibits an f2 dependence on modulation frequency f . Modulation of sample spins at a frequency that minimizes these two contributions typically results in a surface frequency noise power an order of magnitude or more above the thermal limit and may prove incompatible with sample spin relaxation times as well. We show that the frequency modulated force-gradient signal can be used to excite the fundamental resonant mode of the cantilever, resulting in an audio frequency amplitude signal that is readily detected with a low-noise fiber optic interferometer. This technique allows us to modulate the force-gradient signal at a sufficiently high frequency so that substrate-induced frequency noise is evaded without subjecting the signal to the normal f2 detector noise of conventional demodulation.

  19. Modeling of very low frequency (VLF radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

    Directory of Open Access Journals (Sweden)

    S. Palit

    2013-09-01

    Full Text Available X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~60 to 100 km in excess of what is expected to occur due to a quiet sun. Very low frequency (VLF radio wave signals reflected from the D-region of the ionosphere are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class flare and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the D-region of the ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the change in VLF signal. We did the modeling of the VLF signal along the NWC (Australia to IERC/ICSP (India propagation path and compared the results with observations. The agreement is found to be very satisfactory.

  20. Doppler shift simulation of scattered HF signals during the Tromsø HF pumping experiment on 16 February 1996

    Directory of Open Access Journals (Sweden)

    T. D. Borisova

    2002-09-01

    Full Text Available Comparisons between bistatic scatter measurements and simulation results during the Tromsø HF pumping experiment on 16 February 1996 are made. Doppler measurements of an HF diagnostic signal scattered from the field-aligned irregularities (FAIs in the auroral E-region were carried out on the London – Tromsø – St. Petersburg path at 9410 kHz from 21:00 to 22:00 UT. The scattered signals were observed both from natural and artificial ionospheric irregularities located in the vicinity of Tromsø. To simulate the Doppler frequency shifts, fd , of scattered signals, a radio channel model, named CONE, was developed. The model allows for ray tracing, group and phase paths, and Doppler frequency shift calculations. The calculated Doppler shifts were analyzed for dependence on the magnitude and direction of plasma velocities in the scattering volume. It was found that the velocity components in the north-south direction are crucial for explaining the Doppler frequency shifts of the scattered diagnostic signals. To simulate fd , real velocities obtained from the EISCAT UHF radar at an altitude of 278 km and from the digital all-sky imager during the experiment were employed. The simulation results of Doppler frequency shift variations with time are in reasonable agreement with the experimental Doppler shifts of scattered signals on the London – Tromsø – St. Petersburg path.Key words. Ionosphere (active experiments; ionospheric irregularities Radio science (ionospheric propagation

  1. Universality and Realistic Extensions to the Semi-Analytic Simulation Principle in GNSS Signal Processing

    Directory of Open Access Journals (Sweden)

    O. Jakubov

    2012-06-01

    Full Text Available Semi-analytic simulation principle in GNSS signal processing bypasses the bit-true operations at high sampling frequency. Instead, signals at the output branches of the integrate&dump blocks are successfully modeled, thus making extensive Monte Carlo simulations feasible. Methods for simulations of code and carrier tracking loops with BPSK, BOC signals have been introduced in the literature. Matlab toolboxes were designed and published. In this paper, we further extend the applicability of the approach. Firstly, we describe any GNSS signal as a special instance of linear multi-dimensional modulation. Thereby, we state universal framework for classification of differently modulated signals. Using such description, we derive the semi-analytic models generally. Secondly, we extend the model for realistic scenarios including delay in the feed back, slowly fading multipath effects, finite bandwidth, phase noise, and a combination of these. Finally, a discussion on connection of this semi-analytic model and position-velocity-time estimator is delivered, as well as comparison of theoretical and simulated characteristics, produced by a prototype simulator developed at CTU in Prague.

  2. Experimental separation of a frequency spin echo signal

    International Nuclear Information System (INIS)

    Bun'kov, Yu.M.; Dmitriev, V.V.

    1981-01-01

    To study systems with bound nuclear-electron precession CsMnF 2 antiferromagnetic light-plane monocrystal was investigated. Crystal orientation was carried out by roentgenoscopy. Measurements were performed at helium temperatures in the 500-700 MHz frequency range. A NMR pulsed spectrometer with generators of both resonance and doubled frequency was used to produce an echo signal (to study by the parametric echo method). It was shown that the theory of the formation of a frequency modulated echo (FM echo) did not fully describe the properties of the echo signals in systems with dynamic frequency shift (DFS). An intense spin echo signal, which formation was apparently connected with other nonlinear properties of the systems with nuclear-electron precession, was observed. The spin echo signal in magnetics with DFS, which properties correspond to notions of the frequency mechanism of echo formation, was experimentally separated. As a result of the investigations it had been possible to settle contradictions between the theory of FM echo formation and the experimental results for the last 9 years. It turned out that the mechanism of FM echo formation in the magnetics with bound nuclear-electron precession was effective only at large delay times between the pulses. In the range of small delays the FM echo is ''jammed'' by a gigantic echo signal of a nature different from that of the traditional FM signal. The constant of gigantic echo intensity drop at increasing delay between the pulses weakly depends on spin-spin relaxation time [ru

  3. Frequency locking of an extended-cavity quantum cascade laser to a frequency comb for precision mid infrared spectroscopy

    KAUST Repository

    Alsaif, Bidoor; Lamperti, Marco; Gatti, Davide; Laporta, Paolo; Fermann, Martin E.; Farooq, Aamir; Marangoni, Marco

    2017-01-01

    Extended-cavity quantum cascade lasers (EC-QCLs) enable mode-hope-free frequency sweeps in the mid-infrared region over ranges in excess of 100 cm−1, at speeds up to 1 THz/s and with a 100-mW optical power level. This makes them ideally suited for broadband absorption spectroscopy and for the simultaneous detection of multiple gases. On the other hand, their use for precision spectroscopy has been hampered so far by a large amount of frequency noise, resulting in an optical linewidth of about 30 MHz over 50 ms [1]. This is one of the reasons why neither their frequency nor their phase have been so far locked to a frequency comb. Their use in combination with frequency combs has been performed in an open loop regime only [2], which has the merit of preserving the inherently fast modulation speed of these lasers, yet not to afford high spectral resolution and accuracy.

  4. Frequency locking of an extended-cavity quantum cascade laser to a frequency comb for precision mid infrared spectroscopy

    KAUST Repository

    Alsaif, Bidoor

    2017-11-02

    Extended-cavity quantum cascade lasers (EC-QCLs) enable mode-hope-free frequency sweeps in the mid-infrared region over ranges in excess of 100 cm−1, at speeds up to 1 THz/s and with a 100-mW optical power level. This makes them ideally suited for broadband absorption spectroscopy and for the simultaneous detection of multiple gases. On the other hand, their use for precision spectroscopy has been hampered so far by a large amount of frequency noise, resulting in an optical linewidth of about 30 MHz over 50 ms [1]. This is one of the reasons why neither their frequency nor their phase have been so far locked to a frequency comb. Their use in combination with frequency combs has been performed in an open loop regime only [2], which has the merit of preserving the inherently fast modulation speed of these lasers, yet not to afford high spectral resolution and accuracy.

  5. Demonstration of the frequency modulation of optical signals with a high frequency deviation parameter

    International Nuclear Information System (INIS)

    Shamray, A V; Kozlov, A S; Il'ichev, I V; Petrov, M P

    2008-01-01

    A new type of an integrated optical modulator for the frequency coding of optical signals is developed and fabricated. The modulator operation is based on the original technology of the electric control of a Bragg grating. The frequency modulation of an optical signal with the frequency deviation of 25 GHz is demonstrated experimentally. The modular was used to transfer the ASCII code through an optical fibre. (optical communication)

  6. Doppler shift simulation of scattered HF signals during the Tromsø HF pumping experiment on 16 February 1996

    Directory of Open Access Journals (Sweden)

    T. D. Borisova

    Full Text Available Comparisons between bistatic scatter measurements and simulation results during the Tromsø HF pumping experiment on 16 February 1996 are made. Doppler measurements of an HF diagnostic signal scattered from the field-aligned irregularities (FAIs in the auroral E-region were carried out on the London – Tromsø – St. Petersburg path at 9410 kHz from 21:00 to 22:00 UT. The scattered signals were observed both from natural and artificial ionospheric irregularities located in the vicinity of Tromsø. To simulate the Doppler frequency shifts, fd , of scattered signals, a radio channel model, named CONE, was developed. The model allows for ray tracing, group and phase paths, and Doppler frequency shift calculations. The calculated Doppler shifts were analyzed for dependence on the magnitude and direction of plasma velocities in the scattering volume. It was found that the velocity components in the north-south direction are crucial for explaining the Doppler frequency shifts of the scattered diagnostic signals. To simulate fd , real velocities obtained from the EISCAT UHF radar at an altitude of 278 km and from the digital all-sky imager during the experiment were employed. The simulation results of Doppler frequency shift variations with time are in reasonable agreement with the experimental Doppler shifts of scattered signals on the London – Tromsø – St. Petersburg path.

    Key words. Ionosphere (active experiments; ionospheric irregularities Radio science (ionospheric propagation

  7. Input signal shaping based on harmonic frequency response function for suppressing nonlinear optical frequency in frequency-scanning interferometry

    Science.gov (United States)

    Zhu, Yu; Liu, Zhigang; Deng, Wen; Deng, Zhongwen

    2018-05-01

    Frequency-scanning interferometry (FSI) using an external cavity diode laser (ECDL) is essential for many applications of the absolute distance measurement. However, owing to the hysteresis and creep of the piezoelectric actuator inherent in the ECDL, the optical frequency scanning exhibits a nonlinearity that seriously affects the phase extraction accuracy of the interference signal and results in the reduction of the measurement accuracy. To suppress the optical frequency nonlinearity, a harmonic frequency synthesis method for shaping the desired input signal instead of the original triangular wave is presented. The effectiveness of the presented shaping method is demonstrated through the comparison of the experimental results. Compared with an incremental Renishaw interferometer, the standard deviation of the displacement measurement of the FSI system is less than 2.4 μm when driven by the shaped signal.

  8. PSpice modeling of broadband RF cavities for transient and frequency domain simulations

    Energy Technology Data Exchange (ETDEWEB)

    Harzheim, Jens [Institut fuer Theorie Elektromagnetischer Felder, Fachgebiet Beschleunigertechnik, TU Darmstadt (Germany)

    2016-07-01

    In the future accelerator facility FAIR, Barrier-Bucket Systems will play an important role for different longitudinal beam manipulations. As the function of this type of system is to provide single sine gap voltages, the components of the system have to operate in a broad frequency range. To investigate the different effects and to design the different system components, the whole Barrier-Bucket System is to be modeled in PSpice. While for low power signals, the system shows linear behavior, nonlinear effects arise at higher amplitudes. Therefore, simulations in both, frequency and time domain are needed. The highly frequency dependent magnetic alloy ring cores of the future Barrier-Bucket cavity have been mod eled in a first step and based on these models, the whole cavity was analyzed in PSpice. The simulation results show good agreement with former measurements.

  9. Signal Adaptive System for Space/Spatial-Frequency Analysis

    Directory of Open Access Journals (Sweden)

    Veselin N. Ivanović

    2009-01-01

    Full Text Available This paper outlines the development of a multiple-clock-cycle implementation (MCI of a signal adaptive two-dimensional (2D system for space/spatial-frequency (S/SF signal analysis. The design is based on a method for improved S/SF representation of the analyzed 2D signals, also proposed here. The proposed MCI design optimizes critical design performances related to hardware complexity, making it a suitable system for real time implementation on an integrated chip. Additionally, the design allows the implemented system to take a variable number of clock cycles (CLKs (the only necessary ones regarding desirable—2D Wigner distribution-presentation of autoterms in different frequency-frequency points during the execution. This ability represents a major advantage of the proposed design which helps to optimize the time required for execution and produce an improved, cross-terms-free S/SF signal representation. The design has been verified by a field-programmable gate array (FPGA circuit design, capable of performing S/SF analysis of 2D signals in real time.

  10. Every photon counts: improving low, mid, and high-spatial frequency errors on astronomical optics and materials with MRF

    Science.gov (United States)

    Maloney, Chris; Lormeau, Jean Pierre; Dumas, Paul

    2016-07-01

    Many astronomical sensing applications operate in low-light conditions; for these applications every photon counts. Controlling mid-spatial frequencies and surface roughness on astronomical optics are critical for mitigating scattering effects such as flare and energy loss. By improving these two frequency regimes higher contrast images can be collected with improved efficiency. Classically, Magnetorheological Finishing (MRF) has offered an optical fabrication technique to correct low order errors as well has quilting/print-through errors left over in light-weighted optics from conventional polishing techniques. MRF is a deterministic, sub-aperture polishing process that has been used to improve figure on an ever expanding assortment of optical geometries, such as planos, spheres, on and off axis aspheres, primary mirrors and freeform optics. Precision optics are routinely manufactured by this technology with sizes ranging from 5-2,000mm in diameter. MRF can be used for form corrections; turning a sphere into an asphere or free form, but more commonly for figure corrections achieving figure errors as low as 1nm RMS while using careful metrology setups. Recent advancements in MRF technology have improved the polishing performance expected for astronomical optics in low, mid and high spatial frequency regimes. Deterministic figure correction with MRF is compatible with most materials, including some recent examples on Silicon Carbide and RSA905 Aluminum. MRF also has the ability to produce `perfectly-bad' compensating surfaces, which may be used to compensate for measured or modeled optical deformation from sources such as gravity or mounting. In addition, recent advances in MRF technology allow for corrections of mid-spatial wavelengths as small as 1mm simultaneously with form error correction. Efficient midspatial frequency corrections make use of optimized process conditions including raster polishing in combination with a small tool size. Furthermore, a novel MRF

  11. Polysilicon high frequency devices for large area electronics: Characterization, simulation and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Botrel, J L [CEA-LETI 17, rue des Martyrs 38054 Grenoble (France); IMEP 23, rue des Martyrs 38016 Grenoble (France)], E-mail: jean-loius.botrel@cea.fr; Savry, O; Rozeau, O; Templier, F [CEA-LETI 17, rue des Martyrs 38054 Grenoble (France); Jomaah, J [IMEP 23, rue des Martyrs 38016 Grenoble (France)

    2007-07-16

    Laser Crystallised Polysilicon Thin Film Transistors have now sufficient good conduction properties to be used in high-frequency applications. In this work, we report the results for 5 {mu}m long polysilicon TFTs obtained at frequencies up to several hundred MHz for applications such as RFID tags or System-On-Panel. In order to investigate the device operation, DC and AC two-dimensional simulations of these devices in the Effective Medium framework have been performed. In the light of simulation results, the effects of carrier trapping and carrier transit on the device capacitances as a function of dimensions are analysed and compared. An equivalent small-signal circuit which accounts for the behaviour of these transistors in all regions of operation is proposed and a model for the most relevant elements of this circuit is presented. To validate our simulation results, scattering-parameters (S-parameters) measurements are performed for several structures such as multi-finger, serpentine and linear architectures and the most meaningful parameters will be given. Cut-off frequencies as high as 300 MHz and maximum oscillation frequencies of about 600 MHz have been extracted.

  12. Compensation of nonlinearity in a fiber-optic transmission system using frequency-degenerate phase conjugation through counter-propagating dual pump FWM in a semiconductor optical amplifier

    Science.gov (United States)

    Anchal, Abhishek; K, Pradeep Kumar; O'Duill, Sean; Anandarajah, Prince M.; Landais, Pascal

    2018-04-01

    We present a scheme of frequency-degenerate mid-span spectral inversion (MSSI) for nonlinearity compensation in fiber-optic transmission systems. The spectral inversion is obtained by using counter-propagating dual pump four-wave mixing in a semiconductor optical amplifier (SOA). Frequency-degeneracy between signal and conjugate is achieved by keeping two pump frequencies symmetrical about the signal frequency. We simulate the performance of MSSI for nonlinearity compensation by scrutinizing the improvement of the Q-factor of a 200 Gbps QPSK signal transmitted over a standard single mode fiber, as a function of launch power for different span lengths and number of spans. We demonstrate a 7.5 dB improvement in the input power dynamic range and an almost 83% increase in the transmission length for optimum MSSI parameters of -2 dBm pump power and 400 mA SOA current.

  13. A Novel Partial Discharge Ultra-High Frequency Signal De-Noising Method Based on a Single-Channel Blind Source Separation Algorithm

    Directory of Open Access Journals (Sweden)

    Liangliang Wei

    2018-02-01

    Full Text Available To effectively de-noise the Gaussian white noise and periodic narrow-band interference in the background noise of partial discharge ultra-high frequency (PD UHF signals in field tests, a novel de-noising method, based on a single-channel blind source separation algorithm, is proposed. Compared with traditional methods, the proposed method can effectively de-noise the noise interference, and the distortion of the de-noising PD signal is smaller. Firstly, the PD UHF signal is time-frequency analyzed by S-transform to obtain the number of source signals. Then, the single-channel detected PD signal is converted into multi-channel signals by singular value decomposition (SVD, and background noise is separated from multi-channel PD UHF signals by the joint approximate diagonalization of eigen-matrix method. At last, the source PD signal is estimated and recovered by the l1-norm minimization method. The proposed de-noising method was applied on the simulation test and field test detected signals, and the de-noising performance of the different methods was compared. The simulation and field test results demonstrate the effectiveness and correctness of the proposed method.

  14. An intuitive method to automatically detect the common and not common frequencies for two or more time-varying signals

    International Nuclear Information System (INIS)

    Doca, C.; Paunoiu, C.; Doca, L.

    2013-01-01

    Sampling a time-varying signal and his spectral analysis are, both, subjected to theoretically compelling, such as Shannon's theorem and the objectively limiting of the frequencys resolution. After obtaining the signals (Fourier) spectrum, this is processed and interpreted usually by a scientist who, presumably, has sufficient prior information about the monitored signal to conclude, for example, on the significant frequencies. Obviously, processing and interpretation of individual spectra are routine tasks that can be automated by suitable software (PC application). The problems complicate if we need to compare two or more spectra corresponding to different signals and/or phenomena. In the above context, this paper presents an intuitive method for automatic identification of the common and not common frequencies for two or more congruent spectra. The method is illustrated by numerical simulations, and by the results obtained in the analysis of the noise from some experimental measured signals. (authors)

  15. Real-time and high accuracy frequency measurements for intermediate frequency narrowband signals

    Science.gov (United States)

    Tian, Jing; Meng, Xiaofeng; Nie, Jing; Lin, Liwei

    2018-01-01

    Real-time and accurate measurements of intermediate frequency signals based on microprocessors are difficult due to the computational complexity and limited time constraints. In this paper, a fast and precise methodology based on the sigma-delta modulator is designed and implemented by first generating the twiddle factors using the designed recursive scheme. This scheme requires zero times of multiplications and only half amounts of addition operations by using the discrete Fourier transform (DFT) and the combination of the Rife algorithm and Fourier coefficient interpolation as compared with conventional methods such as DFT and Fast Fourier Transform. Experimentally, when the sampling frequency is 10 MHz, the real-time frequency measurements with intermediate frequency and narrowband signals have a measurement mean squared error of ±2.4 Hz. Furthermore, a single measurement of the whole system only requires approximately 0.3 s to achieve fast iteration, high precision, and less calculation time.

  16. Comparisons of measurements and numerical simulations of a nonlinear beam subjected to a multi-harmonic non-ideal input signal

    International Nuclear Information System (INIS)

    Claeys, M.; Sinou, J.J.; Lambelin, J.P.; Alcoverro, B.

    2014-01-01

    This study presents a direct comparison of measured and predicted nonlinear vibrations of a clamped-clamped steel beam. A multi-harmonic comparison of simulations with measurements is performed at the vicinity of the primary resonance. First of all, a nonlinear analytical model of the beam is developed taking into account non-ideal boundary conditions. The Harmonic Balance Method is implemented to estimate the nonlinear behavior of the clamped-clamped beam. This nonlinear method enables to simulate the vibration stationary response of a nonlinear system projected on several harmonics. This study then proposes a method to compare numerical simulations with measurements on all these harmonics. A signal analysis tool is developed to extract the system harmonics' frequency responses from a temporal signal of a swept sine experiment. An evolutionary updating algorithm (Covariance Matrix Adaptation Evolution Strategy), coupled with highly selective filters is used to identify both fundamental frequency and harmonics' amplitude in the temporal signal, at every moment. This tool enables to extract the harmonic amplitudes of the output signal as well as the input signal. The input of the Harmonic Balance Method can then be either an ideal mono-harmonic signal or a multi-harmonic experimental input signal. Finally, the present work focuses on the comparison of experimental and simulated results. From experimental output harmonics and numerical simulations, it is shown that it is possible to distinguish the nonlinearities of the clamped-clamped beam and the effect of the non-ideal input signal. (authors)

  17. Computational expressions for signals in frequency-modulation spectroscopy.

    Science.gov (United States)

    Di Rosa, Michael D; Reiten, M T

    2015-06-01

    General expressions for the signals in frequency-modulation spectroscopy (FMS) appear in the literature but are often reduced to simple analytical equations following the assumption of a weak modulation index. This is little help to the experimentalist who wants to predict signals for modulation depths of the order of unity or greater, where strong FMS signals reside. Here, we develop general formulas for FMS signals in the case of an absorber with a Voigt line shape and then link these expressions to an example and existing numerical code for the line shape. The resulting computational recipe is easy to implement and exercised here to show where the larger FMS signals are found over the coordinates of modulation index and modulation frequency. One can also estimate from provided curves the in-phase FMS signal over a wide range of modulation parameters at either the Lorentzian-broadening or Doppler-broadening limit, or anywhere in between by interpolation.

  18. Phase measurements of very-low-frequency signals from the magnetosphere

    International Nuclear Information System (INIS)

    Paschal, E.V.

    1988-01-01

    The usual methods of spectrum analysis applied to analog tape recordings of very low frequency (VLF) signals extract only magnitude information and ignore phase information. A digital signal-processing system using a recorded constant-frequency pilot tone was developed that can correct tape errors due to wow and flutter, and reconstruct the signal phases. Frequency shifts are corrected during analysis by interpolating between spectral points in the windowed Fourier transform, and the output phases of the synthesized filters are corrected for timing errors. Having signal-component phases as well as magnitudes doubles the available information. Whistler-mode signals from the VLF transmitter at Siple Station, Antarctica, were analyzed as received at Roberval, Quebec. The phase of a non-growing signal is found to give a less-noisy measure of duct motion than Doppler frequency shift, with improved time resolution. Correlations are seen between variations in the whistler-mode phase delay and the earth's magnetic field component D. They are interpreted as Pc 2 micropulsation transients, short compared to the length of the field line, which propagate from equator to ground as Alfven waves

  19. High-frequency signal and noise estimates of CSR GRACE RL04

    Science.gov (United States)

    Bonin, Jennifer A.; Bettadpur, Srinivas; Tapley, Byron D.

    2012-12-01

    A sliding window technique is used to create daily-sampled Gravity Recovery and Climate Experiment (GRACE) solutions with the same background processing as the official CSR RL04 monthly series. By estimating over shorter time spans, more frequent solutions are made using uncorrelated data, allowing for higher frequency resolution in addition to daily sampling. Using these data sets, high-frequency GRACE errors are computed using two different techniques: assuming the GRACE high-frequency signal in a quiet area of the ocean is the true error, and computing the variance of differences between multiple high-frequency GRACE series from different centers. While the signal-to-noise ratios prove to be sufficiently high for confidence at annual and lower frequencies, at frequencies above 3 cycles/year the signal-to-noise ratios in the large hydrological basins looked at here are near 1.0. Comparisons with the GLDAS hydrological model and high frequency GRACE series developed at other centers confirm CSR GRACE RL04's poor ability to accurately and reliably measure hydrological signal above 3-9 cycles/year, due to the low power of the large-scale hydrological signal typical at those frequencies compared to the GRACE errors.

  20. The implementation of a mid-loop model for Doel 1/2 training simulator

    International Nuclear Information System (INIS)

    Houte, U. Van; Damme, M. Van

    1999-01-01

    To cope with upgrade requirements of the Full Scope training simulator of Doel 1/2 (Belgium), a 5-equation model has been implemented for mid-loop operation training. This model will permit to simulate the following conditions: (a) Normal operating conditions; Draining of the primary circuit at vacuum conditions; Venting of the primary loop with the help of a vacuum pump; Filling-up of the primely circuit, (2) Incident and Accident conditions; Loss of RHR (Cavitation of RHR pumps); Reactor heat-up and boiling. In order to simulate the pressurizer water hold-up and loss of steam generator reflux cooling, flooding correlations are used predicting steam generator U-tube and pressurizer surgeline flooding. Loss of horizontal stratification in the hot leg has been taken into account. A steam generator piston model for heat transfer has been implemented. This paper describes the mid-loop model specifications, its implementation and testing in the simulator environment. Special attention is given on how the model has been integrated within the existing simulator. (author)

  1. Time-Frequency Analysis of Signals Generated by Rotating Machines

    Directory of Open Access Journals (Sweden)

    R. Zetik

    1999-06-01

    Full Text Available This contribution is devoted to the higher order time-frequency analyses of signals. Firstly, time-frequency representations of higher order (TFRHO are defined. Then L-Wigner distribution (LWD is given as a special case of TFRHO. Basic properties of LWD are illustrated based on the analysis of mono-component and multi-component synthetic signals and acoustical signals generated by rotating machine. The obtained results confirm usefulness of LWD application for the purpose of rotating machine condition monitoring.

  2. Scheme for efficient extraction of low-frequency signal beyond the quantum limit by frequency-shift detection.

    Science.gov (United States)

    Yang, R G; Zhang, J; Zhai, Z H; Zhai, S Q; Liu, K; Gao, J R

    2015-08-10

    Low-frequency (Hz~kHz) squeezing is very important in many schemes of quantum precision measurement. But it is more difficult than that at megahertz-frequency because of the introduction of laser low-frequency technical noise. In this paper, we propose a scheme to obtain a low-frequency signal beyond the quantum limit from the frequency comb in a non-degenerate frequency and degenerate polarization optical parametric amplifier (NOPA) operating below threshold with type I phase matching by frequency-shift detection. Low-frequency squeezing immune to laser technical noise is obtained by a detection system with a local beam of two-frequency intense laser. Furthermore, the low-frequency squeezing can be used for phase measurement in Mach-Zehnder interferometer, and the signal-to-noise ratio (SNR) can be enhanced greatly.

  3. Instantaneous and Frequency-Warped Signal Processing Techniques for Auditory Source Separation.

    Science.gov (United States)

    Wang, Avery Li-Chun

    This thesis summarizes several contributions to the areas of signal processing and auditory source separation. The philosophy of Frequency-Warped Signal Processing is introduced as a means for separating the AM and FM contributions to the bandwidth of a complex-valued, frequency-varying sinusoid p (n), transforming it into a signal with slowly-varying parameters. This transformation facilitates the removal of p (n) from an additive mixture while minimizing the amount of damage done to other signal components. The average winding rate of a complex-valued phasor is explored as an estimate of the instantaneous frequency. Theorems are provided showing the robustness of this measure. To implement frequency tracking, a Frequency-Locked Loop algorithm is introduced which uses the complex winding error to update its frequency estimate. The input signal is dynamically demodulated and filtered to extract the envelope. This envelope may then be remodulated to reconstruct the target partial, which may be subtracted from the original signal mixture to yield a new, quickly-adapting form of notch filtering. Enhancements to the basic tracker are made which, under certain conditions, attain the Cramer -Rao bound for the instantaneous frequency estimate. To improve tracking, the novel idea of Harmonic -Locked Loop tracking, using N harmonically constrained trackers, is introduced for tracking signals, such as voices and certain musical instruments. The estimated fundamental frequency is computed from a maximum-likelihood weighting of the N tracking estimates, making it highly robust. The result is that harmonic signals, such as voices, can be isolated from complex mixtures in the presence of other spectrally overlapping signals. Additionally, since phase information is preserved, the resynthesized harmonic signals may be removed from the original mixtures with relatively little damage to the residual signal. Finally, a new methodology is given for designing linear-phase FIR filters

  4. A Modified Differential Coherent Bit Synchronization Algorithm for BeiDou Weak Signals with Large Frequency Deviation.

    Science.gov (United States)

    Han, Zhifeng; Liu, Jianye; Li, Rongbing; Zeng, Qinghua; Wang, Yi

    2017-07-04

    BeiDou system navigation messages are modulated with a secondary NH (Neumann-Hoffman) code of 1 kbps, where frequent bit transitions limit the coherent integration time to 1 millisecond. Therefore, a bit synchronization algorithm is necessary to obtain bit edges and NH code phases. In order to realize bit synchronization for BeiDou weak signals with large frequency deviation, a bit synchronization algorithm based on differential coherent and maximum likelihood is proposed. Firstly, a differential coherent approach is used to remove the effect of frequency deviation, and the differential delay time is set to be a multiple of bit cycle to remove the influence of NH code. Secondly, the maximum likelihood function detection is used to improve the detection probability of weak signals. Finally, Monte Carlo simulations are conducted to analyze the detection performance of the proposed algorithm compared with a traditional algorithm under the CN0s of 20~40 dB-Hz and different frequency deviations. The results show that the proposed algorithm outperforms the traditional method with a frequency deviation of 50 Hz. This algorithm can remove the effect of BeiDou NH code effectively and weaken the influence of frequency deviation. To confirm the feasibility of the proposed algorithm, real data tests are conducted. The proposed algorithm is suitable for BeiDou weak signal bit synchronization with large frequency deviation.

  5. Photoacoustic signal and noise analysis for Si thin plate: signal correction in frequency domain.

    Science.gov (United States)

    Markushev, D D; Rabasović, M D; Todorović, D M; Galović, S; Bialkowski, S E

    2015-03-01

    Methods for photoacoustic signal measurement, rectification, and analysis for 85 μm thin Si samples in the 20-20 000 Hz modulation frequency range are presented. Methods for frequency-dependent amplitude and phase signal rectification in the presence of coherent and incoherent noise as well as distortion due to microphone characteristics are presented. Signal correction is accomplished using inverse system response functions deduced by comparing real to ideal signals for a sample with well-known bulk parameters and dimensions. The system response is a piece-wise construction, each component being due to a particular effect of the measurement system. Heat transfer and elastic effects are modeled using standard Rosencweig-Gersho and elastic-bending theories. Thermal diffusion, thermoelastic, and plasmaelastic signal components are calculated and compared to measurements. The differences between theory and experiment are used to detect and correct signal distortion and to determine detector and sound-card characteristics. Corrected signal analysis is found to faithfully reflect known sample parameters.

  6. DC response of dust to low frequency AC signals

    Science.gov (United States)

    McKinlay, Michael; Konopka, Uwe; Thomas, Edward

    2017-10-01

    Macroscopic changes in the shape and equilibrium position of clouds of charged microparticles suspended in a plasma have been observed in response to low frequency AC signals. In these experiments, dusty plasmas consisting of 2-micron diameter silica microspheres suspended between an anode and cathode in an argon, DC glow discharge plasma are produced in a grounded, 6-way cross vacuum chamber. An AC signal, produced by a function generator and amplified by a bipolar op-amp, is superimposed onto the potential from the cathode. The frequencies of the applied AC signals, ranging from tens to hundreds of kHz, are comparable to the ion-neutral collision frequency; well below the ion/electron plasma frequencies, but also considerably higher than the dust plasma frequency. This presentation will detail the experimental setup, present documentation and categorization of observations of the dust response, and present an initial model of the response. This work is supported by funding from the US Dept. of Energy, Grant Number DE-SC0016330, and by the National Science Foundation, Grant Number PHY-1613087.

  7. Biasing vector network analyzers using variable frequency and amplitude signals

    Science.gov (United States)

    Nobles, J. E.; Zagorodnii, V.; Hutchison, A.; Celinski, Z.

    2016-08-01

    We report the development of a test setup designed to provide a variable frequency biasing signal to a vector network analyzer (VNA). The test setup is currently used for the testing of liquid crystal (LC) based devices in the microwave region. The use of an AC bias for LC based devices minimizes the negative effects associated with ionic impurities in the media encountered with DC biasing. The test setup utilizes bias tees on the VNA test station to inject the bias signal. The square wave biasing signal is variable from 0.5 to 36.0 V peak-to-peak (VPP) with a frequency range of DC to 10 kHz. The test setup protects the VNA from transient processes, voltage spikes, and high-frequency leakage. Additionally, the signals to the VNA are fused to ½ amp and clipped to a maximum of 36 VPP based on bias tee limitations. This setup allows us to measure S-parameters as a function of both the voltage and the frequency of the applied bias signal.

  8. Large-Signal DG-MOSFET Modelling for RFID Rectification

    Directory of Open Access Journals (Sweden)

    R. Rodríguez

    2016-01-01

    Full Text Available This paper analyses the undoped DG-MOSFETs capability for the operation of rectifiers for RFIDs and Wireless Power Transmission (WPT at microwave frequencies. For this purpose, a large-signal compact model has been developed and implemented in Verilog-A. The model has been numerically validated with a device simulator (Sentaurus. It is found that the number of stages to achieve the optimal rectifier performance is inferior to that required with conventional MOSFETs. In addition, the DC output voltage could be incremented with the use of appropriate mid-gap metals for the gate, as TiN. Minor impact of short channel effects (SCEs on rectification is also pointed out.

  9. Transverse ion energization and low-frequency plasma waves in the mid-altitude auroral zone: A case study

    International Nuclear Information System (INIS)

    Peterson, W.K.; Shelley, E.G.; Boardsen, S.A.; Gurnett, D.A.; Ledley, B.G.; Sugiura, M.; Moore, T.E.; Waite, J.H.

    1988-01-01

    The transport of ions from the ionosphere to the magnetosphere requires that ions acquire significant energy in directions both transverse and parallel to the magnetic field. There is a considerable body of experimental evidence that shows that transverse energization occurs over a wide range of altitudes on auroral field lines. Many recent analytical and simulation studies have addressed the microphysics involved in transverse ion energization. There are, however, remarkably few published high-resolution plasma and plasma wave observations obtained in the mid-altitude auroral region available to compare with the analytical and simulation studies. Several hundred hours of high-resolution plasma data obtained from the Dynamics Explorer 1 satellite have been surveyed. A wide variety of plasma environments that are difficult to simply characterize were found. We present here a comprehensive set of high-sensitivity, high-resolution plasma wave, ion, and magnetometer data obtained from an evening auroral zone crossing at r/R/sub E/∼3. The total density, thermal structure, and composition of the plasma in this representative interval varied rapidly, as did the character (mode) of low-frequency plasma waves observed. We did not find an unambiguous particle and wave signature of local transverse ion energization, but we did frequently find intervals where local transverse ion heating was consistent with the observations. We also found a downward flowing ion distribution that occurred simultaneously with a region of intense plasma wave emissions primarily below the lower hybrid resonance frequency. copyright American Geophysical Union 1988

  10. Wide-band analog frequency modulation of optic signals using indirect techniques

    Science.gov (United States)

    Fitzmartin, D. J.; Balboni, E. J.; Gels, R. G.

    1991-01-01

    The wideband frequency modulation (FM) of an optical carrier by a radio frequency (RF) or microwave signal can be accomplished independent of laser type when indirect modulation is employed. Indirect modulators exploit the integral relation of phase to frequency so that phase modulators can be used to impress frequency modulation on an optical carrier. The use of integrated optics phase modulators, which are highly linear, enables the generation of optical wideband FM signals with very low intermodulation distortion. This modulator can be used as part of an optical wideband FM link for RF and microwave signals. Experimental results from the test of an indirect frequency modulator for an optical carrier are discussed.

  11. High resolution mid-infrared spectroscopy based on frequency upconversion

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin; Hu, Qi; Tidemand-Lichtenberg, Peter

    2013-01-01

    signals can be analyzed. The obtainable frequency resolution is usually in the nm range where sub nm resolution is preferred in many applications, like gas spectroscopy. In this work we demonstrate how to obtain sub nm resolution when using upconversion. In the presented realization one object point...... high resolution spectral performance by observing emission from hot water vapor in a butane gas burner....

  12. Audiometric Characteristics of a Dutch DFNA10 Family With Mid-Frequency Hearing Impairment.

    Science.gov (United States)

    van Beelen, Eline; Oonk, Anne M M; Leijendeckers, Joop M; Hoefsloot, Elisabeth H; Pennings, Ronald J E; Feenstra, Ilse; Dieker, Hendrik-Jan; Huygen, Patrick L M; Snik, Ad F M; Kremer, Hannie; Kunst, Henricus P M

    2016-01-01

    Mutations in EYA4 can cause nonsyndromic autosomal dominant sensorineural hearing impairment (DFNA10) or a syndromic variant with hearing impairment and dilated cardiomyopathy. A mutation in EYA4 was found in a Dutch family, causing DFNA10. This study is focused on characterizing the hearing impairment in this family. Whole exome sequencing was performed in the proband. In addition, peripheral blood samples were collected from 23 family members, and segregation analyses were performed. All participants underwent otorhinolaryngological examinations and pure-tone audiometry, and 12 participants underwent speech audiometry. In addition, an extended set of audiometric measurements was performed in five family members to evaluate the functional status of the cochlea. Vestibular testing was performed in three family members. Two individuals underwent echocardiography to evaluate the nonsyndromic phenotype. The authors present a Dutch family with a truncating mutation in EYA4 causing a mid-frequency hearing impairment. This mutation (c.464del) leads to a frameshift and a premature stop codon (p.Pro155fsX). This mutation is the most N-terminal mutation in EYA4 found to date. In addition, a missense mutation, predicted to be deleterious, was found in EYA4 in two family members. Echocardiography in two family members revealed no signs of dilated cardiomyopathy. Results of caloric and velocity step tests in three family members showed no abnormalities. Hearing impairment was found to be symmetric and progressive, beginning as a mid-frequency hearing impairment in childhood and developing into a high-frequency, moderate hearing impairment later in life. Furthermore, an extended set of audiometric measurements was performed in five family members. The results were comparable to those obtained in patients with other sensory types of hearing impairments, such as patients with Usher syndrome type IIA and presbyacusis, and not to those obtained in patients with (cochlear

  13. Simulation of X-ray signals

    International Nuclear Information System (INIS)

    Weller, A.

    1980-12-01

    A parameterized form of the local emissivity is used for the simulation of soft X-ray signals obtained on the WENDELSTEIN W VII-A stellarator with a 30 diode array. Numerical calculation of the line integrals for the different viewing angles and for a set of rotation angles covering one full signal period provides simulated periodic signals. In addition radial profiles of the line integrated emmission averaged over some time interval or at specific times, the relative amplitude modulation and the relative phase of the oscillations are calculated. These have to be fitted to the corresponding measured signals and profiles in order to get a reliable picture of the local emissivity. The model can take into account two poloidally asymmetric contributions of the type m = 1,2,3 or 4 (m = poloidal mode number). Each asymmetry can be generated in two ways (modulation of intensity and of geometry parameters). Besides an uniform rotation of the asymmetric terms some specific simple time evolution of the signals can be included (non-uniform rotation, growth of oscillations, sawtooth oscillations). The various input parameters are illustrated and the result of a simulation procedure is presented for a particular discharge in W VII-A. (orig.)

  14. Characterization of a clock based on coherent population trapping in a thermal cesium vapor. Main effects that may affect its mid- and long-term frequency stability

    International Nuclear Information System (INIS)

    Kozlova, Olga

    2013-01-01

    This thesis describes a Cs - buffer gas vapor cell atomic clock based on coherent population trapping (CPT), and the main frequency shifts affecting its mid- and long-term stability. The developed atomic clock based on CPT uses two original techniques: a so-called double-Λ scheme for the CPT-resonance excitation and a temporal Ramsey interrogation technique, which produce a high contrast and narrow resonances with reduced light shift dependence. Generally, the mid and long term stability of the vapor cell atomic clock is limited by the collisional shift induced by alkali-buffer gas collisions and the light shift (or the effects depending on the laser intensity). We report on the study of the collisional shift of Cs clock frequency in the presence of Ne, N 2 or Ar buffer gas, and its temperature dependence. The coefficient values of this dependence for these three buffer gases were revealed (some of them for the first time), allowing us to realise a cell with optimal combination of buffer gases to cancel the temperature dependence around the working temperature. Following the study of the signal amplitude and the coherence relaxation rate the optimal values for such parameters as interrogation cycle, magnetic field, cell temperature, pressure of the buffer gas mixture, etc. were found for the chosen cell. The investigation on the light shift and the effects depending on the laser intensity allowed us to determine the most sensitive parameters (laser intensity ratio, temperature) and to implement the required stabilizations in order to better control them. Finally, the mid- and long-term clock frequency stability was improved by a factor 40, reaching 2.5 10 -14 at 1 hour. (author)

  15. High frequency seismic signal generated by landslides on complex topographies: from point source to spatially distributed sources

    Science.gov (United States)

    Mangeney, A.; Kuehnert, J.; Capdeville, Y.; Durand, V.; Stutzmann, E.; Kone, E. H.; Sethi, S.

    2017-12-01

    During their flow along the topography, landslides generate seismic waves in a wide frequency range. These so called landquakes can be recorded at very large distances (a few hundreds of km for large landslides). The recorded signals depend on the landslide seismic source and the seismic wave propagation. If the wave propagation is well understood, the seismic signals can be inverted for the seismic source and thus can be used to get information on the landslide properties and dynamics. Analysis and modeling of long period seismic signals (10-150s) have helped in this way to discriminate between different landslide scenarios and to constrain rheological parameters (e.g. Favreau et al., 2010). This was possible as topography poorly affects wave propagation at these long periods and the landslide seismic source can be approximated as a point source. In the near-field and at higher frequencies (> 1 Hz) the spatial extent of the source has to be taken into account and the influence of the topography on the recorded seismic signal should be quantified in order to extract information on the landslide properties and dynamics. The characteristic signature of distributed sources and varying topographies is studied as a function of frequency and recording distance.The time dependent spatial distribution of the forces applied to the ground by the landslide are obtained using granular flow numerical modeling on 3D topography. The generated seismic waves are simulated using the spectral element method. The simulated seismic signal is compared to observed seismic data from rockfalls at the Dolomieu Crater of Piton de la Fournaise (La Réunion).Favreau, P., Mangeney, A., Lucas, A., Crosta, G., and Bouchut, F. (2010). Numerical modeling of landquakes. Geophysical Research Letters, 37(15):1-5.

  16. Dispersion compensated mid-infrared quantum cascade laser frequency comb with high power output

    Directory of Open Access Journals (Sweden)

    Q. Y. Lu

    2017-04-01

    Full Text Available Chromatic dispersion control plays an underlying role in optoelectronics and spectroscopy owing to its enhancement to nonlinear interactions by reducing the phase mismatching. This is particularly important to optical frequency combs based on quantum cascade lasers which require negligible dispersions for efficient mode locking of the dispersed modes into equally spaced comb modes. Here, we demonstrated a dispersion compensated mid-IR quantum cascade laser frequency comb with high power output at room temperature. A low-loss dispersive mirror has been engineered to compensate the device’s dispersion residue for frequency comb generation. Narrow intermode beating linewidths of 40 Hz in the comb-working currents were identified with a high power output of 460 mW and a broad spectral coverage of 80 cm-1. This dispersion compensation technique will enable fast spectroscopy and high-resolution metrology based on QCL combs with controlled dispersion and suppressed noise.

  17. Top down and bottom up selection drives variations in frequency and form of a visual signal.

    Science.gov (United States)

    Yeh, Chien-Wei; Blamires, Sean J; Liao, Chen-Pan; Tso, I-Min

    2015-03-30

    The frequency and form of visual signals can be shaped by selection from predators, prey or both. When a signal simultaneously attracts predators and prey selection may favour a strategy that minimizes risks while attracting prey. Accordingly, varying the frequency and form of the silken decorations added to their web may be a way that Argiope spiders minimize predation while attracting prey. Nonetheless, the role of extraneous factors renders the influences of top down and bottom up selection on decoration frequency and form variation difficult to discern. Here we used dummy spiders and decorations to simulate four possible strategies that the spider Argiope aemula may choose and measured the prey and predator attraction consequences for each in the field. The strategy of decorating at a high frequency with a variable form attracted the most prey, while that of decorating at a high frequency with a fixed form attracted the most predators. These results suggest that mitigating the cost of attracting predators while maintaining prey attraction drives the use of variation in decoration form by many Argiope spp. when decorating frequently. Our study highlights the importance of considering top-down and bottom up selection pressure when devising evolutionary ecology experiments.

  18. Simulation of automatic frequency and power regulators

    OpenAIRE

    Borovikov, Yuri Sergeevich; Pischulin, A. Y.; Ufa, Ruslan Alexandrovich

    2015-01-01

    The motivation of the presented research is based on the need for development of new methods and tools for adequate real time simulation of automation control frequency and power regulators of generator played an important role in the planning, design and operation of electric power system. This paper proposes a Hybrid real time simulator of electric power system for simulation of automation control frequency and power regulators of generator. The obtained results of experimental researches o...

  19. Improvement of Frequency Locking Algorithm for Atomic Frequency Standards

    Science.gov (United States)

    Park, Young-Ho; Kang, Hoonsoo; Heyong Lee, Soo; Eon Park, Sang; Lee, Jong Koo; Lee, Ho Seong; Kwon, Taeg Yong

    2010-09-01

    The authors describe a novel method of frequency locking algorithm for atomic frequency standards. The new algorithm for locking the microwave frequency to the Ramsey resonance is compared with the old one that had been employed in the cesium atomic beam frequency standards such as NIST-7 and KRISS-1. Numerical simulations for testing the performance of the algorithm show that the new method has a noise filtering performance superior to the old one by a factor of 1.2 for the flicker signal noise and 1.4 for random-walk signal noise. The new algorithm can readily be used to enhance the frequency stability for a digital servo employing the slow square wave frequency modulation.

  20. Extracting a shape function for a signal with intra-wave frequency modulation.

    Science.gov (United States)

    Hou, Thomas Y; Shi, Zuoqiang

    2016-04-13

    In this paper, we develop an effective and robust adaptive time-frequency analysis method for signals with intra-wave frequency modulation. To handle this kind of signals effectively, we generalize our data-driven time-frequency analysis by using a shape function to describe the intra-wave frequency modulation. The idea of using a shape function in time-frequency analysis was first proposed by Wu (Wu 2013 Appl. Comput. Harmon. Anal. 35, 181-199. (doi:10.1016/j.acha.2012.08.008)). A shape function could be any smooth 2π-periodic function. Based on this model, we propose to solve an optimization problem to extract the shape function. By exploring the fact that the shape function is a periodic function with respect to its phase function, we can identify certain low-rank structure of the signal. This low-rank structure enables us to extract the shape function from the signal. Once the shape function is obtained, the instantaneous frequency with intra-wave modulation can be recovered from the shape function. We demonstrate the robustness and efficiency of our method by applying it to several synthetic and real signals. One important observation is that this approach is very stable to noise perturbation. By using the shape function approach, we can capture the intra-wave frequency modulation very well even for noise-polluted signals. In comparison, existing methods such as empirical mode decomposition/ensemble empirical mode decomposition seem to have difficulty in capturing the intra-wave modulation when the signal is polluted by noise. © 2016 The Author(s).

  1. The Real-time Frequency Spectrum Analysis of Neutron Pulse Signal Series

    International Nuclear Information System (INIS)

    Tang Yuelin; Ren Yong; Wei Biao; Feng Peng; Mi Deling; Pan Yingjun; Li Jiansheng; Ye Cenming

    2009-01-01

    The frequency spectrum analysis of neutron pulse signal is a very important method in nuclear stochastic signal processing Focused on the special '0' and '1' of neutron pulse signal series, this paper proposes new rotation-table and realizes a real-time frequency spectrum algorithm under 1G Hz sample rate based on PC with add, address and SSE. The numerical experimental results show that under the count rate of 3X10 6 s -1 , this algorithm is superior to FFTW in time-consumption and can meet the real-time requirement of frequency spectrum analysis. (authors)

  2. Full molecular dynamics simulations of liquid water and carbon tetrachloride for two-dimensional Raman spectroscopy in the frequency domain

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Ju-Yeon, E-mail: ju8879@kuchem.kyoto-u.ac.jp; Ito, Hironobu, E-mail: h.ito@kuchem.kyoto-u.ac.jp; Tanimura, Yoshitaka, E-mail: tanimura@kuchem.kyoto-u.ac.jp

    2016-12-20

    Frequency-domain two-dimensional (2D) Raman signals, which are equivalent to coherent two-dimensional Raman scattering (COTRAS) signals, for liquid water and carbon tetrachloride were calculated using an equilibrium–nonequilibrium hybrid molecular dynamics (MD) simulation algorithm. An appropriate representation of the 2D Raman spectrum obtained from MD simulations provides an easy-to-understand depiction of structural and dynamical properties. We elucidate mechanisms governing the 2D signal profiles involving anharmonic mode–mode coupling and the nonlinearities of the polarizability for the intermolecular and intramolecular vibrational modes. The predicted signal profiles and intensities can be utilized to analyze recently developed single-beam 2D spectra, whose signals are generated from a coherently controlled pulse, allowing the single-beam measurement to be carried out more efficiently. Moreover, the MD simulation results allow us to visualize the molecular structure and dynamics by comparing the accurately calculated spectrum with experimental result.

  3. Nonlinear optics in germanium mid-infrared fiber material: Detuning oscillations in femtosecond mid-infrared spectroscopy

    Directory of Open Access Journals (Sweden)

    M. Ordu

    2017-09-01

    Full Text Available Germanium optical fibers hold great promise in extending semiconductor photonics into the fundamentally important mid-infrared region of the electromagnetic spectrum. The demonstration of nonlinear response in fabricated Ge fiber samples is a key step in the development of mid-infrared fiber materials. Here we report the observation of detuning oscillations in a germanium fiber in the mid-infrared region using femtosecond dispersed pump-probe spectroscopy. Detuning oscillations are observed in the frequency-resolved response when mid-infrared pump and probe pulses are overlapped in a fiber segment. The oscillations arise from the nonlinear frequency resolved nonlinear (χ(3 response in the germanium semiconductor. Our work represents the first observation of coherent oscillations in the emerging field of germanium mid-infrared fiber optics.

  4. Advanced Time-Frequency Representation in Voice Signal Analysis

    Directory of Open Access Journals (Sweden)

    Dariusz Mika

    2018-03-01

    Full Text Available The most commonly used time-frequency representation of the analysis in voice signal is spectrogram. This representation belongs in general to Cohen's class, the class of time-frequency energy distributions. From the standpoint of properties of the resolution spectrogram representation is not optimal. In Cohen class representations are known which have a better resolution properties. All of them are created by smoothing the Wigner-Ville'a (WVD distribution characterized by the best resolution, however, the biggest harmful interference. Used smoothing functions decide about a compromise between the properties of resolution and eliminating harmful interference term. Another class of time-frequency energy distributions is the affine class of distributions. From the point of view of readability of analysis the best properties are known so called Redistribution of energy caused by the use of a general methodology referred to as reassignment to any time-frequency representation. Reassigned distributions efficiently combine a reduction of the interference terms provided by a well adapted smoothing kernel and an increased concentration of the signal components.

  5. Simulation of automatic frequency and power regulators

    Science.gov (United States)

    Borovikov, Y. S.; Pischulin, A. Y.; Ufa, R. A.

    2015-10-01

    The motivation of the presented research is based on the need for development of new methods and tools for adequate real time simulation of automation control frequency and power regulators of generator played an important role in the planning, design and operation of electric power system. This paper proposes a Hybrid real time simulator of electric power system for simulation of automation control frequency and power regulators of generator. The obtained results of experimental researches of turbine emergency control of generator demonstrate high accuracy of the simulator and possibility of real-time simulation of all the processes in the electric power system without any decomposition and limitation on their duration, and the effectiveness of the proposed simulator in solving of the design, operational and research tasks of electric power system.

  6. Time-frequency analysis of phonocardiogram signals using wavelet transform: a comparative study.

    Science.gov (United States)

    Ergen, Burhan; Tatar, Yetkin; Gulcur, Halil Ozcan

    2012-01-01

    Analysis of phonocardiogram (PCG) signals provides a non-invasive means to determine the abnormalities caused by cardiovascular system pathology. In general, time-frequency representation (TFR) methods are used to study the PCG signal because it is one of the non-stationary bio-signals. The continuous wavelet transform (CWT) is especially suitable for the analysis of non-stationary signals and to obtain the TFR, due to its high resolution, both in time and in frequency and has recently become a favourite tool. It decomposes a signal in terms of elementary contributions called wavelets, which are shifted and dilated copies of a fixed mother wavelet function, and yields a joint TFR. Although the basic characteristics of the wavelets are similar, each type of the wavelets produces a different TFR. In this study, eight real types of the most known wavelets are examined on typical PCG signals indicating heart abnormalities in order to determine the best wavelet to obtain a reliable TFR. For this purpose, the wavelet energy and frequency spectrum estimations based on the CWT and the spectra of the chosen wavelets were compared with the energy distribution and the autoregressive frequency spectra in order to determine the most suitable wavelet. The results show that Morlet wavelet is the most reliable wavelet for the time-frequency analysis of PCG signals.

  7. Effects of the major sudden stratospheric warming event of 2009 on the subionospheric very low frequency/low frequency radio signals

    Science.gov (United States)

    Pal, S.; Hobara, Y.; Chakrabarti, S. K.; Schnoor, P. W.

    2017-07-01

    This paper presents effects of the major sudden stratospheric warming (SSW) event of 2009 on the subionospheric very low frequency/low frequency (VLF/LF) radio signals propagating in the Earth-ionosphere waveguide. Signal amplitudes from four transmitters received by VLF/LF radio networks of Germany and Japan corresponding to the major SSW event are investigated for possible anomalies and atmospheric influence on the high- to middle-latitude ionosphere. Significant anomalous increase or decrease of nighttime and daytime amplitudes of VLF/LF signals by ˜3-5 dB during the SSW event have been found for all propagation paths associated with stratospheric temperature rise at 10 hPa level. Increase or decrease in VLF/LF amplitudes during daytime and nighttime is actually due to the modification of the lower ionospheric boundary conditions in terms of electron density and electron-neutral collision frequency profiles and associated modal interference effects between the different propagating waveguide modes during the SSW period. TIMED/SABER mission data are also used to investigate the upper mesospheric conditions over the VLF/LF propagation path during the same time period. We observe a decrease in neutral temperature and an increase in pressure at the height of 75-80 km around the peak time of the event. VLF/LF anomalies are correlated and in phase with the stratospheric temperature and mesospheric pressure variation, while minimum of mesospheric cooling shows a 2-3 day delay with maximum VLF/LF anomalies. Simulations of VLF/LF diurnal variation are performed using the well-known Long Wave Propagating Capability (LWPC) code within the Earth-ionosphere waveguide to explain the VLF/LF anomalies qualitatively.

  8. Coordinated Primary and Secondary Control with Frequency-Bus-Signaling for Distributed Generation and Storage in Islanded Microgrids

    DEFF Research Database (Denmark)

    Wu, Dan; Tang, Fen; Dragicevic, Tomislav

    2013-01-01

    In this paper, a distributed coordinated control scheme based on frequency-bus-signaling (FBS) method for a low-voltage AC three phase microgrid is proposed. The control scheme is composed by two levels. Firstly a primary local control which is different for the DGs and the ESS is proposed. The ESS...... control is implemented to restore the frequency deviation produced by the primary ESS controller while preserving the coordinated control performance. Real-time simulation results show the feasibility of the proposed approach by showing the operation of the microgrid in different scenarios....

  9. Transformer modeling for low- and mid-frequency electromagnetic transients simulation

    Science.gov (United States)

    Lambert, Mathieu

    In this work, new models are developed for single-phase and three-phase shell-type transformers for the simulation of low-frequency transients, with the use of the coupled leakage model. This approach has the advantage that it avoids the use of fictitious windings to connect the leakage model to a topological core model, while giving the same response in short-circuit as the indefinite admittance matrix (BCTRAN) model. To further increase the model sophistication, it is proposed to divide windings into coils in the new models. However, short-circuit measurements between coils are never available. Therefore, a novel analytical method is elaborated for this purpose, which allows the calculation in 2-D of short-circuit inductances between coils of rectangular cross-section. The results of this new method are in agreement with the results obtained from the finite element method in 2-D. Furthermore, the assumption that the leakage field is approximately 2-D in shell-type transformers is validated with a 3-D simulation. The outcome of this method is used to calculate the self and mutual inductances between the coils of the coupled leakage model and the results are showing good correspondence with terminal short-circuit measurements. Typically, leakage inductances in transformers are calculated from short-circuit measurements and the magnetizing branch is calculated from no-load measurements, assuming that leakages are unimportant for the unloaded transformer and that magnetizing current is negligible during a short-circuit. While the core is assumed to have an infinite permeability to calculate short-circuit inductances, and it is a reasonable assumption since the core's magnetomotive force is negligible during a short-circuit, the same reasoning does not necessarily hold true for leakage fluxes in no-load conditions. This is because the core starts to saturate when the transformer is unloaded. To take this into account, a new analytical method is developed in this

  10. Effect of ion clouds micromotion on measured signal in Fourier transform ion cyclotron resonance: Computer simulation.

    Science.gov (United States)

    Vladimirov, Gleb; Kostyukevich, Yury; Kharybin, Oleg; Nikolaev, Eugene

    2017-08-01

    Particle-in-cell-based realistic simulation of Fourier transform ion cyclotron resonance experiments could be used to generate ion trajectories and a signal induced on the detection electrodes. It has been shown recently that there is a modulation of "reduced" cyclotron frequencies in ion cyclotron resonance signal caused by Coulomb interaction of ion clouds. In this work it was proposed to use this modulation in order to determine frequency difference between an ion of known m/z and all other ions generating signal in ion cyclotron resonance cell. It is shown that with an increase of number of ions in ion cyclotron resonance trap, the modulation index increases, which lead to a decrease in the accuracy of determination of peak intensities by super Fourier transform resolution methods such as filter diagonalization method.

  11. Optimization of carrier frequency and duty cycle for pulse modulation of biological signals.

    Science.gov (United States)

    Tandon, S N; Singh, S; Sharma, P K; Khosla, S

    1980-10-01

    Digital modulation techniques are commonly used for the recording and transmission of biological signals. Hitherto, the choice of subcarrier frequency for recording or transmission of biological signals has been arbitary and this usually results in poor signal to noise ratio (SNR) due to the limited frequency characteristics of the system. In the present study the frequency characteristics of the system (first order approximation) has been taken to be that of a Butterworth filter. Computations based on this assumption show that for a given input signal there exists an optimum subcarrier frequency and a corresponding optimum duty cycle which would give maximum SNR of the system. For convenience, a nomogram has been prepared and it has been shown that for a given frequency response of the system, the nomogram could be used for selecting an optimum subcarrier frequency and a corresponding duty cycle. The theoretical formulations have been verified with experimental work.

  12. Small Displacement Detection of Biological Signals Using the Cyclic Frequency Method

    Directory of Open Access Journals (Sweden)

    Dan Zhang

    2015-01-01

    Full Text Available A new signal processing method called the Cyclic Frequency method is proposed for small displacement detection of vital signals such as heart rate and respiration using the CW radar method. We have presented experimental results of small displacement detection to confirm the validity of the method. The displacement amplitude 2.5 mm can be detected with a propagation frequency of 24.15 GHz. We may increase the propagation frequency for smaller displacement amplitude or target velocity.

  13. High-Frequency Neuromuscular Electrical Stimulation Increases Anabolic Signaling.

    Science.gov (United States)

    Mettler, Joni A; Magee, Dillon M; Doucet, Barbara M

    2018-03-16

    Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation settings to increase muscle mass and strength. However, the effects of NMES on muscle growth are not clear and no human studies have compared anabolic signaling between low-frequency (LF-) and high-frequency (HF-) NMES. The purpose of this study was to determine the skeletal muscle anabolic signaling response to an acute bout of LF- and HF-NMES. Eleven young healthy volunteers (6 men; 5 women) received an acute bout of LF- (20 Hz) and HF- (60 Hz) NMES. Muscle biopsies were obtained from the vastus lateralis muscle prior to the first NMES treatment and 30-mins following each NMES treatment. Phosphorylation of the following key anabolic signaling proteins was measured by Western blot and proteins are expressed as a ratio of phosphorylated to total: mammalian target of rapamycin (mTOR), p70-S6 kinase 1 (S6K1), and eukaryotic initiation factor 4E binding protein 1 (4E-BP1). Compared to Pre-NMES, phosphorylation of mTOR was upregulated 40.2% for LF-NMES (P = 0.018) and 68.4% for HF-NMES (P 0.05). There were no differences between treatment conditions for 4E-BP1 phosphorylation (P > 0.05). An acute bout of LF- and HF-NMES upregulated anabolic signaling with HF-NMES producing a greater anabolic response compared to LF-NMES, suggesting that HF-stimulation may provide a stronger stimulus for processes that initiate muscle hypertrophy. Additionally, the stimulation frequency parameter should be considered by clinicians in the design of optimal NMES treatment protocols.

  14. A novel joint timing/frequency synchronization scheme based on Radon-Wigner transform of LFM signals in CO-OFDM systems

    Science.gov (United States)

    Liu, Jianfei; Wei, Ying; Zeng, Xiangye; Lu, Jia; Zhang, Shuangxi; Wang, Mengjun

    2018-03-01

    A joint timing and frequency synchronization method has been proposed for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) system in this paper. The timing offset (TO), integer frequency offset (FO) and the fractional FO can be realized by only one training symbol, which consists of two linear frequency modulation (LFM) signals with opposite chirp rates. By detecting the peak of LFM signals after Radon-Wigner transform (RWT), the TO and the integer FO can be estimated at the same time, moreover, the fractional FO can be acquired correspondingly through the self-correlation characteristic of the same training symbol. Simulation results show that the proposed method can give a more accurate TO estimation than the existing methods, especially at poor OSNR conditions; for the FO estimation, both the fractional and the integer FO can be estimated through the proposed training symbol with no extra overhead, a more accurate estimation and a large FO estimation range of [ - 5 GHz, 5GHz] can be acquired.

  15. Mid-infrared optical parametric oscillator pumped by an amplified random fiber laser

    Science.gov (United States)

    Shang, Yaping; Shen, Meili; Wang, Peng; Li, Xiao; Xu, Xiaojun

    2017-01-01

    Recently, the concept of random fiber lasers has attracted a great deal of attention for its feature to generate incoherent light without a traditional laser resonator, which is free of mode competition and insure the stationary narrow-band continuous modeless spectrum. In this Letter, we reported the first, to the best of our knowledge, optical parametric oscillator (OPO) pumped by an amplified 1070 nm random fiber laser (RFL), in order to generate stationary mid-infrared (mid-IR) laser. The experiment realized a watt-level laser output in the mid-IR range and operated relatively stable. The use of the RFL seed source allowed us to take advantage of its respective stable time-domain characteristics. The beam profile, spectrum and time-domain properties of the signal light were measured to analyze the process of frequency down-conversion process under this new pumping condition. The results suggested that the near-infrared (near-IR) signal light `inherited' good beam performances from the pump light. Those would be benefit for further develop about optical parametric process based on different pumping circumstances.

  16. Application on technique of joint time-frequency analysis of seismic signal's first arrival estimation

    International Nuclear Information System (INIS)

    Xu Chaoyang; Liu Junmin; Fan Yanfang; Ji Guohua

    2008-01-01

    Joint time-frequency analysis is conducted to construct one joint density function of time and frequency. It can open out one signal's frequency components and their evolvements. It is the new evolvement of Fourier analysis. In this paper, according to the characteristic of seismic signal's noise, one estimation method of seismic signal's first arrival based on triple correlation of joint time-frequency spectrum is introduced, and the results of experiment and conclusion are presented. (authors)

  17. Cortical feedback signals generalise across different spatial frequencies of feedforward inputs.

    Science.gov (United States)

    Revina, Yulia; Petro, Lucy S; Muckli, Lars

    2017-09-22

    Visual processing in cortex relies on feedback projections contextualising feedforward information flow. Primary visual cortex (V1) has small receptive fields and processes feedforward information at a fine-grained spatial scale, whereas higher visual areas have larger, spatially invariant receptive fields. Therefore, feedback could provide coarse information about the global scene structure or alternatively recover fine-grained structure by targeting small receptive fields in V1. We tested if feedback signals generalise across different spatial frequencies of feedforward inputs, or if they are tuned to the spatial scale of the visual scene. Using a partial occlusion paradigm, functional magnetic resonance imaging (fMRI) and multivoxel pattern analysis (MVPA) we investigated whether feedback to V1 contains coarse or fine-grained information by manipulating the spatial frequency of the scene surround outside an occluded image portion. We show that feedback transmits both coarse and fine-grained information as it carries information about both low (LSF) and high spatial frequencies (HSF). Further, feedback signals containing LSF information are similar to feedback signals containing HSF information, even without a large overlap in spatial frequency bands of the HSF and LSF scenes. Lastly, we found that feedback carries similar information about the spatial frequency band across different scenes. We conclude that cortical feedback signals contain information which generalises across different spatial frequencies of feedforward inputs. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  18. Parameter Estimation of Multiple Frequency-Hopping Signals with Two Sensors

    Directory of Open Access Journals (Sweden)

    Le Zuo

    2018-04-01

    Full Text Available This paper essentially focuses on parameter estimation of multiple wideband emitting sources with time-varying frequencies, such as two-dimensional (2-D direction of arrival (DOA and signal sorting, with a low-cost circular synthetic array (CSA consisting of only two rotating sensors. Our basic idea is to decompose the received data, which is a superimposition of phase measurements from multiple sources into separated groups and separately estimate the DOA associated with each source. Motivated by joint parameter estimation, we propose to adopt the expectation maximization (EM algorithm in this paper; our method involves two steps, namely, the expectation-step (E-step and the maximization (M-step. In the E-step, the correspondence of each signal with its emitting source is found. Then, in the M-step, the maximum-likelihood (ML estimates of the DOA parameters are obtained. These two steps are iteratively and alternatively executed to jointly determine the DOAs and sort multiple signals. Closed-form DOA estimation formulae are developed by ML estimation based on phase data, which also realize an optimal estimation. Directional ambiguity is also addressed by another ML estimation method based on received complex responses. The Cramer-Rao lower bound is derived for understanding the estimation accuracy and performance comparison. The verification of the proposed method is demonstrated with simulations.

  19. Theoretical analysis and simulation of a code division multiple access system (cdma for secure signal transmission in wideband channels

    Directory of Open Access Journals (Sweden)

    Stevan M. Berber

    2014-06-01

    Full Text Available Chaotic spreading sequences can increase secrecy and resistance to interception in signal transmission. Chaos-based CDMA systems have been well investigated in the case of flat fading and noise presence in the channel. However, these systems operating in wideband channels, characterized by the frequency selective fading and white Gaussian noise, have not been investigated to the level of understanding their practical applications. This paper presents a detailed mathematical model of a CDMA system based on chaotic spreading sequences. In a theoretical analysis, all signals are represented in the discrete time domain. Using the theory of discrete time stochastic processes, the probability of error expressions are derived in a closed form for a multi-user chaos based CDMA system. For the sake of comparison, the expressions for the probability of error are derived separately for narrowband and wideband channels. The application of the system interleaving technique is investigated in particular, which showed that this technique can substantially improve probability of error in the system.  The system is simulated and the findings of the simulation confirmed theoretically expected results. Possible improvements in the probability of bit error due to multipath channel nature, with and without interleavers, are quantified depending on the random delay and the number of users in the system. In the analyzed system, a simplified version of the wideband channel model, proposed for modern wideband wireless networks, is used. Introduction Over the past years, the demand for wireless communications has increased substantially due to advancements in mobile communication systems and networks. Following these increasing demands, modern communication systems require the ability to handle a large number of users to process and transmit wideband signals through complex frequency selective channels. One of the techniques for transmission of multi-user signals is the

  20. Metrological-grade tunable coherent source in the mid-infrared for molecular precision spectroscopy

    Science.gov (United States)

    Insero, G.; Clivati, C.; D'Ambrosio, D.; Cancio Pastor, P.; Verde, M.; Schunemann, P. G.; Zondy, J.-J.; Inguscio, M.; Calonico, D.; Levi, F.; De Natale, P.; Santambrogio, G.; Borri, S.

    2018-02-01

    We report on a metrological-grade mid-IR source with a 10-14 short-term instability for high-precision spectroscopy. Our source is based on the combination of a quantum cascade laser and a coherent radiation obtained by difference-frequency generation in an orientation-patterned gallium phosphide (OP-GaP) crystal. The pump and signal lasers are locked to an optical frequency comb referenced to the primary frequency standard via an optical fiber link. We demonstrate the robustness of the apparatus by measuring a vibrational transition around 6 μm on a metastable state of CO molecuels with 11 digits of precision.

  1. A portable, differential amplifier for recording high frequency EEG signals and evoked potentials

    International Nuclear Information System (INIS)

    Donos, Cristian; Giurgiu, Liviu; Popescu, Aurel; Mocanu, Marian

    2010-01-01

    In a clinical context, EEG refers to recording the brain's spontaneous electric activity, using small electrodes placed on the scalp. The signals collected are electric 'potentials' measured between two electrodes. Usually, for a healthy adult, these signals have small voltage (10 μV to 100 μV) and frequencies in the 0-40 Hz range. In the scientific literature, there are mentioned EEG signals and evoked potentials that have higher frequencies (up to 600 Hz) and amplitudes lower than 500 ηV. For this reason, building an amplifier capable of recording EEG signals in the ηV range and with frequencies up to couple of kHz is necessary to continue research beyond 600 Hz. We designed a very low noise amplifier that is able to measure/record EEG signals in the ηV range over a very large frequency bandwidth (0.09 Hz -385 kHz).(Author)

  2. Fault Detection in High Speed Helical Gears Considering Signal Processing Method in Real Simulation

    Directory of Open Access Journals (Sweden)

    Amir Ali Tabatabai Adnani

    Full Text Available Abstract In the present study, in order to detect the fault of the gearmeshs, two engaged gears based on research department of a major automotive company have been modeled. First off, by using the CATIA software the fault was induced to the output gear. Then, the faulty gearmesh and non-faulty gearmesh is modeled to find the fault pattern to predict and estimate the failure of the gearmesh. The induced defect is according to the frequently practical fault that takes place to the teeth of gears. In order to record the acceleration signals to calculate the decomposition algorithm, mount the accelerometer on accessible place of the output shaft to recognize the pattern. Then, for more realistic simulation, noise is added to the output signal. At the first step by means of Butterworth low pass digital, the noise has to be removed from signals after that by using the Empirical Mode Decomposition (EMD, signals have decomposed into the Instinct Mode Function (IMF and every IMF were tested by using the Instantaneous Frequency (IF in way of Hillbert Transform (HT. For this purpose a code was developed in MATLAB software. Then, in order to detect the presence of the fault the frequency spectrum of IMF's are created and defect is detected in gearmesh frequency of the spectrum.

  3. A robust multi-frequency mixing algorithm for suppression of rivet signal in GMR inspection of riveted structures

    Science.gov (United States)

    Safdernejad, Morteza S.; Karpenko, Oleksii; Ye, Chaofeng; Udpa, Lalita; Udpa, Satish

    2016-02-01

    The advent of Giant Magneto-Resistive (GMR) technology permits development of novel highly sensitive array probes for Eddy Current (EC) inspection of multi-layer riveted structures. Multi-frequency GMR measurements with different EC pene-tration depths show promise for detection of bottom layer notches at fastener sites. However, the distortion of the induced magnetic field due to flaws is dominated by the strong fastener signal, which makes defect detection and classification a challenging prob-lem. This issue is more pronounced for ferromagnetic fasteners that concentrate most of the magnetic flux. In the present work, a novel multi-frequency mixing algorithm is proposed to suppress rivet signal response and enhance defect detection capability of the GMR array probe. The algorithm is baseline-free and does not require any assumptions about the sample geometry being inspected. Fastener signal suppression is based upon the random sample consensus (RANSAC) method, which iteratively estimates parameters of a mathematical model from a set of observed data with outliers. Bottom layer defects at fastener site are simulated as EDM notches of different length. Performance of the proposed multi-frequency mixing approach is evaluated on finite element data and experimental GMR measurements obtained with unidirectional planar current excitation. Initial results are promising demonstrating the feasibility of the approach.

  4. Methodological aspects in the determination of the auditory filters and critical band at low and mid-frequencies

    DEFF Research Database (Denmark)

    Orellana, Carlos Andrés Jurado; Møller, Henrik; Pedersen, Christian Sejer

    2008-01-01

    or after the experiment, normally being applied afterwards. Due to the non-linear characteristics of the cochlear amplifier, it is arguable whether postexperimental weighting is a proper approach, or whether at low frequencies there will be any difference between pre or post stimuli weighting. Listening......In order to evaluate loudness or audibility of complex sounds, knowledge of the auditory filter characteristics is necessary. At low frequencies, where both the threshold of hearing and dynamic range become considerably frequency dependent, care must be taken to account for this both in the psycho......-acoustical model and the methodological approach. To account for variation in hearing sensitivity at low frequencies, equal loudness contours have been used to weight the stimuli accordingly. At mid and high frequencies, threshold of hearing curves have been used. These stimuli weightings can be applied before...

  5. Towards dual recycling with the aid of time and frequency domain simulations

    International Nuclear Information System (INIS)

    Malec, M; Grote, H; Freise, A; Heinzel, G; Strain, K A; Hough, J; Danzmann, K

    2004-01-01

    Dual recycling, the combination of the interferometric techniques of power and signal recycling, allows the improvement of the shot noise limited sensitivity of interferometric gravitational wave detectors. GEO 600 is the first km-scale gravitational wave detector using dual recycling. The hardware installation is completed and dual recycling has become a great challenge in terms of commissioning of GEO 600. Simulations show that lock acquisition of the optical system can only be achieved in certain detector states. Thus as we need to start with a locked detector in such a specific state, an appropriate strategy is needed to change the state of detector operation without losing lock. The basic concepts and first results based on time and frequency domain simulations will be presented in this paper

  6. Auto-identification of engine fault acoustic signal through inverse trigonometric instantaneous frequency analysis

    Directory of Open Access Journals (Sweden)

    Dayong Ning

    2016-03-01

    Full Text Available The acoustic signals of internal combustion engines contain valuable information about the condition of engines. These signals can be used to detect incipient faults in engines. However, these signals are complex and composed of a faulty component and other noise signals of background. As such, engine conditions’ characteristics are difficult to extract through wavelet transformation and acoustic emission techniques. In this study, an instantaneous frequency analysis method was proposed. A new time–frequency model was constructed using a fixed amplitude and a variable cycle sine function to fit adjacent points gradually from a time domain signal. The instantaneous frequency corresponds to single value at any time. This study also introduced instantaneous frequency calculation on the basis of an inverse trigonometric fitting method at any time. The mean value of all local maximum values was then considered to identify the engine condition automatically. Results revealed that the mean of local maximum values under faulty conditions differs from the normal mean. An experiment case was also conducted to illustrate the availability of the proposed method. Using the proposed time–frequency model, we can identify engine condition and determine abnormal sound produced by faulty engines.

  7. Frequency modulator. Transmission of meteorological signals in LVC

    International Nuclear Information System (INIS)

    Rivero G, P.T.; Ramirez S, R.; Gonzalez M, J.L.; Rojas N, P.; Celis del Angel, L.

    2007-01-01

    The development of the frequency modulator and demodulator circuit for transmission of meteorological signals by means of fiber optics of the meteorology station to the nuclear reactor unit 1 in the Laguna Verde Central in Veracruz is described. (Author)

  8. Mid-IR femtosecond frequency conversion by soliton-probe collision in phase-mismatched quadratic nonlinear crystals

    DEFF Research Database (Denmark)

    Liu, Xing; Zhou, Binbin; Guo, Hairun

    2015-01-01

    in a quadratic nonlinear crystal (beta-barium borate) in the normal dispersion regime due to cascaded (phase-mismatched) second-harmonic generation, and the mid-IR converted wave is formed in the anomalous dispersion regime between. lambda = 2.2-2.4 mu m as a resonant dispersive wave. This process relies...... on nondegenerate four-wave mixing mediated by an effective negative cross-phase modulation term caused by cascaded soliton-probe sum-frequency generation. (C) 2015 Optical Society of America...

  9. System and method for constructing filters for detecting signals whose frequency content varies with time

    Science.gov (United States)

    Qian, S.; Dunham, M.E.

    1996-11-12

    A system and method are disclosed for constructing a bank of filters which detect the presence of signals whose frequency content varies with time. The present invention includes a novel system and method for developing one or more time templates designed to match the received signals of interest and the bank of matched filters use the one or more time templates to detect the received signals. Each matched filter compares the received signal x(t) with a respective, unique time template that has been designed to approximate a form of the signals of interest. The robust time domain template is assumed to be of the order of w(t)=A(t)cos(2{pi}{phi}(t)) and the present invention uses the trajectory of a joint time-frequency representation of x(t) as an approximation of the instantaneous frequency function {phi}{prime}(t). First, numerous data samples of the received signal x(t) are collected. A joint time frequency representation is then applied to represent the signal, preferably using the time frequency distribution series. The joint time-frequency transformation represents the analyzed signal energy at time t and frequency f, P(t,f), which is a three-dimensional plot of time vs. frequency vs. signal energy. Then P(t,f) is reduced to a multivalued function f(t), a two dimensional plot of time vs. frequency, using a thresholding process. Curve fitting steps are then performed on the time/frequency plot, preferably using Levenberg-Marquardt curve fitting techniques, to derive a general instantaneous frequency function {phi}{prime}(t) which best fits the multivalued function f(t). Integrating {phi}{prime}(t) along t yields {phi}{prime}(t), which is then inserted into the form of the time template equation. A suitable amplitude A(t) is also preferably determined. Once the time template has been determined, one or more filters are developed which each use a version or form of the time template. 7 figs.

  10. Real-time GPS Signal Simulator

    Data.gov (United States)

    National Aeronautics and Space Administration — With a minimal FTE investment and no additional procurement funds, the development of a low fidelity orbital GPS Signal simulator would is possible.  This IRAD...

  11. Microprocessor-based simulator of surface ECG signals

    International Nuclear Information System (INIS)

    MartInez, A E; Rossi, E; Siri, L Nicola

    2007-01-01

    In this work, a simulator of surface electrocardiogram recorded signals (ECG) is presented. The device, based on a microcontroller and commanded by a personal computer, produces an analog signal resembling actual ECGs, not only in time course and voltage levels, but also in source impedance. The simulator is a useful tool for electrocardiograph calibration and monitoring, to incorporate as well in educational tasks and in clinical environments for early detection of faulty behaviour

  12. Signal Identification and Isolation Utilizing Radio Frequency Photonics

    Science.gov (United States)

    2017-09-01

    RF filter is the use of either a FIR or an infinite impulse response (IIR) filter. The FIR filter is simply the discrete convolution sum of the...by using a feedback loop of a fixed delay. In this case, the signal will ideally be a summation of an infinite number of delay round trips. While...and Infinite Impulse Response filters. A combination of FIR and IIR filters can be used to identify the center frequency of an RF signal, as seen in

  13. Time-Frequency Analysis and Hermite Projection Method Applied to Swallowing Accelerometry Signals

    Directory of Open Access Journals (Sweden)

    Ervin Sejdić

    2010-01-01

    Full Text Available Fast Hermite projections have been often used in image-processing procedures such as image database retrieval, projection filtering, and texture analysis. In this paper, we propose an innovative approach for the analysis of one-dimensional biomedical signals that combines the Hermite projection method with time-frequency analysis. In particular, we propose a two-step approach to characterize vibrations of various origins in swallowing accelerometry signals. First, by using time-frequency analysis we obtain the energy distribution of signal frequency content in time. Second, by using fast Hermite projections we characterize whether the analyzed time-frequency regions are associated with swallowing or other phenomena (vocalization, noise, bursts, etc.. The numerical analysis of the proposed scheme clearly shows that by using a few Hermite functions, vibrations of various origins are distinguishable. These results will be the basis for further analysis of swallowing accelerometry to detect swallowing difficulties.

  14. Asymptotically exact localized expansions for signals in the time–frequency domain

    International Nuclear Information System (INIS)

    Muzhikyan, Aramazd H; Avanesyan, Gagik T

    2012-01-01

    Based on a unique waveform with strong exponential localization property, an exact mathematical method for solving problems in signal analysis in the time–frequency domain is presented. An analogue of the Gabor frame exposes the non-commutative geometry of the time–frequency plane. Signals are visualized using the constructed graphical representation. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

  15. Chování "Mid Spatial Frequencies" při CNC opracování optických ploch

    Czech Academy of Sciences Publication Activity Database

    Procháska, František; Matoušek, Ondřej; Psota, Pavel; Beneš, Jiří

    2015-01-01

    Roč. 60, č. 10 (2015), s. 293-295 ISSN 0447-6441 R&D Projects: GA MŠk(CZ) LO1206; GA TA ČR(CZ) TA03010843 Institutional support: RVO:61389021 Keywords : Mid Spatial Frequencies * CNC optical surface processing Subject RIV: JP - Industrial Processing

  16. High frequency source localization in a shallow ocean sound channel using frequency difference matched field processing.

    Science.gov (United States)

    Worthmann, Brian M; Song, H C; Dowling, David R

    2015-12-01

    Matched field processing (MFP) is an established technique for source localization in known multipath acoustic environments. Unfortunately, in many situations, particularly those involving high frequency signals, imperfect knowledge of the actual propagation environment prevents accurate propagation modeling and source localization via MFP fails. For beamforming applications, this actual-to-model mismatch problem was mitigated through a frequency downshift, made possible by a nonlinear array-signal-processing technique called frequency difference beamforming [Abadi, Song, and Dowling (2012). J. Acoust. Soc. Am. 132, 3018-3029]. Here, this technique is extended to conventional (Bartlett) MFP using simulations and measurements from the 2011 Kauai Acoustic Communications MURI experiment (KAM11) to produce ambiguity surfaces at frequencies well below the signal bandwidth where the detrimental effects of mismatch are reduced. Both the simulation and experimental results suggest that frequency difference MFP can be more robust against environmental mismatch than conventional MFP. In particular, signals of frequency 11.2 kHz-32.8 kHz were broadcast 3 km through a 106-m-deep shallow ocean sound channel to a sparse 16-element vertical receiving array. Frequency difference MFP unambiguously localized the source in several experimental data sets with average peak-to-side-lobe ratio of 0.9 dB, average absolute-value range error of 170 m, and average absolute-value depth error of 10 m.

  17. An application of time-frequency signal analysis technique to estimate the location of an impact source on a plate type structure

    International Nuclear Information System (INIS)

    Park, Jin Ho; Lee, Jeong Han; Choi, Young Chul; Kim, Chan Joong; Seong, Poong Hyun

    2005-01-01

    It has been reviewed whether it would be suitable that the application of the time-frequency signal analysis techniques to estimate the location of the impact source in plate structure. The STFT(Short Time Fourier Transform), WVD(Wigner-Ville distribution) and CWT(Continuous Wavelet Transform) methods are introduced and the advantages and disadvantages of those methods are described by using a simulated signal component. The essential of the above proposed techniques is to separate the traveling waves in both time and frequency domains using the dispersion characteristics of the structural waves. These time-frequency methods are expected to be more useful than the conventional time domain analyses for the impact localization problem on a plate type structure. Also it has been concluded that the smoothed WVD can give more reliable means than the other methodologies for the location estimation in a noisy environment

  18. Optimization of Quantum-state-preserving Frequency Conversion by Changing the Input Signal

    DEFF Research Database (Denmark)

    Andersen, Lasse Mejling; Reddy, D. V.; McKinstrie, C. J.

    We optimize frequency conversion based on four-wave mixing by using the input modes of the system. We find a 10-25 % higher conversion efficiency relative to a pump-shaped input signal.......We optimize frequency conversion based on four-wave mixing by using the input modes of the system. We find a 10-25 % higher conversion efficiency relative to a pump-shaped input signal....

  19. Power scaling of ultrafast mid-IR source enabled by high-power fiber laser technology

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Gengji

    2017-11-15

    Ultrafast laser sources with high repetition-rate (>10 MHz) and tunable in the mid-infrared (IR) wavelength range of 7-18 μm hold promise for many important spectroscopy applications. Currently, these ultrafast mid- to longwavelength-IR sources can most easily be achieved via difference-frequency generation (DFG) between a pump beam and a signal beam. However, current ultrafast mid- to longwavelength-IR sources feature a low average power, which limits their applications. In this thesis, we propose and demonstrate a novel approach to power scaling of DFG-based ultrafast mid-IR laser sources. The essence of this novel approach is the generation of a high-energy signal beam. Both the pump beam and the signal beam are derived from a home-built Yb-fiber laser system that emits 165-fs pulses centered at 1035 nm with 30-MHz repetition rate and 14.5-W average power (corresponding to 483-nJ pulse energy). We employ fiber-optic self-phase modulation (SPM) to broaden the laser spectrum and generate isolated spectral lobes. Filtering the rightmost spectral lobe leads to femtosecond pulses with >10 nJ pulse energy. Tunable between 1.1-1.2 μm, this SPM-enabled ultrafast source exhibits ∝100 times higher pulse energy than can be obtained from Raman soliton sources in this wavelength range. We use this SPM-enabled source as the signal beam and part of the Yb-fiber laser output as the pump beam. By performing DFG in GaSe crystals, we demonstrate that power scaling of a DFG-based mid-IR source can be efficiently achieved by increasing the signal energy. The resulting mid-IR source is tunable from 7.4 μm to 16.8 μm. Up to 5.04-mW mid-IR pulses centered at 11 μm are achieved. The corresponding pulse energy is 167 pJ, representing nearly one order of magnitude improvement compared with other reported DFG-based mid-IR sources at this wavelength. Despite of low pulse energy, Raman soliton sources have become a popular choice as the signal source. We carry out a detailed study on

  20. Power scaling of ultrafast mid-IR source enabled by high-power fiber laser technology

    International Nuclear Information System (INIS)

    Zhou, Gengji

    2017-11-01

    Ultrafast laser sources with high repetition-rate (>10 MHz) and tunable in the mid-infrared (IR) wavelength range of 7-18 μm hold promise for many important spectroscopy applications. Currently, these ultrafast mid- to longwavelength-IR sources can most easily be achieved via difference-frequency generation (DFG) between a pump beam and a signal beam. However, current ultrafast mid- to longwavelength-IR sources feature a low average power, which limits their applications. In this thesis, we propose and demonstrate a novel approach to power scaling of DFG-based ultrafast mid-IR laser sources. The essence of this novel approach is the generation of a high-energy signal beam. Both the pump beam and the signal beam are derived from a home-built Yb-fiber laser system that emits 165-fs pulses centered at 1035 nm with 30-MHz repetition rate and 14.5-W average power (corresponding to 483-nJ pulse energy). We employ fiber-optic self-phase modulation (SPM) to broaden the laser spectrum and generate isolated spectral lobes. Filtering the rightmost spectral lobe leads to femtosecond pulses with >10 nJ pulse energy. Tunable between 1.1-1.2 μm, this SPM-enabled ultrafast source exhibits ∝100 times higher pulse energy than can be obtained from Raman soliton sources in this wavelength range. We use this SPM-enabled source as the signal beam and part of the Yb-fiber laser output as the pump beam. By performing DFG in GaSe crystals, we demonstrate that power scaling of a DFG-based mid-IR source can be efficiently achieved by increasing the signal energy. The resulting mid-IR source is tunable from 7.4 μm to 16.8 μm. Up to 5.04-mW mid-IR pulses centered at 11 μm are achieved. The corresponding pulse energy is 167 pJ, representing nearly one order of magnitude improvement compared with other reported DFG-based mid-IR sources at this wavelength. Despite of low pulse energy, Raman soliton sources have become a popular choice as the signal source. We carry out a detailed study on

  1. Frequency Diverse Array Radar Signal Processing via Space-Range-Doppler Focus (SRDF Method

    Directory of Open Access Journals (Sweden)

    Chen Xiaolong

    2018-04-01

    Full Text Available To meet the urgent demand of low-observable moving target detection in complex environments, a novel method of Frequency Diverse Array (FDA radar signal processing method based on Space-Rang-Doppler Focusing (SRDF is proposed in this paper. The current development status of the FDA radar, the design of the array structure, beamforming, and joint estimation of distance and angle are systematically reviewed. The extra degrees of freedom provided by FDA radar are fully utilizsed, which include the Degrees Of Freedom (DOFs of the transmitted waveform, the location of array elements, correlation of beam azimuth and distance, and the long dwell time, which are also the DOFs in joint spatial (angle, distance, and frequency (Doppler dimensions. Simulation results show that the proposed method has the potential of improving target detection and parameter estimation for weak moving targets in complex environments and has broad application prospects in clutter and interference suppression, moving target refinement, etc..

  2. Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber.

    Science.gov (United States)

    Shaddad, R Q; Mohammad, A B; Al-Gailani, S A; Al-Hetar, A M

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  3. Complex Signal Kurtosis and Independent Component Analysis for Wideband Radio Frequency Interference Detection

    Science.gov (United States)

    Schoenwald, Adam; Mohammed, Priscilla; Bradley, Damon; Piepmeier, Jeffrey; Wong, Englin; Gholian, Armen

    2016-01-01

    Radio-frequency interference (RFI) has negatively implicated scientific measurements across a wide variation passive remote sensing satellites. This has been observed in the L-band radiometers SMOS, Aquarius and more recently, SMAP [1, 2]. RFI has also been observed at higher frequencies such as K band [3]. Improvements in technology have allowed wider bandwidth digital back ends for passive microwave radiometry. A complex signal kurtosis radio frequency interference detector was developed to help identify corrupted measurements [4]. This work explores the use of ICA (Independent Component Analysis) as a blind source separation technique to pre-process radiometric signals for use with the previously developed real and complex signal kurtosis detectors.

  4. Micro-Doppler Signal Time-Frequency Algorithm Based on STFRFT

    Directory of Open Access Journals (Sweden)

    Cunsuo Pang

    2016-09-01

    Full Text Available This paper proposes a time-frequency algorithm based on short-time fractional order Fourier transformation (STFRFT for identification of a complicated movement targets. This algorithm, consisting of a STFRFT order-changing and quick selection method, is effective in reducing the computation load. A multi-order STFRFT time-frequency algorithm is also developed that makes use of the time-frequency feature of each micro-Doppler component signal. This algorithm improves the estimation accuracy of time-frequency curve fitting through multi-order matching. Finally, experiment data were used to demonstrate STFRFT’s performance in micro-Doppler time-frequency analysis. The results validated the higher estimate accuracy of the proposed algorithm. It may be applied to an LFM (Linear frequency modulated pulse radar, SAR (Synthetic aperture radar, or ISAR (Inverse synthetic aperture radar, for improving the probability of target recognition.

  5. Micro-Doppler Signal Time-Frequency Algorithm Based on STFRFT.

    Science.gov (United States)

    Pang, Cunsuo; Han, Yan; Hou, Huiling; Liu, Shengheng; Zhang, Nan

    2016-09-24

    This paper proposes a time-frequency algorithm based on short-time fractional order Fourier transformation (STFRFT) for identification of a complicated movement targets. This algorithm, consisting of a STFRFT order-changing and quick selection method, is effective in reducing the computation load. A multi-order STFRFT time-frequency algorithm is also developed that makes use of the time-frequency feature of each micro-Doppler component signal. This algorithm improves the estimation accuracy of time-frequency curve fitting through multi-order matching. Finally, experiment data were used to demonstrate STFRFT's performance in micro-Doppler time-frequency analysis. The results validated the higher estimate accuracy of the proposed algorithm. It may be applied to an LFM (Linear frequency modulated) pulse radar, SAR (Synthetic aperture radar), or ISAR (Inverse synthetic aperture radar), for improving the probability of target recognition.

  6. The Time-Frequency Signatures of Advanced Seismic Signals Generated by Debris Flows

    Science.gov (United States)

    Chu, C. R.; Huang, C. J.; Lin, C. R.; Wang, C. C.; Kuo, B. Y.; Yin, H. Y.

    2014-12-01

    The seismic monitoring is expected to reveal the process of debris flow from the initial area to alluvial fan, because other field monitoring techniques, such as the video camera and the ultrasonic sensor, are limited by detection range. For this reason, seismic approaches have been used as the detection system of debris flows over the past few decades. The analysis of the signatures of the seismic signals in time and frequency domain can be used to identify the different phases of debris flow. This study dedicates to investigate the different stages of seismic signals due to debris flow, including the advanced signal, the main front, and the decaying tail. Moreover, the characteristics of the advanced signals forward to the approach of main front were discussed for the warning purpose. This study presents a permanent system, composed by two seismometers, deployed along the bank of Ai-Yu-Zi Creek in Nantou County, which is one of the active streams with debris flow in Taiwan. The three axes seismometer with frequency response of 7 sec - 200 Hz was developed by the Institute of Earth Sciences (IES), Academia Sinica for the purpose to detect debris flow. The original idea of replacing the geophone system with the seismometer technique was for catching the advanced signals propagating from the upper reach of the stream before debris flow arrival because of the high sensitivity. Besides, the low frequency seismic waves could be also early detected because of the low attenuation. However, for avoiding other unnecessary ambient vibrations, the sensitivity of seismometer should be lower than the general seismometer for detecting teleseism. Three debris flows with different mean velocities were detected in 2013 and 2014. The typical triangular shape was obviously demonstrated in time series data and the spectrograms of the seismic signals from three events. The frequency analysis showed that enormous debris flow bearing huge boulders would induce low frequency seismic

  7. The sensitivity of the Arctic sea ice to orbitally induced insolation changes: a study of the mid-Holocene Paleoclimate Modelling Intercomparison Project 2 and 3 simulations

    Directory of Open Access Journals (Sweden)

    M. Berger

    2013-04-01

    Full Text Available In the present work the Arctic sea ice in the mid-Holocene and the pre-industrial climates are analysed and compared on the basis of climate-model results from the Paleoclimate Modelling Intercomparison Project phase 2 (PMIP2 and phase 3 (PMIP3. The PMIP3 models generally simulate smaller and thinner sea-ice extents than the PMIP2 models both for the pre-industrial and the mid-Holocene climate. Further, the PMIP2 and PMIP3 models all simulate a smaller and thinner Arctic summer sea-ice cover in the mid-Holocene than in the pre-industrial control climate. The PMIP3 models also simulate thinner winter sea ice than the PMIP2 models. The winter sea-ice extent response, i.e. the difference between the mid-Holocene and the pre-industrial climate, varies among both PMIP2 and PMIP3 models. Approximately one half of the models simulate a decrease in winter sea-ice extent and one half simulates an increase. The model-mean summer sea-ice extent is 11 % (21 % smaller in the mid-Holocene than in the pre-industrial climate simulations in the PMIP2 (PMIP3. In accordance with the simple model of Thorndike (1992, the sea-ice thickness response to the insolation change from the pre-industrial to the mid-Holocene is stronger in models with thicker ice in the pre-industrial climate simulation. Further, the analyses show that climate models for which the Arctic sea-ice responses to increasing atmospheric CO2 concentrations are similar may simulate rather different sea-ice responses to the change in solar forcing between the mid-Holocene and the pre-industrial. For two specific models, which are analysed in detail, this difference is found to be associated with differences in the simulated cloud fractions in the summer Arctic; in the model with a larger cloud fraction the effect of insolation change is muted. A sub-set of the mid-Holocene simulations in the PMIP ensemble exhibit open water off the north-eastern coast of Greenland in summer, which can provide a fetch

  8. Signal enhancement by spectral equalization of high frequency broadband signals transmitted through optical fibers

    International Nuclear Information System (INIS)

    Lyons, P.B.; Ogle, J.W.; Holzman, M.A.

    1980-01-01

    A new technique is discussed for enhancing the bandwidth and intensity of high frequency (> 1 GHz) analog, spectrally broad (40 nm) signals transmitted through one kilometer of optical fiber. The existing method for bandwidth enhancement of such a signal uses a very narrow (approx. 1 nm) filter between the fiber and detector to limit bandwidth degradation due to material dispersion. Using this method, most of the available optical intensity is rejected and lost. This new technique replaces the narrow-band filter with a spectral equalizer device which uses a reflection grating to disperse the input signal spectrum and direct it onto a linear array of fibers

  9. Bilinear Time-frequency Analysis for Lamb Wave Signal Detected by Electromagnetic Acoustic Transducer

    Science.gov (United States)

    Sun, Wenxiu; Liu, Guoqiang; Xia, Hui; Xia, Zhengwu

    2018-03-01

    Accurate acquisition of the detection signal travel time plays a very important role in cross-hole tomography. The experimental platform of aluminum plate under the perpendicular magnetic field is established and the bilinear time-frequency analysis methods, Wigner-Ville Distribution (WVD) and the pseudo-Wigner-Ville distribution (PWVD), are applied to analyse the Lamb wave signals detected by electromagnetic acoustic transducer (EMAT). By extracting the same frequency component of the time-frequency spectrum as the excitation frequency, the travel time information can be obtained. In comparison with traditional linear time-frequency analysis method such as short-time Fourier transform (STFT), the bilinear time-frequency analysis method PWVD is more appropriate in extracting travel time and recognizing patterns of Lamb wave.

  10. Time-frequency peak filtering for random noise attenuation of magnetic resonance sounding signal

    Science.gov (United States)

    Lin, Tingting; Zhang, Yang; Yi, Xiaofeng; Fan, Tiehu; Wan, Ling

    2018-05-01

    When measuring in a geomagnetic field, the method of magnetic resonance sounding (MRS) is often limited because of the notably low signal-to-noise ratio (SNR). Most current studies focus on discarding spiky noise and power-line harmonic noise cancellation. However, the effects of random noise should not be underestimated. The common method for random noise attenuation is stacking, but collecting multiple recordings merely to suppress random noise is time-consuming. Moreover, stacking is insufficient to suppress high-level random noise. Here, we propose the use of time-frequency peak filtering for random noise attenuation, which is performed after the traditional de-spiking and power-line harmonic removal method. By encoding the noisy signal with frequency modulation and estimating the instantaneous frequency using the peak of the time-frequency representation of the encoded signal, the desired MRS signal can be acquired from only one stack. The performance of the proposed method is tested on synthetic envelope signals and field data from different surveys. Good estimations of the signal parameters are obtained at different SNRs. Moreover, an attempt to use the proposed method to handle a single recording provides better results compared to 16 stacks. Our results suggest that the number of stacks can be appropriately reduced to shorten the measurement time and improve the measurement efficiency.

  11. SIDON: A simulator of radio-frequency networks. Application to WEST ICRF launchers

    Science.gov (United States)

    Helou, Walid; Dumortier, Pierre; Durodié, Frédéric; Goniche, Marc; Hillairet, Julien; Mollard, Patrick; Berger-By, Gilles; Bernard, Jean-Michel; Colas, Laurent; Lombard, Gilles; Maggiora, Riccardo; Magne, Roland; Milanesio, Daniele; Moreau, Didier

    2015-12-01

    SIDON (SImulator of raDiO-frequency Networks) is an in-house developed Radio-Frequency (RF) network solver that has been implemented to cross-validate the design of WEST ICRF launchers and simulate their impedance matching algorithm while considering all mutual couplings and asymmetries. In this paper, the authors illustrate the theory of SIDON as well as results of its calculations. The authors have built time-varying plasma scenarios (a sequence of launchers front-faces L-mode and H-mode Z-matrices), where at each time step (1 millisecond here), SIDON solves the RF network. At the same time, when activated, the impedance matching algorithm controls the matching elements (vacuum capacitors) and thus their corresponding S-matrices. Typically a 1-second pulse requires around 10 seconds of computational time on a desktop computer. These tasks can be hardly handled by commercial RF software. This innovative work allows identifying strategies for the launchers future operation while insuring the limitations on the currents, voltages and electric fields, matching and Load-Resilience, as well as the required straps voltage amplitude/phase balance. In this paper, a particular attention is paid to the simulation of the launchers behavior when arcs appear at several locations of their circuits using SIDON calculator. This latter work shall confirm or identify strategies for the arc detection using various RF electrical signals. One shall note that the use of such solvers in not limited to ICRF launchers simulations but can be employed, in principle, to any linear or linearized RF problem.

  12. Results of PMIP2 coupled simulations of the Mid-Holocene and Last Glacial Maximum – Part 1: experiments and large-scale features

    Directory of Open Access Journals (Sweden)

    Y. Zhao

    2007-06-01

    Full Text Available A set of coupled ocean-atmosphere simulations using state of the art climate models is now available for the Last Glacial Maximum and the Mid-Holocene through the second phase of the Paleoclimate Modeling Intercomparison Project (PMIP2. This study presents the large-scale features of the simulated climates and compares the new model results to those of the atmospheric models from the first phase of the PMIP, for which sea surface temperature was prescribed or computed using simple slab ocean formulations. We consider the large-scale features of the climate change, pointing out some of the major differences between the different sets of experiments. We show in particular that systematic differences between PMIP1 and PMIP2 simulations are due to the interactive ocean, such as the amplification of the African monsoon at the Mid-Holocene or the change in precipitation in mid-latitudes at the LGM. Also the PMIP2 simulations are in general in better agreement with data than PMIP1 simulations.

  13. Masker phase effects in normal-hearing and hearing-impaired listeners: evidence for peripheral compression at low signal frequencies

    DEFF Research Database (Denmark)

    Oxenham, Andrew J.; Dau, Torsten

    2004-01-01

    curvature. Results from 12 listeners with sensorineural hearing loss showed reduced masker phase effects, when compared with data from normal-hearing listeners, at both 250- and 1000-Hz signal frequencies. The effects of hearing impairment on phase-related masking differences were not well simulated...... are affected by a common underlying mechanism, presumably related to cochlear outer hair cell function. The results also suggest that normal peripheral compression remains strong even at 250 Hz....

  14. Narrowband widely tunable CW mid-infrared generator based on difference frequency generation in periodically poled KTP and KTA crystals

    Czech Academy of Sciences Publication Activity Database

    Baravets, Yauhen; Honzátko, Pavel; Todorov, Filip; Gladkov, Petar

    2016-01-01

    Roč. 48, č. 5 (2016), May ISSN 0306-8919 R&D Projects: GA MŠk LD14112 Grant - others:COST(XE) MP1204 Institutional support: RVO:67985882 Keywords : Fiber optics amplifiers * Difference-frequency generation * Mid-infrared tunable laser source Subject RIV: BH - Optics , Masers, Lasers Impact factor: 1.055, year: 2016

  15. 10Be in late deglacial climate simulated by ECHAM5-HAM - Part 2: Isolating the solar signal from 10Be deposition

    Science.gov (United States)

    Heikkilä, U.; Shi, X.; Phipps, S. J.; Smith, A. M.

    2014-04-01

    This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 year time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol-climate model, driven with sea-surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather- or climate-driven noise in the 10Be deposition flux during different stages of climate. The production signal varies at lower frequencies, dominated by the 11 year solar cycle within the 30 year timescale of these experiments. The climatic noise is of higher frequencies than 11 years during the 30 year period studied. We first apply empirical orthogonal function (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis to the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low-frequency components and the long-term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high-frequency components represent climate-driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that

  16. Non-stationary signal analysis based on general parameterized time-frequency transform and its application in the feature extraction of a rotary machine

    Science.gov (United States)

    Zhou, Peng; Peng, Zhike; Chen, Shiqian; Yang, Yang; Zhang, Wenming

    2018-06-01

    With the development of large rotary machines for faster and more integrated performance, the condition monitoring and fault diagnosis for them are becoming more challenging. Since the time-frequency (TF) pattern of the vibration signal from the rotary machine often contains condition information and fault feature, the methods based on TF analysis have been widely-used to solve these two problems in the industrial community. This article introduces an effective non-stationary signal analysis method based on the general parameterized time-frequency transform (GPTFT). The GPTFT is achieved by inserting a rotation operator and a shift operator in the short-time Fourier transform. This method can produce a high-concentrated TF pattern with a general kernel. A multi-component instantaneous frequency (IF) extraction method is proposed based on it. The estimation for the IF of every component is accomplished by defining a spectrum concentration index (SCI). Moreover, such an IF estimation process is iteratively operated until all the components are extracted. The tests on three simulation examples and a real vibration signal demonstrate the effectiveness and superiority of our method.

  17. Impact of MAC Delay on AUV Localization: Underwater Localization Based on Hyperbolic Frequency Modulation Signal.

    Science.gov (United States)

    Kim, Sungryul; Yoo, Younghwan

    2018-01-26

    Medium Access Control (MAC) delay which occurs between the anchor node's transmissions is one of the error sources in underwater localization. In particular, in AUV localization, the MAC delay significantly degrades the ranging accuracy. The Cramer-Rao Low Bound (CRLB) definition theoretically proves that the MAC delay significantly degrades the localization performance. This paper proposes underwater localization combined with multiple access technology to decouple the localization performance from the MAC delay. Towards this goal, we adopt hyperbolic frequency modulation (HFM) signal that provides multiplexing based on its good property, high-temporal correlation. Owing to the multiplexing ability of the HFM signal, the anchor nodes can transmit packets without MAC delay, i.e., simultaneous transmission is possible. In addition, the simulation results show that the simultaneous transmission is not an optional communication scheme, but essential for the localization of mobile object in underwater.

  18. Overview of frequency bandwidth determination techniques of useful signal in case of leaks detection by correlation method

    International Nuclear Information System (INIS)

    Faerman, V A; Avramchuk, V S; Luneva, E E

    2014-01-01

    In this paper an overview of useful signal detection methods on the background of intense noise and limits determination methods of useful signal is presented. The following features are considered: peculiarities of usage of correlation analysis, cross-amplitude spectrum, coherence function, cross-phase spectrum, time-frequency correlation function in case of frequency limits determination as well as leaks detection in pipelines. The possibility of using time-frequency correlation function for solving above named issues is described. Time- frequency correlation function provides information about the signals correlation for each of the investigated frequency bands. Data about location of peaks on the surface plot of a time- frequency correlation function allows making an assumption about the spectral composition of useful signal and its frequency boundaries

  19. Particle-In-Cell Simulations of Asymmetric Dual Frequency Capacitive Discharge Physics

    Science.gov (United States)

    Wu, Alan; Lichtenberg, A. J.; Lieberman, M. A.; Verboncoeur, J. P.

    2003-10-01

    Dual frequency capacitive discharges are finding increasing use for etching in the microelectronics industry. In the ideal case, the high frequency power (typically 27.1-160 MHz) controls the plasma density and the low frequency power (typically 2-13.56 MHz) controls the ion energy. The electron power deposition and the dynamics of dual frequency rf sheaths are not well understood. We report on particle-in-cell computer simulations of an asymmetric dual frequency argon discharge. The simulations are performed in 1D (radial) geometry using the bounded electrostatic code XPDP1. Operating parameters are 27.1/2 MHz high/low frequencies, 10/13 cm inner/outer radii, 3-200 mTorr pressures, and 10^9-10^11 cm-3 densities. We determine the power deposition and sheath dynamics for the high frequency power alone, and with various added low frequency powers. We compare the simulation results to simple global models of dual frequency discharges. Support provided by Lam Research, NSF Grant ECS-0139956, California industries, and UC-SMART Contract SM99-10051.

  20. Frequency identification of vibration signals using video camera image data.

    Science.gov (United States)

    Jeng, Yih-Nen; Wu, Chia-Hung

    2012-10-16

    This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC) can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system.

  1. Frequency Identification of Vibration Signals Using Video Camera Image Data

    Directory of Open Access Journals (Sweden)

    Chia-Hung Wu

    2012-10-01

    Full Text Available This study showed that an image data acquisition system connecting a high-speed camera or webcam to a notebook or personal computer (PC can precisely capture most dominant modes of vibration signal, but may involve the non-physical modes induced by the insufficient frame rates. Using a simple model, frequencies of these modes are properly predicted and excluded. Two experimental designs, which involve using an LED light source and a vibration exciter, are proposed to demonstrate the performance. First, the original gray-level resolution of a video camera from, for instance, 0 to 256 levels, was enhanced by summing gray-level data of all pixels in a small region around the point of interest. The image signal was further enhanced by attaching a white paper sheet marked with a black line on the surface of the vibration system in operation to increase the gray-level resolution. Experimental results showed that the Prosilica CV640C CMOS high-speed camera has the critical frequency of inducing the false mode at 60 Hz, whereas that of the webcam is 7.8 Hz. Several factors were proven to have the effect of partially suppressing the non-physical modes, but they cannot eliminate them completely. Two examples, the prominent vibration modes of which are less than the associated critical frequencies, are examined to demonstrate the performances of the proposed systems. In general, the experimental data show that the non-contact type image data acquisition systems are potential tools for collecting the low-frequency vibration signal of a system.

  2. New method to estimate the frequency stability of laser signals

    International Nuclear Information System (INIS)

    McFerran, J.J.; Maric, M.; Luiten, A.N.

    2004-01-01

    A frequent challenge in the scientific and commercial use of lasers is the need to determine the frequency stability of the output optical signal. In this article we present a new method to estimate this quantity while avoiding the complexity of the usual technique. The new technique displays the result in terms of the usual time domain measure of frequency stability: the square root Allan variance

  3. Mid-Pliocene global climate simulation with MRI-CGCM2.3: set-up and initial results of PlioMIP Experiments 1 and 2

    Directory of Open Access Journals (Sweden)

    Y. Kamae

    2012-05-01

    Full Text Available The mid-Pliocene (3.3 to 3.0 million yr ago, a globally warm period before the Quaternary, is recently attracting attention as a new target for paleoclimate modelling and data-model synthesis. This paper reports set-ups and results of experiments proposed in Pliocene Model Intercomparison Project (PlioMIP using a global climate model, MRI-CGCM2.3. We conducted pre-industrial and mid-Pliocene runs by using the coupled atmosphere-ocean general circulation model (AOGCM and its atmospheric component (AGCM for the PlioMIP Experiments 2 and 1, respectively. In addition, we conducted two types of integrations in AOGCM simulation, with and without flux adjustments on sea surface. General characteristics of differences in the simulated mid-Pliocene climate relative to the pre-industrial in the three integrations are compared. In addition, patterns of predicted mid-Pliocene biomes resulting from the three climate simulations are compared in this study. Generally, difference of simulated surface climate between AGCM and AOGCM is larger than that between the two AOGCM runs, with and without flux adjustments. The simulated climate shows different pattern between AGCM and AOGCM particularly over low latitude oceans, subtropical land regions and high latitude oceans. The AOGCM simulations do not reproduce wetter environment in the subtropics relative to the present-day, which is suggested by terrestrial proxy data. The differences between the two types of AOGCM runs are small over the land, but evident over the ocean particularly in the North Atlantic and polar regions.

  4. Implementation of PLL and FLL trackers for signals with high harmonic content and low sampling frequency

    DEFF Research Database (Denmark)

    Mathe, Laszlo; Iov, Florin; Sera, Dezso

    2014-01-01

    The accurate tracking of phase, frequency, and amplitude of different frequency components from a measured signal is an essential requirement for many digitally controlled equipment. The accurate and robust tracking of a frequency component from a complex signal was successfully applied for example...... in: grid connected inverters, sensorless motor control for rotor position estimation, grid voltage monitoring for ac-dc converters etc. Usually, the design of such trackers is done in continuous time domain. The discretization introduces errors which change the performance, especially when the input...... signal is rich in harmonics and the sampling frequency is close to the tracked frequency component. In this paper different discretization methods and implementation issues, such as Tustin, Backward-Forward Euler, are discussed and compared. A special case is analyzed, when the input signal is reach...

  5. Analysis of Satellite-Based Navigation Signal Reflectometry: Simulations and Observations

    DEFF Research Database (Denmark)

    von Benzon, Hans-Henrik; Høeg, Per; Durgonics, Tibor

    2016-01-01

    on different ocean characteristics. The spectra of the simulated surface reflections are analyzed, and the results from the simulations are compared to measured GPS surface reflections. The measurements were performed using a space-qualified GPS receiver placed on a mountain at the Haleakala observatory...... on the Hawaiian island of Maui. The GPS receiver was during the experiments running in an open-loop configuration. The analysis of both the simulated surface-reflection signals and the measured reflection signals will in general reveal spectral structures of the reflected signals that can lead to extraction...

  6. Instantaneous Real-Time Kinematic Decimeter-Level Positioning with BeiDou Triple-Frequency Signals over Medium Baselines.

    Science.gov (United States)

    He, Xiyang; Zhang, Xiaohong; Tang, Long; Liu, Wanke

    2015-12-22

    Many applications, such as marine navigation, land vehicles location, etc., require real time precise positioning under medium or long baseline conditions. In this contribution, we develop a model of real-time kinematic decimeter-level positioning with BeiDou Navigation Satellite System (BDS) triple-frequency signals over medium distances. The ambiguities of two extra-wide-lane (EWL) combinations are fixed first, and then a wide lane (WL) combination is reformed based on the two EWL combinations for positioning. Theoretical analysis and empirical analysis is given of the ambiguity fixing rate and the positioning accuracy of the presented method. The results indicate that the ambiguity fixing rate can be up to more than 98% when using BDS medium baseline observations, which is much higher than that of dual-frequency Hatch-Melbourne-Wübbena (HMW) method. As for positioning accuracy, decimeter level accuracy can be achieved with this method, which is comparable to that of carrier-smoothed code differential positioning method. Signal interruption simulation experiment indicates that the proposed method can realize fast high-precision positioning whereas the carrier-smoothed code differential positioning method needs several hundreds of seconds for obtaining high precision results. We can conclude that a relatively high accuracy and high fixing rate can be achieved for triple-frequency WL method with single-epoch observations, displaying significant advantage comparing to traditional carrier-smoothed code differential positioning method.

  7. Instantaneous Real-Time Kinematic Decimeter-Level Positioning with BeiDou Triple-Frequency Signals over Medium Baselines

    Directory of Open Access Journals (Sweden)

    Xiyang He

    2015-12-01

    Full Text Available Many applications, such as marine navigation, land vehicles location, etc., require real time precise positioning under medium or long baseline conditions. In this contribution, we develop a model of real-time kinematic decimeter-level positioning with BeiDou Navigation Satellite System (BDS triple-frequency signals over medium distances. The ambiguities of two extra-wide-lane (EWL combinations are fixed first, and then a wide lane (WL combination is reformed based on the two EWL combinations for positioning. Theoretical analysis and empirical analysis is given of the ambiguity fixing rate and the positioning accuracy of the presented method. The results indicate that the ambiguity fixing rate can be up to more than 98% when using BDS medium baseline observations, which is much higher than that of dual-frequency Hatch-Melbourne-Wübbena (HMW method. As for positioning accuracy, decimeter level accuracy can be achieved with this method, which is comparable to that of carrier-smoothed code differential positioning method. Signal interruption simulation experiment indicates that the proposed method can realize fast high-precision positioning whereas the carrier-smoothed code differential positioning method needs several hundreds of seconds for obtaining high precision results. We can conclude that a relatively high accuracy and high fixing rate can be achieved for triple-frequency WL method with single-epoch observations, displaying significant advantage comparing to traditional carrier-smoothed code differential positioning method.

  8. Note: Demodulation of spectral signal modulated by optical chopper with unstable modulation frequency.

    Science.gov (United States)

    Zhang, Shengzhao; Li, Gang; Wang, Jiexi; Wang, Donggen; Han, Ying; Cao, Hui; Lin, Ling; Diao, Chunhong

    2017-10-01

    When an optical chopper is used to modulate the light source, the rotating speed of the wheel may vary with time and subsequently cause jitter of the modulation frequency. The amplitude calculated from the modulated signal would be distorted when the frequency fluctuations occur. To precisely calculate the amplitude of the modulated light flux, we proposed a method to estimate the range of the frequency fluctuation in the measurement of the spectrum and then extract the amplitude based on the sum of power of the signal in the selected frequency range. Experiments were designed to test the feasibility of the proposed method and the results showed lower root means square error than the conventional way.

  9. Traveltime dispersion in an isotropic elastic mantle: strong lower-mantle signal in differential-frequency residuals

    Science.gov (United States)

    Schuberth, Bernhard S. A.; Zaroli, Christophe; Nolet, Guust

    2015-12-01

    We study wavefield effects of direct P- and S-waves in elastic and isotropic 3-D seismic structures derived from the temperature field of a high-resolution mantle circulation model. More specifically, we quantify the dispersion of traveltime residuals caused by diffraction in structures with dynamically constrained length scales and magnitudes of the lateral variations in seismic velocities and density. 3-D global wave propagation is simulated using a spectral element method. Intrinsic attenuation (i.e. dissipation of seismic energy) is deliberately neglected, so that any variation of traveltimes with frequency can be attributed to structural effects. Traveltime residuals are measured at 15, 22.5, 34 and 51 s dominant periods by cross-correlation of 3-D and 1-D synthetic waveforms. Additional simulations are performed for a model in which 3-D structure is removed in the upper 800 km to isolate the dispersion signal of the lower mantle. We find that the structural length scales inherent to a vigorously convecting mantle give rise to significant diffraction-induced body-wave traveltime dispersion. For both P- and S-waves, the difference between long-period and short-period residuals for a given source-receiver pair can reach up to several seconds for the period bands considered here. In general, these `differential-frequency' residuals tend to increase in magnitude with increasing short-period delay. Furthermore, the long-period signal typically is smaller in magnitude than the short-period one; that is, wave-front healing is efficient independent of the sign of the residuals. Unlike the single-frequency residuals, the differential-frequency residuals are surprisingly similar between the `lower-mantle' and the `whole-mantle' model for corresponding source-receiver pairs. The similarity is more pronounced in case of S-waves and varies between different combinations of period bands. The traveltime delay acquired in the upper mantle seems to cancel in these differential

  10. Broadband Signal Enhancement of Seismic Array Data: Application to Long-Period Surface Waves & High Frequency Wavefields

    National Research Council Canada - National Science Library

    Vernon, Frank

    1998-01-01

    .... "Dual-frequency" coherence is useful in identifying overtones and frequency shifts between signals, features which are undetectable by standard coherence measures. We construct a filter to extract only the coherent frequencies from a waveform and show that it significantly increases the signal-noise-ratio for dispersive waveforms.

  11. Verification of frequency scaling laws for capacitive radio-frequency discharges using two-dimensional simulations

    International Nuclear Information System (INIS)

    Vahedi, V.; Birdsall, C.K.; Lieberman, M.A.; DiPeso, G.; Rognlien, T.D.

    1993-01-01

    Weakly ionized processing plasmas are studied in two dimensions using a bounded particle-in-cell (PIC) simulation code with a Monte Carlo collision (MCC) package. The MCC package models the collisions between charged and neutral particles, which are needed to obtain a self-sustained plasma and the proper electron and ion energy loss mechanisms. A two-dimensional capacitive radio-frequency (rf) discharge is investigated in detail. Simple frequency scaling laws for predicting the behavior of some plasma parameters are derived and then compared with simulation results, finding good agreements. It is found that as the drive frequency increases, the sheath width decreases, and the bulk plasma becomes more uniform, leading to a reduction of the ion angular spread at the target and an improvement of ion dose uniformity at the driven electrode

  12. On chip frequency discriminator for microwave photonics signal processing

    NARCIS (Netherlands)

    Marpaung, D.A.I.; Roeloffzen, C.G.H.

    2012-01-01

    Microwave photonics (MWP) techniques for the generation, distribution and pro- cessing of radio frequency (RF) signals have enjoyed a surge of interest in the last few years. The workhorse behind these MWP functionalities is a high performance MWP link. Such a link needs to fulfill several criteria

  13. Pump-To-Signal Intensity Modulation Transfer Characteristics in FOPAs: Modulation Frequency and Saturation Effect

    DEFF Research Database (Denmark)

    Lali-Dastjerdi, Zohreh; Cristofori, Valentina; Lund-Hansen, Toke

    2012-01-01

    This paper reports a comprehensive study of pump- to-signal intensity modulation transfer (IMT) in single-pump fiber optic parametric amplifiers (FOPAs). In particular, the IMT is studied for the first time for high-frequency fluctuations of the pump as well as in the saturated gain regime. The IMT...... cut-off frequency in typical single-pump FOPAs is around 100–200 GHz. The possibilities to shift this frequency based on dispersion and nonlinearities involved in the parametric gain are discussed. The severe IMT to the signal at low modulation frequencies can be suppressed by more than 50...

  14. LOW-FREQUENCY OSCILLATIONS IN GLOBAL SIMULATIONS OF BLACK HOLE ACCRETION

    International Nuclear Information System (INIS)

    O'Neill, Sean M.; Reynolds, Christopher S.; Coleman Miller, M.; Sorathia, Kareem A.

    2011-01-01

    We have identified the presence of large-scale, low-frequency dynamo cycles in a long-duration, global, magnetohydrodynamic (MHD) simulation of black hole accretion. Such cycles have previously been seen in local shearing box simulations, but we discuss their evolution over 1500 inner disk orbits of a global π/4 disk wedge spanning two orders of magnitude in radius and seven scale heights in elevation above/below the disk midplane. The observed cycles manifest themselves as oscillations in azimuthal magnetic field occupying a region that extends into a low-density corona several scale heights above the disk. The cycle frequencies are 10-20 times lower than the local orbital frequency, making them potentially interesting sources of low-frequency variability when scaled to real astrophysical systems. Furthermore, power spectra derived from the full time series reveal that the cycles manifest themselves at discrete, narrowband frequencies that often share power across broad radial ranges. We explore possible connections between these simulated cycles and observed low-frequency quasi-periodic oscillations (LFQPOs) in galactic black hole binary systems, finding that dynamo cycles have the appropriate frequencies and are located in a spatial region associated with X-ray emission in real systems. Derived observational proxies, however, fail to feature peaks with rms amplitudes comparable to LFQPO observations, suggesting that further theoretical work and more sophisticated simulations will be required to form a complete theory of dynamo-driven LFQPOs. Nonetheless, this work clearly illustrates that global MHD dynamos exhibit quasi-periodic behavior on timescales much longer than those derived from test particle considerations.

  15. Bayesian inference on EMRI signals using low frequency approximations

    International Nuclear Information System (INIS)

    Ali, Asad; Meyer, Renate; Christensen, Nelson; Röver, Christian

    2012-01-01

    Extreme mass ratio inspirals (EMRIs) are thought to be one of the most exciting gravitational wave sources to be detected with LISA. Due to their complicated nature and weak amplitudes the detection and parameter estimation of such sources is a challenging task. In this paper we present a statistical methodology based on Bayesian inference in which the estimation of parameters is carried out by advanced Markov chain Monte Carlo (MCMC) algorithms such as parallel tempering MCMC. We analysed high and medium mass EMRI systems that fall well inside the low frequency range of LISA. In the context of the Mock LISA Data Challenges, our investigation and results are also the first instance in which a fully Markovian algorithm is applied for EMRI searches. Results show that our algorithm worked well in recovering EMRI signals from different (simulated) LISA data sets having single and multiple EMRI sources and holds great promise for posterior computation under more realistic conditions. The search and estimation methods presented in this paper are general in their nature, and can be applied in any other scenario such as AdLIGO, AdVIRGO and Einstein Telescope with their respective response functions. (paper)

  16. Gear fault diagnosis based on the structured sparsity time-frequency analysis

    Science.gov (United States)

    Sun, Ruobin; Yang, Zhibo; Chen, Xuefeng; Tian, Shaohua; Xie, Yong

    2018-03-01

    Over the last decade, sparse representation has become a powerful paradigm in mechanical fault diagnosis due to its excellent capability and the high flexibility for complex signal description. The structured sparsity time-frequency analysis (SSTFA) is a novel signal processing method, which utilizes mixed-norm priors on time-frequency coefficients to obtain a fine match for the structure of signals. In order to extract the transient feature from gear vibration signals, a gear fault diagnosis method based on SSTFA is proposed in this work. The steady modulation components and impulsive components of the defective gear vibration signals can be extracted simultaneously by choosing different time-frequency neighborhood and generalized thresholding operators. Besides, the time-frequency distribution with high resolution is obtained by piling different components in the same diagram. The diagnostic conclusion can be made according to the envelope spectrum of the impulsive components or by the periodicity of impulses. The effectiveness of the method is verified by numerical simulations, and the vibration signals registered from a gearbox fault simulator and a wind turbine. To validate the efficiency of the presented methodology, comparisons are made among some state-of-the-art vibration separation methods and the traditional time-frequency analysis methods. The comparisons show that the proposed method possesses advantages in separating feature signals under strong noise and accounting for the inner time-frequency structure of the gear vibration signals.

  17. Distortions in frequency spectra of signals associated with sampling-pulse shapes

    International Nuclear Information System (INIS)

    Njau, E.C.

    1983-04-01

    A method developed earlier by the author [IC/82/44; IC/82/45] is used to investigate distortions introduced into frequency spectra of signals by the shapes of the sampling pulses involved. Conditions are established under which the use of trapezoid or exponentially-edged pulses to digitize signals can make the frequency spectra of the resultant data samples devoid of the main features of the signals. This observation does not, however, apply in any way to cosinusoidally-edged pulses or to pulses with cosine-squared edges. Since parts of the Earth's surface and atmosphere receive direct solar energy in discrete samples (i.e. only from sunrise to sunset) we have extended the technique and attempted to develop a theory that explains the observed solar terrestrial relationships. A very good agreement is obtained between the theory and previous long-term and short-term observations. (author)

  18. Distinguishing low frequency oscillations within the 1/f spectral behaviour of electromagnetic brain signals.

    Science.gov (United States)

    Demanuele, Charmaine; James, Christopher J; Sonuga-Barke, Edmund Js

    2007-12-10

    It has been acknowledged that the frequency spectrum of measured electromagnetic (EM) brain signals shows a decrease in power with increasing frequency. This spectral behaviour may lead to difficulty in distinguishing event-related peaks from ongoing brain activity in the electro- and magnetoencephalographic (EEG and MEG) signal spectra. This can become an issue especially in the analysis of low frequency oscillations (LFOs) - below 0.5 Hz - which are currently being observed in signal recordings linked with specific pathologies such as epileptic seizures or attention deficit hyperactivity disorder (ADHD), in sleep studies, etc. In this work we propose a simple method that can be used to compensate for this 1/f trend hence achieving spectral normalisation. This method involves filtering the raw measured EM signal through a differentiator prior to further data analysis. Applying the proposed method to various exemplary datasets including very low frequency EEG recordings, epileptic seizure recordings, MEG data and Evoked Response data showed that this compensating procedure provides a flat spectral base onto which event related peaks can be clearly observed. Findings suggest that the proposed filter is a useful tool for the analysis of physiological data especially in revealing very low frequency peaks which may otherwise be obscured by the 1/f spectral activity inherent in EEG/MEG recordings.

  19. Seafloor backscatter signal simulation and classification

    Digital Repository Service at National Institute of Oceanography (India)

    Mahale, V.; El Dine, W.G.; Chakraborty, B.

    . In this model a smooth echo envelope is generated then mixed up with multiplicative and additive noise. Several such echo signals were simulated for three types of seafloor. An Artificial Neural Network based classification technique is conceived to classify...

  20. Simulation of time of flight defraction signals for reactor vessel head penetrations

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Tae Hun; Kim, Young Sik; Lee, Jeong Seok [KHNP Central Research Institute, Daejeon (Korea, Republic of)

    2016-08-15

    The simulation of nondestructive testing has been used in the prediction of the signal characteristics of various defects and in the development of the procedures. CIVA, a simulation tool dedicated to nondestructive testing, has good accuracy and speed, and provides a three-dimensional graphical user interface for improved visualization and familiar data displays consistent with an NDE technique. Even though internal validations have been performed by the CIVA software development specialists, an independent validation study is necessary for the assessment of the accuracy of the software prior to practical use. In this study, time of flight diffraction signals of ultrasonic inspection of a calibration block for reactor vessel head penetrations were simulated using CIVA. The results were compared to the experimentally inspected signals. The accuracy of the simulated signals and the possible range for simulation were verified. It was found that, there is a good agreement between the CIVA simulated and experimental results in the A-scan signal, B-scan image, and measurement of depth.

  1. Simulation of time of flight defraction signals for reactor vessel head penetrations

    International Nuclear Information System (INIS)

    Lim, Tae Hun; Kim, Young Sik; Lee, Jeong Seok

    2016-01-01

    The simulation of nondestructive testing has been used in the prediction of the signal characteristics of various defects and in the development of the procedures. CIVA, a simulation tool dedicated to nondestructive testing, has good accuracy and speed, and provides a three-dimensional graphical user interface for improved visualization and familiar data displays consistent with an NDE technique. Even though internal validations have been performed by the CIVA software development specialists, an independent validation study is necessary for the assessment of the accuracy of the software prior to practical use. In this study, time of flight diffraction signals of ultrasonic inspection of a calibration block for reactor vessel head penetrations were simulated using CIVA. The results were compared to the experimentally inspected signals. The accuracy of the simulated signals and the possible range for simulation were verified. It was found that, there is a good agreement between the CIVA simulated and experimental results in the A-scan signal, B-scan image, and measurement of depth

  2. Simulation Analysis of SPWM Variable Frequency Speed Based on Simulink

    Directory of Open Access Journals (Sweden)

    Min-Yan DI

    2014-01-01

    Full Text Available This article is studied on currently a very active field of researching sinusoidal pulse width modulation (SPWM frequency speed control system, and strengthen researched on the simulation model of speed control system with MATLAB / Simulink / Power System simulation tools, thus we can find the best way to simulation. We apply it to the actual conveyor belt, frequency conversion motor, when the obtained simulation results are compared with the measured data, we prove that the method is practical and effective. The results of our research have a guiding role for the future engineering and technical personnel in asynchronous motor SPWM VVVF CAD design.

  3. Analysis of simulated ECT signals obtained at tubesheet and tube expansion area

    International Nuclear Information System (INIS)

    Song, Sung Chul; Lee, Yun Tai; Jung, Hee Sung; Shin, Young Kil

    2006-01-01

    Steam generator(SG) tubes are expanded inside tubesheet holes by using explosive or hydraulic methods to be fixed in the tubesheet. In the tube expansion process, it is important to minimize the crevice gap between tubesheet and expanded tube. In this paper, absolute and differential signals are predicted by a numerical method for several different locations of tube expansion inside and outside the tubesheet and signal variations due to tubesheet, tube expansion and operating frequency are observed. Results show that low frequency is good for detecting tubesheet location in both types of signals and high frequency is suitable for sizing of tube diameter as well as the detection of transition region. Also learned is that the absolute signal is good for measuring tube diameter, while the differential signal is good for locating the top of tubesheet and both ends of the transition region.

  4. Low-frequency electrostatic waves in the ionospheric E-region: a comparison of rocket observations and numerical simulations

    Directory of Open Access Journals (Sweden)

    L. Dyrud

    2006-11-01

    Full Text Available Low frequency electrostatic waves in the lower parts of the ionosphere are studied by a comparison of observations by instrumented rockets and of results from numerical simulations. Particular attention is given to the spectral properties of the waves. On the basis of a good agreement between the observations and the simulations, it can be argued that the most important nonlinear dynamics can be accounted for in a 2-D numerical model, referring to a plane perpendicular to a locally homogeneous magnetic field. It does not seem necessary to take into account turbulent fluctuations or motions in the neutral gas component. The numerical simulations explain the observed strongly intermittent nature of the fluctuations: secondary instabilities develop on the large scale gradients of the largest amplitude waves, and the small scale dynamics is strongly influenced by these secondary instabilities. We compare potential variations obtained at a single position in the numerical simulations with two point potential-difference signals, where the latter is the adequate representation for the data obtained by instrumented rockets. We can demonstrate a significant reduction in the amount of information concerning the plasma turbulence when the latter signal is used for analysis. In particular we show that the bicoherence estimate is strongly affected. The conclusions have implications for studies of low frequency ionospheric fluctuations in the E and F regions by instrumented rockets, and also for other methods relying on difference measurements, using two probes with large separation. The analysis also resolves a long standing controversy concerning the supersonic phase velocities of these cross-field instabilities being observed in laboratory experiments.

  5. Analysis and Simulation of Multi-target Echo Signals from a Phased Array Radar

    OpenAIRE

    Jia Zhen; Zhou Rui

    2017-01-01

    The construction of digital radar simulation systems has been a research hotspot of the radar field. This paper focuses on theoretical analysis and simulation of multi-target echo signals produced in a phased array radar system, and constructs an array antenna element and a signal generation environment. The antenna element is able to simulate planar arrays and optimizes these arrays by adding window functions. And the signal environment can model and simulate radar transmission signals, rada...

  6. Conditional flood frequency and catchment state: a simulation approach

    Science.gov (United States)

    Brettschneider, Marco; Bourgin, François; Merz, Bruno; Andreassian, Vazken; Blaquiere, Simon

    2017-04-01

    Catchments have memory and the conditional flood frequency distribution for a time period ahead can be seen as non-stationary: it varies with the catchment state and climatic factors. From a risk management perspective, understanding the link of conditional flood frequency to catchment state is a key to anticipate potential periods of higher flood risk. Here, we adopt a simulation approach to explore the link between flood frequency obtained by continuous rainfall-runoff simulation and the initial state of the catchment. The simulation chain is based on i) a three state rainfall generator applied at the catchment scale, whose parameters are estimated for each month, and ii) the GR4J lumped rainfall-runoff model, whose parameters are calibrated with all available data. For each month, a large number of stochastic realizations of the continuous rainfall generator for the next 12 months are used as inputs for the GR4J model in order to obtain a large number of stochastic realizations for the next 12 months. This process is then repeated for 50 different initial states of the soil moisture reservoir of the GR4J model and for all the catchments. Thus, 50 different conditional flood frequency curves are obtained for the 50 different initial catchment states. We will present an analysis of the link between the catchment states, the period of the year and the strength of the conditioning of the flood frequency compared to the unconditional flood frequency. A large sample of diverse catchments in France will be used.

  7. Stochastic resonance in a single-mode laser driven by frequency modulated signal and coloured noises

    Institute of Scientific and Technical Information of China (English)

    Jin Guo-Xiang; Zhang Liang-Ying; Cao Li

    2009-01-01

    By adding frequency modulated signals to the intensity equation of gain-noise model of the single-mode laser driven by two coloured noises which are correlated, this paper uses the linear approximation method to calculate the power spectrum and signal-to-noise ratio (SNR) of the laser intensity. The results show that the SNR appears typical stochastic resonance with the variation of intensity of the pump noise and quantum noise. As the amplitude of a modulated signal has effects on the SNR, it shows suppression, monotone increasing, stochastic resonance, and multiple stochastic resonance with the variation of the frequency of a carrier signal and modulated signal.

  8. Distinguishing low frequency oscillations within the 1/f spectral behaviour of electromagnetic brain signals

    Directory of Open Access Journals (Sweden)

    Sonuga-Barke Edmund JS

    2007-12-01

    Full Text Available Abstract Background It has been acknowledged that the frequency spectrum of measured electromagnetic (EM brain signals shows a decrease in power with increasing frequency. This spectral behaviour may lead to difficulty in distinguishing event-related peaks from ongoing brain activity in the electro- and magnetoencephalographic (EEG and MEG signal spectra. This can become an issue especially in the analysis of low frequency oscillations (LFOs – below 0.5 Hz – which are currently being observed in signal recordings linked with specific pathologies such as epileptic seizures or attention deficit hyperactivity disorder (ADHD, in sleep studies, etc. Methods In this work we propose a simple method that can be used to compensate for this 1/f trend hence achieving spectral normalisation. This method involves filtering the raw measured EM signal through a differentiator prior to further data analysis. Results Applying the proposed method to various exemplary datasets including very low frequency EEG recordings, epileptic seizure recordings, MEG data and Evoked Response data showed that this compensating procedure provides a flat spectral base onto which event related peaks can be clearly observed. Conclusion Findings suggest that the proposed filter is a useful tool for the analysis of physiological data especially in revealing very low frequency peaks which may otherwise be obscured by the 1/f spectral activity inherent in EEG/MEG recordings.

  9. Simulation and Analysis of ECT Signals Obtained at Tubesheet and Tube Expansion Area

    International Nuclear Information System (INIS)

    Song, Sung Chul; Lee, Yun Tai; Jung, Hee Sung; Shin, Young Kil

    2006-01-01

    Steam generator (SG) tubes are expanded inside tubesheet holes by using explosive or hydraulic methods to be fixed in a tubesheet. In the tube expansion process, it is important to minimize the crevice gap between expanded tube and tube sheet. In this paper, absolute and differential signals are computed by a numerical method for several different locations of tube expansion inside and outside a tubesheet and signal variations due to tubesheet, tube expansion and operating frequencies are observed. Results show that low frequency is good for detecting tubesheet location in both types of signals and high frequency is suitable for sizing of tube diameter as well as the detection of transition region. Also learned is that the absolute signal is good for measuring tube diameter, while the differential signal is good for locating the top of tubesheet and both ends of the transition region. In the case of mingled anomaly with tube expansion and tubesheet, low frequency inspection is found to be useful to analyze the mixed signal

  10. Frequency-dependent tACS modulation of BOLD signal during rhythmic visual stimulation.

    Science.gov (United States)

    Chai, Yuhui; Sheng, Jingwei; Bandettini, Peter A; Gao, Jia-Hong

    2018-05-01

    Transcranial alternating current stimulation (tACS) has emerged as a promising tool for modulating cortical oscillations. In previous electroencephalogram (EEG) studies, tACS has been found to modulate brain oscillatory activity in a frequency-specific manner. However, the spatial distribution and hemodynamic response for this modulation remains poorly understood. Functional magnetic resonance imaging (fMRI) has the advantage of measuring neuronal activity in regions not only below the tACS electrodes but also across the whole brain with high spatial resolution. Here, we measured fMRI signal while applying tACS to modulate rhythmic visual activity. During fMRI acquisition, tACS at different frequencies (4, 8, 16, and 32 Hz) was applied along with visual flicker stimulation at 8 and 16 Hz. We analyzed the blood-oxygen-level-dependent (BOLD) signal difference between tACS-ON vs tACS-OFF, and different frequency combinations (e.g., 4 Hz tACS, 8 Hz flicker vs 8 Hz tACS, 8 Hz flicker). We observed significant tACS modulation effects on BOLD responses when the tACS frequency matched the visual flicker frequency or the second harmonic frequency. The main effects were predominantly seen in regions that were activated by the visual task and targeted by the tACS current distribution. These findings bridge different scientific domains of tACS research and demonstrate that fMRI could localize the tACS effect on stimulus-induced brain rhythms, which could lead to a new approach for understanding the high-level cognitive process shaped by the ongoing oscillatory signal. © 2018 Wiley Periodicals, Inc.

  11. On-electrode autonomous current generator for multi-frequency EIT

    International Nuclear Information System (INIS)

    Jivet, I; Dragoi, B

    2008-01-01

    The paper presents an autonomous programmable current generator module for multi-frequency EIT systems. The module incorporates all stages from the sine wave generation with frequency and amplitude tuning, D/A converter and filter, a high output resistance voltage-to-current converter to the associated digital communication and control. The paper presents in depth the original digital quadrature signal generator and the output current generator with a high resistance. The other main blocks of the design use current practice specifications, since recent technological solutions proposed in the literature were found appropriate. The proposed signal generator circuit, characterized by a very low complexity, is analyzed in its capacity to produce multiple accurate signals up to 1 MHz in frequency. The precision output current source uses a modified current conveyor of type CCII with a high output resistance and low distortion. The output current frequency spectrum and linearity parameters obtained in the simulations are also described. The simulation results indicate a good linearity and high output resistance with an acceptable output voltage swing. The calculated performance parameters are validated with simulations, and future work for the prototype fabrication of the IC is outlined

  12. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals.

    Science.gov (United States)

    Zhang, Y; Huang, S L; Wang, S; Zhao, W

    2016-05-01

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert-Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of wave detection signals.

  13. Fundamental Frequency and Model Order Estimation Using Spatial Filtering

    DEFF Research Database (Denmark)

    Karimian-Azari, Sam; Jensen, Jesper Rindom; Christensen, Mads Græsbøll

    2014-01-01

    extend this procedure to account for inharmonicity using unconstrained model order estimation. The simulations show that beamforming improves the performance of the joint estimates of fundamental frequency and the number of harmonics in low signal to interference (SIR) levels, and an experiment......In signal processing applications of harmonic-structured signals, estimates of the fundamental frequency and number of harmonics are often necessary. In real scenarios, a desired signal is contaminated by different levels of noise and interferers, which complicate the estimation of the signal...... parameters. In this paper, we present an estimation procedure for harmonic-structured signals in situations with strong interference using spatial filtering, or beamforming. We jointly estimate the fundamental frequency and the constrained model order through the output of the beamformers. Besides that, we...

  14. Low-Frequency Waves in HF Heating of the Ionosphere

    Science.gov (United States)

    Sharma, A. S.; Eliasson, B.; Milikh, G. M.; Najmi, A.; Papadopoulos, K.; Shao, X.; Vartanyan, A.

    2016-02-01

    Ionospheric heating experiments have enabled an exploration of the ionosphere as a large-scale natural laboratory for the study of many plasma processes. These experiments inject high-frequency (HF) radio waves using high-power transmitters and an array of ground- and space-based diagnostics. This chapter discusses the excitation and propagation of low-frequency waves in HF heating of the ionosphere. The theoretical aspects and the associated models and simulations, and the results from experiments, mostly from the HAARP facility, are presented together to provide a comprehensive interpretation of the relevant plasma processes. The chapter presents the plasma model of the ionosphere for describing the physical processes during HF heating, the numerical code, and the simulations of the excitation of low-frequency waves by HF heating. It then gives the simulations of the high-latitude ionosphere and mid-latitude ionosphere. The chapter also briefly discusses the role of kinetic processes associated with wave generation.

  15. Numerical simulation of seismic low-frequency shadows and its application%地震低频伴影的数值模拟与应用

    Institute of Scientific and Technical Information of China (English)

    贺振华; 熊晓军; 边立恩

    2008-01-01

    Strong low-frequency energy beneath a hydrocarbon reservoir is called a seismic low-frequency shadow and can be used as a hydrocarbon indicator (Taner et al., 1979) but the physical mechanism of the observed low-frequency shadow is still unclear. To study the mechanism, we performed seismic numerical simulation of geological models with a hydrocarbon-bearing zone using the 2-D diffusive-viscous wave equation which can effectively model the characteristics of velocity dispersion and transform the seismic data centered in a target layer slice within a time window to the time-frequency domain by using time-frequency signal analysis and sort the frequency gathers to common frequency cubes. Then, we observe the characteristics of the seismic low-frequency shadow in the common frequency cubes. The numerical simulations reveal that the main mechanism of seismic low-frequency shadows is attributed to high attenuation of the medium to high seismic frequency components caused by absorption in the hydrocarbon-filled reservoir. Results from a practical example of seismic low-frequency shadows show that it is possible to identify the reservoir by the low-frequency shadow with high S/N seismic data.

  16. Are greenhouse gas signals of Northern Hemisphere winter extra-tropical cyclone activity dependent on the identification and tracking algorithm?

    Energy Technology Data Exchange (ETDEWEB)

    Ulbrich, Uwe; Grieger, Jens [Freie Univ. Berlin (Germany). Inst. of Meteorology; Leckebusch, Gregor C. [Birmingham Univ. (United Kingdom). School of Geography, Earth and Environmental Sciences] [and others

    2013-02-15

    For Northern Hemisphere extra-tropical cyclone activity, the dependency of a potential anthropogenic climate change signal on the identification method applied is analysed. This study investigates the impact of the used algorithm on the changing signal, not the robustness of the climate change signal itself. Using one single transient AOGCM simulation as standard input for eleven state-of-the-art identification methods, the patterns of model simulated present day climatologies are found to be close to those computed from re-analysis, independent of the method applied. Although differences in the total number of cyclones identified exist, the climate change signals (IPCC SRES A1B) in the model run considered are largely similar between methods for all cyclones. Taking into account all tracks, decreasing numbers are found in the Mediterranean, the Arctic in the Barents and Greenland Seas, the mid-latitude Pacific and North America. Changing patterns are even more similar, if only the most severe systems are considered: the methods reveal a coherent statistically significant increase in frequency over the eastern North Atlantic and North Pacific. We found that the differences between the methods considered are largely due to the different role of weaker systems in the specific methods. (orig.)

  17. Research on the Vibration Insulation of High-Speed Train Bogies in Mid and High Frequency

    Directory of Open Access Journals (Sweden)

    Jia Liu

    2018-01-01

    Full Text Available According to a large amount of the test data, the mid and high frequency vibrations of high-speed bogies are very notable, especially in the 565~616 Hz range, which are just the passing frequencies corresponding to the 22nd to 24th polygonal wear of the wheel. In order to investigate the main cause of wheel higher-order polygon formation, a 3D flexible model of a Chinese high-speed train bogie is developed using the explicit finite element method. The results show that the couple vibration of bogie and wheelset may lead to the high-order wears of wheel. In order to reduce the coupled resonance of the wheelset and the bogie frame, the effects of the stiffness and damping of the primary suspensions, wheelset axle radius, and bogie frame strength on the vibration transmissibility are discussed carefully. The numerical results show that the resonance peaks in high frequency range can be reduced by reducing the stiffness of axle box rotary arm joint, reducing the wheelset axle radius or strengthening the bogie frame location. The related results may provide a reference for structure improvement of the existing bogies and structure design of the new high-speed bogies.

  18. Study on The Extended Range Weather Forecast of Low Frequency Signal Based on Period Analysis Method

    Science.gov (United States)

    Li, X.

    2016-12-01

    Although many studies have explored the MJO and its application for weather forecasting, low-frequency oscillation has been insufficiently studied for the extend range weather forecasting over middle and high latitudes. In China, low-frequency synoptic map is a useful tool for meteorological operation department to forecast extend range weather. It is therefore necessary to develop objective methods to serve the need for finding low-frequency signal, interpretation and application of this signal in the extend range weather forecasting. In this paper, method of Butterworth band pass filter was applied to get low-frequency height field at 500hPa from 1980 to 2014 by using NCEP/NCAR daily grid data. Then period analysis and optimal subset regression methods were used to process the low frequency data of 150 days before the first forecast day and extend the low frequency signal of 500hPa low-frequency high field to future 30 days in the global from June to August during 2011-2014. Finally, the results were test. The main results are as follows: (1) In general, the fitting effect of low frequency signals of 500hPa low-frequency height field by period analysis in the northern hemisphere was better than that in the southern hemisphere, and was better in the low latitudes than that in the high latitudes. The fitting accuracy gradually reduced with the increase of forecast time length, which tended to be stable during the late forecasting period. (2) The fitting effects over the 6 key regions in China showed that except filtering result over Xinjiang area in the first 10 days and 30 days, filtering results over the other 5 key regions throughout the whole period have passed reliability test with level more than 95%. (3) The center and scope of low and high low frequency systems can be fitted well by using the methods mentioned above, which is consist with the corresponding use of the low-frequency synoptic map for the prediction of the extended period. Application of the

  19. The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

    Directory of Open Access Journals (Sweden)

    F. S. E. Vamborg

    2011-02-01

    Full Text Available We have implemented a new albedo scheme that takes the dynamic behaviour of the surface below the canopy into account, into the land-surface scheme of the MPI-ESM. The standard (static scheme calculates the seasonal canopy albedo as a function of leaf area index, whereas the background albedo is a gridbox constant derived from satellite measurements. The new (dynamic scheme additionally models the background albedo as a slowly changing function of organic matter in the ground and of litter and standing dead biomass covering the ground. We use the two schemes to investigate the interactions between vegetation, albedo and precipitation in the Sahel/Sahara for two time-slices: pre-industrial and mid-Holocene. The dynamic scheme represents the seasonal cycle of albedo and the correspondence between annual mean albedo and vegetation cover in a more consistent way than the static scheme. It thus gives a better estimate of albedo change between the two time periods. With the introduction of the dynamic scheme, precipitation is increased by 30 mm yr−1 for the pre-industrial simulation and by about 80 mm yr−1 for the mid-Holocene simulation. The present-day dry bias in the Sahel of standard ECHAM5 is thus reduced and the sensitivity of precipitation to mid-Holocene external forcing is increased by around one third. The locations of mid-Holocene lakes, as estimated from reconstructions, lie south of the modelled desert border in both mid-Holocene simulations. The magnitude of simulated rainfall in this area is too low to fully sustain lakes, however it is captured better with the dynamic scheme. The dynamic scheme leads to increased vegetation variability in the remaining desert region, indicating a higher frequency of green spells, thus reaching a better agreement with the vegetation distribution as derived from pollen records.

  20. Simulation of traffic control signal systems

    Science.gov (United States)

    Connolly, P. J.; Concannon, P. A.; Ricci, R. C.

    1974-01-01

    In recent years there has been considerable interest in the development and testing of control strategies for networks of urban traffic signal systems by simulation. Simulation is an inexpensive and timely method for evaluating the effect of these traffic control strategies since traffic phenomena are too complex to be defined by analytical models and since a controlled experiment may be hazardous, expensive, and slow in producing meaningful results. This paper describes the application of an urban traffic corridor program, to evaluate the effectiveness of different traffic control strategies for the Massachusetts Avenue TOPICS Project.

  1. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y., E-mail: thuzhangyu@foxmail.com; Huang, S. L., E-mail: huangsling@tsinghua.edu.cn; Wang, S.; Zhao, W. [State Key Laboratory of Power Systems, Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China)

    2016-05-15

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert–Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.

  2. Time-frequency energy density precipitation method for time-of-flight extraction of narrowband Lamb wave detection signals

    International Nuclear Information System (INIS)

    Zhang, Y.; Huang, S. L.; Wang, S.; Zhao, W.

    2016-01-01

    The time-of-flight of the Lamb wave provides an important basis for defect evaluation in metal plates and is the input signal for Lamb wave tomographic imaging. However, the time-of-flight can be difficult to acquire because of the Lamb wave dispersion characteristics. This work proposes a time-frequency energy density precipitation method to accurately extract the time-of-flight of narrowband Lamb wave detection signals in metal plates. In the proposed method, a discrete short-time Fourier transform is performed on the narrowband Lamb wave detection signals to obtain the corresponding discrete time-frequency energy density distribution. The energy density values at the center frequency for all discrete time points are then calculated by linear interpolation. Next, the time-domain energy density curve focused on that center frequency is precipitated by least squares fitting of the calculated energy density values. Finally, the peak times of the energy density curve obtained relative to the initial pulse signal are extracted as the time-of-flight for the narrowband Lamb wave detection signals. An experimental platform is established for time-of-flight extraction of narrowband Lamb wave detection signals, and sensitivity analysis of the proposed time-frequency energy density precipitation method is performed in terms of propagation distance, dispersion characteristics, center frequency, and plate thickness. For comparison, the widely used Hilbert–Huang transform method is also implemented for time-of-flight extraction. The results show that the time-frequency energy density precipitation method can accurately extract the time-of-flight with relative error of <1% and thus can act as a universal time-of-flight extraction method for narrowband Lamb wave detection signals.

  3. Sparse Frequency Waveform Design for Radar-Embedded Communication

    Directory of Open Access Journals (Sweden)

    Chaoyun Mai

    2016-01-01

    Full Text Available According to the Tag application with function of covert communication, a method for sparse frequency waveform design based on radar-embedded communication is proposed. Firstly, sparse frequency waveforms are designed based on power spectral density fitting and quasi-Newton method. Secondly, the eigenvalue decomposition of the sparse frequency waveform sequence is used to get the dominant space. Finally the communication waveforms are designed through the projection of orthogonal pseudorandom vectors in the vertical subspace. Compared with the linear frequency modulation waveform, the sparse frequency waveform can further improve the bandwidth occupation of communication signals, thus achieving higher communication rate. A certain correlation exists between the reciprocally orthogonal communication signals samples and the sparse frequency waveform, which guarantees the low SER (signal error rate and LPI (low probability of intercept. The simulation results verify the effectiveness of this method.

  4. Calibration of semi-stochastic procedure for simulating high-frequency ground motions

    Science.gov (United States)

    Seyhan, Emel; Stewart, Jonathan P.; Graves, Robert

    2013-01-01

    Broadband ground motion simulation procedures typically utilize physics-based modeling at low frequencies, coupled with semi-stochastic procedures at high frequencies. The high-frequency procedure considered here combines deterministic Fourier amplitude spectra (dependent on source, path, and site models) with random phase. Previous work showed that high-frequency intensity measures from this simulation methodology attenuate faster with distance and have lower intra-event dispersion than in empirical equations. We address these issues by increasing crustal damping (Q) to reduce distance attenuation bias and by introducing random site-to-site variations to Fourier amplitudes using a lognormal standard deviation ranging from 0.45 for Mw  100 km).

  5. Transmission experiment by the simulated LMFBR model and propagation analysis of acoustic signals

    International Nuclear Information System (INIS)

    Kobayashi, Kenji; Yasuda, Tsutomu; Araki, Hitoshi.

    1981-01-01

    Acoustic transducers to detect a boiling of sodium may be installed in the upper structure and at the upper position of reactor vessel wall under constricted conditions. A set of the experiments of transmission of acoustic vibration to various points of the vessel was performed utilizing the half scale-hydraulic flow test facility simulating reactor vessel over the frequency range 20 kHz -- 100 kHz. Acoustic signals from an installed sound source in the core were measured at each point by both hydrophones in the vessel and vibration pickups on the vessel wall. In these experiments transmission of signals to each point of detectors were clearly observed to background noise level. These data have been summarized in terms of the transmission loss and furthermore are compared with background noise level of flow to estimate the feasibility of detection of sodium boiling sound. The ratio of signal to noise was obtained to be about 13 dB by hydrophone in the upper structure, 8 dB by accelerometer and 16 dB by AE-sensor at the upper position on the vessel in experiments used the simulation model. Sound waves emanated due to sodium boiling also propagate along the wall of the vessel may be predicted theoretically. The result of analysis suggests a capability of detection at the upper position of the reactor vessel wall. Leaky Lamb waves of the first symmetric (L 1 ) and of the antisymmetric (F 1 ) mode and shear horizontal wave (SH) have been derived in light of the attenuation due to coupling to liquid sodium as the traveling modes over the frequency range 10 kHz -- 100 kHz up to 50 mm in thickness of the vessel wall. Leaky Lamb wave (L 1 ) and (SH) mode have been proposed theoretically on the some assumption to be most available to detect the boiling sound of sodium propagating along the vessel wall. (author)

  6. Frequency dependence of the pump-to-signal RIN transfer in fiber optical parametric amplifiers

    DEFF Research Database (Denmark)

    Pakarzadeh Dezfuli Nezhad, Hassan; Rottwitt, Karsten; Zakery, A.

    2009-01-01

    Using a numerical model, the frequency dependence of the pump-to-signal RIN transfer in FOPAs has been investigated. The model includes fiber loss, pump depletion as well as difference in group velocity among interacting beams.......Using a numerical model, the frequency dependence of the pump-to-signal RIN transfer in FOPAs has been investigated. The model includes fiber loss, pump depletion as well as difference in group velocity among interacting beams....

  7. Wavelet analysis for nonstationary signals

    International Nuclear Information System (INIS)

    Penha, Rosani Maria Libardi da

    1999-01-01

    Mechanical vibration signals play an important role in anomalies identification resulting of equipment malfunctioning. Traditionally, Fourier spectral analysis is used where the signals are assumed to be stationary. However, occasional transient impulses and start-up process are examples of nonstationary signals that can be found in mechanical vibrations. These signals can provide important information about the equipment condition, as early fault detection. The Fourier analysis can not adequately be applied to nonstationary signals because the results provide data about the frequency composition averaged over the duration of the signal. In this work, two methods for nonstationary signal analysis are used: Short Time Fourier Transform (STFT) and wavelet transform. The STFT is a method of adapting Fourier spectral analysis for nonstationary application to time-frequency domain. To have a unique resolution throughout the entire time-frequency domain is its main limitation. The wavelet transform is a new analysis technique suitable to nonstationary signals, which handles the STFT drawbacks, providing multi-resolution frequency analysis and time localization in a unique time-scale graphic. The multiple frequency resolutions are obtained by scaling (dilatation/compression) the wavelet function. A comparison of the conventional Fourier transform, STFT and wavelet transform is made applying these techniques to: simulated signals, arrangement rotor rig vibration signal and rotate machine vibration signal Hanning window was used to STFT analysis. Daubechies and harmonic wavelets were used to continuos, discrete and multi-resolution wavelet analysis. The results show the Fourier analysis was not able to detect changes in the signal frequencies or discontinuities. The STFT analysis detected the changes in the signal frequencies, but with time-frequency resolution problems. The wavelet continuos and discrete transform demonstrated to be a high efficient tool to detect

  8. Enhanced detection of a low-frequency signal by using broad squeezed light and a bichromatic local oscillator

    Science.gov (United States)

    Li, Wei; Jin, Yuanbin; Yu, Xudong; Zhang, Jing

    2017-08-01

    We experimentally study a protocol of using the broadband high-frequency squeezed vacuum to detect the low-frequency signal. In this scheme, the lower sideband field of the squeezed light carries the low-frequency modulation signal, and the two strong coherent light fields are applied as the bichromatic local oscillator in the homodyne detection to measure the quantum entanglement of the upper and lower sideband for the broadband squeezed light. The power of one of the local oscillators for detecting the upper sideband can be adjusted to optimize the conditional variance in the low-frequency regime by subtracting the photocurrent of the upper sideband field of the squeezed light from that of the lower sideband field. By means of the quantum correlation of the upper and lower sideband for the broadband squeezed light, the low-frequency signal beyond the standard quantum limit is measured. This scheme is appropriate for enhancing the sensitivity of the low-frequency signal by the aid of the broad squeezed light, such as gravitational waves detection, and does not need to directly produce the low-frequency squeezing in an optical parametric process.

  9. Frequency-Selective Signal Sensing with Sub-Nyquist Uniform Sampling Scheme

    DEFF Research Database (Denmark)

    Pierzchlewski, Jacek; Arildsen, Thomas

    2015-01-01

    In this paper the authors discuss a problem of acquisition and reconstruction of a signal polluted by adjacent- channel interference. The authors propose a method to find a sub-Nyquist uniform sampling pattern which allows for correct reconstruction of selected frequencies. The method is inspired...... by the Restricted Isometry Property, which is known from the field of compressed sensing. Then, compressed sensing is used to successfully reconstruct a wanted signal even if some of the uniform samples were randomly lost, e. g. due to ADC saturation. An experiment which tests the proposed method in practice...

  10. Designing Non-linear Frequency Modulated Signals For Medical Ultrasound Imaging

    DEFF Research Database (Denmark)

    Gran, Fredrik; Jensen, Jørgen Arendt

    2006-01-01

    In this paper a new method for designing non-linear frequency modulated (NLFM) waveforms for ultrasound imaging is proposed. The objective is to control the amplitude spectrum of the designed waveform and still keep a constant transmit amplitude, so that the transmitted energy is maximized....... The signal-to-noise-ratio can in this way be optimized. The waveform design is based on least squares optimization. A desired amplitude spectrum is chosen, hereafter the phase spectrum is chosen, so that the instantaneous frequency takes on the form of a third order polynomial. The finite energy waveform...

  11. Numerical simulation of mid-latitude ionospheric E-region based on SEEK and SEEK-2 observations

    Directory of Open Access Journals (Sweden)

    T. Yokoyama

    2005-10-01

    Full Text Available Observational campaigns of the mid-latitude ionospheric E-region with sounding rockets and ground-based instruments were conducted in 1996 (SEEK and 2002 (SEEK-2. Both of them were successfully conducted to bring important findings about the mid-latitude E-region and quasi-periodic (QP VHF radar echoes. The observational results in the SEEK and the SEEK-2 are compared with numerical simulations and discussed in this paper. While sporadic-E (Es-layers are actually formed by the observed neutral wind, it is difficult for the constant wind shear to produce the sharp Es-layer gradient. However, once they are formed in the lower E-region, they cannot easily be dissipated by the simple diffusive motion. The polarization electric field, calculated under the condition at the rocket launch time, shows similar amplitude and structure to the measurement around the Es-layer altitude. The structure of the plasma density and the electric field above the Es-layer observed in the SEEK-2 showed a wave-like pattern up to an altitude of 150 km. Considering a mapping of the polarization electric field generated within the Es-layers, gravity waves are the possible source of the wave-like structure of the measured electric fields and sub-peaks of the electron density above the main Es-layers. Fluctuation of the measured magnetic field is reproduced by Hall or field-aligned current driven by the polarization electric field. The current theoretical models for QP echoes and the polarization electric field are basically verified by the discussion in this paper. Keywords. Ionospheric irregularities – Mid-latitude ionosphere – Numerical simulation studies

  12. Single photon laser altimeter simulator and statistical signal processing

    Science.gov (United States)

    Vacek, Michael; Prochazka, Ivan

    2013-05-01

    Spaceborne altimeters are common instruments onboard the deep space rendezvous spacecrafts. They provide range and topographic measurements critical in spacecraft navigation. Simultaneously, the receiver part may be utilized for Earth-to-satellite link, one way time transfer, and precise optical radiometry. The main advantage of single photon counting approach is the ability of processing signals with very low signal-to-noise ratio eliminating the need of large telescopes and high power laser source. Extremely small, rugged and compact microchip lasers can be employed. The major limiting factor, on the other hand, is the acquisition time needed to gather sufficient volume of data in repetitive measurements in order to process and evaluate the data appropriately. Statistical signal processing is adopted to detect signals with average strength much lower than one photon per measurement. A comprehensive simulator design and range signal processing algorithm are presented to identify a mission specific altimeter configuration. Typical mission scenarios (celestial body surface landing and topographical mapping) are simulated and evaluated. The high interest and promising single photon altimeter applications are low-orbit (˜10 km) and low-radial velocity (several m/s) topographical mapping (asteroids, Phobos and Deimos) and landing altimetry (˜10 km) where range evaluation repetition rates of ˜100 Hz and 0.1 m precision may be achieved. Moon landing and asteroid Itokawa topographical mapping scenario simulations are discussed in more detail.

  13. Measurement of the Low Frequency Noise of MOSFETs under Large Signal RF Excitation

    NARCIS (Netherlands)

    van der Wel, A.P.; Klumperink, Eric A.M.; Nauta, Bram

    2002-01-01

    A measurement technique [1] is presented that allows measurement of MOSFET low frequency (LF) noise under large signal RF (Radio Frequency) excitation. Measurements indicate that MOSFETS exhibit a reduction in LF noise when they are cycled from inversion to accummulation and that this reduction does

  14. Investigation of the Mössbauer Spectrum Quality as a Dependence on the Frequency of the Velocity Signal

    Science.gov (United States)

    Pechousek, J.; Prochazka, R.; Cuda, J.; Frydrych, J.; Jancik, D.

    2010-07-01

    This paper is focused on a quality characterizing the Mössbauer spectra measured for various frequencies of the velocity signal. Standard electromechanical double-loudspeaker drive and digital PID velocity controller were used for calibration spectra measurement in the frequency interval from 4 up to 100 Hz. Several parameters were evaluated for recommendation of the suitable velocity signal frequency.

  15. Measurement of weak low frequency pressure signal using stretchable polyurethane fiber sensor for application in wearables

    DEFF Research Database (Denmark)

    Kaysir, Md Rejvi; Stefani, Alessio; Lwin, Richard

    2017-01-01

    .e. a capillary) to measure a weak low frequency signal comparable to respiration/heart rate. We characterized the fiber and measured the sensitivity of a PU capillary using a speaker connected to a function generator. The frequency of the modulated signal was recovered using Fourier Transform (FT). This bodes...

  16. Simulation and real-time replacement of missing plasma signals for disruption prediction: an implementation with APODIS

    International Nuclear Information System (INIS)

    Rattá, G A; Vega, J; Murari, A

    2014-01-01

    So far, the best results for real-time disruption prediction on the Joint European Torus (JET) have been achieved with the Advanced Predictor of Disruptions (APODIS). APODIS is a data-driven system whose latest version has been implemented in JET's real time-data network. It has been designed for the real-time analysis of features (mean and frequency values) corresponding to seven plasma signals in order to foresee upcoming disruptions. In this article, non-linear regression techniques are applied to create (off-line) signal models. The models are able to generate (in real-time) ‘synthetic’ signals. Therefore, these ‘synthetic’ signals can be used to replace the original ones in cases where they are in error or missing. APODIS has been tested under these conditions, emulating real-time operation. The simulation results demonstrate that once a signal in error is replaced by the generated ‘synthetic’ one, APODIS performance is considerably improved. The development of the regression models and the implications of the results are detailed and discussed in this paper. (paper)

  17. Simulation of Silicon Photomultiplier Signals

    Science.gov (United States)

    Seifert, Stefan; van Dam, Herman T.; Huizenga, Jan; Vinke, Ruud; Dendooven, Peter; Lohner, Herbert; Schaart, Dennis R.

    2009-12-01

    In a silicon photomultiplier (SiPM), also referred to as multi-pixel photon counter (MPPC), many Geiger-mode avalanche photodiodes (GM-APDs) are connected in parallel so as to combine the photon counting capabilities of each of these so-called microcells into a proportional light sensor. The discharge of a single microcell is relatively well understood and electronic models exist to simulate this process. In this paper we introduce an extended model that is able to simulate the simultaneous discharge of multiple cells. This model is used to predict the SiPM signal in response to fast light pulses as a function of the number of fired cells, taking into account the influence of the input impedance of the SiPM preamplifier. The model predicts that the electronic signal is not proportional to the number of fired cells if the preamplifier input impedance is not zero. This effect becomes more important for SiPMs with lower parasitic capacitance (which otherwise is a favorable property). The model is validated by comparing its predictions to experimental data obtained with two different SiPMs (Hamamatsu S10362-11-25u and Hamamatsu S10362-33-25c) illuminated with ps laser pulses. The experimental results are in good agreement with the model predictions.

  18. Adding a dimension to the infrared spectra of interfaces: 2D SFG spectroscopy via mid-IR pulse shaping

    Science.gov (United States)

    Zanni, Martin

    2012-02-01

    Sum-frequency generation spectroscopy provides an infrared spectrum of interfaces and thus has widespread use in the materials and chemical sciences. In this presentation, I will present our recent work in developing a 2D pulse sequence to generate 2D SFG spectra of interfaces, in analogy to 2D infrared spectra used to measure bulk species. To develop this spectroscopy, we have utilized many of the tricks-of-the-trade developed in the 2D IR and 2D Vis communities in the last decade, including mid-IR pulse shaping. With mid-IR pulse shaping, the 2D pulse sequence is manipulated by computer programming in the desired frequency resolution, rotating frame, and signal pathway. We believe that 2D SFG will become an important tool in the interfacial sciences in an analogous way that 2D IR is now being used in many disciplines.

  19. A Simple Semaphore Signaling Technique for Ultra-High Frequency Spacecraft Communications

    Science.gov (United States)

    Butman, S.; Satorius, E.; Illott, P.

    2005-11-01

    For planetary lander missions such as the upcoming Phoenix mission to Mars, the most challenging phase of the spacecraft-to-ground communications is during the critical phase termed entry, descent, and landing (EDL). At 8.4 GHz (X-band), the signals received by the largest Deep Space Network (DSN) antennas can be too weak for even 1 bit per second (bps) and therefore not able to communicate critical information to Earth. Fortunately, the lander's ultra-high frequency (UHF) link to an orbiting relay can meet the EDL requirements, but the data rate needs to be low enough to fit the capability of the UHF link during some or all of EDL. On Phoenix, the minimum data rate of the as-built UHF radio is 8 kbps and requires a signal level at the Odyssey orbiter of at least minus 120 dBm. For lower signaling levels, the effective data rate needs to be reduced, but without incurring the cost of rebuilding and requalifying the equipment. To address this scenario, a simple form of frequency-shift keying (FSK) has been devised by appropriately programming the data stream that is input to the UHF transceiver. This article describes this technique and provides performance estimates. Laboratory testing reveals that input signal levels at minus 140 dBm and lower can routinely be demodulated with the proposed signaling scheme, thereby providing a 20-dB and greater margin over the 8-kbps threshold.

  20. Simultaneously measured signals in scanning probe microscopy with a needle sensor: frequency shift and tunneling current.

    Science.gov (United States)

    Morawski, Ireneusz; Voigtländer, Bert

    2010-03-01

    We present combined noncontact scanning force microscopy and tunneling current images of a platinum(111) surface obtained by means of a 1 MHz quartz needle sensor. The low-frequency circuit of the tunneling current was combined with a high-frequency signal of the quartz resonator enabling full electrical operation of the sensor. The frequency shift and the tunneling current were detected simultaneously, while the feedback control loop of the topography signal was fed using one of them. In both cases, the free signal that was not connected to the feedback loop reveals proportional-integral controller errorlike behavior, which is governed by the time derivative of the topography signal. A procedure is proposed for determining the mechanical oscillation amplitude by utilizing the tunneling current also including the average tip-sample work function.

  1. A new approach in simulating RF linacs using a general, linear real-time signal processor

    International Nuclear Information System (INIS)

    Young, A.; Jachim, S.P.

    1991-01-01

    Strict requirements on the tolerances of the amplitude and phase of the radio frequency (RF) cavity field are necessary to advance the field of accelerator technology. Due to these stringent requirements upon modern accelerators,a new approach of modeling and simulating is essential in developing and understanding their characteristics. This paper describes the implementation of a general, linear model of an RF cavity which is used to develop a real-time signal processor. This device fully emulates the response of an RF cavity upon receiving characteristic parameters (Q 0 , ω 0 , Δω, R S , Z 0 ). Simulating an RF cavity with a real-time signal processor is beneficial to an accelerator designer because the device allows one to answer fundamental questions on the response of the cavity to a particular stimulus without operating the accelerator. In particular, the complex interactions between the RF power and the control systems, the beam and cavity fields can simply be observed in a real-time domain. The signal processor can also be used upon initialization of the accelerator as a diagnostic device and as a dummy load for determining the closed-loop error of the control system. In essence, the signal processor is capable of providing information that allows an operator to determine whether the control systems and peripheral devices are operating properly without going through the tedious procedure of running the beam through a cavity

  2. Radial plasma drifts deduced from VLF whistler mode signals - A modelling study

    Science.gov (United States)

    Poulter, E. M.; Andrews, M. K.; Bailey, G. J.; Moffett, R. J.

    1984-05-01

    VLF whistler mode signals have previously been used to infer radial plasma drifts in the equatorial plane of the plasmasphere and the field-aligned ionosphere-protonosphere coupling fluxes. Physical models of the plasmasphere consisting of O(+) adn H(+) ions along dipole magnetic field lines, and including radial E x B drifts, are applied to a mid-latitude flux tube appropriate to whistler mode signals received at Wellington, New Zealand, from the fixed frequency VLF transmitter NLK (18.6 kHz) in Seattle, U.S.A. These models are first shown to provide a good representation of the recorded Doppler shift and group delay data. They are then used to simulate the process of deducing the drifts and fluxes from the recorded data. Provided the initial whistler mode duct latitude and the ionospheric contributions are known, the drifts at the equatorial plane can be estimated to about + or - 20 m/s (approximately 10-15 percent), and the two hemisphere ionosphere-protonosphere coupling fluxes to about + or - 10 to the 12th/sq m-sec (approximately 40 percent).

  3. A simulation of the laser interferometer space antenna data stream from galactic white dwarf binaries

    International Nuclear Information System (INIS)

    Benacquista, M J; DeGoes, J; Lunder, D

    2004-01-01

    Gravitational radiation from the galactic population of white dwarf binaries is expected to produce a background signal in the laser interferometer space antenna (LISA) frequency band. At frequencies below 1 mHz, this signal is expected to be confusion limited and has been approximated as Gaussian noise. At frequencies above about 5 mHz, the signal will consist of separable individual sources. We have produced a simulation of the LISA data stream from a population of 90k galactic binaries in the frequency range between 1 and 5 mHz. This signal is compared with the simulated signal from globular cluster populations of binaries. Notable features of the simulation as well as potential data analysis schemes for extracting information are presented

  4. Predicting the performance of a power amplifier using large-signal circuit simulations of an AlGaN/GaN HFET model

    Science.gov (United States)

    Bilbro, Griff L.; Hou, Danqiong; Yin, Hong; Trew, Robert J.

    2009-02-01

    We have quantitatively modeled the conduction current and charge storage of an HFET in terms its physical dimensions and material properties. For DC or small-signal RF operation, no adjustable parameters are necessary to predict the terminal characteristics of the device. Linear performance measures such as small-signal gain and input admittance can be predicted directly from the geometric structure and material properties assumed for the device design. We have validated our model at low-frequency against experimental I-V measurements and against two-dimensional device simulations. We discuss our recent extension of our model to include a larger class of electron velocity-field curves. We also discuss the recent reformulation of our model to facilitate its implementation in commercial large-signal high-frequency circuit simulators. Large signal RF operation is more complex. First, the highest CW microwave power is fundamentally bounded by a brief, reversible channel breakdown in each RF cycle. Second, the highest experimental measurements of efficiency, power, or linearity always require harmonic load pull and possibly also harmonic source pull. Presently, our model accounts for these facts with an adjustable breakdown voltage and with adjustable load impedances and source impedances for the fundamental frequency and its harmonics. This has allowed us to validate our model for large signal RF conditions by simultaneously fitting experimental measurements of output power, gain, and power added efficiency of real devices. We show that the resulting model can be used to compare alternative device designs in terms of their large signal performance, such as their output power at 1dB gain compression or their third order intercept points. In addition, the model provides insight into new device physics features enabled by the unprecedented current and voltage levels of AlGaN/GaN HFETs, including non-ohmic resistance in the source access regions and partial depletion of

  5. ULF wave effects on high frequency signal propagation through the ionosphere

    Directory of Open Access Journals (Sweden)

    C. L. Waters

    2009-07-01

    Full Text Available Variations in the total electron content (TEC of the ionosphere alter the propagation characteristics of EM radiation for frequencies above a few megahertz (MHz. Spatial and temporal variations of the ionosphere TEC influence highly sensitive, ground based spatial measurements such as those used in radio astronomy and Global Positioning System (GPS applications. In this paper we estimate the magnitudes of the changes in TEC and the time delays of high frequency signals introduced by variations in the ionosphere electron density caused by the natural spectrum of ultra-low frequency (ULF wave activity that originates in near-Earth space. The time delays and associated phase shifts depend on the frequency, spatial structure and amplitude of the ULF waves.

  6. Quadratic Frequency Modulation Signals Parameter Estimation Based on Two-Dimensional Product Modified Parameterized Chirp Rate-Quadratic Chirp Rate Distribution.

    Science.gov (United States)

    Qu, Zhiyu; Qu, Fuxin; Hou, Changbo; Jing, Fulong

    2018-05-19

    In an inverse synthetic aperture radar (ISAR) imaging system for targets with complex motion, the azimuth echo signals of the target are always modeled as multicomponent quadratic frequency modulation (QFM) signals. The chirp rate (CR) and quadratic chirp rate (QCR) estimation of QFM signals is very important to solve the ISAR image defocus problem. For multicomponent QFM (multi-QFM) signals, the conventional QR and QCR estimation algorithms suffer from the cross-term and poor anti-noise ability. This paper proposes a novel estimation algorithm called a two-dimensional product modified parameterized chirp rate-quadratic chirp rate distribution (2D-PMPCRD) for QFM signals parameter estimation. The 2D-PMPCRD employs a multi-scale parametric symmetric self-correlation function and modified nonuniform fast Fourier transform-Fast Fourier transform to transform the signals into the chirp rate-quadratic chirp rate (CR-QCR) domains. It can greatly suppress the cross-terms while strengthening the auto-terms by multiplying different CR-QCR domains with different scale factors. Compared with high order ambiguity function-integrated cubic phase function and modified Lv's distribution, the simulation results verify that the 2D-PMPCRD acquires higher anti-noise performance and obtains better cross-terms suppression performance for multi-QFM signals with reasonable computation cost.

  7. Angle-of-arrival-based gesture recognition using ultrasonic multi-frequency signals

    KAUST Repository

    Chen, Hui; Ballal, Tarig; Saad, Mohamed; Al-Naffouri, Tareq Y.

    2017-01-01

    transducer. The 2-D angles of the moving hand are estimated using multi-frequency signals captured by a fixed receiver array. A simple redundant dictionary matching classifier is designed to recognize gestures representing the numbers from `0' to `9

  8. Time-Frequency Characterization of Cerebral Hemodynamics of Migraine Sufferers as Assessed by NIRS Signals

    Directory of Open Access Journals (Sweden)

    Filippo Molinari

    2010-01-01

    Full Text Available Near-infrared spectroscopy (NIRS is a noninvasive system for the real-time monitoring of the concentration of oxygenated (O2Hb and reduced (HHb hemoglobin in the brain cortex. O2Hb and HHb concentrations vary in response to cerebral autoregulation. Sixty-eight women (14 migraineurs without aura, 49 migraineurs with aura, and 5 controls performed breath-holding and hyperventilation during NIRS recordings. Signals were processed using the Choi-Williams time-frequency transform in order to measure the power variation of the very-low frequencies (VLF: 20–40 mHz and of the low frequencies (LF: 40–140 mHz. Results showed that migraineurs without aura present different LF and VLF power levels than controls and migraineurs with aura. The accurate power measurement of the time-frequency analysis allowed for the discrimination of the subjects' hemodynamic patterns. The time-frequency analysis of NIRS signals can be used in clinical practice to assess cerebral hemodynamics.

  9. Time-Frequency Characterization of Cerebral Hemodynamics of Migraine Sufferers as Assessed by NIRS Signals

    Directory of Open Access Journals (Sweden)

    Liboni William

    2010-01-01

    Full Text Available Abstract Near-infrared spectroscopy (NIRS is a noninvasive system for the real-time monitoring of the concentration of oxygenated ( and reduced (HHb hemoglobin in the brain cortex. and HHb concentrations vary in response to cerebral autoregulation. Sixty-eight women (14 migraineurs without aura, 49 migraineurs with aura, and 5 controls performed breath-holding and hyperventilation during NIRS recordings. Signals were processed using the Choi-Williams time-frequency transform in order to measure the power variation of the very-low frequencies (VLF: 20–40 mHz and of the low frequencies (LF: 40–140 mHz. Results showed that migraineurs without aura present different LF and VLF power levels than controls and migraineurs with aura. The accurate power measurement of the time-frequency analysis allowed for the discrimination of the subjects' hemodynamic patterns. The time-frequency analysis of NIRS signals can be used in clinical practice to assess cerebral hemodynamics.

  10. Periodic rotation noise induced by the crosstalk between two beat-frequency signals in multi-oscillator ring laser gyros

    International Nuclear Information System (INIS)

    Lu, Guangfeng; Wang, Zhiguo; Fan, Zhenfang; Luo, Hui

    2014-01-01

    Periodic rotation noise in the outputs of multi-oscillator ring laser gyros (MRLGs) is investigated in this paper for the first time. It is proved theoretically and experimentally that noise is induced by the crosstalk between two beat-frequency signals, which are combined from the left and right circularly polarized counter-propagating beams in MRLGs. Theoretical analysis and experimental results also indicate that the fundamental frequency of this noise is equal to the frequency difference between the two beat-frequency signals and the amplitude of the fundamental component is proportional to the crosstalk ratio between the two beat-frequency signals. Further, the amplitude of the nth-order component is proportional to the nth power of the crosstalk ratio. (paper)

  11. Readout for intersatellite laser interferometry: Measuring low frequency phase fluctuations of high-frequency signals with microradian precision

    DEFF Research Database (Denmark)

    Gerberding, Oliver; Diekmann, Christian; Kullmann, Joachim

    2015-01-01

    Precision phase readout of optical beat note signals is one of the core techniques required for inter-satellite laser interferometry. Future space based gravitational wave detectors like eLISA require such a readout over a wide range of MHz frequencies, due to orbit induced Doppler shifts...

  12. Methods of measurement signal acquisition from the rotational flow meter for frequency analysis

    Directory of Open Access Journals (Sweden)

    Świsulski Dariusz

    2017-01-01

    Full Text Available One of the simplest and commonly used instruments for measuring the flow of homogeneous substances is the rotational flow meter. The main part of such a device is a rotor (vane or screw rotating at a speed which is the function of the fluid or gas flow rate. A pulse signal with a frequency proportional to the speed of the rotor is obtained at the sensor output. For measurements in dynamic conditions, a variable interval between pulses prohibits the analysis of the measuring signal. Therefore, the authors of the article developed a method involving the determination of measured values on the basis of the last inter-pulse interval preceding the moment designated by the timing generator. For larger changes of the measured value at a predetermined time, the value can be determined by means of extrapolation of the two adjacent interpulse ranges, assuming a linear change in the flow. The proposed methods allow analysis which requires constant spacing between measurements, allowing for an analysis of the dynamics of changes in the test flow, eg. using a Fourier transform. To present the advantages of these methods simulations of flow measurement were carried out with a DRH-1140 rotor flow meter from the company Kobold.

  13. Multi-frequencies ECT algorithms to remove sodium noise in ISI of ferromagnetic SG tubes of FBR

    International Nuclear Information System (INIS)

    Mihalache, Ovidiu

    2012-01-01

    The paper presents developments and application of multi-frequency eddy current to be used during In-Service Inspection (ISI) of ferromagnetic steam generator (SG) tubes of Fast Breeder Reactors (FBR). Signal enhancement by means of multi-frequency ECT techniques are validated through 3D simulations of both signals and noise due to sodium forms around SG tube or SP. The purpose of such algorithms is to remove from ECT signal the electromagnetic noise resulting from sodium accumulated outside of SG tubes after SG vessel draining. Finite element method (FEM) simulations are used to analyse different sodium build-up scenarios observed experimentally, and to determine optimal multi-frequency ECT algorithms to suppress the most efficiently sodium noise. Also a new 'window multi-frequency' algorithm is applied and validated using 3-dimensional FEM simulations of SP and sodium forms. (author)

  14. SETI - A preliminary search for narrowband signals at microwave frequencies

    Science.gov (United States)

    Cuzzi, J. N.; Clark, T. A.; Tarter, J. C.; Black, D. C.

    1977-01-01

    In the search for intelligent signals of extraterrestrial origin, certain forms of signals merit immediate and special attention. Extremely narrowband signals of spectral width similar to our own television transmissions are most favored energetically and least likely to be confused with natural celestial emission. A search of selected stars has been initiated using observational and data processing techniques optimized for the detection of such signals. These techniques allow simultaneous observation of 10 to the 5th to 10 to the 6th channels within the observed spectral range. About two hundred nearby (within 80 LY) solar type stars have been observed at frequencies near the main microwave transitions of the hydroxyl radical. In addition, several molecular (hydroxyl) masers and other non-thermal sources have been observed in this way in order to uncover any possible fine spectral structure of natural origin and to investigate the potential of such an instrument for radioastronomy.

  15. Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

    Directory of Open Access Journals (Sweden)

    K. Tatsuta

    2015-11-01

    Full Text Available We investigate quantitatively the effect of geomagnetic storms on the sub-ionospheric VLF/LF (Very Low Frequency/Low Frequency propagations for different latitudes based on 2-year nighttime data from Japanese VLF/LF observation network. Three statistical parameters such as average signal amplitude, variability of the signal amplitude, and nighttime fluctuation were calculated daily for 2 years for 16–21 independent VLF/LF transmitter–receiver propagation paths consisting of three transmitters and seven receiving stations. These propagation paths are suitable to simultaneously study high-latitude, low-mid-latitude and mid-latitude D/E-region ionospheric properties. We found that these three statistical parameters indicate significant anomalies exceeding at least 2 times of their standard deviation from the mean value during the geomagnetic storm time period in the high-latitude paths with an occurrence rate of anomaly between 40 and 50 % presumably due to the auroral energetic electron precipitation. The mid-latitude and low-mid-latitude paths have a smaller influence from the geomagnetic activity because of a lower occurrence rate of anomalies even during the geomagnetically active time period (from 20 to 30 %. The anomalies except geomagnetic storm periods may be caused by atmospheric and/or lithospheric origins. The statistical occurrence rates of ionospheric anomalies for different latitudinal paths during geomagnetic storm and non-storm time periods are basic and important information not only to identify the space weather effects toward the lower ionosphere depending on the latitudes but also to separate various external physical causes of lower ionospheric disturbances.

  16. Mid-infrared-to-mid-ultraviolet supercontinuum enhanced by third-to-fifteenth odd harmonics.

    Science.gov (United States)

    Mitrofanov, A V; Voronin, A A; Mitryukovskiy, S I; Sidorov-Biryukov, D A; Pugžlys, A; Andriukaitis, G; Flöry, T; Stepanov, E A; Fedotov, A B; Baltuška, A; Zheltikov, A M

    2015-05-01

    A high-energy supercontinuum spanning 4.7 octaves, from 250 to 6500 nm, is generated using a 0.3-TW, 3.9-μm output of a mid-infrared optical parametric chirped-pulse amplifier as a driver inducing a laser filament in the air. The high-frequency wing of the supercontinuum spectrum is enhanced by odd-order optical harmonics of the mid-infrared driver. Optical harmonics up to the 15th order are observed in supercontinuum spectra as overlapping, yet well-resolved peaks broadened, as verified by numerical modeling, due to spatially nonuniform ionization-induced blue shift.

  17. Frequency response testing at Experimental Breeder Reactor II using discrete-level periodic signals

    International Nuclear Information System (INIS)

    Rhodes, W.D.; Larson, H.A.

    1990-01-01

    The Experimental Breeder Reactor 2 (EBR-2) reactivity-to-power frequency-response function was measured with pseudo-random, discrete-level, periodic signals. The reactor power deviation was small with insignificant perturbation of normal operation and in-place irradiation experiments. Comparison of results with measured rod oscillator data and with theoretical predictions show good agreement. Moreover, measures of input signal quality (autocorrelation function and energy spectra) confirm the ability to enable this type of frequency response determination at EBR-2. Measurements were made with the pseudo-random binary sequence, quadratic residue binary sequence, pseudo-random ternary sequence, and the multifrequency binary sequence. 10 refs., 7 figs., 3 tabs

  18. Time–frequency analysis of nonstationary complex magneto-hydro-dynamics in fusion plasma signals using the Choi–Williams distribution

    International Nuclear Information System (INIS)

    Xu, L.Q.; Hu, L.Q.; Chen, K.Y.; Li, E.Z.

    2013-01-01

    Highlights: • Choi–Williams distribution yields excellent time–frequency resolution for discrete signal. • CWD method provides clear time–frequency pictures of EAST and HT-7 fast MHD events. • CWD method has advantages to wavelets transform scalogram and the short-time Fourier transform spectrogram. • We discuss about how to choose the windows and free parameter of CWD method. -- Abstract: The Choi–Williams distribution is applied to the time–frequency analysis of signals describing rapid magneto-hydro-dynamic (MHD) modes and events in tokamak plasmas. A comparison is made with Soft X-ray (SXR) signals as well as Mirnov signal that shows the advantages of the Choi–Williams distribution over both continuous wavelets transform scalogram and the short-time Fourier transform spectrogram. Examples of MHD activities in HT-7 and EAST tokamak are shown, namely the onset of coupling tearing modes, high frequency precursors of sawtooth, and low frequency MHD instabilities in edge localized mode (ELM) free in H mode discharge

  19. System and method for earth probing with deep subsurface penetration using low frequency electromagnetic signals

    International Nuclear Information System (INIS)

    Etten, P. van; Brown, R.D.

    1996-01-01

    An earth probing system uses deep penetration of electromagnetic waves into soil and other media. Advantage is taken of lower attenuation of radar in soil by frequencies of about three megahertz or less. Bursts of electromagnetic energy of various frequencies in this range are consecutively transmitted. The transmitting antenna is continuously tuned, so as to maintain resonance during each burst, allowing large circulating currents and high power output. In a receiving antenna system, a dual antenna arrangement is providing for obtaining improved reception. A corresponding dual antenna circuit employs 'a spatial notch filtering', automatic adjustment of antenna gain-frequency variations, as well as compensation for transmitter gain variation. The system may be implemented in a totally analog, totally digital, or hybrid manner. Preferably, a signal processing method detected and digitally samples signal reflected from subsurface layers and buried objects. The invention provides means for removing system distortions and interfering signals, for compensating for aliasing errors and frequency-dependent antenna gain and phase variations, and for avoiding masking errors introduced by strong reflections. (author)

  20. High power frequency comb based on mid-infrared quantum cascade laser at λ ∼ 9 μm

    International Nuclear Information System (INIS)

    Lu, Q. Y.; Razeghi, M.; Slivken, S.; Bandyopadhyay, N.; Bai, Y.; Zhou, W. J.; Chen, M.; Heydari, D.; Haddadi, A.; McClintock, R.; Amanti, M.; Sirtori, C.

    2015-01-01

    We investigate a frequency comb source based on a mid-infrared quantum cascade laser at λ ∼ 9 μm with high power output. A broad flat-top gain with near-zero group velocity dispersion has been engineered using a dual-core active region structure. This favors the locking of the dispersed Fabry-Pérot modes into equally spaced frequency lines via four wave mixing. A current range with a narrow intermode beating linewidth of 3 kHz is identified with a fast detector and spectrum analyzer. This range corresponds to a broad spectral coverage of 65 cm −1 and a high power output of 180 mW for ∼176 comb modes

  1. Femtosecond few-cycle mid-infrared laser pulses

    DEFF Research Database (Denmark)

    Liu, Xing

    The few-cycle pulses of mid-infrared (mid-IR, wavelength 2-10 microns) have attracted increasing attention owing to their great potentials for high order harmonic generation, time-resolved spectroscopy, precision of cutting and biomedical science.In this thesis, mid-IR frequency conversion.......2 - 5.5 μm with only one fixed pump wavelength, a feature absent in Kerr media. Finally, we experimentally observe supercontinuum generation spanning 1.5 octaves, generated in a 10 mm long silicon-rich nitride waveguide pumped by 100 pJ femtosecond pulses from an erbium fiber laser. The waveguide has...

  2. Time-frequency analysis of fusion plasma signals beyond the short-time Fourier transform paradigm: An overview

    International Nuclear Information System (INIS)

    Bizarro, Joao P.S.; Figueiredo, Antonio C.A.

    2008-01-01

    Performing a time-frequency (t-f) analysis on actual magnetic pick-up coil data from the JET tokamak, a comparison is presented between the spectrogram and the Wigner and Choi-Williams distributions. Whereas the former, which stems from the short-time Fourier transform and has been the work-horse for t-f signal processing, implies an unavoidable trade-off between time and frequency resolutions, the latter two belong to a later generation of distributions that yield better, if not optimal joint t-f localization. Topics addressed include signal representation in the t-f plane, frequency identification and evolution, instantaneous-frequency estimation, and amplitude tracking

  3. Small-signal analysis and particle-in-cell simulations of planar dielectric Cherenkov masers for use as high-frequency, moderate-power broadband amplifiers

    International Nuclear Information System (INIS)

    Carlsten, Bruce E.

    2002-01-01

    A small-signal gain analysis of the planar dielectric Cherenkov maser is presented. The analysis results in a Pierce gain solution, with three traveling-wave modes. The analysis shows that the dielectric Cherenkov maser has a remarkable broadband tuning ability near cutoff, while maintaining reasonable gain rates. Numerical simulations verifying the small-signal gain results are presented, using a particle-in-cell code adapted specifically for planar traveling-wave tubes. An instantaneous bandwidth is numerically shown to be very large, and saturated efficiency for a nominal high-power design is shown to be in the range of standard untapered traveling-wave tubes

  4. Evaluation of potential severe accidents during low power and shutdown operations at Surry, Unit 1: Analysis of core damage frequency from internal floods during mid-loop operations. Volume 4

    International Nuclear Information System (INIS)

    Kohut, P.

    1994-07-01

    The major objective of the Surry internal flood analysis was to provide an improved understanding of the core damage scenarios arising from internal flood-related events. The mean core damage frequency of the Surry plant due to internal flood events during mid-loop operations is 4.8E-06 per year, and the 5th and 95th percentiles are 2.2E-07 and 1.8E-05 per year, respectively. Some limited sensitivity calculations were performed on three plant improvement options. The most significant result involves modifications of intake-level structure on the canal, which reduced core damage frequency contribution from floods in mid-loop by about 75%

  5. Wideband Radar Echo Frequency-domain Simulation and Analysis for High Speed Moving Targets

    Directory of Open Access Journals (Sweden)

    Ning Chao

    2014-04-01

    Full Text Available A frequency-domain method is proposed for wideband radar echo simulation of high-speed moving targets. Based on the physical process of electromagnetic waves observing a moving target, a frequency-domain echo model of wideband radar is constructed, and the block diagram of the radar echo simulation in frequency-domain is presented. Then, the impacts of radial velocity and slant range on the matching filtering of LFM radar are analyzed, and some quantitative conclusions on the shift and expansion of the radar profiles are obtained. Simulation results illustrate the correctness and efficiency of the proposed method.

  6. Observing System Simulation Experiments (OSSEs) for the Mid-Columbia Basin

    Energy Technology Data Exchange (ETDEWEB)

    Zack, J; Natenberg, E J; Knowe, G V; Waight, K; Manobianco, J; Hanley, D; Kamath, C

    2011-09-13

    The overall goal of this multi-phased research project known as WindSENSE is to develop an observation system deployment strategy that would improve wind power generation forecasts. The objective of the deployment strategy is to produce the maximum benefit for 1- to 6-hour ahead forecasts of wind speed at hub-height ({approx}80 m). In this phase of the project the focus is on the Mid-Columbia Basin region, which encompasses the Bonneville Power Administration (BPA) wind generation area (Figure 1) that includes the Klondike, Stateline, and Hopkins Ridge wind plants. There are two tasks in the current project effort designed to validate the Ensemble Sensitivity Analysis (ESA) observational system deployment approach in order to move closer to the overall goal: (1) Perform an Observing System Experiment (OSE) using a data denial approach. The results of this task are presented in a separate report. (2) Conduct a set of Observing System Simulation Experiments (OSSE) for the Mid-Colombia basin region. This report presents the results of the OSSE task. The specific objective is to test strategies for future deployment of observing systems in order to suggest the best and most efficient ways to improve wind forecasting at BPA wind farm locations. OSSEs have been used for many years in meteorology to evaluate the potential impact of proposed observing systems, determine tradeoffs in instrument design, and study the most effective data assimilation methodologies to incorporate the new observations into numerical weather prediction (NWP) models (Atlas 1997; Lord 1997). For this project, a series of OSSEs will allow consideration of the impact of new observing systems of various types and in various locations.

  7. Frequency modulation television analysis: Distortion analysis

    Science.gov (United States)

    Hodge, W. H.; Wong, W. H.

    1973-01-01

    Computer simulation is used to calculate the time-domain waveform of standard T-pulse-and-bar test signal distorted in passing through an FM television system. The simulator includes flat or preemphasized systems and requires specification of the RF predetection filter characteristics. The predetection filters are modeled with frequency-symmetric Chebyshev (0.1-db ripple) and Butterworth filters. The computer was used to calculate distorted output signals for sixty-four different specified systems, and the output waveforms are plotted for all sixty-four. Comparison of the plotted graphs indicates that a Chebyshev predetection filter of four poles causes slightly more signal distortion than a corresponding Butterworth filter and the signal distortion increases as the number of poles increases. An increase in the peak deviation also increases signal distortion. Distortion also increases with the addition of preemphasis.

  8. Corticomuscular transmission of tremor signals by propriospinal neurons in Parkinson's disease.

    Directory of Open Access Journals (Sweden)

    Manzhao Hao

    Full Text Available Cortical oscillatory signals of single and double tremor frequencies act together to cause tremor in the peripheral limbs of patients with Parkinson's disease (PD. But the corticospinal pathway that transmits the tremor signals has not been clarified, and how alternating bursts of antagonistic muscle activations are generated from the cortical oscillatory signals is not well understood. This paper investigates the plausible role of propriospinal neurons (PN in C3-C4 in transmitting the cortical oscillatory signals to peripheral muscles. Kinematics data and surface electromyogram (EMG of tremor in forearm were collected from PD patients. A PN network model was constructed based on known neurophysiological connections of PN. The cortical efferent signal of double tremor frequencies were integrated at the PN network, whose outputs drove the muscles of a virtual arm (VA model to simulate tremor behaviors. The cortical efferent signal of single tremor frequency actuated muscle spindles. By comparing tremor data of PD patients and the results of model simulation, we examined two hypotheses regarding the corticospinal transmission of oscillatory signals in Parkinsonian tremor. Hypothesis I stated that the oscillatory cortical signals were transmitted via the mono-synaptic corticospinal pathways bypassing the PN network. The alternative hypothesis II stated that they were transmitted by way of PN multi-synaptic corticospinal pathway. Simulations indicated that without the PN network, the alternating burst patterns of antagonistic muscle EMGs could not be reliably generated, rejecting the first hypothesis. However, with the PN network, the alternating burst patterns of antagonist EMGs were naturally reproduced under all conditions of cortical oscillations. The results suggest that cortical commands of single and double tremor frequencies are further processed at PN to compute the alternating burst patterns in flexor and extensor muscles, and the

  9. Corticomuscular transmission of tremor signals by propriospinal neurons in Parkinson's disease.

    Science.gov (United States)

    Hao, Manzhao; He, Xin; Xiao, Qin; Alstermark, Bror; Lan, Ning

    2013-01-01

    Cortical oscillatory signals of single and double tremor frequencies act together to cause tremor in the peripheral limbs of patients with Parkinson's disease (PD). But the corticospinal pathway that transmits the tremor signals has not been clarified, and how alternating bursts of antagonistic muscle activations are generated from the cortical oscillatory signals is not well understood. This paper investigates the plausible role of propriospinal neurons (PN) in C3-C4 in transmitting the cortical oscillatory signals to peripheral muscles. Kinematics data and surface electromyogram (EMG) of tremor in forearm were collected from PD patients. A PN network model was constructed based on known neurophysiological connections of PN. The cortical efferent signal of double tremor frequencies were integrated at the PN network, whose outputs drove the muscles of a virtual arm (VA) model to simulate tremor behaviors. The cortical efferent signal of single tremor frequency actuated muscle spindles. By comparing tremor data of PD patients and the results of model simulation, we examined two hypotheses regarding the corticospinal transmission of oscillatory signals in Parkinsonian tremor. Hypothesis I stated that the oscillatory cortical signals were transmitted via the mono-synaptic corticospinal pathways bypassing the PN network. The alternative hypothesis II stated that they were transmitted by way of PN multi-synaptic corticospinal pathway. Simulations indicated that without the PN network, the alternating burst patterns of antagonistic muscle EMGs could not be reliably generated, rejecting the first hypothesis. However, with the PN network, the alternating burst patterns of antagonist EMGs were naturally reproduced under all conditions of cortical oscillations. The results suggest that cortical commands of single and double tremor frequencies are further processed at PN to compute the alternating burst patterns in flexor and extensor muscles, and the neuromuscular dynamics

  10. Simulation and fabrication of 0-3 composite PZT films for ultrahigh frequency (100-300 MHz) ultrasonic transducers

    Science.gov (United States)

    Chen, Xiaoyang; Fei, Chunlong; Chen, Zeyu; Chen, Ruimin; Yu, Ping; Chen, Zhongping; Shung, K. Kirk; Zhou, Qifa

    2016-03-01

    This paper presents simulation, fabrication, and characterization of single-element ultrahigh frequency (100-300-MHz) needle ultrasonic transducers based on 0-3 composite Pb(Zr0.52Ti0.48)O3 (PZT) films prepared by using composite ceramic sol-gel film and sol-infiltration technique. The center frequency of the developed transducer at 300-MHz was the highest frequency of PbTiO3 ceramic-based ultrasonic transducers ever reported. Furthermore, a brief description of the composite model was followed by the development of a new expression for predicting the longitudinal velocity, the clamped dielectric constant, and the complex electromechanical coupling coefficient kt of these films, which is very important in ultrasonic transducer design. Moreover, these parameters are difficult to obtain by measuring the frequency dependence of impedance and phase angle because of the weak signal of the previous 0-3 composite films transducer (>100 MHz). The modeling results show that the Cubes model with a geometric factor n = 0.05 fits well with the measured data. This model will be helpful for developing the 0-3 composite systems for ultrahigh frequency ultrasonic transducer design.

  11. Dead-Time Generation in Six-Phase Frequency Inverter

    Directory of Open Access Journals (Sweden)

    Aurelijus Pitrėnas

    2016-06-01

    Full Text Available In this paper control of multi-phase induction drives is discussed. Structure of six-phase frequency inverter is examined. The article deals with dead-time generation circuits in six-phase frequency inverter for transistor control signals. Computer models of dead-time circuits is created using LTspice software package. Simulation results are compared with experimental results of the tested dead-time circuits. Parameters obtained in simulation results are close to the parameters obtained in experimental results.

  12. Traveltime Dispersion in an Isotropic Elastic Mantle: Dominance of the Lower Mantle Signal in Differential-frequency Time Residuals

    Science.gov (United States)

    Schuberth, B. S. A.; Zaroli, C.; Nolet, G.

    2014-12-01

    We study wavefield effects in elastic isotropic 3-D seismic structures derived from the temperature field of a high resolution mantle circulation model. More specifically, we quantify the structural dispersion of traveltime residuals of direct P- and S-waves in a model with realistic length-scales and magnitudes of the variations in seismic velocities and density. 3-D global wave propagation is simulated using a spectral element method, and traveltime residuals are measured in four different frequency bands by cross-correlation of 3-D and 1-D synthetic waveforms. Intrinsic (dissipative) attenuation is deliberately neglected, so that any variation of traveltimes with frequency can be attributed to structural effects. Additional simulations are performed for a model in which 3-D structure is removed in the upper 800 km to isolate the dispersion signal of the lower mantle. One question that we address is whether the structural length-scales inherent to a vigorously convecting mantle give rise to significant body-wave dispersion. In our synthetic dataset, the difference between long-period and short-period traveltime residuals generally increases with increasing short-period residual. However, we do not find an exact linear dependence, and in case of P-waves even non-monotonic behaviour. At largest short-period residuals, average dispersion is on the order of 2 s for both P- and S-waves and even larger when structure is confined to the lower mantle. Dispersion also appears to be asymmetric; that is, larger for negative than for positive residuals. The standard deviations of both P- and S-wave residuals also increase with increasing period and we discuss possible explanations for this behaviour. Overall, wavefield effects in both models are generally stronger for P-waves than for S-waves at the same frequencies. We also find that for certain combinations of periods, the difference between the respective residuals is very similar between the "whole mantle" and the "lower

  13. Tidal Analysis Using Time–Frequency Signal Processing and Information Clustering

    Directory of Open Access Journals (Sweden)

    Antonio M. Lopes

    2017-07-01

    Full Text Available Geophysical time series have a complex nature that poses challenges to reaching assertive conclusions, and require advanced mathematical and computational tools to unravel embedded information. In this paper, time–frequency methods and hierarchical clustering (HC techniques are combined for processing and visualizing tidal information. In a first phase, the raw data are pre-processed for estimating missing values and obtaining dimensionless reliable time series. In a second phase, the Jensen–Shannon divergence is adopted for measuring dissimilarities between data collected at several stations. The signals are compared in the frequency and time–frequency domains, and the HC is applied to visualize hidden relationships. In a third phase, the long-range behavior of tides is studied by means of power law functions. Numerical examples demonstrate the effectiveness of the approach when dealing with a large volume of real-world data.

  14. Versatile silicon-waveguide supercontinuum for coherent mid-infrared spectroscopy

    Science.gov (United States)

    Nader, Nima; Maser, Daniel L.; Cruz, Flavio C.; Kowligy, Abijith; Timmers, Henry; Chiles, Jeff; Fredrick, Connor; Westly, Daron A.; Nam, Sae Woo; Mirin, Richard P.; Shainline, Jeffrey M.; Diddams, Scott

    2018-03-01

    Laser frequency combs, with their unique combination of precisely defined spectral lines and broad bandwidth, are a powerful tool for basic and applied spectroscopy. Here, we report offset-free, mid-infrared frequency combs and dual-comb spectroscopy through supercontinuum generation in silicon-on-sapphire waveguides. We leverage robust fabrication and geometrical dispersion engineering of nanophotonic waveguides for multi-band, coherent frequency combs spanning 70 THz in the mid-infrared (2.5 μm-6.2 μm). Precise waveguide fabrication provides significant spectral broadening with engineered spectra targeted at specific mid-infrared bands. We characterize the relative-intensity-noise of different bands and show that the measured levels do not pose any limitation for spectroscopy applications. Additionally, we use the fabricated photonic devices to demonstrate dual-comb spectroscopy of a carbonyl sulfide gas sample at 5 μm. This work forms the technological basis for applications such as point sensors for fundamental spectroscopy, atmospheric chemistry, trace and hazardous gas detection, and biological microscopy.

  15. Versatile silicon-waveguide supercontinuum for coherent mid-infrared spectroscopy

    Directory of Open Access Journals (Sweden)

    Nima Nader

    2018-03-01

    Full Text Available Laser frequency combs, with their unique combination of precisely defined spectral lines and broad bandwidth, are a powerful tool for basic and applied spectroscopy. Here, we report offset-free, mid-infrared frequency combs and dual-comb spectroscopy through supercontinuum generation in silicon-on-sapphire waveguides. We leverage robust fabrication and geometrical dispersion engineering of nanophotonic waveguides for multi-band, coherent frequency combs spanning 70 THz in the mid-infrared (2.5 μm–6.2 μm. Precise waveguide fabrication provides significant spectral broadening with engineered spectra targeted at specific mid-infrared bands. We characterize the relative-intensity-noise of different bands and show that the measured levels do not pose any limitation for spectroscopy applications. Additionally, we use the fabricated photonic devices to demonstrate dual-comb spectroscopy of a carbonyl sulfide gas sample at 5 μm. This work forms the technological basis for applications such as point sensors for fundamental spectroscopy, atmospheric chemistry, trace and hazardous gas detection, and biological microscopy.

  16. Integrated circuit for processing a low-frequency signal from a seismic detector

    Energy Technology Data Exchange (ETDEWEB)

    Malashevich, N. I.; Roslyakov, A. S.; Polomoshnov, S. A., E-mail: S.Polomoshnov@tsen.ru; Fedorov, R. A. [Research and Production Complex ' Technological Center' of the Moscow Institute of Electronic Technology (Russian Federation)

    2011-12-15

    Specific features for the detection and processing of a low-frequency signal from a seismic detector are considered in terms of an integrated circuit based on a large matrix crystal of the 5507 series. This integrated circuit is designed for the detection of human movements. The specific features of the information signal, obtained at the output of the seismic detector, and the main characteristics of the integrated circuit and its structure are reported.

  17. Investigating Strength and Frequency Effects in Recognition Memory Using Type-2 Signal Detection Theory

    Science.gov (United States)

    Higham, Philip A.; Perfect, Timothy J.; Bruno, Davide

    2009-01-01

    Criterion- versus distribution-shift accounts of frequency and strength effects in recognition memory were investigated with Type-2 signal detection receiver operating characteristic (ROC) analysis, which provides a measure of metacognitive monitoring. Experiment 1 demonstrated a frequency-based mirror effect, with a higher hit rate and lower…

  18. Parallel simulation of radio-frequency plasma discharges

    International Nuclear Information System (INIS)

    Fivaz, M.; Howling, A.; Ruegsegger, L.; Schwarzenbach, W.; Baeumle, B.

    1994-01-01

    The 1D Particle-In-Cell and Monte Carlo collision code XPDP1 is used to model radio-frequency argon plasma discharges. The code runs faster on a single-user parallel system called MUSIC than on a CRAY-YMP. The low cost of the MUSIC system allows a 24-hours-per-day use and the simulation results are available one to two orders of magnitude quicker than with a super computer shared with other users. The parallelization strategy and its implementation are discussed. Very good agreement is found between simulation results and measurements done in an experimental argon discharge. (author) 2 figs., 3 refs

  19. Bispectral pairwise interacting source analysis for identifying systems of cross-frequency interacting brain sources from electroencephalographic or magnetoencephalographic signals

    Science.gov (United States)

    Chella, Federico; Pizzella, Vittorio; Zappasodi, Filippo; Nolte, Guido; Marzetti, Laura

    2016-05-01

    Brain cognitive functions arise through the coordinated activity of several brain regions, which actually form complex dynamical systems operating at multiple frequencies. These systems often consist of interacting subsystems, whose characterization is of importance for a complete understanding of the brain interaction processes. To address this issue, we present a technique, namely the bispectral pairwise interacting source analysis (biPISA), for analyzing systems of cross-frequency interacting brain sources when multichannel electroencephalographic (EEG) or magnetoencephalographic (MEG) data are available. Specifically, the biPISA makes it possible to identify one or many subsystems of cross-frequency interacting sources by decomposing the antisymmetric components of the cross-bispectra between EEG or MEG signals, based on the assumption that interactions are pairwise. Thanks to the properties of the antisymmetric components of the cross-bispectra, biPISA is also robust to spurious interactions arising from mixing artifacts, i.e., volume conduction or field spread, which always affect EEG or MEG functional connectivity estimates. This method is an extension of the pairwise interacting source analysis (PISA), which was originally introduced for investigating interactions at the same frequency, to the study of cross-frequency interactions. The effectiveness of this approach is demonstrated in simulations for up to three interacting source pairs and for real MEG recordings of spontaneous brain activity. Simulations show that the performances of biPISA in estimating the phase difference between the interacting sources are affected by the increasing level of noise rather than by the number of the interacting subsystems. The analysis of real MEG data reveals an interaction between two pairs of sources of central mu and beta rhythms, localizing in the proximity of the left and right central sulci.

  20. Simulating Terrorism: Credible Commitment, Costly Signaling, and Strategic Behavior

    Science.gov (United States)

    Siegel, David A.; Young, Joseph K.

    2009-01-01

    We present two simulations designed to convey the strategic nature of terrorism and counterterrorism. The first is a simulated hostage crisis, designed primarily to illustrate the concepts of credible commitment and costly signaling. The second explores high-level decision making of both a terrorist group and the state, and is designed to…

  1. Time-frequency feature analysis and recognition of fission neutrons signal based on support vector machine

    International Nuclear Information System (INIS)

    Jin Jing; Wei Biao; Feng Peng; Tang Yuelin; Zhou Mi

    2010-01-01

    Based on the interdependent relationship between fission neutrons ( 252 Cf) and fission chain ( 235 U system), the paper presents the time-frequency feature analysis and recognition in fission neutron signal based on support vector machine (SVM) through the analysis on signal characteristics and the measuring principle of the 252 Cf fission neutron signal. The time-frequency characteristics and energy features of the fission neutron signal are extracted by using wavelet decomposition and de-noising wavelet packet decomposition, and then applied to training and classification by means of support vector machine based on statistical learning theory. The results show that, it is effective to obtain features of nuclear signal via wavelet decomposition and de-noising wavelet packet decomposition, and the latter can reflect the internal characteristics of the fission neutron system better. With the training accomplished, the SVM classifier achieves an accuracy rate above 70%, overcoming the lack of training samples, and verifying the effectiveness of the algorithm. (authors)

  2. Imaging of endogenous exchangeable proton signals in the human brain using frequency labeled exchange transfer imaging.

    Science.gov (United States)

    Yadav, Nirbhay N; Jones, Craig K; Hua, Jun; Xu, Jiadi; van Zijl, Peter C M

    2013-04-01

    To image endogenous exchangeable proton signals in the human brain using a recently reported method called frequency labeled exchange transfer (FLEX) MRI. As opposed to labeling exchangeable protons using saturation (i.e., chemical exchange saturation transfer, or CEST), FLEX labels exchangeable protons with their chemical shift evolution. The use of short high-power frequency pulses allows more efficient labeling of rapidly exchanging protons, while time domain acquisition allows removal of contamination from semi-solid magnetization transfer effects. FLEX-based exchangeable proton signals were detected in human brain over the 1-5 ppm frequency range from water. Conventional magnetization transfer contrast and the bulk water signal did not interfere in the FLEX spectrum. The information content of these signals differed from in vivo CEST data in that the average exchange rate of these signals was 350-400 s(-1) , much faster than the amide signal usually detected using direct saturation (∼30 s(-1) ). Similarly, fast exchanging protons could be detected in egg white in the same frequency range where amide and amine protons of mobile proteins and peptides are known to resonate. FLEX MRI in the human brain preferentially detects more rapidly exchanging amide/amine protons compared to traditional CEST experiments, thereby changing the information content of the exchangeable proton spectrum. This has the potential to open up different types of endogenous applications as well as more easy detection of rapidly exchanging protons in diaCEST agents or fast exchanging units such as water molecules in paracest agents without interference of conventional magnetization transfer contrast. Copyright © 2013 Wiley Periodicals, Inc.

  3. On the Frequency Correction in Temperature-Modulated Differential Scanning Calorimetry of Glass Transition

    DEFF Research Database (Denmark)

    Guo, Xiaoju; Mauro, J.C.; Allan, D.C.

    2012-01-01

    Temperature-modulated differential scanning calorimetry (TMDSC) is based on conventional DSC but with a sinusoidally modulated temperature path. Simulations of TMDSC signals were performed for Corning EAGLE XG® glass over a wide range of modulation frequencies. Our results reveal that the frequency...... correction commonly used in the interpretation of TMDSC signals leads to a master nonreversing heat flow curve independent of modulation frequency, provided that sufficiently high frequencies are employed in the TMDSC measurement. A master reversing heat flow curve can also be generated through the frequency...

  4. Power system low frequency oscillation mode estimation using wide area measurement systems

    Directory of Open Access Journals (Sweden)

    Papia Ray

    2017-04-01

    Full Text Available Oscillations in power systems are triggered by a wide variety of events. The system damps most of the oscillations, but a few undamped oscillations may remain which may lead to system collapse. Therefore low frequency oscillations inspection is necessary in the context of recent power system operation and control. Ringdown portion of the signal provides rich information of the low frequency oscillatory modes which has been taken into analysis. This paper provides a practical case study in which seven signal processing based techniques i.e. Prony Analysis (PA, Fast Fourier Transform (FFT, S-Transform (ST, Wigner-Ville Distribution (WVD, Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT, Hilbert-Huang Transform (HHT and Matrix Pencil Method (MPM were presented for estimating the low frequency modes in a given ringdown signal. Preprocessing of the signal is done by detrending. The application of the signal processing techniques is illustrated using actual wide area measurement systems (WAMS data collected from four different Phasor Measurement Unit (PMU i.e. Dadri, Vindyachal, Kanpur and Moga which are located near the recent disturbance event at the Northern Grid of India. Simulation results show that the seven signal processing technique (FFT, PA, ST, WVD, ESPRIT, HHT and MPM estimates two common oscillatory frequency modes (0.2, 0.5 from the raw signal. Thus, these seven techniques provide satisfactory performance in determining small frequency modes of the signal without losing its valuable property. Also a comparative study of the seven signal processing techniques has been carried out in order to find the best one. It was found that FFT and ESPRIT gives exact frequency modes as compared to other techniques, so they are recommended for estimation of low frequency modes. Further investigations were also carried out to estimate low frequency oscillatory mode with another case study of Eastern Interconnect Phasor Project

  5. Low frequency temperature forcing of chemical oscillations.

    Science.gov (United States)

    Novak, Jan; Thompson, Barnaby W; Wilson, Mark C T; Taylor, Annette F; Britton, Melanie M

    2011-07-14

    The low frequency forcing of chemical oscillations by temperature is investigated experimentally in the Belousov-Zhabotinsky (BZ) reaction and in simulations of the Oregonator model with Arrhenius temperature dependence of the rate constants. Forcing with temperature leads to modulation of the chemical frequency. The number of response cycles per forcing cycle is given by the ratio of the natural frequency to the forcing frequency and phase locking is only observed in simulations when this ratio is a whole number and the forcing amplitude is small. The global temperature forcing of flow-distributed oscillations in a tubular reactor is also investigated and synchronisation is observed in the variation of band position with the external signal, reflecting the periodic modulation of chemical oscillations by temperature.

  6. Modeling the frequency of opposing left-turn conflicts at signalized intersections using generalized linear regression models.

    Science.gov (United States)

    Zhang, Xin; Liu, Pan; Chen, Yuguang; Bai, Lu; Wang, Wei

    2014-01-01

    The primary objective of this study was to identify whether the frequency of traffic conflicts at signalized intersections can be modeled. The opposing left-turn conflicts were selected for the development of conflict predictive models. Using data collected at 30 approaches at 20 signalized intersections, the underlying distributions of the conflicts under different traffic conditions were examined. Different conflict-predictive models were developed to relate the frequency of opposing left-turn conflicts to various explanatory variables. The models considered include a linear regression model, a negative binomial model, and separate models developed for four traffic scenarios. The prediction performance of different models was compared. The frequency of traffic conflicts follows a negative binominal distribution. The linear regression model is not appropriate for the conflict frequency data. In addition, drivers behaved differently under different traffic conditions. Accordingly, the effects of conflicting traffic volumes on conflict frequency vary across different traffic conditions. The occurrences of traffic conflicts at signalized intersections can be modeled using generalized linear regression models. The use of conflict predictive models has potential to expand the uses of surrogate safety measures in safety estimation and evaluation.

  7. High power frequency comb based on mid-infrared quantum cascade laser at λ ∼ 9 μm

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Q. Y.; Razeghi, M., E-mail: razeghi@eecs.northwestern.edu; Slivken, S.; Bandyopadhyay, N.; Bai, Y.; Zhou, W. J.; Chen, M.; Heydari, D.; Haddadi, A.; McClintock, R. [Center for Quantum Devices, Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, Illinois 60208 (United States); Amanti, M.; Sirtori, C. [Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot and CNRS, UMR7162, 75205 Paris (France)

    2015-02-02

    We investigate a frequency comb source based on a mid-infrared quantum cascade laser at λ ∼ 9 μm with high power output. A broad flat-top gain with near-zero group velocity dispersion has been engineered using a dual-core active region structure. This favors the locking of the dispersed Fabry-Pérot modes into equally spaced frequency lines via four wave mixing. A current range with a narrow intermode beating linewidth of 3 kHz is identified with a fast detector and spectrum analyzer. This range corresponds to a broad spectral coverage of 65 cm{sup −1} and a high power output of 180 mW for ∼176 comb modes.

  8. Detection of Fatigue Damage by Using High Frequency Nonlinear Laser Ultrasonic Signals

    International Nuclear Information System (INIS)

    Park, Seung Kyu; Park, Nak Kyu; Baik, Sung Hoon; Cheong, Yong Moo; Cha, Byung Heon

    2012-01-01

    The detection of fatigue damage for the components of a nuclear power plant is one of key techniques to prevent a catastrophic accident and the subsequent severe losses. Specifically, it is preferred to detect at an early stage of the fatigue damage. If the fatigue damage that is in danger of growing into a fracture is accurately detected, an appropriate treatment could be carried out to improve the condition. Although most engineers and designers take precautions against fatigue, some breakdowns of nuclear power plant components still occur due to fatigue damage. It is considered that ultrasound testing technique is the most promising method to detect the fatigue damage in many nondestructive testing methods. Laser ultrasound has attracted attention as a noncontact testing technique. Especially, laser ultrasonic signal has wide band frequency spectrum which can provide more accurate information for a testing material. The conventional linear ultrasonic technique is sensitive to gross defects or opened cracks whereas it is less sensitive to evenly distributed micro-cracks or degradation. An alternative technique to overcome this limitation is nonlinear ultrasound. The principal difference between linear and nonlinear technique is that in the latter the existence and characteristics of defects are often related to an acoustic signal whose frequency differs from that of the input signal. This is related to the radiation and propagation of finite amplitude, especially high power, ultrasound and its interaction with discontinuities, such as cracks, interfaces and voids. Since material failure or degradation is usually preceded by some kind of nonlinear mechanical behavior before significant plastic deformation or material damage occurs. The presence of nonlinear terms in the wave equation causes intense acoustic waves to generate new waves at frequencies which are multiples of the initial sound wave frequency. The nonlinear effect can exert a strong effect on the

  9. Radio Frequency Interference: The Study of Rain Effect on Radio Signal Attenuation

    International Nuclear Information System (INIS)

    Roslan Umar; Roslan Umar; Shahirah Syafa Sulan; Atiq Wahidah Azlan; Zainol Abidin Ibrahim

    2015-01-01

    The intensity of radio waves received by radio telescopes is always not subject to human control. In the millimetre band, the propagation of the electromagnetic waves is severely affected by rain rate, dust particle size and drop size in the terms of attenuation, noise and depolarization. At the frequency above 10 GHz, the absorption and scattering by rain cause a reduction in the transmitted signal amplitude which will lead to the reducing of the availability, reliability and performance on the communications link. In this study, the rain effect on radio signal has been investigated. Spectrum analyzer and weather stations were used to obtain the RFI level and rain rate data respectively. The radio frequency interference (RFI) pattern due to rain factor was determined. This will benefit radio astronomer in managing sites for radio observation for radio astronomy purposes. (author)

  10. Automatic Modulation Classification of LFM and Polyphase-coded Radar Signals

    Directory of Open Access Journals (Sweden)

    S. B. S. Hanbali

    2017-12-01

    Full Text Available There are several techniques for detecting and classifying low probability of intercept radar signals such as Wigner distribution, Choi-Williams distribution and time-frequency rate distribution, but these distributions require high SNR. To overcome this problem, we propose a new technique for detecting and classifying linear frequency modulation signal and polyphase coded signals using optimum fractional Fourier transform at low SNR. The theoretical analysis and simulation experiments demonstrate the validity and efficiency of the proposed method.

  11. Analysis of Maneuvering Targets with Complex Motions by Two-Dimensional Product Modified Lv's Distribution for Quadratic Frequency Modulation Signals.

    Science.gov (United States)

    Jing, Fulong; Jiao, Shuhong; Hou, Changbo; Si, Weijian; Wang, Yu

    2017-06-21

    For targets with complex motion, such as ships fluctuating with oceanic waves and high maneuvering airplanes, azimuth echo signals can be modeled as multicomponent quadratic frequency modulation (QFM) signals after migration compensation and phase adjustment. For the QFM signal model, the chirp rate (CR) and the quadratic chirp rate (QCR) are two important physical quantities, which need to be estimated. For multicomponent QFM signals, the cross terms create a challenge for detection, which needs to be addressed. In this paper, by employing a novel multi-scale parametric symmetric self-correlation function (PSSF) and modified scaled Fourier transform (mSFT), an effective parameter estimation algorithm is proposed-referred to as the Two-Dimensional product modified Lv's distribution (2D-PMLVD)-for QFM signals. The 2D-PMLVD is simple and can be easily implemented by using fast Fourier transform (FFT) and complex multiplication. These measures are analyzed in the paper, including the principle, the cross term, anti-noise performance, and computational complexity. Compared to the other three representative methods, the 2D-PMLVD can achieve better anti-noise performance. The 2D-PMLVD, which is free of searching and has no identifiability problems, is more suitable for multicomponent situations. Through several simulations and analyses, the effectiveness of the proposed estimation algorithm is verified.

  12. Analysis on frequency response of trans-impedance amplifier (TIA) for signal-to-noise ratio (SNR) enhancement in optical signal detection system using lock-in amplifier (LIA)

    Science.gov (United States)

    Kim, Ji-Hoon; Jeon, Su-Jin; Ji, Myung-Gi; Park, Jun-Hee; Choi, Young-Wan

    2017-02-01

    Lock-in amplifier (LIA) has been widely used in optical signal detection systems because it can measure small signal under high noise level. Generally, The LIA used in optical signal detection system is composed of transimpedance amplifier (TIA), phase sensitive detector (PSD) and low pass filter (LPF). But commercial LIA using LPF is affected by flicker noise. To avoid flicker noise, there is 2ω detection LIA using BPF. To improve the dynamic reserve (DR) of the 2ω LIA, the signal to noise ratio (SNR) of the TIA should be improved. According to the analysis of frequency response of the TIA, the noise gain can be minimized by proper choices of input capacitor (Ci) and feed-back network in the TIA in a specific frequency range. In this work, we have studied how the SNR of the TIA can be improved by a proper choice of frequency range. We have analyzed the way to control this frequency range through the change of passive component in the TIA. The result shows that the variance of the passive component in the TIA can change the specific frequency range where the noise gain is minimized in the uniform gain region of the TIA.

  13. Traffic signal design and simulation for vulnerable road users safety and bus preemption

    International Nuclear Information System (INIS)

    Lo, Shih-Ching; Huang, Hsieh-Chu

    2015-01-01

    Mostly, pedestrian car accidents occurred at a signalized interaction is because pedestrians cannot across the intersection safely within the green light. From the viewpoint of pedestrian, there might have two reasons. The first one is pedestrians cannot speed up to across the intersection, such as the elders. The other reason is pedestrians do not sense that the signal phase is going to change and their right-of-way is going to be lost. Developing signal logic to protect pedestrian, who is crossing an intersection is the first purpose of this study. In addition, to improve the reliability and reduce delay of public transportation service is the second purpose. Therefore, bus preemption is also considered in the designed signal logic. In this study, the traffic data of the intersection of Chong-Qing North Road and Min-Zu West Road, Taipei, Taiwan, is employed to calibrate and validate the signal logic by simulation. VISSIM 5.20, which is a microscopic traffic simulation software, is employed to simulate the signal logic. From the simulated results, the signal logic presented in this study can protect pedestrians crossing the intersection successfully. The design of bus preemption can reduce the average delay. However, the pedestrian safety and bus preemption signal will influence the average delay of cars largely. Thus, whether applying the pedestrian safety and bus preemption signal logic to an intersection or not should be evaluated carefully

  14. Traffic signal design and simulation for vulnerable road users safety and bus preemption

    Energy Technology Data Exchange (ETDEWEB)

    Lo, Shih-Ching; Huang, Hsieh-Chu [Department of Transportation Technology and Logistics Management, Chung Hua University, No. 707, Sec. 2, WuFu Rd., Hsinchu, 300, Taiwan (China)

    2015-01-22

    Mostly, pedestrian car accidents occurred at a signalized interaction is because pedestrians cannot across the intersection safely within the green light. From the viewpoint of pedestrian, there might have two reasons. The first one is pedestrians cannot speed up to across the intersection, such as the elders. The other reason is pedestrians do not sense that the signal phase is going to change and their right-of-way is going to be lost. Developing signal logic to protect pedestrian, who is crossing an intersection is the first purpose of this study. In addition, to improve the reliability and reduce delay of public transportation service is the second purpose. Therefore, bus preemption is also considered in the designed signal logic. In this study, the traffic data of the intersection of Chong-Qing North Road and Min-Zu West Road, Taipei, Taiwan, is employed to calibrate and validate the signal logic by simulation. VISSIM 5.20, which is a microscopic traffic simulation software, is employed to simulate the signal logic. From the simulated results, the signal logic presented in this study can protect pedestrians crossing the intersection successfully. The design of bus preemption can reduce the average delay. However, the pedestrian safety and bus preemption signal will influence the average delay of cars largely. Thus, whether applying the pedestrian safety and bus preemption signal logic to an intersection or not should be evaluated carefully.

  15. Simulation of Terahertz Frequency Sources. Polar-Optical Phonon Enhancement of Harmonic Generation in Schottky Diodes

    National Research Council Canada - National Science Library

    Gelmont, Boris

    2002-01-01

    ... polar optical vibration frequency When a high frequency input signal is applied to a frequency multiplier device polar-optical phonons can enhance the non-linearities inherent in this device, enabling...

  16. Modeling laser velocimeter signals as triply stochastic Poisson processes

    Science.gov (United States)

    Mayo, W. T., Jr.

    1976-01-01

    Previous models of laser Doppler velocimeter (LDV) systems have not adequately described dual-scatter signals in a manner useful for analysis and simulation of low-level photon-limited signals. At low photon rates, an LDV signal at the output of a photomultiplier tube is a compound nonhomogeneous filtered Poisson process, whose intensity function is another (slower) Poisson process with the nonstationary rate and frequency parameters controlled by a random flow (slowest) process. In the present paper, generalized Poisson shot noise models are developed for low-level LDV signals. Theoretical results useful in detection error analysis and simulation are presented, along with measurements of burst amplitude statistics. Computer generated simulations illustrate the difference between Gaussian and Poisson models of low-level signals.

  17. Simulations of the Mid-Pliocene Warm Period Using Two Versions of the NASA-GISS ModelE2-R Coupled Model

    Science.gov (United States)

    Chandler, M. A.; Sohl, L. E.; Jonas, J. A.; Dowsett, H. J.; Kelley, M.

    2013-01-01

    The mid-Pliocene Warm Period (mPWP) bears many similarities to aspects of future global warming as projected by the Intergovernmental Panel on Climate Change (IPCC, 2007). Both marine and terrestrial data point to high-latitude temperature amplification, including large decreases in sea ice and land ice, as well as expansion of warmer climate biomes into higher latitudes. Here we present our most recent simulations of the mid-Pliocene climate using the CMIP5 version of the NASAGISS Earth System Model (ModelE2-R). We describe the substantial impact associated with a recent correction made in the implementation of the Gent-McWilliams ocean mixing scheme (GM), which has a large effect on the simulation of ocean surface temperatures, particularly in the North Atlantic Ocean. The effect of this correction on the Pliocene climate results would not have been easily determined from examining its impact on the preindustrial runs alone, a useful demonstration of how the consequences of code improvements as seen in modern climate control runs do not necessarily portend the impacts in extreme climates.Both the GM-corrected and GM-uncorrected simulations were contributed to the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Many findings presented here corroborate results from other PlioMIP multi-model ensemble papers, but we also emphasize features in the ModelE2-R simulations that are unlike the ensemble means. The corrected version yields results that more closely resemble the ocean core data as well as the PRISM3D reconstructions of the mid-Pliocene, especially the dramatic warming in the North Atlantic and Greenland-Iceland-Norwegian Sea, which in the new simulation appears to be far more realistic than previously found with older versions of the GISS model. Our belief is that continued development of key physical routines in the atmospheric model, along with higher resolution and recent corrections to mixing parameterisations in the ocean model, have led

  18. The East Asian Summer Monsoon at mid-Holocene: results from PMIP3 simulations

    Directory of Open Access Journals (Sweden)

    W. Zheng

    2013-02-01

    Full Text Available Ten Coupled General Circulation Models (CGCMs participated in the third phase of Paleoclimate Modelling Intercomparison Project (PMIP3 are assessed for the East Asian Summer Monsoon (EASM in both the pre-Industrial (PI, 0 ka and mid-Holocene (MH, 6 ka simulations. Results show that the PMIP3 model median captures well the large-scale characteristics of the EASM, including the two distinct features of the Meiyu rainbelt and the stepwise meridional displacement of the monsoonal rainbelt. At mid-Holocene, the PMIP3 model median shows significant warming (cooling during boreal summer (winter over Eurasia continent that are dominated by the changes of insolation. However, the PMIP3 models fail to simulate a warmer annual mean and winter surface air temperature (TAS over eastern China as derived from proxy records. The EASM at MH are featured by the changes of large-scale circulation over Eastern China while the changes of precipitation are not significant over its sub-domains of the Southern China and the lower reaches of Yangzi River. The inter-model differences for the monsoon precipitation can be associated with different configurations of the changes in large-scale circulation and the water vapour content, of which the former determines the sign of precipitation changes. The large model spread for the TAS over Tibetan Plateau has a positive relationship with the precipitation in the lower reaches of Yangzi River, yet this relationship does not apply to those PMIP3 models in which the monsoonal precipitation is more sensitive to the changes of large-scale circulation. Except that the PMIP3 model median captured the warming of annual mean TAS over Tibetan Plateau, no significant improvements can be concluded when compared with the PMIP2 models results.

  19. Influence of electromagnetic signal of antibiotics excited by low-frequency pulsed electromagnetic fields on growth of Escherichia coli.

    Science.gov (United States)

    Ke, Yin-Lung; Chang, Fu-Yu; Chen, Ming-Kun; Li, Shun-Lai; Jang, Ling-Sheng

    2013-01-01

    Energy medicine (EM) provides a new medical choice for patients, and its advantages are the noninvasive detection and nondrug treatment. An electromagnetic signal, a kind of EM, induced from antibiotic coupling with weak, extremely low-frequency pulsed electromagnetic fields (PEMFs) is utilized for investigating the growth speed of Escherichia coli (E. coli). PEMFs are produced by solenoidal coils for coupling the electromagnetic signal of antibiotics (penicillin). The growth retardation rate (GRR) of E. coli is used to investigate the efficacy of the electromagnetic signal of antibiotics. The E. coli is cultivated in the exposure of PEMFs coupling with the electromagnetic signal of antibiotics. The maximum GRR of PEMFs with and without the electromagnetic signal of antibiotics on the growth of E. coli cells in the logarithmic is 17.4 and 9.08%, respectively. The electromagnetic signal of antibiotics is successfully coupled by the electromagnetic signal coupling instrument to affect the growth of E. coli. In addition, the retardation effect on E. coli growth can be improved of by changing the carrier frequency of PEMFs coupling with the electromagnetic signal of antibiotics. GRR caused by the electromagnetic signal of antibiotics can be fixed by a different carrier frequency in a different phase of E. coli growth.

  20. An analytical method to simulate the H I 21-cm visibility signal for intensity mapping experiments

    Science.gov (United States)

    Sarkar, Anjan Kumar; Bharadwaj, Somnath; Marthi, Visweshwar Ram

    2018-01-01

    Simulations play a vital role in testing and validating H I 21-cm power spectrum estimation techniques. Conventional methods use techniques like N-body simulations to simulate the sky signal which is then passed through a model of the instrument. This makes it necessary to simulate the H I distribution in a large cosmological volume, and incorporate both the light-cone effect and the telescope's chromatic response. The computational requirements may be particularly large if one wishes to simulate many realizations of the signal. In this paper, we present an analytical method to simulate the H I visibility signal. This is particularly efficient if one wishes to simulate a large number of realizations of the signal. Our method is based on theoretical predictions of the visibility correlation which incorporate both the light-cone effect and the telescope's chromatic response. We have demonstrated this method by applying it to simulate the H I visibility signal for the upcoming Ooty Wide Field Array Phase I.

  1. Wideband Small-Signal Input dq Admittance Modeling of Six-Pulse Diode Rectifiers

    DEFF Research Database (Denmark)

    Yue, Xiaolong; Wang, Xiongfei; Blaabjerg, Frede

    2018-01-01

    This paper studies the wideband small-signal input dq admittance of six-pulse diode rectifiers. Considering the frequency coupling introduced by ripple frequency harmonics of d-and q-channel switching function, the proposed model successfully predicts the small-signal input dq admittance of six......-pulse diode rectifiers in high frequency regions that existing models fail to explain. Simulation and experimental results verify the accuracy of the proposed model....

  2. A software sampling frequency adaptive algorithm for reducing spectral leakage

    Institute of Scientific and Technical Information of China (English)

    PAN Li-dong; WANG Fei

    2006-01-01

    Spectral leakage caused by synchronous error in a nonsynchronous sampling system is an important cause that reduces the accuracy of spectral analysis and harmonic measurement.This paper presents a software sampling frequency adaptive algorithm that can obtain the actual signal frequency more accurately,and then adjusts sampling interval base on the frequency calculated by software algorithm and modifies sampling frequency adaptively.It can reduce synchronous error and impact of spectral leakage;thereby improving the accuracy of spectral analysis and harmonic measurement for power system signal where frequency changes slowly.This algorithm has high precision just like the simulations show,and it can be a practical method in power system harmonic analysis since it can be implemented easily.

  3. Simulation of a programmed frequency shift near extraction from the Fermilab Booster

    International Nuclear Information System (INIS)

    Lucas, P.; Kerns, Q.

    1987-03-01

    The longitudinal phase space program ESME has been used to simulate the effects of a linear shift in RF frequency away from that appropriate for the accelerator guide field. This shift takes place in the new Booster low level RF and is used to position the particle bunches in Main Ring buckets in a reproducible fashion. Shifts in frequency are found to generate synchrotron oscillations; however, the simulations show that these can be reduced to acceptable levels by introduction of jumps in RF phase preceding the programmed frequency changes. Lowering the RF voltage near extraction from the Booster, a desirable operational feature, has also been investigated

  4. Human versus Computer Controlled Selection of Ventilator Settings: An Evaluation of Adaptive Support Ventilation and Mid-Frequency Ventilation

    Directory of Open Access Journals (Sweden)

    Eduardo Mireles-Cabodevila

    2012-01-01

    Full Text Available Background. There are modes of mechanical ventilation that can select ventilator settings with computer controlled algorithms (targeting schemes. Two examples are adaptive support ventilation (ASV and mid-frequency ventilation (MFV. We studied how different clinician-chosen ventilator settings are from these computer algorithms under different scenarios. Methods. A survey of critical care clinicians provided reference ventilator settings for a 70 kg paralyzed patient in five clinical/physiological scenarios. The survey-derived values for minute ventilation and minute alveolar ventilation were used as goals for ASV and MFV, respectively. A lung simulator programmed with each scenario’s respiratory system characteristics was ventilated using the clinician, ASV, and MFV settings. Results. Tidal volumes ranged from 6.1 to 8.3 mL/kg for the clinician, 6.7 to 11.9 mL/kg for ASV, and 3.5 to 9.9 mL/kg for MFV. Inspiratory pressures were lower for ASV and MFV. Clinician-selected tidal volumes were similar to the ASV settings for all scenarios except for asthma, in which the tidal volumes were larger for ASV and MFV. MFV delivered the same alveolar minute ventilation with higher end expiratory and lower end inspiratory volumes. Conclusions. There are differences and similarities among initial ventilator settings selected by humans and computers for various clinical scenarios. The ventilation outcomes are the result of the lung physiological characteristics and their interaction with the targeting scheme.

  5. SIM-DSP: A DSP-Enhanced CAD Platform for Signal Integrity Macromodeling and Simulation

    Directory of Open Access Journals (Sweden)

    Chi-Un Lei

    2014-12-01

    Full Text Available Macromodeling-Simulation process for signal integrity verifications has become necessary for the high speed circuit system design. This paper aims to introduce a “VLSI Signal Integrity Macromodeling and Simulation via Digital Signal Processing Techniques” framework (known as SIM-DSP framework, which applies digital signal processing techniques to facilitate the SI verification process in the pre-layout design phase. Core identification modules and peripheral (pre-/post-processing modules have been developed and assembled to form a verification flow. In particular, a single-step discrete cosine transform truncation (DCTT module has been developed for modeling-simulation process. In DCTT, the response modeling problem is classified as a signal compression problem, wherein the system response can be represented by a truncated set of non-pole based DCT bases, and error can be analyzed through Parseval’s theorem. Practical examples are given to show the applicability of our proposed framework.

  6. Top down and bottom up selection drives variations in frequency and form of a visual signal

    OpenAIRE

    Yeh, Chien-Wei; Blamires, Sean J.; Liao, Chen-Pan; Tso, I.-Min

    2015-01-01

    The frequency and form of visual signals can be shaped by selection from predators, prey or both. When a signal simultaneously attracts predators and prey, selection may favour a strategy that minimizes risks while attracting prey. Accordingly, varying the frequency and form of the silken decorations added to their web may be a way that Argiope spiders minimize predation while attracting prey. Nonetheless, the role of extraneous factors renders the influences of top down and bottom up selecti...

  7. Simulation of medical irradiation and X-ray detector signals

    Energy Technology Data Exchange (ETDEWEB)

    Kreisler, Bjoern

    2010-02-08

    This thesis aims for an improved understanding of medical irradiation. Two major parts are investigated: the beam shaping components of a medical linear accelerator, i.e. the source of the radiation, and the signal generation inside semiconductor sensors, i.e. the detection of the radiation. The direct measurement of the spatial and spectral particle distribution in the irradiation beam is not possible with state of the art detectors due to the high particle flux. The development of new advanced detectors is the goal of the first part of this thesis. The focus is set on the signal generation inside the sensor volume of a semiconductor detector. Incoming particles interact with the sensor material and generate clouds of electron hole pairs. These pairs get separated by an applied bias voltage. The motion of the charge clouds is simulated with a finite element programme taking into account the drift and diffusion. Mirror charges are induced on the electrodes which move due to the motion of the charge cloud. The motion of the induced mirror charges leads to the signal that is detected. The transient calculation of the signals is based on Ramo's theorem. The efficient adjoint formulation of the induction solution is adjusted to doped materials, as for example the electric bias field and hence the motion of the charge cloud is changing with the doping level. The effect of the doping of the material on the signal shape is shown together with influences of different voltages and pixel geometries. Smaller pixels and higher bias voltages can lead to shorter signals which is preferable for high flux measurements. Possible count rate improvements are limited by electric break through, high dark current across the sensor layer and charge sharing. Another option to shorten the signals is the use of steering grid electrodes which modify the electric and the weighting field. This results in shorter signals and thus in a higher possible rate. The detailed Monte

  8. Simulation of medical irradiation and X-ray detector signals

    International Nuclear Information System (INIS)

    Kreisler, Bjoern

    2010-01-01

    This thesis aims for an improved understanding of medical irradiation. Two major parts are investigated: the beam shaping components of a medical linear accelerator, i.e. the source of the radiation, and the signal generation inside semiconductor sensors, i.e. the detection of the radiation. The direct measurement of the spatial and spectral particle distribution in the irradiation beam is not possible with state of the art detectors due to the high particle flux. The development of new advanced detectors is the goal of the first part of this thesis. The focus is set on the signal generation inside the sensor volume of a semiconductor detector. Incoming particles interact with the sensor material and generate clouds of electron hole pairs. These pairs get separated by an applied bias voltage. The motion of the charge clouds is simulated with a finite element programme taking into account the drift and diffusion. Mirror charges are induced on the electrodes which move due to the motion of the charge cloud. The motion of the induced mirror charges leads to the signal that is detected. The transient calculation of the signals is based on Ramo's theorem. The efficient adjoint formulation of the induction solution is adjusted to doped materials, as for example the electric bias field and hence the motion of the charge cloud is changing with the doping level. The effect of the doping of the material on the signal shape is shown together with influences of different voltages and pixel geometries. Smaller pixels and higher bias voltages can lead to shorter signals which is preferable for high flux measurements. Possible count rate improvements are limited by electric break through, high dark current across the sensor layer and charge sharing. Another option to shorten the signals is the use of steering grid electrodes which modify the electric and the weighting field. This results in shorter signals and thus in a higher possible rate. The detailed Monte-Carlo simulation of

  9. Improved real-time dynamics from imaginary frequency lattice simulations

    Directory of Open Access Journals (Sweden)

    Pawlowski Jan M.

    2018-01-01

    Full Text Available The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse problem. Here we report on a novel approach to improve the determination of real-time information in the form of spectral functions by setting up a simulation prescription in imaginary frequencies. By carefully distinguishing between initial conditions and quantum dynamics one obtains access to correlation functions also outside the conventional Matsubara frequencies. In particular the range between ω0 and ω1 = 2πT, which is most relevant for the inverse problem may be more highly resolved. In combination with the fact that in imaginary frequencies the kernel of the inverse problem is not an exponential but only a rational function we observe significant improvements in the reconstruction of spectral functions, demonstrated in a simple 0+1 dimensional scalar field theory toy model.

  10. Improved real-time dynamics from imaginary frequency lattice simulations

    Science.gov (United States)

    Pawlowski, Jan M.; Rothkopf, Alexander

    2018-03-01

    The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse problem. Here we report on a novel approach to improve the determination of real-time information in the form of spectral functions by setting up a simulation prescription in imaginary frequencies. By carefully distinguishing between initial conditions and quantum dynamics one obtains access to correlation functions also outside the conventional Matsubara frequencies. In particular the range between ω0 and ω1 = 2πT, which is most relevant for the inverse problem may be more highly resolved. In combination with the fact that in imaginary frequencies the kernel of the inverse problem is not an exponential but only a rational function we observe significant improvements in the reconstruction of spectral functions, demonstrated in a simple 0+1 dimensional scalar field theory toy model.

  11. Using LabVIEW for the design and control of digital signal processing systems. Simulation of the ultra slow extraction at COSY

    International Nuclear Information System (INIS)

    Heinrichs, G.; Rongen, H.; Jamal, R.

    1994-01-01

    For the ultraslow extraction system of the COler SYnchrotron COSY a direct digital synthesis system is being developed. LabVIEW from National Instruments has been chosen as a tool for the simulation of the digital signal processing algorithms as well as the generation of test sequences. In order to generate adjustable band-limited noise centered at a carrier frequency, alternative algorithms have been studied. LabVIEW permits the interactive variation of relevant system parameters by means of a graphical language in order to study the quality of the frequency band limitation as a function of noise parameters, digital accuracy and frequency range and to generate test sequences by means of a real-time function generator. Advantages and limitations of LabVIEW for such applications are discussed. ((orig.))

  12. Dynamic Antarctic ice sheet during the early to mid-Miocene

    Science.gov (United States)

    Gasson, Edward; DeConto, Robert M.; Pollard, David; Levy, Richard H.

    2016-03-01

    Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate-ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet-climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52-0.66‰, or a sea level equivalent change of 30-36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability.

  13. New method to extract radial acceleration of target from short-duration signal at low SNR

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to extract target radial acceleration from radar echo signal at low SNR (signal-to-noise), this paper employed FRFT (fractional Fourier transformation) to analyze short-duration radar echo and studied the relations between signal convergence peaks in matched transformation domain and signal duration and modu- lated frequency of signal. When signal duration is specified, the method of multi- plying sampled signal by the known frequency modulated signal to alter modulated frequency was presented, which generated the new signal with larger convergence peaks than the initial signal in matched transformation domain. Thus, it could successfully estimate the radial acceleration of radar target at low SNR. Simulations were conducted to show the feasibility and effectiveness of the method.

  14. Fundamental investigations of capacitive radio frequency plasmas: simulations and experiments

    International Nuclear Information System (INIS)

    Donkó, Z; Derzsi, A; Hartmann, P; Korolov, I; Schulze, J; Czarnetzki, U; Schüngel, E

    2012-01-01

    Capacitive radio frequency (RF) discharge plasmas have been serving hi-tech industry (e.g. chip and solar cell manufacturing, realization of biocompatible surfaces) for several years. Nonetheless, their complex modes of operation are not fully understood and represent topics of high interest. The understanding of these phenomena is aided by modern diagnostic techniques and computer simulations. From the industrial point of view the control of ion properties is of particular interest; possibilities of independent control of the ion flux and the ion energy have been utilized via excitation of the discharges with multiple frequencies. ‘Classical’ dual-frequency (DF) discharges (where two significantly different driving frequencies are used), as well as discharges driven by a base frequency and its higher harmonic(s) have been analyzed thoroughly. It has been recognized that the second solution results in an electrically induced asymmetry (electrical asymmetry effect), which provides the basis for the control of the mean ion energy. This paper reviews recent advances on studies of the different electron heating mechanisms, on the possibilities of the separate control of ion energy and ion flux in DF discharges, on the effects of secondary electrons, as well as on the non-linear behavior (self-generated resonant current oscillations) of capacitive RF plasmas. The work is based on a synergistic approach of theoretical modeling, experiments and kinetic simulations based on the particle-in-cell approach. (paper)

  15. Gravitational Wave Astrophysics in the Mid-band: progenitors and advanced localizations of Advanced LIGO/Virgo binary-merger events

    Science.gov (United States)

    Cheung, Chi C. Teddy; Hogan, Jason; Graham, Peter; Kasevich, Mark; Rajendran, Surjeet; Saif, Babak; Kerr, Matthew T.; Lovellette, Michael; Wood, Kent S.; Michelson, Peter; MAGIS Team

    2018-01-01

    We consider the scientific potential of gravitational wave (GW) observations in the ~30 mHz to 3 Hz frequency range with the Mid-band Atomic Gravitational-wave Interferometric Sensor (MAGIS). MAGIS is a probe-class space-mission concept, using an atom-based gravitational wave detector, that will provide all-sky strain sensitivities of ~10^-21 sqrt(Hz) and better (1-year) in the GW-frequency mid-band between the LISA/L3 detector (planned 2034 launch) and ground-based Advanced LIGO/Virgo interferometers. Primary gravitational wave astrophysics science in the mid-band include GW observations of the binary black hole population discovered by Advanced LIGO/Virgo at higher-frequencies, prior to their merger stage. For such systems, MAGIS will observe the binaries in their inspiral phase, where system parameters such as eccentricities are most easily constrained, and will provide advanced, degree-scale localizations that would enable electromagnetic observations of possible precursor emission 1-week to 1-month prior to their mergers as well as prompt post-merger transient emission. Joint GW-observations with MAGIS and Advanced LIGO/Virgo covering all stages of binary coalescence will further reduce uncertainties in the GW- localizations and distances, and will be powerful paired with galaxy catalogs, to enable unique galaxy counterpart identifications in the case black hole binary mergers are completely absent of detectable electromagnetic precursor or transient signals. These possibilities for MAGIS extend to neutron star binary systems (black hole - neutron star, neutron star - neutron star), and mid-band prospects for such systems will also be considered.The MAGIS team is a collaboration between institutes in the U.S. including Stanford, AOSense, Harvard, NASA/GSFC, NASA/JPL, NIST, NRL, and UC Berkeley, and international partners at Birmingham, Bordeaux, CNRS, Dusseldorf, Ecole Normale Superieure, Florence, Hannover, and Ulm University.

  16. A hybrid transport-diffusion Monte Carlo method for frequency-dependent radiative-transfer simulations

    International Nuclear Information System (INIS)

    Densmore, Jeffery D.; Thompson, Kelly G.; Urbatsch, Todd J.

    2012-01-01

    Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Implicit Monte Carlo radiative-transfer simulations in optically thick media. In DDMC, particles take discrete steps between spatial cells according to a discretized diffusion equation. Each discrete step replaces many smaller Monte Carlo steps, thus improving the efficiency of the simulation. In this paper, we present an extension of DDMC for frequency-dependent radiative transfer. We base our new DDMC method on a frequency-integrated diffusion equation for frequencies below a specified threshold, as optical thickness is typically a decreasing function of frequency. Above this threshold we employ standard Monte Carlo, which results in a hybrid transport-diffusion scheme. With a set of frequency-dependent test problems, we confirm the accuracy and increased efficiency of our new DDMC method.

  17. Modeling and Assessment of Precise Time Transfer by Using BeiDou Navigation Satellite System Triple-Frequency Signals

    Science.gov (United States)

    Zhang, Pengfei; Zhang, Rui; Liu, Jinhai; Lu, Xiaochun

    2018-01-01

    This study proposes two models for precise time transfer using the BeiDou Navigation Satellite System triple-frequency signals: ionosphere-free (IF) combined precise point positioning (PPP) model with two dual-frequency combinations (IF-PPP1) and ionosphere-free combined PPP model with a single triple-frequency combination (IF-PPP2). A dataset with a short baseline (with a common external time frequency) and a long baseline are used for performance assessments. The results show that IF-PPP1 and IF-PPP2 models can both be used for precise time transfer using BeiDou Navigation Satellite System (BDS) triple-frequency signals, and the accuracy and stability of time transfer is the same in both cases, except for a constant system bias caused by the hardware delay of different frequencies, which can be removed by the parameter estimation and prediction with long time datasets or by a priori calibration. PMID:29596330

  18. Inherent Limitations in Mid-Wave and Long-Wave-IR Upconversion Detector

    DEFF Research Database (Denmark)

    Barh, Ajanta; Tseng, Yu-Pei; Pedersen, Christian

    2017-01-01

    Inherent limitations in terms of optical losses, selection of nonlinear crystal(s), detection efficiency and pumping conditions in mid-wave (3-5 µm) and long-wave (8-12 µm) infrared frequency upconversion modules are investigated in this paper.......Inherent limitations in terms of optical losses, selection of nonlinear crystal(s), detection efficiency and pumping conditions in mid-wave (3-5 µm) and long-wave (8-12 µm) infrared frequency upconversion modules are investigated in this paper....

  19. The Fluxgate Magnetometer Simulation in Comsol Multiphysics

    OpenAIRE

    Kolomeytsev Andrey; Baranov Pavel; Zatonov Ivan

    2018-01-01

    This article describes the fluxgate magnetometer simulation in Comsol Multiphysics software package. The simulation results coincide with the experiment described earlier. Decomposition of the output signal by the Fourier coefficients shows a frequency doubling.

  20. The subjective effect of low frequency content in road traffic noise.

    Science.gov (United States)

    Torija, Antonio J; Flindell, Ian H

    2015-01-01

    Based on subjective listening trials, Torija and Flindell [J. Acoust. Soc. Am. 135, 1-4 (2014)] observed that low frequency content in typical urban main road traffic noise appeared to make a smaller contribution to reported annoyance than might be inferred from its objective or physical dominance. This paper reports a more detailed study which was aimed at (i) identifying the difference in sound levels at which low frequency content becomes subjectively dominant over mid and high frequency content and (ii) investigating the relationship between loudness and annoyance under conditions where low frequency content is relatively more dominant, such as indoors where mid and high frequency content is reduced. The results suggested that differences of at least +30 dB between the low frequency and the mid/high frequency content are needed for changes in low frequency content to have as much subjective effect as equivalent changes in mid and high frequency content. This suggests that common criticisms of the A-frequency weighting based on a hypothesized excessive downweighting of the low frequency content may be relatively unfounded in this application area.

  1. Simulators of tray distillation columns as tools for interpreting gamma-ray scan profile signal

    International Nuclear Information System (INIS)

    Offei-Mensah, P.S.; Gbadago, J.K.; Dagadu, C.P.K.; Danso, K.A.

    2008-01-01

    Simulators of tray distillation columns were used to provide technical guidelines for interpreting signals from gamma ray scans used for analysing malfunctions in distillation columns. The transmitted radiation intensities at 0.05 m intervals were determined from top to bottom of simulators of tray distillation columns exposed to 20 mCi of '1'3'7 Cs. Signals generated from the simulators were identical with the experimental signals obtained from the stabilizer column of the crude oil distillation unit at the Tema Oil Refinery Ghana Limited. Changes in the signal level were observed with changes in diameter, type of material (gasoline, air, debris, steel) and orientation of scan line. The analysis provided accurate interpretation of gamma scan profiles. (au)

  2. High intensity signal of the posterior pituitary. A study with horizontal direction of frequency-encoding and fat suppression MR techniques

    International Nuclear Information System (INIS)

    Arslan, A.

    1999-01-01

    Purpose: To evaluate the consistency of fat in the high intensity signals of the normal neurohypophysis and to differentiate the high signal of posterior pituitary from that of dorsum sella. Sagittal SE T1-weighted images with frequency encoding in the horizontal direction were used in order to differentiate the high signal of posterior pituitary and dorsum sella by the vertically-oriented chemical shift artifact. Material and methods: The sellae of 46 normal volunteers were imaged with a commercially available fat suppression technique and SE sequences with frequency encoding in vertical (25 cases) and horizontal (21 cases) axes. Results: The high signal intensity was absent in 9% of the normal volunteers with no predilection to any specific age group. None of the cases with posterior pituitary high intensity signals showed suppression of the signal with fat suppression technique. A fat suppression technique was helpful in documenting the hyperintensity in 7% of normal volunteers. Nineteen of the 21 (90%) cases with high signal intensity were detected by routine SE T1-weighted images, whereas 18 of the 19 (95%) cases were detected by imaging with frequency encoding in the horizontal direction. Conclusion: The high signal does not indicate the presence of fat. Fat suppression technique and a horizontal direction of frequency encoding help in differentiating the high signal of the neurohypophysis from that of dorsum sella. (orig.)

  3. Performance Analysis of Control Signal Transmission Technique for Cognitive Radios in Dynamic Spectrum Access Networks

    Science.gov (United States)

    Sakata, Ren; Tomioka, Tazuko; Kobayashi, Takahiro

    When cognitive radio (CR) systems dynamically use the frequency band, a control signal is necessary to indicate which carrier frequencies are currently available in the network. In order to keep efficient spectrum utilization, this control signal also should be transmitted based on the channel conditions. If transmitters dynamically select carrier frequencies, receivers have to receive control signals without knowledge of their carrier frequencies. To enable such transmission and reception, this paper proposes a novel scheme called DCPT (Differential Code Parallel Transmission). With DCPT, receivers can receive low-rate information with no knowledge of the carrier frequencies. The transmitter transmits two signals whose carrier frequencies are spaced by a predefined value. The absolute values of the carrier frequencies can be varied. When the receiver acquires the DCPT signal, it multiplies the signal by a frequency-shifted version of the signal; this yields a DC component that represents the data signal which is then demodulated. The performance was evaluated by means of numerical analysis and computer simulation. We confirmed that DCPT operates successfully even under severe interference if its parameters are appropriately configured.

  4. Two models of the sound-signal frequency dependence on the animal body size as exemplified by the ground squirrels of Eurasia (mammalia, rodentia).

    Science.gov (United States)

    Nikol'skii, A A

    2017-11-01

    Dependence of the sound-signal frequency on the animal body length was studied in 14 ground squirrel species (genus Spermophilus) of Eurasia. Regression analysis of the total sample yielded a low determination coefficient (R 2 = 26%), because the total sample proved to be heterogeneous in terms of signal frequency within the dimension classes of animals. When the total sample was divided into two groups according to signal frequency, two statistically significant models (regression equations) were obtained in which signal frequency depended on the body size at high determination coefficients (R 2 = 73 and 94% versus 26% for the total sample). Thus, the problem of correlation between animal body size and the frequency of their vocal signals does not have a unique solution.

  5. An Application of Reassigned Time-Frequency Representations for Seismic Noise/Signal Decomposition

    Science.gov (United States)

    Mousavi, S. M.; Langston, C. A.

    2016-12-01

    Seismic data recorded by surface arrays are often strongly contaminated by unwanted noise. This background noise makes the detection of small magnitude events difficult. An automatic method for seismic noise/signal decomposition is presented based upon an enhanced time-frequency representation. Synchrosqueezing is a time-frequency reassignment method aimed at sharpening a time-frequency picture. Noise can be distinguished from the signal and suppressed more easily in this reassigned domain. The threshold level is estimated using a general cross validation approach that does not rely on any prior knowledge about the noise level. Efficiency of thresholding has been improved by adding a pre-processing step based on higher order statistics and a post-processing step based on adaptive hard-thresholding. In doing so, both accuracy and speed of the denoising have been improved compared to our previous algorithms (Mousavi and Langston, 2016a, 2016b; Mousavi et al., 2016). The proposed algorithm can either kill the noise (either white or colored) and keep the signal or kill the signal and keep the noise. Hence, It can be used in either normal denoising applications or in ambient noise studies. Application of the proposed method on synthetic and real seismic data shows the effectiveness of the method for denoising/designaling of local microseismic, and ocean bottom seismic data. References: Mousavi, S.M., C. A. Langston., and S. P. Horton (2016), Automatic Microseismic Denoising and Onset Detection Using the Synchrosqueezed-Continuous Wavelet Transform. Geophysics. 81, V341-V355, doi: 10.1190/GEO2015-0598.1. Mousavi, S.M., and C. A. Langston (2016a), Hybrid Seismic Denoising Using Higher-Order Statistics and Improved Wavelet Block Thresholding. Bull. Seismol. Soc. Am., 106, doi: 10.1785/0120150345. Mousavi, S.M., and C.A. Langston (2016b), Adaptive noise estimation and suppression for improving microseismic event detection, Journal of Applied Geophysics., doi: http

  6. Angle-of-arrival-based gesture recognition using ultrasonic multi-frequency signals

    KAUST Repository

    Chen, Hui

    2017-11-02

    Hand gestures are tools for conveying information, expressing emotion, interacting with electronic devices or even serving disabled people as a second language. A gesture can be recognized by capturing the movement of the hand, in real time, and classifying the collected data. Several commercial products such as Microsoft Kinect, Leap Motion Sensor, Synertial Gloves and HTC Vive have been released and new solutions have been proposed by researchers to handle this task. These systems are mainly based on optical measurements, inertial measurements, ultrasound signals and radio signals. This paper proposes an ultrasonic-based gesture recognition system using AOA (Angle of Arrival) information of ultrasonic signals emitted from a wearable ultrasound transducer. The 2-D angles of the moving hand are estimated using multi-frequency signals captured by a fixed receiver array. A simple redundant dictionary matching classifier is designed to recognize gestures representing the numbers from `0\\' to `9\\' and compared with a neural network classifier. Average classification accuracies of 95.5% and 94.4% are obtained, respectively, using the two classification methods.

  7. Modeling the effects of Multi-path propagation and scintillation on GPS signals

    Science.gov (United States)

    Habash Krause, L.; Wilson, S. J.

    2014-12-01

    GPS signals traveling through the earth's ionosphere are affected by charged particles that often disrupt the signal and the information it carries due to "scintillation", which resembles an extra noise source on the signal. These signals are also affected by weather changes, tropospheric scattering, and absorption from objects due to multi-path propagation of the signal. These obstacles cause distortion within information and fading of the signal, which ultimately results in phase locking errors and noise in messages. In this work, we attempted to replicate the distortion that occurs in GPS signals using a signal processing simulation model. We wanted to be able to create and identify scintillated signals so we could better understand the environment that caused it to become scintillated. Then, under controlled conditions, we simulated the receiver's ability to suppress scintillation in a signal. We developed a code in MATLAB that was programmed to: 1. Create a carrier wave and then plant noise (four different frequencies) on the carrier wave, 2. Compute a Fourier transform on the four different frequencies to find the frequency content of a signal, 3. Use a filter and apply it to the Fourier transform of the four frequencies and then compute a Signal-to-noise ratio to evaluate the power (in Decibels) of the filtered signal, and 4.Plot each of these components into graphs. To test the code's validity, we used user input and data from an AM transmitter. We determined that the amplitude modulated signal or AM signal would be the best type of signal to test the accuracy of the MATLAB code due to its simplicity. This code is basic to give students the ability to change and use it to determine the environment and effects of noise on different AM signals and their carrier waves. Overall, we were able to manipulate a scenario of a noisy signal and interpret its behavior and change due to its noisy components: amplitude, frequency, and phase shift.

  8. Modeling and Assessment of Precise Time Transfer by Using BeiDou Navigation Satellite System Triple-Frequency Signals

    Directory of Open Access Journals (Sweden)

    Rui Tu

    2018-03-01

    Full Text Available This study proposes two models for precise time transfer using the BeiDou Navigation Satellite System triple-frequency signals: ionosphere-free (IF combined precise point positioning (PPP model with two dual-frequency combinations (IF-PPP1 and ionosphere-free combined PPP model with a single triple-frequency combination (IF-PPP2. A dataset with a short baseline (with a common external time frequency and a long baseline are used for performance assessments. The results show that IF-PPP1 and IF-PPP2 models can both be used for precise time transfer using BeiDou Navigation Satellite System (BDS triple-frequency signals, and the accuracy and stability of time transfer is the same in both cases, except for a constant system bias caused by the hardware delay of different frequencies, which can be removed by the parameter estimation and prediction with long time datasets or by a priori calibration.

  9. Efficient and Robust Detection of GFSK Signals under Dispersive Channel, Modulation Index, and Carrier Frequency Offset Conditions

    Directory of Open Access Journals (Sweden)

    Stephan Weiss

    2005-09-01

    Full Text Available Gaussian frequency shift keying is the modulation scheme specified for Bluetooth. Signal adversities typical in Bluetooth networks include AWGN, multipath propagation, carrier frequency, and modulation index offsets. In our effort to realise a robust but efficient Bluetooth receiver, we adopt a high-performance matched-filter-based detector, which is near optimal in AWGN, but requires a prohibitively costly filter bank for processing of K bits worth of the received signal. However, through filtering over a single bit period and performing phase propagation of intermediate results over successive single-bit stages, we eliminate redundancy involved in providing the matched filter outputs and reduce its complexity by up to 90% (for K=9. The constant modulus signal characteristic and the potential for carrier frequency offsets make the constant modulus algorithm (CMA suitable for channel equalisation, and we demonstrate its effectiveness in this paper. We also introduce a stochastic gradient-based algorithm for carrier frequency offset correction, and show that the relative rotation between successive intermediate filter outputs enables us to detect and correct offsets in modulation index.

  10. Signal noise/interferer combiner unit programmable (SINCUP)

    Science.gov (United States)

    Martinezdepison, Emilio

    1988-12-01

    The Signal Noise Interferer Combiner Unit Programmable (SINCUP) has been developed to facilitate laboratory performance testing of Very Low Frequency (VLF/Low Frequency (LF) receivers. To accomplish this, the unit allows the combining in controlled amounts of various real-world environmental and manmade interference with an information carrying signal. The externally modulated signal is combined with internally/externally generated Gaussian noise and/or with an internally/externally generated interferer. In order to test modern digital processing techniques, such as Adaptive Null Steering, Eigenvector Sorting, and Widrow-Hoff adaptive filters, SINCUP is capable of generating and meeting much higher signal-to-noise plus interference ratios than earlier channel simulators. The present software has been written to accommodate a dynamic signal-to-noise ratio (SNR) range from -60 to +60 dB. Higher dynamic range units could be implemented.

  11. Perceptual Coding of Audio Signals Using Adaptive Time-Frequency Transform

    Directory of Open Access Journals (Sweden)

    Umapathy Karthikeyan

    2007-01-01

    Full Text Available Wide band digital audio signals have a very high data-rate associated with them due to their complex nature and demand for high-quality reproduction. Although recent technological advancements have significantly reduced the cost of bandwidth and miniaturized storage facilities, the rapid increase in the volume of digital audio content constantly compels the need for better compression algorithms. Over the years various perceptually lossless compression techniques have been introduced, and transform-based compression techniques have made a significant impact in recent years. In this paper, we propose one such transform-based compression technique, where the joint time-frequency (TF properties of the nonstationary nature of the audio signals were exploited in creating a compact energy representation of the signal in fewer coefficients. The decomposition coefficients were processed and perceptually filtered to retain only the relevant coefficients. Perceptual filtering (psychoacoustics was applied in a novel way by analyzing and performing TF specific psychoacoustics experiments. An added advantage of the proposed technique is that, due to its signal adaptive nature, it does not need predetermined segmentation of audio signals for processing. Eight stereo audio signal samples of different varieties were used in the study. Subjective (mean opinion score—MOS listening tests were performed and the subjective difference grades (SDG were used to compare the performance of the proposed coder with MP3, AAC, and HE-AAC encoders. Compression ratios in the range of 8 to 40 were achieved by the proposed technique with subjective difference grades (SDG ranging from –0.53 to –2.27.

  12. Estimation of red-light running frequency using high-resolution traffic and signal data.

    Science.gov (United States)

    Chen, Peng; Yu, Guizhen; Wu, Xinkai; Ren, Yilong; Li, Yueguang

    2017-05-01

    Red-light-running (RLR) emerges as a major cause that may lead to intersection-related crashes and endanger intersection safety. To reduce RLR violations, it's critical to identify the influential factors associated with RLR and estimate RLR frequency. Without resorting to video camera recordings, this study investigates this important issue by utilizing high-resolution traffic and signal event data collected from loop detectors at five intersections on Trunk Highway 55, Minneapolis, MN. First, a simple method is proposed to identify RLR by fully utilizing the information obtained from stop bar detectors, downstream entrance detectors and advance detectors. Using 12 months of event data, a total of 6550 RLR cases were identified. According to a definition of RLR frequency as the conditional probability of RLR on a certain traffic or signal condition (veh/1000veh), the relationships between RLR frequency and some influential factors including arriving time at advance detector, approaching speed, headway, gap to the preceding vehicle on adjacent lane, cycle length, geometric characteristics and even snowing weather were empirically investigated. Statistical analysis shows good agreement with the traffic engineering practice, e.g., RLR is most likely to occur on weekdays during peak periods under large traffic demands and longer signal cycles, and a total of 95.24% RLR events occurred within the first 1.5s after the onset of red phase. The findings confirmed that vehicles tend to run the red light when they are close to intersection during phase transition, and the vehicles following the leading vehicle with short headways also likely run the red light. Last, a simplified nonlinear regression model is proposed to estimate RLR frequency based on the data from advance detector. The study is expected to helpbetter understand RLR occurrence and further contribute to the future improvement of intersection safety. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. High-power, continuous-wave, mid-infrared optical parametric oscillator based on MgO:sPPLT.

    Science.gov (United States)

    Chaitanya Kumar, S; Ebrahim-Zadeh, M

    2011-07-01

    We report a stable, high-power, cw, mid-IR optical parametric oscillator using MgO-doped stoichiometric periodically poled LiTaO₃ (MgO:sPPLT) pumped by a Yb fiber laser at 1064 nm. The singly resonant oscillator (SRO), based on a 30 mm long crystal, is tunable over 430 nm from 3032 to 3462 nm and can generate as much as 5.5 W of mid-IR output power, with >4 W of over 60% of the tuning range and under reduced thermal effects, enabling room temperature operation. Idler power scaling measurements at ~3.3 μm are compared with an MgO-doped periodically poled LiNbO₃ cw SRO, confirming that MgO:sPPLT is an attractive material for multiwatt mid-IR generation. The idler output at 3299 nm exhibits a peak-to-peak power stability better than 12.8% over 5 h and frequency stability of ~1 GHz, while operating close to room temperature, and has a linewidth of ~0.2 nm, limited by the resolution of the wavemeter. The corresponding signal linewidth at 1570 nm is ~21 MHz.

  14. The Fluxgate Magnetometer Simulation in Comsol Multiphysics

    Directory of Open Access Journals (Sweden)

    Kolomeytsev Andrey

    2018-01-01

    Full Text Available This article describes the fluxgate magnetometer simulation in Comsol Multiphysics software package. The simulation results coincide with the experiment described earlier. Decomposition of the output signal by the Fourier coefficients shows a frequency doubling.

  15. Level of Automation and Failure Frequency Effects on Simulated Lunar Lander Performance

    Science.gov (United States)

    Marquez, Jessica J.; Ramirez, Margarita

    2014-01-01

    A human-in-the-loop experiment was conducted at the NASA Ames Research Center Vertical Motion Simulator, where instrument-rated pilots completed a simulated terminal descent phase of a lunar landing. Ten pilots participated in a 2 x 2 mixed design experiment, with level of automation as the within-subjects factor and failure frequency as the between subjects factor. The two evaluated levels of automation were high (fully automated landing) and low (manual controlled landing). During test trials, participants were exposed to either a high number of failures (75% failure frequency) or low number of failures (25% failure frequency). In order to investigate the pilots' sensitivity to changes in levels of automation and failure frequency, the dependent measure selected for this experiment was accuracy of failure diagnosis, from which D Prime and Decision Criterion were derived. For each of the dependent measures, no significant difference was found for level of automation and no significant interaction was detected between level of automation and failure frequency. A significant effect was identified for failure frequency suggesting failure frequency has a significant effect on pilots' sensitivity to failure detection and diagnosis. Participants were more likely to correctly identify and diagnose failures if they experienced the higher levels of failures, regardless of level of automation

  16. OPNET simulation Signaling System No.7 (SS7) network interfaces

    OpenAIRE

    Ow, Kong Chung.

    2000-01-01

    This thesis presents an OPNET model and simulation of the Signaling System No.7 (SS7) network, which is dubbed the world's largest data communications network. The main focus of the study is to model one of its levels, the Message Transfer Part Level 3, in accordance with the ITU.T recommendation Q.704. An overview of SS7 that includes the evolution and basics of SS7 architecture is provided to familarize the reader with the topic. This includes the protocol stack, signaling points, signaling...

  17. Cross Time-Frequency Analysis of Gastrocnemius Electromyographic Signals in Hypertensive and Nonhypertensive Subjects

    Science.gov (United States)

    Mitchell, Patrick; Krotish, Debra; Shin, Yong-June; Hirth, Victor

    2010-12-01

    The effects of hypertension are chronic and continuous; it affects gait, balance, and fall risk. Therefore, it is desirable to assess gait health across hypertensive and nonhypertensive subjects in order to prevent or reduce the risk of falls. Analysis of electromyography (EMG) signals can identify age related changes of neuromuscular activation due to various neuropathies and myopathies, but it is difficult to translate these medical changes to clinical diagnosis. To examine and compare geriatrics patients with these gait-altering diseases, we acquire EMG muscle activation signals, and by use of a timesynchronized mat capable of recording pressure information, we localize the EMG data to the gait cycle, ensuring identical comparison across subjects. Using time-frequency analysis on the EMG signal, in conjunction with several parameters obtained from the time-frequency analyses, we can determine the statistical discrepancy between diseases. We base these parameters on physiological manifestations caused by hypertension, as well as other comorbities that affect the geriatrics community. Using these metrics in a small population, we identify a statistical discrepancy between a control group and subjects with hypertension, neuropathy, diabetes, osteoporosis, arthritis, and several other common diseases which severely affect the geriatrics community.

  18. An Experimental and Theoretical Investigation of a Micromirror Under Mixed-Frequency Excitation

    KAUST Repository

    Ilyas, Saad; Ramini, Abdallah; Carreno, Armando Arpys Arevalo; Younis, Mohammad I.

    2015-01-01

    We present an experimental and theoretical investigation of a micromachined mirror under a mixed-frequency signal composed of two harmonic ac sources. The micromirror is made of polyimide as the main structural layer. The experimental and theoretical dynamics are explored via frequency sweeps in the desired neighborhoods. One frequency is fixed while the other frequency is swept through a wide range to study the dynamic responses. To simulate the behavior of the micromirror, it is modeled as a single degree of freedom system, where the parameters of the model are extracted experimentally. A good agreement is reported among the simulation results and the experimental data. These responses are studied under different frequencies and input voltages. The results show interesting dynamics, where the system exhibits primary resonance and combination resonances of additive and subtractive type. The mixed excitation is demonstrated as a way to increase the bandwidth of the resonator near primary resonance, which can be promising for resonant sensing applications in the effort to increase the signal-noise ratio over extended frequency range.

  19. An Experimental and Theoretical Investigation of a Micromirror Under Mixed-Frequency Excitation

    KAUST Repository

    Ilyas, Saad

    2015-01-12

    We present an experimental and theoretical investigation of a micromachined mirror under a mixed-frequency signal composed of two harmonic ac sources. The micromirror is made of polyimide as the main structural layer. The experimental and theoretical dynamics are explored via frequency sweeps in the desired neighborhoods. One frequency is fixed while the other frequency is swept through a wide range to study the dynamic responses. To simulate the behavior of the micromirror, it is modeled as a single degree of freedom system, where the parameters of the model are extracted experimentally. A good agreement is reported among the simulation results and the experimental data. These responses are studied under different frequencies and input voltages. The results show interesting dynamics, where the system exhibits primary resonance and combination resonances of additive and subtractive type. The mixed excitation is demonstrated as a way to increase the bandwidth of the resonator near primary resonance, which can be promising for resonant sensing applications in the effort to increase the signal-noise ratio over extended frequency range.

  20. Proposing New Methods to Enhance the Low-Resolution Simulated GPR Responses in the Frequency and Wavelet Domains

    Directory of Open Access Journals (Sweden)

    Reza Ahmadi

    2014-12-01

    Full Text Available To date, a number of numerical methods, including the popular Finite-Difference Time Domain (FDTD technique, have been proposed to simulate Ground-Penetrating Radar (GPR responses. Despite having a number of advantages, the finite-difference method also has pitfalls such as being very time consuming in simulating the most common case of media with high dielectric permittivity, causing the forward modelling process to be very long lasting, even with modern high-speed computers. In the present study the well-known hyperbolic pattern response of horizontal cylinders, usually found in GPR B-Scan images, is used as a basic model to examine the possibility of reducing the forward modelling execution time. In general, the simulated GPR traces of common reflected objects are time shifted, as with the Normal Moveout (NMO traces encountered in seismic reflection responses. This suggests the application of Fourier transform to the GPR traces, employing the time-shifting property of the transformation to interpolate the traces between the adjusted traces in the frequency domain (FD. Therefore, in the present study two post-processing algorithms have been adopted to increase the speed of forward modelling while maintaining the required precision. The first approach is based on linear interpolation in the Fourier domain, resulting in increasing lateral trace-to-trace interval of appropriate sampling frequency of the signal, preventing any aliasing. In the second approach, a super-resolution algorithm based on 2D-wavelet transform is developed to increase both vertical and horizontal resolution of the GPR B-Scan images through preserving scale and shape of hidden hyperbola features. Through comparing outputs from both methods with the corresponding actual high-resolution forward response, it is shown that both approaches can perform satisfactorily, although the wavelet-based approach outperforms the frequency-domain approach noticeably, both in amplitude and

  1. Digital signals processing using non-linear orthogonal transformation in frequency domain

    Directory of Open Access Journals (Sweden)

    Ivanichenko E.V.

    2017-12-01

    Full Text Available The rapid progress of computer technology in recent decades led to a wide introduction of methods of digital information processing practically in all fields of scientific research. In this case, among various applications of computing one of the most important places is occupied by digital processing systems signals (DSP that are used in data processing remote solution tasks of navigation of aerospace and marine objects, communications, radiophysics, digital optics and in a number of other applications. Digital Signal Processing (DSP is a dynamically developing an area that covers both technical and software tools. Related areas for digital signal processing are theory information, in particular, the theory of optimal signal reception and theory pattern recognition. In the first case, the main problem is signal extraction against a background of noise and interference of a different physical nature, and in the second - automatic recognition, i.e. classification and signal identification. In the digital processing of signals under a signal, we mean its mathematical description, i.e. a certain real function, containing information on the state or behavior of a physical system under an event that can be defined on a continuous or discrete space of time variation or spatial coordinates. In the broad sense, DSP systems mean a complex algorithmic, hardware and software. As a rule, systems contain specialized technical means of preliminary (or primary signal processing and special technical means for secondary processing of signals. Means of pretreatment are designed to process the original signals observed in general case against a background of random noise and interference of a different physical nature and represented in the form of discrete digital samples, for the purpose of detecting and selection (selection of the useful signal and evaluation characteristics of the detected signal. A new method of digital signal processing in the frequency

  2. Amplitude-cyclic frequency decomposition of vibration signals for bearing fault diagnosis based on phase editing

    Science.gov (United States)

    Barbini, L.; Eltabach, M.; Hillis, A. J.; du Bois, J. L.

    2018-03-01

    In rotating machine diagnosis different spectral tools are used to analyse vibration signals. Despite the good diagnostic performance such tools are usually refined, computationally complex to implement and require oversight of an expert user. This paper introduces an intuitive and easy to implement method for vibration analysis: amplitude cyclic frequency decomposition. This method firstly separates vibration signals accordingly to their spectral amplitudes and secondly uses the squared envelope spectrum to reveal the presence of cyclostationarity in each amplitude level. The intuitive idea is that in a rotating machine different components contribute vibrations at different amplitudes, for instance defective bearings contribute a very weak signal in contrast to gears. This paper also introduces a new quantity, the decomposition squared envelope spectrum, which enables separation between the components of a rotating machine. The amplitude cyclic frequency decomposition and the decomposition squared envelope spectrum are tested on real word signals, both at stationary and varying speeds, using data from a wind turbine gearbox and an aircraft engine. In addition a benchmark comparison to the spectral correlation method is presented.

  3. Application of mid-frequency ventilation in an animal model of lung injury: a pilot study.

    Science.gov (United States)

    Mireles-Cabodevila, Eduardo; Chatburn, Robert L; Thurman, Tracy L; Zabala, Luis M; Holt, Shirley J; Swearingen, Christopher J; Heulitt, Mark J

    2014-11-01

    Mid-frequency ventilation (MFV) is a mode of pressure control ventilation based on an optimal targeting scheme that maximizes alveolar ventilation and minimizes tidal volume (VT). This study was designed to compare the effects of conventional mechanical ventilation using a lung-protective strategy with MFV in a porcine model of lung injury. Our hypothesis was that MFV can maximize ventilation at higher frequencies without adverse consequences. We compared ventilation and hemodynamic outcomes between conventional ventilation and MFV. This was a prospective study of 6 live Yorkshire pigs (10 ± 0.5 kg). The animals were subjected to lung injury induced by saline lavage and injurious conventional mechanical ventilation. Baseline conventional pressure control continuous mandatory ventilation was applied with V(T) = 6 mL/kg and PEEP determined using a decremental PEEP trial. A manual decision support algorithm was used to implement MFV using the same conventional ventilator. We measured P(aCO2), P(aO2), end-tidal carbon dioxide, cardiac output, arterial and venous blood oxygen saturation, pulmonary and systemic vascular pressures, and lactic acid. The MFV algorithm produced the same minute ventilation as conventional ventilation but with lower V(T) (-1 ± 0.7 mL/kg) and higher frequency (32.1 ± 6.8 vs 55.7 ± 15.8 breaths/min, P ventilation and MFV for mean airway pressures (16.1 ± 1.3 vs 16.4 ± 2 cm H2O, P = .75) even when auto-PEEP was higher (0.6 ± 0.9 vs 2.4 ± 1.1 cm H2O, P = .02). There were no significant differences in any hemodynamic measurements, although heart rate was higher during MFV. In this pilot study, we demonstrate that MFV allows the use of higher breathing frequencies and lower V(T) than conventional ventilation to maximize alveolar ventilation. We describe the ventilatory or hemodynamic effects of MFV. We also demonstrate that the application of a decision support algorithm to manage MFV is feasible. Copyright © 2014 by Daedalus Enterprises.

  4. Generation of continuously tunable, 5-12 {mu}m radiation by difference frequency mixing of output waves of a KTP optical parametric oscillator in a ZnGeP{sub 2} crystal

    Energy Technology Data Exchange (ETDEWEB)

    Haidar, S [Research Institute of Electrical Communication (RIEC), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai-shi 980-8577 (Japan); Miyamoto, K [Research Institute of Electrical Communication (RIEC), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai-shi 980-8577 (Japan); Ito, H [Research Institute of Electrical Communication (RIEC), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai-shi 980-8577 (Japan)

    2004-12-07

    Signal and idlers waves obtained from a Nd : YAG laser pumped KTP optical parametric oscillator (OPO) are difference frequency mixed in a ZnGeP{sub 2} (ZGP) crystal to generate radiation in the mid-infrared. The KTP OPO is operated in the type-II phase matching mode, and the extraordinary and ordinary waves are tunable from 1.76 {mu}m to 2.36 {mu}m and from 2.61 {mu}m to 1.90 {mu}m, respectively. The orthogonally polarized waves are difference frequency mixed in a ZGP crystal to generate mid-IR radiation tunable from 5 to 12 {mu}m.

  5. Using GPS TEC measurements to probe ionospheric spatial spectra at mid-latitudes

    Science.gov (United States)

    Lay, E. H.; Parker, P. A.; Light, M. E.; Carrano, C. S.; Debchoudhury, S.; Haaser, R. A.

    2017-12-01

    The physics of how random ionospheric structure causes signal degradation is well understood as weak forward scattering through an effective diffraction grating created by plasma irregularities in the ionosphere. However, the spatial scale spectrum of those irregularities required for input into scintillation models and models of traveling ionospheric disturbances is poorly characterized, particularly at the kilometer to tens of kilometer scale lengths important for very-high-frequency (VHF) scintillation prediction. Furthermore, the majority of characterization studies have been performed in low-latitude or high-latitude regions where geomagnetic activity dominates the physical processes. At mid-latitudes, tropospheric and geomagnetic phenomena compete in disturbing the ionosphere, and it is not well understood how these multiple sources affect the drivers that influence the spatial spectrum. In this study, we are interested in mid-latitude electron density irregularities on the order of 10s of kilometers that would affect VHF signals. Data from the GPS networks Japan GEONET and the Plate Boundary Observatory (PBO, UNAVCO) in the western United States were analyzed for this study. Japan GEONET is a dense network of GPS receivers (station spacing of tens of km), with fairly evenly spaced positions over all of Japan. The PBO, on the other hand, has several pockets of extremely dense coverage (station spacing within a few km), but is less dense on average. We analyze a day with a large solar storm (2015/03/17, St. Patrick's Day Storm) to allow high scintillation potential at mid-latitudes, a day with low geomagnetic activity and low thunderstorm activity (2016/01/31), and a day with low geomagnetic activity and high thunderstorm activity (2015/08/02). We then perform two-dimensional spatial analyses on the TEC data from these two networks on scale lengths of 20 to 200 km to infer the spatial scale spectra.

  6. Tropical influence on boreal summer mid-latitude stationary waves

    Energy Technology Data Exchange (ETDEWEB)

    Douville, Herve [Meteo-France/CNRM-GAME, Toulouse (France); CNRM/GMGEC/VDR, Toulouse (France); Bielli, S.; Deque, M.; Tyteca, S.; Voldoire, A. [Meteo-France/CNRM-GAME, Toulouse (France); Cassou, C. [CNRS-Cerfacs, Toulouse (France); Hall, N.M.J. [CNES/LEGOS, Toulouse (France)

    2011-11-15

    While organized tropical convection is a well-known source of extratropical planetary waves, state-of-the-art climate models still show serious deficiencies in simulating accurately the atmospheric response to tropical sea surface temperature (SST) anomalies and the associated teleconnections. In the present study, the remote influence of the tropical atmospheric circulation is evaluated in ensembles of global boreal summer simulations in which the Arpege-Climat atmospheric General Circulation Model (GCM) is nudged towards 6-h reanalyses. The nudging is applied either in the whole tropical band or in a regional summer monsoon domain. Sensitivity tests to the experimental design are first conducted using prescribed climatological SST. They show that the tropical relaxation does not improve the zonal mean extratropical climatology but does lead to a significantly improved representation of the mid-latitude stationary waves in both hemispheres. Low-pass filtering of the relaxation fields has no major effect on the model response, suggesting that high-frequency tropical variability is not responsible for extratropical biases. Dividing the nudging strength by a factor 10 only decreases the magnitude of the response. Model errors in each monsoon domain contribute to deficiencies in the model's mid-latitude climatology, although an exaggerated large-scale subsidence in the central equatorial Pacific appears as the main source of errors for the representation of stationary waves in the Arpege-Climat model. Case studies are then conducted using either climatological or observed SST. The focus is first on summer 2003 characterized by a strong and persistent anticyclonic anomaly over western Europe. This pattern is more realistic in nudging experiments than in simulations only driven by observed SST, especially when the nudging domain is centred over Central America. Other case studies also show a significant tropical forcing of the summer mid-latitude stationary waves

  7. Time-Frequency Analysis of Terahertz Radar Signals for Rapid Heart and Breath Rate Detection

    National Research Council Canada - National Science Library

    Massar, Melody L

    2008-01-01

    We develop new time-frequency analytic techniques which facilitate the detection of a person's heart and breath rates from the Doppler shift the movement of their body induces in a terahertz radar signal...

  8. Anti-fatigue effect of percutaneous stimulation of the hepatic region by mid-frequency pulse current in different diadynamic cycles in soldiers with exercise-induced fatigue

    Directory of Open Access Journals (Sweden)

    Peng-yi DAI

    2012-01-01

    Full Text Available Objective  To investigate the anti-fatigue effect of percutaneous stimulation of the hepatic region with the mid-frequency pulse current in different diadynamic cycles in exercise-induced fatigued soldiers. Methods  One hundred twenty healthy PLA recruits who did not have physical exercise were randomly divided into four groups with thirty ones in each: control, stimulation group A, stimulation group B, and stimulation group C. All the subjects of four groups were ordered intensive training (exercise from Monday to Saturday, with rest on Sunday for five weeks to establish the exercise-induced fatigue model. Each day after the exercise, the recruits of stimulation groups A, B, and C were treated immediately with mid-frequency (1204Hz, current intensity ≤80mA stimulation to the hepatic region with diadynamic cycles of 0.5, 1, and 2 seconds, respectively. No pulse current stimulation was given in the control group. Venous blood was collected before breakfast on Sundays to measure the fasting plasma glucose (FPG and blood lactate (LAC contents, and liver function was determined by determination of alanine aminotransferase (ALT, aspartate aminotransferase (AST, and lactate dehydrogenase (LDH. The 3000-m running performance of the recruits in each group was recorded on the same day. Results  There was no significant difference between the four groups in terms of the FPG level at the end of the first week (P>0.05. At the end of the third and fifth weeks, the FPG level was significantly higher in the three stimulation groups than in the control group (PPP>0.05. At the end of the first, third, and fifth weeks, the ALT, AST, LDH, and LAC levels were significantly lower in every stimulation group than in the control group (PPPPP>0.05. At the end of the first week, there was no significant difference in 3000-m running performance (P>0.05 between the 4 groups. At the end of the third and fifth weeks, the 3000-m running performance was significantly

  9. Decoding the dopamine signal in macaque prefrontal cortex: a simulation study using the Cx3Dp simulator.

    Directory of Open Access Journals (Sweden)

    Isabelle Ayumi Spühler

    Full Text Available Dopamine transmission in the prefrontal cortex plays an important role in reward based learning, working memory and attention. Dopamine is thought to be released non-synaptically into the extracellular space and to reach distant receptors through diffusion. This simulation study examines how the dopamine signal might be decoded by the recipient neuron. The simulation was based on parameters from the literature and on our own quantified, structural data from macaque prefrontal area 10. The change in extracellular dopamine concentration was estimated at different distances from release sites and related to the affinity of the dopamine receptors. Due to the sparse and random distribution of release sites, a transient heterogeneous pattern of dopamine concentration emerges. Our simulation predicts, however, that at any point in the simulation volume there is sufficient dopamine to bind and activate high-affinity dopamine receptors. We propose that dopamine is broadcast to its distant receptors and any change from the local baseline concentration might be decoded by a transient change in the binding probability of dopamine receptors. Dopamine could thus provide a graduated 'teaching' signal to reinforce concurrently active synapses and cell assemblies. In conditions of highly reduced or highly elevated dopamine levels the simulations predict that relative changes in the dopamine signal can no longer be decoded, which might explain why cognitive deficits are observed in patients with Parkinson's disease, or induced through drugs blocking dopamine reuptake.

  10. Decoding the Dopamine Signal in Macaque Prefrontal Cortex: A Simulation Study Using the Cx3Dp Simulator

    Science.gov (United States)

    Spühler, Isabelle Ayumi; Hauri, Andreas

    2013-01-01

    Dopamine transmission in the prefrontal cortex plays an important role in reward based learning, working memory and attention. Dopamine is thought to be released non-synaptically into the extracellular space and to reach distant receptors through diffusion. This simulation study examines how the dopamine signal might be decoded by the recipient neuron. The simulation was based on parameters from the literature and on our own quantified, structural data from macaque prefrontal area 10. The change in extracellular dopamine concentration was estimated at different distances from release sites and related to the affinity of the dopamine receptors. Due to the sparse and random distribution of release sites, a transient heterogeneous pattern of dopamine concentration emerges. Our simulation predicts, however, that at any point in the simulation volume there is sufficient dopamine to bind and activate high-affinity dopamine receptors. We propose that dopamine is broadcast to its distant receptors and any change from the local baseline concentration might be decoded by a transient change in the binding probability of dopamine receptors. Dopamine could thus provide a graduated ‘teaching’ signal to reinforce concurrently active synapses and cell assemblies. In conditions of highly reduced or highly elevated dopamine levels the simulations predict that relative changes in the dopamine signal can no longer be decoded, which might explain why cognitive deficits are observed in patients with Parkinson’s disease, or induced through drugs blocking dopamine reuptake. PMID:23951205

  11. Ecological prediction with nonlinear multivariate time-frequency functional data models

    Science.gov (United States)

    Yang, Wen-Hsi; Wikle, Christopher K.; Holan, Scott H.; Wildhaber, Mark L.

    2013-01-01

    Time-frequency analysis has become a fundamental component of many scientific inquiries. Due to improvements in technology, the amount of high-frequency signals that are collected for ecological and other scientific processes is increasing at a dramatic rate. In order to facilitate the use of these data in ecological prediction, we introduce a class of nonlinear multivariate time-frequency functional models that can identify important features of each signal as well as the interaction of signals corresponding to the response variable of interest. Our methodology is of independent interest and utilizes stochastic search variable selection to improve model selection and performs model averaging to enhance prediction. We illustrate the effectiveness of our approach through simulation and by application to predicting spawning success of shovelnose sturgeon in the Lower Missouri River.

  12. Benefits to Speech Perception in Noise From the Binaural Integration of Electric and Acoustic Signals in Simulated Unilateral Deafness.

    Science.gov (United States)

    Ma, Ning; Morris, Saffron; Kitterick, Pádraig Thomas

    2016-01-01

    This study used vocoder simulations with normal-hearing (NH) listeners to (1) measure their ability to integrate speech information from an NH ear and a simulated cochlear implant (CI), and (2) investigate whether binaural integration is disrupted by a mismatch in the delivery of spectral information between the ears arising from a misalignment in the mapping of frequency to place. Eight NH volunteers participated in the study and listened to sentences embedded in background noise via headphones. Stimuli presented to the left ear were unprocessed. Stimuli presented to the right ear (referred to as the CI-simulation ear) were processed using an eight-channel noise vocoder with one of the three processing strategies. An Ideal strategy simulated a frequency-to-place map across all channels that matched the delivery of spectral information between the ears. A Realistic strategy created a misalignment in the mapping of frequency to place in the CI-simulation ear where the size of the mismatch between the ears varied across channels. Finally, a Shifted strategy imposed a similar degree of misalignment in all channels, resulting in consistent mismatch between the ears across frequency. The ability to report key words in sentences was assessed under monaural and binaural listening conditions and at signal to noise ratios (SNRs) established by estimating speech-reception thresholds in each ear alone. The SNRs ensured that the monaural performance of the left ear never exceeded that of the CI-simulation ear. The advantages of binaural integration were calculated by comparing binaural performance with monaural performance using the CI-simulation ear alone. Thus, these advantages reflected the additional use of the experimentally constrained left ear and were not attributable to better-ear listening. Binaural performance was as accurate as, or more accurate than, monaural performance with the CI-simulation ear alone. When both ears supported a similar level of monaural

  13. Perceptual Coding of Audio Signals Using Adaptive Time-Frequency Transform

    Directory of Open Access Journals (Sweden)

    Karthikeyan Umapathy

    2007-08-01

    Full Text Available Wide band digital audio signals have a very high data-rate associated with them due to their complex nature and demand for high-quality reproduction. Although recent technological advancements have significantly reduced the cost of bandwidth and miniaturized storage facilities, the rapid increase in the volume of digital audio content constantly compels the need for better compression algorithms. Over the years various perceptually lossless compression techniques have been introduced, and transform-based compression techniques have made a significant impact in recent years. In this paper, we propose one such transform-based compression technique, where the joint time-frequency (TF properties of the nonstationary nature of the audio signals were exploited in creating a compact energy representation of the signal in fewer coefficients. The decomposition coefficients were processed and perceptually filtered to retain only the relevant coefficients. Perceptual filtering (psychoacoustics was applied in a novel way by analyzing and performing TF specific psychoacoustics experiments. An added advantage of the proposed technique is that, due to its signal adaptive nature, it does not need predetermined segmentation of audio signals for processing. Eight stereo audio signal samples of different varieties were used in the study. Subjective (mean opinion score—MOS listening tests were performed and the subjective difference grades (SDG were used to compare the performance of the proposed coder with MP3, AAC, and HE-AAC encoders. Compression ratios in the range of 8 to 40 were achieved by the proposed technique with subjective difference grades (SDG ranging from –0.53 to –2.27.

  14. Analysis of Maneuvering Targets with Complex Motions by Two-Dimensional Product Modified Lv’s Distribution for Quadratic Frequency Modulation Signals

    Directory of Open Access Journals (Sweden)

    Fulong Jing

    2017-06-01

    Full Text Available For targets with complex motion, such as ships fluctuating with oceanic waves and high maneuvering airplanes, azimuth echo signals can be modeled as multicomponent quadratic frequency modulation (QFM signals after migration compensation and phase adjustment. For the QFM signal model, the chirp rate (CR and the quadratic chirp rate (QCR are two important physical quantities, which need to be estimated. For multicomponent QFM signals, the cross terms create a challenge for detection, which needs to be addressed. In this paper, by employing a novel multi-scale parametric symmetric self-correlation function (PSSF and modified scaled Fourier transform (mSFT, an effective parameter estimation algorithm is proposed—referred to as the Two-Dimensional product modified Lv’s distribution (2D-PMLVD—for QFM signals. The 2D-PMLVD is simple and can be easily implemented by using fast Fourier transform (FFT and complex multiplication. These measures are analyzed in the paper, including the principle, the cross term, anti-noise performance, and computational complexity. Compared to the other three representative methods, the 2D-PMLVD can achieve better anti-noise performance. The 2D-PMLVD, which is free of searching and has no identifiability problems, is more suitable for multicomponent situations. Through several simulations and analyses, the effectiveness of the proposed estimation algorithm is verified.

  15. Multichannel Recorder for Low Frequency Signals: Application of Oscilloscope as Integrated Mobile Service for a Smartphone

    Directory of Open Access Journals (Sweden)

    Michal Kochlan

    2016-01-01

    Full Text Available Data acquisition and processing are well known for some time. Many applications use powerful hardware to acquire, process, and visualize signal waveforms. But there are some applications that do not have to perform high resolution signal acquisition and process large amount of data, for example, low frequency applications of embedded design and applications for remote power grid monitoring. The paper describes special system for low frequency signal data sample acquisition, processing, and visualization implemented as a service on Android-based smart device. The service makes smart device functioning as an oscilloscope or arbitrary waveform generator which is accessible remotely through Bluetooth. The design respects low power consumption requirements, simplicity, and user friendliness in application design. Application scenario was implemented as wireless data acquisition system for power grid monitoring.

  16. 2-D DOA Estimation of LFM Signals Based on Dechirping Algorithm and Uniform Circle Array

    Directory of Open Access Journals (Sweden)

    K. B. Cui

    2017-04-01

    Full Text Available Based on Dechirping algorithm and uniform circle array(UCA, a new 2-D direction of arrival (DOA estimation algorithm of linear frequency modulation (LFM signals is proposed in this paper. The algorithm uses the thought of Dechirping and regards the signal to be estimated which is received by the reference sensor as the reference signal and proceeds the difference frequency treatment with the signal received by each sensor. So the signal to be estimated becomes a single-frequency signal in each sensor. Then we transform the single-frequency signal to an isolated impulse through Fourier transform (FFT and construct a new array data model based on the prominent parts of the impulse. Finally, we respectively use multiple signal classification (MUSIC algorithm and rotational invariance technique (ESPRIT algorithm to realize 2-D DOA estimation of LFM signals. The simulation results verify the effectiveness of the algorithm proposed.

  17. Dual fiber Bragg gratings configuration-based fiber acoustic sensor for low-frequency signal detection

    Science.gov (United States)

    Yang, Dong; Wang, Shun; Lu, Ping; Liu, Deming

    2014-11-01

    We propose and fabricate a new type fiber acoustic sensor based on dual fiber Bragg gratings (FBGs) configuration. The acoustic sensor head is constructed by putting the sensing cells enclosed in an aluminum cylinder space built by two Cband FBGs and a titanium diaphragm of 50 um thickness. One end of each FBG is longitudinally adhered to the diaphragm by UV glue. Both of the two FBGs are employed for reflecting light. The dual FBGs play roles not only as signal transmission system but also as sensing component, and they demodulate each other's optical signal mutually during the measurement. Both of the two FBGs are pre-strained and the output optical power experiences fluctuation in a linear relationship along with a variation of axial strain and surrounding acoustic interference. So a precise approach to measure the frequency and sound pressure of the acoustic disturbance is achieved. Experiments are performed and results show that a relatively flat frequency response in a range from 200 Hz to 1 kHz with the average signal-to-noise ratio (SNR) above 21 dB is obtained. The maximum sound pressure sensitivity of 11.35mV/Pa is achieved with the Rsquared value of 0.99131 when the sound pressure in the range of 87.7-106.6dB. It has potential applications in low frequency signal detection. Owing to its direct self-demodulation method, the sensing system reveals the advantages of easy to demodulate, good temperature stability and measurement reliability. Besides, performance of the proposed sensor could be improved by optimizing the parameters of the sensor, especially the diaphragm.

  18. Signal-Characteristic analysis with respect to backing material of PVDF-based high-frequency ultrasound for photoacoustic microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jun Su; Chang, Jin Ho [Dept. of Electronic Engineering, Sogang University, Seoul (Korea, Republic of)

    2015-04-15

    Photoacoustic microscopy is capable of providing high-resolution molecular images, and its spatial resolution is typically determined by ultrasonic transducers used to receive the photoacoustic signals. Therefore, ultrasonic transducers for photoacoustic microscopy (PAM) should have a high operating frequency, broad bandwidth, and high signal-reception efficiency. Polyvinylidene fluoride (PVDF) is a suitable material. To take full advantage of this material, the selection of the backing material is crucial, as it influences the center frequency and bandwidth of the transducer. Therefore, we experimentally determined the most suitable backing material among EPO-TEK 301, E-Solder 3022, and RTV. For this, three PVDF high-frequency single-element transducers were fabricated with each backing material. The center frequency and -6 dB bandwidth of each transducer were ascertained by a pulse-echo test. The spatial resolution of each transducer was examined using wire-target images. The experimental results indicated that EPO-TEK 301 is the most suitable backing material for a PAM transducer. This material provides the highest signal magnitude and a reasonable bandwidth because a large portion of the energy propagates toward the front medium, and the PVDF resonates in the half-wave mode.

  19. An amplitude modulated radio frequency plasma generator

    Science.gov (United States)

    Lei, Fan; Li, Xiaoping; Liu, Yanming; Liu, Donglin; Yang, Min; Xie, Kai; Yao, Bo

    2017-04-01

    A glow discharge plasma generator and diagnostic system has been developed to study the effects of rapidly variable plasmas on electromagnetic wave propagation, mimicking the plasma sheath conditions encountered in space vehicle reentry. The plasma chamber is 400 mm in diameter and 240 mm in length, with a 300-mm-diameter unobstructed clear aperture. Electron densities produced are in the mid 1010 electrons/cm3. An 800 W radio frequency (RF) generator is capacitively coupled through an RF matcher to an internally cooled stainless steel electrode to form the plasma. The RF power is amplitude modulated by a waveform generator that operates at different frequencies. The resulting plasma contains electron density modulations caused by the varying power levels. A 10 GHz microwave horn antenna pair situated on opposite sides of the chamber serves as the source and detector of probe radiation. The microwave power feed to the source horn is split and one portion is sent directly to a high-speed recording oscilloscope. On mixing this with the signal from the pickup horn antenna, the plasma-induced phase shift between the two signals gives the path-integrated electron density with its complete time dependent variation. Care is taken to avoid microwave reflections and extensive shielding is in place to minimize electronic pickup. Data clearly show the low frequency modulation of the electron density as well as higher harmonics and plasma fluctuations.

  20. Simulation of power fluctuation of wind farms based on frequency domain

    DEFF Research Database (Denmark)

    Lin, Jin; Sun, Yuanzhang; Li, Guojie

    2011-01-01

    , however, is incapable of completely explaining the physical mechanism of randomness of power fluctuation. To remedy such a situation, fluctuation modeling based on the frequency domain is proposed. The frequency domain characteristics of stochastic fluctuation on large wind farms are studied using...... the power spectral density of wind speed, the frequency domain model of a wind power generator and the information on weather and geography of the wind farms. The correctness and effectiveness of the model are verified by comparing the measurement data with simulation results of a certain wind farm. © 2011...

  1. Nano-Scale Devices for Frequency-Based Magnetic Biosensing

    Science.gov (United States)

    2017-01-31

    show the basic measurement setup (the field is applied perpendicular to the disk plane). A radiofrequency signal is injected across the disk (disks...shown in Fig. 7(a). A spectrum analyser (S.A.) (or a high frequency oscilloscope) is used to measure the radiofrequency STO output signal with Fig...crystals and, via electrical measurements , in magnetic-vortex-containing, isolated micro- and nano-devices. Via micromagnetic simulations, we have largely

  2. Bi-Frequency Modulated Quasi-Resonant Converters: Theory and Applications

    Science.gov (United States)

    Zhang, Yuefeng

    1995-01-01

    To avoid the variable frequency operation of quasi -resonant converters, many soft-switching PWM converters have been proposed, all of them require an auxiliary switch, which will increase the cost and complexity of the power supply system. In this thesis, a new kind of technique for quasi -resonant converters has been proposed, which is called the bi-frequency modulation technique. By operating the quasi-resonant converters at two switching frequencies, this technique enables quasi-resonant converters to achieve the soft-switching, at fixed switching frequencies, without an auxiliary switch. The steady-state analysis of four commonly used quasi-resonant converters, namely, ZVS buck, ZCS buck, ZVS boost, and ZCS boost converter has been presented. Using the concepts of equivalent sources, equivalent sinks, and resonant tank, the large signal models of these four quasi -resonant converters were developed. Based on these models, the steady-state control characteristics of BFM ZVS buck, BFM ZCS buck, BFM ZVS boost, and BFM ZCS boost converter have been derived. The functional block and design consideration of the bi-frequency controller were presented, and one of the implementations of the bi-frequency controller was given. A complete design example has been presented. Both computer simulations and experimental results have verified that the bi-frequency modulated quasi-resonant converters can achieve soft-switching, at fixed switching frequencies, without an auxiliary switch. One of the application of bi-frequency modulation technique is for EMI reduction. The basic principle of using BFM technique for EMI reduction was introduced. Based on the spectral analysis, the EMI performances of the PWM, variable-frequency, and bi-frequency modulated control signals was evaluated, and the BFM control signals show the lowest EMI emission. The bi-frequency modulated technique has also been applied to the power factor correction. A BFM zero -current switching boost converter has

  3. Properties of an improved Gabor wavelet transform and its applications to seismic signal processing and interpretation

    Science.gov (United States)

    Ji, Zhan-Huai; Yan, Sheng-Gang

    2017-12-01

    This paper presents an analytical study of the complete transform of improved Gabor wavelets (IGWs), and discusses its application to the processing and interpretation of seismic signals. The complete Gabor wavelet transform has the following properties. First, unlike the conventional transform, the improved Gabor wavelet transform (IGWT) maps time domain signals to the time-frequency domain instead of the time-scale domain. Second, the IGW's dominant frequency is fixed, so the transform can perform signal frequency division, where the dominant frequency components of the extracted sub-band signal carry essentially the same information as the corresponding components of the original signal, and the subband signal bandwidth can be regulated effectively by the transform's resolution factor. Third, a time-frequency filter consisting of an IGWT and its inverse transform can accurately locate target areas in the time-frequency field and perform filtering in a given time-frequency range. The complete IGW transform's properties are investigated using simulation experiments and test cases, showing positive results for seismic signal processing and interpretation, such as enhancing seismic signal resolution, permitting signal frequency division, and allowing small faults to be identified.

  4. Changes on Mid-Latitude Cyclones due to Global Warming Simulated by a Global 20-km-mesh Atmospheric Model

    Science.gov (United States)

    Miyamoto, K.

    2005-12-01

    I investigate how the intensity and the activity of mid-latitude cyclones change as a result of global warming, based on a time-slice experiment with a super-high resolution Atmospheric General Circulation Model (20-km mesh TL959L60 MRI/JMA AGCM). The model was developed by the RR2002 project "Development of Super High Resolution Global and Regional Climate Models" funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology. In this context, I use a 10-year control simulation with the climatological SST and a 10-year time-slice global warming simulation using the SST anomalies derived from the SRES A1B scenario run with the MRI-CGCM2.3 (T42L30 atmosphere, 0.5-2.0 x 2.5 L23 ocean) corresponding to the end of the 21st century. I have analyzed the sea-level pressure field and the kinetic energy field of the wind at the 500 hPa pressure level associated with mid-latitude transients from October through April. According to a comparison of 10-day average fields between present and future in the North Pacific, some statistically significant changes are found in a warmer climate for the both of sea-level pressure and the kinetic energy fields. In particular, from late winter through early spring, the sea-level pressure decreases on many parts of the whole Pacific. The kinetic energy of the wind becomes higher on center of the basin. Therefore, I suppose the Aleutian Low is likely to settle in longer by about one month than the present. Hereafter, I plan to investigate what kind of phenomena may accompany the changes on mid-latitude transients.

  5. Stable radio frequency dissemination by simple hybrid frequency modulation scheme.

    Science.gov (United States)

    Yu, Longqiang; Wang, Rong; Lu, Lin; Zhu, Yong; Wu, Chuanxin; Zhang, Baofu; Wang, Peizhang

    2014-09-15

    In this Letter, we propose a fiber-based stable radio frequency transfer system by a hybrid frequency modulation scheme. Creatively, two radio frequency signals are combined and simultaneously transferred by only one laser diode. One frequency component is used to detect the phase fluctuation, and the other one is the derivative compensated signal providing a stable frequency for the remote end. A proper ratio of the frequencies of the components is well maintained by parameter m to avoid interference between them. Experimentally, a stable 200 MHz signal is transferred over 100 km optical fiber with the help of a 1 GHz detecting signal, and fractional instability of 2×10(-17) at 10(5) s is achieved.

  6. Estimation of pathological tremor from recorded signals based on adaptive sliding fast Fourier transform

    Directory of Open Access Journals (Sweden)

    Shengxin Wang

    2016-06-01

    Full Text Available Pathological tremor is an approximately rhythmic movement and considerably affects patients’ daily living activities. Biomechanical loading and functional electrical stimulation are proposed as potential alternatives for canceling the pathological tremor. However, the performance of suppression methods is associated with the separation of tremor from the recorded signals. In this literature, an algorithm incorporating a fast Fourier transform augmented with a sliding convolution window, an interpolation procedure, and a damping module of the frequency is presented to isolate tremulous components from the measured signals and estimate the instantaneous tremor frequency. Meanwhile, a mechanism platform is designed to provide the simulation tremor signals with different degrees of voluntary movements. The performance of the proposed algorithm and existing procedures is compared with simulated signals and experimental signals collected from patients. The results demonstrate that the proposed solution could detect the unknown dominant frequency and distinguish the tremor components with higher accuracy. Therefore, this algorithm is useful for actively compensating tremor by functional electrical stimulation without affecting the voluntary movement.

  7. Frequency Stability Enhancement for Low Inertia Systems using Synthetic Inertia of Wind Power

    DEFF Research Database (Denmark)

    Nguyen, Ha Thi; Yang, Guangya; Nielsen, Arne Hejde

    2017-01-01

    stability, this paper proposes supplementary control methods to implement synthetic inertia for doubly-fed induction generator (DFIG) based wind energy system during frequency excursions. Different control strategies and activation schemes are analyzed and implemented on the Western Danish renewable......-based system using-real time digital simulator (RTDS) to propose the best one for the synthetic inertia controller. From the comparative simulation results, it can be concluded that the method using a combination of both the frequency deviation and derivative as input signals, and the under-frequency trigger...

  8. Simulating return signals of a spaceborne high-spectral resolution lidar channel at 532 nm

    Science.gov (United States)

    Xiao, Yu; Binglong, Chen; Min, Min; Xingying, Zhang; Lilin, Yao; Yiming, Zhao; Lidong, Wang; Fu, Wang; Xiaobo, Deng

    2018-06-01

    High spectral resolution lidar (HSRL) system employs a narrow spectral filter to separate the particulate (cloud/aerosol) and molecular scattering components in lidar return signals, which improves the quality of the retrieved cloud/aerosol optical properties. To better develop a future spaceborne HSRL system, a novel simulation technique was developed to simulate spaceborne HSRL return signals at 532 nm using the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) cloud/aerosol extinction coefficients product and numerical weather prediction data. For validating simulated data, a mathematical particulate extinction coefficient retrieval method for spaceborne HSRL return signals is described here. We compare particulate extinction coefficient profiles from the CALIPSO operational product with simulated spaceborne HSRL data. Further uncertainty analysis shows that relative uncertainties are acceptable for retrieving the optical properties of cloud and aerosol. The final results demonstrate that they agree well with each other. It indicates that the return signals of the spaceborne HSRL molecular channel at 532 nm will be suitable for developing operational algorithms supporting a future spaceborne HSRL system.

  9. Simulation of GNSS reflected signals and estimation of position accuracy in GNSS-challenged environment

    DEFF Research Database (Denmark)

    Jakobsen, Jakob; Jensen, Anna B. O.; Nielsen, Allan Aasbjerg

    2015-01-01

    non-line-of-sight satellites. The signal reflections are implemented using the extended geometric path length of the signal path caused by reflections from the surrounding buildings. Based on real GPS satellite positions, simulated Galileo satellite positions, models of atmospheric effect...... on the satellite signals, designs of representative environments e.g. urban and rural scenarios, and a method to simulate reflection of satellite signals within the environment we are able to estimate the position accuracy given several prerequisites as described in the paper. The result is a modelling...... of the signal path from satellite to receiver, the satellite availability, the extended pseudoranges caused by signal reflection, and an estimate of the position accuracy based on a least squares adjustment of the extended pseudoranges. The paper describes the models and algorithms used and a verification test...

  10. Using pulse oximetry to account for high and low frequency physiological artifacts in the BOLD signal.

    Science.gov (United States)

    Verstynen, Timothy D; Deshpande, Vibhas

    2011-04-15

    The BOLD signal not only reflects changes in local neural activity, but also exhibits variability from physiological processes like cardiac rhythms and breathing. We investigated how both of these physiological sources are reflected in the pulse oximetry (PO) signal, a direct measure of blood oxygenation, and how this information can be used to account for different types of noise in the BOLD response. Measures of heart rate, respiration and PO were simultaneously recorded while neurologically healthy participants performed an eye-movement task in a 3T MRI. PO exhibited power in frequencies that matched those found in the independently recorded cardiac and respiration signals. Using the phasic and aphasic properties of these signals as nuisance regressors, we found that the different frequency components of the PO signal could be used to identify different types of physiological artifacts in the BOLD response. A comparison of different physiological noise models found that a simple, down-sampled version of the PO signal improves the estimation of task-relevant statistics nearly as well as more established noise models that may run the risk of over-parameterization. These findings suggest that the PO signal captures multiple sources of physiological noise in the BOLD response and provides a simple and efficient way of modeling these noise sources in subsequent analysis. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Comparison of Forced ENSO-Like Hydrological Expressions in Simulations of the Preindustrial and Mid-Holocene

    Science.gov (United States)

    Lewis, Sophie C.; LeGrande, Allegra N.; Schmidt, Gavin A.; Kelley, Maxwell

    2014-01-01

    Using the water isotope- and vapor source distribution (VSD) tracer-enabled Goddard Institute for Space Studies ModelE-R, we examine changing El Nino-Southern Oscillation (ENSO)-like expressions in the hydrological cycle in a suite of model experiments. We apply strong surface temperature anomalies associated with composite observed El Nino and La Nina events as surface boundary conditions to preindustrial and mid-Holocene model experiments in order to investigate ENSO-like expressions in the hydrological cycle under varying boundary conditions. We find distinct simulated hydrological anomalies associated with El Nino-like ("ENSOWARM") and La Nina-like ("ENSOCOOL") conditions, and the region-specific VSD tracers show hydrological differences across the Pacific basin between El Nino-like and La Nina-like events. The application of ENSOCOOL forcings does not produce climatological anomalies that represent the equal but opposite impacts of the ENSOWARM experiment, as the isotopic anomalies associated with ENSOWARM conditions are generally stronger than with ENSOCOOL and the spatial patterns of change distinct. Also, when the same ENSO-like surface temperature anomalies are imposed on the mid-Holocene, the hydrological response is muted, relative to the preindustrial. Mid-Holocene changes in moisture sources to the analyzed regions across the Pacific reveal potentially complex relationships between ENSO-like conditions and boundary conditions. Given the complex impacts of ENSO-like conditions on various aspects of the hydrological cycle, we suggest that proxy record insights into paleo-ENSO variability are most likely to be robust when synthesized from a network of many spatially diverse archives, which can account for the potential nonstationarity of ENSO teleconnections under different boundary conditions.

  12. Cross-Term Suppression in Time Order Distribution for AWGN Signal

    Directory of Open Access Journals (Sweden)

    WAQAS MAHMOOD

    2017-04-01

    Full Text Available A technique of cross-term suppression in WD (Wigner Distribution for a multi-component signal that is embedded WGN (White Gaussian Noise is proposed. In this technique, an optimized algorithm is developed for time-varying noisy signal and a CAD (Computer Aided Design simulator is designed for Numerical simulations of synthetic signal. In proposed technique, signal components are localized in tf (time frequency plane by STFT (Short Time Fourier Transform. Rectified STFT is computed and Spectral Kurtosis is used to separate a signal components from noise in t-f plane. The t-f plane is segmented and then signal components are filtered out by FFT (Fractional Fourier Transform. Finally, WD (free of cross terms of isolated signal component is computed to obtain high resolution in t-f plane.

  13. ANALISYS OF FRACTIONAL-N FREQUENCY SYNTHESIZERS

    Directory of Open Access Journals (Sweden)

    Boris I. Shakhtarin

    2018-01-01

    Full Text Available Modern information and control systems cannot be imagined without synchronization subsystems. These are the basic elements that provide tracking of the frequency and phase of reference and information signals, the evaluation of information parameters, and the synthesis of reference and clock signals. Frequency synthesizers (FS are widely used due to the high speed of frequency setting, a wide range of frequency grids and minimal phase noise in the operating frequency range. Since with the mass appearance of specialized microprocessors and with the improvement of automatic design systems, the feasibility and repeatability of products has become simpler, digital FS are increasingly being used. The most widely used are FS with a frequency divider on digital elements, which serves to convert the signal of a reference oscillator and a controlled generator. For FS using a divisor with an integer division factor in the feedback loop, there are a number of limitations, such as the lower frequency of the FS and the frequency step of the FS. To solve this problem, divisors with fractional-variable division factors in the feedback loop are used, which allow to obtain the required range and the grid frequency step of the FS. The methods of improving the quality of spectral and dynamic characteristics of digital synthesizers in a given band of frequency detuning are analyzed. The principles of the FS operation with a divisor with a fractionalvariable fission coefficient are described, and structural schemes are given. The results of imitation simulation in the Simulink system of the software package MATLAB of frequency synthesizers with a divisor with a fractional-variable fission factor implemented in various ways are presented, and a comparative analysis of the spectral characteristics of the obtained models is carried out. 

  14. Simulation of neutrons and gamma pulse signal and research on the pulse shape discrimination technology

    International Nuclear Information System (INIS)

    Zuo Guangxia; He Bin; Xu Peng; Qiu Xiaolin; Ma Wenyan; Li Sufen

    2012-01-01

    In neutrons detection, it is important to discriminate the neutron signals from the gamma-ray background. In this article, simulation of neutrons and gamma pulse signals is developed based on the LabVIEW platform. Two digital algorithms of the charge comparison method and the pulse duration time method are realized using 10000 simulation signals. Experimental results show that neutron and gamma pulse signals can be discriminated by the two methods, and the pulse duration time method is better than the charge comparison method. (authors)

  15. MASER: Measuring, Analysing, Simulating low frequency Radio Emissions.

    Science.gov (United States)

    Cecconi, B.; Le Sidaner, P.; Savalle, R.; Bonnin, X.; Zarka, P. M.; Louis, C.; Coffre, A.; Lamy, L.; Denis, L.; Griessmeier, J. M.; Faden, J.; Piker, C.; André, N.; Genot, V. N.; Erard, S.; King, T. A.; Mafi, J. N.; Sharlow, M.; Sky, J.; Demleitner, M.

    2017-12-01

    The MASER (Measuring, Analysing and Simulating Radio Emissions) project provides a comprehensive infrastructure dedicated to low frequency radio emissions (typically Radioastronomie de Nançay and the CDPP deep archive. These datasets include Cassini/RPWS, STEREO/Waves, WIND/Waves, Ulysses/URAP, ISEE3/SBH, Voyager/PRA, Nançay Decameter Array (Routine, NewRoutine, JunoN), RadioJove archive, swedish Viking mission, Interball/POLRAD... MASER also includes a Python software library for reading raw data.

  16. A real scale simulator for high frequency LEMP

    Science.gov (United States)

    Gauthier, D.; Serafin, D.

    1991-01-01

    The real scale simulator is described which was designed by the Centre d'Etudes de Gramat (CEG) to study the coupling of fast rise time Lightning Electromagnetic pulse in a fighter aircraft. The system capability of generating the right electromagnetic environment was studied using a Finite Difference Time Domain (FDTD) computer program. First, data of inside stresses are shown. Then, a time domain and a frequency domain approach is exposed and compared.

  17. A low-jitter RF PLL frequency synthesizer with high-speed mixed-signal down-scaling circuits

    International Nuclear Information System (INIS)

    Tang Lu; Wang Zhigong; Xue Hong; He Xiaohu; Xu Yong; Sun Ling

    2010-01-01

    A low-jitter RF phase locked loop (PLL) frequency synthesizer with high-speed mixed-signal down-scaling circuits is proposed. Several techniques are proposed to reduce the design complexity and improve the performance of the mixed-signal down-scaling circuit in the PLL. An improved D-latch is proposed to increase the speed and the driving capability of the DMP in the down-scaling circuit. Through integrating the D-latch with 'OR' logic for dual-modulus operation, the delays associated with both the 'OR' and D-flip-flop (DFF) operations are reduced, and the complexity of the circuit is also decreased. The programmable frequency divider of the down-scaling circuit is realized in a new method based on deep submicron CMOS technology standard cells and a more accurate wire-load model. The charge pump in the PLL is also realized with a novel architecture to improve the current matching characteristic so as to reduce the jitter of the system. The proposed RF PLL frequency synthesizer is realized with a TSMC 0.18-μm CMOS process. The measured phase noise of the PLL frequency synthesizer output at 100 kHz offset from the center frequency is only -101.52 dBc/Hz. The circuit exhibits a low RMS jitter of 3.3 ps. The power consumption of the PLL frequency synthesizer is also as low as 36 mW at a 1.8 V power supply. (semiconductor integrated circuits)

  18. Fundamental Frequency Estimation of the Speech Signal Compressed by MP3 Algorithm Using PCC Interpolation

    Directory of Open Access Journals (Sweden)

    MILIVOJEVIC, Z. N.

    2010-02-01

    Full Text Available In this paper the fundamental frequency estimation results of the MP3 modeled speech signal are analyzed. The estimation of the fundamental frequency was performed by the Picking-Peaks algorithm with the implemented Parametric Cubic Convolution (PCC interpolation. The efficiency of PCC was tested for Catmull-Rom, Greville and Greville two-parametric kernel. Depending on MSE, a window that gives optimal results was chosen.

  19. Optimization and simulation of MEMS rectilinear ion trap

    Directory of Open Access Journals (Sweden)

    Huang Gang

    2015-04-01

    Full Text Available In this paper, the design of a MEMS rectilinear ion trap was optimized under simulated conditions. The size range of the MEMS rectilinear ion trap’s electrodes studied in this paper is measured at micron scale. SIMION software was used to simulate the MEMS rectilinear ion trap with different sizes and different radio-frequency signals. The ion-trapping efficiencies of the ion trap under these different simulation conditions were obtained. The ion-trapping efficiencies were compared to determine the performance of the MEMS rectilinear ion trap in different conditions and to find the optimum conditions. The simulation results show that for the ion trap at micron scale or smaller, the optimized length–width ratio was 0.8, and a higher frequency of radio-frequency signal is necessary to obtain a higher ion-trapping efficiency. These results have a guiding role in the process of developing MEMS rectilinear ion traps, and great application prospects in the research fields of the MEMS rectilinear ion trap and the MEMS mass spectrometer.

  20. Balancing Vibrations at Harmonic Frequencies by Injecting Harmonic Balancing Signals into the Armature of a Linear Motor/Alternator Coupled to a Stirling Machine

    Science.gov (United States)

    Holliday, Ezekiel S. (Inventor)

    2014-01-01

    Vibrations at harmonic frequencies are reduced by injecting harmonic balancing signals into the armature of a linear motor/alternator coupled to a Stirling machine. The vibrations are sensed to provide a signal representing the mechanical vibrations. A harmonic balancing signal is generated for selected harmonics of the operating frequency by processing the sensed vibration signal with adaptive filter algorithms of adaptive filters for each harmonic. Reference inputs for each harmonic are applied to the adaptive filter algorithms at the frequency of the selected harmonic. The harmonic balancing signals for all of the harmonics are summed with a principal control signal. The harmonic balancing signals modify the principal electrical drive voltage and drive the motor/alternator with a drive voltage component in opposition to the vibration at each harmonic.

  1. Online frequency estimation with applications to engine and generator sets

    Science.gov (United States)

    Manngård, Mikael; Böling, Jari M.

    2017-07-01

    Frequency and spectral analysis based on the discrete Fourier transform is a fundamental task in signal processing and machine diagnostics. This paper aims at presenting computationally efficient methods for real-time estimation of stationary and time-varying frequency components in signals. A brief survey of the sliding time window discrete Fourier transform and Goertzel filter is presented, and two filter banks consisting of: (i) sliding time window Goertzel filters (ii) infinite impulse response narrow bandpass filters are proposed for estimating instantaneous frequencies. The proposed methods show excellent results on both simulation studies and on a case study using angular speed data measurements of the crankshaft of a marine diesel engine-generator set.

  2. Experimental Study of Low Speed Sensorless Control of PMSM Drive Using High Frequency Signal Injection

    Directory of Open Access Journals (Sweden)

    Jyoti Agrawal

    2016-01-01

    Full Text Available Conventional techniques for sensorless control of permanent magnet synchronous motor drive (PMSM, which requires information on rotor position, are reviewed, and recent developments in this area are introduced in this paper along with their inherent advantages and drawbacks. The paper presents an improved method for sensorless speed control of PMSM drive with emphasis placed on signal injection method. This signal injection method examines the control performance of sensorless PMSM drive by injecting signal externally and thereby sensing the rotor position. The main objective of this drive system is to have speed control at standstill and low speed regions. Several tests are carried out to demonstrate the ability of proposed models at different operating conditions with the help of simulation results in Matlab/Simulink environment. Simulation results confirm that the proposed sensorless control approach of PMSM can achieve high performance at standstill and low speeds but not at very high speeds. An experimental setup is implemented using a 1HP surface mounted (SM PMSM and DsPICDEM^TM MCHV-2 development board, to check the validity of simulation results.

  3. Effects of vibration frequency on vibration-assisted nano-scratch process of mono-crystalline copper via molecular dynamics simulation

    Directory of Open Access Journals (Sweden)

    Bo Zhu

    2016-03-01

    Full Text Available It has always been a critical issue to understand the material removal behavior of Vibration-Assisted Machining (VAM, especially on atomic level. To find out the effects of vibration frequency on material removal response, a three-dimensional molecular dynamics (MD model has been established in this research to investigate the effects of scratched groove, crystal defects on the surface quality, comparing with the Von Mises shear strain and tangential force in simulations during nano-scratching process. Comparisons are made among the results of simulations from different vibration frequency with the same scratching feed, depth, amplitude and crystal orientation. Copper potential in this simulation is Embedded-Atom Method (EAM potential. Interaction between copper and carbon atoms is Morse potential. Simulational results show that higher frequency can make groove smoother. Simulation with high frequency creates more dislocations to improve the machinability of copper specimen. The changing frequency does not have evident effects on Von Mises shear strain. Higher frequency can decrease the tangential force to reduce the consumption of cutting energy and tool wear. In conclusion, higher vibration frequency in VAM on mono-crystalline copper has positive effects on surface finish, machinablility and tool wear reduction.

  4. Effects of vibration frequency on vibration-assisted nano-scratch process of mono-crystalline copper via molecular dynamics simulation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Bo; Zhao, Hongwei, E-mail: hwzhao@jlu.edu.cn, E-mail: khl69@163.com; Zhao, Dan; Zhang, Peng; Yang, Yihan; Han, Lei [School of Mechanical Science and Engineering, Jilin University, 5988 Renmin Street, Changchun, Jilin 130025 (China); Kui, Hailin, E-mail: hwzhao@jlu.edu.cn, E-mail: khl69@163.com [School of Transportation, Jilin University, 5988 Renmin Street, Changchun, Jilin 130025 (China)

    2016-03-15

    It has always been a critical issue to understand the material removal behavior of Vibration-Assisted Machining (VAM), especially on atomic level. To find out the effects of vibration frequency on material removal response, a three-dimensional molecular dynamics (MD) model has been established in this research to investigate the effects of scratched groove, crystal defects on the surface quality, comparing with the Von Mises shear strain and tangential force in simulations during nano-scratching process. Comparisons are made among the results of simulations from different vibration frequency with the same scratching feed, depth, amplitude and crystal orientation. Copper potential in this simulation is Embedded-Atom Method (EAM) potential. Interaction between copper and carbon atoms is Morse potential. Simulational results show that higher frequency can make groove smoother. Simulation with high frequency creates more dislocations to improve the machinability of copper specimen. The changing frequency does not have evident effects on Von Mises shear strain. Higher frequency can decrease the tangential force to reduce the consumption of cutting energy and tool wear. In conclusion, higher vibration frequency in VAM on mono-crystalline copper has positive effects on surface finish, machinablility and tool wear reduction.

  5. Control of recollection by slow gamma dominating mid-frequency gamma in hippocampus CA1

    Science.gov (United States)

    Dvorak, Dino; Radwan, Basma; Sparks, Fraser T.; Talbot, Zoe Nicole

    2018-01-01

    Behavior is used to assess memory and cognitive deficits in animals like Fmr1-null mice that model Fragile X Syndrome, but behavior is a proxy for unknown neural events that define cognitive variables like recollection. We identified an electrophysiological signature of recollection in mouse dorsal Cornu Ammonis 1 (CA1) hippocampus. During a shocked-place avoidance task, slow gamma (SG) (30–50 Hz) dominates mid-frequency gamma (MG) (70–90 Hz) oscillations 2–3 s before successful avoidance, but not failures. Wild-type (WT) but not Fmr1-null mice rapidly adapt to relocating the shock; concurrently, SG/MG maxima (SGdom) decrease in WT but not in cognitively inflexible Fmr1-null mice. During SGdom, putative pyramidal cell ensembles represent distant locations; during place avoidance, these are avoided places. During shock relocation, WT ensembles represent distant locations near the currently correct shock zone, but Fmr1-null ensembles represent the formerly correct zone. These findings indicate that recollection occurs when CA1 SG dominates MG and that accurate recollection of inappropriate memories explains Fmr1-null cognitive inflexibility. PMID:29346381

  6. On the undesired frequency chirping in photonic time-stretch systems

    Science.gov (United States)

    Xu, Yuxiao; Chi, Hao; Jin, Tao; Zheng, Shilie; Jin, Xiaofeng; Zhang, Xianmin

    2017-12-01

    The technique of photonic time stretch (PTS) has been intensively investigated in the past decade due to its potential in the acquisition of ultra-high speed signals. The frequency-related RF power fading in the PTS systems with double sideband (DSB) modulation has been well-known, which limits the maximum modulation frequency. Some solutions have been proposed to solve this problem. In this paper, we report another effect, i.e., undesired frequency chirping, which also relates to the performance degradation of PTS systems with DSB modulation, for the first time to our knowledge. Distinct from the nonlinearities caused by nonlinear modulation and square-law photodetection, which is common in radio frequency analog optical links, this frequency chirping originates from the addition of two beating signals with a relative delay after photodetection. A theoretical model for exactly describing the frequency chirping is presented, and is then verified by simulations. Discussion on the method to avoid the frequency chirping is also presented.

  7. Unique portable signal acquisition/processing station

    International Nuclear Information System (INIS)

    Garron, R.D.; Azevedo, S.G.

    1983-01-01

    At Lawrence Livermore National Laboratory, there are experimental applications requiring digital signal acquisition as well as data reduction and analysis. A prototype Signal Acquisition/Processing Station (SAPS) has been constructed and is currently undergoing tests. The system employs an LSI-11/23 computer with Data Translation analog-to-digital hardware. SAPS is housed in a roll-around cart which has been designed to withstand most subtle EMI/RFI environments. A user-friendly menu allows a user to access powerful data acquisition packages with a minimum of training. The software architecture of SAPS involves two operating systems, each being transparent to the user. Since this is a general purpose workstation with several units being utilized, an emphasis on low cost, reliability, and maintenance was stressed during conception and design. The system is targeted for mid-range frequency data acquisition; between a data logger and a transient digitizer

  8. Selection of mother wavelets for the detection of the oscillation frequencies in power signals of nuclear reactors

    International Nuclear Information System (INIS)

    Amador G, R.; Castillo D, R.; Ortiz V, J.

    2007-01-01

    Diverse types of transitory events can lead to oscillations of power in nuclear reactors. In such events, the power monitors provide a signal that contains important characteristics of the transitory one, as the oscillation frequency, tendencies, changes and the instants or periods in those that important events are presented. This characteristics are detected by means of diverse analysis techniques, as Autoregressive methods, Fourier Transform, Fourier Transform in Short Time, Wavelets Transform, among others. Presently work is used the one Wavelets Continuous Transform because it allows to carry out studies of the stationary, quasi-stationary and transitory signals in the Time-scale and Time-scale-spectrum planes. Contrary to other similar works, this work describes a methodology for the selection of the scales and the Wavelet mother to be applied the one Wavelets Continuous Transform, with the objective of detecting to the dominant frequencies of the system. To prove the proposal a broadly well-known real signal of an event of power oscillations it has been used. The obtained results correspond to three families of Wavelets mothers that fulfilled the conditions of scales and central frequency of the proposal. The results show that the value of the certain frequency oscillation in this work is practically the same one reported in other studies with other techniques. (Author)

  9. Simulation model of a wind turbine pitch controller for grid frequency stabilisation

    Energy Technology Data Exchange (ETDEWEB)

    Jauch, Clemens; Cronin, Tom

    2005-06-15

    This paper describes a pitch angle controller that enables an active-stall wind turbine to dampen actively grid frequency oscillations. This builds on previous work in the area of the transient stability control of active-stall turbines. The phenomenon of grid frequency oscillations is explained briefly and then the task for the wind turbine controller defined. The pitch controller that acts as a grid frequency stabiliser is explained in terms of its layout, control sequence and parameters. Finally, a transient fault situation with subsequent grid frequency oscillations is simulated and it is shown how the grid frequency stabiliser works. The performance of the controller is discussed and the conclusion is drawn that grid frequency stabilisation with an active-stall turbine is possible under certain conditions. (Author)

  10. Comparative visual ecophysiology of mid-Atlantic temperate reef fishes

    Directory of Open Access Journals (Sweden)

    Andrij Z. Horodysky

    2013-11-01

    The absolute light sensitivities, temporal properties, and spectral sensitivities of the visual systems of three mid-Atlantic temperate reef fishes (Atlantic spadefish [Ephippidae: Chaetodipterus faber], tautog [Labridae: Tautoga onitis], and black sea bass [Serranidae: Centropristis striata] were studied via electroretinography (ERG. Pelagic Atlantic spadefish exhibited higher temporal resolution but a narrower dynamic range than the two more demersal foragers. The higher luminous sensitivities of tautog and black sea bass were similar to other benthic and demersal coastal mid-Atlantic fishes. Flicker fusion frequency experiments revealed significant interspecific differences at maximum intensities that correlated with lifestyle and habitat. Spectral responses of the three species spanned 400–610 nm, with high likelihood of cone dichromacy providing the basis for color and contrast discrimination. Significant day-night differences in spectral responses were evident in spadefish and black sea bass but not tautog, a labrid with characteristic structure-associated nocturnal torpor. Atlantic spadefish responded to a wider range of wavelengths than did deeper-dwelling tautog or black sea bass. Collectively, these results suggest that temperate reef-associated fishes are well-adapted to their gradient of brighter to dimmer photoclimates, representative of their unique ecologies and life histories. Continuing anthropogenic degradation of water quality in coastal environments, at a pace faster than the evolution of visual systems, may however impede visual foraging and reproductive signaling in temperate reef fishes.

  11. A clutter removal method for the Doppler ultrasound signal based on a nonlinear diffusion equation

    International Nuclear Information System (INIS)

    Li Peng; Xin Pengcheng; Bian Zhengzhong; Yu Gang

    2008-01-01

    Strong clutter components produced by stationary and slow-moving tissue structures render the lower frequency part of the spectrogram useless and degrade the accuracy of clinical ultrasound indices. An adaptive method based on the nonlinear forward-and-backward diffusion equation (FAB-DE) is proposed to remove strong clutter components from the contaminated Doppler signal. The clutter signal is extracted first by the FAB-DE accurately, in which the nonlinear diffusion coefficient function of the FAB-DE locally adjusts according to signal features and the diffusion adaptively switches between forward and backward mode. The present method has been validated by simulated and realistic pulse wave Doppler signals, and compared with the conventional high pass filter and the matching pursuit method. The simulation results, including spectrogram, mean velocity error, standard deviation of mean velocity and signal-to-clutter ratio of a decontaminated signal, demonstrate that the present FAB-DE method can remove clutter sufficiently and retain more low blood components simultaneously as compared with the other two methods. Results of the realistic Doppler blood signal, including spectrogram and low-frequency part of the spectrum, support the conclusion drawn from simulation cases

  12. A New Signal Model for Axion Cavity Searches from N -body Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Lentz, Erik W.; Rosenberg, Leslie J. [Physics Department, University of Washington, Seattle, WA 98195-1580 (United States); Quinn, Thomas R.; Tremmel, Michael J., E-mail: lentze@phys.washington.edu, E-mail: ljrosenberg@phys.washington.edu, E-mail: trq@astro.washington.edu, E-mail: mjt29@astro.washington.edu [Astronomy Department, University of Washington, Seattle, WA 98195-1580 (United States)

    2017-08-20

    Signal estimates for direct axion dark matter (DM) searches have used the isothermal sphere halo model for the last several decades. While insightful, the isothermal model does not capture effects from a halo’s infall history nor the influence of baryonic matter, which has been shown to significantly influence a halo’s inner structure. The high resolution of cavity axion detectors can make use of modern cosmological structure-formation simulations, which begin from realistic initial conditions, incorporate a wide range of baryonic physics, and are capable of resolving detailed structure. This work uses a state-of-the-art cosmological N -body+Smoothed-Particle Hydrodynamics simulation to develop an improved signal model for axion cavity searches. Signal shapes from a class of galaxies encompassing the Milky Way are found to depart significantly from the isothermal sphere. A new signal model for axion detectors is proposed and projected sensitivity bounds on the Axion DM eXperiment (ADMX) data are presented.

  13. MODELLING AND SIMULATION OF HIGH FREQUENCY INVERTER FOR INDUCTION HEATING APPLICATION

    OpenAIRE

    SACHIN S. BANKAR; Dr. PRASAD M. JOSHI

    2016-01-01

    This paper presents modelling and simulation of high frequency inverter for induction heating applications. Induction heating has advantages like higher efficiency, controlled heating, safety and pollution free therefore this technology is used in industrial, domestic and medical applications. The high frequency full bridge inverter is used for induction heating, also MOSFET is used as a switching device for inverter and the control strategy used for inverter is Bipolar PWM control. The size ...

  14. The DECMU: a digital device for delayed analysis of multi-frequency eddy current signals

    International Nuclear Information System (INIS)

    Pigeon, Michel.

    1981-08-01

    A delayed data analysis system has been realized by the CEA and Intercontrole for in-service inspection of steam generators of nuclear plants by multifrequency eddy current testing. This device allows, out of the plant, adjustment during switching of the probes, graph recording and analysis for defect signal qualification. The equipment contains an analog mixing device, as IC3FA multi-frequency appartus, but has in addition a memory allowing data cycling and signal isolation for adjustment or analysis [fr

  15. Simulation and Evaluation of ECT Signals From MRPC Probe in Combo Calibration Standard Tube Using Electromagnetic Numerical Analysis

    International Nuclear Information System (INIS)

    Yoo, Joo Young; Song, Sung Jin; Jung, Hee Jun; Kong, Young Bae

    2006-01-01

    Signals captured from a Combo calibration standard tube play a crucial role in the evaluation of motorized rotating pancake coil (MRPC) probe signals from steam generator (SG) tubes in nuclear power plants (NPPs). Therefore, the Combo tube signals should be consistent and accurate. However, MRPC probe signals are very easily affected by various factors around the tubes so that they can be distorted in their amplitudes and phase angles which are the values specifically used in the evaluation. To overcome this problem, in this study, we explored possibility of simulation to be used as a practical calibration tool far the evaluation of real field signals. For this purpose, we investigated the characteristics of a MRPC probe and a Combo tube. And then using commercial software (VIC-3D) we simulated a set of calibration signals and compared to the experimental signals. From this comparison, we verified the accuracy of the simulated signals. Finally, we evaluated two defects using the simulated Combo tube signals, and the results were compared with those obtained using the actual field calibration signals

  16. Fast 2D Fluid-Analytical Simulation of IEDs and Plasma Uniformity in Multi-frequency CCPs

    Science.gov (United States)

    Kawamura, E.; Lieberman, M. A.; Graves, D. B.

    2014-10-01

    A fast 2D axisymmetric fluid-analytical model using the finite elements tool COMSOL is interfaced with a 1D particle-in-cell (PIC) code to study ion energy distributions (IEDs) in multi-frequency argon capacitively coupled plasmas (CCPs). A bulk fluid plasma model which solves the time-dependent plasma fluid equations is coupled with an analytical sheath model which solves for the sheath parameters. The fluid-analytical results are used as input to a PIC simulation of the sheath region of the discharge to obtain the IEDs at the wafer electrode. Each fluid-analytical-PIC simulation on a moderate 2.2 GHz CPU workstation with 8 GB of memory took about 15-20 minutes. The 2D multi-frequency fluid-analytical model was compared to 1D PIC simulations of a symmetric parallel plate discharge, showing good agreement. Fluid-analytical simulations of a 2/60/162 MHz argon CCP with a typical asymmetric reactor geometry were also conducted. The low 2 MHz frequency controlled the sheath width and voltage while the higher frequencies controlled the plasma production. A standing wave was observable at the highest frequency of 162 MHz. Adding 2 MHz power to a 60 MHz discharge or 162 MHz to a dual frequency 2 MHz/60 MHz discharge enhanced the plasma uniformity. This work was supported by the Department of Energy Office of Fusion Energy Science Contract DE-SC000193, and in part by gifts from Lam Research Corporation and Micron Corporation.

  17. Frequency-chirped readout of spatial-spectral absorption features

    International Nuclear Information System (INIS)

    Chang, Tiejun; Mohan, R. Krishna; Harris, Todd L.; Merkel, Kristian D.; Tian Mingzhen; Babbitt, Wm. Randall

    2004-01-01

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

  18. Shortwave forcing and feedbacks in Last Glacial Maximum and Mid-Holocene PMIP3 simulations.

    Science.gov (United States)

    Braconnot, Pascale; Kageyama, Masa

    2015-11-13

    Simulations of the climates of the Last Glacial Maximum (LGM), 21 000 years ago, and of the Mid-Holocene (MH), 6000 years ago, allow an analysis of climate feedbacks in climate states that are radically different from today. The analyses of cloud and surface albedo feedbacks show that the shortwave cloud feedback is a major driver of differences between model results. Similar behaviours appear when comparing the LGM and MH simulated changes, highlighting the fingerprint of model physics. Even though the different feedbacks show similarities between the different climate periods, the fact that their relative strength differs from one climate to the other prevents a direct comparison of past and future climate sensitivity. The land-surface feedback also shows large disparities among models even though they all produce positive sea-ice and snow feedbacks. Models have very different sensitivities when considering the vegetation feedback. This feedback has a regional pattern that differs significantly between models and depends on their level of complexity and model biases. Analyses of the MH climate in two versions of the IPSL model provide further indication on the possibilities to assess the role of model biases and model physics on simulated climate changes using past climates for which observations can be used to assess the model results. © 2015 The Author(s).

  19. Fast simulation of wind generation for frequency stability analysis in island power systems

    Energy Technology Data Exchange (ETDEWEB)

    Conroy, James [EirGrid, Dublin (Ireland)

    2010-07-01

    Frequency stability is a major issue for power system planning and operation in an island power system such as Ireland. As increasing amounts of variable speed wind generation are added to the system, this issue becomes more prominent, as variable speed wind generation does not provide an inherent inertial response. This lack of an inertial response means that simplified models for variable speed wind farms can be used for investigating frequency stability. EirGrid uses DIgSILENT Power Factory (as well as other software tools) to investigate frequency stability. In PowerFactory, an automation program has been created to convert detailed wind farm representation (as necessary for other types of analysis) to negative load models for frequency stability analysis. The advantage of this approach is much-improved simulation speed without loss of accuracy. This approach can also be to study future wind energy targets, and long-term simulation of voltage stability. (orig.)

  20. Simulation of dust particles in dual-frequency capacitively coupled silane discharges

    International Nuclear Information System (INIS)

    Liu Xiangmei; Song Yuanhong; Xu Xiang; Wang Younian

    2010-01-01

    The behavior of nanoparticles in dual-frequency capacitively coupled silane discharges is investigated by employing a one-dimensional self-consistent fluid model. The numerical simulation tries to trace the formation, charging, growth, and transport of dust particles during the discharge, under the influences of the high- and low-frequency electric sources, as well as the gas pressure. The effects of the presence of the nanoparticles and larger anions on the plasma properties are also discussed, especially, for the bulk potential, electron temperature, and densities of various particles. The calculation results show that the nanoparticle density and charge distribution are mainly influenced by the voltage and frequency of the high-frequency source, while the voltage of the low-frequency source can also exert an effect on the nanoparticle formation, compared with the frequency. As the discharge lasts, the electric potential and electron density keep decreasing, while the electron temperature gets increasing after a sudden drop.

  1. Simulation and Automation of Microwave Frequency Control in Dynamic Nuclear Polarization for Solid Polarized Targets

    Science.gov (United States)

    Perera, Gonaduwage; Johnson, Ian; Keller, Dustin

    2017-09-01

    Dynamic Nuclear Polarization (DNP) is used in most of the solid polarized target scattering experiments. Those target materials must be irradiated using microwaves at a frequency determined by the difference in the nuclear Larmor and electron paramagnetic resonance (EPR) frequencies. But the resonance frequency changes with time as a result of radiation damage. Hence the microwave frequency should be adjusted accordingly. Manually adjusting the frequency can be difficult, and improper adjustments negatively impact the polarization. In order to overcome these difficulties, two controllers were developed which automate the process of seeking and maintaining the optimal frequency: one being a standalone controller for a traditional DC motor and the other a LabVIEW VI for a stepper motor configuration. Further a Monte-Carlo simulation was developed which can accurately model the polarization over time as a function of microwave frequency. In this talk, analysis of the simulated data and recent improvements to the automated system will be presented. DOE.

  2. High-harmonic electron bunching in the field of a signal wave and the use of this effect in cyclotron masers with frequency multiplication

    Directory of Open Access Journals (Sweden)

    I. V. Bandurkin

    2005-01-01

    Full Text Available A method of organizing electron-wave interaction at the multiplied frequency of the signal wave is proposed. This type of electron-wave interaction provides multiplied-frequency electron bunching, which leads to formation of an intense harmonic of the electron current at a selected multiplied frequency of the signal wave. This effect is attractive for the use in klystron-type cyclotron masers with frequency multiplication as a way to increase the output frequency and improve the selectivity.

  3. Simulation research of acousto optic modulator drive based on Multisim

    Science.gov (United States)

    Wang, Shiqian; Guo, Yangkuan; Zhu, Lianqing; Na, Yunxiao; Zhang, Yinmin; Liu, Qianzhe

    2013-10-01

    The acousto optic modulator drive is mainly made with 2 amplitude shift keying (2ASK)circuit, pre-amplifier circuit and power operational amplifier circuit, and the simulation of the acousto optic modulator drive is realized. Firstly, the acousto optic modulator drive works as follows.The modulation function is realized by the analoged switch circuit, and the on-off of the analoged switch chip (CD4066) are controlled by the pulse signal generated by the electronic conversion circuit. The voltage amplification of the modulated signal is achieved by two reverse proportional operation implements voltage amplifier circuit, and the circuit is mainly made with the AD8001 chip. Then the amplified signal is transfered into a two-stage power operational amplifier circuit of class C which is mainly made with the chip of MRF158. Secondly, both of the simulating structures and the union debugging based on the designed system are realized by Multisim. Finally, obtaining the modulation signal of 150(MHz) frequency and 5(μs) pulse width illustrates that a 2ASk modulation of the 150 (MHz)carrier signal and the 20(kHz) modulation signal is achieved. Besides, as the frequency of input signal and amplitude of voltage change, the output power of the power operational amplifier circuit also changes, and the conclusion is drawn that the output power increases when the frequency of input signal decreases and the amplitude of voltage increases. The component selection of the drive's PCB design, the performance parameter and of the actual circuit and the debugging of the actual circuit are based on the simulation results.

  4. Mid-latitude mesospheric clouds and their environment from SOFIE observations

    Science.gov (United States)

    Hervig, Mark E.; Gerding, Michael; Stevens, Michael H.; Stockwell, Robert; Bailey, Scott M.; Russell, James M.; Stober, Gunter

    2016-11-01

    Observations from the Solar Occultation For Ice Experiment (SOFIE) on the Aeronomy of Ice in the Mesosphere (AIM) satellite are used to examine noctilucent clouds (NLC) and their environment at middle latitudes ( 56°N and 52°S). Because SOFIE is uniquely capable of measuring NLC, water vapor, and temperature simultaneously, the local cloud environment can be specified to examine what controls their formation at mid-latitudes. Compared to higher latitudes, mid-latitude NLCs are less frequent and have lower ice mass density, by roughly a factor of five. Compared to higher latitudes at NLC heights, mid-latitude water vapor is only 12% lower while temperatures are more than 10 K higher. As a result the reduced NLC mass and frequency at mid-latitudes can be attributed primarily to temperature. Middle and high latitude NLCs contain a similar amount of meteoric smoke, which was not anticipated because smoke abundance increases towards the equator in summer. SOFIE indicates that mid-latitude NLCs may or may not be associated with supersaturation with respect to ice. It is speculated that this situation is due in part to SOFIE uncertainties related to the limb measurement geometry combined with the non-uniform nature of NLCs. SOFIE is compared with concurrent NLC, temperature, and wind observations from Kühlungsborn, Germany (54°N) during the 2015 summer. The results indicate good agreement in temperature and NLC occurrence frequency, backscatter, and height. SOFIE indicates that NLCs were less frequent over Europe during 2015 compared to other longitudes, in contrast to previous years at higher latitudes that showed no clear longitude dependence. Comparisons of SOFIE and the Solar Backscatter Ultraviolet (SBUV) indicate good agreement in average ice water column (IWC), although differences in occurrence frequency were often large.

  5. Frequency analysis of the visual steady-state response measured with the fast optical signal in younger and older adults

    OpenAIRE

    Tse, Chun-Yu; Gordon, Brian A.; Fabiani, Monica; Gratton, Gabriele

    2010-01-01

    Relatively high frequency activity (>4 Hz) carries important information about the state of the brain or its response to high frequency events. The electroencephalogram (EEG) is commonly used to study these changes because it possesses high temporal resolution and a good signal-to-noise ratio. However, it provides limited spatial information. Non-invasive fast optical signals (FOS) have been proposed as a neuroimaging tool combining spatial and temporal resolution. Yet, this technique has not...

  6. The importance of resolution on the response of mid-latitude transients to enhanced CO2

    International Nuclear Information System (INIS)

    Senior, C.A.

    1994-01-01

    The impact of global warming on the activity of the mid-latitude transients is not well understood. Work with simple models suggests that there will be two competing effects on transient activity. Firstly, there will be a reduction in the baroclinicity due to a smaller pole-equator temperature gradient and secondly there will be increased moisture availability in a warmer atmosphere. A comparison of the mid-latitude transients from two versions of the Hadley Centre for Climate Prediction and Research GCM run at different resolutions is presented and the importance of resolution on the simulation of the high and low frequency variability is discussed. At higher resolution, one of the largest responses of the model to a doubling of atmospheric CO 2 is an enhancement of the westerly flow in the North Atlantic, but this is much reduced at lower resolution. Consistency is sort between changes in the time mean flow and the transient behavior

  7. Gray bootstrap method for estimating frequency-varying random vibration signals with small samples

    Directory of Open Access Journals (Sweden)

    Wang Yanqing

    2014-04-01

    Full Text Available During environment testing, the estimation of random vibration signals (RVS is an important technique for the airborne platform safety and reliability. However, the available methods including extreme value envelope method (EVEM, statistical tolerances method (STM and improved statistical tolerance method (ISTM require large samples and typical probability distribution. Moreover, the frequency-varying characteristic of RVS is usually not taken into account. Gray bootstrap method (GBM is proposed to solve the problem of estimating frequency-varying RVS with small samples. Firstly, the estimated indexes are obtained including the estimated interval, the estimated uncertainty, the estimated value, the estimated error and estimated reliability. In addition, GBM is applied to estimating the single flight testing of certain aircraft. At last, in order to evaluate the estimated performance, GBM is compared with bootstrap method (BM and gray method (GM in testing analysis. The result shows that GBM has superiority for estimating dynamic signals with small samples and estimated reliability is proved to be 100% at the given confidence level.

  8. Filter frequency response of time dependent signal using Laplace transform

    Energy Technology Data Exchange (ETDEWEB)

    Shestakov, Aleksei I. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2018-01-16

    We analyze the effect a filter has on a time dependent signal x(t). If X(s) is the Laplace transform of x and H (s) is the filter Transfer function, the response in frequency space is X (s) H (s). Consequently, in real space, the response is the convolution (x*h) (t), where hi is the Laplace inverse of H. Effects are analyzed and analytically for functions such as (t/tc)2 e-t/t$_c$, where tc = const. We consider lowpass, highpass and bandpass filters.

  9. Method for Estimating the Parameters of LFM Radar Signal

    Directory of Open Access Journals (Sweden)

    Tan Chuan-Zhang

    2017-01-01

    Full Text Available In order to obtain reliable estimate of parameters, it is very important to protect the integrality of linear frequency modulation (LFM signal. Therefore, in the practical LFM radar signal processing, the length of data frame is often greater than the pulse width (PW of signal. In this condition, estimating the parameters by fractional Fourier transform (FrFT will cause the signal to noise ratio (SNR decrease. Aiming at this problem, we multiply the data frame by a Gaussian window to improve the SNR. Besides, for a further improvement of parameters estimation precision, a novel algorithm is derived via Lagrange interpolation polynomial, and we enhance the algorithm by a logarithmic transformation. Simulation results demonstrate that the derived algorithm significantly reduces the estimation errors of chirp-rate and initial frequency.

  10. Power spectrum analysis of the x-ray scatter signal in mammography and breast tomosynthesis projections.

    Science.gov (United States)

    Sechopoulos, Ioannis; Bliznakova, Kristina; Fei, Baowei

    2013-10-01

    To analyze the frequency domain characteristics of the signal in mammography images and breast tomosynthesis projections with patient tissue texture due to detected scattered x-rays. Acquisitions of x-ray projection images of 19 different patient breasts were simulated using previously acquired volumetric patient images. Acquisition of these images was performed with a dedicated breast CT prototype system, and the images were classified into voxels representing skin, adipose, and glandular tissue with a previously validated automated algorithm. The classified three dimensional images then underwent simulated mechanical compression representing that which is performed during acquisition of mammography and breast tomosynthesis images. The acquisition of projection images of each patient breast was simulated using Monte Carlo methods with each simulation resulting in two images: one of the primary (non-scattered) signal and one of the scatter signal. To analyze the scatter signal for both mammography and breast tomosynthesis, two projections images of each patient breast were simulated, one with the x-ray source positioned at 0° (mammography and central tomosynthesis projection) and at 30° (wide tomosynthesis projection). The noise power spectra (NPS) for both the scatter signal alone and the total signal (primary + scatter) for all images were obtained and the combined results of all patients analyzed. The total NPS was fit to the expected power-law relationship NPS(f) = k/f β and the results were compared with those previously published on the power spectrum characteristics of mammographic texture. The scatter signal alone was analyzed qualitatively and a power-law fit was also performed. The mammography and tomosynthesis projections of three patient breasts were too small to analyze, so a total of 16 patient breasts were analyzed. The values of β for the total signal of the 0° projections agreed well with previously published results. As expected, the scatter

  11. Frequency analysis of the visual steady-state response measured with the fast optical signal in younger and older adults.

    Science.gov (United States)

    Tse, Chun-Yu; Gordon, Brian A; Fabiani, Monica; Gratton, Gabriele

    2010-09-01

    Relatively high frequency activity (>4Hz) carries important information about the state of the brain or its response to high frequency events. The electroencephalogram (EEG) is commonly used to study these changes because it possesses high temporal resolution and a good signal-to-noise ratio. However, it provides limited spatial information. Non-invasive fast optical signals (FOS) have been proposed as a neuroimaging tool combining spatial and temporal resolution. Yet, this technique has not been applied to study high frequency brain oscillations because of its relatively low signal-to-noise ratio. Here we investigate the sensitivity of FOS to relatively high-frequency brain oscillations. We measured the steady-state optical response elicited in medial and lateral occipital cortex by checkerboard reversals occurring at 4, 6, and 8Hz in younger and older adults. Stimulus-dependent oscillations were observed at the predicted stimulation frequency. In addition, in the younger adults the FOS steady-state response was smaller in lateral than medial areas, whereas in the older adults it was reversed in these two cortical regions. This may reflect diminished top-down inhibitory control in the older adults. The results indicate that FOS can be used to study the modulation of relatively high-frequency brain oscillations in adjacent cortical regions. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  12. Influence of simulated bone-implant contact and implant diameter on secondary stability: a resonance frequency in vitro study.

    Science.gov (United States)

    Veltri, Mario; González-Martín, Oscar; Belser, Urs C

    2014-08-01

    This study tested the hypothesis of no differences in resonance frequency for standardized amounts of simulated bone-implant contact around implants with different diameters. In addition, it was evaluated if resonance frequency is able to detect a difference between stable and rotation mobile ("spinning") implants. Implants with diameters of 3.3, 4.1 and 4.8 mm were placed in a purposely designed metal mould where liquid polyurethane resin was then poured to obtain a simulated bone-implant specimen. By regulating the mould, it was possible to create the following simulated bone-implant contact groups: 3.3 mm (198.6 mm(2)); 4.1 mm (198.8 mm(2)); 4.8 mm (200.2 mm(2)); 4.8 mm (231.7 mm(2)); 4.8 mm (294.7 mm(2)). Each group included 10 specimens. After resin setting, resonance frequency was measured. On the last group, measurements were repeated after establishing implant rotational mobility. One-way ANOVA tests with post hoc comparisons, a Pearson's correlation coefficient and a t-test for repeated measurements were used to evaluate statistically significant differences. Implants with different diameters but with the same amount of simulated osseointegration revealed no differences in resonance frequency. On the contrary, an increase of simulated bone-implant contact resulted in significantly higher resonance frequency. A clear direct linear correlation resulted between resonance frequency and simulated bone-implant contact. Furthermore, a significant difference resulted between resonance frequency measured before and after creation of rotational mobility. Within the conditions of this study, the secondary stability was correlated with the simulated bone-implant contact. In addition, resonance frequency was able to discern between stable and rotation mobile implants. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Phase Clustering Based Modulation Classification Algorithm for PSK Signal over Wireless Environment

    Directory of Open Access Journals (Sweden)

    Qi An

    2016-01-01

    Full Text Available Promptitude and accuracy of signals’ non-data-aided (NDA identification is one of the key technology demands in noncooperative wireless communication network, especially in information monitoring and other electronic warfare. Based on this background, this paper proposes a new signal classifier for phase shift keying (PSK signals. The periodicity of signal’s phase is utilized as the assorted character, with which a fractional function is constituted for phase clustering. Classification and the modulation order of intercepted signals can be achieved through its Fast Fourier Transform (FFT of the phase clustering function. Frequency offset is also considered for practical conditions. The accuracy of frequency offset estimation has a direct impact on its correction. Thus, a feasible solution is supplied. In this paper, an advanced estimator is proposed for estimating the frequency offset and balancing estimation accuracy and range under low signal-to-noise ratio (SNR conditions. The influence on estimation range brought by the maximum correlation interval is removed through the differential operation of the autocorrelation of the normalized baseband signal raised to the power of Q. Then, a weighted summation is adopted for an effective frequency estimation. Details of equations and relevant simulations are subsequently presented. The estimator proposed can reach an estimation accuracy of 10-4 even when the SNR is as low as -15 dB. Analytical formulas are expressed, and the corresponding simulations illustrate that the classifier proposed is more efficient than its counterparts even at low SNRs.

  14. Radio frequency picosecond phototube

    International Nuclear Information System (INIS)

    Margaryan, A.; Carlini, R.; Ent, R.; Grigoryan, N.; Gyunashyan, K.; Hashimoto, O.; Hovater, K.; Ispiryan, M.; Knyazyan, S.; Kross, B.; Majewski, S.; Marikyan, G.; Mkrtchyan, M.; Parlakyan, L.; Popov, V.; Tang, L.; Vardanyan, H.; Yan, C.; Zhamkochyan, S.; Zorn, C.

    2006-01-01

    We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a 'head-on' geometry is investigated by means of Monte Carlo simulation

  15. Radio frequency picosecond phototube

    Energy Technology Data Exchange (ETDEWEB)

    Margaryan, A. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia)]. E-mail: mat@mail.yerphi.am; Carlini, R. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Ent, R. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Grigoryan, N. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Gyunashyan, K. [Yerevan State University of Architecture and Construction, Yerevan (Armenia); Hashimoto, O. [Tohoku University, Sendai 98-77 (Japan); Hovater, K. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Ispiryan, M. [University of Houston, 4800 Calhoun Rd, Houston TX 77204 (United States); Knyazyan, S. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Kross, B. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Majewski, S. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Marikyan, G. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Mkrtchyan, M. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Parlakyan, L. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Popov, V. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Tang, L. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Vardanyan, H. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Yan, C. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Zhamkochyan, S. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Zorn, C. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States)

    2006-10-15

    We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a 'head-on' geometry is investigated by means of Monte Carlo simulation.

  16. Increased ventilation of Antarctic deep water during the warm mid-Pliocene.

    Science.gov (United States)

    Zhang, Zhongshi; Nisancioglu, Kerim H; Ninnemann, Ulysses S

    2013-01-01

    The mid-Pliocene warm period is a recent warm geological period that shares similarities with predictions of future climate. It is generally held the mid-Pliocene Atlantic Meridional Overturning Circulation must have been stronger, to explain a weak Atlantic meridional δ(13)C gradient and large northern high-latitude warming. However, climate models do not simulate such stronger Atlantic Meridional Overturning Circulation, when forced with mid-Pliocene boundary conditions. Proxy reconstructions allow for an alternative scenario that the weak δ(13)C gradient can be explained by increased ventilation and reduced stratification in the Southern Ocean. Here this alternative scenario is supported by simulations with the Norwegian Earth System Model (NorESM-L), which simulate an intensified and slightly poleward shifted wind field off Antarctica, giving enhanced ventilation and reduced stratification in the Southern Ocean. Our findings challenge the prevailing theory and show how increased Southern Ocean ventilation can reconcile existing model-data discrepancies about Atlantic Meridional Overturning Circulation while explaining fundamental ocean features.

  17. Optimizing signal output: effects of viscoelasticity and difference frequency on vibroacoustic radiation of tissue-mimicking phantoms

    Science.gov (United States)

    Namiri, Nikan K.; Maccabi, Ashkan; Bajwa, Neha; Badran, Karam W.; Taylor, Zachary D.; St. John, Maie A.; Grundfest, Warren S.; Saddik, George N.

    2018-02-01

    Vibroacoustography (VA) is an imaging technology that utilizes the acoustic response of tissues to a localized, low frequency radiation force to generate a spatially resolved, high contrast image. Previous studies have demonstrated the utility of VA for tissue identification and margin delineation in cancer tissues. However, the relationship between specimen viscoelasticity and vibroacoustic emission remains to be fully quantified. This work utilizes the effects of variable acoustic wave profiles on unique tissue-mimicking phantoms (TMPs) to maximize VA signal power according to tissue mechanical properties, particularly elasticity. A micro-indentation method was utilized to provide measurements of the elastic modulus for each biological replica. An inverse relationship was found between elastic modulus (E) and VA signal amplitude among homogeneous TMPs. Additionally, the difference frequency (Δf ) required to reach maximum VA signal correlated with specimen elastic modulus. Peak signal diminished with increasing Δf among the polyvinyl alcohol specimen, suggesting an inefficient vibroacoustic response by the specimen beyond a threshold of resonant Δf. Comparison of these measurements may provide additional information to improve tissue modeling, system characterization, as well as insights into the unique tissue composition of tumors in head and neck cancer patients.

  18. Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing.

    Science.gov (United States)

    Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

    2016-02-17

    The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF₂ microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

  19. MATLAB simulation software used for the PhD thesis "Acquisition of Multi-Band Signals via Compressed Sensing

    DEFF Research Database (Denmark)

    2014-01-01

    MATLAB simulation software used for the PhD thesis "Acquisition of Multi-Band Signals via Compressed Sensing......MATLAB simulation software used for the PhD thesis "Acquisition of Multi-Band Signals via Compressed Sensing...

  20. The mid-IR silicon photonics sensor platform (Conference Presentation)

    Science.gov (United States)

    Kimerling, Lionel; Hu, Juejun; Agarwal, Anuradha M.

    2017-02-01

    Advances in integrated silicon photonics are enabling highly connected sensor networks that offer sensitivity, selectivity and pattern recognition. Cost, performance and the evolution path of the so-called `Internet of Things' will gate the proliferation of these networks. The wavelength spectral range of 3-8um, commonly known as the mid-IR, is critical to specificity for sensors that identify materials by detection of local vibrational modes, reflectivity and thermal emission. For ubiquitous sensing applications in this regime, the sensors must move from premium to commodity level manufacturing volumes and cost. Scaling performance/cost is critically dependent on establishing a minimum set of platform attributes for point, wearable, and physical sensing. Optical sensors are ideal for non-invasive applications. Optical sensor device physics involves evanescent or intra-cavity structures for applied to concentration, interrogation and photo-catalysis functions. The ultimate utility of a platform is dependent on sample delivery/presentation modalities; system reset, recalibration and maintenance capabilities; and sensitivity and selectivity performance. The attributes and performance of a unified Glass-on-Silicon platform has shown good prospects for heterogeneous integration on materials and devices using a low cost process flow. Integrated, single mode, silicon photonic platforms offer significant performance and cost advantages, but they require discovery and qualification of new materials and process integration schemes for the mid-IR. Waveguide integrated light sources based on rare earth dopants and Ge-pumped frequency combs have promise. Optical resonators and waveguide spirals can enhance sensitivity. PbTe materials are among the best choices for a standard, waveguide integrated photodetector. Chalcogenide glasses are capable of transmitting mid-IR signals with high transparency. Integrated sensor case studies of i) high sensitivity analyte detection in

  1. Improving the signal visibility of optical-disk-drive sensors by analyte patterning and frequency-domain analysis

    International Nuclear Information System (INIS)

    Schaefer, S; Chau, K J

    2011-01-01

    One limitation of using compact disks (CDs) and optical disk drives for sensing and imaging of analytes placed on a CD is the fluctuations in the voltage signal from the disk drive generated while reading the data on the CD. In this study, we develop a simple, low-cost strategy for sensing and identification using CDs and optical disk drives that spectrally separates contributions to the voltage signal caused by an analyte intentionally placed onto the CD and that caused by the underlying data on the CD. Analytes are printed onto a CD surface with fixed spatial periodicity. As the laser beam in an optical disk drive scans over the section of the CD containing the analyte pattern, the intensity of the laser beam incident onto the photodiode integrated into the disk drive is modulated at a frequency dependent on the spatial periodicity of the analyte pattern and the speed of the optical-disk-drive motor. Fourier transformation of the voltage signal from the optical disk drive yields peaks in the frequency spectrum with amplitudes and locations that enable analyte sensing and identification, respectively. We study the influence of analyte area coverage, pattern periodicity, and CD rotational frequency on the peaks in the frequency spectrum associated with the patterned analyte. We apply this technique to discriminate differently-colored analytes, perform trigger-free detection of multiple analytes distributed on a single CD, and detect at least two different, overlapped analyte patterns on a single CD. The extension of this technique for sensing and identification of colorimetric chemical reagents is discussed

  2. Suppression of Subsequent N1m Amplitude When the Masker Frequency is Different from the Signal

    Directory of Open Access Journals (Sweden)

    Yuka Uratani

    2014-01-01

    Full Text Available When two tones are presented in a short interval of time, the presentation of the preceding tone (masker suppresses the response evoked by the subsequent tone (signal. To address the processing in forward suppression, we applied 2- and 4-kHz maskers, followed by a 1-kHz signal at varying signal delays (0 to 320 ms and measured the signal-evoked N1m. A two-way analysis of variance revealed a statistically significant effect for signal delay in both masker presentation conditions. The N1m peak amplitude at the signal delay of 320 ms was significantly larger than those of 10, 20, 40, and 80 ms ( p < 0.05. No significant enhancement for the very short signal delay was observed. The results suggest that the enhancement of N1m peak amplitude for short signal delay conditions is maximized when the frequency of the masker is identical to that of the signal.

  3. Mutual Information in Frequency and Its Application to Measure Cross-Frequency Coupling in Epilepsy

    Science.gov (United States)

    Malladi, Rakesh; Johnson, Don H.; Kalamangalam, Giridhar P.; Tandon, Nitin; Aazhang, Behnaam

    2018-06-01

    We define a metric, mutual information in frequency (MI-in-frequency), to detect and quantify the statistical dependence between different frequency components in the data, referred to as cross-frequency coupling and apply it to electrophysiological recordings from the brain to infer cross-frequency coupling. The current metrics used to quantify the cross-frequency coupling in neuroscience cannot detect if two frequency components in non-Gaussian brain recordings are statistically independent or not. Our MI-in-frequency metric, based on Shannon's mutual information between the Cramer's representation of stochastic processes, overcomes this shortcoming and can detect statistical dependence in frequency between non-Gaussian signals. We then describe two data-driven estimators of MI-in-frequency: one based on kernel density estimation and the other based on the nearest neighbor algorithm and validate their performance on simulated data. We then use MI-in-frequency to estimate mutual information between two data streams that are dependent across time, without making any parametric model assumptions. Finally, we use the MI-in- frequency metric to investigate the cross-frequency coupling in seizure onset zone from electrocorticographic recordings during seizures. The inferred cross-frequency coupling characteristics are essential to optimize the spatial and spectral parameters of electrical stimulation based treatments of epilepsy.

  4. Influence of modulation frequency in rubidium cell frequency standards

    Science.gov (United States)

    Audoin, C.; Viennet, J.; Cyr, N.; Vanier, J.

    1983-01-01

    The error signal which is used to control the frequency of the quartz crystal oscillator of a passive rubidium cell frequency standard is considered. The value of the slope of this signal, for an interrogation frequency close to the atomic transition frequency is calculated and measured for various phase (or frequency) modulation waveforms, and for several values of the modulation frequency. A theoretical analysis is made using a model which applies to a system in which the optical pumping rate, the relaxation rates and the RF field are homogeneous. Results are given for sine-wave phase modulation, square-wave frequency modulation and square-wave phase modulation. The influence of the modulation frequency on the slope of the error signal is specified. It is shown that the modulation frequency can be chosen as large as twice the non-saturated full-width at half-maximum without a drastic loss of the sensitivity to an offset of the interrogation frequency from center line, provided that the power saturation factor and the amplitude of modulation are properly adjusted.

  5. Simulation and analysis of surface scintillator signals at the Pierre Auger Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, David; Veberic, Darko; Roth, Markus [Karlsruhe Institute of Technology, Karlsruhe (Germany); Collaboration: Pierre-Auger-Collaboration

    2016-07-01

    To improve reconstruction of cosmic ray primary mass, the Pierre Auger Observatory is upgrading its surface detectors by installing a scintillator on top of each existing water Cherenkov tank. The different responses of the coupled detectors to the components of extensive air showers facilitates estimation of the number of muons reaching Earth's surface, which is correlated with primary mass. Geant4 and the Offline framework are used to simulate the detectors' responses, construct signal traces for individual particle components, and calculate total expected signals. This enables assessment of proposed reconstruction algorithms. An overview of the simulations and selected algorithms is presented here.

  6. Robust frequency diversity based algorithm for clutter noise reduction of ultrasonic signals using multiple sub-spectrum phase coherence

    Energy Technology Data Exchange (ETDEWEB)

    Gongzhang, R.; Xiao, B.; Lardner, T.; Gachagan, A. [Centre for Ultrasonic Engineering, University of Strathclyde, Glasgow, G1 1XW (United Kingdom); Li, M. [School of Engineering, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

    2014-02-18

    This paper presents a robust frequency diversity based algorithm for clutter reduction in ultrasonic A-scan waveforms. The performance of conventional spectral-temporal techniques like Split Spectrum Processing (SSP) is highly dependent on the parameter selection, especially when the signal to noise ratio (SNR) is low. Although spatial beamforming offers noise reduction with less sensitivity to parameter variation, phased array techniques are not always available. The proposed algorithm first selects an ascending series of frequency bands. A signal is reconstructed for each selected band in which a defect is present when all frequency components are in uniform sign. Combining all reconstructed signals through averaging gives a probability profile of potential defect position. To facilitate data collection and validate the proposed algorithm, Full Matrix Capture is applied on the austenitic steel and high nickel alloy (HNA) samples with 5MHz transducer arrays. When processing A-scan signals with unrefined parameters, the proposed algorithm enhances SNR by 20dB for both samples and consequently, defects are more visible in B-scan images created from the large amount of A-scan traces. Importantly, the proposed algorithm is considered robust, while SSP is shown to fail on the austenitic steel data and achieves less SNR enhancement on the HNA data.

  7. Note: The design of thin gap chamber simulation signal source based on field programmable gate array

    International Nuclear Information System (INIS)

    Hu, Kun; Wang, Xu; Li, Feng; Jin, Ge; Lu, Houbing; Liang, Futian

    2015-01-01

    The Thin Gap Chamber (TGC) is an important part of ATLAS detector and LHC accelerator. Targeting the feature of the output signal of TGC detector, we have designed a simulation signal source. The core of the design is based on field programmable gate array, randomly outputting 256-channel simulation signals. The signal is generated by true random number generator. The source of randomness originates from the timing jitter in ring oscillators. The experimental results show that the random number is uniform in histogram, and the whole system has high reliability

  8. LOMEGA: a low frequency, field implicit method for plasma simulation

    International Nuclear Information System (INIS)

    Barnes, D.C.; Kamimura, T.

    1982-04-01

    Field implicit methods for low frequency plasma simulation by the LOMEGA (Low OMEGA) codes are described. These implicit field methods may be combined with particle pushing algorithms using either Lorentz force or guiding center force models to study two-dimensional, magnetized, electrostatic plasmas. Numerical results for ωsub(e)deltat>>1 are described. (author)

  9. Measurement of transient two-phase flow velocity using statistical signal analysis of impedance probe signals

    International Nuclear Information System (INIS)

    Leavell, W.H.; Mullens, J.A.

    1981-01-01

    A computational algorithm has been developed to measure transient, phase-interface velocity in two-phase, steam-water systems. The algorithm will be used to measure the transient velocity of steam-water mixture during simulated PWR reflood experiments. By utilizing signals produced by two, spatially separated impedance probes immersed in a two-phase mixture, the algorithm computes the average transit time of mixture fluctuations moving between the two probes. This transit time is computed by first, measuring the phase shift between the two probe signals after transformation to the frequency domain and then computing the phase shift slope by a weighted least-squares fitting technique. Our algorithm, which has been tested with both simulated and real data, is able to accurately track velocity transients as fast as 4 m/s/s

  10. Estimation of channel impulse response and FPGA simulation

    Directory of Open Access Journals (Sweden)

    YU Longjie

    2015-02-01

    Full Text Available Wideband code division multiple access (WCDMA is a 3G wireless communication network.The common pilot channel in downlink of WCDMA provides an effective method to estimate the channel impulse response.In this paper,universal software radio peripheral (USRP is utilized to sample and process WCDMA signal which is emitted by China Unicom base station.Firstly,the received signal is pre-processed with filtering and down-sampling.Secondly,fast algorithm of WCDMA cell search is fulfilled.Thirdly,frequency shift caused by USRP′s crystal oscillator is checked and compensated.Eventually,channel impulse response is estimated.In this paper,MATLAB is used to describe the above algorithm and field programmable gate array (FPGA is used to simulate algorithm.In the process of simulation,pipeline and IP core multiplexing are introduced.In the case of 32 MHz clock frequency,FPGA simulation time is 80.861 ms.Simulation results show that FPGA is able to estimate the channel impulse response quickly and accurately with less hardware resources.

  11. Compact biomedical pulsed signal generator for bone tissue stimulation

    Science.gov (United States)

    Kronberg, James W.

    1993-01-01

    An apparatus for stimulating bone tissue for stimulating bone growth or treating osteoporosis by applying directly to the skin of the patient an alternating current electrical signal comprising wave forms known to simulate the piezoelectric constituents in bone. The apparatus may, by moving a switch, stimulate bone growth or treat osteoporosis, as desired. Based on low-power CMOS technology and enclosed in a moisture-resistant case shaped to fit comfortably, two astable multivibrators produce the desired waveforms. The amplitude, pulse width and pulse frequency, and the subpulse width and subpulse frequency of the waveforms are adjustable. The apparatus, preferably powered by a standard 9-volt battery, includes signal amplitude sensors and warning signals indicate an output is being produced and the battery needs to be replaced.

  12. High energy eye-safe and mid-infrared optical parametric oscillator

    International Nuclear Information System (INIS)

    Liu, J; Liu, Q; Huang, L; Gong, M

    2010-01-01

    A high energy eye-safe and mid-infrared optical parametric oscillator (OPO) is demonstrated. The nonlinear media is a Y-cut KTA crystal with the length of 20 mm, which is pumped by a Nd:YAG laser. Both eye-safe and mid-infrared laser are output with high energy. When the pump energy is 1 J and the pulse duration is 10 ns, we get 53 mJ idler at 3.632 μm and 151 mJ signal at 1.505 μm. As we know, the idler energy is the highest at the wavelength beyond 3.5 μm and the signal energy is the highest with Y-cut KTA. The results prove that the Y-cut KTA crystal can produce the signal and idler with the energies as high as these in the paper. We have tested the temperature-tuning characters and the coefficient of the idler is 0.26 nm/°C

  13. Detection and classification of defects in ultrasonic NDE signals using time-frequency representations

    Science.gov (United States)

    Qidwai, Uvais; Costa, Antonio H.; Chen, C. H.

    2000-05-01

    The ultrasonic wave, generated by a piezoelectric transducer coupled to the test specimen, propagates through the material and part of its energy is reflected when it encounters an non-homogeneity or discontinuity in its path, while the remainder is reflected by the back surface of the test specimen. Defect echo signals are masked by the characteristics of the measuring instruments, the propagation paths taken by the ultrasonic wave, and are corrupted by additive noise. This leads to difficulties in comparing and analyzing signals, particularly in automated defect identification systems employing different transducers. Further, the multi-component nature of material defects can add to the complexity of the defect identification criteria. With many one-dimensional (1-D) approaches, the multi-component defects can not be detected. Another drawback is that these techniques are not very robust for sharp ultrasonic peaks especially in a very hazardous environment. This paper proposes a technique based on the time-frequency representations (TFRs) of the real defect signals corresponding to artificially produced defects of various geometries in metals. Cohen's class (quadratic) TFRs with Gaussian kernels are then used to represent the signals in the time-frequency (TF) plane. Once the TFR is obtained, various image processing morphological techniques are applied to the TFR (e.g. region of interest masking, edge detection, and profile separation). Based on the results of these operations, a binary image is produced which, in turn, leads to a novel set of features. Using these new features, defects have not only been detected but also classified as flat-cut, angular-cut, and circular-drills. Moreover, with some modifications of the threshold levels of the TFR kernel design, our technique can be used in relatively hostile environments with SNRs as low as 0 dB. Another important characteristic of our approach is the detection of multiple defects. This consists of detection of

  14. Simulation and analysis on ultrasonic testing for the cement grouting defects of the corrugated pipe

    Energy Technology Data Exchange (ETDEWEB)

    Qingbang, Han; Ling, Chen; Changping, Zhu [Changzhou Key Laboratory of Sensor Networks and Environmental Sensing, College of IOT, Hohai University Changzhou, Jiangsu, 213022 (China)

    2014-02-18

    The defects exist in the cement grouting process of prestressed corrugated pipe may directly impair the bridge safety. In this paper, sound fields propagation in concrete structures with corrugated pipes and the influence of various different defects are simulated and analyzed using finite element method. The simulation results demonstrate a much complex propagation characteristic due to multiple reflection, refraction and scattering, where the scattering signals caused by metal are very strong, while the signals scattered by an air bubble are weaker. The influence of defect both in time and frequency domain are found through deconvolution treatment. In the time domain, the deconvolution signals correspond to larger defect display a larger head wave amplitude and shorter arrive time than those of smaller defects; in the frequency domain, larger defect also shows a stronger amplitude, lower center frequency and lower cutoff frequency.

  15. Simulation and analysis on ultrasonic testing for the cement grouting defects of the corrugated pipe

    International Nuclear Information System (INIS)

    Qingbang, Han; Ling, Chen; Changping, Zhu

    2014-01-01

    The defects exist in the cement grouting process of prestressed corrugated pipe may directly impair the bridge safety. In this paper, sound fields propagation in concrete structures with corrugated pipes and the influence of various different defects are simulated and analyzed using finite element method. The simulation results demonstrate a much complex propagation characteristic due to multiple reflection, refraction and scattering, where the scattering signals caused by metal are very strong, while the signals scattered by an air bubble are weaker. The influence of defect both in time and frequency domain are found through deconvolution treatment. In the time domain, the deconvolution signals correspond to larger defect display a larger head wave amplitude and shorter arrive time than those of smaller defects; in the frequency domain, larger defect also shows a stronger amplitude, lower center frequency and lower cutoff frequency

  16. An Extended System Frequency Response Model Considering Wind Power Participation in Frequency Regulation

    Directory of Open Access Journals (Sweden)

    Yi Tang

    2017-11-01

    Full Text Available With increasing penetration of wind power into the power system, wind power participation in frequency regulation is regarded as a beneficial strategy to improve the dynamic frequency response characteristics of power systems. The traditional power system frequency response (SFR model, which only includes synchronous generators, is no longer suitable for power systems with high penetrated wind power. An extended SFR model, based on the reduced-order model of wind turbine generator (WTG and the traditional SFR model, is presented in this paper. In the extended SFR model, the reduced-order model of WTG with combined frequency control is deduced by employing small signal analysis theory. Afterwards, the stability analysis of a closed-loop control system for the extended SFR model is carried out. Time-domain simulations using a test system are performed to validate the effectiveness of the extended SFR model; this model can provide a simpler, clearer and faster way to analyze the dynamic frequency response characteristic for a high-wind integrated power systems. The impact of additional frequency control parameters and wind speed disturbances on the system dynamic frequency response characteristics are investigated.

  17. Ground based mid-IR heterodyne spectrometer concept for planetary atmospheres observations

    Science.gov (United States)

    Garamov, V.; Benderov, O.; Semenov, V.; Spiridonov, M.; Rodin, A.; Stepanov, B.

    2017-09-01

    We present a heterodyne spectrometer concept based on distributed feedback (DFB) quantum cascade lasers (QCL) operated in midle infrared region (MIR). The instrument is assumed to be mount on the Russian infrared observatories. The core features of the concept are compact design, utilizing a novel mid-IR fiber optical components and dynamic local oscillator frequency locking using reference molecule absorption line. The instrument characteristics are similar to modern heterodyne devices THIS (Cologne University, Germany) and MILAHI (Tohoku University, Japan) in terms of fundamental parameters, including spectral resolution, spectral coverage in a single observation. At present moment we created laboratory setup including all necessary elements of MIR heterodyne spectrometer. We have studied different components of noises of our system and found optimal value of LO power. The measured signal to noise ratio (SNR) with MCT PD was about 10 times greater than LO's shot noise (theoretical limit of heterodyne technique SNR) and limited by QCL relative intensity noise (RIN). However, applying additional filtering it is possible to reduce this value better than 5 shot noise level, which is typical to TEC cooled MCT PD. Also we demonstrate heterodyne signal measurements using laboratory black body with temperature of 400 oC.

  18. Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing

    Directory of Open Access Journals (Sweden)

    Simone Borri

    2016-02-01

    Full Text Available The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF2 microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

  19. Non-Pilot-Aided Sequential Monte Carlo Method to Joint Signal, Phase Noise, and Frequency Offset Estimation in Multicarrier Systems

    Directory of Open Access Journals (Sweden)

    Christelle Garnier

    2008-05-01

    Full Text Available We address the problem of phase noise (PHN and carrier frequency offset (CFO mitigation in multicarrier receivers. In multicarrier systems, phase distortions cause two effects: the common phase error (CPE and the intercarrier interference (ICI which severely degrade the accuracy of the symbol detection stage. Here, we propose a non-pilot-aided scheme to jointly estimate PHN, CFO, and multicarrier signal in time domain. Unlike existing methods, non-pilot-based estimation is performed without any decision-directed scheme. Our approach to the problem is based on Bayesian estimation using sequential Monte Carlo filtering commonly referred to as particle filtering. The particle filter is efficiently implemented by combining the principles of the Rao-Blackwellization technique and an approximate optimal importance function for phase distortion sampling. Moreover, in order to fully benefit from time-domain processing, we propose a multicarrier signal model which includes the redundancy information induced by the cyclic prefix, thus leading to a significant performance improvement. Simulation results are provided in terms of bit error rate (BER and mean square error (MSE to illustrate the efficiency and the robustness of the proposed algorithm.

  20. Simulation of SANS signal due to radiation damage in Fe

    International Nuclear Information System (INIS)

    Yu, G.; Schaublin, R.; Spatig, P.; Fikar, J.; Baluc, N.

    2007-01-01

    Full text of publication follows: A wide number of irradiation-induced defects in Fe-base materials (e.g. RAFM steels) have sizes in the range about 0.5 to 1 nm, which are expected to contribute to the irradiation-induced hardening and/or embrittlement phenomena. These defects are at the limit in spatial resolution of transmission electron microscopy (TEM), but they can be investigated using the small angle neutron scattering (SANS) technique, at least in terms of number density and size distribution. Determination of the type of defects (small dislocation loops, interstitials or vacancy clusters, precipitates and cavities, like voids or helium bubbles) is not straightforward. In order to analyze the type of nanometer-sized irradiation-induced defects in Fe-base materials Molecular Dynamics (MD) simulations of various distributions of different types irradiation-induced defects have been performed. The defects investigated consisted in dislocation loops with sizes of 0.5, 1.0 and 2.0 nm and 1/2 a 0 , 1/2 a 0 and a 0 Burgers vectors, cavities, like voids and helium bubbles, with sizes of 0.5, 1.0 and 2.0 nm, MD simulations of atomic displacement cascades were performed using MD samples with a size of 18 x 18 x 18 nm 3 at 10, 300 and 523 K, for PKA energies of 1, 3, 7 and 10 keV. Simulation of the corresponding nuclear SANS signal was performed using the Electron Microscopy Software (EMS) code that was originally designed to simulate TEM images and diffraction patterns and that was modified to simulate the SANS signal. Results of such simulations in pure Fe have been compared to experimental SANS measurements and TEM observations of irradiation-induced defects in Fe-base materials. (authors)

  1. Vibro-Shock Dynamics Analysis of a Tandem Low Frequency Resonator—High Frequency Piezoelectric Energy Harvester

    Directory of Open Access Journals (Sweden)

    Darius Žižys

    2017-04-01

    Full Text Available Frequency up-conversion is a promising technique for energy harvesting in low frequency environments. In this approach, abundantly available environmental motion energy is absorbed by a Low Frequency Resonator (LFR which transfers it to a high frequency Piezoelectric Vibration Energy Harvester (PVEH via impact or magnetic coupling. As a result, a decaying alternating output signal is produced, that can later be collected using a battery or be transferred directly to the electric load. The paper reports an impact-coupled frequency up-converting tandem setup with different LFR to PVEH natural frequency ratios and varying contact point location along the length of the harvester. RMS power output of different frequency up-converting tandems with optimal resistive values was found from the transient analysis revealing a strong relation between power output and LFR-PVEH natural frequency ratio as well as impact point location. Simulations revealed that higher power output is obtained from a higher natural frequency ratio between LFR and PVEH, an increase of power output by one order of magnitude for a doubled natural frequency ratio and up to 150% difference in power output from different impact point locations. The theoretical results were experimentally verified.

  2. [Low-frequency pulsed electromagnetic fields promotes rat osteoblast differentiation in vitro through cAMP/PKA signal pathway].

    Science.gov (United States)

    Fang, Qing-Qing; Li, Zhi-Zhong; Zhou, Jian; Shi, Wen-Gui; Yan, Juan-Li; Xie, Yan-Fang; Chen, Ke-Ming

    2016-11-20

    To study whether low-frequency pulsed electromagnetic fields promotes the differentiation of cultured rat osteoblasts through the cAMP/PKA signal pathway. Rat calvarial osteoblasts isolated by enzyme digestion were exposed to 50 Hz 0.6 mT low-frequency pulsed electromagnetic field for varying lengths of time, and the concentration of cAMP and levels of phosphorylated PKA in the cells were assayed. In cells treated with DDA to inhibit the activity of adenylate cyclase, the changes of ALP activity and transcription of osteogenic gene were detected after exposure to low-frequency pulsed electromagnetic field. The changes of osteogenic gene transcription and protein expression were tested in the osteoblasts pretreated with KT5720 in response to low-frequency pulsed electromagnetic field exposure. The intracellular cAMP concentration in the cells increased significantly at 20 min during exposure to low-frequency pulsed electromagnetic field, began to decrease at 40 min during the exposure, and increased again after a 2-h exposure; the same pattern of variation was also observed in p-PKA level. Application of DDA and KT5720 pretreatment both suppressed the increase in ALP activity and osteogenic gene transcription induced by electromagnetic field exposure. Low- frequency pulsed electromagnetic field exposure improves the differentiation of cultured rat osteoblasts by activating cAMP/PKA signal pathway.

  3. Yb-fiber-pumped mid-infrared picosecond optical parametric oscillator tunable across 6.2-6.7 µm

    Science.gov (United States)

    Kumar, S. Chaitanya; Casals, J. Canals; Parsa, S.; Zawilski, K. T.; Schunemann, P. G.; Ebrahim-Zadeh, M.

    2018-06-01

    We report a high-average-power picosecond optical parametric oscillator (OPO) tunable in the mid-infrared (mid-IR) based on CdSiP2 synchronously pumped by an Yb-fiber laser at 80 MHz repetition rate. Successful operation of this high-repetition-rate singly-resonant picosecond OPO has been enabled by the improved CSP crystal quality over a long interaction length. The OPO can be tuned across 1264-1284 nm in the near-IR signal and 6205-6724 nm in the mid-IR idler by temperature tuning the CSP crystal over 39-134 °C. By deploying a 5% output coupler for the resonant signal, we have extracted up to 44 mW of average power in the near-IR and up to 95 mW of non-resonant idler power at 6205 nm at 6.3% total conversion efficiency, with > 50 mW over > 55% of the mid-IR tuning range. We have investigated temperature-tuning characteristics of the OPO and compared the data with the theoretical calculations using the recent Sellmeier and thermo-optic coefficients for CdSiP2. The signal pulses from the OPO exhibit a Gaussian pulse duration of 19 ps centered at 1284 nm. We have also studied the output power stability of the OPO, resulting in a passive stability better than 1.9% rms for the near-IR signal and 2.4% rms for the mid-IR idler, measured over > 17 h, with both beams in high spatial quality.

  4. "Slow-scanning" in Ground-based Mid-infrared Observations

    Science.gov (United States)

    Ohsawa, Ryou; Sako, Shigeyuki; Miyata, Takashi; Kamizuka, Takafumi; Okada, Kazushi; Mori, Kiyoshi; Uchiyama, Masahito S.; Yamaguchi, Junpei; Fujiyoshi, Takuya; Morii, Mikio; Ikeda, Shiro

    2018-04-01

    Chopping observations with a tip-tilt secondary mirror have conventionally been used in ground-based mid-infrared observations. However, it is not practical for next generation large telescopes to have a large tip-tilt mirror that moves at a frequency larger than a few hertz. We propose an alternative observing method, a "slow-scanning" observation. Images are continuously captured as movie data, while the field of view is slowly moved. The signal from an astronomical object is extracted from the movie data by a low-rank and sparse matrix decomposition. The performance of the "slow-scanning" observation was tested in an experimental observation with Subaru/COMICS. The quality of a resultant image in the "slow-scanning" observation was as good as in a conventional chopping observation with COMICS, at least for a bright point-source object. The observational efficiency in the "slow-scanning" observation was better than that in the chopping observation. The results suggest that the "slow-scanning" observation can be a competitive method for the Subaru telescope and be of potential interest to other ground-based facilities to avoid chopping.

  5. EGC: a time-frequency augmented template-based method for gravitational wave burst search in ground-based interferometers

    International Nuclear Information System (INIS)

    Clapson, Andre-Claude; Barsuglia, Matteo; Bizouard, Marie-Anne; Brisson, Violette; Cavalier, Fabien; Davier, Michel; Hello, Patrice; Leroy, Nicolas; Varvella, Monica

    2008-01-01

    The detection of burst-type events in the output of ground gravitational wave detectors is particularly challenging. The potential variety of astrophysical waveforms, as proposed by simulations and analytic studies in general relativity and the discrimination of actual signals from instrumental noise both are critical issues. Robust methods that achieve reasonable detection performances over a wide range of signals are required. We present here a hybrid burst-detection pipeline related to time-frequency transforms while based on matched filtering to provide robustness against noise characteristics. Studies on simulated noise show that the algorithm has a detection efficiency similar to other methods over very different waveforms and particularly good timing even for low amplitude signals: no bias for most tested waveforms and an average accuracy of 1.1 ms (down to 0.1 ms in the best case). Time-frequency-type parameters, useful for event classification, are also derived for noise spectral densities unfavourable to standard time-frequency algorithms

  6. EGC: a time-frequency augmented template-based method for gravitational wave burst search in ground-based interferometers

    Energy Technology Data Exchange (ETDEWEB)

    Clapson, Andre-Claude; Barsuglia, Matteo; Bizouard, Marie-Anne; Brisson, Violette; Cavalier, Fabien; Davier, Michel; Hello, Patrice; Leroy, Nicolas; Varvella, Monica [LAL, Universite Paris-Sud 11, BP 34, 91898 Orsay (France)

    2008-02-07

    The detection of burst-type events in the output of ground gravitational wave detectors is particularly challenging. The potential variety of astrophysical waveforms, as proposed by simulations and analytic studies in general relativity and the discrimination of actual signals from instrumental noise both are critical issues. Robust methods that achieve reasonable detection performances over a wide range of signals are required. We present here a hybrid burst-detection pipeline related to time-frequency transforms while based on matched filtering to provide robustness against noise characteristics. Studies on simulated noise show that the algorithm has a detection efficiency similar to other methods over very different waveforms and particularly good timing even for low amplitude signals: no bias for most tested waveforms and an average accuracy of 1.1 ms (down to 0.1 ms in the best case). Time-frequency-type parameters, useful for event classification, are also derived for noise spectral densities unfavourable to standard time-frequency algorithms.

  7. High-frequency intrinsic dynamics of the electrocaloric effect from direct atomistic simulations

    Science.gov (United States)

    Lisenkov, S.; Ponomareva, I.

    2018-05-01

    We propose a computational methodology capable of harvesting isothermal heat and entropy change in molecular dynamics simulations. The methodology is applied to study high-frequency dynamics of the electrocaloric effect (ECE) in ferroelectric PbTiO3. ECE is associated with a reversible change in temperature under adiabatic application of electric field or with a reversible change in entropy under isothermal application of the electric field. Accurate assessment of electrocaloric performance requires the knowledge of three quantities: isothermal heat, isothermal entropy change, and adiabatic temperature change. Our methodology allows computations of all these quantities directly, that is, without restoring to the reversible thermodynamical models. Consequently, it captures both reversible and irreversible effects, which is critical for ECE simulations. The approach is well suited to address the dynamics of the ECE, which so far remains underexplored. We report the following basic features of the intrinsic dynamics of ECE: (i) the ECE is independent of the electric field frequency, rate of application, or field profile; (ii) the effect persists up to the frequencies associated with the onset of dielectric losses and deteriorates from there due to the creation of irreversible entropy; and (iii) in the vicinity of the phase transition and in the paraelectric phase the onset of irreversible dynamics occurs at lower frequency as compared to the ferroelectric phase. The latter is attributed to lower intrinsic soft-mode frequencies and and larger losses in the paraelectric phase.

  8. Mid-infrared pulsed laser ultrasonic testing for carbon fiber reinforced plastics.

    Science.gov (United States)

    Kusano, Masahiro; Hatano, Hideki; Watanabe, Makoto; Takekawa, Shunji; Yamawaki, Hisashi; Oguchi, Kanae; Enoki, Manabu

    2018-03-01

    Laser ultrasonic testing (LUT) can realize contactless and instantaneous non-destructive testing, but its signal-to-noise ratio must be improved in order to measure carbon fiber reinforced plastics (CFRPs). We have developed a mid-infrared (mid-IR) laser source optimal for generating ultrasonic waves in CFRPs by using a wavelength conversion device based on an optical parametric oscillator. This paper reports a comparison of the ultrasonic generation behavior between the mid-IR laser and the Nd:YAG laser. The mid-IR laser generated a significantly larger ultrasonic amplitude in CFRP laminates than a conventional Nd:YAG laser. In addition, our study revealed that the surface epoxy matrix of CFRPs plays an important role in laser ultrasonic generation. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Simulation for noise cancellation using LMS adaptive filter

    Science.gov (United States)

    Lee, Jia-Haw; Ooi, Lu-Ean; Ko, Ying-Hao; Teoh, Choe-Yung

    2017-06-01

    In this paper, the fundamental algorithm of noise cancellation, Least Mean Square (LMS) algorithm is studied and enhanced with adaptive filter. The simulation of the noise cancellation using LMS adaptive filter algorithm is developed. The noise corrupted speech signal and the engine noise signal are used as inputs for LMS adaptive filter algorithm. The filtered signal is compared to the original noise-free speech signal in order to highlight the level of attenuation of the noise signal. The result shows that the noise signal is successfully canceled by the developed adaptive filter. The difference of the noise-free speech signal and filtered signal are calculated and the outcome implies that the filtered signal is approaching the noise-free speech signal upon the adaptive filtering. The frequency range of the successfully canceled noise by the LMS adaptive filter algorithm is determined by performing Fast Fourier Transform (FFT) on the signals. The LMS adaptive filter algorithm shows significant noise cancellation at lower frequency range.

  10. Non-stationary component extraction in noisy multicomponent signal using polynomial chirping Fourier transform.

    Science.gov (United States)

    Lu, Wenlong; Xie, Junwei; Wang, Heming; Sheng, Chuan

    2016-01-01

    Inspired by track-before-detection technology in radar, a novel time-frequency transform, namely polynomial chirping Fourier transform (PCFT), is exploited to extract components from noisy multicomponent signal. The PCFT combines advantages of Fourier transform and polynomial chirplet transform to accumulate component energy along a polynomial chirping curve in the time-frequency plane. The particle swarm optimization algorithm is employed to search optimal polynomial parameters with which the PCFT will achieve a most concentrated energy ridge in the time-frequency plane for the target component. The component can be well separated in the polynomial chirping Fourier domain with a narrow-band filter and then reconstructed by inverse PCFT. Furthermore, an iterative procedure, involving parameter estimation, PCFT, filtering and recovery, is introduced to extract components from a noisy multicomponent signal successively. The Simulations and experiments show that the proposed method has better performance in component extraction from noisy multicomponent signal as well as provides more time-frequency details about the analyzed signal than conventional methods.

  11. High Power Mid-Infrared Generation with a Quasi-Phase Matched GaAs Guided-wave Optical Parametric Oscillator

    National Research Council Canada - National Science Library

    Harris, J

    2000-01-01

    ...-power coherent mid-infrared sources. Considerable effort has been devoted over the past decade to the development of mid-IR coherent sources based on nonlinear optical frequency conversion, e.g...

  12. Measuring displacement signal with an accelerometer

    International Nuclear Information System (INIS)

    Han, Sang Bo

    2010-01-01

    An effective and simple way to reconstruct displacement signal from a measured acceleration signal is proposed in this paper. To reconstruct displacement signal by means of double-integrating the time domain acceleration signal, the Nyquist frequency of the digital sampling of the acceleration signal should be much higher than the highest frequency component of the signal. On the other hand, to reconstruct displacement signal by taking the inverse Fourier transform, the magnitude of the significant frequency components of the Fourier transform of the acceleration signal should be greater than the 6 dB increment line along the frequency axis. With a predetermined resolution in time and frequency domain, determined by the sampling rate to measure and record the original signal, reconstructing high-frequency signals in the time domain and reconstructing low-frequency signals in the frequency domain will produce biased errors. Furthermore, because of the DC components inevitably included in the sampling process, low-frequency components of the signals are overestimated when displacement signals are reconstructed from the Fourier transform of the acceleration signal. The proposed method utilizes curve-fitting around the significant frequency components of the Fourier transform of the acceleration signal before it is inverse-Fourier transformed. Curve-fitting around the dominant frequency components provides much better results than simply ignoring the insignificant frequency components of the signal

  13. Laser-induced filaments in the mid-infrared

    International Nuclear Information System (INIS)

    Zheltikov, A M

    2017-01-01

    Laser-induced filamentation in the mid-infrared gives rise to unique regimes of nonlinear wave dynamics and reveals in many ways unusual nonlinear-optical properties of materials in this frequency range. The λ 2 scaling of the self-focusing threshold P cr , with radiation wavelength λ , allows the laser powers transmitted by single mid-IR filaments to be drastically increased without the loss of beam continuity and spatial coherence. When extended to the mid-infrared, laser filamentation enables new methods of pulse compression. Often working around the universal physical limitations, it helps generate few-cycle and subcycle field waveforms within an extraordinarily broad range of peak powers, from just a few up to hundreds of P cr . As a part of a bigger picture, laser-induced filamentation in the mid-infrared offers important physical insights into the general properties of the nonlinear-optical response of matter as a function of the wavelength. Unlike their near-infrared counterparts, which can be accurately described within the framework of perturbative nonlinear optics, mid-infrared filaments often entangle perturbative and nonperturbative nonlinear-optical effects, showing clear signatures of strong-field optical physics. With the role of nonperturbative nonlinear-optical phenomena growing, as a general tendency, with the field intensity and the driver wavelength, extension of laser filamentation to even longer driver wavelengths, toward the long-wavelength infrared, promises a hic sunt dracones land. (topical review)

  14. TITAN: a computer program for accident occurrence frequency analyses by component Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Nomura, Yasushi [Department of Fuel Cycle Safety Research, Nuclear Safety Research Center, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Tamaki, Hitoshi [Department of Safety Research Technical Support, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Kanai, Shigeru [Fuji Research Institute Corporation, Tokyo (Japan)

    2000-04-01

    In a plant system consisting of complex equipments and components for a reprocessing facility, there might be grace time between an initiating event and a resultant serious accident, allowing operating personnel to take remedial actions, thus, terminating the ongoing accident sequence. A component Monte Carlo simulation computer program TITAN has been developed to analyze such a complex reliability model including the grace time without any difficulty to obtain an accident occurrence frequency. Firstly, basic methods for the component Monte Carlo simulation is introduced to obtain an accident occurrence frequency, and then, the basic performance such as precision, convergence, and parallelization of calculation, is shown through calculation of a prototype accident sequence model. As an example to illustrate applicability to a real scale plant model, a red oil explosion in a German reprocessing plant model is simulated to show that TITAN can give an accident occurrence frequency with relatively good accuracy. Moreover, results of uncertainty analyses by TITAN are rendered to show another performance, and a proposal is made for introducing of a new input-data format to adapt the component Monte Carlo simulation. The present paper describes the calculational method, performance, applicability to a real scale, and new proposal for the TITAN code. In the Appendixes, a conventional analytical method is shown to avoid complex and laborious calculation to obtain a strict solution of accident occurrence frequency, compared with Monte Carlo method. The user's manual and the list/structure of program are also contained in the Appendixes to facilitate TITAN computer program usage. (author)

  15. TITAN: a computer program for accident occurrence frequency analyses by component Monte Carlo simulation

    International Nuclear Information System (INIS)

    Nomura, Yasushi; Tamaki, Hitoshi; Kanai, Shigeru

    2000-04-01

    In a plant system consisting of complex equipments and components for a reprocessing facility, there might be grace time between an initiating event and a resultant serious accident, allowing operating personnel to take remedial actions, thus, terminating the ongoing accident sequence. A component Monte Carlo simulation computer program TITAN has been developed to analyze such a complex reliability model including the grace time without any difficulty to obtain an accident occurrence frequency. Firstly, basic methods for the component Monte Carlo simulation is introduced to obtain an accident occurrence frequency, and then, the basic performance such as precision, convergence, and parallelization of calculation, is shown through calculation of a prototype accident sequence model. As an example to illustrate applicability to a real scale plant model, a red oil explosion in a German reprocessing plant model is simulated to show that TITAN can give an accident occurrence frequency with relatively good accuracy. Moreover, results of uncertainty analyses by TITAN are rendered to show another performance, and a proposal is made for introducing of a new input-data format to adapt the component Monte Carlo simulation. The present paper describes the calculational method, performance, applicability to a real scale, and new proposal for the TITAN code. In the Appendixes, a conventional analytical method is shown to avoid complex and laborious calculation to obtain a strict solution of accident occurrence frequency, compared with Monte Carlo method. The user's manual and the list/structure of program are also contained in the Appendixes to facilitate TITAN computer program usage. (author)

  16. Building Modern Vibration Diagnostics Systems Based on the Frequency-Time Transformations of A Measured Signal

    Directory of Open Access Journals (Sweden)

    Yasoveev Vasikh

    2016-01-01

    Full Text Available Basic methods of analysis of vibration transducers signals were reviewed. Continuous wavelet transform, being a time-frequency transform, was found to be an advanced mathematical tool for analysis of vibration signals. Experimental studies revealed obvious changes in the continuous wavelet transform spectrum depending on the existing defects. A method for detection and identification of technological violations based on the analysis of CWT spectrum components and normalized correlation coefficient was suggested. In accordance with the suggested method software for vibration diagnostics was developed.

  17. Early Detection of Amyotrophic Lateral Sclerosis (ALS using the Gait Motor Signal Frequency Analysis

    Directory of Open Access Journals (Sweden)

    Behzad Abedi

    2016-06-01

    Full Text Available Abstract Background: ALS is a progressive neuro-muscular disease, which is characterized by motor neuron loss in the Central Nervous System (CNS and Peripheral Nervous System (PNS. Up to now, no accurate clinical method for diagnosis of the disease have been provided. In most cases, ALS patients are unable to walk normally due to abnormalities in the nervous system. For this reason, one of the most appropriate methods in the diagnosis of ALS from other neurological diseases or from healthy volunteers is the gait motor signal analysis. Materials and Methods: In this study, gait signals available in Physionet database have been used. The database consists of 13 patients with ALS (ALS1, ALS2, …, ALS13 and 16 normal subjects (CO1, CO2, …, CO16. The patients participating in this study had no history of any psychiatric disorders and did not use any assistive device for walking, like wheelchair. The power spectrum of stride, swing, and stance of normal subjects and patients was computed for both left and right legs. To provide appropriate inputs for the classifier, the frequency band of the power spectrum of all signals was divided into eight equal parts. The area of all regions was computed. Three frequency band of the lower range of power spectra selected as inputs of the classifier. Results: In this study, power spectra, as frequency attributes, were used to explore probable differences of time series in both patients and healthy subjects. Conclusion: Artificial Neural Network was used to classify normal and ALS groups with the accuracy of 83% for the test data set. It seems that the present algorithm can be used in discriminating patients from normal subjects in the early stages of the disease.

  18. Ten-watt level picosecond parametric mid-IR source broadly tunable in wavelength

    Science.gov (United States)

    Vyvlečka, Michal; Novák, Ondřej; Roškot, Lukáscaron; Smrž, Martin; Mužík, Jiří; Endo, Akira; Mocek, Tomáš

    2018-02-01

    Mid-IR wavelength range (between 2 and 8 μm) offers perspective applications, such as minimally-invasive neurosurgery, gas sensing, or plastic and polymer processing. Maturity of high average power near-IR lasers is beneficial for powerful mid-IR generation by optical parametric conversion. We utilize in-house developed Yb:YAG thin-disk laser of 100 W average power at 77 kHz repetition rate, wavelength of 1030 nm, and about 2 ps pulse width for pumping of a ten-watt level picosecond mid-IR source. Seed beam is obtained by optical parametric generation in a double-pass 10 mm long PPLN crystal pumped by a part of the fundamental near-IR beam. Tunability of the signal wavelength between 1.46 μm and 1.95 μm was achieved with power of several tens of miliwatts. Main part of the fundamental beam pumps an optical parametric amplification stage, which includes a walk-off compensating pair of 10 mm long KTP crystals. We already demonstrated the OPA output signal and idler beam tunability between 1.70-1.95 μm and 2.18-2.62 μm, respectively. The signal and idler beams were amplified up to 8.5 W and 5 W, respectively, at 42 W pump without evidence of strong saturation. Thus, increase in signal and idler output power is expected for pump power increase.

  19. LPI Radar Waveform Recognition Based on Time-Frequency Distribution

    Directory of Open Access Journals (Sweden)

    Ming Zhang

    2016-10-01

    Full Text Available In this paper, an automatic radar waveform recognition system in a high noise environment is proposed. Signal waveform recognition techniques are widely applied in the field of cognitive radio, spectrum management and radar applications, etc. We devise a system to classify the modulating signals widely used in low probability of intercept (LPI radar detection systems. The radar signals are divided into eight types of classifications, including linear frequency modulation (LFM, BPSK (Barker code modulation, Costas codes and polyphase codes (comprising Frank, P1, P2, P3 and P4. The classifier is Elman neural network (ENN, and it is a supervised classification based on features extracted from the system. Through the techniques of image filtering, image opening operation, skeleton extraction, principal component analysis (PCA, image binarization algorithm and Pseudo–Zernike moments, etc., the features are extracted from the Choi–Williams time-frequency distribution (CWD image of the received data. In order to reduce the redundant features and simplify calculation, the features selection algorithm based on mutual information between classes and features vectors are applied. The superiority of the proposed classification system is demonstrated by the simulations and analysis. Simulation results show that the overall ratio of successful recognition (RSR is 94.7% at signal-to-noise ratio (SNR of −2 dB.

  20. Wavelet analysis of frequency chaos game signal: a time-frequency signature of the C. elegans DNA.

    Science.gov (United States)

    Messaoudi, Imen; Oueslati, Afef Elloumi; Lachiri, Zied

    2014-12-01

    Challenging tasks are encountered in the field of bioinformatics. The choice of the genomic sequence's mapping technique is one the most fastidious tasks. It shows that a judicious choice would serve in examining periodic patterns distribution that concord with the underlying structure of genomes. Despite that, searching for a coding technique that can highlight all the information contained in the DNA has not yet attracted the attention it deserves. In this paper, we propose a new mapping technique based on the chaos game theory that we call the frequency chaos game signal (FCGS). The particularity of the FCGS coding resides in exploiting the statistical properties of the genomic sequence itself. This may reflect important structural and organizational features of DNA. To prove the usefulness of the FCGS approach in the detection of different local periodic patterns, we use the wavelet analysis because it provides access to information that can be obscured by other time-frequency methods such as the Fourier analysis. Thus, we apply the continuous wavelet transform (CWT) with the complex Morlet wavelet as a mother wavelet function. Scalograms that relate to the organism Caenorhabditis elegans (C. elegans) exhibit a multitude of periodic organization of specific DNA sequences.

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

    Directory of Open Access Journals (Sweden)

    Ben Williges

    2015-12-01

    Full Text Available 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.

  2. Science Cases for the Velocity-Resolved Mid-J CO and 13CO and [Nii] Emissions

    Science.gov (United States)

    Okada, Yoko

    2018-01-01

    When studying PDRs, the contribution of shocks to the emission of mid-J CO lines is often debated. Plane-parallel PDR models fail to reproduce strong mid-J CO emissions, frequently leading to the conclusion of a shock contribution, while clumpy PDR models predict a flatter CO ladder in agreement with observations. One way to assign the origin of the mid-J CO lines is to investigate their velocity profile. Observations of mid-J 13CO emission profiles provide additional information as these lines are more likely optically thin. With AtLAST located on Cerro Chajnantor, a better atmospheric transparency compared to the ALMA plateau would enable efficient observations of the CO(6-5) to (8-7) lines. Under best weather conditions, it would be possible to observe up to CO(13-12) and the [NII]205 micron emission, which is essential to distinguish the ionized gas contribution to the [CII] emission observed from SOFIA. High angular resolution mapping in nearby galaxies with a large single dish telescope at high frequencies has a good synergy with interferometric observations at lower frequencies. Note that being at the high site does not compromise the zero-spacing-filling at low frequencies.

  3. Upconversion enhanced degenerate four-wave mixing in the mid-infrared for sensitive detection of acetylene in gas flows

    DEFF Research Database (Denmark)

    Høgstedt, Lasse; Dam, Jeppe Seidelin; Sahlberg, Anna-Lena

    2014-01-01

    We present a new background free method for in situ gas detection that combines degenerate four-wave mixing with an infra-red light detector based on parametric frequency upconversion of infra-red light. The system is demonstrated at mid infrared wavelengths for low concentration measurements...... of acetylene diluted in a N2 gas flow at ambient conditions. It is demonstrated that the system is able to cover more than 100 nm in scanning range and detect concentrations as low as 3 ppm based on the R9e line. A major issue in small signal measurements is scattered light and it is showed how a spatial...

  4. Factors associated with educational mobility in mid-age Australian women.

    Science.gov (United States)

    Tooth, Leigh R; Mishra, Gita D

    2017-02-01

    The educational mobility of mid-age women is rarely studied. We analysed the baseline socio-economic position (SEP) and health factors associated with obtaining further education in 4117 mid-age Australian women between 1996 and 2010 (aged 45-50 at baseline, 62-67 at follow-up) from a population-based study. Women either unemployed or working part-time at baseline had higher odds of a stable low and middle education over time (ORs ranging from 1.61 to 3.86) versus educational mobility. Apart from obesity, characteristics that may signal an unhealthy lifestyle in early mid-life were not useful indicators of women's future educational mobility. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  5. Low-Frequency Beacon Signal Strength Determination.

    Science.gov (United States)

    1980-01-01

    Radio Frequency List , RIS AF-6050-12 [141. Using this value and assum- ing performance for these facilities as indicatcd in FAA Handbook 6050.10, ERP...FAA Handbook 6050. 10 for facilities of appropriate transmitter power, determined from FAA Master Radio Frequency List 6050-12, April 1979...these facilities has not been directly measured and, therefore, values corresponding to transmitter powers given in FAA Master Radio Frequency List , RIS

  6. Upgrading a high-throughput spectrometer for high-frequency (<400 kHz) measurements

    Science.gov (United States)

    Nishizawa, T.; Nornberg, M. D.; Den Hartog, D. J.; Craig, D.

    2016-11-01

    The upgraded spectrometer used for charge exchange recombination spectroscopy on the Madison Symmetric Torus resolves emission fluctuations up to 400 kHz. The transimpedance amplifier's cutoff frequency was increased based upon simulations comparing the change in the measured photon counts for time-dynamic signals. We modeled each signal-processing stage of the diagnostic and scanned the filtering frequency to quantify the uncertainty in the photon counting rate. This modeling showed that uncertainties can be calculated based on assuming each amplification stage is a Poisson process and by calibrating the photon counting rate with a DC light source to address additional variation.

  7. Upgrading a high-throughput spectrometer for high-frequency (<400 kHz) measurements

    International Nuclear Information System (INIS)

    Nishizawa, T.; Nornberg, M. D.; Den Hartog, D. J.; Craig, D.

    2016-01-01

    The upgraded spectrometer used for charge exchange recombination spectroscopy on the Madison Symmetric Torus resolves emission fluctuations up to 400 kHz. The transimpedance amplifier’s cutoff frequency was increased based upon simulations comparing the change in the measured photon counts for time-dynamic signals. We modeled each signal-processing stage of the diagnostic and scanned the filtering frequency to quantify the uncertainty in the photon counting rate. This modeling showed that uncertainties can be calculated based on assuming each amplification stage is a Poisson process and by calibrating the photon counting rate with a DC light source to address additional variation.

  8. Upgrading a high-throughput spectrometer for high-frequency (<400 kHz) measurements

    Energy Technology Data Exchange (ETDEWEB)

    Nishizawa, T., E-mail: nishizawa@wisc.edu; Nornberg, M. D.; Den Hartog, D. J. [University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States); Craig, D. [Wheaton College, Wheaton, Illinois 60187 (United States)

    2016-11-15

    The upgraded spectrometer used for charge exchange recombination spectroscopy on the Madison Symmetric Torus resolves emission fluctuations up to 400 kHz. The transimpedance amplifier’s cutoff frequency was increased based upon simulations comparing the change in the measured photon counts for time-dynamic signals. We modeled each signal-processing stage of the diagnostic and scanned the filtering frequency to quantify the uncertainty in the photon counting rate. This modeling showed that uncertainties can be calculated based on assuming each amplification stage is a Poisson process and by calibrating the photon counting rate with a DC light source to address additional variation.

  9. Modeling the frequency response of microwave radiometers with QUCS

    International Nuclear Information System (INIS)

    Zonca, A; Williams, B; Rubin, I; Meinhold, P; Lubin, P; Roucaries, B; D'Arcangelo, O; Franceschet, C; Mennella, A; Bersanelli, M; Jahn, S

    2010-01-01

    Characterization of the frequency response of coherent radiometric receivers is a key element in estimating the flux of astrophysical emissions, since the measured signal depends on the convolution of the source spectral emission with the instrument band shape. Laboratory Radio Frequency (RF) measurements of the instrument bandpass often require complex test setups and are subject to a number of systematic effects driven by thermal issues and impedance matching, particularly if cryogenic operation is involved. In this paper we present an approach to modeling radiometers bandpasses by integrating simulations and RF measurements of individual components. This method is based on QUCS (Quasi Universal Circuit Simulator), an open-source circuit simulator, which gives the flexibility of choosing among the available devices, implementing new analytical software models or using measured S-parameters. Therefore an independent estimate of the instrument bandpass is achieved using standard individual component measurements and validated analytical simulations. In order to automate the process of preparing input data, running simulations and exporting results we developed the Python package python-qucs and released it under GNU Public License. We discuss, as working cases, bandpass response modeling of the COFE and Planck Low Frequency Instrument (LFI) radiometers and compare results obtained with QUCS and with a commercial circuit simulator software. The main purpose of bandpass modeling in COFE is to optimize component matching, while in LFI they represent the best estimation of frequency response, since end-to-end measurements were strongly affected by systematic effects.

  10. Dust removal in radio-frequency plasmas by a traveling potential modulation

    International Nuclear Information System (INIS)

    Li Yangfang; Jiang Ke; Thomas, Hubertus M.; Morfill, Gregor E.

    2010-01-01

    The dust contamination in plasma deposition processes plays a crucial role in the quality and the yield of the products. To improve the quality and the yield of plasma processing, a favorable way is to remove the dust particles actively from the plasma reactors.Our recent experiments in the striped electrode device show that a traveling plasma modulation allows for a systematic particle removal independent of the reactor size. Besides the rf powered electrode, the striped electrode device includes a segmented electrode that consists of 100 electrically insulated narrow stripes. A traveling potential profile is produced by the modulation of the voltage signals applied on the stripes. The dust particles are trapped in the potential wells and transported with the traveling of the potential profile.The particle-in-cell (PIC) simulation on the potential above the segmented electrode indicates that the traveling potential profile can be realized either by applying low-frequency (0.1-10 Hz) voltage signals with a fixed phase shift between adjacent stripes or high-frequency (10 kHz a circumflex AS 100 MHz) signals with the amplitudes modulated by a low-frequency envelope. The transportation of the dust particles is simulated with a two-dimensional molecular dynamics (MD) code with the potential profile obtained from the PIC simulation. The MD results reproduce the experimental observations successfully.This technology allows for an active removal of the contaminating particles in processing plasmas and it is independent of the reactor size. The removal velocity is controllable by adjusting the parameters for the modulation.

  11. Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy.

    Science.gov (United States)

    Xiong, Wei; Laaser, Jennifer E; Mehlenbacher, Randy D; Zanni, Martin T

    2011-12-27

    In the last ten years, two-dimensional infrared spectroscopy has become an important technique for studying molecular structures and dynamics. We report the implementation of heterodyne detected two-dimensional sum-frequency generation (HD 2D SFG) spectroscopy, which is the analog of 2D infrared (2D IR) spectroscopy, but is selective to noncentrosymmetric systems such as interfaces. We implement the technique using mid-IR pulse shaping, which enables rapid scanning, phase cycling, and automatic phasing. Absorptive spectra are obtained, that have the highest frequency resolution possible, from which we extract the rephasing and nonrephasing signals that are sometimes preferred. Using this technique, we measure the vibrational mode of CO adsorbed on a polycrystalline Pt surface. The 2D spectrum reveals a significant inhomogenous contribution to the spectral line shape, which is quantified by simulations. This observation indicates that the surface conformation and environment of CO molecules is more complicated than the simple "atop" configuration assumed in previous work. Our method can be straightforwardly incorporated into many existing SFG spectrometers. The technique enables one to quantify inhomogeneity, vibrational couplings, spectral diffusion, chemical exchange, and many other properties analogous to 2D IR spectroscopy, but specifically for interfaces.

  12. Real-Time Dynamic Simulation of Korean Power Grid for Frequency Regulation Control by MW Battery Energy Storage System

    Directory of Open Access Journals (Sweden)

    Tae-Hwan Jin

    2016-12-01

    Full Text Available The aim of this study was to develop a real-time dynamic simulator of a power grid with power plant and battery model. The simulator was used to investigate the frequency control characteristics of a megawatt-scale high-capacity energy storage system connected to the electric power grid. In this study, a lithium-ion secondary battery was chosen as one of the batteries for a grid-connected model. The dynamics of the model was analysed in both steady and transient states. The frequency control system of the battery model plays a role in regulating the grid frequency by controlling the power of energy storage systems according to process variables and grid frequencies. The power grid model based on the current power network of South Korea, included power plants, substations and power demands. The power supply is classified by the type of turbine generator as thermal, nuclear, hydro power, pumped power storage, combined power plants, and batteries, including high-capacity energy storage systems rated for a maximum of 500 MW. This study deals with an installed capacity of 87.17 GW and peak load of 77.30 GW in the Korean power grid. For 24 hours of operation, the maximum and minimum power outputs were simulated as 61.59 GW and 46.32 GW, respectively. The commercialized real-time dynamic simulation software ProTRAX was used. The simulation was conducted to observe the operation characteristics of the frequency control system during a breakdown of power plants, as well as under governor-free operation, auto generation control operation, and with the battery energy storage system connected. The results show that the model is valid for each power plant breakdown simulation. They also confirm that the output power and frequency controls of the battery operated well during simulations.

  13. Time of correlation of low-frequency fluctuations in the regional laser Doppler flow signal from human skin

    Science.gov (United States)

    Folgosi-Correa, M. S.; Nogueira, G. E. C.

    2012-06-01

    The laser Doppler flowmetry allows the non-invasive assessment of the skin perfusion in real-time, being an attractive technique to study the human microcirculation in clinical settings. Low-frequency oscillations in the laser Doppler blood flow signal from the skin have been related to the endothelial, endothelial-metabolic, neurogenic and myogenic mechanisms of microvascular flow control, in the range 0.005-0.0095 Hz, 0.0095-0.021 Hz, 0.021-0.052 Hz and 0.052- 0.145 Hz respectively. The mean Amplitude (A) of the periodic fluctuations in the laser Doppler blood flow signal, in each frequency range, derived from the respective wavelet-transformed coefficients, has been used to assess the function and dysfunctions of each mechanism of flow control. Known sources of flow signal variances include spatial and temporal variability, diminishing the discriminatory capability of the technique. Here a new time domain method of analysis is proposed, based on the Time of Correlation (TC) of flow fluctuations between two adjacent sites. Registers of blood flow from two adjacent regions, for skin temperature at 32 0C (basal) and thermally stimulated (42 0C) of volar forearms from 20 healthy volunteers were collected and analyzed. The results obtained revealed high time of correlation between two adjacent regions when thermally stimulated, for signals in the endothelial, endothelial-metabolic, neurogenic and myogenic frequency ranges. Experimental data also indicate lower variability for TC when compared to A, when thermally stimulated, suggesting a new promising parameter for assessment of the microvascular flow control.

  14. Simulation of power fluctuation of wind farms based on frequency domain

    DEFF Research Database (Denmark)

    Lin, Jin; Sun, Yuanzhang; Li, Guojie

    2011-01-01

    The wind power fluctuation model built up in the frequency domain is mathematically equivalent with that in the time domain, and has a clearer physical meaning therefore describes the fluctuation more accurately. However, the simulation of this model is required to deal with the time......-frequency transformation related to the power spectrum density (PSD), which is more special and complicated than normal transformations. Meanwhile, the computational complexity also increases significantly, more computation resources are needed. These problems negatively affect the engineering application of the model....... To overcome these disadvantages, the physical meaning of PSD based on fundamental concepts is presented, so that the specialties of this model compared with conventional ones can be understood. Then the time-frequency transformation algorithm is derived, which is fast to be implemented in digital computers...

  15. Simulation and Experimental Investigation of Structural Dynamic Frequency Characteristics Control

    Directory of Open Access Journals (Sweden)

    Bing Li

    2012-04-01

    Full Text Available In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with different working conditions. Active control is a stable and beneficial method for this, but current active control methods mainly focus on vibration control for reducing the vibration amplitudes in the time domain or frequency domain. In this paper, a new method of dynamic frequency characteristics active control (DFCAC is presented for a flat plate, which can not only accomplish vibration control but also arbitrarily change the dynamic characteristics of the equipment. The proposed DFCAC algorithm is based on a neural network including two parts of the identification implement and the controller. The effectiveness of the DFCAC method is verified by several simulation and experiments, which provide desirable results.

  16. NAFASS: Fluctuation spectroscopy and the Prony spectrum for description of multi-frequency signals in complex systems

    Science.gov (United States)

    Nigmatullin, R. R.; Gubaidullin, I. A.

    2018-03-01

    In this paper, we essentially modernize the NAFASS (Non-orthogonal Amplitude Frequency Analysis of the Smoothed Signals) approach suggested earlier. Actually, we solved two important problems: (a) new and effective algorithm was proposed and (b) we proved that the segment of the Prony spectrum could be used as the fitting function for description of the desired frequency spectrum. These two basic elements open an alternative way for creation of the fluctuation spectroscopy when the segment of the Fourier series can fit any random signal with trend but the dispersion spectrum of the Fourier series ω0 · k(ω0 ≡ 2 π / T) ⇒Ωk(k = 0 , 1 , 2 , . . . , K - 1) is replaced by the specific dispersion law Ωk calculated with the help of original algorithm described below. It implies that any finite signal will have a compact amplitude-frequency response (AFR), where the number of the modes is much less in comparison with the number of data points (K economic data and compare 30-years world prices for meat (beef, chicken, lamb and pork) entering as the basic components to every-day food consumption. These data were taken from the official site http://www.indexmundi.com/commodities/. We fitted these random functions with the high accuracy and calculated the desired ;amplitude-frequency; response for these random price fluctuations. The calculated distribution of the amplitudes (Ack, Ask) and frequency spectrum Ωk (k = 0, 1,…, K-1) allows one to compress initial data (K (number of modes) << N (number of data points), N/K ≅ 20-40) and receive an additional information for their comparison with each other. As the second example, we considered the transcendental/irrational numbers description in the frame of the proposed NAFASS approach, as well. This possibility was demonstrated on the quantitative description of the transcendental number π = 3.1415926535897932…, containing initially 6ṡ104 digits. The results obtained for the second type of data can be useful for

  17. Primary Frequency Response with Aggregated DERs: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Guggilam, Swaroop S.; Dhople, Sairaj V.; Zhao, Changhong; Dall' Anese, Emiliano; Chen, Yu Christine

    2017-03-03

    Power networks have to withstand a variety of disturbances that affect system frequency, and the problem is compounded with the increasing integration of intermittent renewable generation. Following a large-signal generation or load disturbance, system frequency is arrested leveraging primary frequency control provided by governor action in synchronous generators. In this work, we propose a framework for distributed energy resources (DERs) deployed in distribution networks to provide (supplemental) primary frequency response. Particularly, we demonstrate how power-frequency droop slopes for individual DERs can be designed so that the distribution feeder presents a guaranteed frequency-regulation characteristic at the feeder head. Furthermore, the droop slopes are engineered such that injections of individual DERs conform to a well-defined fairness objective that does not penalize them for their location on the distribution feeder. Time-domain simulations for an illustrative network composed of a combined transmission network and distribution network with frequency-responsive DERs are provided to validate the approach.

  18. MRI assessment of mid-urethral ligament changes in female stress urinary incontinence

    International Nuclear Information System (INIS)

    Bai Mei; Liu Hongyi; Han Yue; Xu Guoping; Fang Ping; Zhao Yang; Li Jingjin

    2012-01-01

    Objective: To evaluate the MRI value in changes of mid-urethral ligament injury of female stress urinary incontinence (SUI). Methods: Comparison of MRI changes of mid-urethral ligament on 30 healthy female volunteers and 20 female SUI patients. Chi-square test was used to compare the form of SUI patient's mid-urethral support ligaments. Results: The female mid-urethral support ligaments were composed of 4 groups of ligaments, including the periurethral ligament and pubourethral ligaments (1 pair), and at both sides of the urethra's paraurethral ligaments (1 pair) and suburethral ligament lying dorsal urethra, connecting the urethra and pelvic arcus tendinous fasciae. In normal MRI, ligament was a thin strip and showed low signal on both T 1 WI and T 2 WI, T 2 WI sagittal and cross-section scan was the best combination to show the middle urethral support ligaments changes, with tension; 6 patients (20%) in the 30 patients normal control group could be seen tortuously and slack like around the urethra ligaments. Twenty SUI patients mid-urethral support ligaments were performance laxity or rupture,rates were 39% (47/120) and 42% (50/120) (χ 2 =43.191, P<0.05). On T 2 WI, the ligamentous laxity was floating,and loss tension, also could performance one side extension and thinner than the other side. The ligament rupture was performance of the signal interruption, ligament contracture and one end of ligament attachment points separation. Conclusion: MRI can objective effective evaluate the mid-urethral support ligaments' pathological changes in stress urinary incontinence patients. (authors)

  19. Numerical simulations of eddy current testing signals of steam generator tubes by 3-D finite element method

    International Nuclear Information System (INIS)

    Sakai, Takayuki; Soneda, Naoki

    1996-01-01

    In every inspection of Japanese PWR plants, all of steam generator tubes are inspected using Eddy Current Testing (ECT) method. However, the relationships between the ECT signals and the defect shapes are known only for the representative shapes of defects. In order to improve the reliability of inspections and the capability of ECT probes, development of numerical simulation technique of the ECT signals for arbitrarily shaped defects is essential. In this study, three-dimensional finite element code is developed to simulate the ECT signals for any kinds of defects in the SG tubes. The code is fully vectorized so that it runs on the supercomputers very efficiently. The simulation results agree very well with the experimental results. Sensitivity analyses are performed to investigate the relationships between the defect shapes and the ECT signals. (author)

  20. Fast 2D fluid-analytical simulation of ion energy distributions and electromagnetic effects in multi-frequency capacitive discharges

    Science.gov (United States)

    Kawamura, E.; Lieberman, M. A.; Graves, D. B.

    2014-12-01

    A fast 2D axisymmetric fluid-analytical plasma reactor model using the finite elements simulation tool COMSOL is interfaced with a 1D particle-in-cell (PIC) code to study ion energy distributions (IEDs) in multi-frequency capacitive argon discharges. A bulk fluid plasma model, which solves the time-dependent plasma fluid equations for the ion continuity and electron energy balance, is coupled with an analytical sheath model, which solves for the sheath parameters. The time-independent Helmholtz equation is used to solve for the fields and a gas flow model solves for the steady-state pressure, temperature and velocity of the neutrals. The results of the fluid-analytical model are used as inputs to a PIC simulation of the sheath region of the discharge to obtain the IEDs at the target electrode. Each 2D fluid-analytical-PIC simulation on a moderate 2.2 GHz CPU workstation with 8 GB of memory took about 15-20 min. The multi-frequency 2D fluid-analytical model was compared to 1D PIC simulations of a symmetric parallel-plate discharge, showing good agreement. We also conducted fluid-analytical simulations of a multi-frequency argon capacitively coupled plasma (CCP) with a typical asymmetric reactor geometry at 2/60/162 MHz. The low frequency 2 MHz power controlled the sheath width and sheath voltage while the high frequencies controlled the plasma production. A standing wave was observable at the highest frequency of 162 MHz. We noticed that adding 2 MHz power to a 60 MHz discharge or 162 MHz to a dual frequency 2 MHz/60 MHz discharge can enhance the plasma uniformity. We found that multiple frequencies were not only useful for controlling IEDs but also plasma uniformity in CCP reactors.

  1. Laser frequency stabilization by combining modulation transfer and frequency modulation spectroscopy.

    Science.gov (United States)

    Zi, Fei; Wu, Xuejian; Zhong, Weicheng; Parker, Richard H; Yu, Chenghui; Budker, Simon; Lu, Xuanhui; Müller, Holger

    2017-04-01

    We present a hybrid laser frequency stabilization method combining modulation transfer spectroscopy (MTS) and frequency modulation spectroscopy (FMS) for the cesium D2 transition. In a typical pump-probe setup, the error signal is a combination of the DC-coupled MTS error signal and the AC-coupled FMS error signal. This combines the long-term stability of the former with the high signal-to-noise ratio of the latter. In addition, we enhance the long-term frequency stability with laser intensity stabilization. By measuring the frequency difference between two independent hybrid spectroscopies, we investigate the short-and long-term stability. We find a long-term stability of 7.8 kHz characterized by a standard deviation of the beating frequency drift over the course of 10 h and a short-term stability of 1.9 kHz characterized by an Allan deviation of that at 2 s of integration time.

  2. Microwave Frequency Multiplier

    Science.gov (United States)

    Velazco, J. E.

    2017-02-01

    concerns. We present a theoretical analysis for the beam-wave interactions in the MFM's input and output cavities. We show the conditions required for successful frequency multiplication inside the output cavity. Computer simulations using the plasma physics code MAGIC show that 100 kW of Ka-band (32-GHz) output power can be produced using an 80-kW X-band (8-GHz) signal at the MFM's input. The associated MFM efficiency - from beam power to Ka-band power - is 83 percent. Thus, the overall klystron-MFM efficiency is 42 percent - assuming that a klystron with an efficiency of 50 percent delivers the input signal.

  3. The characteristics and residual stress of aluminum nitride films grown by two-stage sputtering of mid-frequency power

    International Nuclear Information System (INIS)

    Lin, T.-C.; Cheng, H.-E.; Tang, S.-H.; Liu, W.-C.; Lee, Antony H.C.

    2008-01-01

    The [0 0 2] oriented aluminum nitride has a high surface acoustic wave speed and high mechanic-electron couple coefficient. It is a potential material for manufacturing piezoelectric devices in high frequency application. The AlN films deposited onto silicon substrates were fabricated by two-stage sputtering process with mid-frequency generator. The results showed that the film did not have well [0 0 2] preferred orientation at 1.0 and 1.5 kW, and exhibited a [0 0 2] preferred orientation at 2.0 kW. The adhesion was poor when the film had a high preferred orientation because the substrate was damaged by high energetic atoms bombardment. A two-stage growth method was investigated in order to get high [0 0 2] preferred orientation and good adhesion. A good performance was obtained at the first stage power of 1.5 kW and the second stage power of 2.0 kW. The film showed a tensile stress state when the film was deposited at 1.0 kW. In contrast, the stress state was changed to compressive when the films were grown at 2.0 kW. The two-stage growth could succeed not only to get a high [0 0 2] preferred orientation but also to develop a reducing global stress film

  4. Power spectrum model of visual masking: simulations and empirical data.

    Science.gov (United States)

    Serrano-Pedraza, Ignacio; Sierra-Vázquez, Vicente; Derrington, Andrew M

    2013-06-01

    In the study of the spatial characteristics of the visual channels, the power spectrum model of visual masking is one of the most widely used. When the task is to detect a signal masked by visual noise, this classical model assumes that the signal and the noise are previously processed by a bank of linear channels and that the power of the signal at threshold is proportional to the power of the noise passing through the visual channel that mediates detection. The model also assumes that this visual channel will have the highest ratio of signal power to noise power at its output. According to this, there are masking conditions where the highest signal-to-noise ratio (SNR) occurs in a channel centered in a spatial frequency different from the spatial frequency of the signal (off-frequency looking). Under these conditions the channel mediating detection could vary with the type of noise used in the masking experiment and this could affect the estimation of the shape and the bandwidth of the visual channels. It is generally believed that notched noise, white noise and double bandpass noise prevent off-frequency looking, and high-pass, low-pass and bandpass noises can promote it independently of the channel's shape. In this study, by means of a procedure that finds the channel that maximizes the SNR at its output, we performed numerical simulations using the power spectrum model to study the characteristics of masking caused by six types of one-dimensional noise (white, high-pass, low-pass, bandpass, notched, and double bandpass) for two types of channel's shape (symmetric and asymmetric). Our simulations confirm that (1) high-pass, low-pass, and bandpass noises do not prevent the off-frequency looking, (2) white noise satisfactorily prevents the off-frequency looking independently of the shape and bandwidth of the visual channel, and interestingly we proved for the first time that (3) notched and double bandpass noises prevent off-frequency looking only when the noise

  5. Photoacoustic simulation study of chirp excitation response from different size absorbers

    Science.gov (United States)

    Jnawali, K.; Chinni, B.; Dogra, V.; Rao, N.

    2017-03-01

    Photoacoustic (PA) imaging is a hybrid imaging modality that integrates the strength of optical and ultrasound imaging. Nanosecond (ns) pulsed lasers used in current PA imaging systems are expensive, bulky and they often waste energy. We propose and evaluate, through simulations, the use of a continuous wave (CW) laser whose amplitude is linear frequency modulated (chirp) for PA imaging. The chirp signal provides signal-to-side-lobe ratio (SSR) improvement potential and full control over PA signal frequencies excited in the sample. The PA signal spectrum is a function of absorber size and the time frequencies present in the chirp. A mismatch between the input chirp spectrum and the output PA signal spectrum can affect the compressed pulse that is recovered from cross-correlating the two. We have quantitatively characterized this effect. The k-wave Matlab tool box was used to simulate PA signals in three dimensions for absorbers ranging in size from 0.1 mm to 0.6 mm, in response to laser excitation amplitude that is linearly swept from 0.5 MHz to 4 MHz. This sweep frequency range was chosen based on the spectrum analysis of a PA signal generated from ex-vivo human prostate tissue samples. In comparison, the energy wastage by a ns laser pulse was also estimated. For the chirp methodology, the compressed pulse peak amplitude, pulse width and side lobe structure parameters were extracted for different size absorbers. While the SSR increased 6 fold with absorber size, the pulse width decreased by 25%.

  6. A model for generating Surface EMG signal of m. Tibialis Anterior.

    Science.gov (United States)

    Siddiqi, Ariba; Kumar, Dinesh; Arjunan, Sridhar P

    2014-01-01

    A model that simulates surface electromyogram (sEMG) signal of m. Tibialis Anterior has been developed and tested. This has a firing rate equation that is based on experimental findings. It also has a recruitment threshold that is based on observed statistical distribution. Importantly, it has considered both, slow and fast type which has been distinguished based on their conduction velocity. This model has assumed that the deeper unipennate half of the muscle does not contribute significantly to the potential induced on the surface of the muscle and has approximated the muscle to have parallel structure. The model was validated by comparing the simulated and the experimental sEMG signal recordings. Experiments were conducted on eight subjects who performed isometric dorsiflexion at 10, 20, 30, 50, 75, and 100% maximal voluntary contraction. Normalized root mean square and median frequency of the experimental and simulated EMG signal were computed and the slopes of the linearity with the force were statistically analyzed. The gradients were found to be similar (p>0.05) for both experimental and simulated sEMG signal, validating the proposed model.

  7. Micro-simulation of vehicle conflicts involving right-turn vehicles at signalized intersections based on cellular automata.

    Science.gov (United States)

    Chai, C; Wong, Y D

    2014-02-01

    At intersection, vehicles coming from different directions conflict with each other. Improper geometric design and signal settings at signalized intersection will increase occurrence of conflicts between road users and results in a reduction of the safety level. This study established a cellular automata (CA) model to simulate vehicular interactions involving right-turn vehicles (as similar to left-turn vehicles in US). Through various simulation scenarios for four case cross-intersections, the relationships between conflict occurrences involving right-turn vehicles with traffic volume and right-turn movement control strategies are analyzed. Impacts of traffic volume, permissive right-turn compared to red-amber-green (RAG) arrow, shared straight-through and right-turn lane as well as signal setting are estimated from simulation results. The simulation model is found to be able to provide reasonable assessment of conflicts through comparison of existed simulation approach and observed accidents. Through the proposed approach, prediction models for occurrences and severity of vehicle conflicts can be developed for various geometric layouts and traffic control strategies. Copyright © 2013 Elsevier Ltd. All rights reserved.

  8. Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise

    Science.gov (United States)

    Brown, Patrick T.; Li, Wenhong; Cordero, Eugene C.; Mauget, Steven A.

    2015-01-01

    The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much public and scientific attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible unforced states of the climate system (the Envelope of Unforced Noise; EUN). Typically, the EUN is derived from climate models themselves, but climate models might not accurately simulate the correct characteristics of unforced GMT variability. Here, we simulate a new, empirical, EUN that is based on instrumental and reconstructed surface temperature records. We compare the forced GMT signal produced by climate models to observations while noting the range of GMT values provided by the empirical EUN. We find that the empirical EUN is wide enough so that the interdecadal variability in the rate of global warming over the 20th century does not necessarily require corresponding variability in the rate-of-increase of the forced signal. The empirical EUN also indicates that the reduced GMT warming over the past decade or so is still consistent with a middle emission scenario's forced signal, but is likely inconsistent with the steepest emission scenario's forced signal. PMID:25898351

  9. Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise.

    Science.gov (United States)

    Brown, Patrick T; Li, Wenhong; Cordero, Eugene C; Mauget, Steven A

    2015-04-21

    The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much public and scientific attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible unforced states of the climate system (the Envelope of Unforced Noise; EUN). Typically, the EUN is derived from climate models themselves, but climate models might not accurately simulate the correct characteristics of unforced GMT variability. Here, we simulate a new, empirical, EUN that is based on instrumental and reconstructed surface temperature records. We compare the forced GMT signal produced by climate models to observations while noting the range of GMT values provided by the empirical EUN. We find that the empirical EUN is wide enough so that the interdecadal variability in the rate of global warming over the 20(th) century does not necessarily require corresponding variability in the rate-of-increase of the forced signal. The empirical EUN also indicates that the reduced GMT warming over the past decade or so is still consistent with a middle emission scenario's forced signal, but is likely inconsistent with the steepest emission scenario's forced signal.

  10. Analysis of acoustic sound signal for ONB measurement

    International Nuclear Information System (INIS)

    Park, S. J.; Kim, H. I.; Han, K. Y.; Chai, H. T.; Park, C.

    2003-01-01

    The onset of nucleate boiling (ONB) was measured in a test fuel bundle composed of several fuel element simulators (FES) by analysing the aquatic sound signals. In order measure ONBs, a hydrophone, a pre-amplifier, and a data acquisition system to acquire/process the aquatic signal was prepared. The acoustic signal generated in the coolant is converted to the current signal through the microphone. When the signal is analyzed in the frequency domain, each sound signal can be identified according to its origin of sound source. As the power is increased to a certain degree, a nucleate boiling is started. The frequent formation and collapse of the void bubbles produce sound signal. By measuring this sound signal one can pinpoint the ONB. Since the signal characteristics is identical for different mass flow rates, this method can be applicable for ascertaining ONB

  11. Kerr nonlinearity mitigation in 5 × 28-GBd PDM16-QAM signal transmission over a dispersion-uncompensated link with backward-pumpeddistributed Raman amplification

    DEFF Research Database (Denmark)

    Sackey, I.; Da Ros, Francesco; Jazayerifar, M.

    2014-01-01

    We present experimental and numerical investigations of Kerr nonlinearity compensation in a 400-km standard single-mode fiber link with distributed Raman amplification with backward pumping. A dual-pump polarization-independent fiber-based optical parametric amplifier is used for mid-link spectra...... to numerical simulations with good agreement. It is also shown with simulations that a maximum transmission reach of 2400 km enabled by the optical phase conjugator is possible for the WDM signal...

  12. GUM2DFT—a software tool for uncertainty evaluation of transient signals in the frequency domain

    International Nuclear Information System (INIS)

    Eichstädt, S; Wilkens, V

    2016-01-01

    The Fourier transform and its counterpart for discrete time signals, the discrete Fourier transform (DFT), are common tools in measurement science and application. Although almost every scientific software package offers ready-to-use implementations of the DFT, the propagation of uncertainties in line with the guide to the expression of uncertainty in measurement (GUM) is typically neglected. This is of particular importance in dynamic metrology, when input estimation is carried out by deconvolution in the frequency domain. To this end, we present the new open-source software tool GUM2DFT, which utilizes closed formulas for the efficient propagation of uncertainties for the application of the DFT, inverse DFT and input estimation in the frequency domain. It handles different frequency domain representations, accounts for autocorrelation and takes advantage of the symmetry inherent in the DFT result for real-valued time domain signals. All tools are presented in terms of examples which form part of the software package. GUM2DFT will foster GUM-compliant evaluation of uncertainty in a DFT-based analysis and enable metrologists to include uncertainty evaluations in their routine work. (paper)

  13. Implementation of the frequency dependent line model in a real-time power system simulator

    Directory of Open Access Journals (Sweden)

    Reynaldo Iracheta-Cortez

    2017-09-01

    Full Text Available In this paper is described the implementation of the frequency-dependent line model (FD-Line in a real-time digital power system simulator. The main goal with such development is to describe a general procedure to incorporate new realistic models of power system components in modern real-time simulators based on the Electromagnetic Transients Program (EMTP. In this procedure are described, firstly, the steps to obtain the time domain solution of the differential equations that models the electromagnetic behavior in multi-phase transmission lines with frequency dependent parameters. After, the algorithmic solution of the FD-Line model is implemented in Simulink environment, through an S-function programmed in C language, for running off-line simulations of electromagnetic transients. This implementation allows the free assembling of the FD Line model with any element of the Power System Blockset library and also, it can be used to build any network topology. The main advantage of having a power network built in Simulink is that can be executed in real-time by means of the commercial eMEGAsim simulator. Finally, several simulation cases are presented to validate the accuracy and the real-time performance of the FD-Line model.

  14. Influence of Wind Plant Ancillary Frequency Control on System Small Signal Stability

    DEFF Research Database (Denmark)

    Su, Chi; Chen, Zhe

    2012-01-01

    Since large-scale wind farms are increasingly connected to modern power grids, the transmission system operators put more requirements as part of the grid codes on the integration of wind farms. System frequency control which is normally provided by conventional synchronous generators becomes a c...... ratio values of the dominant oscillation modes within the connected power system. All the calculations and simulations are conducted in DIgSILENT PowerFactory 14.0....

  15. Coordinated observation of field line resonance in the mid-tail

    Directory of Open Access Journals (Sweden)

    Y. Zheng

    2006-03-01

    Full Text Available Standing Alfvén waves of 1.1 mHz (~15 min in period were observed by the Cluster satellites in the mid-tail during 06:00-07:00 UT on 8 August 2003. Pulsations with the same frequency were also observed at several ground stations near Cluster's footpoint. The standing wave properties were determined from the electric and magnetic field measurements of Cluster. Data from the ground magnetometers indicated a latitudinal amplitude and phase structure consistent with the driven field line resonance (FLR at 1.1 mHz. Simultaneously, quasi-periodic oscillations at different frequencies were observed in the post-midnight/early morning sector by GOES 12 (l0≈8.7, Polar (l0≈11-14 and Geotail (l0≈9.8. The 8 August 2003 event yields rare and interesting datasets. It provides, for the first time, coordinated in situ and ground-based observations of a very low frequency FLR in the mid-tail on stretched field lines.

  16. High-frequency signal paths in the TMR-86.1 experimental tomography apparatus

    International Nuclear Information System (INIS)

    Obrcian, J.; Jellus, V.; Weis, J.; Frollo, I.

    1990-01-01

    The NMR-based TMR-86.1 tomography apparatus, developed at the Institute of Measurement and Measuring Instrumentation, Slovak Academy of Sciences in Bratislava, Czechoslovakia, enables imaging of the inner structure of biological samples and human limbs no more than 110 mm in diameter, using a measuring matrix containing at most 128x128 elements. The imaged matrix can possess a maximum of 256x256 image elements with 256 brightness steps. The signal paths of the high-frequency excitation-imaging complex of the apparatus are described. Some functional blocks of the apparatus can be used without substantial modifications for the imaging of larger objects such as the human body. From the point of view of the high-frequency pulses for nonselective excitation (so-called 180deg-pulses), the excitation pulse power will have to be increased to at least 1 kW. (author). 5 figs, 7 refs

  17. Method of test signal design for estimating the aircraft aerodynamic parameters

    Science.gov (United States)

    Belokon', S. A.; Zolotukhin, Yu. N.; Filippov, M. N.

    2017-07-01

    A method of test signal design is proposed for studying the aircraft aerodynamic characteristics with the use of the technology of dynamically scaled free-flight models. Simultaneous excitation of all input channels in a prescribed frequency band by a set of mutually orthogonal signals is applied to increase the efficiency. A modified method of calculating the set of mutually orthogonal sinusoidal signals with a small normalized peak factor is presented. Results of simulating the aircraft motion in the MATLAB/Simulink environment with the use of the developed method of test signal design are reported.

  18. Digital timing: sampling frequency, anti-aliasing filter and signal interpolation filter dependence on timing resolution

    International Nuclear Information System (INIS)

    Cho, Sanghee; Grazioso, Ron; Zhang Nan; Aykac, Mehmet; Schmand, Matthias

    2011-01-01

    The main focus of our study is to investigate how the performance of digital timing methods is affected by sampling rate, anti-aliasing and signal interpolation filters. We used the Nyquist sampling theorem to address some basic questions such as what will be the minimum sampling frequencies? How accurate will the signal interpolation be? How do we validate the timing measurements? The preferred sampling rate would be as low as possible, considering the high cost and power consumption of high-speed analog-to-digital converters. However, when the sampling rate is too low, due to the aliasing effect, some artifacts are produced in the timing resolution estimations; the shape of the timing profile is distorted and the FWHM values of the profile fluctuate as the source location changes. Anti-aliasing filters are required in this case to avoid the artifacts, but the timing is degraded as a result. When the sampling rate is marginally over the Nyquist rate, a proper signal interpolation is important. A sharp roll-off (higher order) filter is required to separate the baseband signal from its replicates to avoid the aliasing, but in return the computation will be higher. We demonstrated the analysis through a digital timing study using fast LSO scintillation crystals as used in time-of-flight PET scanners. From the study, we observed that there is no significant timing resolution degradation down to 1.3 Ghz sampling frequency, and the computation requirement for the signal interpolation is reasonably low. A so-called sliding test is proposed as a validation tool checking constant timing resolution behavior of a given timing pick-off method regardless of the source location change. Lastly, the performance comparison for several digital timing methods is also shown.

  19. Correlated inter-regional variations in low frequency local field potentials and resting state BOLD signals within S1 cortex of monkeys.

    Science.gov (United States)

    Wilson, George H; Yang, Pai-Feng; Gore, John C; Chen, Li Min

    2016-08-01

    The hypothesis that specific frequency components of the spontaneous local field potentials (LFPs) underlie low frequency fluctuations of resting state fMRI (rsfMRI) signals was tested. The previous analyses of rsfMRI signals revealed differential inter-regional correlations among areas 3a, 3b, and 1 of primary somatosensory cortex (S1) in anesthetized monkeys (Wang et al. [2013]: Neuron 78:1116-1126). Here LFP band(s) which correlated between S1 regions, and how these inter-regional correlation differences covaried with rsfMRI signals were examined. LFP signals were filtered into seven bands (delta, theta, alpha, beta, gamma low, gamma high, and gamma very high), and then a Hilbert transformation was applied to obtain measures of instantaneous amplitudes and temporal lags between regions of interest (ROI) digit-digit pairs (areas 3b-area 1, area 3a-area 1, area 3a-area 3b) and digit-face pairs (area 3b-face, area 1-face, and area 3a-face). It was found that variations in the inter-regional correlation strengths between digit-digit and digit-face pairs in the delta (1-4 Hz), alpha (9-14 Hz), beta (15-30 Hz), and gamma (31-50 Hz) bands parallel those of rsfMRI signals to varying degrees. Temporal lags between digit-digit area pairs varied across LFP bands, with area 3a mostly leading areas 1/2 and 3b. In summary, the data demonstrates that the low and middle frequency range (1-50 Hz) of spontaneous LFP signals similarly covary with the low frequency fluctuations of rsfMRI signals within local circuits of S1, supporting a neuronal electrophysiological basis of rsfMRI signals. Inter-areal LFP temporal lag differences provided novel insights into the directionality of information flow among S1 areas at rest. Hum Brain Mapp 37:2755-2766, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  20. Digital Tracking Array for FM Signals Based on Off-The-Shelf Wireless Technologies

    National Research Council Canada - National Science Library

    Edmund, Hui K

    2007-01-01

    ... a 2.4 GHz frequency modulation (FM) video signal from an unmanned air vehicle. The tracking is done using a monopulse technique Various numbers of elements were simulated to access the pattern coverage...

  1. New methods to get valid signals at high temperature conditions by using DSP tools of the ASSA (Abnormal Signal Simulation Analyzer)

    International Nuclear Information System (INIS)

    Koo, Kil-Mo; Hong, Seong-Wan; Song, Jin-Ho; Baek, Won-Pil; Jung, Myung-Kwan

    2012-01-01

    A new method to get valid signals under high temperature conditions using DSP (Digital Signal Processing) tools of an ASSA (Abnormal Signal Simulation Analyzer) module through a signal analysis of important circuit modeling under severe accident conditions has been suggested. Already exist, such kinds of DSP technique operated by LabVIEW or MatLab code linked with PSpice code, which have convenient tools as a special function of the ASSA module including a signal reconstruction method. If we can obtain a shift data of the transient parameters such as the time constant of the R-L-C circuit affected by high temperature under a severe accident condition, it will be possible to reconstruct an abnormal signal using a trained deconvolution algorithm as a sort of DSP technique. (author)

  2. Multispectral mid-infrared imaging using frequency upconversion

    DEFF Research Database (Denmark)

    Sanders, Nicolai Højer; Dam, Jeppe Seidelin; Jensen, Ole Bjarlin

    2013-01-01

    It has recently been shown that it is possible to upconvert infrared images to the near infrared region with high quantum efficiency and low noise by three-wave mixing with a laser field [1]. If the mixing laser is single-frequency, the upconverted image is simply a band-pass filtered version...... parameter, allowing for fast tuning and hence potentially fast image acquisition, paving the way for upconversion based real time multispectral imaging. In the present realization the upconversion module consists of an external cavity tapered diode laser in a Littrow configuration with a computer controlled...

  3. Printed silver nanowire antennas with low signal loss at high-frequency radio

    Science.gov (United States)

    Komoda, Natsuki; Nogi, Masaya; Suganuma, Katsuaki; Kohno, Kazuo; Akiyama, Yutaka; Otsuka, Kanji

    2012-05-01

    Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those obtained using etched copper foil antennas, because their surfaces were much smoother than those of etched copper foil antennas. This was the case even though the resistivity of silver nanowire lines was 43-71 μΩ cm, which is much higher than that of etched copper foil (2 μΩ cm). When printed silver nanowire antennas were heated at 100 °C, they achieved signal losses that were much lower than those of silver paste antennas comprising microparticles, nanoparticles, and flakes. Furthermore, using a low temperature process, we succeeded in remotely controlling a commercialized radio-controlled car by transmitting a 2.45 GHz signal via a silver nanowire antenna printed on a polyethylene terephthalate film.Silver nanowires are printable and conductive, and are believed to be promising materials in the field of printed electronics. However, the resistivity of silver nanowire printed lines is higher than that of metallic particles or flakes even when sintered at high temperatures of 100-400 °C. Therefore, their applications have been limited to the replacement of transparent electrodes made from high-resistivity materials, such as doped metallic oxides, conductive polymers, carbon nanotubes, or graphenes. Here we report that using printed silver nanowire lines, signal losses obtained in the high-frequency radio were lower than those

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

    Science.gov (United States)

    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.

  5. Model for spontaneous frequency sweeping of an Alfvén wave in a toroidal plasma

    Science.gov (United States)

    Wang, Ge; Berk, H. L.

    2012-05-01

    We study the frequency chirping signals arising from spontaneously excited toroidial Alfvén eigenmode (TAE) waves that are being driven by an inverted energetic particle distribution whose free energy is tapped from the generic particle/wave resonance interaction. Initially a wave is excited inside the Alfvén gap with a frequency determined from the linear tip model of Rosenbluth, Berk and Van dam (RBV) [1]. Hole/clumps structures are formed and are observed to chirp towards lower energy states. We find that the chirping signals from clump enter the Alfvén continuum which eventually produce more rapid chirping signals. The accuracy of the adiabatic approximation for the mode evolution is tested and verified by demonstrating that a WKB-like decomposition of the time response for the field phase and amplitude agree with the data. Plots of the phase space structure correlate well with the chirping dependent shape of the separatrix structure. A novel aspect of the simulation is that it performed close to the wave frame of the phase space structure, which enables the numerical time step to remain the same during the simulation, independent of the rest frame frequency.

  6. Simulation of the influence high-frequency (2 MHz) capacitive gas discharge and magnetic field on the plasma sheath near a surface in hypersonic gas flow

    International Nuclear Information System (INIS)

    Schweigert, I. V.

    2012-01-01

    The plasma sheath near the surface of a hypersonic aircraft formed under associative ionization behind the shock front shields the transmission and reception of radio signals. Using two-dimensional kinetic particle-in-cell simulations, we consider the change in plasma-sheath parameters near a flat surface in a hypersonic flow under the action of electrical and magnetic fields. The combined action of a high-frequency 2-MHz capacitive discharge, a constant voltage, and a magnetic field on the plasma sheath allows the local electron density to be reduced manyfold.

  7. First evaluation of low frequency noise measurements of in core detector signals in the measuring assembly Rheinsberg

    International Nuclear Information System (INIS)

    Collatz, S.

    1982-01-01

    Reactor noise spectra of in core neutron detectors are measured in the low frequency range (0.03 Hz to 1 Hz) and evaluated. The increase of the effective noise signal value is due to pressure oscillations or oscillations of special steam volume portions. Thus boiling monitoring of reactor cores in PWR type reactors may be possible, if the low frequency noise of the whole set of in core detectors is taken into account

  8. Frequency Domain Multiplexing for Use With NaI[Tl] Detectors

    Science.gov (United States)

    Belling, Samuel; Coherent Collaboration

    2017-09-01

    A process used in many forms of signal communication known as multiplexing is adapted for the purpose of combining signals from NaI[Tl] detectors so that fewer digitizer channels can be used to process the signal information from large experiments within the COHERENT collaboration. Each signal is passed through a ringing circuit to modulate it with a characteristic frequency. Information about the signal can be extracted from its amplitude, frequency, and phase. Simulations in LTSpice show that an operational amplifier circuit with a parallel LRC feedback loop can serve as the modulating circuit. Several such circuits can be constructed and housed compactly in a unit, and fed to an inverting, summing amplifier with tunable gain, such that the signals are carried by one cable. The signals are analyzed based on a Fourier transform after being digitized. The results show that the energy, channel, and time of the original interaction can be recovered by this process. In some cases it is possible through filtering and deconvolution to recover the shape of the original signal. The effort is ongoing, but with the design presented it is possible to multiplex 10 detectors into a single digitizer channel. NSF REU Program at Duke University.

  9. Indirect MRI of 17 o-labeled water using steady-state sequences: Signal simulation and preclinical experiment.

    Science.gov (United States)

    Kudo, Kohsuke; Harada, Taisuke; Kameda, Hiroyuki; Uwano, Ikuko; Yamashita, Fumio; Higuchi, Satomi; Yoshioka, Kunihiro; Sasaki, Makoto

    2018-05-01

    Few studies have been reported for T 2 -weighted indirect 17 O imaging. To evaluate the feasibility of steady-state sequences for indirect 17 O brain imaging. Signal simulation, phantom measurements, and prospective animal experiments were performed in accordance with the institutional guidelines for animal experiments. Signal simulations of balanced steady-state free precession (bSSFP) were performed for concentrations of 17 O ranging from 0.037-1.600%. Phantom measurements with concentrations of 17 O water ranging from 0.037-1.566% were also conducted. Six healthy beagle dogs were scanned with intravenous administration of 20% 17 O-labeled water (1 mL/kg). Dynamic 3D-bSSFP scans were performed at 3T MRI. 17 O-labeled water was injected 60 seconds after the scan start, and the total scan duration was 5 minutes. Based on the result of signal simulation and phantom measurement, signal changes in the beagle dogs were measured and converted into 17 O concentrations. The 17 O concentrations were averaged for every 15 seconds, and compared to the baseline (30-45 sec) with Dunnett's multiple comparison tests. Signal simulation revealed that the relationships between 17 O concentration and the natural logarithm of relative signals were linear. The intraclass correlation coefficient between relative signals in phantom measurement and signal simulations was 0.974. In the animal experiments, significant increases in 17 O concentration (P O. At the end of scanning, mean respective 17 O concentrations of 0.084 ± 0.026%, 0.117 ± 0.038, 0.082 ± 0.037%, and 0.049 ± 0.004% were noted for the cerebral cortex, cerebellar cortex, cerebral white matter, and ventricle. Dynamic steady-state sequences were feasible for indirect 17 O imaging, and absolute quantification was possible. This method can be applied for the measurement of permeability and blood flow in the brain, and for kinetic analysis of cerebrospinal fluid. 2 Technical Efficacy: Stage 1 J. Magn. Reson

  10. Mid infrared LHS system packaging using flexible waveguides

    Science.gov (United States)

    Yu, Chung

    1987-01-01

    As mid IR fiber optic systems are rapidly approaching a reality, so is the feasibility of fiber optic laser heterodyne systems. Laser heterodyne spectroscopy for high resolution monitoring of atmospheric gaseous pollutants is necessarily in the mid IR, the region in which the absorption signature of gaseous species is most prominent. It so happens that the lowest theoretical loss due to Rayleigh-Brillouin scattering also lies in the mid IR. Prospects of highly efficient laser heterodyne systems are thus very good. Such fibers are now beginning to be commercially available, and a test program is being conducted for such fibers with ambient temperature ranging from cryogenic to above room, and stringest mechanical flexibility requirements. Preliminary results are encouraging. A program is being started to explore the possibility of mid IR fiber optic device applications, by taking advantage of this phonon rich region. The potential long interaction length in fibers coupled with predicted extremely low losses point to stimulated Brillouin scattering based devices in the mW range. The generation of backscattered sBs at low laser powers is significant not only as an ultimate power limiting factor for laser transmission in fibers in the mid IR, but also the presence of frequency-shifted multiple order sBs Stokes and antiStokes lines will certainly have severe effect on the laser beats crucial in high resolution heterodyne spectroscopy.

  11. Frequency Analysis of Acoustic Emission Signal to Monitor Damage Evolution in Masonry Structures

    International Nuclear Information System (INIS)

    Masera, D; Bocca, P; Grazzini, A

    2011-01-01

    A crucial aspect in damage evaluation of masonry structures is the analysis of long-term behaviour and for this reason fatigue analysis has a great influence on safety assessment of this structures. Acoustic Emission (AE) are very effective non-destructive techniques applied to identify micro and macro-defects and their temporal evolution in several materials. This technique permits to estimate the velocity of ultrasound waves propagation and the amount of energy released during fracture propagation to obtain information on the criticality of the ongoing process. By means of AE monitoring, an experimental analysis on a set of reinforced and unreinforced masonry walls under variable amplitude and static loading has been carried out. During these tests, the AE signals were recorded. The AE signals were analysed using Fast Fourier Transform (FFT) to examine the frequency distribution of the micro and macro cracking. It possible to evaluate the evolution of the wavelength of the AE signal through the two characteristic peak in the AE spectrum signals and the wave speed of the P or S waves. This wavelength evolution can be represent the microcrak and macrocrack evolution in masonry walls. This procedure permits to estimate the fracture dimension characteristic in several loading condition and for several masonry reinforced condition.

  12. Fast simulation approaches for power fluctuation model of wind farm based on frequency domain

    DEFF Research Database (Denmark)

    Lin, Jin; Gao, Wen-zhong; Sun, Yuan-zhang

    2012-01-01

    This paper discusses one model developed by Riso, DTU, which is capa